publicationDate,title,abstract,id
2018-01-11,Quantum Spin of Elastic Wave,"Unveiling intrinsic spins of propagating waves usually offers people a
fundamental understanding of the geometrical and topological properties of
waves from classical to quantum aspects. A great variety of research has shown
that transverse waves can possess non-trivial quantum spins and topology
without help of strong wave-matter interaction. However, until now we still
lack essential physical insights about the spin and topological nature of
longitudinal waves. Here, demonstrated by elastic waves we uncover unique
quantum spins for longitudinal waves and the mixed longitudinal-transverse
waves that play essential roles in topological spin-momentum locking. Based on
this quantum spin perspective, several abnormal phenomena beyond pure
transverse waves are attributed to the hybrid spin induced by mixed
longitudinal-transverse waves. The intrinsic hybrid spin reveals the complex
spin essence in elastic waves and advances our understanding about their
fundamental topological properties. We also show these spin-dependent phenomena
can be exploited to control the wave propagation, such as non-symmetric elastic
wave excitation by spin pairs, uni-directional Rayleigh wave and spin-selected
elastic wave routing. These findings are generally applicable for arbitrary
waves with longitudinal and transverse components.",1801.03907v1
2011-12-07,Spin Pumping Driven by Bistable Exchange Spin Waves,"Spin pumping driven by bistable exchange spin waves is demonstrated in a
Pt/Y$_3$Fe$_5$O$_{12}$ film under parametric excitation. In the
Pt/Y$_3$Fe$_5$O$_{12}$ film, the spin pumping driven by parametric excitation
selectively enhances the relaxation of short-wavelength exchange spin waves,
indicating strong coupling between the exchange spin waves and spin currents at
the interface through efficient spin transfer. The parametric spin pumping,
furthermore, allows direct access to nonlinear spin wave dynamics in
combination with the inverse spin Hall effect, revealing unconventional
bistability of the exchange spin waves.",1112.1596v2
2008-02-28,Current driven spin-wave instability triggered by the anomalous Hall effect,"We studied the effect of strong electric current on spin waves interacting
relativistically with the current. The spin-wave spectrum is calculated at
arbitrary direction of the wave vector. It is shown that the alternating Hall
current generated by the alternating magnetic moment of the spin waves, reduces
the spin-wave damping. At strong enough unpolarized dc current the damping
changes sign, and the spin-wave amplitude starts to increase exponentially fast
with time. The critical current for the spin-wave instability is determined
mainly by the anomalous Hall effect, and can be much smaller than that for the
spin-torque mechanism of instability.",0802.4150v1
2019-06-05,Spin-Wave Optical Elements: Towards Spin-Wave Fourier Optics,"We perform micromagnetic simulations to investigate the propagation of
spin-wave beams through spin-wave optical elements. Despite spin-wave
propagation in magnetic media being strongly anisotropic, we use axicons to
excite spinwave Bessel-Gaussian beams and gradient-index lenses to focus spin
waves in analogy to conventional optics with light in isotropic media.
Moreover, we demonstrate spin-wave Fourier optics using gradient-index lenses.
These results contribute to the growing field of spin-wave optics.",1906.02301v1
2020-04-16,Magnetic resonance imaging of spin-wave transport and interference in a magnetic insulator,"Spin waves - the elementary excitations of magnetic materials - are prime
candidate signal carriers for low dissipation information processing. Being
able to image coherent spin-wave transport is crucial for developing
interference-based spin-wave devices. We introduce a platform for probing
coherent spin waves based on magnetic resonance imaging with electron spins in
diamond. Focusing on a thin-film magnetic insulator, we quantify spin-wave
amplitudes, visualize the dispersion, and demonstrate time-domain measurements
of spin-wave packets. We use our platform to study spin-wave interference,
revealing uni-directional, autofocused spin-wave patterns with
frequency-controlled numerical apertures. A theoretical analysis explains the
patterns in terms of chiral spin-wave excitation and stray-field coupling to
the sensor spins. These results pave the way for probing spin waves in
atomically thin magnets, even when embedded between opaque materials.",2004.07746v1
2022-03-02,Atomic-Scale Spin-Wave Polarizer Based on a Sharp Antiferromagnetic Domain Wall,"We theoretically study the scattering of spin waves from a sharp domain wall
in an antiferromagnetic spin chain. While the continuum model for an
antiferromagnetic material yields the well-known result that spin waves can
pass through a wide domain wall with no reflection, here we show that, based on
the discrete spin Hamiltonian, spin waves are generally reflected by a domain
wall with a reflection coefficient that increases as the domain-wall width
decreases. Remarkably, we find that, in the interesting case of an atomically
sharp domain wall, the reflection of spin waves exhibits strong dependence on
the state of circular polarization of the spin waves, leading to mainly
reflection for one polarization while permitting partial transmission for the
other, thus realizing an atomic-scale spin-wave polarizer. The polarization of
the transmitted spin wave depends on the orientation of the spin in the sharp
domain wall, which can be controlled by an external field or spin torque. Our
utilization of a sharp antiferromagnetic domain wall as an atomic-scale
spin-wave polarizer leads us to envision that ultra-small magnetic solitons
such as domain walls and skyrmions may enable realizations of atomic-scale
spin-wave scatterers with useful functionalities.",2203.01453v1
2014-09-28,Spin-electron acoustic waves: The Landau damping and ion contribution in the spectrum,"Separated spin-up and spin-down quantum kinetics is derived for more detailed
research of the spin-electron acoustic waves. Kinetic theory allows to obtain
spectrum of the spin-electron acoustic waves including effects of occupation of
quantum states more accurately than quantum hydrodynamics. We apply quantum
kinetic to calculate the Landau damping of the spin-electron acoustic waves. We
have considered contribution of ions dynamics in the spin-electron acoustic
wave spectrum. We obtain contribution of ions in the Landau damping in
temperature regime of classic ions. Kinetic analysis for ion-acoustic, zero
sound, and Langmuir waves at separated spin-up and spin-down electron dynamics
is presented as well.",1409.7885v1
2021-09-30,Spin waves in doped graphene: a time-dependent spin-density-functional approach to collective excitations in paramagnetic two-dimensional Dirac fermion gases,"In spin-polarized itinerant electron systems, collective spin-wave modes
arise from dynamical exchange and correlation (xc) effects. We here consider
spin waves in doped paramagnetic graphene with adjustable Zeeman-type band
splitting. The spin waves are described using time-dependent
spin-density-functional response theory, treating dynamical xc effects within
the Slater and Singwi-Tosi-Land-Sjolander approximations. We obtain spin-wave
dispersions and spin stiffnesses as a function of doping and spin polarization,
and discuss prospects for their experimental observation.",2110.00045v1
1994-06-17,An Upper Bound for the Spin-Wave Spectrum of the Heisenberg Antiferromagnet,"We study the spin-wave spectrum of the Heisenberg antiferromagnet on a
bipartite lattice. The spin-wave spectrum on a N\'eel-ordered ground state is
bounded as $\varepsilon (k) \le c |k| $, where $c$ gives an upper bound for the
spin-wave velocity. In the large-$S$ limit, the upper bound $c$ coincides with
the result of the spin-wave theory.",9406077v1
2015-12-18,Domain Walls as Spin Wave Waveguides,"We numerically demonstrate that domain walls can be used as spin wave
waveguides. We show that gapless spin waves bounded inside a domain wall can be
guided by the domain wall. For Bloch walls, we further show that the bound spin
waves can pass through Bloch lines and corners without reflection. This finding
makes domain-wall-based spin wave devices possible.",1512.05965v2
2022-01-03,Handedness-filter and Doppler shift of spin waves in ferrimagnetic domain walls,"Excitation and propagation of spin waves inside magnetic domain walls has
received attention because of their potentials in spintronic and communication
applications. Besides wave amplitude and frequency, spin-wave has its third
character: handedness, whose manipulation is certainly of interest. We propose
in this Letter that the handedness of low energy spin-wave excitations can be
controlled by tuning the net angular momentum {\delta}s in a ferrimagnetic
(FiM) domain wall, attributing to the inequivalent magnetic sublattices. The
results indicate that the spin-wave dispersion depends on both {\delta}s and
wave handedness. For a positive (negative) {\delta}s, a gapless dispersion is
observed for the left-handed (righ-handed) spin waves, while a frequency gap
appears for the right-handed (left-handed) spin waves. Thus a FiM wall could
serve as a multifold filter of low energy spin-wave in which only spin waves
with particular handedness can propagate. Furthermore, the energy consumption
loss for spin-wave excitation in the wall is much lower than that inside the
domain, while the group velocity is much faster too, demonstrating the
advantages of domain walls serving as spin waveguides. Moreover, the
current-induced spin-wave Doppler shift in the FiM wall is also revealed, and
can be controlled by {\delta}s. This work unveils for the first time the
interesting spin-wave dynamics in FiM domain walls, benefiting future spin-wave
applications.",2201.00623v2
2021-09-28,"Spin wave propagation in uniform waveguide: effects, modulation and its application","With the advent of the post-Moore era, researches on beyond-Complementary
Metal Oxide Semiconductor (CMOS) approaches have been attracted more and more
attention. Magnonics, or spin wave is one of the most promising technology
beyond CMOS, which magnons-quanta for spin waves-process the information
analogous to electronic charges in electronics. Information transmission by
spin waves, which uses the frequency, amplitude and (or) phase to encode
information, has a great many of advantages such as extremely low energy loss
and wide-band frequency. Moreover, using the nonlinear characteristics of spin
waves for information transmission can increase the extra degree of freedom of
information. This review provides a tutorial overview over the effects of spin
wave propagation and recent research progress in uniform spin wave waveguide.
The propagation characteristics of spin waves in uniform waveguides and some
special propagation phenomena such as spin wave beam splitting and
self-focusing are described by combining experimental phenomena and theoretical
formulas. Furthermore, we summarize methods for modulating propagation of spin
wave in uniform waveguide, and comment on the advantages and limitations of
these methods. The review may promote the development of information
transmission technology based on spin waves.",2109.13464v1
2012-08-09,Interference-mediated intensity modulation of spin waves,"The modulation of propagating spin-wave amplitude in Ni81Fe19 (Py) films,
resulting from constructive and destructive interference of spin wave, has been
demonstrated. Spin waves were excited and detected inductively using pulse
inductive time domain measurements. Two electrical impulses were used for
launching two interfering Gaussian spin wave packets in Py films. The applied
bias magnetic field or the separation between two pulses was used for tuning
the amplitude of the resulting spin wave packets. This may thus be useful for
spin wave based low-power information transfer and processing.",1208.1848v1
2019-08-28,Effect of inhomogeneous Dzyaloshinskii-Moriya interaction on antiferromagnetic spin-wave propagation,"We investigate the effect of inhomogeneous Dzyaloshinskii-Moriya interaction
(DMI) on antiferromagnetic spin-wave propagation theoretically and numerically.
We find that antiferromagnetic spin waves can be amplified at a boundary where
the DMI varies. The inhomogeneous DMI also provides a way to construct a
magnonic crystal with forbidden and allowed antiferromagnetic spin-wave bands
in terahertz frequency ranges. In contrast to ferromagnetic spin waves,
antiferromagnetic spin waves experience a polarization-dependent phase shift
when passing through the inhomogeneous DMI, offering a magnonic crystal that
also serves as a spin-wave polarizer.",1908.10650v1
2021-12-07,Curvilinear manipulation of polarized spin wave,"Polarization, the precession direction with respect to the background
magnetization, is an intrinsic degree of freedom of spin wave. Introducing
symmetry breaking mechanisms lies in the heart of lifting the degeneracy
between polarized spin wave modes, and is essential in constructing
polarization-based magnonic devices. Here we show that polarized spin waves can
be naturally harnessed in a curved antiferromagnetic wire via tuning its
curvature and torsion. Specifically, we investigate evolution of polarized spin
wave in a spin wave rotator and a spin wave interferometer based on magnetic
circular helices, and correlate these curvilinear effects to the Berry phase
accumulated along wires.",2112.03748v1
2011-03-24,Spin wave assisted current induced magnetic domain wall motion,"The interaction between the propagating spin waves and the current driven
motion of a transverse domain wall in magnetic nanowires is studied by
micromagnetic simulations. If the speed of domain walls due to current induced
spin transfer torque is comparable to the velocity driven by spin waves, the
speed of domain wall is improved by applying spin waves. The domain wall
velocity can be manipulated by the frequency and amplitude of spin waves. The
effect of spin waves is suppressed in the high current density regime in which
the domain wall is mostly driven by current induced spin transfer torque.",1103.4673v1
2016-01-05,On the rich eight branch spectrum of the oblique propagating longitudinal waves in partially spin polarized electron-positron-ion plasmas,"We consider the separate spin evolution of electrons and positrons in
electron-positron and electron-positron-ion plasmas. We consider oblique
propagating longitudinal waves in this systems. We report presence of the
spin-electron acoustic waves and their dispersion dependencies. In
electron-positron plasmas, similarly to the electron-ion plasmas, we find one
spin-electron acoustic wave (SEAW) at propagation parallel or perpendicular to
the external field and two spin-electron acoustic waves at the oblique
propagation. At the parallel or perpendicular propagation of the longitudinal
waves in electron-positron-ion plasmas we find four branches: the Langmuir
wave, the positron-acoustic wave and pair of waves having spin nature, they are
the SEAW and, as we called it, spin-electron-positron acoustic wave (SEPAW). At
the oblique propagation we find eight longitudinal waves: the Langmuir wave,
Trivelpiece-Gould wave, pair of positron-acoustic waves, pair of SEAWs, and
pair of SEPAWs. Thus, for the first time, we report existence of the second
positron-acoustic wave existing at the oblique propagation and existence of
SEPAWs.",1601.00761v1
2016-07-21,Spin wave and spin flip in hexagonal LuMnO3 single crystal,"Manipulate and control of spin wave and spin flip are crucial for future
developments of magnonic and spintronic devices. We present that the spin wave
in hexagonal LuMnO3 single crystal can be selectively excited with laser
polarization perpendicular to the c-axis of hexagonal LuMnO3 and photon energy
~ 1.8 eV. The selective excitation of spin wave also suggests that the spin
flip can be selectively controlled in hexagonal manganites. In addition, the
physical origin of spin wave correlated with spin flip in hexagonal manganites
is discussed.",1607.06212v1
2024-03-19,Acoustoelectric non-local spin wave power detector for studying magnon-phonon coupling,"We have developed a simple detection scheme to study spin waves excited by
surface acoustic wave (SAW) in ferromagnetic thin films. Metallic antennas made
of Ta and a ferromagnetic element are placed along the SAW propagation path.
The SAW excites spin waves in the ferromagnetic element and induces
acoustoelectric current in the antennas, which are detected as a DC voltage.
The DC voltage takes an extremum at the spin wave resonance condition, which
demonstrates that the antenna acts as a non-local spin wave detector. The
antennas placed before and after the ferromagnetic element along the SAW
propagation path can probe spin wave excitation from reflected and transmitted
SAWs, respectively. Interestingly, we find characteristics of spin wave
excitations that are different for the reflected and transmitted SAWs: the
former excites spin waves with larger frequency with broader linewidth compared
to the latter. The results show that the antennas act as a non-local spin wave
power detector and can be used to map out the spin wave spectra in a unique
way, providing insights into the magnon-phonon coupling in magnetic
nanostructures fabricated on phononic SAW devices.",2403.12745v1
2018-10-29,Manipulating spin wave polarization in synthetic antiferromagnet,"Polarization is a key ingredient of all waves, including the electromagnetic
wave, the acoustic wave, as well as the spin wave. Due to the fixed
ferromagnetic order, the spin wave in ferromagnet is limited to the right
circular polarization. The spin wave in antiferromagnet, however, is endowed
with the full polarization degree of freedom because of the two identical
magnetic sublattices. In the synthetic antiferromagnet, the two magnetic
sublattices are spatially separated into two sublayers. The circular
polarization of spin wave is partially locked to the magnetic sublattice of the
antiferromagnet, thus to the sublayer in synthetic antiferromagnet. Based on
this unique polarization-sublayer locking mechanism, we show that both the
circular spin wave polarizer and retarder (wave-plate) can be straightforwardly
realized using synthetic antiferromagnets by restructuring the sublayers, e.g.
by removing or capping a portion of a sublayer. Manipulating spin wave
polarization by geometrical engineering provides a simple yet powerful paradigm
in harnessing the spin wave polarization for spin information processing.",1810.12149v1
2021-06-04,Imaging spin-wave damping underneath metals using electron spins in diamond,"Spin waves in magnetic insulators are low-damping signal carriers that could
enable a new generation of spintronic devices. The excitation, control, and
detection of spin waves by metal electrodes is crucial for interfacing these
devices to electrical circuits. It is therefore important to understand
metal-induced damping of spin-wave transport, but characterizing this process
requires access to the underlying magnetic films. Here we show that spins in
diamond enable imaging of spin waves that propagate underneath metals in
magnetic insulators, and then use this capability to reveal a 100-fold increase
in spin-wave damping. By analyzing spin-wave-induced currents in the metal, we
derive an effective damping parameter that matches these observations well. We
furthermore detect buried scattering centers, highlighting the technique's
power for assessing spintronic device quality. Our results open new avenues for
studying metal - spin-wave interaction and provide access to interfacial
processes such as spin-wave injection via the spin-Hall effect.",2106.02508v2
2011-11-15,Spin waves in nanosized magnetic films,"We have studied spin excitations in nanosized magnetic films in the
Heisenberg model with magnetic dipole and exchange interactions by the spin
operator diagram technique. Dispersion relations of spin waves in thin magnetic
films (in two-dimensional magnetic monolayers and in two-layer magnetic films)
and the spin-wave resonance spectrum in N-layer structures are found. For thick
magnetic films generalized Landau-Lifshitz equations are derived from first
principles. Landau-Lifshitz equations have the integral (pseudodifferential)
form, but not differential one. Spin excitations are determined by simultaneous
solution of the Landau-Lifshitz equations and the equation for the
magnetostatic potential. For normal magnetized ferromagnetic films the spin
wave damping has been calculated in the one-loop approximation for a diagram
expansion of the Green functions at low temperature. In thick magnetic films
the magnetic dipole interaction makes a major contribution to the relaxation of
long-wavelength spin waves. Thin films have a region of low relaxation of
long-wavelength spin waves. In thin magnetic films four-spin-wave processes
take place and the exchange interaction makes a major contribution to the
damping. It is found that the damping of spin waves propagating in magnetic
monolayer is proportional to the quadratic dependence on the temperature and is
very low for spin waves with small wavevectors. Spin-wave devices on the base
of nanosized magnetic films are proposed -- tunable narrow-band spin-wave
filters with high quality at the microwave frequency range and field-effect
transistor (FET) structures contained nanosized magnetic films under the gate
electrode. Spin-wave resonances in nanosized magnetic films can be used to
construct FET structures operating in Gigahertz and Terahertz frequency bands.",1111.3532v1
2003-12-03,Magnetostatic Spin Waves,"In general, Maxwell's equations require that a wave of magnetic field be
accompanied by a wave of electric field, and vice versa. In magnetic media it
is possible to have waves of magnetization with negligible electric field. We
discuss an example of this based on ferromagnetic spin waves.",0312026v1
2002-01-16,Quantum Spin dynamics of the Bilayer Ferromagnet La(1.2)Sr(1.8)Mn2O7,"We construct a theory of spin wave excitations in the bilayer manganite
La(1.2)Sr(1.8)Mn2O7 based on the simplest possible double-exchange model, but
including leading quantum corrections to the spin wave dispersion and damping.
Comparison is made with recent inelastic neutron scattering experiments. We
find that quantum effects account for some part of the measured damping of spin
waves, but cannot by themselves explain the observed softening of spin waves at
the zone boundary. Furthermore a doping dependence of the total spin wave
dispersion and the optical spin wave gap is predicted.",0201269v1
2023-03-18,Spin waves in a superconductor,"Spin waves that can propagate in normal and superconducting metals are
investigated. Unlike normal metals, the velocity of spin waves becomes
temperature-dependent in a superconductor. The low frequency spin waves survive
within the narrow region below the superconducting transition temperature. At
low temperatures the high frequency waves alone can propagate with an
additional damping due to pair-breaking.",2303.10468v1
2015-12-17,Multi-$Q$ hexagonal spin density waves and dynamically generated spin-orbit coupling: time-reversal invariant analog of the chiral spin density wave,"We study hexagonal spin-channel (""triplet"") density waves with commensurate
$M$-point propagation vectors. We first show that the three $Q=M$ components of
the singlet charge density and charge-current density waves can be mapped to
multi-component $Q=0$ nonzero angular momentum order in three dimensions ($3D$)
with cubic crystal symmetry. This one-to-one correspondence is exploited to
define a symmetry classification for triplet $M$-point density waves using the
standard classification of spin-orbit coupled electronic liquid crystal phases
of a cubic crystal. Through this classification we naturally identify a set of
non-coplanar spin density and spin-current density waves: the chiral spin
density wave and its time-reversal invariant analog. These can be thought of as
$3D$ $L=2$ and $L=4$ spin-orbit coupled isotropic $\beta$-phase orders. In
contrast, uniaxial spin density waves are shown to correspond to
$\alpha$-phases. The non-coplanar triple-$M$ spin-current density wave realizes
a novel $2D$ semimetal state with three flavors of four-component spin-momentum
locked Dirac cones, protected by a crystal symmetry akin to non-symmorphic
symmetry, and sits at the boundary between a trivial and topological insulator.
In addition, we point out that a special class of classical spin states,
defined as classical spin states respecting all lattice symmetries up to global
spin rotation, are naturally obtained from the symmetry classification of
electronic triplet density waves. These symmetric classical spin states are the
classical long-range ordered limits of chiral spin liquids.",1512.05673v3
2017-05-30,Communication and information processing in magnetic nanostructures with edge spin waves,"Low dissipation data processing with spins is one of the promising directions
for future information and communication technologies. Despite a signifcant
progress, the available magnonic devices are not broadband yet and have
restricted capabilities to redirect spin waves. Here we propose a breakthrough
approach to the spin wave manipulation in patterned magnetic nanostructures
with unmatched characteristics, which exploits spin waves analogous to edge
waves propagating along a water-wall boundary. Using theory, micromagnetic
simulations and experiment we investigate spin waves propagating along the
edges in magnetic structures, under an in-plane DC magnetic field inclined with
respect to the edge. The proposed edge spin waves overcome important challenges
faced by previous technologies such as the manipulation of the spin wave
propagation direction, and they substantially improve the capability of
transmitting information at frequencies exceeding 10 GHz. The concept of the
edge spin waves allows to design broad range of logic devices such as
splitters, interferometers, or edge spin wave transistors with unprecedented
characteristics and potentially strong impact on information technologies.",1705.10536v2
2020-12-01,Towards a quantum interface between spin waves and paramagnetic spin baths,"Spin waves have risen as promising candidate information carriers for the
next generation of information technologies. Recent experimental demonstrations
of their detection using electron spins in diamond pave the way towards
studying the back-action of a controllable paramagnetic spin bath on the spin
waves. Here, we present a quantum theory describing the interaction between
spin waves and paramagnetic spins. As a case study we consider an ensemble of
nitrogen-vacancy spins in diamond in the vicinity of an Yttrium-Iron-Garnet
thin film. We show how the back-action of the ensemble results in strong and
tuneable modifications of the spin-wave spectrum and propagation properties.
These modifications include the full suppression of spin-wave propagation and,
in a different parameter regime, the enhancement of their propagation length by
$\sim 50\%$. Furthermore, we show how the spin wave thermal fluctuations induce
a measurable frequency shift of the paramagnetic spins in the bath. This shift
results in a thermal dispersion force that can be measured optically and/or
mechanically with a diamond mechanical resonator. In addition, we use our
theory to compute the spin wave-mediated interaction between the spins in the
bath. We show that all the above effects are measurable by state-of-the-art
experiments. Our results provide the theoretical foundation for describing
hybrid quantum systems of spin waves and spin baths, and establish the
potential of quantum spins as active control, sensing, and interfacing tools
for spintronics.",2012.00540v1
2006-05-12,Spin-Wave Theory of the Multiple-Spin Exchange Model on a Triangular Lattice in a Magnetic Field : 3-Sublattice Structures,"We study the spin wave in the S=1/2 multiple-spin exchange model on a
triangular lattice in a magnetic field within the linear spin-wave theory. We
take only two-, three- and four-spin exchange interactions into account and
restrict ourselves to the region where a coplanar three-sublattice state is the
mean-field ground state. We found that the Y-shape ground state survives
quantum fluctuations and the phase transition to a phase with a 6-sublattice
structure occurs with softening of the spin wave. We estimated the quantum
corrections to the ground state sublattice magnetizations due to zero-point
spin-wave fluctuations.",0605318v1
2018-05-09,Programmable control of spin-wave transmission in a domain-wall spin valve,"Active manipulation of spin waves is essential for the development of
magnon-based technologies. Here, we demonstrate programmable spin-wave
filtering by resetting the spin structure of a pinned 90$^\circ$ N\'{e}el
domain wall in a continuous CoFeB film with abrupt rotations of uniaxial
magnetic anisotropy. Using phase-resolved micro-focused Brillouin light
scattering and micromagnetic simulations, we show that broad 90$^\circ$
head-to-head or tail-to-tail magnetic domain walls are transparent to spin
waves over a broad frequency range. In contrast, magnetic switching to a
90$^\circ$ head-to-tail configuration produces much narrower domain walls at
the same pinning locations. Spin waves are strongly reflected by a resonance
mode in these magnetic domain walls. Based on these results, we propose a
magnetic spin-wave valve with two parallel domain walls. Switching the
spin-wave valve from an open to a close state changes the transmission of spin
waves from nearly 100% to 0% at the resonance frequency. This active control
over spin-wave transport could be utilized in magnonic logic devices or
non-volatile memory elements.",1805.03470v1
2021-12-23,Nutation spin waves in ferromagnets,"Magnetization dynamics and spin waves in ferromagnets are investigated using
the inertial Landau-Lifshitz-Gilbert equation. Taking inertial magnetization
dynamics into account, dispersion relations describing the propagation of
nutation spin waves in an arbitrary direction relative to the applied magnetic
field are derived via Maxwell's equations. It is found that the inertia of
magnetization causes the hybridization of electromagnetic waves and nutation
spin waves in ferromagnets, hybrid nutation spin waves emerge, and the redshift
of frequencies of precession spin waves is initiated, which transforms to
precession-nutation spin waves. These effects depend sharply on the direction
of wave propagation relative to the applied magnetic field. Moreover, the waves
propagating parallel to the applied field are circularly polarized, while the
waves propagating perpendicular to that field are elliptically polarized. The
characteristics of these spin nutation waves are also analyzed.",2112.12503v3
2018-05-21,Tunable spinful matter wave valve,"We investigate the transport problem that a spinful matter wave is incident
on a strong localized spin-orbit-coupled Bose-Einstein condensate in optical
lattices, where the localization is admitted by atom interaction only existing
at one particular site, and the spin-orbit coupling arouse spatial rotation of
the spin texture. We find that tuning the spin orientation of the localized
Bose-Einstein condensate can lead to spin-nonreciprocal / spin-reciprocal
transport, meaning the transport properties are dependent on / independent of
the spin orientation of incident waves. In the former case, we obtain the
conditions to achieve transparency, beam-splitting, and blockade of the
incident wave with a given spin orientation, and furthermore the ones to
perfectly isolate incident waves of different spin orientation, while in the
latter, we obtain the condition to maximize the conversion of different spin
states. The result may be useful to develop a novel spinful matter wave valve
that integrates spin switcher, beam-splitter, isolator, and converter. The
method can also be applied to other real systems, e.g., realizing perfect
isolation of spin states in magnetism, which is otherwise rather difficult.",1805.08129v1
2015-10-20,Evaluation of Spin Waves and Ferromagnetic Resonance Contribution to the Spin Pumping in Ta/CoFeB Structure,"The spin waves and ferromagnetic resonance (FMR) contribution to the spin
pumping signal is studied in the Ta/CoFeB interface under different excitation
bias fields. Ferromagnetic resonance is excited utilizing a coplanar waveguide
and a microwave generator. Using a narrow waveguide of about 3 {\mu}m,
magnetostatic surface spin waves with large wavevector (k) of about 0.81
{\mu}m^-1 are excited. A large k value results in dissociation of spin waves
and FMR frequencies according to the surface spin wave dispersion relation.
Spin waves and FMR contribution to the spin pumping are calculated based on the
area under the Lorentzian curve fitting over experimental results. It is found
that the FMR over spin waves contribution is about 1 at large bias fields in
Ta/CoFeB structure. Based on our spin pumping results, we propose a method to
characterize the spin wave decay constant which is found to be about 5.5 {\mu}m
in the Ta/CoFeB structure at a bias field of 600 Oe.",1510.05745v1
2005-11-21,Excitation of spin waves by spin polarized current,"Numerical and analytical analysis is used to explain recently observed
experimental phenomenon - excitation of spin waves in spin valves due to the
applied spin polarized current. Excited spin waves are being identified and
  Lyapunov stability analysis is being used to identify different regions of
stability depending on the value of the applied current.",0511503v2
2014-09-18,Spin-transfer torque induced spin waves in antiferromagnetic insulators,"We explore the possibility of exciting spin waves in insulating
antiferromagnetic films by injecting spin current at the surface. We analyze
both magnetically compensated and uncompensated interfaces. We find that the
spin current induced spin-transfer torque can excite spin waves in insulating
antiferromagnetic materials and that the chirality of the excited spin wave is
determined by the polarization of the injected spin current. Furthermore, the
presence of magnetic surface anisotropy can greatly increase the accessibility
of these excitations.",1409.5460v2
2014-12-04,Spin waves in semiconductor microcavities,"We show theoretically that a weakly interacting gas of spin-polarized
exciton-polaritons in a semiconductor microcavity supports propagation of spin
waves. The spin waves are characterised by a parabolic dispersion at small
wavevectors which is governed by the polariton-polariton interaction constant.
Due to spin-anisotropy of polariton-polariton interactions the dispersion of
spin waves depends on the orientation of the total polariton spin. For the same
reason, the frequency of homogeneous spin precession/polariton spin resonance
depends on their polarization degree.",1412.1758v2
2017-10-23,Frequency and wavenumber selective excitation of spin waves through coherent energy transfer from elastic waves,"Using spin-wave tomography (SWaT), we have investigated the excitation and
the propagation dynamics of optically-excited magnetoelastic waves, i.e.
hybridized modes of spin waves and elastic waves, in a garnet film. By using
time-resolved SWaT, we reveal the excitation dynamics of magnetoelastic waves
through coherent-energy transfer between optically-excited pure-elastic waves
and spin waves via magnetoelastic coupling. This process realizes frequency and
wavenumber selective excitation of spin waves at the crossing of the dispersion
relations of spin waves and elastic waves. Finally, we demonstrate that the
excitation mechanism of the optically-excited pure-elastic waves, which are the
source of the observed magnetoelastic waves, is dissipative in nature.",1710.08087v2
2022-10-21,Optical spin-wave detection beyond the diffraction limit,"Spin waves are proposed as information carriers for next-generation computing
devices because of their low power consumption. Moreover, their wave-like
nature allows for novel computing paradigms. Conventional methods to detect
spin waves are based either on electrical induction, limiting the downscaling
and efficiency complicating eventual implementation, or on light scattering,
where the minimum detectable spin-wave wavelength is set by the wavelength of
the laser. In this Article we demonstrate magneto-optical detection of spin
waves beyond the diffraction limit using a metallic grating that selectively
absorbs laser light. Specifically, we demonstrate the detection of propagating
spin waves with a wavelength of 700 nm using a diffraction-limited laser spot
with a size of 10 $\mu$m in 20 nm thick Py strips. Additionally, we show that
this grating is selective to the wavelength of the spin wave, providing
wavevector-selective spin-wave detection. This should open up new avenues
towards the integration of the burgeoning fields of photonics and magnonics,
and aid in the optical detection of spin waves in the short-wavelength exchange
regime for fundamental research.",2210.12016v1
2019-10-24,Spin waves in ferromagnetic thin films,"A spin wave is the disturbance of intrinsic spin order in magnetic materials.
In this paper, a spin wave in the Landau-Lifshitz-Gilbert equation is obtained
based on the assumption that the spin wave maintains its shape while it
propagates at a constant velocity. Our main findings include: (1) in the
absence of Gilbert damping, the spin wave propagates at a constant velocity
with the increment proportional to the strength of the magnetic field; (2) in
the absence of magnetic field, at a given time the spin wave converges
exponentially fast to its initial profile as the damping parameter goes to zero
and in the long time the relaxation dynamics of the spin wave converges
exponentially fast to the easy-axis direction with the exponent proportional to
the damping parameter; (3) in the presence of both Gilbert damping and magnetic
field, the spin wave converges to the easy-axis direction exponentially fast at
a small timescale while propagates at a constant velocity beyond that. These
provides a comprehensive understanding of spin waves in ferromagnetic
materials.",1910.11200v1
2018-10-11,"Propagating spin waves in nanometer-thick yttrium iron garnet films: Dependence on wave vector, magnetic field strength and angle","We present a comprehensive investigation of propagating spin waves in
nanometer-thick yttrium iron garnet (YIG) films. We use broadband spin-wave
spectroscopy with integrated coplanar waveguides (CPWs) and microstrip antennas
on top of continuous and patterned YIG films to characterize spin waves with
wave vectors up to 10 rad/$\mu$m. All films are grown by pulsed laser
deposition. From spin-wave transmission spectra, parameters such as the Gilbert
damping constant, spin-wave dispersion relation, group velocity, relaxation
time, and decay length are derived and their dependence on magnetic bias field
strength and angle is systematically gauged. For a 40-nm-thick YIG film, we
obtain a damping constant of $3.5 \times 10^{-4}$ and a maximum decay length of
1.2 mm. Our experiments reveal a strong variation of spin-wave parameters with
magnetic bias field and wave vector. Spin-wave properties change considerably
up to a magnetic bias field of about 30 mT and above a field angle of
$\theta_{H} = 20^{\circ}$, where $\theta_{H} = 0^{\circ}$ corresponds to the
Damon-Eshbach configuration.",1810.04973v1
2018-02-05,Realization of a spin wave switch based on the Spin-Transfer-Torque effect,"We investigate the amplification of externally excited spin waves via the
Spin-Transfer-Torque (STT) effect in combination with the Spin-Hall-Effect
(SHE) employing short current pulses. The results reveal that, in the case of
an overcompensation of the spin wave damping, a strong nonlinear shift of the
spin wave frequency spectrum occurs. In particular, this shift affects the spin
wave amplification using the SHE-STT effect. In contrast, this effect allows
for the realization of a spin wave switch. By determining the corresponding
working point, an efficient spin wave excitation is only possible in the
presence of the SHE-STT effect yielding an increased spin wave intensity of a
factor of 20 compared to the absence of the SHE-STT effect.",1802.01294v1
2022-02-10,Amplifying spin waves along Néel domain wall by spin-orbit torque,"Traveling spin waves in magnonic waveguides undergo severe attenuation, which
tends to result in a finite propagation length of spin waves, even in magnetic
materials with the accessible lowest damping constant, heavily restricting the
development of magnonic devices. Compared with the spin waves in traditional
waveguides, propagating spin waves along strip domain wall are expected to
exhibit enhanced transmission. Here, we demonstrate, theoretically and through
micromagnetic simulations, that spin-orbit torque associated with a
ferromagnet/heavy metal bilayer can efficiently control the attenuation of spin
waves along a N\'eel-type strip domain wall, despite the complexity in the
ground-state magnetization configuration. The direction of the electric current
applied to the heavy-metal layer determines whether these spin waves are
amplified or further attenuated otherwise. Remarkably, our simulations reveal
that the effective current densities required to efficiently tune the decay of
such spin waves are just ~10^10 Am-2, roughly an order smaller than those
required in conventional spin waveguides. Our results will enrich the toolset
for magnonic technologies.",2202.05181v1
2007-09-20,Spin wave resonances in La_{0.7}Sr_{0.3}MnO_{3} films: measurement of spin wave stiffness and anisotropy field,"We studied magnetic field dependent microwave absorption in epitaxial
La$_{0.7}$Sr$_{0.3}$MnO$_{3}$ films using an X-band Bruker ESR spectrometer. By
analyzing angular and temperature dependence of the ferromagnetic and spin-wave
resonances we determine spin-wave stiffness and anisotropy field. The spin-wave
stiffness as found from the spectrum of the standing spin-wave resonances in
thin films is in fair agreement with the results of inelastic neutron
scattering studies on a single crystal of the same composition [Vasiliu-Doloc
et al., J. Appl. Phys. \textbf{83}, 7343 (1998)].",0709.3204v2
2019-10-09,Thermally controlled confinement of spin wave field in a magnonic YIG waveguide,"Methods for detecting spin waves rely on electrodynamical coupling between
the spin wave dipolar field and an inductive probe. While this coupling is
usually treated as constant, in this work, we experimentally and theoretically
show that it is indeed temperature dependent. By measuring the spin wave
magnetic field as a function of temperature of, and distance to the sample, we
demonstrate that there is both a longitudinal and transversal confinement of
the field near the YIG-Air interface. Our results are relevant for spin wave
detection, in particular in the field of spin wave caloritronics",1910.04304v1
2021-06-08,Resonant excitation of twisted spin waves in magnetic vortices using rotating magnetic fields,"Twisted spin waves attracted research attentions lately and the orbital
angular momentum they carry may be utilized in communication and computing
technologies. In this work, we manifest by micromagnetic simulations that
twisted spin wave modes naturally exist in thick ferromagnetic disks. The
twisted spin waves can be readily stimulated using rotating magnetic field when
it is tuned to the eigenfrequency of corresponding modes. We analytically
derive dispersion relation of the twisted spin waves and the results agree well
with the numerical studies. Lastly, we demonstrate that the topological charge
of twisted spin waves can be controlled by the exciting field.",2106.04214v1
2008-10-28,Quantization Of Spin Direction For Solitary Waves In A Uniform Magnetic Field,"It is known that there are nonlinear wave equations with localized solitary
wave solutions. Some of these solitary waves are stable (with respect to a
small perturbation of initial data) and have nonzero spin (nonzero intrinsic
angular momentum in the center of momentum frame). In this paper we consider
vector-valued solitary wave solutions to a nonlinear Klein-Gordon equation and
investigate the behavior of these spinning solitary waves under the influence
of an externally imposed uniform magnetic field. We find that the only
stationary spinning solitary wave solutions have spin parallel or anti-parallel
to the magnetic field direction.",0810.4959v2
2020-09-28,Rolling Waves with Non-Paraxial Phonon Spins,"We demonstrate a new class of elastic waves in the bulk: When longitudinal
and transverse components propagate at the same speed, rolling waves with a
spin that is not parallel to the wave vector can emerge. First, we give a
general definition of spin for traveling waves. Then, since rolling waves
cannot exist in isotropic solids, we derive conditions for anisotropic media
and proceed to design architected materials capable of hosting rolling waves.
Numerically, we show spin manipulations by reflection. Structures reported in
this work can be fabricated using available techniques, opening new
possibilities for spin technologies in acoustics, mechanics and phononics.",2009.13014v1
2021-12-27,Spin-electron-acoustic waves and solitons in high-density degenerate relativistic plasmas,"The spin-electron-acoustic waves (sometimes called the spin-plasmons) can be
found in degenerate electron gas if the spin-up electrons and spin down
electrons move relatively each other. Here, we suggest relativistic
hydrodynamics with the separate spin evolution which allows us to study linear
and nonlinear spin-electron-acoustic waves, including the
spin-electron-acoustic solitons. Presented hydrodynamic model is the
corresponding generalization of the relativistic hydrodynamic model with the
average reverse gamma factor evolution which consists of the equations for
evolution of the following functions the partial concentrations (for spin-up
electrons and spin down electrons), the partial velocity fields, the partial
average reverse relativistic gamma factors, and the partial flux of the reverse
relativistic gamma factors. We find that the relativistic effects decreases the
phase velocity of spin-electron-acoustic waves. Numerical analysis of the
changes of spectra of Langmuir wave, spin-electron-acoustic wave, and
ion-acoustic wave under the change of the spin polarization of electrons is
presented. It is demonstrated that spectra of Langmuir wave and
spin-electron-acoustic wave getting closer to each other in the relativistic
limit. Spin dependence of the amplitude and width of the relativistic
spin-electron-acoustic soliton is demonstrated as well. Reformation of the
bright soliton of potential of the electric field into the dark soliton under
the influence of the relativistic effects is found.",2112.13880v1
2012-08-09,Attenuation characteristics of spin pumping signal due to travelling spin waves,"The authors have investigated the contribution of the surface spin waves to
spin pumping. A Pt/NiFe bilayer has been used for measuring spin waves and spin
pumping signals simultaneously. The theoretical framework of spin pumping
resulting from ferromagnetic resonance has been extended to incorporate spin
pumping due to spin waves. Equations for the effective area of spin pumping due
to spin waves have been derived. The amplitude of the spin pumping signal
resulting from travelling waves is shown to decrease more rapidly with
precession frequency than that resulting from standing waves and show good
agreement with the experimental data.",1208.1837v1
2013-07-29,Current-induced spin wave excitation in Pt|YIG bilayer,"We develop a self-consistent theory for current-induced spin wave excitations
in normal metal-magnetic insulator bilayer systems, thereby establishing the
relation between spin wave excitation and the experimentally controlled
parameters. We fully take into account the complex spin wave spectrum including
dipolar interactions and surface anisotropy as well as the spin-pumping at the
interface. Our results focus on the mode-dependent power close to the critical
currents for spin wave excitation. The major findings are (a) the spin transfer
torque can excite different spin-wave modes simultaneously; (b) spin pumping
counterbalances spin-transfer torque and affects the surface modes more than
the bulk modes; (c) spin pumping inhibits high frequency spin-wave modes,
thereby redshifting the excitation spectrum. We can get agreement with
experiments on yttrium iron garnet|platinum bilayers by postulating the
existence of surface anisotropy modes.",1307.7607v2
2008-03-29,Quantized spin waves and perpendicular standing spin waves stimulated by current in a single-layered ferromagnetic wire,"The rectifying effect of radio-frequency (RF) current is highly sensitive in
terms of the spatial spin distribution and dynamics. It emerged that an
additional spin wave mode was stimulated by the direct-current (DC) current and
that this spin wave was detectable via rectification of the RF current. A
phenomenological model to describe the time-dependent anisotropic
magnetoresistance or time-dependent planer Hall effect is proposed and found to
correlate well to the experimental results. The nonlinear spin dynamics
accompanying additional spin waves are studied as functions of the RF and DC
currents, the external magnetic field, and the applied field direction.",0803.4271v1
2008-12-13,Spin-Transfer Torque in Helical Spin-Density Waves,"The current driven magnetisation dynamics of a helical spin-density wave is
investigated. Expressions for calculating the spin-transfer torque of real
systems from first principles density functional theory are presented. These
expressions are used for calculating the spin-transfer torque for the spin
spirals of Er and fcc Fe at two different lattice volumes. It is shown that the
calculated torque induces a rigid rotation of the order parameter with respect
to the spin spiral axis. The torque is found to depend on the wave vector of
the spin spiral and the spin-polarisation of the Fermi surface states. The
resulting dynamics of the spin spiral is also discussed.",0812.2509v1
2006-01-25,Spin-Dynamical Analysis of Supercell Spin Configurations,"A model-independent approach capable of extracting spin-wave frequencies and
displacement vectors from ensembles of supercell spin configurations is
presented. The method is appropriate for those systems whose spin-dynamical
motion is well characterised by small-amplitude fluctuations that give harmonic
spin waves. First, the the spin-dynamical matrix is described and its
eigenvalues shown to correspond to the spin-wave mode frequencies. The
generalised spin coordinate matrix - a quantity that may be calculated from the
observed spin orientations in an ensemble of spin configurations - is then
introduced and its relationship to the spin-dynamical matrix established. Its
eigenvalues are subsequently shown to be related to the spin-wave mode
frequencies, allowing the extraction of spin-wave dispersion curves from
configurational ensembles. Finally, a quantum-mechanical derivation of the same
results is given, and the method applied as a case study to spin Monte-Carlo
configurations of a 3D Heisenberg ferromagnet.",0601559v2
2020-05-20,Controlling the propagation of dipole-exchange spin waves using local inhomogeneity of the anisotropy,"Spin waves are promising candidates to carry, transport, and process
information. Controlling the propagation characteristics of spin waves in
magnetic materials is an essential ingredient for designing spin-wave based
computing architectures. Here, we study the influence of surface
inhomogeneities on the spin-wave signals transmitted through thin films. We use
micromagnetic simulations to study the spin-wave dynamics in an in-plane
magnetized yttrium iron garnet thin film with a thickness in the nanometre
range in the presence of surface defects in the form of locally introduced
uniaxial anisotropies. These defects are used to demonstrate that the Backward
Volume Magnetostatic Spin Waves (BVMSW) are more responsive to backscattering
in comparison to Magnetostatic Surface Spin Waves (MSSWs). For this particular
defect type, the reason for this behavior can be quantitatively related to the
difference in the magnon band structures for the two types of spin waves. To
demonstrate this, we develop a quasi-analytical theory for the scattering
process. It shows an excellent agreement with the micromagnetic simulations,
sheds light on the backscattering processes and provides a new way to analyze
the spin-wave transmission rates in the presence of surface inhomogeneities in
sufficiently thin films, for which the role of exchange energy in the spin-wave
dynamics is significant. Our study paves the way to designing magnonic logic
devices for data processing which rely on a designed control of the spin-wave
transmission.",2005.09965v2
2023-06-16,Theory of propagating spin wave spectroscopy using inductive antennas: conditions for unidirectional energy flow,"Many recent papers report on the interest of spin waves for applications.
This paper revisits the propagating spin wave spectroscopy when using inductive
transceivers connected to a network analyzer. The spin wave conduit can be made
of a non-reciprocal material. The formalism offers a method to understand,
design and optimize devices harnessing propagating spin waves, including when a
unidirectional energy flow is desired. The concept of the mismatch of helicity
between the spin wave and the magnetic field radiated by antennas is first
clarified. Owing to the form of the susceptibility tensor reflecting the
precession ellipticity, there exists specific orientations of the wavevector
for which a perfect helicity mismatch is reached. The spin waves with this
orientation and this direction of wavevector are ""dark"" in the sense that they
do not couple with the inductive antenna. This leads to single-sided wavevector
generation, that should not to be confused with a unidirectional emission of
energy. A method to calculate the antenna-to-antenna transmission parameter is
then provided. Analytical approximations are then applied on situations that
illustrate the respective role of the direction of the spin wave wavevector
versus that of the group velocity. The often-encountered cases of spin waves
possessing either a V-shaped or a flat dispersion relation are revisited. These
reciprocal dispersion relations lead to amplitude non-reciprocity because of
the helicity mismatch phenomenon. Conversely, for spin waves with a line-shaped
dispersion relation, a quasi-unidirectional emission of spin waves occurs. This
situation can be obtained when using the acoustical spin waves of synthetic
antiferromagnets when the wavevector is close to parallel to the applied field.
We finally show that this configuration can be harnessed to design
reconfigurable frequency filters.",2306.09716v2
2010-08-27,Enhancement of the spin pumping efficiency by spin-wave mode selection,"The spin pumping efficiency of lateral standing spin wave modes in a
rectangular YIG/Pt sample has been investigated by means of the inverse
spin-Hall effect (ISHE). The standing spin waves drive spin pumping, the
generation of spin currents from magnetization precession, into the Pt layer
which is converted into a detectable voltage due to the ISHE. We discovered
that the spin pumping efficiency is significantly higher for lateral standing
surface spin waves rather than for volume spin wave modes. The results suggest
that the use of higher-mode surface spin waves allows for the fabrication of an
efficient spin-current injector.",1008.4714v2
2011-06-22,All-magnonic spin-transfer torque and domain wall propagation,"The spin wave transportation through a transverse magnetic domain wall (DW)
in a magnetic nanowire is studied. It is found that spin wave passes through a
DW without reflection. A magnon, the quantum of the spin wave, carries opposite
spins on the two sides of the DW. As a result, there is a spin angular momentum
transfer from the propagating magnons to the DW. This magnonic spin-transfer
torque can efficiently drive a DW to propagate in the opposite direction to
that of the spin wave.",1106.4382v2
2013-05-07,Spin Wave Excitation in Magnetic Insulator Thin Films by Spin-Transfer Torque,"We describe excitation of dipole-exchange spin waves in insulating magnetic
thin films by spin current injection at the surface of the film. An easy-axis
magnetic surface anisotropy can induce a non-chiral surface spin wave mode with
penetration depth inversely proportional to the strength of the surface
anisotropy, which strongly reduces the critical current and enhances the
excitation power. The importance of the interface spin wave modes on the
excitation spectrum is reduced by spin pumping, which depends on the quality of
the interface as expressed by the spin mixing conductance.",1305.1364v2
2020-12-15,Spin wave spectral probing of possible microstates in building-block of macroscopically degenerate artificial spin ice,"We have investigated the spin wave modes of strongly dipolar coupled, highly
anisotropic nanoislands forming square artificial spin ice system using
micromagnetic simulation in MUMAX3 in combination with Matlab coding.
Artificial spin ice is considered to be formed by the four square ring-type
structure of elliptical cross-section nanoislands. Our results state the direct
relation between the spin wave modes generated and the micro-states formed in
the system. We have shown that single ring type structure can alone be
adequately used to understand the spin wave modes of square artificial spin
ice.",2012.08093v1
2006-01-17,Spin wave instabilities and field induced transitions in heavy fermions,"We study phase transitions in heavy fermion systems due to spin-wave
instabilities. One motivation is to determine the changes in the spin-wave
parameters of a magnetically ordered heavy fermion system as it approaches a
quantum critical point (QCP) by applying pressure. The other more actual is to
provide an alternative approach, based on spin-wave instabilities, for the
magnetic field induced transitions recently observed in antiferromagnetic heavy
fermion materials.",0601385v1
2013-01-23,Characterization of magnetostatic surface spin waves in magnetic thin films: evaluation for microelectronic applications,"The authors have investigated the possibility of utilizing spin waves for
inter- and intra-chip communications, and as logic elements using both
simulations and experimental techniques. Through simulations it has been shown
that the decay lengths of magnetostatic spin waves are affected most by the
damping parameter, and least by the exchange stiffness constant. The damping
and dispersion properties of spin waves limit the attenuation length to several
tens of microns. Thus, we have ruled out the possibility of inter-chip
communications via spin waves. Experimental techniques for the extraction of
the dispersion relationship have also been demonstrated, along with
experimental demonstrations of spin wave interference for amplitude modulation.
The effectiveness of spin wave modulation through interference, along with the
capability of determining the spin wave dispersion relationships electrically
during manufacturing and testing phase of chip production may pave the way for
using spin waves in analog computing wherein the circuitry required for
performing similar functionality becomes prohibitive.",1301.5395v1
2013-09-10,Spin wave excitation patterns generated by spin torque oscillators,"Spin torque nano oscillators (STNO) are nano-scale devices that can convert a
direct current into short wave-length spin-wave excitations in a ferromagnetic
layer. We show that arrays of STNO can be used to create directional spin-wave
radiation similar to electromagnetic antennas. Combining STNO excitations with
planar spin waves also creates interference patterns. We show that these
interference patterns are static and have information on the wavelength and
phase of the spin waves emitted from the STNO.We describe means of actively
controlling spin-wave radiation patterns with the direct current owing through
STNO, which is useful in on-chip communication and information processing and
could be a promising technique for studying short wave-length spin waves in
different materials.",1309.2436v1
2016-10-27,Spin-wave propagation in ultra-thin YIG based waveguides,"Spin-wave propagation in an assembly of microfabricated 20 nm thick, 2.5
{\mu}m wide Yttrium Iron Garnet (YIG) waveguides is studied using propagating
spin-wave spectroscopy (PSWS) and phase resolved micro-focused Brillouin Light
Scattering ({\mu}-BLS) spectroscopy. We show that spin-wave propagation in 50
parallel waveguides is robust against microfabrication induced imperfections.
Spin-wave propagation parameters are studied in a wide range of excitation
frequencies for the Damon-Eshbach (DE) configuration. As expected from its low
damping, YIG allows the propagation of spin waves over long distances (the
attenuation lengths is 25 {\mu}m at \mu$_{0}$H = 45 mT). Direct mapping of spin
waves by {\mu}-BLS allows us to reconstruct the spin-wave dispersion relation
and to confirm the multi-mode propagation in the waveguides, glimpsed by
propagating spin-wave spectroscopy.",1610.08756v1
2019-02-25,Nonreciprocal nano-optics with spin-waves in synthetic antiferromagnets,"Integrated optically-inspired wave-based processing is envisioned to
outperform digital architectures in specific tasks, such as image processing
and speech recognition. In this view, spin-waves represent a promising route
due to their nanoscale wavelength in the GHz frequency range and rich
phenomenology. Here, we realize a versatile optically-inspired platform using
spin-waves, demonstrating the wavefront engineering, focusing, and robust
interference of spin-waves with nanoscale wavelength. In particular, we use
magnonic nanoantennas based on tailored spin-textures for launching spatially
shaped coherent wavefronts, diffraction-limited spin-wave beams, and generating
robust multi-beam interference patterns, which spatially extend for several
times the spin-wave wavelength. Furthermore, we show that intriguing features,
such as resilience to back-reflection, naturally arise from the spin-wave
nonreciprocity in synthetic antiferromagnets, preserving the high quality of
the interference patterns from spurious counterpropagating modes. This work
represents a fundamental step towards the realization of nanoscale
optically-inspired devices based on spin-waves.",1902.09420v2
2016-03-17,Spin-Wave Fiber,"Spin waves are collective excitations propagating in the magnetic medium with
ordered magnetizations. Magnonics, utilizing the spin wave (magnon) as
information carrier, is a promising candidate for low-dissipation computation
and communication technologies. We discover that, due to the
Dzyaloshinskii-Moriya interaction, the scattering behavior of spin wave at a
magnetic domain wall follows a generalized Snell's law, where two magnetic
domains work as two different mediums. Similar to optical total reflection that
occurs at the water-air interfaces, spin waves may experience total reflection
at magnetic domain walls when their incident angle larger than a critical
value. We design a spin wave fiber using a magnetic domain structure with two
domain walls, and demonstrate that such a spin wave fiber can transmit spin
waves over long distance by total internal reflections, in analogy to an
optical fiber. Our design of spin wave fiber opens up new possibilities in pure
magnetic information processing.",1603.05325v1
2020-09-08,Time refraction of spin waves,"We present an experimental study of time refraction of spin waves propagating
in microscopic waveguides under the influence of time-varying magnetic fields.
Using space- and time-resolved Brillouin light scattering microscopy, we
demonstrate that the broken translational symmetry along the time coordinate
can be used to in- or decrease the energy of spin waves during their
propagation. This allows for a broadband and controllable shift of the
spin-wave frequency. Using an integrated design of spin-wave waveguide and
microscopic current line for the generation of strong, nanosecond-long,
magnetic field pulses, a conversion efficiency up to 39% of the carrier
spin-wave frequency is achieved, significantly larger compared to photonic
systems. Given the strength of the magnetic field pulses and its strong impact
on the spin-wave dispersion relation, the effect of time refraction can be
quantified on a length scale comparable to the spin-wave wavelength.
Furthermore, we utilize time refraction to excite spin-wave bursts with pulse
durations in the nanosecond range and a frequency shift depending on the pulse
polarity.",2009.03654v1
2017-01-05,Excitation and detection of short-waved spin waves in ultrathin Ta/CoFeB/MgO-layer system suitable for spin-orbit-torque magnonics,"We report on the excitation and detection of short-waved spin waves with wave
vectors up to about $40\,\mathrm{rad}\,\mu\mathrm{m}^{-1}$ in spin-wave
waveguides made from ultrathin, in-plane magnetized Co$_{8}$Fe$_{72}$B$_{20}$
(CoFeB). The CoFeB is incorporated in a layer stack of Ta/CoFeB/Mgo, a layer
system featuring large spin orbit torques and a large perpendicular magnetic
anisotropy constant. The short-waved spin waves are excited by nanometric
coplanar waveguides and are detected via spin rectification and microfocussed
Brillouin light scattering spectroscopy. We show that the large perpendicular
magnetic anisotropy benefits the spin-wave lifetime greatly, resulting in a
lifetime comparable to bulk systems without interfacial damping. The presented
results pave the way for the successful extension of magnonics to ultrathin
asymmetric layer stacks featuring large spin orbit torques.",1701.01399v1
2020-06-23,An Introduction to Spin Wave Computing,"This paper provides a tutorial overview over recent vigorous efforts to
develop computing systems based on spin waves instead of charges and voltages.
Spin-wave computing can be considered as a subfield of spintronics, which uses
magnetic excitations for computation and memory applications. The tutorial
combines backgrounds in spin-wave and device physics as well as circuit
engineering to create synergies between the physics and electrical engineering
communities to advance the field towards practical spin-wave circuits. After an
introduction to magnetic interactions and spin-wave physics, all relevant basic
aspects of spin-wave computing and individual spin-wave devices are reviewed.
The focus is on spin-wave majority gates as they are the most prominently
pursued device concept. Subsequently, we discuss the current status and the
challenges to combine spin-wave gates and obtain circuits and ultimately
computing systems, considering essential aspects such as gate interconnection,
logic level restoration, input-output consistency, and fan-out achievement. We
argue that spin-wave circuits need to be embedded in conventional CMOS circuits
to obtain complete functional hybrid computing systems. The state of the art of
benchmarking such hybrid spin-wave--CMOS systems is reviewed and the current
challenges to realize such systems are discussed. The benchmark indicates that
hybrid spin-wave--CMOS systems promise ultralow-power operation and may
ultimately outperform conventional CMOS circuits in terms of the
power-delay-area product. Current challenges to achieve this goal include
low-power signal restoration in spin-wave circuits as well as efficient
spin-wave transducers.",2006.12905v3
2021-03-14,Dispersion relation of nutation surface spin waves in ferromagnets,"Inertia effects in magnetization dynamics are theoretically shown to result
in a different type of spin waves, i.e. nutation surface spin waves, which
propagate at terahertz frequencies in in-plane magnetized ferromagnetic thin
films. Considering the magnetostatic limit, i.e. neglecting exchange coupling,
we calculate dispersion relation and group velocity, which we find to be slower
than the velocity of conventional (precession) spin waves. In addition, we find
that the nutation surface spin waves are backward spin waves. Furthermore, we
show that inertia causes a decrease of the frequency of the precession spin
waves, namely magnetostatic surface spin waves and backward volume
magnetostatic spin waves. The magnitude of the decrease depends on the magnetic
properties of the film and its geometry.",2103.07864v2
2023-06-30,Spin Wave Driven Skyrmions in a Bipartite Antiferromagnetic Lattice,"We show that a Skyrmion in a classical bipartite antiferromagnetic lattice
can be spatially displaced in a controlled manner by externally applied spin
waves. We reveal the relation between the Skyrmion motion and the spin wave
properties. To this end, we derive a classical spin wave formalism which is
tailored to the antiferromagnetic two-dimensional square lattice. The
antiferromagnetic spin waves can be classified into two types with respect to
their polarization, with two modes each. The circularly polarized spin waves
oscillate with different amplitudes in the respective sublattices and induce a
Skyrmion Hall effect. The two modes are symmetric under sublattices exchange
and determine the overall sign of the Hall angle. Linearly polarized spin waves
oscillate elliptically, however, with the same amplitude on each sublattice.
These accelerate the Skyrmion solely into their own propagation direction. The
two modes are symmetric under component x-y exchange and impact Bloch- or
N\'eel Skyrmions differently. Our results indicate possible technical
applications of spin-wave driven Skyrmion motion. As one example we propose a
racetrack where spin waves pump Skyrmions along the track in antiferromagnets.",2306.17678v2
2023-08-03,Hybrid Spin and Anomalous Spin-Momentum Locking in Surface Elastic Waves,"Transverse spin of surface waves is a universal phenomenon which has recently
attracted significant attention in optics and acoustics. It appears in gravity
water waves, surface plasmon-polaritons, surface acoustic waves, and exhibits
remarkable intrinsic spin-momentum locking, which has found useful applications
for efficient spin-direction couplers. Here we demonstrate, both theoretically
and experimentally, that the transverse spin of surface elastic (Rayleigh)
waves has an anomalous sign near the surface, opposite to that in the case of
electromagnetic, sound, or water surface waves. This anomalous sign appears due
to the hybrid (neither transverse nor longitudinal) nature of elastic surface
waves. Furthermore, we show that this sign anomaly can be employed for the
selective spin-controlled excitation of symmetric and antisymmetric Lamb modes
propagating in opposite directions in an elastic plate. Our results pave the
way for spin-controlled manipulation of elastic waves and can be important for
a variety of areas, from phononic spin-based devices to seismic waves.",2308.01953v1
2018-03-13,Theory of nonreciprocal spin waves excitation in spin-Hall oscillators with Dzyaloshinkii-Moriya interaction,"A two-dimensional analytical model for the description of the excitation of
nonreciprocal spin waves by spin current in spin-Hall oscillators in the
presence of the interfacial Dzyaloshinskii-Moriya interaction (i-DMI) is
developed. The theory allows one to calculate the threshold current for the
excitation of spin waves, as well as the frequencies and spatial profiles of
the excited spin wave modes. It is found, that the frequency of the excited
spin waves exhibits a quadratic red shift with the i-DMI strength. At the same
time, in the range of small and moderate values of the i-DMI constant, the
averaged wave number of the excited spin waves is almost independent of the
i-DMI, which results in a rather weak dependence on the i-DMI of the threshold
current of the spin wave excitation. The obtained analytical results are
confirmed by the results of micromagnetic simulations.",1803.05061v1
2021-02-24,SU(4) spin waves in the $ν=\pm1$ quantum Hall ferromagnet in graphene,"We study generalized spin waves in graphene under a strong magnetic field
when the Landau-level filling factor is $\nu=\pm 1$. In this case, the ground
state is a particular SU(4) quantum Hall ferromagnet, in which not only the
physical spin is fully polarized but also the pseudo-spin associated with the
valley degree of freedom. The nature of the ground state and the spin-valley
polarization depend on explicit symmetry breaking terms that are also reflected
in the generalised spin-wave spectrum. In addition to pure spin waves, one
encounters valley-pseudo-spin waves as well as more exotic entanglement waves
that have a mixed spin-valley character. Most saliently, the SU(4)
symmetry-breaking terms do not only yield gaps in the spectra, but under
certain circumstances, namely in the case of residual ground-state symmetries,
render the originally quadratic (in the wave vector) spin-wave dispersion
linear.",2102.12438v1
2021-05-06,Spin Wave Interference Detection via Inverse Spin Hall Effect,"In this letter, we present experimental data demonstrating spin wave
interference detection using spin Hall effect (ISHE). Two coherent spin waves
are excited in a yttrium-iron garnet (YIG) waveguide by continuous microwave
signals. The initial phase difference between the spin waves is controlled by
the external phase shifter. The ISHE voltage is detected at a distance of 2 mm
and 4 mm away from the spin wave generating antennae by an attached Pt layer.
Experimental data show ISHE voltage oscillation as a function of the phase
difference between the two interfering spin waves. This experiment demonstrates
an intriguing possibility of using ISHE in spin wave logic circuit converting
spin wave phase into an electric signal",2105.02979v1
2022-07-06,Filtering and imaging of frequency-degenerate spin waves using nanopositioning of a single-spin sensor,"Nitrogen-vacancy (NV) magnetometry is a new technique for imaging spin waves
in magnetic materials. It detects spin waves by their microwave magnetic stray
fields, which decay evanescently on the scale of the spin-wavelength. Here, we
use nanoscale control of a single-NV sensor as a wavelength filter to
characterize frequency-degenerate spin waves excited by a microstrip in a
thin-film magnetic insulator. With the NV-probe in contact with the magnet, we
observe an incoherent mixture of thermal and microwave-driven spin waves. By
retracting the tip, we progressively suppress the small-wavelength modes until
a single coherent mode emerges from the mixture. In-contact scans at low drive
power surprisingly show occupation of the entire iso-frequency contour of the
two-dimensional spin-wave dispersion despite our one-dimensional microstrip
geometry. Our distance-tunable filter sheds light on the spin-wave band
occupation under microwave excitation and opens opportunities for imaging
magnon condensates and other coherent spin-wave modes.",2207.02798v1
2017-02-20,Parametric pumping of spin waves by acoustic waves,"The linear and nonlinear interactions between spin waves (magnons) and
acoustic waves (phonons) in magnetostrictive materials provide an exciting
opportunity for realizing novel microwave signal processing devices and
spintronic circuits. Here we demonstrate the parametric pumping of spin waves
by acoustic waves, the possibility of which has long been theoretically
anticipated but never experimentally realized. Spin waves propagating in a thin
film of yttrium iron garnet (YIG), a magnetostrictive ferrimagnet with low spin
and acoustic wave damping, are pumped using an acoustic resonator driven at
frequencies near twice the spin wave frequency. The observation of a
counter-propagating idler wave and a distinct pump threshold that increases
quadratically with frequency non-degeneracy are evidence of a nonlinear
parametric pumping process consistent with classical theory. This demonstration
of acoustic parametric pumping lays the groundwork for developing new
spintronic and microwave signal processing devices based on amplification and
manipulation of spin waves by efficient, spatially localized acoustic
transducers.",1702.06038v1
1992-11-10,Spin-Wave Theory of the Spiral Phase of the t-J Model,"A graded H.P,realization of the SU(2|1) algebra is proposed.A spin-wave
theory with a condition that the sublattice magnetization is zero is
discussed.The long-range spiral phase is investigated.The spin-spin correlator
is calculated.",9211005v1
2013-11-12,Quantum theory of spin waves in finite chiral spin chains,"We calculate the effect of spin waves on the properties of finite size spin
chains with a chiral spin ground state observed on bi-atomic Fe chains
deposited on Iridium(001). The system is described with a Heisenberg model
supplemented with a Dzyaloshinskii-Moriya (DM) coupling and a uniaxial single
ion anisotropy that presents a chiral spin ground state. Spin waves are studied
using the Holstein-Primakoff (HP) boson representation of spin operators. Both
the renormalized ground state and the elementary excitations are found by means
of Bogoliubov transformation, as a function of the two variables that can be
controlled experimentally, the applied magnetic field and the chain length.
Three main results are found. First, because of the non-collinear nature of the
classical ground state, there is a significant zero point reduction of the
ground state magnetization of the spin spiral. Second, the two lowest energy
spin waves are edge modes in the spin spiral state that, above a critical field
the results into a collinear ferromagnetic ground state, become confined bulk
modes. Third, in the spin spiral state, the spin wave spectrum exhibits
oscillatory behavior as function of the chain length with the same period of
the spin helix.",1311.2695v1
2020-05-04,Spin-orbit-torque magnonics,"The field of magnonics, which utilizes propagating spin waves for nano-scale
transmission and processing of information, has been significantly advanced by
the advent of the spin-orbit torque. The latter phenomenon can allow one to
overcome two main drawbacks of magnonic devices - low energy efficiency of
conversion of electrical signals into spin wave signals, and fast spatial decay
of spin waves in thin-film waveguiding structures. At first glance, the
excitation and amplification of spin waves by spin-orbit torques can seem to be
straightforward. Recent research indicates, however, that the lack of the
mode-selectivity in the interaction of spin currents with dynamic magnetic
modes and the onset of dynamic nonlinear phenomena represent significant
obstacles. Here, we discuss the possible route to overcoming these limitations,
based on the suppression of nonlinear spin-wave interactions in magnetic
systems with perpendicular magnetic anisotropy. We show that this approach
enables efficient excitation of coherent magnetization dynamics and propagating
spin waves in extended spatial regions, and is expected to enable practical
implementation of complete compensation of spin-wave propagation losses.",2005.01391v1
1993-01-13,"Hierarchical wave function, Fock cyclic condition and spin-statistics relation in the spin-singlet fractional quantum Hall effect","We construct the hierarchical wave function of the spin-singlet fractional
quantum Hall effect, which turns out to satisfy Fock cyclic condition. The
spin-statistics relation of the quasi-particles in the spin-singlet fractional
quantum Hall effect is also discussed. Then we use particle-hole conjugation to
check the wave function.",9301015v1
2009-07-16,Reverse Doppler effect in backward spin waves scattered on acoustic waves,"We report on the observation of reverse Doppler effect in backward spin waves
reflected off of surface acoustic waves. The spin waves are excited in a
yttrium iron garnet (YIG) film. Simultaneously, acoustic waves are also
generated. The strain induced by the acoustic waves in the magnetostrictive YIG
film results in the periodic modulation of the magnetic anisotropy in the film.
Thus, in effect, a travelling Bragg grating for the spin waves is produced. The
backward spin waves reflecting off of this grating exhibit a reverse Doppler
shift: shifting down rather than up in frequency when reflecting off of an
approaching acoustic wave. Similarly, the spin waves are shifted up in
frequency when reflecting from receding acoustic waves.",0907.2902v1
2018-07-05,Bridging magnonics and spin-orbitronics,"The emerging field of nano-magnonics utilizes high-frequency waves of
magnetization - the spin waves - for the transmission and processing of
information on the nanoscale. The advent of spin-transfer torque has spurred
significant advances in nano-magnonics, by enabling highly efficient local
spin-wave generation in magnonic nanodevices. Furthermore, the recent emergence
of spin-orbitronics, which utilizes spin-orbit interaction as the source of
spin torque, has provided a unique ability to exert spin torque over spatially
extended areas of magnonic structures, enabling enhanced spin-wave
transmission. Here, we experimentally demonstrate that these advances can be
efficiently combined. We utilize the same spin-orbit torque mechanism for the
generation of propagating spin waves, and for the long-range enhancement of
their propagation, in a single integrated nano-magnonic device. The
demonstrated system exhibits a controllable directional asymmetry of spin wave
emission, which is highly beneficial for applications in non-reciprocal
magnonic logic and neuromorphic computing.",1807.02050v1
2009-05-13,Observation of spin-wave propagation in permalloy microstripes,"We report on the propagation of spin waves in permalloy microstripes. By
means of scanning Kerr microscopy combined with continuous microwave
excitation, we detect the time evolution of spin-wave interference patterns in
an external magnetic field. Assuming transverse spin-wave quantization we can
directly measure the amplitude, phase velocity and damping for the
corresponding transversal wave mode numbers m. We find that the spin-wave
interference pattern is dominated by m=0 and m=2 with phase velocities v_0=71
km/s and v_2=47 km/s, respectively.",0905.2172v1
2019-07-21,Superradiant parametric conversion of spin waves,"Atomic-ensemble spin waves carrying single-photon Fock states exhibit
nonclassical many-body correlations in-between atoms. The same correlations are
inherently associated with single-photon superradiance, forming the basis of a
plethora of quantum light-matter interfaces. We devise a scheme allowing the
preparation of spatially-structured superradiant states in the atomic
two-photon cascade using spin-wave light storage. We thus show that long-lived
atomic ground-state spin waves can be converted to photon pairs opening the way
towards nonlinear optics of spin waves via multi-wave mixing processes.",1907.09001v2
2005-09-15,Cubic magnets with Dzyaloshinskii-Moriya interaction at low T,"Ground state and spin-wave spectrum of cubic magnets with the
Dzyaloshinskii-Moriya interaction (DMI) such as MnSi and FeGe are studied
theoretically. The linear spin-wave theory is developed. The spin-wave spectrum
depends strongly on the magnetic field and strongly anisotropic. It is a result
of incommensurate magnetic structure when the DMI breaks the total spin
conservation law. The spin-wave spectrum is unstable at infinitesimal
perpendicular field. If the gap $\Delta$ is introduced the spectrum becomes
stable. The gap appears due to cubic anisotropy and the spin-wave interaction
considered in the Hartree-Fock approximation. Peculiar properties of the ESR
and neutron scattering in the helical magnets are considered and possibilities
of corresponding experimental studies are discussed.",0509406v1
2011-08-30,Spin Wave Diffraction and Perfect Imaging of a Grating,"We study the diffraction of Damon-Eshbach-type spin waves incident on a
one-dimensional grating realized by micro slits in a thin permalloy film. By
means of time-resolved scanning Kerr microscopy we observe unique diffraction
patterns behind the grating which exhibit replications of the spin-wave field
at the slits. We show that these spin-wave images, with details finer than the
wavelength of the incident Damon-Eshbach spin wavelength, arise from the
strongly anisotropic spin wave dispersion.",1108.5883v1
2014-08-15,Separated spin-up and spin-down evolution of degenerated electrons in two dimensional systems: Dispersion of longitudinal collective excitations in plane and nanotube geometry,"Applying the separated spin evolution quantum hydrodynamics to
two-dimensional electron gas in plane samples and nanotubes located in external
magnetic fields we find new kind of wave in electron gas, which is called the
spin-electron acoustic wave. Separate spin-up electrons and spin-down electrons
evolution reveals in replacement of the Langmuir wave by the couple of hybrid
waves. One of two hybrid waves is the modified Langmuir wave. Another hybrid
wave is the spin-electron acoustic wave. We study dispersion of these waves in
two dimensional structures of electrons. We also consider dependence of
dispersion properties on spin polarisation of electrons in external magnetic
field.",1408.3662v1
2017-12-04,Phase-resolved Spin-Wave Tomography,"The propagation dynamics of spin waves are represented by their dispersion
relations. Recently, we have developed a method, called spin-wave tomography
(SWaT), to obtain dispersion relation of spin waves in the long wavelength
regime, so-called pure magnetostatic waves. In our previous studies on SWaT,
phase information of spin waves was disregarded. In this report, we demonstrate
an advanced SWaT analysis, called phase-resolved spin-wave tomography (PSWaT),
to realize the direct observation of the amplitude and the phase of spin waves.
The PSWaT spectra are obtained by separating the real and the imaginary
components of the complex Fourier transform in the SWaT analysis. We
demonstrate the PSWaT spectra of spin waves excited by the photo-induced
demagnetization in a Bi-doped garnet film, reflecting the characteristic
features of the complex dynamical susceptibility affected by magnetostatic
coupling in the film.",1712.00927v2
2017-12-04,"Faster, farther, stronger: spin transfer torque driven high order propagating spin waves in nano-contact magnetic tunnel junctions","Short wave-length exchange-dominated propagating spin waves will enable
magnonic devices to operate at higher frequencies and higher data transmission
rates.1 While GMR based magnetic nano-contacts are highly efficient injectors
of propagating spin waves2,3, the generated wave lengths are 2.6 times the
nano-contact diameter4, and the electrical signal strength remains much too
weak for practical applications. Here we demonstrate nano-contact based spin
wave generation in magnetic tunnel junction stacks, and observe large discrete
frequency steps consistent with the hitherto ignored possibility of second and
third order propagating spin waves with wave lengths of 120 and 74 nm, i.e.
much smaller than the 150 nm nano-contact. These higher-order propagating spin
waves will not only enable magnonic devices to operate at much higher
frequencies, but also greatly increase their transmission rates and spin wave
propagating lengths, both proportional to the much higher group velocity.",1712.00954v2
2018-01-17,Exploring Hidden Acoustic Spin Underwater,"Investigating wave propagation in fluid enables a variety of important
applications in underwater communications, object detections and unmanned robot
control. Conventionally, momentum and spin reveal fundamental physical
properties about propagating waves. Yet, vast previous research focused on the
orbital angular momentum of acoustics without thinking about the existence
possibility of spin due to the longitudinal wave nature. Here, we show that
underwater acoustic wave processes the non-trivial spin angular momentum
intrinsically, which is associated with its special spin-orbital coupling
relation for longitudinal waves. Furthermore, we demonstrate that this
intrinsic spin, although unobservable in plane wave form, can be detected by
four approaches: wave interference, Gaussian exponential decay form, boundary
evanescent wave, and waveguide mode. We further show that the strong
spin-orbital coupling can be exploited to achieve unidirectional excitation and
backscattering immune transport. We hope the present results can improve the
geometric and topological understanding about underwater acoustic wave and pave
the way on the spin-related underwater applications.",1801.05790v2
2007-04-23,Feasibility Study of Logic Circuits with Spin Wave Bus,"We present a feasibility study of logic circuits utilizing spin waves for
information transmission and processing. As an alternative approach to the
transistor-based architecture, logic circuits with spin wave bus do not use
charge as an information carrier. In this work we describe the general concept
of logic circuits with spin wave bus and illustrate its performance by
numerical simulations based on available experimental data. Theoretical
estimates and results of numerical simulations on signal attenuation, signal
phase velocity, and the minimum spin wave energy required per bit in the spin
bus are obtained. The transport parameters are compared with ones for
conventional electronic transmission lines. Spin Wave Bus is not intended to
substitute traditional metal interconnects since it has higher signal
attenuation and lower signal propagation speed. The potential value of spin
wave bus is, however, an interface between electronic circuits and integrated
spintronics circuits. The logic circuits with spin wave bus allow us to provide
wireless read-in and read-out.",0704.2862v1
2015-06-02,Effects of frustration and cyclic exchange on the spin-1/2 Heisenberg antiferromagnet within the self-consistent spin-wave theory,"The relevance of the quasi-two-dimensional spin-1/2 frustrated quantum
antiferromagnet due to its possibility of modelling the high-temperature
superconducting parent compounds has resulted in numerous theoretical and
experimental studies. This paper presents a detailed research of the influence
of the varying exchange interactions on the model magnetic properties within
the framework of self-consistent spin-wave theory based on Dyson-Maleev
representation. Beside the nearest neighbour interaction within the plane, the
planar frustration up to the third nearest neighbours, cyclic interaction and
the interlayer coupling are taken into account. The detailed description of the
elementary spin excitations, staggered magnetization, spin-wave velocity
renormalization factor and ground-state energy is given. The results are
compared to the predictions of the linear spin-wave theory and when possible
also to the second-order perturbative spin-wave expansion results. Finally,
having at our disposal improved experimental results for the in-plane spin-wave
dispersion in high-$T_c$ copper oxide $\mbox{La}_2\mbox{CuO}_4$, the
self-consistent spin-wave theory is applied to that compound in order to
correct earlier obtained set of exchange parameters and high temperature
spin-wave dispersion.",1506.00773v1
2019-06-20,Purely magnetic logic based on polarized spin waves,"Spin wave, the precession of magnetic order in magnetic materials, is a
collective excitation that carries spin angular momentum. Similar to the
acoustic or optical waves, the spin wave also possesses the polarization degree
of freedom. Although such polarization degrees of freedom are frozen in
ferromagnets, they are fully unlocked in antiferromagnets or ferrimagnets. Here
we introduce the concept of magnetic gating and demonstrate a spin wave analog
of the Datta-Das spin transistor in antiferromagnet. Utilizing the interplay
between polarized spin wave and the antiferromagnetic domain walls, we propose
a universal logic gate of pure magnetic nature, which realizes all Boolean
operations in one single magnetic structure. We further construct a full
functional 4-bit Arithmetic Logic Unit using only sixteen spin wave universal
logic gates, operating in a weaving fashion as a Jacquard loom machine. The
spin wave-based architecture proposed here also sets a model for the future
energy efficient non-volatile computing, the distributed processing-in-memory
computing, and the evolvable neuromorphic computing.",1906.08702v1
2023-02-21,Amplification and frequency conversion of spin waves using acoustic waves,"We numerically study the acoustic parametric amplification of spin waves
using surface acoustic waves (SAW) in a magnetic thin film. First, we
illustrate how the process of parametric spin-wave generation using short-waved
SAWs with a fixed frequency allows to tune frequencies of the generated spin
waves by the applied magnetic field. We further present the amplification of
microwave driven spin waves using this method. The decay length and the
amplitude of the driven spin waves can be amplified up to approximately 2.5 and
10 times compared to the reference signal, respectively. More importantly, the
proposed design can be used as a frequency converter, in which a low (high)
frequency spin-wave mode stimulates the excitation of a high (low) frequency
mode. Our results pave the way in designing highly flexible and efficient
hybrid magnonic device architectures for microwave data transport and
processing.",2302.10614v1
2021-09-10,Electrical spectroscopy of the spin-wave dispersion and bistability in gallium-doped yttrium iron garnet,"Yttrium iron garnet (YIG) is a magnetic insulator with record-low damping,
allowing spin-wave transport over macroscopic distances. Doping YIG with
gallium ions greatly reduces the demagnetizing field and introduces a
perpendicular magnetic anisotropy, which leads to an isotropic spin-wave
dispersion that facilitates spin-wave optics and spin-wave steering. Here, we
characterize the dispersion of a gallium-doped YIG (Ga:YIG) thin film using
electrical spectroscopy. We determine the magnetic anisotropy parameters from
the ferromagnetic resonance frequency and use propagating spin wave
spectroscopy in the Damon-Eshbach configuration to detect the small spin-wave
magnetic fields of this ultrathin weak magnet over a wide range of wavevectors,
enabling the extraction of the exchange constant $\alpha=1.3(2)\times10^{-12}$
J/m. The frequencies of the spin waves shift with increasing drive power, which
eventually leads to the foldover of the spin-wave modes. Our results shed light
on isotropic spin-wave transport in Ga:YIG and highlight the potential of
electrical spectroscopy to map out the dispersion and bistability of
propagating spin waves in magnets with a low saturation magnetization.",2109.05045v1
2017-08-19,Current induced multi-mode propagating spin waves in a spin transfer torque nano-contact with strong perpendicular magnetic anisotropy,"Current induced spin wave excitations in spin transfer torque nano-contacts
are known as a promising way to generate exchange-dominated spin waves at the
nano-scale. It has been shown that when these systems are magnetized in the
film plane, broken spatial symmetry of the field around the nano-contact
induced by the Oersted field opens the possibility for spin wave mode
co-existence including a non-linear self-localized spin-wave bullet and a
propagating mode. By means of micromagnetic simulations, here we show that in
systems with strong perpendicular magnetic anisotropy (PMA) in the free layer,
two propagating spin wave modes with different frequency and spatial
distribution can be excited simultaneously. Our results indicate that in-plane
magnetized spin transfer nano-contacts in PMA materials do not host a solitonic
self-localized spin-wave bullet, which is different from previous studies for
systems with in plane magnetic anisotropy. This feature renders them
interesting for nano-scale magnonic waveguides and crystals since magnon
transport can be configured by tuning the applied current.",1708.05886v1
2018-07-19,Spin-wave amplification and lasing driven by inhomogeneous spin transfer torques,"We show that an inhomogeneity in the spin-transfer torques in a metallic
ferromagnet under suitable conditions strongly amplifies incoming spin waves.
Moreover, at nonzero temperatures the incoming thermally occupied spin waves
will be amplified such that the region with inhomogeneous spin transfer torques
emits spin waves spontaneously, thus constituting a spin-wave laser. We
determine the spin-wave scattering amplitudes for a simplified model and
set-up, and show under which conditions the amplification and lasing occurs.
Our results are interpreted in terms of a so-called black-hole laser, and could
facilitate the field of magnonics, that aims to utilize spin waves in logic and
data-processing devices.",1807.07312v1
2023-05-08,On the Origin of Acoustic Spin and Elastic Spin: Uncovering Hidden Wave Spin of Scalar Fields with Higher-Order Derivative Lagrangian,"Scalar field should have no spin angular momentum according to conventional
understandings in classical field theory. Yet, recent studies demonstrate the
undoubted existence of wave spin endowed by acoustic and elastic longitudinal
waves, which are of irrotational curl-free nature without vorticity and can be
described by scalar fields. Here, to solve this seeming discrepancy, we uncover
the origin of wave spin in scalar fields beyond traditional formalism by
clarifying that the presence of higher order derivatives in scalar field
Lagrangians can give rise to non-vanishing spin. For scalar fields with only
first order derivative, we can make the hidden wave spin emerge, by
constructing a latent field that leads to the original field through a time
derivative so that is of second order. We exemplify the wave spin for elastic
and acoustic fields, as well as for dissipative media, following Noether's
theorem in higher-order derivative Lagrangian. The results would prompt people
to build more comprehensive and fundamental understandings of structural wave
spin in classical fields.",2305.04939v1
2024-03-10,Spin Waves and Spin Currents in Magnon-Phonon Composite Resonator Induced by Acoustic Waves of Various Polarizations,"In this work, we present the results of a systematic experimental study of
linear and parametric spin wave resonant excitation accompanied by spin
currents (spin pumping) in a multifrequency composite bulk acoustic wave
resonator with a ZnO-YIG-GGG-YIG/Pt structure. The features of magnetic
dynamics excitation in YIG films due to magnetoelastic coupling with acoustic
thickness modes of various polarizations are studied. Acoustic spin waves and
spin pumping are detected by simultaneous frequency-field mapping of the
inverse spin Hall effect voltage and the resonant frequencies of thickness
extensional modes. In the parametric range of frequencies and fields, acoustic
spin pumping induced by both shear and longitudinal polarization modes was
observed. Linear acoustic spin waves are excited only by shear thickness
extensional modes because longitudinal acoustic waves do not couple with the
magnetic subsystem in linear regime.",2403.06274v1
2000-04-18,Modified spin-wave description of the nuclear spin relaxation in ferrimagnetic Heisenberg chains,"We make a modified spin-wave description of the nuclear spin relaxation in
Heisenberg alternating-spin chains with antiferromagnetic exchange coupling. In
contrast with the conventional one-dimensional antiferromagnetic spin-wave
theory, which is plagued with the divergence of the sublattice magnetization
even in the ground state, the present spin-wave description is highly
successful over a wide temperature range. The temperature dependence of the
relaxation rate $T_1^{-1}$ significantly varies with the crystalline structure,
exhibiting both ferromagnetic and antiferromagnetic aspects. $T_1^{-1}$ further
shows a unique dependence on the applied field, which turns out an indirect
observation of the quadratic dispersion relations.",0004297v1
2002-08-30,Spin Waves in Random Spin Chains,"We study quantum spin-1/2 Heisenberg ferromagnetic chains with dilute, random
antiferromagnetic impurity bonds with modified spin-wave theory. By describing
thermal excitations in the language of spin waves, we successfully observe a
low-temperature Curie susceptibility due to formation of large spin clusters
first predicted by the real-space renormalization-group approach, as well as a
crossover to a pure ferromagnetic spin chain behavior at intermediate and high
temperatures. We compare our results of the modified spin-wave theory to
quantum Monte Carlo simulations.",0208607v1
2018-03-21,180-degree phase shift of magnetoelastic waves observed by phase-resolved spin-wave tomography,"We have investigated optically-excited magnetoelastic waves by phase-resolved
spin-wave tomography (PSWaT). PSWaT reconstructs dispersion relation of spin
waves together with their phase information by using time-resolved
magneto-optical imaging for spin-wave propagation followed by an analysis based
on the convolution theorem and a complex Fourier transform. In PSWaT spectra
for a Bi-doped garnet film, we found a 180 degree phase shift of magnetoelastic
waves at around the crossing of the dispersion relations of spin and elastic
waves. The result is explained by a coupling between spin waves and elastic
waves through magnetoelastic interaction. We also propose an efficient way for
phase manipulation of magnetoelastic waves by rotating the orientation of
magnetization less than 10 degree.",1803.07697v1
2021-12-31,Spin-injection-generated shock waves and solitons in a ferromagnetic thin film: the spin piston problem,"The unsteady, nonlinear magnetization dynamics induced by spin injection in
an easy-plane ferromagnetic channel subject to an external magnetic field are
studied analytically. Leveraging a dispersive hydrodynamic description, the
Landau-Lifshitz equation is recast in terms of hydrodynamic-like variables for
the magnetization's perpendicular component (spin density) and azimuthal phase
gradient (fluid velocity). Spin injection acts as a moving piston that
generates nonlinear, dynamical spin textures in the ferromagnetic channel with
downstream quiescent spin density set by the external field. In contrast to the
classical problem of a piston accelerating a compressible gas, here, variable
spin injection and field lead to a rich variety of nonlinear wave phenomena
from oscillatory spin shocks to solitons and rarefaction waves. A full
classification of solutions is provided using nonlinear wave modulation theory
by identifying two key aspects of the fluid-like dynamics: subsonic/supersonic
conditions and convex/nonconvex hydrodynamic flux. Familiar waveforms from the
classical piston problem such as rarefaction (expansion) waves and shocks
manifest in their spin-based counterparts as smooth and highly oscillatory
transitions, respectively. The spin shock is an example of a dispersive shock
wave, which arises in many physical systems. New features without a gas
dynamics counterpart include composite wave complexes with ""contact"" spin
shocks and rarefactions. Magnetic supersonic conditions lead to two pronounced
piston edge behaviors including a stationary soliton and an oscillatory
wavetrain. These coherent wave structures have physical implications for the
generation of high frequency spin waves from pulsed injection and persistent,
stable stationary and/or propagating solitons in the presence of magnetic
damping. The analytical results are favorably compared with numerical
simulations.",2112.15301v2
2019-09-11,Determining key spin-orbitronic parameters by means of propagating spin waves,"We characterize spin wave propagation and its modification by an electrical
current in Permalloy(Py)/Pt bilayers with Py thickness between 4 and 20 nm.
First, we analyze the frequency non-reciprocity of surface spin waves and
extract from it the interfacial Dzyaloshinskii-Moriya interaction constant
$D_s$ accounting for an additional contribution due to asymmetric surface
anisotropies. Second, we measure the spin-wave relaxation rate and deduce from
it the Py/Pt spin mixing conductance $g^{\uparrow\downarrow}_{eff}$. Last,
applying a \textit{dc} electrical current, we extract the spin Hall
conductivity $\sigma_{SH}$ from the change of spin wave relaxation rate due to
the spin-Hall spin transfer torque. We obtain a consistent picture of the spin
wave propagation data for different film thicknesses using a single set of
parameters $D_s=0.25$ pJ/m, $g^{\uparrow\downarrow}_{eff} = 3.2\times 10^{19}$
m$^{-2}$ and $\sigma_{SH}=4\times10^{5}$ S/m.",1909.04935v1
2020-05-14,"Modelling spin waves in noncollinear antiferromagnets: spin-flop states, spin spirals, skyrmions and antiskyrmions","Spin waves in antiferromagnetic materials have great potential for
next-generation magnonic technologies. However, their properties and their
dependence on the type of ground-state antiferromagnetic structure are still
open questions. Here, we investigate theoretically spin waves in one- and
two-dimensional model systems with a focus on noncollinear antiferromagnetic
textures such as spin spirals and skyrmions of opposite topological charges. We
address in particular the nonreciprocal spin excitations recently measured in
bulk antiferromagnet $\alpha$--$\text{Cu}_2\text{V}_2\text{O}_7$ utilizing
inelastic neutron scattering experiments [Phys.\ Rev.\ Lett.\ \textbf{119},
047201 (2017)], where we help to characterize the nature of the detected
spin-wave modes. Furthermore, we discuss how the Dzyaloshinskii-Moriya
interaction can lift the degeneracy of the spin-wave modes in antiferromagnets,
resembling the electronic Rashba splitting. We consider the spin-wave
excitations in antiferromagnetic spin-spiral and skyrmion systems and discuss
the features of their inelastic scattering spectra. We demonstrate that
antiskyrmions can be obtained with an isotropic Dzyaloshinskii-Moriya
interaction in certain antiferromagnets.",2005.07250v1
2022-03-19,Spin wave excitation and directional propagation in presence of magnetic charges in square artificial spin ice,"Artificial spin ice is a special class of engineered lattice of highly shape
anisotropic single domain magnetic nanostructures which is used as one of the
model systems to study the spin ice behavior observed in pyrochlore oxides. The
nanomagnets interact via dipolar interaction which results in correlated
magnetization dynamics exhibiting macroscopic spin configuration states. Here,
we exploit the interplay of underlying magnetic state and external bias field
orientation to study controlled spin wave propagation in square Artificial Spin
Ice (sASI) by performing detailed micromagnetic simulations. We report that
careful selection of vertices with local magnetic charges can effectively
direct the anisotropic spin wave in presence of an external field. Further, we
explore the influence of local charges due to the excited state in
even-coordinated vertices as well as uncompensated charges due to
odd-coordinated vertices on spin wave behavior. Our studies suggest that there
is no perceptible difference on spin wave dynamical behavior due to the origin
of local magnetic charge in sASI. Our results of controlled and directional
spin wave propagation in sASI system may be useful for low-power consumption
based all magnonic on-chip devices.",2203.10345v1
2023-07-18,"Propagation of Coupled Acoustic, Electromagnetic and Spin Waves in Saturated Ferromagnetoelastic Solids","We study the propagation of plane waves in an unbounded body of a saturated
ferromagnetoelastic solid. The equations by Tiersten for small fields
superposed on finite initial fields in a saturated ferromagnetoelastic material
are employed, with their quasistatic magnetic field extended to dynamic
electric and magnetic fields for electromagnetic waves. Dispersion relations of
the plane waves are obtained. The cutoff frequencies and long wave
approximation of the dispersion curves are determined. Results show that
acoustic, electromagnetic and magnetic spin waves are coupled in such a
material. For YIG which is a cubic crystal without piezoelectric coupling, the
acoustic and electromagnetic waves are not directly coupled but they can still
interact indirectly through spin waves.",2307.09171v1
2016-07-20,Effect of isoscalar spin-triplet pairings on spin-isospin responses in $sd-$ shell nuclei,"The spin magnetic dipole transitions and the neutron-proton spin-spin
correlations in $sd-$shell even-even nuclei with $N=Z$ are investigated using
shell model wave functions. The isoscalar spin-triplet pairing correlation
provides a substantial quenching effect on the spin magnetic dipole
transitions, especially the isovector (IV) ones. Consequently, an enhanced
isoscalar spin-triplet pairing interaction influences the proton-neutron
spin-spin correlation deduced from the difference between the isoscalar (IS)
and the IV sum rule strengths. The effect of the $\Delta$ ($\Delta_{33}$
resonance)-hole coupling is examined in the IV spin transition and the
spin-spin correlations of the ground states.",1607.05881v2
2009-09-17,Edge spin accumulation: spin Hall effect without bulk spin current,"Spin accumulation in a 2D electron gas with Rashba spin-orbit interaction
subject to an electric field can take place without bulk spin currents (edge
spin Hall effect). This is demonstrated for the collisional regime using the
non-equilibrium distribution function determined from the standard Boltzmann
equation. Spin accumulation originates from interference of incident and
reflected electron waves at the sample boundary.",0909.3156v1
2018-11-03,Tunable Spin Seebeck Diode with Magnonic Spin Tunneling Junction,"We theoretically investigate the spin--wave spin current induced by the spin
Seebeck effect in magnonic spin tunneling junctions (MSTJs) for arbitrary
magnetization directions. We show that the MSTJ functions as a \textit{tunable}
spin Seebeck diode in which the tunneling spin current can be turned on and off
with high efficiency by controlling the magnetization direction.",1811.01141v1
2017-11-19,SU($N$) spin-wave theory: Application to spin-orbital Mott insulators,"We present the application of the SU($N$) ($N>2$) spin-wave theory to
spin-orbital Mott insulators whose ground states exhibit magnetic orders. When
taking both the spin and orbital degrees of freedom into account rather than
projecting onto the Kramers doublet, the lowest spin-orbital locking energy
levels, due to the inevitable spin-orbital multipole exchange interactions, the
SU($N$) spin-wave theory should take the place of the SU($2$) one. To implement
the application, we introduce an efficient general local mean field approach
which involves all the local fluctuations into the SU($N$) linear spin-wave
theory. Our approach is tested firstly by calculating the multipolar spin-wave
spectra of the SU($4$) antiferromagnetic model. Then we apply it to
spin-orbital Mott insulators. It is revealed that the Hund's coupling would
influence the effectiveness of the isospin-$1/2$ representation when the spin
orbital coupling is not large enough. Besides, we also calculate the spin-wave
spectra based on the first principle calculations for two concrete materials,
$\alpha$-RuCl$_3$ and Sr$_2$IrO$_4$. The SU($N$) spin-wave theory appropriately
depicts the low-energy magnons and the spin-orbital excitations qualitatively.",1711.07041v1
2021-03-10,Probing optical spin-currents using THz spin-waves in noncollinear magnetic bilayers,"Optically induced spin currents have proven to be useful in spintronics
applications, allowing for sub-ps all-optical control of magnetization.
However, the mechanism responsible for their generation is still heavily
debated. Here we use the excitation of spin-current induced THz spin-waves in
noncollinear bilayer structures to directly study optical spin-currents in the
time domain. We measure a significant laser-fluence dependence of the spin-wave
phase, which can quantitatively be explained assuming the spin current is
proportional to the time derivative of the magnetization. Measurements of the
absolute spin-wave phase, supported by theoretical calculations and
micromagnetic simulations, suggest that a simple ballistic transport picture is
sufficient to properly explain spin transport in our experiments and that the
damping-like optical STT dominates THz spin-wave generation. Our findings
suggest laser-induced demagnetization and spin-current generation share the
same microscopic origin.",2103.06029v1
2010-01-26,Spin-wave instabilities in spin-transfer-driven magnetization dynamics,"We study the stability of magnetization precessions induced in spin-transfer
devices by the injection of spin-polarized electric currents. Instability
conditions are derived by introducing a generalized, far-from-equilibrium
interpretation of spin-waves. It is shown that instabilities are generated by
distinct groups of magnetostatically coupled spin-waves. Stability diagrams are
constructed as a function of external magnetic field and injected
spin-polarized current. These diagrams show that applying larger fields and
currents has a stabilizing effect on magnetization precessions. Analytical
results are compared with numerical simulations of spin-transfer-driven
magnetization dynamics.",1001.4806v1
2021-06-18,Inelastic spin-wave beam scattering by edge-localized spin waves in ferromagnetic thin film,"Spin waves are promising chargeless information carriers for the future,
energetically efficient beyond-CMOS systems. Among many advantages there are
the ease of achieving nonlinearity, the variety of possible interactions, and
excitation types. Although the rapidly developing magnonic research has already
yielded impressive realizations, multi-mode nonlinear effects, particularly
with the propagating waves and their nanoscale realizations, are still an open
research problem. We study theoretically the dynamic interactions of the spin
waves confined to the edge of a thin ferromagnetic film with the spin-wave beam
incident at this edge. We found the inelastically scattered spin-wave beams at
frequencies increased and decreased by the frequency of the edge spin-wave
relative to the specularly reflected beam. We observed a strong dependence of
the angular shift of the inelastic scattered spin-wave beam on the edge-mode
frequency, which allowed us to propose a magnonic demultiplexing of the signal
encoded in spin waves propagating along the edge. Since dynamic magnetostatic
interactions, which are ubiquitous in the spin-wave dynamics, are decisive in
this process, this indicates the possibility of implementing the presented
effects, also in other configurations and their use in magnonic systems.",2106.09954v3
2021-07-20,Spin-wave dispersion measurement by variable-gap propagating spin-wave spectroscopy,"Magnonics is seen nowadays as a candidate technology for energy-efficient
data processing in classical and quantum systems. Pronounced nonlinearity,
anisotropy of dispersion relations and phase degree of freedom of spin waves
require advanced methodology for probing spin waves at room as well as at mK
temperatures. Yet, the use of the established optical techniques like Brillouin
light scattering (BLS) or magneto optical Kerr effect (MOKE) at ultra-low
temperatures is forbiddingly complicated. By contrast, microwave spectroscopy
can be used at all temperatures but is usually lacking spatial and wavenumber
resolution. Here, we develop a variable-gap propagating spin-wave spectroscopy
(VG-PSWS) method for the deduction of the dispersion relation of spin waves in
wide frequency and wavenumber range. The method is based on the phase-resolved
analysis of the spin-wave transmission between two antennas with variable
spacing, in conjunction with theoretical data treatment. We validate the method
for the in-plane magnetized CoFeB and YIG thin films in $k\perp B$ and
$k\parallel B$ geometries by deducing the full set of material and spin-wave
parameters, including spin-wave dispersion, hybridization of the fundamental
mode with the higher-order perpendicular standing spin-wave modes and surface
spin pinning. The compatibility of microwaves with low temperatures makes this
approach attractive for cryogenic magnonics at the nanoscale.",2107.09363v1
2023-01-16,Antiferromagnetic magnon spintronic based on non-reciprocal and non-degenerated ultra-fast spin-waves in the canted antiferromagnet α-Fe2O3,"Spin-waves in antiferromagnets hold the prospects for the development of
faster, less power-hungry electronics, as well as promising physics based on
spin-superfluids and coherent magnon-condensates. For both these perspectives,
addressing electrically coherent antiferromagnetic spin-waves is of importance,
a prerequisite that has so far been elusive, because unlike
ferromagnets,antiferromagnets couple weakly to radiofrequency fields. Here, we
demonstrate the detection of ultra-fast non-reciprocal spin-waves in the
dipolar-exchange regime of a canted antiferromagnet using both inductive and
spintronic transducers. Using time-of-flight spin-wave spectroscopy on hematite
({\alpha}-Fe2O3), we find that the magnon wave packets can propagate as fast as
20 km/s for reciprocal bulk spin-wave modes and up to 6 km/s for surface-spin
waves propagating parallel to the antiferromagnetic Neel vector. We finally
achieve efficient electrical detection of non-reciprocal spin-wave transport
using non-local inverse spin-Hall effects. The electrical detection of coherent
non-reciprocal antiferromagnetic spin waves paves the way for the development
of antiferromagnetic and altermagnet-based magnonic devices.",2301.06329v2
2011-01-03,The building blocks of magnonics,"Novel material properties can be realized by designing waves' dispersion
relations in artificial crystals. The crystal's structural length scales may
range from nano- (light) up to centimeters (sound waves). Because of their
emergent properties these materials are called metamaterials. Different to
photonics, where the dielectric constant dominantly determines the index of
refraction, in a ferromagnet the spin-wave index of refraction can be
dramatically changed already by the magnetization direction. This allows a
different flexibility in realizing dynamic wave guides or spin-wave switches.
The present review will give an introduction into the novel functionalities of
spin-wave devices, concepts for spin-wave based computing and magnonic
crystals. The parameters of the magnetic metamaterials are adjusted to the
spin-wave k-vector such that the magnonic band structure is designed. However,
already the elementary building block of an antidot lattice, the singular hole,
owns a strongly varying internal potential determined by its magnetic dipole
field and a localization of spin-wave modes. Photo-magnonics reveal a way to
investigate the control over the interplay between localization and
delocalization of the spin-wave modes using femtosecond lasers, which is a
major focus of this review. We will discuss the crucial parameters to realize
free Bloch states and how, by contrast, a controlled localization might allow
to gradually turn on and manipulate spin-wave interactions in spin-wave based
devices in the future.",1101.0479v2
2008-10-30,Magnetoelectric Spin Wave Amplifier for Spin Wave Logic Circuits,"We propose and analyze a spin wave amplifier aimed to enhance the amplitude
of the propagating spin wave via the magnetoelectric effect. The amplifier is a
two-layer multiferroic structure, which comprises piezoelectric and
ferromagnetic materials. By applying electric field to the piezoelectric layer,
the stress is produced. In turn, the stress changes the direction of the easy
axis in the ferromagnetic layer and the direction of the anisotropy field. The
rotation frequency of the easy axis is the same as the frequency of the spin
wave propagating through the ferromagnetic layer. As a result of this two-stage
process, the amplitude of the spin wave can be amplified depending on the angle
of the easy axis rotation. We present results of numerical simulations
illustrating the operation of the proposed amplifier. According to numerical
estimates, the amplitude of the spin wave signal can be increased by several
orders of magnitude. The energy efficiency of the electric-to-magnetic power
conversion is discussed. The proposed amplifier preserves the phase of the
initial signal, which is important for application to logic circuits based on
spin waves.",0810.5586v1
2013-11-08,Spin wave nonreciprocity for logic device applications,"The utilization of spin waves as eigenmodes of the magnetization dynamics for
information processing and communication has been widely explored recently due
to its high operational speed with low power consumption and possible
applications for quantum computations. Previous proposals of spin wave
Mach-Zehnder devices were based on the spin wave phase, a delicate entity which
can be easily disrupted. Here, we propose a complete logic system based on the
spin wave amplitude utilizing the nonreciprocal spin wave behavior excited by
microstrip antennas. The experimental data reveal that the nonreciprocity of
magnetostatic surface spin wave can be tuned by the bias magnetic field.
Furthermore, engineering of the device structure could result in a high
nonreciprocity factor for spin wave logic applications.",1311.1881v1
2017-05-09,Unidirectional control of optically induced spin waves,"Unidirectional control of optically induced spin waves in a rare-earth iron
garnet crystal is demonstrated. We observed the interference of two spin-wave
packets with different initial phases generated by circularly polarized light
pulses. This interference results in unidirectional propagation if the
spin-wave sources are spaced apart at 1/4 of the wavelength of the spin waves
and the initial phase difference is set to pi/2. The propagating direction of
the spin wave is switched by the polarization helicity of the light pulses.
Moreover, in a numerical simulation, applying more than two spin-wave sources
with a suitable polarization and spot shape, arbitrary manipulation of the spin
wave by the phased array method was replicated.",1705.03349v1
2021-09-21,Chiral Surface Wave propagation with Anomalous Spin-momentum Locking,"The ability to control the directionality of surface waves by manipulating
its polarization has been of great significance for applications in spintronics
and polarization-based optics. Surface waves with evanescent tails are found to
possess an inherent in-plane transverse spin which is dependent on the
propagation direction while an out-of-plane transverse spin does not naturally
occur for surface waves and requires a specific surface design. Here, we
introduce a new type of surface waves called chiral surface wave which has two
transverse spins, an in-plane one that is inherent to any surface wave and an
out-of-plane spin which is enforced by the design due to strong x-to-y coupling
and broken rotational symmetry. The two transverse spins are locked to the
momentum. Our study opens a new direction for metasurface designs with enhanced
and controlled spin-orbit interaction by adding an extra degree of freedom to
control the propagation direction as well as the transverse spin of surface
waves.",2109.10314v1
2023-09-29,Evanescent Electron Wave Spin,"Our study shows that an evanescent electron wave exists outside both finite
and infinite quantum wells, by solving exact solutions of the Dirac equation in
a cylindrical quantum well and maintaining wavefunction continuity at the
boundary. Furthermore, we demonstrate that the evanescent wave spins
concurrently with the wave inside the quantum well, by deriving analytical
expressions of the current density in the whole region. Our findings suggest
that it is possible to probe or eavesdrop on quantum spin information through
the evanescent wave spin without destroying the entire spin state. The wave
spin picture interprets spin as a global and deterministic property of the
electron wave that includes both the evanescent and confined wavefunctions.
This suggests that a quantum process or device based on the manipulation and
probing of the electron wave spin is deterministic in nature rather than
probabilistic.",2309.17325v3
2023-10-20,Optical spin waves,"Chirality is inherent to a broad range of systems, including in solid-state
and wave physics. The precession (chiral motion) of electron spins in magnetic
materials, forming spin waves, has various properties and many applications in
magnetism and spintronics. We show that an optical analog of spin waves can be
generated in arrays of plasmonic nanohelices. Such optical waves arise from the
interaction between chiral helix eigenmodes carrying spin angular momentum. We
demonstrate that these optical spin waves are reflected at the interface
between successive domains of enantiomeric nanohelices, forming a heterochiral
lattice, regardless of the wave propagation direction within the lattice.
Optical spin waves may be applied in techniques involving photon spin, ranging
from data processing and storage to quantum optics.",2310.13600v2
2024-03-22,Interference patterns of propagating spin wave in spin Hall oscillator arrays,"In this study, we discuss the observation of spin wave interference generated
by magnetic oscillators. We employ micromagnetic simulations for two coherent
spin Hall nanowire oscillators positioned nearby, horizontally or vertically.
The two nanowires produce circular waves with short wavelengths on the order of
100 nm, which interfere with each other. In the horizontal configuration, the
spin waves exhibit constructive and destructive fringes, indicating
amplification or cancellation of the amplitudes, respectively. The
synchronization of spin waves in the current geometry of the two nanowires is
facilitated by the combination of dipolar field and propagating spin waves.
Additionally, the vertical alignment results in standing spin waves
characterized by multiple antinodes and nodes. These observations are
interpreted using a wave model that incorporates the superposition principle
for each case.",2403.15060v1
2021-07-21,Brillouin Light Scattering from Quantized Spin Waves in Nanowires with Antisymmetric Exchange Interactions,"Antisymmetric exchange interactions lead to non-reciprocal spin-wave
propagation. As a result, spin waves confined in a nanostructure are not
standing waves; they have a time-dependent phase, because counter-propagating
waves of the same frequency have different wavelengths. We report on a
Brillouin light scattering (BLS) study of confined spin waves in Co/Pt
nanowires with strong Dzyaloshinskii-Moriya interactions (DMI). Spin-wave
quantization in narrow ($\lesssim 200$ nm width) wires dramatically reduces the
frequency shift between BLS Stokes and anti-Stokes lines associated with the
scattering of light incident transverse to the nanowires. In contrast, the BLS
frequency shift associated with the scattering of spin waves propagating along
the nanowire length is independent of nanowire width. A model that considers
the chiral nature of modes captures this physics and predicts a dramatic
reduction in frequency shift of light scattered from higher energy spin waves
in narrow wires, which is confirmed by our experiments.",2107.10303v2
2023-08-02,Spin wave amplification through superradiance,"Superradiance is a phenomenon of multiple facets that occurs in classical and
quantum physics under extreme conditions. Here we present its manifestation in
spin waves under an easily realized condition. We show that an interface
between a current-free (normal) ferromagnetic (FM) region and a current-flow
(pumped) FM region can be a spin wave super-mirror whose reflection coefficient
is larger than 1. The super-reflection is the consequence of current-induced
spectrum inversion where phase and group velocities of spin waves are in the
opposite directions. An incident spin wave activates a backward propagating
refractive wave inside pumped FM region. The refractive spin wave re-enters the
normal FM region to constructively interfere with the reflective wave. It
appears that the pumped FM region coherently emits reflective waves, leading to
a super-reflection. The process resembles superradiance of a spinning black
hole through the Hawking radiation process, or Dicke superradiance of cavity
photons inside population inverted media.",2308.00962v1
2015-12-30,Magnetization dynamics and spin pumping induced by standing elastic waves,"The magnetization dynamics induced by standing elastic waves excited in a
thin ferromagnetic film is described with the aid of micromagnetic simulations
taking into account the magnetoelastic coupling between spins and lattice
strains. The simulations have been performed for the 2 nm thick Fe81Ga19 film
dynamically strained by longitudinal and transverse standing waves with various
frequencies, which span a wide range around the resonance frequency nu_res of
coherent magnetization precession in unstrained Fe81Ga19 film. It is found that
standing elastic waves give rise to complex local magnetization dynamics and
spatially inhomogeneous dynamic magnetic patterns. The spatio-temporal
distributions of the magnetization oscillations in standing elastic waves have
the form of standing spin waves with the same wavelength. Remarkably, the
amplitude of magnetization precession does not go to zero at the nodes of these
spin waves, which cannot be precisely described by simple analytical formulae.
In the steady-state regime, the magnetization oscillates with the frequency of
elastic wave, except for the case of longitudinal waves with frequencies well
below nu_res, where the magnetization precesses with a variable frequency
strongly exceeding the wave frequency. The precession amplitude at the
antinodes of standing spin waves strongly increases when the frequency of
elastic wave becomes close to nu_res. The results obtained for the
magnetization dynamics driven by elastic waves are used to calculate the spin
current pumped from the dynamically strained ferromagnet into adjacent
paramagnetic metal. Importantly, the transverse charge current created by the
spin current via the inverse spin Hall effect is high enough to be measured
experimentally.",1512.09051v1
2008-01-30,Spin waves in disordered magnetic systems,"Long-wavelength spin waves in disordered magnetic systems have been
investigated. In the framework of the Heisenberg model with magnetic dipole and
exchange interactions between spins it is found that an additional longitudinal
spin wave mode appears. This mode is characterized by variations of the value
of the magnetic moment density. In order to analyse influence of the magnetic
disorder on spin wave dispersion relations, the special case of volume and
surface spin waves in the Damon-Eshbach (DE) geometry in films with magnetic
disorder is considered. It is revealed strong influence of the magnetic
disorder on surface spin waves, which consist of two branches -- the DE mode
and the longitudinal spin wave mode. Decrease of the ordering parameters leads
to a decrease of the initial frequency and the curve slope of the DE mode
dispersion curve and to an increase of the dispersion curve slope of the
longitudinal mode. If the spin noncollinearity is high, then the DE mode
dispersion assumes a curve with the backward character. It is found that the
dispersion relation of the longitudinal mode is weak temperature dependent. The
developed model can explain the observed double-peak structure of FMR spectra
in magnetic nanocomposites.",0801.4633v1
2016-03-24,Separated spin evolution quantum hydrodynamics of degenerated electrons with spin-orbit interaction and extraordinary wave spectrum,"To consider a contribution of the spin-orbit interaction in the extraordinary
wave spectrum we derive a generalization of the separate spin evolution quantum
hydrodynamics. Applying corresponding nonlinear Pauli equation we include Fermi
spin current contribution in the spin evolution. We find that the spectrum of
extraordinary waves consists of three branches: two of them are well-known
extraordinary waves and the third one is the spin-electron acoustic wave
(SEAW). Earlier SEAWs have been considered in the electrostatic limit. Here we
include the electromagnetic effects in their spectrum at the propagation
perpendicular to the external magnetic field. We find that the SEAW spectrum
considerably changes at the account of transverse part of electric field. We
obtain that the separate spin evolution modifies spectrum of the well-known
extraordinary waves either. A change of the extraordinary wave spectrum due to
the spin-orbit interaction is obtained as well.",1603.07506v1
2017-10-22,Kinetic description of the oblique propagating spin-electron acoustic waves in degenerate plasmas,"Oblique propagation of the spin-electron acoustic waves in degenerate
magnetized plasmas is considered in terms of quantum kinetics with the separate
spin evolution, where the spin-up electrons and the spin-down electrons are
considered as two different species with different equilibrium distributions.
It is considered in the electrostatic limit. Corresponding dispersion equation
is derived. Analytical analysis of the dispersion equation is performed in the
long-wavelength limit to find an approximate dispersion equation describing the
spin-electron acoustic wave. The approximate dispersion equation is solved
numerically. Real and imaginary parts of the spin-electron acoustic wave
frequency are calculated for different values of the parameters describing the
system. It is found that the increase of angle between direction of wave
propagation and the external magnetic field reduces the real and imaginary
parts of spin-electron acoustic wave frequency. The increase of the spin
polarization decreases the real and imaginary parts of frequency either. The
imaginary part of frequency has nonmonotonic dependence on the wave vector
which shows a single maximum. The imaginary part of frequency is small in
compare with the real part for all parameters in the area of applicability of
the obtained dispersion equation.",1710.08040v1
2019-05-09,Bidirectional spin-wave-driven domain wall motion in antiferromagnetically coupled ferrimagnets,"We investigate ferrimagnetic domain wall dynamics induced by circularly
polarized spin waves theoretically and numerically. We find that the direction
of domain wall motion depends on both the circular polarization of spin waves
and the sign of net spin density of ferrimagnet. Below the angular momentum
compensation point, left- (right-) circularly polarized spin waves push a
domain wall towards (away from) the spin-wave source. Above the angular
momentum compensation point, on the other hand, the direction of domain wall
motion is reversed. This bidirectional motion originates from the fact that the
sign of spin-wave-induced magnonic torque depends on the circular polarization
and the subsequent response of the domain wall to the magnonic torque is
governed by the net spin density. Our finding provides a way to utilize a spin
wave as a versatile driving force for bidirectional domain wall motion.",1905.03521v1
2018-06-07,Magnetic domain walls as broadband spin wave and elastic magnetisation wave emitters,"We report on the direct observation of spin wave and elastic wave emission
from magnetic domain walls in ferromagnetic thin films. Driven by alternating
homogeneous magnetic fields the magnetic domain walls act as coherent
magnetisation wave sources. Directional and low damped elastic waves below and
above the ferromagnetic resonance are excited. The wave vector of the
magnetoelastically induced acoustic shear waves is linearly tuned by varying
the excitation frequency. Domain wall emitted magnetostatic surface spin waves
occur at higher frequencies, which characteristics are confirmed by
micromagnetic simulations. The distinct modes of magnetisation wave excitation
from micromagnetic objects are a general physical phenomenon relevant for
dynamic magnetisation processes in structured magnetic films. Magnetic domain
walls can act as reconfigurable antennas for spin wave and elastic wave
generation with control of the wave orientation.",1806.02646v1
2015-06-09,Traveling surface spin-wave resonance spectroscopy using surface acoustic waves,"Coherent gigahertz-frequency surface acoustic waves (SAWs) traveling on the
surface of a piezoelectric crystal can, via the magnetoelastic interaction,
resonantly excite traveling spin waves in an adjacent thin-film ferromagnet.
These excited spin waves, traveling with a definite in-plane wave-vector q
enforced by the SAW, can be detected by measuring changes in the
electro-acoustical transmission of a SAW delay line. Here, we provide a first
demonstration that such measurements constitute a precise and quantitative
technique for spin-wave spectroscopy, providing a means to determine both
isotropic and anisotropic contributions to the spin-wave dispersion and
damping. We demonstrate the effectiveness of this spectroscopic technique by
measuring the spin-wave properties of a Ni thin film for a large range of wave
vectors,q = 2.5 x 10^4 - 8 x 10^4 cm^(-1), over which anisotropic dipolar
interactions vary from being negligible to quite significant.",1506.03056v3
2016-11-18,Propagating spin-wave normal modes: A dynamic matrix approach using plane-wave demagnetizating tensors,"We present a finite-difference micromagnetic approach for determining the
normal modes of spin-waves propagating in extended magnetic films and strips,
which is based on the linearized Landau-Lifshitz equation and uses the dynamic
matrix method. The model takes into account both short range exchange
interactions and long range dipole-dipole interactions. The latter are
accounted for through plane-wave dynamic demagnetization factors, which depend
not only on the geometry and relative positions of the magnetic cells, as usual
demagnetization factors do, but also on the wave vector of the propagating
waves. Such a numerical model is most relevant when the spin-wave medium is
spatially inhomogeneous perpendicular to the direction of propagation, either
in its magnetic properties or in its equilibrium magnetic configuration. We
illustrate this point by studying surface spin-waves in magnetic bilayer films
and spin-waves channelized along magnetic domain walls in perpendicularly
magnetized strips. In both cases, dynamic dipolar interactions produce
non-reciprocity effects, where counter-propagative spin-waves have different
frequencies.",1611.06153v1
2023-05-17,Spin-wave dynamics controlled by tunable ac magnonic crystal,"The magnonic crystal, which has a spatial modulation wave vector $q$, couples
the spin wave with wave vector $k$ to the one with wave vector $k-q$. For a
conventional magnonic crystal with direct current (dc) supply, the spin waves
around $q/2$ are resonantly coupled to the waves near $-q/2$, and a band gap is
opened at $k=\pm q/2$. If instead of the dc current the magnonic crystal is
supplied with an alternating current (ac), then the band gap is \emph{shifted}
to $k$ satisfying $|\omega_{s}(k)-\omega_{s}(k-q)|=\omega_{ac}$; here
$\omega_{s}(k)$ is the dispersion of the spin wave, while $\omega_{ac}$ is the
frequency of the ac modulation. The resulting gap in the case of the ac
magnonic crystal is the half of the one caused by the dc with the same
amplitude of modulation. The time evolution of the resonantly coupled spin
waves controlled by properly suited ac pulses can be well interpreted as the
motion on a Bloch sphere. The tunability of the ac magnonic crystal broadens
the perspective of spin-wave computing.",2305.09876v1
1994-06-27,Quantum melting of the long-range antiferromagnetic order and spin-wave condensation in t-J-V model,"We consider two-dimensional t-J-V model. The wave function of the ground
state is constructed. We demonstrate that the doping by holes results in
condensation of the spin-waves, destruction of the long-range antiferromagnetic
order and formation of the gap in the spin-wave spectrum.",9406105v1
2010-04-18,Spin Orbit Coupling and Spin Waves in Ultrathin Ferromagnets: The Spin Wave Rashba Effect,"We present theoretical studies of the influence of spin orbit coupling on the
spin wave excitations of the Fe monolayer and bilayer on the W(110) surface.
The Dzyaloshinskii-Moriya interaction is active in such films, by virtue of the
absence of reflection symmetry in the plane of the film. When the magnetization
is in plane, this leads to a linear term in the spin wave dispersion relation
for propagation across the magnetization. The dispersion relation thus assumes
a form similar to that of an energy band of an electron trapped on a
semiconductor surfaces with Rashba coupling active. We also show SPEELS
response functions that illustrate the role of spin orbit coupling in such
measurements. In addition to the modifications of the dispersion relations for
spin waves, the presence of spin orbit coupling in the W substrate leads to a
substantial increase in the linewidth of the spin wave modes. The formalism we
have developed applies to a wide range of systems, and the particular system
explored in the numerical calculations provides us with an illustration of
phenomena which will be present in other ultrathin ferromagnet/substrate
combinations.",1004.3066v1
2014-06-24,Oblique propagation of longitudinal waves in magnetized spin-1/2 plasmas: Independent evolution of spin-up and spin-down electrons,"We consider quantum plasmas of electrons and motionless ions. We describe
separate evolution of spin-up and spin-down electrons. We present corresponding
set of quantum hydrodynamic equations. We assume that plasmas are placed in an
uniform external magnetic field. We account different occupation of spin-up and
spin-down quantum states in equilibrium degenerate plasmas. This effect is
included via equations of state for pressure of each species of electrons. We
study oblique propagation of longitudinal waves. We show that instead of two
well-known waves (the Langmuir wave and the Trivelpiece--Gould wave), plasmas
reveal four wave solutions. New solutions exist due to both the separate
consideration of spin-up and spin-down electrons \textit{and} different
occupation of spin-up and spin-down quantum states in equilibrium state of
degenerate plasmas.",1406.6252v1
2021-10-05,Generation of Nonreciprocity of Gapless Spin Waves by Chirality Injection,"In chiral magnets with intrinsic inversion symmetry breaking, it has been
known that two spin waves moving in opposite directions can propagate at
different velocities, exhibiting a phenomenon called magnetochiral
nonreciprocity which allows for realizations of certain spin logic devices such
as a spin-wave diode. Here, we theoretically demonstrate that the spin-wave
nonreciprocity can occur without intrinsic bulk chirality in certain magnets
including easy-cone ferromagnets and easy-cone antiferromagnetic. Specifically,
we show that nonlocal injection of a spin current from proximate normal metals
to easy-cone magnets engenders a non-equilibrium chiral spin texture, on top of
which spin waves exhibit nonreciprocity proportional to the injected spin
current. One notable feature of the discovered nonreciprocal spin waves is its
gapless nature, which can lead to a large thermal rectification effect at
sufficiently low temperatures. We envision that nonlocal electric injection of
chirality into otherwise nonchiral magnets may serve as a versatile route to
realize electrically controllable magnetochiral phenomena in a wide class of
materials.",2110.01867v2
2023-09-10,Non-zero Integral Spin of Acoustic Vortices and Spin-orbit Interaction in Longitudinal Acoustics,"Spin and orbital angular momenta (AM) are of fundamental interest in wave
physics. Acoustic wave, as a typical longitudinal wave, has been well studied
in terms of orbital AM, but still considered unable to carry non-zero integral
spin AM or spin-orbital interaction in homogeneous media due to its spin-0
nature. Here we give the first self-consistent analytical calculations of spin,
orbital and total AM of guided vortices under different boundary conditions,
revealing that vortex field can carry non-zero integral spin AM. We also
introduce for acoustic waves the canonical-Minkowski and kinetic-Abraham AM,
which has aroused long-lasting debate in optics, and prove that only the former
is conserved with the corresponding symmetries. Furthermore, we present the
theoretical and experimental observation of the spin-orbit interaction of
vortices in longitudinal acoustics, which is thought beyond attainable in
longitudinal waves in the absence of spin degree of freedom. Our work provides
a solid platform for future studies of the spin and orbital AM of guided
acoustic waves and may open up a new dimension for acoustic vortex-based
applications such as underwater communications and object manipulations.",2309.04989v1
2003-09-30,Recent Progress of the Low-Dimensional Spin-Wave Theory,"A modified spin-wave theory is developed and applied to low-dimensional
quantum magnets. Double-peaked specific heat for one-dimensional ferrimagnets,
nuclear spin-lattice relaxation in ferrimagnetic chains and clusters, and
thermal behavior of Haldane-gap antiferromagnets are described within the
scheme. Mentioning other bosonic and fermionic representations as well, we
demonstrate that spin waves are still effective in low dimensions.",0310004v1
2003-03-20,Spin waves in La_2CuO_4: band structure and correlation effects,"We calculate the antiferromagnetic spin wave dispersion in the half-filled
(electronic density n=1) Hubbard model for a two-dimensional square lattice,
using the random phase approximation (RPA) in a broken symmetry (spin density
wave) ground state. Our results for the spin wave dispersion, \omega(\vec q),
are compared with high-resolution inelastic neutron scattering performed on
La_2CuO$_4. The effects of different band structures and different values of
the on-site Coulomb interaction on the spin wave spectrum is studied.
Particular attention is put on the high energy dispersion values
\omega(\pi/2,\pi/2) and \omega(0,\pi).",0303409v1
2003-08-14,On the motion of spinning test particles in plane gravitational waves,"The Mathisson-Papapetrou-Dixon equations for a massive spinning test particle
in plane gravitational waves are analysed and explicit solutions constructed in
terms of solutions of certain linear ordinary differential equations. For
harmonic waves this system reduces to a single equation of Mathieu-Hill type.
In this case spinning particles may exhibit parametric excitation by
gravitational fields. For a spinning test particle scattered by a gravitational
wave pulse, the final energy-momentum of the particle may be related to the
width, height, polarisation of the wave and spin orientation of the particle.",0308042v1
2002-03-02,Spin waves in the magnetized plasma of a supernova and its excitation by neutrino fluxes,"The spin effects on electromagnetic waves in a strongly magnetized plasma
with rare collisions is considered with the help of relativistic kinetic
equations, which takes into account the electron spin dynamics in the
selfconsistent electric and magnetic fields. It is shown that for
electromagnetic waves propagating almost perpendicular to ambient magnetic
field the spin effects become essential in the vicinity of electron
gyrofrequency and the corresponding wave dispersion and growth rate of the
electromagnetic spin waves in the presence of intense quasi monoenergetic
fluxes of neutrino is determined.",0203020v1
2009-01-18,Generation of pulse trains by current-controlled magnetic mirrors,"The evolution of a spin-wave packet trapped between two direct
current-carrying wires placed on the surface of a ferrite film is observed by
Brillouin light scattering. The wires act as semi-transparent mirrors confining
the packet. Because the spin-wave energy partially passes through these
mirrors, trains of spin-wave packets are generated outside the trap. A
numerical model of this process is presented and applied to the case when the
current in the wires is dynamically controlled. This dynamical control of the
mirror reflectivity provides new functionalities interesting for the field of
spin-wave logic like that of a spin-wave memory cell.",0901.2704v1
2012-11-06,Spin Wave Scattering in Ferromagnetic Cross,"Spin wave scattering in the right angle ferromagnetic cross was measured.
Shape anisotropy defined magnetization ground states at zero biasing magnetic
fields. Scattering of the spin waves in the center of ferromagnetic cross is
strongly dependent on the amplitude and angle of the biasing magnetic field.
Micromagnetic simulations indicate that low in-plane biasing magnetic fields
rotate the magnetization of the cross center while the arms stay axially
magnetized due to the shape anisotropy. We discuss effect of biasing magnetic
fields on the spin wave scattering and approaches to an effective spin wave
switch based on the fabricated structure.",1211.1259v1
2014-08-14,Design of a spin-wave majority gate employing mode selection,"The design of a microstructured, fully functional spin-wave majority gate is
presented and studied using micromagnetic simulations. This all-magnon logic
gate consists of three-input waveguides, a spin-wave combiner and an output
waveguide. In order to ensure the functionality of the device, the output
waveguide is designed to perform spin-wave mode selection. We demonstrate that
the gate evaluates the majority of the input signals coded into the spin-wave
phase. Moreover, the all-magnon data processing device is used to perform logic
AND-, OR-, NAND- and NOR- operations.",1408.3235v1
2016-04-29,Extraordinary waves in two dimensional electron gas with separate spin evolution and Coulomb exchange interaction,"Hydrodynamics analysis of waves in two-dimensional degenerate electron gas
with the account of separate spin evolution is presented. The transverse
electric field is included along with the longitudinal electric field. The
Coulomb exchange interaction is included in the analysis. In contrast with the
three-dimensional plasma-like mediums the contribution of the transverse
electric field is small. We show the decrease of frequency of both the
extraordinary (Langmuir) wave and the spin-electron acoustic wave due to the
exchange interaction. Moreover, spin-electron acoustic wave has negative
dispersion at the relatively large spin-polarization. Corresponding dispersion
dependencies are presented and analyzed.",1604.08902v1
2018-03-08,First-principles study of spin-wave dispersion in Sm(Fe$_{1-x}$Co$_{x}$)$_{12}$,"We present spin-wave dispersion in Sm(Fe$_{1-x}$Co$_x$)$_{12}$ calculated
based on first-principles. Anisotropy in the lowest branch of the spin-wave
dispersion around the $\Gamma$ point is discussed. Spin-waves propagate more
easily along $a^*$-axis than along $c^*$-axis, especially in SmFe$_{12}$. We
also compare values of the spin-wave stiffness with those obtained from an
experiment. The calculated values are in good agreement with the experimental
values.",1803.03165v3
2020-04-17,Collective coordinate study of spin wave emission from dynamic domain wall,"We study theoretically the spin wave emission from a moving domain wall in a
ferromagnet. Introducing a deformation mode describing a modulation of the wall
thickness in the collective coordinate description, we show that thickness
variation couples to the spin wave linearly and induces spin wave emission. The
dominant emitted spin wave turns out to be polarized in the out-of wall plane
($\phi$)-direction. The emission contributes to the Gilbert damping parameter
proportional to $\hbar\omega_\phi/K$, the ratio of the angular frequency
$\omega_\phi$ of $\phi$ and the easy-axis anisotropy energy $K$.",2004.08082v1
2017-06-09,Spin-wave analysis for Kagome-triangular spin system and coupled spin tubes: low-energy excitation for the cuboc order,"The coupled spin tube system, which is equivalent to a stacked
Kagome-triangular spin system, exhibits the cuboc order -- a non-coplanar spin
order with a twelve-sublattice structure accompanying spontaneous breaking of
the translational symmetry -- in the Kagome-triangular plane. On the basis of
the spin-wave theory, we analyze spin-wave excitations of the planar
Kagome-triangular spin system, where the geometric phase characteristic to the
cuboc spin structure emerges. We further investigate spin-wave excitations and
dynamical spin structure factors for the coupled spin tubes, assuming the
staggered cuboc order.",1706.02879v2
2018-01-08,Spin-resolved inelastic electron scattering by spin waves in noncollinear magnets,"Topological non-collinear magnetic phases of matter are at the heart of many
proposals for future information nanotechnology, with novel device concepts
based on ultra-thin films and nanowires. Their operation requires understanding
and control of the underlying dynamics, including excitations such as
spin-waves. So far, no experimental technique has attempted to probe large
wave-vector spin-waves in non-collinear low-dimensional systems. In this work,
we explain how inelastic electron scattering, being suitable for investigations
of surfaces and thin films, can detect the collective spin-excitation spectra
of non-collinear magnets. To reveal the particularities of spin-waves in such
non-collinear samples, we propose the usage of spin-polarized
electron-energy-loss spectroscopy augmented with a spin-analyzer. With the
spin-analyzer detecting the polarization of the scattered electrons, four
spin-dependent scattering channels are defined, which allow to filter and
select specific spin-wave modes. We take as examples a topological non-trivial
skyrmion lattice, a spin-spiral phase and the conventional ferromagnet. Then we
demonstrate that, counter-intuitively and in contrast to the ferromagnetic
case, even non spin-flip processes can generate spin-waves in non-collinear
substrates. The measured dispersion and lifetime of the excitation modes permit
to fingerprint the magnetic nature of the substrate.",1801.02542v2
2006-06-30,A variational coupled-cluster study of magnon-density-wave excitations in quantum antiferromagnets,"We extend recently proposed variational coupled-cluster method to describe
excitation states of quantum antiferromagnetic bipartite lattices. We reproduce
the spin-wave excitations (i.e., magnons with spin $\pm 1$). In addition, we
obtain a new, spin-zero excitation (magnon-density waves) which has been
missing in all existing spin-wave theories. Within our approximation, this
magnon-density-wave excitation has a nonzero energy gap in a cubic lattice and
is gapless in a square lattice, similar to those charge-density-wave
excitations (plasmons) in quantum electron gases.",0606813v2
2011-03-11,Interference of coherent spin waves in micron-sized ferromagnetic waveguides,"We present experimental observations of the interference of spin-wave modes
propagating in opposite directions in micron-sized NiFe-waveguides. To monitor
the local spin-wave intensity distribution and phase of the formed interference
pattern, we use Brillouin light scattering microscopy. The two-dimensional
spin-wave intensity map can be understood by considering the interference of
several waveguide eigenmodes with different wavevectors quantized across the
width of the stripe. The phase shows a transition from linear dependence on the
space coordinate near the antennas characteristic for propagating waves to
discrete values in the center region characteristic for standing waves.",1103.2248v1
1996-03-26,Spin Diffusion in 2D XY Ferromagnet with Dipolar Interaction,"In the ordered phase of 2D XY ferromagnet the dipolar interaction between
spins induces a strong, relevant interaction between spin-waves. We study
quasi-excitations of the interacting spin-wave 'liquid' in the long wavelength
limit. We employ the Janssen-De-Dominicis method for classical Langevin
equation to find the transformation of the spin-wave excitation into a new
soft-mode excitation in the intermediate range of wavelengths; and into an
anomalous anisotropic diffusion mode excitation at long wavelengths. The
dissipation of a spin-wave at short wavelengths is found to be highly
anisotropic.",9603160v1
1999-09-17,Finite size Spin Wave theory of the triangular Heisenberg model,"We present a finite size spin wave calculation on the Heisenberg
antiferromagnet on the triangular lattice focusing in particular on the
low-energy part of the excitation spectrum. For s=1/2 the good agreement with
the exact diagonalization and quantum Monte Carlo results supports the
reliability of the spin wave expansion to describe the low-energy spin
excitations of the Heisenberg model even in presence of frustration. This
indicates that the spin susceptibility of the triangular antiferromagnet is
very close to the linear spin wave result.",9909268v1
2002-04-03,Spin Waves in Disordered III-V Diluted Magnetic Semiconductors,"We propose a new scheme for numerically computing collective-mode spectra for
large-size systems, using a reformulation of the Random Phase Approximation. In
this study, we apply this method to investigate the spectrum and nature of the
spin-waves of a (III,Mn)V Diluted Magnetic Semiconductor. We use an impurity
band picture to describe the interaction of the charge carriers with the local
Mn spins. The spin-wave spectrum is shown to depend sensitively on the
positional disorder of the Mn atoms inside the host semiconductor. Both
localized and extended spin-wave modes are found. Unusual spin and charge
transport is implied.",0204092v1
2005-01-27,Current-induced macrospin vs spin-wave excitations in spin valves,"The mode dependence of current-induced magnetic excitations in spin valves is
studied theoretically. The torque exerted on the magnetization by transverse
spin currents as well as the Gilbert damping constant are found to depend
strongly on the wave length of the excitation (spin wave). Analytic expressions
are presented for the critical currents that excite a selected spin wave. The
onset of macrospin (zero wavelength) vs finite wavelength instabilities depends
on the device parameters and the current direction, in agreement with recent
experimental findings.",0501672v3
2007-12-17,Field-induced spin excitations in Rashba-Dresselhaus two-dimensional electron systems probed by surface acoustic waves,"A spin-rotation symmetry in spin-orbit coupled two-dimensional electron
systems gives rise to a long-lived spin excitation that is robust against
short-range impurity scattering. The influence of a constant in-plane electric
field on this persistent spin helix is studied. To probe the field-induced
eigen-modes of the spin-charge coupled system, a surface acoustic wave is
exploited that provides the wave-vector for resonant excitation. The approach
takes advantage of methods worked out in the field of space-charge waves. Sharp
resonances in the field dependence of the in-plane and out-of-plane
magnetization are identified.",0712.2647v1
2013-03-20,Spin-pumping and Enhanced Gilbert Damping in Thin Magnetic Insulator Films,"Precessing magnetization in a thin film magnetic insulator pumps spins into
adjacent metals; however, this phenomenon is not quantitatively understood. We
present a theory for the dependence of spin-pumping on the transverse mode
number and in-plane wave vector. For long-wavelength spin waves, the enhanced
Gilbert damping for the transverse mode volume waves is twice that of the
macrospin mode, and for surface modes, the enhancement can be ten or more times
stronger. Spin-pumping is negligible for short-wavelength exchange spin waves.
We corroborate our analytical theory with numerical calculations in agreement
with recent experimental results.",1303.4922v1
2013-07-11,Direct evidence of nuclear spin waves in Nd$_2$CuO$_4$ by high-resolution neutron-spin-echo spectroscopy,"We investigated the dispersion of nuclear spin waves in Nd$_2$CuO$_4$ by
using neutron spin-echo spectroscopy at millikelvin temperatures. Our results
show unambiguously the existence of dispersion of nuclear spin waves in
Nd$_2$CuO$_4$ at T = 30 mK. A fit of the dispersion data with the spin wave
dispersion formula gave the Suhl-Nakamura interaction range to be of the order
of 10 {\AA}.",1307.2998v1
2021-11-24,Spin Hall response at finite wave vector in ferromagnets,"Spin Hall effect at finite wave vector in a ferromagnetic conductor is
theoretically studied by calculating the spin density as the linear response to
an applied electric field. The cases of a spin-orbit interaction due to random
impurities and a localized Rashba interaction are considered. It is shown that
the spin Hall effect has a broad response for the wave vector $q\lesssim 2\kf$
where $\kf $ is the Fermi wave vector. This fact confirms the local nature of
the spin-charge conversion effects.",2111.12247v1
2007-05-25,Inductively Coupled Circuits with Spin Wave Bus for Information Processing,"We describe a new approach to logic devices interconnection by the inductive
coupling via a ferromagnetic film. The information among the distant devices is
transmitted in a wireless manner via a magnetic field produced by spin waves
propagating in the ferromagnetic film, referred to as the spin wave bus. As an
alternative approach to the transistor-based architecture, logic circuits with
spin wave bus do not use charge as an information carrier. A bit of information
can be encoded into the phase or the amplitude of the spin wave signal. We
present experimental data demonstrating inductive coupling through the 100nm
thick NiFe and CoFe films at room temperature. The performance of logic
circuits with spin wave bus is illustrated by numerical modeling based on the
experimental data. Potentially, logic circuits with spin wave bus may resolve
the interconnect problem and provide ""wireless"" read-in and read-out. Another
expected benefit is in the enhanced logic functionality. A set of NOT, AND, and
OR logic gates can be realized in one device structure. The coupling between
the circuits and the spin wave bus can be controlled. We present the results of
numerical simulations showing the controllable switching of a bi-stable logic
cell inductively coupled to the spin wave bus. The shortcomings and limitations
of circuits with spin wave bus are also discussed.",0705.3864v1
2019-01-06,Asymmetric dynamics of edge exchange spin waves in honeycomb nanoribbons with zigzag and bearded edges boundaries,"We report on the theoretical prediction of asymmetric edge spin waves,
propagating in opposite directions on the edges of honeycomb nanoribbons with
zigzag and bearded edges boundaries. The simultaneous propagation of edge spin
waves in the same direction on both edges of these nanoribbons is hence
predicted to be forbidden. These asymmetric edge exchange spin waves are
analogous to the nonreciprocal surface spin waves reported in magnetic thin
films. Their existence is related to the nontrivial symmetry underlying the
nanoribbons under study. The edge and discretized bulk exchange spin waves are
calculated in the long wavelength part of the Brillouin zone using the
classical spin wave theory approach and appropriate boundary conditions. In the
absence of an external magnetic field in our study, the asymmetric edge spin
waves propagate with equal frequencies and opposite directions, since the
energy dispersion relation is independent of the sign of the wavevector
components in the long wavelength part of the Brillouin zone. The edge spin
waves are characterized by linear dispersion relations for magnetically
isotropic nanoribbons. Introducing magnetic anisotropy in the calculation
significantly enhances the energy gap between the edge and bulk spin waves in
both types of nanoribbons. Based on our calculation, the large energy gap
allows separate excitation of bulk and edge modes as their energies are no more
overlapping.",1901.01617v1
2016-06-23,Spin-Hall nano-oscillator with oblique magnetization and Dzyaloshinskii-Moriya interaction as generator of skyrmions and nonreciprocal spin-waves,"Spin-Hall oscillators are promising sources of spin-wave signals for
magnonics applications, and can serve as building blocks for magnonic logic in
ultralow power computation devices. Here, we analytically and micromagnetically
study magnetization dynamics excited in a Spin-Hall oscillator with oblique
magnetization when the spin-Hall effect and interfacial Dzyaloshinskii-Moriya
interaction act simultaneously. Our key results are (i) excitation of
nonreciprocal spin-waves propagating perpendicularly to the in-plane projection
of the static magnetization, (ii) skyrmions generation by pure spin-current,
(iii) excitation of a new spin-wave mode with a spiral spatial profile
originating from a gyrotropic rotation of a dynamical skyrmion. These results
demonstrate that Spin-Hall oscillators can be used as generators of magnetic
skyrmions and different types of propagating spin-waves for magnetic data
storage and signal processing applications.",1606.07280v1
2013-01-16,Mechanical generation of spin current by spin-rotation coupling,"Spin-rotation coupling, which is responsible for angular momentum conversion
between the electron spin and rotational deformations of elastic media, is
exploited for generating spin current. This method requires neither magnetic
moments nor spin-orbit interaction. The spin current generated in nonmagnets is
calculated in presence of surface acoustic waves. We solve the spin diffusion
equation, extended to include spin-rotation coupling, and find that larger spin
currents can be obtained in materials with longer spin lifetimes. Spin
accumulation induced on the surface is predicted to be detectable by
time-resolved Kerr spectroscopy.",1301.3596v1
2003-04-19,Spin-Wave Theory for s=1 Antiferromagnetic Isotropic Chain,"In the paper we describe the modification of spin-wave theory for
one-dimensional isotropic antiferromagnet. This theory enables to obtain the
energy of magnetic excitations of short wave length and correlation function in
agreement with numerical studies.",0304444v1
1999-06-04,Explicit expressions of spin wave functions,"We derive the explicit expressions of the canonical and helicity wave
functions for massive particles with arbitrary spins. Properties of these wave
functions are discussed.",9906250v1
2012-01-25,Spin current induced by the sound wave,"The kinetics of conduction electrons interacting with the field of sound
waves in a constant magnetic field is studied. It is shown that the
longitudinal sound wave propagation occurs transverse spin conductivity, which
has a resonant character.",1201.5231v1
2019-10-09,Transverse spin dynamics of light: the generalized spin-momentum locking for structured guided modes,"Quantum spin-Hall effect, a manifestation of topological properties that
govern the behavior of surface states, was studied intensively in condensed
matter physics resulting in the discovery of topological insulators. The
quantum spin-Hall effect of light was introduced for surface plane-waves which
intrinsically carry transverse optical spin, leading to many intriguing
phenomena and applications in unidirectional waveguiding, metrology and quantum
technologies. In addition to spin, optical waves can exhibit complex
topological properties of vectorial electromagnetic fields, associated with
orbital angular momentum or nonuniform intensity variations. Here, by
considering both spin and angular momentum, we demonstrate a generalized
spin-momentum relationship that governs vectorial properties of guided
electromagnetic waves, extending optical quantum spin-Hall effect to a
two-dimensional vector field of structured guided wave. The effect results in
the appearance of the out-of-plane transverse optical spins, which vary
progressively from the 'up' state to the 'down' state around the energy flow,
and their variation is uniquely locked to the energy propagation direction. The
related spin-momentum locking in a chiral spin swirl is demonstrated with four
kinds of surface structured waves and proven both theoretically and
experimentally. The results provide understanding of the spin dynamics in
electromagnetic guided waves and show great importance in spin optics,
topological photonics and optical spin-based devices and techniques.",1910.03904v2
2021-09-13,One-dimensional force-free numerical simulations of Alfven waves around a spinning black string,"We performed one-dimensional force-free magnetodynamic numerical simulations
of the propagation of Alfven waves along magnetic field lines around a spinning
black-hole-like object, the Banados--Teitelboim--Zanelli black string, to
investigate the dynamic process of wave propagation and energy transport with
Alfven waves. We considered axisymmetric and stationary magnetosphere and
perturbed the background magnetosphere to obtain the linear wave equation for
the Alfven wave mode. The numerical results show that the energy of Alfven
waves monotonically increases as the waves propagate outwardly along the
rotating curved magnetic field line around the ergosphere, where energy seems
not to be conserved, in the case of energy extraction from the black string by
the Blandford--Znajek mechanism. The apparent breakdown of energy conservation
suggests the existence of an additional wave induced by the Alfven wave.
Considering the additional fast magnetosonic wave induced by the Alfven wave,
the energy conservation is recovered. Similar relativistic phenomena, such as
the amplification of Alfven waves and induction of fast magnetosonic waves, are
expected around a spinning black hole.",2109.05703v1
2015-06-07,Spin current evolution in the separated spin-up and spin-down quantum hydrodynamics,"We have developed the quantum hydrodynamic model that describes particles
with spin-up and with spin-down in separate. We have derived the equation of
the spin current evolution as a part of the set of the quantum hydrodynamics
(QHD) equations that treat particles with different projection of spin on the
preferable direction as two different species. We have studied orthogonal
propagation of waves in the external magnetic field and determined the
contribution of quantum corrections due to the Bohm potential and to
magnetization energy of particles with different projections of spin in the
spin current wave dispersion. We have analyzed the limits of weak and strong
magnetic fields.",1506.02259v1
2001-01-30,Effect of nearest- and next-nearest neighbor interactions on the spin-wave velocity of one-dimensional quarter-filled spin-density-wave conductors,"We study spin fluctuations in quarter-filled one-dimensional
spin-density-wave systems in presence of short-range Coulomb interactions. By
applying a path integral method, the spin-wave velocity is calculated as a
function of on-site (U), nearest (V) and next-nearest (V_2) neighbor-site
interactions. With increasing V or V_2, the pure spin-density-wave state
evolves into a state with coexisting spin- and charge-density waves. The
spin-wave velocity is reduced when several density waves coexist in the ground
state, and may even vanish at large V. The effect of dimerization along the
chain is also considered.",0101450v2
2010-08-31,Dynamics of the collective modes of an inhomogeneous spin ensemble in a cavity,"We study the excitation dynamics of an inhomogeneously broadened spin
ensemble coupled to a single cavity mode. The collective excitations of the
spin ensemble can be described in terms of generalized spin waves and, in the
absence of the cavity, the free evolution of the spin ensemble can be described
as a drift in the wave number without dispersion. In this article we show that
the dynamics in the presence of coupling to the cavity mode can be described
solely by a modified time evolution of the wave numbers. In particular, we show
that collective excitations with a well- defined wave number pass without
dispersion from negative to positive valued wave numbers without populating the
zero wave number spin wave mode. The results are relevant for multi-mode
collective quantum memories where qubits are encoded in different spin waves.",1008.5197v2
2017-11-01,Adiabatic Control of Spin-Wave Propagation using Magnetisation Gradients,"Spin waves are of large interest as data carriers for future logic devices.
However, due to the strong anisotropic dispersion relation of dipolar
spin-waves in in-plane magnetised films the realisation of two-dimensional
information transport remains a challenge. Bending of the energy flow is
prohibited since energy and momentum of spin waves cannot be conserved while
changing the direction of wave propagation. Thus, non-linear or non-stationary
mechanisms are usually employed. Here, we propose to use reconfigurable
laser-induced magnetisation gradients to break the system's translational
symmetry. The resulting changes in the magnetisation shift the dispersion
relations locally and allow for operating with different spin-wave modes at the
same frequency. Spin-wave momentum is first transformed via refraction at the
edge of the magnetisation gradient region and then adiabatically modified
inside it. Along these lines the spin-wave propagation direction can be
controlled in a broad frequency range with high efficiency.",1711.00508v1
2016-11-23,Creation of uni-directional spin-wave emitters by utilizing interfacial Dzyaloshinskii-Moriya interaction,"We present an analytic and numerical study of the creation of an
uni-directional spin-wave emission in ultra-thin ferromagnetic films sandwiched
in an asymmetric layer stack. For this we extend the analytical description of
spin waves in spin-wave waveguides by the incorporation of the influence of the
interfacial Dzyaloshinskii-Moriya interaction on the spin-wave propagation. By
exploring the model system Ni$_{81}$Fe$_{19}$/Pt we show that it is possible to
achieve an uni-directional spin-wave emission by combining wave-vector
selective excitation sources with the frequency splitting which arises from
interfacial Dzyaloshinskii-Moriya interaction. Hereby we focus on device
feature sizes and spin-wave wavelengths compatible with state-of-the art
excitation and detection schemes. We demonstrate that the optimum operation
conditions for the non-reciprocal emission can be predicted using the presented
analytical formalism",1611.07841v2
2020-06-15,Femtosecond laser pulse driven caustic spin wave beams,"Controlling the directionality of spin waves is a key ingredient in
wave-based computing methods such as magnonics. In this paper, we demonstrate
this particular aspect by using an all-optical point-like source of continuous
spin waves based on frequency comb rapid demagnetization. The emitted spin
waves contain a range of k-vectors and by detuning the applied magnetic field
slightly off the ferromagnetic resonance (FMR), we observe X-shaped caustic
spin-wave patterns at $70^{\circ}$ propagation angles as predicted by theory.
When the harmonic of the light source approaches theFMR, the caustic pattern
gives way to uniaxial spin-wave propagation perpendicular to the in-plane
component of the applied field. This field-controlled propagation pattern and
directionality of optically emitted short-wavelength spin waves provide
additional degrees of freedom when designing magnonic devices.",2006.08219v1
2022-07-03,Deeply nonlinear excitation of self-normalised exchange spin waves,"Spin waves are ideal candidates for wave-based computing, but the
construction of magnetic circuits is blocked by a lack of an efficient
mechanism to excite long-running exchange spin waves with normalised
amplitudes. Here, we solve the challenge by exploiting the deeply nonlinear
phenomena of forward-volume spin waves in 200 nm wide nanoscale waveguides and
validate our concept with microfocused Brillouin light scattering spectroscopy.
An unprecedented nonlinear frequency shift of >2 GHz is achieved, corresponding
to a magnetisation precession angle of 55{\deg} and enabling the excitation of
exchange spin waves with a wavelength of down to ten nanometres with an
efficiency of >80%. The amplitude of the excited spin waves is constant and
independent of the input microwave power due to the self-locking nonlinear
shift, enabling robust adjustment of the spin wave amplitudes in future on-chip
magnonic integrated circuits.",2207.01121v1
2015-06-07,Experimental observation of the interaction of propagating spin waves with Néel domain walls in a Landau domain structure,"The interaction of propagating dipolar spin waves with magnetic domain walls
is investigated in square-shaped microstructures patterned from the Heusler
compound Co$_2$Mn$_{0.6}$Fe$_{0.4}$Si. Using magnetic force microscopy, the
reversible preparation of a Landau state with four magnetic domains separated
by N\'eel domain walls is confirmed. A local spin-wave excitation using a
microstructured antenna is realized in one of the domains. It is shown by
Brillouin light scattering microscopy (BLS) that the domain structure in the
remanence state has a strong influence on the spin-wave excitation and
propagation. The domain walls strongly reflect the spin waves and can be used
as spin-wave reflectors. A comparison with micromagnetic simulations shows that
the strong reflection is due to the long-range dipolar interaction which has
important implications for the use of these spin waves for exerting an
all-magnonic spin-transfer torque.",1506.02303v1
2018-07-25,Left-handed polarized spin waves in ferromagnets induced by spin-transfer torque,"Polarization is a fundamental property of waves that refers to the
orientation of the oscillations. It has been widely used to encode information
in photonics and phononics. However, the polarization of spin waves is rarely
used yet in magnonics. The reason for this is that only the right-handed
polarized spin waves can be accommodated in ferromagnets. Here, we report that
stable left-handed polarized spin waves can be introduced into ferromagnets if
a spin-polarized electrical current is presented. The right-handed and
left-handed polarized spin waves coexist when the current density is larger
than a critical value while the system keeps stable. The results are confirmed
by micromagnetic simulations. This work provides new playgrounds to study spin
waves and points to new findings for future experimental studies.",1807.09456v2
2019-03-10,Electrical generation and propagation of spin waves in antiferromagnetic thin films,"Electrical generation of THz spin waves is theoretically explored in an
antiferromangetic nanostrip via the current-induced spin-orbit torque. The
analysis based on micromagnetic simulations clearly illustrates that the
Neel-vector oscillations excited at one end of the magnetic strip can propagate
in the form of a traveling wave when the nanostrip axis aligns with the
magnetic easy-axis. A sizable threshold is observed in the driving current
density or the torque to overcome the unfavorable anisotropy as expected. The
generated spin waves are found to travel over a long distance while the angle
of rotation undergoes continuous decay in the presence of non-zero damping. The
oscillation frequency is tunable via the strength of the spin-orbit torque,
reaching the THz regime. Other key characteristics of the spin waves such as
the phase and the chirality can also be modulated actively. The simulation
results further indicate the possibility of wave-like superposition between the
excited spin oscillations, illustrating its application as an efficient source
of spin-wave signals for information processing.",1903.04068v2
2020-03-11,Excitation and relaxation dynamics of spin-waves triggered by ultrafast photo-induced demagnetization in a ferrimagnetic insulator,"Excitation and propagation dynamics of spin waves in an iron-based garnet
film under out-of-plane magnetic field were investigated by time-resolved
magneto-optical imaging. The experimental results and the following data
analysis by phase-resolved spin-wave tomography reveal the excitation of spin
waves triggered by photo-induced demagnetization (PID) along the sample depth
direction. Moreover, the fast relaxation of PID accompanied by the spin
transfer due to spin-wave emission was observed. Possible scenarios of PID in
the garnet film are discussed. Finally, we develop a model for the spin-wave
excitation triggered by PID and explain the magnetic-field dependence in the
amplitude of the observed spin waves.",2003.05159v1
2021-06-28,Fully Resonant Magneto-elastic Spin-wave Excitation by Surface Acoustic Waves under Conservation of Energy and Linear Momentum,"We report on the resonant excitation of spin waves in micro-structured
magnetic thin films by surface acoustic waves (SAWs). The spin waves as well as
the acoustic waves are studied by micro-focused Brillouin light scattering
spectroscopy. Besides the excitation of the ferromagnetic resonance, a process
which does not fulfill momentum conservation, also the excitation of
finite-wavelength spin waves can be observed at low magnetic fields. Using
micromagnetic simulations, we verify that during this excitation both energy
and linear momentum are conserved and fully transferred from the SAW to the
spin wave.",2106.14705v3
2022-01-07,Control of spin waves by spatially modulated strain,"We suggest using spatially modulated strain for control of a spin wave
propagating inside a bulk magnet. The modulation with the wave vector $q=2k$,
by virtue of magnetoelasticity, mixes spin waves with wave vectors near $k$ and
$-k$. This leads to lifting the degeneracy of the symmetric and antisymmetric
eigenstate combinations of these waves. The resulting picture reminds one of a
tunneling particle in a symmetric double-well potential. Here, a moving spin
wave being subjected to the $2k$-lattice modulation after some time alters its
propagation direction to the opposite one, and so on. The effect can be
utilized for the control of the spin-wave propagation that can be useful for
spintronic and magnonic applications. The control may include a delay line
element, filtering, and waveguide of the spin waves.",2201.02691v1
2008-12-09,Spin-Wave Relaxation in a Quantum Hall Ferromagnet,"We study spin wave relaxation in quantum Hall ferromagnet regimes. Spin-orbit
coupling is considered as a factor determining spin nonconservation, and
external random potential as a cause of energy dissipation making spin-flip
processes irreversible. We compare this relaxation mechanism with other
relaxation channels existing in a quantum Hall ferromagnet.",0812.1703v1
1996-12-18,Spin-flip and spin-wave excitations in arbitrarily polarized quantum Hall states,"We study spin-flip and spin-wave excitations for arbitrarily polarized
quantum Hall states by employing a fermionic Chern-Simons gauge theory in the
low Zeeman energy limit. We show that the spin-flip correlation functions do
not get renormalized by the fluctuations of Chern-Simons gauge field. As a
consequence, the excitations for a given integer quantum Hall state are
identical to fractional quantum Hall states in the lowest Landau level having
the same numerator equal to the integer quantum Hall state. Fully and partially
polarized states possess only spin-wave excitations while spin-flip excitations
are possible for all states, irrespective of their polarizations.",9612163v1
2001-09-21,Spin waves in a Bose-condensed atomic spin chain,"The spin dynamics of atomic Bose-Einstein condensates confined in a
one-dimensional optical lattice is studied. The condensates at each lattice
site behave like spin magnets that can interact with each other through both
the light-induced dipole-dipole interaction and the static magnetic
dipole-dipole interaction. We show how these site-to-site dipolar interactions
can distort the ground state spin orientations and lead to the excitation of
spin waves. The dispersion relation of the spin waves is studied and possible
detection schemes are proposed.",0109415v1
2004-04-10,Nuclear Spin-Lattice Relaxation in One-Dimensional Heisenberg Ferrimagnets: Three-Magnon versus Raman Processes,"Nuclear spin-lattice relaxation in one-dimensional Heisenberg ferrimagnets is
studied by means of a modified spin-wave theory. We consider the second-order
process, where a nuclear spin flip induces virtual spin waves which are then
scattered thermally via the four-magnon exchange interaction, as well as the
first-order process, where a nuclear spin directly interacts with spin waves
via the hyperfine interaction. We point out a possibility of the three-magnon
relaxation process predominating over the Raman one and suggest model
experiments.",0404243v2
2007-04-25,Quantized spin excitations in a ferromagnetic microstrip from microwave photovoltage measurements,"Quantized spin excitations in a single ferromagnetic microstrip have been
measured using the microwave photovoltage technique. Several kinds of spin wave
modes due to different contributions of the dipole-dipole and the exchange
interactions are observed. Among them are a series of distinct dipole-exchange
spin wave modes, which allow us to determine precisely the subtle spin boundary
condition. A comprehensive picture for quantized spin excitations in a
ferromagnet with finite size is thereby established. The dispersions of the
quantized spin wave modes have two different branches separated by the
saturation magnetization.",0704.3397v1
2009-07-03,Spin correlations near the surface of a three-dimensional Heisenberg antiferromagnet,"Nearest-neighbor spin correlations are considered near the surface of a
semi-infinite spin-$\frac12$ Heisenberg antiferromagnet on a simple cubic
lattice. In the spin-wave approximation, the excitation spectrum of this model
involves bulk modes -- standing spin waves and a quasi-two-dimensional mode of
surface spin waves. These latter excitations eject the bulk excitations from
the surface region thus dividing the antiferromagnet into two parts with
different excitations. As a result absolute values of the spin correlations
near the surface exceed the bulk value. In the surface region, the pattern of
spin correlations resembles the comb structure recently obtained for the
two-dimensional case.",0907.0532v1
2011-07-06,Spin Seebeck Effect: Amplification of Spin Waves by Thermal Torque,"We observe amplification of spin-wave packets propagating along a film of
yttrium iron garnet (YIG) subject to a transverse temperature gradient. The
amplification is attributed to a spin-transfer thermal torque created by spin
currents generated by means of the spin Seebeck effect that acts on the
magnetization and opposes the relaxation. The experimental data are interpreted
with a simple theoretical model using spin-wave theory that gives an
amplification gain in very good agreement with measurements.",1107.1271v2
2024-02-29,Inertial spin waves in spin spirals,"Inertial effects in spin dynamics emerge on picosecond time scales, giving
rise to nutational excitations at THz frequencies. Here, we describe a general
framework for investigating the precessional and nutational excitations in any
type of spin structure within linear spin-wave theory. We consider the
particular cases of planar and conical spin spirals in detail. We observe a
change in the sign of the curvature of the high-frequency nutational spin-wave
band as the spiral period is decreased when passing from the ferromagnetic to
the antiferromagnetic limit. We identify conditions for the interaction
parameters where the curvature changes sign and asymptotical flat bands are
formed.",2402.19141v1
2010-09-15,Spin-wave interference patterns created by spin-torque nano-oscillators for memory and computation,"Magnetization dynamics in nanomagnets has attracted broad interest since it
was predicted that a dc-current flowing through a thin magnetic layer can
create spin-wave excitations. These excitations are due to spin-momentum
transfer, a transfer of spin angular momentum between conduction electrons and
the background magnetization, that enables new types of information processing.
Here we show how arrays of spin-torque nano-oscillators (STNO) can create
propagating spin-wave interference patterns of use for memory and computation.
Memristic transponders distributed on the thin film respond to threshold tunnel
magnetoresistance (TMR) values thereby detecting the spin-waves and creating
new excitation patterns. We show how groups of transponders create resonant
(reverberating) spin-wave interference patterns that may be used for
polychronous wave computation of arithmetic and boolean functions and
information storage.",1009.4116v1
2013-06-03,Thermodynamics of Ferromagnetic Spin Chains in a Magnetic Field: Impact of the Spin-Wave Interaction,"The thermodynamic properties of ferromagnetic spin chains have been the
subject of many publications. Still, the problem of how the spin-wave
interaction manifest itself in these low-temperature series has been neglected.
Using the method of effective Lagrangians, we explicitly evaluate the partition
function of ferromagnetic spin chains at low temperatures and in the presence
of a magnetic field up to three loops in the perturbative expansion where the
spin-wave interaction sets in. We discuss in detail the renormalization and
numerical evaluation of a particular three-loop graph and derive the
low-temperature series for the free energy density, energy density, heat
capacity, entropy density, as well as the magnetization and the susceptibility.
In the low-temperature expansion for the free energy density, the spin-wave
interaction starts manifesting itself at order $T^{5/2}$. In the pressure, the
coefficient of the $T^{5/2}$-term is positive, indicating that the spin-wave
interaction is repulsive. While it is straightforward to go up to three-loop
order in the effective loop expansion, the analogous calculation on the basis
of conventional condensed matter methods, such as spin-wave theory, appears to
be beyond reach.",1306.0600v1
2018-03-06,Combined Molecular and Spin Dynamics Simulation of BCC Iron with Vacancy Defects,"Utilizing an atomistic computational model which handles both translational
and spin degrees of freedom, combined molecular and spin dynamics simulations
have been performed to investigate the effect of vacancy defects on spin wave
excitations in ferromagnetic iron. Fourier transforms of space and
time-displaced correlation functions yield the dynamic structure factor,
providing characteristic frequencies and lifetimes of the spin wave modes.
Comparison of the system with a 5% vacancy concentration with pure lattice data
shows a decrease in frequency as well as a decrease in lifetime for all
transverse spin wave excitations observed. Additionally, a rugged spin wave
line shape for low-q spin waves indicates the presence of multiple localized
excitations near defect sites resulting in reduced excitation lifetimes due to
increased magnon-magnon scattering. We observe further evidence of increased
magnon-magnon scattering as the peaks in the longitudinal spin wave spectrum
become less distinct.",1803.02468v1
2018-11-28,Rectification of Spin Current in Inversion-Asymmetric Magnets with Linearly-Polarized Electromagnetic Waves,"We theoretically propose a method of rectifying spin current with a
linearly-polarized electromagnetic wave in inversion-asymmetric magnetic
insulators. To demonstrate the proposal, we consider quantum spin chains as a
simple example; these models are mapped to fermion (spinon) models via
Jordan-Wigner transformation. Using a nonlinear response theory, we find that a
dc spin current is generated by the linearly-polarized waves. The spin current
shows rich anisotropic behavior depending on the direction of the
electromagnetic wave. This is a manifestation of the rich interplay between
spins and the waves; inverse Dzyaloshinskii-Moriya, Zeeman, and
magnetostriction couplings lead to different behaviors of the spin current. The
resultant spin current is insensitive to the relaxation time of spinons, a
property of which potentially benefits a long-distance propagation of the spin
current. An estimate of the required electromagnetic wave is given.",1811.11515v1
2018-07-09,Spin wave dynamics in artificial anti spin-ice systems: experimental and theoretical investigations,"Reversed structures of artificial spin-ice systems, where elongated holes
with elliptical shape (antidots) are arranged into a square array with two
orthogonal sublattices, are referred to as anti-squared spin-ice. Using
Brillouin light scattering spectroscopy and plane wave method calculations, we
investigate the spin wave propagation perpendicular to the applied field
direction for two 20 nm thick Permalloy nanostructures which differ by the
presence of single and double elliptical antidots. For the spin waves
propagation along the principal antidot lattice axis, the spectrum consists of
flat bands separated by several frequency gaps which are the effect of spin
wave amplitude confinement in the regions between antidots. Contrarily, for
propagation direction at 45 degrees with respect to the antidot symmetry axis,
straight and narrow channels of propagation are formed, leading to broadening
of bands and closing of the magnonics gaps. Interestingly, in this case, extra
magnonic band gaps occur due to the additional periodicity along this
direction. The width and the position of these gaps depend on the presence of
single or double antidots. In this context, we discuss possibilities for the
tuning of spin wave spectra in anti-squared spin ice structures.",1807.03016v1
2019-03-07,Investigating optically-excited THz standing spin waves using noncollinear magnetic bilayers,"We investigate optically excited THz standing spin waves in noncollinear
magnetic bilayers. Using femtosecond laser-pulse excitation, a spin current is
generated in the first ferromagnetic (FM) layer, and flows through a conductive
spacer layer to be injected into the second (transverse) FM layer, where it
exerts a spin-transfer torque on the magnetization and excites higher-order
standing spin waves. We show that the noncollinear magnetic bilayer is a
convenient tool that allows easy excitation of THz spin waves, and can be used
to investigate the dispersion and thereby the spin wave stiffness parameter in
the thin-film regime. This is experimentally demonstrated using wedge-shaped Co
and CoB (absorption) layers. Furthermore, the damping of these THz spin waves
is investigated, showing a strong increase of the damping with decreasing
absorption layer thickness, much stronger than expected from interface spin
pumping effects. Additionally, a previously unseen sudden decrease in the
damping for the thinnest films is observed. A model for the additional damping
contribution incorporating both these observations is proposed.",1903.02802v1
2014-04-11,Detection and Parameter Estimation of Gravitational Waves from Compact Binary Inspirals with Analytical Double-Precessing Templates,"We study the performance of various analytical frequency-domain templates for
detection and parameter estimation of gravitational waves from spin-precessing,
quasi-circular, compact binary inspirals. We begin by assessing the extent to
which non-spinning, spin-aligned, and the new (analytical, frequency-domain,
small-spin) double-precessing frequency-domain templates can be used to detect
signals from such systems. For effective, dimensionless spin values above
$0.2$, the use of non-spinning or spin-aligned templates for detection purposes
will result in a loss of up to $30%$ of all events, while in the case of the
double-precessing model, this never exceeds $6%$. Moreover, even for signals
from systems with small spins, non-spinning and spin-aligned templates
introduce large biases in the extracted masses and spins. The use of a model
that encodes spin-induced precession effects, such as the double-precessing
model, improves the mass and spin extraction by up to an order of magnitude.
The additional information encoded in the spin-orbit interaction is invaluable
if one wishes to extract the maximum amount of information from gravitational
wave signals.",1404.3180v2
2021-09-12,"Spin excitation spectra in helimagnetic states: proper-screw, cycloid, vortex crystal, and hedgehog lattice","We investigate the spin excitation spectra in chiral and polar magnets by the
linear spin-wave theory for an effective spin model with symmetric and
antisymmetric long-range interactions. In one dimension, we obtain the analytic
form of the dynamical spin structure factor for proper-screw and cycloidal
helical spin states with uniform twists, which shows a gapless mode with strong
intensity at the helical wave number. When introducing spin anisotropy in the
symmetric interactions, we numerically show that the stable spin spirals become
elliptically anisotropic with nonuniform twists and the spin excitation is
gapped. In higher dimensions, we find that similar anisotropy stabilizes
multiple-$Q$ spin states, such as vortex crystals and hedgehog lattices. We
show that the anisotropy in these states manifests itself in the dynamical spin
structure factor: a strong intensity in the transverse components to the wave
number appears only when the helical wave vector and the corresponding easy
axis are perpendicular to each other. Our findings could be useful not only to
identify the spin structure but also to deduce the stabilization mechanism by
inelastic neutron scattering measurements.",2109.05628v2
2020-05-12,Propagation of spin waves through a Néel domain wall,"Spin waves have the potential to be used as a new platform for data transfer
and processing as they can reach wavelengths in the nanometer range and
frequencies in the terahertz range. To realize a spin-wave device, it is
essential to be able to manipulate the amplitude as well as the phase of spin
waves. Several theoretical and recently also experimental works have shown that
the spin-wave phase can be manipulated by the transmission through a domain
wall (DW). Here, we study propagation of spin waves through a DW by means of
micro-focused Brillouin light scattering microscopy ($\mu$BLS). The acquired 2D
spin-wave intensity maps reveal that spin-wave transmission through a N\'eel DW
is influenced by a topologically enforced circular Bloch line in the DW center
and that the propagation regime depends on the spin-wave frequency. In the
first regime, two spin-wave beams propagating around the circular Bloch line
are formed, whereas in the second regime, spin waves propagate in a single
central beam through the circular Bloch line. Phase-resolved $\mu$BLS
measurements reveal a phase shift upon transmission through the domain wall for
both regimes. Micromagnetic modelling of the transmitted spin waves unveils a
distortion of their phase fronts which needs to be taken into account when
interpreting the measurements and designing potential devices. Moreover, we
show, by means of micromagnetic simulations, that an external magnetic field
can be used to move the circular Bloch line within the DW and to manipulate
spin-wave propagation.",2005.05690v2
2020-03-25,Nonreciprocity of spin waves in noncollinear magnets due to the Dzyaloshinskii-Moriya interaction,"Broken inversion symmetry in combination with the spin-orbit interaction
generates a finite Dzyaloshinskii-Moriya interaction (DMI), which can induce
noncollinear spin textures of chiral nature. The DMI is characterized by an
interaction vector whose magnitude, direction and symmetries are crucial to
determine the stability of various spin textures, such as skyrmions and spin
spirals. The DMI can be measured from the nonreciprocity of spin waves in
ferromagnets, which can be probed via inelastic scattering experiments. In a
ferromagnet, the DMI can modify the spin-wave dispersion, moving its minimum
away from the $\Gamma$ point. Spin waves propagating with opposite wavevectors
are then characterized by different group velocities, energies and lifetimes,
defining their nonreciprocity. Here, we address the case of complex spin
textures, where the manifestation of DMI-induced chiral asymmetries remains to
be explored. We discuss such nonreciprocal effects and propose ways of
accessing the magnitude and direction of the DMI vectors in the context of
spin-polarized or spin-resolved inelastic scattering experiments. We show that
only when a periodic magnetic system has finite net magnetization, that is,
when the vector sum of all magnetic moments is nonzero, can it present a total
nonreciprocal spin-wave spectrum. However, even zero-net-magnetization systems,
such as collinear antiferromagnets and cycloidal spin spirals, can have
spin-wave modes that are individually nonreciprocal, while the total spectrum
remains reciprocal.",2003.11649v1
2013-12-11,"Magnonic Band Structure, Complete Bandgap and Collective Spin Wave Excitation in Nanoscale Two--Dimensional Magnonic Crystals","We present the observation of a complete bandgap and collective spin wave
excitation in two-dimensional magnonic crystals comprised of arrays of
nanoscale antidots and nanodots, respectively. Considering that the frequencies
dealt with here fall in the microwave band, these findings can be used for the
development of suitable magnonic metamaterials and spin wave based signal
processing. We also present the application of a numerical procedure, to
compute the dispersion relations of spin waves for any high symmetry direction
in the first Brillouin zone. The results obtained from this procedure has been
reproduced and verified by the well established plane wave method for an
antidot lattice, when magnetization dynamics at antidot boundaries is pinned.
The micromagnetic simulation based method can also be used to obtain
iso--frequency countours of spin waves. Iso--frequency contours are analougous
of the Fermi surfaces and hence, they have the potential to radicalize our
understanding of spin wave dynamics. The physical origin of bands, partial and
full magnonic bandgaps has been explained by plotting the spatial distribution
of spin wave energy spectral density. Although, unfettered by rigid assumptions
and approximations, which afflict most analytical methods used in the study of
spin wave dynamics, micromagnetic simulations tend to be computationally
demanding. Thus, the observation of collective spin wave excitation in the case
of nanodot arrays, which can obviate the need to perform simulations may also
prove to be valuable.",1312.3044v1
2017-07-12,X-Ray Microscopy of Spin Wave Focusing using a Fresnel Zone Plate,"Magnonics, i.e. the artificial manipulation of spin waves, is a flourishing
field of research with many potential uses in data processing within reach.
Apart from the technological applications the possibility to directly influence
and observe these types of waves is of great interest for fundamental research.
Guidance and steering of spin waves has been previously shown and lateral spin
wave confinement has been achieved. However, true spin wave focusing with both
lateral confinement and increase in amplitude has not been shown before. Here,
we show for the first time spin wave focusing by realizing a Fresnel zone plate
type lens. Using x-ray microscopy we are able to directly image the propagation
of spin waves into the nanometer sized focal spot. Furthermore, we observe that
the focal spot can be freely moved in a large area by small variations of the
bias field. Thus, this type of lens provides a steerable intense nanometer
sized spin wave source. Potentially, this could be used to selectively
illuminate magnonic devices like nano oscillators with a steerable spin wave
beam.",1707.03664v1
2017-03-11,Magnonic crystals - prospective structures for shaping spin waves in nanoscale,"We have investigated theoretically band structure of spin waves in magnonic
crystals with periodicity in one-(1D), two- (2D) and three-dimensions (3D). We
have solved Landau-Lifshitz equation with the use of plane wave method, finite
element method in frequency domain and micromagnetic simulations in time domain
to find the dynamics of spin waves and spectrum of their eigenmodes. The spin
wave spectra were calculated in linear approximation. In this paper we show
usefulness of these methods in calculations of various types of spin waves. We
demonstrate the surface character of the Damon-Eshbach spin wave in 1D magnonic
crystals and change of its surface localization with the band number and
wavenumber in the first Brillouin zone. The surface property of the spin wave
excitation is further exploited by covering plate of the magnonic crystal with
conductor. The band structure in 2D magnonic crystals is complex due to
additional spatial inhomogeneity introduced by the demagnetizing field. This
modifies spin wave dispersion, makes the band structure of magnonic crystals
strongly dependent on shape of the inclusions and type of the lattice. The
inhomogeneity of the internal magnetic field becomes unimportant for magnonic
crystals with small lattice constant, where exchange interactions dominate. For
3D magnonic crystals, characterized by small lattice constant, wide magnonic
band gap is found. We show that the spatial distribution of different materials
in magnonic crystals can be explored for tailored effective damping of spin
waves.",1703.04012v1
2017-05-26,Dielectric permeability tensor and linear waves in spin-1/2 quantum kinetics with non-trivial equilibrium spin-distribution functions,"A consideration of waves propagating parallel to the external magnetic field
is presented. The dielectric permeability tensor is derived from quantum
kinetic equations with non-trivial equilibrium spin-distribution functions
(NTESDF) in the linear approximation on amplitude of wave perturbations. In
general case, x- and y-projections of the SDF are nonzero which is called the
non-trivial regime. Corresponding equilibrium solution is found. Contribution
of the NTESDF appears in the dielectric permeability tensor in the additive
form. It is explicitly found here. Corresponding modification in the dispersion
equation for the transverse waves is derived. Contribution of NTESDF in the
spectrum of transverse waves is calculated numerically. It is found that the
term caused by the NTESDF can be comparable with the classic terms for the
relatively small wave vectors and frequencies above the cyclotron frequency. In
majority of regimes, the extra spin caused term dominates over the spin term
found earlier, except the small frequency regime, where their contributions in
the whistler spectrum are comparable. A decrease of the left-hand circularly
polarized wave frequency, an increase of the high-frequency right-hand
circularly polarized wave frequency, and a decrease of frequency changing by an
increase of frequency at the growth of the wave vector for the whistler are
found. A dramatic decrease of the spin wave frequency resulting in several
times larger group velocity of the spin wave is found either. Found dispersion
equations are used for obtaining of an effective quantum hydrodynamics
reproducing these results. This generalization requires the introduction of
corresponding equation of state for the thermal part of the spin current in the
spin evolution equation.",1705.09738v1
2022-03-21,Scattering of spin waves by a Bloch domain wall: effect of the dipolar interaction,"It is known that a Bloch domain wall in an anisotropic ferromagnet is
transparent to spin waves. This result is derived by approximating the dipolar
interaction between magnetic moments by an effective anisotropy interaction. In
this paper we study the the scattering of spin waves by a domain wall taking
into account the full complexity of the dipolar interaction, treating it
perturbatively in the distorted wave Born approximation. Due to the
peculiarities of the dipolar interaction, the implementation of this
approximation is not straightforward. The difficulties are circumvented here by
realizing that the contribution of the dipolar interaction to the spin wave
operator can be split into two terms: i) an operator that commutes with the
spin wave operator in absence of dipolar interaction, and ii) a local operator
suitable to be treated as a perturbation in the distorted wave Born
approximaton. We analyze the scattering parameters obtained within this
approach. It turns out that the reflection coefficient does not vanish in
general, and that the transmitted waves suffer a lateral shift even at normal
incidence. This lateral shift can be greatlty enhanced by making the spin wave
go through an array of well separated domain walls. The outgoing spin wave will
no be attenuated by the scattering at the domain walls since the reflection
coefficient vanishes at normal incidence. This effect may be very useful to
control the spin waves in magnonic devices.",2203.11140v1
2018-08-08,Observation of acoustic spin,"Unlike optical waves, acoustic waves in fluids are described by scalar
pressure fields, and therefore are considered spinless. Here, we demonstrate
experimentally the existence of spin in acoustics. In the interference of two
acoustic waves propagating perpendicularly to each other, we observed the spin
angular momentum in free space as a result of the rotation of local particle
velocity. We successfully measured the acoustic spin, and spin induced torque
acting on a lossy acoustic meta-atom that results from absorption of the spin
angular momentum. The acoustic spin is also observed in the evanescent field of
a guided mode traveling along a metamaterial waveguide. We found spin-momentum
locking in acoustic waves whose propagation direction is determined by the sign
of spin. The observed acoustic spin could open a new door in acoustics and
their applications for the control of wave propagation and particle rotation.",1808.03686v1
2016-03-17,Spin wave amplification using the spin Hall effect in permalloy/platinum bilayers,"We investigate the effect of an electrical current on the attenuation length
of a 900 nm wavelength spin-wave in a permalloy/Pt bilayer using propagating
spin-wave spectroscopy. The modification of the spin-wave relaxation rate is
linear in current density, reaching up to 14% for a current density of
2.3$\times10^{11} $A/m$^2$ in Pt. This change is attributed to the spin
transfer torque induced by the spin Hall effect and corresponds to an effective
spin Hall angle of 0.13, which is among the highest values reported so far. The
spin Hall effect thus appears as an efficient way of amplifying/attenuating
propagating spin waves.",1603.05478v1
2019-12-03,Spin-orbit torque-mediated spin-wave excitation as an alternative paradigm for femtomagnetism,"Laser-induced femtosecond demagnetization, femtomagnetism, offers a potential
route to develop faster magnetic storage devices. It is generally believed that
the traditional spin-wave theory, which is developed for thermally driven slow
demagnetization, can not explain this rapid demagnetization by design. Here we
show that this traditional spin-wave theory, once augmented by laser-induced
spin-orbit torque, provides a highly efficient paradigm for demagnetization, by
capturing low-energy spin-wave excitation that is absent in existing
mechanisms. Our paradigm is different from existing ones, but does not exclude
them. Microscopically, we find that optical spin-orbit torque generates massive
spin waves across several hundred lattice sites, collapsing the long-range
spin-spin correlation within 20 fs. Our finding does not only explain new
experiments, but also establishes an alternative paradigm for femtomagnetism.
It is expected to have far-reaching impacts on future research.",1912.01736v1
2005-07-01,Spin-orbit coupling and spin transport,"Recent achievements in semiconductor spintronics are discussed. Special
attention is paid to spin-orbit interaction, coupling of electron spins to
external electric fields, and spin transport in media with spin-orbit coupling,
including the mechanisms of spin-Hall effect. Importance of spin-transport
parameters at spin-precession wave vector $k_{\rm so}$ is emphasized, and
existence of an universal relation between spin currents and spin accumulation
at the spatial scale of $\ell_{\rm so}\approx k_{\rm so}^{-1}$ is conjectured.",0507007v2
2018-04-10,Measuring the properties of nearly extremal black holes with gravitational waves,"Characterizing the properties of black holes is one of the most important
science objectives for gravitational-wave observations. Astrophysical evidence
suggests that black holes that are nearly extremal (i.e. spins near the
theoretical upper limit) might exist and thus might be among the merging black
holes observed with gravitational waves. In this paper, we explore how well
current gravitational wave parameter estimation methods can measure the spins
of rapidly spinning black holes in binaries. We simulate gravitational-wave
signals using numerical-relativity waveforms for nearly-extremal, merging black
holes. For simplicity, we confine our attention to binaries with spins parallel
or antiparallel with the orbital angular momentum. We find that recovering the
holes' nearly extremal spins is challenging. When the spins are nearly extremal
and parallel to each other, the resulting parameter estimates do recover spins
that are large, though the recovered spin magnitudes are still significantly
smaller than the true spin magnitudes. When the spins are nearly extremal and
antiparallel to each other, the resulting parameter estimates recover the small
effective spin but incorrectly estimate the individual spins as nearly zero. We
study the effect of spin priors and argue that a commonly used prior (uniform
in spin magnitude and direction) hinders unbiased recovery of large black-hole
spins.",1804.03704v2
2011-07-13,Two-Dimensional Propagation of a Photoinduced Spin Wave Packet,"We report the two-dimensional propagation of photoinduced spin wave packets
in Bi-doped rare-earth iron garnet. Spin waves were excited nonthermally and
impulsively by a circularly polarized light pulse via the inverse Faraday
effect. Space- and time resolved spin waves were detected with a
magneto-optical pump-probe technique. We investigated propagation in two
directions, parallel and perpendicular to the magnetic field. Backward volume
magnetostatic waves (BVMSWs) were detected in both directions. The frequency of
BVMSWs depends on the propagation direction. The experimental results agreed
well with the dispersion relation of BVMSWs.",1107.2457v1
2013-11-18,Antiferromagnetic Domain Wall Motion Induced by Spin Waves,"Spin waves in antiferromagnets are linearly or circularly polarized.
Depending on the polarization, traversing spin waves alter the staggered field
in a qualitatively different way. We calculate the drift velocity of a moving
domain wall as a result of spin wave mediated forces, and show that the domain
wall moves in opposite directions for linearly and circularly polarized waves.
The analytical results agree with a micromagnetics simulation of an
antiferromagnetic domain wall driven by a localized and alternating magnetic
field.",1311.4328v2
2015-09-09,Spin wave vortex from the scattering on Bloch point solitons,"The interaction of a spin wave with a stationary Bloch point is studied. The
topological non-trivial structure of the Bloch point manifests in the
propagation of spin waves endowing them with a gauge potential that resembles
the one associated with the interaction of a magnetic monopole and an electron.
By pursuing this analogy, we are led to the conclusion that the scattering of
spin waves and Bloch points is accompanied by the creation of a magnon vortex.
Interference between such a vortex and a plane wave leads to dislocations in
the interference pattern that can be measurable by means of magnon holography.",1509.02891v1
2021-03-15,Magnetically switchable spin wave retarder with $90^\circ$ antiferromagnetic domain wall,"Polarization, denoting the precession direction with respect to the
background magnetization, is an intrinsic degree of freedom of spin wave. Using
magnetic textures to control the spin wave polarization is fundamental and
indispensable toward reprogrammable polarization-based magnonics. Here, we show
that due to the intrinsic cubic anisotropy, a $90^\circ$ antiferromagnetic
domain wall naturally acts as a spin wave retarder (wave-plate). Moreover, for
a $90^\circ$ domain wall pair developed by introducing a second domain in a
homogenous antiferromagnetic wire, the sign of retarding effect can be flipped
by simply switching the direction of the intermediate domain.",2103.08342v2
2021-07-12,Spin wave driven domain wall motion in easy-plane ferromagnets: a particle perspective,"In easy-plane ferromagnets, we show that the interplay between a domain wall
and a spin wave packet can be formulated as the collision of two massive
particles with a gravity-like attraction. In the presence of magnetic
dissipation, the domain wall mimics a particle subject to viscous friction,
while the spin wave packet resembles a particle of variable mass. Due to
attractive nature of the interaction, the domain wall acquires a backward
displacement as a spin wave packet penetrating the domain wall, even though
there is no change in momentum of the wave packet before and after penetration.",2107.05401v2
2023-01-05,Universal scaling between wave speed and size enables nanoscale high-performance reservoir computing based on propagating spin-waves,"Neuromorphic computing using spin waves is promising for high-speed nanoscale
devices, but the realization of high performance has not yet been achieved.
Here we show, using micromagnetic simulations and simplified theory with
response functions, that spin-wave physical reservoir computing can achieve
miniaturization down to nanoscales keeping high computational power comparable
with other state-of-art systems. We also show the scaling of system sizes with
the propagation speed of spin waves plays a key role to achieve high
performance at nanoscales.",2301.02193v1
2015-07-10,Fractionalized spin-wave continuum in spin liquid states on the kagome lattice,"Motivated by spin-wave continuum (SWC) observed in recent neutron scattering
experiments in Herbertsmithite, we use Gutzwiller-projected wave functions to
study dynamic spin structure factor $S(\mathbf{q},\omega)$ of spin liquid
states on the kagome lattice. Spin-1 excited states in spin liquids are
represented by Gutzwiller-projected two-spinon excited wave functions. We
investigate three different spin liquid candidates, spinon Fermi-surface spin
liquid (FSL), Dirac spin liquid (DSL) and random-flux spin liquid (RSL). FSL
and RSL have low energy peaks in $S(\mathbf{q},\omega)$ at $K$ points in the
extended magnetic Brillouin zone, in contrast to experiments where low energy
peaks are found at $M$ points. There is no obviuos contradiction between DSL
and neutron scattering measurements. Besides a fractionalized spin (i.e.
spin-1/2), spinons in DSL carry a fractionalized crystal momentum which is
potentially detectable in SWC in the neutron scattering measurements.",1507.03007v1
2019-04-29,Unconventional spin currents in magnetic films,"A spin current - a flow of spin angular momentum - can be carried either by
spin polarised free electrons or by magnons, the quanta of a moving collective
oscillation of localised electron spins - a spin wave. Traditionally, it was
assumed, that a spin wave in a magnetic film with spin-sink-free surfaces can
transfer energy and angular momentum only along its propagation direction. In
this work, using Brillouin light scattering spectroscopy in combination with a
theory of dipole-exchange spin-wave spectra, we show that in obliquely
magnetized free magnetic films the in-plane propagation of spin waves is
accompanied by a transverse spin current along the film normal without any
corresponding transverse transport of energy.",1904.12610v1
2002-02-14,Effects of Charge Ordering on Spin-Wave of Quarter-Filled Spin-Density-Wave States,"Spin-wave excitations of quarter-filled spin-density-wave state, which
coexists with charge ordering, have been studied for one-dimensional extended
Hubbard model with the nearest-neighbor repulsive interaction (V) and
next-nearest-neighbor one (V_2). We calculate dispersion relations for the
acoustic and optical spin-wave within the random phase approximation. Our
numerical calculation shows that energy spectrum of the acoustic branch is well
described by a simple sine function form. In the states coexisting with
charge-density-wave, the spin-wave velocity decreases with increasing V or V_2.
Our numerical result, that velocity reduces to zero in the limit of large V or
V_2, is analyzed in terms of a spin 1/2 Heisenberg model with effective
antiferromagnetic exchange interaction.",0202227v2
2005-01-28,Spin waves in paramagnetic BCC iron: spin dynamics simulations,"Large scale computer simulations are used to elucidate a longstanding
controversy regarding the existence, or otherwise, of spin waves in
paramagnetic BCC iron. Spin dynamics simulations of the dynamic structure
factor of a Heisenberg model of Fe with first principles interactions reveal
that well defined peaks persist far above Curie temperature T_c. At large wave
vectors these peaks can be ascribed to propagating spin waves, at small wave
vectors the peaks correspond to over-damped spin waves. Paradoxically, spin
wave excitations exist despite only limited magnetic short-range order at and
above T_c.",0501713v1
2007-10-15,"Model for a collimated spin wave beam generated by a single layer, spin torque nanocontact","A model of spin torque induced magnetization dynamics based upon
semi-classical spin diffusion theory for a single layer nanocontact is
presented. The model incorporates effects due to the current induced Oersted
field and predicts the generation of a variety of spatially dependent,
coherent, precessional magnetic wave structures. Directionally controllable
collimated spin wave beams, vortex spiral waves, and localized standing waves
are found to be excited by the interplay of the Oersted field and the
orientation of an applied field. These fields act as a spin wave ``corral''
around the nanocontact that controls the propagation of spin waves in certain
directions.",0710.2890v3
2008-10-30,A Three-Terminal Spin-Wave Device for Logic Applications,"We demonstrate a three-terminal spin wave-based device utilizing spin wave
interference. The device consists of three coplanar transmission lines
inductively coupled to the 100nm thick CoFe film. Two spin wave signals are
excited by microwave fields produced by electric current in two sets of lines,
and the output signal is detected by the third set. The initial phases of the
spin wave signals are controlled by the direction of the current flow in the
excitation set of lines. Experimental data show prominent output signal
modulation as a function of the relative phase (in-phase and out-of phase) of
two input signals. The micrometer scale device operates in the GHz frequency
range and at room temperature. Our experimental results show that spin-wave
devices exploiting spin wave interference may be scaled to micrometer and
nanometer scales for potential logic circuit application.",0810.5589v1
2017-11-24,Antiferromagnetic domain wall motion driven by polarized spin waves,"The control of magnetic domain walls is essential for the magnetic-based
memory and logic applications. As an elementary excitation of magnetic order,
spin wave is capable of moving magnetic domain walls just as the conducting
electric current. Ferromagnetic spin waves can only be right-circularly
polarized. In contrast, antiferromagnetic spin waves have full polarization
degree of freedom, including both left- and right-circular polarizations, as
well as all possible linear or elliptical ones. Here we demonstrate that, due
to the Dzyaloshinskii-Moriya interaction, the spin wave driven domain wall
motion in antiferromagnets strongly depends on the linear polarization
direction of the injected spin waves. Steering domain wall motion by simply
tuning the polarization of spin waves offers new designing principles for
domain-wall based information processing devices.",1711.08929v1
2017-11-28,Spin-wave propagation in the presence of inhomogeneous Dzyaloshinskii-Moriya interactions,"We theoretically investigate spin-wave propagation through a magnetic
metamaterial with spatially modulated Dzyaloshinskii-Moriya interaction. We
establish an effective Sch{\""o}dinger equation for spin-waves and derive
boundary conditions for spin-waves passing through the boundary between two
regions having different Dzyaloshinskii-Moriya interactions. Based on these
boundary conditions, we find that the spin-wave can be amplified at the
boundary and the spin-wave bandgap is tunable either by an external magnetic
field or the strength of Dzyaloshinskii-Moriya interaction, which offers a
spin-wave analogue of the field-effect transistor in traditional electronics.",1711.10082v1
2018-12-20,Unidirectional spin-wave channeling along magnetic domain walls of Bloch type,"From the pioneering work of Winter [Phys. Rev. 124, 452 (1961)], a magnetic
domain wall of Bloch type is known to host a special wall-bound spin-wave mode,
which corresponds to spin-waves being channeled along the magnetic texture.
Using micromagnetic simulations, we investigate spin-waves travelling inside
Bloch walls formed in thin magnetic media with perpendicular-to-plane magnetic
anisotropy and we show that their propagation is actually strongly
nonreciprocal, as a result of dynamic dipolar interactions. We investigate
spin-wave non-reciprocity effects in single Bloch walls, which allows us to
clearly pinpoint their origin, as well as in arrays of parallel walls in stripe
domain configurations. For such arrays, a complex domain-wall-bound spin-wave
band structure develops, some aspects of which can be understood qualitatively
from the single-wall picture by considering that a wall array consists of a
sequence of up/down and down/up walls with opposite non-reciprocities.
Circumstances are identified in which the non-reciprocity is so extreme that
spin-wave propagation inside individual walls becomes unidirectional.",1812.08741v1
2017-06-06,Antiferromagnetic Domain Wall as Spin Wave Polarizer and Retarder,"As a collective quasiparticle excitation of the magnetic order in magnetic
materials, spin wave, or magnon when quantized, can propagate in both
conducting and insulating materials. Like the manipulation of its optical
counterpart, the ability to manipulate spin wave polarization is not only
important but also fundamental for magnonics. With only one type of magnetic
lattice, ferromagnets can only accommodate the right-handed circularly
polarized spin wave modes, which leaves no freedom for polarization
manipulation. In contrast, antiferromagnets, with two opposite magnetic
sublattices, have both left and right circular polarizations, and all linear
and elliptical polarizations. Here we demonstrate theoretically and confirm by
micromagnetic simulations that, in the presence of Dzyaloshinskii-Moriya
interaction, an antiferromagnetic domain wall acts naturally as a spin wave
polarizer or a spin wave retarder (waveplate). Our findings provide extremely
simple yet flexible routes toward magnonic information processing by harnessing
the polarization degree of freedom of spin wave.",1706.01617v1
2017-06-30,Spin-wave propagation in cubic anisotropic materials,"The information carrier of modern technologies is the electron charge whose
transport inevitably generates Joule heating. Spin-waves, the collective
precessional motion of electron spins, do not involve moving charges and thus
avoid Joule heating. In this respect, magnonic devices in which the information
is carried by spin-waves attract interest for low-power computing. However
implementation of magnonic devices for practical use suffers from low spin-wave
signal and on/off ratio. Here we demonstrate that cubic anisotropic materials
can enhance spin-wave signals by improving spin-wave amplitude as well as group
velocity and attenuation length. Furthermore, cubic anisotropic material shows
an enhanced on/off ratio through a laterally localized edge mode, which closely
mimics the gate-controlled conducting channel in traditional field-effect
transistors. These attractive features of cubic anisotropic materials will
invigorate magnonics research towards wave-based functional devices.",1706.10057v1
2019-03-03,Goos-Hanchen Shift of a Spin-Wave Beam at the Interface Between Two Ferromagnets,"Spin waves are promising information carriers which can be used in modern
magnonic devices, characterized by higher performance and lower energy
consumption than presently used electronic circuits. However, before practical
application of spin waves, the efficient control over spin wave amplitude and
phase needs to be developed. We analyze analytically reflection and refraction
of the spin waves at the interface between two ferromagnetic materials. In the
model we consider the system consisting of two semi-infinite ferromagnetic
media, separated by the ultra-narrow interface region with the magnetic
anisotropy. We have found the Goos-Hanchen shift for spin waves in transmission
and reflection, and performed detailed investigations of its dependence on the
anisotropy at the interface and materials surrounding the interface. We have
demonstrated possibility of obtaining Goos-Hanchen shift of several wavelengths
in reflection for realistic material parameters. That proves the possibility
for change of the spin waves phase in ferromagnetic materials at subwavelength
distances, which can be regarded as a metasurface for magnonics.",1903.00861v1
2019-04-25,Controlled interconversion of quantized spin wave modes via local magnetic fields,"In the emerging field of magnonics, spin waves are considered for information
processing and transmission at high frequencies. Towards this end, the
manipulation of propagating spin waves in nanostructured waveguides for novel
functionality has recently been attracting increasing focus of research.
Excitations with uniform magnetic fields in such waveguides favors symmetric
spin wave modes with odd quantization numbers. Interference between multiple
odd spin wave modes leads to a periodic self-focusing effect of the propagating
spin waves. Here we demonstrate, how antisymmetric spin wave modes with even
quantization numbers can be induced by local magnetic fields in a
well-controlled fashion. The resulting interference patterns are discussed
within an analytical model and experimentally demonstrated using microfocused
Brillouin light scattering ({\mu}-BLS).",1904.11613v1
2020-05-06,Observation of evanescent spin waves in the magnetic dipole regime,"We observed spin-wave transmission through an air gap that works as a
prohibited region. The spin waves were excited by circularly polarized pump
pulses via the inverse Faraday effect, and their spatial propagation was
detected through the Faraday effect of probe pulses using a pump-probe imaging
technique. The experimentally observed spin-wave transmission was reproduced
using numerical calculations with a Green's function method and micromagnetic
simulation. We found that the amplitude of the spin waves decays exponentially
in the air gap, which indicates the existence of evanescent spin waves in the
magnetic dipole regime. This finding will pave the way for controllable
amplitudes and phases of spin waves propagating through an artificial magnonic
crystal.",2005.02559v1
2020-07-06,Hippopede curves for modelling radial spin waves in an azimuthal graded magnonic landscape,"We propose a mathematical model for describing radially propagating spin
waves emitted from the core region in a magnetic patch with n vertices in a
magnetic vortex state. The azimuthal anisotropic propagation of surface spin
waves (SSW) into the domain, and confined spin waves (or Winter's Magnons, WM)
in domain walls increases the complexity of the magnonic landscape. In order to
understand the spin wave propagation in these systems, we first use an approach
based on geometrical curves called 'hippopedes', however it provides no insight
into the underlying physics. Analytical models rely on generalized expressions
from the dispersion relation of SSW with an arbitrary angle between
magnetization M and wavenumber k. The derived algebraic expression for the
azimuthal dispersion is found to be equivalent to that of the 'hippopede'
curves. The fitting curves from the model yield a spin wave wavelength for any
given azimuthal direction, number of patch vertices and excitation frequency,
showing a connection with fundamental physics of exchange dominated surface
spin waves. Analytical results show good agreement with micromagnetic
simulations and can be easily extrapolated to any n-corner patch geometry.",2007.02646v2
2021-01-28,Electrical spin-wave spectroscopy in nanoscale waveguides with nonuniform magnetization,"Spin waves modes in magnetic waveguides with width down to 320 nm have been
studied by electrical propagating spin-wave spectroscopy and micromagnetic
simulations for both longitudinal and transverse magnetic bias fields. For
longitudinal bias fields, a 1.3 GHz wide spin-wave band was observed in
agreement with analytical dispersion relations for uniform magnetization.
However, transverse bias field led to several distinct bands, corresponding to
different quantized width modes, with both negative and positive slopes.
Micromagnetic simulations showed that, in this geometry, the magnetization was
nonuniform and tilted due to the strong shape anisotropy of the waveguides.
Simulations of the quantized spin-wave modes in such nonuniformly magnetized
waveguides resulted in spin wave dispersion relations in good agreement with
the experiments.",2101.11983v2
2023-06-08,Unidirectionality of spin waves in Synthetic Antiferromagnets,"We study the frequency non-reciprocity of the spin waves in symmetric
CoFeB/Ru/CoFeB synthetic antiferromagnets stacks set in the scissors state by
in-plane applied fields. Using a combination of Brillouin Light Scattering and
propagating spin wave spectroscopy experiments, we show that the acoustical
spin waves in synthetic antiferromagnets possess a unique feature if their
wavevector is parallel to the applied field: the frequency non-reciprocity due
to layer-to-layer dipolar interactions can be so large that the acoustical spin
waves transfer energy in a unidirectional manner for a wide and bipolar
interval of wavevectors. Analytical modeling and full micromagnetic
calculations are conducted to account for the dispersion relations of the
optical and acoustical spin waves for arbitrary field orientations. Our
formalism provides a simple and direct method to understand and design devices
harnessing unidirectional propagation of spin waves in synthetic
antiferromagnets.",2306.05259v2
2023-07-24,Unidirectional spin wave emission by travelling pair of magnetic field profiles,"We demonstrate that the spin wave Cherenkov effect can be used to design the
unidirectional spin wave emitter with tunable frequency and switchable
direction of emission. In our numerical studies, we propose to use a pair of
traveling profiles of the magnetic field which generate the spin waves, for
sufficiently large velocity of their motion. In the considered system, the spin
waves of shorter (longer) wavelengths are induced at the front (back) of the
moving profiles and interfere constructively or destructively, depending on the
velocity of the profiles. Moreover, we showed that the spin waves can be
confined between the pair of traveling profiles of the magnetic field. This
work opens the perspectives for the experimental studies in hybrid
magnonic-superconducting systems where the magnetic vortices in a
superconductor can be used as moving sources of the magnetic field driving the
spin waves in the ferromagnetic subsystem.",2307.12653v2
1998-12-16,Elementary excitations of magnetically ordered systems with orbital degeneracy,"The Holstein-Primakoff transformation is generalized to develop a quantum
flavor wave theory for spin systems with orbital degeneracy. Elementary
excitations consist of spin, orbital, and spin-orbital waves. Spin and
spin-orbital waves couple each other due to orbital anisotropy and Hund's rule,
resulting in new modes observable by inelastic neutron scattering. In the SU(4)
limit, flavor waves are dispersionless along one or more directions, and give
rise to quantum fluctuations of reduced dimensionality.",9812289v1
1999-09-02,Orbital Polarization and Fluctuation in Manganese Oxides,"In a form which include the mother compound, we studied the extended
Hubbard-type model with the orbital degeneracy for any doping concentration.
Meanfield phase diagram and the spin wave excitation in RPA are calculated. It
turned out that a large orbital polarization is essential to reproduce the
magnetic phases depending on the doping concentration. Base on this result, we
discuss the spin canting, the spin wave dispersion, and spin wave stiffness
from the standing point of the large orbital polarization. We also discuss the
orbital fluctuation which turned out to be important in the ferromagnetic
metallic region where the CMR is observed. Spin wave softening near the zone
boundary is also discussed in this context.",9909023v1
2000-05-09,Spin-Waves in itinerant ferromagnets,"We introduce a novel approach for the investigation of spin-wave excitations
in itinerant ferromagnets. Our theory is based on a variational treatment of
general multi-band Hubbard models which describe elements and compounds of
transition metals. The magnon dispersion is derived approximately as the energy
of a variational spin-wave state in the limit of large spatial dimensions. A
numerical evaluation of our results is feasible for general multi-band models.
As a first application we consider a model with two degenerate orbitals per
lattice site. From our results we can conclude that spin-wave excitations in
strong itinerant ferromagnets are very similar to those in ferromagnetic spin
systems.",0005154v1
2002-07-26,Spin Wave Response in the Dilute Quasi-one Dimensional Ising-like Antiferromagnet CsCo_{0.83}Mg_{0.17}Br_3,"Inelastic neutron scattering profiles of spin waves in the dilute
quasi-one-dimensional Ising-like antiferromagnet CsCo_{0.83}Mg_{0.17}Br_3 have
been investigated. Calculations of S^{xx}(Q,omega), based on an effective spin
Hamiltonian, accurately describe the experimental spin wave spectrum of the 2J
mode. The Q dependence of the energy of this spin wave mode follows the
analytical prediction
omega_{xx}(Q)=(2J)(1-5epsilon^{2}cos^{2}Qa+2epsilon^{2})^{1/2}, calculated by
Ishimura and Shiba using perturbation theory.",0207638v1
2005-08-07,Circular Polarization and Quantum Spin: A Unified Real-Space Picture of Photons and Electrons,"A classical circularly polarized electromagnetic wave carries angular
momentum, and represents the classical limit of a photon, which carries
quantized spin. It is shown that a very similar picture of a circularly
polarized coherent wave can account for both the spin of an electron and its
quantum wave function, in a Lorentz-invariant fashion. The photon-electron
interaction occurs through the usual electromagnetic potentials, modulating the
frequency and wavevector (energy and momentum) of this rotating spin field.
Other quantum particles can also be represented either as rotating spin fields,
or as composites of such fields. Taken together, this picture suggests an
alternative interpretation of quantum mechanics based solely on coherent wave
packets, with no point particles present.",0508064v1
2010-08-26,Localized collapse and revival of coherence in an ultracold Bose gas,"We study the collapse and revival of coherence induced by dipolar spin waves
in a trapped gas of Rb-87 atoms. In particular we observe spatially localized
collapse and revival of Ramsey fringe contrast and show how the pattern of
coherence depends on strength of the spin wave excitation. We find that the
spatial character of the coherence dynamics is incompatible with a simple model
based only on position-space overlap of wave functions. This phenomenon
requires a full phase-space description of the atomic spin using a quantum
Boltzmann transport equation, which highlights spin wave-induced coherent spin
currents and the ensuing dynamics they drive.",1008.4428v1
2014-07-01,Spin waves and spin instabilities in quantum plasmas,"We describe main ideas of method of many-particle quantum hydrodynamics
allows to derive equations for description of quantum plasma evolution. We also
present definitions of collective quantum variables suitable for quantum
plasmas. We show that evolution of magnetic moments (spins) in quantum plasmas
leads to several new branches of wave dispersion: spin-electromagnetic plasma
waves and self-consistent spin waves. Propagation of neutron beams through
quantum plasmas is also considered. Instabilities appearing due to interaction
of magnetic moments of neutrons with plasma are described.",1407.0355v1
2015-11-25,Topological spin waves in the atomic-scale magnetic skyrmion crystal,"We study the spin waves of the triangular skyrmion crystal that emerges in a
two dimensional spin lattice model as a result of the competition between
Heisenberg exchange, Dzyalonshinkii-Moriya interactions, Zeeman coupling and
uniaxial anisotropy. The calculated spin wave bands have a finite Berry
curvature that, in some cases, leads to non-zero Chern numbers, making this
system topologically distinct from conventional magnonic systems. We compute
the edge spin-waves, expected from the bulk-boundary correspondence principle,
and show that they are chiral, which makes them immune to elastic
backscattering. Our results illustrate how topological phases can occur in
self-generated emergent superlattices at the mesoscale.",1511.08244v1
2012-09-09,Neutron Brillouin scattering with pulsed spallation neutron source - spin-wave excitations from ferromagnetic powder samples -,"Neutron Brillouin scattering (NBS) method was developed using a pulsed
spallation neutron source, and the feasibility of NBS was demonstrated by
observing ferromagnetic spin waves in La$_{0.8}$Sr$_{0.2}$MnO$_3$ and SrRuO$_3$
powders. Gapless spin-wave excitations were observed in
La$_{0.8}$Sr$_{0.2}$MnO$_3$, which were continuously extended to the lower
scattering vector $Q$ from previous results using single crystals. The novel
result is a well-defined quadratic $Q$ dependence in the spin-wave dispersion
curve with a large energy gap in SrRuO$_3$ indicating robust spin-orbit
coupling.",1209.1780v1
2018-12-18,Magnetic excitations in frustrated fcc type-III antiferromagnet MnS$_2$,"Spin wave dispersion in the frustrated fcc type-III antiferromagnet MnS$_2$
has been determined by inelastic neutron scattering using a triple-axis
spectrometer. Existence of multiple spin wave branches, with significant
separation between high-energy and low-energy modes highlighting the intrinsic
magnetic frustration effect on the fcc lattice, is explained in terms of a spin
wave analysis carried out for the antiferromagnetic Heisenberg model for this
$S=5/2$ system with nearest and next-nearest-neighbor exchange interactions.
Comparison of the calculated dispersion with spin wave measurement also reveals
small suppression of magnetic frustration resulting from reduced exchange
interaction between frustrated spins, possibly arising from anisotropic
deformation of the cubic structure.",1812.07267v1
2019-05-29,Spin wave propagation in ferrimagnetic $Gd_{x}Co_{1-x}$,"Recent advances in antiferromagnetic spin dynamics using rare-earth (RE) and
transition-metal (TM) ferrimagnets have attracted much interest for spintronic
devices with a high speed and density. In this study, the spin wave properties
in the magnetostatic backward volume mode and surface mode in RE-TM
ferrimagnetic $Gd_{x}Co_{1-x}$ films with various composition x are
investigated using spin wave spectroscopy. The obtained group velocity and
attenuation length are well explained by the ferromagnet-based spin wave theory
when the composition of $Gd_{x}Co_{1-x}$ is far from the compensation point.",1905.12771v1
2017-01-20,Asymmetric Spin-wave Dispersion on Fe(110): Direct Evidence of Dzyaloshinskii--Moriya Interaction,"The influence of the Dzyaloshinskii-Moriya interaction on the spin-wave
dispersion in an Fe double layer grown on W(110) is measured for the first
time. It is demonstrated that the Dzyaloshinskii-Moriya interaction breaks the
degeneracy of spin waves and leads to an asymmetric spin-wave dispersion
relation. An extended Heisenberg spin Hamiltonian is employed to obtain the
longitudinal component of the Dzyaloshinskii-Moriya vectors from the
experimentally measured energy asymmetry.",1701.05854v1
2022-02-23,Nonlinear Coupling of Electromagnetic and Spin-Electron-Acoustic Waves in Spin-polarized Degenerate Relativistic Astrophysical Plasma,"Propagation of the finite amplitude electromagnetic wave through the
partially spin-polarized degenerate plasmas leads to the instability. The
instability happens at the interaction of the electromagnetic wave with the
small frequency longitudinal spin-electron-acoustic waves. Strongest
instability happens in the high density degenerate plasmas with the Fermi
momentum close to $m_{e}c$, where $m_{e}$ is the mass of electron, and $c$ is
the speed of light. The increase of the increment of instability with the
growth of the spin polarization of plasmas is found.",2202.11814v1
2022-12-02,Interplay between spin wave and magnetic vortex,"In this paper, the interplay between spin wave and magnetic vortex is
studied. We find three types of magnon scatterings: skew scattering, symmetric
side deflection and back reflection, which associate with respectively magnetic
topology, energy density distribution and linear momentum transfer torque
within vortex. The vortex core exhibits two translational modes: the intrinsic
circular mode and a coercive elliptical mode, which can be excited based on
permanent and periodic magnon spin-transfer torque effects of spin wave.
Lastly, we propose a vortex-based spin wave valve in which via inhomogeneity
modulation we access arbitrary control of the phase shift.",2212.01172v1
2008-01-31,Cosmological black hole spin evolution by mergers and accretion,"Using recent results from numerical relativity simulations of black hole
mergers, we revisit previous studies of cosmological black hole spin evolution.
We show that mergers are very unlikely to yield large spins, unless alignment
of the spins of the merging holes with the orbital angular momentum is very
efficient. We analyze the spin evolution in three specific scenarios: (1) spin
evolves only through mergers, (2) spin evolves through mergers and prolonged
accretion episodes, (3) spin evolves through mergers and short-lived (chaotic)
accretion episodes. We study how different diagnostics can distinguish between
these evolutionary scenarios, assessing the discriminating power of
gravitational-wave measurements and X-ray spectroscopy. Gravitational radiation
can produce three different types of spin measurements, yielding respectively
the spins of the two black holes in a binary inspiral prior to merger, the spin
of the merger remnant (as encoded in the ringdown waves), and the spin of
``single'' black holes during the extreme mass-ratio inspiral (EMRI) of compact
objects. The latter spin population is also accessible to iron-line
measurements. We compute and compare the spin distributions relevant for these
different observations. If iron-line measurements and gravitational-wave
observations of EMRIs only yield dimensionless spins j=J/M^2>0.9, then
prolonged accretion should be responsible for spin-up, and chaotic accretion
scenarios would be very unlikely. If only a fraction of the whole population of
low-redshift black holes spins rapidly, spin-alignment during binary mergers
(rather than prolonged accretion) could be responsible for spin-ups.",0802.0025v2
2012-08-27,Photo-magnonics,"In the framework of magnonics all-optical femtosecond laser experiments are
used to study spin waves and their relaxation paths. Magnonic crystal
structures based on antidots allow the control over the spin-wave modes. In
these two-dimensional magnetic metamaterials with periodicities in the
wave-length range of dipolar spin waves the spin-wave bands and dispersion are
modified. Hence, a specific selection of spin-wave modes excited by laser
pulses is possible. Different to photonics, the modes depend strongly on the
strength of the magneto-static potential at around each antidot site - the
dipolar field. While this may lead to a mode localization, also for filling
fractions around or below 10%, Bloch states are found in low damping
ferromagnetic metals. In this chapter, an overview of these mechanisms is given
and the connection to spin-wave band spectra calculated from an analytical
model is established. Namely, the plane-wave method yields flattened bands as
well as band gaps at the antidot lattice Brillouin zone boundary.",1208.5383v1
2013-08-02,Extraordinary momentum and spin in evanescent waves,"Momentum and spin represent fundamental dynamical properties of quantum
particles and fields. In particular, propagating optical waves (photons) carry
momentum and longitudinal spin determined by the wave vector and circular
polarization, respectively. Here we show that exactly the opposite can be the
case for evanescent optical waves. A single evanescent wave possesses a spin
component, which is independent of the polarization and is orthogonal to the
wave vector. Furthermore, such a wave carries a momentum component, which is
determined by the circular polarization and is also orthogonal to the wave
vector. We show that these extraordinary properties reveal a fundamental
Belinfante's spin momentum, known in field theory and unobservable in
propagating fields. We demonstrate that the transverse momentum and spin push
and twist a probe Mie particle in an evanescent field. This allows the
observation of `impossible' properties of light and of a fundamental
field-theory quantity, which was previously considered as `virtual'.",1308.0547v3
2014-03-21,Interface boundary conditions for dynamic magnetization and spin wave dynamics in a ferromagnetic layer with the interface Dzyaloshinskii-Moriya interaction,"In this work we derive the interface exchange boundary conditions for the
classical linear dynamics of magnetization in ferromagnetic layers with the
interface Dzyaloshinskii-Moriya interaction (IDMI). We show that IDMI leads to
pinning of dynamic magnetization at the interface. An unusual peculiarity of
the IDMI-based pinning is that its scales as the spin-wave wave number. We
incorporate these boundary conditions into an existing numerical model for the
dynamics of the Damon-Eshbach spin wave in ferromagnetic films. IDMI affects
the dispersion and the frequency non-reciprocity of the traveling Damon-Eshbach
spin wave. For a broad range of film thicknesses L and wave numbers the results
of the numerical simulations of the spin wave dispersion are in a good
agreement with a simple analytical expression which shows that the contribution
of IDMI to the dispersion scales as 1/L, similarly to the effect of other types
of interfacial anisotropy. Suggestions to experimentalists how to detect the
presence of IDMI in a spin wave experiment are given.",1403.5385v4
2019-03-19,Broadband magnetoelastic coupling in magphonic crystals for high-frequency nanoscale spin wave generation,"Spin waves are promising candidates for information carriers in advanced
technology. The interactions between spin waves and acoustic waves in magnetic
nanostructures are of much interest because of their potential application for
spin wave generation, amplification and transduction. We investigate
numerically the dynamics of magnetoelastic excitations in a one-dimensional
magphonic crystal consisting of alternating layers of permalloy and cobalt. We
use the plane wave method and the finite element method for frequency- and
time-domain simulations, respectively. The studied structure is optimized for
hybridization of specific spin-wave and acoustic dispersion branches in the
entire Brillouin zone in a broad frequency range. We show that this type of
periodic structure can be used for efficient generation of high-frequency spin
waves.",1903.08024v1
2021-02-24,Spin waves and high-frequency response in layered superconductors with helical magnetic structure,"We evaluate the spin-wave spectrum and dynamic susceptibility in a layered
superconductors with helical interlayer magnetic structure. We especially focus
on the structure in which the moments rotate 90$^{\circ}$ from layer to layer
realized in the iron pnictide RbEuFe$_{4}$As$_{4}$. The spin-wave spectrum in
superconductors is strongly renormalized due to the long-range electromagnetic
interactions between the oscillating magnetic moments. This leads to strong
enhancement of the frequency of the mode coupled with uniform field and this
enhancement exists only within a narrow range of the c-axis wave vectors of the
order of the inverse London penetration depth. The key feature of materials
like RbEuFe$_{4}$As$_{4}$ is that this uniform mode corresponds to the maximum
frequency of the spin-wave spectrum with respect to c-axis wave vector. As a
consequence, the high-frequency surface resistance acquires a very distinct
asymmetric feature spreading between the bare and renormalized frequencies. We
also consider excitation of spin waves with Josephson effect in a tunneling
contact between helical-magnetic and conventional superconductors and study the
interplay between the spin-wave features and geometrical cavity resonances in
the current-voltage characteristics.",2102.12445v2
2019-01-30,Optimizing propagating spin wave spectroscopy,"The frequency difference between two oppositely propagating spin waves can be
used to probe several interesting magnetic properties, such as the
Dzyaloshinkii-Moriya interaction (DMI). Propagating spin wave spectroscopy is a
technique that is very sensitive to this frequency difference. Here we show
several elements that are important to optimize devices for such a measurement.
We demonstrate that for wide magnetic strips there is a need for de-embedding.
Additionally, for these wide strips there is a large parasitic antenna-antenna
coupling that obfuscates any spin wave transmission signal, which is remedied
by moving to smaller strips. The conventional antenna design excites spin waves
with two different wave vectors. As the magnetic layers become thinner, the
resulting resonances move closer together and become very difficult to
disentangle. In the last part we therefore propose and verify a new antenna
design that excites spin waves with only one wave vector. We suggest to use
this antenna design to measure the DMI in thin magnetic layers.",1901.11108v1
2020-12-08,Nanoscale neural network using non-linear spin-wave interference,"We demonstrate the design of a neural network, where all neuromorphic
computing functions, including signal routing and nonlinear activation are
performed by spin-wave propagation and interference. Weights and
interconnections of the network are realized by a magnetic field pattern that
is applied on the spin-wave propagating substrate and scatters the spin waves.
The interference of the scattered waves creates a mapping between the wave
sources and detectors. Training the neural network is equivalent to finding the
field pattern that realizes the desired input-output mapping. A custom-built
micromagnetic solver, based on the Pytorch machine learning framework, is used
to inverse-design the scatterer. We show that the behavior of spin waves
transitions from linear to nonlinear interference at high intensities and that
its computational power greatly increases in the nonlinear regime. We envision
small-scale, compact and low-power neural networks that perform their entire
function in the spin-wave domain.",2012.04594v1
2016-05-10,Controlling Spin-Polarization in Graphene by Cloaking Magnetic and Spin-Orbit Scatterers,"We consider spin-dependent scatterers with large scattering cross-sections in
graphene -a Zeeman-like and an intrinsic spin-orbit coupling impurity- and show
that a gated ring around them can be engineered to produce an effcient control
of the spin dependent transport, like current spin polarization and spin Hall
angle. Our analysis is based on a spin-dependent partial-waves expansion of the
electronic wave-functions in the continuum approximation, described by the
Dirac equation.",1605.02814v2
2009-08-04,Non-equilibrium Spin Waves in Paramagnetic Metals,"We theoretically study the effect of exchange interaction on the
non-equilibrium spin waves in disordered paramagnetic metals under the spin
injection condition. We show that the gapless spectrum of spin waves,
describing the spin precession in the absence of the applied magnetic field,
changes sign to negative on the paramagnetic side near the ferromagnet -
paramagnet phase transition. The damping of spin waves is small in the limit
when electron-electron exchange energy is larger than the inverse electron mean
free time, while in the opposite limit the propagation of spin waves is
strongly suppressed. We discuss the amplification of the electromagnetic field
by the non-equilibrium spin waves.",0908.0466v2
2016-02-12,Internal dipolar field and soft magnons in periodic nanocomposite magnets,"We study spin wave excitations in a three-dimensional nanocomposite magnet of
exchange coupled hard (SmCo$_5$) and soft (FeCo) phases. The dipolar
interaction splits the spin wave energies into the upper and lower branches of
the spin wave manifold. When the amount of the soft phase is increased the
energy of low-lying spin excitations is considerably softened due to two
reasons: (i) the low- lying mode locked into the soft phase region with a spin
wave gap at ${\bf k}= 0$ which scales approximately proportional to the
anisotropy constant of the soft phase and (ii) the internal dipolar field which
comes from magnetic charges forming at hard-soft boundaries with normals
parallel to the magnetization displaces the spin wave manifold toward the lower
energies. With adding more soft phase the spin wave gap closes and the system
moves to another ground state characterized by the magnetization mismatch
between spins of the hard and soft phases.",1602.04111v1
2017-12-22,Nanomagnonic waveguides based on reconfigurable spin-textures for spin computing,"Magnonics is gaining momentum as an emerging technology for information
processing. The wave character and Joule heating-free propagation of spin-waves
hold promises for highly efficient analog computing platforms, based on
integrated magnonic circuits. Miniaturization is a key issue but, so far, only
few examples of manipulation of spin-waves in nanostructures have been
demonstrated, due to the difficulty of tailoring the nanoscopic magnetic
properties with conventional fabrication techniques. In this Letter, we
demonstrate an unprecedented degree of control in the manipulation of
spin-waves at the nanoscale by using patterned reconfigurable spin-textures. By
space and time-resolved scanning transmission X-ray microscopy imaging, we
provide direct evidence for the channeling and steering of propagating
spin-waves in arbitrarily shaped nanomagnonic waveguides based on patterned
domain walls, with no need for external magnetic fields or currents.
Furthermore, we demonstrate a prototypic nanomagnonic circuit based on two
converging waveguides, allowing for the tunable spatial superposition and
interaction of confined spin-waves modes.",1712.08293v1
2018-05-03,Sculpting the Spin-Wave Response of Artificial Spin Ice via Microstate Selection,"The spin-wave dynamics of the ferromagnetic nanoarrays termed artificial spin
ice (ASI) are known to vary depending on their magnetic microstate. However,
little work has been done to characterise this relationship. Recent advances in
control over the magnetic configuration of ASI bring designs harnessing the
interplay between spin-wave eigenmodes and the microstate within reach,
offering diverse applications including reconfigurable magnonic crystals,
microwave filters and microstate read-out probes. These designs hinge on a
strong understanding of the underlying spin wave-microstate correspondence.
  Here, we analyse the effects of the magnetic microstate on spin-wave spectra
of honeycomb ASI systems via micromagnetic simulation. We find the spin-wave
spectrum to be highly-tunable via the microstate to an enhanced degree relative
to existing magnonic crystals, with mode shifting and (de)activation realised
by reversing individual nanoislands. Symmetries of ASI systems and the
chirality of magnetic defects are found to play important roles in determining
the high-frequency response.",1805.01397v3
2020-08-07,Spin wave excitations in exchange biased IrMn/CoFe bilayers,"Using an atomistic spin model, we have simulated spin wave injection and
propagation into antiferromagnetic IrMn from an exchange coupled CoFe layer.
The spectral characteristics of the exited spin waves have a complex beating
behavior arising from the non-collinear nature of the antiferromagnetic order.
We find that the frequency response of the system depends strongly on the
strength and frequency of oscillating field excitations. We also find that the
strength of excited spin waves strongly decays away from the interfacial layer
with a frequency dependent attenuation. Our findings suggest that spin waves
generated by coupled ferromagnets are too weak to reverse IrMn in their
entirety even with resonant excitation of a coupled ferromagnet. However,
efficient spin wave injection into the antiferromagnet is possible due to the
non-collinear nature of the IrMn spin ordering.",2008.03036v1
2021-04-21,Spin-wave driven bidirectional domain wall motion in kagome antiferromagnets,"We predict a mechanism to controllably manipulate domain walls in kagome
antiferromagnets via a single linearly polarized spin-wave source. We show by
means of atomistic spin dynamics simulations of antiferromagnets with kagome
structure that the speed and direction of the domain wall motion can be
regulated by only tuning the frequency of the applied spin-wave. Starting from
microscopics, we establish an effective action and derive the corresponding
equations of motion for the spin-wave-driven domain wall. Our analytical
calculations reveal that the coupling of two spin-wave modes inside the domain
wall explains the frequency-dependent velocity of the spin texture. Such a
highly tunable spin-wave-induced domain wall motion provides a key component
toward next-generation fast, energy-efficient, and Joule-heating-free
antiferromagnetic insulator devices.",2104.10460v2
2006-09-11,Spin Waves in Ultrathin Ferromagnets: Intermediate Wave Vectors,"Our earlier papers explore the nature of large wave vector spin waves in
ultrathin ferromagnets, and also the properties and damping of spin waves of
zero wave vector, at the center of the two dimensional Brillouin zone, with
application to FMR studies. The present paper explores the behavior of spin
waves in such films at intermediate wave vectors, which connect the two
regimes. For the case of Fe films on Au(100), we study the wave vector
dependence of the linewidth of the lowest frequency mode, to find that it
contains a term which varies as the fourth power of the wave vector. It is
argued that this behavior is expected quite generally. We also explore the
nature of the eigenvectors of the two lowest lying modes of the film, as a
function of wave vector. Interestingly, as wave vector increases, the lowest
mode localizes onto the interface between the film and the substrate, while the
second mode evolves into a surface spin wave, localized on the outer layer. We
infer similar behavior for a Co film on Cu(100), though this evolution occurs
at rather larger wave vectors where, as we have shown previously, the modes are
heavily damped with the consequence that identification of distinct eigenmodes
is problematical.",0609236v1
2017-06-29,Reconfigurable topological spin wave beamsplitters and interferometers,"Conventional magnonic devices use three classes of magnetostatic waves that
require detailed manipulation of magnetization structure that makes the design
and the device/circuitry scalability difficult tasks. Here, we demonstrate that
devices based on topological exchange spin waves do not suffer from the problem
with additional nice features of nano-scale wavelength and high frequency. Two
results are reported. 1) A perpendicular ferromagnet on a honeycomb lattice is
generically a topological magnetic material in the sense that topologically
protected chiral edge spin waves exist in the band gap as long as spin-orbit
induced nearest-neighbor pseudodipolar interaction (and/or next-nearest
neighbor Dzyaloshinskii-Moriya interaction) is present. 2) As a proof of
concept, spin wave beamsplitters and spin wave interferometers are designed by
using domain walls to manipulate the propagation of topologically protected
chiral spin waves. Since magnetic domain walls can be controlled by magnetic
fields or electric current/fields, one can essentially draw, erase and redraw
different spin wave devices and circuitry on the same magnetic plate so that
the proposed devices are reconfigurable and tunable. Devices made from magnetic
topological materials are robust against both internal and external
perturbations such as the spin wave frequency variation and device geometry as
well as defects.",1706.09548v2
2019-10-29,Multi-Layer Restricted Boltzmann Machine Representation of 1D Quantum Many-Body Wave Functions,"We consider representing two classes of 1D quantum wave functions of spin
systems, including the AKLT and CFT correlator wave functions, in terms of
multi-layer restricted Boltzmann machines. In our prescription, the AKLT wave
function can be exactly represented by a 2-layer restricted Boltzmann machine
with five hidden spins per visible spin. The construction can be generalized to
prove that any MPS wave function on $N$ unit cells with finite bond dimension
can be approximated by a 2-layer restricted Boltzmann machine with
$\mathcal{O}(N)$ hidden spins within an error which scales linearly with $N$.
The Haldane-Shastry wave function or a chiral boson CFT correlator wave
function, as any Jastrow type of wave functions, can be exactly written as a
1-layer Boltzmann machine with $\mathcal{O}(N^2)$ hidden spins and $N$ visible
spins. Applying the cumulant expansion, we further find that the chiral boson
CFT correlator wave function (with small vertex operator conformal dimension
$\alpha$, i.e., $\alpha<0.1$) can be approximated, within 99.9\% accuracy up to
22 visible spins, by a 1-layer RBM with $\mathcal{O}(N)$ hidden spins. The
cumulant expansion also leads us to a physically inspiring result in which the
hidden spins of the restricted Boltzmann machine can be interpreted as the
conformal tower of the chiral boson CFT on the cylinder.",1910.13454v1
2021-06-21,Local non-linear excitation of sub-100 nm bulk-type spin waves by edge-localized spin waves in magnetic films,"The excitation of high-frequency short-wavelength spin waves is a challenge
limiting the application of these propagating magnetization disturbances in
information processing systems. We propose a method of local excitation of the
high-frequency spin waves using the non-linear nature of magnetization
dynamics. We demonstrate with numeric simulations that an edge-localized spin
wave can be used to excite plane waves propagating obliquely from the film's
edge at a doubled frequency and over twice shorter in wavelength. The
excitation mechanism is a direct result of the ellipticity of the magnetic
moments precession that is related to the edge-mode propagation. As a
consequence, the magnetization component tangential to the equilibrium
orientation oscillates with doubled temporal and spatial frequencies, which
leads to efficient excitation of the plane spin waves. Threshold-less
non-linear process of short-wavelength spin-wave excitation proposed in our
study is promising for integration with an inductive or point-like spin-torque
source of edge spin waves.",2106.11114v1
2000-02-11,Coexistent State of Charge Density Wave and Spin Density Wave in One-Dimensional Quarter Filled Band Systems under Magnetic Fields,"We theoretically study how the coexistent state of the charge density wave
and the spin density wave in the one-dimensional quarter filled band is
enhanced by magnetic fields. We found that when the correlation between
electrons is strong the spin density wave state is suppressed under high
magnetic fields, whereas the charge density wave state still remains. This will
be observed in experiments such as the X-ray measurement.",0002165v3
2021-08-11,Charge density waves in multiple-$Q$ spin states,"Coupling between spin and charge degrees of freedom in electrons is a source
of various electronic and magnetic properties of solids. We theoretically study
charge density waves induced by the spin-charge coupling in the presence of
magnetic orderings in itinerant magnets. By performing a perturbative
calculation in the weak-coupling limit of the Kondo lattice model, we derive a
useful formula for the relationship between charge and spin density waves,
which can be applied to any magnetic orderings, including noncollinear and
noncoplanar ones composed of multiple spin density waves called multiple-$Q$
magnetic orderings. We demonstrate the predictive power for single-$Q$ and
double-$Q$ states including skyrmion and meron-antimeron crystals on a square
lattice, in comparison with the numerical calculations. Moreover, we show that
the charge density waves contain richer information than the spin density
waves, and are indeed useful in distinguishing the spin textures with similar
spin structure factors. We discuss the relation to bond modulation in terms of
the kinetic bond energy and the vector spin chirality. We also perform
numerical calculations beyond the perturbative regime and find that the charge
density waves can be enhanced when the electron filling is commensurate.
Furthermore, we investigate the effect of the spin-orbit coupling, which can
lead to additional charge density waves owing to effective anisotropic magnetic
interactions in momentum space. Our result will provide a way to identify
complex magnetic orderings and their origins from the charge modulations.",2108.04997v2
2007-03-17,Large-amplitude coherent spin waves exited by spin-polarized current in nanoscale spin valves,"We present spectral measurements of spin-wave excitations driven by direct
spinpolarized current in the free layer of nanoscale
Ir20Mn80/Ni80Fe20/Cu/Ni80Fe20 spin valves. The measurements reveal that
large-amplitude coherent spin wave modes are excited over a wide range of bias
current. The frequency of these excitations exhibits a series of jumps as a
function of current due to transitions between different localized nonlinear
spin wave modes of the Ni80Fe20 nanomagnet. We find that micromagnetic
simulations employing the Landau-Lifshitz-Gilbert equation of motion augmented
by the Slonczewski spin torque term (LLGS) accurately describe the frequency of
the current-driven excitations including the mode transition behavior. However
LLGS simulations give qualitatively incorrect predictions for the amplitude of
excited spin waves as a function of current.",0703458v2
2010-08-21,Dynamical Corrections to Spin Wave Excitations in Quantum Wells due to Coulomb Interactions and Magnetic Ions,"We have measured dispersions of spin-flip waves and spin-flip single-particle
excitations of a spin polarized two-dimensional electron gas in a CdMnTe
quantum well using resonant Raman scattering. We find the energy of the
spin-flip wave to be below the spin-flip single particle excitation continuum,
a contradiction to the theory of spin waves in diluted magnetic semiconductors
put forth in [Phys. Rev. B 70, 045205 (2004)]. We show that the inclusion of
terms accounting for the Coulomb interaction between carriers in the spin wave
propagator leads to an agreement with our experimental results. The dominant
Coulomb contribution leads to an overall red shift of the mixed electron-Mn
spin modes while the dynamical coupling between Mn ions results in a small blue
shift. We provide a simulated model system which shows the reverse situation
but at an extremely large magnetic field.",1008.3663v1
2011-04-04,Electric Control of Spin Currents and Spin-Wave Logic,"Spin waves in insulating magnets are ideal carriers for spin currents with
low energy dissipation. An electric field can modify the dispersion of spin
waves, by directly affecting, via spin-orbit coupling, the electrons that
mediate the interaction between magnetic ions. Our microscopic calculations
based on the super-exchange model indicate that this effect of the electric
field is sufficiently large to be used to effectively control spin currents. We
apply these findings to the design of a spin-wave interferometric device, which
acts as a logic inverter and can be used as a building block for
room-temperature, low-dissipation logic circuits.",1104.0657v2
2020-12-23,Topological spin-plasma waves,"The surface of a topological insulator hosts Dirac electronic states with the
spin-momentum locking, which constrains spin orientation perpendicular to
electron momentum. As a result, collective plasma excitations in the
interacting Dirac liquid manifest themselves as coupled charge- and spin-waves.
Here we demonstrate that the presence of the spin component enables effective
coupling between plasma waves and spin waves at interfaces between the surface
of a topological insulator and insulating magnet. Moreover, the helical nature
of spin-momentum locking textures provides the phase winding in the coupling
between the spin and plasma waves that makes the spectrum of hybridized
spin-plasma modes to be topologically nontrivial. We also show that such
topological modes lead to a large thermal Hall response.",2012.12632v2
2002-03-15,Modified spin-wave study of random antiferromagnetic-ferromagnetic spin chains,"We study the thermodynamics of one-dimensional quantum spin-1/2 Heisenberg
ferromagnetic system with random antiferromagnetic impurity bonds. In the
dilute impurity limit, we generalize the modified spin-wave theory for random
spin chains, where local chemical potentials for spin-waves in ferromagnetic
spin segments are introduced to ensure zero magnetization at finite
temperature. This approach successfully describes the crossover from behavior
of pure one-dimensional ferromagnet at high temperatures to a distinct Curie
behavior due to randomness at low temperatures. We discuss the effects of
impurity bond strength and concentration on the crossover and low temperature
behavior.",0203326v1
2003-10-20,Spin wave spectrum of a disordered double exchange model,"A double exchange model with quenched disorder for conduction electrons is
studied by field theoretical methods. By using a path integral formalism and
replica techniques based on it, an ensemble-averaged spin wave dispersion of
the localized spins is derived. It is shown that the spectrum of the spin wave
has gaps at the multiple of the Fermi wavenumber of the conduction electrons in
the presence of disorder, and hence, quenched disorder for electrons adds a
striking effect to the dynamics of the localized spins. In the strong disorder
limit, the present results suggest spin-glass like behavior due to the
frustration of the exchange coupling.",0310446v1
2005-12-24,Modified spin-wave theory of nuclear magnetic relaxation in one-dimensional quantum ferrimagnets: Three-magnon versus Raman processes,"Nuclear spin-lattice relaxation in one-dimensional Heisenberg ferrimagnets is
studied by means of a modified spin-wave theory. Calculating beyond the
first-order mechanism, where a nuclear spin directly interacts with spin waves
through the hyperfine coupling, we demonstrate that the
exchange-scattering-enhanced three-magnon nuclear relaxation may generally
predominate over the Raman one with increasing temperature and decreasing
field. Recent proton spin-lattice relaxation-time (T_1_) measurements on the
ferrimagnetic chain compound NiCu(C_7_H_6_N_2_O_6_)(H_2_O)_3_2H_2_O suggest
that the major contribution to 1/T_1_ be made by the three-magnon scattering.",0512629v1
2006-01-24,MnO Spin-Wave Dispersion Curves from Powder Diffraction Data,"We describe a model-independent approach for the extraction of spin-wave
dispersion curves from neutron total scattering data. The method utilises a
statistical analysis of real-space spin configurations to calculate
spin-dynamical quantities. The RMCProfile implementation of the reverse Monte
Carlo refinement process is used to generate a large ensemble of supercell spin
configurations from powder diffraction data. Our analysis of these
configurations gives spin-wave dispersion curves that agree well with those
determined independently using neutron triple-axis spectroscopic techniques.",0601558v2
2009-01-01,Generation of GHZ and W states for stationary qubits in spin network via resonance scattering,"We propose a simple scheme to establish entanglement among stationary qubits
based on the mechanism of resonance scattering between them and a
single-spin-flip wave packet in designed spin network. It is found that through
the natural dynamical evolution of an incident single-spin-flip wave packet in
a spin network and the subsequent measurement of the output single-spin-flip
wave packet,multipartite entangled states among n stationary qubits,
Greenberger-Horne-Zeilinger (GHZ) and W states can be generated.",0901.0161v2
2016-05-26,Spin gravitational resonance and graviton detection,"We develop a gravitational analogue of spin magnetic resonance, called spin
gravitational resonance, whereby a gravitational wave interacts with a magnetic
field to produce a spin transition. In particular, an external magnetic field
separates the energy spin states of a spin-1/2 particle, and the presence of
the gravitational wave produces a perturbation in the components of the
magnetic field orthogonal to the gravitational wave propagation. In this
framework we test Dyson's conjecture that individual gravitons cannot be
detected. Although we find no fundamental laws preventing single gravitons
being detected with spin gravitational resonance, we show that it cannot be
used in practice, in support of Dyson's conjecture.",1605.08316v1
2008-06-24,Spin dynamics in point contacts to single ferromagnetic films,"Excitation of magnons or spin-waves driven by nominally unpolarized transport
currents in point contacts of normal and ferromagnetic metals is probed by
irradiating the contacts with microwaves. Two characteristic dynamic effects
are observed: a rectification of off-resonance microwave current by spin-wave
nonlinearities in the point contact conductance, and a resonant stimulation of
spin-wave modes in the nano-contact core by the microwave field. These
observations provide a direct evidence that the magnetoconductance effects
observed are due to GHz spin dynamics at the ferromagnetic interface driven by
the spin transfer torque effect of the transport current.",0806.3805v1
2024-03-20,Electron wave spin in a cavity,"Our study reveals electron spin in a cavity as a stable circulating current
density, characterized by a torus topology. This current density circulates
concentrically beyond the cavity boundary, illustrating the concept of
evanescent wave spin. While the interaction with a uniform magnetic field
aligns with established spin-field observations, our analysis of regional
contributions deviates from particle-based spin predictions. The integration of
charge and spin properties into a single Lorentz covariant entity suggests that
the electron wave constitutes the fundamental and deterministic reality of the
electron.",2403.13696v1
1995-08-21,Standing Spin Wave Resonances in Manganite Films,"We report the first observation of spin wave resonances in 110 nm thick films
of LBMO. The spin wave stiffness follows $D$ = 47 (1 - 3 \times 10$_{-7}$
$T^{5/2}$) meV${\AA_2}$.",9508088v1
1997-07-29,Spin Wave Instability of Itinerant Ferromagnet,"We show variationally that instability of the ferromagnetic state in the
Hubbard model is largely controlled by softening of a long-wavelength spin-wave
excitation, except in the over-doped strong-coupling region where the
individual-particle excitation becomes unstable first. A similar conclusion is
drawn also for the double exchange ferromagnet. Generally the spin-wave
instability may be regarded as a precursor of the metal-insulator transition.",9707300v1
2002-04-09,Spatial resolution of spin waves in an ultra-cold gas,"We present the first spatially resolved images of spin waves in a gas. The
complete longitudinal and transverse spin field as a function of time and space
is reconstructed. Frequencies and damping rates for a standing-wave mode are
extracted and compared with theory.",0204182v1
2005-05-15,Spin Charge Recombination in Projected Wave Functions,"We find spin charge recombination is a generic feature of projected wave
functions. We find this effect is responsible for a series of differences
between mean field theory prediction and the result from projected wave
functions. We also find spin charge recombination plays an important role in
determining the dissipation of supercurrent, the quasiparticle properties and
the hole - hole correlation.",0505369v1
2017-04-20,Coupled mode theory for the acoustic wave and spin wave interaction in the magphonic crystals: Propagating magnetoelastic waves,"We have investigated co-directional and contra-directional couplings between
spin wave and acoustic wave in one-dimensional periodic structure (magphonic
crystal). The system consists of two ferromagnetic layers alternating in space.
We have taken into consideration materials commonly used in magnonics: yttrium
iron garnet, CoFeB, permalloy, and cobalt. The coupled mode theory (CMT)
formalism have been successfully implemented to describe magnetoelastic
interaction as a periodic perturbation in the magphonic crystal. The results of
CMT calculations have been verified by more rigorous simulations by
frequency-domain plane wave method and time-domain finite element method. The
presented resonant coupling in the magphonic crystal is an active in-space
mechanism which spatially transfers energy between propagating spin and
acoustic modes, thus creating propagating magnetoelastic wave. We have shown,
that CMT analysis of the magnetoelastic coupling is an useful tool to optimize
and design a spin wave - acoustic wave transducer based on a magphonic
crystals. The effect of spin wave damping has been included to the model to
discuss the efficiency of such a device. Our model shows that it is possible to
obtain forward conversion of the acoustic wave to the spin wave in case of
co-directional coupling and backward conversion in case of contra-directional
coupling.",1704.06118v1
2014-05-04,Separated spin-up and spin-down quantum hydrodynamics of degenerated electrons: spin-electron acoustic wave appearance,"Quantum hydrodynamic (QHD) model of charged spin-1/2 particles contains
physical quantities defined for all particles of a species including particles
with spin-up and with spin-down. Different population of states with different
spin direction is included in the spin density (magnetization). In this paper
we derive a QHD model, which separately describes spin-up electrons and
spin-down electrons. Hence we consider electrons with different projection of
spin on the preferable direction as two different species of particles. We show
that numbers of particles with different spin direction do not conserve. Hence
the continuity equations contain sources of particles. These sources are caused
by the interactions of spins with magnetic field. Terms of similar nature arise
in the Euler equation. We have that z-projection of the spin density is no
longer an independent variable. It is proportional to difference between
concentrations of electrons with spin-up and electrons with spin-down. In terms
of new model we consider propagation of waves in magnetized plasmas of
degenerate electrons and motionless ions. We show that new form of QHD
equations gives all solutions obtained from traditional form of QHD equations
with no distinguish of spin-up and spin-down states. But it also reveals a
sound-like solution we call the spin-electron acoustic wave. Coincidence of
most solutions is expected since we started derivation with the same basic
equation.",1405.0719v1
2004-04-21,Four-Wave Mixing In BEC Systems With Multiple Spin States,"We calculate the four-wave mixing (FWM) in a Bose-Einstein condensate system
having multiple spin wave packets that are initially overlapping in physical
space, but have nonvanishing relative momentum that cause them to recede from
one another. Three receding condensate atom wave packets can result in
production of a fourth wave packet by the process of FWM due to atom-atom
interactions. We consider cases where the four final wave packets are composed
of 1, 2, 3 and 4 different internal spin components. FWM with 1- or 2-spin
state wave packets is much stronger than 3- or 4-spin state FWM, wherein two of
the coherent moving BEC wave packets form a polarization-grating that rotates
the spin projection of the third wave into that of fourth diffracted wave (as
opposed to the 1- or 2-spin state case where a regular density-grating is
responsible for the diffraction). Calculations of FWM for $^{87}$Rb and
$^{23}$Na condensate systems are presented.",0404499v1
2000-02-14,Spin-flux phase in the Kondo lattice model with classical localized spins,"We provide numerical evidence that a spin-flux phase exists as a ground state
of the Kondo lattice model with classical local spins on a square lattice. This
state manifests itself as a double-Q magnetic order in the classical spins with
spin density at both $(0,\pi)$ and $(\pi,0)$ and further exhibits fermionic
spin currents around an elementary plaquette of the square lattice. We examine
the spin-wave spectrum of this phase. We further discus an extension to a face
centered cubic (FCC) lattice where a spin-flux phase may also exist. On the FCC
lattice the spin-flux phase manifests itself as a triple-Q magnetically ordered
state and may exist in $\gamma$-Mn alloys.",0002211v1
2001-05-09,The Contribution of Hot Electron Spin Polarization to the Magnetotransport in a Spin-Valve Transistor at Finite Temperatures,"The effect of spin mixing due to thermal spin waves and temperature
dependence of hot electron spin polarization to the collector current in a
spin-valve transistor has been theoretically explored. We calculate the
collector current as well as the temperature dependence of magnetocurrent at
finite temperatures to investigate the relative importance of spin mixing and
hot electron spin polarization. In this study the inelastic scattering events
in ferromagnetic layers have been taken into account to explore our interests.
The theoretical calculations suggest that the temperature dependence of hot
electron spin polarization has substantial contribution to the magnetotransport
in the spin-valve transistor.",0105182v1
2007-01-31,Coupled spin-charge drift-diffusion approach for a two-dimensional electron gas with Rashba spin-orbit coupling,"Based on kinetic equations for the density matrix, drift-diffusion equations
are derived for a two-dimensional electron gas with Rashba spin-orbit coupling.
Universal results are obtained for the weak coupling case. Most interesting is
the observation that with increasing spin-orbit coupling strengths there is a
sharp transition between spin diffusion and ballistic spin transport. For
strong spin-orbit coupling, when the elastic scattering time is much larger
than the spin relaxation time, undamped spin-coherent waves are identified. The
existence of these long-lived spin-coherent states is confirmed by exact
analytical results obtained from microscopic kinetic equations valid in the
ballistic regime.",0701782v1
2009-04-13,Semiclassical spin transport in spin-orbit-coupled systems,"This article discusses spin transport in systems with spin-orbit interactions
and how it can be understood in a semiclassical picture. I will first present a
semiclassical wave-packet description of spin transport, which explains how the
microscopic motion of carriers gives rise to a spin current. Due to spin
non-conservation the definition of the spin current has some arbitrariness. In
the second part I will briefly review the physics from a density matrix point
of view, which makes clear the relationship between spin transport and spin
precession and the important role of scattering.",0904.1999v1
2017-08-01,Gravitational Wave Searches for Aligned-Spin Binary Neutron Stars Using Nonspinning Templates,"We study gravitational wave searches for merging binary neutron stars (NSs).
We use nonspinning template waveforms towards the signals emitted from
aligned-spin NS-NS binaries, in which the spins of the NSs are aligned with the
orbital angular momentum. We use the TaylorF2 waveform model, which can
generate inspiral waveforms emitted from aligned-spin compact binaries. We
employ the single effective spin parameter $\chi_{\rm eff}$ to represent the
effect of two component spins ($\chi_1, \chi_2$) on the wave function. For a
target system, we choose a binary consisting of the same component masses of
$1.4 M_{\odot}$ and consider the spins up to $\chi_i= 0.4$, We investigate
fitting factors of the nonspinning templates to evaluate their efficiency in
gravitational wave searches for the aligned-spin NS-NS binaries. We find that
the templates can achieve the fitting factors exceeding $0.97$ only for the
signals in the range of $-0.2 \lesssim \chi_{\rm eff} \lesssim 0$. Therefore,
we demonstrate the necessity of using aligned-spin templates not to lose the
signals outside that range. We also show how much the recovered total mass can
be biased from the true value depending on the spin of the signal.",1708.00426v1
2016-12-13,Spin precession and spin waves in a chiral electron gas: beyond Larmor's theorem,"Larmor's theorem holds for magnetic systems that are invariant under spin
rotation. In the presence of spin-orbit coupling this invariance is lost and
Larmor's theorem is broken: for systems of interacting electrons, this gives
rise to a subtle interplay between the spin-orbit coupling acting on individual
single-particle states and Coulomb many-body effects. We consider a
quasi-two-dimensional, partially spin-polarized electron gas in a semiconductor
quantum well in the presence of Rashba and Dresselhaus spin-orbit coupling.
Using a linear-response approach based on time-dependent density-functional
theory, we calculate the dispersions of spin-flip waves. We obtain analytic
results for small wave vectors and up to second order in the Rashba and
Dresselhaus coupling strengths $\alpha$ and $\beta$. Comparison with
experimental data from inelastic light scattering allows us to extract $\alpha$
and $\beta$ as well as the spin-wave stiffness very accurately. We find
significant deviations from the local density approximation for spin-dependent
electron systems.",1612.04314v1
1997-10-09,Alternating-Spin Ladders,"We investigate a two-leg spin ladder system composed of alternating-spin
chains with two-different kind of spins. The fixed point properties are
discussed by using spin-wave analysis and non-linear sigma model techniques.
The model contains various massive phases, reflecting the interplay between the
bond-alternation and the spin-alternation.",9710082v1
2017-02-03,Enhanced Spin Conductance of a Thin-Film Insulating Antiferromagnet,"We investigate spin transport by thermally excited spin waves in an
antiferromagnetic insulator. Starting from a stochastic Landau-Lifshitz-Gilbert
phenomenology, we obtain the out-of-equilibrium spin-wave properties. In linear
response to spin biasing and a temperature gradient, we compute the spin
transport through a normal metal$|$antiferromagnet$|$normal metal
heterostructure. We show that the spin conductance diverges as one approaches
the spin-flop transition; this enhancement of the conductance should be readily
observable by sweeping the magnetic field across the spin-flop transition. The
results from such experiments may, on the one hand, enhance our understanding
of spin transport near a phase transition, and on the other be useful for
applications that require a large degree of tunability of spin currents. In
contrast, the spin Seebeck coefficient does not diverge at the spin-flop
transition. Furthermore, the spin Seebeck coefficient is finite even at zero
magnetic field, provided that the normal metal contacts break the symmetry
between the antiferromagnetic sublattices.",1702.00975v2
2020-11-06,Acoustic spin Hall effect in strong spin-orbit metals,"We report on the observation of the acoustic spin Hall effect that
facilitates lattice motion induced spin current via spin orbit interaction
(SOI). Under excitation of surface acoustic wave (SAW), we find a spin current
flows orthogonal to the propagation direction of a surface acoustic wave (SAW)
in non-magnetic metals. The acoustic spin Hall effect manifests itself in a
field-dependent acoustic voltage in non-magnetic metal (NM)/ferromagnetic metal
(FM) bilayers. The acoustic voltage takes a maximum when the NM layer thickness
is close to its spin diffusion length, vanishes for NM layers with weak SOI and
increases linearly with the SAW frequency. To account for these results, we
find the spin current must scale with the SOI and the time derivative of the
lattice displacement. Such form of spin current can be derived from a Berry
electric field associated with time varying Berry curvature and/or an
unconventional spin-lattice interaction mediated by SOI. These results, which
imply the strong coupling of electron spins with rotating lattices via the SOI,
show the potential of lattice dynamics to supply spin current in strong spin
orbit metals.",2011.03246v2
1999-01-14,Spin dynamics in the generalized ferromagnetic Kondo model for manganites,"Dynamical spin susceptibility is calculated for the generalized ferromagnetic
Kondo model which describes itinerant $e_{g}$ electrons interacting with
localized $t_{2g}$ electrons with antiferromagnetic coupling. The calculations
done in the mean field approximation show that the spin-wave spectrum of the
system in ferromagnetic state has two branches, acoustic and optic ones.
Self-energy corrections to the spectrum are considered and the acoustic
spin-wave damping is evaluated.",9901141v1
2001-08-23,Filtering spin with tunnel-coupled electron wave guides,"We show how momentum-resolved tunneling between parallel electron wave guides
can be used to observe and exploit lifting of spin degeneracy due to Rashba
spin-orbit coupling. A device is proposed that achieves spin filtering without
using ferromagnets or the Zeeman effect.",0108373v2
2000-07-04,Spin-wave spectrum of a two-dimensional itinerant electron system: Analytic results for the incommensurate spiral phase in the strong-coupling limit,"We study the zero-temperature spin fluctuations of a two-dimensional
itinerant-electron system with an incommensurate magnetic ground state
described by a single-band Hubbard Hamiltonian. We introduce the
(broken-symmetry) magnetic phase at the mean-field (Hartree-Fock) level through
a \emph{spiral spin configuration} with characteristic wave vector
$\gmathbf{Q}$ different in general from the antiferromagnetic wave vector
$\gmathbf{Q_{AF}}$, and consider spin fluctuations over and above it within the
electronic random-phase (RPA) approximation. We obtain a \emph{closed} system
of equations for the generalized wave vector and frequency dependent
susceptibilities, which are equivalent to the ones reported recently by Brenig.
We obtain, in addition, analytic results for the spin-wave dispersion relation
in the strong-coupling limit of the Hubbard Hamiltonian and find that at finite
doping the spin-wave dispersion relation has a \emph{hybrid form} between that
associated with the (localized) Heisenberg model and that associated with the
(long-range) RKKY exchange interaction. We also find an instability of the
spin-wave spectrum in a finite region about the center of the Brillouin zone,
which signals a physical instability toward a different spin- or, possibly,
charge-ordered phase, as, for example, the stripe structures observed in the
high-Tc materials. We expect, however, on physical grounds that for wave
vectors external to this region the spin-wave spectrum that we have determined
should survive consideration of more sophisticated mean-field solutions.",0007044v1
2021-06-20,Parametric generation of spin waves in nano-scaled magnonic conduits,"The research feld of magnonics proposes a low-energy wave-logic computation
technology based on spin waves to complement the established CMOS technology
and provide a basis for emerging unconventional computation architectures.
However, magnetic damping is a limiting factor for all-magnonic logic circuits
and multi-device networks, ultimately rendering mechanisms to effciently
manipulate and amplify spin waves a necessity. In this regard, parallel pumping
is a versatile tool since it allows to selectively generate and amplify spin
waves. While extensively studied in microscopic systems, nano-scaled systems
are lacking investigation to assess the feasibility and potential future use of
parallel pumping in magnonics. Here, we investigate a longitudinally magnetized
100 nm-wide magnonic nano-conduit using space and time-resolved micro-focused
Brillouin-light-scattering spectroscopy. Employing parallel pumping to generate
spin waves, we observe that the non-resonant excitation of dipolar spin waves
is favored over the resonant excitation of short wavelength exchange spin
waves. In addition, we utilize this technique to access the effective spin-wave
relaxation time of an individual nano-conduit, observing a large relaxation
time up to (115.0 +- 7.6) ns. Despite the significant decrease of the pumping
effciency in the investigated nano-conduit, a reasonably small threshold is
found rendering parallel pumping feasible on the nano-scale.",2106.10727v2
2007-05-29,Resonant scattering of spin waves from a region of inhomogeneous magnetic field in a ferromagnetic film,"The transmission of a dipole-dominated spin wave in a ferromagnetic film
through a localised inhomogeneity in the form of a magnetic field produced by a
dc current through a wire placed on the film surface was studied experimentally
and theoretically. It was shown that the amplitude and phase of the transmitted
wave can be simultaneously affected by the current induced field, a feature
that will be relevant for logic based on spin wave transport.
  The direction of the current creates either a barrier or well for spin wave
transmission. The main observation is that the current dependence of the
amplitude of the spin wave transmitted through the well inhomogeneity is
non-monotonic. The dependence has a minimum and an additional maximum. A theory
was constructed to clarify the nature of the maximum. It shows that the
transmission of spin waves through the inhomogeneity can be considered as a
scattering process and that the additional maximum is a scattering resonance.",0705.4191v1
2010-12-21,Non-Volatile Magnonic Logic Circuits Engineering,"We propose a concept of magnetic logic circuits engineering, which takes an
advantage of magnetization as a computational state variable and exploits spin
waves for information transmission. The circuits consist of magneto-electric
cells connected via spin wave buses. We present the result of numerical
modeling showing the magneto-electric cell switching as a function of the
amplitude as well as the phase of the spin wave. The phase-dependent switching
makes it possible to engineer logic gates by exploiting spin wave buses as
passive logic elements providing a certain phase-shift to the propagating spin
waves. We present a library of logic gates consisting of magneto-electric cells
and spin wave buses providing 0 or p phase shifts. The utilization of phases in
addition to amplitudes is a powerful tool which let us construct logic circuits
with a fewer number of elements than required for CMOS technology. As an
example, we present the design of the magnonic Full Adder Circuit comprising
only 5 magneto-electric cells. The proposed concept may provide a route to more
functional wave-based logic circuitry with capabilities far beyond the limits
of the traditional transistor-based approach.",1012.4768v1
2010-12-25,Interaction of a nonlinear spin wave and magnetic soliton in a uniaxial anisotropic ferromagnet,"We study the interaction of a nonlinear spin-wave and magnetic soliton in a
uniaxial anisotropic ferromagnet. By means of a reasonable assumption and a
straightforward Darboux transformation one- and two-soliton solutions in a
nonlinear spin-wave background are obtained analytically, and their properties
are discussed in detail. In the background of a nonlinear spin wave the
amplitude of the envelope soliton has the spatial and temporal period, and
soliton can be trapped only in space. The amplitude and wave number of spin
wave have the different contribution to the width, velocity, and the amplitude
of soliton solutions, respectively. The envelope of solution hold the shape of
soliton, and the amplitude of each envelope soliton keeps invariability before
and after collision which shows the elastic collision of two envelope soliton
in the background of a nonlinear spin wave.",1012.5467v1
2015-09-16,Microwave excitation of spin wave beams in thin ferromagnetic films,"We present an approach enabling generation of narrow spin wave beams in thin
homogeneous ferromagnetic films. The main idea is to match the wave vector of
the spin wave with that corresponding to the spectral maximum of the exciting
microwave magnetic field only locally, in the region of space from which the
beam should be launched. We show that this can be achieved with the aid of a
properly designed coplanar waveguide transducer generating a nonuniform
microwave magnetic field. The resulting two-dimensional spin wave beams
obtained in micromagnetic simulations propagate over distances of several
micrometers. The proposed approach requires neither inhomogeneity of the
ferromagnetic film nor nonuniformity of the biasing magnetic field, and it can
be generalized to yield multiple spin wave beams of different width at the same
frequency. Other possible excitation scenarios and applications of spin wave
beam magnonics are also discussed.",1509.05061v2
2018-03-13,Spin wave localization and guiding by magnon band structure engineering in yttrium iron garnet,"In spintronics the propagation of spin-wave excitations in magnetically
ordered materials can also be used to transport and process information. One of
the most popular materials in this regard is the ferrimagnetic insulator
yttrium-iron-garnet due its exceptionally small spin-wave damping parameter.
While the small relaxation rate allows for large propagation length of magnetic
excitations, it also leads to non-locality of the magnetic properties. By
imaging spin waves their band structure is mapped. In doing so wave vector
selection is shown to suppress dispersion effects to a large extent allowing
for local measurements of spin relaxation. Moreover we demonstrate even higher
control of magnon propagation by employing the wave vector selectivity near an
avoided crossing of different spin-wave modes where the group velocity
approaches zero. Here local engineering of the dispersion allows constructing
magnonic waveguides and at the same time reveals the local relaxation
properties.",1803.04943v3
2020-01-24,Propagating magnetic droplet solitons as moveable nanoscale spin-wave sources with tunable direction of emission,"Magnetic droplets are strongly nonlinear and localized spin-wave solitons
that can be formed in current-driven nanocontacts. Here, we propose a simple
way to launch droplets in an inhomogeneous nanoscopic waveguide. We use the
drift motion of a droplet and show that in a system with broken translational
symmetry, the droplet acquires a linear momentum and propagates. We find that
the droplet velocity can be tuned via the strength of the break in symmetry and
the size of the nanocontact. In addition, we demonstrate that the launched
droplet can propagate up to several micrometers in a realistic system with
reasonable damping. Finally, we demonstrate how an annihilating droplet
delivers its momentum to a highly nonreciprocal spin-wave burst with a tunable
wave vector with nanometer wavelengths. Such a propagating droplet can be used
as a moveable spin-wave source in nanoscale magnonic networks. The presented
method enables full control of the spin-wave emission direction, which can
largely extend the freedom to design integrated magnonic circuits with a single
spin-wave source.",2001.08967v1
2020-01-30,An anomalous refraction of spin waves as a way to guide signals in curved magnonic multimode waveguides,"We present a method for efficient spin wave guiding within the magnonic
nanostructures. Our technique is based on the anomalous refraction in the
metamaterial flat slab. The gradual change of the material parameters
(saturation magnetization or magnetic anisotropy) across the slab allows
tilting the wavefronts of the transmitted spin waves and controlling the
refraction. Numerical studies of the spin wave refraction are preceded by the
analytical calculations of the phase shift acquired by the spin wave due to the
change of material parameters in a confined area. We demonstrate that our
findings can be used to guide the spin waves smoothly in curved waveguides,
even through sharp bends, without reflection and scattering between different
waveguide's modes, preserving the phase -- the quantity essential for wave
computing.",2001.11356v1
2020-02-14,Spin-wave diode and circulator based on unidirectional coupling,"In magnonics, an emerging branch of wave physics characterized by low-energy
consumption, it is highly desirable to realize circuit elements within the
scope of spin-wave computing. Here, based on numerical simulations, we
demonstrate the functionality of the spin-wave diode and the circulator to
steer and manipulate spin waves over a wide range of frequency in the GHz
regime. They take advantage of the unidirectional coupling induced by the
interfacial Dzyaloshinskii-Moriya interaction to transfer the spin wave between
thin ferromagnetic layers in only one direction of propagation. Using the
multilayered structure consisting of Py and Co in direct contact with Pt, we
obtain sub-micrometer-size devices of high efficiency. In the diode, the power
loss ratio between forward and reverse direction reaches 22 dB, while in the
four-port circulator, the efficiency exceeds 13 dB. Thus, our work contributes
to the emerging branch of energy-efficient magnonic logic devices, where,
thanks to short wavelength of spin waves, it is possible to realize nanoscale
devices.",2002.06096v1
2020-07-23,Density Wave Mediated Dzyaloshinskii-Moriya Interactions,"We investigate the effect that density wave states have on the localized
spins of a square lattice. We find that topologically nontrivial density wave
states can induce stable Dzyaloshinskii-Moriya (DM) interactions among the
localized spins of the lattice in the presence of an external magnetic field,
and we study the resulting spin models for both antiferromagnetic and
ferromagnetic backgrounds. While the density wave state itself can contribute
to the the thermal Hall effect, as shown by Li & Lee (arXiv:1905.04248v3),
symmetry considerations preclude the resulting spin excitations from inducing a
further thermal Hall effect. We utilize a Holstein-Primakoff (HP) substitution
about the classical mean-field ground state to calculate the magnon dispersion
for LSCO and find that the density wave induces a weak $d_{x^2-y^2}$
anisotropy; upon calculating the non-Abelian Berry curvature for this magnon
branch we show explicitly that the magnon contribution to $\kappa_{xy}$ is
zero. Finally, we calculate corrections to the magnetic ground state energy,
spin canting angles, and the spin-wave dispersion due to the topological
density wave for ferromagnetic backgrounds. We find that terms linear in the HP
bosons can affect the critical behavior, a point previously overlooked in the
literature.",2007.11719v1
2023-07-19,Checkerboard bubble lattice formed by octuple-period quadruple-$Q$ spin density waves,"We investigate multiple-$Q$ instability on a square lattice at particular
ordering wave vectors. We find that a superposition of quadruple-$Q$ spin
density waves, which are connected by fourfold rotational and mirror
symmetries, gives rise to a checkerboard bubble lattice with a collinear spin
texture as a result of the geometry among the constituent ordering wave vectors
in the Brillouin zone. By performing the simulated annealing for a fundamental
spin model, we show that such a checkerboard bubble lattice is stabilized under
an infinitesimally small easy-axis two-spin anisotropic interaction and
biquadratic interaction at zero field, while it is degenerate with an
anisotropic double-$Q$ state in the absence of the biquadratic interaction. The
obtained multiple-$Q$ structures have no intensities at high-harmonic wave
vectors in contrast to other multiple-$Q$ states, such as a magnetic skyrmion
lattice. We also show that the checkerboard bubble lattice accompanies the
charge density wave and exhibits a nearly flat band dispersion in the
electronic structure. Our results provide another route to realize exotic
multiple-$Q$ spin textures by focusing on the geometry and symmetry in terms of
the wave vectors in momentum space.",2307.10444v1
2019-10-07,Chiral spin-wave velocities induced by all-garnet interfacial Dzyaloshinskii-Moriya interaction in ultrathin yttrium iron garnet films,"Spin waves can probe the Dzyaloshinskii-Moriya interaction (DMI) which gives
rise to topological spin textures, such as skyrmions. However, the DMI has not
yet been reported in yttrium iron garnet (YIG) with arguably the lowest damping
for spin waves. In this work, we experimentally evidence the interfacial DMI in
a 7~nm-thick YIG film by measuring the nonreciprocal spin wave propagation in
terms of frequency, amplitude and most importantly group velocities using all
electrical spin-wave spectroscopy. The velocities of propagating spin waves
show chirality among three vectors, i.e. the film normal direction, applied
field and spin-wave wavevector. By measuring the asymmetric group velocities,
we extract a DMI constant of 16~$\mu$J/m$^{2}$ which we independently confirm
by Brillouin light scattering. Thickness-dependent measurements reveal that the
DMI originates from the oxide interface between the YIG and garnet substrate.
The interfacial DMI discovered in the ultrathin YIG films is of key importance
for functional chiral magnonics as ultra-low spin-wave damping can be achieved.",1910.02599v2
2023-03-08,True amplification of spin waves in magnonic nano-waveguides,"Magnonic nano-devices exploit magnons -- quanta of spin waves -- to transmit
and process information within a single integrated platform that has the
potential to outperform traditional semiconductor-based electronics for low
power applications. The main missing cornerstone of this information
nanotechnology is an efficient scheme for the direct amplification of
propagating spin waves. The recent discovery of spin-orbit torque provided an
elegant mechanism for propagation losses compensation. While partial
compensation of the spin-wave damping has allowed for spin-wave signal
modulation, true amplification - the exponential increase in the spin-wave
intensity during propagation - has so far remained elusive. Here we evidence
the operating conditions to achieve unambiguous amplification using clocked
nanoseconds-long spin-orbit torque pulses in sub-micrometer wide magnonic
waveguides, where the effective magnetization has been engineered to be close
to zero to suppress the detrimental magnon-magnon scattering. As a result, we
achieve an exponential increase in the intensity of propagating spin waves up
to 500 % at a propagation distance of several micrometers. These results pave
the way towards the implementation of energy efficient, cascadable magnonic
architectures for wave-based information processing and complex on-chip
computation.",2303.04695v2
2008-02-26,Dynamical Structure Factor and Spin-Density Separation for a Weakly-Interacting Two-Component Bose Gas,"We show that spin-density separation in a Bose gas is not restricted to 1D
but also occurs in higher dimension. The ratio ($\alpha$) of the intra-species
atom-atom interaction strength to the inter-species interaction strength,
strongly influences the dynamics of spin-density separation and the elementary
excitations. The density wave is phonon-like for all values of $\alpha$. For
$\alpha<1$, spin wave is also phonon-like. The spin waves have a quadratic
dispersion in the $\alpha=1$ coupling regime, while in the phase separated
regime ($\alpha>1$) the spin waves are found to be damped. The dynamical
structure factor (DSF) reveals two distinct peaks corresponding to the density
and spin waves for $\alpha \le 1$. For $\alpha > 1$ there is only one DSF peak
corresponding to the density wave.",0802.3818v5
2012-02-06,High-temperature spin-wave propagation in BiFeO3: relation to the Polomska transition,"In bismuth ferrite thin films the cycloidal spiral spin structure is
suppressed, and as a result the spin-wave magnon branches of long wavelength
are reduced from a dozen to one, at \omega = 19.2 cm-1 (T=4K). This spin wave
has not been measured previously above room temperature, but in the present
work we show via Raman spectroscopy that it is an underdamped propagating wave
until 455 K. This has important room-temperature device implications. The data
show that \omega(T) follows an S=5/2 Brillouin function and hence its Fe+3 ions
are in the high-spin 5/2 state and not the low-spin S=1/2 state. The spin wave
cannot be measured as a propagating wave above 455 K. We also suggest that
since this temperature is coincident with the mysterious ""Polomska transition""
(M. Polomska et al., Phys. Stat. Sol. A 23, 567, (1974)) at 458+/-5 K, that
this may be due to overdamping.",1202.1040v1
2013-08-15,Spin-Wave Propagation in the Presence of Interfacial Dzyaloshinskii-Moriya Interaction,"In ferromagnetic thin films, broken inversion symmetry and spin-orbit
coupling give rise to interfacial Dzyaloshinskii-Moriya interactions. Analytic
expressions for spin-wave properties show that the interfacial
Dzyaloshinskii-Moriya interaction leads to non-reciprocal spin-wave
propagation, i.e. different properties for spin waves propagating in opposite
directions. In favorable situations, it can increase the spin-wave attenuation
length. Comparing measured spin wave properties in ferromagnet$|$normal metal
bilayers and other artificial layered structures with these calculations can
provide a useful characterization of the interfacial Dzyaloshinskii-Moriya
interactions.",1308.3341v1
2013-11-27,Quasi-2D $J_1$-$J_2$ Antiferromagnet $Zn_2VO(PO_4)_2$ and its $Ti$-substituted Derivative - A Spin-wave Analysis,"In this study, we present non-linear spin wave analysis of a quasi 2D
spin-$\frac{1}{2}$ $J_1-J_2$ antiferromagnet at the parameter regime relevant
for the recently studied compound $Zn_2VO(PO_4)_2$. We obtain the temperature
dependence of the spin wave energy, susceptibility and magnetization using
Green's function technique and Hartree-Fock factorization or Tyablikov's
decoupling approximation. The comparison of our numerical results with the
experimental findings is discussed. Magnetic structure factor is calculated and
compared with powder neutron diffraction data. We also study the spin wave
behavior of the compound $Zn_2Ti_{0.25}V_{0.75}O(PO_4)_2$ obtained by partial
chemical substitution of $Ti$ at $V$ sites of the compound $Zn_2VO(PO_4)_2$
(Phys. Rev. B87, 054431). Due to the superlattice structure of the spin
lattice, the substituted compound possess multiple spin wave modes. The spin
wave analysis confirms the quasi-1D nature of the substituted system.",1311.6915v1
2014-06-27,Spin waves along the edge states,"Spin waves have been studied experimentally and by simulations in 1000 nm
side equilateral triangular Permalloy dots in the Buckle state (B, with
in-plane field along the triangle base) and the Y state (Y, with in-plane field
perpendicular to the base). The excess of exchange energy at the triangles
edges creates channels that allow effective spin wave propagation along the
edges inthe B state. These quasi one-dimensional spin waves emitted by the
vertex magnetic charges gradually transform from propagating to standing due to
interference and(as pointed out by simulations) areweakly affected by
smallvariations of the aspect ratio(from equilateral to isosceles dots) or by
interdot dipolar interaction present in our dot arrays. Spin waves excited in
the Y state have mainly a two-dimensional character.Propagation of the spin
waves along the edge states in triangular dots opens possibilities for creation
of new and versatile spintronic devices.",1406.7200v1
2018-12-08,Directional Spin-wave Propagation in the Skyrmion Chain,"The Dzyaloshinskii-Moriya interaction (DMI), favoring a chiral spin structure
like the skyrmion, gives rise to the nonreciprocal propagation of spin waves.
We investigate the propagation of spin waves in a nanostripe with the presence
of a skyrmion chain by using micromagnetic simulations. Through applying a
microwave locally, it is found that when the interval between skyrmions is
large enough, the spin waves can be separated to the counter direction
according to different frequencies. While for the tightly arranged skyrmions,
the skyrmion chain with strong interactions between skyrmions becomes a channel
for spin waves, which is around the frequency of skyrmion breathing and exhibit
a characteristic of directional propagation. This work opens a vista for
skyrmion-based spin wave devices.",1812.03297v2
2021-04-13,Confined dipole and exchange spin waves in a bulk chiral magnet with Dzyaloshinskii-Moriya interaction,"The Dzyaloshinskii-Moriya interaction (DMI) has an impact on excited spin
waves in the chiral magnet Cu$_2$OSeO$_3$ by means of introducing asymmetry on
their dispersion relations. The confined eigenmodes of a chiral magnet are
hence no longer the conventional standing spin waves. Here we report a combined
experimental and micromagnetic modeling study by broadband microwave
spectroscopy we observe confined spin waves up to eleventh order in bulk
Cu$_2$OSeO$_3$ in the field-polarized state. In micromagnetic simulations we
find similarly rich spectra. They indicate the simultaneous excitation of both
dipole- and exchange-dominated spin waves with wavelengths down to (47.2 $\pm$
0.05) nm attributed to the exchange interaction modulation. Our results suggest
DMI to be effective to create exchange spin waves in a bulk sample without the
challenging nanofabrication and thereby to explore their scattering with
noncollinear spin textures.",2104.06240v2
2022-12-22,Hybrid Magnonic-Oscillator System,"We propose a hybrid magnonic-oscillator system based on the combination of a
spin transfer auto-oscillator and a magnonic waveguide to open new perspectives
for spin-wave based circuits. The system is composed of a spin transfer
oscillator based on a vortex state which is dipolarly coupled to a nanoscale
spin-wave waveguide with longitudinal magnetization. In its auto-oscillating
regime, the oscillator emits coherent spin waves with tunable and controllable
frequencies, directions and amplitudes into the waveguide. We demonstrate the
principle of this method using micromagnetic simulations and show that
reconfiguration of the system is possible by changing the chirality and
polarity of the magnetic vortex. Spin waves are emitted into the waveguide with
high non-reciprocity and the preferred direction depends on the core polarity
of the vortex. In contrast, different vortex chiralities lead to different
amplitudes of the emitted waves. Our findings open up a novel way to design an
agile spintronic device for the coherent and tunable generation of propagating
spin waves.",2212.11532v1
2023-07-14,Observation and control of hybrid spin-wave-Meissner-current transport modes,"Superconductors are materials with zero electrical resistivity and the
ability to expel magnetic fields known as the Meissner effect. Their
dissipationless diamagnetic response is central to magnetic levitation and
circuits such as quantum interference devices. Here, we use superconducting
diamagnetism to shape the magnetic environment governing the transport of spin
waves - collective spin excitations in magnets that are promising on-chip
signal carriers - in a thin-film magnet. Using diamond-based magnetic imaging,
we observe hybridized spin-wave-Meissner-current transport modes with strongly
altered, temperature-tunable wavelengths. We extract the temperature-dependent
London penetration depth from the wavelength shifts and realize local control
of spin-wave refraction using a focused laser. Our results demonstrate the
versatility of superconductor-manipulated spin-wave transport and have
potential applications in spin-wave gratings, filters, crystals and cavities.",2307.07581v1
2023-10-10,Spin attributes of structured vector fields constructed by Hertz potentials,"In this paper, we use the Hertz vector potential to define the
electromagnetic vector of different structured wavefields, and analyze the spin
properties of the wavefields. We show that for the single evanescent waves, the
total spin provides by the transverse spin and originates from the spatial
inhomogeneity of the momentum density of the field. However, for non-single
evanescent wave, there may be a part of the extraordinary spin component sE,
and the direction of sE is also perpendicular to the wave propagation
direction. In other words, it is transverse, but it does not originate from the
curl of the wave field momentum density. In addition, we also calculate the
spins of non-planar propagating waves, and analyze the spin characteristics of
these wave fields.",2310.06664v1
2019-01-31,Triplet superconductivity in ferromagnets due to magnon exchange,"We consider the superconducting pairing induced by spin waves exchange in a
ferromagnet with both conduction and localized electrons, the latter being
described as spins. We use the microscopic Eliashberg theory to describe the
pairing of conducting electrons and the RPA approach to treat the localized
spins assuming an exchange coupling between the conducting electrons and spins.
In the framework of non relativistic Hamiltonian twe found that he spin wave
exchange results in equal spin electron pairing described by the two components
of the order parameter, $\Delta^{\uparrow}$ (both spins up) and
$\Delta^{\downarrow}$ (both spins down). Due to the conservation of total spin
projection on the axis of the spontaneous ferromagnetic moment, the spin wave
exchange at low temperatures includes an emission of magnons and an absorption
of thermal magnons by the conduction electrons. The absorption and emission
processes depend differently on the temperature, with the absorption being
progressively suppressed as the temperature drops. As a result, the
superconducting pairing exists only if the electron-spin wave exchange
parameter $g$ exceeds some critical value $g_c$. At $g>g_c$ pairing vanishes if
the temperature drops below the lowest point $T_{cl}$ or increases above the
upper critical point $T_{ch} \approx T_m$ (the Curie temperature) where the
spin waves cease to exist. This behavior inherent to the spin carrying glue is
in an obvious disagreement with the results of conventional BCS approach which
assumes that the effective electron-electron attraction is simply proportional
to the static magnetic susceptibility.",1901.11248v1
2016-10-31,"Kinetic analysis of spin current contribution to spectrum of electromagnetic waves in spin-1/2 plasma, Part II: Dispersion dependencies","The dielectric permeability tensor for spin polarized plasmas derived in
terms of the spin-1/2 quantum kinetic model in six-dimensional phase space in
Part I of this work is applied for study of spectra of high-frequency
transverse and transverse-longitudinal waves propagating perpendicular to the
external magnetic field. Cyclotron waves are studied at consideration of waves
with electric field directed parallel to the external magnetic field. It is
found that the separate spin evolution modifies the spectrum of cyclotron
waves. These modifications increase with the increase of the spin polarization
and the number of the cyclotron resonance. Spin dynamics with no account of the
anomalous magnetic moment gives a considerable modification of spectra either.
The account of anomalous magnetic moment leads to a fine structure of each
cyclotron resonance. So, each cyclotron resonance splits on three waves.
Details of this spectrum and its changes with the change of spin polarization
are studied for the first and second cyclotron waves. A cyclotron resonance
existing at $\omega\approx0.001\mid\Omega_{e}\mid$ due to the anomalous
magnetic moment is also described, where $\mid\Omega_{e}\mid$ is the cyclotron
frequency. The ordinary waves does not have any considerable modification. The
electrostatic and electromagnetic Berstein modes are studied during the
analysis of waves propagating perpendicular to the external magnetic field with
the electric field perturbation directed perpendicular to the external field. A
modification of the oscillatory structure caused by the equilibrium spin
polarization is found in both regimes. Similar modification is found for the
extraordinary wave spectrum.",1611.00046v1
2020-03-26,Magnetoelastic waves in thin films,"This paper discusses the physics of magnetoelasticity and magnetoelastic
waves as well as their mathematical description. Magnetoelastic waves occur as
a result of strong coupling between spin waves and elastic waves in
magnetostrictive ferromagnetic media. In a first part, the basic behavior of
spin waves is reviewed in both bulk ferromagnets as well as in thin films.
Next, elastic waves are discussed with a focus on thin films. Finally, the
interactions between the elastic and magnetic domains are described and it is
shown how this results in the formation of magnetoelastic waves. Based on the
description of bulk magnetoelastic waves, a theory for magnetoelastic waves in
thin films is developed and their dispersion relations are derived. It is shown
that the behavior strongly depends on the geometry of the system, especially on
the polarization of spin and elastic waves and the direction of the
magnetization of the magnetostrictive ferromagnet.",2003.12099v1
2015-03-13,Spin-wave logic devices based on isotropic forward volume magneto-static waves,"We propose the utilization of isotropic forward volume magneto-static spin
waves in modern wave-based logic devices and suggest a concrete design for a
spin-wave majority gate operating with these waves. We demonstrate by numerical
simulations that the proposed out-of-plane magnetized majority gate overcomes
the limitations of anisotropic in-plane magnetized majority gates due to the
high spin-wave transmission through the gate, which enables a reduced energy
consumption of these devices. Moreover, the functionality of the out-of-plane
majority gate is increased due to the lack of parasitic generation of
short-wavelength exchange spin waves.",1503.04101v1
2022-01-11,Parametric Excitation and Instabilities of Spin Waves driven by Surface Acoustic Waves,"The parametric excitation of spin waves by coherent surface acoustic waves is
demonstrated experimentally in metallic magnetic thin film structures. The
involved magnon modes are analyzed with micro-focused Brillouin light
scattering spectroscopy and complementary micromagnetic simulations combined
with analytical modelling are used to determine the origin of the spin-wave
instabilities. Depending on the experimental conditions, we observe spin-wave
instabilities originating from different phonon-magnon and magnon-magnon
scattering processes. Our results demonstrate that an efficient excitation of
high amplitude, strongly nonlinear magnons in metallic ferromagnets is possible
by surface acoustic waves, which opens novel ways to create micro-scaled
nonlinear magnonic systems for logic and data processing that can profit from
the high excitation efficiency of phonons using piezoelectricity.",2201.04033v2
2011-08-05,Magnons and electromagnons in a spin-lattice-coupled frustrated magnet CuFeO2 as seen via inelastic neutron scattering,"We have investigated spin-wave excitations in a four-sublattice (4SL)
magnetic ground state of a frustrated magnet CuFeO2, in which `electromagnon'
(electric-field-active magnon) excitation has been discovered by recent
terahertz time-domain spectroscopy [Seki et al. Phys. Rev. Lett. 105 097207
(2010)]. In previous study, we have identified two spin-wave branches in the
4SL phase by means of inelastic neutron scattering measurements under applied
uniaxial pressure. [T. Nakajima et al. J. Phys. Soc. Jpn. 80 014714 (2011) ] In
the present study, we have performed high-energy-resolution inelastic neutron
scattering measurements in the 4SL phase, resolving fine structures of the
lower-energy spin-wave branch near the zone center. Taking account of the
spin-driven lattice distortions in the 4SL phase, we have developed a model
Hamiltonian to describe the spin-wave excitations. The determined Hamiltonian
parameters have successfully reproduced the spin-wave dispersion relations and
intensity maps obtained in the inelastic neutron scattering measurements. The
results of the spin-wave analysis have also revealed physical pictures of the
magnon and electromagnon modes in the 4SL phase, suggesting that collinear and
noncollinear characters of the two spin-wave modes are the keys to understand
the dynamical coupling between the spins and electric dipole moments in this
system.",1108.1297v1
2013-07-22,Topological quantum phase transition in Kane-Mele-Kondo lattice model,"We systematically explore the ground-state phase diagram of the
Kane-Mele-Kondo lattice model on the honeycomb lattice, in particular, we focus
on its magnetic properties which has not been studied in the previous
publication[Feng, Dai, Chung, and Si, Phys. Rev. Lett. \textbf{111}, 016402
(2013)]. Beside the Kondo insulator found in that paper, two kinds of
antiferromagnetic spin-density-wave phases are identified. One is the normal
antiferromagnetic spin-density-wave state and the other is a nontrivial
topological antiferromagnetic spin-density-wave state with a quantized spin
Hall conductance and a helical edge-state. The quantum spin Hall insulator is
found to be absent since it is always unstable to antiferromagnetic
spin-density-wave states at least at the mean-field level in our model.
Furthermore, the transition between the two spin-density-wave phases are
topological quantum phase transition described by the three-dimensional quantum
electrodynamics, in which conduction electrons contribute to the low-energy
Dirac fermions while the spin-wave fluctuation of local spins gives rise to an
effective dynamic U(1) gauge-field. Such nontrivial transition shows radical
critical thermodynamic, transport and single-particle behaviors, which provide
a fingerprint for this transition. Additionally, the transition of
antiferromagnetic spin-density-wave states to the Kondo insulator is found to
be first-order. The introduction of two novel magnetic phases and their
topological quantum phase transition show rich and intrinsic physics involving
in the Kane-Mele-Kondo lattice model.",1307.5627v2
2000-01-21,Density Wave States of Non-Zero Angular Momentum,"We study the properties of states in which particle-hole pairs of non-zero
angular momentum condense. These states generalize charge- and
spin-density-wave states, in which s-wave particle-hole pairs condense. We show
that the p-wave spin-singlet state of this type has Peierls ordering, while the
d-wave spin-singlet state is the staggered flux state. We discuss model
Hamiltonians which favor p-wave and d-wave density wave order. There are
analogous orderings for pure spin models, which generalize spin-Peierls order.
The spin-triplet density wave states are accompanied by spin-1 Goldstone
bosons, but these excitations do not contribute to the spin-spin correlation
function. Hence, they must be detected with NQR or Raman scattering
experiments. Depending on the geometry and topology of the Fermi surface, these
states may admit gapless fermionic excitations. As the Fermi surface geometry
is changed, these excitations disappear at a transition which is third-order in
mean-field theory. The singlet d-wave and triplet p-wave density wave states
are separated from the corresponding superconducting states by zero-temperature
O(4)-symmetric critical points",0001303v1
2000-10-20,"Composite Spin Waves, Quasi-Particles and Low Temperature resistivity in Double Exchange Systems","We make a quantum description of the electron low temperature properties of
double exchange materials. In these systems there is a strong coupling between
the core spin and the carriers spin. This large coupling makes the low energy
spin waves to be a combination of ion and electron density spin waves. We study
the form and dispersion of these composite spin wave excitations. We also
analyze the spin up and down spectral functions of the temperature dependent
quasi-particles of this system. Finally we obtain that the thermally activated
composite spin waves renormalize the carriers effective mass and this gives
rise to a low temperature resistivity scaling as T ^{5/2}.",0010312v1
2009-10-09,Spin-waves in the $J_{1a}-J_{1b}-J_{2}$ orthorombic square-lattice Heisenberg models: Application to the iron pnictide materials,"Motivated by the observation of spatially anisotropic exchange constants in
the iron pnictide materials, we study the spin-wave spectra of the
$J_{1a}-J_{1b}-J_{2}$ Heisenberg models on a square-lattice with nearest
neighbor exchange $J_{1a}$ along x and $J_{1b}$ along y axis and a second
neighbor exchange $J_2$. We focus on the regime, where the spins order at
($\pi,0$), and compute the spectra by systematic expansions around the Ising
limit. We study both spin-half and spin-one Heisenberg models as well as a
range of parameters to cover various cases proposed for the iron pnictide
materials. The low-energy spectra have anisotropic spin-wave velocities and are
renormalized with respect to linear spin-wave theory by up to 20 percent,
depending on parameters. Extreme anisotropy, consisting of a ferromagnetic
$J_{1b}=- |J_F|$, is best distinguished from a weak anisotropy ($J_{1a}\approx
J_{1b}=J_1$, $J_2>J_1/2$) by the nature of the spin-waves near the wavevectors
($0,\pi$) or ($\pi,\pi$). The reported spectra for the pnictide material
CaFe$_2$As$_2$ clearly imply such an extreme anisotropy.",0910.1793v1
2010-09-25,Micro-Structured Ferromagnetic Tubes for Spin Wave Excitation,"Micron scale ferromagnetic tubes placed on the ends of ferromagnetic CoTaZr
spin waveguides are explored in order to enhance the excitation of Backward
Volume Magnetostatic Spin Waves. The tubes produce a closed magnetic circuit
about the signal line of the coplanar waveguide and are, at the same time,
magnetically contiguous with the spin waveguide. This results in a 10 fold
increase in spin wave amplitude. However, the tube geometry distorts the
magnetic field near the spin waveguide and relatively high biasing magnetic
fields are required to establish well defined spin waves. Only the lowest
(uniform) spin wave mode is excited.",1009.4986v1
2012-11-05,Spin Dynamics and Resonant Inelastic X-ray Scattering in Chromium with Commensurate Spin-Density Wave Order,"We theoretically investigate spin dynamics and $L_3$-edge resonant inelastic
X-ray scattering (RIXS) of Chromium with commensurate spin-density wave (SDW)
order, based on a multi-band Hubbard model composed of 3$d$ and 4$s$ orbitals.
Obtaining the ground state with the SDW mean-field approximation, we calculate
the dynamical transverse and longitudinal spin susceptibility by using
random-phase approximation. We find that a collective spin-wave excitation seen
in inelastic neutron scattering hardly damps up to $\sim$0.6 eV. Above the
energy, the excitation overlaps individual particle-hole excitations as
expected, leading to broad spectral weight. On the other hand, the collective
spin-wave excitation in RIXS spectra has a tendency to be masked by large
spectral weight coming from particle-hole excitations with various orbital
channels. This is in contrast with inelastic neutron scattering, where only
selected diagonal orbital channels contribute to the spectral weight. However,
it may be possible to detect the spin-wave excitation in RIXS experiments in
the future if resolution is high enough.",1211.1598v2
2014-09-08,Dynamic control of spin wave spectra using spin-polarized currents,"We describe a method of controlling the spin wave spectra dynamically in a
uniform nanostripe waveguide through spin-polarized currents. A stable periodic
magnetization structure is observed when the current flows vertically through
the center of nanostripe waveguide. After being excited, the spin wave is
transmitted at the sides of the waveguide. Numerical simulations of spin-wave
transmission and dispersion curves reveal a single, pronounced band gap.
Moreover, the periodic magnetization structure can be turned on and off by the
spin-polarized current. The switching process from full rejection to full
transmission takes place within less than 3ns. Thus, this type magnonic
waveguide can be utilized for low-dissipation spin wave based filters.",1409.2421v2
2014-06-14,Electric-field coupling to spin waves in a centrosymmetric ferrite,"We experimentally demonstrate that the spin-orbit interaction can be utilized
for direct electric-field tuning of the propagation of spin waves in a
single-crystal yttrium iron garnet magnonic waveguide. Magnetoelectric coupling
not due to the spin-orbit interaction, and hence an order of magnitude weaker,
leads to electric-field modification of the spin-wave velocity for waveguide
geometries where the spin-orbit interaction will not contribute. A theory of
the phase shift, validated by the experiment data, shows that, in the exchange
spin wave regime, this electric tuning can have high efficiency. Our findings
point to an important avenue for manipulating spin waves and developing
electrically tunable magnonic devices.",1406.3675v1
2017-10-03,Spin-wave chirality and its manifestations in antiferromagnets,"As first demonstrated by Tang and Cohen in chiral optics, the asymmetry in
the rate of electromagnetic energy absorption between left and right
enantiomers is determined by an optical chirality density [1]. Here, we
demonstrate that this effect can exist in magnetic spin systems. By
constructing a formal analogy with electrodynamics, we show that in
antiferromagnets with broken chiral symmetry the asymmetry in local spin-wave
energy absorption is proportional to a spin-wave chirality density, which is a
direct counterpart of optical zilch. We propose that injection of a pure spin
current into an antiferromagnet may serve as a chiral symmetry breaking
mechanism, since its effect in the spin-wave approximation can be expressed in
terms of additional Lifshitz invariants. We use linear response theory to show
that the spin current induces a nonequilibrium spin-wave chirality density.",1710.01023v2
2017-04-07,Spin wave propagation and spin polarized electron transport in single crystal iron films,"The technique of propagating spin wave spectroscopy is applied to a 20 nm
thick Fe/MgO (001) film. The magnetic parameters extracted from the position of
the resonance peaks are very close to those tabulated for bulk iron. From the
propagating waveforms, a group velocity of 4 km/s and an attenuation length of
about 6 micrometers are extracted for 1.6 micrometers-wavelength spin-wave at
18 GHz. From the measured current-induced spin-wave Doppler shift, we also
extract a surprisingly high degree of spin-polarization of the current of 83%.
This set of results makes single-crystalline iron a promising candidate for
building devices utilizing high frequency spin-waves and spin-polarized
currents.",1704.02217v1
2020-05-22,Signatures of a liquid-crystal transition in spin-wave excitations of skyrmions,"Understanding the spin-wave excitations of chiral magnetic order, such as the
skyrmion crystal (SkX), is of fundamental interest to confirm such exotic
magnetic order. The SkX is realized by competing Dzyaloshinskii-Moriya and
ferromagnetic-exchange interactions with a magnetic field or anisotropy. Here
we compute the dynamical spin structure factor, using Monte Carlo and spin
dynamics simulations, extracting the spin-wave spectrum in the SkX, in the
vicinity of the paramagnet to SkX transition. Inside the SkX, we find six
spin-wave modes, which are supplemented by another mode originating from the
ferromagnetic background. Above the critical temperature $T_s$ for the skyrmion
crystallization, we find a diffusive regime, reminiscent of the
liquid-to-crystal transition, revealing that topological spin texture of
skyrmionic character starts to develop above $T_s$ as the precursor of the SkX.
We discuss the opportunities for the detection of the spin waves of the SkX
using inelastic-neutron-scattering experiments in manganite-iridate
heterostructures.",2005.11399v2
2021-06-05,Extraordinary transverse spin: Hidden vorticity of the energy flow and momentum distributions in propagating light fields,"Spatially inhomogeneous fields of electromagnetic guided modes exhibit a
complex of extraordinary dynamical properties such as the
polarization-dependent transverse momentum, helicity-independent transverse
spin, spin-associated non-reciprocity and unidirectional propagation, etc.
Recently, the remarkable relationship has been established between the spin and
propagation features of such fields, expressed through the spin-momentum
equations [Proc. Natl. Acad. Sci. 118 (2021) e2018816118] connecting the wave
spin with the curl of momentum. Here, the meaning, limitations and specific
forms of this correspondence are further investigated, involving the physically
transparent and consistent examples of paraxial light fields, plane-wave
superpositions and evanescent waves. The conclusion is inferred that the
spin-momentum equation is an attribute of guided waves with well defined
direction of propagation, and it unites the helicity-independent
""extraordinary"" transverse spin with the spatially-inhomogeneous longitudinal
field momentum (energy flow) density. Physical analogies with the layered
hydrodynamic flows and possible generalizations for other wave fields are
discussed. The results can be useful in optical trapping, manipulation and the
data processing techniques.",2106.02849v1
2022-04-27,Gravitational waves from small spin-up and spin-down events of neutron stars,"It was recently reported that there exists a population of ""glitch
candidates"" and ""anti-glitch candidates"" which are effectively small spin-ups
and spin-downs of a neutron star with magnitudes smaller than those seen in
typical glitches. The physical origin of these small events is not yet
understood. In this paper, we outline a model that can account for the changes
in spin, and crucially, is independently testable with gravitational wave
observations. In brief, the model posits that small spin-up/spin-down events
are caused by the excitation and decay of non-axisymmetric $f$-modes which
radiate angular momentum away in a burst-like way as gravitational waves. The
model takes the change in spin frequency as an input and outputs the initial
mode amplitude and the signal-to-noise ratio achievable from gravitational wave
detectors. We find that the model presented here will become falsifiable once
3rd generation gravitational wave detectors, like the Einstein Telescope and
Cosmic Explorer, begin taking data.",2204.12869v3
2022-06-23,Anisotropic magnon damping by zero-temperature quantum fluctuations in ferromagnetic CrGeTe$_3$,"Spin and lattice are two fundamental degrees of freedom in a solid, and their
fluctuations about the equilibrium values in a magnetic ordered crystalline
lattice form quasiparticles termed magnons (spin waves) and phonons (lattice
waves), respectively. In most materials with strong spin-lattice coupling
(SLC), the interaction of spin and lattice induces energy gaps in the spin wave
dispersion at the nominal intersections of magnon and phonon modes. Here we use
neutron scattering to show that in the two-dimensional (2D) van der Waals
honeycomb lattice ferromagnetic CrGeTe3, spin waves propagating within the 2D
plane exhibit an anomalous dispersion, damping, and break-down of quasiparticle
conservation, while magnons along the c axis behave as expected for a local
moment ferromagnet. These results indicate the presence of dynamical SLC
arising from the zero-temperature quantum fluctuations in CrGeTe3, suggesting
that the observed in-plane spin waves are mixed spin and lattice quasiparticles
fundamentally different from pure magnons and phonons.",2206.11962v1
2022-09-14,"Quantum Spin-Wave Theory for non-collinear Spin Structures, a Review","In this review, we trace the evolution of the quantum spin-wave theory
treating non-collinear spin configurations. Non-collinear spin configurations
are consequences of the frustration created by competing interactions. They
include simple chiral magnets due to competing nearest-neighbor (NN) and
next-NN interactions and systems with geometry frustration such as the
triangular antiferromagnet and the Kagom\'e lattice. We review here spin-wave
results of such systems and also systems with the Dzyaloshinskii-Moriya
interaction. Accent is put on these non-collinear ground states which have to
be calculated before applying any spin-wave theory to determine the spectrum of
the elementary excitations from the ground states. We mostly show results
obtained by the use of a Green's function method. These results include the
spin-wave dispersion relation and the magnetizations, layer by layer, as
functions of $T$ in 2D, 3D and thin films. Some new unpublished results are
also included. Technical details and discussion on the method are shown and
discussed.",2209.06771v1
2022-10-10,Charge distribution and spin textures in magic-angle twisted bilayer graphene,"We examine the coexisting spin and charge density waves as a possible ground
state of the magic-angle twisted bilayer graphene. When interactions are not
included, the spectrum of the material has 4 (8 if spin is taken into account)
almost flat almost degenerate bands. Interactions break down the degeneracy
forming an order parameter which is usually assumed to be a spin density wave
with a preset spin structure. Here we take into account a possible charge
density wave contribution to the order parameter, that is, inhomogeneous
distribution of the charge density within a twisted graphene supercell. We also
calculate self-consistently the spin structure of the order parameter. We find
that the density wave order is stable in the whole doping range from $-4$ to
$+4$ extra electrons per supercell. The spin texture changes from collinear at
zero doping to almost coplanar at finite doping. The density wave order shows
nematic distortion when we dope the system. We demonstrate that the local spin
magnetization is much stronger than the charge density variation, unless the
doping exceeds $3$ extra electrons or holes per supercell.",2210.04670v1
1998-10-20,Unconventional ferromagnetic and spin-glass states of the reentrant spin glass Fe0.7Al0.3,"Spin excitations of single crystal Fe0.7Al0.3 were investigated over a wide
range in energy and reciprocal space with inelastic neutron scattering. In the
ferromagnetic phase, propagating spin wave modes become paramagnon-like
diffusive modes beyond a critical wave vector q0, indicating substantial
disorder in the long-range ordered state. In the spin glass phase, spin
dynamics is strongly q-dependent, suggesting remnant short-range spin
correlations. Quantitative model for S(energy,q) in the ``ferromagnetic'' phase
is determined.",9810265v2
2008-11-17,Dynamics in two-leg spin ladder with a four-spin cyclic interaction,"We study two-leg Heisenberg ladder with four-spin cyclic interaction using
the (dynamical) density-matrix renormalization group method. We demonstrate the
dependence of the low-lying excitations in the spin wave, staggered dimer
order, and scalar-chirality order structure factors on the four-spin cyclic
interaction. We find that the cyclic interaction enhances spin-spin
correlations with wave vector around momentum $(q_x,q_y)=(\frac{\pi}{2},0)$.
Also, the presence of long-range order in the staggered dimer and
scalar-chirality phases is confirmed by a $\delta$-function peak contribution
of the structure factors at energy $\omega=0$.",0811.2456v1
2011-03-20,The spin excitations of the block-antiferromagnetic K$_{0.8}$Fe$_{1.6}$Se$_2$,"We study the spin excitations of the newly discovered block-antiferromagnetic
state in K$_{0.8}$Fe$_{1.6}$Se$_2$ using an effective spin Hamiltonian
suggested in the literature. Interestingly in addition to the usual Goldstone
mode, there exists three other ""optical"" spin wave branches. These spin
excitations are the analog of ""optical phonons"" in crystals with more than one
atom per unit cell. We compute the spin wave corrected ordering moment and the
uniform spin susceptibilities.",1103.3884v1
2015-11-26,Spin textures and spin-wave excitations in doped Dirac-Weyl semimetals,"We study correlations and magnetic textures of localized spins, doped in
three-dimensional Dirac semimetals. An effective field theory for magnetic
moments is constructed by integrating out the fermionic degrees of freedom. The
spin correlation shows a strong anisotropy, originating from spin-momentum
locking of Dirac electrons, in addition to the conventional Heisenberg-like
ferromagnetic correlation. The anisotropic spin correlation allows
topologically nontrivial magnetic excitation textures such as a transient
hedgehog state, as well as the ferromagnetic ground state. The spin-wave
dispersion in ferromagnetic Weyl semimetal also becomes anisotropic, being less
dispersed perpendicular to the magnetization.",1511.08381v1
2015-05-12,Nonreciprocal spin wave propagation in chiral-lattice ferromagnets,"Spin current, i.e. the flow of spin angular momentum or magnetic moment, has
recently attracted much attention as the promising alternative for charge
current with better energy efficiency. Genuine spin current is generally
carried by the spin wave (propagating spin precession) in insulating
ferromagnets, and should hold the chiral symmetry when it propagates along the
spin direction. Here, we experimentally demonstrate that such a spin wave spin
current (SWSC) shows nonreciprocal propagation characters in a chiral-lattice
ferromagnet. This phenomenon originates from the interference of chirality
between the SWSC and crystal-lattice, which is mediated by the relativistic
spin-orbit interaction. The present finding enables the design of perfect spin
current diode, and highlights the importance of the chiral aspect in SWSC.",1505.02868v1
2019-01-24,Spin-Wave Theory for the Scalar Chiral Phase in the Multiple-Spin Exchange Model on a Triangular Lattice,"We study the effects of quantum fluctuations on a non-coplanar tetrahedral
spin structure, which has a scalar chiral order, in the spin-1/2 multiple-spin
exchange model with up to the six-spin exchange interactions on a triangular
lattice. We find that, in the linear spin-wave approximation, the tetrahedral
structure survives the quantum fluctuations because spin waves do not soften in
the whole parameter region of the tetrahedral-structure phase evaluated for the
classical system. In the quantum corrections to the ground-state energy,
sublattice magnetization, and scalar chirality, the effects of the quantum
fluctuations are small for the ferromagnetic nearest-neighbor interactions and
for the strong five-spin interactions. The six-spin interactions have little
effect on the quantum corrections in the tetrahedral-structure phase. This
calculation also corrects an error in the previously reported value of scalar
chirality for the spin-1/2 multiple-spin exchange model with up to the
four-spin exchange interactions.",1901.08198v1
2019-07-05,Theory for shift current of bosons: Photogalvanic spin current in ferrimagnetic and antiferromagnetic insulators,"We theoretically study the optical generation of dc spin current (i.e., a
spin-current solar cell) in ordered antiferromagnetic and ferrimagnetic
insulators, motivated by a recent study on the laser-driven spinon spin current
in noncentrosymmetric quantum spin chains [H. Ishizuka and M. Sato, Phys. Rev.
Lett. 122, 197702 (2019)]. Using a non-linear response theory for magnons, we
analyze the dc spin current generated by a linearly-polarized electromagnetic
wave (typically, terahertz or gigahertz waves). Considering noncentrosymmetric
two-sublattice magnets as an example, we find a finite dc spin current
conductivity at $T=0$, where no thermally-excited magnons exist; this is in
contrast to the case of the spinon spin current, in which the optical
transition of the Fermi degenerate spinons plays an essential role. We find
that the dc spin-current conductivity is insensitive to the Gilbert damping,
i.e., it may be viewed as a shift current carried by bosonic particles
(magnons). Our estimate shows that an electric-field intensity of
$E\sim10^4-10^6$ V/cm is sufficient for an observable spin current. Our theory
indicates that the linearly-polarized electromagnetic wave generally produces a
dc spin current in noncentrosymmetric magnetic insulators.",1907.02734v1
2022-09-26,Imprinting spatial helicity structure of vector vortex beam on spin texture in semiconductors,"We present the transfer of the spatially variant polarization of
topologically structured light to the spatial spin texture in a semiconductor
quantum well. The electron spin texture, which is a circular pattern with
repeating spin-up and spin-down states whose repetition rate is determined by
the topological charge, is directly excited by a vector vortex beam with a
spatial helicity structure. The generated spin texture efficiently evolves into
a helical spin wave pattern owing to the spin-orbit effective magnetic fields
in the persistent spin helix state by controlling the spatial wave number of
the excited spin mode. By tuning the repetition length and azimuthal angle, we
simultaneously generate helical spin waves with opposite phases by a single
beam.",2209.12496v1
1995-09-04,Spin-wave condensation and quantum melting of long-range antiferromagnetic order in t-J model,"Ground state wave function of two-dimensional t-J model is found at doping
close to half filling. It is shown that the condensation of Cooper pairs
(superconducting pairing of mobile holes) and the condensation of spin-waves
into spin-liquid state are closely connected. The effective spectrum of $S=1$
excitations, spin-wave gap pseudo-gap $\Delta_M$, magnetic correlation length
$\xi_M$, and static magnetic formfactor $S_M(\bf q)$ are calculated.",9509011v1
1995-09-13,Spin-wave excitation spectra and spectral weights in square lattice antiferromagnets,"Using a recently developed method for calculating series expansions of the
excitation spectra of quantum lattice models, we obtain the spin-wave spectra
for square lattice, $S=1/2$ Heisenberg-Ising antiferromagnets. The calculated
spin-wave spectrum for the Heisenberg model is close to but noticeably
different from a uniformly renormalized classical (large-$S$) spectrum with the
renormalization for the spin-wave velocity of approximately $1.18$. The
relative weights of the single-magnon and multi-magnon contributions to neutron
scattering spectra are obtained for wavevectors throughout the Brillouin zone.",9509077v1
1995-11-17,The incoherent part of the spin-wave polarization operator in the t-J model,"A calculation of the spin-wave polarization operator is very important for
the analysis of the magnetic structure of high temperature superconductors. We
analyze the significance of the incoherent part of the spin-wave polarization
operator within the framework of the t-J model. This part is calculated
analytically for small doping with logarithmic accuracy. We conclude that the
incoherent part of the spin-wave polarization operator is negligible in
comparison with the coherent part.",9511087v2
1996-02-08,Isotropic Spin Wave Theory of Short-Range Magnetic Order,"We present an isotropic spin wave (ISW) theory of short-range order in
Heisenberg magnets, and apply it to square lattice S=1/2 and S=1
antiferromagnets. Our theory has three identical (isotropic) spin wave modes,
whereas the conventional spin wave theory has two transverse and one
longitudinal mode. We calculate temperature dependences of various
thermodynamic observables analytically and find good (several per cent)
agreement with independently obtained numerical results in a broad temperature
range.",9602044v1
1997-12-23,The edge theory of ferromagnetic quantum Hall states,"We propose an effective low-energy theory for ferromagnetic Hall states. It
describes the charge degrees of freedom, on the edge, by a (1 + 1) dimensional
chiral boson theory, and the spin degrees of freedom by the (2 + 1)dimensional
quantum ferromagnet theory in the spin-wave approximation. The usual chiral
boson theory for spinless electrons is modified to include the charge degrees
of freedom with spin. Our total, bulk plus edge, effective action is gauge
invariant and we find a generalized ""chiral anomaly"" in this case. We describe
two, charged and neutral, sets of edge spin-wave solutions. The spreading of
these waves is much larger than the one for the charge (edge) waves and they
have linear dispersion relations.",9712279v1
1999-07-12,"Dynamics of the Compact, Ferromagnetic ν=1 Edge","We consider the edge dynamics of a compact, fully spin polarized state at
filling factor $\nu=1$. We show that there are two sets of collective
excitations localized near the edge: the much studied, gapless, edge
magnetoplasmon but also an additional edge spin wave that splits off below the
bulk spin wave continuum. We show that both of these excitations can soften at
finite wave-vectors as the potential confining the system is softened, thereby
leading to edge reconstruction by spin texture or charge density wave
formation. We note that a commonly employed model of the edge confining
potential is non-generic in that it systematically underestimates the texturing
instability.",9907175v1
2000-10-16,Spin waves in ultrathin ferromagnetic overlayers,"The influence of a non-magnetic metallic substrate on the spin wave
excitations in ultrathin ferromagnetic overlayers is investigated for different
crystalline orientations. We show that spin wave dumping in these systems occur
due to the tunneling of holes from the substrate into the overlayer, and that
the spin wave energies may be considerably affected by the exchange coupling
mediated by the substrate.",0010215v1
2002-03-19,Spin-wave spectrum of copper metaborate in the commensurate phase 10K<T<21K,"We have investigated the spin-wave spectrum of copper metaborate,
CuB$_2$O$_4$, by means of inelastic neutron scattering in the commensurate
magnetic phase. We have found two branches of spin-wave excitations associated
with the two magnetic sublattices Cu(A) and Cu(B), respectively. In the
temperature regime $10K \le T \le 21K$, where only the Cu(A) magnetic moments
are ordered, the interaction between the two sublattices is found to be
negligible. With this approximation we have determined the `easy plane'
exchange parameters of the Cu(A) subsystem within standard spin-wave theory.",0203369v1
2005-02-07,The resonating valence bond wave functions in quantum antiferromagnets,"Projected-BCS wave functions have been proposed as the paradigm for the
understanding of disordered spin states (spin liquids). Here we investigate the
properties of these wave functions showing how Luttinger liquids, dimerized
states, and gapped spin liquids may be described by the same class of wave
functions, which, therefore, represent an extremely flexible variational tool.
A close connection between spin liquids and",0502170v1
2005-06-14,Spin-wave softening and Hund's coupling in ferromagnetic manganites,"Using one-orbital model of hole-doped manganites, we show with the help of
Holstein-Primakov transformation that finite Hund's coupling is responsible for
the spin-wave softening in the ferromagnetic $B$-phase manganites. We obtain an
analytical result for the spin-wave spectrum for $\JH\gg t$. In the limit of
infinte Hund's coupling, the spectrum is the conventional nearest-neighbor
Heisenberg ferromagnetic spin-wave. The $o(t/\JH)$-order correction is negative
and thus accounts for the softening near the zone boundary.",0506321v1
2005-08-25,Interactions of spin waves with a magnetic vortex,"We have investigated azimuthal spin-wave modes in magnetic vortex structures
using time-resolved Kerr microscopy. Spatially resolved phase and amplitude
spectra of ferromagnetic disks with diameters from 5 $\mu$m down to 500 nm
reveal that the lowest order azimuthal spin wave mode splits into a doublet as
the disk size decreases. We demonstrate that the splitting is due to the
coupling between spin waves and the gyrotropic motion of the vortex core.",0508597v1
2006-04-13,Spin-wave instability for parallel pumping in ferromagnetic thin films under oblique field,"Spin-wave instability for parallel pumping is studied theoretically. The
spin-wave instability threshold is calculated in ferromagnetic thin films under
oblique field which has an oblique angle to the film plane. The butterfly curve
of the threshold usually has a cusp at a certain value of the static external
field. While the static field value of the cusp point varies as the oblique
angle changes, the general properties of the butterfly curve show little
noteworthy change. For very thin films, however, multiple cusps of the
butterfly curve can appear due to different standing spin-wave modes, which
indicate a novel feature for thin films under oblique field.",0604329v1
2007-01-19,Excited states of quantum many-body interacting systems: A variational coupled-cluster description,"We extend recently proposed variational coupled-cluster method to describe
excitation states of quantum many-body interacting systems. We discuss, in
general terms, both quasiparticle excitations and quasiparticle-density-wave
excitations (collective modes). In application to quantum antiferromagnets, we
reproduce the well-known spin-wave excitations, i.e. quasiparticle magnons of
spin $\pm 1$. In addition, we obtain new, spin-zero magnon-density-wave
excitations which has been missing in Anserson's spin-wave theory. Implications
of these new collective modes are discussed.",0701482v1
2007-11-29,Realization of XNOR and NAND spin-wave logic gates,"We demonstrate the functionality of spin-wave logic XNOR and NAND gates based
on a Mach-Zehnder type interferometer which has arms implemented as sections of
ferrite film spin-wave waveguides. Logical input signals are applied to the
gates by varying either the phase or the amplitude of the spin waves in the
interferometer arms. This phase or amplitude variation is produced by Oersted
fields of dc current pulses through conductors placed on the surface of the
magnetic films.",0711.4720v1
2008-01-19,Electrical control of magnon propagation in multiferroic BiFeO3 films,"The spin wave spectra of multiferroic BiFeO3 films is calculated using a
phenomenological Landau theory that includes magnetostatic effects. The lowest
frequency magnon dispersion is shown to be quite sensitive to the angle between
spin wave propagation vector and the Neel moment. Since electrical switching of
the Neel moment has recently been demonstrated in this material, the
sensitivity of the magnon dispersion permits direct electrical switching of
spin wave propagation. This effect can be used to construct spin wave logical
gates without current pulses, potentially allowing reduced power dissipation
per logical operation.",0801.3012v1
2008-03-26,Unusual spin-wave population in nickel after femtosecond laser pulse excitation,"The spin-wave relaxation mechanisms after intense laser excitation in
ferromagnetic nickel films are investigated with all-optical pump-probe
experiments. Uniform precession (Kittel mode), Damon-Eshbach surface modes and
perpendicular standing spin waves can be identified by their dispersion f(H).
However, different to other ferromagnets f(H) deviates from the expected
behavior. Namely, a mode discontinuity is observed, that can be attributed to a
non-linear process. Above a critical field the power spectrum reveals a
redistribution of the energy within the spin-wave spectrum populated.",0803.3686v2
2009-01-14,Interface coupling properties and reflection of bulk spin waves from biaxial multilayer ferromagnetic media,"The reflection coefficient of bulk spin waves from multilayer ferromagnetic
structure with periodically modulated parameters of exchange interaction,
uniaxial and rhombic magnetic anisotropy and saturation magnetization is
calculated with a non-ideal coupling between layers. The strong dependence of
spin-wave reflection coefficient on frequency, magnetic field and parameter of
interfacial coupling is revealed. It allows changing the reflection intensity
from 0 to 1 by changing either only external magnetic field value or frequency.
The proposed model of boundary conditions gives the opportunity to take into
account the quality of interfaces when studying the reflection processes of
spin waves in multilayer structures.",0901.2012v1
2009-08-14,Spin-wave interference in three-dimensional rolled-up ferromagnetic microtubes,"We have investigated spin-wave excitations in rolled-up Permalloy microtubes
using microwave absorption spectroscopy. We find a series of quantized
azimuthal modes which arise from the constructive interference of Damon-Eshbach
type spin waves propagating around the circumference of the microtubes, forming
a spin-wave resonator. The mode spectrum can be tailored by the tube's radius
and number of rolled-up layers.",0908.2082v1
2011-03-06,Spin-wave energy dispersion of a frustrated spin-1/2 Heisenberg antiferromagnet on a stacked square lattice,"Effects of interlayer coupling and spatial anisotropy on spin-wave excitation
spectra of a three-dimensional spatially anisotropic, frustrated spin-$\half$
Heisenberg antiferromagnet (HAFM) is investigated for the two ordered phases
using second-order spin-wave expansion. We show that the second-order
corrections to the spin-wave energies are significant and find that the energy
spectra of the three-dimensional HAFM shares similar qualitative features with
the energy spectra of the two-dimensional HAFM on a square lattice. We also
discuss the features that can provide experimental measures for the strength of
the interlayer coupling, spatial anisotropy parameter, and magnetic
frustration.",1103.1155v1
2011-03-29,Spin waves in the block checkerboard antiferromagnetic phase,"Motivated by the discovery of new family 122 iron-based superconductors, we
present the theoretical results on the ground state phase diagram, spin wave
and dynamic structure factor of the extended $J_{1}-J_{2}$ Heisenberg model. In
the reasonable physical parameter region of $K_{2}Fe_{4}Se_{5}$, we fi{}nd the
block checkerboard antiferromagnetic order phase is stable. There are two
acoustic branches and six optical branches spin wave in the block checkerboard
antiferromagnetic phase, which has analytic expression in the high symmetry
points. To compare the further neutron scattering experiments, we discuss the
saddlepoint structure in the magnetic excitation spectrum and calculate the
predicted inelastic neutron scattering pattern based on linear spin wave
theory.",1103.5521v1
2011-11-16,Spatial distribution of spin-wave modes in cylindrical nanowires of finite aspect ratio,"The spin wave modes of cylindrical nanowires of moderate diameter-to-length
ratio are investigated in this article. Based on three dimensional simulations
and analytical calculations we determine the spatial structure of the modes. We
show that standing spin waves and localized edge modes form the discrete
spectrum of the nanowires. Using a simple analytical model we infer an extended
dispersion relation for spin waves in cylinders. Considering the variation of
the demagnetizing (internal) field we show that the localized dipole-exchange
modes at the edges are always present.",1111.3838v1
2012-04-20,Spin Versus Charge Density Wave Order in Graphene-like Systems,"A variational technique is used to study sublattice symmetry breaking by
strong on-site and nearest neighbor interactions in graphene. When interactions
are strong enough to break sublattice symmetry, and with relative strengths
characteristic of graphene, a charge density wave Mott insulator is favored
over the spin density wave condensates. In the spin density wave condensate we
find that introduction of a staggered on-site energy (quasiparticle mass) leads
to a splitting of the fermi velocities and mass gaps of the quasiparticle spin
states.",1204.4531v2
2012-05-21,Emergence of spatial spin-wave correlations in a cold atomic gas,"Rydberg spin waves are optically excited in a quasi-one-dimensional atomic
sample of Rb atoms. Pair-wise spin-wave correlations are observed by a
spatially selective transfer of the quantum state onto a light field and
photoelectric correlation measurements of the light. The correlations are
interpreted in terms of the dephasing of multiply-excited spin waves by
long-range Rydberg interactions.",1205.4708v2
2012-08-09,Spin waves interference from rising and falling edges of electrical pulses,"The authors have investigated the effect of the electrical pulse width of
input excitations on the generated spin waves in a NiFe strip using pulse
inductive time domain measurements. The authors have shown that the spin waves
resulting from the rising- and the falling-edges of input excitation pulses
interfere either constructively or destructively, and have provided conditions
for obtaining spin wave packets with maximum intensity at different bias
conditions.",1208.1836v1
2013-05-14,Ferrimagnetic Spin Wave Resonance and Superconductivity in Carbon Nanotubes,"The phenomenon of ferrimagnetic spin wave resonance [uncompensated
antiferromagnetic spin wave resonance] has been detected for the first time. It
has been observed in carbon nanotubes, produced by high energy ion beam
modification of diamond single crystals in $\ <{100}\ >$ direction.
Peculiarities of spin wave resonance observed allow to insist on the formation
in given nanotubes of $s^+$ superconductivity at room temperature, coexisting
with uncompensated antiferromagnetic ordering.",1305.3256v1
2014-04-29,On conformal higher spin wave operators,"We analyze free conformal higher spin actions and the corresponding wave
operators in arbitrary even dimensions and backgrounds. We show that the wave
operators do not factorize in general, and identify the Weyl tensor and its
derivatives as the obstruction to factorization. We give a manifestly
factorized form for them on (A)dS backgrounds for arbitrary spin and on
Einstein backgrounds for spin 2. We are also able to fix the conformal wave
operator in d=4 for s=3 up to linear order in the Riemann tensor on generic
Bach-flat backgrounds.",1404.7452v2
2014-10-13,Vortex gyration mediated by spin waves driven by an out-of-plane oscillating magnetic field,"In this letter we address the vortex core dynamics involved in gyration
excitation and damping change by out-of-plane oscillating magnetic fields. When
the vortex core is at rest under the effect of in-plane bias magnetic fields,
the spin waves excited by the perpendicular magnetic field can induce obvious
vortex gyration. When simultaneously excite spin waves and vortex gyrotropic
motion, the gyration damping changes. Analysis of the system energy allows us
to explain the origin of the spin-wave-mediated vortex gyration.",1410.3230v1
2017-05-03,Controlling Chiral Domain Walls in Antiferromagnets Using Spin-Wave Helicity,"In antiferromagnets, the Dzyaloshinskii-Moriya interaction lifts the
degeneracy of left- and right-circularly polarized spin waves. This
relativistic coupling increases the efficiency of spin-wave-induced domain wall
motion and leads to higher drift velocities. We show that in biaxial
antiferromagnets, the spin-wave helicity controls both the direction and
magnitude of the magnonic force on chiral domain walls. By contrast, in
uniaxial antiferromagnets, the magnonic force is propulsive with a helicity
dependent strength.",1705.01572v2
2003-12-31,Excitation of Spin Waves in Superconducting Ferromagnets,"This Letter presents a theoretical analysis of propagation of spin waves in a
superconducting ferromagnet. The surface impedance was calculated for the case
when the magnetization is normal to the sample surface. We found the
frequencies at which the impedance and the power absorption have singularities
related to the spin wave propagation, and determined the form of these
singularities. With a suitable choice of parameters, there is a frequency
interval in which two propagating spin waves of the same circular polarization
are generated, one of them having a negative group velocity.",0312720v1
2017-03-09,Spin-wave excitations in the SDW state of iron pnictides: a comparison between the roles of interaction parameters,"We investigate the role of Hund's coupling in the spin-wave excitations of
the ($\pi, 0$) ordered magnetic state within a five-orbital tight-binding model
for iron pnictides. To differentiate between the roles of intraorbital Coulomb
interaction and Hund's coupling, we focus on the self-consistently obtained
mean-field SDW state with a fixed magnetic moment obtained by using different
sets of interaction parameters. We find that the Hund's coupling is crucial for
the description of various experimentally observed characteristics of the
spin-wave excitations including the anisotropy, energy-dependent behavior, and
spin-wave spectral weight distribution.",1703.03228v2
2020-05-06,Angular momentum conservation in counter-propagating vectorially structured light,"It is well-known that electric spin angular momentum and electric orbital
angular momentum are conserved under paraxial propagation of travelling waves
in free-space. Here we study the electric and magnetic angular momentum in
counter-propagating waves and show both theoretically and experimentally that
neither component alone is conserved except in special cases. We attribute this
non-conservation to spin-spin and orbit-orbit coupling between the electric and
magnetic fields. This work generalises previous findings based on travelling
waves, explains the apparent spin-orbit coupling in counter-propagating
paraxial light, and broadens our understanding of angular momentum conservation
in arbitrary structured light waves.",2005.02739v1
2020-12-23,Analytic description of spin waves in dipolar/octupolar pyrochlore magnets,"We derive analytic forms for spin waves in pyrochlore magnets with
dipolar-octupolar interactions, such as ${\rm Nd}_2{\rm Zr}_2{\rm O}_7$. We
obtain full knowledge of the diagonalized magnonic Hamiltonian within the
linear spin wave approximation. We also consider the effect of a ""breathing
mode"" as a perturbation of this system. The breathing mode lifts the degeneracy
of the upper band of the spin wave dispersion along the direction $X\to W$ in
$k$-space.",2012.12500v1
2021-03-05,Universal spin wave damping in magnetic Weyl semimetals,"We analyze the decay of spin waves into Stoner excitations in magnetic Weyl
semimetals. The lifetime of a mode is found to have a universal dependence on
its frequency and momentum, and on a few parameters that characterize the
relativistic Weyl spectrum. At the same time, Gilbert damping by Weyl electrons
is absent. The decay rate of spin waves is calculated perturbatively using the
s-d model of itinerant Weyl or Dirac electrons coupled to local moments. We
show that many details of the Weyl spectrum, such as the momentum-space
locations, dispersions and sizes of the Weyl Fermi pockets, can be deduced
indirectly by probing the spin waves of local moments using inelastic neutron
scattering.",2103.03885v1
2021-12-29,Spin Wave Propagation through Antiferromagnet/Ferromagnet Interface,"We study the problem of controlling spin waves propagation through an
antiferromagnet/ferromagnet interface via tuning material parameters. It is
done by introducing the degree of sublattice noncompensation of antiferromagnet
(DSNA), which is a physical characteristic of finite-thickness interfaces. The
DSNA value can be varied by designing interfaces with a particular disorder or
curvilinear geometry. We describe a spin-wave propagation through any designed
antiferromagnet/ferromagnet interface considering a variable DSNA and
appropriate boundary conditions. As a result, we calculate the physical
transmittance and reflectance of the spin waves as a function of frequency and
show how to control them via the exchange parameters tuning.",2112.14583v1
2022-03-17,Electron Wave Spin in a Quantum Well,"The particle-wave duality of the electron poses a principle question of
whether the spin is a property of the particle or the wave. In this paper, the
wave nature of the spin is studied for an electron inside a two-dimensional
quantum well. By solving the exact $4-$spinor eigen solution to the Dirac
equation, we show that a stable circulating total current density exists inside
the well with a donut shaped topography. A spin value is modified by the
confining geometry of the well. Our analysis also shows that a free electron
Gaussian wavepacket is unstable and experiences quick decoherence.",2203.09437v2
2009-05-18,Bulk Spin-Hall Effect,"We show that a two-dimensional spin-orbit-coupled system in the presence of a
charge/spin-density wave with a wave-vector perpendicular to an applied
electric field supports bulk manifestations of the direct/inverse spin-Hall
effect. We develop a theory of this phenomenon in the framework of the spin
diffusion equation formalism and show that, due to the inhomogeneity created by
a spin-grating, an anomalous bulk charge-density wave is induced away from
sample boundaries. The optimal conditions for the observation of the effect are
determined. The main experimental manifestation of the bulk spin-Hall effect,
the induced charge/spin-density-wave, is characterized by a pi/2-phase shift
relative to the initial non-homogeneous spin/charge-polarization profile and
has a non-monotonic time-varying amplitude.",0905.2771v1
2011-12-21,Direct detection of magnon spin transport by the inverse spin Hall effect,"Conversion of traveling magnons into an electron carried spin current is
demonstrated in a time resolved experiment using a spatially separated
inductive spin-wave source and an inverse spin Hall effect (ISHE) detector. A
short spin-wave packet is excited in a yttrium-iron garnet (YIG) waveguide by a
microwave signal and is detected at a distance of 3 mm by an attached Pt layer
as a delayed ISHE voltage pulse. The delay in the detection appears due to the
finite spin-wave group velocity and proves the magnon spin transport. The
experiment suggests utilization of spin waves for the information transfer over
macroscopic distances in spintronic devices and circuits.",1112.4969v1
2013-07-29,Generalized spin-wave theory: application to the bilinear-biquadratic model,"We present a generalized spin-wave theory (GSWT) for treating spin
Hamiltonians of arbitrary spin $S$. The generalization consists of an extension
of the traditional spin-wave theory from SU(2) to SU($N$). Low energy
excitations are waves of the local order parameter that fluctuates in the
SU($N$) space of unitary transformations of the local spin states, instead of
the SU(2) space of local spin rotations. Since the generators of the SU($N$)
group can be represented as bilinear forms in $N$-flavored bosons, the
low-energy modes of the GSWT are described with $N-1$ different bosons. The
generalization allows treating quantum spin systems whose ground state exhibit
multipolar ordering as well as detecting instabilities of magnetically ordered
states (dipolar ordering) towards higher multipolar orderings. We illustrate
these advantages by applying the GSWT to a bilinear-biquadratic model of
arbitrary spin $S$ on hypercubic lattices.",1307.7731v1
2015-07-07,"Magnetic order, spin waves and fluctuations in the triangular antiferromagnet La2Ca2MnO7","We report magnetic susceptibility, specific heat and muon spin relaxation
(muSR) experiments on the triangular antiferromagnet La2Ca2MnO7 which develops
a genuine two-dimensional, three-sublattice \sqrt{3} \times \sqrt{3} magnetic
order below T_N = 2.8 K. From the susceptibility and specific heat data an
estimate of the exchange interaction is derived. A value for the spin-wave gap
is obtained from the latter data. The analysis of a previously reported
inelastic neutron scattering study yields values for the exchange and spin-wave
gap compatible with the results obtained from macroscopic measurements. An
appreciable entropy is still missing at 10 K that may be ascribed to intense
short-range correlations. The critical paramagnetic fluctuations extend far
above T_N, and can be partly understood in terms of two-dimensional spin-wave
excitations. While no spontaneous muSR field is observed below T_N, persistent
spin dynamics is found. Short-range correlations are detected in this
temperature range. Their relation to a possible molecular spin substructure and
the observed exotic spin fluctuations is discussed.",1507.01740v1
2020-01-21,Nonresonant amplification of coherent spin waves through voltage-induced interface magnetoelectric effect and spin-transfer torque,"We present new mechanism for manipulation of the spin-wave amplitude through
the use of the dynamic charge-mediated magnetoelectric effect in ultrathin
multilayers composed of dielectric thin-film capacitors separated by a
ferromagnetic bilayer. Propagating spin waves can be amplified and attenuated
with rising and decreasing slopes of the oscillating voltage, respectively,
locally applied to the sample. The way the spin accumulation is generated makes
the interaction of the spin-transfer torque with the magnetization dynamics
mode-selective and restricted to some range of spin-wave frequencies, which is
in contrary to known types of the spin-transfer torque effects. The interfacial
nature of spin-dependent screening allows to reduce the thickness of the fixed
magnetization layer to a few nanometers, thus the proposed effect significantly
contributes toward realization of the magnonic devices and also miniaturization
of the spintronic devices.",2001.07474v1
2020-12-23,Parity-controlled spin-wave excitations in synthetic antiferromagnets,"We report in this study the current-induced-torque excitation of acoustic and
optical modes in Ta/NiFe/Ru/NiFe/Ta synthetic antiferromagnet stacks grown on
SiO2/Si substrates. The two Ta layers serve as spin torque sources with the
opposite polarisations both in spin currents and Oersted fields acting on their
adjacent NiFe layers. This can create the odd symmetry of spatial spin torque
distribution across the growth direction, allowing us to observe different
spin-wave excitation efficiency from synthetic antiferromagnets excited by
homogeneous torques. We analyse the torque symmetry by in-plane angular
dependence of symmetric and anti-symmetric lineshape amplitudes for their
resonance and confirm that the parallel (perpendicular) pumping nature for the
acoustic (optical) modes in our devices, which is in stark difference from the
modes excited by spatially homogeneous torques. We also present our macrospin
model for this particular spin-torque excitation geometry, which excellently
supports our experimental observation. Our results offer capability of
controlling spin-wave excitations by local spin-torque sources and we can
explore further spin-wave control schemes based on this concept.",2012.12999v2
2010-03-13,Motion and gravitational wave forms of eccentric compact binaries with orbital-angular-momentum-aligned spins under next-to-leading order in spin-orbit and leading order in spin(1)-spin(2) and spin-squared couplings,"A quasi-Keplerian parameterisation for the solutions of second post-Newtonian
(PN) accurate equations of motion for spinning compact binaries is obtained
including leading order spin-spin and next-to-leading order spin-orbit
interactions. Rotational deformation of the compact objects is incorporated.
For arbitrary mass ratios the spin orientations are taken to be parallel or
anti-parallel to the orbital angular momentum vector. The emitted gravitational
wave forms are given in analytic form up to 2PN point particle, 1.5PN spin
orbit and 1PN spin-spin contributions, where the spins are counted of 0PN
order.",1003.2735v4
2016-02-12,Thermal generation of spin current in a helimagnetic multiferroic hexaferrite,"We report the experimental observation of longitudinal spin Seebeck effect in
a multiferroic helimagnet Ba0.5Sr1.5Zn2Fe12O22. Temperature gradient applied
normal to Ba0.5Sr1.5Zn2Fe12O22/Pt interface generates inverse spin Hall voltage
of spin current origin in Pt, whose magnitude was found to be proportional to
bulk magnetization of Ba0.5Sr1.5Zn2Fe12O22 even through the successive magnetic
transitions among various helimagnetic and ferrimagnetic phases. This finding
demonstrates that the helimagnetic spin wave can be an effective carrier of
spin current. By controlling the population ratio of spin-helicity domains
characterized by clockwise/counter-clockwise manner of spin rotation with use
of poling electric field in the ferroelectric helimagnetic phase, we found that
spin-helicity domain distribution does not affect the magnitude of spin current
injected into Pt. The results suggest that the spin-wave spin current is rather
robust against the spin-helicity domain wall, unlike the case with the
conventional ferromagnetic domain wall.",1602.04011v1
2019-08-27,Inelastic light scattering in the spin cluster Mott insulator Cu$_{2}$OSeO$_{3}$,"Clusters of single spins form the relevant spin entities in the formation of
long-range magnetic order in spin cluster Mott insulators. Such type of spin
order bears resemblance to molecular crystals, and we therefore may expect a
prototypical spin wave spectrum which can be divided into low-energy external
and high-energy internal cluster spin wave modes. Here, we study high-energy
spin cluster excitations in the spin cluster Mott insulator Cu$_{2}$OSeO$_{3}$
by means of spontaneous Raman scattering. Multiple high-energy optical magnon
modes are observed, of which the Raman-activity is shown to originate in the
Elliot-Loudon scattering mechanism. Upon crossing the long-range ordering
transition temperature the magnetic modes significantly broaden, corresponding
to scattering from localized spin excitations within the spin clusters.
Different optical phonon modes show a strong temperature dependence, evidencing
a strong magnetoelectric coupling between optical phonons and the high-energy
spin cluster excitations. Our results support the picture that
Cu$_{2}$OSeO$_{3}$ can be regarded as a solid-state molecular crystal of spin
nature.",1908.10279v1
2007-09-21,Spin-Peierls transition in carbynoid conductors: infrared absorption study,"The results of IR-studies in quasi-1D carbynoid films produced by
dehydrohalogenation of poly(vinilidene fluoride) are in good agreement with the
assumption that carbynoid films studied are generalized spin -Peierls
conductors, the metal to insulator transition in which can be described in the
frame of t-J model. Residual atoms of fluorine, hydrogen and atoms of main
technological impurity oxygen in the form of various complexes in interchain
space are suggested to be spin - (or joint spin - and electrical) conductivity
dopants. Antiferroelectric spin wave resonance (AFESWR) being to be optical
analogue of antiferromagnetic spin wave resonance has been identified for the
first time. Electric spin-Peierls polaron lattice in C-C -bonds is proposed to
be responsible for the observed AFESWR both in starting PWDF films and in
carbynoid B-films (the samples with the least impurity content). Electric spin
moment with pure imaginary value predicted by Dirac as early as 1928 was
identified for the first time. Electric spin-Peierls polarons are proposed to
be electric spin moment carriers. It has been established that topological
solitons, earlier called spin-Peierls solitons (SPS), are simultaneously
active, unlike to topological solitons with nonzero spin in
\textit{trans}-polyacetylene, in both optical and magnetic resonance spectra.It
is explained in suggestion that SPS possess by both electric and magnetic spin
moments which can be considered as two components of complex electromagnetic
spin vector as a single whole. SPS proposed to be consisting of two coupled
domain walls in both magnetic and electric generalized spin density wave
(GSDW), produced by electromagnetic spin-Peierls transition in its generalized
form in $\pi$ - and $\sigma$ -subsystems of carbynoids.",0709.3382v2
2021-01-25,Long-range spin-wave propagation in transversely magnetized nano-scaled conduits,"Magnonics attracts increasing attention in the view of novel low-energy
computation technologies based on spin waves. Recently, spin-wave propagation
in longitudinally magnetized nano-scaled spin-wave conduits was demonstrated,
proving the fundamental feasibility of magnonics at the sub-100 nm scale.
Transversely magnetized nano-conduits, which are of great interest in this
regard as they offer a large group velocity and a potentially chirality-based
protected transport of energy, have not yet been investigated due to their
complex internal magnetic field distribution. Here, we present a study of
propagating spin waves in a transversely magnetized nanoscopic yttrium iron
garnet conduit of 50 nm width. Space and time-resolved micro-focused
Brillouin-light-scattering spectroscopy is employed to measure the spin-wave
group velocity and decay length. A long-range spin-wave propagation is observed
with a decay length of up to (8.0+-1.5) {\mu}m and a large spin-wave lifetime
of up to (44.7+-9.1) ns. The results are supported with micromagnetic
simulations, revealing a single-mode dispersion relation in contrast to the
common formation of localized edge modes for microscopic systems. Furthermore,
a frequency non-reciprocity for counter-propagating spin waves is observed in
the simulations and the experiment, caused by the trapezoidal cross-section of
the structure. The revealed long-distance spin-wave propagation on the
nanoscale is particularly interesting for an application in spin-wave devices,
allowing for long-distance transport of information in magnonic circuits, as
well as novel low-energy device architectures.",2101.10192v1
1998-01-15,Solitary Waves of Planar Ferromagnets and the Breakdown of the Spin-Polarized Quantum Hall Effect,"A branch of uniformly-propagating solitary waves of planar ferromagnets is
identified. The energy dispersion and structures of the solitary waves are
determined for an isotropic ferromagnet as functions of a conserved momentum.
With increasing momentum, their structure undergoes a transition from a form
ressembling a droplet of spin-waves to a Skyrmion/anti-Skyrmion pair. An
instability to the formation of these solitary waves is shown to provide a
mechanism for the electric field-induced breakdown of the spin-polarized
quantum Hall effect.",9801160v1
2015-03-16,Stochastic Quantum Trajectories without a Wave Function,"After summarizing three versions of trajectory-based quantum mechanics, it is
argued that only the original formulation due to Bohm, which uses the
Schr\""odinger wave function to guide the particles, can be readily extended to
particles with spin. To extend the two wave function-free formulations, it is
argued that necessarily particle trajectories not only determine location, but
also spin. Since spin values are discrete, it is natural to revert to a
variation of Bohm's pilot wave formulation due originally to Bell. It is shown
that within this formulation with stochastic quantum trajectories, a wave
function free formulation can be obtained.",1503.04868v1
2012-09-19,Asymmetry of modal profiles of dipole-exchange spin waves in thin high-magnetic moment metallic ferromagnetic films,"The asymmetry of the modal profiles for dipole-exchange spin waves
propagating in in-plane magnetized ferromagnetic films at a right angle to the
applied magnetic field has been investigated theoretically. It was found that
in the large-magnetic moment ferromagnetic metallic films with typical
thicknesses 10-60 nm the fundamental mode of the spectrum is localized at the
surface opposite to the surface of localization of the exchange-free
Damon-Eshbach surface wave. This anomalous localization of the wave does not
affect the non-reciprocity of spin wave excitation by microstrip and coplanar
transducers but may be detected in other types of experiments.",1209.4153v1
2019-06-16,Spin and valley waves in Dirac semimetals with population imbalance,"We find an intervalley wave collective mode in two- and three-dimensional
Dirac semimetals in the presence of a valley population imbalance. The
dispersion relation of this mode is gapless, proportional to the square of the
wave vector at small frequencies, and inversely proportional to the
electron-electron exchange interaction energy. The valley wave serves as an
energy gain source for the external field, that generates the intervalley
transitions. The spin wave analog is discussed for the case of a semimetal with
nonequilibrium spin orientation.",1906.06674v2
2014-10-23,Nanometre-scale probing of spin waves using single electron spins,"Correlated-electron systems support a wealth of magnetic excitations, ranging
from conventional spin waves to exotic fractional excitations in
low-dimensional or geometrically-frustrated spin systems. Probing such
excitations on nanometre length scales is essential for unravelling the
underlying physics and developing new spintronic nanodevices. However, no
established technique provides real-space, few-nanometre-scale probing of
correlated-electron magnetic excitations under ambient conditions. Here we
present a solution to this problem using magnetometry based on single
nitrogen-vacancy (NV) centres in diamond. We focus on spin-wave excitations in
a ferromagnetic microdisc, and demonstrate local, quantitative, and
phase-sensitive detection of the spin-wave magnetic field at ~50 nm from the
disc. We map the magnetic-field dependence of spin-wave excitations by
detecting the associated local reduction in the disc's longitudinal
magnetization. In addition, we characterize the spin-noise spectrum by NV-spin
relaxometry, finding excellent agreement with a general analytical description
of the stray fields produced by spin-spin correlations in a 2D magnetic system.
These complementary measurement modalities pave the way towards imaging the
local excitations of systems such as ferromagnets and antiferromagnets,
skyrmions, atomically assembled quantum magnets, and spin ice.",1410.6423v2
2021-07-22,Spin-orbit torque control of spin waves in a ferromagnetic waveguide,"Spin-orbit torque (SOT) created by a spin current injected into a ferromagnet
by an adjacent heavy metal represents an efficient tool for the excitation and
manipulation of spin waves. Here we report the micromagnetic simulations
describing the influence of SOT on the propagation of spin waves in the
$\mathrm{W}/\mathrm{CoFeB}/\mathrm{MgO}$ nanostructure having
voltage-controlled magnetic anisotropy (VCMA). The simulations show that two
spin waves travelling in the opposite directions can be generated in the center
of the $\mathrm{CoFeB}$ waveguide via the modulation of VCMA induced by a
microwave voltage locally applied to the $\mathrm{MgO}$ nanolayer. The
amplitudes of these waves exponentially decrease with the propagation distance
with similar decay lengths of about 2.5 $\mu$m. In the presence of a direct
electric current injected into the $\mathrm{W}$ film beneath the waveguide
center, the decay lengths of two spin waves change in the opposite way owing to
different directions of the electric currents flowing in the underlying halves
of the $\mathrm{W}$ layer. Remarkably, above the critical current density
$J_\mathrm{W} \approx 2 \times 10^{10}$ A m$^{-2}$, SOT provides the
amplification of the spin wave propagating in one half of the waveguide and
strongly accelerates the attenuation of the wave travelling in the other half.
As a result, a long-distance spin-wave propagation takes place in a half of the
$\mathrm{CoFeB}$ waveguide only. Furthermore, by reversing the polarity of the
dc voltage applied to the heavy-metal layer one can change the propagation area
and switch the travel direction of the spin wave in the ferromagnetic
waveguide. Thus, the $\mathrm{W}/\mathrm{CoFeB}/\mathrm{MgO}$ nanostructure can
be employed as an electrically controlled magnonic device converting the
electrical input signal into a spin signal, which can be transmitted to one of
two outputs of the device.",2107.10795v2
1996-07-25,Charge and Spin Response of the Spin--Polarized Electron Gas,"The charge and spin response of a spin--polarized electron gas is
investigated including terms beyond the random phase approximation. We evaluate
the charge response, the longitudinal and transverse spin response, and the
mixed spin--charge response self--consistently in terms of the susceptibility
functions of a non--interacting system. Exchange--correlation effects between
electrons of spin $\sigma$ and $\sigma^{'}$ are included following Kukkonen and
Overhauser, by using spin--polarization dependent generalized Hubbard local
field factors ${G_\sigma}^{\pm}$ and ${G_{\bar\sigma}}^{\pm}$. The general
condition for charge--density and spin--density--wave excitations of the system
is discussed.",9607178v1
2007-09-21,Spin-orbit mediated anisotropic spin interaction in interacting electron systems,"We investigate interactions between spins of strongly correlated electrons
subject to the spin-orbit interaction. Our main finding is that of a novel,
spin-orbit mediated anisotropic spin-spin coupling of the van der Waals type.
Unlike the standard exchange, this interaction does not require the wave
functions to overlap. We argue that this ferromagnetic interaction is important
in the Wigner crystal state where the exchange processes are severely
suppressed. We also comment on the anisotropy of the exchange between spins
mediated by the spin-orbital coupling.",0709.3521v2
2012-04-20,Composite Spin Liquid in Correlated Topological Insulator - Spin Liquid without Spin-Charge Separation,"In this paper, we found a new type of insulator - composite spin liquid which
can be regarded as a short range B-type topological spin-density-wave.
Composite spin liquid is topological ordered state beyond the classification of
traditional spin liquid states. The elementary excitations are the ""composite
electrons"" with both spin degree of freedom and charge degree of freedom,
together with topological spin texture. This topological state supports chiral
edge mode but no topological degeneracy.",1204.4552v1
2021-05-27,Tunneling spin current in a system with spin degeneracy,"We study theoretically spin current generation from a band insulator with PT
symmetry, which is associated with Zener tunneling in strong dc electric
fields. Each band in this system is doubly degenerate with opposite spins, but
spin rotational symmetry is not preserved in general. We consider the condition
for spin current generation in connection with the nature of the wave function,
which ultimately depends on a geometric quantity known as the shift vector.
From an analysis of a two-band model, we find that the shift vector is
necessary for spin current generation in a PT symmetric system. We also present
zigzag chain models that have shift vectors, and confirm from numerical
calculations that a nonzero tunneling spin current occurs in spin-degenerate
systems.",2105.13162v1
2004-07-28,"Comment on ""Exchange interaction parameters and adiabatic spin-wave spectra of ferromagnets: A 'renormalized magnetic force theorem'""","This is a comment on publication in Phys. Rev. Lett. 90, 087205 (2003):
``Exchange interaction parameters and adiabatic spin-wave spectra of
ferromagnets: A `renormalized magnetic force theorem'''",0407739v1
2017-12-02,Coherent excitation of heterosymmetric spin waves with ultrashort wavelengths,"In the emerging field of magnonics, spin waves are foreseen as signal
carriers for future spintronic information processing and communication
devices, owing to both the very low power losses and a high device
miniaturisation potential predicted for short-wavelength spin waves. Yet, the
efficient excitation and controlled propagation of nanoscale spin waves remains
a severe challenge. Here, we report the observation of high-amplitude,
ultrashort dipole-exchange spin waves (down to 80 nm wavelength at 10 GHz
frequency) in a ferromagnetic single layer system, coherently excited by the
driven dynamics of a spin vortex core. We used time-resolved x-ray microscopy
to directly image such propagating spin waves and their excitation over a wide
range of frequencies. By further analysis, we found that these waves exhibit a
heterosymmetric mode profile, involving regions with anti-Larmor precession
sense and purely linear magnetic oscillation. In particular, this mode profile
consists of dynamic vortices with laterally alternating helicity, leading to a
partial magnetic flux closure over the film thickness, which is explained by a
strong and unexpected mode hybridisation. This spin-wave phenomenon observed is
a general effect inherent to the dynamics of sufficiently thick ferromagnetic
single layer films, independent of the specific excitation method employed.",1712.00681v3
2014-06-11,Spin flip probability of electron due to torsional wave,"The probability of spin flip of an electron due to a torsional wave is
calculated. It is compared to the electromagnetic case, and ways to detect
torsion are discussed.",1406.2965v1
2018-12-21,Active Control of Mode Crossover and Mode Hopping of Spin Waves in a Ferromagnetic Antidot Lattice,"Active control of spin-wave dynamics is demonstrated using broadband
ferromagnetic resonance in two-dimensional Ni80Fe20 antidot lattices arranged
in hexagonal lattice with fixed lattice constant but varying antidot diameter.
A strong modification in the spin-wave spectra is obtained with the variation
in the antidot diameter as well as with the strength and orientation of the
bias magnetic field. A broad band of modes is observed for the lattice with
higher antidot diameter which decreases systematically as the antidot diameter
is reduced. A crossover between the higher frequency branches is achieved in
lattices with higher antidot diameter. In addition, the spin-wave modes in all
lattices show a strong six-fold anisotropic behaviour due to the variation of
internal field distribution as a function of the bias-field orientation. A mode
hopping-like behavior is observed in the angular dispersions of spin-wave
spectra for samples having intermediate hole diameters. Micromagnetic
simulations qualitatively reproduce the experimentally observed spin-wave modes
and the simulated mode profiles reveal the presence of extended and quantized
standing spin-wave modes in these lattices. These observations are significant
for large tunability and anisotropic propagation of spin waves in GHz frequency
magnetic devices.",1812.08929v1
2016-11-17,Parallel pumping for magnon spintronics: Amplification and manipulation of magnon spin currents on the micron-scale,"Magnonics and magnon spintronics aim at the utilization of spin waves and
magnons, their quanta, for the construction of wave-based logic networks via
the generation of pure all-magnon spin currents and their interfacing with
electrical charge transport. The promise of efficient parallel data processing
and low power consumption renders this field one of the most promising research
areas in spintronics. In this context, the process of parallel parametric
amplification, i.e., the conversion of microwave photons into magnons at one
half of the microwave frequency, has proven to be a versatile tool. Its
beneficial and unique properties, such as frequency and mode-selectivity, the
possibility to excite spin waves in a wide wavevector range and the creation of
phase-correlated wave pairs, render it one of the key methods of spin-wave
generation and amplification.
  The application of parallel parametric amplification to micro- and
nanostructures is an important step towards the realization of magnonic
networks. This is motivated not only by the fact that amplifiers are an
important tool for the construction of any extended logic network but also by
the unique properties of parallel parametric amplification, such as a
phase-dependent amplification. Recently, the successful application of parallel
parametric amplification to metallic microstructures has been reported. It has
been demonstrated that parametric amplification provides an excellent tool to
generate and to amplify spin waves in these systems. In particular, the
amplification greatly benefits from the discreteness of the spin-wave spectra.
This opens up new, interesting routes of spin-wave amplification and
manipulation. In this Review, we give an overview over the recent developments
and achievements in this field.",1611.05893v1
2019-01-27,Observation of band narrowing and mode conversion in two-dimensional binary magnonic crystal,"We introduce a new type of binary magnonic crystal, where Ni$_{80}$Fe$_{20}$
nanodots of two different sizes are diagonally connected forming a unit and
those units are arranged in a square lattice. The magnetization dynamics of the
sample is measured by using time-resolved magneto-optical Kerr effect
microscope with varying magnitude and in-plane orientation ($\phi$) of the bias
magnetic field. Interestingly, at $\phi=0^{\circ}$, the spin-wave mode profiles
show frequency selective spatial localization of spin-wave power within the
array. With the variation of $\phi$ in the range $0^{\circ}<\phi\leq
45^{\circ}$, we observe band narrowing due to localized to extended spin-wave
mode conversion. Upon further increase of $\phi$, the spin-wave modes slowly
lose the extended nature and become fully localized again at 90$^{\circ}$. We
have extensively demonstrated the role of magnetostatic stray field
distribution on the rotational symmetries obtained for the spin-wave modes.
From micromagnetic simulations, we find that the dipole-exchange coupling
between the nano-dots leads to remarkable modifications of the spin-wave mode
profiles when compared with arrays of individual small and large dots.
Numerically, we also show that the physical connection between the nano-dots
provides more control points over the spin-wave propagation in the lattice at
different orientations of bias magnetic field. This new type of binary magnonic
crystal may find potential applications in magnonic devices such as spin-wave
waveguide, filter, coupler, and other on-chip microwave communication devices.",1901.09325v1
2022-06-30,Experimental Demonstration of a Spin-Wave Lens Designed with Machine Learning,"We present the design and experimental realization of a device that acts like
a spin-wave lens i.e., it focuses spin waves to a specified location. The
structure of the lens does not resemble any conventional lens design, it is a
nonintuitive pattern produced by a machine learning algorithm. As a spin-wave
design tool, we used our custom micromagnetic solver ""SpinTorch"" that has
built-in automatic gradient calculation and can perform backpropagation through
time for spin-wave propagation. The training itself is performed with the
saturation magnetization of a YIG film as a variable parameter, with the goal
to guide spin waves to a predefined location. We verified the operation of the
device in the widely used mumax3 micromagnetic solver, and by experimental
realization. For the experimental implementation, we developed a technique to
create effective saturation-magnetization landscapes in YIG by direct
focused-ion-beam irradiation. This allows us to rapidly transfer the nanoscale
design patterns to the YIG medium, without patterning the material by etching.
We measured the effective saturation magnetization corresponding to the FIB
dose levels in advance and used this mapping to translate the designed
scatterer to the required dose levels. Our demonstration serves as a proof of
concept for a workflow that can be used to realize more sophisticated spin-wave
devices with complex functionality, e.g., spin-wave signal processors, or
neuromorphic devices.",2207.00055v1
2023-11-09,Skyrmion-Excited Spin Wave Fractal Network,"Magnetic skyrmions exhibit unique, technologically relevant pseudo-particle
behaviors which arise from their topological protection, including
well-defined, three-dimensional dynamic modes that occur at microwave
frequencies. During dynamic excitation, spin waves are ejected into the
interstitial regions between skyrmions, creating the magnetic equivalent of a
turbulent sea. However, since the spin waves in these systems have a
well-defined length scale, and the skyrmions are on an ordered lattice, ordered
structures from spin wave interference can precipitate from the chaos. This
work uses small angle neutron scattering (SANS) to capture the dynamics in
hybrid skyrmions and investigate the spin wave structure. Performing
simultaneous ferromagnetic resonance and SANS, the diffraction pattern shows a
large increase in low-angle scattering intensity which is present only in the
resonance condition. This scattering pattern is best fit using a mass fractal
model, which suggests the spin waves form a long-range fractal network. The
fractal structure is constructed of fundamental units with a size that encodes
the spin wave emissions and are constrained by the skyrmion lattice. These
results offer critical insights into the nanoscale dynamics of skyrmions,
identify a new dynamic spin wave fractal structure, and demonstrates SANS as a
unique tool to probe high-speed dynamics.",2311.05469v1
1993-12-09,Spin-Wave-Spin-Wave Interaction and the Thermodynamics of the Heisenberg Spin Chain,"The low-temperature free energy of the spin S quantum Heisenberg
ferromagnetic chain in a strong magnetic field is obtained in a two-particle
approximation by using exact solution of two-spin-wave problem. The result is
beyond the perturbation theory because it incorporates the both bound and
scattering state contributions, and the scattering effect is essential as well
as the bound state one. In particular the main temperature renormalization of
an exchange constant is found to be linear in temperature instead $T^{3/2}$
corresponded to the perturbation theory result.",9312038v1
1994-08-02,Composite-Fermion Picture for the Spin-Wave Excitation in the fractional quantum Hall system,"Spin-wave excitation mode from the spin-polarized ground state in the
fractional quantum Hall liquid with odd fractions ($\nu=1/3,1/5$) numerically
obtained by the exact diagonalization of finite systems is shown to be
accurately described, for wavelengths exceeding the magnetic length, in terms
of the composite-fermion mean-field approximation for the spin-wave (magnon)
theory formulated in the spherical geometry. This indicates that the composite
picture extends to excited states, and also provides the spin stiffness in
terms of peculiar exchange interactions.",9408004v1
1997-12-01,Spin-wave series for quantum one-dimensional ferrimagnets,"Second-order spin-wave expansions are used to compute the ground-state energy
and sublattice magnetizations of the quantum one-dimensional Heisenberg
ferrimagnet with nearest-neighbor antiferromagnetic interactions and two types
of alternating sublattice spins $S_1>S_2$. It is found that in the extreme
quantum cases $(S_1,S_2)=(1,1/2)$, $(3/2,1)$, and $(3/2,1/2)$, the estimates
for the ground-state energy and sublattice magnetizations differ less than
0.03% for the energy and 0.2% for the sublattice magnetizations from the
recently published density matrix renormalization group numerical calculations.
  The reported results strongly suggest that the quantum Heisenberg
ferrimagnetic chains give another example of a low-dimensional quantum spin
system where the spin-wave approach demonstrates a surprising efficiency.",9712014v1
1998-03-02,Evolution of Hole and Spin Dynamics in High Temperature Superconductors within the Small Hole Density Limit of the t-J Model,"The evolution of hole and spin dynamics in high temperature superconductors
is studied within the self-consistent noncrossing approximation of the t-J
model in the small hole density limit. As the doping concentration is
increased, long-range electron correlations disappear rapidly and the
quasiparticle energy band becomes considerably narrow. At a small hole density
long-range antiferromagnetic order is destroyed leading to the inadequacy of
spin wave basis approximation near small wave vectors. Spin excitations near
the antiferromagnetic zone boundary are strongly renormalized and damped but
they are still well described within spin wave basis approximation.",9803016v1
1999-08-26,Magnons in real materials from density-functional theory,"We present an implementation of the adiabatic spin-wave dynamics of Niu and
Kleinman. This technique allows to decouple the spin and charge excitations of
a many-electron system using a generalization of the adiabatic approximation.
The only input for the spin-wave equations of motion are the energies and Berry
curvatures of many-electron states describing frozen spin spirals. The latter
are computed using a newly developed technique based on constrained
density-functional theory, within the local spin density approximation and the
pseudo-potential plane-wave method. Calculations for iron show an excellent
agreement with experiments.",9908386v1
2004-02-12,Spin Dynamics of Double-Exchange Manganites with Magnetic Frustration,"This work examines the effects of magnetic frustration due to competing
ferromagnetic and antiferromagnetic Heisenberg interactions on the spin
dynamics of the double-exchange model. When the local moments are non-colinear,
a charge-density wave forms because the electrons prefer to sit on lines of
sites that are coupled ferromagnetically. With increasing hopping energy, the
local spins become aligned and the average spin-wave stiffness increases. Phase
separation is found only within a narrow range of hopping energies. Results of
this work are applied to the field-induced jump in the spin-wave stiffness
observed in the manganite Pr$_{1-x}$Ca$_x$MnO$_3$ with $0.3 \le x \le 0.4$.",0402344v1
2006-06-15,Interplay between phase defects and spin polarization in the specific heat of the spin density wave compound (TMTTF)_2Br in a magnetic field,"Equilibrium heat relaxation experiments provide evidence that the ground
state of the commensurate spin density wave (SDW) compound (TMTTF)$_2$Br after
the application of a sufficient magnetic field is different from the
conventional ground state. The experiments are interpreted on the basis of the
local model of strong pinning as the deconfinement of soliton-antisoliton pairs
triggered by the Zeeman coupling to spin degrees of freedom, resulting in a
magnetic field induced density wave glass for the spin carrying phase
configuration.",0606403v1
2006-06-21,Quantum Dynamics of Spin Wave Propagation Through Domain Walls,"Through numerical solution of the time-dependent Schrodinger equation, we
demonstrate that magnetic chains with uniaxial anisotropy support stable
structures, separating ferromagnetic domains of opposite magnetization. These
structures, domain walls in a quantum system, are shown to remain stable if
they interact with a spin wave. We find that a domain wall transmits the
longitudinal component of the spin excitations only. Our results suggests that
continuous, classical spin models described by LLG equation cannot be used to
describe spin wave-domain wall interaction in microscopic magnetic systems.",0606549v1
2006-10-04,Spin-density induced by electromagnetic wave in two-dimensional electron gas,"We consider the magnetic response of a two-dimensional electron gas (2DEG)
with a spin-orbit interaction to a long-wave-length electromagnetic excitation.
We observe that the transverse electric field creates spin polarization
perpendicular to the 2DEG plane. The effect is more prominent in clean systems
with resolved spin-orbit-split subbands, and reaches maximum when the frequency
of the wave matches the subband splitting at the Fermi momentum. The relation
of this effect to the spin-Hall effect is discussed.",0610124v4
2007-06-02,Standing Spin Waves in an Antiferromagnetic Molecular Cr6 Horseshoe,"The antiferromagnetic molecular finite chain Cr6 was studied by inelastic
neutron scattering. The observed magnetic excitations at 2.6 and 4.3 meV
correspond, due to the open boundaries of a finite chain, to standing spin
waves. The determined energy spectrum revealed an essentially classical spin
structure. Hence, various spin-wave theories were investigated in order to
assess their potential for describing the elementary excitations of finite spin
systems.",0706.0247v1
2007-10-11,Direct current voltage induced by microwave signal in a ferromagnetic wire,"Experimental results of rectification of a constant wave radio frequency (RF)
current flowing in a single-layered ferromagnetic wire are presented. We show
that a detailed external magnetic field dependence of the RF current induced a
direct-current voltage spectrum. The mechanism of the rectification is
discussed in a term of the spin transfer torque, and the rectification is
closely related to resonant spin wave excitation with the assistant of the
spin-polarized RF current. The micromagnetic simulation taking into account the
spin transfer torque provides strong evidence which supports the generation of
spin wave excitation by the RF current.",0710.2172v1
2009-05-20,Berry phase and topological spin transport in the chiral d-density wave state,"In this paper we demonstrate the possibility of dissipationless spin
transport in the chiral d-density wave state, by the sole application of a
uniform Zeeman field gradient. The occurrence of these spontaneous spin
currents is attributed to the parity (${\cal P}$) and time-reversal (${\cal
T}$) violation induced by the $d_{xy}+id_{x^2-y^2}$ density wave order
parameter. We calculate the spin Hall conductance and reveal its intimate
relation to the Berry phase which is generated when the Zeeman field is applied
adiabatically. Finally, we demonstrate that in the zero temperature and doping
case, the spin Hall conductance is quantized as it becomes a topological
invariant.",0905.3228v1
2009-11-04,Spin induced nonlinearities in the electron MHD regime,"We consider the influence of the electron spin on the nonlinear propagation
of whistler waves. For this purpose a recently developed electron two-fluid
model, where the spin up- and down populations are treated as different fluids,
is adapted to the electron MHD regime. We then derive a nonlinear Schrodinger
equation for whistler waves, and compare the coefficients of nonlinearity with
and without spin effects. The relative importance of spin effects depend on the
plasma density and temperature as well as the external magnetic field strength
and the wave frequency. The significance of our results to various plasmas are
discussed.",0911.0803v1
2010-05-14,The effect of spin magnetization in the damping of electron plasma oscillations,"The effect of spin of particles in the propagation of plasma waves is studied
using a semi-classical kinetic theory for a magnetized plasma. We focus in the
simple damping effects for the electrostatic wave modes besides Landau damping.
Without taking into account more quantum effects than spin contribution to
Vlasov's equation, we show that spin produces a new damping or instability
which is proportional to the zeroth order magnetization of the system. This
correction depends on the electromagnetic part of the wave which is coupled
with the spin vector.",1005.2573v1
2011-02-27,Cauchy-Born rule and spin density wave for the spin-polarized Thomas-Fermi-Dirac-von Weizsacker model,"The electronic structure (electron charges and spins) of a perfect crystal
under external magnetic field is analyzed using the spin-polarized
Thomas-Fermi-Dirac-von Weizsacker model. An extension of the classical
Cauchy-Born rule for crystal lattices is established for the electronic
structure under sharp stability conditions on charge density wave and spin
density wave. A Landau-Lifschitz type micromagnetic energy functional is
derived.",1102.5545v1
2011-03-12,Effective field theories and spin-wave excitations in helical magnets,"We consider two classes of helical magnets. The first one has magnetic
ordering close to antiferromagnet and the second one has magnetic ordering
close to ferromagnet. The first case is relevant to cuprate superconductors and
the second case is realized in FeSrO$_3$ and FeCaO$_3$. We derive the effective
field theories for these cases and calculate corresponding excitation spectra.
We demonstrate that the ""hourglass"" spin-wave dispersion observed
experimentally in cuprates is a fingerprint of the ""antiferromagnetic spin
spiral state"". We also show that quantum fluctuations are important for the
""ferromagnetic spin spiral"", they influence qualitative features of the
spin-wave dispersion.",1103.2422v1
2011-10-18,Life times and chirality of spin-waves in antiferromagnetic and ferromagnetic FeRh: time depedent density functional theory perspective,"The study of the spin excitations in antiferromagnetic (AFM) and
ferromagnetic (FM) phases of FeRh is reported. We demonstrate that although the
Fe atomic moments are well defined there is a number of important phenomena
absent in the Heisenberg description: Landau damping of spin waves, large Rh
moments induced by the AFM magnons, the formation of the optical magnons
terminated by Stoner excitations. We relate the properties of the spin-wave
damping to the features of the Stoner continuum and compare the chirality of
the spin excitations in AFM, FM and paramagnetic (PM) systems.",1110.3913v1
2012-01-17,Spin wave excitation in magnetic insulators by spin-transfer torque,"We study the excitation of spin waves in magnetic insulators by the
current-induced spin-transfer torque. We predict preferential excitation of
surface spin waves induced by an easy-axis surface anisotropy with critical
current inversely proportional to the penetration depth and surface anisotropy.
The surface modes strongly reduce the critical current and enhance the
excitation power of the current-induced magnetization dynamics.",1201.3442v1
2012-08-17,Spin-torque effect on spin wave modes in magnetic nanowires,"The interaction between a spin polarized dc electrical current and spin wave
modes of a cylindrical nanowire is investigated in this report. We found that
close to the critical current, the uniform mode is suppressed, while the edge
mode starts to propagate into the sample. When the current exceeds the critical
value, this phenomenon is even more accentuated. The edge mode becomes the
uniform mode of the nanowire. The higher spin wave modes are slowly pushed away
by the current until the propagating mode remains.",1208.3661v1
2012-11-27,Short range asymptotic behavior of the wave-functions of interacting spin-half fermionic atoms with spin-orbit coupling: a model study,"We consider spin-half fermionic atoms with isotropic Rashba spin-orbit
coupling in three directions. The interatomic potential is modeled by a square
well potential. We derive the analytic form of the asymptotic wave-functions at
short range of two fermions in the subspace of zero net momentum and zero total
angular momentum. We show that the spin-orbit coupling has perturbative effects
on the short range asymptotic behavior of the wave-functions away from
resonances. We argue that our conclusion should hold generally.",1211.6221v2
2013-10-30,Spin torque ferromagnetic resonance with magnetic field modulation,"We demonstrate a technique of broadband spin torque ferromagnetic resonance
(ST-FMR) with magnetic field modulation for measurements of spin wave
properties in magnetic nanostructures. This technique gives great improvement
in sensitivity over the conventional ST-FMR measurements, and application of
this technique to nanoscale magnetic tunnel junctions (MTJs) reveals a rich
spectrum of standing spin wave eigenmodes. Comparison of the ST-FMR
measurements with micromagnetic simulations of the spin wave spectrum allows us
to explain the character of low-frequency magnetic excitations in nanoscale
MTJs.",1310.7996v1
2013-12-23,Acoustic parametric pumping of spin waves,"Recent experiments demonstrated generation of spin currents by ultrasound. We
can understand this acoustically induced spin pumping in terms of the coupling
between magnetization and lattice waves. Here we study the parametric
excitation of magnetization by longitudinal acoustic waves and calculate the
acoustic threshold power. The induced magnetization dynamics can be detected by
the spin pumping into an adjacent normal metal that displays the inverse spin
Hall effect.",1312.6499v1
2014-04-18,Validity of spin wave theory for the quantum Heisenberg model,"Spin wave theory is a key ingredient in our comprehension of quantum spin
systems, and is used successfully for understanding a wide range of magnetic
phenomena, including magnon condensation and stability of patterns in dipolar
systems. Nevertheless, several decades of research failed to establish the
validity of spin wave theory rigorously, even for the simplest models of
quantum spins. A rigorous justification of the method for the three-dimensional
quantum Heisenberg ferromagnet at low temperatures is presented here. We derive
sharp bounds on its free energy by combining a bosonic formulation of the model
introduced by Holstein and Primakoff with probabilistic estimates and operator
inequalities.",1404.4717v1
2016-04-04,On the distribution of stellar-sized black hole spins,"Black hole spin will have a large impact on searches for gravitational waves
with advanced detectors. While only a few stellar mass black hole spins have
been measured using X-ray techniques, gravitational wave detectors have the
capacity to greatly increase the statistics of black hole spin measurements. We
show what we might learn from these measurements and how the black hole spin
values are influenced by their formation channels.",1604.00778v1
2018-04-27,Spin Waves in Quantum Gases --- The Quality Factor of the Identical Spin Rotation Effect,"Our recent experimental work on electron spin waves in atomic hydrogen gas
has prompted a revisit of the theory of the Identical Spin Rotation Effect
(ISRE). A key characteristic determining the properties of the spin waves is
the quality factor of ISRE. Unfortunately, calculating this quality factor
takes some toil. In this paper we summarize some results of the ISRE theory in
dilute gases. We also derive asymptotic formulae for the quality factor and
examine their accuracy for hydrogen and $^3$He.",1804.10431v1
2015-05-16,Dynamics of a macroscopic spin qubit in spin-orbit coupled Bose-Einstein condensates,"We consider a macroscopic spin qubit based on spin-orbit coupled
Bose-Einstein condensates, where, in addition to the spin-orbit coupling, spin
dynamics strongly depends on the interaction between particles. The evolution
of the spin for freely expanding, trapped, and externally driven condensates is
investigated. For condensates oscillating at the frequency corresponding to the
Zeeman splitting in the synthetic magnetic field, the spin Rabi frequency does
not depend on the interaction between the atoms since it produces only internal
forces and does not change the total momentum. However, interactions and
spin-orbit coupling bring the system into a mixed spin state, where the total
spin is inside rather than on the Bloch sphere. This greatly extends the
available spin space making it three-dimensional, but imposes limitations on
the reliable spin manipulation of such a macroscopic qubit. The spin dynamics
can be modified by introducing suitable spin-dependent initial phases,
determined by the spin-orbit coupling, in the spinor wave function.",1505.04301v1
2014-08-19,Towards the explicit computation of Bohm velocities associated to N-electron wave-functions with arbitrary spin-orientations,"The direct solution of the many-particle Schr\""odinger equation is
computationally inaccessible for more than very few electrons. In order to
surpass this limitation, one of the authors [X. Oriols, Phys. Rev. Lett. 2007,
98 (066803)] has recently proposed a new model to study electron-electron
correlations from Bohm trajectories associated to time-dependent wave-packets
solutions of pseudo single-particle Schr\""odinger equations. In the
aforementioned paper only the orbital exchange interaction is considered
assuming that all electrons have the same spin orientation. Then, the
many-particle wave function is a complex Slater determinant of the
single-particle wave-packets. In the present work the previous formalism is
extended to study many-particle wave functions where the electrons have
different spin orientations.The main difficulty to treat N different electron
spin orientations with time-dependent wave-packets is that one must study all
the possible N!N! products of permutations among spin states. To overcome this
computationally inaccessible problem, in this article the total wave function
is treated as a separated product of two many-particle wave functions, the
first with spin up and the second with spin down. In order to numerically
justify this approximation, the Bohm velocity in different antisymmetric total
wave-function scenarios is computed. The computational results confirms the
accurate validity of our approximation under a large number of cases.",1408.4346v1
2019-12-20,Slow-wave based magnonic diode,"Spin waves, the collective excitations of the magnetic order parameter, and
magnons, the associated quasiparticles, are envisioned as possible data
carriers in future wave-based computing architectures. On the road towards
spin-wave computing, the development of a diode-like device capable of
transmitting spin waves in only one direction, thus allowing controlled signal
routing, is an essential step. Here, we report on the design and experimental
realization of a microstructured magnonic diode in a ferromagnetic bilayer
system. Effective unidirectional propagation of spin waves is achieved by
taking advantage of nonreciprocities produced by dynamic dipolar interactions
in transversally magnetized media, which lack symmetry about their horizontal
midplane. More specifically, dipolar-induced nonreciprocities are used to
engineer the spin-wave dispersion relation of the bilayer system so that the
group velocity is reduced to very low values for one direction of propagation,
and not for the other, thus producing unidirectional slow spin waves. Brillouin
light scattering and propagating spin-wave spectroscopy are used to demonstrate
the diode-like behavior of the device, the composition of which was previously
optimized through micromagnetic simulations. simulations.",1912.09735v1
2020-08-27,Odd-frequency pair density wave correlations in underdoped cuprates,"Pair density waves, identified by Cooper pairs with finite center-of-mass
momentum, have recently been observed in copper oxide based high T$_\textrm{c}$
superconductors (cuprates). A charge density modulation or wave is also
ubiquitously found in underdoped cuprates. Within a general mean-field one-band
model we show that the coexistence of charge density waves and uniform
superconductivity in $d$-wave superconductors like cuprates, generates an
odd-frequency spin-singlet pair density wave, in addition to the even-frequency
counterparts. The strength of the induced odd-frequency pair density wave
depends on the modulation wave vector of the charge density wave, with the
odd-frequency pair density waves even becoming comparable to the even-frequency
ones in parts of the Brillouin zone. We show that a change in the modulation
wave vector of the charge density wave from bi-axial to uni-axial, can enhance
the odd-frequency component of the pair density waves. Such a coexistence of
superconductivity and uni-axial charge density wave has already been
experimentally verified at high magnetic fields in underdoped cuprates. We
further discuss the possibility of an odd-frequency spin-triplet pair density
wave generated in the coexistence regime of superconductivity and spin density
waves, applicable to the iron-based superconductors. Our work thus presents a
route to bulk odd-frequency superconductivity in high T$_c$ superconductors.",2008.12021v2
2012-07-20,Thermal evolution of the full three-dimensional magnetic excitations in the multiferroic BiFeO3,"The idea of embedding and transmitting information within the fluctuations of
the magnetic moments of spins (spin waves) has been recently proposed and
experimentally tested. The coherence of spin waves, which describes how well
defined these excitations are, is of course vital to this process, and themost
significant factor that affects the spin-wave coherence is temperature. Here we
present neutron inelastic scattering measurements of the full threedimensional
spin-wave dispersion in BiFeO3, which is one of the most promising functional
multiferroic material, for temperatures from 5K to 700K. Despite the presence
of strong electromagnetic coupling, the magnetic excitations behave like
conventional magnons over all parts of the Brillouin zone. At low temperature
the spin-waves are well-defined coherent modes, described by a classical model
for a G-type antiferromagnet. A spin-wave velocity softening is already present
at room temperature, and more pronounced damping occurs as the magnetic
ordering temperature TN \sim 640K is approached. In addition, a strong
hybridization of the Fe 3d and O 2p states is found to modify the distribution
of the spin-wave spectral weight significantly, which implies that the spins
are not restricted to the Fe atomic sites as previously believed.",1207.5078v1
2018-12-26,Discretized dynamics of exchange spin wave bulk and edge modes in honeycomb nanoribbons with armchair edge boundaries,"We develop a field theory to study the dynamics of long wavelength exchange
spin wave excitations on honeycomb nanoribbons characterized by armchair edge
boundaries and the N\'eel antiferromagnetic ordering state. Appropriate
boundary conditions are established by requiring that the bulk and edge spins
precess with the same frequency for any given spin wave eigenmode in these
systems. A set of characteristic boundary equations, common for bulk and edge
spin wave modes, are hence derived. The equations of motion for the spin
dynamics are then solved to determine the propagating and evanescent exchange
spin wave modes. We prove in general that the bulk spin wave dynamics is
discretized due to the finite width of the nanoribbon. For an isotropic
magnetic nanoribbon, the Dirac cone is reduced to a single linear dispersion
curve due to this discretization. The number and wavelengths of allowed bulk
modes for isotropic and anisotropic nanoribbons are determined from the derived
characteristic boundary equations. As witnessed by our numerical results for
different examples it is shown that the characteristics of these modes depend
on the width of the nanoribbon and its antiferromagnetic anisotropy. Further,
anisotropic nanoribbons, even those with the slightest anisotropy, present
evanescent modes with non-linear dispersion relations. The spatial variation of
the amplitudes of the evanescent exchange spin waves across the finite widths
of the nanoribbons, is found to be strongly dependent on the system magnetic
anisotropy and its width. The developed theoretical approach is general and can
be applied for nanoribbons with all types of boundary edges.",1812.10204v2
2015-04-23,Universal spin-momentum locking of evanescent waves,"We show the existence of an inherent property of evanescent electromagnetic
waves: spin-momentum locking, where the direction of momentum fundamentally
locks the polarization of the wave. We trace the ultimate origin of this
phenomenon to complex dispersion and causality requirements on evanescent
waves. We demonstrate that every case of evanescent waves in total internal
reflection, surface states and optical fibers/waveguides possesses this
intrinsic spin-momentum locking. We also introduce a universal right-handed
triplet consisting of momentum, decay and spin for evanescent waves. We derive
the Stokes parameters for evanescent waves which reveal an intriguing result -
every fast decaying evanescent wave is inherently circularly polarized with its
handedness tied to the direction of propagation. We also show the existence of
a fundamental angle associated with total internal reflection (TIR) such that
propagating waves locally inherit perfect circular polarized characteristics
from the evanescent wave. This circular TIR condition occurs if and only if the
ratio of permittivities of the two dielectric media exceeds the golden ratio.
Our work leads to a unified understanding of this spin-momentum locking in
various nanophotonic experiments and sheds light on the electromagnetic analogy
with the quantum spin hall state for electrons.",1504.06361v2
2024-02-29,Resonant generation of propagating second-harmonic spin waves in nano-waveguides,"Generation of second-harmonic waves is one of the universal nonlinear
phenomena that have found numerous technical applications in many modern
technologies, in particular, in photonics. This phenomenon also has great
potential in the field of magnonics, which considers the use of spin waves in
magnetic nanostructures to implement wave-based signal processing and
computing. However, due to the strong frequency dependence of the phase
velocity of spin waves, resonant phase-matched generation of second-harmonic
spin waves has not yet been achieved in practice. Here, we show experimentally
that such a process can be realized using a combination of different modes of
nano-sized spin-wave waveguides based on low-damping magnetic insulators. We
demonstrate that our approach enables efficient spatially-extended energy
transfer between interacting waves, which can be controlled by the intensity of
the initial wave and the static magnetic field. The demonstrated approach can
be used for the generation of short-wavelength spin waves that are difficult to
excite directly, as well as for the implementation of novel devices for
magnonic logic and unconventional computing.",2402.18964v1
2022-08-02,Completely Spin-Decoupled Geometric Phase of Metasurface,"Metasurfaces have provided unprecedented degree of freedom (DOF) in
manipulating electromagnetic (EM) waves. Geometric phase can be readily
obtained by rotating the meta-atom of metasurfaces. Nevertheless, such
geometric phases are usually spin-coupled, with the same magnitude but opposite
signs for left_ and right_handed circularly polarized (LCP,RCP) waves. To
achieve independent control on LCP and RCP waves, it is crucial to obtain
spin-decoupled geometric phases. In this paper, we propose to obtain completely
spin-decoupled geometric phases by engineering surface current paths on
meta-atoms. Based on the rotational Doppler effect, the rotation manner is
firstly analyzed and it is found that the essence of generating geometric phase
lies in the rotation of surface current paths on meta-atoms. Since the induced
surface currents paths under LCP and RCP waves always start oppositely and are
mirror-symmetrical with each other, it is natural that the geometric phases be
with the same magnitude and opposite signs when the meta-atoms are rotated. To
obtain spin-decoupled geometric phases, the start point of induced surface
current under one spin should be rotated by an angle while that under the other
spin by another different angle. In this way, LCP and RCP waves can acquire
different geometric phase changes and spin-decoupled geometric phase can be
imparted by metasurfaces. Proof-of-principle prototypes were designed,
fabricated and measured. Both the simulation and experiment results verify
spin-decoupled geometric phases. This work provides a robust means of obtaining
spin-dependent geometric phase and will further adds up to the metasurface DOF
in manipulating EM waves.",2208.04143v1
2005-11-29,Effective spin-wave action for ordered Heisenberg antiferromagnets in a magnetic field,"We derive the effective long-wavelength Euclidean action for the
antiferromagnetic spin-waves of ordered quantum antiferromagnets subject to a
uniform magnetic field. We point out that the magnetic field dependence of the
spin-wave dispersion predicted by the usual O(3)-quantum nonlinear sigma model
disagrees with spin-wave theory. We argue that the nonlinear sigma model does
not take into account all relevant spin-wave interactions and derive a modified
effective action for the long-wavelength spin-waves which contains an
additional quartic interaction. At zero temperature the corresponding vertex is
relevant in the renormalization group sense below three dimensions.",0511706v1
2012-07-24,Interplay of superconductivity and spin density wave order in doped graphene,"We study the interplay between superconductivity and spin density wave order
in graphene doped to 3/8 or 5/8 filling (a Van Hove doping). At this doping
level, the system is known to exhibit weak coupling instabilities to both
chiral d + id superconductivity and to a uniaxial spin density wave. Right at
van Hove doping, the superconducting instability is strongest and emerges at
the highest Tc, but slightly away from van-Hove doping a spin-density-wave
likely emerges first. We investigate whether at some lower temperature
superconductivity and spin-density-waves co-exist. We derive the
Landau-Ginzburg functional describing interplay of the two order parameters.
Our calculations show that superconductivity and spin density wave order do not
co-exist and are separated by first-order transitions, either as a function of
doping or as a function of T.",1207.5802v1
2012-11-21,Spin-wave propagation and transformation in a thermal gradient,"The influence of a thermal gradient on the propagation properties of
externally excited dipolar spin waves in a magnetic insulator waveguide is
investigated. It is shown that spin waves propagating towards a colder region
along the magnetization direction continuously reduce their wavelength. The
wavelength increase of a wave propagating into a hotter region was utilized to
realize its decomposition in the partial waveguide modes which are reflected at
different locations. This influence of temperature on spin-wave properties is
mainly caused by a change in the saturation magnetization and yields promising
opportunities for the manipulation of spin waves in spin-caloritronic
applications.",1211.5017v1
2013-05-22,Spin-wave nonreciprocity based on interband magnonic transitions,"We theoretically demonstrate linear spin-wave nonreciprocity in a Ni80Fe20
nanostripe waveguide, based on interband magnonic transitions induced by a
time-reversal and spatialinversion symmetry breaking magnetic field. An
analytical coupled-mode theory of spin waves, developed to describe the
transitions which are accompanied by simultaneous frequency and wavevector
shifts of the coupled spin waves, is well corroborated by numerical
simulations. Our findings could pave the way for the realization of spin-wave
isolation and the dynamic control of spin-wave propagation in nanoscale
magnonic integrated circuits via an applied magnetic field.",1305.5018v3
2015-06-23,Chirality-dependent transmission of spin waves through domain walls,"Spin-wave technology (magnonics) has the potential to further reduce the size
and energy consumption of information processing devices. In the submicrometer
regime (exchange spin waves), topological defects such as domain walls may
constitute active elements to manipulate spin waves and perform logic
operations. We predict that spin waves that pass through a domain wall in an
ultrathin perpendicular-anisotropy film experience a phase shift that depends
on the orientation of the domain wall (chirality). The effect, which is absent
in bulk materials, originates from the interfacial Dzyaloshinskii-Moriya
interaction and can be interpreted as a geometric phase. We demonstrate
analytically and by means of micromagnetic simulations that the phase shift is
strong enough to switch between constructive and destructive interference. The
two chirality states of the domain wall may serve as a memory bit or spin-wave
switch in magnonic devices.",1506.07038v2
2015-07-06,Spin Wave Eigenmodes of Dzyaloshinskii Domain Walls,"A theory for the spin wave eigenmodes of a Dzyaloshinskii domain wall is
presented. These walls are N\'eel-type domain walls that can appear in
perpendicularly-magnetized ultrathin ferromagnets in the presence of a sizeable
Dzyaloshinskii-Moriya interaction. The mode frequencies for spin waves
propagating parallel and perpendicular to the domain wall are computed using a
continuum approximation. In contrast to Bloch-type walls, it is found that the
spin wave potential associated with Dzyaloshinskii domain walls is not
reflectionless, which leads to a finite scattering cross-section for
interactions between spin waves and domain walls. A gap produced by the
Dzyaloshinskii interaction emerges, and consequences for spin wave driven
domain wall motion and band structures arising from periodic wall arrays are
discussed.",1507.01369v1
2015-09-17,A spin wave diode,"A diode, a device allowing unidirectional signal transmission, is a
fundamental element of logic structures and lies in the heart of modern
information systems. Spin wave or magnon, representing a collective
quasi-particle excitation of the magnetic order in magnetic materials, is a
promising candidate of information carrier for the next generation
energy-saving technologies. Here we propose a scalable and reprogrammable pure
spin wave logic hardware architecture using domain walls and surface anisotropy
stripes as waveguides on a single magnetic wafer. We demonstrate theoretically
the design principle of the simplest logic component, a spin wave diode,
utilizing the chiral bound states in a magnetic domain wall with
Dzyaloshiskii-Moriya interaction, and confirm its performance through
micromagnetic simulations. Our findings open a new vista for realizing
different types of pure spin wave logic components and finally achieving an
energy-efficient and hardware-reprogrammable spin wave computer.",1509.05095v1
2016-02-25,All electrical propagating spin wave spectroscopy with broadband wavevector capability,"We develop an all electrical experiment to perform the broadband
phase-resolved spectroscopy of propagating spin waves in micrometer sized thin
magnetic stripes. The magnetostatic surface spin waves are excited and detected
by scaled down to 125 nm wide inductive antennas, which award ultra broadband
wavevector capability. The wavevector selection can be done by applying an
excitation frequency above the ferromagnetic resonance. Wavevector
demultiplexing is done at the spin wave detector thanks to the rotation of the
spin wave phase upon propagation. A simple model accounts for the main features
of the apparatus transfer functions. Our approach opens an avenue for the all
electrical study of wavevector-dependent spin wave properties including
dispersion spectra or non-reciprocal propagation.",1602.08091v2
2016-08-25,"Spin waves in the AF state of the $t$-$t'$ Hubbard model on the fcc lattice: competing interactions, frustration, and instabilities","Spin waves in the type-III ordered antiferromagnetic state of the frustrated
$t$-$t'$ Hubbard model on the fcc lattice are calculated to investigate
finite-$U$-induced competing interaction and frustration effects on magnetic
excitations and instabilities. Particularly strong competing interactions
generated due to interplay of fcc lattice geometry and magnetic order result in
significant spin wave softening. The calculated spin wave dispersion is found
to be in qualitative agreement with the measured spin wave dispersion in the
pyrite mineral $\rm Mn S_2$ obtained from inelastic neutron scattering
experiments. Instabilities to other magnetic orders (type I, type II, spiral,
non-collinear), as signalled by spin wave energies turning negative, are also
discussed.",1608.07031v1
2016-10-22,Giant nonreciprocal emission of spin waves in Ta/Py bilayers,"Spin waves are propagating disturbances in the magnetization of magnetic
materials. One of their interesting properties is the nonreciprocity,
exhibiting that their amplitude depends on the magnetization direction.
Nonreciprocity in spin waves is of great interest in both fundamental science
and applications, as it offers an extra knob to control the flow of waves for
the technological fields of logics and switch applications. We show a high
nonreciprocity in spin waves from Ta/Py bilayer systems with out-of-plane
magnetic fields. The nonreciprocity depends on the thickness of Ta underlayer
which is found to induce an interfacial anisotropy. The origin of observed high
nonreciprocity is twofold; different polarities of the in-plane magnetization
due to different angles of canted out-of-plane anisotropy and the spin pumping
effect at the Ta/Py interface. Our findings provide an opportunity to engineer
highly efficient nonreciprocal spin wave based applications such as
nonreciprocal microwave devices, magnonic logic gates, and information
transports.",1610.07023v1
2019-11-19,Imaging non-standing spin-waves in confined micron-sized ferromagnetic structures under uniform excitation,"A non-standing character of directly imaged spin-waves in confined
micron-sized ultrathin permalloy (Ni\textsubscript{80}Fe\textsubscript{20})
structures is reported along with evidence of the possibility to alter the
observed state by modifications to the sample geometry. Using micromagnetic
simulations the presence of the spin-wave modes excited in the permalloy
stripes along with the quasi-uniform modes were calculated. The predicted
spin-waves were imaged in direct space using time resolved scanning
transmission X-ray microscopy, combined with a ferromagnetic resonance
excitation scheme (STXM-FMR). STXM-FMR measurements revealed a non-standing
character of the spin-waves. Also it was shown by micromagnetic simulations and
confirmed with STXM-FMR results that the observed character of the spin-waves
can be influenced by the local magnetic fields in different sample geometries.",1911.08281v1
2017-05-05,Nano-patterned magnonic crystals based on ultrathin YIG films,"We demonstrate a microscopic magnonic-crystal waveguide produced by
nano-patterning of a 20 nm thick film of Yttrium Iron Garnet. By using the
phase-resolved micro-focus Brillouin light scattering spectroscopy, we map the
intensity and the phase of spin waves propagating in such a periodic magnetic
structure. Based on these maps, we obtain the dispersion and the attenuation
characteristics of spin waves providing detailed information about the physics
of spin-wave propagation in the magnonic crystal. We show that, in contrast to
the simplified physical picture, the maximum attenuation of spin waves is
achieved close to the edge of the magnonic band gap, which is associated with
non-trivial reflection characteristics of spin waves in non-uniform field
potentials.",1705.02267v1
2019-02-26,A new class of nonreciprocal spin waves on the edges of 2D antiferromagnetic honeycomb nanoribbons,"Antiferromagnetic two-dimensional (2D) materials are currently under
intensive theoretical and experimental investigations in view of their
potential applications in antiferromagnet-based magnonic and spintronic
devices. Recent experimental studies revealed the importance of magnetic
anisotropy and Dzyaloshinskii-Moriya interactions (DMI) on the ordered ground
state and the magnetic excitations in these materials. Here we present a robust
classical field theory approach to analyze the effect of magnetic anisotropy
and Dzyaloshinskii-Moriya interactions (DMI) on the edge and bulk spin waves in
2D antiferromagnetic nanoribbons. We predict the existence of a new class of
nonreciprocal edge spin waves characterized by opposite polarizations in
opposite directions. These novel edge spin waves are induced by the DMI and are
fundamentally different from conventional nonreciprocal spin waves for which
the polarization is independent of the propagation direction. Aside this
breakthrough in the field of antiferromagnetic spin waves, the study further
analysis the effect of the edges structure on the magnetic excitations. In
particular, we show that anisotropic bearded edges nanoribbons act as magnetic
topological insulators with exceptionally interesting potentials for
applications in magnonics.",1902.09704v3
2020-07-15,Nanochannels for Spin-Wave Manipulation in Ni80Fe20 Nanodot Arrays,"Patterned magnetic nanostructures are potential candidates for future energy
efficient, on-chip communication devices. Here, we have experimentally and
numerically studied the role of nanochannels to manipulate spin waves in
Ni80Fe20 connected nanodot arrays of varying filling fraction. Rich spin-wave
spectra are observed in these samples, where the number of spin-wave modes
decreases with increasing filling fraction due to the retrenchment of the
demagnetizing field. The nanochannels affect the spin-wave modes of the
connected dots through dipole-exchange coupling. For all modes the vertical
nanochannels couple the nanodots, except for the highest frequency modes where
all nanochannels act as coupler. This feature is further explored in the
simulation, which reveals that only the highest frequency mode can propagate
through all the nanochannels, analogues to an electronic demultiplexer. This
study will be useful to understand the role of nanochannels in patterned
magnetic nanostructures and their applications in spin-wave based communication
devices.",2007.07685v1
2021-03-18,Cherenkov radiation of spin waves by ultra-fast moving magnetic flux quanta,"Despite theoretical predictions for a Cherenkov-type radiation of spin waves
(magnons) by various propagating magnetic perturbations, fast-enough moving
magnetic field stimuli have not been available so far. Here, we experimentally
realize the Cherenkov radiation of spin waves in a Co-Fe magnonic conduit by
fast-moving (>1 km/s) magnetic flux quanta (Abrikosov vortices) in an adjacent
Nb-C superconducting strip. The radiation is evidenced by the microwave
detection of spin waves propagating a distance of 2 micrometers from the
superconductor and it is accompanied by a magnon Shapiro step in its
current-voltage curve. The spin-wave excitation is unidirectional and
monochromatic, with sub-40 nm wavelengths determined by the period of the
vortex lattice. The phase-locking of the vortex lattice with the excited spin
wave limits the vortex velocity and reduces the dissipation in the
superconductor.",2103.10156v2
2022-01-11,Edge spin wave transmission through a vertex domain wall in triangular dots,"Spin waves (SWs), being usually reflected by domain walls, could also be
channeled along them. Edge domain walls yield the interesting, and potentially
applicable to real devices property of broadband spin waves confinement to the
edges of the structure. Here we investigate through numerical simulations the
propagation of quasi one-dimensional spin waves in triangle-shaped amorphous
YIG ($Y_3Fe_5O_{12}$) micron sized ferromagnets as a function of the angle
aperture. The edge spin waves (ESWs) have been propagated over the corner in
triangles of 2 microns side with a fixed thickness of 85 nm. Parameters such as
superior vertex angle (in the range of 40$^\circ$-75$^\circ$) and applied
magnetic field have been optimized in order to obtain a higher transmission
coefficient of the ESWs over the triangle vertex. We observed that for a
certain aperture angle for which dominated ESW frequency coincides with one of
the localised DW modes, the transmission is maximized near one and the phase
shift drops to $\pi/2$ indicating resonant transmission of ESWs through the
upper corner. We compare the obtained results with existing theoretical models.
These results could contribute to the development of novel basic elements for
spin wave computing.",2201.04054v2
2022-01-21,Eigenmodes of twisted spin-waves in a thick ferromagnetic nanodisk,"Magnetic vortex is topologically nontrivial and commonly found in
ferromagnetic nanodisks. So far, three classes spin-wave eigenmodes, i.e.,
gyrotropic, azimuthal and radial modes, have been identified in ferromagnetic
nanodisks. Here, using micromagnetic simulation and analytical calculation, we
reveal twisted spin-wave modes in a thick permalloy (Ni0.8Fe0.2) nanodisk. The
twisted spin-waves carry topological charges, which sign depends on the core
polarity of the magnetic vortex in the nanodisk. By applying rotating magnetic
fields at one end of the sample, we observe continuous generation of twisted
spin-waves that have characteristic spiral phase front and carry topological
charge l = 1, -1, 2 and -2. The dispersion relation of twisted spin-waves is
derived analytically and the result is in good agreement with micromagnetic
numerical calculations.",2201.08621v1
2022-11-07,Interaction of gapless spin waves and a domain wall in an easy-cone ferromagnet,"We theoretically study the interaction of spin waves and a domain wall in a
quasi-one-dimensional easy-cone ferromagnet. The gapless spin waves on top of a
domain wall are found to exhibit finite reflection in contrast to the
well-known perfect transmission of gapful spin waves in easy-axis magnets.
Based on the obtained scattering properties, we study the thermal-magnon-driven
dynamics of a domain wall subjected to a thermal bias within the
Landau-B\""uttiker formalism, where transmitted magnons are shown to exert the
magnonic torque on the domain wall and thereby drive it with the velocity
linear to the applied thermal bias. The peculiar gapless nature of spin waves
in easy-cone magnets enables the thermally-driven domain-wall motion even at
low temperatures, differing from the easy-axis case where the domain-wall
velocity is exponentially suppressed at low temperatures. Our work suggests
that easy-cone magnets can serve as a useful platform to study the interaction
of gapless spin waves and nonlinear excitations and thereby realize
low-temperature magnon-related phenomena.",2211.03331v1
2023-02-21,Micromagnetic study of inertial spin waves in ferromagnetic nanodots,"Here we report the possibility to excite ultra-short spin waves in
ferromagnetic thin-films by using time-harmonic electromagnetic fields with
terahertz frequency. Such ultra-fast excitation requires to include inertial
effects in the description of magnetization dynamics. In this respect, we
consider the inertial Landau-Lifshitz-Gilbert (iLLG) equation and develop
analytical theory for exchange-dominated inertial spin waves. The theory
predicts a finite limit for inertial spin wave propagation velocity, as well as
spin wave spatial decay and lifetime as function of material parameters. Then,
guided by the theory, we perform numerical micromagnetic simulations that
demonstrate the excitation of ultra-short inertial spin waves (20 nm long)
propagating at finite speed in a confined magnetic nanodot. The results are in
agreement with the theory and provide the order of magnitude of quantities
observable in realistic ultra-fast dynamics experiments.",2302.10759v2
2023-07-19,Zero-field spin waves in YIG nano-waveguides,"Spin-wave based transmission and processing of information is a promising
emerging nano-technology that can help overcome limitations of traditional
electronics based on the transfer of electrical charge. Among the most
important challenges for this technology is the implementation of spin-wave
devices that can operate without the need for an external bias magnetic field.
Here we experimentally demonstrate that this can be achieved using
sub-micrometer wide spin-wave waveguides fabricated from ultrathin films of
low-loss magnetic insulator - Yttrium Iron Garnet (YIG). We show that these
waveguides exhibit a highly stable single-domain static magnetic configuration
at zero field and support long-range propagation of spin waves with gigahertz
frequencies. The experimental results are supported by micromagnetic
simulations, which additionally provide information for optimization of
zero-field guiding structures. Our findings create the basis for the
development of energy-efficient zero-field spin-wave devices and circuits.",2307.09805v1
2023-09-11,Probing Spin Wave Diffraction Patterns of Curved Antennas,"We report on the dependence of curvilinear shaped coplanar waveguides on the
near-field diffraction patterns of spin waves propagating in perpendicularly
magnetized thin films. Implementing the propagating spin waves spectroscopy
techniques on either concentrically or eccentrically shaped antennas, we show
how the link budget is directly affected by the spin wave interference, in good
agreement with near-field diffraction simulations. This work demonstrates the
feasibility to inductively probe a magnon interference pattern with a
resolution down to 1$\mu$m$^2$, and provides a methodology for shaping spin
wave beams from an antenna design. This methodology is successfully implemented
in the case study of a spin wave Young's interference experiment.",2309.05532v1
2023-11-27,Zero-field spin wave turns,"Spin-wave computing, a potential successor to CMOS-based technologies, relies
on the efficient manipulation of spin waves for information processing. While
basic logic devices like magnon transistors, gates, and adders have been
experimentally demonstrated, the challenge for complex magnonic circuits lies
in steering spin waves through sharp turns. In this study we demonstrate with
micromagnetic simulations and Brillouin light scattering microscopy
experiments, that dipolar spin waves can propagate through 90-degree turns
without distortion. The key lies in carefully designed in-plane magnetization
landscapes, addressing challenges posed by anisotropic dispersion. The
experimental realization of the required magnetization landscape is enabled by
spatial manipulation of the uniaxial anisotropy using corrugated magnonic
waveguides. The findings presented in this work should be considered in any
magnonic circuit design dealing with anisotropic dispersion and spin wave
turns.",2311.16335v1
2023-12-13,Detection of Geometric Phases in Spin Waves using Nitrogen-Vacancy Centers,"Due to their robustness, the implementation of geometric phases provides a
reliable and controllable way to manipulate the phase of a spin wave, thereby
paving the way towards functional magnonics-based data processing devices.
Moreover, geometric phases in spin waves are interesting from a fundamental
perspective as they contain information about spin wave band structures and
play an important role in magnon Hall effects. In this paper we propose to
directly measure geometric phases in spin wave systems using the magnetic field
sensing capabilities of nitrogen-vacancy (NV) centers. We demonstrate the
general principles of this method on two systems in which spin waves acquire a
geometric phase, namely a wire with a magnetic domain wall and a system with
position-dependent anisotropy axes, and explicitly show how this phase can be
deduced from the NV center signal.",2312.08137v1
2005-07-28,Transverse spin waves in isotropic ferromagnets,"The comparison of transverse spin wave spectra and its attenuation in
Heisenberg ferromagnet and in ferromagnetic Fermi liquid as well in polarized
Fermi liquid is undertaken. The transverse spin waves frequency in polarized
paramagnetic Fermi liquid as well in a Fermi liquid with spontaneous
magnetization is found to be proportional to the square of the wave vector with
complex diffusion coefficient such that the damping has a finite value
proportional to the scattering rate of quasiparticles at T=0.
  This behavior of polarized Fermi liquid contrasts with the behavior of
Heisenberg ferromagnet in hydrodynamic regime where the transverse spin wave
attenuation appears in terms proportional to the wave vector in fourth power.
  The reactive part of diffusion coefficient in paramagnetic state at T=0
proves to be inversely proportional to magnetization whereas in ferromagnetic
state it is directly proportional to magnetization. The dissipative part of
diffusion coefficient at T=0 in paramagnetic state is polarization independent,
whereas in ferromagnetic state it is proportional to square of magnetization.
Moreover, the spin wave spectrum in ferromagnetic Fermi liquid proves to be
unstable that demonstrates the difficulty of the Fermi liquid description of
itinerant ferromagnetism.",0507676v1
2007-08-13,Total Reflection and Negative Refraction of Dipole-Exchange Spin Waves at Magnetic Interfaces: Micromagnetic Modeling Study,"We demonstrated that dipole-exchange spin waves traveling in geometrically
restricted magnetic thin films satisfy the same laws of reflection and
refraction as light waves. Moreover, we found for the first time novel wave
behaviors of dipole-exchange spin waves such as total reflection and negative
refraction. The total reflection in laterally inhomogeneous thin films composed
of two different magnetic materials is associated with the forbidden modes of
refracted dipole-exchange spin waves. The negative refraction occurs at a 90
degree domain-wall magnetic interface that is introduced by a cubic magnetic
anisotropy in the media, through the anisotropic dispersion of dipole-exchange
spin waves.",0708.1642v1
2010-06-27,Spin wave resonances in antiferromagnets,"Spin wave resonances with enormously large wave numbers corresponding to wave
vectors 10^5-10^6 cm^{-1} are observed in thin plates of FeBO3. The study of
spin wave resonances allows one to obtain information about the spin wave
spectrum. The temperature dependence of a non-uniform exchange constant is
determined for FeBO3. Considerable softening of the magnon spectrum resulting
from the interaction of magnons, is observed at temperatures above 1/3 of the
Neel temperature. The excitation level of spin wave resonances is found to
depend significantly on the inhomogeneous elastic distortions artificially
created in the sample. A theoretical model to describe the observed effects is
proposed.",1006.5192v1
2014-03-11,Overcoming damping in spin wave propagation: A continuous excitation approach to determine time-dependent dispersion diagrams in 2D magnonic crystals,"We propose an alternative micromagnetic approach to determine the spin wave
dispersion relations in magnonic structures. Characteristic of the method is
that a limited area of the system is continuously excited with a spatially
uniform oscillating field, tuned at a given frequency. After a transitory time,
the regime magnetization dynamics is collected and a spatial Fourier analysis
on it determines the frequency vs wave vector relation. Combining several
simulations in any predetermined range of frequencies, at any resolution, we
investigate the dispersion relations for different kinds of magnonic crystals:
a dot array, an antidot array, and a bicomponent film. Especially compared to
traditional pulse-excitation methods this technique has many advantages. First,
the excitation power is concentrated at a single frequency, allowing the
corresponding spin waves to propagate with very low attenuation, resulting in a
higher k-space resolution. Second, the model allows to include very large wave
vector components, necessary to describe the high-frequency response of
non-quantized spin waves in quasi-continuous systems. Finally, we address some
possible experimental opportunities with respect to excitation/detection
techniques over large distances and the observation of the odd/even symmetry of
spin waves using Brillouin light scattering.",1403.2549v1
2018-11-17,Transverse spin and surface waves in acoustic metamaterials,"We consider spin angular momentum density in inhomogeneous acoustic fields:
evanescent waves and surface waves at interfaces with negative-density
metamaterials. Despite being purely longitudinal (curl-free), acoustic waves
possess intrinsic vector properties described by the velocity field. Motivated
by the recent description and observation of the spin properties in elastic and
acoustic waves, we compare these properties with their well-known
electromagnetic counterparts. Surprisingly, both the transverse spin of
evanescent waves and the parameters of surface waves are very similar in
electromagnetism and acoustics. We also briefly analyze the important role of
dispersion in the description of the energy and spin densities in acoustic
metamaterials.",1811.07159v2
2019-08-31,High-fidelity magnonic gates for surface spin waves,"We study the propagation of surface spin waves in two wave guides coupled
through the dipole-dipole interaction. Essential for the observations made here
is the magneto-electric coupling between the spin waves and the effective
ferroelectric polarization. This allows an external electric field to act on
spin waves and to modify the band gaps of magnonic excitations in individual
layers. By an on/off switching of the electric field and/or varying its
strength or direction with respect to the equilibrium magnetization, it is
possible to permit or ban the propagation of the spin waves in selected
waveguide. We propose experimentally feasible nanoscale device operating as a
high fidelity surface wave magnonic gate.",1909.00162v1
2013-10-29,Wave packet dynamics and zitterbewegung of heavy holes in a quantizing magnetic field,"In this work we study wave packet dynamics and $zitterbewegung$, an
oscillatory quantum motion, of heavy holes in III-V semiconductor quantum wells
in presence of a quantizing magnetic field. It is revealed that a Gaussian
wave-packet describing a heavy hole diffuses asymmetrically along the circular
orbit while performing cyclotron motion. The wave packet splits into two peaks
with unequal amplitudes after a certain time depending on spin-orbit coupling
constant. This unequal splitting of the wave packet is attributed to the cubic
Rashba interaction for heavy holes. The difference in the peak amplitudes
disappears with time. At a certain time the two peaks diffuse almost along the
entire cyclotron orbit. Then tail and head of the diffused wave packet
interfere and as a result a completely randomized pattern of the wave packet is
observed. The diffusion rate of the wave packet increases with increase of the
spin-orbit interaction strength. Also strong spin-orbit coupling expedite the
splitting and the randomization of the wave packet. We also study the
$zitterbewegung$ in various physical observables such as position, charge
current and spin angular momentum of the heavy hole. The $zitterbewegung$
oscillations are very much sensitive to the initial wave vector of the Gaussian
wave packet and the strength of the Rashba spin-orbit coupling.",1310.7749v2
1994-07-28,Frustrated Bonds and Long Range Order in Quasi-2D Magnets,"We employ the Schwinger boson mean-field approach to study the effects of
arbitrary frustrated bonds and plaquettes (formed from four frustrated bonds)
in two-dimensional ferro- and antiferromagnets on the spin-wave spectrum and
the correlation length at finite temperatures. We distinguish between strongly
frustrated bonds (plaquettes), when the frustrated coupling $J^\prime$ exceeds
the spin canting threshold $J_c$, and weakly frustrated bonds (plaquettes),
with $J^\prime <J_c, (J_c-J^\prime)/J_c\sim 1$. It is shown that in
antiferromagnets the amplitude of spin-wave scattering on strongly frustrated
bonds or plaquettes grows with the decrease of the temperature. A small amount
of such defects reduces significantly the spin-wave stiffness and the
correlation length at low temperatures. As a result, the quasi-2D N\'eel
temperature is sharply suppressed. Quantum fluctuations are also considered and
their effect on the spin-wave spectrum is shown to be of the order of
$(2S)^{-2}\ln^{-1}2S$ in the large spin limit. For weakly frustrated
(nonfrustrated) defect bonds (plaquettes) the spin-wave stiffness
renormalization is of the order of the dopant concentration and does not depend
on the temperature. The results account for the observed properties of doped
quasi-2D $La_2CuO_{4+x}$.",9407111v1
1999-05-11,Invariant spin coherent states and the theory of quantum antiferromagnet in a paramagnetic phase,"The consistent theory of the Heisenberg quantum antiferromagnet in the
disordered phase with short range antiferromagnetic order was developed on the
basis of the path integral for the spin coherent states. We have presented the
Lagrangian of the theory in a form which is explicitly invariant under
rotations and have found natural variables in the term of which one can
construct a natural perturbation theory. The short wave spin fluctuations are
similar to the spin wave theory ones, and the long wave spin fluctuations are
governed by the nonlinear sigma model. We have also demonstrated that the short
wave spin fluctuations have to be considered accurately in the framework of the
discrete version in time of the path integral. In the framework of our approach
we have obtained the response function for the spin fluctuations for the whole
region of the frequency $\omega$ and the wave vector ${\bf k}$ and have
calculated the free energy of the system.",9905132v3
2003-06-26,Finite-size spin-wave theory of a collinear antiferromagnet,"The ground-state and low-energy properties of the two-dimensional $J_1{-}J_2$
Heisenberg model in the collinear phase are investigated using finite-size
spin-wave theory [Q. F. Zhong and S. Sorella, {\em Europhys. Lett.} {\bf 21},
629 (1993)], and Lanczos exact diagonalizations. For spin one-half -- where the
effects of quantization are the strongest -- the spin-wave expansion turns out
to be quantitatively accurate for $J_2/J_1\gtrsim 0.8$. In this regime, both
the magnetic structure factor and the spin susceptibility are very close to the
spin-wave predictions. The spin-wave estimate of the order parameter in the
collinear phase, $m^\dagger\simeq 0.3$, is in remarkable agreement with recent
neutron scattering measurements on ${\rm Li_2VOSiO_4}$.",0306679v2
2003-09-29,Magnons in CMR pyrochlore Tl2Mn2O7,"Well defined spin waves were observed when the spin dynamics of Tl2Mn2O7, the
first pyrochlore compound found to exhibit colossal magnetoresistance, was
measured [J.W.Lynn et al., Phys.Rev.Lett. 80,4582(1998)], in stark contrast
with the experimental results on the larger family of magnetoresistive
manganites with perovskite structure. In this work, we present our calculation
for the spin waves in Tl2Mn2O7, which we described using the microscopic
generic model proposed recently for this compound [C.I.Ventura and M.A.Gusmao,
Phys.Rev.B 65, 14422(2002)]. We have employed a canonical transformation to
determine perturbatively the effective spin-wave Hamiltonian, obtaining
therefrom the renormalization of the ferromagnetic spin waves related to the
localized Mn$^{4+}$ spins, due to their coupling with the conduction electrons
present. We have calculated the magnon dispersion relations along different
paths in the first Brillouin zone, comparing them with those which are obtained
for an ideal isotropic ferromagnet. This comparison evidences an agreement
between the ferromagnetic magnons obtained from the generic model and the bare
spin waves, such as had been found in neutron scattering experiments.",0309684v1
2004-02-17,Spin Waves in Antiferromagnetic Spin Chains with Long Range Interactions,"We study antiferromagnetic spin chains with unfrustrated long-range
interactions that decays as a power law with exponent $\beta$, using the spin
wave approximation. We find for sufficiently large spin $S$, the Neel order is
stable at T=0 for $\beta < 3$, and survive up to a finite Neel temperature for
$\beta < 2$, validating the spin-wave approach in these regimes. We estimate
the critical values of $S$ and $T$ for the Neel order to be stable. The spin
wave spectra are found to be gapless but have non-linear momentum dependence at
long wave length, which is responsible for the suppression of quantum and
thermal fluctuations and stabilizing the Neel state. We also show that for
$\beta\le 1$ and for a large but finite-size system size $L$, the excitation
gap of the system approaches zero slower than $L^{-1}$, a behavior that is in
contrast to the Lieb-Schulz-Mattis theorem.",0402445v2
2004-12-29,Spin wave analysis of Heisenberg magnets in restricted geometries,"In the last decade it has been proven that the standard spin wave theory was
able to provide accurate zero-temperature results for a number of
low-dimensional Heisenberg spin systems. In this chapter we introduce the main
ingredients of the spin-wave technique using as a working model the two-leg
mixed-spin ferrimagnetic ladder and the Dyson--Maleev boson formalism up to
second order in the spin-wave interaction. In the remainder, we survey typical
applications in low-space dimensionality as well as some recent modifications
of the theory admitting a quantitative analysis in magnetically disordered
phases. The presented spin-wave results are compared with available numerical
estimates.",0412742v1
2007-01-29,"Magnetic Anisotropy, Spin Pinning and Exchange Constants of (Ga,Mn)As films","We present a detailed investigation of exchange-dominated nonpropagating
spin-wave modes in a series of 100 nm Ga$_{1 - x}$Mn$_{x}$As films with Mn
concentrations $x$ ranging from 0.02 to 0.08. The angular and Mn concentration
dependences of spin wave resonance modes have been studied for both as-grown
and annealed samples. Our results indicate that the magnetic anisotropy terms
of Ga$_{1 - x}$Mn$_{x}$As depend on the Mn concentration $x$, but are also
strongly affected by sample growth conditions; moreover, the magnetic
anisotropy of Ga$_{1 - x}$Mn$_{x}$As films is found to be clearly linked to the
Curie temperature. The spin wave resonance spectra consist of a series of well
resolved standing spin-wave modes. The observed mode patterns are consistent
with the Portis volume-inhomogeneity model, in which a spatially nonuniform
anisotropy field acts on the Mn spins. The analysis of these exchange-dominated
spin wave modes, including their angular dependences, allows us to establish
the exchange stiffness constants for Ga$_{1 - x}$Mn$_{x}$As films.",0701717v1
2008-12-22,Spin-wave contributions to current-induced domain wall dynamics,"We examine theoretically the role of spin-waves on current-induced domain
wall dynamics in a ferromagnetic wire. At room temperature, we find that an
interaction between the domain wall and the spin waves appears when there is a
finite difference between the domain wall velocity $\dot{x}_0$ and the spin
current $u$. Three important consequences of this interaction are found.
Firstly, spin-wave emission leads to a Landau-type damping of the
current-induced domain wall motion towards restoring the solution $\dot{x}_0 =
u$, where spin angular momentum is perfectly transfered from the conduction
electrons to the domain wall. Secondly, the interaction leads to a modification
of the domain wall width and mass, proportional to the kinetic energy of the
domain wall. Thirdly, the coupling by the electrical current between the domain
wall and the spin waves leads to temperature-dependent effective wall mass.",0812.4084v1
2011-03-15,Nonlinear wave interaction and spin models in the MHD regime,"Here we consider the influence on the electron spin in the MHD regime.
Recently developed models which include spin-velocity correlations are taken as
a starting point. A theoretical argument is presented, suggesting that in the
MHD regime a single fluid electron model with spin correlations is equivalent
to a model with spin-up and spin-down electrons constituting different fluids,
but where the spin-velocity correlations are omitted. Three wave interaction of
2 shear Alfven waves and a compressional Alfven wave is then taken as a model
problem to evaluate the asserted equivalence. The theoretical argument turns
out to be supported, as the predictions of the two models agree completely.
Furthermore, the three wave coupling coefficients obey the Manley-Rowe
relations, which give further support to the soundness of the models and the
validity of the assumptions made in the derivation. Finally we point out that
the proposed two-fluid model can be incorporated in standard Particle-In-Cell
schemes with only minor modifications.",1103.2932v1
2013-12-17,Superconducting pairing in the spin-density-wave phase of iron pnictides,"Some of the iron pnictides show coexisting superconductivity and
spin-density-wave order. We study the superconducting pairing instability in
the spin-density-wave phase. Assuming that the pairing interaction is due to
spin fluctuations, we calculate the effective pairing interactions in the
singlet and triplet channels by summing the bubble and ladder diagrams taking
the reconstructed band structure into account. The leading pairing
instabilities and the corresponding superconducting gap structures are then
obtained from the superconducting gap equation. We illustrate this approach for
a minimal two-band model of the pnictides. Analytical and numerical results
show that the existence of propagating magnons in the spin-density-wave phase
strongly enhances the pairing in both the singlet and the spin s_z=0 triplet
channel. Over a limited parameter range, a spin s_z=0 triplet p_x-wave state is
the dominant instability. It competes with various singlet states, which have
mostly s^\pm-type structures. We analyze the effect of various symmetry-allowed
interactions on the pairing in some detail.",1312.4720v2
2014-10-26,Spin flip statistics and Spin wave interference patterns in Ising ferromagnetic films: A Monte Carlo study,"The spin wave interference is studied in two dimensional Ising ferromagnet
driven by two coherent spherical magnetic field waves by Monte Carlo
simulation. The spin waves are found to propagate and interfere according to
the classic rule of interference pattern generated by two point sources. The
interference pattern of spin wave is observed in one boundary of the lattice.
The interference pattern is detected and studied by spin flip statistics at
high and low temperatures. The destructive interference is manifested as the
large number of spin flips and vice versa.",1410.7023v4
2016-05-22,Spin control of light with hyperbolic metasurfaces,"Transverse spin angular momentum is an inherent feature of evanescent waves
which may have applications in nanoscale optomechanics, spintronics, and
quantum information technology due to the robust spin-directional coupling.
Here we analyze a local spin angular momentum density of hybrid surface waves
propagating along anisotropic hyperbolic metasurfaces. We reveal that, in
contrast to bulk plane waves and conventional surface plasmons at isotropic
interfaces, the spin of the hybrid surface waves can be engineered to have an
arbitrary angle with the propagation direction. This property allows to tailor
directivity of surface waves via the magnetic control of the spin projection of
quantum emitters, and it can be useful for optically controlled spin transfer.",1605.06781v2
2018-06-22,Spin-flavor oscillations of Dirac neutrinos in a plane electromagnetic wave,"We study spin and spin-flavor oscillations of Dirac neutrinos in a plane
electromagnetic wave with circular polarization. The evolution of massive
neutrinos with nonzero magnetic moments in the field of an electromagnetic wave
is based on the exact solution of the Dirac-Pauli equation. We formulate the
initial condition problem to describe spin-flavor oscillations in an
electromagnetic wave. The transition probabilities for spin and spin-flavor
oscillations are obtained. In case of spin-flavor oscillations, we analyze the
transition and survival probabilities for different neutrino magnetic moments
and various channels of neutrino oscillations. As an application of the
obtained results, we study the possibility of existence of
$\nu_{e\mathrm{L}}\to\nu_{\mu\mathrm{R}}$ oscillations in an electromagnetic
wave emitted by a highly magnetized neutron star. Our results are compared with
findings of other authors.",1806.08719v2
2019-03-28,Acoustic excitation and electrical detection of spin waves and spin currents in hypersonic bulk waves resonator with YIG/Pt system,"We report on the self-consisted semi-analytical theory of magnetoelastic
excitation and electrical detection of spin waves and spin currents in
hypersonic bulk acoustic waves resonator with ZnO-GGG-YIG/Pt layered structure.
Electrical detection of acoustically driven spin waves occurs due to spin
pumping from YIG to Pt and inverse spin Hall (ISHE) effect in Pt as well as due
to electrical response of ZnO piezotransducer. The frequency-field dependences
of the resonator frequencies and ISHE voltage $U_{ISHE}$ are correlated with
experimental ones observed previously. Their fitting allows to determine some
magnetic and magnetoelastic parameters of YIG. The analysis of the YIG film
thickness influence on $U_{ISHE}$ gives the possibility to find the optimal
thickness for maximal $U_{ISHE}$ value.",1903.12130v2
2021-02-05,Symmetry-Driven Spin-Wave Gap Modulation in Nanolayered SrRuO3/SrTiO3 Heterostructures: Implications for Spintronic Applications,"A strong correlation between magnetic interaction and topological symmetries
leads to unconventional magneto-transport behavior. Weyl fermions induce
topologically protected spin-momentum locking, which is closely related to
spin-wave gap formation in magnetic crystals. Ferromagnetic SrRuO3, regarded as
a strong candidate for Weyl semimetal, inherently possesses a nonzero spin-wave
gap owing to its strong magnetic anisotropy. In this paper, we propose a method
to control the spin-wave dynamics by nanolayer designing of the SrRuO3/SrTiO3
superlattices. In particular, the six-unit-cell-thick SrRuO3 layers within the
superlattices undergo a phase transition in crystalline symmetry from
orthorhombic to tetragonal, as the thickness of the SrTiO3 layers is modulated
with atomic-scale precision. Consequently, the magnetic anisotropy, anomalous
Hall conductivity, and spin-wave gap could be systematically manipulated. Such
customization of magnetic anisotropy via nanoscale heterostructuring offers a
novel control knob to tailor the magnon excitation energy for future spintronic
applications, including magnon waveguides and filters. Our nanolayer approach
unveils the important correlation between the tunable lattice degrees of
freedom and spin dynamics in topologically non-trivial magnetic materials.",2102.03008v1
2021-04-14,Spin waves propagating through a stripe magnetic domain structure and their applications to reservoir computing,"Spin waves propagating through a stripe domain structure and reservoir
computing with their spin dynamics have been numerically studied with focusing
on the relation between physical phenomena and computing capabilities. Our
system utilizes a spin-wave-based device that has a continuous magnetic garnet
film and 1-input/72-output electrodes on the top. To control
spatially-distributed spin dynamics, a stripe magnetic domain structure and
amplitude-modulated triangular input waves were used. The spatially-arranged
electrodes detected spin vector outputs with various nonlinear characteristics
that were leveraged for reservoir computing. By moderately suppressing
nonlinear phenomena, our system achieves 100$\%$ prediction accuracy in
temporal exclusive-OR (XOR) problems with a delay step up to 5. At the same
time, it shows perfect inference in delay tasks with a delay step more than 7
and its memory capacity has a maximum value of 21. This study demonstrated that
our spin-wave-based reservoir computing has a high potential for edge-computing
applications and also can offer a rich opportunity for further understanding of
the underlying nonlinear physics.",2104.06794v1
2017-01-14,Paving Spin-Wave Fibers in Magnonic Nanocircuits Using Spin-Orbit Torque,"Recent studies have revealed that domain walls in magnetic nanostructures can
serve as compact, energy-efficient spin-wave waveguides for building magnonic
devices that are considered promising candidates for overcoming the challenges
and bottlenecks of today's CMOS technologies. However, imprinting long
strip-domain walls into magnetic nanowires remains a challenge, especially in
curved geometries. Here, through micromagnetic simulations, we present a method
for writing strip-domain walls into curved magnetic nanowires using spin-orbit
torque. We employ Y-shaped magnetic nanostructures as well as an S-shaped
magnetic nanowire to demonstrate the injection process. In addition, we verify
that the Y-shaped nanostructures that incorporate strip-domain walls can
function as superior spin-wave multiplexers, and that spin-wave propagation
along each conduit can be controllably manipulated. This spin-wave multiplexer
based on strip-domain walls is expected to become a key signal-processing
component in magnon spintronics.",1701.03886v1
2022-01-18,Adiabatic equatorial inspirals of a spinning body into a Kerr black hole,"The detection of gravitational waves from Extreme mass Ratio Inspirals
(EMRIs) by the future space-based gravitational-wave detectors demands the
generation of accurate enough waveform templates. Since the spin of the smaller
secondary body cannot be neglected for the detection and parameter estimation
of EMRIs, we study its influence on the phase of the gravitational waves from
EMRIs with spinning secondary. We focus on generic eccentric equatorial orbits
around a Kerr black hole. To model the spinning secondary object, we use the
Mathisson-Papapetrou-Dixon equations in the pole-dipole approximation.
Furthermore, we linearize in spin the orbital variables and the
gravitational-wave fluxes from the respective orbits. We obtain these fluxes by
using the Teukolsky formalism in the frequency domain. We derive the evolution
equations for the spin induced corrections to the adiabatic evolution of an
inspiral. Finally, through their numerical integration we find the
gravitational-wave phase shift between an inspiral of a spinning and a
non-spinnig body.",2201.07044v1
2023-02-10,Ponderomotive force due to the intrinsic spin for electrostatic waves in a magnetized plasma,"We study the contribution from the electron spin to the ponderomotive force,
using a quantum kinetic model including the spin-orbit correction.
Specifically, we derive an analytical expression for the ponderomotive force,
applicable for electrostatic waves propagating parallel to an external magnetic
field. To evaluate the expression, we focus on the case of Langmuir waves and
on the case of the spin-resonance wave mode, where the classical and spin
contributions to the ponderomotive force are compared. Somewhat surprisingly,
dependent on the parameter regime, we find that the spin contribution to the
ponderomotive force may dominate for the Langmuir wave, whereas the classical
contribution can dominate for the spin resonance mode. Naturally, this does not
prevent the opposite case from being the more common one.",2302.05136v1
2024-02-01,Spin wave-driven variable-phase mutual synchronization in spin Hall nano-oscillators,"Spin-orbit torque can drive auto-oscillations of propagating spin wave (PSW)
modes in nano-constriction spin Hall nano-oscillators (SHNOs). These modes
allow both long-range coupling and the potential of controlling its phase --
critical aspect for nano-magnonics, spin wave logic, and Ising machines. Here,
we demonstrate PSW-driven variable-phase coupling between two nano-constriction
SHNOs and study how their separation and the PSW wave vector impact their
mutual synchronization. In addition to ordinary in-phase mutual
synchronization, we observe, using both electrical measurements and
phase-resolved $\mu-$Brillouin Light Scattering microscopy, mutual
synchronization with a phase that can be tuned from 0 to $\pi$ using the drive
current or the applied field. Micromagnetic simulations corroborate the
experiments and visualize how the PSW patterns in the bridge connecting the two
nano-constrictions govern the coupling. These results advance the capabilities
of mutually synchronized SHNOs and open up new possibilities for applications
in spin wave logic, unconventional computing, and Ising Machines.",2402.00586v1
2013-09-16,Ambipolar spin transport in (111) GaAs quantum wells,"We present a microscopic theory for transport of the spin polarized charge
density wave with both electrons and holes in the $(111)$ GaAs quantum wells.
We analytically show that, contradicting to the commonly accepted belief, the
spin and charge motions are bound together only in the fully polarized system
but can be separated in the case of low spin polarization or short spin
lifetime even when the spatial profiles of spin density wave and charge density
wave overlap with each other. We further show that, the Coulomb drag between
electrons and holes can markedly enhance the hole spin diffusion if the hole
spin motion can be separated from the charge motion. In the high spin polarized
system, the Coulomb drag can boost the hole spin diffusion coefficient by more
than one order of magnitude.",1309.3871v2
2014-07-16,Spin Excitation Spectra of Spin-Orbit Coupled Bosons in Optical Lattice,"Spin-wave excitation plays important roles in the investigation of the
magnetic phases. In this paper, we study the spin-wave excitation spectra of
two-component Bose gases with spin-orbit coupling on a deep square optical
lattice using spin-wave theory. We find that, while the excitation spectrum of
the vortex crystal phase is gapless with a linear dispersion in the vicinity of
the minimum point, the spectra of the commensurate spiral spin phase and the
skyrmion crystal phase are gapped. Significantly, the spin fluctuations
strongly destabilize the classical ground state of the skyrmion phase. It
suggests the emergence of a new state in the phase diagram. Such features of
the spin excitation spectra provide further insights into the exploration of
the exotic spin phases.",1407.4172v1
2015-03-11,Spin-wave-induced spin torque in Rashba spin-orbit coupling system,"We study the effects of Rashba spin-orbit coupling on the spin torque induced
by spin waves, which are the plane wave dynamics of magnetization. The spin
torque is derived from linear response theory, and we calculate the dynamic
spin torque by considering the impurity-ladder-sum vertex corrections. This
dynamic spin torque is divided into three terms: a damping term, a $distortion$
term, and a correction term for the equation of motion. The $distorting$ torque
describes a phenomenon unique to the Rashba spin-orbit coupling system, where
the distorted motion of magnetization precession is subjected to the
anisotropic force from the Rashba coupling. The oscillation mode of the
precession exhibits an elliptical trajectory, and the ellipticity depends on
the strength of the nesting effects, which could be reduced by decreasing the
electron lifetime.",1503.03171v2
2015-09-09,Quantum spin transport and dynamics through a novel F/N junction,"We study the spin transport in the low temperature regime (often referred to
as the precession-dominated regime) between a ferromagnetic Fermi liquid (FFL)
and a normal metal metallic Fermi liquid (NFL), also known as the F/N junction,
which is considered as one of the most basic spintronic devices. In particular,
we explore the propagation of spin waves and transport of magnetization through
the interface of the F/N junction where nonequilibrium spin polarization is
created on the normal metal side of the junction by electrical spin injection.
We calculate the probable spin wave modes in the precession-dominated regime on
both sides of the junction especially on the NFL side where the system is out
of equilibrium. Proper boundary conditions at the interface are introduced to
establish the transport of the spin properties through the F/N junction. A
possible transmission conduction electron spin resonance (CESR) experiment is
suggested on the F/N junction to see if the predicted spin wave modes could
indeed propagate through the junction. Potential applications based on this
novel spin transport feature of the F/N junction are proposed in the end.",1509.02582v1
2015-11-07,Universal Spin-Momentum Locked Optical Forces,"Evanescent electromagnetic waves possess spin-momentum locking, where the
direction of propagation (momentum) is locked to the inherent polarization of
the wave (transverse spin). We study the optical forces arising from this
universal phenomenon and show that the fundamental origin of recently reported
non-trivial optical chiral forces is spin-momentum locking. For evanescent
waves, we show that the direction of energy flow, direction of decay, and
direction of spin follow a right hand rule for three different cases of total
internal reflection, surface plasmon polaritons, and $HE_{11}$ mode of an
optical fiber. Furthermore, we explain how the recently reported phenomena of
lateral optical force on chiral and achiral particles is caused by the
transverse spin of the evanescent field and the spin-momentum locking
phenomenon. Finally, we propose an experiment to identify the unique lateral
forces arising from the transverse spin in the optical fiber and point to
fundamental differences of the spin density from the well-known orbital angular
momentum of light. Our work presents a unified view on spin-momentum locking
and how it affects optical forces on chiral and achiral particles.",1511.02305v1
2018-03-30,Extraordinary SEAWs under influence of the spin-spin interaction and the quantum Bohm potential,"The separate spin evolution (SSE) of electrons causes the existence of the
spin-electron acoustic wave. Extraordinary spin-electron acoustic waves (SEAWs)
propagating perpendicular to the external magnetic field have large
contribution of the transverse electric field. Its spectrum has been studied in
the quasi-classical limit at the consideration of the separate spin evolution.
The spin-spin interaction and the quantum Bohm potential give contribution in
the spectrum extraordinary SEAW. This contribution is studied in this paper.
Moreover, it is demonstrated that the spin-spin interaction leads to the
existence of the extraordinary SEAWs if the SSE is neglected. The hybridization
of the extraordinary SEAW and the lower extraordinary wave in the regime, where
the cyclotron frequency is larger then the Langmuir frequency is studied
either.",1803.11403v1
2020-09-03,Coincidence inelastic neutron scattering for detection of two-spin magnetic correlations,"Inelastic neutron scattering (INS) is one powerful technique to study the
low-energy single-spin dynamics of magnetic materials. A variety of quantum
magnets show novel magnetic correlations such as quantum spin liquids. These
novel magnetic correlations are beyond the direct detection of INS. In this
paper we propose a coincidence technique, coincidence inelastic neutron
scattering (cINS), which can detect the two-spin magnetic correlations of the
magnetic materials. In cINS there are two neutron sources and two neutron
detectors with an additional coincidence detector. Two neutrons from the two
neutron sources are incident on the target magnetic material, and they are
scattered by the electron spins of the magnetic material. The two scattered
neutrons are detected by the two neutron detectors in coincidence with the
coincidence probability described by a two-spin Bethe-Salpeter wave function.
Since the two-spin Bethe-Salpeter wave function defines the momentum-resolved
dynamical wave function with two spins excited, cINS can explicitly detect the
two-spin magnetic correlations of the magnetic material. Thus, it can be
introduced to study the various spin valence bond states of the quantum
magnets.",2009.01680v2
2021-02-15,Emission of Spin-correlated Matter-wave Jets from Spinor Bose-Einstein Condensates,"We report the observation of matter-wave jet emission in a strongly
ferromagnetic spinor Bose-Einstein condensate of $^7$Li atoms. Directional
atomic beams with $|{F=1,m_F=1}\rangle$ and $|{F=1,m_F=-1}\rangle$ spin states
are generated from $|{F=1,m_F=0}\rangle$ state condensates, or vice versa. This
results from collective spin-mixing scattering events, where spontaneously
produced pairs of atoms with opposite momentum facilitates additional
spin-mixing collisions as they pass through the condensates. The matter-wave
jets of different spin states ($|{F=1,m_F=\pm1}\rangle$) can be a macroscopic
Einstein-Podolsky-Rosen state with spacelike separation. Its spin-momentum
correlations are studied by using the angular correlation function for each
spin state. Rotating the spin axis, the inter-spin and intra-spin momentum
correlation peaks display a high contrast oscillation, indicating collective
coherence of the atomic ensembles. We provide numerical calculations that
describe the experimental results at a quantitative level and can identify its
entanglement after 100~ms of a long time-of-flight.",2102.07613v1
2017-10-14,Lorentz-boosted evanescent waves,"Polarization, spin, and helicity are important properties of electromagnetic
waves. It is commonly believed that helicity is invariant under the Lorentz
transformations. This is indeed so for plane waves and their localized
superpositions. However, this is not the case for evanescent waves, which are
well-defined only in a half-space, and are characterized by complex wave
vectors. Here we describe transformations of evanescent electromagnetic waves
and their polarization/spin/helicity properties under the Lorentz boosts along
the three spatial directions.",1710.05145v2
2015-12-25,Surface spin-electron acoustic waves in magnetically ordered metals,"Degenerate plasmas with motionless ions show existence of three surface
waves: the Langmuir wave, the electromagnetic wave, and the zeroth sound.
Applying the separated spin evolution quantum hydrodynamics to half-space
plasma we demonstrate the existence of the surface spin-electron acoustic wave
(SSEAW). We study dispersion of the SSEAW. We show that there is hybridization
between the surface Langmuir wave and the SSEAW at rather small spin
polarization. In the hybridization area the dispersion branches are located
close to each other. In this area there is a strong interaction between these
waves leading to the energy exchange. Consequently, generating the Langmuir
waves with the frequencies close to hybridization area we can generate the
SSEAWs. Thus, we report a method of creation of the SEAWs.",1512.07940v1
2020-11-03,Gravito-magnetic resonance in the field of a gravitational wave,"Using the construction of the Fermi frame, the field of a gravitational wave
can be described in terms of gravito-electromagnetic fields that are transverse
to the propagation direction and orthogonal to each other. In particular, the
gravito-magnetic field acts on spinning particles and we show that, due to the
action of the gravitational wave field, a new phenomenon, that we call
gravito-magnetic resonance, may appear. We give both a classical and a quantum
description of this phenomenon and suggest that it can be used as the basis for
a new type of gravitational wave detectors. Our results highlight the
effectiveness of collective spin excitations, e.g. spin waves in magnetized
materials, in detecting high frequency gravitational waves. Here we suggest
that, when gravitational waves induce a precession of the electron spin, power
is released in the ferromagnetic resonant mode endowed with quadrupole symmetry
of a magnetized sphere. This offers a possible path to the detection of the
gravito-magnetic effects of a gravitational wave.",2011.01663v1
2022-01-26,Spin Wave Electromagnetic Nano-Antenna Enabled by Tripartite Phonon-Magnon-Photon Coupling,"We investigate tripartite coupling between phonons, magnons and photons in a
periodic array of elliptical magnetostrictive nanomagnets delineated on a
piezoelectric substrate to form a two-dimensional two-phase multiferroic
crystal. A surface acoustic wave (phonons) of 5 - 35 GHz frequency launched
into the substrate causes the magnetizations of the nanomagnets to precess at
the frequency of the wave, giving rise to spin waves (magnons). The spin waves,
in turn, radiate electromagnetic waves (photons) into the surrounding space at
the surface acoustic wave frequency. Here, the phonons couple into magnons,
which then couple into photons. This tripartite phonon-magnon-photon coupling
is exploited to implement an extreme sub-wavelength electromagnetic antenna
whose measured radiation efficiency and antenna gain exceed the theoretical
limits for traditional antennas by more than two orders of magnitude at some
frequencies. Micro-magnetic simulations are in excellent agreement with
experimental observations and provide insight into the spin wave modes that
couple into radiating electromagnetic modes to implement the antenna.",2201.11110v1
2016-06-27,Nonreciprocal Transverse Photonic Spin and Magnetization-Induced Electromagnetic Spin-Orbit Coupling,"A study of nonreciprocal transverse-spin angular-momentum-density shifts for
evanescent waves in magneto-optic waveguide media is presented. Their
functional relation to electromagnetic spin- and orbital-momenta is presented
and analyzed. It is shown that the magneto-optic gyrotropy can be
re-interpreted as the nonreciprocal electromagnetic spin-density shift per unit
energy flux, thus providing an interesting alternative physical picture for the
magneto-optic gyrotropy. The transverse spin-density shift is found to be
thickness-dependent in slab optical waveguides. This dependence is traceable to
the admixture of minority helicity components in the transverse spin angular
momentum. It is also shown that the transverse spin is magnetically tunable. A
formulation of electromagnetic spin-orbit coupling in magneto-optic media is
presented, and an alternative source of spin-orbit coupling to non-paraxial
optics vortices is proposed. It is shown that magnetization-induced
electromagnetic spin-orbit coupling is possible, and that it leads to spin to
orbital angular momentum conversion in magneto-optic media evanescent waves.",1606.08334v2
2018-09-07,Spin angular momentum in planar and cylindrical waveguides induced by transverse confinement and intrinsic helicity of guided light,"In recent years, extraordinary spin angular momenta have been investigated in
a variety of structured electromagnetic waves, being of especial interest in
sub-wavelength evanescent fields. Here we demonstrate analytically that, in
planar and cylindrical waveguides supporting transverse electric/magnetic
modes, transverse spin density arises inside the waveguide (different from the
spin induced in the evanescent region outside the waveguide), carrying indeed
longitudinal extraordinary (so-called) Belinfante's spin momentum. Such
contribution depends linearly on the mode transverse wave vector, and is thus
induced by mode confinement. Cylindrical waveguides support in addition hybrid
modes that exhibit a richer phenomenology with not only azimuthal
(confinement-related) spin, but also an intrinsic helicity which leads to
longitudinal spin density and transverse helicity-dependent spin momentum.
Results are indeed presented for configurations relevant to spin-orbit coupling
in nanophotonic waveguides and to manipulating optical forces in
IR-to-microwave water-filled channels. Thus guided modes intrinsically carrying
confinement-induced transverse spin, combined with intrinsic-helicity-induced
longitudinal spin (when hybrid), hold promise of superb devices to control
spin-orbit interaction and optical forces within confined geometries throughout
the electromagnetic spectra.",1809.02406v1
2019-05-04,Skyrmion quantum spin Hall effect,"The quantum spin Hall effect is conventionally thought to require a strong
spin-orbit coupling, producing an effective spin-dependent magnetic field.
However, spin currents can also be present without transport of spins, for
example, in spin-waves or skyrmions. In this paper, we show that topological
skyrmionic spin textures can be used to realize a quantum spin Hall effect.
From basic arguments relating to the single-valuedness of the wave function, we
deduce that loop integrals of the derivative of the Hamiltonian must have a
spectrum that is integer multiples of $ 2 \pi $. By relating this to the spin
current, we form a new quantity called the quantized spin current which obeys a
precise quantization rule. This allows us to derive a quantum spin Hall effect,
which we illustrate with an example of a spin-1 Bose-Einstein condensate.",1905.01459v2
2021-06-29,Spin pumping in noncollinear antiferromagnets,"The ac spin pumping of noncollinear antiferromagnets is theoretically
investigated. Starting from an effective action description of the spin system,
we derive the Onsager coefficients connecting the spin pumping and
spin-transfer torque associated with the dynamics of the SO(3)-valued
antiferromagnetic order parameter. Our theory is applied to a kagome
antiferromagnet resonantly driven by a uniform external magnetic field. We
demonstrate that the reactive (dissipative) spin-transfer torque parameter can
be extracted from the pumped ac spin current in-phase (in quadrature) with the
driving field. Furthermore, we find that the three spin-wave bands of the
kagome AF generate spin currents with mutually orthogonal polarization
directions. This offers a unique way of controlling the spin orientation of the
pumped spin current by exciting different spin-wave modes.",2106.15187v2
2021-01-29,Comparison of Spin-Wave Modes in Connected and Disconnected Artificial Spin Ice Nanostructures Using Brillouin Light Scattering Spectroscopy,"Artificial spin ice systems have seen burgeoning interest due to their
intriguing physics and potential applications in reprogrammable memory, logic
and magnonics. Integration of artificial spin ice with functional magnonics is
a relatively recent research direction, with a host of promising results. As
the field progresses, direct in-depth comparisons of distinct artificial spin
systems are crucial to advancing the field. While studies have investigated the
effects of different lattice geometries, little comparison exists between
systems comprising continuously connected nanostructures, where spin-waves
propagate via dipole-exchange interaction, and systems with nanobars
disconnected at vertices where spin-wave propagation occurs via stray
dipolar-field. Gaining understanding of how these very different coupling
methods affect both spin-wave dynamics and magnetic reversal is key for the
field to progress and provides crucial system-design information including for
future systems containing combinations of connected and disconnected elements.
Here, we study the magnonic response of two kagome spin ices via Brillouin
light scattering, a continuously connected system and a disconnected system
with vertex gaps. We observe distinct high-frequency dynamics and magnetization
reversal regimes between the systems, with key distinctions in spin-wave
localization and mode quantization, microstate-trajectory during reversal and
internal field-profiles. These observations are pertinent for the fundamental
understanding of artificial spin systems and broader design and engineering of
reconfigurable functional magnonic crystals.",2101.12619v2
2007-10-28,Some symmetry properties of spin currents and spin polarizations in multi-terminal mesoscopic spin-orbit coupled systems,"We study theoretically some symmetry properties of spin currents and spin
polarizations in multi-terminal mesoscopic spin-orbit coupled systems. Based on
a scattering wave function approach, we show rigorously that in the equilibrium
state no finite spin polarizations can exist in a multi-terminal mesoscopic
spin-orbit coupled system (both in the leads and in the spin-orbit coupled
region) and also no finite equilibrium terminal spin currents can exist. By use
of a typical two-terminal mesoscopic spin-orbit coupled system as the example,
we show explicitly that the nonequilibrium terminal spin currents in a
multi-terminal mesoscopic spin-orbit coupled system are non-conservative in
general. This non-conservation of terminal spin currents is not caused by the
use of an improper definition of spin current but is intrinsic to
spin-dependent transports in mesoscopic spin-orbit coupled systems. We also
show that the nonequilibrium lateral edge spin accumulation induced by a
longitudinal charge current in a thin strip of \textit{finite} length of a
two-dimensional electronic system with intrinsic spin-orbit coupling may be
non-antisymmetric in general, which implies that some cautions may need to be
taken when attributing the occurrence of nonequilibrium lateral edge spin
accumulation induced by a longitudinal charge current in such a system to an
intrinsic spin Hall effect.",0710.5316v1
2000-12-18,New Origin For Spin Current And Current-Induced Spin Precession In Magnetic Multilayers,"In metallic ferromagnets, an electric current is accompanied by a flux of
angula r momentum, also called spin current. In multilayers, spatial variations
of the spin current correspond to drive torques exerted on a magnetic layer.
These torq ues result in spin precession above a certain current threshold. The
usual kind of spin current is associated with translation of the spin-up and
spin-down Ferm i surfaces in momentum space. We discuss a different kind of
spin current, assoc iated with expansion and contraction of the Fermi surfaces.
It is more nonlocal in nature, and may exist even in locations where the
electrical current density is zero. It is larger than the usual spin current,
in a ratio of 10 or 100, and is dominant in most cases. The new spin current is
proportional to the differenc e Delta-mu = 0.001 eV between spin-up and
spin-down Fermi levels, averaged over the entire Fermi surface. Conduction
processes, spin relaxation, and spin-wave emission in the multilayer can be
described by an equivalent electrical circuit resembling an unbalanced dc
Wheatstone bridge. And Delta-mu corresponds to the output voltage of the
bridge.",0012337v2
2003-10-15,Central limit theorems for the large-spin asymptotics of quantum spins,"We use a generalized form of Dyson's spin wave formalism to prove several
central limit theorems for the large-spin asymptotics of quantum spins in a
coherent state.",0310027v1
2019-02-07,Polarization spin-tensors in two-spinor formalism and Behrends-Fronsdal spin projection operator for $D$-dimensional case,"In the work, the recurrent differential relations that connecting the
polarization spin-tensor of the wave function of a free massive particle of an
arbitrary spin for $D=4$ and new formula of the $D$-dimensional
Behrends-Fronsdal spin projection operator are found.",1902.02570v1
2002-06-21,Novel excitonic states in quantum Hall systems: Bound states of spin waves and a valence band hole,"If the Zeeman energy is small, the lowest energy excitations of a two
dimensional electron gas at filling factor nu=1 are spin waves (spin flip
excitations). At nu slightly larger (smaller) than unity, reversed spin
electrons (spin holes) can form bound states with K spin waves that are known
as skyrmions, S_K^- (antiskyrmions, S_K^+). It is suggested in this work that a
valence hole can also bind K spin waves to form an excitonic complex X_K^+,
analogous to the S_K^+. One spin hole of the S_K^+ is simply replaced by the
valence hole. At nu<=1, a small number of S_K^+'s are present before
introduction of the valence hole. The (S_K^+)-(X_K^+) repulsion leads to
correlations and photoluminescence similar to those of a dilute
electron-(charged-exciton) (e-X^-) system at nu<=1/3. At nu>=1, the
(S_K^-)-(X_K^+) attraction can potentially lead to different behavior.",0206413v1
2010-07-31,Random walk approach to spin dynamics in a two-dimensional electron gas with spin-orbit coupling,"We introduce and solve a semi-classical random walk (RW) model that describes
the dynamics of spin polarization waves in zinc-blende semiconductor quantum
wells. We derive the dispersion relations for these waves, including the
Rashba, linear and cubic Dresselhaus spin-orbit interactions, as well as the
effects of an electric field applied parallel to the spin polarization
wavevector. In agreement with fully quantum mechanical calculations [Kleinert
and Bryksin, Phys. Rev. B \textbf{76}, 205326 (2007)], the RW approach predicts
that spin waves acquire a phase velocity in the presence of the field that
crosses zero at a nonzero wavevector, $q_0$. In addition, we show that the
spin-wave decay rate is independent of field at $q_0$ but increases as
$(q-q_0)^2$ for $q\neq q_0$. These predictions can be tested experimentally by
suitable transient spin grating experiments.",1008.0132v2
2012-12-30,Edge spin excitations and reconstructions of integer quantum Hall liquids,"We study the effect of electron-electron interaction on the charge and spin
structures at the edge of integer quantum Hall liquids, under three different
kinds of confining potentials. Our exact diagonalization calculation for small
systems indicates that the low energy excitations of \nu=1 ferromagnetic state
are bosonic edge spin waves. Instabilities of the ferromagnetic state with
altering confinement strength result from the softening of these edge spin
waves, and formation of edge spin textures. In \nu\lesssim 2 regime, exact
diagonalization on edge electron systems indicates that compact Hartree-Fock
states with different total spin always become ground states in some regions of
parameter space, and the ground states appear in between two compact states are
their edge spin waves. The initial \nu=2 instability is toward the compact
state with total spin 1. Larger systems are studied using a microscopic trial
wave functions, and some quantitative predictions on the edge instabilities for
a certain type of confining potential are reached in the thermodynamic limit.",1212.6743v2
2014-12-09,Spin excitations in the nematic phase and the metallic stripe spin-density wave phase of iron pnictides,"We present a general study of the magnetic excitations within a weak-coupling
five-orbital model relevant to itinerant iron pnictides. As a function of
enhanced electronic correlations, the spin excitations in the symmetry broken
spin-density wave phase evolve from broad low-energy modes in the limit of weak
interactions to sharply dispersing spin wave prevailing to higher energies at
larger interaction strengths. We show how the resulting spin response at high
energies depends qualitatively on the magnitude of the interactions. We also
calculate the magnetic excitations in the nematic phase by including an orbital
splitting, and find a pronounced C_2 symmetric excitation spectrum right above
the transition to long-range magnetic order. Finally, we discuss the C_2 versus
C_4 symmetry of the spin excitations as a function of energy for both the
nematic and the spin-density wave phase.",1412.2912v1
2017-12-01,Spin waves and stability of zigzag order in the Hubbard model with spin-dependent hopping terms - Application to the honeycomb lattice compounds ${\rm Na_2 Ir O_3}$ and ${\rm α- Ru Cl_3}$,"Spin waves in the zigzag ordered state on a honeycomb lattice are
investigated within a Hubbard model with spin-dependent hopping terms. Roles of
the emergent Kitaev, Heisenberg, Dzyaloshinskii-Moriya, and
symmetric-off-diagonal spin interactions are investigated on the stability of
the zigzag order. While the DM interactions are found to destabilize the zigzag
order, the secondary spin-dependent hopping terms (associated with structural
distortions) are shown to strongly stabilize the zigzag order and account for
magnetocrystalline anisotropy, easy axis, and spin wave gap. The calculated
spin wave dispersion and energy scale are in good agreement with inelastic
neutron scattering measurements on $\rm \alpha - RuCl_3$ and $\rm Na_2 Ir O_3$.",1712.00198v2
2019-10-17,Optical storage for 0.53 seconds in a solid-state atomic frequency comb memory using dynamical decoupling,"Quantum memories with long storage times are key elements in long-distance
quantum networks. The atomic frequency comb (AFC) memory in particular has
shown great promise to fulfill this role, having demonstrated multimode
capacity and spin-photon quantum correlations. However, the memory storage
times have so-far been limited to about one millisecond, realized in a
Eu${}^{3+}$ doped Y${}_2$SiO${}_5$ crystal at zero applied magnetic field.
Motivated by studies showing increased spin coherence times under applied
magnetic field, we developed a AFC spin-wave memory utilizing a weak 15 mT
magnetic field in a specific direction that allows efficient optical and spin
manipulation for AFC memory operations. With this field configuration the AFC
spin-wave storage time increased to 40 ms using a simple spin-echo sequence.
Furthermore, by applying dynamical decoupling techniques the spin-wave
coherence time reaches 530 ms, a 300-fold increase with respect to previous AFC
spin-wave storage experiments. This result paves the way towards long duration
storage of quantum information in solid-state ensemble memories.",1910.08009v2
2021-12-22,Surface Cooper pair spin waves in triplet superconductors,"We study the electrodynamics of spin triplet superconductors including
dipolar interactions, which give rise to an interplay between the collective
spin dynamics of the condensate and orbital Meissner screening currents. Within
this theory, we identify a class of spin waves that originate from the coupled
dynamics of the spin-symmetry breaking triplet order parameter and the
electromagnetic field. In particular, we study magnetostatic spin wave modes
that are localized to the sample surface. We show that these surface modes can
be excited and detected using experimental techniques such as microwave spin
wave resonance spectroscopy or nitrogen-vacancy magnetometry, and propose that
the detection of these modes offers a means for the identification of spin
triplet superconductivity.",2112.12146v2
2023-07-25,Spin waves in bilayers of transition-metal dichalcogenides,"Van der Waals magnetic materials are currently of great interest as materials
for applications in future ultrathin nanoelectronics and nanospintronics. Due
to weak coupling between individual monolayers, these materials can be easily
obtained in the monolayer and bilayer forms. The latter are of specific
interest as they may be considered as natural two-dimensional spin valves. In
this paper, we study theoretically spin waves in bilayers of transition metal
dichalcogenides. The considerations are carried within the general spin wave
theory based on effective spin Hamiltonian and Hollstein-Primakoff-Bogolubov
transformation. The spin Hamiltonian includes intra-layer as well as
inter-layer nearest-neighbour exchange interactions, easy-plane anisotropy, and
additionally a weak in-plane easy-axis anisotropy. The bilayer systems consist
of two ferromagnetic (in-plane magnetization) monolayers that are coupled
either ferromagnetically or antiferromagnetically. In the latter case, we
analyse the spin wave spectra in all magnetic phases, i.e. in the
antiferromagnetic, spin-flop, and ferromagnetic ones.",2307.13414v2
2023-12-28,Collective spin oscillations in a magnetized graphene sheet,"We investigate collective spin excitations of graphene electrons with
short-ranged interactions and subject to the external Zeeman magnetic field. We
find that in addition to the familiar Silin spin wave, a collective spin-flip
excitation that reduces to the uniform precession when the wave's momentum
approaches zero, the magnetized graphene supports another collective mode
visible in the transverse spin susceptibility: a collective spin-current mode.
Unlike the Silin wave, this mode is not dictated by the spin-rotational
symmetry but rather owns its existence to the pseudo-spin structure of the
graphene lattice. We find the new collective excitation to become sharply
defined in a finite interval of wave's momenta, the range of which is
determined by the interaction and the magnetization.",2312.16782v1
2024-01-10,Electrical Non-Hermitian Control of Topological Magnon Spin Transport,"Magnonic topological phases realize chiral edge spin waves that are protected
against backscattering, potentially enabling highly efficient spin transport.
Here we show that the spin transport through these magnonic chiral edge states
can be electrically manipulated by non-Hermitian control. We consider the
paradigmatic magnon Haldane model and show that it is transformed into an
effective non-Hermitian magnon Chern insulator by including a
sublattice-dependent spin-orbit torque. In linear spin-wave theory, this
electrically induced torque causes a lasing of the chiral edge magnons along
certain edge directions, leading to an enhancement of the spin-wave amplitude.
This prediction is confirmed by numerical simulations based on the
Landau-Lifshitz-Gilbert equation. For a spin-wave transport setup, in which
magnons are excited by a microwave field and detected with a normal metal
conductor, we find that the magnon amplification is remarkably robust against
disorder, establishing non-Hermitian control as a promising avenue for
topological magnonics.",2401.04967v2
1994-06-02,Inelastic Neutron Scattering from the Spin Ladder Compound (VO)2P2O7,"We present results from an inelastic neutron scattering experiment on the
candidate Heisenberg spin ladder vanadyl pyrophosphate, (VO)2P2O7. We find
evidence for a spin-wave excitation gap of $E_{gap} = 3.7\pm 0.2$ meV, at a
band minimum near $Q=0.8 A^{-1}$. This is consistent with expectations for
triplet spin waves in (VO)2P2O7 in the spin-ladder model, and is to our
knowledge the first confirmation in nature of a Heisenberg antiferromagnetic
spin ladder.",9406016v1
2002-01-31,The spin-1/2 Heisenberg antiferromagnet on a 1/7-depleted triangular lattice: Ground-state properties,"A linear spin-wave approach, a variational method and exact diagonlization
are used to investigate the magnetic long-range order (LRO) of the spin-1/2
Heisenberg antiferromagnet on a two-dimensional 1/7-depleted triangular (maple
leaf) lattice consisting of triangles and hexagons only. This lattice has z=5
nearest neighbors and its coordination number z is therefore between those of
the triangular (z=6) and the kagome (z=4) lattices. Calculating spin-spin
correlations, sublattice magnetization, spin stiffness, spin-wave velocity and
spin gap we find that the classical 6-sublattice LRO is strongly renormalized
by quantum fluctuations, however, remains stable also in the quantum model.",0201584v1
2002-08-13,Spin-Wave Description of Nuclear Spin-Lattice Relaxation in Mn_{12}O_{12} Acetate,"In response to recent nuclear-magnetic-resonance (NMR) measurements on the
molecular cluster Mn_{12}O_{12} acetate, we study the nuclear spin-lattice
relaxation rate 1/T_1 developing a modified spin-wave theory. Our microscopic
new approach, which is distinct from previous macroscopic treatments of the
cluster as a rigid spin of S=10, not only excellently interprets the observed
temperature and applied-field dependences of 1/T_1 for ^{55}Mn nuclei but also
strongly supports the ^{13}C NMR evidence for spin delocalization over the
entire molecule.",0208245v1
2004-07-06,Effect of Spin Current on Uniform Ferromagnetism: Domain Nucleation,"Large spin current applied to a uniform ferromagnet leads to a spin-wave
instability as pointed out recently.
  In this paper, it is shown that such spin-wave instability is absent in a
state containing a domain wall, which indicates that nucleation of magnetic
domains occurs above a certain critical spin current.
  This scenario is supported also by an explicit energy comparison of the two
states under spin current.",0407116v2
2005-10-20,Low-energy Effective Theory for Spin Dynamics of Fluctuating Stripes,"We derive an effective Hamiltonian for spin dynamics of fluctuating smectic
stripes from the t-J model in the weak coupling limit t >> J. Besides the
modulation of spin magnitude, the high energy hopping term would induce a
low-energy anti-ferromagnetic interaction between two neighboring ``blocks of
spins"". Based on the effective Hamiltonian, we applied the linear spin-wave
theory and found that the spin-wave velocity is almost isotropic for
La_{2-x}Sr_x CuO_4 unless the structural effect is considered. The intensity of
the second harmonic mode is found to be about 10% to that of the fundamental
mode.",0510529v1
2006-03-01,Stochastic theory of spin-transfer oscillator linewidths,"We present a stochastic theory of linewidths for magnetization oscillations
in spin-valve structures driven by spin-polarized currents. Starting from a
nonlinear oscillator model derived from spin-wave theory, we derive Langevin
equations for amplitude and phase fluctuations due to the presence of thermal
noise. We find that the spectral linewidths are inversely proportional to the
spin-wave intensities with a lower bound that is determined purely by
modulations in the oscillation frequencies. Reasonable quantitative agreement
with recent experimental results from spin-valve nanopillars is demonstrated.",0603019v1
2007-06-12,Magnetic fingerprint in a ferromagnetic wire: Spin torque diode effect and induction of the DC voltage spectrum inherent in the wire under application for RF current,"We report the rectifying effect of a constant-wave radio frequency (RF)
current by a magnetic domain wall (DW) on a single-layered ferromagnetic wire.
A direct-current (DC) voltage is generated by the spin torque diode effect,
which is a consequence of magnetoresistance oscillation due to the resonant
spin wave excitation induced by the spin-polarized RF current. The DC voltage
spectrum strongly depends on the internal spin structure in the DW, which
corresponds to the magnetic fingerprint of the spin structure in the
ferromagnetic wire.",0706.1733v1
2009-01-20,Role of Bound Magnon in Magnetic Domain Wall Motion,"We report on a quantum description of the domain wall (DW) motion under a
spin current. A bound magnon, which is the zero mode of DW, is found to play a
dominant role in DW dynamics. The bound magnon acquires its inertia by the hard
axis anisotropy and is a free particle even under the spin current. The full
transfer of spin angular momentum from the spin current to DW via the bound
magnon leads to the DW motion with the adiabatic velocity, decoupling of spin
waves from DW, and no Doppler shift in spin waves.",0901.3066v1
2009-03-24,A Finite-temperature First-principles Approach to Spin Fluctuation in BaFe_2As_2,"Thermodynamic flunctuations in BaFe2As2 is addressed with a first-principles
formulation of the Helmholtz energy by accounting for the mixture of various
electronic states each distinguished by different spin orientation
distributions. We find that it is the spin exchange coupling in the inter-plane
c direction that dictates the spin density wave ordering. We quantitatively
predicted the pressure dependence of the spin density wave ordering, the
Schottky anomaly, and the temperature dependence of thermal populations of spin
structures, all in agreement with available experimental data.",0903.4094v1
2010-05-27,Spin transport in coupled spinor Bose gases,"We report direct measurements of spin transport in a trapped, partially
condensed spinor Bose gas. Detailed analyses of spin flux in this
out-of-equilibrium quantum gas are performed by monitoring the flow of atoms in
different hyperfine spin states. The main mechanisms for motion in this system
are exchange scattering and potential energy inhomogeneity, which lead to spin
waves in the normal component and domain formation in the condensate. We find a
large discrepancy in domain formation timescales with those predicted by
potential-driven formation, indicating strong coupling of the condensate to the
normal component spin wave.",1005.5174v2
2012-07-28,Excitations and spin correlations near the interface of two three-dimensional Heisenberg antiferromagnets,"Magnetic excitations and spin correlations near the interface of two
spin-$\frac12$ Heisenberg antiferromagnets are considered using the spin-wave
approximation. When the interaction between boundary spins differs essentially
from exchange constants inside the antiferromagnets, quasi-two-dimensional spin
waves appear in the near-boundary region. They eject bulk magnons from this
region, thereby dividing the antiferromagnets into areas with different
magnetic excitations. The decreased dimensionality of the near-boundary modes
leads to amplified nearest-neighbor spin correlations in the interface area.",1207.6688v1
2012-11-16,Dependence of the Switching Current Density on the Junction Sizes in Spin Transfer Torque,"We investigate the dependence of switching current density on the junction
sizes in the spin transfer torque nanopillar structures by using micromagnetic
simulations. While the macro spin model predicts weak dependence of switching
current density on the junction sizes, we find that the switching current
density is a sensitive function of the junction sizes. It can be explained with
the complicated spin configurations and dynamics during the switching process.
The detail spin configurations and dynamics are determined by spin wave
excitation with the finite wave vector, which is related with the exchange
coupling energy and junction shape.",1211.3785v1
2013-12-04,Excitations and quasi-one-dimensionality in field-induced nematic and spin density wave states,"We study the excitation spectrum and dynamical response functions for several
quasi-one-dimensional spin systems in magnetic fields without dipolar spin
order transverse to the field. This includes both nematic phases, which harbor
""hidden"" breaking of spin-rotation symmetry about the field and have been
argued to occur in high fields in certain frustrated chain systems with
competing ferromagnetic and antiferromagnetic interactions, and spin density
wave states, in which spin-rotation symmetry is truly unbroken. Using
bosonization, field theory, and exact results on the integrable sine-Gordon
model, we establish the collective mode structure of these states, and show how
they can be distinguished experimentally.",1312.0992v1
2014-07-29,Spin-Hall Nano-oscillator: a micromagnetic study,"This letter studies the dynamical behavior of spin-Hall nanoscillators from a
micromagnetic point of view. The model parameters have been identified by
reproducing recent experimental data quantitatively. Our results indicate that
a strongly localized mode is observed for in-plane bias fields such as in the
experiments, while predict the excitation of an asymmetric propagating mode for
large enough out-of plane bias field similarly to what observed in spin-torque
nanocontact oscillators. Our findings show that spin-Hall nanoscillators can
find application as spin-wave emitters for magnonic applications where spin
waves are used for transmission and processing information on nanoscale.",1407.7655v1
2015-08-06,"Helimagnetic thin films: surface reconstruction, surface spin-waves and magnetization","Quantum properties of a helimagnetic thin film of simple cubic lattice with
Heisenberg spin model are studied using the Green's function method. We find
that the spin configuration across the film is strongly non uniform. Using the
exactly determined spin configuration we calculate the spin-wave spectrum and
the layer magnetizations as functions of temperature T. We show the existence
of surface-localized modes which strongly affect the surface magnetization. We
also show that quantum fluctuations cause interesting spin contractions at T =
0 and give rise to a cross-over between layer magnetizations at low T .",1508.01367v1
2015-11-10,Charge and spin density in the helical Luttinger liquid,"The weakly interacting helical Luttinger liquid, due to spin momentum
locking, is characterized by extremely peculiar local observables: we show that
the density-density correlation functions do not exhibit signatures of Friedel
and Wigner oscillations, and that spin-spin correlation functions, which are
strongly anisotropic, witness the formation of a planar spin wave. Moreover, we
demonstrate that the most relevant scattering potentials involving a localized
impurity are not able to modify the electron density, while only magnetic
impurities can pin the planar spin density wave.",1511.03157v1
2016-07-12,Thermal spin dynamics of yttrium iron garnet,"Yttrium Iron Garnet is the prototypical material used to study pure spin
currents. It is a complex material with 20 magnetic atoms in the unit cell.
Almost all theories and experimental analysis approximates this complicated
material to a simple ferromagnet with a single spin wave mode. We use the
method of atomistic spin dynamics to study the temperature evolution of the
full 20 mode exchange spin wave spectrum. Our results show a strong frequency
dependence of the modes in quantitative agreement with neutron scattering
experiments. We find this causes in a reduction in the net spin pumping due to
the thermal occupation of optical modes with the opposite chirality to the FMR
mode.",1607.03263v1
2017-06-15,Misaligned Spin Merging Black Holes in Modified Gravity (MOG),"A promising signature of coalescing black holes is their spin angular
distribution. We consider the aLIGO collaboration gravitational wave
measurements of the binary black hole spins and the predicted modified gravity
(MOG) preference for misaligned spins of the coalescing black holes. In MOG,
during the merger of two black holes, the enhanced strength of gravitation
reduces the effective spin parameter $\chi_{\rm eff}\sim 0$ in agreement with
the measured spin misalignment of the merging black holes observed in the
gravitational wave detections by the aLIGO collaboration.",1706.05035v1
2018-04-10,Conversion of Heat into Charge Current by the Spin Wave Anomalous Nernst Effect,"A novel process of spin conversion from a temperature gradient to a
transverse voltage is addressed in this paper, viz. the anomalous Nernst effect
(ANE) in a ferromagnetic metal. We report that an additional voltage is
superposed on the conventional anomalous Nernst voltage in FePt crystalline
thin films. The dynamics of the local magnetization is modulated by the heat
current and excites spin waves. These generate a conduction electron spin
current via s-d coupling, which flows along the temperature gradient, and the
spin current is converted to a Nernst voltage by the inverse spin Hall effect.",1804.03751v1
2008-06-24,Signal propagation in time-dependent spin transport,"This paper analyzes theoretically the signal propagation in spin transport by
modulating the current passing through magnetic multilayers. Using a
macroscopic description of spin transport based on the dynamical Boltzmann
equation, we show that time-dependent spin transport possesses a wave-like
character that leads to modifications of pure spin-diffusion dynamics. In
particular, the wave-like characteristics allow one to extract a finite spin
signal-propagation velocity.",0806.3843v3
2022-12-11,Spin Excitation in Coupled Honeycomb Lattice Ni$_2$InSbO$_6$,"We performed an inelastic neutron scattering experiment on a polycrystalline
sample of a helimagnet Ni$_2$InSbO$_6$ to construct the spin Hamiltonian.
Well-defined spin-wave excitation with a band energy of 20 meV was observed
below $T_{N} = 76$ K. Using the linear spin-wave theory, the spectrum was
reasonably reproduced with honeycomb spin layers coupled along the stacking
axis (the $c$ axis). The proposed spin model reproduces the soliton lattice
induced by a magnetic field applied perpendicular to the $c$ axis.",2212.05413v1
2023-10-26,Gravitational Spin Hall Effect of Dirac Particle and the Weak Equivalence Principle,"We present a spin-induced none-geodesic effect of Dirac wave packets in a
static uniform gravitational field. Our approach is based on the
Foldy-Wouthuysen transformation of Dirac equation in a curved spacetime, which
predicts the gravitational spin-orbit coupling. Due to this coupling, we find
that the dynamics of the free-fall Dirac wave packets with opposite spin
polarization will yield the transverse splitting in the direction perpendicular
to spin orientation and gravity, which is known as the gravitational spin Hall
effect. Even in a static uniform gravitational field, such effect suggests that
the weak equivalence principle is violated for quantum particles.",2310.17581v1
2023-12-30,Ultrafast X-ray Diffraction Probe of Coherent Spin-state Dynamics in Molecules,"We propose an approach to probe coherent spin-state dynamics of molecules
using circularly polarized hard x-ray pulses. For the dynamically aligned
nitric oxide molecules in a coherent superposition spin-orbit coupled
electronic state that can be prepared through stimulated Raman scattering, we
demonstrate the capability of ultrafast x-ray diffraction to not only reveal
the quantum beating of the coherent spin-state wave packet, but also image the
spatial spin density of the molecule. With circularly polarized ultrafast x-ray
diffraction signal, we show that the electronic density matrix can be
retrieved. The spatio-temporal resolving power of ultrafast x-ray diffraction
paves the way for tracking transient spatial wave function in molecular
dynamics involving spin degree of freedom.",2401.00259v1
2011-06-02,Kinetics of Spin Relaxation in Wires and Channels: Boundary Spin Echo and Tachyons,"In this paper we use a spin kinetic equation to study spin polarization
dynamics in 1D wires and 2D channels. This approach is valid in both diffusive
and ballistic spin transport regimes and, therefore, more general than the
usual spin drift-diffusion equations. In particular, we demonstrate that in
infinite 1D wires with Rashba spin-orbit interaction the exponential spin
relaxation decay can be modulated by an oscillating function. In the case of
spin relaxation in finite length 1D wires, it is shown that an initially
homogeneous spin polarization spontaneously transforms into a persistent spin
helix. An interesting sound waves echo-like behavior of initially localized
spin polarization packet is found in finite length wires. We show that a
propagating spin polarization profile reflects from a system boundary and
returns back to its initial position similarly to the reflectance of sound
waves from an obstacle. Green's function of spin kinetic equation is found for
both finite and infinite 1D systems. Moreover, we demonstrate explicitly that
the spin relaxation in 2D channels with Rashba and Dresselhaus spin-orbit
interactions of equal strength occurs similarly to that in 1D wires of finite
length. Finally, a simple transformation mapping 1D spin kinetic equation into
the Klein-Gordon equation with an imaginary mass is found thus establishing an
interesting connection between semiconductor spintronics and relativistic
quantum mechanics.",1106.0355v1
2000-09-15,Gravitational waves from a spinning particle scattered by a relativistic star: Axial mode case,"We study gravitational waves from a spinning test particle scattered by a
relativistic star using a perturbation method. The present analysis is
restricted to axial modes. By calculating the energy spectrum, the waveforms
and the total energy and angular momentum of gravitational waves, we analyze
the dependence of the emitted gravitational waves on a particle spin. For a
normal neutron star, the energy spectrum has one broad peak whose
characteristic frequency corresponds to the angular velocity at the turning
point (a periastron). Since the turning point is determined by the orbital
parameter, there exists the dependence of the gravitational wave on a particle
spin. We find that the total energy of $l = 2$ gravitational waves gets larger
as the spin increases in the anti-parallel direction to the orbital angular
momentum. For an ultracompact star, in addition to such an orbital
contribution, we find the quasi-normal modes exited by a scattered particle,
whose excitation rate to gravitational waves depends on the particle spin. We
also discuss the ratio of the total angular momentum to the total energy of
gravitational waves and explain its spin dependence.",0009055v1
2014-11-12,Magnonic Holographic Memory: from Proposal to Device,"In this work, we present recent developments in magnonic holographic memory
devices exploiting spin waves for information transfer. The devices comprise a
magnetic matrix and spin wave generating/detecting elements placed on the edges
of the waveguides. The matrix consists of a grid of magnetic waveguides
connected via cross junctions. Magnetic memory elements are incorporated within
the junction while the read-in and read-out is accomplished by the spin waves
propagating through the waveguides. We present experimental data on spin wave
propagation through NiFe and YIG magnetic crosses. The obtained experimental
data show prominent spin wave signal modulation (up to 20 dB for NiFe and 35 dB
for YIG) by the external magnetic field, where both the strength and the
direction of the magnetic field define the transport between the cross arms. We
also present experimental data on the 2-bit magnonic holographic memory built
on the double cross YIG structure with micro-magnets placed on the top of each
cross. It appears possible to recognize the state of each magnet via the
interference pattern produced by the spin waves with all experiments done at
room temperature. Magnonic holographic devices aim to combine the advantages of
magnetic data storage with wave-based information transfer. We present
estimates on the spin wave holographic devices performance, including power
consumption and functional throughput. According to the estimates, magnonic
holographic devices may provide data processing rates higher than 10^18
bits/cm2/s while consuming 0.15uW. Technological challenges and fundamental
physical limits of this approach are also discussed.",1411.3388v1
2021-04-30,A numerical exploration of signal detector arrangement in a spin-wave reservoir computing device,"This paper studies numerically how the signal detector arrangement influences
the performance of reservoir computing using spin waves excited in a
ferrimagnetic garnet film. This investigation is essentially important since
the input information is not only conveyed but also transformed by the spin
waves into high-dimensional information space when the waves propagate in the
film in a spatially distributed manner. This spatiotemporal dynamics realizes a
rich reservoir-computational functionality. First, we simulate spin waves in a
rectangular garnet film with two input electrodes to obtain spatial
distributions of the reservoir states in response to input signals, which are
represented as spin vectors and used for a machine-learning waveform
classification task. The detected reservoir states are combined through readout
connection weights to generate a final output. We visualize the spatial
distribution of the weights after training to discuss the number and positions
of the output electrodes by arranging them at grid points, equiangularly
circular points or at random. We evaluate the classification accuracy by
changing the number of the output electrodes, and find that a high accuracy
($>$ 90\%) is achieved with only several tens of output electrodes regardless
of grid, circular or random arrangement. These results suggest that the spin
waves possess sufficiently complex and rich dynamics for this type of tasks.
Then we investigate in which area useful information is distributed more by
arranging the electrodes locally on the chip. Finally, we show that this device
has generalization ability for input wave-signal frequency in a certain
frequency range. These results will lead to practical design of spin-wave
reservoir devices for low-power intelligent computing in the near future.",2104.14915v1
2019-01-24,Fundamentals of magnon-based computing,"A disturbance in the local magnetic order of a solid body can propagate
across a material just like a wave. This wave is named spin wave, and its
quanta are known as magnons. Recently, physicists proposed the usage of magnons
to carry and process information instead of electrons as it is the case of
electronics. This technology opens access to a new generation of computers in
which data are processed without motion of any real particles like electrons.
This leads to a sizable decrease in the accompanying heating losses and,
consequently, to lower energy consumption, which is crucial due to the ever
increasing demand for computing devices. Moreover, unique properties of spin
waves allow for the utilisation of unconventional computing concepts, giving
the vision of a significantly faster and more powerful next-generation of
information processing systems.
  The current review addresses a selection of fundamental topics that form the
basis of the magnon-based computing and are of primary importance for the
further development of this concept. First, the transport of spin-wave-carried
information in one and two dimensions that is required for the realization of
logic elements and integrated magnon circuits is covered. Second, the
convertors between spin waves and electron (charge and spin) currents are
discussed. These convertors are necessary for the compatibility of magnonic
devices with modern CMOS technology. The paper starts with basics on spin waves
and the related methodology. In addition, the general ideas behind magnon-based
computing are presented. The review finishes with conclusions and an outlook on
the perspective use of spin waves.",1901.08934v1
2019-08-07,Reconfigurable sub-micron spin-wave majority gate with electrical transducers,"Spin waves are excitations in ferromagnetic media that have been proposed as
information carriers in hybrid spintronic devices with much lower operation
power than conventional charge-based electronics. Their wave nature can be
exploited in majority gates by using interference for computation. However, a
scalable spin-wave majority gate that can be co-integrated alongside
conventional electronics is still lacking. Here, we demonstrate a sub-micron
inline spin-wave majority gate with fan-out. Time-resolved imaging of the
magnetization dynamics by scanning transmission x-ray microscopy illustrates
the device operation. All-electrical spin-wave spectroscopy further
demonstrates majority gates with sub-micron dimensions, reconfigurable input
and output ports, and frequency-division multiplexing. Challenges for hybrid
spintronic computing systems based on spin-wave majority gates are discussed.",1908.02546v3
2019-09-10,"Twisting and tweezing the spin wave: on vortices, skyrmions, helical waves, and the magnonic spiral phase plate","Spin waves are the low-energy excitations of magnetically ordered materials.
They are key elements in the stability analysis of the ordered phase and have a
wealth of technological applications. Recently, we showed that spin waves of a
magnetic nanowire may carry a definite amount of orbital angular momentum
components along the propagation direction. This helical, in addition to the
chiral, character of the spin waves is related to the spatial modulations of
the spin wave phase across the wire. It, however, remains a challenge to
generate and control such modes with conventional magnetic fields. Here, we
make the first proposal for a \textit{magnetic} spiral phase plate by
appropriately synthesizing two magnetic materials that have different speeds of
spin waves. It is demonstrated with full-numerical micromagnetic simulations
that despite the complicated structure of demagnetization fields, a homogeneous
spin wave passing through the spiral phase plate attains the required twist and
propagates further with the desired orbital angular momentum. While excitations
from the ordered phase may have a twist, the magnetization itself can be
twisted due to internal fields and forms what is known as a magnetic vortex. We
point out the differences between both types of magnetic phenomena and discuss
their possible interaction.",1909.04457v2
2021-11-30,Comparison of spin-wave transmission in parallel and antiparallel magnetic configurations,"Parallel (P) and antiparallel (AP) configurations are widely applied in
magnetic heterostructures and have significant impacts on the spin-wave
transmission in magnonic devices. In the present study, a theoretical
investigation was conducted into the transmission of exchange-dominated spin
waves with nanoscale wavelengths in a type of heterostructure including two
magnetic media, of which the magnetization state can be set to the P (AP)
configuration by ferromagnetic (antiferromagnetic) interfacial exchange
coupling (IEC). The boundary conditions in P and AP cases were derived, by
which the transmission and reflection coefficients of spin waves were
analytically given and numerically calculated. In the P configuration, a
critical angle $\theta_{\textrm{c}}$ always exists and has a significant
influence on the transmission. Spin waves are refracted and reflected when the
incident angle $\theta_{\textrm{i}}$ is smaller than the critical angle
($\theta_{\textrm{i}} < \theta_{\textrm{c}}$), while total reflection occurs as
$\theta_{\textrm{i}} \geq \theta_{\textrm{c}}$. In the AP configuration, the
spin-wave polarizations of medium 1 and 2 are inverse, that is, right-handed
(RH) and left-handed (LH), leading to the total reflection being independent of
$\theta_{\textrm{i}}$. As demonstrated by the difference in spin-wave
transmission properties between the P ($\theta_{\textrm{i}} <
\theta_{\textrm{c}}$) and AP cases, there is a polarization-dependent
scattering. However, as $\theta_{\textrm{i}}$ exceeds $\theta_{\textrm{c}}$,
the P ($\theta_{\textrm{i}} > \theta_{\textrm{c}}$) case exhibits similarities
with the AP case, where the transmitted waves are found to be evanescent in
medium 2 and their decay lengths are investigated.",2111.15091v2
2016-07-04,The ubiquitous photonic wheel,"A circularly polarized electromagnetic plane wave carries an electric field
that rotates clockwise or counterclockwise around the propagation direction of
the wave. According to the handedness of this rotation, its \emph{longitudinal}
spin angular momentum density is either parallel or antiparallel to the
propagation of light. However, there are also light waves that are not simply
plane and carry an electric field that rotates around an axis perpendicular to
the propagation direction, thus yielding \emph{transverse} spin angular
momentum density. Electric field configurations of this kind have been
suggestively dubbed ""photonic wheels"". It has been recently shown that photonic
wheels are commonplace in optics as they occur in electromagnetic fields
confined by waveguides, in strongly focused beams, in plasmonic and evanescent
waves. In this work we establish a general theory of electromagnetic waves
{propagating along a well defined direction, which carry} transverse spin
angular momentum density. We show that depending on the shape of {these waves,
the} spin density may be either perpendicular to the \emph{mean} linear
momentum (globally transverse spin) or to the linear momentum \emph{density}
(locally transverse spin). We find that the latter case generically occurs only
for non-diffracting beams, such as the Bessel beams. Moreover, we introduce the
concept of \emph{meridional} Stokes parameters to operationally quantify the
transverse spin density. To illustrate our theory, we apply it to the exemplary
cases of Bessel beams and evanescent waves. These results open a new and
accessible route to the understanding, generation and manipulation of optical
beams with transverse spin angular momentum density.",1607.00792v1
2018-07-02,Emission and Propagation of Multi-Dimensional Spin Waves with nanoscale wavelengths in Anisotropic Spin Textures,"Spin waves offer intriguing novel perspectives for computing and signal
processing, since their damping can be lower than the Ohmic losses in
conventional CMOS circuits. For controlling the spatial extent and propagation
of spin waves on the actual chip, magnetic domain walls show considerable
potential as magnonic waveguides. However, low-loss guidance of spin waves with
nanoscale wavelengths, in particular around angled tracks, remains to be shown.
Here we experimentally demonstrate that such advanced control of propagating
spin waves can be obtained using natural features of magnetic order in an
interlayer exchange-coupled, anisotropic ferromagnetic bilayer. Using Scanning
Transmission X-Ray Microscopy, we image generation of spin waves and their
propagation across distances exceeding multiple times the wavelength, in
extended planar geometries as well as along one-dimensional domain walls, which
can be straight and curved. The observed range of wavelengths is between 1
{\mu}m and 150 nm, at corresponding excitation frequencies from 250 MHz to 3
GHz. Our results show routes towards practical implementation of magnonic
waveguides employing domain walls in future spin wave logic and computational
circuits.",1807.00897v2
2017-06-19,Pinned domain wall oscillator as tunable direct current spin wave emitter,"Spin waves are perturbations in the relative orientation of magnetic moments
in a continuous magnetic system, which have been proposed as a new kind of
information carrier for spin-based low power applications. For this purpose, a
major obstacle to overcome is the energy-efficient excitation of coherent short
wavelength spin waves and alternatives to excitation via the Oersted field of
an alternating current need to be explored. Here we show, by means of
micromagnetic simulations, how, in a perpendicularly magnetized thin strip, a
domain wall pinned at a geometrical constriction emits spin waves when forced
to rotate by the application of a low direct current flowing along the strip.
Spin waves propagate only in the direction of the electron's flow at the first
odd harmonic of the domain wall rotation frequency for which propagation is
allowed. Excitation is due to in-plane dipolar stray field of the rotating
domain wall and that the resulting unidirectionality is a consequence of the
domain wall displacement at the constriction. On the other hand, the
application of an external field opposing domain wall depinning breaks the
symmetry for spin wave propagation in the two domains, allowing emission in
both directions but at different frequencies. The results presented define a
new approach to produce tunable high frequency spin wave emitters of easy
fabrication and low power consumption.",1706.05873v1
2024-02-24,Steerable current-driven emission of spin waves in magnetic vortex pairs,"The efficient excitation of spin waves is a key challenge in the realization
of magnonic devices. We demonstrate the current-driven generation of spin waves
in antiferromagnetically coupled magnetic vortices. We employ time-resolved
scanning transmission X-ray microscopy (TR-STXM) to directly image the emission
of spin waves upon the application of an alternating current flowing directly
through the magnetic stack. Micromagnetic simulations allow us to identify the
origin of the excitation to be the current-driven Oersted field, which in the
present system proves to be orders of magnitude more efficient than the
commonly used excitation via stripline antennas. Our numerical studies also
reveal that the spin-transfer torque can lead to the emission of spin waves as
well, yet only at much higher current amplitudes. By using magnetostrictive
materials, we futhermore demonstrate that the direction of the magnon
propagation can be steered by increasing the excitation amplitude, which
modifies the underlying magnetization profile through an additional anisotropy
in the magnetic layers. The demonstrated methods allow for the efficient and
tunable excitation of spin waves, marking a significant advance in the
generation and control of spin waves in magnonic devices.",2402.15831v1
2023-03-14,Electromagnetic Waves Propagation along Tangentially Magnetised Bihyrotropic Layer (with Example of Spin Waves in Ferrite Plate),"Analytically, without magnetostatic approximation, the problem of
electromagnetic wave propagation along arbitrary direction in a tangentially
magnetized bihyrotropic layer has been solved. It is found that one can bring
the Maxwell equations for this problem to the fourth order differential
equation and the obtained biquadratic characteristic equation determines two
different wave numbers kx21 and kx22 describing the wave distribution over the
layer thickness. The dispersion equation describing wave propagation in the
bihyrotropic layer was obtained for the case of real kx21 and kx22 values. It
is shown that in a ferrite plate, which is a special case of a bihyrotropic
layer, three types of wave distribution over the plate thickness can take
place: surface-surface (when kx21 and kx22 are real numbers), volume-surface
(kx21 is imaginary and kx22 is real) and volume-volume distribution (kx21 and
kx22 are imaginary numbers). Characteristics of the surface spin wave in
ferrite plate are investigated. It is found that dependences of the wave
numbers kx21 and kx22 on the wave vector orientation are significantly
different from the similar magnetostatic dependence for a large part of the
wave spectrum.",2303.08800v1
2023-08-07,Water-Wave Vortices and Skyrmions,"Topological wave structures -- phase vortices, skyrmions, merons, etc. -- are
attracting enormous attention in a variety of quantum and classical wave
fields. Surprisingly, these structures have never been properly explored in the
most obvious example of classical waves: water-surface (gravity-capillary)
waves. Here we fill this gap and describe: (i) water-wave vortices of different
orders carrying quantized angular momentum with orbital and spin contributions,
(ii) skyrmion lattices formed by the instantaneous displacements of the
water-surface particles in wave interference, (iii) meron (half-skyrmion)
lattices formed by the spin density vectors, as well as (iv) spatiotemporal
water-wave vortices and skyrmions. We show that all these topological entities
can be readily generated in linear water-wave interference experiments. Our
findings can find applications in microfluidics and show that water waves can
be employed as an attainable playground for emulating universal topological
wave phenomena.",2308.03520v2
2019-03-09,Spin-wave thermodynamics of square-lattice antiferromagnets revisited,"Modifying the conventional spin-wave theory in a novel manner based on the
Wick decomposition, we present an elaborate thermodynamics of square-lattice
quantum antiferromagnets. Our scheme is no longer accompanied by the notorious
problem of an artificial transition to the paramagnetic state inherent in
modified spin waves in the Hartree-Fock approximation. In the cases of spin
$\frac{1}{2}$ and spin $1$, various modified-spin-wave findings for the
internal energy, specific heat, static uniform susceptibility, and dynamic
structure factor are not only numerically compared with quantum Monte Carlo
calculations and Lanczos exact diagonalizations but also analytically expanded
into low-temperature series. Modified spin waves interacting via the Wick
decomposition provide reliable thermodynamics over the whole temperature range
of absolute zero to infinity. Adding higher-order spin couplings such as ring
exchange interaction to the naivest Heisenberg Hamiltonian, we precisely
reproduce inelastic-neutron-scattering measurements of the
high-temperature-superconductor-parent antiferromagnet
$\mathrm{La}_2\mathrm{CuO}_4$. Modifying Dyson-Maleev bosons combined with
auxiliary pseudofermions also yields thermodynamics of square-lattice
antiferromagnets free from thermal breakdown, but it is less precise unless
temperature is sufficiently low. Applying all the schemes to layered
antiferromagnets as well, we discuss the advantages and disadvantages of
modified spin-wave and combined boson-pseudofermion representations.",1903.03769v1
2022-03-24,Writable spin wave nanochannels in an artificial-spin-ice-mediated ferromagnetic thin film,"Magnonics, which employs spin-waves to transmit and process information, is a
promising venue for low-power data processing. One of the major challenges is
the local control of the spin-wave propagation path. Here, we introduce the
concept of writable magnonics by taking advantage of the highly flexible
reconfigurability and rewritability of artificial spin ice systems. Using
micromagnetic simulations, we show that globally switchable spin-wave
propagation and the locally writable spin-wave nanochannels can be realized in
a ferromagnetic thin film underlying an artificial pinwheel spin ice. The
rewritable magnonics enabled by reconfigurable spin wave nanochannels provides
a unique setting to design programmable magnonic circuits and logic devices for
ultra-low power applications.",2203.12812v2
2018-09-05,Constraining black-hole spins with gravitational wave observations,"The observation of gravitational-wave signals from merging black-hole
binaries enables direct measurement of the properties of the black holes. An
individual observation allows measurement of the black-hole masses, but only
limited information about either the magnitude or orientation of the black hole
spins is available, primarily due to the degeneracy between measurements of
spin and binary mass ratio. Using the first six black-hole merger observations,
we are able to constrain the distribution of black-hole spins. We perform model
selection between a set of models with different spin population models
combined with a power-law mass distribution to make inferences about the spin
distribution. We assume a fixed power-law mass distribution on the black holes,
which is supported by the data and provides a realistic distribution of binary
mass-ratio. This allows us to accurately account for selection effects due to
variations in the signal amplitude with spin magnitude, and provides an
improved inference on the spin distribution. We conclude that the first six
LIGO and Virgo observations (Abbott et al. 2016a, 2017a,b,c) disfavour highly
spinning black holes against low spins by an odds-ratio of 15:1; thus providing
strong constraints on spin magnitudes from gravitational-wave observations.
Furthermore, we are able to rule out a population of binaries with completely
aligned spins, even when the spins of the individual black holes are low, at an
odds ratio of 22,000:1, significantly strengthening earlier evidence against
aligned spins (Farr et al. 2017). These results provide important information
that will aid in our understanding on the formation processes of black-holes.",1809.01401v2
2014-09-03,Theory of coupled spin-charge transport due to spin-orbit interaction in inhomogeneous two-dimensional electron liquids,"Spin-orbit interactions in two-dimensional electron liquids are responsible
for many interesting transport phenomena in which particle currents are
converted to spin polarizations and spin currents and viceversa. Prime examples
are the spin Hall effect, the Edelstein effect, and their inverses. By similar
mechanisms it is also possible to partially convert an optically induced
electron-hole density wave to a spin density wave and viceversa. In this paper
we present a unified theoretical treatment of these effects based on quantum
kinetic equations that include not only the intrinsic spin-orbit coupling from
the band structure of the host material, but also the spin-orbit coupling due
to an external electric field and a random impurity potential. The
drift-diffusion equations we derive in the diffusive regime are applicable to a
broad variety of experimental situations, both homogeneous and non-homogeneous,
and include on equal footing ""skew scattering"" and ""side-jump"" from
electron-impurity collisions. As a demonstration of the strength and usefulness
of the theory we apply it to the study of several effects of current
experimental interest: the inverse Edelstein effect, the spin-current swapping
effect, and the partial conversion of an electron-hole density wave to a spin
density wave in a two-dimensional electron gas with Rashba and Dresselhaus
spin-orbit couplings, subject to an electric field.",1409.1202v1
2017-11-30,Oblique propagation of longitudinal spin-electron acoustic waves under the influence of the Coulomb exchange interaction and the quantum Bohm potential,"Influence of the exchange interaction on the properties of the spin-electron
acoustic waves at the oblique propagation of waves relatively to the external
magnetic field in the magnetically ordered metals is studied. The spectra of
the Langmuir wave and the Trivelpiece-Gould wave are also considered. It is
well-known that there are two branches of spectrum of the spin-electron
acoustic waves in this regime. Change their properties under influence of the
exchange interaction is studied. The quantum Bohm potential is included either.
The exchange interaction and quantum Bohm potential gives opposite
contributions, but they do not compensate each other since they have different
dependence on the wave vector. This competition creates a non-monotonical
behavior of the Trivelpiece-Gould wave spectrum. The concavity changes in the
monotonic spectra of the Langmuir wave and the SEAWs are found.",1711.11308v1
2003-11-10,Long-Lived Spin Coherence States,"We study evolution of electron spin coherence having non-homogeneous
direction of spin polarization vector in semiconductor heterostructures. It is
found that the electron spin relaxation time due to the D'yakonov-Perel'
relaxation mechanism essentially depends on the initial spin polarization
distribution. This effect has its origin in the coherent spin precession of
electrons diffusing in the same direction. We predict a long spin relaxation
time of a novel structure: a spin coherence standing wave and discuss its
experimental realization.",0311223v1
2004-10-20,Spin-Transfer Torque and Electron-Magnon Scattering,"According to the spin-torque model, current-driven magnetic dynamics in
ferromagnetic multilayers is determined by the transfer of electron spin
perpendicular to the layers' magnetizations. By separating the largest
contributions to the magnetic dynamics, we demonstrate that the dominant effect
of spin-torque is rather due to the electron spin parallel to the field. We
show that this effect can be equivalently described as stimulated
current-driven excitation of spin-waves, and discuss four specifically
quantum-mechanical aspects of spin-transfer, not described by the spin-torque.",0410520v1
2007-01-09,Spin Supercurrent,"We review the main properties of Spin Waves condensation to a coherent
quantum state, named Homogeneously Precessing Domain (HPD). We describe the
long range coherent transport of magnetization by Spin Supercurrent in
antiferromagnetic superfluid 3He. This quantum phenomenon was discovered 20
years ago. Since then, many magnetic extensions of superconductivity and
superfluidity have been observed: spin Josephson phenomena, spin current
vortices, spin phase slippage, long distance magnetization transport by spin
supercurrents, etc. Several new supercurrent phenomena have been discovered,
like magnetically excited coherent quantum states, NMR in the molecular Landau
field, spin-current turbulence, formation of stable non-topological solitons
etc.",0701182v1
2007-09-13,Spin polarization in biased Rashba-Dresselhaus two-dimensional electron systems,"Based on spin-charge coupled drift-diffusion equations, which are derived
from kinetic equations for the spin-density matrix in a rigorous manner, the
electric-field-induced nonequilibrium spin polarization is treated for a
two-dimensional electron gas with both Rashba and Dresselhaus spin-orbit
coupling. Most emphasis is put on the consideration of the field-mediated spin
dynamics for a model with equal Rashba and Dresselhaus coupling constants, in
which the spin relaxation is strongly suppressed. Weakly damped
electric-field-induced spin excitations are identified, which remind of
space-charge waves in crystals.",0709.2054v1
2008-08-01,Electric-field driven long-lived spin excitations on a cylindrical surface with spin-orbit interaction,"Based on quantum-kinetic equations, coupled spin-charge drift-diffusion
equations are derived for a two-dimensional electron gas on a cylindrical
surface. Besides the Rashba and Dresselhaus spin-orbit interaction, the elastic
scattering on impurities, and a constant electric field are taken into account.
  From the solution of the drift-diffusion equations, a long-lived spin
excitation is identified for spins coupled to the Rashba term on a cylinder
with a given radius. The electric-field driven weakly damped spin waves are
manifest in the components of the magnetization and have the potential for
non-ballistic spin-device applications.",0808.0069v1
2013-05-09,Spin Conductivity in Two-Dimensional Non-Collinear Antiferromagnets,"We propose a method to derive the spin current operator for non-collinear
Heisenberg antiferromagnets. We show that the spin conductivity calculated by
the spectral representation with the spin current satisfies the f-sum rule. We
also study the spin conductivity at T=0 within spin wave theory. We show how
the spin conductivity depends on the external magnetic field with changing
magnon spectrum. We also find that the spin Drude weight vanishes for any
external magnetic field at T=0.",1305.2072v3
2015-04-30,Spin electron acoustic soliton: Separate spin evolution of electrons with exchange interaction,"Separate spin evolution quantum hydrodynamics is generalized to include the
Coulomb exchange interaction. The Coulomb exchange interaction is considered as
the interaction between the spin-down electrons being in the quantum states
occupied by one electron, giving main contribution in the equilibrium. The
generalized model is applied to study the non-linear spin-electron acoustic
waves. Existence of the spin-electron acoustic soliton is demonstrated.
Contributions of the concentration, spin polarization, and exchange interaction
in the properties of the spin electron acoustic soliton are studied.",1504.08234v2
2000-09-27,Data Analysis of Continuous Gravitational Wave Signal: Fourier Transform,"We present the Fourier Transform of continuous gravitational wave for
arbitrary location of detector and source and for any duration of observation
time in which both rotational motion of earth about its spin axis and orbital
motion around sun has been taken into account. We also give the method to
account the spin down of continuous gravitational wave.",0009094v1
2002-09-26,Precession of a particle with anomalous magnetic moment in electromagnetic and gravitational pp-wave fields,"We present an exact solution of the Bargmann-Michel-Telegdi (BMT) equations
for the dynamics of a spin particle in external electromagnetic and
gravitational pp-wave fields. We demonstrate that an anomalous magnetic moment
gives rise to an additional spin rotation which is modulated both by the
electromagnetic and by the gravitational wave periodicities.",0209099v1
2003-01-30,Nuclear Wave Functions for Spin and Pseudospin Partners,"Using relations between wave functions obtained in the framework of the
relativistic mean field theory, we investigate the effects of pseudospin and
spin symmetry breaking on the single nucleon wave functions in spherical
nuclei. In our analysis, we apply both relativistic and non-relativistic
self-consistent models as well as the harmonic oscillator model.",0301098v1
1996-03-18,Renormalization-Group Approach to Spin-Wave Theory of Quantum Heisenberg Ferromagnet,"The renormalization-group method is used to analyze the low-temperature
behaviour of a two-dimentional, spin-$s$ quantum Heisenberg ferromagnet. A set
of recursion equations is derived in an one-loop approximation. The
low-temperature asymptotics of the correlation length and the uniform
susceptibility are obtained. For small spins ($s= 1/2,1$) the results are
essentially different from those in the spin-wave theory.",9603123v1
2004-04-22,On the theory of polarized Fermi liquid,"The transport equation for transverse vibrations of magnetization in spin
polarized Fermi liquid is derived from integral equation for the vertex
function. The dispersion law for the transverse spin waves is established. The
existance of zero-temperature spin-waves attenuation is confirmed. The problem
of similar derivation in ferromagnetic ""Fermi liquid"" is discussed.",0404539v1
1997-10-02,Pseudo-spin Symmetry and Relativistic Single-nucleon Wave Functions,"We show that the occurrence of approximate pseudo-spin symmetry in nuclei is
connected with certain similarities in the relativistic single-nucleon wave
functions of the corresponding pseudo-spin doublets. We perform a case study in
which several examples and the systematics of this connection are explored.",9710011v1
1998-02-17,Electromagnetic Waves in the Vacuum with Torsion and Spin,"Exact radiative wave solutions to the classical homogeneous Maxwell equations
in the vacuum have been found that are not transverse, exhibit both torsion and
spin, and for which the second Poincare invariant, E.B, is not zero. Two four
component rank 3 tensors of spin current and torsion are constructed on
topological grounds. The divergence of each pseudo vector generates the
Poincare invariants of the electromagnetic system.",9802033v1
2009-07-09,Nuclear spin-density wave theory,"Recently [arXiv:0906.5417], we reported a quantum phase transition of 103mRh
excited by bremsstrahlung pumping. The long-lived Moessbauer excitation is
delocalized as a neutral quasiparticle carrying a spin current. This letter
gives a general theory for a nuclear spin-density wave propagating on crystals
consisting of identical nuclei with a multipolar transition.",0907.1446v2
2003-01-23,The spin of the mesons and baryons,"It is shown that the spin of pi (0), eta, Lambda, Sigma (+,-,0), Xi (-,0),
Lambda-c (+), Sigma-c (0), Xi-c (0), and Omega-c (0) mesons and baryons can be
explained by the sum of the angular momentum vectors and spin vectors of the
electromagnetic waves which are in these particles according to the standing
wave model. The spin of the pi (+,-), K (+,-,0), D (+,-,0), and D-S (+,-)
mesons and of the neutron is the sum of the angular momentum vectors of the
oscillations and of the spin vectors of the neutrinos and the electric charges
which are in the cubic lattice of these particles. Spin 1/2 is the consequence
of the superposition of two perpendicular standing waves of equal frequencies
and amplitudes shifted in phase by pi/2. The spin of the antiparticles of the
mesons and baryons is the same as the spin of the ordinary particles.",0301060v3
2004-09-18,Spin wave based quantum storage of electronic spin with a ring array of nuclear spins,"We propose a solid state based protocol to implement the universal quantum
storage for electronic spin qubit. The quantum memory in this scheme is the
spin wave excitation in the ring array of nuclei in a quantum dot. We show that
the quantum information carried by an arbitrary state of the electronic spin
can be coherently mapped onto the spin wave excitations or the magnon states.
With an appropriate external control, the stored quantum state in quantum
memory can be read out reversibly. We also explore in detail the quantum
decoherence mechanism due to the inhomogeneous couplings between the electronic
spin and the nuclear spins.",0409120v3
2011-10-13,Competing Hyperfine and Spin-Orbit Couplings: Spin Relaxation in a Quantum Hall Ferromagnet,"Spin relaxation in a quantum Hall ferromagnet, where filling is $\nu=1, 1/3,
1/5,...$, can be considered in terms of spin wave annihilation/creation
processes. Hyperfine coupling with the nuclei of the GaAs matrix provides spin
non-conservation in the two-dimensional electron gas and determines spin
relaxation in the quantum Hall system. This mechanism competes with spin-orbit
coupling channels of spin-wave decay and can even dominate in a low-temperature
regime where $T$ is much smaller than the Zeeman gap. In this case the
spin-wave relaxation process occurs non-exponentially with time and does not
depend on the temperature. The competition of different relaxation channels
results in crossovers in the dominant mechanism, leading to non-monotonic
behavior of the characteristic relaxation time with the magnetic field. We
predict that the relaxation times should reach maxima at $B\simeq 18\,$T in the
$\nu=1$ Quantum Hall system and at $B\simeq 12\,$T for that of $\nu=1/3\,$. We
estimate these times as $\sim10\,-\,30\,\mu$s and $\sim2\,-\,5\,\mu$s,
respectively.",1110.3006v1
2011-11-21,Wave-diffusion theory of spin transport in metals after ultrashort-pulse excitation,"Spin and charge-current dynamics after ultrafast spin-polarized excitation in
a normal metal are studied theoretically using a wave-diffusion theory. It is
shown analytically how this macroscopic approach correctly describes the
ballistic and diffusive properties of spin and charge transport, but also
applies to the intermediate regime between these two limits. Using the
wave-diffusion equations we numerically analyze spin and charge dynamics after
ultrafast excitation of spin polarized carriers in thin gold films. Assuming
slightly spin-dependent momentum relaxation times, we find that a unified
treatment of diffusive and ballistic transport yields robust signatures in the
spin and charge dynamics, which are in qualitative agreement with recent
experimental results [Phys. Rev. Lett 107, 076601 (2011)]. The influence of
boundary effects on the temporal signatures of spin transport is also studied.",1111.4780v1
2016-06-05,Spin current contribution in the spectrum of collective excitations of degenerate partially polarized spin-1/2 fermions at separate dynamics of spin-up and spin-down fermions,"The spectrum of collective excitations of degenerate partially polarized
spin-1/2 fermions is considered. The spin-up fermions and the spin-down
fermions are considered as different fluids. Corresponding two-fluid
hydrodynamics consistent with a non-linear Pauli equation is suggested. An
equation of state for the spin current caused by the distribution of particles
on different energy levels is suggested for the degenerate regime, where the
spin current is caused by the Pauli blocking. Spectrum of three waves is found
as a solution of the hydrodynamic equations: two sound waves and one spin wave.
Their spectrums are calculated for two regimes: propagation parallel and
perpendicular to the direction of the equilibrium spin polarization.",1606.01562v2
2019-11-13,Tailoring spin wave channels in a reconfigurable artificial spin ice,"Artificial spin ices are ensembles of geometrically-arranged, interacting
nanomagnets which have shown promising potential for the realization of
reconfigurable magnonic crystals. Such systems allow for the manipulation of
spin waves on the nanoscale and their potential use as information carriers.
However, there are presently two general obstacles to the realization of
artificial spin ice-based magnonic crystals: the magnetic state of artificial
spin ices is difficult to reconfigure and the magnetostatic interactions
between the nanoislands are often weak, preventing mode coupling. We
demonstrate, using micromagnetic modeling, that coupling a reconfigurable
artificial spin ice geometry made of weakly interacting nanomagnets to a soft
magnetic underlayer creates a complex system exhibiting dynamically coupled
modes. These give rise to spin wave channels in the underlayer at well-defined
frequencies, based on the artificial spin ice magnetic state, which can be
reconfigured. These findings open the door to the realization of reconfigurable
magnonic crystals with potential applications for data transport and processing
in magnonic-based logic architectures.",1911.05354v4
2020-02-13,Dynamical spin susceptibility of spin-valley half-metal,"A few years ago we predicted theoretically that in systems with nesting of
the Fermi surface the spin-valley half-metal has lower energy than the spin
density wave state. In this paper we suggest a possible way to distinguish
these phases experimentally. We calculate dynamical spin susceptibility tensor
for both states in the framework of the Kubo formalism. Discussed phases have
different numbers of the bands: four bands in the spin-valley half-metal and
only two bands in the spin density wave. Therefore, their susceptibilities, as
functions of frequency, have different number of peaks. Besides, the
spin-valley half-metal does not have rotational symmetry, thus, in general the
off-diagonal components of susceptibility tensor are non-zero. The spin density
wave obeys robust rotational symmetry and off-diagonal components of the
susceptibility tensor are zero. These characteristic features can be observed
in experiments with inelastic neutron scattering.",2002.05504v1
2021-03-14,Gapless spin liquid and pair density wave of the Hubbard model on three-leg triangular cylinders,"We study the ground state properties of the Hubbard model on three-leg
triangular cylinders using large-scale density-matrix renormalization group
simulations. At half-filling, we identify an intermediate gapless spin liquid
phase between a metallic phase at weak coupling and Mott insulating dimer phase
at strong interaction, which has one gapless spin mode and algebraic spin-spin
correlations but exponential decay scalar chiral-chiral correlations. Upon
light doping the gapless spin liquid, the system exhibits power-law
charge-density-wave (CDW) correlations but short-range single-particle,
spin-spin, and chiral-chiral correlations. Similar to CDW correlations, the
superconducting correlations are also quasi-long-ranged but oscillate in sign
as a function of distance, which is consistent with the striped pair-density
wave. When further doping the gapless spin liquid phase or doping the dimer
order phase, another phase takes over, which has similar CDW correlations but
all other correlations decay exponentially.",2103.07998v1
2012-07-26,Detecting binary neutron star systems with spin in advanced gravitational-wave detectors,"The detection of gravitational waves from binary neutron stars is a major
goal of the gravitational-wave observatories Advanced LIGO and Advanced Virgo.
Previous searches for binary neutron stars with LIGO and Virgo neglected the
component stars' angular momentum (spin). We demonstrate that neglecting spin
in matched-filter searches causes advanced detectors to lose more than 3% of
the possible signal-to-noise ratio for 59% (6%) of sources, assuming that
neutron star dimensionless spins, $c\mathbf{J}/GM^2$, are uniformly distributed
with magnitudes between 0 and 0.4 (0.05) and that the neutron stars have
isotropically distributed spin orientations. We present a new method for
constructing template banks for gravitational wave searches for systems with
spin. We present a new metric in a parameter space in which the template
placement metric is globally flat. This new method can create template banks of
signals with non-zero spins that are (anti-)aligned with the orbital angular
momentum. We show that this search loses more than 3% of the maximium
signal-to-noise for only 9% (0.2%) of BNS sources with dimensionless spins
between 0 and 0.4 (0.05) and isotropic spin orientations. Use of this template
bank will prevent selection bias in gravitational-wave searches and allow a
more accurate exploration of the distribution of spins in binary neutron stars.",1207.6406v2
2005-11-02,"Effects of strain, electric, and magnetic fields on lateral electron spin transport in semiconductor epilayers","We construct a spin-drift-diffusion model to describe spin-polarized electron
transport in zincblende semiconductors in the presence of magnetic fields,
electric fields, and off-diagonal strain. We present predictions of the model
for geometries that correspond to optical spin injection from the absorption of
circularly polarized light, and for geometries that correspond to electrical
spin injection from ferromagnetic contacts. Starting with the Keldysh Green's
function description for a system driven out of equilibrium, we construct a
semiclassical kinetic theory of electron spin transport in strained
semiconductors in the presence of electric and magnetic fields. From this
kinetic theory we derive spin-drift-diffusion equations for the components of
the spin density matrix for the specific case of spatially uniform fields and
uniform electron density. We solve the spin-drift-diffusion equations
numerically and compare the resulting images with scanning Kerr microscopy data
of spin-polarized conduction electrons flowing laterally in bulk epilayers of
n-type GaAs. The spin-drift-diffusion model accurately describes the
experimental observations. We contrast the properties of electron spin
precession resulting from magnetic and strain fields. Spin-strain coupling
depends linearly on electron wave vector and spin-magnetic field coupling is
independent of electron wave vector. As a result, spatial coherence of
precessing spin flows is better maintained with strain than with magnetic
fields, and the spatial period of spin precession is independent of the applied
electrical bias in strained structures whereas it is strongly bias dependent
for the case of applied magnetic fields.",0511038v1
2011-07-06,Addressing the spin question in gravitational-wave searches: Waveform templates for inspiralling compact binaries with nonprecessing spins,"This paper presents a post-Newtonian (PN) template family of gravitational
waveforms from inspiralling compact binaries with non-precessing spins, where
the spin effects are described by a single ""reduced-spin"" parameter. This
template family, which reparametrizes all the spin-dependent PN terms in terms
of the leading-order (1.5PN) spin-orbit coupling term \emph{in an approximate
way}, has very high overlaps (fitting factor > 0.99) with non-precessing
binaries with arbitrary mass ratios and spins. We also show that this template
family is ""effectual"" for the detection of a significant fraction of generic
spinning binaries in the comparable-mass regime (m_2/m_1 <~ 10), providing an
attractive and feasible way of searching for gravitational waves (GWs) from
spinning low-mass binaries. We also show that the secular (non-oscillatory)
spin-dependent effects in the phase evolution (which are taken into account by
the non-precessing templates) are more important than the oscillatory effects
of precession in the comparable-mass (m_1 ~= m_2) regime. Hence the
effectualness of non-spinning templates is particularly poor in this case, as
compared to non-precessing-spin templates. For the case of binary neutron stars
observable by Advanced LIGO, even moderate spins (L . S/m^2 ~= 0.015 - 0.1)
will cause considerable mismatches (~ 3% - 25%) with non-spinning templates.
This is contrary to the expectation that neutron-star spins may not be relevant
for GW detection.",1107.1267v2
2018-11-06,Spin of LIGO/VIRGO merging black holes as the result of binary evolution,"Recently discovered bursts of gravitational waves provide a good opportunity
to verify the current view on the evolution of close binary stars. Modern
population synthesis computer programs help to study this evolution from two
main sequence stars up to the formation of compact remnants. To calculate the
evolution of predecessors of black hole (BH) mergers we used the `Scenario
Machine' code. The scenario modelling allowed to describe the evolution of
systems for which the final stage is a BH+BH merger and showed the plausibility
of modern evolutionary scenarios for binary stars and population synthesis
models based on it. We discuss possible values of spins in BH mergers, and give
arguments in favour of different values of spins of BH components in BH mergers
(low spin + low spin, low spin + high spin, high spin + high spin). We predict
that $\geq 50\%$ BH mergers originated through isolated binary evolution should
possess spins of both BHs close to zero (low spin + low spin). Up to
$\approx$10\% of BH mergers are able to consist of two BHs with spins close to
one (high spin + high spin), predecessors of such binaries could be sources of
two gamma ray bursts. The BH with the spin close to one could be formed as the
result of the merger of two BHs formed via the collapse of a fast rotating star
accompanied with a long gamma ray burst and/or a gravitational wave burst with
smaller power in comparison with the merger of two BH remnants of binary
components.",1811.02294v1
2012-11-05,"Class of variational ansaetze for the ""spin-incoherent"" ground-state of a Luttinger liquid coupled to a spin bath","Interacting one-dimensional electron systems are generally referred to as
""Luttinger liquids"", after the effective low-energy theory in which spin and
charge behave as separate degrees of freedom with independent energy scales.
The ""spin-incoherent Luttinger liquid"" describes a finite-temperature regime
that is realized when the temperature is very small relative to the Fermi
energy, but larger than the characteristic spin energy scale. Similar physics
can take place in the ground-state, when a Luttinger Liquid is coupled to a
spin bath, which effectively introduces a ""spin temperature"" through its
entanglement with the spin degree of freedom. We show that the spin-incoherent
state can be written as a factorized wave-function, with a spin wave-function
that can be described within a valence bond formalism. This enables us to
calculate exact expressions for the momentum distribution function and the
entanglement entropy. This picture holds not only for two antiferromagnetically
coupled t-J chains, but also for the t-J-Kondo chain with strongly interacting
conduction electrons. We argue that this theory is quite universal and may
describe a family of problems that could be dubbed ""spin-incoherent"".",1211.0982v1
2017-09-20,Spin-rotation mode in a quantum Hall ferromagnet,"A spin-rotation mode emerging in a quantum Hall ferromagnet due to laser
pulse excitation is studied. This state, macroscopically representing a
rotation of the entire electron spin-system to a certain angle, is not
microscopically equivalent to a coherent turn of all spins as a single-whole
and is presented in the form of a combination of eigen quantum states
corresponding to all possible S_z spin numbers. The motion of the macroscopic
quantum state is studied microscopically by solving a non-stationary
Schroedinger equation and by means of a kinetic approach where damping of the
spin-rotation mode is related to an elementary process, namely, transformation
of a `Goldstone spin exciton' to a `spin-wave exciton'. The system exhibits a
spin stochastizationa mechanism (determined by spatial fluctuations of the
Land'e g-factor) ensuring damping, transverse spin relaxation, but irrelevant
to decay of spin-wave excitons and thus not involving longitudinal relaxation,
i.e., recovery of the S_z number to its equilibrium value.",1709.06811v2
2013-10-10,Spin entanglement and nonlocality of multifermion systems,"Spin density matrices of the system, containing arbitrary even number N of
indistinguishable fermions with spin S = 1/2, described by antisymmetric wave
function, have been calculated. The indistinguishability and the Pauli
principles are proved to determine uniquely spin states, spin correlations and
entanglement of fermion spin states. Increase of the particle number in the
multifermion system reduces the spin correlation in any pair of fermions. The
fully entangled system of N electrons are shown to be composed by pairs with
nonentangled spin states that is the incoherent superposition of the singlet
and triplet states. Any large system of N fermions, such as electrons with spin
S = 1/2, the spin state of any particle are shown to be entangled with the
other part of the system containing N-1 particle. However, the spin state of
this electron is not entangled with any other particle, and spin state of any
electron pair is not entangled. These properties of spin states manifest in the
Einstein-Podolsky-Rosen as confirmation or violation of the Bell inequalities
indicating the presence of non-local quantum spin correlations.",1310.2863v3
2018-01-29,Isoscalar and Isovector spin response in $sd-$ shell nuclei,"The spin magnetic dipole transitions and the neutron-proton spin-spin
correlations in $sd-$shell even-even nuclei with $N=Z$ are investigated using
shell model wave functions taking into accout enhanced isoscalar (IS)
spin-triplet pairing as well as the effective spin operators. It was shown that
the IS pairing and the effective spin operators gives a large quenching effect
on the IV spin transitions to be consistent with observed data by $(p,p')$
experiments. On the other hand, the observed IS spin strength show much smaller
quenching effect than expected by the calculated results. The IS pairing gives
a substantial quenching effect on the spin magnetic dipole transitions,
especially on the isovector (IV) ones. Consequently, an enhanced isoscalar
spin-triplet pairing interaction enlarges the proton-neutron spin-spin
correlation deduced from the difference between the isoscalar (IS) and the IV
sum rule strengths. The beta-decay rates and the IS magnetic moments of
$sd-$shell are also examined in terms of the IS pairing as well as the
effective spin operators.",1801.10039v1
2018-11-23,Self-stabilizing exchange-mediated spin transport,"Long-range spin transport in magnetic systems can be achieved by means of
exchange-mediated spin textures with robust topological winding -- a phenomenon
referred to as spin superfluidity. Its experimental signatures have been
discussed in antiferromagnets which are nearly free of dipolar interaction.
However, in ferromagnets, which possess non-negligible dipole fields,
realization of such spin transport has remained a challenge. Using
micromagnetic simulations, we investigate coherent exchange-mediated spin
transport in extended thin ferromagnetic films. We uncover a two-fluid state,
in which the long-range spin transport by spin textures co-exists with spin
waves, as well as a soliton-screened spin transport regime at high spin
injection biases. Both states are associated with distinct spin texture
reconstructions near the spin injection region and sustain spin transport over
large distances.",1811.09369v2
2000-06-20,Microscopic Theory of Dipole-Exchange Spin Waves in Ferromagnetic Films: Linear and Nonlinear Processes,"The linear and nonlinear processes in ferromagnetic films at low temperatures
T<< Tc are studied in a microscopic theory. Both the long-range magnetic
dipole-dipole and the Heisenberg exchange interactions to nearest and
next-nearest neighbors are included. The results obtained for the linearized
spin-wave spectrum are compared with previous macroscopic theories. For
ultrathin films (or for large wave vectors) the microscopic theory provides
important corrections. The nonlinear dynamics of the spin waves are studied
through a finite-temperature perturbation theory based on Feynman diagrams. We
obtain explicit results for the energy shift and damping (or reciprocal
lifetime) of the dipole-exchange spin waves due to all possible three-magnon
and four-magnon processes involving combinations of the surface and quantized
bulk spin waves at low temperatures. To investigate different dipole
interaction strengths (relative to the exchange) numerical results are
presented using parameters for Fe, EuO, and GdCl3.",0006308v1
2000-06-29,"Coexistence of charge density waves, bond order waves and spin density waves in quasi-one dimensional charge transfer salts","Charge, spin, as well as lattice instabilities are investigated in isolated
or weakly coupled chains of correlated electrons at quarter-filling. Our
analysis is based on extended Hubbard models including nearest neighbor
repulsion and Peierls coupling to lattice degrees of freedom. While treating
the electronic quantum fluctuations exactly, the lattice structure is optimized
self-consistently. We show that, generically, isolated chains undergo
instabilities towards coexisting charge density waves (CDW) and bond order
waves (BOW) insulating spin-gapped phases. The spin and charge gaps of the
BOW-CDW phase are computed. In the presence of an interchain magnetic coupling
spin density waves phases including a CDW or a BOW component are also found.
Our results are discussed in the context of insulating charge transfer salts.",0006460v2
2006-06-09,Spin wave dynamics and the determination of intrinsic Gilbert damping in locally-excited Permalloy thin films,"Time-resolved scanning Kerr effect microscopy has been used to study
magnetization dynamics in Permalloy thin films excited by transient magnetic
pulses generated by a micrometer-scale transmission line structure. The results
are consistent with magnetostatic spin wave theory and are supported by
micromagnetic simulations. Magnetostatic volume and surface spin waves are
measured for the same specimen using different bias field orientations and can
be accurately calculated by k-space integrations over all excited plane wave
components. A single damping constant of Gilbert form is sufficient to describe
both scenarios. The nonuniform pulsed field plays a key role in the spin wave
dynamics, with its Fourier transform serving as a weighting function for the
participating modes. The intrinsic Gilbert damping parameter $\alpha$ is most
conveniently measured when the spin waves are effectively stationary.",0606235v3
2007-01-08,Effect of spatial confinement on spin-wave spectrum: Low temperature deviation from Bloch T3/2 law in Co nanoparticles,"We present the study on Bloch T3/2 law and its applicability in ferromagnetic
cobalt nanoparticles with sizes 25 and 38 nm. Bloch has derived the T3/2 law by
assuming long wave-length spin-waves to be excited at low temperatures. But, in
nanoparticles the wavelength of the spin wave is confined by the size of the
magnetic particle leading to the gap in the spin-wave energy spectrum. The
experimental observation leads to the conclusion that Bloch law is valid at
temperatures higher than the spin-wave energy gap. However, it is not
applicable at low enough temperatures, where the energy gap becomes prominent.
We have demonstrated that a theory recently developed by us [Mandal et al.,
Europhys. Lett. 75, 618 (2006)] explains the variation of magnetization with
temperature accurately. In addition, the hysteresis properties of these cobalt
nanoparticles are also presented here.",0701152v1
2008-08-10,Formation of guided spin-wave bullets in ferrimagnetic film stripes,"The formation of quasi-2D nonlinear spin-wave eigenmodes in longitudinally
magnetized stripes of a ferrimagnetic film, so-called guided spin-wave bullets,
was experimentally observed by using time- and space-resolved Brillouin light
scattering spectroscopy and confirmed by numerical simulation. They represent
stable spin-wave packets propagating along a waveguide structure, for which
both transversal instability and interaction with the side edges of the
waveguide are important. The experiments and the numerical simulation of the
evolution of the spin-wave excitations show that the shape of the formed
packets and their behavior are strongly influenced by the confinement
conditions. The discovery of these modes demonstrates the existence of
quasi-stable nonlinear solutions in the transition regime between
one-dimensional and two-dimensional wave packet propagation.",0808.1399v1
2009-03-21,Scattering of surface and volume spin waves in a magnonic crystal,"The operational characteristics of a magnonic crystal, which was fabricated
as an array of shallow grooves etched on a surface of a magnetic film, were
compared for magnetostatic surface spin waves and backward volume magnetostatic
spin waves. In both cases the formation of rejection frequency bands was
studied as a function of the grooves depth. It has been found that the
rejection of the volume wave is considerably larger than of the surface one.
The influences of the nonreciprocity of the surface spin waves as well as of
the scattering of the lowest volume spin-wave mode into higher thickness volume
modes on the rejection efficiency are discussed.",0903.3686v1
2014-07-25,Transverse spin and momentum in two-wave interference,"We analyze the interference field formed by two electromagnetic plane waves
(with the same frequency but different wave vectors), and find that such field
reveals a rich and highly non-trivial structure of the local momentum and spin
densities. Despite the seemingly-planar and extensively-studied character of
the two-wave system, we find that it possesses a transverse (out-of-plane)
helicity-independent spin density, and also a transverse polarization-dependent
momentum density with unusual physical properties. The polarization-dependent
transverse momentum represents the so-called Belinfante spin momentum, which
does not exert the usual optical pressure and it is considered as `virtual' in
field theory. We perform analytical estimations and exact numerical simulations
of the interaction of the two-wave field with probe Mie particles. The results
of these calculations clearly indicate the straightforward detectability of the
unusual spin and momentum properties in the two-wave field and strongly
motivate their future experimental verifications.",1407.6786v2
2015-03-06,Standing spin wave mode in RFIM at T=0: Patterns and nonequilibrium phases,"The dynamical responses of random field Ising model at zero temperature,
driven by standing magnetic field wave, is studied by Monte Carlo simulation in
two dimensions. The three different kinds of distribution of quenched random
field are used here, uniform, bimodal and Gaussian. In all cases, three
distinct dynamical phases were observed, namely, the pinned, structured and
random. In the pinned phase no spin flip is observed. In the structured phase
standing spin wave modes are observed. The random phase is shown no regular
pattern. For a fixed value of the amplitude of the standing magnetic field
wave, in the region of small quenched field, the system remains in a pinned
phase. In the intermediate range of values of random field, a standing spin
wave mode (structured phase) is observed. The regular pattern of this spin wave
mode disappears for higher values of random field yielding a random phase. The
comprehensive phase baundaries are drawn in all three cases. The boundary of
pinned phase are analytically calculated for uniform and bimodal types of
quenched random fields.",1503.01861v2
2019-11-12,Parametric generation of propagating spin-waves in ultra thin yttrium iron garnet waveguides,"We present the experimental demonstration of the parallel parametric
generation of spin-waves in a microscaled yttrium iron garnet waveguide with
nanoscale thickness. Using Brillouin light scattering microscopy, we observe
the excitation of the first and second waveguide modes generated by a stripline
microwave pumping source. Micromagnetic simulations reveal the wave vector of
the parametrically generated spin-waves. Based on analytical calculations,
which are in excellent agreement with our experiments and simulations, we prove
that the spin-wave radiation losses are the determinative term of the
parametric instability threshold in this miniaturized system. The used method
enables the direct excitation and amplification of nanometer spin-waves
dominated by exchange interactions. Our results pave the way for integrated
magnonics based on insulating nano-magnets.",1911.04926v2
2021-11-03,Efficient geometrical control of spin waves in microscopic YIG waveguides,"We study experimentally and by micromagnetic simulations the propagation of
spin waves in 100-nm thick YIG waveguides, where the width linearly decreases
from 2 to 0.5 micrometers over a transition region with varying length between
2.5 and 10 micrometers. We show that this geometry results in a down-conversion
of the wavelength, enabling efficient generation of waves with wavelengths down
to 350 nm. We also find that this geometry leads to a modification of the group
velocity, allowing for almost-dispersionless propagation of spin-wave pulses.
Moreover, we demonstrate that the influence of energy concentration outweighs
that of damping in these YIG waveguides, resulting in an overall increase of
the spin-wave intensity during propagation in the transition region. These
findings can be utilized to improve the efficiency and functionality of
magnonic devices which use spin waves as an information carrier.",2111.02236v1
2022-08-23,Reversal of nanomagnets by propagating magnons in ferrimagnetic yttrium iron garnet enabling nonvolatile magnon memory,"Despite the unprecedented downscaling of CMOS integrated circuits,
memory-intensive machine learning and artificial intelligence applications are
limited by data conversion between memory and processor. There is a challenging
quest for novel approaches to overcome this so-called von Neumann bottleneck.
Magnons are the quanta of spin waves and transport angular momenta through
magnets. They enable power-efficient computation without charge flow and would
solve the conversion problem if spin wave amplitudes could be stored directly
in a magnetic memory cell. Here, we report the reversal of ferromagnetic
nanostripes by spin waves which propagate through an underlying spin-wave bus
made from yttrium iron garnet. Thereby, the charge-free angular momentum flow
is stored after transmission over a macroscopic distance. We show that spin
waves can reverse large arrays of ferromagnetic stripes at a strikingly small
power level of nW. Combined with the already existing wave logic, our discovery
is path-breaking for the new era of magnonics-based in-memory computation and
beyond von Neumann computer architectures.",2208.10923v1
2022-09-14,Generation of Spin-Wave Pulses by Inverse Design,"The development of fast magnonic information processing nanodevices requires
operating with short spin-wave pulses, but, the shorter the pulses, the more
affected they are by information loss due to broadening and dispersion. The
capability of engineering spin-wave pulses and controlling their propagation
could solve this problem. Here, we provide a method to generate linear
spin-wave pulses with a desired spatial-temporal profile in magnonic waveguides
based on inverse design. As relevant examples, we theoretically predict that
both rectangular and self-compressing spin-wave pulses can be generated in
state-of-the-art waveguides with fidelities >96% using narrow stripline
antennas. The method requires minimal computational overhead and is universal,
i.e., it applies to arbitrary targeted pulse shapes, type of waves (exchange or
dipolar), waveguide materials, and waveguide geometries. It can also be
extended to more complex magnonic structures. Our results could lead to the
utilization of large-scale magnonic circuits for classical and quantum
information processing.",2209.06608v1
2022-10-26,Nonreciprocal collective magnetostatic wave modes in geometrically asymmetric bilayer structure with nonmagnetic spacer,"Nonreciprocity, i.e. inequivalence in amplitudes and frequencies of spin
waves propagating in opposite directions, is a key property underlying
functionality in prospective magnonic devices. Here we demonstrate
experimentally and theoretically a simple approach to induce frequency
nonreciprocity in a magnetostatically coupled ferromagnetic bilayer structure
with a nonmagnetic spacer by its geometrical asymmetry. Using Brillouin light
scattering, we show the formation of two collective spin wave modes in
Fe$_{81}$Ga$_{19}$/Cu/Fe$_{81}$Ga$_{19}$ structure with different thicknesses
of ferromagnetic layers. Experimental reconstruction and theoretical modeling
of the dispersions of acoustic and optical collective spin wave modes reveal
that both possess nonreciprocity reaching several percent at the wavenumber of
$22~\cdot~10^4$ rad cm$^{-1}$. The analysis demonstrates that the shift of the
amplitudes of counter-propagating coupled modes towards either of the layers is
responsible for the nonreciprocity because of the pronounced dependence of spin
wave frequency on the layers thickness. The proposed approach enables the
design of multilayered ferromagnetic structures with a given spin wave
dispersion for magnonic logic gates.",2210.14882v2
2023-06-28,Dissipative Spin-wave Diode and Nonreciprocal Magnonic Amplifier,"We propose an experimentally feasible dissipative spin-wave diode comprising
two magnetic layers coupled via a non-magnetic spacer. We theoretically
demonstrate that the spacer mediates not only coherent interactions but also
dissipative coupling. Interestingly, an appropriately engineered dissipation
engenders a nonreciprocal device response, facilitating the realization of a
spin-wave diode. This diode permits wave propagation in one direction alone,
given that the coherent Dzyaloshinskii- Moriya (DM) interaction is balanced
with the dissipative coupling. The polarity of the diode is determined by the
sign of the DM interaction. Furthermore, we show that when the magnetic layers
undergo incoherent pumping, the device operates as a unidirectional spin-wave
amplifier. The amplifier gain is augmented by cascading multiple magnetic
bilayers. By extending our model to a one-dimensional ring structure, we
establish a connection between the physics of spin-wave amplification and
non-Hermitian topology. Our proposal opens up a new avenue for harnessing
inherent dissipation in spintronic applications.",2306.15916v1
1999-11-29,Spin Waves in Canted Phases: An Application to Doped Manganites,"We present the effective lagrangian for low energy and momentum spin waves in
canted phases at next to leading order in the derivative expansion. The
symmetry breaking pattern SU(2) --> 1 of the internal spin group and that of
the crystallographic space group imply that there is one ferromagnetic and one
antiferromagnetic spin wave. The interaction of the spin waves with the charge
carriers is also discussed for canted, ferromagnetic and antiferromagnetic
phases. All this together allows us to write the doping dependence of the
dispersion relation parameters for doped manganites. We point out that the spin
waves posses distinctive characteristics which may allow us to experimentally
differentiate canted phases from phase separation regions in doped manganites.",9911471v2
2002-08-19,Projected BCS Wave Functions for Low Dimensional Frustrated Spin Systems,"Twenty-five years after the first proposal, the question whether the ground
state of a frustrated spin-half system is well described by a spin-liquid
Resonating Valence Bond (RVB) wave function is still controversial. A
physically transparent representation of a RVB state can be obtained in
fermionic representation with a standard BCS-type pairing wave function,
working in the subspace with fixed number of electrons and no double
occupancies. In this work, we show that, using this variational wave function
with a careful parameterization of the pairing function, it is possible to
obtain an extremely accurate {\em ansatz} for the ground state of the
Heisenberg antiferromagnet with next-nearest neighbors interactions
($J_{1}{-}J_{2}$ model) in the regime of strong frustration. Indeed, in the
spin-half realization of this model, it is known that the combined effect of
frustration and zero-point motion interferes with the mechanism of
spontaneously broken symmetry, giving rise to a non-magnetic phase of purely
quantum-mechanical nature ($J_2/J_1\simeq 0.5$). This wave function is proposed
to represent the generic spin-half RVB ground state in spin liquids.",0208371v1
2007-05-25,"Excitation of self-localized spin-wave ""bullets"" by spin-polarized current in in-plane magnetized magnetic nano-contacts: a micromagnetic study","It was shown by micromagnetic simulation that a current-driven in-plane
magnetized magnetic nano-contact, besides a quasi-linear propagating
(""Slonczewski"") spin wave mode, can also support a nonlinear self-localized
spin wave ""bullet"" mode that exists in a much wider range of bias currents. The
frequency of the ""bullet"" mode lies below the spectrum of linear propagating
spin waves, which makes this mode evanescent and determines its spatial
localization. The threshold current for the excitation of the self-localized
""bullet"" is substantially lower than for the linear propagating mode, but
finite-amplitude initial perturbations of magnetization are necessary to
generate a ""bullet"" in our numerical simulations, where thermal fluctuations
are neglected. Consequently, in these simulations the hysteretic switching
between the propagating and localized spin wave modes is found when the bias
current is varied.",0705.3750v1
2008-05-29,Wave packet dynamics in 2DEG with spin orbit coupling: splitting and zitterbewegung,"We study the effect of splitting and zitterbewegung of 1D and 2D electron
wave packets in the semiconductor quantum well under the influence of the
Rashba spin orbit coupling. Results of our investigations show that the spin
orbit interaction induces dramatic qualitative changes in the evolution of spin
polarized wave packet. The initial wave packet splits into two parts with
different spin polarization propagating with unequal group velocity. This
splitting appears due to the presence of two branches of electron spectrum
corresponding to the stationary states with different chirality. It is
demonstrated also that in the presence of external magnetic field B$
perpendicular to the electron gas plane the wave packet splits into two parts
which rotates with different cyclotron frequencies. It was shown that after
some periods the electron density distributes around cyclotron orbit and the
motion acquire an irregular character. Our calculations were made for both
cases of weak and strong spin orbit coupling.",0805.4489v2
2008-11-03,"Dispersion and spin wave ""tunneling"" in nano-structured magnetostatic spin waveguides","Magnetostatic spin wave dispersion and loss are measured in micron scale spin
wave-guides in ferromagnetic, metallic CoTaZr. Results are in good agreement
with model calculations of spin wave dispersion. The measured attenuation
lengths, of the order of 3um, are several of orders of magnitude shorter than
that predicted from eddy currents in these thin wires. Spin waves effectively
""tunnel"" through air gaps, produced by focused ion beam etching, as large as
1.5 um.",0811.0353v1
2009-05-28,Resonant Nonlinear Damping of Quantized Spin Waves in Ferromagnetic Nanowires,"We use spin torque ferromagnetic resonance to measure the spectral properties
of dipole-exchange spin waves in permalloy nanowires. Our measurements reveal
that geometric confinement has a profound effect on the damping of spin waves
in the nanowire geometry. The damping parameter of the lowest-energy quantized
spin wave mode depends on applied magnetic field in a resonant way and exhibits
a maximum at a field that increases with decreasing nanowire width. This
enhancement of damping originates from a nonlinear resonant three-magnon
confluence process allowed at a particular bias field value determined by
quantization of the spin wave spectrum in the nanowire geometry.",0905.4699v2
2009-07-13,A topological gauge field in nanomagnets: spin wave excitations over a slowly moving magnetization background,"We introduce a topological gauge vector potential which influences spin wave
excitations over arbitrary non-uniform, slowly moving magnetization
distribution. The time-component of the gauge potential plays a principal role
in magnetization dynamics, whereas its spatial components can be often
neglected for typical magnetic nanostructures. As an example, we consider spin
modes excited in the vortex state magnetic dots. It is shown that the vortex/
spin wave interaction can be described as a consequence of the gauge field
arising due to non uniform moving vortex magnetization distribution. The
coupled equations of motion of the vortex and spin waves are solved within
small excitation amplitude approximation. The model yields a giant frequency
splitting of the spin wave modes having non-zero overlapping with the vortex
mode as well as a finite vortex mass of dynamical origin.",0907.2226v1
2009-09-17,Experimental evidence of self-localized and propagating spin wave modes in obliquely magnetized current-driven nanocontacts,"Through detailed experimental studies of the angular dependence of spin wave
excitations in nanocontact-based spin-torque oscillators, we demonstrate that
two distinct spin wave modes can be excited, with different frequency,
threshold currents and frequency tuneability. Using analytical theory and
micromagnetic simulations we identify one mode as an exchange-dominated
propagating spin wave, and the other as a self-localized nonlinear spin wave
bullet. Wavelet-based analysis of the simulations indicates that the apparent
simultaneous excitation of both modes results from rapid mode hopping induced
by the Oersted field.",0909.3331v2
2010-07-06,"Spin waves in the (0,pi) and (0,pi,pi) ordered SDW states of the t-t' Hubbard model: Application to doped iron pnictides","Spin waves in (0,pi) and (0,pi,pi) ordered spin-density-wave (SDW) states of
the t-t' Hubbard model are investigated at finite doping. In the presence of
small t', these composite ferro-antiferromagnetic (F-AF) states are found to be
strongly stabilized at finite hole doping due to enhanced carrier-induced
ferromagnetic spin couplings as in metallic ferromagnets. Anisotropic spin-wave
velocities, spin-wave energy scale of around 200meV, reduced magnetic moment,
and rapid suppression of magnetic order with electron doping x (corresponding
to F substitution of O atoms in La O_{1-x} F_x Fe As or Ni substitution of Fe
atoms in Ba Fe_{2-x} Ni_x As_2) obtained in this model are in agreement with
observed magnetic properties of doped iron pnictides.",1007.0812v1
2011-04-27,Spin Density Waves and Domain Wall Interactions in Nanowires,"We investigated how the dynamics of a domain wall are affected by the
presence of spin density waves in a ferromagnetic wire. Domain walls and other
scattering centres can cause coherent spin density waves to propagate through a
wire when a current is applied. In some cases the spin torque due to these
scattered electrons can be enhanced such that it is on a par with the exchange
and anisotropy energies controlling the shape and dynamics of the domain wall.
In such a case we find that the spin density waves enhance the current induced
domain wall motion, allowing for domain wall motion with smaller current
pulses. Here we consider a system involving two domain walls and focus on how
the motion of the second domain wall is modified by the spin density waves
caused by the presence of the first domain wall.",1104.5175v1
2013-10-23,Exchange-dominated Standing Spin Wave Excitations under microwave irradiation in Ni80Fe20 Thin Films,"We investigated the microwave-assisted DC voltages of ferromagnetic
resonances and exchangedominated standing spin wave excitations in two
different in-plane magnetized permalloy thin films via homodyne detection. The
line shapes of ferromagnetic resonance spectra and the dispersion curves of
ferromagnetic resonance and standing spin wave are in agreement of previous
studies, while further investigations of DC voltage spectra for these two
excitations reveal that 1. unlike ferromagnetic resonance signals, the
anti-symmetrical line shapes of standing spin wave excitations are not depend
on the electromagnetic relative phase of assisted microwave, and 2. linewidths
of their DC voltage spectra are distinct. The complicated spin dynamics of
standing spin wave is consequently discussed by applying
Landau-Lifshitz-Gilbert equation in term of exchange interaction.",1310.6108v1
2016-08-17,Current-induced instability of domain walls in cylindrical nanowires,"We study the current-driven domain wall (DW) motion in cylindrical nanowires
using micromagnetic simulations by implementing the Landau-Lifshitz-Gilbert
equation with nonlocal spin-transfer torque in a finite difference
micromagnetic package. We find that in the presence of DW Gaussian wave packets
(spin waves) will be generated when the charge current is applied to the system
suddenly. And this effect is excluded when using the local spin-transfer
torque. The existence of spin waves emission indicates that transverse domain
walls can not move arbitrarily fast in cylindrical nanowires although they are
free from the Walker limit. We establish an upper-velocity limit for the DW
motion by analyzing the stability of Gaussian wave packets using the local
spin-transfer torque. Micromagnetic simulations show that the stable region
obtained by using nonlocal spin-transfer torque is smaller than that by using
its local counterpart. This limitation is essential for multiple domain walls
since the instability of Gaussian wave packets will break the structure of
multiple domain walls.",1608.04876v2
2018-09-27,Spin wave radiation from vortices in $^3$He-B,"We consider a vortex line in the B phase of superfluid $^3$He under uniformly
precessing magnetization. The magnetization exerts torque on the vortex,
causing its order parameter to oscillate. These oscillations generate spin
waves, which is analogous to an oscillating charge generating electromagnetic
radiation. The spin waves carry energy, causing dissipation in the system.
Solving the equations of spin dynamics, we calculate the energy dissipation
caused by spin wave radiation for arbitrary tipping angles of the magnetization
and directions of the magnetic field, and for both vortex types of $^3$He-B.
For the double-core vortex we also consider the anisotropy of the radiation and
the dependence of the dissipation on twisting of the half cores. The radiated
energy is compared with experiments in the mid-temperature range $T \sim 0.5
T_c$. The dependence of the calculated dissipation on several parameters is in
good agreement with the experiments. Combined with numerically calculated
vortex structure, the radiation theory produces the order of magnitude of the
experimental dissipation. The agreement with the experiments indicates that
spin wave radiation is the dominant dissipation mechanism for vortices in
superfluid $^3$He-B in the mid-temperature range.",1809.10484v1
2018-07-03,Spin pinning and spin-wave dispersion in nanoscopic ferromagnetic waveguides,"Spin waves are investigated in Yttrium Iron Garnet (YIG) waveguides with a
thickness of 39 nm and widths ranging down to 50 nm, i.e., with aspect ratios
thickness over width approaching unity, using Brillouin Light Scattering
spectroscopy. The experimental results are verified by a semi-analytical theory
and micromagnetic simulations. A critical width is found, below which the
exchange interaction suppresses the dipolar pinning phenomenon. This changes
the quantization criterion for the spin-wave eigenmodes and results in a
pronounced modification of the spin-wave characteristics. The presented
semi-analytical theory allows for the calculation of spin-wave mode profiles
and dispersion relations in nano-structures.",1807.01358v3
2017-06-06,Temperature scaling of the Dzyaloshinsky-Moriya interaction in the spin wave spectrum,"The temperature scaling of the micromagnetic Dzyaloshinsky-Moriya exchange
interaction is calculated for the whole range of temperature. We use Green's
function theory to derive the finite-temperature spin wave spectrum of
ferromagnetic systems described by a classical atomistic spin model
Hamiltonian. Within this model, we find universal expressions for the
temperature scaling not only of the Dzyaloshinsky-Moriya interaction but also
of the Heisenberg exchange stiffness and the single-ion anisotropy. In the
spirit of multiscale models, we establish a clear connection between the
atomistic interactions and the temperature-dependent coefficients in the spin
wave spectrum and in the micromagnetic free energy functional. We demonstrate
that the corrections to mean-field theory or the random phase approximation for
the temperature scaling of Dzyaloshinsky-Moriya and Heisenberg exchange
interactions assume very similar forms. In the presence of thermal fluctuations
and Dzyaloshinsky-Moriya interaction an anisotropy-like term emerges in the
spin wave spectrum which, at low temperature, increases with temperature, in
contrast to the decreasing single-ion anisotropy. We evaluate the accuracy of
the theoretical method by comparing it to the spin wave spectrum calculated
from Monte Carlo simulations.",1706.01684v1
2021-11-29,Tailoring High-Frequency Magnonics in Monolayer Chromium Trihalides,"Monolayer chromium trihalides, the archetypal two dimensional (2D) magnetic
materials, are readily suggested as a promising platform for high frequency
magnonics. Here we detail the spin wave properties of monolayer CrBr$_3$ and
CrI$_3$, using spin dynamics simulations parametrized from the first
principles. We reveal that spin wave dispersion can be tuned in a broad range
of frequencies by strain, paving the way towards flexo magnonic applications.
We further show that ever present halide vacancies in these monolayers host
sufficiently strong Dzyaloshinskii Moriya interaction to scatter spin waves,
which promotes design of spin-wave guides by defect engineering. Finally we
discuss the spectra of spin-waves propagating across a moir\'e periodic
modulation of magnetic parameters in a van der Waals heterobilayer, and show
that the nanoscale moir\'e periodicities in such samples are ideal for
realization of a magnonic crystal in the terahertz frequency range. Recalling
the additional tunability of magnetic 2D materials by electronic gating, our
results situate these systems among the front-runners for prospective high
frequency magnonic applications.",2111.14305v1
2022-11-20,Long-distance propagation of high-velocity antiferromagnetic spin waves,"We report on coherent propagation of antiferromagnetic (AFM) spin waves over
a long distance ($\sim$10 $\mu$m) at room temperature in a canted AFM
$\alpha$-Fe$_2$O$_3$ with the Dzyaloshinskii-Moriya interaction (DMI).
Unprecedented high group velocities (up to 22.5 km/s) are characterized by
microwave transmission using all-electrical spin wave spectroscopy. We derive
analytically AFM spin-wave dispersion in the presence of the DMI which accounts
for our experimental results. The AFM spin waves excited by nanometric coplanar
waveguides with large wavevectors enter the exchange regime and follow a
quasi-linear dispersion relation. Fitting of experimental data with our
theoretical model yields an AFM exchange stiffness length of 1.7 angstrom. Our
results provide key insights on AFM spin dynamics and demonstrate high-speed
functionality for AFM magnonics.",2211.10989v1
2023-02-14,Spin wave Hamiltonian and anomalous scattering in NiPS$_3$,"We report a comprehensive spin wave analysis of the semiconducting honeycomb
van der Waal antiferromagnet NiPS$_3$. Using single crystal inelastic neutron
scattering, we map out the full Brillouin zone and fit the observed modes to a
spin wave model with rigorously defined uncertainty. We find that the third
neighbor exchange $J_3$ dominates the Hamiltonian, a feature which we fully
account for by ab-initio density functional theory calculations. We also
quantify the degree to which the three-fold rotation symmetry is broken and
account for the $Q=0$ excitations observed in other measurements, yielding a
spin exchange model which is consistent across multiple experimental probes. We
also identify a strongly reduced static ordered moment and reduced low-energy
intensity relative to the linear spin wave calculations, signaling unexplained
features in the magnetism which requires going beyond the linear spin wave
approximation.",2302.07242v2
2023-04-03,Spin waves in layered antiferromagnets with honeycomb structure,"We develop a description of spin waves in a $3D$ quantum $XY$ antiferromagnet
(AFM) in terms of macroscopic variables, magnetization and N\'eel vector
densities. We consider a layered AFM with spins located on the honeycomb
lattice. In the discussed system, the spectrum of spin waves consists of four
modes, all well captured by our macroscopic description. The gapless mode of
the spin waves, i.e., magnons, is described by a system of equations, which has
a structure general for the Goldstone mode in AFMs. We demonstrate that the
parameters in the spin Hamiltonian can be evaluated by fitting the experimental
data with the results obtained for the four modes using the macroscopic
variable approach. The description of AFM in terms of macroscopic variables can
be easily extended to the case when the lattice of the magnetic substance is
deformed by an external strain or acoustic wave.",2304.00700v1
2020-06-17,Recent Progress on Electrical Excitation and Manipulation of Spin-Waves in Spin Hall Nano-Oscillators,"Spin waves (SWs), the collective precessional motion of spins in a magnetic
system, have been proposed as a promising alternative system with low-power
consumption for encoding information. Spin Hall nano-oscillator (SHNO), a
new-type spintronic nano-device, can electrically excite and control spin waves
in both nanoscale magnetic metals and insulators with low damping by the spin
current due to spin Hall effect. Here, we will review recent progress about
spin-wave excitation and experimental parameters dependent spectrum in SHNOs.
The nanogap SHNOs based on in-plane magnetization Py/Pt exhibits a nonlinear
self-localized bullet soliton localized at the center of the gap between the
electrodes and a secondary high-frequency mode which coexists with the primary
bullet mode at higher currents. While in the nanogap SHNOs with strong
perpendicular magnetic anisotropy (PMA), besides both nonlinear bullet soliton
and propagating spin-wave mode are achieved and controlled by varying the
external magnetic field and current, the magnetic bubble skyrmion mode also can
be excited at a low in-plane magnetic field. These SW modes show
thermal-induced mode hopping behavior at high temperature due to the coupling
between modes mediated by thermal-magnon-mediated scattering. Moreover, thanks
to PMA-induced effective field, a single coherent mode also can be achieved
without applying an external magnetic field. The strong nonlinear effect of
spin-waves makes SHNOs easy to achieve synchronization with external microwave
signals or mutual synchronization between multiple oscillators with improving
the coherence and power of oscillation modes significantly. Spin-waves in SHNOs
with an external free magnetic layer have a wide range of applications from as
a nanoscale signal source of low-power consumption magnonic devices to
spin-based neuromorphic computing systems in the field of artificial
intelligence.",2006.09737v2
2001-12-19,Spin-phonon interaction in doped high-T$_C$ superconductors from density functional calculations,"Effects of coupling between phonon distortions and stripe-like spin waves in
the CuO plane of HgBa$_2$CuO$_4$ are studied by band calculations. Local
exchange enhancements depend sensitively on the local structure around Cu
sites. Interactions where spin waves have twice as long wave length as phonon
waves can lead to a 'dip' in the density of states (DOS) below the Fermi
energy, $E_F$. This type of interaction is compatible with several seemingly
contradictory observations among high-$T_C$ cuprates, like the isotope effect,
anti-ferromagnetic fluctuations, stripes and pseudogaps. It can also account
for a large $T_C$.",0112357v1
1997-01-27,Massless fields in plane wave geometry,"Conformal isometry algebras of plane wave geometry are studied. Then, based
on the requirement of conformal invariance, a definition of masslessness is
introduced and gauge invariant equations of motion, subsidiary conditions, and
corresponding gauge transformations for all plane wave geometry massless spin
fields are constructed. Light cone representation for elements of conformal
algebra acting as differential operators on wavefunctions of massless higher
spin fields is also evaluated. Interrelation of plane wave geometry massless
higher spin fields with ladder representation of $u(2,2)$ algebra is
investigated.",9701141v1
2009-01-15,Spin-Wave Instabilities and Non-Collinear Magnetic Phases of a Geometrically-Frustrated Triangular-Lattice Antiferromagnet,"This paper examines the relation between the spin-wave instabilities of
collinear magnetic phases and the resulting non-collinear phases for a
geometrically-frustrated triangular-lattice antiferromagnet in the high spin
limit. Using a combination of phenomenological and Monte-Carlo techniques, we
demonstrate that the instability wave-vector with the strongest intensity in
the collinear phase determines the wave-vector of a cycloid or the dominant
elastic peak of a more complex non-collinear phase. Our results are related to
the observed multi-ferroic phase of Al-doped CuFeO$_2$.",0901.2336v1
2012-05-08,Quantum phases of Bose-Bose mixtures on a triangular lattice,"We investigate the zero temperature quantum phases of a Bose-Bose mixture on
a triangular lattice using Bosonic Dynamical Mean Field Theory (BDMFT). We
consider the case of total filling one where geometric frustration arises for
asymmetric hopping. We map out a rich ground state phase diagram including
xy-ferromagnetic, spin-density wave, superfluid, and supersolid phases. In
particular, we identify a stripe spin-density wave phase for highly asymmetric
hopping. On top of the spin-density wave, we find that the system generically
shows weak charge (particle) density wave order.",1205.1806v2
2021-07-04,Spin optics for gravitational waves,"We present the geometric optics expansion for circularly polarized
gravitational waves on a curved spacetime background, to subleading order. We
call spin optics to the subleading order geometric optics expansion, which
involves modifying the standard eikonal function by including a specially
chosen helicity-dependent correction. We show that the techniques developed for
the propagation of electromagnetic waves can also be applied to gravitational
waves in the limit of spin optics. However, one needs to account for the
difference in the photon and graviton helicity, which we do here.",2107.02761v3
2023-03-09,Full-waveform tomography reveals iron spin crossover in Earth lower mantle,"Joint interpretation of bulk and shear wave speeds constrains the chemistry
of the deep mantle. At all depths, the diversity of wave speeds cannot be
explained by an isochemical mantle. Between 1000 and 2500 km depth,
hypothetical mantle models containing an electronic spin crossover in (Mg,Fe)O
provide a significantly better fit to the wave-speed distributions, as well as
more realistic temperatures and silica contents, than models without a spin
crossover. Below 2500 km, wave speed distributions are explained by enrichment
in silica towards the core-mantle-boundary. This silica enrichment may
represent the fractionated remains of an ancient basal magma ocean.",2303.05476v1
1998-06-25,Quantum Hall effect anomaly and collective modes in the magnetic-field-induced spin-density-wave phases of quasi-one-dimensional conductors,"We study the collective modes in the magnetic-field-induced spin-density-wave
(FISDW) phases experimentally observed in organic conductors of the Bechgaard
salts family. In phases that exhibit a sign reversal of the quantum Hall effect
(Ribault anomaly), the coexistence of two spin-density waves gives rise to
additional collective modes besides the Goldstone modes due to spontaneous
translation and rotation symmetry breaking. These modes strongly affect the
charge and spin response functions. We discuss some experimental consequences
for the Bechgaard salts.",9806311v2
1999-09-10,Time Evolution of Spin Waves,"A rigorous derivation of macroscopic spin-wave equations is demonstrated. We
introduce a macroscopic mean-field limit and derive the so-called
Landau-Lifshitz equations for spin waves. We first discuss the ferromagnetic
Heisenberg model at T=0 and finally extend our analysis to general spin
hamiltonians for the same class of ferromagnetic ground states.",9909146v1
2000-05-26,Spin and charge excitations in incommensurate spin density waves,"Collective excitations both for spin- and charge-channels are investigated in
incommensurate spin density wave (or stripe) states on two-dimensional Hubbard
model. By random phase approximation, the dynamical susceptibility
\chi(q,\omega) is calculated for full range of (q,\omega) with including all
higher harmonics components. An intricate landscape of the spectra in
\chi(q,\omega) is obtained. We discuss the anisotropy of the dispersion cones
for spin wave excitations, and for the phason excitation related to the motion
of the stripe line. Inelastic neutron experiments on Cr and its alloys and
stripe states of underdoped cuprates are proposed.",0005466v1
2002-10-04,Current-induced spin-wave excitations in a single ferromagnetic layer,"A new current induced spin-torque transfer effect has been observed in a
single ferromagnetic layer without resorting to multilayers. At a specific
current density of one polarity injected from a point contact, abrupt
resistance changes due to current-induced spin wave excitations have been
observed. The critical current at the onset of spin-wave excitations depends
linearly on the external field applied perpendicular to the layer. The observed
effect is due to current-driven heterogeneity in an otherwise uniform
ferromagnetic layer.",0210116v1
2004-11-13,Existence of the Spin-Wave Gap in a Deformed Flat-Band Hubbard Model,"We consider a deformed flat-band Hubbard model under a periodic boundary
condition in arbitrary dimensions. We show that the ground state is only
all-spin-up or -down state. We obtain upper and lower bounds of the one-magnon
spin-wave energy with an arbitrary momentum. This dispersion relation is the
same as that in the XXZ model in the certain parameter region. Therefore the
spin wave has a finite energy gap. These results suggests the our model and the
XXZ model.",0411362v1
2004-05-11,Spin structure of spin-1/2 baryon and spinless meson production amplitudes in photo and hadronic reactions,"The most general spin structures of the spin-1/2 baryon and spinless meson
production operator for both photon and nucleon induced reactions are derived
from the partial-wave expansions of these reaction amplitudes. The present
method provides the coefficients multiplying each spin operator in terms of the
partial-wave matrix elements. The result should be useful in studies of these
reactions based on partial-wave analyses, especially, when spin observables are
considered.",0405030v4
2004-04-20,Wave function collapses in a single spin magnetic resonance force microscopy,"We study the effects of wave function collapses in the oscillating cantilever
driven adiabatic reversals (OSCAR) magnetic resonance force microscopy (MRFM)
technique. The quantum dynamics of the cantilever tip (CT) and the spin is
analyzed and simulated taking into account the magnetic noise on the spin. The
deviation of the spin from the direction of the effective magnetic field causes
a measurable shift of the frequency of the CT oscillations. We show that the
experimental study of this shift can reveal the information about the average
time interval between the consecutive collapses of the wave function",0404105v1
2006-03-07,Stimulated wave of polarization in spin chains,"Stimulated wave of polarization, triggered by a flip of a single spin,
presents a simple model of quantum amplification. Previously, it has been found
that such wave can be excited in a 1D Ising chain with nearest-neighbor
interactions, irradiated by a weak resonant transverse field. Here we explore
models with more realistic Hamiltonians, in particular, with natural
dipole-dipole interactions. Results of simulations for 1D spin chains and rings
with up to nine spins are presented.",0603049v1
2007-01-10,Experimental demonstration of stimulated polarization wave in a chain of nuclear spins,"A stimulated wave of polarization, which implements a simple mechanism of
quantum amplification, is experimentally demonstrated in a chain of four
J-coupled nuclear spins, irradiated by a weak radio-frequency transverse field.
The ""quantum domino"" dynamics, a wave of flipped spins triggered by a flip of
the first spin, has been observed in fully $^{13}$C-labeled sodium butyrate.",0701056v1
2007-05-02,Magneto-elastic waves in crystals of magnetic molecules,"We study magneto-elastic effects in crystals of magnetic molecules. Coupled
equations of motion for spins and sound are derived and the possibility of
strong resonant magneto-acoustic coupling is demonstrated. Dispersion laws for
interacting linear sound and spin excitations are obtained for bulk and surface
acoustic waves. We show that ultrasound can generate inverse population of spin
levels. Alternatively, the decay of the inverse population of spin levels can
generate ultrasound. Possibility of solitary waves of the magnetization
accompanied by the elastic twists is demonstrated.",0705.0371v1
2007-08-09,Spin-wave spectra of a kagome stripe,"We study ground state degeneracy and spin-wave excitations in a 1D version of
a Kagome antiferromagnet -- a Heisenberg antiferromagnet on a Kagome stripe. We
show that for nearest-neighbor interaction, the classical ground state is
infinitely degenerate. For any spin configuration from the degenerate set, the
classical spin-wave spectrum contains, in addition to Goldstone modes, a branch
of zero energy excitations, and a zero mode in another branch. We demonstrate
that the interactions beyond nearest neighbors lift the degeneracy, eliminate a
zero mode, and give a finite dispersion to formerly zero-energy branch, leaving
only Goldstone modes as zero-energy excitations.",0708.1272v1
2009-06-09,Spin-wave theory for dimerized ferromagnetic chains,"We describe a Peierls dimerization which occurs in ferromagnetic spin chains
at finite temperature, within the modified spin-wave theory. Usual spin-wave
theory is modified by introducing a Lagrange multiplier which enforces a
nonmagnetic state at finite temperature. It is shown that this method gives
results in excellent agreement with the density--matrix renormalization group
applied to transfer matrices for dimerized ferromagnetic chains. We study bond
correlation functions and explore the characteristic features of dimerization
in the specific heat.",0906.1758v1
2009-12-25,Near-Boundary and Bulk Regions of a Semi-Infinite Two-Dimensional Heisenberg Antiferromagnet,"Using the spin-wave approximation elementary excitations of a semi-infinite
two-dimensional $S=\frac12$ Heisenberg antiferromagnet are considered. The
spectrum consists of bulk modes -- standing spin waves and a
quasi-one-dimensional mode of boundary spin waves. These latter excitations
eject bulk modes from two boundary rows of sites, thereby dividing the
antiferromagnet into two regions with different dominant excitations. As a
result absolute values of nearest-neighbor spin correlations on the edge exceed
the bulk value.",0912.4958v1
2010-02-23,Planar Dirac diffusion,"We present the results of the planar diffusion of a Dirac particle by step
and barrier potentials, when the incoming wave impinges at an arbitrary angle
with the potential. Except for right-angle incidence this process is
characterized by the appearance of spin flip terms. For the step potential,
spin flip occurs for both transmitted and reflected waves. However, we find no
spin flip in the transmitted barrier result. This is surprising because the
barrier result may be derived directly from a two-step calculation. We
demonstrate that the spin flip cancellation indeed occurs for each particle
(wave packet) contribution.",1002.4324v1
2010-08-11,"Chirality, charge and spin-density wave instabilities of a two-dimensional electron gas in the presence of Rashba spin-orbit coupling","We show that a result equivalent to Overhauser's famous Hartree-Fock
instability theorem can be established for the case of a two-dimensional
electron gas in the presence of Rashba spin-obit coupling. In this case it is
the spatially homogeneous paramagnetic chiral ground state that is shown to be
differentially unstable with respect to a certain class of distortions of the
spin-density-wave and charge-density-wave type. The result holds for all
densities. Basic properties of these inhomogeneous states are analyzed.",1008.1816v1
2010-09-15,Anomalous High-Energy Spin Excitations in La2CuO4,"Inelastic neutron scattering is used to investigate the collective magnetic
excitations of the high-temperature superconductor parent antiferromagnet
La2CuO4. We find that while the lower energy excitations are well described by
spin-wave theory, including one- and two-magnon scattering processes, the
high-energy spin waves are strongly damped near the (1/2,0) position in
reciprocal space and merge into a momentum dependent continuum. This anomalous
damping indicates the decay of spin waves into other excitations, possibly
unbound spinon pairs.",1009.2915v1
2011-12-16,Guiding and Trapping Electron Spin Waves in Atomic Hydrogen Gas,"We present a high magnetic field study of electron spin waves in atomic
hydrogen gas compressed to high densities of 10^18 cm^-3 at temperatures
ranging from 0.26 to 0.6 K. We observed a variety of spin wave modes caused by
the identical spin rotation effect with strong dependence on the spatial
profile of the polarizing magnetic field. We demonstrate confinement of these
modes in regions of strong magnetic field and manipulate their spatial
distribution by changing the position of the field maximum.",1112.3775v3
2014-12-11,Magnetic field induced spin-wave energy focusing,"Spin waves can transport both energy and angular momentum over long distances
as they propagate. However, due to damping, their amplitude decreases
exponentially as they move away from the source, leaving little capability for
manipulating how much energy and angular momentum is to be delivered where.
Here we show that a suitable local reduction of the effective field can lead to
a large accumulation of spin wave energy far from the source. Moreover, both
the location and the amount of energy to be delivered can be controlled
accurately with geometry and externalm magnetic fields. Thus, we put forward a
general, robust and flexible approach to convey both heat and spin in
ferromagnets, which can be directly used in spintronic devices.",1412.4129v1
2015-05-27,Acoustic waves generated by the spin precession,"We study generation of acoustic waves by a precessing spin of a nanoparticle
deposited on the surface of a solid. Our approach elucidates macroscopic
dynamics of the Einstein - de Haas effect. It is based upon solution of
parameter-free equations of motion mandated by the conservation of the total
angular momentum: spin + mechanical. We show that the amplitude of the acoustic
waves generated by the spin precession may be sufficient for detection by a
tunneling electron microscope.",1505.07373v1
2016-05-12,Transmission of spin waves in ordered FeRh epitaxial thin films,"We report on B2-ordering dependence of magnetostatic surface spin waves in
ferromagnetic FeRh at room temperature. Spin waves transmit over a distance
longer than 21 {\mu}m in highly ordered FeRh alloys even with relatively large
spin-orbit interaction. The long-range transmission likely arises from the
induced Rh moments of the ordered FeRh due to ferromagnetic exchange
interaction between Fe and Rh. The results indicate a potential of using FeRh
in spintronic and magnonic applications by integrating with other fascinating
magnetic characteristics of FeRh such as electric field induced magnetic phase
transition.",1605.03798v1
2018-06-19,Scalar Tops and Perturbed Quadrupoles: Probing Fundamental Physics with Spin-Precessing Binaries,"Parity violation in the gravitational interaction has an important impact on
fundamental observables and the evolution of the universe. We here investigate
for the first time our ability to probe the parity violating nature of the
gravitational interaction using gravitational waves from spin-precessing
binaries. Focusing on dynamical Chern-Simons gravity, we derive the
spin-precession equations, calculate the gravitational waves emitted by
spin-precessing, quasi-circular black hole binaries and estimate the level to
which the theory could be constrained with future gravitational wave
observations.",1806.07425v1
2019-08-24,Chiral Pumping of Spin Waves,"We report a theory for the coherent and incoherent chiral pumping of spin
waves into thin magnetic films through the dipolar coupling with a local
magnetic transducer, such as a nanowire. The ferromagnetic resonance of the
nanowire is broadened by the injection of unidirectional spin waves that
generate a non-equilibrium magnetization in only half of the film. A
temperature gradient between the local magnet and film leads to a
unidirectional flow of incoherent magnons, i.e., a chiral spin Seebeck effect.",1908.09141v2
2022-07-30,Inertial spin waves in ferromagnets and antiferromagnets,"Inertial effects in spin dynamics are theoretically predicted to emerge at
ultrashort time scales, but their experimental signatures are often ambiguous.
Here, we calculate the spin-wave spectrum in ferromagnets and two-sublattice
antiferromagnets in the presence of inertial effects. It is shown how
precession and nutation spin waves hybridize with each other, leading to the
renormalization of the frequencies, the group velocities, the effective
gyromagnetic ratios and the effective damping parameters. Possible ways of
distinguishing between the signatures of inertial dynamics and similar effects
explainable within conventional models are discussed.",2208.00131v1
2022-12-29,Localized Spin-Wave Modes and Microwave Absorption in Random-Anisotropy Ferromagnets,"The theory of localized spin-wave excitations in random-anisotropy magnets
has been developed. Starting with a pure Heisenberg ferromagnet, we study the
evolution of standing spin waves in a finite-size sample towards localized
modes on increasing the strength of random anisotropy. Profiles of the
localized modes and their phases are analyzed and visualized in a 2D sample.
Localization length is obtained by several methods and its dependence on random
anisotropy is computed. The connection between the localization of spin
excitations and the broadband nature of the absorption of microwave power by
random-anisotropy magnets is elucidated.",2212.14301v1
2004-04-14,Spin-orbit entanglement in time evolution of radial wave packets in hydrogenic systems,"Time evolution of radial wave packets built from the eigenstates of Dirac
equation for a hydrogenic systems is considered. Radial wave packets are
constructed from the states of different $n$ quantum number and the same lowest
angular momentum. In general they exhibit a kind of breathing motion with
dispersion and (partial) revivals. Calculations show that for some particular
preparations of the wave packet one can observe interesting effects in spin
motion, coming from inherent entanglement of spin and orbital degrees of
freedom. These effects manifest themselves through some oscillations in the
mean values of spin operators and through changes of spatial probability
density carried by upper and lower components of the wave function. It is also
shown that the characteristic time scale of predicted effects (called
$T_{\mathrm{ls}}$) is for radial wave packets much smaller than in other cases,
reaching values comparable to (or even less than) the time scale for the wave
packet revival.",0404084v1
2008-04-07,Phase reciprocity of spin-wave excitation by a microstrip antenna,"Using space-, time- and phase-resolved Brillouin light scattering
spectroscopy we investigate the difference in phase of the two
counterpropagating spin waves excited by the same microwave microstrip
transducer. These studies are performed both for backward volume magnetostatic
waves and magnetostatic surface waves in an in-plane magnetized yttrium iron
garnet film. The experiments show that for the backward volume magnetostatic
spin waves (which are reciprocal and excited symmetrically in amplitude) there
is a phase difference of $\pi$ associated with the excitation process and thus
the phase symmetry is distorted. On the contrary, for the magnetostatic surface
spin waves (which are non-reciprocal and unsymmetrical in amplitude) the phase
symmetry is preserved (there is no phase difference between the two waves
associated with the excitation). Theoretical analysis confirms this effect.",0804.1090v1
2015-11-30,Frequency non-reciprocity of surface spin wave in Permalloy thin films,"Surface spin waves in thin Permalloy films are studied by means of
propagative spin wave spectroscopy. We observe a systematic difference of up to
several tens of MHz when comparing the frequencies of counter-propagating
waves. This frequency non-reciprocity effect is modeled using an analytical
dipole-exchange theory that considers the mutual influence of non-reciprocal
spin wave modal profiles and differences in magnetic anisotropies at the two
film surfaces. At moderate film thickness (20 nm and below), the frequency
non-reciprocity scales linearly with the wave vector and quadratically with the
thickness, whereas a more complex non-monotonic behavior is observed at larger
thickness. Our work suggests that surface wave frequency non-reciprocity can be
used as an accurate spectroscopic probe of magnetic asymmetries in thin
ferromagnetic films.",1511.09351v1
2019-05-20,Topological characterization of classical waves: the topological origin of magnetostatic surface spin waves,"We propose a topological characterization of Hamiltonians describing
classical waves. Applying it to the magnetostatic surface spin waves that are
important in spintronics applications, we settle the speculation over their
topological origin. For a class of classical systems that includes spin waves
driven by dipole-dipole interactions, we show that the topology is
characterized by vortex lines in the Brillouin zone in such a way that the
symplectic structure of Hamiltonian mechanics plays an essential role. We
define winding numbers around these vortex lines and identify them to be the
bulk topological invariants for a class of semimetals. Exploiting the bulk-edge
correspondence appropriately reformulated for these classical waves, we predict
that surface modes appear but not in a gap of the bulk frequency spectrum. This
feature, consistent with the magnetostatic surface spin waves, indicates a
broader realm of topological phases of matter beyond spectrally gapped ones.",1905.07909v1
2017-03-09,Overcoming thermal noise in non-volatile spin wave logic,"Spin waves are propagating disturbances in magnetically ordered materials,
analogous to lattice waves in solid systems and are often described from a
quasiparticle point of view as magnons. The attractive advantages of
Joule-heat-free transmission of information, utilization of the phase of the
wave as an additional degree of freedom and lower footprint area compared to
conventional charge-based devices have made spin waves or magnon spintronics a
promising candidate for beyond-CMOS wave-based computation. However, any
practical realization of an all-magnon based computing system must undergo the
essential steps of a careful selection of materials and demonstrate robustness
with respect to thermal noise or variability. Here, we aim at identifying
suitable materials and theoretically demonstrate the possibility of achieving
error-free clocked non-volatile spin wave logic device, even in the presence of
thermal noise and clock jitter or clock skew.",1703.03460v2
2022-04-15,Experimental Visualization of Dispersion Characteristics of Backward Volume Spin Wave Modes,"Basing on the measurement of spatial spectra (spectra of wavenumbers), the
dispersion characteristics of the first three modes of backward volume spin
wave, propagating along the direction of a constant uniform magnetic field in a
tangentially magnetized ferrite film, were visualized firstly. The study was
carried out by microwave probing of spin waves with subsequent use of spatial
Fourier analysis of the complex wave amplitude for a series of frequencies. It
was found that every m-th mode of the backward volume spins wave can be split
into n satellite modes due to the existence of layers with similar magnetic
parameters in ferrite film. It was found that satellites of the first mode of
this wave are excited most effectively, while satellites of the third mode -
least effectively, and the effectiveness of satellites excitation decreases as
the number n increases. It is found that the theoretical dispersion
dependencies of the first three modes of the wave coincide well with the
experimental dispersion dependencies of the satellite mode that are excited
most effectively.",2204.08293v1
2024-02-18,Double-$Q$ and quadruple-$Q$ instabilities at low-symmetric ordering wave vectors under tetragonal symmetry,"Multiple-$Q$ states are expressed as a superposition of spin density waves at
multiple ordering wave vectors, which results in unconventional complicated
spin textures, such as skyrmion, hedgehog, and vortex. We investigate the
multiple-$Q$ instability by focusing on the low-symmetric ordering wave vectors
in momentum space. By systematically performing the simulated annealing for
effective spin models with various ordering wave vectors on a two-dimensional
square lattice, we classify the magnetic phase diagram into four types
according to the position of the ordering wave vectors. Three out of four cases
lead to a plethora of isotropic multiple-$Q$ instabilities yielding collinear,
coplanar, and noncoplanar double-$Q$ and quadruple-$Q$ magnetic phases, while
the remaining case leads to an anisotropic double-$Q$ instability when the
multiple-spin interaction is introduced. Our results indicate that exotic
multiple-$Q$ phases distinct from the skyrmion crystal phase are expected when
the ordering wave vectors lie on the low-symmetric positions in the Brillouin
zone.",2402.11721v1
2010-08-19,Gravitational Radiations from a Spinning Compact Object around a supermassive Kerr black hole in circular orbit,"The gravitational waves and energy radiations from a spinning compact object
with stellar mass in a circular orbit in the equatorial plane of a supermassive
Kerr black hole are investigated in this paper. The effect how the spin acts on
energy and angular moment fluxes is discussed in detail. The calculation
results indicate that the spin of small body should be considered in
waveform-template production for the upcoming gravitational wave detections. It
is clear that when the direction of spin axes is the same as the orbitally
angular momentum (""positive"" spin), spin can decrease the energy fluxes which
radiate to infinity. For antidirection spin (""negative""), the energy fluxes to
infinity can be enlarged. And the relations between fluxes (both infinity and
horizon) and spin look like quadratic functions. From frequency shift due to
spin, we estimate the wave-phase accumulation during the inspiraling process of
the particle. We find that the time of particle inspiral into the black hole is
longer for positive spin and shorter for negative compared with the nonspinning
particle. Especially, for extreme spin value, the energy radiation near the
horizon of the extreme Kerr black hole is much more than that for the
nonspinning one. And consequently, the maximum binging energy of the extreme
spinning particle is much larger than that of the nonspinning particle.",1008.3324v3
2019-12-16,Spin-current manipulation of photoinduced magnetization dynamics in heavy metal / ferromagnet double layer based nanostructures,"Spin currents offer a way to control static and dynamic magnetic properties,
and therefore they are crucial for next-generation MRAM devices or spin-torque
oscillators. Manipulating the dynamics is especially interesting within the
context of photo-magnonics. In typical $3d$ transition metal ferromagnets like
CoFeB, the lifetime of light-induced magnetization dynamics is restricted to
about 1 ns, which e.g. strongly limits the opportunities to exploit the wave
nature in a magnonic crystal filtering device. Here, we investigate the
potential of spin-currents to increase the spin wave lifetime in a functional
bilayer system, consisting of a heavy metal (8 nm of $\beta$-Tantalum
(Platinum)) and 5 nm CoFeB. Due to the spin Hall effect, the heavy metal layer
generates a transverse spin current when a lateral charge current passes
through the strip. Using time-resolved all-optical pump-probe spectroscopy, we
investigate how this spin current affects the magnetization dynamics in the
adjacent CoFeB layer. We observed a linear spin current manipulation of the
effective Gilbert damping parameter for the Kittel mode from which we were able
to determine the system's spin Hall angles. Furthermore, we measured a strong
influence of the spin current on a high-frequency mode. We interpret this mode
an an exchange dominated higher order spin-wave resonance. Thus we infer a
strong dependence of the exchange constant on the spin current.",1912.07728v1
2020-12-04,Effects of hybridization and spin-orbit coupling to induce odd frequency pairing in two-band superconductors,"The effects of spin independent hybridization potential and spin orbit
coupling on two band superconductor with equal time s-wave inter band pairing
order parameter is investigated theoretically. To study symmetry classes in two
band superconductors the Gorkov equations are solved analytically. By defining
spin singlet and spin triplet s wave order parameter due to two band degree of
freedom the symmetry classes of Cooper pair are studied. For spin singlet case
it is shown that spin independent hybridization generates Cooper pair belongs
to even frequency spin singlet even momentum even band parity (ESEE) symmetry
class for both intraband and interband pairing correlations. For spin triplet
order parameter, intraband pairing correlation generates odd frequency spin
triplet even momentum even band parity (OTEE) symmetry class whereas, interband
pairing correlation generates even frequency spin triplet even momentum odd
band parity ETEO) class. For the spin singlet, spin orbit coupling generates
pairing correlation that belongs to odd frequency spin singlet odd momentum
even band parity (OSOE) symmetry class and even frequency spin singlet even
momentum even band parity (ESEE) for intraband and interband pairing
correlation respectively. In the spin triplet case for itraband and interband
correlation, spin orbit coupling generates even-frequency spin triplet odd
momentum even band parity (ETOE) and even frequency spin triplet even momentum
odd band parity (ETEO) respectively.",2012.02810v1
1996-09-11,Cumulant approach to weakly doped antiferromagnets,"We present a new approach to static and dynamical properties of holes and
spins in weakly doped antiferromagnets in two dimensions. The calculations are
based on a recently introduced cumulant approach to ground--state properties of
correlated electronic systems. The present method allows to evaluate hole and
spin--wave dispersion relations by considering hole or spin excitations of the
ground state. Usually, these dispersions are found from time--dependent
correlation functions. To demonstrate the ability of the approach we first
derive the dispersion relation for the lowest single hole excitation at
half--filling. However, the main purpose of this paper is to focus on the
mutual influence of mobile holes and spin waves in the weakly doped system. It
is shown that low-energy spin excitations strongly admix to the ground--state.
The coupling of spin waves and holes leads to a strong suppression of the
staggered magnetization which can not be explained by a simple rigid--band
picture for the hole quasiparticles. Also the experimentally observed doping
dependence of the spin--wave excitation energies can be understood within our
formalism.",9609098v1
2005-02-08,Landau Damping of Spin Waves in Trapped Boltzmann Gases,"A semiclassical method is used to study Landau damping of transverse
pseudo-spin waves in harmonically trapped ultracold gases in the collisionless
Boltzmann limit. In this approach, the time evolution of a spin is calculated
numerically as it travels in a classical orbit through a spatially dependent
mean field. This method reproduces the Landau damping results for spin-waves in
unbounded systems obtained with a dielectric formalism. In trapped systems, the
simulations indicate that Landau damping occurs for a given spin-wave mode
because of resonant phase space trajectories in which spins are ""kicked out"" of
the mode (in spin space). A perturbative analysis of the resonant and nearly
resonant trajectories gives the Landau damping rate, which is calculated for
the dipole and quadrupole modes as a function of the interaction strength. The
results are compared to a numerical solution of the kinetic equation by Nikuni
et al.",0502189v1
2005-06-21,Spin wave contribution to the nuclear spin-lattice relaxation in triplet superconductors,"We discuss collective spin wave excitations in triplet superconductors with
an easy axis anisotropy for the order parameter. Using a microscopic model for
interacting electrons we estimate the frequency of such excitations in
Bechgaard salts and ruthenate superconductors to be one and twenty GHz
respectively. We introduce an effective bosonic model to describe spin-wave
excitations and calculate their contribution to the nuclear spin lattice
relaxation rate. We find that in the experimentally relevant regime of
temperatures, this mechanism leads to the power law scaling of 1/T_1 with
temperature. For two and three dimensional systems the scaling exponents are
three and five respectively. We discuss experimental manifestations of the spin
wave mechanism of the nuclear spin lattice relaxation.",0506548v1
2008-10-27,Anisotropic itinerant magnetism and spin fluctuations in BaFe2As2: A neutron scattering study,"Neutron scattering measurements were performed to investigate magnetic
excitations in a single-crystal sample of the ternary iron arsenide BaFe2As2, a
parent compound of a recently discovered family of Fe-based superconductors. In
the ordered state, we observe low energy spin-wave excitations with a gap
energy of 9.8(4) meV. The in-plane spin-wave velocity v_ab and out-of-plane
spin-wave velocity v_c measured at 12 meV are 280(150) and 57(7) meV A,
respectively. At high energy, we observe anisotropic scattering centered at the
antiferromagnetic wave vectors. This scattering indicates two-dimensional spin
dynamics, which possibly exist inside the Stoner continuum. At T_N=136(1) K,
the gap closes, and quasi-elastic scattering is observed above T_N, indicative
of short-range spin fluctuations. In the paramagnetic state, the scattering
intensity along the L direction becomes ""rodlike,"" characteristic of
uncorrelated out-of-plane spins, attesting to the two-dimensionality of the
system.",0810.4790v2
2011-02-27,Multiorbital Spin Susceptibility in a Magnetically Ordered State - Orbital versus Excitonic Spin Density Wave Scenario,"We present a general theory of multiorbital spin waves in magnetically
ordered metallic systems. Motivated by the itinerant magnetism of iron-based
superconductors, we compare the magnetic excitations for two different
scenarios: when the magnetic order either sets in on the on-site orbital level;
or when it appears as an electron-hole pairing between different bands of
electron and hole character. As an example we treat the two-orbital model for
iron-based superconductors. For small magnetic moments the spin excitations
look similar in both scenarios. Going to larger interactions and larger
magnetic moments, the difference between both scenarios becomes striking. While
in the excitonic scenario the spin waves form a closed structure over the
entire Brillouin zone and the particle-hole continuum is gapped, the spin
excitations in the orbital scenario can be treated as spin waves only in a
close vicinity to the ordering momenta. The origin of this is a gapless
electronic structure with Dirac cones which is a source of large damping. We
analyze our results in connection with recent neutron scattering measurements
and show that certain features of the orbital scenario with multiple order
parameters can be observed experimentally.",1102.5532v1
2017-05-09,Topological spin dynamics in cubic FeGe near room temperature,"Understanding spin-wave dynamics in chiral magnets is a key step for the
development of high-speed, spin-wave based spintronic devices that take
advantage of chiral and topological spin textures for their operation. Here we
present an experimental and theoretical study of spin-wave dynamics in a cubic
B20 FeGe single crystal. Using the combination of waveguide microwave
absorption spectroscopy (MAS), micromagnetic simulations, and analytical
theory, we identify the resonance dynamics in all magnetic phases (field
polarized, conical, helical, and skyrmion phases). Because the resonance
frequencies of specific chiral spin textures are unique, quantitative agreement
between our theoretical predictions and experimental findings for all resonance
frequencies and spin wave modes enables us to unambiguously identify chiral
magnetic phases and to demonstrate that MAS is a powerful tool to efficiently
extract a magnetic phase diagram. These results provide a new tool to
accelerate the integration of chiral magnetic materials into spintronic
devices.",1705.03397v1
2012-09-07,Chiral Spin Waves in Fermi Liquids with Spin-Orbit Coupling,"We predict the existence of chiral spin waves collective modes in a
two-dimensional Fermi liquid with the Rashba or Dresselhaus spin-orbit
coupling. Starting from the phenomenological Landau theory, we show that the
long-wavelength dynamics of magnetization is governed by the Klein- Gordon
equations. The standing-wave solutions of these equations describe ""particles""
with effective masses, whose magnitudes and signs depend on the strength of the
electron-electron interaction. The spectrum of the spin-chiral modes for
arbitrary wavelengths is determined from the Dyson equation for the interaction
vertex. We propose to observe spin-chiral modes via microwave absorption of
standing waves confined by an in-plane profile of the spin-orbit splitting.",1209.1647v1
2016-03-30,Low-damping transmission of spin waves through YIG/Pt-based layered structures for spin-orbit-torque applications,"We show that in YIG-Pt bi-layers, which are widely used in experiments on the
spin transfer torque and spin Hall effects, the spin-wave amplitude
significantly decreases in comparison to a single YIG film due to the
excitation of microwave eddy currents in a Pt coat. By introducing a novel
excitation geometry, where the Pt layer faces the ground plane of a microstrip
line structure, we suppressed the excitation of the eddy currents in the Pt
layer and, thus, achieved a large increase in the transmission of the
Damon-Eshbach surface spin wave. At the same time, no visible influence of an
external dc current applied to the Pt layer on the spin-wave amplitude in the
YIG-Pt bi-layer was observed in our experiments with YIG films of micrometer
thickness.",1603.09201v1
2021-08-12,Magnetic interactions and spin excitations in van der Waals ferromagnet VI$_3$,"Using a combination of density functional theory (DFT) and spin-wave theory
methods, we investigate the magnetic interactions and spin excitations in
semiconducting VI$_3$. Exchange parameters of monolayer, bilayer, and bulk
forms are evaluated by mapping the magnetic energies of various spin
configurations, calculated using DFT+$U$, onto the Heisenberg model. The
intralayer couplings remain largely unchanged in three forms of VI$_3$, while
the interlayer couplings show stronger dependence on the dimensionality of the
materials. We calculate the spin-wave spectra within a linear spin-wave theory
and discuss how various exchange parameters affect the magnon bands. The
magnon-magnon interaction is further incorporated, and the Curie temperature is
estimated using a self-consistently renormalized spin-wave theory. To
understand the roles of constituent atoms on magnetocrystalline anisotropy
energy (MAE), we resolve MAE into sublattices and find that a strong negative
V-I inter-sublattice contribution is responsible for the relatively small
easy-axis MAE in VI$_3$.",2108.05528v1
2017-03-22,Quantum spin Hall density wave insulator of correlated fermions,"We present the theory of a new type of topological quantum order which is
driven by the spin-orbit density wave order parameter, and distinguished by
$Z_2$ topological invariant. We show that when two oppositely polarized chiral
bands [resulting from the Rashba-type spin-orbit coupling $\alpha_k$, $k$ is
crystal momentum] are significantly nested by a special wavevector ${\bf
Q}\sim(\pi,0)/(0,\pi)$, it induces a spatially modulated inversion of the
chirality ($\alpha_{k+Q}=\alpha_k^*$) between different sublattices. The
resulting quantum order parameters break translational symmetry, but preserve
time-reversal symmetry. It is inherently associated with a $Z_2$-topological
invariant along each density wave propagation direction. Hence it gives a weak
topological insulator in two dimensions, with even number of spin-polarized
boundary states. This phase is analogous to the quantum spin-Hall state, except
here the time-reversal polarization is spatially modulated, and thus it is
dubbed quantum spin-Hall density wave (QSHDW) state. This order parameter can
be realized or engineered in quantum wires, or quasi-2D systems, by tuning the
spin-orbit couping strength and chemical potential to achieve the special
nesting condition.",1703.07629v1
2021-07-19,Damped Dirac magnon in a metallic kagome antiferromagnet FeSn,"The kagome lattice is a fertile platform to explore topological excitations
with both Fermi-Dirac and Bose-Einstein statistics. While relativistic Dirac
Fermions and flat-bands have been discovered in the electronic structure of
kagome metals, the spin excitations have received less attention. Here we
report inelastic neutron scattering studies of the prototypical kagome magnetic
metal FeSn. The spectra display well-defined spin waves extending up to 120
meV. Above this energy, the spin waves become progressively broadened,
reflecting interactions with the Stoner continuum. Using linear spin wave
theory, we determine an effective spin Hamiltonian that reproduces the measured
dispersion. This analysis indicates that the Dirac magnon at the K-point
remarkably occurs on the brink of a region where well-defined spin waves become
unobservable. Our results emphasize the influential role of itinerant carriers
on the topological spin excitations of metallic kagome magnets.",2107.08915v1
2023-01-12,Towards Magnonic Logic and Neuromorphic Computing: Controlling Spin-Waves by Spin-Polarized Current,"Spin-waves (magnons) are among the prime candidates for building fast yet
energy-efficient platforms for information transport and computing. We here
demonstrate theoretically and in state-of-the-art micromagnetic simulation the
effects that strategically-injected spin-polarized current can have on
controlling magnonic transport. We reveal analytically that the Zhang-Li
spin-transfer-torque induced by applied current is analogous to the
Dzyaloshinskii-Moriya interaction for scattering the magnons in the linear
regime, to then provide a generalized Snell's law that describes the spin-wave
propagation across regions with different current densities. We validate the
latter in numerical simulations of realistic systems, and exemplify how these
findings may help advance the design of spin-wave logic and neuromorphic
computing devices.",2301.04922v1
2023-10-02,Breakdown of Linear Spin-Wave Theory in a Non-Hermitian Quantum Spin Chain,"We present the spin-wave theory of the excitation spectrum and quench
dynamics of the non-Hermitian transverse-field Ising model. The complex
excitation spectrum is obtained for a generic hypercubic lattice using the
linear approximation of the Holstein-Primakoff transformation together with the
complex bosonic Bogolyubov transformation. In the one-dimensional case, our
result compares very well with the exact quasiparticle dispersion relation
obtained via a fermionic representation of the problem, at least in the regime
of large dissipation and transverse field. When applied to the quench dynamics
we show however that the linear spin-wave approximation breaks down and the
bosonic theory is plagued by a divergence at finite times. We understand the
origin of this instability using a single mode approximation. While limited to
short times, we show that this approach allows us to characterize the dynamics
arising from the quench of the dissipative term and the structure of the
Lieb-Robinson light-cone of the propagation quantum correlations. Furthermore,
for the one-dimensional case, the linear spin-wave dynamics shows good
agreement with the exact fermionic solution, both for the local magnetization
and the spin-spin correlations.",2310.00985v1
2005-02-14,1/S-expansion study of spin waves in a two-dimensional Heisenberg antiferromagnet,"We study the effects of quantum fluctuations on excitation spectra in the
two-dimensional Heisenberg antiferromagnet by means of the 1/S expansion. We
calculate the spin-wave dispersion and the transverse dynamical structure
factor up to the second order of 1/S in comparison with inelastic neutron
scattering experiments. The spin-wave energy at momentum $(\pi,0)$ is found to
be about 2% smaller than that at $(\pi/2,\pi/2)$ due to the second-order
correction. In addition, we study the dimensional crossover from two dimensions
to one dimension by weakening exchange couplings in one direction. It is found
that the second-order correction becomes large with approaching the quasi-one
dimensional situation and makes the spin-wave energy approach to the des
Cloizeaux-Pearson boundary for $S=1/2$. The transverse dynamical structure
factor is also calculated up to the second order of 1/S. It is shown that the
intensity of spin-wave peak is strongly reduced while the intensity of
three-spin-wave continuum becomes large and exceeds that of the spin-wave peak
in the quasi-one dimensional situation.",0502318v2
2009-07-31,Magnetic Cellular Nonlinear Network with Spin Wave Bus for Image Processing,"We describe and analyze a cellular nonlinear network based on magnetic
nanostructures for image processing. The network consists of magneto-electric
cells integrated onto a common ferromagnetic film - spin wave bus. The
magneto-electric cell is an artificial two-phase multiferroic structure
comprising piezoelectric and ferromagnetic materials. A bit of information is
assigned to the cell's magnetic polarization, which can be controlled by the
applied voltage. The information exchange among the cells is via the spin waves
propagating in the spin wave bus. Each cell changes its state as a combined
effect of two: the magneto-electric coupling and the interaction with the spin
waves. The distinct feature of the network with spin wave bus is the ability to
control the inter-cell communication by an external global parameter - magnetic
field. The latter makes possible to realize different image processing
functions on the same template without rewiring or reconfiguration. We present
the results of numerical simulations illustrating image filtering, erosion,
dilation, horizontal and vertical line detection, inversion and edge detection
accomplished on one template by the proper choice of the strength and direction
of the external magnetic field. We also present numerical assets on the major
network parameters such as cell density, power dissipation and functional
throughput, and compare them with the parameters projected for other
nano-architectures such as CMOL-CrossNet, Quantum Dot Cellular Automata, and
Quantum Dot Image Processor. Potentially, the utilization of spin waves
phenomena at the nanometer scale may provide a route to low-power consuming and
functional logic circuits for special task data processing.",0907.5453v1
2011-02-15,Tunneling properties of Bogoliubov mode and spin wave modes in supercurrent states of a spin-1 ferromagnetic spinor Bose-Einstein condensate,"We investigate tunneling properties of collective excitations in the
ferromagnetic phase of a spin-1 spinor Bose-Einstein condensate (BEC). In
addition to the Bogoliubov mode, this superfluid phase has two spin
excitations, namely, the gapless transverse spin wave and the quadrupolar mode
with a finite excitation gap. In the mean-field theory at T=0, we examine how
these collective modes tunnel through a barrier potential that couples to the
local density of particles. In the presence of supercurrent with a finite
momentum $q$, while the Bogoliubov mode shows the so-called anomalous tunneling
behavior (which is characterized by perfect transmission) in the low energy
limit, the transverse spin-wave transmits perfectly only when the momentum $k$
of this mode coincides with $\pm q$. At $k=\pm q$, the wave function of this
spin wave has the same form as the condensate wave function in the current
carrying state, so that the mechanism of this perfect transmission is found to
be the same as tunneling of supercurrent. Using this fact, the perfect
transmission of the spin wave is proved for a generic barrier potential. We
show that such perfect transmission does not occur in the quadrupolar mode.
Further, we consider the effects of potentials breaking U(1) and spin rotation
symmetries on the transmission properties of excitations. Our results would be
useful for understanding excitation properties of spinor BECs, as well as the
anomalous tunneling phenomenon in Bose superfluids.",1102.3113v1
2019-02-11,Spin-wave phase inverter upon a single nanodefect,"Local modification of magnetic properties of nanoelements is a key to design
future-generation magnonic devices, in which information is carried and
processed via spin waves. One of the biggest challenges here is to fabricate
simple and miniature phase-controlling elements with broad tunability. Here, we
successfully realize such spin-wave phase shifter upon a single nanogroove
milled by focused ion beam in a Co-Fe microsized magnonic waveguide. By varying
the groove depth and the in-plane bias magnetic field we continuously tune the
spin-wave phase and experimentally evidence a complete phase inversion. The
microscopic mechanism of the phase shift is based on the combined action of the
nanogroove as a geometrical defect and the lower spin-wave group velocity in
the waveguide under the groove where the magnetization is reduced due to the
incorporation of Ga ions during the ion-beam milling. The proposed phase
shifter can easily be on-chip integrated with spin-wave logic gates and other
magnonic devices. Our findings are crucial for designing nano-magnonic circuits
and for the development of spin-wave nano-optics.",1902.03758v1
2017-01-09,Spin-Wave Modes in Transition from a Thin Film to a Full Magnonic Crystal,"Spin-wave modes are studied under the gradual transition from a flat thin
film to a 'full' (one-dimensional) magnonic crystal. For this purpose, the
surface of a pre-patterned 36.8 nm thin permalloy film was sequentially ion
milled resulting in magnonic hybrid structures, referred to as
surface-modulated magnonic crystals, with increasing modulation depth. After
each etching step, ferromagnetic resonance measurements were performed yielding
the spin-wave resonance modes in backward-volume and Damon-Eshbach geometry.
The spin-wave spectra of these hybrid systems reveal an even larger variety of
spin-wave states compared to the 'full' magnonic crystal. The measurements are
corroborated by quasi-analytical theory and micromagnetic simulations in order
to study the changing spin-wave mode character employing spin-wave mode
profiles. In backward-volume geometry, a gradual transition from the uniform
mode in the film limit to a fundamental mode in the thin part of the magnonic
crystal was observed. Equivalently, the first and the second film modes are
transform into a center and an edge mode of the thick part of the magnonic
crystal. Simple transition rules from the $n^{\mathrm{th}}$ film mode to the
$m^{\mathrm{th}}$ mode in the 'full' magnonic crystal are formulated unraveling
the complex mode structure particularly in the backward-volume geometry. An
analogous analysis was performed in the Damon-Eshbach geometry.",1702.05675v3
2021-04-09,Measuring the dispersion relations of spin wave bands using time-of-flight spectroscopy,"We develop a generic all-inductive procedure to measure the band structure of
spin waves in a magnetic thin stripe. In contrast to existing techniques, our
method works even if several spin wave branches coexist in the investigated
frequency interval, provided that the branches possess sufficiently different
group velocities. We first measure the microwave scattering matrix of a network
composed of distant antennas inductively coupled to the spin wave bath of the
magnetic film. After a mathematical transformation to the time-domain to get
the transmission impulse response, the different spin wave branches are viewed
as wavepackets that reach successively the receiving antenna after different
travel times. In analogy with time-of flight spectroscopy, the wavepackets are
then separated by time-gating. The time-gated responses are used to recalculate
the contribution of each spin wave branch to the frequency domain scattering
matrix. The dispersion relation of each branch stems from the absolute phase of
the time-gated transmission parameter. The spin wave wavevector can be
determined unambiguously if the results for several propagation distances are
combined, so as to get the dispersion relations.",2104.04262v2
2021-04-16,Implementing a magnonic time-delay reservoir computer model,"Recently we demonstrated experimentally that microwave oscillators based on
the time delay feedback provided by traveling spin waves could operate as
reservoir computers. In the present paper, we extend this concept by adding the
feature of time multiplexing made available by the large propagation
times/distances of traveling spin waves. The system utilizes the nonlinear
behavior of propagating magnetostatic surface spin waves in a yttrium-iron
garnet thin film and the time delay inherent in the active ring configuration
to process time dependent data streams. Higher reservoir dimensionality is
obtained through the time-multiplexing method, emulating ""virtual"" neurons as
temporally separated spin-wave pulses circulating in the active ring below the
auto-oscillation threshold. To demonstrate the efficacy of the concept, the
active ring reservoir computer is evaluated on the short-term memory and parity
check benchmark tasks, and the physical system parameters are tuned to optimize
performance. By incorporating a reference line to mix the input signal directly
onto the active ring output, both the amplitude and phase nonlinearity of the
spin waves can be exploited, resulting in significant improvement on the
nonlinear parity check task. We also find that the fading memory capacity of
the system can be easily tuned by controlling the active ring gain. Finally, we
show that the addition of a second spin-wave delay line configured to transmit
backward volume spin waves can partly compensate dispersive pulse broadening
and enhance the fading memory capacity of the active ring.",2104.07879v1
2017-03-20,Spin-Wave Dynamics in the Presence of Magnetic Vortices,"This chapter describes spin-wave excitations in nanosized dots and rings in
the presence of the vortex state. The special attention is paid to the
manifestation of the competition between exchange and dipolar interactions in
the spin-wave spectrum as well as the correlation between the spectrum and the
stability of the vortex. The calculation method uses the dynamic matrix for an
all-discrete system, the numerical diagonalization of which yields the spectrum
of frequencies and spin-wave profiles of normal modes of the dot. We study
in-plane vortices of two types: a circular magnetization in circular dots and
rings and the Landau state in square rings. We examine the influence of the
dipolar-exchange competition and the geometry of the dot on the stability of
the vortex and on the spectrum of spin waves. We show that the lowest-frequency
mode profile proves to be indicative of the dipolar-to-exchange interaction
ratio and the vortex stability is closely related to the spin-wave profile of
the soft mode. The negative dispersion relation is also shown. Our results
obtained for in-plane vortices are in qualitative agreement with results for
core-vortices obtained from experiments, micromagnetic simulations, and
analytical calculations.",1703.06668v1
2019-01-02,Skyrmion Tubes as Magnonic Waveguides,"Various latest experiments have proven the theoretical prediction that domain
walls in planar magnetic structures can channel spin waves as outstanding
magnonic waveguides, establishing a superb platform for building magnonic
devices. Recently, three-dimensional nanomagnetism has been boosted up and
become a significant branch of magnetism, because three-dimensional magnetic
structures expose a lot of emerging physics hidden behind planar ones and will
inevitably provide broader room for device engineering. Skyrmions and
antiSkyrmions, as natural three-dimensional magnetic configurations, are not
considered yet in the context of spin-wave channeling and steering. Here, we
show that skyrmion tubes can act as nonplanar magnonic waveguides if excited
suitably. An isolated skyrmion tube in a magnetic nanoprism induces spatially
separate internal and edge channels of spin waves; the internal channel has a
narrower energy gap, compared to the edge channel, and accordingly can transmit
signals at lower frequencies. Additionally, we verify that those spin-wave
beams along magnetic nanoprism are restricted to the regions of potential
wells. Transmission of spin-wave signals in such waveguides results from the
coherent propagation of locally driven eigenmodes of skyrmions, i.e., the
breathing and rotational modes. Finally, we find that spin waves along the
internal channels are less susceptible to magnetic field than those along the
edge channels. Our work will open a new arena for spin-wave manipulation and
help bridge skyrmionics and magnonics.",1901.00253v1
2020-06-28,Hydrodynamics of quantum corrections to the Coulomb interaction via the third rank tensor evolution equation: Application to the Langmuir waves and the spin-electron-acoustic waves,"If we study the quantum effects in plasmas in terms of traditional
hydrodynamics via the continuity and Euler equations we find the quantum Bohm
potential and the force of spin-spin interaction. However, if we extend the set
hydrodynamic equations beyond the 13-moments approximation, and include the
third rank tensor evolution equation along with the pressure evolution
equation, we obtain the quantum corrections to the Coulomb interaction. It is
found in contrast with the fact that hydrodynamic equations for the higher rank
tensors do not contain interaction in the classic plasmas studied in the
selfconsistent (meanfield) approximation. Therefore, we present the quantum
hydrodynamic model, where the quantum effects are studied beyond the quantum
Bohm potential. Developed model is considered in two regimes: all electrons in
plasmas are considered as the single fluid, and the separate spin evolution
regime, where electrons with different spin projections are considered as two
different fluids. To illustrate the fundamental meaning of found quantum
effects we demonstrate their contribution in the spectrum of the Langmuir waves
and the spin-electron-acoustic waves. It is worth to mention that the
application of the pressure evolution equation ensures that the contribution of
pressure in the Langmuir wave spectrum is proportional to $(3/5)v_{Fe}^{2}$,
unlike $(1/3)v_{Fe}^{2}$ appearing from hydrodynamics based on the continuity
and Euler equations, where $v_{Fe}$ is the Fermi velocity. Same correction
corresponds on other plasmas phenomena like the speed of sound for
spin-electron-acoustic waves. Moreover, it is found that novel quantum effects
provide the novel wave solutions.",2006.15656v1
2023-06-27,"Three-dimensional spin-wave dynamics, localization and interference in a synthetic antiferromagnet","Spin waves are collective perturbations in the orientation of the magnetic
moments in magnetically ordered materials. Their rich phenomenology is
intrinsically three-dimensional; however, the three-dimensional imaging of spin
waves has so far not been possible. Here, we image the three-dimensional
dynamics of spin waves excited in a synthetic antiferromagnet, with nanoscale
spatial resolution and sub-ns temporal resolution, using time-resolved magnetic
laminography. In this way, we map the distribution of the spin-wave modes
throughout the volume of the structure, revealing unexpected depth-dependent
profiles originating from the interlayer dipolar interaction. We experimentally
demonstrate the existence of complex three-dimensional interference patterns
and analyze them via micromagnetic modelling. We find that these patterns are
generated by the superposition of spin waves with non-uniform amplitude
profiles, and that their features can be controlled by tuning the composition
and structure of the magnetic system. Our results open unforeseen possibilities
for the study and manipulation of complex spin-wave modes within nanostructures
and magnonic devices.",2306.15404v2
2017-12-21,Exchange-torque-induced excitation of perpendicular standing spin waves in nanometer-thick YIG films,"Spin waves in ferrimagnetic yttrium iron garnet (YIG) films with ultralow
magnetic damping are relevant for magnon-based spintronics and low-power
wave-like computing. The excitation frequency of spin waves in YIG is rather
low in weak external magnetic fields because of its small saturation
magnetization, which limits the potential of YIG films for high-frequency
applications. Here, we demonstrate how exchange-coupling to a CoFeB film
enables efficient excitation of high-frequency perpendicular standing spin
waves (PSSWs) in nanometer-thick (80 nm and 295 nm) YIG films using uniform
microwave magnetic fields. In the 295-nm-thick YIG film, we measure intense
PSSW modes up to 10th order. Strong hybridization between the PSSW modes and
the ferromagnetic resonance mode of CoFeB leads to characteristic anti-crossing
behavior in broadband spin-wave spectra. A dynamic exchange torque at the
YIG/CoFeB interface explains the excitation of PSSWs. The localized torque
originates from exchange coupling between two dissimilar magnetization
precessions in the YIG and CoFeB layers. As a consequence, spin waves are
emitted from the YIG/CoFeB interface and PSSWs form when their wave vector
matches the perpendicular confinement condition. PSSWs are not excited when the
exchange coupling between YIG and CoFeB is suppressed by a Ta spacer layer.
Micromagnetic simulations confirm the exchange-torque mechanism.",1712.08204v1
2020-01-30,Electrical spectroscopy of forward volume spin waves in perpendicularly magnetized materials,"We study the potential of all-electrical inductive techniques for the
spectroscopy of propagating forward volume spin waves. We develop a
one-dimensional model to account for the electrical signature of spin-wave
reflection and transmission between inductive antennas and validate it with
experiments on a perpendicularly magnetized Co/Ni multilayer. We describe the
influence of the antenna geometry and antenna-to-antenna separation, as well as
that of the material parameters on the lineshape of the inductive signals. For
a finite damping, the broadband character of the antenna emission in the wave
vector space imposes to take into account the growing decoherence of the
magnetization waves upon their spatial propagation. The transmission signal can
be viewed as resulting from two contributions: a first one from propagating
spin-waves leading to an oscillatory phase of the broadband transmission
coefficient, and another one originating from the distant induction of
ferromagnetic resonance because of the long-range stray fields of realistic
antennas. Depending on the relative importance of these two contributions, the
decay of the transmitted signal with the propagation distance may not be
exponential and the oscillatory character of the spin-wave phase upon
propagation may be hidden. Our model and its experimental validation allow to
define geometrical and material specifications to be met to enable the use of
forward volume spin waves as efficient information carriers.",2001.11483v1
2020-10-29,Atomic spin-wave control and spin-dependent kicks with shaped subnanosecond pulses,"The absorption of traveling photons resonant with electric dipole transitions
of an atomic gas naturally leads to electric dipole spin wave excitations. For
a number of applications, it would be highly desirable to shape and coherently
control the spatial waveform of the spin waves before spontaneous emission can
occur. This paper details a recently developed optical control technique to
achieve this goal, where counter-propagating, shaped sub-nanosecond pulses
impart sub-wavelength geometric phases to the spin waves by cyclically driving
an auxiliary transition. In particular, we apply this technique to reversibly
shift the wave vector of a spin wave on the $D2$ line of laser-cooled $^{87}$Rb
atoms, by driving an auxiliary $D1$ transition with shape-optimized pulses, so
as to shut off and recall superradiance on demand. We investigate a
spin-dependent momentum transfer during the spin-wave control process, which
leads to a transient optical force as large as $\sim 1\hbar k$/ns, and study
the limitations to the achieved $70\sim 75\%$ spin wave control efficiency by
jointly characterizing the spin-wave control and matterwave acceleration. Aided
by numerical modeling, we project potential future improvements of the control
fidelity to the $99\%$ level when the atomic states are better prepared and by
equipping a faster and more powerful pulse shaper. Our technique also enables a
background-free measurement of the superradiant emission to unveil the precise
scaling of the emission intensity and decay rate with optical depth.",2010.16066v2
2017-11-21,Eavesdropping on spin waves inside the domain-wall nanochannel via three-magnon processes,"One recent breakthrough in the field of magnonics is the experimental
realization of reconfigurable spin-wave nanochannels formed by magnetic domain
wall with a width of $10-100$ nm [Wagner \emph{et al}., Nat. Nano. \textbf{11},
432 (2016)]. This remarkable progress enables an energy-efficient spin-wave
propagation with a well-defined wave vector along its propagating path inside
the wall. In the mentioned experiment, a micro-focus Brillouin light scattering
spectroscopy was taken in a line-scans manner to measure the frequency of the
bounded spin wave. Due to their localization nature, the confined spin waves
can hardly be detected from outside the wall channel, which guarantees the
information security to some extent. In this work, we theoretically propose a
scheme to detect/eavesdrop on the spin waves inside the domain-wall nanochannel
via nonlinear three-magnon processes. We send a spin wave in one magnetic
domain to interact with the bounded mode in the wall. Two kinds of three-magnon
processes, i.e., confluence and splitting, are expected to occur. The
confluence process is conventional. We predict a stimulated three-magnon
splitting (or ""magnon laser"") effect: the presence of a bound magnon
propagating along the domain wall channel assists the splitting of the incident
wave into two modes, one of which is identical to the bound mode in the
channel. Micromagnetic simulations confirm our theoretical analysis. These
results demonstrate that one is able to uniquely infer the spectrum of the
spin-wave in the domain-wall nanochannel once we know both the injection and
the transmitted waves.",1711.07615v2
2012-10-30,Spin-singlet Gaffnian wave function for fractional quantum Hall systems,"We characterize in detail a wave function conceivable in fractional quantum
Hall systems where a spin or equivalent degree of freedom is present. This wave
function combines the properties of two previously proposed quantum Hall wave
functions, namely the non-Abelian spin-singlet state and the nonunitary
Gaffnian wave function. This is a spin-singlet generalization of the
spin-polarized Gaffnian, which we call the ""spin-singlet Gaffnian"" (SSG). In
this paper we present evidence demonstrating that the SSG corresponds to the
ground state of a certain local Hamiltonian, which we explicitly construct,
and, further, we provide a relatively simple analytic expression for the unique
ground-state wave functions, which we define as the zero energy eigenstates of
that local Hamiltonian. In addition, we have determined a certain nonunitary,
rational conformal field theory which provides an underlying description of the
SSG and we thus conclude that the SSG is ungapped in the thermodynamic limit.
In order to verify our construction, we implement two recently proposed
techniques for the analysis of fractional quantum Hall trial states: The ""spin
dressed squeezing algorithm"", and the ""generalized Pauli principle"".",1210.8143v3
2021-02-13,Accumulation and control of spin waves in magnonic dielectric microresonators by a comb of ultrashort laser pulses,"Spin waves in magnetic microresonators are at the core of modern magnonics.
Here we demonstrate a new method of tunable excitation of different spin wave
modes in magnetic microdisks by using a train of laser pulses coming at a
repetition rate higher than the decay rate of spin precession. The microdisks
are etched in a transparent bismuth iron garnet film and the light pulses
influence the spins nonthermally through the inverse Faraday effect. The high
repetition rate of the laser stimulus of 10 GHz establishes an interplay
between the spin wave resonances in the frequency and momentum domains. As a
result, scanning of the focused laser spot near the disk boarder changes
interference pattern of the magnons and leads to a resonant dependence of the
spin wave amplitude on the external magnetic field. Apart from that, we
achieved a switching between volume and surface spin waves by a small variation
of the external magnetic field.",2102.07021v4
2021-02-26,Gapless Spin Wave Transport through a Quantum Canted-Antiferromagnet,"In the Landau levels of a two-dimensional electron system or when flat bands
are present, e.g. in twisted van der Waals bilayers, strong electron-electron
interaction gives rise to quantum Hall ferromagnetism with spontaneously broken
symmetries in the spin and isospin sectors. Quantum Hall ferromagnets support a
rich variety of low-energy collective excitations that are instrumental to
understand the nature of the magnetic ground states and are also potentially
useful as carriers of quantum information. Probing such collective excitations,
especially their dispersion {\omega}(k), has been experimentally challenging
due to small sample size and measurement constraints. In this work, we
demonstrate an all-electrical approach that integrates a Fabry-P\'erot cavity
with non-equilibrium transport to achieve the excitation, wave vector selection
and detection of spin waves in graphene heterostructures. Our experiments
reveal gapless, linearly dispersed spin wave excitations in the E = 0 Landau
level of bilayer graphene, thus providing direct experimental evidence for a
predicted canted antiferromagnetic order. We show that the gapless spin wave
mode propagates with a high group velocity of several tens of km/s and
maintains phase coherence over a distance of many micrometers. Its dependence
on the magnetic field and temperature agree well with the hydrodynamic theory
of spin waves. These results lay the foundation for the quest of spin
superfluidity in this high-quality material. The resonant cavity technique we
developed offers a powerful and timely method to explore the collective
excitation of many spin and isospin-ordered many-body ground states in van der
Waals heterostructures and open the possibility of engineering magnonic
devices.",2103.00018v1
2024-01-31,Magnetic polarons beyond linear spin-wave theory: Mesons dressed by magnons,"When a mobile hole is doped into an antiferromagnet, its movement will
distort the surrounding magnetic order and yield a magnetic polaron. The
resulting complex interplay of spin and charge degrees of freedom gives rise to
very rich physics and is widely believed to be at the heart of high-temperature
superconductivity in cuprates. In this paper, we develop a quantitative
theoretical formalism, based on the phenomenological parton description, to
describe magnetic polarons in the strong coupling regime. We construct an
effective Hamiltonian with weak coupling to the spin-wave excitations in the
background, making the use of standard polaronic methods possible. Our starting
point is a single hole doped into an AFM described by a 'geometric string'
capturing the strongly correlated hopping processes of charge and spin degrees
of freedom, beyond linear spin-wave approximation. Subsequently, we introduce
magnon excitations through a generalized 1/S expansion and derive an effective
coupling of these spin-waves to the hole plus the string (the meson) to arrive
at an effective polaron Hamiltonian with density-density type interactions.
After making a Born-Oppenheimer-type approximation, this system is solved using
the self-consistent Born approximation to extract the renormalized polaron
properties. We apply our formalism (i) to calculate beyond linear spin-wave
ARPES spectra, (ii) to reveal the interplay of ro-vibrational meson
excitations, and (ii) to analyze the pseudogap expected at low doping.
Moreover, our work paves the way for exploring magnetic polarons out-of
equilibrium or in frustrated systems, where weak-coupling approaches are
desirable and going beyond linear spin-wave theory becomes necessary.",2402.00130v1
2015-02-26,Unsteady self-sustained detonation waves in flake aluminum dust/air mixtures,"Self-sustained detonation waves in flake aluminum dust/air mixtures have been
studied in a tube of diameter 199 mm and length 32.4 m. A pressure sensor array
of 32 sensors mounted around certain circumferences of the tube was used to
measure the shape of the detonation front in the circumferential direction and
pressure histories of the detonation wave. A two-head spin detonation wave
front was observed for the aluminum dust/air mixtures, and the cellular
structure resulting from the spinning movement of the triple point was
analyzed. The variations in velocity and overpressure of the detonation wave
with propagation distance in a cell were studied. The interactions of waves in
triple-point configurations were analyzed and the flow-field parameters were
calculated. Three types of triple-point configuration exist in the wave front
of the detonation wave of an aluminum dust/air mixture. Both strong and weak
transverse waves exist in the unstable self-sustained detonation wave.",1503.01045v1
2022-03-03,Spin Hall effects and the localization of massless spinning particles,"The spin Hall effects of light represent a diverse class of
polarization-dependent physical phenomena involving the dynamics of
electromagnetic wave packets. In a medium with an inhomogeneous refractive
index, wave packets can be effectively described by massless spinning particles
following polarization-dependent trajectories. Similarly, in curved spacetime
the gravitational spin Hall effect of light is represented by
polarization-dependent deviations from null geodesics. In this paper, we
analyze the equations of motion describing the gravitational spin Hall effect
of light. We show that these equations are a special case of the
Mathisson-Papapetrou equations for spinning objects in general relativity. This
allows us to use several known results for the Mathisson-Papapetrou equations,
and apply them to the study of electromagnetic wave packets. We derive
conservation laws, we discuss the limits of validity of the spin Hall
equations, and we study how the energy centroids of wave packets, effectively
described as massless spinning particles, depend on the external choice of a
timelike vector field, representing a family of observers. In flat spacetime,
the relativistic Hall effect and the Wigner(-Souriau) translations are
recovered, while our equations also provide a generalization of these effects
in arbitrary spacetimes. We construct a large class of wave packets that can be
described by the spin Hall equations, but also find its limits by giving
examples of wave packets which are more general and are not described by the
spin Hall equations. Lastly, we examine the assumption that electromagnetic
wave packets are massless. While this is approximately true in many contexts,
it is not exact. We show that failing to carefully account for the limitations
of the massless approximation results in the appearance of unphysical centroids
which are nowhere near the wave packet itself.",2203.01753v2
1996-06-04,Direct Hopf Bifurcation in Parametric Resonance of Hybridized Waves,"We study parametric resonance of interacting waves having the same wave
vector and frequency. In addition to the well-known period-doubling instability
we show that under certain conditions the instability is caused by a Hopf
bifurcation leading to quasiperiodic traveling waves. It occurs, for example,
if the group velocities of both waves have different signs and the damping is
weak. The dynamics above the threshold is briefly discussed. Examples
concerning ferromagnetic spin waves and surface waves of ferro fluids are
discussed.",9605006v1
2004-09-26,The improvement wave equations of relativistic and non-relativistic quantum mechanics,"In this work, we follow the idea of the De Broglie's matter waves and the
analogous method that Schr\""{o}dinger founded wave equation, but we apply the
more essential Hamilton principle instead of the minimum action principle of
Jacobi which was used in setting up Schr\""{o}dinger wave equation. Thus, we
obtain a novel non-relativistic wave equation which is different from the
Schr\""{o}dinger equation, and relativistic wave equation including free and
non-free particle. In addition, we get the spin 1/2 particle wave equation in
potential field.",0409176v1
2009-03-09,An EOM-assisted wave-vector-resolving Brillouin light scattering setup,"Brillouin light scattering spectroscopy is a powerful technique which
incorporates several extensions such as space-, time-, phase- and wave-vector
resolution.
  Here, we report on the improvement of the wave-vector resolution by including
an electro-optical modulator. This provides a reference to calibrate the
position of the diaphragm hole which is used for wave-vector selection. The
accuracy of this calibration is only limited by the accuracy of the wave-vector
measurement itself. To demonstrate the validity of the approach the wave
vectors of dipole-dominated spin waves excited by a microstrip antenna were
measured.",0903.1536v1
2021-08-16,Losses of Interface Waves in Plasmonic and Gyrotropic Structures,"The loss mechanisms of slow interface waves in the layered resonant media are
examined and illustrated by the examples of (i) surface plasmon polaritons in
an isotropic plasma layer, (ii) magnetoplasmons in magnetised plasma and (iii)
spin waves in ferrimagnetic layers. It is shown that losses of all these
interface waves grow at the same rate of Im(gamma) ~ Re(gamma^3), where gamma
is the wavenumber. These abnormal losses are caused by vortices of the power
flow of the interface waves near their resonance cut-off. The basic properties
of the slow interface waves discussed in the paper are inherent to the waves of
hyperbolic type in the layered resonant media.",2108.07180v1
2015-12-05,Kinetic theory of spin-polarized systems in electric and magnetic fields with spin-orbit coupling: II. RPA response functions and collective modes,"The spin and density response functions in the random phase approximation
(RPA) are derived by linearizing the kinetic equation including a magnetic
field, the spin-orbit coupling, and mean fields with respect to an external
electric field. Different polarization functions appear describing various
precession motions showing Rabi satellites due to an effective Zeeman field.
The latter turns out to consist of the mean-field magnetization, the magnetic
field, and the spin-orbit vector. The collective modes for charged and neutral
systems are derived and a threefold splitting of the spin waves dependent on
the polarization and spin-orbit coupling is shown. The dielectric function
including spin-orbit coupling, polarization and magnetic fields is presented
analytically for long wave lengths and in the static limit. The dynamical
screening length as well as the long-wavelength dielectric function shows an
instability in charge modes, which are interpreted as spin segregation and
domain formation. The spin response describes a crossover from damped
oscillatory behavior to exponentially damped behavior dependent on the
polarization and collision frequency. The magnetic field causes ellipsoidal
trajectories of the spin response to an external electric field and the
spin-orbit coupling causes a rotation of the spin axes. The spin-dephasing
times are extracted and discussed in dependence on the polarization, magnetic
field, spin-orbit coupling and single-particle relaxation times.",1512.01661v1
2003-04-17,Field-Induced Spin-Density-Wave Phases in Quasi-One-Dimensional Conductors: Theory versus Experiment,"We show that ""Quantizied Nesting"" model misses important features of the
magnetic field-induced spin-density-wave (FISDW) phase diagram. Among them are:
1) the FISDW wave vector is not strictly quantized; 2) in some compounds, the
FISDW diagram consists of two regions: a) at low temperatures, there are jumps
of the wave vector (i.e., the first order transitions between FISDW phases), b)
at high temperatures the jumps and the first order transitions disappear but
the wave vector is still a non-trivial function of a magnetic field. These are
in agreement with the experiments on (TMTSF)2PF6.",0304406v1
2005-10-31,Coexistence of double-Q spin density wave and multi-Q pair density wave in cuprate oxide superconductors,"Spatial 4a x 4a modulations, with a the lattice constant of CuO_2 planes, or
the so called checkerboards can arise from double-Q spin density wave (SDW)
with Q_1 = (pm pi/a, pm 3 pi/4a) and Q_2 = (pm 3 pi/4a, pm pi/a). When multi-Q
pair density wave, that is, the condensation of d gamma-wave Cooper pairs with
zero total momenta, pm 2Q_1, pm 2Q_2, pm 4Q_1, pm 4Q_2, and so on is induced by
the SDW, gaps can have fine structures similar to those of the so called
zero-temperature pseudogaps.",0510829v1
2012-04-11,Magnetostatic spin waves and magnetic-wave chaos in ferromagnetic films. II. Numerical simulations of non-linear waves,"A method and some results of numeric simulations of magnetostatic spin waves
in ferromagnetic films are exponded, in comparison with the theory earlier
presented in arXiv preprint 1204.0200. In particular, roles of films finiteness
(edges) and defects in formation of linear and non-linear magnetostatic wave
patterns, excitation and evolution of two-dimensional solitons, and chaotic
non-linear ferromagnetic resonance are considered.",1204.2423v1
2017-01-05,Wave Packet Dynamics in the Majorana Equation,"In the Majorana equation for particles with arbitrary spin, wave packets
occur due to not only the uncertainty that affects position and momentum but
also due to infinite components with decreasing mass that form the Majorana
spinor. In this paper, we prove that such components contribute to increase the
spreading of wave packets. Moreover, Zitterbewegung takes place in both the
time propagation of Dirac wave packets and in Majorana wave packets. However,
it shows a peculiar fine structure. Finally, group velocity always remains
subluminal and contributions due to infinite components decrease progressively
as spin increases.",1701.03012v1
2014-03-24,Spin wave imaging in atomically designed nanomagnets,"The spin dynamics of all ferromagnetic materials are governed by two types of
collective excitations: spin waves and domain walls. The fundamental processes
underlying these collective modes, such as exchange interactions and magnetic
anisotropy, all originate at the atomic scale; yet, conventional probing
techniques, based on neutron and photon scattering, provide high resolution in
reciprocal space, and thereby poor spatial resolution. Here we present direct
imaging of spin waves in individual chains of ferromagnetically coupled $S=2$
Fe atoms, assembled one by one on a Cu$_2$N surface using a scanning tunnelling
microscope. We are able to map the spin dynamics of these designer nanomagnets
with atomic resolution, in two complementary ways. First, atom to atom
variations of the amplitude of the quantized spin wave excitations, predicted
by theory, are probed using inelastic electron tunnelling spectroscopy. Second,
we observe slow stochastic switching between two opposite magnetisation states,
whose rate varies strongly depending on the location of the tip along the
chain. Our observations, combined with model calculations, reveal that switches
of the chain are initiated by a spin wave excited state which has its antinodes
at the edges of the chain, followed by a domain wall shifting through the chain
from one end to the other. This approach opens the way towards atomic scale
imaging of other types of spin excitations, such as spinons and fractional
end-states, in engineered spin chains.",1403.5890v1
2014-07-02,Spin Waves in Ferromagnetic Insulators Coupled via a Normal Metal,"Herein, we study the spin-wave dispersion and dissipation in a ferromagnetic
insulator--normal metal--ferromagnetic insulator system. Long-range dynamic
coupling because of spin pumping and spin transfer lead to collective magnetic
excitations in the two thin-film ferromagnets. In addition, the dynamic dipolar
field contributes to the interlayer coupling. By solving the
Landau-Lifshitz-Gilbert-Slonczewski equation for macrospin excitations and the
exchange-dipole volume as well as surface spin waves, we compute the effect of
the dynamic coupling on the resonance frequencies and linewidths of the various
modes. The long-wavelength modes may couple acoustically or optically. In the
absence of spin-memory loss in the normal metal, the spin-pumping-induced
Gilbert damping enhancement of the acoustic mode vanishes, whereas the optical
mode acquires a significant Gilbert damping enhancement, comparable to that of
a system attached to a perfect spin sink. The dynamic coupling is reduced for
short-wavelength spin waves, and there is no synchronization. For intermediate
wavelengths, the coupling can be increased by the dipolar field such that the
modes in the two ferromagnetic insulators can couple despite possible small
frequency asymmetries. The surface waves induced by an easy-axis surface
anisotropy exhibit much greater Gilbert damping enhancement. These modes also
may acoustically or optically couple, but they are unaffected by thickness
asymmetries.",1407.0635v1
2022-10-19,Improving the spin-down limits of the continuous gravitational waves emitted from rotating triaxial pulsars,"The spin-down limit of the continuous gravitational wave strain from pulsars
assumed to be triaxial stars rotating about a principal moment of inertia axis
depends upon the value of the intrinsic spin frequency derivative of the
pulsar, among other parameters. In order to get more accurate intrinsic spin
frequency derivative values, dynamical effects contributing to the measured
spin frequency derivative values must be estimated via more realistic
approaches. In this work, we calculated improved values for the spin-down limit
of the continuous gravitational wave strain (assuming that pulsars are triaxial
stars rotating about a principal moment of inertia axis) for a set of 237
pulsars for which a targeted search for continuous gravitational waves was
recently carried out by the LIGO-Virgo-KAGRA (LVK) Collaboration. We used
`GalDynPsr', a Python-based public package, to calculate more realistic values
for the intrinsic spin frequency derivatives and, consequently, we get more
realistic values of the spin-down limit. The realistic values that we obtain
for the intrinsic spin frequency derivatives can also provide a valuable
contribution to improving the sensitivity of searches for continuous
gravitational waves from known pulsars.",2210.10355v2
2023-10-09,Mapping of Spin-Wave Transport in Thulium Iron Garnet Thin Films Using Diamond Quantum Microscopy,"Spin waves, collective dynamic magnetic excitations, offer crucial insights
into magnetic material properties. Rare-earth iron garnets offer an ideal
spin-wave (SW) platform with long propagation length, short wavelength,
gigahertz frequency, and applicability to magnon spintronic platforms. Of
particular interest, thulium iron garnet (TmIG) has attracted a huge interest
recently due to its successful growth down to a few nanometers, observed
topological Hall effect and spin orbit torque-induced switching effects.
However, there is no direct spatial measurement of its SW properties. This work
uses diamond nitrogen vacancy (NV) magnetometry in combination with SW
electrical transmission spectroscopy to study SW transport properties in TmIG
thin films. NV magnetometry allows probing spin waves at the sub-micrometer
scale, seen by the amplification of the local microwave magnetic field due to
the coupling of NV spin qubits with the stray magnetic field produced by the
microwave-excited spin waves. By monitoring the NV spin resonances, the SW
properties in TmIG thin films are measured as function of the applied magnetic
field, including their amplitude, decay length (~ 50 um), and wavelength (0.8 -
2 um). These results pave the way for studying spin qubit-magnon interactions
in rare-earth magnetic insulators, relevant to quantum magnonics applications.",2310.06188v4
2013-12-19,Dynamics of a localized spin excitation close to the spin-helix regime,"The time evolution of a local spin excitation in a (001)-confined
two-dimensional electron gas subjected to Rashba and Dresselhaus spin-orbit
interactions of similar strength is investigated theoretically and compared
with experimental data. Specifically, the consequences of the finite spatial
extension of the initial spin polarization is studied for non-balanced Rashba
and Dresselhaus terms and for finite cubic Dresselhaus spin-orbit interaction.
We show that the initial out-of-plane spin polarization evolves into a helical
spin pattern with a wave number that gradually approaches the value $q_0$ of
the persistent spin helix mode. In addition to an exponential decay of the spin
polarization that is proportional to both the spin-orbit imbalance and the
cubic Dresselhaus term, the finite width $w$ of the spin excitation reduces the
spin polarization by a factor that approaches $\exp(-q_0^2 w^2/2)$ at longer
times.",1312.5529v1
2015-05-13,Excitations in a spin-polarized tow-dimensional electron gas,"A remarkably long-lived spin plasmon may exist in two-dimensional electron
liquids with imbalanced spin up and spin down population. Predictions for this
interesting mode by Agarwal et al. [Phys. Rev. B 90, 155409 (2014)] are based
on the random phase approximation. We here show how to account for spin
dependent correlations from known ground state pair correlation functions and
study the consequences on the various spin dependent longitudinal response
functions. The spin plasmon dispersion relation and its critical wave vector
for Landau damping by minority spins turn out to be significantly lowered. We
further demonstrate that spin dependent effective interactions imply a rich
structure in the excitation spectrum of the partially spin-polarized system.
Most notably, we find a ""magnetic antiresonance"", where the imaginary part of
both, the spin-spin as well as the density-spin response function vanish. The
resulting minimum in the double-differential cross section is awaiting
experimental confirmation.",1505.03370v3
2017-10-30,Spin-transfer Antiferromagnetic Resonance,"Currents can induce spin excitations in antiferromagnets, even when they are
insulating. We investigate how spin transfer can cause antiferromagnetic
resonance in bilayers and trilayers that consist of one antiferromagnetic
insulator and one or two metals. An ac voltage applied to the metal generates a
spin Hall current that drives the magnetic moments in the antiferromagnet. We
consider excitation of the macrospin mode and of transverse standing-spin-wave
modes. By solving the Landau-Lifshitz-Gilbert equation in the antiferromagnetic
insulator and the spin-diffusion equation in the normal metal, we derive
analytical expressions for the spin-Hall-magnetoresistance and spin-pumping
inverse-spin-Hall dc voltages. In bilayers, the two contributions compensate
each other and cannot easily be distinguished. We present numerical results for
a MnF$_2|$Pt bilayer. Trilayers facilitate separation of the
spin-Hall-magnetoresistance and spin-pumping voltages, thereby revealing more
information about the spin excitations. We also compute the decay of the pumped
spin current through the antiferromagnetic layer as a function of frequency and
the thickness of the antiferromagnetic layer.",1710.10909v1
2019-09-30,Ultrathin SnTe films as a route towards all-in-one spintronics devices,"Spin transistors based on a semiconducting channel attached to ferromagnetic
electrodes suffer from fast spin decay and extremely low spin
injection/detection efficiencies. Here, we propose an alternative all-in-one
spin device whose operation principle relies on electric manipulation of the
spin lifetime in two-dimensional (2D) SnTe, in which the sizable spin Hall
effect eliminates the need for using ferromagnets. In particular, we explore
the persistent spin texture (PST) intrinsically present in the ferroelectric
phase which protects the spin from decoherence and supports extraordinarily
long spin lifetime. Our first-principles calculations followed by symmetry
arguments revealed that such a spin wave mode can be externally detuned by
perpendicular electric field, leading to spin randomization and decrease in
spin lifetime. We further extend our analysis to ultrathin SnTe films and
confirm the emergence of PST as well as a moderate enhancement of intrinsic
spin Hall conductivity. The recent room-temperature observation of the
ferroelectric phase in 2D-SnTe suggests that novel all-electric spintronics
devices are within reach.",1909.13865v2
2000-08-23,"Two-step contribution to the spin-longitudinal and spin-transverse cross sections of the quasielastic (p,n) reactions","The two-step contribution to the spin-longitudinal and the spin-transverse
cross sections of ^{12}C,^{40}Ca(p,n) reactions at 494 MeV and 346 MeV is
calculated. We use a plane-wave approximation and evaluate the relative
contributions from the one-step and the two-step processes. We found that the
ratios of the two-step to the one-step processes are larger in the
spin-transverse cross sections than in the spin-longitudinal ones. Combining
these results with the distorted-wave impulse approximation (DWIA) results we
obtained considerable two-step contributions to the spin-longitudinal and the
spin-transverse cross sections. The two-step processes are important in
accounting for the underestimation of the DWIA results for the
spin-longitudinal and the spin-transverse cross sections.",0008045v2
2006-05-23,All-electrical control of single ion spins in a semiconductor,"We propose a method for all-electrical initialization, control and readout of
the spin of single ions substituted into a semiconductor. Mn ions in GaAs form
a natural example. In the ion's ground state the Mn core spin magnetic moment
locks antiparallel to the spin and orbital magnetic moment of a bound valence
hole from the GaAs host. Direct electrical manipulation of the ion spin is
possible because electric fields manipulate the orbital wave function of the
hole, and through the spin-orbit coupling the spin is reoriented as well.
Coupling two or more ion spins can be achieved using electrical gates to
control the size of the valence hole wave function near the semiconductor
surface. This proposal for coherent manipulation of individual ionic spins and
controlled coupling of ionic spins via electrical gates alone may find
applications in extremely high density information storage and in scalable
coherent or quantum information processing.",0605203v2
2008-07-14,Electric-field induced spin excitations in two-dimensional spin-orbit coupled systems,"Rigorous coupled spin-charge drift-diffusion equations are derived from
quantum-kinetic equations for the spin-density matrix that incorporate effects
due to k-linear spin-orbit interaction, an in-plane electric field, and the
elastic scattering on nonmagnetic impurities. The explicit analytical solution
for the induced magnetization exhibits a pole structure, from which the
dispersion relations of spin excitations are identified. Applications of the
general approach refer to the excitation of long-lived field-induced spin waves
by optically generated spin and charge patterns. This approach transfers
methods known in the physics of space-charge waves to the treatment of spin
eigenmodes. In addition, the amplification of an oscillating electric field by
spin injection is demonstrated.",0807.2142v1
2012-05-10,"3D quaternionic condensations, Hopf invariants, and skyrmion lattices with synthetic spin-orbit coupling","We study the topological configurations of the two-component condensates of
bosons with the $3$D $\vec{\sigma}\cdot \vec{p}$ Weyl-type spin-orbit coupling
subject to a harmonic trapping potential. The topology of the condensate
wavefunctions manifests in the quaternionic representation. In comparison to
the $U(1)$ complex phase, the quaternionic phase manifold is $S^3$ and the spin
orientations form the $S^2$ Bloch sphere through the 1st Hopf mapping. The
spatial distributions of the quaternionic phases exhibit the 3D skyrmion
configurations, and the spin distributions possess non-trivial Hopf invariants.
Spin textures evolve from the concentric distributions at the weak spin-orbit
coupling regime to the rotation symmetry breaking patterns at the intermediate
spin-orbit coupling regime. In the strong spin-orbit coupling regime, the
single-particle spectra exhibit the Landau-level type quantization. In this
regime, the three-dimensional skyrmion lattice structures are formed when
interactions are below the energy scale of Landau level mixings. Sufficiently
strong interactions can change condensates into spin-polarized plane-wave
states, or, superpositions of two plane-waves exhibiting helical spin spirals.",1205.2162v3
2014-10-28,A solution of the Boltzmann transport equations for spin and charge transport in a solid. Spin Proximity effect,"A solution of the modified Boltzmann transport equations is found, which
describes features of the spin and charge transport in a solid. Two
modifications of the Boltzmann transport equation were introduced. The first
modification describes the fact that a delocalized electrons can either be of
the running-wave type or the standing-wave type and electrons of different
types contribute differently to the transport. The second modification includes
the fact that the direction of the electron spin may not be conserved after
frequent electron scatterings. The origins and features of the spin proximity,
spin injection and spin detection effects are described. An enhancement of spin
detection and spin injection efficiencies in the vicinity of an interface are
predicted. The physical mechanism of an enlargement of spin accumulation due to
the conventional Hall effect is described.",1410.7511v1
2015-03-26,Spin nematic fluctuations near a spin-density-wave phase,"We study an interacting electronic system exhibiting a spin nematic
instability. Using a phenomenological form for the spin fluctuation spectrum
near the spin-density-wave (SDW) phase, we compute the spin nematic
susceptibility in energy and momentum space as a function of temperature and
the magnetic correlation length xi. The spin nematic instability occurs when xi
reaches a critical value xi_{cr}, i.e., its transition temperature T_{SN} is
always higher than the SDW critical temperature T_{SDW}. In particular, xi_{cr}
decreases monotonically with increasing T_{SN}. Concomitantly, low-energy
nematic fluctuations are present in a wider temperature region as T_{SN}
becomes higher. Approaching the spin nematic instability, the nematic spectral
function at zero momentum exhibits a central peak as a function of energy for a
finite temperature and a soft mode at zero temperature. These properties
originate from the general feature that the imaginary part of the
spin-fluctuation bubble has a term linear in energy and its coefficient is
proportional to the square of temperature. Furthermore we find that the nematic
spectral function exhibits a diffusive peak around zero momentum and zero
energy without clear dispersive features. A possible phase diagram for the spin
nematic and SDW transitions is also discussed.",1503.07646v1
2015-04-14,Spin dynamics in relativistic light-matter interaction,"Various spin effects are expected to become observable in light-matter
interaction at relativistic intensities. Relativistic quantum mechanics
equipped with a suitable relativistic spin operator forms the theoretical
foundation for describing these effects. Various proposals for relativistic
spin operators have been offered by different authors, which are presented in a
unified way. As a result of the operators' mathematical properties only the
Foldy-Wouthuysen operator and the Pryce operator qualify as possible proper
relativistic spin operators. The ground states of highly charged hydrogen-like
ions can be utilized to identify a legitimate relativistic spin operator
experimentally. Subsequently, the Foldy-Wothuysen spin operator is employed to
study electron-spin precession in high-intensity standing light waves with
elliptical polarization. For a correct theoretical description of the predicted
electron-spin precession relativistic effects due to the spin angular momentum
of the electromagnetic wave has to be taken into account even in the limit of
low intensities.",1504.03489v1
2017-09-28,Spin-orbit interaction of light induced by transverse spin angular momentum engineering,"We report the first demonstration of a direct interaction between the
extraordinary transverse spin angular momentum in evanescent waves and the
intrinsic orbital angular momentum in optical vortex beams. By tapping the
evanescent wave of whispering gallery modes in a micro-ring-based optical
vortex emitter and engineering the transverse spin state carried therein, a
transverse-spin-to-orbital conversion of angular momentum is predicted in the
emitted vortex beams. Numerical and experimental investigations are presented
for the proof-of-principle demonstration of this unconventional interplay
between the spin and orbital angular momenta, which could provide new
possibilities and restrictions on the optical angular momentum manipulation
techniques on the sub-wavelength scale. This phenomenon further gives rise to
an enhanced spin-direction coupling effect in which waveguide or surface modes
are unidirectional excited by incident optical vortex, with the directionality
jointly controlled by spin-orbit states. Our results enrich the spin-orbit
interaction phenomena by identifying a previously unknown pathway between the
polarization and spatial degrees of freedom of light, and can enable a variety
of functionalities employing spin and orbital angular momenta of light in
applications such as communications and quantum information processing.",1709.09811v1
2008-06-05,Magnetization Relaxation and Collective Spin Excitations in Correlated Double--Exchange Ferromagnets,"We study spin relaxation and dynamics of collective spin excitations in
correlated double--exchange ferromagnets. For this, we introduce an expansion
of the Green's functions equations of motion that treats non--perturbativerly
all correlations between a given number of spin and charge excitations and
becomes exact within a sub--space of states. Our method treats relaxation
beyond Fermi's Golden Rule while recovering previous variational results for
the spin--wave dispersion. We find that the momentum dependence of the
spin--wave dephasing rate changes qualitatively due to the on--site Coulomb
interaction, in a way that resembles experiment, and depends on its interplay
with the magnetic exchange interaction and itinerant spin lifetime. We show
that the collective spin relaxation and its dependence on the carrier
concentration depends sensitively on three--body correlations between a spin
excitation and a Fermi sea electron and hole. The above spin dynamics can be
controlled via the itinerant carrier population.",0806.0938v2
2017-04-06,Spin-valley half-metal as a prospective material for spin-valley-tronics,"Half-metallicity (full spin polarization of the Fermi surface) usually occurs
in strongly correlated electron systems. We demonstrate that doping a
spin-density wave insulator in the weak-coupling regime may also stabilize
half-metallic states. The undoped spin-density wave is formed by four nested
bands [i.e., each band is characterized by charge (electron/hole) and spin
(up/down) labels]. Of these four bands only two accumulate the doped carriers,
forming a half-metallic two-valley Fermi surface. Depending on parameters, the
spin polarizations of the electron-like and hole-like valleys may be (i)
parallel or (ii) antiparallel. The Fermi surface of (i) is fully spin-polarized
(similar to usual half-metals). Case (ii), referred to as ""a spin-valley
half-metal"", corresponds to complete polarization with respect to the
spin-valley operator. The properties of these states are discussed.",1704.01727v1
2021-01-09,Many-particle Quantum Hydrodynamics of Spin-1 Bose-Einstein Condensates,"We develop a novel model of the magnetized spin-1 Bose-Einstein condensate
(BEC) of neutral atoms, using the method of many-particle quantum hydrodynamic
(QHD) and propose an original derivation of the system of continual equations.
We consider bosons with a spin-spin interaction and a short range interaction
in the first order in the interaction radius, on the of basis of the
self-consistent field approximation of the QHD equations. We demonstrate that
the dynamics of the fluid velocity and magnetization is determined by a
nontrivial modification of the Euler and Landau-Lifshitz equation, and show
that a nontrivial modification of the spin density evolution equation contains
the spin torque effect that arises from the self-interactions between spins of
the bosons. The properties of the dispersion spectrum of collective excitations
are described. We obtain the new contribution of the self-interaction of spins
in the spin wave spectrum together with the influence of an external magnetic
field and spin-spin interactions between polarized particles. The anisotropic
spin wave instability is predicted.",2101.03422v1
2021-12-02,Spin dynamics of the spin chain antiferromagnet RbFeS$_2$,"We report transport and inelastic neutron scattering studies on electronic
properties and spin dynamics of the quasi-one-dimensional spin chain
antiferromagnet RbFeS$_2$. An antiferromagnetic phase transition at
$T_N\approx195$ K and dispersive spin waves with a spin gap of 5 meV are
observed. By modeling the spin excitation spectra using linear spin wave
theory, intra and inter-chain exchange interactions are found to be
$SJ_1=100(5)$ meV and $SJ_3=0.9(3)$ meV, respectively, together with a small
single-ion anisotropy of $SD_{zz}=0.04(1)$ meV. Comparison with previous
results for other materials in the same class of Fe$^{3+}$ spin chain systems
reveals that although the magnetic order sizes show significant variation from
1.8 to 3.0$\mu_B$ within the family of materials, the exchange interactions
$SJ$ are nevertheless quite similar, analogous to the iron pnictide
superconductors where both localized and delocalized electrons contribute to
the spin dynamics.",2112.00951v3
2022-01-04,Mechanism of antisymmetric spin polarization in centrosymmetric multiple-$Q$ magnets based on bilinear and biquadratic spin cross products,"We investigate how to engineer an antisymmetric spin-split band structure
under spin density waves with finite ordering wave vectors in centrosymmetric
systems without the relativistic spin-orbit coupling. On the basis of a
perturbative analysis for the spin-charge coupled model in centrosymmetric
itinerant magnets, we show that nonzero chiral-type bilinear and biquadratic
spin cross products in momentum space under the magnetic orderings are related
to an antisymmetric spin polarization in the electronic band structure. We
apply the derived formula to the single-$Q$ cycloidal spiral and double-$Q$
noncoplanar states including the meron-antimeron and skyrmion crystals. Our
results present a clue to realize a giant antisymmetric spin splitting driven
by magnetic phase transitions in the centrosymmetric lattice structures without
the spin-orbit coupling.",2201.01354v1
2024-02-11,Inferring small neutron star spins with neutron star-black hole mergers,"The precise measurement of neutron star (NS) spins can provide important
insight into the formation and evolution of compact binaries containing NS.
While traditional methods of NS spin measurement rely on pulsar observations,
gravitational wave detections offer a complementary avenue. However,
determining component spins with gravitational waves is hindered by the small
dimensionless spins of the NS and the degeneracy in the mass and spin
parameters. This degeneracy can be addressed by the inclusion of higher-order
modes in the waveform, which are important for systems with unequal masses.
This study shows the suitability of neutron star-black hole mergers, which are
naturally mass-asymmetric, for precise NS spin measurements. We explore the
effects of the black hole masses and spins, higher-mode content, inclination
angle, and detector sensitivity on the measurement of NS spin. We find that
networks with next-generation observatories like the Cosmic Explorer and the
Einstein Telescope can distinguish NS dimensionless spin of 0.04 (0.1) from
zero at $1-\sigma$ confidence for events within $\sim 350$ $(\sim 1000)$ Mpc.
Networks with A+ and A$^{\sharp}$ detectors achieve similar distinction within
$\sim 30$ $(\sim 70)$ Mpc and $\sim 50$ $(\sim 110)$ Mpc, respectively.",2402.07075v1
1995-01-30,On the spin density wave transition in a two dimensional spin liquid,"Strongly correlated two dimensional electrons are believed to form a spin
liquid in some regimes of density and temperature. As the density is varied,
one expects a transition from this spin liquid state to a spin density wave
antiferromagnetic state. In this paper we show that it is self-consistent to
assume that this transition is second order and, on this assumption, determine
the critical behavior of the $2p_F$ susceptibility, the NMR rates $T_1$ and
$T_2$ and the uniform susceptibility. We compare our results to data on high
$T_c$ materials.",9501133v1
1997-07-07,Spin Liquid Phases in 2D Frustrated XY Model,"In this paper we consider the $J_1-J_2-J_3$ classical and quantum 2D XY
model. Spin wave calculations show that a spin liquid phase still exists in the
quantum case as for Heisenberg models. We formulate a semiclassical approach of
these models based on spin wave action and use a variational method to study
the role played by vortices. Liquid and crystal phases of vortex could emerge
in this description. These phases seem to be directly correlated with the spin
liquid one and to its crystalline interpretation.",9707074v1
1998-08-18,Spin-density-functional theory of circular and elliptical quantum dots,"Using spin-density-functional theory, we study the electronic states of a
two-dimensional parabolic quantum dot with up to N=58 electrons. We observe a
shell structure for the filling of the dot with electrons. Hund's rule
determines the spin configuration of the ground state, but only up to 22
electrons. At specific N, the ground state is degenerate, and a small
elliptical deformation of the external potential induces a rotational
charge-density-wave (CDW) state. Previously identified spin-density-wave (SDW)
states are shown to be artifacts of broken spin symmetry in density-functional
theory.",9808193v1
1999-08-16,Current-driven Magnetization Reversal and Spin Wave Excitations in Co/Cu/Co Pillars,"Using thin film pillars ~100 nm in diameter, containing two ferromagnetic Co
layers of different thicknesses separated by a paramagnetic Cu spacer, we
examine effects of torques due to spin-polarized currents flowing perpendicular
to the layers. In accordance with spin-transfer theory, spin-polarized
electrons flowing from the thin to the thick Co layer can switch the magnetic
moments of the layers antiparallel, while a reversed electron flow causes
switching to a parallel state. When large magnetic fields are applied, the
current no longer fully reverses the magnetic moment, but instead stimulates
spin-wave excitations.",9908231v1
2000-12-10,Theory of spin wave excitations of metallic A-type antiferromagnetic manganites,"The spin dynamic of the metallic A-type antiferromagnetic manganites is
studied. An effective nearest-neighbour Heisenberg spin wave dispersion is
derived from the double exchange model taking into account the superexchange
interaction between the core spins. The result of inelastic neutron scattering
experiment on ${Nd}_{0.45}{Sr}_{0.55}{Mn} {O}_{3}$ is qualitatively reproduced.
Comparing theory with experimental data two main parameters of the model:
nearest-neighbour electron transfer amplitude and superexchange coupling
between the core spins are estimated.",0012166v2
2002-10-10,Spin wave theory for antiferromagnetic XXZ spin model on a triangle lattice in the presence of an external magnetic field,"Spin wave theory is applied to a quantum antiferromagnetic XXZ model on a
triangle lattice in the presence of an in-plane magnetic field. The effect of
the field is found to enhance the quantum fluctuation and to reduce the
sublattice magnetization at the intermediate field strength in the anisotropic
case. The possible implication to the field driven quantum phase transition
from a spin solid to a spin liquid is discussed.",0210222v1
2003-06-10,Correlation functions for 1d interacting fermions with spin-orbit coupling,"We compute correlation functions for one-dimensional electron systems which
spin and charge degrees of freedom are coupled through spin-orbit coupling.
Charge density waves, spin density waves, singlet- triplet- superconducting
fluctuations are studied. We show that the spin-orbit interaction modify the
exponents and the phase diagram of the system, changing the dominant
fluctuations and making new susceptibilities diverge for low temperature.",0306251v1
2003-08-06,Exciton Spin Relaxation Time in Quantum Dots Measured by Continuous-Wave Photoluminescence Spectroscopy,"We demonstrate a new method of measuring the exciton spin relaxation time in
semiconductor nanostructures by continuous-wave photoluminescence. We find that
for self-assembled CdTe quantum dots the degree of circular polarization of
emission is larger when exciting polarized excitons into the lower energy spin
state than in the case when the excitons are excited into the higher energy
spin state. A simple rate equation model gives the exciton spin relaxation time
in CdTe quantum dots equal to 4.8+/-0.3 ns, significantly longer than the
quantum dot exciton recombination time 300 ps.",0308116v1
2004-11-10,Maxwell Equation for the Coupled Spin-Charge Wave Propagation,"We show that the dissipationless spin current in the ground state of the
Rashba model gives rise to a reactive coupling between the spin and charge
propagation, which is formally identical to the coupling between the electric
and the magnetic fields in the 2+1 dimensional Maxwell equation. This analogy
leads to a remarkable prediction that a density packet can spontaneously split
into two counter propagation packets, each carrying the opposite spins. In a
certain parameter regime, the coupled spin and charge wave propagates like a
transverse ""photon"". We propose both optical and purely electronic experiments
to detect this effect.",0411276v1
2005-05-18,Spin Dynamics in the Two-Dimensional Spin 1/2 Heisenberg Antiferromagnet,"We present low-temperature dynamic properties of the quantum two-dimensional
antiferromagnetic Heisenberg model with spin S=1/2. The calculation of the
dynamic correlation function is performed by combining a projection operator
formalism and the modified spin-wave theory (MSW), which gives a gap in the
dispersion relation for finite temperatures. The so calculated dynamic
correlation function shows a double peak structure.We also obtain the spin-wave
damping and compare our results to experimental data and to theoretical results
obtained by other authors using different approaches.",0505458v1
2005-07-01,Spin accumulation in ballistic Rashba bar,"We propose an analytic model to study intrinsic spin polarization effect in a
ballistic Rashba bar with two semi-infinite leads. The wave functions expanded
with plane waves in Rashba bar are required to satisfy boundary conditions at
both longitudinal and transverse interfaces. We find out-of-plane spin Hall
accumulation effect can be induced in the Rashba bar even with large dimensions
by injecting unpolarized current from the lead. The longitudinal in-plane spin
Hall effect, however, becomes obscure in large-size sample. An interesting
direction-flipping of the out-of-plane spin accumulation is predicted by
altering the Rashba coupling strength.",0507025v1
2005-08-29,Spin-Phonon Coupling in High-T_c Copper Oxides,"Band calculations on HgBa$_2$CuO$_4$ and La$_{(2-x)}$Sr$_x$CuO$_4$ with
phonon and spin-waves within the CuO planes show that partial gaps are created
at various energies depending on wavelengths. Spin and phonon gaps appear at
different energies when the modulations are along [1,1,0], while they are at
the same energy for modulations along [1,0,0].
  It is shown that the ability to form gaps and antiferromagnetic waves is
correlated with the strength of the interaction parameter $\lambda_{sf}$ for
spin fluctuations. Many unusual properties of the high-T$_C$ oxides can be
understood from spin-phonon coupling.",0508672v1
2006-02-23,Two-dimensional electron scattering in regions of nonuniform spin-orbit coupling,"We present a theoretical study of elastic spin-dependent electron scattering
caused by a nonuniform Rashba spin-orbit coupling strength. Using the
spin-generalized method of partial waves the scattering amplitude is exactly
derived for the case of a circular shape of scattering region. We found that
the polarization of the scattered waves are strongly anisotropic functions of
the scattering angle. This feature can be utilized to design a good
all-electric spin-polarizer. General properties of the scattering process are
also investigated in the high and low energy limits.",0602560v1
2006-06-02,Magnetically tuned spin dynamics resonance,"We present the experimental observation of a magnetically tuned resonance
phenomenon resulting from spin mixing dynamics of ultracold atomic gases. In
particular we study the magnetic field dependence of spin conversion in F=2
87Rb spinor condensates in the crossover from interaction dominated to
quadratic Zeeman dominated dynamics. We discuss the observed phenomenon in the
framework of spin dynamics as well as matter wave four wave mixing. Furthermore
we show that the validity range of the single mode approximation for spin
dynamics is significantly extended in the regime of high magnetic field.",0606046v1
2006-06-02,Parametric instability of homogeneous precession of spin in the superfluid 3He-B,"Stability of homogeneous precession of spin due to parametric excitation of
spin waves is considered as the explanation of the ""catastrophic relaxation"",
that is observed in the superfluid 3He-B. It is shown, that at sufficiently low
temperatures homogeneous precession of spin becomes unstable (Suhl
instability). At zero temperature increments of growth for all spin wave modes
are found. Estimation of the temperature of transition to the unstable state is
made.",0606054v1
2006-10-13,Efficient switching of Rashba spin splitting in wide modulation-doped quantum wells,"We demonstrate that the size of the electric-field-induced Rashba spin
splitting in an 80 nm wide modulation-doped InGaSb quantum well can depend
strongly on the spatial variation of the electric field. In a slightly
asymmetric quantum well it can be an order of magnitude stronger than for the
average uniform electric field. For even smaller asymmetry spin subbands can
have wave functions and/or expectation values of the spin direction that are
completely changed as the in-plane wave vector varies. The Dresselhaus effect
can give an anticrossing at which the spin rapidly flips.",0610371v1
2007-02-07,Damping of antiferromagnetic spin waves by valence fluctuations in the double layer perovskite YBaFe2O5,"Inelastic neutron scattering experiments show that spin dynamics in the
charge ordered insulating ground state of the double-layer perovskite YBaFe2O5
is well described in terms of eg superexchange interactions. Above the Verwey
transition at TV = 308 K, t2g double exchange-type conduction within
antiferromagnetic FeO2--BaO--FeO2 double layers proceeds by an electron hopping
process that requires a spin flip of the five-fold coordinated Fe ions, costing
an energy 5<J>S^2 of approximately 0.1 eV. The hopping process disrupts
near-neighbor spin correlations, leading to massive damping of zone-boundary
spin waves.",0702181v1
2002-07-02,Gravitational Waves from Spinning Compact Binaries,"Binary systems of rapidly spinning compact objects, such as black holes or
neutron stars, are prime targets for gravitational wave astronomers. The
dynamics of these systems can be very complicated due to spin-orbit and
spin-spin couplings. Contradictory results have been presented as to the nature
of the dynamics. Here we confirm that the dynamics - as described by the second
post-Newtonian approximation to general relativity - is chaotic, despite claims
to the contrary. When dissipation due to higher order radiation reaction terms
are included, the chaos is dampened. However, the inspiral-to-plunge transition
that occurs toward the end of the orbital evolution does retain an imprint of
the chaotic behaviour.",0207016v1
2006-04-05,Self interaction of spins in binary systems,"Beyond point mass effects various contributions add to the radiative
evolution of compact binaries. We present all the terms up to the second
post-Newtonian order contributing to the rate of increase of gravitational wave
frequency and the number of gravitational wave cycles left until the final
coalescence for binary systems with spin, mass quadrupole and magnetic dipole
moments, moving on circular orbit. We evaluate these contributions for some
famous or typical compact binaries and show that the terms representing the
self interaction of individual spins, given for the first time here, are
commensurable with the proper spin-spin contributions for the recently
discovered double pulsar J0737-3039.",0604022v1
2004-09-02,Spinning particle in an external linearized gravitational wave field,"We study the interaction of a scalar and a spinning particle with a coherent
linearized gravitational wave field treated as a classical spin two external
field. The spin degrees of freedom of the spinning particle are described by
skew-commuting variables. We derive the explicit expressions for the
eigenfunctions and the Green's functions of the theory. The discussion is exact
within the approximation of neglecting radiative corrections and we prove that
the result is completely determined by the semiclassical contribution.",0409027v1
2005-07-28,Quantum entanglement dynamics and decoherence wave in spin chains at finite temperatures,"We analyze the quantum entanglement at the equilibrium in a class of exactly
solvable one-dimensional spin models at finite temperatures and identify a
region where the quantum fluctuations determine the behavior of the system. We
probe the response of the system in this region by studying the spin dynamics
after projective measurement of one local spin which leads to the appearance of
the ``decoherence wave''. We investigate time-dependent spin correlation
functions, the entanglement dynamics, and the fidelity of the quantum
information transfer after the measurement.",0507266v1
2008-03-06,Spin inversion devices with Fano anti-resonances,"Analyzing spin transport of quasi-2D electrons gas moving through a
semiconductor wave guide subject to a sectionally homogeneous tilted magnetic
field, we found well-defined selection rules for resonant and antiresonant spin
carrier transmission. Based on these selection rules and the band shift induced
by the magnetic field strength and the tilting angles, we propose an efficient
spin inversion device. For a polarized incoming electron beam, we can determine
from our theoretical approach, physical conditions for spin-inversion
efficiency up to 80%. We visualize this mechanism in terms of conductance and
the spacial behavior of the wave function amplitude along the superlattice.",0803.0993v2
2008-03-25,Long range order for lattice dipoles,"We consider a system of classical Heisenberg spins on a cubic lattice in
dimensions three or more, interacting via the dipole-dipole interaction. We
prove that at low enough temperature the system displays orientational long
range order, as expected by spin wave theory. The proof is based on reflection
positivity methods. In particular, we demonstrate a previously unproven
conjecture on the dispersion relation of the spin waves, first proposed by
Froehlich and Spencer, which allows one to apply infrared bounds for estimating
the long distance behavior of the spin-spin correlation functions.",0803.3576v1
2008-09-23,The Spin Distribution of Millisecond X-ray Pulsars,"The spin frequency distribution of accreting millisecond X-ray pulsars cuts
off sharply above 730 Hz, well below the breakup spin rate for most neutron
star equations of state. I review several different ideas for explaining this
cutoff. There is currently considerable interest in the idea that gravitational
radiation from rapidly rotating pulsars might act to limit spin up by
accretion, possibly allowing eventual direct detection with gravitational wave
interferometers. I describe how long-term X-ray timing of fast accreting
millisecond pulsars like the 599 Hz source IGR J00291+5934 can test the
gravitational wave model for the spin frequency limit.",0809.4031v1
2008-09-24,Gated combo nanodevice for sequential operations on single electron spin,"An idea for a nanodevice in which an arbitrary sequence of three basic
quantum single qubit gates - negation, Hadamard and phase shift - can be
performed on a single electron spin. The spin state is manipulated using the
spin-orbit coupling and the electron trajectory is controlled by the electron
wave function self-focusing mechanism due to the electron interaction with the
charge induced on metal gates. We present results of simulations based on
iterative solution of the time dependent Schr\""odinger equation in which the
subsequent operations on the electron spin can be followed and controlled.
Description of the moving electron wave packet requires evaluation of the
electric field within the entire nanodevice in each time step.",0809.4195v1
2009-03-09,d-Wave Spin Density Wave phase in the Attractive Hubbard Model with Spin Polarization,"We investigate the possibility of unconventional spin density wave (SDW) in
the attractive Hubbard model with finite spin polarization. We show that
pairing and density fluctuations induce the transverse d-wave SDW near the
half-filling. This novel SDW is related to the d-wave superfluidity induced by
antiferromagnetic spin fluctuations, in the sense that they are connected with
each other through Shiba's attraction-repulsion transformation. Our results
predict the d-wave SDW in real systems, such as cold Fermi atom gases with
population imbalance and compounds involving valence skipper elements.",0903.1491v1
2009-03-12,Simulation of a spin-wave instability from atomistic spin dynamics,"We study the spin dynamics of a Heisenberg model at finite temperature in the
presence of an external field or a uniaxial anisotropy. For the case of the
uniaxial anisotropy our simulations show that the macro moment picture breaks
down. An effect which we refer to as a spin-wave instability (SWI) results in a
non-dissipative Bloch-Bloembergen type relaxation of the macro moment where the
size of the macro moment changes, and can even be made to disappear. This
relaxation mechanism is studied in detail by means of atomistic spin dynamics
simulations.",0903.2186v1
2010-09-13,Helical spin textures in dipolar Bose-Einstein condensates,"We numerically study elongated helical spin textures in ferromagnetic spin-1
Bose-Einstein condensates subject to dipolar interparticle forces. Stationary
states of the Gross-Pitaevskii equation are solved and analyzed for various
values of the helical wave vector and dipolar coupling strength. We find two
helical spin textures which differ by the nature of their topological defects.
The spin structure hosting a pair of Mermin-Ho vortices with opposite mass
flows and aligned spin currents is stabilized for a nonzero value of the
helical wave vector.",1009.2372v3
2012-04-27,Spin-dependent electron grating effect from helical magnetization in multiferroic tunnel junctions,"In multiferroic oxides with a transverse helical magnetic order, the
magnetization exchange coupling is sinusoidally space-dependent. We
theoretically investigate the spin-dependent electron grating effect in
normal-metal/helical-multiferroic/ferromagnettic heterojunctions. The spin wave
vector of the spiral can be added or subtracted from the electron spacial wave
vector inducing spin-conserved and spin-flipped diffracted transmission and
reflection. The predicted grating effect can be controlled by magnetization
exchange coupling strength, the helicity spatial period, and the magnetization
of the ferromagnetic layer.",1204.6095v1
2012-12-24,Landau versus Spin Superfluidity in Spinor Bose-Einstein Condensates,"We consider a spin-1/2 Bose-Einstein condensate prepared initially in a
single spin projection. The two channels of excitations existing in such a
system (namely density and spin waves) are discussed and we show how pure spin
waves can be excited in the presence of local magnetic defects. We analyze the
role played by spin excitations on the Landau superfluidity criterion and
demonstrate the absence of absolute superfluidity for the antiferromagnetic
condensate. In the ferromagnetic case, we identify two critical velocities for
the breakdown of superfluidity.",1212.5894v2
2013-07-05,Spin liquid phase due to competing classical orders in the semiclassical theory of the Heisenberg model with ring exchange on an anisotropic triangular lattice,"Linear spin wave theory shows that ring exchange induces a quantum disordered
region in the phase diagram of the title model. Spin wave spectra show that
this is a direct manifestation of competing classical orders. A spin liquid is
found in the `Goldilocks zone' of frustration, where the quantum fluctuations
are large enough to cause strong competition between different classical
orderings but not strong enough to stabilize spiral order. We note that the
spin liquid phases of $\kappa$-(BEDT-TTF)${_2}X$ and $Y$[Pd(dmit)$_2$]$_2$ are
found in this Goldilocks zone.",1307.1535v1
2014-11-03,Inelastic-impurity-scattering-induced spin texture and topological transitions in surface electron waves,"Inelastic scattering off magnetic impurities in a spin-chiral two-dimensional
electron gas, e.g., the Rashba system, is shown to generate topological changes
in the spin texture of the electron waves emanating from the scattering center.
While elastic scattering gives rise to a purely in-plane spin texture for an
in-plane magnetic scat- tering potential, out-of-plane components emerge upon
activation of inelastic scattering processes. This property leads to a
possibility to make controlled transitions between trivial and nontrivial
topologies of the spin texture.",1411.0377v3
2015-09-08,Anomalous Hall effect driven by dipolar spin waves in uniform ferromagnets,"A new type of anomalous Hall effect is shown to arise from the interaction of
conduction electrons with dipolar spin waves in ferromagnets. This effect
exists even in homogeneous ferromagnets without relativistic spin-orbit
coupling. The leading contribution to the Hall conductivity is proportional to
the chiral spin correlation of dynamical spin textures and is physically
understood in terms of the skew scattering by dipolar magnons.",1509.02284v1
2016-09-15,Route toward high-speed nano-magnonics,"We study experimentally the possibility to utilize pulses of pure spin
current, produced via the nonlocal spin injection mechanism, to generate short
packets of spin waves propagating in nanoscale magnetic waveguides. The
spatially and time-resolved micro-focus Brillouin light scattering spectroscopy
measurements demonstrate that the excitation by spin current results in
extremely fast transient response, enabling efficient generation of short
spin-wave packets with duration down to a few nanoseconds. The proposed method
opens a route for the implementation of high-speed magnonic systems for
transmission and processing of information on the nanoscale.",1609.04526v1
2012-09-27,Spin effects on gravitational waves from inspiraling compact binaries at second post-Newtonian order,"We calculate the gravitational waveform for spinning, precessing compact
binary inspirals through second post-Newtonian order in the amplitude. When
spins are collinear with the orbital angular momentum and the orbits are
quasi-circular, we further provide explicit expressions for the
gravitational-wave polarizations and the decomposition into spin-weighted
spherical-harmonic modes. Knowledge of the second post-Newtonian spin terms in
the waveform could be used to improve the physical content of analytical
templates for data analysis of compact binary inspirals and for more accurate
comparisons with numerical-relativity simulations.",1209.6349v2
2020-08-19,Loop spin effects in intense background fields,"Radiative and non-radiative electron spin flip probabilities are analysed in
both plane wave and focussed laser backgrounds. We provide a simple and
physically transparent description of spin dynamics in plane waves, and
demonstrate that there exists a kinematic regime in which the usual leading
order perturbative hierarchy of QED is reversed, and non-radiative loop effects
dominate over radiative tree-level spin-flips. We show that while this
loop-dominance becomes suppressed in focussed laser pulses due to a high
sensitivity to field geometry, there is nevertheless a regime in which, in
principle, loop effects on spin transitions can be discerned.",2008.08578v1
2020-11-13,Non-symmetric spin-pumping in a multiferroic heterostructure,"We present spin pumping experiments in Co/Pt bilayers grown on Al2O3(0001)
and on ferroelectric Y-cut LiNbO3 substrates. Spin pumping is triggered by
resonant ferromagnetic resonance induced by surface acoustic waves. We observe
that spin pumping efficiency varies when both the magnetization vector and the
acoustic wave vector are reversed in Pt/Co/LiNbO3. This phenomenon is not
observed in Pt/Co/Al2O3. We propose that the in-plane electric polarization of
LiNbO3 is at the origin of the observed phenomenon. These observations open up
the perspective of an electric field control of spin pumping efficiency.",2011.06872v1
2019-03-30,Background noise pushes azimuthal instabilities away from spinning states,"Azimuthal instabilities occur in rotationally symmetric systems, either as
spinning (rotating) waves or standing waves. We make use of a novel ansatz to
derive a differential equation characterizing the state of these instabilities
in terms of their amplitude, orientation, nature (standing/spinning) and
temporal phase. For the first time we show how source terms determine
quantitatively the system preference for spinning and/or standing states. In
particular we find that, when present, background noise pushes the system away
from spinning states and towards standing states, consistently with
experiments.",1904.00213v1
2024-01-29,Dissipative effects on the propagation of spin modes,"In relativistic hydrodynamics with spin, following de Groot--van Leeuwen--van
Weert's energy-momentum and spin tensor definitions, we analyze the propagation
of spin degrees of freedom. We deduce an analytical formula for spin wave
velocity, finding that it approaches half the speed of light in the
ultra-relativistic limit. Only transverse degrees of freedom propagate, similar
to electromagnetic waves. Additionally, we explore dissipative effects and
determine the damping coefficients for Maxwell-J\""uttner statistics.",2401.16007v1
2004-12-20,Current induced spin injection and surface torque in ferromagnetic metallic junctions,"Joint influence of two effects, namely, nonequilibrium spin injection by
current, and current induced surface torque, on spin-valve type ferromagnetic
metallic junctions is considered theoretically. The CPP configuration is
assumed. The consideration is based on solving a coupled set of equations of
motion for the mobile electron and lattice magnetizations. Boundary conditions
are derived from the total magnetization flux continuity condition. A
dispersion relation is derived for current dependent spin-wave fluctuations.
The fluctuations become unstable under current density exceeding some threshold
value. Joint action of the longitudinal spin injection and the torque lowers
the instability threshold. The spin injection softens spin wave frequency near
the threshold and can pin magnetization at the injecting contact. The pinning
rises under the current increasing, so that the appearance of new spin-wave
resonance lines can be observed.",0412523v1
2005-12-26,Spin waves in a band ferromagnet: spin-rotationally symmetric study with self-energy and vertex corrections,"First-order quantum corrections to the transverse spin-fluctuation propagator
are obtained within a systematic inverse-degeneracy 1/N expansion, which
provides a spin-rotationally symmetric scheme for including self-energy and
vertex corrections while preserving the Goldstone mode. An expression is
obtained for the spin-wave stiffness constant including all first-order quantum
corrections, and the dominant contribution is shown to yield a strong reduction
due to a correlation-induced enhancement in the exchange-energy gain upon spin
twisting. The quantum reduction factor U/W highlights the subtlety in the
characteristic competition in a band ferromagnet between interaction U and
bandwidth W. Quantum corrections also yield an intrinsic spin-wave damping
mechanism due to coupling between spin and charge fluctuations.",0512648v2
2010-05-12,Spin effects in the phasing of gravitational waves from binaries on eccentric orbits,"We compute here the spin-orbit and spin-spin couplings needed for an accurate
computation of the phasing of gravitational waves emitted by comparable-mass
binaries on eccentric orbits at the second post-Newtonian (PN) order. We use a
quasi-Keplerian parametrization of the orbit free of divergencies in the zero
eccentricity limit. We find that spin-spin couplings induce a residual
eccentricity for coalescing binaries at 2PN, of the order of
$10^{-4}$-$10^{-3}$ for supermassive black hole binaries in the LISA band.
Spin-orbit precession also induces a non-trivial pattern in the evolution of
the eccentricity, which could help to reduce the errors on the determination of
the eccentricity and spins in a gravitational wave measurement.",1005.2046v1
2012-05-10,"Multiboson spin-wave theory for Ba2CoGe2O7, a spin-3/2 easy-plane Neel antiferromagnet with strong single-ion anisotropy","We consider the square-lattice antiferromagnetic Heisenberg Hamiltonian
extended with a single-ion axial anisotropy term as a minimal model for the
multiferroic Ba2CoGe2O7. Developing a multiboson spin-wave theory, we
investigate the dispersion of the spin excitations in this spin-3/2 system. As
a consequence of a strong single-ion anisotropy, a stretching (longitudinal)
spin-mode appears in the spectrum. The inelastic neutron scattering spectra of
Zheludev et al. [Phys. Rev. B 68, 024428 (2003)] are successfully reproduced by
the low energy modes in the multiboson spin-wave theory, and we anticipate the
appearance of the spin stretching modes at 4meV that can be identified using
the calculated dynamical spin structure factors. We expect the appearance of
spin stretching modes for any S>1/2 compound where the single-ion anisotropy is
significant.",1205.2196v2
2015-01-07,Quadratic-in-spin effects in the orbital dynamics and gravitational-wave energy flux of compact binaries at the 3PN order,"We investigate the dynamics of spinning binaries of compact objects at the
next-to-leading order in the quadratic-in-spin effects, which corresponds to
the third post-Newtonian order (3PN). Using a Dixon-type multipolar formalism
for spinning point particles endowed with spin-induced quadrupoles and
computing iteratively in harmonic coordinates the relevant pieces of the PN
metric within the near zone, we derive the post-Newtonian equations of motion
as well as the equations of spin precession. We find full equivalence with
available results. We then focus on the far-zone field produced by those
systems and obtain the previously unknown 3PN spin contributions to the
gravitational-wave energy flux by means of the multipolar post-Minkowskian
(MPM) wave generation formalism. Our results are presented in the
center-of-mass frame for generic orbits, before being further specialized to
the case of spin-aligned, circular orbits. We derive the orbital phase of the
binary based on the energy balance equation and briefly discuss the relevance
of the new terms.",1501.01529v1
2015-08-06,Large spin-wave bullet in a ferrimagnetic insulator driven by spin Hall effect,"Due to its transverse nature, spin Hall effects (SHE) provide the possibility
to excite and detect spin currents and magnetization dynamics even in magnetic
insulators. Magnetic insulators are outstanding materials for the investigation
of nonlinear phenomena and for novel low power spintronics applications because
of their extremely low Gilbert damping. Here, we report on the direct imaging
of electrically driven spin-torque ferromagnetic resonance (ST-FMR) in the
ferrimagnetic insulator Y$_3$Fe$_5$O$_{12}$ based on the excitation and
detection by SHEs. The driven spin dynamics in Y$_3$Fe$_5$O$_{12}$ is directly
imaged by spatially-resolved microfocused Brillouin light scattering (BLS)
spectroscopy. Previously, ST-FMR experiments assumed a uniform precession
across the sample, which is not valid in our measurements. A strong spin-wave
localization in the center of the sample is observed indicating the formation
of a nonlinear, self-localized spin-wave `bullet'.",1508.01427v1
2018-06-13,Phase-locking between different partial-waves in atom-ion spin-exchange collisions,"We present a joint experimental and theoretical study of spin dynamics of a
single $^{88}$Sr$^+$ ion colliding with an ultracold cloud of Rb atoms in
various hyperfine states. While spin-exchange between the two species occurs
after 9.1(6) Langevin collisions on average, spin-relaxation of the Sr$^+$ ion
Zeeman qubit occurs after 48(7) Langevin collisions which is significantly
slower than in previously studied systems due to a small second-order
spin-orbit coupling. Furthermore, a reduction of the endothermic spin-exchange
rate was observed as the magnetic field was increased. Interestingly, we found
that, while the phases acquired when colliding on the spin singlet and triplet
potentials vary largely between different partial waves, the singlet-triplet
phase difference, which determines the spin-exchange cross-section, remains
locked to a single value over a wide range of partial-waves which leads to
quantum interference effects.",1806.05150v2
2019-02-08,Spin dynamics of a millisecond pulsar orbiting closely around a massive black hole,"We investigate the spin dynamics of a millisecond pulsar (MSP) in a tightly
bounded orbit around a massive black hole. These binaries are progenitors of
the extreme-mass-ratio-inspirals (EMRIs) and intermediate-mass-ratio-inspirals
(IMRIs) gravitational wave events. The Mathisson-Papapetrou-Dixon (MPD)
formulation is used to determine the orbital motion and spin modulation and
evolution. We show that the MSP will not be confined in a planar Keplerian
orbit and its spin will exhibit precession and nutation induced by spin-orbit
coupling and spin-curvature interaction. These spin and orbital behaviours will
manifest observationally in the temporal variations in the MSP's pulsed
emission and, with certain geometries, in the self-occultation of the pulsar's
emitting poles. Radio pulsar timing observations will be able to detect such
signatures. These extreme-mass-ratio binaries (EMRBs) and
intermediate-mass-ratio binaries (IMRBs) are also strong gravitational wave
sources. Combining radio pulsar timing and gravitational wave observations will
allow us to determine the dynamics of these systems in high precision and hence
the subtle behaviours of spinning masses in strong gravity.",1902.03146v1
2020-03-27,Electrical detection of unconventional transverse spin-currents in obliquely magnetized thin films,"In a typical experiment in magnonics, thin films are magnetized in-plane and
spin waves only carry angular momentum along their spatial propagation
direction. Motivated by the experiments of Bozhko et al. [Phys. Rev. Research
2, 023324 (2020)], we show theoretically that for obliquely magnetized thin
films, exchange-dipolar spin waves are accompanied by a transverse
spin-current. We propose an experiment to electrically detect this transverse
spin-current with Pt strips on top of a YIG film, by comparing the induced
spin-current for spin waves with opposite momenta. We predict the relative
difference to be of the order $10^{-4}$, for magnetic fields tilted at least
$30^{\circ}$ out of plane. This transverse spin-current is the result of the
long range dipole-dipole interaction and the inversion symmetry breaking of the
interface.",2003.12520v4
2021-02-20,Observation of Coherent Spin Waves in a Three-Dimensional Artificial Spin Ice Structure,"Harnessing high-frequency spin dynamics in three-dimensional (3D)
nanostructures may lead to paradigm-shifting, next generation devices including
high density spintronics and neuromorphic systems. Despite remarkable progress
in fabrication, the measurement and interpretation of spin dynamics in complex
3D structures remain exceptionally challenging. Here we take a first step and
measure coherent spin waves within a 3D artificial spin ice (ASI) structure
using Brillouin light scattering. The 3D-ASI was fabricated by using a
combination of two-photon lithography and thermal evaporation. Two spin-wave
modes were observed in the experiment whose frequencies showed a monotonic
variation with the applied field strength. Numerical simulations qualitatively
reproduced the observed modes. The simulated mode profiles revealed the
collective nature of the modes extending throughout the complex network of
nanowires while showing spatial quantization with varying mode quantization
numbers. The study shows a well-defined means to explore high-frequency spin
dynamics in complex 3D spintronic and magnonic structures.",2102.10270v1
2022-04-29,All-magnonic Stern-Gerlach effect in antiferromagnets,"The Stern-Gerlach (SG) effect is well known as the spin-dependent splitting
of a beam of atoms carrying magnetic moments by a magnetic-field gradient,
leading to the concept of electron spin. Antiferromagnets can accommodate two
magnon modes with opposite spin polarizations, which is equivalent to the spin
property of electrons. Here, we propose the existence of an all-magnonic SG
effect in antiferromagnetic magnonic system, where a linearly polarized
spin-wave beam is deflected by a straight Dzyaloshinskii-Moriya interaction
(DMI) interface into two opposite polarized spin-wave beams propagating in two
discrete directions. Moreover, we observe bi-focusing of antiferromagnetic spin
waves induced by a curved DMI interface, which can also spatially separate
thermal magnons with opposite polarizations. Our findings provide a unique
perspective to understand the rich phenomena associated with antiferromagnetic
magnon spin and would be helpful for polarization-dependent application of
antiferromagnetic spintronic devices.",2204.13942v1
2022-11-02,Spin wave excitations in a nanowire spin-torque oscillator with perpendicular magnetic anisotropy,"Spin torque oscillators (STOs) are emerging microwave devices that can
potentially be used in spin-logic devices and the next-generation high-speed
computing architecture. Thanks to their non-linear nature, STOs are easily
tunable by the magnetic field and the dc current. Spin Hall nano-oscillators
(SHNOs) are promising types of STOs and most of the current studies focus on
localized modes that can be easily excited. Here, we study using micromagnetic
simulations, the nature of the spin-torque-induced excitations in nanowire
devices made of perpendicular magnetic anisotropy (PMA) material. Our results
showed that upon including PMA the excitation of localized and propagating spin
wave modes is feasible. We study the nature of the mode excitations as a
function of the PMA strength (\text{K}$_u$), and the current. Indeed, we
estimate a critical value of \text{K}$_u$ to allow for the excitation of the
propagating spin wave. We attribute this mode selectivity between localized and
propagating modes to a switch in the sign of the nonlinearity of the system
from negative to positive at a non-zero \text{K}$_u$ which is supported by
analytical calculations. Our results provide deep insight into engineering
reconfigurable microwave devices for future magnonic and computational
applications.",2211.01078v1
2023-02-27,Spin Hall effects in the sky,"In many areas of physics, the propagation of wave packets carrying intrinsic
angular momentum is generally influenced by spin-orbit interactions. This is
the main mechanism behind spin Hall effects, which result in wave packets
following spin-dependent trajectories. Spin Hall effects have been observed in
several experiments for electrons in condensed matter systems and for light
propagating in inhomogeneous optical media. Similar effects have also been
predicted for wave packets propagating in inhomogeneous gravitational fields.
We give a brief introduction to gravitational spin Hall effects, emphasizing
the analogies with the spin Hall effect of light in optics. Furthermore, we
review the most promising astrophysical avenues that could lead to experimental
observations of the gravitational spin Hall effect.",2302.13634v2
2023-03-13,Coherent THz Spin Dynamics in Antiferromagnets Beyond the Approximation of the Néel vector,"Controlled generation of coherent spin waves with highest possible
frequencies and the shortest possible wavelengths is a cornerstone of
spintronics and magnonics. Here, using the Heisenberg antiferromagnet RbMF$_3$,
we demonstrate that laser-induced THz spin dynamics corresponding to pairs of
mutually coherent counter propagating spin waves with the wavevectors up to the
edge of the Brillouin zone cannot be understood in terms of magnetization and
antiferromagnetic (N\'eel) vectors, conventionally used to describe spin waves.
Instead, we propose to model such spin dynamics using the spin correlation
function. We derive a quantum-mechanical equation of motion for the latter and
emphasize that, unlike the magnetization and antiferromagnetic vectors the spin
correlations in antiferromagnets do not exhibit inertia.",2303.06996v4
2023-06-24,Causality and stability analysis for the minimal causal spin hydrodynamics,"We perform the linear analysis of causality and stability for a minimal
extended spin hydrodynamics up to second order of the gradient expansion. The
first order spin hydrodynamics, with a rank-3 spin tensor being antisymmetric
for only the last two indices, are proved to be acausal and unstable. We then
consider the minimal causal spin hydrodynamics up to second order of the
gradient expansion. We derive the necessary causality and stability conditions
for this minimal causal spin hydrodynamics. Interestingly, the satisfaction of
the stability conditions relies on the equations of state for the spin density
and chemical potentials. Moreover, different with the conventional relativistic
dissipative hydrodynamics, the stability of the theory seems to be broken at
the finite wave-vector when the stability conditions are fulfilled at small and
large wave-vector limits. It implies that the behavior in small and large
wave-vector limits may be insufficient to determine the stability conditions
for spin hydrodynamics in linear mode analysis.",2306.13880v3
2009-12-28,Wave-Particle Duality and the Hamilton-Jacobi Equation,"The Hamilton-Jacobi equation of relativistic quantum mechanics is revisited.
The equation is shown to permit solutions in the form of breathers
(oscillating/spinning solitons), displaying simultaneous particle-like and
wave-like behavior. The de Broglie wave thus acquires a clear deterministic
meaning of a wave-like excitation of the classical action function. The problem
of quantization in terms of the breathing action function and the double-slit
experiment are discussed.",0912.5156v1
2016-01-05,Spinning swimming of Volvox by tangential helical wave,"The swimming of a sphere by means of tangential helical waves running along
its surface is studied on the basis of the Stokes equations. Two types of
tangential waves are found. The first of these is associated with a pressure
disturbance and leads to a higher rate of net rotation than the second one for
the same power. It is suggested that the helical waves are relevant for the
rotational swimming of Volvox.",1601.00755v1
1997-01-15,Spin dynamics of the spin-Peierls compound CuGeO_3 under magnetic field,"The magnetic field--driven transition in the spin-Peierls system CuGeO_3
associated with the closing of the spin gap is investigated numerically. The
field dependence of the spin dynamical structure factor (seen by inelastic
neutron scattering) and of the momentum dependent static susceptibility are
calculated. In the dimerized phase (H<H_c), we suggest that the strong field
dependence of the transverse susceptibility could be experimentally seen from
the low temperature spin-echo relaxation rate 1/T_{2G} or the second moment of
the NMR spectrum. Above H_c low energy spin excitations appear at
incommensurate wave vectors where the longitudinal susceptibility chi_{zz}(q)
peaks.",9701107v1
1998-03-31,The spin-Peierls instability in spin 1/2 XY chain in the non adiabatic limit,"The spin-Peierls instability in spin 1/2 XY chain coupled to dispersionless
phonons of frequency $\omega$ has been studied in the nonadiabatic limit. We
have chosen the Lang-Firsov variational wave function for the phonon subsystem
to obtain an effective spin Hamiltonian. The effective spin Hamiltonian is then
solved in the framework of mean-field approximation. We observed a dimerized
phase when g is less than a critical value and an anti-ferromagnetic phase when
it is greater than a critical value . The variation of lattice distortion,
dimerized order parameter and energy gap with spin phonon coupling parameter
has also been investigated here.",9803378v1
2002-11-05,"SU(4) Spin-Orbital Two-Leg Ladder, Square and Triangle Lattices","Based on the generalized valence bond picture, a Schwinger boson mean field
theory is applied to the symmetric SU(4) spin-orbital systems. For a two-leg
SU(4) ladder, the ground state is a spin-orbital liquid with a finite energy
gap, in good agreement with recent numerical calculations. In two-dimensional
square and triangle lattices, the SU(4) Schwinger bosons condense at
(\pi/2,\pi/2) and (\pi/3,\pi/3), respectively. Spin, orbital, and coupled
spin-orbital static susceptibilities become singular at the wave vectors, twice
of which the bose condensation arises at. It is also demonstrated that there
are spin, orbital, and coupled spin-orbital long-range orderings in the ground
state.",0211074v1
2005-04-26,Spin lifetimes and strain-controlled spin precession of drifting electrons in zinc blende type semiconductors,"We study the transport of spin polarized electrons in n-GaAs using spatially
resolved continuous wave Faraday rotation. From the measured steady state
distribution, we determine spin relaxation times under drift conditions and, in
the presence of strain, the induced spin splitting from the observed spin
precession. Controlled variation of strain along [110] allows us to deduce the
deformation potential causing this effect, while strain along [100] has no
effect. The electric field dependence of the spin lifetime is explained
quantitatively in terms of an increase of the electron temperature.",0504668v1
2005-08-31,Quantum Spin Effect and Short-Range Order above the Curie Temperature,"Using quantum Heisenberg model calculations with Green's function technique
generalized for arbitrary spins, we found that for a system of small spins the
quantum spin effects significantly contribute to the magnetic short-range order
and strongly affect physical properties of magnets. The spin dynamics
investigation confirms that these quantum spin effects favor the persistence of
propagating spin-wave excitations above the Curie temperature. Our
investigation suggests a reconsideration of prevailing point of view on finite
temperature magnetism to include quantum effects and the magnetic short-range
order.",0508781v1
2006-10-03,Non-diffusive spin dynamics in a two-dimensional electron gas,"We describe measurements of spin dynamics in the two-dimensional electron gas
in GaAs/GaAlAs quantum wells. Optical techniques, including transient
spin-grating spectroscopy, are used to probe the relaxation rates of spin
polarization waves in the wavevector range from zero to $6\times 10^4$
cm$^{-1}$. We find that the spin polarization lifetime is maximal at nonzero
wavevector, in contrast with expectation based on ordinary spin diffusion, but
in quantitative agreement with recent theories that treat diffusion in the
presence of spin-orbit coupling.",0610054v1
2007-09-26,Spin-polarized Current-induced Instability in Spin-Valve with Antiferromagnetic Layer,"In the framework of phenomenological model we consider dynamics of a
compensated collinear antiferromagnet (AFM) in the presence of spin-polarised
current. The model is based on the assumption that AFM spins are localised and
spin torque is transferred to each magnetic sublattice independently. It is
shown that in AFM spin current i) can be a source of the ""negative friction"";
and ii) modifies spin-wave frequencies. Equilibrium state of AFM can be
destabilized by the current polarized in parallel to AFM vector. Threshold
current at which the loss of stability takes place depends upon the magnetic
anisotropy of AFM.",0709.4172v1
2007-09-26,Two Sides of Spin Concept,"The notion of the spin is shown to have two constituents, as exemplified by
the spin of the electron. The first one is related to the form of the wave
equation and determines the fermion or boson particle type. This implies the
spin taking strictly half-integer or integer number. The second side of spin
manifestation is related to the physical nature of the spin of the electron
(and the corresponding magnetic moment) in the interaction resulting in
nonuniform motion. It is shown that in this manifestation spin is no more fixed
constant.",0709.4191v2
2010-03-09,Laser-catalyzed spin-exchange process in a Bose-Einstein condensate,"We show theoretically that it is possible to optically control collective
spin-exchange processes in spinor Bose condensates through virtual
photoassociation. The interplay between optically induced spin exchange and
spin-dependent collisions provides a flexible tool for the control of atomic
spin dynamics, including enhanced or inhibited quantum spin oscillations, the
optically-induced ferromagnetic-to-antiferromagnetic transition, and coherent
matter-wave spin conversion.",1003.1812v1
2010-06-24,Circularly polarized modes in magnetized spin plasmas,"The influence of the intrinsic spin of electrons on the propagation of
circularly polarized waves in a magnetized plasma is considered. New eigenmodes
are identified, one of which propagates below the electron cyclotron frequency,
one above the spin-precession frequency, and another close to the
spin-precession frequency.\ The latter corresponds to the spin modes in
ferromagnets under certain conditions. In the nonrelativistic motion of
electrons, the spin effects become noticeable even when the external magnetic
field $B_{0}$ is below the quantum critical\ magnetic field strength, i.e.,
$B_{0}<$ $B_{Q} =4.4138\times10^{9}\, \mathrm{T}$ and the electron density
satisfies $n_{0} \gg n_{c}\simeq10^{32}$m$^{-3}$. The importance of electron
spin (paramagnetic) resonance (ESR) for plasma diagnostics is discussed.",1006.4878v1
2011-02-15,Kondo Spin Screening Cloud in Two-dimensional Electron Gas with Spin-orbit Couplings,"A spin-1/2 Anderson impurity in a semiconductor quantum well with Rashba and
Dresselhaus spin-orbit couplings is studied by using a variational wave
function method. The local magnetic moment is found to be quenched at low
temperatures. The spin-spin correlations of the impurity and the conduction
electron density show anisotropy in both spatial and spin spaces, which
interpolates the Kondo spin screenings of a conventional metal and of a surface
of three-dimensional topological insulators.",1102.2947v1
2013-06-04,Collective Spin-Hall Effect for Electron-Hole Gratings,"We show that an electric field parallel to the wavefronts of an electron-hole
grating in a GaAs quantum well generates, via the electronic spin Hall effect,
a spin grating of the same wave vector and with an amplitude that can exceed 1%
of the amplitude of the initial density grating. We refer to this phenomenon as
""collective spin Hall effect"". A detailed study of the coupled-spin charge
dynamics for quantum wells grown in different directions reveals rich features
in the time evolution of the induced spin density, including the possibility of
generating a helical spin grating.",1306.0889v1
2015-01-13,Spin effects induced by thermal perturbation in a normal metal/magnetic insulator system,"Using one of the methods of quantum nonequilibrium statistical physics we
have investigated the spin transport transverse to the normal
metal/ferromagnetic insulator interface in hybrid nanostructures. An
approximation of the effective parameters, when each of the interacting
subsystems (electron spin, magnon, and phonon) is characterized by its own
effective temperature have been considered. The generalized Bloch equations
which describe the spin-wave current propagation in the dielectric have been
derived. Finally, two sides of the spin transport ""coin"" have been revealed:
the diffusive nature of the magnon motion and magnon relaxation processes,
responsible for the spin pumping and the spin-torque effect.",1501.02983v1
2015-04-27,Helical Spin Order from Topological Dirac and Weyl Semimetals,"We study dynamical mass generation and the resultant helical spin orders in
topological Dirac and Weyl semimetals, including the edge states of quantum
spin Hall insulators, the surface states of weak topological insulators, and
the bulk materials of Weyl semimetals. In particular, the helical spin textures
of Weyl semimetals manifest the spin-momentum locking of Weyl fermions in a
visible manner. The spin-wave fluctuations of the helical order carry electric
charge density; therefore, the spin textures can be electrically controlled in
a simple and predictable manner.",1504.07178v2
2016-10-30,"Kinetic analysis of spin current contribution to spectrum of electromagnetic waves in spin-1/2 plasma, Part I: Dielectric permeability tensor for magnetized plasmas","The dielectric permeability tensor for spin polarized plasmas is derived in
terms of the spin-1/2 quantum kinetic model in six-dimensional phase space.
Expressions for the distribution function and spin distribution function are
derived in linear approximations on the path of dielectric permeability tensor
derivation. The dielectric permeability tensor is derived the spin-polarized
degenerate electron gas. It is also discussed at the finite temperature regime,
where the equilibrium distribution function is presented by the spin-polarized
Fermi-Dirac distribution. Consideration of the spin-polarized equilibrium
states opens possibilities for the kinetic modeling of the thermal spin current
contribution in the plasma dynamics.",1610.09689v1
2016-11-29,Spin-sensitive atom mirror via spin-orbit interaction,"Based on the spin-orbit coupling recently implemented in a neutral cold-atom
gas, we propose a scheme to realize spin-dependent scattering of cold atoms. In
particular we consider a matter wave packet of cold-atom gas impinging upon a
step potential created by the optical light field, inside of which the atoms
are subject to spin-orbit interaction. We show that the proposed system can act
as a spin polarizer or spin-selective atom mirror for the incident atomic beam.
The principle and the operating parameter regime of the system are carefully
discussed.",1611.09617v1
2022-08-23,Acoustic spin current generation in superconductors,"We theoretically study the generation of spin current due to a surface
acoustic wave (SAW) in a superconductor. We model an s-wave superconductor as
the mean-field Hamiltonian and calculate spin current generated via
spin-vorticity coupling based on kinetic theory. The results suggest that the
spin current can be driven in a single superconductor layer, and our estimation
suggests that the detectable magnitude of the spin current can be generated in
aluminum. Our proposal may contribute to the advancement of spin transport in
superconductors from application and fundamental physics aspects.",2208.10744v1
2022-10-17,Topological spin defects of light,"Topological defects are found in a variety of systems, and their existence
are robust under perturbations due to their topological nature. Here we
introduce a new type of topological defects found in electromagnetic waves:
topological spin defects. Such a defect is associated with a point where the
electromagnetic spin density is zero, and generically have a nontrivial
topological spin texture surrounding the defect point. Due to such spin
texture, a topological spin defect possesses a quantized topological charge. We
provide examples where isolated defect point, periodic or quasi-periodic defect
lattices can be created. Such topological spin defect points may find
applications in 3D imaging and nanoparticle manipulation.",2210.08694v1
2023-06-08,Spin entanglement in neutron-proton scattering,"In this Letter, I work out spin entanglement properties of neutron-proton
scattering using the exact S-matrix, generalizing previous works based on S
wave. The dependence of spin entanglement on momentum, scattering angle, and
initial spin configuration is investigated for realistic nuclear forces, while
low-energy properties of spin entanglement are analyzed within the framework of
pionless effective field theory at leading order. New connections are found
between spin entanglement and symmetry enhancement of strong interactions.
These results lead to a more complete understanding of how spin entanglement is
generated via neutron-proton interaction. They also lay the theoretical
foundation for controllable production of entangled nucleon-nucleon pairs in
future experiments.",2306.04918v1
2018-02-02,Spin wave emission by spin-orbit torque antennas,"We study the generation of propagating spin waves in Ta/CoFeB waveguides by
spin-orbit torque antennas and compare them to conventional inductive antennas.
The spin-orbit torque was generated by a transverse microwave current across
the magnetic waveguide. The detected spin wave signals for an in-plane
magnetization across the waveguide (Damon-Eshbach configuration) exhibited the
expected phase rotation and amplitude decay upon propagation when the current
spreading was taken into account. Wavevectors up to about 6 rad/$\mu$m could be
excited by the spin-orbit torque antennas despite the current spreading,
presumably due to the non-uniformity of the microwave current. The relative
magnitude of generated anti-damping spin-Hall and Oersted fields was calculated
within an analytic model and it was found that they contribute approximately
equally to the total effective field generated by the spin-orbit torque
antenna. Due to the ellipticity of the precession in the ultrathin waveguide
and the different orientation of the anti-damping spin-Hall and Oersted fields,
the torque was however still dominated by the Oersted field. The prospects for
obtaining a pure spin-orbit torque response are discussed, as are the energy
efficiency and the scaling properties of spin-orbit torque antennas.",1802.00861v2
2023-11-09,Which black hole is spinning? Probing the origin of black-hole spin with gravitational waves,"Theoretical studies of angular momentum transport suggest that isolated
stellar-mass black holes are born with negligible dimensionless spin magnitudes
$\chi \lesssim 0.01$. However, recent gravitational-wave observations indicate
$\gtrsim 40\%$ of binary black hole systems contain at least one black hole
with a non-negligible spin magnitude. One explanation is that the first-born
black hole spins up the stellar core of what will become the second-born black
hole through tidal interactions. Typically, the second-born black hole is the
``secondary'' (less-massive) black hole, though, it may become the ``primary''
(more-massive) black hole through a process known as mass-ratio reversal. We
investigate this hypothesis by analysing data from the third gravitational-wave
transient catalog (GWTC-3) using a ``single-spin'' framework in which only one
black hole may spin in any given binary. Given this assumption, we show that at
least $28\%$ (90% credibility) of the LIGO--Virgo--KAGRA binaries contain a
primary with significant spin, possibly indicative of mass-ratio reversal. We
find no evidence for binaries that contain a secondary with significant spin.
However, the single-spin framework is moderately disfavoured (natural log Bayes
factor $\ln B = 3.1$) when compared to a model that allows both black holes to
spin. If future studies can firmly establish that most merging binaries contain
two spinning black holes, it may call into question our understanding of
formation mechanisms for binary black holes or the efficiency of angular
momentum transport in black hole progenitors.",2311.05182v3
2023-11-20,Evolution of internal gravity waves in meso-scale eddies,"We investigate the effect of wave-eddy interaction and dissipation of
internal gravity waves propagating in a coherent meso-scale eddy simulated
using a novel numerical model called the Internal Wave Energy Model based on
the six-dimensional radiative transfer equation. We use an idealized mean flow
structure and stratification, motivated by observations of a coherent eddy in
the Canary Current System. In a spin-down simulation using the Garret-Munk
model spectrum as initial conditions, we find that wave energy decreases at the
eddy rim. Lateral shear leads to wave energy gain due to a developing
horizontal anisotropy outisde the eddy and at the rim, while vertical shear
leads to wave energy loss which is enhanced at the eddy rim. Wave energy loss
by wave dissipation due to vertical shear dominates over horizontal shear. Our
results show similar behaviour of the internal gravity wave in a cyclonic as
well as an anticyclonic eddy. Wave dissipation by vertical wave refraction
occurs predominantly at the eddy rim near the surface, where related vertical
diffusivities range from $\kappa \approx \mathcal{O}(10^{-7})$ to
$\mathcal{O}(10^{-5}) \, \rm m^2s^{-1}$.",2311.11916v1
2015-08-31,Interaction driven exotic quantum phases in spin-orbit coupled spin$-1$ bosons,"We study the interplay between large-spin, spin-orbit coupling, and
superfluidity for bosons in a two dimensional optical lattice, focusing on the
spin-1 spin-orbit coupled system recently realized at the Joint Quantum
Institute [Campbell et. al., arXiv:1501.05984]. We find a rich quantum phase
diagram, where, in addition to the conventional phases ---superfluid and
insulator--- contained in the spin-$1$ Bose-Hubbard model, there are new
lattice symmetry breaking phases. For weak interactions, the interplay between
two length scales, the lattice momentum and the spin-orbit wave-vector induce a
phase transition from a uniform superfluid to a phase where bosons
simultaneously condense at the center and edge of the Brillouin zone at a
non-zero spin-orbit strength. This state is characterized by spin density wave
order, which arises from the spin-$1$ nature of the system. Interactions
suppress spin density wave order, and favor a superfluid \textit{only} at the
Brillouin zone edge. This state has spatially oscillating mean field order
parameters, but a homogeneous density. We show that the spin density wave
superfluid phase survives in a two dimensional harmonic trap, and thus
establish that our results are directly applicable to experiments on $^{87}$Rb,
$^7$Li, and $^{41}$K.",1509.00005v2
2021-09-29,Prospects for measuring off-axis spins of binary black holes with Plus-era gravitational-wave detectors,"The mass and spin properties of binary black holes (BBHs) inferred from their
gravitational-wave signatures reveal important clues about how these systems
form. BBHs originating from isolated binary evolution are expected to have
spins preferentially aligned with their orbital angular momentum, whereas there
is no such preference in binaries formed via dynamical assembly. The fidelity
with which near-future gravitational-wave detectors can measure off-axis spins
will have implications for the study of BBH formation channels. In this work,
we examine the degree to which the Advanced LIGO Plus (A+) and Advanced Virgo
Plus (AdV+) interferometric detectors can measure both aligned and misaligned
spins. We compare spin resolution between the LIGO-Virgo network operating at
either A+/AdV+ (""Plus"") sensitivity or Advanced-era design (""Design"")
sensitivity using simulated BBH gravitational-wave signals injected into
synthetic detector noise. The signals are distributed over the mass-spin
parameter space of likely BBH systems, accounting for the effects of precession
and higher-order modes. We find that the Plus upgrades yield significant
improvements in spin estimation for systems with unequal masses and moderate or
large spins. Using simulated signals modelled after different types of
hierarchical BBH mergers, we also conclude that the Plus detector network will
yield substantially improved spin estimates for 1G+2G binaries compared to the
Design network.",2109.14571v2
2023-05-15,Tidal Spin-up of Black Hole Progenitor Stars,"Gravitational wave observations indicate the existence of merging black holes
(BHs) with high spin ($a\gtrsim0.3$), whose formation pathways are still an
open question. A possible way to form those binaries is through the tidal
spin-up of a Wolf-Rayet (WR) star by its BH companion. In this work, we
investigate this scenario by directly calculating the tidal excitation of
oscillation modes in WR star models, determining the tidal spin-up rate, and
integrating the coupled spin-orbit evolution for WR-BH binaries. We find that,
for short-period orbits and massive WR stars, the tidal interaction is mostly
contributed by standing gravity modes, in contrast to Zahn's model of traveling
waves which is frequently assumed in the literature. The standing modes are
less efficiently damped than traveling waves, meaning that prior estimates of
tidal spin-up may be overestimated. We show that tidal synchronization is
rarely reached in WR-BH binaries, and the resulting BH spins have $a \lesssim
0.4$ for all but the shortest-period ($P_{\rm orb} \! \lesssim 0.5 \, {\rm d}$)
binaries. Tidal spin-up in lower-mass systems is more efficient, providing an
anticorrelation between the mass and spin of the BHs, which could be tested in
future gravitational wave data. Nonlinear damping processes are poorly
understood but may allow for more efficient tidal spin-up. We also discuss a
new class of gravito-thermal modes that appear in our calculations.",2305.08356v2
2024-04-06,Spin-charge-lattice coupling across the charge density wave transition in a Kagome lattice antiferromagnet,"Understanding spin and lattice excitations in a metallic magnetic ordered
system form the basis to unveil the magnetic and lattice exchange couplings and
their interactions with itinerant electrons. Kagome lattice antiferromagnet
FeGe is interesting because it displays rare charge density wave (CDW) deep
inside the antiferromagnetic ordered phase that interacts with the magnetic
order. We use neutron scattering to study the evolution of spin and lattice
excitations across the CDW transition $T_{\rm CDW}$ in FeGe. While spin
excitations below $\sim$100 meV can be well described by spin waves of a spin-1
Heisenberg Hamiltonian, spin excitations at higher energies are centered around
the Brillouin zone boundary and extend up to $\sim180$ meV consistent with
quasiparticle excitations across spin-polarized electron-hole Fermi surfaces.
Furthermore, $c$-axis spin wave dispersion and Fe-Ge optical phonon modes show
a clear hardening below $T_{\rm CDW}$ due to spin-charge-lattice coupling but
with no evidence for a phonon Kohn anomaly. By comparing our experimental
results with density functional theory calculations in absolute units, we
conclude that FeGe is a Hund's metal in the intermediate correlated regime
where magnetism has contributions from both itinerant and localized electrons
arising from spin polarized electronic bands near the Fermi level.",2404.04459v1
2017-07-22,Transverse spinning of light with globally unique handedness,"Access to the transverse spin of light has unlocked new regimes in
topological photonics and optomechanics. To achieve the transverse spin of
nonzero longitudinal fields, various platforms that derive transversely
confined waves based on focusing, interference, or evanescent waves have been
suggested. Nonetheless, because of the transverse confinement inherently
accompanying sign reversal of the field derivative, the resulting transverse
spin handedness experiences spatial inversion, which leads to a mismatch
between the densities of the wavefunction and its spin component and hinders
the global observation of the transverse spin. Here, we reveal a globally pure
transverse spin in which the wavefunction density signifies the spin
distribution, by employing inverse molding of the eigenmode in the spin basis.
Starting from the target spin profile, we analytically obtain the potential
landscape and then show that the elliptic-hyperbolic transition around the
epsilon-near-zero permittivity allows for the global conservation of transverse
spin handedness across the topological interface between anisotropic
metamaterials. Extending to the non-Hermitian regime, we also develop
annihilated transverse spin modes to cover the entire Poincare sphere of the
meridional plane. Our results enable the complete transfer of optical energy to
transverse spinning motions and realize the classical analogy of 3-dimensional
quantum spin states.",1707.07099v1
2020-03-02,Higher-order Quantum Spin Hall Effect of Light,"Band topology and related spin (or pseudo-spin) physics of photons provide us
with a new dimension for manipulating light, which is potentially useful for
information communication and data storage. Especially, the quantum spin Hall
effect of light, where electromagnetic waves propagate along surfaces of
samples with strong spin-momentum locking, paves the way for achieving
topologically protected photonic spin transport. Recently, the conventional
bulk-edge correspondence of the band topology has been extended to higher-order
cases that enables the explorations of topological states with codimensions
larger than 1 such as hinge and corner states. Here, for the first time, we
demonstrate a higherorder quantum spin Hall effect of light by utilizing an
all-dielectric C6v-symmetric photonic crystal. We observe corner states with
opposite pseudospin polarizations at different corners owing to nontrivial
higher-order topology and finite spin-spin coupling. By applying the
spin-polarized excitation sources, we can selectively excite the corner states
at different spatial positions through spin-momentum-locked decaying edge
states, resembling the quantum spin Hall effect in a higher-order manner. Our
work which breaks the barriers between the spin photonics and higher-order
topology opens the frontiers for studying lower-dimensional spinful classical
surface waves and supports explorations in robust communications.",2003.00933v1
1996-02-28,Static and Dynamic Spin Structure Factors of Frustrated Heisenberg Antiferromagnet,"Using the modified spin-wave theory we calculate static and dynamic spin
structure factors in spin-liquid state of the J1-J2 model. The spectrum of
excitations in the vector channel is discussed. The developed technique can
also be applied to the t-J model describing copper oxide superconductors.",9602150v1
2006-02-07,Sublattice Asymmetric Reductions of Spin Values on Stacked Triangular Lattice Antiferromagnet CsCoBr$_3$,"We study the reductions of spin values of the ground state on a stacked
triangular antiferromagnet using the spin-wave approach. We find that the spin
reductions have sublattice asymmetry due to the cancellation of the molecular
field. The sublattice asymmetry qualitatively analyzes the NMR results of
CsCoBr$_3$.",0602165v1
2010-12-27,The multi-state CASPT2 spin-orbit method,"We propose the multi-state complete-active-space second-order perturbation
theory spin-orbit method (MS-CASPT2-SO) for electronic structure calculations.
It is a two-step spin-orbit coupling method that does not make use of energy
shifts and that intrinsically guarantees the correct characters of the small
space wave functions that are used to calculate the spin-orbit couplings, in
contrast with previous two-step methods.",1012.5572v1
2014-05-12,Spin spin interaction and the relativistic Rabi formula,"The interaction of an electromagnetic wave with spin (polarized light) and an
electron is computed. Specifically the spin flip probability is computed using
the Dirac equation for an electron trapped in a uniform magnetic field.",1405.2947v2
1999-11-18,Time-resolved optical observation of spin-wave dynamics,"We have created a nonequilibrium population of antiferromagnetic spin-waves
in Cr2O3, and characterized its dynamics, using frequency- and time-resolved
nonlinear optical spectroscopy of the exciton-magnon transition. We observe a
time-dependent pump-probe line shape, which results from excitation induced
renormalization of the spin-wave band structure. We present a model that
reproduces the basic characteristics of the data, in which we postulate the
optical nonlinearity to be dominated by interactions with long-wavelength
spin-waves, and the dynamics to be due to spin-wave thermalization.",9911294v1
2003-08-13,Resonating valence bond wave function for the two dimensional fractional spin liquid,"The unconventional low-lying spin excitations, recently observed in neutron
scattering experiments on ${\rm Cs_2 Cu Cl_4}$, are explained with a spin
liquid wave function. The dispersion relation as well as the wave vector of the
incommensurate spin correlations are well reproduced within a projected BCS
wave function with gapless and fractionalized spin-1/2 excitations around the
nodes of the BCS gap function. The proposed wave function is shown to be very
accurate for one-dimensional spin-1/2 systems, and remains similarly accurate
in the two-dimensional model corresponding to ${\rm Cs_2 Cu Cl_4}$, thus
representing a good ansatz for describing spin fractionalization in two
dimensions.",0308252v2
2004-07-16,Interaction and dynamical binding of spin waves or excitons in quantum Hall systems,"Interaction between spin waves (or excitons) moving in the lowest Landau
level is studied using numerical diagonalization. Becuse of complicated
statistics obeyed by these composite particles, their effective interaction is
completely different from the dipole-dipole interaction predicted in the model
of independent (bosonic) waves. In particular, spin waves moving in the same
direction attract one another which leads to their dynamical binding. The
interaction pseudopotentials V_[up,up](k) and V_[up,down](k) for two spin waves
with equal wavevectors k and moving in the same or opposite directions have
been calculated and shown to obey power laws V(k) ~ k^alpha at small k. A high
value of alpha_[up,up]~4 explains the occurrence of linear bands in the spin
excitation spectra of quantum Hall droplets.",0407449v1
2006-06-05,Can the Landau-Lifshitz equation explain the spin-wave instability in ferromagnetic thin films for parallel pumping?,"Spin-wave instability is studied analytically in the case of parallel pumping
for thin films under external field perpendicular to the film plane. It is
examined whether the instability threshold derived from only the
Landau-Lifshitz (LL) equation can explain experimental instability threshold
without using the microscopically-derived spin-wave line width, which is
conventionally used. It is revealed that the butterfly curve cannot be
explained from only the LL equation at least in an analytical way. By contrast,
for the case of perpendicular pumping, the Suhl instability was well explained
from the LL equation. The difference between the two cases comes from the
nonlinear terms describing the relaxation of spin waves. It is suggested how
the nonlinear terms in the LL equation should be related to the spin-wave line
width for parallel pumping.",0606106v1
2008-02-14,Coriolis Effect in Optics: Unified Geometric Phase and Spin-Hall Effect,"We examine the spin-orbit coupling effects that appear when a wave carrying
intrinsic angular momentum interacts with a medium. The Berry phase is shown to
be a manifestation of the Coriolis effect in a non-inertial reference frame
attached to the wave. In the most general case, when both the direction of
propagation and the state of the wave are varied, the phase is given by a
simple expression that unifies the spin redirection Berry phase and the
Pancharatnam--Berry phase. The theory is supported by the experiment
demonstrating the spin-orbit coupling of electromagnetic waves via a surface
plasmon nano-structure. The measurements verify the unified geometric phase,
demonstrated by the observed polarization-dependent shift (spin-Hall effect) of
the waves.",0802.2114v2
2008-04-03,On the coupling between spinning particles and cosmological gravitational waves,"The influence of spin in a system of classical particles on the propagation
of gravitational waves is analyzed in the cosmological context of primordial
thermal equilibrium. On a flat Friedmann-Robertson-Walker metric, when the
precession is neglected, there is no contribution due to the spin to the
distribution function of the particles. Adding a small tensor perturbation to
the background metric, we study if a coupling between gravitational waves and
spin exists that can modify the evolution of the distribution function, leading
to new terms in the anisotropic stress, and then to a new source for
gravitational waves. In the chosen gauge, the final result is that, in the
absence of other kind of perturbations, there is no coupling between spin and
gravitational waves.",0804.0572v1
2008-12-09,Quantized spin waves in the metallic state of magnetoresistive manganites,"High resolution spin waves measurements have been carried out in
ferromagnetic (F) La(1-x)(Sr,Ca)xMnO3 with x(Sr)=0.15, 0.175, 0.2, 0.3 and
x(Ca)=0.3. In all q-directions, close to the zone boundary, the spin wave
spectra consist of several energy levels, with the same values in the metallic
and the x\approx 1/8 ranges. Mainly the intensity varies, jumping from the
lower energy levels determined in the x\approx 1/8 range to the higher energy
ones observed in the metallic state. On the basis of a quantitative agreement
found for x(Sr)=0.15 in a model of ordered 2D clusters, the spin wave anomalies
of the metallic state can be interpreted in terms of quantized spin waves
within the same 2D clusters, embedded in a 3D matrix.",0812.1715v2
2009-02-13,A spin-wave frequency doubler by domain wall oscillation,"We present a new mechanism for spin-wave excitation using a pinned domain
wall which is forced to oscillate at its eigenfrequency and radiates spin
waves. The domain wall acts as a frequency doubler, as the excited spin waves
have twice the frequency of the domain wall oscillation. The investigations
have been carried out using micromagnetic simulations and enable the
determination of the main characteristics of the excited spin-waves such as
frequency, wavelength, and velocity. This behavior is understood by the
oscillation in the perpendicular magnetization which shows two anti-nodes
oscillating out of phase with respect to each other.",0902.2321v1
2009-12-10,Magnonic crystal based forced dominant wavenumber selection in a spin-wave active ring,"Spontaneous excitation of the dominant mode in a spin-wave active ring -- a
self-exciting positive-feedback system incorporating a spin-wave transmission
structure -- occurs at a certain threshold value of external gain. In general,
the wavenumber of the dominant mode is extremely sensitive to the properties
and environment of the spin-wave transmission medium, and is almost impossible
to predict. In this letter, we report on a backward volume magnetostatic
spin-wave active ring system incorporating a magnonic crystal. When mode
enhancement conditions -- readily predicted by a theoretical model -- are
satisfied, the ring geometry permits highly robust and consistent forced
dominant wavenumber selection.",0912.2029v3
2010-05-11,NMR Measurements of Power-Law Behavior in the Spin-Wave and Critical Regions of Ferromagnetic EuO,"Precision continuous-wave NMR measurements have been carried out over the
entire magnetization curve of EuO and are presented in tabular form. Two very
closely spaced resonances are observed and are attributed to domain and
domain-wall signals. Both of the signals are useful for analysis in the
spin-wave region. Only the domain signal is measurable above ~50K. The latter
is used for fitting Tc and the critical exponent beta. The critical-region fits
agree with previous measurements, within experimental error. The
low-temperature data exhibit a clear-cut T^2 behavior, at variance with the
expectations of conventional spin-wave theory. This result is discussed in
relation to two semi-empirical spin-wave schemes, one formulated by N.
Bykovetz, and one by U. Koebler. The NMR signal at 4.2K gives no indication of
a quadrupole splitting, in contradiction to the interpretation of several
previous spin-echo NMR spectra observed in EuO. This issue remains unresolved.",1005.1692v1
2011-09-09,Mode conversion by symmetry breaking of propagating spin waves,"We study spin-wave transport in a microstructured Ni81Fe19 waveguide
exhibiting broken translational symmetry. We observe the conversion of a beam
profile composed of symmetric spin-wave width modes with odd numbers of
antinodes n=1,3,... into a mixed set of symmetric and asymmetric modes. Due to
the spatial homogeneity of the exciting field along the used microstrip
antenna, quantized spin-wave modes with an even number n of antinodes across
the stripe's width cannot be directly excited. We show that a break in
translational symmetry may result in a partial conversion of even spin-wave
waveguide modes",1109.1958v2
2012-08-25,Spin dynamics of possible density wave states in the pseudogap phase of the high temperature superconductors,"In a recent inelastic neutron scattering experiment in the pseudogap state of
the high temperature superconductor $\mathrm{YBa_{2}Cu_{3}O_{6.6}}$ an unusual
`vertical' dispersion of the spin excitations with a large in-plane anisotropy
was observed. In this paper we discuss in detail the spin susceptibility of the
singlet $d$-density wave, the triplet $d$-density wave, as well as the more
common spin density wave orders with hopping anisotropies. From numerical
calculations within the framework of random phase approximation, we find nearly
vertical dispersion relations for spin excitations with anisotropic
incommensurability at low energy $\omega \le 90 meV$, which are reminiscent of
the experiments. At very high energy $\omega \ge 165 meV$, we also find
energy-dependent incommensurability. Although there are some important
difference between the three cases, unpolarized neutron measurements cannot
discriminate between these alternate possibilities; the vertical dispersion,
however, is a distinct feature of all three density wave states in contrast to
the superconducting state, which shows an hour-glass shape dispersion.",1208.5108v1
2013-03-07,Chiral spin-wave edge modes in dipolar magnetic thin films,"Based on a linearized Landau-Lifshitz equation, we show that two-dimensional
periodic allay of ferromagnetic particles coupled with magnetic dipole-dipole
interactions supports chiral spin-wave edge modes, when subjected under the
magnetic field applied perpendicular to the plane. The mode propagates along a
one-dimensional boundary of the system in a unidirectional way and it always
has a chiral dispersion within a band gap for spin-wave volume modes. Contrary
to the well-known Damon-Eshbach surface mode, the sense of the rotation depends
not only on the direction of the field but also on the strength of the field;
its chiral direction is generally determined by the sum of the so-called Chern
integers defined for spin-wave volume modes below the band gap. Using simple
tight-binding descriptions, we explain how the magnetic dipolar interaction
endows spin-wave volume modes with non-zero Chern integers and how their values
will be changed by the field.",1303.1630v3
2013-04-08,Electronic phase separation in iron pnictides,"A mechanism for electronic phase separation in iron pnictides is proposed. It
is based on the competition between commensurate and incommensurate
spin-density-wave phases in a system with an imperfect doping-dependent nesting
of a multi-sheeted Fermi surface. We model the Fermi surface by two elliptical
electron pockets and three circular hole pockets. The interaction between a
charge carrier in a hole band and a carrier in an electron band leads to the
formation of spin-density-wave order. The commensurate spin density wave in the
parent compound transforms to the incommensurate phase when doping is
introduced. We show that, for certain parameter values, the uniform state is
unstable with respect to phase separation. The resulting inhomogeneous state
consists of regions of commensurate and incommensurate spin-density-wave
phases. Our results are in qualitative agreement with recent observations of
incommensurate spin density waves and electronic inhomogeneity in iron
pnictides.",1304.2175v2
2013-10-12,Role of Anion Ordering in the Coexistence of Spin-Density-Wave and Superconductivity in (TMTSF)2ClO4,"Using various transport and magnetotransport probes we study the coexistence
of spin-density wave and superconductor states in (TMTSF)2ClO4 at various
degrees of ClO4 anions ordering. In the two-phase complex state when both
superconductivity and spin-density wave are observed in transport, we find
prehistory effects, enhancement of the superconducting critical field, and
strong spatial anisotropy of the superconducting state. These features are
inconsistent with the conventional model of structural inhomogeneities produced
by anion ordering transition. We reveal instead that superconductor and
spin-density wave regions overlap on the temperature -- dimerization gap V
phase diagram, where V is varied by anion ordering. The effect of anion
ordering on (TMTSF)2ClO4 properties is thus analogous to that of pressure on
(TMTSF)2X (X=PF6 or AsF6), thereby unifying general picture of the coexistence
of superconductivity and spin-density wave in these compounds.",1310.3434v1
2013-11-25,Spin-wave excitation and propagation in microstructured waveguides of yttrium iron garnet (YIG)/Pt bilayers,"We present an experimental study of spin-wave excitation and propagation in
microstructured waveguides patterned from a 100 nm thick yttrium iron garnet
(YIG)/platinum (Pt) bilayer. The life time of the spin waves is found to be
more than an order of magnitude higher than in comparably sized metallic
structures despite the fact that the Pt capping enhances the Gilbert damping.
Utilizing microfocus Brillouin light scattering spectroscopy, we reveal the
spin-wave mode structure for different excitation frequencies. An exponential
spin-wave amplitude decay length of 31 {\mu}m is observed which is a
significant step towards low damping, insulator based micro-magnonics.",1311.6305v1
2014-03-27,Driving spin and charge in quantum wells by surface acoustic waves,"Recent experiments have shown the potential of surface acoustic waves as a
mean for transporting charge and spin in quantum wells. In particular, they
have proven highly effective for the coherent transport of spin-polarized wave
packets, suggesting their potential in spintronics applications. Motivated by
these experimental observations, we have theoretically studied the spin and
charge dynamics in a quantum well under surface acoustic waves. We show that
the dynamics acquires a simple and transparent form in a reference frame
co-moving with the surface acoustic wave. Our results, e.g., the calculated
spin relaxation and precession lengths, are in excellent agreement with recent
experimental observations.",1403.6960v2
2014-04-14,Cavity-enhanced storage in an optical spin-wave memory,"We report on the experimental demonstration of an optical spin-wave memory,
based on the atomic frequency comb (AFC) scheme, where the storage efficiency
is strongly enhanced by an optical cavity. The cavity is of low finesse, but
operated in an impedance matching regime to achieve high absorption in our
intrinsically low-absorbing Eu3+:Y2SiO5 crystal. For storage of optical pulses
as an optical excitation (AFC echoes), we reach efficiencies of 53% and 28% for
2 and 10 microseconds delays, respectively. For a complete AFC spin-wave memory
we reach an efficiency of 12%, including spin-wave dephasing, which is a
12-fold increase with respect to previous results in this material. This result
is an important step towards the goal of making efficient and long-lived
quantum memories based on spin waves, in the context of quantum repeaters and
quantum networks.",1404.3489v1
2014-04-22,Spin-wave-induced correction to the conductivity of ferromagnets,"We calculate the correction to the conductivity of a disordered ferromagnetic
metal due to spin-wave-mediated electron--electron interactions. This
correction is the generalization of the Altshuler-Aronov correction to
spin-wave-mediated interactions. We derive a general expression for the
conductivity correction to lowest order in the spin-wave-mediated interaction
and for the limit that the exchange splitting $\Delta$ is much smaller than the
Fermi energy. For a ""clean"" ferromagnet with $\Delta\tau_{\rm el}/\hbar \gg 1$,
with $\tau_{\rm el}$ the mean time for impurity scattering, we find a
correction $\delta \sigma \propto -T^{5/2}$ at temperatures $T$ above the spin
wave gap. In the opposite, ""dirty"" limit, $\Delta\tau_{\rm el}/\hbar \ll 1$,
the correction is a non-monotonous function of temperature.",1404.5437v1
2014-10-02,Spin wave non-reciprocity and beating in permalloy by time-resolved magneto-optical Kerr effect,"We have studied the propagation characteristics of spin wave modes in a
permalloy stripe by time-resolved magneto-optical Kerr effect techniques. We
observe a beating interference pattern in the time domain under the influence
of an electrical square pulse excitation at the center of the stripe. We also
probe the non-reciprocal behavior of propagating spin waves with a dependence
on the external magnetic field. Spatial dependence studies show that localized
edge mode spin waves have a lower frequency than spin waves in the center of
the stripe, due to the varying magnetization vector across the width of the
stripe.",1410.0441v1
2014-11-04,A micro-sized parametric spin-wave amplifier,"We present the experimental observation of the localized amplification of
externally excited spin waves in a transversely in-plane magnetized
Ni$_{81}$Fe$_{19}$ magnonic waveguide by means of parallel pumping. By
employing microfocussed Brillouin light scattering spectroscopy, we analyze the
dependency of the amplification on the applied pumping power and on the delay
between the input spin-wave packet and the pumping pulse. We show that there
are two different operation regimes: At large pumping powers, the spin-wave
packet needs to enter the amplifier before the pumping is switched on in order
to be amplified while at low powers the spin-wave packet can arrive at any time
during the pumping pulse.",1411.0830v1
2015-02-22,Excitation and detection of propagating spin waves at the single magnon level,"Ferro- and ferrimagnets play host to small-signal, microwave-frequency
magnetic excitations called spin waves, the quanta of which are known as
magnons. Over the last decade, the field of spin-wave dynamics has contributed
much to our understanding of fundamental magnetism. To date, experiments have
focussed overwhelmingly on the study of room-temperature systems within
classical limits. Here we demonstrate, for the first time, the excitation and
detection of propagating spin waves at the single magnon level. Our results
allow us to project that coupling of propagating spin-wave excitations to
quantum circuits is achievable, enabling fundamental quantum-level studies of
magnon systems and potentially opening doors to novel hybrid quantum
measurement and information processing devices.",1502.06263v1
2015-04-10,Influence of magnetic surface anisotropy on spin wave reflection from the edge of ferromagnetic film,"We study propagation of the Gaussian beam of spin waves and its reflection
from the edge of thin yttrium-iron-garnet film with in-plane magnetization
perpendicular to this edge. We have performed micromagnetic simulations
supported by analytical calculations to investigate influence of the surface
magnetic anisotropy present at the film edge on the reflection, especially in
the context of the Goos-Hanchen effect. We have shown the appearance of a
negative lateral shift between reflected and incident spin wave beams' spots.
This shift is particularly sensitive to the surface magnetic anisotropy value
and is a result of the Goos-Hanchen shift which is sensitive to the magnitude
of the anisotropy and of the bending of spin wave beam. We have demonstrated
that the demagnetizing field provide graded increase of the refractive index
for spin waves, which is responsible for the bending.",1504.02668v2
2015-09-17,Antiferromagnetic Spin Wave Field-Effect Transistor,"In a collinear antiferromagnet with easy-axis anisotropy, symmetry dictates
that the spin wave modes must be doubly degenerate. Theses two modes,
distinguished by their opposite polarization and available only in
antiferromagnets, give rise to a novel degree of freedom to encode and process
information. We show that the spin wave polarization can be manipulated by an
electric field induced Dzyaloshinskii-Moriya interaction and magnetic
anisotropy. We propose a prototype spin wave field-effect transistor which
realizes a gate-tunable magnonic analog of the Faraday effect, and demonstrate
its application in THz signal modulation. Our findings open up the exciting
possibility of digital data processing utilizing antiferromagnetic spin waves
and enable the direct projection of optical computing concepts onto the
mesoscopic scale.",1509.05295v3
2015-10-08,"Orbital order, spin waves, and doping effects in the $(π,0)$ SDW state --- comparative study of the three band models for iron pnictides","Aimed at identifying the role of microscopic Hamiltonian parameters on spin
wave excitations, orbital order, and magnetic moments in the $(\pi,0)$ SDW
state, two different three band models for iron pnictides are compared --- one
at two-third filling ($n=4$) and another at half filling $(n=3)$ --- both of
which yield qualitatively correct Fermi surface structure in the paramagnetic
state. Spin wave analysis of the model at $n=4$ shows instability of the SDW
state, which is attributed to weakly developed magnetic moments and weak
magnetic couplings due to overfilling, as inferred from the observed
stabilization of the SDW state and enhancement of magnetic excitation energies
upon hole doping. In contrast, the model at $n=3$ (half filling) yields a
gapped SDW state with well developed magnetic moments and the calculated spin
wave excitations are in excellent agreement with INS experiments. The sign of
the orbital order ($n_{xz} - n_{yz} \approx +0.2$) is also in agreement with
experiments. Both the zone boundary spin wave energies in the F and AF
directions as well as the orbital order are shown to peak near half filling,
highlighting the correlation between orbital order and SDW state stabilization.",1510.02276v1
2015-12-09,Entanglement between Lowly and Highly Lying Atomic Spin Waves,"Establishing a quantum interface between different physical systems is of
special importance for developing the practical versatile quantum networks.
Entanglement between low- and high-lying atomic spin waves is essential for
building up Rydberg-based quantum information engineering, otherwhile be more
helpful to study the dynamics behavior of entanglement under external pertur-
bations. Here, we report on the successful storage of a single photon as a
high-lying atomic spin wave in quantum regime. Via storing a K-vector
entanglement between single photon and lowly lying spin wave, we thereby
experimentally realize the entanglement between low- and high-lying atomic spin
waves in two separated atomic systems. This makes our experiment the primary
demonstration of Rydberg quantum memory of entanglement, making a primary step
toward the construction of a hybrid quantum interface.",1512.02772v3
2016-01-11,Nonlinear effects in the propagation of optically generated magnetostatic volume mode spin waves,"Recent experimental work has demonstrated optical control of spin wave
emission by tuning the shape of the optical pulse (Satoh et al.\ Nature
Photonics, 6, 662 (2012)). We reproduce these results and extend the scope of
the control by investigating nonlinear effects for large amplitude excitations.
We observe an accumulation of spin wave power at the center of the initial
excitation combined with short-wavelength spin waves. These kind of nonlinear
effects have not been observed in earlier work on nonlinearities of spin waves.
Our observations pave the way for the manipulation of magnetic structures at a
smaller scale than the beam focus, for instance in devices with all-optical
control of magnetism.",1601.02511v5
2016-01-27,Quantification of a propagating spin-wave-packet created by an ultrashort laser pulse in a thin film of magnetic metal,"Coherent spin-wave generation by focused ultrashort laser pulse irradiation
was investigated for a permalloy thin film at micrometer scale using an
all-optical space and time-resolved magneto-optical Kerr effect. The spin-wave
packet propagating perpendicular to magnetization direction was clearly
observed, however that propagating parallel to the magnetization direction was
not observed. The propagation length, group velocity, center frequency, and
packet-width of the observed spin-wave packet were evaluated and quantitatively
explained in terms of the propagation of a magneto-static spin-wave driven by
ultrafast change of an out-of-plane demagnetization field induced by the
focused-pulse laser.",1601.07247v1
2016-04-25,Excitation of spin wave modes of a magnetic dot existing in a shifted vortex-state by an out-of-plane oscillating magnetic field,"Excitation of spin wave modes of a vortex-state magnetic dot by an
out-of-plane oscillating magnetic field is studied numerically in the presence
of a static in-plane magnetic field. It is shown, that the application of the
in-plane static field shifts the position of the vortex core and leads to the
separate excitation of different azimuthal dipolar spin waves my perpendicular
oscillating field. It is also shown that the excited dipolar azimuthal spin
waves excite the gyrotropic mode of the vortex core rotation and, depending on
the excitation frequency, cause a significant modification (increase or
decrease) of the apparent dissipation rate of the gyrotropic mode. The last
effect can be explained by the nonlinear parametric interaction between the
gyrotropic mode and the dipolar spin wave modes with different azimuthal
indices.",1604.07161v1
2016-07-26,Transverse azimuthal dephasing of vortex spin wave in a hot atomic gas,"Optical fields with orbital angular momentum (OAM) interact with medium have
many remarkable properties with its unique azimuthal phase, showing many
potential applications in high capacity information processing, high precision
measurement etc. The dephasing mechanics of optical fields with OAM in an
interface between light and matter plays a vital role in many areas of physics.
In this work, we study the transverse azimuthal dephasing of OAM spin wave in a
hot atomic gas via OAM storage. The transverse azimuthal phase difference
between the control and probe beams is mapped onto the spin wave, which
essentially results in dephasing of atomic spin wave. The dephasing of OAM spin
wave can be controlled by the parameters of OAM topological charge and beam
waist. Our results are helpful for studying OAM light interaction with matter,
maybe hold a promise in OAM-based quantum information processing.",1607.07689v1
2016-09-27,Spin-wave dynamics in FeGe helimagnet: studied by small-angle neutron scattering,"We have studied the spin-wave stiffness of the Dzyaloshinskii-Moriya
helimagnet FeGe in a temperature range from 225~K up to $T_C \approx$~278.7~K
by small-angle neutron scattering. The method we have used is based on [S. V.
Grigoriev et al. Phys. Rev. B \textbf{92} 220415(R) (2015)] and was extended
here for the application in polycrystalline samples. We confirm the validity of
the anisotropic spin-wave dispersion for FeGe caused by the
Dzyaloshinskii-Moriya interaction. We have shown that the spin-wave stiffness
$A$ for FeGe helimagnet decreases with a temperature as $A(T) =
194(1-0.7(T/T_C)^{4.2})$ meV\AA$^2$. The finite value of the spin-wave
stiffness $A = 58$ meV\AA$^2$ at $T_C$ classifies the order-disorder phase
transition in FeGe as being the first order one.",1609.08358v1
2018-01-19,Nonabelian magnonics in antiferromagnets,"We present a semiclassical formalism for antiferromagnetic (AFM) magnonics
which promotes the central ingredient of spin wave chirality, encoded in a
quantity called magnonic isospin, to a first-class citizen of the theory. We
use this formalism to unify results of interest from the field under a single
chirality-centric formulation. Our main result is that the isospin is governed
by unitary time evolution, through a Hamiltonian projected down from the full
spin wave dynamics. Because isospin is SU(2)-valued, its dynamics on the Bloch
sphere are precisely rotations - which, in general, do not commute.
Consequently, the induced group of operations on AFM spin waves is nonabelian.
This is a paradigmatic departure from ferromagnetic magnonics, which operates
purely within the abelian group generated by spin wave phase and amplitude. Our
investigation of this nonabelian magnonics in AFM insulators focuses on
studying several simple gate operations, and offering in broad strokes a
program of study for interesting new logic families in antiferromagnetic spin
wave systems",1801.06535v3
2018-01-25,Electrical generation and detection of spin waves in a quantum Hall ferromagnet,"Spin waves are collective excitations of magnetic systems. An attractive
setting for studying long-lived spin-wave physics is the quantum Hall (QH)
ferromagnet, which forms spontaneously in clean two-dimensional electron
systems at low temperature and in a perpendicular magnetic field. We used
out-of-equilibrium occupation of QH edge channels in graphene to excite and
detect spin waves in magnetically ordered QH states. Our experiments provide
direct evidence for long distance spin wave propagation through different
ferromagnetic phases in the N=0 Landau level, as well as across the insulating
canted antiferromagnetic phase. Our results will enable experimental
investigation of the fundamental magnetic properties of these exotic
two-dimensional electron systems.",1801.08534v2
2018-11-01,Population Synthesis of Accreting Neutron Stars Emitting Gravitational Waves,"The fastest-spinning neutron stars in low-mass X-ray binaries, despite having
undergone millions of years of accretion, have been observed to spin well below
the Keplerian break-up frequency. We simulate the spin evolution of synthetic
populations of accreting neutron stars in order to assess whether gravitational
waves can explain this behaviour and provide the distribution of spins that is
observed. We model both persistent and transient accretion and consider two
gravitational-wave-production mechanisms that could be present in these
systems: thermal mountains and unstable $r$-modes. We consider the case of no
gravitational-wave emission and observe that this does not match well with
observation. We find evidence for gravitational waves being able to provide the
observed spin distribution; the most promising mechanisms being a permanent
quadrupole, thermal mountains and unstable $r$-modes. However, based on the
resultant distributions alone it is difficult to distinguish between the
competing mechanisms.",1811.00550v2
2018-11-12,Ultra-narrow spin wave metasurface for focusing application,"In this paper we show that the phase shift of the spin waves can be
controlled in transmission through metasurface represented as an ultra-narrow
non-magnetic spacer separating two ferromagnetic films. We design this
metasurface to present the focusing of spin waves in an Co thin film. For this
purpose we exploit the strength of the interlayer exchange coupling
interactions of RKKY type which allows to control the phase of the transmitted
and reflected spin waves in the wide range of angles [$-\pi/2$;$\pi/2$]. We
combined this phase-shift dependency with the lens equation to demonstrate
numerically the lens for spin waves based on ultra-narrow metasurface.",1811.04613v2
2019-11-25,Snell's law for spin waves at a 90-degree domain wall,"We report experimental observation of the refraction and re ection of
propagating magnetostatic spin waves crossing a 90-degree domain wall (DW) in
terms of time-resolved magneto-optical imaging. Due to the magnetization
rotation across the 90-degree DW, the dispersion relation of magnetostatic spin
waves rotates by 90 degrees, which results in the change in the propagation
dynamics of spin waves in both sides of the DW. We observe the refraction and
re ection of magnetosatatc spin waves at the 90-degree DW, and reveal their
characteristics, such as negative refraction. The incident-angle dependence of
the refraction angle is explained by the wavenumber conservation along the DW,
same as the case of Snell's law for light.",1911.10659v1
2017-05-08,Deviation and precession effects in the field of a weak gravitational wave,"Deviation and precession effects of a bunch of spinning particles in the
field of a weak gravitational plane wave are studied according to the
Mathisson-Papapetrou-Dixon (MPD) model. Before the passage of the wave the
particles are at rest with associated spin vector aligned along a given
direction with constant magnitude. The interaction with the gravitational wave
causes the particles to keep moving on the 2-plane orthogonal to the direction
of propagation of the wave, with the transverse spin vector undergoing
oscillations around the initial orientation. The transport equations for both
the deviation vector an spin vector between two neighboring world lines of such
a congruence are then solved by a suitable extension of the MPD model off the
spinning particle's world line. In order obtain measurable physical quantities
a ""laboratory"" has been set up by constructing a Fermi coordinate system
attached to a reference world line. The {\it exact} transformation between TT
coordinates and Fermi coordinates is derived too.",1705.02794v1
2017-05-25,Spin-wave spectroscopy on Dzyaloshinskii-Moriya interaction in room-temperature chiral magnets hosting skyrmions,"Propagation character of spin wave was investigated for chiral magnets FeGe
and Co-Zn-Mn alloys, which can host magnetic skyrmions near room temperature.
On the basis of the frequency shift between counter-propagating spin waves, the
magnitude and sign of Dzyaloshinskii-Moriya (DM) interaction were directly
evaluated. The obtained magnetic parameters quantitatively account for the size
and helicity of skyrmions as well as their materials variation, proving that
the DM interaction plays a decisive role in the skyrmion formation in this
class of room-temperature chiral magnets. The propagating spin-wave
spectroscopy can thus be an efficient tool to study DM interaction in bulk
single-phase compounds. Our results also demonstrate a function of spin-wave
diode based on chiral crystal structures at room temperature.",1705.09001v1
2018-07-27,Optimization of Multi-Frequency Magnonic Waveguides with Enhanced Group Velocities by Exchange Coupled Ferrimagnet/Ferromagnet Bilayers,"We report broadband spectroscopy and numerical analysis by which we explore
propagating spin waves in a magnetic bilayer consisting of a 23 nm thick
permalloy film deposited on 130 nm thick $Y_{3}Fe_{5}O_{12}$. In the bilayer,
we observe a characteristic mode that exhibits a considerably larger group
velocity at small in-plane magnetic field than both the magnetostatic and
perpendicular standing spin waves. Using the finite element method, we confirm
the observations by simulating the mode profiles and dispersion relations. They
illustrate the hybridization of spin wave modes due to exchange coupling at the
interface. The high-speed propagating mode found in the bilayer can be utilized
to configure multi-frequency spin wave channels enhancing the performance of
spin wave based logic devices.",1807.10508v2
2018-02-12,Dynamics of a magnetic skyrmionium driven by spin waves,"The magnetic skyrmionium is a skyrmion-like structure but carries a zero net
skyrmion number, which can be used as a building block for non-volatile
information processing devices. Here, we study the dynamics of a magnetic
skyrmionium driven by propagating spin waves. It is found that the skyrmionium
can be effectively driven into motion by spin waves showing tiny skyrmion Hall
effect, of which the mobility is much better than that of the skyrmion at the
same condition. We also show that the skyrmionium mobility depends on the
nanotrack width and damping coefficient, and can be controlled by an external
out-of-plane magnetic field. Besides, we demonstrate the skyrmionium motion
driven by spin waves is inertial. Our results indicate that the skyrmionium is
a promising building block for building spin-wave spintronic devices.",1802.03868v2
2016-12-07,Non-volatile spin wave majority gate at the nanoscale,"A spin wave majority fork-like structure with feature size of 40\,nm, is
presented and investigated, through micromagnetic simulations. The structure
consists of three merging out-of-plane magnetization spin wave buses and four
magneto-electric cells serving as three inputs and an output. The information
of the logic signals is encoded in the phase of the transmitted spin waves and
subsequently stored as direction of magnetization of the magneto-electric cells
upon detection. The minimum dimensions of the structure that produce an
operational majority gate are identified. For all input combinations, the
detection scheme employed manages to capture the majority phase result of the
spin wave interference and ignore all reflection effects induced by the
geometry of the structure.",1612.02170v1
2017-06-10,Spin wave nonreciprocity and magnonic band structure in thin permalloy film induced by dynamical coupling with an array of Ni stripes,"An efficient way for the control of spin wave propagation in a magnetic
medium is the use of periodic patterns known as magnonic crystals (MCs).
However, the fabrication of MCs especially bi-components, with periodicity on
nanoscale, is a challenging task due to the requirement for sharp interfaces.
An alternative method to circumvent this problem is to use homogeneous
ferromagnetic film with modified periodically surrounding. The structure is
also suitable for exploiting nonreciprocal properties of the surface spin
waves. In this work, we demonstrate that the magnonic band structure forms in
thin permalloy film due to dynamical magnetostatic coupling with Ni stripes
near its surface. We show, that the band gap width can be systematically tuned
by the changing interlayer thickness between film and stripes. We show also the
effect of nonreciprocity, which is seen at the band gap edge shifted from the
Brillouin zone boundary and also in nonreciprocal interaction of propagating
spin waves in Py film with the standing spin waves in Ni stripes. Our findings
open possibility for further investigation and exploitation of the
nonreciprocity and band structure in magnonic devices.",1706.03202v1
2020-09-07,Field-theory spin and momentum in water waves,"Spin is a fundamental yet nontrivial intrinsic angular-momentum property of
quantum particles or fields, which appears within relativistic field theory.
The spin density in wave fields is described by the theoretical
Belinfante-Rosenfeld construction based on the difference between the canonical
and kinetic momentum densities. These quantities are usually considered as
abstract and non-observable per se. Here, we demonstrate, both theoretically
and experimentally, that the Belinfante-Rosenfeld construction naturally arises
in gravity (water surface) waves. There, the canonical momentum is associated
with the generalized Stokes-drift phenomenon, while the spin is generated by
subwavelength circular motion of water particles. Thus, we directly observe
these fundamental field-theory properties as microscopic mechanical properties
of a classical wave system. Our findings shed light onto the nature of spin and
momentum in wave fields, demonstrate the universality of relativistic
field-theory concepts, and offer a new platform for their studies.",2009.03245v4
2020-11-02,Simulating Spin Waves in Entropy Stabilized Oxides,"The entropy stabilized oxide
Mg$_{0.2}$Co$_{0.2}$Ni$_{0.2}$Cu$_{0.2}$Zn$_{0.2}$O exhibits antiferromagnetic
order and magnetic excitations, as revealed by recent neutron scattering
experiments. This observation raises the question of the nature of spin wave
excitations in such disordered systems. Here, we investigate theoretically the
magnetic ground state and the spin-wave excitations using linear spin-wave
theory in combination with the supercell approximation to take into account the
extreme disorder in this magnetic system. We find that the experimentally
observed antiferromagnetic structure can be stabilized by a rhombohedral
distortion together with large second nearest neighbor interactions. Our
calculations show that the spin-wave spectrum consists of a well-defined
low-energy coherent spectrum in the background of an incoherent continuum that
extends to higher energies.",2011.01288v1
2021-04-23,Spin-wave frequency combs,"We experimentally demonstrate the generation of spin-wave frequency combs
based on the nonlinear interaction of propagating spin waves in a
microstructured waveguide. By means of time and space-resolved Brillouin light
scattering spectroscopy, we show that the simultaneous excitation of spin waves
with different frequencies leads to a cascade of four-magnon scattering events
which ultimately results in well-defined frequency combs. Their spectral weight
can be tuned by the choice of amplitude and frequency of the input signals.
Furthermore, we introduce a model for stimulated four-magnon scattering which
describes the formation of spin-wave frequency combs in the frequency and time
domain.",2104.11491v2
2021-08-23,Reconfigurable 3D magnonic crystal: tunable and localized spin-wave excitations in CoFeB meander-shaped film,"In this work, we study experimentally by broadband ferromagnetic resonance
measurements, the dependence of the spin-wave excitation spectra on the
magnetic applied field in CoFeB meander-shaped films. Two different
orientations of the external magnetic field were explored, namely parallel or
perpendicular to the lattice cores. The interpretation of the field dependence
of the frequency and spatial profiles of major spin-wave modes were obtained by
micromagnetic simulations. We show that the vertical segments lead to the
easy-axis type of magnetic anisotropy and support the in-phase and out-of-phase
spin-wave precession amplitude in the vertical segments. The latter could
potentially be used for the design of tunable metasurfaces or in magnetic
memories based on meandering 3D magnetic films.",2108.10232v1
2021-10-21,Generation of perfect-cavity-enhanced atom-photon entanglement with a millisecond lifetime via a spatially-multiplexed cavity,"A qubit memory is the building block for quantum information. Cavity-enhanced
spin-wave-photon entanglement has been achieved by applying dual-control modes.
However, owing to cross readouts between the modes, the qubit retrieval
efficiency is about one quarter lower than that for a single spin-wave mode at
all storage times. Here, we overcome cross readouts using a multiplexed ring
cavity. The cavity is embedded with a polarization interferometer, and we
create a write-out photonic qubit entangled with a magnetic-field-insensitive
spin-wave qubit by applying a single-mode write-laser beam to cold atoms. The
spin-wave qubit is retrieved with a single-mode read-laser beam, and the
quarter retrieval-efficiency loss is avoided at all storage times. Our
experiment demonstrates 50% intrinsic retrieval efficiency for 540 microsecond
storage time, which is 13.5 times longer than the best reported result.
Importantly, our multiplexed-cavity scheme paves one road to generate
perfect-cavity-enhanced and large-scale multiplexed spin-wave-photon
entanglement with a long lifetime.",2110.10971v1
2019-01-30,Propagation of Spin Waves Through an Interface Between Ferromagnetic and Antiferromagnetic Materials,"Boundary conditions for order parameters at an interface between
ferromagnetic (FM) and two-sublattice antiferromagnetic (AFM) materials were
obtained in the continuous medium approximation similarly to the approach which
allows one to take into account the finite thickness of the FM/FM interface,
which is much less than spin wave length. Three order parameters are considered
inside an interface of finite thickness with the magnetization
$\mathbf{\text{M}}$ of FM, magnetizations of both sublattices
$\mathbf{\text{M}}_{1}$ and $\mathbf{\text{M}}_{2}$ of AFM. The uniform and
non-uniform exchange between all order parameters are taken into account to the
interface energy. Using these boundary conditions, the excitation of a surface
evanescent spin wave is considered in AFM when the spin wave in FM falls onto
this interface. The coefficients and the phases of transmission and reflection
of spin wave through the FM/AFM interface are derived.",1901.10988v1
2019-04-01,Inelastic spin-wave scattering by Bloch domain wall flexure oscillations,"The calculations of the inelastic spin wave scattering by flexure vibrations
of the Bloch domain wall (Winters magnons) in thin magnetic films are
presented. The approach is based on the interaction of the propagating spin
waves with the dynamical emergent electromagnetic field generated by the moving
inhomogeneous magnetization texture (domain wall). The probability of the spin
wave scattering for the Winters magnon emission and absorption processes
essentially rises with the spin wave scattering angle increase up to 900. The
angular dependence of the scattering probability is essentially stronger for
the magnon absorption processes that allow distinguishing these elementary
emission/absorption processes experimentally.",1904.00596v1
2019-04-25,Spin-wave propagation in metallic CoFe films determined by microfocused frequency-resolved magneto-optic Kerr effect,"We investigated the magnetization dynamics of a patterned
Co$_{25}$Fe$_{75}$-based heterostructure with a novel optical measurement
technique that we call microfocused frequency-resolved magneto optic Kerr
effect ($\mu$FR-MOKE). We measured the magnetic field dependence of the
dynamical spin-wave susceptibility and recorded a spatial map of the spin-waves
excited by a microwave antenna. We compare these results to those obtained on
the same sample with the established microfocused Brillouin light scattering
technique. With both techniques, we find a spin-wave propagation length of
5.6$\mu$m at 10GHz. Furthermore, we measured the dispersion of the wavevector
and the spin-wave propagation length as a function of the external magnetic
field. These results are in good agreement with existing literature and with
the employed Kalinkos-Slavin model.",1904.11273v1
2019-07-10,Spin-Wave Multiplexed Atom-Cavity Electrodynamics,"We introduce multiplexed atom-cavity quantum electrodynamics with an atomic
ensemble coupled to a single optical cavity mode. Multiple Raman dressing beams
establish cavity-coupled spin-wave excitations with distinctive spatial
profiles. Experimentally, we demonstrate the concept by observing spin-wave
vacuum Rabi splittings, selective superradiance, and interference in the
cavity-mediated interactions of two spin waves. We highlight that the current
experimental configuration allows rapid, interchangeable cavity-coupling to 4
profiles with an overlap parameter of less than 10%, enough to demonstrate, for
example, a quantum repeater network simulation in the cavity. With further
improvements to the optical multiplexing setup, we infer the ability to access
more than $10^3$ independent spin-wave profiles.",1907.04921v2
2019-08-09,Sustained coherent spin wave emission using frequency combs,"We demonstrate sustained coherent emission of spin waves in NiFe films using
rapid demagnetization from high repetition rate femtosecond laser pulse trains.
As the pulse separation is shorter than the magnon decay time, magnons having a
frequency equal to a multiple of the 1 GHz repetition-rate are coherently
amplified. Using scanning micro-Brillouin Light Scattering (BLS) we observe
this coherent amplification as strong peaks spaced 1 GHz apart. The BLS counts
vs. laser power exhibit a stronger than parabolic dependence consistent with
counts being proportional to the square of the magnetodynamic amplitude, and
the demagnetization pulse strength being described by a Bloch law. Spatial spin
wave mapping demonstrates how both localized and propagating spin waves can be
excited, and how the propagation direction can be directly controlled. Our
results demonstrate the versatility of BLS spectroscopy for rapid
demagnetization studies and enable a new platform for photo-magnonics where
sustained coherent spin waves can be utilized.",1908.03388v2
2019-10-16,Spin-Wave frequency division multiplexing in an yttrium iron garnet microstripe magnetized by inhomogeneous field,"Spin waves are promising candidates for information processing and
transmission in a broad frequency range. In the realization of magnonic
devices, the frequency depended division of the spin wave frequencies is a
critical function for parallel information processing. In this work, we
demonstrate a proof-of-concept spin-wave frequency division multiplexing method
by magnetizing a homogenous magnetic microstripe with an inhomogeneous field.
The symmetry breaking additional field is introduced by a permalloy stripe
simply placed in lateral proximity to the waveguide. Spin waves with different
frequencies can propagate independently, simultaneously and separately in space
along the shared waveguide. This work brings new potentials for parallel
information transmission and processing in magnonics.",1910.07136v1
2019-12-29,Synchronized excitation of magnetization dynamics via spin waves in Bi-YIG thin film by slot line waveguide,"We have studied magnetization dynamics of a single Bi-YIG thin film by means
of the high frequency power response induced by a slot line waveguide. Multiple
absorption peaks that correspond to excitement states in magnetization dynamics
appeared without the ferromagnetic resonance (FMR) condition. The peaks were
strongly influenced by a waveguide line width and a distance between the lines.
Micromagnetics simulation reveals that each line induces a local magnetization
dynamics oscillation and generates spin waves. The spin wave that propagates
from one of the lines interferences with the other side of local magnetization
dynamics oscillation around the other line, resulting in an amplification of
the oscillation when they are in synchronization with each other. This
amplification occurs at both sides of the lines by the interference. Thus, the
possible mechanism of the excitation in the magnetization dynamics oscillation
is the synchronization of mutual magnetization dynamics oscillation via spin
waves. This technique resonantly excites the local magnetization dynamics
without the FMR condition, which is applicable as a highly coherent spin waves
source.",1912.12663v1
2020-01-16,Evidence of standing spin-waves in a van der Waals magnetic material,"Spin-waves have been studied for data storage, communication and logic
circuits in the field of spintronics based on their potential to substitute
electrons. Recent discovery of magnetism in two-dimensional (2D) systems such
as monolayer CrI$_3$ and Cr$_2$Ge$_2$Te$_6$ has led to a renewed interest in
such applications of magnetism in the 2D limit. Here we present direct evidence
of standing spin-waves along with the uniform precessional resonance modes in
van der Waals magnetic material, CrCl$_3$. Our experiment is the first direct
observation of standing spin-wave modes, set up across a thickness of 20
$\mu$m, in a van der Waals material. We detect standing spin-waves in the
vicinity of both, optical and acoustic, branches of the antiferromagnetic
resonance. We also observe magnon-magnon coupling, softening of resonance modes
with temperature and extract the evolution of interlayer exchange field as a
function of temperature.",2001.05981v1
2020-05-21,Effect of Dzyaloshinskii-Moriya interaction on magnetic vortex switching driven by radial spin waves,"We theoretically investigate the radial-spin-wave induced magnetic vortex
switching in the presence of Dzyaloshinskii-Moriya interaction (DMI). From
micromagnetic simulations, we observe a circular-to-radial vortex phase
transition by increasing the DMI strength. The radial spin-wave excitation
spectrum for each magnetization configuration is analyzed, showing that the
frequency of spin-wave mode with a given radial node number monotonically
increases (decreases) with the DMI parameter of the radial (circular) vortex.
Interestingly, we find that the DMI can significantly facilitate the polarity
switching of the circular vortex driven by radial spin waves. Our work provides
a new insight into the DMI effect on the vortex dynamics and is helpful for
designing fast all-magnonic memory devices.",2005.10440v1
2020-06-28,Geometrical interpretation of the wave-pilot theory and manifestation of the spinor fields,"Using the hydrodynamical formalism of quantum mechanics for a Schrodinger
spinning particle, developed by T. Takabayashi, J. P. Vigier and followers,
that involves vortical flows, we propose the new geometrical interpretation of
the wave-pilot theory. The spinor wave in this interpretation represents an
objectively real field and the evolution of a material particle controlled by
the wave is a manifestation of the geometry of space. We assume this field to
have a geometrical nature, basing on the idea that the intrinsic angular
momentum, the spin, modifies the geometry of the space, which becomes a
manifold, that is represented as a vector bundle with a base formed by the
translational coordinates and time, and the fiber of the bundle, specified at
each point by the field of an tetrad $e^a_{\mu}$, forms from the bilinear
combinations of spinor wave function. It was shown, that the spin vector
rotates following the geodesic of the space with torsion and the particle moves
according to the geometrized guidance equation. This fact explains the
self-action of the spinning particle. We show that the curvature and torsion of
the spin vector line is determined by the space torsion of the absolute
parallelism geometry.",2006.15709v1
2020-10-09,Skew scattering and side jump of spin wave across magnetic texture,"Spin wave and magnetic texture are two elementary excitations in magnetic
systems, and their interaction leads to rich magnetic phenomena. By describing
the spin wave and the magnetic texture using their own collective coordinates,
we find that they interact as classical particles traveling in mutual
electromagnetic fields. Based on this unified collective coordinate model, we
find that both skew scattering and side jump may occur as spin wave passing
through magnetic textures. The skew scattering is associated with the magnetic
topology of the texture, while the side jump is correlated to the total
magnetization of the texture. We illustrate the concepts of skew scattering and
side jump by investigating the spin wave trajectories across the topological
magnetic Skyrmion and the topologically trivial magnetic bubble respectively.",2010.04626v1
2020-12-17,Geometric magnonics with chiral magnetic domain walls,"Spin wave, the collective excitation of magnetic order, is one of the
fundamental angular momentum carriers in magnetic systems. Understanding the
spin wave propagation in magnetic textures lies in the heart of developing pure
magnetic information processing schemes. Here we show that the spin wave
propagation across a chiral domain wall follows simple geometric trajectories,
similar to the geometric optics. And the geometric behaviors are qualitatively
different in normally magnetized film and tangentially magnetized film. We
identify the lateral shift, refraction, and total reflection of spin wave
across a ferromagnetic domain wall. Moreover, these geometric scattering
phenomena become polarization-dependent in antiferromagnets, indicating the
emergence of spin wave birefringence inside antiferromagnetic domain wall.",2012.09420v1
2021-01-08,Compact tunable YIG-based RF resonators,"We report on the design, fabrication, and characterization of compact tunable
yttrium iron garnet (YIG) based RF resonators based on $\mu$m-sized spin-wave
cavities. Inductive antennas with both ladder and meander configurations were
used as transducers between spin waves and RF signals. The excitation of
ferromagnetic resonance and standing spin waves in the YIG cavities led to
sharp resonances with quality factors up to 350. The observed spectra were in
excellent agreement with a model based on the spin-wave dispersion relations in
YIG, showing a high magnetic field tunability of about 29 MHz/mT.",2101.02909v4
2021-03-05,Local heat emission due to unidirectional spin-wave heat conveyer effect observed by lock-in thermography,"Lock-in thermography measurements were performed to reveal heat source
distribution induced by the unidirectional spin-wave heat conveyer effect
(USHCE) of magnetostatic surface spin waves. When the magnetostatic surface
spin waves are excited in an yttrium iron garnet slab, the lock-in thermography
images show spatially biased sharp and complicated heating patterns, indicating
the importance of edge spin-wave dynamics for USHCE. The accessibility to the
local heat emission properties allows us to clarify a capability of remote
heating realized by USHCE; it can transfer energy for heating even through a
macro-scale air gap between two magnetic materials owing to the long-range
dipole-dipole coupling.",2103.03694v1
2021-03-10,Experimental Demonstration of a Rowland Spectrometer for Spin Waves,"We experimentally demonstrate the operation of a spin-wave Rowland
spectrometer. In the proposed device geometry, spin waves are coherently
excited on a diffraction grating and form an interference pattern that
spatially separates spectral components of the incoming signal. The diffraction
grating was created by focused-ion-beam irradiation, which was found to locally
eliminate the ferrimagnetic properties of YIG, without removing the material.
We found that in our experiments spin waves were created by an indirect
mechanism, by exploiting nonlinear resonance between the grating and the
coplanar waveguide. Our work paves the way for complex spin-wave optic devices
-- chips that replicate the functionality of integrated optical devices on a
chip-scale.",2103.06165v1
2021-05-06,Short spin waves detection by means of the magneto-optical intensity effect,"It is proposed a novel method of the spectrally selective detection of the
short spin waves (or magnons) by means of the transverse magneto-optical (MO)
intensity effect in transmission in the magnetoplasmonic nanostructure. The
method is based on the analysis of the MO effect spectrum versus the modulation
of the sample magnetization (i.e. spin wave) and related spatial symmetry
breaking in the magnetic layer. The spatial symmetry breaking leads to the
appearance of MO effect modulation at the normal incidence of light in the
spectral range of the optical states (SPP and waveguide modes) and the breaking
of the antisymmetry of the effect with respect to the sign of the incidence
angle of light. Besides it is revealed that the magnitude of the MO effect
varies with respect to the phase shift between the spin wave and the plasmonic
grating as a harmonic function with a period equal to the magnon wavelength.
All these facts allow to detect the spin waves of the certain wavelength
propagating in the nanostructure by measuring of the MO effect in the
nanostructure.",2105.02539v1
2021-06-21,First experimental demonstration of a scalable linear majority gate based on spin waves,"We report on the first experimental demonstration of majority logic operation
using spin waves in a scaled device with an in-line input and output layout.
The device operation is based on the interference of spin waves generated and
detected by inductive antennas in an all-electrical microwave circuit. We
demonstrate the full truth table of a majority logic function with the ability
to distinguish between strong and weak majority, as well as an inverted
majority function by adjusting the operation frequency. Circuit performance
projections predict low energy consumption of spin wave based compared to CMOS
for large arithmetic circuits.",2106.11192v1
2021-09-30,Linear and continuous variable spin-wave processing using a cavity-coupled atomic ensemble,"Spin-wave excitations in ensembles of atoms are gaining attention as a
quantum information resource. However, current techniques with atomic spin
waves do not achieve universal quantum information processing. We conduct a
theoretical analysis of methods to create a high-capacity universal quantum
processor and network node using an ensemble of laser-cooled atoms, trapped in
a one-dimensional periodic potential and coupled to a ring cavity. We describe
how to establish linear quantum processing using a lambda-scheme in a
rubidium-atom system, calculate the expected experimental operational
fidelities. Second, we derive an efficient method to achieve linear
controllability with a single ensemble of atoms, rather than two-ensembles as
proposed in [K. C. Cox et al. Spin-Wave Quantum Computing with Atoms in a
Single-Mode Cavity, preprint 2021]. Finally, we propose to use the spin-wave
processor for continuous-variable quantum information processing and present a
scheme to generate large dual-rail cluster states useful for deterministic
computing.",2109.15246v1
2021-11-30,Nonreciprocity of spin waves in a double layer ferromagnet with Dzyaloshinskii-Moriya interactions,"In this paper, boundary conditions for Landau-Lifshitz equations at the
interface between two ferromagnets with different Dzyaloshinskii-Moriya
interactions are derived. We calculated and verified the analytical expression
for the energy flux density continuity for the spin-wave propagation through
the interface between two ferromagnets with/without Dzyaloshinskii-Moriya
interactions considering the boundary conditions mentioned. Analytical
expressions for reflection, transmission coefficients and the nonreciprocity
factor are calculated in the case of spin-wave propagation through a double
layer ferromagnet with/without Dzyaloshinskii-Moriya interactions in the
first/second layer. Two principally different types of nonreciprocity effects
for spin waves are revealed in such a double layer system. The material
parameters of a double layer ferromagnet with/without Dzyaloshinskii-Moriya
interactions in the first/second layer are found for which the extremely high
nonreciprocity factor (>10) is expected according to the results of
calculations. The results of the paper deepen the knowledge about the spin-wave
propagation control in magnonic devices.",2111.15244v1
2022-03-08,Interplay between nonlinear spectral shift and nonlinear damping of spin waves in ultrathin YIG waveguides,"We use the phase-resolved imaging to directly study the nonlinear
modification of the wavelength of spin waves propagating in 100-nm thick,
in-plane magnetized YIG waveguides. We show that, by using moderate microwave
powers, one can realize spin waves with large amplitudes corresponding to
precession angles in excess of 10 degrees and nonlinear wavelength variation of
up to 18 percent in this system. We also find that, at large precession angles,
the propagation of spin waves is strongly affected by the onset of nonlinear
damping, which results in a strong spatial dependence of the wavelength. This
effect leads to a spatially dependent controllability of the wavelength by the
microwave power. Furthermore, it leads to the saturation of nonlinear spectral
shift's effects several micrometers away from the excitation point. These
findings are important for the development of nonlinear, integrated spin-wave
signal processing devices and can be used to optimize their characteristics.",2203.04018v1
2022-04-14,Micro magnet location using spin waves,"In this work, we present experimental data demonstrating the feasibility of
magnetic object location using spin waves. The test structure includes a
Y$_3$Fe$_2$(FeO$_4$)$_3$) (YIG) film with four micro-antennas placed on the
edges. A constant in-plane bias magnetic field is provided by NdFeB permanent
magnet. Two antennas are used for spin wave excitation while the other two are
used for the inductive voltage measurement. There are nine selected places for
the magnet on the film. The magnet was subsequently placed in all nine
positions and spin wave transmission and reflection were measured. The obtained
experimental data show the difference in the output signal amplitude depending
on the magnet position. All nine locations can be identified by the frequency
and the amplitude of the absolute minimum in the output power. All experiments
are accomplished at room temperature. Potentially, spin waves can be utilized
for remote magnetic bit read-out. The disadvantages and physical constraints of
this approach are also discussed.",2204.07238v1
2022-07-10,Semimetallic spin-density wave state in iron pnictides,"We examine the existence of semimetallic spin-density wave states in iron
pnictides. In the experimentally observed metallic spin-density wave state, the
symmetry-protected Dirac cones are located away from the Fermi surface giving
rise to tiny pockets and there are also additional Fermi pockets such as one
around $\Gamma$. We find that the location of a pair of Dirac points with
respect to the Fermi surface exhibits significant sensitivity to the orbital
splitting between the $d_{xz}$ and $d_{yz}$ orbitals. Besides, in the presence
of orbital splitting, the Fermi pockets not associated with the Dirac cones,
can be suppressed so that a semimetallic spin-density wave state can be
realized. We explain these finding in terms of difference in the slopes and
orbital contents of the bands which form the Dirac cone, and obtain the
necessary conditions dependent on these two and other parameters for the
coexisting Dirac semimetallic and spin-density wave states. Additionally, the
topologically protected edge states are studied in the ribbon geometry when the
same are oriented either along $x$ or $y$ axes.",2207.04365v1
2022-11-23,Anatomy of spin wave driven magnetic texture motion via magnonic torques,"The interplay between spin wave and magnetic texture represents the
information exchange between the fast and slow dynamical parts of magnetic
systems. Here we formulate a set of magnonic torques acting on background
magnetic texture, by extracting time-invariant information from the fast
precessing spin waves. Under the frame of magnonic torques, we use theoretical
formulations and micromagnetic simulations to investigate the spin wave driven
domain wall motion in two typical symmetry-breaking situations: the rotational
symmetry broken by the Dzyaloshinkii-Moriya interaction, and the translational
symmetry broken by magnetic damping. The torque-based microscopic analyses
provide compact yet quantitative tools to reinterpret the magnetic texture
dynamics induced by spin wave, beyond the conventional framework of global
momentum conservation.",2211.12958v1
2023-02-25,Magnonic Hall Effect and Magnonic Holography of Hopfions,"Hopfions are localized and topologically non-trivial magnetic configurations
that have received considerable attention in recent years. Through a
micromagnetic approach, we analyze the scattering of spin waves by magnetic
hopfions. We show that the spin waves experience an emergent electromagnetic
field related to the topological properties of the hopfion. We find that spin
waves propagating along the hopfion symmetry axis are deflected by the magnetic
texture, which acts as a convergent or divergent lens, depending on the spin
wave propagation direction. The effect differs for spin waves propagating along
the plane perpendicular to the symmetry axis. In the last case, they respond
with a skew scattering and a closely related Aharonov-Bohm effect. This allows
probing the existence of a magnetic hopfion by magnonic holography.",2302.13190v1
2023-04-05,High-energy spin waves in the spin-1 square-lattice antiferromagnet La$_2$NiO$_4$,"Inelastic neutron scattering is used to study the magnetic excitations of the
$S=1$ square-lattice antiferromagnet La$_2$NiO$_4$. We find that the spin waves
cannot be described by a simple classical (harmonic) Heisenberg model with only
nearest-neighbor interactions. The spin-wave dispersion measured along the
antiferromagnetic Brillouin-zone boundary shows a minimum energy at the
$(1/2,0)$ position as is observed in some $S=1/2$ square-lattice
antiferromagnets. Thus, our results suggest that the quantum dispersion
renormalization effects or longer-range exchange interactions observed in
cuprates and other $S=1/2$ square-lattice antiferromagnets are also present in
La$_2$NiO$_4$. We also find that the overall intensity of the spin-wave
excitations is suppressed relative to linear spin-wave theory indicating that
covalency is important. Two-magnon scattering is also observed.",2304.02546v2
2023-07-04,Probing general relativistic spin-orbit coupling with gravitational waves from hierarchical triple systems,"Wave packets propagating in inhomogeneous media experience a coupling between
internal and external degrees of freedom and, as a consequence, follow
spin-dependent trajectories. These are known as spin Hall effects, which are
well known in optics and condensed matter physics. Similarly, the gravitational
spin Hall effect is expected to affect the propagation of gravitational waves
on curved spacetimes. In this general-relativistic setup, the curvature of
spacetime acts as impurities in a semiconductor or inhomogeneities in an
optical medium, leading to a frequency- and polarization-dependent propagation
of wave packets. In this letter, we study this effect for strong-field lensed
gravitational waves generated in hierarchical triple black hole systems in
which a stellar-mass binary merges near a more massive black hole. We calculate
how the gravitational spin Hall effect modifies the gravitational waveforms and
show its potential for experimental observation. If detected, these effects
will bear profound implications for astrophysics and tests of general
relativity.",2307.01903v1
2023-08-28,Spin wave mode conversion in an in-plane magnetized microscale T-shaped YIG magnonic splitter,"As one of the fundamental magnonic devices, a magnonic splitter device has
been proposed and spin wave propagation in this device has been studied
numerically and experimentally. In the present work, we fabricated a T-shaped
magnonic splitter with 6 $\mu$m-wide three arms using a 100 nm-thick yttrium
iron garnet film and, using time-resolved magneto-optic Kerr microscopy,
observed that spin waves split into both, the vertical and the horizontal
direction at the junction. Analyzing the results, we found that spin wave modes
are converted into another during the splitting process and the splitting
efficiency is dominantly dependent on the 1st order of incoming spin waves.",2308.14327v1
2009-07-02,Gravitational-wave detectability of equal-mass black-hole binaries with aligned spins,"Binary black-hole systems with spins aligned or anti-aligned to the orbital
angular momentum provide the natural ground to start detailed studies of the
influence of strong-field spin effects on gravitational wave observations of
coalescing binaries. Furthermore, such systems may be the preferred end-state
of the inspiral of generic supermassive binary black-hole systems. In view of
this, we have computed the inspiral and merger of a large set of binary systems
of equal-mass black holes with spins parallel to the orbital angular momentum
but otherwise arbitrary. Our attention is particularly focused on the
gravitational-wave emission so as to quantify how much spin effects contribute
to the signal-to-noise ratio, to the horizon distances, and to the relative
event rates for the representative ranges in masses and detectors. As expected,
the signal-to-noise ratio increases with the projection of the total black hole
spin in the direction of the orbital momentum. We find that equal-spin binaries
with maximum spin aligned with the orbital angular momentum are more than
""three times as loud"" as the corresponding binaries with anti-aligned spins,
thus corresponding to event rates up to 30 times larger. We also consider the
waveform mismatch between the different spinning configurations and find that,
within our numerical accuracy, binaries with opposite spins S_1=-S_2 cannot be
distinguished whereas binaries with spin S_1=S_2 have clearly distinct
gravitational-wave emissions. Finally, we derive a simple expression for the
energy radiated in gravitational waves and find that the binaries always have
efficiencies E_rad/M > 3.6%, which can become as large as E_rad/M = 10% for
maximally spinning binaries with spins aligned with the orbital angular
momentum.",0907.0462v2
2009-09-21,Spin Waves and Switching: The Dynamics of Exchange - Biased Co Core - CoO Shell Nanoparticles,"The utility of nanoscaled ferromagnetic particles requires both stabilized
moments and maximized switching speeds. During reversal, the spatial modulation
of the nanoparticle magnetization evolves in time, and the energy differences
between each new configuration are accomodated by the absorption or emission
spin waves with different wavelengths and energy profiles. The switching speed
is limited by how quickly this spin wave energy is dissipated. We present here
the first observation of dispersing spin waves in a nanoscaled system, using
neutron scattering to detect spin waves in the CoO shells of exchange biased Co
core- CoO shell nanoparticles. Their dispersion is little affected by finite
size effects, but the spectral weight shifts to energies and wave vectors which
increase with decreasing system size. Core-shell coupling leads to a
substantial enhancement of the CoO spin wave population above its conventional
thermal level, suggesting a new mechanism for dissipating core switching
energy.",0909.3833v1
2018-04-14,Interplay of Wave Localization and Turbulence in Spin Seebeck Effect,"One of the most important discoveries in spintronics is the spin Seebeck
effect (SSE) recently observed in both insulating and (semi-)conducting
magnets. However, the very existence of the effect in transverse configuration
is still a subject of current debates, due to conflicting results reported in
different experiments. Present understanding of the SSE is mainly based on a
particle-like picture with the local equilibrium approximation (LEA), i.e.,
spatially resolved temperature-field assumed to describe the system. In this
work, we abandon the LEA to some extent and develop a wave theory to explain
the SSE, by highlighting the interplay between wave localization and
turbulence. We show that the emerging SSE with a sign change in the
high/low-temperature regions is closely related to the extendedness of the spin
wave that senses an average temperature of the system. On the one hand,
ubiquitous disorders (or magnetic field gradients) can strongly suppress the
transverse spin Seebeck effect (TSSE) due to Anderson (or Wannier-Zeeman)
spin-wave localization. On the other hand, the competing wave turbulence of
interacting magnons tends to delocalize the wave, and thus remarkably revives
the TSSE before the magnon self-trapping. Our theory provides a promising route
to resolve the heated debate on TSSE with a clear experiment scheme to test it
in future spin caloritronic devices.",1804.05157v1
2020-09-04,Experimental observation of the curvature-induced asymmetric spin-wave dispersion in hexagonal nanotubes,"Theoretical and numerical studies on curved magnetic nano-objects predict
numerous exciting effects that can be referred to as magneto-chiral effects,
which do not originate from the intrinsic Dzyaloshinskii-Moriya interaction or
surface-induced anisotropies. The origin of these chiral effects is the
isotropic exchange or the dipole-dipole interaction present in all magnetic
materials but renormalized by the curvature. Here, we demonstrate
experimentally that curvature induced effects originating from the
dipole-dipole interaction are directly observable by measuring spin-wave
propagation in magnetic nanotubes with hexagonal cross section using time
resolved scanning transmission X-ray microscopy. We show that the dispersion
relation is asymmetric upon reversal of the wave vector when the propagation
direction is perpendicular to the static magnetization. Therefore
counter-propagating spin waves of the same frequency exhibit different
wavelenghts. Hexagonal nanotubes have a complex dispersion, resulting from
spin-wave modes localised to the flat facets or to the extremely curved regions
between the facets. The dispersion relations obtained experimentally and from
micromagnetic simulations are in good agreement. %The asymmetric spin-wave
transport is present for all modes, promoting hexagonal nanotubes for magnonic
applications. These results show that spin-wave transport is possible in 3D,
and that the dipole-dipole induced magneto-chiral effects are significant.",2009.02238v1
2016-11-23,Magnetometer Based On Spin Wave Interferometer,"We describe magnetic field sensor based on spin wave interferometer. Its
sensing element consists of a magnetic cross junction with four micro-antennas
fabricated at the edges. Two of these antennas are used for spin wave
excitation and two others antennas are used for the detection of the inductive
voltage produced by the interfering spin waves. Two waves propagating in the
orthogonal arms of the cross may accumulate significantly different phase
shifts depending on the magnitude and the direction of the external magnetic
field. This phenomenon is utilized for magnetic field sensing. The sensitivity
has maximum at the destructive interference condition, where a small change of
the external magnetic field results in a drastic increase of the inductive
voltage as well as the change of the output phase. We report experimental data
obtained on a micrometer scale Y3Fe2(FeO4)3 cross structure. The change of the
inductive voltage near the destructive interference point exceeds 40 dB per 1
Oe. At the same time, the phase of the output exhibit a {\pi}-phase shift
within 1 Oe. The data are collected for three different orientations of the
sensor in magnetic field at room temperature. Taking into account low thermal
noise in ferrite structures, the maximum sensitivity of spin wave magnetometer
may exceed atta Tesla. Other appealing advantages include compactness, fast
data acquisition and wide temperature operating range. The physical limits of
spin wave interferometers are also discussed.",1611.08015v1
2014-01-29,Nonreciprocal Dispersion of Spin Waves in Ferromagnetic Thin Films Covered with a Finite-Conductivity Metal,"We study the effect of one-side metallization of a uniform ferromagnetic thin
film on its spin-wave dispersion relation in the Damon-Eshbach geometry. Due to
the finite conductivity of the metallic cover layer on the ferromagnetic film
the spin-wave dispersion relation may be nonreciprocal only in a limited
wave-vector range. We provide an approximate analytical solution for the
spin-wave frequency, discuss its validity and compare it with numerical
results. The dispersion is analyzed systematically by varying the parameters of
the ferromagnetic film, the metal cover layer and the value of the external
magnetic field. The conclusions drawn from this analysis allow us to define a
structure based on a 30 nm thick CoFeB film with an experimentally accessible
nonreciprocal dispersion relation in a relatively wide wave-vector range.",1401.7454v1
2015-03-26,Lagrangian geometrical optics of nonadiabatic vector waves and spin particles,"Linear vector waves, both quantum and classical, experience
polarization-driven bending of ray trajectories and polarization dynamics that
can be interpreted as the precession of the ""wave spin"". Both phenomena are
governed by an effective gauge Hamiltonian, which vanishes in leading-order
geometrical optics. This gauge Hamiltonian can be recognized as a
generalization of the Stern-Gerlach Hamiltonian that is commonly known for
spin-1/2 quantum particles. The corresponding reduced Lagrangians for
continuous nondissipative waves and their geometrical-optics rays are derived
from the fundamental wave Lagrangian. The resulting Euler-Lagrange equations
can describe simultaneous interactions of $N$ resonant modes, where $N$ is
arbitrary, and lead to equations for the wave spin, which happens to be a
$(N^2-1)$-dimensional spin vector. As a special case, classical equations for a
Dirac particle $(N=2)$ are deduced formally, without introducing additional
postulates or interpretations, from the Dirac quantum Lagrangian with the Pauli
term. The model reproduces the Bargmann-Michel-Telegdi equations with added
Stern-Gerlach force.",1503.07829v1
2018-07-31,Electrostatic Langmuir and SEAWs in spin polarized plasma double layer,"The quantum hydrodynamic model of the electrostatic waves in the two parallel
layers of two dimensional electron gases (2DEGs) is developed. It is considered
for two regimes: classic regime and quantum regime with the separate spin
evolution. Two Langmuir-like waves are found in classic case which have an
interference-like pattern in the frequency dependence on concentration
$\omega^{2}\sim(n_{01}+n_{02}\pm2\sqrt{n_{01}n_{02}})$. They appear instead of
two 2D Langmuir waves in noninteracting 2DEGs. The spectrum of four waves is
found in the quantum regime. Two extra waves are related to the separate spin
evolution and associated to the spin-electron acoustic waves. The influence of
the quantum Bohm potential is considered either.",1807.11894v1
2018-10-09,Non-uniform spin wave softening in 2D magnonic crystals as a tool for opening omnidirectional magnonic band gaps,"By means of the plane wave method we study spin wave dynamics in
two-dimensional bi-component magnonic crystals based on a squeezed hexagonal
lattice and consist of a permalloy thin film with cobalt inclusions. We explore
the dependence of a spin wave frequency on the external magnetic field,
especially in weak fields where the mode softening takes place. For considered
structures, the mode softening proves to be highly non-uniform on both the mode
number and the wave vector. We found this effect to be responsible for the
omnidirectional band gap opening. Moreover, we show that the enhancement of the
demagnetizing field caused by the squeezing of the structure is of crucial
importance for the non-uniform mode softening. This allows us to employ this
mechanism to design magnonic gaps with different sensitivity for the tiny
change of the external field. The effects we have found should be useful in
designing and optimization of spin wave filters highly tunable by a small
external magnetic field.",1810.04005v3
2021-08-26,Gravitational waves from spinning neutron stars as not-quite-standard sirens,"As is well known, gravitational wave detections of coalescing binaries are
standard sirens, allowing a measurement of source distance by gravitational
wave means alone. In this paper we explore the analogue of this capability for
continuous gravitational wave emission from individual spinning neutron stars,
whose spin-down is driven purely by gravitational wave emission. We show that
in this case, the distance measurement is always degenerate with one other
parameter, which can be taken to be the moment of inertia of the star. We
quantify the accuracy to which such degenerate measurements can be made. We
also discuss the practical application of this method to scenarios where one or
other of distance or moment of inertia is constrained, breaking this degeneracy
and allowing a measurement of the remaining parameter. We consider a broad
range of possible, unknown parameters, as well as we present results for the
aLIGO and Einstein Telescope sensitivities. Our results will be of use
following the eventual detection of a neutron star spinning down through such
gravitational wave emission.",2108.11710v2
2017-03-11,Confined states in photonic-magnonic crystals with complex unit cell,"We have investigated multifunctional periodic structures in which
electromagnetic waves and spin waves can be confined in the same areas. Such
simultaneous localization of both sorts of excitations can potentially enhance
the interaction between electromagnetic waves and spin waves. The system we
considered has a form of one dimensional photonic-magnonic crystal with two
types of magnetic layers (thicker and thinner ones) separated by sections of
the dielectric photonic crystals. We focused on the electromagnetic defect
modes localized in the magnetic layers (areas where spin waves can be exited)
and decaying in the sections of conventional (nonmagnetic) photonic crystals.
We showed how the change of relative thickness of two types of the magnetic
layers can influence on the spectrum of spin waves and electromagnetic defect
modes, both localized in magnetic parts of the system.",1703.04013v1
2021-12-29,Excitation and detection of coherent sub-terahertz magnons in ferromagnetic and antiferromagnetic heterostructures,"Excitation of coherent high-frequency magnons (quanta of spin waves) is
critical to the development of high-speed magnonic devices. Here we
computationally demonstrate the excitation of coherent sub-terahertz (THz)
magnons in ferromagnetic (FM) and antiferromagnetic (AFM) thin films by a
photoinduced picosecond acoustic pulse. Analytical calculations are also
performed to reveal the magnon excitation mechanism. Through spin pumping and
spin-charge conversion, these magnons can inject sub-THz charge current into an
adjacent heavy-metal film which in turn emits electromagnetic (EM) waves. Using
a dynamical phase-field model that considers the coupled dynamics of acoustic
waves, spin waves, and EM waves, we show that the emitted EM wave retains the
spectral information of all the sub-THz magnon modes and has a sufficiently
large amplitude for near-field detection. These predictions indicate that the
excitation and detection of sub-THz magnons can be realized in rationally
designed FM or AFM thin-film heterostructures via ultrafast optical-pump
THz-emission-probe spectroscopy.",2112.14749v2
2023-05-29,Spinning Partial Waves for Scattering Amplitudes in $d$ Dimensions,"Partial wave decomposition is one of the main tools within the modern
S-matrix studies. We present a method to compute partial waves for $2\to2$
scattering of spinning particles in arbitrary spacetime dimension. We identify
partial waves as matrix elements of the rotation group with definite covariance
properties under a subgroup. This allows to use a variety of techniques from
harmonic analysis in order to construct a novel algebra of weight-shifting
operators. All spinning partial waves are generated by the action of these
operators on a set of known scalar seeds. The text is accompanied by a {\it
Mathematica} notebook to automatically generate partial waves. These results
pave the way to a systematic studies of spinning S-matrix bootstrap and
positivity bounds.",2305.18523v2
2004-02-09,Spin Waves in Striped Phases,"In many antiferromagnetic, quasi-two-dimensional materials, doping with holes
leads to ""stripe"" phases, in which the holes congregate along antiphase domain
walls in the otherwise antiferromagnetic texture. Using a suitably parametrized
two-dimensional Heisenberg model on a square lattice, we study the spin wave
spectra of well-ordered spin stripes, comparing bond-centered antiphase domain
walls to site-centered antiphase domain walls for a range of spacings between
the stripes and for stripes both aligned with the lattice (""vertical"") and
oriented along the diagonals of the lattice (""diagonal""). Our results establish
that there are qualitative differences between the expected neutron scattering
responses for the bond-centered and site-centered cases. In particular,
bond-centered stripes of odd spacing generically exhibit more elastic peaks
than their site-centered counterparts. For inelastic scattering, we find that
bond-centered stripes produce more spin wave bands than site-centered stripes
of the same spacing and that bond-centered stripes produce rather isotropic low
energy spin wave cones for a large range of parameters, despite local
microscopic anisotropy. We find that extra scattering intensity due to the
crossing of spin wave modes (which may be linked to the ""resonance peak"" in the
cuprates) is more likely for diagonal stripes, whether site- or bond-centered,
whereas spin wave bands generically repel, rather than cross, when stripes are
vertical.",0402231v2
2006-03-28,Renormalization of the spin-wave spectrum in three-dimentional ferromagnets with dipolar interaction,"Renormalization of the spin-wave spectrum is discussed in a cubic ferromagnet
with dipolar forces at $T_C\gg T\ge0$. First 1/S-corrections are considered in
detail to the bare spectrum $\epsilon_{\bf k} = \sqrt{Dk^2 (Dk^2 +
S\omega_0\sin^2\theta_{\bf k})}$, where $D$ is the spin-wave stiffness,
$\theta_{\bf k}$ is the angle between $\bf k$ and the magnetization and
$\omega_0$ is the characteristic dipolar energy. In accordance with previous
results we obtain the thermal renormalization of constants $D$ and $\omega_0$
in the expression for the bare spectrum. Besides, a number of previously
unknown features are revealed. We observe terms which depend on azimuthal angle
of the momentum $\bf k$. It is obtained an isotropic term proportional to $k$
which makes the spectrum linear rather than quadratic when $\sin\theta_{\bf
k}=0$ and $k \ll \omega_0/D$. In particular a spin-wave gap proportional to
$\sin\theta_{\bf k}$ is observed. Essentially, thermal contribution from the
Hartree-Fock diagram to the isotropic correction as well as to the spin-wave
gap are proportional to the demagnetizing factor in the direction of domain
magnetization. This nontrivial behavior is attributed to the long-range nature
of the dipolar interaction. It is shown that the gap screens infrared
singularities of the first 1/S-corrections to the spin-wave stiffness and
longitudinal dynamical spin susceptibility (LDSS) obtained before. We
demonstrate that higher order 1/S-corrections to these quantities are small at
$T\ll\omega_0$. However the analysis of the entire perturbation series is still
required to derive the spectrum and LDSS when $T\gg\omega_0$.",0603741v2
2007-09-04,Spin Wave Magnetic NanoFabric: A New Approach to Spin-based Logic Circuitry,"We propose and describe a magnetic NanoFabric which provides a route to
building reconfigurable spin-based logic circuits compatible with conventional
electron-based devices. A distinctive feature of the proposed NanoFabric is
that a bit of information is encoded into the phase of the spin wave signal. It
makes possible to transmit information without the use of electric current and
utilize wave interference for useful logic functionality. The basic elements
include voltage-to-spin wave and wave-to-voltage converters, spin waveguides, a
modulator, and a magnetoelectric cell. As an example of a magnetoelectric cell,
we consider a two-phase piezoelectric-piezomagnetic system, where the spin wave
signal modulation is due to the stress-induced anisotropy caused by the applied
electric field. The performance of the basic elements is illustrated by
experimental data and results of numerical modeling. The combination of the
basic elements let us construct magnetic circuits for NOT and Majority logic
gates. Logic gates AND, OR, NAND and NOR are shown to be constructed as the
combination of NOT and a reconfigurable Majority gates. The examples of
computational architectures such as Cellular Automata, Cellular Nonlinear
Network and Field Programmable Gate Array are described. The main advantage of
the proposed NanoFabric is in the ability to realize logic gates with less
number of devices than it required for CMOS-based circuits. Potentially, the
area of the elementary reconfigurable Majority gate can be scaled down to
0.1um2. The disadvantages and limitations of the proposed NanoFabric are
discussed.",0709.0521v1
2010-11-12,Spin-Wave Spectrum in `Single-Domain' Magnetic Ground State of Triangular Lattice Antiferromagnet CuFeO2,"By means of neutron scattering measurements, we have investigated spin-wave
excitation in a collinear four-sublattice (4SL) magnetic ground state of a
triangular lattice antiferromagnet CuFeO2, which has been of recent interest as
a strongly frustrated magnet, a spin-lattice coupled system and a multiferroic.
To avoid mixing of spin-wave spectrum from magnetic domains having three
different orientations reflecting trigonal symmetry of the crystal structure,
we have applied uniaxial pressure on [1-10] direction of a single crystal
CuFeO2. By elastic neutron scattering measurements, we have found that only 10
MPa of the uniaxial pressure results in almost 'single domain' state in the 4SL
phase. We have thus performed inelastic neutron scattering measurements using
the single domain sample, and have identified two distinct spin- wave branches.
The dispersion relation of the upper spin-wave branch cannot be explained by
the previous theoretical model [R. S. Fishman: J. Appl. Phys. 103 (2008)
07B109]. This implies the importance of the lattice degree of freedom in the
spin-wave excitation in this system, because the previous calculation neglected
the effect of the spin-driven lattice distortion in the 4SL phase. We have also
discussed relationship between the present results and the recently discovered
""electromagnon"" excitation.",1011.2859v1
2020-06-03,Stochastic Core Spin-Up in Massive Stars -- Implications of 3D Simulations of Oxygen Shell Burning,"It has been suggested based on analytic theory that even in non-rotating
supernova progenitors stochastic spin-up by internal gravity waves (IGWs)
during the late burning stages can impart enough angular momentum to the core
to result in neutron star birth spin periods below 100ms, and a relatively firm
upper limit of 500ms for the spin period. We here investigate this process
using a 3D simulation of oxygen shell burning in a $3M_\odot$ He star. Our
model indicates that stochastic spin-up by IGWs is less efficient than
previously thought. We find that the stochastic angular momentum flux carried
by waves excited at the shell boundary is significantly smaller for a given
convective luminosity and turnover time than would be expected from simple
dimensional analysis. This can be explained by noting that the waves launched
by overshooting convective plumes contain modes of opposite angular wave number
with similar amplitudes, so that the net angular momentum of excited wave
packets almost cancels. We find that the wave-mediated angular momentum flux
from the oxygen shell follows a random walk, but again dimensional analysis
overestimates the random walk amplitudes since the correlation time is only a
fraction of the convective turnover time. Extrapolating our findings over the
entire life time of the last burning stages prior to collapse, we predict that
the core angular momentum from stochastic spin-up would translate into long
birth spin periods of several seconds for low-mass progenitors and no less than
100ms even for high-mass progenitors.",2006.02146v2
2021-07-21,Scattering in Black Hole Backgrounds and Higher-Spin Amplitudes: Part I,"The scattering of massless waves of helicity $|h|=0,\frac{1}{2},1$ in
Schwarzschild and Kerr backgrounds is revisited in the long-wavelenght regime.
Using a novel description of such backgrounds in terms of gravitating massive
particles, we compute classical wave scattering in terms of $2\to 2$ QFT
amplitudes in flat space, to all orders in spin. The results are Newman-Penrose
amplitudes which are in direct correspondence with solutions of the
Regge-Wheeler/Teukolsky equation. By introducing a precise prescription for the
point-particle limit, in Part I of this work we show how both agree for $h=0$
at finite values of the scattering angle and arbitrary spin orientation.
  Associated classical observables such as the scattering cross sections, wave
polarizations and time delay are studied at all orders in spin. The effect of
the black hole spin on the polarization and helicity of the waves is found in
agreement with previous analysis at linear order in spin. In the particular
limit of small scattering angle, we argue that wave scattering admits a
universal, point-particle description determined by the eikonal approximation.
We show how our results recover the scattering eikonal phase with spin up to
second post-Minkowskian order, and match it to the effective action of null
geodesics in a Kerr background. Using this correspondence we derive classical
observables such as polar and equatorial scattering angles.
  This study serves as a preceding analysis to Part II, where the Gravitational
Wave ($h=2$) case will be studied in detail.",2107.10179v2
2023-07-20,"The Role of $r$-Modes in Pulsar Spindown, Pulsar Timing and Gravitational Waves","Pulsars are fast-spinning neutron stars that lose their rotational energy via
various processes such as gravitational and electromagnetic radiation, particle
acceleration, and mass loss processes. Pulsar energy dissipation can be
quantified by a spin-down equation that measures the rate of change of pulsar
rotational frequency as a function of the frequency itself. We explore the
pulsar spin-down equation and consider the spin-down term up to the seventh
order in frequency. The seventh-order spin-down term accounts for energy
carried away in the form of gravitational radiation due to a current-type
quadrupole in the pulsar induced by r-modes. We derive analytical formulae of
pulsar r-mode gravitational wave frequency in terms of pulsar compactness,
tidal deformability, r-mode amplitude, and gravitational wave amplitude. We
find solutions to the above relationships using the Lambert-Tsallis and
Lambert-W functions. We also present an analytic solution of the pulsar
rotational period from the spin-down equation and numerically verify it for the
Crab pulsar PSR B0531+21. Accurate analysis of pulsar energy loss, spin-down,
and gravitational wave emission are relevant for precise pulsar timing,
improving the knowledge of neutron star equation of state, and the search for
continuous gravitational waves with 3-rd generation ground-based and
space-based gravitational wave detectors.",2307.11270v2
2012-04-01,Magnetostatic spin waves and magnetic-wave chaos in ferromagnetic films. I. Theory of magnetostatic waves in plates under arbitrary anisotropy and external fields,"General phenomenological theory of magnetic spin waves in ferromagnetic media
is originally reformulated and applied to analysis of magnetostatic waves in
films and plates with arbitrary nisotropy under arbitrary external field. Exact
expressions are derived for propagator of linear waves between antennae
(inductors) and mutual impedances of antennae, and exact unified dispersion
equation is obtained which describes all types of magnetostatic wave
eigen-modes. Characteristic frequencies (spectra) and some other important
properties of main modes are analytically considered and graphically
illustrated. Besides, several aspects of non-linear excitations and
magnetic-wave chaos are discussed, including two-dimensional ""non-linear
Schrodinger equations"" for magnetostatic wave packets and envelope solitons.",1204.0200v1
1998-01-15,Obervation of non-linear stationary spin waves in superfluid 3He-B,"Due to its broken spin and orbit rotation symmetries, superfluid $^3$He plays
a unique role for testing rotational quantum properties on a macroscopic scale.
In this system the orbital momentum forms textures that provide an effective
potential well for the creation of stationary spin waves. In the limit of the
lowest temperatures presently attainable, we observe by NMR techniques a
profound change in the spin dynamics. The NMR line shape becomes asymmetric,
strongly hysteretic and displays substantial frequency shifts. This behavior,
quantitatively described by an anharmonic oscillator model, indicates that the
parameters of the potential well depend on the spin waves amplitude, and
therefore that the orbital motion is not damped in this new regime, not
considered by the standard Leggett-Takagi theory. This regime of non-linear
stationary spin waves is shown to give rise to the pulsed NMR ""Persistent
Signals"" reported recently.",9801159v1
1999-09-14,Spin Wave Theory of Double Exchange Magnets,"An isotropic half-metallic double exchange magnet with a direct superexchange
coupling between the localized spins is studied within the spin-wave (1/S)
expansion. The momentum dependence of the spin wave spectrum (including quantum
corrections) in the ferromagnetic phase at T=0 is investigated. Based on the
calculated spin wave spectrum of the canted state, it is shown that as long as
the external magnetic field is not too strong, the double exchange --
superexchange competition does not result in a stabilization of a
two-sublattice canted spin ordering.",9909213v3
2005-07-28,Theory of transverse spin dynamics in a polarized Fermi liquid and an itinerant ferromagnet,"The linear equations for transverse spin dynamics in a weakly polarized
degenerate Fermi liquid with arbitrary relationship between temperature and
polarization are derived from Landau-Silin phenomenological kinetic equation
with general form of two-particle collision integral. Unlike the previous
treatment where Fermi velocity and density of states have been taken as
constants independent of polarization here we made derivation free from this
assumption. The obtained equations are applicable for description of spin
dynamics in paramagnetic Fermi liquid with finite polarization as well in an
itinerant ferromagnet. In both cases transverse spin wave frequency is found to
be proportional to the square of the wave vector with complex constant of
proportionality (diffusion coefficient) such that the damping has a finite
value at T=0. The polarization dependence of the diffusion coefficient is found
to be different for a polarized Fermi liquid and for an itinerant ferromagnet.
These conclusions are confirmed by derivation of transverse spin wave
dispersion law in frame of field theoretical methods from the integral equation
for the vortex function. It is shown that similar derivation taking into
consideration the divergency of static transverse susceptibility also leads to
the same attenuating spin wave spectrum.",0507675v1
2005-08-19,Spin-waves in antiferromagnetic single crystal LiFePO$_4$,"Spin-wave dispersions in the antiferromagnetic state of single crystal
LiFePO$_4$ were determined by inelastic neutron scattering measurements. The
dispersion curves measured from the (010) reflection along both {\it a}$^\ast$
and {\it b}$^\ast$ reciprocal-space directions reflect the anisotropic coupling
of the layered Fe$^{2+}$ (S = 2) spin-system. The spin-wave dispersion curves
were theoretically modeled using linear spin-wave theory by including in the
spin-Hamiltonian in-plane nearest- and next-nearest-neighbor interactions ({\it
J}$_1$ and {\it J}$_2$), inter-plane nearest-neighbor interactions ({\it
J}$_\bot$) and a single-ion anisotropy ({\it D}). A weak (010) magnetic peak
was observed in elastic neutron scattering studies of the same crystal
indicating that the ground state of the staggered iron moments is not along
(010) direction, as previously reported from polycrystalline samples studies,
but slightly rotated away from this axis.",0508480v1
2006-03-10,Magnetic Structure and Spin Waves in the Kagomé Jarosite compound ${\bf KFe_3(SO_4)_2(OH)_6}$,"We present a detailed study of the magnetic structure and spin waves in the
Fe jarosite compound ${\rm KFe_3(SO_4)_2(OH)_6}$ for the most general
Hamiltonian involving one- and two-spin interactions which are allowed by
symmetry. We compare the calculated spin-wave spectrum with the recent neutron
scattering data of Matan {\it et al.} for various model Hamiltonians which
include, in addition to isotropic Heisenberg exchange interactions between
nearest ($J_1$) and next-nearest ($J_2$) neighbors, single ion anisotropy and
Dzyaloshinskii-Moriya (DM) interactions. We concluded that DM interactions are
the dominant anisotropic interaction, which not only fits all the splittings in
the spin-wave spectrum but also reproduces the small canting of the spins out
of the Kagom\'e plane. A brief discussion of how representation theory
restricts the allowed magnetic structure is also given.",0603280v1
2007-01-08,Quantum corrections to the spin-wave spectrum of La$_2$CuO$_4$ in an external magnetic field,"The effects of quantum fluctuations on the magnetic field dependence of the
spin-wave gaps in the lamellar antiferromagnet La$_2$CuO$_4$ are considered.
Nonlinear corrections to the spin-wave spectrum are calculated to leading order
in 1/S, where $S$ is the localized spin. The nearest-neighbor exchange
interactions between the Cu spins as well as the Dzyaloshinskii-Moriya
interactions are taken into account. Using the experimental values of the
components of the $g$-factor tensor, we get a satisfactory agreement with the
experimental results for the field dependence of the gaps by Gozar {\it et al.}
[Phys. Rev. Lett. {\bf 93}, 027001 (2004)], and obtain consistent values of the
in-plane and inter-plane coupling constants. The field dependence of the
dispersion of spin waves propagating perpendicular to the CuO$_2$ planes is
also discussed.",0701143v1
2000-03-16,Fields on the Poincare group: arbitrary spin description and relativistic wave equations,"In this paper, starting from pure group-theoretical point of view, we develop
a regular approach to describing particles with different spins in the
framework of a theory of scalar fields on the Poincare group. Such fields can
be considered as generating functions for conventional spin-tensor fields. The
cases of 2, 3, and 4 dimensions are elaborated in detail. Discrete
transformations $C,P,T$ are defined for the scalar fields as automorphisms of
the Poincare group. Doing a classification of the scalar functions, we obtain
relativistic wave equations for particles with definite spin and mass. There
exist two different types of scalar functions (which describe the same mass and
spin), one related to a finite-dimensional nonunitary representation and
another one related to an infinite-dimensional unitary representation of the
Lorentz subgroup. This allows us to derive both usual finite-component wave
equations for spin-tensor fields and positive energy infinite-component wave
equations.",0003146v2
2008-04-09,Multiferroic materials for spin-based logic devices,"Logical devices based on spin waves offer the potential to avoid dissipation
mechanisms that limit devices based on either the charge or spin of mobile
electrons. Multiferroic magnetoelectrics, which are materials that combine
ferroelectric and magnetic order, allow direct switching of magnetic order and
thence of spin-wave properties using an applied electric field. The intrinsic
coupling between polarization and magnetic moments, generated by strong
electronic correlations in these multiferroic materials, is argued to provide
new approaches to spin-wave injection and spin-wave switching using applied
voltages with no external magnetic field. These effects are shown to arise in a
phenomenological Landau theory of coupled electronic and magnetic orders in
multiferroic BiFeO3, and found to depend subtly on differences between the
crystalline and film states of this material.",0804.1539v1
2009-09-07,Spin excitations in the excitonic spin-density-wave state of the iron pnictides,"Motivated by the iron pnictides, we examine the spin excitations in an
itinerant antiferromagnet where a spin-density wave (SDW) originates from an
excitonic instability of nested electron-like and hole-like Fermi pockets.
Using the random phase approximation (RPA), we derive the Dyson equation for
the transverse susceptibility in the excitonic SDW state. The Dyson equation is
solved for two different two-band models, describing an antiferromagnetic
insulator and metal, respectively. We determine the collective spin-wave
dispersions and also consider the single-particle continua. The results for the
excitonic models are compared with each other and also contrasted with the
well-known SDW state of the Hubbard model. Despite the qualitatively different
SDW states in the two excitonic models, their magnetic response shows many
similarities. We conclude with a discussion of the relevance of the excitonic
SDW scenario to the iron pnictides.",0909.1222v2
2010-01-15,Neutrino emission from spin waves in neutron spin-triplet superfluid,"The linear response of a neutron spin-triplet superfluid onto external weak
axial-vector field is studied for the case of $^{3}P_{2}$ pairing with a
projection of the total angular momentum $m_{j}=0$. The problem is considered
in the BCS approximation discarding Fermi-liquid effects. The anomalous
axial-vector vertices of neutron quasiparticles possess singularities at some
frequencies which specify existence of undamped spin-density waves in the
Cooper condensate. The spin waves are of a low excitation energy and are
kinematically able to decay into neutrino pairs through neutral weak currents.
We evaluate the neutrino emissivity from the spin wave decays in the bulk
neutron superfluid in old neutron stars. This calculation predicts significant
energy losses from within a neutron star at lowest temperatures when all other
mechanisms of neutrino emission are killed by the neutron and proton
superfluidity.",1001.2617v2
2010-01-21,Quantized antiferromagnetic spin waves in the molecular Heisenberg ring CsFe$_8$,"We report on inelastic neutron scattering (INS) measurements on the molecular
spin ring CsFe$_8$, in which eight spin-5/2 Fe(III) ions are coupled by
nearest-neighbor antiferromagnetic Heisenberg interaction. We have recorded INS
data on a non-deuterated powder sample up to high energies at the
time-of-flight spectrometers FOCUS at PSI and MARI at ISIS, which clearly show
the excitation of spin waves in the ring. Due to the small number of spin
sites, the spin-wave dispersion relation is not continuous but quantized.
Furthermore, the system exhibits a gap between the ground state and the first
excited state. We have modeled our data using exact diagonalization of a
Heisenberg-exchange Hamiltonian together with a small single-ion anisotropy
term. Due to the molecule's symmetry, only two parameters $J$ and $D$ are
needed to obtain excellent agreement with the data. The results can be well
described within the framework of the rotational-band model as well as
antiferromagnetic spin-wave theories.",1001.3755v1
2010-02-26,Correlation Effects in the Stochastic Landau-Lifshitz-Gilbert Equation,"We analyze the Landau-Lifshitz-Gilbert equation when the precession motion of
the magnetic moments is additionally subjected to an uniaxial anisotropy and is
driven by a multiplicative coupled stochastic field with a finite correlation
time $\tau$. The mean value for the spin wave components offers that the
spin-wave dispersion relation and its damping is strongly influenced by the
deterministic Gilbert damping parameter $\alpha$, the strength of the
stochastic forces $D$ and its temporal range $\tau$. The spin-spin-correlation
function can be calculated in the low correlation time limit by deriving an
evolution equation for the joint probability function. The stability analysis
enables us to find the phase diagram within the $\alpha-D$ plane for different
values of $\tau$ where damped spin wave solutions are stable. Even for zero
deterministic Gilbert damping the magnons offer a finite lifetime. We detect a
parameter range where the deterministic and the stochastic damping mechanism
are able to compensate each other leading to undamped spin-waves. The onset is
characterized by a critical value of the correlation time. An enhancement of
$\tau$ leads to an increase of the oscillations of the correlation function.",1002.4958v1
2010-08-05,Influence of spin waves on transport through a quantum-dot spin valve,"We study the influence of spin waves on transport through a single-level
quantum dot weakly coupled to ferromagnetic electrodes with noncollinear
magnetizations. Side peaks appear in the differential conductance due to
emission and absorption of spin waves. We, furthermore, investigate the
nonequilibrium magnon distributions generated in the source and drain lead. In
addition, we show how magnon-assisted tunneling can generate a fullly
spin-polarized current without an applied transport voltage. We discuss the
influence of spin waves on the current noise. Finally, we show how the magnonic
contributions to the exchange field can be detected in the finite-frequency
Fano factor.",1008.0948v2
2012-01-30,"Exchange constants and spin waves of the orbital ordered, non-collinear spinel MnV$_2$O$_4$","We study the exchange constants of MnV$_2$O$_4$ using magnetic force theorem
and local spin density approximation of density functional theory supplemented
with a correction due to on-site Hubbard interaction U. We obtain the exchanges
for three different orbital orderings of the Vanadium atoms of the spinel. We
then map the exchange constants to a Heisenberg model with single-ion
anisotropy and solve for the spin-wave excitations in the non-collinear, low
temperature phase of the spinel. The single-ion anisotropy parameters are
obtained from an atomic multiplet exact-diagonalization program, taking into
effect the crystal-field splitting and the spin-orbit coupling. We find good
agreement between the spin waves of one of our orbital ordered setups with
previously reported experimental spin waves as determined by neutron
scattering. We can therefore determine the correct orbital order from various
proposals that exist in the literature.",1201.6375v2
2013-06-28,"The role of orbital order in the stabilization of the $(π,0)$ ordered magnetic state in a minimal two-band model for iron pnictides","Spin wave excitations and stability of the ($\pi,0$) ordered magnetic state
are investigated in a minimal two-band itinerant-electron model for iron
pnictides. Presence of hopping anisotropy generates a strong ferro-orbital
order in the $d_{xz}$ and $d_{yz}$ Fe orbitals. The orbital order sign is as
observed in experiments. The induced ferro-orbital order strongly enhances the
spin wave energy scale and stabilizes the magnetic state by optimizing the
strength of the emergent AF and F spin couplings through optimal band fillings
in the two orbitals. The calculated spin-wave dispersion is in quantitative
agreement with neutron scattering measurements. Finite inter-orbital Hund's
coupling is shown to further enhance the spin wave energies state by coupling
the two magnetic sub-systems. A more realistic two-band model with less hopping
anisotropy is also considered which yields not only the circular hole pockets,
also correct ferro-orbital order and emergent F spin coupling.",1306.6727v2
2013-08-12,Oscillating spin-orbit interaction as a source of spin-polarized wave packets in two-terminal nanoscale devices,"Ballistic transport through nanoscale devices with time-dependent Rashba-type
spin-orbit interaction (SOI) can lead to spin-polarized wave packets that
appear even for completely unpolarized input. The SOI that oscillates in a
finite domain generates density and spin polarization fluctuations that leave
the region as propagating waves. Particularly, spin polarization has space and
time dependence even in regions without SOI. Our results are based on an
analytic solution of the time-dependent Schr\""odinger equation. The relevant
Floquet quasi-energies that are obtained appear in the energy spectrum of both
the transmitted and reflected waves.",1308.2552v2
2014-05-09,Magnetic excitations and anomalous spin wave broadening in multiferroic FeV2O4,"We report on the different roles of two orbital-active Fe$^{2+}$ at the A
site and V$^{3+}$ at the B site in the magnetic excitations and on the
anomalous spin wave broadening in FeV$_{2}$O$_{4}$. FeV$_{2}$O$_{4}$ exhibits
three structural transitions and successive paramagnetic (PM)-collinear
ferrimagnetic (CFI)-noncollinear ferrimagnetic (NCFI) transitions. The
high-temperature tetragonal/PM -orthorhombic/CFI transition is accompanied by
the appearance of an energy gap with a high magnitude in the magnetic
excitations due to strong spin-orbit coupling induced anisotropy at the
Fe$^{2+}$ site. While there is no measurable increase in the energy gap from
the orbital ordering of V$^{3+}$ at the orthorhombic/CFI-tetragonal/NCFI
transition, anomalous spin wave broadening is observed in the orthorhombic/CFI
state due to V$^{3+}$ spin fluctuations at the B site. The spin wave broadening
is also observed at the zone boundary without softening, which is discussed in
terms of magnon-phonon coupling.",1405.2272v2
2015-07-12,On a mechanism of high-temperature superconductivity: Spin-electron acoustic wave as a mechanism for the Cooper pair formation,"We have found the mechanism of the electron Cooper pair formation via the
electron interaction by means of the spin-electron acoustic waves. This
mechanism takes place in metals with rather high spin polarization, like
ferromagnetic, ferrimagnetic and antiferromagnetic materials. The spin-electron
acoustic wave mechanism leads to transition temperatures 100 times higher than
the transition temperature allowed by the electron-phonon interaction.
Therefore, spin-electron acoustic waves give the explanation for the
high-temperature superconductivity. We find that the transition temperature has
strong dependence on the electron concentration and the spin polarization of
the electrons.",1507.03295v2
2018-03-26,Theoretical spin-wave dispersions in the antiferromagnetic phase AF1 of MnWO$_4$ based on the polar atomistic model in P2,"The spin wave dispersions of the low temperature antiferromagnetic phase
(AF1) MnWO$_4$ have been numerically calculated based on the recently reported
non-collinear spin configuration with two different canting angles. A
Heisenberg model with competing magnetic exchange couplings and single-ion
anisotropy terms could properly describe the spin wave excitations, including
the newly observed low-lying energy excitation mode $\omega_2$=0.45 meV
appearing at the magnetic zone centre. The spin wave dispersion and intensities
are highly sensitive to two differently aligned spin-canting sublattices in the
AF1 model. Thus this study reinsures the otherwise hardly provable hidden polar
character in MnWO$_4$.",1803.09475v1
2018-06-18,Nonreciprocal spin waves in a chiral antiferromagnet without the Dzyaloshinskii-Moriya interaction,"Non-reciprocal spin wave can facilitate the realization of spin wave logic
devices. It has been demonstrated that the non-reciprocity can emerge when an
external magnetic field is applied to chiral magnets, of which spin structures
depend crucially on an asymmetric exchange interaction, that is, the
Dzyaloshinskii-Moriya interaction (DMI). Here we demonstrate that the
non-reciprocity can arise even without the DMI. We demonstrate this idea for
the chiral antiferromagnet Ba$_2$NbFe$_3$Si$_2$O$_{14}$, of which DMI is very
small and chiral spin structure arises mainly from the competition between
symmetric exchange interactions. We show that when an external magnetic field
is applied, asymmetric energy gap shift occurs and the spin wave becomes
non-reciprocal from the competition between symmetric exchange interactions and
the external magnetic field.",1806.06517v3
2016-12-03,First-principles investigation of spin wave dispersions in surface-reconstructed Co thin films on W(110),"We computed spin wave dispersions of surface-reconstructed Co films on the
W(110) surface in the adiabatic approximation. The magnetic exchange
interactions are obtained via first-principles electronic structure
calculations using the Korringa-Kohn-Rostoker Green function method. We analyze
the strength and oscillatory behavior of the intralayer and interlayer magnetic
interactions and investigate the resulting spin wave dispersions as a function
of the thickness of Co films. In particular, we highlight and explain the
strong impact of hybridization of the electronic states at the Co-W interface
on the magnetic exchange interactions and on the spin wave dispersions. We
compare our results to recent measurements based on electron energy loss
spectroscopy [E. Michel, H. Ibach, and C.M. Schneider, Phys. Rev. B 92, 024407
(2015)]. Good overall agreement with experimental findings can be obtained by
considering the possible overestimation of the spin splitting, stemming from
the local spin density approximation, and adopting an appropriate correction.",1612.00910v2
2019-04-18,Magnonic Analogue Black/White Hole Horizon in Superfluid $^3$He-B: experiment,"We provide experimental details of the first experiment made in zero
temperature limit ($\sim$ 600\,$\mu$K) studying the magnonic black/white hole
horizon analogue using absolutely pure physical system based on the spin
superfluidity in superfluid $^3$He-B. We show that spin precession waves
propagating on the background of the spin super-currents in a channel between
two Bose-Einstein condensates of magnons in form of homogeneously precessing
domains mimic the properties of the black/white horizon. Once the white hole
horizon is formed and blocks the propagation of the spin-precession waves
between two domains, we observed an amplification effect, i.e. when the energy
of the spin precession waves reflected from the horizon is higher than the
energy of the excited spin precession waves before horizon was formed.
Moreover, the estimated temperature of the spontaneous Hawking radiation in
this model system is about four orders of magnitude lower than the system's
background temperature what makes it a promising tool to study the effect of
spontaneous Hawking radiation.",1904.09183v1
2019-09-10,Anisotropic magnetic excitations of a frustrated bilinear-biquadratic spin model -- Implications for spin waves of detwinned iron pnictides,"Elucidating the nature of spin excitations is important to understanding the
mechanism of superconductivity in the iron pnictides. Motivated by recent
inelastic neutron scattering measurements in the nearly 100% detwinned
BaFe$_{2}$As$_{2}$, we study the spin dynamics of an $S=1$ frustrated
bilinear-biquadratic Heisenberg model in the antiferromagnetic phase with
wavevector $(\pi,0)$. The biquadratic interactions are treated in a dynamical
way using a flavor-wave theory in an $SU(3)$ representation. Besides the magnon
(dipolar) excitations, the biquadratic interactions give rise to quadrupolar
excitations at high energies. We find that the quadrupolar wave significantly
influences, in an energy dependent way, the anisotropy between the spin
excitation spectra along the $(\pi,0)$ and $(0,\pi)$ directions in the wave
vector space. Our theoretical results capture the essential behavior of the
spin dynamics measured in the antiferromagnetic phase of the detwinned
BaFe$_2$As$_2$. More generally, our results underscore the importance of
electron correlation effects for the microscopic physics of the iron pnictides.",1909.04555v2
2020-02-13,Representations of tensor rotations and the geometry of spin 1/2,"Making use of the real sl(2,R) Lie group algebra generating a spin 1/2 Lie
group allows to create an explicitly given Lorentz invariant fermion wave. As
the generators are real valued they can be interpreted as a deformation tensor
in particular as a deformation tensor of space. Therefore, it is possible to
model a heuristic purely geometric representation of spin 1/2 in Minkowski
space. However the bigger surprise is that this wave has the space-time
structure of gravitational waves, which are understood to be spin 2 waves.
Given that the uniqueness of angular momentum representations still holds, the
examination of tensor rotations reveals the existence of different
representations of tensor rotations with a different angular parameter due to
an unaccounted basic symmetry of symmetric tensors, where the spin 1/2
representation is a specific representation of tensor rotations corresponding
to the quantum theoretical approach. The seeming contradiction is fully
resolved and allows in addition to understand the notion of different
representations of spin in tensors, again related to different representations
of the tensor.",2002.05560v1
2021-12-15,Spin Waves and Dirac Magnons in a Honeycomb Lattice Zig-zag Antiferromagnet BaNi2(AsO4)2,"The topological properties of massive and massless fermionic quasiparticles
have been intensively investigated over the past decade in topological
materials without magnetism. Recently, the bosonic analogs of such
quasiparticles arising from spin waves have been reported in the
two-dimensional (2D) honeycomb lattice ferromagnet/antiferromagnet and the 3D
antiferromagnet. Here we use time-of-flight inelastic neutron scattering to
study spin waves of the S = 1 honeycomb lattice antiferromagnet BaNi2(AsO4)2,
which has a zig-zag antiferromagnetic (AF) ground state identical to that of
the Kitaev quantum spin liquid candidate alpha-RuCl3. We determine the magnetic
exchange interactions in the zig-zag AF ordered phase, and show that spin waves
in BaNi2(AsO4)2 have symmetry-protected Dirac points inside the Brillouin zone
boundary. These results provide a microscopic understanding of the zig-zag AF
order and associated Dirac magnons in honeycomb lattice magnets, and are also
important for establishing the magnetic interactions in Kitaev quantum spin
liquid candidates.",2112.07915v1
2022-06-01,Exceptional spin wave dynamics in an antiferromagnetic honeycomb lattice,"We theoretically investigate possible effects of electric current on the spin
wave dynamics for the N\'{e}el-type antiferromagnetic order in a honeycomb
lattice. Based on a general vector decomposition of the spin polarization of
conduction electrons, we find that there can exist reciprocal and nonreciprocal
terms in the current-induced torque acting on the local spins in the system.
Furthermore, we show that the reciprocal terms will cause the spin wave Doppler
effect, while the nonreciprocal terms can induce rich non-Hermitian topological
phenomena in the spin wave dynamics, including exceptional points, bulk Fermi
arc, non-Hermitian skin effect, etc. Our results indicate the capability to
manipulate non-Hermitian magnons in magnetic materials by electric current,
which could be important for both fundamental physics and technology
applications.",2206.00723v1
2022-06-21,Faraday patterns in spin-orbit coupled Bose-Einstein condensates,"We study the Faraday patterns generated by spin-orbit-coupling induced
parametric resonance in a spinor Bose-Einstein condensate with repulsive
interaction. The collective elementary excitations of the Bose-Einstein
condensate, including density waves and spin waves, are coupled as the result
of the Raman-induced spin-orbit coupling and a quench of the relative phase of
two Raman lasers without the modulation of any of the system's parameters. We
observed several higher parametric resonance tongues at integer multiples of
the driving frequency and investigated the interplay between Faraday
instabilities and modulation instabilities when we quench the
spin-orbit-coupled Bose-Einstein condensate from zero-momentum phase to
plane-wave phase. If the detuning is equal to zero, the wave number of
combination resonance barely changes as the strength of spin-orbit coupling
increases. If the detuning is not equal to zero after a quench, a single
combination resonance tongue will split into two parts.",2206.10222v1
1998-06-30,Structure and Spin Dynamics of La$_{0.85}$Sr$_{0.15}$MnO$_3$,"Neutron scattering has been used to study the structure and spin dynamics of
La$_{0.85}$Sr$_{0.15}$MnO$_3$. The magnetic structure of this system is
ferromagnetic below T_C = 235 K. We see anomalies in the Bragg peak intensities
and new superlattice peaks consistent with the onset of a spin-canted phase
below T_{CA} = 205 K, which appears to be associated with a gap at q = (0, 0,
0.5) in the spin-wave spectrum. Anomalies in the lattice parameters indicate a
concomitant lattice distortion. The long-wavelength magnetic excitations are
found to be conventional spin waves, with a gapless (< 0.02 meV) isotropic
dispersion relation $E = Dq^2$. The spin stiffness constant D has a $T^{5/2}$
dependence at low T, and the damping at small q follows $q^4T^{2}$. An
anomalously strong quasielastic component, however, develops at small wave
vector above 200 K and dominates the fluctuation spectrum as T -> T_C. At
larger q, on the other hand, the magnetic excitations become heavily damped at
low temperatures, indicating that spin waves in this regime are not eigenstates
of the system, while raising the temperature dramatically increases the
damping. The strength of the spin-wave damping also depends strongly on the
symmetry direction in the crystal. These anomalous damping effects are likely
due to the itinerant character of the $e_g$ electrons.",9806381v1
2000-09-27,Microscopic theory of the two-dimensional quantum antiferromagnet in a paramagnetic phase,"We have developed a consistent theory of the Heisenberg quantum
antiferromagnet in the disordered phase with a short range antiferromagnetic
order on the basis of the path integral for spin coherent states. We have
presented the Lagrangian of the theory in a form which is explicitly invariant
under rotations and found natural variables in terms of which one can construct
a natural perturbation theory. The short wave spin fluctuations are similar to
those in the spin wave theory and they are of the order of the parameter $1/2s$
where $s$ is the spin magnitude. The long wave spin fluctuations are governed
by the nonlinear sigma model and are of the order of the the parameter 1/N,
where $N$ is the number of field components. We also have shown that the short
wave spin fluctuations must be evaluated accurately and the continuum limit in
time of the path integral must be performed after all summation over the
frequencies $\omega$. In the framework of our approach we have obtained the
response function for the spin fluctuations for all region of the frequency
$\omega$ and the wave vector ${\bf k}$ and have calculated the free energy of
the system. We have also reproduced the known results for the spin correlation
length in the lowest order in 1/N.",0009427v2
2007-04-12,Temperature-driven transition from the Wigner Crystal to the Bond-Charge-Density Wave in the Quasi-One-Dimensional Quarter-Filled band,"It is known that within the interacting electron model Hamiltonian for the
one-dimensional 1/4-filled band, the singlet ground state is a Wigner crystal
only if the nearest neighbor electron-electron repulsion is larger than a
critical value. We show that this critical nearest neighbor Coulomb interaction
is different for each spin subspace, with the critical value decreasing with
increasing spin. As a consequence, with the lowering of temperature, there can
occur a transition from a Wigner crystal charge-ordered state to a spin-Peierls
state that is a Bond-Charge-Density Wave with charge occupancies different from
the Wigner crystal. This transition is possible because spin excitations from
the spin-Peierls state in the 1/4-filled band are necessarily accompanied by
changes in site charge densities. We apply our theory to the 1/4-filled band
quasi-one-dimensional organic charge-transfer solids in general and to 2:1
tetramethyltetrathiafulvalene (TMTTF) and tetramethyltetraselenafulvalene
(TMTSF) cationic salts in particular. We believe that many recent experiments
strongly indicate the Wigner crystal to Bond-Charge-Density Wave transition in
several members of the TMTTF family. We explain the occurrence of two different
antiferromagnetic phases but a single spin-Peierls state in the generic phase
diagram for the 2:1 cationic solids. The antiferromagnetic phases can have
either the Wigner crystal or the Bond-Charge-Spin-Density Wave charge
occupancies. The spin-Peierls state is always a Bond-Charge-Density Wave.",0704.1656v2
2011-02-18,{\it Ab initio} studies of spin-spiral waves and exchange interactions in 3{\it d} transition metal atomic chains,"The total energy of the transverse spin-spiral wave as a function of the wave
vector for all 3$d$ transition metal atomic chains has been calculated within
{\it ab initio} density functional theory with generalized gradient
approximation. It is predicted that at the equilibrium bond length, the V, Mn,
and Fe chains have a stable spin spiral structure, whilst the magnetic ground
state of the Cr, Co and Ni chains remains to be collinear. Furthermore, all the
exchange interaction parameters of the 3$d$ transition metal chains are
evaluated by using the calculated energy dispersion relations of the
spin-spiral waves. Interestingly, it is found that the magnetic couplings in
the V, Mn and Cr chains are frustrated (i.e., the second near neighbor exchange
interaction is antiferromagnetic), and this leads to the formation of the
stable spin-spiral structure in these chains. The spin-wave stiffness constant
of these 3$d$ metal chains is also evaluated and is found to be smaller than
its counterpart in bulk and monolayer systems. The upper limit (in the order of
100 Kelvins) of the possible magnetic phase transition temperature in these
atomic chains is also estimated within the mean field approximation. The
electronic band structure of the spin-spiral structures have also been
calculated. It is hoped that the interesting findings here of the stable
spin-spiral structure and frustrated magnetic interaction in the 3$d$
transition metal chains would stimulate further theoretical and experimental
research in this field.",1102.3737v1
2015-05-14,"First-principles calculations of exchange interactions, spin waves, and temperature dependence of magnetization in inverse-Heusler-based spin gapless semiconductors","Employing first principles electronic structure calculations in conjunction
with the frozen-magnon method we calculate exchange interactions, spin-wave
dispersion, and spin-wave stiffness constants in inverse-Heusler-based spin
gapless semiconductor (SGS) compounds Mn$_2$CoAl, Ti$_2$MnAl, Cr$_2$ZnSi,
Ti$_2$CoSi and Ti$_2$VAs. We find that their magnetic behavior is similar to
the half-metallic ferromagnetic full-Heusler alloys, i.e., the intersublattice
exchange interactions play an essential role in the formation of the magnetic
ground state and in determining the Curie temperature, $T_\mathrm{c}$. All
compounds, except Ti$_2$CoSi possess a ferrimagnetic ground state. Due to the
finite energy gap in one spin channel, the exchange interactions decay sharply
with the distance, and hence magnetism of these SGSs can be described
considering only nearest and next-nearest neighbor exchange interactions. The
calculated spin-wave dispersion curves are typical for ferrimagnets and
ferromagnets. The spin-wave stiffness constants turn out to be larger than
those of the elementary 3$d$-ferromagnets. Calculated exchange parameters are
used as input to determine the temperature dependence of the magnetization and
$T_\mathrm{c}$ of the SGSs. We find that the $T_\mathrm{c}$ of all compounds is
much above the room temperature. The calculated magnetization curve for
Mn$_2$CoAl as well as the Curie temperature are in very good agreement with
available experimental data. The present study is expected to pave the way for
a deeper understanding of the magnetic properties of the inverse-Heusler-based
SGSs and enhance the interest in these materials for application in spintronic
and magnetoelectronic devices.",1505.03632v1
2019-11-04,Spin-helix driven insulating phase in two dimensional lattice,"Motivated by emergent $SU(2)$ symmetry in the spin orbit coupled system, we
study the spin helix driven insulating phase in two dimensional lattice. When
both Rashba and Dresselhaus spin orbit couplings are present, the perfect Fermi
surface nesting occurs at a special condition depending on the lattice
geometry. In this case, the energies of spin up at any wave vector $\vec{k}$
are equivalent to the ones of spin down at $\vec{k}\!+\!\vec{Q}$ with so-called
the \textit{shifting wave vector} $\vec{Q}$. Thus, the system stabilizes
magnetic insulator with spiral like magnetic ordering even in the presence of
tiny electron-electron interaction where the magnetic ordering wave vector is
proportional to $\vec{Q}$. We first show the condition for existence of the
\textit{shifting wave vector} in general lattice model and emergent $SU(2)$
symmetry in the spin orbit coupled system. Then, we exemplify this in square
lattice at half filling and discuss the insulating phase with (non-) coplanar
spin density wave and charge order. Our study emphasizes possible new types of
two dimensional magnetic materials and can be applicable to various van-der
Waals materials and their heterostructures with the control of electric field,
strain and pressure.",1911.01440v1
2021-08-01,Directional excitation of a high-density magnon gas using coherently driven spin waves,"Controlling magnon densities in magnetic materials enables driving spin
transport in magnonic devices. We demonstrate the creation of large,
out-of-equilibrium magnon densities in a thin-film magnetic insulator via
microwave excitation of coherent spin waves and subsequent multi-magnon
scattering. We image both the coherent spin waves and the resulting incoherent
magnon gas using scanning-probe magnetometry based on electron spins in
diamond. We find that the gas extends unidirectionally over hundreds of
micrometers from the excitation stripline. Surprisingly, the gas density far
exceeds that expected for a boson system following a Bose-Einstein distribution
with a maximum value of the chemical potential. We characterize the momentum
distribution of the gas by measuring the nanoscale spatial decay of the
magnetic stray fields. Our results show that driving coherent spin waves leads
to a strong out-of-equilibrium occupation of the spin-wave band, opening new
possibilities for controlling spin transport and magnetic dynamics in target
directions.",2108.00467v1
2017-01-09,Spin-Wave versus Joule Heating in Spin-Hall-Effect/Spin-Transfer-Torque Driven Cr/Heusler/Pt Waveguides,"We present a time-resolved study of the DC-current driven magnetization
dynamics in a microstructured Cr/Heusler/Pt waveguide by means of Brillouin
light scattering. A reduction of the effective spin-wave damping via the
spin-transfer-torque effect leads to a strong increase in the magnon density.
This is accompanied by a decrease of the spin-wave frequencies. By evaluating
the time scales of these effects, the origin of this frequency shift can be
identified. However, recently, we found that the experimental setup partially
influences the decay of the spin-wave intensity after the current pulse is
switched off. Thus, further investigations on the presented effect are needed
to allow for a more detailed analysis. For this reason, we need to withdraw the
manuscript at this point and might publish an updated version later.",1701.02094v2
2023-05-07,Effect of random antiferromagnetic exchange on the spin waves in a three-dimensional Heisenberg ferromagnet,"Neutron scattering is used to study spin waves in the three-dimensional
Heisenberg ferromagnet YTiO$_3$, with spin-spin exchange disorder introduced
$via$ La-substitution at the Y site. No significant changes are observed in the
spin-wave dispersion up to a La concentration of 20%. However, a strong
broadening of the spectrum is found, indicative of shortened spin-wave
lifetimes. Density-functional theory calculations predict minimal changes in
exchange constants as a result of average structural changes due to La
substitution, in agreement with the data. The absence of significant changes in
the spin-wave dispersion, the considerable lifetime effect, and the reduced
ordered magnetic moment previously observed in the La-substituted system are
qualitatively captured by an isotropic, nearest-neighbor, three-dimensional
Heisenberg ferromagnet model with random antiferromagnetic exchange. We
therefore establish Y$_{1-x}$La$_x$TiO$_3$ as a model system to study the
effect of antiferromagnetic spin-exchange disorder in a three-dimensional
Heisenberg ferromagnet.",2305.04280v1
2020-12-17,Energy-efficient spin injector into semiconductors driven by elastic waves,"Generation of spin imbalance in nonmagnetic semiconductors is crucial for the
functioning of many spintronic devices. An attractive design of spin injectors
into semiconductors is based on a spin pumping from a precessing ferromagnet,
typically excited by a microwave magnetic field leading to a high power
consumption of the device. Here we describe theoretically a spin injector with
greatly reduced energy losses, in which the magnetic dynamics is excited by an
elastic wave injected into a ferromagnet-semiconductor heterostructure. To
demonstrate the efficient functioning of such an injector, we perform
micromagnetoelastic simulations of the coupled elastic and magnetic dynamics in
Ni films and Ni/GaAs bilayers. For thick Ni films, it is shown that a
monochromatic acoustic wave generates a spin wave with the same frequency and
wavelength, which propagates over distances of several micrometers at the
excitation frequencies close to the frequency of ferromagnetic resonance. The
simulations of Ni/GaAs bilayers with Ni thicknesses comparable to the
wavelength of the injected acoustic wave demonstrate the development of a
steady-state magnetization precession at the Ni/GaAs interface. The amplitude
of such a precession has a maximum at Ni thickness amounting to three quarters
of the wavelength of the elastic wave, which is explained by an analytical
model. Using simulation data obtained for the magnetization precession at the
Ni/GaAs interface, we evaluate the spin current pumped into GaAs and calculate
the spin accumulation in it by solving the spin diffusion equation. Then the
electrical signals resulting from the spin flow and the inverse spin Hall
effect are determined via the numerical solution of the Laplace's equation. It
is shown that amplitudes of these ac signals are large enough for experimental
measurement, which indicates an efficient acoustically driven spin pumping into
GaAs.",2012.09531v1
2003-01-31,Entanglement of Electron Spin and Orbital States in Spintronic Quantum Transport,"An electron within a mesoscopic (quantum-coherent) spintronic structure is
described by a single wave function which, in the presence of both charge
scattering and spin-orbit coupling, encodes an information about {\em
entanglement} of its spin and orbital degrees of freedom. The quantum state--an
{\em improper} mixture--of experimentally detectable spin subsystem is
elucidated by evaluating quantum information theory measures of entanglement in
the scattering states which determine {\em quantum transport} properties of
spin-polarized electrons injected into a two-dimensional disordered Rashba
spin-split conductor that is attached to the ferromagnetic source and drain
electrodes. Thus, the Landauer transmission matrix, traditionally evaluated to
obtain the spin-resolved conductances, also yields the reduced spin density
operator allowing us to extract quantum-mechanical measures of the detected
electron spin-polarization and spin-coherence, thereby pointing out how to
avoid detrimental {\em decoherence} effects on spin-encoded information
transport through semiconductor spintronic devices.",0301614v3
2012-11-09,Interaction induced staggered spin-orbit order in two-dimensional electron gas,"We propose and formulate an interaction induced staggered spin-orbit order as
a new emergent phase of two-dimensional Fermi gases. We show that when some
form of inherent spin-splitting via Rashba-type spin-orbit coupling renders two
helical Fermi surfaces to become significantly `nested', a Fermi surface
instability arises. To lift this degeneracy, a spontaneous symmetry breaking
spin-orbit density wave develops, causing a surprisingly large quasiparticle
gapping with chiral electronic states. Since the staggered spin-orbit order is
associated with a condensation energy, quantified by the gap value, destroying
such spin-orbit interaction costs sufficiently large perturbation field or
temperature or de-phasing time. BiAg$_2$ surface state is shown to be a
representative system for realizing such novel spin-orbit interaction with
tunable and large strength, and the spin-splitting is decoupled from charge
excitations. These functional properties are relevant for spin-electronics,
spin-caloritronics, and spin-Hall effect applications.",1211.2018v1
2013-08-20,Hole Spin Helix: Anomalous Spin Diffusion in Anisotropic Strained Hole Quantum Wells,"We obtain the spin-orbit interaction and spin-charge coupled transport
equations of a two-dimensional heavy hole gas under the influence of strain and
anisotropy. We show that a simple two-band Hamiltonian can be used to describe
the holes. In addition to the well-known cubic hole spin-orbit interaction,
anisotropy causes a Dresselhaus-like term, and strain causes a Rashba term. We
discover that strain can cause a shifting symmetry of the Fermi surfaces for
spin up and down holes. We predict an enhanced spin lifetime associated with a
spin helix standing wave similar to the Persistent Spin Helix which exists in
the two-dimensional electron gas with equal Rashba and Dresselhaus spin-orbit
interactions. These results may be useful both for spin-based experimental
determination of the Luttinger parameters of the valence band Hamiltonian and
for creating long-lived spin excitations.",1308.4248v3
2016-08-23,The effect of spin-orbit coupling on the effective-spin correlation in YbMgGaO4,"Motivated by the recent experiments on the triangular lattice spin liquid
YbMgGaO$_4$, we explore the effect of spin-orbit coupling on the effective-spin
correlation of the Yb local moments. We point out the anisotropic interaction
between the effective-spins on the nearest neighbor bonds is sufficient to
reproduce the spin-wave dispersion of the fully polarized state in the presence
of strong magnetic field normal to the triangular plane. We further evaluate
the effective-spin correlation within the mean-field spherical approximation.
We explicitly demonstrate that, the nearest-neighbor anisotropic effective-spin
interaction, originating from the strong spin-orbit coupling, enhances the
effective-spin correlation at the M points in the Brillouin zone. We identify
these results as the strong evidence for the anisotropic interaction and the
strong spin-orbit coupling in YbMgGaO$_4$.",1608.06445v2
2016-08-26,RKKY oscillations in the spin relaxation rates of atomic scale nanomagnets,"Exchange interactions with itinerant electrons are known to act as a
relaxation mechanism for individual local spins. The same exchange interactions
are also known to induce the so called RKKY indirect exchange interaction
between two otherwise decoupled local spins. Here we show that both the spin
relaxation and the RKKY coupling can be seen as the dissipative and reactive
response to the coupling of the local spins with the itinerant electrons. We
thereby predict that the spin relaxation rates of magnetic nanostructures of
exchanged coupled local spins, such as as nanoengineered spin chains, have an
oscillatory dependence on $k_F d$ , where $k_F$ is the Fermi wave length and
$d$ is the inter-spin distance, very much like the celebrated oscillations in
the RKKY interaction. We demonstrate that both $T_1$ and $T_2$ can be enhanced
or suppressed, compared to the single spin limit, depending on the interplay
between the Fermi surface and the nanostructure geometrical arrangement. Our
results open a route to engineer spin relaxation and decoherence in atomically
designed spin structures.",1608.07462v2
2019-04-24,Enhanced spin-triplet pairing in magnetic junctions with s-wave superconductors,"A common path to superconducting spintronics, Majorana fermions, and
topologically-protected quantum computing relies on spin-triplet
superconductivity. While naturally occurring spin-triplet pairing is elusive
and even common spin-triplet candidates, such as Sr$_2$RuO$_4$, support
alternative explanations, proximity effects in heterostructures can overcome
these limitations. It is expected that robust spin-triplet superconductivity in
magnetic junctions should rely on highly spin-polarized magnets or complex
magnetic multilayers. Instead, we predict that the interplay of interfacial
spin-orbit coupling and the barrier strength in simple magnetic junctions, with
only a small spin polarization and s-wave superconductors, can lead to nearly
complete spin-triplet superconducting proximity effects. This peculiar behavior
arises from an effective perfect transparency: interfacial spin-orbit coupling
counteracts the native potential barrier for states of a given spin and wave
vector. We show that the enhanced spin-triplet regime is characterized by a
huge increase in conductance magnetoanisotropy, orders of magnitude larger than
in the normal state.",1904.10773v1
2023-01-28,Self-driven Hybrid Atomic Spin Oscillator,"A self-driven hybrid atomic spin oscillator is demonstrated in theory and
experiment with a vapor Rb-Xe dual-spin system. The raw signal of Rb spin
oscillation is amplified, phase-shifted and sent back to drive the Xe spins
coherently. By fine tuning the driving field strength and phase, a
self-sustaining spin oscillation signal with zero frequency shift is obtained.
The effective coherence time is infinitely prolonged beyond the intrinsic
coherence time of Xe spins, forming a hybrid atomic spin oscillator. Spectral
analysis indicates that a frequency resolution of 13.1 nHz is achieved,
enhancing the detection sensitivity for magnetic field. Allan deviation
analysis shows that the spin oscillator can operate in continuous wave mode
like a spin maser. The prototype spin oscillator can be easily implanted into
other hybrid spin systems and enhance the detection sensitivity of alkali
metal-noble gas comagnetometers.",2301.12121v2
2011-01-10,Radiation of caustic beams from a collapsing bullet,"Collapse of an intense (2+1)-dimensional wave packet in a medium with cubic
nonlinearity and a two-dimensional dispersion of an order higher than parabolic
is studied both theoretically and experimentally. The carrier waves are
microwave backward volume spin waves which propagate in a stripe made from a
thin ferrimagnetic film and the packet is a spin-wave bullet. We show that
before being self-destroyed the bullet irradiates untrapped dispersive waves,
which is in agreement with a previous theoretical prediction. Since, in
addition, the ferromagnetic medium is characterized by an induced uniaxial
anisotropy, this radiation takes the form of narrow beams of continuous waves
at very specific angles to its propagation direction. Based on our theoretical
calculations we find that these beams are caustic beams and the angles are the
characteristic spin-wave caustic angles modified by the motion of the source.",1101.1696v2
2018-05-18,Spinning Particles in Twisted Gravitational Wave Spacetimes,"Twisted gravitational waves (TGWs) are nonplanar waves with twisted rays that
move along a fixed direction in space. We study further the physical
characteristics of a recent class of Ricci-flat solutions of general relativity
representing TGWs with wave fronts that have negative Gaussian curvature. In
particular, we investigate the influence of TGWs on the polarization of test
electromagnetic waves and on the motion of classical spinning test particles in
such radiation fields. To distinguish the polarization effects of twisted waves
from plane waves, we examine the theoretical possibility of existence of
spin-twist coupling and show that this interaction is generally consistent with
our results.",1805.07080v6
2018-06-11,Explicit inclusion of spin-orbit contribution in THSR wave function,"The Tohsaki-Horiuchi-Schuck-Roepke (THSR) wave function has been successfully
used for the studies of gas-like nature of alpha clusters in various nuclei
including the so-called Hoyle state of 12C and four alpha states of 16O. In
standard alpha cluster models, however, each alpha cluster wave function has
spin zero because of its spatial symmetry and antisymmetrization effect. Thus
the non-central interactions do not contribute, and this situation is the same
in the THSR wave function. In this work, the spin-orbit contribution, which is
found to be quite important at short alpha-alpha distances, is taken into
account in the THSR wave function by combing it with antisymmetrized quasi
cluster model (AQCM). The application to 12C is presented. The
multi-integration in the original THSR wave function is carried out by using
Monte Carlo technique, which is called Monte Carlo THSR wave function. For the
nucleon-nucleon interaction, the Tohsaki interaction, which contains
finite-range three-body terms and simultaneously reproduces the saturation
properties of nuclear systems, the alpha-alpha scattering phase shift, and the
size and binding energy of 4He, is adopted.",1806.03817v1
2019-02-25,Driving magnetization dynamics in an on-demand magnonic crystal by magneto-elastic interaction,"Using spatial light interference of ultrafast laser pulses, we generate a
lateral modulation in the magnetization profile of an otherwise uniformly
magnetized film, whose magnetic excitation spectrum is monitored via the
coherent and resonant interaction with elastic waves. We find an unusual
dependence of the magnetoelastic coupling as the externally applied magnetic
field is angle- and field-tuned relative to the wave vector of the
magnetization modulation, which can be explained by the emergence of spatially
inhomogeneous spin-wave modes. In this regard, the spatial light interference
methodology can be seen as a user-configurable, temporally windowed, on-demand
magnonic crystal, potentially of arbitrary two-dimensional shape, which allows
control and selectivity of the spatial distribution of spin waves. Calculations
of spin waves using a variety of methods, demonstrated here using the
plane-wave method and micromagnetic simulation, can identify the spatial
distribution and associated energy scales of each excitation, which opens the
door to a number of excitation methodologies beyond our chosen elastic wave
excitation.",1902.09186v1
2020-04-07,Nonreciprocal Dzyaloshinskii-Moriya magnetoacoustic waves,"We study the interaction of surface acoustic waves with spin waves in
ultra-thin CoFeB/Pt bilayers. Due to the interfacial Dzyaloshinskii-Moriya
interaction (DMI), the spin wave dispersion is non-degenerate for oppositely
propagating spin waves in CoFeB/Pt. In combination with the additional
nonreciprocity of the magnetoacoustic coupling itself, highly nonreciprocal
acoustic wave transmission through the magnetic film is observed. We
systematically characterize the magnetoacoustic wave propagation in a thickness
series of CoFeB($d$)/Pt samples as a function of magnetic field magnitude and
direction, and at frequencies up to 7 GHz. We quantitatively model our results
to extract the strength of the DMI and magnetoacoustic driving fields.",2004.03535v2
2023-09-20,On spin optics for gravitational waves lensed by a rotating object,"We study gravitational lensing of gravitational waves taking into account the
spin of a graviton coupled with a dragged spacetime made by a rotating object.
We decompose the phase of gravitational waves into helicity-dependent and
independent components with spin optics, analyzing waves whose wavelengths are
shorter than the curvature radius of a lens object. We analytically confirm
that the trajectory of gravitational waves splits depending on the helicity,
generating additional time delay and elliptical polarization onto the
helicity-independent part. We exemplify monotonic gravitational waves lensed by
a Kerr black hole and derive the analytical expressions of corrections in phase
and magnification. The corrections are enhanced for longer wavelengths,
potentially providing a novel probe of rotational properties of lens objects in
low-frequency gravitational-wave observations in the future.",2309.11024v2
2006-08-30,Spin-quadrupole ordering of spin-3/2 ultracold fermionic atoms in optical lattices in the one-band Hubbard model,"Based on a generalized one-band Hubbard model, we study magnetic properties
of Mott insulating states for ultracold spin-3/2 fermionic atoms in optical
lattices. When the \textit{s}-wave scattering lengths for the total spin
$S=2,0$ satisfy conditions $a_{2}>a_{0}>0$, we apply a functional integral
approach to the half filled case, where the spin-quadrupole fluctuations
dominate. On a 2D square lattice, the saddle point solution yields a staggered
spin-quadrupole ordering at zero temperature with symmetry breaking from SO(5)
to SO(4). Both spin and spin-quadrupole static structure factors are
calculated, displaying highly anisotropic spin antiferromagnetic fluctuations
and antiferroquadrupole long-range correlations, respectively. When Gaussian
fluctuations around the saddle point are taken into account, spin-quadrupole
density waves with a linear dispersion are derived. Compared with the spin
density waves in the half filled spin-1/2 Hubbard model, the quadrupole density
wave velocity is saturated in the strong-coupling limit, and there are no
transverse spin-quadrupole mode couplings, as required by the SO(4) invariance
of the effective action. Finally, in the strong-coupling limit of the model
Hamiltonian, we derive the effective hyperfine spin-exchange interactions for
the Mott insulating phases in the quarter filled and half filled cases,
respectively.",0608673v3
2008-12-01,Antiferromagnet-based nuclear spin model of scalable quantum register with inhomogeneous magnetic field,"As a nuclear spin model of scalable quantum register, the one-dimensional
chain of the magnetic atoms with nuclear spins 1/2 substituting the basic atoms
in the plate of nuclear spin free easy-axis 3D antiferromagnet is considered.
It is formulated the generalized antiferromagnet Hamiltonian in spin-wave
approximation (low temperatures) considering the inhomogeneous external
magnetic field, which is directed along the easy axis normally to plane of the
plate and has a constant gradient along the nuclear spin chain. Assuming a weak
gradient, the asymptotic expression for coefficients of unitary transformations
to the diagonal form of antiferromagnet Hamiltonian is found. With this result
the expression for indirect interspin coupling, which is due to hyperfine
nuclear electron coupling in atoms and the virtual spin wave propagation in
antiferromagnet ground state, was evaluated.
  It is shown that the inhomogeneous magnetic field essentially modifies the
characteristics of indirect interspin coupling. The indirect interaction
essentially grows and even oscillates in relation to the interspin distance
when the local field value in the middle point of two considered nuclear spin
is close to the critical field for quantum phase transition of spin-flop type
in bulk antiferromagnet or close to antiferromagnetic resonance. Thus, the
external magnetic field, its gradient, microwave frequency and power can play
the role of control parameters for qubit states.
  Finally, the one and two qubit states decoherence and longitudinal relaxation
rate are caused by the interaction of nuclear spins with virtual spin waves in
antiferromagnet ground state are calculated.",0812.0135v1
2015-10-12,"On equation of state for the ""thermal"" part of the spin current: Pauli principle contribution in the spin wave spectrum in cold fermion system","Spin evolution opened a large field in quantum plasma research. The spin
waves in plasmas were considered among new phenomena considered in spin-1/2
quantum plasmas. The spin density evolution equation found by means of the
many-particle quantum hydrodynamics shows existence of the ""thermal"" part of
the spin current, which is an analog of the thermal pressure, or the Fermi
pressure for degenerate electron gas, existing in the Euler equation. However,
this term has been dropped, since there has not been found any equation of
state for the thermal part of the spin current (TPSC), like we have for the
pressure. In this paper we derive the equation of state for the TPSC and apply
it for study of spectrum of collective excitations in spin-1/2 quantum plasmas.
We focus our research on the spectrum of spin waves, since this spectrum is
affected by the thermal part of the spin current. We consider two kinds of
plasmas: electron-ion plasma with motionless ions and degenerate electrons, and
degenerate electron-positron plasmas. We also present the non-linear Pauli
equation with the spinor pressure term containing described effects. The
thermal part of the flux of spin current existing in the spin current evolution
equation is also derived. We also consider the contribution of the TPSC in the
grand generalized vorticity evolution.",1510.03468v1
2016-05-10,New investigations on the transverse spin of structured optical fields,"Guided waves and surface waves can be taken as two typical examples of
structured optical fields with the transverse spin. Analytical derivations are
developed to demonstrate that (i) guided waves also carry the transverse spin
that depends on the mean direction of propagation, which may have important
applications in spin-dependent unidirectional optical interfaces; (ii) the
quantization form of the transverse spin is for the first time revealed, which
is not obvious and related to an ellipticity; (iii) from a unified point of
view, the transverse spin can be attributed to the presence of an effective
rest mass of structured optical fields; (iv) the transverse spin can also be
described by the spin matrix of the photon field; (v) unlike a free optical
field whose spin projection on the propagation direction is the only
observable, owing to the effective rest mass, the spin projection of structured
optical fields on other directions is also an observable, such that one can
develop an optical analogy of spintronics. A preliminary idea about the
potential applications of the transverse spin is presented, but an in-depth and
complete study will be presented in our next work.",1605.03103v2
2017-10-30,Quantum Spin-Hall Effect of Light at Bound States in the Continuum,"The discovery of the topological nature of free-space light and its quantum
chiral behavior has recently raised large attention. This important scientific
endeavor features spin-based integrated quantum technologies. Herein, we
discuss a novel phenomenon based on a resonantly-enhanced quantum spin-Hall
transport of light observed in a dielectric resonator operating near the
bound-state-in-continuum (BIC) regime. The BIC mode is characterized by a
transverse photonic spin angular momentum density extended on a macroscopic
area. As such, the experimental excited mode in near-BIC regime generates
resonant surface waves characterized by spin-momentum locking and that
propagate along the symmetry axes of the structure. In addition, the generated
side waves are interpreted as an abrupt nonparaxial redirection of the exciting
far field light, which is responsible for the spin-to-orbital angular momentum
conversion evidenced in the spin-orbit asymmetry measured in the intensity of
the side waves. The experimental results are in excellent agreement with a
model that combines geometric parallel transport of light polarization and
spin-momentum locking. In addition, breaking the excitation symmetry leads to a
total spin-directive coupling. Our results reveal the possibility of a
BIC-enhanced macroscopic spin-directive coupling, a novel fundamental mechanism
of light-spin manipulation that will have strong impact on emerging quantum
technologies.",1710.10862v1
2021-04-19,Experimental observation of transverse spin of plasmon polaritons in a single-crystalline silver nanowire,"We report the experimental observation of the transverse spin and associated
spin-momentum locking of surface plasmon polaritons (SPPs) excited in a
plasmonic single crystalline silver nanowire (AgNW). In contrast to the SPPs
excited in metal films, the electromagnetic field components of the evanescent
SPP mode propagating along the long axis ($x$ axis) of the NW can decay along
two longitudinal planes ($x$-$y$ and $x$-$z$ planes), resulting in two
orthogonal transverse spin components ($s_z$ and $s_y$). Analysis of the
opposite circular polarization components of the decaying SPP mode signal in
the longitudinal plane ($x$-$y$) reveals spin dependent biasing of the signal
and hence the existence of transverse spin component ($s_z$). The corresponding
transverse spin density ($s_3$) in the Fourier plane reveals spin-momentum
locking, where the helicity of the spin is dictated by the wave-vector
components of the SPP evanescent wave. Further, the results are corroborated
with three-dimensional numerical calculations. The presented results showcase
how a chemically prepared plasmonic AgNW can be harnessed to study optical
spins in evanescent waves, and can be extrapolated to explore sub-wavelength
effects including directional spin coupling and optical nano-manipulation.",2104.09303v2
2020-01-16,The Low Effective Spin of Binary Black Holes and Implications for Individual Gravitational-Wave Events,"While the Advanced LIGO and Virgo gravitational-wave experiments now
regularly observe binary black hole mergers, the evolutionary origin of these
events remains a mystery. Analysis of the binary black hole spin distribution
may shed light on this mystery, offering a means of discriminating between
different binary formation channels. Using the data from Advanced LIGO and
Virgo's first and second observing runs, here we seek to carefully characterize
the distribution of effective spin among binary black holes, hierarchically
measuring the distribution's mean $\mu$ and variance $\sigma^2$ while
accounting for selection effects and degeneracies between spin and other black
hole parameters. We demonstrate that the known population of binary black holes
have spins that are both small, with $\mu \sim 0$, and very narrowly
distributed, with $\sigma^2 \leq 0.07$ at 95% credibility. We then explore what
these ensemble properties imply about the spins of individual binary black hole
mergers, re-analyzing existing gravitational-wave events with a
population-informed prior on their effective spin. The binary black hole
GW170729, which previously excluded effective spin equal to zero, is now
consistent with zero effective spin at ~10% credibility. More broadly, we find
that uninformative spin priors generally yield overestimates for the effective
spin magnitudes of compact binary mergers.",2001.06051v2
2023-07-18,Effect of Spin Orbit Coupling in non-centrosymmetric half-Heusler alloys,"Spin-orbit coupled electronic structure of two representative non-polar
half-Heusler alloys, namely 18 electron compound CoZrBi and 8 electron compound
SiLiIn have been studied in details. An excursion through the Brillouin zone of
these alloys from one high symmetry point to the other revealed rich local
symmetry of the associated wave vectors resulting in non-trivial spin splitting
of the bands and consequent diverse spin textures in the presence of spin-orbit
coupling. Our first principles calculations supplemented with low energy
$\boldsymbol{k.p}$ model Hamiltonian revealed the presence of linear
Dresselhaus effect at the X point having $D_{2d}$ symmetry and Rashba effect
with both linear and non-linear terms at the L point with $C_{3v}$ point group
symmetry. Interestingly we have also identified non-trivial Zeeman spin
splitting at the non-time reversal invariant W point and a pair of
non-degenerate bands along the path $\Gamma$ to L displaying vanishing spin
polarization due to the non-pseudo polar point group symmetry of the wave
vectors. Further a comparative study of CoZrBi and SiLiIn suggest, in addition,
to the local symmetry of the wave vectors, important role of the participating
orbitals in deciding the nature and strength of spin splitting. Our
calculations identify half-Heusler compounds with heavy elements displaying
diverse spin textures may be ideal candidate for spin valleytronics where spin
textures can be controlled by accessing different valleys around the high
symmetry k-points.",2308.03760v2
2024-01-11,Gravitational waves carry information beyond effective spin parameters but it is hard to extract,"Gravitational wave observations of binary black hole mergers probe their
astrophysical origins via the binary spin, namely the spin magnitudes and
directions of each component black hole, together described by six degrees of
freedom. However, the emitted signals primarily depend on two effective spin
parameters that condense the spin degrees of freedom to those parallel and
those perpendicular to the orbital plane. Given this reduction in
dimensionality between the physically relevant problem and what is typically
measurable, we revisit the question of whether information about the component
spin magnitudes and directions can successfully be recovered via
gravitational-wave observations, or if we simply extrapolate information about
the distributions of effective spin parameters.To this end, we simulate three
astrophysical populations with the same underlying effective-spin distribution
but different spin magnitude and tilt distributions, on which we conduct full
individual-event and population-level parameter estimation. We find that
parameterized population models can indeed qualitatively distinguish between
populations with different spin magnitude and tilt distributions at current
sensitivity. However, it remains challenging to either accurately recover the
true distribution or to diagnose biases due to model misspecification. We
attribute the former to practical challenges of dealing with high-dimensional
posterior distributions, and the latter to the fact that each individual event
carries very little information about the full six spin degrees of freedom.",2401.05613v1
2016-05-18,Standing magnetic wave on Ising ferromagnet: Nonequilibrium phase transition,"The dynamical response of an Ising ferromagnet to a plane polarised standing
magnetic field wave is modelled and studied here by Monte Carlo simulation in
two dimensions. The amplitude of standing magnetic wave is modulated along the
direction x. We have detected two main dynamical phases namely, pinned and
oscillating spin clusters. Depending on the value of field amplitude the system
is found to undergo a phase transition from oscillating spin cluster to pinned
as the system is cooled down. The time averaged magnetisation over a full cycle
of magnetic field oscillations is defined as the dynamic order parameter. The
transition is detected by studying the temperature dependences of the variance
of the dynamic order parameter, the derivative of the dynamic order parameter
and the dynamic specific heat. The dependence of the transition temperature on
the magnetic field amplitude and on the wavelength of the magnetic field wave
is studied at a single frequency. A comprehensive phase boundary is drawn in
the plane described by the temperature and field amplitude for two different
wavelengths of the magnetic wave. The variation of instantaneous line
magnetisation during a period of magnetic field oscillation for standing wave
mode is compared to those for the propagating wave mode. Also the probability
that a spin at any site, flips, is calculated. The above mentioned variations
and the probability of spin flip clearly distinguish between the dynamical
phases formed by propagating magnetic wave and by standing magnetic wave in an
Ising ferromagnet.",1605.05643v2
2024-01-04,Symmetry of the coupling between surface acoustic waves and spin waves in synthetic antiferromagnets,"Synthetic antiferromagnets host spin waves that are highly tunable. It is of
practical interest to analyze the symmetry of their coupling to surface
acoustic waves with the design of hybrid devices in view. For this we calculate
the layer-resolved susceptibility tensor of a synthetic antiferromagnet, the
effective magneto-elastic and magneto-rotation fields associated to a
travelling elastic wave, and the power irreversibly transferred by the elastic
wave to the magnetic layers. We consider Rayleigh-type surface acoustic waves:
(a) that travel in an elastically isotropic, non-piezoelectric substrate, or
(b) that propagate along the X direction at the surface of a Z-cut LiNbO$_3$
substrate, or (c) that are guided in a thin Z-cut LiNbO$_3$ film grown on a
sapphire substrate. In particular, we show that the complementary angular
dependencies of the acoustic and optical spin wave modes in synthetic
antiferromagnets makes it possible to excite spin waves for any relative
orientation of magnetization and acoustic wavevector. In addition, we discuss
the symmetries of the driving fields and of the energy transferred to the
magnetic degree of freedom. We evidence new interaction channels coupling the
magnetization eigenmodes when elastic anisotropy and piezoelectricity of the
substrate are considered.",2401.02263v1
2012-02-17,Spin-stretching modes in anisotropic magnets: spin-wave excitations in the multiferroic Ba2CoGe2O7,"We studied spin excitations of the multiferroic Ba2CoGe2O7 in high magnetic
fields up to 33 T. In the electron spin resonance and far infrared absorption
spectra we found several spin excitations beyond the two conventional magnon
modes expected for such a two-sublattice antiferromagnet. We show that a
multi-boson spin-wave theory can capture these unconventional modes, that
include spin-stretching modes associated with an oscillating magnetic dipole
(or only quadrupole) moment. The lack of the inversion symmetry allows these
modes to become electric dipole active. We expect that the spin-stretching
modes can be generally observed in inelastic neutron scattering and light
absorption experiments in a broad class of ordered S > 1/2 spin systems with
strong single-ion anisotropy and/or non-centrosymmetric lattice structure.",1202.3996v2
2012-06-04,Von Neumann Entropy Spectra and Entangled Excitations in Spin-Orbital Models,"We consider the low-energy excitations of one-dimensional spin-orbital models
which consist of spin waves, orbital waves, and joint spin-orbital excitations.
Among the latter we identify strongly entangled spin-orbital bound states which
appear as peaks in the von Neumann entropy (vNE) spectral function introduced
in this work. The strong entanglement of bound states is manifested by a
universal logarithmic scaling of the vNE with system size, while the vNE of
other spin-orbital excitations saturates. We suggest that spin-orbital
entanglement can be experimentally explored by the measurement of the dynamical
spin-orbital correlations using resonant inelastic x-ray scattering, where
strong spin-orbit coupling associated with the core hole plays a role.",1206.1062v1
2013-02-28,Number and spin densities in the ground state of a trapped mixture of two pseudospin-1/2 Bose gases with interspecies spin-exchange interaction,"We consider the ground state of a mixture of two pseudospin-$\1/2$ Bose gases
with interspecies spin exchange in a trapping potential. In the mean field
approach, the ground state can be described in terms of four wave functions
governed by a set of coupled Gross-Pitaevskii-like (GP-like) equations, which
differ from the usual GP equations in the existence of an interference term due
to spin-exchange coupling between the two species. Using these GP-like
equations, we calculate such ground state properties as chemical potentials,
density profiles and spin density profiles, which are directly observable in
experiments. We compare the cases with and without spin exchange. It is
demonstrated that the spin exchange between the two species lowers the chemical
potentials, tends to equalize the wave functions of the two pseudospin
components of each species, and thus homogenizes the spin density. The novel
features of the density and spin density profiles can serve as experimental
probes of this novel Bose system.",1302.7217v1
2013-10-07,Simulations of electric-dipole spin resonance for spin-orbit-coupled quantum dots in Overhauser field: fractional resonances and selection rules,"We consider spin rotations in single- and two-electron quantum dots that are
driven by external AC electric field with two mechanisms that couple the
electron spatial motion and the spin degree of freedom: the spin-orbit
interaction and a random fluctuation of the Overhauser field due to nuclear
spin bath. We perform a systematic numerical simulation of the driven system
using a finite difference approach with an exact account taken for the
electron-electron correlation. The simulation demonstrates that the electron
oscillation in fluctuating nuclear field is translated into an effective
magnetic field during the electron wave packet motion. The effective magnetic
field drives the spin transitions according to the electric-dipole spin
resonance mechanism. We find distinct signatures of selection rules for direct
and higher-order transitions in terms of the spin-orbital symmetries of the
wave functions. The selection rules are violated by the random fluctuation of
the Overhauser field.",1310.1689v1
2016-07-27,"Initial data for black hole-neutron star binaries, with rotating stars","The coalescence of a neutron star with a black hole is a primary science
target of ground-based gravitational wave detectors. Constraining or measuring
the neutron star spin directly from gravitational wave observations requires
knowledge of the dependence of the emission properties of these systems on the
neutron star spin. This paper lays foundations for this task, by developing a
numerical method to construct initial data for black hole--neutron star
binaries with arbitrary spin on the neutron star. We demonstrate the robustness
of the code by constructing initial-data sets in large regions of the parameter
space. In addition to varying the neutron star spin-magnitude and
spin-direction, we also explore neutron star compactness, mass-ratio, black
hole spin, and black hole spin-direction. Specifically, we are able to
construct initial data sets with neutron stars spinning near centrifugal
break-up, and with black hole spins as large as $S_{\rm BH}/M_{\rm BH}^2=0.99$.",1607.07962v1
2017-12-03,Two-spinor description of massive particles and relativistic spin projection operators,"On the basis of the Wigner unitary representations of the covering group
ISL(2,C) of the Poincar\'{e} group, we obtain spin-tensor wave functions of
free massive particles with arbitrary spin. The wave functions automatically
satisfy the Dirac-Pauli-Fierz equations. In the framework of the two-spinor
formalism we construct spin-vectors of polarizations and obtain conditions that
fix the corresponding relativistic spin projection operators (Behrends-Fronsdal
projection operators). With the help of these conditions we find explicit
expressions for relativistic spin projection operators for integer spins
(Behrends-Fronsdal projection operators) and then find relativistic spin
projection operators for half integer spins. These projection operators
determine the nominators in the propagators of fields of relativistic
particles. We deduce generalizations of the Behrends-Fronsdal projection
operators for arbitrary space-time dimensions D>2.",1712.00833v2
2019-11-11,Theory and phase-field simulations on electrical control of spin cycloids in a multiferroic,"Cycloidal spin orders are common in multiferroics. One of the prototypical
examples is BiFeO3 (BFO) which shows a large polarization and a cycloidal
antiferromagnetic order at room temperature. Here we employ Landau theory and
phase-field simulations to analyze the coupled switching dynamics of
polarization and cycloidal antiferromagnetic orders in BFO. We are able to
identify 14 types of transitional spin structures between two cycloids and 9
electric-field-induced spin switching paths. We demonstrate the
electric-field-induced rotation of wave vectors of the cycloidal spins and
discover 2 types of cycloidal spin switching dynamics: fast local spin flips
and slow rotation of wave vectors. Also, we construct road maps to achieve the
switching between any two spin cycloids through multi-step applications of
electric fields. The work provides a theoretical framework for the
phenomenological description of spin cycloids and a fundamental understanding
of the switching mechanisms to achieve electrical control of magnetic orders.",1911.04023v2
2017-10-12,Quasiclassical theory of spin dynamics in superfluid $^3$He: kinetic equations in the bulk and spin response of surface Majorana states,"We develop a theory based on the formalism of quasiclassical Green's
functions to study the spin dynamics in superfluid $^3$He. First, we derive
kinetic equations for the spin-dependent distribution function in the bulk
superfluid reproducing the results obtained earlier without quasiclassical
approximation. Then we consider a spin dynamics near the surface of fully
gapped $^3$He-B phase taking into account spin relaxation due to the
transitions in the spectrum of localized fermionic states. The lifetime of
longitudinal and transverse spin waves is calculate taking into account the
Fermi-liquid corrections which lead to the crucial modification of fermionic
spectrum and spin responses.",1710.04468v2
2018-04-25,"Spinning Mellin Bootstrap: Conformal Partial Waves, Crossing Kernels and Applications","We study conformal partial waves (CPWs) in Mellin space with totally
symmetric external operators of arbitrary integer spin. The exchanged spin is
arbitrary, and includes mixed symmetry and (partially)-conserved
representations. In a basis of CPWs recently introduced in arXiv:1702.08619, we
find a remarkable factorisation of the external spin dependence in their Mellin
representation. This property allows a relatively straightforward study of
inversion formulae to extract OPE data from the Mellin representation of
spinning 4pt correlators and in particular, to extract closed-form expressions
for crossing kernels of spinning CPWs in terms of the hypergeometric function
${}_4F_3$. We consider numerous examples involving both arbitrary internal and
external spins, and for both leading and sub-leading twist operators. As an
application, working in general $d$ we extract new results for ${\cal
O}\left(1/N\right)$ anomalous dimensions of double-trace operators induced by
double-trace deformations constructed from single-trace operators of generic
twist and integer spin. In particular, we extract the anomalous dimensions of
double-trace operators $[\mathcal{O}_J\Phi]_{n,l}$ with ${\cal O}_J$ a
single-trace operator of integer spin $J$.",1804.09334v2
2019-03-08,Intra- and inter-orbital correlated electron spin dynamics in $\rm Sr_2 Ir O_4$: spin-wave gap and spin-orbit exciton,"Transformation of Coulomb interaction terms to the pseudo-orbital basis
constituted by $J=1/2$ and $3/2$ states arising from spin-orbit coupling
provides a versatile tool. This formalism is applied to investigate magnetic
anisotropy effects on low-energy spin-wave excitations as well as high-energy
spin-orbit exciton modes in $\rm Sr_2 Ir O_4$. The Hund's coupling term
explictly yields easy-plane anisotropy, resulting in gapless (in-plane) and
gapped (out-of-plane) modes, in agreement with recent resonant inelastic x-ray
scattering (RIXS) measurements. The collective mode of inter-orbital,
spin-flip, particle-hole excitations with appropriate interaction strengths and
renormalized spin-orbit gap yields two well-defined propagating spin-orbit
exciton modes, with energy scale and dispersion in good agreement with RIXS
studies.",1903.03360v1
2021-02-03,Spin-governed topological surfaces and broken spin-momentum locking in a gyromagnetic medium,"Topology of isofrequency surfaces plays a crucial role in characterizing the
interaction of an electromagnetic wave with a medium. Thus, engineering the
topology in complex media is leading to novel applications, ranging from
super-resolution microscopy with hyperbolic metamaterials to sub-wavelength
waveguiding structures. Here, we investigate the spin-governed nature of
isofrequency surfaces in a general gyromagnetic medium. We show that gyrotropy
also plays an important role in the topological properties of a medium, along
with the anisotropic permeability and permittivity. Even though the topology
primarily depends on permeability, gyrotropy can suppress or support the
existence of certain topological surfaces. We reveal the connection between the
gyrotropy imposed constraints and the photonic spin-profile of the topological
surfaces. The spin-profile along the isofrequency surface is locked to the
material, resulting in the non-reciprocity and breaking of the spin-momentum
locking in the gyromagnetic medium. Further, we show that the conflict between
spin-momentum locking and material locked spin leads to asymmetric mode profile
and gyrotropy-induced cutoff in guided wave structures. Our work provides
important insights into the underlying link between topology, spin, and
non-reciprocity in gyrotropic media.",2102.02027v1
2019-01-21,"Magnonics: Spin Waves Connecting Charges, Spins and Photons","Spin waves (SW) are the excitation of the spin system in a ferromagnetic
condensed matter body. They are collective excitations of the electron system
and, from a quasi-classical point of view, can be understood as a coherent
precession of the electrons' spins. Analogous to photons, they are also
referred to as magnons indicating their quasi-particle character. The
collective nature of SWs is established by the short-range exchange interaction
as well as the non-local magnetic dipolar interaction, resulting in coherence
of SWs from mesoscopic to even macroscopic length scales. As one consequence of
this collective interaction, SWs are ""charge current free"" and, therefore, less
subject to dissipation caused by scattering with impurities on the atomic
level. This is a clear advantage over diffusive transport in spintronics that
not only uses the charge of an electron but also its spin degree of freedom.
Any (spin) current naturally involves motion and, thus, scattering of electrons
leading to excessive heating as well as losses. This renders SWs a promising
alternative to electric (spin) currents for the transport of spin information -
one of the grand challenges of condensed matter physics.",1901.07021v1
2019-07-02,Spin-orbit interaction and snake states in graphene $p$-$n$ junctions,"We study a model of a $p$-$n$ junction in single-layer graphene in the
presence of a perpendicular magnetic field and spin-orbit interactions. By
solving the relevant quantum-mechanical problem for a potential step, we
determine the exact spectrum of spin-resolved dispersive Landau levels. Close
to zero energy, we find a pair of linearly dispersing zero modes, which possess
a wave-vector-dependent spin polarization and can be regarded as quantum
analogous of spinful snake states. We show that the Rashba spin-orbit
interaction, in particular, produces a wave vector shift between the
dispersions of these modes with observable interference effects. These effects
can in principle provide a way to detect the presence of Rashba spin-orbit
interaction and measure its strength. Our results suggest that a graphene
$p$-$n$ junction in the presence of strong spin-orbit interaction could be used
as a building block in a spin field-effect transistor.",1907.01233v2
2019-07-17,Transverse photon spin beyond interfaces,"Photons possess spin degree of freedom, corresponding to clockwise and
counter clockwise rotating direction of the fields. Photon spin plays an
important role in various applications such as optical communications,
information processing and sensing. In conventional isotropic media, photon
spin is aligned with the propagation direction of light, obeying spin momentum
locking. Interestingly, at certain interfaces, the surface waves decaying away
from the interface possess a photon spin transverse to its propagation, opening
exciting opportunities for observation of spin dependent unidirectional
excitation in confined systems. Here we propose and realize transverse photon
spin (T-spin) in the interior of a bulk medium, without relying on the presence
of any interfaces. We show the complete mapping of the T-spin of surface modes
to that of the bulk modes by introducing the coupling between electric and
magnetic responses along orthogonal directions, i.e., the bianisotropy, into
the medium. We further discover that an interface formed by two bianisotropic
media of opposite orientations supports edge-dependent propagating modes with
tunable cutoff frequencies. Our results provide a new platform for manipulating
the spin orbit interaction of electromagnetic waves.",1907.07654v1
2022-01-18,Spin generalizations of the Benjamin-Ono equation,"We present new soliton equations related to the $A$-type spin Calogero-Moser
(CM) systems introduced by Gibbons and Hermsen. These equations are spin
generalizations of the Benjamin-Ono (BO) equation and the recently introduced
non-chiral intermediate long-wave (ncILW) equation. We obtain multi-soliton
solutions of these spin generalizations of the BO equation and the ncILW
equation via a spin-pole ansatz where the spin-pole dynamics is governed by the
spin CM system in the rational and hyperbolic cases, respectively. We also
propose physics applications of the new equations, and we introduce a spin
generalization of the standard intermediate long-wave equation which
interpolates between the matrix Korteweg-de Vries equation, the Heisenberg
ferromagnet equation, and the spin BO equation.",2201.07269v1
2022-02-18,Intrinsic spin-momentum dynamics of surface electromagnetic waves in complex dispersive system,"Spin-momentum locking is an intrinsic property of surface electromagnetic
fields and its study has led to the discovery of photonic spin lattices and
diverse applications. Previously, dispersion was ignored in the spin-momentum
locking, giving rise to abnormal phenomena contradictory to the physical
realities. Here, we formulate four dispersive spin-momentum equations for
surface waves, revealing universally that the transverse spin vector is locked
with the momentum. The locking property obeys the right-hand rule in the
dielectric but the left-hand rule in the dispersive metal/magnetic materials.
In addition to the dispersion, the structural features can affect the
spin-momentum locking significantly. Remarkably, an extraordinary longitudinal
spin originating from the coupling polarization ellipticity is uncovered even
for the purely polarized state. We further demonstrate the spin-momentum
locking properties with diverse photonic topological lattices by engineering
the rotating symmetry. The findings open up opportunities for designing robust
nanodevices with practical importance in chiral quantum optics.",2202.09007v1
2022-03-26,Spin and Contextuality in Extended de Broglie-Bohm-Bell Quantum Mechanics,"This paper introduces an extension of the de Broglie-Bohm-Bell formulation of
quantum mechanics, which includes intrinsic particle degrees of freedom, such
as spin, as elements of reality. To evade constraints from the Kochen-Specker
theorem the discrete spin values refer to a specific basis -- i.e., a single
spin vector orientation for each particle; these spin orientations are,
however, not predetermined, but dynamic and guided by the (reduced, spin-only)
wave function of the system, which is conditional on the realized location
values of the particles. In this way, the unavoidable contextuality of spin is
provided by the wave function and its realized particle configuration, whereas
spin is still expressed as a local property of the individual particles. This
formulation, which furthermore features a rigorous discrete-time stochastic
dynamics, allows for numerical simulations of particle systems with entangled
spin, such as Bohm's version of the EPR experiment.",2203.14034v1
2022-06-14,Broadband microwave detection using electron spins in a hybrid diamond-magnet sensor chip,"Quantum sensing has developed into a main branch of quantum science and
technology. It aims at measuring physical quantities with high resolution,
sensitivity, and dynamic range. Electron spins in diamond are powerful magnetic
field sensors, but their sensitivity in the microwave regime is limited to a
narrow band around their resonance frequency. Here, we realize broadband
microwave detection using spins in diamond interfaced with a thin-film magnet.
A pump field locally converts target microwave signals to the sensor-spin
frequency via the non-linear spin-wave dynamics of the magnet. Two
complementary conversion protocols enable sensing and high-fidelity spin
control over a gigahertz bandwidth, allowing characterization of the spin-wave
band at multiple gigahertz above the sensor-spin frequency. The pump-tunable,
hybrid diamond-magnet sensor chip opens the way for spin-based sensing in the
100-gigahertz regime at small magnetic bias fields.",2206.07013v1
2023-02-20,Néel-Vector Switching and THz Spin-Wave Excitation in Mn$_2$Au due to Femtosecond Spin-Transfer Torques,"Efficient and fast manipulation of antiferromagnets has to date remained a
challenging task, hindering their application in spintronic devices. For
ultrafast operation of such devices, it is highly desirable to be able to
control the antiferromagnetic order within picoseconds - a timescale that is
difficult to achieve with electrical circuits. Here, we demonstrate that bursts
of spin-polarized hot-electron currents emerging due to laser-induced ultrafast
demagnetization are able to efficiently excite spin dynamics in
antiferromagnetic Mn$_2$Au by exerting a spin-transfer torque on femtosecond
timescales. We combine quantitative superdiffusive transport and atomistic
spin-model calculations to describe a spin-valve-type trilayer consisting of
Fe$|$Cu$|$Mn$_2$Au. Our results demonstrate that femtosecond spin-transfer
torques can switch the Mn$_2$Au layer within a few picoseconds. In addition, we
find that spin waves with high frequencies up to several THz can be excited in
Mn$_2$Au.",2302.09822v1
2023-03-29,Asymptotic gravitational-wave fluxes from a spinning test body on generic orbits around a Kerr black hole,"This work provides gravitational wave energy and angular momentum asymptotic
fluxes from a spinning body moving on generic orbits in a Kerr spacetime up to
linear in spin approximation. To achieve this, we have developed a new
frequency domain Teukolsky equation solver that calculates asymptotic
amplitudes from generic orbits of spinning bodies with their spin aligned with
the total orbital angular momentum. However, the energy and angular momentum
fluxes from these orbits in the linear in spin approximation are appropriate
for adiabatic models of extreme mass ratio inspirals even for spins non-aligned
to the orbital angular momentum. To check the newly obtained fluxes, they were
compared with already known frequency domain results for equatorial orbits and
with results from a time domain Teukolsky equation solver called Teukode for
off-equatorial orbits. The spinning body framework of our work is based on the
Mathisson-Papapetrou-Dixon equations under the Tulczyjew-Dixon spin
supplementary condition.",2303.16798v1
2023-08-30,Spin Rotations in a Bose-Einstein Condensate Driven by Counterflow and Spin-independent Interactions,"We observe spin rotations caused by atomic collisions in a non-equilibrium
Bose-condensed gas of $^{87}$Rb. Reflection from a pseudomagnetic barrier
creates counterflow in which forward- and backward-propagating matter waves
have partly transverse spin directions. Even though inter-atomic interaction
strengths are state-independent, the indistinguishability of parallel spins
leads to spin dynamics. A local magnetodynamic model, which captures the
salient features of the observed spin textures, highlights an essential
connection between four-wave mixing and collisional spin rotation. The observed
phenomenon has previously been thought to exist only in nondegenerate gases;
our observations and model clarify the nature of these effective-magnetic spin
rotations.",2308.16069v1
2023-11-15,Broad-Wavevector Spin Pumping of Flat-Band Magnons,"We report the experimental observation of large spin pumping signals in
YIG/Pt system driven by broad-wavevector spin-wave spin current. 280 nm-wide
microwave inductive antennas offer broad-wavevector excitation which, in
combination with quasi-flatband of YIG, allows a large number of magnons to
participate in spin pumping at a given frequency. Through comparison with
ferromagnetic resonance spin pumping, we attribute the enhancement of the spin
current to the multichromatic magnons. The high efficiency of spin current
generation enables us to uncover nontrivial propagating properties in ultra-low
power regions. Additionally, our study achieves the spatially separated
detection of magnons, allowing the direct extraction of the decay length. The
synergistic combination of the capability of broad-wavevector excitation,
enhanced voltage signals, and nonlocal detection provides a new avenue for the
electrical exploration of spin waves dynamics.",2311.09098v1
2018-07-11,Probing the Dzyaloshinskii-Moriya interaction via the propagation of spin waves in ferromagnetic thin films,"The Dzyaloshinskii-Moriya interaction (DMI) has attracted considerable recent
attention owing to the intriguing physics behind and the fundamental role it
played in stabilizing magnetic solitons, such as magnetic skyrmions and chiral
domain walls. A number of experimental efforts have been devoted to probe the
DMI, among which the most popular method is the Brillouin light scattering
spectroscopy (BLS) to measure the frequency difference of spin waves with
opposite wave vectors $\pm\mathbf{k}$ perpendicular to the in-plane
magnetization $\mathbf{m}$. Such a technique, however, is not applicable for
the cases of $\mathbf{k}\parallel\mathbf{m}$, since the spin-wave reciprocity
is recovered then. For a narrow magnetic strip, it is also difficult to measure
the DMI strength using BLS because of the spatial resolution limit of lights.
To fill these gaps, we propose to probe the DMI via the propagation of spin
waves in ferromagnetic films. We show that the DMI can cause the
non-collinearity of the group velocities of spin waves with
$\pm\mathbf{k}\parallel\mathbf{m}$. In heterogeneous magnetic thin films with
different DMIs, negative refractions of spin waves emerge at the interface
under proper conditions. These findings enable us to quantify the DMI strength
by measuring the angle between the two spin-wave beams with
$\pm\mathbf{k}\parallel\mathbf{m}$ in homogeneous film and by measuring the
incident and negative refraction angles in heterogeneous films. For a narrow
magnetic strip, we propose a nonlocal scheme to determine the DMI strength via
nonlinear three-magnon processes. We implement theoretical calculations and
micromagnetic simulations to verify our ideas. The results presented here are
helpful for future measurement of the DMI and for designing novel spin-wave
spintronic devices.",1807.04025v2
2015-06-17,Spin Casimir Effect in Non-collinear Quantum Antiferromagnets,"The Casimir effect is a general phenomenon in physics, which arises when the
vacuum fluctuation of an arbitrary field is modified by static or slowly
varying boundary. However, its spin version is rarely addressed, mainly due to
the fact that a macroscopic boundary in quantum spin systems is hard to define.
In this article, we explore the spin Casimir effect induced by the zero-point
fluctuation of spin waves in a general non-collinear ordered quantum
antiferromagnet. This spin Casimir effect results in a spin torque between
local spins and further causes various singular and divergent results in the
framework of spin-wave theory, which invalidate the standard $1/S$ expansion
procedure. To avoid this dilemma, we develop a self-consistent spin-wave
expansion approach, which preserves the spin-wave expansion away from
singularities and divergence. A detailed spin-wave analysis of the
antiferromagnetic spin-1/2 Heisenberg model on a spatially anisotropic
triangular lattice is undertaken within our approach. Our results indicate that
the spiral order is only stable in the region $0.5<\alpha<1.2$, where $\alpha$
is the ratio of the coupling constants. In addition, the instability in the
region $1.2<\alpha<2$ is owing to the spin Casimir effect instead of the
vanishing sublattice magnetization. And this extended spiral instable region
may host some quantum disordered phases besides the quantum order by disorder
induced Neel phase. Furthermore, our method provides an efficient and
convenient tool that can estimate the correct exchange parameters and outline
the quantum phase diagrams, which can be useful for experimental fitting
processes in frustrated quantum magnets.",1506.05211v2
2001-01-24,Effects of dipolar field in the spin dynamics of a Fermi liquid,"We study spin dynamics of a normal Fermi liquid taking into account the
demagnetizing field produced by the spin system itself. Linear solutions of the
spin dynamics equations in the form of standing spin waves in a finite volume
of liquid are found. At almost all known experimental conditions the influence
of demagnetizing field can be satisfactorily described by the first order of
perturbation theory. We carried out perturbational calculations for two
geometries of experimental cell -- spherical and finite-cylindrical. We
performed also exact numerical simulations of the spin wave spectra in a
spherical cell at an arbitrary strength of the demagnetizing field.
  The obtained results are applied in particular to conditions of recent
experiment (G.Vermeulen and A.Roni, Phys. Rev. Lett. 86, 248 (2001)) related to
the problem of zero temperature transverse relaxation in a polarized Fermi
liquid. We found that not taking into account demagnetizing field leads to
negligible errors in the measured relaxation time, thus supporting the
conclusion of the absence of zero temperature spin wave damping.",0101368v3
2005-07-22,Spin waves in a one-dimensional spinor Bose gas,"We study a one-dimensional (iso)spin 1/2 Bose gas with repulsive
delta-function interaction by the Bethe Ansatz method and discuss the
excitations above the polarized ground state. In addition to phonons the system
features spin waves with a quadratic dispersion. We compute analytically and
numerically the effective mass of the spin wave and show that the spin
transport is greatly suppressed in the strong coupling regime, where the
isospin-density (or ``spin-charge'') separation is maximal. Using a
hydrodynamic approach, we study spin excitations in a harmonically trapped
system and discuss prospects for future studies of two-component ultracold
atomic gases.",0507513v1
1996-02-19,Gravitational waves from a spinning particle in circular orbits around a rotating black hole,"Using the Teukolsky and Sasaki-Nakamura formalisms for the perterbations
around a Kerr black hole, we calculate the energy flux of gravitational waves
induced by a {\it spinning} particle of mass $\mu$ and spin $S$ moving in
circular orbits near the equatorial plain of a rotating black hole of mass $M
(\gg \mu)$ and spin $Ma$. The calculations are performed by using the recently
developed post-Newtonian expansion technique of the Teukolsky equation. To
evaluate the source terms of perturbations caused by a {\it spinning} particle,
we used the equations of motion of a spinning particle derived by Papapetrou
and the energy momentum tensor of a spinning particle derived by Dixon. We
present the post-Newtonian formula of the gravitational wave luminosity up to
the order $(v/c)^5$ beyond the quadrupole formula including the linear order of
particle spin. The results obtained in this paper will be an important
guideline to the post-Newtonian calculation of the inspiral of two spinning
compact objects.",9602038v1
1993-04-28,Semiclassical analysis of two- and three-spin antiferromagnets and anyons on a sphere,"We do a semiclassical analysis for two or three spins which are coupled
antiferromagnetically to each other. The semiclassical wave functions transform
correctly under permutations of the spins if one takes into account the
Wess-Zumino term present in the path integral for spins. The Wess-Zumino term
here is a total derivative which has no effect on the energy spectrum. The
semiclassical problem is related to that of anyons moving on a sphere with the
statistics parameter $\theta$ being $2 \pi S$ for two spins and $3 \pi S$ for
three spins. Finally, we present a novel way of deriving the semiclassical wave
functions from the spin wave functions.",9304151v1
2008-01-21,First principles study on the spin transfer torques,"An efficient first principles method was developed to calculate spin transfer
torques in layered system with noncollinear magnetization. The complete
scattering wave function is determined by matching the wave function in the
scattering region with the Bloch states in the leads. The spin transfer torques
are obtained with aid of the scattering wave function. We applied our method to
the ferromagnetic spin valve and found that the material (Co, Ni and Ni80Fe20)
dependence of the spin transfer torques could be well understood by the Fermi
surface. Ni has much longer spin injection penetration length than Co.
Interfacial disorder is also considered. It is found that the spin transfer
torques could be enhanced by the interfacial disorder in some system.",0801.3135v1
2008-07-23,Time-resolved and continuous-wave optical spin pumping of semiconductor quantum wells,"Experimental and theoretical studies of all-optical spin pump and probe of
resident electrons in CdTe/(Cd,Mg)Te semiconductor quantum wells are reported.
A two-color Hanle-MOKE technique (based on continuous-wave excitation) and
time-resolved Kerr rotation in the regime of resonant spin amplification (based
on pulsed excitation) provide a complementary measure of electron spin
relaxation time. Influence of electron localization on long-lived spin
coherence is examined by means of spectral and temperature dependencies.
Various scenarios of spin polarization generation (via the trion and exciton
states) are analyzed and difference between continuous-wave and pulsed
excitations is considered. Effects related to inhomogeneous distribution of
$g$-factor and anisotropic spin relaxation time on measured quantities are
discussed.",0807.3640v1
2008-08-04,Ballistic magneto-thermal transport in a Heisenberg spin chain at low temperatures,"We study ballistic thermal transport in Heisenberg spin chain with
nearest-neighbor ferromagnetic interactions at low temperatures. Explicit
expressions for transmission coefficients are derived for thermal transport in
a periodic spin chain of arbitrary junction length by a spin-wave model. Our
analytical results agree very well with the ones from nonequilibrium Green's
function method. Our study shows that the transmission coefficient oscillates
with the frequency of thermal wave. Moreover, the thermal transmission shows
strong dependence on the intrachain coupling, the length of the spin chain, and
the external magnetic field. The results demonstrate the possibility of
manipulating spin-wave propagation and magnetothermal conductance in the
spin-chain junction by adjusting the intrachain coupling and/or the external
magnetic field.",0808.0380v2
2009-03-13,"Spin-wave velocities, density of magnetic excitations, and NMR relaxation in ferro-pnictides","We perform an analysis of the experimentally known temperature dependence of
the staggered magnetization in the antiferromagnetic phase. This analysis
allows us to put an upper limit on the unknown value of the spin wave velocity
along the stripes of equal spin direction (spin stripes). The velocity is about
ten times smaller than the velocity perpendicular to the spin stripes. The
strongly anisotropic spin-wave dispersion implies a high density of low energy
magnetic excitations. We demonstrate that this high density strongly enhances
the $^{75}$As NMR spin-lattice relaxation via the Raman scattering of magnons.
We derive the polarization dependence of this relaxation channel and find very
good agreement with experimental data. The high density of low energy magnetic
excitations deduced from our phenomenological analysis supports the scenario
that ferro-pnictides are close to a quantum phase transition.",0903.2313v2
2009-03-27,Dynamical magnetoelectric effects induced by the Dzyaloshinskii-Moriya interaction in multiferroics,"We study the dynamical interplay between ferroelectricity and magnetism in a
multiferroic with a helical magnetic order. We show that the dynamical
exchange-striction induces a biquadratic interaction between the spins and
transverse phonons resulting in quantum fluctuations of the spontaneous
ferroelectric polarization $\mathbf{P}$ in the ferroelectric phase. The
hybridization between the spin wave and the fluctuation of the electric
polarization leads to low-lying transverse phonon modes. Those are
perpendicular to $\mathbf{P}$ and to the helical spins at small wave vector but
then turn parallel to $\mathbf{P}$ at a wave vector close to the magnetic
modulation vector. For helical magnetic structure, the spin chirality which
determines the direction of $\mathbf{P}$, also possesses a long-range order.
Due to the dynamical Dzyaloshiskii-Moriya interaction, the spin-chirality is
strongly coupled to the spin fluctuation which implies an on-site inversion of
the spin-chirality in the ordered spin-1/2 system and results in a finite
scattering intensity of polarized neutrons from a cycloidal helimagnet.",0903.4751v1
2009-04-16,Antiferromagnetism in the magnetoelectric effect single crystal LiMnPO$_4$,"Elastic and inelastic neutron scattering studies reveal details of the
antiferromagnetic tansition and intriguing spin-dynamics in the
magneto-electric effect single crystal LiMnPO$_4$. The elastic scattering
studies confirm the system is antiferromagnetic (AFM) below $T_N$=33.75 K with
local magnetic moments (Mn$^{2+}$; $S = 5/2$) that are aligned along the
crystallographic a-axis. The spin-wave dispersion curves propagating along the
three principal axes, determined by inelastic scattering, are adequately
modeled in the linear spin-wave framework assuming a spin-Hamiltonian that is
parameterized by inter- and in-plane nearest- and next-nearest-neighbor
interactions, and by easy-plane anisotropy. The temperature dependence of the
spin dynamics makes this an excellent model many-body spin system to address
the question of the relationship between spin-wave excitations and the order
parameter.",0904.2580v1
2009-06-19,Overhauser's spin-density wave in exact-exchange spin density functional theory,"The spin density wave (SDW) state of the uniform electron gas is investigated
in the exact exchange approximation of noncollinear spin density functional
theory (DFT). Unlike in Hartree-Fock theory, where the uniform paramagnetic
state of the electron gas is unstable against formation of the spin density
wave for all densities, in exact-exchange spin-DFT this instability occurs only
for densities lower than a critical value. It is also shown that, although in a
suitable density range it is possible to find a non-interacting SDW ground
state Slater determinant with energy lower than the corresponding paramagnetic
state, this Slater determinant is not a self-consistent solution of the
Optimized Effective Potential (OEP) integral equations of noncollinear
spin-DFT. A selfconsistent solution of the OEP equations which gives an even
lower energy can be found using an excited-state Slater determinant where only
orbitals with single-particle energies in the lower of two bands are occupied
while orbitals in the second band remain unoccupied even if their energies are
below the Fermi energy.",0906.3721v2
2010-08-31,"Spin-flip excitations, spin waves, and magneto-excitons in graphene Landau levels at integer filling factors","We study collective electronic excitations in graphene in the integer quantum
Hall regime, concentrating mainly on excitations with spin reversal such as
spin-flip and spin-wave excitations. We show that these excitations are
correctly accounted for in the time-dependent Hartree-Fock and strong magnetic
field approximations, in contrast to spin-conserving (magneto-exciton) modes
which involve a strong Landau-level mixing at non-zero wave vectors. The
collective excitations are discussed in view of prominent theorems, such as
Kohn's and Larmor's. Whereas the latter remains valid in graphene and yields
insight into the understanding of spin-dependent modes, Kohn's theorem does not
apply to relativistic electrons in graphene. We finally calculate the exchange
correction to the chemical potential in the weak magnetic field limit.",1008.5304v2
2011-08-22,Acoustic spin pumping: Direct generation of spin currents from sound waves in Pt/Y3Fe5O12 hybrid structures,"Using a Pt/Y3Fe5O12 (YIG) hybrid structure attached to a piezoelectric
actuator, we demonstrate the generation of spin currents from sound waves. This
""acoustic spin pumping"" (ASP) is caused by the sound wave generated by the
piezoelectric actuator, which then modulates the distribution function of
magnons in the YIG layer and results in a pure-spin-current injection into the
Pt layer across the Pt/YIG interface. In the Pt layer, this injected spin
current is converted into an electric voltage due to the inverse spin-Hall
effect (ISHE). The ISHE voltage induced by the ASP is detected by measuring
voltage in the Pt layer at the piezoelectric resonance frequency of the
actuator coupled with the Pt/YIG system. The frequency-dependent measurements
enable us to separate the ASP-induced signals from extrinsic heating effects.
Our model calculation based on the linear response theory provides us with a
qualitative and quantitative understanding of the ASP in the Pt/YIG system.",1108.4238v1
2011-10-06,Spin pumping with coherent elastic waves,"We show that the resonant coupling of phonons and magnons can be exploited to
generate spin currents at room temperature. Surface acoustic wave (SAW) pulses
with a frequency of 1.55 GHz and duration of 300 ns provide coherent elastic
waves in a ferromagnetic thin film/normal metal (Co/Pt) bilayer. We use the
inverse spin Hall voltage in the Pt as a measure for the spin current and
record its evolution as a function of time and external magnetic field
magnitude and orientation. Our experiments show that a spin current is
generated in the exclusive presence of a resonant elastic excitation. This
establishes acoustic spin pumping as a resonant analogue to the spin Seebeck
effect.",1110.1187v2
2013-02-18,Engineering spin waves in a high-spin ultracold Fermi gas,"We report on the detailed study of multi-component spin-waves in an s=3/2
Fermi gas where the high spin leads to novel tensorial degrees of freedom
compared to s = 1/2 systems. The excitations of a spin-nematic state are
investigated from the linear to the nonlinear regime, where the tensorial
character is particularly pronounced. By tuning the initial state we engineer
the tensorial spin-wave character, such that the magnitude and sign of the
counterflow spin-currents are effectively controlled. A comparison of our data
with numerical and analytical results shows excellent agreement.",1302.4323v3
2013-08-26,Spin turbulence with small spin magnitude in spin-1 spinor Bose-Einstein condensates,"We theoretically and numerically study spin turbulence (ST) with small spin
magnitude in spin-1 spinor Bose-Einstein condensates by using the spin-1 spinor
Gross-Pitaevskii (GP)equations. This kind of ST is realized in two cases: (i)
with antiferromagnetic interaction and (ii) with ferromagnetic interaction
under a static magnetic field. The ST with small spin magnitude can exhibit two
characteristic power laws in the spectrum of the spin-dependent interaction
energy: -1 and -7/3 power laws in the low- and high-wave-number regions,
respectively. These power laws are derived from a Kolmogorov-type dimensional
scaling analysis for the equations of motion of the spin vector and nematic
tensor. To confirm these power laws, we perform a numerical calculation of the
spin-1 spinor GP equations in a two-dimensional uniform system. In case (i),
the -7/3 power law appears in the high-wave-number region, but the spectrum in
the low-wave-number region deviates from the -1 power law. In contrast, both -1
and -7/3 power laws are found to clearly appear in case (ii).",1308.5504v1
2015-02-11,Quantum spin Hall effect of light,"Maxwell's equations, formulated 150 years ago, ultimately describe properties
of light, from classical electromagnetism to quantum and relativistic aspects.
The latter ones result in remarkable geometric and topological phenomena
related to the spin-1 massless nature of photons. By analyzing fundamental spin
properties of Maxwell waves, we show that free-space light exhibits an
intrinsic quantum spin Hall effect, i.e., surface modes with strong
spin-momentum locking. These modes are evanescent waves that form, e.g.,
surface plasmon-polaritons at vacuum-metal interfaces. Our findings illuminate
the unusual transverse spin in evanescent waves and explain recent experiments
demonstrating the transverse spin-direction locking in the excitation of
surface optical modes. This deepens our understanding of Maxwell's theory,
reveals analogies with topological insulators for electrons, and offers
applications for robust spin-directional optical interfaces.",1502.03319v3
2015-10-21,Reconfigurable spin wave band structure of artificial square spin ice,"Artificial square spin ices are structures composed of magnetic elements
arranged on a geometrically frustrated lattice and located on the sites of a
two-dimensional square lattice, such that there are four interacting magnetic
elements at each vertex. Using a semi-analytical approach, we show that square
spin ices exhibit a rich spin wave band structure that is tunable both by
external magnetic fields and the configuration of individual elements. Internal
degrees of freedom can give rise to equilibrium states with bent magnetization
at the edges leading to characteristic excitations; in the presence of
magnetostatic interactions these form separate bands analogous to impurity
bands in semiconductors. Full-scale micromagnetic simulations corroborate our
semi-analytical approach. Our results show that artificial square spin ices can
be viewed as reconfigurable and tunable magnonic crystals that can be used as
metamaterials for spin-wave-based applications at the nanoscale.",1510.06385v2
2016-04-18,Spin-transfer torques in antiferromagnets: efficiency and quantification method,"We formulate a theory of spin-transfer torques in antiferromagnets, which
covers the small to large limits of the exchange coupling energy relative to
the kinetic energy of the inter-sublattice electron dynamics. Our theory
suggests a natural definition of the efficiency of spin-transfer torques in
antiferromagnets in terms of well-defined material parameters, revealing that
the charge current couples predominantly to the antiferromagnetic order
parameter and the sublattice-canting moment in, respectively, the limits of
large and small exchange coupling. The effects can be quantified by analyzing
the antiferromagnetic spin-wave dispersions in the presence of charge current:
in the limit of large exchange coupling the spin-wave Doppler shift always
occurs, whereas, in the opposite limit, the only spin-wave modes to react to
the charge current are ones that carry a pronounced sublattice-canting moment.
The findings offer a framework for understanding and designing spin-transfer
torques in antiferromagnets belonging to different classes of sublattice
structures such as, e.g., bipartite and layered antiferromagnets.",1604.05277v2
2017-11-27,Surprises from the spins: astrophysics and relativity with detections of spinning black-hole mergers,"Measurements of black-hole spins are of crucial importance to fulfill the
promise of gravitational-wave astronomy. On the astrophysics side, spins are
perhaps the cleanest indicator of black-hole evolutionary processes, thus
providing a preferred way to discriminate how LIGO's black holes form. On the
relativity side, spins are responsible for peculiar dynamical phenomena (from
precessional modulations in the long inspiral to gravitational-wave recoils at
merger) which encode precious information on the underlying astrophysical
processes. I present some examples to explore this deep and fascinating
interplay between spin dynamics (relativity) and environmental effects
(astrophysics). Black-hole spins indeed hide remarkable surprises on both
fronts: morphologies, resonances, constraints on supernova kicks, multiple
merger generations and more...",1711.10038v1
2017-12-22,Gravitational waves from spinning binary black holes at the leading post-Newtonian orders at all orders in spin,"We determine the binding energy, the total gravitational wave energy flux,
and the gravitational wave modes for a binary of rapidly spinning black holes,
working in linearized gravity and at leading orders in the orbital velocity,
but to all orders in the black holes' spins. Though the spins are treated
nonperturbatively, surprisingly, the binding energy and the flux are given by
simple analytical expressions which are finite (respectively third- and
fifth-order) polynomials in the spins. Our final results are restricted to the
important case of quasi-circular orbits with the black holes' spins aligned
with the orbital angular momentum.",1712.08603v2
2017-02-03,Research Note: The Expected Spins of Gravitational Wave Sources With Isolated Field Binary Progenitors,"We explore the consequences of dynamical evolution of field binaries composed
of a primary black hole (BH) and a Wolf-Rayet (WR) star in the context of
gravitational wave (GW) source progenitors. We argue, from general
considerations, that the spin of the WR-descendent BH will be maximal in a
significant number of cases due to dynamical effects. In other cases, the spin
should reflect the natal spin of the primary BH which are currently
theoretically unconstrained. We argue that the three currently published LIGO
systems (GW150914, GW151226, LVT151012) suggest that this spin is small. The
resultant effective spin distribution of gravitational wave sources should thus
be bi-model if this classic GW progenitor channel is indeed dominant. While
this is consistent with the LIGO detections thus far, it is in contrast to the
three best-measured high-mass x-ray binary (HMXB) systems. A comparison of the
spin distribution of HMXBs and GW sources should ultimately reveal whether or
not these systems arise from similar astrophysical channels.",1702.00885v1
2020-06-15,Magnetic Droplet Solitons,"Magnetic droplet solitons are dynamical magnetic textures that form due to an
attractive interaction between spin waves in thin films with perpendicular
magnetic anisotropy. Spin currents and the spin torques associated with these
currents enable their formation as they provide a means to excite
non-equilibrium spin wave populations and compensate their decay. Recent years
have seen rapid advances in experiments that realize and study magnetic
droplets. Important advances include the first direct x-ray images of droplets,
determination of their threshold and sustaining currents, measurement of their
generation and annihilation time and evidence for drift instabilities, which
can limit their lifetime in spin-transfer nanocontacts. This article reviews
these studies and contrasts these solitons to other types of spin-current
excitations such as spin-wave bullets, and static magnetic textures, including
magnetic vortices and skyrmions. Magnetic droplet solitons can also serve as
current controlled microwave frequency oscillators with potential applications
in neuromorphic chips as nonlinear oscillators with memory.",2006.08808v2
2022-03-10,Mass$\unicode{x2013}$spin Re-Parameterization for Rapid Parameter Estimation of Inspiral Gravitational-Wave Signals,"Estimating the source parameters of gravitational waves from compact binary
coalescence(CBC) is a key analysis task in gravitational-wave astronomy. To
deal with the increasing detection rate of CBC signals, optimizing the
parameter estimation analysis is crucial. The analysis typically employs a
stochastic sampling technique such as Markov Chain Monte Carlo(MCMC), where the
source parameter space is explored and regions of high Bayesian posterior
probability density are found. One of the bottlenecks slowing down the analysis
is the non-trivial correlation between masses and spins of colliding objects,
which makes the exploration of mass$\unicode{x2013}$spin space extremely
inefficient. We introduce a new set of mass$\unicode{x2013}$spin sampling
parameters which makes the posterior distribution to be simple in the new
parameter space, regardless of the true values of the parameters. The new
parameter combinations are obtained as the principal components of the Fisher
matrix for the restricted 1.5 post-Newtonian waveform. Our re-parameterization
improves the efficiency of MCMC by a factor of $\sim10$ for binary neutron star
with narrow-spin prior ($|\vec{\chi}|<0.05$) and $\sim100$ with broad-spin
prior ($|\vec{\chi}|<0.99$), under the assumption that the binary has spins
aligned with its orbital angular momentum.",2203.05216v1
2014-11-06,Ising-nematic order in the bilinear-biquadratic model for the iron pnictides,"Motivated by the recent inelastic neutron scattering (INS) measurements in
the iron pnictides which show a strong anisotropy of spin excitations in
directions perpendicular and parallel to the ordering wave-vector even above
the magnetic transition temperature $T_N$, we study the frustrated Heisenberg
model with a biquadratic spin-spin exchange interaction. Using the Dyson-Maleev
(DM) representation, which proves appropriate for all temperature regimes, we
find that the spin-spin dynamical structure factors are in excellent agreement
with experiment, exhibiting breaking of the $C_4$ symmetry even into the
paramagnetic region $T_N<T<T_{\sigma}$ which we refer to as the Ising-nematic
phase. In addition to the Heisenberg spin interaction, we include the
biquadratic coupling $K (\mathbf{S}_i\cdot \mathbf{S}_j)^2$ and study its
effect on the dynamical temperature range $T_{\sigma}-T_N$ of the Ising-nematic
phase. We find that this range reduces dramatically when even small values of
the interlayer exchange $J_c$ and biquadratic coupling $K$ are included. To
supplement our analysis, we benchmark the results obtained using the DM method
against those from different non-linear spin-wave theories, including the
recently developed generalized spin-wave theory (GSWT), and find good
qualitative agreement among the different theoretical approaches as well as
experiment for both the spin-wave dispersions and the dynamical structure
factors.",1411.1462v2
2015-08-30,Spin-transfer torque based damping control of parametrically excited spin waves in a magnetic insulator,"The damping of spin waves parametrically excited in the magnetic insulator
Yttrium Iron Garnet (YIG) is controlled by a dc current passed through an
adjacent normal-metal film. The experiment is performed on a macroscopically
sized YIG(100nm)/Pt(10nm) bilayer of 4x2 mm^2 lateral dimensions. The spin-wave
relaxation frequency is determined via the threshold of the parametric
instability measured by Brillouin light scattering (BLS) spectroscopy. The
application of a dc current to the Pt film leads to the formation of a
spin-polarized electron current normal to the film plane due to the spin Hall
effect (SHE). This spin current exerts a spin transfer torque (STT) in the YIG
film and, thus, changes the spin-wave damping. Depending on the polarity of the
applied dc current with respect to the magnetization direction, the damping can
be increased or decreased. The magnitude of its variation is proportional to
the applied current. A variation in the relaxation frequency of +/-7.5% is
achieved for an applied dc current density of 5*10^10 A/m^2.",1508.07517v1
2017-12-03,Stochastic gravitational-wave background from spin loss of black holes,"Although spinning black holes are shown to be stable in vacuum in general
relativity, there exists exotic mechanisms that can convert the spin energy of
black holes into gravitational waves. Such waves may be very weak in amplitude,
since the spin-down could take a long time, and a direct search may not be
feasible. We propose to search for the stochastic background associated with
the spin-down, and we relate the level of this background to the formation rate
of spinning black holes from the merger of binary black holes, as well as the
energy spectrum of waves emitted by the spin-down process. We argue that
current LIGO-Virgo observations are not inconsistent with the existence of a
spin-down process, as long as it is slow enough. On the other hand, the
background may still exist as long as a moderate fraction of spin energy is
emitted within Hubble time. This stochastic background could be one interesting
target of next generation GW detector network, such as LIGO Voyager, and could
be extracted from total stochastic background.",1712.00784v3
2019-09-27,Type II $t-J$ model in superconducting nickelate Nd$_{1-x}$Sr$_x$NiO$_2$,"The recent observation of superconductivity at relatively high temperatures
in hole doped NdNiO$_2$ has generated considerable interest, particularly due
to its similarity with the infinite layer cuprates. Building on the observation
that the Ni$^{2+}$ ions resulting from hole doping are commonly found in the
spin-triplet state, we introduce and study a variant of the $t-J$ model in
which the holes carry S=1. We name this new model the Type II $t-J$ model. We
find two distinct mechanisms for $d$ wave superconductivity. In both scenarios
the pairing is driven by the spin coupling $J$. However, coherence is gained in
distinct ways in these two scenarios. In the first case, the spin-one holes
condense leading to a $d$ wave superconductor along with spin-symmetry
breaking. Different orders including spin-nematic orders are possible. This
scenario is captured by a spin one slave boson theory. In the second scenario,
a coherent and symmetric $d$ wave superconductor is achieved from ""Kondo
resonance"": spin one holes contribute two electrons to form large Fermi surface
together with the spin 1/2 singly occupied sites. The large Fermi surface then
undergoes $d$ wave pairing because of spin coupling $J$, similar to heavy
fermion superconductor. We propose a three-fermion parton theory to treat these
two different scenarios in one unified framework and calculate its doping phase
diagram within a self consistent mean field approximation. Our study shows that
a combination of ""cuprate physics"" and ""heavy fermion physics"" may emerge in
the type II $t-J$ model.",1909.12865v2
2021-07-19,Reconfigurable Training and Reservoir Computing in an Artificial Spin-Vortex Ice via Spin-Wave Fingerprinting,"Strongly-interacting artificial spin systems are moving beyond mimicking
naturally-occurring materials to emerge as versatile functional platforms, from
reconfigurable magnonics to neuromorphic computing. Typically artificial spin
systems comprise nanomagnets with a single magnetisation texture: collinear
macrospins or chiral vortices. By tuning nanoarray dimensions we achieve
macrospin/vortex bistability and demonstrate a four-state metamaterial
spin-system 'Artificial Spin-Vortex Ice' (ASVI). ASVI can host Ising-like
macrospins with strong ice-like vertex interactions, and weakly-coupled
vortices with low stray dipolar-field. Vortices and macrospins exhibit
starkly-differing spin-wave spectra with analogue-style mode-amplitude control
and mode-frequency shifts of df = 3.8 GHz.
  The enhanced bi-textural microstate space gives rise to emergent physical
memory phenomena, with ratchet-like vortex training and history-dependent
nonlinear fading memory when driven through global field cycles. We employ
spin-wave microstate fingerprinting for rapid, scaleable readout of vortex and
macrospin populations and leverage this for spin-wave reservoir computation.
ASVI performs linear and non-linear mapping transformations of diverse input
signals as well as chaotic time-series forecasting. Energy costs of machine
learning are spiralling unsustainably, developing low-energy neuromorphic
computation hardware such as ASVI is crucial to achieving a zero-carbon
computational future.",2107.08941v3
2022-12-16,Spin excitations in the kagome-lattice metallic antiferromagnet Fe$_{0.89}$Co$_{0.11}$Sn,"Kagome-lattice materials have attracted tremendous interest due to the broad
prospect for seeking superconductivity, quantum spin liquid states, and
topological electronic structures. Among them, the transition-metal kagome
lattices are high-profile objects for the combination of topological
properties, rich magnetism, and multiple-orbital physics. Here we report an
inelastic neutron scattering study on the spin dynamics of a kagome-lattice
antiferromagnetic metal Fe$_{0.89}$Co$_{0.11}$Sn. Although the magnetic
excitations can be observed up to $\sim$250 meV, well-defined spin waves are
only identified below $\sim$90 meV and can be modeled using Heisenberg exchange
with ferromagnetic in-plane nearest-neighbor coupling $J_1$, in-plane
next-nearest-neighbor coupling $J_2$, and antiferromagnetic (AFM) interlayer
coupling $J_c$ under linear spin-wave theory. Above $\sim$90 meV, the spin
waves enter the itinerant Stoner continuum and become highly damped
particle-hole excitations. At the K point of the Brillouin zone, we reveal a
possible band crossing of the spin wave, which indicates a potential Dirac
magnon. Our results uncover the evolution of the spin excitations from the
planar AFM state to the axial AFM state in Fe$_{0.89}$Co$_{0.11}$Sn, solve the
magnetic Hamiltonian for both states, and confirm the significant influence of
the itinerant magnetism on the spin excitations.",2212.08590v2
2005-03-17,Transverse Spin-Orbit Force in the Spin Hall Effect in Ballistic Semiconductor Wires,"We introduce the spin and momentum dependent {\em force operator} which is
defined by the Hamiltonian of a {\em clean} semiconductor quantum wire with
homogeneous Rashba spin-orbit (SO) coupling attached to two ideal (i.e., free
of spin and charge interactions) leads. Its expectation value in the
spin-polarized electronic wave packet injected through the leads explains why
the center of the packet gets deflected in the transverse direction. Moreover,
the corresponding {\em spin density} will be dragged along the transverse
direction to generate an out-of-plane spin accumulation of opposite signs on
the lateral edges of the wire, as expected in the phenomenology of the spin
Hall effect, when spin-$\uparrow$ and spin-$\downarrow$ polarized packets
(mimicking the injection of conventional unpolarized charge current) propagate
simultaneously through the wire. We also demonstrate that spin coherence of the
injected spin-polarized wave packet will gradually diminish (thereby
diminishing the ``force'') along the SO coupled wire due to the entanglement of
spin and orbital degrees of freedom of a single electron, even in the absence
of any impurity scattering.",0503415v2
2020-11-17,Observational Constraints on Black Hole Spin,"The spin of a black hole is an important quantity to study, providing a
window into the processes by which a black hole was born and grew. Further,
spin can be a potent energy source for powering relativistic jets and energetic
particle acceleration. In this review, I describe the techniques currently used
to detect and measure the spins of black holes. It is shown that: (1) Two well
understood techniques, X-ray reflection spectroscopy and thermal continuum
fitting, can be used to measure the spins of black holes that are accreting at
moderate rates. There is a rich set of other electromagnetic techniques
allowing us to extend spin measurements to lower accretion rates. (2) Many
accreting supermassive black holes are found to be rapidly-spinning, although a
population of more slowly spinning black holes emerges at masses above
$M>3\times 10^7\,M_\odot$ as expected from recent structure formation models.
(3) Many accreting stellar-mass black holes in X-ray binary systems are rapidly
spinning and must have been born in this state. (4) The advent of gravitational
wave astronomy has enabled the detection of spin effects in merging binary
black holes. Most of the pre-merger black holes are found to be slowly
spinning, a notable exception being an object that may itself be a merger
product. (5) The stark difference in spins between the black hole X-ray binary
and the binary black hole populations shows that there is a diversity of
formation mechanisms. Given the array of new electromagnetic and gravitational
wave capabilities currently being planned, the future of black hole spin
studies is bright.",2011.08948v1
2020-07-17,A new spin on LIGO-Virgo binary black holes,"Gravitational waves from binary black holes have the potential to yield
information on both of the intrinsic parameters that characterize the compact
objects: their masses and spins. While the component masses are usually
resolvable, the component spins have proven difficult to measure. This
limitation stems in great part from our choice to inquire about the spins of
the most and least massive objects in each binary, a question that becomes
ill-defined when the masses are equal. In this paper we show that one can ask a
different question of the data: what are the spins of the objects with the
highest and lowest dimensionless spins in the binary? We show that this can
significantly improve estimates of the individual spins, especially for binary
systems with comparable masses. When applying this parameterization to the
first 13 gravitational-wave events detected by the LIGO-Virgo collaboration
(LVC), we find that the highest-spinning object is constrained to have nonzero
spin for most sources and to have significant support at the Kerr limit for
GW151226 and GW170729. A joint analysis of all the confident binary black hole
detections by the LVC finds that, unlike with the traditional parametrization,
the distribution of spin magnitude for the highest-spinning object has
negligible support at zero spin. Regardless of the parameterization used, the
configuration where all of the spins in the population are aligned with the
orbital angular momentum is excluded from the 90% credible interval for the
first ten events and from the 99% credible interval for all current confident
detections.",2007.09156v2
2022-11-11,Short wavelength electrostatic wave measurement using MMS spacecraft,"Determination of the wave mode of short-wavelength electrostatic waves along
with their generation mechanism requires reliable measurement of the wave
electric field. We investigate the reliability of the electric field
measurement for short-wavelength waves observed by MMS. We develop a method,
based on spin-plane interferometry, to reliably determine the full 3D wave
vector of the observed waves. We test the method on synthetic data and then
apply it to ion acoustic wave bursts measured in situ in the solar wind. By
studying the statistical properties of ion acoustic waves in the solar wind we
retrieve the known results that the wave propagation is predominantly
field-aligned. We also determine the wavelength of the waves. We find that the
distribution peaks at around 100 m, which when normalized to the Debye length
corresponds to scales between 10 and 20 Debye lengths.",2211.06221v1
2023-03-30,A search technique to observe precessing compact binary mergers in the advanced detector era,"Gravitational-wave signals from compact binary coalescences are most
efficiently identified through matched filter searches, which match the data
against a pre-generated bank of gravitational-wave templates. Although
different techniques for performing the matched filter, as well as generating
the template bank, exist, currently all modelled gravitational-wave searches
use templates that restrict the component spins to be aligned (or anti-aligned)
with the orbital angular momentum. This means that current searches are less
sensitive to gravitational-wave signals generated from binaries with generic
spins (precessing), suggesting that, potentially, a significant fraction of
signals may remain undetected. In this work we introduce a matched filter
search that is sensitive to signals generated from precessing binaries and can
realistically be used during a gravitational-wave observing run. We take
advantage of the fact that a gravitational-wave signal from a precessing binary
can be decomposed into a power series of five harmonics, to show that a
generic-spin template bank, which is only $\sim 3\times$ larger than existing
aligned-spin banks, is needed to increase our sensitive volume by $\sim 100\%$
for neutron star black hole binaries with total mass larger than $17.5\,
M_{\odot}$ and in-plane spins $>0.67$. In fact, our generic spin search
performs as well as existing aligned-spin searches for neutron star black hole
signals with insignificant in-plane spins, but improves sensitivity by
$\sim60\%$ on average across the full generic spin parameter space. We
anticipate that this improved technique will identify significantly more
gravitational-wave signals, and, ultimately, help shed light on the unknown
spin distribution of binaries in the universe.",2303.17364v1
1999-05-16,Experimental Generation and Observation of Intrinsic Localized Spin Wave Modes in an Antiferromagnet,"By driving with a microwave pulse the lowest frequency antiferromagnetic
resonance of the quasi 1-D biaxial antiferromagnet (C_2 H_5 NH_3)_2 CuCl_4 into
an unstable region intrinsic localized spin waves have been generated and
detected in the spin wave gap. These findings are consistent with the
prediction that nonlinearity plus lattice discreteness can lead to localized
excitations with dimensions comparable to the lattice constant.",9905025v1
1992-12-14,Spin-Wave Theory and Finite-Size Scaling for the Heisenberg Antiferromagnet,"Spin-wave perturbation theory for the Heisenberg antiferromagnet at zero
temperature is used to compute the finite-lattice corrections to the ground
state energy, the staggered magnetization and the energy gap. The dispersion
relation, the spin-wave velocity and the bulk ground state energy to order
$O(1/S^2)$ are also computed for the square lattice. The results agree very
well with the predictions of Neuberger and Ziman and Fisher.",9212020v1
1995-02-10,The influence of structure disorder on mean atomic momentum fluctuations and a spin-wave spectrum,"The relation between atomic momenta fluctuations and density fluctuations is
obtained in frames of mean-field approximation. Using two-time temperature
Green functions within Tyablikov approximation the equations for spin
excitation energy and damping are obtained. The asymptotics of energy and
damping in the long-wave limit are investigated and the anomalous behaviour of
spin-wave stiffness constant is discussed.",9502042v1
1996-07-24,Long Wavelength Anomalous Diffusion Mode in the 2D XY Dipole Magnet,"In 2D XY ferromagnet the dipole force induces a strong interaction between
spin-waves in the long-wavelength limit. The major effect of this interaction
is the transformation of a propagating spin-wave into a diffusion mode. We
study the anomalous dynamics of such diffusion modes. We find that the
Janssen-De Dominics functional, which governs this dynamics, approaches the
non-Gaussian fixed-point. A spin-wave propagates by an anomalous anisotropic
diffusion with the dispersion relation: $i\omega{\sim}k_{y}^{\Delta_y}$ and
$i\omega{\sim}k_{x}^{\Delta_x}$, where ${\Delta_y}=47/27$ and
${\Delta_x}=47/36$. The low-frequency response to the external magnetic field
is found.",9607168v1
1997-03-02,On the Self-Consistent Spin-Wave Theory of Two-Dimensional Magnets With Impurities,"The self-consistent spin-wave theory is applied to investigate the
magnetization distribution around the impurity in isotropic and easy-axis
two-dimensional ferro- and antiferromagents. The temperature dependences of
host magnetization disturbance and impurity magnetization are calculated. The
short-range order in the isotropic case is investigated. Importance of dynamic
and kinematic interactions of spin waves is demonstrated.",9703010v1
1998-12-02,Theory of Orbital Excitation and Resonant Inelastic X-ray Scattering in Manganites,"We study theoretically the collective orbital excitation named orbital wave
in the orbital ordered manganites.The dispersion relation of the orbital wave
is affected by the static spin structure through the coupling between spin and
orbital degrees of freedom. As a probe to detect the dispersion relation, we
propose two possible methods by utilizing resonant inelastic x-ray scattering.
The transition probability of the orbital wave scattering is formulated, and
the momentum and polarization dependences of the structure factor are
calculated in several types of the orbital and spin structures. The elastic
x-ray scattering in the L-edge case to observe the orbital ordering is also
discussed.",9812028v1
1999-05-24,Temperature behavior of the magnon modes of the square lattice antiferromagnet,"A spin-wave theory of short-range order in the square lattice Heisenberg
antiferromagnet is formulated. With growing temperature from T=0 a gapless mode
is shown to arise simultaneously with opening a gap in the conventional
spin-wave mode. The spectral intensity is redistributed from the latter mode to
the former. For low temperatures the theory reproduces results of the modified
spin-wave theory by M.Takahashi, J.E.Hirsch et al. and without fitting
parameters gives values of observables in good agreement with Monte Carlo
results in the temperature range 0 <= T < 0.8J where J is the exchange
constant.",9905340v1
1999-11-23,New Spin-Wave Mode in Weak Ferromagnetic Fermi Liquids,"We study a phenomenological model for weak ferromagnetic Fermi liquids and
investigate the properties of the spin waves in the model. The Landau kinetic
equation is used to derive, in addition to the known Goldstone mode, a new
spin-wave mode -- the first Silin-like ferromagnetic mode. We discuss the role
of the interaction parameter F^a_1 on the behavior of the Goldstone mode and
the first Silin-like ferromagnetic mode.",9911363v1
2000-05-29,Orbital-ordering-induced anomalous softening of the ferromagnetic spin waves in perovskite manganites,"Spin wave excitations were measured in the ferromagnetic phase of
Nd$_{1/2}$Sr$_{1/2}$MnO$_{3}$ by neutron scattering. This compound is located
in proximity to the A-type antiferromagnetic state, and it shows a clear
anisotropy and anomalous softening of the spin wave excitations. The softening
in the ferromagnetic phase is induced by the orbital ordering.",0005497v2
2001-07-10,Resonating Valence Bond Wave Functions for Strongly Frustrated Spin Systems,"The Resonating Valence Bond (RVB) theory for two-dimensional quantum
antiferromagnets is shown to be the correct paradigm for large enough ``quantum
frustration''. This scenario, proposed long time ago but never confirmed by
microscopic calculations, is very strongly supported by a new type of
variational wave function, which is extremely close to the exact ground state
of the $J_1{-}J_2$ Heisenberg model for $0.4 \lesssim J_2/J_1\lesssim 0.5$.
This wave function is proposed to represent the generic spin-half RVB ground
state in spin liquids.",0107204v1
2002-10-18,Spin-Wave Description of Haldane-gap antiferromagnets,"Modifying the conventional antiferromagnetic spin-wave theory which is
plagued by the difficulty of the zero-field sublattice magnetizations diverging
in one dimension, we describe magnetic properties of Haldane-gap
antiferromagnets. The modified spin waves, constituting a grand canonical
bosonic ensemble so as to recover the sublattice symmetry, not only depict well
the ground-state correlations but also give useful information on the
finite-temperature properties.",0210399v3
2003-03-20,About possible Phonon to Magnon alignment in 2 dimensions and theory of superconductivity in Copper-Oxide planes,"We suggest that the phonon dispersion in cuprates becomes strongly
anisotropic due to interaction with spin waves; moreover the phonon dispersion
becomes singular along $|k_x|=|k_y|$ directions. This would allow more
electrons to form Cooper pairs and increase temperature of the superconducting
transition. The interaction of phonons with spin waves is more important than
the interaction of phonons with free electrons, because spin waves do not have
the Fermi surface constrain.",0303402v5
2003-03-22,A long-wave action of spin Hamiltonians and the inverse problem of the calculus of variations,"We suggest a method of derivation of the long-wave action of the model spin
Hamiltonians using the non-linear partial differential equations of motions of
the individual spins. According to the Vainberg's theorem the set of these
equations are (formal) potential if the symmetry analysis for the Frechet
derivatives of the system is true. The case of Heisenberg (anti)ferromagnets is
considered. It is shown the functional whose stationary points are described by
the equations coincides with the long-wave action and includes the non-trivial
topological term (Berry phase).",0303479v1
2004-04-03,Electromagnetic analog of Rashba spin-orbit interaction in wave guides filled with ferrite,"We consider infinitely long electromagnetic wave guide filled with a ferrite.
The wave guide has arbitrary but constant cross-section $. We show that Maxwell
equations are equivalent to the Schr\""odinger equation for single electron in
the two-dimensional quantum dot of the form D with account of the Rashba
spin-orbit interaction. The spin-orbit constant is determining by components of
magnetic permeability of the ferrite. The upper component of electron spinor
function corresponds to the z-th component electric field, while the down
component $\chi$ related to the z-th component of magnetic field by relation
(30).",0404072v1
2004-07-29,Field-induced spin density wave in (TMTSF)$_2$NO$_3$,"Interlayer magnetoresistance of the Bechgaard salt (TMTSF)$_2$NO$_3$ is
investigated up to 50 teslas under pressures of a few kilobars. This compound,
the Fermi surface of which is quasi two-dimensional at low temperature, is a
semi metal under pressure. Nevertheless, a field-induced spin density wave is
evidenced at 8.5 kbar above $\sim$ 20 T. This state is characterized by a
drastically different spectrum of the quantum oscillations compared to the low
pressure spin density wave state.",0407764v2
2004-09-17,Solitary waves on finite-size antiferromagnetic quantum Heisenberg spin rings,"Motivated by the successful synthesis of several molecular quantum spin rings
we are investigating whether such systems can host magnetic solitary waves. The
small size of these spin systems forbids the application of a classical or
continuum limit. We therefore investigate whether the time-dependent
Schroedinger equation itself permits solitary waves. Example solutions are
obtained via complete diagonalization of the underlying Heisenberg Hamiltonian.",0409456v3
2005-03-08,The temperature dependence of interlayer exchange coupling - spin waves vs. spacer effects,"There are different mechanisms proposed to be responsible for the temperature
dependence of the interlayer exchange coupling (IEC), namely a smearing out of
the spacer or interface Fermi surface and excitations and interactions of spin
waves. We propose a possibility to separate both effects by calculating the
excitation spectrum of an extended Heisenberg model and connecting the results
with ferromagnetic resonance (FMR) experiments. To solve the Heisenberg model
we use an approximation that was shown to yield excellent results. In this
paper the main idea of this procedure is explained and a detailed investigation
of the spin wave contribution to the temperature dependence of FMR resonance
frequencies and fields is carried out.",0503178v1
2005-08-30,Current induced transverse spin-wave instability in thin ferromagnets: beyond linear stability analysis,"A sufficiently large unpolarized current can cause a spin-wave instability in
thin nanomagnets with asymmetric contacts. The dynamics beyond the instability
is understood in the perturbative regime of small spin-wave amplitudes, as well
as by numerically solving a discretized model. In the absence of an applied
magnetic field, our numerical simulations reveal a hierarchy of instabilities,
leading to chaotic magnetization dynamics for the largest current densities we
consider.",0508732v1
2005-11-11,Magnonics: Experiment to Prove the Concept,"An experimental scheme for studying spin wave propagation across thin film
samples is proposed. An experiment upon a periodically layered nanowire is
numerically simulated, while the sample might equally well be a continuous film
or an array of elements (e.g. nanowires) that either have uniform composition
or are periodically layered as in a magnonic crystal. The experiments could be
extended to study domain wall induced spin wave phase shifts, and used for
creation of the spin wave magnetic logic devices.",0511290v1
2005-11-11,Spin wave spectrum of a magnonic crystal with an isolated defect,"Real magnonic crystals - periodic magnetic media for spin wave (magnon)
propagation - may contain some defects. We report theoretical spin wave spectra
of a one dimensional magnonic crystal with an isolated defect. The latter is
modeled by insertion of an additional layer with thickness and magnetic
anisotropy values different from those of the magnonic crystal constituent
layers. The defect layer leads to appearance of several localized defect modes
within the magnonic band gaps. The frequency and the number of the defect modes
may be controlled by varying parameters of the constituent layers of the
magnonic crystal.",0511295v1
2006-11-30,Theory of Brillouin Light Scattering from Ferromagnetic Nanospheres,"We develop the theory of Brillouin light scattering (BLS) from spin wave
modes in ferromagnetic nanospheres, within a framework that incorporates the
spatial variation of the optical fields within the sphere. Our recent theory of
exchange dipole spin wave modes of the sphere provides us with eigenvectors.
When properly normalized, these eigenvectors allow calculation of the absolute
cross section of various modes which contribute to BLS spectrum. We then
present explicit calculation of the BLS spectrum associated with the first few
dipole/exchange spin wave modes with emphasis on their relative intensity.",0611785v1
1993-05-18,Spin Structure of the Pion in a Light-Cone Representation,"The spin structure of the pion is discussed by transforming the wave function
for the pion in the naive quark model into a light-cone representation. It is
shown that there are higher helicity ($\lambda_{1}+\lambda_{2}=\pm1$) states in
the full light-cone wave function for the pion besides the ordinary helicity
($\lambda_{1}+\lambda_{2}=0$) component wave functions as a consequence from
the Melosh rotation relating spin states in light-front dynamics and those in
instant-form dynamics. Some low energy properties of the pion, such as the
electromagnetic form factor, the charged mean square radius, and the weak decay
constant, could be interrelated in this representation with reasonable
parameters.",9305283v1
2004-12-18,Relativistic wave equations for interacting massive particles with arbitrary half-intreger spins,"New formulation of relativistic wave equations (RWE) for massive particles
with arbitrary half-integer spins s interacting with external electromagnetic
fields are proposed. They are based on wave functions which are irreducible
tensors of rank $n ($n=s-\frac12$) antisymmetric w.r.t. n pairs of indices,
whose components are bispinors. The form of RWE is straightforward and free of
inconsistencies associated with the other approaches to equations describing
interacting higher spin particles.",0412213v1
2006-05-16,Detection of Gravitational Wave - An Application of Relativistic Quantum Information Theory,"We show that a passing gravitational wave may influence the spin entropy and
spin negativity of a system of $N$ massive spin-1/2 particles, in a way that is
characteristic of the radiation. We establish the specific conditions under
which this effect may be nonzero. The change in spin entropy and negativity,
however, is extremely small. Here, we propose and show that this effect may be
amplified through entanglement swapping. Relativistic quantum information
theory may have a contribution towards the detection of gravitational wave.",0605135v1
2007-11-05,Projected p-wave superconducting wave-functions for topological orders,"In this paper we develop a sysmatical theory for topological orders by the
projected p-wave superconducting (SC) wave-functions and unify the different
topological orders for spin models into the fermionic picture. We found that
the energy for the fermions at k=(0,0), (0, pi), (pi, 0), (pi, pi) acts as a
topological invariable to characterize 16 universal classes of different
topological orders for the spin models with translation invariance. Based on
the projected p-wave SC wave-functions the topological properties for the known
topological orders in the exact solved spin models are obtained. Finally new
types of topological orders are predicted.",0711.0571v1
2007-12-07,The Hartree-Fock ground state of the three-dimensional electron gas,"In 1962, Overhauser showed that within Hartree-Fock (HF) the electron gas is
unstable to a spin density wave (SDW) instability. Determining the true HF
ground state has remained a challenge. Using numerical calculations for finite
systems and analytic techniques, we study the HF ground state of the 3D
electron gas. At high density, we find broken spin symmetry states with a
nearly constant charge density. Unlike previously discussed spin wave states,
the observed wave vector of the SDW is smaller than $2 k_F$. The
broken-symmetry state originates from pairing instabilities at the Fermi
surface, a model for which is proposed.",0712.1194v1
2008-02-13,FMR induced Josephson Current in a Superconductor/Ferromagnet/Superconductor Junction,"We propose the phase dynamics induced by spin waves in a
superconductor/ferromagnet/superconductor (SC/FM/SC) Josephson junction. The
resistively shunted junction (RSJ) model, which describes the dynamics of
superconducting phase difference, is extended to include the spin wave
excitation by ferromagnetic resonance (FMR) using the gauge invariant phase
difference between two s-wave superconductors. The current-voltage
characteristics show step structures when the magnetization in FM is driven by
tuning the microwave frequency to FMR in the SC/FM/SC junction. The result
presents a new route to observe the spin wave excitation using the Josephson
effect.",0802.1755v2
2008-02-21,Coherent Control of spin-orbit precession with shaped laser pulses,"Spin precession in Rubidium atoms is investigated through a pump-probe
technique. The excited wave packet corresponds to a precession of spin and
orbital angular momentum around the total angular momentum. We show that using
shaped laser pulses allows us to control this dynamics. With a Fourier
transform limited pulse, the wave packet is initially prepared in the bright
state (coupled to the initial state) whereas a pulse presenting a $\pi $ step
in the spectral phase prepares the wave packet in the dark state (uncoupled to
the initial state).",0802.2986v1
2008-04-14,Dissipation characteristics of quantized spin waves in nano-scaled magnetic ring structures,"The spatial profiles and the dissipation characteristics of spin-wave
quasi-eigenmodes are investigated in small magnetic Ni$_{81}$Fe$_{19}$ ring
structures using Brillouin light scattering microscopy. It is found, that the
decay constant of a mode decreases with increasing mode frequency. Indications
for a contribution of three-magnon processes to the dissipation of higher-order
spin-wave quasi-eigenmodes are found.",0804.2200v1
2008-05-27,Scattering of backward spin waves in a one-dimensional magnonic crystal,"Scattering of backward volume magnetostatic spin waves from a one-dimensional
magnonic crystal, realized by a grating of shallow grooves etched into the
surface of an yttrium-iron garnet film, was experimentally studied. Rejection
frequency bands were clearly observed. The rejection efficiency and the
frequency width of the rejection bands increase with increasing groove depth. A
theoretical model based on the analogy of a spin-wave film-waveguide with a
microwave transmission line was used to interpret the obtained experimental
results.",0805.4142v1
2008-10-22,Probing of a parametrically pumped magnon gas with a non-resonant packet of traveling spin waves,"The magnon gas created by spatially localized longitudinal parametric pumping
in an yttrium-iron-garnet film is probed by a traveling packet of spin waves
non-resonant with the pumping field. The analysis of the influence of the
magnon gas on the amplitude and phase of the propagating spin waves allows to
determine characteristic properties of the parametrically pumped magnon gas. A
simple theoretical model is proposed from which the magnon density in the
pumping region is calculated.",0810.4033v1
2008-11-21,Frequency-dependent reflection of spin waves from a magnetic inhomogeneity induced by a surface DC-current,"The reflectivity of a highly localized magnetic inhomogeneity is
experimentally studied. The inhomogeneity is created by a dc-current carrying
wire placed on the surface of a ferrite film. The reflection of propagating
dipole-dominated spin-wave pulses is found to be strongly dependent on the
spin-wave frequency if the current locally increases the magnetic field. In the
opposite case the frequency dependence is negligible.",0811.3491v1
2009-01-13,Refractive index and Snell's Law for Dipolar-Exchange Spin-Waves in a Confined Planar Structure,"We derived the analytical forms of refractive index and Snell law for
dipolar-exchange spin waves of reflection and refraction at a magnetically
heterogeneous interface in a geometrically confined planer structure composed
of different magnetic thin films from a microscopic scattering approach. A
novel behavior, the optical total reflection, was demonstrated for spin waves
with a specific interface between Yttrium iron garnet (Y3Fe5O12) and Permalloy
(Ni80Fe20), by analytical and micromagnetic numerical calculations.",0901.1700v2
2009-12-25,A linearized spin-wave theory for thermodynamics of quantum Heisenberg antiferromagnet on a square lattice,"The thermodynamics of the quantum Heisenberg antiferromagnet on a square
lattice is revisited through a linearized spin-wave theory which is well
defined at any finite temperature. We re-examine in details the temperature
dependence of the free energy, the internal energy, the entropy and the
specific heat. Most conclusions of the thermodynamics in previous studies can
be reproduced in our linearized spin-wave theory. Specially, our calculation at
low temperature $T<J$ agrees quantitatively with the numerical Quantum Monte
Carlo simulation and high temperature series expansions.",0912.4965v1
2010-07-25,Optical excitation of nonlinear spin waves,"We demonstrate a technique for exciting spin waves in an ultracold gas of
Rb-87 atoms based on tunable AC Stark potentials. This technique allows us to
excite normal modes of spin waves with arbitrary amplitudes in the trapped gas,
including dipole, quadrupole, octupole, and hexadecapole modes. These modes
exhibit strong nonlinearities, which manifest as amplitude dependence of the
excitation frequencies and departure from sinusoidal behavior. Our results are
in good agreement with a full treatment of a quantum Boltzmann transport
equation.",1007.4339v2
2011-04-19,Chaotic Spin-Wave Solitons in Magnetic Film Feedback Rings,"Chaotic spin-wave solitons in magnetic film active feedback rings were
observed for the first time. At some ring gain level, one observes the
self-generation of a single spin-wave soliton pulse in the ring. When the pulse
circulates in the ring, its amplitude varies chaotically with time. Numerical
simulations based on a gain-loss nonlinear Schr\""odinger equation reproduce the
observed responses.",1104.3871v1
2011-08-22,Spin Density Wave in Insulating Ferromagnetic Frustrated Chain LiCuVO$_4$,"We study field induced quantum phase in weakly-coupled ferromagnetic
frustrated chain LiCuVO$_4$ by neutron diffraction technique. A new
incommensurate magnetic peak is observed at $H \ge 8.5$ T. The field dependent
propagation vector is identified with the spin density wave correlation in the
theoretically predicted magnetic quadrupole order. Quantum fluctuation,
geometrical frustration, and interchain interaction induce the exotic spin
density wave long-range order in the insulating magnet.",1108.4255v1
2011-09-09,Theoretical Investigation of the Magnetic Order in FeAs,"The magnetic structure of the iron monoarsenide FeAs is studied using
first-principles calculations. We consider the collinear and non-collinear
(spin-spiral wave) magnetic ordering and magnetic anisotropy. It is
analitically shown that a magnetic triaxial anisotropy results in a sum of two
spin-spiral waves with opposite directions of wave vectors and different spin
amplitudes, so that the magnetic moments in two perpendicular directions do not
equal each other.",1109.1924v1
2011-12-07,"Retrieval of multiple spin waves from a weakly excited, metastable atomic ensemble","The emission of light from a multiply excited atomic ensemble is examined and
it is shown how symmetric (spin-wave) and non-symmetric states of excitation
radiate into spatially separate field modes. This observation has potential
application to single photon generation and spin wave entanglement, since in
the presence of atomic interactions it can result in isolated single photon
emission into a phase-matched field mode.",1112.1735v2
2012-01-31,Generation of Multipartite Continuous-variable Entanglements via Atomic Spin Wave,"We present a proof-of-principle way to generate nondegenerate multipartite
continuous-variable entanglements via atomic spin wave induced by the strong
coupling and probe fields in the Lambda-type electromagnetically induced
transparency configuration in an atomic ensemble. Quantum
correlated/anti-correlated and entangled Stokes and anti-Stokes fields,
simultaneously produced through scattering the applied laser fields off the
atomic spin wave, can be achieved. This method can, in principle, be extended
to flexibly and conveniently create multicolor multipartite entangled
narrow-band fields to any desired order with long correlation time, which may
find promising applications in quantum information processing and quantum
networks.",1201.6577v1
2012-05-11,Magnetic penetration depth in the presence of a spin-density wave in multiband superconductors at zero temperature,"We present a theoretical description of the London penetration depth of a
multi-band superconductor in the case when both superconducting and
spin-density wave orders coexist. We focus on clean systems and zero
temperature to emphasize the effect of the two competing orders. Our
calculation shows that the supefluid density closely follows the evolution of
the superconducting order parameter as doping is increased, saturating to a BCS
value in the pure superconducting state. Furthermore, we predict a strong
anisotropic in-pane penetration depth induced by the spin-density wave order.",1205.2564v1
2012-05-25,Spin wave amplification driven by heat flow: the role of damping and exchange interaction,"In this article we report on micromagnetic simulations performed on a
permalloy nanostructure in presence of a uniform thermal gradient. Our
numerical simulations show that heat flow is an effective mean to compensate
the damping, and that the gradients at which spin-wave amplification is
observed are experimentally accessible. In particular, we have studied the role
of the Gilbert damping parameter on spin-wave amplification.",1205.5650v2
2013-11-12,Nonreciprocity engineering in magnetostatic spin waves,"Magnetostatic surface spin waves (MSSW) excited from a coplanar waveguide
antenna travel in different directions with different amplitudes. This effect,
called nonreciprocity of MSSW, has been investigated by micromagnetic
simulations. The ratio of amplitude of two counter propagating spin waves, the
nonreciprocity parameter {\kappa}, is obtained for different ferromagnetic
materials, such as NiFe (Py), CoFeAl, yttrium iron garnet (YIG), and GaMnAs. A
device schematic has been proposed in which {\kappa} can be tuned to a large
value by varying simple geometrical parameters of the device.",1311.2686v1
2014-11-10,Magnon spectrum in ferromagnets with a skyrmion,"The analysis of the spin wave excitations in two-dimensional isotropic
Heisenberg ferromagnet is performed with a single skyrmion in the ground state.
We employ the ideas of semiclassical quantization method, duly modified for the
use of the lattice model and Maleyev-Dyson boson representation of spin
operators. The resulting Schr\""odinger equation for magnons describes the
dispersion and wave functions of spin-wave excitations with strictly
non-negative spectrum. In contrast to usual ferromagnet, we demonstrate the
existence of three zero modes, corresponding to conformal symmetries
spontaneously violated by the skyrmion configuration.",1411.2452v2
2014-12-19,Spin waves in one-dimensional bi-component quasicrystals,"We studied finite Fibonacci sequence of Co and Py stripes aligned
side-by-side and in direct contact with each other. Calculations based on
continuous model including exchange and dipole interactions were performed for
structures feasible for fabrication and characterization of main properties of
magnonic quasicrystals. We have shown the fractal structure of the magnonic
spectrum with a number of magnonics gaps of different width. Also localization
of spin waves in quasicrystals and existence of surface spin waves in finite
quaiscrystal structure is demonstrated.",1412.6301v4
2015-01-06,Spin Wave Diffraction Control and Read-out with a Quantum Memory for Light,"A scheme for control and read-out of diffracted spins waves to propagating
light fields is presented. Diffraction is obtained via sinusoidally varying
lights shifts and ideal one-to-one mapping to light is realized using a
gradient echo quantum memory. We also show that dynamical control of the
diffracted spin waves spatial orders can be implemented to realize a quantum
pulse sequencer for temporal modes that have high time-bandwidth products. Full
numerical solutions suggest that both co-propagating and couterpropagating
light shift geometries can be used, making the proposal applicable to hot and
cold atomic vapours as well as solid state systems with two-level atoms.",1501.01194v1
2015-03-16,Detection of spin waves in permalloy using planar Hall effect,"Rectification of microwave oscillations of magnetization in a permalloy film
is realized using planar Hall effect. Two different rectified signals are
obtained: a signal from the linearly excited uniform magnetization precession
at the frequency of the external pumping and a signal from the pairs of
contra-propagating short-wavelength spin waves parametrically generated at a
half of the pumping frequency. The second, most unusual, rectified signal is
caused by the uniform component of the dynamic magnetization created due to the
interference of the phase correlated pairs of parametric spin waves.",1503.04638v1
2015-11-30,Study of the Spin-weighted Spheroidal Wave Equation in the Case of s=3/2,"In this paper, we use the means of super-symmetric quantum mechanics to study
of the Spin-weighted Spheroidal Wave in the case of s=3/2. We obtain some
interesting results: the first-five terms of the super-potential, the general
form of the super-potential. The ground eigen-function and eigenvalue of the
equation are also given. According these results, we make use of the shape
invariance property to compute the exited eigenvalues and eigen-functions.
These results help us to understand the Spin-weighted Spheroidal Wave and show
that it is integral.",1512.00514v1
2016-01-04,Direct and inverse cascades of spin-wave turbulence in spin-1 ferromagnetic spinor Bose-Einstein condensates,"We theoretically and numerically study spin-wave turbulence in spin-1
ferromagnetic spinor Bose-Einstein condensates, finding direct and inverse
cascades with power-law behavior. To derive these power exponents analytically,
the conventional weak wave turbulence theory is applied to the spin-1 spinor
Gross-Pitaevskii equation. Thus, we obtain the $-7/3$ and $-5/3$ power laws in
the transverse spin correlation function for the direct and inverse cascades,
respectively. To confirm these power laws, numerical calculations are performed
that obtain results consistent with these power laws.",1601.00446v2
2016-04-25,Bias-free spin-wave phase shifter for magnonic logic,"A design of a magnonic phase shifter operating without an external bias
magnetic field is proposed. The phase shifter uses a localized collective spin
wave mode propagating along a domain wall ""waveguide"" in a dipolarly-coupled
magnetic dot array existing in a chessboard antiferromagnetic (CAFM) ground
state. It is demonstrated numerically that remagnetization of a single magnetic
dot adjacent to the domain wall waveguide introduces a controllable phase shift
in the propagating spin wave mode without significant change of the mode
amplitude. It is also demonstrated that a logic XOR gate can be realized in the
same system.",1604.07337v1
2016-06-27,Spin wave power flow and caustics in ultrathin ferromagnets with the Dzyaloshinskii-Moriya interaction,"The Dzyaloshinskii-Moriya interaction in ultrathin ferromagnets can result in
nonreciprocal propagation of spin waves. We examine theoretically how spin wave
power flow is influenced by this interaction. We show that the combination of
the dipole-dipole and Dzyaloshinskii-Moriya interactions can result in
unidirectional caustic beams in the Damon-Eshbach geometry. Morever,
self-generated interface patterns can also be induced from a point-source
excitation.",1606.08159v2
2016-10-19,Resonant Magnetization Switching Conditions of an Exchange-coupled Bilayer under Spin Wave Excitation,"We systematically investigated the spin wave-assisted magnetization switching
(SWAS) of a L10-FePt / Ni81Fe19 (Permalloy; Py) exchange-coupled bilayer using
a pulse-like rf field (hrf) and mapped the switching events in the magnetic
field (H) - hrf frequency (f) plane to reveal the switching conditions. The
switching occurred only in a limited region following the dispersion
relationship of the perpendicular standing spin wave (PSSW) modes in Py. The
results indicate that SWAS is a resonant magnetization switching process, which
is different from the conventional microwave assisted switching, and has the
potential to be applied to selective switching for multilevel recording media.",1610.05864v1
2018-06-04,An analog magnon adder for all-magnonic neurons,"Spin-waves are excellent data carriers with a perspective use in neuronal
networks: Their lifetime gives the spin-wave system an intrinsic memory, they
feature strong nonlinearity, and they can be guided and steered through
extended magnonic networks. In this work, we present a magnon adder that
integrates over incoming spin-wave pulses in an analog fashion. Such an adder
is a linear prequel to a magnonic neuron, which would integrate over the
incoming pulses until a certain nonlinearity is reached. In this work, the
adder is realized by a resonator in combination with a parametric amplifier
which is just compensating the resonator losses.",1806.01389v1
2018-06-20,Influence of quadratic Zeeman effect on spin waves in dipolar lattices,"A lattice of particles with dipolar magnetic moments is considered under the
presence of quadratic Zeeman effect. Two types of this effect are taken into
account, the effect due to an external nonresonant magnetic field and the
effect caused by an alternating quasiresonance electromagnetic field. The
presence of the alternating-field quadratic Zeeman effect makes it possible to
efficiently vary the sample characteristics. The main attention is payed to the
study of spin waves whose properties depend on the quadratic Zeeman effect. By
varying the quadratic Zeeman-effect parameter it is possible to either suppress
or stabilize spin waves.",1806.07607v1
2012-09-06,Excitation modes of vortices in sub-micron magnetic disks,"Classical and quantum theory of spin waves in the vortex state of a
mesoscopic sub-micron magnetic disk has been developed with account of the
finite mass density of the vortex. Oscillations of the vortex core resemble
oscillations of a charged string in a potential well in the presence of the
magnetic field. Conventional gyroscopic frequency appears as a gap in the
spectrum of spin waves of the vortex. The mass of the vortex has been computed
that agrees with experimental findings. Finite vortex mass generates a
high-frequency branch of spin waves. Effects of the external magnetic field and
dissipation have been addressed.",1209.1375v1
2019-06-24,Graded index lenses for spin wave steering,"We use micromagnetic modelling to demonstrate the operation of graded index
lenses designed to steer forward-volume magnetostatic spin waves by 90 and 180
degrees. The graded index profiles require the refractive index to diverge in
the lens center, which, for spin waves, can be achieved by modulating the
saturation magnetization or external magnetic field in a ferromagnetic film by
a small amount. We also show how the 90$^\circ$ lens may be used as a beam
divider. Finally, we analyse the robustness of the lenses to deviations from
their ideal profiles.",1906.09985v1
2018-04-27,Angular Dependent Magnetization Dynamics with Mirror-symmetric Excitations in Artificial Quasicrystalline Nanomagnet Lattices,"We report angle-dependent spin-wave spectroscopy on aperiodic
quasicrystalline magnetic lattices, i.e., Ammann, Penrose P2 and P3 lattices
made of large arrays of interconnected Ni$_{80}$Fe$_{20}$ nanobars. Spin-wave
spectra obtained in the nearly saturated state contain distinct sets of
resonances with characteristic angular dependencies for applied in-plane
magnetic fields. Micromagnetic simulations allow us to attribute detected
resonances to mode profiles with specific mirror symmetries. Spectra in the
reversal regime show systematic emergence and disappearance of spin wave modes
indicating reprogrammable magnonic characteristics.",1804.10630v1
2019-03-22,Spin-wave coupling to electromagnetic cavity fields in dysposium ferrite,"Coupling of spin-waves with electromagnetic cavity field is demonstrated in
an antiferromagnet, dysprosium ferrite (DyFeO3). By measuring transmission at
0.2-0.35 THz and sweeping sample temperature, magnon-photon coupling signatures
were found at crossings of spin-wave resonances with Fabry-Perot cavity modes
formed in samples. The obtained spectra are explained in terms of classical
electrodynamics and a microscopic model.",1903.09590v2
2021-02-23,Fast acquisition of spin-wave dispersion by compressed sensing,"For the realization of magnonic devices, spin-wave dispersions need to be
identified. Recently, the time-resolved pump-probe imaging method combined with
the Fourier transform was demonstrated for obtaining the dispersions in the
lower-wavenumber regime. However, the measurement takes a long time when the
sampling rate is sufficiently high. Here, we demonstrated the fast acquisition
of spin-wave dispersions by using the compressed sensing technique. Further, we
quantitatively evaluated the consistency of the results. Our results can be
applied to other various pump-probe measurements, such as observations based on
the electro-optical effects.",2102.11626v1
2021-04-19,A Thesaurus for Common Priors in Gravitational-Wave Astronomy,"In gravitational-wave data analysis, we regularly work with a host of
non-trivial prior probabilities on compact binary masses, redshifts, and spins.
We must regularly manipulate these priors, computing the implied priors on a
transformed basis of parameters or reweighting posterior samples from one prior
to another. Here, I detail some common manipulations, presenting a table of
Jacobians with which to transform priors between mass parametrizations,
describing the conversion between source- and detector-frame priors, and
deriving analytic expressions for priors on the ""effective spin"" parameters
regularly invoked in gravitational-wave astronomy.",2104.09508v1
2019-04-19,How does the photon's spin affect Gravitational Wave measurements?,"We study the effect of the polarization of light beams on the time delay
measured in Gravitational Wave experiments. To this end, we consider the
Mathisson-Papapetrou-Dixon equations in a gravitational wave background, with
two of the possible spin supplementary conditions: by Frenkel-Pirani, or by
Tulczyjew. In the first case, photons follow a null geodesic and thus no spin
effect is present. The second case shows a deviation of the photons from the
null geodesic, resulting in a tiny effect on the measured time delay of photons
depending on their polarization state.",1904.09260v2
2020-05-12,Analysis in k-space of Magnetization Dynamics Driven by Strong Terahertz Fields,"Demagnetization in a thin film due to a terahertz pulse of magnetic field is
investigated. Linearized LLG equation in the Fourier space to describe the
magnetization dynamics is derived, and spin waves time evolution is studied.
Finally, the demagnetization due to spin waves dynamics and recent experimental
observations on similar magnetic system are compared. As a result of it, the
marginal role of spin waves dynamics in loss of magnetization is established.",2005.05742v1
2020-05-26,Spoken digit classification using a spin-wave delay-line active-ring reservoir computing,"As a test of general applicability, we use the recently proposed spin-wave
delay line active-ring reservoir computer to perform the spoken digit
recognition task. On this, classification accuracies of up to 93% are achieved.
The tested device prototype employs improved spin wave transducers (antennas).
Therefore, in addition, we also let the computer complete the short-term memory
(STM) task and the parity check (PC) tasks, because the fading memory and
nonlinearity are essential to reservoir computing performance. The resulting
STM and PC capacities reach maximum values of 4.77 and 1.47 respectively.",2005.12557v1
2020-07-15,Spin wave theory of one-dimensional generalized Kitaev model,"In this work, we perform a combination of classical and spin wave analysis on
the one-dimensional spin-$S$ Kitaev-Heisenberg-Gamma model in the region of an
antiferromagnetic Kitaev coupling. Four phases are found, including a N\'eel
ordered phase, a phase with $O_h\rightarrow D_3$ symmetry breaking, and
""$D_3$-breaking I, II"" phases which both break $D_3$ symmetries albeit in
different ways, where $O_h$ is the full octahedral group and $D_3$ is the
dihedral group of order six. The lowest-lying spin wave mass is calculated
perturbatively in the vicinity of the hidden SU(2) symmetric ferromagnetic
point.",2007.07509v1
2011-11-14,Importance of including small body spin effects in the modelling of intermediate mass-ratio inspirals. II Accurate parameter extraction of strong sources using higher-order spin effects,"We improve the numerical kludge waveform model introduced in [1] in two ways.
We extend the equations of motion for spinning black hole binaries derived by
Saijo et al. [2] using spin-orbit and spin-spin couplings taken from
perturbative and post-Newtonian (PN) calculations at the highest order
available. We also include first-order conservative self-force corrections for
spin-orbit and spin-spin couplings, which are derived by comparison to PN
results. We generate the inspiral evolution using fluxes that include the most
recent calculations of small body spin corrections, spin-spin and spin-orbit
couplings and higher-order fits to solutions of the Teukolsky equation. Using a
simplified version of this model in [1], we found that small body spin effects
could be measured through gravitational wave observations from
intermediate-mass ratio inspirals (IMRIs) with mass ratio eta ~ 0.001, when
both binary components are rapidly rotating. In this paper we study in detail
how the spin of the small/big body affects parameter measurement using a
variety of mass and spin combinations for typical IMRIs sources. We find that
for IMRI events of a moderately rotating intermediate mass black hole (IMBH) of
ten thousand solar masses, and a rapidly rotating central supermassive black
hole (SMBH) of one million solar masses, gravitational wave observations made
with LISA at a fixed signal-to-noise ratio (SNR) of 1000 will be able to
determine the inspiralling IMBH mass, the central SMBH mass, the SMBH spin
magnitude, and the IMBH spin magnitude to within fractional errors of ~0.001,
0.001, 0.0001, and 9%, respectively. LISA can also determine the location of
the source in the sky and the SMBH spin orientation to within ~0.0001
steradians. We show that by including conservative corrections up to 2.5PN
order, systematic errors no longer dominate over statistical errors for IMRIs
with typical SNR ~1000.",1111.3243v3
2014-04-18,"Hydrodynamic and kinetic models for spin-1/2 electron-positron quantum plasmas: Annihilation interaction, helicity conservation, and wave dispersion in magnetized plasmas","We discuss complete theory of spin-1/2 electron-positron quantum plasmas,
when electrons and positrons move with velocities mach smaller than the speed
of light. We derive a set of two fluid quantum hydrodynamic equations
consisting of the continuity, Euler, spin (magnetic moment) evolution equations
for each species. We explicitly include the Coulomb, spin-spin, Darwin and
annihilation interactions. The annihilation interaction is the main topic of
the paper. We consider contribution of the annihilation interaction in the
quantum hydrodynamic equations and in spectrum of waves in magnetized
electron-positron plasmas. We consider propagation of waves parallel and
perpendicular to an external magnetic field. We also consider oblique
propagation of longitudinal waves. We derive set of quantum kinetic equations
for electron-positron plasmas with the Darwin and annihilation interactions. We
apply the kinetic theory for the linear wave behavior in absence of external
fields. We calculate contribution of the Darwin and annihilation interactions
in the Landau damping of the Langmuir waves. We should mention that the
annihilation interaction does not change number of particles in the system. It
does not related to annihilation itself, but it exists as a result of
interaction of an electron-positron pair via conversion of the pair into
virtual photon. A pair of the non-linear Schrodinger equations for
electron-positron plasmas including the Darwin and annihilation interactions.
Existence of conserving helicity in electron-positron quantum plasmas of
spinning particles with the Darwin and annihilation interactions is
demonstrated. We show that annihilation interaction plays an important role in
quantum electron-positron plasmas giving contribution of the same magnitude as
the spin-spin interaction.",1404.4899v1
2014-11-19,Variational Monte Carlo Method in the Presence of Spin-Orbit Interaction and Its Application to the Kitaev and Kitaev-Heisenberg Model,"We propose an accurate variational Monte Carlo method applicable in the
presence of the strong spin-orbit interaction. Our variational wave functions
consist of generalized Pfaffian-Slater wave functions that involve mixtures of
singlet and triplet Cooper pairs, Jastrow-Gutzwiller-type pro- jections, and
quantum number projections. The generalized wave functions allow any symmetry
breaking states, ranging from magnetic and/or charge ordered states to
superconducting states and their fluctuations, on equal footing without any ad
hoc ansatz for variational wave functions. We de- tail our optimization scheme
for the generalized Pfaffian-Slater wave functions with complex-number
variational parameters. Generalized quantum number projections are also
introduced, which im- poses the conservation of not only spin and momentum
quantum numbers but also Wilson loops. As a demonstration of the capability of
the present variational Monte Carlo method, the accuracy and efficiency of the
present method is tested for the Kitaev and Kitaev-Heisenberg models. The
Kitaev model serves as a critical benchmark of the present method: The exact
ground state of the model is a typical gapless quantum spin liquid far beyond
the applicability range of simple mean-field wave functions. The newly
introduced quantum number projections precisely reproduce the ground state
degeneracy of the Kitaev spin liquids, in addition to their ground state
energy. Our framework offers accurate solutions for the systems where strong
electron correlation and spin-orbit interaction coexist.",1411.5198v2
2018-06-21,"Flat Bands, Indirect Gaps, and Unconventional Spin-Wave Behavior Induced by a Periodic Dzyaloshinskii-Moriya Interaction","Periodically patterned metamaterials are known for exhibiting wave properties
similar to the ones observed in electronic band structures in crystal lattices.
In particular, periodic ferromagnetic materials are characterized by the
presence of bands and bandgaps in their spin-wave spectrum at tunable GHz
frequencies. Recently, the fabrication of magnets hosting Dzyaloshinskii-Moriya
interactions has been pursued with high interest since properties such as the
stabilization of chiral spin textures and nonreciprocal spin-wave propagation
emerge from this antisymmetric exchange coupling. In this context, to further
engineer the magnon band structure, we propose the implementation of magnonic
crystals with periodic Dzyaloshinskii-Moriya interactions, which can be
obtained, for instance, via patterning of periodic arrays of heavy-metals wires
on top of an ultrathin magnetic film. We demonstrate through theoretical
calculations and micromagnetic simulations that such systems show an unusual
evolution of the standing spin waves around the gaps in areas of the film that
are in contact with the heavy-metal wires. We also predict the emergence of
indirect gaps and flat bands and, effects that depend on the strength of the
Dzyaloshinskii-Moriya interaction. This study opens new routes towards
engineered metamaterials for spin-wave-based devices.",1806.08333v2
2014-06-23,Role of electron-phonon interaction in a magnetically driven mechanism for superconductivity,"We use the renormalization group method to examine the effect of phonon
mediated interaction on d-wave superconductivity, as driven by spin
fluctuations in a quasi-one-dimensional electron system. The influence of a
tight-binding electron-phonon interaction on the spin-density-wave and d-wave
superconducting instability lines is calculated for arbitrary temperature,
phonon frequency and antinesting of the Fermi surface.The domain of
electron-phonon coupling strength where spin-density-wave order becomes
unstable against the formation of a bond-order-wave or Peierls state is
determined at weak antinesting. We show the existence of a positive isotope
effect for spin-density-wave and d-wave superconducting critical temperatures
which scales with the antinesting distance from quantum critical point where
the two instabilities merge. We single out a low phonon frequency zone where
the bond-oder-wave ordering gives rise to triplet f-wave superconductivity
under nesting alteration, with both orderings displaying a negative isotope
effect. We also study the electron-phonon strengthening of spin fluctuations at
the origin of extended quantum criticality in the metallic phase above
superconductivity. The impact of our results on quasi-one-dimensional organic
conductors like the Bechgaard salts where a Peierls distortion is absent and
superconductivity emerges near a spin-density-wave state under pressure is
emphasized.",1406.6086v2
2023-06-28,Suppression of the spin waves nonreciprocity due to interfacial Dzyaloshinskii Moriya interaction by lateral confinement in magnetic nanostructures,"Despite the huge recent interest towards chiral magnetism related to the
interfacial Dzyaloshinskii Moriya interaction (iDMI) in layered systems, there
is a lack of experimental data on the effect of iDMI on the spin waves
eigenmodes of laterally confined nanostructures. Here we exploit Brillouin
Light Scattering (BLS) to analyze the spin wave eigenmodes of non-interacting
circular and elliptical dots, as well as of long stripes, patterned starting
from a Pt(3.4 nm)/CoFeB(0.8 nm) bilayer, with lateral dimensions ranging from
100 nm to 400 nm. Our experimental results, corroborated by micromagnetic
simulations based on the GPU-accelerated MuMax3 software package, provide
evidence for a strong suppression of the frequency asymmetry between
counter-propagating spin waves (corresponding to either Stokes or anti-Stokes
peaks in BLS spectra), when the lateral confinement is reduced from 400 nm to
100 nm, i.e. when it becomes lower than the light wavelength. Such an evolution
reflects the modification of the spin wave character from propagating to
stationary and indicates that the BLS based method of quantifying the i-DMI
strength from the frequency difference of counter propagating spin waves is not
applicable in the case of magnetic elements with lateral dimension below about
400 nm.",2306.16310v1
2024-03-20,All-magnonic repeater based on bistability,"Bistability, a universal phenomenon found in diverse fields such as biology,
chemistry, and physics, describes a scenario in which a system has two stable
equilibrium states and resets to one of the two states. The ability to switch
between these two states is the basis for a wide range of applications,
particularly in memory and logic operations. Here, we present a universal
approach to achieve bistable switching in magnonics, the field processing data
using spin waves. As an exemplary application, we use magnonic bistability to
experimentally demonstrate the still missing magnonic repeater. A pronounced
bistable window is observed in a 1um wide magnonic conduit under an external rf
drive characterized by two magnonic stable states defined as low and high
spin-wave amplitudes. The switching between these two states is realized by
another propagating spin wave sent into the rf driven region. This magnonic
bistable switching is used to design the magnonic repeater, which receives the
original decayed and distorted spin wave and regenerates a new spin wave with
amplified amplitude and normalized phase. Our magnonic repeater is proposed to
be installed at the inputs of each magnonic logic gate to overcome the
spin-wave amplitude degradation and phase distortion during previous
propagation and achieve integrated magnonic circuits or magnonic neuromorphic
networks.",2403.13276v1
2000-01-08,Gravitational Waves from Low-Mass X-ray Binaries: a Status Report,"We summarize the observations of the spin periods of rapidly accreting
neutron stars. If gravitational radiation is responsible for balancing the
accretion torque at the observed spin frequencies of ~300 Hz, then the
brightest of these systems make excellent gravitational wave sources for
LIGO-II and beyond. We review the recent theoretical progress on two mechanisms
for gravitational wave emission: mass quadrupole radiation from deformed
neutron star crusts and current quadrupole radiation from r-mode pulsations in
neutron star cores.",0001129v1
2000-07-19,Scattering of Dirac Waves off Kerr Black Holes,"Chandrasekhar separated the Dirac equation for spinning and massive particles
in Kerr geometry into radial and angular parts. Here we solve the complete wave
equation and find out how the Dirac wave scatters off Kerr black holes. The
eigenfunctions, eigenvalues and reflection and transmission co-efficients are
computed. We compare the solutions with several parameters to show how a
spinning black hole distinguishes mass and energy of incoming waves. Very close
to the horizon the solutions become independent of the particle parameters
indicating an universality of the behaviour.",0007277v1
2000-05-16,Coexistent States of Charge Density Wave and Spin Density Wave in One-Dimensional Systems with the Inter-site Coulomb Interaction under the Electron Filling Control,"The coexistent state of the spin density wave (SDW) and the charge density
wave (CDW) in the one-dimensional systems is studied by the mean field
approximation at T=0 in various electron-filling cases. We find that the
coexistent state of SDW and CDW is stabilized when the on-site and the
inter-site Coulomb interactions have the values estimated for the organic
conductors. The ground state energies have cusp-like minima at 1/4, 3/8, 5/12,
7/16, 7/20 and 9/20-fillings.",0005256v1
2002-04-02,Projected wave functions for fractionalized phases of quantum spin systems,"Gutzwiller projection allows a construction of an assortment of variational
wave functions for strongly correlated systems. For quantum spin S=1/2 models,
Gutzwiller-projected wave functions have resonating-valence-bond structure and
may represent states with fractional quantum numbers for the excitations. Using
insights obtained from field-theoretical descriptions of fractionalization in
two dimensions, we construct candidate wave functions of fractionalized states
by projecting specific superconducting states. We explicitly demonstrate the
presence of topological order in these states.",0204043v1
2003-10-31,Conversion of dislocation oscillation waves to spin ones in the vicinity of OPT temperatures,"Dislocation waves in magnetic crystals in the vicinity of orientation phase
transition (OPT) temperatures are considered in a frame of the field theory of
the defects. The singularities of the dislocation flows, elastic deformations
and magnetization occur if the magnetic subsystem is inhomogeneous and the
dispersion of the media is not taken into account. Media dispersion causes a
regularity of these parameters and a conversion of the spin wave to the
dislocation wave.",0310762v1
2003-11-12,Hartree-Fock energy of a density wave in a spin polarized two-dimensional electron gas,"We calculate the Hartree-Fock energy of a density-wave in a spin polarized
two-dimensional electron gas using a short-range repulsive interaction. We find
that the stable ground state for a short-range potential is always either the
paramagnetic state or the uniform ferromagnetic state. The energy of a
density-wave state is, however, reduced by a factor proportional to (1 -
zeta^2), where zeta is the polarization of the electron gas. Since this
situation occurs in the most unfavorable conditions (short-range repulsive
interaction) it is therefore conceivable that by including higher order
many-body corrections to the interaction a density-wave ground state is indeed
found to be stable.",0311292v1
2005-02-25,Triplet superconducting pairing and density-wave instabilities in organic conductors,"Using a renormalization group approach, we determine the phase diagram of an
extended quasi-one-dimensional electron gas model that includes interchain
hopping, nesting deviations and both intrachain and interchain repulsive
interactions. We find a close proximity of spin-density- and
charge-density-wave phases, singlet d-wave and triplet f-wave superconducting
phases. There is a striking correspondence between our results and recent
puzzling experimental findings in the Bechgaard salts, including the
coexistence of spin-density-wave and charge-density-wave phases and the
possibility of a triplet pairing in the superconducting phase.",0502614v2
2003-02-12,Detectability of Gravitational Waves from SN 1987A,"We discuss the potential for detection of gravitational waves from a rapidly
spinning neutron star produced by supernova 1987A taking the parameters claimed
by Middleditch et al. (2000) at face value. Asssuming that the dominant
mechanism for spin down is gravitational waves emitted by a freely precessing
neutron star, it is possible to constrain the wobble angle, the effective
moment of inertai of the precessing crust and the crust cracking stress limit.
Our analysis, suggests that, if the interpretation of the Middleditch data is
correct, the compact remnant of SN 1987A may well provide a reliable and
predictable source of gravitational waves well within the capability of LIGO
II.",0302050v1
1997-06-20,Time development of a wave packet and the time delay,"A one-dimensional scattering problem off a $\delta$-shaped potential is
solved analytically and the time development of a wave packet is derived from
the time-dependent Schr\""odinger equation. The exact and explicit expression of
the scattered wave packet supplies us with interesting information about the
""time delay"" by potential scattering in the asymptotic region. It is
demonstrated that a wave packet scattered by a spin-flipping potential can give
us quite a different value for the delay times from that obtained without
spin-degrees of freedom.",9706048v1
2009-07-21,Non-resonant wave front reversal of spin waves used for microwave signal processing,"It is demonstrated that non-resonant wave front reversal (WFR) of spin-wave
pulses caused by pulsed parametric pumping can be effectively used for
microwave signal processing. When the frequency band of signal amplification by
pumping is narrower than the spectral width of the signal, the non-resonant WFR
can be used for the analysis of the signal spectrum. In the opposite case the
non-resonant WFR can be used for active (with amplification) filtering of the
input signal.",0907.3652v1
2009-08-29,Cavity-Mediated Strong Matter Wave Bistability in a Spin-1 Condensate,"We study matter wave bistability in a spin-1 Bose-Einstein condensate
dispersively coupled to a unidirectional ring cavity. A unique feature is that
the population exchange among different modes of matter fields are accomplished
via the spin-exchange collisions. We show that the interplay between the atomic
spin mixing and the cavity light field can lead to a strong matter wave
nonlinearity, making matter wave bistability in a cavity at the single-photon
level achievable.",0908.4333v1
2011-02-02,Skyrmion-antiSkyrmion pairs in Ultracold Atomic Gases,"We study theoretically the dynamics of two-component Bose-Einstein
condensates in two dimensions, which admit topological excitations related to
the Skyrmions of nuclear physics. We show that there exists a branch of
uniformly propagating solitary waves characterised by a conserved momentum.
These excitations exhibit a cross-over from spatially extended spin-wave states
at low momentum to a localised ""spin-wave droplet"" at intermediate momentum; at
still higher momentum, the configuration evolves continuously into a
Skyrmion-antiSkyrmion pair. We discuss how these solitary waves can be
generated and studied in experiment.",1102.0340v1
2013-06-26,"Actuation, propagation, and detection of transverse magnetoelastic waves in ferromagnets","We study propagation of ultrasonic waves through a ferromagnetic medium with
special attention to the boundary conditions at the interface with an
ultrasonic actuator. In analogy to charge and spin transport in conductors, we
formulate the energy transport through the system as a scattering problem. We
find that the magneto-elastic coupling leads to a non-vanishing magnetic
(elastic) energy accompanying the acoustic (spin) waves with a resonantly
enhanced effect around the dispersion relation anti-crossing point. We
demonstrate the physics of excitation of magnetization dynamics via acoustic
waves injection around the ferromagnetic resonance frequency.",1306.6268v2
2014-05-15,Radiative corrections to the Coulomb law and model of dense quantum plasmas: Dispersion of waves in magnetized quantum plasmas,"Two kinds of the quantum electrodynamic radiative corrections to
electromagnetic interaction and their influence on properties of highly dense
quantum plasmas are considered. Linear radiative correction to the Coulomb
interaction are considered. Its contribution in the spectrum of the Langmuir
waves is presented. The second kind of the radiative corrections is related to
nonlinearity of the Maxwell equations for strong electromagnetic field. Its
contribution in spectrum of transverse waves of magnetized plasmas is briefly
discussed. At consideration of the Langmuir wave spectrum we included effect of
different distribution of the spin-up and spin-down electrons revealing in a
shift of the Fermi pressure.",1405.3914v1
2014-11-06,Non-reciprocity of spin wave propagation induced by the interface Dzyaloshinskii-Moriya interaction in Py/Pt film structures,"Results of a comprehensive study by means of Brillouin spectroscopy,
complemented by Ferromagnetic Resonance characterization, of spin waves (SW)
propagating in Py/Pt bi-layers, characterized by pronounced interface
Dzyaloshinskii-Moriya interactions (IDMI) are reported. Non-conventional wave
behavior of SW travelling in opposite directions, characterized by
non-reciprocity with respect to the inversion of the sign of the SW
wave-number, has been revealed. The value of the effective IDMI constant D has
been estimated.",1411.1684v1
2015-11-13,Nonlinear Radiation Damping of Nuclear Spin Waves and Magnetoelastic Waves in Antiferromagnets,"Parallel pumping of nuclear spin waves in antiferromagnetic CsMnF3 at liquid
helium temperatures and magnetoelastic waves in antiferromagnetic FeBO3 at
liquid nitrogen temperature in a helical resonator was studied. It was found
that the absorbed microwave power is approximately equal to the irradiated
power from the sample and that the main restriction mechanism of absortption in
both cases is defined by the nonlinear radiation damping predicted about two
decades ago. We believe that the nonlinear radiation damping is a common
feature of parallel pumping technique of all normal magnetic excitations and it
can be detected by purposeful experiments.",1511.04396v1
2018-11-06,Parametrically squeezed states of microwave magnons in yttrium iron garnet films,"We demonstrate theoretically, and confirm experimentally, that nonlinear spin
waves excited in thin yttrium iron garnet films are good candidates for
squeezing vacuum quantum noise. The experimental demonstration is in the form
of a measurement of spin-wave induced modulation instability (IMI) conducted in
the classical regime. The experiment evidences strong phase locking of an idler
wave parametrically generated in the film with a deterministic small-signal
wave launched into the film from an external source. The theory predicts that
the same behaviour will be observed for vacuum quantum noise, resulting in
squeezing of the noise.",1811.02104v1
2018-07-17,A Luneburg lens for spin waves,"We report on the theory of a Luneburg lens for forward-volume magnetostatic
spin waves, and verify its operation via micromagnetic modelling. The lens
converts a plane wave to a point source (and vice versa) by a designed graded
index, realised here by either modulating the thickness or the saturation
magnetization in a circular region. We find that the lens enhances the wave
amplitude by 5 times at the lens focus, and 47% of the incident energy arrives
in the focus region. Furthermore, small deviations in the profile can still
result in good focusing, if the lens index is graded smoothly.",1807.06705v1
2019-02-18,The quantum theory and topological features of photon,"In this paper, we have proposed the spinor wave equation of free and non-free
photon. On this basis, we given the spin operators and spin wave functions of
photon, and calculated the wave function of photon in vacuum and medium. In
addition, we have given the quantum Berry phase and Chern number with the
photon wave function, which can be used to studied the quantum topological
features of photon in one-dimensional period medium.",1902.06596v1
2021-03-03,The studies on phonons and magnons in (Ni80Fe20/Au/Co/Au) multilayers of different number of repetitions,"In Ni80Fe20/Au/Co/Au deposited on silicon substrate the interaction between
spin waves and surface acoustic waves is observed by Brillion light scattering
spectroscopy. We show that by changing the number of receptions in the
multilayer we can tune the dispersion of surface acoustic waves (SAWs) not
affecting significantly fundamentals spin wave (SW) mode. As a result, we can
control (activate or deactivate) the magnetoelastic interaction between
fundamental SW mode and SAWs by the thickness of the magnetostrictive
multilayer.",2103.02686v2
2023-03-06,Leaky Wave Antenna by Spin Photonic Topological Insulators Using 30-degree rhombic unit cell,"A new spin photonic topological insulator model with a 30-degree rhombic unit
cell is presented and analyzed. Topological band gaps and the robustness
against the defects are shown. The edge modes are studied via full-wave
simulation of a ribbon of unit cells. By using the structure in the fast wave
region, a leaky wave antenna is proposed with a gain of 18.2dB.",2303.07117v2
2023-05-11,Correlation-enhanced interaction of a Bose-Einstein condensate with parametric magnon pairs and virtual magnons,"Nonlinear interactions are crucial in science and engineering. Here, we
investigate wave interactions in a highly nonlinear magnetic system driven by
parametric pumping leading to Bose--Einstein condensation of spin-wave quanta
-- magnons. Using Brillouin light scattering spectroscopy in yttrium-iron
garnet films, we found and identified a set of nonlinear processes resulting in
off-resonant spin-wave excitations -- virtual magnons. In particular, we
discovered a dynamically-strong, correlation-enhanced four-wave interaction
process of the magnon condensate with pairs of parametric magnons having
opposite wavevectors and fully correlated phases.",2305.06896v1
1994-08-19,Spin dynamics of the doped t-J model,"We present a new method for studying the low energy excitations in finite
cluster systems and apply it to clarify the nature of the low energy spin
excitations in the moderately doped t-J model.
  We find that the character of the low energy spin excitations changes within
the Brillouin zone, with the dominant excitation for momentum transfer (pi,pi)
being a spin wave-like collective mode.
  Spin excitations with momentum transfer different from (pi,pi) have
particle-hole character. We give an explicit construction of a low energy
collective spin mode in a system with `almost broken symmetry' and demonstrate
its validity by explicit numerical check.",9408057v1
1995-05-26,A Spin Model for Investigating Chirality,"Spin chirality has generated great interest recently both from possible
applications to flux phases and intrinsically, as an example of a several-site
magnetic order parameter that can be long-ranged even where simpler order
parameters are not. Previous work (motivated by the flux phases) has focused on
antiferromagnetic chiral order; we construct a model in which the chirality
orders ferromagnetically and investigate the model's behavior as a function of
spin. Enlisting the aid of exact diagonalization, spin-waves, perturbation
theory, and mean fields, we conclude that the model likely has long-ranged
chiral order for spins 1 and greater and no non-trivial chiral order for spin
1/2.",9505143v1
1997-07-15,Alternating spin chains with singlet ground states,"We investigate low-energy properties of the alternating spin chain model
composed of spin $s_1$ and $s_2$ with a singlet ground state. After examining
the spin-wave spectrum in detail, we map low-energy spin excitations to the
O(3) non-linear sigma model in order to take into account quantum fluctuations.
Analyzing the topological term in the resulting sigma model, we discuss how the
massless or massive excitations are developed, especially according to the
topological nature of the alternating spin system.",9707148v1
1998-10-30,Two-Dimensional Quantum Spin Systems with Ladder and Plaquette Structure,"We investigate low-energy properties of two-dimensional quantum spin systems
with the ladder and plaquette structures, which are described by a generalized
antiferromagnetic Heisenberg model with both of the bond and spin alternations.
By exploiting a non-linear $\sigma$ model technique and a modified spin wave
approach, we evaluate the spin gap and the spontaneous magnetization to discuss
the quantum phase transition between the ordered and disordered states. We
argue how the spin-gapped phase is driven to the antiferromagnetic phase in the
phase diagram.",9810414v1
1999-05-19,Oscillation modes of two-dimensional nanostructures within the time-dependent local-spin-density approximation,"We apply the time-dependent local-spin-density approximation as general
theory to describe ground states and spin-density oscillations in the linear
response regime of two-dimensional nanostructures of arbitrary shape. For this
purpose, a frequency analysis of the simulated real-time evolution is
performed. The effect on the response of the recently proposed spin-density
waves in the ground state of certain parabolic quantum dots is considered. They
lead to the prediction of a new class of excitations, soft spin-twist modes,
with energies well below that of the spin dipole oscillation.",9905288v2
1999-07-23,Spin relaxation in semiconductor quantum dots,"We have studied the physical processes responsible for the spin -flip in GaAs
quantum dots. We have calculated the rates for different mechanisms which are
related to spin-orbit coupling and cause a spin-flip during the inelastic
relaxation of the electron in the dot both with and without a magnetic field.
We have shown that the zero-dimensional character of the problem when electron
wave functions are localized in all directions leads to freezing out of the
most effective spin-flip mechanisms related to the absence of the inversion
centers in the elementary crystal cell and at the heterointerface and, as a
result, to unusually low spin-flip rates.",9907367v1
2001-08-01,Order from disorder: Quantum spin gap in magnon spectra of LaTiO_3,"A theory of the anisotropic superexchange and low energy spin excitations in
a Mott insulator with t_{2g} orbital degeneracy is presented. We observe that
the spin-orbit coupling induces frustrating Ising-like anisotropy terms in the
spin Hamiltonian, which invalidate noninteracting spin wave theory. The
frustration of classical states is resolved by an order from disorder
mechanism, which selects a particular direction of the staggered moment and
generates a quantum spin gap. The theory explains well the observed magnon gaps
in LaTiO_3. As a test case, a specific prediction is made on the splitting of
magnon branches at certain momentum directions.",0108016v2
2001-08-11,Spin dynamics from time-dependent spin density-functional theory,"We derive the spin-wave dynamics of a magnetic material from the
time-dependent spin density functional theory in the linear response regime.
The equation of motion for the magnetization includes, besides the static spin
stiffness, a ""Berry curvature"" correction and a damping term. A gradient
expansion scheme based on the homogeneous spin-polarized electron gas is
proposed for the latter two quantities, and the first few coefficients of the
expansion are calculated to second order in the Coulomb interaction.",0108193v1
2003-05-19,Spin-phonon interaction and band effects in the high-T_C superconductor HgBa_2CuO_4,"Band calculations show that a stripe-like anti-ferromagnetic spin wave is
enforced by a 'half-breathing' phonon distortion within the CuO plane of
HgBa_2CuO_4. This spin-phonon coupling is increased further by shear distortion
and by increased distance between Cu and apical oxygens. The effects from
spin-phonon coupling are consistent with many observations in high-T_C
materials. Spin-phonon coupling can be important for the mechanism of spin
fluctuations and superconductivity, although the effects are quantitatively
weak when using the local density potential.",0305438v1
2003-06-23,Normal-superfluid interaction dynamics in a spinor Bose gas,"Coherent behavior of spinor Bose-Einstein condensates is studied in the
presence of a significant uncondensed (normal) component. Normal-superfluid
exchange scattering leads to a near-perfect local alignment between the spin
fields of the two components. Through this spin locking, spin-domain formation
in the condensate is vastly accelerated as the spin populations in the
condensate are entrained by large-amplitude spin waves in the normal component.
We present data evincing the normal-superfluid spin dynamics in this regime of
complicated interdependent behavior.",0306584v1
2003-07-01,Spin clustering and ferromagnetic couplings in a dilute magnetic semiconductor,"Ferromagnetic couplings in spin clusters are shown to be strongly enhanced
compared to those for an ordered impurity arrangement, even for the same spin
separation and hole doping. The consequent energy-enhancement of the
cluster-localized spin-wave modes indicates a potentially significant role of
positional Mn disorder in enhancing $T_{\rm C}$. Within a simple model
involving two spin-excitation energy scales corresponding to weakly and
strongly coupled spins, the temperature dependence of magnetization is found to
be in good agreement with the SQUID magnetization data for Ga$_{1-x}$Mn$_x$As.",0307009v1
2003-11-05,Spin nematics in the bilinear-biquadratic S=1 spin chain,"We report the existence of an extended critical, nondimerized region in the
phase diagram of the bilinear-biquadratic spin-one chain. The dominant power
law correlations are ferroquadrupolar, i.e. spin nematic in character. Another
known critical region is also characterized by dominant quadrupolar
correlations, although with a different wave vector. Our results show that spin
nematic correlations play an important role in quantum magnets with spin S >= 1
in regions between antiferromagnetic and ferromagnetic phases.",0311082v1
2004-10-01,Spin interferometry with electrons in nanostructures: A road to spintronic devices,"The wave nature of electrons in semiconductor nanostructures results in
spatial interference effects similar to those exhibited by coherent light. The
presence of spin-orbit coupling renders interference in spin space and in real
space interdependent, making it possible to manipulate the electron's spin
state by addressing its orbital degree of freedom. This suggests the utility of
electronic analogs of optical interferometers as blueprints for new spintronics
devices. We demonstrate the usefulness of this concept using the Mach-Zehnder
interferometer as an example. Its spin-dependent analog realizes a
spin-controlled field-effect transistor without magnetic contacts and may be
used as a quantum logical gate.",0410008v1
2004-10-08,Spin-dependent resonant tunneling in symmetrical double-barrier structure,"A theory of resonant spin-dependent tunneling has been developed for
symmetrical double-barrier structures grown of non-centrosymmetrical
semiconductors. The dependence of the tunneling transparency on the spin
orientation and the wave vector of electrons leads to (i) spin polarization of
the transmitted carriers in an in-plane electric field, (ii) generation of an
in-plane electric current under tunneling of spin-polarized carriers. These
effects originated from spin-orbit coupling-induced splitting of the resonant
level have been considered for double-barrier tunneling structures.",0410198v1
2004-10-29,How many electrons are needed to flip a local spin?,"Considering the spin of a local magnetic atom as a quantum mechanical
operator, we illustrate the dynamics of a local spin interacting with a
ballistic electron represented by a wave packet. This approach improves the
semi-classical approximation and provides a complete quantum mechanical
understanding for spin transfer phenomena. Sending spin-polarized electrons
towards a local magnetic atom one after another, we estimate the minimum number
of electrons needed to flip a local spin.",0410775v1
2005-08-30,Effects of spin current on ferromagnets,"When a spin-polarized current flows through a ferromagnet, the local
magnetization receives a spin torque. Two consequences of this spin torque are
studied. First, the uniformly magnetized ferromagnet becomes unstable if a
sufficiently large current is applied. The characteristics of the instability
include spin wave generation and magnetization chaos. Second, the spin torque
has profound effects on the structure and dynamics of the magnetic domain wall.
A detail analysis on the domain wall mass, kinetic energy and wall depinning
threshold is given.",0508735v1
2006-08-28,Inverse Spin Hall Effect by Spin Injection,"Motivated by a recent experiment[Nature {\bf 442}, 176 (2006)], we present a
quantitative microscopic theory to investigate the inverse spin-Hall effect
with spin injection into aluminum considering both intrinsic and extrinsic
spin-orbit couplings using the orthogonalized-plane-wave method. Our
theoretical results are in good agreement with the experimental data. It is
also clear that the magnitude of the anomalous Hall resistivity is mainly due
to contributions from extrinsic skew scattering, while its spatial variation is
determined by the intrinsic spin-orbit coupling.",0608594v2
2001-01-03,Collision of spinning black holes in the close limit,"In this paper we consider the collision of spinning holes using first order
perturbation theory of black holes (Teukolsky formalism). With these results
(along with ones, we published in the past) one can predict the properties of
the gravitational waves radiated from the late stage inspiral of two spinning,
equal mass black holes. Also we note that the energy radiated by the head-on
collision of two spinning holes with spins (that are equal and opposite)
aligned along the common axis is more than the case in which the spins are
perpendicular to the axis of the collision.",0101015v1
2000-07-06,Spin Structure of Many-Body Systems with Two-Body Random Interactions,"We investigate the spin structure of many-fermion systems with a
spin-conserving two-body random interaction. We find a strong dominance of
spin-0 ground states and considerable correlations between energies and wave
functions of low-lying states with different spin, but no indication of
pairing. The spectral densities exhibit spin-dependent shapes and widths, and
depend on the relative strengths of the spin-0 and spin-1 couplings in the
two-body random matrix. The spin structure of low-lying states can largely be
explained analytically.",0007013v1
2003-09-19,Spatial Localization and Relativistic Transformation of Quantum Spins,"The purity of a reduced state for spins that is pure in the rest frame will
most likely appear to degrade because spin and momentum become mixed when
viewed by a moving observer. We show that such a boost-induced decrease in spin
purity observed in a moving reference frame is intrinsically related to the
spatial localization properties of the wave package observed in the rest frame.
Furthermore, we prove that, for any localized pure state with separable spin
and momentum in the rest frame, its reduced density matrix for spins inevitably
appears to be mixed whenever viewed from a moving reference frame.",0309144v2
2004-06-02,Entanglement of electron spins in superconductors,"We investigate entanglement of two electron spins forming Cooper pairs in an
s-wave superconductor. The two-electron space-spin density matrix is obtained
from the BCS ground state using a two-particle Green's function. It is
demonstrated that a two spin state is not given by a spin singlet state but by
a Werner state. It is found that the entanglement length, within which two
spins are entangled, is not the order of the coherence length but the order of
the Fermi wave length.",0406013v1
2007-05-29,Parametric spin excitations in lateral quantum dots,"In this work, the spin dynamics of a single electron under parametric
modulation of a lateral quantum dot's electrostatic potential in the presence
of spin-orbit coupling is investigated. Numerical and theoretical calculations
demonstrate that, by squeezing and/or moving the electron's wave function, spin
rotations with Rabi frequencies on the order of tens of megahertz can be
achieved with experimentally accessible parameters in both parabolic and square
lateral quantum dots. Applications of parametric excitations for determining
spin-orbit coupling parameters and for increasing the spin polarization in the
electronic ground are demonstrated.",0705.4231v2
2007-10-16,Influences of an impurity on the transport properties of one-dimensional antisymmetric spin filter,"The influences of an impurity on the spin and the charge transport of
one-dimensional antisymmetric spin filter are investigated using bosonization
and Keldysh formulation and the results are highlighted against those of
spinful Luttinger liquids. Due to the dependence of the electron spin
orientation on wave number the spin transport is not affected by the impurity,
while the charge transport is essentially identical with that of spinless
one-dimensional Luttinger liquid.",0710.3088v1
2008-05-09,"Spin dynamics in (III,Mn)V ferromagnetic semiconductors: the role of correlations","We address the role of correlations between spin and charge degrees of
freedom on the dynamical properties of ferromagnetic systems governed by the
magnetic exchange interaction between itinerant and localized spins. For this
we introduce a general theory that treats quantum fluctuations beyond the
Random Phase Approximation based on a correlation expansion of the Green's
function equations of motion. We calculate the spin susceptibility, spin--wave
excitation spectrum, and magnetization precession damping. We find that
correlations strongly affect the magnitude and carrier concentration dependence
of the spin stiffness and magnetization Gilbert damping.",0805.1320v2
2009-05-15,Spin polarization of half-quantum vortex in systems with equal spin pairing,"We present a variational analysis for a half-quantum vortex (HQV) in the
equal-spin-pairing superfluid state which, under suitable conditions, is
believed to be realized in Sr2RuO4 and 3He-A. Our approach is based on a
description of the HQV in terms of a BCS-like wave function with a
spin-dependent boost. We predict a novel feature: the HQV, if stable, should be
accompanied by a non-zero spin polarization. Such a spin polarization would
exist in addition to the one induced by the Zeeman coupling to the external
field and hence may serve as an indicator in experimental search for HQV.",0905.2631v1
2009-10-30,Gravitational waveforms from unequal-mass binaries with arbitrary spins under leading order spin-orbit coupling,"The paper generalizes the structure of gravitational waves from orbiting
spinning binaries under leading order spin-orbit coupling, as given in the work
by K\""onigsd\""orffer and Gopakumar [PRD 71, 024039 (2005)] for single-spin and
equal-mass binaries, to unequal-mass binaries and arbitrary spin
configurations. The orbital motion is taken to be quasi-circular and the
fractional mass difference is assumed to be small against one. The emitted
gravitational waveforms are given in analytic form.",0910.5931v2
2010-03-22,Dynamical central peak and spinon deconfinement in frustrated spin chains,"Studying the dynamical spin structure factor in frustrated spin chains with
spontaneously dimerized ground state we show that besides the gapped spin-wave
excitations there appears at finite temperatures also a sharp central peak. The
latter can be attributed to deconfined spinons, accounted well within the
variational approach. The central peak remains well pronounced within the local
spin dynamics and may be relevant for experiments on materials with 1D
frustrated spin chains.",1003.4232v1
2010-05-24,Application of entanglement conditions to spin systems,"There have been numerous studies of entanglement in spin systems. These have
usually focussed on examining the entanglement between individual spins or
determining whether the state of the system is completely separable. Here we
present conditions that allow us to determine whether blocks of spins are
entangled. We show that sometimes these conditions can detect entanglement
better than conditions involving individual spins. We apply these conditions to
study entanglement in spin wave states, both when there are only a few magnons
present and also at finite temperature.",1005.4448v1
2013-03-07,Thickness dependence of the degree of spin polarization of the electrical current in permalloy thin films,"Spin-polarized electrical transport is investigated in $
Al_{2}O_{3}/Ni_{80}Fe_{20}/Al_{2}O_{3}$ thin films for permalloy thickness
between 6 and 20nm. The degree of spin-polarization of the current flowing in
the plane of the film is measured through the current induced spin wave Doppler
shift. We find that it decreases as the film thickness decreases, from 0.72 at
20nm to 0.46 at 6nm. This decrease is attributed to a spin depolarization
induced by the film surfaces. A model is proposed which takes into account the
contributions of the different sources of electron scattering (alloy disorder,
phonons, thermal magnons, grain boundaries, film surfaces) to the measured
spin-dependent resistivities.",1303.1692v1
2013-08-26,Ferromagnetic spin-orbital liquid of dipolar fermions in zigzag lattices,"Two-component dipolar fermions in zigzag optical lattices allow for the
engineering of spin-orbital models. We show that dipolar lattice fermions
permit the exploration of a regime typically unavailable in solid-state
compounds that is characterized by a novel spin-liquid phase with a finite
magnetization and spontaneously broken SU(2) symmetry. This peculiar spin
liquid may be understood as a Luttinger liquid of composite particles
consisting of bound states of spin waves and orbital domain walls moving in an
unsaturated ferromagnetic background. In addition, we show that the system
exhibits a boundary phase transitions involving non-local entanglement of edge
spins.",1308.5519v1
2013-09-02,Proposal for a local heating driven spin current generator,"We propose a two-terminal spin-orbit interferometer with a hot molecule
inserted in one of its arms to generate pure spin currents. Local heating is
achieved by coupling the vibrational modes of the molecule to a third
(phononic) reservoir. We show that this spin calorimetric effect is due to the
combined influence of spin-dependent wave interference and inelastic
scattering. Remarkably, the device converts heat flow into spin-polarized
current even without applying any voltage or temperature difference to the
electronic terminals.",1309.0366v1
2021-04-05,Thermal Hall Effect of Chiral Spin Fluctuations,"Using a two-dimensional square lattice Heisenberg model with a Rashba-type
Dzyaloshinskii-Moriya interaction, we demonstrate that chiral spin fluctuations
can give rise to a thermal Hall effect in the absence of any static spin
texture or momentum space topology. It is shown by means of Monte Carlo and
stochastic spin dynamics simulations that the thermal Hall response is finite
at elevated temperature outside of the linear spin wave regime and consistent
with the presence of thermal fluctuation-induced nontrivial topology. Our
result suggests that the high-fluctuation phases outside of the conventional
regime of magnonics may yet be a promising area of exploration for spin-based
electronics.",2104.02168v1
2003-12-29,"Spin-Orbit Ordering, Momentum Space Coexistence, and Cuprate Superconductivity","Motivated by the energetic advantage of achieving coherent enhancement of
effective spin-dependent interactions through approximate nesting, we propose
specific forms of spin ordering, whose form varies over the Fermi surface, for
the cuprate superconductors. Competing ""spin-orbit"" orderings involving order
parameters in spatial $d_{x^2-y^2}$ and $d_{xy}$ waves at commensurate and
incommensurate wavevectors, phase separated in momentum space, support behavior
suggestive of observed phenomena. The $d_{xy}$ spin-orbit fluctuation induces
an effective interaction that favors $d_{x^2-y^2}$-wave pairing, as required
for the observed superconductivity. Anisotropic spin susceptibility is a
crucial prediction of our mechanism.",0312685v1
2008-07-16,Upper and lower limits on the Crab pulsar's astrophysical parameters set from gravitational wave observations by LIGO: braking index and energy considerations,"The Laser Interferometer Gravitational Observatory (LIGO) has recently
reached the end of its fifth science run (S5), having collected more than a
year worth of data. Analysis of the data is still ongoing but a positive
detection of gravitational waves, while possible, is not realistically expected
for most likely sources. This is particularly true for what concerns
gravitational waves from known pulsars. In fact, even under the most optimistic
(and not very realistic) assumption that all the pulsar's observed spin-down is
due to gravitational waves, the gravitational wave strain at earth from all the
known isolated pulsars (with the only notable exception of the Crab pulsar)
would not be strong enough to be detectable by existing detectors. By August
2006, LIGO had produced enough data for a coherent integration capable to
extract signal from noise that was weaker than the one expected from the Crab
pulsar's spin-down limit. No signal was detected, but beating the spin-down
limit is a considerable achievement for the LIGO Scientific Collaboration
(LSC). It is customary to translate the upper limit on strain from a pulsar
into a more astrophysically significant upper limit on ellipticity. Once the
spin-down limit has been beaten, it is possible to release the constraint that
all the spin-down is due to gravitational wave emission. A more complete model
with diverse braking mechanisms can be used to set limits on several
astrophysical parameters of the pulsar. This paper shows possible values of
such parameters for the Crab pulsar given the current limit on gravitational
waves from this neutron star.",0807.2485v1
2010-08-10,Numerical study of the spin-1/2 Heisenberg antiferromagnet on a 48-site triangular lattice,"We numerically study the magnetization and the dispersion relation of a
frustrated quantum spin system. Our method, which is named the stochastic state
selection method, is a kind of Monte Carlo method to give eigenstates of the
system through statistical averaging processes.
  Using the stochastic state selection method with some constraints, we make a
successful study of the spin-1/2 Heisenberg antiferromagnet on a 48-site
triangular lattice. We calculate the sublattice magnetization and the static
structure function in the ground state. Our result on the sublattice
magnetization is consistent with the value given by the linear spin wave
theory. This adds an evidence for the analysis based on the spontaneous
symmetry breaking of the semi-classical Neel order in the ground state.
  We also evaluate the low-lying one magnon spectra of the model with all wave
vectors available on a 48-site triangular lattice. We find that at the ordering
wave vector there is a Goldstone mode, which is in good agreement with the
result from the spin wave analysis. The magnon spectra with other wave vectors,
however, are quite different from results obtained by the linear spin wave
theory. We observe a flat dispersion relation with a strong downward
renormalization. Our results are compatible with those recently reported in the
series expansion study and in the order 1/S calculation of the spin wave
analysis.",1008.1612v1
2014-09-24,Angular Momentum Transport via Internal Gravity Waves in Evolving Stars,"Recent asteroseismic advances have allowed for direct measurements of the
internal rotation rates of many sub-giant and red giant stars. Unlike the
nearly rigidly rotating Sun, these evolved stars contain radiative cores that
spin faster than their overlying convective envelopes, but slower than they
would in the absence of internal angular momentum transport. We investigate the
role of internal gravity waves in angular momentum transport in evolving low
mass stars. In agreement with previous results, we find that convectively
excited gravity waves can prevent the development of strong differential
rotation in the radiative cores of Sun-like stars. As stars evolve into
sub-giants, however, low frequency gravity waves become strongly attenuated and
cannot propagate below the hydrogen burning shell, allowing the spin of the
core to decouple from the convective envelope. This decoupling occurs at the
base of the sub-giant branch when stars have surface temperatures of roughly
5500 K. However, gravity waves can still spin down the upper radiative region,
implying that the observed differential rotation is likely confined to the deep
core near the hydrogen burning shell. The torque on the upper radiative region
may also prevent the core from accreting high-angular momentum material and
slow the rate of core spin-up. The observed spin-down of cores on the red giant
branch cannot be totally attributed to gravity waves, but the waves may enhance
shear within the radiative region and thus increase the efficacy of
viscous/magnetic torques.",1409.6835v1
2016-09-19,Geometrical complexity of the antidots unit cell effect on the spin wave excitations spectra,"We have investigated theoretically (with micromagnetic simulations and plane
wave method) and experimentally (with ferromagnetic resonance and Brillouin
light scattering) three types of antidot lattices (ADLs) based on permalloy
thin films with increased complexity of the unit cell: simple square,
bi-component square and wave-like ADL. We have found that placing a small
additional antidot in the center of the unit cell of the square ADL modify
significantly the spin wave spectrum and its dependence on the orientation of
the in-plane magnetic field. We also check the further changes of spin wave
spectrum resulting from the introduction of air-gaps connecting small and large
antidots. In particular, the presence of small antidots change the dependence
of the frequency of the fundamental mode on the angle of the in-plane applied
magnetic field. The air-gaps strongly discriminates the propagation of spin
waves in two principal direction of ADL lattice, orthogonal to each other. In
spite of these spectral changes, the spatial distribution of the spin wave
amplitude generally preserves some similarities for all three structures. We
also highlighted out the role of defects in the ADL in the observed spectra.
The obtained results can be interesting for the magnonics applications of the
magnonic crystals.",1609.05663v1
2019-06-12,Frequency-Division Multiplexing in Magnonic Logic Networks Based on Caustic-Like Spin-Wave Beams,"Wave-based data processing by spin waves and their quanta, magnons, is a
promising technique to overcome the challenges which CMOS-based logic networks
are facing nowadays. The advantage of these quasi-particles lies in their
potential for the realization of energy efficient devices on the micro- to
nanometer scale due to their charge-less propagation in magnetic materials. In
this paper, the frequency dependence of the propagation direction of
caustic-like spin-wave beams in microstructured ferromagnets is studied by
micromagnetic simulations. Based on the observed alteration of the propagation
angle, an approach to spatially combine and separate spin-wave signals of
different frequencies is demonstrated. The presented magnetic structure
constitutes a prototype design of a passive circuit enabling frequency-division
multiplexing in magnonic logic networks. It is verified that spin-wave signals
of different frequencies can be transmitted through the device simultaneously
without any interaction or creation of spurious signals. Due to the wave-based
approach of computing in magnonic networks, the technique of frequency-division
multiplexing can be the basis for parallel data processing in single magnonic
devices, enabling the multiplication of the data throughput.",1906.04993v2
2020-08-21,Magnons Parametric Pumping in Bulk Acoustic Waves Resonator,"We report on the experimental observation of excitation and detection of
parametric spin waves and spin currents in the bulk acoustic wave resonator.
The hybrid resonator consists of ZnO piezoelectric film, yttrium iron garnet
(YIG) films on gallium gadolinium garnet substrate, and a heavy metal Pt layer.
Shear bulk acoustic waves are electrically excited in the ZnO layer due to
piezoeffect at the resonant frequencies of the resonator. The magnetoelastic
interaction in the YIG film emerges magnons (spin waves) excitation by acoustic
waves either on resonator's eigenfrequencies or the half-value frequencies at
supercritical power. We investigate acoustic pumping of magnons at the
half-value frequencies and acoustic spin pumping from parametric magnons, using
the inverse spin Hall effect in the Pt layer. The constant electric voltage in
the Pt layer, depending on the frequency, the magnetic field, and the pump
power, was systematically studied. We explain the low threshold obtained (~0.4
mW) by the high efficiency of electric power transmission into the acoustic
wave in the resonator.",2008.09520v1
2021-04-14,Finite-element dynamic-matrix approach for spin-wave dispersions in magnonic waveguides with arbitrary cross section,"We present a numerical approach to efficiently calculate spin-wave
dispersions and spatial mode profiles in magnetic waveguides of arbitrarily
shaped cross section with any non-collinear equilibrium magnetization which is
translationally invariant along the waveguide. Our method is based on the
propagating-wave dynamic-matrix approach by Henry et al. and extends it to
arbitrary cross sections using a finite-element method. We solve the linearized
equation of motion of the magnetization only in a single waveguide cross
section which drastically reduces computational effort compared to common
three-dimensional micromagnetic simulations. In order to numerically obtain the
dipolar potential of individual spin-wave modes, we present a plane-wave
version of the hybrid finite-element/boundary-element method by Frekdin and
Koehler which, for the first time, we extend to a modified version of the
Poisson equation. Our method is applied to several important examples of
magnonic waveguides including systems with surface curvature, such as magnetic
nanotubes, where the curvature leads to an asymmetric spin-wave dispersion. In
all cases, the validity of our approach is confirmed by other methods. Our
method is of particular interest for the study of curvature-induced or
magnetochiral effects on spin-wave transport but also serves as an efficient
tool to investigate standard magnonic problems.",2104.06943v1
2020-01-24,Dynamics of Spiral Spin Waves in Magnetic Nano-patches: Influence of Thickness and Shape,"We explore the dynamics of spiral spin waves in Permalloy nano-elements with
variable aspect ratio of geometric dimensions, and their potential use as
improved spin wave emitters with no or little biasing field required. Numerical
results show that above a certain thickness, propagating spiral waves can be
obtained in circular and square shaped elements in a flux closure state.
VNA-FMR experiments on 20 nm (thin) and 80 nm (thick) samples confirm two type
of spectra corresponding to different dispersions for thinner and thicker
elements. We show that, for the thicker films, the vortex core region acts as a
source of large amplitude spiral spin waves, which dominate over other modes.
In case of the thinner elements, these modes are critically damped. For
different shapes of the patch, we show that a rich collection of confined
propagating modes can also be excited, modifying the final wave front and
enriching the potential of the nano-dot as a spin wave emitter. We give an
explanation for the intense spiral modes from the perspective of a balance of
dipolar and exchange energies in the sample.",2001.09053v1
2022-03-10,"Momentum, angular momentum, and spin of waves in an isotropic collisionless plasma","We examine the momentum and angular momentum (including spin) properties of
linear waves, both longitudinal (Langmuir) and transverse (electromagnetic), in
an isotropic nonrelativistic collisionless electron plasma. We focus on
conserved quantities associated with the translational and rotational
invariance of the wave fields with respect to the homogeneous medium; these are
sometimes called pseudo-momenta. There are two types of the momentum and
angular momentum densities: (i) the kinetic ones associated with the energy
flux density and the symmetrized (Belinfante) energy-momentum tensor and (ii)
the canonical ones associated with the conserved Noether currents and canonical
energy-momentum tensor. We find that the canonical momentum and spin densities
of Langmuir waves are similar to those of sound waves in fluids or gases; they
are expressed via the electron velocity field. In turn, the momentum and spin
densities of electromagnetic waves can be written either in the forms known for
free-space electromagnetic fields, involving only the electric field, or in the
dual-symmetric forms involving both electric and magnetic fields, as well as
the effective permittivity of plasma. We derive these properties both within
the phenomenological macroscopic approach and microscopic Lagrangian field
theory for the coupled electromagnetic fields and electrons. Finally, we
explore implications of the canonical momentum and spin densities in transport
and electrodynamic phenomena: the Stokes drift, the wave-induced magnetization
(inverse Faraday effect), etc.",2203.05240v2
2006-08-21,Driven coherent oscillations of a single electron spin in a quantum dot,"The ability to control the quantum state of a single electron spin in a
quantum dot is at the heart of recent developments towards a scalable
spin-based quantum computer. In combination with the recently demonstrated
exchange gate between two neighbouring spins, driven coherent single spin
rotations would permit universal quantum operations. Here, we report the
experimental realization of single electron spin rotations in a double quantum
dot. First, we apply a continuous-wave oscillating magnetic field, generated
on-chip, and observe electron spin resonance in spin-dependent transport
measurements through the two dots. Next, we coherently control the quantum
state of the electron spin by applying short bursts of the oscillating magnetic
field and observe about eight oscillations of the spin state (so-called Rabi
oscillations) during a microsecond burst. These results demonstrate the
feasibility of operating single-electron spins in a quantum dot as quantum
bits.",0608459v1
2011-01-27,Magnetic excitations in one-dimensional spin-orbital models,"We study the dynamics and thermodynamics of one-dimensional spin-orbital
models relevant for transition metal oxides. We show that collective spin,
orbital, and combined spin-orbital excitations with infinite lifetime can
exist, if the ground state of both sectors is ferromagnetic. Our main focus is
the case of effectively ferromagnetic (antiferromagnetic) exchange for the spin
(orbital) sector, respectively, and we investigate the renormalization of spin
excitations via spin-orbital fluctuations using a boson-fermion representation.
We contrast a mean-field decoupling approach with results obtained by treating
the spin-orbital coupling perturbatively. Within the latter self-consistent
approach we find a significant increase of the linewidth and additional
structures in the dynamical spin structure factor as well as Kohn anomalies in
the spin-wave dispersion caused by the scattering of spin excitations from
orbital fluctuations. Finally, we analyze the specific heat c(T) by comparing a
numerical solution of the model obtained by the density-matrix renormalization
group with perturbative results. At low temperatures T we find numerically c(T)
T pointing to a low-energy effective theory with dynamical critical exponent
z=1.",1101.5301v1
2011-05-21,Quantum states and linear response in dc and electromagnetic fields for charge current and spin polarization of electrons at Bi/Si interface with giant spin-orbit coupling,"An expansion of the nearly free-electron model constructed by Frantzeskakis,
Pons and Grioni [Phys. Rev. B {\bf 82}, 085440 (2010)] describing quantum
states at Bi/Si(111) interface with giant spin-orbit coupling is developed and
applied for the band structure and spin polarization calculation, as well as
for the linear response analysis for charge current and induced spin caused by
dc field and by electromagnetic radiation. It is found that the large
spin-orbit coupling in this system may allow resolving the spin-dependent
properties even at room temperature and at realistic collision rate. The
geometry of the atomic lattice combined with spin-orbit coupling leads to an
anisotropic response both for current and spin components related to the
orientation of the external field. The in-plane dc electric field produces only
the in-plane components of spin in the sample while both the in-plane and
out-of-plane spin components can be excited by normally propagating
electromagnetic wave with different polarizations.",1105.4215v1
2013-04-17,Universal spin dynamics in two-dimensional Fermi gases,"Harnessing spins as carriers for information has emerged as an elegant
extension to the transport of electrical charges. The coherence of such spin
transport in spintronic circuits is determined by the lifetime of spin
excitations and by spin diffusion. Fermionic quantum gases are a unique system
to study the fundamentals of spin transport from first principles since
interactions can be precisely tailored and the dynamics is on time scales which
are directly observable. In particular at unitarity, spin transport is dictated
by diffusion and is expected to reach a universal, quantum-limited diffusivity
on the order of hbar/m. Here, we study the non-equilibrium dynamics of a
two-dimensional Fermi gas following a quench into a metastable, transversely
polarized spin state. Using the spin-echo technique, we measure the yet lowest
transverse spin diffusion constant of 0.25(3) hbar/m. For weak interactions, we
observe a coherent collective transverse spin-wave mode that exhibits mode
softening when approaching the hydrodynamic regime.",1304.4980v1
2015-06-02,Nonlocal Magnetoresistance Mediated by Spin Superfluidity,"The electrical response of two diffusive metals is studied when they are
linked by a magnetic insulator hosting a topologically stable (superfluid) spin
current. We discuss how charge currents in the metals induce a spin
supercurrent state, which in turn generates a magnetoresistance that depends on
the topology of the electrical circuit. This magnetoresistance relies on phase
coherence over the entire magnet and gives direct evidence for spin
superfluidity. We show that driving the magnet with an ac current allows
coherent spin transport even in the presence of U(1)-breaking magnetic
anisotropy that can preclude dc superfluid transport. Spin transmission in the
ac regime shows a series of resonance peaks as a function of frequency. The
peak locations, heights, and widths can be used to extract static interfacial
properties, e.g., the spin-mixing conductance and effective spin Hall angle,
and to probe dynamic properties such as the spin-wave dispersion. Thus, ac
transport may provide a simpler route to realizing nonequilbrium coherent spin
transport and a useful way to characterize the magnetic system, serving as a
precursor to the realization of dc superfluid spin transport.",1506.01059v2
2015-07-15,Spin photonics and spin-photonic devices with dielectric metasurfaces,"Dielectric metasurfaces with spatially varying birefringence and high
transmission efficiency can exhibit exceptional abilities for controlling the
photonic spin states. We present here some of our works on spin photonics and
spin-photonic devices with metasurfaces. We develop a hybrid-order Poincare
sphere to describe the evolution of spin states of wave propagation in the
metasurface. Both the Berry curvature and the Pancharatnam-Berry phase on the
hybrid-order Poincare sphere are demonstrated to be proportional to the
variation of total angular momentum. Based on the spin-dependent property of
Pancharatnam-Berry phase, we find that the photonic spin Hall effect can be
observed when breaking the rotational symmetry of metasurfaces. Moreover, we
show that the dielectric metasurfaces can provide great flexibility in the
design of novel spin-photonic devices such as spin filter and spin-dependent
beam splitter.",1507.04064v2
2017-09-01,Scaling of the Rashba spin-orbit torque in magnetic domain walls,"Spin-orbit torque in magnetic domain walls was investigated by solving the
Pauli-Schr\""{o}dinger equation for the itinerant electrons. The Rashba
interaction considered is derived from the violation of inversion symmetry at
interfaces between ferromagnets and heavy metals. In equilibrium, the Rashba
spin-orbit interaction gives rise to a torque corresponding to the
Dzyaloshinskii-Moriya interaction. When there is a current flowing, the
spin-orbit torque experienced by the itinerant electrons in short domain walls
has both field-like and damping-like components. However, when the domain wall
width is increased, the damping-like component, which is the counterpart of the
non-adiabatic spin transfer torque, decreases rapidly at the domain wall
center. In contrast to the non-adiabatic spin transfer torque, the damping-like
spin-orbit torque does not approach to zero far away from the domain wall
center, even in the adiabatic limit. The scattering of spin-up and spin-down
wave functions, which is caused by the Rashba spin-orbit interaction and the
spatial variation of magnetization profile in the domain wall, gives rise to
the finite damping-like spin-orbit torque.",1709.00187v3
2019-11-06,High spin mixing conductance and spin interface transparency at $Co_2Fe_{0.4}Mn_{0.6}Si$ Heusler alloy and Pt interface,"Ferromagnetic materials exhibiting low magnetic damping ($\alpha$) and
moderately high saturation magnetization are required from the viewpoints of
generation, transmission and detection of spin wave. Since spin-to-charge
conversion efficiency is another important parameter, high spin mixing
conductance ($g_{r}^{\uparrow \downarrow}$) is the key for efficient
spin-to-charge conversion. Full Heusler alloys e.g. $Co_2Fe_{0.4}Mn_{0.6}Si$
(CFMS), which are predicted to be 100$\%$ spin polarized, possess low $\alpha$.
However, the $g_{r}^{\uparrow \downarrow}$ at the interface between CFMS and a
paramagnet has not fully been understood. Here, we report the investigations of
spin pumping and inverse spin Hall effect in $CFMS/Pt$ bilayers. Damping
analysis indicates the presence of significant spin pumping at the interface of
CFMS and Pt, which is also confirmed by the detection of inverse spin Hall
voltage. We show that in CFMS/Pt the $g_{r}^{\uparrow \downarrow}$
(1.77$\times$10$^{20}$m$^{-2}$) and interface transparency (84$\%$) are higher
compared to values reported for other ferromagnet/heavy metal systems.",1911.02230v1
2014-06-04,Long-lived spin plasmons in a spin-polarized two-dimensional electron gas,"Collective charge-density modes (plasmons) of the clean two-dimensional
unpolarized electron gas are stable, for momentum conservation prevents them
from decaying into single-particle excitations. Collective spin-density modes
(spin plasmons) possess no similar protection and rapidly decay by production
of electron-hole pairs. Nevertheless, if the electron gas has a sufficiently
high degree of spin polarization ($P>1/7$, where $P$ is the ratio of the
equilibrium spin density and the total electron density, for a parabolic
single-particle spectrum) we find that a long-lived spin-plasmon---a collective
mode in which the densities of up and down spins oscillate with opposite
phases---can exist within a ""pseudo gap"" of the single-particle excitation
spectrum. The ensuing collectivization of the spin excitation spectrum is quite
remarkable and should be directly visible in Raman scattering experiments. The
predicted mode could dramatically improve the efficiency of coupling between
spin-wave-generating devices, such as spin-torque oscillators.",1406.0986v2
2018-12-10,A Spin-Optical Nano Device,"The photon spin is an important resource for quantum information processing
as is the electron spin in spintronics. However, for subwavelength confined
optical excitations, polarization as a global property of a mode cannot be
defined. Here, we show that any polarization state of a plane-wave photon can
reversibly be mapped to a pseudo-spin embodied by the two fundamental modes of
a subwavelength plasmonic two-wire transmission line. We design a device in
which this pseudo-spin evolves in a well-defined fashion throughout the device
reminiscent of the evolution of photon polarization in a birefringent medium
and the behaviour of electron spins in the channel of a spin field-effect
transistor. The significance of this pseudo-spin is enriched by the fact that
it is subject to spin-orbit locking. Combined with optically active materials
to exert external control over the pseudo-spin precession, our findings could
enable spin-optical transistors, i.e. the routing and processing of quantum
information with light on a subwavelength scale.",1812.03721v1
2019-05-19,Persistent spin helix in Rashba-Dresselhaus ferroelectric CsBiNb2O7,"Ferroelectric Rashba semiconductors (FERSC) are a novel class of
multifunctional materials showing a giant Rashba spin splitting which can be
reversed by switching the electric polarization. Although they are excellent
candidates as channels in spin field effect transistors, the experimental
research has been limited so far to semiconducting GeTe, in which ferroelectric
switching is often prevented by heavy doping and/or large leakage currents.
Here, we report that CsBiNb2O7, a layered perovskite of Dion-Jacobson type, is
a robust ferroelectric with sufficiently strong spin-orbit coupling and spin
texture reversible by electric field. Moreover, we reveal that its topmost
valence band's spin texture is quasi-independent from the momentum, as a result
of the low symmetry of its ferroelectric phase. The peculiar spin polarization
pattern in the momentum space may yield the so-called ""persistent spin helix"",
a specific spin-wave mode which protects the spin from decoherence in diffusive
transport regime, potentially ensuring a very long spin lifetime in this
material.",1905.07744v2
2017-03-27,Spin-incoherent Luttinger liquid of one-dimensional spin-1 Tonks-Girardeau Bose gas: Spin-dependent properties,"Spin-incoherent Luttinger liquid (SILL) is a different universal class from
the Luttinger liquid.\ This difference results from the spin incoherence of the
system when the thermal energy of the system is higher than the spin excitation
energy.\ We consider one-dimensional spin-$1$ Bose gas in the SILL regime and
investigate its spin-dependent many-body properties.\ In Tonks-Girardeau limit,
we are able to write down the general wave functions in a harmonic trap.\ We
numerically calculate the spin-dependent (spin-plus, minus, and $0$) momentum
distributions in the sector of zero magnetization which allows to demonstrate
the most significant spin-incoherent feature compared to the spinless or
spin-polarized case.\ In contrast to the spinless Bose gas, the momentum
distributions are broadened and in the large momentum limit follow the same
asymptotic $1/p^4$ dependence but with reduced coefficients.\ While the density
matrices and momentum distributions differ between different spin components
for small $N$, at large $N$ they approach each other.\ We show these by
analytic arguments and numerical calculations up to $N$ $=$ $16$.",1703.08949v1
2021-09-01,Triplon current generation in solids,"A triplon refers to a fictitious particle that carries angular momentum $S =
1$ corresponding to the elementary excitation in a broad class of quantum
dimerized spin systems. Such systems without magnetic order have long been
studied as a testing ground for quantum properties of spins. Although triplons
have been found to play a central role in thermal and magnetic properties in
dimerized magnets with singlet correlation, a spin angular momentum flow
carried by triplons, a triplon current, has not been detected yet. Here we
report spin Seebeck effects induced by a triplon current: triplon spin Seebeck
effect, using a spin-Peierls system CuGeO$_3$. The result shows that the
heating-driven triplon transport induces spin current whose sign is positive,
opposite to the spin-wave cases in magnets. The triplon spin Seebeck effect
persists far below the spin-Peierls transition temperature, being consistent
with a theoretical calculation for triplon spin Seebeck effects.",2109.00352v1
2022-11-24,Elastic Valley Spin Controlled Chiral Coupling in Topological Valley Phononic Crystals,"Distinct from the phononic valley pseudo-spin, the real physical spin of
elastic waves adds a novel tool-kit capable of envisaging the valley-spin
physics of topological valley phononic crystals from a local viewpoint. Here,
we report the observation of local elastic valley spin as well as the hidden
elastic spin-valley locking mechanism overlooked before. We demonstrate that
the selective one-way routing of valley phonon states along the topological
interface can be reversed by imposing the elastic spin meta-source at different
interface locations with opposite valley-spin correspondence. We unveil the
physical mechanism of selective directionality as the elastic spin controlled
chiral coupling of valley phonon states, through both analytical theory and
experimental measurement of the opposite local elastic spin density at
different interface locations for different transport directions. The elastic
spin of valley topological edge phonons can be extended to other topological
states and offers new tool to explore topological metamaterials.",2211.15389v1
2012-08-06,Microscopic theory for the Doppler velocimetry of spin propagation in semiconductor quantum wells,"We provide a microscopic theory for the Doppler velocimetry of spin
propagation in the presence of spatial inhomogeneity, driving electric field
and the spin orbit coupling in semiconductor quantum wells in a wide range of
temperature regime based on the kinetic spin Bloch equation. It is analytically
shown that under an applied electric field, the spin density wave gains a
time-dependent phase shift $\phi(t)$. Without the spin-orbit coupling, the
phase shift increases linearly with time and is equivalent to a normal Doppler
shift in optical measurements. Due to the joint effect of spin-orbit coupling
and the applied electric field, the phase shift behaviors differently at the
early and the later stages. At the early stage, the phase shifts are the same
with or without the spin-orbit coupling. While at the later stage, the phase
shift deviates from the normal Doppler one when the spin-orbit coupling is
present. The crossover time from the early normal Doppler behavior to the
anomalous one at the later stage is inversely proportional to the spin
diffusion coefficient, wave vector of the spin density wave and the spin-orbit
coupling strength. In the high temperature regime, the crossover time becomes
large as a result of the decreased spin diffusion coefficient. The analytic
results capture all the quantitative features of the experimental results,
while the full numerical calculations agree quantitatively well with the
experimental data obtained from the Doppler velocimetry of spin propagation
[Yang {\it et al.}, Nat. Phys. {\bf 8}, 153 (2012)]. We further predict that
the coherent spin precession, originally thought to be broken down at high
temperature, is robust up to the room temperature for narrow quantum wells. We
point out that one has to carry out the experiments longer to see the effect of
the coherent spin precession at higher temperature due to the larger crossover
time.",1208.1081v2
2016-02-09,Characterizing the parent Hamiltonian for a complete set of orthogonal wave functions: An inverse quantum problem,"We study the inverse problem of constructing an appropriate Hamiltonian from
a physically reasonable set of orthogonal wave functions for a quantum spin
system. Usually, we are given a local Hamiltonian and try to characterize the
relevant wave functions and energies (the spectrum) of the system. Here, we
take the opposite approach; starting from a collection of orthogonal wave
functions, our goal is to characterize the associated parent Hamiltonian, to
see how the wave functions and the energy values determine the structure of the
parent Hamiltonian. Specifically, we obtain (quasi) local Hamiltonians by a
complete set of (multilayer) product states and a local mapping of the energy
values to the wave functions. On the other hand, a complete set of tree wave
functions (having a tree structure) results to nonlocal Hamiltonians and
operators which flip simultaneously all the spins in a single branch of the
tree graph. We observe that even for a given set of wave functions, the energy
spectrum can significantly change the nature of interactions in the
Hamiltonian. These effects can be exploited in a quantum engineering problem
optimizing an objective functional of the Hamiltonian.",1602.03120v2
2016-12-19,Extending geometrical optics: A Lagrangian theory for vector waves,"Even when neglecting diffraction effects, the well-known equations of
geometrical optics (GO) are not entirely accurate. Traditional GO treats wave
rays as classical particles, which are completely described by their
coordinates and momenta, but vector-wave rays have another degree of freedom,
namely, their polarization. The polarization degree of freedom manifests itself
as an effective (classical) ""wave spin"" that can be assigned to rays and can
affect the wave dynamics accordingly. A well-known manifestation of
polarization dynamics is mode conversion, which is the linear exchange of
quanta between different wave modes and can be interpreted as a rotation of the
wave spin. Another, less-known polarization effect is the polarization-driven
bending of ray trajectories. This work presents an extension and reformulation
of GO as a first-principle Lagrangian theory, whose effective-gauge Hamiltonian
governs the aforementioned polarization phenomena simultaneously. As an
example, the theory is applied to describe the polarization-driven divergence
of right-hand and left-hand circularly polarized electromagnetic waves in
weakly magnetized plasma.",1612.06184v2
2023-05-10,Symmetry and nonlinearity of spin wave resonance excited by focused surface acoustic waves,"The use of a complex ferromagnetic system to manipulate GHz surface acoustic
waves is a rich current topic under investigation, but the high-power nonlinear
regime is under-explored. We introduce focused surface acoustic waves, which
provide a way to access this regime with modest equipment. Symmetry of the
magneto-acoustic interaction can be tuned by interdigitated transducer design
which can introduce additional strain components. Here, we compare the impact
of focused acoustic waves versus standard unidirectional acoustic waves in
significantly enhancing the magnon-phonon coupling behavior. Analytical
simulation results based on modified Landau-Lifshitz-Gilbert theory show good
agreement with experimental findings. We also report nonlinear input power
dependence of the transmission through the device. This experimental
observation is supported by the micromagnetic simulation using mumax3 to model
the nonlinear dependence. These results pave the way for extending the
understanding and design of acoustic wave devices for exploration of
acoustically driven spin wave resonance physics.",2305.06259v1
2001-12-12,Quantum Effects and Broken Symmetries in Frustrated Antiferromagnets,"We investigate the interplay between frustration and zero-point quantum
fluctuations in the ground state of the triangular and $J_1{-}J_2$ Heisenberg
antiferromagnets, using finite-size spin-wave theory, exact diagonalization,
and quantum Monte Carlo methods. In the triangular Heisenberg antiferromagnet,
by performing a systematic size-scaling analysis, we have obtained strong
evidences for a gapless spectrum and a finite value of the thermodynamic order
parameter, thus confirming the existence of long-range N\'eel order.The good
agreement between the finite-size spin-wave results and the exact and quantum
Monte Carlo data also supports the reliability of the spin-wave expansion to
describe both the ground state and the low-energy spin excitations of the
triangular Heisenberg antiferromagnet. In the $J_1{-}J_2$ Heisenberg model, our
results indicate the opening of a finite gap in the thermodynamic excitation
spectrum at $J_2/J_1 \simeq 0.4$, marking the melting of the antiferromagnetic
N\'eel order and the onset of a non-magnetic ground state. In order to
characterize the nature of the latter quantum-disordered phase we have computed
the susceptibilities for the most important crystal symmetry breaking
operators. In the ordered phase the effectiveness of the spin-wave theory in
reproducing the low-energy excitation spectrum suggests that the uniform spin
susceptibility of the model is very close to the linear spin-wave prediction.",0112207v1
1997-10-31,Non-precessional spin-orbit effects on gravitational waves from inspiraling compact binaries to second post-Newtonian order,"We derive all second post-Newtonian (2PN), non-precessional effects of spin-
orbit coupling on the gravitational wave forms emitted by an inspiraling binary
composed of spinning, compact bodies in a quasicircular orbit. Previous post-
Newtonian calculations of spin-orbit effects (at 1.5PN order) relied on a fluid
description of the spinning bodies. We simplify the calculations by introducing
into post-Newtonian theory a delta-function description of the influence of the
spins on the bodies' energy-momentum tensor. This description was recently used
by Mino, Shibata, and Tanaka (MST) in Teukolsky-formalism analyses of particles
orbiting massive black holes, and is based on prior work by Dixon. We compute
the 2PN contributions to the wave forms by combining the MST energy-momentum
tensor with the formalism of Blanchet, Damour, and Iyer for evaluating the
binary's radiative multipoles, and with the well-known 1.5PN order equations of
motion for the binary. Our results contribute at 2PN order only to the
amplitudes of the wave forms. The secular evolution of the wave forms' phase,
the quantity most accurately measurable by LIGO, is not affected by our results
until 2.5PN order, at which point other spin-orbit effects also come into play.
We plan to evaluate the entire 2.5PN spin-orbit contribution to the secular
phase evolution in a future paper, using the techniques of this paper.",9710134v1
2000-10-18,The phase of a quantum mechanical particle in curved spacetime,"We investigate the quantum mechanical wave equations for free particles of
spin 0,1/2,1 in the background of an arbitrary static gravitational field in
order to explicitly determine if the phase of the wavefunction is $S/\hbar =
\int p_{\mu} dx^{\mu} / \hbar$, as is often quoted in the literature. We work
in isotropic coordinates where the wave equations have a simple managable form
and do not make a weak gravitational field approximation. We interpret these
wave equations in terms of a quantum mechanical particle moving in medium with
a spatially varying effective index of refraction. Due to the first order
spatial derivative structure of the Dirac equation in curved spacetime, only
the spin 1/2 particle has \textit{exactly} the quantum mechanical phase as
indicated above. The second order spatial derivative structure of the spin 0
and spin 1 wave equations yield the above phase only to lowest order in
$\hbar$. We develop a WKB approximation for the solution of the spin 0 and spin
1 wave equations and explore amplitude and phase corrections beyond the lowest
order in $\hbar$. For the spin 1/2 particle we calculate the phase appropriate
for neutrino flavor oscillations.",0010065v1
2010-10-13,Electric-field control of spin waves at room temperature in multiferroic BiFeO3,"To face the challenges lying beyond current CMOS-based technology, new
paradigms for information processing are required. Magnonics proposes to use
spin waves to carry and process information, in analogy with photonics that
relies on light waves, with several advantageous features such as potential
operation in the THz range and excellent coupling to spintronics. Several
magnonic analog and digital logic devices have been proposed, and some
demonstrated. Just as for spintronics, a key issue for magnonics is the large
power required to control/write information (conventionally achieved through
magnetic fields applied by strip lines, or by spin transfer from large
spin-polarized currents). Here we show that in BiFeO3, a room-temperature
magnetoelectric material, the spin wave frequency (>600 GHz) can be tuned
electrically by over 30%, in a non-volatile way and with virtually no power
dissipation. Theoretical calculations indicate that this effect originates from
a linear magnetoelectric effect related to spin-orbit coupling induced by the
applied electric field. We argue that these properties make BiFeO3 a promising
medium for spin wave generation, conversion and control in future magnonics
architectures.",1010.2678v1
2014-12-01,Experimental and Numerical Understanding of Localized Spin Wave Mode Behavior in Broadly Tunable Spatially Complex Magnetic Configurations,"Spin wave modes confined in a ferromagnetic film by the spatially
inhomogeneous magnetic field generated by a scanned micromagnetic tip of a
ferromagnetic resonance force microscope (FMRFM) enable microscopic imaging of
the internal fields and spin dynamics in nanoscale magnetic devices. Here we
report a detailed study of spin wave modes in a thin ferromagnetic film
localized by magnetic field configurations frequently encountered in FMRFM
experiments, including geometries in which the probe magnetic moment is both
parallel and antiparallel to the applied uniform magnetic field. We demonstrate
that characteristics of the localized modes, such as resonance field and
confinement radius, can be broadly tuned by controlling the orientation of the
applied field relative to the film plane. Micromagnetic simulations accurately
reproduce our FMRFM spectra allowing quantitative understanding of the
localized modes. Our results reveal a general method of generating tightly
confined spin wave modes in various geometries with excellent spatial
resolution that significantly facilitates the broad application of FMRFM. This
paves the way to imaging of magnetic properties and spin wave dynamics in a
variety of contexts for uncovering new physics of nanoscale spin excitations.",1412.0726v1
2018-10-28,Magnetic Resonance in Defect Spins mediated by Spin Waves,"In search of two level quantum systems that implement a qubit, the
nitrogen-vacancy (NV) center in diamond has been intensively studied for years.
Despite favorable properties such as remarkable defect spin coherence times,
the addressability of NV centers raises some technical issues. The coupling of
a single NV center to an external driving field is limited to short distances,
since an efficient coupling requires the NV to be separated by only a few
microns away from the source. As a way to overcome this problem, an enhancement
of coherent coupling between NV centers and a microwave field has recently been
experimentally demonstrated using spin waves propagating in an adjacent yttrium
iron garnet (YIG) film [1]. In this paper we analyze the optically detected
magnetic resonance spectra that arise when an NV center is placed on top of a
YIG film for a geometry similar to the one in the experiment. We analytically
calculate the oscillating magnetic field of the spin wave on top of the YIG
surface to determine the coupling of spin waves to the NV center. We compare
this coupling to the case when the spin waves are absent and the NV center is
driven only with the antenna field and show that the calculated coupling
enhancement is dramatic and agrees well with the one obtained in the recent
experiment.",1810.11841v1
2021-05-12,Coherent spin-wave transport in an antiferromagnet,"Magnonics is a research field complementary to spintronics, in which the
quanta of spin waves (magnons) replace electrons as information carriers,
promising less energy dissipation. The development of ultrafast nanoscale
magnonic logic circuits calls for new tools and materials to generate coherent
spin waves with frequencies as high, and wavelengths as short, as possible.
Antiferromagnets can host spin waves at THz frequencies and are therefore seen
as a future platform for the fastest and the least dissipative transfer of
information. However, the generation of short-wavelength coherent propagating
magnons in antiferromagnets has so far remained elusive. Here we report the
efficient emission and detection of a nanometer-scale wavepacket of coherent
propagating magnons in antiferromagnetic DyFeO3 using ultrashort pulses of
light. The subwavelength nanoscale confinement of the laser field due to large
absorption creates a strongly non-uniform spin excitation profile, thereby
enabling the propagation of a broadband continuum of coherent THz spin waves.
The wavepacket features magnons with detected wavelengths down to 125 nm and
supersonic velocities up to 13 km/s that propagate over macroscopic distances.
The long-sought source of coherent short-wavelength spin carriers demonstrated
here opens up new prospects for THz antiferromagnetic magnonics and coherence
mediated logic devices at THz frequencies.",2105.05886v1
2021-12-16,Parametric resonance of spin waves in ferromagnetic nanowires tuned by spin Hall torque,"We present a joint experimental and theoretical study of parametric resonance
of spin wave eigenmodes in Ni$_{80}$Fe$_{20}$/Pt bilayer nanowires. Using
electrically detected magnetic resonance, we measure the spectrum of spin wave
eigenmodes in transversely magnetized nanowires and study parametric excitation
of these eigenmodes by a microwave magnetic field. We also develop an
analytical theory of spin wave eigenmodes and their parametric excitation in
the nanowire geometry that takes into account magnetic dilution at the nanowire
edges. We measure tuning of the parametric resonance threshold by antidamping
spin Hall torque from a direct current for the edge and bulk eigenmodes, which
allows us to independently evaluate frequency, damping and ellipticity of the
modes. We find good agreement between theory and experiment for parametric
resonance of the bulk eigenmodes but significant discrepancies arise for the
edge modes. The data reveals that ellipticity of the edge modes is
significantly lower than expected, which can be attributed to strong
modification of magnetism at the nanowire edges. Our work demonstrates that
parametric resonance of spin wave eigenmodes is a sensitive probe of magnetic
properties at edges of thin-film nanomagnets.",2112.09222v1
1996-10-21,Geometro-Stochastically Quantized Fields with Internal Spin Variables,"The use of internal variables for the description of relativistic particles
with arbitrary mass and spin in terms of scalar functions is reviewed and
applied to the stochastic phase space formulation of quantum mechanics.
Following Bacry and Kihlberg a four-dimensional internal spin space $\bar S$ is
chosen possessing an invariant measure and being able to represent integer as
well as half integer spins. $\bar S$ is a homogeneous space of the group $SL(2,
C)$ parametrized in terms of spinors $\a\in C_2$ and their complex conjugates
$\bar\a$. The generalized scalar quantum mechanical wave functions may be
reduced to yield irreducible components of definite physical mass and spin
$[m,s]$, with $m\ge 0$ and $s=0, 1/2, 1, 3/2 ...$, with spin described in terms
of the usual $(2s+1)$-component fields. Viewed from the internal space
description of spin this reduction amounts to a restriction of the variable
$\a$ to a compact subspace of $\bar S$, i.e. a ``spin shell'' $S^2_{r=2s}$ of
radius $r=2s$ in $ C_2$. This formulation of single particles or single
antiparticles of type $[m,s]$ is then used to study the geometro- stochastic
(i.e. quantum) propagation of amplitudes for arbitrary spin on a curved
background space-time possessing a metric and axial vector torsion treated as
external fields. A Poincar\'e gauge covariant path integral-like representation
for the probability amplitude (generalized wave function) of a particle with
arbitrary spin is derived satisfying a second order wave equation on the
Hilbert bundle constructed over curved space-time. The implications for the
stochastic nature of polarization effects in the presence of gravitation are
pointed out and the extension to Fock bundles of bosonic and fermionic type is
briefly mentioned.",9610046v1
2012-10-24,An effectual template bank for the detection of gravitational waves from inspiralling compact binaries with generic spins,"We report the construction of a three-dimensional template bank for the
search for gravitational waves from inspiralling binaries consisting of
spinning compact objects. The parameter space consists of two dimensions
describing the mass parameters and one ""reduced-spin"" parameter, which
describes the secular (non-precessing) spin effects in the waveform. The
template placement is based on an efficient stochastic algorithm and makes use
of the semi-analytical computation of a metric in the parameter space. We
demonstrate that for ""low-mass"" ($m_1 + m_2 \lesssim 12\,M_\odot$) binaries,
this template bank achieves effective fitting factors $\sim0.92$--$0.99$
towards signals from generic spinning binaries in the advanced detector era
over the entire parameter space of interest (including binary neutron stars,
binary black holes, and black hole-neutron star binaries). This provides a
powerful and viable method for searching for gravitational waves from generic
spinning low-mass compact binaries. Under the assumption that spin magnitudes
of black-holes [neutron-stars] are uniformly distributed between 0--0.98 [0 --
0.4] and spin angles are isotropically distributed, the expected improvement in
the average detection volume (at a fixed signal-to-noise-ratio threshold) of a
search using this reduced-spin bank is $\sim20-52\%$, as compared to a search
using a non-spinning bank.",1210.6666v2
2021-10-26,Understanding how fast black holes spin by analysing data from the second gravitational-wave catalogue,"The Advanced LIGO and Virgo detectors have now observed approximately 50
black-hole-binary mergers, from which we can begin to infer how rapidly
astrophysical black holes spin. The LIGO-Virgo Collaboration (LVC) analysis of
detections up to the end of the first half of the third observing run (O3a)
appeared to uncover a distribution of spin magnitudes that peaks at $\sim$0.2.
This is surprising: is there a black-hole formation mechanism that prefers a
particular, non-zero spin magnitude, or could this be the cumulative effect of
multiple formation processes? We perform an independent analysis of the most
recent gravitational-wave catalogue, and find that (a) the support for the LVC
spin-magnitude is tenuous; in particular, adding or removing just one signal
from the catalogue can remove the statistical preference for this distribution,
and (b) we find potential evidence for two spin sub-populations in the observed
black holes; one with extremely low spins and one with larger spin magnitudes.
We make the connection that these spin sub-populations could be correlated with
the mass of the binary, with more massive binaries preferring larger spin
magnitudes, and argue that this may provide evidence for hierarchical mergers
in the second gravitational-wave catalogue.",2110.13542v2
2017-03-20,Hierarchical analysis of gravitational-wave measurements of binary black hole spin-orbit misalignments,"Binary black holes may form both through isolated binary evolution and
through dynamical interactions in dense stellar environments. The formation
channel leaves an imprint on the alignment between the black hole spins and the
orbital angular momentum. Gravitational waves from these systems directly
encode information about the spin--orbit misalignment angles, allowing them to
be (weakly) constrained. Identifying sub-populations of spinning binary black
holes will inform us about compact binary formation and evolution. We simulate
a mixed population of binary black holes with spin--orbit misalignments
modelled under a range of assumptions. We then develop a hierarchical analysis
and apply it to mock gravitational-wave observations of these populations.
Assuming a population with dimensionless spin magnitudes of $\chi = 0.7$, we
show that tens of observations will make it possible to distinguish the
presence of subpopulations of coalescing binary black holes based on their spin
orientations. With $100$ observations it will be possible to infer the relative
fraction of coalescing binary black holes with isotropic spin directions
(corresponding to dynamical formation in our models) with a fractional
uncertainty of $\sim 40\%$. Meanwhile, only $\sim 5$ observations are
sufficient to distinguish between extreme models---all binary black holes
either having exactly aligned spins or isotropic spin directions.",1703.06873v2
2021-11-26,The effect of spin mismodeling on gravitational-wave measurements of the binary neutron star mass distribution,"The binary neutron star (BNS) mass distribution measured with
gravitational-wave observations has the potential to reveal information about
the dense matter equation of state, supernova physics, the expansion rate of
the universe, and tests of General Relativity. As most current
gravitational-wave analyses measuring the BNS mass distribution do not
simultaneously fit the spin distribution, the implied population-level spin
distribution is the same as the spin prior applied when analyzing individual
sources. In this work, we demonstrate that introducing a mismatch between the
implied and true BNS spin distributions can lead to biases in the inferred mass
distribution. This is due to the strong correlations between the measurements
of the mass ratio and spin components aligned with the orbital angular momentum
for individual sources. We find that applying a low-spin prior which excludes
the true spin magnitudes of some sources in the population leads to
significantly overestimating the maximum neutron star mass and underestimating
the minimum neutron star mass at the population level with as few as six BNS
detections. The safest choice of spin prior that does not lead to biases in the
inferred mass distribution is one which allows for high spin magnitudes and
tilts misaligned with the orbital angular momentum.",2111.13619v2
2022-06-22,Probing Laser-Induced Spin-Current Generation in Synthetic Ferrimagnets Using Spin Waves,"Several rare-earth transition-metal ferrimagnetic systems exhibit all-optical
magnetization switching upon excitation with a femtosecond laser pulse.
Although this phenomenon is very promising for future opto-magnetic data
storage applications, the role of non-local spin transport in these systems is
scarcely understood. Using Co/Gd and Co/Tb bilayers we isolate the contribution
of the rare-earth materials to the generated spin currents by using the
precessional dynamics they excite in an adjacent ferromagnetic layer as a
probe. By measuring THz standing spin-waves as well as GHz homogeneous
precessional modes, we probe both the high- and low-frequency components of
these spin currents. The low-frequency homogeneous mode indicates a significant
contribution of Gd to the spin current, but not from Tb, consistent with the
difficulty in achieving all-optical switching in Tb-containing systems.
Measurements on the THz frequency spin waves reveal the inability of the
rare-earth generated spin currents to excite dynamics at the sub-ps timescale.
We present modelling efforts using the $s$-$d$ model, which effectively
reproduce our results and allow us to explain the behavior in terms of the
temporal profile of the spin current.",2206.10934v1
2023-10-06,Effective-One-Body Numerical-Relativity waveform model for Eccentric spin-precessing binary black hole coalescence,"Waveform models are important to gravitational wave data analysis. People
recently pay much attention to the waveform model construction for eccentric
binary black hole coalescence. Several Effective-One-Body Numerical-Relativity
waveform models of eccentric binary black hole coalescence have been
constructed. But none of them can treat orbit eccentricity and spin-precessing
simultaneously. The current paper focuses on this problem. The authors
previously have constructed waveform model for spin-aligned eccentric binary
black hole coalescence $\texttt{SEOBNRE}$. Here we extend such waveform model
to describe eccentric spin-precessing binary black hole coalescence. We
calculate the 2PN orbital radiation-reaction forces and the instantaneous part
of the decomposed waveform for a general spinning precessing binary black hole
system in effective-one-body (EOB) coordinates. We implement these results
based on our previous $\texttt{SEOBNRE}$ waveform model. We have also compared
our model waveforms to both SXS and RIT numerical relativity waveforms. We find
good consistency between our model and numerical relativity. Based on our new
waveform model, we analyze the impact of the non-perpendicular spin
contributions on waveform accuracy. We find that the non-perpendicular spin
contributions primarily affect the phase of the gravitational waveforms. For
the current gravitational wave detectors, this contribution is not significant.
The future detectors may be affected by such non perpendicular spin
contributions. More importantly our $\texttt{SEOBNRE}$ waveform model, as the
first theoretical waveform model to describe eccentric spin-precessing binary
black hole coalescence, can help people to analyze orbit eccentricity and spin
precession simultaneously for gravitational wave detection data.",2310.04552v1
2006-10-10,Frequency Evolution of the Gravitational Waves for Compact Binaries,"We present here a complete list of contributions to the gravitational wave
frequency evolution from compact binaries on circular orbits up to the second
post-Newtonian order by including the interaction of magnetic dipole moments,
quadrupole-monopole interactions together with the spin-orbit, the spin-spin
and the self-interaction spin contributions. We apply our results to the
Manchester et al. model of the J0737-3039A-B double pulsar.",0610290v1
1995-03-09,Spin Dynamics of the Triangular Heisenberg Antiferromagnet: A Schwinger Boson Approach,"We have analyzed the two-dimensional antiferromagnetic Heisenberg model on
the triangular lattice using a Schwinger boson mean-field theory. By expanding
around a state with local $120^\circ$ order, we obtain, in the limit of
infinite spin, results for the excitation spectrum in complete agreement with
linear spin wave theory (LSWT). In contrast to LSWT, however, the modes at the
ordering wave vectors acquire a mass for finite spin. We discuss the origin of
this effect.",9503048v1
1996-02-05,Spin Excitation Spectrum of La$_{1-x}A_x$MnO$_3$,"As an effective model to describe perovskite-type manganates (La,$A$)MnO$_3$,
the double-exchange model on a cubic lattice is investigated. Spin excitation
spectrum of the model in the ground state is studied using the spin wave
approximation. Spin wave dispersion relation observed in the inelastic neutron
scattering experiment of La$_{0.7}$Pb$_{0.3}$MnO$_3$ is reproduced. Effective
values for the electron bandwidth as well as Hund's coupling is estimated from
the data.",9602017v1
1996-04-23,Dynamics of coupled quantum spin chains,"Static and dynamical properties of weakly coupled antiferromagnetic spin
chains are treated using a mean--field approximation for the interchain
coupling and exact results for the resulting effective one--dimensional
problem. Results for staggered magnetization, N\'eel temperature and spin wave
excitations are in agreement with experiments on $\rm KCuF_3$. The existence of
a narrow longitudinal mode is predicted. The results are in agreement with
general scaling arguments, contrary to spin wave theory.",9604144v2
1996-10-14,Low Temperature Properties of Quantum Antiferromagnetic Chains with Alternating Spins S=1 and 1/2,"We study the low-temperature properties of S=1 and 1/2 alternating spin
chains with antiferromagnetic nearest-neighbor exchange couplings using
analytical techniques as well as a quantum Monte Carlo method. The spin-wave
approach predicts two different low-lying excitations, which are gapped and
gapless, respectively. The structure of low-lying levels is also discussed by
perturbation theory in the strength of the Ising anisotropy. These analytical
findings are compared with the results of quantum Monte Carlo calculations and
it turns out that spin-wave theory well describes the present system. We
conclude that the quantum ferrimagnetic chain exhibits both ferromagnetic and
antiferromagnetic aspects.",9610109v1
1999-08-31,Linear spin and orbital wave theory for undoped manganites,"We present a linear spin and orbital wave theory to account for the spin and
orbital orderings observed experimentally in undoped manganite. It is found
that the anisotropy of the magnetic structure is closely related to the orbital
ordering, and the Jahn-Teller effect stabilizes the orbital ordering. The phase
diagram and the low energy excitation spectra for both spin and orbital
orderings are obtained. The calculated critical temperatures can be
quantitatively comparable to the experimental data.",9908464v1
1999-10-04,Longitudinal magnetic excitations in classical spin systems,"Using spin dynamics simulations we predict the splitting of the longitudinal
spin wave peak in all antiferromagnets with single site anisotropy into two
peaks separated by twice the energy gap at the Brillouin zone center. This
phenomenon has yet to be observed experimentally but can be easily investigated
through neutron scattering experiments on MnF$_2$ and FeF$_2$. We have also
determined that for all classical Heisenberg models the longitudinal
propagative excitations are entirely multiple spin-wave in nature.",9910031v1
2000-01-31,Magnon dispersions in quantum Heisenberg ferrimagnetic chains at zero temperature,"Within the Dyson-Maleev boson formalism, we study the zero-temperature magnon
dispersions in a family of one-dimensional quantum Heisenberg ferrimagnets
composed of two different spins $(S_1,S_2)$ in the elementary cell. It is shown
that the spin-wave theory can produce precise quantitative results for the
low-energy excitations. The spin-stiffness constant $\rho_s$ and the optical
magnon gap $\Delta$ of different $(S_1,S_2)$ ferrimagnetic systems are
calculated, respectively, to second and third order in the quasiparticle
interaction. The spin-wave results are compared with available numerical
estimates.",0001441v1
2001-11-28,Spin Excitations in La2CuO4: Consistent Description by Inclusion of Ring-Exchange,"We consider the square lattice Heisenberg antiferromagnet with plaquette ring
exchange and a finite interlayer coupling leading to a consistent description
of the spin-wave excitation spectrum in La2CuO4. The values of the in-plane
exchange parameters, including ring-exchange J_{\Box}, are obtained
consistently by an accurate fit to the experimentally observed in-plane
spin-wave dispersion, while the out-of-plane exchange interaction is found from
the temperature dependence of the sublattice magnetization at low temperatures.
The fitted exchange interactions J=151.9 meV and J_{\Box}=0.24 J give values
for the spin stiffness and the Neel temperature in excellent agreement with the
experimental data.",0111533v1
2002-11-15,Collective modes in unconventional density waves,"We have investigated the collective modes of unconventional charge and spin
density waves (UCDW, USDW) in quasi-one dimensional systems in random phase
approximation. The density correlator regains its normal state form due to the
phase degree of freedom of the condensate. The possible effect of impurities is
also discussed. From this, the current-current correlation function is
evaluated through charge conservation. The spin susceptibility of USDW remains
anisotropic an spite of the lack of any periodic modulation of the spin
density. In UCDW, the spin response gets weaker in all three directions as the
temperature is lowered.",0211316v1
2003-06-07,Microscopic Wave Functions of Spin Singlet and Nematic Mott States of Spin-One Bosons in High Dimensional Bipartite Lattices,"We present microscopic wave functions of spin singlet Mott insulating states
and nematic Mott insulating states. We also investigate quantum phase
transitions between the spin singlet Mott phase and the nematic Mott phase in
both large-N limit and small-N limit (N being the number of particles per site)
in high dimensional bipartite lattices. In the mean field approximation
employed in this article we find that phase transitions are generally weakly
first order.",0306198v2
2004-02-25,Spin Dynamics of a Canted Antiferromagnet in a Magnetic Field,"The spin dynamics of a canted antiferromagnet with a quadratic spin-wave
dispersion near $\vq =0$ is shown to possess a unique signature. When the
anisotropy gap is negligible, the spin-wave stiffness $\dsw (\vq, B) =
(\omega_{\vq}-B)/q^2$ depends on whether the limit of zero field or zero
wavevector is taken first. Consequently, $\dsw $ is a strong function of
magnetic field at a fixed wavevector. Even in the presence of a sizeable
anisotropy gap, the field dependence of both $\dsw $ and the gap energy
distinguishes a canted antiferromagnet from a phase-separated mixture
containing both ferromagnetic and antiferromagnetic regions.",0402633v2
2004-06-21,"Magnetic susceptibility, exchange interactions and spin-wave spectra in the local spin density approximation","Starting from exact expression for the dynamical spin susceptibility in the
time-dependent density functional theory a controversial issue about exchange
interaction parameters and spin-wave excitation spectra of itinerant electron
ferromagnets is reconsidered. It is shown that the original expressions for
exchange integrals based on the magnetic force theorem (J. Phys. F14 L125
(1984)) are optimal for the calculations of the magnon spectrum whereas static
response function is better described by the ``renormalized'' magnetic force
theorem by P. Bruno (Phys. Rev. Lett. 90, 087205 (2003)). This conclusion is
confirmed by the {\it ab initio} calculations for Fe and Ni.",0406488v1
2005-02-22,Dynamics of weakly coupled random antiferromagnetic quantum spin chains,"We study the low-energy collective excitations and dynamical response
functions of weakly coupled random antiferromagnetic spin-1/2 chains. The
interchain coupling leads to Neel order at low temperatures. We use the
real-space renormalization group technique to tackle the intrachain couplings
and treat the interchain couplings within the Random Phase Approximation (RPA).
We show that the system supports collective spin wave excitations, and
calculate the spin wave velocity and spectra weight within RPA. Comparisons
will be made with inelastic neutron scattering experiments
quasi-one-dimensional disordered spin systems such as doped CuGeO$_3$",0502530v2
2005-04-12,Spin-charge separation in cold Fermi-gases: a real time analysis,"Using the adaptive time-dependent density-matrix renormalization group method
for the 1D Hubbard model, the splitting of local perturbations into separate
wave packets carrying charge and spin is observed in real-time. We show the
robustness of this separation beyond the low-energy Luttinger liquid theory by
studying the time-evolution of single particle excitations and density wave
packets. A striking signature of spin-charge separation is found in 1D cold
Fermi gases in a harmonic trap at the boundary between liquid and
Mott-insulating phases. We give quantitative estimates for an experimental
observation of spin-charge separation in an array of atomic wires.",0504299v2
2006-06-30,Spin-Wave Lifetimes Throughout the Brillouin Zone,"We use a neutron spin-echo method with $\mu$eV resolution to determine the
lifetimes of spin waves in the prototypical antiferromagnet MnF$_2$ over the
entire Brillouin zone. A theory based on the interaction of magnons with
longitudinal spin fluctuations provides an excellent, parameter-free
description of the data, except at the lowest momenta and temperatures. This is
surprising, given the prominence of alternative theories based on magnon-magnon
interactions in the literature. The results and technique open up a new avenue
for the investigation of fundamental concepts in magnetism. The technique also
allows measurement of the lifetimes of other elementary excitations (such as
lattice vibrations) throughout the Brillouin zone.",0606814v1
2000-09-20,Gravitational waves and spinning test particles,"The motion of a classical spinning test particle in the field of a weak plane
gravitational wave is studied. It is found that the characteristic dimensions
of the particle's orbit is sensitive to the ratio of the spin to the mass of
the particle. The results are compared with the corresponding motion of a
particle without spin.",0009070v1
2003-12-23,Gravitational waves interacting with a spinning charged particle in the presence of a uniform magnetic field,"The equations which determine the response of a spinning charged particle
moving in a uniform magnetic field to an incident gravitational wave are
derived in the linearized approximation to general relativity. We verify that
1) the components of the 4-momentum, 4-velocity and the components of the
spinning tensor, both electric and magnetic moments, exhibit resonances and 2)
the co-existence of the uniform magnetic field and the GW are responsible for
the resonances appearing in our equations. In the absence of the GW, the
magnetic field and the components of the spin tensor decouple and the magnetic
resonances disappear.",0312102v1
2005-10-25,Beam Splitter for Spin Waves in Quantum Spin Network,"We theoretically design and analytically study a controllable beam splitter
for the spin wave propagating in a star-shaped (e.g., a $Y$-shaped beam) spin
network. Such a solid state beam splitter can display quantum interference and
quantum entanglement by the well-aimed controls of interaction on nodes. It
will enable an elementary interferometric device for scalable quantum
information processing based on the solid system.",0510194v3
2007-04-26,Coupling of phonons and spin waves in triangular antiferromagnet,"We investigate the influence of the spin-phonon coupling in the triangular
antiferromagnet where the coupling is of the exchange-striction type. The
magnon dispersion is shown to be modified significantly at wave vector (2pi,0)
and its symmetry-related points, exhibiting a roton-like minimum and an
eventual instability in the dispersion. Various correlation functions such as
equal-time phonon correlation, spin-spin correlation, and local magnetization
are calculated in the presence of the coupling.",0704.3510v2
2007-09-17,Magnetic order and spin fluctuations in low-dimensional insulating systems,"The current theoretical and experimental situations are reviewed for
low-dimensional insulating systems with a low magnetic transition temperature
TM and pronounced short-range magnetic order above this temperature. Both the
standard and self-consistent spin-wave theories are shown to be insufficient to
quantitatively describe the experimental data on these systems.
Field-theoretical approaches taking into account the contribution of the
spin-fluctuation excitations (neglected in the spin-wave theories) to the
thermodynamic properties of ferro- and antiferromagnets are discussed.",0709.2690v1
2008-04-30,Phase diagram of the t-U-J1-J2 chain at half filling,"We investigate the half-filled Hubbard chain with additional nearest- and
next-nearest-neighbor spin exchange, J1 and J2, using bosonization and the
density-matrix renormalization group. For J2 = 0 we find a spin-density-wave
phase for all positive values of the Hubbard interaction U and the Heisenberg
exchange J1. A frustrating spin exchange J2 induces a bond-order-wave phase.
For some values of J1, J2 and U, we observe a spin-gapped metallic Luther-Emery
phase.",0804.4810v1
2008-07-03,Zero-size objects in Riemann-Cartan spacetime,"We use the conservation law of the stress-energy and spin tensors to study
the motion of massive zero-size objects in Riemann-Cartan geometry. The
resultant world line equations turn out to exhibit a novel spin-curvature
coupling. In particular, the spin of the Dirac particle does not couple to the
background curvature. This is a consequence of its truly zero size which
consistently rules out the orbital degrees of freedom. As a test of
consistency, the wave packet solution of the free Dirac equation is considered.
It is shown that the wave packet spin and orbital angular momentum disappear
simultaneously in the zero-size limit.",0807.0596v1
2008-07-20,$^{77}$Se NMR investigation of the field-induced spin-density-wave transitions in (TMTSF)$_2$ClO$_4$,"Complementary $^{77}$Se nuclear magnetic resonance (NMR) and electrical
transport have been used to correlate the spin density dynamics with the
subphases of the field-induced spin density wave (FISDW) ground state in \tmt.
We find that the peaks in the spin-lattice relaxation rate 1/T$_1$ appear
within the metal-FISDW phase boundary and/or at first-order subphase
transitions. In the quantum limit above 25 T, the NMR data gives an insight
into the FISDW electronic structure.",0807.3119v1
2008-11-19,Excitation of spin waves on a cylindrical semiconductor heterostructure with Rashba spin-orbit interaction,"Elementary excitations in a paramagnetic semiconductor quantum well confined
to a cylindrical surface are theoretically studied on the basis of coupled
spin-charge drift-diffusion equations. The electric-field-mediated eigenmodes
are optically excited by an oscillating interference pattern, which induces a
current in the outer circuit. For a cylinder with a given radius, sharp
resonances are predicted to occur in the steady-state current response, which
are due to weakly damped spin remagnetization waves.",0811.3070v1
2009-02-20,Properties of high-$T_c$ copper oxides from band models of spin-phonon coupling,"The mechanism of spin-phonon coupling (SPC) and possible consequencies for
the properties of high-$T_C$ copper oxides are presented. The results are based
on ab-initio LMTO band calculations and a nearly free-electron (NFE) model of
the band near $E_F$. Many observed properties are compatible with SPC, as for
the relation between doping and $\vec{q}$ for spin excitations and their energy
dependence. The main pseudogap is caused by SPC and waves along [1,0,0], but it
is suggested that secondary waves, generated along [1,1,0], contribute to a
'waterfall' structure. Conditions for optimal $T_C$, and the possiblities for
spin enhancement at the surface are discussed.",0902.3580v1
2009-07-13,Low Temperature Limit of Stability of Coherent Precession of Spin in the Superfluid 3He-B,"It is shown that instability of homogeneous precession is caused by combined
effect of anisotropy of spin wave velocities and dipole interaction. In the
principal order on the ratio of the Leggett frequency to the Larmor frequency
the increments of growth of spin wave amplitudes are found. The magnitude of
the maximum increment for all deviation angles of spin from its equilibrium
orientation is calculated. The estimation is made of the minimum temperature
down to which the precession is stable.",0907.2119v1
2010-02-13,Spin and Charge Dynamics Ruled by Antiferromagnetic Order in Iron Pnictides,"We examine the spin and charge excitations in antiferromagnetic iron
pnictides by mean-field calculations with a random phase approximation in a
five-band itinerant model. The calculated excitation spectra reproduce well
spin-wave dispersions observed in inelastic neutron scattering, with a
realistic magnetic moment for CaFe$_2$As$_2$. A particle-hole gap is found to
be crucial to obtain consistent results; we predict the spin wave in LaFeAsO
disappears at a lower energy than in CaFe$_2$As$_2$. We analyze that the charge
dynamics to make predictions for resonant inelastic x-ray scattering spectra.",1002.2701v2
2010-02-16,ADM canonical formulation with spin and application to post-Newtonian approximations,"Recently, different methods succeeded in calculating the spin dynamics at
higher orders in the post-Newtonian (PN) approximation. This is an essential
step toward the determination of more accurate templates for gravitational
waves, to be used in future gravitational wave astronomy. We focus on the
extension of the ADM canonical formalism to spinning binary black holes. Using
the global Poincare invariance of asymptotically flat spacetimes as the most
important guiding consistency condition, this extension can be constructed
order by order in the PN approximation. We were able to reach a high order both
in the spin power and the PN counting.",1002.3057v1
2010-10-17,Exact solution for large amplitude circularly polarized electromagnetic waves in incompressible spin quantum Hall magnetohydrodynamics,"It is shown that incompressible spin quantum Hall magnetohydrodynamics allows
an exact solution for the propagation of a circularly polarized electromagnetic
wave. The solution is obtained assuming a condition between the fluid velocity
and the magnetic field which eliminates the nonlinear terms in Maxwell
equations. As a result of the coupling with spin, the propagation mode depends
on the amplitude of the magnetic field. From the full solution, the limits of
small and large wavenumber are studied obtaining linear and a nonlinear
spin-modified modes.",1010.3452v1
2011-01-18,Magnetic Excitations in the Site-Centered Stripe Phase: Spin Wave Theory of Coupled Three-Leg Ladders,"The success of models of coupled two-leg spin ladders in describing the
magnetic excitation spectrum of La_{2-x}Ba_xCuO_4 had been interpreted
previously as evidence for bond-centered stripes. In a recent article, however,
we have determined the magnetic coupling induced by the charge stripes between
bond- or site-centered spin stripes modeled by two- or three-leg ladders,
respectively. We found that only the site-centered models order. We further
indicated excellent agreement of a fully consistent analysis of coupled
three-leg ladders using a spin wave theory of bond with the experimental data.
Here, we provide a full and detailed account of this analysis.",1101.3434v1
2011-08-05,One-dimensional physics in transition-metal nanowires: Phases and elementary excitations,"We used the Hartree-Fock approximation to classify the electronic phases that
might occur in a transition metal nanowire. The important features of this
situation are orbital degeneracy (or near-degeneracy) and interactions favoring
locally high-spin configurations. In this circumstance, spin density wave and
triplet superconductivity states are favored. If the interactions favor locally
low-spin configurations as in the previously studied spin ladder systems,
orbital density wave and singlet superconductivity are observed.",1108.1389v1
2012-03-07,Anomalous Behavior of Spin Systems with Dipolar Interactions,"We study the properties of spin systems realized by cold polar molecules
interacting via dipole-dipole interactions in two dimensions. Using a spin wave
theory, that allows for the full treatment of the characteristic long-distance
tail of the dipolar interaction, we find several anomalous features in the
ground state correlations and the spin wave excitation spectrum, which are
absent in their counterparts with short range interaction. The most striking
consequence is the existence of true long-range order at finite temperature for
a two-dimensional phase with a broken U(1) symmetry.",1203.1624v2
2013-03-10,Spin Dynamics of Trimers on a Distorted Kagomé Lattice,"We treat the ground state, elementary excitations, and neutron scattering
cross section for a system of trimers consisting of three tightly bound spins
1/2 on a distorted Kagom\'e lattice, subject to isotropic nearest neighbor
(usually antiferromagnetic) Heisenberg interactions. The interactions between
trimers are assumed to be weak compared to the intra trimer interactions. We
compare the spin-wave excitation spectrum of trimers with that obtained from
standard spin-wave theory and attribute the differences at low energy to the
fact that the trimer formulation includes exactly the effects of intra-trimer
zero point motion. Application to existing systems is briefly discussed.",1303.2320v1
2014-10-08,$\mathbb Z_2$ slave-spin theory of a strongly correlated Chern insulator,"We calculate the phase diagram of the topological honeycomb model in the
presence of strong interactions. We concentrate on half filling and employ a
${\mathbb Z}_{2}$ slave-spin method to find a band insulator with staggered
density, a spin-density-wave and a Mott insulating phase. Both the band
insulator and the spin-density wave come in various topological varieties.
Finally, we calculate the response function relevant for lattice modulation
spectroscopy with cold atomic gases in optical lattices.",1410.2001v1
2015-01-26,"Illustration of spin-half wave-functions, and other fractional-spin structures","We provide an illustration of a geometric structure that exhibits the
spin-half wave-function characteristics, namely that its full rotation displays
a phase inversion. We show that general fractional-spin geometric structures
are possible, along with sketchy discussions concerning group-theoretical and
quantum descriptions, as well as pose some queries. Synthesis of a
$(PF_3)_n$-chain polymer in the form of a twisted ring is proposed as a
realization of a quazi-spin-1/3 structure.",1501.06292v1
2018-10-10,The geometro-hydrodynamical formalism of quantum spinning particle,"We present the development of the realistic geometro-hydrodynamical formalism
of quantum mechanics for the spinning particle, that involves the vortical
flows and is based on the idea, that the spinor wave represents a new type of
physical field, propagating in space-time and influencing the corpuscule
embedded in the wave. We assume that this new field created by the intrinsic
spin of the particle and can produce new intrinsic forces and torques affecting
the particle with spin. We derive and discuss physical effects of this field.",1810.04716v1
2016-03-10,Resonant excitation of the spin-wave current in hybrid nanostructures,"Using the non-equilibrium statistical operator method (NSO), we have
investigated the spin transport through the interface in a
semiconductor/ferromagnetic insulator hybrid structure. We have analyzed the
approximation of effective parameters, when each of the considered subsystems
(conduction electrons, magnons, and phonons) is characterized by its effective
temperature. We have constructed the macroscopic equations, describing the
spin-wave current caused by both resonantly excited spin system of conduction
electrons and by an inhomogeneous thermal field in the ferromagnetic insulator.",1603.03207v1
2021-10-13,Spin elastodynamic motive force,"The spin-motive force (SMF) in a simple ferromagnetic monolayer caused by a
surface acoustic wave is studied theoretically via spin-vorticity coupling
(SVC). The SMF has two mechanisms. The first is the SVC-driven SMF, which
produces the first harmonic electromotive force, and the second is the
interplay between the SVC and the magentoelastic coupling, which produces the
d.c. and second harmonic electromotive forces. We show that these electric
voltages induced by a Rayleigh-type surface acoustic wave can be detected in
polycrystalline nickel. No sophisticated device structures, non-collinear
magnetic structures, or strong spin-orbit materials are used in our approach.
Consequently, it is intended to broaden the spectrum of SMF applications
considerably.",2110.06552v1
2008-06-19,Dirac particle in gravitational field,"Classical dynamics of spinning zero-size objects in an external gravitational
field is derived from the conservation law of the stress-energy and spin
tensors. The resulting world line equations differ from those in the existing
literature. In particular, the spin of the Dirac particle does not couple to
the background curvature. As a check of consistency, the wave packet solution
of the free Dirac equation is considered. The resulting equations are shown to
include a constraint that relates the wave packet spin to its orbital angular
momentum. In the zero-size limit, both contributions to the total angular
momentum disappear simultaneously.",0806.3228v1
2008-06-25,Spin polarized transport driven by square voltage pulses in a quantum dot system,"We calculate current, spin current and tunnel magnetoresistance (TMR) for a
quantum dot coupled to ferromagnetic leads in the presence of a square wave of
bias voltage. Our results are obtained via time-dependent nonequilibrium Green
function. Both parallel and antiparallel lead magnetization alignments are
considered. The main findings include a wave of spin accumulation and spin
current that can change sign as the time evolves, spikes in the TMR signal and
a TMR sign change due to an ultrafast switch from forward to reverse current in
the emitter lead.",0806.4193v1
2016-11-05,Magnonic analog of relativistic Zitterbewegung in an antiferromagnetic spin chain,"We theoretically investigate the spin wave (magnon) excitations in a
classical antiferromagnetic spin chain with easy-axis anisotropy. We obtain a
Dirac-like equation by linearizing the Landau- Lifshitz-Gilbert equation in
this antiferromagnetic system, in contrast to the ferromagnetic system in which
a Schr\""{o}dinger equation is derived. The Hamiltonian operator in the
Dirac-like equation is a pseudo-Hermitian. We compute and demonstrate the
relativistic Zitterbewegung (trembling motion) in the antiferromagnetic spin
chain by measuring the expectation values of the wave packet position.",1611.01512v2
2020-10-05,Localized excitations and scattering of spin waves in ferromagnetic chains containing magnetic nanoclusters,"The spectrum of localized excitations in an anisotropic one-dimensional
ferromagnet containing a spin cluster of arbitrary size is found exactly within
the framework of the discrete Takeno-Homma model. The boundaries of stability
of spin nanoclusters are determined, depending on their size, and the exchange
and the anisotropy parameter of the ferromagnet. The problem of the spin waves
scattering against nanoclusters is solved and explicit analytical expressions
for their reflection and transmission coefficients are obtained. A model of a
metamaterial consisting of weakly interacting magnetic molecular nanoclusters
and possessing revealed dynamic properties is proposed.",2010.01861v1
2022-09-28,Unidirectional magnetic coupling,"We show that interlayer Dzyaloshinskii-Moriya interaction in combination with
non-local Gilbert damping gives rise to unidirectional magnetic coupling. That
is, the coupling between two magnetic layers -- say the left and right layer --
is such that dynamics of the left layer leads to dynamics of the right layer,
but not vice versa. We discuss the implications of this result for the magnetic
susceptibility of a magnetic bilayer, electrically-actuated spin-current
transmission, and unidirectional spin-wave packet generation and propagation.
Our results may enable a route towards spin-current and spin-wave diodes and
further pave the way to design spintronic devices via reservoir engineering.",2209.14179v1
2023-11-30,Antiferromagnetic droplet soliton driven by spin current,"We demonstrate that a spin current flowing through a nano-contact into a
uniaxial antiferromagnet with first- and second-order anisotropy can excite a
self-localized dynamic magnetic soliton, known as a spin-wave droplet in
ferromagnets. The droplet nucleates at a certain threshold current with the
frequency of the N\'eel vector precession laying below the antiferromagnetic
resonance. The frequency exhibits nonlinear behavior with the increasing of
applied current. At the high value of applied torque, the soliton mode
transforms, and the oscillator emits spin waves propagating in the
antiferromagnetic layer.",2311.18583v1
2024-03-15,Chiral-stress-energy-momentum tensor for covariant description of spin and torque densities of light,"The measurement of the spin angular momentum of circularly polarized light by
Beth [Phys. Rev. 50, 115 (1936)] can be explained by using a microscopic torque
density. However, the experiment does not resolve the space- and time-dependent
evolution of the spin density of light and the wave plate and the covariant
form of the microscopic torque density. Here we focus on the covariant
description of the helicity, spin, and torque densities of light in materials
using the chiral-stress-energy-momentum tensor. We also perform simulations of
Gaussian light pulses in quarter-wave-plate geometries made of birefringent and
dielectric materials.",2403.10466v1
1993-01-26,Order of Two-Dimensional Isotropic Dipolar Antiferromagnets,"The question of the existence of order in two-dimensional isotropic dipolar
Heisenberg antiferromagnets is studied. It is shown that the dipolar
interaction leads to a gap in the spin-wave energy and a nonvanishing order
parameter. The resulting finite N\'eel-temperature is calculated for a square
lattice by means of linear spin-wave theory.",9301033v1
1994-10-07,Crossover from Spin-Density-Wave to Neel-like Ground state,"The characterization and evolution of a Spin Density Wave into the Quantum
Neel ground state is considered in the context of a weak coupling theory of the
half-filled Hubbard model. Magnetic properties obtained from this weak coupling
approach in one dimension compare favorably with exact results from Bethe
ansatz (BA). A study of the evolution of several length scales from weak to
strong coupling is also presented.",9410019v1
1994-10-19,Spin Wave Frequency and Critical Dynamics of Ferromagnets Below T_C,"Employing mode-coupling theory we show that the amplitude of the spin wave
frequency scaling function for the isotropic Heisenberg Hamiltonian is
universal. Theoretical and experimental values for Fe, Ni, Co, EuO, and EuS
agree quite well. Recent measurements of the longitudinal line width in Ni are
explained quantitatively.",9410073v1
1997-03-25,"Spin waves and phase diagram of one-dimensional, dipolar antiferromagnets","We report on the properties of a dipolar, antiferromagnetic chain in the
framework of linear spin-wave theory. The phase diagram is calculated for an
arbitrary ratio of dipolar interaction to exchange interaction and for fields
both parallel and perpendicular to the chain direction. The calculated
magnetization is compared with experimental measurements for RbMnBr_3, a quasi
one-dimensional antiferromagnet.",9703218v1
1998-12-15,Spinon Superconductivity and Superconductivities Mediated by Spin-Waves and Phonons in Cuprates,"The disclosure of spinon superconductivity and superconductivity mediated by
spin-waves in hole-doped Bi2212 cuprate raises the question about the origin of
the superconductivity in other cuprates and specially in an electron-doped NCCO
cuprate.",9812245v2
2000-04-18,Topological Defects in Spin Density Waves,"The rich order parameter of Spin Density Waves allows for unusual object of a
complex topological nature: a half-integer dislocation combined with a
semi-vortex of a staggered magnetization. It becomes energetically preferable
to ordinary dislocation due to enhanced Coulomb interactions in the
semiconducting regime. Generation of these objects changes e.g. the narrow band
noise frequency.",0004313v1
2002-01-10,Spin wave dispersion in La2CuO4,"We calculate the antiferromagnetic spin wave dispersion in the half-filled
Hubbard model for a two-dimensional square lattice and find it to be in
excellent agreement with recent high-resolution inelastic neutron scattering
performed on La2CuO4 [Phys. Rev. Lett. 86, 5377 (2001)].",0201151v2
2002-05-07,Spin-wave spectrum in La2CuO4 -- double occupancy and competing interaction effects,"The recently observed spin-wave energy dispersion along the AF zone boundary
in La2CuO4 is discussed in terms of double occupancy and competing interaction
effects in the $t-t'$ Hubbard model on a square lattice.",0205117v1
2005-01-28,Magnetic Phase Transition in FeRh,"Density functional calculations are performed to investigate the phase
transition in FeRh alloy. The effective exchange coupling, the critical
temperature of magnetic phase transition and the adiabatic spin wave spectrum
have been obtained. Different contributions to the free energy of different
phases are estimated. It has been found that the antiferro-ferromagnetic
transition in FeRh occurs mostly due to the spin wave excitations.",0501701v1
2005-10-10,Recent results on energy relaxation in disordered charge and spin density waves,"We briefly review different approaches used recently to describe collective
effects in the strong pinning model of disordered charge and spin density
waves, in connection with the CRTBT very low temperature heat relaxation
experiments.",0510217v1
2005-10-30,Domain instability during precessional magnetization reversal,"Spin wave equations in the non-equilibrium precessing state of a
ferromagnetic system are found. They show a spin-wave instability towards
growing domains of stable magnetization. Precession of the uniform
magnetization mode is described by the Landau Lifshitz equation with the
exponentially growing in time effective Gilbert dissipation constant that could
have both signs. On the developed stages of the domain instability a
non-stationary picture of domain chaos is observed.",0510817v1
2002-08-25,Spinning particles in gravitational wave spacetime,"The dynamics of pseudo-classical spinning particles in spacetime of
gravitational plane waves of general polarization and harmonic profile is
studied. The resulting equations of motion are solved exactly and the results
are compared with those of the other approaches. The relative accelerations of
nearby particles is also calculated.",0208072v1
2005-10-20,Charged particles with spin in a gravitational wave and a uniform magnetic field,"We study the motion of a pseudo-classical charged particle with spin in the
space-time of a gravitational pp wave in the presence of a uniform magnetic
field.",0510094v2
2006-01-13,Symmetric discrete quotients of supersymmetric Hpp-waves and spin structures,"We explore the importance of the choice of spin structure in determining the
amount of supersymmetry preserved by a symmetric M-theory background
constructed by quotienting a supersymmetric Hpp-wave with a discrete subgroup
in the centraliser of its isometry group.",0601087v1
2005-01-05,Stimulated wave of polarization in 1D Ising chain,"It is demonstrated that in one-dimensional Ising chain with nearest-neighbor
interactions, irradiated by a weak resonant transverse field, a stimulated wave
of flipped spins can be triggered by a flip of a single spin. This analytically
solvable model illustrates mechanisms of quantum amplification and quantum
measurement.",0501022v1
2007-10-01,Next to leading order gravitational wave emission and dynamical evolution of compact binary systems with spin,"Compact binary systems with spinning components are considered. Finite size
effects due to rotational deformation are taken into account. The dynamical
evolution and next to leading order gravitational wave forms are calculated,
taking into account the orbital motion up to the first post-Newtonian
approximation.",0710.0258v2
2007-10-04,Quantum-mechanical Landau-Lifshitz equation,"Quantum-mechanical analogue of Landau-Lifshitz equation has been derived. It
has been established that Landau-Lifshitz equation is fundamental physical
equation underlying the dynamics of spectroscopic transitions and transitional
phenomena. New phenomenon is predicted: electrical spin wave resonance (ESWR)
being to be electrical analogue of magnetic spin wave resonance.",0710.1058v3
2009-03-01,Excitonic spin density wave state in iron pnictides,"We examine the appearance of a spin density wave in the FeAs parent compounds
due to an excitonic instability. Using a realistic four-band model, we show
that the magnetic state depends very sensitively upon the details of the band
structure. We demonstrate that an orthorhombic distortion of the crystal
enhances the stability of the antiferromagnetic order.",0903.0124v1
2010-10-13,"Comment on ""Composite excitation of Josephson phase and spin waves in ferromagnetic Josephson junctions"" (S.Hikino, M.Mori, S.Takahashi, and S.Maekawa, arXiv:1009.3551)","We clarify the applicability of the quasistatic approximation used in Ref.
[\onlinecite{VE}], where coupled spin and Josephson plasma waves have been
predicted to exist in SIFS Josephson junctions. We show, contrary to the claim
of the authors of Ref. [\onlinecite{Maekawa}], that this approximation is very
accurate in realistic systems studied experimentally.",1010.2680v1
2020-12-04,Spin Wave Electromagnetic Nonlinear Interaction to Move RF Limiter Frequency Range to Higher Frequencies,"It is shown here that the usual operating frequencies for RF limiters, in the
nominal 5, 11 or 15 GHz center frequencies, can be lifted up into the much
higher frequencies of the 40 to 60 GHz range by a new formula developed from
fundamental spin wave electromagnetic interactions in magnetic material
characterized by a magnetization M.",2012.05687v1
1994-03-11,The hole-hole superconducting pairing in t-J model induced by the long-range spin-wave exchange,"Long-range $(r \sim p_F^{-1} \gg lattice \ spacing)$ spin-wave exchange
produces a very strong pairing of the holes. The different symmetry solutions
of BCS-type equation for the superconducting gap $\Delta$ are found. The most
strong pairing corresponds to $d$-wave symmetry. The physical reasons for the
strong pairing are: 1)large velocity of the spin-wave, 2) a ``collapse'' effect
in the attractive potential (-1/r^2) describing the interaction between two
holes induced by spin-wave exchange. 3)strongly asymmetric hole dispersion. At
concentration of the holes $\delta \sim 0.01-0.3$ we get $\Delta \sim T_c \sim
\epsilon_F$. At very low concentration of the holes the many-body wave function
of the ground state decays into the product of two-hole bound states.",9403045v1
2000-03-29,Role of Phase Variables in Quarter-Filled Spin Density Wave States,"Several kinds of spin density wave (SDW) states with both quarter-filled band
and dimerization are reexamined for a one-dimensional system with on-site,
nearest-neighbor and next-nearest-neighbor repulsive interactions, which has
been investigated by Kobayashi et al. (J. Phys. Soc. Jpn. 67 (1998) 1098).
Within the mean-field theory, the ground state and the response to the density
variation are calculated in terms of phase variables, $\theta$ and $\phi$,
where $\theta$ expresses the charge fluctuation of SDW and $\phi$ describes the
relative motion between density wave with up spin and that with down spin
respectively. It is shown that the exotic state of coexistence of 2k_F-SDW and
2k_F-charge density wave (CDW) is followed by 4k_F-SDW but not by 4k_F-CDW
where k_F denotes a Fermi wave vector. The harmonic potential with respect to
the variation of $\theta$ and/or $\phi$ disappears for the interactions, which
lead to the boundary between the pure 2k_F-SDW state and the corresponding
coexistent state.",0003464v1
1999-10-20,Signature of chaos in gravitational waves from a spinning particle,"A spinning test particle around a Schwarzschild black hole shows a chaotic
behavior, if its spin is larger than a critical value. We discuss whether or
not some peculiar signature of chaos appears in the gravitational waves emitted
from such a system. Calculating the emitted gravitational waves by use of the
quadrupole formula, we find that the energy emission rate of gravitational
waves for a chaotic orbit is about 10 times larger than that for a circular
orbit, but the same enhancement is also obtained by a regular ""elliptic"" orbit.
A chaotic motion is not always enhance the energy emission rate maximally. As
for the energy spectra of the gravitational waves, we find some characteristic
feature for a chaotic orbit. It may tell us how to find out a chaotic behavior
of the system. Such a peculiar behavior, if it will be found, may also provide
us some additional informations to determine parameters of a system such as a
spin.",9910064v1
2003-04-17,Spin Waves as Metric in a Kinetic Space-Time,"1) A wave equation is derived from the kinetic equations governing media with
rotational as well as translational degrees of freedom. In this wave the
fluctuating quantity is a vector, the bulk spin. The transmission is similar to
compressive waves but propagation is possible even in the limit of
incompressibility, where such disturbances could become dominant. 2) In this
context a kinetic theory of space-time is introduced, in which hypothetical
constituents of the space-time manifold possess such a rotational degree of
freedom (spin). Physical fields (i.e. electromagnetic or gravitational) in such
a theory are represented as moments of a statistical distribution of these
constituents. The spin wave equation from 1) is treated as a candidate for
governing light and metric. Such a theory duplicates to first order Maxwell's
equations of electromagnetism, Schrodinger's equation for the electron, and the
Lorentz transformations of special relativity. Slight deviations from the
classical approach are predicted and should be experimentally verifiable.",0304063v5
1997-02-21,New mechanism of collapse and revival in wave packet dynamics due to spin-orbit interaction,"The article discusses the properties of time evolution of wave packets in a
few systems. Dynamics of wave packet motion for Rydberg atoms with the
hierarchy of collapses and revivals is briefly reviewed. The main part of the
paper focuses on the new mechanism of quantum reccurrences in wave packet
dynamics. This mechanism can occur (in principle) in any physical system with
strong enough spin-orbit interaction. We discuss here the SPIN_ORBIT PENDULUM
effect that consists in different motions of subpackets possessing different
spin fields and results in oscillations of a fraction of average angular
momentum between spin and ordinary subspaces. The evolution of localized wave
packet into toroidal objects and backwards (for other class of initial
conditions) is also subject to discussion.",9702044v1
2007-11-15,Electromagnetic wave-particle with spin and magnetic moment,"An axisymmetric static solution of a nonlinear electrodynamics is considered
as a massive charged particle with spin and magnetic moment. A linearization of
the nonlinear electrodynamics around the static solution is investigated. The
appropriate problem for linear waves around the static solution is considered.
This wave part of the particle solution is considered to provide the
appropriate wave properties for the particle. It has been found that the right
(experimentally proved) formula for frequency of this wave appears
theoretically for the static solution with ring singularity.",0711.2499v1
2010-09-07,Critical Correlations for Short-Range Valence-Bond Wave Functions on the Square Lattice,"We investigate the arguably simplest $SU(2)$-invariant wave functions capable
of accounting for spin-liquid behavior, expressed in terms of nearest-neighbor
valence-bond states on the square lattice and characterized by different
topological invariants. While such wave-functions are known to exhibit
short-range spin correlations, we perform Monte Carlo simulations and show that
four-point correlations decay algebraically with an exponent $1.16(4)$. This is
reminiscent of the {\it classical} dimer problem, albeit with a slower decay.
Furthermore, these correlators are found to be spatially modulated according to
a wave-vector related to the topological invariants. We conclude that a
recently proposed spin Hamiltonian that stabilizes the here considered
wave-function(s) as its (degenerate) ground-state(s) should exhibit gapped spin
and gapless non-magnetic excitations.",1009.1307v2
2011-10-19,Spin Waves in 2D ferromagnetic square lattice stripe,"In this work, the area and edges spin wave calculations were carried out
using the Heisenberg Hamiltonian and the tridiagonal method for the 2D
ferromagnetic square lattice stripe, where the SW modes are characterized by a
1D in-plane wave vector $q_x$. The results show a general and an unexpected
feature that the area and edge spin waves only exist as optic modes. This
behavior is also seen in 2D Heisenberg antiferromagnetic square lattice. This
absence of the acoustic modes in the 2D square lattice is explained by the fact
that the geometry constrains for NN exchange inside the square lattice allow
only optical modes. We suggest that this unexpected behavior of spin waves in
the 2D square lattice may be useful in realizing an explanation for HTS.",1110.4369v1
2012-02-15,Self-consistent spin waves in magnetized BEC,"We obtain equations of quantum hydrodynamic (QHD) for magnetized spin-1
neutral Bose-Einstein condensate (BEC). System of QHD equations contains the
equation of magnetic moment evolution (an analog of the Bloch equation). We
account spin-spin interaction along with the short range interaction. We
consider self-consistent field approximation of QHD equations. Starting from
QHD equation we derive the Gross-Pitaevskii equation for magnetized BEC. We
show that Gross-Pitaevskii equation exists under condition that the magnetic
moment direction is not change. Using obtained QHD equations we study the
dispersion of collective excitation. As in electrically polarized BEC [P. A.
Andreev, L. S. Kuz'menkov, arXiv: 1201.2440], in the magnetically polarized BEC
there is second wave mode (polarization mode or spin wave), in addition to the
Bogoliubov's mode. Second wave solution appears due to the magnetic moment
evolution. The influence of magnetization on dispersion of Bogoliubov's mode is
found. We found strong difference of dispersion properties of waves in
magnetized BEC from electrically polarized BEC.",1202.3398v1
2013-05-06,The Pilot-Wave Perspective on Spin,"The alternative pilot-wave theory of quantum phenomena -- associated
especially with Louis de Broglie, David Bohm, and John Bell -- reproduces the
statistical predictions of ordinary quantum mechanics, but without recourse to
special \emph{ad hoc} axioms pertaining to measurement. That (and how) it does
so is relatively straightforward to understand in the case of position
measurements and, more generally, measurements whose outcome is ultimately
registered by the position of a pointer. Despite a widespread belief to the
contrary among physicists, the theory can also account successfully for
phenomena involving spin. The main goal of the paper is to explain how the
pilot-wave theory's account of spin works. Along the way, we provide
illuminating comparisons between the orthodox and pilot-wave accounts of spin
and address some puzzles about how the pilot-wave theory relates to the
important theorems of Kochen and Specker and Bell.",1305.1280v2
2015-04-14,Vestigial chiral and charge orders from bidirectional spin-density waves: Application to the iron-based superconductors,"Recent experiments in optimally hole-doped iron arsenides have revealed a
novel magnetically ordered ground state that preserves tetragonal symmetry,
consistent with either a charge-spin density wave (CSDW), which displays a
non-uniform magnetization, or a spin-vortex crystal (SVC), which displays a
non-collinear magnetization. Here we show that, similarly to the partial
melting of the usual stripe antiferromagnet into a nematic phase, either of
these phases can also melt in two stages. As a result, intermediate
paramagnetic phases with vestigial order appears: a checkerboard charge
density-wave for the CSDW ground state, characterized by an Ising-like order
parameter, and a remarkable spin-vorticity density-wave for the SVC ground
state -- a triplet d-density wave characterized by a vector chiral order
parameter. We propose experimentally detectable signatures of these phases,
show that their fluctuations can enhance the superconducting transition
temperature, and discuss their relevance to other correlated materials.",1504.03656v3
2015-05-04,Composite spin and quadrupole wave in the ordered phase of Tb$_{2+x}$Ti$_{2-x}$O$_{7+y}$,"The hidden ordered state of the frustrated pyrochlore oxide
Tb$_{2+x}$Ti$_{2-x}$O$_{7+y}$ is possibly one of the two electric multipolar,
or quadrupolar, states of the effective pseudospin-1/2 Hamiltonian derived from
crystal-field ground state doublets of non-Kramers Tb$^{3+}$ ions. These
long-range orders are antiparallel or parallel alignments of transverse
pseudospin components representing electric quadrupole moments, which cannot be
observed as magnetic Bragg reflections by neutron scattering. However
pseudospin waves of these states are composite waves of the magnetic-dipole and
electric-quadrupole moments, and can be partly observed by inelastic magnetic
neutron scattering. We calculate these spin-quadrupole waves using linear
spin-wave theory and discuss previously observed low-energy magnetic excitation
spectra of a polycrystalline sample with $x = 0.005$ ($T_{\text{c}} = 0.5 $ K).",1505.00503v5
2015-09-03,Spin effects in Kapitza-Dirac scattering at light with elliptical polarization,"The Kapitza-Dirac effect, which refers to electron scattering at standing
light waves, is studied in the Bragg regime with counterpropagating
elliptically polarized electromagnetic waves with the same intensity,
wavelength, and degree of polarization for two different setups. In the first
setup, where the electric-field components of the counterpropagating waves have
the same sense of rotation, we find distinct spin effects. The spins of the
scattered electrons and of the nonscattered electrons, respectively, precess
with a frequency that is of the order of the Bragg-reflection Rabi frequency.
When the electric-field components of the counterpropagating waves have an
opposite sense of rotation, which is the second considered setup, the standing
wave has linear polarization, and no spin effects can be observed. Our results
are based on numerical solutions of the time-dependent Dirac equation and the
analytical solution of a relativistic Pauli equation, which accounts for the
leading relativistic effects.",1509.01150v2
2016-02-24,Exchange stiffness in ultrathin perpendicularly-magnetized CoFeB layers determined using spin wave spectroscopy,"We measure the frequencies of spin waves in nm-thick perpendicularly
magnetized FeCoB systems, and model the frequencies to deduce the exchange
stiffness of this material in the ultrathin limit. For this, we embody the
layers in magnetic tunnel junctions patterned into circular nanopillars of
diameters ranging from 100 to 300 nm and we use magneto-resistance to determine
which rf-current frequencies are efficient in populating the spin wave modes.
Micromagnetic calculations indicate that the ultrathin nature of the layer and
the large wave vectors used ensure that the spin wave frequencies are
predominantly determined by the exchange stiffness, such that the number of
modes in a given frequency window can be used to estimate the exchange. For 1
nm layers the experimental data are consistent with an exchange stiffness A= 20
pJ/m, which is slightly lower that its bulk counterpart. The thickness
dependence of the exchange stiffness has strong implications for the numerous
situations that involve ultrathin films hosting strong magnetization gradients,
and the micromagnetic description thereof.",1602.07421v1
2016-09-23,Spin waves in rings of classical magnetic dipoles,"We theoretically and numerically investigate spin waves that occur in systems
of classical magnetic dipoles that are arranged at the vertices of a regular
polygon and interact solely via their magnetic fields. There are certain
limiting cases that can be analyzed in detail. One case is that of spin waves
as infinitesimal excitations from the system's ground state, where the
dispersion relation can be determined analytically. The frequencies of these
infinitesimal spin waves are compared with the peaks of the Fourier transform
of the thermal expectation value of the autocorrelation function calculated by
Monte Carlo simulations. In the special case of vanishing wave number an exact
solution of the equations of motion is possible describing synchronized
oscillations with finite amplitudes. Finally, the limiting case of a dipole
chain with $N\longrightarrow \infty$ is investigated and completely solved.",1609.07264v2
2012-09-17,Nonlinear emission of spin-wave caustics from an edge mode of a micro-structured Co2Mn0.6Fe0.4Si waveguide,"Magnetic Heusler materials with very low Gilbert damping are expected to show
novel magnonic transport phenomena. We report nonlinear generation of higher
harmonics leading to the emission of caustic spin-wave beams in a low-damping,
micro-structured Co2Mn0.6Fe0.4Si Heusler waveguide. The source for the higher
harmonic generation is a localized edge mode formed by the strongly
inhomogeneous field distribution at the edges of the spin-wave waveguide. The
radiation characteristics of the propagating caustic waves observed at twice
and three times the excitation frequency are described by an analytical
calculation based on the anisotropic dispersion of spin waves in a magnetic
thin film.",1209.3669v2
2018-02-01,Theory of spin and lattice wave dynamics excited by focused laser pulses,"We develop a theory of the spin wave dynamics excited by ultrafast focused
laser pulses in a magnetic film. We take into account both volume and surface
spin wave modes in the presence of applied, dipolar and magnetic anisotropy
fields and include the dependence on laser spot exposure size and magnetic
damping. We show that the sound waves generated by local heating by an
ultrafast focused laser pulse can excite a wide spectrum of spin waves (on top
of a dominant magnon-phonon contribution). Good agreement with recent
experiments supports the validity of the model.",1802.00178v2
2020-08-10,Evidence of pair-density wave in doping Kitaev spin liquid on the honeycomb lattice,"We study the effects of doping the Kitaev model on the honeycomb lattice
where the spins interact via the bond-directional interaction $J_K$, which is
known to have a quantum spin liquid as its exact ground state. The effect of
hole doping is studied within the $t$-$J_K$ model on a three-leg cylinder using
density-matrix renormalization group. Upon light doping, we find that the
ground state of the system has quasi-long-range charge-density-wave
correlations but short-range single-particle correlations. The dominant pairing
channel is the even-parity superconducting pair-pair correlations with
$d$-wave-like symmetry, which oscillate in sign as a function of separation
with a period equal to that of the spin-density wave and two times the
charge-density wave. Although these correlations fall rapidly (possibly
exponentially) at long distances, this is never-the-less the first example
where a pair-density wave is the strongest SC order on a bipartite lattice. Our
results may be relevant to ${\rm Na_2IrO_3}$ and $\alpha$-${\rm RuCl_3}$ upon
doping.",2008.03858v1
2017-10-25,Co- and contra-directional vertical coupling between ferromagnetic layers with grating for short-wavelength spin wave generation,"The possibility to generate short spin waves is of great interest in the
field of magnonics nowadays. We present an effective and technically affordable
way of conversion of long spin waves, which may be generated by conventional
microwave antenna, to the short, sub-micrometer waves. It is achieved by
grating-assisted resonant dynamic dipolar interaction between two ferromagnetic
layers separated by some distance. We analyze criteria for the optimal
conversion giving a semi-analytical approach for the coupling coefficient. We
show by the numerical calculations the efficient energy transfer between layers
which may be either of co-directional or contra-directional type. Such a system
may operate either as a short spin wave generator or a frequency filter, moving
foreward possible application of magnonics.",1710.09138v1
2021-04-22,Bistable nanomagnet as programmable phase inverter for spin waves,"To realize spin wave logic gates programmable phase inverters are essential.
We image with phase-resolved Brillouin light scattering microscopy propagating
spin waves in a one-dimensional magnonic crystal consisting of dipolarly
coupled magnetic nanostripes. We demonstrate phase shifts upon a single
nanostripe of opposed magnetization. Using micromagnetic simulations we model
our experimental finding in a wide parameter space of bias fields and wave
vectors. We find that low-loss phase inversion is achieved, when the internal
field of the oppositely magnetized nanostripe is tuned such that the latter
supports a resonant standing spin wave mode with odd quantization number at the
given frequency. Our results are key for the realization of phase inverters
with optimized signal transmission.",2104.11015v1
2004-05-05,Spin waves in a Bose Ferromagnet,"It is shown that the ferromagnetic transition takes place always above
Bose-Einstein condensation in ferromagnetically coupled spinor Bose gases. We
describe the Bose ferromagnet within Ginzburg-Landau theory by a ""two-fluid""
model below Bose-Einstein condensation. Both the Bose condensate and the normal
phase are spontaneously magnetized. As a main result we show that spin waves in
the two fluids are coupled together so as to produce only one mixed spin-wave
mode in the coexisting state. The long wavelength spectrum is quadratic in the
wave vector ${\bf k}$, consistent with usual ferromagnetism theory, and the
spin-wave stiffness coefficient $c_s$ includes contributions from both the two
phases, implying the ""two-fluid"" feature of the system. $c_s$ can show a sharp
bend at the Bose-Einstein condensation temperature.",0405094v1
2017-03-16,All-Angle Collimation for Spin Waves,"We studied the effect of collimation for monochromatic beams of spin waves,
resulting from the refraction at the interface separating two magnetic
half-planes. The collimation was observed in broad range of the angles of
ncidence for homogenous Co and Py half-planes, due to significant intrinsic
anisotropy of spin wave propagation in these materials. The effect exists for
the sample saturated by in plane magnetic field tangential to the interface.
The collimation for all possible angles of incidence was found in the system
where the incident spin wave is refracted on the interface between homogeneous
and periodically patterned layers of YIG. The refraction was investigated by
the analysis of isofrequency dispersion contours of both pairs materials, i.e.,
uniform YIG/patterned YIG and Co/Py, which are calculated with the aid of the
plane wave method. Besides, the refraction in Co/Py system was studied using
micromagnetic simulations.",1703.05548v1
2019-10-25,Twisted magnon as a magnetic tweezer,"Wave fields with spiral phase dislocations carrying orbital angular momentum
(OAM) have been realized in many branches of physics, such as for photons,
sound waves, electron beams, and neutrons. However, the OAM states of magnons
(spin waves)$-$the building block of modern magnetism$-$and particularly their
implications have yet to be addressed. Here, we theoretically investigate the
twisted spin-wave generation and propagation in magnetic nanocylinders. The OAM
nature of magnons is uncovered by showing that the spin-wave eigenmode is also
the eigenstate of the OAM operator in the confined geometry. Inspired by
optical tweezers, we predict an exotic ""magnetic tweezer"" effect by showing
skyrmion gyrations under twisted magnons in exchange coupled
nanocylinder$|$nanodisk heterostructure, as a practical demonstration of
magnonic OAM to manipulate topological spin defects. Our study paves the way
for the emerging magnetic manipulations by harnessing the OAM degree of freedom
of magnons.",1910.11528v2
2020-07-30,Resonant subwavelength control of the phase of spin waves reflected from a ferromagnetic film edge,"Using frequency-domain finite element calculations cross-checked with
micromagnetic simulations, we demonstrate that the phase of spin waves
reflected from an interface between a permalloy film and a bilayer can be
controlled by changing dimensions of the bilayer. Treating the bilayer formed
by the permalloy film and a ferromagnetic stripe as a segment of a multi-mode
waveguide, we show that spin-wave Fabry-Perot resonances of one of its modes
are responsible for the high sensitivity of the phase of reflected waves to
stripe width and the stripe-film separation. Thus, the system is a unique
realization of a fully magnonic Gires-Tournois interferometer based on a
two-modes resonator, which can be treated as a magnonic counterpart of a
metasurface, since it enables manipulation of the phase of spin waves at
subwavelength distances. Knowledge gained from these calculations might be used
to design magnonic devices such as flat lenses or magnetic particle detectors.",2007.15226v5
2021-01-28,Néel domain wall as a tunable filter for optically excited magnetostatic waves,"We present a concept of a tunable optical excitation of spin waves and
filtering their spectra in a ferromagnetic film with 180$^{\circ}$ N\'eel
domain wall. We show by means of micromagnetic simulation that the fluence of
the femtosecond laser pulse and its position with respect to the domain wall
affect the frequencies of the excited spin waves, and the presence of the
domain wall plays crucial role in control of the spin waves' spectrum. The
predicted effects are understood by analyzing the changes of the spin waves'
dispersion under the impact of the laser pulse.",2101.11931v3
2022-11-10,High wave vector non-reciprocal spin wave beams,"We report unidirectional transmission of micron-wide spin waves beams in a 55
nm thin YIG. We downscaled a chiral coupling technique implementing Ni80Fe20
nanowires arrays with different widths and lattice spacing to study the
non-reciprocal transmission of exchange spin waves down to lambda = 80 nm. A
full spin wave spectroscopy analysis of these high wavevector coupled-modes
shows some difficulties to characterize their propagation properties, due to
both the non-monotonous field dependence of the coupling efficiency, and also
the inhomogeneous stray field from the nanowires.",2211.05514v2
2023-04-11,Sensitive detection of millimeter wave electric field by driving trapped surface-state electrons,"Sensitive detection of electromagnetic wave electric field plays an important
role for electromagnetic communication and sensing. Here, we propose a quantum
sensor to sensitively detect the electric field of the millimeter (mm) wave.
The quantum sensor consists of many surface-state electrons trapped
individually on liquid helium by a scalable electrode-network at the bottom of
the helium film. On such a chip, each of the trapped electrons can be
manipulated by the biased dc-current to deliver the strong spin-orbit
couplings. The mm wave signal to be detected is applied to non-dispersively
drive the orbital states of the trapped electrons, just resulting in the Stark
shifts of the dressed spin-orbital states. As a consequence, the electric field
of the applied mm wave could be detected sensitively by using the spin-echo
interferometry of the long-lived spin states of the electrons trapped on liquid
helium. The reasonable accuracy of the detection and also the feasibility of
the proposal are discussed.",2304.05154v1
2023-06-09,Ordering in SU(4)-symmetric model of AA bilayer graphene,"We examine possible ordered states of AA stacked bilayer graphene arising due
to electron-electron coupling. We show that under certain assumptions the
Hamiltonian of the system possesses an SU(4) symmetry. The multicomponent order
parameter is described by a $4\times4$ matrix $\hat{Q}$, for which a mean-field
self-consistency equation is derived. This equation allows Hermitian and
non-Hermitian solutions. Hermitian solutions can be grouped into three
topologically-distinct classes. First class corresponds to the charge density
wave. Second class includes spin density wave, valley density wave, and
spin-valley density wave. An ordered state in the third class is a combination
of all the aforementioned density-wave types. For anti-Hermitian $\hat{Q}$ the
ordered states are characterized by spontaneous inter-layer loop currents
flowing in the bilayer. Depending on the topological class of the solution
these currents can carry charge, spin, valley, and spin-valley quanta. We also
discuss the special case when matrix $\hat{Q}$ is not Hermitian and not
anti-Hermitian. Utility and weak points of the proposed SU(4)-based
classification scheme of the ordered states are analyzed.",2306.05796v2
2023-06-28,Chern insulating state with double-$Q$ ordering wave vectors at the Brillouin zone boundary,"Magnetic multiple-$Q$ states consisting of multiple spin density waves are a
source of unconventional topological spin textures, such as skyrmion and
hedgehog. We theoretically investigate a topologically nontrivial double-$Q$
state with a net spin scalar chirality on a two-dimensional square lattice. We
find that a double-$Q$ spiral superposition of the ordering wave vectors
located at the Brillouin zone boundary gives rise to unconventional noncoplanar
spin textures distinct from the skyrmion crystal. We show that such a
double-$Q$ state is stabilized by the interplay among the easy-axis anisotropic
interaction, high-harmonic wave-vector interaction, and external magnetic
field. Furthermore, the obtained double-$Q$ state becomes a Chern insulating
state with a quantum Hall conductivity when the Fermi level is located in the
band gaps. Our present results provide another platform to realize topological
magnetic states other than skyrmion crystals by focusing on the symmetry of
constituent ordering wave vectors in momentum space.",2306.15854v1
2008-04-17,"A study of the quantum classical crossover in the spin dynamics of the 2D S=5/2 antiferromagnet Rb2MnF4: neutron scattering, computer simulations, and analytic theories","We report comprehensive inelastic neutron scattering measurements of the
magnetic excitations in the 2D spin-5/2 Heisenberg antiferromagnet Rb2MnF4 as a
function of temperature from deep in the Neel ordered phase up to paramagnetic,
0.13 < kBT/4JS < 1.4. Well defined spin-waves are found for wave-vectors larger
than the inverse correlation length $\eta^{-1}$ for temperatures up to near the
Curie-Weiss temperature, $\Theta_{CW}$. For wave-vectors smaller than
$\eta^{-1}$, relaxational dynamics occurs. The observed renormalization of
spin-wave energies, and evolution of excitation line-shapes, with increasing
temperature are quantitatively compared with finite-temperature spin-wave
theory, and computer simulations for classical spins. Random phase
approximation calculations provide a good description of the low-temperature
renormalisation of spin-waves. In contrast, lifetime broadening calculated
using the first Born approximation shows, at best, modest agreement around the
zone boundary at low temperatures. Classical dynamics simulations using an
appropriate quantum-classical correspondence were found to provide a good
description of the intermediate- and high-temperature regimes over all
wave-vector and energy scales, and the crossover from quantum to classical
dynamics observed around $\Theta_{CW}/S$, where the spin S=5/2. A
characterisation of the data over the whole wave-vector/energy/temperature
parameter space is given. In this, $T^2$ behaviour is found to dominate the
wave-vector and temperature dependence of the line widths over a large
parameter range, and no evidence of hydrodynamic behaviour or dynamical scaling
behaviour found within the accuracy of the data sets.",0804.2901v2
2001-01-05,"Comment on ""Gravity Waves, Chaos, and Spinning Compact Binaries""","In this comment, I argue that chaotic effects in binary black hole inspiral
will not strongly impact the detection of gravitational waves from such
systems.",0101024v1
2009-09-23,Wave-particle duality and the Hamilton action,"The Hamilton-Jacobi equation of relativistic quantum mechanics is revisited.
The equation is shown to permit solutions in the form of breathers
(oscillating/spinning solitons), displaying simultaneous particle-like and
wave-like behaviour.",0909.4195v1
2014-10-21,Electromagnetic space-time crystals. III. Dispersion relations for partial solutions,"Partial solutions of the Dirac equation describing an electron motion in
electromagnetic crystals created by plane waves with linear and circular
polarizations are treated. It is shown that the electromagnetic crystal formed
by circularly polarized waves possesses the spin birefringence.",1410.5536v1
2017-07-01,Intrinsic translational symmetry breaking in a doped Mott insulator,"A central issue of Mott physics, with symmetries being fully retained in the
spin background, concerns the charge excitation. In a two-leg spin ladder with
spin gap, an injected hole can exhibit either a Bloch wave or a density wave by
tuning the ladder anisotropy through a `quantum critical point' (QCP). The
nature of such a QCP has been a subject of recent studies by density matrix
renormalization group (DMRG). In this paper, we reexamine the ground state of
the one doped hole, and show that a two-component structure is present in the
density wave regime in contrast to the single component in the Bloch wave
regime. In the former, the density wave itself is still contributed by a
standing-wave-like component characterized by a quasiparticle spectral weight
$Z$ in a finite-size system. But there is an additional charge incoherent
component emerging, which intrinsically breaks the translational symmetry
associated with the density wave. The partial momentum is carried away by
neutral spin excitations. Such an incoherent part does not manifest in the
single-particle spectral function, directly probed by the angle-resolved
photoemission spectroscopy (ARPES) measurement, however it is demonstrated in
the momentum distribution function. The Landau's one-to-one correspondence
hypothesis for a Fermi liquid breaks down here. The microscopic origin of this
density wave state as an intrinsic manifestation of the doped Mott physics will
be also discussed.",1707.00068v2
2005-01-05,Post-Newtonian accurate parametric solution to the dynamics of spinning compact binaries in eccentric orbits: The leading order spin-orbit interaction,"We derive Keplerian-type parametrization for the solution of post-Newtonian
(PN) accurate conservative dynamics of spinning compact binaries moving in
eccentric orbits. The PN accurate dynamics that we consider consists of the
third post-Newtonian accurate conservative orbital dynamics influenced by the
leading order spin effects, namely the leading order spin-orbit interactions.
The orbital elements of the representation are explicitly given in terms of the
conserved orbital energy, angular momentum and a quantity that characterizes
the leading order spin-orbit interactions in Arnowitt, Deser, and Misner-type
coordinates. Our parametric solution is applicable in the following two
distinct cases: (i) the binary consists of equal mass compact objects, having
two arbitrary spins, and (ii) the binary consists of compact objects of
arbitrary mass, where only one of them is spinning with an arbitrary spin. As
an application of our parametrization, we present gravitational wave
polarizations, whose amplitudes are restricted to the leading quadrupolar
order, suitable to describe gravitational radiation from spinning compact
binaries moving in eccentric orbits. The present parametrization will be
required to construct `ready to use' reference templates for gravitational
waves from spinning compact binaries in inspiralling eccentric orbits. Our
parametric solution for the post-Newtonian accurate conservative dynamics of
spinning compact binaries clearly indicates, for the cases considered, the
absence of chaos in these systems. Finally, we note that our parametrization
provides the first step in deriving a fully second post-Newtonian accurate
`timing formula', that may be useful for the radio observations of relativistic
binary pulsars like J0737-3039.",0501011v1
2008-04-02,Spin-stiffness of anisotropic Heisenberg model on square lattice and possible mechanism for pinning of the electronic liquid crystal direction in YBCO,"Using series expansions and spin-wave theory we calculate the spin-stiffness
anisotropy $\rho_{sx}/\rho_{sy}$ in Heisenberg models on the square lattice
with anisotropic couplings $J_x,J_y$. We find that for the weakly anisotropic
spin-half model ($J_x\approx J_y$), $\rho_{sx}/\rho_{sy}$ deviates
substantially from the naive estimate $\rho_{sx}/\rho_{sy} \approx J_x/J_y$. We
argue that this deviation can be responsible for pinning the electronic liquid
crystal direction, a novel effect recently discovered in YBCO. For
completeness, we also study the spin-stiffness for arbitrary anisotropy
$J_x/J_y$ for spin-half and spin-one models. In the limit of $J_y/J_x\to 0$,
when the model reduces to weakly coupled chains, the two show dramatically
different behavior. In the spin-one model, the stiffness along the chains goes
to zero, implying the onset of Haldane-gap phase, whereas for spin-half the
stiffness along the chains increases monotonically from a value of $0.18 J_x$
for $J_y/J_x=1$ towards $0.25 J_x$ for $J_y/J_x\to 0$. Spin-wave theory is
extremely accurate for spin-one but breaks down for spin-half presumably due to
the onset of topological terms.",0804.0400v1
2008-08-12,Renormalized 2PN spin contributions to the accumulated orbital phase for LISA sources,"We give here a new third post-Newtonisn (3PN) spin-spin contribution (in the
PN parameter $\epsilon $) to the accumulated orbital phase of a compact binary,
arising from the spin-orbit precessional motion of the spins. In the equal mass
case this contribution vanishes, but LISA sources of merging supermassive
binary black holes have typically a mass ratio of 1:10. For such non-equal
masses this 3PN correction is periodic in time, with period approximately
$\epsilon ^{-1}$ times larger than the period of gravitational waves. We derive
a renormalized and simpler expression of the spin-spin coefficient at 2PN, as
an average over the time-scale of this period of the combined 2PN and 3PN
contribution. We also find that for LISA sources the quadrupole-monopole
contribution to the phase dominates over the spin-spin contribution, while the
self-spin contribution is negligible even for the dominant spin. Finally we
define a renormalized total spin coefficient $\bar{\sigma}$ to be employed in
the search for gravitational waves emitted by LISA sources.",0808.1704v2
2014-03-01,Measuring the spin of black holes in binary systems using gravitational waves,"Compact binary coalescences are the most promising sources of gravitational
waves (GWs) for ground based detectors. Binary systems containing one or two
spinning black holes are particularly interesting due to spin-orbit (and
eventual spin-spin) interactions, and the opportunity of measuring spins
directly through GW observations. In this letter we analyze simulated signals
emitted by spinning binaries with several values of masses, spins, orientation,
and signal-to-noise ratio. We find that spin magnitudes and tilt angles can be
estimated to accuracy of a few percent for neutron star--black hole systems and
$\sim$ 5-30% for black hole binaries. In contrast, the difference in the
azimuth angles of the spins, which may be used to check if spins are locked
into resonant configurations, cannot be constrained. We observe that the best
performances are obtained when the line of sight is perpendicular to the
system's total angular momentum, and that a sudden change of behavior occurs
when a system is observed from angles such that the plane of the orbit can be
seen both from above and below during the time the signal is in band. This
study suggests that the measurement of black hole spin by means of GWs can be
as precise as what can be obtained from X-ray binaries.",1403.0129v2
2019-06-12,Binary neutron star mergers: Effects of spin and post-merger dynamics,"Spin can have significant effects on the electromagnetic transients
accompanying binary neutron star mergers. The measurement of spin can provide
important information about binary formation channels. In the absence of a
strong neutron star spin prior, the degeneracy of spin with other parameters
leads to significant uncertainties in their estimation, in particular limiting
the power of gravitational waves to place tight constraints on the nuclear
equation of state. Thus detailed studies of highly spinning neutron star
mergers are essential to understand all aspects of multimessenger observation
of such events. We perform a systematic investigation of the impact of neutron
star spin---considering dimensionless spin values up to $a_{\rm NS}=0.33$---on
the merger of equal mass, quasicircular binary neutron stars using fully
general-relativistic simulations. We find that the peak frequency of the
post-merger gravitational wave signal is only weakly influenced by the neutron
star spin, with cases where the spin is aligned (antialigned) with the orbital
angular momentum giving slightly lower (higher) values compared to the
irrotational case. We find that the one-arm instability arises in a number of
cases, with some dependence on spin. Spin has a pronounced impact on the mass,
velocity, and angular distribution of the dynamical ejecta, and the mass of the
disk that remains outside the merger remnant. We discuss the implications of
these findings on anticipated electromagnetic signals, and on constraints that
have been placed on the equation of state based on multimessenger observations
of GW170817.",1906.05288v2
2016-03-08,Searching for Gravitational Waves from Compact Binaries with Precessing Spins,"Current searches for gravitational waves from compact-object binaries with
the LIGO and Virgo observatories employ waveform models with spins aligned (or
anti-aligned) with the orbital angular momentum. Here, we derive a new
statistic to search for compact objects carrying generic (precessing) spins.
Applying this statistic, we construct banks of both aligned- and generic-spin
templates for binary black holes and neutron-star--black-hole binaries, and
compare the effectualness of these banks towards simulated populations of
generic-spin systems. We then use these banks in a pipeline analysis of
Gaussian noise to measure the increase in background incurred by using generic-
instead of aligned-spin banks. Although the generic-spin banks have a factor of
ten to twenty more templates than the aligned-spin banks, we find an overall
improvement in signal recovery at fixed false-alarm rate for systems with
high-mass ratio and highly precessing spins ---up to 60\% for
neutron-star--black-hole mergers. This gain in sensitivity comes at a small
loss of sensitivity ($\lesssim$4\%) for systems that are already well-covered
by aligned-spin templates. Since the observation of even a single binary merger
with misalinged spins could provide unique astrophysical insights into the
formation of these sources, we recommend that the method described here be
developed further to mount a viable search for generic-spin binary mergers in
LIGO/Virgo data.",1603.02444v2
2017-06-23,Ferroic collinear multilayer magnon spin valve,"Information transport and processing by pure magnonic spin currents in
insulators is a promising alternative to conventional charge-current driven
spintronic devices. The absence of Joule heating as well as the reduced spin
wave damping in insulating ferromagnets has been suggested to enable the
implementation of efficient logic devices. After the proof of concept for a
logic majority gate based on the superposition of spin waves has been
successfully demonstrated, further components are required to perform complex
logic operations. A key component is a switch that corresponds to a
conventional magnetoresistive spin valve. Here, we report on magnetization
orientation dependent spin signal detection in collinear magnetic multilayers
with spin transport by magnonic spin currents. We find in Y3Fe5O12|CoO|Co
tri-layers that the detected spin signal depends on the relative alignment of
Y3Fe5O12 and Co. This demonstrates a spin valve behavior with an effect
amplitude of 120% in our systems. We demonstrate the reliability of the effect
and investigate the origin by both temperature and power dependent
measurements, showing that spin rectification effects and a magnetic layer
alignment dependent spin transport effect result in the measured signal.",1706.07592v1
2022-04-22,Inducing spin-order with an impurity: phase diagram of the magnetic Bose polaron,"We investigate the formation of magnetic Bose polaron, an impurity atom
dressed by spin-wave excitations, in a one-dimensional spinor Bose gas. In
terms of an effective potential model the impurity is strongly confined by the
host excitations which can even overcome the impurity-medium repulsion leading
to a self-localized quasi-particle state. The phase diagram of the attractive
and self-bound repulsive magnetic polaron, repulsive non-magnetic (Fr{\""
o}hlich-type) polaron and impurity-medium phase-separation regimes is explored
with respect to the Rabi-coupling between the spin components, spin-spin
interactions and impurity-medium coupling. The residue of such magnetic
polarons decreases substantially in both strong attractive and repulsive
branches with strong impurity-spin interactions, illustrating significant
dressing of the impurity. The impurity can be used to probe and maneuver the
spin polarization of the magnetic medium while suppressing ferromagnetic
spin-spin correlations. It is shown that mean-field theory fails as the spinor
gas approaches immiscibility since the generated spin-wave excitations are
prominent. Our findings illustrate that impurities can be utilized to generate
controllable spin-spin correlations and magnetic polaron states which can be
realized with current cold atom setups.",2204.10960v1
2022-08-04,Numerical-relativity surrogate modeling with nearly extremal black-hole spins,"Numerical relativity (NR) simulations of binary black hole (BBH) systems
provide the most accurate gravitational wave predictions, but at a high
computational cost -- especially when the black holes have nearly extremal
spins (i.e. spins near the theoretical upper limit) or very unequal masses.
Recently, the technique of Reduced Order Modeling (ROM) has enabled the
construction of surrogate models trained on an existing set of NR waveforms.
Surrogate models enable the rapid computation of the gravitational waves
emitted by BBHs. Typically these models are used for interpolation to compute
gravitational waveforms for BBHs with mass ratios and spins within the bounds
of the training set. Because simulations with nearly extremal spins are so
technically challenging, surrogate models almost always rely on training sets
with only moderate spins. In this paper, we explore how well surrogate models
can extrapolate to nearly extremal spins when the training set only includes
moderate spins. For simplicity, we focus on one-dimensional surrogate models
trained on NR simulations of BBHs with equal masses and equal, aligned spins.
We assess the performance of the surrogate models at higher spin magnitudes by
calculating the mismatches between extrapolated surrogate model waveforms and
NR waveforms, by calculating the differences between extrapolated and NR
measurements of the remnant black-hole mass, and by testing how the surrogate
model improves as the training set extends to higher spins. We find that while
extrapolation in this one-dimensional case is viable for current detector
sensitivities, surrogate models for next-generation detectors should use
training sets that extend to nearly extremal spins.",2208.02927v1
1999-10-21,Effective action and collective modes in quasi-one-dimensional spin-density-wave systems,"We derive the effective action describing the long-wavelength low-energy
collective modes of quasi-one-dimensional spin-density-wave (SDW) systems,
starting from the Hubbard model within weak coupling approximation. The
effective action for the spin-wave mode corresponds to an anisotropic
non-linear sigma model together with a Berry phase term. We compute the spin
stiffness and the spin-wave velocity. We also obtain the effective action for
the sliding mode (phason) taking into account the density fluctuations from the
outset and in presence of a weak external electromagnetic field. This leads to
coupled equations for the phase of the SDW condensate and the charge density
fluctuations. We also calculate the conductivity and the density-density
correlation function.",9910343v2
2005-02-09,Weak ferromagnetism and spiral spin structures in honeycomb Hubbard planes,"Within the Hartree Fock- RPA analysis, we derive the spin wave spectrum for
the weak ferromagnetic phase of the Hubbard model on the honeycomb lattice.
Assuming a uniform magnetization, the polar (optical) and acoustic branches of
the spin wave excitations are determined. The bipartite lattice geometry
produces a q-dependent phase difference between the spin wave amplitudes on the
two sub-lattices. We also find an instability of the uniform weakly magnetized
configuration to a weak antiferromagnetic spiraling spin structure, in the
lattice plane, with wave vector Q along the Gamma-K direction, for electron
densities n>0.6. We discuss the effect of diagonal disorder on both the
creation of electron bound states, enhancement of the density of states, and
the possible relevance of these effects to disorder induced ferromagnetism, as
observed in proton irradiated graphite.",0502249v2
2006-01-20,Spin Structure Factor of the Frustrated Quantum Magnet Cs_2CuCl_4,"The ground state properties and neutron structure factor for the
two-dimensional antiferromagnet on the triangular lattice, with uni-directional
anisotropy in the nearest-neighbor exchange couplings and a weak
Dzyaloshinskii-Moriya (DM) interaction, are studied. This Hamiltonian has been
used to interpret neutron scattering measurements on the spin 1/2 spiral
spin-density-wave system, Cs_2CuCl_4, [R. Coldea, et al., Phys. Rev. B 68,
134424 (2003)]. Calculations are performed using a 1/S expansion, taking into
account interactions between spin-waves. The ground state energy, the shift of
the ordering wave-vector, Q, and the local magnetization are all calculated to
order 1/S^2. The neutron structure factor, obtained using anharmonic spin-wave
Green's functions to order 1/S, is shown to be in reasonable agreement with
published neutron data, provided that slightly different parameters are used
for the exchange and DM interactions than those inferred from measurements in
high magnetic field.",0601486v1
2006-09-04,Magnetization reversal and nonexponential relaxation via instabilities of internal spin waves in nanomagnets,"A magnetic particle with atomic spins ordered in an unstable direction is an
example of a false vacuum that decays via excitation of internal spin waves.
Coupled evolution of the particle's magnetization (or the vacuum state) and
spin waves, considered in the time-dependent vacuum frame, leads to a peculiar
relaxation that is very fast at the beginning but slows down to a
nonexponential long tail at the end. The two main scenarios are linear and
exponential spin-wave instabilities. For the former, the longitudinal and
transverse relaxation rates have been obtained analytically. Numerical
simulations show that the particle's magnetization strongly decreases in the
middle of reversal and then recovers.",0609074v2
2007-09-04,Soft Spin Wave Near nu=1: Evidence for a Magnetic Instability in Skyrmion Systems,"The ground state of the two dimensional electron gas near $\nu$=1 is
investigated by inelastic light scattering measurements carried down to very
low temperatures. Away from $\nu$=1, the ferromagnetic spin wave collapses and
a new low-energy spin wave emerges below the Zeeman gap. The emergent spin wave
shows soft behavior as its energy increases with temperature and reaches the
Zeeman energy for temperatures above 2 K. The observed softening indicates an
instability of the two dimensional electron gas towards a magnetic order that
breaks spin rotational symmetry. We discuss our findings in light of the
possible existence of a Skyrme crystal.",0709.0541v2
2009-03-24,Nematicity as a route to a magnetic field-induced spin density wave order; application to the high temperature cuprates,"The electronic nematic order characterized by broken rotational symmetry has
been suggested to play an important role in the phase diagram of the high
temperature cuprates. We study the interplay between the electronic nematic
order and a spin density wave order in the presence of a magnetic field. We
show that a cooperation of the nematicity and the magnetic field induces a
finite coupling between the spin density wave and spin-triplet staggered flux
orders. As a consequence of such a coupling, the magnon gap decreases as the
magnetic field increases, and it eventually condenses beyond a critical
magnetic field leading to a field-induced spin density wave order. Both
commensurate and incommensurate orders are studied, and the experimental
implications of our findings are discussed.",0903.3993v2
2009-10-03,Non-collinear spin-spiral phase for the uniform electron gas within Reduced-Density-Matrix-Functional Theory,"The non-collinear spin-spiral density wave of the uniform electron gas is
studied in the framework of Reduced-Density-Matrix-Functional Theory. For the
Hartree-Fock approximation, which can be obtained as a limiting case of
Reduced-Density-Matrix-Functional Theory, Overhauser showed a long time ago
that the paramagnetic state of the electron gas is unstable with respect to the
formation of charge or spin density waves. Here we not only present a detailed
numerical investigation of the spin-spiral density wave in the Hartree-Fock
approximation but also investigate the effects of correlations on the
spin-spiral density wave instability by means of a recently proposed
density-matrix functional.",0910.0534v1
2010-07-19,Spin waves in zigzag graphene nanoribbons and the stability of edge ferromagnetism,"We study the low energy spin excitations of zigzag graphene nanoribbons of
varying width. We find their energy dispersion at small wave vector to be
dominated by antiferromagnetic correlations between the ribbon's edges, in
accrodance with previous calculations. We point out that spin wave lifetimes
are very long due to the semi-conducting nature of the electrically neutral
nanoribbons. However, application of very modest gate voltages cause a
discontinuous transition to a regime of finite spin wave lifetime. By further
increasing doping the ferromagnetic alignments along the edge become unstable
against transverse spin fluctuations. This makes the experimental detection of
ferromagnetism is this class of systems very delicate, and poses a difficult
challenge to the possible uses of these nanoribbons as basis for spintronic
devices.",1007.3285v2
2011-02-17,A-phase origin in B20 helimagnets,"A-phase origin in cubic helimagnets ($M n S i,F e G e$ etc) is explained. It
is shown that its upper bound is a result of the spin-wave instability at
$H_\perp>\sqrt{8/3}\Delta=H_{A2}$ where $H_\perp$ are the magnetic field
perpendicular to the helix axis $\m k$ and $\Delta$ the spin-wave gap
respectively. The last appears due to the spin-wave interaction if one takes
into account that the Dzyaloshinskii-Moriya interaction acts between different
spins. The infra-red divergences (IRD) in the 1/S series for the magnetic
energy at $H_\perp\to H_{A2}$ are responsible for the lower A-phase boundary
$H_{A1}$. It is shown that the A-phase exists at all $T<T_C$ but if $T\ll T_C$
it is very narrow and can not be observed. However in the critical region just
below $T_C$ its width increasing strongly. Preliminary estimations demonstrate
semi-quantitative agreement with the existing experimental data.
  The existence of the spin-wave gap is a crucial point of our consideration.
In Appendix A we present its derivation in more transparent form than in
previous publication.",1102.3524v1
2011-03-09,Magnetization and magnon excitation energies of the magnetic semiconductors EuTe and EuO on the basis of the renormalized spin wave theory,"We present analytic expressions for the temperature dependent magnetization
and magnon dispersion relation of the antiferromagnetic (AFM) EuTe and the
ferromagnetic (FM) EuO. These bulk semiconductors represent concentrated spin
systems for which the interaction between magnons has to be taken into account.
We do this using the renormalized spin wave theory. A higher order Green's
function according to Tjablikov is used for their description. As a result, we
obtain a modified Bloch- T3/2 law, for low temperatures and high magnetic
fields. A full analytic expression is given for the sublattice magnetization of
the AFM EuTe (B0=0), with a N\'eel temperature of TN = 9.81 K. The
magnetization curves {\sigma}N(T) of EuO (for 0 \leq T \leq 0.68TC) and
{\sigma}R(T) (for 0.82TC < T < TC) agree well with experiment. The spin wave
excitation energy perfectly matches experimental data from inelastic neutron
scattering. In the case of EuTe the magnon excitation energies exhibit a
characteristic maximum. For q = 0, an energy gap Eg occurs in the spin wave
spectrum, a consequence of the AFM exchange interaction J2(T). Such energy gaps
exist in the spectrum of magnon excitation energies only in systems with AFM
interactions.",1103.1831v1
2011-05-31,Topological Entanglement Entropy of Z2 Spin liquids and Lattice Laughlin states,"We study entanglement properties of candidate wave-functions for SU(2)
symmetric gapped spin liquids and Laughlin states. These wave-functions are
obtained by the Gutzwiller projection technique. Using Topological Entanglement
Entropy \gamma\ as a tool, we establish topological order in chiral spin liquid
and Z2 spin liquid wave-functions, as well as a lattice version of the Laughlin
state. Our results agree very well with the field theoretic result \gamma =log
D where D is the total quantum dimension of the phase. All calculations are
done using a Monte Carlo technique on a 12 times 12 lattice enabling us to
extract \gamma\ with small finite size effects. For a chiral spin liquid
wave-function, the calculated value is within 4% of the ideal value. We also
find good agreement for a lattice version of the Laughlin \nu =1/3 phase with
the expected \gamma=log \sqrt{3}.",1106.0015v3
2011-07-11,Coherent manipulation of spin wave vector for polarization of photons in an atomic ensemble,"We experimentally demonstrate the manipulation of two-orthogonal components
of a spin wave in an atomic ensemble. Based on Raman two-photon transition and
Larmor spin precession induced by magnetic field pulses, the coherent rotations
between the two components of the spin wave is controllably achieved.
Successively, the two manipulated spin-wave components are mapped into two
orthogonal polarized optical emissions, respectively. By measuring Ramsey
fringes of the retrieved optical signals, the \pi/2-pulse fidelity of ~96% is
obtained. The presented manipulation scheme can be used to build an arbitrary
rotation for qubit operations in quantum information processing based on atomic
ensembles.",1107.1914v1
2013-04-22,Magnetic anisotropic energy gap and low energy spin wave excitation in antiferromagnetic block phase of K2Fe4Se5,"Neutron scattering experiments were performed to investigate magnetic order
and magnetic excitations in ternary iron chalcogenide K2Fe4Se5. The formation
of a superlattice structure below 580 K together with the decoupling between
the Fe-vacancy order-disorder transition and the antiferromagnetic order
transition appears to be a common feature in the A2Fe4Se5 family. The study of
spin dynamics of K2Fe4Se5 reveals two distinct energy gaps at the magnetic
Brillouin zone center, which indicates the presence of magnetic anisotropy and
the decrease of local symmetry due to electronic and orbital anisotropy. The
low-energy spin wave excitations of K2Fe4Se5 can be properly described by
linear spin wave theory within a Heisenberg model. Compared to iron pnictides,
K2Fe4Se5 exhibits a more two-dimensional magnetism as characterized by large
differences not only between out-of-plane and in-plane spin wave velocities,
but also between out-of-plane and in-plane exchange interactions.",1304.5950v1
2013-08-29,Control of Propagating Spin Waves via Spin Transfer Torque in a Metallic Bilayer Waveguide,"We investigate the effect of a direct current on propagating spin waves in a
CoFeB/Ta bilayer structure. Using the micro-Brillouin light scattering
technique, we observe that the spin wave amplitude may be attenuated or
amplified depending on the direction of the current and the applied magnetic
field. Our work suggests an effective approach for electrically controlling the
propagation of spin waves in a magnetic waveguide and may be useful in a number
of applications such as phase locked nano-oscillators and hybrid information
processing devices.",1308.6357v2
2013-11-21,Wave patterns generated by a flow of two-component Bose-Einstein condensate with spin-orbit interaction past a localized obstacle,"It is shown that spin-orbit interaction leads to drastic changes in wave
patterns generated by a flow of two-component Bose-Einstein condensate (BEC)
past an obstacle. The combined Rashba and Dresselhaus spin-orbit interaction
affects in different ways two types of excitations---density and polarization
waves---which can propagate in a two-component BEC. We show that the density
and polarization ""ship wave"" patterns rotate in opposite directions around the
axis located at the obstacle position and the angle of rotation depends on the
strength of spin-orbit interaction. This rotation is accompanied by narrowing
of the Mach cone. The influence of spin-orbit coupling on density solitons and
polarization breathers is studied numerically.",1311.5387v1
2013-12-19,Gravitational waves from spinning compact object binaries: New post-Newtonian results,"We report on recent results obtained in the post-Newtonian framework for the
modelling of the gravitational waves emitted by binary systems of spinning
compact objects (black holes and/or neutron stars). These new results are
obtained at the spin-orbit (linear-in-spin) level and solving Einstein's field
equations iteratively in harmonic coordinates as well as the multipolar
post-Newtonian formalism. The dynamics of the binary was tackled at the
next-to-next-to-leading order, corresponding to the 3.5 post-Newtonian (PN)
order for maximally spinning objects, and the result is found to be consistent
with a previously obtained reduced Hamiltonian in the ADM approach. The
corresponding contribution to the energy flux emitted by the binary was
obtained at the 3.5PN order, as well as the next-to-leading 4PN tail
contribution to this flux, an imprint of the non-linearity in the propagation
of the wave. These new terms can be used to build more accurate PN templates
for the next generation of gravitational wave detectors. We give an
illustrative estimate of the quantitative relevance of the new terms in the
orbital phasing of the binary.",1312.5375v1
2014-02-25,Linear spin wave theory for single-Q incommensurate magnetic structures,"Linear spin wave theory provides the leading term in the calculation of the
excitation spectra of long-range ordered magnetic systems as a function of
$1/\sqrt{S}$. This term is acquired using the Holstein-Primakoff approximation
of the spin operator and valid for small $\delta S$ fluctuations of the ordered
moment. We propose an algorithm that allows magnetic ground states with general
moment directions and single-Q incommensurate ordering wave vector using a
local coordinate transformation for every spin and a rotating coordinate
transformation for the incommensurability. Finally we show, how our model can
determine the spin wave spectrum of the magnetic C-site langasites with
incommensurate order.",1402.6069v4
2015-04-01,Direct observation and imaging of a spin-wave soliton with $p-$like symmetry,"The prediction and realization of magnetic excitations driven by electrical
currents via the spin transfer torque effect, enables novel magnetic
nano-devices where spin-waves can be used to process and store information. The
functional control of such devices relies on understanding the properties of
non-linear spin-wave excitations. It has been demonstrated that spin waves can
show both an itinerant character, but also appear as localized solitons. So
far, it was assumed that localized solitons have essentially cylindrical,
$s-$like symmetry. Using a newly developed high-sensitivity time-resolved
magnetic x-ray microscopy, we instead observe the emergence of a novel
localized soliton excitation with a nodal line, i.e. with $p-$like symmetry.
Micromagnetic simulations identify the physical mechanism that controls the
transition from $s-$ to $p-$like solitons. Our results suggest a potential new
pathway to design artificial atoms with tunable dynamical states using
nanoscale magnetic devices.",1504.00144v1
2015-05-07,Flat-band ferromagnetism in a topological Hubbard model,"We study the flat-band ferromagnetic phase of a topological Hubbard model
within a bosonization formalism and, in particular, determine the spin-wave
excitation spectrum. We consider a square lattice Hubbard model at 1/4-filling
whose free-electron term is the \pi-flux model with topologically nontrivial
and nearly flat energy bands. The electron spin is introduced such that the
model either explicitly breaks time-reversal symmetry (correlated flat-band
Chern insulator) or is invariant under time-reversal symmetry (correlated
flat-band $Z_2$ topological insulator). We generalize for flat-band Chern and
topological insulators the bosonization formalism [Phys. Rev. B 71, 045339
(2005)] previously developed for the two-dimensional electron gas in a uniform
and perpendicular magnetic field at filling factor \nu=1. We show that, within
the bosonization scheme, the topological Hubbard model is mapped into an
effective interacting boson model. We consider the boson model at the harmonic
approximation and show that, for the correlated Chern insulator, the spin-wave
excitation spectrum is gapless while, for the correlated topological insulator,
gapped. We briefly comment on the possible effects of the boson-boson
(spin-wave--spin-wave) coupling.",1505.01685v1
2015-08-09,Spin contamination and noncollinearity in general complex Hartree-Fock wave functions,"An expression for the square of the spin operator expectation value,
\textless{} S^2\textgreater{}, is obtained for a general complex Hartree-Fock
(GCHF) wave function and decomposed into four contributions: The main one whose
expression is formally identical to the restricted (open-shell) Hartree-Fock
expression. A spin contamination one formally analogous to that found for spin
unrestricted Hartree-Fock wave functions. A noncollinearity contribution
related to the fact that the wave function is not an eigenfunction of the
spin-S\_z operator. A perpendicularity contribution related to the fact that
the spin density is not constrained to be zero in the xy-plane. All these
contributions are evaluated and compared for the H\_2O^+ system. The
optimization of the collinearity axis is also considered.",1508.02058v2
2015-12-16,"On the existence conditions of surface spin wave modes in (Ga,Mn)As thin films","Spin-wave resonance (SWR) is a newly emerged method for studying surface
magnetic anisotropy and surface spin-wave modes (SSWMs) in (Ga,Mn)As thin
films. The existence of SSWMs in (Ga,Mn)As thin films has recently been
reported in the literature; SSWMs have been observed in the in-plane
configuration (with variable azimuth angle $\phi_M$ between the in-plane
magnetization of the film and the surface [100] crystal axis), in the azimuth
angle range between two in-plane critical angles $\phi_{c1}$ and $\phi_{c2}$.
We show here that cubic surface anisotropy is an essential factor determining
the existence conditions of the above-mentioned SSWMs: conditions favorable for
the occurrence of surface spin-wave modes in a (Ga,Mn)As thin film in the
in-plane configuration are fulfilled for those azimuth orientations of the
magnetization of the sample that lie around the hard axes of cubic magnetic
anisotropy. This implies that a hard cubic anisotropy axis can be regarded in
(Ga,Mn)As thin films as an easy axis for surface spin pinning.",1512.05140v1
2017-12-09,Magnonic waveguide based on exchange-spring magnetic structure,"We propose to use a soft/hard exchange-spring coupling bilayer magnetic
structure to introduce a narrow channel for spin-wave propagation. We show by
micromagnetic simulations that broad-band Damon-Eshbach geometry spin waves can
be strongly localized into the channel and propagate effectively with a proper
high group velocity. The beamwidth of the bound mode spin waves is almost
independent from the frequency and is smaller than 24nm. For a low-frequency
excitation, we further investigate the appearance of two other spin beams in
the lateral of the channel. In contrast to a domain wall, the channel formed by
exchange-spring coupling can be easier to realize in experimental scenarios and
holds stronger immunity to surroundings. This work is expected to open new
possibilities for energy-efficient spin-wave guiding as well as to help shape
the field of beam magnonics.",1712.03392v1
2018-07-30,Topological spin excitations in honeycomb ferromagnet CrI$_3$,"In two dimensional honeycomb ferromagnets, bosonic magnon quasiparticles
(spin waves) may either behave as massless Dirac fermions or form topologically
protected edge states. The key ingredient defining their nature is the
next-nearest neighbor Dzyaloshinskii-Moriya (DM) interaction that breaks the
inversion symmetry of the lattice and discriminates chirality of the associated
spin-wave excitations. Using inelastic neutron scattering, we find that spin
waves of the insulating honeycomb ferromagnet CrI$_3$ ($T_C=61$ K) have two
distinctive bands of ferromagnetic excitations separated by a $\sim$4 meV gap
at the Dirac points. These results can only be understood by considering a
Heisenberg Hamiltonian with DM interaction, thus providing experimental
evidence that spin waves in CrI$_3$ can have robust topological properties
useful for dissipationless spintronic applications.",1807.11452v3
2018-02-26,Unusual spin-wave dynamics in core-shell magnetic nanodisks,"We investigated the spin dynamics of a vortex state in a core-shell magnetic
nanodisk driven by an oscillating field applied perpendicular to the disk plane
by means of micromagnetic simulations. The nanodisk comprises a Py (Fe0.2Ni0.8)
core of 100 nm in radius, surrounded by a 50 nm thick Fe shell. Fourier
transform analyses show that the Py core and the Fe shell dominate spin-wave
oscillation at the fundamental and higher order radial modes, respectively. For
oscillating driving field tuned to the fundamental eigenfrequency, the Py/Fe
interface effectively confines spin-wave excitation in the Py core region. This
effect leads to significantly more rapid vortex core (VC) reversal in
comparison to homogeneous disks. Our work demonstrates that the higher order
modes can drive much faster VC reversal than the fundamental mode, in sharp
contrast to the results obtained in homogeneous disks. With excitation levels
up to 30 mT, we find strong nonlinear spin-wave dynamics in the system, which
results in mode frequency redshifting, therefore the observation of the most
rapid VC reversals below eigenfrequencies and VC switching in wide ranges of
frequencies.",1802.09181v1
2018-12-20,Tunable Angle Dependent Magnetization Dynamics in Ni80Fe20 Nano-cross Structures of Varying Size,"We demonstrate a large angular dependence of magnetization dynamics in
Ni80Fe20 nano-cross arrays of varying sizes. By subtle variation of the
azimuthal angle of an in-plane bias magnetic field, the spin configuration and
the ensuing spin-wave dynamics, including mode softening, mode splitting, mode
crossover and mode merging, can be drastically varied to the extent that a
frequency minimum corresponding to mode softening converts to a mode crossover,
various mode splitting and mode crossover disappear and additional mode
splitting appears. Numerically simulated spin-wave spectra and phase profiles
revealed the nature of various spin-wave modes and the origin of above
variation of the dynamics with bias-field angle. All of these above
observations are further modified with the variation of dimensions of the
nano-cross. The numerically calculated magnetostatic field distributions
further supports the variation of dynamics with bias-field angle. These results
open a new avenue for engineering the nano-cross based magnetic devices such as
magnetic storage, spin-wave logic and on-chip data communication devices.",1812.08393v1
2016-12-08,Damped spin-wave excitations in the itinerant antiferromagnet $γ$-Fe$_{0.7}$Mn$_{0.3}$,"The collective spin-wave excitations in the antiferromagnetic state of
$\gamma$-Fe$_{0.7}$Mn$_{0.3}$ were investigated using the inelastic neutron
scattering technique. The spin excitations remain isotropic up to the high
excitation energy, ${\hbar\omega}= 78$ meV. The excitations gradually become
broad and damped above 40 meV. The damping parameter ${\gamma}$ reaches 110(16)
meV at ${\hbar\omega} = 78$ meV, which is much larger than that for other
metallic compounds, e.g., CaFe$_2$As$_2$ (24 meV),
La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$ ($52-72$ meV), and Mn$_{90}$Cu$_{10}$ (88
meV). In addition, the spin-wave dispersion shows a deviation from the relation
$({\hbar\omega})^2 = c^2q^2 + {\Delta}^2$ above 40 meV. The group velocity
above this energy increases to 470(40) meV{\AA}, which is higher than that at
the low energies, $c = 226(5)$ meV{\AA}. These results could suggest that the
spin-wave excitations merge with the continuum of the individual particle-hole
excitations at 40 meV.",1612.02515v2
2017-02-26,Magnon-photon coupling in antiferromagnets,"Magnon-photon coupling in antiferromagnets has many attractive features that
do not exist in ferro- or ferrimagnets. We show quantum-mechanically that, in
the absence of an external field, one of the two degenerated spin wave bands
couples with photons while the other does not. The photon mode anticrosses with
the coupled spin waves when their frequencies are close to each other. Similar
to its ferromagnetic counterpart, the magnon-photon coupling strength is
proportional to the square root of number of spins $\sqrt{N}$ in
antiferromagnets. An external field removes the spin wave degeneracy and both
spin wave bands couple to the photons, resulting in two anticrossings between
the magnons and photons. Two transmission peaks were observed near the
anticrossing frequency. The maximum damping that allows clear discrimination of
the two transmission peaks is proportional to $\sqrt{N}$ and it's well below
the damping of antiferromagnetic insulators. Therefore the strong magnon-photon
coupling can be realized in antiferromagnets and the coherent information
transfer between the photons and magnons is possible.",1702.07977v1
2017-06-02,Coherent Terahertz Spin-Wave Emission Associated with Ferrimagnetic Domain Wall Dynamics,"We theoretically study the dynamics of ferrimagnetic domain walls in the
presence of Dzyaloshinskii-Moriya interaction. We find that an application of a
DC magnetic field can induce terahertz spin-wave emission by driving
ferrimagnetic domain walls, which is not possible for ferromagnetic or
antiferromagnetic domain walls. Dzyaloshinskii-Moriya interaction is shown to
facilitate the teraherz spin-wave emission in wide ranges of net angular
momentum by increasing the Walkerbreakdown field. Moreover, we show that
spin-orbit torque combined with Dzyaloshinskii-Moriya interaction also drives a
fast ferrimagnetic domain wall motion with emitting terahertz spin-waves in
wide ranges of net angular momentum.",1706.00549v1
2021-08-08,Shock-wave-like emission of spin waves induced by interfacial Dzyaloshinskii-Moriya interaction,"We investigated spin wave (SW) propagation and emission in thin film systems
with strong interfacial Dzyaloshinskii-Moriya interaction (DMI) utilizing
micromagnetic simulation. The effect of DMI on SW propagation is analogous to
the flow of magnetic medium leading to the spin Doppler effect, and a
spin-polarized current can enhance or suppress it. It is demonstrated that, for
a Doppler velocity exceeding a critical value, a shock-wave-like emission of
SWs with a cone-shape emerges from a magnetically irregular point as the cone
apex. The cone angle is quantitatively determined by the DMI-induced Doppler
velocity. Combining the interfacial DMI and the spin-polarized current, a
constant SW emission by a static source is demonstrated, which provides a
promising route to efficiently generate SWs with tunable frequency.",2108.03686v1
2016-11-02,Surface effects on ferromagnetic resonance in magnetic nanocubes,"We study the effect of surface anisotropy on the spectrum of spin-wave
excitations in a magnetic nanocluster and compute the corresponding absorbed
power. For this, we develop a general numerical method based on the (undamped)
Landau-Lifshitz equation, either linearized around the equilibrium state
leading to an eigenvalue problem or solved using a symplectic technique. For
box-shaped clusters, the numerical results are favorably compared to those of
the finite-size linear spin-wave theory. Our numerical method allows us to
disentangle the contributions of the core and surface spins to the spectral
weight and absorbed power. In regard to the recent developments in synthesis
and characterization of assemblies of well defined nano-elements, we study the
effects of free boundaries and surface anisotropy on the spin-wave spectrum in
iron nanocubes and give orders of magnitude of the expected spin-wave
resonances. For an 8 nm iron nanocube, we show that the absorbed power spectrum
should exhibit a low-energy peak around 10 GHz, typical of the uniform mode,
followed by other low-energy features that couple to the uniform mode but with
a stronger contribution from the surface. There are also high-frequency
exchange-mode peaks around 60 GHz.",1611.00614v1
2016-11-12,Parametric resonance of magnetization excited by electric field,"Manipulation of magnetization by electric field is a central goal of
spintronics because it enables energy-efficient operation of spin-based
devices. Spin wave devices are promising candidates for low-power information
processing but a method for energy-efficient excitation of short-wavelength
spin waves has been lacking. Here we show that spin waves in nanoscale magnetic
tunnel junctions can be generated via parametric resonance induced by electric
field. Parametric excitation of magnetization is a versatile method of
short-wavelength spin wave generation, and thus our results pave the way
towards energy-efficient nanomagnonic devices.",1611.03963v1
2019-10-25,Nutation Wave as a Platform for Ultrafast Spin Dynamics in Ferromagnets,"At short time scales the inertia term becomes relevant for the magnetization
dynamics of ferromagnets and leads to nutation for the magnetization vector.
For the case of spatially extended magnetic systems, for instance Heisenberg
spin chains with isotropic spin-exchange interaction, this leads to the
appearance of a novel collective excitation, the ""nutation wave"", whose
properties are elucidated by analytic arguments and numerical studies. The
one--particle excitations can be identified as relativistic massive particles.
These particles, the ""nutatons"", acquire their mass via the Brout-Englert-Higgs
mechanism, through the interaction of the wave with an emergent topological
gauge field. This spin excitation would appear as a peak in the spectrum of the
scattering structure factor in inelastic neutron scattering experiments. The
high frequency and speed of the nutation wave can open new paths for realizing
ultrafast spin dynamics.",1910.11897v3
2020-05-21,Non-Hermitian coherent coupling of nanomagnets by exchange spin waves,"Non-Hermitian physics has recently attracted much attention in optics and
photonics. Less explored is non-Hermitian magnonics that provides opportunities
to take advantage of the inevitable dissipation of magnons or spin waves in
magnetic systems. Here we demonstrate non-Hermitian coherent coupling of two
distant nanomagnets by fast spin waves with sub-50 nm wavelengths. Magnons in
two nanomagnets are unidirectionally phase-locked with phase shifts controlled
by magnon spin torque and spin-wave propagation. Our results are attractive for
analog neuromorphic computing that requires unidirectional information
transmission.",2005.10452v1
2020-05-22,Dipolar spin waves in uniaxial easy-axis antiferromagnets: A natural topological nodal-line semimetal,"The existence of the magnetostatic surface spin waves in ferromagnets, known
as Damon-Eshbach mode, was recently demonstrated to originate from the topology
of the dipole-dipole interaction. In this work, we study the topological
characteristics of magnons in easy-axis antiferromagnets with uniaxial
anisotropy. The dipolar spin waves are found to be, driven by the dipole-dipole
interaction, in a topological nodal-line semimetal phase, which hosts
Damon-Eshbach-type surface modes due to the bulk-edge correspondence. The long
wavelength character of dipolar spin waves makes our proposal valid for any
natural uniaxial easy-axis antiferromagnet, and thus enriches the candidates of
topological magnonic materials. In contrast to the nonreciprocal property in
ferromagnetic case, the surface modes with opposite momentum coexist at each
surface, but with different chiralities. Such a chirality-momentum or
spin-momentum locking, similar to that of electronic surface states in
topological insulators, offers the opportunity to design novel chirality-based
magnonic devices in antiferromagnets.",2005.10971v1
2021-05-24,Cavity magnomechanics with surface acoustic waves,"Magnons, namely spin waves, are collective spin excitations in ferromagnets,
and their control through coupling with other excitations is a key technology
for future hybrid spintronic devices. Although strong coupling has been
demonstrated with microwave photonic structures, an alternative approach
permitting high density integration and minimized electromagnetic crosstalk is
required. Here we report a planar cavity magnomechanical system, where the
cavity of surface acoustic waves enhances the spatial and spectral power
density to thus implement magnon-phonon coupling at room temperature.
Excitation of spin-wave resonance involves significant acoustic power
absorption, whereas the collective spin motion reversely exerts a back-action
force on the cavity dynamics. The cavity frequency and quality-factor are
significantly modified by the back-action effect, and the resultant
cooperativity exceeds unity, suggesting coherent interaction between magnons
and phonons. The demonstration of a chip-scale magnomechanical system paves the
way to the development of novel spin-acoustic technologies for classical and
quantum applications.",2105.11127v1
2023-04-21,Magnetic Structures and Spin-wave Excitations in Rare-Earth Iron Garnets near the Compensation Temperature,"We introduce a simple model for the ferrimagnetic non-collinear ``magnetic
umbrella"" states of rare-earth iron garnets (REIG), common when the rare-earth
moments have non-zero orbital angular momentum. The spin-wave excitations are
calculated within linear spin wave theory and temperature effects via
mean-field theory. This could be used to determine the magnetic polarization of
each mode and thereby the spin currents generated by thermal excitations
including the effects of mixed chirality. The spectra reproduce essential
features seen in more complete models, with hybridization between the rare
earth crystal field excitations and the propagating mode on the iron moments.
By the symmetry of the model, only one rare earth mode hybridizes, inducing a
gap at zero wave number and level repulsion at finite frequency. At the
compensation point, the hybridization gap closes and finally, as we approach
the N\'eel temperature, the hybridization gap appears to reopen. The chirality
of the lowest mode changes its sign around the frequency at which the level
repulsion occurs. This is important to estimate the spin current generation in
REIGs.",2304.10695v1
2023-10-01,Spin and orbital angular momenta of electromagnetic waves in classical and quantum electrodynamics,"A plane, monochromatic electromagnetic wave propagating in free space can
have a certain amount of spin angular momentum but cannot possess any orbital
angular momentum. Even the spin angular momentum of the plane-wave is difficult
to evaluate without resort to certain mathematical limit arguments. Both spin
and orbital angular momenta can be computed for a wavepacket of finite duration
and finite cross-sectional area using standard methods of classical
electrodynamics. Extending these results to finite wavepackets in quantum
electrodynamics requires subtle arguments in conjunction with the multimodal
structure of the wavepacket. This paper presents some of the nuances of
classical as well as quantum-optical methods for analyzing the spin and orbital
angular momenta of electromagnetic waves.",2310.00575v1
2024-01-16,Spin Waves in Ferrimagnets near the Angular Magnetization Compensation Temperature: A Micromagnetic Study,"Spin wave propagation along a ferrimagnetic strip with out-of-plane
magnetization is studied by means of micromagnetic simulations. The
ferrimagnetic material is considered as formed by two antiferromagnetically
coupled sublattices. Two critical temperatures can be defined for such systems:
that of magnetization compensation and that of angular momentum compensation,
both different due to distinct Land\'e factors for each sub-lattice. Spin waves
in the strip are excited by a spin current injected at one of its edges. The
obtained dispersion diagrams show exchange-dominated forward volume spin waves.
For a given excitation frequency, N\'eel vector describes highly eccentric
orbits, the eccentricity depending on temperature, whose semi-major axis are
oriented differently at distinct locations on the FiM strip.",2401.08235v1
2008-10-27,"Spin polarized two-dimensional electron gas embedded in semimagnetic quantum well : ground state, spin responses, spin excitations, Raman spectrum","We present theoretical aspects of spin polarized two dimensional electron gas
(SP2DEG) which can be achieved in doped semimagnetic quantum wells. This
original model system has been recently studied by magneto Raman scattering
experiments has given a new access to spin resolved excitations and spectrum of
the SP2DEG. Starting from the Diluted Magnetic Semiconductor (DMS) Hamiltonian
in presence of the Coulomb interaction between conduction electrons, we define
the conditions to reach such a SP2DEG. The equilibrium state is studied at low
temperature; in particular a theory for the degree of spin polarization is
derived. Dynamical spin susceptibilities are further calculated in the
framework of a spin density functional formalism already developed in the past.
We then derive spin conserving and spin flip excitations dispersions using a
recent determination of the SP2DEG correlation energy corrected from the
thickness of the well. The SP2DEG presents two key features: the spin flip
wave, which existence is a direct consequence of the Coulomb interaction
between the spin polarized electrons, with a dispersion and energy range
typical to the SP2DEG obtained in DMS, the spin density fluctuations exhibiting
a specific collective behaviour when the spin polarization is increased. The
dissipation spectrum through these excitations is studied in detail. Particular
attention is given to the spectrum determined by resonant Raman scattering. We
show, indeed, that the latter gives unique access to the spin-fluctuations
spectrum of the SP2DEG.",0810.4872v1
2009-03-26,Emergence of the persistent spin helix in semiconductor quantum wells,"According to Noethers theorem, for every symmetry in nature there is a
corresponding conservation law. For example, invariance with respect to spatial
translation corresponds to conservation of momentum. In another well-known
example, invariance with respect to rotation of the electrons spin, or SU(2)
symmetry, leads to conservation of spin polarization. For electrons in a solid,
this symmetry is ordinarily broken by spin-orbit coupling, allowing spin
angular momentum to flow to orbital angular momentum. However, it has recently
been predicted that SU(2) can be achieved in a two-dimensional electron gas,
despite the presence of spin-orbit coupling. The corresponding conserved
quantities include the amplitude and phase of a helical spin density wave
termed the persistent spin helix. SU(2) is realized, in principle, when the
strength of two dominant spin-orbit interactions, the Rashba (strength
parameterized by \alpha) and linear Dresselhaus (\beta_1), are equal. This
symmetry is predicted to be robust against all forms of spin-independent
scattering, including electron-electron interactions, but is broken by the
cubic Dresselhaus term (\beta_3) and spin-dependent scattering. When these
terms are negligible, the distance over which spin information can propagate is
predicted to diverge as \alpha approaches \beta_1. Here we observe
experimentally the emergence of the persistent spin helix in GaAs quantum wells
by independently tuning \alpha and \beta_1. Using transient spin-grating
spectroscopy, we find a spin-lifetime enhancement of two orders of magnitude
near the symmetry point.........",0903.4709v2
2014-08-20,Coherent transport and manipulation of spins in indirect exciton nanostructures,"We report on the coherent control and transport of indirect exciton (IX)
spins in GaAs double quantum well (DQW) nanostructures. The spin dynamics was
investigated by optically generating spins using a focused, circularly
polarized light spot and by probing their spatial distribution using spatially
and polarization resolved photoluminescence spectroscopy. Optically injected
exciton spins precess while diffusing over distances exceeding 20 {\mu}m from
the excitation spot with a spatial precession frequency that depends on the
spin transport direction as well as on the bias applied across the DQW
structure. This behavior is attributed to the spin precession in the effective
magnetic field induced by the spin-orbit interaction. From the dependence of
the spin dynamics on the transport direction, bias and external magnetic fields
we directly determined the Dresselhaus and Rashba spin splitting coefficients
for the structure. The precession dynamics is essentially independent on the IX
density, thus indicating that the long spin lifetimes are not associated with
IX collective effects. The latter, together with the negligible contribution of
holes to the spin dynamics, are rather attributed to spatial separation of the
electron and hole wave functions by the electric field, which reduces the
electron-hole exchange interaction. Coherent spin precession over long
transport distances as well as the control of the spin vector using electric
and magnetic fields open the way for the application of IX spins in the quantum
information processing.",1408.4547v1
2018-01-13,Tailoring multilayer quantum wells for spin devices,"The electron spin dynamics in multilayer GaAs/AlGaAs quantum wells,
containing high-mobility dense two-dimensional electron gases, have been
studied using time-resolved Kerr rotation and resonant spin amplification
techniques. The electron spin dynamics was regulated through the wave function
engineering and quantum confinement in multilayer quantum wells. We observed
the spin coherence with a remarkably long dephasing time T2* > 13 ns for the
structure doped beyond metal-insulator transition. Dyakonov-Perel spin
relaxation mechanism, as well as the inhomogeneity of electron g-factor, was
suggested as the major limiting factors for the spin coherence time. In the
metallic regime, we found that the electron-electron collisions become dominant
over microscopic scattering on the electron spin relaxation with the
Dyakonov-Perel mechanism. Furthermore, the data analysis indicated that in our
structure, due to the spin relaxation anisotropy, Dyakonov-Perel spin
relaxation mechanism is efficient for the spins oriented in-plane and
suppressed along the quantum well growth direction resulting in the enhancement
of T2*. Our findings, namely, long-lived spin coherence persisting up to about
room temperature, spin polarization decay time with and without a magnetic
field, the spin-orbit field, single electron relaxation time, transport
scattering time, and the electron-electron Coulomb scattering time highlight
the attractiveness of n-doped multilayer systems for spin devices.",1801.04426v1
2022-07-13,Jahn-Teller states mixed by spin-orbit coupling in an electromagnetic field,"Spin-orbit coupling plays a pivotal role in condensed matter physics. For
instance, spin-orbit interactions affect the magnetization and transport
dynamics in solids, while spins and momenta are locked in topological matter.
Alternatively, spin-orbit entanglement may play an important role in exotic
phenomena, like quantum spin liquids in 4d and 5d systems. An interesting
question is how electronic states mixed by spin orbit coupling interact with
electromagnetic fields, which may hold potential to tune their properties and
reveal interesting physics. Motivated by our recent discovery of large
gyrotropic signals in some Jahn-Teller manganites, here we explore the
interaction of light with spin-mixed states in a d4 transition metal. We show
that spin-orbit mixing enables electronic transitions that are sensitive to
circularly polarized light, giving rise to a gyrotropic response that increases
with spin-orbit coupling. Interestingly, photoexcited transitions that involve
spin reversal are behind such gyrotropic resonances. Additionally, we find that
the interaction with the electromagnetic field depends strongly on the relative
orientation of the propagation of light with respect to Jahn-Teller distortions
and spin quantization. We suggest that such interactions offer the opportunity
to use electromagnetic waves at optical wavelengths to entangle orbital and
spin degrees of freedom. Our approach, which includes a group-theoretical
treatment of spin-orbit coupling, has wide applicability and provides a
versatile tool to explore the interaction of electromagnetic fields with
electronic states in transition metals with arbitrary spin-orbit coupling
strength and pointgroup symmetries.",2207.06501v1
2002-04-18,"Ballistic spin transport through electronic stub tuners: spin precession, selection, and square-wave transmission","Ballistic spin transport is studied through electronic tuners with double
stubs attached to them. The spins precess due to the spin-orbit interaction.
Injected polarized spins can exit the structure polarized in the opposite
direction. A nearly square-wave spin transmission, with values 1 and 0, can be
obtained using a periodic system of symmetric stubs and changing their length
or width. The gaps in the transmission can be widened using asymmetric stubs.
An additional modulation is obtained upon combining stub structures with
different values of the spin-orbit strength.",0204391v1
1992-11-19,Spin effects in the inspiral of coalescing compact binaries,"We derive the contributions of spin-orbit and spin-spin coupling to the
gravitational radiation from coalescing binary systems of spinning compact
objects. We calculate spin effects in the symmetric, trace-free radiative
multipoles that determine the gravitational waveform, and the rate of energy
loss. Assuming a balance between energy radiated and orbital energy lost, we
determine the spin effects in the evolution of the orbital frequency and
orbital radius. Assuming that a laser interferometric gravitational observatory
can track the gravitational-wave frequency (twice the orbital frequency) as it
sweeps through its sensitive bandwidth between about 10 Hz and one kHz, we
estimate the accuracy with which the spins of the component bodies can be
determined from the gravitational-wave signal.",9211025v1
2004-10-01,Modeling and Simulations of a Single-Spin Measurement using MRFM,"We review the quantum theory of a single spin magnetic resonance force
microscopy (MRFM). We concentrate on the novel technique called oscillating
cantilever-driven adiabatic reversals (OSCAR), which has been used for a single
spin detection (Dan Rugar, Talk on the 2004 IEEE NTC Quantum Device Technology
Workshop). First we describe the quantum dynamics of the cantilever-spin system
using simple estimates in the spirit of the mean field approximation. Then we
present the results of our computer simulations of the Schrodinger equation for
the wave function of the cantilever-spin system and of the master equation for
the density matrix of the system. We demonstrate that the cantilever behaves
like a quasi-classical measurement device which detects the spin projection
along the effective magnetic field. We show that the OSCAR technique provides
continuous monitoring of the single spin, which could be used to detect the
mysterious quantum collapses of the wave function of the cantilever-spin
system.",0410002v1
2007-08-29,Spin-charge separation in a strongly correlated spin-polarized chain,"We combine the first-quantized path-integral formalism and bosonization to
develop a phenomenological theory for spin-charge coupled dynamics in
one-dimensional (1D) ferromagnetic systems with strong interparticle repulsion,
at low temperatures. We assume an effective spin-charge separation and retain
the standard Luttinger-liquid plasmon branch, which is explicitly coupled to a
ferromagnetic spin-wave texture with a quadratic dispersion. The dynamic spin
structure severely suppresses the plasmon peak in the single-particle
propagator, in both fermionic and bosonic systems. Our analysis provides an
effective theory for the new universality class of 1D ferromagnetic systems,
capturing both the trapped spin and propagating spin-wave regimes of the
long-time behavior.",0708.4012v4
2008-11-14,Hall Effect of Spin Waves in Frustrated Magnets,"We examine a possible spin Hall effect for localized spin systems with no
charge degrees of freedom. In this scenario, a longitudinal magnetic field
gradient induces a transverse spin current carried by spin wave excitations
with an anomalous velocity which is associated with the Berry curvature raised
by spin chirality, in analogy with anomalous Hall effects in itinerant electron
systems. Our argument is based on a semiclassical equations of motion
applicable to general spin systems. Also, a microscopic model of frustrated
magnets which exhibits the anamalous spin Hall effect is presented.",0811.2263v6
2009-09-14,Collective modes of a helical liquid,"We study low energy collective modes and transport properties of the ""helical
metal"" on the surface of a topological insulator. At low energies, electrical
transport and spin dynamics at the surface are exactly related by an operator
identity equating the electric current to the in-plane components of the spin
degrees of freedom. From this relation it follows that an undamped spin wave
always accompanies the sound mode in the helical metal -- thus it is possible
to `hear' the sound of spins. In the presence of long range Coulomb
interactions, the surface plasmon mode is also coupled to the spin wave, giving
rise to a hybridized ""spin-plasmon"" mode. We make quantitative predictions for
the spin-plasmon in ${\rm Bi}_2{\rm Se}_3$, and discuss its detection in a
spin-grating experiment.",0909.2477v2
2010-07-08,Spin induced multipole moments for the gravitational wave flux from binary inspirals to third Post-Newtonian order,"Using effective field theory techniques we calculate the source multipole
moments needed to obtain the spin contributions to the power radiated in
gravitational waves from inspiralling compact binaries to third Post-Newtonian
order (3PN). The multipoles depend linearly and quadratically on the spins and
include both spin(1)spin(2) and spin(1)spin(1) components. The results in this
paper provide the last missing ingredient required to determine the phase
evolution to 3PN including all spin effects which we will report in a separate
paper.",1007.1312v2
2011-08-14,Observation of non-conventional spin waves in composite fermion ferromagnets,"We find unexpected low energy excitations of fully spin-polarized
composite-fermion ferromagnets in the fractional quantum Hall liquid, resulting
from a complex interplay between a topological order manifesting through new
energy levels and a magnetic order due to spin polarization. The lowest energy
modes, which involve spin reversal, are remarkable in displaying unconventional
negative dispersion at small momenta followed by a deep roton minimum at larger
momenta. This behavior results from a nontrivial mixing of spin-wave and
spin-flip modes creating a spin-flip excitonic state of composite-fermion
particle-hole pairs. The striking properties of spin-flip excitons imply highly
tunable mode couplings that enable fine control of topological states of
itinerant two-dimensional ferromagnets.",1108.2901v1
2012-04-15,Classical Aspects of Higher Spin Topologically Massive Gravity,"We study the classical solutions of three dimensional topologically massive
gravity (TMG) and its higher spin generalization, in the first order
formulation. The action of higher spin TMG has been proposed in arXiv:1110.5113
to be of a Chern-Simons-like form. The equations of motion are more complicated
than the ones in pure higher spin AdS$_3$ gravity, but are still tractable. As
all the solutions in higher spin gravity are automatically the solutions of
higher spin TMG, we focus on other solutions. We manage to find the AdS pp-wave
solutions with higher spin hair, and find that the nonvanishing higher spin
fields may or may not modify the pp-wave geometry. In order to discuss the
warped spacetime, we introduce the notion of special Killing vector, which is
defined to be the symmetry on the frame-like fields. We reproduce various
warped spacetimes of TMG in our framework, with the help of special Killing
vectors.",1204.3282v2
2012-08-20,Reversal and Termination of Current-Induced Domain Wall Motion via Magnonic Spin-Transfer Torque,"We investigate the domain wall dynamics of a ferromagnetic wire under the
combined influence of a spin-polarized current and magnonic spin-transfer
torque generated by an external field, taking also into account Rashba
spin-orbit coupling interactions. It is demonstrated that current-induced
motion of the domain wall may be completely reversed in an oscillatory fashion
by applying a magnonic spin-transfer torque as long as the spin-wave velocity
is sufficiently high. Moreover, we show that the motion of the domain wall may
be fully terminated by means of the generation of spin-waves, suggesting the
possibility to pin the domain-walls to predetermined locations. We also discuss
how strong spin-orbit interactions modify these results.",1208.4108v1
2013-05-17,Doping dependence of the spin excitations in Fe-based superconductors Fe1+yTe1-xSex,"The Fe1+yTe1-xSex series of materials is one of the prototype families of
Fe-based superconductors. To provide further insight into these materials we
present systematic inelastic neutron scattering measurements of the low energy
spin excitations for x=0.27, 0.36, 0.40, 0.49. These measurements show an
evolution of incommensurate spin excitations towards the (1/2 1/2 0) wave
vector with doping. Concentrations (x=0.40 and 0.49) which exhibit the most
robust superconducting properties have spin excitations closest to (1/2 1/2 0)
and also exhibit a strong spin resonance in the spin excitation spectrum below
Tc. The resonance signal appears to be closer to (1/2 1/2 0) than the
underlying spin excitations. We discuss the possible relationship between
superconductivity and spin excitations at the (1/2 1/2 0) wave vector and the
role that interstitial Fe may play.",1305.4108v2
2013-07-19,Waves in the unseen : theory of spin excitations in a quantum spin nematic,"The idea that a quantum magnet could act like a liquid crystal, breaking
spin-rotation symmetry without breaking time-reversal symmetry, holds an
abiding fascination. However, the very fact that spin nematic states do not
break time-reversal symmetry renders them ""invisible"" to the most common probes
of magnetism - they do not exhibit magnetic Bragg peaks, a static splitting of
lines in NMR spectra, or oscillations in muSR. Nonetheless, as a consequence of
breaking spin-rotation symmetry, spin-nematic states do possess a
characteristic spectrum of dispersing excitations which could be observed in
experiment. With this in mind, we develop a symmetry-based description of
long-wavelength excitations in a spin-nematic state, based on an SU(3)
generalisation of the quantum non-linear sigma model. We use this field theory
to make explicit predictions for inelastic neutron scattering, and argue that
the wave-like excitations it predicts could be used to identify the symmetries
broken by the otherwise unseen spin-nematic order.",1307.5131v2
2013-08-16,Quantum kinetics of spinning neutral particles: General theory and Spin wave dispersion,"Plasma physics give an example of physical system of particles with the long
range interaction. At small velocity of particles we can consider the plasma
approximately as a system of particles with the Coulomb interaction. The
Coulomb interaction is isotropic. Systems of spinning neutral particles have
long-range anisotropic interparticle interaction. So, they can reveal more
reach properties than plasma. Furthermore for studying of systems of spinning
particles we can develop kinetic and hydrodynamic methods analogous to used for
the plasma. We derive kinetic equations by a new method, which is the
generalization of the many-particle quantum hydrodynamics. Obtained set of
kinetic equations is truncated, so we have closed set of two equations. One of
them is the kinetic equation for quantum distribution function. The second
equation is the equation for the spin-distribution. Which describes the spin
kinetic evolution and gives contribution in time evolution of the distribution
function. Our method allows to obtain equations as for three dimensional system
of particles and for low dimensional systems. So, we consider spin waves in
three- and two dimensional systems of neutral spinning particles.",1308.3715v1
2014-02-17,Incommensurate spin density wave as a signature of spin-orbit coupling,"Close to half filling and in the limit of strong interactions the Hubbard
model leads a spin Hamiltonian. In its original isotropic form this is the
Heisenberg model with antiferromagnetic coupling $J$. On a square lattice there
is no frustration and the ground state is a classical antiferromagnet denoted
by the commensurate order vector ${\bf Q}=(\pi,\pi)$. In this work we show that
the inclusion of spin orbit coupling (SOC) in the fermionic Hubbard model on a
square lattice leads to an incommensurate spin density wave (ISDW) in the
strong interactions limit at half filling. In this limit the Hubbard model
leads to a non-diagonal and anisotropic spin Hamiltonian which exhibits the
incommensurate spin order as its classical ground state. We note that an ISDW
can be found in systems regardless of spin orbit-coupling due to nesting and
lattice distortion. These effects, however, can usually be recognized by
experimental probes.",1402.4093v1
2014-11-30,Quantum Theory of Helimagnetic Thin Films,"We study properties of a helimagnetic thin film with quantum Heisenberg spin
model by using the Green's function method. Surface spin configuration is
calculated by minimizing the spin interaction energy. It is shown that the
angles between spins near the surface are strongly modified with respect to the
bulk configuration. Taking into account this surface spin reconstruction, we
calculate self-consistently the spin-wave spectrum and the layer magnetizations
as functions of temperature up to the disordered phase. The spin-wave spectrum
shows the existence of a surface-localized branch which causes a low surface
magnetization. We show that quantum fluctuations give rise to a crossover
between the surface magnetization and interior-layer magnetizations at low
temperatures. We calculate the transition temperature and show that it depends
strongly on the helical angle. Results are in agreement with existing
experimental observations on the stability of helical structure in thin films
and on the insensitivity of the transition temperature with the film thickness.
We also study effects of various parameters such as surface exchange and
anisotropy interactions. Monte Carlo simulations for the classical spin model
are also carried out for comparison with the quantum theoretical result.",1412.0184v1
2015-09-11,Non-perturbative Correlation Effects in Diluted Magnetic Semiconductors,"The effects of carrier-impurity correlations due to a Kondo-like spin-spin
interaction in diluted magnetic semiconductors are investigated. These
correlations are not only responsible for a transfer of spins between the
carriers and the impurities, but also produce non-perturbative effects in the
spin dynamics such as renormalization of the precession frequency of the
carrier spins, which can reach values of several percent in CdMnTe quantum
wells. In two-dimensional systems, the precession frequency renormalization for
a single electron spin with defined wave vector shows logarithmic divergences
similar to those also known from the Kondo problem in metals. For smooth
electron distributions, however, the divergences disappear due to the
integrability of the logarithm. A possible dephasing mechanism caused by the
wave-vector dependence of the electron spin precession frequencies is found to
be of minor importance compared to the spin transfer from the carrier to the
impurity system. In the Markov limit of the theory, a quasi-equilibrium
expression for the carrier-impurity correlation energy can be deduced
indicating the formation of strongly correlated carrier-impurity states for
temperatures in the mK range.",1509.03442v1
2017-02-22,Is spin superfluidity possible in YIG films?,"Recently it was suggested that stationary spin supercurrents (spin
superfluidity) are possible in the magnon condensate observed in
yttrium-iron-garnet (YIG) magnetic films under strong external pumping. Here we
analyze this suggestion. From topology of the equilibrium order parameter in
YIG one must not expect energetic barriers making spin supercurrents
metastable. However some small barriers of dynamical origin are possible
nevertheless. The critical phase gradient (analog of the Landau critical
velocity in superfluids) is proportional to intensity of the coherent spin wave
(number of condensed magnons). The conclusion is that although spin
superfluidity in YIG films is possible in principle, the published claim of its
observation is not justified.
  The analysis revealed that the widely accepted spin-wave spectrum in YIG
films with magnetostatic and exchange interaction required revision. This led
to revision of non-linear corrections, which determine stability of the magnon
condensate with and without spin supercurrents.",1702.06994v2
2021-04-30,Unstable binary black-hole spins: post-Newtonian theory and numerical relativity,"Spin precession occurs in binary black holes whose spins are misaligned with
the orbital angular momentum. Otherwise, the spin configuration is constant and
the subsequent binary dynamics and gravitational-wave emission are much
simpler. We summarize a series of works which has shown that, while three of
the aligned configurations are stable equilibria, the `up-down' configuration,
in which the heavier (lighter) black hole is (anti) aligned with the orbital
angular momentum, is unstable when perturbed; at a critical point in the
inspiral the black hole spins begin to tilt wildly as precession takes over. We
present two equivalent approaches to derive the instability onset based on
multitimescale post-Newtonian techniques, and point out that the instability
has a predictable endpoint. Finally, we demonstrate the presence of this
precessional instability in the strong-field regime of numerical relativity
with simulations of aligned-spin binaries lasting $\sim100$ orbits before
merger. The spins of up-down systems can tilt by $\sim90^\circ$, leaving a
notable imprint in the emitted gravitational-wave signals and providing a
possible mechanism to form precessing systems in astrophysical environments
from which sources are preferentially born with (anti) aligned spins.",2104.15011v1
2021-10-24,Spin dynamics in the skyrmion-host lacunar spinel GaV4S8,"In the lacunar spinel GaV4S8, the interplay of spin, charge, and orbital
degrees of freedom produces a rich phase diagram that includes an unusual
Neel-type skyrmion phase composed of molecular spins. To provide insight into
the interactions underlying this complex phase diagram, we study the spin
excitations in GaV4S8 through inelastic neutron scattering measurements on
polycrystalline and single-crystal samples. Using linear spin-wave theory, we
describe the spin-wave excitations using a model where V4 clusters decorate an
FCC lattice. The effective cluster model includes a ferromagnetic interaction
and a weaker antisymmetric Dzyaloshinskii-Moriya (DM) interaction between the
neighboring molecular spins. Our work clarifies the spin interactions in GaV4S8
and supports the picture of interacting molecular clusters.",2110.12322v2
2020-01-18,Giant photonic spin Hall effect near the Dirac points,"The origin of spin-orbit interaction of light at a conventional optical
interface lies in the transverse nature of the photon polarization: The
polarizations associated with the plane-wave components experience slightly
different rotations in order to satisfy the transversality after reflection or
refraction. Recent advances in topological photonic materials provide crucial
opportunities to reexamine the spin-orbit interaction of light at the unique
optical interface. Here, we establish a general model to describe the
spin-orbit interaction of light in the photonic Dirac metacrystal. We find a
giant photonic spin Hall effect near the Dirac points when a Gaussian beam
impinges at the interface of the photonic Dirac metacrystal. The giant photonic
spin Hall effect is attribute to the strong spin-orbit interaction of light,
which manifests itself as the large polarization rotations of different
plane-wave components. We believe that these results may provide insight into
the fundamental properties of the spin-orbit interaction of light in the
topological photonic systems.",2001.06609v1
2020-05-02,Anisotropic Spin-Acoustic Resonance in Silicon Carbide at Room Temperature,"We report on acoustically driven spin resonances in atomic-scale centers in
silicon carbide at room temperature. Specifically, we use a surface acoustic
wave cavity to selectively address spin transitions with magnetic quantum
number differences of $\pm$1 and $\pm$2 in the absence of external microwave
electromagnetic fields. These spin-acoustic resonances reveal a non-trivial
dependence on the static magnetic field orientation, which is attributed to the
intrinsic symmetry of the acoustic fields combined with the peculiar properties
of a half-integer spin system. We develop a microscopic model of the
spin-acoustic interaction, which describes our experimental data without
fitting parameters. Furthermore, we predict that traveling surface waves lead
to a chiral spin-acoustic resonance, which changes upon magnetic field
inversion. These results establish silicon carbide as a highly-promising hybrid
platform for on-chip spin-optomechanical quantum control enabling engineered
interactions at room temperature.",2005.00787v1
2020-07-07,Unidirectional spin transport of a spin-orbit-coupled atomic matter wave using a moving Dirac $δ$-potential well,"We study the transport of a spin-orbit-coupled atomic matter wave using a
moving Dirac $\delta$-potential well. In a spin-orbit-coupled system, bound
states can be formed in both ground and excited energy levels with a Dirac
$\delta$ potential. Because Galilean invariance is broken in a
spin-orbit-coupled system, moving of the potential will induce a
velocity-dependent effective detuning. This induced detuning breaks the spin
symmetry and makes the ground-state transporting channel be spin-$\uparrow$
($\downarrow$) favored while makes the excited-state transporting channel be
spin-$\downarrow$ ($\uparrow$) favored for a positive-direction
(negative-direction) transporting. When the $\delta$-potential well moves at a
small velocity, both the ground-state and the excited-state channels contribute
to the transportation, and thus both the spin components can be efficiently
transported. However, when the moving velocity of the $\delta$-potential well
exceeds a critical value, the induced detuning is large enough to eliminate the
excited bound state, and makes the ground bound state the only transporting
channel, in which only the spin-$\uparrow$ ($\downarrow$) component can be
efficiently transported in a positive (negative) direction. This work
demonstrates a prototype of unidirectional spin transport.",2007.03147v1
2022-06-23,Valley spin-acoustic resonance in MoS${\bf _2}$ monolayers,"The band structure of a monolayer MoS$_2$ comprises of spin-split subbands,
owing to the mutual presence of broken inversion symmetry and strong spin-orbit
coupling. In the conduction band, spin-valley coupled subbands cross each other
at finite momenta, and they are valley-degenerate. When exposed to surface
acoustic waves, the emerging strain-induced effective magnetic field can give
rise to spin-flip transitions between the spin-split subbands in the vicinity
of subbands crossing point, resulting in the emergence of a spin-acoustic
resonance and the acoustoelectric current. An external magnetic field breaks
the valley degeneracy resulting in the valley-selective splitting of
spin-acoustic resonances both in surface acoustic wave absorption and
acoustoelectric current.",2206.11551v1
2004-06-03,Phase diagram of the half-filled two-dimensional SU(N) Hubbard-Heisenberg model: a quantum Monte Carlo study,"We investigate the phase diagram of the half-filled SU(N) Hubbard-Heisenberg
model with hopping t, exchange J and Hubbard U, on a square lattice. In the
large-N limit, and as a function of decreasing values of t/J, the model shows a
transition from a d-density wave state to a spin dimerized insulator. A similar
behavior is observed at N=6 whereas at N=2 a spin density wave insulating
ground state is stabilized. The N=4 model, has a d-density wave ground state at
large values of t/J which as a function of decreasing values of t/J becomes
unstable to an insulating state with no apparent lattice and spin broken
symmetries. In this state, the staggered spin-spin correlations decay as a
power-law,resulting in gapless spin excitations at q = (pi,pi). Furthermore,
low lying spin modes with small spectral weight are apparent around the wave
vectors q = (0,pi) and q = (pi,0). This gapless spin liquid state is equally
found in the SU(4) Heisenberg model in the self-adjoint antisymmetric
representation. An interpretation of this state in terms of a pi-flux phase is
offered. Our results stem from projective (T=0) quantum Monte-Carlo simulations
on lattice sizes ranging up to 24 X 24.",0406074v1
1995-08-04,The spin of the nucleon in its rest system,"The spin dependent structure functions, g$_{1p}$ of the proton and g$_{1n}$
of the neutron, calculated in the nucleon rest frame using a relativistic quark
model wave function, are compared with recent experiments.",9508228v1
2009-04-10,Template banks to search for compact binaries with spinning components in gravitational wave data,"Gravitational waves from coalescing compact binaries are one of the most
promising sources for detectors such as LIGO, Virgo and GEO600. If the
components of the binary posess significant angular momentum (spin), as is
likely to be the case if one component is a black hole, spin-induced precession
of a binary's orbital plane causes modulation of the gravitational-wave
amplitude and phase. If the templates used in a matched-filter search do not
accurately model these effects then the sensitivity, and hence the detection
rate, will be reduced. We investigate the ability of several search pipelines
to detect gravitational waves from compact binaries with spin. We use the
post-Newtonian approximation to model the inspiral phase of the signal and
construct two new template banks using the phenomenological waveforms of
Buonanno, Chen and Vallisneri. We compare the performance of these template
banks to that of banks constructed using the stationary phase approximation to
the non-spinning post-Newtonian inspiral waveform currently used by LIGO and
Virgo in the search for compact binary coalescence. We find that, at the same
false alarm rate, a search pipeline using phenomenological templates is no more
effective than a pipeline which uses non-spinning templates. We recommend the
continued use of the non-spinning stationary phase template bank until the
false alarm rate associated with templates which include spin effects can be
substantially reduced.",0904.1715v1
2018-07-09,Cavity-induced emergent topological spin textures in a Bose Einstein condensate,"The coupled nonlinear dynamics of ultracold quantum matter and
electromagnetic field modes in an optical resonator exhibits a wealth of
intriguing collective phenomena. Here we study a $\Lambda$-type,
three-component Bose-Einstein condensate coupled to four dynamical running-wave
modes of a ring cavity, where only two of the modes are externally pumped.
However, the unpumped modes play a crucial role in the dynamics of the system
due to coherent back-scattering of photons. On a mean- field level we identify
three fundamentally different steady-state phases with distinct characteristics
in the density and spatial spin textures: a combined density and spin wave, a
continuous spin spiral with a homogeneous density, and a spin spiral with a
modulated density. The spin-spiral states, which are topological, are
intimately related to cavity-induced spin-orbit coupling emerging beyond a
critical pump power. The topologically trivial density-wave--spin-wave state
has the characteristics of a supersolid with two broken continuous symmetries.
The transitions between different phases are either simultaneously topological
and first order, or second order. The proposed setup allows the simulation of
intriguing many-body quantum phenomena by solely tuning the pump amplitudes and
frequencies, with the cavity output fields serving as a built-in nondestructive
observation tool.",1807.03316v1
2019-05-06,Direct Visualization of Spatial inhomogeneity of Spin Stripes Order in La1.72Sr0.28NiO4,"In several strongly correlated electron systems, defects, charge and local
lattice distortions are found to show complex inhomogeneous spatial
distributions. There is growing evidence that such inhomogeneity plays a
fundamental role in unique functionality of quantum complex materials.
La1.72Sr0.28NiO4 is a prototypical strongly correlated material showing spin
striped order associated with lattice and charge modulations. In this work we
present the spatial distribution of the spin organization by applying micro
X-ray diffraction to La1.72Sr0.28NiO4, mapping the spin-density-wave order
below the 120K onset temperature. We find that the spin-density-wave order
shows the formation of nanoscale puddles with large spatial fluctuations. The
nano-puddle density changes on the microscopic scale forming a multiscale phase
separation extending from nanoscale to micron scale with scale-free
distribution. Indeed spin-density-wave striped puddles are disconnected by
spatial regions with different stripe orientation or negligible
spin-density-wave order. The present work highlights the complex nanoscale
phase separation of spin stripes in nickelate perovskites and opens the
question of the energetics at domain interfaces",1905.02124v2
2017-03-14,Waveform measurement of charge- and spin-density wave packets in a Tomonaga-Luttinger liquid,"In contrast to a free electron system, a Tomonaga-Luttinger (TL) liquid in a
one dimensional (1D) electron system hosts charge and spin excitations as
independent entities. When an electron wave packet is injected into a TL
liquid, it transforms into wave packets carrying either charge or spin that
propagate at different group velocities and move away from each other. This
process, known as spin-charge separation, is the hallmark of TL physics. While
the existence of these TL eigenmodes has been identified in momentum- or
frequency-resolved measurements, their waveforms, which are a direct
manifestation of 1D electron dynamics, have been long awaited to be measured.
In this study, we present a time domain measurement for the
spin-charge-separation process in an asymmetric chiral TL liquid comprising
quantum Hall (QH) edge channels. We measure the waveforms of both charge and
spin excitations by combining a spin filter with a time-resolved charge
detector. Spatial separation of charge- and spin-wave packets over a distance
exceeding 200 um was confirmed. In addition, we found that the 1D electron
dynamics can be controlled by tuning the electric environment. These
experimental results provide fundamental information about non-equilibrium
phenomena in actual 1D electron systems.",1703.04833v1
2019-07-17,Neutron Scattering Study of Magnetic Anisotropy in a Tetragonal Antiferromagnet Bi$_2$CuO$_4$,"We present a comprehensive study of magnon excitations in the tetragonal
easy-plane anti-ferromagnet Bi$_2$CuO$_4$ using inelastic neutron scattering
and spin wave analyses. The nature of low energy magnons, and hence the
anisotropy in this material, has been controversial. We show unambiguously that
the low energy magnon spectrum consists of a gapped and a gapless mode, which
we attribute to out-of-plane and in-plane spin fluctuations, respectively. We
modelled the observed magnon spectrum using linear spin wave analysis of a
minimal anisotropic spin model motivated by the lattice symmetry. By studying
the magnetic field dependence of the (1, 0, 0) Bragg peak intensity and the
in-plane magnon intensity, we observed a spin-flop transition in the $ab$ plane
at $\sim0.4$~T which directly indicates the existence of a small in-plane
anisotropy that is classically forbidden. It is only by taking into account
magnon zero-point fluctuations beyond the linear spin wave approximation, we
could explain this in-plane anisotropy and its magnitude, the latter of which
is deduced from critical field of the spin-flop transition. The microscopic
origins of the observed anisotropic interactions are also discussed. We found
that our data is inconsistent with a large Dzyaloshinskii-Moriya interaction,
which suggests a potential departure of Bi$_2$CuO$_4$ from the conventional
theories of magnetic anisotropy for other cuprates.",1907.07784v2
2004-10-19,MHD tidal waves on a spinning magnetic compact star,"In an X-ray binary system, the companion star feeds the compact neutron star
with plasma materials via accretions. The spinning neutron star is likely
covered with a thin ""magnetized ocean"" and may support {\it magnetohydrodynamic
(MHD) tidal waves}. While modulating the thermal properties of the ocean, MHD
tidal waves periodically shake the base of the stellar magnetosphere that traps
energetic particles, including radiating relativistic electrons. For a radio
pulsar, MHD tidal waves in the stellar surface layer may modulate radio
emission processes and leave indelible signatures on timescales different from
the spin period. Accretion activities are capable of exciting these waves but
may also obstruct or obscure their detections meanwhile. Under fortuitous
conditions, MHD tidal waves might be detectable and offer valuable means to
probe properties of the underlying neutron star. Similar situations may also
occur for a cataclysmic variable -- an accretion binary system that contains a
rotating magnetic white dwarf. This Letter presents the theory for MHD tidal
waves in the magnetized ocean of a rotating degenerate star and emphasizes
their potential diagnostics in X-ray and radio emissions.",0410428v1
2002-06-04,Delocalization and spin-wave dynamics in ferromagnetic chains with long-range correlated random exchange,"We study the one-dimensional quantum Heisenberg ferromagnet with exchange
couplings exhibiting long-range correlated disorder with power spectrum
proportional to $1/k^{\alpha}$, where $k$ is the wave-vector of the modulations
on the random coupling landscape. By using renormalization group, integration
of the equations of motion and exact diagonalization, we compute the spin-wave
localization length and the mean-square displacement of the wave-packet. We
find that, associated with the emergence of extended spin-waves in the
low-energy region for $\alpha > 1$, the wave-packet mean-square displacement
changes from a long-time super-diffusive behavior for $\alpha <1$ to a
long-time ballistic behavior for $\alpha > 1$. At the vicinity of $\alpha =1$,
the mobility edge separating the extended and localized phases is shown to
scale with the degree of correlation as $E_c\propto (\alpha -1)^{1/3}$.",0206038v1
1999-05-15,Electromagnetic radiation of the travelling spin wave propagating in an antiferromagnetic plate. Exact solution,"The exact solution of radiation problem of a spin wave travelling in an
antiferromagnetic (AFM) plate was found. The spin wave with in-plane
oscillations of antiferromagnetism vector was considered. In this case the
magnetization vector is oscillating being perpendicular to the AFM plate and
depends on time and plane coordinates as travelling wave does. This model
allows to obtain exact analytical expression for Hertzian vector and,
consequently, the retarded potentials and field strengths as well. It is shown
that expressions obtained describe Cherenkov radiation caused by the travelling
wave. The radiated electromagnetic wave is the TEM type if a phase velocity
exceeds the speed of light. Otherwise electric and magnetic field values
exponentially decrease in the direction normal to the plate. The energy losses
were evaluated also.",9905036v1
2009-12-03,Partial-wave contributions to pairing in nuclei,"We present a detailed study of partial-wave contributions of nuclear forces
to pairing in nuclei. For T=1, J=0 pairing, partial waves beyond the standard
1S0 channel play an interesting role for the pair formation in nuclei. The
additional contributions are dominated by the repulsive 3P1 partial wave. Their
effects, and generally spin-triplet nuclear forces between paired nucleons, are
influenced by the interplay of spin-orbit partners. We explore the impact of
including partial waves beyond the 1S0 channel on neutron-neutron pairing gaps
in semi-magic isotopic chains. In addition, we show that nuclear forces favor
T=1, J=0 over T=0, J=1 pairing, except in low-j orbitals. This is in contrast
to the free-space motivation that suggests the formation of deuteron-like T=0
pairs in N=Z nuclei. The suppression of T=0 pairing is because the 3S1 strength
is distributed on spin-orbit partners and because of the effects of the
repulsive 1P1 channel and of D waves.",0912.0697v1
2012-08-13,Ground state of spin-1 Bose-Einstein condensates with spin-orbit coupling in a Zeeman field,"We systematically investigate the weakly trapped spin-1 Bose-Einstein
condensates with spin-orbit coupling in an external Zeeman field. We find that
the mean-field ground state favors either a magnetized standing wave phase or
plane wave phase when the strength of Zeeman field is below a critical value
related to the strength of spin-orbit coupling. Zeeman field can induce the
phase transition between standing wave and plane wave phases, and we determine
the phase boundary analytically and numerically. The magnetization of these two
phases responds to the external magnetic field in a very unique manner, the
linear Zeeman effect magnetizes the standing wave phase along the direction of
the magnetic field, but the quadratic one demagnetizes the plane wave phase.
When the strength of Zeeman field surpasses the critical value, the system is
completely polarized to a ferromagnetic state or polar state with zero
momentum.",1208.2514v1
2013-08-23,Impact of eddy currents on the dispersion relation of surface spin waves in thin conducting magnetic films,"We propose a rigorous solution to a long-standing problem of the impact of
eddy currents on the dispersion relation of surface spin waves propagating in
thin conducting magnetic films. Our results confirm the prediction of the
Almeida-Mill's exchange-free theory that the inclusion of the eddy current
contribution results in a deviation of the dispersion curve for the fundamental
mode from the Damon-Eshbach law and a substantial linewidth broadening in a
large wave vector range. We show that the decrease in the spin wave frequency
is due to an increase in the in-plane component of the dynamic magnetic field
within the conducting film. The decrease in the frequency is accompanied by a
drastic change in the asymmetry of the modal profiles for the waves. This
effect is not observable in magneto-insulating films and therefore it is
unambiguously attributed to eddy currents that appear in conducting films only.
We also show that the wave vector range in which eddy currents affect the
dispersion curve is strongly correlated with the value of the film
conductivity. This result holds for conducting films with the thickness 10-100
nm, which are considered promising for future magnonic and spintronic
applications.",1308.5040v1
2016-06-09,Snell's Law for Spin Waves,"We report the experimental observation of Snell's law for magneto-static spin
waves in thin ferromagnetic Permalloy films by imaging incident, refracted and
reflected waves. We use a thickness step as the interface between two media
with different dispersion relation. Since the dispersion relation for
magneto-static waves in thin ferromagnetic films is anisotropic, deviations
from the isotropic Snell's law known in optics are observed for incidence
angles larger than 25\textdegree{} with respect to the interface normal between
the two magnetic media. Furthermore, we can show that the thickness step
modifies the wavelength and the amplitude of the incident waves. Our findings
open up a new way of spin wave steering for magnonic applications.",1606.02895v1
2016-10-27,Observation of Self-Cavitating Envelope Dispersive Shock Waves in Yttrium Iron Garnet Thin Films,"The formation and properties of envelope dispersive shock wave (DSW)
excitations from repulsive nonlinear waves in a magnetic film are studied.
Experiments involve the excitation of a spin-wave step pulse in a low-loss
magnetic Y$_3$Fe$_5$O$_{12}$ thin film strip, in which the spin-wave amplitude
increases rapidly, realizing the canonical Riemann problem of shock theory.
Under certain conditions, the envelope of the spin-wave pulse evolves into a
DSW that consists of an expanding train of nonlinear oscillations with
amplitudes increasing from front to back, terminated by a black soliton. The
onset of DSW self-cavitation, indicated by a point of zero power and a
concomitant 180 phase jump, is observed for sufficiently large steps,
indicative of the bidirectional dispersive hydrodynamic nature of the DSW. The
experimental observations are interpreted with theory and simulations of the
nonlinear Schr\""odinger equation.",1610.08846v3
2022-11-21,Spin Hall effect of radiofrequency waves in magnetized plasmas,"In inhomogeneous media, electromagnetic-wave rays deviate from the
trajectories predicted by the leading-order geometrical optics. This effect,
called the spin Hall effect of light, is typically neglected in ray-tracing
codes used for modeling waves in plasmas. Here, we demonstrate that the spin
Hall effect can be significant for radiofrequency waves in toroidal magnetized
plasmas whose parameters are in the ballpark of those used in fusion
experiments. For example, an electron-cyclotron wave beam can deviate by as
large as ten wavelengths ($\sim 0.1\,\text{m}$) relative to the lowest-order
ray trajectory in the poloidal direction. We calculate this displacement using
gauge-invariant ray equations of extended geometrical optics, and we also
compare our theoretical predictions with full-wave simulations.",2211.11705v5
2022-12-19,Confined phase singularities reveal the spin-to-orbital angular momentum conversion of sound waves,"We identify an acoustic process in which the conversion of angular momentum
between its spin and orbital form takes place. The interaction between an
evanescent wave propagating at the interface of two immiscible fluids and an
isolated droplet is considered. The elliptical motion of the fluid supporting
the incident wave is associated with a simple state of spin angular momentum, a
quantity recently introduced for acoustic waves in the literature. We
experimentally observe that this field predominantly forces a directional wave
transport circling the droplet's interior, revealing the existence of confined
phase singularities. The circulation of the phase, around a singular point, is
characteristic of angular momentum in its orbital form, thereby demonstrating
the conversion mechanism. The numerical and experimental observations presented
in this work have implications for the fundamental understanding of the angular
momentum of acoustic waves, and for applications such as particle manipulation
with radiation forces or torques, acoustic sensing and imaging.",2212.09439v2
2023-01-03,"Caustic spin wave beams in soft, thin films: properties and classification","In the context of wave propagation, caustics are usually defined as the
envelope of a finite-extent wavefront; folds and cusps in a caustic result in
enhanced wave amplitudes. Here, we tackle a related phenomenon, namely the
existence of well-defined beams originating solely from the geometric
properties of the corresponding dispersion relation. This directional emission,
termed caustic beam, is enabled by a stationary group velocity direction, and
has been observed first in the case of phonons. We propose an overview of this
""focusing"" effect in the context of spin waves excited in soft, thin
ferromagnetic films. Based on an analytical dispersion relation, we provide
tools for a systematic survey of caustic spin wave beams. Our theoretical
approach is validated by time-resolved microscopy experiments using the
magneto-optical Kerr effect. Then, we identify two cases of particular interest
both from fundamental and applicative perspectives. Indeed, both of them enable
broadband excitations (in terms of wave vectors) to result in narrowband beams
of low divergence.",2301.01220v1
2021-12-30,Topological materials for full-vector elastic waves,"Elastic wave manipulation is important in a wide variety of scales in
applications including information processing in tiny elastic devices and noise
control in big solid structures. The recent emergence of topological materials
opens a new avenue toward modulating elastic waves in solids. However, because
of the full-vector feature, and the complicated couplings of the longitudinal
and transverse components of elastic waves, manipulating elastic waves is
generally difficult, compared with manipulating acoustic waves (scalar waves)
and electromagnetic waves (vectorial waves but transverse only). Up to date,
topological materials, including insulators and semimetals, have been realized
for acoustic and electromagnetic waves. Although topological materials of
elastic waves have also been reported, the topological edge modes observed all
lie on the domain wall. A natural question can be asked: whether there exists
an elastic metamaterial with the topological edge modes on its own boundary
only? Here, we report a 3D metal-printed bilayer metamaterial, insulating
topologically the elastic waves. By introducing the chiral interlayer
couplings, the spin-orbit couplings for elastic waves are induced, which give
rise to nontrivial topological properties. The helical edge states with the
vortex feature are demonstrated on the boundary of the single topological
phase. We further show a heterostructure of the metamaterial, which exhibits
tunable edge transport. Our work may have potential in devices based on elastic
waves in solids.",2201.04950v1
1998-11-23,Spin-Wave Excitations of Half-Filled Kondo Lattice Model,"The spin excitations in the antiferromagnetic phase of half-filled Kondo
lattice model are studied by means of the decoupling approximation for spin
Green's function. The spin-wave spectrum is calculated as a function of Kondo
coupling, and this is used to calculate the thermodynamic quantities at low
temperatures. The N\'{e}el temperature of the form
  $T_{\rm N}=0.087{J}^2\ln{(1/J)}$ is obtained for the 3-dimensional case in
the weak-coupling limit. It is pointed out that the ratio of the spin-wave
velocity to the N\'{e}el temperature $v_s/T_{\rm N}$ is enhanced as the Kondo
coupling becomes small, reflecting the long-range nature of effective
interactions between localized spins.",9811316v1
2000-11-28,Spin wave dispersion softening in the ferromagnetic Kondo lattice model for manganites,"Spin dynamics is calculated in the ferromagnetic (FM) state of the
generalized Kondo lattice model taking into account strong on-site correlations
between e_g electrons and antiferromagnetic (AFM) exchange among t_{2g} spins.
Our study suggests that competing FM double-exchange and AFM super-exchange
interaction lead to a rather nontrivial spin-wave spectrum. While spin
excitations have a conventional Dq^2 spectrum in the long-wavelength limit,
there is a strong deviation from the spin-wave spectrum of the isotropic
Heisenberg model close to the zone boundary. The relevance of our results to
the experimental data are discussed.",0011464v1
2005-06-04,Soliton solution of continuum magnetization-equation in conducting ferromagnet with a spin-polarized current,"Exact soliton solutions of a modified Landau-Lifshitz equation for the
magnetization of conducting ferromagnet in the presence of a spin-polarized
current are obtained by means of inverse scattering transformation. From the
analytical solution effects of spin-current on the frequency, wave number, and
dispersion law of spin wave are investigated. The one-soliton solution
indicates obviously current-driven precession and periodic shape-variation as
well. The inelastic collision of solitons by which we mean the shape change
before and after collision appears due to the spin current. We, moreover, show
that complete inelastic collisions can be achieved by adjusting spectrum and
current parameters. This may lead to a potential technique for shape control of
spin wave.",0506103v1
2005-11-09,Current driven magnetization dynamics in helical spin density waves,"A mechanism is proposed for manipulating the magnetic state of a helical spin
density wave using a current. In this paper, we show that a current through a
bulk system with a helical spin density wave induces a spin transfer torque,
giving rise to a rotation of the order parameter.The use of spin transfer
torque to manipulate the magnetization in bulk systems does not suffer from the
obstacles seen for magnetization reversal using interface spin transfer torque
in multilayered systems. We demonstrate the effect by a quantitative
calculation of the current induced magnetization dynamics of Erbium. Finally we
propose a setup for experimental verification.",0511224v2
2006-01-22,Thermodynamic properties of the ferrimagnetic spin chains in the presence of a magnetic field,"We have implemented three approaches to describe the thermodynamic properties
of ferrimagnetic ($S=5/2, s=2$) spin chains. The application of cumulant
expansion has been generalized to the ferrimagnetic chain in the presence of an
external magnetic field. Using cumulants, we have obtained the field dependent
effective Hamiltonian in terms of the classical variables up to the second
order of quantum corrections. Thermodynamic functions, the internal energy, the
specific heat and the magnetic susceptibility are obtained from the effective
Hamiltonian. We have also examined the modified spin wave theory to derive the
same physical properties. Finally, we have studied our model using quantum
Monte Carlo simulation to obtain accurate results. The comparison of the above
results and also the high temperature series expansion shows that cumulant
expansion gives good results for moderate and high temperature regions while
the modified spin wave theory is good for low temperatures. Moreover, the
convergence regions of the cumulant expansion and the modified spin wave theory
overlap each other which propose these two as a set of complement methods to
get the thermodynamic properties of spin models.",0601494v1
2006-02-18,Spin waves in quasi-equilibrium spin systems,"Using the Landau Fermi liquid theory we have discovered a new regime for the
propagation of spin waves in a quasi-equilibrium spin systems. We have
determined the dispersion relation for the transverse spin waves and found that
one of the modes is gapless. The gapless mode corresponds to the precessional
mode of the magnetization in a paramagnetic system in the absence of an
external magnetic field. One of the other modes is gapped which is associated
with the precession of the spin current around the internal field. The gapless
mode has a quadratic dispersion leading to some interesting thermodynamic
properties including a $T^{3/2}$ contribution to the specific heat. We also
show that these modes make significant contributions to the dynamic structure
function.",0602435v1
2006-03-03,Spin-flop transitions and spin-wave gaps in La_2CuO_4,"We study the spin-wave spectrum and the spin-flop transitions in La_2CuO_4 in
a uniform magnetic field at zero temperature. Using the non-linear sigma-model,
we show that a field applied along the orthorhombic b direction leads to a
two-step rotation of the staggered magnetization, first in the bc and then in
the ac plane, until the order parameter is completely aligned along the c axis.
In contrast, for a perpendicular magnetic field, we find a conventional
spin-flop transition induced by the competition between the field and the
interlayer coupling. A comparison with recent measurements of the
field-dependence of the in-plane spin-wave gap shows a beautiful agreement
between theory and experiments.",0603061v2
2007-03-07,Effective action of the weakly doped t-J model and spin-wave excitations in the spin-glass phase of La_{2-x}Sr_xCuO_4,"We derive the low-energy effective field theory of the extended t-J model in
the regime of light doping. The action includes a previously unknown Berry
phase term, which is discussed in detail. We use this effective field theory to
calculate spin-wave excitations in the disordered spin spiral state of
La_{2-x}Sr_xCuO_4 (the spin-glass phase). We predict an excitation spectrum
with two distinct branches: The in-plane mode has the usual linear spin-wave
dispersion and the out-of-plane mode shows non-trivial doping dependent
features. We also calculate the intensities for inelastic neutron scattering in
these modes.",0703172v1
2008-02-29,Numerical Relativity meets Data Analysis: Spinning Binary Black Hole Case,"We present a study of the gravitational waveforms from a series of spinning,
equal-mass black hole binaries focusing on the harmonic content of the waves
and the contribution of the individual harmonics to the signal-to-noise ratio.
The gravitational waves were produced from two series of evolutions with black
holes of initial spins equal in magnitude and anti-aligned with each other. In
one series the magnitude of the spin is varied; while in the second, the
initial angle between the black-hole spins and the orbital angular momentum
varies. We also conduct a preliminary investigation into using these waveforms
as templates for detecting spinning binary black holes. Since these runs are
relativity short, containing about two to three orbits, merger and ringdown, we
limit our study to systems of total mass greater than 50 solar masses. This
choice ensures that our waveforms are present in the ground-based detector band
without needing addition gravitational wave cycles. We find that while the mode
contribution to the signal-to-noise ratio varies with the initial angle, the
total mass of the system caused greater variations in the match.",0802.4427v1
2010-04-26,Spin density wave in oxypnictide superconductors in a three-band model,"The spin density wave and its temperature dependence in oxypnictide are
studied in a three-band model. The spin susceptibilities with various
interactions are calculated in the random phase approximation(PPA). It is found
that the spin susceptibility peaks around the M point show a spin density
wave(SDW) with momentum (0, $\pi$) and a clear stripe-like spin configuration.
The intra-band Coulomb repulsion enhances remarkably the SDW but the Hund's
coupling weakens it. It is shown that a new resonance appears at higher
temperatures at the $\Gamma$ point indicating the formation of a paramagnetic
phase. There is a clear transition from the SDW phase to the paramagnetic
phase.",1004.4570v1
2010-11-16,Photon spin operator and Pauli matrix,"Any polarization vector of a plane wave can be decomposed into a pair of
mutually orthogonal base vectors, known as a polarization basis. Regarding this
decomposition as a quasi-unitary transformation from a three-component vector
to a corresponding two-component spinor, one is led to a representation
formalism for the photon spin. The spin operator $\hat{\boldsymbol \gamma}$
defined on the space of unit spinors, referred to as the Jones space, has only
component along the wave vector and is represented by one of the Pauli matrices
in the commonly used polarization basis. It is deformed by the quasi-unitary
transformation from the spin operator that is defined on the space of unit
polarization vectors, referred to as the Pancharatnam space. On the basis of
this theory, it is shown that the Cartesian components of spin operator
$\hat{\boldsymbol \gamma}$ are mutually commutative and the spin angular
momentum in units of $\hbar$ is exactly the component of the Stokes vector
along the wave vector.",1011.3608v1
2012-01-13,Does a Surface Polariton Have Spin?,"We consider a p-polarized surface electromagnetic wave (a classical surface
polariton) at the interface between the vacuum and a metal or left-handed
medium. We show that the evanescent electromagnetic waves forming the surface
polariton inevitably possess a backward spin energy flow, which, together with
a superluminal orbital energy flow, form the total Poynting vector. This spin
energy flow generates a well-defined (but not quantized) spin angular momentum
of surface polaritons which is orthogonal to the propagation direction. The
spin of evanescent waves arises from the imaginary longitudinal component of
the electric field which makes the polarization effectively elliptical in the
propagation plane. We also examine the connection between the spin and
chirality of evanescent modes.",1201.2746v3
2012-10-09,"Spin Wave Excitations in AFe$_{1.5}$Se$_2$ (A=K, Tl): Analytical Study","We have analytically solved the spin wave excitations for the intercalated
ternary iron-selenide AFe$_{1.5}$Se$_2$ (A=K, Tl) in the $4\times 2$ collinear
antiferromagnetic order. It is found that there are one acoustic branch
(gapless Goldstone mode) and two gapful optical branches of spin wave
excitations with each in double degeneracy. By examining the non-imaginary
excitation frequency condition, we can determine the corresponding phase
boundary. The exchange couplings between Fe moments in AFe$_{1.5}$Se$_2$ are
derived based on the first-principles total energy calculations. The Fe spin is
found to be $S=3/2$ through computing the antiferromagnetic quantum
fluctuation. And it is further found that a very small spin-orientation
anisotropy can remarkably suppress the antiferromagnetic quantum fluctuation.
The spin dynamical structure factors are calculated and discussed in
association with neutron inelastic scattering experiment.",1210.2668v1
2012-11-30,Paramagnetic spin excitations in insulating Rb$_{0.8}$Fe$_{1.6}$Se$_2$,"We use neutron scattering to study temperature dependent spin excitations in
insulating antiferromagnetic (AF) Rb$_{0.8}$Fe$_{1.6}$Se$_2$. In the
low-temperature AF state, spin waves can be accurately described by a local
moment Heisenberg Hamiltonian. On warming to around the Neel temperature of
T_N=500$ K, low-energy (E<30meV) paramagnetic spin excitations form
Lorentzian-like quasielastic peaks centered at the AF wave vectors associated
with spin waves, while high-energy (E>50meV) spin excitations become heavily
damped. Upon further warming to above the structural distortion temperature of
T_s=524K, the entire paramagnetic excitations become overdamped. These results
suggest that AF Rb$_{0.8}$Fe$_{1.6}$Se$_2$ is not a copper-oxide-like Mott
insulator, and has less electron correlations compared with metallic iron
pnictides and iron chalcogenides.",1211.7328v1
2014-01-06,Order by Disorder Spin Wave Gap in the XY Pyrochlore Magnet Er2Ti2O7,"The recent determination of a robust spin Hamiltonian for the
anti-ferromagnetic XY pyrochlore Er2Ti2O7 reveals a most convincing case of the
""order by quantum disorder"" (ObQD) mechanism for ground state selection. This
mechanism relies on quantum fluctuations to remove an accidental symmetry of
the magnetic ground state, and selects a particular ordered spin structure
below T_N=1.2K. The removal of the continuous degeneracy results in an energy
gap in the spectrum of spin wave excitations, long wavelength pseudo-Goldstone
modes. We have measured the ObQD spin wave gap at a zone center in Er2Ti2O7,
using low incident energy neutrons and the time-of-flight inelastic scattering
method. We report a gap of Delta =0.053 +/- 0.006 meV, which is consistent with
upper bounds placed on it from heat capacity measurements and roughly
consistent with theoretical estimate of ~ 0.02 meV, further validating the spin
Hamiltonian that led to that prediction. The gap is observed to vary with
square of the order parameter, and goes to zero for T ~ T_N.",1401.1176v2
2014-03-12,Crossover from spin-waves to diffusive spin excitations in underdoped Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$,"Using inelastic neutron scattering, we show that the onset of
superconductivity in underdoped Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$ coincides
with a crossover from well-defined spin waves to overdamped and diffusive spin
excitations. This crossover occurs despite the presence of long-range stripe
antiferromagnetic order for samples in a compositional range from x=0.04-0.055,
and is a consequence of the shrinking spin-density wave gap and a corresponding
increase in the particle-hole (Landau) damping. The latter effect is captured
by a simple itinerant model relating Co doping to changes in the hot spots of
the Fermi surface. We argue that the overdamped spin fluctuations provide a
pairing mechanism for superconductivity in these materials.",1403.2793v1
2014-04-03,Spin liquid phase in the semiclassical theory of the Heisenberg model on an anisotropic triangular lattice with ring exchange,"We investigate the effect of ring-exchange on the ground-state properties and
magnetic excitations of the $S = 1/2$ Heisenberg model on the anisotropic
triangular lattice with ring-exchange at $T = 0$ using linear spin-wave theory.
Classically, we find stable N\'{e}el, spiral and collinear magnetically ordered
phases. Upon including quantum fluctuations to the model, linear spin-wave
theory shows that ring exchange induces a large quantum disordered region in
the phase diagram, completely wiping out the classically stable collinear
phase. Analysis of the spin-wave spectra for each of these three models
demonstrates that the large spin-liquid phase observed in the full model is a
direct manifestation of competing classical orders. To understand the origin of
these competing phases we introduce models where either the four spin
contributions from ring exchange, or the renormalization of the Heisenberg
terms due to ring exchange are neglected. We find that these two terms favor
rather different physics.",1404.0769v1
2016-07-03,Spin waves and magnetic exchange interactions in the spin ladder compound RbFe$_2$Se$_3$,"We report an inelastic neutron scattering study of the spin waves of the
one-dimensional antiferromagnetic spin ladder compound RbFe$_2$Se$_3$. The
results reveal that the products, $SJ$'s, of the spin $S$ and the magnetic
exchange interactions $J$'s along the antiferromagnetic (leg) direction and the
ferromagnetic (rung) direction are comparable with those for the stripe ordered
phase of the parent compounds of the iron-based superconductors. The
universality of the $SJ$'s implies nearly universal spin wave dynamics and the
irrelevance of the fermiology for the existence of the stripe antiferromagnetic
order among various Fe-based materials.",1607.00639v1
2018-01-10,Spin dynamics and Andreev-Bashkin effect in mixtures of one-dimensional Bose gases,"We investigate the propagation of spin waves in two-component mixtures of
one-dimensional Bose gases interacting through repulsive contact potentials. By
using quantum Monte Carlo methods we calculate static ground-state properties,
such as the spin susceptibility and the spin structure factor, as a function of
both the intra-species and inter-species coupling strength and we determine the
critical parameters for phase separation. In homogeneous mixtures, results of
the velocity of spin waves and of its softening close to the critical point of
phase separation are obtained by means of a sum-rule approach. We quantify the
non-dissipative drag effect, resulting from the Andreev-Bashkin current-current
interaction between the two components of the gas, and we show that in the
regime of strong coupling it causes a significant suppression of the spin-wave
velocity.",1801.03446v2
2018-02-05,Micromagnetic view on ultrafast magnon generation by femtosecond spin current pulses,"In this Article we discuss a micromagnetic modelling approach to describe the
ultrafast spin-transfer torque excitation of coherent and incoherent magnons on
the nanoscale. Implementing the action of a femtosecond spin current pulse
entering an orthogonally magnetized thin ferromagnetic film, we reproduce
recent experimental results and reveal the factors responsible for the unequal
excitation efficiency of various spin waves. Our findings are in an excellent
agreement with the results of an analytical description of spin-wave excitation
based on classical kinetic equations. Furthermore, we suggest an experimental
design allowing for the excitation of laterally propagating spin waves beyond
the optical diffraction limit. Our findings demonstrate that the classical
micromagnetic picture retains its predictive and interpretative power on
femtosecond temporal and nanometer spatial scales.",1802.01305v1
2021-04-22,Spin orbit torque nano-oscillators by dipole field-localized spin wave modes,"We demonstrate a high-quality spin orbit torque nano-oscillator comprised of
spin wave modes confined by the magnetic field by the strongly inhomogeneous
dipole field of a nearby micromagnet. This approach enables variable spatial
confinement and systematic tuning of magnon spectrum and spectral separations
for studying the impact of multi-mode interactions on auto-oscillations. We
find these dipole field-localized spin wave modes exhibit good characteristic
properties as auto-oscillators--narrow linewidth and large amplitude--while
persisting up to room temperature. We find that the linewidth of the
lowest-lying localized mode is approximately proportional to temperature in
good agreement with theoretical analysis of the impact of thermal fluctuations.
This demonstration of a clean oscillator with tunable properties provides a
powerful tool for understanding the fundamental limitations and linewidth
contributions to improve future spin-Hall oscillators.",2104.10838v3
2019-04-22,An overview of the gravitational spin Hall effect,"In General Relativity, the propagation of electromagnetic waves is usually
described by the vacuum Maxwell's equations on a fixed curved background. In
the limit of infinitely high frequencies, electromagnetic waves can be
localized as point particles, following null geodesics. However, at finite
frequencies, electromagnetic waves can no longer be treated as point particles
following null geodesics, and the spin angular momentum of light comes into
play, via the spin-curvature coupling. We will refer to this effect as the
gravitational spin Hall effect of light. Here, we review a series of
theoretical results related to the gravitational spin Hall effect of light, and
we compare the predictions of different models. The analogy with the spin Hall
effect in Optics is also explored, since in this field the effect is well
understood, both theoretically and experimentally.",1904.09963v1
2019-09-18,Micromagnetic Modeling of Telegraphic Mode Jumping in Microwave Spin Torque Oscillators,"The time domain stability of microwave spin torque oscillators (STOs) has
been investigated by systematic micromagnetic simulations. A model based on
internal spin wave reflection at grain boundaries with reduced exchange
coupling was implemented and used to study the oscillator under quasi-stable
operating conditions. Telegraphic mode jumping between two operating
frequencies (23.3 and 24.1 GHz) was observed in the time domain with
characteristic dwell times in the range of 10-100 ns. The oscillating volume
was shown to have a different shape at the distinct operating frequencies. The
shape difference is governed by spin wave reflections at the grain boundaries.
The resulting non-linear behavior of the oscillator was shown to be a
collective effect of spin wave scattering at different locations within a few
spin wavelengths from the nano-contact.",1909.08431v1
2020-01-13,Gate-tunable spin waves in antiferromagnetic atomic bilayers,"The emergence of two-dimensional (2D) layered magnetic materials has opened
an exciting playground for both fundamental studies of magnetism in 2D and
explorations of spinbased applications. Remarkable properties, including spin
filtering in magnetic tunnel junctions and gate control of magnetic states,
have recently been demonstrated in 2D magnetic materials. While these studies
focus on the static properties, dynamic magnetic properties such as excitation
and control of spin waves have remained elusive. Here we excite spin waves and
probe their dynamics in antiferromagnetic CrI3 bilayers by employing an
ultrafast optical pump/magneto-optical Kerr probe technique. We identify
sub-terahertz magnetic resonances under an in-plane magnetic field, from which
we determine the anisotropy and interlayer exchange fields and the spin damping
rates. We further show tuning of antiferromagnetic resonances by tens of
gigahertz through electrostatic gating. Our results shed light on magnetic
excitations and spin dynamics in 2D magnetic materials, and demonstrate their
unique potential for applications in ultrafast data storage and processing.",2001.04044v1
2020-10-01,"Spinor wave equation, relativistic condition, and nonlocality of photon spin","The purpose of this paper is to derive the photon spin and to deduce its
properties from a pair of quantum equations for the photon. To this end,
Darwin's equations are reinterpreted so as to meet the need of the quantum
mechanics of the photon. It is found that the photon wavefunction transforms
under Lorentz transformation as a spinor. The relativistic nature of the photon
is expressed through a constraint equation on the wavefunction in such a way
that the wave equation, which takes on the form of the Schr\""{o}dinger
equation, is not Lorentz covariant unless the constraint equation is taken into
account. The wave equation predicts the existence of a kind of spin, an
intrinsic degree of freedom. But the constraint equation makes the spin
nonlocal in the sense that no unique local density exists for the spin in
position space. The nonlocality of the photon spin is a reflection of the
nonlocality of the photon itself.",2010.00241v1
2022-02-08,Spin waves in spin hydrodynamics,"The propagation properties of spin degrees of freedom are analyzed in the
framework of relativistic hydrodynamics with spin based on the de Groot--van
Leeuwen--van Weert definitions of the energy-momentum and spin tensors. We
derive the analytical expression for the spin wave velocity for arbitrary
statistics and show that it goes to half the speed of light in the
ultra-relativistic limit. We find that only the transverse degrees of freedom
propagate, analogously to electromagnetic waves. Finally, we consider the
effect of dissipative corrections and calculate the damping coefficients for
the case of Maxwell-J\""uttner statistics.",2202.03952v2
2022-04-04,Spin-dependent phenomena at chiral temporal interfaces,"Temporally varying electromagnetic media have been extensively investigated
recently to unveil new means for controlling light. However, spin-dependent
phenomena in such media have not been explored thoroughly. Here, we reveal the
existence of spin-dependent phenomena at a temporal interface between chiral
and dielectric media. In particular, we show theoretically and numerically that
due to the material discontinuity in time, linearly polarized light is split
into forward-propagating right-handed and left-handed circularly polarized
waves having different angular frequencies and it the same phase velocities.
This salient effect allows complete temporal separation of the two spin states
of light with high efficiency. In addition, a phenomenon of spin-dependent
gain/loss is observed. Furthermore, we show that when the dielectric medium is
switched again to the original chiral medium, the right- and left-handed
circularly polarized light waves (with different angular frequencies) merge to
form a linearly polarized wave. Our findings extend spin-dependent interactions
of light from space to space-time.",2204.01574v3
2022-04-27,Elastic Spin and Orbital Angular Momenta,"Motivated by recent theoretical and experimental interest in the spin and
orbital angular momenta of elastic waves, we revisit canonical wave momentum,
spin, and orbital angular momentum in isotropic elastic media. We show that
these quantities are described by simple universal expressions, which differ
from the results of [G. J. Chaplain et al., Phys. Rev. Lett. 128, 064301
(2022)] and do not require separation of the longitudinal and transverse parts
of the wavefield. For cylindrical elastic modes, the normalized z-component of
the total (spin+orbital) angular momentum is quantized and equals the azimuthal
quantum number of the mode, while the orbital and spin parts are not quantized
due to the spin-orbit geometric-phase effects. In contrast to the claims of the
above article, longitudinal, transverse, and `hybrid' contributions to the
angular momenta are equally important and cannot be neglected. As another
application of the general formalism, we calculate the transverse spin angular
momentum of a surface Rayleigh wave.",2204.13037v3
2022-12-05,Spin wavepackets in the Kagome ferromagnet Fe$_3$Sn$_2$: propagation and precursors,"The propagation of spin waves in magnetically ordered systems has emerged as
a potential means to shuttle quantum information over large distances.
Conventionally, the arrival time of a spin wavepacket at a distance, $d$, is
assumed to be determined by its group velocity, $v_g$. He we report
time-resolved optical measurements of wavepacket propagation in the Kagome
ferromagnet Fe$_3$Sn$_2$ that demonstrate the arrival of spin information at
times significantly less than $d/v_g$. We show that this spin wave ""precursor""
originates from the interaction of light with the unusual spectrum of
magnetostatic modes in Fe$_3$Sn$_2$. Related effects may have far-reaching
consequences toward realizing long-range, ultrafast spin wave transport in both
ferromagnetic and antiferromagnetic systems.",2212.02498v1
2023-09-07,"Neutron spin echo is a ""quantum tale of two paths''","We describe an experiment that strongly supports a two-path interferometric
model in which the spin-up and spin-down components of each neutron propagate
coherently along spatially separated parallel paths in a typical neutron spin
echo small angle scattering (SESANS) experiment. Specifically, we show that the
usual semi-classical, single-path treatment of Larmor precession of a polarized
neutron in an external magnetic field predicts a damping as a function of the
spin echo length of the SESANS signal obtained with a periodic phase grating
when the transverse width of the neutron wave packet is finite. However, no
such damping is observed experimentally, implying either that the Larmor model
is incorrect or that the transverse extent of the wave packet is very large. In
contrast, we demonstrate theoretically that a quantum-mechanical
interferometric model in which the two mode-entangled (i.e. intraparticle
entangled) spin states of a single neutron are separated in space when they
interact with the grating accurately predicts the measured SESANS signal, which
is independent of the wave packet width.",2309.03987v2
2023-02-06,Accurate calculation of gravitational wave memory,"Gravitational wave memory is an important prediction of general relativity.
The detection of the gravitational wave memory can be used to test general
relativity and to deduce the property of the gravitational wave source.
Quantitative model is important for such detection and signal interpretation.
Previous works on gravitational wave memory always use the energy flux of
gravitational wave to calculate memory. Such relation between gravitational
wave energy and memory has only been validated for post-Newtonian
approximation. The result of numerical relativity about gravitational wave
memory is not confident yet. Accurately calculating memory is highly demanded.
Here we propose a new method to calculate the gravitational wave memory. This
method is based on Bondi-Metzner-Sachs theory. Consequently our method does not
need slow motion and weak field conditions for gravitational wave source. Our
new method can accurately calculate memory if the non-memory waveform is known.
As an example, we combine our method with matured numerical relativity result
about non-memory waveform for binary black hole coalescence. We calculate the
waveform for memory which can be used to aid memory detection and gravitational
wave source understanding. Our calculation result confirms preliminary
numerical relativity result about memory. We find out the dependence of the
memory amplitude to the mass ratio and the spins of the two spin aligned black
holes.",2302.02642v1
2010-02-09,Searching for gravitational waves emitted by binaries with spinning components,"In this thesis we consider the data analysis problem of detecting
gravitational waves emitted by inspiraling binary systems. Detection of
gravitational waves will open a new window on the Universe enabling direct
detection of systems such as binary black holes for the first time. In the
first Chapter we show how gravitational waves are derived from Einstein's
General theory of Relativity and discuss the emission of gravitational waves
from inspiraling binaries and how this radiation may be detected using laser
interferometers. Around two thirds of stars inhabit binary systems. As they
orbit each other they will emit both energy and angular momentum in the form of
gravitational waves which will inevitably lead to their inspiral and eventual
merger. To date, searches for gravitational waves emitted during the inspiral
of binary systems have concentrated on systems with non-spinning components. In
Chapter 2 we detail the first dedicated search for binaries consisting of
spinning stellar mass compact objects. We analysed 788 hours of data collected
during the third science run (S3) of the LIGO detectors, no detection of
gravitational waves was made and we set an upper limit on the rate of
coalescences of stellar mass binaries. The inspiral of stellar mass compact
objects into super massive black holes will radiate gravitational waves at
frequencies detectable by the planned space-based LISA mission. In Chapter 3 we
describe the development and testing of a computationally cheap method to
detect the loudest few extreme mass ratio inspiral events that LISA will be
sensitive to.",1002.1876v1
2023-08-07,Inhomogeneous high temperature melting and decoupling of charge density waves in spin-triplet superconductor UTe2,"Periodic spatial modulations of the superfluid density, or pair density
waves, have now been widely detected in unconventional superconductors, either
as the primary or the secondary states accompanying charge density waves.
Understanding how these density waves emerge, or conversely get suppressed by
external parameters, provides an important insight into their nature. Here we
use spectroscopic imaging scanning tunneling microscopy to study the evolution
of density waves in the heavy fermion spin-triplet superconductor UTe2 as a
function of temperature and magnetic field. We discover that charge
modulations, composed of three different wave vectors gradually weaken but
persist to a surprisingly high temperature T_CDW ~ 10-12 K. By tracking the
local amplitude of modulations, we find that these modulations become spatially
inhomogeneous, and form patches that shrink in size with higher temperature or
with applied magnetic field. Interestingly, one of the density wave vectors
along the mirror symmetry has a slightly different temperature onset, thus
revealing an unexpected decoupling of the three-component CDW state.
Importantly, T_CDW determined from our work matches closely to the temperature
scale believed to be related to magnetic fluctuations, providing the first
possible connection between density waves observed by surface probes and bulk
measurements. Combined with magnetic field sensitivity of the modulations, this
could point towards an important role of spin fluctuations or short-range
magnetic order in the formation of the primary charge density wave.",2308.03721v1
2005-02-01,Can Frustration Preserve a Quasi-Two-Dimensional Spin Fluid?,"Using spin-wave theory, we show that geometric frustration fails to preserve
a two-dimensional spin fluid. Even though frustration can remove the interlayer
coupling in the ground-state of a classical anti-ferromagnet, spin layers
innevitably develop a quantum-mechanical coupling via the mechanism of ``order
from disorder''. We show how the order from disorder coupling mechanism can be
viewed as a result of magnon pair tunneling, a process closely analogous to
pair tunneling in the Josephson effect. In the spin system, the Josephson
coupling manifests itself as a a biquadratic spin coupling between layers, and
for quantum spins, these coupling terms are as large as the inplane coupling.
An alternative mechanism for decoupling spin layers occurs in classical XY
models in which decoupled ""sliding phases"" of spin fluid can form in certain
finely tuned conditions. Unfortunately, these finely tuned situations appear
equally susceptible to the strong-coupling effects of quantum tunneling,
forcing us to conclude that in general, geometric frustration cannot preserve a
two-dimensional spin fluid.",0502003v2
2005-11-11,The time dependence of muon spin relaxation spectra and spin correlation functions,"The existing theory of the microscopic interpretation of the dynamical
contribution to zero-field muon depolarization spectra in a longitudinal
geometry is developed. The predicted relaxation of the muon depolarization is
calculated from two forms of the spin correlation function. First, when the
spin correlation function has an exponential form with a single wave vector
dependent relaxation rate is considered, it is shown that this form of the spin
correlation function reproduces the slow and fast fluctuation limits of
stochastic spin theory regardless of the choice of microscopic spin model.
Second, if the spin correlation function is a homogeneous scaling function
(such as a power-law decay with time), as suggested by the mode-coupling theory
of spin dynamics, this results in a stretched exponential relaxation of the
muon spectra. For simple spin diffusion, the muon spectra are shown to be relax
with a root-exponential form.",0511288v1
2010-06-15,Non-magnetic Stern-Gerlach Experiment from Electron Diffraction,"Using the wave nature of the electrons, we demonstrate that a transverse spin
current can be generated simply by the diffraction through a single slit in the
spin-orbital coupling system of the two-dimensional electron gas. The
diffracted electron picks up the transverse momentum. The up spin electron goes
one way and the down spin electron goes the other, producing the coherent spin
current. In the system of spin-orbital coupling $\sim10^{-13}$ eV$\cdot$m, the
\emph{out-of-plane} component of the spin of the electron can be generated up
to 0.42 $\hbar$. Based on this effect, a novel device of grating to distill
spin is designed. Two first diffraction peaks of electron carry different
spins, duplicating the non-magnetic version of Stern-Gerlach experiment. The
direction of the spin current can be controlled by the gate voltage with low
energy cost.",1006.2872v1
2010-11-23,Spin Period Evolution of Recycled Pulsar in Accreting Binary,"We investigate the spin-period evolutions of recycled pulsars in binary
accreting systems. Taking both the accretion induced field decay and spin-up
into consideration, we calculate their spin-period evolutions influenced by the
initial magnetic-field strengths, initial spin-periods and accretion rates,
respectively. The results indicate that the minimum spin-period (or maximum
spin frequency) of millisecond pulsar (MSP) is independent of the initial
conditions and accretion rate when the neutron star (NS) accretes $\sim>
0.2\ms$. The accretion torque with the fastness parameter and gravitational
wave (GW) radiation torque may be responsible for the formation of the minimum
spin-period (maximum spin frequency). The fastest spin frequency (716 Hz) of
MSP can be inferred to associate with a critical fastness parameter about
$\omega_{c}=0.55$. Furthermore, the comparisons with the observational data are
presented in the field-period ($B-P$) diagram.",1011.5013v1
2012-07-27,Spin transition rates in nanowire superlattices: Rashba spin-orbit coupling effects,"We investigate the influence of Rashba spin-orbit coupling in a parabolic
nanowire modulated by longitudinal periodic potential. The modulation potential
can be obtained from realistically grown supperlattices (SLs). Our study shows
that the Rashba spin-orbit interaction induces the level crossing point in the
parabolic nanowire SLs. We estimate large anticrossing width (approximately 117
$\mu eV$) between singlet-triplet states. We study the phonon and
electromagnetic field mediated spin transition rates in the parabolic nanowire
SLs. We report that the phonon mediated spin transition rate is several order
of magnitude larger than the electromagnetic field mediated spin transition
rate. Based on the Feynman disentangling technique, we find the exact spin
transition probability. For the case wave vector $k=0$, we report that the
transition probability can be tuned in the form of resonance at fixed time
interval. For the general case ($k\neq 0$), we solve the Riccati equation and
find that the arbitrary values of $k$ induces the damping in the transition
probability. At large value of Rashba spin-orbit coupling coefficients for
($k\neq 0$), spin transition probability freezes.",1207.6580v2
2014-12-18,Spinor Bose gas in an elongated trap,"We examine a spinor Bose gas confined by an elongated trap. Since a
spin-independent energy is much higher than a spin-dependent energy in alkali
species, the system exhibits different properties by changing a radial
confinement. We show that if a spin-dependent coupling is positive, a
spin-liquid condensate, which breaks the charge U(1) symmetry but preserves the
spin rotational symmetry, can be realized in an intermediate confinement
regime. Properties of the spin-liquid condensate are visible if a temperature
is lower than a spin gap to characterize the spin-disorder property. If a
temperature is higher than the gap but lower than a spin-dependent coupling, on
the other hand, a regime in which a spin sector is described by a semiclassical
wave emerges. A characterization in each regime by means of correlation
functions and topological solitons is also discussed.",1412.6066v2
2015-02-13,Spin Dynamics with Inertia in Metallic Ferromagnets,"Non-adiabatic contribution of environmental degrees of freedom yields
effective inertia of spin in effective spin dynamics. In this paper, we study
several aspects of the inertia of spin in metallic ferromagnets. (i) a concrete
expression of the spin inertia $m_s$: $m_s=\hbar S_c/(2g_{\rm sd})$, where
$S_c$ is the spin polarization of conduction electrons and $g_{\rm sd}$ is the
$sd$ coupling constant. (ii) dynamical behavior of spin with inertia, discussed
from viewpoints of a spinning top and of a particle on a sphere. (iii) behavior
of spin waves and domain walls in the presence of inertia, and behavior of spin
with inertia in the case of a time-dependent magnetic field.",1502.04107v2
2015-05-06,Reexamination of the Elliott-Yafet spin-relaxation mechanism,"We analyze spin-dependent carrier dynamics due to incoherent electron-phonon
scattering, which is commonly referred to as Elliott-Yafet (EY) spin-relaxation
mechanism. For this mechanism one usually distinguishes two contributions: (1)
from the electrostatic interaction together with spin-mixing in the wave
functions, which is often called the Elliott contribution, and (2) the
phonon-modulated spin-orbit interaction, which is often called the Yafet or
Overhauser contribution. By computing the reduced electronic density matrix, we
improve Yafet's original calculation, which is not valid for pronounced spin
mixing as it equates the pseudo-spin polarization with the spin polarization.
The important novel quantity in our calculation is a torque operator that
determines the spin dynamics. The contribution (1) to this torque vanishes
exactly. From this general result, we derive a modified expression for the
Elliott-Yafet spin relaxation time.",1505.01432v2
2015-07-22,Observation of correlated spin-orbit order in a strongly anisotropic quantum wire system,"Quantum wires with spin-orbit coupling provide a unique opportunity to
simultaneously control the coupling strength and the screened Coulomb
interactions where new exotic phases of matter can be explored. Here we report
on the observation of an exotic spin-orbit density wave in Pb-atomic wires on
Si(557) surfaces by mapping out the evolution of the modulated spin-texture at
various conditions with spin- and angle-resolved photoelectron spectroscopy.
The results are independently quantified by surface transport measurements. The
spin polarization, coherence length, spin dephasing rate, and the associated
quasiparticle gap decrease simultaneously as the screened Coulomb interaction
decreases with increasing excess coverage, providing a new mechanism for
generating and manipulating a spin-orbit entanglement effect via electronic
interaction. Despite clear evidence of spontaneous spin-rotation symmetry
breaking and modulation of spin-momentum structure as a function of excess
coverage, the average spin-polarization over the Brillouin zone vanishes,
indicating that time-reversal symmetry is intact as theoretically predicted.",1507.06152v1
2015-07-23,Minimal Model of Spin-Transfer Torque and Spin Pumping caused by Spin Hall Effect,"In the normal metal/ferromagnetic insulator bilayer (such as
Pt/Y$_{3}$Fe$_{5}$O$_{12}$) and the normal metal/ferromagnetic metal/oxide
trilayer (such as Pt/Co/AlO$_{x}$) where spin injection and ejection are
achieved by the spin Hall effect in the normal metal, we propose a minimal
model based on quantum tunneling of spins to explain the spin-transfer torque
and spin pumping caused by the spin Hall effect. The ratio of their
damping-like to field-like component depends on the tunneling wave function
that is strongly influenced by generic material properties such as interface
$s-d$ coupling, insulating gap, and layer thickness, yet the spin relaxation
plays a minor role. The quantified result renders our minimal model an
inexpensive tool for searching for appropriate materials.",1507.06447v2
2016-04-06,Strong spin-orbit fields and Dyakonov-Perel spin dephasing in supported metallic films,"Spin dephasing by the Dyakonov-Perel mechanism in metallic films deposited on
insulating substrates is revealed, and quantitatively examined by means of
density functional calculations combined with a kinetic equation. The
surface-to-substrate asymmetry, probed by the metal wave functions in thin
films, is found to produce strong spin-orbit fields and a fast Larmor
precession, giving a dominant contribution to spin decay over the Elliott-Yafet
spin relaxation up to a thickness of 70 nm. The spin dephasing is oscillatory
in time with a rapid (sub-picosecond) initial decay. However, parts of the
Fermi surface act as spin traps, causing a persistent tail signal lasting 1000
times longer than the initial decay time. It is also found that the decay
depends on the direction of the initial spin polarization, resulting in a
spin-dephasing anisotropy of 200% in the examined cases.",1604.01559v1
2016-04-21,Electron spin filter and polarizer in a standing light wave,"We demonstrate the theoretical feasibility of spin-dependent diffraction and
spin-polarization of an electron in two counter-propagating, circularly
polarized laser beams. The spin-dynamics appears in a two-photon process of the
Kapitza-Dirac effect in the Bragg regime. We show the spin-dependence of the
diffraction process by comparison of the time-evolution of a spin-up and
spin-down electron in a relativistic quantum simulation. We further discuss the
spin properties of the scattering by studying an analytically approximated
solution of the time-evolution matrix. A classification scheme in terms of
unitary or non-unitary propagation matrices is used for establishing a
generalized and spin-independent description of the spin properties in the
diffraction process.",1604.06201v5
2017-07-27,Are the observed black hole mergers spins consistent with field binary progenitors?,"One of the puzzles in the recent observations of gravitational waves from
binary black hole mergers is the observed low (projected) spins of the
progenitor black holes. In two of the four events, GW150914, and the recent
GW170104, the observed spins are most likely negative (but consistent with
zero). In the third case LVT151012 it is practically zero and only in the forth
case, GW151226, the spin is positive but low. These observations are puzzling
within the field binary scenario in which positive higher spins are expected.
Considering the most favorable Wolfe Rayet (WR) progenitors we estimate the
expected spin distribution for different evolution scenarios and compare it to
the observations. With typical parameters one expects a significant fraction
($\ge 25\%$) of the mergers to have high effective spin values. However due to
uncertainties in the outcome of the common envelope phase (typical separation
and whether the stars are rotating or not) and in the late stages of massive
star evolution (the strength of the winds) one cannot rule our scenarios in
which the expected spins are low. While observations of high effective spin
events will support this scenario, further observations of negative spin events
would rule it out.",1707.08978v1
2019-06-01,Coherent ac spin current transmission across an antiferromagnetic CoO insulator,"The recent discovery of spin-current transmission through antiferromagnetic
(AFM) insulating materials opens up unprecedented opportunities for fundamental
physics and spintronics applications. The great mystery currently surrounding
this topic is: how could THz AFM magnons mediate a GHz spin current? This
mis-match of frequencies becomes particularly critical for the case of coherent
ac spin-current, raising the fundamental question of whether a GHz ac
spin-current can ever keep its coherence inside an AFM insulator and so drive
the spin precession of another FM layer coherently? Utilizing element- and
time-resolved x-ray pump-probe measurements on Py/Ag/CoO/Ag/Fe75Co25/MgO(001)
heterostructures, we demonstrate that a coherent GHz ac spin current pumped by
the permalloy (Py) ferromagnetic resonance (FMR) can transmit coherently across
an antiferromagnetic CoO insulating layer to drive a coherent spin precession
of the FM Fe75Co25 layer. Further measurement results favor thermal magnons
rather than evanescent spin waves as the mediator of the coherent ac spin
current in CoO.",1906.00155v1
2008-06-27,Controllable spin-current blockade in a Hubbard chain,"We investigate the spin/charge transport in a one-dimensional strongly
correlated system by using the adaptive time-dependent density-matrix
renormalization group method. The model we consider is a non-half-filled
Hubbard chain with a bond of controllable spin-dependent electron hoppings,
which is found to cause a blockade of spin current with little influence on
charge current. We have considered (1) the spread of a wave packet of both spin
and charge in the Hubbard chain and (2) the spin and charge currents induced by
a spin-dependent voltage bias that is applied to the ideal leads attached at
the ends of this Hubbard chain. It is found that the spin-charge separation
plays a crucial role in the spin-current blockade, and one may utilize this
phenomenon to observe the spin-charge separation directly.",0806.4494v1
2021-06-14,Quantum spin liquid in an RKKY-coupled two-impurity Kondo system,"We consider a 2-impurity Kondo system with spin-exchange coupling within the
conduction band. Our numerical renormalization group calculations show that for
strong intraband spin correlations the competition of these correlations with
Kondo spin screening stabilizes a metallic spin-liquid phase of the localized
spins without geometric frustration. For weak Kondo coupling the spin liquid
and the Kondo singlet phase are separated by two quantum phase transitions and
an intermediate RKKY spin-dimer phase, while beyond a critical coupling they
are connected by a crossover. The results suggest how a quantum spin liquid may
be realized in heavy-fermion systems near a spin-density wave instability.",2106.07519v3
2021-12-06,Unified formulation of interfacial magnonic pumping from non-collinear magnets,"We establish a general formulation for spin current pumped by magnons at the
interface between a normal metal and a magnetic insulator, valid for any
non-collinear magnetic configuration in the linear spin wave regime. This
current is generated by driving the system in a non-equilibrium state, covering
setups such as thermal spin injection (spin Seebeck effect) or spin voltage by
irradiation of the insulator (spin pumping). We illustrate the formula in the
special case of a honeycomb topological ferromagnet, for simplicity, and cover
both the spin Seebeck and spin-pumping setups. We show how the topological
parameters influence the spin current and propose a way to obtain a
contribution mainly from the topological edge magnons in the spin pumping case.",2112.02946v1
2022-03-08,Spin excitations of a proximate Kitaev quantum spin liquid realized in Cu$_2$IrO$_3$,"Magnetic moments arranged at the corners of a honeycomb lattice are predicted
to form a novel state of matter, Kitaev quantum spin liquid, under the
influence of frustration effects between bond-dependent Ising interactions.
Some layered honeycomb iridates and related materials, such as
Na$_{2}$IrO$_{3}$ and $\alpha$-RuCl$_{3}$, are proximate to Kitaev quantum spin
liquid, but bosonic spin-wave excitations associated with undesirable
antiferromagnetic long-range order mask the inherent properties of Kitaev
Hamiltonian. Here, we use $^{63}$Cu nuclear quadrupole resonance to uncover the
low energy spin excitations in the nearly ideal honeycomb lattice of effective
spin $S = 1/2$ at the Ir$^{4+}$ sites in Cu$_{2}$IrO$_{3}$. We demonstrate
that, unlike Na$_{2}$IrO$_{3}$, Ir spin fluctuations exhibit no evidence for
critical slowing down toward magnetic long range order in zero external
magnetic field. Moreover, the low energy spin excitation spectrum is dominated
by a mode that has a large excitation gap comparable to the Ising interactions,
a signature expected for Majorana fermions of Kitaev quantum spin liquid.",2203.04261v1
2024-02-06,The spin alignment of rho mesons in a pion gas,"We study the spin alignment of neutral rho mesons in a pion gas using spin
kinetic or Boltzmann equations. The $\rho\pi\pi$ coupling is given by the
chiral effective theory. The collision terms at the leading and next-to-leading
order in spin Boltzmann equations are derived. The evolution of the spin
density matrix of the neutral rho meson is simulated with different initial
conditions. The numerical results show that the interaction of pions and
neutral rho mesons creates very small spin alignment in the central rapidity
region if there is no rho meson in the system at the initial time. Such a small
spin alignment in the central rapidity region will decay rapidly toward zero in
later time. If there are rho mesons with a sizable spin alignment at the
initial time the spin alignment will also decrease rapidly. We also considered
the effect on $\rho_{00}$ from the elliptic flow of pions in the blast wave
model. With vanishing spin alignment at the initial time, the deviation of
$\rho_{00}$ from 1/3 is positive but very small.",2402.03672v1
2013-04-11,Intrinsic Spin Hall Effect at Oxide Interfaces: a Simple Model,"An asymmetric triangular potential well provides the simplest model for the
confinement of mobile electrons at the interface between two insulating oxides,
such as LaAlO_3 and SrTiO_3 (LAO/STO). These electrons have been recently shown
to exhibit a large spin-orbit coupling of the Rashba type, i.e., linear in the
in-plane momentum. In this paper we study the intrinsic spin Hall effect due to
Rashba coupling in an asymmetric triangular potential well. Besides splitting
each subband into two branches of opposite helicity, the spin-orbit interaction
causes the wave function in the direction perpendicular to the plane of the
quantum well (the z direction) to depend on the in-plane wave vector k. In
contrast to the extreme asymmetric case, i.e., the wedge-shaped quantum well,
for which the intrinsic spin Hall effect vanishes due to vertex corrections, we
find that the asymmetric well supports a non-vanishing intrinsic spin Hall
conductivity, which increases in magnitude as the well becomes more symmetric.
The spin Hall conductivity is found to be proportional to the square of the
spin-orbit coupling constant and, in the limit of low carrier density, depends
only on the effective mass renormalization associated with the k-dependence of
the wave functions in the z direction. Its origin lies in the non-vanishing
matrix elements of the spin current between subbands corresponding to different
states of quantized motion perpendicular to the plane of the well.",1304.3476v2
2016-08-03,Coupling a Surface Acoustic Wave to an Electron Spin in diamond via a Dark State,"The emerging field of quantum acoustics explores interactions between
acoustic waves and artificial atoms and their applications in quantum
information processing. In this experimental study, we demonstrate the coupling
between a surface acoustic wave (SAW) and an electron spin in diamond by taking
advantage of the strong strain coupling of the excited states of a nitrogen
vacancy center, while avoiding the short lifetime of these states. The SAW-spin
coupling takes place through a lamda-type three-level system where two ground
spin states couple to a common excited state through a phonon-assisted as well
as a direct dipole optical transition. Both coherent population trapping and
optically-driven spin transitions have been realized. The coherent population
trapping demonstrates the coupling between a SAW and an electron spin coherence
through a dark state. The optically-driven spin transitions, which resemble the
sideband transitions in a trapped ion system, can enable the quantum control of
both spin and mechanical degrees of freedom and potentially a trapped-ion-like
solid state system for applications in quantum computing. These results
establish an experimental platform for spin-based quantum acoustic, bridging
the gap between spintronics and quantum acoustics.",1608.01356v1
2017-06-05,Distinguishing Spin-Aligned and Isotropic Black Hole Populations With Gravitational Waves,"The first direct detections of gravitational waves from merging binary black
holes open a unique window into the binary black hole formation environment.
One promising environmental signature is the angular distribution of the black
hole spins; systems formed through dynamical interactions among already-compact
objects are expected to have isotropic spin orientations whereas binaries
formed from pairs of stars born together are more likely to have spins
preferentially aligned with the binary orbital angular momentum. We consider
existing gravitational wave measurements of the binary effective spin, the
best-measured combination of spin parameters, in the four likely binary black
hole detections GW150914, LVT151012, GW151226, and GW170104. If binary black
hole spin magnitudes extend to high values we show that the data exhibit a
$2.4\sigma$ ($0.015$ odds ratio) preference for an isotropic angular
distribution over an aligned one. By considering the effect of 10 additional
detections, we show that such an augmented data set would enable in most cases
a preference stronger than $5\sigma$ ($2.9 \times 10^{-7}$ odds ratio). The
existing preference for either an isotropic spin distribution or low spin
magnitudes for the observed systems will be confirmed (or overturned)
confidently in the near future.",1706.01385v2
2019-04-03,Collective spinon spin wave in a magnetized U(1) spin liquid,"We study the transverse dynamical spin susceptibility of the two dimensional
U(1) spinon Fermi surface spin liquid in a small applied Zeeman field. We show
that both short-range interactions, present in a generic Fermi liquid, as well
as gauge fluctuations, characteristic of the U(1) spin liquid, qualitatively
change the result based on the frequently assumed non-interacting spinon
approximation. Short-range interaction leads to a new collective mode: a
""spinon spin wave"" which splits off from the two-spinon continuum at small
momentum and disperses downward. Gauge fluctuations renormalize the
susceptibility, providing non-zero power law weight in the region outside the
spinon continuum and giving the spin wave a finite lifetime, which scales as
momentum squared. We also study the effect of Dzyaloshinskii-Moriya anisotropy
on the zero momentum susceptibility, which is measured in electron spin
resonance (ESR), and obtain a resonance linewidth linear in temperature and
varying as $B^{2/3}$ with magnetic field $B$ at low temperature. Our results
form the basis for a theory of inelastic neutrons scattering, ESR, and resonant
inelastic x-ray scattering (RIXS) studies of this quantum spin liquid state.",1904.02117v2
2020-06-12,Spin Excitations and Spin Wave Gap in the Ferromagnetic Weyl Semimetal Co$_3$Sn$_2$S$_2$,"We report a comprehensive neutron scattering study on the spin excitations in
the magnetic Weyl semimetal Co$_3$Sn$_2$S$_2$ with quasi-two-dimensional
structure. Both in-plane and out-of-plane dispersions of the spin waves are
revealed in the ferromagnetic state, similarly dispersive but damped spin
excitations persist into the paramagnetic state. The effective exchange
interactions have been estimated by a semi-classical Heisenberg model to
consistently reproduce the experimental $T_C$ and spin stiffness. However, a
full spin wave gap below $E_g=2.3$ meV is observed at $T=4$ K, much larger than
the estimated magnetic anisotropy energy ($\sim0.6$ meV), while its temperature
dependence indicates a significant contribution from the Weyl fermions. These
results suggest that Co$_3$Sn$_2$S$_2$ is a three-dimensional correlated system
with large spin stiffness, and the low-energy spin dynamics could interplay
with the topological electron states.",2006.07339v2
2022-09-06,The population properties of spinning black holes using Gravitational-wave Transient Catalog 3,"Binary black holes formed via different pathways are predicted to have
distinct spin properties. Measuring these properties with gravitational waves
provides an opportunity to unveil the origins of binary black holes. Recent
work draws conflicting conclusions regarding the spin distribution observed by
LIGO--Virgo--KAGRA (LVK). Some analyses suggest that a fraction of the observed
black-hole spin vectors are significantly misaligned (by $>90^\circ$) relative
to the orbital angular momentum. This has been interpreted to mean that some
binaries in the LVK dataset are assembled dynamically in dense stellar
environments. Other analyses find support for a sub-population of binaries with
negligible spin and no evidence for significantly misaligned spin -- a result
consistent with the field formation scenario. In this work, we study the spin
properties of binary black holes in the third LVK gravitational-wave transient
catalog. We find that there is insufficient data to resolve the existence of a
sub-population of binaries with negligible black-hole spin (the presence of
this sub-population is supported by a modest Bayes factor of 1.7). We find
modest support for the existence of mergers with extreme spin tilt angles $>
90^\circ$ (the presence of extreme-tilt binaries is favored by a Bayes factor
of 10.1). Only one thing is clear: at least some of the LVK binaries formed in
the field. At most $89\%$ of binaries are assembled dynamically (99\%
credibility), though, the true branching fraction could be much lower, even
negligible.",2209.02206v2
2001-10-15,Persistent Currents in Charge-density Wave Systems,"The inductive exchange of carriers between closed Fermi surface sections
subject to Landau quantization and open Fermi surface sections subject to
charge-density wave (or spin-density wave) formation is shown to give rise to
persistent currents. This mechanism may explain recent experimental data in
certain organic conductors in high magnetic fields.",0110278v1
2003-02-16,New Zero-Resistance States in Heterostructures: Anderson-Brinkman-Phillips Charge Density Waves and New States,"Recently, observed zero-resistance states are interpreted by
Anderson-Brinkman and Phillips as charge density waves. We point out the
existence of charge-density waves, superconducting states and new states
including a state of zero charge and finite spin.",0302320v1
2006-05-02,Waves in the Griffiths-Podolsky Metric,"Perturbations form an important section of black hole analyses. This paper
deals with the effect of perturbations as in the delineation of waves that
occur. It makes use of the spin coefficients from [3] to represent the general
equations of waves in an accelerating black hole proposed in [2].",0605020v2
2007-01-23,Spin Angular Momentum Imparted by Gravitational Waves,"Following the demonstration that gravitational waves impart linear momentum,
it is argued that if they are polarized they should impart angular momentum to
appropriately placed 'test rods' in their path. A general formula for this
angular momentum is obtained and used to provide expressions for the angular
momentum imparted by plane and cylindrical gravitational waves.",0701126v1
2007-03-01,Localized Asymmetric Atomic Matter Waves in Two-Component Bose-Einstein Condensates Coupled with Two Photon Microwave Field,"We investigate localized atomic matter waves in two-component Bose-Einstein
condensates coupled by the two photon microwave field. Interestingly, the
oscillations of localized atomic matter waves will gradually decay and finally
become non-oscillating behavior even if existing coupling field. In particular,
atom numbers occupied in two different hyperfine spin states will appear
asymmetric occupations after some time evolution.",0703001v1
2006-06-29,Quantum wave equations and non-radiating electromagnetic sources,"A connection between classical non-radiating sources and free-particle wave
equations in quantum mechanics is rigorously made. It is proven that
free-particle wave equations for all spins have currents which can be defined
which are non-radiating electromagnetic sources. It is also proven that the
advanced and retarded fields are exactly equal for these sources. Implications
of these results are discussed.",0606245v2
2017-06-06,Driven spin wave modes in XY ferromagnet: Nonequilibrium phase transition,"The dynamical responses of XY ferromagnet driven by linearly polarised
propagating and standing magnetic field wave have been studied by Monte Carlo
simulation in three dimensions. In the case of propagating magnetic field wave
(with specified amplitude, frequency and the wavelength), the low temperature
dynamical mode is a propagating spin wave and the system becomes structureless
(or random) in the high temperature. A dynamical symmetry breaking phase
transition is observed at a finite (nonzero) temperature. This symmetry
breaking is confirmed by studying the statistical distribution of the angle of
the spin vector. The dynamic nonequilibrium transition temperature was found to
decrease as the amplitude of the propagating magnetic field wave increased. A
comprehensive phase boundary is drawn in the plane formed by temperature and
amplitude of propagating field wave. The phase boundary was observed to shrink
(in the low temperature side) for longer wavelength of the propagating magnetic
wave. In the case of standing magnetic field wave, the low temperature
excitation is a standing spin wave which becomes structureless (or random) in
the high temperature. Here also, like the case of propagating magnetic wave, a
dynamical symmetry breaking nonequilibrium phase transition was observed. A
comprehensive phase boundary is drawn. Unlike the case of propagating magnetic
wave, the phase boundary does not show any systematic variation with the
wavelength of the standing magnetic field wave. In the limit of vanishingly
small amplitude of the field, the phase boundaries approach the recent Monte
Carlo estimate of equilibrium transition temperature.",1706.01619v6
2021-01-30,Pair density wave solution for self-consistent model,"In the t-U-V Hubbard model on the square lattice we found self-consistent
analytic solution for the ground state with coexisting d-wave symmetric bond
ordered pair density wave (PDW) and spin (SDW) or charge (CDW) density waves,
as observed in some high-temperature superconductors. In particular, the
solution gives the same periodicity for CDW and PDW, and a pseudogap in the
fermi-excitation spectrum.",2102.00144v1
2019-09-08,Holographic charge density wave from D2-D8,"We have considered D2-D8 model and obtain a numerical solution that exhibits
spatially modulated phases corresponding to a charge density wave and a spin
density wave. We have analysed behavior of the free energy density for
different values of the chemical potential and the magnetic field.",1909.03458v2
2021-12-25,Relativistic electron wave packets featuring persistent quantum backflow,"Closed-form, normalizable solutions of Dirac's equation propagating within a
semi-infinite cylindrical waveguide are obtained in terms of ordinary and
modified Bessel functions. These relativistic wave packets induce quantum
backflow on a cross-section of the cylinder at practically any distance along
the waveguide, becoming spin-polarized in the nonrelativistic limit. The
predicted backflow is stable in time and is manifest regardless of the initial
wave function.",2112.13180v1
2010-04-28,Bar-mode instability of rapidly spinning black hole in higher dimensions: Numerical simulation in general relativity,"Numerical-relativity simulation is performed for rapidly spinning black holes
(BHs) in a higher-dimensional spacetime of special symmetries for the
dimensionality $6 \leq d \leq 8$. We find that higher-dimensional BHs, spinning
rapidly enough, are dynamically unstable against nonaxisymmetric bar-mode
deformation and spontaneously emit gravitational waves, irrespective of $d$ as
in the case $d=5$ \cite{SY09}. The critical values of a nondimensional spin
parameter for the onset of the instability are $q:=a/\mu^{1/(d-3)} \approx
0.74$ for $d=6$, $\approx 0.73$ for $d=7$, and $\approx 0.77$ for $d=8$ where
$\mu$ and $a$ are mass and spin parameters. Black holes with a spin smaller
than these critical values ($q_{\rm crit}$) appear to be dynamically stable for
any perturbation. Longterm simulations for the unstable BHs are also performed
for $d=6$ and 7. We find that they spin down as a result of gravitational-wave
emission and subsequently settle to a stable stationary BH of a spin smaller
than $q_{\rm crit}$. For more rapidly spinning unstable BHs, the timescale, for
which the new state is reached, is shorter and fraction of the spin-down is
larger. Our findings imply that a highly rapidly spinning BH with $q > q_{\rm
crit}$ cannot be a stationary product in the particle accelerators, even if it
would be formed as a consequence of a TeV-gravity hypothesis. Its implications
for the phenomenology of a mini BH are discussed.",1004.4970v1
2013-06-20,"Magnetic orders, excitations, and phase transitions in Fe_1+yTe","We study the magnetic properties of Fe_1+y Te, a parent compound of the
iron-based high-temperature superconductors. Motivated by recent neutron
scattering experiments, we show that a spin-1 exchange model, supplemented by a
single-ion spin anisotropy, accounts well for the experimentally observed low
temperature magnetic phase diagram, that exhibits a commensurate bicollinear
order at low Fe dopings (y < 0.12) and an incommensurate spin-spiral order at
high Fe dopings (y > 0.12). We suggest that the commensurate-incommensurate
transition at y = 0.12 is due to the competition between the exchange
interaction and the local spin anisotropy. At low Fe dopings, the single-ion
spin anisotropy is strong and pins the spins along the easy axis, which,
together with the spatially anisotropic exchanges, induces a unusual
bicollinear commensurate magnetic order. The low-energy spin-wave excitation is
gapped due to the explict breaking of spin-rotational symmetry by the local
spin anisotropy. At high Fe dopings, the single-ion anisotropy is weak, and the
exchange favors an incommensurate coplanar state. The incommensurate magnetic
wavevector averages out the spin anisotropy so that a gapless low-energy
spin-wave excitation is obtained. We also analyze the low-energy hydrodynamic
model and use it to describe the magneto-structural transition and the static
and dynamical spin structure factors across the magnetic ordering transitions.",1306.4730v2
2016-09-22,Magnetization oscillations and waves driven by pure spin currents,"Recent advances in the studies of pure spin currents - flows of angular
momentum (spin) not accompanied by the electric currents - have opened new
horizons for the emerging technologies based on the electron's spin degree of
freedom, such as spintronics and magnonics. The main advantage of pure spin
current, as compared to the spin-polarized electric current, is the possibility
to exert spin transfer torque on the magnetization in thin magnetic films
without electrical current flow through the material. In addition to minimizing
Joule heating and electromigration effects, this characteristic enables the
implementation of spin torque devices based on the low-loss insulating magnetic
materials, and offers an unprecedented geometric flexibility. Here we review
the recent experimental achievements in investigations of magnetization
oscillations excited by pure spin currents in different magnetic nanosystems
based on metallic and insulating magnetic materials. We discuss the spectral
properties of spin-current nano-oscillators, and relate them to the spatial
characteristics of the excited dynamic magnetic modes determined by the
spatially-resolved measurements. We also show that these systems support
locking of the oscillations to external microwave signals, as well as their
mutual synchronization, and can be used as efficient nanoscale sources of
propagating spin waves.",1609.06899v1
2018-06-19,Spin-Precessing Black Hole Binaries in Dynamical Chern-Simons Gravity,"Gravitational waves from spin-precessing binaries exhibit amplitude
oscillations that provide an invaluable method to extract the spins of the
inspiraling compact objects. The spin-spin and spin-orbit interactions that
cause this effect are sensitive to the fundamental nature of gravity, which
will allow us to constrain modified theories of gravity using gravitational
wave observations of precessing binaries. We here consider precessing black
hole binaries in dynamical Chern-Simons gravity, an effective theory of gravity
that enhances parity violating interactions. We model the black holes as
modified point particles using effective field theory, and derive the
spin-precession equations for a binary system by working within the
post-Newtonian formalism. We find that the spin-spin and quadrupole-monopole
interactions of General Relativity are modified due to an interaction between
the scalar dipoles of the two black holes and the modified black hole
quadrupole as a result of the violation of the no hair theorems. These
modifications enter the precession equations at leading post-Newtonian order.
We further show that these precession equations admit seven constants of motion
when neglecting radiation reaction, with only the mass-weighted effective spin
being modified from General Relativity. We discuss how these may be used to
reduce the precession equations to quadrature and the possibility of
constructing analytic Fourier domain waveforms for generic spin-precessing
binaries in dCS gravity.",1806.07431v2
2019-12-11,Coherent transfer of spin angular momentum by evanescent spin waves within antiferromagnetic NiO,"Insulating antiferromagnets are efficient and robust conductors of spin
current. To realise the full potential of these materials within spintronics,
the outstanding challenges are to demonstrate scalability down to nanometric
lengthscales and the transmission of coherent spin currents. Here, we report
the coherent transfer of spin angular momentum by excitation of evanescent spin
waves of GHz frequency within antiferromagnetic NiO at room temperature. Using
element-specific and phase-resolved x-ray ferromagnetic resonance, we probe the
injection and transmission of ac spin current, and demonstrate that insertion
of a few nanometre thick epitaxial NiO(001) layer between a ferromagnet and
non-magnet can even enhance the flow of spin current. Our results pave the way
towards coherent control of the phase and amplitude of spin currents at the
nanoscale, and enable the realization of spin-logic devices and spin current
amplifiers that operate at GHz and THz frequencies.",1912.05621v1
2021-03-23,Spin excitations in metallic kagome lattice FeSn and CoSn,"In two-dimensional (2D) metallic kagome lattice materials, destructive
interference of electronic hopping pathways around the kagome bracket can
produce nearly localized electrons, and thus electronic bands that are flat in
momentum space. When ferromagnetic order breaks the degeneracy of the
electronic bands and splits them into the spin-up majority and spin-down
minority electronic bands, quasiparticle excitations between the spin-up and
spin-down flat bands should form a narrow localized spin-excitation Stoner
continuum coexisting with well-defined spin waves in the long wavelengths. Here
we report inelastic neutron scattering studies of spin excitations in 2D
metallic Kagome lattice antiferromagnetic FeSn and paramagnetic CoSn, where
angle resolved photoemission spectroscopy experiments found spin-polarized and
nonpolarized flat bands, respectively, below the Fermi level. Although our
initial measurements on FeSn indeed reveal well-defined spin waves extending
well above 140 meV coexisting with a flat excitation at 170 meV, subsequent
experiments on CoSn indicate that the flat mode actually arises mostly from
hydrocarbon scattering of the CYTOP-M commonly used to glue the samples to
aluminum holder. Therefore, our results established the evolution of spin
excitations in FeSn and CoSn, and identified an anomalous flat mode that has
been overlooked by the neutron scattering community for the past 20 years.",2103.12873v3
2021-11-04,Apples and Oranges: Comparing black holes in X-ray binaries and gravitational-wave sources,"The component black holes (BHs) observed in gravitational-wave (GW) binary
black hole (BBH) events tend to be more massive and slower spinning than those
observed in black hole X-ray binaries (BH-XRBs). Without modeling their
evolutionary histories, we investigate whether these apparent tensions in the
BH populations can be explained by GW observational selection effects alone. We
find that this is indeed the case for the discrepancy between BH masses in BBHs
and the observed high-mass X-ray binaries (HMXBs), when we account for
statistical uncertainty from the small sample size of just three HMXBs. On the
other hand, the BHs in observed low-mass X-ray binaries (LMXBs) are
significantly lighter than the astrophysical BBH population, but this may just
be due to a correlation between component masses in a binary system. Given
their light stellar companions, we expect light BHs in LMXBs. The observed
spins in HMXBs and LMXBs, however, are in tension with the inferred BBH spin
distribution at the $>99.9\%$ level. We discuss possible scenarios behind the
significantly larger spins in observed BH-XRBs. One possibility is that a small
subpopulation (conservatively $<30\%$) of BBHs have rapidly spinning primary
components, indicating that they may have followed a similar evolutionary
pathway to the observed HMXBs. In LMXBs, it has been suggested that BHs can
spin up by accretion. If LMXB natal spins follow the BBH spin distribution, we
find LMXBs must gain an average dimensionless spin of $0.47^{+0.10}_{-0.11}$,
but if their natal spins follow the observed HMXB spins, the average spinup
must be $<0.03$.",2111.02935v2
2024-02-23,Spin Doctors: How to diagnose a hierarchical merger origin,"Gravitational-wave observations provide the unique opportunity of studying
black hole formation channels and histories -- but only if we can identify
their origin. One such formation mechanism is the dynamical synthesis of black
hole binaries in dense stellar systems. Given the expected isotropic
distribution of component spins of binary black hole in gas-free dynamical
environments, the presence of anti-aligned or in-plane spins with respect to
the orbital angular momentum is considered a tell-tale sign of a merger's
dynamical origin. Even in the scenario where birth spins of black holes are
low, hierarchical mergers attain large component spins due to the orbital
angular momentum of the prior merger. However, measuring such spin
configurations is difficult. Here, we quantify the efficacy of the spin
parameters encoding aligned-spin ($\chieff$) and in-plane spin ($\chip$) at
classifying such hierarchical systems. Using Monte Carlo cluster simulations to
generate a realistic distribution of hierarchical merger parameters from
globular clusters, we can infer mergers' $\chieff$ and $\chip$. The cluster
populations are simulated using Advanced LIGO-Virgo sensitivity during the
detector network's third observing period and projections for design
sensitivity. Using a ""likelihood-ratio""-based statistic, we find that $\sim2\%$
of the recovered population by the current gravitational-wave detector network
has a statistically significant $\chip$ measurement, whereas no $\chieff$
measurement was capable of confidently determining a system to be anti-aligned
with the orbital angular momentum at current detector sensitivities. These
results indicate that measuring spin-precession through $\chip$ is a more
detectable signature of a hierarchical mergers and dynamical formation than
anti-aligned spins.",2402.15066v1
2010-03-25,Spin superfluidity and magnon BEC,"The spin superfluidity -- superfluidity in the magnetic subsystem of a
condensed matter - is manifested as the spontaneous phase-coherent precession
of spins first discovered in 1984 in 3He-B. This superfluid current of spins -
spin supercurrent - is one more representative of superfluid currents known or
discussed in other systems, such as the superfluid current of mass and atoms in
superfluid 4He; superfluid current of electric charge in superconductors;
superfluid current of hypercharge in Standard Model of particle physics;
superfluid baryonic current and current of chiral charge in quark matter; etc.
Spin superfluidity can be described in terms of the Bose condensation of spin
waves - magnons. We discuss different phases of magnon superfluidity, including
those in magnetic trap; and signatures of magnons superfluidity: (i) spin
supercurrent, which transports the magnetization on a macroscopic distance more
than 1 cm long; (ii) spin current Josephson effect which shows interference
between two condensates; (iii) spin current vortex - a topological defect which
is an analog of a quantized vortex in superfluids, of an Abrikosov vortex in
superconductors, and cosmic strings in relativistic theories; (iv) Goldstone
modes related to the broken U(1) symmetry - phonons in the spin-superfluid
magnon gas; etc. We also touch the topic of spin supercurrent in general
including spin Hall and intrinsic quantum spin Hall effects.",1003.4889v3
2018-09-24,Quantum spin-transfer torque induced nonclassical magnetization dynamics and electron-magnetization entanglement,"The standard spin-transfer torque (STT)---where spin-polarized current drives
dynamics of magnetization viewed as a classical vector---requires
noncollinearity between electron spins carried by the current and magnetization
of a ferromagnetic layer. However, recent experiments [A. Zholud et al., Phys.
Rev. Lett. 119, 257201 (2017)] observing magnetization dynamics in spin valves
at cryogenic temperatures, even when electron spin is collinear to
magnetization, point at overlooked quantum effects in STT which can lead to
highly nonclassical magnetization states. Using fully quantum many-body
treatment, where an electron injected as spin-polarized wave packet interacts
with local spins comprising the anisotropic quantum Heisenberg ferromagnetic
chain, we define quantum STT as any time evolution of local spins due to
initial many-body state not being an eigenstate of electron+local-spins system.
For time evolution caused by injected spin-down electron scattering off local
up-spins, entanglement between electron subsystem and local spins subsystem
takes place leading to decoherence and, therefore, shrinking of the total
magnetization but without rotation from its initial orientation which explains
the experiments. Furthermore, the same processes---entanglement and thereby
induced decoherence---are present also in standard noncollinear geometry,
together with the usual magnetization rotation. This is because STT in quantum
many-body picture is caused only by electron spin-down factor state, and the
only difference between collinear and noncollinear geometries is in relative
size of the contribution of initial many-body state containing such factor
state to superpositions of separable many-body quantum states generated during
time evolution.",1809.09090v1
2019-05-27,Spin-Cooling of the Motion of a Trapped Diamond,"Observing and controlling macroscopic quantum systems has long been a driving
force in research on quantum physics. In this endeavor, strong coupling between
individual quantum systems and mechanical oscillators is being actively
pursued. While both read-out of mechanical motion using coherent control of
spin systems and single spin read-out using pristine oscillators have been
demonstrated, temperature control of the motion of a macroscopic object using
long-lived electronic spins has not been reported. Here, we observe both a
spin-dependent torque and spin-cooling of the motion of a trapped microdiamond.
Using a combination of microwave and laser excitation enables the spin of
nitrogen-vacancy centers to act on the diamond orientation and to cool the
diamond libration via a dynamical back-action. Further, driving the system in
the non-linear regime, we demonstrate bistability and self-sustained coherent
oscillations stimulated by the spin-mechanical coupling, which offers prospects
for spin-driven generation of non-classical states of motion. Such a levitating
diamond operated as a compass with controlled dissipation has implications in
high-precision torque sensing, emulation of the spin-boson problem and probing
of quantum phase transitions. In the single spin limit and employing ultra-pure
nano-diamonds, it will allow quantum non-demolition read-out of the spin of
nitrogen-vacancy centers under ambient conditions, deterministic entanglement
between distant individual spins and matter-wave interferometry.",1905.11509v2
2019-10-16,"Thermal Hall effect, spin Nernst effect, and spin density induced by thermal gradient in collinear ferrimagnets from magnon-phonon interaction","We theoretically study the intrinsic thermal Hall and spin Nernst effect in
collinear ferrimagnets on a honeycomb lattice with broken inversion symmetry.
The broken inversion symmetry allows in-plane Dzyaloshinskii-Moriya interaction
between the nearest neighbors, which does not affect the magnon spectrum in the
linear spin wave theory. However, the Dzyaloshinskii-Moriya interaction can
induce large Berry curvature in the magnetoelastic excitation spectrum through
the magnon-phonon interaction to produce thermal Hall current. Furthermore, we
find that the magnetoelastic excitations transport spin, which is inherited
from the magnon bands. Therefore, the thermal Hall current is accompanied by
spin Nernst current. Because the magnon-phonon interaction does not conserve
the spin, we also study the spin density induced by thermal gradient in the
presence of magnon-phonon interaction. We find that the intrinsic part of the
spin density shows no asymmetric spin accumulation near the boundary of the
system having a stripe geometry. However, because of the magnon-phonon
interaction, we find nonzero total spin density in the system having armchair
edges. The extrinsic part of the spin density, on the other hand, shows
asymmetric spin accumulation near the boundary for both armchair and zigzag
edges because of the magnon-phonon interaction. In addition, we find nonzero
total spin density in the system having zigzag edge.",1910.07206v2
2021-11-07,A correctly scaling rigorously spin-adapted and spin-complete open-shell CCSD implementation for arbitrary high-spin states,"In this paper, we report on a correctly scaling novel coupled cluster singles
and doubles (CCSD) implementation for arbitrary high-spin open-shell states.
The chosen cluster operator is completely spin-free, i.e. employs spatial
substitutions only. It is composed of our recently developed L\""owdin-type
operators (doi: 10.1063/5.0026762), which ensure (1) spin completeness and (2)
spin adaption i.e. spin purity of the CC wave function. In contrast to the
proof-of-concept matrix-representation-based implementation presented there,
the present implementation relies on second quantization and factorized tensor
contractions. The generated singles and doubles operators are embedded in an
equation generation engine. In the latter, Wick's theorem is used to derive
prefactors arising from spin integration directly from the spin-free full
contraction patterns. The obtained Wick terms composed of products of Kronecker
deltas are represented by special non-antisymmetrized Goldstone diagrams.
Identical (redundant) diagrams are identified by solving the underlying graph
isomorphism problem. All non-redundant graphs are then automatically translated
to locally -- one term at a time -- factorized tensor contractions. Finally,
the spin-adapted and spin-complete (SASC) CCS and CCSD variants are applied to
a set of small molecular test systems. Both correlation energies and amplitude
norms hint towards a reasonable convergence of the SASC-CCSD method for a BCH
series truncation of order four. In comparison to spin orbital CCSD, SASC-CCSD
leads to slightly improved correlation energies with differences of up to 0.886
mE_H (0.98% w.r.t. spin orbital CCSD(T)).",2111.04186v1
2023-03-04,Quantum sensing of paramagnetic spins in liquids with spin qubits in hexagonal boron nitride,"Paramagnetic ions and radicals play essential roles in biology and medicine,
but detecting these species requires a highly sensitive and ambient-operable
sensor. Optically addressable spin color centers in 3D semiconductors have been
used for detecting paramagnetic spins as they are sensitive to the spin
magnetic noise. However, the distance between spin color centers and target
spins is limited due to the difficulty of creating high-quality spin defects
near the surface of 3D materials. Here, we show that spin qubits in hexagonal
boron nitride (hBN), a layered van der Waals (vdW) material, can serve as a
promising sensor for nanoscale detection of paramagnetic spins in liquids. We
first create shallow spin defects in close proximity to the hBN surface, which
sustain high-contrast optically detected magnetic resonance (ODMR) in liquids.
Then we demonstrate sensing spin noise of paramagnetic ions in water based on
spin relaxation measurements. Finally, we show that paramagnetic ions can
reduce the contrast of spin-dependent fluorescence, enabling efficient
detection by continuous wave ODMR. Our results demonstrate the potential of
ultrathin hBN quantum sensors for chemical and biological applications.",2303.02326v1
2023-10-23,Microscopic theory of spin Seebeck effect in antiferromagnets,"We develop a microscopic theory for the spin Seebeck effect (SSE) in N\'eel
and canted phases of antiferromagnetic insulators. We calculate the DC spin
current tunneling from the antiferromagnet to an attached metal, incorporating
the spin-wave theory and the non-equilibrium Green's function approach. Our
result shows a sign change of the spin current at the spin-flop phase
transition between N\'eel and canted phases, which is in agreement with a
recent experiment for the SSE of $\rm Cr_2O_3$ in a semi-quantitative level.
The sign change can be interpreted from the argument based on the density of
states of up- and down-spin magnons, which is related to the polarized-neutron
scattering spectra. The theory also demonstrates that the spin current in the
N\'eel phase is governed by the magnon correlation, while that in the canted
phase consists of two parts: Contributions from not only the magnon dynamics
but also the static transverse magnetization. This result leads to a prediction
that at sufficiently low temperatures, the spin current non-monotonically
changes as a function of magnetic field in the canted phase. Towards a more
unified understanding of the SSE in antiferromagnets, we further discuss some
missing links of theories of SSE: Interface properties, effects of the
transverse spin moment in the canted phase, the spin-orbit coupling in the
metal, etc. Finally, we compare the SSE of antiferromagnets with those of
different magnetic phases such as ferromagnets, ferrimagnets, an
one-dimensional spin liquid, a spin-nematic liquid, and a spin-Peierls
(dimerized) phase.",2310.15292v2
2021-12-21,Fast long-wavelength exchange spin waves in partially-compensated Ga:YIG,"Spin waves in yttrium iron garnet (YIG) nano-structures attract increasing
attention from the perspective of novel magnon-based data processing
applications. For short wavelengths needed in small-scale devices, the group
velocity is directly proportional to the spin-wave exchange stiffness constant
$\lambda_\mathrm{ex}$. Using wave vector resolved Brillouin Light Scattering
(BLS) spectroscopy, we directly measure $\lambda_\mathrm{ex}$ in Ga-substituted
YIG thin films and show that it is about three times larger than for pure YIG.
Consequently, the spin-wave group velocity overcomes the one in pure YIG for
wavenumbers $k > 4$ rad/$\mu$m, and the ratio between the velocities reaches a
constant value of around 3.4 for all $k > 20$ rad/$\mu$m. As revealed by
vibrating-sample magnetometry (VSM) and ferromagnetic resonance (FMR)
spectroscopy, Ga:YIG films with thicknesses down to 59 nm have a low Gilbert
damping ($\alpha < 10^{-3}$), a decreased saturation magnetization $\mu_0
M_\mathrm{S}~\approx~20~$mT and a pronounced out-of-plane uniaxial anisotropy
of about $\mu_0 H_{\textrm{u1}} \approx 95 $ mT which leads to an out-of-plane
easy axis. Thus, Ga:YIG opens access to fast and isotropic spin-wave transport
for all wavelengths in nano-scale systems independently of dipolar effects.",2112.11348v1
2001-01-26,Approach to the metal-insulator transition in La(1-x)CaxMnO3 (0<x<.2): magnetic inhomogeneity and spin wave anomaly,"We describe the evolution of the static and dynamic spin correlations of
La$_{1-x}$Ca$_x$MnO$_3$, for x=0.1, 0.125 and 0.2, where the system evolves
from the canted magnetic state towards the insulating ferromagnetic state,
approaching the metallic transition (x=0.22).
  In the x=0.1 sample, the observation of two spin wave branches typical of two
distinct types of magnetic coupling, and of a modulation in the elastic diffuse
scattering characteristic of ferromagnetic inhomogeneities, confirms the static
and dynamic inhomogeneous features previously observed at x$<$0.1. The
anisotropic q-dependence of the intensity of the low-energy spin wave suggests
a bidimensionnal character for the static inhomogeneities. At x=0.125, which
corresponds to the occurence of a ferromagnetic and insulating state, the two
spin wave branches reduce to a single one, but anisotropic. At this
concentration, an anomaly appears at {\bf q$_0$}=(1.25,1.25,0), that could be
related to an underlying periodicity, as arising from (1.5,1.5,0)
superstructures.
  At x=0.2, the spin-wave branch is isotropic. In addition to the anomaly
observed at q$_0$, extra magnetic excitations are observed at larger q, forming
an optical branch. The two dispersion curves suggest an anti-crossing behavior
at some {\bf q$_0$'} value, which could be explained by a folding due to an
underlying perodicity involving four cubic lattice spacings.",0101414v1
2017-08-29,Spin wave damping arising from phase coexistence below $T_c$ in colossal magnetoresistive La$_{0.7}$Ca$_{0.3}$MnO$_3$,"While the spin dynamics of La$_{0.7}$Ca$_{0.3}$MnO$_3$ in the ferromagnetic
phase are known to be unconventional, previous measurements have yielded
contradictory results regarding the damping of spin wave excitations. Neutron
spectroscopy measurements on a sample with a transition temperature of
$T_c$=257 K, higher than most single crystals, unambiguously reveal an
anomalous increase in spin wave damping for excitations approaching the
Brillouin zone boundary along the [$100$] direction that cannot be explained as
an artifact due to a noninteracting phonon branch. Spin waves throughout the
($HK0$) plane display a common trend where the spin wave damping is dependent
upon the excitation energy, increasing for energies above roughly 15 meV and
reaching a full width at half maximum of at least 20 meV. The results are
consistent with a model of intrinsic spatial inhomogeneity with phase separated
regions approximately 18 {\AA} in size persisting over a large range of
temperatures below $T_c$.",1708.08960v2
2018-08-01,Raman fingerprint of two terahertz spin wave branches in a two-dimensional honeycomb Ising ferromagnet,"Two-dimensional (2D) magnetism has been long sought-after and only very
recently realized in atomic crystals of magnetic van der Waals materials. So
far, a comprehensive understanding of the magnetic excitations in such 2D
magnets remains missing. Here we report polarized micro-Raman spectroscopy
studies on a 2D honeycomb ferromagnet CrI3. We show the definitive evidence of
two sets of zero-momentum spin waves at frequencies of 2.28 terahertz (THz) and
3.75 THz, respectively, that are three orders of magnitude higher than those of
conventional ferromagnets. By tracking the thickness dependence of both spin
waves, we reveal that both are surface spin waves with lifetimes an order of
magnitude longer than their temporal periods. Our results of two branches of
high-frequency, long-lived surface spin waves in 2D CrI3 demonstrate intriguing
spin dynamics and intricate interplay with fluctuations in the 2D limit, thus
opening up opportunities for ultrafast spintronics incorporating 2D magnets.",1808.00168v3
2019-02-27,Anomalous phase ordering of a quenched ferromagnetic superfluid,"Coarsening dynamics, the canonical theory of phase ordering following a
quench across a symmetry breaking phase transition, is thought to be driven by
the annihilation of topological defects. Here we show that this understanding
is incomplete. We simulate the dynamics of an isolated spin-1 condensate
quenched into the easy-plane ferromagnetic phase and find that the mutual
annihilation of spin vortices does not take the system to the equilibrium
state. A nonequilibrium background of long wavelength spin waves remain at the
Berezinskii-Kosterlitz-Thouless temperature, an order of magnitude hotter than
the equilibrium temperature. The coarsening continues through a second much
slower scale invariant process with a length scale that grows with time as
$t^{1/3}$. This second regime of coarsening is associated with spin wave energy
transport from low to high wavevectors, bringing about the the eventual
equilibrium state. Because the relevant spin waves are noninteracting, the
transport occurs through a dynamic coupling to other degrees of freedom of the
system. The transport displays features of a spin wave energy cascade,
providing a potential profitable connection with the emerging field of spin
wave turbulence. Strongly coupling the system to a reservoir destroys the
second regime of coarsening, allowing the system to thermalise following the
annihilation of vortices.",1902.10792v4
2020-08-19,Impact of intra-grain spin wave reflections on nano-contact spin torque oscillators,"We investigate the origin of the experimentally observed varying
current-frequency nonlinearity of the propagating spin wave mode in
nano-contact spin torque oscillators. Nominally identical devices with 100 nm
diameter are characterized by electrical microwave measurements and show large
variation in the generated frequency as a function of drive current. This
quantitative and qualitative device-to-device variation is described in terms
of continuous and discontinuous nonlinear transitions between linear current
intervals. The thin film grain microstructure in our samples is determined
using atomic force and scanning electron microscopy to be on the scale of 30
nm. Micromagnetic simulations show that the reflection of spin waves against
the grain boundaries results in standing wave resonance configurations. For a
simulated device with a single artificial grain, the frequency increases
linearly with the drive current until the decreased wavelength eventually
forces another spin wave anti-node to be formed. This transition results in a
discontinuous step in the frequency versus current relation. Simulations of
complete, randomly generated grain microstructures additionally shows
continuous nonlinearity and a resulting device-to-device variation in frequency
that is similar to the experimental levels. The impact of temperature from 4 K
to 300 K on the resonance mode-transition nonlinearity and frequency noise is
investigated using simulations and it is found that the peak levels of the
spectral linewidth as a function of drive current agrees quantitatively with
typical levels found in experiments at room temperature.",2008.08357v1
2021-08-23,High-accuracy simulations of highly spinning binary neutron star systems,"With an increasing number of expected gravitational-wave detections of binary
neutron star mergers, it is essential that gravitational-wave models employed
for the analysis of observational data are able to describe generic compact
binary systems. This includes systems in which the individual neutron stars are
millisecond pulsars for which spin effects become essential. In this work, we
perform numerical-relativity simulations of binary neutron stars with aligned
and anti-aligned spins within a range of dimensionless spins of $\chi \sim
[-0.28,0.58]$. The simulations are performed with multiple resolutions, show a
clear convergence order and, consequently, can be used to test existing
waveform approximants. We find that for very high spins gravitational-wave
models that have been employed for the interpretation of GW170817 and GW190425
are not capable of describing our numerical-relativity dataset. We verify
through a full parameter estimation study in which clear biases in the estimate
of the tidal deformability and effective spin are present. We hope that in
preparation of the next gravitational-wave observing run of the Advanced LIGO
and Advanced Virgo detectors our new set of numerical-relativity data can be
used to support future developments of new gravitational-wave models.",2108.10429v1
2019-09-05,Extraction of Dzyaloshinksii-Moriya interaction from propagating spin waves validated,"The interfacial Dzyaloshinksii-Moriya interaction (iDMI) is of great interest
in thin-film magnetism because of its ability to stabilize chiral spin
textures. It can be quantified by investigating the frequency non-reciprocity
of oppositely propagating spin waves. However, as the iDMI is an interface
interaction the relative effect reduces when the films become thicker making
quantification more difficult. Here, we utilize all-electrical Propagating Spin
Wave Spectroscopy (PSWS) to disentangle multiple contributions to spin wave
frequency non-reciprocity to determine the iDMI. This is done by investigating
non-reciprocities across a wide range of magnetic layer thicknesses (from 4 to
26 nm) in Pt/Co/Ir, Pt/Co/Pt, and Ir/Co/Pt stacks. We find the expected sign
change in the iDMI when inverting the stack order, and a negligible iDMI for
the symmetric Pt/Co/Pt. We additionally extract a difference in surface
anisotropies and find a large contribution due to the formation of different
crystalline phases of the Co, which is corroborated using nuclear magnetic
resonance and high-resolution transmission-electron-microscopy measurements.
These insights will open up new avenues to investigate, quantify and
disentangle the fundamental mechanisms governing the iDMI, and pave a way
towards engineered large spin-wave non-reciprocities for magnonic applications.",1909.02467v1
2019-10-04,Spin-wave directional anisotropies in antiferromagnetic Ba$_{3}$NbFe$_{3}$Si$_{2}$O$_{14}$,"Ba$_{3}$NbFe$_{3}$Si$_{2}$O$_{14}$ (langasite) is structurally and
magnetically single domain chiral with the magnetic helicity induced through
competing symmetric exchange interactions. Using neutron scattering, we show
that the spin-waves in antiferromagnetic langasite display directional
anisotropy. On applying a time reversal symmetry breaking magnetic field along
the $c$-axis, the spin wave energies differ when the sign is reversed for
either the momentum transfer $\pm$ $\vec{Q}$ or applied magnetic field $\pm$
$\mu_{0}$H. When the field is applied within the crystallographic $ab$-plane,
the spin wave dispersion is directionally \textit{isotropic} and symmetric in
$\pm$ $\mu_{0}$H. However, a directional anisotropy is observed in the spin
wave intensity. We discuss this directional anisotropy in the dispersion in
langasite in terms of a field induced precession of the dynamic unit cell
staggered magnetization. Directional anisotropy, or often referred to as non
reciprocal responses, can occur in antiferromagnetic phases in the absence of
the Dzyaloshinskii-Moriya interaction or other effects resulting from
spin-orbit coupling.",1910.01977v2
2020-01-31,Temperature dependence of spin pinning and spin-wave dispersion in nanoscopic ferromagnetic waveguides,"The field of magnonics attracts significant attention due to the possibility
of utilizing information coded into the spin-wave phase or amplitude to perform
computation operations on the nanoscale. Recently, spin waves were investigated
in Yttrium Iron Garnet (YIG) waveguides with widths ranging down to 50 nm and
aspect ratios thickness over width approaching unity. A critical width was
found, below which the exchange interaction suppresses the dipolar pinning
phenomenon and the system becomes unpinned. Here we continue these
investigations and analyse the pinning phenomenon and spin-wave dispersions as
a function of temperature, thickness and material of choice. Higher order
modes, the influence of a finite wavevector along the waveguide and the impact
of the pinning phenomenon on the spin-wave lifetime are discussed as well as
the influence of a trapezoidal cross section and edge roughness of the
waveguides. The presented results are of particular interest for potential
applications in magnonic devices and the incipient field of quantum magnonics
at cryogenic temperatures.",2002.00003v1
2021-09-30,Selection rules and dynamic magnetoelectric effect of the spin waves in multiferroic BiFeO$_3$,"We report the magnetic field dependence of the THz absorption and
non-reciprocal directional dichroism spectra of BiFeO$_3$ measured on the three
principal crystal cuts for fields applied along the three principal directions
of each cut. From the systematic study of the light polarization dependence we
deduced the optical selection rules of the spin-wave excitations. Our THz data,
combined with small-angle neutron scattering results showed that i) an in-plane
magnetic field rotates the $\mathbf{q}$ vectors of the cycloids perpendicular
to the magnetic field, and ii) the selection rules are mostly determined by the
orientation of the $\mathbf{q}$ vector with respect to the electromagnetic
fields. We observed a magnetic field history dependent change in the strength
and the frequency of the spin-wave modes, which we attributed to the change of
the orientation and the length of the cycloidal $\mathbf{q}$ vector,
respectively. Finally, we compared our experimental data with the results of
linear spin-wave theory that reproduces the magnetic field dependence of the
spin-wave frequencies and most of the selection rules, from which we identified
the spin-polarization coupling terms relevant for the optical magnetoelectric
effect.",2109.14990v1
2022-09-29,Spin Dynamics in Patterned Magnetic Multilayers with Perpendicular Magnetic Anisotropy,"The magnetization dynamics in nanostructures has been extensively studied in
the last decades, and nanomagnetism has evolved significantly over that time,
discovering new effects, developing numerous applications, and identifying
promising new directions. This includes magnonics, an emerging research field
oriented on the study of spin-wave dynamics and their applications. In this
context, thin ferromagnetic films with perpendicular magnetic anisotropy (PMA)
offer interesting opportunities to study spin waves, in particular, due to
out-of-plane magnetization in remanence or at relatively weak external magnetic
fields. This is the only magnetization configuration offering isotropic
in-plane spin-wave propagation within the sample plane, the forward volume
magnetostatic spin-wave geometry. The isotropic dispersion relation is highly
important in designing signal-processing devices, offering superior prospects
for direct replicating various concepts from photonics into magnonics.
Analogous to photonic or phononic crystals, which are the building blocks of
optoelectronics and phononics, magnonic crystals are considered as key
components in magnonics applications. Arrays of nanodots and structured
ferromagnetic thin films with a periodic array of holes, popularly known as
antidot lattices based on PMA multilayers have been recently studied. Novel
magnonic properties related to propagating spin-wave modes, exploitation of the
band gaps, and confined modes, were demonstrated. Also, the existence of
nontrivial magnonic band topologies has been shown. Moreover, the combination
of PMA and Dzyaloshinskii-Moriya interaction leads to the formation of chiral
magnetization states, including N\'eel domain walls, skyrmions, and skyrmionium
states.",2209.14824v2
2022-11-03,Spin-orbit and exchange proximity couplings in graphene/1T-TaS$_2$ heterostructure triggered by a charge density wave,"Proximity-induced fine features and spin-textures of the electronic bands in
graphene-based van der Waals heterostructures can be explored from the point of
tailoring a twist angle. Here we study spin-orbit coupling and exchange
coupling engineering of graphene states in the proximity of 1T-TaS$_2$ not
triggering the twist, but a charge density wave in 1T-TaS$_2$-a realistic
low-temperature phase. Using density functional theory and effective model we
found that the emergence of the charge density wave in 1T-TaS$_2$ significantly
enhances Rashba spin-orbit splitting in graphene and tilts the spin texture by
a significant Rashba angle-in a very similar way as in the conventional
twist-angle scenarios. Moreover, the partially filled Ta $d$-band in the charge
density wave phase leads to the spontaneous emergence of the in-plane magnetic
order that transgresses via proximity from 1T-TaS$_2$ to graphene, hence,
simultaneously superimposing along the spin-orbit also the exchange coupling
proximity effect. To describe this intricate proximity landscape we have
developed an effective model Hamiltonian and provided a minimal set of
parameters that excellently reproduces all the spectral features predicted by
the first-principles calculations. Conceptually, the charge density wave
provides a highly interesting knob to control the fine features of electronic
states and to tailor the superimposed proximity effects-a sort of twistronics
without twist.",2211.02153v2
2023-01-30,Transverse spin angular momentum of space-time surface plasmon polariton wave packet,"In addition to longitudinal spin angular momentum (SAM) along the axis of
propagation of light, spatially structured electromagnetic fields such as
evanescent waves and focused beams have recently been found to possess
transverse SAM in the direction perpendicular to the axis of propagation. In
particular, the SAM of SPPs with spatial structure has been extensively studied
in the last decade after it became clear that evanescent fields with spatially
structured energy flow generate threedimensional spin texture. Here we present
numerical calculations of the space-time surface plasmon polariton (ST-SPP)
wave packet, a plasmonic bullet that propagates at an arbitrary group velocity
while maintaining its spatial distribution. ST-SPP wave packets with complex
spatial structure and energy flow density distribution determined by the group
velocity are found to propagate with accompanying three-dimensional spin
texture and finite topological charge density. Furthermore, the spatial
distribution of the spin texture and topological charge density determined by
the spatial structure of the SPP is controllable, and the deformation
associated with propagation is negligible. ST-SPP wave packets, which can
stably transport customizable three-dimensional spin textures and topological
charge densities, can be excellent subjects of observation in studies of
spinphotonics and optical topological materials.",2301.12654v2
2013-01-14,Polarised Electromagnetic wave propagation through the ferromagnet: Phase boundary of dynamic phase transition,"The dynamical responses of ferromagnet to the propagating electromagnetic
field wave passing through it are modelled and studied here by Monte Carlo
simulation in two dimensional Ising ferromagnet. Here, the electromagnetic wave
is linearly polarised in such a way that the direction of magnetic field is
parallel to that of the magnetic momemts (spins). The coherent propagating mode
of spin-clusters is observed. The time average magnetisation over the full
cycle (time) of the field defines the order parameter of the dynamic
transition. Depending on the value of the temperature and the amplitude of the
propagating magnetic field wave, a dynamical phase transition is observed. The
dynamic transition was detected by studying the temperature dependences of the
dynamic order parameter, the variance of the dynamic order parameter, the
derivative of the dynamic order parameter and the dynamic specific heat. The
phase boundaries of the dynamic transitions were drawn for two different values
of the wave lengths of the propagating magnetic field wave. The phase boundary
was observed to shrink (inward) for lower speed of propagation of the EM wave.
The divergence of the releavant length scale was observed at the transition
point.",1301.3071v2
2014-01-16,Odd and Even Partial Waves of ηπ^- and η'π^- in 191 GeV/c π^-p,"In the year 2008 COMPASS recorded diffractive events of the signature
\pi^-(191 GeV) p --> X_fast p. We present results of the analysis of the
subsystems X = \eta(')\pi^-. Besides the known resonances a_2(1320), a_4(2040),
we study the properties of the spin-exotic P+ wave, and all other
natural-exchange partial waves up to spin J = 6. We find a striking difference
between the two final states: whereas the even partial waves J = 2, 4, 6 in the
two systems are related by phase-space factors, the odd partial waves are
relatively suppressed in the \eta\pi^- system. The relative phases between the
even waves appear identical whereas the phase between the D and P waves behave
quite differently, suggesting different resonant and non-resonant contributions
in the two odd-angular-momentum systems. Branching ratios and parameters of the
well-known resonances a_2 and a_4 are measured.",1401.4067v1
2016-02-18,Atom-light superposition oscillation and Ramsey-like atom-light interferometer,"Coherent wave splitting is crucial in interferometers. Normally, the waves
after this splitting are of the same type. But recent progress in interaction
between atom and light has led to the coherent conversion of photon to atomic
excitation. This makes it possible to split an incoming light wave into a
coherent superposition state of atom and light and paves the way for an
interferometer made of different types of waves. Here we report on a Rabi-like
coherent-superposition oscillation observed between atom and light and a
coherent mixing of light wave with excited atomic spin wave in a Raman process.
We construct a new kind of hybrid interferometer based on the atom-light
coherent superposition state. Interference fringes are observed in both optical
output intensity and atomic output in terms of the atomic spin wave strength
when we scan either or both of the optical and atomic phases. Such a hybrid
interferometer can be used to interrogate atomic states by optical detection
and will find its applications in precision measurement and quantum control of
atoms and light.",1602.05685v1
2021-06-10,Steering visible Dyakonov surface waves at the hyperbolic metasurface,"Dyakonov surface wave existing at the interface with anisotropy offers a
promising way of guiding light in two-dimension with almost no loss. However,
predicted decades ago, the experimental demonstration of the Dyakonov surface
wave seems always challenging for the weak anisotropic indices from the natural
materials. Here we experimentally demonstrated a Dyakonov surface wave mode
propagating in a hyperbolic metasurface at the visible frequency. Dyakonov
surface waves at the two surfaces of the metasurface can be supported
simultaneously by the hyperbolic anisotropy and form a Dyakonov typed mode with
low loss and a large allowed angle band. A detailed theoretical analysis and
numerical simulations prove that the electric field of such a surface wave mode
shows transverse spin, whose direction is determined by the orientations of the
hyperbolic anisotropy and surface normal, based on which we experimentally
observed the photonic spin Hall effect of the surface wave mode in our
metasurface.",2106.05699v1
1994-06-27,Quantum Phase Transition in the Frustrated Heisenberg Antiferromagnet,"Using the J_1-J_2 model, we present a description of quantum phase transition
from Neel ordered to the spin-liquid state based on the modified spin wave
theory. The general expression for the gap in the spectrum in the spin-liquid
phase is presented.",9406106v2
1996-02-15,Spectral properties of Luther-Emery systems,"We calculate the spectral function of the Luther-Emery model which describes
one-dimensional fermions with gapless charge and gapped spin degrees of
freedom. We find a true singularity with interaction dependent exponents on the
gapped spin dispersion and a finite maximum depending on the magnitude of the
spin gap, on a shifted charge dispersion. We apply these results to
photoemission experiments on charge density wave systems and discuss the
spectral properties of a one-dimensional Mott insulator.",9602087v1
1998-07-22,Spin excitations in ferromagnetic manganites,"An effective one-band Hamiltonian for colossal-magnetoresistance (CMR)
manganites is constructed and the spin excitations are determined. Fitting the
experimental data by the derived spin-wave dispersion gives an e_g -electron
hopping amplitude of about 0.2 eV in agreement with LDA band calculations.",9807294v1
2001-08-05,Low Energy Behaviour of XXZ Antiferromagnetic Spin Chain,"Zero temperature phase diagram of XXZ spin chain in external magnetic field
is investigated at low energies using path integral approach.It has been shown
by spin wave analysis and then by nonlinear sigma model transformation that
below some critical field the system undergoes quantum Kosterlitz-Thouless
phase transition.Above that critical field for low anisotropies the system is
saturated while at strong anisotropy the system has Ising antiferromagnetic
order.",0108086v1
2003-01-30,"The Mixed Spin S=(1/2,1) XXZ Ferrimagnet at Zero Temperature","Linked cluster series expansions about the Ising limit are used to study
ground state preperties, viz. ground state energy, magnetization and excitation
spectra, for mixed spin S=(1/2,1) quantum ferrimagnets on simple bipartite
lattices in 1, 2, and 3-dimensions. Results are compared to second-order spin
wave theory and, in general, excellent agreement is obtained.",0301580v1
2005-11-11,Spin current as a response to external stress,"It is theoretically predicted that a traveling shear wave will create a spin
current in certain direct-gap (for example III-V compound) semiconductors with
contributions from both the valence bands and the conduction band (for
$n$-doped semiconductors). We show that this spin-current is a property of the
Fermi-Dirac sea, and is controlled by a geometric phase accumulated by the
strain-induced Rashba parameters in a cycle.",0511270v1
1997-03-25,Post-Newtonian Approximation for Spinning Particles,"Using an energy-momentum tensor for spinning particles due to Dixon and
Bailey-Israel, we develop the post-Newtonian approximation for N spinning
particles in a self-contained manner. The equations of motion are derived
directly from this energy-momentum tensor. Following the formalism of Epstein-
Wagoner, we also obtain the waveform and the luminosity of the gravitational
wave generated by these particles.",9703071v1
2007-09-06,Spin-gravity coupling and gravity-induced quantum phases,"External gravitational fields induce phase factors in the wave functions of
particles. The phases are exact to first order in the background gravitational
field, are manifestly covariant and gauge invariant and provide a useful tool
for the study of spin-gravity coupling and of the optics of particles in
gravitational or inertial fields. We discuss the role that spin-gravity
coupling plays in particular problems.",0709.0819v1
2009-04-09,Interacting two helical edge modes in quantum spin Hall systems,"We study theoretically the two interacting one-dimensional helical modes at
the edges of the quantum spin Hall systems. A new type of inter-edge correlated
liquid (IECL) without the spin gap is found. This liquid shows the diverging
density wave (DW) and superconductivity (SC) correlations much stronger than
those of the spinfull electrons. Possible experimental observations are also
discussed.",0904.1453v2
2009-12-31,Spin light mode of massive neutrino radiative decay in matter,"Using the exact solutions for the Dirac neutrino wave function in presence of
matter we study the spin light mode in the process of neutrino transition from
initial heavier to final lighter state. The spin light is emitted due to the
neutrino nonzero transitional magnetic moment.",1001.0101v1
2012-11-26,Electron spin motion in the delta-function pulse,"We formulate the Bargman-Michel-Telegdi (BMT) equation for electron spin
motion in a plane wave and in the Dirac delta-function pulse. We compare the
BMT solution with the Wolkow solution of the Dirac equation. The Wolkow
solution for the spin is not identical with the solution following from the BMT .",1211.5889v1
2006-04-10,Polarization Transport of Transverse Acoustic Waves: Berry Phase and Spin Hall Effect of Phonons,"We carry out a detailed analysis of the short-wave (semiclassical)
approximation for the linear equations of the elasticity in a smoothly
inhomogeneous isotropic medium. It is shown that the polarization properties of
the transverse waves are completely analogous to those of electromagnetic waves
and can be considered as spin properties of optical phonons. In particular, the
Hamiltonian of the transverse waves contains an additional term of the phonon
spin-orbit interaction arising from the Berry gauge potential in the momentum
space. This potential is diagonal in the basis of the circularly polarized
waves and corresponds to the field of two `magnetic monopoles' of opposite
signs for phonons of opposite helicities. This leads to the appearance of the
Berry phase in the equation for the polarization evolution and an additional
``anomalous velocity'' term in the ray equations. The anomalous velocity has
the form of the `Lorentz force' caused by the Berry gauge field in momentum
space and gives rise to the transverse transport of waves of opposite
helicities in opposite directions. This is a manifestation of the spin Hall
effect of optical phonons. The effect directly relates to the conservation of
total angular momentum of phonons and also influences reflection from a sharp
boundary (acoustic analogue of the transverse Ferdorov--Imbert shift).",0604248v4
2019-04-10,Optical excitation of propagating magnetostatic waves in an epitaxial Galfenol film by an ultrafast magnetic anisotropy change,"Using a time-resolved optically-pumped scanning optical microscopy technique
we demonstrate the laser-driven excitation and propagation of spin waves in a
20-nm film of a ferromagnetic metallic alloy Galfenol epitaxially grown on a
GaAs substrate. In contrast to previous all-optical studies of spin waves we
employ laser-induced thermal changes of magnetocrystalline anisotropy as an
excitation mechanism. A tightly focused 70-fs laser pulse excites packets of
magnetostatic surface waves with a $e^{-1}$ propagation length of 3.4 $\mu$m,
which is comparable with that of permalloy. As a result, laser-driven
magnetostatic spin waves are clearly detectable at distances up to 10 $\mu$m,
which promotes epitaxial Galfenol films to the limited family of materials
suitable for magnonic devices. A pronounced in-plane magnetocrystalline
anisotropy of the Galfenol film offers an additional degree of freedom for
manipulating the spin waves' parameters. Reorientation of an in-plane external
magnetic field relative to the crystallographic axes of the sample tunes the
frequency, amplitude and propagation length of the excited waves.",1904.05171v2
2020-06-15,Gravitational shock waves and scattering amplitudes,"We study gravitational shock waves using scattering amplitude techniques.
After first reviewing the derivation in General Relativity as an
ultrarelativistic boost of a Schwarzschild solution, we provide an alternative
derivation by exploiting a novel relation between scattering amplitudes and
solutions to Einstein's field equations. We prove that gravitational shock
waves arise from the classical part of a three point function with two massless
scalars and a graviton. The region where radiation is localized has a
distributional profile and it is now recovered in a natural way, thus bypassing
the introduction of singular coordinate transformations as used in General
Relativity. The computation is easily generalized to arbitrary dimensions and
we show how the exactness of the classical solution follows from the absence of
classical contributions at higher loops. A classical double copy between
gravitational and electromagnetic shock waves is also provided and for a
spinning source, using the exponential form of three point amplitudes, we infer
a remarkable relation between gravitational shock waves and spinning ones, also
known as gyratons. Using this property, we infer a family of exact solutions
describing gravitational shock waves with spin. We then compute the phase shift
of a particle in a background of shock waves finding agreement with an earlier
computation by Amati, Ciafaloni and Veneziano for particles in the high energy
limit. Applied to a gyraton, it provides a result for the scattering angle to
all orders in spin.",2006.08283v2
2024-04-16,Reconfigurable spin-wave platform based on interplay between nanodots and waveguide in hybrid magnonic crystal,"We present a hybrid magnonic crystal composed of a chain of nanodots with
strong perpendicular magnetic anisotropy and Dzyaloshinskii-Moriya interaction,
positioned above a permalloy waveguide. The study examines two different
magnetization states in the nanodots: a single-domain state and an egg-shaped
skyrmion state. Due to the dipolar coupling between the dot and the waveguide,
a strongly bound hybrid magnetization texture is formed in the system. Our
numerical results show complex spin-wave spectra, combining the effects of
periodicity, magnetization texture, and hybridization of the propagating waves
in the waveguide with the dot/skyrmion modes. The systems are characterized by
different band gap sizes. For the skyrmion state, the azimuthal modes confined
to the skyrmion domain wall lead to the formation of flat bands at low
frequencies, while at higher frequencies we identify among them modes
interacting with the propagating waves, which can introduce additional
non-Bragg band gaps, as well as isolated modes leading to the formation of
bound states. On the other hand, the system with a single-domain state in
nanodots offers a wide range of frequencies where the spin waves are
predominantly in the waveguide. Thus, the study shows that the proposed hybrid
magnonic crystals have many distinct functionalities, highlighting their
reconfigurable potential, magnon-magnon couplings, mode localization, and bound
states overlapping with the propagating waves. This opens up potential
applications in analog and quantum magnonics, spin-wave filtering, and the
establishment of magnonic neural networks.",2404.10493v1
2003-04-17,Antiferromagnetism and d-wave superconductivity in (doped) Mott insulators: A wave function approach,"We propose a class of wave functions that provide a unified description of
antiferromagnetism and d-wave superconductivity in (doped) Mott insulators. The
wave function has a Jastrow form and prohibits double occupancies. In the
absence of holes, the wave function describes antiferromagnetism accurately.
Off diagonal long range order develops at finite doping and the superconducting
order parameter has d-wave symmetry. We also show how nodal quasiparticles and
neutral spin excitations can be constructed from this wave function.",0304388v2
2003-09-24,Orbital Wave and its Observation in Orbital Ordered Titanates and Vanadates,"We present a theory of the collective orbital excitation termed orbital wave
in perovskite titanates and vanadates with the triply degenerate $t_{2g}$
orbitals. The dispersion relations of the orbital waves for the orbital ordered
LaVO$_3$, YVO$_3$ and YTiO$_3$ are examined in the effective spin-orbital
coupled Hamiltonians associated with the Jahn-Teller type couplings. We propose
possible scattering processes for the Raman and inelastic neutron scatterings
from the orbital wave and calculate the scattering spectra for titanates and
vanadates. It is found that both the excitation spectra and the observation
methods of the orbital wave are distinct qualitatively from those for the $e_g$
orbital ordered systems.",0309538v2
2005-03-14,Surface spin waves in superconducting and insulating ferromagnets,"Surface magnetization waves are studied on a semi-infinite magnetic medium in
the perpendicular geometry. Both superconducting and insulating ferromagnets
are considered. Exchange and dipole energies are taken into account, as well as
retardation effects. At large wave vectors, the spectrum for a superconductor
and insulator is the same, though for the former the branch is terminated much
earlier than for the latter due to excitation of plasmons. At small wave
vectors, the surface wave is more robust in the superconductor since it is
separated from the bulk continuum by a finite gap.",0503340v1
1999-06-07,Gravitational waves and massless particle fields,"These notes address the planar gravitational wave solutions of general
relativity in empty space-time, and analyze the motion of test particles in the
gravitational wave field. Next we consider related solutions of the Einstein
equations for the gravitational field accompanied by long-range wave fields of
scalar, spinor and vector type, corresponding to particles of spin s=(0,1/2,1).
The motion of test masses in the combined gravitational and scalar, spinor or
vector wave fields is discussed.",9906026v2
1993-09-17,Generalized Relativistic Meson Wave Function,"We study the most general, relativistic, constituent $q{\overline q}$ meson
wave function within a new covariant framework. We find that by including a
tensor wave function component, a pure valence quark model is now capable of
reproducing not only all static pion data ($f_\pi$, $\langle r_\pi^2 \rangle$)
but also the distribution amplitude, form factor $(F_\pi(Q^2))$, and structure
functions. Further, our generalized spin wave function provides a much better
detailed description of meson properties than models using a simple
relativistic extension of the $S=L=0$ nonrelativistic wave function.",9309284v1
2016-05-14,Universal One-dimensional Atomic Gases Near Odd-wave Resonance,"We show the renormalization of contact interaction for odd-wave scattering in
one-dimension(1D). Based on the renormalized interaction, we exactly solve the
two-body problem in a harmonic trap, and further explore the universal
properties of spin-polarized fermions near odd-wave resonance using the
operator product expansion method. It is found that the high-momentum
distribution behaves as $C/k^2$, with $C$ the odd-wave contact. Various
universal relations are derived. Our work suggests a new universal system
emergent in 1D with large odd-wave scattering length.",1605.04363v3
2020-11-20,Confined magnetoelastic waves in thin waveguides,"The characteristics of confined magnetoelastic waves in nanoscale
ferromagnetic magnetostrictive waveguides have been investigated by a
combination of analytical and numerical calculations. The presence of both
magnetostriction and inverse magnetostriction leads to the coupling between
confined spin waves and elastic Lamb waves. Numerical simulations of the
coupled system have been used to extract the dispersion relations of the
magnetoelastic waves as well as their mode profiles.",2011.10326v1
2021-01-11,Relativistic wave--particle duality for spinors,"We propose that relativistic wave--particle duality can be embodied in a
relation $\langle u^i\rangle=\bar{\psi}\gamma^i\psi/\bar{\psi}\psi$, which
determines the mean four-velocity of the fermion particle associated with a
Dirac wave function. We use the Einstein--Cartan theory of gravity with
torsion, which incorporates the spin-orbit interaction in curved spacetime.
This relation is satisfied by a spinor plane wave and it is consistent with the
energy-momentum tensor for particles. We suggest that spacetime guides the
evolution of a wave function, that in turn guides the mean motion of the
associated particle. Consequently, spacetime guides the motion of particles.
The exact motion is limited by the uncertainty principle.",2101.04212v1
2022-06-13,Searches for Continuous-Wave Gravitational Radiation,"Now that detection of gravitational wave signals from the coalescence of
extra-galactic compact binary star mergers has become nearly routine, it is
intriguing to consider other potential gravitational wave signatures. Here we
examine the prospects for discovery of continuous gravitational waves from
fast-spinning neutron stars in our own galaxy and from more exotic sources.
Potential continuous-wave sources are reviewed, search methodologies and
results presented and prospects for imminent discovery discussed.",2206.06447v2
2020-03-14,Enhanced longevity of the spin helix in low-symmetry quantum wells,"In a semiconductor, collective excitations of spin textures usually decay
rather fast due to D'yakonov-Perel' spin relaxation. The latter arises from
spin-orbit coupling, which induces wave-vector-dependent spin rotations that,
in conjunction with random disorder scattering, generate spin decoherence.
However, symmetries occurring under certain conditions can prevent the
relaxation of particular homogeneous and inhomogeneous spin textures. The
inhomogeneous spin texture, termed as persistent spin helix, is especially
appealing as it enables us to manipulate the spin orientation while retaining a
long spin lifetime. Recently, it was predicted that such symmetries can be
realized in zinc-blende two-dimensional electron gases if at least two
growth-direction Miller indices agree in modulus and the coefficients of the
Rashba and linear Dresselhaus spin-orbit couplings are suitably matched [PRL
117, 236801 (2016)]. In the present paper, we systematically analyze the impact
of the symmetry-breaking cubic Dresselhaus spin-orbit coupling, which
generically coexists in these systems, on the stability of the emerging spin
helices with respect to the growth direction. We find that, as an interplay
between orientation and strength of the effective magnetic field induced by the
cubic Dresselhaus terms, the spin relaxation is weakest for a low-symmetry
growth direction that can be well approximated by a [225] lattice vector. These
quantum wells yield a 30\% spin-helix lifetime enhancement compared to
[001]-oriented electron gases and, remarkably, require a negligible Rashba
coefficient. The rotation axis of the corresponding spin helix is only slightly
tilted out of the quantum-well plane. This makes the experimental study of the
spin-helix dynamics readily accessible for conventional optical spin
orientation measurements where spins are excited and detected along the
quantum-well growth direction.",2003.06544v2
2020-01-17,Thermal spin transport and spin in thermoelectrics,"This article reviews the principles that govern the combined transport of
spin, heat, and charge. The extensive thermodynamic quantity associated with
spin transport is the magnetization; its Onsager-conjugate force is in general
the derivative of the free energy with respect to the magnetization. Spins are
carried in one of two ways: (1) by spin-polarized free electrons in magnetic
metals and doped semiconductors, or (2) by spin waves (magnons) that reside on
localized electrons on unfilled d- or f-shells of transition metal or
rare-earth elements. The paper covers both cases in separate chapters. In both
cases, it is possible to define a spin chemical potential whose gradient is the
more practical conjugate force to spin transport. The paper further describes
the anomalous Hall, spin Hall, and inverse spin Hall effects in magnetic and
non-magnetic solids with strong spin-orbit coupling because these effects are
used to generate and measure spin fluxes. Spin transport across interfaces is
described next, and includes spin pumping and spin transfer torque. The final
chapter then puts all these concepts together to describe the spin-Seebeck,
spin-Peltier, and magnon-drag effects, which exist in ferromagnetic,
antiferromagnetic, and even paramagnetic solids. Magnon-drag, in particular, is
a high-temperature effect that boosts the thermopower of metals by an order of
magnitude and that of semiconductors by a factor of 2 or 3 above the electronic
diffusion thermopower. This is the only example where a spin-driven effect is
larger than a charge-driven effect. Magnon drag leads a simple binary
paramagnetic semiconductor, MnTe, to have zT > 1 without optimization. This
shows how adding spin as an additional design parameter in thermoelectrics
research is a new and promising approach toward the quest for high-zT
materials.",2001.06366v1
1999-05-20,Spin dynamics simulation of the three-dimensional XY model: Structure factor and transport properties,"We present extensive Monte-Carlo spin dynamics simulations of the classical
XY model in three dimensions on a simple cubic lattice with periodic boundary
conditions. A recently developed efficient integration algorithm for the
equations of motion is used, which allows a substantial improvement of
statistics and large integration times. We find spin wave peaks in a wide range
around the critical point and spin diffusion for all temperatures. At the
critical point we find evidence for a violation of dynamic scaling in the sense
that independent components of the dynamic structure factor S(q,w) require
different dynamic exponents in order to obtain scaling. Below the critical
point we investigate the dispersion relation of the spin waves and the
linewidths of S(q,w) and find agreement with mode coupling theory. Apart from
strong spin wave peaks we observe additional peaks in S(q,w) which can be
attributed to two-spin wave interactions. The overall lineshapes are also
discussed and compared to mode coupling predictions. Finally, we present first
results for the transport coefficient D(q,w) of the out-of-plane magnetization
component at the critical point, which is related to the thermal conductivity
of He4 near the superfluid-normal transition.",9905295v1
2000-12-01,Magnetic and orbital ordering in cuprates and manganites,"The mechanisms of magnetic and orbital interactions due to double exchange
(DE) and superexchange (SE) in transition metal oxides with degenerate e_g
orbitals are presented. Specifically, we study the effective spin-orbital
models derived for the d^9 ions as in KCuF_3, and for the d^4 ions as in
LaMnO_3, for spins S=1/2 and S=2, respectively. Such models are characterized
by three types of elementary excitations: spin waves, orbital waves, and
spin-and-orbital waves. The SE interactions between Cu^{2+} (d^9) ions are
inherently frustrated, which leads to a new mechanism of spin liquid which
operates in three dimensions. The SE between Mn^{3+} (d^4) ions explains the
A-type antiferromagnetic order in LaMnO_3 which coexists with the orbital
order. In contrast, the ferromagnetic metallic phase and isotropic spin waves
observed in doped manganites are explained by DE for degenerate e_g orbitals.
It is shown that although a hole does not couple to spin excitations in
ferromagnetic planes of LaMnO_3, the orbital excitations change the energy
scale for the coherent hole propagation and cause a large redistribution of
spectral weight. Finally, we point out some open problems in the present
understanding of doped manganites.",0012013v1
2005-08-08,Site dilution of quantum spins in the honeycomb lattice,"We discuss the effect of site dilution on both the magnetization and the
density of states of quantum spins in the honeycomb lattice, described by the
antiferromagnetic Heisenberg spin-S model. For this purpose a real-space
Bogoliubov-Valatin transformation is used. In this work we show that for the
S>1/2 the system can be analyzed in terms of linear spin wave theory. For spin
S=1/2, however, the linear spin wave approximation breaks down. In this case,
we have studied the effect of dilution on the staggered magnetization using the
Stochastic Series Expansion Monte Carlo method. Two main results are to be
stressed from the Monte Carlo method: (i) a better value for the staggered
magnetization of the undiluted system, m=0.2677(6); (ii) a finite value of the
staggered magnetization of the percolating cluster at the classical percolation
threshold, showing that there is no quantum critical transition driven by
dilution in the Heisenberg model. In the solution of the problem using linear
the spin wave method we pay special attention to the presence of zero energy
modes. Using a combination of linear spin wave analysis and the recursion
method we were able to obtain the thermodynamic limit behavior of the density
of states for both the square and the honeycomb lattices. We have used both the
staggered magnetization and the density of states to analyze neutron scattering
experiments and Neel temperature measurements on quasi-two- -dimensional
honeycomb systems. Our results are in quantitative agreement with experimental
results on Mn_pZn_{1-p}PS_3 and on the Ba(Ni_pMg_{1-p})_2V_2O_8.",0508204v1
2007-02-01,Intensity of Brillouin light scattering from spin waves in magnetic multilayers with noncollinear spin configurations: Theory and experiment,"The scattering of photons from spin waves (Brillouin light scattering -- BLS)
is a well-established technique for the study of layered magnetic systems. The
information about the magnetic state and properties of the sample is contained
in the frequency position, width, and intensity of the BLS peaks. Previously
[Phys. Rev. B 67, 184404 (2003)], we have shown that spin wave frequencies can
be conveniently calculated within the ultrathin film approach, treating the
intralayer exchange as an effective bilinear interlayer coupling between thin
virtual sheets of the ferromagnetic layers. Here we give the consequent
extension of this approach to the calculation of the Brillouin light scattering
(BLS) peak intensities. Given the very close relation of the BLS cross-section
to the magneto-optic Kerr effect (MOKE), the depth-resolved longitudinal and
polar MOKE coefficients calculated numerically via the usual magneto-optic
formalism can be employed in combination with the spin wave precessional
amplitudes to calculate full BLS spectra for a given magnetic system. This
approach allows an easy calculation of BLS intensities even for noncollinear
spin configurations including the exchange modes. The formalism is applied to a
Fe/Cr/Fe/Ag/Fe trilayer system with one antiferromagnetically coupling spacer
(Cr). Good agreement with the experimental spectra is found for a wide variety
of spin configurations.",0702021v1
2013-11-11,Three-dimensional light-matter interface for collective spin squeezing in atomic ensembles,"We study the three-dimensional nature of the quantum interface between an
ensemble of cold, trapped atomic spins and a paraxial laser beam, coupled
through a dispersive interaction. To achieve strong entanglement between the
collective atomic spin and the photons, one must match the spatial mode of the
collective radiation of the ensemble with the mode of the laser beam while
minimizing the effects of decoherence due to optical pumping. For ensembles
coupling to a probe field that varies over the extent of the cloud, the set of
atoms that indistinguishably radiates into a desired mode of the field defines
an inhomogeneous spin wave. Strong coupling of a spin wave to the probe mode is
not characterized by a single parameter, the optical density, but by a
collection of different effective atom numbers that characterize the coherence
and decoherence of the system. To model the dynamics of the system, we develop
a full stochastic master equation, including coherent collective scattering
into paraxial modes, decoherence by local inhomogeneous diffuse scattering, and
backaction due to continuous measurement of the light entangled with the spin
waves. This formalism is used to study the squeezing of a spin wave via
continuous quantum nondemolition (QND) measurement. We find that the greatest
squeezing occurs in parameter regimes where spatial inhomogeneities are
significant, far from the limit in which the interface is well approximated by
a one-dimensional, homogeneous model.",1311.2328v2
2018-03-23,Direct observation of incommensurate magnetism in Hubbard chains,"The interplay between magnetism and doping is at the origin of exotic
strongly correlated electronic phases and can lead to novel forms of magnetic
ordering. One example is the emergence of incommensurate spin-density waves
with a wave vector that does not match the reciprocal lattice. In one dimension
this effect is a hallmark of Luttinger liquid theory, which also describes the
low energy physics of the Hubbard model. Here we use a quantum simulator based
on ultracold fermions in an optical lattice to directly observe such
incommensurate spin correlations in doped and spin-imbalanced Hubbard chains
using fully spin and density resolved quantum gas microscopy. Doping is found
to induce a linear change of the spin-density wave vector in excellent
agreement with Luttinger theory predictions. For non-zero polarization we
observe a decrease of the wave vector with magnetization as expected from the
Heisenberg model in a magnetic field. We trace the microscopic origin of these
incommensurate correlations to holes, doublons and excess spins which act as
delocalized domain walls for the antiferromagnetic order. Finally, when
inducing interchain coupling we observe fundamentally different spin
correlations around doublons indicating the formation of a magnetic polaron.",1803.08892v1
2020-11-09,Classical many-body chaos with and without quasiparticles,"We study correlations, transport and chaos in a Heisenberg magnet as a
classical model many-body system. By varying temperature and dimensionality, we
can tune between settings with and without symmetry breaking and accompanying
collective modes or quasiparticles. We analyse both conventional and
out-of-time-ordered spin correlators (`decorrelators') to track the spreading
of a spatiotemporally localised perturbation -- the wingbeat of the butterfly
-- as well as transport coefficients and Lyapunov exponents. We identify a
number of qualitatively different regimes. Trivially, at $T=0$, there is no
dynamics at all. In the limit of low temperature, $T=0^+$, integrability
emerges, with infinitely long-lived magnons; here the wavepacket created by the
perturbation propagates ballistically, yielding a lightcone at the spin wave
velocity which thus subsumes the butterfly velocity; inside the lightcone, a
pattern characteristic of the free spin wave spectrum is visible at short
times. On top of this, residual interactionslead to spin wave lifetimes which,
while divergent in this limit, remain finite at any nonzero $T$. At the longest
times, this leads to a `standard' chaotic regime; for this regime, we show that
the Lyapunov exponent is simply proportional to the inverse spin-wave lifetime.
Visibly strikingly, between this and the `short-time' integrable regimes, a
scarred regime emerges: here, the decorrelator is spatiotemporally highly
non-uniform, being dominated by rare and random scattering events seeding
secondary lightcones. As the spin correlation length decreases with increasing
$T$, the distinction between these regimes disappears and at high temperature
the previously studied chaotic paramagnetic regime emerges. For this, we
elucidate how, somewhat counterintuitively, the ballistic butterfly velocity
arises from a diffusive spin dynamics.",2011.04700v1
2019-07-05,Propagation length of antiferromagnetic magnons governed by domain configurations,"The compensated magnetic order and characteristic, terahertz frequencies of
antiferromagnetic materials makes them promising candidates to develop a new
class of robust, ultra-fast spintronic devices. The manipulation of
antiferromagnetic spin-waves in thin films is anticipated to lead to new exotic
phenomena such as spin-superfluidity, requiring an efficient propagation of
spin-waves in thin films. However, the reported decay length in thin films has
so far been limited to a few nanometers. In this work, we achieve efficient
spin-wave propagation, over micrometer distances, in thin films of the
insulating antiferromagnet hematite with large magnetic domains whilst
evidencing much shorter attenuation lengths in multidomain thin films. Through
transport and magnetic imaging, we conclude on the role of the magnetic domain
structure and spin-wave scattering at domain walls to govern the transport. We
manipulate the spin transport by tailoring the domain configuration through
field cycle training. For the appropriate crystalline orientation, zero-field
spin-transport is achieved across micrometers, as required for device
integration.",1907.02751v2
2021-01-29,Dynamically stable negative-energy states induced by spin-transfer torques,"We investigate instabilities of the magnetic ground state in ferromagnetic
metals that are induced by uniform electrical currents, and, in particular, go
beyond previous analyses by including dipolar interactions. These instabilities
arise from spin-transfer torques that lead to Doppler shifted spin waves. For
sufficiently large electrical currents, spin-wave excitations have negative
energy with respect to the uniform magnetic ground state, while remaining
dynamically stable due to dissipative spin-transfer torques. Hence, the uniform
magnetic ground state is energetically unstable, but is not able to dynamically
reach the new ground state. We estimate this to happen for current densities $
j\gtrsim (1-D/D_c)10^{13} \mathrm{A/m^2} $ in typical thin film experiments,
with $ D $ the Dzyaloshinskii-Moriya interaction constant, and $ D_c $ the
Dzyaloshinskii-Moriya interaction that is required for spontaneous formation of
spirals or skyrmions. These current densities can be made arbitrarily small for
ultrathin film thicknesses at the order of nanometers, due to surface- and
interlayer effects. From an analogue gravity perspective, the stable negative
energy states are an essential ingredient to implement event horizons for
magnons -- the quanta of spin waves -- giving rise to e.g. Hawking radiation
and can be used to significantly amplify spin waves in a so-called black-hole
laser.",2101.12544v1
2021-12-17,Combined unitary and symmetric group approach applied to low-dimensional spin systems,"A novel combined unitary and symmetric group approach is used to study the
spin-$\frac{1}{2}$ Heisenberg model and related Fermionic systems in a
spin-adapted representation, using a linearly-parameterised Ansatz for the
many-body wave function. We show that a more compact ground state wave function
representation is obtained when combining the symmetric group, $\mathcal{S}_n$,
in the form of permutations of the underlying lattice site ordering, with the
cumulative spin-coupling based on the unitary group, $\mathrm{U}(n)$. In
one-dimensional systems the observed compression of the wave function is
reminiscent of block-spin renormalization group approaches, and allows us to
study larger lattices (here taken up to 80 sites) with the spin-adapted full
configuration interaction quantum Monte Carlo method, which benefits from the
sparsity of the Hamiltonian matrix and the corresponding sampled eigenstates
that emerge from the reordering. We find that in an optimal lattice ordering
the configuration state function with highest weight already captures with high
accuracy the spin-spin correlation function of the exact ground state wave
function. This feature is found for more general lattice models, such as the
Hubbard model, and ab initio quantum chemical models, in this work exemplified
by a one-dimensional hydrogen chain. We also provide numerical evidence that
the optimal lattice ordering for the unitary group approach is not generally
equivalent to the optimal ordering obtained for methods based on matrix-product
states, such as the density-matrix renormalization group approach.",2112.09594v1
2022-04-05,Single domain stripe order in a high-temperature superconductor,"The coupling of spin, charge and lattice degrees of freedom results in the
emergence of novel states of matter across many classes of strongly correlated
electron materials. A model example is unconventional superconductivity, which
is widely believed to arise from the coupling of electrons via spin
excitations. In cuprate high-temperature superconductors, the interplay of
charge and spin degrees of freedom is also reflected in a zoo of charge and
spin-density wave orders that are intertwined with superconductivity. A key
question is whether the different types of density waves merely coexist or are
indeed directly coupled. Here we use a novel neutron diffraction technique with
superior beam-focusing that allows us to probe the subtle spin-density wave
order in the prototypical high-temperature superconductor La1.88Sr0.12CuO4
under applied uniaxial pressure to demonstrate that it is immediately coupled
with charge-density wave order. Our result shows that suitable models for
high-temperature superconductivity must equally account for charge and spin
degrees of freedom via uniaxial charge-spin stripe fluctuations.",2204.02304v1
2022-10-04,The BKT Transition and its Dynamics in a Spin Fluid,"We study the effect of particle mobility on phase transitions in a spin fluid
in two dimensions. The presence of a phase transition of the BKT universality
class is shown in an off-lattice model of particles with purely repulsive
interaction employing computer simulations. A critical spin wave region $0 < T
< T_{\textrm{BKT}}$ is found with a non-universal exponent $\eta(T)$ that
follows the shape suggested by BKT theory, including a critical value
consistent with $\eta_{\textrm{BKT}} = 1/4$. One can observe a transition from
power-law decay to exponential decay in the static correlation functions at the
transition temperature $T_{\textrm{BKT}}$, which is supported by finite-size
scaling analysis. A critical temperature $T_{\textrm{BKT}} = 0.17(1)$ is
suggested. Investigations into the dynamic aspects of the phase transition are
carried out. The short-time behavior of the incoherent spin autocorrelation
function agrees with the Nelson-Fisher prediction, whereas the long-time
behavior differs from the finite-size scaling known for the static XY model.
Analysis of coherent spin wave dynamics shows that the spin wave peak is a
propagating mode that can be reasonably well fitted by hydrodynamic theory. The
mobility of the particles strongly enhances damping of the spin waves, but the
model lies still within the dynamic universality class of the standard XY
model.",2210.01838v1
2000-08-18,Millimeter-Wave Spectroscopy of the Organic spin-Peierls System b'-(ET)2SF5CF2SO3,"The first purely organic BEDT-TTF spin-Peierls system, b'-(ET)2SF5CF2SO3, has
been confirmed using a high-frequency electron spin resonance (EPR) cavity
perturbation technique. The material exhibits the characteristics of a
quasi-one-dimensional (1D) Heisenberg antiferromagnetic spin system above 30 K,
but undergoes a second-order transition, at TSP = 33 K, to a singlet ground
state, due to a progressive spin-lattice dimerization. The spin-Peierls state
is evidenced by a sharp drop in the spin susceptibility below 24 K for the
magnetic field parallel to each of the three principle axes (i.e. H7a, H7b, and
H7c). The 1D chain axis has been identified as the crystallographic b axis from
the g value analysis. The singlet-triplet gap, Ds(0) = 114 (+-21)K, was
determined using a modified BCS theory. Also, we describe in some detail the
millimeter-wave vector network analyzer (MVNA) for researchers who have
interest in precision EPR measurements at higher magnetic fields and
frequencies.",0008281v1
2001-03-20,Antiferromagnetically coupled alternating spin chains,"The effect of antiferromagnetic interchain coupling in alternating spin
(1,1/2) chains is studied by mean of a spin wave theory and density matrix
renormalization group (DMRG). In particular, two limiting cases are
investigated, the two-leg ladder and its two dimensional (2D) generalization.
Results of the ground state properties like energy, spin gap, magnetizations,
and correlation functions are reported for the whole range of the interchain
coupling $J_{\perp}$. For the 2D case the spin wave results predict a smooth
dimensional crossover from 1D to 2D keeping the ground state always ordered.
For the ladder system, the DMRG results show that any $J_{\perp}>0$ drives the
system to a gapped ground state. Furthermore the behaviour of the correlation
functions closely resemble the uniform spin-1/2 ladder. For $J_{\perp}$ lower
than 0.3, however, the gap behaves quadratically as $\Delta\sim0.6
J^2_{\perp}$. Finally, it is argued that the behaviour of the spin gap for an
arbitrary number of mixed coupled spin chains is analogous to that of the
uniform spin-1/2 chains.",0103424v1
2001-09-10,Dimensional crossover in alternating spin chains,"The effect of antiferromagnetic interchain coupling in alternating spin
(1,1/2) chains is studied by mean of spin wave theory and density matrix
renormalization group(DMRG). Two limiting cases are investigated, the two-leg
ladder and its two dimensional (2D) generalization. For the 2D case, spin wave
approximation predicts a smooth dimensional crossover keeping the ground state
ordered, whereas in the ladder case the DMRG results show a gapped ground state
for any $J_{\perp}>0$. Furthermore, the behavior of the correlation functions
closely resemble the uniform spin-1/2 ladder. However, for small $J_{\perp}$,
the gap behaves quadratically as $\Delta\sim0.6 J^2_{\perp}$. Similarly to
uniform spin chains, it is conjectured an analogous spin gap behavior for an
arbitrary number of mixed spin chains",0109179v1
2002-11-26,Spin dynamics of stripes,"The spin dynamics of stripes in high-temperature superconductors and related
compounds is studied in the framework of a spin-wave theory for a simple
spin-only model. The magnon dispersion relation and the magnetic structure
factor are calculated for diagonal and vertical stripes. Acoustical as well as
optical bands are included in the analysis. The incommensurability and the
$\pi$ resonance appear as complementary features of the band structure at
different energy scales. The dependence of spin-wave velocities and resonance
frequencies on the stripe spacing and coupling is calculated. At low doping,
the resonance frequency is found to scale roughly inversely proportional to the
stripe spacing. The favorable comparison of the results with experimental data
suggests that the spin-only model provides a suitable and simple basis for
calculating and understanding the spin dynamics of stripes.",0211593v1
2003-10-27,Transverse spin dynamics in a spin-polarized Fermi liquid,"The linear equations for transverse spin dynamics in weakly polarised
degenerate Fermi liquid with arbitrary relationship between temperature and
polarization are derived from Landau-Silin phenomenological kinetic equation
with general form of two-particle collision integral. The temperature and
polarization dependence of the spin current relaxation time is established. It
is found in particular that at finite polarization transverse spin wave damping
has a finite value at T=0. The analogy between temperature dependences of spin
waves attenuation and ultrasound absorption in degenerate Fermi liquid at
arbitrary temperature is presented. We also discuss spin-polarized Fermi liquid
in the general context of the Fermi-liquid theory and compare it with ""Fermi
liquid"" with spontaneous magnetization.",0310620v2
2004-02-16,Magnetic excitations in a bond-centered stripe phase: Spin waves far from the semi-classical limit,"Using a spin-only model, we compute spin excitation spectra in a
bond-centered stripe state with long-range magnetic order. We employ a bond
operator formalism, which naturally captures both dimerization and broken spin
symmetry in a unified framework. At low energies, the spin excitations resemble
spin waves, but at higher energies they are very similar to spin-1 excitations
of isolated spin ladders. Our theory does well describe neutron scattering data
[J. M. Tranquada et al., Nature 429, 534 (2004)] on LaBaCuO, pointing towards
bond order in this material.",0402377v2
2004-06-25,Excitations of incoherent spin-waves due to spin-transfer torque,"As predicted by Slonczewski and Berger, the possibility of exciting microwave
oscillations in a nanomagnet by a spin-polarized current has been recently
demonstrated. This observation opens very important perspectives of
applications in RF components. However, some unresolved inconsistencies are
found when interpreting the magnetization dynamics results within the coherent
spin-torque model (CSM). In some cases, the telegraph noise caused by
spin-currents could not be described quantitatively by the CSM. This led to
controversies about the need of an effective magnetic temperature model (ETM).
Here we interpret the experimental results of Kiselev et al. [Nature 425, 380
(2003)] using micromagnetic simulations. We point out the key role played by
incoherent spin-waves excitation due to spin-transfer effects. The incoherence
is caused by the spatial inhomogeneities of the local fields, generating a
distribution of local precession frequencies. It results in telegraph noise at
zero temperature associated with transitions between attraction wells in phase
space.",0406628v3
2005-05-24,Valence-bond-solid order in antiferromagnets with spin-lattice coupling,"We propose that a valence-bond-solid (VBS) order can be stabilized in certain
two-dimensional antiferromagnets due to spin-lattice coupling. In contrast to
the VBS state of the Affleck-Kennedy-Lieb-Tesaki (AKLT) type in which the spin
$2S$ and the lattice coordination $z$ must be commensurate, the spin-lattice
coupling-induced VBS state can occur when $2S$ is not an integer multiple of
$z$. As a concrete example, S=2 spins on the triangular network with $z=6$ is
discussed. Within the Schwinger boson mean-field theory it is shown that the
ground state is given by the $\sqrt{3}\times\sqrt{3}$ modulation of the valence
bond amplitudes for sufficiently strong spin-lattice coupling. Using the
corresponding AKLT wave function, we work out the excitation spectrum for this
state within the single-mode approximation. The calculated spectrum should
provide a new type of collective mode which is distinct from the spin wave
excitations of the magnetically ordered ground state.",0505573v5
1995-07-13,Monte Carlo Study of the Yukawa Coupled Two Spin Ising Model,"We consider a particular 4 state spin system composed of two Ising spins
(~$s_x, \; \sigma_x$~) with independent hopping parameters $\kappa_1,
\kappa_2$, coupled by a bilinear Yukawa term, $y s_x \sigma_x$. The Yukawa term
is solely responsible for breaking the global $ Z_2 \times Z_2$ symmetry down
to $Z_2$. This model is intended as an illustration of general coupled Higgs
system where scalars can arise both as composite and elementary excitations.
For the Ising example in 2d, we give convincing numerical evidence of the
universality of the two spin system with the one spin Ising model, by Monte
Carlo simulations and finite scaling analysis . We also show that as we
approach the phase transition, universality arises by a separation of low mass
spin waves from an extra set of spin waves with an energy gap that diverges as
the correlations length diverges",9507015v1
2007-08-27,Spin dynamics in a one-dimensional ferromagnetic Bose gas,"We investigate the propagation of spin excitations in a one-dimensional (1D)
ferromagnetic Bose gas. While the spectrum of longitudinal spin waves in this
system is sound-like, the dispersion of transverse spin excitations is
quadratic making a direct application of the Luttinger Liquid (LL) theory
impossible. By using a combination of different analytic methods we derive the
large time asymptotic behavior of the spin-spin dynamical correlation function
for strong interparticle repulsion. The result has an unusual structure
associated with a crossover from the regime of trapped spin wave to an open
regime and does not have analogues in known low-energy universality classes of
quantum 1D systems.",0708.3638v2
2007-11-27,Non-linear dynamics and two-dimensional solitons for spin $ S=1$ ferromagnets with biquadratic exchange,"We develop a consistent semiclassical theory of spin dynamics for an
isotropic ferromagnet with a spin $ S=1$ taking into consideration both
bilinear and biquadratic over spin operators exchange interaction. For such
non-Heisenberg magnets, a peculiar class of spin oscillations and waves, for
which the quantum spin expectation value $ {\rm {\bf m}}=<{\rm {\bf S}}>$ does
not change it direction, but changes in length, is presented. Such
``longitudinal'' excitations do not exist in regular magnets, dynamics of which
are described in terms of the Landau-Lifshitz equation or by means of the spin
Heisenberg Hamiltonian. We demonstrate the presence of non-linear uniform
oscillations and waves, as well as self-localized dynamical excitations
(solitons) with finite energy. A possibility of excitation of such oscillations
by ultrafast laser pulse is discussed.",0711.4285v1
2008-01-28,Modulated spin waves and robust quasi-solitons in classical Heisenberg rings,"We investigate the dynamical behavior of finite rings of classical spin
vectors interacting via nearest-neighbor isotropic exchange in an external
magnetic field. Our approach is to utilize the solutions of a continuum version
of the discrete spin equations of motion (EOM) which we derive by assuming
continuous modulations of spin wave solutions of the EOM for discrete spins.
This continuous EOM reduces to the Landau-Lifshitz equation in a particular
limiting regime. The usefulness of the continuum EOM is demonstrated by the
fact that the time-evolved numerical solutions of the discrete spin EOM closely
track the corresponding time-evolved solutions of the continuum equation. Of
special interest, our continuum EOM possesses soliton solutions, and we find
that these characteristics are also exhibited by the corresponding solutions of
the discrete EOM. The robustness of solitons is demonstrated by considering
cases where initial states are truncated versions of soliton states and by
numerical simulations of the discrete EOM equations when the spins are coupled
to a heat bath at finite temperatures.",0801.4262v1
2008-04-04,"Spin-charge coupling in a band ferromagnet: magnon-energy reduction, anomalous softening, and damping","The effects of correlation-induced coupling between spin and charge
fluctuations on spin-wave excitations in a band ferromagnet are investigated by
including self-energy and vertex corrections within a systematic
inverse-degeneracy expansion scheme which explicitly preserves the Goldstone
mode. Arising from the scattering of a magnon into intermediate spin-excitation
states (including both magnon and Stoner excitations) accompanied with charge
fluctuations in the majority spin band, this spin-charge coupling results not
only in a substantial reduction of magnon energies but also in anomalous
softening and significant magnon damping for zone-boundary modes lying within
the Stoner gap. Our results are in good qualitative agreement with recent
spin-wave excitation measurements in colossal magneto-resistive manganites and
ferromagnetic ultrathin films of transition metals.",0804.0680v1
2008-07-10,Spin rotations induced by electron running on closed trajectories in gated semiconductor nanodevices,"A design for a quantum gate performing transformations of a single electron
spin is presented. The spin rotations are performed by the electron going
around the closed loops in a gated semiconductor device. We demonstrate the
operation of NOT, phase-flip and Hadamard quantum gates, i.e. the single-qubit
gates which are most commonly used in the algorithms. The proposed devices
employ the self-focusing effect for the electron wave packet interacting with
the electron gas on the electrodes and the Rashba spin-orbit coupling. Due to
the self-focusing effect the electron moves in a compact wave packet. The
spin-orbit coupling translates the spatial motion of the electron into the
rotations of the spin. The device does not require microwave radiation and
operates using low constant voltages. It is therefore suitable for selective
single-spin rotations in larger registers.",0807.1627v2
2009-01-15,Spin Rotation Technique for Non-Collinear Magnetic Systems: Application to the Generalized Villain Model,"This work develops a new generalized technique for determining the static and
dynamic properties of any non-collinear magnetic system. By rotating the spin
operators into the local spin reference frame, we evaluate the zeroth, first,
and second order terms in a Holstein-Primakoff expansion, and through a Green's
functions approach, we determine the structure factor intensities for the
spin-wave frequencies. To demonstrate this technique, we examine the spin-wave
dynamics of the generalized Villain model with a varying interchain
interaction. The new interchain coupling expands the overall phase diagram with
the realization of two non-equivalent canted spin configurations. The
rotational Holstein-Primakoff expansion provides both analytical and numerical
results for the spin dynamics and intensities of these phases.",0901.2332v2
2009-08-18,Dynamic spin susceptibility in the t-J model,"A relaxation-function theory for the dynamic spin susceptibility in the
$t$--$J$ model is presented. By a sum-rule-conserving generalized mean-field
approximation (GMFA), the two-spin correlation functions of arbitrary range,
the staggered magnetization, the uniform static susceptibility, and the
antiferromagnetic correlation length are calculated in a wide region of hole
doping and temperaturs. A good agreement with available exact diagonalization
(ED) data is found. The correlation length is in reasonable agreement with
neutron-scattering experiments on La_{2-\delta}Sr_\delta)CuO_4. Going beyond
the GMFA, the self-energy is calculated in the mode-coupling approximation. The
spin dynamics at arbitrary frequencies and wave vectors is studied for various
temperatures and hole doping. At low doping a spin-wave-type behavior is found
as in the Heisenberg model, while at higher doping a strong damping caused by
hole hopping occurs, and a relaxation-type spin dynamics is observed in
agreement with the ED results. The local spin susceptibility and its (\omega/T)
scaling behavior are calculated in a reasonable agreement with experimental and
ED data.",0908.2557v2
2011-08-18,"Bands, spin fluctuations and traces of Fermi surfaces in angle-resolved photoemission intensities for high-$T_C$ cuprates","The band structures of pure and hole doped La$_2$CuO$_4$ with
antiferromagnetic (AFM) spin-fluctuations are calculated and compared to
spectral weights of ARPES. It is shown that observations of coexisting Fermi
surface (FS) arcs and closed FS pockets are consistent with modulated AFM spin
fluctuations of varying wave lengths. Large variations of strong spin
fluctuations make the outer part of the FS break diffuse at low doping. This
part of the FS is suppressed at high doping when spin fluctuations are weak.
The resulting superimposed spectral weight has features both from FS arcs and
closed pockets. A connection between results of ARPES, neutron scattering, and
band results for the modulated AFM spin wave state, suggests that spin-phonon
coupling is an important mechanism for the %pseudogap and other properties of
the cuprates.",1108.3775v1
2011-09-05,Nucleon resonances in the fourth resonance region,"Nucleon and $\Delta$ resonances in the fourth resonance region are studied in
a multichannel partial-wave analysis which includes nearly all available data
on pion- and photo-induced reactions off protons. In the high-mass range, above
1850\,MeV, several alternative solutions yield a good description of the data.
For these solutions, masses, widths, pole residues and photo-couplings are
given. In particular, we find evidence for nucleon resonances with
spin-parities $J^P=1/2^+...7/2^+$. For one set of solutions, there are four
resonances forming naturally a spin-quartet of resonances with orbital angular
momentum L=2 and spin S=3/2 coupling to $J=1/2,...,7/2$. Just below 1.9\,GeV we
find a spin doublet of resonances with $J^P=1/2^-$ and $3/2^-$. Since a spin
partner with $J^P=5/2^-$ is missing at this mass, the two resonances form a
spin doublet which must have a symmetric orbital-angular-momentum wave function
with L=1. For another set of solutions, the four positive-parity resonances are
accompanied by mass-degenerate negative-parity partners -- as suggested by the
conjecture of chiral symmetry restoration. The possibility of a $J^P=1/2^+,
3/2^+$ spin doublet at 1900\,MeV belonging to a 20-plet is discussed.",1109.0970v1
2011-10-31,Spin excitations and mechanisms of superconductivity in cuprates,"A microscopic theory of spin excitations in strongly-correlated electronic
systems within the t-J model is discussed. An exact representation for the
dynamic spin susceptibility is derived. In the normal state, the excitation
spectrum reveals a crossover from spin-wave-like excitations at low doping to
overdamped paramagnons above the optimal doping. At low temperatures, the
resonance mode at the antiferromagnetic wave vector Q = \pi(1,1) emerges which
is explained by a strong suppression of the spin excitation damping caused by a
spin gap at Q rather than by opening of a superconducting gap. A major role of
spin excitations in the d-wave superconducting pairing in cuprates is stressed
in discussing mechanisms of high-Tc superconductivity within the Hubbard model
in the limit of strong correlations, while electron-phonon interaction and a
well-screened weak Coulomb interaction are not essential.",1110.6715v1
2012-10-03,Waves of spin-current in magnetized dielectrics,"Spin-current is an important physical quantity in present day spintronics and
it might be very usefull in the physics of quantum plasma of spinning
particles. Thus it is important to have an equation of the spin-current
evolution. This equation naturally appears as a part of a set of the quantum
hydrodynamics (QHD) equations. Consequently, we present the set of the QHD
equations derived from the many-particle microscopic Schrodinger equation,
which consists of the continuity equation, the Euler equation, the Bloch
equation and equation of the spin-current evolution. We use these equations to
study dispersion of the collective excitations in the three dimensional samples
of the magnetized dielectrics. We show that dynamics of the spin-current leads
to formation of new type of the collective excitations in the magnetized
dielectrics, which we called spin-current waves.",1210.1090v2
2013-01-24,Soliton dynamics of an atomic spinor condensate on a Ring Lattice,"We study the dynamics of macroscopically-coherent matter waves of an
ultra-cold atomic spin-one or spinor condensate on a ring lattice of six sites
and demonstrate a novel type of spatio-temporal internal Josephson effect.
Using a discrete solitary mode of uncoupled spin components as an initial
condition, the time evolution of this many-body system is found to be
characterized by two dominant frequencies leading to quasiperiodic dynamics at
various sites. The dynamics of spatially-averaged and spin-averaged degrees of
freedom, however, is periodic enabling an unique identification of the two
frequencies. By increasing the spin-dependent atom-atom interaction strength we
observe a resonance state, where the ratio of the two frequencies is a
characteristic integer multiple and the spin-and-spatial degrees of freedom
oscillate in ""unison"". Crucially, this resonant state is found to signal the
onset to chaotic dynamics characterized by a broad band spectrum. In a
ferromagnetic spinor condensate with attractive spin-dependent interactions,
the resonance is accompanied by a transition from oscillatory- to
rotational-type dynamics as the time evolution of the relative phase of the
matter wave of the individual spin projections changes from bounded to
unbounded.",1301.5851v1
2013-03-24,Spin-Transfer Torques in Helimagnets,"We theoretically investigate current-induced magnetization dynamics in
chiral-lattice helimagnets. Spin-orbit coupling in non-centrosymmetric crystals
induces a reactive spin-transfer torque that has not been previously
considered. We demonstrate how the torque is governed by the crystal symmetry
and acts as an effective magnetic field along the current direction in cubic
B20-type crystals. The effects of the new torque are computed for
current-induced dynamics of spin-spirals and the Doppler shift of spin waves.
In current-induced spin-spiral motion, the new torque tilts the spiral
structure. The spin waves of the spiral structure are initially displaced by
the new torque, while the dispersion relation is unaffected.",1303.5921v2
2014-03-27,Itinerant magnetism in Weyl spin-orbit coupled Fermi gas,"Magnetic ordering of itinerant fermionic systems is at the forefront of
condensed matter physics dating back to Stoner's instability. Spin-orbit
coupling (SOC) which couples two essential ingredients of an itinerant
fermionic system, namely spin and orbital motion, opens up new horizons to this
long-standing problem. Here we report that the itinerant ferromagnetism is
absent in 3D Fermi gas with a Weyl SOC and various itinerant spin density waves
emerge instead, which is deeply rooted in the unique symmetry and spin-momentum
locking effect in spin-orbit coupled systems. What is more appealing is that,
the strong SOC provides a new and efficient mechanism to realize itinerant spin
density waves at extremely weak repulsion---a significant benefit for present
ultra-cold atom experiment. These novel phenomena can be probed by Bragg
spectroscopy, time of flight imaging and {\sl In-Situ } measurements in
ultra-cold atom experiment.",1403.7031v6
2014-07-03,Design local spin models for Gutzwiller-projected parton wave functions,"We introduce a method to design a local spin Hamiltonian to realize a
Gutzwiller-projected parton wave functions (GPWF) as its ground state. For
example, the Dirac spin liquid (DSL) state is quite close to the true ground
state of the spin-1/2 Heisenberg model on kagome lattice. We examine what kind
of perturbations we should add in order to drive the DSL to more stable chiral
spin liquid (CSL), valence bond solid (VBS) or Gutzwiller-projected spin Hall
(GSH) states. We compute the two-body reduced-density-matrices (2-RDM) of GPWFs
for those target states, and compare them to the 2-RDM of the DSL. This allows
us to design local spin models with only two-body interactions that may realize
those interesting target states. Our results agree very well with recent
numerical calculations for CSL on kagome lattice. We also study spin-1 systems
on kagome lattice, and design local spin models that may realize CSL, VBS and
symmetry-protected topological (SPT) states. Our work establishes a directional
guide for further numerical simulations.",1407.0869v1
2014-10-23,Gravitational waves from spinning compact binaries in hyperbolic orbits,"Compact binaries in hyperbolic orbits are plausible gravitational wave (GW)
sources for the upcoming and planned GW observatories. We develop an efficient
prescription to compute post-Newtonian (PN) accurate ready-to-use GW
polarization states for spinning compact binaries, influenced by the dominant
order spin-orbit interactions, in hyperbolic orbits. This is achieved by
invoking the 1.5PN accurate quasi-Keplerian parameterization for the radial
sector of the orbital dynamics. We probe the influences of spins and
gravitational radiation reaction on $h_+$ and $h_{\times}$ during the
hyperbolic passage. It turns out that both polarization states exhibit the
memory effect for GWs from spinning compact binaries in hyperbolic orbits. In
contrast, only cross polarization state exhibits the memory effect for GWs from
non-spinning compact binaries. Additionally, we compute 1PN accurate amplitude
corrected GW polarization states for hyperbolic non-spinning compact binaries
in a fully parametric manner and perform initial comparisons with the existing
waveforms.",1410.6311v3
2015-01-28,Spin Current in Junctions composed of Multi-band Superconductors with a Spin-density Wave,"We calculate a nondissipative spin current and show that it can flow with or
without a charge current. We consider a two-band model which can be applied to
the description of Fe-based pnictides in coexistence regime of
superconductivity and spin-density wave. Using quasiclassical Green's functions
approach and tunneling Hamiltonian method we show that there exists a
possibility to switch off the Josephson current while leaving the spin current
finite. Moreover, it is possible to have the critical Josephson current and the
critical spin current being proportional to each other, thus giving a
possibility to measure the spin current via the Josephson current. The
underlying mechanism is the interfering hopping of electron--hole pairs between
different bands of the superconductors composing the junction. This is an
intrinsic property of the system and provides a unique and natural way to
utilize junctions made solely of pnictides in promising applications in
spintronics devices.",1501.07280v1
2016-02-27,Nonlinear separate spin evolution in degenerate electron-positron-ion plasmas,"The non-linear evolution of spin-electron acoustic, positron-acoustic, and
spin-electron-positron acoustic waves is considered. It is demonstrated that
weakly nonlinear dynamics of each wave leads to the soliton formation.
Altogether, we report on existence of three different solitons. The
spin-electron acoustic soliton known for electron-ion plasmas is described for
electron-positron-ion plasmas for the first time. The existence of the
spin-electron-positron acoustic soliton is reported for the first time. The
positron-acoustic soliton and the spin-electron-positron acoustic soliton arise
as the areas of a positive electric potential. The spin-electron acoustic
soliton behaves as the area of a negative electric potential at the relatively
small positron imbalance $n_{0p}/n_{0e}=0.1$ and as the area of a positive
electric potential at the relatively large positron imbalance
$n_{0p}/n_{0e}=0.5$.",1602.08640v1
2016-04-06,Antiferromagnetic domain wall motion driven by spin-orbit torques,"We theoretically investigate dynamics of antiferromagnetic domain walls
driven by spin-orbit torques in antiferromagnet/heavy metal bilayers. We show
that spin-orbit torques drive antiferromagnetic domain walls much faster than
ferromagnetic domain walls. As the domain wall velocity approaches the maximum
spin-wave group velocity, the domain wall undergoes Lorentz contraction and
emits spin-waves in the terahertz frequency range. The interplay between spin
orbit torques and the relativistic dynamics of antiferromagnetic domain walls
leads to the efficient manipulation of antiferromagnetic spin textures and
paves the way for the generation of high frequency signals in antiferromagnets.",1604.01473v1
2016-04-11,All-Optical Study of Tunable Ultrafast Spin Dynamics in [Co/Pd]-NiFe Systems: The Role of Spin-Twist Structure on Gilbert Damping,"We investigate optically induced ultrafast magnetization dynamics in [Co(0.5
nm)/Pd(1 nm)]x5/NiFe(t) exchange-spring samples with tilted perpendicular
magnetic anisotropy using a time-resolved magneto-optical Kerr effect
magnetometer. The competition between the out-of-plane anisotropy of the hard
layer, the in-plane anisotropy of the soft layer and the applied bias field
reorganizes the spins in the soft layer, which are modified further with the
variation in t. The spin-wave spectrum, the ultrafast demagnetization time, and
the extracted damping coefficient all depend on the spin distribution in the
soft layer, while the latter two also depend on the spin-orbit coupling between
the Co and Pd layers. The spin-wave spectra change from multimode to
single-mode as t increases. At the maximum field reached in this study, H=2.5
kOe, the damping shows a nonmonotonic dependence on t with a minimum at t=7.5
nm. For t<7.5 nm, intrinsic effects dominate, whereas for t>7.5 nm, extrinsic
effects govern the damping mechanisms.",1604.02998v1
2019-03-27,Observing Black Holes Spin,"The spin of a black hole retains the memory of how the black hole grew, and
can be a potent source of energy for powering relativistic jets. To understand
the diagnostic power and astrophysical significance of black hole spin,
however, we must first devise observational methods for measuring spin. Here, I
describe the current state of black hole spin measurements, highlighting the
progress made by X-ray astronomers, as well as the current excitement of
gravitational wave and radio astronomy based techniques. Today's spin
measurements are already constraining models for the growth of supermassive
black holes and giving new insights into the dynamics of stellar core-collapse,
as well as hinting at the physics of relativistic jet production. Future X-ray,
radio, and gravitational wave observatories will transform black hole spin into
a precision tool for astrophysics and test fundamental theories of gravity.",1903.11704v1
2020-11-09,Spin-wave dynamics and symmetry breaking in an artificial spin ice,"Artificial spin ices are periodic arrangements of interacting nanomagnets
successfully used to investigate emergent phenomena in the presence of
geometric frustration. Recently, it has been shown that artificial spin ices
can be used as building blocks for creating functional materials, such as
magnonic crystals, and support a large number of programmable magnetic states.
We investigate the magnetization dynamics in a system exhibiting anisotropic
magnetostatic interactions owing to locally broken structural inversion
symmetry. We find a rich spin-wave spectrum and investigate its evolution in an
external magnetic field. We determine the evolution of individual modes, from
building blocks up to larger arrays, highlighting the role of symmetry breaking
in defining the mode profiles. Moreover, we demonstrate that the mode spectra
exhibit signatures of long-range interactions in the system. These results
contribute to the understanding of magnetization dynamics in spin ices beyond
the kagome and square ice geometries and are relevant for the realization of
reconfigurable magnonic crystals based on spin ices.",2011.04505v2
2017-01-18,Finite Temperature Phases of Two Dimensional Spin-Orbit Coupled Bosons,"We determine the finite temperature phase diagram of two dimensional bosons
with two hyperfine (pseudo-spin) states coupled via Rashba-Dresselhaus
spin-orbit interaction using classical field Monte Carlo calculations. For
anisotropic spin-orbit coupling, we find a transition to a
Berenzinskii-Kosterlitz-Thouless superfluid phase with quasi-long range order.
We show that the spin-order of the quasi-condensate is driven by the anisotropy
of interparticle interaction, favoring either a homogeneous plane wave state or
stripe phase with broken translational symmetry. Both phases show
characteristic behavior in the algebraically decaying spin density correlation
function. For fully isotropic interparticle interaction, our calculations
indicate a fractionalized quasi-condensate where the mean-field degeneracy of
plane wave and stripe phase remains robust against critical fluctuations. In
the case of fully isotropic spin-orbit coupling, the circular degeneracy of the
single particle ground state destroys the algebraic ordered phase in the
thermodynamic limit, but a cross-over remains for finite size systems.",1701.05002v1
2017-03-02,On the nonlinear NMR and magnon BEC in antiferromagnetic materials with coupled electron-nuclear spin precession,"We present a new study of nonlinear NMR and Bose-Einstein Condensation (BEC)
of nuclear spin waves in antiferromagnetic MnCO3 with coupled electron and
nuclear spins. In particular, we show that the observed behaviour of NMR
signals strongly contradicts the conventional description of paramagnetic
ensembles of noninteracting spins based on the phenomenological Bloch
equations. We present a new theoretical description of the coupled
electron-nuclear spin precession, which takes into account an indirect
relaxation of nuclear spins via the electron subsystem. We show that the
magnitude of the nuclear magnetization is conserved for arbitrary large
excitation powers, which is drastically different from the conventional heating
scenario derived from the Bloch equations. This provides strong evidence that
the coherent precession of macroscopic nuclear magnetization observed
experimentally can be identified with BEC of nuclear spin waves with k=0.",1703.00614v2
2019-04-05,First-principles Study of Spin-wave Excitations of 3$d$ Transition Metals with Linear Combination of Pseudo-atomic Orbitals,"We have employed the generalized Bloch theorem to evaluate the spin stiffness
constants of 3$d$ transition metals (bcc-Fe, fcc-Co, and fcc-Ni) within the
linear combination of pseudo-atomic orbitals (LCPAO). The spin stiffness
constants were obtained by fitting the spin-wave energy curve, which relates to
the total energy difference and the spiral vectors. In order to convince the
reliable spin stiffness constants, we also provided the convergences of spin
stiffness constants in terms of the cutoff radius and the number of orbitals.
After observing the specific cutoff radius and the basis orbital, at which the
spin stiffness constant converges, we used those two parameters to compute the
Curie temperature by using the mean field approximation and the random phase
approximation. For the latter approximation, we applied the so-called Debye
approximation, which is intended to reduce very significantly many required
wavevectors to evaluate the Curie temperature. We claimed that our results are
in good agreement with both other calculations and experiments.",1904.02982v1
2020-06-30,Multi-solitons of the half-wave maps equation and Calogero-Moser spin-pole dynamics,"We consider the half-wave maps (HWM) equation which provides a continuum
description of the classical Haldane-Shastry spin chain on the real line. We
present exact multi-soliton solutions of this equation. Our solutions describe
solitary spin excitations that can move with different velocities and interact
in a non-trivial way. We make an ansatz for the solution allowing for an
arbitrary number of solitons, each described by a pole in the complex plane and
a complex spin variable, and we show that the HWM equation is satisfied if
these poles and spins evolve according to the dynamics of an exactly solvable
spin Calogero-Moser (CM) system with certain constraints on initial conditions.
We also find first order equations providing a B\""acklund transformation of
this spin CM system, generalize our results to the periodic HWM equation, and
provide plots that visualize our soliton solutions.",2006.16826v1
2020-10-13,Effects of spin-orbit torque on the ferromagnetic and exchange spin wave modes in ferrimagnetic CoGd alloy,"We use micro-focus Brillouin light scattering spectroscopy to study the
effects of spin-orbit torque on thermal spin waves in almost angular-momentum
compensated ferrimagnetic CoGd alloy films. The spin-orbit torque is produced
by the electric current flowing in the Pt layer adjacent to CoGd. Both the
ferromagnetic and the exchange modes are detected in our measurements. The
intensity and the linewidth of the ferromagnetic mode are modified by the
spin-orbit torque. In contrast, the properties of the exchange mode are
unaffected by the spin-orbit torque. We also find that the frequencies and the
linewidths of both modes are significantly modified by Joule heating, due to
the strong temperature dependence of the magnetic properties of CoGd in the
vicinity of angular momentum compensation point. Our results provide insight
into the mechanisms that can enable the implementation of sub-THz magnetic
nano-oscillators based on ferrimagnetic materials, as well as related effects
in antiferromagnets.",2010.06615v1
2020-10-22,Spin-current version of solar cells in non-centrosymmetric magnetic insulators,"Photovoltaic effect, e.g., solar cells, converts light into DC electric
current. This phenomenon takes place in various setups such as in
noncentrosymmetric crystals and semiconductor pn junctions. Recently, we
proposed a theory for producing DC spin current in magnets using
electromagnetic waves, i.e., the spin-current counterpart of the solar cells.
Our calculation shows that the nonlinear conductivity for the spin current is
nonzero in a variety of noncentrosymmetric magnets, implying that the
phenomenon is ubiquitous in inversion-asymmetric materials with magnetic
excitations. Intuitively, this phenomenon is a bulk photovoltaic effect of
magnetic excitations, where electrons and holes, visible light, and
inversion-asymmetric semiconductors are replaced with magnons or spinons, THz
or GHz waves, and asymmetric magnetic insulators, respectively. We also show
that the photon-driven spin current is shift current type, and as a result, the
current is stable against impurity scattering. This bulk photovoltaic spin
current is in sharp contrast to that of well-known spin pumping that takes
place at the interface between a magnet and a metal.",2010.11795v1
2021-07-27,Spin transport-induced damping of coherent THz spin dynamics in iron,"We study the damping of perpendicular standing spin-waves (PSSWs) in
ultrathin Fe films at frequencies up to 2.4 THz. The PSSWs are excited by
optically generated ultrashort spin current pulses, and probed optically in the
time domain. Analyzing the wavenumber and thickness dependence of the damping,
we demonstrate that at sufficiently large wave vectors $k$ the damping is
dominated by spin transport effects scaling with k^4 and limiting the frequency
range of observable PSSWs. Although this contribution is known to originate in
the spin diffusion, we argue that at moderate and large k a more general
description is necessary and develop a model where the 'transverse spin mean
free path' is the a key parameter, and estimate it to be ~0.5 nm.",2107.12812v2
2021-09-14,Magnon Condensation in Dimerized Antiferromagnets with Spin-Orbit Coupling,"Bose-Einstein condensation (BEC) of triplet excitations triggered by a
magnetic field, sometimes called magnon BEC, in dimerized antiferromagnets
gives rise to a long-range antiferromagnetic order in the plane perpendicular
to the applied magnetic field. To explore the effects of spin-orbit coupling on
magnon condensation, we study a spin model on a distorted honeycomb lattice
with dimerized Heisenberg exchange ($J$ terms) and uniform off-diagonal
exchange ($\Gamma'$ terms) interactions. Via variational Monte Carlo
calculations and spin-wave theory, we find that an out-of-plane magnetic field
can induce different types of long-range magnetic orders, no matter if the
ground state is a non-magnetic dimerized state or an ordered N\'{e}el state.
Furthermore, the critical properties of field-driven phase transitions in the
presence of spin-orbit couplings, as illustrated from spin-wave spectrum and
interpreted by effective field theory, can be different from the conventional
magnon BEC. Our study is helpful to understand the rich phases of spin-orbit
coupled antiferromagnets induced by magnetic fields.",2109.06518v2
2021-11-15,Phase diagram and post-quench dynamics in a double spin-chain system in transverse fields,"We propose and explore the physics of a toy multiferroic model by coupling
two distinct dipolar XXZ models in transverse fields. We determine first the
rich ground-state phase diagram of the model using density matrix
renormalization group techniques. Then, we explore the dynamics of the system
after global and local quenches, using the time-evolving block decimation
algorithm. After a global quench, the system displays decaying coupled
oscillations of the electric and magnetic spins, in agreement with the
Eigenstate Thermalization Hypothesis (ETH) for many-body interacting quantum
systems. Notably, the spin-spin interactions lead to a sizeable quadratic shift
in the oscillation frequency as the inter-chain coupling is increased. Local
quenches lead to a light-cone-like propagation of excitations. In this case,
the inter-chain coupling drives a transfer of energy between the chains that
generates a novel fast spin-wave mode along the 'magnetic' chain at the speed
of the 'electric' spin-wave. This suggests a limited control mechanism for
faster information transfer in magnetic spin chains using electric fields that
harnesses the electric dipoles as intermediaries.",2111.07831v1
2022-05-31,Propagation of spin channel waves,"A mutilated model is constructed to approximate the collision term of spin
Boltzmann equation that incorporates newly appearing collisional invariants
i.e, the total angular momentum. With recourse to degenerate perturbation
theory, the dispersion relations of hydrodynamic modes are formulated, among
which spin modes are responsible for spin equilibration. We find that the
non-locality does not change the sound speed but slows down the propagation of
spin channel waves. The damping rates of spin modes are close to those of
spinless modes over a reasonable parameter value range. The results reveal that
both spin and momentum should be treated simultaneously in a unified transport
framework. In the nonrelativistic limit, the short-wavelength behavior for
normal modes is also explored and there exists a critical point for every
distinct discrete mode over which only quasiparticle modes contribute.",2205.15755v2
2022-07-19,"Magnetic interactions in AB-stacked kagome lattices: magnetic structure, symmetry, and duality","We present the results of an extensive study of the phase diagram and spin
wave excitations for a general spin model on a hexagonal AB-stacked kagome
system. The boundaries of the magnetic phases are determined via a combination
of numerical (Monte Carlo) and analytical (Luttinger-Tisza) methods. We also
determine the phase coexistence regions by considering the instabilities in the
spin wave spectra. Depending on the strength of the spin-orbit coupling (SOC),
some spin and lattice rotations become decoupled, leading to considerably
larger symmetry groups than typical magnetic groups. Thus, we provide a
detailed symmetry description of the magnetic Hamiltonian with negligible,
weak, and intermediate strength of SOC. The spin symmetry in these three cases
has a strong effect on the splittings observed in the spin excitation spectra.
We further identify a number of self-duality transformations that map the
Hamiltonian onto itself. These transformations describe the symmetry of the
parameter space and provide an exact mapping between the properties of
different magnetic orders and lead to accidental degeneracies. Finally, we
discuss the physical relevance of our findings in the context of
$\mathrm{Mn}_3X$ compounds.",2207.09297v1
2022-09-01,Spin contributions to the gravitational-waveform modes for spin-aligned binaries at the 3.5PN order,"We complete the post-Newtonian (PN) prediction at the 3.5PN order for the
spin contributions to the gravitational waveforms emitted by inspiraling
compact binaries, in the case of quasi-circular, equatorial orbits, where both
spins are aligned with the orbital angular momentum. Using results from the
multipolar post-Minkowskian wave generation formalism, we extend previous works
that derived the dynamics and gravitational-wave energy flux and phasing, by
computing the full waveform decomposed in spin-weighted spherical harmonics.
This new calculation requires the computation of multipolar moments of higher
multipolar order, new quadratic-in-spin contributions to the hereditary tail
terms entering at the 3.5PN order, as well as other non-linear interactions
between moments. When specialized to the test-mass limit, our results are
equivalent to those obtained in the literature for the waveform emitted by a
test-mass in equatorial, circular orbits around a Kerr black hole. We also
compute the factorized modes for use in effective-one-body waveform models,
correcting the 2.5PN nonspinning and 3PN quadratic-in-spin terms in the (2,1)
mode used in current models.",2209.00374v2
2022-12-02,Coherent magnon-induced domain wall motion in a magnetic insulator channel,"Advancing the development of spin-wave devices requires high-quality
low-damping magnetic materials where magnon spin currents can propagate
efficiently and interact effectively with local magnetic textures. We show that
magnetic domain walls (DW) can modulate spin-wave transport in perpendicularly
magnetized channels of Bi-doped yttrium-iron-garnet (BiYIG). Conversely, we
demonstrate that the magnon spin current can drive DW motion in the BiYIG
channel device by means of magnon spin-transfer torque. The DW can be reliably
moved over 15 um distances at zero applied magnetic field by a magnon spin
current excited by an RF pulse as short as 1 ns. The required energy for
driving DW motion is orders of magnitude smaller than those reported for
metallic systems. These results facilitate low-switching-energy magnonic
devices and circuits where magnetic domains can be efficiently reconfigured by
magnon spin currents flowing within magnetic channels.",2212.01408v1
2023-05-25,Dynamics of the antiferromagnetic spin ice phase in pyrochlore spinels,"Motivated by the classical spin-nematic state observed in the breathing
pyrochlore spinel LiGa$_{0.95}$In$_{0.05}$Cr$_4$O$_8$, we theoretically discuss
spin dynamics in models of spin-lattice coupling in these materials.
Semiclassical dynamical simulations successfully recover the key features of
inelastic neutron-scattering experiments on
LiGa$_{0.95}$In$_{0.05}$Cr$_4$O$_8$: a broad finite-energy peak alongside a
continuum of scattering near the (200) wave vector that extends from the
elastic line to high energies. To interpret this result, we develop a
small-fluctuation theory for the spin-ice-like nematic ground states, analogous
to linear spin-wave theory for conventionally ordered magnets, which reproduces
the numerical simulation results quantitatively. In particular, we find that
the inelastic peak is well explained by collective modes confined to
ferromagnetic loops of the underlying nematic order. In addition, we find a
sharp, linearly dispersing mode in the dynamical structure factor, which
originates in long-wavelength fluctuations of the nematic director: We believe
identifying this mode will be an interesting target for future experiments on
these materials. We also outline potential future applications of our methods
to both pyrochlore spinels and other spin-nematic systems.",2305.16386v1
2023-09-22,Laser-induced real-space topology control of spin wave resonances,"Femtosecond laser excitation of materials that exhibit magnetic spin textures
promises advanced magnetic control via the generation of ultrafast and
non-equilibrium spin dynamics. We explore such possibilities in ferrimagnetic
[Fe(0.35 nm)/Gd(0.40 nm)]$_{160}$ multilayers, which host a rich diversity of
magnetic textures from stripe domains at low magnetic fields, a dense
bubble/skyrmion lattice at intermediate fields, and a single domain state for
high magnetic fields. Using femtosecond magneto-optics, we observe distinct
coherent spin wave dynamics in response to a weak laser excitation allowing us
to unambiguously identify the different magnetic spin textures. Moreover,
employing strong laser excitation we show that we achieve versatile control of
the coherent spin dynamics via non-equilibrium and ultrafast transformation of
magnetic spin textures by both creating and annihilating bubbles/skyrmions. We
corroborate our findings by micromagnetic simulations and by Lorentz
transmission electron microscopy before and after laser exposure.",2309.12956v1
2024-01-24,Building a bridge between comparable and extreme mass ratio black hole binaries: a single spin precessing model for the final state,"Modelling the gravitational wave signal from binaries beyond comparable mass
is an important open issue in gravitational wave astronomy. For non-spinning
binaries and when the spins are aligned with the orbital angular momentum, some
first studies concerning the transition between the comparable and extreme mass
ratio regime are already available, which suggest that extreme mass ratio
results at times extrapolate to comparable mass ratios with surprising
precision. Here we study the case of misaligned spins: We present new NR
simulations performed with the Einstein Toolkit code at mass ratios up to 18
and construct a heterogeneous dataset that spans all mass ratios, including
data from NR simulations, numerical approximations to extreme mass ratio
binaries, and data from the geodesic approximation. As a first application we
provide fits for the remnant mass and spin magnitude in single spin precessing
systems, omitting consideration of the in-plane spin orientation. These fits
demonstrate accuracy comparable to the state-of-the-art NRSur7dq4EmriRemnant
model, all while retaining the simplicity and efficiency inherent in previous
phenomenological fits.",2401.13342v2
2024-03-20,Emission of fast-propagating spin waves by an antiferromagnetic domain wall driven by spin current,"Antiferromagnets (AFMs) have great benefits for spintronic applications such
as high frequencies (up to THz), high speeds (up to tens of km/s) of magnetic
excitations, and field-free operation. Advanced devices will require high-speed
propagating spin waves (SWs) as signal carriers, i.e., SWs with high k-vectors,
the excitation of which remains challenging. We show that a domain wall (DW) in
anisotropic AFM driven by the spin current can be a source of such propagating
SWs with high frequencies and group velocities. In the proposed generator, the
spin current, with polarization directed along the easy anisotropy axis,
excites the precession of the N\'eel vector within the DW. The threshold
current is defined by the value of the anisotropy in the hard plane, and the
frequency of the DW precession is tuneable by the strength of the spin current.
We show that the above precession of spins inside the DW leads to robust
emission of high-frequency propagating SWs into the AFM strip with very short
wavelengths comparable to the exchange length, which is hard to achieve by any
other method.",2403.13949v1
2017-02-10,Spin memory effect for compact binaries in the post-Newtonian approximation,"The spin memory effect is a recently predicted relativistic phenomenon in
asymptotically flat spacetimes that become nonradiative infinitely far in the
past and future. Between these early and late times, the magnetic-parity part
of the time integral of the gravitational-wave strain can undergo a nonzero
change; this difference is the spin memory effect. Families of freely falling
observers around an isolated source can measure this effect, in principle, and
fluxes of angular momentum per unit solid angle (or changes in superspin
charges) generate the effect. The spin memory effect had not been computed
explicitly for astrophysical sources of gravitational waves, such as compact
binaries. In this paper, we compute the spin memory in terms of a set of
radiative multipole moments of the gravitational-wave strain. The result of
this calculation allows us to establish the following results about the spin
memory: (i) We find that the accumulation of the spin memory behaves in a
qualitatively different way from that of the displacement memory effect for
nonspinning, quasicircular compact binaries in the post-Newtonian
approximation: the spin memory undergoes a large secular growth over the
duration of the inspiral, whereas for the displacement effect this increase is
small. (ii) The rate at which the spin memory grows is equivalent to a
nonlinear, but nonoscillatory and nonhereditary effect in the gravitational
waveform that had been previously calculated for nonspinning, quasicircular
compact binaries. (iii) This rate of build-up of the spin memory could
potentially be detected by future gravitational-wave detectors by carefully
combining the measured waveforms from hundreds of gravitational-wave detections
of compact binaries.",1702.03300v3
2017-11-28,Non-radiating angularly accelerating electron waves,"Accelerating electrons are known to radiate electromagnetic waves, a property
that is central to the concept of many devices, from antennas to synchrotrons.
While the electrodynamics of accelerating charged particles is well understood,
the same is not true for charged matter waves: would a locally accelerating
charged matter wave, like its particle counterpart, radiate? Here we construct
a novel class of matter waves, angular accelerating electron waves, by
superpositions of twisted electrons carrying orbital angular momentum. We study
the electrodynamic behaviour of such accelerating matter waves and reveal the
generation of a solenoidal magnetic field in each component, and an
accelerating electron wave that does not radiate. These novel properties will
have practical impact in spin flipping of qubits for quantum information
processing, have been suggested for control of time dilation and length
contraction, and raise fundamental questions as to the nature of wave-particle
duality in the context of radiating charged matter.",1711.10114v1
2018-03-28,Massless surface wave,"An interface between two media is topologically stable two-dimensional object
where 3D-symmetry breaks which allows for existence of many exotic excitations.
A direct way to explore surface excitations is to investigate their interaction
with the surface waves, such as very well known capillary-gravity waves and
crystallization waves. Helium remains liquid down to absolute zero where bulk
excitations are frozen out and do not mask the interaction of the waves with
the surface states. Here we show the possibility of the new, massless wave
which can propagate along the surface between two different superfluids phases
of $^3$He. The displacement of the surface in this wave occurs due to the
transition of helium atoms from one phase to another, so that there is no flow
of particles as densities of phases are equal. We calculate the dispersion of
the wave in which the inertia is provided by spin supercurrents, and the
restoring force is magnetic field gradient. We calculate the dissipation of the
wave and show the preferable conditions to observe it.",1803.10489v1
2019-12-18,Penetration of wind-generated near-inertial waves into a turbulent ocean,"An idealized storm scenario is examined in which a wind-generated inertial
wave interacts with a turbulent baroclinic quasi-geostrophic flow. The flow is
initialized by spinning up a Eady model with a realistic stratification
profile. The storm is modeled as an initial value problem for a mixed-layer
confined, horizontally-uniform inertial oscillation. The primordial inertial
oscillation then evolves under the effects of advection, refraction, dispersion
and dissipation. Waves feedback onto the flow by modifying its potential
vorticity. In the first few days, refraction dominates and wave energy is
attracted (repelled) by regions of negative (positive) vorticity. Wave energy
is subsequently drained down anticyclonic pipes. This drainage halts as wave
energy encounters weakening vorticity. After a week or two, wave energy
accumulates at the bottom of negative vorticity features, i.e. along
filamentary structures at shallow depths and in larger anticyclones at greater
depths. Wave feedback tends to weaken vortices and thus slow down wave
penetration. This effect, however, is found to be weak even for vigorous
storms.",1912.08323v1
2023-05-11,Searches for continuous gravitational waves from neutron stars: A twenty-year retrospective,"Seven years after the first direct detection of gravitational waves, from the
collision of two black holes, the field of gravitational wave astronomy is
firmly established. A first detection of continuous gravitational waves from
rapidly-spinning neutron stars could be the field's next big discovery. I
review the last twenty years of efforts to detect continuous gravitational
waves using the LIGO and Virgo gravitational wave detectors. I summarise the
model of a continuous gravitational wave signal, the challenges to finding such
signals in noisy data, and the data analysis algorithms that have been
developed to address those challenges. I present a quantitative analysis of 297
continuous wave searches from 80 papers, published from 2003 to 2022, and
compare their sensitivities and coverage of the signal model parameter space.",2305.07106v2
2024-04-11,Vortex-carrying solitary gravity waves of large amplitude,"In this paper, we study two-dimensional traveling waves in finite-depth water
that are acted upon solely by gravity. We prove that, for any supercritical
Froude number (non-dimensionalized wave speed), there exists a continuous
one-parameter family $\mathcal{C}$ of solitary waves in equilibrium with a
submerged point vortex. This family bifurcates from an irrotational uniform
flow, and, at least for large Froude numbers, extends up to the development of
a surface singularity. These are the first rigorously constructed gravity
wave-borne point vortices without surface tension, and notably our formulation
allows the free surface to be overhanging. We also provide a numerical
bifurcation study of traveling periodic gravity waves with submerged point
vortices, which strongly suggests that some of these waves indeed overturn.
Finally, we prove that at generic solutions on $\mathcal{C}$ $\unicode{x2013}$
including those that are large amplitude or even overhanging $\unicode{x2013}$
the point vortex can be desingularized to obtain solitary waves with a
submerged hollow vortex. Physically, these can be thought of as traveling waves
carrying spinning bubbles of air.",2404.08074v1
2021-09-21,Wave Function Identity: A New Symmetry for 2-electron Systems in an Electromagnetic Field,"Stationary-state Schr{\""o}dinger-Pauli theory is a description of electrons
with a spin moment in an external electromagnetic field. For 2-electron systems
as described by the Schr{\""o}dinger-Pauli theory Hamiltonian with a symmetrical
binding potential, we report a new symmetry operation of the electronic
coordinates. The symmetry operation is such that it leads to the equality of
the transformed wave function to the wave function. This equality is referred
to as the Wave Function Identity. The symmetry operation is a two-step process:
an interchange of the spatial coordinates of the electrons whilst keeping their
spin moments unchanged, followed by an inversion. The Identity is valid for
arbitrary structure of the binding potential, arbitrary electron interaction of
the form $w(|{\bf{r}} - {\bf{r}}'|)$, all bound electronic states, and
arbitrary dimensionality. It is proved that the exact wave functions satisfy
the Identity. On application of the permutation operation for fermions to the
identity, it is shown that the parity of the singlet states is even and that of
triplet states odd. As a consequence, it follows that at electron-electron
coalescence, the singlet state wave functions satisfy the cusp coalescence
constraint, and triplet state wave functions the node coalescence condition.
Further, we show that the parity of the singlet state wave functions about all
points of electron-electron coalescence is even, and that of the triplet state
wave functions odd. The Wave Function Identity and the properties on parity,
together with the Pauli principle, are then elucidated by application to the
$2$-dimensional $2$-electron `artificial atoms' or semiconductor quantum dots
in a magnetic field in their first excited singlet $2^{1}S$ and triplet $2^{3}
S$ states.",2109.10338v1
1992-09-11,Spin liquid phase for the frustrated Quantum Heisenberg Antiferromagnet on a square lattice,"The existance of a spin disordered ground state for the frustrated Quantum
Heisenberg Antiferromagnet on a square lattice is reconsidered. It is argued
that there is a unique action which is continuous through the whole phase
diagram, except at the Lifshitz point, so that the Neel and helicoidal states
can not coexist and there has to be an intermediate spin liquid state. To show
it, a detailed study combining Spin-Wave theory, Schwinger Bosons Mean Field
Theory and a scaling analysis of the appropriate hydrodynamic action is
performed. When done carefully, all these theories agree and strongly support
the existance of the spin liquThe manuscript has eight figures, which are
available upon request to the author. e-mail address is
ferrer@physics.rutgers.edu",9209009v1
1994-05-09,One-Dimensional Kondo Lattice at Half Filling: Charge Properties,"The model of Kondo chain with $M$-fold degenerate band of conduction
electrons of spin 1/2 at half filling interacting with localized spins $S$ is
studied. It is shown that due to the instanton effects the spin sector reveals
itself in optical conductivity. Namely, the density of the charge current at
large wave vector $k \approx \pi$ is proportional to the density of topological
charge of the staggered magnetization. As a consequence, the optical
conductivity at $k = \pi$ would either have a gap equal to three spin gaps (for
$|M - 2S| = $(even) when the spin spectrum is gapful), or show a psedogap
$\sigma(\omega, k = \pi) \sim \omega^2$ for $|M - 2S|$ = (odd).",9405024v1
1997-12-02,Mixed spin ladders with exotic ground states,"We study the ""mixed spin"" isotropic ladder system having S=1 spins on one leg
and S=1/2 spins on the other, with general-type exchange interactions between
spins on neighboring rungs. A set of model Hamiltonians with exact ground
states in the form of a certain matrix product wave function is obtained. We
show that sufficiently strong frustration can lead to exotic singlet ground
states with infinite (exponential) degeneracy. We also list a couple of rather
simple models with nontrivial ground states, including a model with only
bilinear exchange.",9712022v1
1998-03-12,Frustrated quantum Heisenberg ferrimagnetic chains,"We study the ground-state properties of weakly frustrated Heisenberg
ferrimagnetic chains with nearest and next-nearest neighbor antiferromagnetic
exchange interactions and two types of alternating sublattice spins S_1 > S_2,
using 1/S spin-wave expansions, density-matrix renormalization group, and
exact- diagonalization techniques. It is argued that the zero-point spin
fluctuations completely destroy the classical commensurate- incommensurate
continuous transition. Instead, the long-range ferrimagnetic state disappears
through a discontinuous transition to a singlet state at a larger value of the
frustration parameter. In the ferrimagnetic phase we find a disorder point
marking the onset of incommensurate real-space short-range spin-spin
correlations.",9803150v1
1998-10-05,Quantum critical point with competing propagating and diffusive spin excitations,"Feedback effects due to spin fluctuation induced precursors in the fermionic
quasiparticle spectrum are taken into account in the description of a quantum
critical point of itinerant spin systems. A correlation length dependent spin
damping occurs, leading to a dynamical scaling with z\approx 1 which
non-trivially competes with the conventional spin wave behavior. We obtain,
within a one loop renormalization group approach, a quantitative explanation
for the scaling behavior seen in underdoped cuprate superconductors.",9810041v1
1999-09-01,Dynamic spin susceptibility in the t-J model,"Dynamic spin susceptibility is calculated for the t-J model in the
paramagnetic phase by applying the memory function method in terms of the
Hubbard operators. A self-consistent system of equations for the memory
function is obtained within the mode coupling approximation. Both itinerant
hole excitations and localized spin fluctuations give contributions to the
memory function. Spin dynamics have a diffusive character in the hydrodynamic
limit; spin-wave-like excitations are regained in the high-frequency region.",9909019v1
2000-02-01,Rashba spin splitting in two-dimensional electron and hole systems,"In two-dimensional (2D) hole systems the inversion asymmetry induced spin
splitting differs remarkably from its familiar counterpart in the conduction
band. While the so-called Rashba spin splitting of electron states increases
linearly with in-plane wave vector k_|| the spin splitting of heavy hole states
can be of third order in k_|| so that spin splitting becomes negligible in the
limit of small 2D hole densities. We discuss consequences of this behavior in
the context of recent arguments on the origin of the metal-insulator transition
observed in 2D systems.",0002003v1
2001-07-24,Analytical expressions for the spin-spin local-field factor and the spin-antisymmetric exchange-correlation kernel of a two-dimensional electron gas,"We present an analytical expression for the static many-body local field
factor $G_{-}(q)$ of a homogeneous two-dimensional electron gas, which
reproduces Diffusion Monte Carlo data and embodies the exact asymptotic
behaviors at both small and large wave number $q$. This allows us to also
provide a closed-form expression for the spin-antisymmetric exchange and
correlation kernel $K^{-}_{xc}(r)$ which represents a key input for
spin-density functional studies of inhomogeneous electronic systems.",0107501v1
2001-12-29,Longitudinal spin waves in a dilute Bose gas,"We present a kinetic theory for a dilute noncondensed Bose gas of two-level
atoms that predicts the transient spin segregation observed in a recent
experiment. The underlying mechanism driving spin currents in the gas is due to
a mean field effect arising from the quantum interference between the direct
and exchange scattering of atoms in different spin states. We numerically solve
the spin Boltzmann equation, using a one dimensional model, and find excellent
agreement with experimental data.",0112487v1
2003-08-29,Magnetic Order and Dynamics in Stripe-Ordered La2-xSrxNiO4,"We have studied magnetic correlations in several compositions of
stripe-ordered La2-xSrxNiO4. In this paper we show how polarized-neutron
scattering has helped uncover important features of the magnetic ordering and
spin dynamics. In particular, polarization analysis has enabled us (1) to
characterize a spin reorientation transition, (2) to identify anisotropy gaps
in the spin excitation spectrum, and (3) to investigate an anomalous dip in the
spin-wave intensity suggestive of coupling between collective spin and charge
excitations.",0308631v1
2003-10-01,Rashba coupling in quantum dots: exact solution,"We present an analytic solution to the problem of the Rashba spin-orbit
coupling in semiconductor quantum dots. We calculate the exact energy spectrum,
wave-functions, and spin--flip relaxation times. We discuss various effects
inaccessible via perturbation theory. In particular, we find that the effective
gyromagnetic ratio is strongly suppressed by the spin-orbit coupling. The
spin-flip relaxation rate has a maximum as a function of the spin-orbit
coupling and is therefore suppressed in both the weak- and strong coupling
limits.",0310024v2
2005-08-31,Order by disorder and gauge-like degeneracy in quantum pyrochlore antiferromagnet,"The (three-dimensional) pyrochlore lattice antiferromagnet with Heisenberg
spins of large spin length $S$ is a highly frustrated model with an macroscopic
degeneracy of classical ground states. The zero-point energy of (harmonic
order) spin wave fluctuations distinguishes a subset of these states. I derive
an approximate but illuminating {\it effective Hamiltonian}, acting within the
subspace of Ising spin configurations representing the {\it collinear} ground
states. It consists of products of Ising spins around loops, i.e has the form
of a $Z_2$ lattice gauge theory. The remaining ground state entropy is still
infinite but not extensive, being $O(L)$ for system size $O(L^3)$. All these
ground states have unit cells bigger than those considered previously.",0509005v1
2006-06-15,Optical spin pumping of modulation doped electrons probed by a two-color Kerr rotation technique,"We report on optical spin pumping of modulation electrons in CdTe-based
quantum wells with low intrinsic electron density (by 10^10 cm^{-2}). Under
continuous wave excitation, we reach a steady state accumulated spin density of
about 10^8 cm^{-2}. Using a two-color Hanle-MOKE technique, we find a spin
relaxation time of 34 ns for the localized electrons in the nearly unperturbed
electron gas. Independent variation of the pump and probe energies demonstrates
the presence of additional non-localized electrons in the quantum well, whose
spin relaxation time is substantially shorter.",0606419v1
2006-07-04,Scattering induced spin orientation and spin currents in gyrotropic structures,"It is shown that additional contributions both to current-induced spin
orientation and to the spin Hall effect arise in quantum wells due to gyrotropy
of the structures. Microscopically, they are related to basic properties of
gyrotropic systems, namely, linear in the wave vector terms in the matrix
element of electron scattering and in the energy spectrum. Calculation shows
that in high-mobility structures the contribution to the spin Hall current
considered here can exceed the term originated from the Mott skew scattering.",0607074v1
2006-07-08,Harper-Hofstadter problem for 2D electron gas with ${\bf k}$-linear Rashba spin-orbit coupling,"The Harper-Hofstadter problem for two-dimensional electron gas with Rashba
spin-orbit coupling subject to periodic potential and perpendicular magnetic
field is studied analytically and numerically. The butterfly-like energy
spectrum, spinor wave functions as well as the spin density and average spin
polarization are calculated for actual parameters of semiconductor structure.
Our calculations show that in two-dimensional electron gas subject to periodic
potential and uniform magnetic field the effects of energy spectrum splitting
caused by large spin-orbit Rashba coupling can be observed experimentally.",0607216v1
2007-03-08,Spin transverse force and quantum transverse transport,"We present a brief review on spin transverse force, which exerts on the spin
as the electron is moving in an electric field. This force, analogue to the
Lorentz force on electron charge, is perpendicular to the electric field and
spin current carried by the electron. The force stems from the spin-orbit
coupling of electrons as a relativistic quantum effect, and could be used to
understand the Zitterbewegung of electron wave packet and the quantum
transverse transport of electron in a heuristic way.",0703196v1
2007-03-11,Resonant switching using spin valves,"Using micromagnetics we demonstrate that the r.f. field produced by a spin
valve can be used to reverse the magnetization in a magnetic nanoparticle. The
r.f. field is generated using a current that specifically excites a uniform
spin wave in the spin valve. This current is swept such that the
chirped-frequency generated by the valve matches the angular dependent resonant
frequency of the anisotropy-dominated magnetic nanoparticle, as a result of
which the magnetization reversal occurs. The switching is fast, requires
currents similar to those used in recent experiments with spin valves, and is
stable with respect to small perturbations. This phenomenon can potentially be
employed in magnetic information storage devices or recently discussed magnetic
computing schemes.",0703271v1
2001-04-24,Extra Spin-Rotation Coupling Effect in a Radiating Kerr Space-time,"Source-less wave equations are derived for massless scalar, neutrino and
electromagnetic perturbations of a radiating Kerr space-time, and the Hawking
radiation of massless particles with spin $s =0, 1/2$ and 1 in this geometry is
investigated by using a method of the generalized tortoise coordinate
transformation. An extra interaction between the spin of particles and the
rotation of the hole displays in the thermal spectra of Hawking radiation of
massless particles with spin $s = 1/2, 1$ in the evaporating Kerr space-time.
The character of such effect is its obvious dependence on different helicity
states of particles with higher spin.",0104074v1
2006-04-21,The Hyperfine Einstein-Infeld-Hoffmann Potential,"We use recently developed effective field theory techniques to calculate the
third order post-Newtonian correction to the spin-spin potential between two
spinning objects. This correction represents the first contribution to the
spin-spin interaction due to the non-linear nature of general relativity and
will play an important role in forthcoming gravity wave experiments.",0604099v1
1997-12-11,Greybody Factors for Black Holes in Four Dimensions: Particles with Spin,"We compute the emission spectrum of minimally coupled particles with spin
that are Hawking radiated from four dimensional black holes in string theory.
For a range of the black hole parameters the result has a product structure
that may be interpreted in terms of the respective right- and left-moving
thermal correlation functions of an effective string model. For spin-one and
spin-two particles a novel cancellation between contributions to the wave
function is needed to ensure this outcome. The form of the spectra suggests
that the four-dimensional effective string description is ``heterotic'':
particles with spin are emitted from the right-moving sector, only.",9712118v1
2005-09-13,The continuous spin limit of higher spin field equations,"We show that the Wigner equations describing the continuous spin
representations can be obtained as a limit of massive higher-spin field
equations. The limit involves a suitable scaling of the wave function, the mass
going to zero and the spin to infinity with their product being fixed. The
result allows to transform the Wigner equations to a gauge invariant
Fronsdal-like form. We also give the generalisation of the Wigner equations to
higher dimensions with fields belonging to arbitrary representations of the
massless little group.",0509092v2
2005-04-08,Spin as the Basis for Quantum Mechanics: A New Semiclassical Model for Electron Spin,"A simple real-space model for the free-electron wavefunction with spin is
proposed, based on coherent vortices on the scale of h/mc, rotating at mc^2/h.
This reproduces the proper values for electron spin and magnetic moment.
Transformation to a moving reference frame turns this into a wave with the de
Broglie wavelength. The mapping of the real two-dimensional vector phasor to
the complex plane satisfies the Schrodinger equation. This suggests a
fundamental role for spin in quantum mechanics.",0504068v1
2007-06-13,Bispinor Formulation of Spin 3/2 Field Theory,"In this paper, we investigate an alternative formulation for spin 3/2 field
equation. First we will review equation of motion of Dirac and Maxwell, and
then construct the equation for spin 3/2 in the similar fashion. Our method
actually a generalization of relativistic equation of motion based on spin
operator and Hamiltonian similar to Dirac and Maxwell equation in ref. [1] pp.
50. Furthermore, we could not bring the equation to the Klein Gordon limit for
every wave function component in spin 3/2 formalism.",0706.1910v4
2007-12-07,Scattering of Spin-Zero and Spin-Half Particles in Momentum-Helicity Basis,"Scattering of 2 particles of spin 0 and 1/2 is evaluated based on a basis
constructed from the momentum and the helicity states (the momentum-helicity
basis). This shortly called three-dimensional (3D) technique is a good
alternative to the standard partial wave (PW) technique especially for higher
energies, where PW calculations may become not feasible. Taking as input a
simple spin-orbit potential model we calculate as an example the spin averaged
differential cross section and polarization.",0712.1101v1
2008-11-11,"Spin susceptibility, phase diagram, and quantum criticality in the electron-doped high Tc Superconductor Ba[Fe(1-x)Co(x)]2As2","We report a systematic investigation of Ba[Fe(1-x)Co(x)]2As2 based on
transport and 75-As NMR measurements, and establish the electronic phase
diagram. We demonstrate that doping progressively suppresses the uniform spin
susceptibility and low frequency spin fluctuations. The optimum superconducting
phase emerges at x_c~0.08 when the tendency toward spin ordering completely
diminishes. Our findings point toward the presence of a quantum critical point
near x_c between the SDW (spin density wave) and superconducting phases.",0811.1617v1
2008-11-13,Cooling into the Spin-Nematic State for a Spin-1 Bose gase in an optical lattice,"The possibility of adiabatically cooling a spin-1 polar Bose gas to a
spin-nematic phase is theoretically discussed. The relation between the order
parameter of the final spin-nematic phase and the starting temperature of the
spinor Bose gas is obtained both using the mean-field approach for the high
temperature and spin-wave approach for the low temperature. We find that there
exists a good possibility to reach the spin-nematic ordering starting with
spinor antiferromagnetic Bose gases.",0811.2054v1
2008-11-28,Effect of Nonlocal Spin-Transfer Torque on Current-Induced Magnetization Dynamics,"Using the self-consistent model, we present nonlocal spin-transfer effects
caused by the feedback between inhomogeneous magnetization and spin-transfer
torque on the current-induced magnetization dynamics in nanomagnets. The
nonlocal effects can substantially improve the coherence time of precession in
nanomagnets and thus reduce the linewidth of power spectrum. This narrow
linewidth results from the nonlinear damping of spin-waves due to the nonlocal
spin torque which is inherent and thus should be considered in future
experiments.",0811.4649v1
2009-09-15,Critical current density for spin transfer torque switching with composite free layer structure,"Critical current density of composite free layer (CFL) in magnetic tunneling
junction is investigated. CFL consists of two exchange coupled ferromagnetic
layers, where the coupling is parallel or anti-parallel. Instability condition
of the CFL under the spin transfer torque, which is related with critical
current density, is obtained by analytic spin wave excitation model and
confirmed by macro-spin Landau-Lifshitz-Gilbert equation. The critical current
densities for the coupled two identical layers are investigated with various
coupling strengths, and spin transfer torque efficiencies.",0909.2711v1
2009-10-13,Boltzmann theory of magnetoresistance due to a spin spiral,"We studied the magnetoresistance due to a spin spiral by solving the
Boltzmann equation. The scattering rates of conduction electrons are calculated
by using the non-perturbative wave function of the conduction electrons and the
non-equilibrium distribution function is obtained by numerically solving the
Boltzmann equation. These enable us to calculate the resistivity of a
sufficiently thin spin spiral. A magnetoresistance ratio of more than 50% is
predicted for a spin spiral with high spin polarization (>0.8) and a small
period (about 1-2 nm).",0910.2308v2
2010-08-06,Ferromagnetic phases in spin-Fermion systems,"Spin-Fermion systems which obtain their magnetic properties from a system of
localized magnetic moments being coupled to conducting electrons are
considered. The dynamical degrees of freedom are spin-$s$ operators of
localized spins and spin-1/2 Fermi operators of itinerant electrons.
Renormalized spin-wave theory, which accounts for the magnon-magnon
interaction, and its extension are developed to describe the two ferrimagnetic
phases in the system: low temperature phase $0<T<T^{*}$, where all electrons
contribute the ordered ferromagnetic moment, and high temperature phase
$T^{*}<T<T_C$, where only localized spins form magnetic moment. The
magnetization as a function of temperature is calculated. The theoretical
predictions are utilize to interpret the experimentally measured
magnetization-temperature curves of $UGe_2$..",1008.1148v1
2010-10-26,Spin Fidelity for Three-qubit Greenberger-Horne-Zeilinger and W States Under Lorentz Transformations,"Constructing the reduced density matrix for a system of three massive
spin$-\frac{1}{2}$ particles described by a wave packet with Gaussian momentum
distribution and a spin part in the form of GHZ or W state, the fidelity for
the spin part of the system is investigated from the viewpoint of moving
observers in the jargon of special relativity. Using a numerical approach, it
turns out that by increasing the boost speed, the spin fidelity decreases and
reaches to a non-zero asymptotic value that depends on the momentum
distribution and the amount of momentum entanglement.",1010.5330v1
2012-03-27,Spin dynamics in the Kapitza-Dirac effect,"Electron spin dynamics in Kapitza-Dirac scattering from a standing laser wave
of high frequency and high intensity is studied. We develop a fully
relativistic quantum theory of the electron motion based on the time-dependent
Dirac equation. Distinct spin dynamics, with Rabi oscillations and complete
spin-flip transitions, is demonstrated for Kapitza-Dirac scattering involving
three photons in a parameter regime accessible to future high-power X-ray laser
sources. The Rabi frequency and, thus, the diffraction pattern is shown to
depend crucially on the spin degree of freedom.",1204.0239v2
2012-06-15,Spin noise in quantum dot ensembles,"We study theoretically spin fluctuations of resident electrons or holes in
singly charged quantum dots. The effects of external magnetic field and
effective fields caused by the interaction of electron and nuclei spins are
analyzed. The fluctuations of spin Faraday, Kerr and ellipticity signals
revealing the spin noise of resident charge carriers are calculated for the
continuous wave probing at the singlet trion resonance.",1206.3479v2
2013-02-14,Spin-Hall Conductivity and Electric Polarization in Metallic Thin Films,"We predict theoretically that, when a normal metallic thin film (without bulk
spin-orbit coupling, such as Cu or Al) is sandwiched by two insulators, two
prominent effects arise due to the interfacial spin-orbit coupling: a giant
spin-Hall conductivity due to the surface scattering and a transverse electric
polarization due to the spin-dependent phase shift in the spinor wave
functions.",1302.3490v2
2013-06-25,Designing a Spin-Seebeck Diode,"Using micromagnetic simulations, we have investigated spin dynamics in a
spin-valve bi-layer in the presence of a thermal gradient. The direction and
the intensity of the gradient allow to excite the spin wave modes of each layer
selectively. This permits to synchronize the magnetization precession of the
two layers and to rectify the flows of energy and magnetization through the
system. Our study yields promising opportunities for applications in spin
caloritronics and nanophononics devices.",1306.5924v2
2014-01-27,Spin chains and classical strings in rotating Rindler-AdS space,"In this paper, we study the spin chain and string excitation in the rotating
Rindler-$AdS_3$ proposed in [12]. We obtain a one-parameter deformed $SL(2)$
spin chain at the fast spin limit. Two-spin GKP-like solutions are studied at
short and long string limits. General ansatz for the giant magnons and the
spiky strings are analyzed in detail for various $\beta$. At last, we explore
its counterpart in analytic continuation and pp-wave limit.",1401.6915v1
2014-03-17,Massive twistor particle with spin generated by Souriau-Wess-Zumino term and its quantization,"We present new model of D=4 relativistic massive particle with spin and we
describe its quantization. The model is obtained by an extension of standard
relativistic phase space description of massive spinless particle by adding new
topological Souriau-Wess-Zumino term which depends on spin fourvector variable.
We describe equivalently our model as given by the free two-twistor action with
suitable constraints. An important tool in our derivation is the spin-dependent
twistor shift, which modifies standard Penrose incidence relations. The
quantization of the model provides the wave function with correct mass and spin
eigenvalues.",1403.4127v1
2016-02-02,Magnetization Dynamics of Topological Defects and the Spin Solid in Kagome Artificial Spin Ice,"We report broadband spin-wave spectroscopy on kagome artificial spin ice
(ASI) made of large arrays of interconnected Ni$_{80}$Fe$_{20}$ nanobars.
Spectra taken in saturated and disordered states exhibit a series of resonances
with characteristic magnetic field dependencies. Making use of micromagnetic
simulations, we identify resonances that reflect the spin-solid-state and
monopole-antimonopole pairs on Dirac strings. The latter resonances allow for
the generation of highly-charged vertices in ASIs via microwave assisted
switching. Our findings open further perspectives for fundamental studies on
ASIs and their usage in reprogrammable magnonics.",1602.00918v1
2019-11-05,Spin chains and classical strings in two parameters $q$-deformed AdS$_3\times$S$^3$,"In this paper, we study the spin chain and string excitation in the
two-parameters $q$-deformed AdS$_3\times$S$^3$ proposed by Hoare. We obtain the
deformed spin chain model at the fast spin limit for choices of deformed
parameters. General ansatz for giant magnons are studied in great detail and
complicated dispersion relation is treated perturbatively. We also study
several types of hanging string solutions and their charges and spins are
analyzed numerically. At last, we explore its pp-wave limit and find its
solution only depends on the difference of deformed parameters.",1911.01567v1
2012-09-20,Quench dynamics in spin crossover induced by high pressure,"In this paper we have studied analytically and numerically dynamics of spin
crossover induced by time-dependent pressure. We show that quasi static
pressure, with a slow dependence on time, yields a spin crossover leading to
transition from the state of quantum system with high spin (HS) to the low spin
(LS). However, a quench dynamics under shock-wave load is more complicated. The
final state of the system depends on the amplitude and pulse velocity,
resulting in the mixture of the HS and LS states.",1209.4567v1
2018-02-21,Spin-fluctuations drive the inverse magnetocaloric effect in Mn5Si3,"Inelastic neutron scattering measurements were performed on single crystals
of the antiferromagnetic compound Mn5Si3 in order to investigate the relation
between the spin dynamics and the magneto-thermodynamic properties. It is shown
that among the two stable antiferromagnetic phases of this compound, the high
temperature one has an unusual magnetic excitation spectrum where propagative
spin-waves and diffuse spin-fluctuations coexist. Moreover, it is evidenced
that the inverse magnetocaloric effect of Mn5Si3, the cooling by adiabatic
magnetization, is associated with field induced spin-fluctuations.",1802.07511v1
2019-02-11,Magnon excitations in $Cs_2CuAl_4O_8$ - a bond alternating S=1/2 spin chain with next nearest neighbor coupling,"A recent density functional theory (DFT) based analysis, complemented with
Quantum Monte Carlo calculations revealed a highly spin-frustrating nature of
the one-dimensional spin-$\frac{1}{2}$ compound $Cs_2CuAl_4O_8$ that comprises
of unique bond alternations and relatively strong next nearest neighbor
interactions. This article gives a brief account on possible magnon excitations
that can appear in the ground state of such systems. We find that the spin
waves obtained on top of coplanar helical reference states show multiple magnon
modes (both acoustic and optical). However, those magnon modes turn out to be
stable only in the absence of bond alternations.",1902.04008v1
2020-11-11,Polariton spin jets through optical control,"We demonstrate spin polarized jets in extended systems of ballistic
exciton-polariton condensates in semiconductor microcavities using optical
non-resonant excitation geometries. The structure of the spin jets is
determined by the digitally reprogrammable, spatially non-uniform, degree of
circular polarization of the excitation laser. The presence of the laser
excitation, strong particle interactions, and spin-relaxation leads to a
tunable spin-dependent potential landscape for polaritons, with the appearance
of intricate polarization patterns due to coherent matter-wave interference.
Our work realizes polarization-structured coherent light sources in the absence
of gauge fields.",2011.05725v1
2008-06-19,Anomalous Spin Response in Non-centrosymmetric Compounds,"We examine static spin susceptibilities $\chi_{\alpha\beta}({\bf q})$ of spin
components $S_{\alpha}$ and $S_{\beta}$ in the non-centrosymmetric tetragonal
system. These show anomalous momentum dependences like $\chi_{xx}({\bf
q})-\chi_{yy}({\bf q})\sim q_x^2-q_y^2$ and $\chi_{xy}({\bf q})+\chi_{yx}({\bf
q})\sim q_x q_y$, which vanish in centrosymmetric systems. The magnitudes of
the anomalous spin susceptibilities are enhanced by the on-site Coulomb
interaction, especially, around an ordering wave vector. The significant and
anomalous momentum dependences of these susceptibilities are explained by a
group theoretical analysis. As the direct probe of the anomalous spin
susceptibility, we propose a polarized neutron scattering experiment.",0806.3214v1
2019-12-09,Double-$Q$ Chiral Stripe in the $d$-$p$ Model with Strong Spin-Charge Coupling,"We investigate the stability of multiple-$Q$ spiral states in $d$-$p$
electron systems with the strong spin-charge coupling. By using variational
calculations on a square lattice, we find that the double-$Q$ state with the
scalar chirality density wave, which has been studied in the weak spin-charge
coupling regime, becomes the ground state even in the strong spin-charge
coupling regime by considering the effect of the $d$-$p$ hybridization. We also
show that the regions where the double-$Q$ state is stabilized are widely
extended for introducing the antiferromagnetic superexchange interaction
between nearest-neighbor localized spins.",1912.03906v1
2022-02-23,General Spin Sums in Quantum Field Theory,"In Quantum Field Theory, scattering amplitudes are computed from propagators
which, for internal lines, are built upon spin/polarization-sum relationships.
In turn, these are normally constructed upon plane-wave solutions of the free
field equations. A question that may now arise is whether such
spin/polarization-sums can be generalized. In the past, there has been a first
attempt at generalizing spin sums for fermionic fields in terms of the
Michel-Wightman identities. In this paper, we aim to find the most general spin
sums for fermionic fields within the range of QFT.",2203.04087v3
2022-05-30,Fledgling quantum spin Hall effect in pseudo gap phase of Bi2212,"We study the emergence of the quantum spin Hall (QSH) states for the
pseudo-gap (PG) phase of Bi2212 bilayer system, assumed to be D-density
wave(DDW) ordered, starting with a strong Rashba spin-orbit coupling(SOC)
armed, and the time reversal symmetry (TRS) complaint Bloch Hamiltonian. The
presence of strong SOC gives rise to non-trivial, spin-momentum locked spin
texture tunable by electric field. The emergence of quantum anomalous Hall
effect with TRS broken Chiral DDW Hamiltonian of Das Sarma et al. is found to
be possible.",2205.15010v1
2023-06-02,Chiral electrons and spin selectivity at chiral-achiral interfaces,"Chiral molecules can selectively transport electrons of a particular spin
orientation, yet the underlying mechanism remain poorly understood. Here, we
present theoretical evidence that electrons propagating through chiral
materials with screw symmetry exhibit chirality themselves and carry
symmetry-induced pseudo-angular momentum (PAM) which must be characterized by
both spin and orbital components. The chiral electron transport is PAM
polarized, with counterpropagating states exhibiting opposite PAM. At
chiral-achiral interfaces, the PAM polarization is converted to spin
polarization due to wave function matching, thereby establishing a novel
principle for the chiral-induced spin selectivity.",2306.01664v2
2023-07-31,Spin-frame field theory of a three-sublattice antiferromagnet,"We present a nonlinear field theory of a three-sublattice hexagonal
antiferromagnet. The order parameter is the spin frame, an orthogonal triplet
of vectors related to sublattice magnetizations and spin chirality. The
exchange energy, quadratic in spin-frame gradients, has three coupling
constants, only two of which manifest themselves in the bulk. As a result, the
three spin-wave velocities satisfy a universal relation. Vortices generally
have an elliptical shape with the eccentricity determined by the Lam\'e
parameters.",2307.16853v2
2023-08-31,Schwinger boson symmetric spin liquids of Shastry-Sutherland model,"Motivated by recent experimental and numerical evidences of deconfined
quantum critical point and quantum spin-liquid states in spin-$1/2$ Heisenberg
model on Shastry-Sutherland lattice, we studied possible symmetric spin liquid
states and their proximate ordered states under Schwinger boson formalism. We
found a symmetric gapped $Z_2$ spin-liquid state for intermediate model
parameter $0.66 < J_1/J_2 < 0.71$ under mean-field approximation. The Schwinger
boson mean-field picture is partially supported by exact-diagonalization and
self-consistent spin wave theory results.",2308.16563v3
2023-12-13,Cubic action for Spinning Black Holes from massive higher-spin gauge symmetry,"Scattering of two Kerr Black Holes emitting gravitational waves can be
captured by an effective theory of a massive higher-spin field interacting with
the gravitational field. While other compact objects should activate a
multitude of non-minimal interactions it is the black holes that should be
captured by the simplest minimal interaction. Implementing massive higher-spin
symmetry via a string-inspired BRST approach we construct an action that
reproduces the correct cubic amplitude of Arkani-Hamed--Huang--Huang. The same
is achieved for the root-Kerr theory, i.e. for the minimal electromagnetic
interaction of a massive higher-spin field.",2312.08184v1
1995-12-05,Phase Diagram for Charge Density Waves in a Magnetic Field,"The influence of an external magnetic field on a quasi one-dimensional system
with a charge density wave (CDW) instability is treated within the random phase
approximation which includes both CDW and spin density wave correlations. We
show that the CDW is sensitive to both orbital and Pauli effects of the field.
In the case of perfect nesting, the critical temperature decreases monotonously
with the field, and the wave vector of the instability starts to shift above
some critical value of magnetic field. Depending on the ratio between the spin
and charge coupling constants and on the direction of the applied magnetic
field, the wave vector shift is either parallel ($CDW_x$ order) or
perpendicular ($CDW_y$ order) to the most conducting direction. The $CDW_x$
order is a field dependent linear combination of the charge and spin density
waves and is sensible only to the Pauli effect. The wave vector shift in
$CDW_y$ depends on the interchain coupling, but the critical temperature does
not. This order is affected by the confinement of the electronic orbits. By
increasing the relative strength of the orbital effect with respect to the
Pauli effect, one can destroy the $CDW_y$, establishing either a $CDW_x$, or a
$CDW_0$ (corresponding to perfect nesting wave vector). We also show that by
increasing the imperfect nesting parameter, one passes from the regime where
the critical temperature decreases with the field to the regime where it is
initially enhanced by the orbital effect and eventually suppressed by the Pauli
effect. For a bad nesting, the quantized phases of the field-induced CDW
appear.",9512033v1
2019-03-22,Unidirectional Maxwellian Spin Waves,"We develop a unified perspective of unidirectional topological edge waves in
non-reciprocal media. We focus on the inherent role of photonic spin in
non-reciprocal gyroelectric media, ie. magnetized metals or magnetized
insulators. We first review the concept of a Maxwell Hamiltonian in
non-reciprocal media, which immediately reveals that the gyrotropic coefficient
behaves as a photon mass in two dimensions. Similar to the Dirac mass, this
photonic mass opens bandgaps in the energy dispersion of bulk propagating
waves. Within these bulk photonic bandgaps, three distinct classes of
Maxwellian edge waves exist - each arising from subtle differences in boundary
conditions. On one hand, the edge wave solutions are rigorous photonic analogs
of Jackiw-Rebbi electronic edge states. On the other hand, for the exact same
system, they can be high frequency photonic counterparts of the integer quantum
Hall effect, familiar at zero frequency. Our Hamiltonian approach also predicts
the existence of a third distinct class of Maxwellian edge wave exhibiting
topological protection. The Maxwellian edge state in this unique
\textit{quantum gyroelectric phase of matter} necessarily requires a sign
change in gyrotropy arising from non-locality (spatial dispersion). A signature
property of these topological electromagnetic edge states is that they are
oblivious to the contacting medium, ie. they occur at the interface of the
quantum gyroelectric phase and any medium (even vacuum). Furthermore, the
Maxwellian spin waves exhibit photonic spin-1 quantization in exact analogy
with their supersymmetric spin-\sfrac{1}{2} counterparts. The goal of this
paper is to discuss these three foundational classes of edge waves in a unified
perspective while providing in-depth derivations, taking into account
non-locality and various boundary conditions.",1903.09278v1
1992-04-10,Spin Singlet Quantum Hall Effect and Nonabelian Landau-Ginzburg Theory,"We show that the Halperin-Haldane SQHE wave function can be written in the
form of a product of a wave function for charged semions in a magnetic field
and a wave function for the Chiral Spin Liquid of neutral spin-$\12$ semions.
We introduce field-theoretic model in which the electron operators are
factorized in terms of charged spinless semions (holons) and neutral spin-$\12$
semions (spinons). Broken time reversal symmetry and short ranged spin
correlations lead to $SU(2)_{k=1}$ Chern-Simons term in Landau-Ginzburg action
for SQHE phase. We construct appropriate coherent states for SQHE phase and
show the existence of $SU(2)$ valued gauge potential. This potential appears as
a result of ``spin rigidity"" of the ground state against any displacements of
nodes of wave function from positions of the particles and reflects the
nontrivial monodromy in the presence of these displacements. We argue that
topological structure of $SU(2)_{k=1}$ Chern-Simons theory unambiguously
dictates {\it semion} statistics of spinons.",9204002v1
1994-07-08,$J_1-J_2$ Quantum Heisenberg Antiferromagnet: Improved Spin-Wave Theories Versus Exact-Diagonalization Data,"We reconsider the results cocerning the extreme-quantum $S=1/2$
square-lattice Heisenberg antiferromagnet with frustrating diagonal couplings
($J_1-J_2$ model) drawn from a comparison with exact-diagonalization data. A
combined approach using also some intrinsic features of the self-consistent
spin-wave theory leads to the conclusion that the theory strongly overestimates
the stabilizing role of quantum flutcuations in respect to the N\'{e}el phase
in the extreme-quantum case $S=1/2$. On the other hand, the analysis implies
that the N\'{e}el phase remains stable at least up to the limit $J_{2}/J_{1} =
0.49$ which is pretty larger than some previous estimates. In addition, it is
argued that the spin-wave ansatz predicts the existence of a finite range
($J_{2}/J_{1}<0.323$ in the linear spin-wave theory) where the Marshall-Peierls
sigh rule survives the frustrations.",9407042v1
1996-08-21,The effect of magnetic dipolar interactions on the interchain spin wave dispersion in CsNiF_3,"Inelastic neutron scattering measurements were performed on the ferromagnetic
chain system CsNiF_3 in the collinear antiferromagnetic ordered state below T_N
= 2.67K. The measured spin wave dispersion was found to be in good agreement
with linear spin wave theory including dipolar interactions. The additional
dipole tensor in the Hamiltonian was essential to explain some striking
phenomena in the measured spin wave spectrum: a peculiar feature of the
dispersion relation is a jump at the zone center, caused by strong dipolar
interactions in this system. The interchain exchange coupling constant and the
planar anisotropy energy were determined within the present model to be J'/k_B
= -0.0247(12)K and A/k_B = 3.3(1)K. This gives a ratio J/J' \approx 500, using
the previously determined intrachain coupling constant J/k_B = 11.8$. The small
exchange energy J' is of the same order as the dipolar energy, which implies a
strong competition between the both interactions.",9608085v1
1999-03-15,Interplay of spin density wave and superconductivity with different pairing symmetry,"A model study for the coexistence of the spin density wave and
superconductivity is presented. With reference to the recent angle resolved
photo emmission experimental data in high T_c cuprates, presence of the nested
pieces of bands is assumed. The single band Hubbard model, therefore, when
treated within the Hatree-Fock mean field theory leads to a spin density wave
(SDW) ground state. The superconductivity (SC) is assumed to be due to a
generalised attractive potential with a separable form without specifying to
any particular origin. It therefore allows a comparative study of the
coexistence of superconductivity of different order parameter symmetry with the
spin density wave state. We find that the phase diagram, comprising of the
amplitudes of the respective gaps (SC and SDW) Vs. band filling resembles to
that of the high T_c cuprates only when the order parameter of the
superconducting phase has d-wave symmetry. Thermal variation of different order
parameters (e.g, SC and SDW) also show interesting coexistence and reentrance
behaviors that are consistent with experimental observations, specially for the
borocarbides.",9903234v1
2001-02-04,Spin wave specific heat in quasiperiodic Fibonacci structures,"The energy spectra of a variety of collective modes on quasiperiodic
structures exhibit a complex fractal profile. Among the modes that have
attracted particular attention in this context, are the spin wave spectra of
quasiperiodic magnetic multilayers that obey a substitutional sequence of the
Fibonacci type. They are described within the framework of the Heisenberg
theory. In order to have a deep insight on the relevant thermodynamical
implications of the above mentioned energy spectra's fractal profile, we have
performed analytical and numerical calculations of the spin wave specific heat
associated with successive hierarchical sequences of the Fibonacci
quasiperiodic structures. The spectra show interesting oscillatory behavior in
the low-temperature region, which can be traced back to the spin wave's
self-similar energy spectrum.",0102046v1
2001-02-07,Interplay between spin-density-wave and superconducting states in quasi-one-dimensional conductors,"The interference between spin-density-wave and superconducting instabilities
in quasi-one-dimensional correlated metals is analyzed using the
renormalization group method. At the one-loop level, we show how the
interference leads to a continuous crossover from a spin-density-wave state to
unconventional superconductivity when deviations from perfect nesting of the
Fermi surface exceed a critical value. Singlet pairing between electrons on
neighboring stacks is found to be the most favorable symmetry for
superconductivity. The consequences of non uniform spin-density-wave pairing on
the structure of phase diagram within the crossover region is also discussed.",0102139v1
2001-06-18,Low-frequency dynamics of disordered XY spin chains and pinned density waves: from localized spin waves to soliton tunneling,"A long-standing problem of the low-energy dynamics of a disordered XY spin
chain is re-examined. The case of a rigid chain is studied where the quantum
effects can be treated quasiclassically. It is shown that as the frequency
decreases, the relevant excitations change from localized spin waves to
two-level systems to soliton-antisoliton pairs. The linear-response correlation
functions are calculated. The results apply to other periodic glassy systems
such as pinned density waves, planar vortex lattices, stripes, and disordered
Luttinger liquids.",0106350v3
2001-10-16,Analytical and numerical study of hardcore bosons in two dimensions,"We study various properties of bosons in two dimensions interacting only via
onsite hardcore repulsion. In particular, we use the lattice spin-wave
approximation to calculate the ground state energy, the density, the condensate
density and the superfluid density in terms of the chemical potential. We also
calculate the excitation spectrum, $\omega({\bf k})$. In addition, we performed
high precision numerical simulations using the stochastic series expansion
algorithm. We find that the spin-wave results describe extremely well the
numerical results over the {\it whole} density range $0\leq \rho \leq 1$. We
also compare the lattice spin-wave results with continuum results obtained by
summing the ladder diagrams at low density. We find that for $\rho \leq 0.1$
there is good agreement, and that the difference between the two methods
vanishes as $\rho^2$ for $\rho \to 0$. This offers the possibility of obtaining
precise continuum results by taking the continuum limit of the spin-wave
results for all densities. Finaly, we studied numerically the finite
temperature phase transition for the entire density range and compared with low
density predictions.",0110314v1
2002-02-02,Spin Wave Propagation in the Domain State of a Random Field Magnet,"Inelastic neutron scattering with high wave-vector resolution has
characterized the propagation of transverse spin wave modes near the
antiferromagnetic zone center in the metastable domain state of a random field
Ising magnet. A well-defined, long wavelength excitation is observed despite
the absence of long-range magnetic order. Direct comparisons with the spin wave
dispersion in the long-range ordered antiferromagnetic state reveal no
measurable effects from the domain structure. This result recalls analogous
behavior in thermally disordered anisotropic spin chains but contrasts sharply
with that of the phonon modes in relaxor ferroelectrics.",0202038v2
2005-04-04,Theory of Spin-Wave Frequency Gaps in 3D Magnonic Crystals. Application to Manganites,"his study is an investigation of spin wave spectrum in macrostructures
composed of two ferromagnetic materials and showing a 3D periodicity: spherical
ferromagnetic grains disposed in the nodes of a 3D crystal lattice are embedded
in a matrix with different ferromagnetic properties. Frequency ranges forbidden
to spin wave propagation are found in the calculated magnonic spectra. Both the
position and the width of the gaps are found to depend on the magnetic
(exchange and magnetization) contrasts in the composite material, as well as on
its structural parameters (filling fraction, crystal lattice type). Having
applied our theory to interpretation of the existence of a spin wave gap in
doped manganites, recently revealed in neutron scattering experiments by S.
Hennion {\em et al.}, we obtained a good (though approximate) quantitative
agreement with the experimental results. A working hypothesis is proposed on
this basis, supposing that certain manganites can be treated as natural 3D
magnonic crystals.",0504073v1
2005-05-16,Spin Waves in a Periodically Layered Magnetic Nanowire,"We report a simple theoretical derivation of the spectrum and damping of spin
waves in a cylindrical periodically structured magnetic nanowire (cylindrical
magnonic crystal) in the ""effective medium"" approximation. The dependence of
the ""effective"" magnetic parameters upon the individual layer parameters is
shown to be different from the arithmetic average over the volume of the
superlattice. The formulae that are obtained can be applied firstly in the
description of spin wave dispersion in the first allowed band of the structure;
and secondly in the design of a magnonic crystal with band-gaps in an arbitrary
part of the spin wave spectrum.",0505382v1
2005-11-19,Measurement of spin waves and activation volumes in superparamagnetic Fe films on GaAs(100),"Spin wave frequencies are observed in ultra-thin Fe/GaAs(100) films at
temperatures where the spontaneous zero field magnetization is zero. The films
exhibit good cyrstalline structure, and the effect of magnetic anisotropies is
apparent even though no zero field spin wave energy gap exists. An analysis is
given in terms of a superparamagnetic model in which the film is treated as a
network of non-interacting single domain magnetic islands. A spin wave analysis
provides a means to separate measured values of anisotropy parameters from
products involving anisotropy and island volume. In this way, a measure of the
activation volume associated with superparamagnetic islands is obtained for
different Fe film thicknesses. Results suggest that the island lateral area
increases with increasing film thickness.",0511482v1
1992-02-08,Spin Singlet Quantum Hall Effect and Nonabelian Landau-Ginzburg Theory,"In this paper we present a theory of Singlet Quantum Hall Effect (SQHE). We
show that the Halperin-Haldane SQHE wave function can be written in the form of
a product of a wave function for charged semions in a magnetic field and a wave
function for the Chiral Spin Liquid of neutral spin-$\12$ semions. We introduce
field-theoretic model in which the electron operators are factorized in terms
of charged spinless semions (holons) and neutral spin-$\12$ semions (spinons).
Broken time reversal symmetry and short ranged spin correlations lead to
$SU(2)_{k=1}$ Chern-Simons term in Landau-Ginzburg action for SQHE phase. We
construct appropriate coherent states for SQHE phase and show the existence of
$SU(2)$ valued gauge potential. This potential appears as a result of ``spin
rigidity"" of the ground state against any displacements of nodes of wave
function from positions of the particles and reflects the nontrivial monodromy
in the presence of these displacements.",9202029v1
2006-11-10,Eikonal Approximation in AdS/CFT: Conformal Partial Waves and Finite N Four-Point Functions,"We introduce the impact-parameter representation for conformal field theory
correlators of the form A ~ < O_1 O_2 O_1 O_2 >. This representation is
appropriate in the eikonal kinematical regime, and approximates the conformal
partial-wave decomposition in the limit of large spin and dimension of the
exchanged primary. Using recent results on the two-point function < O_1 O_1
>_{shock} in the presence of a shock wave in Anti-de Sitter, and its relation
to the discontinuity of the four-point amplitude A across a kinematical
branch-cut, we find the high spin and dimension conformal partial- wave
decomposition of all tree-level Anti-de Sitter Witten diagrams. We show that,
as in flat space, the eikonal kinematical regime is dominated by the T-channel
exchange of the massless particle with highest spin (graviton dominance). We
also compute the anomalous dimensions of the high-spin O_1 O_2 composites.
Finally, we conjecture a formula re-summing crossed-ladder Witten diagrams to
all orders in the gravitational coupling.",0611123v1
2005-09-30,Macroscopic quantum information channel via the polarization-sensitive interaction between the light and spin subsystems,"We discuss the quantum information channel, which is based on coherent and
polarization sensitive interaction of light and atomic spin waves. We show that
the joint Heisenberg dynamics of the polarization Stokes components of light
and of the angular momenta of atoms has a wave nature and can be properly
described in terms of the macroscopic polariton-type spin wave created in the
sample. The principles of the quantum memory and readout protocols via the wave
coupling of the output time modes in the light subsystem and the output spatial
modes in the spin subsystem are demonstrated.",0509220v1
2007-04-05,Partially disordered state near ferromagnetic transition in MnSi,"The polarized neutron scattering in helimagnetic MnSi at low $T$ reveals
existence of a partially disordered chiral state at ambient pressure in the
magnetic field applied along $<111>$ axis below the first order transition to
the non-chiral ferromagnetic state. This unexpected phenomenon is explained by
the analysis of the spin-wave spectrum. We demonstrate that the square of the
spin-wave gap becomes negative under magnetic field applied along $<111>$ and
$<110>$ but not along the $<100>$ direction. It is a result of competition
between the spin-wave interaction and cubic anisotropy. This negative sign
means an instability of the spin wave spectrum for the helix and leads to a
destruction of the helical order, giving rise to the partially disordered state
below the first order ferromagnetic transition.",0704.0683v1
2007-07-09,"Comment on ""Multiferroicity Induced by Dislocated Spin-Density Waves""","I show that the claims in Phys. Rev. Lett. 98, 257602 by Betouras et al
concerning YMn2O5 are incorect.",0707.1327v1
2007-11-16,Spin waves and local magnetizations on the Penrose tiling,"We consider a Heisenberg antiferromagnet on the Penrose tiling, a
quasiperiodic system having an inhomogeneous Neel-ordered ground state. Spin
wave energies and wavefunctions are studied in the linear spin wave
approximation. A linear dispersion law is found at low energies, as in other
bipartite antiferromagnets, with an effective spin wave velocity lower than in
the square lattice. Spatial properties of eigenmodes are characterized in
several different ways. At low energies, eigenstates are relatively extended,
and show multifractal scaling. At higher energies, states are more localized,
and, depending on the energy, confined to sites of a specified coordination
number. The ground state energy of this antiferromagnet, and local staggered
magnetizations are calculated. Perpendicular space projections are presented in
order to show the underlying simplicity of this ""complex"" ground state. A
simple analytical model, the two-tier Heisenberg star, is presented to explain
the staggered magnetization distribution in this antiferromagnetic system.",0711.2670v3
2007-12-18,Dynamics Of Proton Spin : Role Of $qqq$ Force,"The analytic structure of the $qqq$ wave function, obtained recently in the
high momentum regime of QCD, is employed for the formulation of baryonic
transition amplitudes via quark loops. A new aspect of this study is the role
of a direct ($Y$-shaped, Mercedes-Benz type) $qqq$ force in generating the
$qqq$ wave function. The dynamics is that of a Salpeter-like equation (3D
support for the kernel) formulated covariantly on the light front, a la
Markov-Yukawa Transversality Principle (MYTP) which warrants a 2-way
interconnection between the 3D and 4D Bethe-Salpeter (BSE) forms for 2 as well
as 3 fermion quarks. The dynamics of this 3-body force shows up through a
characteristic singularity in the hypergeometric differential equation for the
3D wave function $\phi$, corresponding to a $negative$ eigenvalue of the spin
operator $i \sigma_1.\sigma_2\times \sigma_3$ which is an integral part of the
$qqq$ force. As a first application of this wave function to the problem of the
proton spin anomaly, the two-gluon contribution to the anomaly yields an
estimate of the right sign, although somewhat smaller in magnitude.
  Keywords: 3bodyforce; proton-spin; 2gluon anomaly; fractional correction
$\theta$",0712.2896v1
2008-04-04,Modification of the thermal spin-wave spectrum in a Ni81Fe19 stripe by a domain wall,"The thermal spin-wave distribution in a Ni81Fe19 stripe with an asymmetric
transverse domain wall has been investigated using Brillouin light scattering
microscopy. Clear evidence has been found that the existence of the domain wall
influences the spin-wave distribution of the thermal modes. The thermal
spin-wave modes are quantized due to the confinement in radial direction. They
vanish near the domain wall and a new mode evolves inside this complex domain
wall structure. This effect is attributed to a change of the effective internal
field in the domain wall region. The experimental results agree well with
static and dynamic micromagnetic simulations.",0804.0734v2
2008-11-03,Dispersion in magnetostatic CoTaZr spin wave-guides,"Magnetostatic spin wave dispersion and loss are measured in micron scale spin
wave-guides in ferromagnetic, metallic CoTaZr. Results are in good agreement
with model calculations of spin wave dispersion and up to three different modes
are identified. Attenuation lengths of the order of 3 microns are several of
orders of magnitude shorter than that predicted from eddy currents in these
thin wires.",0811.0350v2
2009-01-19,Chiral asymmetry of the spin-wave spectra in ultrathin magnetic films,"We raise the possibility that the chiral degeneracy of the magnons in
ultrathin films can be lifted due to the presence of Dzyaloshinskii-Moriya
interactions. By using simple symmetry arguments, we discuss under which
conditions such a chiral asymmetry occurs. We then perform relativistic first
principles calculations for an Fe monolayer on W(110) and explicitly reveal the
asymmetry of the spin-wave spectrum in case of wave-vectors parallel to the
(001) direction. Furthermore, we quantitatively interpret our results in terms
of a simplified spin-model by using calculated Dzyaloshinskii-Moriya vectors.
Our theoretical prediction should inspire experiments to explore the asymmetry
of spin-waves, with a particular emphasis on the possibility to measure the
Dzyaloshinskii-Moriya interactions in ultrathin films.",0901.2671v1
2009-02-13,Anomalous spin-waves and the commensurate-incommensurate magnetic phase transition in LiNiPO4,"Detailed spin-wave spectra of magneto-electric LiNiPO4 have been measured by
neutron scattering at low temperatures in the commensurate (C)
antiferromagnetic (AF) phase with ordering temperature 20.8 K. An anomalous
low-energy mode is observed at the modulation vector of the incommensurate (IC)
AF phase appearing above the 20.8 K. A linear spin-wave model based on
Heisenberg exchange couplings and single ion anisotropies accounts for all the
observed spin-wave dispersions and intensities. Along the b axis an unusually
strong next-nearest-neighbor AF coupling competes with the dominant
nearest-neighbor AF exchange interaction and causes the IC structure.",0902.2288v1
2009-06-19,Bounding the mass of the graviton with gravitational waves: Effect of spin precessions in massive black hole binaries,"Observations of gravitational waves from massive binary black hole systems at
cosmological distances can be used to search for a dependence of the speed of
propagation of the waves on wavelength, and thereby to bound the mass of a
hypothetical graviton. We study the effects of precessions of the spins of the
black holes and of the orbital angular momentum on the process of parameter
estimation using matched filtering of gravitational-wave signals vs.
theoretical template waveforms. For the proposed space interferometer LISA, we
show that precessions, and the accompanying modulations of the gravitational
waveforms, are effective in breaking degeneracies among the parameters being
estimated, and effectively restore the achievable graviton-mass bounds to
levels obtainable from binary inspirals without spin. For spinning, precessing
binary black hole systems of equal masses (10^6 solar masses) at 3 Gpc, the
bounds on the graviton Compton wavelength achievable are of the order of 5 X
10^{16} km.",0906.3602v2
2009-07-22,Fluctuating spin density waves in metals,"Recent work has used a U(1) gauge theory to describe the physics of Fermi
pockets in the presence of fluctuating spin density wave order. We generalize
this theory to an arbitrary band structure and ordering wavevector. The
transition to the large Fermi surface state, without pockets induced by local
spin density wave order, is described by embedding the U(1) gauge theory in a
SU(2) gauge theory. The phase diagram of the SU(2) gauge theory shows that the
onset of spin density wave order in the Fermi liquid occurs either directly, in
the framework discussed by Hertz, or via intermediate non-Fermi liquid phases
with Fermi surfaces of fractionalized excitations. We discuss application of
our results to the phase diagram of the cuprates.",0907.3732v2
2009-08-17,Demonstration of atomic frequency comb memory for light with spin-wave storage,"We present a light-storage experiment in a praseodymium-doped crystal where
the light is mapped onto an inhomogeneously broadened optical transition shaped
into an atomic frequency comb. After absorption of the light the optical
excitation is converted into a spin-wave excitation by a control pulse. A
second control pulse reads the memory (on-demand) by reconverting the spin-wave
excitation to an optical one, where the comb structure causes a photon-echo
type rephasing of the dipole moments and directional retrieval of the light.
This combination of photon echo and spin-wave storage allows us to store
sub-microsecond (450ns) pulses for up to 20 microseconds. The scheme has a high
potential for storing multiple temporal modes in the single photon regime,
which is an important resource for future long-distance quantum communication
based on quantum repeaters.",0908.2309v2
2009-10-04,Zero temperature phases of the frustrated J1-J2 antiferromagnetic spin-1/2 Heisenberg model on a simple cubic lattice,"At zero temperature magnetic phases of the quantum spin-1/2 Heisenberg
antiferromagnet on a simple cubic lattice with competing first and second
neighbor exchanges (J1 and J2) is investigated using the non-linear spin wave
theory. We find existence of two phases: a two sublattice Neel phase for small
J2 (AF), and a collinear antiferromagnetic phase at large J2 (CAF). We obtain
the sublattice magnetizations and ground state energies for the two phases and
find that there exists a first order phase transition from the AF-phase to the
CAF-phase at the critical transition point, pc = 0.28. Our results for the
value of pc are in excellent agreement with results from Monte-Carlo
simulations and variational spin wave theory. We also show that the quartic 1/S
corrections due spin-wave interactions enhance the sublattice magnetization in
both the phases which causes the intermediate paramagnetic phase predicted from
linear spin wave theory to disappear.",0910.0638v2
2009-11-10,Spin-wave propagation in a microstructured magnonic crystal,"Transmission of microwave spin waves through a microstructured magnonic
crystal in the form of a permalloy waveguide of a periodically varying width
was studied experimentally and theoretically. The spin wave characteristics
were measured by spatially-resolved Brillouin light scattering microscopy. A
rejection frequency band was clearly observed. The band gap frequency was
controlled by the applied magnetic field. The measured spin-wave intensity as a
function of frequency and propagation distance is in good agreement with a
model calculation.",0911.1920v1
2010-01-20,Precise probing spin wave mode frequencies in the vortex state of circular magnetic dots,"We report on detailed broadband ferromagnetic resonance measurements of
azimuthal and radial spin wave excitations in circular Permalloy dots in the
vortex ground state. Dots with aspect ratio (Beta =height over radius) varied
from 0.03 to 0.1 were explored. We found that for Beta exceeding approximately
0.05, variation of the spin wave eigenfrequencies with Beta deviates from the
predicted dependence. The frequency splitting of two lowest azimuthal modes was
observed. The experimentally observed dependence of the frequency splitting on
beta was reasonably well described by dynamic splitting model accounting the
spin-waves and, vortex gyrotropic mode interaction.",1001.3605v1
2010-03-31,Magnonic Crystal with Two-Dimensional Periodicity as a Waveguide for Spin Waves,"We describe a simple method of including dissipation in the spin wave band
structure of a periodic ferromagnetic composite, by solving the Landau-Lifshitz
equation for the magnetization with the Gilbert damping term. We use this
approach to calculate the band structure of square and triangular arrays of Ni
nanocylinders embedded in an Fe host. The results show that there are certain
bands and special directions in the Brillouin zone where the spin wave lifetime
is increased by more than an order of magnitude above its average value. Thus,
it may be possible to generate spin waves in such composites decay especially
slowly, and propagate especially large distances, for certain frequencies and
directions in ${\bf k}$-space.",1003.6092v1
2010-06-26,Spin-Orbit Coupled Spinor Bose-Einstein Condensates,"An effective spin-orbit coupling can be generated in cold atom system by
engineering atom-light interactions. In this letter we study spin-1/2 and
spin-1 Bose-Einstein condensates with Rashba spin-orbit coupling, and find that
the condensate wave function will develop non-trivial structures. From
numerical simulation we have identified two different phases. In one phase the
ground state is a single plane wave, and often we find the system splits into
domains and an array of vortices plays the role as domain wall. In this phase,
time-reversal symmetry is broken. In the other phase the condensate wave
function is a standing wave and it forms spin stripe. The transition between
them is driven by interactions between bosons. We also provide an analytical
understanding of these results and determines the transition point between the
two phases.",1006.5148v4
2010-07-03,"Second-order quantum corrections for the frustrated, spatially anisotropic, spin-1/2 Heisenberg antiferromagnet on a square lattice","The effects of quantum fluctuations due to directional anisotropy and
frustration between nearest neighbors and next-nearest neighbors of the quantum
spin-1/2 Heisenberg antiferromagnet on a square lattice are investigated using
spin-wave expansion. We have calculated the spin-wave energy dispersion in the
entire Brillouin zone, renormalized spin-wave velocities, and the magnetization
up to second order in 1/S expansion for the antiferromagnetic Neel and
collinear antiferromagnetic stripe phases. It is shown that the second-order
corrections become significant with increase in frustration. With these
corrections magnetizations and spin-wave velocities for both the phases become
zero at the quantum critical points as expected from other numerical and
analytical methods. We have shown that the transition between the two ordered
phases are always separated by the disordered paramagnetic phase.",1007.0502v4
2010-07-19,Standing spin-wave mode structure and linewidth in partially disordered perpendicularly magnetized sub-micron Permalloy disc arrays,"Standing spin wave mode frequencies and linewidths in partially disordered
perpendicular magnetized arrays of sub-micron Permalloy discs are measured
using broadband ferromagnetic resonance and compared to analytical results from
a single, isolated disc. The measured mode structure qualitatively reproduces
the structure expected from the theory. Fitted demagnetizing parameters
decrease with increasing array disorder. The frequency difference between the
first and second radial modes is found to be higher in the measured array
systems than predicted by theory for an isolated disc. The relative frequencies
between successive spin wave modes are unaffected by reduction of the
long-range ordering of discs in the array. An increase in standing spin wave
resonance linewidth at low applied magnetic fields is observed and grows more
severe with increased array disorder.",1007.3062v5
2010-09-18,Composite excitation of Josephson phase and spin waves in Josephson junctions with ferromagnetic insulator,"Coupling of Josephson-phase and spin-waves is theoretically studied in a
superconductor/ferromagnetic insulator/superconductor (S/FI/S) junction.
Electromagnetic (EM) field inside the junction and the Josephson current
coupled with spin-waves in FI are calculated by combining Maxwell and
Landau-Lifshitz-Gilbert equations. In the S/FI/S junction, it is found that the
current-voltage (I-V) characteristic shows two resonant peaks. Voltages at the
resonant peaks are obtained as a function of the normal modes of EM field,
which indicates a composite excitation of the EM field and spin-waves in the
S/FI/S junction. We also examine another type of junction, in which a
nonmagnetic insulator (I) is located at one of interfaces between S and FI. In
such a S/I/FI/S junction, three resonant peaks appear in the I-V curve, since
the Josephson-phase couples to the EM field in the I layer.",1009.3551v3
2010-09-28,The magnonic limit of domain wall propagation in ferromagnetic nanotubes,"We report a study on the field-driven propagation of vortex-like domain walls
in ferromagnetic nanotubes. This particular geometry gives rise to a special
feature of the static wall configuration, which significantly influences its
dynamics. Unlike domain walls in flat strips, the left-right symmetry of domain
wall propagation is broken. Furthermore, the domain wall velocity is not
limited by the Walker breakdown. Under sufficiently large magnetic fields, the
domain wall velocity reaches the velocity of spin waves (about 1000 m/s) and is
thereafter connected with a direct emission of spin waves. The moving domain
wall maintains its main structure but has characteristic spin-wave tails
attached. The spatial profile of this topological soliton is determined by the
spin-wave dispersion.",1009.5552v1
2011-07-07,Method to characterize spinons as emergent elementary particles,"We develop a technique to directly study spinons (emergent spin S = 1/2
particles) in quantum spin models in any number of dimensions. The size of a
spinon wave packet and of a bound pair (a triplon) are defined in terms of
wave-function overlaps that can be evaluated by quantum Monte Carlo
simulations. We show that the same information is contained in the spin-spin
correlation function as well. We illustrate the method in one dimension. We
confirm that spinons are well defined particles (have exponentially localized
wave packet) in a valence-bond-solid state, are marginally defined (with
power-law shaped wave packet) in the standard Heisenberg critical state, and
are not well defined in an ordered N\'eel state (achieved in one dimension
using long-range interactions).",1107.1439v2
2011-08-16,Magnetic rogue wave in a perpendicular anisotropic ferromagnetic nanowire with spin-transfer torque,"We present the current controlled motion of dynamic soliton embedded in spin
wave background in ferromagnetic nanowire. With the stronger breather character
we get the novel magnetic rogue wave and clarify its formation mechanism. The
generation of magnetic rogue wave is mainly arose from the accumulation of
energy and magnons toward to its central part. We also observe that the
spin-polarized current can control the exchange rate of magnons between
envelope soliton and background, and the critical current condition is obtained
analytically. Even more interesting is that the spin-transfer torque plays the
completely opposite role for the cases of below and above the critical value.",1108.3252v2
2011-10-26,SpinWaves in Ferromagnetic Dots 2D Honeycomb Lattice Stripes,"In this work, the spin wave calculations were carried out using the
Heisenberg Hamiltonian to study the allowed spin waves of zigzag and armchair
edged stripes for ferromagnetic nanodots arrayed in a 2D honeycomb lattice
\cite{Selim2011}. The Hamiltonian is used to construct the $\mathbf{E}$ matrix
which encodes the exchange flow of magnons in the stripes. It is found that the
allowed spin wave modes are the eigenvalues of the $\mathbf{E}$ matrix and
therefore it is used to study the effects of the stripe width, edge exchange,
the edge uniaxial anisotropy, and impurities on the allowed spin waves of
stripes. The obtained results almost coincide with the results of graphene
nanoribbons described by tight binding Hamiltonian for electronic excitations.
Therefore, we suggest the fabrication of the magnetic counterpart to graphene
as a new technology in the field of spintronic devices and magnetic
applications.",1110.5716v1
2011-12-19,About spin electromagnetic wave-particle with ring singularity,"An axisymmetric space-localized solution of nonlinear electrodynamics is
considered as massive charged particle with spin and magnetic moment. The
appropriate solution for nonlinear electrodynamics with ring singularity is
investigated. In view of this problem the system of toroidal waves in linear
electrodynamics is considered. The problem with boundary conditions on the
singular ring of the toroidal coordinate system is investigated. The boundary
conditions are taken taking into account the conformity between the toroidal
and cylindrical waves on the ring. In this case the singular ring looks like
convolute axis of cylindrical system. The appropriate system of wave modes are
obtained in an integral form with the help of source function.",1112.4437v1
2012-04-16,Topological chiral magnonic edge mode in a magnonic crystal,"Topological phases have been explored in various fields in physics such as
spintronics, photonics, liquid helium, correlated electron system and
cold-atomic system. This leads to the recent foundation of emerging materials
such as topological band insulators, topological photonic crystals and
topological superconductors/superfluid. In this paper, we propose a topological
magnonic crystal which provides protected chiral edge modes for magnetostatic
spin waves. Based on a linearized Landau-Lifshitz equation, we show that a
magnonic crystal with the dipolar interaction acquires spin-wave volume-mode
band with non-zero Chern integer. We argue that such magnonic systems are
accompanied by the same integer numbers of chiral spin-wave edge modes within a
band gap for the volume-mode bands. In these edge modes, the spin wave
propagates in a unidirectional manner without being scattered backward, which
implements novel fault-tolerant spintronic devices.",1204.3349v3
2012-08-17,Spin-wave excitations and superconducting resonant mode in Cs(x)Fe(2-y)Se2,"We report neutron inelastic scattering measurements on the normal and
superconducting states of single-crystalline Cs0.8Fe1.9Se2. Consistent with
previous measurements on Rb(x)Fe(2-y)Se2, we observe two distinct spin
excitation signals: (i) spin-wave excitations characteristic of the block
antiferromagnetic order found in insulating A(x)Fe(2-y)Se2 compounds, and (ii)
a resonance-like magnetic peak localized in energy at 11 meV and at an in-plane
wave vector of (0.25, 0.5). The resonance peak increases below Tc = 27 K, and
has a similar absolute intensity to the resonance peaks observed in other
Fe-based superconductors. The existence of a magnetic resonance in the spectrum
of Rb(x)Fe(2-y)Se2 and now of Cs(x)Fe(2-y)Se2 suggests that this is a common
feature of superconductivity in this family. The low energy spin-wave
excitations in Cs0.8Fe1.9Se2 show no measurable response to superconductivity,
consistent with the notion of spatially separate magnetic and superconducting
phases.",1208.3610v2
2012-11-20,Microscopic magnetic structuring of a spin-wave waveguide by ion implantation in a Ni(81)Fe(19) layer,"We investigate the spin-wave excitation in microscopic waveguides fabricated
by localized Cr+ ion implantation in a ferromagnetic Ni(81)Fe(19) film. We
demonstrate that spin-wave waveguides can be conveniently made by this
technique. The magnetic patterning technique yields an increased damping and a
reduction in saturation magnetization in the implanted regions that can be
extracted from Brillouin light scattering measurements of the spin-wave
excitation spectra. Furthermore, the waveguide performance as well as the
internal field of the waveguide depend on the doping fluence. The results prove
that localized ion implantation is a powerful tool for the patterning of magnon
spintronic devices.",1211.4786v1
2013-01-29,Single-photon-level optical storage in a solid-state spin-wave memory,"A long-lived quantum memory is a firm requirement for implementing a quantum
repeater scheme. Recent progress in solid-state rare-earth-ion-doped systems
justifies their status as very strong candidates for such systems. Nonetheless
an optical memory based on spin-wave storage at the single-photon-level has not
been shown in such a system to date, which is crucial for achieving the long
storage times required for quantum repeaters. In this letter we show that it is
possible to execute a complete atomic frequency comb (AFC) scheme, including
spin-wave storage, with weak coherent pulses of $\bar{n} = 2.5 \pm 0.6$ photons
per pulse. We discuss in detail the experimental steps required to obtain this
result and demonstrate the coherence of a stored time-bin pulse. We show a
noise level of $(7.1 \pm 2.3)10^{-3}$ photons per mode during storage, this
relatively low-noise level paves the way for future quantum optics experiments
using spin-waves in rare-earth-doped crystals.",1301.6924v1
2013-03-05,"Angle-Dependent Spin-Wave Resonance Spectroscopy of (Ga,Mn)As Films","A modeling approach for standing spin-wave resonances based on a
finite-difference formulation of the Landau-Lifshitz-Gilbert equation is
presented. In contrast to a previous study [Bihler et al., Phys. Rev. B 79,
045205 (2009)], this formalism accounts for elliptical magnetization precession
and magnetic properties arbitrarily varying across the layer thickness,
including the magnetic anisotropy parameters, the exchange stiffness, the
Gilbert damping, and the saturation magnetization. To demonstrate the
usefulness of our modeling approach, we experimentally study a set of (Ga,Mn)As
samples grown by low-temperature molecular-beam epitaxy by means of
electrochemical capacitance-voltage measurements and angle-dependent standing
spin-wave resonance spectroscopy. By applying our modeling approach, the angle
dependence of the spin-wave resonance data can be reproduced in a simulation
with one set of simulation parameters for all external field orientations. We
find that the approximately linear gradient in the out-of-plane magnetic
anisotropy is related to a linear gradient in the hole concentrations of the
samples.",1303.1192v1
2013-04-26,A micro-structured ion-implanted magnonic crystal,"We investigate spin-wave propagation in a microstructured magnonic-crystal
waveguide fabricated by localized ion implantation. The irradiation caused a
periodic variation in the saturation magnetization along the waveguide. As a
consequence, the spin-wave transmission spectrum exhibits a set of frequency
bands, where spin-wave propagation is suppressed. A weak modification of the
saturation magnetization by 7% is sufficient to decrease the spin-wave
transmission in the band gaps by a factor of 10. These results evidence the
applicability of localized ion implantation for the fabrication of efficient
micron- and nano-sized magnonic crystals for magnon spintronic applications.",1304.7122v1
2013-05-21,Effect of Hole Shape on Spin-Wave Band Structure in One-Dimensional Magnonic Antidot Waveguide,"We present the possibility of tuning the spin-wave band structure,
particularly the bandgaps in a nanoscale magnonic antidot waveguide by varying
the shape of the antidots. The effects of changing the shape of the antidots on
the spin-wave dispersion relation in a waveguide have been carefully monitored.
We interpret the observed variations by analysing the equilibrium magnetic
configuration and the magnonic power and phase distribution profiles during
spin-wave dynamics. The inhomogeneity in the exchange fields at the antidot
boundaries within the waveguide is found to play a crucial role in controlling
the band structure at the discussed length scales. The observations recorded
here will be important for future developments of magnetic antidot based
magnonic crystals and waveguides.",1305.4812v2
2013-05-28,Magnonic band gaps in waveguides with a periodic variation of the saturation magnetization,"We present a micromagnetic analysis of spin-wave propagation in a magnonic
crystal realized as a permalloy spin-wave waveguide with a spatial periodical
variation of its saturation magnetization. Frequency band gaps were clearly
observed in the spin-wave transmission spectra and their origin is traced back
to an overlap of individual band gaps of the fundamental and the higher order
spin-wave width modes. The control of the depth, width and the position in
frequency and space of the rejection band gaps by the width areas with a
reduced magnetization and by the modulation level, are discussed in this study.",1305.6619v1
2013-07-17,Low-amplitude magnetic vortex core reversal by non-linear interference between azimuthal spin waves and the vortex gyromode,"We demonstrate a non-linear interference due to an active 'dual frequency'
excitation of both, the sub-GHz vortex gyromode and multi-GHz magneto-static
spin waves in ferromagnetic micrometer sized platelets in the vortex state.
When the sub-GHz vortex gyromode is excited simultaneously a significant
broadband reduction of the switching threshold for spin wave mediated vortex
core reversal is observed in both, experiments and micromagnetic simulations.
Consequently, the magnetic field amplitudes required for vortex core reversal
can be lowered by nearly one order of magnitude. Moreover, additional spin wave
resonance frequencies are found which emerge only if the vortex gyromode is
actively excited simultaneously which can be explained by frequency doubling
and by the broken symmetry of the vortex state.",1307.4548v1
2014-05-04,Charge and Spin Density Waves observed through their spatial fluctuations by coherent and simultaneous X-ray diffraction,"Spatial uctuations of spin density wave (SDW) and charge density wave (CDW)
in chromium have been compared by combining coherent and simultaneous X-ray
diffraction experiments. Despite their close relationship, spatial fluctuations
of the spin and of the charge density waves display a very different behavior:
the satellite reflection associated to the charge density displays speckles
while the spin one displays an impressive long-range order. This observation is
hardly compatible with the commonly accepted magneto-elastic origin of CDW in
chromium and is more consistent with a purely electronic scenario where CDW is
the second harmonic of SDW. A BCS model taking into account a second order
nesting predicts correctly the existence of a CDW and explains why the CDW is
more sensitive to punctual defects.",1405.0738v2
2014-11-14,Lifetimes of Magnons in Two-Dimensional Diluted Ferromagnetic Systems,"Spin dynamics in low dimensional magnetic systems has been of fundamental
importance for a long time and has currently received an impetus owing to the
emerging field of nanoelectronics. Knowledge of the spin wave lifetimes, in
particular, can be favorable for future potential applications. We investigate
the low-temperature spin wave excitations in two-dimensional disordered
ferromagnetic systems, with a particular focus on the long wavelength magnon
lifetimes. A semi-analytical Green's functions based approach is used to
determine the dynamical spectral functions, for different magnetic impurity
concentrations, from which the intrinsic linewidth is extracted. We obtain an
unambiguous $q^4$ scaling of the magnon linewidth which is ascribed to the
disorder induced damping of the spin waves, thereby settling a longstanding
unresolved issue on the wave-vector dependence. Our findings are also in good
agreement with previous theoretical studies on Heisenberg ferromagnets.
Additionally, we demonstrate the futility of using the low moments associated
with the spectral densities to evaluate the magnon dispersions and lifetimes.",1411.3876v2
2014-11-26,Pattern Recognition with Magnonic Holographic Memory Device,"In this work, we present experimental data demonstrating the possibility of
using magnonic holographic devices for pattern recognition. The prototype
eight-terminal device consists of a magnetic matrix with micro-antennas placed
on the periphery of the matrix to excite and detect spin waves. The principle
of operation is based on the effect of spin wave interference, which is similar
to the operation of optical holographic devices. Input information is encoded
in the phases of the spin waves generated on the several edges of the magnonic
matrix, while the output corresponds to the amplitude of the inductive voltage
produced by the interfering spin waves on the other side of the matrix. The
level of the output voltage depends on the combination of the input phases as
well as on the internal structure of the magnonic matrix. Experimental data
collected for several magnonic matrixes show the unique output signatures in
which maxima and minima correspond to specific input phase patterns.
Potentially, magnonic holographic devices may provide a higher storage density
compare to the optical counterparts due to a shorter wavelength and
compatibility with conventional electronic devices. The challenges and
shortcoming of the magnonic holographic devices are also discussed.",1411.7082v1
2014-12-02,A rigorous two-dimensional model for the stripline ferromagnetic resonance response of metallic ferromagnetic films,"In this work we constructed a two-dimensional numerical model for calculation
of the stripline ferromagnetic resonance (FMR) response of metallic
ferromagnetic films. We also conducted numerical calculations by using this
software. The calculations demonstrated that the eddy current contribution to
the FMR response decreases with a decrease in the stripline width. The most
important manifestations of the conductivity (eddy current) effect are
excitation of the higher-order standing spin waves across the film thickness in
the materials for which the standing spin wave peaks would be absent in cavity
FMR measurements and strong dependence of the off-resonance series conductance
of the stripline on the stripline width. Whereas the contribution of the eddy
currents to the stripline FMR response can be very significant, because wide
striplines (100nm+) are conventionally used for the FMR measurements, it is
negligible in the case of excitation of spin waves, just because very narrow
stripline transducers (0.5-5micron wide) are required in order to excite spin
waves in metallic ferromagnetic films in a noticeable frequency/applied field
range.",1412.0777v1
2014-12-12,Spin waves in micro-structured yttrium iron garnet nanometer-thick films,"We investigated the spin-wave propagation in a micro-structured yttrium iron
garnet waveguide of $40$ nm thickness. Utilizing spatially-resolved Brillouin
light scattering microscopy, an exponential decay of the spin-wave amplitude of
$(10.06 \pm 0.83)$ $\mu$m was observed. This leads to an estimated Gilbert
damping constant of $\alpha=(8.79\pm 0.73)\times 10^{-4}$, which is larger than
damping values obtained through ferromagnetic resonance measurements in
unstructured films. The theoretically calculated spatial interference of
waveguide modes was compared to the spin-wave pattern observed experimentally
by means of Brillouin light scattering spectroscopy.",1412.4032v1
2015-01-16,A solid state spin-wave quantum memory for time-bin qubits,"We demonstrate the first solid-state spin-wave optical quantum memory with
on-demand read-out. Using the full atomic frequency comb scheme in a \PrYSO
crystal, we store weak coherent pulses at the single-photon level with a signal
to noise ratio $> 10$. Narrow-band spectral filtering based on spectral hole
burning in a second \PrYSO crystal is used to filter out the excess noise
created by control pulses to reach an unconditional noise level of $(2.0 \pm
0.3) \times10^{-3}$ photons per pulse. We also report spin-wave storage of
photonic time-bin qubits with conditional fidelities higher than a measure and
prepare strategy, demonstrating that the spin-wave memory operates in the
quantum regime. This makes our device the first demonstration of a quantum
memory for time-bin qubits, with on demand read-out of the stored quantum
information. These results represent an important step for the use of
solid-state quantum memories in scalable quantum networks.",1501.03980v2
2015-05-05,Three-dimensional Character of the Magnetization Dynamics in Magnetic Vortex Structures - Hybridization of Flexure Gyromodes with Spin Waves,"Three-dimensional linear spin-wave eigenmodes of a Permalloy disk having
finite thickness are studied by micromagnetic simulations based on the
Landau-Lifshitz-Gilbert equation. The eigenmodes found in the simulations are
interpreted as linear superpositions (hybridizations) of 'approximate'
three-dimensional eigenmodes, which are the fundamental gyromode $G_0$, the
spin-wave modes and the higher-order gyromodes $G_N$ (flexure modes), the
thickness dependence of which is represented by perpendicular standing spin
waves. This hybridization leads to new and surprising dependencies of the mode
frequencies on the disk thickness. The three-dimensional character of the
eigenmodes is essential to explain the recent experimental results on
vortex-core reversal observed in relatively thick Permalloy disks.",1505.01148v2
2015-06-12,Criticality at the Haldane-insulator charge-density-wave quantum phase transition,"Exploiting the entanglement concept within a matrix-product-state based
infinite density-matrix renormalization group approach, we show that the
spin-density-wave and bond-order-wave ground states of the one-dimensional
half-filled extended Hubbard model give way to a symmetry-protected topological
Haldane state in case an additional alternating ferromagnetic spin interaction
is added. In the Haldane insulator the lowest entanglement level features a
characteristic twofold degeneracy. Increasing the ratio between
nearest-neighbor and local Coulomb interaction $V/U$, the enhancement of the
entanglement entropy, the variation of the charge, spin and neutral gaps, and
the dynamical spin/density response signal a quantum phase transition to a
charge-ordered state. Below a critical point, which belongs to the universality
class of the tricritical Ising model with central charge 7/10, the model is
critical with $c=1/2$ along the transition line. Above this point, the
transition between the Haldane insulator and charge-density-wave phases becomes
first order.",1506.04003v2
2015-06-17,Local spin-density-wave order inside vortex cores in multiband superconductors,"Coexistence of antiferromagnetic order with superconductivity in many
families of newly discovered iron-based superconductors has renewed interest to
this old problem. Due to competition between the two types of order, one can
expect appearance of the antiferromagnetism inside the cores of the vortices
generated by the external magnetic field. The structure of a vortex in type II
superconductors holds significant importance from the theoretical and the
application points of view. Here we consider the internal vortex structure in a
two-band s$_\pm$ superconductor near a spin-density-wave instability. We treat
the problem in a completely self-consistent manner within the quasiclassical
Eilenberger formalism. We study the structure of the s$_\pm$ superconducting
order and magnetic field-induced spin-density-wave order near an isolated
vortex. We examine the effect of this spin-density-wave state inside the vortex
cores on the local density of states.",1506.05440v2
2015-12-04,Polarization dependence of nonlinear wave mixing of spinor polaritons in semiconductor microcavities,"The pseudo-spin dynamics of propagating exciton-polaritons in semiconductor
microcavities are known to be strongly influenced by TE-TM splitting. As a
vivid consequence, in the Rayleigh scattering regime, the TE-TM splitting gives
rise to the optical spin Hall effect (OSHE). Much less is known about its role
in the nonlinear optical regime in which four-wave mixing for example allows
the formation of spatial patterns in the polariton density, such that hexagons
and two-spot patterns are observable in the far field. Here we present a
detailed analysis of spin-dependent four-wave mixing processes, by combining
the (linear) physics of TE-TM splitting with spin-dependent nonlinear
processes, i.e., exciton-exciton interaction and fermionic phase-space filling.
Our combined theoretical and experimental study elucidates the complex physics
of the four-wave mixing processes that govern polarization and orientation of
off-axis modes.",1512.01378v1
2016-02-03,Two-dimensional dispersion of magnetostatic volume spin waves,"The dipolar (magnetostatic) interaction dominates the behavior of spin waves
in magnetic films in the long-wavelength regime. In an in-plane magnetized
film, volume modes exist with a negative group velocity (backward volume
magnetostatic spin waves), in addition to the forward surface-localized mode
(Damon-Eshbach). Inside the film of finite thickness $L$, the volume modes have
a nontrivial spatial dependence, and their two-dimensional dispersion relations
$\omega(\mathbf{k})$ can be calculated only numerically. We present explicit
perturbative expressions for the profiles and frequencies of the volume modes,
taking into account an in-plane applied field and uniaxial anisotropy, for the
regimes $\lVert \mathbf{k}L \rVert \gg 1$ and $\lVert \mathbf{k}L \rVert \ll
1$, which together provide a good indication of the behavior of the modes for
arbitrary wavevector $\mathbf{k}$. Moreover, we derive a very accurate
semianalytical expression for the dispersion relation $\omega(\mathbf{k})$ of
the lowest-frequency mode that is straightforward to evaluate using standard
numerical routines. Our results are useful to quickly interpret and control the
excitation and propagation of spin waves in (opto-)magnetic experiments.",1602.01362v1
2016-04-26,Modulated spin helicity stabilized by incommensurate orbital density waves in a quadruple perovskite manganite,"Through a combination of neutron diffraction and Landau theory we describe
the spin ordering in the ground state of the quadruple perovskite manganite
CaMn7O12 - a magnetic multiferroic supporting an incommensurate orbital density
wave that onsets above the magnetic ordering temperature, TN1 = 90 K. The
multi-k magnetic structure in the ground state was found to be a
nearly-constant-moment helix with modulated spin helicity, which oscillates in
phase with the orbital occupancies on the Mn3+ sites via trilinear
magneto-orbital coupling. Our phenomenological model also shows that, above TN2
= 48 K, the primary magnetic order parameter is locked into the orbital wave by
an admixture of helical and collinear spin density wave structures.
Furthermore, our model naturally explains the lack of a sharp dielectric
anomaly at TN1 and the unusual temperature dependence of the electrical
polarisation.",1604.07747v1
2016-07-05,Non-classical correlations between a C-band telecom photon and a stored spin-wave,"Future ground-based quantum information networks will likely use single
photons transmitted through optical fibers to entangle individual network
nodes. To extend communication distances and overcome limitations due to photon
absorption in fibers the concept of quantum repeaters has been proposed. For
that purpose, it is required to achieve quantum correlations between the
material nodes and photons at telecom wavelengths which can be sent over long
distances in optical fibers. Here we demonstrate non-classical correlation
between a frequency converted telecom C-band photon and a spin-wave stored in
an atomic ensemble quantum memory. The photons emitted from the ensemble and
heralding the spin-waves are converted from 780 nm to 1552 nm by means of an
all-solid-state integrated waveguide non-linear device. We show ultra-low noise
operation of the device enabling a high signal to noise ratio of the converted
single photon, leading to a high spin-wave heralding efficiency. The presented
work is an enabling step towards the practical entanglement of remote quantum
memories and the entanglement of quantum systems operating at different
wavelengths.",1607.01350v1
2016-09-27,Sewing Greenberger-Horne-Zeilinger states with a quantum zipper,"A mechanism of a chiral spin wave rotation is introduced to systematically
generate mesoscopic Greenberger-Horne-Zeilinger states.",1609.08589v1
2017-08-21,Micromagnetic simulations of magnetoelastic spin wave excitation in scaled magnetic waveguides,"We study the excitation of spin waves in scaled magnetic waveguides using the
magnetoelastic effect. In uniformly magnetized systems, normal strains parallel
or perpendicular to the magnetization direction do not lead to spin wave
excitation since the magnetoelastic torque is zero. Using micromagnetic
simulations, we show that the nonuniformity of the magnetization in submicron
waveguides due to the effect of the demagnetizing field leads to the excitation
of spin waves for oscillating normal strains both parallel and perpendicular to
the magnetization. The excitation by biaxial normal in-plane strain was found
to be much more efficient than by uniaxial normal out-of-plane strain. For
narrow waveguides with widths of 200\,nm, the excitation efficiency of biaxial
normal in-plane strain was comparable to that of shear strain.",1708.06428v1
2018-03-26,Tunable Snell's law for spin waves in heterochiral magnetic films,"Thin ferromagnetic films with an interfacially induced DMI exhibit nontrivial
asymmetric dispersion relations that lead to unique and useful magnonic
properties. Here we derive an analytical expression for the magnon propagation
angle within the micromagnetic framework and show how the dispersion relation
can be approximated with a comprehensible geometrical interpretation in the
k-space of the propagation of spin waves. We further explore the refraction of
spin waves at DMI interfaces in heterochiral magnetic films, after deriving a
generalized Snell's law tunable by an in-plane magnetic field, that yields
analytical expressions for critical incident angles. The found asymmetric
Brewster angles at interfaces of regions with different DMI strengths,
adjustable by magnetic field, support the conclusion that heterochiral
ferromagnetic structures are an ideal platform for versatile spin-wave guides.",1803.09648v1
2014-06-23,Magnon-Driven Domain-Wall Motion with the Dzyaloshinskii-Moriya Interaction,"We study domain wall (DW) motion induced by spin waves (magnons) in the
presence of Dzyaloshinskii-Moriya interaction (DMI). The DMI exerts a torque on
the DW when spin waves pass through the DW, and this torque represents a linear
momentum exchange between the spin wave and the DW. Unlike angular momentum
exchange between the DW and spin waves, linear momentum exchange leads to a
rotation of the DW plane rather than a linear motion. In the presence of an
effective easy plane anisotropy, this DMI induced linear momentum transfer
mechanism is significantly more efficient than angular momentum transfer in
moving the DW.",1406.5997v2
2014-06-27,Observation of propagating edge spin waves modes,"Broadband magnetization response of equilateral triangular 1000 nm Permalloy
dots has been studied under an in-plane magnetic field, applied parallel
(buckle state) and perpendicular (Y state) to the triangles base. Micromagnetic
simulations identify edge spin waves (E-SWs) in the buckle state as SWs
propagating along the two adjacent edges. These quasi one-dimensional spin
waves emitted by the vertex magnetic charges gradually transform from
propagating to standing due to interference and are weakly affected by dipolar
interdot interaction and variation of the aspect ratio. Spin waves in the Y
state have a two dimensional character. These findings open perspectives for
implementation of the E-SWs in magnonic crystals and thin films.",1406.7186v1
2018-12-13,Spin-Orbital Density Wave and a Mott Insulator in a Two-Orbital Hubbard Model on a Honeycomb Lattice,"Inspired by recent discovery of correlated insulating states in twisted
bilayer graphene (TBG), we study a two-orbital Hubbard model on the honeycomb
lattice with two electrons per unit cell. Based on the real-space density
matrix renormalization group (DMRG) simulation, we identify a metal-insulator
transition around $U_c/t=2.5\sim3$. In the vicinity of $U_c$, we find strong
spin/orbital density wave fluctuations at commensurate wavevectors, accompanied
by weaker incommensurate charge density wave (CDW) fluctuations. The
spin/orbital density wave fluctuations are enhanced with increasing system
sizes, suggesting the possible emergence of long-range order in the two
dimensional limit. At larger $U$, our calculations indicate a possible
nonmagnetic Mott insulator phase without spin or orbital polarization. Our
findings offer new insights into correlated electron phenomena in twisted
bilayer graphene and other multi-orbital honeycomb materials.",1812.05661v3
2019-02-19,Spatial spin-wave modulator for quantum memory assisted adaptive measurements,"Utilization of the spatial degree of freedom vastly enhances informational
capacity of light at the cost of stringent requirements on the processing
devices. Multi-mode quantum memories constitute a viable candidate for quantum
and classical information processing; however, full utilization of the assets
of high-dimensionality requires a flexible processing technique. We employ a
spatially varying ac-Stark effect to perform arbitrary 1D phase modulation of a
coherent spin-wave state stored in a wavevector-multiplexed quantum memory. A
far-field and an interferometric near-field characterizations of the introduced
phase profiles are presented. Additionally, coherence between temporally
separated partial readouts of a single coherent spin-wave state is
demonstrated, offering possible applications in adaptive measurements via
conditional spin-wave modulation.",1902.07255v1
2019-06-19,Edge localization of spin waves in antidot multilayers with perpendicular magnetic anisotropy,"We study the spin-wave dynamics in nanoscale antidot lattices based on Co/Pd
multilayers with perpendicular magnetic anisotropy. Using time-resolved
magneto-optical Kerr effect measurements we demonstrate that the variation of
the antidot shape introduces significant change in the spin-wave spectra,
especially in the lower frequency range. By employing micromagnetic simulations
we show that additional peaks observed in the measured spectra are related to
narrow shell regions around the antidots, where the magnetic anisotropy is
reduced due to the Ga+ ion irradiation during the focused ion beam milling
process of the antidot fabrication. The results point at new possibilities for
exploitation of localized spin waves in out-of-plane magnetized thin films,
which are easily tunable and suitable for magnonics applications.",1906.08109v2
2019-06-21,Goos-Hänchen effect of spin waves at heterochiral interfaces,"We theoretically investigate the Goos-H\""{a}nchen (GH) effect of spin-wave
beams reflected from the interface between two ferromagnetic films with
different Dzyaloshinskii-Moriya interactions (DMIs). The formula of the GH
shift as functions of the incident angle and material parameters is derived
analytically. We show that the GH effect occurs only when spin waves are
totally reflected at the interface and vanishes otherwise. We further explore
the GH shift of spin waves by narrow DMI strips of different widths. It is
found that the induced shift is independent of the strip width down to $10$ nm,
offering a novel approach to measure the DMI strength of ultra-narrow magnetic
strips which is out the scope of current technology. Full micromagnetic
simulations compare well with our theoretical findings. Strong distortion of
edge magnetizations for narrower strips however generates a width dependence of
the GH shift. The results presented in this work are helpful for understanding
the GH effect in chiral magnets and for quantifying the DMI parameter in
magnetic strips of sub-$50$ nm scales.",1906.08999v2
2016-03-03,Cloaking the magnons,"We propose two approaches to cloak the spin waves (magnons) by investigating
magnetization dynamics. One approach is based on a spatially inhomogeneous
anisotropic magnetic moment tensor. The other mechanism is using a spatially
inhomogeneous anisotropic gyromagnetic factor tensor and an inhomogeneous
external magnetic field. For both approaches, the damping tensor is also
inhomogeneous and anisotropic. The magnetic characteristic functions of the
magnetic materials have been theoretically derived for both mechanisms. A
non-magnetic core, which prevents magnons from entering and consequently
distorts the spin wave propagation, can be cloaked by a structured magnetic
shell to redirect the spin wave around the core using the above design
mechanisms. We discuss the feasibility of the proposed mechanisms in an
ensemble of quantum dot molecules and magnetic semiconductors. The proposed
approaches shed light on transformation magnonics, and can be utilized for
future spin-wave lenses, concentrators, low back-scattering waveguides, and
ultimately quantum computing.",1603.01000v1
2016-12-15,Experimental prototype of a spin-wave majority gate,"Featuring low heat dissipation, devices based on spin-wave logic gates
promise to comply with increasing future requirements in information
processing. In this work, we present the experimental realization of a majority
gate based on the interference of spin waves in an Yttrium-Iron-Garnet-based
waveguiding structure. This logic device features a three-input combiner with
the logic information encoded in the phase of the spin waves. We show that the
phase of the output signal represents the majority of the phase of the input
signals. A switching time of about 10 ns in the prototype device provides
evidence for the ability of sub-nanosecond data processing in future
down-scaled devices.",1612.07708v1
2017-10-25,Collective spin waves in arrays of Permalloy nanowires with single-side periodically modulated width,"We have experimentally and numerically investigated the dispersion of
collective spin waves prop-agating through arrays of longitudinally magnetized
nanowires with periodically modulated width. Two nanowire arrays with
single-side modulation and different periodicity of modulation were studied and
compared to the nanowires with homogeneous width. The spin-wave dispersion,
meas-ured up to the third Brillouin zone of the reciprocal space, revealed the
presence of two dispersive modes for the width-modulated NWs, whose amplitude
of magnonic band depends on the modula-tion periodicity, and a set of
nondispersive modes at higher frequency. These findings are different from
those observed in homogeneous width NWs where only the lowest mode exhibits
sizeable dis-persion. The measured spin-wave dispersion has been satisfactorily
reproduced by means of dynam-ical matrix method. Results presented in this work
are important in view of the possible realization of frequency tunable magnonic
device.",1710.09163v1
2018-04-16,Quantum optics of spin waves through ac Stark modulation,"We bring the set of linear quantum operations, important for many fundamental
studies in photonic systems, to the material domain of collective excitations
known as spin waves. Using the ac Stark effect we realize quantum operations on
single excitations and demonstrate a spin-wave analogue of Hong-Ou-Mandel
effect, realized via a beamsplitter implemented in the spin wave domain. Our
scheme equips atomic-ensemble-based quantum repeaters with quantum information
processing capability and can be readily brought to other physical systems,
such as doped crystals or room-temperature atomic ensembles.",1804.05854v2
2019-03-03,Spin wave damping in periodic and quasiperiodic magnonic structures,"We investigated the lifetime of spin wave eigenmodes in periodic and
quasiperiodic sequences of Py and Co wires. Those materials differ
significantly in damping coefficients, therefore, the spatial distribution of
the mode amplitude within the structure is important for the lifetime of
collective spin wave excitations. Modes of the lower frequencies prefer to
concentrate in Py wires, because of the lower FMR frequency for this material.
This inhomogeneous distribution of amplitude of modes (with lower amplitude in
material of higher damping and with higher amplitude in material of lower
damping) is preferable for extending the lifetime of the collective excitations
beyond the volume average of lifetimes for solid materials. We established the
relation between the profile of the mode and its lifetime for periodic and
quasiperiodic structures. We performed also the comparative studies in order to
find the differences resulting from complexity of the structure and enhancement
of localization in quasiperiodic system on the lifetime of spin waves.",1903.00856v1
2019-03-11,Spin waves in thin films and magnonic crystals with Dzyaloshinskii-Moriya interactions,"The influence of the Dzyaloshinskii-Moriya interaction in ultra-thin
ferromagnetic films and chiral magnonic crystals on the behavior of spin waves
is reviewed. During the last decade, it has been shown, both theoretically and
experimentally, that this anisotropic exchange interaction produces
non-reciprocal features on the spin-wave spectrum of a magnetic system, a
phenomenon that occurs both for bulk and interfacial Dzyaloshinskii-Moriya
coupling. More recently, the concept of a chiral magnonic crystal has been
introduced, where the interfacial Dzyaloshinskii-Moriya interaction is
periodic. The effect of this periodicity include additional features such as
flat bands, indirect gaps, and an unusual spin-wave evolution.",1903.04288v2
2019-05-08,Nanoscale spin-wave wake-up receiver,"We present the concept of a passive spin-wave device which is able to
distinguish different radio-frequency pulse trains and validate its
functionality using micromagnetic simulations. The information is coded in the
phase of the individual pulses which are transformed into spin-wave packets.
The device splits every incoming packet into two arms, one of which is coupled
to a magnonic ring which introduces a well-defined time delay and phase shift.
Since the time delay is matched to the pulse repetition rate, adjacent packets
interfere in a combiner which makes it possible to distinguish simple pulse
train patterns by the read-out of the time-integrated spin-wave intensity in
the output. Due to its passive construction, this device may serve as an
energy-efficient wake-up receiver used to activate the main receiver circuit in
power critical IoT applications.",1905.03006v1
2019-05-13,Unmodelled Clustering Methods for Gravitational Wave Populations of Compact Binary Mergers,"The mass and spin distributions of compact binary gravitational-wave sources
are currently uncertain due to complicated astrophysics involved in their
formation. Multiple sub-populations of compact binaries representing different
evolutionary scenarios may be present among sources detected by Advanced LIGO
and Advanced Virgo. In addition to hierarchical modelling, unmodelled methods
can aid in determining the number of sub-populations and their properties. In
this paper, we apply Gaussian mixture model clustering to 1000 simulated
gravitational-wave compact binary sources from a mixture of five
sub-populations. Using both mass and spin as input parameters, we determine how
many binary detections are needed to accurately determine the number of
sub-populations and their mass and spin distributions. In the most difficult
case that we consider, where two sub-populations have identical mass
distributions but differ in their spin, which is poorly constrained by
gravitational-wave detections, we find that ~ 400 detections are needed before
we can identify the correct number of sub-populations.",1905.04825v2
2020-03-08,The effect of material defects on resonant spin wave modes in a nanomagnet,"We have theoretically studied how resonant spin wave modes in an elliptical
nanomagnet are affected by fabrication defects, such as small local thickness
variations. Our results indicate that defects of this nature, which can easily
result from the fabrication process, or are sometimes deliberately introduced
during the fabrication process, will significantly alter the frequencies,
magnetic field dependence of the frequencies, and the power and phase profiles
of the resonant spin wave modes. They can also spawn new resonant modes and
quench existing ones. All this has important ramifications for multi-device
circuits based on spin waves, such as phase locked oscillators for neuromorphic
computing, where the device-to-device variability caused by defects can be
inhibitory.",2003.03833v1
2020-03-23,Spin-wave gap collapse in Rh-doped Sr2IrO4,"We use resonant inelastic x-ray scattering (RIXS) at the Ir L3 edge to study
the effect of hole doping upon the Jeff=1/2 Mott-insulating state in Sr2IrO4,
via Rh replacement of the Ir site. The spin-wave gap, associated with XY-type
spin-exchange anisotropy, collapses with increasing Rh content, prior to the
suppression of the Mott-insulating state and in contrast to electron doping via
La substitution of the Sr site. At the same time, despite heavy damping, the
d-d excitation spectra retain their overall amplitude and dispersion character.
A careful study of the spin-wave spectrum reveals that deviations from the
J1-J2-J3 Heisenberg used to model the pristine system disappear at intermediate
doping levels. These findings are interpreted in terms of a modulation of Ir-Ir
correlations due to the influence of Rh impurities upon nearby Ir wave
functions, even as the single-band Jeff=1/2 model remains valid up to full
carrier delocalization. They underline the importance of the transition metal
site symmetry when doping pseudospin systems such as Sr2IrO4.",2003.10343v1
2020-09-17,Spin-wave focusing induced skyrmion generation,"We propose a new method to generate magnetic skyrmions through spin-wave
focusing in chiral ferromagnets.A lens is constructed to focus spin waves by a
curved interface between two ferromagnetic thin films with different
perpendicular magnetic anisotropies. Based on the principle of identical
magnonic path length, we derive the lens contour that can be either elliptical
or hyperbolical depending on the magnon refractive index. Micromagnetic
simulations are performed to verify the theoretical design. It is found that
under proper condition magnetic skyrmions emerge near the focus point of the
lens where the spin-wave intensity has been significantly enhanced. A close
investigation shows that a magnetic droplet first forms and then converts to
the skyrmion accompanying with a change of topological charge. Phase diagram
about the amplitude and duration-time of the exciting field for skyrmion
generation is obtained. Our findings would be helpful for designing novel
spintronic devices combining the advantages of skyrmionics and magnonics.",2009.08091v1
2020-11-02,Spin wave propagation in corrugated waveguides,"Curvature-induced effects allow us to tailor the static and dynamic response
of a magnetic system with a high degree of freedom. We study corrugated
magnonic waveguides deposited on a sinusoidally modulated substrate prepared by
focused electron beam deposition. The surface curvature in films with
thicknesses comparable to the amplitude of modulation locally modifies the
contributions of dipolar and exchange energies and results in an effective
anisotropy term which can be tuned on-demand based on the exact geometry. We
show, by Brillouin light scattering microscopy, that without the presence of an
external magnetic field, spin waves propagate over a distance 10$\times$larger
in the corrugated waveguide than in the planar waveguide. Further, we analyze
the influence of the modulation amplitude on spin-wave propagation and conclude
that for moderate modulation amplitudes, the spin-wave decay length is not
affected. For larger amplitudes, the decay length decreases linearly with
increasing modulation.",2011.01274v1
2020-11-23,Asymmetric spin wave dispersion due to a saturation magnetization gradient,"We demonstrate using micromagnetic simulations and a theoretical model that a
gradient in the saturation magnetization ($M_s$) of a perpendicularly
magnetized ferromagnetic film induces a non-reciprocal spin wave propagation
and, consequently an asymmetric dispersion relation. The $M_s$ gradient adds a
linear potential to the spin wave equation of motion consistent with the
presence of a force. We consider a transformation from an inertial reference
frame in which the $M_s$ is constant to an accelerated reference frame where
the resulting inertial force corresponds to the force from the $M_s$ gradient.
As in the Doppler effect, the frequency shift leads to an asymmetric dispersion
relation. Additionally, we show that under certain circumstances,
unidirectional propagation of spin waves can be achieved which is essential for
the design of magnonic circuits. Our results become more relevant in light of
recent experimental works in which a suitable thermal landscape is used to
dynamically modulate the saturation magnetization.",2011.11148v2
2021-08-02,Spin Wave Computing using pre-recorded magnetization patterns,"We propose a novel type of a spin wave computing device, based on a bilayer
structure which includes a bias layer, made from a hard magnetic material and a
propagation layer, made from a magnetic material with low damping, for example,
Yttrium Garnet (YiG) or Permalloy. The bias layer maintains a stable
pre-recorded magnetization pattern, generating a bias field with a desired
spatial dependence, which in turn sets the equilibrium magnetization inside the
propagation layer. When an external source applies an RF field or spinwave to
the propagation layer, excited spin waves scatter on the magnetization's
inhomogenuities, resulting in a complex interference behavior. One thus has the
ability to adjust spin wave propagation properties simply by altering the
magnetization in the bias layer. We demonstrate that the phenomenon can be
utilized to perform a variety of computational operations, including Fourier
Transform, Vector-Matrix multiplication and Grover search algorithm, with the
operational parameters exceeding conventional designs by orders of magnitude.",2108.00909v1
2021-10-04,Lumped circuit model for inductive antenna spin-wave transducers,"We derive a lumped circuit model for inductive antenna spin-wave transducers
in the vicinity of a ferromagnetic medium. The model considers the antenna's
Ohmic resistance, its inductance, as well as the additional inductance due to
the excitation of ferromagnetic resonance or spin waves in the ferromagnetic
medium. As an example, the additional inductance is discussed for a wire
antenna on top of a ferromagnetic waveguide, a structure that is characteristic
for many magnonic devices and experiments. The model is used to assess the
scaling properties and the energy efficiency of inductive antennas. Issues
related to scaling antenna transducers to the nanoscale and possible solutions
are also addressed.",2110.01318v3
2016-11-29,Superdirectional Beam of Surface Spin Wave,"The visualized diffraction patterns of surface spin wave excited by
arbitrarily oriented linear transducer are investigated experimentally in the
plane of tangentially magnetized ferrite film for the case where the transducer
length D is much larger than the wavelength L. It is shown experimentally and
theoretically that the angular width of diffracted surface spin wave beam in
anisotropic ferrite film can take values greater or less than L/D and can also
be zero. For the last case superdirectional (nonexpanding) beam of the surface
spin wave is observed experimentally: the smearing of the beam energy along the
film plane is absent and the length of the beam trajectory is maximal (~50 mm).",1611.09595v2
2017-03-20,Spin-wave excitations in the SDW state of doped iron pnictides,"We investigate the spin-wave excitations in the spin-density wave state of
doped iron pnictides within a five-orbital model. We find that the excitations
along ($\pi, 0$)$\rightarrow$($\pi, \pi$) are very sensitive to the doping
whereas they do not exhibit a similar sensitivity along ($0, 0$) $\rightarrow$
($\pi, 0$). Secondly, anisotropy in the excitations around ($\pi, 0$) with an
elliptical shape grows on moving towards the hole-doped region for low energy,
whereas it decreases for the high-energy excitations on the contrary. Thirdly,
spin-wave spectral weight shifts towards the low-energy region on moving away
from zero doping. We find these features to be in qualitative agreement with
the inelastic neutron-scattering measurements for the doped pnictides.",1703.06601v1
2019-01-18,Magnon-Fluxon interaction in a ferromagnet/superconductor heterostructure,"Ferromagnetism and superconductivity are most fundamental phenomena in
condensed matter physics. Entailing opposite spin orders, they share an
important conceptual similarity: Disturbances in magnetic ordering in magnetic
materials can propagate in the form of spin waves (magnons) while magnetic
fields penetrate superconductors as a lattice of magnetic flux quanta
(fluxons). Despite a rich choice of wave and quantum phenomena predicted,
magnon-fluxon coupling has not been observed experimentally so far. Here, we
clearly evidence the interaction of spin waves with a flux lattice in
ferromagnet/superconductor Py/Nb bilayers. We demonstrate that, in this system,
the magnon frequency spectrum exhibits a Bloch-like band structure which can be
tuned by the biasing magnetic field. Furthermore, we observe Doppler shifts in
the frequency spectra of spin waves scattered on a flux lattice moving under
the action of a transport current in the superconductor.",1901.06156v1
2019-09-16,Skyrmions and spin waves in frustrated ferromagnets at low applied magnetic field,"A continuum model of frustrated ferromagnets is analyzed in detail in the
regime of low applied magnetic field, $H_0<1/4$, where the ground state is a
spatially varying conical spiral. By changing variables to a corotating spin
field, the model is reformulated as a gauged sigma model in a fixed background
gauge, allowing the construction of stable isolated Skyrmions, and stable
multi-Skyrmion clusters, which approach the conical ground state at spatial
infinity. Owing to the spatial anisotropy induced by the ground state, these
Skyrmions exhibit only discrete symmetries, and are of neither N\'eel nor Bloch
type. These Skyrmions are continuously connected to the more familar solutions
in the high field regime ($H_0>1/4$), acquiring axial symmetry in the limit
$H_0\rightarrow 1/4$. The propagation of small amplitude spin waves through the
conical ground state is also analyzed and is found to depend strongly on both
$H_0$ and propagation direction relative to the ground state. In contrast to
spin waves in the high field regime ($H_0>1/4$) there is no spectral gap: waves
may propagate with any angular frequency.",1909.07970v2
2019-09-21,Deterministic generation and partial retrieval of a spin-wave excitation in an atomic ensemble,"In this paper, we report a generation of a spin-wave excitation (SWE) with a
near-unity () probability in a given time (~730). Such deterministic generation
relies on a feedback scheme with a millisecond quantum memory. The millisecond
memory is achieved by maximizing the wavelength of the spin wave and storing
the SWE as the magnetic-field-insensitive transition. We then demonstrate
partial retrievals of the spin wave by applying a first read pulse whose area
is smaller than the value of . The remained SWE is fully retrieved by a second
pulse. Anti-correlation function between the detections in the first and second
readouts has been measured, which shows that the partial-retrieval operation on
the SWE is in the quantum regime. The presented experiment represents an
important step towards the realization of the improved DLCZ quantum repeater
protocol proposed in Phys. Rev. A 77, 062301 (2008).",1909.09766v1
2019-12-11,Reservoir computing using a spin-wave delay line active ring resonator,"The authors demonstrate the use of a propagating spin waves for implementing
a reservoir computing architecture. The proposed concept utilises an active
ring resonator comprising a magnetic thin film delay line integrated into a
feedback loop. These systems exhibit strong nonlinearity and delayed response
behaviour, two important properties required for an effective reservoir
computing implementation. In a simple design, we exploit the nonlinear damping
of spin waves at different feedback gains to inject input data into the active
ring resonator and use a microwave diode to read out the amplitude of the spin
waves circulating in the ring. We employ two baseline tasks, namely the short
term memory and parity check tasks, to evaluate the suitability of this
architecture for processing time series data.",1912.05119v1
2020-01-18,Off-axial focusing of spin-wave lens in the presence of Dzyaloshinskii-Moriya interaction,"We theoretically study the effect of Dzyaloshinskii-Moriya interaction (DMI)
on the focusing of a spin-wave lens that is constructed by a circular interface
between two magnetic films. We analytically derive the generalized Snell's law
in the curved geometry and the position of the focal point which exhibits a
peculiar off-axial focusing behavior. We uncover a strong dependence of the
focal point on both the material parameters and the frequency of incident spin
waves. Full micromagnetic simulations compare well with theoretical
predictions. Our findings would be helpful to manipulate spin waves in chiral
magnets and to design functional magnonic devices.",2001.06604v1
2020-02-11,Sub-micrometer near-field focusing of spin waves in ultrathin YIG films,"We experimentally demonstrate tight focusing of a spin wave beam excited in
extended nanometer-thick films of Yttrium Iron Garnet by a simple microscopic
antenna functioning as a single-slit near-field lens. We show that the focal
distance and the minimum transverse width of the focal spot can be controlled
in a broad range by varying the frequency/wavelength of spin waves and the
antenna geometry. The experimental data are in good agreement with the results
of numerical simulations. Our findings provide a simple solution for
implementation of magnonic nano-devices requiring local concentration of the
spin-wave energy.",2002.04284v1
2021-06-17,Anomalous spin waves in CsFeCl$_{3}$ and RbFeCl$_{3}$,"We investigate magnetic excitations in the $S=1$ easy-plan-type triangular
antiferromagnets CsFeCl$_{3}$ and RbFeCl$_{3}$ through a combination of
inelastic neutron scattering measurements and spin-wave theory calculations
based on an established exchange-coupling Hamiltonian. We show that in either
material the model falls short of providing an adequate description of the
measured intensities and for RbFeCl$_{3}$ even fails to reproduce the measured
dispersion relation. The most striking discrepancy is a very anisotropic
azimuthal intensity distribution in the acoustic spin-wave branches in the
long-wavelength limit, which is incompatible with spin-wave theory on a
fundamental level. The observed anomalies are attributed to long-range dipolar
interactions.",2106.09447v2
2021-09-22,Theory of the dipole-exchange spin wave spectrum in ferromagnetic films with in-plane magnetization revisited,"We present a refinement of the widely accepted spin-wave spectrum that
Kalinikos and Slavin computed for magnetic films with an in-plane magnetization
(1986). The spin wave spectrum that follows from the diagonal approximation in
this theory becomes inaccurate for relatively thick films, as has already been
noted by Kreisel et al. (2009). Rather than solving an integrodifferential
equation which follows from the magnetostatic Green's function, as done by
Kalinikos and Slavin, we impose the exchange and magnetostatic boundary
conditions on bulk spin-wave solutions. This boundary problem has an accurate
analytical solution which is quantitatively different from the commonly used
diagonal theory for magnetic films.",2109.10597v2
2021-09-30,Spin-Wave Quantum Computing with Atoms in a Single-Mode Cavity,"We present a method for network-capable quantum computing that relies on
holographic spin-wave excitations stored collectively in ensembles of qubits.
We construct an orthogonal basis of spin waves in a one-dimensional array and
show that high-fidelity universal linear controllability can be achieved using
only phase shifts, applied in both momentum and position space. Neither
single-site addressability nor high single-qubit cooperativity is required, and
the spin waves can be read out with high efficiency into a single cavity mode
for quantum computing and networking applications.",2109.15252v1
2021-11-15,Nonstanding spin waves in a single rectangular permalloy microstrip under uniform magnetic excitation,"Ferromagnetic resonance modes in a single rectangular Ni$_{80}$Fe$_{20}$
microstrip were directly imaged using time-resolved scanning transmission x-ray
microscopy combined with a phase-locked ferromagnetic resonance excitation
scheme and the findings were corroborated by micromagnetic simulations.
Although under uniform excitation in a single confined microstructure typically
standing spin waves are expected, all imaged spin waves showed a nonstanding
character both, at and off resonance, the latter being additionally detected
with microantenna-based ferromagnetic resonance. The effect of the edge quality
on the spin waves was observed in micromagnetic simulations.",2111.07773v3
2021-12-21,Nonreciprocal spin-wave dynamics in Pt/Co/W/Co/Pt multilayers,"We present a detailed study of the spin-wave dynamics in single Pt/Co/W and
double Pt/Co/W/Co/Pt ferromagnetic layer systems. The dispersion of spin waves
was measured by wavevector-resolved Brillouin light scattering spectroscopy
while the in-plane and out-of-plane magnetization curves were measured by
alternating gradient field magnetometry. The interfacial Dzyaloshinskii-Moriya
interaction induced nonreciprocal dispersion relation was demonstrated for both
single and double ferromagnetic layers and explicated by numerical simulations
and theoretical formulas. The results indicate the crucial role of the order of
layers deposition on the magnetic parameters. A significant difference between
the perpendicular magnetic anisotropy constant in double ferromagnetic layer
systems conduces to the decline of the interlayer interactions and different
dispersion relations for the spin-wave modes. Our study provides a significant
contribution to the realization of the multifunctional nonreciprocal magnonic
devices based on ultrathin ferromagnetic/heavy-metal layer systems.",2112.11206v1
2022-01-11,All-sky analysis of astrochronometric signals induced by gravitational waves,"We introduce a unified formalism to describe both timing and astrometric
perturbations induced on astrophysical point sources by gravitational waves
using a complex spin field on the sphere. This allows the use of spin-weighted
spherical harmonics to analyse ""astrochronometric"" observables. This approach
simplifies the interpretation and simulation of anisotropies induced in the
observables by gravitational waves. It also allows a simplified derivation of
angular cross-spectra of the observables and their relationship with
generalised Hellings-Downs correlation functions. The spin-weighted formalism
also allows an explicit connection between correlation components and the spin
of gravitational wave polarisations and any presence of chirality. We also
calculate expected signal-to-noise ratios for observables to compare the
utility of timing and deflection observables.",2201.03903v1
2022-04-11,"On the ""old"" and ""new"" relativistic wave equations for the particle having spin s=3/2","Relativistic wave equation of motion without redundant components for the
particle having spin 3/2 has been considered. In order to show the newness a
comparison with the known equations for the spin s=3/2 field is given.
Therefore, the brief review of the relativistic wave equations for the particle
with spin s=3/2 is given. In our equation the wave function for the
particle-antiparticle doublet has only 8 components. The consideration is
carried out both at the level of relativistic quantum mechanics and at the
level of local field theory. The extended Foldy--Wouthuysen transformation,
which gives the operator link between these two levels is suggested.",2204.05167v2
2022-04-27,Magnetochiral Properties of Spin Waves Existing in Nanotubes with Axial and Circumferential Magnetization,"We report experimental studies of spin-wave excitations in individual 22 nm
thick Ni80Fe20 nanotubes with diameters of about 150 nm by means of Brillouin
light-scattering (BLS) spectroscopy. Irradiated by microwaves we resolve sets
of discrete resonances in the center of nanotubes ranging from 2.5 to 12.5 GHz.
Comparing to a recent theoretical work and micromagnetic simulations, we
identify different characteristic eigenmodes depending on the axial, mixed or
vortex configuration. The mixed and vortex states give rise to modes with
helical phase profiles substantiating an unusual nature of modes attributed to
non-reciprocal spin waves. Our findings provide microscopic insight into
tubular spin-wave nanocavities and magnetochiral effects for 3D nanomagnonics.",2204.12995v1
2022-05-05,Spin-wave localization on phasonic defects in one-dimensional magnonic quasicrystal,"We report on the evolution of the spin-wave spectrum under structural
disorder introduced intentionally into one-dimensional magnonic quasicrystal.
We study theoretically a system composed of ferromagnetic strips arranged in a
Fibonacci sequence. We considered several stages of disorder in the form of
phasonic defects, where different rearrangements of strips are introduced. By
transition from the quasiperiodic order towards disorder, we show a gradual
degradation of spin-waves fractal spectra and closing of the frequency gaps. In
particular, the phasonic defects lead to the disappearance of the van Hove
singularities at the frequency gap edges by moving modes into the frequency
gaps and appearing new modes inside the frequency gaps. These modes disperse
and eventually can close the gap, with increasing disorder levels. The work
reveals how the the presence of disorder modifies the intrinsic spin wave
localization existing in undefected magnonic quasicrystals. The paper
contributes to the knowledge of magnonic Fibonacci quasicrystals and opens the
way to study of the phasonic defects in two-dimensional magnonic quasicrystals.",2205.02702v2
2022-05-17,Polarization manipulation of giant photonic spin Hall effect using wave-guiding effect,"In plasmonic systems, the enhanced photonic spin Hall effect (PSHE) was
previously possible only for horizontal polarization. By employing the
wave-guiding surface plasmon resonance (WG-SPR) effect, we report a giant
photonic spin Hall effect (G-PSHE) of reflected light for both horizontal and
vertical polarization waves. We investigated the polarization-manipulated
G-PSHE in the Kretschmann configuration with an additional glass dielectric
layer. This additional dielectric layer allowed us to achieve millimeter-scale
(more than 2 mm to sub-millimeter) G-PSHE. We achieved polarization
manipulation by designing novel structures employing wave-guiding and SPR
theory. Using a simulation study, we investigated the impact of an additional
thin dielectric layer on G-PSHE. This study enables the potential application
of both horizontal and vertical polarization-based quantum devices and sensors
for which light spin plays a pivotal role.",2205.08258v1
2022-07-07,Experimental Demonstration of High-Performance Physical Reservoir Computing with Nonlinear Interfered Spin Wave Multi-Detection,"Physical reservoir computing, which is a promising method for the
implementation of highly efficient artificial intelligence devices, requires a
physical system with nonlinearity, fading memory, and the ability to map in
high dimensions. Although it is expected that spin wave interference can
perform as highly efficient reservoir computing in some micromagnetic
simulations, there has been no experimental verification to date. Herein, we
demonstrate reservoir computing that utilizes multidetected nonlinear spin wave
interference in an yttrium iron garnet single crystal. The subject computing
system achieved excellent performance when used for hand-written digit
recognition, second-order nonlinear dynamical tasks, and nonlinear
autoregressive moving average (NARMA). It is of particular note that normalized
mean square errors (NMSEs) for NARMA2 and second-order nonlinear dynamical
tasks were 1.81x10-2 and 8.37x10-5, respectively, which are the lowest figures
for any experimental physical reservoir so far reported. Said high performance
was achieved with higher nonlinearity and the large memory capacity of
interfered spin wave multi-detection.",2207.03216v1
2022-08-24,Stimulated amplification of propagating spin waves,"Spin-wave amplification techniques are key to the realization of magnon-based
computing concepts. We introduce a novel mechanism to amplify spin waves in
magnonic nanostructures. Using the technique of rapid cooling, we create a
non-equilibrium state in excess of high-energy magnons and demonstrate the
stimulated amplification of an externally seeded, propagating spin wave. Using
an extended kinetic model, we qualitatively show that the amplification is
mediated by an effective energy flux of high energy magnons into the low energy
propagating mode, driven by a non-equilibrium magnon distribution.",2208.11455v2
2022-11-01,Nonlocal optical conductivity of Fermi surface nesting materials,"We investigate the nonlocal optical conductivity of Fermi surface nesting
materials which support charge density waves or spin density waves. The
nonlocal optical conductivity contains information of correlations in electron
fluids which could not be accessed by standard optical probes. Half metal
emerges from doping a charge density wave and similarly spin-valley half metal
emerges from doping a spin density wave. Based on the parabolic band
approximation, we find the Drude peak is shifted to higher frequency and splits
into two peaks in the nonlocal optical conductivity. We attribute this to the
two Fermi velocities in the half-metal or spin-valley half metal states.",2211.00244v1
2022-11-20,Spin-wave spectra in antidot lattice with inhomogeneous perpendicular magnetocrystalline anisotropy,"Magnonic crystals are structures with periodically varied magnetic properties
that are used to control collective spin-wave excitations. With micromagnetic
simulations, we study spin-wave spectra in a 2D antidot lattice based on a
multilayered thin film with perpendicular magnetic anisotropy (PMA). We show
that the modification of the PMA near the antidot edges introduces interesting
modifications to the spin-wave spectra, even in a fully saturated state. In
particular, the spectra split in two types of excitations, bulk modes with
amplitude concentrated in a homogeneous part of antidot lattice, and edge modes
with an amplitude localized in the rims of reduced PMA at the antidot edges.
Their dependence on the geometrical or material parameters is distinct but at
resonance conditions fulfilled, we found strong hybridization between bulk and
radial edge modes. Interestingly, the hybridization between the fundamental
modes in bulk and rim is of magnetostatic origin but the exchange interactions
determine the coupling between higher-order radial rim modes and the
fundamental bulk mode of the antidot lattice.",2211.11002v1
2022-12-13,Spin wave spectra of single crystal CoPS$_3$,"The spin waves in single crystals of the layered van der Waals
antiferromagnet CoPS$_3$ have been measured using inelastic neutron scattering.
The data show four distinct spin wave branches with large ($\gtrsim 14$ meV)
energy gaps at the Brillouin zone center indicating significant anisotropy. The
data were modelled using linear spin wave theory derived from a Heisenberg
Hamiltonian. Exchange interactions up to the third nearest-neighbour in the
layered planes were required to fit the data with ferromagnetic $J_1 = -1.37$
meV between first neighbours, antiferromagnetic $J_3 = 3.0$ meV between third
neighbours, and a very small $J_2 = 0.09$ meV between second neighbours. A
biaxial single-ion anisotropy was required, with a collinear term $D^x = -0.77$
meV for the axis parallel to the aligned moment direction and a coplanar term
$D^z=6.07$ meV for an axis approximately normal to the layered crystal planes.",2212.06479v1
2023-02-14,"Singlet, Triplet and Pair Density Wave Superconductivity in the Doped Triangular-Lattice Moiré System","Recent experimental progress has established the twisted bilayer transition
metal dichalcogenide (TMD) as a highly tunable platform for studying many-body
physics. Particularly, the homobilayer TMDs under displacement field are
believed to be described by a generalized triangular-lattice Hubbard model with
a spin-dependent hopping phase $\theta$. To explore the effects of $\theta$ on
the system, we perform density matrix renormalization group calculations for
the relevant triangular lattice t-J model. By changing $\theta$ at small hole
doping, we obtain a region of quasi-long-range superconducting order coexisting
with charge and spin density wave within $0<\theta<\pi/3$. The
superconductivity is composed of a dominant spin singlet $d$-wave and a
subdominant triplet $p$-wave pairing. Intriguingly, the $S_z=\pm 1$ triplet
pairing components feature pair density waves. In addition, we find a region of
triplet superconductivity coexisting with charge density wave and
ferromagnetism within $\pi/3<\theta<2\pi/3$, which is related to the former
phase at smaller $\theta$ by a combined operation of spin-flip and gauge
transformation. Our findings provide insights and directions for experimental
search for exotic superconductivity in twisted TMD systems.",2302.06765v3
2023-04-17,Geometric phase and a nonreciprocal spin wave circular polarizer,"We show that spin wave acquires a polarization-dependent geometric phase
along a cyclic trajectory of non-coplanar magnetizations in antiferromagnets.
Specifically, we demonstrate that a cyclic set of 90 degree antiferromagnetic
domain walls simultaneously introduce geometric and dynamic phases to spin
wave, and thus leads to asymmetric magnitude of overall phase for
left-/right-circular components. Based on the polarization-dependent phase, we
propose theoretically and confirm by micromagnetic simulations that, a
Mach-Zehner interferometer with cyclic 90 degree domain walls in one arm and
homogenous domain in the other arm, naturally acts as a spin wave circular
polarizer. Moreover, the circular polarizer has intrinsic nonreciprocity, which
filters opposite polarization in opposite propagation direction.",2304.08071v1
2023-07-14,Gravitational partial-wave absorption from scattering amplitudes,"We study gravitational absorption effects using effective on-shell scattering
amplitudes. We develop an in-in probability-based framework involving plane-
and partial-wave coherent states for the incoming wave to describe the
interaction of the wave with a black hole or another compact object. We connect
this framework to a simplified single-quantum analysis. The basic ingredients
are mass-changing three-point amplitudes, which model the leading absorption
effects and a spectral-density function of the black hole. As an application,
we consider a non-spinning black hole that may start spinning as a consequence
of the dynamics. The corresponding amplitudes are found to correspond to
covariant spin-weighted spherical harmonics, the properties of which we
formulate and make use of. We perform a matching calculation to
general-relativity results at the cross-section level and derive the effective
absorptive three-point couplings. They are found to behave as ${\cal
O}(G_\text{Newton}^{s+1})$, where $s$ is the spin of the outgoing massive
state.",2307.07504v3
2023-12-28,Quantum Weyl-Heisenberg antiferromagnet,"Beginning from the conventional square-lattice nearest-neighbor
antiferromagnetic Heisenberg model, we allow the $J_x$ and $J_y$ couplings to
be anisotropic, with their values depending on the bond orientation. The
emergence of anisotropic, bond-dependent, couplings should be expected to occur
naturally in most antiferromagnetic compounds which undergo structural
transitions that reduce the point-group symmetry at lower temperature. Using
the spin-wave approximation, we study the model in several parameter regimes by
diagonalizing the reduced Hamiltonian exactly, and computing the edge spectrum
and Berry connection vector, which show clear evidence of localized topological
charges. We discover phases that exhibit Weyl-type spin-wave dispersion,
characterized by pairs of degenerate points and edge states, as well as phases
supporting lines of degeneracy. We also identify a parameter regime in which
there is an exotic state hosting gapless linear spin-wave dispersions with
different longitudinal and transverse spin-wave velocities.
  Author email info: prosenberg15@gmail.com and manousakis@gmail.com",2312.17028v1
2023-12-31,Multiplexed entanglement swapping with atomic-ensemble-based quantum memories in the single excitation regime,"Entanglement swapping (ES) between memory repeater links is critical for
establishing quantum networks via quantum repeaters. So far, ES with
atomic-ensemble-based memories has not been achieved. Here, we experimentally
demonstrated ES between two entangled pairs of spin-wave memories via
Duan-Lukin-Cirac-Zoller scheme. With a cloud of cold atoms inserted in a
cavity, we produce non-classically-correlated spin-wave-photon pairs in 12
spatial modes and then prepare two entangled pairs of spin-wave memories via a
multiplexed scheme. Via single-photon Bell measurement on retrieved fields from
two memories, we project the two remaining memories never entangled previously
into an entangled state with the measured concurrence of C = 0.0124(0.003). The
successful probability of ES in our scheme is increased by three times,
compared with that in non-multiplexed scheme. Our presented work shows that the
generation of entanglement (C>0) between the remaining memory ensembles
requires the average cross-correlation function of the spin-wave-photon pairs
to be >30 .",2401.00519v1
2024-03-23,Spatial Control of Hybridization-Induced Spin-Wave Transmission Stop Band,"Spin-wave (SW) propagation close to the hybridization-induced transmission
stop band is investigated within a trapezoid-shaped 200\,nm thick yttrium iron
garnet (YIG) film using time-resolved magneto-optic Kerr effect (TR-MOKE)
microscopy and broadband spin wave spectroscopy, supported by micromagnetic
simulations. The gradual reduction of the effective field within the structure
leads to local variations of the SW dispersion relation and results in a SW
hybridization at a fixed position in the trapezoid where the propagation
vanishes since the SW group velocity approaches zero. By tuning external field
or frequency, spatial control of the spatial stop band position and spin-wave
propagation is demonstrated and utilized to gain transmission control over
several microstrip lines.",2403.15840v1
2009-12-17,An improved effective-one-body Hamiltonian for spinning black-hole binaries,"Building on a recent paper in which we computed the canonical Hamiltonian of
a spinning test particle in curved spacetime, at linear order in the particle's
spin, we work out an improved effective-one-body (EOB) Hamiltonian for spinning
black-hole binaries. As in previous descriptions, we endow the effective
particle not only with a mass m, but also with a spin S*. Thus, the effective
particle interacts with the effective Kerr background (having spin S_Kerr)
through a geodesic-type interaction and an additional spin-dependent
interaction proportional to S*. When expanded in post-Newtonian (PN) orders,
the EOB Hamiltonian reproduces the leading order spin-spin coupling and the
spin-orbit coupling through 2.5PN order, for any mass-ratio. Also, it
reproduces all spin-orbit couplings in the test-particle limit. Similarly to
the test-particle limit case, when we restrict the EOB dynamics to spins
aligned or antialigned with the orbital angular momentum, for which circular
orbits exist, the EOB dynamics has several interesting features, such as the
existence of an innermost stable circular orbit, a photon circular orbit, and a
maximum in the orbital frequency during the plunge subsequent to the inspiral.
These properties are crucial for reproducing the dynamics and
gravitational-wave emission of spinning black-hole binaries, as calculated in
numerical relativity simulations.",0912.3517v2
2012-07-12,Anomalous and spin Hall effects in hcp cobalt from GGA + U calculations,"We have calculated the intrinsic anomalous and spin Hall conductivities, spin
and orbital magnetic moments and also spin polarization of Hall currentsin
hexagonal cobalt within the density functional theory with the generalized
gradient approximation (GGA) plus on-site Coulomb interaction (GGA+$U$). The
accurate all-electron full-potential linearized augmented plane wave method is
used. We find that the anomalous Hall conductivity (AHC) ($\sigma_{xy}^A$) and
orbital magnetic moment ($m_o$) of cobalt with the magnetization being along
the c-axis ($m//c$) calculated in the GGA+$U$ scheme with $U = 1.6$ eV and $J =
0.9$ eV agree rather well with the corresponding experimental values while, in
contrast, the $\sigma_{xy}^A$ and $m_o$ from the GGA calculations are
significantly smaller than the measured ones. This suggests that moderate $U =
1.6$ eV and $J = 0.9$ eV are appropriate for Co metals. The calculated AHC and
spin Hall conductivity (SHC) ($\sigma^S$) are highly anisotropic, and the ratio
of the Hall conductivity for $m//c$ to that for the magnetization being
in-plane ($m//ab$) from the GGA+$U$ calculations, is $\sim$16.0 for the AHC and
$\sim$6.0 for the SHC. For $m//c$, the spin-up and spin-down Hall currents are
found to flow in the same direction. The magnitude of the calculated Hall
current spin polarization ($P^H$) is large and $P^H = -0.61$. Remarkably, for
$m//ab$, the spin-up and spin-down Hall currents are predicted to flow in the
opposite directions. This indicates that the Hall current contains both
spin-polarized charge current and pure spin current, resulting in the magnitude
of the Hall current spin polarization ($P^H = -1.59$) being larger than 1.0.",1207.2876v1
2021-08-29,Nuclear spin-wave quantum register for a solid state qubit,"Solid-state nuclear spins surrounding individual, optically addressable
qubits provide a crucial resource for quantum networks, computation and
simulation. While hosts with sparse nuclear spin baths are typically chosen to
mitigate qubit decoherence, developing coherent quantum systems in nuclear
spin-rich hosts enables exploration of a much broader range of materials for
quantum information applications. The collective modes of these dense nuclear
spin ensembles provide a natural basis for quantum storage, however, utilizing
them as a resource for single spin qubits has thus far remained elusive. Here,
by using a highly coherent, optically addressed 171Yb3+ qubit doped into a
nuclear spin-rich yttrium orthovanadate crystal, we develop a robust quantum
control protocol to manipulate the multi-level nuclear spin states of
neighbouring 51V5+ lattice ions. Via a dynamically-engineered spin exchange
interaction, we polarise this nuclear spin ensemble, generate collective spin
excitations, and subsequently use them to implement a long-lived quantum
memory. We additionally demonstrate preparation and measurement of maximally
entangled 171Yb--51V Bell states. Unlike conventional, disordered nuclear spin
based quantum memories, our platform is deterministic and reproducible,
ensuring identical quantum registers for all 171Yb qubits. Our approach
provides a framework for utilising the complex structure of dense nuclear spin
baths, paving the way for building large-scale quantum networks using single
rare-earth ion qubits.",2108.12723v1
2017-04-21,A new high-temperature quantum spin liquid with polaron spins,"The existence of a quantum spin liquid (QSL) in which quantum fluctuations of
spins are sufficiently strong to preclude spin ordering down to zero
temperature was originally proposed theoretically more than 40 years ago, but
its experimental realisation turned out to be very elusive. Here we report on
an almost ideal spin liquid state that appears to be realized by atomic-cluster
spins on the triangular lattice of a charge-density wave (CDW) state of
1T-TaS$_2$. In this system, the charge excitations have a well-defined gap of
$\sim 0.3$ eV, while nuclear magnetic quadrupole resonance and muon spin
relaxation experiments reveal that the spins show gapless quantum spin liquid
dynamics and no long range magnetic order down to 70~mK. Canonical $T^{2}$
power-law temperature dependence of the spin relaxation dynamics characteristic
of a QSL is observed from 200~K to $T_f= 55$ K. Below this temperature we
observe a new gapless state with reduced density of spin excitations and high
degree of local disorder signifying new quantum spin order emerging from the
QSL.",1704.06450v1
2020-10-12,Generic Field-Driven Phenomena in Kitaev Spin Liquids: Canted Magnetism and Proximate Spin Liquid Physics,"Topological spin liquids in two spatial dimensions are stable phases in the
presence of a small magnetic field, but may give way to field-induced phenomena
at intermediate field strengths. Sandwiched between the low-field spin liquid
physics and the high-field spin-polarized phase, the exploration of magnetic
phenomena in this intermediate regime however often remains elusive to
controlled analytical approaches. Here we numerically study such
intermediate-field magnetic phenomena for two representative Kitaev models (on
the square-octagon and decorated honeycomb lattice) that exhibit either Abelian
or non-Abelian topological order in the low-field limit. Using a combination of
exact diagonalization and density matrix renormalization group techniques, as
well as linear spin-wave theory, we establish the generic features of Kitaev
spin liquids in an external magnetic field. While ferromagnetic models
typically exhibit a direct transition to the polarized state at a relatively
low field strength, antiferromagnetic couplings not only substantially
stabilizes the topological spin liquid phase, but generically lead to the
emergence of a distinct field-induced intermediate regime, separated by a
crossover from the high-field polarized regime. Our results suggest that, for
most lattice geometries, this regime generically exhibits significant spin
canting, antiferromagnetic spin-spin correlations, and an extended proximate
spin liquid regime at finite temperatures. Notably, we identify a symmetry
obstruction in the original honeycomb Kitaev model that prevents, at least for
certain field directions, the formation of such canted magnetism without
breaking symmetries -- consistent with the recent numerical observation of an
extended gapless spin liquid in this case.",2010.05921v1
2022-01-05,Equatorial orbits of spinning test particle in rotating boson star,"In this paper, we study the circular orbit of the spinning test particle in
the background of a rotating boson star. Using the pole-dipole approximation
and neglecting the back-reaction of the spinning test particle on the
spacetime, the equation of motion of the spinning test particle is described by
the Mathisson-Papapetrou-Dixon equation. We solve this equation under the
Tulczyjew spin-supplementary condition and obtain the four-momentum and
four-velocity of the spinning test particle. Quite different from the spinless
particle, the effective potential of the spinning particle with zero orbital
angular momentum goes to infinite at the center of the rotating boson star.
This will lead to the fact that the spinning particle can not pass through the
center of the boson star. However, when the spin angular momentum and orbital
angular momentum satisfy $2\bar{s}+\bar{l}=0$, the effective potential is not
divergent anymore and the spinning particle can pass through the center of the
rotating boson star. {We still investigate how the spin affects the structure
of the circular orbits and we find that the spin will induce the larger or
smaller regions of no circular orbits, unstable circular orbits, and stable
circular orbits.} Moreover, the radius and energy of the circular orbit will be
decreased or increased by the particle spin. These results will have an
important application in testing the gravitational waves in the boson star
background.",2201.01498v3
2022-11-08,From Elastic Spin to Phonon Spin: Symmetry and Fundamental Relations,"This work is mainly based on postgraduate lectures at Tongji University since
2020 spring. We firstly revisit the elastic spin and orbital angular momentum
[Proc. Natl. Acad. Sci. USA 115, 9951 (2018)] but more general for anisotropic
systems by applying Noether's theorem to the elastic Lagrangian and by applying
the symmetry argument in the field theory. Then, fundamental relations between
elastic energy flux and elastic spin are uncovered. In particular cases, the
wave spin is closely related to the vorticity of energy flux and momentum.
Secondly, we move forward from the elastic spin to revisit the phonon spin
[Fizika Tverdogo Tela 3, 2160 (1961)] by applying the second quantization to
elastic fields. We show that the uncovered phonon spin, a polarized
elastic-vibration quanta, is generally not restricted to transverse phonon
modes, but applying to general phonon modes, such as the longitudinal phonon
modes, surface phonon modes, and hybridized phonon modes, regarded as a
consequence of mode interferences. The elastic spin and phonon spin originate
from the local rotating of the field polarization in time domain, not the local
circulation (vorticity) of displacement or velocity in space domain. It is
hopeful that the present results could advance the fundamental understanding of
phonon spin and elastic spin, and promote the spin phononics for hybrid quantum
sensing and technology with multiple degrees of freedom.",2211.04959v2
2023-09-11,Scalable spin squeezing in two-dimensional arrays of dipolar large-$S$ spins,"Controlling the quantum many-body state of arrays of qudits, possessing a
large local Hilbert space, opens the path to a broad range of possibilities for
many-particle entanglement, interesting both for fundamental quantum science,
as well as for potential metrological applications. In this work we
theoretically show that the spin-spin interactions realized in two-dimensional
Mott insulators of large-spin magnetic atoms (such as Cr, Er or Dy) lead to
scalable spin squeezing along the non-equilibrium unitary evolution initialized
in a coherent spin state. An experimentally relevant perturbation to the
collective squeezing dynamics is offered by a quadratic Zeeman shift, which
leads instead to squeezing of individual spins. Making use of a truncated
cumulant expansion for the quantum fluctuations of the spin array, we show
that, for sufficiently small quadratic shifts, the spin squeezing dynamics is
akin to that produced by the paradigmatic one-axis-twisting (OAT) model -- as
expected from an effective separation between collective spin and spin-wave
variables. Spin squeezing with OAT-like scaling is shown to be protected by the
robustness of long-range ferromagnetic order to quadratic shifts in the
equilibrium phase diagram of the system, that we reconstruct via quantum Monte
Carlo and mean-field theory.",2309.05368v1
2023-11-06,Three-dimensional checkerboard spin structure on a breathing pyrochlore lattice,"The standard approach to realize a spin liquid state is through magnetically
frustrated states, relying on ingredients such as the lattice geometry,
dimensionality, and magnetic interaction type of the spins. While Heisenberg
spins on a pyrochlore lattice with only antiferromagnetic nearest neighbors
interactions are theoretically proven disordered, spins in real systems
generally include longer-range interactions. The spatial correlations at longer
distances typically stabilize a long-range order rather than enhancing a spin
liquid state. Both states can, however, be destroyed by short-range static
correlations introduced by chemical disorder. Here, using disorder-free
specimens with a clear long-range antiferromagnetic order, we refine the spin
structure of the Heisenberg spinel ZnFe2O4 through neutron magnetic
diffraction. The unique wave vector (1, 0, 1/2) leads to a spin structure that
can be viewed as alternatively stacked ferromagnetic and antiferromagnetic
tetrahedra in a three-dimensional checkerboard form. Stable coexistence of
these opposing types of clusters is enabled by the bipartite
breathing-pyrochlore crystal structure, leading to a second order phase
transition at 10 K. The diffraction intensity of ZnFe2O4 is an exact complement
to the inelastic scattering intensity of several chromate spinel systems which
are regarded as model classical spin liquids. Our results challenge this
attribution, and suggest instead of the six-spin ring-mode, spin excitations in
chromate spinels are closely related to the (1, 0, 1/2) type of spin order and
the four-spin ferromagnetic cluster locally at one tetrahedron.",2311.02823v1
2007-02-21,Frequency- and transverse wave-vector-dependent spin Hall conductivity in two-dimensional electron gas with disorder,"We determine wave number $q$ and frequency $\omega$ dependent spin Hall
conductivity $\sigma_{yx}^s(q, \omega)$ for a disordered two dimensional
electron system with Rashba spin orbit interaction when $\q$ is {\it
transverse} to the electric field. Both the conventional definition of spin
current and its new definition which takes care of the conservation of spins,
have been considered. The spin Hall conductivitivities for both of these
definitions are qualitatively similar. $\sigma_{yx}^s(q, \omega)$ is zero at
$q=0, \omega =0$ and is maximum at $q=0$ and at small but finite $\omega$ whose
value depends on different parameters of the system. Interestingly for $\omega
\to 0$, $\sigma_{yx}^s(q)$ resonates when $\Lambda \simeq L_{so}$ which are the
wavelength $(\Lambda = 2\pi/q)$ of the electric field's spatial variation and
the length for one cycle of spin precession respectively. The sign of the
out-of-plane component of the electrons' spin flips when the sign of electric
field changes due to its spatial variation along transverse direction. It
changes the mode of spin precession from clockwise to anti-clockwise or {\it
vice versa} and consequently a finite spin Hall current flows in the bulk of
the system.",0702487v4
2008-12-23,Recoil velocity at 2PN order for spinning black hole binaries,"We compute the flux of linear momentum carried by gravitational waves emitted
from spinning binary black holes at 2PN order for generic orbits. In particular
we provide explicit expressions of three new types of terms, namely
next-to-leading order spin-orbit terms at 1.5 PN order, spin-orbit tail terms
at 2PN order, and spin-spin terms at 2PN order. Restricting ourselves to
quasi-circular orbits, we integrate the linear momentum flux over time to
obtain the recoil velocity as function of orbital frequency. We find that in
the so-called superkick configuration the higher-order spin corrections can
increase the recoil velocity up to about a factor 3 with respect to the
leading-order PN prediction. Furthermore, we provide expressions valid for
generic orbits, and accurate at 2PN order, for the energy and angular momentum
carried by gravitational waves emitted from spinning binary black holes.
Specializing to quasi-circular orbits we compute the spin-spin terms at 2PN
order in the expression for the evolution of the orbital frequency and found
agreement with Mik\'oczi, Vas\'uth and Gergely. We also verified that in the
limit of extreme mass ratio our expressions for the energy and angular momentum
fluxes match the ones of Tagoshi, Shibata, Tanaka and Sasaki obtained in the
context of black hole perturbation theory.",0812.4413v2
2012-02-03,Prototype effective-one-body model for nonprecessing spinning inspiral-merger-ringdown waveforms,"We first use five non-spinning and two mildly spinning (chi_i \simeq -0.44,
+0.44) numerical-relativity waveforms of black-hole binaries and calibrate an
effective-one-body (EOB) model for non-precessing spinning binaries, notably
its dynamics and the dominant (2,2) gravitational-wave mode. Then, we combine
the above results with recent outcomes of small-mass-ratio simulations produced
by the Teukolsky equation and build a prototype EOB model for detection
purposes, which is capable of generating inspiral-merger-ringdown waveforms for
non-precessing spinning black-hole binaries with any mass ratio and individual
black-hole spins -1 \leq chi_i \lesssim 0.7. We compare the prototype EOB model
to two equal-mass highly spinning numerical-relativity waveforms of black holes
with spins chi_i = -0.95, +0.97, which were not available at the time the EOB
model was calibrated. In the case of Advanced LIGO we find that the mismatch
between prototype-EOB and numerical-relativity waveforms is always smaller than
0.003 for total mass 20-200 M_\odot, the mismatch being computed by maximizing
only over the initial phase and time. To successfully generate merger waveforms
for individual black-hole spins chi_i \gtrsim 0.7, the prototype-EOB model
needs to be improved by (i) better modeling the plunge dynamics and (ii)
including higher-order PN spin terms in the gravitational-wave modes and
radiation-reaction force.",1202.0790v2
2013-06-10,Testing the validity of the single-spin approximation in inspiral-merger-ringdown waveforms,"Gravitational-wave signals from black-hole binaries with non-precessing spins
are described by four parameters -- each black hole's mass and spin. It has
been shown that the dominant spin effects can be modeled by a \emph{single}
spin parameter, leading to the development of several \emph{three-parameter}
waveform models. Previous studies indicate that these models should be adequate
for gravitational-wave detection. In this paper we focus on the systematic
biases that would result from using them to estimate binary parameters, and
consider a one-parameter family of configurations at one choice of mass ratio
and effective single spin. We find that for low-mass binaries within that
family of configurations, where the observable waveform is dominated by the
inspiral, the systematic bias in all physical parameters is smaller than the
parameter uncertainty due to degeneracies between the mass ratio and the spins,
at least up to signal-to-noise ratios (SNRs) of 50. For higher-mass binaries,
where the merger and ringdown make a greater contribution to the observed
signal, the bias in the mass ratio is comparable to its uncertainty at SNRs of
only $\sim$30, and the bias in the measurement of the total spin is
\emph{larger} than the uncertainty defined by the 90% confidence region even at
an SNR of only 10. Although this bias may be mitigated in future models by a
better choice of single-effective-spin parameter, these results suggest that it
may be possible to accurately measure \emph{both} black-hole spins in
intermediate-mass binaries.",1306.2320v1
2015-12-07,An anisotropic spin model of strong spin-orbit-coupled triangular antiferromagnets,"Motivated by the recent experimental progress on the strong
spin-orbit-coupled rare earth triangular antiferromagnet, we analyze the highly
anisotropic spin model that describes the interaction between the
spin-orbit-entangled Kramers' doublet local moments on the triangular lattice.
We apply the Luttinger-Tisza method, the classical Monte Carlo simulation, and
the self-consistent spin wave theory to analyze the anisotropic spin
Hamiltonian. The classical phase diagram includes the 120-degree state and two
distinct stripe ordered phases. The frustration is very strong and
significantly suppresses the ordering temperature in the regimes close to the
phase boundary between two ordered phases. Going beyond the semiclassical
analysis, we include the quantum fluctuations of the spin moments within a
self-consistent Dyson-Maleev spin-wave treatment. We find that the strong
quantum fluctuations melt the magnetic order in the frustrated regions. We
explore the magnetic excitations in the three different ordered phases as well
as in strong magnetic fields. Our results provide a guidance for the future
theoretical study of the generic model and are broadly relevant for strong
spin-orbit-coupled triangular antiferromagnets such as YbMgGaO4, RCd3P3,
RZn3P3, RCd3As3, RZn3As3, and R2O2CO3.",1512.02151v3
2016-09-20,Efficiency of nonspinning templates in gravitational wave searches for aligned-spin binary black holes,"We study the efficiency of nonspinning waveform templates in gravitational
wave searches for aligned-spin binary black holes (BBHs). We use PhenomD, which
is the most recent phenomenological waveform model designed to generate the
full inspiral-merger-ringdown waveforms emitted from BBHs with the spins
aligned with the orbital angular momentum. Here, we treat the effect of
aligned-spins with a single spin parameter $\chi$. We consider the BBH signals
with moderately small spins in the range of $-0.4\leq \chi \leq 0.4$. Using
nonspinning templates, we calculate fitting factors of the aligned-spin signals
in a wide mass range up to $\sim 100 M_{\odot}$. We find that the signals with
negative spins can have higher fitting factors than those with positive spins.
If $\chi = 0.3$, only the highly asymmetric-mass signals can have the fitting
factors exceeding the threshold of 0.965, while the fitting factors for all of
the signals can be larger than the threshold if $\chi = -0.3$. We demonstrate
that the discrepancy between the regions of a positive and a negative spins is
due to the physical boundary ($\eta \leq 0.25$) of the template parameter
space. We also show that the recovered mass parameters can be significantly
biased from the true parameters. We examine the impact of the systematic bias
on the parameter estimation by comparing the bias with the statistical error.",1609.06039v2
2016-10-21,An electric-field representation of the harmonic XY model,"The two-dimensional harmonic XY (HXY) model is a spin model in which the
classical spins interact via a piecewise parabolic potential. We argue that the
HXY model should be regarded as the canonical classical lattice spin model of
phase fluctuations in two-dimensional condensates, as it is the simplest model
that guarantees the modular symmetry of the experimental systems. Here we
formulate a lattice electric-field representation of the HXY model and contrast
this with an analogous representation of the Villain model and the
two-dimensional Coulomb gas with a purely rotational auxiliary field. We find
that the HXY model is a spin-model analogue of a lattice electric-field model
of the Coulomb gas with an auxiliary field, but with a temperature-dependent
vacuum (electric) permittivity that encodes the coupling of the spin vortices
to their background spin-wave medium. The spin vortices map to the Coulomb
charges, while the spin-wave fluctuations correspond to auxiliary-field
fluctuations. The coupling explains the striking differences in the
high-temperature asymptotes of the specific heats of the HXY model and the
Coulomb gas with an auxiliary field. Our results elucidate the propagation of
effective long-range interactions throughout the HXY model (whose interactions
are purely local) by the lattice electric fields. They also imply that global
spin-twist excitations (topological-sector fluctuations) generated by local
spin dynamics are ergodically excluded in the low-temperature phase. We discuss
the relevance of these results to condensate physics.",1610.06692v2
2017-12-08,Numerical Relativity Simulations of Precessing Binary Neutron Star Mergers,"We present the first set of numerical relativity simulations of binary
neutron mergers that include spin precession effects and are evolved with
multiple resolutions. Our simulations employ consistent initial data in general
relativity with different spin configurations and dimensionless spin magnitudes
$\sim 0.1$. They start at a gravitational-wave frequency of $\sim392$~Hz and
cover more than $1$ precession period and about 15 orbits up to merger. We
discuss the spin precession dynamics by analyzing coordinate trajectories,
quasi-local spin measurements, and energetics, by comparing spin aligned,
antialigned, and irrotational configurations. Gravitational waveforms from
different spin configuration are compared by calculating the mismatch between
pairs of waveforms in the late inspiral. We find that precession effects are
not distinguishable from nonprecessing configurations with aligned spins for
approximately face-on binaries, while the latter are distinguishable from a
nonspinning configurations. Spin precession effects are instead clearly visible
for approximately edge-on binaries.
  For the parameters considered here, precession does not significantly affect
the characteristic postmerger gravitational-wave frequencies nor the mass
ejection. Our results pave the way for the modeling of spin precession effects
in the gravitational waveform from binary neutron star events.",1712.02992v1
2020-04-09,Massive Spinning Bosons on the Celestial Sphere,"A natural extension of the Pasterski-Shao-Strominger (PSS) prescription is
described, enabling the map of Minkowski space amplitudes with massive spinning
external legs to the celestial sphere to be performed. An integral
representation for the conformal primary wave function (CPW) of massive
spinning bosons on the celestial sphere is derived explicitly for spin-one and
-two. By analogy with the spin-zero case, the spinning bulk-to-boundary
propagator on Euclidean AdS is employed to extend the massive CPW integral
representation to arbitrary integer spin, and to describe the appropriate
inverse transform of massive spinning CPWs back to the plane wave basis in
Minkowski space. Subsequently, a massive spin-$s$ momentum operator
representation on the celestial sphere is determined, and used in conjunction
with known Lorentz generators to derive Poincar\'e symmetry constraints on
generic massive spinning two-, three- and four-point celestial amplitude
structures. Finally, as a consistency check, three-point Minkowski space
amplitudes of two massless scalars and a spin-one or -two massive boson are
explicitly mapped to the celestial sphere, and the resulting three-point
function coefficients are confirmed to be in exact agreement with the results
obtained from Poincar\'e symmetry constraints.",2004.04309v2
2017-02-14,Quantum spin liquid and magnetic order in a two-dimensional non-symmorphic lattice: considering the distorted Kagome lattice of Volborthite,"The Kagome-lattice-based material, Volborthite, $\mathrm{Cu_3 V_2 O_7 (OH)_2
\cdot 2 H_2 O}$, has been considered as a promising platform for discovery of
unusual quantum ground states due to the frustrated nature of spin
interactions. Here we explore possible quantum spin liquid and magnetically
ordered phases in a two-dimensional non-symmorphic lattice described by $p2gg$
layer space group, which is consistent with the spatial anisotropy of the spin
model derived from density functional theory (DFT) for Volborthite. Using the
projective symmetry group (PSG) analysis and Schwinger boson mean field theory,
we classify possible spin liquid phases with bosonic spinons and investigate
magnetically ordered phases connected to such states. It is shown, in general,
that only translationally invariant mean field states are allowed in
two-dimensional non-symmorphic lattices, which simplifies the classification
considerably. The mean field phase diagram of the DFT-derived spin model is
studied and it is found that possible quantum spin liquid phases are connected
to two types of magnetically ordered phases, a coplanar incommensurate $(q,0)$
spiral order as the ground state and a closely competing coplanar commensurate
$(\pi,\pi)$ spin density wave order. In addition, periodicity enhancement of
the two-spinon continuum, a signature of symmetry fractionalization, is found
in the spin liquid phases connected to the $(\pi,\pi)$ spin density wave order.
We discuss relevance of these results to recent and future experiments on
Volborthite.",1702.04360v2
2016-11-22,Gravitational waves and mass ejecta from binary neutron star mergers: Effect of the stars' rotation,"We present new (3+1) dimensional numerical relativity simulations of the
binary neutron star (BNS) mergers that take into account the NS spins. We
consider different spin configurations, aligned or antialigned to the orbital
angular momentum, for equal and unequal mass BNS and for two equations of
state. All the simulations employ quasiequilibrium circular initial data in the
constant rotational velocity approach, i.e. they are consistent with Einstein
equations and in hydrodynamical equilibrium. We study the NS rotation effect on
the energetics, the gravitational waves (GWs) and on the possible
electromagnetic (EM) emission associated to dynamical mass ejecta. For
dimensionless spin magnitudes of $\chi\sim0.1$ we find that spin-orbit
interactions and also spin-induced-quadrupole deformations affect the
late-inspiral-merger dynamics. The latter is, however, dominated by finite-size
effects. Spin (tidal) effects contribute to GW phase differences up to 5 (20)
radians accumulated during the last eight orbits to merger. Similarly, after
merger the collapse time of the remnant and the GW spectrogram are affected by
the NSs rotation. Spin effects in dynamical ejecta are clearly observed in
unequal mass systems in which mass ejection originates from the tidal tail of
the companion. Consequently kilonovae and other EM counterparts are affected by
spins. We find that spin aligned to the orbital angular momentum leads to
brighter EM counterparts than antialigned spin with luminosities up to a factor
of two higher.",1611.07367v1
2017-04-12,Absorption and generation of femtosecond laser-pulse excited spin currents in non-collinear magnetic bilayers,"Spin currents can be generated on an ultrafast timescale by excitation of a
ferromagnetic (FM) thin film with a femtosecond laser-pulse. Recently, it has
been demonstrated that these ultrafast spin currents can transport angular
momentum to neighbouring FM layers, being able to change both the magnitude and
orientation of the magnetization in the adjacent layer. In this work, both the
generation and absorption of these optically excited spin currents are
investigated. This is done using non-collinear magnetic bilayers, i.e. two FM
layers separated by a conductive spacer. Spin currents are generated in a Co/Ni
multilayer with out-of-plane (OOP) anisotropy, and absorbed by a Co layer with
an in-plane (IP) anisotropy. This behaviour is confirmed by careful analysis of
the laser-pulse induced magnetization dynamics, whereafter it is demonstrated
that the transverse spin current is absorbed very locally near the injection
interface of the IP layer (90% within the first approx. 2 nm). Moreover, it
will also be shown that this local absorption results in the excitation of THz
standing spin waves within the IP layer. The dispersion measured for these high
frequency spin waves shows a discrepancy with respect to the theoretical
predictions, for which a first explanation involving intermixed interface
regions is proposed. Lastly, the spin current generation is investigated using
different number of repeats for the Co/Ni multilayer, which proves to be of
great relevance for identifying the optical spin current generation mechanism.",1704.03746v1
2019-08-02,Tunable pure spin supercurrents and the demonstration of a superconducting spin-wave device,"Recent ferromagnetic resonance experiments and theory of Pt/Nb/Ni8Fe2
proximity-coupled structures strongly suggest that spin-orbit coupling (SOC) in
Pt in conjunction with a magnetic exchange field in Ni8Fe2 are the essential
ingredients to generate a pure spin supercurrent channel in Nb. Here, by
substituting Pt for a perpendicularly magnetized Pt/Co/Pt spin-sink, we are
able to demonstrate the role of SOC, and show that pure spin supercurrent
pumping efficiency across Nb is tunable by controlling the magnetization
direction of Co. By inserting a Cu spacer with weak SOC between Nb and
Pt/(Co/Pt) spin-sink, we also prove that Rashba type SOC is key for forming and
transmitting pure spin supercurrents across Nb. Finally, by engineering these
properties within a single multilayer structure, we demonstrate a prototype
superconducting spin-wave (SW) device in which lateral SW propagation is
gateable via the opening or closing of a vertical pure spin supercurrent
channel in Nb.",1908.00873v3
2022-04-25,Scattering phenomena for spin transport in Kitaev spin liquid,"The Kitaev model exhibits a canonical quantum spin liquid as a ground state
and hosts two fractional quasiparticles, itinerant Majorana fermion and
localized flux excitation. The former can carry heat and spin modulations in
the quantum spin liquid, but the role of the latter remains unknown for the
transport phenomena. Here, we focus on spin transport in the presence of
excited fluxes and report that they yield strong interference in the
propagation of the Majorana fermions, which feel gauge-like potential emergent
around the fluxes. We examine the transient spin dynamics triggered by a pulsed
magnetic field at an edge. In the absence of excited fluxes, the magnetic-field
pulse creates the plane wave of the Majorana fermions, which flows in the
quantum spin liquid. Although this wave does not accompany the change of local
spin moments in bulk, it induces local moments at the side opposite to the edge
under the magnetic-field pulse. We observe the spatial modulation of induced
spin moments when fluxes are excited in the bulk region. This behavior is more
striking than the case of lattice defects. Moreover, we find that, although the
amplitude of the spatial change is almost independent of the distance between
lattice defects, it is strongly enhanced by increasing the distance for the
case of excited fluxes. The difference is understood from the influence on the
itinerant Majorana fermions; the lattice defects change the system locally, but
flux excitations alter all the transfer integrals on the string connecting
them. The present results will provide another route to observing intrinsic
flux excitations distinguished from extrinsic effects such as lattice defects.",2204.11578v1
2022-06-01,Signatures of spin precession and nutation in isolated black-hole binaries,"The spin precession of binary black holes (BBHs) that originate from isolated
high-mass binary stars is determined by the interplay of phenomena such as
tides, winds, accretion, common-envelope evolution, natal kicks, and stellar
core-envelope coupling. In previous work, we identified regions of the
parameter space that may produce BBHs with large misalignments from natal kicks
and high spin magnitudes from three mechanisms - tides, accretion, or
inheritance via minimal core-envelope coupling. Here, we explore the spin
precession of such BBHs using five parameters that describe the amplitude and
frequency with which the orbital angular momentum precesses and nutates about
the total angular momentum, modulating the gravitational-wave emission.
Precession is generally possible for sufficiently strong natal kicks provided
at least one of the black holes is spinning. Nutation is a consequence of
spin-spin coupling and depends on the three spin-up mechanisms. Tidal
synchronization can leave a distinct correlation between the aligned effective
spin and the nutation frequency, but does not produce large nutations. When a
black hole accretes $\gtrsim 20\%$ of its companion's envelope, the precession
frequency and amplitude are large. A much smaller amount of accretion, e.g.,
$\approx 2\%$, is needed to provide a large precession frequency and amplitude
when the accretor is a Wolf-Rayet (WR) star. The inheritance of high natal WR
spins ($\gtrsim 5\%$ of their maximum breakup value) via minimal core-envelope
coupling is the most promising mechanism for producing nutating BBHs, implying
that a measurement of nutation from gravitational-wave observations may suggest
isolated-binary origin with minimal core-envelope coupling.",2206.00391v2
2023-01-18,Charged magnons on the surface of a topological insulator,"We study a system of two-dimensional Dirac electrons (as is realized on the
surface of a 3D topological insulator) coupled to an array of localized spins.
The spins are coupled ferromagnetically to each other, forming an ordered
ground state with low-energy spin-wave excitations (magnons). The Dirac
electrons couple to the spins through a spin-dependent effective Zeeman field.
The out-of-plane effective Zeeman field therefore serves as a Dirac mass that
gaps the electronic spectrum. Once a spin is flipped, it creates a surrounding
domain in which the sign of the Dirac mass is opposite to that of the rest of
the sample. Therefore, an electronic bound state appears on the domain wall, as
predicted by Jackiw and Rebbi. However, in a quantum magnet, a localized spin
flip does not produce an eigenstate. Instead, the eigenstates correspond to
delocalized spin waves (magnons). As in the case of the single flipped spin,
the delocalized magnon also binds an in-gap electronic state. We name this
excitation a `Jackiw-Rebbi-Magnon' (JRM) and study its signature in the dynamic
spin susceptibility. When the sample is tunnel-coupled to an electronic
reservoir, a magnon produced in a system without any electrons hybridizes with
a JRM (which binds a single electron), producing magnon-JRM polaritons. For
such a system, we identify a quantum phase transition when the magnon-JRM
polariton energy falls below that of the fully polarized ferromagnetic ground
state.",2301.07754v2
2003-01-11,Coherent transport of neutral atoms in spin-dependent optical lattice potentials,"We demonstrate the controlled coherent transport and splitting of atomic wave
packets in spin-dependent optical lattice potentials. Such experiments open
intriguing possibilities for quantum state engineering of many body states.
After first preparing localized atomic wave functions in an optical lattice
through a Mott insulating phase, we place each atom in a superposition of two
internal spin states. Then state selective optical potentials are used to split
the wave function of a single atom and transport the corresponding wave packets
in two opposite directions. Coherence between the wave packets of an atom
delocalized over up to 7 lattice sites is demonstrated.",0301169v1
1998-09-02,Group Theoretical Examination of the Relativistic Wave Equations on Curved Spaces. III. Real reducible spaces,"The group theoretical approach to the relativistic wave equations on the real
reducible spaces for spin~0, 1/2 and~1 massless particles is considered. The
invariant wave equations which determine the appropriate irreducible
representations are constructed. The coincidence of these equations with the
general-covariant Klein-Gordon, Weyl and Maxwell equations on the corresponding
spaces is shown. The explicit solutions of these equations possessing a
simplicity and physical transparency are obtained in the form of so-called
""plane waves"" without using the method of separation of variables. The
invariance properties of these ""plane waves"" for the spinless particles under
the group $SO(3,1)$ were used for the construction of the invariant spin~0,1/2
and~1 two-point functions on the $H^3$. Secondly quantized spin~0,1/2 and~1
fields on the ${\Bbb R}^{1}\otimes H^{3}$ are constructed; their propagators
which are their (anti)commutators in different points, are expressed in terms
of the mentioned two-point functions. From here the ${\Bbb R}^{1}\otimes
  SO(3,1)$-invariance follows.",9809011v1
2011-04-29,Tail-induced spin-orbit effect in the gravitational radiation of compact binaries,"Gravitational waves contain tail effects which are due to the back-scattering
of linear waves in the curved space-time geometry around the source. In this
paper we improve the knowledge and accuracy of the two-body inspiraling
post-Newtonian (PN) dynamics and gravitational-wave signal by computing the
spin-orbit terms induced by tail effects. Notably, we derive those terms at 3PN
order in the gravitational-wave energy flux, and 2.5PN and 3PN orders in the
wave polarizations. This is then used to derive the spin-orbit tail effects in
the phasing through 3PN order. Our results can be employed to carry out more
accurate comparisons with numerical-relativity simulations and to improve the
accuracy of analytical templates aimed at describing the whole process of
inspiral, merger and ringdown.",1104.5659v2
2014-03-06,A method for narrow-band searches of continuous gravitational wave signals,"Targeted searches of continuous waves from spinning neutron stars normally
assume that the frequency of the gravitational wave signal is at a given known
ratio with respect to the rotational frequency of the source, e.g. twice for an
asymmetric neutron star rotating around a principal axis of inertia. In fact
this assumption may well be invalid if, for instance, the gravitational wave
signal is due to a solid core rotating at a slightly different rate with
respect to the star crust. In this paper we present a method for {\it
narrow-band} searches of continuous gravitational wave signals from known
pulsars in the data of interferometric detectors. This method assumes source
position is known to high accuracy, while a small frequency and spin-down range
around the electromagnetic-inferred values is explored. Barycentric and
spin-down corrections are done with an efficient time-domain procedure.
Sensitivity and computational efficiency estimates are given and results of
tests done using simulated data are also discussed.",1403.1484v1
2015-06-17,Continuous wave approach for simulating Ferromagnetic Resonance in nanosized elements,"We present a numerical approach to simulate the Ferromagnetic Resonance (FMR)
of micron and nanosized magnetic elements by a micromagnetic finite difference
method. In addition to a static magnetic field a linearly polarized oscillating
magnetic field is utilized to excite and analyze the spin wave excitations
observed by Ferromagnetic Resonance in the space- and time-domain. Our
continuous wave approach (CW) provides an alternative to the common simulation
method, which uses a pulsed excitation of the magnetic system. It directly
models conventional FMR-experiments and permits the determination of the real
and imaginary part of the complex dynamic susceptibility without the need of
post-processing. Furthermore not only the resonance fields, but also
linewidths, ellipticity, phase relations and relative intensities of the
excited spin wave modes in a spectrum can be determined and compared to
experimental data. The magnetic responses can be plotted as a function of
spatial dimensions yielding a detailed visualization of the spin wave modes and
their localization as a function of external magnetic field and frequency. This
is illustrated for the case of a magnetic micron sized stripe.",1506.05292v1
2017-07-04,Dirac electron in a chiral space-time crystal created by counterpropagating circularly polarized plane electromagnetic waves,"The family of solutions to the Dirac equation for an electron moving in an
electromagnetic lattice with the chiral structure created by counterpropagating
circularly polarized plane electromagnetic waves is obtained. At any nonzero
quasimomentum, the dispersion equation has two solutions which specify bispinor
wave functions describing electron states with different energies and mean
values of momentum and spin operators. The inversion of the quasimomentum
results in two other linearly independent solutions. These four basic wave
functions are uniquely defined by eight complex scalar functions (structural
functions), which serve as convenient building blocks of the relations
describing the electron properties. These properties are illustrated in
graphical form over a wide range of quasimomentums. The superpositions of two
basic wave functions describing different spin states and corresponding to (i)
the same quasimomentum (unidirectional electron states with the spin
precession) and (ii) the two equal-in-magnitude but oppositely directed
quasimomentums (bidirectional electron states) are also treated.",1707.01140v2
2018-03-05,Theory of magnetoelastic resonance in a mono-axial chiral helimagnet,"We study magnetoelastic resonance phenomena in a mono-axial chiral helimagnet
belonging to hexagonal crystal class. By computing the spectrum of coupled
elastic wave and spin wave, it is demonstrated how hybridization occurs
depending on their chirality. Specific features of the magnetoelastic resonance
are discussed for the conical phase and the soliton lattice phase stabilized in
the mono-axial chiral helimagnet. The former phase exhibits appreciable
non-reciprocity of the spectrum, the latter is characterized by a
multi-resonance behavior. We propose that the non-reciprocal spin wave around
the forced-ferromagnetic state has potential capability to convert the linearly
polarized elastic wave to circularly polarized one with the chirality opposite
to the spin wave chirality.",1803.01691v2
2018-12-20,One-dimensional two-component fermions with contact even-wave repulsion and SU(2) breaking near-resonant odd-wave attraction,"We consider a one-dimensional (1D) two-component atomic Fermi gas with
contact interaction in the even-wave channel (Yang-Gaudin model) and study the
effect of an SU(2) symmetry breaking near-resonant odd-wave interaction within
one of the components. Starting from the microscopic Hamiltonian, we derive an
effective field theory for the spin degrees of freedom using the bosonization
technique. It is shown that at a critical value of the odd-wave interaction
there is a first-order phase transition from a phase with zero total spin and
zero magnetization to the spin-segregated phase where the magnetization locally
differs from zero.",1812.08677v2
2016-03-21,Engineering chiral density waves and topological band structures by multiple-$Q$ superpositions of collinear up-up-down-down orders,"Magnetic orders characterized by multiple ordering vectors harbor
noncollinear and noncoplanar spin textures and can be a source of unusual
electronic properties through the spin Berry phase mechanism. We theoretically
show that such multiple-$Q$ states are stabilized in itinerant magnets in the
form of superpositions of collinear up-up-down-down (UUDD) spin states, which
accompany the density waves of vector and scalar chirality. The result is drawn
by examining the ground state of the Kondo lattice model with classical
localized moments, especially when the Fermi surface is tuned to be partially
nested by the symmetry-related commensurate vectors. We unveil the instability
toward the multiple-$Q$ UUDD states with chirality density waves, using the
perturbative theory, variational calculations, and large-scale Langevin
dynamics simulations. We also show that the chirality density waves can induce
rich nontrivial topology of electronic structures, such as the massless Dirac
semimetal, Chern insulator with quantized topological Hall response, and
peculiar edge states which depend on the phase of chirality density waves at
the edges.",1603.06646v1
2019-03-11,Wave Functions and Leptonic Decays of Bottom Mesons In the Relativistic Potential Model,"We study the wave functions and purely leptonic decays of $b$-flavored mesons
(pseudoscalars, vector mesons, and higher excited states that are well
established in experiment) in the relativistic potential model based on our
previous works. The wave functions are obtained by solving the wave equation
including the spin-spin and spin-orbit corrections in the effective potential.
The decay constants of $B$, $B^*$ and some of their excited states that have
been found in experiment are calculated with these wave functions. Then the
branching fractions of the purely leptonic decay modes of these bottom mesons
are studied. Our results are in well agreement with experiment data for decay
modes that have been measured in experiments. We also provide predictions for
some yet unmeasured channels, which are useful for experimental test in the
future.",1903.04295v1
2020-12-15,Propagation of polarized gravitational waves,"The propagation of high-frequency gravitational waves can be analyzed using
the geometrical optics approximation. In the case of large but finite
frequencies, the geometrical optics approximation is no longer accurate, and
polarization-dependent corrections at first order in wavelength modify the
propagation of gravitational waves via a spin-orbit coupling mechanism. We
present a covariant derivation from first principles of effective ray equations
describing the propagation of polarized gravitational waves, up to first-order
terms in wavelength, on arbitrary spacetime backgrounds. The effective ray
equations describe a gravitational spin Hall effect for gravitational waves and
are of the same form as those describing the gravitational spin Hall effect of
light, derived from Maxwell's equations.",2012.08363v1
2020-12-21,Inverse Faraday Effect in an Optomagnonic Waveguide,"Single-mode high-index-contrast waveguides have been ubiquitously exploited
in optical, microwave, and phononic structures for achieving enhanced
wave-matter interactions. Although micro-scale optomechanical and
electro-optical devices have been widely studied, optomagnonic devices remain a
grand challenge at the microscale. Here, we introduce a planar optomagnonic
waveguide platform based on a ferrimagnetic insulator that simultaneously
supports single transverse mode of spin waves (magnons) and highly confined
optical modes. The co-localization of spin and light waves gives rise to
enhanced inverse Faraday effect, and as a result, magnons are excited by an
effective magnetic field generated by interacting optical photons. Moreover,
the strongly enhanced optomagnonic interaction allows us to observe such effect
using low-power (milliwatt level) light signals in the continuous-wave form, as
opposed to high-intensity (megawatt peak power) light pulses that are typically
required in magnetic bulk materials or thin films. The optically-driven magnons
are detected electrically with preserved phase coherence, showing the
feasibility for launching spin waves with low-power continuous optical fields.",2012.11119v2
2021-05-23,Multifunctional operation of the double-layer ferromagnetic structure coupled by a rectangular nanoresonator,"The use of spin waves as a signal carrier requires developing the functional
elements allowing for multiplexing and demultiplexing information coded at
different wavelengths. For this purpose, we propose a system of thin
ferromagnetic layers dynamically coupled by a rectangular ferromagnetic
resonator. We show that a single and double, clockwise and counter-clockwise,
circulating modes of the resonator offer a wide possibility of control of
propagating waves. Particularly, at frequency related to the double-clockwise
circulating spin-wave mode of the resonator, the spin wave excited in one layer
is transferred to the second one where it propagates in the backward direction.
Interestingly, the wave excited in the second layer propagates in the forward
direction only in that layer. This demonstrates add-drop filtering, as well as
circulator functionality. Thus, the proposed system can become an important
part of future magnonic technology for signal routing.",2105.10875v1
2022-12-14,Measuring neutron-star distances and properties with gravitational-wave parallax,"Gravitational-wave astronomy allows us to study objects and events invisible
to electromagnetic waves. So far, only signals triggered by coalescing binaries
have been detected. However, as the interferometers' sensitivities improve over
time, we expect to observe weaker signals in the future, e.g. emission of
continuous gravitational waves from spinning, isolated neutron stars. Parallax
is a well-known method, widely used in electromagnetic astronomical
observations, to estimate the distance to a source. In this work, we consider
the application of the parallax method to gravitational-wave searches and
explore possible distance estimation errors. We show that detection of parallax
in the signal from a spinning down source can constrain the neutron star moment
of inertia. For instance, we found that the relative error of the moment of
inertia estimation is smaller than $10\%$ for all sources closer than 300 pc,
for the assumed birth frequency of 700 Hz, ellipticity $\geq 10^{-7}$ and for
two years of observations by the Einstein Telescope, assuming spin down due
purely to quadrupolar gravitational radiation.",2212.07506v3
2023-05-04,Quasilinear theory of Brillouin resonances in rotating magnetized plasmas,"Both spin and orbital angular momentum can be exchanged between a rotating
wave and a rotating magnetized plasma. Through resonances the spin and orbital
angular momentum of the wave can be coupled to both the cyclotron rotation and
the drift rotation of the particles. It is however shown that the Landau and
cyclotron resonance conditions which classically describe resonant
energy-momentum exchange between waves and particles are no longer valid in a
rotating magnetized plasma column. In this case a new resonance condition which
involves a resonant matching between the wave frequency, the cyclotron
frequency modified by inertial effects and the harmonics of the guiding center
rotation is identified. A new quasilinear equation describing orbital and spin
angular momentum exchanges through these new Brillouin resonances is then
derived, and used to expose the wave driven radial current responsible for
angular momentum absorption.",2305.02671v1
2023-10-16,Gravitational wave analogues in spin nematics and cold atoms,"Many large-scale phenomena in our Universe, such as gravitational waves, are
challenging to reproduce in laboratory settings. However, parallels with
condensed matter systems can provide alternative routes for experimental
accessibility. Here we show how spin nematic phases provide a low-energy avenue
for accessing the physics of linearized gravity, and in particular that their
Goldstone modes are relativistically-dispersing massless spin-2 excitations,
analogous to gravitational waves. We show at the level of the action that the
low-energy effective field theory describing a spin nematic is in
correspondence with that of linearized gravity. We then explicitly identify a
microscopic model of a spin-1 magnet whose excitations in the low energy limit
are relativistically dispersing, massless spin-2 Bosons which are in one-to-one
correspondence with gravitational waves and, supported by simulation, outline a
procedure for directly observing these analogue waves in a cold gas of
$^{23}$Na atoms.",2310.10078v1
2014-11-11,Magnonic Charge Pumping via Spin-Orbit Coupling,"The interplay between spin, charge, and orbital degrees of freedom has led to
the development of spintronic devices like spin-torque oscillators, spin-logic
devices, and spin-transfer torque magnetic random-access memories. In this
development spin pumping, the process where pure spin-currents are generated
from magnetisation precession, has proved to be a powerful method for probing
spin physics and magnetisation dynamics. The effect originates from direct
conversion of low energy quantised spin-waves in the magnet, known as magnons,
into a flow of spins from the precessing magnet to adjacent normal metal leads.
The spin-pumping phenomenon represents a convenient way to electrically detect
magnetisation dynamics, however, precessing magnets have been limited so far to
pump pure spin currents, which require a secondary spin-charge conversion
element such as heavy metals with large spin Hall angle or multi-layer layouts
to be detectable. Here, we report the experimental observation of charge
pumping in which a precessing ferromagnet pumps a charge current, demonstrating
direct conversion of magnons into high-frequency currents via the relativistic
spin-orbit interaction. The generated electric current, differently from spin
currents generated by spin-pumping, can be directly detected without the need
of any additional spin to charge conversion mechanism and amplitude and phase
information about the relativistic current-driven magnetisation dynamics. The
charge-pumping phenomenon is generic and gives a deeper understanding of the
recently observed spin-orbit torques, of which it is the reciprocal effect and
which currently attract interest for their potential in manipulating magnetic
information. Furthermore, charge pumping provides a novel link between
magnetism and electricity and may find application in sourcing alternating
electric currents.",1411.2779v1
2019-09-23,"Coherent spin dynamics of solitons in the organic spin chain compounds ($o$-DMTTF)$_2X$ ($X$ = Cl, Br)","We studied the magnetic properties, in particular dynamics, of the correlated
spins associated with natural defects in the organic spin chain compounds
($o$-DMTTF)$_2X$ ($X$ = Br, Cl) by means of electron spin resonance (ESR)
spectroscopy. Both materials exhibit spin-Peierls transitions at temperatures
around 50 K [P. Foury-Leylekian et al. Phys. Rev. B 84, 195134 (2011)], which
allow a separation of the properties of defects inside the chains from the
magnetic response of the spin chains. Indeed, continuous wave ESR measurements
performed over a wide temperature range evidence the evolution of the spin
dynamics from being governed by the spins in the chains at elevated
temperatures to a low-temperature regime which is dominated by defects within
the spin-dimerized chains. Such defects polarize the antiferromagnetically
coupled spins in their vicinity, thereby leading to a finite local alternating
magnetization around the defect site which can be described in terms of a
soliton, i.e. a spin 1/2 quasiparticle built of many correlated spins, pinned
to the defect. In addition, contributions of triplon excitations of the
spin-dimerized state to the ESR response below the transition temperature were
observed which provides a spectroscopic estimate for the spin-gap of the
studied systems. Moreover, details of spin dynamics deep in the spin-Peierls
phase were investigated by pulse ESR experiments which revealed
Rabi-oscillations as signatures of coherent spin dynamics. From a comparison of
the characteristic damping times of the Rabi oscillations with measurements of
the spin relaxation times by means of primary-echo decay and CPMG methods it
becomes evident that inhomogeneities in local magnetic fields strongly
contribute to the soliton decoherence.",1909.10301v2
2006-07-03,Persistent current generation by small polarons in a spin-density wave background,"Persistent current generation by small polarons embedded in a spin-density
wave background in a two dimensional lattice is theoretically studied. When the
embedded small polarons become cores of merons and antimerons (vortices in spin
configuration with winding numbers +1 and -1, respectively), a spin Berry phase
arises from the spiral spin texture of the merons and antimerons, and generates
a spin current around the polarons. Electric current is, however, absent due to
the exact cancellation of the up- and down-spin electron currents. By addition
of an imaginary magnetic flux that negates the fictitious magnetic flux from
the spin Berry phase, the state with merons and antimerons is stabilized and
non-zero electric current appears; this imaginary flux becomes a real one when
side-by-side bipolaronic cores of merons and antimerons are formed, where the
real flux arises spontaneously from the wave function for the motion of the
system as a whole; thus, the bipolarons serve as pumps for the persistent
electric current. It is also shown that a Nernst signal stems from thermal
diffusion of the bipolarons. Implications of the present results to anomalous
properties of cuprate superconductors, including the enhanced Nernst signal,
Drude peak, and Fermi arc are also discussed. The present result suggests the
appearance of the phase variable or ``Nambu-Goldstone'' mode for the
superconductivity without the breakdown of the global U(1) gauge invariance in
the cuprates.",0607033v1
2013-05-26,"Final spin and radiated energy in numerical simulations of binary black holes with equal masses and equal, aligned or anti-aligned spins","The behavior of merging black holes (including the emitted gravitational
waves and the properties of the remnant) can currently be computed only by
numerical simulations. This paper introduces ten numerical relativity
simulations of binary black holes with equal masses and equal spins aligned or
anti-aligned with the orbital angular momentum. The initial spin magnitudes
have $|\chi_i| \lesssim 0.95$ and are more concentrated in the aligned
direction because of the greater astrophysical interest of this case. We
combine this data with five previously reported simulations of the same
configuration, but with different spin magnitudes, including the highest spin
simulated to date, $\chi_i \approx 0.97$. This data set is sufficiently
accurate to enable us to offer improved analytic fitting formulae for the final
spin and for the energy radiated by gravitational waves as a function of
initial spin. The improved fitting formulae can help to improve our
understanding of the properties of binary black hole merger remnants and can be
used to enhance future approximate waveforms for gravitational wave searches,
such as Effective-One-Body waveforms.",1305.5991v2
2014-11-15,Cubic order spin effects in the dynamics and gravitational wave energy flux of compact object binaries,"We investigate cubic-in-spin effects for inspiralling compact objects
binaries, both in the dynamics and the energy flux emitted in gravitational
waves, at the leading post-Newtonian order. We use a Lagrangian formalism to
implement finite-size effects, and extend it at cubic order in the spins, which
corresponds to the octupolar order in a multipolar decomposition. This
formalism allows us to derive the equation of motion, equations of precession
for the spin, and stress-energy tensor of each body in covariant form, and
admits a formal generalization to any multipolar order. For spin-induced
multipoles, i.e. in the case where the rotation of the compact object is sole
responsible for the additional multipole moments, we find a unique structure
for the octupolar moment representing cubic-in-spin effects. We apply these
results to compute the associated effects in the dynamics of compact binary
systems, and deduce the corresponding terms in the energy loss rate due to
gravitational waves. These effects enter at the third-and-a-half post-Newtonian
order, and can be important for binaries involving rapidly spinning black
holes. We provide simplified results for spin-aligned, circular orbits, and
discuss the quantitative importance of the new contributions.",1411.4118v2
2017-02-13,"Lieb and hole-doped ferrimagnetism, spiral, resonating valence-bond states, and phase separation in large-U $AB_{2}$ Hubbard chains","The ground state (GS) properties of the quasi-one-dimensional $AB_2$ Hubbard
model are investigated taking the effects of charge and spin quantum
fluctuations on equal footing. In the strong-coupling regime, we derive a
low-energy Lagrangian suitable to describe the ferrimagnetic phase at half
filling and the phases in the hole-doped regime. At half filling, a
perturbative spin-wave analysis allows us to find the GS energy, sublattice
magnetizations, and Lieb total spin per unit cell of the effective quantum
Heisenberg model, in very good agreement with previous results. In the
challenging hole doping regime away from half filling, we derive the
corresponding $t\textrm{-}J$ Hamiltonian. Under the assumption that charge and
spin quantum correlations are decoupled, the evolution of the second-order
spin-wave modes in the doped regime unveils the occurrence of spatially
modulated spin structures and the emergence of phase separation in the presence
of resonating-valence-bond states. We also calculate the doping-dependent GS
energy and total spin per unit cell, in which case it is shown that the spiral
ferrimagnetic order collapses at a critical hole concentration. Notably, our
analytical results in the doped regime are in very good agreement with density
matrix renormalization group studies, where our assumption of spin-charge
decoupling is numerically supported by the formation of charge-density waves in
anti-phase with the modulation of the magnetic structure.",1702.03609v4
2021-02-19,Observation of higher-order non-Hermitian skin effect,"Hermitian theories play a major role in understanding the physics of most
phenomena. It has been found only in the past decade that non-Hermiticity
enables unprecedented effects such as exceptional points, spectral
singularities and bulk Fermi arcs. Recent studies further show that
non-Hermiticity can fundamentally change the topological band theory, leading
to the non-Hermitian band topology and non-Hermitian skin effect, as confirmed
in one-dimensional (1D) systems. However, in higher dimensions, these
non-Hermitian effects remain unexplored in experiments. Here, we demonstrate
the spin-polarized, higher-order non-Hermitian skin effect in two-dimensional
(2D) acoustic metamaterials. Using a lattice of coupled whisper-gallery
acoustic resonators, we realize a spinful 2D higher-order topological insulator
(HOTI) where the spin-up and spin-down states are emulated by the
anti-clockwise and clockwise modes, respectively. We find that the
non-Hermiticity drives wave localizations toward opposite edge boundaries
depending on the spin polarizations. More interestingly, for finite systems
with both edge and corner boundaries, the higher-order non-Hermitian skin
effect leads to wave localizations toward two corner boundaries for the bulk,
edge and corner states in a spin-dependent manner. We further show that such a
non-Hermitian skin effect enables rich wave manipulation through the loss
configuration in each unit-cell. The reported spin-dependent, higher-order
non-Hermitian skin effect reveals the interplay between higher-order topology
and non-Hermiticity, which is further enriched by the spin degrees of freedom.
This unveils a new horizon in the study of non-Hermitian physics and the design
of non-Hermitian metamaterials.",2102.09825v1
2021-12-10,"Observation and control of collective spin-wave mode-hybridisation in chevron arrays and square, staircase and brickwork artificial spin ices","Dipolar magnon-magnon coupling has long been predicted in nano-patterned
artificial spin systems. However, observation of such phenomena and related
collective spin-wave signatures have until recently proved elusive or limited
to low-power edge-modes which are difficult to measure experimentally. Here we
describe the requisite conditions for dipolar mode-hybridisation, how it may be
controlled, why it was not observed earlier and how strong coupling may occur
between nanomagnet bulk-modes. We experimentally investigate four
nano-patterned artificial spin system geometries: `chevron' arrays, `square',
`staircase' and `brickwork' artificial spin ices. We observe significant
dynamic dipolar-coupling in all systems with relative coupling strengths and
avoided-crossing gaps supported by micromagnetic-simulation results. We
demonstrate reconfigurable mode-hybridisation regimes in each system via
microstate control, and in doing so elucidate the underlying dynamics governing
dynamic dipolar-coupling with implications across reconfigurable magnonics. We
demonstrate that confinement of the bulk-modes via edge effects play a critical
role in dipolar hybridised-modes, and treating nanoislands as a coherently
precessing macro-spins or standing spin-waves are insufficient to capture
experimentally-observed coupling phenomena. Finally, we present a
parameter-space search detailing how coupling strength may be tuned via
nanofabrication-dimensions and material properties.",2112.05354v1
2023-09-04,Unconventional p-wave magnets,"The electronic structure of atoms is organized into even and odd-parity-wave
s, p, d, ... orbitals. An analogous classification of condensed matter phases
emerged with the discovery of conventional s-wave superconductivity in mercury,
followed by the discoveries of unconventional p-wave superfluidity in $^{3}$He
and unconventional d-wave superconductivity in cuprates. To date, the known
counterparts in magnetism have been the conventional ferromagnets with s-wave
spin polarization in the electronic structure, and the recently discovered
altermagnets[1-3] with unconventional d-wave and higher even-parity wave spin
polarization[1,2,4-7]. Here we identify the long-sought magnetic counterpart of
unconventional p-wave superfluidity[8,9] -- the unconventional magnet with
p-wave spin polarization[10,11]. We show that that collinear p-wave
spin-polarization arises in a coplanar spin-symmetry subset of a class of
noncentrosymmetric and noncolinear magnetic crystals with combined
time-reversal and lattice translation symmetry. Contrary to common
assumptions[12-15], we show that noncollinear magnets from this class
universally exhibit nonrelativistic spin splittings and that these odd-parity
wave spin splittings preserve time-reversal symmetry of the band structure. We
predict large spin splitings reaching 500 meV by first-principles calculations
and we identify 60 realistic material candidates. Inspired by the rich and
anisotropic properties of superfluid $^{3}$He[8,9] our result opens up a wide
range of possibilities to investigate unconventional p-wave order parameters in
crystals and their exploitation in spintronics and topological physics[16-21].",2309.01607v2
2023-10-09,Spin susceptibility in interacting two-dimensional semiconductors and bilayer systems at first order: Kohn anomalies and spin density wave ordering,"This work is an analytic theoretical study of a 2D semiconductor with a Fermi
surface that is split by the Zeeman coupling of electron spins to an external
magnetic field in the presence of electron-electron interactions. For the first
time, we calculate the spin susceptibility for long-range and finite-range
interactions diagrammatically, and find a resonant peak structure at the Kohn
anomaly already in first-order perturbation theory. In contrast to the
density-density correlator that is suppressed due to the large electrostatic
energy required to stabilize charge density order, the spin susceptibility does
not suffer from electrostatic screening effects, thus favouring
spin-density-wave order in 2D semiconductors. Our results impose significant
consequences for determining magnetic phases in 2D semiconductors. For example,
a strongly enhanced Kohn anomaly may result in helical ordering of magnetic
impurities due to the RKKY interaction. Furthermore, the spin degree of freedom
can equally represent a layer pseudospin in the case of bilayer materials. In
this case, the external ""magnetic field"" is a combination of layer bias and
interlayer hopping. The sharp peak of the 2D static spin susceptibility may
then be responsible for dipole-density-wave order in bilayer materials at large
enough electron-phonon coupling.",2310.05555v1
2022-01-31,Precisely computing bound orbits of spinning bodies around black holes I: General framework and results for nearly equatorial orbits,"Very large mass ratio binary black hole systems are of interest both as a
clean limit of the two-body problem in general relativity, as well as for their
importance as sources of low-frequency gravitational waves. At lowest order,
the smaller body moves along a geodesic of the larger black hole's spacetime.
Post-geodesic effects include the gravitational self force, which incorporates
the backreaction of gravitational-wave emission, and the spin-curvature force,
which arises from coupling of the small body's spin to the black hole's
spacetime curvature. In this paper, we describe a method for precisely
computing bound orbits of spinning bodies about black holes. Our analysis
builds off of pioneering work by Witzany which demonstrated how to describe the
motion of a spinning body to linear order in the small body's spin. Exploiting
the fact that in the large mass-ratio limit spinning-body orbits are close to
geodesics and using closed-form results due to van de Meent describing
precession of the small body's spin along black hole orbits, we develop a
frequency-domain formulation of the motion which can be solved very precisely.
We examine a range of orbits with this formulation, focusing in this paper on
orbits which are eccentric and nearly equatorial (i.e., the orbit's motion is
$\mathcal{O}(S)$ out of the equatorial plane), but for which the small body's
spin is arbitrarily oriented. We discuss generic orbits with general small-body
spin orientation in a companion paper. We characterize the behavior of these
orbits and show how the small body's spin shifts the frequencies $\Omega_r$ and
$\Omega_\phi$ which affect orbital motion. These frequency shifts change
accumulated phases which are direct gravitational-wave observables,
illustrating the importance of precisely characterizing these quantities for
gravitational-wave observations. (Abridged)",2201.13334v2
2003-06-06,Light scattering observations of spin reversal excitations in the fractional quantum Hall regime,"Resonant inelastic light scattering experiments access the low lying
excitations of electron liquids in the fractional quantum Hall regime in the
range $2/5 \geq \nu \geq 1/3$. Modes associated with changes in the charge and
spin degrees of freedom are measured. Spectra of spin reversed excitations at
filling factor $\nu \gtrsim 1/3$ and at $\nu \lesssim 2/5$ identify a structure
of lowest spin-split Landau levels of composite fermions that is similar to
that of electrons. Observations of spin wave excitations enable determinations
of energies required to reverse spin. The spin reversal energies obtained from
the spectra illustrate the significant residual interactions of composite
fermions. At $\nu = 1/3$ energies of spin reversal modes are larger but
relatively close to spin conserving excitations that are linked to activated
transport. Predictions of composite fermion theory are in good quantitative
agreement with experimental results.",0306179v1
2003-06-08,"Spin-exchange interactions of spin-one bosons in optical lattices: singlet, nematic and dimerized Phases","We consider insulating phases of cold spin-1 bosonic particles with
antiferromagnetic interactions, such as Na-23, in optical lattices. We show
that spin-exchange interactions give rise to several distinct phases, which
differ in their spin correlations. In two- and three- dimensional lattices
insulating phases with odd number of particles per site are always nematic. For
insulating states with even number of particles per site there is always a
spin-singlet phase and there may also be a first-order transition into the
nematic phase. The nematic phase breaks spin rotational symmetry, but preserves
time reversal symmetry, and has gapless spin-wave excitations. The spin singlet
phase does not break spin symmetry and has a gap to all excitations. In
one-dimensional lattices insulating phases with odd number of particles per
site always have a regime where translational symmetry is broken and the ground
state is dimerized. We discuss signatures of various phases in Bragg scattering
and time-of-flight measurements.",0306204v2
2003-11-26,Topological spin pumps I,"We have established a semiclassical kinetic approach for various spin
correlated pumping phenomena incorporating spin rotation in wave functions into
transport equations. We employ this technique to study topological pumps and
illustrate spin pumping in a few models where various spin configurations or
topological motors drive adiabatic pumps. In the Rashba model we find that a
topological spin pump is driven by a meron with positive one half skyrmion
charge, the size of which can be controlled by external gates or Zeeman fields.
In the Dresselhaus model on the other hand, electron spins are pumped out by a
negative meron. We examine effects of Zeeman fields on topological spin pumping
and responses of fermi seas in various pumps. The phenomena of topological
pumping are attributed to topological Stern-Gerlach splitting and occur in a
transverse direction along which charge pumping currents either vanish or are
negligible. The transport equations established here might also be applied for
the studies of anomalous Hall effect and spin Hall effect as demonstrated in
one of appendices.",0311612v3
2005-02-08,Monte Carlo Simulations of Spin-Diffusion in a 2-D Heisenberg Paramagnet,"We study spin diffusion and spin waves in paramagnetic quantum crystals
(solid He-3, for example) by direct simulation of a square lattice of atoms
interacting via a nearest-neighbor Heisenberg exchange Hamiltonian. Recently,
Cowan and Mullin have used a moments method to study spin transport at
arbitrary polarizations. We test their analytic results by calculating the
statistical spin correlation function from molecular dynamics simulations using
a Monte Carlo algorithm to average over initial spin configurations. Since it
is not practical to diagonalize the S=1/2 exchange Hamiltonian for a lattice
which is of sufficient size to study long-wavelength (hydrodynamic)
fluctuations, we instead study the S -> infinity limit and treat each spin as a
vector with a classical equation of motion. We compare our simulations with the
assumptions of the moments method regarding the short-time behavior and the
long exponential tail of the correlation function. We also present our
numerical results for the polarization dependence of the longitudinal spin
diffusion coefficient and the complex transverse spin diffusion coefficient.",0502214v1
2005-06-27,Spin transverse force on spin current in an electric field,"As a relativistic quantum mechanical effect, it is shown that the electric
field exerting a transverse force on an electron spin 1/2 only if the electron
is moving and the spin is polarized along the electric field. The spin force,
analogue to the Lorentz for on an electron charge in a magnetic field, is
perpendicular to the electric field and the spin current polarized anong the
electric field. This spin-dependent force can be used to understand the
zitterbewegung of electron wave packet with spin-orbit coupling and is relevant
to the generation of the charge Hall effect driven by the spin current in
semiconductors.",0506676v2
2006-03-14,Spin-orbit lateral superlattices: energy bands and spin polarization in 2DEG,"The Bloch spinors, energy spectrum and spin density in energy bands are
studied for the two-dimensional electron gas (2DEG) with Rashba spin-orbit (SO)
interaction subject to one-dimensional (1D) periodic electrostatic potential of
a lateral superlattice. The space symmetry of the Bloch spinors with spin
parity is studied. It is shown that the Bloch spinors at fixed quasimomentum
describe the standing spin waves with the wavelength equal to the superlattice
period. The spin projections in these states have the components both parallel
and transverse to the 2DEG plane. The anticrossing of the energy dispersion
curves due to the interplay between the SO and periodic terms is observed,
leading to the spin flip. The relation between the spin parity and the
interband optical selection rules is discussed, and the effect of magnetization
of the SO superlattice in the presence of external electric field is predicted.",0603364v1
2006-05-29,Disturbance of spin equilibrium by current through the interface of noncollinear ferromagnets,"Boundary conditions are derived that determine the penetration of spin
current through an interface of two non-collinear ferromagnets with an
arbitrary angle between their magnetization vectors. We start from the
well-known transformation properties of an electron spin wave functions under
the rotation of a quantization axis. It allows directly find the connection
between partial electric current densities for different spin subbands of the
ferromagnets. No spin scattering is assumed in the near interface region, so
that spin conservation takes place when electron intersects the boundary. The
continuity conditions are found for partial chemical potential differences in
the situation. Spatial distribution of nonequilibrium electron magnetizations
is calculated under the spin current flowing through a contact of two
semi-infinite ferromagnets. The distribution describes the spin accumulation
effect by current and corresponding shift of the potential drop at the
interface. These effects appear strongly dependent on the relation between spin
contact resistances at the interface.",0605694v2
2006-12-08,Spin transport in Heisenberg antiferromagnets,"We analyze spin transport in insulating antiferromagnets described by the XXZ
Heisenberg model in two and three dimensions. Spin currents can be generated by
a magnetic-field gradient or, in systems with spin-orbit coupling,
perpendicular to a time-dependent electric field. The Kubo formula for the
longitudinal spin conductivity is derived analogously to the Kubo formula for
the optical conductivity of electronic systems. The spin conductivity is
calculated within interacting spin-wave theory. In the Ising regime, the XXZ
magnet is a spin insulator. For the isotropic Heisenberg model, the
dimensionality of the system plays a crucial role: In d=3 the regular part of
the spin conductivity vanishes linearly in the zero frequency limit, whereas in
d=2 it approaches a finite zero frequency value.",0612215v1
2003-04-21,Spin symmetry in the anti-nucleon spectrum,"We discuss spin and pseudo-spin symmetry in the spectrum of single nucleons
and single anti-nucleons in a nucleus. As an example we use relativistic mean
field theory to investigate single anti-nucleon spectra. We find a very well
developed spin symmetry in single anti-neutron and single anti-proton spectra.
The dominant components of the wave functions of the spin doublet are almost
identical. This spin symmetry in anti-particle spectra and the pseudo-spin
symmetry in particle spectra have the same origin. However it turns out that
the spin symmetry in anti-nucleon spectra is much better developed than the
pseudo-spin symmetry in normal nuclear single particle spectra.",0304067v2
2007-09-26,Spin-orbital effects in magnetized quantum wires and spin chains,"We present analysis of the interacting quantum wire problem in the presence
of magnetic field and spin-orbital interaction. We show that an interesting
interplay of Zeeman and spin-orbit terms, facilitated by the electron-electron
interaction, results in the spin-density wave (SDW) state when the magnetic
field and spin-orbit axes are orthogonal. We show that this instability is
enhanced in a closely related problem of Heisenberg spin chain with asymmetric
uniform Dzyaloshinskii-Moriya (DM) interaction. Magnetic field in the direction
perpendicular to the DM anisotropy axis results in staggered long-range
magnetic order along the orthogonal to the applied field direction. We explore
consequences of the uniform DM interaction for the electron spin resonance
(ESR) measurements, and point out that they provide way to probe right- and
left-moving excitations of the spin chain separately.",0709.4246v3
2008-07-08,"Spin rotation, spin filtering, and spin transfer in directional tunneling through non-centrosymmetric semiconductor barriers","We consider spin-dependent tunneling through a gallium arsenide barrier, a
material which has no inversion symmetry. We are dealing with free electrons,
with one effective mass and a spin-splitting in the barrier material. When we
take into account both the spin-orbit interaction and the absence of the
inversion symmetry, the evanescent states in the barrier are spin split and the
tunneling process can become rather involved. Along some crystallographic
directions, the incident wave experiences spin filtering during the tunneling.
These results open stimulating perspectives for spin manipulation in tunnel
devices.",0807.1243v3
2010-03-01,The qubit states decoherence in antiferromagnet-based nuclear spin model of quantum register,"This study deals with the further development of nuclear spin model of
scalable quantum register, which presents the one-dimensional chain of the
magnetic atoms with nuclear spins 1/2, substituting the basic atoms in the
plate of nuclear spin-free easy-axis 3D antiferromagnet. The decoherence rates
of one qubit state and entanglement state of two removed qubits and
longitudinal relaxation rates are caused by the interaction of nuclear
spins-qubits with virtual spin waves in antiferromagnet ground state were
calculated. It was considered also one qubit adiabatic decoherence, is caused
by the interaction of nuclear spin of quantum register with nuclear spins of
randomly distributed isotopes, substituting the basic nuclear spin-free
isotopes of antiferromagnet. We have considered finally encoded DFS
(Decoherence-Free Subspaces) logical qubits are constructed on clusters of the
four-physical qubits, given by the two states with zero total angular momentum.",1003.0170v2
2010-04-03,Spin-selective Peierls transition in interacting one-dimensional conductors with spin-orbit interaction,"Interacting one-dimensional conductors with Rashba spin-orbit coupling are
shown to exhibit a spin-selective Peierls-type transition into a mixed
spin-charge-density-wave state. The transition leads to a gap for one-half of
the conducting modes, which is strongly enhanced by electron-electron
interactions. The other half of the modes remains in a strongly renormalized
gapless state and conducts opposite spins in opposite directions, thus
providing a perfect spin filter. The transition is driven by magnetic field and
by spin-orbit interactions. As an example we show for semiconducting quantum
wires and carbon nanotubes that the gap induced by weak magnetic fields or
intrinsic spin-orbit interactions can get renormalized by 1 order of magnitude
up to 10 - 30 K.",1004.0467v2
2010-04-08,Coupling of bonding and antibonding electron orbitals in double quantum dots by spin-orbit interaction,"We perform a systematic exact diagonalization study of spin-orbit coupling
effects for stationary few-electron states confined in quasi two-dimensional
double quantum dots. We describe the spin-orbit-interaction induced coupling
between bonding and antibonding orbitals and its consequences for
magneto-optical absorption spectrum. The spin-orbit coupling for odd electron
numbers (one, three) %only weakly perturbs the ground-state wave functions.
%Nevertheless, %the spin-orbit interaction opens avoided crossings between low
energy excited levels of opposite spin orientation and opposite spatial parity.
For two-electrons the spin-orbit coupling allows for low-energy optical
transitions that are otherwise forbidden by spin and parity selection rules. We
demonstrate that the energies of optical transitions can be significantly
increased by an in-plane electric field but only for odd electron numbers.
Occupation of single-electron orbitals and effects of spin-orbit coupling on
electron distribution between the dots are also discussed.",1004.1250v1
2011-10-06,Spin and pseudospin symmetry along with orbital dependency of the Dirac-Hulthen problem,"The role of the Hulthen potential on the spin and pseudospin symmetry
solutions is investigated systematically by solving the Dirac equation with
attractive scalar S(r) and repulsive vector V(r) potentials. The spin and
pseudospin symmetry along with orbital dependency (pseudospin-orbit and
spin-orbit dependent couplings) of the Dirac equation are included to the
solution by introducing the Hulthen-square approximation. This effective
approach is based on forming the spin and pseudo-centrifugal kinetic energy
term from the square of the Hulthen potential. The analytical solutions of the
Dirac equation for the Hulthen potential with the spin-orbit and
pseudospin-orbit-dependent couplings are obtained by using the Nikiforov-Uvarov
(NU) method. The energy eigenvalue equations and wave functions for various
degenerate states are presented for several spin-orbital, pseudospin-orbital
and radial quantum numbers under the condition of the spin and pseudospin
symmetry. Keywords: Spin and pseudospin symmetry; orbital dependency; Dirac
equation; Hulthen potential; Nikiforov-Uvarov Method.",1110.1225v1
2012-03-21,Persistent narrowing of nuclear-spin fluctuations in InAs quantum dots using laser excitation,"We demonstrate the suppression of nuclear spin fluctuations in an InAs
quantum dot and measure the timescales of the spin narrowing effect. By
initializing for tens of milliseconds with two continuous wave diode lasers,
fluctuations of the nuclear spins are suppressed via the hole assisted dynamic
nuclear polarization feedback mechanism. The fluctuation narrowed state
persists in the dark (absent light illumination) for well over one second even
in the presence of a varying electron charge and spin polarization. Enhancement
of the electron spin coherence time (T2*) is directly measured using coherent
dark state spectroscopy. By separating the calming of the nuclear spins in time
from the spin qubit operations, this method is much simpler than the spin echo
coherence recovery or dynamic decoupling schemes.",1203.4742v1
2012-08-27,Non-adiabatically driven electron in quantum wire with spin-orbit interaction,"An exact solution is derived for the wave function of an electron in a
semiconductor quantum wire with spin-orbit interaction and driven by external
time dependent harmonic confining potential. The formalism allows analytical
expressions for various quantities to be derived, such as spin and pseudo-spin
rotations, energy and occupation probabilities for excited states. It is
demonstrated how perfect spin and pseudo-spin flips can be achieved at high
frequencies of order \omega, the confining potential level spacing. By an
appropriately chosen driving term, spin manipulation can be exactly performed
far into the non-adiabatic regime. Implications for spin-polarised emission and
spin-dependent transport are also discussed.",1208.5359v1
2012-12-15,Transverse spin gradient functional for non-collinear spin density functional theory,"We present a novel functional for spin density functional theory aiming at
the description of non-collinear magnetic structures. The construction of the
functional employs the spin-spiral-wave state of the uniform electron gas as
reference system. We show that the functional depends on transverse gradients
of the spin magnetization, i.e., in contrast to the widely used local spin
density approximation, the functional is sensitive to local changes of the
direction of the spin magnetization. As a consequence the exchange-correlation
magnetic field is not parallel to the spin magnetization and a local
spin-torque is present in the ground state of the Kohn-Sham system. As a
proof-of-principle we apply the functional to a Chromium mono-layer in the
non-collinear ${120^{\circ}}$-N{\'e}el state.",1212.3658v2
2012-12-21,Next-to-next-to-leading order spin-orbit effects in the near-zone metric and precession equations of compact binaries,"We extend our previous work devoted to the computation of the
next-to-next-to-leading order spin-orbit correction (corresponding to 3.5PN
order) in the equations of motion of spinning compact binaries, by: (i)
Deriving the corresponding spin-orbit terms in the evolution equations for the
spins, the conserved integrals of the motion and the metric regularized at the
location of the particles (obtaining also the metric all-over the near zone but
with some lower precision); (ii) Performing the orbital reduction of the
precession equations, near-zone metric and conserved integrals to the center-
of-mass frame and then further assuming quasi-circular orbits (neglecting
gravitational radiation reaction). The results are systematically expressed in
terms of the spin variables with conserved Euclidean norm instead of the
original antisymmetric spin tensors of the pole-dipole formalism. This work
paves the way to the future computation of the next-to-next-to-leading order
spin-orbit terms in the gravitational-wave phasing of spinning compact
binaries.",1212.5520v2
2013-04-04,Dynamics of Antiferromagnets Driven by Spin Current,"When a spin-polarized current flows through a ferromagnetic (FM) metal,
angular momentum is transferred to the background magnetization via
spin-transfer torques. In antiferromagnetic (AFM) materials, however, the
corresponding problem is unsolved. We derive microscopically the dynamics of an
AFM system driven by spin current generated by an attached FM polarizer, and
find that the spin current exerts a driving force on the local staggered order
parameter. The mechanism does not rely on the conservation of spin angular
momentum, nor does it depend on the induced FM moments on top the AFM
background. Two examples are studied: (i) A domain wall is accelerated to a
terminal velocity by purely adiabatic effect where the Walker's break-down is
avoided; and (ii) Spin injection modifies the AFM resonance frequency, and spin
current injection triggers spin wave instability of local moments above a
threshold.",1304.1284v5
2013-04-25,Spin blocker made of semiconductor double quantum well using the Rashba effect,"We propose a lateral spin-blockade device that uses an InGaAs/InAlAs double
quantum well (DQW), where the values of the Rashba spin-orbit parameter
$\alpha_{\rm R}$ are opposite in sign but equal in magnitude between the
constituent quantum wells (QW). By tuning the channel length of DQW and the
magnitude of the externally applied in-plane magnetic field, one can block the
transmission of one spin (e.g., spin-down) component, leading to a
spin-polarized current. Such a spin-blocking effect, brought about by wave
vector matching of the spin-split Fermi surfaces between the two QWs, paves the
way for a new scheme of spin-polarized electric current generation for future
spintronics applications based on semiconductor band engineering.",1304.6992v1
2013-10-23,Effect of Quantum Spin Fluctuation on Scalar Chiral Ordering in the Kondo Lattice Model on a Triangular Lattice,"Spin scalar chiral ordering gives rise to nontrivial topological characters
and peculiar transport properties. We here examine how quantum spin
fluctuations affect the spin scalar chiral ordering in itinerant electron
systems. We take the Kondo lattice model on a triangular lattice, and perform
the linear spin wave analysis in the Chern insulator phases with spin scalar
chiral ordering obtained in the case that the localized spins are classical. We
find that, although the quantum fluctuation destabilizes the spin scalar chiral
phase at 3/4 filling that originates from the perfect nesting of Fermi surface,
it retains the phase at 1/4 filling that is induced by an effective positive
biquadratic interaction. The reduction of the ordered magnetic moment by the
zero-point quantum fluctuation is considerably small, compared with those in
spin-only systems. The results suggest that the Chern insulator at 1/4 filling
remains robust under quantum fluctuations.",1310.6292v1
2013-12-27,Spin Transfer Torque and Electric Current in Helical Edge States in Quantum Spin Hall Devices,"We study the dynamics of a quantum spin Hall edge coupled to a magnet with
its own dynamics. Using spin transfer torque principles, we analyze the
interplay between spin currents in the edge state and dynamics of the axis of
the magnet, and draw parallels with circuit analogies. As a highlighting
feature, we show that while coupling to a magnet typically renders the edge
state insulating by opening a gap, in the presence of a small potential bias,
spin-transfer torque can restore perfect conductance by transferring angular
momentum to the magnet. In the presence of interactions within the edge state,
we employ a Luttinger liquid treatment to show that the edge, when subject to a
small voltage bias, tends to form a unique dynamic rotating spin wave state
that naturally couples into the dynamics of the magnet. We briefly discuss
realistic physical parameters and constraints for observing this interplay
between quantum spin Hall and spin-transfer torque physics.",1312.7303v1
2014-01-03,Spin Liquid Condensate of Spinful Bosons,"We introduce the concept of a bosonic spin liquid condensate (SLC), where
spinful bosons in a lattice form a zero-temperature spin disordered charge
condensate that preserves the spin rotation symmetry, but breaks the U(1)
symmetry due to a spinless order parameter with charge one. It has an energy
gap to all the spin excitations. We show that such SLC states can be realized
in a system of spin $S\ge 2$ bosons. In particular, we analyze the SLC phase
diagram in the spin 2 case using a mean-field variational wave function method.
We show there is a direct analogy between the SLC and the
resonating-valence-bond (RVB) state.",1401.0593v2
2014-03-13,Coupling theory of emergent spin electromagnetic field and electromagnetic field,"In ferromagnetic metals, an effective electromagnetic field which couples to
conduction electron spin is induced by the sd exchange interaction. We
investigate how this effective field, spin electromagnetic field, interacts
with the ordinary electromagnetic field by deriving an effective Hamiltonian
based on the path-integral formalism. It turns out that the dominant coupling
term is the product of the electric field and the spin gauge field. This term
descrives the spin-transfer effect, as was pointed out before. The electric
field couples also to the spin electric field, but this contribution is smaller
than the spin-transfer contribution in the low frequency regime. The magnetic
field couples to the spin magnetic field, and this interaction suggests an
intriguing intrinsic mechanism of frustration in very weak metallic
ferromagnets under a uniform magnetic field. We also propose a voltage
generation mechanism due to a non-linear effect of non-monochromatic spin wave
excitation.",1403.3214v3
2014-04-21,Graphene with wedge disclination in the presence of intrinsic and Rashba spin orbit couplings,"In this article, the modified Kane-Mele Hamiltonian is derived for graphene
with wedge disclination and spin orbit couplings (intrinsic and Rashba). The
wedge disclination changes the flat lattice into the conical lattice and hence
modifies the spin orbit couplings. The Hamiltonian is exactly solved for the
intrinsic spin orbit interaction and perturbatively for the Rashba spin orbit
interaction. It is shown that there exists the Kramer's degenerate midgap
localized spin separated fluxon states around the defect. These zero energy
spin separated states occur at the external magnetic flux value
$\Phi\pm\Delta\Phi$. The external magnetic flux $\Phi$ is introduced to make
the wave-function periodic when the electron circulates around the defect. It
is found that this separation occurs due to the effect of the conical curvature
on the spin orbit coupling. Further, we find these results are robust to the
addition of the Rashba spin orbit interaction which is important for the
application to spintronics and nanoelectronics.",1404.5150v2
2014-09-09,Electron-spin dynamics in elliptically polarized light waves,"We investigate the coupling of the spin angular momentum of light beams with
elliptical polarization to the spin degree of freedom of free electrons. It is
shown that this coupling, which is of similar origin as the well-known
spin-orbit coupling, can lead to spin precession. The spin-precession frequency
is proportional to the product of the laser-field's intensity and its spin
density. The electron-spin dynamics is analyzed by employing exact numerical
methods as well as time-dependent perturbation theory based on the fully
relativistic Dirac equation and on the nonrelativistic Pauli equation that is
amended by a relativistic correction that accounts for the light's spin
density.",1409.2647v2
2014-09-17,Arbitrary Spin Galilean Oscillator,"The so-called Dirac oscillator was proposed as a modification of the free
Dirac equation which reproduces many of the properties of the simple harmonic
oscillator but accompanied by a strong spin-orbit coupling term. It has yet to
be extended successfully to the arbitrary spin S case primarily because of the
unwieldiness of general spin Lorentz invariant wave equations. It is shown here
using the formalism of totally symmetric multispinors that the Dirac oscillator
can, however, be made to accommodate spin by incorporating it into the
framework of Galilean relativity. This is done explicitly for spin zero and
spin one as special cases of the arbitrary spin result. For the general case it
is shown that the coefficient of the spin-orbit term has a 1/S behavior by
techniques which are virtually identical to those employed in the derivation of
the g-factor carried out over four decades ago.",1409.5101v1
2015-04-08,Spin Seebeck Power Conversion,"Spin caloritronics is the science and technology to control spin, charge, and
heat currents in magnetic nanostructures. The spin degree of freedom provides
new strategies for thermolelectric power generation that have not yet been
fully explored. After an elementary introduction into conventional
thermoelectrics and spintronics, we give a brief review of the physics of spin
caloritronics. We discuss spin-dependent thermoelectrics based on the the
two-current model in metallic magnets as well as the spin Seebeck and Peltier
effects that are based on spin wave excitations in ferromagnets. We derive
expressions for the efficiency and figure of merit ZT of several spin
caloritronic devices.",1504.02002v1
2015-04-20,Emergent topological properties in interacting one-dimensional systems with spin-orbit coupling,"We present analysis of a single channel interacting quantum wire problem in
the presence of spin-orbit interaction. The spin-orbit coupling breaks the
spin-rotational symmetry from SU(2) to U(1) and breaks inversion symmetry. The
low-energy theory is then a two band model with a difference of Fermi
velocities $\delta v$. Using bosonization and a two-loop renormalization group
procedure we show that electron-electron interactions can open a gap in the
spin sector of the theory when the interaction strength $U$ is smaller than
$\delta v$ in appropriate units. For repulsive interactions, the resulting
strong coupling phase is of the spin-density-wave type. We show that this phase
has peculiar emergent topological properties. The gapped spin sector behaves as
a topological insulator, with zero-energy edge modes with fractional spin. On
the other hand, the charge sector remains critical, meaning the entire system
is metallic. However, this bulk electron liquid as a whole exhibits properties
commonly associated with the one-dimensional edge states of two-dimensional
spin-Hall insulators, in particular, the conduction of $2e^2/h$ is robust
against nonmagnetic impurities.",1504.05016v2
2015-09-20,Spin-axion coupling,"We establish a new covariant phenomenological model, which describes an
influence of pseudoscalar (axion) field on spins of test massive particles. The
model includes general relativistic equations of particle motion and spin
evolution in background pseudoscalar (axion), electromagnetic and gravitational
fields. It describes both the direct spin-axion coupling of the gradient type
and indirect spin-axion interaction mediated by electromagnetic fields. Special
attention is paid to the direct spin-axion coupling caused by the gradient of
the pseudoscalar (axion) field. We show that it describes a spin precession,
when the pseudoscalar (axion) field is inhomogeneous and/or non-stationary.
Applications of the model, which correspond to the three types of four-vectors
attributed to the gradient of the pseudoscalar (axion) field (time-like,
space-like, and null), are considered in detail. These are the spin precessions
induced by relic cosmological axions, axions distributed around spherically
symmetric static objects, and axions in a gravitational wave field,
respectively. We discuss features of the obtained exact solutions and some
general properties of the axionically induced spin rotation.",1509.06058v2
2016-01-05,Dynamics of interacting fermions in spin-dependent potentials,"Recent experiments with dilute trapped Fermi gases observed that weak
interactions can drastically modify spin transport dynamics and give rise to
robust collective effects including global demagnetization, macroscopic spin
waves, spin segregation, and spin self-rephasing. In this work we develop a
framework for studying the dynamics of weakly interacting fermionic gases
following a spin-dependent change of the trapping potential which illuminates
the interplay between spin, motion, Fermi statistics, and interactions. The key
idea is the projection of the state of the system onto a set of lattice spin
models defined on the single-particle mode space. Collective phenomena,
including the global spreading of quantum correlations in real space, arise as
a consequence of the long-ranged character of the spin model couplings. This
approach achieves good agreement with prior measurements and suggests a number
of directions for future experiments.",1601.01004v3
2016-04-15,Determining the spin-orbit coupling via spin-polarized spectroscopy of magnetic impurities,"We study the spin-resolved spectral properties of the impurity states
associated to the presence of magnetic impurities in two-dimensional, as well
as one-dimensional systems with Rashba spin-orbit coupling. We focus on Shiba
bound states in superconducting materials, as well as on impurity states in
metallic systems. Using a combination of a numerical T-matrix approximation and
a direct analytical calculation of the bound state wave function, we compute
the local density of states (LDOS) together with its Fourier transform (FT). We
find that the FT of the spin-polarized LDOS, a quantity accessible via
spin-polarized STM, allows to accurately extract the strength of the spin-orbit
coupling. Also we confirm that the presence of magnetic impurities is strictly
necessary for such measurement, and that non-spin-polarized experiments cannot
have access to the value of the spin-orbit coupling.",1604.04623v3
2016-07-19,Electrical detection of spiral spin structures in Pt|Cu_2OSeO_3 heterostructures,"The interaction between the itinerant spins in metals and localized spins in
magnetic insulators thus far has only been explored in collinear spin systems,
such as garnets. Here, we report the spin-Hall magnetoresistance (SMR)
sensitive to the surface magnetization of the spin-spiral material, Cu_2OSeO_3.
We experimentally demonstrate that the angular dependence of the SMR changes
drastically at the transition between the helical spiral and the conical spiral
phases. Furthermore, the sign and magnitude of the SMR in the conical spiral
state are controlled by the cone angle. We show that this complex behaviour can
be qualitatively explained within the SMR theory initially developed for
collinear magnets. In addition, we studied the spin Seebeck effect (SSE), which
is sensitive to the bulk magnetization. It originates from the conversion of
thermally excited low-energy spin waves in the magnet, known as magnons, into
the spin current in the adjacent metal contact (Pt). The SSE displays
unconventional behavior where not only the magnitude but also the phase of the
SSE vary with the applied magnetic field.",1607.05630v1
2017-08-28,Observation of quantum spin noise in a 1D light-atoms quantum interface,"We observe collective quantum spin states of an ensemble of atoms in a
one-dimensional light-atom interface. Strings of hundreds of cesium atoms
trapped in the evanescent fiel of a tapered nanofiber are prepared in a
coherent spin state, a superposition of the two clock states. A weak quantum
nondemolition measurement of one projection of the collective spin is performed
using a detuned probe dispersively coupled to the collective atomic observable,
followed by a strong destructive measurement of the same spin projection. For
the coherent spin state we achieve the value of the quantum projection noise 40
dB above the detection noise, well above the 3 dB required for reconstruction
of the negative Wigner function of nonclassical states. We analyze the effects
of strong spatial inhomogeneity inherent to atoms trapped and probed by the
evanescent waves. We furthermore study temporal dynamics of quantum
fluctuations relevant for measurement-induced spin squeezing and assess the
impact of thermal atomic motion. This work paves the road towards observation
of spin squeezed and entangled states and many-body interactions in 1D spin
ensembles.",1708.08387v2
2017-11-20,Precessional dynamics of black hole triples: binary mergers with near-zero effective spin,"The binary black hole mergers detected by Advanced LIGO/Virgo have shown no
evidence of large black hole spins. However, because LIGO/Virgo best measures
the effective combination of the two spins along the orbital angular momentum
($\chi_{\rm eff}$), it is difficult to distinguish between binaries with
slowly-spinning black holes and binaries with spins lying in the orbital plane.
Here, we study the spin dynamics for binaries with a distant black hole
companion. For spins initially aligned with the orbital angular momentum of the
binary, we find that $\chi_{\rm eff}$ ""freezes"" near zero as the orbit decays
through the emission of gravitational waves. Through a population study, we
show that this process predominantly leads to merging black hole binaries with
near-zero $\chi_{\rm eff}$. We conclude that if the detected black hole
binaries were formed in triples, then this would explain their low $\chi_{\rm
eff}$ without the need to invoke near-zero spins or initially large spin-orbit
angles.",1711.07142v2
2018-09-20,Entangling Distant Spin qubits via a Magnetic Domain Wall,"The scalability of quantum networks based on solid-state spin qubits is
hampered by the short range of natural spin-spin interactions. Here, we propose
a scheme to entangle distant spin qubits via the soft modes of an
antiferromagnetic domain wall (DW). As spin qubits, we focus on quantum
impurities (QI's) placed in the vicinity of an insulating antiferromagnetic
thin film. The low-energy modes harbored by the DW are embedded in the
antiferromagnetic bulk, whose intrinsic spin-wave dynamics have a gap that can
exceed the THz range. By setting the QI frequency and the temperature well
within the bulk gap, we focus on the dipolar interaction between the QI and two
soft modes localized at the DW. One is a string-like mode associated with
transverse displacements of the DW position, while the dynamics of the other,
corresponding to planar rotations of the Neel order parameter, constitute a
spin superfluid. By choosing the geometry in which the QI does not couple to
the string mode, we use an external magnetic field to control the gap of the
spin superfluid and the qubit-qubit coupling it engenders. We suggest that a
tunable micron-range coherent coupling between qubits can be established using
common antiferromagnetic materials.",1809.07785v1
2018-07-03,Large spin current generation by the spin Hall effect in mixed crystalline phase Ta thin films,"Manipulation of the magnetization in heavy-metal/ferromagnetic bilayers via
the spin-orbit torque requires high spin Hall conductivity of the heavy metal.
We measure inverse spin Hall voltage using a co-planar wave-guide based
broadband ferromagnetic resonance set-up in Py/Ta system with varying
crystalline phase of Ta. We demonstrate a strong correlation between the
measured spin mixing conductance and spin Hall conductivity with the
crystalline phase of Ta thin films. We found a large spin Hall conductivity of
$-2439~(\hbar/e)~\Omega^{-1}$cm$^{-1}$ for low-resistivity (68 $\mu\Omega-$cm)
Ta film having mixed crystalline phase, which we attribute to an extrinsic
mechanism of the spin Hall effect.",1807.01127v1
2018-10-29,Superconductivity in the Hubbard model: a hidden-order diagnostics from the Luther-Emery phase on ladders,"Short-range antiferromagnetic correlations are known to open a spin gap in
the repulsive Hubbard model on ladders with $M$ legs, when $M$ is even. We show
that the spin gap originates from the formation of correlated pairs of
electrons with opposite spin, captured by the hidden ordering of a spin-parity
operator. Since both spin gap and parity vanish in the two-dimensional limit,
we introduce the fractional generalization of spin parity and prove that it
remains finite in the thermodynamic limit. Our results are based upon
variational wave functions and Monte Carlo calculations: performing a finite
size-scaling analysis with growing $M$, we show that the doping region where
the parity is finite coincides with the range in which superconductivity is
observed in two spatial dimensions. Our observations support the idea that
superconductivity emerges out of spin gapped phases on ladders, driven by a
spin-pairing mechanism, in which the ordering is conveniently captured by the
finiteness of the fractional spin-parity operator.",1810.12268v2
2014-06-05,Electric control of spin injection into a ferroelectric semiconductor,"Electric-field control of spin-dependent properties has become one of the
most attractive phenomena in modern materials research due the promise of new
device functionalities. One of the paradigms in this approach is to
electrically toggle the spin polarization of carriers injected into a
semiconductor using ferroelectric polarization as a control parameter. Using
first-principles density functional calculations, we explore the effect of
ferroelectric polarization of electron-doped BaTiO3 (n-BaTiO3) on the
spin-polarized transmission across the SrRuO3/n-BaTiO3 (001) interface. Our
study reveals that the interface transmission is negatively spin-polarized and
that ferroelectric polarization reversal leads to a change in the transport
spin polarization from -65% to -98%. We show that this effect stems from the
large difference in Fermi wave vectors between up- and down-spins in
ferromagnetic SrRuO3 and a change in the transport regime driven by
ferroelectric polarization switching. The predicted sizeable change in the spin
polarization provides a non-volatile mechanism to electrically control spin
injection in semiconductor-based spintronics devices.",1406.1434v1
2019-06-26,Electric Dipole Spin Resonance of 2D Semiconductor Spin Qubits,"Monolayer transition metal dichalcogenides (TMDs) offer a novel
two-dimensional platform for semiconductor devices. One such application,
whereby the added low dimensional crystal physics (i.e. optical spin selection
rules) may prove TMDs a competitive candidate, are quantum dots as qubits. The
band structure of TMD monolayers offers a number of different degrees of
freedom and combinations thereof as potential qubit bases, primarily electron
spin, valley isospin and the combination of the two due to the strong spin
orbit coupling known as a Kramers qubit. Pure spin qubits in monolayer MoX$_2$
(where X=S or Se) can be achieved by energetically isolating a single valley
and tuning to a spin degenerate regime within that valley by a combination of a
sufficiently small quantum dot radius and large perpendicular magnetic field.
Within such a TMD spin qubit, we theoretically analyse single qubit rotations
induced by electric dipole spin resonance. We employ a rotating wave
approximation within a second order time dependent Schrieffer-Wolf effective
Hamiltonian to derive analytic expressions for the Rabi frequency of single
qubit oscilations, and optimise the mechanism or the parameters to show
oscilations up to $250\,{\rm MHz}$.",1906.11350v1
2020-03-14,Position and spin in relativistic quantum mechanics,"The problem of the position and spin in relativistic quantum mechanics is
analyzed in detail. It is definitively shown that the position and spin
operators in the Foldy-Wouthuysen representation (but not in the Dirac one) are
quantum-mechanical counterparts of the classical position and spin variables.
The probabilistic interpretation is valid only for Foldy-Wouthuysen wave
functions. The relativistic spin operators are discussed. The spin-orbit
interaction does not exist for a free particle if the conventional operators of
the orbital angular momentum and the rest-frame spin are used. Alternative
definitions of the orbital angular momentum and the spin are based on
noncommutative geometry, do not satisfy standard commutation relations, and can
allow the spin-orbit interaction.",2003.06572v2
2021-02-18,Spin distribution of binary black holes formed in open clusters,"We performed direct N-body simulations of open clusters with four different
metallicities. To investigate the effective spins of merging binary black holes
(BBHs) originated from these open clusters, we calculated the spin evolution of
Wolf-Rayet (WR) stars with close companion stars (BBH progenitors), taking into
account stellar wind mass loss and tidal spin-up of the WR stars. We found that
BBH progenitors with smaller semi-major axes evolve to merging BBHs with
greater effective spins because of strong tidal forces. In the local Universe,
about 16% of merging BBHs get effective spins larger than 0.1 even if BHs and
their progenitors do not get spin angular momenta other than tidal forces
exerted by their companion stars. If we assume that WR stars have flat and
isotropic distribution of dimensionless spins just after common envelope
phases, the effective spin distribution of merging BBHs is similar to that
inferred from gravitational wave observations with LIGO and Virgo.",2102.09323v1
2021-10-21,Extrinsic spin angular momentum carried by plasmonic vortex in terahertz cylindrical corrugated waveguide,"An electromagnetic surface wave carrying orbital angular momentum (AM) is
called plasmonic vortex that also carries spin AM originating from evanescent
field. In this study, spin and orbital AM of plasmonic vortex in a terahertz
cylindrical corrugated waveguide (CCW) are analyzed. We report the extrinsic
spin AM of the plasmonic vortex for the first time. The extrinsic spin AM is
produced by the rotation of the polarization of the plasmonic vortex whose
rotation axis is positioned at the vicinity of the CCW wall. The extrinsic spin
AM depends on the intrinsic orbital AM and radius of CCW. The plasmonic vortex
with sufficiently large orbital AM carries large spin AM per photon. This large
extrinsic spin AM expands degree of freedom of the spin AM and would be applied
to various terahertz technologies.",2110.10893v1
2021-05-20,Spin-orbital-momentum locking under odd-parity magnetic quadrupole ordering,"Odd-parity magnetic and magnetic toroidal multipoles in the absence of both
spatial-inversion and time-reversal symmetries are sources of multiferroic and
nonreciprocal optical phenomena. We investigate electronic states caused by an
emergent odd-parity magnetic quadrupole (MQ) as a representative example of
magnetic odd-parity multipoles. It is shown that spontaneous ordering of the MQ
leads to an antisymmetric spin-orbital polarization in momentum space, which
corresponds to a spin-orbital momentum locking at each wave vector. By symmetry
argument, we show that the orbital or sublattice degree of freedom is
indispensable to give rise to the spin-orbital momentum locking. We demonstrate
how the electronic band structures are modulated by the MQ ordering in the
three-orbital system, in which the MQ is activated by the spin-dependent
hybridization between the orbitals with different spatial parities. The
spin-orbital momentum locking is related with the microscopic origin of
cross-correlated phenomena, e.g., the magnetic-field-induced symmetric and
antisymmetric spin polarization in the band structure, the current-induced
distortion, and the magnetoelectric effect. We also discuss similar
spin-orbital momentum locking in antiferromagnet where the MQ degree of freedom
is activated through the antiferromagnetic spin structure in a sublattice
system.",2105.09444v1
2021-05-28,Spin-orbit interactions of transverse sound,"Spin-orbit interactions (SOIs) endow light with intriguing properties and
applications such as photonic spin-Hall effects and spin-dependent vortex
generations. However, it is counterintuitive that SOIs can exist for sound,
which is a longitudinal wave that carries no intrinsic spin. Here, we
theoretically and experimentally demonstrate that airborne sound can possess
artificial transversality in an acoustic micropolar metamaterial and thus carry
both spin and orbital angular momentum. This enables the realization of
acoustic SOIs with rich phenomena beyond those in conventional acoustic
systems. We demonstrate that acoustic activity of the metamaterial can induce
coupling between the spin and linear crystal momentum k, which leads to
negative refraction of the transverse sound. In addition, we show that the
scattering of the transverse sound by a dipole particle can generate
spin-dependent acoustic vortices via the geometric phase effect. The acoustic
SOIs can provide new perspectives and functionalities for sound manipulations
beyond the conventional scalar degree of freedom and may open an avenue to the
development of spin-orbit acoustics.",2105.13558v1
2021-09-16,Ground States of Heisenberg Spin Clusters from Projected Hartree-Fock Theory,"We apply Projected Hartree-Fock theory (PHF) for approximating ground states
of Heisenberg spin clusters. Spin-rotational, point-group and
complex-conjugation symmetry are variationally restored from a broken-symmetry
mean-field reference, where the latter corresponds to a product of local spin
states. A fermionic formulation of the Heisenberg model furnishes a conceptual
connection to PHF applications in quantum chemistry and detailed equations for
a self-consistent field optimization of the reference state are provided.
Different PHF variants are benchmarked for ground-state energies and spin-pair
correlation functions of antiferromagnetic spin rings and three different
polyhedra, with various values of the local spin-quantum number s. The low
computational cost and the compact wave-function representation make PHF a
promising complement to existing approaches for ground states of molecular spin
clusters, particularly for large s and moderately large N. The present work may
also motivate future explorations of more accurate post-PHF methods for
Heisenberg spin clusters.",2109.08041v1
2021-09-22,Hopfion Dynamics in Chiral Magnets,"Resonant spin dynamics of topological spin textures are correlated with their
topological nature, which can be employed to understand this nature. In this
study, we present resonant spin dynamics of three-dimensional topological spin
texture, i.e., Neel and Bloch hopfions. Using micromagnetic simulations, we
stabilize Bloch and Neel hopfions with bulk and interfacial
Dzyaloshinskii-Moriya interaction (DMI), respectively. We identify the ground
state spin configuration of both hopfions, effects of anisotropies, geometric
confinements, and demagnetizing fields. To confirm topological nature, Hopf
number is calculated for each spin texture. Then, we calculate the resonance
frequencies and spin-wave modes of spin precessions under multiple magnetic
fields. Unique resonance frequencies and specific magnetic field dependence can
help to guide experimental studies to identify the three-dimensional
topological spin texture of hopfions in functioning chiral magnets when imaging
is not possible.",2109.10758v1
2021-12-21,Spin accumulation without spin current,"The spin Hall (SH) effect is a phenomenon in which the spin current flows
perpendicular to an applied electric field and causes the spin accumulation at
the boundaries. However, in the presence of spin-orbit couplings, the spin
current is not well defined. Here, we calculate the spin response to an
electric-field gradient, which naturally appears at the boundaries. We derive a
generic formula using the Bloch wave functions and the phenomenological
relaxation time. We also calculate the response for the uniform Rashba model
with $\delta$-function nonmagnetic disorder within the first-order Born
approximation and corresponding vertex corrections. We find the nonzero spin
accumulation, although the SH conductivity exactly vanishes.",2112.11043v3
2024-01-12,Spin Resonance Spectroscopy with an Electron Microscope,"Coherent spin resonance methods, such as nuclear magnetic resonance and
electron spin resonance spectroscopy, have led to spectrally highly sensitive,
non-invasive quantum imaging techniques. Here, we propose a pump-probe spin
resonance spectroscopy approach, designed for electron microscopy, based on
microwave pump fields and electron probes. We investigate how quantum spin
systems couple to electron matter waves through their magnetic moments and how
the resulting phase shifts can be utilized to gain information about the states
and dynamics of these systems. Notably, state-of-the-art transmission electron
microscopy provides the means to detect phase shifts almost as small as that
due to a single electron spin. This could enable state-selective observation of
spin dynamics on the nanoscale and indirect measurement of the environment of
the examined spin systems, providing information, for example, on the atomic
structure, local chemical composition and neighboring spins.",2401.06496v1
2022-04-11,Curvilinear spin-wave dynamics beyond the thin-shell approximation: Magnetic nanotubes as a case study,"Surface curvature of magnetic systems can lead to many static and dynamic
effects which are not present in flat systems of the same material. These
emergent magnetochiral effects can lead to frequency nonreciprocity of spin
waves, which has been shown to be a bulk effect of dipolar origin and is
related to a curvature-induced symmetry breaking in the magnetic volume
charges. So far, such effects have been investigated theoretically mostly for
thin shells, where the spatial profiles of the spin waves can be assumed to be
homogeneous along the thickness. Here, using a finite-element dynamic-matrix
approach, we investigate the transition of the spin-wave spectrum from thin to
thick curvilinear shells, at the example of magnetic nanotubes in the vortex
state. With increasing thickness, we observe the appearance of higher-order
radial modes which are strongly hybridized and resemble the
perpendicular-standing-waves (PSSWs) in flat films. Along with an increasing
dispersion asymmetry, we uncover the curvature-induced non-reciprocity of the
mode profiles. This is explained in a very simple picture general for thick
curvilinear shells, considering the inhomogeneity of the emergent geometric
volume charges along the thickness of the shell. Such curvature-induced
mode-profile asymmetry also leads to non-reciprocal hybridization which can
facilitate unidirectional spin-wave propagation. With that, we also show how
curvature allows for nonlinear three-wave splitting of a higher-order radial
mode into secondary modes which can also propagate unidirectionally. We believe
that our study provides a significant contribution to the understanding of the
spin-wave dynamics in curvilinear magnetic systems, but also advertises these
for novel magnonic applications.",2204.05065v1
1993-09-29,A Bosonic Mean-Field Theory for Frustrated Heisenberg Antiferromagnets in Two Dimensions,"We use a recently developed bosonic mean-field theory (MFT) to study the
ordered ground states of frustrated Heisenberg antiferromagnets (FHAFM) in two
dimensions. We emphasize the role of condensates in satisfying the MF
variational equations and their relation to spin correlation functions at low
temperatures. Our results are similar to those obtained using Schwinger boson
MFT. However, we emphasize here that our MFT has three bosons at each site and
that it is not necessary to rotate the quantization axes on appropriate
sub-lattices to align all the spins ferromagnetically. This MFT is also closely
related to a new spin-wave theory which enables us to obtain the spin-wave
spectrum easily (without any rotation of axes) for an entire class of
three-dimensionally ordered states. For the FHAFM on a triangular lattice, we
use this theory to compute the spin-wave spectrum for all values of $~J_2 ~/J_1
~$ and demonstrate the phenomenon of order from disorder. (1 figure not
included. Hard copy available on request.)",9309054v1
1997-02-05,Landau Theory of Stripe Phases in Cuprates and Nickelates,"We consider a Landau theory of coupled charge and spin-density wave order
parameters as a simple model for the ordering that has been observed
experimentally in the La_2NiO_4 and La_2CuO_4 families of doped
antiferromagnets. The period of the charge-density wave is generically half
that of the spin-density wave, or equivalently the charges form antiphase
domain walls in the antiferromagnetic order. A sharp distinction exists between
the case in which the ordering is primarily charge driven (which produces a
sequence of transitions in qualitative agreement with experiment) or spin
driven (which does not). We also find that stripes with non-collinear spin
order (i.e. spiral phases) are possible in a region of the phase diagram where
the transition is spin driven; the spiral is circular only when there is no
charge order, and is otherwise elliptical with an eccentricity proportional to
the magnitude of the charge order.",9702055v1
1997-03-25,Phase Diagram of the Half-Filled Extended Hubbard Model in Two Dimensions,"We consider an extended Hubbard model of interacting fermions on a lattice.
The fermion kinetic energy corresponds to a tight binding Hamiltonian with
nearest neighbour (-t) and next nearest neighbour (t') hopping matrix elements.
In addition to the onsite Hubbard interaction (U) we also consider a nearest
neighbour repulsion (V). We obtain the zero temperature phase diagram of our
model within the Hartree-Fock approximation. We consider ground states having
charge and spin density wave ordering as well as states with orbital
antiferromagnetism or spin nematic order. The latter two states correspond to
particle-hole binding with $d_{x^2-y^2}$ symmetry in the charge and spin
channels respectively. For $t' = 0$, only the charge density wave and spin
density wave states are energetically stable. For non-zero t', we find that
orbital antiferromagnetism (or spin nematic) order is stable over a finite
portion of the phase diagram at weak coupling. This region of stability is seen
to grow with increasing values of t'.",9703213v1
1999-02-10,Low Temperature Static and Dynamic Behavior of the Two-Dimensional Easy-Axis Heisenberg Model,"We apply the self-consistent harmonic approximation (SCHA) to study static
and dynamic properties of the two-dimensional classical Heisenberg model with
easy-axis anisotropy. The static properties obtained are magnetization and spin
wave energy as functions of temperature, and the critical temperature as a
function of the easy-axis anisotropy. We also calculate the dynamic correlation
functions using the SCHA renormalized spin wave energy. Our analytical results,
for both static properties and dynamic correlation functions, are compared to
numerical simulation data combining cluster-Monte Carlo algorithms and Spin
Dynamics. The comparison allows us to conclude that far below the transition
temperature, where the SCHA is valid, spin waves are responsible for all
relevant features observed in the numerical simulation data; topological
excitations do not seem to contribute appreciably. For temperatures closer to
the transition temperature, there are differences between the dynamic
correlation functions from SCHA theory and Spin Dynamics; these may be due to
the presence of domain walls and solitons.",9902149v1
1999-02-11,Neutron Scattering Study of Spin Density Wave Order in the Superconducting State of Excess-Oxygen-Doped La2CuO4+y,"We report neutron scattering measurements of spin density wave order within
the superconducting state of a single crystal of predominately stage-4
La2CuO4+y with a Tc(onset) of 42 K. The low temperature elastic magnetic
scattering is incommensurate with the lattice and is characterized by
long-range order in the copper-oxide plane with the spin direction identical to
that in the insulator. Between neighboring planes, the spins exhibit
short-range correlations with a stacking arrangement reminiscent of that in the
undoped antiferromagnetic insulator. The elastic magnetic peak intensity
appears at the same temperature within the errors as the superconductivity,
suggesting that the two phenomena are strongly correlated. These observations
directly reveal the persistent influence of the antiferromagnetic order as the
doping level increases from the insulator to the superconductor. In addition,
our results confirm that spin density wave order for incommensurabilities near
1/8 is a robust feature of the La2CuO4-based superconductors.",9902157v2
2000-01-04,Roton Instability of the Spin Wave Excitation in the Fully Polarized Quatum Hall State and the Phase Diagram at $ν= 2$,"We consider the effect of interactions on electrons confined to two
dimensions at Landau level filling $\nu=2$, with the specific aim to determine
the range of parameters where the fully polarized state is stable. We calculate
the charge and the spin density collective modes in random phase approximation
(RPA) including vertex corrections (also known as time dependent Hartree Fock),
and treating the Landau level mixing accurately within the subspace of a single
particle hole pair. It is found that the spin wave excitation mode of the fully
polarized state has a roton minimum which deepens as a result of the
interaction induced Landau level mixing, and the energy of the roton vanishes
at a critical Zeeman energy signaling an instability of the fully polarized
state at still lower Zeeman energies. The feasibility of the experimental
observation of the roton minimum in the spin wave mode and its softening will
be discussed. The spin and charge density collective modes of the unpolarized
state are also considered, and a phase diagram for the $\nu =2$ state as a
function of $r_{S}$ and the Zeeman energy is obtained.",0001036v1
2005-06-24,Spin dynamics of the quasi two dimensional spin-1/2 quantum magnet Cs_2CuCl_4,"We study dynamical properties of the anisotropic triangular quantum
antiferromagnet Cs_2CuCl_4. Inelastic neutron scattering measurements have
established that the dynamical spin correlations cannot be understood within a
linear spin wave analysis. We go beyond linear spin wave theory by taking
interactions between magnons into account in a 1/S expansion. We determine the
dynamical structure factor and carry out extensive comparisons with
experimental data. We find that compared to linear spin wave theory a
significant fraction of the scattering intensity is shifted to higher energies
and strong scattering continua are present. However, the 1/S expansion fails to
account for the experimentally observed large quantum renormalization of the
exchange energies.",0506667v1
2006-01-02,Three--body Correlation Effects on the Spin Dynamics of Double--Exchange Ferromagnets,"We present a variational calculation of the spin wave excitation spectrum of
double--exchange ferromagnets in different dimensions. Our theory recovers the
Random Phase approximation and 1/S expansion results as limiting cases and can
be used to study the intermediate exchange coupling and electron concentration
regime relevant to the manganites. In particular, we treat exactly the long
range three--body correlations between a Fermi sea electron--hole pair and a
magnon excitation and show that they strongly affect the spin dynamics in the
parameter range relevant to experiments in the manganites. The manifestations
of these correlations are many-fold. We demonstrate that they significantly
change the ferromagnetic phase boundary. In addition to a decrease in the
magnon stiffness, we obtain an instability of the ferromagnetic state against
spin wave excitations close to the Brillouin zone boundary.Within a range of
intermediate concentrations, we find a strong softening of the spin wave
dispersion as compared to the Heisenberg ferromagnet with the same stiffness,
which changes into hardening for other concentrations. We discuss the relevance
of these results to experiments in colossal magnetoresistance ferromagnets.",0601025v2
2006-02-02,Spin waves in the Frustrated Kagome Lattice Antiferromagnet KFe3(OH)6(SO4)2,"The spin wave excitations of the ideal S=5/2 Kagome lattice antiferromagnet
KFe3(OH)6(SO4)2 have been measured using high-resolution inelastic neutron
scattering. We directly observe a flat mode which corresponds to a lifted ""zero
energy mode,"" verifying a fundamental prediction for the Kagome lattice. A
simple Heisenberg spin Hamiltonian provides an excellent fit to our spin wave
data. The antisymmetric Dzyaloshinskii-Moriya interaction is the primary source
of anisotropy and explains the low temperature magnetization and spin
structure.",0602036v2
2006-04-10,Impurity Scattering of Wave Packets on a Lattice,"Quantum transport in a lattice is distinct from its counterpart in continuum
media. Even a free wave packet travels differently in a lattice than in the
continuum. We describe quantum scattering in a one dimensional lattice using
three different formulations and illustrate characteristics of quantum
transport such as resonant transmission. We demonstrate the real time
propagation of a wave packet and its phase shift due to impurity
configurations. Spin-flip scattering is also taken into account in a spin chain
system. We show how individual spins in the chain evolve as a result of a
spin-flip interaction between an incoming electron and a spin chain.",0604261v1
2007-02-21,"Spin waves throughout the Brillouin zone and magnetic exchange coupling in ferromagnetic metallic manganites La$_{1-x}$Ca$_{x}$MnO$_3$ ($x=0.25,0.30$)","Using time-of-flight and triple-axis inelastic neutron spectroscopy, we
determine spin wave excitations throughout the Brillouin zone for ferromagnetic
manganites La$_{1-x}$Ca$_x$MnO$_3$ ($x=0.25,0.3$) in their low temperature
metallic states. While spin wave excitations in the long wavelength limit (spin
stiffness $D$) have similar values for both compounds, the excitations near the
Brillouin zone boundary of La$_{0.7}$Ca$_{0.3}$MnO$_3$ are considerable
softened in all symmetry directions compared to that of
La$_{0.75}$Ca$_{0.25}$MnO$_3$. A Heisenberg model with the nearest neighbor and
the fourth neighbor exchange interactions can describe the overall dispersion
curves fairly well. We compare the data with various theoretical models
describing the spin excitations of ferromagnetic manganites.",0702504v1
2003-11-04,Avoiding superluminal propagation of higher spin waves via projectors onto W^2 invariant subspaces,"We propose to describe higher spins as invariant subspaces of the Casimir
operators of the Poincar\'{e} Group, P^{2}, and the squared Pauli-Lubanski
operator, W^{2}, in a properly chosen representation, \psi(p) (in momentum
space), of the Homogeneous Lorentz Group. The resulting equation of motion for
any field with s\neq0 is then just a specific combination of the respective
covariant projectors. We couple minimally electromagnetism to this equation and
show that the corresponding wave fronts of the classical solutions propagate
causally. Furthermore, for (s,0)+(0,s) representations, the formalism predicts
the correct gyromagnetic factor, g_{s}=1/s. The advocated method allows to
describe any higher spin without auxiliary conditions and by one covariant
matrix equation alone. This master equation is only quadratic in the momenta
and its dimensionality is that of \psi(p). We prove that the suggested master
equation avoids the Velo-Zwanziger problem of superluminal propagation of
higher spin waves and points toward a consistent description of higher spin
quantum fields.",0311055v2
2001-11-27,"Parity Doubling, Zitterbewegung, and Rest Mass for Spin 1","A 6-component ""wave function"" (not field, but S-matrix interpretable) for a
massive spin-1 particle parallels the Dirac ""chirality-doubled"" 4-component
wave function for a spin-1/2 particle, by pairing two wave functions for same
spin but opposite ""handedness"". The correlated ""opposite-parity"" pair of
complex 3-vectors defines a fluctuating spin-correlated lightlike ``internal
velocity"" as well as an independent ""external rapidity"". Extension from
fermions to vector bosons of the velocity-fluctuation (""zitterbewegung"")
interpretation of rest mass weakens theoretical motivation for elementary
scalar bosons.",0111250v1
2005-01-01,Equatorial and related non-equilibrium states in magnetization dynamics of ferromagnets: Generalization of Suhl's spin-wave instabilities,"We investigate the nonlinear dynamics underlying the evolution of a 2-D
nanoscale ferromagnetic film with uniaxial anisotropy in the presence of
perpendicular pumping. Considering the associated Landau-Lifshitz spin
evolution equation with Gilbert damping together with Maxwell equation for the
demagnetization field, we study the dynamics in terms of the stereographic
variable. We identify several new fixed points for suitable choice of external
field in a rotating frame of reference. In particular, we identify explicit
equatorial and related fixed points of the spin vector in the plane transverse
to the anisotropy axis when the pumping frequency coincides with the amplitude
of the static parallel field. We then study the linear stability of these novel
fixed points under homogeneous and spin wave perturbations and obtain a
generalized Suhl's instability criterion, giving the condition for exponential
growth of P-modes under spin wave perturbations. Two parameter phase diagrams
(in terms of amplitudes of static parallel and oscillatory perpendicular
magnetic fields) for stability are obtained, which differ qualitatively from
those for the conventional ferromagnetic resonance near thermal equilibrium and
are amenable to experimental tests.",0501002v2
2004-02-21,Topological spin transport of photons: the optical Magnus Effect and Berry Phase,"The paper develops a modified geometrical optics (GO) of smoothly
inhomogeneous isotropic medium, which takes into account two topological
phenomena: Berry phase and the optical Magnus effect. By using the analogy
between a quasi-classical motion of a quantum particle with a spin and GO of an
electromagnetic wave in smoothly inhomogeneous media, we have introduced the
standard gauge potential associated with the degeneracy in the wave momentum
space. This potential corresponds to the Dirac-monopole-like field (Berry
curvature), which causes the topological spin (polarization) transport of
photons. The deviations of waves of right-hand and left-hand helicity occur in
the opposite directions and orthogonally to the principal direction of motion.
This produces a spin current directed across the principal motion. The
situation is similar to the anomalous Hall effect for electrons. In addition, a
simple scheme of the experiment allowing one to observe the topological spin
splitting of photons has been suggested.",0402110v1
2009-02-21,Inelastic Neutron Scattering Studies of the Spin and Lattice Dynamics in Iron Arsenide Compounds,"Neutrons have played an important role in advancing our understanding of the
pairing mechanism and the symmetry of the superconducting energy gap in the
iron arsenide compounds. Neutron measurements of the phonon density-of-state
are in good agreement with ab initio calculations, provided the magnetism of
the iron atoms is taken into account. However, the predicted superconducting
transition temperatures are less than 1 K, making a conventional phononic
mechanism for superconductivity highly unlikely. Measurements of the spin
dynamics within the spin density wave phase of the parent compounds show
evidence of strongly dispersive spin waves with exchange interactions
consistent with the observed magnetic order. Antiferromagnetic fluctuations
persist in the normal phase of the superconducting compounds, but they are more
diffuse. Below Tc, there is evidence compounds that these fluctuations condense
into a resonant spin excitation at the antiferromagnetic wavevector with an
energy that scales with Tc, consistent with unconventional superconductivity of
extended-s+/- wave symmetry.",0902.3760v1
2010-01-06,Photonic Phase Gate via an Exchange of Fermionic Spin Waves in a Spin Chain,"We propose a new protocol for implementing the two-qubit photonic phase gate.
In our approach, the pi phase is acquired by mapping two single photons into
atomic excitations with fermionic character and exchanging their positions. The
fermionic excitations are realized as spin waves in a spin chain, while photon
storage techniques provide the interface between the photons and the spin
waves. Possible imperfections and experimental systems suitable for
implementing the gate are discussed.",1001.0968v3
2010-06-07,"Theory of spin waves in ferromagnetic (Ga,Mn)As","The collective behavior of spins in a dilute magnetic semiconductor is
determined by their mutual interactions and influenced by the underlying
crystal structure. Hence, we begin with the atomic quantum-mechanical
description of this system using the proposed variational-perturbation
calculus, and then turn to the emerging macroscopic picture employing
phenomenological constants. Within this framework we study spin waves and
exchange stiffness in the p-d Zener model of (Ga,Mn)As, its thin layers and
bulk crystals described by the spds* tight-binding approximation. Analyzing the
anisotropic part of exchange, we find that the Dzyaloshinskii-Moriya
interaction may lead to the cycloidal spin arrangement and uniaxial in-plane
anisotropy in thin layers, resulting in a surface-like anisotropy in thicker
films. We also derive and discuss the spin-wave contribution to magnetization
and Curie temperature. Our theory reconstructs the values of stiffness
determined from the temperature dependence of magnetization, but reproduces
only partly those obtained from analyzing precession modes in (Ga,Mn)As thin
films.",1006.1271v4
2010-10-04,Anisotropic surface transport in topological insulators in proximity to a helical spin density wave,"We study the effects of spatially localized breakdown of time reversal
symmetry on the surface of a topological insulator (TI) due to proximity to a
helical spin density wave (HSDW). The HSDW acts like an externally applied
one-dimensional periodic(magnetic) potential for the spins on the surface of
the TI, rendering the Dirac cone on the TI surface highly anisotropic. The
decrease of group velocity along the direction $\hat{x}$ of the applied spin
potential is twice as much as that perpendicular to $\hat{x}$. At the Brillouin
zone boundaries (BZB) it also gives rise to new semi-Dirac points which have
linear dispersion along $\hat{x}$ but quadratic dispersion perpendicular to
$\hat{x}$. The group velocity of electrons at these new semi-Dirac points is
also shown to be highly anisotropic. Experiments using TI systems on
multiferroic substrates should realize our predictions. We further discuss the
effects of other forms of spin density wave on the surface transport property
of topological insulator.",1010.0683v2
2010-11-03,Temporal behavior of the inverse spin Hall voltage in a magnetic insulator-nonmagnetic metal structure,"It is demonstrated that upon pulsed microwave excitation, the temporal
behavior of a spin-wave induced inverse spin Hall voltage in a magnetic
insulator-nonmagnetic metal structure is distinctly different from the temporal
evolution of the directly excited spin-wave mode from which it originates. The
difference in temporal behavior is attributed to the excitation of long-lived
secondary spin-wave modes localized at the insulator-metal interface.",1011.0889v2
2011-06-27,Effect of intraband Coulomb repulsion on the excitonic spin-density wave,"We present a study of the magnetic ground state of a two-band model with
nested electron and hole Fermi surfaces and both interband and intraband
Coulomb interactions. Our aim is to understand how the excitonic
spin-density-wave (ESDW) state induced by the interband Coulomb repulsion is
affected by the intraband interactions. We first determine the magnetic
instabilities of our model in an unbiased way by employing the random-phase
approximation (RPA) to calculate the static spin susceptibility in the
paramagnetic state. From this, we construct the mean-field phase diagram,
demonstrating the robustness of the ESDW against the intraband interaction. We
then calculate the RPA transverse spin susceptibility in the ESDW state and
show that the intraband Coulomb repulsion significantly renormalizes the
paramagnon line shape and suppresses the spin-wave velocity. We conclude with a
discussion of the relevance of this suppression for the commensurate ESDW state
of Mn-doped Cr alloys.",1106.5315v2
2011-10-03,A novel nonlinear spin wave theory for the spin 1/2 antiferromagnetic Heisenberg model on a triangular lattice,"We extend the nonlinear spin wave theory (NLSWT) for the spin 1/2
antiferromagnetic Heisenberg model on a triangular lattice (TAFHM). This novel
NLSWT considers the corrections one order higher in 1/S than the linear spin
wave theory (LSWT). It also distinguishes in which circumstance the negative
energy excitation, the sign of the breakdown of LSWT, shall be renormalized to
be positive both by a boson normal ordering and a self-consistent iteration. We
draw a phase diagram by testing the stability of various magnetic orders for
different parameters. In particular, the incommensurate configuration is found
unstable by our study. The new phase transition point (PTP) of the collinear
configuration agrees well with various previous studies.",1110.0377v2
2011-11-24,Spin-Wave Modes and Their Intense Excitation Effects in Skyrmion Crystals,"We theoretically study spin-wave modes and their intense excitations
activated by microwave magnetic fields in the skyrmion-crystal phase of
insulating magnets by numerically analyzing a two-dimensional spin model using
the Landau-Lifshitz-Gilbert equation. Two peaks of spin-wave resonances with
frequencies of ~1 GHz are found for in-plane a.c. magnetic field where
distribution of the out-of-plane spin components circulates around each
skyrmion core. Directions of the circulations are opposite between these two
modes, and hence the spectra exhibit salient dependence on the circular
polarization of irradiating microwave. A breathing-type mode is also found for
out-of-plane a.c. magnetic field. By intensively exciting these collective
modes, melting of the skyrmion crystal accompanied by a red shift of the
resonant frequency is achieved within nano seconds.",1111.5667v1
2012-06-27,Discrete antiferromagnetic spin-wave excitations in the giant ferric wheel Fe18,"The low-temperature elementary spin excitations in the AFM molecular wheel
Fe18 were studied experimentally by inelastic neutron scattering and
theoretically by modern numerical methods, such as dynamical density matrix
renormalization group or quantum Monte Carlo techniques, and analytical
spin-wave theory calculations. Fe18 involves eighteen spin-5/2 Fe(III) ions
with a Hilbert space dimension of 10^14, constituting a physical system that is
situated in a region between microscopic and macroscopic. The combined
experimental and theoretical approach allowed us to characterize and discuss
the magnetic properties of Fe18 in great detail. It is demonstrated that
physical concepts such as the rotational-band or L&E-band concepts developed
for smaller rings are still applicable. In particular, the higher-lying
low-temperature elementary spin excitations in Fe18 or AFM wheels in general
are of discrete antiferromagnetic spin-wave character.",1206.6203v1
2012-08-17,Routes to heavy-fermion superconductivity,"Superconductivity in lanthanide- and actinide-based heavy-fermion metals can
have different microscopic origins. Among others, Cooper pair formation based
on fluctuations of the valence, of the quadrupole moment or of the spin of the
localized 4f/5f shell have been proposed. Spin-fluctuation mediated
superconductivity in CeCu2Si2 was demonstrated by inelastic neutron scattering
to exist in the vicinity of a spin-density-wave quantum critical point. The
isostructural HF compound YbRh2Si2 which is prototypical for a Kondo-breakdown
quantum critical point has so far not shown any sign of superconductivity down
to approximately 10mK. In contrast, results of de-Haas-van-Alphen experiments
by Shishido et al. (J. Phys. Soc. Jpn. 74, 1103 (2005)) suggest
superconductivity in CeRhIn5 close to an antiferromagnetic quantum critical
point beyond the spin-density-wave type, at which the Kondo effect breaks down.
For the related compound CeCoIn5 however, a field-induced quantum critical
point of spin-density-wave type is extrapolated to exist inside the
superconducting phase.",1208.3684v1
2013-06-08,Systematic Effective Field Theory Analysis of the D=2+1 Quantum XY Model at Low Temperatures,"The low-temperature properties of the (2+1)-dimensional quantum XY model are
studied within the framework of effective Lagrangians up to three-loop order.
At zero temperature, the system is characterized by a spontaneously broken spin
rotation symmetry, O(2) $\to$ 1, where the corresponding Goldstone bosons are
the spin waves or magnons. Even though there is no spontaneously broken order
at finite $T$, the low-temperature behavior of the system is still governed by
the spin waves. The partition function is evaluated and various thermodynamic
quantities, including the order parameter, are derived in the presence of a
weak external field. In particular, we show that the spin-wave interaction is
repulsive at low temperatures, its magnitude depending on the strength of the
external field. We compare our results with those for the (2+1)-dimensional
antiferromagnetic Heisenberg model which, at T=0, exhibits the spontaneously
broken spin rotation symmetry O(3) $\to$ O(2).",1306.1944v1
2013-09-19,Wave packet dynamics in the one-dimensional extended Hubbard model,"Using time-dependent density-matrix renormalization group, we study the time
evolution of electronic wave packets in the one-dimensional extended Hubbard
model with on-site and nearest neighbor repulsion, U and V, respectively. As
expected, the wave packets separate into spin-only and charge-only excitations
(spin-charge separation). Charge and spin velocities exhibit non-monotonic
dependence on V. For small and intermediate values of V, both velocities
increase with V. However, the charge velocity exhibits a stronger dependence
than that of the spin, leading to a more pronounced spin-charge separation.
Charge fractionalization, on the other hand, is weakly affected by V. The
results are explained in terms of Luttinger liquid theory in the weak-coupling
limit, and an effective model in the strong-coupling regime.",1309.5119v1
2014-01-17,Nonreciprocal spin-wave channeling along textures driven by the Dzyaloshinskii-Moriya interaction,"Ultrathin metallic ferromagnets on substrates with strong spin-orbit coupling
can exhibit induced chiral interactions of the Dzyaloshinskii-Moriya (DM) form.
For systems with perpendicular anisotropy, the presence of DM interactions has
important consequences for current-driven domain-wall motion and underpins
possible spintronic applications involving skyrmions. We show theoretically how
spin textures driven by the DM interaction allow nonreciprocal channeling of
spin waves, leading to measurable features in magnetic wires, dots, and domain
walls. Our results provide methods for detecting induced DM interactions in
metallic multilayers and controlling spin wave propagation in ultrathin
nanostructures.",1401.4439v3
2014-07-13,A Renormalization-Group Study of the Symmetry-Breaking Order Parameters in Spin-Orbit Coupled Iridates and Related Systems,"We study the competition between various forms of density-wave-like order
parameters that may arise in multi-orbital correlated materials with strong
spin-orbit coupling (SOC) within a renormalization-group (RG) approach. The
calculations are restricted to models with two spin-orbit split bands having
strong inter-band Fermi surface nesting. We find that for such Fermi surface
topology, the interplay between the inter-band nesting and SOC strongly
enhances the inter-orbital Coulomb interaction (relative to other interactions)
as the system approaches a stable fixed point. This results in an exotic
spin-orbit density wave (SODW) to become the energetically favorable
symmetry-broken state. While the conclusions are generic to such a Fermi
surface topology, the band structure and the numerical results are presented
for the iridate systems. We also find that the electronic fingerprints of the
SODW are in better agreement with various experimental results than a
conventional spin density wave (SDW), explaining the long-standing problem of
the origin of the metal-insulator transition in these systems.",1407.3440v1
2014-09-04,Electron with arbitrary pseudo spins in multilayer graphene,"Using the low-energy effective Hamiltonian of the ABC-stacked multilayer
graphene, pseudo spin coupling to real orbital angular momentum of electron in
multilayer graphene is investigated. We show that electron wave function in
N-layer graphene mimics behavior of particle with spin of N/2. It is said that
for N greater than 1 the low-energy effective Hamiltonian for ABC-stacked
graphene is no longer used to describe pseudo spin 1/2-particle wave function.
The wave function of electron in multilayer graphene may behave like fermionic
(or bosonic) particle when N is odd (or even). This work proposes a theory of
graphene as a host material of electron with arbitrary pseudo spins, tunable by
changing number of graphene layers.",1409.1426v3
2014-12-30,Detecting crystal symmetry fractionalization from the ground state: Application to $\mathbb Z_2$ spin liquids on the kagome lattice,"In quantum spin liquid states, the fractionalized spinon excitations can
carry fractional crystal symmetry quantum numbers, and this symmetry
fractionalization distinguishes different topologically ordered spin liquid
states. In this work we propose a simple way to detect signatures of such
crystal symmetry fractionalizations from the crystal symmetry representations
of the ground state wave function. We demonstrate our method on projected
$\mathbb Z_2$ spin liquid wave functions on the kagome lattice, and show that
it can be used to classify generic wave functions. Particularly our method can
be used to distinguish several proposed candidates of $\mathbb Z_2$ spin liquid
states on the kagome lattice.",1501.00009v2
2015-05-28,Incommensurate spin density wave at a ferromagnetic quantum critical point in a three-dimensional parabolic semimetal,"We explore the ferromagnetic quantum critical point in a three-dimensional
semimetallic system with upward- and downward-dispersing bands touching at the
Fermi level. Evaluating the static spin susceptibility to leading order in the
coupling between the fermions and the fluctuating ferromagnetic order
parameter, we find that the ferromagnetic quantum critical point is masked by
an incommensurate, longitudinal spin density wave phase. We first analyze an
idealized model which, despite having strong spin-orbit coupling, still
possesses O(3) rotational symmetry generated by the total angular momentum
operator. In this case, the direction of the incommensurate spin density wave
propagation can point anywhere, while the magnetic moment is aligned along the
direction of propagation. Including symmetry-allowed anisotropies in the
fermion dispersion and the coupling to the order parameter field, however, the
ordering wavevector instead breaks a discrete symmetry and aligns along either
the [111] or [100] direction, depending on the signs and magnitudes of these
two types of anisotropy.",1505.07685v1
2015-06-17,Partial-wave and helicity operators for the scattering of two hadrons in lattice QCD,"Partial-wave operators for lattice QCD are developed in order to facilitate
the identification of the spins of two-hadron scattering states corresponding
to zero total momentum. Taking the periodic boundary conditions for lattice
states into account, orthogonal sets of partial-wave operators for orbital
angular momentum are identified. When combined with the intrinsic spins of the
hadrons, orthogonal sets of parent operators for total angular momentum $J$ and
projection $M$ are obtained. The parent operators are subduced to irreducible
representations of the octahedral group in order to obtain descendant operators
for use in lattice calculations. The descendant operators retain orthogonality
with respect to $J$. The spin of a state can be identified by the spin of
parent operators that dominate creation of the state. For nonzero total
momentum, operators are developed for a range of helicities and they are
subduced to irreducible representations corresponding to the different
directions of total momentum. Sets of operators that include a sufficient range
of helicities allow identification of spin $J$ when a state couples to
operators with helicities less than or equal to $J$, but not to operators with
higher helicities.",1506.05492v1
2016-05-30,Gauge invariant gluon spin operator for spinless non-linear wave solutions,"We consider non-linear wave type solutions with mass scale parameter and
vahished canonical spin density operator in a pure SU(2) quantum chtomodynamics
(QCD). A new stationary solution which can be treated as a system of static
Wu-Yang monopole dressed in off-diagonal gluon field is proposed. A remarkable
feature of such a solution is that it possesses a finite energy density
everywhere. All considered non-linear wave type solutions have common features:
presence of a mass scale parameter, non-vanishing projection of the color
magnetic field along the propagation direction and zero spin density. The last
property requires revision of the gauge invariant definition of the spin
density operator which supposed to be massless vector field in the classical
theory. We construct a gauge invariant definition of the classical gluon spin
density which is unique and Lorentz frame independent.",1605.09154v4
2016-06-06,Spin-Wave and Electromagnon Dispersions in Multiferroic MnWO4 as Observed by Neutron Spectroscopy: Isotropic Heisenberg Exchange versus Anisotropic Dzyaloshinskii-Moriya Interaction,"High resolution inelastic neutron scattering reveals that the elementary
magnetic excitations in multiferroic MnWO4 consist of low energy dispersive
electromagnons in addition to the well-known spin-wave excitations. The latter
can well be modeled by a Heisenberg Hamiltonian with magnetic exchange coupling
extending to the 12th nearest neighbor. They exhibit a spin-wave gap of 0.61(1)
meV. Two electromagnon branches appear at lower energies of 0.07(1) meV and
0.45(1) meV at the zone center. They reflect the dynamic magnetoelectric
coupling and persist in both, the collinear magnetic and paraelectric AF1
phase, and the spin spiral ferroelectric AF2 phase. These excitations are
associated with the Dzyaloshinskii-Moriya exchange interaction, which is
significant due to the rather large spin-orbit coupling.",1606.01954v1
2016-10-10,"Spin-Wave Spectrum in Magnetic Nanodot with Continuous Transition between Vortex, Bloch-type Skyrmion and Néel-type Skyrmion States","We study spin-wave excitations in a circular ferromagnetic nanodot in
different inhomogeneous, topologically non-trivial magnetization states,
specifically, vortex and skyrmion states. Gradual change in the strength of the
out-of-plane magnetic anisotropy and the Dzyaloshinskii-Moriya exchange
interaction leads to continuous phase transitions between different stable
magnetic configurations and allows for mapping of dynamic spin modes in and
between the vortex, Bloch-type skyrmion and N\'eel-type skyrmion states. Our
study elucidates the connections between gyrotropic modes, azimuthal spin waves
and breathing modes in various stable magnetization states and helps to
understand the rich spin excitation spectrum on the skyrmion background.",1610.02859v1
2017-11-06,Quantum gap and spin-wave excitations in the Kitaev model on a triangular lattice,"We study the effects of quantum fluctuations on the dynamical generation of a
gap and on the evolution of the spin-wave spectra of a frustrated magnet on a
triangular lattice with bond-dependent Ising couplings, analog of the Kitaev
honeycomb model. The quantum fluctuations lift the subextensive degeneracy of
the classical ground-state manifold by a quantum order-by-disorder mechanism.
Nearest-neighbor chains remain decoupled and the surviving discrete degeneracy
of the ground state is protected by a hidden model symmetry. We show how the
four-spin interaction, emergent from the fluctuations, generates a spin gap
shifting the nodal lines of the linear spin-wave spectrum to finite energies.",1711.02016v1
2017-11-22,Irreversible Markov chains in spin models: Topological excitations,"We analyze the convergence of the irreversible event-chain Monte Carlo
algorithm for continuous spin models in the presence of topological
excitations. In the two-dimensional XY model, we show that the local nature of
the Markov-chain dynamics leads to slow decay of vortex-antivortex correlations
while spin waves decorrelate very quickly. Using a Frechet description of the
maximum vortex-antivortex distance, we quantify the contributions of
topological excitations to the equilibrium correlations, and show that they
vary from a dynamical critical exponent z \sim 2 at the critical temperature to
z \sim 0 in the limit of zero temperature. We confirm the event-chain
algorithm's fast relaxation (corresponding to z = 0) of spin waves in the
harmonic approximation to the XY model. Mixing times (describing the approach
towards equilibrium from the least favorable initial state) however remain much
larger than equilibrium correlation times at low temperatures. We also describe
the respective influence of topological monopole-antimonopole excitations and
of spin waves on the event-chain dynamics in the three-dimensional Heisenberg
model.",1711.08375v1
2018-01-22,Universal relations for spin-orbit coupled Fermi gas near an s-wave resonance,"The synthetic spin-orbit coupled quantum gases is widely studied both
experimentally and theoretically in recent years. As previous studies show,
this modification of single-body dispersion will in general couple different
partial waves and thus distort the wave-function of bound states which
determines the short-distance behavior of many-body wave function. In this
work, we focus on the two-component Fermi gas with one-dimensional or
three-dimensional spin-orbit coupling near an s-wave resonance. Using the
method of effective field theory and the operator product expansion, we derive
universal relations for both systems, and obtain the momentum distribution
matrix $\left<\psi^\dagger_a(\mathbf{q})\psi_b(\mathbf{q})\right>$ at large
$\mathbf{q}$ ($a,b$ are spin index), which shows anisotropic features. We also
discuss the experimental implication of these results depending on the
realization of the spin-orbit coupling.",1801.07001v2
2018-10-23,Magnonic Analogue of Black/White Hole Horizon in Superfluid $^3$He-B,"We report on theoretical model and experimental results of the experiment
made in a limit of absolute zero temperature ($\sim$ 600\,$\mu$K) studying the
spin wave analogue of black/white hole horizon using spin (magnonic)
superfluidity in superfluid $^3$He-B. As an experimental tool simulating the
properties of the black/white horizon we used the spin-precession waves
propagating on the background of the spin super-currents between two
Bose-Einstein condensates of magnons in form of homogeneously precessing
domains. We provide experimental evidence of the white hole formation for spin
precession waves in this system, together with observation of an amplification
effect. Moreover, the estimated temperature of the spontaneous Hawking
radiation in this system is about four orders of magnitude lower than the
system's background temperature what makes it a promising tool to study the
effect of spontaneous Hawking radiation.",1810.09890v2
2016-12-26,Magnetic excitations in a three-orbital model for the strongly spin-orbit coupled iridates: Effect of mixing between the J=1/2 and 3/2 sectors,"A three-orbital-model approach for studying spin wave excitations in the
strongly spin-orbit coupled layered perovskite iridates is presented which
provides a unified description of magnetic excitations as well as the
electronic band structure. The calculated spin wave dispersions with realistic
three-band parameters are in excellent agreement with the RIXS data for
iridates, including the strong AF zone boundary dispersion in the single-layer
compound $\rm Sr_2 Ir O_4$ and the large anisotropy gap in the bilayer compound
$\rm Sr_3 Ir_2 O_7$. The RIXS spin wave data is shown to provide evidence of
mixing between the J=1/2 and 3/2 sectors in both compounds.",1612.08360v1
2017-06-20,"Optical Momentum, Spin, and Angular Momentum in Dispersive Media","We examine the momentum, spin, and orbital angular momentum of structured
monochromatic optical fields in dispersive inhomogeneous isotropic media. There
are two bifurcations in this general problem: the Abraham-Minkowski dilemma and
the kinetic (Poynting-like) versus canonical (spin-orbital) pictures. We show
that the kinetic Abraham momentum describes the energy flux and group velocity
of the wave in the medium. At the same time, we introduce novel canonical
Minkowsky-type momentum, spin, and orbital angular momentum densities of the
field. These quantities exhibit fairly natural forms, analogous to the
Brillouin energy density, as well as multiple advantages as compared with
previously considered formalisms. We apply this general theory to inhomogeneous
surface plasmon-polariton (SPP) waves at a metal-vacuum interface and show that
SPPs carry a ""super-momentum"", proportional to the wave vector $k_{p} >
\omega/c$, and a transverse spin, which can change its sign depending on the
frequency $\omega$.",1706.06406v2
2021-02-24,Quantum hydrodynamics of the spinor Bose-Einstein condensate at non-zero temperatures,"Finite temperature hydrodynamic model is derived for the spin-1 ultracold
bosons by the many-particle quantum hydrodynamic method. It is presented as the
two fluid model of the BEC and normal fluid. The linear and quadratic Zeeman
effects are included. Scalar and spin-spin like short-range interactions are
considered in the first order by the interaction radius. It is also represented
as the set of two nonlinear Pauli equations. The spectrum of the bulk
collective excitations is considered for the ferromagnetic phase in the small
temperature limit. The spin wave is not affected by the presence of the small
temperature in the described minimal coupling model, where the thermal part of
the spin-current of the normal fluid is neglected. The two sound waves are
affected by the spin evolution in the same way as the change of spectrum of the
single sound wave in BEC, where speed of sound is proportional to $g_{1}+g_{2}$
with $g_{i}$ are the interaction constants.",2102.12538v1
2019-01-24,Spin and orbital angular momenta of acoustic beams,"We analyze spin and orbital angular momenta in monochromatic acoustic wave
fields in a homogeneous medium. Despite being purely longitudinal (curl-free),
inhomogeneous acoustic waves generically possess nonzero spin angular momentum
density caused by the local rotation of the vector velocity field. We show that
the integral spin of a localized acoustic wave vanishes in agreement with the
spin-0 nature of longitudinal phonons. We also show that the helicity or
chirality density vanishes identically in acoustic fields. As an example, we
consider nonparaxial acoustic Bessel beams carrying well-defined integer
orbital angular momentum, as well as nonzero local spin density, with both
transverse and longitudinal components. We describe the nontrivial polarization
structure in acoustic Bessel beams and indicate a number of observable
phenomena, such as nonzero energy density and purely-circular transverse
polarization in the center of the first-order vortex beams.",1901.08962v3
2019-07-10,How to search for gravitational waves from $r$-modes of known pulsars,"Searches for continuous gravitational waves from known pulsars so far have
been targeted at or near the spin frequency or double the spin frequency of
each pulsar, appropriate for mass quadrupole emission. But some neutron stars
might radiate strongly through current quadrupoles via $r$-modes, which
oscillate at about four thirds the spin frequency. We show for the first time
how to construct searches over appropriate ranges of frequencies and spin-down
parameters to target $r$-modes from known pulsars. We estimate computational
costs and sensitivities of realistic $r$-mode searches using the coherent
$\mathcal{F}$-statistic, and find that feasible searches for known pulsars can
beat spin-down limits on gravitational wave emission even with existing LIGO
and Virgo data.",1907.04946v1
2019-07-16,Singular spin-flip interactions for the 1D Schrödinger operator,"We consider singular self-adjoint extensions for one-dimensional
Schr\""{o}dinger operator for two-component wave function within the framework
of the distribution theory for discontinuous test functions
\cite{funcan_deltadistr_kurasov_jmathan1996}. We show that among
$\mathds{C}^{4}$-parameter set of boundary conditions with state mixing there
is only $\mathds{R}^2$-parameter subset compatible with the spin interpretation
of the two-component structure of the wave function. For the spin
interpretation of such wave function they can be identified as the point-like
spin-momentum (Rashba) interactions. We suggest their physical realizations
based on the regularized form of the Hamiltonian which couples the electrical
field inhomogeneity to spin.",1907.06893v4
2019-10-08,Spatial coherence of spin-orbit-coupled Bose gases,"Spin-orbit-coupled Bose-Einstein condensates (SOBECs) exhibit two new phases
of matter, now known as the stripe and plane-wave phases. When two interacting
spin components of a SOBEC spatially overlap, density modulations with
periodicity given by the spin-orbit coupling strength appear. In equilibrium,
these components fully overlap in the miscible stripe phase, and overlap only
in a domain wall in the immiscible plane-wave phase. Here we probe the density
modulation present in any overlapping region with optical Bragg scattering, and
observe the sudden drop of Bragg scattering as the overlapping region shrinks.
Using an atomic analogue of the Talbot effect, we demonstrate the existence of
long-range coherence between the different spin components in the stripe phase
and surprisingly even in the phase-separated plane-wave phase.",1910.03613v1
2020-01-15,Yttrium Iron Garnet Thickness Influence on the Spin Pumping in the Bulk Acoustic Wave Resonator,"The features of phonon-magnon interconversion in acoustic resonator determine
the efficiency of spin pumping from YIG into Pt that may be detected
electrically through the inverse spin Hall effect (ISHE). Based on the methods
developed in previous works for calculating resonator structures with a
piezoelectric (ZnO) and a magnetoelastic layer in contact with the heavy metal
(YIG/Pt), we present the results of numerical calculations of YIG film
thickness influence on acoustically driven spin waves. We obtain some YIG film
thickness regions with various behavior of dc ISHE voltage $U_{ISHE}$. At
micron and submicron thicknesses, the higher spin wave resonance (SWR) modes
(both even and odd) can be generated with efficiency comparable and even
exceeding that of the main mode. The absolute maximum of $U_{ISHE}$ is achieved
at the thickness about $s_1 \approx 208$ nm under the excitation of the first
SWR.",2001.05385v1
2021-01-12,Temperature dependent appearance of exotic matter makes nascent neutron stars spin faster,"Neutron stars offer the opportunity to study the behaviour of matter at
densities and temperatures inaccessible to terrestrial experiments.
Gravitational-wave observations of binary neutron star coalescences can
constrain the neutron-star equation of state before and after merger. After the
neutron star binary merges, hyperons can form in the remnant, changing the
behaviour of the neutron-star equation of state. In this study, we use
finite-entropy equations of state to show that a post-merger remnant can spin
up due to cooling. The magnitude of the spin-up depends on the neutron-star
equation of state. If hyperons are present, the post-merger spin-up changes the
peak gravitational-wave frequency by $\sim 540$ Hz, when the entropy per baryon
drops from $s=2$ $k_B$ to $s=0$ $k_B$. If hyperons are not present, the
post-merger spin-up changes by $\sim 360$ Hz, providing a gravitational-wave
signature for exotic matter. We expect the same qualitative behaviour whenever
temperature dependent phase transitions are triggered.",2101.04782v1
2021-12-08,Topological Doping and Superconductivity in Cuprates: An Experimental Perspective,"Hole doping into a correlated antiferromagnet leads to topological stripe
correlations, involving charge stripes that separate antiferromagnetic spin
stripes of opposite phase. Topological spin stripe order causes the spin
degrees of freedom within the charge stripes to feel a geometric frustration
with their environment. In the case of cuprates, where the charge stripes have
the character of a hole-doped two-leg spin ladder, with corresponding pairing
correlations. Anti-phase Josephson coupling across the spin stripes can lead to
pair-density-wave order, in which broken translation symmetry of the
superconducting wave function is accommodated by pairs with finite momentum.
This scenario has now been experimentally verified by recently reported
measurements on La$_{2-x}$Ba$_x$CuO$_4$ with $x=1/8$. While pair-density-wave
order is not common as a cuprate ground state, it provides a basis for
understanding the uniform $d$-wave order that is more typical in
superconducting cuprates.",2112.04557v1
2022-01-13,Gravitational radiation from inspiralling compact objects: Spin effects to fourth Post-Newtonian order,"The linear- and quadratic-in-spin contributions to the binding potential and
gravitational-wave flux from binary systems are derived to
next-to-next-to-leading order in the Post-Newtonian (PN) expansion of general
relativity, including finite-size and tail effects. The calculation is carried
out through the worldline effective field theory framework. We find agreement
in the overlap with the available PN literature and test-body limit. As a
direct application, we complete the knowledge of spin effects in the evolution
of the orbital phase for aligned-spin circular orbits to fourth PN order. We
estimate the impact of the new results in the number of accumulated
gravitational-wave cycles. We find they will play an important role in
providing reliable physical interpretation of gravitational-wave signals from
spinning binaries with future detectors such as LISA and the Einstein
Telescope.",2201.05138v1
2023-01-04,Covariant orbital-spin scheme for any spin based on irreducible tensor,"In hadron spectrum physics, the partial wave analysis is a primary method
used to extract properties of hadronic resonances. The covariant orbital-spin
coupling scheme holds unique advantages over other partial wave methods due to
its Lorentz covariant form and determined orbital-spin quantum numbers. This
paper presents a general form of the covariant orbital-spin coupling scheme
based on the irreducible tensor of the homogeneous proper Lorentz group and its
little groups. A systematic procedure for constructing partial wave amplitude
in a Lorentz covariant way is provided, which can be applied to both massive
and massless particles. Specific examples are also included.",2301.01575v3
2023-03-22,Classification and emergence of quantum spin liquids in chiral Rydberg models,"We investigate the nature of quantum phases arising in chiral interacting
Hamiltonians recently realized in Rydberg atom arrays. We classify all possible
fermionic chiral spin liquids with $\mathrm{U}(1)$ global symmetry using parton
construction on the honeycomb lattice. The resulting classification includes
six distinct classes of gapped quantum spin liquids: the corresponding
variational wave functions obtained from two of these classes accurately
describe the Rydberg many-body ground state at $1/2$ and $1/4$ particle
density. Complementing this analysis with tensor network simulations, we
conclude that both particle filling sectors host a spin liquid with the same
topological order of a $\nu=1/2$ fractional quantum Hall effect. At density
$1/2$, our results clarify the phase diagram of the model, while at density
$1/4$, they provide an explicit construction of the ground state wave function
with almost unit overlap with the microscopic one. These findings pave the way
to the use of parton wave functions to guide the discovery of quantum spin
liquids in chiral Rydberg models.",2303.12829v2
2023-04-27,Coherent magnetization dynamics in strongly quenched Ni thin films,"The remagnetization process after ultrafast demagnetization can be described
by relaxation mechanisms between the spin, electron, and lattice reservoirs.
Thereby, collective spin excitations in form of spin waves and their angular
momentum transfer play an important role on the longer timescales. In this
work, we address the question whether the strength of demagnetization affects
the coherency and the phase of the excited spin waves. We present a study of
coherent magnetization dynamics in thin nickel films after ultrafast
demagnetization using the all-optical, time-resolved magneto-optical
Kerr-effect (tr-MOKE) technique. The largest coherent oscillation amplitude was
observed for strongly quenched systems, showing the conservation of coherency
for demagnetizations of up to 90%. Moreover, the phase of the excited
spin-waves increases with pump power, indicating a delayed start of the
precession during the remagnetization.",2304.14325v1
2023-10-09,Ordered phases and superconductivity in two-dimensional electron systems subject to pair spin-orbit interaction,"Pair spin-orbit interaction can emerge in strongly-interacting systems
characterized by a large spin-orbit coupling. Here we study the role of this
interaction in stabilizing ordered and unconventional superconducting phases.
We find that, if the system avoids superconductivity, the order realized is a
combination of charge-density and spin-vorticity waves. The latter is
reminiscent of a loop-current state, albeit in the spin, rather in the charge,
channel. If the system becomes superconducting, the order parameter assumes the
form of a paired density wave, i.e. pairing occurs at finite momentum.
Intriguingly, one of the possible pairings acquires a form analogous to
Amperean superconductivity. However, the order parameter here is always a blend
of paired density wave and Amperean pairing, rather than being purely one or
the other.",2310.06190v1
2023-11-17,Superradiance in the Kerr-Taub-NUT spacetime,"Superradiance is the effect of field waves being amplified during reflection
from a charged or rotating black hole. In this paper, we study the low-energy
dynamics of super-radiant scattering of massive scalar and massless higher spin
field perturbations in a generic axisymmetric stationary Kerr-Taub-NUT
(Newman-Unti-Tamburino) spacetime, which represents sources with both
gravitomagnetic monopole moment (magnetic mass) and gravitomagnetic dipole
moment (angular momentum). We obtain a generalized Teukolsky master equation
for all spin perturbation fields. The equations are separated into their
angular and radial parts. The angular equations lead to spin-weighted
spheroidal harmonic functions that generalize those in Kerr spacetime. We
identify an effective spin as a coupling between frequency (or energy) and the
NUT parameter. The behaviors of the radial wave function near the horizon and
at the infinite boundary are studied. We provide analytical expressions for
low-energy observables such as emission rates and cross sections of all
massless fields with spin, including scalar, neutrino, electromagnetic,
Rarita-Schwinger, and gravitational waves.",2311.10559v1
2023-11-25,Spin pumping in YIG-Pt structures: the role of the van Hove singularities,"Spin pumping by surface and backward volume magnetostatic waves in YIG/Pt
structures is experimentally studied and analyzed. It is shown that at
frequencies corresponding to van Hove singularities in the density of states of
the spin wave spectrum, an increase in the efficiency of electron-magnon
scattering and spin current generation takes place. The obtained results are
important for spin wave-based spintronic devices development.",2311.15096v1
2023-11-27,Evidence of spin density waves in La$_3$Ni$_2$O$_{7-δ}$,"The recently discovered superconductivity with critical temperature $T_{c}$
up to 80 K in the Ruddlesden-Popper phases La$_3$Ni$_2$O$_{7-\delta}$ under
pressure has drawn great attention. Here we report the positive muon spin
relaxation ($\mu^+$SR) study of polycrystalline La$_3$Ni$_2$O$_{7-\delta}$
under ambient pressure. The zero-field $\mu^+$SR experiments reveal the
existence of static long range magnetic order in La$_3$Ni$_2$O$_{7-\delta}$,
and the the muon spin depolarization spectra are consistent with the spin
density wave internal field distribution. The weak transverse field $\mu^+$SR
measurements suggest the bulk magnetic transition near $T_{\rm{N}}=148$ K. This
is the first research which discovers the existence of the spin density wave in
La$_3$Ni$_2$O$_{7-\delta}$ microscopically.",2311.15717v1
2024-01-28,Magnetic interactions and excitations in SrMnSb$_2$,"The magnetic interactions in the antiferromagnetic (AFM) Dirac semimetal
candidate SrMnSb$_2$ are investigated using \textit{ab initio} linear response
theory and inelastic neutron scattering (INS). Our calculations reveal that the
first two nearest in-plane couplings ($J_1$ and $J_2$) are both AFM in nature,
indicating a significant degree of spin frustration, which aligns with
experimental observations. The orbital resolution of exchange interactions
shows that $J_1$ and $J_2$ are dominated by direct and superexchange,
respectively. In a broader context, a rigid-band model suggests that electron
doping fills the minority spin channel and results in a decrease in the AFM
coupling strength for both $J_1$ and $J_2$. To better compare with INS
experiments, we calculate the spin wave spectra within a linear spin wave
theory framework, utilizing the computed exchange parameters. The calculated
spin wave spectra exhibit overall good agreement with measurements from INS
experiments, although with a larger magnon bandwidth. Introducing additional
electron correlation within the Mn-$3d$ orbitals can promote electron
localization and reduce the magnetic coupling, further improving the agreement
with experiments.",2401.15572v1
2024-02-02,THz spin-wave excitations in the transverse conical phase of BiFeO$_3$,"Although BiFeO$_3$ is one of the most studied multiferroic materials, recent
magnetization and neutron scattering studies have revealed a new magnetic phase
in this compound - the transverse conical phase. To study the collective spin
excitations of this phase, we performed THz spectroscopy in magnetic fields up
to 17 T at and above room temperature. We observed five spin-wave branches in
the magnetic phase with long wavelength conical modulation. Using a numerical
spin dynamics model we found two kinds of excitations with magnetic moments
oscillating either along or perpendicular to the static fields. Remarkably, we
detected strong directional dichroism, an optical manifestation of the
magnetoelectric effect, for two spin-wave modes of the conical phase. According
to our experiments, the stability of the conical state is sensitive to the
magnetic field history and it can become (meta)stable at or close to zero
magnetic field, which may allow exploiting its magnetoelectric properties at
room temperature.",2402.01417v1
2008-02-07,Spin-wave interaction in two-dimensional ferromagnets with dipolar forces,"We discuss the spin-wave interaction in two-dimensional (2D) Heisenberg
ferromagnet (FM) with dipolar forces at $T_C\gg T\ge0$ using 1/S expansion. A
comprehensive analysis is carried out of the first 1/S corrections to the
spin-wave spectrum. In particular, similar to 3D FM discussed in our previous
paper A.V. Syromyatnikov, PRB {\bf 74}, 014435 (2006), we obtain that the
spin-wave interaction leads to the {\it gap} in the spectrum $\epsilon_{\bf k}$
renormalizing greatly the bare gapless spectrum at small momenta $k$.
Expressions for the spin-wave damping $\Gamma_{\bf k}$ are derived
self-consistently and it is concluded that magnons are well-defined
quasi-particles in both quantum and classical 2D FMs at small $T$. We observe
thermal enhancement of both $\Gamma_{\bf k}$ and $\Gamma_{\bf k}/\epsilon_{\bf
k}$ at small momenta. In particular, a peak appears in $\Gamma_{\bf k}$ and
$\Gamma_{\bf k}/\epsilon_{\bf k}$ at small $k$ and at any given direction of
$\bf k$. If $S\sim1$ the height of the peak in $\Gamma_{\bf k}/\epsilon_{\bf
k}$ is not larger than a value proportional to $T/D\ll1$, where $D$ is the
spin-wave stiffness. In the case of large spins $S\gg1$ the peak in
$\Gamma_{\bf k}/\epsilon_{\bf k}$ cannot be greater than that of the classical
2D FM found at $k=0$ which height is small only {\it numerically}: $\Gamma_{\bf
0}/\epsilon_{\bf 0}\approx0.16$ for the simple square lattice. Frustrating
next-nearest-neighbor exchange coupling increases $\Gamma_{\bf 0}/\epsilon_{\bf
0}$ in classical 2D FM only slightly. We find expressions for spin Green's
functions and the magnetization. The latter differs from the well-known result
by S.V. Maleev, Sov. Phys. JETP {\bf 43}, 1240 (1976). The effect of the
exchange anisotropy is also discussed briefly.",0802.0958v1
2000-07-18,Dirac equation in Kerr geometry and its solution,"Chandrasekhar separated the Dirac equation for spinning and massive particles
in Kerr geometry into radial and angular parts. In the present review, we
present solutions of the complete wave equation and discuss how the Dirac wave
scatters off Kerr black holes. The eigenfunctions, eigenvalues and reflection
and transmission co-efficients are computed for different Kerr parameters. We
compare the solutions with several parameters to show how a spinning black hole
distinguishes mass and energy of incoming waves. Very close to the horizon, the
solutions become independent of the particle parameters indicating an
universality of the behaviour.",0007253v1
1993-11-24,Phason modes in spin-density wave in the presence of long-range Coulomb interaction,"We study the effect of long-range Coulomb interaction on the phason in
spin-density wave (SDW) within mean field theory. In the longitudinal limit and
in the absence of SDW pinning the phason is completely absorbed by the plasmon
due to the Anderson-Higgs mechanism. In the presence of SDW pinning or when the
wave vector {\bf q} is tilted from the chain direction, though the plasmon
still almost exhausts the optical sum rule, another optical mode appears at
$\omega < 2\Delta(T)$, with small optical weight. This low frequency mode below
the SDW gap may be accessible to electron energy loss spectroscopy (EELS).",9311056v1
1994-12-09,Quantum Hall Effect in Three-dimensional Field-Induced Spin Density Wave Phases with a Tilted Magnetic Field,"The quantum Hall effect in the three-dimensional anisotropic tight-binding
electrons is investigated in the field-induced spin density wave phases with a
magnetic field tilted to any direction. The Hall conductivity, $\sigma_{xy}$
and $\sigma_{xz}$, are shown to be quantized as a function of the wave vector
of FISDW, while $\sigma_{yz}$ stays zero, where $x$ is the most conducting
direction and $y$ and $z$ are perpendicular to $x$.",9412043v1
1998-04-03,Susceptibilities and Correlation Functions of the Anisotropic Spherical Model,"The static transverse and longitudinal correlation functions (CF) of a
3-dimensional ferromagnet are calculated for the exactly solvable anisotropic
spherical model (ASM) determined as the limit D \to \infty of the classical
D-component vector model. The results are nonequivalent to those for the
standard spherical model of Berlin and Kac even in the isotropic case. Whereas
the transverse CF has the usual Ornstein-Zernike form for small wave vectors,
the longitudinal CF shows a nontrivial behavior in the ordered region caused by
spin-wave fluctuations. In particular, in the isotropic case below T_c one has
S_{zz}(k) \propto 1/k (the result of the spin-wave theory) for k \lsim \kappa_m
\propto T_c-T.",9804044v1
1998-07-22,"Theory of Coexisting Charge and Spin-Density Waves in (TMTTF)_2Br, (TMTSF)_2PF_6 and alpha-(BEDT-TTF)_2MHg(SCN)_4","Recent experiments indicate that the spin-density waves (SDWs) in
(TMTTF)_2Br, (TMTSF)_2PF_6 and alpha-(BEDT-TTF)_2MHg(SCN)_4 are highly
unconventional and coexist with charge-density waves (CDWs). We present a
microscopic theory of this unusual CDW-SDW coexistence.
  A complete understanding requires the explicit inclusion of strong Coulomb
interactions, lattice discreteness, the anisotropic two-dimensional nature of
the lattice, and the correct bandfilling within the starting Hamiltonian.",9807308v1
2000-03-21,Stripe orders in the extended Hubbard model,"We study stripe orders of charge and spin density waves in the extended
Hubbard model with the nearest-neighbor Coulomb repulsion V within the mean
field approximation. We obtain V vs. T(temperature) phase diagram for the
on-site Coulomb interaction U/t=8.0 and the filling n=0.8, here t is a
nearest-neighbor transfer energy. Our result shows that the diagonal stripe
spin density wave state (SDW) is stable for small V, but for large V the most
stable state changes to a charge density wave-antiferromagnetic (CDW-AF) state.
Especially we find at low temperature and for a certain range of value of V, a
vertical stripe CDW-AF state becomes stable.",0003347v1
2000-03-27,Quarter-filled spin density wave states with long-range Coulomb interaction,"Spin density wave (SDW) states at quarter-filling, which coexist with charge
density wave (CDW) states, have been examined where the critical temperature is
calculated for an extended Hubbard model with long range repulsive
interactions. Within the mean-field theory, it is shown that the first order
transition occurs with decreasing temperature for interactions located around
the boundary between SDW state and CDW state.",0003422v2
2000-11-14,Odd-Frequency Density Waves: Non-Fermi-Liquid Metals with an Order Parameter,"We consider states with a charge- or spin-density wave order parameter which
is odd in frequency, so that the order parameter vanishes at zero frequency and
there is a conventional Fermi surface. Such states break translational symmetry
and, therefore, are not conventional Fermi liquids. In the odd-frequency
spin-density wave case, there are Goldstone bosons and the low-energy spectrum
is manifestly different from that of a Fermi liquid. We discuss a simple model
which gives rise to such ordered states. The frequency-dependence of the gap
leads to an unusual temperature dependence for various thermodynamic and
transport properties, notably the resistivity.",0011234v2
2001-09-04,Phase Diagram of One-Dimensional Extended Hubbard Model at Half Filling,"We reexamine the ground-state phase diagram of the one-dimensional
half-filled Hubbard model with on-site and nearest-neighbor repulsive
interactions. We calculate second-order corrections to coupling constants in
the g-ology to show that the bond-charge-density-wave (BCDW) phase exists for
weak couplings in between the charge density wave (CDW) and spin density wave
(SDW) phases. We find that the umklapp scattering of parallel-spin electrons
destabilizes the BCDW state and gives rise to a bicritical point where the
CDW-BCDW and SDW-BCDW continuous-transition lines merge into the CDW-SDW
first-order transition line.",0109051v1
2003-06-04,"Chiral Symmetry and Collective Excitations in p-wave, d-wave and f-wave Superconductors","We discuss the origin of charge density wave (CDW) and spin density wave
(SDW) in p-wave, d-wave and f-wave superconductors. To describe the low-energy
quasiparticle excitation of p-wave case, we introduce a two- (one for time and
one for space) dimensional massless Dirac model. After the non-Abelian
bosonization is performed, the charge and spin density waves emerge from the
model. By using this scheme, we try to explain the characteristic aspect of
phase diagrams of various compounds, oxides and organic superconductors. The
purpose of this paper is to make an argument that the dimensionality of the
nodal excitation in superconductors plays an important role in the
determination of the structure of the phase diagram.",0306095v1
2004-08-17,Collective Spin-Density-Wave Response Perpendicular to the Chains of the Quasi One-Dimensional Conductor (TMTSF)2PF6,"Microwave experiments along all three directions of the spin-density-wave
model compound (TMTSF)$_2$PF$_6$ reveal that the pinned mode resonance is
present along the $a$ and $b^{\prime}$ axes. The collective transport is
considered to be the fingerprint of the condensate. In contrast to common quasi
one-dimensional models, the density wave also slides in the perpendicular
$b^{\prime}$ direction. The collective response is absent along the least
conducting $c^*$ direction.",0408382v1
2005-01-26,Resonant Nernst effect in the metallic and field-induced spin density wave states of (TMTSF)2ClO4,"We examine an unusual phenomenon where, in tilted magnetic fields near magic
angles parallel to crystallographic planes, a ""giant"" resonant Nernst signal
has been observed by Wu et al.[Phys. Rev. Lett. 91 56601(2003)] in the metallic
state of an organic conducting Bechgaard salt. We show that this effect appears
to be a general feature of these materials, and is also present in the field
induced spin density wave phase with even larger amplitude. Our results place
new restrictions on models that treat the metallic state as an unconventional
density wave or as a state with finite Cooper pairing.",0501649v1
2005-08-26,Resonance mode in $B_{1g}$ Raman scattering -- a way to distinguish between spin-fluctuation and phonon-mediated $d-$wave superconductivity,"We argue that Raman scattering in $B_{1g}$ symmetry allows one to distinguish
between phonon-mediated and magnetically-mediated $d-$wave superconductivity.
In spin mediated superconductors, $B_{1g}$ Raman intensity develops a resonance
at a frequency $\omega_{res} < 2\Delta_{max}$, whose origin is similar to a
neutron resonance. In phonon-mediated $d-$wave superconductors, such a
resonance does not develop. Several extensions of the argument are presented.",0508643v2
2006-05-13,Scattering wave function approach to multi-terminal mesoscopic system with spin-orbit coupling,"In this paper,we present a detailed formulation to solve the scattering wave
function for a multi-terminal mesoscopic system with spin-orbit coupling. In
addition to terminal currents, all local quantities can be calculated
explicitly by taking proper ensemble average in the Landauer-Buttiker's spirit
using the scattering wave functions. Based on this formulation, we derive some
rigorous results for equilibrium state. Furthermore, some new symmetry
relations are found for the typical two terminal structure in which a
semiconductor bar with Rashba or/and Dresselhaus SO coupling is sandwiched
symmetrically between two leads. These symmetry property can provide accuracy
tests for experimental measurements and numerical calculations.",0605361v1
2004-11-17,Integral equations for the spin-weighted spheroidal wave function,"Integral equations for the spin-weighted spheroidal wave functions is given.
For the prolate spheroidal wave function with m=0, there exists the integral
equation whose kernel is(sin x)/x, and the sinc function kernel (sin x)/x is of
great mathematical significance. In the paper, we also extend the similar sinc
function kernel (sin x)/x to the case m and s both are not zero, which
interestingly turn out as some kind of Hankel transformation.",0411087v2
2000-12-13,An Attack to Quantum Cryptography from Space,"The promise of secure cryptographic quantum key distribution schemes is based
on the use of quantum effects in the spin space. We point out that in fact in
many current quantum cryptography protocols the space part of the wave function
is neglected. However exactly the space part of the wave function describes the
behaviour of particles in ordinary real three-dimensional space. As a result
such schemes can be secure against eavesdropping attacks in the abstract spin
space but could be insecure in the real three-dimensional space. We discuss an
approach to the security of quantum key distribution in space by using Bell's
inequality and a special preparation of the space part of the wave function.",0012054v1
2007-04-11,On the existence of chaotic circumferential waves in spinning disks,"We use a third-order perturbation theory and Melnikov's method to prove the
existence of chaos in spinning circular disks subject to a lateral point load.
We show that the emergence of transverse homoclinic and heteroclinic points
respectively lead to a random reversal in the traveling direction of
circumferential waves and a random phase shift of magnitude $\pi$ for both
forward and backward wave components. These long-term phenomena occur in
imperfect low-speed disks sufficiently far from fundamental resonances.",0704.1406v1
2007-07-12,Properties of high-T$_C$ copper oxides from the nearly-free electron model,"The generic band structure of high-T$_C$ copper oxides is simulated by the
nearly free-electron model (NFE) in two dimensions (2-D) with parameters from
band calculations. Interaction between phonons and spin waves will cause
potential modulations and pseudogaps, and the strength of the modulations, the
wave lengths and the doping, are all related. A Fermi-surface ""arc"" is found
for dynamic spin/phonon waves. The confinement of superconductivity between two
limiting dopings can be a result of competition with the pseudogap at low
doping and weak coupling at high doping.",0707.1804v1
2007-07-16,Angular Momentum Imparted To Test Particles by Gravitational Waves,"What are gravitational waves? How do they propagate? and what is their energy
content? These questions are addressed in the first two chapters. In the third
chapter the pseudo-Newtonian formalism and its extension is reviewed in general
and the formula for the momentum imparted to test particles in arbitrary
spacetimes is reviewed in particular. In chapter four the analysis of a paper
claiming to determine the spin for gravitational waves is given, and compared
with the spin given by a geodesic analysis. It is demonstrated that the other
claim is inconsistent. Finally in chapter five a summary of the work is given
with the conclusion.",0707.2318v1
2007-12-03,Bright and dark solitary waves in a one-dimensional spin-polarized gas of fermionic atoms with p-wave interactions in a hard-wall trap,"In this paper we elucidate the physics underlying the fact that both bright
and dark solitary waves can arise in a one-dimensional spin-polarized gas of
fermionic atoms with attractive three-dimensional p-wave interactions in a
hard-wall trap. This is possible since the one-dimensional fermion system can
be mapped to a system of bosons described by the Lieb-Liniger model with either
repulsive or attractive delta-function interactions which can support solitary
waves.",0712.0355v1
2009-07-07,Multiband Superconductivity in Spin Density Wave Metals,"We study the emergence of multiband superconductivity with $s$- and $d-$wave
symmetry on the background of spin density wave (SDW). We show that the SDW
coherence factors renormalize the momentum dependence of the superconducting
(SC) gap, yielding a SC state with an \emph{unconventional} s-wave symmetry.
Interband Cooper pair scattering stabilizes superconductivity in both
symmetries. With increasing SDW order, the s-wave state is more strongly
suppressed than the d-wave state. Our results are universally applicable to
two-dimensional systems with a commensurate SDW.",0907.1296v1
2010-02-03,Massless and Massive Gauge-Invariant Fields in the Theory of Relativistic Wave Equations,"In this work consideration is given to massless and massive gauge-invariant
spin 0 and spin 1 fields (particles) within the scope of a theory of the
generalized relativistic wave equations with an extended set of the Lorentz
group representations. The results obtained may be useful as regards the
application of a relativistic wave-equation theory in modern field models.",1002.0720v1
2012-04-24,"Magnetostatic Spin Waves and Magnetic-Wave Chaos in Ferromagnetic Films. III. Numeric Simulations of Microwave-Band Magnetic Chaos, Its Synchronization and Application to Secure Communication","Selected results of original numeric simulations of non-linear magnetostatic
spin waves and microwave-frequency magnetic chaos in ferrite films are
expounded, as third part of the work whose first two parts are recent arXive
preprints 1204.0200 and 1204.2423 . Especially we consider crucial role of
parametric processes in creating the chaos and simultaneously obstacles to its
synchronization, and examine some possibilities of good enough synchronization
(to an extent allowing its use for direct secure communication in microwave
band).",1204.5410v1
2013-04-09,Instability of Walker Propagating Domain Wall in Magnetic Nanowires,"Stability of the well-known Walker propagating domain wall (DW) solution of
the Landau-Lifshitz-Gilbert equation is analytically investigated.
Surprisingly, the Walker's rigid body propagating DW mode is not stable against
the spin wave/wavepacket emission. In the low field region only stern spin
waves are emitted while both stern and bow waves are generated under high
fields. In a high enough field, but below the Walker breakdown field, the
Walker solution could be convective/absolute unstable if the transverse
magnetic anisotropy is larger than a critical value, corresponding to a
significant modification of the DW profile and DW propagating speed.",1304.2439v1
2014-11-19,Spin waves scattering on a Bloch point,"We show that, after a transformation, the dynamics of linear perturbations
(spin waves) around a singular Bloch point soliton is formally equivalent to a
quantum system of an electron in a magnetic monopole field. The analytical
solution to this problem is known and allows us to find the spectrum and the
scattering of a wave in a Bloch point field.",1411.5096v1
2014-12-18,Coherent elastic excitation of spin waves,"We model the injection of elastic waves into a ferromagnetic film (F) by a
non-magnetic transducer (N). We compare the configurations in which the
magnetization is normal and parallel to the wave propagation. The lack of axial
symmetry in the former results in the emergence of evanescent interface states.
We compute the energy-flux transmission across the N$|$F interface and
sound-induced magnetization dynamics in the ferromagnet. We predict efficient
acoustically induced pumping of spin current into a metal contact attached to
F.",1412.5820v2
2015-10-29,Spontaneous symmetry breaking in correlated wave functions,"We show that Jastrow-Slater wave functions, in which a density-density
Jastrow factor is applied onto an uncorrelated fermionic state, may possess
long-range order even when all symmetries are preserved in the wave function.
This fact is mainly related to the presence of a sufficiently strong Jastrow
term (also including the case of full Gutzwiller projection, suitable for
describing spin models). Selected examples are reported, including the spawning
of N\'eel order and dimerization in spin systems, and the stabilization of
charge and orbital order in itinerant electronic systems.",1510.08653v2
2016-01-31,Application of the Mössbauer spectroscopy to study harmonically modulated electronic structures: case study of charge- and spin-density waves in Cr and its alloys,"Relevance of the M\""ossbauer spectroscopy in the study of harmonically
modulated electronic structures i.e. spin-density waves (SDWs) and
charge-density waves (CDWs) is presented and discussed. First, the effect of
various parameters pertinent to the SDWs and CDWs is outlined on simulated
119Sn spectra and distributions of the hyperfine field and the isomer shift.
Next, various examples of the 119Sn spectra measured on single-crystals and
polycrystalline samples of Cr and Cr-V are reviewed.",1602.00272v1
2018-01-09,Dirac particles in a gravitational shock wave,"Using the Newman-Penrose formalism we calculate the positive energy momentum
eigenstates of the Dirac equation for a plane polarized grav- itational wave
pulse. We then consider Dirac particles whose spins are polarized in each
orthonormal coordinate direction prior to the arrival of the gravitational wave
pulse, and determine how the spins are changed by the pulse after its
departure.",1801.02756v3
2014-06-12,Gyratonic pp-waves and their impulsive limit,"We investigate a class of gravitational pp-waves which represent the exterior
vacuum field of spinning particles moving with the speed of light. Such exact
spacetimes are described by the original Brinkmann form of the pp-wave metric
including the often neglected off-diagonal terms. We put emphasis on a clear
physical and geometrical interpretation of these off-diagonal metric
components. We explicitly analyze several new properties of these spacetimes
associated with the spinning character of the source, such as rotational
dragging of frames, geodesic deviation, impulsive limits and the corresponding
behavior of geodesics.",1406.3227v2
2004-05-27,Excitation of magnetostatic spin waves in ferromagnetic films,"The torque equation of nonlinear spin dynamics is considered in the
magnetostatic approximation. In this framework, exact expressions for
propagator of linear magnetostatic waves in ferromagnetic film between two
antennas and corresponding mutual impedance of the antennas are derived, under
conditions of uniform but arbitrarily oriented static magnetization and
arbitrary anisotropy. The results imply also full description of spectrum of
the waves.",0405640v1
2023-07-05,Lifshitz model in the presence of spin-orbit coupling,"Wave function of a localized state created by a short-range impurity in two
dimensions falls off with distance, r, from the impurity as r^{-1/2}exp(-r/a),
where ""a"" is the localization radius. With randomly positioned identical
impurities with low concentration, n<<a^{-2}, the level smears into a band due
to the overlap of the impurity wave functions. This is the essence of the
Lifshitz model. We demonstrate that, upon incorporation of the spin-orbit
coupling, the impurity wave functions acquire oscillating factors which,
subsequently, modify their overlap. As a result of such modification, the
density of states develops singularities at certain energies.",2307.01971v1
2023-10-26,Spontaneously sliding multipole spin density waves in cold atoms,"We report on the observation of spontaneously drifting coupled spin and
quadrupolar density waves in the ground state of laser driven Rubidium atoms.
These laser-cooled atomic ensembles exhibit spontaneous magnetism via light
mediated interactions when submitted to optical feedback by a retro-reflecting
mirror. Drift direction and chirality of the waves arise from spontaneous
symmetry breaking. The observations demonstrate a novel transport process in
out-of-equilibrium magnetic systems.",2310.17305v2
2024-01-16,Wave packet treatment of neutrino flavour and spin oscillations in galactic and extragalactic magnetic fields,"We consider neutrino flavour and spin oscillations in a magnetic field using
formalism of wave packets. Decoherence effects due to neutrino wave packets
separation are studied. The considered effects are especially important for
describing astrophysical neutrino oscillations, since they propagate on
kiloparsec scale and bigger. The obtained results are of interest for neutrino
telescopes IceCube, Baikal-GVD and KM3NeT, and also can be applied for
description of supernovae neutrino oscillations effects would be detected by
JUNO and Hyper-Kamiokande.",2401.08724v2
2004-05-28,Hyperfine interaction in a quantum dot: Non-Markovian electron spin dynamics,"We have performed a systematic calculation for the non-Markovian dynamics of
a localized electron spin interacting with an environment of nuclear spins via
the Fermi contact hyperfine interaction. This work applies to an electron in
the s -type orbital ground state of a quantum dot or bound to a donor impurity,
and is valid for arbitrary polarization p of the nuclear spin system, and
arbitrary nuclear spin I in high magnetic fields. In the limit of p=1 and
I=1/2, the Born approximation of our perturbative theory recovers the exact
electron spin dynamics. We have found the form of the generalized master
equation (GME) for the longitudinal and transverse components of the electron
spin to all orders in the electron spin--nuclear spin flip-flop terms. Our
perturbative expansion is regular, unlike standard time-dependent perturbation
theory, and can be carried-out to higher orders. We show this explicitly with a
fourth-order calculation of the longitudinal spin dynamics. In zero magnetic
field, the fraction of the electron spin that decays is bounded by the
smallness parameter \delta=1/p^{2}N, where N is the number of nuclear spins
within the extent of the electron wave function. However, the form of the decay
can only be determined in a high magnetic field, much larger than the maximum
Overhauser field. In general the electron spin shows rich dynamics, described
by a sum of contributions with non-exponential decay, exponential decay, and
undamped oscillations. There is an abrupt crossover in the electron spin
asymptotics at a critical dimensionality and shape of the electron envelope
wave function. We propose a scheme that could be used to measure the
non-Markovian dynamics using a standard spin-echo technique, even when the
fraction that undergoes non-Markovian dynamics is small.",0405676v2
2004-12-29,An analytic study of the gravitational wave pulsar signal with spin down effects,"In this work, we present the analytic treatment of the Fourier Transform (FT)
of the Gravitational Wave (GW) signal from a pulsar including spin down
corrections in a parametrized model discussed by Brady et. al. The formalism
lends itself to a development of the FT in terms of well known special
functions and integrals defining the spin down moments.",0412646v1
2005-06-23,A short note on climbing gravity improbable: Superradiant ring fellowship of launching the high Lorentz-factor outflows/jets,"The spin energy extraction from a rotating black hole by amplification of
scalar waves inside superradiance resonance wedge cavity (ring), followed by
jet formation via magnetic reconnection assisted by the amplified scalar
fields, is proposed. This mechanism may explain the availability of energy for
as well as the formation of relativistic jets with high Lorentz-factor in
microquasars and quasars. It is speculated that it may also explain that the
spin of the central black hole, which facilitates the formation of
superradiance cavity, which in turn would produce the amplified scalar waves by
taking the hole's spin energy, is the source for the distinction between
radio-loud and radio-quiet active galaxies.",0506557v1
1992-11-24,Possible Quantum Spin Liquid States on the Triangular and Kagome Lattices,"The frustrated spin-one-half Heisenberg model on triangualr and Kagome
Lattices is mapped onto a single specis of fermion carrying statistical flux.
The corresponding Chern-Simons gauge theory is analyzed at the Gaussian level
and found to be massive. This provides a new motivation for the spin-liquid
Kalmeyer-Laughlin wave function. Good overlap of this wave function with the
numerical ground state is found for small clusters.",9211017v1
1993-10-11,Half-Integral Spin-Singlet Quantum Hall Effect,"We provide numerical evidence that the ground state of a short range
interaction model at $\nu=1/2$ is incompressible and spin-singlet for a wide
range of repulsive interactions. Furthermore it is accurately described by a
trial wave function studied earlier. For the Coulomb interaction we find that
this wave function provides a good description of the lowest lying spin-singlet
state, and propose that fractional quantum Hall effect would occur at $\nu=1/2$
if this state became the global ground state.",9310020v1
1994-04-18,Intensity correlations in electronic wave propagation in a disordered medium: the influence of spin-orbit scattering,"We obtain explicit expressions for the correlation functions of transmission
and reflection coefficients of coherent electronic waves propagating through a
disordered quasi-one-dimensional medium with purely elastic diffusive
scattering in the presence of spin-orbit interactions. We find in the metallic
regime both large local intensity fluctuations and long-range correlations
which ultimately lead to universal conductance fluctuations. We show that the
main effect of spin-orbit scattering is to suppress both local and long-range
intensity fluctuations by a universal symmetry factor 4. We use a scattering
approach based on random transfer matrices.",9404054v1
1997-09-26,Scaling relation of spin wave lifetime in double-exchange systems,"Spin excitation spectrum of CMR manganites are studied from both theoretical
and experimental sides. Scaling relations for the spin wave lifetime in the
electronic model with double-exchange interaction is observed, which is
consistent with results for neutron inelastic scattering experiments for
(La,Y)$_{0.8}$Sr$_{0.2}$MnO$_3$. Roles of other interactions and degrees of
freedom such as polaron effects are also discussed.",9709294v1
1998-03-20,Transitions between Phases with Equal Wave Numbers in a Double Ising Spin Model. Application to Betaine Calcium Chloride Dihydrate,"A Double Ising Spin model for uniaxially structurally modulated materials
exhibits as a special feature phase transitions between phases with equal wave
numbers but different pseudo spin configurations. The character of these
`internal' transitions is investigated in mean field approximation, with the
mean field transfer matrix method, and in Monte Carlo simulations. The
structural changes at the transitions are characterized by different strengths
of harmonics in a Fourier analysis of the spatial modulation. A dielectric
anomaly in the phase diagram of betaine calcium chloride dihydrate (BCCD) and
seemingly contradictory structure analyses are explained.",9803252v1
1998-04-06,Helical spin-density wave in doped V2O3,"Recent neutron scattering and nuclear magnetic resonance experiments have
revealed that the low temperature phase of doped V_{2-y}O_3 is an itinerant
antiferromagnet with a helical spin structure. We use a band structure
calculation as the point of departure to show that these experiments are in
agreement with mean field results for an Overhauser spin-density wave state.
The influences of a finite life-time and of dilute magnetic impurities are
discussed.",9804052v1
1999-04-26,Magnon Damping by magnon-phonon coupling in Manganese Perovskites,"Inelastic neutron scattering was used to systematically investigate the
spin-wave excitations (magnons) in ferromagnetic manganese perovskites. In
spite of the large differences in the Curie temperatures ($T_C$s) of different
manganites, their low-temperature spin waves were found to have very similar
dispersions with the zone boundary magnon softening. From the wavevector
dependence of the magnon lifetime effects and its correlation with the
dispersions of the optical phonon modes, we argue that a strong magneto-elastic
coupling is responsible for the observed low temperature anomalous spin
dynamical behavior of the manganites.",9904372v1
1999-07-12,Quantum Hall Transitions in Field Induced Spin Density Wave Systems,"Field Induced Spin Density Wave (FISDW) systems exhibit coexistence phases
between well defined quantum Hall plateau phases with even integers 2N and 2N'.
We show that a disordered coexistence region accounts for the observed peaks in
the longitudinal resistivity as the field varies between plateaux. It also
results in a random spin mixing which yields two energy split extended states.
The longitudinal resistance is expected to show peaks witha temperature (T)
dependent width proportional to the kappa's power of T. The peak width should
saturate below the non-nesting interlayer coupling of order 40 mK",9907170v1
1999-07-19,Spin waves in a two dimensional p-wave superconductor: Sr$_2$RuO$_4$,"We study spin excitations in a two dimensional p-wave superconductor with
${\vec \Delta} = {\hat d}({\hat k}_1 \pm i {\hat k}_2)$ symmetry in the context
of the newly discovered superconducting Sr$_2$RuO$_4$. The polarization and
spectrum of spin wave excitations are identified and their experimental
consequences are discussed.",9907276v2
2001-05-31,Phase transition and spin-wave dispersion in quantum Hall bilayers at filling factor nu=1,"We present an effective Hamiltonian for a bilayer quantum Hall system at
filling factor $\nu=1$ neglecting charge fluctuations. Our model is formulated
in terms of spin and pseudospin operators and is an exact representation of the
system within the above approximation. We analyze its low-lying excitations in
terms of spin-wave theory. Moreover we add to previous first-principle
exact-diagonalization studies concentrating on the quantum phase transition
seen in this system.",0105625v2
2001-08-24,Influence of disorder on the ferromagnetism in diluted magnetic semiconductors,"Influence of disorder on the ferromagnetic phase transition in diluted
(III,Mn)V semiconductors is investigated analytically. The regime of small
disorder is addressed, and the enhancement of the critical temperature by
disorder is found both in the mean field approximation and from the analysis of
the zero temperature spin stiffness. Due to disorder, the spin wave
fluctuations around the ferromagnetically ordered state acquire a finite mass.
At large charge carrier band width, the spin wave mass squared becomes
negative, signaling the breakdown of the ferromagnetic ground state and the
onset of a noncollinear magnetic order.",0108396v2
2001-10-16,"Spin Waves, Phase Separation, and Interphase Boundaries in Double Exchange Magnets","We study a classical double exchange magnet with direct antiferromagnetic
superexchange coupling, J, between the localized spins. It is shown that the
de-stabilization of the ferromagnetic ground state with increasing J leads to
phase separation; the latter always preempts the spin-wave instability
(softening of the magnon spectrum). It is also found that the boundaries
separating the ferromagnetic and antiferromagnetic areas of the sample tend to
be abrupt.",0110322v2
2002-05-08,Superconductor-to-Spin-Density-Wave Transition in Quasi-One-Dimensional Metals with Ising Anisotropy,"We study a mechanism for superconductivity in quasi-one-dimensional materials
with Ising anisotropy. In an isolated chain Ising anisotropy opens a spin gap;
if inter-chain coupling is sufficiently weak, single particle hopping is
suppressed and the physics of coupled chains is controlled by a competition
between pair hopping and exchange interaction. Spin density wave and triplet
superconductivity phases are found separated by a first order phase transition.
For particular parameter values a second order transition described by SO(4)
symmetry is found.",0205166v1
2002-09-23,Rigorous Proof of Pseudospin Ferromagnetism in Two-Component Bosonic Systems with Component-Independent Interactions,"For a two-component bosonic system, the components can be mapped onto a
pseudo-spin degree of freedom with spin quantum number S=1/2. We provide a
rigorous proof that for a wide-range of real Hamiltonians with component
independent mass and interaction, the ground state is a ferromagnetic state
with pseudospin fully polarized. The spin-wave excitations are studied and
found to have quadratic dispersion relations at long wave length.",0209529v1
2003-02-24,Study of low-energy magnetic excitations in single-crystalline CeIn3 by inelastic neutron scattering,"Inelastic neutron scattering experiments were performed on single crystals of
the heavy-fermion compound CeIn$_{3}$ for temperatures below and above the
N\'eel temperature, $T_N$. In the antiferromagnetically ordered phase,
well-defined spin-wave excitations with a bandwidth of 2 meV are observed. The
spin waves coexist with quasielastic (QE) Kondo-type spin-fluctuations and
broadened crystal-field (CF) excitations below $T_N$. Above $T_N$, only the QE
and CF excitations persist, with a weak temperature dependence.",0302487v1
2003-04-02,Current-induced transverse spin wave instability in a thin nanomagnet,"We show that an unpolarized electric current incident perpendicular to the
plane of a thin ferromagnet can excite a spin-wave instability transverse to
the current direction if source and drain contacts are not symmetric. The
instability, which is driven by the current-induced ``spin-transfer torque'',
exists for one current direction only.",0304069v2
2003-06-30,A chiral spin liquid wave function and the Lieb-Schulz-Mattis theorem,"We study a chiral spin liquid wave function defined as a Gutwziller projected
BCS state with a complex pairing function. After projection, spontaneous
dimerization is found for any odd but finite number of chains, thus satisfying
the Lieb-Schultz-Mattis theorem, whereas for even number of chains there is no
dimerization. The two-dimensional thermodynamic limit is consistently reached
for large number of chains since the dimer order parameter vanishes in this
limit. This property clearly supports the possibility of a spin liquid ground
state in two dimensions with a gap to all {\em physical} excitations and with
no broken translation symmetry.",0306732v1
2003-07-09,Photoemission study of the spin-density wave state in thin films of Cr,"Angle-resolved photoemission (PE) was used to characterize the spin-density
wave (SDW) state in thin films of Cr grown on W(110). The PE data were analysed
using results of local spin density approximation layer-Korringa-Kohn-Rostoker
calculations. It is shown that the incommensurate SDW can be monitored and
important parameters of SDW-related interactions, such as coupling strength and
energy of collective magnetic excitations, can be determined from the
dispersion of the renormalized electronic bands close to the Fermi energy. The
developed approach can readily be applied to other SDW systems including
magnetic multilayer structures.",0307196v1
2004-01-24,Static and Dynamic Properties of Antiferromagnetic Heisenberg Ladders: Fermionic versus Bosonic Approaches,"In terms of spinless fermions via the Jordan-Wigner transformation along a
snake-like path and spin waves modified so as to restore the sublattice
symmetry, we investigate static and dynamic properties of two-leg
antiferromagnetic Heisenberg ladders. The specific heat is finely reproduced by
the spinless fermions, whereas the magnetic susceptibility is well described by
the modified spin waves. The nuclear spin-lattice relaxation rate is discussed
in detail with particular emphasis on its novel field dependence.",0401477v1
2004-06-05,Perturbative calculation of the spin-wave dispersion in a disordered double-exchange model,"We study the spin-wave dispersion of localized spins in a disordered
double-exchange model using the perturbation theory with respect to the
strength of the disorder potential. We calculate the dispersion upto the
next-leading order, and extensively examine the case of one-dimension. We show
that in that case, disorder yields anomalous gapped-like behavior at the Fermi
wavenumber of the conduction electrons.",0406134v1
2005-04-26,Spin-Polarized Standing Waves in the Fermi Surface of a Ferromagnetic Thin Film,"The spin-selective electron reflection at a ferromagnetic-paramagnetic
interface is investigated using Fe films on a W(110) substrate. Angle-resolved
photoemission of the majority and minority Fermi surfaces of the Fe film is
used to probe standing wave formation. Intense quantum well states resulting
from interfacial reflection are observed exclusively for majority states. Such
high spin polarization is explained by the Fermi surface topology of the
connecting substrate, and we argue that Fe/W is a particularly suitable
interface for that purpose.",0504670v1
2006-06-07,Pseudogap enhancement due to magnetic impurities in d-density waves,"We study the effect of quantum magnetic impurities on d-wave spin density
waves (d-SDW). The impurity spins are aligned coherently according to the spin
space anisotropy of the condensate. Both the order parameter and transition
temperature increases due to the coherent interplay between magnetic scatterers
and d-SDW. This can explain the recent experimental data on the pseudogap
enhancement of Ni substituted NdBa_2{Cu_{1-y}Ni_y}O_6.8 from Pimenov et al.
(Phys. Rev. Lett. 94, 227003 (2005)).",0606176v1
2006-09-13,Spin-wave dispersion in half-doped LaSrNiO,"Recent neutron scattering measurements reveal spin and charge ordering in the
half-doped nickelate, La$_{3/2}$ Sr$_{1/2}$ NiO$_4$. Many of the features of
the magnetic excitations have been explained in terms of the spin waves of
diagonal stripes with weak single-ion anisotropy. However, an optical mode
dispersing away from the (\pi,\pi) point was not captured by this theory. We
show here that this apparent optical mode is a natural consequence of stripe
twinning in a diagonal stripe pattern with a magnetic coupling structure which
is two-fold symmetric, i.e. one possessing the same spatial rotational symmetry
as the ground state.",0609300v1
1999-10-12,"Gravity Waves, Chaos, and Spinning Compact Binaries","Spinning compact binaries are shown to be chaotic in the Post-Newtonian
expansion of the two body system. Chaos by definition is the extreme
sensitivity to initial conditions and a consequent inability to predict the
outcome of the evolution. As a result, the spinning pair will have
unpredictable gravitational waveforms during coalescence. This poses a
challenge to future gravity wave observatories which rely on a match between
the data and a theoretical template.",9910040v3
1994-09-23,Motion of Spin-1/2 Particles in External Gravitational and Electromagnetic Fields,"(Talk presented at the 7th Marcel Grossmann Meeting on General Relativity,
Stanford, CA, July 24-30, 1994) We study the semi-classical limit of the
solution of the Dirac equation in a background electromagnetic/gravitational
plane wave. We show that the exact solution corresponding to an asymptotically
fixed incoming momentum satisfies constraints consistent with the classical
notion of a spinning particle. In order to further analyze the motion of a
spinning particle in this external inhomogeneous field one has to consider
wave-packet superpositions of these exact solutions. We are currently
investigating the existence of a classical theory of a phenomenological spin
tensor which reproduces our quantum-mechanical results.",9409147v1
2003-06-28,On Equations for a Spin-2 Particle in External Gravitational Field,"30-component, of the first order, equation for a spin 2 particle, equivalent
to the second order Pauli-Fierz one, is generalized to presence of an external
electromagnetic field as well as a curved background space-time geometry. The
essential property of the generally covariant wave equation obtained is that
here from the very beginning, in accordance with requirement of the Pauli-Fierz
approach, a set of additional relations on 30-component wave function for
eliminating complementary spin 0 and spin 1 fields is present at the starting
equation.",0306286v1
2004-08-05,The novel aspect of hydrogen atom: the fine structure and spin can be derived by single component wavefunction,"The fine structure of hydrogen energy was calculated by using the usual
momentum-wavefunction relation directly, rather than establishing the
well-known Dirac wave equation. As the results, the energy levels are
completely the same as that of the Dirac wave equation, while the wavefunction
is single component that is quite different from Dirac's four component
wavefunction, the most important thing is that the present calculation brings
out electronic spin in a new way which has never been reported and indicates
that the electronic spin is a kind of orbital motion.",0408025v1
2007-06-14,Spin-waves in a complex magnetic system: nonextensive approach,"In this paper we analyze the spin-wave excitations (magnons) of an
inhomogeneous spin system within the Boltzmann-Gibbs framework and then connect
the results with the nonextensive approach (in the sense of Tsallis
statistics). Considering an equivalence between those two frameworks, we could
connect the entropic parameter q with moments of the distribution of exchange
integrals of the inhomogenous system. It ratifies the idea that the entropic
parameter is connected to the microscopic properties of the system.",0706.2201v2
2007-10-19,Paramagnonlike excitations and spin diffusion in magnetic resonance studies of copper oxide superconductors,"The relaxation function theory for a doped two-dimensional Heisenberg
antiferromagnetic system in the paramagnetic state for all wave vectors through
the Brillouin zone is presented in view of low frequency response of high-$T_c$
copper oxide superconductors. We deduced the regions of long lifetime [$T
\lesssim 400(1-4x)$ K] and ""overdamped"" [$T \gtrsim 700(1-4x)$ K]
paramagnonlike excitations in the temperature ($T$)-doping index ($x$) phase
diagram from plane oxygen nuclear spin-lattice relaxation rate $^{17}(1/T_1)$
data in up to optimally doped La$_{2-x}$Sr$_{x}$CuO$_{4}$ thus providing the
regimes for the spin wave concept and the ''overdamped'' mode.",0710.3615v1
2009-06-30,Quantum phase transition of the 103mRh spin-density wave,"We induce a quantum phase transition of the 103mRh excitation at the critical
density of 10^{12} cm^{-3} by bremsstrahlung pumping at 300 K. A massive 103mRh
spin-density wave carrying a spin current moves on the identical 103Rh matrix
like a quantum fluid. The collapse-and-revival spectral evolution indicates
that the collective nuclear excitation undergoes dynamic Bose-Einstein
condensation. Applying an external magnetic field, we observe the
Onsager-Feynman quantization, which gives further evidence of the superfluidic
phase.",0906.5417v1
2009-10-15,Dixon's extended bodies and impulsive gravitational waves,"The ""reaction"" of an extended body to the passage of an exact plane
gravitational wave is discussed following Dixon's model. The analysis performed
shows several general features, e.g. even if initially absent, the body
acquires a spin induced by the quadrupole structure, the center of mass moves
from its initial position, as well as certain ""spin-flip"" or ""spin-glitch""
effects which are being observed.",0910.2846v1
2010-11-04,Spin wave calculation of the field-dependent magnetization pattern around an impurity in Heisenberg antiferromagnets,"We consider the magnetic-field dependent spatial magnetization pattern around
a general impurity embedded in a Heisenberg antiferromagnet using both an
analytical and a numerical spin wave approach. The results are compared to
quantum Monte Carlo simulations. The decay of the magnetization pattern away
from the impurity follows a universal form which reflects the properties of the
pure antiferromagnetic Heisenberg model. Only the overall magnitude of the
induced magnetization depends also on the size of the impurity spin and the
impurity coupling.",1011.1271v1
2010-11-15,Study of the Spin-weighted Spheroidal Equation in the Case of s=1,"We present series study of using the method of super-symmetric quantum
mechanics(SUSYQM) solving the spin-weighted spheroidal wave equation. In this
paper, we obtain the first four terms of super-potential of the spin-weighted
spheroidal wave equation in the case of s=1. These results may help summary the
general form for the n-th term of the super-potential, which is proved correct
by means of induction. We finally compute the ground eigenvalues and ground
eigenfunction. All the results may be of significative for studies of
electromagnetic radiation processes near rotating black holes and compute
radiation reaction in curved space-time.",1011.4045v1
2010-11-19,Spin waves in magnetic quantum wells with Coulomb interaction and $sd$ exchange coupling,"We theoretically describe the spin excitation spectrum of a two dimensional
electron gas embedded in a quantum well with localized magnetic impurities.
Compared to the previous work, we introduce equations that allow to consider
the interplay between the Coulomb interaction of delocalized electrons and the
$sd$ exchange coupling between electrons and magnetic impurities. Strong
qualitative changes are found : mixed waves propagate below the single particle
continuum, an anticrossing gap is open at a specific wavevector and the kinetic
damping due to the electron motion strongly influences the coupling strength
between electrons and impurities spins.",1011.4422v1
2011-04-01,Spin waves cause non-linear friction,"Energy dissipation is studied for a hard magnetic tip that scans a soft
magnetic substrate. The dynamics of the atomic moments are simulated by solving
the Landau-Lifshitz-Gilbert (LLG) equation numerically. The local energy
currents are analysed for the case of a Heisenberg spin chain taken as
substrate. This leads to an explanation for the velocity dependence of the
friction force: The non-linear contribution for high velocities can be
attributed to a spin wave front pushed by the tip along the substrate.",1104.0197v2
2011-07-05,Magnetic field and quark matter in the core,"Magnetic properties of quark matter are discussed in the light of the
observation of pulsars. Our works about spontaneous spin polarization and spin
density wave are reviewed and their implications on compact-star phenomena are
discussed. In particular, the former subject may be directly related to the
origin of strong magnetic fields. An inhomogeneous state emerges following the
chiral transition, where a kind of spin density wave develops.",1107.0807v2
2011-09-02,Gravitational Waves and the Maximum Spin Frequency of Neutron Stars,"In this Letter we re-examine the idea that gravitational waves are required
as a braking mechanism to explain the observed maximum spin-frequency of
neutron stars. We show that for millisecond X-ray pulsars, the existence of
spin equilibrium as set by the disk/magnetosphere interaction is sufficient to
explain the observations. We show as well that no clear correlation exists
between the neutron star magnetic field B and the X-ray outburst luminosity Lx
when considering an enlarged sample size of millisecond X-ray pulsars.",1109.0536v1
2011-12-13,Spectral properties of one-dimensional spiral spin density wave states,"We provide a full characterization of the spectral properties of spiral spin
density wave (SSDW) states which emerge in one-dimensional electron systems
coupled to localized magnetic moments or quantum wires with spin-orbit
interactions. We derive analytic results for the spectral function, local
density of states and optical conductivity in the low-energy limit by using
field theory techniques. We identify various collective modes and show that the
spectrum strongly depends on the interaction strength between the electrons.
The results provide characteristic signatures for an experimental detection of
SSDW states.",1112.3045v2
2012-01-17,Four Wave Mixing from Fe3+ Spins in Sapphire,"Fe3+ ions in sapphire exhibit an Electron Spin Resonance (ESR) which
interacts strongly with high-Q Whispering Gallery (WG) modes at microwave
frequencies. We report the first observation of a third-order paramagnetic
nonlinear susceptibility in such a resonator at cryogenic temperatures, and the
first demonstration of four wave mixing (FWM) using this parametric
nonlinearity. This observation of an all-microwave nonlinearity is an enabling
step towards a host of quantum measurement and control applications which
utilize spins in solids.",1201.3421v1
2012-03-07,Temperature Induced Spin Density Wave in Magnetic Doped Topological Insulators,"We study the magnetic properties of topological insulators doped with
isoelectronic magnetic impurities. We obtain that at zero temperature the
impurities order ferromagnetically, but when raising the temperature the
topological insulator undergoes a first order phase transition to a spin
density wave phase before the system reaches the paramagnetic phase. The origin
of this phase is the non-trivial dependence of the topological insulator spin
susceptibility on the momentum. We analyze the coupling of the non-uniform
magnetic phase with the Dirac electronic system that occurs at the surfaces of
the topological insulators.",1203.1436v2
2012-03-13,Spin induced multipole moments for the gravitational wave amplitude from binary inspirals to 2.5 Post-Newtonian order,"Using the NRGR effective field theory formalism we calculate the remaining
source multipole moments necessary to obtain the spin contributions to the
gravitational wave amplitude to 2.5 Post-Newtonian (PN) order. We also
reproduce the tail contribution to the waveform linear in spin at 2.5PN arising
from the nonlinear interaction between the current quadrupole and the mass
monopole.",1203.2962v2
2012-06-15,Kinks and waterfalls as signatures of competing order in angle-resolved photoemission spectra of La_{2-x}Sr_xCuO_4,"We show that the so-called kinks and waterfalls observed in angle-resolved
photoemission spectra of La2-xSrxCuO4, a prototypical high-Tc superconducting
cuprate, result from the coupling of quasiparticles with two distinct nearly
critical collective modes with finite characteristic wave vectors, typical of
charge and spin fluctuations near a stripe instability. Both phonon-like charge
and spin collective modes are needed to account for the kinked quasiparticle
dispersions. This clarifies the long-standing question whether kinks are due to
phonons or spin waves and the nature of the bosonic mediators of the
electron-electron effective interaction in La2-xSrxCuO4.",1206.3427v1
2012-08-01,Spin density wave and superconductivity in CaFe_{1-x}Co_{x}AsF studied by nuclear magnetic resonance,"We performed nuclear magnetic resonance (NMR) measurements to investigate the
evolution of spin-density-wave (SDW) and superconducting (SC) states upon
electron doping in CaFe_{1-x}Co_{x}AsF, which exhibits an intermediate phase
diagram between those of LaFeAsO_{1-x}F_x and Ba(Fe_{1-x}Co_x)_2As_2. We found
that homogeneous coexistence of the incommensurate SDW and SC states occurs
only in a narrow doping region around the crossover regime, which supports
S_{+-}-wave symmetry. However, only the structural phase transition survives
upon further doping, which agrees with predictions from orbital fluctuation
theory. The transitional features upon electron doping imply that both spin and
orbital fluctuations are involved in the superconducting mechanism.",1208.0141v2
2012-12-17,Electromagnetic soliton-particle with spin and magnetic moment,"Electromagnetic soliton-particle with both quasi-static and quick-oscillating
wave parts is considered. Its mass, spin, charge, and magnetic moment appear
naturally when the interaction with distant solitons is considered. The
substantiation of Dirac equation for the wave part of the interacting
soliton-particle is given.",1212.4468v1
2013-03-12,Thermally excited spin waves in a nano-structure: thermal gradient vs. constant temperature,"Using micromagnetic simulations, we have investigated spin dynamics in a
nanostructure in the presence of thermal fluctuations. In particular, we have
studied the effects of a uniform temperature and of a uniform thermal gradient.
In both cases, the stochastic field leads to an increase of the precession
angle of the magnetization, and to a mild decreas of the linewidth of the
resonance peaks. Our results indicate that the Gilbert damping parameter plays
the role of control parameter for the amplification of spin waves.",1303.2895v1
2013-03-31,Semi classical modeling of isotropic Non-Heisenberg magnets for spin S=1 and linear quadrupole excitation dynamics,"In this paper, equations describing one-dimensional Non-Heisenberg model are
studied by use of generalized coherent states in real parameterization and then
dissipative spin wave equation for dipole and quadrupole branches is obtained
if there is a small linear excitation from the ground state. Finally, it is
shown that for such exchange-isotropy Hamiltonians, optical branch of spin wave
is non-dissipative.",1304.0245v1
2013-04-02,Asymptotic spectrum of the oblate spin-weighted spheroidal harmonics: a WKB analysis,"Spin-weighted spheroidal harmonics play a central role in the mathematical
description of diverse physical phenomena, including black-hole perturbation
theory and wave scattering. We present a novel and compact derivation of the
asymptotic eigenvalues of these important functions. Our analysis is based on a
simple trick which transforms the corresponding spin-weighted spheroidal
angular equation into a Schr\""odinger-like wave equation which is amenable to a
standard WKB analysis.",1304.0529v1
2013-08-14,Electrical Detection of Spin Wave Resonance in a Permalloy Thin Strip,"We investigated the microwave-induced DC response of spin wave resonance
(SWR) in a permalloy thin strip via electrical detection. Our experimental
results obtained by sweeping the external field reveal that: 1. the amplitude
of SWR signals depend on the direction of external field and, 2. unlike the DC
response of ferromagnetic resonance, SWR spectra are always anti-symmetrical.
The spin dynamics are discussed based on these unusual signals in resonant
condition.",1308.3069v1
2013-09-19,Equivariant and self-similar standing waves for a Hamiltonian hyperbolic-hyperbolic spin-field system,"In this paper we study the existence of special symmetric solutions to a
Hamiltonian hyperbolic-hyperbolic coupled spin-field system, where the spins
are maps from $\mathbb R^{2+1}$ into the sphere $\S^2$ or the pseudo-sphere
$\H^2$. This model was introduced in \cite{Martina} and it is also known as the
{\it hyperbolic-hyperbolic generalized Ishimori system}. Relying on the
hyperbolic coordinates introduced in \cite{KNZ11}, we prove the existence of
equivariant standing waves in both regular hyperbolic coordinates as well as
similarity variables, and describe their asymptotic behaviour.",1309.5066v2
2013-10-12,Inversion Phenomena of the Anisotropies of the Hamiltonian and the Wave Function in Quantum Spin Chains,"We investigate the inversion phenomena between the XXZ anisotropies of the
Hamiltonian and the wave function in quantum spin chains. We focus on the S=1/2
geometrically frustrated 3-leg ladder system with the XXZ interaction
anisotropy. By use of the degenerate perturbation theory from the strong rung
coupling limit, we have obtained the ground-state phase diagram. In some
parameter regions, the Tomonaga-Luttinger spin liquid state is realized in
spite of the Ising-like anisotropy, and the Neel state in spite of the XY-like
anisotropy.",1310.3394v1
2014-05-07,Spin structure factor and quantum phases of frustrated spin-1/2 chains,"The static structure factor S(q) of frustrated spin-1/2 chains with isotropic
exchange and a singlet ground state (GS) diverges at wave vector q_m when the
GS has quasi-long-range order (QLRO) with periodicity 2\pi/q_m but S(q_m) is
finite in bond-order-wave (BOW) phases with finite-range spin correlations.
Exact diagonalization and density matrix renormalization group (DMRG)
calculations of S(q) indicate a decoupled phase with QLRO and q_m = \pi/2 in
chains with large antiferromagnetic exchange between second neighbors. S(q_m)
identifies quantum phase transitions based on GS spin correlations.",1405.1578v1
2014-08-21,Scattering by an electromagnetic radiation field,"Motion of test particles in the gravitational field associated with an
electromagnetic plane wave is investigated. The interaction with the radiation
field is modeled by a force term {\it \`a la} Poynting-Robertson entering the
equations of motion given by the 4-momentum density of radiation observed in
the particle's rest frame with a multiplicative constant factor expressing the
strength of the interaction itself. Explicit analytical solutions are obtained.
Scattering of fields by the electromagnetic wave, i.e., scalar (spin 0),
massless spin $\frac12$ and electromagnetic (spin 1) fields, is studied too.",1408.4958v1
2014-11-14,Magnetic order and spin excitations in layered Heisenberg antiferromagnets with compass-model anisotropies,"The spin-wave excitation spectrum, the magnetization, and the N\'{e}el
temperature for the quasi-two-dimensional spin-1/2 antiferromagnetic Heisenberg
model with compass-model interaction in the plane proposed for iridates are
calculated in the random phase approximation. The spin-wave spectrum agrees
well with data of Lanczos diagonalization. We find that the Neel temperature is
enhanced by the compass-model interaction and is close to the experimental
value for Ba2IrO4.",1411.3920v2
2015-04-03,Solitons in a continuous classical Haldane-Shastry spin chain,"Motivated by Polychronakos' discovery that solitons exist in the hydrodynamic
equations of continuum version of the Calogero model, we seek solitons in the
classical dynamics of a continuum version of the Haldane-Shastry spin chain. We
have obtained analytic multi-lump solitary wave solutions for our spin-field
equation, and these solutions possess interesting topological features. We have
performed numerical collision experiments showing that these solitary waves
survive collisions, and thus suggest the existence of true multi-soliton
solutions.",1504.00873v1
2016-01-30,Low-Temperature Spin-Wave Approximation for the Heisenberg Ferromagnet,"We study the low temperature thermodynamics of the quantum Heisenberg
ferromagnet in three dimension for any value of the spin $ S \geq 1/2 $. We
report on a rigorous proof of the validity of the spin-wave approximation for
the excitation spectrum, at the level of the first non-trivial contribution to
the free energy as the inverse temperature $ \beta \to \infty $.",1602.00155v1
2018-09-26,Resonant magnetic induction tomography of a magnetized sphere,"We demonstrate the structural imaging of magnetostatic spin-wave modes hosted
in a millimeter-sized ferromagnetic sphere. Unlike for low-dimensional magnetic
materials, there is no prior technique to image these modes in bulk magnetized
solid of revolution. Based on resonant magnetic induction tomography in the
microwave range, our approach ensures the robust identification of these
non-trivial spin-wave modes by establishing their azimuthal and polar
dependences, starting point of magnonic fundamental studies and hybrid systems
with complex spin textures well beyond the uniform precession mode.",1809.09785v2
2021-04-27,Field-driven dynamics of magnetic Hopfions,"We present micromagnetic simulations on resonant spin wave modes of magnetic
Hopfions up to 15 GHz driven by external magnetic fields. A sharp transition is
found around 32 mT coinciding with a transition from Hopfions to magnetic
torons. The modes exhibit characteristic amplitudes in frequency space
accompanied by unique localization patterns in real space, and are found to be
robust to damping around topological features, particularly vortex lines in
Hopfions and Bloch points in torons. The marked differences in spin wave
spectra between Hopfions, torons and target skyrmions can serve as fingerprints
in future experimental validation studies of these novel 3d topological spin
textures.",2104.13349v1
2019-09-10,Enhanced Detectability of Spinning Primordial Black Holes,"Primordial black holes which are produced during an epoch of matter
domination are expected to spin rapidly. It is shown that this leads to an
enhancement of the detectability of the stochastic gravitational-wave
background from their mergers. For a specific model, we explicitly demonstrate
that this yields a $50\,\%$ increase of the gravitational-wave amplitude as
compared to the non-spinning case.",1909.04742v2
2020-07-30,Derivation of the Half-Wave Maps Equation from Calogero--Moser Spin Systems,"We prove that the energy-critical half-wave maps equation \[ \partial_t
\mathbf{S} =\mathbf{S} \times |\nabla| \mathbf{S}, \quad (t,x) \in \mathbb{R}
\times \mathbb{T} \] arises as an effective equation in the continuum limit of
completely integrable Calogero-Moser classical spin systems with inverse square
$1/r^2$ interactions on the circle. We study both the convergence to
global-in-time weak solutions in the energy class as well as short-time strong
solutions of higher regularity. The proofs are based on Fourier methods and
suitable discrete analogues of fractional Leibniz rules and Kato-Ponce-Vega
commutator estimates.
  In a companion paper, we further extend our arguments to study the real line
case and more general spin interactions.",2007.15323v1
2020-12-02,Effects of exchange distortions in the magnetic Kagome lattice,"This study examines the effect of distorted triangular magnetic interactions
in the Kagome lattice. Using a Holstein-Primakoff expansion, we determine the
analytical solutions for classical energies and the spin-wave modes for various
magnetic configurations. By understanding the magnetic phase diagram, we
characterize the changes in the spin waves and examine the spin distortions of
the ferromagnetic (FM), Antiferrimagnetic (AfM), and 120$^{\circ}$ phases that
are produced by variable exchange interactions and lead to various
non-collinear phases, which provides a deeper understanding of the magnetic
fingerprints of these configurations for experimental characterization and
identification.",2012.00910v1
2021-01-18,Quantum fluctuation effects on the ordered Moments in a two dimensional frustrated ferrimagnet,"We propose a novel two-dimensional (2D)frustrated quantum spin-1/2
anisotropic Heisenberg model with alternating ferromagnetic and
antiferromagnetic magnetic chains along one direction and antiferromagnetic
interactions along the other. The (mean-field) ground state is ferrimagnetic in
certain range of the interaction space. Spin-wave theory analysis of the
reduction of ordered moments at inequivalent spin sites and the instability of
the spin waves suggest a quantum phase transition which has the characteristics
of both the frustrated two-dimensional antiferromagnetic S=1/2 ($J_1, J_2$)
model and 1D S$_1$=1, S$_2$=1/2 quantum ferrimagnetic model.",2101.07300v1
2021-12-27,Penrose limit of MNa solution and spin chains in three-dimensional field theories,"In three dimensions, a theory with spontaneous breaking of supersymmetry was
described holographically by the Maldacena-Nastase (MNa) solution. We revisit
the issue of its Penrose limit, and compare the resulting pp wave and its
string eigenstates to a sector of the theory on 5-branes reduced on $S^3$, and
a spin chain-like system. We obtain many of the features of the pp wave
analysis, but a complete matching still eludes us. We suggest possible
explanations for the resulting partial mismatch, and compare against other spin
chains for 3-dimensional field theories with gravity duals.",2112.13802v2
2022-04-19,Spin correlations in the frustrated ferro-antiferromagnet SrZnVO(PO4)2 near saturation,"Single crystal elastic and inelastic neutron scattering experiments are
performed on the frustrated ferro-antiferromagnet SrZnVO(PO4)2 in high magnetic
fields. The fully polarized state, the presaturation phase and the
columnar-antiferromagnetic phase just bellow the presaturation phase were
investigated. The observed renormalization of spin wave bandwidths,
re-distribution of intensities between different branches and non-linearities
in the magnetization curve are all indicative of strong deviations from
classical spin wave theory. The previously observed presaturation transition is
attributed to a staggered pattern of Dzyaloshinskii-Moriya interactions.",2204.08778v2
2023-03-20,Electron Wave Spin in Excited States,"The wave spin of an electron can be fully characterized by the current
density calculated from the exact four-spinor solution of the Dirac equation.
In the excited states of the electron in a magnetic field-free quantum well,
the current density has a multiple vortex topology. The interaction of the
current with a magnetic potential produces a finer structure of anomalous
Zeeman splitting. When the magnetic potential is comparable to the size of the
individual vortices, fractional or zero spin effects can be observed.",2303.10855v1
2023-09-09,Teukolsky-like equations with various spins in spherically symmetric spacetime,"We study the wave equations with various spins on the background of the
general spherically symmetric spacetime. We obtain the unified expression of
the Teukolsky-like master equations and the corresponding radial equations with
the general spins. We also discuss the gauge dependence in the
gravitational-wave equations, which have appeared in the previous studies.",2309.04758v2
2010-07-23,Intrinsic selection biases of ground-based gravitational wave searches for high-mass BH-BH mergers,"The next generation of ground-based gravitational wave detectors may detect a
few mergers of comparable-mass M\simeq 100-1000 Msun (""intermediate-mass'', or
IMBH) spinning black holes. Black hole spin is known to have a significant
impact on the orbit, merger signal, and post-merger ringdown of any binary with
non-negligible spin. In particular, the detection volume for spinning binaries
depends significantly on the component black hole spins. We provide a fit to
the single-detector and isotropic-network detection volume versus (total) mass
and arbitrary spin for equal-mass binaries. Our analysis assumes matched
filtering to all significant available waveform power (up to l=6 available for
fitting, but only l<= 4 significant) estimated by an array of 64 numerical
simulations with component spins as large as S_{1,2}/M^2 <= 0.8. We provide a
spin-dependent estimate of our uncertainty, up to S_{1,2}/M^2 <= 1. For the
initial (advanced) LIGO detector, our fits are reliable for
$M\in[100,500]M_\odot$ ($M\in[100,1600]M_\odot$). In the online version of this
article, we also provide fits assuming incomplete information, such as the
neglect of higher-order harmonics. We briefly discuss how a strong selection
bias towards aligned spins influences the interpretation of future
gravitational wave detections of IMBH-IMBH mergers.",1007.4213v2
2013-07-06,Accuracy of gravitational waveform models for observing neutron-star--black-hole binaries in Advanced LIGO,"Gravitational waves radiated by the coalescence of compact-object binaries
containing a neutron star and a black hole are one of the most interesting
sources for the ground-based gravitational-wave observatories Advanced LIGO and
Advanced Virgo. Advanced LIGO will be sensitive to the inspiral of a $1.4\,
M_\odot$ neutron star into a $10\,M_\odot$ black hole to a maximum distance of
$\sim 900$ Mpc. Achieving this sensitivity and extracting the physics imprinted
in observed signals requires accurate modeling of the binary to construct
template waveforms. In a NSBH binary, the black hole may have significant
angular momentum (spin), which affects the phase evolution of the emitted
gravitational waves. We investigate the ability of post-Newtonian (PN)
templates to model the gravitational waves emitted during the inspiral phase of
NSBH binaries. We restrict the black hole's spin to be aligned with the orbital
angular momentum and compare several approximants. We examine restricted
amplitude waveforms that are accurate to 3.5PN order in the orbital dynamics
and complete to 2.5PN order in the spin dynamics. We also consider PN waveforms
with the recently derived 3.5PN spin-orbit and 3PN spin-orbit tail corrections.
We compare these approximants to the effective-one-body model. For all these
models, large disagreements start at low to moderate black hole spins,
particularly for binaries where the spin is anti-aligned with the orbital
angular momentum. We show that this divergence begins in the early inspiral at
$v \sim 0.2$ for $\chi_{BH} \sim 0.4$. PN spin corrections beyond those
currently known will be required for optimal detection searches and to measure
the parameters of neutron star--black hole binaries. While this complicates
searches, the strong dependence of the gravitational-wave signal on the spin
dynamics will make it possible to extract significant astrophysical
information.",1307.1757v2
2018-11-14,"Anisotropic-Exchange Magnets on a Triangular Lattice: Spin Waves, Accidental Degeneracies, and Dual Spin Liquids","We present an extensive overview of the phase diagram, spin-wave excitations,
and finite-temperature transitions of the anisotropic-exchange magnets on an
ideal nearest-neighbor triangular lattice. We investigate transitions between
five principal classical phases of the corresponding model: ferromagnetic,
N\'{e}el, its dual, and the two stripe phases. Transitions are identified by
the spin-wave instabilities and by the Luttinger-Tisza approach. Some of the
transitions are direct and others occur via intermediate phases with more
complicated forms of ordering. In a portion of the N\'{e}el phase, we find
spin-wave instabilities to a long-range spiral-like state. In the stripe
phases, quantum fluctuations are mostly negligible, leaving the ordered moment
nearly saturated even for the $S=1/2$ case. However, for a two-dimensional
surface of the full 3D parameter space, the spin-wave spectrum in one of the
stripe phases exhibits an enigmatic accidental degeneracy manifested by
pseudo-Goldstone modes. As a result, despite the nearly classical ground state,
the ordering transition temperature in a wide region of the phase diagram is
significantly suppressed from the mean-field expectation. We identify this
accidental degeneracy as due to an exact correspondence to an extended
Kitaev-Heisenberg model with emergent symmetries that naturally lead to the
pseudo-Goldstone modes. There are previously studied dualities within the
Kitaev-Heisenberg model on the triangular lattice that are exposed here in a
wider parameter space. One important implication of this correspondence for the
$S=1/2$ case is the existence of a region of the spin-liquid phase that is dual
to the spin-liquid phase discovered recently by us. We complement our studies
by the density-matrix renormalization group of the $S=1/2$ model to confirm
some of the duality relations and to verify the existence of the dual
spin-liquid phase.",1811.05983v4
2023-08-09,Competing itinerant and local spin interactions in kagome metal FeGe,"Two-dimensional kagome metals consisting of corner-sharing triangles offer a
unique platform for studying strong electron correlations and band topology due
to its geometrically frustrated lattice structure. The similar energy scales
between spin, lattice, and electronic degrees of freedom in these systems give
rise to competing quantum phases such as charge density wave (CDW), magnetic
order, and superconductivity. For example, kagome metal FeGe first exhibits
A-type collinear antiferromagnetic (AFM) order at T_N ~ 400 K, then establishes
a CDW phase coupled with AFM ordered moment below T_CDW ~ 100 K, and finally
forms a $c$-axis double cone AFM structure around T_Canting ~ 60 K. Here we use
neutron scattering to demonstrate the presence of gapless incommensurate spin
excitations associated with the double cone AFM structure at temperatures well
above T_Canting and T_CDW that merge into gapped commensurate spin waves from
the A-type AFM order. While commensurate spin waves follow the Bose population
factor and can be well described by a local moment Heisenberg Hamiltonian, the
incommensurate spin excitations first appear below T_N where AFM order is
commensurate, start to deviate from the Bose population factor around T_CDW,
and peaks at T_Canting, consistent with a critical scattering of a second order
magnetic phase transition, as a function of decreasing temperature. By
comparing these results with density functional theory calculations, we
conclude that the incommensurate magnetic structure arises from the nested
Fermi surfaces of itinerant electrons and the formation of a spin density wave
order. The temperature dependence of the incommensurate spin excitations
suggests a coupling between spin density wave and CDW order, likely due to flat
electronic bands near the Fermi level around T_N and associated electron
correlation effects.",2308.04815v1
2009-06-25,Intermediate-statistics spin waves,"In this paper, we show that spin waves, the elementary excitation of the
Heisenberg magnetic system, obey a kind of intermediate statistics with a
finite maximum occupation number n. We construct an operator realization for
the intermediate statistics obeyed by magnons, the quantized spin waves, and
then construct a corresponding intermediate-statistics realization for the
angular momentum algebra in terms of the creation and annihilation operators of
the magnons. In other words, instead of the Holstein-Primakoff representation,
a bosonic representation subject to a constraint on the occupation number, we
present an intermediate-statistics representation with no constraints. In this
realization, the maximum occupation number is naturally embodied in the
commutation relation of creation and annihilation operators, while the
Holstein-Primakoff representation is a bosonic operator relation with an
additional putting-in-by-hand restriction on the occupation number. We deduce
the intermediate-statistics distribution function for magnons. On the basis of
these results, we calculate the dispersion relations for ferromagnetic and
antiferromagnetic spin waves. The relations between the intermediate statistics
that magnons obey and the other two important kinds of intermediate statistics,
Haldane-Wu statistics and the fractional statistics of anyons, are discussed.
We also compare the spectrum of the intermediate-statistics spin wave with the
exact solution of the one-dimensional s = 1/2 Heisenberg model, which is
obtained by the Bethe ansatz method. For ferromagnets, we take the
contributions from the interaction between magnons (the quartic contribution),
the next-to-nearest neighbor interaction, and the dipolar interaction into
account for comparison with the experiment.",0906.4818v1
2013-03-29,Next-to-next-to-leading order spin-orbit effects in the gravitational wave flux and orbital phasing of compact binaries,"We compute the next-to-next-to-leading order spin-orbit contributions in the
total energy flux emitted in gravitational waves by compact binary systems.
Such contributions correspond to the post-Newtonian order 3.5PN for maximally
spinning compact objects. Continuing our recent work on the
next-to-next-to-leading spin-orbit terms at 3.5PN order in the equations of
motion, we obtain the spin-orbit terms in the multipole moments of the compact
binary system up to the same order within the multipolar post-Newtonian wave
generation formalism. Our calculation of the multipole moments is valid for
general orbits and in an arbitrary frame; the moments are then reduced to the
center-of-mass frame and the resulting energy flux is specialized to
quasi-circular orbits. The test-mass limit of our final result for the flux
agrees with the already known Kerr black hole perturbation limit. Furthermore
the various multipole moments of the compact binary reduce in the one-body case
to those of a single boosted Kerr black hole. We briefly discuss the
implications of our result for the gravitational-wave flux in terms of the
binary's phase evolution, and address its importance for the future detection
and parameter estimation of signals in gravitational wave detectors.",1303.7412v2
2013-06-16,Zero-Field Fiske Resonance Coupled with Spin-waves in Ferromagnetic Josephson Junctions,"AC Josephson current density in a Josephson junction with DC bias is
spatially modulated by an external magnetic field, and induces an
electromagnetic (EM) field inside the junction. The current-voltage ($I$-$V$)
curve exhibits peaks due to the resonance between the EM field and the
spatially modulated AC Josephson current density. This is called {\it Fiske
resonance}. Such a spatially modulated Josephson current density can be also
induced by a non-uniform insulating barrier and the Fiske resonance appears
without external magnetic field. This is called zero-field Fiske resonance
(ZFFR). In this paper, we theoretically study the ZFFR coupled with spin-waves
in a superconductor/ferromagnetic insulator/superconductor junction
(ferromagnetic Josephson junction) with a non-uniform ferromagnetic insulating
barrier. The resonant mode coupled with spin-waves can be induced without
external magnetic field. We find that the $I$-$V$ curve shows resonant peaks
associated with composite excitations of spin-waves and the EM field in the
junction. The voltage at the resonance is obtained as a function of the normal
modes of EM field. The ZFFRs coupled with spin-waves are found as peak
structures in the DC Josephson current density as a function of bias voltage.",1306.3652v2
2013-08-01,Magnetostatic wave analog of integer quantum Hall state in patterned magnetic films,"A magnetostatic spin wave analog of integer quantum Hall (IQH) state is
proposed in realistic patterned ferromagnetic thin films. Due to magnetic shape
anisotropy, magnetic moments in a thin film lie within the plane, while all
spin-wave excitations are fully gapped. Under an out-of-plane magnetic field,
the film acquires a finite magnetization, where some of the gapped magnons
become significantly softened near a saturation field. It is shown that, owing
to a spin-orbit locking nature of the magnetic dipolar interaction, these soft
spin-wave volume-mode bands become chiral volume-mode bands with finite
topological Chern integers. A bulk-edge correspondence in IQH physics suggests
that such volume-mode bands are accompanied by a chiral magnetostatic spin-wave
edge mode. The existence of the edge mode is justified both by micromagnetic
simulations and by band calculations based on a linearized Landau-Lifshitz
equation. Employing intuitive physical arguments, we introduce proper
tight-binding models for these soft volume-mode bands. Based on the
tight-binding models, we further discuss possible applications to other systems
such as magnetic ultrathin films with perpendicular magnetic anisotropy (PMA).",1308.0199v3
2018-07-06,Spin wave modes in a cylindrical nanowire in crossover dipolar-exchange regime,"Nanoscale magnetic systems have been studied extensively in various
geometries, such as wires of different cross-sections, arrays of wires, dots,
rings, etc. Such systems have interesting physical properties and promising
applications in advanced magnetic devices. Uniform magnetic nanowires are the
basic structures which were broadly investigated. However, some of their
dynamical properties, like: (anti)crossing between the spin wave modes and
impact of the magnetic field on spin wave spectrum, still need to be exploited.
We continue this research by investigation of the spin wave dynamics in solid
Ni nanowire of the circular cross-section. We use two approaches:
semi-analytical calculations and numerical computations based on finite element
method. We solve coupled Landau-Lifshitz and Maxwell equations and consider
both magnetostatic and exchange interactions. We identify the dispersion
brunches and its (anti)crossing by plotting the spatial profiles of spin wave
amplitudes and magnetostatic potential. We also check how we can tune the
spectrum of the modes by application of the external magnetic field and how it
affects the modes and their dominating type of interaction.",1807.02580v3
2018-10-15,Multiplexed spin-wave-photon entanglement source using temporal-multimode memories and feedforward-controlled readout,"The sources, which generate atom-photon quantum correlations or entanglement
based on quantum memory, are basic blocks for building quantum repeaters (QRs).
For achieving highly entanglement-generation rates in ensemble-based QRs,
spatial-, temporal- and spectral-multimode memories are needed. The previous
temporal-multimode memories are based on rephrasing mechanisms in
inhomogeneous-broadened media. Here, by applying a train of multi-direction
write pulses into a homogeneous-broadened atomic ensemble to induce
Duan-Lukin-Cirac-Zoller-like Raman processes, we prepare up to 19 pairs of
modes, namely, a spin-wave mode and a photonic time bin. Spin-wave-photon
(i.e., atom-photon) entanglement is probabilistically produced in the mode
pairs. As a proof-in-principle demonstration, we show that the multiplexed
source using all the spin-wave modes and feed-forward-control readout increases
spin-wave-photon entanglement generation rate by a factor of $\sim$18.3,
compared to non-multiplexed source using the individual modes. The measured
Bell parameter for the multiplexed source is $2.30\pm 0.02$ combined with a
memory lifetime of $30\mu s$.",1810.06143v2
2019-03-02,Excitation of unidirectional exchange spin waves by a nanoscale magnetic grating,"Magnon spintronics is a prosperous field that promises beyond-CMOS technology
based on elementary excitations of the magnetic order that act as information
carriers for future computational architectures. Unidirectional propagation of
spin waves is key to the realization of magnonic logic devices. However,
previous efforts to enhance the Damon-Eshbach-type nonreciprocity did not
realize (let alone control) purely unidirectional propagation. Here we
experimentally demonstrate excitations of unidirectional exchange spin waves by
a nanoscale magnetic grating consisting of Co nanowires fabricated on an
ultrathin yttrium iron garnet film. We explain and model the nearly perfect
unidirectional excitation by the chirality of the magneto-dipolar interactions
between the Kittel mode of the nanowires and the exchange spin waves of the
film. Reversal of the magnetic configurations of film and nanowire array from
parallel to antiparallel changes the direction of the excited spin waves. Our
results raise the prospect of a chiral magnonic logic without the need for
fragile surface states.",1903.00638v1
2020-03-06,Quantum-router: Storing and redirecting light at the photon level,"We propose a method for spatially re-routing single photons or light in a
coherent state with small average photon number by purely electronic means,
i.e. without using mechanical devices such as micro-mirror arrays. The method
is based on mapping the quantum state of the incoming light onto a spin-wave in
an atomic ensemble as is done in quantum memories of light. Then the wavevector
of the spin-wave is modified in a controlled way by an applied magnetic field
gradient. Finally, by re-applying the same control beam as for storing, the
signal pulse is released in a new direction that depends on the deflected
wavevector of the spin-wave. We show by numerical simulation that efficiencies
can be achieved for arbitrary deflection angles in the plane that are
comparable with simple photon storage and re-emission in forward direction, and
propose a new method for eliminating the stored momentum as source of
decoherence in the quantum memory. In a reasonable parameter regime, the
re-routing should be achievable on a time-scale on the order of few to
$\sim100$ microseconds, depending on the deflection angle. The shifts in the
wavevector that can be achieved using the Zeeman-effect, with otherwise minimal
changes to the spin-wave, can also be used to complement existing ac-Stark
spin-wave manipulation methods.",2003.03363v3
2020-03-17,Electrical generation and detection of terahertz signal based on spin-wave emission from ferrimagnets,"Terahertz (THz) signals, mainly generated by photonic or electronic
approaches, are being sought for various applications, whereas the development
of magnetic source might be a necessary step to harness the magnetic nature of
electromagnetic radiation. We show that the relativistic effect on the
current-driven domain-wall motion induces THz spin-wave emission in
ferrimagnets. The required current density increases dramatically in materials
with strong exchange interaction and rapidly exceeds 1012 A m-2, leading to the
device breakdown and thus the lack of experimental evidence. By translating the
collective magnetization oscillations into voltage signals, we propose a
three-terminal device for the electrical detection of THz spin wave. Through
material engineering, wide frequency range from 264 GHz to 1.1 THz and uniform
continuous signals with improved output power can be obtained. As a reverse
effect, the spin wave generated in this system is able to move ferrimagnetic
domain wall. Our work provides guidelines for the experimental verification of
THz spin wave, and could stimulate the design of THz spintronic oscillators for
wideband applications as well as the all-magnon spintronic devices.",2003.07750v1
2020-11-23,Fanout of 2 Triangle Shape Spin Wave Logic Gates,"Having multi-output logic gates saves much energy because the same structure
can be used to feed multiple inputs of next stage gates simultaneously. This
paper proposes novel triangle shape fanout of 2 spin wave Majority and XOR
gates; the Majority gate is achieved by phase detection, whereas the XOR gate
is achieved by threshold detection. The proposed logic gates are validated by
means of micromagnetic simulations. Furthermore, the energy and delay are
estimated for the proposed structures and compared with the state-of-the-art
spin wave logic gates, and 16nm and 7nm CMOS. The results demonstrate that the
proposed structures provide energy reduction of 25%-50% in comparison to the
other 2-output spin-wave devices while having the same delay, and energy
reduction between 43x and 0.8x when compared to the 16nm and 7nm CMOS while
having delay overhead between 11x and 40x.",2011.11324v5
2019-01-27,Observation of angle-dependent mode conversion and mode hopping in 2D annular antidot lattice,"We report spin-wave excitations in annular antidot lattice fabricated from 15
nm-thin Ni80Fe20 flm. The nanodots of 170 nm diameters are embedded in the 350
nm (diameter) antidot lattice to form the annular antidot lattice, which is
arranged in a square lattice with edge-to-edge separation of 120 nm. A strong
anisotropy in the spin-wave modes are observed with the change in orientation
angle ({\phi}) of the in-plane bias magnetic field by using Time-resolved
Magneto-optic Kerr microscope. A fattened fourfold rotational symmetry, mode
hopping and mode conversion leading to mode quenching for three prominent
spin-wave modes are observed in this lattice with the variation of the bias
field orientation. Micromagnetic simulations enable us to successfully
reproduce the measured evolution of frequencies with the orientation of bias
magnetic field, as well as to identify the spatial profles of the modes. The
magnetostatic field analysis, suggest the existence of magnetostatic coupling
between the dot and antidot in annular antidot sample. Further local
excitations of some selective spin-wave modes using numerical simulations
showed the anisotropic spin-wave propagation through the lattice.",1901.09324v2
2019-07-25,Excitation and propagation of spin waves in non-uniformly magnetized waveguides,"The characteristics of spin waves in ferromagnetic waveguides with nonuniform
magnetization have been investigated for situations where the shape anisotropy
field of the waveguide is comparable to the external bias field. Spin-wave
generation was realized by the magnetoelastic effect by applying normal and
shear strain components, as well as by the Oersted field emitted by an
inductive antenna. The magnetoelastic excitation field has a nonuniform profile
over the width of the waveguide because of the nonuniform magnetization
orientation, whereas the Oersted field remains uniform. Using micromagnetic
simulations, we indicate that both types of excitation fields generate
quantised width modes with both odd and even mode numbers as well as tilted
phase fronts. We demonstrate that these effects originate from the average
magnetization orientation with respect to the main axes of the magnetic
waveguide. Furthermore, it is indicated that the excitation efficiency of the
second-order mode generally surpasses that of the first-order mode due to their
symmetry. The relative intensity of the excited modes can be controlled by the
strain state as well as by tuning the dimensions of the excitation area.
Finally, we demonstrate that the nonreciprocity of spin-wave radiation due to
the chirality of an Oersted field generated by an inductive antenna is absent
for magnetoelastic spin-wave excitation.",1907.11145v3
2020-10-27,Gravitational waves from mountains in newly born millisecond magnetars,"In this paper we study the spin-evolution and gravitational-wave luminosity
of a newly born millisecond magnetar, formed either after the collapse of a
massive star or after the merger of two neutron stars. In both cases we
consider the effect of fallback accretion, and consider the evolution of the
system due to the different torques acting on the star, namely the spin up
torque due to accretion and spin-down torques due to magnetic dipole radiation,
neutrino emission, and gravitational wave emission linked to the formation of a
`mountain' on the accretion poles. Initially the spin period is mostly affected
by the dipole radiation, but at later times accretion spin the star up rapidly.
We find that a magnetar formed after the collapse of a massive star can accrete
up to 1 M_{\odot} , and survive on the order of 50 s before collapsing to a
black hole. The gravitational wave strain, for an object located at 1 Mpc, is
h_c \sim 10^{-23} at kHz frequencies, making this a potential target for next
generation ground based detectors. A magnetar formed after a binary neutron
star merger, on the other hand, accretes at the most 0.2 M_{\odot}, and emits
gravitational waves with a lower maximum strain of the order of h_c \sim
10^{-24} , but also survives for much longer times, and may possibly be
associated with the X-ray plateau observed in the light curve of a number of
short gamma-ray burst.",2010.15574v2
2021-12-25,Spin-wave-driven skyrmion dynamics in ferrimagnets: Effect of net angular momentum,"Searching for low-power-consuming and high-efficient methods for well
controllable driving of skyrmion motion is one of the most concerned issues for
future spintronic applications, raising high concern with an appreciated choice
of magnetic media and driving scenario. In this work, we propose a novel
scenario of spin wave driven skyrmion motion in a ferrimagnetic (FiM) lattice
with the net angular momentum {\delta}s. We investigate theoretically the
effect of both {\delta}s and the circular polarization of spin wave on the
skyrmion dynamics. It is revealed that the momentum onto the skyrmion imposed
by the excited spin wave can be partitioned into a ferromagnetic term plus an
antiferromagnetic term. The ratio of these two terms and consequently the Hall
angle of skyrmion motion can be formulated as the functions of {\delta}s,
demonstrating the key role of {\delta}s as an effective control-parameter for
the skyrmion motion. Moreover, the spin wave frequency dependent skyrmion
motion is discussed, predicting the frequency enhanced skyrmion Hall motion.
This work thus represents an essential contribution to understand the skyrmion
dynamics in a FiM lattice.",2112.13232v2
2021-12-27,Variational Approach to Quantum Spin Liquid in a Rydberg Atom Simulator,"Recently the Rydberg blockade effect has been utilized to realize quantum
spin liquid on the kagome lattice. Evidence of quantum spin liquid has been
obtained experimentally by directly measuring non-local string order. In this
letter, we report a BCS-type variational wave function study of the spin liquid
state in this model. This wave function is motivated by mapping the Rydberg
blockade model to a lattice gauge theory, where the local gauge conservations
replace the role of constraints from the Rydberg blockade. We determine the
variational parameter from the experimental measurement of the Rydberg atom
population. Then we compare the predictions of this deterministic wave function
with the experimental measurements of non-local string order. Combining the
measurements on both open and closed strings, we extract the fluctuations only
associated with the closed-loop as an indicator of the topological order. The
prediction from our wave function agrees reasonably well with the experimental
data without any fitting parameter. Our variational wave function provides a
simple and intuitive picture of the quantum spin liquid in this system that can
be generalized to various generalizations of the current model.",2112.13688v3
2022-04-12,Generation of highly retrievable atom photon entanglement with a millisecond lifetime via a spatially multiplexed cavity,"Qubit memory that is entangled with photonic qubit is the building block for
long distance quantum repeaters. Cavity enhanced and long lived spin wave
photon entanglement has been demonstrated by applying dual laser beams onto
optical-lattice atoms. However, owing to cross readouts by two beams, retrieval
efficiency of spin wave qubit is decreased by one quarter compared to that of
single mode spin wave at all storage times. Here, by coupling cold atoms to two
modes of a polarization interferometer based cavity, we achieve perfect qubit
retrieval in cavity enhanced and long lived atom photon entanglement. A write
laser beam is applied onto cold atoms, we then create a magnetic field
insensitive spin wave qubit that is entangled with the photonic qubit encoded
onto two arms of the interferometer. The spin wave qubit is retrieved by a read
beam, which avoids the cross readouts. Our experiment demonstrates 540{\mu}s
storage time at 50% intrinsic qubit retrieval efficiency, which is 13.5 times
longer than the best reported result.",2204.05794v2
2022-06-10,Observing high-k magnons with Mie-resonance-enhanced Brillouin light scattering,"Magnonics is a prospective beyond CMOS technology which uses magnons, the
quanta of spin waves, for low-power information processing. Many magnonic
concepts and devices were recently demonstrated at macro- and microscale, and
now these concepts need to be realized at nanoscale. Brillouin light scattering
spectroscopy and microscopy (BLS) has become a standard technique for spin wave
visualization and characterization, and enabled many pioneering magnonic
experiments. However, due to its fundamental limit in maximum detectable magnon
momentum, the conventional BLS cannot be used to detect nanoscale spin waves.
Here we show that optically induced Mie resonances in dielectric nanoparticles
can be used to extend the range of accessible spin wave wavevectors beyond the
BLS fundamental limit. The method is universal and can be used in many magnonic
experiments dealing with thermally excited as well as coherently excited
high-momentum, short-wavelength spin waves. This discovery significantly
extends the usability and relevance of the BLS technique for nanoscale magnonic
research.",2206.05178v3
2022-12-05,Propagating spin-wave spectroscopy in nanometer-thick YIG films at millikelvin temperatures,"Performing propagating spin-wave spectroscopy of thin films at millikelvin
temperatures is the next step towards the realisation of large-scale integrated
magnonic circuits for quantum applications. Here we demonstrate spin-wave
propagation in a $100\,\mathrm{nm}$-thick yttrium-iron-garnet film at the
temperatures down to $45 \,\mathrm{mK}$, using stripline nanoantennas deposited
on YIG surface for the electrical excitation and detection. The clear
transmission characteristics over the distance of $10\,\mu \mathrm{m}$ are
measured and the subtracted spin-wave group velocity and the YIG saturation
magnetisation agree well with the theoretical values. We show that the
gadolinium-gallium-garnet substrate influences the spin-wave propagation
characteristics only for the applied magnetic fields beyond $75\,\mathrm{mT}$,
originating from a GGG magnetisation up to $47 \,\mathrm{kA/m}$ at $45
\,\mathrm{mK}$. Our results show that the developed fabrication and measurement
methodologies enable the realisation of integrated magnonic quantum
nanotechnologies at millikelvin temperatures.",2212.02257v3
2023-05-06,Thermal features of Heisenberg antiferromagnets on edge- versus corner-sharing triangular-based lattices: A message from spin waves,"We construct modified spin-wave thermodynamics for frustrated noncollinear
antiferromagnets for the first time. The well-known modified spin-wave theory
for collinear antiferromagnets diagonalizes a bosonic Hamiltonian subject to
the constraint that the total staggered magnetization be zero. Applying this
scheme as it is to frustrated noncollinear antiferromagnets ends in a poor
thermodynamics, missing the optimal ground state and breaking the local U(1)
rotational symmetry. We find a new double-constraint modification scheme to
overcome this difficulty, which is tuned especially to frustrated spiral
magnets but spontaneously goes back to the standard single-constraint condition
at the onset of a collinear N\'eel-ordered classical ground state.
  We apply this new scheme to triangular-based polyhedral and planar
antiferromagnets with particular interest in a possible contrast between edge-
versus corner-sharing geometries. Under such circumstances that very few
methods are available to calculate finite-temperature properties of frustrated
noncollinear quantum magnets in the thermodynamic limit, our newly developed
modified spin-wave theory predicts that the specific heat of the kagome-lattice
Heisenberg antiferromagnet in the corner-sharing geometry remains having both
mid-temperature broad maximum and low-temperature narrow peak in the
thermodynamic limit, while the specific heat of the triangular-lattice
Heisenberg antiferromagnet in the edge-sharing geometry retains a
low-temperature sharp peak followed by a mid-temperature weak anormaly in the
thermodynamic limit.",2305.03958v1
2024-01-19,Exploration of magnon-magnon coupling in an antidot lattice: The role of non-uniform magnetization texture,"We numerically study the spin wave dynamics in an antidot lattice based on a
Co/Pd multilayer structure with reduced perpendicular magnetic anisotropy at
the edges of the antidots. This structure forms a magnonic crystal with a
periodic antidot pattern and a periodic magnetization configuration consisting
of out-of-plane magnetized bulk and in-plane magnetized rims. Our results show
the different behavior of spin waves in the bulk and in the rims under varying
out-of-plane external magnetic field strength, revealing complex spin-wave
spectra and hybridizations between the modes of these two subsystems. A
particularly strong magnon-magnon coupling, due to exchange interactions, is
found between the fundamental bulk spin-wave mode and the second-order radial
rim modes. However, the dynamical coupling between the spin-wave modes at low
frequencies, involving the first-order radial rim modes, is masked by the
changes in the static magnetization at the bulk-rim interface with magnetic
field changes. The study expands the horizons of magnonic-crystal research by
combining periodic structural patterning and non-collinear magnetization
texture to achieve strong magnon-magnon coupling, highlighting the significant
role of exchange interactions in the coupling.",2401.10540v2
2024-02-05,Understanding voltage-controlled magnetic anisotropy effect for the manipulation of dipolar-dominated propagating spin waves,"Spin waves, known for their ability to propagate without the involvement of
moving charges, hold immense promise for on-chip information transfer and
processing, offering a path toward post-CMOS computing technologies. This study
investigates the potential synergy between propagating Damon-Eshbach spin waves
and voltage-controlled magnetization in the pursuit of environmentally
sustainable computing solutions. Employing micromagnetic simulations, we assess
the feasibility of utilizing spin waves in DE mode in conjunction with
localized voltage-induced alterations in surface anisotropy to enable
low-energy logic operations. Our findings underscore the critical importance of
selecting an optimal excitation frequency and gate width, which significantly
influence the efficiency of the phase shift induced in propagating spin waves.
Notably, we demonstrate that a realistic phase shift of 2.5$\left[ \pi \
\text{mrad}\right]$ can be achieved at a Co(5nm)/MgO material system via the
VCMA effect. Moreover, by tuning the excitation frequency, Co layer thickness,
gate width, and the use of a GdO\textsubscript{x} dielectric, we illustrate the
potential to enhance the phase shift by a factor of 200 when compared to MgO
dielectrics. This research contributes valuable insights towards developing
next-generation computing technologies with reduced energy consumption.",2402.03033v1
2016-05-31,The mechanical back-action of a spin-wave resonance in a magnetoelastic thin film on a surface acoustic wave,"Surface acoustic waves (SAWs) traveling on the surface of a piezoelectric
crystal can, through the magnetoelastic interaction, excite traveling spin-wave
resonance in a magnetic film deposited on the substrate. This spin-wave
resonance in the magnetic film creates a time dynamic surface stress of
magnetoelastic origin that acts back on the surface of the piezoelectric and
modifies the SAW propagation. Unlike previous analyses that treat the
excitation as a magnon-phonon polariton, here the magnetoelastic film is
treated as a perturbation modifying boundary conditions on the SAW. We use
acoustical perturbation theory to find closed form expressions for the
back-action surface stress and strain fields and the resultant SAW velocity
shifts and attenuation. We demonstrate that the shear stress fields associated
with this spin-wave back-action also generate effective surface currents on the
piezoelectric both in-phase and out-of-phase with the driving SAW potential.
Characterization of these surface currents and their applications in
determination of the magnetoelastic coupling are discussed. The perturbative
calculation is carried out explicitly to first order (a regime corresponding to
many experimental situations of current interest) and we provide a sketch of
the implications of the theory at higher order.",1605.09475v2
2024-01-24,Spin Seebeck Effect as a Probe for Majorana Fermions in Kitaev Spin Liquids,"Quantum entanglement in strongly correlated electron systems often leads to
exotic elementary excitations. Quantum spin liquids (QSLs) provide a
paradigmatic example, where the elementary excitations are described by
fractional quasiparticles such as spinons. However, such fractional
quasiparticles behave differently from electrons, making their experimental
identification challenging. Here, we theoretically investigate the spin Seebeck
effect, which is a thermoelectric response via a spin current, as an efficient
probe of the fractional quasiparticles in QSLs, focusing on the Kitaev
honeycomb model. By comprehensive studies using the real-time dynamics, the
perturbation theory, and the linear spin-wave theory based on the tunnel
spin-current theory, we find that the spin current is induced by thermal
gradient in the Kitaev spin liquid, via the low-energy fractional Majorana
excitations. This underscores the ability of Majorana fermions to carry spin
current, despite lacking spin angular momentum. Furthermore, we find that the
induced spin current changes its sign depending on the sign of the Kitaev
interaction, indicating that the Majorana fermions contribute to the spin
current with (up-)down-spin like nature when the exchange coupling is
(anti)ferromagnetic. Thus, in contrast to the negative spin current already
found in a one-dimensional QSL, our finding reveals that the spin Seebeck
effect can exhibit either positive or negative signals, contingent upon the
nature of fractional excitations in the QSLs. We also clarify contrasting
field-angle dependence between the Kitaev spin liquid in the low-field limit
and the high-field ferromagnetic state, which is useful for the experimental
identification. Our finding suggests that the spin Seebeck effect could be used
not only to detect fractional quasiparticles emerging in QSLs but also to
generate and control them.",2401.13175v1
2008-09-02,Wave packet dynamics in a monolayer graphene,"The dynamics of charge particles described by Gaussian wave packet in
monolayer graphene is studied analytically and numerically. We demonstrate that
the shape of wave packet at arbitrary time depends on correlation between the
initial electron amplitudes $\psi_1(\vec r,0)$ and $\psi_2(\vec r,0)$ on the
sublattices $A$ and $B$ correspondingly (i.e. pseudospin polarization). For the
transverse pseudospin polarization the motion of the center of wave packet
occurs in the direction perpendicular to the average momentum $ {\vec
p_0}=\hbar \vec{k_0}$. Moreover, in this case the initial wave packet splits
into two parts moving with opposite velocities along $ {\vec p_0}$. If the
initial direction of pseudospin coincides with average momentum the splitting
is absent and the center of wave packet is displaced at $t>0$ along the same
direction. The results of our calculations show that all types of motion
experience {\it zitterbewegung}. Besides, depending on initial polarization the
velocity of the packet center may have the constant component $v_c=uf(a)$,
where $u\approx 10^8 cm/s$ is the Fermi velocity and $f(a)$ is a function of
the parameter $a=k_0d$ ($d$ is the initial width of wave packet). As a result,
the direction of the packet motion is determined not only by the orientation of
the average momentum, but mainly by the phase difference between the up- and
low- components of the wave functions. Similar peculiarities of the dynamics of
2D electron wave packet connected with initial spin polarization should take
place in the semiconductor quantum well under the influence of the Rashba
spin-orbit coupling.",0809.0367v2
2012-04-04,Similar zone-center gaps in the low-energy spin-wave spectra of NaFeAs and BaFe2As2,"We report results of inelastic-neutron-scattering measurements of low-energy
spin-wave excitations in two structurally distinct families of iron-pnictide
parent compounds: Na(1-{\delta})FeAs and BaFe2As2. Despite their very different
values of the ordered magnetic moment and N\'eel temperatures, T_N, in the
antiferromagnetic state both compounds exhibit similar spin gaps of the order
of 10 meV at the magnetic Brillouin-zone center. The gap opens sharply below
T_N, with no signatures of a precursor gap at temperatures between the
orthorhombic and magnetic phase transitions in Na(1-{\delta})FeAs. We also find
a relatively weak dispersion of the spin-wave gap in BaFe2As2 along the
out-of-plane momentum component, q_z. At the magnetic zone boundary (q_z = 0),
spin excitations in the ordered state persist down to 20 meV, which implies a
much smaller value of the effective out-of-plane exchange interaction, J_c, as
compared to previous estimates based on fitting the high-energy spin-wave
dispersion to a Heisenberg-type model.",1204.0875v2
2013-04-25,Statistical and systematic errors for gravitational-wave inspiral signals: A principal component analysis,"Identifying the source parameters from a gravitational-wave measurement alone
is limited by our ability to discriminate signals from different sources and
the accuracy of the waveform family employed in the search. Here we address
both issues in the framework of an adapted coordinate system that allows for
linear Fisher-matrix type calculations of waveform differences that are both
accurate and computationally very efficient. We investigate statistical errors
by using principal component analysis of the post-Newtonian (PN) expansion
coefficients, which is well conditioned despite the Fisher matrix becoming ill
conditioned for larger numbers of parameters. We identify which combinations of
physical parameters are most effectively measured by gravitational-wave
detectors for systems of neutron stars and black holes with aligned spin. We
confirm the expectation that the dominant parameter of the inspiral waveform is
the chirp mass. The next dominant parameter depends on a combination of the
spin and the symmetric mass ratio. In addition, we can study the systematic
effect of various spin contributions to the PN phasing within the same
parametrization, showing that the inclusion of spin-orbit corrections up to
next-to-leading order, but not necessarily of spin-spin contributions, is
crucial for an accurate inspiral waveform model. This understanding of the
waveform structure throughout the parameter space is important to set up an
efficient search strategy and correctly interpret future gravitational-wave
observations.",1304.7017v2
2016-09-07,Magnonic Interferometric Switch for Multi-Valued Logic Circuits,"We investigated a possible use of the magnonic interferometric switches in
multi-valued logic circuits. The switch is a three-terminal device consisting
of two spin channels where input, control, and output signals are spin waves.
Signal modulation is achieved via the interference between the source and gate
spin waves. We report experimental data on a micrometer scale prototype based
on Y3Fe2(FeO4)3 structure. The output characteristics are measured at different
angles of the bias magnetic field. The On/Off ratio of the prototype exceeds 36
dB at room temperature. Experimental data is complemented by the theoretical
analysis and the results of micro magnetic simulations showing spin wave
propagation in a micrometer size magnetic junction. We also present the results
of numerical modeling illustrating the operation of a nanometer-size switch
consisting of just 20 spins in the source-drain channel. The utilization of
spin wave interference as a switching mechanism makes it possible to build
nanometer-scale logic gates, and minimize energy per operation, which is
limited only by the noise margin. The utilization of phase in addition to
amplitude for information encoding offers an innovative route towards
multi-state logic circuits. We describe possible implementation of the
three-value logic circuits based on the magnonic interferometric switches. The
advantages and shortcomings inherent in interferometric switches are also
discussed.",1609.02217v1
2018-06-09,Mapping out the spin-wave modes of constriction-based spin Hall nano-oscillators in weak in-plane fields,"We experimentally study the auto-oscillating spin-wave modes in
NiFe/$\beta-$W constriction-based spin Hall nano-oscillators as a function of
bias current, in-plane applied field strength, and azimuthal field angle, in
the low-field range of 40-80 mT. We observe two different spin-wave modes: i) a
linear-like mode confined to the minima of the internal field near the edges of
the nanoconstriction, with weak frequency dependencies on the bias current and
the applied field angle, and ii) a second, lower frequency mode that has
significantly higher threshold current and stronger frequency dependencies on
both bias current and the external field angle. Our micromagnetic modeling
qualitatively reproduces the experimental data and reveals that the second mode
is a spin-wave bullet and that the SHNO mode hops between the two modes,
resulting in a substantial increase in linewidths. In contrast to the
linear-like mode, the bullet is localized in the middle of the constriction and
shrinks with increasing bias current. Utilizing intrinsic frequency doubling at
zero field angle we can reach frequencies above 9 GHz in fields as low as 40
mT, which is important for the development of low-field spintronic oscillators
with applications in microwave signal generation and neuromorphic computing.",1806.03473v1
2018-12-17,Spin-adapted selected configuration interaction in a determinant basis,"Selected configuration interaction (SCI) methods, when complemented with a
second-order perturbative correction, provide near full configuration
interaction (FCI) quality energies with only a small fraction of the Slater
determinants of the FCI space. However, a selection criterion based on
determinants alone does not ensure a spin-pure wave function. In other words,
such SCI wave functions are not eigenfunctions of the $S^2$ operator. In many
situations (bond breaking, magnetic system, excited state, etc), having a
spin-adapted wave function is essential for a quantitatively correct
description of the system. Here, we propose an efficient algorithm which, given
an arbitrary determinant space, generates all the missing Slater determinants
allowing one to obtain spin-adapted wave functions while avoiding manipulations
involving configuration state functions. For example, generating all the
possible determinants with 6 spin-up and 6 spin-down electrons in 12 open
shells takes 21 CPU cycles per generated Slater determinant. The selection is
still done with individual determinants, and one can take advantage of the
basis of configuration state functions in the diagonalization of the
Hamiltonian to reduce significantly the memory footprint.",1812.06902v3
2019-01-26,All optical detection of picosecond spin-wave dynamics in two-dimensional annular antidot lattice,"Novel magnetic structures with precisely controlled dimensions and shapes at
the nanoscale have potential applications in spin logic, spintronics and other
spin-based communication devices. We report the fabrication of two-dimensional
bi-structure magnonic crystal in the form of embedded nanodots in a periodic
Ni80Fe20 antidot lattice structure (annular antidot) by focused ion-beam
lithography. The spin-wave spectra of the annular antidot sample,studied for
the first time by a time-resolved magneto-optic Kerr effect microscopy show a
remarkable variation with bias field, which is important for the above device
applications. The optically induced spin-wave spectra show multiple modes in
the frequency range 14.7 GHz to 3.5 GHz due to collective interactions between
the dots and antidots as well as the annular elements within the whole array.
Numerical simulations qualitatively reproduce the experimental results, and
simulated mode profiles reveal the spatial distribution of the spin wave modes
and internal magnetic fields responsible for these observations. It is observed
that the internal field strength increases by about 200 Oe inside each dot
embedded within the hole of annular antidot lattice as compared to pure antidot
lattice and pure dot lattice. The stray field for the annular antidot lattice
is found to be significant (0.8kOe) as opposed to the negligible values of the
same for the pure dot lattice and pure antidot lattice. Our findings open up
new possibilities for development of novel artificial crystals.",1901.09152v1
2020-07-13,Spin Wave Generation via Localized Spin-Orbit Torque in an Antiferromagnet-Topological Insulator Heterostructure,"The spin-orbit torque induced by a topological insulator (TI) is
theoretically examined for spin wave generation in a neighboring
antiferromagnetic thin film. The investigation is based on the micromagnetic
simulation of N\'{e}el vector dynamics and the analysis of transport properties
in the TI. The results clearly illustrate that propagating spin waves can be
achieved in the antiferromagnetic thin-film strip through localized excitation,
traveling over a long distance. The oscillation amplitude gradually decays due
to the non-zero damping as the N\'{e}el vector precesses around the magnetic
easy axis with a fixed frequency. The frequency is also found to be tunable via
the strength of the driving electrical current density. While both the bulk and
the surface states of the TI contribute to induce the effective torque, the
calculation indicates that the surface current plays a dominant role over the
bulk counterpart except in the heavily degenerate cases. Compared to the more
commonly applied heavy metals, the use of a TI can substantially reduce the
threshold current density to overcome the magnetic anisotropy, making it an
efficient choice for spin wave generation. The N\'{e}el vector dynamics in the
nano-oscillator geometry are examined as well.",2007.06663v1
2022-03-31,Gravitational Waves in Einstein-Cartan Theory: On the Effects of Dark Matter Spin Tensor,"This article studies the effects of an arbitrary dark matter spin tensor on
the propagation of gravitational wave amplitude in the context of
Einstein-Cartan theory. We choose to work with an arbitrary spin tensor
because, given our ignorance of the nature of dark matter, it is sensible not
to make further hypotheses on its spin and not to assume any particular model
for its spin tensor (or its vanishing). The analysis focuses on a
\textquotedblleft weak-torsion regime,\textquotedblright\ such that
gravitational wave emission, at leading and subleading orders, does not deviate
from standard General Relativity. We show that, in principle, the background
torsion induced by an eventual dark matter spin component could lead to an
anomalous dampening or amplification of the gravitational wave amplitude, after
going across a long cosmological distance. We assess the importance of this
torsion-induced anomalous amplitude propagation for binary black hole mergers
in a way as model-free as possible in Einstein-Cartan gravity. It is possible
to prove that at its best, for realistic late-universe cosmological scenarios,
the effect is tiny and falls below detection thresholds, even for near-future
interferometers such as LISA. Therefore, detecting this effect may not be
impossible, but it is still beyond our technological capabilities. As a
model-independent result in the Einstein-Cartan context, it also implies that
mergers are robust standard sirens without considering any potential
dark-matter-induced torsional effects.",2204.00090v2
2022-04-26,"Frustrated Antiferromagnetic Triangular Lattice with Dzyaloshinskii-Moriya Interaction: Ground States, Spin Waves, Skyrmion Crystal, Phase Transition","We study in this article a triangular lattice with Heisenberg spins
interacting with each other via an antiferromagnetic exchange interaction $J$
and a Dzyaloshinskii-Moriya (DM) interaction $D$, between nearest-neighbors
(NN). We consider two cases: the first case in which the DM vector $\mathbf D$
is perpendicular to the lattice plane and the second case where it lies in the
plane. A magnetic field $H$ is applied perpendicular to the spin plane in both
cases. The ground state (GS) of this system is calculated by minimizing the
energy using the very fast steepest-descent method in the two cases. In the
case of perpendicular $\mathbf D$ with $H=0$, the GS is periodic. We
analytically determine the GS configuration which is characterized by two
well-defined angles. We calculate the spin-wave spectrum in this case which
shows that for small wave vectors the spin waves are forbidden in the system.
When $H\neq 0$, the GS in the perpendicular $\mathbf D$ case shows no
skyrmions. However, in the case of in-plane $\mathbf D$ with $H\neq 0$, we find
a crystal of skyrmions at $T=0$ composed of three interpenetrating skyrmion
sublattice crystals, in agreement with low-$T$ spin textures found in earlier
works. We show by Monte Carlo simulations that this skyrmion crystal is stable
at finite temperatures below a critical temperature.",2204.12248v2
2022-09-06,Dynamic coupling and spin-wave dispersions in a magnetic hybrid system made of an artificial spin-ice structure and an extended NiFe underlayer,"We present a combined experimental and numerical study of the spin-wave
dispersion in NiFe artificial spin-ice (ASI) system consisting of an array of
stadium-shaped nanoislands deposited on the top of a continuous NiFe film with
nonmagnetic spacer layers of varying thickness. The spin-wave dispersion,
measured by wavevector resolved Brillouin light scattering spectroscopy in the
Damon-Eshbach configuration, consists of a rich number of modes, with either
stationary or propagating character. We find that the lowest frequency mode
displays a bandwidth of approximately 0.5 GHz, which is independent of the
presence of the film underneath. On the contrary, the BLS intensity of some of
the detected modes strongly depends on the presence of the extended thin-film
underlayer. Micromagnetic simulations unveil the details of the dynamic
coupling between ASI lattice and film underlayer. Interestingly, the ASI
lattice facilitates dynamics of the film either specific wavelengths or
intensity modulation peculiar to the modes of the ASI elements imprinted in the
film. Our results demonstrate that propagating spin waves can be modulated at
the nanometer length scale by harnessing the dynamic mode coupling in the
vertical, i.e., the out-of-plane direction of suitably designed magnonic
structures.",2209.02783v1
2022-11-30,Stark control of solid-state quantum memory with spin-wave storage,"Quantum memories for quantum communication need to be able to store photons
for an extended time and then to release them on demand. This can be achieved
in atomic frequency comb ensemble based quantum memories by control pulses that
transfer the excitation to and from long-lived spin states. However, such
pulses can give rise to coherent and incoherent noise due to their interaction
with the memory ensemble. In this article, we experimentally demonstrate the
ability to switch off the coherent noise from such control pulses during the
echo emission in a spin-wave quantum memory, using the linear Stark effect in
rare-earth-ion doped crystals. By applying an electric field pulse, the echo
emission was coherently switched off prior to the first spin transfer pulse,
and the stored data pulse was restored only when both an optical recall pulse
and a re-phasing electrical pulse were applied, giving a high degree of control
of both desired and undesired emissions. We estimate the effectiveness of this
technique by turning off the free induction decay of a narrow ensemble of ions.
This technique can thus improve the noise performance of spin-wave storage at
the single photon level by quenching coherent optical radiation created by the
strong control pulses. The method demonstrated here represents a
proof-of-principle that the spin-wave storage scheme can be combined with Stark
control. The combined scheme serves as an addition to the toolbox of techniques
that can be used to realize a full version of a quantum repeater.",2211.17206v1
2023-02-01,A Brillouin light scattering study of the spin-wave magnetic field dependence in a magnetic hybrid system made of an artificial spin-ice structure and a film underlayer,"We present a combined Brillouin light scattering and micromagnetic simulation
investigation of the magnetic-field dependent spin-wave spectra in a hybrid
structure made of permalloy (NiFe) artificial spin-ice (ASI) systems, composed
of stadium-shaped nanoislands, deposited on the top of an unpatterned permalloy
film with a nonmagnetic spacer layer. The thermal spin-wave spectra were
recorded by Brillouin light scattering (BLS) as a function of the magnetic
field applied along the symmetry direction of the ASI sample. Magneto-optic
Kerr effect magnetometry was used to measure the hysteresis loops in the same
orientation as the BLS measurements. The frequency and intensity of several
spin-wave modes detected by BLS were measured as a function of the applied
magnetic field. Micromagnetic simulations enabled us to identify the modes in
terms of their frequency and spatial symmetry and to extract information about
the existence and strength of the dynamic coupling, relevant only to a few
modes of a given hybrid system. Using this approach, we suggest a way to
understand if dynamic coupling between ASI and film modes is present or not,
with interesting implications for the development of future three-dimensional
magnonic applications and devices.",2302.00483v1
2023-11-12,A 50-spin surface acoustic wave Ising machine,"Time-multiplexed Spinwave Ising Machines (SWIMs) have unveiled a route
towards miniaturized, low-cost, and low-power solvers of combinatorial
optimization problems. While the number of supported spins is limited by the
nonlinearity of the spinwave dispersion, other collective excitations, such as
surface acoustic waves (SAWs), offer a linear dispersion. Here, we demonstrate
an all-to-all, fully FPGA reprogrammable, 50-spin surface acoustic wave-based
Ising machine (SAWIM), using a 50-mm-long Lithium Niobate SAW delay line,
off-the-shelf microwave components, and a low-cost FPGA. The SAWIM can solve
any 50-spin MAX-CUT problem, with arbitrary coupling matrices, in less than 340
$\mu$s consuming only 0.62 mJ, corresponding to close to 3000 solutions per
second and a figure of merit of 1610 solutions/W/s. We compare the SAWIM
computational results with those of a 100-spin optical Coherent Ising machine
and find a higher probability of solution. Moreover, we demonstrate that there
is an optimum overall coupling strength between spins at which the probability
of the exact solution reaches 100%. The SAWIM illustrates the general merits of
solid state wave-based time-multiplexed Ising machines in the microwave domain
as versatile platforms for commercially feasible high-performance solvers of
combinatorial optimization problems.",2311.06830v1
1997-06-24,"Is the ground state of alpha-(BEDT-TTF)2MHg(SCN)4[M=K,Rb,Tl] a charge-density wave or a spin-density wave?","The nature of the low-temperature phase of the quasi-two-dimensional
conductors $\alpha-(BEDT-TTF)_2{M}Hg(SCN)_4$[{M}=K,Rb,Tl] is considered. It is
argued that the magnetic field dependence of the phase diagram is more
consistent with a charge-density wave, rather than a spin-density wave ground
state. The phase diagram of a charge-density wave in a magnetic field is
discussed using a Ginzburg-Landau free energy derived from microscopic theory.
New experiments are proposed to test the charge-density-wave hypothesis and
detect an additional high field phase.",9706235v2
2003-11-20,Quantum Wave Resistance of Schrodinger functions,"The new concept of quantum wave-impedance (QWI), Z is introduced to answer
the question whether there is impedance to a Schrodinger wave. Z will be an
analogue of Maxwell's free space impedance (376.7 ohm) for electromagnetic
waves. We show, for free particle wave function, the value of Z is in general
not zero and purely real (resistive). As in quantum hall (QHE), Z can be
expressed in terms of the fine structure constant, the electromagnetic
permittivity and permeability of free space. Z is a determinant of the
partitioning and flow of charge and energy transported by the quantum system.
The scale factor of Z is about 12.9 kilo-ohms (per spin), so the corresponding
wave conductance G is (77.5 micro-mho, per spin) double the unit of Landaur
conductance. As functions of the quantum numbers (l,m,n) Z shows, peaks,
valleys and plateaus; also as in QHE, both integer and fractional steps may be
obtained. In microwave and optical technology, conventional impedance is an
essential parameter. The quantum impedance defined here will be no exception in
future technology.",0311479v1
2007-01-02,Quasi-One-Dimensional Spin-Density-Wave States with Two Kinds of Periodic Potentials and a Interchain Misfit,"Spin density wave (SDW) states of a quasi-one-dimensional system with an
incommensurate wave vector perpendicular to the chain have been studied in the
presence of two kinds of commensurate potentials, which originate in a
quarter-filled band and dimerization along the chain. In terms of a phase
variable of the SDW order parameter, we treat classically the two-dimensional
Hamiltonian, which includes both acoustic excitations with long wave length and
a vortex excitation with short wave length. A phase diagram on the plane of
temperature and chemical potential (where the latter corresponds to the
deviation of the transverse wave vector from the commensurate one) exhibits a
variety of states given by the commensurate SDW state without charge density,
the commensurate SDW state with charge density, the incommensurate SDW state
and the disordered state.",0701038v1
1997-02-21,Time dependent partial waves and vortex rings in the dynamics of wave packets,"We have found a new class of time dependent partial waves which are solutions
of time dependent Schr\""odinger equation for three dimensional harmonic
oscillator. We also showed the decomposition of coherent states of harmonic
oscillator into these partial waves. This decomposition appears perticularly
convenient for a description of the dynamics of a wave packet representing a
particle with spin when the spin--orbit interaction is present in the
hamiltonian. An example of an evolution of a localized wave packet into a torus
and backwards, for a particular initial conditions is analysed in analytical
terms and shown with a computer graphics.",9702043v1
2009-12-09,Formation of Random Dark Envelope Solitons from Incoherent Waves,"This letter reports experimental results on a new type of soliton: the random
temporal dark soliton. One excites an incoherent large-amplitude propagating
spin-wave packet in a ferromagnetic film strip with a repulsive, instantaneous
nonlinearity. One then observes the random formation of dark solitons from this
wave packet. The solitons appear randomly in time and in position relative to
the entire wave packet. They can be gray or black. For wide and/or very strong
spin-wave packets, one also observes multiple dark solitons. In spite of the
randomness of the initial wave packets and the random formation processes, the
solitons show signatures that are found for conventional coherent dark
solitons.",0912.1833v1
2015-07-01,Time-dependent many-variable variational Monte Carlo method for nonequilibrium strongly correlated electron systems,"We develop a time-dependent variational Monte Carlo (t-VMC) method for
quantum dynamics of strongly correlated electrons. The t-VMC method has been
recently applied to bosonic systems and quantum spin systems. Here, we propose
a time-dependent trial wave function with many variational parameters, which is
suitable for nonequilibrium strongly correlated electron systems. As the trial
state, we adopt the generalized pair-product wave function with correlation
factors and quantum-number projections. This trial wave function has been
proven to accurately describe ground states of strongly correlated electron
systems. To show the accuracy and efficiency of our trial wave function in
nonequilibrium states as well, we present our benchmark results for relaxation
dynamics during and after interaction quench protocols of fermionic Hubbard
models. We find that our trial wave function well reproduces the exact results
for the time evolution of physical quantities such as energy, momentum
distribution, spin structure factor, and superconducting correlations. These
results show that the t-VMC with our trial wave function offers an efficient
and accurate way to study challenging problems of nonequilibrium dynamics in
strongly correlated electron systems.",1507.00274v2
2017-08-09,Weak localization of magnons in chiral magnets,"We report on the impact of the Dzyaloshinskii-Moriya interaction on the
coherent backscattering of spin waves in a disordered magnetic material. This
interaction breaks the inversion symmetry of the spin-wave dispersion relation,
such that $\omega_\mathbf{k} = \omega_{2\mathbf{K}^\mathrm{I}-\mathbf{k}} \neq
\omega_{-\mathbf{k}}$, where $\mathbf{K}^\mathrm{I}$ is related to the
Dzyaloshinskii-Moriya vectors. As a result of numerical investigations we find
that the backscattering peak of a wave packet with initial wave vector
$\mathbf{k}_0$ shifts from $-\mathbf{k}_0$ to
$2\mathbf{K}^\mathrm{I}-\mathbf{k}_0$, such that the backscattering wave vector
and the initial wave vector are in general no longer antiparallel. The shifted
coherence condition is explained by a diagrammatic approach and opens up an
avenue to measure sign and magnitude of the Dzyaloshinskii-Moriya interaction
in weakly disordered chiral magnets.",1708.02807v1
2018-11-21,"Memory, Penrose Limits and the Geometry of Gravitational Shockwaves and Gyratons","The geometric description of gravitational memory for strong gravitational
waves is developed, with particular focus on shockwaves and their spinning
analogues, gyratons. Memory, which may be of position or velocity-encoded type,
characterises the residual separation of neighbouring `detector' geodesics
following the passage of a gravitational wave burst, and retains information on
the nature of the wave source. Here, it is shown how memory is encoded in the
Penrose limit of the original gravitational wave spacetime and a new `timelike
Penrose limit' is introduced to complement the original plane wave limit
appropriate to null congruences. A detailed analysis of memory is presented for
timelike and null geodesic congruences in impulsive and extended gravitational
shockwaves of Aichelburg-Sexl type, and for gyratons. Potential applications to
gravitational wave astronomy and to quantum gravity, especially infra-red
structure and ultra-high energy scattering, are briefly mentioned.",1811.08827v2
2020-09-14,Global propagation of massive quantum fields in the plane gravitational waves and electromagnetic backgrounds,"The behavior of massive quantum fields in the general plane wave spacetime
and external, non-plane, electromagnetic waves is studied. The asymptotic
conditions, the ""in"" (""out"") states and the cross sections are analysed. It is
observed that, despite of the singularities encountered, the global form of
these states can be obtained: at the singular points the Dirac delta-like
behavior emerges and there is a discrete change of phase of the wave function
after passing through each singular point. The relations between these phase
corrections and local charts are discussed. Some examples of waves of infinite
range (including the circularly polarized ones) are presented for which the
explicit form of solutions can be obtained. All these results concern both the
scalar as well as spin one-half fields; in the latter case the change of the
spin polarization after the general sandwich wave has passed is studied.",2009.06518v3
2020-09-30,Rotating wave approximation for quadrupole interaction with high spin,"Rotating wave approximation in a quantum spin system driven by a linearly
polarized alternating magnetic field with quadrupole interaction presents is
investigated in detail in this paper. The conventional way to employ the
rotating wave approximation is to assume the dynamics being restricted in the
reduced Hilbert space. However, when the driving strength is relatively strong
or the driving is off resonant, the leakage from the target resonance subspace
along with the effects from the counter-rotating terms cannot be neglected
anymore. We propose the rotating wave approximation applied in the full Hilbert
space to take the leakage from the target resonance subspace into account. To
include the effects from the counter-rotating terms, we utilize the
counterrotating hybridized rotating wave method in the reduced Hilbert space.
The performance of these rotating wave approximation methods is compared by
estimating the state fidelity as well as the operator fidelity and the results
reveal that different methods may be employed for different practical
circumstances.",2009.14380v2
2021-10-28,Newman-Penrose-Debye formalism for fields of various spins in pp-wave backgrounds,"Using Newman-Penrose formalism in tetrad and spinor notation, we perform
separation of variables in the wave equations for massless fields of various
spins s=1/2, 1, 3/2, 2 on the background of exact plane-fronted gravitational
wave metrics. Then, applying Wald's method of adjoint operators, we derive
equations for Debye potentials generating these fields and find inverse
projection operators expressing multicomponet fields in terms of scalar
potentials. For a number of shock wave backgrounds, as a special case of
non-vacuum pp-waves, the exact solutions for Debye potentials are constructed
explicitly. The possibility of generalization to the case of massive fields, in
particular, construction of exact solutions to the Dirac and Proca equations
are discussed. These results can be used in supergravity models on pp-wave
backgrounds.",2110.15046v1
2020-01-20,Alphonons as the quanta of the Alfvén waves,"In a magnetized plasma, both the transverse and longitudinal Alfv\'en waves
carry an average energy density that, for each mode of oscillation, resembles
the classical energy of a harmonic oscillator with unit mass and angular
frequency that depends on the background magnetic field and plasma density. We
employ this fact to introduce a pair of canonical variables for the underlying
classical system, and then use the canonical quantization procedure to express
the Alfv\'en wave velocity (or the corresponding plasma displacement vector) in
terms of creation and annihilation operators. We thus introduce the concept of
Alphonons as the quanta for the Alfv\'en wave packets and study their
characteristic features. The corresponding quanta (Alphonons) carry spin one
for the transverse Alfv\'en wave and spin zero for the longitudinal Alfv\'en
wave. We obtained behavior of thermodynamic quantities for an Alphonon system
(e.g., free energy, entropy, specific heat). We showed that for the Alphonon
system the spectral energy density obeys the Planck's black body radiation law.",2001.08112v1
2020-05-29,Bound states of spin-orbit coupled cold atoms in a Dirac delta-function potential,"Dirac delta-function potential is widely studied in quantum mechanics because
it usually can be exactly solved and at the same time is useful in modeling
various physical systems. Here we study a system of delta-potential trapped
spinorbit coupled cold atoms. The spin-orbit coupled atomic matter wave has two
kinds of evanescent modes, one of which has pure imaginary wavevector and is an
ordinary evanescent wave; while the other with a complex number wave vector is
recognized as oscillating evanescent wave. We identified the eigenenergy
spectra and the existence of bound states in this system. The bound states can
be constructed analytically using the two kinds of evanescent modes and we
found that they exhibit typical features of stripe phase, separated phase or
zero-momentum phase. In addition to that, the properties of semi-bound states
are also discussed, which is a localized wave packet on a plane wave
background.",2005.14604v1
2020-07-27,Knotted Polarizations and Spin in 3D Polychromatic Waves,"We consider complex 3D polarizations in the interference of several vector
wave fields with different commensurable frequencies and polarizations. We show
that the resulting polarizations can form knots, and interfering three waves is
sufficient to generate a variety of Lissajous, torus, and other knot types. We
describe the spin angular momentum, generalized Stokes parameters and degree of
polarization for such knotted polarizations, which can be regarded as
partially-polarized. Our results are generic for any vector wave fields,
including, e.g., optical and acoustic waves. As a directly-observable example,
we consider knotted trajectories of water particles in the interference of
surface water (gravity) waves with three different frequencies.",2007.13307v2
2022-03-17,Traveling Wave Form Description for Dirac Field and Its Deduction To Pauli Equation Type Forms in Quantum Mechanics,"We derive an equivalent traveling wave form description for Dirac field. In
the non-relativistic limit, such form can reduce to inverse-Galilean
transformed Schrodinger-type equation. We find that, the resulting
two-component Schrodinger-type equation from the reduction of traveling wave
form description of Dirac field is different to the naive Galilean transformed
Schrodinger equation. Taking into account the interactions of the system to
electromagnetic field by adding proper forms of covariant derivative, the
traveling wave form description for Pauli equation can be similarly obtained in
the non-relativistic limit. Such descriptions allow one to choose arbitrary
convenient reference frame for quantum system involving spins. Using
Bargmann-Wigner formalism for field with arbitrary spin $s\geq 1/2$, which
satisfy Dirac-type equations in all its indices, the traveling wave description
for such a field can be similarly obtained from the traveling wave form
description of Dirac field, for example, for the spin-3/2 Rarita-Schwinger
field and spin-2 gravitational field.",2203.09005v1
2023-05-15,Extreme mass-ratio inspiral of a spinning body into a Kerr black hole I: Evolution along generic trajectories,"The study of spinning bodies moving in curved spacetime has relevance to
binary black hole systems with large mass ratios, as well as being of formal
interest. At zeroth order in a binary's mass ratio, the smaller body moves on a
geodesic of the larger body's spacetime. Post-geodesic corrections describing
forces driving the small body's worldline away from geodesics must be
incorporated to model the system accurately. An important post-geodesic effect
is the gravitational self-force, which describes the small body's interaction
with its own spacetime curvature. This effect includes the backreaction due to
gravitational-wave emission that leads to the inspiral of the small body into
the black hole. When a spinning body orbits a black hole, its spin couples to
spacetime curvature. This introduces another post-geodesic correction known as
the spin-curvature force. An osculating geodesic integrator that includes both
the backreaction due to gravitational waves and spin-curvature forces can be
used to generate a spinning-body inspiral. In this paper, we use an osculating
geodesic integrator to combine the leading backreaction of gravitational waves
with the spin-curvature force. Our analysis only includes the leading
orbit-averaged dissipative backreaction, and examines the spin-curvature force
to leading order in the small body's spin. This is sufficient to build generic
inspirals of spinning bodies, and serves as a foundation for further work
examining how to include secondary spin in large-mass-ratio waveform models.",2305.08919v2
2011-03-31,Acoustic spin pumping as the origin of the long-range spin Seebeck effect,"The spin Seebeck effect (SSE) is known as the generation of 'spin voltage' in
a magnet as a result of a temperature gradient. Spin voltage stands for the
potential for spins, which drives a spin current. The SSE is of crucial
importance in spintronics and energy-conversion technology, since it enables
simple and versatile generation of spin currents from heat. The SSE has been
observed in a variety of materials ranging from magnetic metals and
semiconductors to magnetic insulators. However, the mechanism, the long-range
nature, of the SSE in metals is still to be clarified. Here we found that,
using a Ni81Fe19/Pt bilayer wire on an insulating sapphire plate, the
long-range spin voltage induced by the SSE in magnetic metals is due to
phonons. Under a temperature gradient in the sapphire, surprisingly, the
voltage generated in the Pt layer is shown to reflect the wire position,
although the wire is isolated both electrically and magnetically. This
non-local voltage is direct evidence that the SSE is attributed to the coupling
of spins and phonons. We demonstrate this coupling by directly injecting sound
waves, which realizes the acoustic spin pumping. Our finding opens the door to
""acoustic spintronics"" in which phonons are exploited for constructing
spin-based devices.",1103.6120v1
2011-08-08,"Spin-Orbital Locking, Emergent Pseudo-Spin, and Magnetic order in Honeycomb Lattice Iridates","The nature of the effective spin Hamiltonian and magnetic order in the
honeycomb iridates is explored by considering a trigonal crystal field effect
and spin-orbit coupling. Starting from a Hubbard model, an effective spin
Hamiltonian is derived in terms of an emergent pseudo-spin-1/2 moment in the
limit of large trigonal distortions and spin-orbit coupling. The present
pseudo-spins arise from a spin-orbital locking and are different from the jeff
= 1/2 moments that are obtained when the spin-orbit coupling dominates and
trigonal distortions are neglected. The resulting spin Hamiltonian is
anisotropic and frustrated by further neighbour interactions. Mean field theory
suggests a ground state with 4-sublattice zig-zag magnetic order in a parameter
regime that can be relevant to the honeycomb iridate compound Na2IrO3, where
similar magnetic ground state has recently been observed. Various properties of
the phase, the spin-wave spectrum and experimental consequences are discussed.
The present approach contrasts with the recent proposals to understand iridate
compounds starting from the strong spin-orbit coupling limit and neglecting
non-cubic lattice distortions.",1108.1806v3
2015-03-17,Successive magnetic transitions relating to itinerant spins and localized Cu spins in La2-xSrxCu1-yFeyO4: Possible existence of stripe correlations in the overdoped regime,"In order to investigate the relationship between the so-called stripe
correlations and the high-Tc superconductivity, we have carried out magnetic
susceptibility and zero-field muon-spin-relaxation measurements in partially
Fe-substituted La2-xSrxCu1-yFeyO4 (LSCFO). It has been found that the Fe
substitution induces successive magnetic transitions in the overdoped regime,
namely, a spin-glass transition of Fe3+ spins due to the RKKY interaction based
on itinerant spins at higher temperatures and a stripe-order transition of
localized Cu2+ spins at lower temperatures. The stripe-order transition
disappears at the hole concentration of ~0.28 per Cu which coincides with the
endpoint of the superconductivity in pristine La2-xSrxCuO4, suggesting that the
stripe correlations are closely related to the high-Tc superconductivity in the
overdoped regime as well as in the underdoped regime. As for the spin-glass
state, it has been found that the contribution of polarized itinerant spins to
the muon-spin depolarization is not negligible. Taking into account
neutron-scattering results by R.-H. He et al. [Phys. Rev. Lett. 107, 127002
(2011)] that a spin-density-wave (SDW) order has been observed in overdoped
LSCFO, the present results demonstrate the presence of a novel coexistent state
of a SDW order and a spin-glass state.",1503.04902v1
2015-07-25,Quantum entanglement in the one-dimensional spin-orbital SU(2)$\otimes XXZ$ model,"We investigate the phase diagram and the spin-orbital entanglement of a
one-dimensional SU(2)$\otimes XXZ$ model with SU(2) spin exchange and
anisotropic $XXZ$ orbital exchange interactions and negative exchange coupling.
As a unique feature, the spin-orbital entanglement entropy in the entangled
ground states increases here linearly with system size. In the case of Ising
orbital interactions we identify an emergent phase with long-range spin-singlet
dimer correlations triggered by a quadrupling of correlations in the orbital
sector. The peculiar translational invariant spin-singlet dimer phase has
finite von Neumann entanglement entropy and survives when orbital quantum
fluctuations are included. It even persists in the isotropic
SU(2)$\otimes$SU(2) limit. Surprisingly, for finite transverse orbital coupling
the long-range spin singlet correlations also coexist in the antiferromagnetic
spin and alternating orbital phase making this phase also unconventional.
Moreover we also find a complementary orbital singlet phase that exists in the
isotropic case but does not extend to the Ising limit. The nature of
entanglement appears essentially different from that found in the frequently
discussed model with positive coupling. Furthermore we investigate the
collective spin and orbital wave excitations of the disentangled
ferromagnetic-spin/ferro-orbital ground state and explore the continuum of
spin-orbital excitations. Interestingly one finds among the latter excitations
two modes of exciton bound states. Their spin-orbital correlations differ from
the remaining continuum states and exhibit logarithmic scaling of the von
Neumann entropy with increasing system size.",1507.07103v1
2016-02-25,Phase diagram and collective excitation in excitonic insulator: from the orbital physics viewpoint,"Excitonic insulating system is studied from the viewpoints of the orbital
physics in strongly correlated electron systems. An effective model Hamiltonian
for low-energy electronic states is derived from the two-orbital Hubbard model
with a finite energy difference corresponding to the crystalline field
splitting. The effective model is represented by the spin operators and the
pseudo-spin operators for the spin-state degrees of freedom. The ground state
phase diagram is analyzed by the mean-field approximation. In addition to the
low-spin state and high-spin state phases, two kinds of the excitonic
insulating phases emerge as a consequence of the competition between the
crystalline field effect and the Hund coupling. The excitonic transition is
classified to be an Ising-like transition reflecting a spontaneous breaking of
the $Z_2$ symmetry. Magnetic structures in the two excitonic insulating phases
are different from each other; an antiferromagnetic order and a spin nematic
order. Collective excitations in each phase are examined by using the
generalized spin-wave method. The Goldstone modes in the excitonic insulating
phases appear in the dynamical correlation functions for the spins and
pseudo-spin operators. Both the transverse and longitudinal spin excitation
modes are active in the two excitonic insulating phases in contrast to the
low-spin state and high-spin state phases. Connections of the present results
to the perovskite cobalt oxides are discussed.",1602.07831v2
2018-11-10,Spin-valley half-metal in systems with Fermi surface nesting,"Half-metals have fully spin polarized charge carriers at the Fermi surface.
Such polarization usually occurs due to strong electron--electron correlations.
Recently [Phys. Rev. Lett. {\bf{119}}, 107601 (2017)], we have demonstrated
theoretically that adding (or removing) electrons to systems with Fermi surface
nesting also stabilizes the half-metallic states even in the weak-coupling
regime. In the absence of doping, the ground state of the system is a spin or
charge density wave, formed by four nested bands. Each of these bands is
characterized by charge (electron/hole) and spin (up/down) labels. Only two of
these bands accumulate charge carriers introduced by doping, forming a
half-metallic two-valley Fermi surface. Analysis demonstrates that two types of
such half-metallicity can be stabilized. The first type corresponds to the full
spin polarization of the electrons and holes at the Fermi surface. The second
type, with antiparallel spins in electron-like and hole-like valleys, is
referred to as a ""spin-valley half-metal"" and corresponds to the complete
polarization with respect to the spin-valley operator. We analyze spin and
spin-valley currents and possible superconductivity in these systems. We show
that spin or spin-valley currents can flow in both half-metallic phases.",1811.04202v1
2020-03-05,The Evolution of Primordial Black Holes and their Final Observable Spins,"Primordial black holes in the mass range of ground-based gravitational-wave
detectors can comprise a significant fraction of the dark matter. Mass and spin
measurements from coalescences can be used to distinguish between an
astrophysical or a primordial origin of the binary black holes. In standard
scenarios the spin of primordial black holes is very small at formation.
However, the mass and spin can evolve through the cosmic history due to
accretion. We show that the mass and spin of primordial black holes are
correlated in a redshift-dependent fashion, in particular primordial black
holes with masses below ${\cal O}(30)M_\odot$ are likely non-spinning at any
redshift, whereas heavier black holes can be nearly extremal up to redshift
$z\sim10$. The dependence of the mass and spin distributions on the redshift
can be probed with future detectors such as the Einstein Telescope. The mass
and spin evolution affect the gravitational waveform parameters, in particular
the distribution of the final mass and spin of the merger remnant, and that of
the effective spin of the binary. We argue that, compared to the
astrophysical-formation scenario, a primordial origin of black hole binaries
might better explain the spin distribution of merger events detected by
LIGO-Virgo, in which the effective spin parameter of the binary is compatible
to zero except possibly for few high-mass events. Upcoming results from
LIGO-Virgo third observation run might reinforce or weaken these predictions.",2003.02778v2
2019-10-21,High-frequency magnon excitation due to femtosecond spin-transfer torques,"Femtosecond laser pulses can induce ultrafast demagnetization as well as
generate bursts of hot electron spin currents. In trilayer spin valves
consisting of two metallic ferromagnetic layers separated by a nonmagnetic one,
hot electron spin currents excited by an ultrashort laser pulse propagate from
the first ferromagnetic layer through the spacer reaching the second magnetic
layer. When the magnetizations of the two magnetic layers are noncollinear,
this spin current exerts a torque on magnetic moments in the second
ferromagnet. Since this torque is acting only within the sub-ps timescale, it
excites coherent high-frequency magnons as recently demonstrated in
experiments. Here, we calculate the temporal shape of the hot electron spin
currents using the superdiffusive transport model and simulate the response of
the magnetic system to the resulting ultrashort spin-transfer torque pulse by
means of atomistic spin-dynamics simulations. Our results confirm that the
acting spin-current pulse is short enough to excite magnons with frequencies
beyond 1 THz, a frequency range out of reach for current induced spin-transfer
torques. We demonstrate the formation of thickness dependent standing spin
waves during the first picoseconds after laser excitation. In addition, we vary
the penetration depth of the spin-transfer torque to reveal its influence on
the excited magnons. Our simulations clearly show a suppression effect of
magnons with short wavelengths already for penetration depths in the range of 1
nm confirming experimental findings reporting penetration depths below $2\,
{\rm nm}$.",1910.09412v1
2022-11-08,Spin effects in Spherical Harmonic Modes of Gravitational Waves from Eccentric Compact Binary Inspirals,"We compute the leading and sub-leading spin effects through the second
post-Newtonian order (2PN) in spherical harmonic modes of gravitational
waveforms from inspiralling compact binaries in non-circular orbits with
non-precessing components. The two spin couplings, linear-in-spin (spin-orbit;
SO) and quadratic-in-spin (spin-spin; SS), that appear in 2PN waveforms are
computed with desired accuracy and explicit expressions for relevant modes are
derived. The modes that have spin corrections through 2PN include $(\ell,
|m|)$=$((2,2),\,(2,1),\,(3,3),\,(3,2),\,(3,1),\,(4,3),\,(4,1))$ modes. Closed
form expressions for these modes for compact binaries in general orbits as well
as in elliptical orbits are being provided. While the general orbit results can
be used to study signals from binaries in orbits of arbitrary shape and nature,
elliptical orbit results are applicable to systems with arbitrary
eccentricities. We also express the elliptical orbit results as leading
eccentric corrections to the circular results. Our prescription represents, the
first, fully analytical treatment that combines spins, eccentricity and higher
modes together and completes computation of spin effects through 2PN order.
These should find immediate applications in inspiral-merger-ringdown modelling
for eccentric mergers including the effect of non-precessing spins and higher
modes as well as in parameter estimation analyses employing inspiral waveform.",2211.04155v2
2023-02-14,Collapsar Gamma-ray Bursts Grind their Black Hole Spins to a Halt,"The spin of a newly formed black hole (BH) at the center of a massive star
evolves from its natal value due to two competing processes: accretion of gas
angular momentum that increases the spin, and extraction of BH angular momentum
by outflows that decreases the spin. Ultimately, the final, equilibrium spin is
set by the balance between both processes. In order for the BH to launch
relativistic jets and power a $ \gamma $-ray burst (GRB), the BH magnetic field
needs to be dynamically important. Thus, we consider the case of a magnetically
arrested disk (MAD) driving the spin evolution of the BH. By applying the
semi-analytic MAD BH spin evolution model of Lowell et al. (2023) to
collapsars, we show that if the BH accretes $ \sim 20\% $ of its initial mass,
its dimensionless spin inevitably reaches small values, $ a \lesssim 0.2 $. For
such spins, and for mass accretion rates inferred from collapsar simulations,
we show that our semi-analytic model reproduces the energetics of typical GRB
jets, $L_{\rm jet}\sim10^{50}\,\,{\rm erg\,s^{-1}}$. We show that our
semi-analytic model reproduces the nearly constant power of typical GRB jets.
If the MAD onset is delayed, this allows powerful jets at the high end of the
GRB luminosity distribution, $L_{\rm jet}\sim10^{52}\,\,{\rm erg\,s^{-1}}$, but
the final spin remains low, $ a \lesssim 0.3 $. These results are consistent
with the low spins inferred from gravitational wave detections of binary BH
mergers. In a companion paper, Gottlieb et al. (2023), we use GRB observations
to constrain the natal BH spin to be $ a \simeq 0.2 $.",2302.07281v1
2023-02-22,Quantum sensing and imaging with spin defects in hexagonal boron nitride,"Color centers in hexagonal boron nitride (hBN) have recently emerged as
promising candidates for a new wave of quantum applications. Thanks to hBN's
high stability and 2-dimensional (2D) layered structure, color centers in hBN
can serve as robust quantum emitters that can be readily integrated into
nanophotonic and plasmonic structures on a chip. More importantly, the recently
discovered optically addressable spin defects in hBN provide a quantum
interface between photons and electron spins for quantum sensing applications.
The most well-studied hBN spin defects, the negatively charged boron vacancy
($V_B^-$) spin defects, have been used for quantum sensing of static magnetic
fields, magnetic noise, temperature, strain, nuclear spins, paramagnetic spins
in liquids, RF signals, and beyond. In particular, hBN nanosheets with spin
defects can form van der Waals (vdW) heterostructures with 2D magnetic or other
materials for in situ quantum sensing and imaging. This review summarizes the
rapidly evolving field of nanoscale and microscale quantum sensing with spin
defects in hBN. We introduce basic properties of hBN spin defects, quantum
sensing protocols, and recent experimental demonstrations of quantum sensing
and imaging with hBN spin defects. We also discuss methods to enhance their
sensitivity. Finally, we envision some potential developments and applications
of hBN spin defects.",2302.11169v2
2023-08-02,Constraining the nature of dark compact objects with spin-induced octupole moment measurement,"Various theoretical models predict the existence of exotic compact objects
that can mimic the properties of black holes (BHs). Gravitational waves (GWs)
from the mergers of compact objects have the potential to distinguish between
exotic compact objects and BHs. The measurement of spin-induced multipole
moments of compact objects in binaries provides a unique way to test the nature
of compact objects. The observations of GWs by LIGO and Virgo have already put
constraints on the spin-induced quadrupole moment, the leading order
spin-induced moment. In this work, we develop a Bayesian framework to measure
the spin-induced octupole moment, the next-to-leading order spin-induced
moment. The precise measurement of the spin-induced octupole moment will allow
us to test its consistency with that of Kerr BHs in general relativity and
constrain the allowed parameter space for non-BH compact objects. For various
simulated compact object binaries, we explore the ability of the LIGO and Virgo
detector network to constrain the spin-induced octupole moment of compact
objects. We find that LIGO and Virgo at design sensitivity can constrain the
symmetric combination of component spin-induced octupole moments of binary for
dimensionless spin magnitudes $\sim 0.8$. Further, we study the possibility of
simultaneously measuring the spin-induced quadrupole and octupole moments.
Finally, we perform this test on selected GW events reported in the third GW
catalog. These are the first constraints on spin-induced octupole moment using
full Bayesian analysis.",2308.01309v2
2023-11-20,Ground state of the $S$=1/2 pyrochlore Heisenberg antiferromagnet: A quantum spin liquid emergent from dimensional reduction,"The quantum antiferromagnet on the pyrochlore lattice offers an archetypal
frustrated system, which potentially realizes a quantum spin liquid
characterized by the absence of standard spontaneous symmetry breaking even at
zero temperature, unusually as an isotropic 3D system. Despite tremendous
progress in the literature, however, the nature of the ground state of the
fully quantum-mechanical spin Hamiltonian on the pyrochlore lattice still
remains elusive. Here, we show that an unconventional type of quantum spin
liquid is born out from the pyrochlore system after the self-organized
dimensional reduction leading to confined states in 2D layers. This conclusion
is obtained from state-of-the-art variational Monte Carlo (VMC) simulations at
zero temperature. Quantum spin liquids triggered by the emergent dimensional
reduction is an unexplored route of the spin-liquid formation. The dimensional
reduction from 3D to 2D is a consequence of a conventional spontaneous symmetry
breaking, while the resultant decoupling of layers enables the emergence of a
2D quantum spin liquid that is adiabatically disconnected from trivial product
states and exhibits strong quantum entanglement. The stabilized quantum spin
liquid exhibits an algebraic decay of correlations and vanishing excitation gap
in the thermodynamic limit. The wave-function structure supports the
fractionalization of the spin into spinons. This spin-liquid ground state
persists in the presence of spin-orbit interactions, which expands the
possibilities of realizing quantum spin liquids in real pyrochlore-structured
materials.",2311.11561v1
2011-06-19,Oscillatory Energy Exchange Between Waves Coupled by a Dynamic Artificial Crystal,"We describe a general mechanism of controllable energy exchange between waves
propagating in a dynamic artificial crystal. We show that if a spatial
periodicity is temporarily imposed on the transmission properties of a
wave-carrying medium whilst a wave is inside, this wave is coupled to a
secondary counter-propagating wave and energy oscillates between the two. The
oscillation frequency is determined by the width of the spectral band gap
created by the periodicity and the frequency difference between the coupled
waves. The effect is demonstrated with spin waves in a dynamic magnonic
crystal.",1106.3722v1
2017-03-07,Partial waves in $B_s^* \bar B_s^*$ production in $e^+e^-$ annihilation near threshold,"The production of the vector meson pairs $B_s^* \bar B_s^*$ in the $e^+e^-$
annihilation is generally contributed by two $P$ wave amplitudes with different
total spin $S$ of the mesons, $S=0$ and $S=2$, and also by an $F$ wave
amplitude. Belle has recently reported a study of the available data at the
energy of the $\Upsilon(5S)$ peak in terms of the two $P$ wave contributions
only. It is argued here that although at this energy the $F$ wave should be
quite suppressed, especially for the strange-bottom vector mesons, the
particular studied angular distribution is very sensitive to a presence of even
small $F$ wave amplitude due to a significant interference with the dominant
$S=2$ $P$ wave. Thus the available data are not conclusive with regards to the
partial wave structure of the production amplitude. Additional angular
correlations are discussed that can be measured for a full amplitude analysis
of the production process.",1703.02524v1
1995-09-22,Critical Dynamics of Magnets,"We review our current understanding of the critical dynamics of magnets above
and below the transition temperature with focus on the effects due to the
dipole--dipole interaction present in all real magnets. Significant progress in
our understanding of real ferromagnets in the vicinity of the critical point
has been made in the last decade through improved experimental techniques and
theoretical advances in taking into account realistic spin-spin interactions.
We start our review with a discussion of the theoretical results for the
critical dynamics based on recent renormalization group, mode coupling and spin
wave theories. A detailed comparison is made of the theory with experimental
results obtained by different measuring techniques, such as neutron scattering,
hyperfine interaction, muon--spin--resonance, electron--spin--resonance, and
magnetic relaxation, in various materials. Furthermore we discuss the effects
of dipolar interaction on the critical dynamics of three--dimensional isotropic
antiferromagnets and uniaxial ferromagnets. Special attention is also paid to a
discussion of the consequences of dipolar anisotropies on the existence of
magnetic order and the spin--wave spectrum in two--dimensional ferromagnets and
antiferromagnets. We close our review with a formulation of critical dynamics
in terms of nonlinear Langevin equations.",9509141v1
1996-04-17,Spin-gap phase in nearly-half-filled one-dimensional conductors coupled with phonons,"Asymptotic properties of nearly-half-filled one-dimensional conductors
coupled with phonons are studied through a renormalization group method. Due to
spin-charge coupling via electron-phonon interaction, the spin correlation
varies with filling as well as the charge correlation. Depending on the
relation between cut-off energy scales of the Umklapp process and of the
electron-phonon interaction, various phases appear. We found a metallic phase
with a spin gap and a dominant charge- density-wave correlation near half
filling between a gapless density-wave phase (like in the doped repulsive
Hubbard model) and a superconductor phase with a spin gap. The spin gap is
produced by phonon-assisted backward scatterings which are interfered with the
Umklapp process constructively or destructively depending on the character of
electron-phonon coupling.",9604096v2
1998-05-13,Aharonov-Anandan Effect Induced by Spin-Orbit Interaction and Charge-Density-Waves in Mesoscopic Rings,"We study the spin-dependent geometric phase effect in mesoscopic rings of
charge-density-wave(CDW) materials. When electron spin is explicitly taken into
account, we show that the spin-dependent Aharonov-Casher phase can have a
pronounced frustration effects on such CDW materials with appropriate electron
filling. We show that this frustration has observable consequences for
transport experiment. We identify a phase transition from a Peierls insulator
to metal, which is induced by spin-dependent phase interference effects.
Mesoscopic CDW materials and spin-dependent geometric phase effects, and their
interplay, are becoming attractive opportunities for exploitation with the
rapid development of modern fabrication technology.",9805160v1
1998-08-07,Electromagnetic Interactions in the Quantum Hall Ferromagnet,"The $\nu =1$ quantum Hall ground state in samples like GaAs is well known to
be ferromagnetic. The global SU(2) spin symmetry of the microscopic action is
broken down to a U(1) symmetry by the ground state. The Goldstone bosons
corresponding to this spontaneous breaking of symmetry are the ferromagnetic
magnons which are neutral spin waves. In addition, there are topologically
nontrivial, electrically charged spin excitations known as spin skyrmions,
which in these samples are the favoured charge carriers. In this letter, we
look into the electromagnetic coupling of these spin excitations. The discrete
symmetries P and T are also broken by the ground state and we find that to the
leading order, the electromagnetic interaction of the spin waves occurs through
a nonminimal coupling given by a Chern-Simons like term containing both the
electromagnetic potentials and the two Euler angles that specify the coset
SU(2)/U(1) and thereby, the Goldstone bosons.",9808081v1
1998-09-27,Hidden spin-current conservation in 2d Fermi liquids,"We report the existence of regimes of the two dimensional Fermi liquid that
show unusual conservation of the spin current and may be tuned by varying some
parameter like the density of fermions. We show that for reasonable models of
the effective interaction the spin current may be conserved in general in 2d,
not only for a particular regime. Low temperature spin waves propagate
distinctively in these regimes and entirely new ``spin-acoustic'' modes are
predicted for scattering-dominated temperature ranges. These new
high-temperature propagating spin waves provide a clear signature for the
experimental search of such regimes.",9809364v2
1999-01-02,Andreev Reflection and Spin Injection into $s-$ and $d-$wave Superconductors,"We study the effect of spin injection into $s-$ and $d-$wave superconductors,
with an emphasis on the interplay between boundary and bulk spin transport
properties. The quantities of interest include the amount of non-equilibrium
magnetization ($m$), as well as the induced spin-dependent current ($I_s$) and
boundary voltage ($V_s$). In general, the Andreev reflection makes each of the
three quantities depend on a different combination of the boundary and bulk
contributions. The situation simplifies either for half-metallic ferromagnets
or in the strong barrier limit, where both $V_s$ and $m$ depend solely on the
bulk spin transport/relaxation properties. The implications of our results for
the on-going spin injection experiments in high $T_c$ cuprates are discussed.",9901004v2
2001-04-27,Raman scattering study of phonon and spin modes in (TMTSF)2PF6,"We have studied polarized Raman spectra of (TMTSF)2PF6 single crystals in the
wide spectral and temperature range using different laser energies. We observed
and assigned 23 Raman active modes. The carbon C=C in-phase and out-of-phase
stretching modes at 1464 cm-1 and 1602 cm-1 show strong
electron-molecular-vibration coupling. The mode at about 1565 cm-1 is
temperature independent below 50 K due to the methyl group motion freezing. For
(TMTSF)2PF6 in the spin density wave phase for a temperature induced
dimensionality 1D (quarter filled dimerized linear chain with correlated
electrons) the spin gapless magnon spectra have been calculated. No evidence of
spin-lattice coupling or spin-related modes is found in the Raman spectra in
the spin density wave phase.",0104528v1
2002-03-08,Pinning of dynamic spin density wave fluctuations in the cuprate superconductors,"We present a theory of the pinning of dynamic spin density wave (SDW)
fluctuations in a d-wave superconductor by local imperfections which preserve
spin-rotation invariance, such as impurities or vortex cores. The pinning leads
to static spatial modulations in spin-singlet observables, while the SDW
correlations remain dynamic: these are the `Friedel oscillations' of a spin-gap
antiferromagnet. We connect the spectrum of these modulations as observed by
scanning tunnelling microscopy to the dynamic spin structure factor measured by
inelastic neutron scattering.",0203176v2
2003-05-14,Spin Orientation and Spin Precession in Inversion-Asymmetric Quasi Two-Dimensional Electron Systems,"Inversion asymmetry induced spin splitting of the electron states in quasi
two-dimensional (2D) systems can be attributed to an effective magnetic field B
which varies in magnitude and orientation as a function of the in-plane wave
vector k||. Using a realistic 8x8 Kane model that fully takes into account spin
splitting because of both bulk inversion asymmetry and structure inversion
asymmetry we investigate the spin orientation and the effective field B for
different configurations of a quasi 2D electron system. It is shown that these
quantities depend sensitively on the crystallographic direction in which the
quasi 2D system was grown as well as on the magnitude and orientation of the
in-plane wave vector k||. These results are used to discuss how spin-polarized
electrons can precess in the field B(k||). As a specific example we consider
GaInAs-InP quantum wells.",0305315v1
2003-08-12,Persistent spin currents in mesoscopic Haldane gap spin rings,"Using a modified spin-wave approach, we show that in the presence of an
inhomogeneous magnetic field or an in plane inhomogeneous electric field a
mesoscopic antiferromagnetic Heisenberg ring with integer spin (i.e., a Haldane
gap system) exhibits a persistent circulating spin current. Due to quantum
fluctuations the current has a finite limit on the order of -g mu_B c/L at zero
temperature, provided the staggered correlation length xi exceeds the
circumference L of the ring, in close analogy to ballistic charge currents in
mesoscopic normal metal rings. Here c is the spin-wave velocity, g is the
gyromagnetic ratio and mu_B is the Bohr magneton. For xi<<L the current is
exponentially suppressed.",0308230v2
2004-01-08,Anisotropic Spin Diffusion in Trapped Boltzmann Gases,"Recent experiments in a mixture of two hyperfine states of trapped Bose gases
show behavior analogous to a spin-1/2 system, including transverse spin waves
and other familiar Leggett-Rice-type effects. We have derived the kinetic
equations applicable to these systems, including the spin dependence of
interparticle interactions in the collision integral, and have solved for
spin-wave frequencies and longitudinal and transverse diffusion constants in
the Boltzmann limit. We find that, while the transverse and longitudinal
collision times for trapped Fermi gases are identical, the Bose gas shows
diffusion anisotropy. Moreover, the lack of spin isotropy in the interactions
leads to the non-conservation of transverse spin, which in turn has novel
effects on the hydrodynamic modes.",0401123v1
2004-12-16,Spin and Spin-Wave Dynamics in Josephson Junctions,"We extend the Keldysh formulation to quantum spin systems and derive exact
equations of motion. This allows us to explore the dynamics of single spins and
of ferromagnets when these are inserted between superconducting leads. Several
new effects are reported. Chief amongst these are nutations of single S=1/2
spins in Josephson junctions. These nutations are triggered by the
superconducting pairing correlations in the leads. Similarly, we find that on
rather universal grounds, magnets display unconventional spin wave dynamics
when placed in Josephson junctions. These lead to modifications in the
tunneling current.",0412410v4
2005-03-10,Dynamics of a domain wall and spin-wave excitations driven by a mesoscopic current,"The dynamics of a domain wall driven by a spin-polarized current in a
mesoscopic system is studied numerically. Spin-mixing in the states of the
conduction electrons is fully taken into account. When the Fermi energy of the
electrons is larger than the exchange energy ($E_{\rm F}>J_{\rm sd}$), the spin
precession induces spin wave excitations in the local spins which contribute
towards the displacement of the domain wall. The resulting average velocity is
found to be much smaller than the one obtained in the adiabatic limit. For
$E_{\rm F}<J_{\rm sd}$, the results are consistent with the adiabatic
approximation except for the region below the critical current where a residual
domain wall velocity is found.",0503247v1
2006-06-19,Spin Diffusion in Trapped Gases: Anisotropy in Dipole and Quadrupole Modes,"Recent experiments in a mixture of two hyperfine states of trapped Bose gases
show behavior analogous to a spin-1/2 system, including transverse spin waves
and other familiar Leggett-Rice-type effects. We have derived the kinetic
equations applicable to these systems, including the spin dependence of
interparticle interactions in the collision integral, and have solved for
spin-wave frequencies and longitudinal and transverse diffusion constants in
the Boltzmann limit. We find that, while the transverse and longitudinal
collision times for trapped Fermi gases are identical, the Bose gas shows
unusual diffusion anisotropy in both dipole and quadrupole modes. Moreover, the
lack of spin isotropy in the interactions leads to the non-conservation of
transverse spin, which in turn has novel effects on the hydrodynamic modes.",0606490v1
2006-08-20,Spin-orbit induced spin-density wave in a quantum wire,"We present analysis of the interacting quantum wire problem in the presence
of magnetic field and spin-orbit interaction. We show that an interesting
interplay of Zeeman and spin-orbit terms, facilitated by the electron-electron
interaction, results in the spin-density wave (SDW) state when the magnetic
field and spin-orbit axes are orthogonal. This strongly affects charge
transport through the wire: with SDW stabilized, single particle backscattering
off an nonmagnetic impurity becomes irrelevant. Sensitivity of the effect to
the direction of the magnetic field can be used for experimental verification
of this proposal.",0608433v2
2003-04-09,Relativistic Wave Equation for Fields with Two Mass and Spin States,"I suggest wave equations for the scalar, pseudoscalar, vector, and
pseudovector fields with different masses for spin zero and one states. Tensor,
matrix, and quaternion formulations of fields with two mass and spin states are
considered. This is the generalization of the Dirac-K\""ahler equation on the
case of different masses of fields with spin one and zero. The equation
matrices obtained are simple linear combinations of matrix elements in the
16-dimensional space. Spin projection operators and solutions of equations (for
spin one) in the form of matrix-dyads are obtained. The canonical quantization
of fields under consideration is studied. The anomalous interaction of the
scalar, pseudoscalar, vector, and pseudovector fields with the external
electromagnetic field is considered. Three constants which characterize the
anomalous magnetic moment and quadrupole electric moment of a particle are
introduced.",0304091v2
2008-05-22,Pseudogap Value in the Energy Spectrum of LaOFeAs: Fixed Spin Moment Treatment,"The experimental data available up to date in literature corresponding to the
paramagnetic - spin density wave transition in nonsuperconducting LaOFeAs are
discussed. In particular, we pay attention that upon spin density wave
transition there is a relative decrease of the density of states on the Fermi
level and a pseudogap formation. The values of these quantities are not
properly described in frames of the density functional theory. The agreement of
them with experimental estimations becomes more accurate with the use of fixed
spin moment procedure when iron spin moment is set to experimental value.
Strong electron correlations which are not included into the present
calculation scheme may lead both to the decrease of spin moment and
renormalization of energy spectrum in the vicinity of the Fermi level for
correct description of discussed characteristics.",0805.3453v1
2008-08-18,Low energy spin waves and magnetic interactions in SrFe$_2$As$_2$,"We report inelastic neutron scattering studies of magnetic excitations in
antiferromagnetically ordered SrFe$_{2}$As$_{2}$ ($T_{N}=220$ K), the parent
compound of the FeAs-based superconductors. At low temperatures (T=7 K), the
spectrum of magnetic excitations $S(Q,\hbar \omega)$ consists of a Bragg peak
at the elastic position ($\hbar \omega =0$ meV), a spin gap ($ \Delta \leq 6.5$
meV), and sharp spin wave excitations at higher energies. Based on the observed
dispersion relation, we estimate the effective magnetic exchange coupling using
a Heisenberg model. On warming across $T_{N} $, the low temperature spin gap
rapidly closes, with weak critical scattering and spin-spin correlations in the
paramagnetic state. The antiferromagnetic order in SrFe$_{2}$As$_{2}$ is
therefore consistent with a first order phase transition, similar to the
structural lattice distortion.",0808.2455v2
2008-08-21,High energy spin excitations in BaFe2As2,"We report neutron scattering measurements of cooperative spin excitations in
antiferromagnetically ordered BaFe2As2, the parent phase of an iron pnictide
superconductor. The data extend up to ~100meV and show that the spin excitation
spectrum is sharp and highly dispersive. By fitting the spectrum to a linear
spin-wave model we estimate the magnon bandwidth to be in the region of 0.17eV.
The large characteristic spin fluctuation energy suggests that magnetism could
play a role in the formation of the superconducting state.",0808.2836v2
2008-09-17,Cavity-QED based on collective magnetic dipole coupling: spin ensembles as hybrid two-level systems,"We analyze the magnetic dipole coupling of an ensemble of spins to a
superconducting microwave stripline structure, incorporating a Josephson
junction based transmon qubit. We show that this system is described by an
embedded Jaynes-Cummings model: in the strong coupling regime, collective
spin-wave excitations of the ensemble of electrons pick up the nonlinearity of
the cavity mode, such that the two lowest eigenstates of the coupled spin-wave
+ microwave-cavity + Josephson-junction system define a hybrid two-level
system. The proposal described here enables the use of spin ensembles as qubits
which can be coherently manipulated and coupled using the same
nonlinear-cavity. Possibility of strong-coupling cavity-QED with
magnetic-dipole transitions opens up the possibility of extending previously
proposed quantum information processing protocols to spins in silicon or
graphene, without the need for single-electron confinement.",0809.2909v1
2008-10-14,Connecting spin and statistics in quantum mechanics,"The spin-statistics connection is derived in a simple manner under the
postulates that the original and the exchange wave functions are simply added,
and that the azimuthal phase angle, which defines the orientation of the spin
part of each single-particle spin-component eigenfunction in the plane normal
to the spin-quantization axis, is exchanged along with the other parameters.
The spin factor (-1)^2s belongs to the exchange wave function when this
function is constructed so as to get the spinor ambiguity under control. This
is achieved by effecting the exchange of the azimuthal angle by means of
rotations and admitting only rotations in one sense. The procedure works in
Galilean as well as in Lorentz-invariant quantum mechanics. Relativistic
quantum field theory is not required.",0810.2399v4
2010-02-15,High Field ESR and Magnetization of the Triangular Lattice Antiferromagnet NiGa2S4,"We report the experimental and the analytical results of electron spin
resonance (ESR) and magnetization in high magnetic fields up to about 68 T of
the quasi two-dimensional triangular lattice antiferromagnet NiGa$_2$S$_4$.
  From the temperature evolution of the ESR absorption linewidth, we find a
distinct disturbing of the development of the spin correlation by
$Z_2$-vortices between 23 K and 8.5 K. Below $T_{\rm{v}}=8.5$ K, spin-wave
calculations based on a 57$^{\circ}$ spiral spin order well explains the
frequency dependence of the ESR resonance fields and high field magnetization
processes for $H$$\parallel$$c$ and $H$$\perp$$c$, although the magnetization
for $H$$\perp$$c$ at high fields is different from the calculated one.
Furthermore, we explain the field independent specific heat with
$T^2$-dependence by the same spin-wave calculation, but the magnitude of the
specific heat is much less than the observed one. Accordingly, these results
suggest the occurrence of a $Z_2$ vortex-induced topological transition at
$T_{\rm{v}}$ and may indicate quantum effects beyond the descriptions based on
the above classical spin models.",1002.3068v1
2010-05-03,Collective spin mode in a multi-component system of coupled itinerant and localized electrons,"We study collective spin excitations of a magnetically ordered state in a
multi-component system composed of both itinerant electrons and local moments.
Here the induced spin-density-wave (SDW) ordering of itinerant electrons and
the collinear antiferromangetic (AF) ordering of local moments are locked
together via a Hund's rule coupling. We show that the Goldstone theorem still
holds at the RPA level with the gapless spin wave protected inside the small
SDW gap of itinerant electrons, which, however, is fragile in the presence of
ion-anisotropy. A gapped out-of-phase spin mode extending over a much wider
energy scale above the SDW gap is found to be more robust against the
ion-anisotropy, which is mainly contributed by the local moment fluctuations.
While the scattering between the Goldstone mode and itinerant electrons
diminishes within the SDW gap, the out-of-phase mode will strongly interact
with itinerant electrons and thus dominate the spin and charge dynamics in such
an ordered phase. Possible relevance of such a model to the iron-pnictides will
be also discussed.",1005.0421v1
2010-08-05,A unit vector for characterizing the spin polarization of free electron,"New degrees of freedom having the form of a unit vector are identified for
characterizing the spin polarization of free electron. It is shown that when
only the spin is considered, the non-commutativity of the Cartesian components
of the Pauli vector allows us to use the azimuthal angle of a second direction,
denoted by unit vector $\mathbf I$, with respect to the quantization direction
to characterize the spin polarization. The rotation of $\mathbf I$ through an
angle about the quantization axis leads to a rotation of the spin polarization
vector through twice the angle about the same axis. Discussions are also made
in Heisenberg picture as well. Upon utilizing this approach to a free electron
and letting the quantization direction for each plane wave be the wave vector,
we arrive at a representation in which the unit vector $\mathbf I$ functions as
an independent index to characterize the spin polarization.",1008.0924v1
2010-11-17,Rapid collapse of spin waves in non-uniform phases of the second Landau level,"The spin degree of freedom in quantum phases of the second Landau level is
probed by resonant light scattering. The long wavelength spin wave, which
monitors the degree of spin polarization, is at the Zeeman energy in the fully
spin-polarized state at $\nu$=3. At lower filling factors the intensity of the
Zeeman mode collapses indicating loss of polarization. A novel continuum of
low-lying excitations emerges that dominates near $\nu$=8/3 and $\nu$=5/2.
Resonant Rayleigh scattering reveals that quantum fluids for $\nu<3$ break up
into robust domain structures. While the state at $\nu$=5/2 is considered to be
fully polarized, these results reveal unprecedented roles for spin degrees of
freedom.",1011.3857v2
2011-03-05,Orbital elementary excitations as probes of entanglement and quantum phase transitions of collective spins in an entangled Bose-Einstein condensate,"A mixture of two species of pseudospin-1/2 Bose gases exhibits interesting
interplay between spin and orbital degrees of freedom. Expectation values of
various quantities of the collective spins of the two species play crucial
roles in the Gross-Pitaevskii-like equations governing the four orbital wave
functions in which Bose-Einstein condensation occurs. Consequently, the
elementary excitations of these orbital wave functions reflect properties of
the collective spins. When the coupling between the two collective spins is
isotropic, the energy gap of the gapped orbital excitation peaks, while there
is a quantum phase transition in the ground state of the effective Hamiltonian
of the two collective spins, which have previously been found to be maximally
entangled.",1103.1022v1
2011-03-16,Enhancement of spin coherence in a spin-1 Bose condensate by dynamical decoupling approaches,"We present a theoretical investigation on the enhancement of the spin
coherence with periodic, concatenated, or Uhrig dynamical decoupling $N$-pulse
sequences in a $^{87}$Rb spin-1 Bose condensate, where the intrinsic dynamical
instability in such a ferromagnetically interacting condensate causes spin
decoherence and eventually leads to a multiple spatial-domain structure or a
spin texture. Our results show that all the three sequences successfully
enhance the spin coherence by pushing the wave vector of the most unstable mode
in the condensate to a larger value. Among the three sequences with the same
number of pulses, the concatenated one shows the best performance in preserving
the spin coherence. Interestingly, we find that all the three sequences exactly
follow the same enhancement law, $k_- T^{1/2} = c$, with $k_-$ the wave vector
of the most unstable mode, $T$ the sequence period, and $c$ a
sequence-dependent constant. Such a law between $k_-$ and $T$ is also derived
analytically for an attractive scalar Bose condensate subjecting to a periodic
dynamical decoupling sequence.",1103.3087v2
2011-11-08,Time-dependent spin-wave theory,"We generalize the spin-wave expansion in powers of the inverse spin to
time-dependent quantum spin models describing rotating magnets or magnets in
time-dependent external fields. We show that in these cases, the spin operators
should be projected onto properly defined rotating reference frames before the
spin components are bosonized using the Holstein-Primakoff transformation. As a
first application of our approach, we calculate the reorganization of the
magnetic state due to Bose-Einstein condensation of magnons in the magnetic
insulator yttrium-iron garnet; we predict a characteristic dip in the
magnetization which should be measurable in experiments.",1111.2052v2
2012-06-15,Competition between stripe and checkerboard magnetic instabilities in Mn-doped BaFe2As2,"Inelastic neutron scattering measurements on Ba(Fe0.925Mn0.075)2As2 manifest
spin fluctuations at two different wavevectors in the Fe square lattice,
(1/2,0) and (1/2,1/2), corresponding to the expected stripe spin-density wave
order and checkerboard antiferromagnetic order, respectively. Below T_N=80 K,
long-range stripe magnetic ordering occurs and sharp spin wave excitations
appear at (1/2,0) while broad and diffusive spin fluctuations remain at
(1/2,1/2) at all temperatures. Low concentrations of Mn dopants nucleate local
moment spin fluctuations at (1/2,1/2) that compete with itinerant spin
fluctuations at (1/2,0) and may disrupt the development of superconductivity.",1206.3486v1
2012-08-10,Spin-Nematic and Spin-Density-Wave Orders in Spatially Anisotropic Frustrated Magnets in a Magnetic Field,"We develop a microscopic theory of finite-temperature spin-nematic orderings
in three-dimensional spatially anisotropic magnets consisting of weakly-coupled
frustrated spin-1/2 chains with nearest-neighbor and next-nearest-neighbor
couplings in a magnetic field. Combining a field theoretical technique with
density-matrix renormalization group results, we complete finite-temperature
phase diagrams in a wide magnetic-field range that possess spin-bond-nematic
and incommensurate spin-density-wave ordered phases. The effects of a four-spin
interaction are also studied. The relevance of our results to
quasi-one-dimensional edge-shared cuprate magnets such as LiCuVO4 is discussed.",1208.2235v2
2012-10-04,Projected BCS states and spin Hamiltonians for the SO(n)_1 Wess-Zumino-Witten model,"We propose a class of projected BCS wave functions and derive their parent
spin Hamiltonians. These wave functions can be formulated as infinite Matrix
Product States constructed by chiral correlators of Majorana fermions. In 1D,
the spin Hamiltonians can be viewed as SO(n) generalizations of Haldane-Shastry
models. We numerically compute the spin-spin correlation functions and Renyi
entropies for n=5 and 6. Together with the results for n=3 and 4, we conclude
that these states are critical and their low-energy effective theory is the
SO(n)_1 Wess-Zumino-Witten model. In 2D, we show that the projected BCS states
are chiral spin liquids, which support non-Abelian anyons for odd n and Abelian
anyons for even n.",1210.1481v3
2013-02-01,Electronic Properties and Persistent Spin Currents of Nanospring under Static Magnetic Field,"Relativistic electronic properties of a nanospring under a static magnetic
field are theoretically investigated in the present study. The wave equation
accounting for the spin-orbit interaction is derived for the nanospring as a
special case of the Pauli equation for a spin-1/2 particle confined to a curved
surface under an electromagnetic field. We define the helical momentum operator
and show that it commutes with the Hamiltonian owing to the helical geometry of
the nanospring. The energy eigenstates are hence also the eigenstates of the
helical momentum. We solve the equation numerically to obtain the surface wave
functions and the energy spectra. The electronic properties are systematically
examined by varying the parameters that characterize the system. It is
demonstrated that either the nonzero spin-orbit interaction or the nonzero
external magnetic field suffices for the occurrence of the persistent spin
current on the nanospring. Two different mechanisms are shown to generate the
persistent spin current. One employs the spin-orbit interaction coming from the
local inversion asymmetry on the surface, while the other employs the curvature
coupling with the external magnetic field.",1302.0066v1
2013-04-21,On a consistent macroscopic description for a spin quantum plasma with interparticle interactions,"Quantum mechanical averaging of the particle concentration operator is an
effective starting point for derivation of the many-particle quantum
hydrodynamic equations. In many-particle quantum systems, we have to separate
the ordered motion of the local center of mass (velocity field), the thermal,
and the quantum motion. The quantum mechanical average process, invoked here,
is completely determined, and is different from the usual averaging processes
that introduces undefined probabilities for quantum states. It is shown that
the Madelung decomposition for the $N$-particle spinor wave function allows the
correct introduction of the velocity field, and gives explicit expressions for
the quantum contributions to both the momentum, and the spin flux. The
formalism also contains plasma effects produced by the Coulomb and spin-spin
interparticle interactions. It is shown that both interactions appear in plasma
dynamics as effective electric and magnetic fields. As result we find a fully
coherent description for spin quantum plasma in the self-consistent field
approximation for interparticle interactions. A simple consequence - the change
brought about by interparticle correlations on the propagation of electrostatic
waves in a spin quantum plasma - is discussed.",1304.5780v1
2013-08-08,Strong coupling theory of spin and orbital excitations in Sr2IrO4,"We study the low-lying excitations in 5d transition-metal oxide Sr_2IrO_4 on
the localized electron picture. We find that Hund's coupling together with the
spin-orbit interaction leads to exchange anisotropy which causes the spin wave
gap. Introducing the isospin operators acting on Kramers' doublet in Ir atoms,
we derive the effective spin Hamiltonian from a multi-orbital Hubbard model
with the t_{2g} orbitals in the square lattice. We introduce the Green's
functions including the anomalous type for the boson operators by expanding the
spin operators in terms of boson operators in the lowest order of 1/S, and
solve the coupled equations of motion for those functions. Two modes are found
to emerge with slightly different energies, in contrast to the spin waves in
the isotropic Heisenberg model. At the $\Gamma$-point, one mode has the zero
excitation energy while another has a finite energy. They have the same
excitation energy at the M point, but still have different energies at the X
point.",1308.1816v2
2013-11-01,Coherent Magnetism and Spin-Orbit Interaction in Garnet Films Probed with Femtosecond Magneto-Optical Four Wave Mixing,"We report about the dephasing of the spins states in a Garnet film excited by
femtosecond laser pulses. It is shown that magneto-optical four-wave-mixing
signals are efficiently generated and controlled with an external static
magnetic field. The self-diffraction of either two or three femtosecond pulses
allows us determining independently the coherent response time ($T_2$ < 50 fs)
and the population relaxation, which occurs in several steps. After the laser
induced demagnetization, the spin-lattice relaxation is the dominant mechanism
($T_{1,spin-lat}$ < 1.35 ps) and the precession of the magnetization takes
place at later times ($T_{1,prec}$ < 150 ps). The coherent response of the
spins states is modeled with a multi-level hydrogen-like system, taking into
account the fundamental relativistic quantum dynamics of the spins. Our
experimental approach is general and opens the way to investigating quantum
magnetism in ordered magnetic systems useful for applications in information
and communications technologies.",1311.0080v1
2014-01-24,Wavenumber-dependent Gilbert damping in metallic ferromagnets,"New terms to the dynamical equation of magnetization motion, associated with
spin transport, have been reported over the past several years. Each newly
identified term is thought to possess both a real and an imaginary effective
field leading to fieldlike and dampinglike torques on magnetization. Here we
show that three metallic ferromagnets possess an imaginary effective-field term
which mirrors the well-known real effective-field term associated with exchange
in spin waves. Using perpendicular standing spin wave resonance between 2-26
GHz, we evaluate the magnitude of the finite-wavenumber ($k$) dependent Gilbert
damping $\alpha$ in three typical device ferromagnets, Ni$_{79}$Fe$_{21}$, Co,
and Co$_{40}$Fe$_{40}$B$_{20}$, and demonstrate for the first time the presence
of a $k^2$ term as $\Delta\alpha=\Delta\alpha_0+A_{k}\cdot k^2$ in all three
metals. We interpret the new term as the continuum analog of spin pumping,
predicted recently, and show that its magnitude, $A_{k}$=0.07-0.1 nm$^2$, is
consistent with transverse spin relaxation lengths as measured by conventional
(interlayer) spin pumping.",1401.6467v2
2015-05-05,Plasmons in spin polarized graphene: a new way to measure spin polarization,"We study the collective charge excitations (plasmons) in spin polarized
graphene, and derive explicit expressions for their dispersion in the undamped
regime. From this, we are able to calculate the critical wave vector beyond
which the plasmon enters the electron-hole continuum, its quality factor
decreasing sharply. We find that the value of the critical wave vector is
strongly spin polarization-dependent, in a way that has no analog in ordinary
two-dimensional electron gases. The origin of this effect is in the coupling
between the plasmon and the inter-band electron-hole pairs of the minority spin
carriers. We show that the effect is robust with respect to the inclusion of
disorder and we suggest that it can be exploited to experimentally determine
the spin polarization of graphene.",1505.01095v2
2016-04-12,Ultrafast non-thermal laser excitation of gigahertz longitudinal and shear acoustic waves in spin-crossover molecular crystals [$Fe(PM-AzA)_{2}$$(NCS)_{2}$],"We report GHz longitudinal as well as shear acoustic phonons photoexcitation
and photodetection using femtosecond laser pulses in a spin-crossover molecular
crystal. From our experimental observation of time domain Brillouin scattering
triggered by the photoexcitation of acoustic waves across the low-spin (LS) to
high-spin (HS) thermal crossover, we reveal a link between molecular spin state
and photoexcitation of coherent GHz acoustic phonons. In particular, we
experimentally evidence an unconventional non-thermal pathway for the laser
excitation of GHz phonons. We also provide experimental insight on the optical
and mechanical parameters evolution across the LS/HS spin crossover temperature
T$_{1/2}$.",1604.03297v4
2016-07-08,Semiclassical ground-state phase diagram and multi-Q phase of a spin-orbit coupled model on triangular lattice,"Motivated by recent experiments on the frustrated quantum magnetic compound
YbMgGaO4, we study an effective spin model on triangular lattice taking into
account the effects of the spin-orbit coupling. We determine the classical
ground-state phase diagram of this model, which includes a 120 degree Neel and
two collinear antiferromagnetic phases. In the vicinity of the phase boundary
between the Neel and collinear phases, we identify three intermediate
non-collinear antiferromagnetic phases. In each of them the magnetic moments
are ordered at multiple incommensurate wave vector Q values. We further study
the effects of quantum fluctuations in this model via a linear spin-wave
theory. We find that the spin excitation gap of the non-collinear multi-Q
antiferromagnetic state is finite but can be vanishingly small, and this state
is unstable to a spin liquid phase under strong quantum fluctuations in some
large J_{z+-} regime.",1607.02295v1
2016-08-13,Topological transport of sound mediated by spin-redirection geometric phase,"When a dynamic system undergoes a cyclic evolution, a geometric phase that
depends only on the path traversed in parameter space can arise in addition to
the normal dynamical phase. These geometric phases have profound impacts in
both quantum and classical physics. In addition to the geometric phase
associated with band structures in reciprocal space that has led to the
discovery of topological insulators, the spin-redirection geometric phase
induced by the $SO$(3) rotation of states in real space can also give rise to
intriguing phenomena such as the photonic analog of the spin Hall effect. By
exploiting the orbital angular momentum of sound vortices, we theoretically and
experimentally demonstrate the spin-redirection geometric phase effects in
airborne sound, which is a scalar wave without spin. We show that these
effects, associated with the helical transport of sound, can be used to control
the flow of sound. This finding opens new possibilities for the manipulation of
scalar wave propagation by exploiting spin-redirection geometric phases.",1608.03976v3
2016-09-05,Spin excitations in optimally P-doped BaFe2(As0.7P0.3)2superconductor,"We use inelastic neutron scattering to study temperature and energy
dependence of spin excitations in optimally P-doped BaFe2(As0.7P0.3)2
superconductor (Tc = 30 K) throughout the Brillouin zone. In the undoped state,
spin waves and paramagnetic spin excitations of BaFe2As2 stem from
antiferromagnetic (AF) ordering wave vector QAF= (1/-1,0) and peaks near zone
boundary at (1/-1,1/-1) around 180 meV. Replacing 30% As by smaller P to induce
superconductivity, low-energy spin excitations of BaFe2(As0.7P0.3)2form a
resonance in the superconducting state and high-energy spin excitations now
peaks around 220 meV near (1/-1,1/-1). These results are consistent with
calculations from a combined density functional theory and dynamical mean field
theory, and suggest that the decreased average pnictogen height in
BaFe2(As0.7P0.3)2 reduces the strength of electron correlations and increases
the effective bandwidth of magnetic excitations.",1609.01021v1
2017-08-02,Long-distance excitation of nitrogen-vacancy centers in diamond via surface spin waves,"Coherent communication over mesoscale distances is a necessary condition for
the application of solid-state spin qubits to scalable quantum information
processing. Among other routes under study, one possibility entails the
generation of magnetostatic surface spin waves (MSSW) dipolarly coupled to
shallow paramagnetic defects in wide-bandgap semiconductors. As an initial step
in this direction, here we make use of room-temperature MSSWs to mediate the
interaction between the microwave field from an antenna and the spin of a
nitrogen-vacancy (NV) center in diamond. We show that this transport spans
distances exceeding 3 mm, a manifestation of the MSSW robustness and long
diffusion length. Using the NV spin as a local sensor, we find that the MSSW
amplitude grows linearly with the applied microwave power, suggesting this
approach could be extended to amplify the signal from neighboring spin qubits
by several orders of magnitude.",1708.00596v1
2017-08-08,Projector quantum Monte Carlo with averaged vs. explicit spin-orbit effects: applications to tungsten molecular systems,"We present a recently developed projector quantum Monte Carlo method for
calculations of electronic structure in systems with spin-orbit interactions.
The method solves for many-body eigenstates in the presence of spin-orbit using
the fixed-phase approximation.The trial wave function is built from
two-component spinors and explicit Jastrow correlation factors while the core
electrons are eliminated by relativistic effective core potentials with
explicit spin-orbit terms. We apply this method to WO and W$_2$ molecules that
enable us to build multi-reference wave functions and analyze in detail the
impact of both electron correlations and of spin-orbit terms. These
developments open new opportunities for calculations of systems with
significant spin-orbit effects by many-body quantum Monte Carlo methods.",1708.02571v1
2017-11-27,"Magnetic properties, spin waves and interaction between spin excitations and 2D electrons in interface layer in Y3Fe5O12 / AlOx / GaAs-heterostructures","We describe synthesis of submicron Y3Fe5O12 (YIG) films sputtered on
GaAs-based substrates and present results of the investigation of ferromagnetic
resonance (FMR), spin wave propagation and interaction between spin excitations
and 2D electrons in interface layer in YIG / AlOx / GaAs-heterostructures. It
is found that the contribution of the relaxation process to the FMR linewidth
is about 2 % of the linewidth \Delta H. At the same time, for all samples FMR
linewidths are high. Sputtered YIG films have magnetic inhomogeneity, which
gives the main contribution to the FMR linewidth. Transistor structures with
two-dimensional electron gas (2DEG) channels in AlOx / GaAs interface governed
by YIG-film spin excitations are designed. An effective influence of spin
excitations on the current flowing through the GaAs 2DEG channel is observed.
Light illumination results in essential changes in the FMR spectrum. It is
found that an increase of the 2DEG current leads to an inverse effect, which
represents essential changes in the FMR spectrum.",1711.09814v1
2018-03-19,Terahertz radiation by subpicosecond spin-polarized photocurrent originating from Dirac electrons in a Rashba-type polar semiconductor,"The spin-splitting energy bands induced by the relativistic spin-orbit
interaction in solids provide a new opportunity to manipulate the
spin-polarized electrons on the sub-picosecond time scale. Here, we report one
such example in a bulk Rashba-type polar semiconductor BiTeBr. Strong terahertz
electromagnetic waves are emitted after the resonant excitation of the
interband transition between the Rashba-type spin-splitting energy bands with a
femtosecond laser pulse circularly polarized. The phase of the emitted
terahertz waves is reversed by switching the circular polarization. This
suggests that the observed terahertz radiation originates from the
subpicosecond spin-polarized photocurrents, which are generated by the
asymmetric depopulation of the Dirac state. Our result provides a new way for
the current-induced terahertz radiation and its phase control by the circular
polarization of incident light without external electric fields.",1803.06826v1
2018-06-11,Extraordinary spin density and energy back-flow under interference,"A novel phenomenon was reported recently that the ""local optical spin
density"" based on Poynting vector might be counter-intuitively opposite to the
integrated spin orientation while the one related to the canonical expression
might not [Leader, Phys. Lett. B 779, 385-387 (2018)]. However, the ""local
optical spin density"" of the canonical expression can also be
counter-intuitively opposite to the integrated spin orientation under the
interference of plane waves, even if all of the plane waves possess the same
polarization handedness. Moreover, the interference fields might acquire a
transverse spin density (perpendicular to the propagation plane), which can
have more well-controlled relations with the polarization. Meantime, in such a
case its energy flux exhibits counter-intuitive back-flow and a circular motion
(vortex) in the propagation plane locally, which implies a transverse local
orbital angular momentum density.",1806.03893v1
2020-09-14,Many-Body Phases of a Planar Bose-Einstein Condensate with Cavity-Induced Spin-Orbit Coupling,"We explore the many-body phases of a two-dimensional Bose-Einstein condensate
with cavity-mediated dynamic spin-orbit coupling. By the help of two transverse
non-interfering, counterpropagating pump lasers and a single standing-wave
cavity mode, two degenerate Zeeman sub-levels of the quantum gas are Raman
coupled in a double-$\Lambda$-configuration. Beyond a critical pump strength
the cavity mode is populated via coherent superradiant Raman scattering from
the two pump lasers, leading to the appearance of a dynamical spin-orbit
coupling for the atoms. We identify three quantum phases with distinct atomic
and photonic properties: the normal ``homogeneous'' phase, the superradiant
``spin-helix'' phase, and the superradiant ``supersolid spin-density-wave''
phase. The latter exhibits an emergent periodic atomic density distribution
with an orthorhombic centered rectangular-lattice structure due to the
interplay between the coherent photon scattering into the resonator and the
collision-induced momentum coupling. The transverse lattice spacing of the
emergent crystal is set by the dynamic spin-orbit coupling.",2009.06475v1
2021-04-28,Emission of electromagnetic radiation due to spin-flip transitions in a ferromagnet,"We theoretically analyze a possibility of electromagnetic wave emission due
to electron transitions between spin subbands in a ferromagnet. Different
mechanisms of such spin-flip transitions are cousidered. One mechanism is the
electron transitions caused by magnetic field of the wave. Another mechanism is
due to Rashba spin-orbit interaction. While two mentioned mechanisms exist in a
homogeneously magnetized ferromagnet, there are two other mechanisms that exist
in non-collinearly magnetized medium. First mechanism is known and is due to
the dependence of exchange interaction constant on the quasimomentum of
conduction electrons. Second one exists in any non-collinearly magnetized
medium. We study these mechanisms in a non-collinear ferromagnet with
helicoidal magnetization distribution. The estimations of probabilities of
electron transitions due to different mechanisms are made for realistic
parameters, and we compare the mechanisms. We also estimate the radiation power
and threshold current in a simple model in which spin is injected into the
ferromagnet by a spin-polarized electric current through a tunnel barrier.",2104.13943v1
2021-10-19,Ising and XY paramagnons in two-dimensional 2H-NbSe$_2$,"Paramagnons are the collective modes that govern the spin response of nearly
magnetic conductors. In some cases they mediate electron pairing leading to
superconductivity. This scenario may occur in 2H-NbSe$_2$ monolayers, that
feature spin-valley coupling on account of spin-orbit interactions and their
lack of inversion symmetry. Here we explore spin anisotropy of paramagnons both
for non-centrosymmetric Kane-Mele-Hubbard models for 2H-NbSe$_2$ monolayers
described with a DFT-derived tight-binding model. In the infinite wavelength
limit we find spatially uniform paramagnons with energies around $1$~meV that
feature a colossal off-plane uniaxial magnetic anisotropy, with quenched
transversal spin response. At finite wave vectors, longitudinal and transverse
channels reverse roles: XY fluctuations dominate within a significant portion
of the Brillouin zone. Our results show that 2H-NbSe$_2$ is close to a
Coulomb-driven in-plane (XY) spin density wave instability.",2110.09809v2
2016-10-31,Student project: Of spinning coins and merging black holes,"For the past decade, the SAIL labs at the University of Sydney have been
challenging students with short research projects that elucidate basic
principles of physics. These include the development of instruments launched on
cubesats, balloons, on telescopes or placed out in the field. This experiment
is inspired by the spectacular 2015 discovery of merging black holes with the
Laser Interferometric Gravitational-Wave Observatory (LIGO). Students are
profoundly inspired by LIGO, and for good reason, but it is challenging to
construct a table top demonstration of a gravitational wave observatory.
Instead we consider chirps which are remarkable transient phenomena in nature
involving both frequency and amplitude modulation, as we can demonstrate with a
spinning coin. In the case of the LIGO event, orbital energy is being released
as gravitational radiation; for the spinning coin, its spin/orbit energy is
being released dissipatively (sound, heat, air viscosity). Our experiment
involves a simple device to spin a coin remotely. This aids repeatability and
allows us to spin the coin within a vacuum chamber to examine the contribution
of air viscosity.",1611.00070v1
2019-12-23,Applied electric field on zigzag graphene nanoribbons: reduction of spin stiffness and appearance of spiral spin density waves,"We investigated the reduction of the spin stiffness and the appearance of the
spiral spin density waves when the electric field is applied on the zigzag
graphene nanoribbons for the ferromagnetic and antiferromagnetic edge states.
For that purpose, we exploited the generalized Bloch theorem combined with a
constraint method to keep the direction of the magnetic moment of the carbon
atom at the edges. We found that the ground state of ferromagnetic
configuration is unstable and leads to the spiral ground state while the ground
state of the antiferromagnetic configuration is robust. We also showed that the
spin stiffness in the ferromagnetic and antiferromagnetic configurations
reduces as the electric field increases. Thus, we justified that not only the
spin stiffness but also the ground state of the zigzag graphene nanoribbons can
be controlled by the electric field.",1912.10670v1
2020-05-06,Relativistic electron spin dynamics in a strong unipolar laser field,"The behavior of an electron spin interacting with a linearly polarized laser
field is analyzed. In contrast to previous considerations of the problem, the
initial state of the electron represents a localized wave packet, and a spatial
envelope is introduced for the laser pulse, which allows one to take into
account the finite size of both objects. Special attention is paid to
ultrashort pulses possessing a high degree of unipolarity. Within a classical
treatment (both nonrelativistic and relativistic), proportionality between the
change of the electron spin projections and the electric field area of the
pulse is clearly demonstrated. We also perform calculations of the electron
spin dynamics according to the Dirac equation. Evolving the electron wave
function in time, we compute the mean values of the spin operator in various
forms. It is shown that the classical relativistic predictions are accurately
reproduced when using the Foldy-Wouthuysen operator. The same results are
obtained when using the Lorentz transformation and the nonrelativistic (Pauli)
spin operator in the particle's rest frame.",2005.02839v1
2020-06-12,Symmetry Approach to Chiral Optomagnonics in Antiferromagnetic Insulators,"We discuss several aspects of chiral optomagnonics in antiferromagnetic
insulators by considering common symmetries between the electromagnetic field
and spin excitations. This approach allows us to look at optical and magnetic
materials from similar perspectives, and discuss useful analogies between them.
We show that spin waves in collinear antiferromagnets and the electromagnetic
field in vacuum are both invariant under the same eight-dimensional algebra of
symmetry transformations. By such analogy, we can extend the concept of optical
chirality to antiferromagnetic insulators, and demonstrate that the spin-wave
dynamics in these materials in the presence of a spin current is similar to
that of the light inside chiral metamaterials. Photo-excitation of magnonic
spin currents is also discussed from the symmetry point of view. It is
demonstrated that a direct magnonic spin photocurrent can be exited by
circularly polarized light, which can be considered as a magnonic analogue of
the photogalvanic effect. We also note that the Zitterbewegung process should
appear and may play a role in photo-excitation processes.",2006.07399v1
2020-06-29,Collective excitations in spin-polarized bilayer graphene,"We calculate the plasmon frequency and damping rate of plasma oscillations in
a spin-polarized BLG system. Using the long wavelength approximation for
dynamical dielectric function, we obtain an analytical expression for plasmon
frequency showing that the degree of spin polarization P has negligible effect
on the long wavelength plasmon frequency. Numerical calculations demonstrate
that the degree of spin polarization affects slightly (strongly) plasmon
frequency at small (large) wave-vectors and the maximum value of damping rate
increases with increasing P. We also study the effects of carrier density and
substrate dielectric constant on plasmon properties for different value of spin
polarization. The numerically calculated critical wave-vector, at which the
plasmon dispersion curve hits the edge of electron-hole continuum, decreases
with P and can be used to determine experimentally the degree of spin
polarization.",2006.16042v2
2020-10-06,Emergent spin dynamics enabled by lattice interactions in a bicomponent artificial spin ice,"Artificial spin ice (ASI) are arrays on nanoscaled magnets that can serve
both as models for frustration in atomic spin ice as well as for exploring new
spin-wave-based strategies to transmit, process, and store information. Here,
we exploit the intricate interplay of the magnetization dynamics of two
dissimilar ferromagnetic metals arranged on complimentary lattice sites in a
square ASI to effectively modulate the spin-wave properties. We show that the
interaction between the two sublattices results in unique spectra attributed to
each sublattice and we observe inter- and intra-lattice dynamics facilitated by
the distinct magnetization properties of the two materials. The dynamic
properties are systematically studied by angular-dependent broadband
ferromagnetic resonance and confirmed by micromagnetic simulations. We show
that the combination of materials with dissimilar magnetic properties enables
the realization of a wide range of two-dimensional structures potentially
opening the door to new concepts in nanomagnonics.",2010.03008v1
2021-03-17,Micromagnetic description of twisted spin spirals in the B20 chiral magnet FeGe from first principles,"Using the model of classical Heisenberg exchange and Dzyaloshinskii-Moriya
(DM) interaction we show that the ground state of B20 FeGe chiral magnet is a
superposition of twisted helical spin-density waves formed by different
sublattices of the crystal. Such twisted spin-density waves propagate in the
same direction but with different phases and different directions of the
rotation axes. We derive an advanced micromagnetic expression describing the
exchange and DM interaction for such magnetic structures. By employing
first-principles calculations based on density functional theory and using our
micromagnetic model we show that the magnitude of the spin-spiral twist in B20
FeGe is of the same order as global spiraling. While the energy difference
between the ground state of twisted spirals and the FM state is in good
agreement with the experimental results, for the spin spirals without a twist
it is smaller by factor three. In addition, we verify our results by employing
spin dynamics simulations. This calls for new experiments exploring the ground
state properties of B20 chiral magnets.",2103.09800v2
2021-05-07,Field-angle dependence of thermal Hall conductivity in magnetically ordered Kitaev-Heisenberg system,"We study magnetic excitations and thermal Hall effect on the
Kitaev-Heisenberg model under magnetic fields. By employing the spin-wave
theory for the magnetic orders realized in this model, we examine the
topological nature of the spin-wave dispersions and calculate the thermal Hall
conductivity. The comprehensive investigations on the field-angle dependence
clarify that the thermal Hall conductivity is sensitive to the spin ordered
pattern and excitation spectra of magnons; this quantity is enhanced by the
noncoplanar spin configurations and small magnon gap in the excitation
spectrum. On the other hand, we also find a common feature in the field-angle
dependence of the thermal Hall conductivity. It vanishes when the magnetic
field is on the planes spanned by the spin axes. We reveal that the behavior is
intrinsic to the Kitaev -Heisenberg model in an applied field and demonstrate
that the introduction of the off-diagonal spin interaction causes the
disappearance of the feature in the thermal Hall conductivity.",2105.03113v1
2021-05-25,Robust exceptional point of arbitrary order in coupled spinning cylinders,"Exceptional points (EPs), i.e., non-Hermitian degeneracies at which
eigenvalues and eigenvectors coalesce, can be realized by tuning the gain/loss
contrast of different modes in non-Hermitian systems or by engineering the
asymmetric coupling of modes. Here we demonstrate a mechanism that can achieve
EPs of arbitrary order by employing the non-reciprocal coupling of spinning
cylinders sitting on a dielectric waveguide. The spinning motion breaks the
time-reversal symmetry and removes the degeneracy of opposite chiral modes of
the cylinders. Under the excitation of a linearly polarized plane wave, the
chiral mode of one cylinder can unidirectionally couple to the same mode of the
other cylinder via the spin-orbit interaction associated with the evanescent
wave of the waveguide. The structure can give rise to arbitrary-order EPs that
are robust against spin-flipping perturbations, in contrast to conventional
systems relying on spin-selective excitations. In addition, we show that
higher-order EPs in the proposed system are accompanied by enhanced optical
isolation, which may find applications in designing novel optical isolators,
nonreciprocal optical devices, and topological photonics.",2105.11629v1
2021-09-17,Current-Induced Spin-Wave Doppler Shift in Antiferromagnets,"We theoretically study the spin dynamics in antiferromagnets (AFs)under the
influence of an electric current. We identify two different sources of
spin-transfer torques that stem from uniform (${\boldsymbol v}_n$) and
staggered (${\boldsymbol v}_\ell$) electron spin densities. While the former is
well recognized, the latter is often overlooked. We show that both
${\boldsymbol v}_n$ and ${\boldsymbol v}_\ell$ contribute equally to the
spin-wave Doppler shift. Microscopic calculations are presented for electrons
on a two-dimensional square lattice with nearest-neighbor ($t$) and
next-nearest-neighbor ($t'$) hopping, which interpolate two opposite transport
regimes of strongly-coupled AF ($t'/t \ll 1$) and two weakly coupled
ferromagnets ($t'/t \gg 1$). In the AF transport regime ($t'/t \ll 1$),
${\boldsymbol v}_n$ and ${\boldsymbol v}_\ell$ have opposite signs, and the
sign of the Doppler shift depends on band filling; ${\boldsymbol v}_n$
(${\boldsymbol v}_\ell$) is dominant near the AF gap (near the band bottom or
the top). As $t'/t$ is increased, ${\boldsymbol v}_n$ undergoes a sign change
whereas ${\boldsymbol v}_\ell$ does not. In the limit of vanishing $t$,
${\boldsymbol v}_n$ and ${\boldsymbol v}_\ell$ coincide and the spin-transfer
torque reduces to that of ferromagnets.",2109.08432v1
2021-11-24,Spin Polarization through A Molecular Junction Based on Nuclear Berry Curvature Effects,"We explore the effects of spin-orbit coupling on nuclear wave packet motion
near an out-of-equilibrium molecular junction, where nonzero Berry curvature
emerges as the antisymmetric part of the electronic friction tensor. The
existence of nonzero Berry curvature mandates that different nuclear wave
packets (associated with different electronic spin states) experience different
nuclear Berry curvatures, i.e. different pseudo-magnetic fields. Furthermore,
for a generic, two-orbital two-lead model (representing the simplest molecular
junction), we report significant spin polarization of the {\em electronic}
current with decaying and oscillating signatures in the large voltage limit --
all as a result of {\em nuclear} motion. These results are consistent with
magnetic AFM chiral-induced spin selectivity experiments. Altogether, our
results highlight an essential role for Berry curvature in condensed phase
dynamics, where spin separation survives dissipation to electron-hole pair
creation and emerges as one manifestation of nuclear Berry curvature.",2111.12815v2
2022-03-01,turboMagnon -- A code for the simulation of spin-wave spectra using the Liouville-Lanczos approach to time-dependent density-functional perturbation theory,"We introduce turboMagnon, an implementation of the Liouville-Lanczos approach
to linearized time-dependent density-functional theory, designed to simulate
spin-wave spectra in solid-state materials. The code is based on the
noncollinear spin-polarized framework and the self-consistent inclusion of
spin-orbit coupling that allow to model complex magnetic excitations. The spin
susceptibility matrix is computed using the Lanczos recursion algorithm that is
implemented in two flavors - the non-Hermitian and the pseudo-Hermitian one.
turboMagnon is open-source software distributed under the terms of the GPL as a
component of Quantum ESPRESSO. As with other components, turboMagnon is
optimized to run on massively parallel architectures using native mathematical
libraries (LAPACK and FFTW) and a hierarchy of custom parallelization layers
built on top of MPI. The effectiveness of the code is showcased by computing
magnon dispersions for the CrI$_3$ monolayer, and the importance of the
spin-orbit coupling is discussed.",2203.01120v2
2022-03-10,Pair-density-wave and chiral superconductivity in twisted bilayer transition-metal-dichalcogenides,"We theoretically explore possible unconventional superconductivity induced by
weak repulsive interactions in twisted bilayer TMD (e.g. WSe$_2$) in the
presence of an out-of-plane electric field. Using renormalization group (RG)
analysis, we show that topological chiral superconducting states with Chern
number $\mathcal{N}=1,2,4$ (namely $p+ip$, $d+id$, $g+ig$) appear over a large
parameter region with moire filling factor around $n=1$. At some special values
of applied electric field and in the presence of a weak out-of-plane Zeeman
field, spin-polarized pair density wave (PDW) superconductivity can emerge.
This spin-polarized PDW state can be probed by experiments such as
spin-polarized STM measuring spin-resolved pairing gap and quasi-particle
interference. Moreover, the spin-polarized PDW could lead to spin-polarized
superconducting diode effect.",2203.05480v2
2022-06-15,Terahertz Slonczewski propagating spin waves and large output voltage in antiferromagnetic spin-Hall nano-oscillators,"We study theoretically antiferromagnet (AFM) based spin-Hall nano-oscillators
(SHNOs) consisting of a nano-constriction (NC) in a thin-film uniaxial AFM. By
solving the derived SW equation we evidence radially propagating spin waves
(SWs) at THz frequencies similar to the Slonczewski SWs known at GHz
frequencies for a ferromagnet-based SHNO. We predict a minimum threshold
current for a specific NC radius accessible by the state-of-the-art
nanotechnology. The exchange interaction enhanced spin pumping for AFMs leads
to a strong thickness dependent threshold frequency. We show that the uniaxial
AFMs generate ac electrical fields via spin pumping that are three orders of
magnitude larger than reported for biaxial AFMs. Our work enhances the
fundamental understanding of current-driven SWs in AFM-SHNOs and enables
optimization of practical devices in terms of material choice, device geometry,
and frequency tunability. The propagating SWs offer remote THz signal
generation and an efficient means for synchronization of SHNOs when aiming at
high power.",2206.07844v3
2022-10-28,Stripe order and spin dynamics in triangular-lattice antiferromagnet KErSe$_{2}$: A single-crystal study with a theoretical description,"The rare-earth triangular-lattice chalcogenide is a great platform for
exploring both spin liquids and novel magnetic orders with anisotropic spin
interactions and magnetic frustrations. Here, we report the thermodynamic and
neutron scattering measurements of rare-earth triangular-lattice chalcogenide
KErSe$_{2}$, using single-crystal samples. Our experiments revealed a
long-range stripe order below 0.2 K. Although the magnetic order was
three-dimensional, magnetic excitations exhibited negligible modulation along
the z direction, indicating very weak interlayer coupling. Furthermore,
magnetic excitation developed a well-defined spin-wave dispersion with a gap of
$\sim$0.03 meV at M points. Both the stripe order and spin-wave excitations
could be quantitatively understood from the anisotropic spin interactions of
the Er$^{3+}$ Kramers doublets.",2210.15867v1
2022-11-24,Elliptic soliton solutions of the spin non-chiral intermediate long-wave equation,"We construct elliptic multi-soliton solutions of the spin non-chiral
intermediate long-wave (sncILW) equation with periodic boundary conditions.
These solutions are obtained by a spin-pole ansatz including a dynamical
background term; we show that this ansatz solves the periodic sncILW equation
provided the spins and poles satisfy the elliptic $A$-type spin Calogero-Moser
(sCM) system with certain constraints on the initial conditions. The key to
this result is a B\""{a}cklund transformation for the elliptic sCM system which
includes a non-trivial dynamical background term. We also present solutions of
the sncILW equation on the real line and of the spin Benjamin-Ono equation
which generalize previously obtained solutions by allowing for a non-trivial
background term.",2211.13791v1
2022-11-30,"Universal Relations of Energy Flow, Acoustic Spin and Torque for Near-Field Acoustic Tweezers","Acoustic spin, radiation torque, energy flow, and reactive power are of
significant importance from both fundamental and practical aspects, responsible
for flexible tweezer manipulations and near-field sound directionality.
Nevertheless, the intrinsic relations among these physical quantities are far
from clear. Here, we prove the universal geometric relations among them in
acoustics, independent on wave structure details. Particularly, we connect
acoustic spin and torque to the cross product of time-averaged energy flow and
reactive power, as well as to the local vorticity of energy flow. These
relations are universally valid, verified in a variety of different acoustic
systems. We also demonstrate the multipole mechanical torques and forces
generated in three acoustic near-field sources: Janus, Huygens and Spin
sources, applying on small lossy particles. These universal geometric relations
uncover hidden locking relations beyond simple spin-momentum locking of
near-field waves, and show the basic principles between the acoustic spin,
radiation torque, and energy flow, reactive power.",2212.00028v1
2023-03-05,Coupling of magnetism and Dirac fermions in YbMnSb2,"We report inelastic neutron scattering measurements of magnetic excitations
in YbMnSb2, a low-carrier-density Dirac semimetal in which the
antiferromagnetic Mn layers are interleaved with Sb layers that host Dirac
fermions. We observe a considerable broadening of spin waves, which is
consistent with substantial spin fermion coupling. The spin wave damping,
$\gamma$, in YbMnSb2 is roughly twice larger compared to that in a sister
material, YbMnBi2, where an indication of a small damping consistent with
theoretical analysis of the spin-fermion coupling was reported. The inter-plane
interaction between the Mn layers in YbMnSb2 is also much stronger, suggesting
that the interaction mechanism is rooted in the same spin-fermion coupling. Our
results establish the systematics of spin-fermion interactions in layered
magnetic Dirac materials.",2303.02587v2
2023-04-05,Control of 4-magnon-scattering in a magnonic waveguide by pure spin current,"We use a pure spin current originating from the spin Hall effect to generate
a spin-orbit torque (SOT) strongly reducing the effective damping in an
adjacent ferromagnet. Due to additional microwave excitation, large spin-wave
amplitudes are achieved exceeding the threshold for 4-magnon scattering, thus
resulting in additional spin-wave signals at discrete frequencies. Two or more
modes are generated below and above the directly pumped mode with equal
frequency spacing. It is shown how this nonlinear process can be controlled in
magnonic waveguides by the applied dc current and the microwave pumping power.
The sudden onset of the nonlinear effect after exceeding the thresholds can be
interpreted as spiking phenomenom which makes the effect potentially
interesting for neuromorphic computing applications. Moreover, we investigated
this effect under microwave frequency and external field variation. The
appearance of the additional modes was investigated in the time-domain
revealing a time delay between the directly excited and the simultaneously
generated nonlinear modes. Furthermore, spatially resolved measurements show
different spatial decay lengths of the directly pumped mode and nonlinear
modes.",2304.02708v1
2023-04-25,Parameter estimation of binary black holes in the endpoint of the up-down instability,"Black-hole binary spin precession admits equilibrium solutions corresponding
to systems with (anti-) aligned spins. Among these, binaries in the up-down
configuration, where the spin of the heavier (lighter) black hole is co-
(counter-) aligned with the orbital angular momentum, might be unstable to
small perturbations of the spin directions. The occurrence of the up-down
instability leads to gravitational-wave sources that formed with aligned spins
but are detected with precessing spins. We present a Bayesian procedure based
on the Savage-Dickey density ratio to test the up-down origin of
gravitational-wave events. This is applied to both simulated signals, which
indicate that achieving strong evidence is within the reach of current
experiments, and the LIGO/Virgo events released to date, which indicate that
current data are not informative enough.",2304.13063v2
2023-05-15,Magnetic bubble crystal in tetragonal magnets,"A magnetic bubble crystal is a two-dimensional soliton lattice consisting of
multiple spin density waves similar to a magnetic skyrmion crystal.
Nevertheless, the emergence of the bubble crystal with a collinear spin texture
is rare compared to that of the skyrmion crystal with a noncoplanar spin
texture. Here we theoretically report the stabilization mechanisms of the
bubble crystal in tetragonal magnets. By performing numerical calculations
based on an efficient steepest descent method for an effective spin model with
magnetic anisotropy and multiple spin interactions in momentum space on a
two-dimensional square lattice, we construct magnetic field-temperature phase
diagrams for various sets of model parameters. We find that the bubble crystal
is stabilized at finite temperatures near the skyrmion crystal by an easy-axis
anisotropic two-spin interaction. Through a detailed analysis, we also show
that the high-harmonic wave-vector interaction and the biquadratic interaction
play important roles in the stability of the bubble crystal. Our results
indicate a close relationship between the bubble crystal and the skyrmion
crystal in terms of the stabilization mechanisms, which suggests the
possibility of the bubble crystal in the skyrmion-hosting materials by
controlling the easy-axis magnetic anisotropy through external and/or chemical
pressure.",2305.08333v1
2023-07-21,Ancestral Spin Information in Gravitational Waves from Black Hole Mergers,"The heaviest black holes discovered through gravitational waves have masses
that are difficult to explain with current standard stellar models. This
discrepancy may be due to a series of hierarchical mergers, where the observed
black holes are themselves the products of previous mergers. Here we present a
method to estimate the masses and spins of previous generations of black holes
based on the masses and spins of black holes in a binary. Examining the merger
GW190521, we find that assuming black hole spins that are consistent with those
of merger remnants will alter the reconstructed ancestral spins when compared
to results with uninformed priors. At the same time, the inclusion of black
hole spins does not significantly affect the mass distributions of the
ancestral black holes.",2307.11856v1
2023-09-25,The hidden spin-momentum locking and topological defects in unpolarized light fields,"Electromagnetic waves characterized by intensity, phase, and polarization
degrees of freedom are widely applied in data storage, encryption, and
communications. However, these properties can be substantially affected by
phase disorders and disturbances, whereas high-dimensional degrees of freedom
including momentum and angular momentum of electromagnetic waves can offer new
insights into their features and phenomena, for example topological
characteristics and structures that are robust to these disturbances. Here, we
discover and demonstrate theoretically and experimentally spin-momentum locking
and topological defects in unpolarized light. The coherent spin is locked to
the kinetic momentum except for a small coupling spin term, due to the
simultaneous presence of transverse magnetic and electric components in
unpolarized light. To cancel the coupling term, we employ a metal film acting
as a polarizer to form some skyrmion-like spin textures at the metal/air
interface. Using an in-house scanning optical microscopic system to image the
out-of-plane spin density of the focused unpolarized vortex light, we obtained
experimental results that coincide well with our theoretical predictions. The
theory and technique promote the applications of topological defects in optical
data storage, encryption, and decryption, and communications.",2309.13997v1
2023-10-24,Complex Poynting vector in gyromagnetic media and its impact on power flow in guided modes,"In this paper, we show the relation between the time-varying spinning nature
of the instantaneous Poynting vector and the phasor form of the complex
Poynting vector in the bulk of the gyromagnetic medium. We show the presence of
a transverse reactive power component in the bulk of the gyrotropic medium,
even for plane wave propagation. We use a simple quantification technique of
Poynting vector spin to analyze the rotation of the instantaneous Poynting
vector using the complex phasor form of the time-averaged Poynting vector. For
a transverse electric mode, we show the similarity between the Poynting vector
spin and the photonic spin of the magnetic field. The Poynting vector spin is
then used to represent the transverse power transfer across a ferrite-air
interface supporting TE surface wave modes. Considering a gyromagnetic
ferrite-filled rectangular waveguide following the TE mode profile, we show the
correspondence between the Poynting vector spin and the overall positive and
backward power flow. We analytically propose a mechanism to engineer the region
of the waveguide supporting backward and forward power propagation.",2310.15867v1
2023-10-25,Spin-eccentricity interplay in merging binary black holes,"Orbital eccentricity and spin precession are precious observables to infer
the formation history of binary black holes with gravitational-wave data. We
present a post-Newtonian, multi-timescale analysis of the binary dynamics able
to capture both precession and eccentricity over long inspirals. We show that
the evolution of an eccentric binary can be reduced that of effective source on
quasi-circular orbits, coupled to a post-Newtonian prescription for the secular
evolution of the eccentricity. Our findings unveil an interplay between
precession and eccentricity: the spins of eccentric binaries precess on shorter
timescales and their nutation amplitude is altered compared to black holes on
quasi-circular orbits, consequently affecting the so-called spin morphology.
Even if binaries circularize by the time they enter the sensitivity window of
our detectors, their spin orientations retain some memory of the past evolution
on eccentric orbits, thus providing a new link between gravitational-wave
detection and astrophysical formation. At the same time, we point out that
residual eccentricity should be considered a source of systematics when
reconstructing the past history of black-hole binaries using the spin
orientations.",2310.16893v2
2024-02-05,Orientation-dependent Josephson effect in spin-singlet superconductor/altermagnet/spin-triplet superconductor junctions,"We study the Josephson effect in the spin-singlet
superconductor/altermagnet/spin-triplet superconductor junctions using the
Green's function method. The current-phase difference relationships in the
junctions strongly depend on the orientation of altermagnet and the types of
the Cooper pairs. For the orientation angle equal to odd multiples of $\pi/4$,
the current-phase difference relationships are of the $\sin{2\phi}$ type, which
are irrespective of the pairing wave functions in superconductors. For the
other orientation angles, the emergence of the lowest order current becomes
possible and its form, $\sin\phi$ or $\cos\phi$, depends on the pairing wave
functions in superconductors. The $\phi_{0}$ phase and the $0$-$\pi$ transition
can be realized in our junctions due to the appearance of the lowest order
current. The selection rules for the lowest order current are presented. The
symmetric relations satisfied by the current-phase difference relationships are
analyzed through considering the transformations of the junctions under the
mirror reflection, the time-reversal and the spin rotation operations. Our
results not only provide a method to detect the intrinsic spin-triplet
superconductivity but also possess application values in the design of the
field-free quantum devices.",2402.02810v1
2009-04-02,Nonlinear Waves in Disordered Diatomic Granular Chains,"We investigate the propagation and scattering of highly nonlinear waves in
disordered granular chains composed of diatomic (two-mass) units of spheres
that interact via Hertzian contact. Using ideas from statistical mechanics, we
consider each diatomic unit to be a ""spin"", so that a granular chain can be
viewed as a spin chain composed of units that are each oriented in one of two
possible ways. Experiments and numerical simulations both reveal the existence
of two different mechanisms of wave propagation: In low-disorder chains, we
observe the propagation of a solitary pulse with exponentially decaying
amplitude. Beyond a critical level of disorder, the wave amplitude instead
decays as a power law, and the wave transmission becomes insensitive to the
level of disorder. We characterize the spatio-temporal structure of the wave in
both propagation regimes and propose a simple theoretical interpretation for
such a transition. Our investigation suggests that an elastic spin chain can be
used as a model system to investigate the role of heterogeneities in the
propagation of highly nonlinear waves.",0904.0426v3
2011-03-30,Prospects of observing continuous gravitational waves from known pulsars,"Several past searches for gravitational waves from a selection of known
pulsars have been performed with data from the science runs of the Laser
Inferometer Gravitational-wave Observatory (LIGO) gravitational wave detectors.
So far these have lead to no detection, but upper limits on the gravitational
wave amplitudes have been set. Here we study our intrinsic ability to detect,
and estimate the gravitational wave amplitude for non-accreting pulsars. Using
spin-down limits on emission as a guide we examine amplitudes that would be
required to observe known pulsars with future detectors (Advanced LIGO,
Advanced Virgo and the Einstein Telescope), assuming that they are triaxial
stars emitting at precisely twice the known rotation frequency. Maximum allowed
amplitudes depend on the stars' equation of state (e.g. a normal neutron star,
a quark star, a hybrid star) and the theoretical mass quadrupoles that they can
sustain. We study what range of quadrupoles, and therefore equations of state,
would be consistent with being able to detect these sources. For globular
cluster pulsars, with spin-downs masked by accelerations within the cluster, we
examine what spin-down values gravitational wave observations would be able to
set. For all pulsars we also alternatively examine what internal magnetic
fields they would need to sustain observable ellipticities.",1103.5867v2
2011-06-20,Symmetric Rotating Wave Approximation for the Generalized Single-Mode Spin-Boson System,"The single-mode spin-boson model exhibits behavior not included in the
rotating wave approximation (RWA) in the ultra and deep-strong coupling
regimes, where counter-rotating contributions become important. We introduce a
symmetric rotating wave approximation that treats rotating and counter-rotating
terms equally, preserves the invariances of the Hamiltonian with respect to its
parameters, and reproduces several qualitative features of the spin-boson
spectrum not present in the original rotating wave approximation both
off-resonance and at deep strong coupling. The symmetric rotating wave
approximation allows for the treatment of certain ultra and deep-strong
coupling regimes with similar accuracy and mathematical simplicity as does the
RWA in the weak coupling regime. Additionally, we symmetrize the generalized
form of the rotating wave approximation to obtain the same qualitative
correspondence with the addition of improved quantitative agreement with the
exact numerical results. The method is readily extended to higher accuracy if
needed. Finally, we introduce the two-photon parity operator for the two-photon
Rabi Hamiltonian and obtain its generalized symmetric rotating wave
approximation. The existence of this operator reveals a parity symmetry similar
to that in the Rabi Hamiltonian as well as another symmetry that is unique to
the two-photon case, providing insight into the mathematical structure of the
two-photon spectrum, significantly simplifying the numerics, and revealing some
interesting dynamical properties.",1106.3800v2
2014-07-28,New wave equation for ultrarelativistic particles,"Starting from first principles and general assumptions based on the
energy-momentum relation of the Special Theory of Relativity we present a novel
wave equation for ultrarelativistic matter. This wave equation arises when
particles satisfy the condition, $p>>m$, i.e, when the energy-momentum relation
can be approximated by, $E\simeq p+\frac{m^{2}}{2p}$. Interestingly enough,
such as the Dirac equation, it is found that this wave equation includes spin
in a natural way. Furthermore, the free solutions of this wave equation contain
plane waves that are completely equivalent to those of the theory of neutrino
oscillations. Therefore, the theory reproduces some standard results of the
Dirac theory in the limit $p>>m$, but offers the possibility of an explicit
Lorentz Invariance Violation of order, $\mathcal{O}((mc)^{4}/p^{2})$. As a
result, the theory could be useful to test small departures from Dirac equation
and Lorentz Invariance at very high energies. On the other hand, the wave
equation can also describe particles of spin 1 by a simple substitution of the
spin operators, $\boldsymbol{\sigma}\rightarrow\boldsymbol{\alpha}$. In
addition, it naturally admits a Lagrangian formulation and a Hamiltonian
formalism. We also discuss the associated conservation laws that arise through
the symmetry transformations of the Lagrangian.",1407.7391v4
2020-08-06,Generation and manipulation of chiral terahertz waves emitted from the three-dimensional topological insulator Bi2Te3,"Arbitrary manipulation of broadband terahertz waves with flexible
polarization shaping at the source has great potential in expanding real
applications such as imaging, information encryption, and all-optically
coherent control of terahertz nonlinear phenomena. Topological insulators
featuring unique spin-momentum locked surface state have already exhibited very
promising prospects in terahertz emission, detection and modulation, which may
lay a foundation for future on-chip topological insulator-based terahertz
systems. However, polarization shaped terahertz emission with prescribed
manners of arbitrarily manipulated temporal evolution of the amplitude and
electric-field vector direction based on topological insulators have not yet
been explored. Here we systematically investigated the terahertz radiation from
topological insulator Bi2Te3 nanofilms driven by femtosecond laser pulses, and
successfully realized the generation of efficient chiral terahertz waves with
controllable chirality, ellipticity, and principle axis. The convenient
engineering of the chiral terahertz waves was interpreted by photogalvanic
effect induced photocurrent, while the linearly polarized terahertz waves
originated from linear photogalvanic effect induced shift currents. We believe
our works not only help further understanding femtosecond coherent control of
ultrafast spin currents in light-matter interaction but also provide an
effective way to generate spin-polarized terahertz waves and accelerate the
proliferation of twisting the terahertz waves at the source.",2008.02534v1
1996-07-08,Critical dynamics in the 2d classical XY-model: a spin dynamics study,"Using spin-dynamics techniques we have performed large-scale computer
simulations of the dynamic behavior of the classical three component XY-model
(i.e. the anisotropic limit of an easy-plane Heisenberg ferromagnet), on square
lattices of size up to 192^2, for several temperatures below, at, and above
T_KT. The temporal evolution of spin configurations was determined numerically
from coupled equations of motion for individual spins by a fourth order
predictor-corrector method, with initial spin configurations generated by a
hybrid Monte Carlo algorithm. The neutron scattering function S(q,omega) was
calculated from the resultant space-time displaced spin-spin correlation
function. Pronounced spin-wave peaks were found both in the in-plane and the
out-of-plane scattering function over a wide range of temperatures. The
in-plane scattering function S^xx also has a large number of clear but weak
additional peaks, which we interpret to come from two-spin-wave scattering. In
addition, we observed a small central peak in S^xx, even at temperatures well
below the phase transition. We used dynamic finite size scaling theory to
extract the dynamic critical exponent z. We find z=1.00(4) for all T <= T_KT,
in excellent agreement with theoretical predictions, although the shape of
S(q,omega) is not well described by current theory.",9607063v1
2010-06-04,The Accreting Millisecond X-ray Pulsar IGR J00291+5934: Evidence for a Long Timescale Spin Evolution,"Accreting Millisecond X-ray Pulsars like IGR J00291+5934 are important
because it is possible to test theories of pulsar formation and evolution. They
give also the possibility to constrain gravitational wave emission theories and
the equation of state of ultra dense matter. Particularly crucial to our
understanding is the measurement of the long term spin evolution of the
accreting neutron star. An open question is whether these accreting pulsars are
spinning up during an outburst and spinning down in quiescence as predicted by
the recycling scenario. Until now it has been very difficult to measure
torques, due to the presence of fluctuations in the pulse phases that
compromise their measurements with standard coherent timing techniques. By
applying a new method, I am now able to measure a spin up during an outburst
and a spin down during quiescence. I ascribe the spin up
(Fdot=5.1(3)x10^{-13}\Hz/s) to accretion torques and the spin down
(Fdot=-3.0(8)x10^{-15} Hz/s) to magneto dipole torques, as those observed in
radio pulsars. Both values nicely fit in the recycling scenario and I infer the
existence of a magnetic field for the pulsar of B~2x10^{8} G. No evidence for
an enhanced spin down due to gravitational wave emission is found. The
accretion torques are smaller than previously reported and there is strong
evidence for an ordered process that is present in all outbursts that might be
connected with a motion of the hot spot on the neutron star surface.",1006.0815v2
2011-09-29,Dynamical spin structure factors of quantum spin nematic states,"Dynamical spin structure factors of quantum spin nematic states are
calculated in a spin-1/2 square-lattice J1-J2 model with ferromagnetic J1 and
competing antiferromagnetic J2 interactions. To this end, we use a fermion
representation, generalizing it to N flavors. We begin with a spin-triplet
pairing state of fermion fields, called Z2 planar state, which is a stable
saddle-point solution in the large-N limit in a finite parameter range where
the couplings J1 and J2 compete strongly [R. Shindou and T. Momoi, Phys. Rev. B
80, 064410 (2009)]. Using a large-N expansion, we take into account
fluctuations around this saddle point up to corrections of order 1/N. The
dynamical spin structure factors thus obtained signify the existence of gapless
q-linear director-wave (spin-wave) modes at q=(0,0) and gapped `gauge-field'
like collective modes at q=(pi,pi), whose spectral weight vanishes as a linear
and quadratic function of the momentum respectively. The low-energy collective
modes contain fluctuations of nematic-director, spin, and gauge degrees of
freedom. Associated with the gapless q-linear modes, we evaluate the
temperature dependence of the nuclear spin relaxation rate 1/T1 in the
low-temperature regime as 1/T1 \propto T^{2d-1}, where d is the effective
spatial dimension.",1109.6464v3
2013-04-12,"Space group symmetry, spin-orbit coupling and the low energy effective Hamiltonian for iron based superconductors","We construct the symmetry adapted low energy effective Hamiltonian for the
electronic states in the vicinity of the Fermi level in iron based
superconductors. We use Luttinger's method of invariants, expanding about Gamma
and M points in the Brillouin zone corresponding to two iron unit cell, and
then matching the coefficients of the expansion to the 5- and 8-band models. We
then use the method of invariants to study the effects of the spin-density wave
order parameters on the electronic spectrum, with and without spin-orbit
coupling included. Among the results of this analysis is the finding that the
nodal spin-density wave is unstable once spin-orbit coupling is included.
Similar analysis is performed for the A_{1g} spin singlet superconducting
state. Without spin-orbit coupling there is one pairing invariant near the
Gamma point, but two near the M point. This leads to an isotropic spectral gap
at the hole Fermi surface near Gamma, but anisotropic near M. The relative
values of these three parameters determine whether the superconducting state is
s_{++}, s_{+-}, or nodal. Inclusion of spin-orbit coupling leads to additional
mixing of spin triplet pairing, with one additional pairing parameter near
Gamma and one near M. This leads to an anisotropic spectral gap near both hole
and electron Fermi surfaces, the latter no longer cross, but rather split.",1304.3723v1
2013-07-25,Next-to-leading tail-induced spin-orbit effects in the gravitational radiation flux of compact binaries,"The imprint of non-linearities in the propagation of gravitational waves ---
the tail effect --- is responsible for new spin contributions to the energy
flux and orbital phasing of spinning black hole binaries. The spin-orbit
(linear in spin) contribution to this effect is currently known at leading
post-Newtonian order, namely 3PN for maximally spinning black holes on
quasi-circular orbits. In the present work, we generalize these tail-originated
spin-orbit terms to the next-to-leading 4PN order. This requires in particular
extending previous results on the dynamical evolution of precessing compact
binaries. We show that the tails represent the only spin-orbit terms at that
order for quasi-circular orbits, and we find perfect agreement with the known
result for a test particle around a Kerr black hole, computed by perturbation
theory. The BH-horizon absorption terms have to be added to the PN result
computed here. Our work completes the knowledge of the spin-orbit effects to
the phasing of compact binaries up to the 4PN order, and will allow the
building of more faithful PN templates for the inspiral phase of black hole
binaries, improving the capabilities of ground-based and space-based
gravitational wave detectors.",1307.6793v2
2014-01-27,Helical order in one-dimensional magnetic atom chains and possible emergence of Majorana bound states,"We theoretically obtain the phase diagram of localized magnetic impurity
spins arranged in a one-dimensional chain on top of a one- or two-dimensional
electron gas with Rashba spin-orbit coupling. The interactions between the
spins are mediated by the Ruderman-Kittel-Kasuya-Yosida (RKKY) mechanism
through the electron gas. Recent work predicts that such a system may
intrinsically support topological superconductivity when a helical spin-density
wave is formed in the spins, and superconductivity is induced in the electron
gas. We analyze, using both analytical and numerical techniques, the conditions
under which such a helical spin state is stable in a realistic situation in the
presence of disorder. We show that it becomes unstable towards the formation of
(anti) ferromagnetic domains if the disorder in the impurity spin positions
$\delta R$ becomes comparable with the Fermi wave length. We also examine the
stability of the helical state against Gaussian potential disorder in the
electronic system using a diagrammatic approach. Our results suggest that in
order to stabilize the helical spin state, and thus the emergent topological
superconductivity, a sufficiently strong Rashba spin-orbit coupling, giving
rise to Dzyaloshinskii-Moriya interactions, is required.",1401.7048v2
2016-05-20,Two-dimensional terahertz magnetic resonance spectroscopy of collective spin waves,"Nonlinear manipulation of nuclear and electron spins is the basis for all
advanced methods in magnetic resonance including multidimensional nuclear
magnetic and electron spin resonance spectroscopies, magnetic resonance
imaging, and in recent years, quantum control over individual spins. The
methodology is facilitated by the ease with which the regime of strong coupling
can be reached between radiofrequency or microwave magnetic fields and nuclear
or electron spins respectively, typified by sequences of magnetic pulses that
control the magnetic moment directions. The capabilities meet a bottleneck,
however, for far-infrared magnetic resonances characteristic of correlated
electron materials, molecular magnets, and proteins that contain high-spin
transition metal ions. Here we report the development of two-dimensional
terahertz magnetic resonance spectroscopy and its use for direct observation of
the nonlinear responses of collective spin waves (magnons). The spectra show
magnon spin echoes and 2-quantum signals that reveal pairwise correlations
between magnons at the Brillouin zone center. They also show resonance-enhanced
second-harmonic and difference-frequency signals. Our methods are readily
generalizable to multidimensional magnetic resonance spectroscopy and nonlinear
coherent control of terahertz-frequency spin systems in molecular complexes,
biomolecules, and materials.",1605.06476v3
2018-10-16,Spin-torque oscillation in a magnetic insulator probed by a single-spin sensor,"Coherent, self-sustained oscillation of magnetization in spin-torque
oscillators (STOs) is a promising source for on-chip, nanoscale generation of
microwave magnetic fields. Such fields could be used for local excitation of
spin-wave resonances, control of spin qubits, and studies of paramagnetic
resonance. However, local characterization of fields emitted by an STO has
remained an outstanding challenge. Here, we use the spin of a single
nitrogen-vacancy (NV) defect in diamond to probe the magnetic fields generated
by an STO in a microbar of ferromagnetic insulator yttrium-iron-garnet (YIG).
The combined spectral resolution and sensitivity of the NV sensor allows us to
resolve multiple spin-wave modes and characterize their damping. When damping
is decreased sufficiently via spin injection, the modes auto-oscillate, as
indicated by a strongly reduced linewidth, a diverging magnetic power spectral
density, and synchronization of the STO frequency to an external microwave
source. These results open the way for quantitative, nanoscale mapping of the
microwave signals generated by STOs, as well as harnessing STOs as local probes
of mesoscopic spin systems.",1810.07306v1
2016-12-21,"Spin Pumping, Dissipation, and Direct and Alternating Inverse Spin Hall Effects in Magnetic Insulator-Normal Metal Bilayers","We theoretically consider the spin-wave mode- and wavelength-dependent
enhancement of the Gilbert damping in magnetic insulator--normal metal bilayers
due to spin pumping as well as the enhancement's relation to direct and
alternating inverse spin Hall voltages in the normal metal. In the
long-wavelength limit, including long-range dipole interactions, the ratio of
the enhancement for transverse volume modes to that of the macrospin mode is
equal to two. With an out-of-plane magnetization, this ratio decreases with
both an increasing surface anisotropic energy and mode number. If the surface
anisotropy induces a surface state, the enhancement can be an order of
magnitude larger than for to the macrospin. With an in-plane magnetization, the
induced dissipation enhancement can be understood by mapping the anisotropy
parameter to the out-of-plane case with anisotropy. For shorter wavelengths, we
compute the enhancement numerically and find good agreement with the analytical
results in the applicable limits. We also compute the induced direct- and
alternating-current inverse spin Hall voltages and relate these to the magnetic
energy stored in the ferromagnet. Because the magnitude of the direct spin Hall
voltage is a measure of spin dissipation, it is directly proportional to the
enhancement of Gilbert damping. The alternating spin Hall voltage exhibits a
similar in-plane wave-number dependence, and we demonstrate that it is greatest
for surface-localized modes.",1612.07020v2
2019-01-07,Spin dynamics of edge-sharing spin chains in SrCa13Cu24O41,"The low-energy magnetic excitation from the highly Ca-doped
quasi-one-dimensional magnet SrCa13Cu24O41 was studied in the magnetic ordered
state by using inelastic neutron scattering. We observed the gapless spin-wave
excitation, dispersive along the a and c axes but nondispersive along the b
axis. Such excitations are attributed to the spin wave from the spin-chain
sublattice. Model fitting to the experimental data gives the nearest-neighbour
interaction Jc as 5.4 meV and the interchain interaction Ja = 4.4 meV. Jc is
antiferromagnetic and its value is close to the nearest-neighbour interactions
of the similar edge-sharing spin-chain systems such as CuGeO3. Comparing with
the hole-doped spin chains in Sr14Cu24O41, which shows a spin gap due to spin
dimers formed around Zhang-Rice singlets, the chains in SrCa13Cu24O41 show a
gapless excitation in this study. We ascribe such a change from gapped to
gapless excitations to holes transferring away from the chain sublattice into
the ladder sublattice upon Ca doping.",1901.02102v1
2020-02-05,Spin Resonances in Iron-Selenide High-Tc Superconductors by Proximity to Hidden Spin Density Wave,"Recent inelastic neutron scattering studies by Pan et al., Nature
Communications 8, 123 (2017), find evidence for spin excitations at energies
above the quasi-particle gap in an iron-selenide high-Tc superconductor. The
momenta of the spin excitations form a diamond around the checkerboard
wavevector, Q_AF, that is associated with the square lattice of iron atoms that
makes up the system. It has been suggested that such a ""hollowed-out""
spin-excitation spectrum is due to hidden Neel order. We study such a hidden
spin-density wave (hSDW) state that results from nested Fermi surfaces at the
center and at the corner of the unfolded Brillouin zone. It emerges within mean
field theory from an extended Hubbard model over a square lattice of iron atoms
that contain the minimal d_xz and d_yz orbitals. Opposing Neel order exists
over the isotropic d+ = d_xz + i d_yz and d- = d_xz - i d_yz orbitals. The
dynamical spin susceptibility of the hSDW is computed within the random phase
approximation, at perfect nesting. Unobservable Goldstone modes that disperse
acoustically are found at Q_AF. A threshold is found in the spectrum of
observable spin excitations that forms a ""floating ring"" at Q_AF also. The ring
threshold moves down in energy toward zero with increasing Hund's Rule
coupling, while it moves up in energy with increasing magnetic frustration.
Comparison with the normal-state features of the spin-excitation spectrum shown
by electron-doped iron selenide is made. Also, recent predictions of a Lifshitz
transition from the nested Fermi surfaces to Fermi surface pockets at the
corner of the folded Brillouin zone will be discussed.",2002.01732v2
2021-07-20,Measuring binary black hole orbital-plane spin orientations,"Binary black hole spins are among the key observables for gravitational wave
astronomy. Among the spin parameters, their orientations within the orbital
plane, $\phi_1$, $\phi_2$ and $\Delta \phi=\phi_1-\phi_2$, are critical for
understanding the prevalence of the spin-orbit resonances and merger recoils in
binary black holes. Unfortunately, these angles are particularly hard to
measure using current detectors, LIGO and Virgo. Because the spin directions
are not constant for precessing binaries, the traditional approach is to
measure the spin components at some reference stage in the waveform evolution,
typically the point at which the frequency of the detected signal reaches 20
Hz. However, we find that this is a poor choice for the orbital-plane spin
angle measurements. Instead, we propose measuring the spins at a fixed
dimensionless time or frequency near the merger. This leads to significantly
improved measurements for $\phi_1$ and $\phi_2$ for several gravitational wave
events. Furthermore, using numerical relativity injections, we demonstrate that
$\Delta \phi$ will also be better measured near the merger for louder signals
expected in the future. Finally, we show that numerical relativity surrogate
models are key for reliably measuring the orbital-plane spin orientations, even
at moderate signal-to-noise ratios like $\sim 30-45$.",2107.09692v4
2022-03-31,Constraining black-hole binary spin precession and nutation with sequential prior conditioning,"We investigate the detectability of sub-dominant spin effects in merging
black-hole binaries using current gravitational-wave data. Using a
phenomenological model that separates the spin dynamics into precession
(azimuthal motion) and nutation (polar motion), we present constraints on the
resulting amplitudes and frequencies. We also explore current constraints on
the spin morphologies, indicating if binaries are trapped near spin-orbit
resonances. We dissect such weak effects from the signals using a sequential
prior conditioning approach, where parameters are progressively re-sampled from
their posterior distribution. This allows us to investigate whether the data
contain additional information beyond what is already provided by quantities
that are better measured, namely the masses and the effective spin. For the
current catalog of events, we find no significant measurements of weak spin
effects such as nutation and spin-orbit locking. We synthesize a source with a
high nutational amplitude and show that near-future detections will allow us to
place powerful constraints, hinting that we may be at the cusp of detecting
spin nutations in gravitational-wave data.",2204.00026v3
2022-05-24,Which black hole formed first? Mass-ratio reversal in massive binary stars from gravitational-wave data,"Population inference of gravitational-wave catalogues is a useful tool to
translate observations of black-hole mergers into constraints on compact-binary
formation. Different formation channels predict identifiable signatures in the
astrophysical distributions of source parameters, such as masses and spins. One
example within the scenario of isolated binary evolution is mass-ratio
reversal: even assuming efficient core-envelope coupling in massive stars and
tidal spin-up of the stellar companion by the first-born black hole, a compact
binary with a lighter, non-spinning first-born black hole and a heavier,
spinning second-born black hole can still form through mass transfer from the
initially more to less massive progenitor. Using current LIGO/Virgo
observations, we measure the fraction of sources in the underlying population
with this mass-spin combination and interpret it as a constraint on the
occurrence of mass-ratio reversal in massive binary stars. We modify commonly
used population models by including negligible-spin subpopulations and, most
crucially, non-identical component spin distributions. We do not find evidence
for subpopulations of black holes with negligible spins and measure the
fraction of massive binary stars undergoing mass-ratio reversal to be
consistent with zero and $<32\%$ ($99\%$ confidence). The dimensionless spin
peaks around $0.2\unicode{x2013}0.3$ appear robust, however, and are yet to be
explained by progenitor formation scenarios.",2205.12329v2
2022-11-10,Static and dynamic magnetic properties of the spin-5/2 triangle lattice antiferromagnet Na3Fe(PO4)2 studied by 31P NMR,"$^{31}$P nuclear magnetic resonance (NMR) measurements have been carried out
to investigate the magnetic properties and spin dynamics of Fe$^{3+}$ ($S$ =
5/2) spins in the two-dimensional triangular lattice (TL) compound
Na$_3$Fe(PO$_4$)$_2$. The temperature ($T$) dependence of nuclear spin-lattice
relaxation rates ($1/T_1$) shows a clear peak around N\'eel temperature,
$T_{\rm N} = 10.9$~K, corresponding to an antiferromagnetic (AFM) transition.
From the temparature dependence of NMR shift ($K$) above $T_{\rm N}$, an
exchange coupling between Fe$^{3+}$ spins was estimated to be $J/k_{\rm
B}\simeq 1.9$~K using the spin-5/2 Heisenberg isotropic-TL model. The
temperature dependence of $1/T_1T$ divided by the magnetic susceptibility
($\chi$), $1/T_1T\chi$, above $T_{\rm N}$ proves the AFM nature of spin
fluctuations below $\sim$ 50 K in the paramagnetic state. In the magnetically
ordered state below $T_{\rm N}$, the characteristic rectangular shape of the
NMR spectra is observed, indicative of a commensurate AFM state in its ground
state. The strong temperature dependence of 1/$T_1$ in the AFM state is well
explained by the two-magnon (Raman) process of the spin waves in a 3D
antiferromagnet with a spin-anisotropy energy gap of 5.7 K. The temperature
dependence of sublattice magnetization is also well reproduced by the spin
waves. Those results indicate that the magnetically ordered state of
Na$_3$Fe(PO$_4$)$_2$ is a conventional 3D AFM state, and no obvious spin
frustration effects were detected in its ground state.",2211.05921v1
2024-03-15,Spontaneous spin chirality reversal and competing phases in the topological magnet EuAl$_4$,"We demonstrate the spontaneous reversal of spin chirality in a single crystal
sample of the intermetallic magnet EuAl$_4$. We solve the nanoscopic nature of
each of the four magnetically phases of EuAl$_4$ using resonant magnetic x-ray
scattering, and demonstrate all four phases order with single-k incommensurate
magnetic modulation vectors. Below 15.4 K the system forms a spin density
modulated spin structure where the spins are orientated in the ab plane
perpendicular to the orientation of the magnetic propagation vector. Below 13.2
K a second spin density wave orders with moments aligned parallel to the
c-axis, such that the two spin density wave orders coexist. Below 12.2 K a
magnetic helix of a single chirality is stabilised across the entire sample.
Below 10 K the chirality of the magnetic helix reverses, and the sample remains
a single chiral domain. Concomitant with the establishment of the helical
magnetic ordering is the lowering of the crystal symmetry to monoclinic, as
evidenced the formation of uniaxial charge and spin strip domains. A group
theoretical analysis demonstrates that below 12.2 K the symmetry lowers to
polar monoclinic, which is necessary to explain the observed asymmetry in the
chiral states of the magnetic helix and the spin chiral reversal. We find that
in every magnetically ordered phase of EuAl4 the in-plane moment is
perpendicular to the orientation of the magnetic propagation vector, which we
demonstrate is favoured by magnetic dipolar interactions.",2403.10159v1
2021-09-03,Building better spin models for merging binary black holes: Evidence for non-spinning and rapidly spinning nearly aligned sub-populations,"Recent work paints a conflicting portrait of the distribution of black hole
spins in merging binaries measured with gravitational waves. Some analyses find
that a significant fraction of merging binaries contain at least one black hole
with a spin tilt $>90^\circ$ with respect to the orbital angular momentum
vector, which has been interpreted as a signature for dynamical assembly. Other
analyses find the data are consistent with a bimodal population in which some
binaries contain black holes with negligible spin while the rest contain black
holes with spin vectors preferentially aligned with the orbital angular
momentum vector. In this work, we scrutinize models for the distribution of
black hole spins to pinpoint possible failure modes in which the model yields a
faulty conclusion. We reanalyze data from the second LIGO--Virgo
gravitational-wave transient catalog (GWTC-2) using a revised spin model, which
allows for a sub-population of black holes with negligible spins. In agreement
with recent results by Roulet et al., we show that the GWTC-2 detections are
consistent with two distinct sub-populations. We estimate that $29-75\%$ (90\%
credible interval) of merging binaries contain black holes with negligible spin
$\chi \approx 0$. The remaining binaries are part of a second sub-population in
which the spin vectors are preferentially (but not exactly) aligned to the
orbital angular momentum. The black holes in this second sub-population are
characterized by spins of $\chi\sim0.45$. We suggest that the inferred spin
distribution is consistent with the hypothesis that all merging binaries form
via the field formation scenario.",2109.02424v3
2022-12-10,Collective dynamics of polarized spin-half fermions in relativistic heavy-ion collisions,"Relativistic hydrodynamics has been quite successful in describing the
properties of strongly-interacting matter produced in heavy-ion collision
experiments. Recently, there has been a significant advancement in this field
to explain the spin polarization of hadrons emitted in these processes.
Although current models have successfully explained some of the experimental
data based on spin-vorticity coupling, they still lack a clear understanding of
differential measurements. This is an indication that the spin needs to be
treated as an independent degree of freedom whose dynamics is not entirely
bound to flow circulation. In particular, if the spin is a macroscopic property
of the system, in equilibrium its dynamics should follow hydrodynamic laws. In
this thesis, we develop a framework of relativistic perfect-fluid hydrodynamics
which includes spin degrees of freedom from kinetic theory, and use it for
modeling the dynamics of matter produced in relativistic heavy-ion collisions.
Following experimental observations, we assume that the polarization effects
are small and derive conservation laws for net-baryon current, energy-momentum
tensor, and spin tensor based on the de Groot-van Leeuwen-van Weert
pseudogauge. Subsequently, we present various properties of the spin
polarization tensor and its components, analyze the propagation properties of
the spin polarization components, and derive the spin-wave velocity for
arbitrary statistics. We find that only the transverse spin components
propagate, analogously to the EM waves. Finally, we study the spacetime
evolution of spin polarization for the systems respecting certain spacetime
symmetries and calculate the mean spin polarization per particle, which can be
compared to the experimental data. We find that, for some observables, our spin
polarization results agree qualitatively with the experimental findings and
other model calculations.",2212.06569v2
2023-04-07,A model of wave function collapse in a quantum measurement of spin as the Schroedinger equation solution of a system with a simple harmonic oscillator in a bath,"We present a set of exact system solutions to a model we developed to study
wave function collapse in the quantum spin measurement process. Specifically,
we calculated the wave function evolution for a simple harmonic oscillator of
spin \frac{1}{2}, with its magnetic moment in interaction with a magnetic
field, coupled to an environment that is a bath of harmonic oscillators. The
system's time evolution is described by the direct product of two independent
Hilbert spaces: one that is defined by an effective Hamiltonian, which
represents a damped simple harmonic oscillator with its potential well divided
into two, based on the spin and the other that represents the effect of the
bath, i.e., the Brownian motion. The initial states of this set of wave
functions form an orthonormal basis, defined as the eigenstates of the system.
If the system is initially in one of these states, the final result is
predetermined, i.e., the measurement is deterministic. If the bath is initially
in the ground state,and the wave function is initially a wave packet at the
origin, it collapses into one of the two potential wells depending on the
initial spin. If the initial spin is a vector in the Bloch sphere not parallel
to the magnetic field, the final distribution among the two potential wells is
given by the Born rule applied to the initial spin state with the well-known
ground state width. Hence, the result is also predetermined. We discuss its
implications to the Bell theorem[1]. We end with a summary of the implications
for the understanding of the statistical interpretation of quantum mechanics.",2304.03865v2
2024-03-11,Simulating Meson Scattering on Spin Quantum Simulators,"Studying high-energy collisions of composite particles, such as hadrons and
nuclei, is an outstanding goal for quantum simulators. However, preparation of
hadronic wave packets has posed a significant challenge, due to the complexity
of hadrons and the precise structure of wave packets. This has limited
demonstrations of hadron scattering on quantum simulators to date. Observations
of confinement and composite excitations in quantum spin systems have opened up
the possibility to explore scattering dynamics in spin models. In this article,
we develop two methods to create entangled spin states corresponding to wave
packets of composite particles in analog quantum simulators of Ising spin
Hamiltonians. One wave-packet preparation method uses the blockade effect
enabled by beyond-nearest-neighbor Ising spin interactions. The other method
utilizes a quantum-bus-mediated exchange, such as the native spin-phonon
coupling in trapped-ion arrays. With a focus on trapped-ion simulators, we
numerically benchmark both methods and show that high-fidelity wave packets can
be achieved in near-term experiments. We numerically study scattering of wave
packets for experimentally realizable parameters in the Ising model and find
inelastic-scattering regimes, corresponding to particle production in the
scattering event, with prominent and distinct experimental signals. Our
proposal, therefore, demonstrates the potential of observing inelastic
scattering in near-term quantum simulators.",2403.07061v2
2001-10-26,The spin evolution of nascent neutron stars,"The loss of angular momentum due to unstable r-modes in hot young neutron
stars has been proposed as a mechanism for achieving the spin rates inferred
for young pulsars. One factor that could have a significant effect on the
action of the r-mode instability is fallback of supernova remnant material. The
associated accretion torque could potentially counteract any gravitational-wave
induced spin-down, and accretion heating could affect the viscous damping rates
and hence the instability. We discuss the effects of various external agents on
the r-mode instability scenario within a simple model of supernova fallback on
to a hot young magnetized neutron star. We find that the outcome depends
strongly on the strength of the star's magnetic field. Our model is capable of
generating spin rates for young neutron stars that accord well with initial
spin rates inferred from pulsar observations. The combined action of r-mode
instability and fallback appears to cause the spin rates of neutron stars born
with very different spin rates to converge, on a timescale of about a year. The
results suggest that stars with magnetic fields $\le10^{13}$ G could emit a
detectable gravitational wave signal for perhaps several years after the
supernova event. Stars with higher fields (magnetars) are unlikely to emit a
detectable gravitational wave signal via the r-mode instability. The model also
suggests that the r-mode instability could be extremely effective in preventing
young neutron stars from going dynamically unstable to the bar-mode.",0110573v2
2004-10-25,Spin Dynamics of Half-Doped La3/2Sr1/2NiO4,"We report polarized- and unpolarized- neutron inelastic scattering
measurements of the magnetic excitation spectrum in the spin-charge ordered
phase of La3/2Sr1/2NiO4. Up to energies of ~30 meV we observe broad magnetic
modes characteristic of a near checkerboard ordering. A linear spin-wave model
for an ideal checkerboard ordering with a single antiferromagnetic exchange
interaction J' = 5.8 +/- 0.5 meV between next-nearest-neighbour spins on Ni2+
sites, together with a small XY-like single-ion anisotropy, provides a
reasonable description of the measured dispersion. Above 30 meV the excitations
are not fully consistent with the linear spin-wave model, with modes near the
two-dimensional reciprocal space wavevector (0.5,0.5) having an anomalously
large intensity. Furthermore, two additional dispersive modes not predicted by
spin wave theory were observed, both of which are probably magnetic. One
disperses away from (0.5,0.5) in the energy range between 50-56 meV, and the
other appears around (h,k) type positions (h,k = integer) in the energy range
31-39 meV. We propose a model in which these anomalous features are explained
by the existence of discommensurations in the checkerboard ordering. At low
energies there is additional diffuse scattering centred on the magnetic
ordering wavevector. We associate this diffuse scattering with dynamic
antiferromagnetic correlations between spins attached to the doped holes.",0410636v1
2005-07-29,Frustrated two-level impurities in two-dimensional antiferromagnets,"Dynamical properties of the impurity spin-$\frac12$ in 2D and quasi-2D
Heisenberg antiferromagnets (AFs) at $T\ge0$ are discussed. The specific case
of an impurity coupled symmetrically to two neighboring host spins is
considered. The specific feature of this problem is that the defect is
degenerate (frustrated) being located in zero molecular field. It is shown that
this problem can be described by spin-boson model without tunneling term and
with a more complex interaction. We demonstrate that the effect of the host
system on the defect is completely described by the spectral function. It is
found within the spin-wave approximation that for not too small $\omega$ the
spectral function is proportional to $\omega^2/J^3$, where $J$ is the exchange
constant between the host spins. The defect dynamical susceptibility is derived
using Abrikosov's pseudofermion technique and diagrammatic expansion. The
calculations are performed within the fourth order of the dimensionless
coupling parameter $f$. It is found that transverse impurity susceptibility
$\chi_\perp(\omega)$ has a Lorenz peak with the width proportional to
$f^4J(T/J)^3$ which disappears at T=0, and a non-resonant term. The later term
diverges logarithmically as $\omega,T \to 0$. The static susceptibility
$\chi(0)$ has the free-spin-like contribution $1/(4T)$, and a logarithmic
correction proportional to $f^2\ln(J/T)$. The influence of finite concentration
of the defects $n$ on the low-temperature properties of AF is also
investigated. A logarithmic correction to spin-wave velocity of the form
$nf^4\ln|J/\omega|$ and an anomalous damping of spin waves proportional to
$nf^4|\omega|$ are obtained.",0507704v2
2000-08-07,Distorted wave impulse approximation analysis for spin observables in nucleon quasi-elastic scattering and enhancement of the spin-longitudinal response,"We present a formalism of distorted wave impulse approximation (DWIA) for
analyzing spin observables in nucleon inelastic and charge exchange reactions
leading to the continuum. It utilizes response functions calculated by the
continuum random phase approximation (RPA), which include the effective mass,
the spreading widths and the \Delta degrees of freedom. The Fermi motion is
treated by the optimal factorization, and the non-locality of the
nucleon-nucleon t-matrix by an averaged reaction plane approximation. By using
the formalism we calculated the spin-longitudinal and the spin-transverse cross
sections, ID_q and ID_p, of 12C, 40Ca (\vec{p},\vec{n}) at 494 and 346 MeV. The
calculation reasonably reproduced the observed ID_q, which is consistent with
the predicted enhancement of the spin-longitudinal response function R_L.
However, the observed ID_p is much larger than the calculated one, which was
consistent with neither the predicted quenching nor the spin-transverse
response function R_T obtained by the (e,e') scattering. The Landau-Migdal
parameter g'_N\Delta for the N\Delta transition interaction and the effective
mass at the nuclear center m^*(r=0) are treated as adjustable parameters. The
present analysis indicates that the smaller g'_{N\Delta}(\approx 0.3) and
m^*(0) \approx 0.7 m are preferable. We also investigate the validity of the
plane wave impulse approximation (PWIA) with the effective nucleon number
approximation for the absorption, by means of which R_L and R_T have
conventionally been extracted.",0008012v2
2010-09-07,Hidden itinerant-spin phase in heavily-overdoped La2-xSrxCuO4 revealed by dilute Fe doping: A combined neutron scattering and angle-resolved photoemission study,"We demonstrated experimentally a direct way to probe a hidden propensity to
the formation of spin density wave (SDW) in a non-magnetic metal with strong
Fermi surface nesting. Substituting Fe for a tiny amount of Cu (1%) induced an
incommensurate magnetic order below 20 K in heavily-overdoped La2-xSrxCuO4
(LSCO). Elastic neutron scattering suggested that this order cannot be ascribed
to the localized spins on Cu or doped Fe. Angle-resolved photoemission
spectroscopy (ARPES), combined with numerical calculations, revealed a strong
Fermi surface nesting inherent in the pristine LSCO that likely drives this
order. The heavily-overdoped Fe-doped LSCO thus represents the first plausible
example of the long-sought ""itinerant-spin extreme"" of cuprates, where the
spins of itinerant doped holes define the magnetic ordering ground state. This
finding complements the current picture of cuprate spin physics that highlights
the predominant role of localized spins at lower dopings. The demonstrated set
of methods could potentially apply to studying hidden density-wave
instabilities of other ""nested"" materials on the verge of density wave
ordering.",1009.1417v3
2011-04-07,The magnetic phase diagram of an extended J1-J2 model on a modulated square lattice and its implications for the antiferromagnetic phase of KyFexSe2,"Motivated by the experimentally observed $\sqrt{5} \times \sqrt{5}$ iron
vacancy order and a block spin antiferromagnetic phase with large magnetic
moment in $\mathrm{K}_{0.8}\mathrm{Fe}_{1.6}\mathrm{Se}_2$, we study the
magnetic phase diagram of an extended $J_1-J_2$ model on a 1/5-depleted square
lattice with $\sqrt{5} \times \sqrt{5}$ vacancy order, using a classical Monte
Carlo analysis. The magnetic phase diagram involves various
antiferromagnetically ordered phases, and most of them have higher order
commensuration. We find that the experimentally relevant block-spin state
occupies a significant portion of the phase diagram, and we discuss the spin
dynamics of this phase using a linear spin-wave analysis. Based on our spin
wave calculations in different parameter regimes corresponding to the block
spin antiferromagnetic phase, we show how spin-wave degeneracy along the high
symmetry directions of the magnetic Brillouin zone can provide information
regarding the underlying exchange couplings. We have also analyzed the magnetic
phase diagram of a $J_1-J_2$ model on two different modulated square lattices
relevant for $\mathrm{K}_y\mathrm{Fe}_{1.5}\mathrm{Se}_2$, which respectively
exhibit 1/4-depleted $2\times2$ and $4\times2$ vacancy ordering.",1104.1445v2
2012-03-17,Accurate ab initio spin densities,"We present an approach for the calculation of spin density distributions for
molecules that require very large active spaces for a qualitatively correct
description of their electronic structure. Our approach is based on the
density-matrix renormalization group (DMRG) algorithm to calculate the spin
density matrix elements as basic quantity for the spatially resolved spin
density distribution. The spin density matrix elements are directly determined
from the second-quantized elementary operators optimized by the DMRG algorithm.
As an analytic convergence criterion for the spin density distribution, we
employ our recently developed sampling-reconstruction scheme [J. Chem. Phys.
2011, 134, 224101] to build an accurate complete-active-space
configuration-interaction (CASCI) wave function from the optimized matrix
product states. The spin density matrix elements can then also be determined as
an expectation value employing the reconstructed wave function expansion.
Furthermore, the explicit reconstruction of a CASCI-type wave function provides
insights into chemically interesting features of the molecule under study such
as the distribution of $\alpha$- and $\beta$-electrons in terms of Slater
determinants, CI coefficients, and natural orbitals. The methodology is applied
to an iron nitrosyl complex which we have identified as a challenging system
for standard approaches [J. Chem. Theory Comput. 2011, 7, 2740].",1203.3888v2
2013-09-24,Many-body corrections to ESR energy and spin-wave excitations in two-dimensional systems with Bychkov-Rashba spin splitting,"We report effects of electron-electron (\emph{e-e}) interaction on electron
spin resonance (ESR) in perpendicular magnetic field in two-dimensional (2D)
systems with Bychkov-Rashba spin splitting induced by spin-orbit interaction
(SOI) and structural inversion asymmetry (SIA). Using the Hartree-Fock
approximation, we demonstrate that the SIA results in non-zero many-body
corrections to the ESR energy and the energy of spin wave excitations. We
discover that the \emph{e-e} interaction in 2D systems with SIA not only can
enhance the ESR energy but can also lead to the ESR energy reduction. The
magnitude of this effect exhibits remarkable features in a wide range of
parameters relevant to experiment: it is found to be rather sensitive to the
sign of g-factor and the filling factor of Landau levels $\nu$. We derive
analytical expressions for many-body corrections to ESR energy and the
dispersion of spin wave excitations for the case of $\nu\leq 2$. We have found
out that \emph{e-e} interaction does not affect the ESR energy in the case of
filling of the lowest Landau level ($\nu\leq 1$) in 2D systems with positive
g-factors even at arbitrarily large values of Bychkov-Rashba constant. The
many-body renormalization of ESR energy in the case of fractional Quantum Hall
effect is also discussed.",1309.6098v1
2013-10-21,Improving the sensitivity of a search for coalescing binary black holes with non-precessing spins in gravitational wave data,"We demonstrate the implementation of a sensitive search pipeline for
gravitational waves from coalescing binary black holes whose components have
spins aligned with the orbital angular momentum. We study the pipeline recovery
of simulated gravitational wave signals from aligned-spin binary black holes
added to real detector noise, comparing the pipeline performance with
aligned-spin filter templates to the same pipeline with non-spinning filter
templates. Our results exploit a three-parameter phenomenological waveform
family that models the full inspiral-merger-ringdown coalescence and treats the
effect of aligned spins with a single effective spin parameter \chi. We
construct template banks from these waveforms by a stochastic placement method
and use these banks as filters in the recently-developed gstlal search
pipeline. We measure the observable volume of the analysis pipeline for binary
black hole signals with total mass in [15,25] solar masses and \chi in [0,
0.85]. We find an increase in observable volume of up to 45% for systems with
0.2 <= \chi <= 0.85 with almost no loss of sensitivity to signals with 0 <=
\chi <= 0.2. We demonstrate this analysis on 25.9 days of data obtained from
the Hanford and Livingston detectors in LIGO's fifth observation run.",1310.5633v1
2015-03-24,Micro-focused Brillouin light scattering study of the magnetization dynamics driven by Spin Hall effect in a transversely magnetized NiFe nanowire,"We employed micro-focused Brillouin light scattering to study the
amplification of the thermal spin wave eigenmodes by means of a pure spin
current, generated by the spin-Hall effect, in a transversely magnetized
Pt(4nm)/NiFe(4nm)/SiO2(5nm) layered nanowire with lateral dimensions 500x2750
nm2. The frequency and the cross section of both the center (fundamental) and
the edge spin wave modes have been measured as a function of the intensity of
the injected dc electric current. The frequency of both modes exhibits a clear
redshift while their cross section is greatly enhanced on increasing the
intensity of the injected dc. A threshold-like behavior is observed for a value
of the injected dc of 2.8 mA. Interestingly an additional mode, localized in
the central part of the nanowire, appears at higher frequency on increasing the
intensity of the injected dc above the threshold value. Micromagnetic
simulations were used to quantitatively reproduce the experimental results and
to investigate the complex non-linear dynamics induced by the spin-Hall effect,
including the modification of the spatial profile of the spin wave modes and
the appearance of the extra mode above the threshold.",1503.06968v1
2015-12-15,Can we measure individual black-hole spins from gravitational-wave observations?,"Measurements of black-hole spins from gravitational-wave observations of
black-hole binaries with ground-based detectors are expected to be hampered by
partial degeneracies in the gravitational-wave phasing: between the two
component spins, and between the spins and the binary's mass ratio, at least
for signals that are dominated by the binary's inspiral. Through the merger and
ringdown, however, a different set of degeneracies apply. This suggests the
possibility that, if the inspiral, merger and ringdown are all within the
sensitive frequency band of a detector, we may be able to break these
degeneracies and more accurately measure both spins. In this work we
investigate our ability to measure individual spins for non-precessing
binaries, for a range of configurations and signal strengths, and conclude that
in general the spin of the larger black hole will be measurable (at best) with
observations from Advanced LIGO and Virgo. This implies that in many
applications waveform models parameterized by only one \emph{effective spin}
will be sufficient. Our work does not consider precessing binaries or
sub-dominant harmonics, although we provide some arguments why we expect that
these will not qualitatively change our conclusions.",1512.04955v1
2019-08-06,Searching for ultralight bosons within spin measurements of a population of binary black hole mergers,"Ultralight bosons can form clouds around rotating black holes if their
Compton wavelength is comparable to the black hole size. The boson cloud spins
down the black hole through a process called superradiance, lowering the black
hole spin to a characteristic value. It has been suggested that spin
measurements of the black holes detected by ground-based gravitational-wave
detectors can be used to constrain the mass of ultralight bosons.
Unfortunately, a measurement of the individual black hole spins is often
uncertain, resulting in inconclusive results. Instead, we use hierarchical
Bayesian inference to combine information from multiple gravitational-wave
sources and obtain stronger constraints. We show that hundreds of high
signal-to-noise ratio gravitational-wave detections are enough to exclude
(confirm) the existence of non-interacting bosons in the mass range
$\left[10^{-13},3\times 10^{-12}\right]~\rm{eV}$
$\left([10^{-13},10^{-12}]~\rm{eV}\right)$. The precise number depends on the
distribution of black hole spins at formation and the mass of the boson. From
the few uninformative spin measurements of binary black hole mergers detected
by LIGO and Virgo in their first two observing runs, we cannot draw
statistically significant conclusions.",1908.02312v4
2019-10-16,Ultra-high frequency magnetic resonance through strain-spin coupling in perpendicular magnetic multi-layers,"The interaction between strain and spin has received intensive attention in
the scientific community due to its abundant physical phenomena and huge
technological impact. Until now, there is no experimental report on ultra-high
frequency magnetic resonance through the strain-spin coupling for any
technologically relevant perpendicular magnetic material. Here we report the
experimental detection of the acoustic strain waves that have a response time
on the order of 10 picoseconds in perpendicular magnetic [Co/Pd]n multilayers
via a femtosecond laser pulse excitation. Through direct measurements of
acoustic strain waves, we observe an ultra-high frequency magnetic resonance up
to 60 GHz in [Co/Pd]n multilayers. We further report a theoretical model of the
strain-spin interaction. Our model reveals that the energy could be transferred
efficiently from the strain to the spins and well explains the existence of a
steady resonance state through exciting the spin system. The physical origins
of the resonance between strain waves and magnetic precession and the requested
conditions for obtaining magnetic resonance within thin magnetic films have
also been discussed after thorough analysis. These combined results point out a
potential pathway to enable an extremely high frequency (EHF) magnetic
resonance through the strain-spin coupling.",1910.07147v2
2020-01-17,Methods of electron transport in ab initio theory of spin stiffness,"We present an ab initio theory of the spin-wave stiffness tensor for ordered
and disordered itinerant ferromagnets with pair exchange interactions derived
from a method of infinitesimal spin rotations. The resulting formula bears an
explicit form of a linear-response coefficient which involves one-particle
Green's functions and effective velocity operators encountered in a recent
theory of electron transport. Application of this approach to ideal metal
crystals yields more reliable values of the spin stiffness than traditional
ill-convergent real-space lattice summations. The formalism can also be
combined with the coherent potential approximation for an effective-medium
treatment of random alloys, which leads naturally to an inclusion of
disorder-induced vertex corrections to the spin stiffness. The calculated
concentration dependence of the spin-wave stiffness of random fcc Ni-Fe alloys
can be ascribed to a variation of the reciprocal value of alloy magnetization.
Calculations for random iron-rich bcc Fe-Al alloys reveal that their spin-wave
stiffness is strongly reduced owing to the atomic ordering; this effect takes
place due to weakly coupled local magnetic moments of Fe atoms surrounded by a
reduced number of Fe nearest neighbors.",2001.06279v2
2021-03-19,Spin-Injection-Generated Shock Waves and Solitons in a Ferromagnetic Thin Film,"Unsteady nonlinear magnetization dynamics are studied in an easy-plane
ferromagnetic channel subject to spin injection at one edge. The model
Landau-Lifshitz equation is known to support steady-state solutions, termed
dissipative exchange flows (DEFs) or spin superfluids. In this work, by means
of numerical simulations and theoretical analysis, we provide a full
description of the injection-induced, large-amplitude, nonlinear magnetization
dynamics up to the steady state. The dynamics prior to reaching steady state
are driven by spin injection, the perpendicular applied magnetic field, the
exchange interaction, and local demagnetizing fields. We show that the dynamics
take well-defined profiles in the form of rarefaction waves (RW), dispersive
shock waves (DSW), and solitons. The combination of these building blocks
depends on the interplay between the spin injection strength and the applied
magnetic field. A solitonic feature at the injection boundary, signaling the
onset of the magnetic ""supersonic"" condition at the injection edge, rapidly
develops and persists in the steady-state configuration of a contact soliton
DEF. We also demonstrate the existence of sustained soliton-train dynamics in
long time that can only arise in a nonzero applied magnetic field scenario. The
dynamical evolution of spin-injection-induced magnetization dynamics presented
here may help guide observations in long-distance spin transport experiments.",2103.10616v1
2022-07-29,Sensitivity of spin-aligned searches for neutron star-black hole systems using future detectors,"Current searches for gravitational waves from compact-binary objects are
primarily designed to detect the dominant gravitational-wave mode and assume
that the binary components have spins which are aligned with the orbital
angular momentum. These choices lead to observational biases in the observed
distribution of sources. Sources with significant spin-orbit precession or
unequal-mass-ratios, which have non-negligible contributions from sub-dominant
gravitational-wave modes, may be missed; in particular, this may significantly
suppress or bias the observed neutron star -- black hole (NSBH) population. We
simulate a fiducial population of NSBH mergers and determine the impact of
using searches that only account for the dominant-mode and aligned spin. We
compare the impact for the Advanced LIGO design, A+, LIGO Voyager, and Cosmic
Explorer observatories. We find that for a fiducial population where the spin
distribution is isotropic in orientation and uniform in magnitude, we will miss
$\sim 25\%$ of sources with mass-ratio $q > 6$ and up to $\sim 60 \%$ of highly
precessing sources $(\chi_p > 0.5)$, after accounting for the approximate
increase in background. In practice, the true observational bias can be even
larger due to strict signal-consistency tests applied in searches. The
observation of low spin, unequal-mass-ratio sources by Advanced LIGO design and
Advanced Virgo may in part be due to these selection effects. The development
of a search sensitive to high mass-ratio, precessing sources may allow the
detection of new binaries whose spin properties would provide key insights into
the formation and astrophysics of compact objects.",2207.14645v1
2022-08-05,Scattering of gravitational waves off spinning compact objects with an effective worldline theory,"We study the process, within classical general relativity, in which an
incident gravitational plane wave, of weak amplitude and long wavelength,
scatters off a massive spinning compact object, such as a black hole or neutron
star. The amplitude of the asymptotic scattered wave, considered here at linear
order in Newton's constant $G$ while at higher orders in the object's multipole
expansion, is a valuable characterization of the response of the object to
external gravitational fields. This amplitude coincides with a classical
($\hbar\to0$) limit of a quantum 4-point (object and graviton in, object and
graviton out) gravitational Compton amplitude, at the tree (linear-in-$G$)
level. Such tree-level Compton amplitudes are key building blocks in
generalized-unitary-based approaches to the post-Minkowskian dynamics of
binaries of spinning compact objects. In this paper, we compute the classical
amplitude using an effective worldline theory to describe the compact object,
determined by an action functional for translational and rotational degrees of
freedom, including couplings of spin-induced higher multipole moments to
spacetime curvature. We work here up to the levels of quadratic-in-spin
quadrupole and cubic-in-spin octupole couplings, respectively involving Wilson
coefficients $C_2$ and $C_3$. For the special case $C_2=C_3=1$ corresponding to
a black hole, we find agreement through cubic-in-spin order between our
classical amplitude and previous conjectures arising from considerations of
quantum scattering amplitudes. We also present new results for general $C_2$
and $C_3$, anticipating instructive comparisons with results from effective
quantum theories.",2208.03170v2
2023-04-12,Co-existence of charge density wave and anti-ferromagnetic coupling in the spin-chain compound Ba$_6$Cr$_2$S$_{10}$,"Here we have performed detailed first principles calculations for the
electronic structure and magnetic properties of Ba$_6$Cr$_2$S$_{10}$ to study
the origin of the anti-ferromagnetic exchange interaction between spins on Cr
ions for the spin-chain compound Ba$_6$Cr$_2$S$_{10}$ synthesised recently.
Most importantly, we have found the co-existence of a charge density wave phase
along one line and an anti-ferromagnetic spin chain along another. The
dimerization of sulfur atoms loosely bonded with Ba atoms drives the system
into an insulating state owing to the formation of charge density wave.
Meanwhile, the small size of the effective Hubbard $U$ parameter ($\sim 0.5$
eV) due to electrostatic screening mainly accounts for the anti-ferromagnetic
ground state. This co-existence equips us with a platform to tune the charge
and spin degrees of freedom independently. Moreover, there exists a
next-nearest-neighbouring anti-ferromagnetic interaction along the chain, which
could bring forward spin frustration and hence quantum spin liquid.",2304.06156v3
2023-02-15,Lorentz transformation of three dimensional gravitational wave tensor,"Recently there are more and more interest on the gravitational wave of moving
sources. This introduces a Lorentz transformation problem of gravitational
wave. Although Bondi-Metzner-Sachs (BMS) theory has in principle already
included the Lorentz transformation of gravitational wave, the transformation
of the three dimensional gravitational wave tensor has not been explicitly
calculated before. Within four dimensional spacetime, gravitational wave have
property of `boost weight zero' and `spin weight 2'. This fact makes the
Lorentz transformation of gravitational wave difficult to understand. In the
current paper we adopt the traditional three dimensional tensor description of
gravitational wave. Such a transverse-traceless tensor describes the
gravitational wave freedom directly. We derive the explicit Lorentz
transformation of the gravitational wave tensor. The transformation is similar
to the Lorentz transformation for electric field vector and magnetic field
vector which are three dimensional vectors. Based on the deduced Lorentz
transformation of the gravitational wave three dimensional tensor, we can
construct the gravitational waveform of moving source with any speed if only
the waveform of the corresponding rest waveform is given. As an example, we
apply our method to the effect of kick velocity of binary black hole. The
adjusted waveform by the kick velocity is presented.",2302.07532v1
2007-08-15,Spin relaxation in $n$-type GaAs quantum wells with transient spin grating,"By solving the kinetic spin Bloch equations, we study the time evolution of
the transient spin grating, whose spin polarization varies periodically in real
space, confined in (001) GaAs quantum wells. With this study we can investigate
the properties of both the spin transport and the spin relaxation at the same
time. The Fourier component of the spin signal decays double exponentially with
two decay rates $1/\tau_+$ and $1/\tau_-$. In high temperature regime, the
average of these two rates varies with the grating wave-vector $q$
quadratically, i.e., $(1/\tau_++1/\tau_-)/2=D_sq^2+1/\tilde{\tau}_s$, with
$D_s$ and $\tilde{\tau}_s$ representing the spin diffusion coefficient and the
average of the out-of-plane and the in-plane spin relaxation times
respectively. $\tau_{\pm}$ calculated from our theory are in good agreement
with the experimental data by Weber {\em et al.} [Phys. Rev. Lett. {\bf 98},
076604 (2007)]. By comparing $D_s$ with and without the electron-electron
Coulomb scattering, we calculate the contribution of Coulomb drag to the spin
diffusion coefficient. With the transient spin grating result, we further
reveal the relations among different characteristic parameters such as spin
diffusion coefficient $D_s$, spin relaxation time $\tau_s$, and spin injection
length $L_s$. We show that in the presence of the Dresselhaus and/or Rashba
spin-orbit coupling, the widely used relation $L_s=\sqrt{D_s\tau_s}$ is
generally inaccurate and can even be very wrong in some special cases. We
present an accurate way to extract the steady-state transport characteristic
parameters from the transient spin grating signals.",0708.1975v4
2016-12-29,The magnetic Hamiltonian and phase diagram of the quantum spin liquid Ca10Cr7O28,"A spin liquid is a new state of matter with topological order where the spin
moments continue to fluctuate coherently down to the lowest temperatures rather
than develop static long-range magnetic order as found in conventional magnets.
For spin liquid behavior to arise in a material the magnetic Hamiltonian must
be ""frustrated"" where the combination of lattice geometry, interactions and
anisotropies gives rise to competing spin arrangements in the ground state.
Theoretical Hamiltonians which produce spin liquids are spin ice, the Kitaev
honeycomb model and the Heisenberg kagome antiferromagnet. Spin liquid behavior
however in real materials is rare because they can only approximate these
Hamiltonians and often have weak higher order terms that destroy the spin
liquid state. Ca10Cr7O28 is a new quantum spin liquid with magnetic Cr5+ ions
that possess quantum spin number S=1/2. The spins are entirely dynamic in the
ground state and the excitation spectrum is broad and diffuse as is typical of
spinons which are the excitations of a spin liquid. In this paper we determine
the Hamiltonian of Ca10Cr7O28 using inelastic neutron scattering under high
magnetic field to induce a ferromagnetic ground state and spin-wave excitations
that can be fitted to extract the interactions. We further explore the phase
diagram by using inelastic neutron scattering and heat capacity measurements
and establish the boundaries of the spin liquid phase as a function of magnetic
field and temperature. Our results show that Ca10Cr7O28 consists of distorted
kagome bilayers with several isotropic ferromagnetic and antiferromagnetic
interactions where unexpectedly the ferromagnetic interactions are stronger
than the antiferromagnetic ones. This complex Hamiltonian does not correspond
to any known spin liquid model and points to new directions in the search for
quantum spin liquid behavior.",1612.09149v1
2020-07-25,Spin and Eccentricity Evolution in Triple Systems: from the Lidov-Kozai Interaction to the Final Merger of the Inner Binary,"We study the spin and eccentricity evolution of black-hole (BH) binaries that
are perturbed by tertiary masses and experience the Lidov-Kozai (LK)
excitation. We focus on three aspects. Firstly, we study the spin-orbit
alignment of the inner binary following the approach outlined by Antonini et
al. [MNRAS 480, L58 (2018)] and Liu and Lai [ApJ 863, 68 (2018)], yet allowing
the spins to have random initial orientations. We confirm the existence of a
dynamical attractor that drives the spin-orbit angle at the end of the LK
evolution to a value given by the initial angle between the spin and the outer
orbital angular momentum (instead of to a specific value of the effective
spin). Secondly, we follow the (inner) binary's evolution further to the merger
to study the final spin-spin alignment. We generalize the effective potential
theory to include orbital eccentricity, which allows us to efficiently evolve
the system in the early inspiral stages. We further find that the spin-spin and
spin-orbit alignments are correlated and the correlation is determined by the
initial spin-orbit angle. For systems with the spin vectors initially in the
orbital plane, the final spins strongly disfavor an aligned configuration and
could thus lead to a greater value of the GW recoil than a uniform spin-spin
alignment would predict. Lastly, we study the maximum eccentricity excitation
that can be achieved during the LK process, including the effects of
gravitational-wave radiation. We find that when the tertiary mass is a
super-massive BH and the inner binary is massive, then even with the maximum LK
excitation, the residual eccentricity is typically less than 0.1 when the
binary's orbital frequency reaches 10 Hz, and a decihertz detector would be
necessary to follow such a system's orbital evolution.",2007.12978v2
1997-10-11,A new paradigm for two-dimensional spin-liquids,"Motivated by the geometry of the materials Na_2 Ti_2 As_2 O and Na_2 Ti_2
Sb_2 O, we study a square-lattice Heisenberg antiferromagnet with spins located
at the bond-centers. The largest exchange constant J couples neighboring spins
in a given row or column. This leads to a mesh of isolated spin-chains running
along the X and Y axes. A weaker exchange constant J' couples the
nearest-neighbor spins on the lattice. Classically, J' fails to fix the
relative spin orientation for different chains and hence the ground state is
highly degenerate. Quantum order by disorder effect is studied by spin-wave
theory and numerical methods. It is shown that a 4-sublattice order is favored
by quantum fluctuations. However, several arguments are presented that suggest
that the ground state of the system remains disordered, thus providing us with
a paradigm for a two-dimensional spin-liquid.",9710109v1
2001-12-16,Magnetic phases of the mixed-spin $J_1-J_2$ Heisenberg model on a square lattice,"We study the zero-temperature phase diagram and the low-energy excitations of
a mixed-spin ($S_1>S_2$) $J_1-J_2$ Heisenberg model defined on a square lattice
by using a spin-wave analysis, the coupled cluster method, and the Lanczos
exact-diagonalization technique. As a function of the frustration parameter
$J_2/J_1$ ($ >0$), the phase diagram exhibits a quantized ferrimagnetic phase,
a canted spin phase, and a mixed-spin collinear phase. The presented results
point towards a strong disordering effect of the frustration and quantum spin
fluctuations in the vicinity of the classical spin-flop transition. In the
extreme quantum system $(S_1,S_2)=(1,{1/2})$, we find indications of a new
quantum spin state in the region $0.46< J_2/J_1<0.5$",0112295v2
2002-03-14,Interaction Of Electrons With Spin Waves In The Bulk And In Multilayers,"The exchange interaction between electrons and magnetic spins is considerably
enhanced near interfaces, in magnetic multilayers. As a result, a dc current
can be used to generate spin oscillations. We review theory and experimental
evidence. The s-d exchange interaction causes a rapid precession of itinerant
conduction-electron spins s around the localized spins S of magnetic electrons.
Because of the precession, the time-averaged interaction torque between s and S
vanishes. An interface between a magnetic layer and a spacer causes a local
coherence between the precession phases of differnt electrons, within 10 nm
from the interface, and restores the torque. Also, a second magnetic layer with
pinned S is used to prepare s in a specific direction. the current-induced
drive torque of s on S in the active layer may be calculated from the spin
current (Slonczewski) or from the spin imbalance Delta-mu (Berger). Spin
current and Delta-mu are proportional to each other, and can arise from
Fermi-surface translation, as well as from expansion/contraction.",0203314v1
2002-07-11,Quantum disorder due to singlet formation: The Plaquette lattice,"I study the order/disorder transition due to singlet formation in a quantum
spin system by means of exact diagonalization. The systems is build by spin 1/2
on a two-dimensional square lattice with two different kinds of
antiferromagnetic Heisenberg interactions. The interaction J_p connects 4
nearest neighbor spins on a plaquette. The interaction J_n connects the
plaquettes with each other. If J_p=J_n the systems reduces to the simple square
lattice case. If one of the interactions becomes sufficiently larger then the
other the purely quantum effect of singlet formation drives the system into a
disordered phase with only short range correlations in the plaquettes and a
spin gap. I study the transition point by evaluating the spin gap and spin-spin
correlations. I compare the results with previously calculated data from a
non-linear sigma model approach, spin wave theory and series expansion
calculations. I confirm a critical value of J_n \approx 0.6 for the quantum
phase transition point.",0207303v1
2002-12-19,Non-ideality of quantum operations with the electron spin of a 31P donor in a Si crystal due to interaction with a nuclear spin system,"We examine a 31P donor electron spin in a Si crystal to be used for the
purposes of quantum computation. The interaction with an uncontrolled system of
29Si nuclear spins influences the electron spin dynamics appreciably. The
hyperfine field at the 29Si nuclei positions is non-collinear with the external
magnetic field. Quantum operations with the electron wave function, i.e. using
magnetic field pulses or electrical gates, change the orientation of hyperfine
field and disturb the nuclear spin system. This disturbance produces a
deviation of the electron spin qubit from an ideal state, at a short time scale
in comparison with the nuclear spin diffusion time. For H_ext=9 T, the
estimated error rate is comparable to the threshold value required by the
quantum error correction algorithms. The rate is lower at higher external
magnetic fields.",0212501v2
2003-04-24,Ferromagnetism in a dilute magnetic semiconductor -- Generalized RKKY interaction and spin-wave excitations,"Carrier-mediated ferromagnetism in a dilute magnetic semiconductor has been
studied using i) a single-impurity based generalized RKKY approach which goes
beyond linear response theory, and ii) a mean-field-plus-spin-fluctuation
(MF+SF) approach within a (purely fermionic) Hubbard-model representation of
the magnetic impurities, which incorporates dynamical effects associated with
finite frequency spin correlations in the ordered state. Due to a competition
between the magnitude of the carrier spin polarization and its oscillation
length scale, the ferromagnetic spin coupling is found to be optimized with
respect to both hole doping concentration and impurity-carrier spin coupling
energy $J$ (or equivalently $U$). The ferromagnetic transition temperature
$T_c$, deteremined within the spin-fluctuation theory, corresponds closely with
the observed $T_c$ values. Positional disorder of magnetic impurities causes
significant stiffening of the high-energy magnon modes. We also explicitly
study the stability/instability of the mean-field ferromagnetic state, which
highlights the role of competing AF interactions causing spin twisting and
noncollinear ferromagnetic ordering.",0304557v2
2004-04-16,Slowing down of spin relaxation in two dimensional systems by quantum interference effects,"The effect of weak localization on spin relaxation in a two-dimensional
system with a spin-split spectrum is considered. It is shown that the spin
relaxation slows down due to the interference of electron waves moving along
closed paths in opposite directions. As a result, the averaged electron spin
decays at large times as $1/t$. It is found that the spin dynamics can be
described by a Boltzmann-type equation, in which the weak localization effects
are taken into account as nonlocal-in-time corrections to the collision
integral. The corrections are expressed via a spin-dependent return
probability. The physical nature of the phenomenon is discussed and it is shown
that the ""nonbackscattering"" contribution to the weak localization plays an
essential role. It is also demonstrated that the magnetic field, both
transversal and longitudinal, suppresses the power tail in the spin
polarization.",0404391v2
2004-11-05,Properties and Detection of Spin Nematic Order in Strongly Correlated Electron Systems,"A spin nematic is a state which breaks spin SU(2) symmetry while preserving
translational and time reversal symmetries. Spin nematic order can arise
naturally from charge fluctuations of a spin stripe state. Focusing on the
possible existence of such a state in strongly correlated electron systems, we
build a nematic wave function starting from a t-J type model. The nematic is a
spin-two operator, and therefore does not couple directly to neutrons. However,
we show that neutron scattering and Knight shift experiments can detect the
spin anisotropy of electrons moving in a nematic background. We find the mean
field phase diagram for the nematic taking into account spin-orbit effects.",0411159v2
2004-11-28,Non-Markovian dynamics of a localized electron spin due to the hyperfine interaction,"We review our theoretical work on the dynamics of a localized electron spin
interacting with an environment of nuclear spins. Our perturbative calculation
is valid for arbitrary polarization p of the nuclear spin system and arbitrary
nuclear spin I in a sufficiently large magnetic field. In general, the electron
spin shows rich dynamics, described by a sum of contributions with exponential
decay, non-exponential decay, and undamped oscillations. We have found an
abrupt crossover in the long-time spin dynamics at a critical shape and
dimensionality of the electron envelope wave function. We conclude with a
discussion of our proposed scheme to measure the relevant dynamics using a
standard spin-echo technique.",0411690v1
2005-10-25,Non-equilibrium spin polarization effects in spin-orbit coupling system and contacting metallic leads,"We study theoretically the current-induced spin polarization effect in a
two-terminal mesoscopic structure which is composed of a semiconductor
two-dimensional electron gas (2DEG) bar with Rashba spin-orbit (SO) interaction
and two attached ideal leads. The nonequilibrium spin density is calculated by
solving the scattering wave functions explicitly within the ballistic transport
regime. We found that for a Rashba SO system the electrical current can induce
spin polarization in the SO system as well as in the ideal leads. The induced
polarization in the 2DEG shows some qualitative features of the intrinsic spin
Hall effect. On the other hand, the nonequilibrium spin density in the ideal
leads, after being averaged in the transversal direction, is independent of the
distance measured from the lead/SO system interface, except in the vicinity of
the interface. Such a lead polarization effect can even be enhanced by the
presence of weak impurity scattering in the SO system and may be detectable in
real experiments.",0510664v2
2005-11-04,Lattice effects on the spin dynamics in antiferromagnetic molecular rings,"We investigate spin dynamics in antiferromagnetic (AF) molecular rings at
finite temperature in the presence of spin-phonon (s-p) interaction. We derive
a general expression for the spin susceptibility in the weak s-p coupling limit
and then we focus on the low-frequency behavior, in order to discuss a possible
microscopic mechanism for nuclear relaxation in this class of magnetic
materials. To lowest order in a perturbative expansion, we find that the
susceptibility takes a Lorentzian profile and all spin operators ($S^x$, $S^y,
S^z$) contribute to spin dynamics at wave vectors $q\ne 0$. Spin anisotropies
and local s-p coupling play a key role in the proposed mechanism. Our results
prove that small changes in the spatial symmetry of the ring induce qualitative
changes in the spin dynamics at the nuclear frequency, providing a novel
mechanism for nuclear relaxation. Possible experiments are proposed.",0511118v1
2006-05-22,Geometrical phase effects on the Wigner distribution of Bloch electrons,"We investigate the dynamics of Bloch electrons using a density operator
method and connect this approach with previous theories based on wave packets.
We study non-interacting systems with negligible disorder and strong spin-orbit
interactions, which have been at the forefront of recent research on
spin-related phenomena. We demonstrate that the requirement of gauge invariance
results in a shift in the position at which the Wigner function of Bloch
electrons is evaluated. The present formalism also yields the correction to the
carrier velocity arising from the Berry phase. The gauge-dependent shift in
carrier position and the Berry phase correction to the carrier velocity
naturally appear in the charge and current density distributions. In the
context of spin transport we show that the spin velocity may be defined in such
a way as to enable spin dynamics to be treated on the same footing as charge
dynamics. Aside from the gauge-dependent position shift we find additional,
gauge-covariant multipole terms in the density distributions of spin, spin
current and spin torque.",0605528v1
1998-08-11,The pseudo-spin symmetry in Zr and Sn isotopes from the proton drip line to the neutron drip line,"Based on the Relativistic continuum Hartree-Bogoliubov (RCHB) theory, the
pseudo-spin approximation in exotic nuclei is investigated in Zr and Sn
isotopes from the proton drip line to the neutron drip line. The quality of the
pseudo-spin approximation is shown to be connected with the competition between
the centrifugal barrier (CB) and the pseudo-spin orbital potential (PSOP). The
PSOP depends on the derivative of the difference between the scalar and vector
potentials $dV/dr$. If $dV/dr = 0$, the pseudo-spin symmetry is exact. The
pseudo-spin symmetry is found to be a good approximation for normal nuclei and
to become much better for exotic nuclei with highly diffuse potential, which
have $dV/dr \sim 0$. The energy splitting of the pseudo-spin partners is
smaller for orbitals near the Fermi surface (even in the continuum) than the
deeply bound orbitals. The lower components of the Dirac wave functions for the
pseudo-spin partners are very similar and almost equal in magnitude.",9808026v1
2000-09-26,Spin-axis relaxation in spin-exchange collisions of alkali atoms,"We present calculations of spin-relaxation rates of alkali-metal atoms due to
the spin-axis interaction acting in binary collisions between the atoms. We
show that for the high-temperature conditions of interest here, the spin
relaxation rates calculated with classical-path trajectories are nearly the
same as those calculated with the distorted-wave Born approximation. We compare
these calculations to recent experiments that used magnetic decoupling to
isolate spin relaxation due to binary collisions from that due to the formation
of triplet van-der-Waals molecules. The values of the spin-axis coupling
coefficients deduced from measurements of binary collision rates are consistent
with those deduced from molecular decoupling experiments. All the experimental
data is consistent with a simple and physically plausible scaling law for the
spin-axis coupling coefficients.",0009078v2
2007-02-05,Decoherence of two-electron spin states in quantum dots,"The time evolution of spin states of two electrons interacting with a nuclear
spin bath in a quantum dot system is studied. The hyperfine interaction between
the electrons and the nuclear spins is modeled by an isotropic Heisenberg
interaction, and the interaction between the electron spins by Heisenberg
exchange. Depending on the extent of the overlap between the spatial wave
functions of the electrons, there are two physically different cases, namely
the two qubits either interact with the same set of nuclear spins or they see
different nuclear spin environment. In the two cases, the decoherence of the
two-qubit state is studied analytically. We have identified a class of
two-qubit states which have a rich dynamics when the exchange interaction
between the qubits becomes large in comparison to the hyperfine interaction
strengths. The decoherence time scale is determined as a function of the
bath-spin distribution and the polarizations of the initial two-qubit state.
States with large decoherence times are identified by performing a minimization
over all the two-qubit pure states.",0702035v1
2007-07-04,On the environmental decoherence and spin interference in mesoscopic loop structures,"Mechanisms of 'environmental decoherence' such as surface scattering,
Elliot-Yafet process and precession mechanisms, as well as their influence on
the spin phase relaxation are considered and compared. It is shown that the
'spin ballistic' regime is possible, when the phase relaxation length for the
spin part of the wave function (WF)is much greater than the phase relaxation
length for the 'orbital part'. In the presence of an additional magnetic field,
the spin part of the electron's WF acquires a phase shift due to additional
spin precession about that field. If the structure length is chosen to be
greater than the phase relaxation length for the 'orbital part' and less than
the phase relaxation length for the spin part of WF, it is possible to 'wash
out' the quantum interference related to the phase coherence of the 'orbital
part' of the WF, retaining at the same time that related to the phase coherence
of the spin part and, hence, to reveal corresponding conductance oscillations.",0707.0631v1
2007-12-12,Eliminating spin contamination in auxiliary-field quantum Monte Carlo: realistic potential energy curve of F2,"The use of an approximate reference state wave function |Phi_r> in electronic
many-body methods can break the spin symmetry of Born-Oppenheimer
spin-independent Hamiltonians. This can result in significant errors,
especially when bonds are stretched or broken. A simple spin-projection method
is introduced for auxiliary-field quantum Monte Carlo (AFQMC) calculations,
which yields spin-contamination-free results, even with a spin-contaminated
|Phi_r>. The method is applied to the difficult F2 molecule, which is unbound
within unrestricted Hartree-Fock (UHF). With a UHF |Phi_r>, spin contamination
causes large systematic errors and long equilibration times in AFQMC in the
intermediate, bond-breaking region. The spin-projection method eliminates these
problems, and delivers an accurate potential energy curve from equilibrium to
the dissociation limit using the UHF |Phi_r>. Realistic potential energy curves
are obtained with a cc-pVQZ basis. The calculated spectroscopic constants are
in excellent agreement with experiment.",0712.1935v1
2011-02-18,Numerical Simulation of Spin-Chirality Switching in Multiferroics via Intense Electromagnon Excitations,"Chirality, i.e., the right- and left-handedness of structure, is one of the
key concepts in many fields of science including biology, chemistry and
physics, and its manipulation is an issue of vital importance. The electron
spins in solids can form chiral configurations. In perovskite manganites RMnO3
(R=Tb, Dy,...etc), the Mn-spins form a cycloidal structure, which induces
ferroelectric polarization (P) through the relativistic spin-orbit interaction.
This magnetism-induced ferroelectricity (multiferroics) and associated
infrared-active spin waves (electromagnons) open a promising route to control
the spins by purely electric means in a very short time. In this paper, we show
theoretically with an accurate spin Hamiltonian for TbMnO3 that a picosecond
optical pulse can switch the spin chirality by intensely exciting the
electromagnons with a terahertz frequency.",1102.3762v1
2011-11-02,Proposal for a Datta-Das transistor in the quantum Hall regime,"We propose a resonant spin-field-effect transistor for chiral spin-resolved
edge states in the integer quantum Hall effect with Rashba spin-orbit
interaction. It employs a periodic array of voltage-controlled top gates that
locally modulate the Rashba spin-orbit interaction. Strong resonant spin-field
effect is achieved when the array periodicity matches the inverse of the
wave-vector difference of the two chiral states involved. Well-known techniques
of separately contacting the edge states make it possible to selectively
populate and read out the edge states, allowing full spin readout. The resonant
nature of the spin-field effect and the adiabatic character of the edge states
guarantee a high degree of robustness with respect to disorder. Our device
represents the quantum Hall version of the all-electrical Datta-Das spin-field
effect transistor.",1111.0675v3
2012-01-08,Spin-orbit coupled Fermi liquid theory of ultra-cold magnetic dipolar fermions,"We investigate Fermi liquid states of the ultra-cold magnetic dipolar Fermi
gases in the simplest two-component case including both thermodynamic
instabilities and collective excitations. The magnetic dipolar interaction is
invariant under the simultaneous spin-orbit rotation, but not under either the
spin or the orbit one. Therefore, the corresponding Fermi liquid theory is
intrinsically spin-orbit coupled. This is a fundamental feature of magnetic
dipolar Fermi gases different from electric dipolar ones. The Landau
interaction matrix is calculated and is diagonalized in terms of the spin-orbit
coupled partial-wave channels of the total angular momentum J. The leading
thermodynamic instabilities lie in the channels of ferromagnetism hybridized
with the ferronematic order with J = 1+ and the spin-current mode with J = 1-,
where + and - represent even and odd parities, respectively. An exotic
propagating collective mode is identified as spin-orbit coupled Fermi surface
oscillations in which spin distribution on the Fermi surface exhibits a
topologically nontrivial hedgehog configuration.",1201.1607v3
2012-03-29,Theory of spin dynamics of magnetic adatoms traced by time-resolved scanning tunneling spectroscopy,"The inelastic scanning tunneling microscopy (STM) has been shown recently
(Loth et al. Science 329, 1628 (2010)) to be extendable as to access the
nanosecond, spin-resolved dynamics of magnetic adatoms and molecules. Here we
analyze theoretically this novel tool by considering the time-resolved spin
dynamics of a single adsorbed Fe atom excited by a tunneling current pulse from
a spin-polarized STM tip. The adatom spin-configuration can be controlled and
probed by applying voltage pulses between the substrate and the spin-polarized
STM tip. We demonstrate how, in a pump-probe manner, the relaxation dynamics of
the sample spin is manifested in the spin-dependent tunneling current. Our
model calculations are based on the scattering theory in a wave-packet
formulation. The scheme is nonpertubative and hence, is valid for all voltages.
The numerical results for the tunneling probability and the conductance are
contrasted with the prediction of simple analytical models and compared with
experiments.",1203.6476v1
2012-08-15,Paired chiral spin liquid with a Fermi surface in S=1 model on the triangular lattice,"Motivated by recent experiments on Ba3NiSb2O9, we investigate possible
quantum spin liquid ground states for spin S=1 Heisenberg models on the
triangular lattice. We use Variational Monte Carlo techniques to calculate the
energies of microscopic spin liquid wave functions where spin is represented by
three flavors of fermionic spinon operators. These energies are compared with
the energies of various competing three-sublattice ordered states. Our approach
shows that the antiferromagnetic Heisenberg model with biquadratic term and
single-ion anisotropy does not have a low-temperature spin liquid phase.
However, for an SU(3)-invariant model with sufficiently strong ring-exchange
terms, we find a paired chiral quantum spin liquid with a Fermi surface of
deconfined spinons that is stable against all types of ordering patterns we
considered. We discuss the physics of this exotic spin liquid state in relation
with the recent experiment and suggest new ways to test this scenario.",1208.3231v2
2012-10-09,Spectral Characteristics of the Microwave Emission by the Spin Hall Nano-Oscillator,"We utilized microwave spectroscopy to study the magnetization oscillations
locally induced in a Permalloy film by a pure spin current, which is generated
due to the spin Hall effect in an adjacent Pt layer. The oscillation frequency
is lower than the ferromagnetic resonance of Permalloy, indicating that the
oscillation forms a self-localized nonpropagating spin-wave soliton. At
cryogenic temperatures, the spectral characteristics are remarkably similar to
the traditional spin-torque nano-oscillators driven by spin-polarized currents.
However, the linewidth of the oscillation increases exponentially with
temperature and an additional peak appears in the spectrum below the
ferromagnetic resonance, suggesting that the spectral characteristics are
determined by interplay between two localized dynamical states.",1210.2758v2
2013-05-16,Interplay between spin-orbit interactions and a time-dependent electromagnetic field in monolayer graphene,"We apply a circularly and linearly polarized terahertz field on a monolayer
of graphene taking into account spin-orbit interactions of the intrinsic and
Rashba type. It turns out that the field can not only be used to induce a gap
in the energy spectrum, but also to close an existing gap due to the different
reaction of the spin components on circularly polarized light. Signatures of
spin-orbit coupling on the density of states of the driven system can be
observed even for energies where the static density of states is independent of
spin-orbit interactions. Furthermore it is shown that the time evolution of the
spin polarization and the orbital dynamics of an initial wave packet can be
modulated by varying the ratio of the spin-orbit coupling parameters. Assuming
that the system acquires a quasi stationary state, the optical conductivity of
the irradiated sample is calculated. Our results confirm the multi step nature
of the conductivity obtained recently, where the number of intermediate steps
can be changed by adjusting the spin-orbit coupling parameters and the
orientation of the field.",1305.3810v2
2013-06-25,Bosonic Mott Insulator with Meissner Currents,"We introduce a generic bosonic model exemplifying that (spin) Meissner
currents can persist in insulating phases of matter. We consider two species of
interacting bosons on a lattice. Our model exhibits separation of charge (total
density) and spin (relative density): The charge sector is gapped in a bosonic
Mott insulator phase with total density one, while the spin sector remains
superfluid due to interspecies conversion. Coupling the spin sector to the
gauge fields yields a spin Meissner effect reflecting the long-range spin
superfluid coherence. We investigate the resulting phase diagram and describe
other possible spin phases of matter in the Mott regime possessing chiral
currents as well as a spin-density wave phase. The model presented here is
realizable in Josephson junction arrays and in cold atom experiments.",1306.5986v3
2013-07-03,General theory of feedback control of a nuclear spin ensemble in quantum dots,"We present a microscopic theory of the nonequilibrium nuclear spin dynamics
driven by the electron and/or hole under continuous wave pumping in a quantum
dot. We show the correlated dynamics of the nuclear spin ensemble and the
electron and/or hole under optical excitation as a quantum feedback loop and
investigate the dynamics of the many nuclear spins as a nonlinear collective
motion. This gives rise to three observable effects: (i) hysteresis, (ii)
locking (avoidance) of the pump absorption strength to (from) the natural
resonance, and (iii) suppression (amplification) of the fluctuation of weakly
polarized nuclear spins, leading to prolonged (shortened) electron spin
coherence time. A single nonlinear feedback function as a ""measurement"" of the
nuclear field operator in the quantum feedback loop is constructed which
determines the different outcomes of the three effects listed above depending
on the feedback being negative or positive. The general theory also helps to
put in perspective the wide range of existing theories on the problem of a
single electron spin in a nuclear spin bath.",1307.0897v1
2013-07-09,Anisotropic spin fluctuations in the quasi one-dimensional frustrated magnet LiCuVO_4,"We report results of NMR experiments on a single crystal of the quasi
one-dimensional frustrated magnet LiCuVO_4. The NMR spectra of ^7Li and ^{51}V
nuclei indicate a helical spin order in a magnetic field of 4 T with the
helical spin plane perpendicular to the field and a spin-density-wave (SDW)
order at 10 T with modulation in the magnitude of the moments aligned along the
field, in agreement with earlier reports. The nuclear spin-lattice relaxation
rate 1/T_1 at ^{51}V nuclei, which is selectively coupled to the transverse
spin fluctuations perpendicular to the field, shows a pronounced peak near the
helical ordering temperature in the field of 4 T applied along the a-axis. In
the field of 10 T, however, such a peak is absent. Instead 1/T_1 at ^7Li nuclei
probing longitudinal spin fluctuations shows divergent behavior towards the SDW
ordering temperature. These results are qualitatively consistent with the
theoretical description that the SDW correlation is due to bound magnon pairs,
which produce an energy gap in the transverse spin excitation spectrum.",1307.2346v1
2013-10-28,Coulomb-driven organization and enhancement of spin-orbit fields in collective spin excitations,"Spin-orbit (SO) fields in a spin-polarized electron gas are studied by
angle-resolved inelastic light scattering on a CdMnTe quantum well. We
demonstrate a striking organization and enhancement of SO fields acting on the
collective spin excitation (spin-flip wave). While individual electronic SO
fields have a broadly distributed momentum dependence, giving rise to
D'yakonov-Perel' dephasing, the collective spin dynamics is governed by a
single collective SO field which is drastically enhanced due to many-body
effects. The enhancement factor is experimentally determined. These results
provide a powerful indication that these constructive phenomena are universal
to collective spin excitations of conducting systems.",1310.7613v1
2013-11-12,Leggett's Modes in Magnetic Systems with Jahn-Teller distortion,"Leggett's mode is a collective excitation corresponding to the oscillation of
the relative phase of the order parameters in a two band superconductor, with
frequency proportional to interband coupling. We report on the existence of
modes, similar to Leggett's mode, in magnetic systems with Jahn-Teller
distortion. The minimal Kugel-Khomskii model, which describes simultaneously
both the spin and the orbital order, is studied. The dynamical degrees of
freedom are spin-$s$ operators of localized spins and pseudospin-$\tau$
operators, which respond to the orbital degeneracy and satisfy the similar
commutation relation with those of the spin operators. In the case of
""antiferro"" spin and pseudospin order the system possesses two
antiferromagnetic magnons with equal spin-wave velocities and two Leggett's
modes with equal gaps proportional to the square root of the spin-pseudospin
interaction constant. In the case of ""ferro"" spin and pseudospin order the
system possesses one ferromagnetic magnon and one Leggett's mode with gap
proportional to the spin-pseudospin interaction constant.",1311.2733v3
2013-11-20,Vanishing spin gap in a competing spin-liquid phase in the kagome Heisenberg antiferromagnet,"We provide strong numerical evidence, using improved variational wave
functions, for a ground state with vanishing spin gap in the spin-$1/2$ quantum
Heisenberg model on the kagome lattice. Starting from the algebraic $U(1)$
Dirac spin liquid state proposed by Y. Ran $et al.$ [Phys. Rev. Lett. $98$,
$117205$ ($2007$)] and iteratively applying a few Lanczos steps, we compute the
lowest $S=2$ excitation constructed by exciting spinons close to the Dirac
nodes. Our results are compatible with a vanishing spin gap in the
thermodynamic limit and in consonance with a power-law decay of long distance
spin-spin correlations in real space. The competition with a gapped
(topological) spin liquid is discussed.",1311.5038v2
2014-11-03,Effective potentials and morphological transitions for binary black-hole spin precession,"We derive an effective potential for binary black-hole (BBH) spin precession
at second post-Newtonian order. This effective potential allows us to solve the
orbit-averaged spin-precession equations analytically for arbitrary mass ratios
and spins. These solutions are quasiperiodic functions of time: after a fixed
period the BBH spins return to their initial relative orientations and jointly
precess about the total angular momentum by a fixed angle. Using these
solutions, we classify BBH spin precession into three distinct morphologies
between which BBHs can transition during their inspiral. We also derive a
precession-averaged evolution equation for the total angular momentum that can
be integrated on the radiation-reaction time and identify a new class of
spin-orbit resonances that can tilt the direction of the total angular momentum
during the inspiral. Our new results will help efforts to model and interpret
gravitational waves from generic BBH mergers and predict the distributions of
final spins and gravitational recoils.",1411.0674v2
2014-11-14,Spin Correlations in Quantum Wires,"We consider theoretically spin correlations in an 1D quantum wire with
Rashba-Dresselhaus spin-orbit interaction (RDI). The correlations of
non-interacting electrons display electron-spin resonance at a frequency
proportional to the RDI coupling. Interacting electrons on varying the
direction of external magnetic field transit from the state of Luttinger liquid
(LL) to the spin density wave (SDW) state. We show that the two-time total spin
correlations of these states are significantly different. In the LL the
projection of total spin to the direction of the RDI induced field is conserved
and the corresponding correlator is equal to zero. The correlators of two
components perpendicular to the RDI field display a sharp ESR driven by RDI
induced intrinsic field. In contrast, in the SDW state the longitudinal
projection of spin dominates, whereas the transverse components are suppressed.
This prediction indicates a simple way for experimental diagnostic of the SDW
in a quantum wire.",1411.4084v2
2015-05-23,Long distance transport of magnon spin information in a magnetic insulator at room temperature,"The transport of spin information has been studied in various materials, such
as metals, semiconductors and graphene. In these materials, spin is transported
by diffusion of conduction electrons. Here we study the diffusion and
relaxation of spin in a magnetic insulator, where the large bandgap prohibits
the motion of electrons. Spin can still be transported, however, through the
diffusion of non-equilibrium magnons, the quanta of spin wave excitations in
magnetically ordered materials. Here we show experimentally that these magnons
can be excited and detected fully electrically in linear response, and can
transport spin angular momentum through the magnetic insulator yttrium iron
garnet (YIG) over distances as large as 40 micrometer. We identify two
transport regimes: the diffusion limited regime for distances shorter than the
magnon relaxation length, and the relaxation limited regime for larger
distances. With a model similar to the diffusion-relaxation model for electron
spin transport in (semi)conducting materials, we extract the magnon relaxation
length lambda = 9.4 micrometer in a 200 nm thin YIG film at room temperature.",1505.06325v1
2015-08-11,Thermal generation of spin current in an antiferromagnet,"Longitudinal spin Seebeck effect has been investigated for an uniaxial
antiferromagnetic insulator Cr2O3, characterized by a spin-flop transition
under magnetic field along the c-axis. We have found that temperature gradient
applied normal to Cr2O3/Pt interface induces inverse spin Hall voltage of spin
current origin in Pt, whose magnitude turns out to be always proportional to
magnetization in Cr2O3. The observed voltage shows significant enhancement for
the lower temperature region, which can be ascribed to the phonon-drag effect
on the relevant spin excitations. The above results establish that
antiferromagnetic spin waves with high frequency above 100 GHz can be an
effective carrier of spin current.",1508.02555v1
2015-11-24,Inverse Spin Hall Effect from pulsed Spin Current in Organic Semiconductors with Tunable Spin-Orbit Coupling,"Exploration of spin-currents in organic semiconductors (OSECs) induced by
resonant microwave absorption in ferromagnetic substrates has been of great
interest for potential spintronics applications. Due to the inherently weak
spin-orbit coupling (SOC) of OSECs, their inverse spin Hall effect (ISHE)
response is very subtle; limited by the microwave power applicable under
continuous-wave (cw) excitation. Here we introduce a novel approach for
generating significant ISHE signals using pulsed ferromagnetic resonance, where
the ISHE is ~2-3 orders of magnitude larger compared to cw excitation. This
strong ISHE enables us to investigate a variety of OSECs ranging from
pi-conjugated polymers with strong SOC that contain intrachain platinum atoms,
to weak SOC polymers, to C60 films, where the SOC is predominantly caused by
the molecule surface curvature. The pulsed-ISHE technique offers a robust route
for efficient injection and detection schemes of spin-currents at room
temperature, and paves the way for spin-orbitronics in plastic materials.",1511.07848v1
2016-06-17,Spin dynamics of an individual Cr atom in a semiconductor quantum dot under optical excitation,"We studied the spin dynamics of a Cr atom incorporated in a II-VI
semiconductor quantum dot using photon correlation techniques. We used recently
developed singly Cr-doped CdTe/ZnTe quantum dots (A. Lafuente-Sampietro {\it et
al.}, [1]) to access the spin of an individual magnetic atom. Auto-correlation
of the photons emitted by the quantum dot under continuous wave optical
excitation reveals fluctuations of the localized spin with a timescale in the
10 ns range. Cross-correlation gives quantitative transfer time between Cr spin
states. A calculation of the time dependence of the spin levels population in
Cr-doped quantum dots shows that the observed spin dynamics is controlled by
the exciton-Cr interaction. These measurements also provide a lower bound in
the 20 ns range for the intrinsic Cr spin relaxation time.",1606.05476v1
2016-07-05,One particle self correlations for a separable representation of the singlet spin state beyond standard Quantum Mechanics,"A new pure quantum state, isotropic in spin variables, is defined in an
extended spin phase space beyond standard quantum mechanics. It allows to
represent the entangled singlet state in separable form. The statistical
correlations between Alice and Bob measurements become self correlations
between hidden spin values for each particle, together with perfect anti
correlation between spin values on the pair. Alice determines through
measurement on her particle the value of spin in some direction. Spin in
another direction is inferred from Bob measurement on the companion. Bell's
inequalities are violated because of the wave like behaviour of quantum
systems. In full analogy with the two slit experiment, interference terms
between spin field components appear determining the contextual character of
quantum distributions of probability.",1607.01153v1
2016-07-16,Measurement of spin pumping voltage separated from extrinsic microwave effects,"Conversions between spin and charge currents are core technologies in recent
spintronics. In this article, we provide methods for estimating inverse spin
Hall effects (ISHEs) induced by using microwave-driven spin pumping (SP) as a
spin-current generator. ISHE and SP induce an electromotive force at the
ferromagnetic or spin-wave resonance, which offers a valuable electric way to
study spin physics in materials. At the resonance, a microwave for exciting the
magnetization dynamics induces an additional electromotive force via rf-current
rectification and thermoelectric effects. We discuss methods to separate the
signals generated from such extrinsic microwave effects by controlling sample
structures and configurations. These methods are helpful in performing accurate
measurements on ISHE induced by SP, enabling quantitative studies on the
conversion between spin and charge currents on various kinds of materials.",1607.04716v1
2018-08-28,An Intrinsic Spin Orbit Torque Nano-Oscillator,"Spin torque and spin Hall effect nanooscillators generate high intensity spin
wave auto oscillations on the nanoscale enabling novel microwave applications
in spintronics, magnonics, and neuromorphic computing. For their operation,
these devices require externally generated spin currents either from an
additional ferromagnetic layer or a material with a high spin Hall angle. Here
we demonstrate highly coherent field and current tunable microwave signals from
nanoconstrictions in single 15 and 20 nm thick permalloy layers. Using a
combination of spin torque ferromagnetic resonance measurements, scanning
microBrillouin light scattering microscopy, and micromagnetic simulations, we
identify the autooscillations as emanating from a localized edge mode of the
nanoconstriction driven by spin orbit torques. Our results pave the way for
greatly simplified designs of auto oscillating nanomagnetic systems only
requiring a single ferromagnetic layer.",1808.09330v1
2019-02-07,Area Propagator and Boosted Spin Networks in Loop Quantum Gravity,"Quantum states of geometry in loop quantum gravity are defined as spin
networks, which are graph dressed with SU(2) representations. A spin network
edge carries a half-integer spin, representing basic quanta of area, and the
standard framework imposes an area matching constraint along the edge: it
carries the same spin at its source and target vertices. In the context of
coarse-graining, or equivalently of the definition of spin networks as
projective limits of graphs, it appears natural to introduce excitations of
curvature along the edges. An edge is then treated similarly to a propagator
living on the links of Feynman diagrams in quantum field theory: curvature
excitations create little loops -- tadpoles -- which renormalize it. This
relaxes the area matching condition, with different spins at both ends of the
edge. We show that this is equivalent to combining the usual SU(2) holonomy
along the edge with a Lorentz boost into SL(2,C) group elements living on the
spin network edges, underlining the fact that the Ashtekar-Barbero connection
carries extrinsic curvature degrees of freedom. This finally leads us to
introduce a new notion of area waves in loop quantum gravity.",1902.02722v2
2020-08-24,Enhancement of Spin-charge Conversion in Dilute Magnetic Alloys by Kondo Screening,"We derive a kinetic theory capable of dealing both with large spin-orbit
coupling and Kondo screening in dilute magnetic alloys. We obtain the collision
integral non-perturbatively and uncover a contribution proportional to the
momentum derivative of the impurity scattering S-matrix. The latter yields an
important correction to the spin diffusion and spin-charge conversion
coefficients, and fully captures the so-called side-jump process without
resorting to the Born approximation (which fails for resonant scattering), or
to otherwise heuristic derivations. We apply our kinetic theory to a quantum
impurity model with strong spin-orbit, which captures the most important
features of Kondo-screened Cerium impurities in alloys such as
La$_{1-x}$Cu$_6$. We find 1) a large zero-temperature spin Hall conductivity
that depends solely on the Fermi wave number and 2) a transverse spin diffusion
mechanism that modifies the standard Fick's diffusion law. Our predictions can
be readily verified by standard spin-transport measurements in metal alloys
with Kondo impurities.",2008.10185v2
2020-08-27,Incommensurate Spin Fluctuations in the Spin-triplet Superconductor Candidate UTe$_2$,"Spin-triplet superconductors are of extensive current interest because they
can host topological state and Majorana ferimons important for quantum
computation. The uranium based heavyfermion superconductor UTe$_2$ has been
argued as a spin-triplet superconductor similar to UGe$_2$, URhGe, and UCoGe,
where the superconducting phase is near (or coexists with) a ferromagnetic (FM)
instability and spin-triplet electron pairing is driven by FM spin
fluctuations. Here we use neutron scattering to show that although UTe$_2$
exhibits no static magnetic order down to 0.3 K, its magnetism is dominated by
incommensurate spin fluctuations near antiferromagnetic (AF) ordering wave
vector and extends to at least 2.6 meV. We are able to understand the dominant
incommensurate spin fluctuations of UTe$_2$ in terms of its electronic
structure calculated using a combined density functional and dynamic mean field
theory.",2008.12377v1
2019-03-06,Weak Localization in Systems with Chiral Spin Textures and Skyrmion Crystals,"Theory of interference-induced quantum corrections to conductivity is
developed for two dimensional systems with chiral spin textures including
skyrmions. The effect of exchange interaction between electrons and spin
textures on weak localization of electronic waves is studied. The spin
dephasing rates are calculated as functions of the spin texture size. The
anomalous magnetoresistance is shown to be governed by the size and
magnetization spatial distribution of the spin textures. The effect of average
magnetization-induced spin splitting on weak localization is analyzed. The
sign-alternating weak-antilocalization magnetoresistance is demonstrated for
skyrmion crystals. We argue that analysis of the low-field magnetoresistance
serves as an independent tool for an experimental detection of chiral spin
textures and, in particular, skyrmions.",1903.02269v1
2020-11-29,Spin Seebeck Effect in Nonmagnetic Excitonic Insulators,"We propose a mechanism of the spin Seebeck effect attributed to excitonic
condensation in a nonmagnetic insulator. We analyze a half-filled two-orbital
Hubbard model with a crystalline field splitting in the strong coupling limit.
In this model, the competition between the crystalline field and electron
correlations brings about an excitonic insulating state, where the two orbitals
are spontaneously hybridized. Using the generalized spin-wave theory and
Boltzmann transport equation, we find that a spin current generated by a
thermal gradient is observed in the excitonic insulating state without magnetic
fields. The spin Seebeck effect originates from spin-split collective
excitation modes although the ground state does not exhibit any magnetic
orderings. This peculiar phenomenon is inherent in the excitonic insulating
state, whose order parameter is time-reversal odd and yields a spin splitting
for the collective excitation modes. We also find that the spin current is
strongly enhanced and its direction is inverted in the vicinity of the phase
transition to another magnetically ordered phase. We suggest that the present
phenomenon is possibly observed in perovskite cobaltites with the
GdFeO$_3$-type lattice distortion.",2011.14337v1
2021-04-07,Acoustically induced coherent spin trapping,"Hybrid spin-optomechanical quantum systems offer high flexibility,
integrability and applicability for quantum science and technology.
Particularly, on-chip surface acoustic waves (SAWs) can efficiently drive spin
transitions in the ground states (GSs) of atomic-scale, color centre qubits,
which are forbidden in case of the more frequently used electromagnetic fields.
Here, we demonstrate that strain-induced spin interactions within their
optically excited state (ES) can exceed by two orders of magnitude the ones
within the GS. This gives rise to novel physical phenomena, such as the
acoustically induced coherent spin trapping (CST) unvealed here. The CST
manifests itself as the spin preservation along one particular direction under
the coherent drive of the GS and ES by the same acoustic field. Our findings
provide new opportunities for the coherent control of spin qubits with
dynamically generated strain fields that can lead towards the realization of
future spin-acoustic quantum devices.",2104.03011v1
2021-04-13,Theory of spin-Hall magnetoresistance in the AC (terahertz) regime,"In bilayers consisting of a normal metal (N) with spin-orbit coupling and a
ferromagnet (F), the combination of the spin-Hall effect, the spin-transfer
torque, and the inverse spin-Hall effect gives a small correction to the
in-plane conductivity of N, which is referred to as spin-Hall magnetoresistance
(SMR). We here present a theory of the SMR and the associated off-diagonal
conductivity corrections for frequencies up to the terahertz regime. We show
that the SMR signal has pronounced singularities at the spin-wave frequencies
of F, which identifies it as a potential tool for all-electric spectroscopy of
magnon modes. A systematic change of the magnitude of the SMR at lower
frequencies is associated with the onset of a longitudinal magnonic
contribution to spin transport across the F-N interface.",2104.06518v2
2021-08-30,Entanglement Limits in Hybrid Spin-Mechanical Systems,"We investigate how to generate continuous-variable entanglement between
distant optomechanical and spin systems, by transferring input two-mode
squeezed vacuum state to the system. Such a setup has been proposed for
backaction evading gravitational-wave measurement, squeezing the output noise
below the standard quantum limit. We find that the spin cavity entanglement
saturates to a particular value when no mechanics are involved even though the
entanglement of the input beam increases steadily, and drops down when the
mechanical oscillator interacts with the cavity. Our study also reveals that
the spin optical readout rate enables the robustness of the spin-cavity
entanglement with input squeezing whereas the optomechanical coupling strength
disables it. The entanglement reaches its maximum when the effective resonance
frequency and bandwidth of the cavity match the spin system. Determining
collective quadrature fluctuations, our analysis also shows that even though
the entanglement between spin and cavity, and cavity and mechanics is
significantly present; it is still impossible to obtain entanglement between
spin and mechanical oscillator.",2108.13216v1
2016-11-15,Spin-Valley Beam Splitter in Graphene,"The fourfold spin-valley degenerate degrees of freedom in bulk graphene can
support rich physics and novel applications associated with multicomponent
quantum Hall effects and linear conductance filtering. In this work, we study
how to break the spin-valley degeneracy of electron beams spatially. We propose
a spin-valley beam splitter in a gated ferromagnetic/pristine/strained graphene
structure. We demonstrate that, in a full resonant tunneling regime for all
spin-valley beam components, the formation of quasi-standing waves can lead
four giant lateral Goos-H\""{a}nchen shifts as large as the transverse beam
width, while the interplay of the two modulated regions can lead difference of
resonant angles or energies for the four spin-valley flavors, manifesting an
effective spin-valley beam splitting effect. The beam splitting effect is found
to be controllable by the gating and strain.",1611.04722v1
2016-12-31,Spin Transport and Accumulation in 2D Weyl Fermion System,"In this work, we study the spin Hall effect and Rashba-Edelstein effect of a
2D Weyl fermion system in the clean limit using the Kubo formalism. Spin
transport is solely due to the spin-torque current in this strongly spin-orbit
coupled (SOC) system, and chiral spin-flip scattering off non-SOC scalar
impurities, with potential strength $V$ and size $a$, gives rise to a
skew-scattering mechanism for the spin Hall effect. The key result is that the
resultant spin-Hall angle has a fixed sign, with $\theta^{SH} \sim O
\left(\tfrac{V^2}{v_F^2/a^2} (k_F a)^4 \right)$ being a strongly-dependent
function of $k_F a$, with $k_F$ and $v_F$ being the Fermi wave-vector and Fermi
velocity respectively. This, therefore, allows for the possibility of tuning
the SHE by adjusting the Fermi energy or impurity size.",1701.00074v3
2017-03-27,Micromagnetic simulations of spin-torque driven magnetisation dynamics with spatially resolved spin transport and magnetisation texture,"We present a simple and fast method to simulate spin-torque driven
magnetisation dynamics in nano-pillar spin-valve structures. The approach is
based on the coupling between a spin transport code based on random matrix
theory and a micromagnetics finite-elements software. In this way the spatial
dependence of both spin transport and magnetisation dynamics is properly taken
into account. Our results are compared with experiments. The excitation of the
spin-wave modes, in- cluding the threshold current for steady state
magnetisation precession and the nonlinear frequency shift of the modes are
reproduced correctly. The giant magneto resistance effect and the magnetisa-
tion switching also agree with experiment. The similarities with recently
described spin-caloritronics devices are also discussed.",1703.08959v2
2020-05-29,Microscopic Theory of the Spin Hall Magnetoresistance,"We consider a microscopic theory for the spin Hall magnetoresistance (SMR).
We generally formulate a spin conductance at an interface between a normal
metal and a magnetic insulator in terms of spin susceptibilities. We reveal
that SMR is composed of static and dynamic parts. The static part, which is
almost independent of the temperature, originates from spin flip caused by an
interfacial exchange coupling. However, the dynamic part, which is induced by
the creation or annihilation of magnons, has an opposite sign from the static
part. By the spin-wave approximation, we predict that the latter results in a
nontrivial sign change of the SMR signal at a finite temperature. In addition,
we derive the Onsager relation between spin conductance and thermal
spin-current noise.",2005.14494v3
2020-12-11,Compositional effect on auto-oscillation behavior of Ni100-xFex/Pt spin Hall nano-oscillators,"We demonstrate the compositional effect on the magnetodynamic and
auto-oscillations properties of Ni100-xFex/Pt (x= 10 to 40) nanoconstriction
based spin Hall nano-oscillators. Using spin-torque ferromagnetic resonance
(ST-FMR) performed on microstrips, we measure a significant reduction in both
damping and spin Hall efficiency with increasing Fe content, which lowers the
spin pumping contribution. The strong compositional effect on spin Hall
efficiency is primarily attributed to the increased saturation magnetization in
Fe-rich devices. As a direct consequence, higher current densities are required
to drive spin-wave auto-oscillations at higher microwave frequencies in Fe-rich
nano-constriction devices. Our results establish the critical role of the
compositional effect in engineering the magnetodynamic and auto-oscillation
properties of spin Hall devices for microwav eand magnonic applications.",2012.06121v2
2021-05-19,Approximations to the spin of close Black-hole-Wolf-Rayet binaries,"Population synthesis studies of binary black-hole mergers often lack robust
black-hole spin estimates as they cannot accurately follow tidal spin-up during
the late black-hole-Wolf-Rayet evolutionary phase. We provide an analytical
approximation of the dimensionless second-born black-hole spin given the binary
orbital period and Wolf-Rayet stellar mass at helium depletion or carbon
depletion. These approximations are obtained from fitting a sample of around
$10^5$ detailed MESA simulations that follow the evolution and spin up of close
black-hole--Wolf-Rayet systems with metallicities in the range
$[10^{-4},1.5Z_\odot]$. Following the potential spin up of the Wolf-Rayet
progenitor, the second-born black-hole spin is calculated using up-to-date core
collapse prescriptions that account for any potential disk formation in the
collapsing Wolf-Rayet star. The fits for second-born black hole spin provided
in this work can be readily applied to any astrophysical modeling that relies
on rapid population synthesis, and will be useful for the interpretation of
gravitational-wave sources using such models.",2105.09077v1
2021-06-21,Filtering states with total spin on a quantum computer,"Starting from a general wave function described on a set of spins/qubits, we
propose several quantum algorithms to extract the components of this state on
eigenstates of the total spin ${\bf S}^2$ and its azimuthal projection $S_z$.
The method plays the role of total spin projection and gives access to the
amplitudes of the initial state on a total spin basis. The different algorithms
have various degrees of sophistication depending on the requested tasks. They
can either solely project onto the subspace with good total spin or completely
uplift the degeneracy in this subspace. After each measurement, the state
collapses to one of the spin eigenstates that could be used for
post-processing. For this reason, we call the method Total Quantum Spin
filtering (TQSf). Possible applications ranging from many-body physics to
random number generators are discussed.",2106.10867v1
2021-07-06,The Spin and Orientation of the Black Hole in XTE J1908$+$094,"NuSTAR observed the black hole candidate XTE J1908$+$094 during its 2013 and
2019 outbursts. We use relativistic reflection to measure the spin of the black
hole through 19 different assumptions of relxill flavors and parameter
combinations. The most favored model in terms of Deviance Information Criterion
(DIC) measures the spin of the black hole to be $a = 0.55^{+0.29}_{-0.45}$, and
an inclination of $\theta=27^{+2}_{-3}$ degrees ($1\sigma$ statistical errors).
We look at the effects of coronal geometry assumptions and density of the
accretion disk on the spin prediction. All 19 tested models provide consistent
spin estimates. We discuss the evolution of spin measurement techniques using
relativistic reflection in X-ray binaries and discuss the implications of this
spin measurement in reconciling the distributions of stellar mass black hole
spin measurements made through X-ray and gravitational wave observations.",2107.02810v1
2021-07-19,Dimensional reduction by geometrical frustration in a cubic antiferromagnet composed of tetrahedral clusters,"Dimensionality is a critical factor in determining the properties of solids
and is an apparent built-in character of the crystal structure. However, it can
be an emergent and tunable property in geometrically frustrated spin systems.
Here, we study the spin dynamics of the tetrahedral cluster antiferromagnet,
pharmacosiderite, via muon spin resonance and neutron scattering. We find that
the spin correlation exhibits a two-dimensional characteristic despite the
isotropic connectivity of tetrahedral clusters made of spin 5/2 Fe3+ ions in
the three-dimensional cubic crystal, which we ascribe to two-dimensionalisation
by geometrical frustration based on spin wave calculations. Moreover, we
suggest that even one-dimensionalisation occurs in the decoupled layers,
generating low-energy and one-dimensional excitation modes, causing large spin
fluctuation in the classical spin system. Pharmacosiderite facilitates studying
the emergence of low-dimensionality and manipulating anisotropic responses
arising from the dimensionality using an external magnetic field.",2107.08735v1
2022-01-22,Elasto-Dynamical Induced Spin and Charge Pumping in Bulk Heavy Metals,"Analogous to the Spin-Hall Effect (SHE), {\it ab initio} electronic structure
calculations reveal that acoustic phonons can induce charge (spin) current
flowing along (normal to) its propagation direction. Using Floquet approach we
have calculated the elastodynamical-induced charge and spin pumping in bulk Pt
and demonstrate that: (i) While the longitudinal charge pumping is an intrinsic
observable, the transverse pumped spin-current has an extrinsic origin that
depends strongly on the electronic relaxation time; (ii) The longitudinal
charge current
  is of nonrelativstic origin, while the transverse spin current is a
relativistic effect that to lowest order scales linearly with the spin-orbit
coupling strength; (iii) both charge and spin pumped currents have parabolic
dependence on the amplitude of the elastic wave.",2201.09121v1
2022-12-15,Identification of acoustically induced spin resonances of Si vacancy centers in 4H-SiC,"The long-lived and optically addressable spin states of silicon vacancies
($\mathrm{V}_\mathrm{Si}$) in 4H-SiC make them promising qubits for quantum
communication and sensing. These color centers can be created in both the
hexagonal (V1) and in the cubic (V2) local crystallographic environments of the
4H-SiC host. While the spin of the V2 center can be efficiently manipulated by
optically detected magnetic resonance at room temperature, spin control of the
V1 centers above cryogenic temperatures has so far remained elusive. Here, we
show that the dynamic strain of surface acoustic waves can overcome this
limitation and efficiently excite magnetic resonances of V1 centers up to room
temperature. Based on the width and temperature dependence of the acoustically
induced spin resonances of the V1 centers, we attribute them to transitions
between spin sublevels in the excited state. The acoustic spin control of both
kinds of $\mathrm{V}_\mathrm{Si}$ centers in their excited states opens new
ways for applications in quantum technologies based on spin-optomechanics.",2212.07704v2
2023-01-25,Self-adjointness of a class of multi-spin-boson models with ultraviolet divergences,"We study a class of quantum Hamiltonian models describing a family of $N$
two-level systems (spins) coupled with a structured boson field of positive
mass, with a rotating-wave coupling mediated by form factors possibly
exhibiting ultraviolet divergences (hence, non-normalizable). Spin-spin
interactions which do not modify the total number of excitations are also
included. Generalizing previous results in the single-spin case, we provide
explicit expressions for the self-adjointness domain and the resolvent operator
of such models, both of them carrying an intricate dependence on both the
spin-field and spin-spin coupling via a family of concatenated propagators.
This construction is also shown to be stable, in the norm resolvent sense,
under approximations of the form factors via normalizable ones, for example an
ultraviolet cutoff.",2301.10694v3
2023-02-04,"Calculating spin-lattice interactions in ferro- and antiferromagnets: the role of symmetry, dimension and frustration","Recently, the interplay between spin and lattice degrees of freedom has
gained a lot of attention due to its importance for various fundamental
phenomena as well as for spintronic and magnonic applications. Examples are
ultrafast angular momentum transfer between the spin and lattice subsystems
during ultrafast demagnetization, frustration driven by structural distortions
in transition metal oxides, or in acoustically driven spin-wave resonances. In
this work, we provide a systematic analysis of spin-lattice interactions for
ferro- and antiferromagnetic materials and focus on the role of lattice
symmetries and dimensions, magnetic order, and the relevance of spin-lattice
interactions for angular momentum transfer as well as magnetic frustration. For
this purpose, we use a recently developed scheme which allows an efficient
calculation of spin-lattice interaction tensors from first principles. In
addition to that, we provide a more accurate and self consistent scheme to
calculate ab initio spin lattice interactions by using embedded clusters which
allows to benchmark the performance of the scheme introduced previously.",2302.02066v2
2023-03-08,Exploring Spin AGP Ansatze for Strongly Correlated Spin Systems,"The antisymmetrized geminal power (AGP), a wave function equivalent to
number-projected Hartree--Fock--Bogoliubov (HFB), and number-projected
Bardeen--Cooper--Schrieffer (BCS) when working in the paired (natural orbitals)
basis, has proven to be an excellent reference for strong pairing interactions.
Several correlation methods have also been applied on top of AGP. In this work,
we show how AGP can also be applied to spin systems by simply basing its
formulation on a spin $su(2)$ algebra. We here implement spin AGP and spin
AGP-based correlation techniques and benchmark them on the XXZ and
$\mathrm{J_1-J_2}$ Heisenberg models, both in 1 and 2 dimensions. Our results
indicate that spin AGP is a promising starting point for modeling spin systems.",2303.04925v4
2023-05-07,Lectures on spintronics and magnonincs,"In this series of lectures, we discuss the basic theoretical concepts of
magnonics and spintronics. We first briefly recall the relevant topics from
quantum mechanics, electrodynamics of continuous media, and basic theory of
magnetism. We then discuss the classical theory of magnetic dynamics:
ferromagnetic and antiferromagnetic resonance, dynamic susceptibilities, and
spin waves. We open the main discussion with phenomena of spin and exchange
spin currents, spin torques, the spin Hall effect, and the spin Hall and Hanle
magnetoresistance. Special emphasis is given to the effects of spin transfer
torque and spin pumping, where we follow the celebrated derivation utilizing
Landauer quantum multi-channel scattering matrix approach. Finally, we outline
the most important features distinguishing antiferromagnetic dynamics from
ferromagnetic one, which make antiferromagnets particularly promising material
candidates for spintronics and magnonics.",2305.04385v1
2023-06-14,Multipolar spin liquid in an exactly solvable model for $j_\mathrm{eff} = \frac{3}{2}$ moments,"We study an exactly solvable model with bond-directional quadrupolar and
octupolar interactions between spin-orbital entangled $j_{\mathrm{eff}} =
\frac{3}{2}$ moments on the honeycomb lattice. We show that this model features
a multipolar spin liquid phase with gapless fermionic excitations. In the
presence of perturbations that break time-reversal and rotation symmetries, we
find Abelian and non-Abelian topological phases in which the Chern number
evaluates to $0$, $\pm 1$, and $\pm 2$. We also investigate quantum phase
transitions out of the multipolar spin liquid using a parton mean-field
approach and orbital wave theory. In the regime of strong
integrability-breaking interactions, the multipolar spin liquid gives way to
ferroquadrupolar-vortex and antiferro-octupolar ordered phases that harbor a
hidden spin-$\frac{1}{2}$ Kitaev spin liquid. Our work unveils mechanisms for
unusual multipolar orders and quantum spin liquids in Mott insulators with
strong spin-orbit coupling.",2306.08624v2
2023-07-12,Chirality-controlled spin scattering through quantum interference,"Chirality-induced spin selectivity has been reported in many experiments, but
a generally accepted theoretical explanation has not yet been proposed. Here,
we introduce a simple model system of a straight cylindrical free-electron
wire, containing a helical string of atomic scattering centers, with spin-orbit
interaction. The advantage of this simple model is that it allows deriving
analytical expressions for the spin scattering rates, such that the origin of
the effect can be easily followed. We find that spin-selective scattering can
be viewed as resulting from constructive interference of partial waves
scattered by the spin-orbit terms. We demonstrate that forward scattering rates
are independent of spin, while back scattering is spin dependent over wide
windows of energy. Although the model does not represent the full details of
electron transmission through chiral molecules, it clearly reveals a mechanism
that could operate in chiral systems.",2307.06201v1
2023-09-26,Constraining the LIGO/Virgo AGN channel with black hole spins,"Merging black holes (BH) are expected to produce remnants with large
dimensionless spin parameters ($a_{\rm spin} \sim 0.7$). However, gravitational
wave (GW) observations with LIGO/Virgo suggest that merging BH are consistent
with modestly positive but not high spin ($a_{\rm spin} \sim 0.2$), causing
tension with models suggesting that high mass mergers are produced by
hierarchical merger channels. Some BH also show evidence for strong in-plane
spin components. Here we point out that \emph{spin down} of BH due to eccentric
prograde post-merger orbits within the gas of an active galactic nucleus (AGN)
disk can yield BH with masses in the upper mass gap, but only modestly positive
$a_{\rm spin}$, and thus observations of BH with low spin \emph{do not} rule
out hierarchical models. We also point out that the fraction of BBH mergers
with significant in-plane spin components is a strong test of interactions
between disk binary black holes (BBH) and nuclear spheroid orbiters. Spin
magnitude and spin tilt constraints from LIGO/Virgo observations of BBH are an
excellent test of dynamics of black holes in AGN disks, disk properties and the
nuclear clusters interacting with AGN.",2309.15213v1
2024-01-20,Phonon-mediated spin transport in quantum paraelectric metals,"The concept of ferroelectricity is now often extended to include continuous
inversion symmetry-breaking transitions in various metals and doped
semiconductors. Paraelectric metals near ferroelectric quantum criticality,
which we term `quantum paraelectric metals,' typically possess soft transverse
optical phonons that have Rashba-type coupling to itinerant electrons in the
presence of spin-orbit coupling. We find through the Kubo formula calculation
that such Rashba electron-phonon coupling has a profound impact on electron
spin transport. While the spin Hall effect arising from non-trivial electronic
band structures has been studied extensively, we find here the presence of the
Rashba electron-phonon coupling can give rise to spin current, including spin
Hall current, in response to an inhomogeneous electric field even with a
completely trivial band structure. Furthermore, this spin conductivity displays
unconventional characteristics, such as quadrupolar symmetry associated with
the wave vector of the electric field and a thermal activation behavior
characterized by scaling laws dependent on the phonon frequency to temperature
ratio. These findings shed light on exotic electronic transport phenomena
originating from ferroelectric quantum criticality, highlighting the intricate
interplay of charge and spin degrees of freedom.",2401.11164v1
2024-02-01,Quantum liquid states of spin solitons in a ferroelectric spin-Peierls state,"In this study, we performed high-magnetic-field magnetization, dielectric,
and ultrasound measurements on an organic salt showing a ferroelectric
spin-Peierls (FSP) state, which is in close proximity to a quantum critical
point. In contrast to the sparsely distributed gas-like spin solitons typically
observed in conventional spin-Peierls (SP) states, the FSP state exhibits dense
liquid-like spin solitons resulting from strong quantum fluctuations, even at
low fields. Nevertheless, akin to conventional SP systems, a
magnetic-field-induced transition is observed in the FSP state. In conventional
high-field SP states, an emergent wave vector results in the formation of a
spin-soliton lattice. However, in the present high-field FSP state, the strong
quantum fluctuations preclude the formation of such a soliton lattice, causing
the dense solitons to remain in a quantum-mechanically melted state. This
observation implies the realization of a quantum liquid--liquid transition of
topological particles carrying spin and charge in a ferroelectric insulator.",2402.00391v1
2024-02-02,Photonic Spin-Orbit Coupling Induced by Deep-Subwavelength Structured Light,"We demonstrate both theoretically and experimentally beam-dependent photonic
spin-orbit coupling in a two-wave mixing process described by an equivalent of
the Pauli equation in quantum mechanics. The considered structured light in the
system is comprising a superposition of two orthogonal spin-orbit-coupled
states defined as spin up and spin down equivalents. The spin-orbit coupling is
manifested by prominent pseudo spin precession as well as
spin-transport-induced orbital angular momentum generation in a photonic
crystal film of wavelength thickness. The coupling effect is significantly
enhanced by using a deep-subwavelength carrier envelope, different from
previous studies which depend on materials. The beam-dependent coupling effect
can find intriguing applications; for instance, it is used in precisely
measuring variation of light with spatial resolution up to 15 nm.",2402.01080v1
2024-02-12,Continuum of spin excitations in an ordered magnet,"Continuum of spin excitations observed in inelastic neutron scattering
experiments are often considered as a strong evidence of quantum spin liquid
formation. When quantum spin liquid is indeed the ground state of a
disorder-free magnetic compound, the elementary excitation is no longer the
conventional spin waves (magnons). Instead, the magnons fractionalize into
spinons, leaving only a two-spinon continuum detectable in inelastic neutron
scattering experiments. For a clean ordered antiferromagnet, it was unclear if
we can observe a continuous spectrum similar to the ones in a quantum spin
liquid state. Here we show that the magnetically ordered state in
Na$_2$BaCo(PO$_4$)$_2$ is able to host a spin excitation continuum induced by
strong quantum fluctuations. Thus, a second thought is necessary when
concluding such continuum as signature of quantum spin liquid in new material
explorations.",2402.07730v1
2024-04-02,Understanding spin currents from magnon dispersion and polarization: Spin-Seebeck effect and neutron scattering study on Tb3Fe5O12,"Magnon spin currents in the ferrimagnetic garnet Tb3Fe5O12 with 4f electrons
were examined through the spin-Seebeck effect and neutron scattering
measurements. The compound shows a magnetic compensation, where the
spin-Seebeck signal reverses above and below Tcomp = 249.5(4) K. Unpolarized
neutron scattering unveils two major magnon branches with finite energy gaps,
which are well-explained in the framework of spin-wave theory. Their
temperature dependencies and the direction of the precession motion of magnetic
moments, i.e. magnon polarization, defined using polarized neutrons, explain
the reversal at Tcomp and decay of the spin-Seebeck signals at low
temperatures. We illustrate an example that momentum- and energy-resolved
microscopic information is a prerequisite to understanding the magnon spin
current.",2404.01603v1
2001-01-22,Threshold electric field in unconventional density waves,"As it is well known most of charge density wave (CDW) and spin density wave
(SDW) exhibit the nonlinear transport with well defined threshold electric
field E_T. Here we study theoretically the threshold electric field of
unconventional density waves. We find that the threshold field increases
monotonically with temperature without divergent behaviour at T_c, unlike the
one in conventional CDW. The present result in the 3D weak pinning limit
appears to describe rather well the threshold electric field observed recently
in the low-temperature phase (LTP) of alpha-(BEDT-TTF)_2KHg(SCN)_4.",0101332v1
2004-11-02,Atom interferometric detection of the pairing order parameter in a Fermi gas,"We propose two interferometric schemes to experimentally detect the onset of
pair condensation in a two spin-component Fermi gas. Two atomic wave-packets
are coherently extracted from the gas at different positions and are mixed by a
matter-wave beam splitter: we show that the spatial long range order of the
atomic pairs in the gas then reflects in the atom counting statistics in the
output channels of the beam splitter. Alternatively, the same long range order
is also shown to create a matter-wave grating in the overlapping region of the
two extracted wave-packets, grating that can be revealed by a light scattering
experiment.",0411059v1
1994-01-19,Hadronic Wave Functions in the Instanton Model,"We study hadronic wave functions using an instanton model for the QCD vacuum.
The wave functions are defined in terms of gauge invariant Bethe Salpeter
amplitudes which we have determined numerically using a Monte Carlo simulation
of the instanton ensemble. We find that the pion and the proton, as well as the
rho meson and the delta have very similar wave functions but observe a sizeable
splitting between mesons or baryons with different spin. We compare our results
with data obtained in lattice gauge simulations.",9401289v1
1999-03-12,About spin precession in electromagnetic wave,"It is shown that two ways of the description of the 1/2-spin precession in a
circularly polarized electromagnetic wave: on the basis of the
Bargmann-Michel-Telegdi equation and on the basis of the Dirac equation with
Pauli term give the same result in the second order on the wave's field for
arbitrary wave length.",9903336v1
2005-01-04,A special non-linear equation of mathematical physics - the equation of the curvilinear electromagnetic wave,"A special non-linear equation of curvilinear electromagnetic wave is
presented. The particularity of this equation lies in the fact that in matrix
form it is mathematically equivalent to the Dirac electron equation. It is
shown that the solution of this is the motion of the plane-polarized
electromagnetic wave on a circular trajectory. It is also shown that such
twirled wave can be considered as a massive charge particle with a spin of one
half, similar to electron. The non-linear equation and its Lagrangian of these
EM particles are founded.",0501009v2
2000-08-17,Wave Packet Echoes in the Motion of Trapped Atoms,"We experimentally demonstrate and systematically study the stimulated revival
(echo) of motional wave packet oscillations. For this purpose, we prepare wave
packets in an optical lattice by non-adiabatically shifting the potential and
stimulate their reoccurence by a second shift after a variable time delay. This
technique, analogous to spin echoes, enables one even in the presence of strong
dephasing to determine the coherence time of the wave packets. We find that for
strongly bound atoms it is comparable to the cooling time and much longer than
the inverse of the photon scattering rate.",0008083v1
2009-04-06,Nonlinear electromagnetic wave equations for superdense magnetized plasmas,"By using the quantum hydrodynamic and Maxwell equations, we derive nonlinear
electron-magnetohydrodynamic (MHD), Hall-MHD, and dust Hall-MHD equations for
dense quantum magnetoplasmas. The nonlinear equations include the
electromagnetic, the electron pressure gradient, as well as the quantum
electron tunneling and electron spin forces. They are useful for investigating
a number of wave phenomena including linear and nonlinear electromagnetic
waves, as well as three-dimensional electromagnetic wave turbulence spectra
arising from the mode coupling processes in dense magnetoplasmas.",0904.0897v1
2009-05-21,Creating traveling waves from standing waves from the gyrotropic paramagnetic properties of Fe$^{3+}$ ions in a high-Q whispering gallery mode sapphire resonator,"We report observations of the gyrotropic change in magnetic susceptibility of
the Fe$^{3+}$ electron paramagnetic resonance at 12.037GHz (between spin states
$|1/2>$ and $|3/2>$) in sapphire with respect to applied magnetic field.
Measurements were made by observing the response of the high-Q Whispering
Gallery doublet (WGH$_{\pm17,0,0}$) in a Hemex sapphire resonator cooled to 5
K. The doublets initially existed as standing waves at zero field and were
transformed to traveling waves due to the gyrotropic response.",0905.3435v1
2010-06-09,Wave Equations for Invariant Infeld-van der Waerden Wave Functions for Photons and Their Physical Significance,"The inner structure of the {\gamma}{\epsilon}-formalisms of Infeld and van
der Waerden admits the occurrence of spin-tensor electromagnetic fields which
bear invariance under the action of the generalized Weyl gauge group. A concise
derivation of the wave equations for such fields is carried out explicitly
along with the construction of a set of torsionless covariant-derivative
expressions. It is emphatically pointed out that the integration of the wave
equations arising herein may under certain circumstances produce significant
insights into the situation concerning the description of some physical
properties of the cosmic microwave background.",1006.1691v1
2010-07-05,Rabi Waves in Carbon Nanotubes - Experiment,"Rabi waves have been experimentally registered for the first time by Raman
scattering studies of zigzag nanotubes, produced by high energy ion beam
modification of natural diamond single crystals. Antiferroelectric spin wave
resonance has been detected for the first time in Raman spectroscopy practice
in given samples. Substantial qualitative and quantitative changes in Raman
spectra in dependence on propagation direction of laser excitation wave have
been found.",1007.0654v2
2011-04-27,Topological density wave states of non-zero angular momentum,"The pseudogap state of high temperature superconductors is a profound
mystery. It has tantalizing evidence of a number of broken symmetry states, not
necessarily conventional charge and spin density waves. Here we explore a class
of more exotic density wave states characterized by topological properties
observed in recently discovered topological insulators. We suggest that these
rich topological density wave states deserve closer attention in not only high
temperature superconductors but in other correlated electron states, as in
heavy fermions.",1104.5053v2
2011-06-27,Exact Piecewise Flat Gravitational Waves,"We generalize our previous linear result [1] in obtaining gravitational waves
from our piecewise flat model for gravity in 3+1 dimensions to exact piecewise
flat configurations describing exact planar gravitational waves. We show
explicitly how to construct a piecewise flat spacetime that describes an
impulsive plane wavefront. From these wavefronts more general plane waves may
be constructed.",1106.5380v2
2013-07-03,Electronic crystals: an experimental overview,"This article reviews the static and dynamic properties of spontaneous
superstructures formed by electrons. Representations of such electronic
crystals are charge density waves and spin density waves in inorganic as well
as organic low dimensional materials. A special attention is paid to the
collective effects in pinning and sliding of these superstructures, and the
glassy properties at low temperature. Charge order and charge
disproportionation which occur in organic materials resulting from correlation
effects are analysed. Experiments under magnetic field, and more specifically
field-induced charge density waves are discussed. Properties of meso- and
nanostructures of charge density waves are also reviewed.",1307.0929v1
2017-12-16,Recent searches for continuous gravitational waves,"Gravitational wave astronomy opened dramatically in September 2015 with the
LIGO discovery of a distant and massive binary black hole coalescence. The more
recent discovery of a binary neutron star merger, followed by a gamma ray burst
and a kilonova, reinforces the excitement of this new era, in which we may soon
see other sources of gravitational waves, including continuous, nearly
monochromatic signals. Potential continuous wave (CW) sources include rapidly
spinning galactic neutron stars and more exotic possibilities, such as emission
from axion Bose Einstein ""clouds"" surrounding black holes. Recent searches in
Advanced LIGO data are presented, and prospects for more sensitive future
searches discussed.",1712.05897v1
2017-05-12,Wave packet dynamics of Bogoliubov quasiparticles: quantum metric effects,"We study the dynamics of the Bogoliubov wave packet in superconductors and
calculate the supercurrent carried by the wave packet. We discover an anomalous
contribution to the supercurrent, related to the quantum metric of the Bloch
wave function. This anomalous contribution is most important for flat or
quasiflat bands, as exemplified by the attractive Hubbard models on the Creutz
ladder and sawtooth lattice. Our theoretical framework is general and can be
used to study a wide variety of phenomena, such as spin transport and exciton
transport.",1705.04542v2
2019-09-10,Evanescent Waves and Superluminal Behavior of Matter,"An evanescent wave is a non-propagating wave with an imaginary wave vector.
In this study, we prove that these are solutions of the tachyon-like Klein
Gordon equation, and that in the tunneling of ultrarelativistic half integer
spin particles they describe superluminal states arising from interactions
between a particle and barrier. These states decay as a particle emerges from
the opposite side of a potential barrier, conserving the same initial energy
but not necessarily the same mass. The obtained theory is applied to the
neutrino, to explain flavor oscillations during free flight and determine the
conditions that maximize the probability of their occurrence.",1909.06180v1
2022-11-03,Properties and Patterns of Polarized Gravitational Waves,"We discuss polarization of gravitational radiation within the standard
framework of linearized general relativity. The recent experimental discovery
of gravitational waves provides the impetus to revisit the implications of the
spin-rotation-gravity coupling for polarized gravitational radiation;
therefore, we consider the coupling of helicity of gravitational waves to the
rotation of an observer or the gravitomagnetic field of a rotating astronomical
source. Observational possibilities regarding polarization-dependent effects in
connection with future gravitational wave detectors are briefly explored.",2211.01691v3
2012-10-02,Localizing the Angular Momentum of Linear Gravity,"In a previous article [Phys. Rev. D 82 104040 (2010)], we derived an
energy-momentum tensor for linear gravity that exhibited positive energy
density and causal energy flux. Here we extend this framework by localizing the
angular momentum of the linearized gravitational field, deriving a
gravitational spin tensor which possesses similarly desirable properties. By
examining the local exchange of angular momentum (between matter and gravity)
we find that gravitational intrinsic spin is localized, separately from orbital
angular momentum, in terms of a gravitational spin tensor. This spin tensor is
then uniquely determined by requiring that it obey two simple physically
motivated algebraic conditions. Firstly, the spin of an arbitrary
(harmonic-gauge) gravitational plane wave is required to flow in the direction
of propagation of the wave. Secondly, the spin tensor of any
transverse-traceless gravitational field is required to be traceless. (The
second condition ensures that local field redefinitions suffice to cast our
gravitational energy-momentum tensor and spin tensor as sources of gravity in a
quadratic approximation to general relativity.) Additionally, the following
properties arise in the spin tensor spontaneously: all transverse-traceless
fields have purely spatial spin, and any field generated by a static
distribution of matter will carry no spin at all. Following the structure of
our previous paper, we then examine the (spatial) angular momentum exchanged
between the gravitational field and an infinitesimal detector, and develop a
microaveraging procedure that renders the process gauge-invariant. The exchange
of nonspatial angular momentum (i.e., moment of energy) is also analyzed,
leading us to conclude that a gravitational wave can displace the center of
mass of the detector; this conclusion is also confirmed by a first principles
treatment of the system. Finally, we discuss...",1210.0831v1
2019-05-01,The inertial wave activity during spin-down in a rapidly penny shaped cylinder. Part II The inertial wave of maximum frequency trigger,"In an earlier paper, Oruba, Soward & Dormy (J.Fluid Mech., vol.818, 2017,
pp.205-240) considered the primary quasi-steady geostrophic (QG) motion of a
constant density fluid of viscosity $\nu$ that occurs during linear spin-down
in a cylindrical container of radius $L$ and height $H$, rotating rapidly
(angular velocity $\Omega$) about its axis of symmetry subject to mixed rigid
and stress-free boundary conditions for the case $L=H$. Direct Numerical
Simulation (DNS) at large $L= 10 H$ and Ekman number $E=\nu/H^2\Omega=10^{-3}$
by Oruba, Soward & Dormy (J.Fluid Mech., sub judice and referred to as Part I)
reveals significant inertial wave activity on the spin-down time-scale. The
analytic study in Part I, based on $E\ll 1$, builds on the results of Greenspan
& Howard (J.Fluid Mech., vol.17, 1963, pp.385-404) for an infinite plane layer
$L\to\infty$. At large but finite distance $r^\dag$ from the symmetry axis, the
meridional (QG-)flow, that causes the QG-spin down, is blocked by the lateral
boundary $r^\dag=L$, which provides the primary QG-trigger for the inertial
waves studied in Part I. For the laterally unbounded layer, Greenspan & Howard
also identified inertial waves of maximum frequency (MF), which are a
manifestation of the transient Ekman layer. The blocking of the MF-waves by the
lateral boundary provides a secondary MF-trigger for yet more inertial waves.
Here we obtain analytic results for the wave activity caused by the
combined-trigger (QG+MF) that faithfully captures the character of the
laterally unbounded base flow including its transients. The results are
compared with the inertial wave part of the DNS (the so called ""filtered DNS""
or simply ""FNS""), for which the agreement is excellent and accounts for minor
discrepancies evident in the Part I results for the QG-trigger.",1905.00481v1
2020-12-20,Tidal response and near-horizon boundary conditions for spinning exotic compact objects,"Teukolsky equations for $|s|=2$ provide efficient ways to solve for curvature
perturbations around Kerr black holes. Imposing regularity conditions on these
perturbations on the future (past) horizon corresponds to imposing an in-going
(out-going) wave boundary condition. For exotic compact objects (ECOs) with
external Kerr spacetime, however, it is not yet clear how to physically impose
boundary conditions for curvature perturbations on their boundaries. We address
this problem using the Membrane Paradigm, by considering a family of fiducial
observers (FIDOs) that float right above the horizon of a linearly perturbed
Kerr black hole. From the reference frame of these observers, the ECO will
experience tidal perturbations due to in-going gravitational waves, respond to
these waves, and generate out-going waves. As it also turns out, if both
in-going and out-going waves exist near the horizon, the Newman Penrose (NP)
quantity $\psi_0$ will be numerically dominated by the in-going wave, while the
NP quantity $\psi_4$ will be dominated by the out-going wave. In this way, we
obtain the ECO boundary condition in the form of a relation between $\psi_0$
and the complex conjugate of $\psi_4$, in a way that is determined by the ECO's
tidal response in the FIDO frame. We explore several ways to modify
gravitational-wave dispersion in the FIDO frame, and deduce the corresponding
ECO boundary condition for Teukolsky functions. We subsequently obtain the
boundary condition for $\psi_4$ alone, as well as for the Sasaki-Nakamura and
Detweiler's functions. As it also turns out, reflection of spinning ECOs will
generically mix between different $\ell$ components of the perturbations
fields, and be different for perturbations with different parities. We also
apply our boundary condition to computing gravitational-wave echoes from
spinning ECOs, and solve for the spinning ECOs' quasi-normal modes.",2012.10842v1
2005-08-09,Many-spin effects in inelastic neutron scattering and electron paramagnetic resonance of molecular nanomagnets,"Many molecular magnetic clusters, such as single-molecule magnets, are
characterized by spin ground states with defined total spin S exhibiting
zero-field-splittings. In this work, the spectroscopic intensities of the
transitions within the ground-state multiplet are analyzed. In particular, the
effects of a mixing with higher-lying spin multiplets, which is produced by
anisotropic interactions and is neglected in the standard single-spin
description, are investigated systematically for the two experimental
techniques of inelastic neutron scattering (INS) and electron paramagnetic
resonance (EPR), with emphasis on the former technique. The spectroscopic
transition intensities are calculated analytically by constructing
corresponding effective spin operators perturbationally up to second order and
consequently using irreducible tensor operator techniques. Three main effects
of spin mixing are observed. Firstly, a pronounced dependence of the INS
intensities on the momentum transfer Q, with a typical oscillatory behavior,
emerges in first order, signaling the many-spin nature of the wave functions in
exchange-coupled clusters. Secondly, as compared to the results of a
first-order calculation, the intensities of the transitions within the spin
multiplet are affected differently by spin mixing. This allows one, thirdly, to
differentiate the higher-order contributions to the cluster magnetic anisotropy
which come from the single-ion ligand-field terms and spin mixing,
respectively. The analytical results are illustrated by means of the three
examples of an antiferromagnetic heteronuclear dimer, the Mn-[3 x 3] grid
molecule, and the single-molecule magnet Mn12.",0508225v1
2007-09-21,Weak and strong coupling limits of the two-dimensional Fröhlich polaron with spin-orbit Rashba interaction,"The continuous progress in fabricating low-dimensional systems with large
spin-orbit couplings has reached a point in which nowadays materials may
display spin-orbit splitting energies ranging from a few to hundreds of meV.
This situation calls for a better understanding of the interplay between the
spin-orbit coupling and other interactions ubiquitously present in solids, in
particular when the spin-orbit splitting is comparable in magnitude with
characteristic energy scales such as the Fermi energy and the phonon frequency.
  In this article, the two-dimensional Fr\""ohlich electron-phonon problem is
reformulated by introducing the coupling to a spin-orbit Rashba potential,
allowing for a description of the spin-orbit effects on the electron-phonon
interaction. The ground state of the resulting Fr\""ohlich-Rashba polaron is
studied in the weak and strong coupling limits of the electron-phonon
interaction for arbitrary values of the spin-orbit splitting. The weak coupling
case is studied within the Rayleigh-Schr\""odinger perturbation theory, while
the strong-coupling electron-phonon regime is investigated by means of
variational polaron wave functions in the adiabatic limit. It is found that,
for both weak and strong coupling polarons, the ground state energy is
systematically lowered by the spin-orbit interaction, indicating that the
polaronic character is strengthened by the Rashba coupling. It is also shown
that, consistently with the lowering of the ground state, the polaron effective
mass is enhanced compared to the zero spin-orbit limit. Finally, it is argued
that the crossover between weakly and strongly coupled polarons can be shifted
by the spin-orbit interaction.",0709.3429v2
2008-02-09,Spin dynamics near the critical doping in weakly-superconducting underdoped YBa2Cu3O6.35 (Tc=18K),"Using neutron scattering we have determined the magnetic structure and
fluctuations in the YBa2Cu3O6.35 superconductor (Tc=18 K). The long-range
ordered collinear spins of the insulating antiferromagnet are replaced by a
commensurate central mode arising from slow, isotropically polarized,
short-range spin correlations. The inelastic spectrum up to 30 meV is broad in
wave vector and commensurate. In contrast to the the resonance peak of higher
Tc superconductors, the spins exhibit a single overdamped spectrum whose rate
of relaxation decreases on cooling and saturates at 5 meV below 50 K. As the
relaxation rate saturates the quasi-static spin correlations grow and become
resolution limited in energy. The spin susceptibility at high temperatures
illustrates that the dominant energy scale is set by the temperature. At low
temperatures, the scale length is geometric and not linked by velocity to
dynamic widths. There is no observable suppression of the spin fluctuations or
central mode upon the onset of superconductivity. The spins respond not to
coherent charge pairs but to hole doping allowing coexistence of glassy short
range spin order with superconductivity. Since the physics of the weakly
superconducting system YBCO6.35 must connect continuously with that in more
strongly superconducting YBCO6.5, we find that neither incommensurate
stripe-like spin modulations nor a well-defined neutron spin resonance are
essential for the onset with doping of pairing in a high temperature cuprate
superconductor.",0802.1252v1
2010-05-14,Conductance oscillations of a spin-orbit stripe with polarized contacts,"We investigate the linear conductance of a stripe of spin-orbit interaction
in a 2D electron gas; that is, a 2D region of length $\ell$ along the transport
direction and infinite in the transverse one in which a spin-orbit interaction
of Rashba type is present. Polarization in the contacts is described by means
of Zeeman fields. Our model predicts two types of conductance oscillations:
Ramsauer oscillations in the minority spin transmission, when both spins can
propagate, and Fano oscillations when only one spin propagates. The latter are
due to the spin-orbit coupling with quasibound states of the non propagating
spin. In the case of polarized contacts in antiparallel configuration Fano-like
oscillations of the conductance are still made possible by the spin orbit
coupling, even though no spin component is bound by the contacts. To describe
these behaviors we propose a simplified model based on an ansatz wave function.
In general, we find that the contribution for vanishing transverse momentum
dominates and defines the conductance oscillations. Regarding the oscillations
with Rashba coupling intensity, our model confirms the spin transistor
behavior, but only for high degrees of polarization. Including a position
dependent effective mass yields additional oscillations due to the mass jumps
at the interfaces.",1005.2480v1
2010-05-31,Fermionic theory for quantum antiferromagnets with spin S > 1/2,"The fermion representation for S = 1/2 spins is generalized to spins with
arbitrary magnitudes. The symmetry properties of the representation is analyzed
where we find that the particle-hole symmetry in the spinon Hilbert space of S
=1/2 fermion representation is absent for S > 1/2. As a result, different path
integral representations and mean field theories can be formulated for spin
models. In particular, we construct a Lagrangian with restored particle-hole
symmetry, and apply the corresponding mean field theory to one dimensional (1D)
S = 1 and S = 3/2 antiferromagnetic Heisenberg models, with results that agree
with Haldane's conjecture. For a S = 1 open chain, we show that Majorana
fermion edge states exist in our mean field theory. The generalization to spins
with arbitrary magnitude S is discussed. Our approach can be applied to higher
dimensional spin systems. As an example, we study the geometrically frustrated
S = 1 AFM on triangular lattice. Two spin liquids with different pairing
symmetries are discussed: the gapped px + ipy-wave spin liquid and the gapless
f-wave spin liquid. We compare our mean field result with the experiment on
NiGa2S4, which remains disordered at low temperature and was proposed to be in
a spin liquid state. Our fermionic mean field theory provide a framework to
study S > 1/2 spin liquids with fermionic spinon excitations.",1005.5626v2
2010-07-07,Edge spin accumulation in a ballistic regime,"We consider a mesoscopic {\it ballistic} structure with Rashba spin-orbit
splitting of the electron spectrum. The ballistic region is attached to the
leads with a voltage applied between them. We calculate the edge spin density
which appears in the presence of a charge current through the structure due to
the difference in populations of electrons coming from different leads.
Combined effect of the boundary scattering and spin precession leads to
oscillations of the edge polarization with the envelope function decaying as a
power law of the distance from the boundary. The problem is solved with the use
of scattering states. The simplicity of the method allows to gain an insight
into the underlaying physics. We clarify the role of the unitarity of
scattering for the problem of edge spin accumulation. In case of a straight
boundary it leads to exact cancellation of all long-wave oscillations of the
spin density. As a result, only the Friedel-like spin density oscillations with
the momentum 2k_F survive. However, this appears to be rather exceptional case.
In general, the smooth spin oscillations with the spin precession length
recover, as it happens, e.g., for the wiggly boundary. We demonstrate also,
that there is no relation between the spin current in the bulk, which is zero
in the considered case, and the edge spin accumulation.",1007.1133v1
2014-08-18,"Neutral Collective Modes in Spin-Polarized Fractional Quantum Hall States at Filling Factors 1/3, 2/5, 3/7, and 4/9","We determine the lowest and higher order collective modes in both
spin-conserving and spin-reversed sectors by calculating energy differences of
the appropriate linear combinations of different levels of
composite-fermion-excitons and the fully spin-polarized ground states at
filling factors $\nu=1/3$, 2/5, 3/7, and 4/9. Apart from providing the detailed
study of previously reported modes that have also been observed in the
experiments, we predict additional higher energy modes at different filling
factors. The lowest and the next higher spin-conserving modes have equal number
of ""magneto-rotons"" and the number is the same as the number of filled
effective Landau-like levels of composite fermions. The higher energy modes at
$\nu =1/3$ merge with the lowest mode at long-wavelength. The spin-conserving
modes do not merge at other filling factors. Apart from showing zero-energy
spin-wave mode at zero momentum, thanks to Larmor's theorem, the lowest
spin-reversed modes at the ferromagnetic ground states of $\nu=2/5$, 3/7, and
4/9 display one or more ""spin-rotons"" at negative energies signalling the
unstable fully polarized ground states at sufficiently small Zeeman energies.
The high energy spin-reversed modes also have spin-rotons but at positive
energies. The energies of these excitations depend on the finite width of the
quantum well as the Coulomb interaction gets screened. We determine finite
thickness correction to the Coulomb interaction by the standard method of local
density approximation and use them to calculate the critical energies such as
rotons, long-wavelength, and short-wavelength modes which are detectable in
inelastic light scattering experiments.",1408.3939v1
2014-11-25,Impact of precession on aligned-spin searches for neutron-star--black-hole binaries,"The inclusion of aligned-spin effects in gravitational-wave search pipelines
for neutron-star--black-hole binary coalescence has been shown to increase the
astrophysical reach with respect to search methods where spins are neglected
completely, under astrophysically reasonable assumptions about black-hole
spins. However, theoretical considerations and population synthesis models
suggest that many of these binaries may have a significant misalignment between
the black-hole spin and the orbital angular momentum, which could lead to
precession of the orbital plane during the inspiral and a consequent loss in
detection efficiency if precession is ignored. This work explores the effect of
spin misalignment on a search pipeline that completely neglects spin effects
and on a recently-developed pipeline that only includes aligned-spin effects.
Using synthetic but realistic data, which could reasonably represent the first
scientific runs of advanced-LIGO detectors, the relative sensitivities of both
pipelines are shown for different assumptions about black-hole spin magnitude
and alignment with the orbital angular momentum. Despite the inclusion of
aligned-spin effects, the loss in signal-to-noise ratio due to precession can
be as large as $40\%$, but this has a limited impact on the overall detection
rate: even if precession is a predominant feature of neutron-star--black-hole
binaries, an aligned-spin search pipeline can still detect at least half of the
signals compared to an idealized generic precessing search pipeline.",1411.6815v2
2015-06-29,Synchronous Spin-Exchange Optical Pumping,"We describe a new approach to precision NMR with hyperpolarized gases
designed to mitigate NMR frequency shifts due to the alkali spin exchange
field. The electronic spin polarization of optically pumped alkali atoms is
square-wave modulated at the noble-gas NMR frequency and oriented transverse to
the DC Fourier component of the NMR bias field. Noble gas NMR is driven by
spin-exchange collisions with the oscillating electron spins. On resonance, the
time-average torque from the oscillating spin-exchange field produced by the
alkali spins is zero. Implementing the NMR bias field as a sequence of alkali
2$ \pi $-pulses enables synchronization of the alkali and noble gas spins
despite a 1000-fold discrepancy in gyromagnetic ratio. We demonstrate this
method with Rb and Xe, and observe novel NMR broadening effects due to the
transverse oscillating spin exchange field. When uncompensated, the
spin-exchange field at high density broadens the NMR linewidth by an order of
magnitude, with an even more dramatic suppression (up to 70x) of the phase
shift between the precessing alkali and Xe polarizations. When we introduce a
transverse compensation field, we are able to eliminate the spin-exchange
broadening and restore the usual NMR phase sensitivity. The projected
quantum-limited sensitivity is better than 1 nHz/$\sqrt{\rm Hz}$.",1506.08797v1
2015-06-30,Precessional instability in binary black holes with aligned spins,"Binary black holes on quasicircular orbits with spins aligned with their
orbital angular momentum have been testbeds for analytic and numerical
relativity for decades, not least because symmetry ensures that such
configurations are equilibrium solutions to the spin-precession equations. In
this work, we show that these solutions can be unstable when the spin of the
higher-mass black hole is aligned with the orbital angular momentum and the
spin of the lower-mass black hole is anti-aligned. Spins in these
configurations are unstable to precession to large misalignment when the binary
separation $r$ is between the values $r_{\rm ud\pm}= (\sqrt{\chi_1} \pm \sqrt{q
\chi_2})^4 (1-q)^{-2} M$, where $M$ is the total mass, $q \equiv m_2/m_1$ is
the mass ratio, and $\chi_1$ ($\chi_2$) is the dimensionless spin of the more
(less) massive black hole. This instability exists for a wide range of spin
magnitudes and mass ratios and can occur in the strong-field regime near
merger. We describe the origin and nature of the instability using recently
developed analytical techniques to characterize fully generic spin precession.
This instability provides a channel to circumvent astrophysical spin alignment
at large binary separations, allowing significant spin precession prior to
merger affecting both gravitational-wave and electromagnetic signatures of
stellar-mass and supermassive binary black holes.",1506.09116v2
2016-05-02,Electrical Detection of Magnetization Dynamics via Spin Rectification Effects,"The purpose of this article is to review the current status of a frontier in
dynamic spintronics and contemporary magnetism, in which much progress has been
made in the past decade, based on the creation of a variety of micro- and
nano-structured devices that enable electrical detection of magnetization
dynamics. The primary focus is on the physics of spin rectification effects,
which are well suited for studying magnetization dynamics and spin transport in
a variety of magnetic materials and spintronic devices. Intended to be
intelligible to a broad audience, the paper begins with a pedagogical
introduction, comparing the methods of electrical detection of charge and spin
dynamics in semiconductors and magnetic materials respectively. After that it
provides a comprehensive account of the theoretical study of both the angular
dependence and line shape of electrically detected ferromagnetic resonance
(FMR), which is summarized in a handbook formate easy to be used for analyzing
experimental data. We then review and examine the similarity and differences of
various spin rectification effects found in ferromagnetic films, magnetic
bilayers and magnetic tunnel junctions, including a discussion of how to
properly distinguish spin rectification from the spin pumping/inverse spin Hall
effect generated voltage. After this we review the broad applications of
rectification effects for studying spin waves, nonlinear dynamics, domain wall
dynamics, spin current, and microwave imaging. We also discuss spin
rectification in ferromagnetic semiconductors. The paper concludes with both
historical and future perspectives, by summarizing and comparing three
generations of FMR spectroscopy which have been developed for studying
magnetization dynamics.",1605.00710v2
2021-10-01,Spin liquid in twisted homobilayers group-VI gichalcogenides,"Twisted transition metal dichalcogenide (TMD) homobilayers have recently
emerged as a powerful platform for studying correlated insulating states. In
the strongly correlated limit, we construct an effective spin Hamiltonian on a
honeycomb lattice that includes the Heisenberg interaction and nonsymmetric
interactions such as a Dzyaloshinskii-Moriya interaction and a Kane-Mele
coupling for the Mott-insulating phase at half-filling. For the twisted TMD
homobilayers, the spin-orbit coupling in the Hubbard model, which is expected
to induce the antisymmetric exchange couplings in the effective spin
Hamiltonian, is a highly tunable and experimentally accessible quantity that
can be tuned by an applied electric field. In this study, we investigate
classical and quantum phase diagrams of the effective spin Hamiltonian using
analytical and numerical methods. We show that the model exhibits a rich
classical phase diagram including an antiferromagnetic (AFM) phase, a planar
spiral ordered phase with high classical degeneracy, a $z$-AFM phase, a
noncoplanar phase, a noncollinear phase, and a 120$^{\circ}$-AFM phase. In the
quantum treatment, we calculate low-energy magnon excitation spectrum, ground
state energy, and static spin structure factor using linear spin-wave theory
and density matrix renormalization group methods to compose the quantum phase
diagram of the effective spin Hamiltonian. Beyond the Heisenberg interaction,
we find that the existence of these antisymmetric couplings is responsible for
the quantum spin liquid, $z$-AFM, noncoplanar, and 120$^{\circ}$ phases.
Twisted TMD homobilayers, therefore, offer rich platforms for realizing rich
phases of matter such as quantum spin liquid, noncoplanar, and 120$^{\circ}$,
resulting from the spin-orbit coupling.",2110.00536v1
2008-06-10,"Spin-orbit effects in Na$_4$Ir$_3$O$_8$, a hyper-kagomé lattice antiferromagnet","We consider spin-orbit coupling effects in Na$_4$Ir$_3$O$_8$, a material in
which Ir$^{4+}$ spins form an hyper-kagom\'{e} lattice, a three-dimensional
network of corner-sharing triangles. We argue that both low temperature
thermodynamic measurements and the impurity susceptibility induced by dilute
substitution of Ti for Ir are suggestive of significant spin-orbit effects.
Because of uncertainties in the crystal-field parameters, we consider two
limits in which the spin-orbit coupling is either weak or strong compared to
the non-cubic atomic splittings. A semi-microscopic calculation of the exchange
Hamiltonian confirms that indeed large antisymmetric Dzyaloshinskii-Moriya (DM)
and/or symmetric exchange anisotropy may be present. In the strong spin-orbit
limit, the Ir-O-Ir superexchange contribution consists of unfrustrated strong
symmetric exchange anisotropy, and we suggest that spin-liquid behavior is
unlikely. In the weak spin-orbit limit, and for strong spin-orbit and direct
Ir-Ir exchange, the Hamiltonian consists of Heisenberg and DM interactions. The
DM coupling is parametrized by a three component DM vector (which must be
determined empirically). For a range of orientation of this vector, frustration
is relieved and an ordered state occurs. For other orientations, even the
classical ground states are very complex. We perform spin-wave and exact
diagonalization calculations which suggest the persistence of a quantum spin
liquid in the latter regime. Applications to Na$_4$Ir$_3$O$_8$ and broader
implications are discussed.",0806.1573v3
2019-01-21,"Edelstein effects, spin-transfer torque, and spin pumping caused by pristine surface states of topological insulators","The Edelstein effect caused by the pristine surface states of
three-dimensional topological insulators is investigated by means of a
semiclassical approach. The combined effect of random impurity scattering and
the spin-momentum locking of the gapless Dirac cone yields a current-induced
surface spin accumulation independent from chemical potential and temperature.
In a nearby ferromagnet that does not make direct contact with the topological
insulator, the bound state nature of the pristine surface state causes a
spin-transfer torque that is entirely field-like, whose magnitude is highly
influenced by the interface cleanliness and the quantum well state of the
ferromagnet. Through incorporating quantum tunneling into Bloch equation, the
spin pumping mediated by the pristine surface state is shown to be described by
the same spin mixing conductance as the spin-transfer torque, and a
semiclassical approach is proposed to explain the inverse Edelstein effect that
converts the spin pumping spin current into a charge current. Consistency of
these results with various experiments will be elaborated in detail.",1901.06953v2
2019-12-16,Dynamics of reconfigurable artificial spin ice: towards magnonic functional materials,"Over the past few years, the study of magnetization dynamics in artificial
spin ices has become a vibrant field of study. Artificial spin ices are
ensembles of geometrically arranged, interacting magnetic nanoislands, which
display frustration by design. These were initially created to mimic the
behavior in rare earth pyrochlore materials and to study emergent behavior and
frustration using two-dimensional magnetic measurement techniques. Recently, it
has become clear that it is possible to create artificial spin ices, which can
potentially be used as functional materials. In this Perspective, we review the
resonant behavior of spin ices (which is in the GHz frequency range), focusing
on their potential application as magnonic crystals. In magnonic crystals, spin
waves are functionalized for logic applications by means of band structure
engineering. While it has been established that artificial spin ices can
possess rich mode spectra, the applicability of spin ices to create magnonic
crystals hinges upon their reconfigurability. Consequently, we describe recent
work aiming to develop techniques and create geometries allowing full
reconfigurability of the spin ice magnetic state. We also discuss experimental,
theoretical, and numerical methods for determining the spectral response of
artificial spin ices, and give an outlook on new directions for reconfigurable
spin ices.",1912.07280v2
2020-05-08,Spin selectivity through time-reversal symmetric helical junctions,"Time-reversal symmetric charge and spin transport through a molecule
comprising two-orbital channels and connected to two leads is analyzed. It is
demonstrated that spin-resolved currents are generated when spin-flip processes
are accompanied by a flip of the orbital channels. This surprising finding does
not contradict Bardarson's theorem [J. H. Bardarson, J. Phys. A: Math. Theor.
41, 405203 (2008)] for two-terminal junctions: the transmission does possess
two pairs of doubly-degenerate eigenvalues as required by the theorem. The
spin-filtering effect is explicitly demonstrated for a two-terminal chiral
molecular junction, modeled by a two-orbital tight-binding chain with
intra-atomic spin-orbit interactions (SOI). In the context of transport through
organic molecules like DNA, this effect is termed ""chirality-induced spin
selectivity"" (CISS). The model exhibits spin-splitting without breaking
time-reversal symmetry: the intra-atomic SOI induces concomitant spin and
orbital flips. Examining these transitions from the point of view of the Bloch
states in an infinite molecule, it is shown that they cause shifts in the Bloch
wave numbers, of the size of the reciprocal single turn, whose directions
depend on the left-and right-handedness of the helix. As a result, spin-up and
spin-down states propagate in the opposite directions, leading to the CISS
effect. To further substantiate our picture, we present an
analytically-tractable expression for the 8$\times$8 scattering matrix of such
a (single) molecule.",2005.04041v2
2021-05-05,Effects of spin-phonon coupling in frustrated Heisenberg models,"The existence and stability of spin-liquid phases represent a central topic
in the field of frustrated magnetism. While a few examples of spin-liquid
ground states are well established in specific models (e.g. the Kitaev model on
the honeycomb lattice), recent investigations have suggested the possibility of
their appearance in several Heisenberg-like models on frustrated lattices. An
important related question concerns the stability of spin liquids in the
presence of small perturbations in the Hamiltonian. In this respect, the
magnetoelastic interaction between spins and phonons represents a relevant and
physically motivated perturbation, which has been scarcely investigated so far.
In this work, we study the effect of the spin-phonon coupling on prototypical
models of frustrated magnetism. We adopt a variational framework based upon
Gutzwiller-projected wave functions implemented with a spin-phonon Jastrow
factor, providing a full quantum treatment of both spin and phonon degrees of
freedom. The results on the frustrated $J_1-J_2$ Heisenberg model on one- and
two-dimensional (square) lattices show that, while a valence-bond crystal is
prone to lattice distortions, a gapless spin liquid is stable for small
spin-phonon couplings. In view of the ubiquitous presence of lattice
vibrations, our results are particularly important to demonstrate the
possibility that gapless spin liquids may be realized in real materials.",2105.02244v2
2021-06-12,Spin pumping and inverse spin Hall effect in CoFeB/C$_{60}$ bilayers,"Pure spin current based research is mostly focused on ferromagnet (FM)/heavy
metal (HM) system. Because of the high spin orbit coupling (SOC) these HMs
exhibit short spin diffusion length and therefore possess challenges for device
application. Low SOC (elements of light weight) and large spin diffusion length
make the organic semiconductors (OSCs) suitable for future spintronic
applications. From theoretical model it is explained that, due to $\pi$ -
$\sigma$ hybridization the curvature of the C$_{60}$ molecules may increase the
SOC strength. Here, we have investigated spin pumping and inverse spin hall
effect (ISHE) in CoFeB/C$_{60}$ bilayer system using coplanar wave guide based
ferromagnetic resonance (CPW-FMR) set-up. We have performed angle dependent
ISHE measurement to disentangle the spin rectification effects for example
anisotropic magnetoresistance, anomalous Hall effect etc. Further, effective
spin mixing conductance (g$_{eff}^{\uparrow\downarrow}$) and spin Hall angle
($\theta_{SH}$) for C$_{60}$ have been reported here. The evaluated value for
$\theta_{SH}$ is 0.055.",2106.06829v2
2021-11-21,Flying electron spin control gates,"The control of ""flying"" (or moving) spin qubits is an important functionality
for the manipulation and exchange of quantum information between remote
locations on a chip. Typically, gates based on electric or magnetic fields
provide the necessary perturbation for their control either globally or at
well-defined locations. Here, we demonstrate the dynamic control of moving
electron spins via contactless gates that move together with the spin. The
concept is realized using electron spins trapped and transported by moving
potential dots defined by a surface acoustic wave (SAW). The SAW strain at the
electron trapping site, which is set by the SAW amplitude, acts as a
contactless, tunable gate that controls the precession frequency of the flying
spins via the spin-orbit interaction. We show that the degree of precession
control in moving dots exceeds previously reported results for unconstrained
transport by an order of magnitude and is well accounted for by a theoretical
model for the strain contribution to the spin-orbit interaction. This flying
spin gate permits the realization of an acoustically driven optical
polarization modulator based on electron spin transport, a key element for
on-chip spin information processing with a photonic interface.",2111.10808v1
2022-12-23,Dropping Anchor: Understanding the Populations of Binary Black Holes with Random and Aligned Spin Orientations,"The relative spin orientations of black holes (BHs) in binaries encode their
evolutionary history: BHs assembled dynamically should have isotropically
distributed spins, while spins of the BHs originating in the field should be
aligned with the orbital angular momentum. In this article, we introduce a
simple population model for these dynamical and field binaries that uses spin
orientations as an anchor to disentangle these two evolutionary channels. We
then analyze binary BH mergers in the Third Gravitational-Wave Transient
Catalog (GWTC-3) and ask whether BHs from the isotropic-spin population possess
different distributions of mass ratio, spin magnitudes, or redshifts from the
preferentially-aligned-spin population. We find no compelling evidence that
binary BHs in GWTC-3 have different source-property distributions depending on
their spin alignment, but we do find that the dynamical and field channels
cannot both have mass-ratio distributions that strongly favor equal masses. We
give an example of how this can be used to provide insights into the various
processes that drive these BHs to merge. We also find that the current
detections are insufficient in extracting differences in spin magnitude or
redshift distributions of isotropic and aligned spin populations.",2212.12113v2
2023-01-03,Binary black hole spins: model selection with GWTC-3,"The origin of the spins of stellar-mass black holes is still controversial,
and angular momentum transport inside massive stars is one of the main sources
of uncertainty. Here, we apply hierarchical Bayesian inference to derive
constraints on spin models from the 59 most confident binary black hole merger
events in the third gravitational-wave transient catalogue (GWTC-3). We
consider up to five parameters: chirp mass, mass ratio, redshift, effective
spin, and precessing spin. For model selection, we use a set of binary
population synthesis simulations spanning drastically different assumptions for
black hole spins and natal kicks. In particular, our spin models range from
maximal to minimal efficiency of angular momentum transport in stars. We find
that, if we include the precessing spin parameter into our analysis, models
predicting only vanishingly small spins are in tension with GWTC-3 data. On the
other hand, models in which most spins are vanishingly small, but that also
include a sub-population of tidally spun-up black holes are a good match to the
data. Our results show that the precessing spin parameter has a crucial impact
on model selection.",2301.01312v3
2012-01-25,Spin-Density-Wave Gap with Dirac Nodes and Two-Magnon Raman Scattering in BaFe2As2,"Raman selection rules for electronic and magnetic excitations in BaFe2As2
were theoretically investigated and applied them to the separate detection of
the nodal and anti-nodal gap excitations at the spin density wave (SDW)
transition and the separate detection of the nearest and the next nearest
neighbor exchange interaction energies. The SDW gap has Dirac nodes, because
many orbitals participate in the electronic states near the Fermi energy. Using
a two-orbital band model the electronic excitations near the Dirac node and the
anti-node are found to have different symmetries. Applying the symmetry
difference to Raman scattering the nodal and anti-nodal electronic excitations
are separately obtained. The low-energy spectra from the anti-nodal region have
critical fluctuation just above TSDW and change into the gap structure by the
first order transition at TSDW, while those from the nodal region gradually
change into the SDW state. The selection rule for two-magnon scattering from
the stripe spin structure was obtained. Applying it to the two-magnon Raman
spectra it is found that the magnetic exchange interaction energies are not
presented by the short-range superexchange model, but the second derivative of
the total energy of the stripe spin structure with respect to the moment
directions. The selection rule and the peak energy are expressed by the
two-magnon scattering process in an insulator, but the large spectral weight
above twice the maximum spin wave energy is difficult to explain by the decayed
spin wave. It may be explained by the electronic scattering of itinerant
carriers with the magnetic self-energy in the localized spin picture or the
particle-hole excitation model in the itinerant spin picture. The magnetic
scattering spectra are compared to the insulating and metallic cuprate
superconductors whose spins are believed to be localized.",1201.5207v1
2015-12-17,Disorder-promoted $C_4$-symmetric magnetic order in iron-based superconductors,"In most iron-based superconductors, the transition to the magnetically
ordered state is closely linked to a lowering of structural symmetry from
tetragonal ($C_{4}$) to orthorhombic ($C_{2}$). However, recently, a regime of
$C_{4}$-symmetric magnetic order has been reported in certain hole-doped
iron-based superconductors. This novel magnetic ground state can be understood
as a double-$\mathbf{Q}$ spin density wave characterized by two order
parameters $\mathbf{M}_{1}$ and $\mathbf{M}_{2}$ related to each of the two
$\mathbf{Q}$ vectors. Depending on the relative orientations of the order
parameters, either a noncollinear spin-vortex crystal or a nonuniform
charge-spin density wave could form. Experimentally, M\""ossbauer spectroscopy,
neutron scattering, and muon spin rotation established the latter as the
magnetic configuration of some of these optimally hole-doped iron-based
superconductors. Theoretically, low-energy itinerant models do support a
transition from single-$\mathbf{Q}$ to double-$\mathbf{Q}$ magnetic order, but
with nearly-degenerate spin-vortex crystal and charge-spin density wave states.
In fact, extensions of these low-energy models including additional electronic
interactions tip the balance in favor of the spin-vortex crystal, in apparent
contradiction with the recent experimental findings. In this paper, we revisit
the phase diagram of magnetic ground states of low-energy multi-band models in
the presence of weak disorder. We show that impurity scattering not only
promotes the transition from $C_{2}$ to $C_{4}$-magnetic order, but it also
favors the charge-spin density wave over the spin-vortex crystal phase.
Additionally, in the single-$\mathbf{Q}$ phase, our analysis of the nematic
coupling constant in the presence of disorder supports the experimental finding
that the splitting between the structural and stripe-magnetic transition is
enhanced by disorder.",1512.05747v1
1996-08-24,Variational state based on the Bethe ansatz solution and a correlated singlet liquid state in the one-dimensional t-J model,"The one-dimensional t-J model is investigated by the variational Monte Carlo
method. A variational wave function based on the Bethe ansatz solution is newly
proposed, where the spin-charge separation is realized, and a long-range
correlation factor of Jastrow-type is included. In most regions of the phase
diagram, this wave function provides an excellent description of the
ground-state properties characterized as a Tomonaga-Luttinger liquid; Both of
the amplitude and exponent of correlation functions are correctly reproduced.
For the spin-gap phase, another trial state of correlated singlet pairs with a
Jastrow factor is introduced. This wave function shows generalized Luther-Emery
liquid behavior, exhibiting enhanced superconducting correlations and
exponential decay of the spin correlation function. Using these two variational
wave functions, the whole phase diagram is determined. In addition, relations
between the correlation exponent and variational parameters in the trial
functions are derived.",9608114v1
1998-08-25,Localization in non-chiral network models for two-dimensional disordered wave mechanical systems,"Scattering theoretical network models for general coherent wave mechanical
systems with quenched disorder are investigated. We focus on universality
classes for two dimensional systems with no preferred orientation: Systems of
spinless waves undergoing scattering events with broken or unbroken time
reversal symmetry and systems of spin 1/2 waves with time reversal symmetric
scattering. The phase diagram in the parameter space of scattering strengths is
determined. The model breaking time reversal symmetry contains the critical
point of quantum Hall systems but, like the model with unbroken time reversal
symmetry, only one attractive fixed point, namely that of strong localization.
Multifractal exponents and quasi-one-dimensional localization lengths are
calculated numerically and found to be related by conformal invariance.
Furthermore, they agree quantitatively with theoretical predictions. For
non-vanishing spin scattering strength the spin 1/2 systems show
localization-delocalization transitions.",9808273v1
2006-02-08,Investigation of the presence of charge order in magnetite by measurement of the spin wave spectrum,"Inelastic neutron scattering results on magnetite (Fe3O4) show a large
splitting in the acoustic spin wave branch, producing a 7 meV gap midway to the
Brillouin zone boundary at q = (0,0,1/2) and E = 43 meV. The splitting occurs
below the Verwey transition temperature, where a metal-insulator transition
occurs simultaneously with a structural transformation, supposedly caused by
the charge ordering on the iron sublattice. The wavevector (0,0,1/2)
corresponds to the superlattice peak in the low symmetry structure. The
dependence of the magnetic superexchange on changes in the crystal structure
and ionic configurations that occur below the Verwey transition affect the spin
wave dispersion. To better understand the origin of the observed splitting, we
have constructed a series of Heisenberg models intended to reproduce the
pairwise variation of the magnetic superexchange arising from both small
crystalline distortions and charge ordering. We find that none of the models
studied predicts the observed splitting, whose origin may arise from
charge-density wave formation or magnetoelastic coupling.",0602214v1
2006-09-30,Ground and excited states of spinor Fermi gases in tight waveguides and the Lieb-Liniger-Heisenberg model,"The ground and excited states of a one-dimensional (1D) spin-1/2 Fermi gas
(SFG) with both attractive zero-range odd-wave interactions and repulsive
zero-range even-wave interactions are mapped exactly to a 1D
Lieb-Liniger-Heisenberg (LLH) model with delta-function repulsions depending on
isotropic Heisenberg spin-spin interactions, such that the complete SFG and LLH
energy spectra are identical. The ground state in the ferromagnetic phase is
given exactly by the Lieb-Liniger (LL) Bethe ansatz, and that in the
antiferromagnetic phase by a variational method combining Bethe ansatz
solutions of the LL and 1D Heisenberg models. There are excitation branches
corresponding to LL type I and II phonons and spin waves, the latter behaving
quadratically for small wave number in the ferromagnetic phase and linearly in
the antiferromagnetic phase.",0610016v1
2004-03-02,How to lasso a plane gravitational wave,"Beginning with the stress-energy tensor of an elastic string this paper
derives a relativistic string and its form in a parallel transported Fermi
frame including its reduction in the Newtonian limit to a Cosserat string. In a
Fermi frame gravitational curvature is seen to induce three dominant relative
acceleration terms dependent on: position, velocity and position, strain and
position, respectively. An example of a string arranged in an axially flowing
ring (a lasso) is shown to have a set of natural frequencies that can be
parametrically excited by a monochromatic plane gravitational wave. The lasso
also exhibits, in common with spinning particles, oscillation about geodesic
motion in proportion to spin magnitude and wave amplitude when the spin axis
lies in the gravitational wave front. Coordinate free notation is used
throughout including the development of the properties of the Fermi frame.",0403010v1
1998-02-18,The nucleon wave function in light-front dynamics,"The general spin structure of the relativistic nucleon wave function in the
$3q$-model is found. It contains 16 spin components, in contrast to 8 ones
known previously, since in a many-body system the parity conservation does not
reduce the number of the components. The explicitly covariant form of the wave
function automatically takes into account the relativistic spin rotations,
without introducing any Melosh rotation matrices. It also reduces the
calculations to the standard routine of the Dirac matrices and of the trace
techniques. In examples of the proton magnetic moment and of the axial nucleon
form factor, with a particular wave function, we reproduce the results of the
standard approach. Calculations beyond the standard assumptions give different
results.",9802053v1
2007-08-28,Exact density matrix of the Gutzwiller wave function: II. Minority spin component,"The density matrix, i.e. the Fourier transform of the momentum distribution,
is obtained analytically for all magnetization of the Gutzwiller wave function
in one dimension with exclusion of double occupancy per site. The present
result complements the previous analytic derivation of the density matrix for
the majority spin. The derivation makes use of a determinantal form of the
squared wave function, and multiple integrals over particle coordinates are
performed with the help of a diagrammatic representation. In the thermodynamic
limit, the density matrix at distance x is completely characterized by
quantities v_c x and v_s x, where v_s and v_c are spin and charge velocities in
the supersymmetric t-J model for which the Gutzwiller wave function gives the
exact ground state. The present result then gives the exact density matrix of
the t-J model for all densities and all magnetization at zero temperature.
Discontinuity, slope, and curvature singularities in the momentum distribution
are identified. The momentum distribution obtained by numerical Fourier
transform is in excellent agreement with existing result.",0708.3773v1
2008-12-17,Variational RVB wave function for the spin-1/2 Heisenberg Model on honeycomb lattice,"In this work, a long-range resonating valence bond state is proposed as a
variational wave function for the ground state of the $S=1/2$ antiferromagnetic
Heisenberg model on the honeycomb lattice. Employing Variational Monte Carlo
(VMC) method, we show that the ground state energy obtained from such RVB wave
function, lies well below the energy of the N\'eel state and compares very well
to the energies evaluated from spin-wave theory and series expansion method. We
also obtain the spin-spin correlation function along zig-zag and armchair
directions and find that the two correlations are different, which indicates
the anisotropic nature of the system. We compare our results with the square
lattice and we show that although the quantum fluctuations on honeycomb lattice
are much stronger, but do not completely destroy the magnetic order.",0812.3229v1
2010-08-12,Singlet versus triplet particle-hole condensates in quantum oscillations in cuprates,"Quantum oscillations in a tilted magnetic field offer the possibility of
distinguishing singlet versus triplet order parameters in the particle hole
channel provided the measurements reflect a putative ``normal'' state of a
density wave obtained by applying by high magnetic field at low temperatures. A
theoretical analysis is given that compares spin density wave, a singlet
$d$-density wave, and a triplet $d$-density wave. While the existence of a spin
zero in the oscillation amplitude is a necessary consequence of a singlet order
parameter, a triplet order parameter may or may not exhibit a spin zero, making
it a quantitative issue that depends on the actual extremal orbits on the Fermi
surface. Nonetheless, a theoretical analysis can shed light on the striking
recent measurements in $\mathrm{YBa_{2}Cu_{3}O_{6+\delta}}$.",1008.2030v3
2010-09-21,Entanglement of light-shift compensated atomic spin waves with telecom light,"Entanglement of a 795 nm light polarization qubit and an atomic Rb spin wave
qubit for a storage time of 0.1 s is observed by measuring the violation of
Bell's inequality (S = 2.65 \pm 0.12). Long qubit storage times are achieved by
pinning the spin wave in a 1064 nm wavelength optical lattice, with a
magic-valued magnetic field superposed to eliminate lattice-induced dephasing.
Four-wave mixing in a cold Rb gas is employed to perform light qubit conversion
between near infra red (795 nm) and telecom (1367 nm) wavelengths, and after
propagation in a telecom fiber, to invert the conversion process. Observed Bell
inequality violation (S = 2.66 \pm 0.09), at 10 ms storage, confirms
preservation of memory/light entanglement through the two stages of light qubit
frequency conversion.",1009.4180v1
2011-09-02,Spherical waves of spin 1 particle in anti de Sitter space-time,"Three possible techniques to deal with a vector particle in the anti de
Sitter cosmological model are viewed: Duffin-Kemmer-Petiau matrix formalism
based on the general tetrad recipe, group theory 5-dimensional approach based
on the symmetry group SO(3.2), anda tetrad form of Maxwell equations in complex
Riemann-Silberstein-Majorana-Oppenheimer representation. In the first part, a
spin 1 massive field is considered in static coordinates of the anti de Sitter
space-time in tetrad-based approach. The complete set of spherical wave
solutions with quantum numbers (\epsilon, j,m,l) is constructed; angular
dependence in wave functions is described with the help of Wigner functions.
The energy quantization rule has been found. Transition to massless case of
electromagnetic field is specified, and electromagnetic solutions in Lorentz
gauge have been constructed. In the second part, the problem of a particle with
spin 1 is considered on the base of 5-dimensional wave equation specified in
the same static coordinates. In the third part, a rarely used approach, based
on tetrad form of Maxwell equations in complex representation is examined in
the anti de Sitter model.",1109.0387v1
2011-09-23,Spin waves in a skyrmion crystal,"We derive the spectrum of low-frequency spin waves in skyrmion crystals
observed recently in noncentrosymmetric ferromagnets. We treat the skyrmion
crystal as a superposition of three helices whose wavevectors form an
equilateral triangle. The low-frequency spin waves are Goldstone modes
associated with displacements of skyrmions. Their dispersion is determined by
the elastic properties of the skyrmion crystal and by the kinetic terms of the
effective Lagrangian, which include both kinetic energy and a Berry-phase term
reflecting a nontrivial topology of magnetization. The Berry-phase term acts
like an effective magnetic field, mixing longitudinal and transverse vibrations
into a gapped cyclotron mode and a twist wave with a quadratic dispersion.",1109.4990v3
2012-01-02,Localized domain-wall excitations in patterned magnetic dots probed by broadband ferromagnetic resonance,"We investigate the magnetization dynamics in circular Permalloy dots with
spatially separated magnetic vortices interconnected by domain walls (double
vortex state). We identify a novel type of quasi one-dimensional (1D) localised
spin wave modes confined along domain walls, connecting each of two vortex
cores with two edge half-antivortices. Variation of the mode eigenfrequencies
with the dot size is in quantitative agreement with the developed model, which
considers a dipolar origin of the localized 1D spin waves or so-called
Winter\'s magnons [J.M. Winter, Phys.Rev. 124, 452 (1961)]. These spin waves
are analogous to the displacement waves of strings, and could be excited in a
wide class of patterned magnetic nanostructures possessing domain walls, namely
in triangular, square, circular or elliptic magnetic dots.",1201.0482v1
2012-06-07,"Hybridization of electromagnetic, spin and acoustic waves in magnetic having conical spiral ferromagnetic order","The spectrum of hybrid electromagnetic-spin-acoustic waves for magnetic
having conical spiral ferromagnetic structure defined by heterogeneous exchange
and relativistic interactions have been received. The possibility of resonant
interaction of spin, electromagnetic and acoustic waves has been shown. The
electromagnetic waves reflectance from the half-infinity layer of magnetic
having conical spiral ferromagnetic order has been calculated for different
values of external magnetic field (angle of spiral). The acoustic Faradey
effect has been considered.",1206.1421v2
2013-04-08,Intrinsic and extrinsic mirror symmetry breaking in anti-dot spin-wave waveguides,"We theoretically study the spin-wave spectra in magnonic waveguides
periodically patterned with square anti-dots in nanoscale with pinned
magnetization at the edges. We show that the breaking of the mirror symmetry of
the waveguide by the structural changes can result in a magnonic band gap
closing. These intrinsic symmetry breaking can be compensated by properly
chosen asymmetric external bias magnetic field, i.e. in an extrinsic way. As a
result the magnonic gaps existing in the ideal symmetric structure can be
recovered. The model used for the explanation also suggests that this idea
could be generic both for exchange and dipolar interaction regimes of
spin-waves and also for other types of waves, e.g., electrons in the graphene
ribbons.",1304.1799v1
2015-01-30,Spin and pair density wave glasses,"Spontaneous breaking of translational symmetry---known as `density wave'
order---is common in nature. However such states are strongly sensitive to
impurities or other forms of frozen disorder leading to fascinating glassy
phenomena. We analyze impurity effects on a particularly ubiquitous form of
broken translation symmetry in solids: a Spin Density Wave (SDW) with spatially
modulated magnetic order. Related phenomena occur in Pair Density Wave (PDW)
superconductors where the superconducting order is spatially modulated. For
weak disorder, we find that the SDW / PDW order can generically give way to a
SDW / PDW glass---new phases of matter with a number of striking properties,
which we introduce and characterize here. In particular, they exhibit an
interesting combination of conventional (symmetry-breaking) and spin glass
(Edwards-Anderson) order. This is reflected in the dynamic response of such a
system, which---as expected for a glass---is extremely slow in certain
variables, but---surprisingly---is fast in others. Our results apply to all
uniaxial metallic SDW systems where the ordering vector is incommensurate with
the crystalline lattice. In addition, the possibility of a PDW glass has
important consequences for some recent theoretical and experimental work on
$La_{2-x}Ba_xCu_2O_4$.",1502.00002v1
2015-07-09,Competition between excitonic charge and spin density waves: Influence of electron-phonon and Hund's rule couplings,"We analyze the stability of excitonic ground states in the two-band Hubbard
model with additional electron-phonon and Hund's rule couplings using a
combination of mean-field and variational cluster approaches. We show that both
the interband Coulomb interaction and the electron-phonon interaction will
cooperatively stabilize a charge density wave (CDW) state which typifies an
""excitonic"" CDW if predominantly triggered by the effective interorbital
electron-hole attraction or a ""phononic"" CDW if mostly caused by the coupling
to the lattice degrees of freedom. By contrast, the Hund's rule coupling
promotes an excitonic spin density wave. We determine the transition between
excitonic charge and spin density waves and comment on a fixation of the phase
of the excitonic order parameter that would prevent the formation of a
superfluid condensate of excitons. The implications for exciton condensation in
several material classes with strongly correlated electrons are discussed.",1507.02494v2
2015-09-22,A semianalytic Fisher matrix for precessing binaries with a single significant spin,"Gravitational waves from a binary with a single dynamically significant spin,
notably including precessing black hole-neutron star (BH-NS) binaries, let us
constrain that binary's properties: the two masses and the dominant black hole
spin. Based on a straightforward fourier transform of $h(t)$ enabled by the
corotating frame, we show the Fisher matrix for precessing binaries can be
well-approximated by an extremely simple semianalytic approximation. This
approximation can be easily understood as a weighted average of independent
information channels, each associated with one gravitational wave harmonic.
Generalizing previous studies of nonprecessing binaries to include critical
symmetry-breaking precession effects required to understand plausible
astrophysical sources, our ansatz can be applied to address how well
gravitational wave measurements can address a wide range of astrophysical and
fundamental questions. Our approach provides a simple method to assess what
parameters gravitational wave detectors can measure, how well, and why.",1509.06581v1
2016-10-31,Quantum hydrodynamics in the rotating reference frame,"In this paper we apply quantum hydrodynamics (QHD) to study the quantum
evolution of a system of spinning particles and particles that have the
electric dipole moments EDM in the rotating reference frame. The method
presented is based on the many-particle microscopic Schrodinger equation in the
rotating reference frame. Fundamental QHD equations for charged or neutral
spinning and EDM-bearing particles were shaped due to this method and contain
the spin-dependent inertial force field. The polarization dynamics in systems
of neutral particles in the rotating frame is shown to cause formation of a new
type of waves, the dipole-inertial waves. We have analyzed elementary
excitations in a system of neutral polarized fluids placed into an external
electric field in 2D and 3D cases. We predict the novel type of 2D
dipole-inertial wave and 3D - polarization wave modified by rotation in systems
of particles with dipole-dipole interactions.",1610.09848v1
2017-08-26,Subwavelength and directional control of flexural waves in zone-folding induced topological plates,"Inspired by the quantum spin Hall effect shown by topological insulators, we
propose a plate structure that can be used to demonstrate the pseudo-spin Hall
effect for flexural waves. The system consists of a thin plate with
periodically arranged resonators mounted on its top surface. We extend a
technique based on the plane wave expansion method to identify a double Dirac
cone emerging due to the zone-folding in frequency band structures. This
particular design allows us to move the double Dirac cone to a lower frequency
than the resonating frequency of local resonators. We then manipulate the
pattern of local resonators to open subwavelength Bragg band gaps that are
topologically distinct. Building on this method, we verify numerically that a
waveguide at an interface between two topologically distinct resonating plate
structures can be used for guiding low-frequency, spin-dependent one-way
flexural waves along a desired path with bends.",1708.07994v2
2018-01-29,Topological spin-Hall edge states of flexural wave in perforated metamaterial plates,"This paper investigates the pseudo-spin based edge states for flexural waves
in a honeycomb perforated phononic plate, which behaves an elastic analogue of
the quantum spin Hall effect. We utilize finite element method to analyse the
dispersion for flexural waves based on Mindlin's plate theory. Topological
transition takes place around a double Dirac cone at $\Gamma$ point by
adjusting the sizes of perforated holes. We develop an effective Hamiltonian to
describe the bands around the two doubly degenerated states and analyse the
topological invariants. This further leads us to observe the topologically
protected edge states localized at the interface between two lattices. We
demonstrate the unidirectional propagation of the edge waves along topological
interface, as well as their robustness against defects and sharp bends.",1801.09558v3
2018-06-05,Backscattering immunity of dipole-exchange magnetostatic surface spin waves,"The existence of backscattering-immune spin-wave modes is demonstrated in
magnetic thin films of nano-scale thickness. Our results reveal that chiral
Magneto Static Surface Waves (cMSSWs), which propagate perpendicular to the
magnetization direction in an in-plane magnetized thin film, are robust against
backscattering from surface defects. cMSSWs are protected against various types
of surface inhomogeneities and defects as long as their frequency lies inside
the gap of the volume modes. Our explanation is independent of the topology of
the modes and predicts that this robustness is a consequence of symmetry
breaking of the dynamic magnetic fields of cMSSWs due to the off-diagonal part
of the dipolar interaction tensor, which is present both for long- (dipole
dominated) and short-wavelength (exchange dominated) spin waves. Micromagnetic
simulations confirm the robust character of the cMSSWs. Our results open a new
direction in designing highly efficient magnonic logic elements and devices
employing cMSSWs in nano-scale thin films.",1806.01554v3
2018-11-15,Pair Density Wave in the Doped $t$-$J$ Model with Ring Exchange on a Triangular Lattice,"In our previous work [arXiv:1803.00999, Phys. Rev. Lett. 121, 046401 (2018)],
we found a quantum spin liquid phase with a spinon Fermi surface in the two
dimensional spin-1/2 Heisenberg model with four-spin ring exchange on a
triangular lattice. In this work we dope the spinon Fermi surface phase by
studying the $t$-$J$ model with four-spin ring exchange. We perform density
matrix renormalization group calculations on four-leg cylinders of a triangular
lattice and find that the dominant pair correlation function is that of a pair
density wave; i.e., it is oscillatory while decaying with distance with a power
law. The doping dependence of the period is studied. This is the first example
where pair density wave is the dominant pairing in a generic strongly
interacting system where the pair density wave cannot be explained as a
composite order and no special symmetry is required.",1811.06538v3
2018-07-31,Fresnel diffraction of spin waves,"The propagation of magnetostatic forward volume waves excited by a
constricted coplanar waveguide is studied via inductive spectroscopy
techniques. A series of devices consisting of pairs of sub-micrometer size
antennae is used to perform a discrete mapping of the spin wave amplitude in
the plane of a 30-nm thin YIG film. We found that the spin wave propagation
remains well focused in a beam shape of width comparable to the constriction
length and that the amplitude within the constriction displays oscillations,
two features which are explained in terms of near-field Fresnel diffraction
theory.",1807.11754v1
2018-02-28,Multigap Superconductivity in a charge density wave superconductor LaPt2Si2,"The superconducting gap structure of a charge density wave (CDW)
superconductor LaPt$_2$Si$_2$ ($T_c$ = 1.6~K) having a quasi two dimensional
crystal structure has been investigated using muon spin rotation/relaxation
($\mu$SR) measurements carried out in transverse field (TF), zero field (ZF)
and longitudinal field (LF) geometries. Rigorous analysis of TF-$\mu$SR spectra
in the superconducting state corroborates that the temperature dependence of
the effective penetration depth, $\lambda_L$, derived from muon spin
depolarization, fits to an isotropic $s+s-$wave model suggesting that the Fermi
surface contains two gaps of different magnitude rather than an isotropic gap
expected for a conventional $s-$wave superconductor. On the other hand, ZF
$\mu$SR data do not show any significant change in muon spin relaxation rate
above and below the superconducting transition indicating the fact that
time-reversal symmetry is preserved in the system.",1802.10414v2
2018-08-23,Stationary and non-stationary solutions of the evolution equation for neutrino in matter,"We study solutions of the equation which describes the evolution of a
neutrino propagating in dense homogeneous medium in the framework of the
quantum field theory. In the two-flavor model the explicit form of Green
function is obtained, and as a consequence the dispersion law for a neutrino in
matter is derived. It is shown that there exist both the solutions describing
the stationary states and the solutions describing the spin-flavor coherent
states of the neutrino. The stationary states may be different from the mass
eigenstates, and the wave function of a state with a definite flavor should be
constructed as a linear combination of the wave functions of the stationary
states with coefficients, which depend on the mixing angle in matter. In the
ultra-relativistic limit the wave functions of the spin-flavor coherent states
coincide with the solutions of the quasi-classical evolution equation.
Quasi-classical approximation of the wave functions of spin-flavor coherent
states is used to calculate the probabilities of transitions between neutrino
states with definite flavor and helicity.",1808.07926v2
2020-03-01,Backward magnetostatic surface spin waves in exchange coupled Co/FeNi bilayers,"Propagation of backward magnetostatic surface spin waves (SWs) in exchange
coupled Co/FeNi bilayers are studied by using Brillouin light scattering (BLS)
technique. Two types of SWs modes were identified in our BLS measurements. They
are magnetostatic surface waves (MSSWs) mode and perpendicular standing spin
waves (PSSWs) mode. The dispersion relations of MSSWs obtained from the Stokes
and Anti-Stokes measurements display respectively positive and negative group
velocities. The Anti-Stokes branch with positive phase velocities and negative
group velocities, known as backward magnetostatic surface mode originates from
the magnetostatic interaction of the bilayer. The experimental data are in good
agreement with the theoretical calculations. Our results are useful for
understanding the SWs propagation and miniaturizing SWs storage devices.",2003.00481v1
2020-03-04,Spin-wave Talbot effect in thin ferromagnetic film,"The Talbot effect has been known in optics since XIX century and found
various technological applications. In this paper, we demonstrate with the help
of micromagnetic simulations this self-imaging phenomenon for spin waves
propagating in a thin ferromagnetic film magnetized out-of-plane. We show that
the main features of the obtained Talbot carpets for spin waves can be
described, to a large extent, by the approximate analytical formulas yielded by
the general analysis of the wave phenomena. Our results indicate a route to a
feasible experimental realisation of the Talbot effect at low and high
frequencies and offer interesting effects and possible applications in
magnonics.",2003.02138v2
2021-04-14,Coexistence of vortex arrays and surface capillary waves in spinning prolate superfluid He-4 nanodroplets,"Within Density Functional Theory, we have studied the interplay between
vortex arrays and capillary waves in spinning prolate He-4 droplets made of
several thousands of helium atoms. Surface capillary waves are ubiquitous in
prolate superfluid He-4 droplets and, depending on the size and angular
momentum of the droplet, they may coexist with vortex arrays. We have found
that the equilibrium configuration of small prolate droplets is vortex-free,
evolving towards vortex-hosting as the droplet size increases. This result is
in agreement with a recent experiment [S.M. O'Connell et al., Phys. Rev. Lett.
124, 215301 (2020)], where it has been disclosed that vortex arrays and
capillary waves coexist in the equilibrium configuration of very large drops.
Contrarily to viscous droplets executing rigid body rotation, the stability
phase diagram of spinning He-4 droplets cannot be universally described in
terms of dimensionless angular momentum and angular velocity variables:
instead, the rotational properties of superfluid helium droplets display a
clear dependence on the droplet size and the number of vortices they host.",2104.06712v2
2021-10-11,Gravitational-wave population inference at past time infinity,"Population studies of stellar-mass black-hole binaries have become major
players in gravitational-wave astronomy. The underlying assumptions are that
the targeted source parameters refer to the same quantities for all events in
the catalog and are included when modeling selection effects. Both these points
have so far been neglected when estimating the orientations of the black-hole
spins. In particular, the detector-frame gravitational-wave frequency used to
define frequency-dependent quantities (e.g., 20 Hz) introduces an inconsistent
reference between events at the population level. We solve both issues by
modeling binary black-hole populations and selection effects at past time
infinity, corresponding to the well-defined reference frequency of 0 Hz. We
show that, while current gravitational-wave measurement uncertainties obfuscate
the influence of reference frequency in population inference, ignoring spins
when estimating selection effects leads to an over-prediction of spin alignment
in the underlying astrophysical distribution of merging black holes.",2110.05507v2
2017-01-17,Mutually attracting spin waves in the square-lattice quantum antiferromagnet,"The Heisenberg model for S=1/2 describes the interacting spins of electrons
localized on lattice sites due to strong repulsion. It is the simplest
strong-coupling model in condensed matter physics with wide-spread
applications. Its relevance has been boosted further by the discovery of curate
high-temperature superconductors. In leading order, their undoped parent
compounds realize the Heisenberg model on square-lattices. Much is known about
the model, but mostly at small wave vectors, i.e., for long-range processes,
where the physics is governed by spin waves (magnons), the Goldstone bosons of
the long-range ordered antiferromagnetic phase. Much less, however, is known
for short-range processes, i.e., at large wave vectors. Yet these processes are
decisive for understanding high-temperature superconductivity. Recent reports
suggest that one has to resort to qualitatively different fractional
excitations, spinons. By contrast, we present a comprehensive picture in terms
of dressed magnons with strong mutual attraction on short length scales. The
resulting spectral signatures agree strikingly with experimental data",1701.04730v2
2017-01-31,Spin waves in planar quasicrystal of Penrose tiling,"We investigated two-dimensional magnonic structures which are the
counterparts of photonic quasicrystals forming Penrose tiling. We considered
the slab composed of Ni (or Py) disks embedded in Fe (or Co) matrix. The disks
were arranged in quasiperiodic Pernose-like structure. The infinite
quasicrystal was approximated by its rectangular section with periodic boundary
conditions applied. This approach allowed us to use the plane wave method to
find the frequency spectrum of eigenmodes for spin waves and their spatial
profiles. The calculated integrated density of states shows more distictive
magnonic gaps for the structure composed of materials of high magnetic contrast
(Ni and Fe) and relatively high filling fraction. This proves the impact of
quasiperiodic long-range order on the spectrum of spin waves. We also
investigated the localization of SW eingenmodes resulting from the
quasipeiodicity of the structure.",1701.09125v1
2019-01-17,Magnonic band structure in a Co/Pd stripe domain system investigated by Brillouin light scattering and micromagnetic simulations,"By combining Brillouin Light Scattering and micromagnetic simulations we
studied the spin-wave dynamics of a Co/Pd thin film multilayer, features a
stripe domain structure at remanence. The periodic up and down domains are
separated by cork-screw type domain walls. The existence of these domains
causes a scattering of the otherwise bulk and surface spin-wave modes, which
form mode families, similar to a one dimensional magnonic crystal. The
dispersion relation and mode profiles of spin waves are measured for
transferred wave vector parallel and perpendicular to the domain axis.",1901.05985v1
2019-04-12,High-efficiency terahertz spin-decoupled meta-coupler for spoof surface plasmon excitation and beam steering,"Spoof surface plasmon (SSP) meta-couplers that efficiently integrate other
diversified functionalities into a single ultrathin device are highly desirable
in the modern microwave and terahertz fields. However, the diversified
functionalities, to the best of our knowledge, have not been applied to
circular polarization meta-couplers because of the spin coupling between the
orthogonal incident waves. In this paper, we propose and numerically
demonstrate a terahertz spin-decoupled bifunctional meta-coupler for SSP
excitation and beam steering. The designed meta-coupler is composed of a
coupling metasurface and a propagating metasurface. The former aims at
realizing anomalous reflection or converting the incident waves into SSP under
the illumination of the left or right circular polarization waves,
respectively, and the latter are used to guide out the excited SSP. The
respective converting efficiency can reach 82% and 70% at 0.3THz for the right
and left circular polarization incident waves. Besides, by appropriately
adjusting the reflection phase distribution, many other diversified
functionalities can also be integrated into the meta-coupler. Our study may
open up new routes for polarization-related SSP couplers, detectors, and other
practical terahertz devices.",1904.06133v1
2019-09-29,Quantum phases and collective excitations of a spin-orbit-coupled Bose-Einstein condensate in a one-dimensional optical lattice,"The ground state of a spin-orbit-coupled Bose gas in a one-dimensional
optical lattice is known to exhibit a mixed regime, where the condensate wave
function is given by a superposition of multiple Bloch-wave components, and an
unmixed one, in which the atoms occupy a single Bloch state. The unmixed regime
features two unpolarized Bloch-wave phases, having quasimomentum at the center
or at the edge of the first Brillouin zone, and a polarized Bloch-wave phase at
intermediate quasimomenta. By calculating the critical values of the Raman
coupling and of the lattice strength at the transitions among the various
phases, we show the existence of a tricritical point where the mixed, the
polarized and the edge-quasimomentum phases meet, and whose appearance is a
consequence of the spin-dependent interaction. Furthermore, we evaluate the
excitation spectrum in the unmixed regime and we characterize the behavior of
the phonon and the roton modes, pointing out the instabilities occurring when a
phase transition is approached.",1909.13317v1
2021-11-04,Control of the phase of reflected spin-waves from magnonic Gires-Tournois interferometer of subwavelength width,"The phase is one of the fundamental properties of a wave that allows to
control interference effects and can be used to efficiently encode information.
We examine numerically a magnonic resonator of the Gires-Tournois
interferometer type, which enables the control of the phase of spin waves
reflected from the edges of the ferromagnetic film. The considered
interferometer consists of a Py thin film and a thin, narrow Py stripe placed
above its edge, both coupled magnetostatically. We show that the resonances and
the phase of the reflected spin waves are sensitive for a variation of the
geometrical parameters of this bi-layerd part of the system. The high
sensitivity to film, stripe, and non-magnetic spacer thicknesses, offers a
prospect for developing magnonic metasurfaces and sensors.",2111.02678v1
2021-11-26,A modal approach to modelling spin wave scattering,"Efficient numerical methods are required for the design of optimised devices.
In magnonics, the primary computational tool is micromagnetic simulations,
which solve the Landau-Lifshitz equation discretised in time and space.
However, their computational cost is high, and the complexity of their output
hinders insight into the physics of the simulated system, especially in the
case of multimode propagating wave-based devices. We propose a finite-element
modal method allowing an efficient solution of the scattering problem for
dipole-exchange spin waves propagating perpendicularly to the magnetisation
direction. The method gives direct access to the scattering matrix of the whole
system and its components. We extend the formula for the power carried by a
magnetostatic mode in the Damon-Eshbach configuration to the case with
exchange, allowing the scattering coefficients to be normalised to represent
the fraction of the input power transferred to each output channel. We apply
the method to the analysis of spin-wave scattering on a basic functional block
of magnonic circuits, consisting of a resonator dynamically coupled to a thin
film. The results and the method are validated by comparison with micromagnetic
simulations.",2111.13448v2
2022-05-25,"Mountain formation by repeated, inhomogeneous crustal failure in a neutron star","The elastic crust of a neutron star fractures repeatedly as it spins down
electromagnetically. An idealised, macroscopic model of inhomogeneous crustal
failure is presented based on a cellular automaton with nearest-neighbour
tectonic interactions involving strain redistribution and thermal dissipation.
Predictions are made of the size and waiting-time distributions of failure
events, as well as the rate of failure as the star spins down. The last failure
event typically occurs when the star spins down to approximately 1% of its
birth frequency with implications for rotational glitch activity. Neutron stars
are commonly suggested as sources of continuous gravitational waves. The output
of the automaton is converted into predictions of the star's mass ellipticity
and gravitational wave strain as functions of its age, with implications for
future observations with instruments such as the Laser Interferometer
Gravitational Wave Observatory (LIGO), the Virgo interferometer, or the Kamioka
Gravitational Wave Detector (KAGRA).",2205.15026v2
2023-03-09,Phase-resolved optical characterization of nanoscale spin waves,"We study theoretically and experimentally the process of Brillouin light
scattering on an array of silicon disks on a thin Permalloy layer. We show that
phase-resolved Brillouin light scattering microscopy performed on an array of
weakly interacting dielectric nanoresonators can detect nanoscale waves and
measure their dispersion. In our experiment, we were able to map the evolution
of the phase of the spin wave with a wavelength of 209 nm with a precision of 6
nm. These results demonstrate the feasibility of all-optical phase-resolved
characterization of nanoscale spin waves.",2303.05339v1
2023-03-15,The Dynamical Stripes in Spin-Orbit Coupled Bose-Einstein Condensates with Josephson Junctions,"The Josephson dynamics of the Bose-Einstein condensation with Raman-induced
spin-orbit coupling is investigated. A quasi-1D trap is divided into two
reservoirs by an optical barrier. Before the tunneling between the reservoirs
is turned on, the system stays in its equilibrium ground state. For different
spin-orbit coupling parameters and interaction strengthes, the ground state
displays a rich phase diagram. In this work we focus on the plane wave phase
and the stripe phase. Our calculation shows that, when the tunneling is turned
on, the plane wave phase evolves into a dynamical stripe phase, that is, the
density of the particle changes from uniform to periodically modulated.
Basically, this stripe is described by a sine function and the wave length, the
amplitude and the initial phase of the function are all varying with time. If
the system stays in stripe phase initially, the stripes become ``sliding"" when
the tunneling is turned on, which reflects the running of one of the phases of
the wave function.",2303.08585v1
2023-12-31,Magnetic order and strongly-correlated effects in the one-dimensional Ising-Kondo lattice,"We investigate the magnetic order and related strongly-correlated effects in
an one-dimensional Ising-Kondo lattice with transverse field. This model is the
anisotropic limit of the conventional isotropic Kondo lattice model, in the
sense that the itinerant electrons interact with the localized magnetic moments
via only longitudinal Kondo exchange. Adopting the numerical
density-matrix-renormalization group method, we map out the ground-state phase
diagram in various parameter spaces. Depending on the Kondo coupling and
filling number, three distinct phases, including a metallic paramagnetic, a
metallic ferromagnetic, and a gapped spin-density wave phase, are obtained. The
spin-density wave is characterized by an ordering wave vector which coincides
with the nesting wave vector of the Fermi surface. This makes the corresponding
magnetic transition a spin analog of the Peierls transition occurring in the
one-dimensional metal. Moreover, by analyzing the momentum distribution
function and charge correlation function, the conduction electrons are shown to
behave like free spinless fermions in the ferromagnetic phase. We finally
discuss the effect of the repulsive Hubbard interaction between conduction
electrons. Our work enriches the Kondo physics and deepens the current
understanding of the heavy fermion compounds.",2401.00432v1
2016-09-01,Spinning test-body orbiting around Schwarzschild black hole: circular dynamics and gravitational-wave fluxes,"We consider a spinning test-body in circular motion around a nonrotating
black hole and analyze different prescriptions for the body's dynamics. We
compare, for the first time, the Mathisson-Papapetrou formalism under the
Tulczyjew spin-supplementary-condition (SSC), the Pirani SSC and the
Ohashi-Kyrian-Semerak SSC, and the spinning particle limit of the
effective-one-body Hamiltonian of [Phys.~Rev.~D.90,~044018(2014)]. We analyze
the four different dynamics in terms of the ISCO shifts and in terms of the
coordinate invariant binding energies, separating higher-order spin
contributions from spin-orbit contributions. The asymptotic gravitational wave
fluxes produced by the spinning body are computed by solving the inhomogeneous
$(2+1)D$ Teukolsky equation and contrasted for the different cases. For small
orbital frequencies $\Omega$, all the prescriptions reduce to the same dynamics
and the same radiation fluxes. For large frequencies, ${x \equiv (M
\Omega)^{2/3} >0.1 }$, where $M$ is the black hole mass, and especially for
positive spins (aligned with orbital angular momentum) a significant
disagreement between the different dynamics is observed. The ISCO shifts can
differ up to a factor two for large positive spins; for the
Ohashi-Kyrian-Semerak and the Pirani SSC the ISCO diverges around dimensionless
spins $\sim0.52$ and $\sim0.94$ respectively. In the spin-orbit part of the
energetics the deviation from the Hamiltonian dynamics is largest for the
Ohashi-Kyrian-Semerak SSC; it exceeds $10\%$ for $x>0.17$. The Tulczyjew and
the Pirani SSCs behave compatible across almost the whole spin and frequency
range. Our results will have direct application in including spin effects to
effective-one-body waveform models for circularized binaries in the
extreme-mass-ratio limit.",1609.00356v2
1996-11-07,Beyond Uncertainty: the internal structure of electrons and photons,"The wave-structure of moving electrons is analyzed on a fundamental level by
employing a modified de Broglie relation. Formalizing the wave-function $\psi$
in real notation yields internal energy components due to mass oscillations.
The wave-features can then be referred to physical waves of discrete frequency
$\nu$ and the classical dispersion relation $\lambda \nu = u $, complying with
the classical wave equation. Including external potentials yields the
Schr\""odinger equation, which, in this context, is arbitrary due to the
internal energy components. It can be established that the uncertainty
relations are an expression of this, fundamental, arbitrariness. Electrons and
photons can be described by an identical formalism, providing formulations
equivalent to the Maxwell equations. The wave equations of intrinsic particle
properties are Lorentz invariant considering total energy of particles,
although transformations into a moving reference frame lead to an increase of
intrinsic potentials. Interactions of photons and electrons are treated
extensively, the results achieved are equivalent to the results in quantum
theory. Electrostatic interactions provide, a posteriori, a justification for
the initial assumption of electron-wave stability: the stability of electron
waves can be referred to vanishing intrinsic fields of interaction. The concept
finally allows the conclusion that a significant correlation for a pair of spin
particles in EPR--like measurements is likely to violate the uncertainty
relations.",9611009v3
2009-06-22,Nonlinear aspects of quantum plasma physics,"Dense quantum plasmas are ubiquitous in planetary interiors and in compact
astrophysical objects, in semiconductors and micro-mechanical systems, as well
as in the next generation intense laser-solid density plasma interaction
experiments and in quantum x-ray free-electron lasers. In contrast to classical
plasmas, one encounters extremely high plasma number density and low
temperature in quantum plasmas. The latter are composed of electrons, positrons
and holes, which are degenerate. Positrons (holes) have the same (slightly
different) mass as electrons, but opposite charge. The degenerate charged
particles (electrons, positrons, holes) follow the Fermi-Dirac statistics. In
quantum plasmas, there are new forces associated with i) quantum statistical
electron and positron pressures, ii) electron and positron tunneling through
the Bohm potential, and iii) electron and positron angular momentum spin.
Inclusion of these quantum forces provides possibility of very high-frequency
dispersive electrostatic and electromagnetic waves (e.g. in the hard x-ray and
gamma rays regimes) having extremely short wavelengths. In this review paper,
we present theoretical backgrounds for some important nonlinear aspects of
wave-wave and wave-electron interactions in dense quantum plasmas.
Specifically, we shall focus on nonlinear electrostatic electron and ion plasma
waves, novel aspects of 3D quantum electron fluid turbulence, as well as
nonlinearly coupled intense electromagnetic waves and localized plasma wave
structures. Also discussed are the phase space kinetic structures and
mechanisms that can generate quasi-stationary magnetic fields in dense quantum
plasmas. The influence of the external magnetic field and the electron angular
momentum spin on the electromagnetic wave dynamics is discussed.",0906.4051v4
2014-01-31,Symmetry-projected Wave Functions in Quantum Monte Carlo Calculations,"We consider symmetry-projected Hartree--Fock trial wave functions in
constrained-path Monte Carlo (CPMC) calculations. Previous CPMC calculations
have mostly employed Hartree--Fock (HF) trial wave functions, restricted or
unrestricted. The symmetry-projected HF approach results in a hierarchy of wave
functions with increasing quality: the more symmetries that are broken and
restored in a self-consistent manner, the higher the quality of the trial wave
function. This hierarchy is approximately maintained in CPMC calculations: the
accuracy in the energy increases and the statistical variance decreases when
further symmetries are broken and restored. Significant improvement is achieved
in CPMC with the best symmetry-projected trial wave functions over those from
simple HF. We analyze and quantify the behavior using the two-dimensional
repulsive Hubbard model as an example. In the sign-problem-free region, where
CPMC can be made exact but a constraint is deliberately imposed here,
spin-projected wave functions remove the constraint bias. Away from
half-filling, spatial symmetry restoration in addition to that of the spin lead
to highly accurate results from CPMC. Since the computational cost of
symmetry-projected HF trial wave functions in CPMC can be made to scale
algebraically with system size, this provides a potentially general approach
for accurate calculations in many-fermion systems.",1402.0018v1
2016-08-24,Dynamic Stimulation of Superconductivity With Resonant Terahertz Ultrasonic Waves,"An experiment is proposed to stimulate a superconducting thin film with
terahertz (THz) acoustic waves, which is a regime not previously tested. For a
thin film on a piezoelectric substrate, this can be achieved by coupling the
substrate to a tunable coherent THz electromagnetic source. Suggested materials
for initial tests are a niobium film on a quartz substrate, with a BSCCO
intrinsic Josephson junction (IJJ) stack. This will create acoustic standing
waves on the nm scale in the thin film. A properly tuned standing wave will
enable electron diffraction across the Fermi surface, leading to electron
localization perpendicular to the substrate. This is expected to reduce the
effective dimensionality, and enhance the tendency for superconducting order
parallel to the substrate, even well above the superconducting critical
temperature. This enhancement can be observed by measuring the in-plane
critical current and the perpendicular tunneling gap. A similar experiment may
be carried out for a cuprate thin film, although the conduction electrons might
be more responsive to spin waves than to acoustic waves. These experiments
address a novel regime of large momentum transfer to the electrons, which
should be quite distinct from the more traditional regime of large energy
transfer obtained from direct electromagnetic stimulation. The experiments are
also motivated in part by novel theories of the superconducting state involving
dynamic charge-density waves and spin-density waves. Potential device
applications are discussed.",1609.02003v1
2017-12-13,Role of fluctuations for density-wave instabilities: Failure of the mean-field description,"Density-wave instabilities have been observed and studied in a multitude of
materials. Most recently, in the context of unconventional superconductors like
the iron-based superconductors, they have excited considerable interest. We
analyze the fluctuation corrections to the equation of state of the
density-wave order parameter for commensurate charge-density waves and
spin-density waves due to perfect nesting. For XY magnets, we find that
contributions due to longitudinal and transverse fluctuations cancel each
other, making the mean-field analysis of the problem controlled. This is
consistent with the analysis of fluctuation corrections to the BCS theory of
superconductivity [S. Kos, A. J. Millis, and A. I. Larkin, Phys. Rev. B 70,
214531 (2004)]. However, this cancellation does not occur in density-wave
systems when the order parameter is a real $N$-component object with $N\neq2$.
Then, the number of transverse fluctuating modes differs from the number of
longitudinal fluctuating modes. Indeed, in the case of charge-density waves as
well as spin-density waves with Heisenberg symmetry, we find that fluctuation
corrections are not negligible, and hence mean-field theories are not
justified. These singular fluctuations originate from the intermediate
length-scale regime, with wavelengths between the lattice constant and the
$T=0$ correlation length. The resulting logarithmic fluctuation contributions
to the gap equation originate from the derivative of the anomalous polarization
function, and the crucial process is an interaction of quasiparticles through
the exchange of fluctuations.",1712.04679v2
2021-05-26,Gravitational-wave echoes from spinning exotic compact objects: numerical waveforms from the Teukolsky equation,"We present numerical waveforms of gravitational-wave echoes from spinning
exotic compact objects (ECOs) that result from binary black hole coalescence.
We obtain these echoes by solving the Teukolsky equation for the $\psi_4$
associated with gravitational waves that propagate toward the horizon of a Kerr
spacetime, and process the subsequent reflections of the horizon-going wave by
the surface of the ECO, which lies right above the Kerr horizon. The
trajectories of the infalling objects are modified from Kerr geodesics, such
that the gravitational waves propagating toward future null infinity match
those from merging black holes with comparable masses. In this way, the
corresponding echoes approximate to those from comparable-mass mergers. For
boundary conditions at the ECO surface, we adopt recent work using the membrane
paradigm, which relates $\psi_0$ associated with the horizon-going wave and
$\psi_4$ of the wave that leaves the ECO surface. We obtain $\psi_0$ of the
horizon-going wave from $\psi_4$ using the Teukolsky-Starobinsky relation. The
echoes we obtain turn out to be significantly weaker than those from previous
studies that generate echo waveforms by modeling the ringdown part of binary
black hole coalescence waveforms as originating from the past horizon.",2105.12313v1
1993-07-29,Spin Dynamics in the Normal State of High T_c Superconductors,"We summarize our recent theoretical studies on the spin dynamics in the
normal state of the metallic cuprates. The contrasting wave vector dependence
of the dynamical spin structure factor $S({\bf q}, \omega )$ in LaSrCuO and
YBaCuO systems are attributed to the differences in the fermiology, in
conjunction with strong Coulomb correlations. These effects are found to
account also for the anomalous temperature and frequency dependence of $S({\bf
q}, \omega )$. We conclude that the low energy spin dynamics of the metallic
cuprates are described in terms of correlated quasiparticles with a Luttinger
Fermi surface and a non-zero antiferromagnetic exchange interaction.",9307062v1
1995-06-05,Theory of the Spin Gap in High Temperature Superconductors,"We analyze pairing in two dimensional spin liquids. We argue that interplane
pairing enhanced by magnetic correlations is the most plausible explanation of
the spin gap phenomenon observed in underdoped cuprates. The details of the
pairing theory depend on the in-plane antiferromagnetic correlations. We
consider two models: $2p_F$ correlations induced by a strong gauge field
interaction and undamped spin waves. We estimate the pairing temperature $T_s$
and the angular dependence of the gap function and discuss physical
consequences.",9506019v1
1995-10-18,Zero field muon spin lattice relaxation rate in a Heisenberg ferromagnet at low temperature,"We provide a theoretical framework to compute the zero field muon spin
relaxation rate of a Heisenberg ferromagnet at low temperature. We use the
linear spin wave approximation. The rate, which is a measure of the spin
lattice relaxation induced by the magnetic fluctuations along the easy axis,
allows one to estimate the magnon stiffness constant.",9510096v1
1998-05-24,Spin Dynamics for the t-J Model,"The spin dynamics at the finite temperature for the t-J model in the
underdoped and optimal doped regimes is studied within the fermion-spin theory.
It is shown that the dynamical spin structure factor spectrum at the
antiferromagnetic wave vector $Q=(\pi,\pi)$ are separated as low- and
high-frequency parts, respectively, but the high-frequency part is suppressed
in the dynamical susceptibility spectrum $\chi^{''}(Q,\omega)$, while the
low-frequency part is the temperature dependent, which are in qualitative
agreement with the experiments and numerical simulations.",9805308v2
1998-08-26,Orbital Ordering Induced Antiferromagnetic Spin Fluctuations in the Ferromagnetic State of 50 % Hole-doped Manganites: Pr{1/2}Sr{1/2}MnO3 and Nd{1/2}Sr{1/2}MnO3,"We report inelastic neutron scattering results on the spin dynamics in the 50
% hole-doped manganites, Pr{1/2}Sr{1/2}MnO3 and Nd{1/2}Sr{1/2}MnO3. In the
paramagnetic phase, these systems exhibit a ridge-type diffuse scattering,
indicating a two-dimensional ferromagnetic (FM) correlation. With decreasing
temperature, the systems enter the FM state, but simultaneously they develop
A-type antiferromagnetic spin fluctuations. The spin wave dispersion in the FM
state is strongly anisotropic. These behaviors can be consistently interpreted
from a viewpoint of the underlying orbital ordering.",9808286v1
1999-03-12,Phase Diagrams from Topological Transitions: The Hubbard Chain with Correlated Hopping,"The quantum phase diagram of the Hubbard chain with correlated hopping is
accurately determined through jumps in $\pi$ in the charge and spin Berry
phases. The nature of each thermodynamic phase, and the existence of charge and
spin gaps, is confirmed by calculating correlation functions and other
fundamental quantities using numerical methods, and symmetry arguments.
Remarkably we find striking similarities between the stable phases for moderate
on-site Coulomb repulsion: spin Peierls, spin-density-wave and triplet
superconductor, and those measured in (TMTSF)$_2$X.",9903213v1
1999-11-24,Exactly solvable spin ladder model with degenerate ferromagnetic and singlet states,"We study the spin ladder model with interactions between spins on neighboring
rungs. The model Hamiltonian with the exact singlet ground state degenerated
with ferromagnetic state is obtained. The singlet ground state wave function
has a special recurrent form and depends on two parameters. Spin correlations
in the singlet ground state show double-spiral structure with period of spirals
equals to the system size. For special values of parameters they have
exponential decay. The spectrum of the model is gapless and there are
asymptotically degenerated excited states for special values of parameters in
the thermodynamic limit.",9911394v1
1999-12-18,Nuclear spin relaxation in ordered bimetallic chain compounds,"A theoretical interpretation is given to recent proton spin relaxation-time
(T_1) measurements on NiCu(C_7H_6N_2O_6)(H_2O)_3$\cdot$2H_2O, which is an ideal
one-dimensional ferrimagnetic Heisenberg model system of alternating spins 1
and 1/2. The relaxation rate T_1^{-1} is formulated in temrs of the spin-wave
theory and is evaluated by the use of a quantum Monte Carlo method.
Calculations of the temperature and applied-field (H) dependences of T_1^{-1}
are in total agreement with the experimental findings. T_1 behaves as
$T_1^{-1}\propto H^{-1/2}$, which turns out an indirect observation of the
quadratic dispersion relations dominating the low-energy physics of quantum
ferrimagnets.",9912340v1
2000-11-21,Fast Incomplete Decoherence of Nuclear Spins in Quantum Hall Ferromagnet,"A scenario of quantum computing process based on the manipulation of a large
number of nuclear spins in Quantum Hall (QH) ferromagnet is presented. It is
found that vacuum quantum fluctuations in the QH ferromagnetic ground state at
filling factor $\nu =1$, associated with the virtual excitations of spin waves,
lead to fast incomplete decoherence of the nuclear spins. A fundamental upper
bound on the length of the computer memory is set by this fluctuation effect.",0011361v2
2001-01-29,Possible high $T_c$ superconductivity mediated by antiferromagnetic spin fluctuations in systems with Fermi surface pockets,"We propose that if there are two small pocket-like Fermi surfaces, and the
spin susceptibility is pronounced around a wave vector {\bf Q} that bridges the
two pockets, the spin-singlet superconductivity mediated by spin fluctuations
may have a high transition temperature. Using the fluctuation exchange
approximation, this idea is confirmed for the Hubbard on a lattice with
alternating hopping integrals, for which $T_c$ is estimated to be almost an
order of magnitude larger than those for systems with a large connected Fermi
surface.",0101427v1
2001-03-21,Superconducting 2D system with lifted spin degeneracy: Mixed singlet-triplet state,"Motivated by recent experimental findings, we have developed a theory of the
superconducting state for 2D metals without inversion symmetry modeling the
geometry of a surface superconducting layer in a field-effect-transistor or
near the boundary doped by adsorbed ions. In such systems the two-fold spin
degeneracy is lifted by spin-orbit interaction, and singlet and triplet
pairings are mixed in the wave function of the Cooper pairs. As a result, spin
magnetic susceptibility becomes anisotropic and Knight shift retains finite and
rather high value at T=0.",0103449v1
2001-07-27,Incommensurate magnetic ordering in Sr_2Ru_(1-x)Ti_xO_4,"In $\rm Sr_2RuO_4$ the spin excitation spectrum is dominated by
incommensurate fluctuations at q=(0.3 0.3 q$_z$), which arise from
Fermi-surface nesting. We show that upon Ti substitution, known to suppress
superconductivity, a short range magnetic order develops with a propagation
vector (0.307 0.307 1). This finding confirms that superconducting $\rm
Sr_2RuO_4$ is extremely close to an incommensurate spin density wave
instability. In addition, the ordered moment in \srton ~ points along the
c-direction, which indicates that the incommensurate spin fluctuations exhibit
the anisotropy required to explain a p-wave spin triplet pairing.",0107579v2
2002-01-05,Exact results on spin glass models,"Exact and/or rigorous results are reviewed for the Ising and XY/Villain spin
glasses in finite dimensions, such as the exact energy, correlation identities
and a functional relation between the distribution functions of ferromagnetic
and spin glass order parameters. This last relation is useful to prove that the
phase space is not complex on a line in the phase diagram. The spin wave theory
neglecting periodicity is shown to give exact results for the Villain model on
a line in the phase diagram. Implications of this fact on the
renormalization-group results for the random-phase XY/Villain model in two
dimensions are discussed.",0201056v1
2002-03-08,High-Energy Spin Dynamics in La$_{1.69}$Sr$_{0.31}$NiO$_4$,"We have mapped out the spin dynamics in a stripe-ordered nickelate,
La$_{2-x}$Sr$_{x}$NiO$_{4}$ with $x \simeq 0.31$, using inelastic neutron
scattering. We observe spin-wave excitations up to 80 meV emerging from the
incommensurate magnetic peaks with an almost isotropic spin-velocity: $\hbar
c_s\sim 0.32$ eV \AA, very similar to the velocity in the undoped, insulating
parent compound, La$_{2}$NiO$_{4}$. We also discuss the similarities and
differences of the inferred spin-excitation spectrum with those reported in
superconducting high-$T_c$ cuprates.",0203187v1
2002-09-21,Castaing's instability in a trapped ultra-cold gas,"We consider a trapped ultra-cold gas of (non-condensed) bosons with two
internal states (described by a pseudo spin) and study the stability of a
longitudinal pseudo spin polarization gradient. For this purpose, we
numerically solve a kinetic equation corresponding to a situation close to an
experiment at JILA. It shows the presence of Castaing's instability of
transverse spin polarization fluctuations at long wavelengths. This phenomenon
could be used to create spontaneous transverse spin waves.",0209506v2
2002-11-05,Spin stiffness and quantum fluctuations in C-type and A-type antiferromagnets,"We present a systematic study of quantum fluctuations in the C-type and
A-type antiferromagnetic (AF) phases in cubic lattices and in bilayer systems.
Using the linear spin-wave theory, we show that the spin stiffness and the
quantum corrections to the order parameter and energy obtained for C-AF and
A-AF phases decrease with the increasing number of ferromagnetic bonds.
Therefore, the quantum spin effects in LaMnO_3 and in LaVO_3 are rather small,
suggesting the magnetic moments of 3.91 and 1.89 Bohr's magneton, respectively.
They cannot explain the strong reduction of the magnetic order parameter
observed in cubic vanadates.",0211095v1
2003-03-18,Transport equations for a two-dimensional electron gas with spin-orbit interaction,"The transport equations for a two-dimensional electron gas with spin-orbit
interaction are presented. The distribution function is a 2x2-matrix in the
spin space. Particle and energy conservation laws determine the expressions for
the electric current and the energy flow. The derived transport equations are
applied to the spin-splitting of a wave packed and to the calculation of the
structure factor and the dynamic conductivity.",0303362v2
2003-06-04,Nuclear Spin Dynamics in Parabolic Quantum Wells,"We present a detailed analytical and numerical analysis of the nuclear spin
dynamics in parabolic quantum wells. The shallow potential of parabolic quantum
wells permits substantial modification of the electronic wave function in small
electric fields. The nuclear spin relaxation via the hyperfine interaction
depends on the electronic local density of states, therefore the local nuclear
relaxation time depends sensitively on the electric field. For an inhomogeneous
nuclear magnetization, such as generated by dynamic nuclear polarization, the
total nuclear magnetization dynamics can similarly be altered. We examine this
effect quantitatively and the effect of temperature, field, well thickness, and
nuclear spin diffusion.",0306098v2
2003-11-25,The Antiferromagnetic Sawtooth Lattice - the study of a two spin variant,"Generalising recent studies on the sawtooth lattice, a two-spin variant of
the model is considered. Numerical studies of the energy spectra and the
relevant spin correlations in the problem are presented. Perturbation theory
analysis of the model explaining some of the features of the numerical data is
put forward and the spin wave spectra of the model corresponding to different
phases are investigated.",0311560v1
2004-06-22,Co-operative density wave and giant spin gap in the quarter-filled zigzag ladder,"Strong co-operative interactions occur between four different broken
symmetries involving charge-ordering and bond distortions in the quarter-filled
correlated zigzag electron ladder. The ground state is singlet, with spin gap
several times larger than in the spin-Peierls state of the one-dimensional
quarter-filled chain with the same parameters. We propose the quarter-filled
zigzag electron ladder model for several different organic charge-transfer
solids with coupled pairs of quasi-one-dimensional stacks, the spin-gap
transition temperatures in which are unusually high.",0406525v2
2004-07-19,Voltage Dependence of Spin Polarized Tunneling,"A mesoscopic spin valve is used to determine the effective spin polarization
of electrons tunneling from and into ferromagnetic transition metals at finite
voltages. The tunneling spin polarization from the ferromagnet (FM) slowly
decreases with bias, but drops faster and even inverts with voltage when
electrons tunnel into it. A bias-dependent free electron model shows that in
the former case electrons originate near the Fermi level of the FM with large
polarization whereas in the latter, electrons tunnel into hot electron states
for which the polarization is significantly reduced. The change in sign is
ascribed to the detailed matching of the electron wave function through the
tunnel barrier.",0407489v1
2004-10-19,Magnetic properties of the two-dimensional Heisenberg model on a triangular lattice,"The spin Green's function of the antiferromagnetic Heisenberg model on a
triangular lattice is calculated using Mori's projection operator technique. At
T=0 the spin excitation spectrum is shown to have gaps at the wave vectors of
the classical Neel ordering. This points to the absence of the
antiferromagnetic long-range order in the ground state. The calculated spin
correlation on the neighboring sites of the same sublattice is in good
agreement with the value derived from exact diagonalization. The temperature
dependencies of the spin correlations and the gaps are calculated.",0410468v1
2004-11-02,Spin dynamics in the stripe phase of the cuprates,"Within a model that supports stripe spin and charge order coexisting with a
d$_{x^2-y^2}$-wave superconducting phase, we study the self-consistently
obtained electronic structure and the associated transverse dynamical spin
susceptibility. In the coexisting phase of superconducting and static stripe
order, the resulting particle-hole continuum can strongly damp parts of the
low-energy spin wave branches. This provides insight into recent inelastic
neutron scattering data revealing the dispersion of the low-energy collective
magnetic modes of lanthanum based cuprate superconductors.",0411065v1
2004-11-27,Geometric spin dephasing of carriers with strong spin-orbit coupling,"It has been shown that the geometric Berry-phase shift acquired by the
components of the light hole (LH) spinor during an adiabatic collision is equal
to the angular distance traveled by the wave vector. For LH, geometric
dephasing leads to equality between angular and crystal momentum relaxation
time. I will show that the same mechanism is completely ineffective for heavy
and split-off holes in bulk crystals, and in electron QSLs in spherical
nanostructures. This non-model result suggests that these carriers may be
considered as the stern candidates for implementation of dissipationless spin
currents (Spin Hall effect) and fault-tolerant qubits.",0411683v1
2005-11-18,The Union Jack model: a quantum spin model with frustration on the square lattice,"A new quantum spin model with frustration, the `Union Jack' model on the
square lattice, is analyzed using spin-wave theory. For small values of the
frustrating coupling $\alpha$, the system is N{\' e}el ordered as usual, while
for large $\alpha$ the frustration is found to induce a canted phase. The
possibility of an intermediate spin-liquid phase is discussed.",0511451v1
2005-12-17,Spin polarization of light atoms in jellium: Detailed electronic structures,"We revisit the problem of the spontaneous magnetization of an {\em sp}
impurity atom in a simple metal host. The main features of interest are: (i)
Formation of the spherical spin density/charge density wave around the
impurity; (ii) Considerable decrease in the size of the pseudoatom in the
spin-polarized state as compared with the paramagnetic one, and (iii) Relevance
of the electron affinity of the isolated atom to this spin polarization, which
is clarified by tracing the transformation of the pseudoatom into an isolated
negative ion in the low-density limit of the enveloping electron gas.",0512417v1
2006-03-20,Triplet superconductivity in a 1D itinerant electron system with transverse spin anisotropy,"In this paper we study the ground state phase diagram of a one-dimensional
t-J-U model away from half-filling. In the large-bandwidth limit and for
ferromagnetic exchange with easy-plane anisotropy a phase with gapless charge
and massive spin excitations, characterized by the coexistence of triplet
superconducting and spin density wave instabilities is realized in the ground
state. With increasing ferromagnetic exchange transitions into a ferrometallic
and then a spin gapped triplet superconducting phase take place.",0603504v1
2006-04-12,Spin diffusion and the anisotropic spin-1/2 Heisenberg chain,"Measurements of the spin-lattice relaxation rate 1/T_1 by nuclear magnetic
resonance for the one-dimensional Heisenberg antiferromagnet Sr_2CuO_3 have
provided evidence for a diffusion-like contribution at finite temperature and
small wave-vector. By analyzing real-time data for the auto- and
nearest-neighbor spin-spin correlation functions obtained by the density-matrix
renormalization group I show that such a contribution indeed exists for
temperatures T>J, where J is the coupling constant, but that it becomes
exponentially suppressed for T << J. I present evidence that the
frequency-dependence of 1/T_1 in the Heisenberg case is smoothly connected to
that in the free fermion case where the exponential suppression of the
diffusion-like contribution is easily understood.",0604327v1
2006-05-06,Evidence for multimagnon-mediated nuclear spin relaxation in the intertwining double-cain ferrimagnet $Ca_3 Cu_3 (PO_4)_4$,"The nuclear spin-lattice relaxation time $T_1$ of $^{31}P$ nuclei in the
title compound is measured for the first time and interpreted in terms of a
modified spin-wave theory. We establish a novel scenario for one-dimensional
ferrimagnetic spin dynamics -- it is three-magnon processes enhanced by
exchange scattering, rather than Raman processes, that make the major
contribution to $1/T_1$.",0605157v2
2006-09-21,Charge stripe order from antiphase spin spirals in the spin-Fermion model,"We revisit the ground state of the spin-Fermion model within a semiclassical
approximation. We demonstrate that antiphase spin spirals, or pi-spirals, whose
chirality alternates between consecutive rows (or columns) of local moments,
have, for sufficiently high carrier concentration, lower energy than the
traditional Shraiman and Siggia spirals. Furthermore, pi-spirals give rise to
modulated hopping, anisotropic 1D transport, and charge density wave formation.
Finally, we discuss the relevance of pi-spirals to the physics of charge stripe
formation in cuprates, such as La(2-x)Sr(x)CuO4.",0609539v1
2006-11-27,Probing $n$-Spin Correlations in Optical Lattices,"We propose a technique to measure multi-spin correlation functions of
arbitrary range as determined by the ground states of spinful cold atoms in
optical lattices. We show that an observation of the atomic version of the
Stokes parameters, using focused lasers and microwave pulsing, can be related
to $n$-spin correlators. We discuss the possibility of detecting not only
ground state static spin correlations, but also time-dependent spin wave
dynamics as a demonstrative example using our proposed technique.",0611689v2
2006-12-07,"Magnetism, spin-wave relaxation and spiral exchange in a trilayer magnetic junction","We study the non-collinear exchange coupling across a trilayer magnetic
junction consisting of two ferromagnets separated by a thin dilute magnetic
semiconductor containing itinerant carriers with finite spin relaxation. It is
remarkable that, by increasing the spin relaxation, the critical temperature is
substantially enhanced and the shape of the magnetization curve becomes more
mean-field like. We attribute these interesting changes to the broken
time-reversal symmetry which suppresses the oscillatory
Ruderman-Kittel-Kasuya-Yosida interaction. Our argument is further strengthened
by the emergence of the non-collinear spiral exchange coupling across the
trilayer magnetic junction with finite spin relaxation.",0612177v1
2007-02-13,Metamorphosis of a Quantum Hall Bilayer State into a Composite Fermion Metal,"Composite fermion metal states emerge in quantum Hall bilayers at total
Landau level filling factor $\nu_T$=1 when the tunneling gap collapses by
application of in-plane components of the external magnetic field. Evidence of
this transformation is found in the continua of spin excitations observed by
inelastic light scattering below the spin-wave mode at the Zeeman energy. The
low-lying spin modes are interpreted as quasiparticle excitations with
simultaneous changes in spin orientation and composite fermion Landau level
index.",0702317v1
2007-03-27,Universal temperature dependence of the magnetization of gapped spin chains,"Temperature dependence of the magnetization of the Haldane spin chain at
finite magnetic field is analyzed systematically. Quantum Monte Carlo data
indicates a clear minimum of magnetization as a function of temperature in the
gapless regime. On the basis of the Tomonaga-Luttinger liquid theory, we argue
that this minimum is rather universal and can be observed for general axially
symmetric quasi-one-dimensional spin systems. Our argument is confirmed by the
magnetic-field dependence of the spin-wave velocity obtained numerically. One
can estimate a magnitude of the gap of any such systems by fitting the
experimental data with the magnetization minimum.",0703727v1
1997-03-28,Total intrinsic spin for plane gravity waves,"A quantity which measures total intrinsic spin along the z axis is
constructed for planar gravity (fields dependent on z and t only), in both the
Ashtekar complex connection formalism and in geometrodynamics. The total spin
is conserved but (surprisingly) is not a surface term. This constant of the
motion coincides with one of four observables previously discovered by Husain
and Smolin. Two more of those observables can be interpreted physically as
raising and lowering operators for total spin.",9703086v1
1999-08-19,Pair production and solutions of the wave equation for particles with arbitrary spin,"We investigate the theory of particles with arbitrary spin and anomalous
magnetic moment in the Lorentz representation (0,s)X(s,0), in an external
constant and uniform electromagnetic field. We obtain the density matrix of
free particles in pure spin states. The differential probability of pair
producing particles with arbitrary spin by an external constant uniform
electromagnetic field has been found using the exact solutions. We have
calculated the imaginary and real parts of the Lagrangian in an electromagnetic
field that takes into account vacuum polarization.",9908410v1
2001-11-03,Wave Equation Solutions and Pair Production for Arbitrary Spin Particles,"We investigate the theory of particles with arbitrary spin and magnetic
moment in the Lorentz representation (0,s)X(s,0) in an external constant and
uniform electromagnetic field. We obtain the density matrix of free particles
in pure spin states. The differential probability of pair producing particles
with arbitrary spin by an external constant and uniform electromagnetic field
is found using the exact solutions. We calculate the imaginary and real parts
of the Lagrangian in an electromagnetic field that takes into account the
vacuum polarization.",0111033v1
2001-10-06,Pair Production and Vacuum Polarization of Arbitrary Spin Particles with EDM and AMM,"The exact solutions of the wave equation for arbitrary spin particles with
electric dipole and magnetic moments in the constant and uniform
electromagnetic field were found. The differential probability of pair
production of particles by an external electromagnetic field has been
calculated on the basis of the exact solutions. We have also estimated the
imaginary part of the constant and uniform electromagnetic field. The nonlinear
corrections to the Maxwell Lagrangian have been calculated taking into account
the vacuum polarization of arbitrary spin particles. The role of electric
dipole and magnetic moments of arbitrary spin particles in instability of the
vacuum is discussed.",0110061v1
2002-12-16,"Retraction of ""Half-integer spin representations of the graded extension of so(2,1) Lie algebra: Spin 3/2 particle in the Dirac-Oscillator potential""","The representation of the superalgebra SO(2,1) which is given by Eq. (3.1)
and which resulted in the relativistic wave equation (4.1) is fully reducible.
In fact, its even part is the direct sum of two spin 1/2 representations of the
Lorentz group and does not represent spin 3/2 particle as we claimed.
Consequently, we retract our claim and withdraw the manuscript.",0212173v2
2002-12-25,"Retraction of ""On a theory of half-integral spin particles with gauge invariant coupling to the electromagnetic potential: Towards higher spin QED""","The representation of the superalgebra so(2,1) that resulted in the
relativistic wave equation (2.1) and Eq. (2.4) is fully reducible. In fact, its
even part that lead to Eq. (3.1) is the direct sum of two spin 1/2
representations of the Lorentz group and does not represent spin 3/2 particle
as we claimed. Consequently, we retract our claim and withdraw the manuscript.",0212301v3
2003-08-22,Bitwistor formulation of massive spinning particle,"Twistor formulation of massive arbitrary spin particle has been constructed.
Twistor space of such particle is formed two twistors and two complex scalars
which form together 'bosonic supertwistor'. The formulation is deduced from
space-time one for spinning particle by means of introducing auxiliary harmonic
variables and consequent partial fixing of gauges. It is carried out the
canonical quantization of twistor massive particle with nonzero spin. It is
found the eigenvalues of Casimir operators on particle states and harmonic
expansion of wave function in spectrum.",0308154v1
2005-03-17,Infinite spin particles,"We show that Wigner's infinite spin particle classically is described by a
reparametrization invariant higher order geometrical Lagrangian. The model
exhibit unconventional features like tachyonic behaviour and momenta
proportional to light-like accelerations. A simple higher order superversion
for half-odd integer particles is also derived. Interaction with external
vector fields and curved spacetimes are analyzed with negative results except
for (anti)de Sitter spacetimes. We quantize the free theories covariantly and
show that the resulting wave functions are fields containing arbitrary large
spins. Closely related infinite spin particle models are also analyzed.",0503136v1
1995-05-30,Spin-Orbit Pendulum: the Microscopic Stern-Gerlach Effect,"The motion of a particle with a spin in spherical harmonic oscillator
potential with spin-orbit interaction is studied. We have focus our attention
on spatial motion of wave packets, giving a description complementary to motion
of spin discussed already in [1]. The particular initial conditions studied
here lead to the most transparent formulas and can be treated analytically. A
strong analogy with the Stern-Gerlach experiment is suggested. [1] R.Arvieu and
P.Rozmej, Phys.Rev.A50 (1994) 4376.",9505021v2
1998-12-23,On discrete symmetry for spin 1/2 and spin 1 particles in external monopole field and quantum-mechanical property of self-conjugacy,"Particles of spin 1/2 and 1 in external Abelian monopole field are
considered. P-inversion like operators N-s commuting with the respective
Hamiltonians are constructed: N(bisp.) is diagonalized onto the relevant wave
functions, whereas N(vect.) does not. Such a paradox is rationalized through
noting that both these operators are not self-conjugate. It is shown that any
N-parity selection rules cannot be produced. Non-Abelian problems for doublets
of spin 1/2 and 1 particles are briefly discussed; the statement is given of
that corresponding discrete operators are self-conjugate and selection rules
are available.",9812066v1
2007-07-25,Spin projected unrestricted Hartree-Fock ground states for harmonic quantum dots,"We report results for the ground state energies and wave functions obtained
by projecting spatially unrestricted Hartree Fock states to eigenstates of the
total spin and the angular momentum for harmonic quantum dots with $N\leq 12$
interacting electrons including a magnetic field states with the correct
spatial and spin symmetries have lower energies than those obtained by the
unrestricted method. The chemical potential as a function of a perpendicular
magnetic field is obtained. Signature of an intrinsic spin blockade effect is
found.",0707.3705v1
2007-09-12,Two Ferromagnetic Phases in Spin-Fermion Systems,"We consider spin-fermion systems which get their magnetic properties from a
system of localized magnetic moments being coupled to conducting electrons. The
dynamical degrees of freedom are spin-$s$ operators of localized spins and
spin-1/2 fermi operators of itinerant electrons. We develop modified spin-wave
theory and obtain that system has two ferromagnetic phases. At the
characteristic temperature T* the magnetization of itinerant electrons becomes
zero, and high temperature ferromagnetic phase (T*<T<T_C) is a phase where only
localized electrons give contribution to the magnetization of the system. An
anomalous increasing of magnetization below T* is obtained in a good agrement
with experimental measurements of the ferromagnetic phase of UGe2.",0709.1759v2
2007-10-18,Hidden multiferroic order in graphene zigzag ribbons,"The insulating magnetic phase in graphene zigzag ribbons, predicted both by
density functional and mean field Hubbard model calculations, is described
without additional approximations with a BCS wave function of two phase-locked
condensates of spin-polarized electron-hole pairs. The associated order
parameter is the spin dipole operator that features both magnetic and electric
order and accounts for the spin-resolved ferroelectricity of the system. Each
condensate is associated to a spin-dependent dipole and their relative phase
locking sets the total electric dipole and total magnetization equal to zero.",0710.3484v1
2007-11-05,Magnetic excitations in vanadium spinels,"We study magnetic excitations in vanadium spinel oxides AV$_2$O$_4$ (A=Zn,
Mg, Cd) using two models: first one is a superexchange model for vanadium S=1
spins, second one includes in addition spin-orbit coupling, and crystal
anisotropy. We show that the experimentally observed magnetic ordering can be
obtained in both models, however the orbital ordering is different with and
without spin-orbit coupling and crystal anisotropy. We demonstrate that this
difference strongly affects the spin-wave excitation spectrum above the
magnetically ordered state, and argue that the neutron measurement of such
dispersion is a way to distinguish between the two possible orbital orderings
in AV$_2$O$_4$.",0711.0732v1
2007-11-12,Chiral Odd Generalized Parton Distributions in Impact Parameter Space,"We investigate the chiral odd generalized parton distributions (GPDs) for the
quantum fluctuations of an electron in QED. The light-front wave function
(LFWF) of this system gives a template for the quark spin-one diquark structure
of the valence LFWF of the proton. We express the GPDs in terms of overlaps of
LFWFs and obtain their representation in impact parameter space when the
momentum transfer is purely transverse. We show the spin-orbit correlation
effect of the two-particle LFWF as well as the correlation between the
constituent spin and the transverse spin of the target.",0711.1566v2
2007-12-31,Direct optical detection of pure spin current in semiconductors,"We suggest a new practical scheme for the direct detection of pure spin
current by using the two-color Faraday rotation of optical quantum interference
process (QUIP) in a semiconductor system. We demonstrate theoretically that the
Faraday rotation of QUIP depends sensitively on the spin orientation and wave
vector of the carriers, and can be tuned by the relative phase and the
polarization direction of the $\omega$ and $2\omega$ laser beams. By adjusting
these parameters, the magnitude and direction of the spin current can be
detected.",0801.0180v1
2008-04-17,Spin Effects for Neutrinos and Electrons Moving in Dense Matter,"We shortly summarize the present status of neutrino magnetic moment studies
(theory and experiment). Then we discuss the quasiclassical treatment of
neutrino spin evolution in matter. After that we come to the quantum approach
to description of neutrino and electron motion in matter on the basis of the
quantum wave equations exact solutions method with special focus on spin
effects.",0804.2829v2
2008-07-29,Thermally activated Peierls dimerization in ferromagnetic spin chains,"We demonstrate that a Peierls dimerization can occur in ferromagnetic spin
chains activated by thermal fluctuations. The dimer order parameter and
entanglement measures are studied as functions of the modulation of the
magnetic exchange interaction and temperature, using a spin-wave theory and the
density-matrix renormalization group. We discuss the case where a periodic
modulation is caused by spin-phonon coupling and the case where electronic
states effectively induce such a modulation. The importance of the latter for a
number of transition metal oxides is highlighted.",0807.4693v1
2008-08-02,Electric-field control of a hydrogenic donor's spin in a semiconductor,"An AC electric field applied to a donor-bound electron in a semiconductor
modulates the orbital character of its wave function, which affects the
electron's spin dynamics via the spin-orbit interaction. Numerical calculations
of the spin dynamics of a hydrogenic donor (Si) embedded in GaAs, using a
real-space multi-band k.p formalism, show the high symmetry of the hydrogenic
donor state results in strongly nonlinear dependences of the electronic g
tensor on applied fields. A nontrivial consequence is that the most rapid Rabi
oscillations occur for electric fields modulated at a subharmonic of the Larmor
frequency.",0808.0208v1
2008-09-04,Impurity states in antiferromagnetic Iron Arsenides,"We explore theoretically impurity states in the antiferromagnetic
spin-density wave state of the iron arsenide. Two types of impurity models are
employed: one has only the intraband scattering while the other has both the
intraband and interband scattering with the equal strength. Interestingly, the
impurity bound state is revealed around the impurity site in the energy gap for
both models. However, the impurity state is doubly degenerate with respect to
spin for the first case; while the single impurity state is observed in either
the spin-up or spin-down channel for the second one. The impurity-induced
variations of the local density of states are also examined.",0809.0795v1
2008-10-22,Magnetism Localization in Spin-Polarized One-Dimensional Anderson-Hubbard Model,"In order to study an interplay of disorder, correlation, and spin imbalance
on antiferromagnetism, we systematically explore the ground state of
one-dimensional spin-imbalanced Anderson-Hubbard model by using the
density-matrix renormalization group method. We find that disorders localize
the antiferromagnetic spin density wave induced by imbalanced fermions and the
increase of the disorder magnitude shrinks the areas of the localized
antiferromagnetized regions. Moreover, the antiferromagnetism finally
disappears above a large disorder. These behaviors are observable in atomic
Fermi gases loaded on optical lattices and disordered strongly-correlated
chains under magnetic field.",0810.3953v1
2008-11-26,An exact spin liquid state on the kagome lattice with topological order,"We find an exact spin liquid state without time reversal symmetry on the
kagome lattice with odd number of electrons per unit cell and explicit wave
functions for all eigenstates. We also obtain that all spin-spin correlations
are zero except trivial cases. We then show that there are anyonic excitations
in our model. Finally, we demonstrate the existence of ground state degeneracy
and gapless edge states indicating nontrivial topological order in our model.
We also label all eiginstates on torus by local and global string operators.",0811.4342v1
2009-07-31,New Correlated Model of Colossal Magnetoresistive Manganese Oxides,"A new minimal model is constructed for the doped manganese oxides which
exhibit colossal magnetoresistance (CMR), involving broad spin-majority
conduction band as well as nearly localised spin-minority electron states. A
simple mean field analysis yields a temperature-dependent hybridised band
structure with suppressed carrier weight at the Fermi level. Spin stiffness is
complex, indicating unusually strong spin wave damping. Experimental and
theoretical investigations are needed to further verify the relevance of the
proposed model.",0907.5512v3
2009-10-10,Spin Order and Excitations in Triangular Antiferromagnet La2Ca2MnO7,"We report a spin S = 3/2 triangular antiferromagnet with nearest-neighbor
coupling J = 0.29 meV in La2Ca2MnO7. A genuinely two-dimensional,
three-sublattice order develops below 2.80 K << the Weiss constant (25 K). The
spin excitations deviate substantially from linear spin-wave theory, suggesting
that magnon breakdown occurs in the material. Such a breakdown has been
anticipated in recent theoretical studies, although the excitation spectrum
remains to be accounted for.",0910.1904v1
2010-04-11,Extra Spin-Wave mode in Quantum Hall systems. Beyond the Skyrmion Limit,"We report on the observation of a new spin mode in a quantum Hall system in
the vicinity of odd electron filling factors under experimental conditions
excluding the possibility of Skyrmion excitations. The new mode having
presumably zero energy at odd filling factors emerges at small deviations from
odd filling factors and couples to the spin-exciton. The existence of an extra
spin mode assumes a nontrivial magnetic order at partial fillings of Landau
levels surrounding quantum Hall ferromagnets other then the Skyrmion crystal.",1004.1840v1
2010-07-19,Ray trajectories for a spinning cosmic string and a manifestation of self-cloaking,"A study of ray trajectories was undertaken for the Tamm medium which
represents the spacetime of a cosmic spinning string, under the
geometric-optics approximation. Our numerical studies revealed that: (i) rays
never cross the string's boundary; (ii) the Tamm medium supports evanescent
waves in regions of phase space that correspond to those regions of the
string's spacetime which could support closed timelike curves; and (iii) a
spinning string can be slightly visible while a non-spinning string is almost
perfectly invisible.",1007.3113v1
2010-11-11,Perturbative effects of spinning black holes with applications to recoil velocities,"Recently, we proposed an enhancement of the Regge-Wheeler-Zerilli formalism
for first-order perturbations about a Schwarzschild background that includes
first-order corrections due to the background black-hole spin. Using this
formalism, we investigate gravitational wave recoil effects from a spinning
black-hole binary system analytically. This allows us to better understand the
origin of the large recoils observed in full numerical simulation of spinning
black hole binaries.",1011.2767v1
2010-11-19,"Anisotropic spin fluctuations and superconductivity in ""115'' heavy fermion compounds: 59Co NMR study in PuCoGa5","We report results of $^{59}$Co nuclear magnetic resonance measurements on a
single crystal of superconducting PuCoGa5 in its normal state. The nuclear
spin-lattice relaxation rates and the Knight shifts as a function of
temperature reveal an anisotropy of spin fluctuations with finite wave vector
q. By comparison with the isostructural members, we conclude that
antiferromagnetic XY-type anisotropy of spin fluctuations plays an important
role in mediating superconductivity in these heavy fermion materials.",1011.4466v1
2011-03-02,Spin dependence of the antinucleon-nucleon interaction,"The status of our present knowledge on the antinucleon-nucleon interaction at
low and medium energies is discussed. Special emphasis is put on aspects
related to its spin dependence which are relevant for experiments planned by
the PAX collaboration. Predictions for the spin-dependent antiproton-proton
cross sections sigma_1 and sigma_2 are presented, utilizing antinucleon-nucleon
potential models developed by the Juelich group, and compared to results based
on the amplitudes of the Nijmegen partial-wave analysis.",1103.0462v1
2011-04-12,Compact objects with spin parameter $a_* > 1$,"In 4-dimensional General Relativity, black holes are described by the Kerr
solution and are completely specified by their mass $M$ and by their spin
angular momentum $J$. A fundamental limit for a black hole in General
Relativity is the Kerr bound $|a_*| \le 1$, where $a_* = J/M^2$ is the spin
parameter. Future experiments will be able to probe the geometry around these
objects and test the Kerr black hole hypothesis. Interestingly, if these
objects are not black holes, the accretion process may spin them up to $a_* >
1$.",1104.2218v1
2011-07-07,Neutron experiments to search for new spin-dependent interactions,"The consideration is presented of possible neutron experiments to search for
new short-range spin-dependent forces. The spin-dependent nucleon-nucleon
interaction between neutron and nuclei may cause different effects: phase shift
of a neutron wave in neutron interferometers of different kind, in particular
of the Lloyd mirror configuration, neutron spin rotation in the pseudo-magnetic
field, and transverse deflection of polarized neutron beam by a slab of
substance. Estimates of sensitivity of these experiments are performed.",1107.1481v2
2012-01-25,Quantum strings in quantum spin ice,"We study quantum spin ice in an external magnetic field applied along a
$<100>$ direction. When quantum spin fluctuations are weak, elementary
excitations are quantum strings with monopoles at their ends manifested as
multiple spin-wave branches in the dynamical structure factor. Strong quantum
fluctuations make the string tension negative and give rise to the
deconfinement of monopoles. We discuss our results in the light of recent
neutron scattering experiments in $\mathrm{Yb_2Ti_2O_7}$",1201.5314v3
2012-02-08,Role of spin-orbit coupling on the electronic structure and properties of SrPtAs,"The effect of spin-orbit coupling on the electronic structure of the layered
iron-free pnictide superconductor, SrPtAs, has been studied using the full
potential linearized augmented plane wave method. The anisotropy in Fermi
velocity, conductivity and plasma frequency stemming from the layered structure
are found to be enhanced by spin-orbit coupling. The relationship between
spin-orbit interaction and the lack of two-dimensional inversion in the PtAs
layers is analyzed within a tight-binding Hamiltonian based on the
first-principles calculations. Finally, the band structure suggests that
electron doping could increase $T_c$.",1202.1604v1
2012-04-09,Ising model: secondary phase transition,"Lttice-spin phonons are considered, which make the heat capacity at the
critical temperature satisfy experimental observations better. There is a BEC
phase transition in an Ising model attributable to the lattice-spin phonons. We
proved that the spin-wave theory only is available after BEC transition, and
the magnons have the same characteristics as the lattice-spin phonons',
resulting from quantum effect. Energy-level overlap effect at ultralow
temperature is found. A prediction of BEC phase transition in a crystal is put
forward as our theory generalization.",1204.1807v1
2012-06-18,"Combined Theory of Basis Sets of Spinors for Particles with Arbitrary Spin in Position, Momentum and Four-Dimensional Spaces","The 2(2s+1)-component relativistic basis spinors for the arbitrary spin
particles are established in position, momentum and four-dimensional spaces,
where s=0,1 / 2,1, 3 / 2, 2, ... . These spinors for integral- and
half-integral spins are reduced to the independent sets of one- and
twocomponent spinors, respectively. Relations presented in this study can be
useful in the linear combination of atomic orbitals approximation for the
solution of generalized Dirac equation of arbitrary spin particles introduced
by the author when the orthogonal basis sets of relativistic exponential type
spinor wave functions and Slater type spinor orbitals in position, momentum and
four -dimensional spaces are employed.",1206.3942v1
2013-07-31,Relativistic symmetries in Rosen-Morse potential and tensor interaction using the Nikiforov-Uvarov method,"Approximate analytical bound-state solutions of the Dirac particle in the
field of both attractive and repulsive RM potentials including Coulomb-like
tensor (CLT) potential are obtained for arbitrary spin-orbit quantum number The
Pekeris approximation is used to deal with the spin-orbit coupling terms In the
presence of exact spin and pseudospin (p-spin) symmetries, the energy
eigenvalues and the corresponding normalized two-component wave functions are
found by using the parametric generalization of the Nikiforov-Uvarov (NU)
method. The numerical results show that the CLT interaction removes
degeneracies between spin and p-spin state doublets.",1307.8311v1
2014-02-25,Spin state in the propagation of quantum relativistic particles along classical trajectories,"We address the propagation of the spin along classical trajectories for a
1/2-spin particle obeying the Dirac equation with scalar potentials. Focusing
on classical trajectories as the exact propagation of wave-function
discontinuities we find an explicit spin-transport law for the case of the
Dirac oscillator. In the general case we examine the spin propagation along
classical trajectories emerging as an approximation of the quantum dynamics via
the mechanical analog of the optical eikonal asymptotic approach. Throughout we
establish as many parallels as possible with the equivalent situation for the
electromagnetic field.",1402.6063v2
2014-04-08,General complex Spin Weak Values obtained in Matter-Wave Interferometer Experiments,"Weak values of the spin operator Sz of massive particles, more precisely
neutrons, have been experimentally determined by applying a novel measurement
scheme. This is achieved by coupling the neutron's spin weakly to its spatial
degree of freedom in a single-neutron interferometer setup. The real and
imaginary parts as well as the modulus of the weak value are obtained by a
systematical variation of pre- and post-selected ensembles, which enables to
study the complex properties of spin weak values.",1404.2125v1
2014-08-09,Mutual Phase Locking of Very Nonidentical Spin Torque Nanooscillators via Spin Wave Interaction,"In this paper the mutual phase locking theory of very nonidentical
spin-torque nanooscillators, which is based on the Slavin-Tiberkevich model,
considering the theory of nonlinear oscillations, is developed. Using
generalized Adler equation we calculate phase-locking region of the system with
spinwave coupling in the parameter plane - distance between nanocontacts and
radii difference. We describe trajectories of such a system in the phase space
and show the effect of a broadband synchronization. We introduce a
generalization of this approach to the ensembles of spin-torque nanooscillators",1408.2141v1
2016-06-05,"Comment on ""$Z_{2}$ spin liquid phase on the kagome lattice: a new saddle point"", by Tao Li [arXiv:1601.02165 (2016)]","In a recent paper [arXiv:1601.02165], Tao Li claimed that a gapped
$\mathbb{Z}_2$ spin liquid, obtained using projected Gutzwiller fermionic wave
functions, can be stabilized in the Heisenberg model on the kagome lattice. We
perform very accurate variational calculations and confirm with unprecedented
accuracy the fact, that the $\mathbb{Z}_{2}$ spin liquid is a local energy
minimum that goes away with system size, thus reaffirming the scenario of a
gapless $U(1)$ Dirac spin liquid ground state.",1606.02255v1
2016-08-21,Spin correlation functions and quasiparticle decay,"We study one-dimensional anisotropic XXZ spin-$\frac12$ model with
ferromagnetic sign of the coupling and $z-z$ exchange constant $J_z = \Delta
J$, where $\Delta < 1$, and $J$ is the coupling within XY spin plane. We
calculate damping of low-energy excitations with $\omega \ll T $ due to their
scattering from thermal excitation bath with temperature $T \ll J$, taking into
account nonzero curvature of the excitation spectrum, $\epsilon(q) = u q +
\delta\epsilon(q)$. We calculate also longitudinal spin-spin correlation
function $\langle S^z(x,t)S^z(0,0) \rangle$ at $x \approx ut$ and find the
shape of the spreading ""wave packet"".",1608.05937v1
2017-08-31,Highly efficient optical pumping of spin defects in silicon carbide for stimulated microwave emission,"We investigate the pump efficiency of silicon vacancy-related spins in
silicon carbide. For a crystal inserted into a microwave cavity with a
resonance frequency of 9.4 GHz, the spin population inversion factor of 75 with
the saturation optical pump power of about 350 mW is achieved at room
temperature. At cryogenic temperature, the pump efficiency drastically
increases, owing to an exceptionally long spin-lattice relaxation time
exceeding one minute. Based on the experimental results, we find realistic
conditions under which a silicon carbide maser can operate in continuous-wave
mode and serve as a quantum microwave amplifier.",1709.00052v1
2018-09-20,Highly Efficient Induction of Spin Polarization by Circularly-Polarized Electromagnetic Waves in the Rashba Spin-Orbit Systems,"We theoretically demonstrate that a rotating electric-field component of
circularly polarized microwave or terahertz light can induce electron-spin
polarization within a few picoseconds in a two-dimensional electron system with
the Rashba spin-orbit interaction by taking advantage of the magnetoelectric
coupling. The efficiency turns out to be several orders of magnitude greater
than that of conventional methods, indicating high potential of this technique
for future spintronics.",1809.07513v1
2017-05-03,Spin Resonance and Magnetic Order in an Unconventional Superconductor,"Unconventional superconductivity in many materials is believed to be mediated
by magnetic fluctuations. It is an open question how magnetic order can emerge
from a superconducting condensate and how it competes with the magnetic spin
resonance in unconventional superconductors. Here we study a model d-wave
superconductor that develops spin-density wave order, and find that the spin
resonance is unaffected by the onset of static magnetic order. This result
suggests a scenario, in which the resonance in Nd0.05Ce0.95CoIn5 is a
longitudinal mode with fluctuating moments along the ordered magnetic moments.",1705.01255v2
2018-10-23,Spin-locking metasurface for surface plasmon routing,"The spin-dependent routing of surface plasmons on metal by use of mirror
symmetric periodic metasurface is presented and analyzed. We incorporate the
intrinsic transverse spin angular momentum of the plasmonic wave in order to
efficiently couple the incident light carrying circular polarization to a
desired direction. The combination of the oblique incidence of polarized light
with the accurately designed momentum matching properties of the grating
provides a perfect way to achieve a spin-locking metasurface that routes the
plasmonic beams.",1810.09895v1
2017-06-18,Lorentz covariant and gauge invariant description of orbital and spin angular momentum and the non-symmetric energy momentum tensor,"Starting from covariant expressions, a gauge independent separation of
orbital and spin angular momentum for electrodynamics is presented. This
results from the non-symmetric canonical energy momentum tensor of the
electromagnetic field. The origin of the difficulty is discussed and a
covariant gauge invariant spin vector is derived. The paradox concerning the
spin angular momentum of a plane wave finds a natural solution.",1706.07665v2
2017-06-24,Magnon cotunneling through a quantum dot,"I consider a single-level quantum dot coupled to two reservoirs of spin waves
(magnons). Such systems have been studied recently from the point of view of
possible coupling between electronic and magnonic spin currents. However,
usually weakly coupled systems were investigated. When coupling between the dot
and reservoirs is not weak, then higher order processes play a role and have to
be included. Here I consider cotunneling of magnons through a spin-occupied
quantum dot, which can be understood as a magnon (spin) leakage current in
analogy to leakage currents in charge-based electronics. Particular emphasis
has been put on investigating the effect of magnetic field and temperature
difference between the magnonic reservoirs.",1706.07914v1
2019-03-08,Spin-perturbed orbits near black holes,"Inspirals of rotating stellar-mass compact objects into massive black holes
are influenced by the spin-curvature coupling, which drives the compact body
away from geodesic motion due to its rotation. I formulate the Hamilton-Jacobi
equation for a spinning test body orbiting a Kerr black hole, solve it to
linear order in spin, and use the perturbative solution to compute the
fundamental frequencies of motion along the orbit. This result provides one of
the necessary ingredients for waveform models for the upcoming space-based
gravitational-wave detector LISA.",1903.03649v1
2019-03-19,Quantum corrections to a spin-orbit coupled Bose-Einstein Condensate,"We study systematically the quantum corrections to a weakly interacting
Bose-Einstein condensate with spin-orbit coupling. We show that quantum
fluctuations, enhanced by the spin-orbit coupling, modify quantitatively the
mean-field properties such as the superfluid density, spin polarizability, and
sound velocity. We find that the phase boundary between the plane wave and zero
momentum phases is shifted to a smaller transverse field. We also calculate the
Beliaev and Landau damping rates and find that the Landau process dominates the
quasiparticle decay even at low temperature.",1903.08182v3
2020-09-22,Variational and parquet-diagram calculations for neutron matter. II. Twisted Chain Diagrams,"We develop a manifestly microscopic method to deal with strongly interacting
nuclear systems that have different interactions in spin-singlet and
spin-triplet states. In a first step we analyze variational wave functions that
have been suggested to describe such systems, and demonstrate that the
so-called commutator contributions can have important effects whenever the
interactions in the spin-singlet and the spin-triplet states are very
different. We then identify these contributions as terms that correspond, in
the language of perturbation theory, to non-parquet diagrams. We include these
diagrams in a way that is suggested by the Jastrow-Feenberg approach and show
that the corrections from non-parquet contributions are, at short distances,
larger than all other many-body effects.",2009.10849v1
2003-12-14,Theory of spin waves in diluted-magnetic-semiconductor quantum wells,"We present a theory of collective spin excitations in
diluted-magnetic-semiconductor quantum wells in which local magnetic moments
are coupled via a quasi-two-dimensional gas of electrons or holes. In the case
of a ferromagnetic state with partly spin-polarized electrons, we find that the
Goldstone collective mode has anomalous $k^4$ dispersion and that for symmetric
quantum wells odd parity modes do not disperse at all. We discuss the gap in
the collective excitation spectrum which appears when spin-orbit interactions
are included.",0312347v2
2008-06-04,External magnetic field effects on a distorted kagome antiferromagnet,"We report bulk magnetization, and elastic and inelastic neutron scattering
measurements under an external magnetic field, $H$, on the weakly coupled
distorted kagome system, Cu_{2}(OD)_3Cl. Our results show that the ordered
state below 6.7 K is a canted antiferromagnet and consists of large
antiferromagnetic $ac$-components and smaller ferromagnetic $b$-components. By
first-principle calculations and linear spin wave analysis, we present a simple
spin hamiltonian with non-uniform nearest neighbor exchange interactions
resulting in a system of coupled spin trimers with a single-ion anisotropy that
can qualitatively reproduce the spin dynamics of Cu_{2}(OD)_3Cl.",0806.0767v1
2008-06-05,On the possibility of metamaterial properties in spin plasmas,"The fluid theory of plasmas is extended to include the properties of electron
spin. The linear theory of waves in a magnetized plasma is presented, and it is
shown that the spin effects causes a change of the magnetic permeability.
Furthemore, by changing the direction of the external magnetic field, the
magnetic permability may become negative. This leads to instabilities in the
long wavelength regimes. If these can be controlled, however, the spin plasma
becomes a metamaterial for a broad range of frequencies, i.e. above the ion
cyclotron frequency but below the electron cyclotron frequency. The
consequences of our results are discussed.",0806.0912v1
2017-01-17,Vortex pairs in a spin-orbit coupled Bose-Einstein condensate,"Static and dynamic properties of vortices in a two-component Bose-Einstein
condensate with Rashba spin-orbit coupling are investigated. The mass current
around a vortex core in the plane-wave phase is found to be deformed by the
spin-orbit coupling, and this makes the dynamics of the vortex pairs quite
different from those in a scalar Bose-Einstein condensate. The velocity of a
vortex-antivortex pair is much smaller than that without spin-orbit coupling,
and there exist stationary states. Two vortices with the same circulation move
away from each other or unite to form a stationary state.",1701.04591v1
2019-10-01,Magnetic excitation in relativistic heavy ion collisions,"In this note we study the conversion of nucleons into deltas induced by a
strong magnetic field in ultraperipheral relativistic heavy ion collisions. The
interaction Hamiltonian couples the magnetic field to the spin operator, which,
acting on the spin part of the wave function, converts a spin 1/2 into a spin
3/2 state. We estimate this transition probability and calculate the cross
section for delta production. This process can in principle be measured, since
the delta moves close to the beam and decays almost exclusively into pions.
Forward pions may be detected by forward calorimeters.",1910.00711v1
2019-10-14,Multifractality in aperiodic quantum spin chains,"Recently has been investigated that the ground-state wavefunction of the one
dimensional quantum spin-1/2 chain models is multifractal in general with
non-trivial fractal dimension. We are studying this phenomena for the quantum
Ising chain with an aperiodic perturbation. By performing a block real-space
renormalization approach, we obtain the ground-state wave function and we
extract the generalized fractal dimension and the multifractal spectrum. For a
spin chain with negative wandering exponent the multifractal quantities have
the same behavior with the unperturbed chain while for a spin chain with a
vanishing wandering exponent are dependent on the coupling ratio. Finally, for
a spin chain with positive wandering exponent, the multifractal quantities
present a different non-linear behavior.",1910.05931v1
2020-01-28,Spin-dependent two-photon Bragg scattering in the Kapitza-Dirac effect,"We present the possibility of spin-dependent Kapitza-Dirac scattering based
on a two-photon interaction only. The interaction scheme is inspired from a
Compton scattering process, for which we explicitly show the mathematical
correspondence to the spin-dynamics of an electron diffraction process in a
standing light wave. The spin effect has the advantage that it already appears
in a Bragg scattering setup with arbitrary low field amplitudes, for which we
have estimated the diffraction count rate in a realistic experimental setup at
available X-ray free-electron laser facilities.",2001.10177v2
2022-10-13,Sound Waveguiding by Spinning: An Avenue towards Unidirectional Acoustic Spinning Fibers,"Waveguiding in general and acoustic waveguiding in particular are possible at
the condition of having a transverse ""discontinuity"" or modulation of the
refractive index. We propose here a radically different approach that relies on
imposing spinning on a column of air, leading to high modified acoustic
refractive indices for specific azimuthal modes. Such discovery may be
leveraged to realize not only the airborne acoustic counterpart of the optical
fiber, i.e., the acoustic spinning fiber (ASF), but also nonreciprocal
unidirectional waveguiding mechanism, reminiscent of the ''acoustic Zeeman
effect''. The concept is demonstrated in the realm of acoustics, yet it can be
applicable to other wave systems, e.g., photonics or elastodynamics.",2210.09061v1
2023-12-22,Hyperbolic Spin Waves in Magnetic Polar Metals,"We demonstrate the emergence of collective spin modes with hyperbolic
dispersion in three-dimensional spin-orbit coupled polar metals magnetized by
intrinsic ordering or applied fields. These particle-hole bound states exist
for arbitrarily weak repulsive interactions; they are optically accessible and
can be used to generate pure spin current when magnetization is tilted away
from the polar axis. We suggest material hosts for these excitations and
discuss their potential relevance to nanoscale spintronic and polaritonic
applications.",2312.14377v2
2006-04-07,Resonant Tidal Excitations of Inertial Modes in Coalescing Neutron Star Binaries,"We study the effect of resonant tidal excitation of inertial modes in neutron
stars during binary inspiral. For spin frequencies less than 100 Hz, the phase
shift in the gravitational waveform associated with the resonance is small and
does not affect the matched filtering scheme for gravitational wave detection.
For higher spin frequencies, the phase shift can become significant. Most of
the resonances take place at orbital frequencies comparable to the spin
frequency, and thus significant phase shift may occur only in the
high-frequency band (hundreds of Hertz) of gravitational wave. The exception is
a single odd-paity $m=1$ mode, which can be resonantly excited for misaligned
spin-orbit inclinations, and may occur in the low-frequency band (tens of
Hertz) of gravitational wave and induce significant (>> 1 radian) phase shift.",0604163v2
1996-05-22,High-Frequency Spin Waves in YBa2Cu3O6.15,"Pulsed neutron spectroscopy is used to make absolute measurements of the
dynamic magnetic susceptibility of insulating YBa2Cu3O6.15. Acoustic and
optical modes, derived from in- and out-of-phase oscillation of spins in
adjacent CuO2 planes, dominate the spectra and are observed up to 250 meV. The
optical modes appear first at 74 meV. Linear-spin-wave theory gives an
excellent description of the data and yields intra- and inter-layer exchange
constants of J_parallel =125 meV and J_perp = 11 meV respectively and a
spin-wave intensity renormalization Z_chi = 0.4.",9605139v2
1998-07-14,Reorientation of Spin Density Waves in Cr(001) Films induced by Fe(001) Cap Layers,"Proximity effects of 20 \AA thin Fe layers on the spin density waves (SDWs)
in epitaxial Cr(001) films are revealed by neutron scattering. Unlike in bulk
Cr we observe a SDW with its wave vector Q pointing along only one {100}
direction which depends dramatically on the film thickness t_{Cr}. For t_{Cr} <
250 \AA the SDW propagates out-of-plane with the spins in the film plane. For
t_{Cr} > 1000 \AA the SDW propagates in the film plane with the spins
out-of-plane perpendicular to the in-plane Fe moments. This reorientation
transition is explained by frustration effects in the antiferromagnetic
interaction between Fe and Cr across the Fe/Cr interface due to steps at the
interface.",9807212v2
1999-10-18,Field-induced magnetic reorientation and effective anisotropy of a ferromagnetic monolayer within spin wave theory,"The reorientation of the magnetization of a ferromagnetic monolayer is
calculated with the help of many-body Green's function theory. This allows, in
contrast to other spin wave theories, a satisfactory calculation of magnetic
properties over the entire temperature range of interest since interactions
between spin waves are taken into account. A Heisenberg Hamiltonian plus a
second-order uniaxial single-ion anisotropy and an external magnetic field is
treated by the Tyablikov (Random Phase Approximation: RPA) decoupling of the
exchange interaction term and the Anderson-Callen decoupling of the anisotropy
term. The orientation of the magnetization is determined by the spin components
$\la S^\alpha\ra$ ($\alpha=x,y,z$), which are calculated with the help of the
spectral theorem. The knowledge of the orientation angle $\Theta_0$ allows a
non-perturbative determination of the temperature dependence of the effective
second-order anisotropy coefficient. Results for the Green's function theory
are compared with those obtained with mean-field theory (MFT). We find
significant differences between these approaches.",9910280v1
1999-10-28,Magnetic Properties of Weakly Doped Antiferromagnets,"We study the spin excitations and the transverse susceptibility of a
two-dimensional antiferromagnet doped with a small concentration of holes in
the t-J model. The motion of holes generates a renormalization of the magnetic
properties. The Green's functions are calculated in the self-consistent Born
approximation. It is shown that the long-wavelength spin waves are
significantly softened and the shorter-wavelength spin waves become strongly
damped as the doping increases. The spin wave velocity is reduced by the
coherent motion of holes, and not increased as has been claimed elsewhere. The
transverse susceptibility is found to increase considerably with doping, also
as a result of coherent hole motion. Our results are in agreement with
experimental data for the doped copper oxide superconductors.",9910474v1
1999-11-24,Exactly solvable two-dimensional quantum spin models,"A method is proposed for constructing an exact ground-state wave function of
a two-dimensional model with spin 1/2. The basis of the method is to represent
the wave function by a product of fourth-rank spinors associated with the sites
of a lattice and the metric spinors corresponding to bonds between nearest
neighbor sites. The function so constructed is an exact wave function of a
14-parameter model. The special case of this model depending on one parameter
is analyzed in detail. The ground state is always a nondegenerate singlet, and
the spin correlation functions decay exponentially with distance. The method
can be generalized for models with spin 1/2 to other types of lattices.",9911399v1
2000-01-06,Soft spin waves in the low temperature thermodynamics of Pr_{0.7}Ca_{0.3}MnO_{3},"We present a detailed magnetothermal study of Pr(0.7)Ca(0.3)MnO(3), a
perovskite manganite in which an insulator-metal transition can be driven by
magnetic field, but also by pressure, visible light, x-rays, or high currents.
We find that the field-induced transition is associated with an enormous
release of energy which accounts for its strong irreversibility. In the
ferromagnetic metallic state, specific heat and magnetization measurements
indicate a much smaller spin wave stiffness than that seen in any other
manganite, which we attribute to spin waves among the ferromagnetically ordered
Pr moments. The coupling between the Pr and Mn spins may also provide a basis
for understanding the low temperature phase diagram of this most unusual
manganite.",0001065v2
2000-10-26,Fingerprints of spin-fermion pairing in cuprates,"We demonstrate that the feedback effect from bosonic excitations on fermions,
which in the past allowed one to verify the phononic mechanism of a
conventional, $s-$wave superconductivity, may also allow one to experimentally
detect the ``fingerprints'' of the pairing mechanism in cuprates. We argue that
for spin-mediated $d-$wave superconductivity, the fermionic spectral function,
the density of states, the tunneling conductance through an insulating
junction, and the optical conductivity are affected by the interaction with
collective spin excitations, which below $T_c$ are propagating, magnon-like
quasiparticles with gap $\Delta_s$.
  We show that the interaction with a propagating spin excitation gives rise to
singularities at frequencies $\Delta + \Delta_s$ for the spectral function and
the density of states, and at
  $2\Delta + \Delta_s$ for tunneling and optical conductivities, where $\Delta$
is the maximum value of the $d-$wave gap. We further argue that recent optical
measurements also allow one to detect subleading singularities at $4\Delta$ and
$2\Delta + 2\Delta_s$. We consider the experimental detection of these
singularities as a strong evidence in favor of the magnetic scenario for
superconductivity in cuprates.",0010403v1
2000-12-01,Spin-wave theory for finite classical magnets and superparamagnetic relation,"Analytical calculations based on finite-size spin-wave theory and Monte Carlo
(MC) simulations are performed to investigate the validity of the well-known
relation m(H,T)=M(H,T)B_D[M(H,T)NH/T] between the induced magnetization m of
the magnetic particle and its intrinsic magnetization M for the Ising and
isotropic classical models [B_D(x) is the Langevin function, D is the number of
spin components, N is the number of atoms in the particle]. It follows from
general arguments and from our analytical results for the Heisenberg model at T
<< T_c that this relation is not exact for any finite D and nonzero
temperature. Nevertheless, corrections to this formula remain very small
practically in the whole range T<T_c if N >> 1, as confirmed by our Monte Carlo
calculations. At T <~ T_c/4 there is a good agreement between the
  MC and finite-size spin-wave calculations for the field dependence of m and M
for the Heisenberg model with free boundary conditions.",0012017v2
2000-12-24,Magnetic order and spin-waves in the quasi-1D S=1/2 antiferromagnet ${\bf BaCu_{2}Si_{2}O_{7}}$,"Elastic and inelastic neutron scattering were used to study the ordered phase
of the quasi-one-dimensional spin-1/2 antiferromagnet ${\rm
BaCu_{2}Si_{2}O_{7}}$. The previously proposed model for the low-temperature
magnetic structure was confirmed. Spin wave dispersion along several
reciprocal-space directions was measured and inter-chain, as well as in-chain
exchange constants were determined. A small gap in the spin wave spectrum was
observed and attributed to magnetic anisotropy effects. The results are
discussed in comparison with existing theories for weakly-coupled quantum spin
chain antiferromagnets.",0012452v1
2002-05-21,Linear spin waves in a trapped Bose gas,"An ultra-cold Bose gas of two-level atoms can be thought of as a spin-1/2
Bose gas. It supports spin-wave collective modes due to the exchange mean
field. Such collective spin oscillations have been observed in recent
experiments at JILA with ${}^{87}$Rb atoms confined in a harmonic trap. We
present a theory of the spin-wave collective modes based on the moment method
for trapped gases. In the collisionless and hydrodynamic limits, we derive
analytic expressions for the frequencies and damping rates of modes with dipole
and quadrupole symmetry. We find that the frequency for a given mode is given
by a temperature independent function of the peak density $n$, and falls off as
$1/n$. We also find that, to a very good approximation, excitations in the
radial and axial directions are decoupled. We compare our model to the
numerical integration of a one dimensional version of the kinetic equation and
find very good qualitative agreement. The damping rates, however, show the
largest deviation for intermediate densities, where one expects Landau damping
-- which is unaccounted for in our moment approach -- to play a significant
role.",0205450v1
2003-10-20,Current-driven excitations in magnetic multilayers: a brief review,"In 1996, Berger and Slonczewski independently predicted that a large enough
spin-polarized dc current density sent perpendicularly through a ferromagnetic
layer could produce magnetic excitations (spin-waves) or reversal of
magnetization (switching). In the past few years, both current-driven switching
and current-driven excitation of spin-waves have been observed. The switching
is of potential technological interest for direct 'writing' of magnetic random
access memory (MRAM) or magnetic media. The spin-wave generation could provide
a new source of dc generated microwave radiation. We describe what has been
learned experimentally about these two related phenomena, and some models being
tested to explain these observations.",0310467v1
2004-11-13,Theory of polarized Fermi liquid,"The dispersion law of transverse spin waves known in the Stoner-Hubbard model
of itinerant ferromagnetism corresponds to that is well known in more broder
and well controlled approach of Fermi-liquid theory. Making use the
quantum-field theoretical approach we derive the dispersion law for the
transverse spin waves in a weakly polarized Fermi liquid at T=0. Along with the
dissipationless part inversely proportional to the polarization it contains
also the finite zero-temperature damping. It is shown that similar derivation
for ""ferromagnetic Fermi liquid"" taking into consideration the divergency of
static transverse susceptibility also leads to the same attenuating spin wave
spectrum. Hence, in both cases we deal in fact with spin polarized Fermi liquid
but not with isotropic itinerant ferromagnet where the zero temperature
atenuation is prohibited by Goldstone theorem. It demonstrates, the troubles of
the Fermi liquid formulation of a theory of itinerant ferromagnetic systems.",0411361v1
2005-01-05,Magnetic susceptibility of a CuO2 plane in the La2CuO4 system: I. RPA treatment of the Dzyaloshinskii-Moriya Interactions,"Motivated by recent experiments on undoped La2CuO4, which found pronounced
temperature-dependent anisotropies in the low-field magnetic susceptibility, we
have investigated a two-dimensional square lattice of S=1/2 spins that interact
via Heisenberg exchange plus the symmetric and anti-symmetric
Dzyaloshinskii-Moriya anisotropies. We describe the transition to a state with
long-ranged order, and find the spin-wave excitations, with a mean-field
theory, linear spin-wave analysis, and using Tyablikov's RPA decoupling scheme.
We find the different components of the susceptibility within all of these
approximations, both below and above the N'eel temperature, and obtain evidence
of strong quantum fluctuations and spin-wave interactions in a broad
temperature region near the transition.",0501086v1
2005-06-28,A macroscopic persistent current generation by merons in a spin density wave ordered state,"We show that a stable spontaneous current appears in a system of a spin
density wave order with merons, vortices in the spin configuration with winding
number +1. A meron in the spin density wave order modifies the boundary
condition for eigenfunctions around it to a sign-change one. As a consequence,
two types of stable current states, one with a clockwise circulation and the
other with a counterclockwise one, arise. When a magnetic field is present, one
produces a diamagnetic current is chosen. A collection of such currents results
in a large diamagnetic current; and if the meron density is sufficiently large,
a perfect diamagnetism is realized. The stability of this diamagnetic current
is attributed to the topological nature of the merons, and as long as the
distribution of the merons remains the same the current will persist even in a
macroscopic system.",0506747v1
2005-08-24,Spin-Wave Relaxation in Diluted Magnetic Semiconductors within the Self-Consistent Green's Function Approach,"We employ a self-consistent Green's function approach to investigate the
spin-wave relaxation \Gamma(p) in diluted magnetic semiconductors. We find the
trend of the spin-wave relaxation strongly depends on the ratio of the
itinerant and impurity spin densities. For density ratios in the
Ruderman-Kittel-Kasuya-Yosida phase, \Gamma(p) decreases even though thermal
fluctuations increase. On the other hand, in the strong coupling phase, an
interesting peak structure appears. We discuss the implications of our
numerical results for experiments.",0508565v3
2006-01-18,Spin-density-wave order in cuprates,"We study the nature of the two-dimensional quantum critical point separating
two phases with and without long-range spin-density-wave order, which has been
recently observed in cuprate superconductors. We consider the
Landau-Ginzburg-Wilson Hamiltonian associated with the spin-density critical
modes, perform a mean-field analysis of the phase diagram, and study the
corresponding renormalization-group flow in two different perturbative schemes
at five and six loops, respectively. The analysis supports the existence of a
stable fixed point in the full theory whose basin of attraction includes
systems with collinear spin-density-wave order, as observed in experiments. The
stable fixed point is characterized by an enlarged O(4)xO(3) symmetry. The
continuous transition observed in experiments is expected to belong to this
universality class. The corresponding critical exponents are nu = 0.9(2) and
eta = 0.15(10).",0601404v1
2006-12-05,Multi-component gap solitons in spinor Bose-Einstein condensates,"We model the nonlinear behaviour of spin-1 Bose-Einstein condensates (BECs)
with repulsive spin-independent interactions and either ferromagnetic or
anti-ferromagnetic (polar) spin-dependent interactions, loaded into a
one-dimensional optical lattice potential. We show that both types of BECs
exhibit dynamical instabilities and may form spatially localized
multi-component structures. The localized states of the spinor matter waves
take the form of vector gap solitons and self-trapped waves that exist only
within gaps of the linear Bloch-wave band-gap spectrum. Of special interest are
the nonlinear localized states that do not exhibit a common spatial density
profile shared by all condensate components, and consequently cannot be
described by the single mode approximation (SMA), frequently employed within
the framework of the mean-field treatment. We show that the non-SMA states can
exhibits Josephson-like internal oscillations and self-magnetisation, i.e.
intrinsic precession of the local spin. Finally, we demonstrate that
non-stationary states of a spinor BEC in a lattice exhibit coherent undamped
spin-mixing dynamics, and that their controlled conversion into a stationary
state can be achieved by the application of an external magnetic field.",0612104v1
2001-04-04,Interaction between gravitational waves and domain walls,"We study the gravitational perturbations of thick domain walls. The
refraction index and spin properties of the solutions interior to the wall are
analyzed in detail. It is shown that the gravitational waves suffer a
refraction process by domain walls. The reflection and transmission
coefficients are derived in the thin wall limit. In relation to the spin
content, it is shown that the ``$\times$'' helicity 2 gravitational wave mode
maintains in the domain wall the same polarization state as in vacuum. On the
contrary, the ``+'' mode, of pure helicity 2 in vacuum, is contaminated inside
the wall with a spin 0 state, as well as with spin 2, helicity 0 and 1 states.",0104015v2
2006-06-04,Dynamic generation of entangling wave packets in XY spin system with decaying long range couplings,"We study the dynamic generation of spin entanglement between two distant
sites in an XY model with $1/r^{2}$-decay long range couplings. Due to the
linear dispersion relation $\epsilon (k)\sim |k|$ of magnons in such model, we
show that a well-located spin state can be dynamically split into two moving
entangled local wave packets without changing their shapes. Interestingly, when
such two wave packets meet at the diametrically opposite site after the fast
period $\tau =\pi $, the initial well-located state can be recurrent
completely. Numerical calculation is performed to confirm the analytical result
even the ring system of sizes $N$ up to several thousands are considered. The
truncation approximation for the coupling strengths is also studied. Numerical
simulation shows that the above conclusions still hold even the range of the
coupling strength is truncated at a relative shorter scale comparing to the
size of the spin system.",0606029v1
2008-03-15,Effects of disorder on atomic density waves and spin-singlet dimers in one-dimensional optical lattices,"Using the Bethe-ansatz density-functional theory, we study a one-dimensional
Hubbard model of confined attractively interacting fermions in the presence of
a uniformly distributed disorder. The strongly-correlated Luther-Emery nature
of the attractive one-dimensional Hubbard model is fully taken into account as
the reference system in the density-functional theory. The effects of the
disorder are investigated on the atomic-density waves in the
weak-to-intermediate attractive interaction and on the spin-singlet dimers of
doubly occupied sites in the strongly attractive regime. It is found that
atomic density waves are sensitive to the disorder and the spin-singlet dimers
of doubly occupied sites are quite unstable against the disorder. We also show
that very weak disorder could smear the singularities in the stiffness, thus
suppress the spin-singlet pairs.",0803.2312v2
2009-02-09,Magnetization reversal via internal spin waves in magnetic nanoparticles,"By numerically solving the equations of motion for atomic spins we show that
internal spin-wave processes in large enough magnetic particles, initially in
unstable states, lead to complete magnetization reversal and thermalization.
The particle's magnetization strongly decreases in the middle of reversal and
then recovers. We identify two main scenarios, exponential and linear spin-wave
instabilities. For the latter, the longitudinal and transverse relaxation rates
have been obtained analytically. Orientation dependence of these rates leads to
a nonexponential relaxation of the particle's magnetization at long times.",0902.1492v1
2009-03-17,Microscopic spin-wave theory for yttrium-iron garnet films,"Motivated by recent experiments on thin films of the ferromagnetic insulator
yttrium-iron garnet (YIG), we have developed an efficient microscopic approach
to calculate the spin-wave spectra of these systems. We model the
experimentally relevant magnon band of YIG using an effective quantum
Heisenberg model on a cubic lattice with ferromagnetic nearest neighbor
exchange and long-range dipole-dipole interactions. After a bosonization of the
spin degrees of freedom via a Holstein-Primakoff transformation and a
truncation at quadratic order in the bosons, we obtain the spin-wave spectra
for experimentally relevant parameters without further approximation by
numerical diagonalization, using efficient Ewald summation techniques to carry
out the dipolar sums. We compare our numerical results with two different
analytic approximations and with predictions based on the phenomenological
Landau-Lifshitz equation.",0903.2847v2
2009-07-03,"Phonon anomalies in pure and underdoped R{1-x}K{x}Fe{2}As{2} (R = Ba, Sr) investigated by Raman light scattering","We present a detailed temperature dependent Raman light scattering study of
optical phonons in Ba{1-x}K{x}Fe{2}As{2} (x ~ 0.28, superconducting Tc ~ 29 K),
Sr{1-x}K{x}Fe{2}As{2} (x ~ 0.15, Tc ~ 29 K) and non-superconducting
BaFe{2}As{2} single crystals. In all samples we observe a strong continuous
narrowing of the Raman-active Fe and As vibrations upon cooling below the
spin-density-wave transition Ts. We attribute this effect to the opening of the
spin-density-wave gap. The electron-phonon linewidths inferred from these data
greatly exceed the predictions of ab-initio density functional calculations
without spin polarization, which may imply that local magnetic moments survive
well above Ts. A first-order structural transition accompanying the
spin-density-wave transition induces discontinuous jumps in the phonon
frequencies. These anomalies are increasingly suppressed for higher potassium
concentrations. We also observe subtle phonon anomalies at the superconducting
transition temperature Tc, with a behavior qualitatively similar to that in the
cuprate superconductors.",0907.0560v2
2009-10-17,Spin waves in a spin-1 Bose gas,"We present a theory of spin waves in a non-condensed gas of spin-1 bosons:
providing both analytic calculations of the linear theory, and full numerical
simulations of the nonlinear response. We highlight the role of spin-dependent
contact interactions in the dynamics of a thermal gas. Although these
interactions are small compared to the thermal energy, they set the scale for
low energy long wavelength spin waves. In particular, we find that the polar
state of Rb-87 is unstable to collisional mixing of magnetic sublevels even in
the normal state. We augment our analytic calculations by providing full
numerical simulations of a trapped gas, explicitly demonstrating this
instability. Further we show that for strong enough anti-ferromagnetic
interactions, the polar gas is unstable. Finally we explore coherent population
dynamics in a collisionless transversely polarized gas.",0910.3268v1
2009-12-16,Coupling of spin and orbital excitations in the iron-based superconductor FeSe(0.5)Te(0.5),"We present a combined analysis of neutron scattering and photoemission
measurements on superconducting FeSe(0.5)Te(0.5). The low-energy magnetic
excitations disperse only in the direction transverse to the characteristic
wave vector (1/2,0,0), whereas the electronic Fermi surface near (1/2,0,0)
appears to consist of four incommensurate pockets. While the spin resonance
occurs at an incommensurate wave vector compatible with nesting, neither
spin-wave nor Fermi-surface-nesting models can describe the magnetic
dispersion. We propose that a coupling of spin and orbital correlations is key
to explaining this behavior. If correct, it follows that these nematic
fluctuations are involved in the resonance and could be relevant to the pairing
mechanism.",0912.3205v2
2010-05-27,Spin waves in diluted magnetic quantum wells,"We study collective spin excitations in two-dimensional diluted magnetic
semiconductors, placed into external magnetic field. Two coupled modes of the
spin waves (the electron and ion modes) are found to exist in the system along
with a number of the ion spin excitations decoupled from the electron system.
We calculate analytically the spectrum of the waves taking into account the
exchange interaction of itinerant electrons both with each other and with
electrons localized on the magnetic ions. The interplay of these interactions
leads to a number of intriguing phenomena including tunable anticrossing of the
modes and a field-induced change in a sign of the group velocity of the ion
mode.",1005.5138v2
2010-07-12,Instabilities near the onset of spin density wave order in metals,"We discuss the low energy theory of two-dimensional metals near the onset of
spin density wave order. It is well known that such a metal has a
superconducting instability induced by the formation of spin-singlet pairs of
electrons, with the pairing amplitude changing sign between regions of the
Fermi surface connected by the spin density wave ordering wavevector. Here we
review recent arguments that there is an additional instability which is nearly
as strong: towards the onset of a modulated bond order which is locally an
Ising-nematic order. This new instability is a consequence of an emergent
""pseudospin"" symmetry of the low energy theory---the symmetry maps the
sign-changing pairing amplitude to the bond order parameter.",1007.1968v3
2010-08-05,A model-independent analysis of p + p --> pp(1S0) + gamma,"The pp hard bremsstrahlung reaction, p + p --> pp(1S0) + gamma, in which the
two protons in the final state are in the 1S0 state, is investigated
theoretically. Here, the most general spin structure of the NN hard
bremsstrahlung reaction, consistent with symmetry principles, is derived from a
partial-wave expansion of this amplitude. Based on this spin structure, it is
shown that there are only four independent spin matrix elements in this
reaction, which is a direct consequence of reflection symmetry in the reaction
plane. It is also shown that it requires at least eight independent observables
to determine them uniquely. The present method provides the coefficients
multiplying each spin operator in terms of the partial-wave or, equivalently,
multipole amplitudes. Some observables are expressed explicitly in terms of
these multipoles and a partial-wave analysis is performed. The results should
be useful in the analyses of the experimental data on the p + p --> pp(1S0) +
gamma reaction being taken, in particular, at the COSY accelerator facility, as
well as in providing some theoretical guidance to the future experiments in
this area.",1008.0943v2
2010-08-30,Neutrino cooling and spin-down of rapidly rotating compact stars,"The gravitational-wave instability of r-modes in rapidly rotating compact
stars is believed to spin them down to angular frequencies of about a tenth of
the Kepler frequency soon after their birth in a Supernova. We point out that
the r-mode perturbation also impacts the neutrino cooling and viscosity in hot
compact stars via processes that restore weak equilibrium. We illustrate this
fact with a simple model of spin-down due to gravitational wave emission in
compact stars composed entirely of three-flavor degenerate quark matter (a
strange quark star). Non-equilibrium neutrino cooling of this oscillating fluid
matter is quantified. Our results imply that a consistent treatment of thermal
and spin-frequency evolution of a young and hot compact star is a requisite in
estimating the persistence of gravitational waves from such a source.",1008.4985v1
2010-12-23,Non-collinear spin-density wave antiferromagnetism in FeAs,"We present the magnetic structure of the itinerant monoarsenide, FeAs, with
the B31 structure. Powder neutron diffraction confirms incommensurate modulated
magnetism with wavevector $\mathbf{q} = (0.395\pm0.001)\mathbf{c}^*$ at 4 K,
but cannot distinguish between a simple spiral and a collinear spin-density
wave structure. Polarized single crystal diffraction confirms that the
structure is best described as a non-collinear spin-density wave arising from a
combination of itinerant and localized behavior with spin amplitude along the
b-axis direction being (15 $\pm$ 5)% larger than in the a-direction.
Furthermore, the propagation vector is temperature dependence, and the
magnetization near the critical point indicates a two-dimensional Heisenberg
system. The nature of the magnetism in the simplest iron arsenide is of
fundamental importance in understanding the interplay between localized and
itinerant magnetism and superconductivity.",1012.5311v2
2011-04-21,Unified quantitative model for magnetic and electronic spectra of the undoped cuprates,"Using low-energy projection of the one-band t-t'-t""-Hubbard model we derive
an effective spin-Hamiltonian and its spin-wave expansion to order 1/S. We fit
the spin-wave dispersion of several parent compounds to the high-temperature
superconducting cuprates: La2CuO4, Sr2CuO2Cl2 and Bi2Sr2YCu2O8. Our accurate
quantitative determination of the one-band Hubbard model parameters allows
prediction and comparison to experimental results of measurable quantities such
as staggered moment, double occupancy density, spin-wave velocity and bimagnon
excitation spectrum and density of states, which is discussed in relation to
K-edge RIXS and Raman experiments.",1104.4224v1
2011-04-21,Field-Induced Spin-Exciton Condensation in dx2-y2-wave Superconducting CeCoIn5,"The implications of the spin exciton mechanism are exposed in the context of
a Spin Density Wave (SDW) instability occurring inside the superconducting
phase of a layered heavy electron compound. In this model a magnetic field
serves as a tuning parameter bringing the system to the point where the
transverse spin correlations are enhanced due to dx2 -y2 -wave
superconductivity and induces an instability to a phase with coexisting
superconductivity and SDW order. The model considers electrons in a crystal
with antiferromagnetic interactions and provides restrictions on the Fermi
surface characteristics and on the ordering wave-vector (that can be
commensurate or incommensurate close to commensuration). The applications of
the model are addressed to the low-temperature/high-magnetic-field phase of
CeCoIn5 [M. Kenzelmann et al., Science 321, 1652 (2008), Phys. Rev. Lett. 104,
127001 (2010)].",1104.4309v3
2011-05-27,Mechanisms of nonlinear spin-wave emission from a microwave driven nanocontact,"We present a micromagnetic study of linear and nonlinear spin-wave modes
excited in an extended permalloy thin film by a microwave driven nanocontact.
We show that the linear mode having the frequency equal to the excitation
frequency (f) is driven by the ac Oersted field component perpendicular to the
static external field (applied in-plane of the sample). The nonlinear mode with
the frequency f /2 is excited as an independent eigenmode within a parametric
longitudinal pumping process (due ac Oersted field component parallel to the
bias field). Spectral positions of those modes are determined both in the space
and phase domain. The results are important for the transfer of information
coded into spin-waves between nanocontacts, and for synchronization of spin
transfer torque nano-oscillators.",1105.5512v1
2011-07-29,"Spin-wave excitations in the ferromagnetic-metallic and in the charge, orbital and spin ordered states in Nd$_{1-x}$Sr$_{x}$MnO$_{3}$ with x$\approx$0.5","Inelastic neutron scattering experiments have been performed on single
crystals of Nd$_{1-x}$Sr$_{x}$MnO$_{3}$ with x$\approx$0.5. Colossal
magnetoresistance (CMR) in the manganites arises from the interplay between a
ferromagnetic metallic and antiferromagnetic charge and orbital ordered
insulating state. Therefore, it appears important to compare these phases
concerning their underlying magnetic interaction parameters. Our investigations
of the spin-wave disperion in the AFM ordered state of
Nd$_{0.5}$Sr$_{0.5}$MnO$_{3}$ exhibits a strongly anisotropic stiffness. The
sign of the anisotropy is characteristic for the site-centered model for charge
and orbital ordering in half-doped manganites. Within this model, linear
spin-wave theory yields a perfect description of the experimental dispersion.
Furthermore, magnetic excitations in the ferromagnetic metallic state of
Nd$_{1-x}$Sr$_{x}$MnO$_{3}$ with x=0.49 and x=0.50 exhibit nearly the same
magnon dispersion which can be described with a Heisenberg model including
nearest-neighbor interactions.",1107.5882v1
2012-01-11,Plasmons in single- and double-component helical liquids: Application to two-dimensional topological insulators,"The plasmon excitations in proposed single- and double-component helical
liquid (HL) models are investigated within the random-phase approximation, by
calculating the density-density, spin-density and spin-spin waves. The effect
due to broken time-reversal symmetry on intraband-plasmon dispersion relation
in the single-component HL system is analyzed and compared to those of
well-known cases, such as conventional quasi-one-dimensional electron gases and
armchair graphene nanoribbons. The equivalence between the density-density wave
in the single-component HL to the coupled spin-density and density-density
waves in the double-component HL is shown here and explained, in addition to
the difference between intraband and interband-plasmon excitations in these two
systems. Since the two-component HL can physically be thought of as a Kramers
pair in two-dimensional topological insulators, our proposed single-component
HL model with broken time-reversal symmetry, which is an artificial construct,
can be viewed as an ""effective"" model in this sense and its prediction may be
verified in realistic systems in future experiments.",1201.2359v2
2012-02-13,Crossover from inelastic magnetic scattering of Cooper pairs to spin-wave dispersion produces low-energy kink in cuprates,"We present GW based self-energy calculations for the state of coexisting
spin-density wave and d-wave superconductivity in a series of cuprate
superconductors. In these systems, the spin resonance spectrum exhibits the
typical `hour-glass' form, whose upward and downward dispersion branches come
from the gapped spin-wave and magnetic scattering of Cooper pairs,
respectively. We show that the crossover between these two different dispersion
features leads to an abrupt change in slope in the quasiparticle self-energy,
and hence the low-energy kink commences in the single-particle quasiparticle
spectrum. The calculated electron-bosonic coupling strength agrees well with
experimental data as a function of temperature, doping and material. The
results demonstrate that the electronic correlations dominate the quasiparticle
spectra of cuprates near the low-energy kink, suggesting a relatively smaller
role for phonons in this energy range.",1202.2596v1
2012-12-10,Continuous wave solutions in spinor Bose-Einstein condensates,"We find analytic continuous wave (cw) solutions for spinor Bose-Einstein
condenates (BECs) in a magnetic field that are more general than those
published to date. For particles with spin F=1 in a homogeneous one-dimensional
trap, there exist cw states in which the chemical potential and wavevectors of
the different spin components are different from each other. We include linear
and quadratic Zeeman splitting. Linear Zeeman splitting, if the magnetic field
is constant and uniform, can be mathematically eliminated by a gauge
transformation, but quadratic Zeeman effects modify the cw solutions in a way
similar to non-zero differences in the wavenumbers between the different spin
states. The solutions are stable fixed points within the continuous wave
framework, and the coherent spin mixing frequencies are obtained.",1212.2082v3
2013-03-28,Spin wave mode coexistence on the nano-scale: A consequence of the Oersted field induced asymmetric energy landscape,"It has been argued that if multiple spin wave modes are competing for the
same centrally located energy source, as in a nanocontact spin torque
oscillator, that only one mode should survive in the steady state. Here, the
experimental conditions necessary for mode coexistence are explored. Mode
coexistence is facilitated by the local field asymmetries induced by the
spatially inhomogeneous Oersted field, which leads to a physical separation of
the modes, and is further promoted by spin wave localization at reduced applied
field angles. Finally, both simulation and experiment reveal a low frequency
signal consistent with the intermodulation of two coexistent modes.",1303.7148v1
2013-06-07,Theory of carrier-mediated magnonic superlattices,"We present a minimal one-dimensional model of collective spin excitations in
itinerant ferromagnetic superlattices within the regime of parabolic
spin-carrier dispersion. We discuss the cases of weakly and strongly modulated
magnetic profiles finding evidences of antiferromagnetic correlations for
long-wave magnons (especially significant in layered systems), with an insight
into the ground state properties. In addition, the presence of local minima in
the magnonic dispersion suggests the possibility of (thermal) excitation of
spin waves with a relatively well controlled wave length. Some of these
features could be experimentally tested in DMS superlattices based on thin
doped magnetic layers, acting as natural interfaces between (spin)electronic
and magnonic degrees of freedom.",1306.1658v2
2013-09-20,"Ground state and Spin-Wave dynamics in Brownmillerite SrCoO2.5, A combined Hybrid Functional and LSDAU study","We theoretically investigate the ground state magnetic properties of the
brownmillerite phase of SrCoO2.5. Strong correlations within Co d electrons are
treated within the local spin density approximations of Density Functional
theory (DFT) with Hubbard U corrections (LSDAU) and results are compared with
the Heyd Scuzeria Ernzerhof (HSE) functional. The parameters computed with a U
value of 7.5 eV are found to match closely to those computed within the HSE
functional. A G type antiferromagnetic structure is found to be the most stable
one, consistent with experimental observation. By mapping the total energies of
different magnetic configurations onto a Heisenberg Hamiltonian we compute the
magnetic exchange interaction parameters, J, between the nearest neighbor Co
atoms. The J s obtained are then used to compute the spin wave frequencies and
inelastic neutron scattering intensities. Among four spin wave branches, the
lowest energy mode was found to have the largest scattering intensity at the
magnetic zone center, while the other modes becomes dominant at different
momenta. These predictions can be tested by experimentally.",1309.5287v1
2014-04-08,Resonant Spin Wave Excitation by Terahertz Magnetic Near-field Enhanced with Split Ring Resonator,"Excitation of antiferromagnetic spin waves in HoFeO$_{3}$ crystal combined
with a split ring resonator (SRR) is studied using terahertz (THz)
electromagnetic pulses. The magnetic field in the vicinity of the SRR induced
by the incident THz electric field component excites and the Faraday rotation
of the polarization of a near-infrared probe pulse directly measures
oscillations that correspond to the antiferromagnetic spin resonance mode. The
good agreement of the temperature-dependent magnetization dynamics with the
calculation using the two-lattice Landau-Lifshitz-Gilbert equation confirms
that the spin wave is resonantly excited by the THz magnetic near-field
enhanced at the LC resonance frequency of the SRR, which is 20 times stronger
than the incident magnetic field.",1404.2179v1
2014-10-24,Non-linear spin-wave excitation at low bias fields,"Non-linear magnetization dynamics is essential for the operation of many
spintronics devices. For microwave assisted switching of magnetic elements the
low field regime is of particular interest. In addition a large number of
experiments uses high amplitude FMR in order to generate d.c. currents via spin
pumping mechanism. Here we use time resolved X-ray magnetic circular dichroism
experiments to determine the number density of excited magnons in magnetically
soft Ni_80Fe_20 thin films at small bias fields and large rf-excitation
amplitudes. Our data shows that the common model of non-linear ferromagnetic
resonance is not suitable to describe the low bias field limit. Here we derive
a new model of parametric spin-wave excitation which correctly predicts
threshold amplitudes and decay rates also at low bias fields. In fact a new
series of critical modes with amplitude phase oscillations is found,
generalizing the theory of parametric spin-wave excitation.",1410.6693v1
2014-11-12,Electric-Field Control over Spin-Wave and Current Induced Domain Wall Motion and Magnonic Torques in Multiferroics,"We discover that the way spin-waves exert magnetic torques in multiferroic
materials can cause not only domain wall motion, but also magnetization
dynamics for homogeneous magnetization textures. Interestingly, the domain wall
motion can be controlled via purely electrical means with the spin-waves being
generated by an ac electric field $E$ while the direction of the wall motion
also is sensitive to an applied dc $E$ field. Moreover, we determine the
interaction between spin-transfer torque from an electric current and a
magnetic domain wall in multiferroics and show that the Walker breakdown
threshold scales with the magnitude of a perpendicular electric field, offering
a way to control the properties of domain wall propagation via electric gating.",1411.3327v2
2015-10-05,Universality in antiferromagnetic strange metals,"We propose a theory of metals at the spin-density wave quantum critical point
in spatial dimension $d=2$. We provide a first estimate of the full set of
critical exponents (dynamical exponent $z=2.13$, correlation length $\nu
=1.02$, spin susceptibility $\gamma = 0.96$, electronic non-Fermi liquid
$\eta^f_\tau = 0.53$, spin-wave Landau damping $\eta^b_\tau = 1.06$), which
determine the universal power-laws in thermodynamics and response functions in
the quantum-critical regime relevant for experiments in heavy-fermion systems
and iron pnictides. We present approximate numerical and analytical solutions
of Polchinski-Wetterich type flow equations with soft frequency regulators for
an effective action of electrons coupled to spin-wave bosons. Performing the
renormalization group in frequency -instead of momentum- space allows to track
changes of the Fermi surface shape and to capture Landau damping during the
flow. The technique is easily generalizable from models retaining only patches
of the Fermi surface to full, compact Fermi surfaces.",1510.01331v3
2016-04-05,Matter-wave interferometers using TAAP rings,"We present two novel matter-wave Sagnac interferometers based on ring- shaped
time-averaged adiabatic potentials (TAAP). For both the atoms are put into a
superposition of two different spin states and manipulated independently using
elliptically polarized rf-fields. In the first interferometer the atoms are
accelerated by spin-state-dependent forces and then travel around the ring in a
matter-wave guide. In the second one the atoms are fully trapped during the
entire interferometric sequence and are moved around the ring in two
spin-state-dependent ""buckets"". Corrections to the ideal Sagnac phase are
investigated for both cases. We experimentally demonstrate the key atom-optical
elements of the interferometer such as the independent manipulation of two
different spin states in the ring-shaped potentials under identical
experimental conditions.",1604.01212v1
2017-05-24,General Covariant Equations for Fields of Arbitrary Spin,"To obtain a generalized wave equation for a field in general covariant form,
one must define covariant differentiation of a generalized wave function
describing particles with arbitrary spin. Gel'fand and Iaglom, Dirac, and Fierz
and Pauli have studied the generalized wave equation in the special theory of
relativity. In this paper, the Gel'fand-Iaglom field equation was generalized
to the curved space based on the veilbein framework. The general covariant
field equations for arbitrary spin were obtained. More importantly, in this
work, we introduced the gauge covariant derivative with the local Lorentz
transformation, which is the foundation for a gauge theory of gravitation.",1707.02217v1
2017-07-30,Incommensurate magnetism near quantum criticality in CeNiAsO,"Two phase transitions in the tetragonal strongly correlated electron system
CeNiAsO were probed by neutron scattering and zero field muon spin rotation.
For $T <T_{N1}$ = 8.7(3) K, a second order phase transition yields an
incommensurate spin density wave with wave vector $\textbf{k} = (0.44(4), 0,
0)$. For $T < T_{N2}$ = 7.6(3) K, we find co-planar commensurate order with a
moment of $0.37(5)~\mu_B$, reduced to $30 \%$ of the saturation moment of the
$|\pm\frac{1}{2}\rangle$ Kramers doublet ground state, which we establish by
inelastic neutron scattering. Muon spin rotation in $\rm CeNiAs_{1-x}P_xO$
shows the commensurate order only exists for x $\le$ 0.1 so the transition at
$x_c$ = 0.4(1) is from an incommensurate longitudinal spin density wave to a
paramagnetic Fermi liquid.",1707.09645v2
2017-11-15,"The enigmatic spin evolution of PSR J0537-6910: r-modes, gravitational waves and the case for continued timing","We discuss the unique spin evolution of the young X-ray pulsar PSR
J0537-6910, a system in which the regular spin down is interrupted by glitches
every few months. Drawing on the complete timing data from the Rossi X-ray
Timing Explorer (RXTE, from 1999-2011), we argue that a trend in the
inter-glitch behaviour points to an effective braking index close to $n=7$,
much larger than expected. This value is interesting because it would accord
with the neutron star spinning down due to gravitational waves from an unstable
r-mode. We discuss to what extent this, admittedly speculative, scenario may be
consistent and if the associated gravitational-wave signal would be within
reach of ground based detectors. Our estimates suggest that one may, indeed, be
able to use future observations to test the idea. Further precision timing
would help enhance the achievable sensitivity and we advocate a joint observing
campaign between the Neutron Star Interior Composition ExploreR (NICER) and the
LIGO-Virgo network.",1711.05550v1
2018-01-09,Unidirectional spin density wave state in metallic (Sr1-xLax)2IrO4,"Materials that exhibit both strong spin orbit coupling and electron
correlation effects are predicted to host numerous new electronic states. One
prominent example is the Jeff =1/2 Mott state in Sr2IrO4, where introducing
carriers is predicted to manifest high temperature superconductivity analogous
to the S=1/2 Mott state of La2CuO4. While bulk superconductivity currently
remains elusive, anomalous quasi-particle behaviors paralleling those in the
cuprates such as pseudogap formation and the formation of a d-wave gap are
observed upon electron-doping Sr2IrO4. Here we establish a magnetic parallel
between electron-doped Sr2IrO4 and hole-doped La2CuO4 by unveiling a spin
density wave state in electron-doped Sr2IrO4. Our magnetic resonant x-ray
scattering data reveal the presence of an incommensurate magnetic state
reminiscent of the diagonal spin density wave state observed in the monolayer
cuprate (La1-xSrx)2CuO4. This link supports the conjecture that the quenched
Mott phases in electron-doped Sr2IrO4 and hole-doped La2CuO4 support common
competing electronic phases.",1801.03076v1
2018-03-02,Spin-wave induced phonon resonance in multiferroic BiFeO$_3$,"We report the direct observation of a ""resonance"" mode in the lowest-energy
optic phonon very near the zone center around (111) in the multiferroic
BiFeO$_3$ using neutron scattering methods. The phonon scattering intensity is
enhanced when antiferromagnetic (AFM) order sets in at T$_N = 640$~K, and it
increases on cooling. This ""resonance"" is confined to a very narrow region in
energy-momentum space where no spin-wave excitation intensity is expected, and
it can be modified by an external magnetic field. Our results suggest the
existence of a novel coupling between the lattice and spin fluctuations in this
multiferroic system in which the spin-wave excitations are mapped onto the
lattice vibrations via the Dzyaloshinskii-Moriya (DM) interaction.",1803.01041v1
2014-06-01,A Neutron Scattering Study of the H-T Phase Diagram of the Bond Frustrated ZnCr2S4,"Detailed neutron scattering measurements on the bond frustrated magnet
ZnCr2S4 reveal a rich H-T phase diagram. The field dependence of the two
subsequent antiferromagnetic transitions follows closely that of recently
reported structural instabilities, providing further evidence for spin driven
Jahn-Teller physics. The incommensurate helical ordered phase below TN1 = 15.5
K exhibits gapless spin wave excitations, whereas a spin wave gap (about 2 meV)
opens below TN2 = 8 K as the system undergoes a first-order transition to a
commensurate collinear ordered phase. The spin wave gap is closed by a strong
magnetic field.",1406.0211v1
2019-02-08,Field-tuned spin excitation spectrum of $kπ$-skyrmion,"We study spin-wave excitation modes of $k\pi$ skyrmion in a magnetic nanodot
under an external magnetic field along $z$-direction using micromagnetic
simulations based on Landau-Lifshitz-Gilbert equation. We find that a
transition of $k\pi$ skyrmion to other skyrmion-like structures appears under
some critical external field, the corresponding spin-wave spectra are simulated
for each state in the process of applying magnetic field. For skyrmion, the
frequencies of excitation modes increases and then decreases with the low
frequency modes splitting at a critical magnetic field. In addition to the well
known two in-plane rotational modes and a out-of-plane breathing mode of
skyrmion, a higher number of excitation modes are found with increasing $k$
($k=2, 3$). The excitation modes vary as a function of magnetic field, and the
excitation frequencies for different modes exhibit a rapid or slight change
depending on the field induced change of magnetization profile. Our study
indicates the rich spin-wave excitations for $k\pi$ skyrmion and opens a
possibility in theoretical or experimental investigation of magnonics
application.",1902.02901v2
2019-02-28,Magnetic structure and spin waves in the frustrated ferro-antiferromagnet Pb$_2$VO(PO$_4$)$_2$,"Single crystal neutron diffraction, inelastic neutron scattering and electron
spin resonance experiments are used to study the magnetic structure and spin
waves in Pb$_2$VO(PO$_4$)$_2$, a prototypical layered $S=1/2$ ferromagnet with
frustrating next nearest neighbor antiferromagnetic interactions. The observed
excitation spectrum is found to be inconsistent with a simple square lattice
model previously proposed for this material. At least four distinct exchange
coupling constants are required to reproduce the measured spin wave dispersion.
The degree of magnetic frustration is correspondingly revised and found to be
substantially smaller than in all previous estimates.",1902.11172v3
2020-08-21,Spin waves in skyrmionic structures with various topological charges,"Equilibrium properties and localised magnon excitations are investigated in
topologically distinct skyrmionic textures. The observed shape of the
structures and their orientation on the lattice is explained based on their
vorticities and the symmetry of the crystal. The transformation between
different textures and their annihilation as a function of magnetic field is
understood based on the energy differences between them. The angular momentum
spin-wave eigenmodes characteristic of cylindrically symmetric structures are
combined in the distorted spin configurations, leading to avoided crossings in
the magnon spectrum. The susceptibility of the skyrmionic textures to
homogeneous external fields is calculated, revealing that a high number of
modes become detectable due to the hybridization between the angular momentum
eigenmodes. These findings should contribute to the observation of spin waves
in distorted skyrmionic structures via experiments and numerical simulations,
widening the range of their possible applications in magnonic devices.",2008.09392v2
2017-02-07,Topological Charge/spin density Wave in InAs/GaSb Quantum Wells under an In-plane Magnetic Field,"We study interaction effect of quantum spin Hall state in InAs/GaSb quantum
wells under an in-plane magnetic field by using the self-consistent mean field
theory. We construct a phase diagram as a function of intra-layer and
inter-layer interactions, and identify two novel phases, a charge/spin density
wave phase and an exciton condensate phase. The charge/spin density wave phase
is topologically non-trivial with helical edge transport at the boundary, while
the exciton condensate phase is topologically trivial. The Zeeman effect is
strongly renormalized due to interaction in certain parameter regimes of the
system, leading to a much smaller g-factor, which may stabilize the helical
edge transport.",1702.02058v1
2017-02-28,Anatomy of Geodesic Witten Diagrams,"We revisit the so-called ""Geodesic Witten Diagrams"" (GWDs) \cite{ScalarGWD},
proposed to be the holographic dual configuration of scalar conformal partial
waves, from the perspectives of CFT operator product expansions. To this end,
we explicitly consider three point GWDs which are natural building blocks of
all possible four point GWDs, discuss their gluing procedure through
integration over spectral parameter, and this leads us to a direct
identification with the integral representation of CFT conformal partial waves.
As a main application of this general construction, we consider the holographic
dual of the conformal partial waves for external primary operators with spins.
Moreover, we consider the closely related ""split representation"" for the bulk
to bulk spinning propagator, to demonstrate how ordinary scalar Witten diagram
with arbitrary spin exchange, can be systematically decomposed into scalar
GWDs. We also discuss how to generalize to spinning cases.",1702.08818v3
2017-06-08,Equations of Motion and Frequency Dependence of Magnon-Induced Domain Wall Motion,"Spin waves can induce domain wall motion in ferromagnets. We derive the
equations of motion for a transverse domain wall driven by spin waves. Our
calculations show that the magnonic spin-transfer torque does not cause
rotation-induced Walker breakdown. The amplitude of spin waves that are excited
by a localized microwave field depends on the spatial profile of the field and
the excitation frequency. By taking this frequency dependence into account, we
show that a simple one-dimensional model may reproduce much of the puzzling
frequency dependence observed in early numerical studies.",1706.02709v2
2017-10-10,Magnetic spin-orbit interaction directs Bloch surface waves,"We study the directional excitation of optical surface waves controlled by
the magnetic field of light. We theoretically predict that a spinning magnetic
dipole develops a tunable unidirectional coupling of light to TE-polarized
Bloch surface waves (BSWs). Experimentally, we show that the helicity of light
projected onto a subwavelength groove milled in the top layer of a 1D photonic
crystal (PC) controls the power distribution between two TE-polarized BSWs
excited on both sides of the groove. Such a phenomenon is shown to be mediated
solely by the helicity of the magnetic field of light, thus revealing a
magnetic spin-orbit interaction. Remarkably, this magnetic optical effect is
clearly observed with a near-field coupler governed by an electric dipole
moment: it is of the same order of magnitude as the electric optical effects
involved in the coupling. The magnetic spin-orbit interaction opens new degrees
of freedom in the manipulation of light and offers appealing novel
opportunities in the development of integrated optical functionalities.",1710.03584v2
2018-04-18,Spin dynamics from time-dependent density functional perturbation theory,"We present a new method to model spin-wave excitations in magnetic solids,
based on the Liouville-Lanczos approach to time-dependent density functional
perturbation theory. This method avoids computationally expensive sums over
empty states and naturally deals with the coupling between spin and charge
fluctuations, without ever explicitly computing charge-density
susceptibilities. Spin-wave excitations are obtained with one Lanczos chain per
magnon wave-number and polarization, avoiding the solution of the
linear-response problem for every individual value of frequency, as other
state-of-the-art approaches do. Our method is validated by computing magnon
dispersions in bulk Fe and Ni, resulting in agreement with previous theoretical
studies in both cases, and with experiment in the case of Fe. The disagreement
in the case of Ni is also comparable with that of previous computations.",1804.06573v2
2018-04-22,Magnetic Droplet Soliton Nucleation in Oblique Fields,"We study the auto-oscillating magnetodynamics in orthogonal spin torque
nano-oscillators (STNOs) as a function of the out-of-plane (OOP) magnetic field
angle. In perpendicular fields and at OOP field angles down to approximately 50
degrees we observe the nucleation of a droplet. However, for field angles below
50 degrees, experiments indicate that the droplet gives way to propagating spin
waves, in agreement with our micromagnetic simulations. Theoretical
calculations show that the physical mechanism behind these observations is the
sign changing of spin-wave nonlinearity (SWN) by angle. In addition, we show
that the presence of a strong perpendicular magnetic anisotropy (PMA) free
layer in the system reverses the angular dependence of the SWN and dynamics in
STNOs with respect to the known behavior determined for the in-plane magnetic
anisotropy free layer. Our results are of fundamental interest in understanding
the rich dynamics of nanoscale solitons and spin-wave dynamics in STNOs.",1804.08047v2
2019-03-01,Nanoscale X-Ray Imaging of Spin Dynamics in Yttrium Iron Garnet,"Time-resolved scanning transmission x-ray microscopy (TR-STXM) has been used
for the direct imaging of spin wave dynamics in thin film yttrium iron garnet
(YIG) with spatial resolution in the sub 100 nm range. Application of this
x-ray transmission technique to single crystalline garnet films was achieved by
extracting a lamella (13x5x0.185 $\mathrm{\mu m^3}$) of liquid phase epitaxy
grown YIG thin film out of a gadolinium gallium garnet substrate. Spin waves in
the sample were measured along the Damon-Eshbach and backward volume directions
of propagation at gigahertz frequencies and with wavelengths in a range between
100~nm and 10~$\mathrm{\mu}$m. The results were compared to theoretical models.
Here, the widely used approximate dispersion equation for dipole-exchange spin
waves proved to be insufficient for describing the observed Damon-Eshbach type
modes. For achieving an accurate description, we made use of the full
analytical theory taking mode-hybridization effects into account.",1903.00498v1
2020-03-25,Magnon Trap by Chiral Spin Pumping,"Chiral spin pumping is the generation of a unidirectional spin current in
half of ferromagnetic films or conductors by dynamic dipolar stray fields from
close-by nanomagnets. We formulate a general theory of long-range chiral
interactions between magnets mediated by unidirectional traveling waves, e.g.,
spin waves in a magnetic film or microwaves in a waveguide. The traveling waves
emitted by an excited magnet can be perfectly trapped by a second, initially
passive, magnet by a dynamical interference effect. When both magnets are
excited by a uniform microwave, the chiral interaction between them creates a
large imbalance in their magnon numbers.",2003.11581v2
2019-07-01,DC spinmotive force from microwave-active resonant dynamics of skyrmion crystal under a tilted magnetic field,"We theoretically show that a temporally oscillating spin-driven electromotive
force or voltage with a large DC component can be generated by exciting
microwave-active spin-wave modes of a skyrmion crystal confined in a quasi
two-dimensional magnet under a tilted magnetic field. The DC component and the
AC amplitude of the oscillating electric voltage is significantly enhanced when
the microwave frequency is tuned to an eigenfrequency of the peculiar spin-wave
modes of the skyrmion crystal called ``rotation modes"" and ``breathing mode"",
whereas the sign of the DC component depends on the microwave polarization and
on the spin-wave mode. These results provide an efficient means to convert
microwaves to a DC electric voltage by using skyrmion-hosting magnets and to
switch the sign of the voltage via tuning the microwave frequency, which are
important capabilities for spintronic devices.",1907.00621v1
2019-07-03,Spin wave excitations of magnetic metalorganic materials,"The Organic Materials Database (OMDB) is an open database hosting about
22,000 electronic band structures, density of states and other properties for
stable and previously synthesized 3-dimensional organic crystals. The web
interface of the OMDB offers various search tools for the identification of
novel functional materials such as band structure pattern matching and density
of states similarity search. In this work the OMDB is extended to include
magnetic excitation properties. For inelastic neutron scattering we focus on
the dynamical structure factor $S(\mathbf{q},\omega)$ which contains
information on the excitation modes of the material. We introduce a new dataset
containing atomic magnetic moments and Heisenberg exchange parameters for which
we calculate the spin wave spectra and dynamic structure factor with linear
spin wave theory and atomistic spin dynamics. We thus develop the materials
informatics tools to identify novel functional organic and metalorganic
magnets.",1907.01817v2
2019-07-22,Plaquette instability competing with bicollinear ground state in detwinned FeTe,"We use inelastic neutron scattering to show that long-range spin waves
arising from the static bicollinear antiferromagnetic (AF) order in FeTe, which
have twofold rotational symmetry in a fully detwinned crystal, rapidly dissolve
above $E\approx 26$ meV into ridges of scattering with fourfold rotational
symmetry and a nearly isotropic magnetic fluctuation spectrum. With increasing
temperature above $T_N\approx 68$ K, the twofold spin waves change into broad
regions of scattering with fourfold symmetry. Since the scattering patterns
from plaquette magnetic order generated within a bilinear biquadratic
Hamiltonian have fourfold rotational symmetry consistent with the high-energy,
spin-isotropic spin waves of FeTe, we conclude that the bicollinear AF state in
FeTe is quasidegenerate with plaquette magnetic order, providing evidence for
the strongly frustrated nature of the local moments in iron chalcogenide family
of iron-based superconductors.",1907.09420v1
2019-09-25,Parent Hamiltonian Reconstruction of Jastrow-Gutzwiller Wavefunctions,"Variational wave functions have been a successful tool to investigate the
properties of quantum spin liquids. Finding their parent Hamiltonians is of
primary interest for the experimental simulation of these strongly correlated
phases, and for gathering additional insights on their stability. In this work,
we systematically reconstruct approximate spin-chain parent Hamiltonians for
Jastrow-Gutzwiller wave functions, which share several features with quantum
spin liquid wave-functions in two dimensions. Firstly, we determine the
different phases encoded in the parameter space through their correlation
functions and entanglement content. Secondly, we apply a recently proposed
entanglement-guided method to reconstruct parent Hamiltonians to these states,
which constrains the search to operators describing relativistic low-energy
field theories - as expected for deconfined phases of gauge theories relevant
to quantum spin liquids. The quality of the results is discussed using
different quantities and comparing to exactly known parent Hamiltonians at
specific points in parameter space. Our findings provide guiding principles for
experimental Hamiltonian engineering of this class of states.",1909.11327v3
2019-12-20,Numerical Study of Multiple Helical Spin Density Waves and Vortex Spin Structures in Itinerant Electron System,"Multiple spin density waves and related vortex-type magnetic structures in
the itinerant electron system with inversion symmetry have been investigated on
the basis of the Hubbard model and the generalized Hartree-Fock approximation
combined with the recursion method. Possible magnetic phase diagram on the fcc
lattice is presented in the space of the Coulomb interaction strength and the
electron occupation number. It is found that the 2Q multiple helical spin
density waves (SDW) with half-skyrmion half-antiskyrmion paired structure, the
3Q multiple helical SDW with 3 dimensional type vortex structure, the 4Q
multiple SDW with partially ordered state, and a new type of 12Q multiple SDW
showing both the half-skyrmion-type vortex structure and the partially ordered
state can be stabilized around the Stoner instability line. The stability of
their structures is explained on the basis of their electronic structures.",1912.09651v1
2020-01-22,Resonant Precession Modulation Based Magnetic Field Receivers,"Antenna technology provides the crucial interface between electronic devices
and electromagnetic waves required for wireless communications. This technology
has operated under largely the same general principles for over a century,
resulting in stagnation of advancements in modern times and fundamentally
limiting the extent to which potential applications of wireless communications
may be realized. Herein we propose a novel concept for antenna operation
employing the nonlinear precession dynamics of subatomic spins. An
electromagnetic wave incident on a precessing spin will serve to modulate the
spin frequency of precession. Antennas operating based on a detection of these
spin dynamics are then able to fully characterize the incident wave while
achieving substantial amplifications, higher sensitivities, and smaller form
factors as compared to conventional antennas. A preliminary experimental
implementation of the proposed concept establishes its feasibility and is
already able to demonstrate significant amplification and size benefits.",2001.08059v1
2020-02-12,The role of gravitational recoil in the assembly of massive black hole seeds,"When two black holes merge, the asymmetric emission of gravitational waves
provides an impulse to the merged system; this gravitational wave recoil
velocity can be up to 4000 km s$^{-1}$, easily fast enough for the black hole
to escape its host galaxy. We combine semi-analytic modeling with cosmological
zoom-in simulations of a Milky Way-type galaxy to investigate the role of black
hole spin and gravitational recoil in the epoch of massive black hole seeding.
We sample four different spin distributions (random, aligned, anti-aligned, and
zero spin), and compare the resulting merger rates, occupation fractions, and
MBH-host relations with what is expected by excluding the effect of recoil. The
inclusion of gravitational recoil and MBH spin in the assembly of MBH seeds can
reduce the final $z=5$ MBH mass by up to an order of magnitude. The MBH
occupation fraction, however, remains effectively unaltered due to episodes of
black hole formation following a recoil event. While electromagnetic detections
of these events are unlikely, LISA is ideally suited to detect gravitational
wave signals from such events.",2002.04740v1
2020-05-07,Ultrafast All Optical Magnetization Control for Broadband Terahertz Spin Wave Generation,"Terahertz spin waves could be generated on-demand via all-optical
manipulation of magnetization by femtosecond laser pulse. Here, we present an
energy balance model, which explains the energy transfer rates from laser pulse
to electron bath coupled with phonon, spin, and magnetization of five different
magnetic metallic thin films: Iron, Cobalt, Nickel, Gadolinium and Ni$_{2}$MnSn
Heusler alloy. Two types of transient magnetization dynamics emerge in metallic
magnetic thin films based on their Curie temperatures (T$_{C}$): type I (Fe,
Co, and Ni with T$_{C}$ > room temperature, RT) and type II films (Gd and
Ni$_{2}$MnSn with T$_{C}$ $\approx$ RT). We study the effect of laser fluence
and pulse width for single Gaussian laser pulses and the effect of metal film
thickness on magnetization dynamics. Spectral dynamics show that broadband spin
waves up to 24 THz could be generated by all-optical manipulation of
magnetization in these nanofilms.",2005.03493v1
2021-06-02,Effective exchange interaction for terahertz spin waves in iron layers,"The exchange stiffness is a central material parameter of all ferromagnetic
materials. Its value controls the Curie temperature as well as the dynamic
properties of spin waves to a large extend. Using ultrashort spin current
pulses we excite perpendicular standing spin waves (PSSW) in ultrathin
epitaxial iron layers at frequencies of up to 2.4 THz. Our analysis shows that
for the PSSWs the observed exchange stiffness of iron is about 20% smaller
compared to the established iron bulk value. In addition, we find an
interface-related reduction of the effective exchange stiffness for layers with
the thickness below 10 nm. To understand and discuss the possible mechanisms of
the exchange stiffness reduction we develop an analytical 1D-model. In doing so
we find that the interface induced reduction of the exchange stiffness is
mode-dependent.",2106.01066v1
2021-06-02,Spontaneous emergence of a spin state for an emitter in a time-varying medium,"Time varying media can dramatically modify the emission of embedded sources
by producing time reversed waves refocusing on the source. Here we show that
such a back action can create an angular momentum by setting the source in a
spontaneous spin state. We experimentally implement this coupling using
self-propelled bouncing droplets sources coupled to the surface waves they emit
on a parametrically excited bath. The spin state dynamics result from a
self-organized interplay between the source motion and the time reversed waves.
The discrete stability analysis agrees with the experimental observations. In
addition, we show that these spin states provide a unique opportunity for an
experimental access to parameters enabling comparison and calibration of the
various existing models.",2106.01448v3
2021-09-08,Excitonic wave-packet evolution in a two-orbital Hubbard model chain: A real-time real-space study,"Motivated by experimental developments introducing the concept of spin-orbit
separation, we study the real-space time evolution of an excitonic wave-packet
using a two-orbital Hubbard model. The exciton is created by exciting an
electron from a lower energy half-filled orbital to a higher energy empty
orbital. We carry out the real-time dynamics of the resulting excitonic
wave-packet, using the time-dependent density matrix renormalization group
method. We find clear evidence of charge-spin and spin-orbit separation in
real-space, by tracking the time evolution of local observables. We show that
the velocity of the orbiton can be tuned by varying the inter-orbital
interactions. We also present a comparative study of a hole (in one orbital)
and exciton (in two orbitals) dynamics in one-dimensional systems. Moreover, we
analyze the dynamics of an exciton with spin-flip excitation, where we observe
fractionalized spinons induced by Hund's interaction.",2109.03618v1
2021-12-19,Engineering spin wave spectra in thick Ni$_{80}$Fe$_{20}$ rings by using competition between exchange and dipolar fields,"Control of the spin wave dynamics in nanomagnetic elements is very important
for the realization of a broad range of novel magnonic devices. Here we study
experimentally the spin wave resonance in thick ferromagnetic rings (100 nm)
using perpendicular ferromagnetic resonance spectroscopy. Different from what
was observed for the continuous film of the same thickness, or from ring with
similar lateral dimensions but with lower thicknesses, the spectra of thick
patterned rings show a non-monotonic dependence of the mode intensity on the
resonance field for a fixed frequency. To explain this effect, the theoretical
approach by considering the dependence of the mode profiles on both the radial
and axial coordinates was developed. It was demonstrated that such unusual
behavior is a result of the competition between exchange and dipolar fields
acting at the spin excitations in the structure under study. The calculations
are in a good agreement with the experimental results.",2112.13657v1
2022-01-27,Simultaneous measurement of the exchange parameter and saturation magnetization using propagating spin waves,"The exchange interaction in ferromagnetic ultra-thin films is a critical
parameter in magnetization-based storage and logic devices, yet the accurate
measurement of it remains a challenge. While a variety of approaches are
currently used to determine the exchange parameter, each has its limitations,
and good agreement among them has not been achieved. To date, neutron
scattering, magnetometry, Brillouin light scattering, spin-torque ferromagnetic
resonance spectroscopy, and Kerr microscopy have all been used to determine the
exchange parameter. Here we present a novel method that exploits the wavevector
selectivity of Brillouin light scattering to measure the spin wave dispersion
in both the backward volume and Damon-Eshbach orientations. The exchange,
saturation magnetization, and magnetic thickness are then determined by a
simultaneous fit of both dispersion branches with general spin wave theory
without any prior knowledge of the thickness of a magnetic ""dead layer"". In
this work, we demonstrate the strength of this technique for ultrathin metallic
films, typical of those commonly used in industrial applications for magnetic
random-access memory.",2201.11270v1
2022-02-14,Mode splitting of spin waves in magnetic nanotubes with discrete symmetries,"We investigate how geometry influences spin dynamics in polygonal magnetic
nanotubes. We find that lowering the rotational symmetry of nanotubes by
decreasing the number of planar facets, splits an increasing number of
spin-wave modes, which are doubly degenerate in cylindrical tubes. This
symmetry-governed splitting is distinct form the topological one recently
observed in cylindrical nanotubes. Doublet modes with half-integer or integer
multiple azimuthal periods of the number of facets, split to singlet pairs with
lateral standing-wave profiles of opposing mirror-plane symmetries.
Furthermore, the polygonal geometry facilitates the hybridization of modes with
different azimuthal periods but the same symmetry, manifested in avoided level
crossings. These phenomena, unimaginable in cylindrical geometry, provide new
tools to control spin dynamics on nanoscale. The presented concept can be
generalized to nano-objects of versatile geometries and order parameters,
offering new routes to engineer dynamic response in nanoscale devices.",2202.06601v1
2022-05-07,Interplay between the extended s-wave symmetry of the gap and the spin-orbit coupling in the low-electron concentration regime of quasi-two-dimensional superconductors,"We analyze the real-space paired state with the $\mathbf{k}$-dependent
superconducting gap in the presence of Rashba type spin-orbit coupling and
external magnetic field. We show that the $extended$ $s$-$wave$ pairing
symmetry is the most probable scenario to appear in the low-electron
concentration regime. According to our study, the van Hove singularity induced
by the spin-orbit coupling may lead to a significant enhancement of the
superconducting gap, critical temperature and critical magnetic field.
Moreover, the combined effect of the spin-orbit coupling and the external
magnetic field results in a non-zero total momentum of the Cooper pairs, which
is a characteristic feature of the so-called helical state. In such situation,
due to the C$_4$ symmetry breaking, a small $d$-$wave$ and $p$-$wave$
contributions to the pairing appear, which significantly change the character
of the helical state. The obtained results are discussed in the context of the
experimental data related with the unconventional superconducting features of
the transition metal oxide interfaces as well as the recently reported
supercurrent diode effect.",2205.03632v3
2022-05-11,Chiral standing spin waves in skyrmion lattice,"This work studies the resonance excitations of the three-dimensional
skyrmions lattice in the finite thickness plate of an isotropic chiral magnet
using spin dynamics simulations. We found that the absorption spectra and
resonance modes differ from those predicted by the two-dimensional model and
the model of the unconfined bulk crystal. The features observed on the spectra
can be explained by the formation of chiral standing spin waves, which,
contrary to conventional standing spin waves, are characterized by the helical
profile of dynamic magnetization of fixed chirality defined by the
Dzyaloshinskii-Moriya interaction. In this case, the dynamic susceptibility
becomes a function of the plate thickness, which gives rise to an interesting
effect that manifests itself in periodical fading of the intensity of
corresponding modes and makes excitation of these modes impossible at specific
thicknesses.",2205.05466v1
2022-08-08,Covariant formulation of spin optics for electromagnetic waves,"We develop geometric optics expansion up to the subleading order for
circularly polarized electromagnetic waves on curved spacetime. This subleading
order geometric optics expansion, in which the conventional eikonal function is
modified by inserting a carefully chosen helicity-dependent correction, is
called spin optics. We derive the propagation and polarization equations in the
spin optics approximation as electromagnetic waves travel in curved spacetime.
Polarization-dependent deviation of the light ray trajectory from the geodesic,
describing the gravitational spin Hall effect, is observed. We also establish
an analogy with the related phenomena (optical Magnus effect) of condensed
matter physics.",2208.04725v2
2022-11-20,Plasmon-magnon interactions in two-dimensional honeycomb magnets,"Two-dimensional honeycomb ferromagnets offer the unprecedented opportunity to
study interactions between collective modes that in standard bulk ferromagnets
do not cross paths. Indeed, they harbor an optical spin-wave branch, i.e. a
spin wave which disperses weakly near the Brillouin zone center. When doped
with free carriers, they also host the typical gapless plasmonic mode of 2D
itinerant electron/hole systems. When the plasmon branch meets the optical
spin-wave branch, energy and momentum matching occurs, paving the way for
interactions between the charge and spin sector. In this Letter we present a
microscopic theory of such plasmon-magnon interactions, which is based on a
double random phase approximation. We comment on the possibility to unveil this
physics in recently isolated 2D honeycomb magnets such as ${\rm Cr}_2{\rm
Ge}_2{\rm Te}_6$.",2211.11098v1
2022-12-25,Optical mirages from spinless beams,"Spin-orbit interactions of light are ubiquitous in multiple branches of
nanophotonics, including optical wave localization. In that framework, it is
widely accepted that circularly polarized beams lead to spin-dependent apparent
shifts of dipolar targets commonly referred to as optical mirages. In contrast,
these optical mirages vanish when the illumination comes from a spinless beam
such as a linearly polarized wave. Here we show that optical localization
errors emerge for particles sustaining electric and magnetic dipolar response
under the illumination of spinless beams. As an example, we calculate the
optical mirage for the scattering by a high refractive index nanosphere under
the illumination of a linearly polarized plane wave carrying null spin,
orbital, and total angular momentum. Our results point to an overlooked
interference between the electric and magnetic dipoles rather than the
spin-orbit interactions of light as the origin for the tilted position of the
nanosphere.",2212.12972v1
2023-01-20,Giant spin-vorticity coupling excited by shear-horizontal surface acoustic waves,"A non-magnetic layer can inject spin-polarized currents into an adjacent
ferromagnetic layer via spin vorticity coupling (SVC), inducing spin wave
resonance (SWR). In this work, we present the theoretical model of SWR
generated by shear-horizontal surface acoustic wave (SH-SAW) via SVC, which
contains distinct vorticities from well-studied Rayleigh SAW. Both Rayleigh-
and SH-SAW delay lines have been designed and fabricated with a Ni81Fe19/Cu
bilayer integrated on ST-cut quartz. Given the same wavelength, the measured
power absorption of SH-SAW is four orders of magnitudes higher than that of the
Rayleigh SAW. In addition, a high-order frequency dependence of the SWR is
observed in the SH-SAW, indicating SVC can be strong enough to compare with
magnetoelastic coupling.",2301.08586v1
2023-03-06,Larmor precession in strongly correlated itinerant electron systems,"Many-electron systems undergo a collective Larmor precession in the presence
of a magnetic field. In a paramagnetic metal, the resulting spin wave provides
insight into the correlation effects generated by the electron-electron
interaction. Here, we use dynamical mean-field theory to investigate the
collective Larmor precession in the strongly correlated regime, where dynamical
correlation effects such as quasiparticle lifetimes and non-quasiparticle
states are essential. We study the spin excitation spectrum, which includes a
dispersive Larmor mode as well as electron-hole excitations that lead to Stoner
damping. We also extract the momentum-resolved damping of slow spin waves. The
accurate theoretical description of these phenomena relies on the Ward
identity, which guarantees a precise cancellation of self-energy and vertex
corrections at long wavelengths. Our findings pave the way towards a better
understanding of spin wave damping in correlated materials.",2303.03468v2
2024-01-30,Partial tidal disruptions of spinning eccentric white dwarfs by spinning intermediate mass black holes,"Intermediate mass black holes (IMBHs, $\sim 10^2-10^5M_{\odot}$) are often
dubbed as the missing link between stellar mass ($\lesssim 10^2M_{\odot}$) and
super-massive ($\gtrsim 10^{5-6} M_{\odot}$) black holes. Observational
signatures of these can result from tidal disruption of white dwarfs (WDs),
which would otherwise be captured as a whole by super-massive black holes.
Recent observations indicate that IMBHs might be rapidly spinning, while it is
also known that isolated white dwarfs might have large spins, with spin periods
of the order of minutes. Here, we aim to understand the effects of ``coupling''
between black hole and stellar spin, focussing on the tidal disruption of
spinning WDs in the background of spinning IMBHs. Using smoothed particle
hydrodynamics, we perform a suite of numerical simulations of partial tidal
disruptions, where spinning WDs are in eccentric orbits about spinning IMBHs.
We take a hybrid approach, where we integrate the Kerr geodesic equations while
being in a regime where we can treat the internal stellar fluid dynamics in the
Newtonian limit. We find substantial effects of the ``coupling'' between the
black hole spin and the spin of the white dwarf, although the pericenter
distance of the white dwarf is taken to be large enough so that the Newtonian
limit of its fluid dynamics is a robust approximation. In particular, the core
mass, the bound tail mass, and the mass difference between the two tidal tails
strongly depend on such ``coupled'' spin effects. However, the late time
fallback rate of the debris behaves similar to the non-spinning cases. We also
compute gravitational wave amplitudes and find that while the black hole spin
influences the same, there is no evidence of influence of stellar spin on such
amplitudes in our regime of interest.",2401.17031v1
2004-03-30,"Effective interactions, Fermi-Bose duality, and ground states of ultracold atomic vapors in tight de Broglie waveguides","Derivation of effective zero-range one-dimensional (1D) interactions between
atoms in tight waveguides is reviewed, as is the Fermi-Bose mapping method for
determination of exact and strongly-correlated states of ultracold bosonic and
fermionic atomic vapors in such waveguides, including spin degrees of freedom.
Odd-wave 1D interactions derived from 3D p-wave scattering are included as well
as the usual even-wave interactions derived from 3D s-wave scattering, with
emphasis on the role of 3D Feshbach resonances for selectively enhancing s-wave
or p-wave interactions. A duality between 1D fermions and bosons with
zero-range interactions suggested by Cheon and Shigehara is shown to hold for
the effective 1D dynamics of a spinor Fermi gas with both even and odd-wave
interactions and that of a spinor Bose gas with even and odd-wave interactions,
with even(odd)-wave Bose coupling constants inversely related to odd(even)-wave
Fermi coupling constants. Some recent applications of Fermi-Bose mapping to
determination of many-body ground states of Bose gases and of both magnetically
trapped, spin-aligned and optically trapped, spin-free Fermi gases are
described, and a new generalized Fermi-Bose mapping is used to determine the
phase diagram of ground-state total spin of the spinor Fermi gas as a function
of the even and odd-wave coupling constants.",0403721v1
2015-03-22,Superconducting and charge-density-wave orders in the spin-fermion model: a comparative analysis,"We present comparative analysis of superconducting and charge-density-wave
orders in the spin-fluctuation scenario for the cuprates. That spin-fluctuation
exchange gives rise to d-wave superconductivity is well known. Several groups
recently argued that the same spin-mediated interaction may also account for
charge-density-wave order with momenta $(Q,0)$ or $(0,Q)$, detected in
underdoped cuprates. This has been questioned on the basis that
charge-density-wave channel mixes fermions from both nested and anti-nested
regions on the Fermi surface, and fermions in the anti-nested region do not
have a natural tendency to form a bound state, even if the interaction is
attractive. We show that anti-nesting is not an obstacle for charge order, but
to see this one needs to go beyond the conventional Eliashberg approximation.
We show that in the prefect nesting/antinesting case, when the velocities of
hot fermions are either parallel or antiparallel, the onset temperatures in
superconducting and charge-density-wave channels are of comparable strength for
any magnetic correlation length $\xi$. The superconducting $T_{\rm sc}$ is
larger than $T_{\rm cdw}$, but only numerically. When the velocities of hot
fermions are not strictly parallel/antiparallel, $T_{\rm cdw}$ progressively
decreases as $\xi$ decreases and vanishes at some critical $\xi$.",1503.06372v2
2015-10-22,Spin density wave instabilities in the NbS2 monolayer,"In the present work, we study the magnetic properties of the NbS2 monolayer
by first-principles calculations. The transition metal dichalcogenides (TMDC)
are a family of laminar materials presenting exciting properties such as charge
density waves (CDW), superconductivity and metal-insulating transitions among
others. 2H-NbS2 is a particular case within the family, because it is the only
one that is superconductor without exhibiting a CDW order. Although no long
range magnetic order was experimentally observed in the TMDC, we show here that
the single monolayer of NbS2 is on the verge of a spin density wave (SDW)
phase. Our calculations indicate that a wave-like magnetic order is stabilized
in the NbS2 monolayer in the presence of magnetic defects or within zig-zag
nanoribbons, due to the presence of unpaired electrons. We calculate the real
part of the bare electronic susceptibilty and the corresponding nesting
function of the clean NbS2 monolayer, showing that there are strong electronic
instabilities at the same wavevector asociated with the calculated SDWs, also
corresponding with one of the main nesting vectors of the Fermi surface. We
conclude that the physical mechanism behind the spin-wave instabilities are the
nesting properties, accentuated by the quasi 2D character of this system, and
the rather strong Coulomb interactions of the 4d band of the Nb atom. We also
estimate the amplitude of the spin-fluctuations and find that they are rather
large, as expected for a system on the verge of a quantum critical transition.",1510.06477v2
2015-11-24,Multivariate quantum memory as controllable delayed multiport beamsplitter,"The addressability of parallel spatially multimode quantum memory for light
allows one to control independent collective spin waves within the same cold
atomic ensemble. Generally speaking, there are transverse and longitudinal
degrees of freedom of the memory that one can address by a proper choice of the
pump (control) field spatial pattern. Here we concentrate on the mutual
evolution and transformation of quantum states of the longitudinal modes of
collective spin coherence in the cavity-based memory scheme. We assume that
these modes are coherently controlled by the pump waves of the on--demand
transverse profile, that is, by the superpositions of waves propagating in the
directions, close to orthogonal to the cavity axis. By the write-in, this
allows one to couple a time sequence of the incoming quantized signals to a
given set of superpositions of orthogonal spin waves. By the readout, one can
retrieve quantum states of the collective spin waves that are controllable
superpositions of the initial ones and are on demand coupled to the output
signal sequence. In general case, the memory is able to operate as a
controllable delayed multi-port beamsplitter, capable of transformation of the
delays, the durations and time shapes of signals in the sequence.
  We elaborate the theory of such light--matter interface for the spatially
multivariate cavity-based off--resonant Raman--type quantum memory. Since in
order to speed up the manipulation of complex signals in multivariate memories
it might be of interest to store relatively short light pulses of a given time
shape, we also address some issues of the cavity-based memory operation beyond
the bad cavity limit.",1511.07787v1
2016-08-08,Bethe-Salpeter wave functions of $η_c(2S)$ and $ψ(2S)$ states from full lattice QCD,"We discuss the internal structure of radially excited charmonium mesons based
on the equal-time and Coulomb gauge Bethe-Salpeter (BS) amplitudes, which are
obtained in lattice QCD. Our simulations are performed with a relativistic
heavy-quark action for the charm quark on the 2+1 flavor PACS-CS gauge
configurations at the lightest pion mass, $M_{\pi}=156(7)$ MeV. The variational
method is applied to the study of optimal charmonium operator for ground and
first excited states of $S$-wave charmonia. We successfully calculate the BS
wave functions of $\eta_c(2S)$ and $\psi(2S)$ states, as well as $\eta_c(1S)$
and $J/\psi$ states, and then estimate the root-mean-square radii of both the
$1S$ and $2S$ charmonium states. We also examine whether a series of the BS
wave functions from the ground state to excited states can be described by a
single set of the spin-independent and spin-dependent interquark potentials
with a unique quark mass. It is found that the quark kinetic mass and, both the
central and spin-spin charmonium potentials, determined from the $2S$ wave
functions, fairly agree with the ones from the $1S$ wave functions. This
strongly supports the validity of the potential description for the charmonium
system, at least, below open-charm threshold.",1608.02340v2
2016-09-11,Decoherence and determinism in a one-dimensional cloud-chamber model,"The hypothesis by Sparenberg et al. (2013) that the particular linear tracks
appearing in the measurement of a spherically-emitting radioactive source in a
cloud chamber are determined by the (random) positions of atoms or molecules
inside the chamber is further explored in the framework of a recently
established one-dimensional model by Carlone et al. (2015). In this model,
meshes of localized spins 1/2 play the role of the cloud-chamber atoms and the
spherical wave is replaced by a linear superposition of two wave packets moving
from the origin to the left and to the right, evolving deterministically
according to the Schr\""odinger equation. We first revisit these results using a
time-dependent approach, where the wave packets impinge on a symmetric
two-sided detector. We discuss the evolution of the wave function in the
configuration space and stress the interest of a non-symmetric detector in a
quantum-measurement perspective. Next we use a time-independent approach to
study the scattering of a plane wave on a single-sided detector. Preliminary
results are obtained, analytically for the single-spin case and numerically for
up to 8 spins. They show that the spin-excitation probabilities are sometimes
very sensitive to the parameters of the model, which corroborates the idea that
the measurement result could be determined by the atom positions. The possible
origin of decoherence and entropy increase in future models is finally
discussed.",1609.03217v2
2019-05-17,Testing the multipole structure and conservative dynamics of compact binaries using gravitational wave observations: The spinning case,"In an earlier work [S. Kastha et al., PRD {\bf 98}, 124033 (2018)], we
developed the {\it parametrized multipolar gravitational wave phasing formula}
to test general relativity, for the non-spinning compact binaries in
quasi-circular orbit. In this paper, we extend the method and include the
important effect of spins in the inspiral dynamics. Furthermore, we consider
parametric scaling of PN coefficients of the conserved energy for the compact
binary, resulting in the parametrized phasing formula for non-precessing
spinning compact binaries in quasi-circular orbit. We also compute the
projected accuracies with which the second and third generation ground-based
gravitational wave detector networks as well as the planned space-based
detector LISA will be able to measure the multipole deformation parameters and
the binding energy parameters. Based on different source configurations, we
find that a network of third-generation detectors would have comparable ability
to that of LISA in constraining the conservative and dissipative dynamics of
the compact binary systems. This parametrized multipolar waveform would be
extremely useful not only in deriving the first upper limits on any deviations
of the multipole and the binding energy coefficients from general relativity
using the gravitational wave detections, but also for science case studies of
next generation gravitational wave detectors.",1905.07277v1
2022-09-12,Unidirectional propagation of spin waves excited by femtosecond laser pulses in a planar waveguide,"Low-energy magnonic logic circuits are an actively developing field of modern
magnetism. The potential benefits of magnonics for data processing are vitally
dependent on units based on non-reciprocal propagation of spin waves in analogy
to semiconductor diodes and transistors in electronics. In this article, we
suggest the approach to realize non-reciprocal propagation of spin waves in a
ferromagnetic metallic waveguide by exciting them with femtosecond laser pulse.
Using micromagnetic modeling, we show that the combination of an external
magnetic field and the position of the excitation laser spot across the
waveguide leads to unidirectional propagation of the excited spin-wave packet.
The results are crucial for the design of hybrid magnonic-photonic circuits in
future generations of data processing devices.",2209.05611v3
2024-02-06,Spin-density-wave transition in double-layer nickelate La3Ni2O7,"Recently, a signature of high-temperature superconductivity above the liquid
nitrogen temperature (77 K) was reported for La3Ni2O7 under pressure. This
finding immediately stimulates intense interest in the possible high-Tc
superconducting mechanism in double-layer nickelates. Interestingly, the
pressure-dependent phase diagram inferred from transport measurements indicates
that superconductivity under high pressure emerges from the suppression of a
density-wave-like transition at ambient pressure, which is similar to
high-temperature superconductors. Therefore, clarifying the exact nature of the
density-wave-like transition is important for determining the mechanism of
superconductivity in double-layer nickelates. Here, nuclear magnetic resonance
(NMR) spectroscopy of 139La nuclei was performed to study the density-wave-like
transition in a single crystal of La3Ni2O7. The temperature-dependent 139La NMR
spectrum and nuclear spin-lattice relaxation rate (1/T1) provide unambiguous
evidence for a spin-density-wave (SDW) transition with a transition temperature
TSDW of ~ 150 K. Furthermore, the anisotropic splitting of the NMR spectrum
suggests a possible double spin stripe with magnetic moments along the c axis.
In addition, the present NMR measurements also revealed spatial inhomogeneity
of magnetism due to inner apical oxygen vacancies. All these results will be
helpful for building a connection between superconductivity and magnetic
interactions in double-layer nickelates.",2402.03952v1
2001-10-18,Damping of spin waves and singularity of the longitudinal modes in the dipolar critical regime of the Heisenberg-ferromagnet EuS,"By inelastic scattering of polarized neutrons near the (200)-Bragg
reflection, the susceptibilities and linewidths of the spin waves and the
longitudinal spin fluctuations were determined separately. By aligning the
momentum transfers q perpendicular to both \delta S_sw and the spontaneous
magnetization M_s, we explored the statics and dynamics of these modes with
transverse polarizations with respect to q. In the dipolar critical regime,
where the inverse correlation length kappa_z(T) and q are smaller than the
dipolar wavenumber q_d, we observe:(i) the static susceptibility of \delta
S_sw^T(q) displays the Goldstone divergence while for \delta S_z^T(q) the
Ornstein-Zernicke shape fits the data with a possible indication of a
thermal(mass-)renormalization at the smallest q-values, i.e. we find
indications for the predicted 1/q divergence of the longitudinal
susceptibility; (ii) the spin wave dispersion as predicted by the
Holstein-Primakoff theory revealing q_d=0.23(1)\AA^{-1}in good agreement with
previous work in the paramagnetic and ferromagnetic regime of EuS; (iii) within
experimental error, the (Lorentzian) linewidths of both modes turn out to be
identical with respect to the q^2-variation, the temperature independence and
the absolute magnitude. Due to the linear dispersion of the spin waves they
remain underdamped for q<q_d. These central results differ significantly from
the well known exchange dominated critical dynamics, but are quantitatively
explained in terms of dynamical scaling and existing data for T>=T_C. The
available mode-mode coupling theory, which takes the dipolar interactions fully
into account, describes the gross features of the linewidths but not all
details of the T- and q-dependencies. PACS: 68.35.Rh, 75.40.Gb",0110371v1
2010-11-04,The effect of the pseudogap on suppressing high energy inelastic neutron scattering in superconducting YBa2Cu3O6.5,"We have measured the spin fluctuations in the YBa2Cu3O6.5 (YBCO6.5, Tc=59 K)
superconductor at high-energy transfers above ~ 100 meV. Within experimental
error, the momentum dependence is isotropic at high-energies, similar to that
measured in the insulator for two dimensional spin waves, and the dispersion
extrapolates back to the incommensurate wave vector at the elastic position.
This result contrasts with previous expectations based on measurements around
50 meV which were suggestive of a softening of the spin-wave velocity with
increased hole doping. Unlike the insulator, we observe a significant reduction
in the intensity of the spin excitations for energy transfers above ~ 100 meV
similar to that observed above ~ 200 meV in the YBCO6.35 (Tc=18 K)
superconductor as the spin waves approach the zone boundary. We attribute this
high energy scale with a second gap and find agreement with measurements of the
pseudogap in the cuprates associated with electronic anomalies along the
antinodal positions. In addition, we observe a sharp peak at around 400 meV
whose energy softens with increased hole doping. We discuss possible origins of
this excitation including a hydrogen related molecular excitation and a
transition of electronic states between d levels.",1011.1277v1
2010-12-24,Superfluid phases of triplet pairing and neutrino emission from neutron stars,"Neutrino energy losses through neutral weak currents in the triplet-spin
superfluid neutron liquid are studied for the case of condensate involving
several magnetic quantum numbers. Low-energy excitations of the multicomponent
condensate in the timelike domain of the energy and momentum are analyzed.
Along with the well-known excitations in the form of broken Cooper pairs, the
theoretical analysis predicts the existence of collective waves of spin density
at very low energy. Because of a rather small excitation energy of spin waves,
their decay leads to a substantial neutrino emission at the lowest
temperatures, when all other mechanisms of neutrino energy loss are killed by a
superfluidity. Neutrino energy losses caused by the pair recombination and
spin-wave decays are examined in all of the multicomponent phases that might
represent the ground state of the condensate, according to modern theories, and
for the case when a phase transition occurs in the condensate at some
temperature. Our estimate predicts a sharp increase in the neutrino energy
losses followed by a decrease, along with a decrease in the temperature, that
takes place more rapidly than it would without the phase transition. We
demonstrate the important role of the neutrino radiation caused by the decay of
spin waves in the cooling of neutron stars.",1012.5387v1
2011-05-10,Magnetic-crystallographic phase diagram of superconducting parent compound Fe$_{1+x}$Te,"hrough neutron diffraction experiments, including spin-polarized
measurements, we find a collinear incommensurate spin-density wave with
propagation vector $ \mathbf k = $ ($0.4481(4) \, \,0 \, \, \frac1 2$) at base
temperature in the superconducting parent compound Fe$_{1+x}$Te. This critical
concentration of interstitial iron corresponds to $x \approx 12%$ and leads
crystallographic phase separation at base temperature. The spin-density wave is
short-range ordered with a correlation length of 22(3) \AA, and as the ordering
temperature is approached its propagation vector decreases linearly in the
H-direction and becomes long-range ordered. Upon further populating the
interstitial iron site, the spin-density wave gives way to an incommensurate
helical ordering with propagation vector $ \mathbf k =$ ($0.3855(2) \, \,0 \,
\, \frac1 2$) at base temperature. For a sample with $x \approx 9(1) %$, we
also find an incommensurate spin-density wave that competes with the
bicollinear commensurate ordering close to the N\'eel point. The shifting of
spectral weight between competing magnetic orderings observed in several
samples is supporting evidence for the phase separation being electronic in
nature, and hence leads to crystallographic phase separation around the
critical interstitial iron concentration of 12%. With results from both powder
and single crystal samples, we construct a magnetic-crystallographic phase
diagram of Fe$_{1+x}$Te for $ 5% < x <17%$",1105.1937v1
2013-10-01,Linear Spin Wave Analysis for General Magnetic Orders in the Kondo Lattice Model,"We extend the formulation of the spin wave theory for the Kondo lattice
model, which was mainly used for the ferromagnetic metallic state, to general
magnetic orders including complex noncollinear and noncoplanar orders. The 1/S
expansion is reformulated in the matrix form depending on the size of the
magnetic unit cell. The noncollinearity and noncoplanarity of the localized
moments are properly taken into account by the matrix elements of the
para-unitary matrix used in the diagonalization of the Bogoliubov-de Gennes
type Hamiltonian for magnons. We apply the formulation within the linear spin
wave approximation to a typical noncollinear case, the $120^{\circ}$ N{\'e}el
order on a triangular lattice at half filling. We calculate the magnon
excitation spectrum and the quantum correction to the magnitude of ordered
moments as functions of the strength of the Hund's-rule coupling, $J_{\rm
H}/t$. We find that the magnon excitation shows softening at $J_{\rm H}/t
\simeq 2.9$, which indicates that the $120^{\circ}$ order is destabilized for
smaller $J_{\rm H}/t$. On the other hand, we show that the $120^{\circ}$ order
is stable in the entire range of $J_{\rm H}/t \gtrsim 2.9$, and, in the limit
of $J_{\rm H}/t \to \infty$, the form of the spin wave spectrum approaches that
for the antiferromagnetic Heisenberg model, while the bandwidth is proportional
to $t^2/J_{\rm H}$. The reduction of the ordered moment is smaller than that
for the spin-only model, except in the vicinity of the softening.",1310.0176v1
2016-09-01,The role of the internal demagnetizing field in a surface-modulated magnonic crystal,"Magnonic crystals with locally alternating properties and specific
periodicities exhibit interesting effects, such as a multitude of different
spin-wave states and large band gaps. This work aims for demonstrating and
understanding the key role of local demagnetizing fields in such systems. To
achieve this, hybrid structures are investigated consisting of a continuous
thin film with a stripe modulation on top favorable due to the adjustability of
the magnonic effects with the modulation size. For a direct access to the spin
dynamics, a magnonic crystal was reconstructed from `bottom-up', i.e., the
structural shape as well as the internal field landscape of the structure were
experimentally obtained on the nanoscale using electron holography.
Subsequently, both properties were utilized to perform dynamic response
calculations. The simulations yield the frequency-field dependence as well as
the angular dependence of spin waves in a magnonic crystal and reveal the
governing role of the internal field landscape around the backward-volume
geometry. The complex angle-dependent spin-wave behavior is described for a 360
degree in-plane rotation of an external field by connecting the internal field
landscape with the individual spin-wave localization.",1609.00342v3
2017-11-20,Temperature dependent relaxation of dipole-exchange magnons in yttrium iron garnet films,"Low energy consumption enabled by charge-free information transport, which is
free from ohmic heating, and the ability to process phase-encoded data by
nanometer-sized interference devices at GHz and THz frequencies are just a few
benefits of spin-wave-based technologies. Moreover, when approaching cryogenic
temperatures, quantum phenomena in spin-wave systems pave the path towards
quantum information processing. In view of these applications, the lifetime of
magnons$-$spin-wave quanta$-$is of high relevance for the fields of magnonics,
magnon spintronics and quantum computing. Here, the relaxation behavior of
parametrically excited magnons having wavenumbers from zero up to $6\cdot 10^5
\mathrm{rad~cm}^{-1}$ was experimentally investigated in the temperature range
from 20 K to 340 K in single crystal yttrium iron garnet (YIG) films
epitaxially grown on gallium gadolinium garnet (GGG) substrates as well as in a
bulk YIG crystal$-$the magnonic materials featuring the lowest magnetic damping
known so far. As opposed to the bulk YIG crystal in YIG films we have found a
significant increase in the magnon relaxation rate below 150 K$-$up to 10.5
times the reference value at 340 K$-$in the entire range of probed wavenumbers.
This increase is associated with rare-earth impurities contaminating the YIG
samples with a slight contribution caused by coupling of spin waves to the spin
system of the paramagnetic GGG substrate at the lowest temperatures.",1711.07517v1
2018-11-06,Toward low-latency coincident precessing and coherent aligned-spin gravitational-wave searches of compact binary coalescences with particle swarm optimization,"We investigate the use of particle swarm optimization (PSO) algorithm for
detection of gravitational-wave signals from compact binary coalescences. We
show that the PSO is fast and effective in searching for gravitational wave
signals. The PSO-based aligned-spin coincident multi-detector search recovers
appreciably more gravitational-wave signals, for a signal-to-noise ratio (SNR)
of 10, the PSO based aligned-spin search recovers approximately 26 $\%$ more
events as compared to the template bank searches. The PSO-based aligned-spin
coincident search uses 48k matched-filtering operations, and provides a better
parameter estimation accuracy at the detection stage, as compared to the PyCBC
template-bank search in LIGO's second observation run (O2) with 400k template
points. We demonstrate an effective PSO-based precessing coincident search with
320k match-filtering operations per detector. We present results of an all-sky
aligned-spin coherent search with 576k match-filtering operations per detector,
for some examples of two-, three-, and four-detector networks constituting of
the LIGO detectors in Hanford and Livingston, Virgo and KAGRA. Techniques for
background estimation that are applicable to real data for PSO-based coincident
and coherent searches are also presented.",1811.02401v2
2012-09-13,Random field Ising model swept by propagating magnetic field wave: Athermal nonequilibrium phase diagram,"The dynamical steady state behaviour of the random field
  Ising ferromagnet swept by a propagating magnetic field wave is studied at
zero temperature by Monte Carlo simulation in two dimensions. The distribution
of the random field is bimodal type. For a fixed set of values of the frequency
and wavelength of propagating magnetic field wave and the strength of the
random field, four distinct dynamical steady states or nonequilibrium phases
were identified. These four nonequilibrium phases are characterised by
different values of structure factors. State of first kind, where all spins are
parallel (up). The second one is, the propagating type, where the sharp strips
formed by parallel spins are found to move coherently. The third one is also
propagating type, where the boundary of the strips of spins is not very sharp.
The fourth kind, shows no propagation of stripes of magnetic spins, forming a
homogeneous distribution of up and down spins. This is disordered phase The
appearance of these four dynamical phases or modes depends on the value of the
amplitude of propagating magnetic field wave and the strength of random
(static) field. A phase diagram has also been drawn, in the plane formed by the
amplitude of propagating field and the strength of random field. It is checked
that, the existence of these dynamical phases is neither a finite size effect
nor a transient phenomenon.",1209.2841v2
2020-04-22,Excitation of high-frequency magnon modes in magnetoelastic films by short strain pulses,"Development of energy efficient techniques for generation of spin waves
(magnons) is important for implementation of low-dissipation spin-wave-based
logic circuits and memory elements. A promising approach to achieve this goal
is based on the injection of short strain pulses into ferromagnetic films with
a strong magnetoelastic coupling between spins and strains. Here we report
micromagnetoelastic simulations of the magnetization and strain dynamics
excited in Fe$_{81}$Ga$_{19}$ films by picosecond and nanosecond acoustic
pulses created in a GaAs substrate by a transducer subjected to an optical or
electrical impulse. The simulations performed via the numerical solution of the
coupled Landau-Lifshitz-Gilbert and elastodynamic equations show that the
injected strain pulse induces an inhomogeneous magnetization precession in the
ferromagnetic film. The precession lasts up to 1 ns and can be treated as a
superposition of magnon modes having the form of standing spin waves. For
Fe$_{81}$Ga$_{19}$ films with nanoscale thickness, up to seven (six) distinct
modes have been revealed under free-surface (pinning) magnetic boundary
conditions. Remarkably, magnon modes with frequencies over 1 THz can be excited
by acoustic pulses with an appropriate shape and duration in the films
subjected to a moderate external magnetic field. This finding shows that short
strain pulses represent a promising tool for the generation of THz spin waves
necessary for the implementation of high-speed magnonic devices.",2004.10838v1
2017-03-09,Quantum Monte Carlo with variable spins: fixed-phase and fixed-node approximations,"We study several aspects of the recently introduced fixed-phase spin-orbit
diffusion Monte Carlo (FPSODMC) method, in particular, its relation to the
fixed-node method and its potential use as a general approach for electronic
structure calculations. We illustrate constructions of spinor-based wave
functions with the full space-spin symmetry without assigning up or down spin
labels to particular electrons, effectively ""complexifying"" even ordinary
real-valued wave functions. Interestingly, with proper choice of the simulation
parameters and spin variables, such fixed-phase calculations enable one to
reach also the fixed-node limit. The fixed-phase solution provides a
straightforward interpretation as the lowest bosonic state in a given effective
potential generated by the many-body approximate phase. In addition, the
divergences present at real wave function nodes are smoothed out to lower
dimensionality, decreasing thus the variation of sampled quantities and making
the sampling also more straightforward. We illustrate some of these properties
on calculations of selected first-row systems that recover the fixed-node
results with quantitatively similar levels of the corresponding biases. At the
same time, the fixed-phase approach opens new possibilities for more general
trial wave functions with further opportunities for increasing accuracy in
practical calculations.",1703.03481v1
2019-12-22,First-principles study of magnon-phonon interactions in gadolinium iron garnet,"We obtained the spin-wave spectrum based on a first-principles method of
exchange constants, calculated the phonon spectrum by the first-principles
phonon calculation method, and extracted the broadening of the magnon spectrum,
$\Delta \omega$, induced by magnon-phonon interactions in gadolinium iron
garnet (GdIG). Using the obtained exchange constants, we reproduce the
experimental Curie temperature and the compensation temperature from spin
models using Metropolis Monte Carlo (MC) simulations. In the lower-frequency
regime, the fitted positions of the magnon-phonon dispersion crossing points
are consistent with the inelastic neutron scattering experiment. We found that
the $\Delta \omega$ and magnon wave vector $k$ have a similar relationship in
YIG. The broadening of the acoustic spin-wave branch is proportional to
$k^{2}$, while that of the YIG-like acoustic branch and the optical branch are
a constant. At a specific $k$, the magnon-phonon thermalization time of
$\tau_{mp}$ are approximately $10^{-9}$~s, $10^{-13}$~s, and $10^{-14}$~s for
acoustic branch, YIG-like acoustic branch, and optical branch, respectively.
This research provides specific and effective information for developing a
clear understanding of the spin-wave mediated spin Seebeck effect and
complements the lack of lattice dynamics calculations of GdIG.",1912.10432v1
2019-12-27,Localized spin waves at low temperatures in a Cobalt Carbide nanocomposite,"We study magnetic, transport and thermal properties of Cobalt carbide
nanocomposite with a mixture of Co2C and Co3C phases in 1:1 ratio, with an
average particle diameter of 40$\pm 15$ nm. We show that the behavior of the
nanocomposite is completely different from that of either Co3C or Co2C. We
observed that with decreasing temperature the saturation magnetization MS(T)
increases, however, below 100 K, there is a steep rise. A detail analysis shows
the increase in MS(T) down to 100 K is explained via the surface spin freezing
model. However, below 100 K the steep increase in MS(T) is explained by a
finite size effect related to a confinement of spin waves within the nano
particles. The measurement of heat capacity shows broad peak at 100 K along
with presence of another anomaly at a lower temperature 43 K(=Tex). Resistance
measurement in the nanocomposite shows metallic behavior at high T with an
unusual anomaly appearing at Tex, which is near the T regime where MS(T) begins
to increase steeply. A measurement of the temperature gradients across the
sample thickness indicates an abrupt change in thermal conductivity at Tex
which suggests a phase transition at Tex. Our results are explained in terms of
a transformation from a magnetically coupled state with a continuous spectrum
of spin waves into a magnetically decoupled state below 100 K with confined
spin waves.",1912.12085v1
2021-05-11,On the connection between magnetic interactions and the spin-wave gap of the insulating phase of NaOsO$_{3}$,"The scenario of a metal-insulator transition driven by the onset of
antiferromagnetic order in NaOsO$_3$ calls for a trustworthy derivation of the
underlying effective spin Hamiltonian. To determine the latter we rely on {\it
ab initio} electronic-structure calculations, linear spin-wave theory, and
comparison to experimental data of the corresponding magnon spectrum. We arrive
this way to Heisenberg couplings that are $\lesssim$45\% to$\lesssim$63\%
smaller than values presently proposed in the literature and
Dzyaloshinskii-Moriya interactions in the region of 15\% of the Heisenberg
exchange $J$. These couplings together with the symmetric anisotropic exchange
interaction and single-ion magnetocrystalline anisotropy successfully reproduce
the magnon dispersion obtained by resonant inelastic X-ray scattering
measurements. In particular, the spin-wave gap fully agrees with the measured
one. We find that the spin-wave gap is defined from a subtle interplay between
the single-ion anisotropy, the Dzyaloshinskii-Moriya exchange and the symmetric
anisotropic exchange interactions. The results reported here underpin the
local-moment description of NaOsO$_3$, when it comes to analyzing the magnetic
excitation spectra. Interestingly, this comes about from a microscopic theory
that describes the electron system as Bloch states, adjusted to a mean-field
solution to Hubbard-like interactions.",2105.04893v2
2021-11-02,Non-equilibrium self-assembly of spin-wave solitons in FePt nanoparticles,"Magnetic nanoparticles such as FePt in the L10-phase are the bedrock of our
current data storage technology. As the grains become smaller to keep up with
technological demands, the superparamagnetic limit calls for materials with
higher magneto-crystalline anisotropy. This in turn reduces the magnetic
exchange length to just a few nanometers enabling magnetic structures to be
induced within the nanoparticles. Here we describe the existence of spin-wave
solitons, dynamic localized bound states of spin-wave excitations, in FePt
nanoparticles. We show with time-resolved X-ray diffraction and micromagnetic
modeling that spin-wave solitons of sub-10 nm sizes form out of the
demagnetized state following femtosecond laser excitation. The measured soliton
spin-precession frequency of 0.1 THz positions this system as a platform to
develop miniature devices capable of filling the THz gap.",2111.01649v1
2022-03-04,Reservoir Computing with Spin Waves in Skyrmion Crystal,"Magnetic skyrmions are nanometric spin textures characterized by a quantized
topological invariant in magnets and often emerge in a crystallized form called
skyrmion crystal in an external magnetic field. We propose that magnets hosting
a skyrmion crystal possess high potential for application to reservoir
computing, which is one of the most successful information processing
techniques inspired by functions of human brains. Our skyrmion-based reservoir
exploits precession dynamics of magnetizations, i.e., spin waves, propagating
in the skyrmion crystal. Because of complex interferences and slow relaxations
of the spin-wave dynamics, the skyrmion spin-wave reservoir attains several
important characteristics required for reservoir computing, e.g., the
generalization ability, the nonlinearity, and the short-term memory. We
investigate these properties by imposing three standard tasks to test the
performances of reservoir, i.e., the duration-estimation task, the short-term
memory task, and the parity-check task. Through these investigations, we
demonstrate that magnetic skyrmion crystals are promising materials for
spintronics reservoir devices. Because magnetic skyrmions emerge spontaneously
in magnets via self-organization process under application of a static magnetic
field, the proposed skyrmion reservoir requires neither advanced
nanofabrication nor complicated manufacturing for production in contrast to
other previously proposed magnetic reservoirs constructed with fabricated
spintronics devices. Our proposal is expected to realize a breakthrough in the
research of spintronics reservoirs of high performance.",2203.02160v1
2022-09-12,Holes and magnetic polarons in a triangular lattice antiferromagnet,"The intricate interplay between charge motion and magnetic order in
geometrically frustrated lattices is central for the properties of many
two-dimensional quantum materials. The triangular lattice antiferromagnet is a
canonical example of a frustrated system, and here we analyse the dynamics of a
hole in such a lattice focusing on observables that have become accessible in a
new generation of experiments. Using the $t$-$J$ model, we solve the problem
exactly within linear spin wave theory in the limit of strong magnetic
interactions, showing that the ground state is described by a coherent state of
spin waves. The derivation highlights the crucial role played by the
interaction between a static hole and the neighboring spins, which originates
in the geometric frustration and has often been omitted in earlier works.
Furthermore, we show that the non-equilibrium dynamics after a hole has
abruptly been inserted at a lattice site is given exactly by a coherent state
with time-dependent oscillatory coefficients. Physically, this describes a
burst of magnetic frustration propagating through only two-thirds of the
lattice sites, since a destructive interference of spin waves leaves spins
parallel to that removed by the hole unperturbed. After the wave has propagated
through the lattice, the magnetization relaxes to that of the ground state. We
then use our analytical solution to benchmark the widely used self-consistent
Born approximation (SCBA), showing that it is very accurate also for a
triangular lattice. The magnetic polaron spectrum is analysed for general
magnetic interactions using the SCBA, and we compare our results with those for
a square lattice.",2209.05131v1
2022-09-21,Performance enhancement of a spin-wave-based reservoir computing system utilizing different physical conditions,"The authors have numerically studied how to enhance reservoir computing
performance by thoroughly extracting their spin-wave device potential for
higher-dimensional information generation. The reservoir device has a 1-input
exciter and 120-output detectors on the top of a continuous magnetic garnet
film for spin-wave transmission. For various nonlinear and fading-memory
dynamic phenomena distributing in the film space, small in-plane magnetic
fields were used to prepare stripe domain structures and various damping
constants at the film sides and bottom were explored. The ferromagnetic
resonant frequency and relaxation time of spin precession clearly characterized
the change in spin dynamics with the magnetic field and damping constant. The
common input signal for reservoir computing was a 1 GHz cosine wave with random
6-valued amplitude modulation. A basic 120-dimensional reservoir output vector
was obtained from time-series signals at the 120 output detectors under each of
the three magnetic field conditions. Then, 240- and 360-dimensional reservoir
output vectors were also constructed by concatenating two and three basic ones,
respectively. In nonlinear autoregressive moving average (NARMA) prediction
tasks, the computational performance was enhanced as the dimension of the
reservoir output vector becomes higher and a significantly low prediction error
was achieved for the 10th-order NARMA using the 360-dimensional vector and
optimum damping constant. The results are clear evidence that the collection of
diverse output signals efficiently increases the dimensionality effective for
reservoir computing, i.e., reservoir-state richness. This paper demonstrates
that performance enhancement through various configuration settings is a
practical approach for on-chip reservoir computing devices with small numbers
of real output nodes.",2209.10123v1
2024-03-13,Hybrid magnon-phonon cavity for large-amplitude terahertz spin-wave excitation,"Terahertz (THz) spin waves or their quanta, magnons, can be efficiently
excited by acoustic phonons because these excitations have similar wavevectors
in the THz regime. THz acoustic phonons can be produced using photoacoustic
phenomena but typically have a low population and thus a relatively low
displacement amplitude. The magnetization amplitude and population of the
acoustically excited THz magnons are thus usually small. Using analytical
calculations and dynamical phase-field simulations, we show that a freestanding
metal/magnetic-insulator (MI)/dielectric multilayer can be designed to produce
large-amplitude THz spin wave via cavity-enhanced magnon-phonon interaction.
The amplitude of the acoustically excited THz spin wave in the freestanding
multilayer is predicted to be more than ten times larger than in a
substrate-supported multilayer. Acoustically excited nonlinear magnon-magnon
interaction is demonstrated in the freestanding multilayer. The simulations
also indicate that the magnon modes can be detected by probing the charge
current in the metal layer generated via spin-charge conversion across the
MI/metal interface and the resulting THz radiation. Applications of the
freestanding multilayer in THz optoelectronic transduction are computationally
demonstrated.",2403.08186v1
1996-10-08,Low-Lying Excited States and Low-Temperature Properties of an Alternating Spin-1 / Spin-1/2 Chain : A DMRG study,"We report spin wave and DMRG studies of the ground and low-lying excited
states of uniform and dimerized alternating spin chains. The DMRG procedure is
also employed to obtain low-temperature thermodynamic properties of the system.
The ground state of a 2N spin system with spin-1 and spin-1/2 alternating from
site to site and interacting via an antiferromagnetic exchange is found to be
ferrimagnetic with total spin $s_G=N/2$ from both DMRG and spin wave analysis.
Both the studies also show that there is a gapless excitation to a state with
spin $s_G-1$ and a gapped excitation to a state with spin $s_G+1$.
Surprisingly, the correlation length in the ground state is found to be very
small from both the studies for this gapless system. For this very reason, we
show that the ground state can be described by a variational ``ansatz'' of the
product type. DMRG analysis shows that the chain is susceptible to a
conditional spin-Peierls' instability. The DMRG studies of magnetization,
magnetic susceptibility ($\chi$) and specific heat show strong magnetic-field
dependence. The product $\chi T$ shows a minimum as a function of
temperature($T$) at low-magnetic fields and the minimum vanishes at
high-magnetic fields. This low-field behaviour is in agreement with earlier
experimental observations. The specific heat shows a maximum as a function of
temperature and the height of the maximum increases sharply at high magnetic
fields. It is hoped that these studies will motivate experimental studies at
high-magnetic fields.",9610080v1
1997-09-26,Spin holography II,"The interference of the directly emitted photoelectron wave and the wave
scattered coherently by neighboring atoms gives holographic fringes in the
photoelectron emission intensity $I(\hat{\bf R})$. In the electron emission
holography technique in surface physics, $I(\hat{\bf R})$ is inverted
holographically to give a 3D-image of the environment of the source atom.
Earlier, we pointed out that the polarization pattern ${\bf P}(\hat{\bf R})$
similarly can be viewed as a hologram of the spin environment of the source
atom by virtue of the exchange scattering of the photoelectron by the
neighboring atoms. In this paper, we point out that spin-orbit correlations in
the photoelectron initial state are responsible for holographic spin-dependent
contributions to the intensity hologram $I(\hat{\bf R})$, even if the directly
emitted photoelectrons are unpolarized. This remarkable result implies that the
emission intensity contains spin information just as the polarization pattern
${\bf P}(\hat{\bf R})$. Although the spin dependent signal in the hologram is
rather small ($\sim 5 \% $ in most cases of interest), we show how spin
information can be extracted from the intensity hologram, making use of the
point symmetry of the environment of the source atom. This way of analyzing
photoelectron intensity holograms to extract short-range spin information opens
up a new avenue for surface magnetism studies.",9709302v1
2002-05-10,Spin-dynamics simulations of the triangular antiferromagnetic XY model,"Using Monte Carlo and spin-dynamics methods, we have investigated the dynamic
behavior of the classical, antiferromagnetic XY model on a triangular lattice
with linear sizes $L \leq 300$. The temporal evolutions of spin configurations
were obtained by solving numerically the coupled equations of motion for each
spin using fourth-order Suzuki-Trotter decompositions of exponential operators.
  From space- and time-displaced spin-spin correlation functions and their
space-time Fourier transforms we obtained the dynamic structure factor $S({\bf
q},w)$ for momentum ${\bf q}$ and frequency $\omega$. Below
$T_{KT}$(Kosterlitz-Thouless transition), both the in-plane ($S^{xx}$) and the
out-of-plane ($S^{zz}$) components of $S({\bf q},\omega)$ exhibit very strong
and sharp spin-wave peaks. Well above $T_{KT}$, $S^{xx}$ and $S^{zz}$
apparently display a central peak, and spin-wave signatures are still seen in
$S^{zz}$. In addition, we also observed an almost dispersionless domain-wall
peak at high $\omega$ below $T_{c}$(Ising transition), where long-range order
appears in the staggered chirality. Above $T_{c}$, the domain-wall peak
disappears for all $q$. The lineshape of these peaks is captured reasonably
well by a Lorentzian form. Using a dynamic finite-size scaling theory, we
determined the dynamic critical exponent $z$ = 1.002(3). We found that our
results demonstrate the consistency of the dynamic finite-size scaling theory
for the characteristic frequeny $\omega_{m}$ and the dynamic structure factor
$S({\bf q},\omega)$ itself.",0205227v1
2004-05-17,A quasi-physical family of gravity-wave templates for precessing binaries of spinning compact objects: Application to double-spin precessing binaries,"The gravitational waveforms emitted during the adiabatic inspiral of
precessing binaries with two spinning compact bodies of comparable masses,
evaluated within the post-Newtonian approximation, can be reproduced rather
accurately by the waveforms obtained by setting one of the two spins to zero,
at least for the purpose of detection by ground-based gravitational-wave
interferometers. Here we propose to use this quasi-physical family of
single-spin templates to search for the signals emitted by double-spin
precessing binaries, and we find that its signal-matching performance is
satisfactory for source masses (m1,m2) in [3,15]Msun x [3,15]Msun. For this
mass range, using the LIGO-I design sensitivity, we estimate that the number of
templates required to yield a minimum match of 0.97 is ~320,000. We discuss
also the accuracy to which the single-spin template family can be used to
estimate the parameters of the original double-spin precessing binaries.",0405090v3
2007-07-17,Quarkonium and hydrogen spectra with spin dependent relativistic wave equation,"A non-linear non-perturbative relativistic atomic theory introduces spin in
the dynamics of particle motion. The resulting energy levels of Hydrogen atom
are exactly same as the Dirac theory. The theory accounts for the energy due to
spin-orbit interaction and for the additional potential energy due to spin and
spin-orbit coupling. Spin angular momentum operator is integrated into the
equation of motion. This requires modification to classical Laplacian operator.
Consequently the Dirac matrices and the k operator of Dirac's theory are
dispensed with. The theory points out that the curvature of the orbit draws on
certain amount of kinetic and potential energies affecting the momentum of
electron and the spin-orbit interaction energy constitutes a part of this
energy. The theory is developed for spin 1/2 bound state single electron in
Coulomb potential and then further extended to quarkonium physics by
introducing the linear confining potential. The unique feature of this
quarkonium model is that the radial distance can be exactly determined and does
not have a statistical interpretation. The established radial distance is then
used to determine the wave function. The observed energy levels are used as the
input parameters and the radial distance and the string tension are predicted.
This ensures 100% conformance to all observed energy levels for the heavy
quarkonium.",0707.2431v7
2012-12-25,Competition between $T$=1 and $T$=0 pairing in $pf$-shell nuclei with $N=Z$,"The pairing correlation energy for two-nucleon configurations with the
spin-parity and isospin of $J^\pi=0^+$, $T$=1 and $J^\pi=1^+$, $T$=0 are
calculated with $T$=1 and $T$=0 pairing interactions, respectively. To this
end, we consider the $(1f2p)$ shell model space, including single-particle
angular momenta of $l=3$ and $l=1$. It is pointed out that a two-body matrix
element of the spin-triplet $T$=0 pairing is weakened substantially for the
$1f$ orbits, even though the pairing strength is much larger than that for the
spin-singlet $T$=1 pairing interaction. In contrast, the spin-triplet pairing
correlations overcome the spin-singlet pairing correlations for the $2p$
configuration, for which the spin-orbit splitting is smaller than that for the
$1f$ configurations, if the strength for the T=0 pairing is larger than that
for the T=1 pairing by 50% or more. Using the Hartree-Fock wave functions, it
is also pointed out that the mismatch of proton and neutron radial wave
functions is at most a few % level, even if the Fermi energies are largely
different in the proton and neutron mean-field potentials. These results imply
that the configuration with $J^\pi=0^+$, $T$=1 is likely in the ground state of
odd-odd $pf$ shell nuclei even under the influence of the strong spin-triplet
$T$=0 pairing, except at the middle of the $pf$ shell, in which the odd proton
and neutron may occupy the $2p$ orbits. These results are consistent with the
observed spin-parity $J^{\pi}=0^+$ for all odd-odd $pf$ shell nuclei except for
$^{58}_{29}$Cu, which has $J^{\pi}=1^+$.",1212.5992v1
2016-07-12,Charge density wave with meronlike spin texture induced by a lateral superlattice in a two-dimensional electron gas,"The combined effect of a lateral square superlattice potential and the
Coulomb interaction on the ground state of a two-dimensional electron gas in a
perpendicular magnetic field is studied for different rational values of
$\Gamma$, the inverse of the number of flux quanta per unit cell of the
external potential, at filling factor $\nu =1$ in Landau level $N=0.$ When
Landau level mixing and disorder effects are neglected, increasing the strength
$W_{0}$ of the potential induces a transition, at a critical strength
$W_{0}^{\left( c\right) },$ from a uniform and fully spin polarized state to a
two-dimensional charge density wave (CDW) with a meronlike spin texture at each
maximum and minimum of the CDW. The collective excitations of this vortex-CDW
are similar to those of the Skyrme crystal that is expected to be the ground
state near filling factor $\nu =1$. In particular, a broken U(1) symmetry in
the vortex-CDW results in an extra gapless phase mode that could provide a fast
channel for the relaxation of nuclear spins. The average spin polarization $%
S_{z}$ changes in a continuous or discontinuous manner as $W_{0}$ is increased
depending on whether $\Gamma \in \left[ 1/2,1\right] $ or $\Gamma \in \left[
0,1/2\right] .$ The phase mode and the meronlike spin texture disappear at
large value of $W_{0},$ leaving as the ground state a partially spin-polarized
CDW if $\Gamma \neq 1/2$ or a spin-unpolarized CDW if $\Gamma =1/2.$",1607.03403v1
2017-08-24,Hierarchy of exchange interactions in the triangular-lattice spin-liquid YbMgGaO$_{4}$,"The spin-1/2 triangular lattice antiferromagnet YbMgGaO$_{4}$ has attracted
recent attention as a quantum spin-liquid candidate with the possible presence
of off-diagonal anisotropic exchange interactions induced by spin-orbit
coupling. Whether a quantum spin-liquid is stabilized or not depends on the
interplay of various exchange interactions with chemical disorder that is
inherent to the layered structure of the compound. We combine time-domain
terahertz spectroscopy and inelastic neutron scattering measurements in the
field polarized state of YbMgGaO$_{4}$ to obtain better microscopic insights on
its exchange interactions. Terahertz spectroscopy in this fashion functions as
high-field electron spin resonance and probes the spin-wave excitations at the
Brillouin zone center, ideally complementing neutron scattering. A global
spin-wave fit to all our spectroscopic data at fields over 4T, informed by the
analysis of the terahertz spectroscopy linewidths, yields stringent constraints
on $g$-factors and exchange interactions. Our results paint YbMgGaO$_{4}$ as an
easy-plane XXZ antiferromagnet with the combined and necessary presence of
sub-leading next-nearest neighbor and weak anisotropic off-diagonal
nearest-neighbor interactions. Moreover, the obtained $g$-factors are
substantially different from previous reports. This works establishes the
hierarchy of exchange interactions in YbMgGaO$_{4}$ from high-field data alone
and thus strongly constrains possible mechanisms responsible for the observed
spin-liquid phenomenology.",1708.07503v3
2018-01-11,Spin-isotropic continuum of spin excitations in antiferromagnetically ordered Fe$_{1.07}$Te,"Unconventional superconductivity typically emerges in the presence of
quasi-degenerate ground states, and the associated intense fluctuations are
likely responsible for generating the superconducting state. Here we use
polarized neutron scattering to study the spin space anisotropy of spin
excitations in Fe$_{1.07}$Te exhibiting bicollinear antiferromagnetic (AF)
order, the parent compound of FeTe$_{1-x}$Se$_x$ superconductors. We confirm
that the low energy spin excitations are transverse spin waves, consistent with
a local-moment origin of the bicollinear AF order. While the ordered moments
lie in the $ab$-plane in Fe$_{1.07}$Te, it takes less energy for them to
fluctuate out-of-plane, similar to BaFe$_2$As$_2$ and NaFeAs. At energies above
$E\gtrsim20$ meV, we find magnetic scattering to be dominated by an isotropic
continuum that persists up to at least 50 meV. Although the isotropic spin
excitations cannot be ascribed to spin waves from a long-range ordered local
moment antiferromagnet, the continuum can result from the bicollinear magnetic
order ground state of Fe$_{1.07}$Te being quasi-degenerate with plaquette
magnetic order.",1801.04019v1
2017-02-28,Tidal interactions in spin-orbit misaligned systems,"Spin-orbit misalignments have been detected in exoplanetary systems and
binary star systems. Tidal interactions may have played an important role in
the evolution of the spin-orbit angle. In this study, we investigate the tidal
interactions in spin-orbit misaligned systems. In particular, we focus on the
tidal response of a rotating fluid body to the obliquity tide, which may be
important for the evolution of the spin-orbit angle but hardly affects the
orbital evolution. The obliquity tide also provides a torque for the mutual
precession of the spin and orbital axes around the total angular momentum
vector, which has not yet been considered in previous studies on the tidal
interactions. In this paper, we first formulate a set of linearized equations
describing the tidal response in spin-orbit misaligned systems, taking into
account the precessional motion. Numerical solutions in a homogeneous fluid and
in a polytrope of index 1 show that dissipative inertial waves can be excited
on top of precession by the obliquity tide in the presence of a rigid core. The
tidal quality factor associated with the obliquity tide $Q'_{210}$ can be
several orders of magnitude smaller than those associated with other tidal
components if their frequencies fall outside the frequency range of inertial
waves. Therefore, it is possible that the spin-orbit misalignment undergoes
much more rapid decay than the orbital decay in hot Jupiter systems owing to
the enhanced dissipation of the obliquity tide.",1702.08805v1
2019-07-29,Anomalous diffusion and localization in a positionally disordered quantum spin array,"Disorder in quantum systems can lead to the disruption of long-range order in
the ground state and to the localization of the elementary excitations - famous
examples thereof being the Bose glass of interacting bosons in a disordered or
quasi-periodic environment, or the localized phase of spin chains mapping onto
fermions. Here we present a two-dimensional quantum Ising model - relevant to
the physics of Rydberg-atom arrays - in which positional disorder of the spins
induces a randomization of the spin-spin couplings and of an on-site
longitudinal field. This form of disorder preserves long-range order in the
ground state, while it localizes the elementary excitations above it,
faithfully described as spin waves: the spin-wave spectrum is partially
localized for weak disorder (seemingly exhibiting mobility edges between
localized and extended, yet non-ergodic states), while it is fully localized
for strong disorder. The regime of partially localized excitations exhibits a
very rich non-equilibrium dynamics following a low-energy quench: correlations
and entanglement spread with a power-law behavior whose exponent is a
continuous function of disorder, interpolating between ballistic and arrested
transport. Our findings expose a stark dichotomy between static and dynamical
properties of disordered quantum spin systems, which is readily accessible to
experimental verification using quantum simulators of closed quantum many-body
systems.",1907.12511v1
2020-10-13,"Large band splitting with tunable spin polarization in two-dimensional ferroelectric GaXY (X= Se, Te; Y= Cl, Br, I) family","It has been generally accepted that the spin-orbit coupling effect in
noncentrosymmetric materials leads to the band splitting and non-trivial spin
polarization in the momentum space. However, in some cases, zero net spin
polarization in the split bands may occurs, dubbed as the band splitting with
vanishing spin polarization (BSVSP) effect, protected by non-pseudo-polar point
group symmetry of the wave vector in the first Brillouin zone [Liu et. al.,
Nat. Commun. \textbf{10}, 5144 (2019)]. In this paper, by using
first-principles calculations, we show that the BSVSP effect emerges in
two-dimensional (2D) nonsymmorphic Ga$XY$ ($X$= Se, Te; $Y$= Cl, Br, I) family,
a new class of 2D materials having in-plane ferroelectricity. Taking the GaTeCl
monolayer as a representative example, we observe the BSVSP effect in the split
bands along the $X-M$ line located in the proximity of the conduction band
minimum. By using $\vec{k}\cdot\vec{p}$ Hamiltonian derived based on the
symmetry analysis, we clarify that such effect is originated from the
cancellation of the local spin polarization, enforced by non-pseudo-polar
$C_{2v}$ point group symmetry of the wave vector along the $X-M$ line.
Importantly, we find that the spin polarization can be effectively induced by
applying an external out-of-plane electric field, indicating that an
electrically tunable spin polarization for spintronic applications is
plausible.",2010.06191v2
2021-02-27,Quantum phases of spin-1 system on 3/4 and 3/5 skewed ladders,"We study the quantum phase transitions of frustrated antiferromagnetic
Heisenberg spin-1 systems on the 3/4 and 3/5 skewed two leg ladder geometries.
These systems can be viewed as arising by periodically removing rung bonds from
a zigzag ladder. We find that in large systems, the ground state (gs) of the
3/4 ladder switches from a singlet to a magnetic state for $J_1 \ge 1.82$; the
gs spin corresponds to ferromagnetic alignment of effective $S = 2$ objects on
each unit cell. The gs of antiferromagnetic exchange Heisenberg spin-1 system
on a 3/5 skewed ladder is highly frustrated and has spiral spin arrangements.
The amplitude of the spin density wave in the 3/5 ladder is significantly
larger compared to that in the magnetic state of the 3/4 ladder. The gs of the
system switches between singlet state and low spin magnetic states multiple
times on tuning $J_1$ in a finite size system. The switching pattern is
nonmonotonic as a function of $J_1$, and depends on the system size. It appears
to be the consequence of higher $J_1$ favoring higher spin magnetic state and
the finite system favoring a standing spin wave. For some specific parameter
values, the magnetic gs in the 3/5 system is doubly degenerate in two different
mirror symmetry subspaces. This degeneracy leads to spontaneous spin parity and
mirror symmetry breaking giving rise to spin current in the gs of the system.",2103.00150v2
2021-06-10,Magnetic field effect on topological spin excitations in CrI$_3$,"The search for topological spin excitations in recently discovered
two-dimensional (2D) van der Waals (vdW) magnetic materials is important
because of their potential applications in dissipation-less spintronics. In the
2D vdW ferromagnetic (FM) honeycomb lattice CrI$_3$(T$_C$= 61 K), acoustic and
optical spin waves were found to be separated by a gap at the Dirac points. The
presence of such a gap is a signature of topological spin excitations if it
arises from the next nearest neighbor(NNN) Dzyaloshinskii-Moriya (DM) or
bond-angle dependent Kitaev interactions within the Cr honeycomb lattice.
Alternatively, the gap is suggested to arise from an electron correlation
effect not associated with topological spin excitations. Here we use inelastic
neutron scattering to conclusively demonstrate that the Kitaev interactions and
electron correlation effects cannot describe spin waves, Dirac gap and their
in-plane magnetic field dependence. Our results support the DM interactions
being the microscopic origin of the observed Dirac gap. Moreover, we find that
the nearest neighbor (NN) magnetic exchange interactions along the axis are
antiferromagnetic (AF)and the NNN interactions are FM. Therefore, our results
unveil the origin of the observedcaxisAF order in thin layers of CrI$_3$,
firmly determine the microscopic spin interactions in bulk CrI$_3$, and provide
a new understanding of topology-driven spin excitations in 2D vdW magnets.",2106.05899v1
2022-12-05,Boundary Layers of Circumplanetary Disks around Spinning Planets I. Effects of Rossby Waves,"Gas giant planets are believed to accrete from their circumplanetary disks
(CPDs). The CPDs usually involve accretion through the boundary layer (BL) in
the vicinity of planets. Prior studies have concentrated on the BL of
non-spinning planets. We investigate the influence of planetary spin on the
wave behaviors within the BL. The rotation profile in such BLs would show sharp
transition from the rigid rotation to the Keplerian rotation. We examine the
angular momentum transport in these BL in terms of linear perturbation
analysis. We find that the global inertia-acoustic mode associated with
spinning planets would give rise to the inflow of angular momentum and the
accretion of gas. In this work, we identify a new kind of global mode, namely
the Rossby mode. The Rossby mode can lead to the outflow of angular momentum
and the decretion of gas from a spinning planet. The Rossby mode provide a
negative feedback that regulates the planetary spin and mass. We compare the
growth rate of the two modes as a function of the width of BL, the Mach number
and the spin rate of planet. Our results reveal the underlying hydrodynamic
mechanism of terminal spins and asymptotic mass of the giant planets.",2212.02311v1
1999-09-16,Diffractive production of S and D wave vector mesons in DIS,"In this work the production of vector mesons in diffractive DIS is analyzed,
with an emphasis on the impact of the internal spin structure of a vector meson
upon its virtual photoproduction rate. We derived the full sets of s-channel
helicity conserving and violating amplitudes for pure S and D wave vector
mesons and found a striking difference between S and D wave vector meson
production. First, in the case of helicity conserving amplitudes, D wave vector
mesons were found to exhibit dramatically different Q^2-behavior due to
abnormally large higher twist contributions. Besides, we found that helicity
conserving amplitudes for S and D states are numerically comparable, which
makes the physical rho meson very sensitive to D wave admixture. Second, the
helicity violating amplitudes turned out large both for S and D wave states of
light vector mesons and for D wave heavy vector mesons as well.
  Aiming at producing sort of a manual on the diffractive vector meson
production, we carried out all calculations in a pedagogical manner with
maximally full presentation of intermediate steps and accompanied them with
detailed qualitative discussion.",9909394v1
2007-09-07,Properties of charge density waves in La$_{2-x}$Ba$_{x}$CuO$_4$,"We report a comprehensive x-ray scattering study of charge density wave
(stripe) ordering in $\rm La_{2-x}Ba_xCuO_4 (x \approx 1/8)$, for which the
superconducting $T_c$ is greatly suppressed. Strong superlattice reflections
corresponding to static ordering of charge stripes were observed in this
sample. The structural modulation at the lowest temperature was deduced based
on the intensity of over 70 unique superlattice positions surveyed. We found
that the charge order in this sample is described with one-dimensional charge
density waves, which have incommensurate wave-vectors (0.23, 0, 0.5) and (0,
0.23, 0.5) respectively on neighboring $\rm CuO_2$ planes. The structural
modulation due to the charge density wave order is simply sinusoidal, and no
higher harmonics were observed. Just below the structural transition
temperature, short-range charge density wave correlation appears, which
develops into a large scale charge ordering around 40 K, close to the spin
density wave ordering temperature. However, this charge ordering fails to grow
into a true long range order, and its correlation length saturates at $\sim
230\AA$, and slightly decreases below about 15 K, which may be due to the onset
of two-dimensional superconductivity.",0709.1130v1
2008-12-28,Interference of interacting matter waves,"The phenomenon of matter wave interference lies at the heart of quantum
physics. It has been observed in various contexts in the limit of
non-interacting particles as a single particle effect. Here we observe and
control matter wave interference whose evolution is driven by interparticle
interactions. In a multi-path matter wave interferometer, the macroscopic
many-body wave function of an interacting atomic Bose-Einstein condensate
develops a regular interference pattern, allowing us to detect and directly
visualize the effect of interaction-induced phase shifts. We demonstrate
control over the phase evolution by inhibiting interaction-induced dephasing
and by refocusing a dephased macroscopic matter wave in a spin-echo type
experiment. Our results show that interactions in a many-body system lead to a
surprisingly coherent evolution, possibly enabling narrow-band and
high-brightness matter wave interferometers based on atom lasers.",0812.4836v1
2021-01-17,The relevance of pion-exchange contributions versus contact terms in the chiral effective field theory description of nucleon-nucleon scattering,"The standard way to demonstrate the relevance of chiral symmetry for the NN
interaction is to consider higher partial waves of NN scattering which are
controlled entirely by chiral pion-exchanges (since contacts vanish). However,
in applications of NN-potentials to nuclear structure and reactions, the lower
partial waves are the important ones, making the largest contributions. Lower
partial waves are sensitive to the short-range potential, and so, when the
short-range contacts were to dominate over the chiral pion-contributions in
lower partial waves, then the predictions from ""chiral potentials"" would have
little to do with chiral symmetry. To address this issue, we investigate
systematically the role of the (chiral) one- and two-pion exchanges, on the one
hand, and the effect of the contacts, on the other hand, in the lower partial
waves of NN scattering. We are able to clearly identify the signature of chiral
symmetry in lower partial waves. Our study has also a pedagogical spin-off as
it demonstrates in detail how the reproduction of the lower partial-wave phase
shifts comes about from the various ingredients of the theory.",2101.06792v1
2022-07-26,Detecting the gravitational wave memory effect with TianQin,"The gravitational wave memory effect is a prediction of general relativity.
The presence of memory effect in gravitational wave signals not only provides
the chance to test an important aspect of general relativity, but also
represents a potentially non-negligible contribution to the waveform for
certain gravitational wave events. In this paper, we study the prospect of
detecting the gravitational wave memory effect directly with the planned
space-based gravitational wave detector -- TianQin. We find that during its 5
years operation, for the gravitational wave signals that could be detected by
TianQin, about $0.5\sim2.0$ signals may contain displacement memory effect with
signal-to-noise ratios (SNRs) greater than 3. This suggests that the chance for
TianQin to detect the displacement memory effect directly is low but not fully
negligible. In contrast, the chance to detect the spin memory is negligible. We
also study that in which parameter space, the memory effect is expected to be
significant in waveform modeling.",2207.13009v2
2004-11-10,Coherent wave-packet evolution in coupled bands,"We develop a formalism for treating coherent wave-packet dynamics of charge
and spin carriers in degenerate and nearly degenerate bands. We consider the
two-band case carefully in view of spintronics applications, where transitions
between spin-split bands often occur even for relatively weak electromagnetic
fields. We demonstrate that much of the semiclassical formalism developed for
the single-band case can be generalized to multiple bands, and examine the
nontrivial non-Abelian corrections arising from the additional degree of
freedom. Along with the center of mass motion in crystal momentum and real
space, one must also include a pseudo-spin to characterize the dynamics between
the bands. We derive the wave packet energy up to the first order gradient
correction and obtain the equations of motion for the real- and $k$-space
center of the wave-packet, as well as for the pseudo-spin. These equations
include the non-Abelian Berry curvature terms and a non-Abelian correction to
the group velocity. As an example, we apply our formalism to describe coherent
wave-packet evolution under the action of an electric field, demonstrating that
it leads to electrical separation of up and down spins. A sizable separation
will be observed, with a large degree of tunability, making this mechanism a
practical method of generating a spin polarization. We then turn our attention
to a magnetic field, where we recover Larmor precession, which cannot be
obtained from a single-band point of view. In this case, the gradient energy
correction can be regarded as due to a magnetic moment from the self-rotation
of the wave-packet, and we calculate its value for the light holes in the
spherical four-band Luttinger model.",0411285v2
2016-06-08,Hidden Markov model tracking of continuous gravitational waves from a neutron star with wandering spin,"Gravitational wave searches for continuous-wave signals from neutron stars
are especially challenging when the star's spin frequency is unknown a priori
from electromagnetic observations and wanders stochastically under the action
of internal (e.g. superfluid or magnetospheric) or external (e.g. accretion)
torques. It is shown that frequency tracking by hidden Markov model (HMM)
methods can be combined with existing maximum likelihood coherent matched
filters like the F-statistic to surmount some of the challenges raised by spin
wandering. Specifically it is found that, for an isolated, biaxial rotor whose
spin frequency walks randomly, HMM tracking of the F-statistic output from
coherent segments with duration T_drift = 10d over a total observation time of
T_obs = 1yr can detect signals with wave strains h0 > 2e-26 at a noise level
characteristic of the Advanced Laser Interferometer Gravitational Wave
Observatory (Advanced LIGO). For a biaxial rotor with randomly walking spin in
a binary orbit, whose orbital period and semi-major axis are known
approximately from electromagnetic observations, HMM tracking of the
Bessel-weighted F-statistic output can detect signals with h0 > 8e-26. An
efficient, recursive, HMM solver based on the Viterbi algorithm is
demonstrated, which requires ~10^3 CPU-hours for a typical, broadband (0.5-kHz)
search for the low-mass X-ray binary Scorpius X-1, including generation of the
relevant F-statistic input. In a ""realistic"" observational scenario, Viterbi
tracking successfully detects 41 out of 50 synthetic signals without spin
wandering in Stage I of the Scorpius X-1 Mock Data Challenge convened by the
LIGO Scientific Collaboration down to a wave strain of h0 = 1.1e-25, recovering
the frequency with a root-mean-square accuracy of <= 4.3e-3 Hz.",1606.02412v1
2017-07-14,Nonequilibrium phase transition in spin-S Ising ferromagnet driven by Propagating and Standing magnetic field wave,"The dynamical response of spin-S (S=1, 3/2, 2, 3) Ising ferromagnet to the
plane propagating wave , standing magnetic field wave and uniformly oscillating
field with constant frequency are studied separately in two dimensions by
extensive Monte Carlo simulation. Depending upon the strength of the magnetic
field and the value of the spin state of the Ising spin lattice two different
dynamical phases are observed. For a fixed value of S and the amplitude of the
propagating magnetic field wave the system undergoes a dynamical phase
transition from propagating phase to pinned phase as the temperature of the
system is cooled down. Similarly in case with standing magnetic wave the system
undergoes dynamical phase transition from high temperature phase where spins
oscillates coherently in alternate bands of half wavelength of the standing
magnetic wave to the low temperature pinned or spin frozen phase. For a fixed
value of the amplitude of magnetic field oscillation the transition temperature
is observed to decrease to a limiting value as the value of spin S is
increased. The time averaged magnetisation over a full cycle of the magnetic
field oscillation plays the role of the dynamic order parameter. A
comprehensive phase boundary is drawn in the plane of magnetic field amplitude
and dynamic transition temperature. It is found that the phase boundary shrinks
inwards for high value of spin state S. Also in the low temperature (and high
field) region the phase boundaries are closely spaced.",1707.04404v4
2020-06-05,Imitation of spin density wave order in Cu$_3$Nb$_2$O$_8$,"Spin density waves, based on modulated local moments, are usually associated
with metallic materials, but have recently been reported in insulators which
display coupled magnetic and structural order parameters. We discuss one such
example, the multiferroic Cu$_3$Nb$_2$O$_8$, which is reported to undergo two
magnetic phase transitions, first to a spin density wave phase at $T_N \approx
26.5K$, and then to a helicoidal structure coupled to an electric polarization
below $T_2 \approx 24K$ [R. D. Johnson, et al., Phys. Rev. Lett., 107, 137205
(2011)] which breaks the crystallographic inversion symmetry. We apply
spherical polarimetry to confirm the low-temperature magnetic structure, yet
only observe a single magnetic phase transition to helicoidal order. We argue
that the reported spin density wave originates from a decoupling of the
components of the magnetic order parameter, as allowed by symmetry and driven
by thermal fluctuations. This provides a mechanism for the magnetic, but not
nuclear, structure to break inversion symmetry thereby creating an intermediate
phase where the structure imitates a spin density wave. As the temperature is
reduced, this intermediate structure destabilizes the crystal such that a
structural chirality is induced, as reflected by the emergence of the electric
polarization, and the imitation spin density wave relaxes into a generic
helicoid. This provides a situation where the magnetic structure breaks
inversion symmetry while the crystal structure remains centrosymmetric.",2006.03425v1
2020-07-04,Time-domain imaging of curling modes in a confined magnetic vortex and a micromagnetic study exploring the role of spiral spin waves emitted by the core,"The curling spin wave modes of a ferromagnetic vortex confined to a
microscale disc have been directly imaged in response to a microwave field
excitation using time-resolved scanning Kerr microscopy. Micromagnetic
simulations have been used to explore the interaction of gyrotropic vortex core
dynamics with the curling modes observed in the region of circulating in-plane
magnetization. Hybridization of the fundamental gyrotropic mode with the
degenerate, lowest-frequency, azimuthal modes has previously been reported to
lead to their splitting and counter propagating motion, as we observe in our
spectra and measured images. The curling nature of the modes can be ascribed to
asymmetry in the static and dynamic magnetization across the disc thickness,
but here we also present evidence that spiral spin waves emitted by the core
can influence the spatial character of higher frequency curling modes for which
hybridization is only permitted with gyrotropic modes of the same sense of
azimuthal motion. While it is challenging to identify if such modes are truly
hybridized from the mode dispersion in a confined disc, our simulations reveal
that spiral spin waves from the core may act as mediators of the interaction
between the core dynamics and azimuthal modes. At higher frequency, modes with
radial character only do not exhibit marked curling, but instead show evidence
of interaction with spin waves generated at the edge of the disc. The measured
spatio-temporal character of the observed curling modes is accurately
reproduced by our simulations, which reveal the emission of propagating
short-wavelength spiral spin waves from both core and edge regions of the disc.
Our simulations suggest that the propagating modes are not inconsequential, but
may play a role in the dynamic overlap required for hybridization of modes of
the core and in-plane magnetised regions.",2007.02043v2
2015-03-02,Phonon enhancement of electronic orders and negative isotope effect in the Hubbard-Holstein model on a square lattice,"Looking for superconductors with higher transition temperature requires a
guiding principle. In conventional superconductors, electrons pair up into
Cooper pairs via the retarded attraction mediated by electron-phonon coupling.
Higher-frequency phonon (or smaller atomic mass) leads to higher
superconducting transition temperature, known as the isotope effect.
Furthermore, superconductivity is the only instability channel of the metallic
normal state. In correlated systems, the above simple scenario could be easily
violated. The strong local interaction is poorly screened, and this conspires
with a featured Fermi surface to promote various competing electronic orders,
such as spin-density-wave, charge-density-wave and unconventional
superconductivity. On top of the various phases, the effect of electron-phonon
coupling is an intriguing issue. Using the functional renormalization group,
here we investigated the interplay between the electron correlation and
electron-phonon coupling in a prototype Hubbard-Holstein model on a square
lattice. At half-filling, we found spin-density-wave and charge-density-wave
phases and the transition between them, while no superconducting phase arises.
Upon finite doping, d-wave/s-wave superconductivity emerges in proximity to
spin-density-wave/charge-density-wave phases. Surprisingly, lower-frequency
Holstein-phonons are either less destructive, or even beneficial, to the
various phases, resulting in a negative isotope effect. We discuss the
underlying mechanism behind and the implications of such anomalous effects.",1503.00471v1
2015-03-03,Skyrmions in a density wave state: a mechanism for chiral superconductivity,"Broken symmetry states characterizing density waves of higher angular
momentum in correlated electronic systems are intriguing objects. In the scheme
of characterization by angular momentum, conventional charge and spin density
waves correspond to zero angular momentum. Here we explore a class of exotic
density wave states that have topological properties observed in recently
discovered topological insulators. These rich topological density wave states
deserve closer attention in not only high temperature superconductors but in
other correlated electron states, as in heavy fermions, of which an explicit
example will be discussed.The state discussed has non-trivial charge $2e$
skyrmionic spin texture. These skyrmions can condense into a charged
superfluid. Alternately, they can fractionalize into merons and anti-merons.
The fractionalized particles that are confined in skyrmions in the insulating
phase, can emerge at a deconfined quantum critical point, which separates the
insulating and the superconducting phases. These fractional particles form a
two-component spin-singlet chiral $(d_{x^2-y^2}\pm id_{xy})$ wave
superconducting state that breaks time reversal symmetry. Possible connections
of this exotic order to the superconducting state in the heavy-fermion material
URu$_2$Si$_2$ are suggested. The direct evidence of such a chiral
superconducting state is polar Kerr effect that was observed recently.",1503.01126v1
2018-08-21,Metastable bound states of the two-dimensional bi-magnetoexcitons in the lowest Landau levels approximation,"The possible existence of the bound states of the interacting two-dimensional
(2D) magnetoexcitons in the lowest Landau levels (LLLs) approximation was
investigated using the Landau gauge description. The magnetoexcitons taking
part in the formation of the bound state with resultant wave vector k= 0 have
opposite in-plane wave vectors and look as two electric dipoles with the arms
oriented in-plane perpendicularly to the corresponding wave vectors. The bound
state of two antiparallel dipoles moving with equal probability in any
direction of the plane with equal but antiparallel wave vectors is
characterized by the variational wave function of the relative motion depending
on the modulus | k |. The spins of two electrons and the effective spins of two
holes forming the bound states were combined separately in the symmetric or in
the antisymmetric forms for electrons and holes. In the case of the variational
wave function the maximum density of the magnetoexcitons in the momentum space
representation is concentrated on the in-plane ring. The stable bound states of
the bimagnetoexciton molecule do not exist for both spin orientations. Instead
of them, a deep metastable bound state with the activation barrier comparable
with the ionization potential of the magnetoexciton with k =0 was revealed.",1808.06841v1
2020-11-13,Modeling and searching for a stochastic gravitational-wave background from ultralight vector bosons,"Ultralight bosons, which are predicted in a variety of beyond-Standard-Model
scenarios as dark-matter candidates, can trigger the superradiant instability
around spinning black holes. This instability gives rise to oscillating boson
condensates which then dissipate through the emission of nearly monochromatic
gravitational waves. Such systems are promising sources for current and future
gravitational-wave detectors. In this work, we consider minimally-coupled,
massive vector bosons, which can produce a significantly stronger
gravitational-wave signal compared to the scalar case. We adopt recently
obtained numerical results for the gravitational-wave flux, and astrophysical
models of black hole populations that include both isolated black holes and
binary merger remnants, to compute and study in detail the stochastic
gravitational-wave background emitted by these sources. Using a Bayesian
framework, we search for such a background signal emitted using data from the
first and second observing runs of Advanced LIGO. We find no evidence for such
a signal. Therefore, the results allow us to constrain minimally coupled vector
fields with masses in the range $0.8\times10^{-13}\mathrm{eV}\leq m_b\leq
6.0\times10^{-13}\mathrm{eV}$ at 95% credibility, assuming optimistically that
the dimensionless spin distribution for the isolated black hole population is
uniform in the range $[0,1]$. With more pessimistic assumptions, a narrower
range around $m_b\approx 10^{-13}\mathrm{eV}$ can still be excluded as long as
the upper end of the uniform distribution for dimensionless black hole spin is
$\gtrsim 0.2$.",2011.06995v2
1997-02-03,Magnetohydrodynamics in Superconducting-Superfluid Neutron Stars,"MHD equations are presented for the mixture of superfluid neutrons,
superconducting protons, and normal electrons believed to exist in the outer
cores of neutron stars. The dissipative effects of electron viscosity and
mutual friction due to electron-vortex scattering are also included. It is
shown that Alfven waves are replaced by cyclotron- vortex waves that have not
been previously derived from MHD theory. The cyclotron- vortex waves are
analogous to Alfven waves with the tension due to the magnetic energy density
replaced by the vortex energy density. The equations are then put into a
simplified form useful for studying the effects of the interior magnetic field
on the dynamics. Of particular interest is the crust-core coupling time which
can be inferred from pulsar glitch observations. The hypothesis that
cyclotron-vortex waves play a significant role in the core spin-up during a
glitch is used to place limits on the interior magnetic field. The results are
compared with those of other studies.",9702032v3
2002-11-07,The exchange coupling and spin waves in metallic magnets: removal of the long-wave approximation,"A well-known connection between the magnetic susceptibility and the effective
exchange parameter is analyzed. It is shown that all current computational
schemes use a long-wave approximation which is suitable only for localized
moments systems. A corresponding smallness parameter is derived in real and
recipical space. General 'inverse susceptibility' approach is combined with a
multiple scattering theory and applied for the studies of elementary metals Fe,
Ni and Gd. It is shown that the proposed approach significantly improves the
description of the exchange coupling between nearest atoms, the spin wave
spectrum at large wave vectors for the itinerant degrees of freedom in metallic
magnets. A consistent usage of this method leads to the proper description of
magnetic short-range order effects.",0211144v2
1999-12-15,Gravitational waves from the r-modes of rapidly rotating neutron stars,"Since the last Amaldi meeting in 1997 we have learned that the r-modes of
rapidly rotating neutron stars are unstable to gravitational radiation reaction
in astrophysically realistic conditions. Newborn neutron stars rotating more
rapidly than about 100Hz may spin down to that frequency during up to one year
after the supernova that gives them birth, emitting gravitational waves which
might be detectable by the enhanced LIGO interferometers at a distance which
includes several supernovae per year. A cosmological background of these events
may be detectable by advanced LIGO. The spins (about 300Hz) of neutron stars in
low-mass x-ray binaries may also be due to the r-mode instability (under
different conditions), and some of these systems in our galaxy may also produce
detectable gravitational waves--see the review by G. Ushomirsky in this volume.
Much work is in progress on developing our understanding of r-mode astrophysics
to refine the early, optimistic estimates of the detectability of the
gravitational waves.",9912065v1
2004-04-30,Gravitational Waves from Chaotic Dynamical System,"To investigate how chaos affects gravitational waves, we study the
gravitational waves from a spinning test particle moving around a Kerr black
hole, which is a typical chaotic system. To compare the result with those in
non-chaotic dynamical system, we also analyze a spinless test particle, which
orbit can be complicated in the Kerr back ground although the system is
integrable. We estimate the emitted gravitational waves by the multipole
expansion of a gravitational field. We find a striking difference in the energy
spectra of the gravitational waves. The spectrum for a chaotic orbit of a
spinning particle, contains various frequencies, while some characteristic
frequencies appear in the case of a spinless particle.",0404124v1
2006-08-15,"Errata for ``Global existence and scattering for the nonlinear Schrodinger equation on Schwarzschild manifolds'', ``Semilinear wave equations on the Schwarzschild manifold I: Local Decay Estimates'', and ``The wave equation on the Schwarzschild metric II: Local Decay for the spin 2 Regge Wheeler equation''","In ``Global existence and scattering for the nonlinear Schrodinger equation
on Schwarzschild manifolds'' (math-ph/0002030), ``Semilinear wave equations on
the Schwarzschild manifold I: Local Decay Estimates'' (gr-qc/0310091), and
``The wave equation on the Schwarzschild metric II: Local Decay for the spin 2
Regge Wheeler equation'' (gr-qc/0310066), local decay estimates were proven for
the (decoupled) Schrodinger, wave, and Regge-Wheeler equations on the
Schwarzschild manifold, using commutator methods. Here, we correct a step in
the commutator argument. The corrected argument works either for radial
semilinear equations or general linear equations. This recovers the results in
math-ph/0002030 and gr-qc/0310066, but does not recover the non radial, large
data, semilinear result asserted in the gr-qc/0310091.",0608073v3
2001-08-07,Spectrally stable encapsulated vortices for nonlinear Schroedinger equations,"A large class of multidimensional nonlinear Schroedinger equations admit
localized nonradial standing wave solutions that carry nonzero intrinsic
angular momentum. Here we provide evidence that certain of these spinning
excitations are spectrally stable. We find such waves for equations in two
space dimensions with focusing-defocusing nonlinearities, such as
cubic-quintic. Spectrally stable waves resemble a vortex (non-localized
solution with asymptotically constant amplitude) cut off at large radius by a
kink layer that exponentially localizes the solution.
  For the evolution equations linearized about a localized spinning wave, we
prove that unstable eigenvalues are zeros of Evans functions for a finite set
of ordinary differential equations. Numerical computations indicate that there
exist spectrally stable standing waves having central vortex of any degree.",0108009v2
2007-09-19,Wave Excitation in Disks Around Rotating Magnetic Stars,"The accretion disk around a rotating magnetic star (neutron star, white dwarf
or T Tauri star) is subjected to periodic vertical magnetic forces from the
star, with the forcing frequency equal to the stellar spin frequency or twice
the spin frequency. This gives rise bending waves in the disk that may
influence the variabilities of the system. We study the excitation, propagation
and dissipation of these waves using a hydrodynamical model coupled with a
generic model description of the magnetic forces. The $m=1$ bending waves are
excited at the Lindblad/vertical resonance, and propagate either to larger
radii or inward toward the corotation resonance where dissipation takes place.
While the resonant torque is negligible compared to the accretion torque, the
wave nevertheless may reach appreciable amplitude and can cause or modulate
flux variabilities from the system. We discuss applications of our result to
the observed quasi-periodic oscillations from various systems, in particular
neutron star low-mass X-ray binaries.",0709.3086v2
2007-11-07,Role of Interlayer Electron Hopping for Spin Density Wave State in the Zero-Gap Organic Conductor,"We investigate the formation of density waves in the zero-gap state (ZGS)
which has been found in the quasi-two-dimensional organic conductor
$\alpha$-(BEDT-TTF)$_2$I$_3$ salt under the hydrostatic pressure. The ZGS
exhibits the cone-like dispersion for both the conduction band and the valence
band which degenerate each other at the two-dimensional wave vectors,
$\pm\mib{k}_0$ forming a zero gap. By using the extended Hubbard model with
repulsive interaction we calculate the onset temperature of the spin density
wave (SDW) as a function of the interlayer electron hopping, which by itself
does not break the cone-like dispersion. It is shown that the SDW with wave
number $2\mib{k}_0$ is induced by the combined effect of the interaction, the
inter-band excitation across the zero-gap and the interlayer hopping.",0711.1066v1
2009-12-06,Compact Binary Coalescences in the Band of Ground-based Gravitational-Wave Detectors,"As the ground-based gravitational-wave telescopes LIGO, Virgo, and GEO 600
approach the era of first detections, we review the current knowledge of the
coalescence rates and the mass and spin distributions of merging neutron-star
and black-hole binaries. We emphasize the bi-directional connection between
gravitational-wave astronomy and conventional astrophysics. Astrophysical input
will make possible informed decisions about optimal detector configurations and
search techniques. Meanwhile, rate upper limits, detected merger rates, and the
distribution of masses and spins measured by gravitational-wave searches will
constrain astrophysical parameters through comparisons with astrophysical
models. Future developments necessary to the success of gravitational-wave
astronomy are discussed.",0912.1074v2
2010-05-30,Observing the phase space trajectory of an entangled matter wave packet,"We observe the phase space trajectory of an entangled wave packet of a
trapped ion with high precision. The application of a spin dependent light
force on a superposition of spin states allows for coherent splitting of the
matter wave packet such that two distinct components in phase space emerge. We
observe such motion with a precision of better than 9% of the wave packet
extension in both momentum and position, corresponding to a 0.8 nm position
resolution. We accurately study the effect of the initial ion temperature on
the quantum entanglement dynamics. Furthermore, we map out the phonon
distributions throughout the action of the displacement force. Our
investigation shows corrections to simplified models of the system evolution.
The precise knowledge of these dynamics may improve quantum gates for ion
crystals and lead to entangled matter wave states with large displacements.",1005.5547v2
2013-09-17,Canonical formalism and quantization of a massless spinning bosonic particle in four dimensions,"A twistor model of a free massless spinning particle in 4-dimensional
Minkowski space is studied in terms of spacetime and spinor variables. This
model is specified by a simple action, referred to here as the gauged Shirafuji
action, that consists of twistor variables and gauge fields on the
1-dimensional parameter space. We consider the canonical formalism of the model
by following the Dirac formulation for constrained Hamiltonian systems. In the
subsequent quantization procedure, we obtain a plane-wave solution with
momentum spinors. From this solution and coefficient functions, we construct
positive-frequency and negative-frequency spinor wave functions defined on
complexified Minkowski space. It is shown that the Fourier-Laplace transforms
of the coefficient functions lead to the spinor wave functions expressed as the
Penrose transforms of the corresponding holomorphic functions on twistor space.
We also consider the exponential generating function for the spinor wave
functions and derive a novel representation for each of the spinor wave
functions.",1309.4169v3
2013-11-04,Non-reciprocal Oersted field contribution to the current-induced frequency shift of magnetostatic surface waves,"The influence of an electrical current on the propagation of magnetostatic
surface waves is investigated in a relatively thick (40 nm) permalloy film both
experimentally and theoretically. Contrary to previously studied thinner films
where the dominating effect is the current-induced spin-wave Doppler shift, the
magnetic field generated by the current (Oersted field) is found to induce a
strong non-reciprocal frequency shift which overcompensates the Doppler shift.
The measured current induced frequency shift is in agreement with the developed
theory. The theory relates the sign of of the frequency shift to the spin wave
modal profiles. The good agreement between the experiment and the theory
confirms a recent prediction of a counter-intuitive mode localization for
magnetostatic surface waves in the dipole-exchange regime.",1311.0676v1
2016-01-13,Magnetic fluctuations in pair density wave superconductors,"Pair density wave superconductivity constitutes a novel electronic condensate
proposed to be realized in certain unconventional superconductors. Establishing
its potential existence is important for our fundamental understanding of
superconductivity in correlated materials. Here we compute the dynamical
magnetic susceptibility in the presence of a pair density wave ordered state,
and study its fingerprints on the spin-wave spectrum including the neutron
resonance. In contrast to the standard case of d-wave superconductivity, we
show that the pair density wave phase exhibits neither a spin-gap nor a
magnetic resonance peak, in agreement with a recent neutron scattering
experiment on underdoped La$_{1.905}$Ba$_{0.095}$CuO$_4$ [Z. Xu et al., Phys.
Rev. Lett. 113, 177002 (2014)].",1601.03251v2
2016-04-18,Topological density-wave states in a particle-hole symmetric Weyl metal,"We study the instabilities of a particle-hole symmetric Weyl metal with both
electron and hole Fermi surfaces (FS) around the Weyl points. For a repulsive
interaction, we find that the leading instability is towards a longitudinal
spin-density-wave order (SDW$_z$). Besides, there exist three degenerate
subleading instabilities: a charge-density-wave (CDW) instability and two
transverse spin-density-wave (SDW$_{x,y}$) instabilities. For an attractive
interaction the leading instabilities are towards two pair-density-wave orders
(PDW) which pair the two FS's separately. Both the PDW and SDW$_z$ order
parameters fully gap out FS's, while the CDW and SDW$_{x,y}$ ones leave line
nodes on both FS's. For the SDW$_z$ and the PDW states, the surface Fermi arc
in the metallic state evolves to a chiral Fermi line which passes the
projection of the Weyl points and traverses the full momentum space. For the
CDW state, the line node projects to a ""drumhead"" band localized on the
surface, which can lead to a topological charge polarization. We verify the
surface states by numerically simulating the angular-resolved photoemission
spectroscopy data.",1604.05311v2
2017-08-10,Spin Hall effect of gravitational waves,"Gravitons possess a Berry curvature due to their helicity. We derive the
semiclassical equations of motion for gravitons taking into account the Berry
curvature. We show that this quantum correction leads to the splitting of the
trajectories of right- and left-handed gravitational waves in curved space, and
that this correction can be understood as a topological phenomenon. This is the
spin Hall effect (SHE) of gravitational waves. We find that the SHE of
gravitational waves is twice as large as that of light. Possible future
observations of the SHE of gravitational waves can potentially test the quantum
nature of gravitons beyond the classical general relativity.",1708.03113v3
2018-07-25,Topological Sound,"Recently, we witnessed a tremendous effort to conquer the realm of acoustics
as a possible playground to test with sound waves topologically protected wave
propagation. Acoustics differ substantially from photonic and electronic
systems since longitudinal sound waves lack intrinsic spin polarization and
breaking the time-reversal symmetry requires additional complexities that both
are essential in mimicking the quantum effects leading to topologically robust
sound propagation. In this article, we review the latest efforts to explore
with sound waves topological states of quantum matter in two- and
three-dimensional systems where we discuss how spin and valley degrees of
freedom appear as highly novel ingredients to tailor the flow of sound in the
form of one-way edge modes and defect-immune protected acoustic waves. Both
from a theoretical stand point and based on contemporary experimental
verifications, we summarize the latest advancements of the flourishing research
frontier on topological sound.",1807.09544v1
2020-08-17,Robust acoustic pulling using chiral surface waves,"We show that long-range and robust acoustic pulling can be achieved by using
a pair of one-way chiral surface waves supported on the interface between two
phononic crystals composed of spinning cylinders with equal but opposite
spinning velocities embedded in water. When the chiral surface mode with a
relative small Bloch wave vector is excited, the particle located in the
interface waveguide will scatter the excited surface mode to another chiral
surface mode with a greater Bloch wave vector, resulting in an acoustic pulling
force, irrespective of the size and material of the particle. Thanks to the
backscattering immunity of the chiral surface waves against local disorders,
the particle can be pulled following a flexible trajectory as determined by the
shape of the interface. As such, this new acoustic pulling scheme overcomes
some of the limitations of the traditional acoustic pulling using structured
beams, such as short pulling distances, straight-line type pulling and strong
dependence on the scattering properties of the particle. Our work may also
inspire the application of topological acoustics to acoustic manipulations.",2008.07062v1
2017-03-30,Entanglement isn't just for spin,"Quantum entanglement occurs not just in discrete systems such as spins, but
also in the spatial wave functions of systems with more than one degree of
freedom. It is easy to introduce students to entangled wave functions at an
early stage, in any course that discusses wave functions. Doing so not only
prepares students to learn about Bell's theorem and quantum information
science, but can also provide a deeper understanding of the principles of
quantum mechanics and help fight against some common misconceptions. Here I
introduce several pictorial examples of entangled wave functions that depend on
just two spatial variables. I also show how such wave functions can arise
dynamically, and describe how to quantify their entanglement.",1703.10620v1
2019-01-18,Four-wave mixing in spin-orbit coupled Bose-Einstein condensates,"We describe possibilities of spontaneous, degenerate four-wave mixing (FWM)
processes in spin-orbit coupled Bose-Einstein condensates. Phase matching
conditions (i.e., energy and momentum conservation laws) in such systems allow
one to identify four different configurations characterized by involvement of
distinct spinor states in which such a process can take place. We derived these
conditions from first principles and then illustrated dynamics with direct
numerical simulations. We found, among others, the unique configuration, where
both probe waves have smaller group velocity than pump wave and proved
numerically that it can be observed experimentally under proper choice of the
parameters. We also reported the case when two different FWM processes can
occur simultaneously. The described resonant interactions of matter waves is
expected to play important role in the experiments of BEC with artificial gauge
fields. Beams created by FWM processes are important source of correlated
particles and can be used the experiments testing quantum properties of atomic
ensembles.",1901.06173v3
2019-01-25,Gravitational Waves with Orbital Angular Momentum,"Compact orbiting binaries like the black hole binary system observed in
GW150914 carry large amount of orbital angular momentum. The post-ringdown
compact object formed after merger of such a binary configuration has only spin
angular momentum, and this results in a large orbital angular momentum excess.
One significant possibility is that the gravitational waves generated by the
system carry away this excess orbital angular momentum. An estimate of this
excess is made. Arguing that plane gravitational waves cannot possibly carry
any orbital angular momentum, a case is made in this paper for gravitational
wave beams carrying orbital angular momentum, akin to optical beams.
Restricting to certain specific beam-configurations, we predict that such beams
may produce a new type of strain, in addition to the longitudinal strains
measured at aLIGO for GW150914 and GW170817. Current constraints on
post-ringdown spins, derived within the planewave approximation of
gravitational waves, therefore stand to improve. The minimal modification that
might be needed on a laser-interferometer detector (like aLIGO or VIRGO) to
detect such additional strains is also briefly discussed.",1901.08804v3
2021-01-03,First searches for gravitational waves from r-modes of the Crab pulsar,"We present the first searches for gravitational waves from r-modes of the
Crab pulsar, coherently and separately integrating data from three stretches of
the first two observing runs of Advanced LIGO using the F-statistic. The second
run was divided in two by a glitch of the pulsar roughly halfway through. The
frequencies and derivatives searched were based on radio measurements of the
pulsar's spin-down parameters as described in Caride et al., Phys. Rev. D 100,
064013 (2019). We did not find any evidence of gravitational waves. Our best
90% confidence upper limits on gravitational wave intrinsic strain were 1.5e-25
for the first run, 1.3e-25 for the first stretch of the second run, and 1.1e-25
for the second stretch of the second run. These are the first upper limits on
gravitational waves from r-modes of a known pulsar to beat its spin-down limit,
and they do so by more than an order of magnitude in amplitude or two orders of
magnitude in luminosity.",2101.00714v1
2021-11-16,Learning from the Frequency Content of Continuous Gravitational Wave Signals,"Spinning neutron stars can emit long-lived gravitational waves. There are
several mechanisms that can produce such continuous wave emission. These
mechanisms relate to the strains in the elastic crust, the star's magnetic
field, superfluidity of the neutron fluid, and bulk oscillations of the entire
star. In this chapter we describe how the frequency content of the
gravitational wave signal, and its relation to any electromagnetically observed
spin frequency, can be used to constrain the mechanism producing the
gravitational waves. These ideas will be of use in the event of the first
detections of such signals, and help convert a detection into useful physical
insight.",2111.08561v1
2022-01-17,Giant Microwave Sensitivity of Magnetic Array by Long-Range Chiral Interaction Driven Skin Effect,"Non-Hermitian skin effect was observed in one-dimensional systems with
short-range chiral interaction. Long-range chiral interaction mediated by
traveling waves also favors the accumulation of energy, but has not yet showed
non-Hermitian topology. Here we find that the strong interference brought by
the wave propagation is detrimental for accumulation. By suppression of
interference via the damping of traveling waves, we predict the non-Hermitian
skin effect of magnetic excitation in a periodic array of magnetic nanowires
that are coupled chirally via spin waves of thin magnetic films. The local
excitation of a wire at one edge by weak microwaves of magnitude $\sim \mu{\rm
T}$ leads to a considerable spin-wave amplitude at the other edge, i.e. a
remarkable functionality useful for sensitive, non-local, and non-reciprocal
detection of microwaves.",2201.06189v1
2022-02-18,Phase-locking matter-wave interferometer of vortex states,"Matter-wave interferometer of ultracold atoms with different linear momenta
has been extensively studied in theory and experiment. The vortex matter-wave
interferometer with different angular momenta is applicable as a quantum sensor
for measuring the rotation, interatomic interaction, geometric phase, etc. Here
we report the first experimental realization of a vortex matter-wave
interferometer by coherently transferring the optical angular momentum to an
ultracold Bose condensate. After producing a lossless interferometer with atoms
only populating the two spin states, we demonstrate that the phase difference
between the interferences in the two spin states is locked on $\pi$. We also
demonstrate the robustness of this out-of-phase relation, which is independent
of the angular-momentum difference between the two interfering vortex states,
constituent of Raman optical fields and expansion of the condensate. The
experimental results agree well with the calculation from the unitary evolution
of wave packet in quantum mechanics. This work opens a new way to build a
quantum sensor and measure the atomic correlation in quantum gases.",2202.09001v1
2022-11-06,General-relativistic pilot-wave quantum mechanics with torsion,"We propose that the four-velocity of a Dirac particle is related to its
relativistic wave function by $u^i=\bar{\psi}\gamma^i\psi/\bar{\psi}\psi$. We
associate the four-momentum of a spinor with a generator of translation, given
by a covariant derivative. We associate the intrinsic angular momentum
four-tensor of a spinor with a generator of rotation in the spinor
representation of the Lorentz group. We use the covariant conservation laws for
the spin and energy$-$momentum tensors for a spinor field in the presence of
the Einstein$-$Cartan torsion to show that if the wave satisfies the Dirac
equation, then the four-velocity, four-momentum, and spin four-tensor satisfy
the classical Mathisson$-$Papapetrou equations of motion. We show that these
equations reduce to the geodesic equation of motion. Consequently, the motion
of a particle guided by the four-velocity in the pilot-wave quantum mechanics
coincides with the geodesic motion of the particle determined by the geometry
of spacetime, representing a relativistic wave$-$particle duality.",2211.03234v2
2023-01-23,Gravitational-wave tails of memory,"Gravitational-wave tails are linear waves that backscatter on the curvature
of space-time generated by the total mass-energy of the source. The non-linear
memory effect arises from gravitational waves sourced by the stress-energy
distribution of linear waves themselves. These two effects are due to quadratic
multipolar interactions (mass-quadrupole and quadrupole-quadrupole) and are
well known. Also known are the tails generated by tails themselves (cubic
""tails-of-tails"") and the tails generated by tails-of-tails or vice versa
(quartic ""tails-of-tails-of-tails""). In this work, we focus on the cubic
""tails-of-memory"" corresponding to the mass-quadrupole-quadrupole interaction,
as well as the ""spin-quadrupole tails"", which are due to the cubic interaction
between the mass, the total angular momentum and the quadrupole. The
tails-of-memory and the spin-quadrupole tails contribute to the asymptotic
waveform at the fourth-post-Newtonian (4PN) order beyond quadrupolar radiation.",2301.09395v2
2023-02-22,Advanced magnon-optic effects with spin-wave leaky modes,"We numerically demonstrate the excitation of leaky spin waves (SWs) guided
along a ferromagnetic stripe by an obliquely incident SW beam on the thin film
edge placed below the stripe. During propagation, leaky waves emit energy back
to the layer in the form of plane waves and several laterally shifted parallel
SW beams. This resonance excitation, combined with interference effects of the
reflected and re-emitted waves, results in the magnonic Woods anomaly and
significant increase of the Goos-Hanchen shift magnitude. Hence, we provide a
unique platform to control SW reflection and to transfer SWs from a 2D platform
into the 1D guiding mode that can be used to form a transdimensional magnonic
router.",2302.11507v3
2023-12-14,"Tripartite Phonon-Magnon-Plasmon Coupling, Parametric Amplification, and Formation of a Phonon-Magnon-Plasmon Polariton in a Two-Dimensional Periodic Array of Magnetostrictive/Plasmonic Bilayered Nanodots","Coupling between spin waves (SWs) and other types of waves in nanostructured
magnetic media has garnered increased attention in recent years because of the
rich physics and the potential to produce disruptive technologies. Among this
family of intriguing phenomena, we recently reported a new one: coupling
between SWs and hybridized phonon-plasmon waves, resulting in tripartite
coupling of magnons, phonons, and plasmons. Here, this acousto-plasmo-magnonic
phenomenon is studied in a two-dimensional periodic array of bilayered [Co/Al]
nanodots on a silicon substrate, where the Co is a magnetostrictive constituent
responsive to magneto-elastic coupling and the Al acts as a source of surface
plasmons. Time-resolved magneto-optical-Kerr-effect microscopy revealed
parametric amplification and strong coupling between two spin wave modes
mediated by a hybrid phonon-plasmon wave. The strong coupling forms a new
quasi-particle: the phonon-plasmonmagnon polariton.",2312.09343v1
2017-07-26,Fermi wave vector for the non-fully spin polarized composite-fermion Fermi sea,"The fully spin polarized composite fermion (CF) Fermi sea at half filled
lowest Landau level has a Fermi wave vector $k^*_{\rm F}=\sqrt{4\pi\rho_e}$,
where $\rho_e$ is the density of electrons or composite fermions, supporting
the notion that the interaction between composite fermions can be treated
perturbatively. Away from $\nu=1/2$, the area is seen to be consistent with
$k^*_{\rm F}=\sqrt{4\pi\rho_e}$ for $\nu<1/2$ but $k^*_{\rm
F}=\sqrt{4\pi\rho_h}$ for $\nu>1/2$, where $\rho_h$ is the density of holes in
the lowest Landau level. This result is consistent with particle-hole symmetry
in the lowest Landau level. We investigate in this article the Fermi wave
vector of the spin-singlet CF Fermi sea (CFFS) at $\nu=1/2$, for which
particle-hole symmetry is not a consideration. Using the microscopic CF theory,
we find that for the spin-singlet CFFS the Fermi wave vectors for up and down
spin CFFSs at $\nu=1/2$ are consistent with $k^{*\uparrow,\downarrow}_{\rm
F}=\sqrt{4\pi\rho^{\uparrow,\downarrow}_e}$, where
$\rho^{\uparrow}_e=\rho^{\downarrow}_e=\rho_e/2$, which implies that the
residual interactions between composite fermions do not cause a
non-perturbative correction for non-fully spin polarized CFFS either. Our
results suggest the natural conjecture that for arbitrary spin polarization the
CF Fermi wave vectors are given by $k^{*\uparrow}_{\rm
F}=\sqrt{4\pi\rho^{\uparrow}_e}$ and $k^{*\downarrow}_{\rm
F}=\sqrt{4\pi\rho^{\downarrow}_e}$.",1707.08623v3
2020-08-05,Orbital-selective spin waves in detwinned NaFeAs,"The existence of orbital-dependent electronic correlations has been
recognized as an essential ingredient to describe the physics of iron-based
superconductors. NaFeAs, a parent compound of iron based superconductors,
exhibits a tetragonal-to-orthorhombic lattice distortion below $T_s\approx 60$
K, forming an electronic nematic phase with two 90$^\circ$ rotated (twinned)
domains, and orders antiferromagnetically below $T_N\approx 42$ K. We use
inelastic neutron scattering to study spin waves in uniaxial pressure-detwinned
NaFeAs. By comparing the data with combined density functional theory and
dynamical mean-field theory calculations, we conclude that spin waves up to an
energy scale of $E_\text{crossover} \approx 100$ meV are dominated by
$d_{yz}$-$d_{yz}$ intra-orbital scattering processes, which have the two-fold
($C_2$) rotational symmetry of the underlying lattice. On the other hand, the
spin wave excitations above $E_\text{crossover}$, which have approximately
fourfold ($C_4$) rotational symmetry, arise from the $d_{xy}$-$d_{xy}$
intra-orbital scattering that controls the overall magnetic bandwidth in this
material. In addition, we find that the low-energy ($E\approx 6$ meV) spin
excitations change from approximate $C_4$ to $C_2$ rotational symmetry below a
temperature $T^\ast$ ($>T_s$), while spin excitations at energies above
$E_\text{crossover}$ have approximate $C_4$ rotational symmetry and are weakly
temperature dependent. These results are consistent with angle resolved
photoemission spectroscopy measurements, where the presence of an uniaxial
strain necessary to detwin NaFeAs also raises the onset temperature $T^\ast$ of
observable orbital-dependent band splitting to above $T_s$, thus supporting the
notion of orbital selective spin waves in the nematic phase of iron-based
superconductors.",2008.02314v1
2023-03-01,Rotor/spin-wave theory for quantum spin models with U(1) symmetry,"The static and dynamics properties of finite-size lattice quantum spin models
which spontaneously break a continuous $U(1)$ symmetry in the thermodynamic
limit are of central importance for a wide variety of physical systems, from
condensed matter to quantum simulation. Such systems are characterized by a
Goldstone excitation branch, terminating in a zero mode whose theoretical
treatment within a linearized approach leads to divergencies on finite-size
systems, revealing that the assumption of symmetry breaking is ill-defined away
from the thermodynamic limit. In this work we show that, once all its
non-linearities are taken into account, the zero mode corresponds exactly to a
U(1) quantum rotor, related to the Anderson tower of states expected in systems
showing symmetry breaking in the thermodynamic limit. The finite-momentum
modes, when weakly populated, can be instead safely linearized (namely treated
within spin-wave theory) and effectively decoupled from the zero mode. This
picture leads to an approximate separation of variables between rotor and
spin-wave ones, which allows for a correct description of the ground-state and
low-energy physics. Most importantly, it offers a quantitative treatment of the
finite-size non-equilibrium dynamics -- following a quantum quench -- dominated
by the zero mode, for which a linearized approach fails. Focusing on the 2$d$
XX model with power-law decaying interactions, we compare our equilibrium
predictions with unbiased quantum Monte Carlo results and exact
diagonalization; and our non-equilibrium results with time-dependent
variational Monte Carlo. The agreement is remarkable for all interaction
ranges, and it improves the longer the range. Our rotor/spin-wave theory
defines a successful strategy for the application of spin-wave theory and its
extensions to finite-size systems at equilibrium or away from it.",2303.00380v2
2014-05-26,Implementing a search for aligned-spin neutron star -- black hole systems with advanced ground based gravitational wave detectors,"We study the effect of spins on searches for gravitational waves from compact
binary coalescences in realistic simulated early advanced LIGO data. We
construct a detection pipeline including matched filtering, signal-based
vetoes, a coincidence test between different detectors, and an estimate of the
rate of background events. We restrict attention to neutron star--black hole
(NS-BH) binary systems, and we compare a search using non-spinning templates to
one using templates that include spins aligned with the orbital angular
momentum. To run the searches we implement the binary inspiral matched-filter
computation in PyCBC, a new software toolkit for gravitational-wave data
analysis. We find that the inclusion of aligned-spin effects significantly
increases the astrophysical reach of the search. Considering astrophysical
NS-BH systems with non-precessing black hole spins, for dimensionless spin
components along the orbital angular momentum uniformly distributed in $(-1,
1)$, the sensitive volume of the search with aligned-spin templates is
increased by $\sim 50\%$ compared to the non-spinning search; for signals with
aligned spins uniformly distributed in the range $(0.7,1)$, the increase in
sensitive volume is a factor of $\sim 10$.",1405.6731v3
2018-01-30,Observing and measuring the neutron-star equation-of-state in spinning binary neutron star systems,"LIGO and Virgo recently observed the first binary neutron star merger,
demonstrating that gravitational-waves offer the ability to probe how matter
behaves in one of the most extreme environments in the Universe. However, the
gravitational-wave signal emitted by an inspiraling binary neutron star system
is only weakly dependent on the equation of state and extracting this
information is challenging. Previous studies have focused mainly on binary
systems where the neutron stars are spinning slowly and the main imprint of
neutron star matter in the inspiral signal is due to tidal effects. For
binaries with non-negligible neutron-star spin the deformation of the neutron
star due to its own rotation introduces additional variations in the emitted
gravitational-wave signal. Here we explore whether highly spinning binary
neutron-star systems offer a better chance to measure the equation-of-state
than weakly spinning binary-neutron star systems. We focus on the dominant
adiabatic quadrupolar effects and consider three main questions. First, we show
that equation-of-state effects can be significant in the inspiral waveforms,
and that the spin-quadrupole effect dominates for rapidly rotating neutron
stars. Second, we show that variations in the spin-quadrupole phasing are
strongly degenerate with changes in the component masses and spins, and
neglecting these terms has a negligible impact on the number of observations
with second generation observatories. Finally, we explore the bias in the
masses and spins that would be introduced by using incorrect equation-of-state
terms. Using a novel method to rapidly evaluate an approximation of the
likelihood we show that assuming the incorrect equation-of-state when measuring
source parameters can lead to a significant bias. We also find that the ability
to measure the equation-of-state is improved when considering spinning systems.",1801.09972v1
2022-05-05,Parity Violation in Spin-Precessing Binaries: Gravitational Waves from the Inspiral of Black Holes in Dynamical Chern-Simons Gravity,"Spin precession in compact binaries is intricately tuned to the multipole
structure of the underlying bodies. For black holes, violations of the no-hair
theorems induced by modifications to general relativity correct the precession
dynamics, which in turn imprints onto the amplitude and phase modulations of
the gravitational waves emitted by the binary. Recently, the spin precession
equations were derived up to second order in spin for dynamical Chern-Simons
gravity, a parity violating modified theory of gravity. We here solve these
equations and construct, for the first time, analytic expressions for the time-
and frequency-domain gravitational waves emitted in the quasi-circular inspiral
of spin-precessing black hole binaries in a modified theory of gravity using
the post-Newtonian approximation. Working within the small coupling
approximation and using multiple scale analysis, we show that the corrections
to the nutation phase enter at relative 1PN order, and the corrections to the
precession angle and Thomas phase enter at relative 0PN order. Making use of
the stationary phase approximation and shifted uniform asymptotics, we find
that the Fourier phase of the waveform is characterized by three modifications,
two due to the back-reaction of the precession dynamics onto the spin-orbit and
spin-spin couplings that enter at 1.5PN and 2PN orders, and a 2PN modification
due to the emission of dipole radiation. We also find that back-reaction of the
precession dynamics forces the dCS corrections to the Fourier amplitude to
enter at 0PN order, as opposed to 2PN order, as expected for spin-aligned
binaries. Our work lays the first foundational stones to build an
inspiral-merger-ringdown phenomenological model for spin-precessing binaries in
a modified theory of gravity.",2205.02675v2
2022-06-11,Field evolution of magnetic phases and spin dynamics in the honeycomb lattice magnet Na2Co2TeO6: 23Na NMR study,"We report on the results of 23Na NMR in the honeycomb lattice magnet
Na2Co2TeO6 which has been nominated as a Kitaev material. Measurements of
magnetic shift and width of the NMR line as functions of temperature and
magnetic field show that a spin-disordered phase does not appear up to a field
of 9 T. In the antiferromagnetic phase just below the Neel temperature TN, we
find a temperature region extending down to ~TN/2 where the nuclear
spin-lattice relaxation rate 1/T1 remains enhanced and is further increased by
a magnetic field. This region crosses over to a low temperature region
characterized by the rapidly decreasing 1/T1 which is less field-sensitive.
These observations suggest incoherent spin excitations with a large spectral
weight at low energies in the intermediate temperature region transforming to
more conventional spin-wave excitations at low temperatures. The drastic change
of the low-energy spin dynamics is likely caused by strong damping of spin
waves activated only in the intermediate temperature region, which may be
realized for triple-q magnetic order possessing partially-disordered moments as
scattering centers of spin waves. In the paramagnetic phase near TN, dramatic
field suppression of 1/T1 is observed. From analysis of the temperature
dependence of 1/T1 based on the renormalized-classical description of a
two-dimensional quantum antiferromagnet, we find the field-dependent spin
stiffness constant that scales with TN as a function of magnetic field. This
implies field suppression of the energy scale characterizing both
two-dimensional spin correlations and three-dimensional long-range order, which
may be associated with an increasing effect of frustration in magnetic fields.",2206.05409v3
2003-04-02,LISA observations of rapidly spinning massive black hole binary systems,"Binary systems of massive black holes will be detectable by the Laser
Interferometer Space Antenna (LISA) throughout the entire Universe.
Observations of gravitational waves from this class of sources will have
important repercussions on our understanding of the behaviour of gravity in the
highly non-linear relativistic regime, the distribution and interaction of
massive black holes at high redshift and the formation and evolution of cosmic
structures. It is therefore important to address how accurately LISA can
measure the source parameters and explore the implications for astronomy and
cosmology. Present observations and theoretical models suggest that massive
black holes could be spinning, possibly rapidly in some cases. In binary
systems, the relativistic spin-orbit interaction causes the orbital plane to
precess in space producing a characteristic signature on the emitted
gravitational waves. In this paper we investigate the effect of spins on the
gravitational wave signal registered at the LISA output and the implications
for parameter estimation. We consider the in-spiral phase of binary systems in
circular orbit undergoing the so-called ""simple precession"" and we approximate
the gravitational radiation at the restricted 1.5PN order. We show that the
presence of spins changes dramatically the signature of the signal recorded by
LISA. As a consequence, the mean square errors associated to the parameter
measurements are significantly smaller than the ones obtained when the effect
of spins is neglected. For a binary system of two $10^6 \Ms$ black holes, the
angular resolution and the relative error on the luminosity distance improve by
a factor $\approx$ 3-to-10; the fractional errors on the chirp mass and the
reduced mass decrease by a factor $\sim 10$ and $\sim 10^3$, respectively.",0304051v1
2001-02-13,From the Square Lattice to the Checkerboard Lattice : Spin Wave and Large-n Analysis,"Within a spin wave analysis and a fermionic large-n limit, it is shown that
the antiferromagnetic Heisenberg model on the checkerboard lattice may have
different ground states, depending on the spin size $S$. Through an additional
exchange interaction that corresponds to an inter-tetrahedra coupling, the
stability of the N\'eel state has been explored for all cases from the square
lattice to the isotropic checkerboard lattice. Away from the isotropic limit
and within the linear spin wave approximation, it is shown that there exists a
critical coupling for which the local magnetization of the N\'eel state
vanishes for any value of the spin $S$. One the other hand, using the
Dyson-Maleev approximation, this result is valid only in the case $S= \frac12$
and the limit between a stable and an unstable N\'eel state is at S=1. For $S=
\frac12$, the fermionic large-n limit suggests that the ground state is a
valence bond solid build with disconnected 4-spins singlets. This analysis
indicates that for low spin and in the isotropic limit, the checkerboard
antiferromagnet may be close to an instability between an ordered S=0 ground
state and a magnetized ground state.",0102233v4
2003-07-01,Observation of extended scattering continua characteristic of spin fractionalization in the 2D frustrated quantum magnet Cs2CuCl4 by neutron scattering,"The magnetic excitations of the quasi-2D spin-1/2 Heisenberg antiferromagnet
on an anisotropic triangular lattice Cs2CuCl4 are explored throughout the 2D
Brillouin zone using inelastic neutron scattering. In the spin liquid phase
above the transition to magnetic order extended excitation continua are
observed, characteristic of fractionalization of S=1 spin waves into pairs of
deconfined S=1/2 spinons and the hallmark of a resonating-valence-bond (RVB)
state. The weak inter-layer couplings stabilize incommensurate spiral order at
low temperatures and in this phase sharp magnons carrying a small part of the
total scattering weight are observed at low energies below the continuum lower
boundary. Linear spin-wave theory including one- and two-magnon processes can
describe the sharp magnon excitation, but not the dominant continuum
scattering, which instead is well described by a parameterized two-spinon
cross-section. Those results suggest a cross-over in the nature of excitations
from S=1 spin waves at low energies to S=1/2 spinons at medium to high
energies, which could be understood if Cs2CuCl4 was in the close proximity of a
transition between a fractional spin liquid and a magnetically-ordered phase.",0307025v1
2005-06-14,"Orbital order, anisotropic spin couplings, and the spin-wave spectrum of the ferromagnetic Mott insulator YTiO3","Using a point-charge calculation of the electrostatic crystal field, we
determine the non-degenerate orbital ground state of the ferromagnetic Mott
insulator YTiO3, which is found to agree perfectly with experiment. Based on
the orbital order, we obtain by perturbation theory an effective spin
Hamiltonian that describes the magnetic superexchange between nearest-neighbor
Ti ions. The superexchange Hamiltonian includes, in addition to the isotropic
Heisenberg coupling, antisymmetric (Dzyaloshinskii-Moriya) and symmetric
anisotropy terms, caused by the spin-orbit interaction on the Ti ions. We find
ferromagnetic Heisenberg couplings for Ti-Ti bonds in the crystallographic ab
planes, but antiferromagnetic ones for Ti-Ti bonds between planes, in
contradiction with experiment (which gives ferromagnetic couplings for both).
Difficulties in calculating realistic values for the isotropic couplings of
YTiO3 have been already reported in the literature. We discuss possible origins
for these discrepancies. However, the much smaller values we obtain for the
symmetric and antisymmetric anisotropies may be expected to be reliable. We
therefore combine the experimentally-deduced isotropic coupling with the
calculated anisotropic ones to determine the magnetic order of the Ti ions,
which is found to be in satisfactory agreement with experiment. Based on this
magnetic order, we derive the spin-wave spectrum. We find an acoustic branch
with a very small zone-center gap and three optical spin-wave modes with
sizeable zone-center gaps. The acoustic branch reproduces the one reported in
experiment, and the optical ones are in a satisfactory agreement with
experiment, upon a proper folding of the magnetic Brillouin zone.",0506328v1
2007-04-09,Excitation Spectrum Gap and Spin-Wave Stiffness of XXZ Heisenberg Chains: Global Renormalization-Group Calculation,"The anisotropic XXZ spin-1/2 Heisenberg chain is studied using
renormalization-group theory. The specific heats and nearest-neighbor spin-spin
correlations are calculated thoughout the entire temperature and anisotropy
ranges in both ferromagnetic and antiferromagnetic regions, obtaining a global
description and quantitative results. We obtain, for all anisotropies, the
antiferromagnetic spin-liquid spin-wave velocity and the Isinglike
ferromagnetic excitation spectrum gap, exhibiting the spin-wave to spinon
crossover. A number of characteristics of purely quantum nature are found: The
in-plane interaction s_i^x s_j^x + s_i^y s_j^y induces an antiferromagnetic
correlation in the out-of-plane s_i^z component, at higher temperatures in the
antiferromagnetic XXZ chain, dominantly at low temperatures in the
ferromagnetic XXZ chain, and, in-between, at all temperatures in the XY chain.
We find that the converse effect also occurs in the antiferromagnetic XXZ
chain: an antiferromagnetic s_i^z s_j^z interaction induces a correlation in
the s_i^xy component. As another purely quantum effect, (i) in the
antiferromagnet, the value of the specific heat peak is insensitive to
anisotropy and the temperature of the specific heat peak decreases from the
isotropic (Heisenberg) with introduction of either type (Ising or XY)
anisotropy; (ii) in complete contrast, in the ferromagnet, the value and
temperature of the specific heat peak increase with either type of anisotropy.",0704.1064v2
2007-04-09,Spin Dynamics Of $qqq$ Wave Function On Light Front In High Momentum Limit Of QCD : Role Of $qqq$ Force,"The contribution of a spin-rich $qqq$ force (in conjunction with pairwise
$qq$ forces) to the analytical structure of the $qqq$ wave function is worked
out in the high momentum regime of QCD where the confining interaction may be
ignored, so that the dominant effect is $Coulombic$. A distinctive feature of
this study is that the spin-rich $qqq$ force is generated by a $ggg$ vertex (a
genuine part of the QCD Lagrangian) wherein the 3 radiating gluon lines end on
as many quark lines, giving rise to a (Mercedes-Benz type) $Y$-shaped diagram.
The dynamics is that of a Salpeter-like equation (3D support for the kernel)
formulated covariantly on the light front, a la Markov-Yukawa Transversality
Principle (MYTP) which warrants a 2-way interconnection between the 3D and 4D
Bethe-Salpeter (BSE) forms for 2 as well as 3 fermion quarks. With these
ingredients, the differential equation for the 3D wave function $\phi$ receives
well-defined contributions from the $qq$ and $qqq$ forces. In particular a
$negative$ eigenvalue of the spin operator $i \sigma_1.\sigma_2\times \sigma_3$
which is an integral part of the $qqq$ force, causes a characteristic
singularity in the differential equation, signalling the dynamical effect of a
spin-rich $qqq$ force not yet considered in the literature. The potentially
crucial role of this interesting effect vis-a-vis the so-called `spin anomaly'
of the proton, is a subject of considerable physical interest.",0704.1103v1
2012-10-30,Mode- and size-dependent Landau-Lifshitz damping in magnetic nanostructures: Evidence for non-local damping,"We demonstrate a strong dependence of the effective damping on the nanomagnet
size and the particular spin-wave mode that can be explained by the theory of
intralayer transverse-spin-pumping. The effective Landau-Lifshitz damping is
measured optically in individual, isolated nanomagnets as small as 100 nm. The
measurements are accomplished by use of a novel heterodyne magneto-optical
microwave microscope with unprecedented sensitivity. Experimental data reveal
multiple standing spin-wave modes that we identify by use of micromagnetic
modeling as having either localized or delocalized character, described
generically as end- and center-modes. The damping parameter of the two modes
depends on both the size of the nanomagnet as well as the particular spin-wave
mode that is excited, with values that are enhanced by as much as 40% relative
to that measured for an extended film. Contrary to expectations based on the ad
hoc consideration of lithography-induced edge damage, the damping for the
end-mode decreases as the size of the nanomagnet decreases. The data agree with
the theory for damping caused by the flow of intralayer transverse
spin-currents driven by the magnetization curvature. These results have serious
implications for the performance of nanoscale spintronic devices such as
spin-torque-transfer magnetic random access memory.",1210.8118v3
2014-04-14,"Chiral spin density wave, spin-charge-Chern liquid and d+id superconductivity in 1/4-doped correlated electronic systems on the honeycomb lattice","Recently two interesting candidate quantum phases --- the chiral spin density
wave state featuring anomalous quantum Hall effect and the d+id superconductor
--- were proposed for the Hubbard model on the honeycomb lattice at 1/4 doping.
Using a combination of exact diagonalization, density matrix renormalization
group, the variational Monte Carlo method and quantum field theories, we study
the quantum phase diagrams of both the Hubbard model and t-J model on the
honeycomb lattice at 1/4-doping. The main advantage of our approach is the use
of symmetry quantum numbers of ground state wavefunctions on finite size
systems (up to 32 sites) to sharply distinguish different quantum phases. Our
results show that for $1\lesssim U/t< 40$ in the Hubbard model and for $0.1<
J/t<0.80(2)$ in the t-J model, the quantum ground state is either a chiral spin
density wave state or a spin-charge-Chern liquid, but not a d+id
superconductor. However, in the t-J model, upon increasing $J$ the system goes
through a first-order phase transition at $J/t=0.80(2)$ into the d+id
superconductor. Here the spin-charge-Chern liquid state is a new type of
topologically ordered quantum phase with Abelian anyons and fractionalized
excitations. Experimental signatures of these quantum phases, such as tunneling
conductance, are calculated. These results are discussed in the context of
1/4-doped graphene systems and other correlated electronic materials on the
honeycomb lattice.",1404.3452v3
2015-05-12,Superconducting phase diagram of itinerant antiferromagnets,"We study the phase diagram of the Hubbard model in the weak-coupling limit
for coexisting spin-density-wave order and spin-fluctuation-mediated
superconductivity. Both longitudinal and transverse spin fluctuations
contribute significantly to the effective interaction potential, which creates
Cooper pairs of the quasi-particles of the antiferromagnetic metallic state. We
find a dominant $d_{x^2-y^2}$-wave solution in both electron- and hole-doped
cases. In the quasi-spin triplet channel, the longitudinal fluctuations give
rise to an effective attraction supporting a $p$-wave gap, but are overcome by
repulsive contributions from the transverse fluctuations which disfavor
$p$-wave pairing compared to $d_{x^2-y^2}$. The sub-leading pair instability is
found to be in the $g$-wave channel, but complex admixtures of $d$ and $g$ are
not energetically favored since their nodal structures coincide. Inclusion of
interband pairing, in which each fermion in the Cooper pair belongs to a
different spin-density-wave band, is considered for a range of electron dopings
in the regime of well-developed magnetic order. We demonstrate that these
interband pairing gaps, which are non-zero in the magnetic state, must have the
same parity under inversion as the normal intraband gaps. The self-consistent
solution to the full system of five coupled gap equations give intraband and
interband pairing gaps of $d_{x^2-y^2}$ structure and similar gap magnitude. In
conclusion, the $d_{x^2-y^2}$ gap dominates for both hole and electron doping
inside the spin-density-wave phase.",1505.03003v2
2016-07-12,Thermodynamic transport theory of spin waves in ferromagnetic insulators,"We use the Boltzmann transport theory in the relaxation time approximation to
describe the thermal transport of spin waves in a ferromagnet. By treating spin
waves as magnon excitations we are able to compute analytically and numerically
the coefficients of the constitutive thermo-magnetic transport equations. As a
main result, we find that the absolute thermo-magnetic power coefficient
$\epsilon_M$, relating the gradient of the potential of the magnetization
current and the gradient of the temperature, in the limit of low temperature
and low field, is a constant $\epsilon_M = -0.6419 \, k_B/\mu_B$. The theory
correctly describes the low-temperature and magnetic-field dependencies of spin
Seebeck experiments. Furthermore, the theory predicts that in the limit of very
low temperatures the spin Peltier coefficient $\Pi_M$, relating the heat and
the magnetization currents, tends to a finite value which depends on the
amplitude of the magnetic field. This indicates the possibility to exploit the
spin Peltier effect as an efficient cooling mechanism in cryogenics.",1607.03301v3
2016-07-20,Electron dynamics in graphene with spin-orbit couplings and periodic potentials,"We use both continuum and lattice models to study the energy-momentum
dispersion and the dynamics of a wave packet for an electron moving in graphene
in the presence of spin-orbit couplings and either a single potential barrier
or a periodic array of potential barriers. Both Kane-Mele and Rashba spin-orbit
couplings are considered. A number of special things occur when the Kane-Mele
and Rashba couplings are equal in magnitude. In the absence of a potential, the
dispersion then consists of both massless Dirac and massive Dirac states. A
periodic potential is known to generate additional Dirac points; we show that
spin-orbit couplings generally open gaps at all those points, but if the two
spin-orbit couplings are equal, some of the Dirac points remain gapless. We
show that the massless and massive states respond differently to a potential
barrier; the massless states transmit perfectly through the barrier at normal
incidence while the massive states reflect from it. In the presence of a single
potential barrier, we show that there are states localized along the barrier.
Finally, we study the time evolution of a wave packet in the presence of a
periodic potential. We discover special points in momentum space where there is
almost no spreading of a wave packet; there are six such points in graphene
when the spin-orbit couplings are absent.",1607.05904v2
2016-08-20,"Hybrid excitations due to crystal-field, spin-orbit coupling and spin-waves in LiFePO$_4$","We report on the spin waves and crystal field excitations in single crystal
LiFePO$_4$ by inelastic neutron scattering over a wide range of temperatures,
below and above the antiferromagnetic transition of this system. In particular,
we find extra excitations below $T_N=50$ K that are nearly dispersionless and
are most intense around magnetic zone centers. We show that these excitations
correspond to transitions between thermally occupied excited states of
Fe$^{2+}$ due to splitting of the $S=2$ levels that arise from crystal field
and spin-orbit interaction. These excitations are further amplified by the
highly distorted nature of the oxygen octahedron surrounding the iron atoms.
Above $T_N$, magnetic fluctuations are observed up to at least 720~K, with
additional excitation around 4 meV, likely caused by single-ion splittings
through spin-orbit and crystal field interactions. The latter weakens slightly
at 720~K compared to 100~K, which is consistent with calculated cross-sections
using a single-ion model. Our theoretical analysis, using the MF-RPA model,
provides both detailed spectra of the Fe $d-$ shell and estimates of the
average ordered magnetic moment and $T_N$. By applying the MF-RPA model to a
number of existing spin-wave results from other Li$M$PO$_4$ ($M=$ Mn, Co, and
Ni), we are able to obtain reasonable predictions for the moment sizes and
transition temperatures.",1608.05761v1
2016-09-27,Identical Spin Rotation Effect and Electron Spin Waves in Quantum Gas of Atomic Hydrogen,"We present an experimental study of electron spin waves in atomic hydrogen
gas compressed to high densities of $\sim 5 \times 10^{18}$ cm$^{-3}$ at
temperatures ranging from 0.26 to 0.6 K in strong magnetic field of 4.6 T.
Hydrogen gas is in a quantum regime when the thermal de Broglie wavelength is
much larger than the s-wave scattering length. In this regime the identical
particle effects play major role in atomic collisions and lead to the Identical
Spin Rotation effect (ISR). We observed a variety of spin wave modes caused by
this effect with strong dependence on the magnetic potential caused by
variations of the polarizing magnetic field. We demonstrate confinement of the
ISR modes in the magnetic potential and manipulate their properties by changing
the spatial profile of magnetic field. We have found that at a high enough
density of H gas the magnons accumulate in their ground state in the magnetic
trap and exhibit long coherence, which has a profound effect on the electron
spin resonance spectra. Such macroscopic accumulation of the ground state
occurs at a certain critical density of hydrogen gas, where the chemical
potential of the magnons becomes equal to the energy of their ground state in
the trapping potential.",1609.08432v2
2018-09-17,Injection locking of multiple auto-oscillation modes in a tapered nanowire spin Hall oscillator,"Spin Hall oscillators (SHO) are promising candidates for the generation,
detection and amplification of high frequency signals, that are tunable through
a wide range of operating frequencies. They offer to be read out electrically,
magnetically and optically in combination with a simple bilayer design. Here,
we experimentally study the spatial dependence and spectral properties of
auto-oscillations in SHO devices based on Pt(7 nm)/\
Ni$_{\mathrm{80}}$Fe$_{\mathrm{20}}$(5 nm) tapered nanowires. Using Brillouin
light scattering microscopy, we observe two individual self-localized spin-wave
bullets that oscillate at two distinct frequencies (5.2 GHz and 5.45 GHz) and
are localized at different positions separated by about 750 nm within the SHO.
This state of a tapered SHO has been predicted by a Ginzburg-Landau
auto-oscillator model, but not yet been directly confirmed experimentally. We
demonstrate that the observed bullets can be individually synchronized to
external microwave signals, leading to a frequency entrainment, linewidth
reduction and increase in oscillation amplitude for the bullet that is selected
by the microwave frequency. At the same time, the amplitude of other parasitic
modes decreases, which promotes the single-mode operation of the SHO. Finally,
the synchronization of the spin-wave bullets is studied as a function of the
microwave power. We believe that our findings promote the realization of
extended spin Hall oscillators accomodating several distinct spin-wave bullets,
that jointly cover an extended range of tunability.",1809.06291v1
2018-10-16,Spin-wave-induced lateral temperature gradient in a YIG thin film/GGG system excited in an ESR cavity,"Lateral thermal gradient of an yttrium iron garnet (YIG) film under the
microwave application in the cavity of the electron spin resonance system (ESR)
was measured at room temperature by fabricating a Cu/Sb thermocouple onto it.
To date, thermal transport in YIG films caused by the Damon-Eshbach mode (DEM)
- the unidirectional spin-wave heat conveyer effect - was demonstrated only by
the excitation using coplanar waveguides. Here we show that effect exists even
under YIG excitation using the ESR cavity - tool often employed to realize spin
pumping. The temperature difference observed around the ferromagnetic resonance
(FMR) field under the 4 mW microwave power peaked at 13 mK. The observed
thermoelectric signal indicates the imbalance of the population between the
DEMs that propagate near the top and bottom surfaces of the YIG film. We
attribute the DEM population imbalance to the different magnetic damping near
the top and bottom YIG surfaces. Additionally, the spin wave dynamics of the
system were investigated using the micromagnetic simulations. The micromagnetic
simulations confirmed the existence of the DEM imbalance in the system with the
increased Gilbert damping at one of the YIG interfaces. The reported results
are indispensable for the quantitative estimation of the electromotive force in
the spin-charge conversion experiments using ESR cavities.",1810.06875v1
2020-11-08,Gravitational Waves from Disks Around Spinning Black Holes: Simulations in Full General Relativity,"We present fully general-relativistic numerical evolutions of
self-gravitating tori around spinning black holes with dimensionless spin $a/M
= 0.7$ parallel or anti-parallel to the disk angular momentum. The initial
disks are unstable to the hydrodynamic Papaloizou-Pringle Instability which
causes them to grow persistent orbiting matter clumps. The effect of black hole
spin on the growth and saturation of the instability is assessed. We find that
the instability behaves similarly to prior simulations with non-spinning black
holes, with a shift in frequency due to spin-induced changes in disk orbital
period. Copious gravitational waves are generated by these systems, and we
analyze their detectability by current and future gravitational wave
observatories for large range of masses. We find that systems of $10 M_\odot$ -
relevant for black hole-neutron star mergers - are detectable by Cosmic
Explorer out to $\sim300$ Mpc, while DECIGO (LISA) will be able to detect
systems of $1000 M_\odot$ ($10^5M_\odot$) - relevant for disks forming in
collapsing supermassive stars - out to cosmological redshift of $z\sim5$
($z\sim 1$). Computing the accretion rate of these systems we find that these
systems may also be promising sources of coincident electromagnetic signals.",2011.04077v1
2021-02-16,Spin Wave Based Full Adder,"Spin Waves (SWs) propagate through magnetic waveguides and interfere with
each other without consuming noticeable energy, which opens the road to new
ultra-low energy circuit designs. In this paper we build upon SW features and
propose a novel energy efficient Full Adder (FA) design consisting of The FA 1
Majority and 2 XOR gates, which outputs Sum and Carry-out are generated by
means of threshold and phase detection, respectively. We validate our proposal
by means of MuMax3 micromagnetic simulations and we evaluate and compare its
performance with state-of-the-art SW, 22nm CMOS, Magnetic Tunnel Junction
(MTJ), Spin Hall Effect (SHE), Domain Wall Motion (DWM), and Spin-CMOS
implementations. Our evaluation indicates that the proposed SW FA consumes
22.5% and 43% less energy than the direct SW gate based and 22nm CMOS
counterparts, respectively. Moreover it exhibits a more than 3 orders of
magnitude smaller energy consumption when compared with state-of-the-art MTJ,
SHE, DWM, and Spin-CMOS based FAs, and outperforms its contenders in terms of
area by requiring at least 22% less chip real-estate.",2102.08108v3
2016-12-30,High-temperature charge density wave correlations in La$_{1.875}$Ba$_{0.125}$CuO$_{4}$ without spin-charge locking,"Although all superconducting cuprates display charge-ordering tendencies,
their low-temperature properties are distinct, impeding efforts to understand
the phenomena within a single conceptual framework. While some systems exhibit
stripes of charge and spin, with a locked periodicity, others host charge
density waves (CDWs) without any obviously related spin order. Here we use
resonant inelastic x-ray scattering (RIXS) to follow the evolution of charge
correlations in the canonical stripe ordered cuprate
La$_{1.875}$Ba$_{0.125}$CuO$_{4}$ (LBCO~$1/8$) across its ordering transition.
We find that high-temperature charge correlations are unlocked from the
wavevector of the spin correlations, signaling analogies to CDW phases in
various other cuprates. This indicates that stripe order at low temperatures is
stabilized by the coupling of otherwise independent charge and spin density
waves, with important implications for the relation between charge and spin
correlations in the cuprates.",1701.00022v5
2021-07-07,Locking of skyrmion cores on a centrosymmetric discrete lattice: onsite versus offsite,"A magnetic skyrmion crystal (SkX) with a swirling spin configuration, which
is one of topological spin crystals as a consequence of an interference between
multiple spin density waves, shows a variety of noncoplanar spin patterns
depending on a way of superposing the waves. By focusing on a phase degree of
freedom among the constituent waves in the SkX, we theoretically investigate a
position of the skyrmion core on a discrete lattice, which is relevant with the
symmetry of the SkX. The results are obtained for the double exchange
(classical Kondo lattice) model on a discrete triangular lattice by the
variational calculations. We find that the skyrmion cores in both two SkXs with
the skyrmion number of one and two are locked at the interstitial site on the
triangular lattice, while it is located at the onsite by introducing a
relatively large easy-axis single-ion anisotropy. The variational parameters
and the resultant Fermi surfaces in each SkX spin texture are also discussed.
The different symmetry of the Fermi surfaces depending on the core position is
obtained when the skyrmion crystal is commensurate with the lattice. The
different Fermi-surface topology is directly distinguished by an electric probe
of angle-resolved photoemission spectroscopy. Furthermore, we show that the
SkXs obtained by the variational calculations are also confirmed by numerical
simulations on the basis of the kernel polynomial method and the Langevin
dynamics for the double exchange model and the simulated annealing for an
effective spin model.",2107.03500v2
2021-12-11,Anisotropic long-range spin transport in canted antiferromagnetic orthoferrite YFeO$_3$,"In antiferromagnets, the efficient propagation of spin-waves has until now
only been observed in the insulating antiferromagnet hematite, where circularly
(or a superposition of pairs of linearly) polarized spin-waves propagate over
long distances. Here, we report long-distance spin-transport in the
antiferromagnetic orthoferrite YFeO$_3$, where a different transport mechanism
is enabled by the combined presence of the Dzyaloshinskii-Moriya interaction
and externally applied fields. The magnon decay length is shown to exceed
hundreds of nano-meters, in line with resonance measurements that highlight the
low magnetic damping. We observe a strong anisotropy in the magnon decay
lengths that we can attribute to the role of the magnon group velocity in the
propagation of spin-waves in antiferromagnets. This unique mode of transport
identified in YFeO$_3$ opens up the possibility of a large and technologically
relevant class of materials, i.e., canted antiferromagnets, for long-distance
spin transport.",2112.05947v1
2022-01-10,Impact of extreme spins and mass ratios on the post-merger observables of high-mass binary neutron stars,"The gravitational-wave events GW170817 and GW190425 have led to a number of
important insights on the equation of state of dense matter and the properties
of neutron stars, such as their radii and the maximum mass. Some of these
conclusions have been drawn on the basis of numerical-relativity simulations of
binary neutron-star mergers with vanishing initial spins. While this may be a
reasonable assumption in equal-mass systems, it may be violated in the presence
of large mass asymmetries accompanied by the presence of high spins. To
quantify the impact of high spins on multi-messenger gravitational-wave events,
we have carried out a series of high-mass binary neutron-star mergers with a
highly spinning primary star and large mass asymmetries that have been modelled
self-consistently using two temperature-dependent equations of state. We show
that, when compared with equal-mass, irrotational binaries, these systems can
lead to significant differences in the remnant lifetime, in the dynamical
ejecta, in the remnant disc masses, in the secular ejecta, and on the bulk
kilonova properties. These differences could be exploited to remove the
degeneracy between low- and high-spin priors in the detection of gravitational
waves from binary neutron-star mergers.",2201.03632v2
2022-06-30,Origin and dynamics of umbrella states in rare-earth iron garnets,"Rare-earth iron garnets $R_{3}$Fe$_{5}$O$_{12}$ are fascinating insulators
with very diverse magnetic phases. Their strong potential in spintronic devices
has encouraged a renewal of interest in the study of their low temperature spin
structures and spin wave dynamics. A striking feature of rare-earth garnets
with $R$-ions exhibiting strong crystal-field effects like Tb-, Dy-, Ho-, and
Er-ions is the observation of low-temperature non-collinear magnetic structures
featuring ""umbrella-like"" arrangements of the rare-earth magnetic moments. In
this study, we demonstrate that such umbrella magnetic states are naturally
emerging from the crystal-field anisotropies of the rare-earth ions. By means
of a general model endowed with only the necessary elements from the crystal
structure, we show how umbrella-like spin structures can take place and
calculate the canting-angle as a result of the competition between the
exchange-interaction of the rare-earth and the iron ions as well as the
crystal-field anisotropy. Our results are compared to experimental data, and a
study of the polarised spin wave dynamics is presented. Our study improves the
understanding of umbrella-like spin structures and paves the way for more
complex spin wave calculations in rare-earth iron garnets with non-collinear
magnetic phases.",2207.00017v2
2022-07-11,Emergence of bond-dependent highly anisotropic magnetic interactions in Sr$_4$RhO$_6$: a theoretical study,"The quantum spin liquid states as a natural ground state of the Kitaev model
has led to a quest for new materials candidates hosting Kitaev physics. Yet,
there are very few material candidates in this category. Using a combination of
$ab$ $initio$ and model Hamiltonian methods, we propose that Ruddlesden-Popper
compound Sr$_4$RhO$_6$ belongs to this category. With a tight-binding model and
exact diagonalization approach, we show that despite substantial trigonal-like
distortion, the electronic and magnetic properties of Sr$_4$RhO$_6$ can be well
described in terms of pseudo-spin = 1/2 states. Magnetic interactions among
pseudo-spins, estimated using the second-order perturbation method are highly
bond-dependent anisotropic in nature with two particularly noticeable features,
antiferromagnetic Kitaev and Dzyaloshinskii-Moriya interactions. The gaped
spin-wave spectra of Sr$_4$RhO$_6$ obtained with linear spin-wave theory is
consistent with the underlying magnetic frustration. Additional analysis of the
role of individual or a particular combination of magnetic interactions reveals
that the spin-wave spectra of Sr$_4$RhO$_6$ is a combined effect of the highly
anisotropic interactions and a relatively simpler minimal model may not be
plausible in the current case. The crucial insights about coupling between the
local structural features and magnetic properties of Sr$_4$RhO$_6$ obtained in
this study may be helpful for future studies belonging to this class.",2207.05045v3
2024-02-19,Designed spin-texture-lattice to control anisotropic magnon transport in antiferromagnets,"Spin waves in magnetic materials are promising information carriers for
future computing technologies due to their ultra-low energy dissipation and
long coherence length. Antiferromagnets are strong candidate materials due, in
part, to their stability to external fields and larger group velocities.
Multiferroic aniferromagnets, such as BiFeO$_3$ (BFO), have an additional
degree of freedom stemming from magnetoelectric coupling, allowing for control
of the magnetic structure, and thus spin waves, with electric field.
Unfortunately, spin-wave propagation in BFO is not well understood due to the
complexity of the magnetic structure. In this work, we explore long-range spin
transport within an epitaxially engineered, electrically tunable,
one-dimensional (1D) magnonic crystal. We discover a striking anisotropy in the
spin transport parallel and perpendicular to the 1D crystal axis. Multiscale
theory and simulation suggests that this preferential magnon conduction emerges
from a combination of a population imbalance in its dispersion, as well as
anisotropic structural scattering. This work provides a pathway to
electrically-reconfigurable magnonic crystals in antiferromagnets.",2402.12341v1
2001-09-28,Gravity Waves from Rotating Neutron Stars and Evaluation of Fast Chirp Transform Techniques,"X-ray observations suggest that neutron stars in low mass X-ray binaries
(LMXB) are rotating with frequencies from 300 - 600 Hz. These spin rates are
significantly less than the break-up rates for essentially all realistic
neutron star equations of state, suggesting that some process may limit the
spin frequencies of accreting neutron stars to this range. If the accretion
induced spin up torque is in equilibrium with gravitational radiation losses,
these objects could be interesting sources of gravity waves. I present a brief
summary of current measurements of neutron star spins in LMXBs based on the
observations of high-Q oscillations during thermonuclear bursts (so called
``burst oscillations''). Further measurements of neutron star spins will be
important in exploring the gravitational radiation hypothesis in more detail.
To this end I also present a study of fast chirp transform (FCT) techniques as
described by Jenet & Prince (2000) in the context of searching for the chirping
signals observed during X-ray bursts.",0109559v1
1995-10-13,Modified Spin Wave Thoery of the Bilayer Square Lattice Frustrated Quantum Heisenberg Antiferromagnet,"The ground state of the square lattice bilayer quantum antiferromagnet with
nearest and next-nearest neighbour intralayer interaction is studied by means
of the modified spin wave method. For weak interlayer coupling, the ground
state is found to be always magnetically ordered while the quantum disordered
phase appear for large enough interlayer coupling. The properties of the
disordered phase vary according to the strength of the frustration. In the
regime of weak frustration, the disordered ground state is an almost
uncorrelated assembly of interlayer dimers, while in the strongly frustrated
regime the quantum spin liquid phase which has considerable N\'eel type short
range order appears. The behavior of the sublattice magnetization and spin-spin
correlation length in each phase is discussed.",9510072v1
1996-06-16,Conduction band spin splitting and negative magnetoresistance in ${\rm A}_3{\rm B}_5$ heterostructures,"The quantum interference corrections to the conductivity are calculated for
an electron gas in asymmetric quantum wells in a magnetic field. The theory
takes into account two different types of the spin splitting of the conduction
band: the Dresselhaus terms, both linear and cubic in the wave vector, and the
Rashba term, linear in wave vector. It is shown that the contributions of these
terms into magnetoconductivity are not additive, as it was traditionally
assumed. While the contributions of all terms of the conduction band splitting
into the D'yakonov--Perel' spin relaxation rate are additive, in the
conductivity the two linear terms cancel each other, and, when they are equal,
in the absence of the cubic terms the conduction band spin splitting does not
show up in the magnetoconductivity at all. The theory agrees very well with
experimental results and enables one to determine experimentally parameters of
the spin-orbit splitting of the conduction band.",9606112v1
1998-02-13,Spin and orbital excitations in magnetic insulators with Jahn-Teller ions,"The elementary excitations of a model Hamiltonian that captures the low
energy behavior of a simple two-fold degenerate Hubbard Hamiltonian with Hund's
rule coupling, is studied. The phase diagram in the mean-field limit and in a
two-site approach reveals a rich variety of phases where both the orbital and
the spin degrees of freedom are ordered. We show that besides usual spin waves
(magnons) there exist also orbital waves (orbitons) and, most interestingly, in
a completely ferromagnetically coupled system, a combined spin-orbital
excitation which can be visualized as a bound state of magnons and orbitons.
For a completely degenerate system the bound states are found to be the lowest
lying elementary excitations, both in one- and two-dimensions. Finally we
extend our treatment to almost-degenerate systems. This can serve as an example
that the elementary excitations in orbitally degenerate strongly correlated
electron systems in general carry both spin and orbital character.",9802146v1
1998-04-06,Effect of next-nearest neighbor hopping on the spin dynamics in antiferromagnets,"Recently, inelastic neutron scattering (INS) experiments on the insulating
parent compounds of high-T_c materials were analyzed to extract the value of
the superexchange constant $J$. Starting point of the analysis was the
nearest-neighbor Heisenberg model. Motivated by recent ARPES experiments, we
consider the effects of a next-nearest neighbor hopping, $t'$ in the strong
coupling limit of the spin-density wave formalism, where it leads to an
antiferromagnetic exchange $J'>0$ between next-nearest neighbor spins. We show
that a finite $J'$ (a) changes the spin-wave velocity and thus the value of $J$
extracted from the INS data, yielding almost identical values for $J$ in
La_2CuO_4 and YBa_2Cu_3O_{6.15}, and (b) leads to a considerable change in the
high-frequency spin-dynamics. Finally, we calculate the 1/S quantum corrections
in the presence of $J'$ and discuss their relevance for the INS data.",9804069v2
1998-08-18,Itinerant Electron Ferromagnetism in the Quantum Hall Regime,"We report on a study of the temperature and Zeeman-coupling-strength
dependence of the one-particle Green's function of a two-dimensional (2D)
electron gas at Landau level filling factor $\nu =1$ where the ground state is
a strong ferromagnet. Our work places emphasis on the role played by the
itinerancy of the electrons, which carry the spin magnetization and on
analogies between this system and conventional itinerant electron ferromagnets.
We discuss the application to this system of the self-consistent Hartree-Fock
approximation, which is analogous to the band theory description of metallic
ferromagnetism and fails badly at finite temperatures because it does not
account for spin-wave excitations. We go beyond this level by evaluating the
one-particle Green's function using a self-energy, which accounts for
quasiparticle spin-wave interactions. We report results for the temperature
dependence of the spin magnetization, the nuclear spin relaxation rate, and
2D-2D tunneling conductances. Our calculations predict a sharp peak in the
tunneling conductance at large bias voltages with strength proportional to
temperature. We compare with experiment, where available, and with predictions
based on numerical exact diagonalization and other theoretical approaches.",9808186v1
2000-01-01,Characterization of ferrimagnetic Heisenberg chains according to the constituent spins,"The low-energy structure and the thermodynamic properties of ferrimagnetic
Heisenberg chains of alternating spins $S$ and $s$ are investigated by the use
of numerical tools as well as the spin-wave theory. The elementary excitations
are calculated through an efficient quantum Monte Carlo technique featuring
imaginary-time correlation functions and are characterized in terms of
interacting spin waves. The thermal behavior is analyzed with particular
emphasis on its ferromagnetic and antiferromagnetic dual aspect. The extensive
numerical and analytic calculations lead to the classification of the
one-dimensional ferrimagnetic behavior according to the constituent spins: the
ferromagnetic ($S>2s$), antiferromagnetic ($S<2s$), and balanced ($S=2s$)
ferrimagnetism.",0001004v1
2001-01-03,Spin and Current Correlation Functions in the \bf d-density Wave State of the Cuprates,"We calculate the spin-spin and current-current correlation functions in
states exhibiting d_{{x^2}-{y^2}}-density wave (DDW) order, d_{{x^2}-{y^2}}
superconducting order (DSC), or both types of order. The spin-spin correlation
functions in a state with both DDW and DSC order and in a state with DDW order
alone, respectively, illuminate the resonant peak seen in the superconducting
state of the underdoped cuprates and the corresponding feature seen in the
pseudogap regime. The current-current correlation function in a state with both
DDW and DSC order evinces a superfluid density with doping dependence which is
consistent with that of the underdoped cuprates. These calculations strengthen
the identification of the pseudogap with DDW order and of the underdoped
cuprates with a state with both DDW and DSC order.",0101027v2
2001-04-13,Non-Abelian spin-singlet quantum Hall states: wave functions and quasihole state counting,"We investigate a class of non-Abelian spin-singlet (NASS) quantum Hall
phases, proposed previously. The trial ground and quasihole excited states are
exact eigenstates of certain k+1-body interaction Hamiltonians. The k=1 cases
are the familiar Halperin Abelian spin-singlet states. We present closed-form
expressions for the many-body wave functions of the ground states, which for
k>1 were previously defined only in terms of correlators in specific conformal
field theories. The states contain clusters of k electrons, each cluster having
either all spins up, or all spins down. The ground states are non-degenerate,
while the quasihole excitations over these states show characteristic
degeneracies, which give rise to non-Abelian braid statistics. Using conformal
field theory methods, we derive counting rules that determine the degeneracies
in a spherical geometry. The results are checked against explicit numerical
diagonalization studies for small numbers of particles on the sphere.",0104250v1
2001-04-15,Effective classical Hamiltonians for spin systems: A closed form with quantum spin-wave effects,"Thermodynamic properties of any quantum spin system can be described by the
formally exact, although in general intractable, effective classical Hamilton
function \cal H. Here we obtain an explicit form of \cal H which applies at T
<< J S^2, where J is the exchange and S in the spin value, and incorporates
quantum effects at the level of the spin-wave theory (SWT). For a quantum
Hamiltonian \hat H of Heisenberg form, \cal H is also Heisenberg but with a
long-range effective exchange J_{ij}^{eff}, which is the price for including
quantum effects. For three-dimensional magnets, classical SWT with \cal H
yields the same results as quantum SWT for the original system, in the
antiferromagnetic case with the 1/S correction to the ground-state energy.",0104269v1
2001-05-03,Spin waves in the spiral phase of a doped antiferromagnet: a strong-coupling approach,"We study spin fluctuations in the spiral phase of the two-dimensional Hubbard
model at low doping on the basis of the spin-particle-hole coherent-state path
integral. In the strong correlation limit, we obtain an analytical expression
of the spin-wave excitations over the entire Brillouin zone except in the
vicinity of ${\bf q}=0$. We discuss the validity of the Hartree-Fock and
random-phase approximations in the strong-coupling limit, and compare our
results with previous numerical and analytical calculations. Although the
spiral phase is unstable, as shown by a negative mean-field compressibility and
the presence of imaginary spin-fluctuation modes, we expect the
short-wavelength fluctuation modes (with real energies) to survive in the
actual ground-state of the system.",0105063v1
2004-03-24,Phase diagram and magnetic collective excitations of the Hubbard model in graphene sheets and layers,"We discuss the magnetic phases of the Hubbard model for the honeycomb lattice
both in two and three spatial dimensions. A ground state phase diagram is
obtained depending on the interaction strength
  U and electronic density n. We find a first order phase transition between
ferromagnetic regions where the spin is maximally polarized (Nagaoka
ferromagnetism) and regions with smaller magnetization (weak ferromagnetism).
When taking into account the possibility of spiral states, we find that the
lowest critical U is obtained for an ordering momentum different from zero. The
evolution of the ordering momentum with doping is discussed. The magnetic
excitations (spin waves) in the antiferromagnetic insulating phase are
calculated from the random-phase-approximation for the spin susceptibility. We
also compute the spin fluctuation correction to the mean field magnetization by
virtual emission/absorpion of spin waves. In the large $U$ limit, the
renormalized magnetization agrees qualitatively with the Holstein-Primakoff
theory of the Heisenberg antiferromagnet, although the latter approach produces
a larger renormalization.",0403605v2
2005-04-07,Observation of spin-wave characteristics in the two-dimensional ferromagnetic ordering of in-plane spins,"The role of dipolar interactions and anisotropy are important to obtain,
otherwise forbidden, ferromagnetic ordering at finite temperature for ions
arranged in two-dimensional (2D) arrays (monolayers). Here we demonstrate that
conventional low temperature magnetometry and polarized neutron scattering
measurements can be performed to study ferromagnetic ordering of in-plane spins
in 2D systems using a multilayer stack of non-interacting monolayers of
gadolinium ions. The spontaneous magnetization is absent in the heterogenous
magnetic phase observed here and the saturation value of the net magnetization
was found to depend on the applied magnetic field. The net magnetization rises
exponentially with lowering temperature and then reaches saturation following a
$T\ln(\beta T)$ dependence. These findings verify predictions of the spin-wave
theory of 2D in-plane spin system with ferromagnetic interaction and will
initiate further theoretical development.",0504155v1
2005-09-13,Coherent spinor dynamics in a spin-1 Bose condensate,"Collisions in a thermal gas are perceived as random or incoherent as a
consequence of the large numbers of initial and final quantum states accessible
to the system. In a quantum gas, e.g. a Bose-Einstein condensate or a
degenerate Fermi gas, the phase space accessible to low energy collisions is so
restricted that collisions be-come coherent and reversible. Here, we report the
observation of coherent spin-changing collisions in a gas of spin-1 bosons.
Starting with condensates occupying two spin states, a condensate in the third
spin state is coherently and reversibly created by atomic collisions. The
observed dynamics are analogous to Josephson oscillations in weakly connected
superconductors and represent a type of matter-wave four-wave mixing. The
spin-dependent scattering length is determined from these oscillations to be
-1.45(18) Bohr. Finally, we demonstrate coherent control of the evolution of
the system by applying differential phase shifts to the spin states using
magnetic fields.",0509341v2
2005-09-25,Quantum Nonlinear Sigma Model for Arbitrary Spin Heisenberg Antiferromagnets,"In this Letter, we derive a quantum nonlinear sigma model (QNLSM) for quantum
Heisenberg antiferromagnets (QHA) with arbitrary S (spin) values. A upper limit
of the low temperature is naturally carried out for the reliability of the
QNLSM. The S dependence of the effective coupling constant and the spin wave
velocity in the QNLSM are also obtained explicitly. The resulting spin wave
velocity for 2-dim spin-1/2 QHA highly concurs with the experimental data of
high $T_c$ compound La2CuO4. The predicted correlation lengths for 2d QHA and
spin-gap magnitudes for 1d QHA also agrees with the accurate numerical results.",0509628v2
2005-12-24,Fermionic versus bosonic descriptions of one-dimensional spin-gapped antiferromagnets,"In terms of spinless fermions and spin waves, we describe magnetic properties
of a spin-1/2 ferromagnetic-antiferromagnetic bond-alternating chain which
behaves as a Haldane-gap antiferromagnet. On one hand, we employ the
Jordan-Wigner transformation and treat the fermionic Hamiltonian within the
Hartree-Fock approximation. On the other hand, we employ the Holstein-Primakoff
transformation and modify the conventional spin-wave theory so as to restore
the sublattice symmetry. We calculate the excitation gap, the specific heat,
the magnetic susceptibility, magnetization curves, and the nuclear spin-lattice
relaxation rate with varying bond alternation. These schemes are further
applied to a bond-alternating tetramerized chain which behaves as a
ferrimagnet. The fermionic language is particularly stressed as a useful tool
to investigate one-dimensional spin-gapped antiferromagnets, while the bosonic
one works better for ferrimagnets.",0512631v1
2006-01-31,Field Induced Order and Spin Waves in the Pyrochlore Antiferromagnet Tb2Ti2O7,"High resolution time-of-flight neutron scattering measurements on Tb2Ti2O7
reveal a rich low temperature phase diagram in the presence of a magnetic field
applied along [110]. In zero field at T=0.4 K, terbium titanate is a highly
correlated cooperative paramagnet with disordered spins residing on a
pyrochlore lattice of corner-sharing tetrahedra. Application of a small field
condenses much of the magnetic diffuse scattering, characteristic of the
disordered spins, into a new Bragg peak characteristic of a polarized
paramagnet. At higher fields, a magnetically ordered phase is induced, which
supports spin wave excitations indicative of continuous, rather than Ising-like
spin degrees of freedom.",0601715v1
2006-05-15,Solution of the problem of catastrophic relaxation of homogeneous spin precession in superfluid $^3$He-B,"The quantitative analysis of the ""catastrophic relaxation"" of the coherent
spin precession in $^3$He-B is presented. This phenomenon has been observed
below the temperature about 0.5 T$_c$ as an abrupt shortening of the induction
signal decay. It is explained in terms of the decay instability of homogeneous
transverse NMR mode into spin waves of the longitudinal NMR. Recently the cross
interaction amplitude between the two modes has been calculated by Sourovtsev
and Fomin \cite{SF} for the so-called Brinkman-Smith configuration, i.e. for
the orientation of the orbital momentum of Cooper pairs along the magnetic
field, ${\bf L}\parallel {\bf H}$. In their treatment, the interaction is
caused by the anisotropy of the speed of the spin waves. We found that in the
more general case of the non-parallel orientation of ${\bf L}$ corresponding to
the typical conditions of experiment, the spin-orbital interaction provides the
additional interaction between the modes. By analyzing experimental data we are
able to distinguish which contribution is dominating in different regimes.",0605386v1
2006-10-12,Fermi liquid instabilities in the spin channel,"We study the Fermi surface instabilities of the Pomeranchuk type in the spin
triplet channel with high orbital partial waves ($F_{l}^a ~(l>0)$). The ordered
phases are classified into two classes, dubbed the $\alpha$ and $\beta$-phases
by analogy to the superfluid $^3$He-A and B-phases. The Fermi surfaces in the
$\alpha$-phases exhibit spontaneous anisotropic distortions, while those in the
$\beta$-phases remain circular or spherical with topologically non-trivial spin
configurations in momentum space. In the $\alpha$-phase, the Goldstone modes in
the density channel exhibit anisotropic overdamping. The Goldstone modes in the
spin channel have nearly isotropic underdamped dispersion relation at small
propagating wavevectors. Due to the coupling to the Goldstone modes, the spin
wave spectrum develops resonance peaks in both the $\alpha$ and $\beta$-phases,
which can be detected in inelastic neutron scattering experiments. In the
p-wave channel $\beta$-phase, a chiral ground state inhomogeneity is
spontaneously generated due to a Lifshitz-like instability in the originally
nonchiral systems. Possible experiments to detect these phases are discussed.",0610326v2
2000-10-26,The fate of chaotic binaries,"A typical stellar mass black hole with a lighter companion is shown to
succumb to a chaotic precession of the orbital plane. As a result, the optimal
candidates for the direct detection of gravitational waves by Earth based
interferometers can show irregular modulation of the waveform during the last
orbits before plunge. The precession and the subsequent modulation of the
gravitational radiation depends on the mass ratio, eccentricity, and spins. The
smaller the mass of the companion, the more prominent the effect of the
precession. The most important parameters are the spin magnitudes and
misalignments. If the spins are small and nearly aligned with the orbital
angular momentum, then there will be no chaotic precession while increasing
both the spin magnitudes and misalignments increases the erratic precession. A
large eccentricity can be induced by large, misaligned spins but does not seem
to be required for chaos. An irregular precession of the orbital plane will
generate irregularities in the gravitational wave frequency but may have a
lesser effect on the total number of cycles observed.",0010100v3
2004-05-10,"""Square Root"" of the Proca Equation: Spin-3/2 Field Equation","New equations describing particles with spin 3/2 are derived. The non-local
equation with the unique mass can be considered as ""square root"" of the Proca
equation in the same sense as the Dirac equation is related to the
Klein-Gordon-Fock equation. The local equation describes spin 3/2 particles
with three mass states. The equations considered involve fields with spin-3/2
and spin-1/2, i.e. multi-spin 1/2, 3/2. The projection operators extracting
states with definite energy, spin, and spin projections are obtained. All
independent solutions of the local equation are expressed through projection
matrices. The first order relativistic wave equation in the 20-dimensional
matrix form, the relativistically invariant bilinear form and the corresponding
Lagrangian are given. Two parameters characterizing non-minimal electromagnetic
interactions of fermions are introduced, and the quantum-mechanical Hamiltonian
is found. It is proved that there is only causal propagation of waves in the
approach considered.",0405088v5
2004-03-26,Numerical analysis of the existence and stability of nonlinear excitations in a parametric model of ferromagnetic chain,"A parametrized spin model was recently introduced and intended for
one-dimensional ferromagnets with a deformable Zeeman energy. This model is
revisited and given more realistic interpretation in terms of a model for
ferromagnetic systems with nonconvex anisotropies. A main virtue of the
improved form is its exact reduction to the discrete Remoissenet-Peyrard model,
i.e. a parametrized version of the Takeno-Homma's discrete sine-Gordon model.
The spin-wave phase of the improved parametrized spin model is investigated
assuming both harmonic and anharmonic excitations. Intrinsic-self-localized
modes, regarded as zone-boundary breather spin waves, are pointed out by
simulating the nonlinear difference equations describing the spin equilibrium
positions in the chain, and are shown to exist irrespective of values of the
model parameter. Domain-wall textures of the model are also numerically
examined in terms of kink solitons and with regard to the parametrization.",0403048v1
2004-02-04,The Operator form of 3H (3He) and its Spin Structure,"An operator form of the 3N bound state is proposed. It consists of eight
operators formed out of scalar products in relative momentum and spin vectors,
which are applied on a pure 3N spin 1/2 state. Each of the operators is
associated with a scalar function depending only on the magnitudes of the two
relative momenta and the angle between them. The connection between the
standard partial wave decomposition of the 3N bound state and the operator form
is established, and the decomposition of these scalar function in terms of
partial wave components and analytically known auxiliary functions is given.
That newly established operator form of the 3N bound state exhibits the
dominant angular and spin dependence analytically. The scalar functions are
tabulated and can be downloaded. As an application the spin dependent nucleon
momentum distribution in a polarized 3N bound state is calculated to illustrate
the use of the new form of the 3N bound state.",0402015v1
2007-06-19,Probing the Role of the Barrier Layer in Magnetic Tunnel Junction Transport,"Magnetic tunnel junctions with a ferrimagnetic barrier layer have been
studied to understand the role of the barrier layer in the tunneling process -
a factor that has been largely overlooked until recently. Epitaxial oxide
junctions of highly spin polarized La0.7Sr0.3MnO3 and Fe3O4 electrodes with
magnetic NiMn2O4 (NMO) insulating barrier layers provide a magnetic tunnel
junction system in which we can probe the effect of the barrier by comparing
junction behavior above and below the Curie temperature of the barrier layer.
When the barrier is paramagnetic, the spin polarized transport is dominated by
interface scattering and surface spin waves; however, when the barrier is
ferrimagnetic, spin flip scattering due to spin waves within the NMO barrier
dominates the transport.",0706.2726v2
2008-04-18,Towards quantum optics and entanglement with electron spin ensembles in semiconductors,"We discuss a technique and a material system that enable the controlled
realization of quantum entanglement between spin-wave modes of electron
ensembles in two spatially separated pieces of semiconductor material. The
approach uses electron ensembles in GaAs quantum wells that are located inside
optical waveguides. Bringing the electron ensembles in a quantum Hall state
gives selection rules for optical transitions across the gap that can
selectively address the two electron spin states. Long-lived superpositions of
these electron spin states can then be controlled with a pair of optical fields
that form a resonant Raman system. Entangled states of spin-wave modes are
prepared by applying quantum-optical measurement techniques to optical signal
pulses that result from Raman transitions in the electron ensembles.",0804.2953v1
2008-10-13,Antiferromagnetism in two-dimensional quasicrystals,"Quasiperiodic structures possess long range positional order, but are freed
of constraints imposed by translational invariance. For spins interacting via
Heisenberg couplings, one may expect therefore to find novel magnetic
configurations in such structures. We have studied magnetic properties for
simple two dimensional models, as a first step towards understanding
experimentally studied magnetic quasicrystals such as the Zn-Mg-R(rare earth)
compounds. We analyse properties of the antiferromagnetic ground state and
magnon excitation modes for bipartite tilings such as the octagonal and Penrose
tilings. In the absence of frustration, one has an inhomogeneous Neel-ordered
ground state, with local quantum fluctuations of the local staggered magnetic
order parameter. We study the spin wave spectrum and wavefunctions of such
antiferromagnets within the linear spin wave approximation. Some results for
spin-spin correlations in these systems are discussed.",0810.2312v1
2009-05-04,Direct current control of three magnon scattering processes in spin-valve nanocontacts,"We have investigated the generation of spin waves in the free layer of an
extended spin-valve structure with a nano-scaled point contact driven by both
microwave and direct electric current using Brillouin light scattering
microscopy. Simultaneously with the directly excited spin waves, strong
nonlinear effects are observed, namely the generation of eigenmodes with
integer multiple frequencies (2 \emph{f}, 3 \emph{f}, 4 \emph{f}) and modes
with non-integer factors (0.5 \emph{f}, 1.5 \emph{f}) with respect to the
excitation frequency \emph{f}. The origin of these nonlinear modes is traced
back to three magnon scattering processes. The direct current influence on the
generation of the fundamental mode at frequency \emph{f} can be related to the
spin-transfer torque, while the efficiency of three-magnon-scattering processes
is controlled by the Oersted field as an additional effect of the direct
current.",0905.0323v1
2009-08-11,Spontaneous Vortex Lattices in Quasi 2D Dipolar Spinor Condensates,"Motivated by recent experiments\cite{BA}\cite{BB}, we study quasi 2D
ferromagnetic condensates with various aspect ratios. We find that in zero
magnetic field, dipolar energy generates a local energy minimum with all the
spins lie in the 2D plane forming a row of {\em circular} spin textures with
{\em alternating} orientation, corresponding to a packing of vortices of {\em
identical} vorticity in different spin components. In a large magnetic field,
the system can fall into a long lived dynamical state consisting of an array of
elliptic and hyperbolic Mermin-Ho spin textures, while the true equilibrium is
an uniaxial spin density wave with a single wave-vector along the magnetic
field, and a wavelength similar to the characteristic length of the long lived
vortex array state.",0908.1593v1
2010-02-16,"Orbital Ordering and Unfrustrated $(π,0)$ Magnetism from Degenerate Double Exchange in the Iron Pnictides","The magnetic excitations of the iron pnictides are explained within a
degenerate double-exchange model. The local-moment spins are coupled by
superexchanges $J_1$ and $J_2$ between nearest and next-nearest neighbors,
respectively, and interact with the itinerant electrons of the degenerate
$d_{xz}$ and $d_{yz}$ orbitals via a ferromagnetic Hund exchange. The latter
stabilizes $(\pi,0)$ stripe antiferromagnetism due to emergent ferro-orbital
order and the resulting kinetic energy gain by hopping preferably along the
ferromagnetic spin direction. Taking the quantum nature of the spins into
account, we calculate the magnetic excitation spectra in the presence of both,
super- and double-exchange. A dramatic increase of the spin-wave energies at
the competing N\'eel ordering wave vector is found, in agreement with recent
neutron scattering data. The spectra are fitted to a spin-only model with a
strong spatial anisotropy and additional longer ranged couplings along the
ferromagnetic chains. Over a realistic parameter range, the effective couplings
along the chains are negative corresponding to unfrustrated stripe
antiferromagnetism.",1002.3165v3
2010-05-26,Disappearance of static magnetic order and evolution of spin fluctuations in Fe$_{1+δ}$Se$_{x}$Te$_{1-x}$,"We report neutron scattering studies on static magnetic orders and spin
excitations in the Fe-based chalcogenide system
Fe$_{1+\delta}$Se$_{x}$Te$_{1-x}$ with different Fe and Se compositions.
Short-range static magnetic order with the ""bicollinear"" spin configuration is
found in all non-superconducting samples, with strong low-energy magnetic
excitations near the $(0.5,0)$ in-plane wave-vector (using the two-Fe unit
cell) for Se doping up to 45%. When the static order disappears and bulk
superconductivity emerges, the spectral weight of the magnetic excitations
shifts to the region of reciprocal space near the in-plane wave-vector
$(0.5,0.5)$, corresponding to the ""collinear"" spin configuration. Our results
suggest that spin fluctuations associated with the collinear magnetic structure
appear to be universal in all Fe-based superconductors, and there is a strong
correlation between superconductivity and the character of the magnetic
order/fluctuations in",1005.4856v1
2010-06-25,"Bond-order wave phase, spin solitons and thermodynamics of a frustrated linear spin-1/2 Heisenberg antiferromagnet","The linear spin-1/2 Heisenberg antiferromagnet with exchanges $J_1$, $J_2$
between first and second neighbors has a bond-order wave (BOW) phase that
starts at the fluid-dimer transition at $J_2/J_1 = 0.2411$ and is particularly
simple at $J_2/J_1 = 1/2$. The BOW phase has a doubly degenerate singlet ground
state, broken inversion symmetry and a finite energy gap $E_m$ to the lowest
triplet state.
  The interval $0.4<J_2/J_1<1.0$ has large $E_m$ and small finite size
corrections. Exact solutions are presented up to $N=28$ spins with either
periodic or open boundary conditions and for thermodynamics up to $N=18$. The
elementary excitations of the BOW phase with large $E_m$ are topological
spin-1/2 solitons that separate BOWs with opposite phase in a regular array of
spins. The molar spin susceptibility $\chi_M(T)$ is exponentially small for $T
\ll E_m$ and increases nearly linearly with $T$ to a broad maximum. $J_1$,
$J_2$ spin chains approximate the magnetic properties of the BOW phase of
Hubbard-type models and provide a starting point for modeling alkali-TCNQ
salts.",1006.5052v1
2010-07-14,Coupled Spin-Phonon Excitations in Helical Multiferroics,"Both the Dzyaloshiskii-Moriya interaction and the exchange-striction are
shown to affect dynamically the magnetoelectric excitations in the perovskite
multiferroic RMnO3. The exchange-striction results in a biquadratic interaction
between the spins and the transverse phonons, giving rise to quantum
fluctuations of the ferroelectric polarization P. This leads to low-lying
phonon modes that are perpendicular to P and to the helical spins at small wave
vector but are parallel to P at a wave vector close to the magnetic modulation
vector. For spin-1/2 helimagnet, the local polarization can be completely
reversed by the spin fluctuation, and so does the direction of the on-site spin
chirality, which allows for a finite differential scattering intensity of
polarized neutrons from a cycloidal magnet.",1007.2273v1
2010-07-29,Larmor precession reexamined: Testable correction and its ramifications,"For a spin-polarized plane wave passing through a spin-rotator containing
uniform magnetic field, we provide a detailed analysis for solving the
appropriate Schr\""{o}dinger equation. A modified expression for spin precession
is obtained which reduces to the standard Larmor precession relation when
kinetic energy is very large compared to the spin-magnetic field interaction.
We show that there are experimentally verifiable regimes of departure from the
standard Larmor precession formula. The treatment is then extended to the case
of a spin-polarized wave packet passing through a uniform magnetic field. The
results based on the standard expression for Larmor precession and that
obtained from the modified formula are compared in various regimes of the
experimental parameters.",1007.5179v2
2010-09-05,Graphene-based electronic spin lenses,"We theoretically demonstrate the capability of a ferromagnetic-normal (FN)
interface in graphene to focus an electron-wave with a certain spin direction.
The essential feature is the negative refraction Klein tunneling, which is
spin-resolved when the exchange energy of F graphene exceeds its Fermi energy.
Exploiting this property, we propose a graphene NFN electronic spin lens
through which an unpolarized electronic beam can be collimated with a finite
spin-polarization. Our study reveals that magnetic graphene has the potential
to be the electronic counterpart of the recently discovered photonic chiral
meta-materials that exhibit a negative refractive index for only one direction
of the circular polarization of the photon-wave.",1009.0904v1
2010-10-25,Spin entanglement of two spin-1/2 particles in a classical gravitational field,"The effect of a classical gravitational field on the spin entanglement of a
system of two spin-1/2 particles moving in the curved spacetime is discussed.
The system is described by a two-particle Gaussian wave packet represented in
the momentum space and both the acceleration of the system and the curvature of
the spacetime cause to produce a Wigner rotation acting on the wave packet as
it moves along a path in the curved spacetime. By calculating the reduced
density operator at a final point, we focus on the spin entanglement of the
system. In a spherically symmetric and static gravitational field, for example
a charged black hole, there can be particular paths on which the Wigner
rotation is trivial and so the initial reduced density matrix remains intact.
This causes the spin entanglement to be invariant during the motion. The spin
entanglement descends to zero by increasing the angular velocity of the mean
centroid of the system as well increasing the proper time during which the
centroid moves on its circular path around the center.",1010.5107v1
2011-07-14,The dimerized ferromagnetic Heisenberg chain,"Ferromagnetic, in contrast to antiferromagnetic, Heisenberg chains can
undergo a Spin-Peierls dimerization only at finite temperatures. They show
reentrant behavior as a function of temperature, which might play a role for
systems with small effective elastic constants as, for example, monatomic
chains on surfaces. We investigate the physical properties of the dimerized
ferromagnetic Heisenberg chain using a modified spin-wave theory. We calculate
the exponentially decaying spin and dimer correlation functions, analyze the
temperature dependence of the corresponding coherence lengths, the
susceptibility, as well as the static and dynamic spin structure factor. By
comparing with numerical data obtained by the density-matrix renormalization
group applied to transfer matrices, we find that the modified spin wave theory
yields excellent results for all these quantities for a wide range of
dimerizations and temperatures.",1107.2772v1
2011-09-22,Spin-orbital physics for p orbitals in alkali RO_2 hyperoxides --- generalization of the Goodenough-Kanamori rules,"We derive a realistic spin-orbital model at finite Hund's exchange for alkali
hyperoxides. We find that, due to the geometric frustration of the oxygen
lattice, spin and orbital waves destabilize both spin and p-orbital order in
almost all potential ground states. We show that the orbital order induced by
the lattice overrules the one favoured by superexchange and that this, together
with the large interorbital hopping, leads to generalized Goodenough-Kanamori
rules. They (i) lift the geometric frustration of the lattice, and (ii) explain
the observed layered C-type antiferromagnetic order in alkali hyperoxides. This
is confirmed by a spin-wave dispersion with no soft-mode behavior presented
here as a prediction for future experiments.",1109.4756v1
2012-02-09,Itinerant half-metal spin-density-wave state on the hexagonal lattice,"We consider electrons on a honeycomb or triangular lattice doped to the
saddle point of the bandstructure. We assume system parameters are such that
spin density wave (SDW) order emerges below a temperature $T_N$ and investigate
the nature of the SDW phase. We argue that at $T < T_N$ the system develops a
uniaxial SDW phase whose ordering pattern breaks $O(3) \times Z_4$ symmetry and
corresponds to an eight site unit cell with non-uniform spin moments on
different sites. This state is a half-metal -- it preserves full original Fermi
surface, but has gapless charged excitations in one spin branch only. It allows
for electrical control of spin currents and is desirable for nano-science.",1202.2127v1
2012-03-12,"Effects of ring exchange interaction on the Neel phase of two-dimensional, spatially anisotropic, frustrated Heisenberg quantum antiferromagnet","Higher order quantum effects on the magnetic phase diagram induced by
four-spin ring exchange on plaquettes are investigated for a two-dimensional
quantum antiferromagnet with S=1/2. Spatial anisotropy and frustration are
allowed for. Using a perturbative spin-wave expansion up to second order in 1/S
we obtain the spin-wave energy dispersion, sublattice magnetization, and the
magnetic phase diagram. We find that for substantial four-spin ring exchange
the quantum fluctuations are stronger than in the standard Heisenberg model. A
moderate amount of four-spin ring exchange couplings stabilizes the ordered
antiferromagnetic Neel state while a large amount renders it unstable.
Comparison with inelastic neutron scattering data points toward a moderate ring
exchange coupling of 27% to 29% of the nearest-neighbor exchange coupling.",1203.2598v2
2012-04-04,Magnetic adatom induced skyrmion-like spin texture in surface electron waves,"When a foreign atom is placed on a surface of a metal, the surrounding sea of
electrons responds screening the additional charge leading to oscillations or
ripples. On surfaces, those electrons are sometimes confined to two-dimensional
surface states, whose spin-degeneracy is lifted due to the Rashba effect
arising from the spin-orbit interaction of electrons and the inversion
asymmetric environment. It is believed that at least for a single adatom
scanning tunneling microscopy measurements are insensitive to the Rashba
splitting i.e. no signatures in the charge oscillations will be observed.
Resting on scattering theory, we demonstrate that, if magnetic, one single
adatom is enough to visualize the presence of the Rashba effect in terms of an
induced spin-magnetization of the surrounding electrons exhibiting a twisted
spin texture described as superposition of two skyrmionic waves of opposite
chirality.",1204.0999v1
2012-05-29,Spin excitations in K$_{2}$Fe$_{4+x}$Se$_{5}$: linear response approach,"Using \emph{ab initio} linear response techniques we calculate spin wave
spectra in K$_{2}$Fe$_{4+x}$Se$_{5}$, and find it to be in excellent agreement
with a recent experiment. The spectrum can be alternatively described rather
well by localized spin Hamiltonian restricted to first and second nearest
neighbor couplings. We confirm that exchange coupling between nearest neighbor
Fe magnetic moments is strongly anisotropic, and show directly that in the
ideal system this anisotropy has itinerant nature which can be imitated by
introducing higher order terms in effective localized spin Hamiltonian
(biquadratic coupling). In the real system, structural relaxation provides an
additional source of the exchange anisotropy of approximately the same
magnitude. The dependence of spin wave spectra on filling of Fe vacancy sites
is also discussed.",1205.6404v1
2012-06-21,Two-Nucleon Scattering without partial waves using a momentum space Argonne V18 interaction,"We test the operator form of the Fourier transform of the Argonne V18
potential by computing selected scattering observables and all Wolfenstein
parameters for a variety of energies. These are compared to the GW-DAC database
and to partial wave calculations. We represent the interaction and transition
operators as expansions in a spin-momentum basis. In this representation the
Lippmann-Schwinger equation becomes a six channel integral equation in two
variables. Our calculations use different numbers of spin-momentum basis
elements to represent the on- and off-shell transition operators. This is
because different numbers of independent spin-momentum basis elements are
required to expand the on- and off-shell transition operators. The choice of on
and off-shell spin-momentum basis elements is made so that the coefficients of
the on-shell spin-momentum basis vectors are simply related to the
corresponding off-shell coefficients.",1206.5026v2
2012-10-25,Gravitational waveforms for black hole binaries with unequal masses,"We derived a post-Newtonian (PN) inspiral only gravitational waveform for
unequal mass, spinning black hole binaries. Towards the end of the inspiral the
larger spin dominates over the orbital angular momentum (while the smaller spin
is negligible), hence the name Spin-Dominated Waveforms (SDW). Such systems are
common sources for future gravitational wave detectors and during the inspiral
the largest amplitude waves are emitted exactly in its last part. The SDW
waveforms emerge as a double expansion in the PN parameter and the ratio of the
orbital angular momentum to the dominant spin.",1210.6807v1
2012-11-08,Photoinduced spin-order destructions in one-dimensional extended Hubbard model,"By employing the time-dependent Lanczos method, the nonequilibrium process of
the half-filled one-dimensional extended Hubbard model under the irradiation of
a transient laser pulse is investigated. We show that in the spin-density-wave
(SDW) phase, the antiferromagnetic spin correlations are impaired by the
photoinduced charge carriers. Near the phase boundary between the SDW and
charge-density-wave (CDW) phases, a local enhancement of charge (spin) order
that is absent in the original SDW (CDW) phase can be realized with proper
laser frequency and strength. The possibility of restoration of spin orders
from the CDW phase by optical means is discussed.",1211.1749v1
2012-12-19,Mesoscopic mean-field theory for spin-boson chains in quantum optical systems,"We present a theoretical description of a system of many spins strongly
coupled to a bosonic chain. We rely on the use of a spin-wave theory describing
the Gaussian fluctuations around the mean-field solution, and focus on
spin-boson chains arising as a generalization of the Dicke Hamiltonian. Our
model is motivated by experimental setups such as trapped ions, or atoms/qubits
coupled to cavity arrays. This situation corresponds to the cooperative
(E$\otimes$$\beta$) Jahn-Teller distortion studied in solid-state physics.
However, the ability to tune the parameters of the model in quantum optical
setups opens up a variety of novel intriguing situations. The main focus of
this paper is to review the spin-wave theoretical description of this problem
as well as to test the validity of mean-field theory. Our main result is that
deviations from mean-field effects are determined by the interplay between
magnetic order and mesoscopic cooperativity effects, being the latter strongly
size-dependent.",1212.4709v1
2013-02-14,Faithful Solid State Optical Memory with Dynamically Decoupled Spin Wave Storage,"We report an optical memory in a rare earth doped crystal with long storage
times, up to 20 ms, together with an optical bandwidth of 1.5 MHz. This is
obtained by transferring optical coherences to nuclear spin coherences, which
were then protected against environmental noise by dynamical decoupling. With
this approach, we achieved a 33 fold increase in spin wave storage time over
the intrinsic spin coherence lifetime. Comparison between different decoupling
sequences indicates that sequences insensitive to initial spin coherence
increase retrieval efficiency. Finally, an interference experiment shows that
relative phases of input pulses are preserved through the whole storage process
with a visibility close to 1, demonstrating the usefulness of dynamical
decoupling for extending the storage time of quantum memories.",1302.3358v1
2013-06-24,Spinon confinement: dynamics of weakly coupled Hubbard chains,"Using large-scale determinant quantum Monte Carlo simulations in combination
with the stochastic analytical continuation, we study two-particle dynamical
correlation functions in the anisotropic square lattice of weakly coupled
one-dimensional (1D) Hubbard chains at half-filling and in the presence of weak
frustration. The evolution of the static spin structure factor upon increasing
the interchain coupling is suggestive of the transition from the power-law
decay of spin-spin correlations in the 1D limit to long-range antiferromagnetic
order in the quasi-1D regime and at $T=0$. In the numerically accessible regime
of interchain couplings, the charge sector remains gapped. The low-energy
momentum dependence of the spin excitations is well described by the linear
spin-wave theory with the largest intensity located around the
antiferromagnetic wave vector. This magnon mode corresponds to a bound state of
two spinons. At higher energies the spinons deconfine and we observe signatures
of the two-spinon continuum which progressively fade away as a function of
interchain hopping.",1306.5775v2
2013-09-29,Longitudinal spin excitations and magnetic anisotropy in antiferromagnetically ordered BaFe2As2,"We report on a spin-polarized inelastic neutron scattering study of spin
waves in the antiferromagnetically ordered state of BaFe2As2. Three distinct
excitation components are identified, with spins fluctuating along the c-axis,
perpendicular to the ordering direction in the ab-plane, and parallel to the
ordering direction. While the first two ""transverse"" components can be
described by a linear spin-wave theory with magnetic anisotropy and inter-layer
coupling, the third ""longitudinal"" component is generically incompatible with
the local moment picture. It points towards a contribution of itinerant
electrons to the magnetism already in the parent compound of this family of
Fe-based superconductors.",1309.7553v1
2013-12-04,Magnetic excitation in resonant inelastic x-ray scattering of Sr$_2$IrO$_4$: A localized spin picture,"We study the magnetic excitations in 5d transition-metal oxide Sr$_2$IrO$_4$
on the basis of the Heisenberg model with small anisotropic terms on a square
lattice. We calculate the correlation functions by using the Green's functions
in the spin-wave approximation. The spin waves are split into two modes with
slightly different energies due to the anisotropic terms. It is shown that the
spin correlation functions of the y and z components are composed of a single
peak corresponding to each mode. We analyze the process of resonant inelastic
x-ray scattering (RIXS) without relying on the fast collision approximation to
obtain the local scattering operator. The RIXS intensity is derived as a sum of
the correlation functions of the y and z spin components. We demonstrate that
the RIXS intensity as a function of energy shows two-peak structure brought
about by the two modes, which could be observed in the RIXS experiment.",1312.1071v2
2013-12-05,Doping asymmetry of superconductivity coexisting with antiferromagnetism in spin fluctuation theory,"We generalize the theory of Cooper pairing by spin excitations in the
metallic antiferromagnetic state to include situations with electron and/or
hole pockets. We show that Cooper pairing arises from transverse spin waves and
from gapped longitudinal spin fluctuations of comparable strength. However,
each of these interactions, projected on a particular symmetry of the
superconducting gap, acts primarily within one type of pocket. We find a
nodeless $d_{x^2-y^2}$-wave state is supported primarily by the longitudinal
fluctuations on the electron pockets, and both transverse and longitudinal
fluctuations support nodeless odd-parity spin singlet $p-$wave symmetry on the
hole pockets. Our results may be relevant to the asymmetry of the AF/SC
coexistence state in the cuprate phase diagram, as well as for the ""nodal gap""
observed recently for strongly underdoped cuprates.",1312.1507v2
2014-01-05,Magnon-Mediated Dzyaloshinskii-Moriya Torque in Homogeneous Ferromagnets,"In thin magnetic layers with structural inversion asymmetry and spin-orbit
coupling, a Dzyaloshinskii-Moriya interaction arises at the interface. When a
spin wave current ${\bf j}_m$ flows in a system with a homogeneous
magnetization {\bf m}, this interaction produces an effective field-like torque
on the form ${\bf T}_{\rm FL}\propto{\bf m}\times({\bf z}\times{\bf j}_m)$ as
well as a damping-like torque, ${\bf T}_{\rm DL}\propto{\bf m}\times[({\bf
z}\times{\bf j}_m)\times{\bf m}]$ in the presence of spin-wave relaxation
(${\bf z}$ is normal to the interface). These torques mediated by the magnon
flow can reorient the time-averaged magnetization direction and display a
number of similarities with the torques arising from the electron flow in a
magnetic two dimensional electron gas with Rashba spin-orbit coupling. This
magnon-mediated spin-orbit torque can be efficient in the case of magnons
driven by a thermal gradient.",1401.0883v2
2014-02-14,Spin-Precession: Breaking the Black Hole--Neutron Star Degeneracy,"Mergers of compact stellar remnant are prime targets for the LIGO/Virgo
gravitational wave detectors. One hopes that the gravitational wave signals
from these merger events can be used to study the mass and spin distribution of
stellar remnants, and provide information about black hole horizons and the
material properties of neutron stars. However, it has been suggested that
degeneracies in the way that the star's mass and spin are imprinted in the
waveforms may make it impossible to distinguish between black holes and neutron
stars. Here we show that the precession of the orbital plane due to spin-orbit
coupling breaks the mass-spin degeneracy, and allows us to distinguish between
standard neutron stars and alternative possibilities, such as black holes or
exotic neutron stars with large masses and spins.",1402.3581v2
2014-05-12,Quantum spin models for the SU(n)_1 Wess-Zumino-Witten model,"We propose 1D and 2D lattice wave functions constructed from the SU(n)_1
Wess-Zumino-Witten (WZW) model and derive their parent Hamiltonians. When all
spins in the lattice transform under SU(n) fundamental representations, we
obtain a two-body Hamiltonian in 1D, including the SU(n) Haldane-Shastry model
as a special case. In 2D, we show that the wave function converges to a class
of Halperin's multilayer fractional quantum Hall states and belongs to chiral
spin liquids. Our result reveals a hidden SU(n) symmetry for this class of
Halperin states. When the spins sit on bipartite lattices with alternating
fundamental and conjugate representations, we provide numerical evidence that
the state in 1D exhibits quantum criticality deviating from the expected
behaviors of the SU(n)_1 WZW model, while in 2D they are chiral spin liquids
being consistent with the prediction of the SU(n)_1 WZW model.",1405.2950v2
2014-10-21,Bose-Einstein condensation with spin-orbit coupling,"The recent realization of synthetic spin-orbit coupling represents an
outstanding achievement in the physics of ultracold quantum gases. In this
review we explore the properties of a spin-orbit-coupled Bose-Einstein
condensate with equal Rashba and Dresselhaus strengths. This system presents a
rich phase diagram, which exhibits a tricritical point separating a
zero-momentum phase, a spin-polarized plane-wave phase, and a stripe phase. In
the stripe phase translational invariance is spontaneously broken, in analogy
with supersolids. Spin-orbit coupling also strongly affects the dynamics of the
system. In particular, the excitation spectrum exhibits intriguing features,
including the suppression of the sound velocity, the emergence of a roton
minimum in the plane-wave phase, and the appearance of a double gapless band
structure in the stripe phase. Finally, we discuss a combined procedure to make
the stripes visible and stable, thus allowing for a direct experimental
detection.",1410.5526v2
2015-02-26,Magnetic phase diagram of an Fe monolayer on W(110) and Ta(110) surfaces based on ab initio calculations,"We present detailed investigations of the magnetic properties of an Fe
monolayer on W and Ta (110) surfaces based on the ab initio screened
Korringa-Kohn-Rostoker method. By calculating tensorial exchange coupling
coefficients, the ground states of the systems are determined using atomistic
spin dynamics simulations. Different types of ground states are found in the
systems as a function of relaxation of the Fe layer. In case of W(110)
substrate this is reflected in a reorientation of the easy axis from in-plane
to out-of-plane. For Ta(110) a switching appears from the ferromagnetic state
to a cycloidal spin spiral state, then to another spin spiral state with a
larger wave vector and, for large relaxations, a rotation of the normal vector
of the spin spiral is found. Classical Monte Carlo simulations indicate
temperature-induced transitions between the different magnetic phases observed
in the Fe/Ta(110) system. These phase transitions are analyzed both
quantitatively and qualitatively by finite-temperature spin wave theory.",1502.07510v2
2015-04-10,Spatially Resolved Detection of a Spin-Entanglement Wave in a Bose-Hubbard Chain,"Entanglement is an essential property of quantum many-body systems. However,
its local detection is challenging and was so far limited to spin degrees of
freedom in ion chains. Here we measure entanglement between the spins of atoms
located on two lattice sites in a one-dimensional Bose-Hubbard chain which
features both local spin- and particle-number fluctuations. Starting with an
initially localized spin impurity, we observe an outwards propagating
entanglement wave and show quantitatively how entanglement in the spin sector
rapidly decreases with increasing particle-number fluctuations in the chain.",1504.02582v1
2016-01-11,Bose-Fermi Mapping and Multi-Branch Spin Chain Model for Strongly Interacting Quantum Gases in One-Dimension: Dynamics and Collective Excitations,"We show that the wave function of a one dimensional spinor gas with contact
$s$-wave interaction, either bosonic or fermionic, can be mapped to the direct
product of the wave function of a spinless Fermi gas with short-range $p$-wave
interaction and that of a spin system governed by spin parity projection
operators. Applying this mapping to strongly interacting spinor gases, we
obtain a generalized spin chain model that captures both the static and
dynamics properties of the system. Using this spin chain model, we investigate
the breathing mode frequency and the quench dynamics of strongly interacting
harmonically trapped spinor gases.",1601.02556v2
2016-02-04,Investigation of the unidirectional spin heat conveyer effect in a 200nm thin Yttrium Iron Garnet film,"We have investigated the unidirectional spin wave heat conveyer effect in
sub-micron thick yttrium iron garnet (YIG) films using lock-in thermography
(LIT). Although the effect is small in thin layers this technique allows us to
observe asymmetric heat transport by magnons which leads to asymmetric
temperature profiles differing by several mK on both sides of the exciting
antenna, respectively. Comparison of Damon-Eshbach and backward volume modes
shows that the unidirectional heat flow is indeed due to non-reciprocal
spin-waves. Because of the finite linewidth, small asymmetries can still be
observed when only the uniform mode of ferromagnetic resonance is excited. The
latter is of extreme importance for example when measuring the inverse
spin-Hall effect because the temperature differences can result in
thermovoltages at the contacts. Because of the non-reciprocity these
thermovoltages reverse their sign with a reversal of the magnetic field which
is typically deemed the signature of the inverse spin-Hall voltage.",1602.01662v1
2016-04-22,Nanoscale control of heat and spin conductance in artificial spin chains,"We describe a mechanism to control energy and magnetisation currents in an
artificial spin-chain, consisting of an array of Permalloy nano-disks coupled
through the magneto-dipolar interaction. The chain is kept out of equilibrium
by two thermal baths with different temperatures connected to its ends, which
control the current propagation. Transport is enhanced by applying a uniform
radio frequency pump field resonating with some of the spin-wave modes of the
chain. Moreover, the two currents can be controlled independently by tuning the
static field applied on the chain. Thus we describe two effective means for the
independent control of coupled currents and the enhancement of thermal and
spin-wave conductivity in a realistic magnonics device, suggesting that similar
effects could be observed in a large class of nonlinear oscillating systems.",1604.06572v3
2016-09-12,Spin excitations in hole-overdoped iron-based superconductors,"Understanding the overall features of magnetic excitation is essential for
clarifying the mechanism of Cooper pair formation in iron-based
superconductors. In particular, clarifying the relationship between magnetism
and superconductivity is a central challenge because magnetism may play a key
role in their exotic superconductivity. BaFe2As2 is one of ideal systems for
such investigation because its superconductivity can be induced in several
ways, allowing a comparative examination. Here we report a study on the spin
fluctuations of the hole-overdoped iron-based superconductors Ba1-xKxFe2As2 (x
= 0.5 and 1.0; Tc = 36 K and 3.4 K, respectively) over the entire Brillouin
zone using inelastic neutron scattering. We find that their spin spectra
consist of spin wave and chimney-like dispersions. The chimney-like dispersion
can be attributed to the itinerant character of magnetism. The band width of
the spin wave-like dispersion is almost constant from the non-doped to
optimum-doped region, which is followed by a large reduction in the overdoped
region. This suggests that the superconductivity is suppressed by the reduction
of magnetic exchange couplings, indicating a strong relationship between
magnetism and superconductivity in iron-based superconductors.",1609.03335v1
2017-08-18,General treatment of quantum and classical spinning particles in external fields,"We develop the general theory of spinning particles with electric and
magnetic dipole moments moving in arbitrary electromagnetic, inertial and
gravitational fields. Both the quantum-mechanical and classical dynamics is
investigated. We start from the covariant Dirac equation extended to a
spin-${\frac 12}$ fermion with anomalous magnetic and electric dipole moments
and then perform the relativistic Foldy-Wouthuysen transformation. This
transformation allows us to obtain the quantum-mechanical equations of motion
for the physical operators in the Schr\""odinger form and to establish the
classical limit of relativistic quantum mechanics. The results obtained are
then compared to the general classical description of the spinning particle
interacting with electromagnetic, inertial and gravitational fields. The
complete agreement between the quantum mechanics and the classical theory is
proven in the general case. As an application of the results obtained, we
consider the dynamics of a spinning particle in a gravitational wave and
analyze the prospects of using the magnetic resonance setup to find possible
manifestations of the gravitational wave on spin.",1708.05601v2
2017-11-08,Collinear Spin-density-wave Order and Anisotropic Spin Fluctuations in the Frustrated $J_1$--$J_2$ Chain Magnet NaCuMoO$_4$(OH),"The phase diagram of the quasi-one-dimensional magnet NaCuMoO$_4$(OH) is
established through single-crystal NMR and heat-capacity measurements. The
$^{23}$Na and $^1$H NMR experiments indicate a spiral and a collinear
spin-density-wave (SDW) order below and above $B_c$ = 1.5-1.8 T, respectively.
Moreover, in the paramagnetic state above the SDW transition temperature, the
nuclear spin-lattice relaxation rate $1/T_1$ indicates anisotropic spin
fluctuations that have gapped excitations in the transverse spectrum but
gapless ones in the longitudinal spectrum. These static and dynamic properties
are well described by a theoretical model assuming quasi-one-dimensional chains
with competing ferromagnetic nearest-neighbor interactions $J_1$ and
antiferromagnetic next-nearest-neighbor interactions $J_2$ ($J_1$-$J_2$
chains). Because of the excellent crystal quality and good one dimensionality,
NaCuMoO$_4$(OH) is a promising compound to elucidate the unique physics of the
frustrated $J_1$-$J_2$ chain.",1711.03175v1
2017-12-07,Spin waves in coupled YIG/Co heterostructures,"We investigate yttrium iron garnet (YIG)/cobalt (Co) heterostructures using
broadband ferromagnetic resonance (FMR). We observe an efficient excitation of
perpendicular standing spin waves (PSSWs) in the YIG layer when the resonance
frequencies of the YIG PSSWs and the Co FMR line coincide. Avoided crossings of
YIG PSSWs and the Co FMR line are found and modeled using mutual spin pumping
and exchange torques. The excitation of PSSWs is suppressed by a thin aluminum
oxide (AlOx) interlayer but persists with a copper (Cu) interlayer, in
agreement with the proposed model.",1712.02561v1
2018-05-04,Spin wave effects in transport between a ferromagnet and a Weyl semimetal surface,"We experimentally investigate spin-polarized transport between a
ferromagnetic Ni electrode and a surface of Weyl semimetal, realized in a thick
WTe$_2$ single crystal. For highly-transparent Ni-WTe$_2$ planar junctions, we
observe non-Ohmic $dV/dI(I)$ behavior with an overall increase of differential
resistance $dV/dI$ with current bias, which is accomplished by current-induced
switchings. This behavior is inconsistent with trivial interface scattering,
but it is well known for spin-polarized transport with magnon emission. Thus,
we interpret the experimental results in terms of spin wave excitation in spin
textures in the WTe$_2$ topological surface states, which is supported by the
obtained magnetic field and temperature $dV/dI(I)$ dependencies.",1805.01838v2
2018-06-25,Quench dynamics of quantum spin models with flat bands of excitations,"We investigate the unitary evolution following a quantum quench in quantum
spin models possessing a (nearly) flat band in the linear excitation spectrum.
Inspired by the perspective offered by ensembles of individually trapped
Rydberg atoms, we focus on the paradigmatic trasverse-field Ising model on two
dimensional lattices featuring a flat band as a result of destructive
interference effects (Lieb and Kagom\'e lattice); or a nearly flat band due to
a strong energy mismatch among sublattices (triangular lattice). Making use of
linear spin-wave theory, we show that quantum quenches, equipped with
single-spin imaging, can directly reveal the spatially localized nature of the
dispersionless excitations, and their slow propagation or lack of propagation
altogether. Moreover we show that Fourier analysis applied to the post-quench
time evolution of wavevector-dependent quantities allows for the spectroscopic
reconstruction of the flat bands. Our results pave the way for future
experiments with Rydberg quantum simulators, which can extend our linear
spin-wave study to the fully nonlinear regime, characterized by the appearance
of dense, strongly interacting gases of dispersionless excitations.",1806.09722v1
2017-04-30,Angular Dependent Magnetization Dynamics of Kagome Artificial Spin Ice Incorporating Topological Defects,"We report angular-dependent spin-wave spectroscopy on kagome artificial spin
ice made of large arrays of interconnected Ni80Fe20 nanobars. Spectra taken in
saturated and disordered states exhibit a series of resonances with
characteristic in-plane angular dependencies. Micromagnetic simulations allow
us to interpret characteristic resonances of a two-step magnetization reversal
of the nanomagnets. The dynamic properties are consistent with topological
defects that are provoked via a magnetic field applied at specific angles.
Simulations that we performed on previously investigated kagome artificial spin
ice consisting of isolated nanobars show characteristic discrepancies in the
spin wave modes which we explain by the absence of vertices.",1705.00270v1
2014-06-26,High-Energy Damping by Particle-Hole Excitations in the Spin-Wave Spectrum of Iron-Based Superconductors,"Using a degenerate double-exchange model, we investigate the spin excitation
spectra of iron pnictides. The model consists of local spin moments on each Fe
site, as well as itinerant electrons from the degenerate $d_{xz}$ and $d_{yz}$
orbitals. The local moments interact with each other through antiferromagnetic
$J_{1}$-$J_{2}$ Heisenberg interactions, and they couple to the itinerant
electrons through a ferromagnetic Hund coupling. We employ the fermionic spinon
representation for the local moments and perform a generalized random-phase
approximation calculation on both spinons and itinerant electrons. We find that
in the $\left(\pi,0\right)$ magnetically-ordered state, the spin-wave
excitation at $\left(\pi,\pi\right)$ is pushed to a higher energy due to the
presence of itinerant electrons, which is consistent with a previous study
using the Holstein-Primakoff transformation. In the paramagnetic state, the
particle-hole continuum keeps the collective spin excitation near
$\left(\pi,\pi\right)$ at a higher energy even without any $C_{4}$ symmetry
breaking. The implications for recent high temperature neutron scattering
measurements will be discussed.",1406.6737v3
2014-06-29,Spin-Fluctuation-Driven Nematic Charge-Density-Wave in Cuprate Superconductors: Impact of Aslamazov-Larkin-Type Vertex Correction,"We present a microscopic derivation of the nematic charge-density-wave (CDW)
formation in cuprate superconductors based on the three-orbital d-p Hubbard
model, by introducing the vertex correction (VC) into the charge
susceptibility. The CDW instability at $q=(\Delta_{FS},0)$, $(0,\Delta_{FS})$
appears when the spin fluctuations are strong, due to the strong charge-spin
interference represented by the VC. Here, $\Delta_{FS}$ is the wavenumber
between the neighboring hot spots. The obtained spin-fluctuation-driven CDW is
expressed as the ""intra-unit-cell orbital order"" accompanied by the charge
transfer between the neighboring atomic orbitals, which is actually observed by
the STM measurements. We predict that the cuprate CDW and the nematic orbital
order in Fe-based superconductors are closely related spin-fluctuation-driven
phenomena.",1406.7520v3
2018-02-08,Direct observation of spin excitation anisotropy in the paramagnetic orthorhombic state of BaFe$_{2-x}$Ni$_x$As$_2$,"We use transport and inelastic neutron scattering measurements to investigate
single crystals of iron pnictide BaFe$_{2-x}$Ni$_{x}$As$_{2}$ ($x=0,0.03$),
which exhibit a tetragonal-to-orthorhombic structural transition at $T_s$ and
stripe antiferromagnetic order at $T_N$ ($T_s\geq T_N$).
  Using a tunable uniaxial pressure device, we detwin the crystals and study
their transport and spin excitation properties at antiferromagnetic wave vector
$S_1(1,0)$ and its 90$^\circ$ rotated wave vector $S_2(0,1)$ under different
pressure conditions. We find that uniaxial pressure necessary to detwin and
maintain single domain orthorhombic antiferromagnetic phase of
BaFe$_{2-x}$Ni$_{x}$As$_{2}$ induces resistivity and spin excitation anisotropy
at temperatures above zero pressure $T_s$. In uniaxial pressure-free detwinned
sample, spin excitation anisotropy between $S_1(1,0)$ and $S_2(0,1)$ first
appear in the paramagnetic orthorhombic phase below $T_s$. These results are
consistent with predictions of spin nematic theory, suggesting the absence of
structural or nematic phase transition above $T_s$ in iron pnictides.",1802.02713v1
2018-12-22,Atomic antiferromagnetic domain wall propagation beyond the relativistic limit,"We theoretically investigate the dynamics of atomic domain walls (DWs) in
antiferromagnets driven by a spin-orbit field. For a DW with the width of a few
lattice constants, we identify a Peierls-like pinning effect, with the
depinning field exponentially decaying with the DW width, so that a spin-orbit
field moderately larger than the threshold can drive the propagation of an
atomic DW in a step-wise manner. For a broad DW, the Peierls pinning is
negligibly small. However, the external spin-orbit field can induce a fast DW
propagation, accompanied by a significant shrinking of its width down to atomic
scales. Before stepping into the pinning region, noticeable spin waves are
emitted at the tail of the DW. The spin-wave emission event not only broadens
the effective width of the DW, but also pushes the DW velocity over the
magnonic barrier, which is generally believed to be the relativistic limit of
the DW speed. While the existing dynamic theory based on the continuum
approximation fails in the atomic scale, we develop an energy conversion theory
to interpret the DW dynamics beyond the relativistic limit.",1812.09540v1
2019-06-01,Polarized inelastic neutron scattering of non-reciprocal spin waves in MnSi,"We report spin-polarized inelastic neutron scattering of the dynamical
structure factor of the conical magnetic helix in the cubic chiral magnet MnSi.
We find that the spectral weight of spin-flip scattering processes is
concentrated on single branches for wavevector transfer parallel to the helix
axis as inferred from well-defined peaks in the neutron spectra. In contrast,
for wavevector transfers perpendicular to the helix the spectral weight is
distributed among different branches of the magnon band structure as reflected
in broader features of the spectra. Taking into account the effects of
instrumental resolution, our experimental results are in excellent quantitative
agreement with parameter-free theoretical predictions. Whereas the dispersion
of the spin waves in MnSi appears to be approximately reciprocal at low
energies and small applied fields, the associated spin-resolved spectral weight
displays a pronounced non-reciprocity that implies a distinct non-reciprocal
response in the limit of vanishing uniform magnetization at zero magnetic
field.",1906.00221v3
2019-06-27,Spin-polarized electronic surface states of Re(0001): an ab-initio investigation,"We study the electronic structure of the Re(0001) surface by means of
ab-initio techniques based on the Fully Relativistic (FR) Density Functional
Theory (DFT) and the Projector Augmented-Wave (PAW) method. We identify the
main surface states and resonances and study in detail their energy dispersion
along the main symmetry lines of the SBZ. Moreover, we discuss the effect of
spin-orbit coupling on the energy splittings and the spin-polarization of the
main surface states and resonances. Whenever possible, we compare the results
with previously studied heavy metals surfaces. We find empty resonances,
located below a gap similar to the L-gap of the (111) fcc surfaces, that have a
downward dispersion and cross the Fermi level, similarly to the recently
studied Os(0001) surface. Their spin polarization at the Fermi level is similar
to that predicted by the Rashba model, but the usual level crossing at
$\bar{\Gamma}$ is not found with our slab thickness. Moreover, for selected
states, we follow the spin polarization along the high symmetry lines,
discussing its behavior with respect to ${\bf k}_{\parallel}$, the wave-vector
parallel to the surface.",1906.12196v1
2016-03-10,Spin and quadrupolar orders in the spin-1 bilinear-biquadratic model for iron-based superconductors,"Motivated by recent experimental and theoretical progresses of the magnetic
properties of iron-based superconductors, we provide a comprehensive analysis
of the spin-1 bilinear-biquadratic (BBQ) model on the square lattice. Using
variational approach in the mean-field level, we identify the existence of
various magnetic phases, including conventional spin dipolar orderings (ferro-
or antiferromagnet), novel quadrupolar (spin nematic) orderings and mixed
dipolar-quadrupolar orderings. In contrast to the usual Heisenberg model, the
elementary excitations of the spin-1 BBQ model are described by the flavor-wave
theory within the SU(3) representation. By fitting the experimental spin-wave
dispersion, we determine the refined exchange couplings corresponding to the
collinear antiferromagnetic iron pnictides. We also present the dynamic
structure factors of both spin dipolar and quadrupolar components with
connections to the future experiments.",1603.03273v2
2016-03-21,Modified spin-wave theory and spin liquid behavior of cold bosons on an inhomogeneous triangular lattice,"Ultracold bosons in a triangular lattice are a promising candidate for
observing quantum spin liquid behavior. Here we investigate, for such system,
the role of a harmonic trap giving rise to an inhomogeneous density. We
construct a modified spin-wave theory for arbitrary filling, and predict the
breakdown of order for certain values of the lattice anisotropy. These regimes,
identified with the spin liquid phases, are found to be quite robust upon
changes in the filling factor. This result is backed by an exact
diagonalization study on a small lattice.",1603.06561v2
2017-02-16,Robust antiferromagnetic spin waves across the metal-insulator transition in hole-doped BaMn$_{2}$As$_{2}$,"BaMn$_{2}$As$_{2}$ is an antiferromagnetic insulator where a metal-insulator
transition occurs with hole doping via the substitution of Ba with K. The
metal-insulator transition causes only a small suppression of the N\'eel
temperature ($T_\mathrm{N}$) and the ordered moment, suggesting that doped
holes interact weakly with the Mn spin system. Powder inelastic neutron
scattering measurements were performed on three different powder samples of
Ba$_{1-x}$K$_{x}$Mn$_{2}$As$_{2}$ with $x=$0, 0.125 and 0.25 to study the
effect of hole doping and metallization on the spin dynamics of these
compounds. We compare the neutron intensities to a linear spin wave theory
approximation to the $J_{1}-J_{2}-J_{c}$ Heisenberg model. Hole doping is found
to introduce only minor modifications to the exchange energies and spin gap.
The changes observed in the exchange constants are consistent with the small
drop of $T_\mathrm{N}$ with doping.",1702.05082v1
2017-06-15,The low-temperature highly correlated quantum phase in the charge-density-wave 1T-TaS_2 compound,"A prototypical quasi-2D metallic compound, 1T-TaS_2 has been extensively
studied due to an intricate interplay between a Mott-insulating ground state
and a charge density-wave (CDW) order. In the low-temperature phase, 12 out of
13 Ta_{4+} 5\textit{d}-electrons form molecular orbitals in hexagonal
star-of-David patterns, leaving one 5\textit{d}-electron with \textit{S} = 1/2
spin free. This orphan quantum spin with a large spin-orbit interaction is
expected to form a highly correlated phase of its own. And it is most likely
that they will form some kind of a short-range order out of a strongly
spin-orbit coupled Hilbert space. In order to investigate the low-temperature
magnetic properties, we performed a series of measurements including neutron
scattering and muon experiments. The obtained data clearly indicate the
presence of the short-ranged phase and put the upper bound on ~ 0.4
\textit{\mu}_B for the size of the magnetic moment, consistent with the
orphan-spin scenario.",1706.04735v1
2019-03-03,Dynamical mode coupling and coherence in spin Hall nano-oscillator with perpendicular magnetic anisotropy,"We experimentally study the dynamical modes excited by spin current in Spin
Hall nano-oscillators based on the Pt/[Co/Ni] multilayers with perpendicular
magnetic anisotropy. Both propagating spin wave and localized solitonic modes
of the oscillation are achieved and controlled by varying the applied magnetic
field and current. At room temperature, the generation linewidth broadening
associated with mode hopping was observed at currents close to the transition
between different modes and in the mode coexistence regimes. The mode hopping
was suppressed at cryogenic temperatures, confirming that the coupling between
modes is mediated by thermal magnons. We also demonstrate that coherent
single-mode oscillations with linewidth of 5 MHz can be achieved without
applying external magnetic field. Our results provide insight into the
mechanisms controlling the dynamical coherence in nanomagnetic oscillators, and
guidance for optimizing their applications in spin wave-based electronics.",1903.00822v1
2019-03-07,Interplay between spin dynamics and crystal field in multiferroic compound HoMnO$_3$,"In the multiferroic hexagonal manganite HoMnO3, inelastic neutron scattering
and synchrotron based THz spectroscopy have been used to investigate the spin
waves associated to the Mn order together with Ho crystal field excitations.
While the Mn order sets in first below 80 K, a spin reorientation occurs below
37 K, a rare feature in the rare earth manganites. We show that severalHo
crystal field excitations are present in the same energy range as the magnons,
and that they are all affected by the spin reorientation. Moreover, several
anomalous features are observed in the excitations at low temperature. Our
analysis and calculations for the Mn spin waves and Ho crystal field
excitations support Mn-Ho coupling mechanisms as well as coupling to the
lattice affecting the dynamics.",1903.03009v1
2019-03-19,Giant localised spin-Peltier effect due to ultrafast domainwalls motion in antiferromagnetic metals,"Spin thermo-electric phenomena have attracted wide attention recently, e.g.
the Spin Peltier effect (SPE) heat generation by magnonic spin currents. Here
we find that the Spin Peltier ef-fect also manifests as a heat wave
accompanying fast moving magnetic textures. High speed andextreme magnetic
excitation localisation are paramount for efficient transfer of energy from
thespin-degrees of freedom to electrons and lattice. While satisfying both
conditions is subject to se-vere restrictions in ferromagnets, we find that
domain walls in antiferomagnets can overcome theselimitations due to their
potential ultrahigh mobility and ultra-small widths originating from the
rel-ativistic contraction. To illustrate our findings, we show that electric
current driven domain wallmotion in the antiferromagnetic metal Mn2Au can carry
a localised heat wave with the maximumamplitude up to 1 K . Since domain walls
are well localised nanoscale magnetic objects, this effecthas the potential for
nanoscale heating sensing and functionalities.",1903.08034v1
2020-09-21,Impurity induced magnetic ordering in Sr$_2$RuO$_4$,"Ti substituting Ru in Sr$_2$RuO$_4$ in small concentrations induces
incommensurate spin density wave order with a wave vector $\boldsymbol{Q}
\simeq (2 \pi /3, 2 \pi /3)$ corresponding to the nesting vector of two out of
three Fermi surface sheets. We consider a microscopic model for these two bands
and analyze the correlation effects leading to magnetic order through
non-magnetic Ti-doping. For this purpose we use a position dependent mean field
approximation for the microscopic model and a phenomenological Ginzburg-Landau
approach, which both deliver consistent results and allow us to examine the
inhomogeneous magnetic order. Spin-orbit coupling additionally leads to spin
currents around each impurity, which in combination with the magnetic
polarization produce a charge current pattern. This is also discussed within a
gauge field theory in both charge and spin channel. This spin-orbit coupling
effect causes an interesting modification of the magnetic structure, if
currents run through the system. Our findings allow a more detailed analysis of
the experimental data for Sr$_{2}$Ru$_{1-x}$Ti$_{x}$O$_{4}$. In particular, we
find that the available measurements are consistent with our theoretical
predictions.",2009.10086v2
2020-11-30,Spin-Wave Doppler Shift by Magnon Drag in Magnetic Insulators,"The Doppler shift of the quasiparticle dispersion by charge currents is
responsible for the critical supercurrents in superconductors and instabilities
of the magnetic ground state of metallic ferromagnets. Here we predict an
analogous effect in thin films of magnetic insulators in which microwaves
emitted by a proximity stripline generate coherent chiral spin currents that
cause a Doppler shift in the magnon dispersion. The spin-wave instability is
suppressed by magnon-magnon interactions that limit spin currents to values
close to but below the threshold for the instability. The spin current
limitations by the backaction of magnon currents on the magnetic order should
be considered as design parameters in magnonic devices.",2011.15008v2
2021-02-19,Critical Energy Dissipation in a Binary Superfluid Gas by a Moving Magnetic Obstacle,"We study the critical energy dissipation in an atomic superfluid gas with two
symmetric spin components by an oscillating magnetic obstacle. Above a certain
critical oscillation frequency, spin-wave excitations are generated by the
magnetic obstacle, demonstrating the spin superfluid behavior of the system.
When the obstacle is strong enough to cause density perturbations via local
saturation of spin polarization, half-quantum vortices (HQVs) are created for
higher oscillation frequencies, which reveals the characteristic evolution of
critical dissipative dynamics from spin-wave emission to HQV shedding. Critical
HQV shedding is further investigated using a pulsed linear motion of the
obstacle, and we identify two critical velocities to create HQVs with different
core magnetization.",2102.09826v2
2021-04-26,Interpretation of multiple solutions in fully iterative GF2 and GW schemes using local analysis of two-particle density matrices,"Due to non-linear structure, iterative Green's function methods can result in
multiple different solutions even for simple molecular systems. In contrast to
the wave-function methods, a detailed and careful analysis of such molecular
solutions was not performed before. In this work, we use two-particle density
matrices to investigate local spin and charge correlators that quantify the
charge-resonance and covalent characters of these solutions. When applied
within unrestricted orbital set, spin correlators elucidate the broken symmetry
of the solutions, containing necessary information for building effective
magnetic Hamiltonians. Based on GW and GF2 calculations of simple molecules and
transition metal complexes, we construct Heisenberg Hamiltonians,
four-spin-four-center corrections, as well as biquadratic spin-spin
interactions. These Hamiltonian parametrizations are compared to prior
wave-function calculations.",2104.12751v1
2016-11-17,Proposal for quantum many-body simulation and torsional matter-wave interferometry with a levitated nanodiamond,"Hybrid spin-mechanical systems have great potentials in sensing, macroscopic
quantum mechanics, and quantum information science. In order to induce strong
coupling between an electron spin and the center-of-mass motion of a mechanical
oscillator, a large magnetic gradient is usually required, which is difficult
to achieve. Here we show that strong coupling between the electron spin of a
nitrogen-vacancy (NV) center and the torsional vibration of an optically
levitated nanodiamond can be achieved in a uniform magnetic field. Thanks to
the uniform magnetic field, multiple spins can strongly couple to the torsional
vibration at the same time. We propose to utilize this new coupling mechanism
to realize the Lipkin-Meshkov-Glick (LMG) model by an ensemble of NV centers in
a levitated nanodiamond. The quantum phase transition in the LMG model and
finite number effects can be observed with this system. We also propose to
generate torsional superposition states and realize torsional matter-wave
interferometry with spin-torsional coupling.",1611.05599v2
2017-04-12,On the origin of magnetic anisotropy in two dimensional CrI$_3$,"The observation of ferromagnetic order in a monolayer of CrI$_3$ has been
recently reported, with a Curie temperature of 45 Kelvin and off-plane easy
axis. Here we study the origin of magnetic anisotropy, a necessary ingredient
to have magnetic order in two dimensions, combining two levels of modeling,
density functional calculations and spin model Hamiltonians. We find two
different contributions to the magnetic anisotropy of the material, both
favoring off-plane magnetization and contributing to open a gap in the spin
wave spectrum. First, ferromagnetic super-exchange across the $\simeq $ 90
degree Cr-I-Cr bonds, are anisotropic, due to the spin orbit interaction of the
ligand I atoms. Second, a much smaller contribution that comes from the single
ion anisotropy of the $S=3/2$ Cr atom. Our results permit to establish the XXZ
Hamiltonian, with a very small single ion anisotropy, as the adequate spin
model for this system. Using spin wave theory we estimate the Curie temperature
and we highlight the essential role played by the gap that magnetic anisotropy
induces on the magnon spectrum.",1704.03849v4
2019-01-17,Magnon Condensation in a Dense Nitrogen-Vacancy Spin Ensemble,"The feasibility of creating a Bose-Einstein condensate of magnons using a
dense ensemble of nitrogen-vacancy spin defects in diamond is investigated.
Through assessing a density-dependent spin exchange interaction strength and
the magnetic phase transition temperature ($T_c$) using the
Sherrington-Kirkpatrick model, the minimum temperature-dependent concentration
for magnetic self-ordering is estimated. For a randomly dispersed spin
ensemble, the calculated average exchange constant exceeds the average dipole
interaction strengths for concentrations approximately greater than 70 ppm,
while $T_c$ is estimated to exceed 10 mK beyond 90 ppm, reaching 300 K at a
concentration of approximately 450 ppm. On this basis, the existence of
dipole-exchange spin waves and their plane-wave dispersion is postulated and
estimated using a semiclassical magnetostatic description. This is discussed
along with a $T_c$-based estimate of the four-magnon scattering rate, which
indicates magnons and their condensation may be detectable in thin films for
concentrations greater than 90 ppm.",1901.05818v1
2019-04-08,Orbital Edelstein effect from density-wave order,"Coupling between charge and spin, and magnetoelectric effects more generally,
have been an area of great interest for several years, with the sought-after
ability to control magnetic degrees of freedom via charge currents serving as
an impetus. The orbital Edelstein effect (OEE) is a kinetic magnetoelectric
effect consisting of a bulk orbital magnetization induced by a charge current.
It is the orbital analogue of the spin Edelstein effect in spin-orbit coupled
materials, in which a charge current drives nonzero electron spin
magnetization. The OEE has recently been investigated in the context of Weyl
semimetals and Weyl metals. Motivated by these developments, we study a model
of electrons without spin-orbit coupling which exhibits line nodes that get
gapped out by via symmetry breaking due to an interaction-induced charge
density wave order. This model is shown to exhibit a temperature dependent OEE,
which appears due to symmetry reduction into a gyrotropic crystal class.",1904.04280v1
2019-04-15,Spin-Orbit-Torque Driven Propagating Spin Waves,"Spin-orbit torque (SOT) can drive sustained spin wave (SW) auto-oscillations
in a class of emerging microwave devices known as spin Hall nano-oscillators
(SHNOs), which have highly non-linear properties governing robust mutual
synchronization at frequencies directly amenable to high-speed neuromorphic
computing. However, all demonstrations have relied on localized SW modes
interacting through dipolar coupling and/or direct exchange. As nanomagnonics
requires propagating SWs for data transfer, and additional computational
functionality can be achieved using SW interference, SOT driven propagating SWs
would be highly advantageous. Here, we demonstrate how perpendicular magnetic
anisotropy can raise the frequency of SOT driven auto-oscillations in magnetic
nano-constrictions well above the SW gap, resulting in the efficient generation
of field and current tunable propagating SWs. Our demonstration greatly extends
the functionality and design freedom of SHNOs enabling long range SOT driven SW
propagation for nanomagnonics, SW logic, and neuro-morphic computing, directly
compatible with CMOS technology.",1904.06945v1
2019-04-19,Spin wave dispersion of 3d ferromagnets based on QSGW calculations,"We calculate transverse spin susceptibility in the linear response method
based on the ground states determined in the quasi-particle self-consistent
$GW$ (QSGW) method. Then we extract spin wave (SW) dispersions from the
susceptibility. We treat bcc Fe, hcp Co, fcc Ni, and B2-type FeCo. Because of
the better description of the independent-particle picture in QSGW, calculated
spin stiffness constants for Fe, Co, and Ni give much better agreement with
experiments in QSGW than that in the local density approximation (LDA), where
the stiffness for Ni in LDA is two times bigger than the experiment. For Co,
both acoustic and optical branches of SWs agree with the experiment. As for
FeCo, we have some discrrepancy between the spin stiffness in QSGW and that in
the experiment. We may need further theoretical and experimental investigations
on the discrepancy.",1904.09093v3
2019-08-14,Short-scale quantum kinetic theory including spin-orbit interactions,"We present a quantum kinetic theory for spin-$1/2$ particles, including the
spin-orbit interaction, retaining particle dispersive effects to all orders in
$\hbar$, based on a gauge-invariant Wigner transformation. Compared to previous
works, the spin-orbit interaction leads to a new term in the kinetic equation,
containing both the electric and magnetic fields. Like other models with
spin-orbit interactions, our model features ""hidden momentum"". As an example
application, we calculate the dispersion relation for linear electrostatic
waves in a magnetized plasma, and electromagnetic waves in a unmagnetized
plasma. In the former case, we compare the Landau damping due to spin-orbit
interactions to that due to the free current. We also discuss our model in
relation to previously published works.",1908.05131v1
2019-10-08,Metastable bound states of the quasi-bimagnetoexcitons in the lowest Landau levels approximation,"Four different spin structures of two electrons and of two holes situated on
the lowest Landau levels (LLLs) are taken into account to investigate possible
bound states of the two-dimensional magnetic biexciton formed of two
magnetoexcitons with opposite wave vectors and antiparallel dipole moments. The
singlet and triplet states of the spins of two electrons and of two holes
separately, as well as of two para- and two ortho-magnetoexcitons are
considered. The general expressions describing the binding energy of the bound
states and the normalization conditions characterized by the effective spin
parameter for the corresponding wave functions are derived. The most favorable
of the four considered spin configurations happened to be the triplet-triplet
spin structure of two electrons and of two holes. In its frame a metastable
bound state with activation barrier comparable with two ionization potentials
of the magnetoexciton is revealed .",1910.03930v1
2020-01-27,Acoustic ferromagnetic resonance and spin pumping induced by surface acoustic waves,"Voltage induced magnetization dynamics of magnetic thin films is a valuable
tool to study anisotropic fields, exchange couplings, magnetization damping and
spin pumping mechanism. A particularly well established technique is the
ferromagnetic resonance (FMR) generated by the coupling of microwave photons
and magnetization eigenmodes in the GHz range. Here we review the basic
concepts of the so-called acoustic ferromagnetic resonance technique (a-FMR)
induced by the coupling of surface acoustic waves (SAW) and magnetization of
thin films. Interestingly, additional to the benefits of the microwave excited
FMR technique, the coupling between SAW and magnetization also offers fertile
ground to study magnon-phonon and spin rotation couplings. We describe the
in-plane magnetic field angle dependence of the a-FMR by measuring the
absorption / transmission of SAW and the attenuation of SAW in the presence of
rotational motion of the lattice, and show the consequent generation of spin
current by acoustic spin pumping.",2001.09581v1
2020-05-06,Phase Shift in Skyrmion Crystals,"The skyrmion crystal is a periodic array of a swirling topological spin
texture. Since it is regarded as an interference pattern by multiple helical
spin density waves, the texture changes with the relative phases among the
constituent waves. Although the phase degree of freedom is relevant to not only
magnetism but also transport properties, its effect has not been elucidated
thus far. We here theoretically show that a phase shift can occur in the
skyrmion crystals to stabilize tetra-axial vortex crystals with staggered
scalar spin chirality. This leads to spontaneous breaking of the lattice
symmetry, which results in nonreciprocal transport phenomena even without the
relativistic spin-orbit coupling. We show that such a phase shift is driven by
long-range chirality interactions or thermal fluctuations in spin-charge
coupled systems.",2005.03168v1
2020-06-10,Quantum-Critical Spin-Density Waves in Iron-Selenide High-Tc Superconductors,"Hidden spin-density waves (hSDW) with Neel ordering vector (pi,pi) have been
proposed recently as parent groundstates to electron-doped iron-selenide
superconductors. Doping such groundstates can result in visible electron-type
Fermi surface pockets and faint hole-type Fermi surface pockets at the corner
of the folded Brillouin zone. A Cooper pair instability that alternates in sign
between the electron-type and the hole-type Fermi surfaces has recently been
predicted. The previous is due to the interaction of electrons and holes with
hidden spin fluctuations connected with hSDW order that is near a
quantum-critical point. Quantum criticality is tuned in by increasing the
strength of Hund's Rule from the hSDW state. We find that the exchange of
hidden spin fluctuations by electrons/holes in the critical hSDW state results
in asymptotic freedom. In particular, the strength of spin-flip interactions
becomes weaker and weaker on length scales that are shorter and shorter
compared to the range of hSDW order. We then argue that string states that
connect well-separated particle/hole excitations in the hSDW are robust. This
suggests a picture where the hole degrees of freedom mentioned previously are
confined.",2006.05680v1
2020-07-28,Variational wave functions for the spin-Peierls transition in the Su-Schrieffer-Heeger model with quantum phonons,"We introduce variational wave functions to evaluate the ground-state
properties of spin-phonon coupled systems described by the Su-Schrieffer-Heeger
model. Quantum spins and phonons are treated on equal footing within a Monte
Carlo sampling, and different regimes are investigated. We show that the
proposed variational Ansatz yields good agreement with previous density-matrix
renormalization group results in one dimension and is able to accurately
describe the spin-Peierls transition. This variational approach is neither
constrained by the magnetoelastic-coupling strength nor by the dimensionality
of the systems considered, thus allowing future investigations in more general
cases, which are relevant to spin-liquid and topological phases in two spatial
dimensions.",2007.14406v2
2021-01-20,Cubic spin-orbit coupling and anomalous Josephson effect in planar junctions,"Spin-orbit coupling in two-dimensional systems is usually characterized by
Rashba and Dresselhaus spin-orbit coupling (SOC) linear in the wave vector.
However, there is a growing class of materials which instead support dominant
SOC cubic in the wave vector (cSOC), while their superconducting properties
remain unexplored. By focusing on Josephson junctions in Zeeman field with
superconductors separated by a normal cSOC region, we reveal a strongly
anharmonic current-phase relation and complex spin structure. An experimental
cSOC tunability enables both tunable anomalous phase shift and supercurrent,
which flows even at the zero-phase difference in the junction. A fingerprint of
cSOC in Josephson junctions is the f-wave spin-triplet superconducting
correlations, important for superconducting spintronics and supporting Majorana
bound states.",2101.08272v2
2021-06-08,Spectral-fingerprinting: Microstate readout via remanence ferromagnetic resonance in artificial spin systems,"Artificial spin ices are magnetic metamaterials comprising
geometrically-tiled interacting nanomagnets. There is significant interest in
these systems for reconfigurable magnonics due to their vast microstate
landscape. Studies to-date have focused on the in-field GHz spin-wave response,
convoluting effects from applied field, nanofabrication-imperfections
('quenched disorder') and microstate-dependent dipolar field landscapes. Here,
we study artificial spin ices in pure and disordered microstates and evaluate
their zero-field spectra. Removing the applied field allows us to deconvolute
contributions to reversal dynamics and spin-wave spectra, directly measuring
the dipolar field landscape and quenched disorder. Mode-amplitude provides
population readout of nanomagnet magnetisation direction, and hence net
magnetisation as well as local vertex populations. We demonstrate
microstate-fingerprinting via distinct spectral-readout of three microstates
with identical (zero) magnetisation, supported by simulation. These results
establish remanence 'spectral-fingerprinting' as a rapid, scalable on-chip
readout of both magnetic state and nanoscale dipolar field texture, a critical
step in realising next-generation functional magnonic devices.",2106.04406v2
2021-06-18,Electronic and Magnetic Properties of Building Blocks of Mn and Fe Atomic Chains on Nb(110),"We present results for the electronic and magnetic structure of Mn and Fe
clusters on Nb(110) surface, focusing on building blocks of atomic chains as
possible realizations of topological superconductivity. The magnetic ground
states of the atomic dimers and most of the monatomic chains are determined by
the nearest-neighbor isotropic interaction. The dependence on the
crystallographic direction as well as on the atomic coordination number is
analyzed via an orbital decomposition of this isotropic interaction based on
the spin-cluster expansion and the difference in the local density of states
between ferromagnetic and antiferromagnetic configurations. A spin-spiral
ground state is obtained for Fe chains along the [$1\overline{1}0$] direction
as a consequence of the frustration of the isotropic interactions. Here, a flat
spin-spiral dispersion relation is identified, which can stabilize spin spirals
with various wave vectors together with the magnetic anisotropy. This may lead
to the observation of spin spirals of different wave vectors and chiralities in
longer chains instead of a unique ground state.",2106.09977v1
2021-09-06,Polarized solitons in higher-spin wave dark matter,"We first show that the effective non-relativistic theory of gravitationally
interacting, massive integer-spin fields (spin-$0$, $1$, and $2$ in particular)
is described by a $2s+1$ component Schr\""{o}dinger-Poisson action, where $s$ is
the spin of the field. We then construct $s+1$ distinct, gravitationally
supported solitons in this non-relativistic theory from identically polarized
plane waves. Such solitons are extremally polarized, with macroscopically large
spin, but no orbital angular momentum. These $s+1$ solitons form a basis set,
out of which partially polarized solitons can be constructed. All such solitons
are ground states, have a spherically symmetric energy density but not field
configurations. We discuss how solitons in higher-spin fields can be
distinguished from scalar solitons, and potential gravitational and
non-gravitational probes of them.",2109.04892v2
2021-12-03,Magnetic field-induced deformation of the spin-density wave microphases in Ca$_3$Co$_2$O$_6$,"The frustrated triangular Ising magnet Ca$_3$Co$_2$O$_6$ has long been known
for an intriguing combination of extremely slow spin dynamics and peculiar
magnetic orders, such as the evenly-spaced non-equilibrium metamagnetic
magnetization steps and the long-wavelength spin density wave (SDW) order, the
latter of which is essentially an emergent crystal of solitons. Recently, an
elaborate field-cooling protocol to bypass the low-field SDW phase was proposed
to overcome the extraordinarily long timescale of spin relaxation that impeded
previous experimental studies in equilibrium, which may point to a deep
connection between the low-temperature slow relaxation and the cooling process
passing through the low-field SDW phase. As the first step to elucidate the
conjectured connection, we investigate the magnetic field-induced deformation
of the SDW state and incommensurate-commensurate transitions, thereby mapping
out the equilibrium in-field phase diagram for a realistic three-dimensional
lattice spin model by using Monte Carlo simulations. We also discuss
Ginzburg-Landau theory that includes several Umklapp terms as well as an
effective sine-Gordon model, which can qualitatively explain the observed
magnetic field-induced deformation of the SDW microphases.",2112.01701v2
2022-01-31,Searching for mass-spin correlations in the population of gravitational-wave events: the GWTC-3 case study,"One fundamental goal of the newly born gravitational wave astronomy is
discovering the origin of the observed binary black hole mergers. Towards this
end, identifying features in the growing wealth of data may help in
distinguishing different formation pathways. While large uncertainties still
affect the binary formation models, spin-mass relations remain characteristic
features of specific classes of channels. By focusing on the effective inspiral
spin $\chi_\text{eff}$, the best reconstructed spin-related merger parameter,
we show that current GWTC-3 data support the hypothesis that a fraction of
events may display mass-spin correlations similar to one expected by dynamical
formation channels of either astrophysical or primordial nature. We quantify
the Bayesian evidence in favour of those models, which are substantially
preferred when compared to the Gaussian phenomenological model adopted to
describe the distribution of $\chi_\text{eff}$ in the recent LIGO/Virgo/KAGRA
population analyses.",2201.13098v2
2022-06-24,Ground state selection by magnon interactions in the fcc antiferromagnet,"We study the nearest-neighbor Heisenberg antiferromagnet on a face-centered
cubic lattice with arbitrary spin S. The model exhibits degenerate classical
ground states including two collinear structures AF1 and AF3 described by
different propagation vectors that are prime candidates for the quantum ground
state. We compute the energy for each of the two states as a function of S
using the spin-wave theory that includes magnon-magnon interaction in a
self-consistent way and the numerical coupled cluster method. Our results
unambiguously demonstrate that quantum fluctuations stabilize the AF1 state for
realistic values of spin. Transition to the harmonic spin-wave result, which
predicts the AF3 state, takes place only for S > 10. We also study quantum
renormalization of the magnon spectra for both states as a function of spin.",2206.12102v1
2022-09-01,\textit{Ab initio} study on spin fluctuations of itinerant kagome magnet FeSn,"Kagome antiferromagnetic metal FeSn has become an attracting platform for the
exploration of novel electronic states, such as topological Dirac states and
the formation of flat bands by localized electrons. Apart from the electronic
properties, Dirac magnons and flat magnon bands have also been proposed by
applying simplified Heisenberg models to kagome magnetic systems.Inelastic
neutron scattering studies on FeSn found well defined magnon dispersions at low
energies,but magnons at high energies are strongly dampled, which can not be
explained by localized spin models. In this paper, we utilize both linear spin
wave theory and time-dependent density functional perturbation theory to
investigate spin fluctuations of FeSn. Through the comparison of calculated
spin wave spectra and Stoner continuum, we explicitly show that the damping of
magnons at high energies are due to the Landau damping, and the appearance of
high energy optical-magnon like branches at the M and K point are resulted by
relatively low Stoner excitation intensity at those regions.",2209.00187v1
2022-09-23,Spin-texture topology in curved circuits driven by spin-orbit interactions,"Interferometry is a powerful technique used to extract valuable information
about the wave function of a system. In this work, we study the response of
spin carriers to the effective field textures developed in curved
one-dimensional interferometric circuits subject to the joint action of Rashba
and Dresselhaus spin-orbit interactions. By using a quantum network technique,
we establish that the interplay between these two non-Abelian fields and the
circuit's geometry modify the geometrical characteristics of the spinors,
particularly on square circuits, leading to the localisation of the electronic
wave function and the suppression of the quantum conductance. We propose a
topological interpretation by classifying the corresponding spin textures in
terms of winding numbers.",2209.11653v3
2022-11-23,Long-range order in the XY model on the honeycomb lattice,"Using the reflection positivity method we provide the rigorous proof of the
existence of long range magnetic order for the XY model on the honeycomb
lattice for large spins $S\ge 2$. This stays in contrast with the result
obtained using the {\it same} method but on the square lattice -- which gives a
stable long-range order for spins $S\ge 1$. We suggest that the difference
between these two cases stems from the enhanced quantum spin fluctuations on
the honeycomb lattice. Using linear spin-wave theory we show that the enhanced
fluctuations are due to the overall much higher kinetic energy of the spin
waves on the honeycomb lattice (with Dirac points) than on the square lattice
(with good nesting properties).",2211.13178v2
2022-12-08,Semiclassical analysis of Dirac fields on curved spacetime,"We present a semiclassical analysis for Dirac fields on an arbitrary
spacetime background and in the presence of a fixed electromagnetic field. Our
approach is based on a Wentzel-Kramers-Brillouin approximation, and the results
are analyzed at leading and next-to-leading order in the small expansion
parameter $\hbar$. Taking into account the spin-orbit coupling between the
internal and external degrees of freedom of wave packets, we derive effective
ray equations with spin-dependent terms. These equations describe the
gravitational spin Hall effect of localized Dirac wave packets. We treat both
massive and massless Dirac fields and show how a covariantly defined Berry
connection and the associated Berry curvature govern the semiclassical
dynamics. The gravitational spin Hall equations are shown to be particular
cases of the Mathisson-Papapetrou equations for spinning objects.",2212.04414v2
2023-03-03,Influence of spin on tunneling times in the super-relativistic regime,"For the relativistic tunneling effect described using Dirac's equation, in
[Phys. Rev. A 70, 052112 (2004)] the authors presented the deduction of a
general result that allows for the determination of the phase time (group
delay) as the sum of the particle dwell time inside a potential barrier and of
the self-interference delay associated with the incident and reflected wave
functions interaction. In this article, a mathematical model is derived through
a construction analogous to the proposal mentioned above, but based on an
alternative representation for Dirac's equation. This representation is similar
to the one introduced in [Found. Phys. 45, 1586 (2015)]. Thus, from the
application of this model in the study of the tunneling effect in the absence
of an external magnetic field, the influence of spin on the tunneling times is
described. More specifically, the tunneling time is obtained as the sum of the
dwell times inside the potential barrier for particles with spin up and spin
down and the self-interaction time associated with the incident and reflected
wave functions for particles with spin up.",2303.01873v2
2023-07-13,Tracking Berry curvature effect in molecular dynamics by ultrafast magnetic x-ray scattering,"The spin-dependent Berry force is a genuine effect of Berry curvature in
molecular dynamics, which can dramatically result in spatial spin separation
and change of reaction pathways. However, the way to probe the effect of Berry
force remains challenging, because the time-reversal (TR) symmetry required for
opposite Berry forces conflicts with TR symmetry breaking spin alignment needed
to observe the effect, and the net effect could be transient for a molecular
wave packet. We demonstrate that in molecular photodissociation, the
dissociation rates can be different for molecules with opposite initial spin
directions due to Berry force. We showcase that the spatially separated spin
density, which is transiently induced by Berry force as the molecular wave
packet passes through conical intersection, can be reconstructed from the
circular dichroism (CD) of ultrafast non-resonant magnetic x-ray scattering
using free electron lasers.",2307.06523v1
2023-10-26,Spin wave behavior of a novel hopfion-like chiral state in Co/Pt nanodiscs,"This work discusses the rich phase diagram of non-trivial chiral spin
textures in confined ferromagnetic/heavy-metal (FM/HM) bilayer nanomagnets of
circular cross-section. These spin textures are realized as a minimum-energy
ground state during an external bias field sweep for a range of nanomagnet's
diameter (d). Our study, based on micromagnetic simulations, has revealed a
novel Hopfion-like state which can be stabilized for a wide range of diameters
and external magnetic fields. We explored the dynamical characteristics of this
novel Hopfion-like state under a transient magnetic field applied along the
plane's perpendicular direction. Simulation results have demonstrated the
excitation of nonreciprocal spin wave (SW) modes for this novel chiral state,
in contrast to other stabilized chiral states. These modes are characterized as
breathing and quantized radial modes, which also exhibit hybridization with
azimuthal modes. The resonant SW modes have been used to demonstrate the
switching from a Hopfion-like state to a skyrmion within a few nanoseconds of
SW excitation. Furthermore, we establish a correlation between the behavior of
excited SW modes as a function of external magnetic field strength and
underlying chiral spin texture states.",2310.17460v1
2023-11-08,Time evolution of coherent wave propagation and spin relaxation in spin-orbit coupled systems,"We investigate, both numerically and analytically, the time evolution of a
particle in an initial plane wave state as it is subject to elastic scattering
in a two-dimensional disordered system with Rashba spin-orbit coupling (SOC).
In the analytic calculation, we treat the SOC non-perturbatively, and the
disorder perturbatively using the Diffuson and the Cooperon. We calculate the
time dependence of coherent backscattering (CBS) as a function of the strength
of the SOC. We identify weak and strong SOC regimes, and give the relevant time
and energy scales in each case. By studying the time dependence of the
anisotropy of the disorder-averaged momentum distribution we identify the spin
relaxation time. We find a crossover from D'yakonov-Perel' spin relaxation for
weak SOC to Elliot-Yafet like behaviour for strong SOC.",2311.04613v2
1996-10-31,Density Waves in a Transverse Electric Field,"In a quasi-one-dimensional conductor with an open Fermi surface, a Charge or
a Spin Density Wave phase can be destroyed by an electric field perpendicular
to the direction of high conductivity. This mechanism, due to the breakdown of
electron-hole symmetry, is very similar to the orbital destruction of
superconductivity by a magnetic field, due to time-reversal symmetry.",9611016v1
2000-12-22,Optical response in one dimensional Mott Insulators,"We study the optical response of a Mott Hubbard system in the framework of
the half--filled Extended Hubbard Model using the Density Matrix
Renormalization Group (DMRG) method. We discuss the appearance of excitonic
features inside the spectral gap as the system goes from the Spin Density Wave
(SDW) to the Charge Density Wave (CDW) phase.",0012443v1
2002-07-28,Sliding Density-Wave in Sr_{14}Cu_{24}O_{41} Ladder Compounds,"We used transport and Raman scattering measurements to identify the
insulating state of self-doped spin 1/2 two-leg ladders of Sr_{14}Cu_{24}O_{41}
as a weakly pinned, sliding density wave with non-linear conductivity and a
giant dielectric response that persists to remarkably high temperatures.",0207666v1
2002-12-20,Lockin to Weak Ferromagnetism in TbNi2B2C and ErNi2B2C,"This article describes a model in which ferromagnetism necessarily
accompanies a spin-density-wave lockin transition in the borocarbide structure
provided the commensurate phase wave vector satisfies Q = (m/n)a* with m even
and n odd. The results account for the magnetic properties of TbNi2B2C, and are
also possibly relevant also for those of ErNi2B2C.",0212535v1
2004-11-08,Integrable multi atom matter-radiation models without rotating wave approximation,"Interacting matter-radiation models close to physical systems are proposed,
which without rotating wave approximation and with matter-matter interactions
are Bethe ansatz solvable.
  This integrable system is constructed from the elliptic
  Gaudin model at high spin limit, where radiative excitation can be included
perturbatively.",0411166v1
1995-10-23,Newman-Penrose Formalism for Gravitational Shock Waves,"First order perturbations for the fields with spin on the background metric
of the gravitational shock waves are discussed. Applying the Newman -- Penrose
formalism, exact solutions of the perturbation equations are obtained. For
particle physics, this would be one approach to the problem of scattering
paticle at Planck energy.",9510043v1
2007-01-11,"Heun equation, Teukolsky equation, and type-D metrics","Starting with the whole class of type-D vacuum backgrounds with cosmological
constant we show that the separated Teukolsky equation for zero rest-mass
fields with spin $s=\pm 2$ (gravitational waves), $s=\pm 1$ (electromagnetic
waves) and $s=\pm 1/2$ (neutrinos) is an Heun equation in disguise.",0701064v2
1994-04-19,A Three Configurations Diquark Model for Baryons,"The wave functions in the diquark-quark model for baryons are modified to
take into account the effect of the different masses of the quarks in diquark
formation. A spatial wave function is introduced multiplying each flavour-spin
configuration in the quark-diquark model. Futhermore a numerical coefficient is
introduced which weighes the contribution of each configuration.",9404298v1
2001-07-10,"Parametric Resonance Amplification of Neutrino Oscillations in Electromagnetic Wave with Varying Amplitude and ""Castle Wall"" Magnetic Field","Within the Lorentz invariant formalizm for description of neutrino evolution
in electromagnetic fields and matter we consider neutrino spin oscillations in
the electromagnetic wave with varying amplitude and in ""castle wall"" magnetic
field. It is shown for the first time that the parametric resonances of
neutrino oscillations in such systems can occur.",0107109v1
1994-09-09,Chiral Fermions on Quantum Four-Spheres,"We construct wave functions and Dirac operator of spin $1/2$ fermions on
quantum four-spheres. The construction can be achieved by the q-deformed
differential calculus which is manifestly $SO(5)_q$ covariant. We evaluate the
engenvalue of the Dirac operator on wave functions of the spinors and show that
we can define the chiral fermions in such a way that the massless Dirac
operator anti-commutes with $\gamma_5$.",9409045v1
1999-12-31,Relativistic particle interaction with a weak electromagnetic field,"Schrodinger equation with two-component wave function which describes a
relativistic spin 1/2 particle in a weak electromagnetic field is obtained. In
the same approximation Schrodinger equation with traditional norm condition and
one-component wave function for a spinless particle is obtained as well. To
construct it Foldy-Wouthuysen procedure with the electron charge value as the
small parameter is used.",9912294v1
2007-12-19,New Class of Gravitational Wave Templates for Inspiralling Compact Binaries,"Compact binaries inspiralling along quasi-circular orbits are the most
plausible gravitational wave (GW) sources for the operational, planned and
proposed laser interferometers. We provide new class of restricted
post-Newtonian accurate GW templates for non-spinning compact binaries
inspiralling along PN accurate quasi-circular orbits. Arguments based on data
analysis, theoretical and astrophysical considerations are invoked to show why
these time-domain Taylor approximants should be interesting to various GW data
analysis communities.",0712.3236v1
2008-01-23,Observations of time delayed all-optical routing in a slow light regime,"We report an observation of a delayed all-optical routing/switching
phenomenon based on ultraslow group velocity of light via nondegenerate
four-wave mixing processes in a defected solid medium. Unlike previous
demonstrations of enhanced four-wave mixing processes using the slow light
effects, the present observation demonstrates a direct retrieval of the
resonant Raman-pulse excited spin coherence into photon coherence through
coherence conversion processes.",0801.3501v1
2008-02-11,Omega meson production in pp collisions with a polarized beam,"Model independent formulae are derived for the beam analyzing power $A_y$ and
beam to meson spin transfers in $pp \to pp \omega$ taking into consideration
all the six threshold partial wave amplitudes covering the $Ss, Sp$ and $Ps$
channels. Attention is also focussed on the empirical determination of the
lowest three partial wave amplitudes $f_1, f_2, f_3$ without any discrete
ambiguities.",0802.1474v1
2008-08-22,Kinks in a non-linear massive sigma model,"We describe the kink solitary waves of a massive non-linear sigma model with
an ${\mathbb S}^2$ sphere as the target manifold. Our solutions form a moduli
space of non-relativistic solitary waves in the long wavelength limit of
ferromagnetic linear spin chains.",0808.3052v1
2008-12-18,Macroscopic quantum effects generated by the acoustic wave in a molecular magnet,"We have shown that the size of the magnetization step due to resonant spin
tunneling in a molecular magnet can be strongly affected by sound. The
transverse acoustic wave can also generate macroscopic quantum beats of the
magnetization during the field sweep.",0812.3590v1
2012-08-30,Free from spurious solutions integral equation for three-magnon bound states in 1D XXZ ferromagnet,"A new integral equation for three-magnon bound states in XXZ spin chain is
suggested. Unlike the one presented by C. K. Majumdar about 40 years ago this
equation does not have spurious solutions. Such an advantage is a result of
decomposition of the wave function in the Bloch basis rather than in the basis
of flat waves.",1208.6177v1
2014-07-22,Decoding the final state in binary black hole mergers,"We demonstrate that in binary black hole mergers there is a direct
correlation between the frequency of the gravitational wave at peak amplitude
and the mass and spin of the final black hole. This correlation could
potentially assist with the analysis of gravitational wave observations from
binary black hole mergers.",1407.5989v1
2022-09-28,"Wave equations in conformally separable, accreting, rotating black holes","The Teukolsky wave equations governing fields of spin 0, $\tfrac{1}{2}$, 1,
$\tfrac{3}{2}$, and 2 are generalized to the case of conformally separable
solutions for accreting, rotating black holes.",2209.14752v2
2023-09-30,Multibaryon configurations in a simple chromomagnetic model,"In this work, we study the multibaryon configurations in a simple
chromomagnetic model. We first construct the wave function of the multibaryon
states using the multiquark configuration. We consider all possible quantum
numbers assuming the spatial part of the wave function to be totally symmetric.
Then, we calculate the color-spin factors for tetrabaryons, pentabaryons and
hexabaryons in the flavor SU(3) breaking case.",2310.00383v1
2021-08-14,"Relativistic Mechanics Theory for Electrons that Exhibits Spin, Zitterbewegung, Superposition and Produces Dirac's Wave Equation","A neo-classical relativistic mechanics theory is presented where the spin of
an electron is a natural part of its space-time path as a point particle. The
fourth-order equation of motion corresponds to the same Lagrangian function in
proper time as in special relativity except for an additional spin energy term.
The total motion can be decomposed into a sum of a local spin motion about a
point and a global motion of this point, called the spin center. The global
motion is sub-luminal and obeys Newton's second law in proper time, the time
for a clock fixed at the spin center, while the total motion occurs at the
speed of light c, consistent with the eigenvalues of Dirac's velocity operators
having magnitude c. The local spin motion corresponds to Schr\""odinger's
zitterbewegung and is a perpetual motion, which for a free electron has a
circular path in the spin-center frame. In an electro-magnetic field, this spin
motion generates magnetic and electric dipole energies through the Lorentz
force on the electron's point charge. The corresponding electric dipole energy
is consistent with the spin-orbit coupling term in the corrected Pauli
non-relativistic Hamiltonian but the magnetic dipole energy is one half of that
in Dirac's theory. By defining a spin tensor as the angular momentum of the
electron's total motion about its spin center, the fundamental equations of
motion can be re-written in an identical form to those of the Barut-Zanghi
electron theory. These equations of motion can then be expressed using
operators applied to a state function of proper time satisfying a
Dirac-Schr\""odinger spinor equation. The operators produce dynamic variables
without any probability implications. For the free electron, the state function
satisfies Dirac's relativistic wave equation when the Lorentz transformation is
applied to express proper time in terms of an observer's space-time
coordinates.",2108.07267v3
2016-11-03,Parameter estimation for heavy binary-black holes with networks of second-generation gravitational-wave detectors,"The era of gravitational-wave astronomy has started with the discovery of the
binary black hole coalescences (BBH) GW150914 and GW151226 by the LIGO
instruments. These systems allowed for the first direct measurement of masses
and spins of black holes. The component masses in each of the systems have been
estimated with uncertainties of over 10\%, with only weak constraints on the
spin magnitude and orientation. In this paper we show how these uncertainties
will be typical for this type of source when using advanced detectors. Focusing
in particular on heavy BBH of masses similar to GW150914, we find that typical
uncertainties in the estimation of the source-frame component masses will be
around 40\%. We also find that for most events the magnitude of the component
spins will be estimated poorly: for only 10\% of the systems the uncertainties
in the spin magnitude of the primary (secondary) BH will be below 0.7 (0.8).
Conversely, the effective spin along the angular momentum can be estimated more
precisely than either spins, with uncertainties below 0.16 for 10\% of the
systems. We also quantify how often large or negligible primary spins can be
excluded, and how often the sign of the effective spin can be measured. We show
how the angle between the spin and the orbital angular momentum can only seldom
be measured with uncertainties below 60$^\circ$. We then investigate how the
measurement of spin parameters depends on the inclination angle and the total
mass of the source. We find that when precession is present, uncertainties are
smaller for systems observed close to edge-on. Contrarily to what happens for
low-mass, inspiral dominated, sources, for heavy BBH we find that large spins
aligned with the orbital angular momentum can be measured with small
uncertainty. We also show how spin uncertainties increase with the total mass.
Finally...",1611.01122v4
1999-10-26,Spin dynamics simulations of the magnetic dynamics of RbMnF$_3$ and direct comparison with experiment,"Spin-dynamics techniques have been used to perform large-scale simulations of
the dynamic behavior of the classical Heisenberg antiferromagnet in simple
cubic lattices with linear sizes $L\leq 60$. This system is widely recognized
as an appropriate model for the magnetic properties of RbMnF$_3$.
Time-evolutions of spin configurations were determined numerically from coupled
equations of motion for individual spins using a new algorithm implemented by
Krech {\it etal}, which is based on fourth-order Suzuki-Trotter decompositions
of exponential operators. The dynamic structure factor was calculated from the
space- and time-displaced spin-spin correlation function. The crossover from
hydrodynamic to critical behavior of the dispersion curve and spin-wave
half-width was studied as the temperature was increased towards the critical
temperature. The dynamic critical exponent was estimated to be $z=(1.43\pm
0.03)$, which is slightly lower than the dynamic scaling prediction, but in
good agreement with a recent experimental value. Direct, quantitative
comparisons of both the dispersion curve and the lineshapes obtained from our
simulations with very recent experimental results for RbMnF$_3$ are presented.",9910429v1
1999-12-20,Spin dynamics simulations of excitations and critical dynamics in RbMnF_3,"Spin-dynamics simulations have been used to investigate the dynamic behavior
of RbMnF_3, treating it as a classical Heisenberg antiferromagnet on a simple
cubic lattice. Time-evolutions of spin configurations were determined
numerically from coupled equations of motion for individual spins using a new
algorithm which is based on Suzuki-Trotter decompositions of exponential
operators. The dynamic structure factor was calculated from the space- and
time-displaced spin-spin correlation function. The crossover from hydrodynamic
to critical behavior of the dispersion curve and spin-wave half-width was
studied as the temperature was increased towards the critical value. The
dynamic critical exponent was estimated to be z=(1.43\pm 0.03), which is
slightly lower than the dynamic scaling prediction, but in good agreement with
a recent experimental value. Comparisons are made of both the dispersion curve
and the lineshapes obtained from our simulations with very recent experimental
results for RbMnF_3 are presented.",9912374v1
2001-04-07,The simulation of the spin ground states of the coulomb clusters in a broad 2D parabolic well,"By variational Monte-Carlo method developed Ceperley et al. for the
simulation of fermi systems in macroscopic confining potential well we simulate
various spin ground states of the coulomb clusters with 2,3 and 4 particles in
a broad two-dimensional (2D) parabolic well. In this method quantum state
numbers determining the variational wave function are not the numbers of well
quantum states but numbers of the equilibrium spatial positions of particles
that give a minimum of the system potential energy. The ground states with
parallel, antiparallel spins and as well, as bose state are simulated. For the
cluster with three particles it is also simulated the state when two particles
have one direction of spin and third opposite. The simulation shows that
clusters with parallel spins have lower ground state energy than clusters with
other spin configurations and bose state. That reminds a Hund's rule in atomic
physics when in not full filled atomic shells electrons prefer to have a state
with parallel spins.",0104125v1
2001-07-12,Neutron scattering study of dipolar spin ice Ho_2Sn_2O_7: Frustrated pyrochlore magnet,"By means of neutron scattering techniques we have investigated the frustrated
pyrochlore magnet Ho_2Sn_2O_7, which was found to show a ferromagnetic spin-ice
behavior below T \simeq 1.4 K by susceptibility measurements. High-resolution
powder-neutron-diffraction shows no detectable disorder of the lattice, which
implies appearance of a random magnetic state solely by frustrated geometry,
i.e., the corner sharing tetrahedra. Magnetic inelastic-scattering spectra show
that Ho magnetic moments behave as an Ising spin system at low temperatures,
and that the spin fluctuation has static character. The system remains in a
short-range ordered state down to T = 0.4 K. By analyzing the wave-number
dependence of the magnetic scattering using a mean field theory, it is
clarified that the Ising spins interact via the dipolar interaction. Therefore
we conclude that Ho_2Sn_2O_7 belongs to the dipolar-spin-ice family. Slow spin
dynamics is exhibited as thermal hysteresis and time dependence of the magnetic
scattering.",0107278v2
2002-03-07,Nuclear spin relaxation in integral and fractional quantum Hall systems,"We report on the numerical study of the relaxation rates of nuclear spins
coupled through the hyperfine interaction to a two dimensional electron gas
(2DEG) at magnetic fields corresponding to both fractional and integral Landau
level (LL) fillings nu. The Hamiltonians of up to 20 interacting electrons are
diagonalized exactly in the spherical geometry, neglecting finite layer width,
disorder, and LL mixing. The spectral functions tau^-1(E) describing response
of the 2DEG to the reversal of an embedded localized spin are calculated. In a
(locally) incompressible nu=1 or 1/3 state, the finite Coulomb energy of short
spin waves, together with the small nuclear Zeeman energy, prevent nuclear spin
relaxation even in the limit of vanishing electron Zeeman energy E_Z. However,
we find that the nuclear spins can couple to the internal excitations of mobile
finite-size skyrmions that appear in the 2DEG at sufficiently low E_Z and at nu
slightly different from 1 or 1/3. The experimentally observed dependence of
nuclear spin relaxation rate on E_Z and nu is qualitatively explained in terms
of the occurrence of skyrmions and antiskyrmions of various topological charge.",0203160v2
2002-04-18,Spin-current modulation and square-wave transmission through periodically stubbed electron waveguides,"Ballistic spin transport through waveguides, with symmetric or asymmetric
double stubs attached to them periodically, is studied systematically in the
presence of a weak spin-orbit coupling that makes the electrons precess. By an
appropriate choice of the waveguide length and of the stub parameters injected
spin-polarized electrons can be blocked completely and the transmission shows a
periodic and nearly square-type behavior, with values 1 and 0, with wide gaps
when only one mode is allowed to propagate in the waveguide. A similar behavior
is possible for a certain range of the stub parameters even when two-modes can
propagate in the waveguide and the conductance is doubled. Such a structure is
a good candidate for establishing a realistic spin transistor. A further
modulation of the spin current can be achieved by inserting defects in a
finite-number stub superlattice. Finite-temperature effects on the spin
conductance are also considered.",0204415v1
2002-09-12,Spin-depedent transmission of holes through periodically modulated diluted magnetic semiconductor waveguides,"We study spin transport of holes through stubless or stubbed waveguides
modulated periodically by diluted magnetic semiconductor (DMS) sections of
width b1 . Injected holes of up (down) spin feel a periodically modulated
barrier (well) potential in the DMS sections and have different transmission
(T) coefficients. T oscillates with b1 for spin-down and decreases fast for
spin-up holes while the relative polarization Pr depends nearly periodically on
the stub height. Using asymmetric stubs leads to a nearly square-wave pattern
in T and to wide plateaus in Pr . T oscillates with the length between the DMS
sections. With two DMS sections per unit, T shows periodically wide gaps for
spin-down holes when a DMS width is varied. The results can be used to create
efficient spin filters.",0209294v1
2003-11-07,Electron spin dynamics in quantum dots and related nanostructures due to hyperfine interaction with nuclei,"We review and summarize recent theoretical and experimental work on electron
spin dynamics in quantum dots and related nanostructures due to hyperfine
interaction with surrounding nuclear spins. This topic is of particular
interest with respect to several proposals for quantum information processing
in solid state systems. Specifically, we investigate the hyperfine interaction
of an electron spin confined in a quantum dot in an s-type conduction band with
the nuclear spins in the dot. This interaction is proportional to the square
modulus of the electron wave function at the location of each nucleus leading
to an inhomogeneous coupling, i.e. nuclei in different locations are coupled
with different strength. In the case of an initially fully polarized nuclear
spin system an exact analytical solution for the spin dynamics can be found.
For not completely polarized nuclei, approximation-free results can only be
obtained numerically in sufficiently small systems. We compare these exact
results with findings from several approximation strategies.",0311159v1
2004-06-07,Absence of long-range order in a spin-half Heisenberg antiferromagnet on the stacked kagome lattice,"We study the ground state of a spin-half Heisenberg antiferromagnet on the
stacked kagome lattice by using a spin-rotation-invariant Green's-function
method. Since the pure two-dimensional kagome antiferromagnet is most likely a
magnetically disordered quantum spin liquid, we investigate the question
whether the coupling of kagome layers in a stacked three-dimensional system may
lead to a magnetically ordered ground state. We present spin-spin correlation
functions and correlation lengths. For comparison we apply also linear spin
wave theory. Our results provide strong evidence that the system remains
short-range ordered independent of the sign and the strength of the interlayer
coupling.",0406162v2
2005-12-29,Current-induced magnetization dynamics in disordered itinerant ferromagnets,"Current-driven magnetization dynamics in ferromagnetic metals are studied in
a self-consistent adiabatic local-density approximation in the presence of
spin-conserving and spin-dephasing impurity scattering. Based on a quantum
kinetic equation, we derive Gilbert damping and spin-transfer torques entering
the Landau-Lifshitz equation to linear order in frequency and wave vector.
Gilbert damping and a current-driven dissipative torque scale identically and
compete, with the result that a steady current-driven domain-wall motion is
insensitive to spin dephasing in the limit of weak ferromagnetism. A uniform
magnetization is found to be much more stable against spin torques in the
itinerant than in the \textit{s}-\textit{d} model for ferromagnetism. A dynamic
spin-transfer torque reminiscent of the spin pumping in multilayers is
identified and shown to govern the current-induced domain-wall distortion.",0512715v4
2006-02-20,Exact Landau Levels in Two-Dimensional Electron Systems with Rashba and Dresselhaus Spin-Orbit Interactions in a Perpendicular Magnetic Field,"We study a two-dimensional electron system in the presence of both Rashba and
Dresselhaus spin-orbit interactions in a perpendicular magnetic field. Defining
two suitable boson operators and using the unitary transformations we are able
to obtain the exact Landau levels in the range of all the parameters. When the
strengths of the Rashba and Dresselhaus spin-orbit interactions are equal, a
new analytical solution for the vanishing Zeeman energy is found, where the
orbital and spin wave functions of electron are separated. It is also shown
that in this case the Zeeman and spin-orbit splittings are independent of the
Landau level index $n$. Due to the Zeeman energy, new crossing between the
eigenstates $|n, k, s=1, \sigma>$ and $|n+1, k, s^\prime =-1, \sigma^\prime>$
is produced at certain magnetic field for larger Rashba spin-orbit coupling.
This degeneracy leads to a resonant spin Hall conductance if it happens at the
Fermi level.",0602473v1
2006-08-16,"Influence of subband mixing, due to spin-orbit interaction, on the transmission through periodically modulated waveguides","Ballistic spin transport, through periodically stubbed waveguides, is studied
in the presence of a weak spin-orbit interaction (SOI) and the resulting
subband mixing. By an appropriate choice of the waveguide length and of the
stub parameters injected spin-polarized electrons can be blocked completely and
the transmission shows a periodic and nearly square-wave pattern with wide gaps
when only one mode is allowed to propagate in the waveguide. Relative to the
case when subband mixing is neglected, the transmission changes drastically as
a function of the incident electron energy or of the stub height, as it
exhibits new peaks or dips, but remains robust as a function of the stubs'
degree of asymmetry. Varying the strength of the SOI parameter changes the
relative contribution to the total transmission or conductance of the spin-up
and spin-down states. The structure considered is a reasonable candidate for
establishing a spin transistor.",0608371v1
2007-01-21,Rashba quantum wire: exact solution and ballistic transport,"The effect of Rashba spin-orbit interaction in quantum wires with hard-wall
boundaries is discussed. The exact wave function and eigenvalue equation are
worked out pointing out the mixing between the spin and spatial parts. The
spectral properties are also studied within the perturbation theory with
respect to the strength of the spin-orbit interaction and diagonalization
procedure. A comparison is done with the results of a simple model, the
two-band model, that takes account only of the first two sub-bands of the wire.
Finally, the transport properties within the ballistic regime are analytically
calculated for the two-band model and through a tight-binding Green function
for the entire system. Single and double interfaces separating regions with
different strengths of spin-orbit interaction are analyzed injecting carriers
into the first and the second sub-band. It is shown that in the case of a
single interface the spin polarization in the Rashba region is different from
zero, and in the case of two interfaces the spin polarization shows
oscillations due to spin selective bound states.",0701508v2
1994-07-08,The Spin Structure of the Proton in a Non-relativistic Quark Model,"The spin structure of the proton is investigated in the framework of an
extended quark potential model which in addition to the conventional
$3q$--structure also takes into account $(3q)(q\bar q)$--admixtures in the
proton wave function. For reasons of parity such admixtures contain an odd
orbital angular momentum thus allowing the proton spin to be shared among quark
spins and orbital angular momenta. We show that only certain admixtures are
suited for a significant reduction of the quark spin content of the proton as
suggested by the EMC--result. Within a Hamiltonian model quark spin
contributions to the proton spin down to $0.5$ can be reproduced easily.",9407258v1
1996-08-27,Spin Factor in Path Integral Representation for Dirac Propagator in External Fields,"We study the spin factor problem both in $3+1$ and $2+1$ dimensions which are
essentially different for spin factor construction. Doing all Grassmann
integrations in the corresponding path integral representations for Dirac
propagator we get representations with spin factor in arbitrary external field.
Thus, the propagator appears to be presented by means of bosonic path integral
only. In $3+1$ dimensions we present a simple derivation of spin factor
avoiding some unnecessary steps in the original brief letter (Gitman,
Shvartsman, Phys. Lett. {\bf B318} (1993) 122) which themselves need some
additional justification. In this way the meaning of the surprising possibility
of complete integration over Grassmann variables gets clear. In $2+1$
dimensions the derivation of the spin factor is completely original. Then we
use the representations with spin factor for calculations of the propagator in
some configurations of external fields. Namely, in constant uniform
electromagnetic field and in its combination with a plane wave field.",9608179v1
2000-12-30,"(1/2,1/2) Representation space: An ab initio construct","A careful ab initio construction of the finite-mass (1/2,1/2) representation
space of the Lorentz group reveals it to be a spin-parity multiplet. In
general, it does not lend itself to a single-spin interpretation. We find that
the (1/2,1/2) representation space for massive particles naturally bifurcates
into a triplet and a singlet of opposite relative intrinsic parties. The
text-book separation into spin one and spin zero states occurs only for certain
limited kinematical settings. We construct a wave equation for the (1/2,1/2)
multiplet, and show that the particles and antiparticles in this representation
space do not carry a definite spin but only a definite relative intrinsic
parity. In general, both spin one and spin zero are covariantly inseparable
inhabitants of massive vector fields. This last observation suggests that
scalar particles, such as the Higgs, are natural inhabitants of massive
(1/2,1/2) representation space.",0101009v2
1994-07-01,"Relativistic treatment of spin-transfer observables in quasielastic $(\vec{\bf p},\vec{\bf n})$ scattering","We calculate all spin-transfer observables for the quasielastic
$(\vec{p},\vec{n})$ reaction in a relativistic plane-wave impulse
approximation. The nuclear-structure information is contained in a large set of
nuclear-response functions that are computed in nuclear matter using a
relativistic random-phase approximation to the Walecka model. A reduced value
of the nucleon mass in the medium induces important dynamical changes in the
residual isovector interaction relative to its nonrelativistic counterpart. As
a result, good agreement is found for all spin observables --- including the
spin-longitudinal to spin-transverse ratio --- when compared to the original
($q=1.72$~fm$^{-1}$) NTOF experiment. In contrast, the spin-longitudinal to
spin-transverse ratio is underpredicted at $q=1.2$~fm$^{-1}$ and overpredicted
at $q=2.5$~fm$^{-1}$. We comment on the role of distortions as a possible
solution to this discrepancy.",9407001v1
2002-02-01,Spin Solitons and Quantum Control of Spin Chain Dynamics,"Experiments in coherent spectroscopy correspond to control of quantum
mechanical ensembles guiding them from initial to final target states by
unitary transformations. The control inputs (pulse sequences) that accomplish
these unitary transformations should take as little time as possible so as to
minimize the effects of relaxation and to optimize the sensitivity of the
experiments. Here, we present a radically different and generally applicable
approach to efficient control of dynamics in spin chains of arbitrary length.
The approach relies on the creation of localized spin waves, ``spin solitons'',
and efficient propagation of these soliton states through the spin chain. The
methods presented are expected to find immediate applications in control of
spin dynamics in coherent spectroscopy and quantum information processing.",0202013v2
2007-01-12,Non-Abelian gauge field theory of the spin-orbit interaction and a perfect spin filter,"We point out that the Rashba and Dresselhaus spin-orbit interactions in two
dimensions can be regarded as a Yang-Mills non-Abelian gauge field. The
physical field generated by the gauge field gives the electron wave function a
spin-dependent phase which is frequently called the Aharonov-Casher phase.
Applying on an AB ring this non-Abelian field together with the usual vector
potential, we can make the interference condition completely destructive for
one component of the spin while completely constructive for the other component
of the spin over the entire energy range. This enables us to construct a
perfect spin filter.",0701076v1
1994-11-02,Spin pseudo-gap and interplane coupling in Y_2Ba_4Cu_7O_{15}: a ^{63}Cu nuclear spin-spin relaxation study,"We report measurements of the Gaussian contribution, T_{2G}, to the plane
^{63}Cu nuclear spin--spin relaxation time in the YBa_2Cu_3O_7 and YBa_2Cu_4O_8
blocks of normal and superconducting Y_2Ba_4Cu_7O_{15}. The data confirm our
previous results that adjacent CuO_2 planes have different doping levels and
that these planes are strongly coupled. -- The static spin susceptibility at
the anti-ferromagnetic wave vector exhibits a Curie--Weiss like temperature
dependence in the normal state. -- The Y_2Ba_4Cu_7O_{15} data are incompatible
with a phase diagram based on a single CuO_2 plane theory and suggest that the
appearance of a spin gap implies interplane coupling. Additional data for
YBa_2Cu_4O_8 and YBa_2Cu_3O_{6.982} are in accord with the single plane theory.
-- The temperature dependence of T_{2G,ind} below T_c excludes isotropic s-wave
superconductivity in all three compounds.",9411001v1
2007-09-03,Magnetic Ordering of Nuclear Spins in an Interacting 2D Electron Gas,"We investigate the magnetic behavior of nuclear spins embedded in a 2D
interacting electron gas using a Kondo lattice model description. We derive an
effective magnetic Hamiltonian for the nuclear spins which is of the RKKY type
and where the interactions between the nuclear spins are strongly modified by
the electron-electron interactions. We show that the nuclear magnetic ordering
at finite temperature relies on the (anomalous) behavior of the 2D static
electron spin susceptibility, and thus provides a connection between
low-dimensional magnetism and non-analyticities in interacting 2D electron
systems. Using various perturbative and non-perturbative approximation schemes
in order to establish the general shape of the electron spin susceptibility as
function of its wave vector, we show that the nuclear spins locally order
ferromagnetically, and that this ordering can become global in certain regimes
of interest. We demonstrate that the associated Curie temperature for the
nuclear system increases with the electron-electron interactions up to the
millikelvin range.",0709.0164v2
2007-09-27,Neel to Spin-Glass-like Phase Transition versus Dilution in Geometrically Frustrated ZnCr_{2-2x}Ga_{2x}O_4,"ZnCr2O4 undergoes a first order spin-Peierls-like phase transition at 12.5 K
from a cubic spin liquid phase to a tetragonal Neel state. Using powder
diffraction and single crystal polarized neutron scattering, we determined the
complex spin structure of the Neel phase. This phase consisted of several
magnetic domains with different characteristic wave vectors. This indicates
that the tetragonal phase of ZnCr2O4 is very close to a critical point
surrounded by many different Neel states. We have also studied, using elastic
and inelastic neutron scattering techniques, the effect of nonmagnetic dilution
on magnetic correlations in ZnCr_{2-2x}Ga_{2x}O_4 (x=0.05 and 0.3). For x=0.05,
the magnetic correlations do not change qualitatively from those in the pure
material, except that the phase transition becomes second order. For x= 0.3,
the spin-spin correlations become short range. Interestingly, the spatial
correlations of the frozen spins in the x=0.3 material are the same as those of
the fluctuating moments in the pure and the weakly diluted materials.",0709.4475v1
2008-04-15,"Spin-phonon coupling, q-dependence of spin excitations and high-T$_C$ superconductivity from band models","An understanding of spin excitations in cuprates is essential since the
mechanism of high-T$_C$ superconductivity might be linked to spin fluctuations.
Band calculations for long ""1-dimensional"" unit cells of La$_2$CuO$_4$ show
that the coupling between antiferromagnetic spin waves and phonons is larger
for distortions of oxygens than for Cu or La. When this result is applied to a
2-dimensional, free-electron like band, it leads to a q-dependent spin
excitation spectrum in good agreement with recent experiments. It is argued
that important parameters for spin-phonon coupling, which comes out from the
comparison between experiment and theory, are relevant for the mechanism of
superconductivity, and are large enough to explain a high T$_C$.",0804.2403v1
2008-05-07,Observation of Anomalous Spin Segregation in a Trapped Fermi Gas,"We report the observation of spin segregation, i.e., separation of spin
density profiles, in a trapped ultracold Fermi gas of $^6$Li with a
magnetically tunable scattering length close to zero. The roles of the spin
components are inverted when the sign of the scattering length is reversed. The
observed density profiles are in qualitative agreement with the spin-wave
theory applied previously to explain spin segregation in a Bose gas, but
disagree in amplitude by two orders of magnitude. The observed atomic density
profiles are far from equilibrium, yet they persist for $\simeq$ 5 seconds in a
trap with an axial frequency of $\simeq$ 150 Hz. We attribute this long
lifetime to Fermi statistics: The scattering amplitude is nonzero only for
atoms in opposite states, and vanishes for atoms in the same state. By
measuring the magnetic field at which spin segregation ceases, we precisely
determine the zero crossing in the scattering length of $^6$Li as $527.5\pm0.2$
G.",0805.1036v1
2008-07-18,Can binary mergers produce maximally spinning black holes?,"Gravitational waves carry away both energy and angular momentum as binary
black holes inspiral and merge. The relative efficiency with which they are
radiated determines whether the final black hole of mass $M_f$ and spin $S_f$
saturates the Kerr limit ($\chi_f \equiv S_f/M_f^2 \leq 1$). Extrapolating from
the test-particle limit, we propose expressions for $S_f$ and $M_f$ for mergers
with initial spins aligned or anti-aligned with the orbital angular momentum.
We predict the the final spin at plunge for equal-mass non-spinning binaries to
better than 1%, and that equal-mass maximally spinning aligned mergers lead to
nearly maximally spinning final black holes ($\chi_f \simeq 0.9988$). We also
find black holes can always be spun up by aligned mergers provided the mass
ratio is small enough.",0807.3043v1
2008-10-08,Transverse spin diffusion in ferromagnets,"We discuss the dissipative diffusion-type term of the form
$\mathbf{m}\times\nabla^2\partial_t\mathbf{m}$ in the phenomenological
Landau-Lifshitz equation of ferromagnetic precession, which describes enhanced
Gilbert damping of finite-momentum spin waves. This term arises physically from
itinerant-electron spin flows through a perturbed ferromagnetic configuration
and can be understood to originate in the ferromagnetic spin pumping in the
continuum limit. We develop a general phenomenology as well as provide
microscopic theory for the Stoner and s-d models of ferromagnetism, taking into
account disorder and electron-electron scattering. The latter is manifested in
our problem through the Coulomb drag between the spin bands. The spin diffusion
is identified in terms of the transverse spin conductivity, in analogy with the
Einstein relation in the kinetic theory.",0810.1340v2
2009-02-09,"Spin-induced non-geodesic motion, gyroscopic precession, Wigner rotation and EPR correlations of massive spin 1/2 particles in a gravitational field","We investigate in a covariant manner the spin-induced non-geodesic motion of
massive spin 1/2 particles in an arbitrary gravitational field for trajectories
that are initially geodesic when spin is ignored. Using the WKB approximation
for the wave function in curved spacetime, we compute the O(hbar) correction to
the Wigner rotation of the spin 1/2 particle, whose O(1) contribution is zero
on timelike geodesics. We develop conditions for the motion of observers in
which the Wigner rotation is null. For the spherically symmetric Schwarzschild
metric, we consider specific examples of particle motion in the equatorial
plane for (i) circular orbits and (ii) radially infalling trajectories. For the
former case we consider the entanglement for a perfectly anti-correlated EPR
entangled pair of spins as the separate qubits traverse the circular orbit in
same direction.",0902.1396v1
2009-03-26,Spin Excitations in BaFe1.84Co0.16As2 Superconductor Observed by Inelastic Neutron Scattering,"Superconductivity appears to compete against the spin-density-wave in Fe
pnictides. However, optimally cobalt doped samples show a quasi-two-dimensional
spin excitation centered at the (0.5, 0.5, L) wavevector, ""the spin resonance
peak"", that is strongly tied to the onset of superconductivity. By inelastic
neutron scattering on single crystals we show the similarities and differences
of the spin excitations in BaFe1.84Co0.16As2, with respect to the spin
excitations in the high-temperature superconducting cuprates. As in the
cuprates the resonance occurs as an enhancement to a part of the spin
excitation spectrum which extends to higher energy transfer and higher
temperature. However, unlike in the cuprates, the resonance peak in this
compound is asymmetric in energy.",0903.4621v3
2009-05-15,Dual Spin Filter Effect in a Zigzag Graphene Nanoribbon,"By first principle calculations, a dual spin filter effect under finite bias
voltages is demonstrated in an antiferromagnetic junction of symmetric zigzag
graphene nanoribbon (ZGNR). Unlike conventional spin filter devices using half
metallic materials, the up- and down-spin electrons are unidirectionally
filtered in the counter direction of the bias voltage, making the junction a
dual spin filter. On the contrary, asymmetric ZGNRs do not exhibit such a spin
filter effect. By analyzing Wannier functions and a tight-binding model, we
clarify that an interplay between the spin polarized band structure of $\pi$
and $\pi^*$ states near the Fermi level and decoupling of the interband hopping
of the two states, arising from the symmetry of the wave functions, plays a
crucial role in the effect.",0905.2461v1
2009-06-11,The influence of the discretized Rashba spin-orbit interaction on the Harper model,"The movement of the electrons under the simultaneous influence of a scalar
periodic potential and of a uniform transversal magnetic field is described by
the well-known second order discrete Harper equation. This equation originates
from a two-dimensional energy dispersion law under the minimal substitution.
Here one deals with the Harper model under the additional influence of the
discretized spin orbit interaction. Converting the spin-orbit interaction in
terms of discrete derivatives opens the way for analytical and numerical
studies. One finds coupled equations for the spin dependent wave functions,
which leads to an appreciable alteration of the nested energy subbands
characterizing the self-similar structure of the usual Harper spectrum. To this
aim the transfer matrix method has been applied to selected spin-up and
spin-down wavefunctions. Accordingly, very manifestations of spinfiltering and
of spin correlations are accounted for. Our energy-bands calculations show that
the splitting effect implemented by such wavefunctions is appreciable.",0906.2054v1
2009-07-14,Upstanding Rashba spin in honeycomb lattices: Electrically reversible surface spin polarization,"The spin-split states subject to Rashba spin-orbit coupling in
two-dimensional systems have long been accepted as pointing inplane and
perpendicular to the corresponding wave vectors. This is in general true for
free electron model, but exceptions do exist elsewhere. Within the
tight-binding model, we unveil the unusual upstanding behavior of those Rashba
spins around $\bar{K}$ and $\bar{K}^{\prime}$ points in honeycomb lattices. Our
calculation (i) explains the recent experiment of the Tl/Si(111)-$(1\times1)$
surface alloy [Phys. Rev. Lett. \textbf{102}, 096805 (2009)], where abrupt
upstanding spin states near $\bar{K}$ are observed, and (ii) predicts an
electrically reversible out-of-plane surface spin polarization.",0907.2411v3
2010-02-17,Spin symmetry in Dirac negative energy spectrum in density-dependent relativistic Hartree-Fock theory,"The spin symmetry in the Dirac negative energy spectrum and its origin are
investigated for the first time within the density-dependent relativistic
Hartree-Fock (DDRHF) theory. Taking the nucleus $^{16}$O as an example, the
spin symmetry in the negative energy spectrum is found to be a good
approximation and the dominant components of the Dirac wave functions for the
spin doublets are nearly identical. In comparison with the relativistic Hartree
approximation where the origin of spin symmetry lies in the equality of the
scalar and vector potentials, in DDRHF the cancellation between the Hartree and
Fock terms is responsible for the better spin symmetry properties and
determines the subtle spin-orbit splitting. These conclusions hold even in the
case when significant deviations from the G-parity values of the
meson-antinucleon couplings occur.",1002.3309v1
2010-08-06,Multifrequency spin resonance in diamond,"Magnetic resonance techniques provide a powerful tool for controlling spin
systems, with applications ranging from quantum information processing to
medical imaging. Nevertheless, the behavior of a spin system under strong
excitation remains a rich dynamical problem. In this paper, we examine spin
resonance of the nitrogen-vacancy center in diamond under conditions outside
the regime where the usual rotating wave approximation applies, focusing on
effects of multifrequency excitation and excitation with orientation parallel
to the spin quantization axis. Strong-field phenomena such as multiphoton
transitions and coherent destruction of tunneling are observed in the spectra
and analyzed via numerical and analytic theory. In addition to illustrating the
response of a spin system to strong multifrequency excitation, these
observations may inform techniques for manipulating electron-nuclear spin
quantum registers.",1008.1103v1
2010-11-07,Understanding spin glass transition as a dynamic phenomenon,"Existing theories explain spin glass transition in terms of a phase
transition and order parameters, and assume the existence of a distinct spin
glass phase. In addition to problems related to clarifying the nature of this
phase, the common challenge is to explain profound dynamic effects. Here, we
propose that the main experimental results of spin glass transition can be
understood in an entirely dynamic picture, without a reference to a distinct
spin glass phase, phase transition and order parameters. In this theory, the
susceptibility cusp at the glass transition temperature is due to the dynamic
crossover between the high-temperature relaxational and low-temperature spin
wave, or elastic, regime. The crossover takes place when $t=\tau$, where $t$ is
observation time and $\tau$ is relaxation time. Time-dependent effects,
inconsistent with the phase transition approach, and the logarithmic increase
of $T_g$ with field frequency in particular, originate as the immediate
consequence of the proposed picture. We comment on the behavior of non-linear
susceptibility. In our discussion, we explore similarities between the spin and
structural glass transitions.",1011.1676v3
2010-11-11,Anomalous spin-resolved point-contact transmission of holes due to cubic Rashba spin-orbit coupling,"Evidence is presented for the finite wave vector crossing of the two lowest
one-dimensional spin-split subbands in quantum point contacts fabricated from
two-dimensional hole gases with strong spin-orbit interaction. This phenomenon
offers an elegant explanation for the anomalous sign of the spin polarization
filtered by a point contact, as observed in magnetic focusing experiments.
Anticrossing is introduced by a magnetic field parallel to the channel or an
asymmetric potential transverse to it. Controlling the magnitude of the
spin-splitting affords a novel mechanism for inverting the sign of the spin
polarization.",1011.2676v2
2011-03-29,Mixed-Spin Pairing Condensates in Heavy Nuclei,"We show that the Bogoliubov-de Gennes equations for nuclear ground-state wave
functions support solutions in which the condensate has a mixture of
spin-singlet and spin-triplet pairing. We find that such mixed-spin condensates
do not occur when there are equal numbers of neutrons and protons, but only
when there is an isospin imbalance. Using a phenomenological Hamiltonian, we
predict that such nuclei may occur in the physical region within the proton
dripline. We also solve the Bogoliubov-de Gennes equations with variable
constraints on the spin-singlet and spin-triplet pairing amplitudes. For nuclei
that exhibit this new pairing behavior, the resulting energy surface can be
rather soft, suggesting that there may be low-lying excitations associated with
the spin mixing.",1103.5793v2
2011-07-13,Spin-Singlet Quantum Hall States and Jack Polynomials with a Prescribed Symmetry,"We show that a large class of bosonic spin-singlet Fractional Quantum Hall
model wave-functions and their quasi-hole excitations can be written in terms
of Jack polynomials with a prescribed symmetry. Our approach describes new
spin-singlet quantum Hall states at filling fraction nu = 2k/(2r-1) and
generalizes the (k,r) spin-polarized Jack polynomial states. The NASS and
Halperin spin singlet states emerge as specific cases of our construction. The
polynomials express many-body states which contain configurations obtained from
a root partition through a generalized squeezing procedure involving spin and
orbital degrees of freedom. The corresponding generalized Pauli principle for
root partitions is obtained, allowing for counting of the quasihole states. We
also extract the central charge and quasihole scaling dimension, and propose a
conjecture for the underlying CFT of the (k, r) spin-singlet Jack states.",1107.2534v1
2011-09-19,Spin dynamics in finite cyclic XY model,"Evolution of the z-component of a single spin in the finite cyclic XY spin
1/2 chain is studied. Initially one selected spin is polarized while other
spins are completely unpolarized and uncorrelated. Polarization of the selected
spin as a function of time is proportional to the autocorrelation function at
infinite temperature. Initialization of the selected spin gives rise to two
wave packets moving in opposite directions and winding over the circle. We
express the correlation function as a series in winding number and derive
tractable approximations for each term. This allows to give qualitative
explanation and quantitative description to various finite-size effects such as
partial revivals and transition from regular to erratic behavior.",1109.4127v3
2011-10-14,Spin Liquid Phases for Spin-1 systems on the Triangular lattice,"Motivated by recent experiments on material Ba3NiSb2O9, we propose two novel
spin liquid phases (A and B) for spin-1 systems on a triangular lattice. At the
mean field level, both spin liquid phases have gapless fermionic spinon
excitations with quadratic band touching, thus in both phases the spin
susceptibility and C_v/T saturate to a constant at zero temperature, which are
consistent with the experimental results on Ba3NiSb2O9. On the lattice scale,
these spin liquid phases have Sp(4) ~ SO(5) gauge fluctuation; while in the
long wavelength limit this Sp(4) gauge symmetry is broken down to U(1)xZ_2 in
type A spin liquid phase, and broken down to Z_4 in type B phase. We also
demonstrate that the $A$ phase is the parent state of the ferro-quadrupole
state, nematic state, and the noncollinear spin density wave state.",1110.3328v1
2011-10-18,Collective excitations on a surface of topological insulator,"We study collective excitations in a helical electron liquid on a surface of
three-dimensional topological insulator. Electron in helical liquid obeys
Dirac-like equation for massless particless and direction of its spin is
strictly determined by its momentum. Due to this spin-momentum locking,
collective excitations in the system manifest themselves as coupled charge- and
spin-density waves. We develop quantum field-theoretical description of
spin-plasmons in helical liquid and study their properties and internal
structure. Value of spin polarization arising in the system with excited
spin-plasmons is calculated. We also consider the scattering of spin-plasmons
on magnetic and nonmagnetic impurities and external potentials, and show that
the scattering occurs mainly into two side lobes. Analogies with Dirac electron
gas in graphene are discussed.",1110.4023v1
2011-11-15,Spin and Charge Structure of the Surface States in Topological Insulators,"We investigate the spin and charge densities of surface states of the
three-dimensional topological insulator $Bi_2Se_3$, starting from the continuum
description of the material [Zhang {\em et al.}, Nat. Phys. 5, 438 (2009)]. The
spin structure on surfaces other than the 111 surface has additional complexity
because of a misalignment of the contributions coming from the two sublattices
of the crystal. For these surfaces we expect new features to be seen in the
spin-resolved ARPES experiments, caused by a non-helical spin-polarization of
electrons at the individual sublattices as well as by the interference of the
electron waves emitted coherently from two sublattices. We also show that the
position of the Dirac crossing in spectrum of surface states depends on the
orientation of the interface. This leads to contact potentials and surface
charge redistribution at edges between different facets of the crystal.",1111.3650v4
2012-05-15,Dynamic Critical Scaling of the Holographic Spin Fluctuations,"Criticality with strong coupling is described by a theory in the vicinity of
a non-Gaussian fixed point. The holographic duality conjectures that a theory
at a non-Gaussian fixed point with strong coupling is dual to a gravitational
theory. In this paper, we present a holographic theory in treating the strongly
coupled critical spin fluctuations in quasi-2-dimension. We show that a
universal frequency over temperature scaling law is a rather general property
of the critical ac spin susceptibility at strongly coupled limit. Explicit
results for the dynamic scaling of spin susceptibility are obtained in large-N
and large 't Hooft limit. We argue that such critical scaling are in good
agreement with a number of experiments, some of which can not be explained by
any perturbative spin-density-wave theory. Our results strongly suggest that
the anomalous behavior of non-Fermi liquids in materials is closely related to
the spin fluctuations described through the non-Gaussian fixed point. The
exotic properties of non-Fermi liquids can be viewed as the Fermi liquids
coupling to strongly coupled critical spin fluctuations.",1205.3267v2
2012-07-16,Microscopic Study of Edge Excitations of Spin-Polarized and Spin-Unpolarized $ν=2/3$ Fractional Quantum Hall Effect,"The edge of spin unpolarized or spin polarized $\nu=2/3$ fractional quantum
Hall states is predicted by the effective theory to support a backward moving
neutral mode in addition to a forward moving charge mode. We study this issue
from a microscopic perspective where these states are identified with effective
filling factor of 2 of composite fermions, but with an effective magnetic field
that is antiparallel to the external field. A simple counting from the
composite fermion description suggests that there might be two backward moving
edge modes, but explicit calculations show that one of these is projected out
of the low energy sector, while the remaining mode provides a good microscopic
account of the actual counter propagating edge mode. The forward moving modes
are identified as ""Schur modes,"" obtained by multiplying the ground state wave
function by the symmetric Schur polynomials. The edge of the 2/3 spin
unpolarized state provides a particularly striking realization of ""spin charge
separation"" in a one dimensional Tomonaga Luttinger liquids, with the spin and
charge modes moving in opposite directions.",1207.3566v1
2013-04-17,Unconventional magnetism via optical pumping of interacting spin systems,"We consider strongly interacting systems of effective spins, subject to
dissipative spin-flip processes associated with optical pumping. We predict the
existence of novel magnetic phases in the steady-state of this system, which
emerge due to the competition between coherent and dissipative processes.
Specifically, for strongly anisotropic spin-spin interactions, we find
ferromagnetic, antiferromagnetic, spin-density-wave, and staggered-XY steady
states, which are separated by nonequilibrium phase transitions meeting at a
Lifshitz point. These transitions are accompanied by quantum correlations,
resulting in spin squeezing. Experimental implementations in ultracold atoms
and trapped ions are discussed.",1304.4959v2
2013-07-31,Transitions Between Chiral Spin Liquids and Z2 Spin Liquids,"The Kalmeyer-Laughlin chiral spin liquids (CSL) and the Z2 spin liquids are
two of the simplest topologically ordered states. Here I develop a theory of a
direct quantum phase transition between them. Each CSL is characterized by an
integer n and is topologically equivalent to the 1/2n Laughlin fractional
quantum Hall (FQH) state. Depending on the parity of n, the transition from the
CSL is either to a ""twisted"" version of the Z2 spin liquid, the ""doubled
semion"" model, or the conventional Z_2 spin liquid (""toric code""). In the
presence of SU(2) spin symmetry, the triplet gap remains open through the
transition and only singlet operators acquire algebraic correlations. An
essential observation is that the CSL/Laughlin FQH states can be understood in
terms of bosonic integer quantum Hall (BIQH) states of Schwinger bosons or
vortices, respectively. I propose several novel many-body wave functions that
can interpolate through the transition.",1307.8194v1
2013-11-19,Parity-Mixed Superconductivity in Locally Non-centrosymmetric System,"We study the parity-mixed superconductivity in locally non-centrosymmetric
systems. In multilayer systems an inhomogeneous Rashba spin-orbit coupling is
induced by the local violation of inversion symmetry. Our previous study
revealed that a pair-density wave (PDW) phase, with a sign-modulated order
parameter, is stabilized in the spin-singlet multilayer superconductors owing
to the spin-orbit coupling. In this letter, we show that the uniform
spin-triplet superconductivity emerges through parity mixing in the PDW phase,
taking into account a weak interaction in the spin-triplet channel, which was
neglected in our previous study. The spin-triplet superconducting phase is
nonunitary owing to field-induced parity mixing. The critical magnetic field is
markedly increased by the emergence of spin-triplet superconductivity. We
calculate the density of states and analyze the signature specific to this
phase.",1311.4660v1
2013-12-22,Quantum phases in the frustrated Heisenberg model on the bilayer honeycomb lattice,"We use a combination of analytical and numerical techniques to study the
phase diagram of the frustrated Heisenberg model on the bilayer honeycomb
lattice. Using the Schwinger boson description of the spin operators followed
by a mean field decoupling, the magnetic phase diagram is studied as a function
of the frustration coupling $J_{2}$ and the interlayer coupling $J_{\bot}$.
  The presence of both magnetically ordered and disordered phases is
investigated by means of the evaluation of ground-state energy, spin gap, local
magnetization and spin-spin correlations. We observe a phase with a spin gap
and short range N\'eel correlations that survives for non-zero
next-nearest-neighbor interaction and interlayer coupling. Furthermore, we
detect signatures of a reentrant behavior in the melting of N\'eel phase and
symmetry restoring when the system undergoes a transition from an on-layer
nematic valence bond crystal phase to an interlayer valence bond crystal phase.
We complement our work with exact diagonalization on small clusters and
dimer-series expansion calculations, together with a linear spin wave approach
to study the phase diagram as a function of the spin $S$, the frustration and
the interlayer couplings.",1312.6324v2
2014-03-05,Test of Einstein Equivalence Principle for 0-spin and half-integer-spin atoms: Search for spin-gravity coupling effects,"We report on a conceptually new test of the equivalence principle performed
by measuring the acceleration in Earth's gravity field of two isotopes of
strontium atoms, namely, the bosonic $^{88}$Sr isotope which has no spin vs the
fermionic $^{87}$Sr isotope which has a half-integer spin. The effect of
gravity upon the two atomic species has been probed by means of a precision
differential measurement of the Bloch frequency for the two atomic matter waves
in a vertical optical lattice. We obtain the values $\eta = (0.2\pm
1.6)\times10^{-7}$ for the E\""otv\""os parameter and
$k=(0.5\pm1.1)\times10^{-7}$ for the coupling between nuclear spin and gravity.
This is the first reported experimental test of the equivalence principle for
bosonic and fermionic particles and opens a new way to the search for the
predicted spin-gravity coupling effects.",1403.1161v2
2014-05-28,Conditional control of donor nuclear spins in silicon using Stark shifts,"Electric fields can be used to tune donor spins in silicon using the Stark
shift, whereby the donor electron wave function is displaced by an electric
field, modifying the hyperfine coupling between the electron spin and the donor
nuclear spin. We present a technique based on dynamic decoupling of the
electron spin to accurately determine the Stark shift, and illustrate this
using antimony donors in isotopically purified silicon-28. We then demonstrate
two different methods to use a DC electric field combined with an applied
resonant radio-frequency (RF) field to conditionally control donor nuclear
spins. The first method combines an electric-field induced conditional phase
gate with standard RF pulses, and the second one simply detunes the spins
off-resonance. Finally, we consider different strategies to reduce the effect
of electric field inhomogeneities and obtain above 90% process fidelities.",1405.7420v1
2014-08-29,High performance current and spin diode of atomic carbon chain between transversely symmetric ribbon electrodes,"We demonstrate that giant current and high spin rectification ratios can be
achieved in atomic carbon chain devices connected between two symmetric
ferromagnetic zigzag-graphene-nanoribbon electrodes. The spin dependent
transport simulation is carried out by density functional theory combined with
the non-equilibrium Green's function method. It is found that the transverse
symmetries of the electronic wave functions in the nanoribbons and the carbon
chain are critical to the spin transport modes. In the parallel magnetization
configuration of two electrodes, pure spin current is observed in both linear
and nonlinear regions. However, in the antiparallel configuration, the spin-up
(down) current is prohibited under the positive (negative) voltage bias, which
results in a spin rectification ratio of order 104. When edge carbon atoms are
substituted with boron atoms to suppress the edge magnetization in one of the
electrodes, we obtain a diode with current rectification ratio over 10e6.",1408.6910v1
2014-10-03,Neutron Scattering Studies of the Ferroelectric Distortion and Spin Dynamics in the Type-1 Multiferroic Perovskite Sr0.56Ba0.44MnO3,"The magnetic order, spin dynamics, and crystal structure of the multiferroic
Sr0.56Ba0.44MnO3 have been investigated using neutron and x-ray scattering.
Ferroelectricity develops at TC=305 K with a polarization of 4.2 microC/cm2
associated with the displacements of the Mn ions, while the Mn4+ spins order
below TN = 200 K into a simple G-type commensurate magnetic structure. Below TN
the ferroelectric order decreases dramatically demonstrating that the two order
parameters are strongly coupled. The ground state spin dynamics are
characterized by a spin gap of 4.6(5) meV and the magnon density of states
peaking at 43 meV. Detailed spin wave simulations with a gap and isotropic
exchange of J=4.8(2) meV describe the excitation spectrum well. Above TN strong
spin correlations coexist with robust ferroelectric order.",1410.0922v1
2015-03-12,Gate-control of spin-motive force and spin-torque in Rashba SOC systems,"The introduction of a strong Rashba spin orbit coupling (SOC) had been
predicted to enhance the spin motive force (SMF) [see Phys. Rev. Lett. {\bf
108}, 217202 (2012)]. In this work, we predict further enhancement of the SMF
by time modulation of the Rashba coupling $\alpha_R$, which induces an
additional electric field $E^R_d={\dot \alpha_R} m_e/e\hbar({\hat z}\times
{\mathbf m})$. When the modulation frequency is higher than the magnetization
precessing frequency, the amplitude of this field is significantly larger than
previously predicted results. Correspondingly, the spin torque on the
magnetization is also effectively enhanced. Additionally, the nature of SOC
induced spin torque in the system can be transformed from damping to
antidamping-like by modulating ${\dot \alpha_R}$. We also suggest a biasing
scheme to achieve rectification of SMF, {\it i.e.}, by application of a square
wave voltage at the resonant frequency. Finally, we numerically estimate the
resulting spin torque field arising from a Gaussian pulse time modulation of
$\alpha_R$.",1503.03651v2
2015-03-17,Exploring the transport properties of polytypic and twin-plane nanowires: from tunneling phase-time to spin-orbit interaction effects,"The variety of nanowire crystal structures gave rise to unique and novel
transport phenomena. In particular, we have explored the superlattice profile
generated by strain field modulation in twinplane nanowires for the tuning of
transport channels and the built-in spin-orbit potential profile of polytypic
nanowires, in order to realize a spin filter. The Multicomponent Scattering
Approach has been used in terms of the Transfer Matrix Method to describe the
phase-time of charge carriers. This system showed advantages for attaining
conditions for the propagation of wave packets with negative group velocity.
Moreover, the spin transport effect of a potential profile with volumetric
spin-orbit bulk inversion asymmetry, as present on polytypic nanowires, was
described through the Reverse Runge-Kutta Method. Using the peculiar symmetry
of the excited states we have characterized a dominant spin dependence on
structural parameters that results in effective spin filtering.",1503.05223v1
2015-07-04,Antiferromagnetic Heisenberg Spin Chain of a Few Cold Atoms in a One-Dimensional Trap,"We report on the deterministic preparation of antiferromagnetic Heisenberg
spin chains consisting of up to four fermionic atoms in a one-dimensional trap.
These chains are stabilized by strong repulsive interactions between the two
spin components without the need for an external periodic potential. We
independently characterize the spin configuration of the chains by measuring
the spin orientation of the outermost particle in the trap and by projecting
the spatial wave function of one spin component on single-particle trap levels.
Our results are in good agreement with a spin-chain model for fermionized
particles and with numerically exact diagonalizations of the full few-fermion
system.",1507.01117v2
2015-07-17,Transverse spin and spin-orbit coupling in silicon waveguides,"Evanescent and tightly confined propagating waves exhibit a remarkable
transverse spin density since the longitudinal component of the electric field
is not negligible. In this work, we obtain via numerical simulations the
electric field components of the fundamental guided modes of two waveguides
typically used in silicon photonics: the strip and the slot waveguide. We
obtain the relation between transverse and longitudinal field components, the
transverse spin densities and other important parameters, such as the
longitudinal component of the so-called Belinfante spin momentum density. By
asymmetrically placing a circularly-polarized point-like dipole source in
regions showing local circular polarization, the guided mode is excited
unidirectionally via spin-orbit coupling. In contrast to metal plates
supporting surface plasmons, the multimode behavior of silicon waveguides
results in different spin-orbit coupling properties for each guided mode. Our
results may find application in silicon photonic devices, integrated quantum
optics and polarization manipulation at the nanoscale.",1507.04859v2
2015-08-27,Localization and spin transport in honeycomb structures with spin-orbit coupling,"Transfer-matrix methods are used for a tight-binding description of electron
transport in graphene-like geometries, in the presence of spin-orbit couplings.
Application of finite-size scaling and phenomenological renormalization
techniques shows that, for strong enough spin-orbit interactions and increasing
on-site disorder, this system undergoes a metal-insulator transition
characterized by the exponents $\nu=2.71(8)$, $\eta=0.174(2)$. We show how one
can extract information regarding spin polarization decay with distance from an
injection edge, from the evolution of wave-function amplitudes in the
transfer-matrix approach. For (relatively weak) spin-orbit coupling intensity
$\mu$, we obtain that the characteristic length $\Lambda_s$ for
spin-polarization decay behaves as $\Lambda_s \propto \mu^{-2}$.",1508.06873v2
2015-10-09,Single-electron Spin Resonance in a Quadruple Quantum Dot,"Electron spins in semiconductor quantum dots are good candidates of quantum
bits for quantum information processing. Basic operations of the qubit have
been realized in recent years: initialization, manipulation of single spins,
two qubit entanglement operations, and readout. Now it becomes crucial to
demonstrate scalability of this architecture by conducting spin operations on a
scaled up system. Here, we demonstrate single-electron spin resonance in a
quadruple quantum dot. A few-electron quadruple quantum dot is formed within a
magnetic field gradient created by a micro-magnet. We oscillate the wave
functions of the electrons in the quantum dots by applying microwave voltages
and this induces electron spin resonance. The resonance energies of the four
quantum dots are slightly different because of the stray field created by the
micro-magnet and therefore frequency-resolved addressable control of the
electron spin resonance is possible.",1510.02547v1
2015-10-13,Interacting spin-orbit-coupled spin-1 Bose-Einstein condensates,"The recent experimental realization of spin-orbit (SO) coupling for spin-1
ultracold atoms opens an interesting avenue for exploring SO-coupling-related
physics in large-spin systems, which is generally unattainable in electronic
materials. In this paper, we study the effects of interactions between atoms on
the ground states and collective excitations of SO-coupled spin-1 Bose-Einstein
condensates (BECs) in the presence of a spin-tensor potential. We find that
ferromagnetic interaction between atoms can induce a stripe phase exhibiting
in-phase or out-of-phase modulating patterns between spin-tensor and
zero-spin-component density waves. We characterize the phase transitions
between different phases using the spin-tensor density as well as the
collective dipole motion of the BEC. We show that there exists a double
maxon-roton structure in the Bogoliubov-excitation spectrum, attributed to the
three band minima of the SO-coupled spin-1 BEC.",1510.03787v3
2015-11-17,Do micromagnets expose spin qubits to charge and Johnson noise?,"An ideal quantum dot spin qubit architecture requires a local magnetic field
for one-qubit rotations. Such an inhomogeneous magnetic field, which could be
implemented via a micromagnet, couples the qubit subspace with background
charge fluctuations causing dephasing of spin qubits. In addition, a
micromagnet generates magnetic field evanescent-wave Johnson noise. We derive
an effective Hamiltonian for the combined effect of a slanting magnetic field
and charge noise on a single-spin qubit and estimate the free induction decay
dephasing times T2* for Si and GaAs. The effect of the micromagnet on Si qubits
is comparable in size to that of spin-orbit coupling at an applied field of
B=1T, whilst dephasing in GaAs is expected to be dominated by spin-orbit
coupling. Tailoring the magnetic field gradient can efficiently reduce T2* in
Si. In contrast, the Johnson noise generated by a micromagnet will only be
important for highly coherent spin qubits.",1511.05247v1
2015-11-18,Transformation of spin current by antiferromagnetic insulators,"It is demonstrated theoretically that a thin layer of an anisotropic
antiferromagnetic (AFM) insulator can effectively conduct spin current by
excitation of a pair of evanescent AFM spin wave modes. The spin current
flowing through the AFM is not conserved due to the interaction between the
excited AFM modes and the AFM lattice, and, depending on the excitation
conditions, can be either attenuated or enhanced. When the phase difference
between the excited evanescent modes is close to $\pi/2$, there is an optimum
AFM thickness for which the output spin current reaches a maximum, that can
significantly exceed the magnitude of the input spin current. The spin current
transfer through the AFM depends on the ambient temperature and increases
substantially when temperature approaches the Neel temperature of the AFM
layer.",1511.05785v4
2015-12-08,Multi-orbital quantum antiferromagnetism in iron pnictides --- effective spin couplings and quantum corrections to sublattice magnetization,"Towards understanding the multi-orbital quantum antiferromagnetism in iron
pnictides, effective spin couplings and spin fluctuation induced quantum
corrections to sublattice magnetization are obtained in the $(\pi,0)$ AF state
of a realistic three band interacting electron model involving $xz$, $yz$, and
$xy$ Fe 3d orbitals. The $xy$ orbital is found to be mainly responsible for the
generation of strong ferromagnetic spin coupling in the $b$ direction, which is
critically important to fully account for the spin wave dispersion as measured
in inelastic neutron scattering experiments. The ferromagnetic spin coupling is
strongly suppressed as the $xy$ band approaches half filling, and is ascribed
to particle-hole exchange in the partially filled $xy$ band. The strongest AF
spin coupling in the $a$ direction is found to be in the orbital off diagonal
sector involving the $xz$ and $xy$ orbitals. First order quantum corrections to
sublattice magnetization are evaluated for the three orbitals, and yield a
significant $37\%$ average reduction from the Hartree-Fock value.",1512.02398v1
2016-01-19,Spin injection and spin transport in paramagnetic insulators,"We investigate the spin injection and the spin transport in paramagnetic
insulators described by simple Heisenberg interactions using auxiliary particle
methods. Some of these methods allow access to both paramagnetic states above
magnetic transition temperatures and magnetic states at low temperatures. It is
predicted that the spin injection at an interface with a normal metal is rather
insensitive to temperatures above the magnetic transition temperature. On the
other hand below the transition temperature, it decreases monotonically and
disappears at zero temperature. We also analyze the bulk spin conductance. It
is shown that the conductance becomes zero at zero temperature as predicted by
linear spin wave theory but increases with temperature and is maximized around
the magnetic transition temperature. These findings suggest that the compromise
between the two effects determines the optimal temperature for spintronics
applications utilizing magnetic insulators.",1601.04925v2
2016-01-27,Observation of magnon-mediated current drag in Pt/yttrium iron garnet/Pt(Ta) trilayers,"Pure spin current, a flow of spin angular momentum without flow of any
companying net charge, is generated in two common ways. One makes use of the
spin Hall effect in normal metals (NM) with strong spin-orbit coupling, such as
Pt or Ta. The other utilizes the collective motion of magnetic moments or spin
waves with the quasi-particle excitations called magnons. A popular material
for the latter is yttrium iron garnet, a magnetic insulator (MI). Here we
demonstrate in NM/MI/NM trilayers that these two types of spin currents are
interconvertible across the interfaces, predicated as the magnon-mediated
current drag phenomenon. The transmitted signal scales linearly with the
driving current without a threshold and follows the power-law with n ranging
from 1.5 to 2.5. Our results indicate that the NM/MI/NM trilayer structure can
serve as a scalable pure spin current valve device which is an essential
ingredient in spintronics.",1601.07429v1
2016-04-19,Spin-1 Quantum Walks,"We study the quantum walks of two interacting spin-1 bosons. We derive an
exact solution for the time-dependent wave function that describes the
two-particle dynamics governed by the one-dimensional spin-1 Bose-Hubbard
model. We show that propagation dynamics in real space and mixing dynamics in
spin space are correlated via the spin-dependent interaction in this system.
The spin-mixing dynamics has two characteristic frequencies in the limit of
large spin-dependent interactions. One of the characteristic frequencies is
determined by the energy difference between two bound states, and the other
frequency relates to the cotunneling process of a pair of spin-1 bosons.
Furthermore, we numerically analyze the growth of the spin correlations in
quantum walks. We find that long-range spin correlations emerge showing a clear
dependence on the sign of the spin-dependent interaction and the initial state.",1604.05407v1
2016-09-26,Elastic Spin Hall effect in Mechanical Graphene,"We show that spin-orbit interaction and elastic spin-Hall effect can exist in
a classical mechanical system consisting of a two-dimensional honeycomb lattice
of masses and springs. The band structure shows the presence of splitting at K
point induced by the difference of longitudinal and transverse elastic
constant, and this splitting can be regarded as an effective Dresselhaus-type
spin-orbit coupling. Interestingly, as an initial displacement away from the
equilibrium is applied, the time evolution simulation shows that waves of
different spin polarization propagates along different directions at the Gamma
and K point, which is characteristic of spin-Hall effect. Several cases for
spin-Hall effect are also discussed.",1609.08061v1
2017-07-17,"Ab initio calculation of spin fluctuation spectra using time dependent density functional perturbation theory, planewaves, and pseudopotentials","We present an implementation of time-dependent density functional
perturbation theory for spin fluctuations, based on planewaves and
pseudopotentials. We compute the dynamic spin susceptibility self-consistently
by solving the time-dependent Sternheimer equation, within the adiabatic local
density approximation to the exchange and correlation kernel. We demonstrate
our implementation by calculating the spin susceptibility of representative
elemental transition metals, namely bcc Fe, fcc Ni and bcc Cr. The calculated
magnon dispersion relations of Fe and Ni are in agreement with previous work.
The calculated spin susceptibility of Cr exhibits a soft-paramagnon
instability, indicating the tendency of the Cr spins to condense in a
incommensurate spin density wave phase, in agreement with experiment.",1707.05219v1
2017-08-11,Evolution of small-mass-ratio binaries with a spinning secondary,"We calculate the evolution and gravitational-wave emission of a spinning
compact object inspiraling into a substantially more massive (non-rotating)
black hole. We extend our previous model for a non-spinning binary [Phys. Rev.
D 93, 064024] to include the Mathisson-Papapetrou-Dixon spin-curvature force.
For spin-aligned binaries we calculate the dephasing of the inspiral and
associated waveforms relative to models that do not include spin-curvature
effects. We find this dephasing can be either positive or negative depending on
the initial separation of the binary. For binaries in which the spin and
orbital angular momentum are not parallel, the orbital plane precesses and we
use a more general osculating element prescription to compute inspirals.",1708.03720v1
2017-09-23,Spin precession in spin-orbit coupled weak links: Coulomb repulsion and Pauli quenching,"A simple model for the transmission of pairs of electrons through a weak
electric link in the form of a nanowire made of a material with strong electron
spin-orbit interaction (SOI) is presented, with emphasis on the effects of
Coulomb interactions and the Pauli exclusion principle. The constraints due to
the Pauli principle are shown to ""quench"" the coherent SOI-induced precession
of the spins when the spatial wave packets of the two electrons overlap
significantly. The quenching, which results from the projection of the pair's
spin states onto spin-up and spin-down states on the link, breaks up the
coherent propagation in the link into a sequence of coherent hops that add
incoherently. Applying the model to the transmission of Cooper pairs between
two superconductors, we find that in spite of Pauli quenching, the Josephson
current oscillates with the strength of the SOI, and may even change its sign.
Conditions for an experimental detection of these features are discussed.",1709.08022v2
2017-11-04,Spin excitation anisotropy in optimal-isovalent-doped superconductor BaFe2(As0.7P0.3)2,"We use neutron polarization analysis to study spin excitation anisotropy in
the optimal-isovalent-doped superconductor BaFe2(As0.7P0.3)2 (Tc = 30 K).
Different from optimally hole and electron-doped BaFe2As2, where there is a
clear spin excitation anisotropy in the paramagnetic tetragonal state well
above Tc, we find no spin excitation anisotropy for energies above 2 meV in the
normal state of BaFe2(As0.7P0.3)2. Upon entering the superconducting state,
significant spin excitation anisotropy develops at the antiferromagnetic (AF)
zone center QAF = (1, 0, L = odd), while magnetic spectrum is isotropy at the
zone boundary Q = (1, 0, L = even). By comparing temperature, wave vector, and
polarization dependence of the spin excitation anisotropy in BaFe2(As0.7P0.3)2
and hole-doped Ba0.67K0.33Fe2As2 (Tc = 38 K), we conclude that such anisotropy
arises from spin-orbit coupling and is associated with the nearby AF order and
superconductivity.",1711.01497v1
2017-11-28,The magnetic and electric transverse spin density of spatially confined light,"When a beam of light is laterally confined, its field distribution can
exhibit points where the local magnetic and electric field vectors spin in a
plane containing the propagation direction of the electromagnetic wave. The
phenomenon indicates the presence of a non-zero transverse spin density. Here,
we experimentally investigate this transverse spin density of both magnetic and
electric fields, occurring in highly-confined structured fields of light. Our
scheme relies on the utilization of a high-refractive-index nano-particle as
local field probe, exhibiting magnetic and electric dipole resonances in the
visible spectral range. Because of the directional emission of dipole moments
which spin around an axis parallel to a nearby dielectric interface, such a
probe particle is capable of locally sensing the magnetic and electric
transverse spin density of a tightly focused beam impinging under normal
incidence with respect to said interface. We exploit the achieved experimental
results to emphasize the difference between magnetic and electric transverse
spin densities.",1711.10268v1
2017-12-18,Spin supersolid phase in coupled alternating spin chains,"We study the ground state phase diagram of a two dimensional mixed-spin
system of coupled alternating spin-1 and $1/2$ chains with a stripe supersolid
phase. Utilizing different analytical and numerical approaches such as mean
field approximation, cluster mean field theory and linear spin wave theory, we
demonstrate that our system displays a rich ground state phase diagram
including novel stripe supersolid, solids with different fillings and
super-counterfluid phases, in addition to a stripe solid with half filling,
superfluid and Mott insulating phases. In order to find a minimal mixed-spin
model for stripe supersolidity, in the second part of the paper we consider two
kinds of mixed-spin system of coupled alternating spin-1 and $1/2$ chains with
(i) anisotropic nearest neighbor interactions, (ii) anisotropic hoppings and
study their ground state phase diagrams. We demonstrate that, for the systems
with uniform hoppings, the repulsive intra-chains interactions are necessary
for stripe supersolidity. In this case the minimal two dimensional mixed-spin
model is a system of spin-1 and spin-1/2 XXZ chains, interacting via a XY
Hamiltonian. In the case of anisotropic hoppings, a system of coupled Ising
chains is the minimal model.",1712.06270v1
2018-05-21,Spin Response and Collective Modes in Simple Metal Dichalcogenides,"Transition metal dichalcogenide (TMD) monolayers are interesting materials in
part because of their strong spin-orbit coupling. This leads to intrinsic
spin-splitting of opposite signs in opposite valleys, so the valleys are
intrinsically spin-polarized when hole-doped. We study spin response in a
simple model of these materials, with an eye to identifying sharp collective
modes (i.e, spin-waves) that are more commonly characteristic of ferromagnets.
We demonstrate that such modes exist for arbitrarily weak repulsive
interactions, even when they are too weak to induce spontaneous ferromagnetism.
The behavior of the spin response is explored for a range of hole dopings and
interaction strengths.",1805.08223v2
2018-06-06,Effect of electron correlations on spin excitation bandwidth in Ba$_{0.75}$K$_{0.25}$Fe$_{2}$As$_{2}$ as seen via time-of-flight inelastic neutron scattering,"We use inelastic neutron scattering (INS) to investigate the effect of
electron correlations on spin dynamics in the iron-based superconductor
Ba$_{0.75}$K$_{0.25}$Fe$_{2}$As$_{2}$. Our INS data show a spin-wave-like
dispersive feature, with a zone boundary energy of 200 meV. A first principles
analysis of dynamical spin susceptibility, incorporating the mass
renormalization factor of 3, as determined by angle-resolved photoemission
spectroscopy, provides a reasonable description of the observed spin
excitations. This analysis shows that electron correlations in the Fe-3$d$
bands yield enhanced effective electron masses, and consequently, induce
substantial narrowing of the spin excitation bandwidth. Our results highlight
the importance of electron correlations in an itinerant description of the spin
excitations in iron-based superconductors.",1806.02097v1
2017-05-22,The Spin Distribution of Fast Spinning Neutron Stars in Low Mass X-Ray Binaries: Evidence for Two Sub-Populations,"We study the current sample of rapidly rotating neutron stars in both
accreting and non-accreting binaries in order to determine whether the spin
distribution of accreting neutron stars in low-mass X-ray binaries can be
reconciled with current accretion torque models. We perform a statistical
analysis of the spin distributions and show that there is evidence for two
sub-populations among low-mass X-ray binaries, one at relatively low spin
frequency, with an average of ~300 Hz and a broad spread, and a peaked
population at higher frequency with average spin frequency of ~575 Hz. We show
that the two sub-populations are separated by a cut-point at a frequency of
~540 Hz. We also show that the spin frequency of radio millisecond pulsars does
not follow a log-normal distribution and shows no evidence for the existence of
distinct sub-populations. We discuss the uncertainties of different accretion
models and speculate that either the accreting neutron star cut-point marks the
onset of gravitational waves as an efficient mechanism to remove angular
momentum or some of the neutron stars in the fast sub-population do not evolve
into radio millisecond pulsars.",1705.07669v1
2014-06-17,Spectral function of the $U \rightarrow \infty$ one dimensional Hubbard model at finite temperature and the crossover to the spin incoherent regime,"The physics of the strongly interacting Hubbard chain (with $t/U \ll 1$) at
finite temperatures undergoes a crossover to a spin incoherent regime when the
temperature is very small relative to the Fermi energy, but larger than the
characteristic spin energy scale. This crossover can be understood by means of
Ogata and Shiba's factorized wave function, where charge and spin are totally
decoupled, and assuming that the charge remains in the ground state, while the
spin is thermally excited and at an effective ""spin temperature"". We use the
time-dependent density matrix renormalization group method (tDMRG) to calculate
the dynamical contributions of the spin, to reconstruct the single-particle
spectral function of the electrons. The crossover is characterized by a
redistribution of spectral weight both in frequency and momentum, with an
apparent shift by $k_F$ of the minimum of the dispersion.",1406.4471v1
2018-02-20,Collective Yu-Shiba-Rusinov states in magnetic clusters at superconducting surfaces,"We study the properties of collective Yu-Shiba-Rusinov (YSR) states generated
by multiple magnetic adatoms (clusters) placed on the surface of a
superconductor. For magnetic clusters with equal distances between their
constituents, we demonstrate the formation of effectively spin-unpolarized YSR
states with subgap energies independent of the spin configuration of the
magnetic impurities. We solve the problem analytically for arbitrary spin
structure and analyze both spin-polarized (dispersive energy levels) and
spin-unpolarized (pinned energy levels) solutions. While the energies of the
spin-polarized solutions can be characterized solely by the net magnetic moment
of the cluster, the wave functions of the spin-unpolarized solutions
effectively decouple from it. This decoupling makes them stable against thermal
fluctuation and detectable in scanning tunneling microscopy experiments.",1802.07121v2
2016-03-15,A Realization of the Haldane-Kane-Mele Model in a System of Localized Spins,"We theoretically study a spin Hamiltonian for spin-orbit-coupled ferromagnets
on the honeycomb lattice. We find that the effective Hamiltonian for magnons, a
quanta of spin-wave excitations from ordered states, is equivalent to the
Haldane model for electrons in the honeycomb lattice, which indicates the
nontrivial topology of the magnon bands and the existence of the associated
edge state. We also take the Schwinger boson (or bosonic spinon)
representations of spins that are applicable both to ordered and disordered
phases. We show that the spinon bands within the mean-field treatment are
topologically nontrivial, which causes a spin Nernst effect, by adopting the
properties of the Kane-Mele model. A feasible experimental realization of the
spin Hamiltonian is proposed.",1603.04827v2
2017-02-13,Collective spin excitations of helices and magnetic skyrmions: review and perspectives of magnonics in non-centrosymmetric magnets,"Magnetic materials hosting correlated electrons play an important role for
information technology and signal processing. The currently used ferro-, ferri-
and antiferromagnetic materials provide microscopic moments (spins) that are
mainly collinear. Recently more complex spin structures such as spin helices
and cycloids have regained a lot of interest. The interest has been initiated
by the discovery of the skyrmion lattice phase in non-centrosymmetric helical
magnets. In this review we address how spin helices and skyrmion lattices
enrich the microwave characteristics of magnetic materials. When discussing
perspectives for microwave electronics and magnonics we focus particularly on
insulating materials as they avoid eddy current losses, offer low spin-wave
damping, and might allow for electric field control of collective spin
excitations. Thereby, they further fuel the vision of magnonics operated at low
energy consumption.",1702.03668v1
2017-02-21,Holon Wigner Crystal in a Lightly Doped Kagome Quantum Spin Liquid,"We address the problem of a lightly doped spin-liquid through a large-scale
density-matrix renormalization group (DMRG) study of the $t$-$J$ model on a
Kagome lattice with a small but non-zero concentration, $\delta$, of doped
holes. It is now widely accepted that the undoped ($\delta=0$) spin 1/2
Heisenberg antiferromagnet has a spin-liquid groundstate. Theoretical arguments
have been presented that light doping of such a spin-liquid could give rise to
a high temperature superconductor or an exotic topological Fermi liquid metal
(FL$^\ast$). Instead, we infer that the doped holes form an insulating
charge-density wave state with one doped-hole per unit cell - i.e. a Wigner
crystal (WC). Spin correlations remain short-ranged, as in the spin-liquid
parent state, from which we infer that the state is a crystal of spinless
holons (WC$^\ast$), rather than of holes. Our results may be relevant to Kagome
lattice Herbertsmithite $\rm ZnCu_3(OH)_6Cl_2$ upon doping.",1702.06577v2
2019-03-17,Spin Photonics in 3D Whispering Gallery Mode Resonators,"Whispering gallery modes are known for having orbital angular momentum,
however the interplay of local spin density, orbital angular momentum, and the
near-field interaction with quantum emitters is much less explored. Here, we
study the spin-orbital interaction of a circularly polarized dipole with the
whispering gallery modes (WGMs) of a spherical resonator. Using an exact dyadic
Green's function approach, we show that the near-field interaction between the
photonic spin of a circularly polarized dipole and the local spin density of
whispering gallery modes gives rise to unidirectional behaviour where modes
with either positive or negative orbital angular momentum are excited. We show
that this is a manifestation of spin-momentum locking using the whispering
gallery modes of the spherical resonator. We discuss the requirements for
possible experimental demonstrations using Zeeman transitions in cold atoms or
quantum dots, and outline potential applications of these previously overlooked
properties. Our work firmly establishes local spin density, momentum and decay
as a universal right-handed electromagnetic triplet for evanescent waves.",1903.07184v2
2019-05-29,Highly conductive and complete spin filtering of nickel atomic contacts in a nitrogen atmosphere,"Generating efficient and highly spin-polarized currents through nanoscale
junctions is essential in the field of nanoelectronics and spintronics. In this
paper, using $ab$ $initio$ electron transport calculations, we predict highly
conductive and perfect spin filtering of nickel atomic contacts in a nitrogen
environment, where a single N$_2$ molecule sits in parallel (energetically most
favorable) between two nickel electrodes. Such a particular performance is due
to the wave function orthogonality between majority spin $s$-like states of
ferromagnetic electrodes and the lowest unoccupied molecular orbital of the
N$_2$ molecule, and thus, majority spin electrons are completely blocked at the
interface. For the minority spin, on the contrary, two almost saturated
conducting channels were formed due to the effective coupling between
$d_{zx,zy}$ of the Ni atom and $p_{x,y}$ of the N atom, resulting in large
conductance of about 1$G_0$ ($=2e^2/h$). As a consequence, a single N$_2$
molecule acts as a highly conductive and half-metallic conductor. On the other
hand, the CO and NO incorporated molecular junctions exhibit rather low
conductance with a partially spin-polarized current.",1905.12606v1
2020-11-04,Effects of Short-Distance Modifications to General Relativity in Spinning Binary Systems,"We investigate the possibility of testing short distance modifications to
General Relativity via higher curvature terms in the fundamental gravity
Lagrangian by analysing their impact on observations of spinning astronomical
binary systems. By using effective field theory methods applied to the 2-body
problem, generic lower bounds on the short-distance scale accompanying high
curvature terms can be set. In particular we extend known results by deriving
spin-dependent effects in binding energy, radiation emission process, and spin
precession equations in binary systems, which are the fundamental ingredients
to observe spin-dependent effects in gravitational wave detections from compact
binary coalescences and spin precession in double binary pulsars.",2011.02124v3
2021-02-22,Quantum sensing of photonic spin density,"Photonic spin density (PSD) in the near-field gives rise to exotic phenomena
such as photonic skyrmions, optical spin-momentum locking and unidirectional
topological edge waves. Experimental investigation of these phenomena requires
a nanoscale probe that directly interacts with PSD. Here, we propose and
demonstrate that the nitrogen-vacancy (NV) center in diamond can be used as a
quantum sensor for detecting the spinning nature of photons. This room
temperature magnetometer can measure the local polarization of light in
ultra-subwavelength volumes through photon-spin-induced virtual transitions.
The direct detection of light's spin density at the nanoscale using NV centers
in diamond opens a new frontier for studying exotic phases of photons as well
as future on-chip applications in spin quantum electrodynamics (sQED).",2102.11373v1
2021-04-27,Magnon modes as a joint effect of surface ferromagnetism and spin-orbite coupling in CoSi chiral topological semimetal,"CoSi single crystal is a known realization of a chiral topological semimetal
with simultaneously broken mirror and inversion symmetries. In addition to the
symmetry-induced spin-orbit coupling, surface ferromagnetism is known in
nominally diamagnetic CoSi structures, which appears due to the distorted bonds
and ordered vacancies near the surface. We experimentally investigate electron
transport through a thin CoSi flake at high current density. Surprisingly, we
demonstrate $dV/dI(I)$ curves which are qualitatively similar to ones for
ferromagnetic multilayers with characteristic $dV/dI$ magnon peaks and
unconventional magnetic field evolution of the peaks' positions. We understand
these observations as a result of current-induced spin polarization due to the
significant spin-orbit coupling in CoSi. Scattering of non-equilibrium
spin-polarized carriers within the surface ferromagnetic layer is responsible
for the precessing spin-wave excitations, so the observed magnon modes are the
joint effect of surface ferromagnetism and spin-orbit coupling in a CoSi chiral
topological semimetal. Thus, thin CoSi flakes behave as magnetic conductors
with broken inversion symmetry, which is important for different spintronic
phenomena.",2104.13252v1
2021-10-14,Dresselhaus spin-orbit interaction in the p-AlGaAs/GaAs/AlGaAs structure with a square quantum well: Surface Acoustic Waves Study,"The effect of spin-orbit interaction was studied in a high-quality
$p$-AlGaAs/GaAs/AlGaAs structure with a square quantum well using acoustic
methods. The structure grown on a GaAs (100) substrate was symmetrically doped
with carbon on both sides of the quantum well. Shubnikov-de Haas-type
oscillations of the ac conductance of two-dimensional holes were measured. At a
low magnetic field $B <$2 T conductance oscillations undergo beating induced by
a spin-orbit interaction. Analysis of the beating character made it possible to
separate the conductance contributions from the two heavy holes subbands split
by the spin-orbit interaction. For each of the subbands the values of the
effective masses and quantum relaxation times have been determined, and then
the energy of the spin-orbit interaction was obtained. The quantum well
profile, as well as the small magnitude of the spin-orbit interaction, allowed
us to conclude that the spin-orbit splitting is governed by the Dresselhaus
mechanism.",2110.07302v1
2004-05-18,Gapless Excitation above a Domain Wall Ground State in a Flat Band Hubbard Model,"We construct a set of exact ground states with a localized ferromagnetic
domain wall and with an extended spiral structure in a deformed flat-band
Hubbard model in arbitrary dimensions. We show the uniqueness of the ground
state for the half-filled lowest band in a fixed magnetization subspace. The
ground states with these structures are degenerate with all-spin-up or
all-spin-down states under the open boundary condition. We represent a spin
one-point function in terms of local electron number density, and find the
domain wall structure in our model. We show the existence of gapless
excitations above a domain wall ground state in dimensions higher than one. On
the other hand, under the periodic boundary condition, the ground state is the
all-spin-up or all-spin-down state. We show that the spin-wave excitation above
the all-spin-up or -down state has an energy gap because of the anisotropy.",0405388v4
2017-03-01,Spin-Momentum Locking in the Near Field of Metal Nanoparticles,"Light carries both spin and momentum. Spin-orbit interactions of light come
into play at the subwavelength scale of nano-optics and nano-photonics, where
they determine the behaviour of light. These phenomena, in which the spin
affects and controls the spatial degrees of freedom of light, are attracting
rapidly growing interest. Here we present results on the spin-momentum locking
in the near field of metal nanostructures supporting localized surface
resonances. These systems can confine light to very small dimensions below the
diffraction limit, leading to a striking near-field enhancement. In contrast to
the propagating evanescent waves of surface plasmon-polariton modes, the
electromagnetic near-field of localized surface resonances does not exhibit a
definite position-independent momentum or polarization. Our results can be
useful to investigate the spin-orbit interactions of light for complex
evanescent fields. Note that the spin of the incident light can control the
rotation direction of the canonical momentum.",1703.00205v2
2017-04-07,Spin current and second harmonic generation in non-collinear magnetic systems: the hydrodynamic model,"We report a theoretical study of the second harmonic generation in a
noncollinearly magnetized conductive medium with equilibrium spin current. The
hydrodynamic model is used to unravel the mechanism of a novel effect of the
double frequency signal generation due to the spin current. According to our
calculations, this second harmonic response appears due to the ""non-adiabatic""
spin polarization of the conduction electrons induced by the oscillations in
the non-uniform magnetization forced by the electric field of the
electromagnetic wave. Together with the linear velocity response this leads to
the generation of the double frequency spin current. This spin current is
converted to the electric current via the inverse Spin Hall effect, and the
double-frequency electric current emits the second harmonic radiation.",1704.02229v4
2019-07-16,Current-driven Rashba Field in a Magnetic Quantum Well,"In materials lacking inversion symmetry, the spin-orbit coupling enables the
direct connection between the electron's spin and its linear momentum, a
phenomenon called inverse spin galvanic effect. In magnetic materials, this
effect promotes current-driven torques that can be used to control the
magnetization direction electrically. In this work, we investigate the
current-driven inverse spin galvanic effect in a quantum well consisting in a
magnetic material embedded between dissimilar insulators. Assuming the presence
of Rashba spin-orbit coupling at the interfaces, we investigate the nature of
the non-equilibrium spin density and the influence of the quantum well
parameters. We find that the torque is governed by the interplay between the
number of states participating to the transport and their spin chirality, the
penetration of the wave function into the tunnel barriers, and the strength of
the Rashba term.",1907.07116v1
2020-02-08,Hole spin-flip transitions in a self-assembled quantum dot,"In this work, we investigate hole spin-flip transitions in a single
self-assembled InGaAs/GaAs quantum dot. We find the hole wave functions using
the 8-band $kp$ model and calculate phonon-assisted spin relaxation rates for
the ground-state Zeeman doublet. We systematically study the importance of
various admixture- and direct spin-phonon mechanisms giving rise to the
transition rates. We show that the biaxial and shear strain constitute dominant
spin-admixture coupling mechanisms. Then, we demonstrate that hole spin
lifetime can be increased if a quantum dot is covered by a strain-reducing
layer. Finally, we show that the spin relaxation can be described by an
effective model.",2002.03195v1
2020-07-02,Magnetic-field-induced reorientation in the SDW and the spin-stripe phases of the frustrated spin-1/2 chain compound $β$-TeVO$_4$,"$\beta$-TeVO$_4$ is a frustrated spin 1/2 zig-zag chain system,where
spin-density-wave (SDW), vector chiral (VC)and an exotic dynamic spin-stripe
phase compete at low temperatures. Here we use torque magnetometry to study the
anisotropy of these phases in magnetic fields of up to 5 T. Our results show
that the magnetic-field-induced spin reorientation occurs in the SDW and in the
spin stripe phases for $\mu_0 H \geq 2$~T. The observed spin reorientation is a
new element of the anisotropic phase diagram for the field directions in the
$ac$ and $a^*b$ crystallographic planes. The presented results should help
establishing the model of anisotropic magnetic interactions, which are
responsible for the formation of complex magnetic phases in $\beta$-TeVO$_4$
and similar quantum systems.",2007.00932v1
2020-07-16,Spin torque and persistent currents caused by percolation of topological surface states,"The topological insulator/ferromagnetic metal (TI/FMM) bilayer thin films
emerged as promising topological surface state-based spintronic devices, most
notably in their efficiency of current-induced spin torque. Using a cubic
lattice model, we reveal that the surface state Dirac cone of the TI can
gradually merge into or be highly intertwined with the FMM bulk bands, and the
surface states percolate into the FMM and eventually hybridize with the quantum
well states therein. The magnetization can distort the spin-momentum locking of
the surface states and yield an asymmetric band structure, which causes a
laminar flow of room temperature persistent charge current. Moreover, the
proximity to the FMM also promotes a persistent laminar spin current. Through a
linear response theory, we elaborate that both the surface state and the FMM
bulk bands contribute to the current-induced spin torque, and their real wave
functions render the spin torque predominantly field-like, with a magnitude
highly influenced by the degree of the percolation of the surface states. On
the other hand, impurities can change the spin polarization expected from the
Edelstein effect and generate a damping-like torque, and produce a torque even
when the magnetization points in-plane and orthogonal to the current direction.",2007.08055v1
2021-03-25,Perfect flat band with chirality and charge ordering out of strong spin-orbit interaction,"Spin-orbit interaction established itself as a major role player for emergent
phenomena in modern condensed matter including a topological insulator, spin
liquid and spin-dependent transports. However, its function is rather limited
to adding topological nature to each phases of matter. We prove by our spinor
line graph theory that a very strong spin-orbit interaction realized in 5d
pyrochlore electronic systems generates multiply degenerate perfect flat bands.
Unlike any of the previous flat bands, the electrons living there localize in
real space by destructively interfering with each other in a spin selective
manner ruled by the SU(2) gauge field. These electrons avoid the Coulomb
interaction by self-organizing their localized wave functions. This gives rise
to the trimerized charge ordering hand in hand with a stiff spin chirality,
which may explain the recently found exotic low-temperature insulating phase of
CsW2O6.",2103.13672v2
2021-07-22,Variability of electron and hole spin qubits due to interface roughness and charge traps,"Semiconductor spin qubits may show significant device-to-device variability
in the presence of spin-orbit coupling mechanisms. Interface roughness, charge
traps, layout or process inhomogeneities indeed shape the real space wave
functions, hence the spin properties. It is, therefore, important to understand
how reproducible the qubits can be, in order to assess strategies to cope with
variability, and to set constraints on the quality of materials and
fabrication. Here we model the variability of single qubit properties (Larmor
and Rabi frequencies) due to disorder at the Si/SiO$_2$ interface (roughness,
charge traps) in metal-oxide-semiconductor devices. We consider both electron
qubits (with synthetic spin-orbit coupling fields created by micro-magnets) and
hole qubits (with intrinsic spin-orbit coupling). We show that charge traps are
much more limiting than interface roughness, and can scatter Rabi frequencies
over one order of magnitude. We discuss the implications for the design of spin
qubits and for the choice of materials.",2107.10902v2
2021-09-08,Gravity with a Dynamical Spinning Aether,"Einstein-aether theory is extended by allowing for spinning degrees of
freedom of the aether. In addition to the acceleration, shear, expansion, and
vorticity of the aether velocity field, a spin rotation describing the dynamics
of a classical intrinsic angular momentum of the aether is introduced as a
kinematic quantity. The action of Einstein-aether theory is augmented by a term
quadratic in the spin rotation and by coupling terms with the vorticity and the
acceleration. Besides breaking the Lorentz boost invariance, the theory breaks
the invariance under spatial rotations in the direction of the aether velocity.
In the weak field limit, there is a linear relationship between the spin
rotation, the vorticity, and the acceleration. Linearized wave solutions
correspond to the ones of Einstein-aether theory where the speeds of the spin 0
and spin 1 mode are modified. The extension of Einstein-aether theory has a
natural formulation in the framework of a teleparallel geometry where the
kinematic quantities become torsion fields.",2109.03700v1
2022-01-04,Quantum dynamics of Gaudin magnets,"Quantum dynamics of many-body systems is a fascinating and significant
subject for both theory and experiment. The question of how an isolated
many-body system evolves to its steady state after a sudden perturbation or
quench still remains challenging. In this paper, using the Bethe ansatz wave
function, we study the quantum dynamics of an inhomogeneous Gaudin magnet. We
derive explicit analytical expressions for various local dynamic quantities
with an arbitrary number of flipped bath spins, such as: the spin distribution
function, the spin-spin correlation function, and the Loschmidt echo. We also
numerically study the relaxation behavior of these dynamic properties, gaining
considerable insight into coherence and entanglement between the central spin
and the bath. In particular, we find that the spin-spin correlations relax to
their steady value via a nearly logarithmic scaling, whereas the Loschmidt echo
shows an exponential relaxation to its steady value. Our results advance the
understanding of relaxation dynamics and quantum correlations of long-range
interacting models of Gaudin type.",2201.01025v1
2022-01-31,Theory of Silicon Spin Qubit Relaxation in a Synthetic Spin-Orbit Field,"We develop the theory of single-electron silicon spin qubit relaxation in the
presence of a magnetic field gradient. Such field gradients are routinely
generated by on-chip micromagnets to allow for electrically controlled quantum
gates on spin qubits. We build on a valley-dependent envelope function theory
that enables the analysis of the electron wave function in a silicon quantum
dot with an arbitrary roughness at the interface. We assume the presence of
single-layer atomic steps at a Si/SiGe interface and study how the presence of
a gradient field modifies the spin-mixing mechanisms. We show that our
theoretical modeling can quantitatively reproduce results of experimental
measurements of qubit relaxation in silicon in the presence of a micromagnet.
We further study in detail how a field gradient can modify the EDSR Rabi
frequency of a silicon spin qubit. While this strongly depends on the details
of the interface roughness, interestingly, we find that adding a micromagnet on
top of a spin qubit with an ideal interface can even reduce the EDSR frequency
within some interval of the external magnetic field strength.",2201.13173v2
2022-02-15,Linear mode analysis from spin transport equation,"We provide a linear analysis on normal modes of the spin Boltzmann equation
proposed in \cite{Weickgenannt:2021cuo}, where the non-diagonal or polarized
part of the transition rate is neglected to ensure the Hermitian property of
linearized collision operator. As an instrumental element of spin kinetic
theory, the conservation of total angular momentum is explicitly considered,
thus our analysis is relevant to the recent investigation on the issue of local
spin polarization. By treating the linearized collision operator as an
evolution operator, solving the normal modes turns out a degenerate
perturbation problem in quantum mechanics. The dispersion relations of spinless
modes are in accordance with well-known calculations, while the frequencies of
spin modes are also determined up to second-order in wave vector and the second
order expressions are only formal solutions to be further determined. Moreover,
the relaxation of spin density is related to our linear mode analysis, which
shall play a big role in investigating the issues of the local spin
polarization in the relativistic heavy-ion collisions.",2202.07373v5
2022-03-28,Stable mass transfer can explain massive binary black hole mergers with a high spin component,"Recent gravitational wave observations showed that binary black hole (BBH)
mergers with massive components are more likely to have high effective spins.
In the model of isolated binary evolution, BH spins mainly originate from the
angular momenta of the collapsing cores before BH formation. Both observations
and theories indicate that BHs tend to possess relatively low spins, the origin
of fast-spinning BHs remains a puzzle. We investigate an alternative process
that stable Case A mass transfer may significantly increase BH spins during the
evolution of massive BH binaries. We present detailed binary evolution
calculations and find that this process can explain observed high spins of some
massive BBH mergers under the assumption of mildly super-Eddington accretion.",2203.14529v1
2022-04-28,Field-Assisted Sub-Terahertz Spin Pumping and Auto-Oscillation in NiO,"Spin pumping converting sub-terahertz electromagnetic waves to DC spin
currents has recently been demonstrated in antiferromagnets (AFMs) with
easy-axis magnetic anisotropy. However, easy-plane AFMs such as NiO, which are
easier to prepare experimentally, are considered to be bad candidates for spin
pumping because the N\'{e}el vector oscillation is linearly polarized, placing
a major restriction on the material choice for practical applications. Through
a case study of NiO, we show that an applied magnetic field below the spin-flop
transition can substantially modify the polarization of the resonance
eigenmodes, which enables coherent sub-terahertz spin pumping as strong as that
in easy-axis AFMs. In addition, we find that an applied magnetic field can
significantly reduce the threshold of N\'{e}el vector auto-oscillation
triggered by spin-transfer torques. These prominent field-assisted effects can
greatly facilitate spintronic device engineering in the sub-terahertz frequency
regime.",2204.13283v2
2022-10-04,Spin-orbit enhancement in Si/SiGe heterostructures with oscillating Ge concentration,"We show that Ge concentration oscillations within the quantum well region of
a Si/SiGe heterostructure can significantly enhance the spin-orbit coupling of
the low-energy conduction-band valleys. Specifically, we find that for Ge
oscillation wavelengths near $\lambda = 1.57~\text{nm}$ with an average Ge
concentration of $\bar{n}_{\text{Ge}} = 5\%$ in the quantum well region, a
Dresselhaus spin-orbit coupling is induced, at all physically relevant electric
field strengths, which is over an order of magnitude larger than what is found
in conventional Si/SiGe heterostructures without Ge concentration oscillations.
This enhancement is caused by the Ge concentration oscillations producing
wave-function satellite peaks a distance $2 \pi/\lambda$ away in momentum space
from each valley, which then couple to the opposite valley through Dresselhaus
spin-orbit coupling. Our results indicate that the enhanced spin-orbit coupling
can enable fast spin manipulation within Si quantum dots using electric dipole
spin resonance in the absence of micromagnets. Indeed, our calculations yield a
Rabi frequency $\Omega_{\text{Rabi}}/B > 500~\text{MHz/T}$ near the optimal Ge
oscillation wavelength $\lambda = 1.57~\text{nm}$.",2210.01700v2
2022-12-27,Electric-field-driven spin resonance by on-surface exchange coupling to a single-atom magnet,"Coherent control of individual atomic and molecular spins on surfaces has
recently been demonstrated by using electron spin resonance (ESR) in a scanning
tunneling microscope (STM). Here we present a combined experimental and
modeling study of the ESR of a single hydrogenated Ti atom that is
exchange-coupled to a Fe adatom located in 0.6-0.8 nm away. Continuous wave and
pulsed ESR of the Ti spin showed a Rabi rate with two contributions, one from
the tip and the other from the Fe, whose spin interactions with Ti were
modulated by the radio-frequency electric field. The Fe contribution is
comparable to the tip, as revealed from its dominance when the tip was
retracted, and tunable using a vector magnetic field. Our new ESR scheme allows
on-surface individual spins to be addressed and coherently controlled without
the need for magnetic interaction with a tip. This study establishes a feasible
implementation of spin-based multi-qubit systems on surfaces.",2212.13380v2
2022-12-30,Unique determination of localized basis in molecular spin,"Localized basis plays an important role in comprehending the magnetic
dynamics in molecular spins from a physics perspective. Nonetheless, the
uniqueness and rigor of its determination have received limited attention. In
this study, we propose a new determination of the localized basis applicable to
both non-Kramers and Kramers molecular spin systems, leveraging the
time-reversal symmetry of the spin Hamiltonian and the molecular spin's main
magnetic axis. By introducing this, we establish a distinct and practical means
of determining the localized basis, enabling the association of a molecular
spin wave function with either an ""up"" or ""down"" magnetic moment orientation in
molecular spins. This finding facilitates a comprehensive interpretation of
magnetic dynamics and simplifies the construction of theoretical models for
materials analysis.",2212.14639v3
2023-06-29,Spin Seebeck effect in the classical easy-axis antiferromagnetic chain,"By molecular dymanics simulations we study the spin Seebeck effect as a
function of magnetic field in the prototype classical easy-axis
antiferromagnetic chain, in the far-out of equilibrium as well as linear
response regime. We find distinct behavior in the low field antiferromagnetic,
middle field canted and high field ferromagnetic phase. In particular, in the
open boundary system at low temperatures, we observe a divergence of the spin
current in the spin-flop transition between the antiferromagnetic and canted
phase, accompanied by a change of sign in the generated spin current by the
temperture gradient. These results are corroborated by a simple spin-wave
phenomenological analysis and simulations in the linear response regime. They
shed light on the spin current sign change observed in experiments in bulk
antiferromagnetic materials.",2306.16840v3
1994-07-28,Quantum disordered phase in a doped antiferromagnet,"A quantitative description of the transition to a quantum disordered phase in
a doped antiferromagnet is obtained with a U(1) gauge-theory, where the gap in
the spin-wave spectrum determines the strength of the gauge-fields. They
mediate an attractive long-range interaction whose possible bound-states
correspond to charge-spin separation and pairing.",9407112v1
1997-09-13,Spin-density Wave in Ising-coupled Antiferromagnetic Chains,"The effect of anisotropy in the nearest-neighbor spin interactions that
couple $N\geq 2$ consecutive spin-1/2 antiferromagnetic chains is studied
theoretically by considering the limit where the coupling is purely of the
Ising type. An analysis based on the equivalent Luttinger model reveals that
the groundstate is an Ising antiferromagnet in general.",9709153v1
1998-04-01,The two-leg t-J ladder: a spin liquid generated by Gutzwiller projection of magnetic bands,"The ground state of the two-leg Heisenberg ladder is identified as an RVB
type spin liquid, which is generated by Gutzwiller projection of tight-binding
bands with flux pi per plaquet. Explicit trial wave functions for the magnon
and hole excitations are formulated in terms of spinons and holons.",9804002v3
2000-10-17,Spin-Orbit Coupling in the ab initio Pseudopotential Framework,"We describe the implementation of total angular momentum dependent
pseudopotentials in a plane wave formulation of density functional theory. Our
approach thus goes beyond the scalar-relativistic approximation usually made in
ab initio pseudopotential calculations and explicitly includes spin-orbit
coupling. We outline the necessary extensions and compare the results to
available all-electron calculations and experimental data.",0010225v1
2001-01-31,Effective Theory For Quantum Spin System In Low Dimension - Beyond Long-Wavelength Limit,"An effective theory for quantum spin system in low dimension is constructed
in the finite-q regime. It is shown that there are field configurations for
which Wess-Zumino term contributes to the partition functions as topological
term for ferromagnet as well as antiferromagnet in both one and two dimensional
lattice,in contrast to the long wave length regime.",0101466v1
2001-02-02,Gate-Controlled Electron Spin Resonance in a GaAs/AlGaAs Heterostructure,"The electron spin resonance (ESR) of two-dimensional electrons is
investigated in a gated GaAs/AlGaAs heterostructure. We found that the ESR
resonance frequency can be turned by means of a gate voltage. The front and
back gates of the heterostructure produce opposite g-factor shift, suggesting
that electron g-factor is being electrostatically controlled by shifting the
equilibrium position of the electron wave function from one epitaxial layer to
another with different g-factors.",0102044v1
2004-12-15,Nuclear Magnetic Relaxation in the Ferrimagnetic Chain Compound NiCu(C_7_H_6_N_2_O_6_)(H_2_O)_3_2H_2_O: Three-Magnon Scattering?,"Recent proton spin-lattice relaxation-time (T_1_) measurements on the
ferrimagnetic chain compound NiCu(C_7_H_6_N_2_O_6_)(H_2_O)_3_2H_2_O are
explained by an elaborately modified spin-wave theory. We give a strong
evidence of the major contribution to 1/T_1_ being made by the three-magnon
scattering rather than the Raman one.",0412389v1
2006-11-09,Spin density wave formation in graphene facilitated by the in-plane magnetic field,"We suggest that by applying a magnetic field lying in the plane of graphene
layer one may facilitate an excitonic condensation of electron-hole pairs with
opposite spins and chiralities. The provided calculations yield a conservative
estimate for the transition temperature $T_c \sim 0.1 B$.",0611251v1
2007-02-05,Rabi oscillations from ultrasound in spin systems,"It is shown that ultrasound in the GHz range can generate space-time Rabi
oscillations between spin states of molecular magnets. We compute dynamics of
the magnetization generated by surface acoustic waves and discuss conditions
under which this novel quantum effect can be observed.",0702116v1
1998-03-05,On the spin-rotation-gravity coupling,"The inertial and gravitational properties of intrinsic spin are discussed and
some of the recent work in this area is briefly reviewed. The extension of
relativistic wave equations to accelerated systems and gravitational fields is
critically examined. A nonlocal theory of accelerated observers is presented
and its predictions are compared with observation.",9803017v1
2004-03-13,World-line deviation and spinning particles,"A set of world-line deviation equations is derived in the framework of
Mathisson-Papapetrou-Dixon description of pseudo-classical spinning particles.
They generalize the geodesic deviation equations. We examine the resulting
equations for particles moving in the space-time of a plane gravitational wave.",0403055v1
2007-02-01,Spin-2 particles in gravitational fields,"We give a solution of the wave equation for massless, or massive spin-2
particles propagating in a gravitational background. The solution is covariant,
gauge-invariant and exact to first order in the background gravitational field.
The background contribution is confined to a phase factor from which
geometrical and physical optics can be derived. The phase also describes
Mashhoon's spin-rotation coupling and, in general, the spin-gravity
interaction.",0702008v1
1998-01-15,The Spin Symmetry of Heavy Baryons in the Framework of the B.S. Equation,"We construct the B.S. equation for baryons. The most general form of the B.S.
wave function is given. In the heavy quark limit we show clearly that the spin
symmetry exists in heavy baryon states.",9801309v1
2005-02-23,Unified approach to photo and electro-production of mesons with arbitrary spins,"A new approach to identify the independent amplitudes along with their
partial wave multipole expansions, for photo and electro-production is
suggested,which is generally applicable to mesons with arbitrary spin-parity.
These amplitudes facilitate direct identification of different resonance
contributions.",0502073v2
2005-02-22,Quantum Mechanics without Complex Numbers: A Simple Model for the Electron Wavefunction Including Spin,"A simple real-space model for the electron wavefunction is suggested, based
on a transverse wave with helicity, rotating at mc^2/h. The mapping of the real
two-dimensional vector phasor to the complex plane permits this to satisfy the
standard time-dependent Schroedinger equation. This model is extended to
provide an intuitive physical picture of electron spin. Implications of this
model are discussed.",0502139v1
2007-06-26,Birefringence (rotation of polarization plane and spin dichroism) of deuterons in carbon target,"Birefringence phenomenon for deuteron with energy up 20 MeV in carbon target
is considered. The estimation for spin dichroism and for angle of rotation of
polarization plane of deuterons is presented. It is shown that magnitude of the
phenomenon strongly depends on behavior of the deuteron wave functions on small
distance between nucleon in deuteron.",0706.3808v2
2007-12-12,Search of S3 LIGO data for gravitational wave signals from spinning black hole and neutron star binary inspirals,"We report on the methods and results of the first dedicated search for
gravitational waves emitted during the inspiral of compact binaries with
spinning component bodies. We analyze 788 hours of data collected during the
third science run (S3) of the LIGO detectors. We searched for binary systems
using a detection template family designed specially to capture the effects of
the spin-induced precession of the orbital plane. We present details of the
techniques developed to enable this search for spin-modulated gravitational
waves, highlighting the differences between this and other recent searches for
binaries with non-spinning components. The template bank we employed was found
to yield high matches with our spin-modulated target waveform for binaries with
masses in the asymmetric range 1.0 Msol < m1 < 3.0 Msol and 12.0 Msol < m2 <
20.0 Msol which is where we would expect the spin of the binary's components to
have significant effect. We find that our search of S3 LIGO data had good
sensitivity to binaries in the Milky Way and to a small fraction of binaries in
M31 and M33 with masses in the range 1.0 Msol < m1, m2 < 20.0 Msol. No
gravitational wave signals were identified during this search. Assuming a
binary population with spinning components and Gaussian distribution of masses
representing a prototypical neutron star - black hole system with m1 ~ 1.35
Msol and m2 ~ 5 Msol, we calculate the 90%-confidence upper limit on the rate
of coalescence of these systems to be 15.9 yr^-1 L_10^-1, where L_10 is 10^10
times the blue light luminosity of the Sun.",0712.2050v3
2008-01-23,Mixing of heavy baryons in the bag model calculations,"Spin-spin interaction causes the mixing between ground state wave functions
of baryons containing three quarks of different flavors. We examine the effect
of this mixing on the baryon masses in the framework of the modified bag model.",0801.3570v1
2009-09-10,Hydrodynamic Limit for the Spin Dynamics of the Heisenberg Chain,"We show that Quantum-Monte-Carlo calculations of the dynamic structure factor
of the isotropic spin-1/2 antiferromagnetic chain at intermediate temperatures
corroborate a picture of diffusive spin dynamics at finite frequencies in the
low-energy long wave-length limit and are in good agreement with recent
predictions for this by J. Sirker, R. G. Pereira, and I. Affleck
[arXiv:0906.1978v1].",0909.1972v1
2010-03-03,Ultra-relativistic grazing collisions of black holes,"We study gravitational wave emission, zoom-whirl behavior and the resulting
spin of the remnant black hole in highly boosted collisions of equal-mass, non
spinning black-hole binaries with generic impact parameter.",1003.0882v1
2010-08-13,Bose-Einstein Condensation in the presence of an artificial spin-orbit interaction,"Bose-Einstein condensation in the presence of a synthetic spin-momentum
interaction is considered, focusing on the case where a Dirac or Rashba
potential is generated via a tripod scheme. We found that the ground states can
be either plane wave states or superpositions of them, each characterized by
their unique density distributions.",1008.2263v2
2011-04-11,Self-consistent spin-wave theory for a frustrated Heisenberg model with biquadratic exchange in the columnar phase and its application to iron pnictides,"Recent neutron scattering studies revealed the three dimensional character of
the magnetism in the iron pnictides and a strong anisotropy between the
exchange perpendicular and parallel to the spin stripes. We extend studies of
the J1-J2-Jc Heisenberg model with S = 1 using self-consistent spin-wave
theory. A discussion of two scenarios for the instability of the columnar phase
is provided. The relevance of a biquadratic exchange term between in-plane
nearest neighbors is discussed. We introduce mean-field decouplings for
biquadratic terms using the Dyson-Maleev and the Schwinger boson
representation. Remarkably their respective mean-field theories do not lead to
the same results, even at zero temperature. They are gauged in the N'eel phase
in comparison to exact diagonalization and series expansion. The J1-J2-Jc model
is analyzed under the influence of the biquadratic exchange Jbq and a detailed
description of the staggered magnetization and of the magnetic excitations is
given. The biquadratic exchange increases the renormalization of the in-plane
exchange constants which enhances the anisotropy between the exchange parallel
and perpendicular to the spin stripes. Applying the model to iron pnictides, it
is possible to reproduce the spin-wave dispersion for CaFe2As2 in the direction
perpendicular to the spin stripes and perpendicular to the planes.
Discrepancies remain in the direction parallel to the spin stripes which can be
resolved by passing from S = 1 to S = 2. In addition, results for the dynamical
structure factor within the self-consistent spin-wave theory are provided.",1104.1954v2
2011-07-21,On the linear forms of the Schrodinger equation,"Generalizing the linearisation procedure used by Dirac and later by
L\'evy-Leblond, we derive the first-order non-relativistic wave equations for
particles of spin 1 and spin 3/2 starting from the Schrodinger equation.",1107.4271v1
2011-12-06,Rashba spin-orbit interaction in quantum ring with confining potential of finite depth,"We present the exact wave functions and energy levels for an electron in a
two-dimensional quantum ring with confining potential of finite depth in the
presence of the Rashba spin-orbit interaction.",1112.1276v1
2012-01-14,Semiclassical description of anisotropic magnets for spin S=1,"In this paper, nonlinear equations describing one-dimensional non-Heisenberg
ferromagnetic model are studied by use of generalized coherent states in a real
parameterization. Also dissipative spin wave equation for dipole and quadruple
branches is obtained if there is a small linear excitation from the ground
state.",1201.3020v1
2012-05-21,Multifractality of eigenfunctions in spin chains,"We investigate different one-dimensional quantum spin-1/2 chain models and by
combining analytical and numerical calculations prove that their ground state
wave functions in the natural spin basis are multifractals with, in general,
non-trivial fractal dimensions.",1205.4541v1
2013-11-10,A strong laser impact on spin precession of a charged particle in the semi-relativistic interaction regime,"In the present note new effects concerned the dynamics of a charged spin-1/2
particle in a strong monochromatic plane wave background are discussed beyond
the conventional dipole approximation. Namely using the semiclassical approach
in the semi-relativistic regime it is shown that the magnetic forces associated
with the laser field have been retained and alter the spin evolution
appreciably.",1311.2316v1
2018-11-16,Kinetic Spin Decoherence in a Gravitational Field,"We consider a wave packet of a spin-1/2 particle in a gravitational field,
the effect of which can be described in terms of a succession of local inertial
frames. It is shown that integrating out of the momentum yields a spin mixed
state, with the entropy dependent on the deviation of metric from the flat
spacetime. The decoherence occurs even if the particle is static in the
gravitational field.",1811.06947v1
2018-02-15,Effects of Symmetry Breaking in Resonance Phenomena,"We show that resonance phenomena can be treated as nonequilibrium phase
transitions. Resonance phenomena, similar to equilibrium phase transitions, are
accompanied by some kind of symmetry breaking and can be characterized by order
parameters. This is demonstrated for spin-wave resonance, helicon resonance,
and spin-reversal resonance.",1802.05589v1
2020-09-21,Thermal Hall effect from two-dimensional Schwinger-boson gas with Rashba spin-orbit interaction: application to ferromagnets with in-plane Dzyaloshinskii-Moriya interaction,"Recently, uncovering the sources of thermal Hall effect in insulators has
become an important issue. In the case of ferromagnetic insulators, it is well
known that Dzyaloshinskii-Moriya (DM) interaction can induce magnon thermal
Hall effect. Specifically, the DM vector parallel to the magnetization
direction induces complex magnon hopping amplitudes, so that magnons act as if
they feel Lorentz force. However, the DM vector which is orthogonal to the
magnetization direction has hitherto been neglected as a possible source of
magnon thermal Hall effect. This is because they play no role in the linear
spin wave theory, an often invoked approximation when computing the magnon
thermal Hall effect. Here, we challenge this expectation by presenting the
self-consistent Schwinger-boson mean field study of two-dimensional magnets
with ferromagnetic Heisenberg interaction and in-plane DM interaction. We find
that the relevant Schwinger-boson mean field Hamiltonian takes the form of
two-dimensional electron gas with Rashba spin-orbit interaction, which is known
to show anomalous Hall effect, spin Hall effect, and Rashba-Edelstein effect,
whose thermal counterparts also appear in our system. Importantly, the thermal
Hall effect can be induced when out-of-plane magnetic field is applied, and
persists even when the magnetic field is large, so that the spins are
significantly polarized, and the linear spin wave theory is expected to be a
reasonable approximation. Since the linear spin wave theory predicts vanishing
thermal Hall effect, our result implies that linear spin wave is not a
sufficient approximation, and that magnon-magnon interaction must be taken into
account to predict the correct thermal Hall conductivity.",2009.09621v1
2008-06-26,A Microscopic Theory of Odd-freqeuncy Pairing in the Two-dimensional Extended Hubbard Model,"We present a microscopic theory of fluctuation-mediated pairing mechanism in
a two-dimensional extended Hubbard model. In contrast to conventional wisdom,
odd-frequency spin-triplet pairing can be stabilized near the spin-density-wave
critical point. Favorable conditions for the odd-frequency pairing are the
presence of geometrical frustration and off-site Coulomb interaction.",0806.4241v1
2017-03-07,Quantum diffusion of electromagnetic fields of ultrarelativistic spin-half particles,"We compute electromagnetic fields created by a relativistic charged spin-half
particle in empty space at distances comparable to the particle Compton
wavelength. The particle is described as a wave packet evolving according to
the Dirac equation. It produces the electromagnetic field that is essentially
different from the Coulomb field due to the quantum diffusion effect.",1703.02606v1
2019-07-08,Coexisting spin resonance and long-range magnetic order of Eu in EuRbFe$_4$As$_4$,"Magnetic excitations and magnetic structure of EuRbFe$_4$As$_4$ were
investigated by inelastic neutron scattering (INS), neutron diffraction, and
random phase approximation (RPA) calculations. Below the superconducting
transition temperature $T_\text{c}=36.5$~K, the INS spectra exhibit the neutron
spin resonances at $Q_\text{res}=1.27(2)$~$\text{\AA}^{-1}$ and
$1.79(3)$~$\text{\AA}^{-1}$. They correspond to the $\mathbf{Q}=(0.5,0.5,1)$
and $(0.5,0.5,3)$ nesting wave vectors, showing three dimensional nature of the
band structure. The characteristic energy of the neutron spin resonance is
$E_\text{res}=17.7(3)$~meV corresponding to $5.7(1)k_\text{B}T_\text{c}$.
Observation of the neutron spin resonance mode and our RPA calculations in
conjunction with the recent optical conductivity measurements are indicative of
the $s_\pm$ superconducting pairing symmetry in EuRbFe$_4$As$_4$. In addition
to the neutron spin resonance mode, upon decreasing temperature below the
magnetic transition temperature $T_\text{N}=15$~K, the spin wave excitation
originating in the long-range magnetic order of the Eu sublattice was observed
in the low-energy inelastic channel. Single-crystal neutron diffraction
measurements demonstrate that the magnetic propagation vector of the Eu
sublattice is $\mathbf{k}=(0, 0, 0.25)$, representing the three-dimensional
antiferromagnetic order. Linear spin wave calculations assuming the obtained
magnetic structure with the intra- and inter-plane nearest neighbor exchange
couplings of $J_1/k_\text{B}=-1.31$~K and $J_c/k_\text{B}=0.08$~K can reproduce
quantitatively the observed spin wave excitation. Our results show that
superconductivity and long-range magnetic order of Eu coexist in
EuRbFe$_4$As$_4$ whereas the coupling between them is rather weak.",1907.03839v1
2020-06-03,Eliashberg theory of a multiband non-phononic spin glass superconductor,"I solved the Eliashberg equations for multiband non-phononic $s\pm$ wave spin
glass superconductor and I calculated the temperature dependence of the gaps
and superfluid density that reveals unusual behavior as non monotonic
temperature dependence and reentrant superconductivity. For particular values
of input parameters the phase diagram is still more complex with two different
ranges of temperature where the superconductivity appears.",2006.02063v3
2022-04-26,Hot-lines topology and the fate of the spin resonance mode in three-dimensional unconventional superconductors,"In the quasi-two-dimensional (quasi-2D) copper- and iron-based
superconductors, the onset of superconductivity is accompanied by a prominent
peak in the magnetic spectrum at momenta close to the wave-vector of the nearby
antiferromagnetic state. Such a peak is well described in terms of a spin
resonance mode, i.e., a spin-1 exciton theoretically predicted for quasi-2D
superconductors with a sign-changing gap. The same theories, however, indicate
that such a resonance mode should be absent in a three-dimensional (3D) system
with a spherical Fermi surface. This raises the question of the fate of the
spin resonance mode in layered unconventional superconductors that are not
strongly anisotropic, such as certain heavy-fermion compounds and potentially
the newly discovered nickelate superconductor NdNiO$_2$. Here, we use the
random-phase-approximation to calculate the dynamical spin susceptibility of 3D
superconductors with a $d_{x^2-y^2}$-wave gap symmetry and corrugated
cylindrical-like Fermi surfaces. By varying the out-of-plane hopping anisotropy
$t_z/t$, we demonstrate that the appearance of a spin resonance mode is
determined by the topology of the hot lines -- i.e. lines on the Fermi surface
that are connected by the magnetic wave-vector. For an in-plane
antiferromagnetic wave-vector, the hot lines undergo a topological transition
from open lines to closed loops at a critical $t_z/t$ value. The closed hot
lines cross the nodal superconducting lines, making the spin resonance mode
overdamped and incoherent. In contrast, for an out-of-plane antiferromagnetic
wave-vector, the hot lines remain open and the spin resonance mode remains
sharp. We discuss the experimental implications of our results for the
out-of-plane dispersion of the spin resonance mode and, more generally, for
inelastic neutron scattering experiments on unconventional superconductors.",2204.12434v2
2023-04-21,Soft Magnons in Anisotropic Ferromagnets,"We discuss spin-wave transport in anisotropic ferromagnets with an emphasis
on the zeroes of the band edges as a function of a magnetic field. An
associated divergence of the magnon spin should be observable by enhanced
magnon conductivities in non-local experiments, especially in two-dimensional
ferromagnets.",2304.10709v1
1995-05-23,Gauge Theory for a Doped Antiferromagnet in a Rotating Reference-Frame,"We study a doped antiferromagnet (AF) using a rotating reference-frame.
Whereas in the laboratory reference-frame with a globally fixed
spin-quantization axis (SQA) the long-wavelength, low-energy physics is given
by the O(3) non-linear $\sigma$-model with current-current interactions between
the fermionic degrees of freedom and the order-parameter field for the
spin-background, an alternative description in form of an U(1) gauge theory can
be derived by choosing the SQA defined by the local direction of the
order-parameter field via a SU(2) rotation of the fermionic spinor. Within a
large-$N$ expansion of this U(1) gauge theory we obtain the phase diagram for
the doped AF and identify the relevant terms due to doping that lead to a
quantum phase transition at $T=0$ from the antiferromagnetically ordered N\'eel
phase to the quantum-disordered (QD) spin-liquid phase. Furthermore, we
calculate the propagator of the corresponding U(1) gauge field, which mediates
a long-range transverse interaction between the bosonic and fermionic fields.
It is found that the strength of the propagator is proportional to the gap of
the spin-excitations. Therefore, we expect as a consequence of this long-range
interaction the formation of bound states when the spin-gap opens, i.e.\ in the
QD spin-liquid phase. The possible bound states are spin-waves with a (spin-)
gap in the excitation spectrum, spinless fermions and pairs of fermions. Thus,
an alternative picture for charge-spin separation emerges, with composite
charge-separated excitations. Moreover, the present treatment shows an intimate
connection between the opening of the spin-gap and charge-spin separation as
well as pairing.",9505105v1
2006-06-05,Phenomenological theory of current driven exchange switching in ferromagnetic nanojunctions,"Phenomenological approach is developed in the theory of spin-valve type
ferromagnetic junctions to describe exchange switching by current flowing
perpendicular to interfaces. Forward and backward current switching effects are
described and they may be principally different in nature. Mobile electron
spins are considered as being free in all the contacting ferromagnetic layers.
Joint action of the following two current effects is investigated: the
nonequilibrium longitudinal spin-injection effective field and the transverse
spin-transfer surface torque. Dispersion relation for fluctuations is derived
and solved for a junction model having spatially localized spin transfer
torque: depth of the torque penetration into the free layer is assumed much
smaller than the total free layer thickness. Some critical value of the well
known Gilbert damping constant is established for the first time. Spin transfer
torque dominates in the instability threshold determination for small enough
damping constants, while the spin-injection effective field dominates for high
damping. Fine interplay between spin transfer torque and spin injection is
necessary to provide a hysteretic behavior of the resistance versus current
dependence. The state diagram building up shows the possibility of
non-stationary (time dependent) nonlinear states arising due to instability
development. Calculations lead to the instability rise time values of the order
of 0.1 ns. Spin wave resonance frequency spectrum softening occurs under the
current growing to the instability threshold. Magnetization fluctuations above
the threshold rise oscillating with time for low damping, but rise
aperiodically and much more rapid for high damping.",0606102v2
2006-06-27,"Surface states, Friedel oscillations, and spin accumulation in p-doped semiconductors","We consider a hole-doped semiconductor with a sharp boundary and study the
boundary spin accumulation in response to a charge current. First, we solve
exactly a single-particle quantum mechanics problem described by the isotropic
Luttinger model in half-space and construct an orthonormal basis for the
corresponding Hamiltonian. It is shown that the complete basis includes two
types of eigenstates. The first class of states contains conventional incident
and reflected waves, while the other class includes localized surface states.
Second, we consider a many-body system in the presence of a charge current
flowing parallel to the boundary. It is shown that the localized states
contribute to spin accumulation near the surface. We also show that the spin
density exhibits current-induced Friedel oscillations with three different
periods determined by the Fermi momenta of the light and heavy holes. We find
an exact asymptotic expression for the Friedel oscillations far from the
boundary. We also calculate numerically the spin density profile and compute
the total spin accumulation, which is defined as the integral of the spin
density in the direction perpendicular to the boundary. The total spin
accumulation is shown to fit very well the simple formula S ~(1 - m_L/m_H)^2,
where m_L and m_H are the light- and heavy-hole masses. The effects of disorder
are discussed. We estimate the spin relaxation time in the Luttinger model and
argue that spin physics cannot be described within the diffusion approximation.",0606670v1
2007-01-04,Rashba interferometers: Spin-dependent single and two-electron interference,"Quantum transport in semiconductor nanostructures can be described
theoretically in terms of the propagation and scattering of electron
probability waves. Within this approach, elements of a phase-coherent electric
circuit play a role similar to quantum-optical devices that can be
characterised by scattering matrices. Electronic analogues of well-know optical
interferometers have been fabricated and used to study special features of
charge carriers in solids. We present results from our theoretical
investigation into the interplay between spin precession and quantum
interference in an electronic Mach-Zehnder interferometer with spin-orbit
coupling of the Rashba type. Intriguing spin-dependent transport effects occur,
which can be the basis for novel spintronic devices such as a magnet-less
spin-controlled field-effect transistor and a variety of single-qubit gates.
Their functionality arises entirely from spin-dependent interference of each
single input electron with itself. We have also studied two-electron
interference effects for the spin-dependent Mach-Zehnder interferometer,
obtaining analytical expressions for its two-fermion-state scattering matrix.
Using this result, we consider ways to generate two-electron output states for
which the Rashba spin-subband quantum number and the output-arm index are
entangled. Combining spin-dependent interference in our proposed Mach-Zehnder
interferometer with a projective charge measurement at the output enables
entanglement generation. As our particular scheme involves tuneable spin
precession, electric-field control of entanglement production can be achieved.",0701065v3
2011-12-20,Ferromagnetic order of nuclear spins coupled to conduction electrons: a combined effect of the electron-electron and spin-orbit interactions,"We analyze the ordered state of nuclear spins embedded in an interacting
two-dimensional electron gas (2DEG) with Rashba spin-orbit interaction (SOI).
Stability of the ferromagnetic nuclear-spin phase is governed by nonanalytic
dependences of the electron spin susceptibility $\chi^{ij}$ on the momentum
($\tilde{\mathbf{q}}$) and on the SOI coupling constant ($\alpha$). The uniform
($\tq=0$) spin susceptibility is anisotropic (with the out-of-plane component,
$\chi^{zz}$, being larger than the in-plane one, $\chi^{xx}$, by a term
proportional to $U^2(2k_F)|\alpha|$, where $U(q)$ is the electron-electron
interaction). For $\tq \leq 2m^*|\alpha|$, corrections to the leading,
$U^2(2k_F)|\alpha|$, term scale linearly with $\tq$ for $\chi^{xx}$ and are
absent for $\chi^{zz}$. This anisotropy has important consequences for the
ferromagnetic nuclear-spin phase: $(i)$ the ordered state--if achieved--is of
an Ising type and $(ii)$ the spin-wave dispersion is gapped at $\tq=0$. To
second order in $U(q)$, the dispersion a decreasing function of $\tq$, and
anisotropy is not sufficient to stabilize long-range order. However,
renormalization in the Cooper channel for $\tq\ll2m^*|\alpha|$ is capable of
reversing the sign of the $\tq$-dependence of $\chi^{xx}$ and thus stabilizing
the ordered state. We also show that a combination of the electron-electron and
SO interactions leads to a new effect: long-wavelength Friedel oscillations in
the spin (but not charge) electron density induced by local magnetic moments.
The period of these oscillations is given by the SO length $\pi/m^*|\alpha|$.",1112.4786v2
2013-01-08,Magnetic anisotropy in hole-doped superconducting Ba 0.67K 0.33Fe 2As2 probed by polarized inelastic neutron scattering,"We use polarized inelastic neutron scattering (INS) to study spin excitations
of optimally hole-doped superconductor Ba$_{0.67}$K$_{0.33}$Fe$_2$As$_{2}$
($T_c=38$ K).
  In the normal state, the imaginary part of the dynamic susceptibility,
$\chi^{\prime\prime}(Q,\omega)$, shows magnetic anisotropy for energies below
$\sim$7 meV with c-axis polarized spin excitations larger than that of the
in-plane component. Upon entering into the superconducting state, previous
unpolarized INS experiments have shown that spin gaps at $\sim$5 and 0.75 meV
open at wave vectors $Q=(0.5,0.5,0)$ and $(0.5,0.5,1)$, respectively, with a
broad neutron spin resonance at $E_r=15$ meV. Our neutron polarization analysis
reveals that the large difference in spin gaps is purely due to different spin
gaps in the c-axis and in-plane polarized spin excitations, resulting resonance
with different energy widths for the c-axis and in-plane spin excitations. The
observation of spin anisotropy in both opitmally electron and hole-doped
BaFe$_2$As$_2$ is due to their proximity to the AF ordered BaFe$_2$As$_2$ where
spin anisotropy exists below $T_N$.",1301.1397v1
2013-07-17,"Anisotropic Quantum Spin Hall Effect, Spin-Orbital Textures and Mott Transition","We investigate the interplay between topological effects and Mott physics in
two dimensions on a graphene-like lattice, via a tight-binding model containing
an anisotropic spin-orbit coupling on the next-nearest-neighbour links and the
Hubbard interaction. We thoroughly analyze the resulting phases, namely a
topological band insulator phase or anisotropic quantum Spin Hall phase until
moderate interactions, a N\'eel and Spiral phase at large interactions in the
Mott regime, as well as the formation of a spin-orbital texture in the bulk at
the Mott transition. The emergent magnetic orders at large interactions are
analyzed through a spin wave analysis and mathematical arguments. At weak
interactions, by analogy with the Kane-Mele model, the system is described
through a Z_2 topological invariant. In addition, we describe how the
anisotropic spin-orbit coupling already produces an exotic spin texture at the
edges. The physics at the Mott transition is described in terms of a U(1) slave
rotor theory. Taking into account gauge fluctuations around the mean-field
saddle point solution, we show how the spin texture now proliferates into the
bulk above the Mott critical point. The latter emerges from the response of the
spinons under the insertion of monopoles and this becomes more pronounced as
the spin-orbit coupling becomes prevalent. We discuss implications of our
predictions for thin films of the iridate compound Na2IrO3 and also
graphene-like systems.",1307.4597v2
2014-01-23,Tidal evolution of the spin-orbit angle in exoplanetary systems,"The angle between the stellar spin and the planetary orbit axes (spin-orbit
angle) is supposed to carry valuable information on the initial condition of
the planet formation and the subsequent migration history. Indeed current
observations of the Rossiter- McLaughlin effect have revealed a wide range of
spin-orbit misalignments for transiting exoplanets. We examine in detail the
tidal evolution of a simple system comprising a Sun-like star and a hot Jupiter
adopting the equilibrium tide and the inertial wave dissipation effects
simultaneously. We find that the combined tidal model works as a very efficient
realignment mechanism; it predicts three distinct states of the spin-orbit
angle (i.e., parallel, polar, and anti-parallel orbits) for a while, but the
latter two states eventually approach the parallel spin-orbit configuration.
The intermediate spin-orbit angles as measured in recent observations are
difficult to be achieved. Therefore the current model cannot reproduce the
observed broad distribution of the spin-orbit angles, at least in its simple
form. This indicates that the observed diversity of the spin-orbit angles may
emerge from more complicated interactions with outer planets and/or may be the
consequence of the primordial misalignment between the proto-planetary disk and
the stellar spin, which requires future detailed studies.",1401.5876v1
2015-02-27,"Phonon mediated spin relaxation in a moving quantum dot: Doppler shift, Cherenkov radiation, and spin relaxation boom","We study relaxation of a moving spin qubit caused by phonon noise. As we vary
the speed of the qubit, we observe several interesting features in spin
relaxation and the associated phonon emission, induced by Doppler effect. In
particular, in the supersonic regime, the phonons emitted by the relaxing qubit
is concentrated along certain directions, similar to the shock waves produced
in classical Cherenkov effect. As the speed of the moving qubit increases from
the subsonic regime to the supersonic regime, the qubit experiences a peak in
the spin relaxation rate near the speed of sound, which we term a spin
relaxation boom in analogy to the classical sonic boom. We also find that the
moving spin qubit may have a lower relaxation rate than a static qubit, which
hints at the possibility of coherence-preserving transportation for a spin
qubit. While the physics we have studied here has strong classical analogies,
we do find that quantum confinement for the spin qubit plays an important role
in all the phenomena we observe. Specifically, it produces a correction on the
Cherenkov angle, and removes the divergence in relaxation rate at the sonic
barrier. It is our hope that our results would encourage further research into
approaches for transferring and preserving quantum information in spin qubit
architectures.",1503.00014v1
2015-04-07,Hexagonal Plaquette Spin-spin Interactions and Quantum Magnetism in a Two-dimensional Ion Crystal,"We propose a trapped ion scheme en route to realize spin Hamiltonians on a
Kagome lattice which, at low energies, are described by emergent Z2 gauge
fields, and support a topological quantum spin liquid ground state. The
enabling element in our scheme is the hexagonal plaquette spin-spin
interactions in a 2D ion crystal. For this, the phonon-mode spectrum of the
crystal is engineered by standing-wave optical potentials or by using Rydberg
excited ions, thus generating localized phonon-modes around a hexagon of ions
selected out of the entire two-dimensional crystal. These tailored modes can
mediate spin-spin interactions between ion-qubits on a hexagonal plaquette when
subject to state-dependent optical dipole forces. We discuss how these
interactions can be employed to emulate a generalized Balents-Fisher-Girvin
model in minimal instances of one and two plaquettes. This model is an
archetypical Hamiltonian in which gauge fields are the emergent degrees of
freedom on top of the classical ground state manifold. Under realistic
situations, we show the emergence of a discrete Gauss's law as well as the
dynamics of a deconfined charge excitation on a gauge-invariant background
using the two-plaquettes trapped ions spin-system. The proposed scheme in
principle allows further scaling in a future trapped ion quantum simulator, and
we conclude that our work will pave the way towards the simulation of emergent
gauge theories and quantum spin liquids in trapped ion systems.",1504.01474v1
2015-05-13,Time-reversal symmetric U(1) quantum spin liquids,"We study possible quantum $U(1)$ spin liquids in three dimensions with
time-reversal symmetry. We find a total of 7 families of such $U(1)$ spin
liquids, distinguished by the properties of their emergent electric/magnetic
charges. We show how these spin liquids are related to each other. Two of these
classes admit nontrivial protected surface states which we describe. We show
how to access all of the 7 spin liquids through slave particle (parton)
constructions. We also provide intuitive loop gas descriptions of their ground
state wave functions. One of these phases is the `topological Mott insulator'
conventionally described as a topological insulator of an emergent fermionic
`spinon'. We show that this phase admits a remarkable dual description as a
topological insulator of emergent fermionic magnetic monopoles. This results in
a new (possibly natural) surface phase for the topological Mott insulator and a
new slave particle construction. We describe some of the continuous quantum
phase transitions between the different $U(1)$ spin liquids. Each of these
seven families of states admits a finer distinction in terms of their surface
properties which we determine by combining these spin liquids with symmetry
protected topological phases. We discuss lessons for materials such as
pyrochlore quantum spin ices which may harbor a $U(1)$ spin liquid. We suggest
the topological Mott insulator as a possible ground state in some range of
parameters for the quantum spin ice Hamiltonian.",1505.03520v2
2015-09-05,Antiferromagnetic nuclear spin helix and topological superconductivity in $^{13}$C nanotubes,"We investigate the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction arising
from the hyperfine coupling between localized nuclear spins and conduction
electrons in interacting $^{13}$C carbon nanotubes. Using the Luttinger liquid
formalism, we show that the RKKY interaction is sublattice dependent,
consistent with the spin susceptibility calculation in noninteracting carbon
nanotubes, and it leads to an antiferromagnetic nuclear spin helix in
finite-size systems. The transition temperature reaches up to tens of mK, due
to a strong boost by a positive feedback through the Overhauser field from
ordered nuclear spins. Similar to GaAs nanowires, the formation of the helical
nuclear spin order gaps out half of the conduction electrons, and is therefore
observable as a reduction of conductance by a factor of 2 in a transport
experiment. The nuclear spin helix leads to a density wave combining spin and
charge degrees of freedom in the electron subsystem, resulting in synthetic
spin-orbit interaction, which induces non-trivial topological phases. As a
result, topological superconductivity with Majorana fermion bound states can be
realized in the system in the presence of proximity-induced superconductivity
without the need of fine tuning the chemical potential. We present the phase
diagram as a function of system parameters, including the pairing gaps, the gap
due to the nuclear spin helix, and the Zeeman field perpendicular to the
helical plane.",1509.01685v2
2018-01-01,Application of a new method to study the spin equilibrium of Aql X-1: the possibility of gravitational radiation,"Accretion via disks can make neutron stars in low-mass X-ray binaries (LMXBs)
fast spinning, and some of these stars are detected as millisecond pulsars.
Here we report a practical way to find out if a neutron star in a transient
LMXB has reached the spin equilibrium by disk--magnetosphere interaction alone,
and if not, to estimate this spin equilibrium frequency. These can be done
using specific measurable source luminosities, such as the luminosity
corresponding to the transition between the accretion and propeller phases, and
the known stellar spin rate. Such a finding can be useful to test if the spin
distribution of millisecond pulsars, as well as an observed upper cutoff of
their spin rates, can be explained using disk--magnetosphere interaction alone,
or additional spin-down mechanisms, such as gravitational radiation, are
required. Applying our method, we find that the neutron star in the transient
LMXB Aql X--1 has not yet reached the spin equilibrium by disk--magnetosphere
interaction alone. We also perform numerical computations, with and without
gravitational radiation, to study the spin evolution of Aql X--1 through a
series of outbursts and to constrain its properties. While we find that the
gravitational wave emission from Aql X--1 cannot be established with certainty,
our numerical results show that the gravitational radiation from Aql X--1 is
possible, with a $1.6\times10^{37}$ g cm$^2$ upper limit of the neutron star
misaligned mass quadrupole moment.",1801.00498v1
2018-09-13,Normal Modes in Magnetized Two-Fluid Spin Quantum Plasmas,"We extend the classical two-fluid magnetohydrodynamic (MHD) formalism to
include quantum effects such as electron Fermi pressure, Bohm pressure and spin
couplings. At scales smaller than the electron skin-depth, the Hall effect and
electron inertia must be taken into account, and can overlap with the quantum
effects. We write down the full set of two-fluid quantum MHD (QMHD) and analyze
the relative importance ofthese effects in the high density environments of
neutron star atmospheres and white dwarf interiors, finding that for a broad
range of parameters all these effects are operative. Of all spin interactions
we analyze only the spin-magnetic coupling, as it is linear in $\hbar$ and
consequently it is the strongest spin effect. We re-obtain the classical
two-fluid MHD dispersion relations corresponding to the magnetosonic and
Alfv\'en modes, modified by quantum effects. In the zero-spin case, for
propagation parallel to the magnetic field, we find that the frequency of the
fast mode is due to quantum effects modified by electron inertia, while the
frequency of the Alfv\'en-slow sector has no quantum corrections. For
perpendicular propagation, the fast-mode frequency is the same as for the
parallel propagation plus a correction due only to classical two-fluid effects.
When spin is considered, a whistler mode appears, which is due to two-fluid
spin-magnetic interaction. There are no modifications due to spin for parallel
propagation of magnetosonic and Alfv\'en waves, while for perpendicular prop
agation a dispersive term due to spin arises in the two-fluid expression for
the fast magnetosonic mode.",1809.05056v1
2018-10-30,Charge-spin response and collective excitations in Weyl semimetals,"Weyl semimetals are characterized by unconventional electromagnetic response.
We present analytical expressions for all components of the frequency- and
wave-vector-dependent charge-spin linear-response tensor of Weyl fermions. The
spin-momentum locking of the Weyl Hamiltonian leads to a coupling between
charge and longitudinal spin fluctuations, while transverse spin fluctuations
remain decoupled from the charge. A real Weyl semimetal with multiple Weyl
nodes can show this charge-spin coupling in equilibrium if its crystal symmetry
is sufficiently low. All Weyl semimetals are expected to show this coupling if
they are driven into a non-equilibrium stationary state with different
occupations of Weyl nodes, for example by exploiting the chiral anomaly. Based
on the response tensor, we investigate the low-energy collective excitations of
interacting Weyl fermions. For a local Hubbard interaction, the charge-spin
coupling leads to a dramatic change of the zero-sound dispersion: its velocity
becomes independent of the interaction strength and the chemical potential and
is given solely by the Fermi velocity. In the presence of long-range Coulomb
interactions, the coupling transforms the plasmon modes into spin plasmons. For
real Weyl semimetals with multiple Weyl nodes, the collective modes are
strongly affected by the presence of parallel static electric and magnetic
fields, due to the chiral anomaly. In particular, the zero-sound frequency at
fixed momentum and the spin content of the spin plasmons go through cusp
singularities as the chemical potential of one of the Weyl cones is tuned
through the Weyl node. We discuss possible experiments that could provide
smoking-gun evidence for Weyl physics.",1810.12560v2
2018-02-04,MOCCA-SURVEY Database I: Assessing GW kick retention fractions for BH-BH mergers in globular clusters,"Anisotropy of gravitational wave (GW) emission results in a net momentum
gained by the black hole (BH) merger product, leading to a recoil velocity up
to $\sim10^3\text{ km s}^{-1}$, which may kick it out of a globular cluster
(GC). We estimate GW kick retention fractions of merger products assuming
different models for BH spin magnitude and orientation (MS0 - random, MS1 -
spin as a function of mass and metalicity, MS2 - constant value of $0.5$). We
check how they depend on BH-BH merger time and properties of the cluster. We
analyze the implications of GW kick retention fractions on intermediate massive
BH (IMBH) formation by repeated mergers in a GC. We also calculate final spin
of the merger product, and investigate how it correlates with effective spin of
the binary. We used data from MOCCA (MOnte Carlo Cluster simulAtor) GC
simulations to get a realistic sample of BH-BH mergers, assigned each BH spin
value according to a studied model, and calculated recoil velocity and final
spin based on most recent theoretical formulas. We discovered that for
physically motivated models, GW kick retention fractions are about $30\%$ and
display small dependence on assumptions about spin, but are much more prone to
cluster properties. In particular, we discovered a strong dependence of GW kick
retention fractions on cluster density. We also show that GW kick retention
fractions are high in final life stages of the cluster, but low at the
beginning. Finally, we derive formulas connecting final spin with effective
spin for primordial binaries, and with maximal effective spin for dynamical
binaries.",1802.01192v2
2017-02-23,Correlation effects and hidden spin-orbit entangled electronic order in parent and electron-doped iridates Sr$_2$IrO$_4$,"Analogs of the high-T$_c$ cuprates have been long sought after in transition
metal oxides. Due to the strong spin-orbit coupling (SOC), the $5d$ perovskite
iridates Sr$_2$IrO$_4$ exhibit a low-energy electronic structure remarkably
similar to the cuprates. Whether a superconducting state exists as in the
cuprates requires understanding the correlated spin-orbit entangled electronic
states. Recent experiments discovered hidden order in the parent and electron
doped iridates, some with striking analogies to the cuprates, including Fermi
surface pockets, Fermi arcs, and pseudogap. Here, we study the correlation and
disorder effects in a five-orbital model derived from the band theory. We find
that the experimental observations are consistent with a $d$-wave spin-orbit
density wave order that breaks the symmetry of a joint two-fold spin-orbital
rotation followed by a lattice translation. There is a Berry phase and a
plaquette spin flux due to spin procession as electrons hop between Ir atoms,
akin to the intersite SOC in quantum spin Hall insulators. The associated
staggered circulating $J_\text{eff}=1/2$ spin current can be probed by advanced
techniques of spin-current detection in spintronics. This electronic order can
emerge spontaneously from the intersite Coulomb interactions between the
spatially extended iridium $5d$ orbitals, turning the metallic state into an
electron doped quasi-2D Dirac semimetal with important implications on the
possible superconducting state suggested by recent experiments.",1702.07070v4
2021-02-26,Quantum structured light: Non-classical spin texture of twisted single-photon pulses,"Classical structured light with controlled polarization and orbital angular
momentum (OAM) of electromagnetic waves has varied applications in optical
trapping, bio-sensing, optical communications and quantum simulations. The
classical electromagnetic theory of such structured light beams and pulses have
advanced significantly over the last two decades. However, a framework for the
quantum density of spin and OAM for single-photons remains elusive. Here, we
develop a theoretical framework and put forth the concept of quantum structured
light for space-time wavepackets at the single-photon level. Our work marks a
paradigm shift beyond scalar-field theory as well as the paraxial approximation
and can be utilized to study the quantum properties of the spin and OAM of all
classes of twisted quantum light pulses. We capture the uncertainty in full
three-dimensional (3D) projections of vector spin demonstrating their quantum
behavior beyond the conventional concept of classical polarization. Even in
laser beams with high OAM along the propagation direction, we predict the
existence of large OAM quantum fluctuations in the transverse plane which can
be verified experimentally. We show that the spin density generates modulated
helical texture beyond the paraxial limit and exhibits distinct statistics for
Fock-state vs. coherent-state twisted pulses. We introduce the quantum
correlator of photon spin density to characterize the nonlocal spin noise
providing a rigorous parallel with fermionic spin noise operators. Our work
paves the way for quantum spin-OAM physics in twisted single photon pulses and
also opens explorations for new phases of light with long-range spin order.",2102.13248v3
2019-10-10,Spin-textures of the Bose-Einstein condensates with three kinds of spin-1 atoms,"We have performed a quantum mechanic calculation (including solving the
coupled Gross-Pitaevskii equations to obtain the spatial wave functions, and
diagonalizing the spin-dependent Hamiltonian in the spin-space to obtain the
total spin state) together with an analytical analysis based on a classical
model. Then, according to the relative orientations of the spins $S_A$, $S_B$
and $S_C$ of the three species, the spin-textures of the ground state can be
classified into two types. In Type-I the three spins are either parallel or
anti-parallel to each others, while in Type-II they point to different
directions but remain to be coplanar. Moreover, according to the magnitudes of
$S_A$, $S_B$ and $S_C$ the spin-textures can be further classified into four
kinds, namely, $p$+$p$+$p$ (all atoms of each species are in singlet-pairs),
one species in $f$ (fully polarized) and two species in $q$ (a mixture of
polarized atoms and singlet-pairs), two in $f$ and one in $q$, and $f$+$f$+$f$.
Other combinations are not allowed. The scopes of the parameters that supports
a specific spin-texture have been specified. A number of
spin-texture-transitions have been found. For Type-I, the critical values at
which a transition takes place are given by simple analytical formulae,
therefore these values can be predicted.",1910.04381v1
2020-07-15,Electrical Control of Coherent Spin Rotation of a Single-Spin Qubit,"Nitrogen vacancy (NV) centers, optically-active atomic defects in diamond,
have attracted tremendous interest for quantum sensing, network, and computing
applications due to their excellent quantum coherence and remarkable
versatility in a real, ambient environment. One of the critical challenges to
develop NV-based quantum operation platforms results from the difficulty to
locally address the quantum spin states of individual NV spins in a scalable,
energy-efficient manner. Here, we report electrical control of the coherent
spin rotation rate of a single-spin qubit in NV-magnet based hybrid quantum
systems. By utilizing electrically generated spin currents, we are able to
achieve efficient tuning of magnetic damping and the amplitude of the dipole
fields generated by a micrometer-sized resonant magnet, enabling electrical
control of the Rabi oscillation frequency of NV spins. Our results highlight
the potential of NV centers in designing functional hybrid solid-state systems
for next-generation quantum-information technologies. The demonstrated coupling
between the NV centers and the propagating spin waves harbored by a magnetic
insulator further points to the possibility to establish macroscale
entanglement between distant spin qubits.",2007.07543v1
2021-03-11,Long-range spin transport on the surface of topological Dirac semimetal,"We theoretically propose the long-range spin transport mediated by the
gapless surface states of topological Dirac semimetal (TDSM). Low-dissipation
spin current is a building block of next-generation spintronics devices. While
conduction electrons in metals and spin waves in ferromagnetic insulators
(FMIs) are the major carriers of spin current, their propagation length is
inevitably limited due to the Joule heating or the Gilbert damping. In order to
suppress dissipation and realize long-range spin transport, we here make use of
the spin-helical surface states of TDSMs, such as $\mathrm{Cd_3 As_2}$ and
$\mathrm{Na_3 Bi}$, which are robust against disorder. Based on a junction of
two FMIs connected by a TDSM, we demonstrate that the magnetization dynamics in
one FMI induces a spin current on the TDSM surface flowing to the other FMI. By
both the analytical transport theory on the surface and the numerical
simulation of real-time evolution in the bulk, we find that the induced spin
current takes a universal semi-quantized value that is insensitive to the
microscopic coupling structure between the FMI and the TDSM. We show that this
surface spin current is robust against disorder over a long range, which
indicates that the TDSM surface serves as a promising system for realizing
spintronics devices.",2103.06519v1
2022-03-08,Cavity Quantum Electrodynamics Effects of Optically Cooled Nitrogen-Vacancy Centers Coupled to a High Frequency Microwave Resonator,"Recent experiments demonstrated the cooling of a microwave mode of a
high-quality dielectric resonator coupled to optically cooled nitrogen-vacancy
(NV) spins in diamond. Our recent theoretical study [arXiv:2110.10950] pointed
out the cooled NV spins can be used to realize cavity quantum electrodynamics
effects (C-QED) at room temperature. In this article, we propose to modify the
setup used in a recent diamond maser experiment [Nature 55, 493-496 (2018)],
which features a higher spin transition frequency, a lower spin-dephasing rate
and a stronger NV spins-resonator coupling, to realize better microwave mode
cooling and the room-temperature CQED effects. To describe more precisely the
optical spin cooling and the collective spin-resonator coupling, we extend the
standard Jaynes-Cumming model to account for the rich electronic and spin
levels of the NV centers. Our calculations show that for the proposed setup it
is possible to cool the microwave mode from $293$ K (room temperature) to $116$
K, which is about $72$ K lower than the previous records, and to study the
intriguing dynamics of the CQED effects under the weak-to-strong coupling
transition by varying the laser power. With simple modifications, our model can
be applied to, e.g., other solid-state spins or triplet spins of pentacene
molecules, and to investigate other effects, such as the operations of pulsed
and continuous-wave masing.",2203.04102v1
2022-03-11,"Modelling the formation of the first two neutron star-black hole mergers, GW200105 and GW200115: metallicity, chirp masses and merger remnant spins","The two neutron star-black hole mergers (GW200105 and GW200115) observed in
gravitational waves by advanced LIGO and Virgo, mark the first ever discovery
of such binaries in nature. We study these two neutron star-black hole systems
through isolated binary evolution, using a grid of population synthesis models.
Using both mass and spin observations (chirp mass, effective spin and remnant
spin) of the binaries, we probe their different possible formation channels in
different metallicity environments. Our models only support LIGO data when
assuming the black hole is non spinning. Our results show a strong preference
that GW200105 and GW200115 formed from stars with sub-solar metallicities
$Z\lesssim 0.005$. Only two metal-rich ($Z=0.02$) models are in agreement with
GW200115. We also find that chirp mass and remnant spins jointly aid in
constraining the models, whilst the effective spin parameter does not add any
further information. We also present the observable (i.e. post selection
effects) median values of spin and mass distribution from all our models, which
maybe used as a reference for future mergers. Further, we show that the remnant
spin parameter distribution exhibits distinguishable features in different
neutron star-black hole sub-populations. We find that non-spinning, first born
black holes dominate significantly the merging neutron star-black hole
population, ensuring electromagnetic counterparts to such mergers a rare
affair.",2203.05850v2
2022-05-17,No evidence that the majority of black holes in binaries have zero spin,"The spin properties of merging black holes observed with gravitational waves
can offer novel information about the origin of these systems. The magnitude
and orientations of black hole spins offer a record of binaries' evolutionary
history, encoding information about massive stellar evolution and the
astrophysical environments in which binary black holes are assembled. Recent
analyses of the binary black hole population have yielded conflicting portraits
of the black hole spin distribution. Some work suggests that black hole spins
are small but non-zero and exhibit a wide range of misalignment angles relative
to binaries' orbital angular momenta. Other work concludes that the majority of
black holes are non-spinning while the remainder are rapidly rotating and
primarily aligned with their orbits. We revisit these conflicting conclusions,
employing a variety of complementary methods to measure the distribution of
spin magnitudes and orientations among binary black hole mergers. We find that
the existence of a sub-population of black hole with vanishing spins is not
required by current data. Should such a sub-population exist, we conclude that
it must contain $\lesssim 60\%$ of binaries. Additionally, we find evidence for
significant spin-orbit misalignment among the binary black hole population,
with some systems exhibiting misalignment angles greater than $90^{\circ}$, and
see no evidence for an approximately spin-aligned sub-population.",2205.08574v2
2022-06-11,Chirality as Generalized Spin-Orbit Interaction in Spintronics,"This review focuses on the chirality observed in the excited states of the
magnetic order, dielectrics, and conductors that hold transverse spins when
they are evanescent. Even without any relativistic effect, the transverse spin
of the evanescent waves are locked to the momentum and the surface normal of
their propagation plane. This chirality thereby acts as a generalized
spin-orbit interaction, which leads to the discovery of various chiral
interactions between magnetic, phononic, electronic, photonic, and plasmonic
excitations in spintronics that mediate the excitation of quasiparticles into a
single direction, leading to phenomena such as chiral spin and phonon pumping,
chiral spin Seebeck, spin skin, magnonic trap, magnon Doppler, and spin diode
effects. Intriguing analogies with electric counterparts in the nano-optics and
plasmonics exist. After a brief review of the concepts of chirality that
characterize the ground state chiral magnetic textures and chirally coupled
magnets in spintronics, we turn to the chiral phenomena of excited states. We
present a unified electrodynamic picture for dynamical chirality in spintronics
in terms of generalized spin-orbit interaction and compare it with that in
nano-optics and plasmonics. Based on the general theory, we subsequently review
the theoretical progress and experimental evidence of chiral interaction, as
well as the near-field transfer of the transverse spins, between various
excitations in magnetic, photonic, electronic and phononic nanostructures at
GHz time scales. We provide a perspective for future research before concluding
this article.",2206.05535v2
2023-06-03,Manipulating chiral-spin transport with ferroelectric polarization,"A collective excitation of the spin structure in a magnetic insulator can
transmit spin-angular momentum with negligible dissipation. This quantum of a
spin wave, introduced more than nine decades ago, has always been manipulated
through magnetic dipoles, (i.e., timereversal symmetry). Here, we report the
experimental observation of chiral-spin transport in multiferroic BiFeO3, where
the spin transport is controlled by reversing the ferroelectric polarization
(i.e., spatial inversion symmetry). The ferroelectrically controlled magnons
produce an unprecedented ratio of up to 18% rectification at room temperature.
The spin torque that the magnons in BiFeO3 carry can be used to efficiently
switch the magnetization of adja-cent magnets, with a spin-torque efficiency
being comparable to the spin Hall effect in heavy metals. Utilizing such a
controllable magnon generation and transmission in BiFeO3, an alloxide,
energy-scalable logic is demonstrated composed of spin-orbit injection,
detection, and magnetoelectric control. This observation opens a new chapter of
multiferroic magnons and paves an alternative pathway towards low-dissipation
nanoelectronics.",2306.02185v1
2023-07-10,Spin transport properties of spinel vanadate-based heterostructures,"Spin-orbit coupling and breaking of inversion symmetry are necessary
ingredients to enable a pure spin current-based manipulation of the
magnetization via the spin-orbit torque effect. Currently, magnetic insulator
oxides with non-dissipative characteristics are being explored. When combined
with non-magnetic heavy metals, known for their large spin-orbit coupling, they
offer promising potential for energy-efficient spin-orbitronics applications.
The intrinsic electronic correlations characterizing those strongly correlated
oxides hold the promises to add extra control-knobs to the desired efficient
spin-wave propagation and abrupt magnetization switching phenomena. Spinel
vanadate FeV2O4 (FVO) exhibits several structural phase transitions which are
accompanied by an intricate interplay of magnetic, charge and orbital
orderings. When grown as a thin film onto SrTiO3, the compressive strain state
induces a perpendicular magnetic anisotropy, making FVO-based heterostructures
desirable for spin-orbitronics applications. In this study, we have optimised
the deposition of stoichiometric and epitaxial Pt/FVO heterostructures by
Pulsed Laser Deposition and examined their spin-related phenomena. From
angle-dependent magnetotransport measurements, we observed both Anisotropic
Magnetoresistance (AMR) and Spin Hall Magnetoresistance (SMR) effects. Our
findings show the SMR component as the primary contributor to the overall
magnetoresistance, whose high value of 0.12% is only comparable to properly
optimized oxide-based systems.",2307.04389v1
2014-04-30,3D Structures of equatorial waves and the resulting superrotation in the atmosphere of a tidally locked hot Jupiter,"Three-dimensional equatorial trapped waves excited by stellar isolation and
the resulting equatorial superrotating jet in a vertical stratified atmosphere
of a tidally-locked hot Jupiter are investigated. Taking the hot Jupiter HD
189733b as a fiducial example, we analytically solve a set of linear equations
subject to stationary stellar heating with a uniform zonal-mean flow included.
We also extract wave information in the final equilibrium state of the
atmosphere from the radiative hydrodynamical simulation for HD 189733b by
Dobbs-Dixon & Agol (2013). We find that the analytic wave solutions are able to
qualitatively explain the three-dimensional simulation results. Studying the
vertical structure of waves allows us to explore new wave features such as the
westward tilt of wavefronts related to the Rossby-wave resonance as well as
double gyres of dispersive Rossby waves. We also make an attempt to apply our
linear wave analysis to explain some numerical features associated with the
equatorial jet development seen in the GCM by Showman & Polvani (2011). During
the spin-up phase of the equatorial jet, the acceleration of the jet as a
result of the divergence of the wave momentum flux can be in principle boosted
by the Rossby-wave resonance as the superrotating jet speed is close to the
phase speed of the Rossby waves. However, we also find that as the jet speed
increases, the Rossby-wave structure shifts eastward, while the Kelvin-wave
structure remains approximately stationary, leading to the decline of the
acceleration rate. Our analytic model of jet evolution implies that there
exists only one stable equilibrium state of the atmosphere, possibly implying
that the final state of the atmosphere is independent of initial conditions in
the linear regime. Limitations and future improvements are also discussed.",1405.0003v2
2020-01-13,External and internal wave functions: de Broglie's double-solution theory?,"We propose an interpretative framework for quantum mechanics corresponding to
the specifications of Louis de Broglie's double-solution theory. The principle
is to decompose the evolution of a quantum system into two wave functions: an
external wave function corresponding to the evolution of its center of mass and
an internal wave function corresponding to the evolution of its internal
variables in the center-of-mass system. Mathematical decomposition is only
possible in certain cases because there are many interactions linking these two
parts. In addition, these two wave functions will have different meanings and
interpretations. The external wave function ""pilots"" the center of mass of the
quantum system: it corresponds to the Broglie pilot wave. When the Planck
constant tends to zero, it results mathematically from the convergence of the
square of the module and the phase of the external wave function to a density
and a classical action verifying the Hamilton-Jacobi statistical equations.
This interpretation explains all the measurement results, namely those yielded
by interference, spin measurement (Stern and Gerlach) and non-locality (EPR-B)
experiments. For the internal wave function, several interpretations are
possible : the one of the pilot wave can be applied in cascade to the internal
wave function. However, the interpretation proposed by Erwin Schr{\""o}dinger at
the Solvay Congress in 1927 and restricted to the internal wave function is
also possible. For Schr{\""o}dinger, the particles are extended and the square
of the module of the (internal) wave function of an electron corresponds to the
density of its charge in space. We present many arguments in favour of this
interpretation, which like the pilot wave interpretation is realistic and
deterministic. Finally, we will see that this double interpretation serves as a
frame of reference by which to better understand the debates on the
interpretation of quantum mechanics and to review the relationships between
gravity and quantum mechanics.",2001.04807v1
2012-06-28,Twisted electron in a strong laser wave,"Electrons carrying orbital angular momentum (OAM) have recently been
discovered theoretically and obtained experimentally that opens up
possibilities for using them in high-energy physics. We consider such a twisted
electron moving in external field of a plane electromagnetic wave and study how
this field influences the electron's OAM. Being motivated by the development of
high-power lasers, we focus our attention on a classically strong field regime
for which $-e^2 \bar {A^2}/m_e^2 c^4 \gtrsim 1$. It is shown that along with
the well-known ""plane-wave"" Volkov solution, Dirac equation also has the
""non-plane-wave"" solutions, which possess OAM and a spin-orbit coupling, and
generalize the free-electron's Bessel states. Motion of the electron with OAM
in a circularly polarized laser wave reveals a twofold character: the
wave-packet center moves along a classical helical trajectory with some quantum
transverse broadening (due to OAM) existing even for a free electron. Using the
twisted states, we calculate the electron's total angular momentum and predict
its shift in the strong-field regime that is analogous to the well-known shifts
of the electron's momentum and mass (and to a less known shift of its spin) in
intense fields. Since the electron's effective angular momentum is conserved in
a plane wave, as well as in some more general field configurations, we discuss
several possibilities for accelerating non-relativistic twisted electrons by
using the focused and combined electromagnetic fields.",1206.6622v3
2018-04-17,Fate of the open-shell singlet ground state in the experimentally accessible acenes: a quantum Monte Carlo study,"By means of the Jastrow correlated antisymmetrized geminal power (JAGP) wave
function and quantum Monte Carlo (QMC) methods, we study the ground state
properties of the oligoacene series, up to the nonacene. The JAGP is the
accurate variational realization of the resonating-valence-bond (RVB) ansatz
proposed by Pauling and Wheland to describe aromatic compounds. We show that
the long-ranged RVB correlations built in the acenes' ground state are
detrimental for the occurrence of open-shell diradical or polyradical
instabilities, previously found by lower-level theories. We substantiate our
outcome by a direct comparison with another wave function, tailored to be an
open-shell singlet (OSS) for long-enough acenes. By comparing on the same
footing the RVB and OSS wave functions, both optimized at a variational QMC
level, and further projected by the lattice regularized diffusion Monte Carlo
(LRDMC) method, we prove that the RVB wave function has always a lower
variational energy and better nodes than the OSS, for all molecular species
considered in this work. The entangled multi-reference RVB state acts against
the electron edge localization implied by the OSS wave function, and weakens
the diradical tendency for higher oligoacenes. These properties are reflected
by several descriptors, including wave function parameters, bond length
alternation, aromatic indices, and spin-spin correlation functions. In this
context, we propose a new aromatic index estimator suitable for geminal wave
functions. For the largest acenes taken into account, the long-range decay of
the charge-charge correlation functions is compatible with a quasi-metallic
behavior.",1804.06276v1
2020-03-23,Physical realization of complex dynamical pattern formation in magnetic active feedback rings,"We report the clean experimental realization of cubic-quintic complex
Ginzburg-Landau physics in a single driven, damped system. Four numerically
predicted categories of complex dynamical behavior and pattern formation are
identified for bright and dark solitary waves propagating around an active
magnetic thin film-based feedback ring: (1) periodic breathing; (2) complex
recurrence; (3) spontaneous spatial shifting; and (4) intermittency. These
nontransient, long lifetime behaviors are observed in microwave spin wave
envelopes circulating within a dispersive, nonlinear yttrium iron garnet
waveguide operating in a ring geometry where the net losses are directly
compensated for via linear amplification on each round trip O(100 ns). The
behaviors exhibit periods ranging from tens to thousands of round trip times
O($\mu$ s) and are stable for 1000s of periods O(ms). We present 10
observations of these dynamical behaviors which span the experimentally
accessible ranges of attractive cubic nonlinearity, dispersion, and external
field strength that support the self-generation of backward volume spin waves
in a four-wave-mixing dominant regime. Three-wave splitting is not explicitly
forbidden and is treated as an additional source of nonlinear losses. Each of
these long lifetime behaviors of bright solitary waves was previously
numerically predicted to be observable. The dynamical pattern formation of dark
solitary waves in attractive nonlinearity, however, is entirely novel and is
reported for both the periodic breather and complex recurrence behaviors. All
behaviors are identified in the group velocity co-moving frame.",2003.10541v2
2020-09-09,Plane and Stripe Wave Phases of a Spin-Orbit Coupled Bose-Einstein Condensate in an Optical Lattice with a Zeeman Field,"A weakly interacting, spin-orbit coupled, ultracold, dilute Bose gas on a
two-dimensional square lattice with an external Zeeman field is studied. We
explore the plane and stripe wave phases of the system involving nonzero
condensate momenta, which occur when the Zeeman field is below a critical
value. Their excitation spectra are found using Bogoliubov theory and by two
different routes. The validity of each method to obtain the excitation spectrum
is discussed, and it is found that projection on the lowest single-particle
band is an excellent approximation in the plane wave phase, while it is a poor
approximation in the stripe wave phase. While the plane wave phase has a phonon
minimum at its single condensate momentum, revealing a nonzero sound velocity
of the excitations, the stripe wave phase has quadratic minima at its two
condensate momenta showing zero sound velocity of the excitations. We discuss
how the presence of more than one condensate momentum is essential for these
differences between the two phases. Additionally, it is emphasized that the
zero sound velocity in the stripe wave phase is a lattice effect, since
continuum studies of the same phase have shown nonzero sound velocity.",2009.04538v2
1994-06-08,Hole-hole superconducting pairing in the t-J model induced by spin-wave exchange,"We study numerically the hole pairing induced by spin-wave exchange. The
contact hole-hole interaction is taken into account as well. It is assumed that
antiferromagnetic order is preserved at all scales relevant to pairing. The
strongest pairing is obtained for the d-wave symmetry of the gap. Dependence of
the value of the gap on hole concentration and temperature is presented. For
the critical temperature we obtain Tc about 100 K at the hole concentration
delta = 0.2-0.3.",9406039v2
1996-11-05,Chiral Metal as a Heisenberg Ferromagnet,"The two dimensional surface of an integer quantum hall multilayer is mapped
onto a Heisenberg spin-chain with ferromagnetic coupling. Using this mapping it
is shown non-perturbatively that the surface states constitute a very
anisotropic metal in the infinite size limit. For multilayers of finite size,
two diffusive mesoscopic regimes are identified and the conductance
fluctuations are calculated perturbatively for both. The Heisenberg spin-chain
representation is used to study the directed wave problem and the exact result
is obtained that the mean-square deflection of a directed wave grows as the
square root of the propagation of the distance.",9611035v1
1997-03-24,A theoretical investigation of the specific heat of superlattices in a magnetic field,"We analyze the specific heat variations as a function of an external magnetic
field of a simple model of superlattice that includes (i) in--plane
ferromagnetic exchange, (ii) interplane ferromagnetic exchange, (iii) dipolar
interactions, (iv) magnetocristalline anisotropy. The calculations are carried
out at the spin wave level. The interplay between the existence of a canting
transition and the anisotropy of the structure generates non trivial behavior
for the spin wave contribution to the low temperature specific heat as a
function of an external magnetic field when dipolar interactions and
magnetocristalline anisotropy are taken into account.",9703202v1
1997-09-26,Spin wave mediated non-reciprocal effects in antiferromagnets,"By using an effective field theory for the electromagnetic interaction of
spin waves, we show that, in certain antiferromagnets, the latter induce
non-reciprocal effects in the microwave region, which should be observable in
the second harmonic generation and produce gyrotropic birefringency. We
calculate the various (non-linear) susceptibilities in terms of a few
parameters the order of magnitude of which is under control.",9709299v4
1999-01-21,Interplay between Mesoscopic and Microscopic Fluctuations in Ferromagnets,"A model of a ferromagnet is considered, in which there arise mesoscopic
fluctuations of paramagnetic phase. The presence of these fluctuations
diminishes the magnetization of the ferromagnet, softens the spin-wave
spectrum, increases the spin-wave attenuation, shortens the magnon free path,
lowers the critical point, and can change the order of phase transition. A
special attention is paid to the interplay between these mesoscopic
paramagnetic fluctuations and microscopic fluctuations due to magnons. One of
the main results of this interplay is an essential extension of the region of
parameters where the ferromagnet-paramagnet phase transition is of first order.",9901213v1
1999-05-21,Theory of Unconventional Spin Density Wave: A Possible Mechanism of the Micromagnetism in U-based Heavy Fermion Compounds,"We propose a novel spin density wave (SDW) state as a possible mechanism of
the anomalous antiferromagnetism, so-called the micromagnetism, in URu_2Si_2
below 17.5[K]. In this new SDW, the electron-hole pair amplitude changes its
sign in the momentum space as in the case of the unconventional
superconductivity. It is shown that this state can be realized in an extended
Hubbard model within the mean field theory. We also examine some characteristic
properties of this SDW to compare with the experimental results. All these
properties well explain the unsolved problem of the micromagnetism.",9905316v1
1999-05-21,"Comment on ""Theory of Unconventional Spin Density Wave: A Possible Mechanism of the Micromagnetism in U-based Heavy Fermion Compounds""","In the recent letter [1] by H. Ikeda and Y. Ohashi, a new, very attractive
idea is proposed for the explanation of the micromagnetism in U-based heavy
fermion compounds. For this sake a nontrivial spin density wave (d-SDW) is
introduced. Our goal is to claim, that in the model considered, the mean-field
analysis is incomplete: the ferromagnetic state missed by [1] overcomes d-SDW
in a large region of the phase diagram (Fig.1 in [1]).",9905321v1
1999-11-10,Topological coupling of dislocations and magnetization vorticity in Spin Density Waves,"The rich order parameter of Spin Density Waves allows for an unusual object
of a complex topological nature: a half-integer dislocation combined with a
semi-vortex of the staggered magnetization. It becomes energetically preferable
to ordinary dislocation due to enhanced Coulomb interactions in the
semiconducting regime. Generation of these objects changes the narrow band
noise frequency.",9911143v1
2000-08-07,"Comment on ""Theory of diluted magnetic semiconductor ferromagnetism""","In this comment, we emphasize that the self-consistent spin wave theory in a
recent paper [J. K""onig, H.-H. Lin, and A. H. MacDonald, Phys. Rev. Lett. 84,
5628 (2000)] leads to incorrect results both at low temperatures and near T_c.
Thus we suggest another self-consistent spin wave approximation to remedy these
flaws.",0008098v1
2000-09-14,Effects of Next-Nearest-Neighbor Repulsion on One-Dimensional Quarter-Filled Electron Systems,"We examine effects of the next-nearest-neighbor repulsion on electronic
states of a one-dimensional interacting electron system which consists of
quarter-filled band and interactions of on-site and nearest-neighbor repulsion.
We derive the effective Hamiltonian for the electrons around wave number $\pm
\kf$ ($\kf$: Fermi wave number) and apply the renormalization group method to
the bosonized Hamiltonian. It is shown that the next-nearest-neighbor repulsion
makes $4\kf$-charge ordering unstable and suppresses the spin fluctuation.
Further the excitation gaps and spin susceptibility are also evaluated.",0009208v1
2000-12-06,Magnons in the ferromagnetic Kondo-lattice model,"The magnetic properties of the ferromagnetic Kondo-lattice model (FKLM) are
investigated. Starting from an analysis of the magnon spectrum in the spin-wave
regime, we examine the ferromagnetic stability as a function of the occupation
of the conduction band $n$ and the strength $J$ of the coupling between the
localised moments and the conduction electrons. From the properties of the
spin-wave stiffness $D$ the ferromagnetic phase at zero temperature is derived.
Using an approximate formula the critical temperature $T_c$ is calculated as a
function of $J$ and $n$.",0012086v1
2001-01-10,The Néel order for a frustrated antiferromagnetic Heisenberg model: beyond linear spin-wave theory,"Within Dyson-Maleev (DM) transformation and self-consistent mean-field
treatment, the N\'eel order/disorder transition is studied for an
antiferromagnetic Heisenberg model which is defined on a square lattice with a
nearest neighbour exchange $J_1$ and a next-nearest neighbour exchange $J_2$
along only one of the diagonals. It is found that the N\'eel order may exist up
to $J_2/J_1=0.572$, beyond its classically stable regime. This result
qualitatively improves that from linear spin-wave theory based on
Holstein-Primakoff transformation.",0101145v1
2001-02-05,Magnetic Vortices in High Temperature Superconductors,"It is suggested that modes, observed in recent neutron scattering experiments
by Lake {\it et al.}, on La$_{2-x}$Sr$_x$CuO$_4$ in strong magnetic fields
($\approx$ 7 T), are due to the existence of antiferromagnetic moments
associated with the cores of vortices generated by the field. These moments
form one-dimensional chains along the $c$-axis (the vortex axis), which at
finite temperatures are disordered. At temperatures higher than 10 K the
correlation length gets shorter than the lattice parameter, resulting in no
scattering from coherent spin-waves above that temperature. The bandwidth of
the spin-waves is estimated to be $\approx$ 4 meV in accordance with the
observations.",0102070v2
2001-05-11,Spectacular doping dependence of interlayer exchange and other results on spin waves in bilayer manganites,"We report the measurement of spin waves in the bilayer colossal
magnetoresistive manganites La(2-2x)Sr(1+2x)Mn2O7 with x=0.30, 0.35 and 0.40.
For x=0.35 and 0.40 the entire acoustic and optic dispersion relations are
reasonably well described by those for a bilayer Heisenberg Hamiltonian with
nearest neighbour exchange only. The in-plane coupling is only weakly dependent
on x, but the coupling between the planes of a bilayer changes by a factor of
four. The results directly reveal the change from mixed and character of the
orbitals to mostly character with increasing hole concentration.",0105230v1
2002-03-06,Multifractality at the spin quantum Hall transition,"Statistical properties of critical wave functions at the spin quantum Hall
transition are studied both numerically and analytically (via mapping onto the
classical percolation). It is shown that the index $\eta$ characterizing the
decay of wave function correlations is equal to 1/4, at variance with the
$r^{-1/2}$ decay of the diffusion propagator. The multifractality spectra of
eigenfunctions and of two-point conductances are found to be
close-to-parabolic, $\Delta_q\simeq q(1-q)/8$ and $X_q\simeq q(3-q)/4$.",0203134v1
2002-06-24,Magnetic oscillations and field induced spin density waves in (TMTSF)_2ClO_4,"We report an analysis of the effects of magnetic field on a
quasi-one-dimensional band of interacting electrons with a transverse
dimerizing potential. One-particle problem in bond-antibond representation is
solved exactly. The resulting propagator is used to calculate the
spin-density-wave (SDW) response of the interacting system within the matrix
RPA for the SDW susceptibility. We predict the magnetic field induced
transition of the first order between interband SDW_0 and intraband SDW_(+-)
phases. We reproduce the rapid oscillations with a period of 260 Tesla and the
overal profile of the TMTSF_2ClO_4 phase diagram.",0206466v1
2002-06-30,Spatially Resolved Dynamics of Localized Spin-Wave Modes in Ferromagnetic Wires,"We have observed localized spin-wave modes in individual thin-film
ferromagnetic wires using time-resolved Kerr microscopy as a micron-scale
spectroscopic probe. The localization is due to the partial demagnetization of
a wire when an external field is applied in the plane of the film and
perpendicular to the long axis of the wire. Spatially-resolved spectra
demonstrate the existence of distinct modes at the edges of a rectangular wire.
Spectral images clearly show the crossover of the two edge modes into a single
mode in low applied fields, in agreement with the results of micromagnetic
simulations.",0207022v1
2002-07-12,Absence of the Effects of Vortices in the Gauge Glass,"We calculate several correlation functions and distribution functions of
dynamical variables for the gauge glass and the Villain model using the spin
wave approximation and the gauge transformation. The results show that the spin
wave approximation gives the exact solutions on the Nishimori line in the phase
diagram. This implies that vortices play no role in the thermodynamic behavior
of the system as long as some correlation and distribution functions are
concerned. These results apply to any dimensions including the two-dimensional
case.",0207310v1
2002-08-05,New Magnetic Excitations in the Spin-Density-Wave of Chromium,"Low-energy magnetic excitations of chromium have been reinvestigated with a
single-Q crystal using neutron scattering technique. In the transverse
spin-density-wave phase a new type of well-defined magnetic excitation is found
around (0,0,1) with a weak dispersion perpendicular to the wavevector of the
incommensurate structure. The magnetic excitation has an energy gap of E ~ 4
meV and at (0,0,1) exactly corresponds to the Fincher mode previously studied
only along the incommensurate wavevector.",0208084v1
2002-09-10,Hidden Quantum Critical Point in a Ferromagnetic Superconductor,"We consider a coexistence phase of both Ferromagnetism and superconductivity
and solve the self-consistent mean-field equations at zero temperature. The
superconducting gap is shown to vanish at the Stoner point whereas the
magnetization doesn't. This indicates that the para-Ferro quantum critical
point becomes a hidden critical point. The effective mass in such a phase gets
enhanced whereas the spin wave stiffness is reduced as compared to the pure FM
phase. The spin wave stiffness remains finite even at the para-Ferro quantum
critical point.",0209237v1
2002-10-15,Spin-wave Hamiltonian in double-exchange systems,"A simple derivation of the effective spin-wave Hamiltonian for a
double-exchange system with infinitely large Hund's-rule coupling is
demonstrated. The formalism can be applied to models with arbitrary range of
hopping as well as those with randomness. The result shows that, within the
leading order of the 1/S expansion, one magnon excitation spectrum can be
described by the Heisenberg model.",0210333v1
2002-10-25,Spin-wave theory at constant order parameter,"We derive the low-temperature properties of spin-S quantum Heisenberg magnets
from the Gibbs free energy G(M) for fixed order parameter M. Assuming that the
low-lying elementary excitations of the system are renormalized spin waves, we
show that a straightforward 1/S expansion of G(M) yields qualitatively correct
results for the low-temperature thermodynamics, even in the absence of
long-range magnetic order. We explicitly calculate the two-loop correction to
the susceptibility of the ferromagnetic Heisenberg chain and show that it
quantitatively modifies the mean-field result.",0210578v2
2002-12-05,Spin density wave and pseudogap in HTSC cuprates,"The evidence for the spin density wave (SDW) nature of the pseudogap in HTSC
cuprates is presented from resistive and direct gap measurements (ARPES,
tunneling experiments, etc.). Its d-wave symmetry mimics the symmetry of the
order parameter measured in the SC state. The magnetic phase $H-T$ diagram for
HTSC cuprates is formed. The possible influence of an additional (SDW) order
parameter on the vortex structure in the applied magnetic field is analysed.
The behavior is discussed in terms of itinerant electron systems with interplay
between superconductivity and magnetism.",0212128v1
2003-02-27,Spin waves and the origin of commensurate magnetism in Ba2CoGe2O7,"The square-lattice antiferromagnet Ba2CoGe2O7 is studied by means of neutron
diffraction and inelastic scattering. This material is isostructural to the
well-known Dzyaloshinskii-Moriya helimagnet Ba2CuGe2O7, but exhibits
commensurate long-range Neel order at low temperatures. Measurements of the
spin wave dispersion relation reveal strong in-plane anisotropy that is the
likely reason for the suppression of helimagnetism.",0302592v1
2003-10-15,Commensurability Transition and Stripe Phases in the Ginzburg-Landau Theory,"We phenomenologically describe the thermodynamics of charge and spin density
waves in doped high-$T_{c}$ oxides. We have explicitly calculated stable
non-homogeneous solutions in the incompressible spin driven stripe phase, where
stripes are static soliton-like charge density waves (CDW), and in the vicinity
of their critical point, where CDW's become harmonic. Our phase diagram points
to a commensurability transition separating the low (LI) and high (HI)
incommensurable phases. Besides, we demonstrate by rigorous group symmetry
arguments that the stripe criticality is compatible with a second order phase
transition.",0310364v1
2004-09-01,Mesoscopic quantized properties of magnetic-dipolar-mode oscillations in disk ferromagnetic particles,"Magnetic dipolar mode or magnetostatic (MS) oscillations in ferrite samples
have the wavelength much smaller than the electromagnetic wavelength at the
same frequency and, at the same time, much larger than the exchange interaction
spin wavelength. This intermediate position between the electromagnetic and
spin wave (exchange interaction) processes reveals very special behaviors of
the geometrical effects. It was shown recently that magnetic dipolar mode
oscillations in a normally magnetized ferromagnetic disk are characterized by
discrete energy levels resulting from the structural confinement. In this
article we give results of the energy spectra in MS wave ferrite disks taking
into account nonhomogeneity of the internal DC magnetic field.",0409023v1
2004-11-22,Direct Observation of Non-Monotonic dx2-y2-Wave Superconducting Gap in Electron-Doped High-Tc Superconductor Pr0.89LaCe0.11CuO4,"We performed high-resolution angle-resolved photoemission spectroscopy on
electron-doped high-Tc superconductor Pr0.89LaCe0.11CuO4 to study the
anisotropy of the superconducting gap. The observed momentum dependence is
basically consistent with the dx2-y2-wave symmetry, but obviously deviates from
the monotonic dx2-y2 gap function. The maximum gap is observed not at the zone
boundary, but at the hot spot where the antiferromagnetic spin fluctuation
strongly couples to the electrons on the Fermi surface. The present
experimental results unambiguously indicate the spin-mediated pairing mechanism
in electron-doped high-Tc superconductors.",0411547v1
2004-12-09,Modified Spin-Wave Theory for Nanomagnets : Application to the Keplerate Molecule Mo(72)Fe(30),"We adapt Takahashi's modified spin-wave theory to the context of
nano-magnets, and apply it to the molecular compound based on the giant
magnetic molecule Mo(72)Fe(30). This involves solving numerically the
mean-field equations and then forcing the sublattice magnetizations to zero by
means of local chemical potentials for the magnons. We have thus constructed a
quantum state with no local magnetization at all temperatures, appropriate to a
finite-size system, but with strong correlations. We compare theoretical
results to specific heat and ESR measurements.",0412244v1
2005-02-04,Coexistence of Spin Density Wave and Triplet Superconductivity,"We discuss the possibility of coexistence of spin density wave
(antiferromagnetism) and triplet superconductivity as a particular example of a
broad class of systems where the interplay of magnetism and superconductivity
is important. We focus on the case of quasi-one-dimensional metals, where it is
known experimentally that antiferromagnetism is in close proximity to triplet
superconductivity in the temperature versus pressure phase diagram. Over a
narrow range of pressures, we propose an intermediate non-uniform phase
consisting of alternating antiferromagnetic and triplet superconducting
stripes. Within the non-uniform phase there are also changes between two and
three dimensional behavior.",0502140v1
2005-03-29,Dipole-exchange spin waves in Fibonacci magnetic multilayers,"A microscopic model is employed to calculate the spectrum of spin waves in
quasiperiodic magnetic multilayers in the dipole-exchange regime. Results are
presented for structures in which thin ferromagnetic films are separated by
non-magnetic spacers following a Fibonacci sequence and extend previous
magnetostatic calculations. The results show the splitting of the frequency
bands and the mode mixing caused by the dipolar interaction between the films
as a function of spacer thickness, as well as the fractal aspect of the
spectrum induced by the non-periodic aspect of the structure.",0503683v1
2005-03-31,Spectroscopy of Magnetic Excitations in Magnetic Superconductors Using Vortex Motion,"In magnetic superconductors a moving vortex lattice is accompanied by an ac
magnetic field which leads to the generation of spin waves. At resonance
conditions the dynamics of vortices in magnetic superconductors changes
drastically, resulting in strong peaks in the dc I-V characteristics at
voltages at which the washboard frequency of vortex lattice matches the spin
wave frequency $\omega_s({\bf g})$, where ${\bf g}$ are the reciprocal vortex
lattice vectors. We show that if washboard frequency lies above the magnetic
gap, peaks in the I-V characteristics in borocarbides and cuprate layered
magnetic superconductors are strong enough to be observed over the background
determined by the quasiparticles.",0504006v1
2005-08-17,Magnonic Crystal Theory of the Spin-Wave Frequency Gap in Low-Doped $La_{1-x}Ca_{x}MnO_{3}$ Manganites,"A theory of three-dimensional (3D) hypothetical magnonic crystal (conceived
as the magnetic counterpart of the well-known photonic crystal) is developed
and applied to explain the existence of a spin-wave frequency gap recently
revealed in low-doped manganites $La_{1-x}Ca_{x}MnO_{3}$ by neutron scattering.
A successful confrontation with the experimental results allows us to formulate
a working hypothesis that certain manganites could be regarded as 3D magnonic
crystals existing in nature.",0508389v1
2005-09-21,Spin Dependent Tunneling in FM|semiconductor|FM structures,"Here we show that ordinary band structure codes can be used to understand the
mechanisms of coherent spin-injection at interfaces between ferromagnets and
semiconductors. This approach allows the screening of different material
combinations for properties useful for obtaining high tunneling
magnetoresistance (TMR). We used the Vienna Ab-initio Simulation Code (VASP) to
calculate the wave function character of each band in periodic epitaxial
Fe(100)|GaAs(100) and Fe(100)|ZnSe(100) structures. It is shown that Fe wave
functions of different symmetry near Fermi energy decay differently in the GaAs
and ZnSe.",0509561v1
2005-11-07,Ferroelectricity induced by acentric spin-density waves in YMn$_2$O$_5$,"The commensurate and incommensurate magnetic structures of the
magnetoelectric system YMn$_{2}$O$_{5}$, as determined from neutron
diffraction, were found to be spin-density waves lacking a global center of
symmetry. We propose a model, based on a simple magneto-elastic coupling to the
lattice, which enables us to predict the polarization based entirely on the
observed magnetic structure. Our data accurately reproduce the
temperature-dependence of the spontaneous polarization, in particular its sign
reversal at the commensurate-incommensurate transition.",0511174v1
2005-11-08,Magnetic Excitations in the Quasi-1D Ising-like Antiferromagnet TlCoCl$_3$,"Neutron inelastic scattering measurements have been performed in order to
investigate the magnetic excitations in the quasi-1D Ising-like antiferromagnet
TlCoCl$_3$. We observed the magnetic excitation, which corresponds to the
spin-wave excitation continuum corresponding to the domain-wall pair excitation
in the 1D Ising-like antiferromagnet. According to the Ishimura-Shiba theory,
we analyzed the observed spin-wave excitation, and the exchange constant $2J$
and the anistropy $\epsilon$ were estimated as 14.7 meV and 0.14 in TlCoCl$_3$,
respectively.",0511179v1
2005-11-21,Controlling the Suhl instability: a numerical study,"Magnetization reversal (switching) using either r.f. fields or brute-force
precessional switching is currently thought to ultimately be limited by the
non-linear excitation of non-uniform spin waves, the so-called Suhl
instability. Here we show (numerically, for the case of a sphere) that this
instability can be suppressed by choosing the applied field and/or sphere
diameter in such a way that the frequencies of the modes that can be excited
through non-linear processes are off-resonance. While the results cannot be
explained by a traditional model based on plane waves, they can be understood
by projecting the actual state onto the small amplitude spin resonant
eigenfunctions.",0511496v1
2005-11-23,The pseudogap phase in (TaSe_4)_2I,"We have developed the mean-field theory of coexisting charge-density waves
(CDW) and unconventional charge-density waves (UCDW). The double phase
transition manifests itself in the thermodynamic quantities and in the magnetic
response, such as spin susceptibility and spin-lattice relaxation rate. Our
theory applies to quasi-one dimensional (TaSe_4)_2I, where above the CDW
transition, thermal fluctuations die out rapidly, but robust pseudogap
behaviour is still detected. We argue, that the fluctuations are suppressed due
to UCDW, which partially gaps the Fermi surface, and causes non-Fermi-liquid
(pseudogap) behaviour.",0511576v1
2006-01-17,Microwave Response and Spin Waves in Superconducting Ferromagnets,"Excitation of spin waves is considered in a superconducting ferromagnetic
slab with the equilibrium magnetization both perpendicular and parallel to the
surface. The surface impedance is calculated and its behavior near propagation
thresholds is analyzed. Influence of non-zero magnetic induction at the surface
is considered in various cases. The results provide a basis for investigation
of materials with coexisting superconductivity and magnetism by microwave
response measurements.",0601386v2
2006-01-20,Structure of fermion nodes and nodal cells,"We study nodes of fermionic ground state wave functions. For 2D and higher we
prove that spin-polarized, noninteracting fermions in a harmonic well have two
nodal cells for arbitrary system size. The result extends to other
noninteracting/mean-field models such as fermions on a sphere, in a periodic
box or in Hartree-Fock atomic states. Spin-unpolarized noninteracting states
have multiple nodal cells, however, interactions and many-body correlations
generally relax the multiple cells to the minimal number of two. With some
conditions, this is proved for interacting 2D and higher dimensions harmonic
fermion systems of arbitrary size using the Bardeen-Cooper-Schrieffer
variational wave function. Implications and extent of these results are briefly
discussed.",0601485v1
2006-06-05,"Su(1,2) Algebraic Structure of the XYZ Antiferromagnetic Model in Linear Spin-Wave Frame","The $XYZ$ antiferromagnetic model in linear spin-wave frame is shown
explicitly to have an $su(1,2)$ algebraic structure: the Hamiltonian can be
written as a linear function of the $su(1,2)$ algebra generators. Based on it,
the energy eigenvalues are obtained by making use of the similar
transformations, and the algebraic diagonalization method is investigated. Some
numerical solutions are given, and the results indicate that only one group
solution could be accepted in physics.",0606096v1
2006-06-13,Rectification of radio frequency current in ferromagnetic nanowire,"We report the rectification of a constant wave radio frequency (RF) current
by using a single-layer magnetic nanowire; a direct-current voltage is
resonantly generated when the RF current flows through the nanowire. The
mechanism of the rectification is discussed in terms of the spin torque diode
effect reported for magnetic tunnel junction devices and the rectification is
shown to be direct attributable to resonant spin wave excitation by the RF
current.",0606305v2
2006-07-07,Softening of Spin-Wave Stiffness near the Ferromagnetic Phase Transition in Diluted Magnetic Semiconductors,"Employing the self-consistent Green's function approach, we studied the
temperature dependence of the spin-wave stiffness in diluted magnetic
semiconductors. Note that the Green's function approach includes the spatial
and temperature fluctuations simultaneously which was not possible within
conventional Weiss mean-field theory. It is rather interesting that we found
the stiffness becomes dramatically softened as the critical temperature is
approached, which seems to explain the mysterious sharp drop of magnetization
curves in samples within diffusive regime.",0607201v1
2006-10-02,Interplay between different states in heavy fermion physics,"Calorimetry experiments under high pressure were used to clarify the
interplay between different states such as superconductivity and
antiferromagnetism in CeRhIn5, spin density wave and large moment
antiferromagnetism in URu2Si2. Evidences are given on the re-entrance of
antiferromagnetism under magnetic field in the superconducting phase of CeRhIn5
up to pc = 2.5 GPa where the Neel temperature will collapse in the absence of
superconductivity. For URu2Si2 measurements up to 10 GPa support strongly the
coexistence of spin density wave and large moment antiferromagnetism at high
pressures.",0610042v1
2006-10-06,Quantum entanglement generation with surface acoustic waves,"We propose a scheme to produce spin entangled states for two interacting
electrons. One electron is bound in a well in a semiconductor quantum wire and
the second electron is transported along the wire, trapped in a surface
acoustic wave potential (SAW) minimum. We investigate the conditions for which
the Coulomb interaction between the two electrons induces entanglement.
Detailed numerical investigation reveals that the two electrons can be fully
spin entangled depending on the confinement characteristics of the well and the
SAW potential amplitude.",0610168v1
2006-10-16,Quantum Scattering of Distinguishable Bosons using an Ultracold Atom Collider,"We describe a new implementation of magnetic collider for investigating cold
collisions between ultracold atomic clouds in different spin states, and we use
this to investigate scattering involving both even and odd order partial waves.
Our method relies on the axial assymetry of a double-well magnetic trap to
selectively prepare the spin state in each cloud. We measure the energy
dependence of s, p and d partial wave phase shifts in collisions up to 300
microKelvin between ^{87}Rb atoms in the 5S_{1/2}, F=1, m_F=-1 and 5S_{1/2},
F=2, m_F=1 states.",0610445v1
2006-12-28,Charge density wave in the spin ladder of Sr$_{14-x}$Ca$_x$Cu$_{24}$O$_{41}$,"We consider a multiband charge transfer model for a single spin ladder
describing the holes in Sr$_{14-x}$Ca$_x$Cu$_{24}$O$_{41}$. Using Hartree-Fock
approximation we show how the charge density wave, with its periodicity
dependent on doping as recently observed in the experiment, can be stabilized
by purely electronic many-body interactions.",0612669v1
2007-01-23,Observation of Spin Wave Soliton Fractals in Magnetic Film Active Feedback Rings,"The manifestation of fractals in soliton dynamics has been observed for the
first time. The experiment utilized self-generated spin wave envelope solitons
in a magnetic film based active feedback ring. At high ring gain, the soliton
that circulates in the ring breathes in a fractal pattern. The corresponding
power frequency spectrum shows a comb structure, with each peak in the comb
having its own comb, and so on, to finer and finer scales.",0701537v1
2007-02-05,Hidden symmetries in Bechgaard salt (TMTSF)2NO3,"Among known Bechgaard and Fabre salts (TMTSF)2NO3 is unique since it never
becomes superconducting even under pressure. Also, though (TMTSF)2NO3 undergoes
the spin density wave (SDW) transition, the low temperature transport is
semimetallic and gapless. We propose: a) the absence of the superconductivity
is due to the inverse symmetry breaking associated with the anion ordering at
45K; b) the SDW state below 9K should be unconventional as seen from the angle
dependent magnetoresistance oscillation (AMRO); c) a new phase diagram for
Bechgaard salts, where unconventional spin density wave (USDW) occupies the
prominent space.",0702096v1
2000-10-27,The r-mode instability in rotating neutron stars,"In this review we summarize the current understanding of the
gravitational-wave driven instability associated with the so-called r-modes in
rotating neutron stars. We discuss the nature of the r-modes, the detailed
mechanics of the instability and its potential astrophysical significance. In
particular we discuss results regarding the spin-evolution of nascent neutron
stars, the detectability of r-mode gravitational waves and mechanisms limiting
the spin-rate of accreting neutron stars in binary systems.",0010102v1
2001-01-10,"Comment on ""Gravity Waves, Chaos, and Spinning Compact Binaries""","Levin (gr-qc/9910040) has shown that spinning compact binaries can be chaotic
at second post-Newtonian order. However, when higher order dissipational
effects are included, the dynamics will no longer be chaotic, though the
evolution may still be unpredictable in a practical sense. I discuss some of
the additional work that needs to be done to decide how this unpredictability
might affect gravitational wave detectors such as LIGO.",0101041v1
2003-09-09,Parametric phenomena of the particle dynamics in a periodic gravitational wave field,"We establish exactly solvable models for the motion of neutral particles,
electrically charged point and spin particles (U(1) symmetry), isospin
particles (SU(2) symmetry), and particles with color charges (SU(3) symmetry)
in a gravitational wave background. Special attention is devoted to parametric
effects induced by the gravitational field. In particular, we discuss
parametric instabilities of the particle motion and parametric oscillations of
the vectors of spin, isospin, and color charge.",0309049v1
2003-07-22,Partial Wave Analyses of $J/ψ\toγK^+K^-$ and $γ K^0_SK^0_S$,"Results are presented on $J/\psi $ radiative decays to $K^+K^-$ and
$K^0_SK^0_S$ based on a sample of 58M $J/\psi$ events taken with the BES II
detector. A partial wave analysis is carried out using the relativistic
covariant tensor amplitude method in the 1-2 GeV mass range. There is
conspicuous production due to the $f'_2(1525)$ and $f_0(1710)$. The latter
peaks at a mass of $1740\pm 4^{+10}_{-25}$ MeV with a width of
$166{^{+5}_{-8}}{^{+15}_{-10}}$ MeV. Spin 0 is strongly preferred over spin 2.
For the $f'_2(1525)$, the helicity amplitude ratios are determined to be $x^2 =
1.00\pm0.28^{+1.06}_{-0.36}$ and $y^2 = 0.44\pm{0.08}^{+0.10}_{-0.56}$.",0307058v1
1997-10-10,Scaling Contributions to the Free Energy in the 1/N Expansion of O(N) Nonlinear Sigma Models in d-Dimensions,"Within the 1/N expansion of O(N) nonlinear $\sigma$ models for $d \leq 4$ it
is possible to separate consistently the spin-wave and the massive-mode
contributions to the scaling part of the free energy near criticality, and to
evaluate them to $O(1/N)$. For critical dimensions $d = 2+2/n$ the Abe-Hikami
anomaly is recovered, while for $d=2$ the removal of the spin-wave term is
justified.",9710041v2
1993-01-26,Neutron Acceleration in Uniform Electromagnetic Fields,"The question as to whether neutron acceleration can occur in uniform
electromagnetic fields is examined. Although such an effect has been predicted
using the canonical equations of motion some doubt has been raised recently as
to whether it is in principle observable for a spin 1/2 particle. To resolve
this issue a gedanken experiment is proposed and analyzed using a wave packet
construction for the neutron beam. By allowing arbitrary orientation for the
neutron spin as well as for the electric and magnetic fields a non vanishing
acceleration of the center of the neutron wave packet is found which confirms
the predictions of the canonical formalism.",9301110v1
1996-05-26,D=6 massive spinning particle,"The massive spinning particle in six-dimensional Minkowski space is described
as a mechanical system with the configuration space ${\ R}% ^{5,1}\times {\
CP}^3$. The action functional of the model is unambigiously determined by the
requirement of identical (off-shell) conservation for the phase-space
counterparts of three Casimir operators of Poincar\'e group. The model is shown
to be exactly solvable. Canonical quantization of the model leads to the
equations on wave functions which prove to be equivalent to the relativistic
wave equations for the irreducible $6d$ fields.",9605186v1
1999-09-27,Zero Energy States for SU(N): A Simple Exercise in Group Theory ?,"We show that the requirement of $S_3\times Spin(d)$ invariance for a
``asymptotically free'' SU(3)-Cartan subalgebra wave-function does {\em not}
give a unique candidate for a SU(3)-invariant zero energy state of the d=9
supersymmetric matrix model - nor does it rule out the existence of such a
state in the case d=3. For d=9 we explicitly construct various $S_3\times
Spin(9)$-invariant wave-functions.}",9909191v2
2004-11-28,Generation of spin-wave dark solitons with phase engineering,"We generate experimentally spin-wave envelope dark solitons from rectangular
high-frequency dark input pulses with externally introduced phase shifts in
yttrium-iron garnet magnetic fims. We observe the generation of both odd and
even numbers of magnetic dark solitons when the external phase shift varies.
The experimental results are in a good qualitative agreement with the theory of
the dark-soliton generation in magnetic films developed earlier [Phys. Rev.
Lett. 82, 2583 (1999)].",0411056v1
1996-10-10,The Representation Transformation of Multiquark Wave Functions,"It is shown that the representation transformations of multiquark wave
functions between different coupling schemes are just the Racah coefficients of
the permutation group. The transformation coefficients between the flavor-spin
(FS) and the color-spin (CS) schemes are obtained. As an example, the expansion
of the physical bases in terms of symmetry bases in the CS scheme are given for
the interesting cases $YIJ = 201, 210, 000$.",9610017v1
2001-01-02,New Forms of Deuteron Equations and Wave Function Representations,"A recently developed helicity basis for nucleon-nucleon (NN) scattering is
applied to th e deuteron bound state. Here the total spin of the deuteron is
treated in such a helicity representation. For the bound state, two sets of two
coupled eigenvalue equations are developed, where the amplitudes depend on two
and one variable, respectively. Numerical illustrations based on the realistic
Bonn-B NN potential are given. In addition, an `operator form' of the deuteron
wave function is presented, and several momentum dependent spin densities are
derived and shown, in which the angular dependence is given analytically.",0101009v1
2006-11-27,Partial-wave analysis of $K^+$ nucleon scattering,"We have performed a partial-wave analysis of K$^+$-nucleon scattering in the
momentum range from 0 to 1.5 GeV/c addressing the uncertainties of the results
and comparing them with several previous analyses. It is found that the
treatment of the reaction threshold behavior is particularly important. We find
a T=0 scattering length which is not consistent with zero, as has been claimed
by other analyses. The T=0 phase shifts for $\ell>0$ are consistent with a pure
spin-orbit potential. Some indications for the production of a T=0 pentaquark
with spin-parity D5/2+ are discussed.",0611095v2
1998-10-08,Geometrical properties of intelligent spin states and time evolution of coherent states,"We remind the properties of the intelligent (and quasi-intelligent) spin
states introduced by Aragone et al. We use these states to construct families
of coherent wave packets on the sphere and we sketch the time evolution of
these wave packets for a rigid body molecule.",9810024v2
2006-12-16,Topological Photon,"We associate intrinsic energy equal to $h\nu/2$ with the spin angular
momentum of photon and propose a topological model based on orbifold in space
and tifold in time as topological obstructions. The model is substantiated
using vector wavefield disclinations. The physical photon is suggested to be a
particle like topological photon and a propagating wave such that the energy
$h\nu$ of photon is equally divided between spin energy and translational
energy corresponding to linear momentum of $h\nu/c$. The enigma of
wave-particle duality finds natural resolution and the proposed model gives new
insights into the phenomena of interference and emission of radiation.",0612139v1
1995-08-10,Integer spin particles necessarily produce half-integer angular momentum in a simple complex and periodic Hamiltonian,"Exact wave functions are is derived from an azimuthally periodic a
self-consistent quantum Hamiltonian in 2+1 dimensions using both the
Klein-Gordon and the Schroedinger equations. It isWe shown that, curiously, for
both relativistic and non-relativistic equations, integer spin wave equations
necessarily produce half-integer angular momentum in this potential. We find
additionally that the higher energy, relativistic, solutions require an
asymptotically free potential, while the lower energy, Schroedinger, solutions
can exist in a potential that grows linearly with r. These are purely
mathematical results, however we speculate on possible physical
interpretations.",9508001v2
2007-04-26,On the Non-relativistic Limit of Linear Wave Equations for Zero and Unity Spin Particles,"The non-relativistic limit of the linear wave equation for zero and unity
spin bosons of mass $m$ in the Duffin-Kemmer-Petiau representation is
investigated by means of a unitary transformation, analogous to the
Foldy-Wouthuysen canonical transformation for a relativistic electron. The
interacting case is also analyzed, by considering a power series expansion of
the transformed Hamiltonian, thus demonstrating that all features of particle
dynamics can be recovered if corrections of order $1/m^{2}$ are taken into
account through a recursive iteration procedure.",0704.3462v2
2007-05-16,On The Recently Discovered Pulsations From RX J1856.5-3754,"An explanation of the recently discovered 7 s pulsations from the isolated
neutron star RX J1856.5-3754 is presented. It is assumed that the real spin
period of this source is $\approx1$ s, whereas the observed spin-modulation is
caused by the presence of a nearly transverse, very low frequency drift waves
in the pulsar magnetosphere. It is supposed that the period of the drift wave
is equal to a recently observed one. The simulated lightcurve is plotted, the
angular parameters are defined and the value of the pulsed fraction of only
$\sim 1.2%$ is explained.",0705.2316v1
2007-07-26,"Spin wave dispersion based on the quasiparticle self-consistent $GW$ method: NiO, MnO and $α$-MnAs","We present spin wave dispersions in MnO, NiO, and $\alpha$-MnAs based on the
quasiparticle self-consistent $GW$ method (\qsgw), which determines an optimum
quasiparticle picture. For MnO and NiO, \qsgw results are in rather good
agreement with experiments, in contrast to the LDA and LDA+U description. For
$\alpha$-MnAs, we find a collinear ferromagnetic ground state in \qsgw, while
this phase is unstable in the LDA.",0707.3850v2
2007-08-29,Exact wave functions of electron in a quantum dot with account of the Rashba spin-orbit interaction,"We present the exact wave functions and energy levels of electron in a
two-dimensional circular quantum dot in the presence of the Rashba spin-orbit
interaction. The confinement is described by the realistic potential well of
finite depth.",0708.3904v3
2007-12-25,"Nonrelativistic, Quasirelativistic and Relativistic Sets of Wave Functions, and Slater Orbitals of Particles with Arbitrary Spin","Using the complete orthonormal basis sets of nonrelativistic and
quasirelativistic orbitals introduced by the author in previous papers for
particles with arbitrary spin the new analytical relations for the -component
relativistic tensor wave functions and tensor Slater orbitals in coordinate,
momentum and four-dimensional spaces are derived, where. The relativistic
tensor function sets are expressed through the corresponding nonrelativistic
and quasirelativistic orbitals. The analytical formulas for overlap integrals
over relativistic tensor Slater orbitals with the same screening constants in
coordinate space are also derived.",0712.4065v1
2008-01-02,Spinning Particle with Anomalous Magnetic Moment in an External Plane Wave Field,"In this paper we study the interaction of a Dirac-Pauli particle with an
electromagnetic plane wave, by using a previously given generalization of the
pseudo-classical Lagrangian for a spinning particle with an anomalous magnetic
moment. We derive the explicit expressions for the eigenfunctions and the
Green's functions of the theory. We discuss the validity of the semi-classical
approach by comparing the wavefunctions with the (pseudo)-classical solutions
of the Hamilton-Jacobi equation.",0801.0392v1
2008-01-04,Diagonal charge modulation in the insulating La$_{2-x}$Sr$_x$CuO$_4$,"We show that, due to the Dzyaloshinskii-Moriya and the XY anisotropies, the
disordered diagonal spin spiral in the insulating La$_{2-x}$Sr$_x$CuO$_4$
generates a diagonal charge density wave (CDW) with the wave vector twice of
that of the spin spiral. The amplitude of the CDW depends on values of the
anisotropies, the doping level, and on the density of states at the chemical
potential. Based on available experimental data we estimate that for 4% doping
the amplitude of CDW is about 1/10 of the doping level. We believe that this
mechanism explains the CDW observed recently in Zn-codoped detwinned
La$_{2-x}$Sr$_x$CuO$_4$.",0801.0614v1
2008-02-04,Nodal quasiparticles and the onset of spin density wave order in the cuprates,"We present a theory for the onset of spin density wave order in the
superconducting ground state of the cuprates. We compute the scaling dimensions
of allowed perturbations of a `relativistic' fixed point with O(4)xO(3)
symmetry, including those associated with the fermionic nodal Bogoliubov
quasiparticles. Analyses of up to six loops show that all perturbations with
square lattice symmetry are likely irrelevant. We demonstrate that the fermion
spectral functions are primarily damped by the coupling to fluctuations of a
composite field with Ising nematic order. We also discuss the influence of
quenched disorder.",0802.0199v1
2008-07-03,Competitions of magnetism and superconductivity in FeAs-based materials,"Using the numerical unrestricted Hartree-Fock approach, we study the ground
state of a two-orbital model describing newly discovered FeAs-based
superconductors. We observe the competition of a $(0, \pi)$ mode spin-density
wave and the superconductivity as the doping concentration changes. There might
be a small region in the electron-doping side where the magnetism and
superconductivity coexist. The superconducting pairing is found to be spin
singlet, orbital even, and mixed s$_{xy}$ + d$_{x^{2}-y^{2}}$ wave (even
parity).",0807.0587v1
2008-08-29,Spin-wave mediated quantum corrections to the conductivity in thin ferromagnetic gadolinium films,"We present a study of quantum corrections to the conductivity of thin
ferromagnetic gadolinium films. In situ magneto-transport measurements were
performed on a series of thin films with thickness d < 135A. For sheet
resistances R0 < 4011 Ohm and temperatures T < 30K, we observe a linear
temperature dependence of the conductivity in addition to the logarithmic
temperature dependence expected from well known quantum corrections in two
dimensions. We show that such a linear T-dependence can arise from a spin-wave
mediated Altshuler-Aronov type correction.",0808.4103v1
2008-12-10,Transverse field-induced effects in carbon nanotubes,"We investigate the properties of conduction electrons in single-walled
armchair carbon nanotubes (SWNT) in the presence of both transverse electric
and magnetic fields. We find that these fields provide a controlled means of
tuning low-energy band structure properties such as inducing gaps in the
spectrum, breaking various symmetries and altering the Fermi velocities. We
show that the fields can strongly affect electron-electron interaction,
yielding tunable Luttinger liquid physics, the possibility of spin-charge-band
separation, and a competition between spin-density-wave and charge-density-wave
order. For short tubes, the fields can alter boundary conditions and associated
single-particle level spacings as well as quantum dot behavior.",0812.1851v1
2009-01-29,Quasi-long-range order in the 2D XY model with random phase shifts,"We study the square-lattice XY model in the presence of random phase shifts.
We consider two different disorder distributions with zero average shift and
investigate the low-temperature quasi-long-range order phase which occurs for
sufficiently low disorder. By means of Monte Carlo simulations we determine
several universal quantities which are then compared with the analytic
predictions of the random spin-wave theory. We observe a very good agreement
which indicates that the universal long-distance behavior in the whole
low-disorder low-temperature phase is fully described by the random spin-wave
theory.",0901.4682v1
2009-02-16,Spin-density wave Fermi surface reconstruction in underdoped YBa2Cu3O6+x,"We consider the reconstruction expected for the Fermi surface of underdoped
YBa2Cu3O6+x in the case of a collinear spin-density wave with a characteristic
vector Q=(pi[1+/-2 delta],pi), assuming an incommensurability delta~0.06
similar to that found in recent neutron scattering experiments. A Fermi surface
possibly consistent with the multiple observed quantum oscillation frequencies
is obtained. From the low band masses expected using this model as compared
with experiment, a uniform enhancement of the quasiparticle effective mass over
the Fermi surface by a factor of ~7 is indicated. Further predictions of the
Fermi surface topology are made, which may potentially be tested by experiment
to indicate the relevance of this model to underdoped YBa2Cu3O6+x.",0902.2741v1
2009-02-18,Field-induced transition from parallel to perpendicular parametric pumping for a microstrip transducer,"Microstrip transducers used for the excitation of spin waves in magnetic
films possess two characteristic properties: high spatial localization of the
microwave magnetic field and the presence of field components parallel and
perpendicular to the bias field.
  Here, the effects of these features on the process of parametric pumping are
presented. By microwave measurements of the spin-wave instability threshold a
transition from parallel pumping to perpendicular pumping at the critical field
$H_{\rm c}$ with the minimal threshold is observed. This transition is
accompanied by a sharp threshold increase above the critical field due to the
spatial confinement of the pump region.",0902.3157v1
2009-04-11,Coupled Superconducting Phase and Ferromagnetic Order Parameter Dynamics,"Via a direct coupling between the magnetic order parameter and the singlet
Josephson supercurrent, we detect spin-wave resonances, and their dispersion,
in ferromagnetic Josephson junctions in which the usual insulating or metallic
barrier is replaced with a weak ferromagnet. The coupling arises within the
Fraunhofer interferential description of the Josephson effect, because the
magnetic layer acts as a time dependent phase plate. A spin-wave resonance at a
frequency ws implies a dissipation that is reflected as a depression in the
current-voltage curve of the Josephson junction when hbar ws = 2eV. We have
thereby performed a resonance experiment on only 10^7 Ni atoms.",0904.1780v1
2009-04-29,Final state polarization of protons in $pp \to pp ω$,"Model independent formulae are derived for the polarizations and spin
correlations of protons in the final state of $pp \to pp\omega $, taking into
consideration all the six threshold partial wave amplitudes $f_1, ..., f_6$
covering $Ss, Sp$ and $Ps$ channels. It is shown that these measurements of the
final state spin observables, employing only an unpolarized beam and an
unpolarized target, may be utilized to complement measurements, at the double
differential level, suggested earlier [Phys. Rev. \textbf{C78}, 01210(R)(2009)]
so that all the six partial wave amplitudes may be determined empirically.",0904.4607v2
2009-05-04,The most generalized analytical approximation to the solution of single-mode spin-boson model without rotating-wave approximation,"The single-mode spin-boson model (SMSBM) has extensive application in
different subfields of physics. In the absence of rotating-wave approximation
(RWA), we try to solve SMSBM analytically. We argue that the analytical
expression obtained is the most exact approximation to the solution of the
system under the assumption of Abel-Ruffini theorem, which works for a wide
range of the parameters such as coupling strength and detuning and would be
practical for currently available experiments.",0905.0426v1
2009-05-08,Fermionic bound states on a one-dimensional lattice,"We study bound states of two fermions with opposite spins in an extended
Hubbard chain. The particles interact when located both on a site or on
adjacent sites. We find three different types of bound states. Type U is
predominantly formed of basis states with both fermions on the same site, while
two states of type V originate from both fermions occupying neighbouring sites.
Type U, and one of the states from type V, are symmetric with respect to spin
flips. The remaining one from type V is antisymmetric. V-states are
characterized by a diverging localization length below some critical wave
number. All bound states become compact for wave numbers at the edge of the
Brilloin zone.",0905.1255v1
2009-06-12,DMRG analysis of the SDW-CDW crossover region in the 1D half-filled Hubbard-Holstein model,"In order to clarify the physics of the crossover from a spin-density-wave
(SDW) Mott insulator to a charge-density-wave (CDW) Peierls insulator in
one-dimensional (1D) systems, we investigate the Hubbard-Holstein Hamiltonian
at half filling within a density matrix renormalisation group (DMRG) approach.
Determining the spin and charge correlation exponents, the momentum
distribution function, and various excitation gaps, we confirm that an
intervening metallic phase expands the SDW-CDW transition in the weak-coupling
regime.",0906.2355v2
2009-08-28,Solitons: from Charge Density Waves to FFLO in superconductors,"This short review aims to summarize on ""What the Charge Density Waves can
tell to other inhomogeneous states in strongly correlated systems, particularly
to spin-polarized superconductors"". We shall update on expanding observations
of solitons in quasi 1D CDW conductors and link them to the growing information
and demands related to inhomogeneous spin-polarized states in superconductors.
The related theory, existent or awaited for, stretches from solitons in 1D
models to vortex-like elementary excitations in 2D,3D ordered incommensurate
CDWs and superconductors.",0908.4249v1
2009-08-31,Microwave screening by conduction currents in thin magnetic films: application in stripline broadband FMR,"Ferromagnetic resonance in conducting magnetic bilayers was studied using
microstrip transducers. It was found that excitation or suppression of standing
spin waves could be achieved through enhanced inhomogeneity of eddy currents in
the bilayer caused by finite thickness. This effect is observable in films with
thicknesses below the magnetic skin depth and can be used to study standing
spin wave modes in heterostructures.",0908.4443v2
2009-09-02,Ferroelectrical spin wave resonance,"New phenomenon is experimentally identified: ferroelectrical spin wave
resonance (FE SWR), which consist in characteristic splitting of vibration
(electronic-vibration) levels in optical spectra of interacting localized
centers. Spectral positions of ESWR lines are determined in linear approach by
quadratic dispersion law. It has been found that the values of resonance mode
amplitudes are inversely proportional to mode numbers (by low excitation
level). The prediction that Raman-ESWR and IR-ESWR are characterized by
splitting constants with different values has been confirmed. Their ratio is
approximately equal two (by the frequencies of zero modes reduced to the same
value). It is independent argument for FE SWR identification.",0909.0467v1
2009-10-22,Spin density wave dislocation in chromium probed by coherent x-ray diffraction,"We report on the study of a magnetic dislocation in pure chromium. Coherent
x-ray diffraction profiles obtained on the incommensurate Spin Density Wave
(SDW) reflection are consistent with the presence of a dislocation of the
magnetic order, embedded at a few micrometers from the surface of the sample.
Beyond the specific case of magnetic dislocations in chromium, this work may
open up a new method for the study of magnetic defects embedded in the bulk.",0910.4252v1
2009-11-30,Quantum Phases of Bose-Hubbard Model in Optical Superlattices,"In this paper, we analyze the quantum phases of multiple component
Bose-Hubbard model in optical superlattices, using a mean-field method, the
decoupling approximation. We find that the phase diagrams exhibit complected
patterns and regions with various Charge Density Wave (CDW) for both one- and
two- component cases. We also analyze the effective spin dynamics for the
two-component case in strong-coupling region at unit filling, and show the
possible existence of a Spin Density Wave (SDW) order.",0911.5536v1
2010-03-17,Non-dispersive optics using storage of light,"We demonstrate the non-dispersive deflection of an optical beam in a
Stern-Gerlach magnetic field. An optical pulse is initially stored as a
spin-wave coherence in thermal rubidium vapour. An inhomogeneous magnetic field
imprints a phase gradient onto the spin wave, which upon reacceleration of the
optical pulse leads to an angular deflection of the retrieved beam. We show
that the obtained beam deflection is non-dispersive, i.e. its magnitude is
independent of the incident optical frequency. Compared to a Stern-Gerlach
experiment carried out with propagating light under the conditions of
electromagnetically induced transparency, the estimated suppression of the
chromatic aberration reaches 10 orders of magnitude.",1003.3389v1
2010-05-04,Pair Density Wave correlations in the Kondo-Heisenberg Model,"We show, using density matrix renormalization group calculations complemented
by field theoretic arguments, that the spin gapped phase of the one dimensional
Kondo-Heisenberg model exhibits quasi-long range superconducting correlations
{\it only} at a non-zero momentum. The local correlations in this phase
resemble those of the pair density wave state which was recently proposed to
describe the phenomenology of the striped ordered high temperature
superconductor {La$_{2-x}$Ba$_x$% CuO$_4$}, in which the spin, charge, and
superconducting orders are strongly intertwined.",1005.0623v2
2010-06-21,Magnonic spin-wave modes in CoFeB antidot lattices,"In this manuscript time-resolved magneto-optical Kerr effect experiments on
structured CoFeB films are presented. The geometries considered are two
dimensional square lattices of micrometer-sized antidots, fabricated by a
focused ion beam. The spin-wave spectra of these magnonic crystals show a novel
precessional mode, which can be related to a Bloch state at the zone boundary.
Additionally, another magnetic mode of different nature appears, whose
frequency displays no dependence on the externally applied magnetic field.
These findings are interpreted as delocalized and localized modes,
respectively.",1006.4038v1
2010-10-01,The quantum effects of the spin and the Bohm potential in the oblique propagation of magnetosonic waves,"We study the quantum corrections to the oblique propagation of the
magnetosonic waves in a warm quantum magnetoplasma composed by mobile ions and
electrons. We use a fluid formalism to include quantum corrections due to the
Bohm potential and to magnetization energy of electrons due to its spin. The
effects of both quantum corrections are shown in the dispersion relation for
perpendicular, parallel and oblique propagation. We find that the quantum
contributions to the low-frequency depends on the type of propagation we are
studying.",1010.0058v1
2010-10-29,Magnetic and Electronic Raman Scattering at the Nodal Spin-Density-Wave Transition in BaFe2As2,"Two magnon excitations and the nodal spin density wave (SDW) gap were
observed in BaFe2As2 by Raman scattering. Below the SDW transition temperature
(TSDW) nodal SDW gap opens together with new excitations in reconstructed
electronic states. The two-magnon peak remains above TSDW and moreover the
energy increases a little. The change from the long-range ordered state to the
short-range correlated state is compared to the cuprate superconductors.",1010.6151v1
2010-11-17,Lifshitz transition in two-dimensional spin-density wave models,"We argue that both pocket-disappearing and neck-disrupting types of Lifshitz
transitions can be realized in two-dimensional spin-density wave models for
underdoped cuprates, and study both types of transitions with impurity
scattering treated in the self-consistent Born approximation. We first solve
for the electron self-energy from the self-consistent equation, and then study
the low-temperature electrical conductivity and thermopower. Close to the
Lifshitz transition, the thermopower is strongly enhanced. For the
pocket-disappearing type, it has a sharp peak, while for the neck-disrupting
type, it changes sign at the transition, with its absolute value peaked on both
sides of the transition. We discuss possible applications to underdoped
cuprates.",1011.3881v1
2010-12-20,Probing La(0.7)Sr(0.3)MnO3 multilayers via spin wave resonances,"La(0.7)Sr(0.3)MnO3/BiFeO3 and La(0.7)Sr(0.3)MnO3/PbZr20Ti80O3 epitaxial
heterostructures have been grown on SrTiO3 substrates. Spin wave resonances are
used to study interface properties of the ferromagnetic La(0.7)Sr(0.3)MnO3. We
find that the addition of the BiFeO3 or PbZr20Ti80O3 causes out-of-plane
surface pinning of the La(0.7)Sr(0.3)MnO3. We are able to place new limits on
the exchange constant D of La(0.7)Sr(0.3)MnO3 grown on these substrates and
confirm the presence of uniaxial and biaxial anisotropies caused by the SrTiO3
substrate.",1012.4273v1
2010-12-27,Anomalous Scattering of Low-lying Excitations in a Spin-1 Bose-Einstein Condensate,"We present the simplest theory of perfect tunneling of an excitation in a
Bose-Einstein condensate (BEC) through an impurity potential with an arbitrary
shape in the low-momentum limit. That is for the transverse spin wave in the
ferromagnetic phase of a spin-1 BEC. This mode obeys a Schr\""odinger-type
equation; yet, effects of the potential on its transmission coefficient $T$ and
on its scattering cross section $sigma$ vanish in that limit. The order
parameter determines $T$, and the momentum $p$-dependence of $sigma$ exhibits a
Rayleigh scattering type ($sigma propto p^{4}$). These properties are common
between two types of Nambu-Goldstone modes: this spin wave and the Bogoliubov
mode.",1012.5618v1
2011-06-06,Chiral spin-wave excitations of the spin-5/2 trimers in the langasite compound Ba3NbFe3Si2O14,"The inelastic scattering of neutrons from magnetic excitations in the
antiferromagnetic phase of the langasite compound Ba3NbFe3Si2O14 is analyzed
theoretically. In the calculations presented, the strongly coupled spin-5/2 Fe
triangles are accounted for as trimerized units. The weaker interactions
between the trimers are included within the mean-field/random-phase
approximation. The theory is compared with linear spin-wave theory, and a model
is developed which leads to good agreement with the published results from
unpolarized and polarized neutron-scattering experiments.",1106.1052v1
2011-07-16,Dephasing of multiparticle Rydberg excitations for fast entanglement generation,"An approach to fast entanglement generation based on Rydberg dephasing of
collective excitations (spin-waves) in large, optically thick atomic ensembles
is proposed. Long-range $1/r^3$ atomic interactions are induced by microwave
mixing of opposite-parity Rydberg states. Required long coherence times are
achieved via four-photon excitation and read-out of long wavelength spin-waves.
The dephasing mechanism is shown to have favorable, approximately exponential,
scaling for entanglement generation.",1107.3202v2
2011-09-30,Dephasing in ferromagnetic nanowires: The role of spin waves,"We present a calculation of the dephasing time of electrons in a ferromagnet
relevant for the conductance fluctuations. We focus on the contribution from
the interaction with spin waves. Explicit results are presented for a
quasi-one-dimensional systems. Going beyond previous calculations, we do not
restrict ourselves to the limit of a small exchange splitting compared to the
electronic elastic scattering time, nor does our calculation rely on the
diffusion approximation to describe electronic transport.",1109.6796v1
2011-12-14,Dynamics of Thermal Effects in the Spin-Wave Theory of Quantum Antiferromagnets,"We derive a master equation that allows us to study non-equilibrium dynamics
of a quantum antiferromagnet. By resorting to spin-wave theory, we obtain a
closed analytic form for the magnon decay rates. These turn out to be closely
related to form factors, which are experimentally accessible by means of
neutron and Raman scattering. Furthermore, we compute the time evolution of the
staggered magnetization showing that, for moderate temperatures, the magnetic
order is not spoiled even if the coupling is fully isotropic.",1112.3158v3
2012-02-29,Spin wave modes in magnetic nanodisks under in-plane magnetic field,"The size dependence of spin wave modes in a circular Permalloy (Py) nanodisk
under an in-plane magnetic field is systematically studied by using
micromagnetics simulations. We show that as the disk diameter is increased, the
resonance frequency of the backward mode deceases while that of the uniform
mode increases. The avoided crossing of resonance frequencies of the uniform
mode and the backward mode appears in the plot of the size dependence of
resonance frequencies and the backward mode turns into the so-called ""edge
mode"" for large nanodisks.",1202.6464v1
2012-03-19,Quasi-plane waves for a particle with spin 1/2 on the background of Lobachevsky geometry: simulating of a special medium,"In the paper complete systems of exact solutions for Dirac and Weyl equations
in the Lobachevsky space are constructed on the base of the method of
separation of the variables in quasi-cartesian coordinates. An extended
helicity operator is introduced. It is shown that solution constructed when
translating to the limit of vanishing curvature coincide with common plane wave
solutions on Minkowski space going in opposite z-directions. It is shown the
problem posed in Lobachevsky space simulates a situation in the flat space for
a quantum-mechanical particle of spin 1/2 in a 2-dimensional potential barrier
smoothly rising to infinity on the right.",1203.4288v1
2012-04-18,Domain wall heat conductance in ferromagnetic wires,"We present a theoretical study of heat transport in electrically insulating
ferromagnetic wires containing a domain wall. In the regime of validity of
continuum micromagnetism a domain wall is found to have no effect on the heat
conductance. However, spin waves are found to be reflected by domain walls with
widths of a few lattice spacings, which is associated with emergence of an
additional spin wave bound state. The resulting domain wall heat conductance
should be significant for thin films of Yttrium Iron Garnet with sharply
defined magnetic domains.",1204.4008v2
2012-06-27,Domain wall propagation through spin wave emission,"We theoretically study field-induced domain wall (DW) motion in an
electrically insulating ferromagnet with hard- and easy-axis anisotropies. DWs
can propagate along a dissipationless wire through spin wave emission locked
into the known soliton velocity at low fields. In the presence of damping, the
mode appears before the Walker breakdown field for strong out-of-plane magnetic
anisotropy, and the usual Walker rigid-body propagation mode becomes unstable
when the field is between the maximal-DW-speed field and Walker breakdown
field.",1206.6244v1
2012-08-27,Spin-wave modes and band structure of rectangular CoFeB antidot lattices,"We present an investigation of rectangular antidot lattices in a CoFeB film.
Magnonic band structures are numerically calculated, and band gaps are
predicted which shift in frequency by 0.9 GHz when rotating the external field
from the long to the short axis of the unit cell. We demonstrate by
time-resolved experiments that magnonic dipolar surface modes are split in
frequency by 0.6 GHz which agrees well with the theoretical prediction. These
findings provide the basis for directional spin-wave filtering with magnonic
devices.",1208.5339v1
2012-11-28,Correlation enhanced phase sensitive Raman scattering in atomic vapors,"We theoretically propose a method to enhance Raman scattering by injecting a
seeded light field which is correlated with the initially prepared atomic spin
wave. Such a light-atom correlation leads to an interference in the Raman
scattering. The interference is sensitive to the relative phase between the
seeded light field and initially prepared atomic spin wave. For constructive
interference, the Raman scattering is greatly enhanced. Such an enhanced Raman
scattering may find applications in quantum information, nonlinear optics and
optical metrology due to its simplicity.",1211.6540v2
2013-03-15,Phases of attractive spin-imbalanced fermions in square lattices,"We determine the relative stability of different ground-state phases of
spin-imbalanced popula- tions of attractive fermions in square lattices. The
phases are systematically characterized by the symmetry of the order parameter
and the real- and momentum-space structures using Hartree- Fock-Bogoliubov
theory. We find several type of unidirectional Larkin-Ovchinikov-type phases.
We discuss the effect of commensuration between the ordering wave vector and
the density imbalance, and describe the mechanism of Fermi surface
reconstruction and pairing for various orders. A robust supersolid phase is
shown to exist when the ordering wave vector is diagonally directed.",1303.3812v2
2013-05-13,Testing general relativity using gravitational waves from binary neutron stars: Effect of spins,"We present a Bayesian data analysis pipeline for testing GR using
gravitational wave signals from coalescing compact binaries, and in particular
binary neutron stars. In this study, we investigate its performance when
sources with spins are taken into account.",1305.2963v2
2013-08-06,Optical helicity of interfering waves,"Helicity is a property of light which is familiar from particle physics but
less well-known in optics. In this paper we recall the explicit form taken by
the helicity of light within classical electromagnetic theory and reflect upon
some of its remarkable characteristics. The helicity of light is related to,
but is distinct from, the spin of light. To emphasise this fact, we draw a
simple analogy between the helicity of light and electric charge and between
the spin of light and electric current. We illustrate this and other
observations by examining various superpositions of plane waves explicitly.",1308.1308v1
2013-09-03,Bose-Einstein Condensates with Cavity-Mediated Spin-Orbit Coupling,"We propose a novel scheme to generate the spin-orbit coupling for a
condensate placed inside an optical cavity by using a standing wave and a
traveling wave. It is shown that the interplay of the laser lights and the
cavity gives rise to rich quantum phases. Our scheme also generates an
nontrivial lattice of the magnetic flux, which may facilitate the study of the
exotic quantum phases.",1309.0606v1
2013-10-02,Spin wave theory for 2D disordered hard-core bosons,"A spin-wave (SW) approach for hard-core bosons is presented to treat the
problem of two dimensional boson localization in a random potential. After a
short review of the method to compute 1/S-corrected observables, the case of
random on-site energy is discussed. Whereas the mean-field solution does not
display a Bose glass (BG) phase, 1/S corrections do capture BG physics. In
particular, the localization of SW excitations is discussed through the inverse
participation ratio.",1310.0601v1
2014-01-28,Enhancement of Electronic Spin Susceptibility in Pauli Limited Unconventional Superconductors,"We calculate the wave-vector dependent electronic spin susceptibility
$\chi_{\alpha\beta}(\mathbf q, \mathbf H_0)$ of a d-wave superconductor in
uniform magnetic field $\mathbf{H}_0$ with Pauli pair-breaking. We find that
the transverse component of the susceptibility tensor can be greater than its
normal state value; the longitudinal component also slightly increases but in a
very limited range of $q$s. We identify several wave vectors $\{\mathbf
q_\perp,\mathbf q_\parallel\}$, that correspond to the maxima of either
$\chi_\perp$ or $\chi_\parallel$. We compare our results with available data on
the high-field phase in heavy-fermion CeCoIn$_5$.",1401.7268v1
2014-05-14,Generation of magnonic spin wave traps,"Spatially resolved measurements of the magnetization dynamics induced by an
intense laser pump-pulse reveal that the frequencies of resulting spin wave
modes depend strongly on the distance to the pump center. This can be
attributed to a laser generated temperature profile. On a CoFeB thin film
magnonic crystal, Damon-Eshbach modes are expected to propagate away from the
point of excitation. The experiments show that this propagation is frustrated
by the strong temperature gradient",1405.3470v1
2014-07-15,Transport measurements of the spin wave gap of thin Mn films,"Temperature dependent transport measurements on ultrathin antiferromagnetic
Mn films reveal a heretofore unknown non-universal weak localization correction
to the conductivity which extends to disorder strengths greater than 100
k$\Omega$ per square. The inelastic scattering of electrons off of gapped
antiferromagnetic spin waves gives rise to an inelastic scattering length which
is short enough to place the system in the 3d regime. The extracted fitting
parameters provide estimates of the energy gap ($\Delta = 16$ K) and exchange
energy ($\bar{J} = 320$ K).",1407.4138v1
2014-11-14,Two-leg fermionic Hubbard ladder system in the presence of state-dependent hopping,"We study a two-leg fermionic Hubbard ladder model with a state-dependent
hopping. We find that, contrary to the case without a state-dependent hopping,
for which the system has a superfluid nature regardless of the sign of the
interaction at incommensurate filling, in the presence of such a hopping a
spin-triplet superfluid, spin- density wave and charge-density wave phases
emerge. We examine our results in the light of recent experiments on
periodically-driven optical lattices in cold atoms. We give protocols allowing
us to realize the spin-triplet superfluid elusive in the cold atoms.",1411.3905v2
2014-11-17,Curved magnonic waveguides based on domain walls,"The channeling of spin waves with domain walls in ultrathin ferromagnetic
films is demonstrated theoretically and through micromagnetics simulations. It
is shown that propagating excitations localized to the wall, which appear in
the frequency gap of bulk spin wave modes, can be guided effectively in curved
geometries and can propagate in close proximity to other channels with no
perceptible scattering or loss in coherence. For N\'eel-type walls arising from
an interfacial Dzyaloshinskii-Moriya interaction, the channeling is strongly
nonreciprocal and group velocities can exceed 1 km/s in the long wavelength
limit for certain propagation directions.",1411.4525v1
2015-01-27,Orbital angular momentum in a nonchiral topological superconductor,"We investigate the bulk orbital angular momentum in a two-dimensional
time-reversal broken topological superconductor with the Rashba spin-orbit
interaction, the Zeeman interaction, and the $s$-wave pairing potential. Prior
to the topological phase transition, we find the crossover from $s$ wave to $p$
wave. For the large spin-orbit interaction, even in the topological phase,
$L_z/N$ does not reach $-1/2$, which is the intrinsic value in chiral $p$-wave
superconductors. Here $L_z$ and $N$ are the bulk orbital angular momentum and
the total number of electrons at zero temperature, respectively. Finally, we
discuss the effects of nonmagnetic impurities.",1501.06677v2
2015-03-17,Topological phase in a $d_{x^2-y^2}+(p+ip)$ superconductor in presence of spin-density-wave,"We consider a mean-field Hamiltonian for a $d_{x^2-y^2}+(p+ip)$
superconductor(SC) in presence of spin-density-wave(SDW) order. This is due to
the fact that the non-commutativity of any two orders produces the third one.
The energy spectrum of such a Hamiltonian is shown to be gapped and it yields a
topological phase in addition to the conventional one. A phase diagram
characterizing different topological phases is construted. The Chern numbers
and hence the nature of the topological phases are determined. The edge state
spectrum and the possibility of whether the vortex state harbouring the zero
modes are discussed.",1503.04969v1
2015-04-07,Dynamic Consequences of Optical Spin-Orbit Interaction,"When circularly polarized wave scatters off a sphere, the scattered field
forms a vortex with spiraling energy flow. This is due to the transformation of
spin angular momentum into orbital one. Here we demonstrate that during this
scattering an anomalous force can be induced that acts in a direction
perpendicular to the propagation of incident wave. The appearance of this
lateral force is made possible by the presence of an interface in the vicinity
of scattering object. Besides radiation pressure and tractor-beam pulling
forces, this lateral force is another type of non-conservative force that can
be produced with unstructured light beams.",1504.01766v1
2015-04-30,Thermoelectric transport in the topological phase due to the coexistence of superconductivity and spin-density-wave,"We study the thermoelectric transport in two dimensional topological system
which has coexistence of superconductivity(SC) and spin-density wave(SDW). The
SC is presumed to be of $d_{x^2-y^2}+(p_x + i p_y) $ type whereas the SDW order
parameter is of $BCS$ symmetry. The Hamiltonian describing such a coexistence
phase is shown to have topological phase in addition to the conventional one.
The transport properties in such topological system have two distinct
contributions: (i) the surface/edge and (ii) the bulk. The competition between
the surface/edge versus the bulk transport is analyzed in different parameter
regimes and the possibility of enhancing the figure of merit is discussed.",1504.08207v1
2015-07-24,Upper bounds of spin-density wave energies in the homogeneous electron gas,"Studying the jellium model in the Hartree-Fock approximation, Overhauser has
shown that spin density waves (SDW) can lower the energy of the Fermi gas, but
it is still unknown if these SDW are actually relevant for the phase diagram.
In this paper, we give a more complete description of SDW states. We show that
a modification of the Overhauser ansatz explains the behavior of the jellium at
high density compatible with previous Hartree-Fock simulations.",1507.06884v1
2015-10-21,"Comment on ""Approximate solutions of the Dirac equation for the Rosen-Morse potential including the spin-orbit centrifugal term""","It is shown that the application of the Nikiforov-Uvarov method by Ikhdair
for solving the Dirac equation with the radial Rosen-Morse potential plus the
spin-orbit centrifugal term is inadequate because the required conditions are
not satisfied. The energy spectra given are incorrect and the wave functions
are not physically acceptable. We clarify the problem and prove that the spinor
wave functions are expressed in terms of the generalized hypergeometric
functions. The energy eigenvalues for the bound states are given by the
solution of a transcendental equation involving the hypergeometric function.",1510.06447v2
2015-11-20,Two-dimensional quantum rings with oscillating spin-orbit interaction strength: A wave function picture,"We determine the relevant spinor valued wave functions for a two-dimensional
quantum ring in the presence of Rashba-type spin-orbit interaction (SOI). The
case of constant SOI strength is considered first, then we investigate the
physical consequences of time-dependent (oscillating) SOI strength. Floquet's
method is applied to find time-dependent eigenspinors, and it is shown that the
Floquet quasienergies and thus their differences (the generalized Rabi
frequencies) are determined by the radial boundary conditions. Time evolution
of various initial states is calculated.",1511.06570v1
2015-12-06,Conduction-electron spin resonance in two-dimensional structures,"The infuence of the conduction-electron spin magnetization density, induced
in a two-dimensional electron layer by a microwave electromagnetic field, on
the rejection and transmission of the field is considered. Because of the
induced magnetization and electric current, both the electric and magnetic
components of the field should have jumps on the layer. A way to match the
waves on two sides of the layer, valid when the quasi-two-dimensional electron
gas is in the one-mode state, is proposed. By following this way, the
amplitudes of transmitted and rejected waves as well as the absorption
coefficient are evaluated.",1512.01791v1
2016-04-13,Resistivity Minimum in Highly Frustrated Itinerant Magnets,"We study the transport properties of frustrated itinerant magnets comprising
localized {\it classical} moments, which interact via exchange with the
conduction electrons. Strong frustration stabilizes a liquidlike spin state,
which extends down to temperatures well below the effective
Ruderman-Kittel-Kasuya-Yosida interaction scale. The crossover into this state
is characterized by spin structure factor enhancement at wave vectors smaller
than twice the Fermi wave vector magnitude. The corresponding enhancement of
electron scattering generates a resistivity upturn at decreasing temperatures.",1604.03620v2
2017-08-21,URu$_2$Si$_2$ under intense magnetic fields: from hidden order to spin-density wave,"A review of recent state-of-the-art pulsed field experiments performed on
URu$_2$Si$_2$ under a magnetic field applied along its easy magnetic axis
$\mathbf{c}$ is given. Resistivity, magnetization, magnetic susceptibility,
Shubnikov-de Haas, and neutron diffraction experiments are presented,
permitting to emphasize the relationship between Fermi surface reconstructions,
the destruction of the hidden-order and the appearance of a spin-density wave
state in a high magnetic field.",1708.06122v1
2018-09-18,Simulating excitation spectra with projected entangled-pair states,"We develop and benchmark a technique for simulating excitation spectra of
generic two-dimensional quantum lattice systems using the framework of
projected entangled-pair states (PEPS). The technique relies on a variational
ansatz for capturing quasiparticle excitations on top of a PEPS ground state.
Our method perfectly captures the quasiparticle dispersion relation of the
square-lattice transverse-field Ising model, and reproduces the spin-wave
velocity and the spin-wave anomaly in the square-lattice Heisenberg model with
high precision.",1809.06747v1
2018-09-22,Modulation instability associated nonlinear dynamics of spin-orbit coupled Bose-Einstein condensates,"We study pattern-forming nonlinear dynamics starting from a continuous wave
state of quasi-one-dimensional two-component Bose-Einstein condensates with
synthetic spin-orbit coupling induced by Raman lasers. Modulation instability
can occur even when the miscibility condition due to the interatomic
interactions is satisfied. We find that the initial stage of the nonlinear
development is consistent with the prediction of modulation instability, where
the two primary and secondary instability bands lead to the spontaneous growth
of the modulation and the subsequent complicated dynamics of pattern formation.
At later stages of the evolution, the wave functions undergo clear separation
in the momentum space, reflected in the dispersion of the single particle
Hamiltonian.",1809.08491v2
2019-06-13,Antiferromagnetism and spin density waves in 3D Dirac semimetals,"We perform mean-field study of possible magnetic instabilities in Dirac
semimetals. We find that Dirac electrons naturally host antiferromagnetic or
spin density wave ground states, though their specific configurations may vary
depending on specific model, as well as chemical potential and temperature. We
also discuss paramagnetic susceptibility of Dirac semimetals. In the cases,
when Dirac electrons do not have orbital momentum, the magnetic properties may
be $\mu$ and $T$ independent.",1906.05883v2
2018-04-09,Microwave non-reciprocity of magnon excitations in a non-centrosymmetric antiferromagnet Ba$_2$MnGe$_2$O$_7$,"We have investigated the microwave non-reciprocity for a non-centrosymmetric
antiferromagnet Ba$_2$MnGe$_2$O$_7$. The magnon modes expected by the
conventional spin wave theory for staggered antiferromagnets are certainly
observed. The magnitudes of exchange interaction and magnetic anisotropy are
obtained by the comparison with the theory. The microwave non-reciprocity is
identified for one of these mode. The relative magnitude of microwave
non-reciprocity can be explained with use of spin wave theory and Kubo formula.",1804.03250v1
2018-04-24,Elastic quantum spin-Hall effect in Kagome lattices,"A Quantum Spin-Hall Insulator (QSHI) is implemented into a simple mass-spring
Kagome lattice. The transition from the trivial state to the topological one is
described by an invariant Chern number function of a contrast parameter. The
band diagram and helical edge states characteristic of QSHI are obtained by a
combination of numerical and analytical methods. In particular, these states
are shown to be Stoneley wave solutions to a set of asymptotic continuous
motion equations. Last, scatterless propagation of polarized topological edge
waves around sharp corners is demonstrated and robustness is assessed through a
parametric study.",1804.09131v1
2019-05-10,Lagrangian formulation for emergent elastic waves in magnetic emergent crystals,"Magnetic emergent crystals are periodic alignment of ""particle-like"" spin
textures that emerge in magnets. Instead of focusing on an individual spin or a
macroscopic magnetization field, we analyze the dynamical behaviors of these
novel states by taking a solid-state point of view. Based on variational
principles, the basic equations for lattice dynamics of any emergent
crystalline states appearing in magnetic materials is established. For small
amplitude emergent elastic waves propagating in emergent crystals, the basic
equations reduce to an eigenvalue problem, from which the dispersion relation
and vibrational patterns for all emergent phonons are determined at the long
wavelength limit.",1905.03991v1
2020-03-12,Unification of the wave and guidance equations for spin 1/2,"We generalize our previous unification of the Schrodinger and guidance
equations in a single inhomogeneous Schrodinger equation to a Riemannian
manifold with an external vector potential. A special case yields the unified
theory for a spin 1/2 rigid rotator. The theory is proved to be symmetrical
under the Galileo group, the unified field that integrates the particle and
guiding wave being a 2-spinor.",2003.06058v2
2020-03-30,Geometric phase of very slow neutrons,"The geometric phase (GP) acquired by a neutron passing through a uniform
magnetic field elucidates a subtle interplay between its spatial and spin
degrees of freedom. In the standard setup using thermal neutrons, the kinetic
energy is much larger than the typical Zeeman split. This causes the spin to
undergo nearly perfect precession around the axis of the magnetic field and the
GP becomes a function only of the corresponding cone angle. Here, we perform a
plane wave analysis of the GP of very slow neutrons, for which the precession
feature breaks down. Purely quantum-mechanical matter wave effects, such as
resonance, reflection, and tunneling, become relevant for the behavior of the
GP in this low energy scattering regime.",2003.13737v1
2021-08-19,Chiral pair density wave states generated by spin supercurrents,"We report that spin supercurrents in magnetic superconductors and
superconductor/ferromagnetic insulator bilayers can induce the
Dzyaloshinskii-Moriya interaction which strength is proportional to the
superconducting order parameter amplitude. This effect leads to the existence
of inhomogeneous parity-breaking ground states combining the chiral magnetic
helix and the pair density wave orders. The formation of such states takes
place via the penetration of chiral domain walls at the threshold temperature
below the superconducting transition. We find regimes with both the single and
the re-entrant transitions into the inhomogeneous states with decreasing
temperature. The predicted hybrid chiral states can be found in the existing
structures with realistic parameters and materials combinations.",2108.08862v1
2008-06-25,"Mossbauer Spectroscopy Determination of iron foreign phases in the Superconducting Systems; RAsFeO1-x, RAsFeO1-xFx and Sr1-xKxFe2As2","The recently discovered superconducting - spin density wave materials,
containing Fe and As, have raised huge interest. However most materials
prepared to date, suffer from a varying degree of content of foreign Fe-As
phases, Fe2As, FeAs2 and FeAs, which can lead to wrong conclusions concerning
the properties of these materials. We show here that Mossbauer Spectroscopy is
able to determine quite easily the relative content of the foreign phases. This
procedure is demonstrated by a study of seven samples of superconducting or
spin density wave materials, prepared in three different laboratories.",0806.4078v1
2017-04-03,The Relativistic Bound States of a Non Central Potential,"We investigate the relativistic effects of a moving particle in the field of
a pseudo-harmonic oscillatory ring-shaped potential under the spin and
pseudo-spin symmetric Dirac wave equation. We obtain the bound state energy
eigenvalue equation and the corresponding two-components spinor wave functions
by using the formalism of Suppersymmetric Quantum Mechanics (SUSYQM).
Furthermore, the non-relativistic limits are obtained by simply making a proper
replacement of parameters. The thermodynamic properties are shortly studied.
Our numerical results for the energy eigenvalues are presented too.",1704.00769v1
2019-04-22,Stripe structures in phase separated magnetic oxides,"We investigate the phase separated inhomogeneous charge and spin states in
magnetic oxides. In particular, we study one dimensional harmonic waves and
stripe structures. We show that harmonic spin charge waves are unstable and
inevitably transform into two or three dimensional structures, while the stripe
structures can be stable for certain parameters. Such stripe structures may
allow the control of magnetic state with electric field in a magnetic oxide
thin film.",1904.10053v1
2019-10-09,Scattering of exchange spin waves from regions of modulated magnetization,"We investigate the reflection coefficient of spin waves propagating in an
ultra-thin ferromagnetic film with regions where saturation magnetization is
modulated. We find analytically and using micromagnetic simulations that there
are transmission resonances that depend on the width of the regions and on the
energy of excitation. Our results resemble the quantum mechanical
Ramsauer-Townsend effect in which an electron with certain energies can
propagate above a potential field without scattering. Our findings are useful
for reconfigurable magnonic devices where the saturation magnetization can be
dynamically controlled via a thermal landscape.",1910.04303v1
2019-12-06,3D Analytical Model of Skyrmions and Skyrmion-like Structures in a Two-sublattice Antiferromagnet with Dzyaloshinskii-Moriya Interaction,"The analytical model is developed for description of skyrmions and
skyrmion-like magnetic structures in a two-sublattice antiferromagnet with
uniaxial magnetic anisotropy and Dzyaloshinskii-Moriya interaction.
Relativistic contraction of skyrmion size in the direction of motion is
demonstrated for subcritical case when the skyrmion velocity is less than spin
wave velocity in antiferromagnet. Lorentz-like supercritical transformation are
found for skyrmion-like magnetic structures moving with velocity greater than
spin wave velocity in antiferromagnet.",1912.03057v1
2020-07-07,Maxwell equations in a curved spacetime: Spin optics approximation,"We study propagation of high-frequency electromagnetic waves in a curved
spacetime. We demonstrate how a modification of the standard geometric optics
allows one to include the helicity dependent corrections into the equations of
motion of circularly polarized beams of radiation. As a result, polarized light
rays are still null but not geodesic curves. To achieve these results we
construct null frames associated with a set of (non-geodesic) null rays and use
these frames for description of the high-frequency wave propagation. We call
this approach spin optics approximation. It is completely covariant and it can
be used in an arbitrary time-dependent gravitational field.",2007.03743v1
2021-01-22,Optical polarization skyrmionic fields in free space,"We construct optical beams in free space with robust skyrmionic structures in
their polarization fields, both in the electric spin vector for near-circular
fields and in the polarization direction for near-linear fields, and for both
Bloch (spiral) and N\'eel (hedgehog) textures. These structures are made
possible by the spin-orbit coupling of tightly-focused nonparaxial optics as
applied to higher-order Full-Poincar\'e beams, as well as by standing-wave
configurations comprising forwards- and backwards-propagating waves. Our
constructions show near-uniform circular and linear polarizations, providing a
high degree of topological protection in the absence of nonlinear interactions.",2101.09254v2
2021-01-28,Vortex propagation and phase transitions in a chiral antiferromagnetic nanostripe,"We study a vortex in a nanostripe of an antiferromagnet with easy-plane
anisotropy and interfacial Dzyloshinskii-Moriya interaction. The vortex has
hybrid chirality being N\'eel close to its center and Bloch away from it.
Propagating vortices can acquire velocities up to a maximum value that is lower
than the spin wave velocity. When the vortex is forced to exceed the maximum
velocity, phase transitions occur to a nonflat spiral, vortex chain, and flat
spiral, successively. The vortex chain is a topological configuration
stabilised in the stripe geometry. Theoretical arguments lead to the general
result that the velocity of localized excitations in chiral magnets cannot
reach the spin wave velocity.",2101.12172v1
2021-05-14,Exploring Evaporating Primordial Black Holes with Gravitational Waves,"Primordial black holes (PBHs) from the early Universe have been connected
with the nature of dark matter and can significantly affect cosmological
history. We show that coincidence dark radiation and density fluctuation
gravitational wave signatures associated with evaporation of $\lesssim10^9$ g
PBHs can be used to explore and obtain important hints about the formation
mechanisms of spinning and non-spinning PBHs spanning orders of magnitude in
mass-range, which is challenging to do otherwise.",2105.06816v2
2022-02-27,Dual function spin-wave logic gates based on electric field control magnetic anisotropy boundary,"Spin waves (SWs) have been considered a promising candidate for encoding
information with lower power consumption. Here, we propose the dual function SW
logic gates based on the electric field controlling the SW propagation in the
Fe film of Fe/BaTiO3 heterostructure with the motion of magnetic anisotropy
boundary (MAB). We show micromagnetic simulations to validate the AND-OR and
NAND-NOR logic gates. Our research may find a path for simplifying integrated
logic circuits using such dual function SW logic gates.",2202.13258v1
2022-09-18,Nucleon spin decomposition with one dynamical gluon,"We solve for the light-front wave functions of the nucleon from a light-front
quantum chromodynamics (QCD) effective Hamiltonian with three-dimensional
confinement. We obtain solutions using constituent three quarks combined with
three quarks and one gluon Fock components. The resulting light-front wave
functions provide a good quality description of the nucleon's quark
distribution functions following QCD scale evolution. We present the effects
from incorporating a dynamical gluon on the nucleon's gluon densities, helicity
distribution and orbital angular momentum that constitutes the nucleon spin sum
rule.",2209.08584v1
2022-10-27,Renormalization of spin$\unicode{x2013}$boson interactions mediated by singular form factors,"We study and discuss the extension of the rotating-wave
spin$\unicode{x2013}$boson model, together with more general models describing
a system$\unicode{x2013}$field coupling with a similar rotating-wave structure,
to interactions mediated by possibly singular (non-normalizable) form factors
satisfying a weaker growth constraint. To this purpose, a construction of
annihilation and creation operators as continuous maps on a scale of Fock
spaces, together with a rigorous renormalization procedure, is employed.",2210.15267v1
2023-03-22,Superconductivity in lightly doped Hubbard model on honeycomb lattice,"We have performed large-scale density-matrix renormalization group studies of
the lightly doped Hubbard model on the honeycomb lattice on long three and
four-leg cylinders. We find that the ground state of the system upon lightly
doping is consistent with that of a superconducting state with coexisting
quasi-long-range superconducting and charge density wave orders. Both the
superconducting and charge density wave correlations decay as a power law at
long distances with corresponding exponents $K_{sc}<2$ and $K_c<2$. On the
contrary, the spin-spin and single-particle correlations decay exponentially,
although with relatively long correlation lengths.",2303.12348v1
2023-09-13,Relations between the Worldline Quantum Field Theory and scattering amplitudes for particles with spin,"The Worldline Quantum Field Theory (WQFT) has proven to be an efficient tool
for calculating observables in gravitational wave physics. In contrast to other
QFT-based techniques in the realm of gravitational wave physics, it makes the
classical limit very apparent. However, a natural question remains: How does it
relate to ordinary quantum field theories that we know from particle physics?
This question will be addressed by extending existing approaches to a
description including spin. Furthermore, it will be explicitly shown that the
WQFT can retain quantum contributions by summing up infinite towers of
worldline loops.",2309.07318v1
2023-10-07,Electromagnetic angular momentum of quantized wavepackets in free space,"A single electromagnetic plane-wave propagating in free space possesses
neither spin nor orbital angular momentum. Both types of angular momentum arise
from interference between pairs of plane-waves having the same temporal
frequency {\omega} but differing k-vectors k_1 and k_2. While it is fairly
straightforward to evaluate a wavepacket's spin and orbital angular momenta in
the (k,{\omega}) continuum by means of Fourier transformation, obtaining the
same results by discretizing the (k,{\omega}) space, then attempting to
approach the continuum limit via an infinite enlargement of the spatial volume
under consideration, is fraught with danger.",2310.04877v1
2024-02-27,Adiabatically-manipulated systems interacting with spin baths beyond the Rotating Wave Approximation,"The Stimulated Raman Adiabatic Passage on a three-state system interacting
with a spin bath is considered focusing on the efficiency of the population
transfer. Our analysis is based on the perturbation treatment of the
interaction term evaluated beyond the Rotating Wave Approximation, thus
focusing on the limit of weak system-bath coupling. The analytical expression
of the correction to the efficiency and consequent numerical analysis show that
in most of the cases the effects of the environment are negligible, confirming
the robustness of the population transfer.",2402.17661v1
2024-03-01,Quantum spin representation for the Navier-Stokes equation,"We develop a quantum representation for Newtonian viscous fluid flows by
establishing a mapping between the Navier-Stokes equation (NSE) and the
Schr\""odinger-Pauli equation (SPE). The proposed nonlinear SPE incorporates the
two-component wave function and the imaginary diffusion. Consequently,
classical fluid flow can be interpreted as a non-Hermitian quantum spin system.
Using the SPE-based numerical simulation of viscous flows, we demonstrate the
quantum/wave-like behavior in flow dynamics. Furthermore, the SPE equivalent to
the NSE can facilitate the quantum simulation of fluid dynamics.",2403.00596v1
2024-03-03,Spin and Orbital Angular Momenta of Electromagnetic Waves: From Classical to Quantum Forms,"Angular momenta of electromagnetic waves are important both in concepts and
applications. In this work, we systematically discuss two types of angular
momenta, i.e., spin angular momentum and orbital angular momentum in various
cases, e.g., with source and without source, in classical and quantum forms.
Numerical results demonstrating how to extract the topological charge of a
classical vortex beam by spectral method are also presented.",2403.01504v1
2024-03-11,Ising model with non-reciprocal interactions,"Effective interactions that violate Newton's third law of action-reaction
symmetry are common in systems where interactions are mediated by a
non-equilibrium environment. Extensive Monte Carlo simulations are carried out
on a two-dimensional Ising model, where the interactions are modified
non-reciprocally. We demonstrate that the critical temperature decreases as the
non-reciprocity increases and this decrease depends only on the magnitude of
non-reciprocity. Further, travelling spin waves due to the local fluctuations
in magnetisation are observed and these spin waves travel opposite to the
non-reciprocity vector.",2403.06875v1
1997-04-28,Formation of Millisecond Pulsars from Accretion Induced Collapse and Constraints on Pulsar Gamma Ray Burst Models,"We study accretion induced collapse of magnetized white dwarfs as an origin
of millisecond pulsars. We apply magnetized accretion disk models to the
pre-collapse accreting magnetic white dwarfs and calculate the white dwarf spin
evolution. If the pulsar magnetic field results solely from the flux-frozen
fossil white dwarf field, a typical millisecond pulsar is born with a field
strength $\sim 10^{11}-10^{12}G$. The uncertainty in the field strength is
mainly due to the uncertain physical parameters of the magnetized accretion
disk models. A simple correlation between the pulsar spin $\Omega_*$ and the
magnetic field $B_*$, $(\Omega_*/10^4s^{-1})\sim (B_{*}/10^{11}G)^{-4/5}$, is
derived for a typical accretion rate $\sim 5\times 10^{-8}M_{\sun}/yr$. This
correlation remains valid for a wide pre-collapse physical conditions unless
the white dwarf spin and the binary orbit are synchronized prior to accretion
induced collapse. We critically examine the possibility of spin-orbit
synchronization in close binary systems. Using idealized homogeneous ellipsoid
models, we compute the electromagnetic and gravitational wave emission from the
millisecond pulsars and find that electromagnetic dipole emission remains
nearly constant while millisecond pulsars may spin up rather than spin down as
a result of gravitational wave emission. We also derive the physical conditions
under which electromagnetic emission from millisecond pulsars formed by
accretion induced collapse can be a source of cosmological gamma-ray bursts. We
find that relativistic beaming of gamma-ray emission and precession of
gamma-ray emitting jets are required unless the dipole magnetic field strengths
are $>10^{15}$G; such strong dipole fields are in excess of those allowed from
the accretion induced collapse formation process except in spin-orbit
synchronization.",9704268v1
1998-03-27,Skyrmions in quantum Hall ferromagnets as spin-waves bound to unbalanced magnetic flux quanta,"A microscopic description of (baby)skyrmions in quantum Hall ferromagnets is
derived from a scattering theory of collective (neutral) spin modes by a bare
quasiparticle. We start by mapping the low lying spectrum of spin waves in the
uniform ferromagnet onto that of free moving spin excitons, and then we study
their scattering by the defect of charge. In the presence of this disturbance,
the local spin stiffness varies in space, and we translate it into an
inhomogeneus metric in the Hilbert space supporting the excitons. An attractive
potencial is then required to preserve the symmetry under global spin
rotations, and it traps the excitons around the charged defect. The
quasiparticle now carries a spin texture. Textures containing more than one
exciton are described within a mean-field theory, the interaction among the
excitons being taken into account through a new renormalization of the metric.
The number of excitons actually bound depends on the Zeeman coupling, that
plays the same role as a chemical potencial. For small Zeeman energies, the
defect binds many excitons which condensate. As the bound excitons have a unit
of angular momentum, provided by the quantum of magnetic flux left unbalanced
by the defect of charge, the resulting texture turns out to be a topological
excitation of charge 1. Its energy is that given by the non-linear sigma model
for the ground state in this topological sector, i.e. the texture is a
skyrmion.",9803333v1
2007-05-25,Matched Filtering of Numerical Relativity Templates of Spinning Binary Black Holes,"Tremendous progress has been made towards the solution of the
binary-black-hole problem in numerical relativity. The waveforms produced by
numerical relativity will play a role in gravitational wave detection as either
test-beds for analytic template banks or as template banks themselves. As the
parameter space explored by numerical relativity expands, the importance of
quantifying the effect that each parameter has on first the detection of
gravitational waves and then the parameter estimation of their sources
increases. In light of this, we present a study of equal-mass, spinning
binary-black-hole evolutions through matched filtering techniques commonly used
in data analysis. We study how the match between two numerical waveforms varies
with numerical resolution, initial angular momentum of the black holes and the
inclination angle between the source and the detector. This study is limited by
the fact that the spinning black-hole-binaries are oriented axially and the
waveforms only contain approximately two and a half orbits before merger. We
find that for detection purposes, spinning black holes require the inclusion of
the higher harmonics in addition to the dominant mode, a condition that becomes
more important as the black-hole-spins increase. In addition, we conduct a
preliminary investigation of how well a template of fixed spin and inclination
angle can detect target templates of arbitrary spin and inclination for the
axial case considered here.",0705.3829v2
2010-06-07,Spin down during quiescence of the fastest known accretion-powered pulsar,"We present a timing solution for the 598.89 Hz accreting millisecond pulsar,
IGR J00291+5934, using Rossi X-ray Timing Explorer data taken during the two
outbursts exhibited by the source on 2008 August and September. We estimate the
neutron star spin frequency and we refine the system orbital solution. To
achieve the highest possible accuracy in the measurement of the spin frequency
variation experienced by the source in-between the 2008 August outburst and the
last outburst exhibited in 2004, we re-analysed the latter considering the
whole data set available. We find that the source spins down during quiescence
at an average rate of {\nu}dot_{sd}=(-4.1 +/- 1.2)E-15 Hz/s. We discuss
possible scenarios that can account for the long-term neutron star spin-down in
terms of either magneto-dipole emission, emission of gravitational waves, and a
propeller effect. If interpreted in terms of magneto-dipole emission, the
measured spin down translates into an upper limit to the neutron star magnetic
field, B<=3E+08 G, while an upper limit to the average neutron star mass
quadrupole moment of Q<=2E+36 g cm^2 is set if the spin down is interpreted in
terms of the emission of gravitational waves.",1006.1303v2
2010-06-23,Non-Abelian Topological Orders and Majorana Fermions in Spin-Singlet Superconductors,"The non-Abelian topological order for superconductors is characterized by the
existence of zero-energy Majorana fermions in edges of systems and in a vortex
of a macroscopic condensate, which obey the non-Abelian statistics. This paper
is devoted to an extensive study on the non-Abelian topological phase of
spin-singlet superconductors with the Rashba spin-orbit interaction proposed in
our previous letter [M. Sato, Y. Takahashi, and S. Fujimoto, Phys. Rev. Lett.
103, 020401 (2009)]. We mainly consider the s-wave pairing state and the d+id
pairing state. In the case of d+id-wave pairing, Majorana fermions appear in
almost all parameter regions of the mixed state under an applied magnetic
field, provided that the Fermi level crosses k-points in the vicinity of the
Gamma point or the M point in the Brillouin zone, while in the case of s-wave
pairing, a strong magnetic field, the Zeeman energy of which is larger than the
superconducting gap is required to realize the topological phase. We clarify
that Majorana fermions in Rashba spin-singlet superconductors are much more
stable than those realized in spin-triplet p+ip superconductors in certain
parameter regions. We also investigate the topological number which ensures the
topological stability of the phase in detail. Furthermore, as a byproduct, we
found that topological order is also realized in conventional spin (or charge)
density wave states with the Rashba spin-orbit interaction, for which massless
Dirac fermions appear in the edge of the systems and charge fractionalization
occurs.",1006.4487v2
2013-04-29,Quantum Hall Effect of Two-Component Bosons at Fractional and Integral Fillings,"We investigate the feasibility of many candidate quantum Hall states for
two-component bosons in the lowest Landau level. We identify interactions for
which spin-singlet incompressible states occur at filling factors $\nu=2/3$,
4/5 and 4/3, and spin-partially-polarized states at filling factors 3/4 and
3/2, where ""spin"" serves as a generic label for the two components. We study
ground states, excitations, edge states and entanglement spectrum for systems
with up to 16 bosons, and construct explicit trial wave functions to clarify
the underlying physics. The composite fermion theory very accurately describes
the ground states as well as excitations at $\nu=2/3$, 4/5 and 3/4, although it
is less satisfactory for the $\nu=3/2$ state. For $\nu=4/3$ a ""non-Abelian
spin-singlet"" state has been proposed to occur for a 2-body contact
interaction; we find that it is more likely that the actual state here is a
spin-singlet state of reverse-flux-attached composite fermions at filling
$\nu^*=4$. We also consider incompressible states at integral filling factors
$\nu=1$ and 2. The incompressible state at $\nu=1$ is shown to be well
described by the parton-based Jain spin-singlet wave function, and the
incompressible state at $\nu=2$ as the spin-singlet state of
reverse-flux-attached composite fermions at $\nu^*=2$.",1304.7553v2
2016-05-27,First step towards a Devil's Staircase in Spin Crossover materials First step towards Devil's Staircase in Spin Crossover materials,"The devil is in the detail: Periodic and aperiodic spin-state concentration
waves form during ""Devil's staircase""-type spincrossover in a new bimetallic 2D
coordination polymer {Fe[(Hg(SCN)3)2](4,4'-bipy)2}n.The unprecedented
bimetallic 2D coordination polymer {Fe[(Hg(SCN)3)2](4,4'-bipy)2}n exhibits a
thermal high-spin (HS)$low-spin (LS) staircase-like conversion characterized by
a multi-step dependence of the HS molar fraction gHS. Between the fully HS
(gHS=1) and LS (gHS=0) phases, two steps associated with different ordering
appear in terms of spin-state concentration waves (SSCW). On the gHS=0.5 step,
a periodic SSCW forms with a HS-LS-HS-LS sequence. On the gHS=0.34 step, the 4D
superspace crystallography structural refinement reveals an aperiodic SSCW,
with a HS-LS sequence incommensurate with the molecular lattice. The formation
of these different long-range spatially ordered structures of LS and HS states
during the multi-step spin-crossover is discussed within the framework of
""Devil's staircase""-type transitions. Spatially modulated phases are known in
various types of materials but are uniquely related to molecular HS/LS
bistability in this case.",1605.08561v1
2017-07-27,Electron spin resonance for the detection of long-range spin nematic order,"In this paper we propose that electron spin resonance (ESR) measurements
enable us to detect the long-range spin nematic order. We show that the
frequency of the paramagnetic resonance peak in the ESR spectrum is shifted by
the ferroquadrupolar order parameter together with other quantities. The
ferroquadrupolar order parameter is extractable from the angular dependence of
the frequency shift. In contrast, the antiferroquadrupolar order parameter is
usually invisible in the frequency shift. Instead, the long-range
antiferroquadrupolar order yields a characteristic resonance peak in the ESR
spectrum, which we call a magnon-pair resonance peak. This resonance
corresponds to the excitation of the bound magnon pair at the wave vector $\bm
k={\bm 0}$. Reflecting the condensation of bound magnon pairs, the field
dependence of the magnon-pair resonance frequency shows a singular upturn at
the saturation field. Moreover, the intensity of the magnon-pair resonance peak
shows a characteristic angular dependence and it vanishes when the magnetic
field is parallel to one of the axes that diagonalize the weak anisotropic
interactions. We confirm these general properties of the magnon-pair resonance
peak in the spin nematic phase by studying an $S=1$ bilinear-biquadratic model
on the square lattice in the linear flavor-wave approximation. In addition, we
argue applications to the $S=1/2$ frustrated ferromagnets and also the $S=1/2$
orthogonal dimer spin system SrCu$_2$(BO$_3$)$_2$, both of which are candidate
materials of spin nematics. Our theory for the antiferroquadrupolar ordered
phase is consistent with many features of the magnon-pair resonance peak
experimentally observed in the low-magnetization regime of
SrCu$_2$(BO$_3$)$_2$.",1707.08784v2
2017-12-13,Persistence of the gapless spin liquid in the breathing kagome Heisenberg antiferromagnet,"The nature of the ground state of the spin $S=1/2$ Heisenberg antiferromagnet
on the kagome lattice with breathing anisotropy (i.e., with different
superexchange couplings $J_{\vartriangle}$ and $J_{\triangledown}$ within
elementary up- and down-pointing triangles) is investigated within the
framework of Gutzwiller projected fermionic wave functions and Monte Carlo
methods. We analyze the stability of the U(1) Dirac spin liquid with respect to
the presence of fermionic pairing that leads to a gapped $\mathbb{Z}_{2}$ spin
liquid. For several values of the ratio $J_{\triangledown}/J_{\vartriangle}$,
the size scaling of the energy gain due to the pairing fields and the
variational parameters are reported. Our results show that the energy gain of
the gapped spin liquid with respect to the gapless state either vanishes for
large enough system size or scales to zero in the thermodynamic limit.
Similarly, the optimized pairing amplitudes (responsible for opening the spin
gap) are shown to vanish in the thermodynamic limit. Our outcome is
corroborated by the application of one and two Lanczos steps to the gapless and
gapped wave functions, for which no energy gain of the gapped state is detected
when improving the quality of the variational states. Finally, we discuss the
competition with the ""simplex"" $\mathbb{Z}_{2}$ resonating-valence-bond spin
liquid, valence-bond crystal, and nematic states in the strongly anisotropic
regime, i.e., $J_{\triangledown} \ll J_{\vartriangle}$.",1712.04579v2
2018-05-09,Universal scaling relationship between classical and quantum correlations in critical quantum spin chains,"We numerically investigate classical and quantum correlations in
one-dimensional quantum critical systems. The infinite matrix product state
(iMPS) representation is employed in order to consider an infinite-size spin
chain. By using the infinite time-evolving block decimation algorithm, iMPS
ground state wave functions are obtained at critical points for the
transverse-field spin-$1/2$ XY model. From the ground state wave functions, we
calculate classical and quantum correlations and mutual information. All of the
correlations are found to exhibit a power-law decay with the increments of the
lattice distance for both the transition lines of the Ising universality class
and the Gaussian universality class. Such power-law scaling behaviors of the
correlations manifest the existence of diversing correlation lengths, which
means scale invariance. The critical features of the correlations can be
characterized by introducing a critical exponent of the power-law decaying
correlations. Similar to the critical exponent $\eta$ of the spin-spin
correlation for the universality classes in the transverse-field XY model, we
calculate the critical exponents of the two-spin classical and quantum
correlations as well as that of the corresponding mutual information. All of
the correlations have the same critical exponents, i.e.,
$\eta^{I}=\eta^{C}=\eta^{D}$ at a critical point, where the superscripts $I$,
$C$, and $D$ stand for mutual information, classical correlation, and quantum
correlation, respectively. Furthermore, the critical exponent $\eta$ of the
spin-spin correlation is shown to relate to $\eta = \eta^\alpha/2$ with $\alpha
\in \{ I, C, D\}$.",1805.03464v1
2018-11-30,Spin excitation spectra of the two dimensional $S=1/2$ Heisenberg model with a checkerboard structure,"We study the spin excitation spectra of the two-dimensional spin-$1/2$
Heisenberg model with a checkerboard structures using stochastic analytic
continuation of the imaginary-time correlation function obtained from a quantum
Monte Carlo simulation. The checkerboard models have two different
antiferromagnetic nearest-neighbor interactions $J_{1}$ and $J_{2}$, and the
tuning parameter $g$ is defined as $J_{2}/J_{1}$. The dynamic spin structure
factors are systematically calculated in all phases of the models as well as at
the critical points. To give a full understanding of the dynamic spectra, spin
wave theory is employed to explain some features of numerical results,
especially for the low-energy part. When $g$ is close to $1$, the features of
the spin excitation spectra of each checkerboard model are roughly the same as
those of the original square lattice antiferromagnetic Heisenberg model, and
the high-energy continuum among them is discussed. In contrast to the other
checkerboard structures investigated in this paper, the $3\times 3$
checkerboard model has distinctive excitation features, such as a gap between a
low-energy gapless branch and a gapped high-energy part that exists when $g$ is
small. The gapless branch in this case can be regarded as a spin wave in
N$\mathrm{\acute{e}}$el order formed by a ""block spin"" in each $3\times 3$
plaquette with an effective exchange interaction originating from
renormalization. One unexpected finding is that the continuum also appears in
this low-energy branch.",1811.12753v2
2018-08-26,Intertwined Spin and Orbital Density Waves in MnP Uncovered by Resonant Soft X-ray Scattering,"Unconventional superconductors are often characterized by numerous competing
and even intertwined orders in their phase diagrams. In particular, the
electronic nematic phases, which spontaneously break rotational symmetry and
often simultaneously involve spin, charge and/or orbital orders, appear
conspicuously in both the cuprate and iron-based superconductors. The
fluctuations associated with these phases may provide the exotic pairing glue
that underlies their high-temperature superconductivity. Helimagnet MnP, the
first Mn-based superconductor under pressure, lacks high rotational symmetry.
However our resonant soft X-ray scattering (RSXS) experiment discovers novel
helical orbital density wave (ODW) orders in this three-dimensional,
low-symmetry system, and reveals intertwined ordering phenomena in
unprecedented detail. In particular, a ODW forms with half the period of the
spin order and fully develops slightly above the spin ordering temperature,
their domains develop simultaneously, yet the spin order domains are larger
than those of the ODW, and they cooperatively produce another ODW with 1/3 the
period of the spin order. These observations provide a comprehensive picture of
the intricate interplay between spin and orbital orders in correlated
materials, and they suggest that nematic-like physics ubiquitously exists
beyond two-dimensional and high-symmetry systems, and the superconducting
mechanism of MnP is likely analogous to those of cuprate and iron-based
superconductors.",1808.08562v1
2021-10-11,Topological phonons in an inhomogeneously strained silicon-1: Evidence of long-distance spin transport and unidirectional magnetoresistance of phonons,"Transverse acoustic waves in an inhomogeneous medium are analogues to
electromagnetic waves and will exhibit topological behavior due to the Berry
gauge potential in the momentum space due to inhomogeneity. The inhomogeneous
(or gradient) medium can be created using an applied strain gradient in a
semiconductor thin film (silicon) since the phonon frequency and dispersion
will be a function of the local strain along the strain gradient direction. As
a consequence, topological phonon mediated spin and heat transport can be
engineered in the semiconductor thin films. Here, we present evidence of a
long-distance (100 um) spin transport in the freestanding Si thin film sample
under an applied strain gradient using transverse spin-Nernst effect
measurement. The long-distance spin transport was attributed to the topological
spin-Hall effect of phonons in an inhomogeneous medium. The inhomogeneous
medium was validated using unidirectional magnetoresistance of phonons where
the magnitude of the coefficient of the non-reciprocal response at room
temperature was as large as reported in the BiTeBr at low temperatures. The
topological phonons also manifested the topological Nernst effect. This work
not only enhances the current understanding of inhomogeneous systems but also
lays the foundation of the topological and spin phononics.",2110.04936v1
2019-04-03,Spin waves and spin-state transitions in a ruthenate high-temperature antiferromagnet,"Ruthenium compounds play prominent roles in materials research ranging from
oxide electronics to catalysis, and serve as a platform for fundamental
concepts such as spin-triplet superconductivity, Kitaev spin-liquids, and
solid-state analogues of the Higgs mode in particle physics. However, basic
questions about the electronic structure of ruthenates remain unanswered,
because several key parameters (including the Hund's-rule, spin-orbit, and
exchange interactions) are comparable in magnitude, and their interplay is
poorly understood - partly due to difficulties in synthesizing sizable single
crystals for spectroscopic experiments. Here we introduce a resonant inelastic
x-ray scattering (RIXS) technique capable of probing collective modes in
microcrystals of $4d$-electron materials. We present a comprehensive set of
data on spin waves and spin-state transitions in the honeycomb antiferromagnet
SrRu$_{2}$O$_{6}$, which possesses an unusually high N\'eel temperature. The
new RIXS method provides fresh insight into the unconventional magnetism of
SrRu$_{2}$O$_{6}$, and enables momentum-resolved spectroscopy of a large class
of $4d$ transition-metal compounds.",1904.01930v2
2020-05-29,Long-distance spin-transport across the Morin phase transition up to room temperature in ultra-low damping single crystals of the antiferromagnet α-Fe2O3,"Antiferromagnetic materials can host spin-waves with polarizations ranging
from circular to linear depending on their magnetic anisotropies. Until now,
only easy-axis anisotropy antiferromagnets with circularly polarized spin-waves
were reported to carry spin-information over long distances of micrometers. In
this article, we report long-distance spin-transport in the easy-plane canted
antiferromagnetic phase of hematite and at room temperature, where the linearly
polarized magnons are not intuitively expected to carry spin. We demonstrate
that the spin-transport signal decreases continuously through the easy-axis to
easy-plane Morin transition, and persists in the easy-plane phase through
current induced pairs of linearly polarized magnons with dephasing lengths in
the micrometer range. We explain the long transport distance as a result of the
low magnetic damping, which we measure to be below 0.0001 as in the best
ferromagnets. All of this together demonstrates that long-distance transport
can be achieved across a range of anisotropies and temperatures, up to room
temperature, highlighting the promising potential of this insulating
antiferromagnet for magnon-based devices.",2005.14414v5
2020-06-16,Block orbital-selective Mott insulators: a spin excitation analysis,"We present a comprehensive study of the spin excitations - as measured by the
dynamical spin structure factor $S(q,\omega)$ - of the so-called block-magnetic
state of low-dimensional orbital-selective Mott insulators. We realize this
state via both a multi-orbital Hubbard model and a generalized Kondo-Heisenberg
Hamiltonian. Due to various competing energy scales present in the models, the
system develops periodic ferromagnetic islands of various shapes and sizes,
which are antiferromagnetically coupled. The 2$\times$2 particular case was
already found experimentally in the ladder material BaFe$_2$Se$_3$ that becomes
superconducting under pressure. Here we discuss the electronic density as well
as Hubbard and Hund coupling dependence of $S(q,\omega)$ using density matrix
renormalization group method. Several interesting features were identified: (1)
An acoustic (dispersive spin-wave) mode develops. (2) The spin-wave bandwidth
establishes a new energy scale that is strongly dependent on the size of the
magnetic island and becomes abnormally small for large clusters. (3) Optical
(dispersionless spin excitation) modes are present for all block states studied
here. In addition, a variety of phenomenological spin Hamiltonians have been
investigated but none matches entirely our results that were obtained primarily
at intermediate Hubbard $U$ strengths. Our comprehensive analysis provides
theoretical guidance and motivation to crystal growers to search for
appropriate candidate materials to realize the block states, and to neutron
scattering experimentalists to confirm the exotic dynamical magnetic properties
unveiled here, with a rich mixture of acoustic and optical features.",2006.09495v2
2021-07-25,Inferring spin tilts at formation from gravitational wave observations of binary black holes: Interfacing precession-averaged and orbit-averaged spin evolution,"Two important parameters inferred from the gravitational wave signals of
binaries of precessing black holes are the spin tilt angles, i.e., the angles
at which the black holes' spin axes are inclined with respect to the binary's
orbital angular momentum. The LIGO-Virgo parameter estimation analyses
currently provide spin tilts at a fiducial reference frequency, often the
lowest frequency used in the data analysis. However, the most astrophysically
interesting quantities are the spin tilts when the binary was formed, which can
be significantly different from those at the reference frequency for strongly
precessing binaries. The spin tilts at formally infinite separation are a good
approximation to the tilts at formation in many formation channels and can be
computed efficiently for binary black holes using precession-averaged
evolution. Here, we present a new code for computing the tilts at infinity that
combines the precession-averaged evolution with orbit-averaged evolution at
high frequencies and illustrate its application to GW190521 and other binary
black hole detections from O3a. We have empirically determined the transition
frequency between the orbit-averaged and precession-averaged evolution to
produce tilts at infinity with a given accuracy. We also have regularized the
precession-averaged equations in order to obtain good accuracy for the very
close-to-equal-mass binary parameters encountered in practice. This
additionally allows us to investigate the singular equal-mass limit of the
precession-averaged expressions, where we find an approximate scaling of $1/(1
- q)$ with the mass ratio $q$.",2107.11902v2
2022-04-22,A spintronic analog of the Landauer residual resistivity dipole on the surface of a disordered topological insulator,"The Landauer ""residual resistivity dipole"" is a well-known concept in
electron transport through a disordered medium. It is formed when a
defect/scatterer reflects an impinging electron causing negative charges to
build up on one side of the scatterer and positive charges on the other. This
results in the formation of a microscopic electric dipole that affects the
resistivity of the medium. Here, we show that an equivalent entity forms in
spin polarized electron transport through the surface of a disordered
topological insulator (TI). When electrons reflect from a scatterer on the TI
surface, a spin imbalance forms around the scatterer, resulting in a spin
current that flows either in the same or the opposite direction as the injected
spin current and hence either increases or decreases the spin resistivity. It
also destroys spin-momentum locking and produces a magnetic field around the
scatterer. The latter will cause transiting spins to precess as they pass the
scatterer, thereby radiating electromagnetic waves and implementing an
oscillator. If an alternating current is passed through the TI instead of a
static current, the magnetic field will oscillate with the frequency of the
current and radiate electromagnetic waves of the same frequency, thus making
the scatterer act as a miniature antenna.",2204.10927v1
2022-06-30,Characterization of merging black holes with two precessing spins,"Spin precession in merging black-hole binaries is a treasure trove for both
astrophysics and fundamental physics. There are now well-established strategies
to infer from gravitational-wave data whether at least one of the two black
holes is precessing. In this paper we tackle the next-in-line target, namely
the statistical assessment that the observed system has two precessing spins.
We find that the recently developed generalization of the effective precession
spin parameter $\chi_\mathrm{p}$ is a well-suited estimator to this task. With
this estimator, the occurrence of two precessing spins is a necessary (though
not sufficient) condition to obtain values $1<\chi_\mathrm{p}\leq 2$. Confident
measurements of gravitational-wave sources with $\chi_\mathrm{p}$ values in
this range can be taken as a conservative assessment that the binary presents
two precessing spins. We investigate this argument using a large set of >100
software injections assuming anticipated LIGO/Virgo sensitivities for the
upcoming fourth observing run, O4. Our results are very encouraging, suggesting
that, if such binaries exist in nature and merge at a sufficient rate, current
interferometers are likely to deliver the first confident detection of merging
black holes with two precessing spins. We investigate prior effects and
waveform systematics and, though these need to be better investigated, did not
find any confident false-positive case among all the configurations we tested.
Our assessment should thus be taken as conservative.",2207.00030v2
2022-09-21,Zig-Zag magnetic order and potential Kitaev interactions in the spin-1 honeycomb lattice KNiAsO$_4$,"Despite the exciting implications of the Kitaev spin-Hamiltonian, finding and
confirming the quantum spin liquid state has proven incredibly difficult.
Recently the applicability of the model has been expanded through the
development of a microscopic description of a spin-1 Kitaev interaction. Here
we explore a candidate spin-1 honeycomb system, KNiAsO$_4$ , which meets many
of the proposed criteria to generate such an interaction. Bulk measurements
reveal an antiferromagnetic transition at $\sim$ 19 K which is generally robust
to applied magnetic fields. Neutron diffraction measurements show magnetic
order with a $\textbf{k}=(\frac{3}{2},0,0)$ ordering vector which results in
the well-known ``zig-zag"" magnetic structure thought to be adjacent to the
spin-liquid ground state. Field dependent diffraction shows that while the
structure is robust, the field can tune the direction of the ordered moment.
Inelastic neutron scattering experiments show a well defined gapped spin-wave
spectrum with no evidence of the continuum expected for fractionalized
excitations. Modeling of the spin waves shows that the extended Kitaev
spin-Hamiltonians is generally necessary to model the spectra and reproduce the
observed magnetic order. First principles calculations suggest that the
substitution of Pd on the Ni sublattice may strengthen the Kitaev interactions
while simultaneously weakening the exchange interactions thus pushing
KNiAsO$_4$ closer to the spin-liquid ground state.",2209.10651v1
2022-11-14,Eccentricity or spin precession? Distinguishing subdominant effects in gravitational-wave data,"Eccentricity and spin precession are key observables in gravitational-wave
astronomy, encoding precious information about the astrophysical formation of
compact binaries together with fine details of the relativistic two-body
problem. However, the two effects can mimic each other in the emitted signals,
raising issues around their distinguishability. Since inferring the existence
of both eccentricity and spin precession simultaneously is -- at present -- not
possible, current state-of-the-art analyses assume that either one of the
effects may be present in the data. In such a setup, what are the conditions
required for a confident identification of either effect? We present simulated
parameter inference studies in realistic LIGO/Virgo noise, studying events
consistent with either spin precessing or eccentric binary black hole
coalescences and recovering under the assumption that either of the two effects
may be at play. We quantify how the distinguishability of eccentricity and spin
precession increases with the number of visible orbital cycles, confirming that
the signal must be sufficiently long for the two effects to be separable. The
threshold depends on the injected source, with inclination, eccentricity, and
effective spin playing crucial roles. In particular, for injections similar to
GW190521, we find that it is impossible to confidently distinguish eccentricity
from spin precession.",2211.07528v3
2023-10-24,"Mergers of double neutron stars with one high-spin component: brighter kilonovae and fallback accretion, weaker gravitational waves","Neutron star (NS) mergers where both stars have negligible spins are commonly
considered as the most likely ``standard'' case. In globular clusters, however,
the majority of NSs have been spun up to millisecond (ms) periods and, based on
observed systems, we estimate that a non-negligible fraction of all double NS
mergers ($\sim 4\pm2\;\%$) contains one component with a spin of a (few) ms. We
use the Lagrangian numerical relativity code \SpB to simulate mergers where one
star has no spin and the other has a dimensionless spin parameter of
$\chi=0.5$. Such mergers exhibit several distinct signatures compared to
irrotational cases. They form only one, very pronounced spiral arm and they
dynamically eject an order of magnitude more mass of unshocked material at the
original, very low electron fraction. One can therefore expect particularly
bright, red kilonovae. Overall, the spinning case collisions are substantially
less violent and they eject smaller amounts of shock-generated
semi-relativistic material. Therefore, the ejecta produce a weaker blue/UV
kilonova {\em precursor} signal, but -- since the total amount is larger --
brighter kilonova {\em afterglows} months after the merger. The spinning cases
also have significantly more fallback accretion and thus could power late-time
X-ray flares. Since the post-merger remnant loses energy and angular momentum
significantly less efficiently to gravitational waves, such systems can delay a
potential collapse to a black hole and are therefore candidates for
merger-triggered gamma-ray bursts with longer emission time scales.",2310.15920v2
2024-03-13,Synergy between Spin and Orbital Angular Momenta on a Möbius Strip,"Spin and orbital angular momenta are fundamental physical characteristics
described by polarization and spatial degrees of freedom, respectively.
Polarization is a feature of vector fields while spatial phase gradient
determines the orbital angular momentum ubiquitous to any scalar field. Common
wisdom treats these two degrees of freedom as distinct and independent
principles to manipulate wave propagations. Here, we demonstrate their synergy.
This is achieved by introducing two orthogonal $p$-orbitals as eigenbases,
whose spatial modal features are exploited to generate orbital angular momenta
and the associated orbital orientations provide means to simultaneously
manipulate polarizations. Through periodic modulation and directional coupling,
we realize a full cyclic evolution of the synchronized and synergized
spin-orbital angular momenta. Remarkably, this evolution acquires a nontrivial
geometric phase, leading to its representation on a M\""obius strip.
Experimentally, an acoustic cavity array is designed, whose dipole resonances
precisely mimic the $p$-orbitals. The acoustic waves, uniquely, see the
pressure (scalar) field as a spatial feature and carry an intrinsic
polarization defined by the velocity (vector) field, serving as an ideal
platform to observe the synergy of spin and orbital angular momenta. Based on
such a property, we further showcase a spin-orbital-Hall effect, highlighting
the intricate locking of handedness, directionality, spin density and spatial
mode profile. Our study unveils a fundamental connection between spin and
orbital angular momenta, promising avenues for novel applications in
information coding and high-capacity communications.",2403.08276v1
2004-06-10,Spin dynamics in a doped-Mott-insulator superconductor,"We present a systematic study of spin dynamics in a superconducting ground
state, which itself is a doped-Mott-insulator and can correctly reduce to an
antiferromagnetic (AF) state at half-filling with an AF long-range order
(AFLRO). Such a doped Mott insulator is described by a mean-field theory based
on the phase string formulation of the t-J model. We show that the spin wave
excitation in the AFLRO state at half-filling evolves into a resonancelike peak
at a finite energy in the superconducting state, which is located around the AF
wave vectors. The width of such a resonancelike peak in momentum space decides
a spin correlation length scale which is inversely proportional to the square
root of doping concentration, while the energy of the resonancelike peak scales
linearly with the doping concentration at low doping. An important prediction
of the theory is that, while the total spin sum rule is satisfied at different
doping concentrations, the weight of the resonancelike peak does not vanish,
but is continuously saturated to the weight of the AFLRO at zero-doping limit.
Besides the low-energy resonancelike peak, we also show that the high-energy
excitations still track the spin wave dispersion in momentum space,
contributing to a significant portion of the total spin sum rule. The
fluctuational effect beyond the mean-field theory is also examined, which is
related to the broadening of the resonancelike peak in energy space. In
particular, we discuss the incommensurability of the spin dynamics by pointing
out that its visibility is strongly tied to the low-energy fluctuations below
the resonancelike peak. We finally investigate the interlayer coupling effect
on the spin dynamics as a function of doping, by considering a bilayer system.",0406239v2
2010-02-25,Wannier-function approach to spin excitations in solids,"We present a computational scheme to study spin excitations in magnetic
materials from first principles. The central quantity is the transverse spin
susceptibility, from which the complete excitation spectrum, including
single-particle spin-flip Stoner excitations and collective spin-wave modes,
can be obtained. The susceptibility is derived from many-body perturbation
theory and includes dynamic correlation through a summation over ladder
diagrams that describe the coupling of electrons and holes with opposite spins.
In contrast to earlier studies, we do not use a model potential with adjustable
parameters for the electron-hole interaction but employ the random-phase
approximation. To reduce the numerical cost for the calculation of the
four-point scattering matrix we perform a projection onto maximally localized
Wannier functions, which allows us to truncate the matrix efficiently by
exploiting the short spatial range of electronic correlation in the partially
filled d or f orbitals. Our implementation is based on the FLAPW method.
Starting from a ground-state calculation within the LSDA, we first analyze the
matrix elements of the screened Coulomb potential in the Wannier basis for the
3d transition-metal series. In particular, we discuss the differences between a
constrained nonmagnetic and a proper spin-polarized treatment for the
ferromagnets Fe, Co, and Ni. The spectrum of single-particle and collective
spin excitations in fcc Ni is then studied in detail. The calculated spin-wave
dispersion is in good overall agreement with experimental data and contains
both an acoustic and an optical branch for intermediate wave vectors along the
[100] direction. In addition, we find evidence for a similar double-peak
structure in the spectral function along the [111] direction.",1002.4897v1
2018-09-26,Phenomenological model for the gravitational-wave signal from precessing binary black holes with two-spin effects,"The properties of compact binaries, such as masses and spins, are imprinted
in the gravitational-waves they emit and can be measured using parameterised
waveform models. Accurately and efficiently describing the complicated
precessional dynamics of the various angular momenta of the system in these
waveform models is the object of active investigation. One of the key models
extensively used in the analysis of LIGO and Virgo data is the
single-precessing-spin waveform model IMRPhenomPv2. In this article we present
a new model IMRPhenomPv3 which includes the effects of two independent spins in
the precession dynamics. Whereas IMRPhenomPv2 utilizes a single-spin
frequency-dependent post-Newtonian rotation to describe precession effects, the
improved model, IMRPhenomPv3, employs a double-spin rotation that is based on
recent developments in the description of precessional dynamics. Besides
double-spin precession, the improved model benefits from a more accurate
description of precessional effects. We validate our new model against a large
set of precessing numerical-relativity simulations. We find that IMRPhenomPv3
has better agreement with the inspiral portion of precessing binary-black-hole
simulations and is more robust across a larger region of the parameter space
than IMRPhenomPv2. As a first application we analyse, for the first time, the
gravitational-wave event GW151226 with a waveform model that describes two-spin
precession. Within statistical uncertainty our results are consistent with
published results. IMRPhenomPv3 will allow studies of the measurability of
individual spins of binary black holes using GWs and can be used as a
foundation upon which to build further improvements, such as modeling
precession through merger, extending to higher multipoles, and including tidal
effects.",1809.10113v1
2020-02-19,Formation of low-spinning 100 Msun black holes,"It is speculated that a merger of two massive stellar-origin BHs in a dense
stellar environment may lead to the formation of a massive BH in the
pair-instability mass gap (50-135 Msun). Such a merger-formed BH is expected to
typically have a high spin (a=0.7). If such a massive BH acquires another BH it
may lead to another merger detectable by LIGO/Virgo in gravitational waves.
Acquiring a companion may be hindered by gravitational-wave kick/recoil, which
accompanies the first merger and may quickly remove the massive BH from its
parent globular or nuclear cluster. We test whether it is possible for a
massive merger-formed BH in the pair-instability gap to be retained in its
parent cluster and have low spin. Such a BH would be indistinguishable from a
primordial BH. We employed results from numerical relativity calculations of
black hole mergers to explore the range of gravitational-wave recoil velocities
for various combinations of merging BH masses and spins. We compared
merger-formed massive BH speeds with typical escape velocities from globular
and nuclear clusters. We show that a globular cluster is highly unlikely to
form and retain a 100 Msun BH if the spin of the BH is low (a<0.3) as such BHs
acquire high recoil speeds (>200 km/s) that exceed typical escape speeds from
globular clusters (50 km/s). However, a very low-spinning (a=0.1) and massive
(100 Msun) BH could be formed and retained in a galactic nuclear star cluster.
Even though such massive merger-formed BHs with such low spins acquire high
speeds during formation (400 km/s), they may avoid ejection since massive
nuclear clusters have high escape velocities (300-500 km/s). A future detection
of a massive BH in the pair-instability mass gap with low spin would therefore
not be proof of the existence of primordial BHs, which are sometimes claimed to
have low spins and arbitrarily high masses.",2002.08050v2
2005-06-20,Wave attractors and the asymptotic dissipation rate of tidal disturbances,"Linear waves in bounded inviscid fluids do not generally form normal modes
with regular eigenfunctions. Examples are provided by inertial waves in a
rotating fluid contained in a spherical annulus, and internal gravity waves in
a stratified fluid contained in a tank with a non-rectangular cross-section.
For wave frequencies in the ranges of interest, the inviscid linearized
equations are spatially hyperbolic and their characteristic rays are typically
focused on to wave attractors. When these systems experience periodic forcing,
for example of tidal origin, the response of the fluid can become localized in
the neighbourhood of a wave attractor. In this paper I define a prototypical
problem of this form and construct analytically the long-term response to a
periodic body force in the asymptotic limit of small viscosity. The vorticity
of the fluid is localized in a detached shear layer close to the wave attractor
in such a way that the total rate of dissipation of energy is asymptotically
independent of the viscosity. I further demonstrate that the same asymptotic
dissipation rate is obtained if a non-viscous damping force is substituted for
the Navier-Stokes viscosity. I discuss the application of these results to the
problem of tidal forcing in giant planets and stars, where the excitation and
dissipation of inertial waves may make a dominant, or at least important,
contribution to the orbital and spin evolution.",0506450v1
2010-01-22,On internal wave breaking and tidal dissipation near the centre of a solar-type star,"We study the fate of internal gravity waves, which are excited by tidal
forcing by a short-period planet at the interface of convection and radiation
zones, approaching the centre of a solar-type star. We study at what amplitude
these wave are subject to instabilities. These instabilities lead to wave
breaking whenever the amplitude exceeds a critical value. Below this value, the
wave reflects perfectly from the centre of the star. Wave breaking results in
spinning up the central regions of the star, and the formation of a critical
layer, which acts as an absorbing barrier for ingoing waves. As these waves are
absorbed, the star is spun up from the inside out. This results in an important
amplitude dependence of the tidal quality factor Q'. If the tidal forcing
amplitude exceeds the value required for wave breaking, efficient dissipation
results over a continuous range of tidal frequencies, leading to Q' \approx
10^5 (P/1day)^(8/3), for the current Sun. This varies by less than a factor of
5 throughout the range of G and K type main sequence stars, for a given orbit.
We predict fewer giant planets with orbital periods of less than about 2 days
around such stars, if they cause breaking at the centre, due to the efficiency
of this process. This mechanism would, however, be ineffective in stars with a
convective core, such as WASP-18, WASP-12 and OGLE-TR-56, perhaps partly
explaining the survival of their close planetary companions.",1001.4009v1
2011-07-20,The impact of a stochastic gravitational-wave background on pulsar timing parameters,"Gravitational waves are predicted by Einstein's theory of general relativity
as well as other theories of gravity. The rotational stability of the fastest
pulsars means that timing of an array of these objects can be used to detect
and investigate gravitational waves. Simultaneously, however, pulsar timing is
used to estimate spin period, period derivative, astrometric, and binary
parameters. Here we calculate the effects that a stochastic background of
gravitational waves has on pulsar timing parameters through the use of
simulations and data from the millisecond pulsars PSR J0437--4715 and PSR
J1713+0747. We show that the reported timing uncertainties become
underestimated with increasing background amplitude by up to a factor of
$\sim10$ for a stochastic gravitational-wave background amplitude of $A=5\times
10^{-15}$, where $A$ is the amplitude of the characteristic strain spectrum at
one-year gravitational wave periods. We find evidence for prominent
low-frequency spectral leakage in simulated data sets including a stochastic
gravitational-wave background. We use these simulations along with independent
Very Long Baseline Interferometry (VLBI) measurements of parallax to set a
2--sigma upper limit of $A\le9.1\times 10^{-14}$. We find that different
supermassive black hole assembly scenarios do not have a significant effect on
the calculated upper limits. We also test the effects that ultralow--frequency
(10$^{-12}$--10$^{-9}$ Hz) gravitational waves have on binary pulsar parameter
measurements and find that the corruption of these parameters is less than
those due to $10^{-9}$--$10^{-7}$ Hz gravitational waves.",1107.4014v1
2020-11-30,Phase Shift of Planetary Waves and Wave--Jet Resonance on Tidally Locked Planets,"Recent studies found that atmospheric superrotation (i.e., west-to-east winds
over the equator) on tidally locked planets can modify the phase of planetary
waves. But, a clear relationship between the superrotation and the magnitude of
the phase shift was not examined. In this study, we re-investigate this problem
using a two-dimensional (2D) linear shallow water model with a specified
uniform zonal flow. We find that the degree of the phase shift is a monotonic
but nonlinear function of the strength of the mean flow, and the phase shift
has two limits of -$\pi$ and +$\pi$. The existence of these limits can be
explained using the energy balance of the whole system. We further show that a
resonance between the Rossby wave and the mean flow occurs when the speed of an
eastward jet approaches to the westward phase speed of the Rossby wave, or a
resonance between the Kelvin wave and the mean flow happens when the speed of a
westward jet approaches to the eastward phase speed of the Kelvin wave. The
resonance mechanism is the same as that found in the previous studies on Earth
and hot Jupiters. Moreover, in the spin-up period of a 3D global atmospheric
general circulation simulation for tidally locked rocky planet, we also find
these two phenomena: phase shift and wave--jet resonance. This study improves
the understanding of wave--mean flow interactions on tidally locked planets.",2011.14553v1
2021-01-16,Scope out multiband gravitational-wave observations of GW190521-like binary black holes with space gravitational wave antenna B-DECIGO,"The gravitational wave event, GW190521 is the most massive binary black hole
merger observed by ground-based gravitational wave observatories LIGO/Virgo to
date. While the observed gravitational-wave signal is mainly in the merger and
ringdown phases, the inspiral gravitational-wave signal of GW190521-like binary
will be more visible by space-based detectors in the low-frequency band. In
addition, the ringdown gravitational-wave signal will be more loud with the
next generation (3G) of ground-based detectors in the high-frequency band,
displaying a great potential of the multiband gravitational wave observations.
In this paper, we explore the scientific potential of multiband observations of
GW190521-like binaries with milli-Hz gravitational wave observatory: LISA,
deci-Hz observatory: B-DECIGO, and (next generation of) hecto-Hz observatories:
aLIGO and ET. In the case of quasicircular evolution, the triple-band
observation by LISA, B-DECIGO and ET will provide parameter estimation errors
of the masses and spin amplitudes of component black holes at the level of
order 1% -- 10%. This would allow consistency tests of general relativity in
the strong-field at an unparalleled precision, particularly with the ""B-DECIGO
+ ET"" observation. In the case of eccentric evolution, the multiband
signal-to-noise ratio by ""B-DECIGO + ET"" observation would be larger than 100
for a five year observation prior to coalescence, even with high final
eccentricities.",2101.06402v3
2023-07-31,Interaction renormalization and validity of kinetic equations for turbulent states,"We consider turbulence of waves that interact weakly via four-wave scattering
(sea waves, plasma waves, spin waves, and many others). In the first
non-vanishing order in the interaction, the occupation number of waves satisfy
a closed kinetic equation which has stationary solutions describing turbulent
cascades. We show that a straightforward perturbation theory beyond the kinetic
equation gives terms that generally diverge both at small (IR) and large (UV)
wavenumbers for a direct cascade. The analysis up to the third order identifies
the most UV-divergent terms. In order to gain qualitative analytic control, we
sum a subset of the most UV divergent term, to all orders, giving a
perturbation theory which is generally free from UV divergence, showing that
turbulence becomes independent of the dissipation scale when it goes to zero.
On the contrary, the ever-present IR divergence means that the effective
coupling is parametrically larger than the naive estimate and grows with the
pumping scale (similar to anomalous scaling in fluid turbulence). This suggests
that the kinetic equation does not describe wave turbulence even of arbitrarily
small level if the cascade is sufficiently long. We show that the character of
strong turbulence is determined by the sign of the coupling, that is, whether
the effective four-wave interaction is enhanced or suppressed by collective
effects. The enhancement possibly signals that strong turbulence is dominated
by multi-wave bound states (solitons, shocks, cusps), similar to confinement in
quantum chromodynamics.",2308.00033v3
2008-10-29,Higher-order spin effects in the amplitude and phase of gravitational waveforms emitted by inspiraling compact binaries: Ready-to-use gravitational waveforms,"We provide ready-to-use time-domain gravitational waveforms for spinning
compact binaries with precession effects through 1.5PN order in amplitude and
compute their mode decomposition using spin-weighted -2 spherical harmonics. In
the presence of precession, the gravitational-wave modes (l,m) contain
harmonics originating from combinations of the orbital frequency and precession
frequencies. We find that the gravitational radiation from binary systems with
large mass asymmetry and large inclination angle can be distributed among
several modes. For example, during the last stages of inspiral, for some
maximally spinning configurations, the amplitude of the (2,0) and (2,1) modes
can be comparable to the amplitude of the (2,2) mode. If the mass ratio is not
too extreme, the l=3 and l=4 modes are generally one or two orders of magnitude
smaller than the l = 2 modes. Restricting ourselves to spinning, non-precessing
compact binaries, we apply the stationary-phase approximation and derive the
frequency-domain gravitational waveforms including spin-orbit and spin(1)-
spin(2) effects through 1.5PN and 2PN order respectively in amplitude, and
2.5PN order in phase. Since spin effects in the amplitude through 2PN order
affect only the first and second harmonics of the orbital phase, they do not
extend the mass reach of gravitational-wave detectors. However, they can
interfere with other harmonics and lower or raise the signal-to-noise ratio
depending on the spin orientation. These ready-to-use waveforms could be
employed in the data-analysis of the spinning, inspiraling binaries as well as
in comparison studies at the interface between analytical and numerical
relativity.",0810.5336v3
2012-12-26,Anomalous spin precession and spin Hall effect in semiconductor quantum wells,"Spin-orbit (SO) interactions give a spin-dependent correction r_so to the
position operator, referred to as the anomalous position operator. We study the
contributions of r_so to the spin-Hall effect (SHE) in quasi two-dimensional
(2D) semiconductor quantum wells with strong band structure SO interactions
that cause spin precession. The skew scattering and side-jump scattering terms
in the SHE vanish, but we identify two additional terms in the SHE, due to
r_so, which have not been considered in the literature so far. One term
reflects the modification of the spin precession due to the action of the
external electric field (the field drives the current in the quantum well),
which produces, via r_so, an effective magnetic field perpendicular to the
plane of the quantum well. The other term reflects a similar modification of
the spin precession due to the action of the electric field created by random
impurities, and appears in a careful formulation of the Born approximation. We
refer to these two effects collectively as anomalous spin precession and we
note that they contribute to the SHE to the first order in the SO coupling
constant even though they formally appear to be of second order. In electron
systems with weak momentum scattering, the contribution of the anomalous spin
precession due to the external electric field equals 1/2 the usual side-jump
SHE, while the additional impurity-dependent contribution depends on the form
of the band structure SO coupling. For band structure SO linear in wave vector
the two additional contributions cancel. For band structure SO cubic in wave
vector only the contribution due to external electric field is present, and can
be detected through its density dependence. In 2D hole systems both anomalous
spin precession contributions vanish identically.",1212.6262v2
2013-02-13,Relativistic mergers of compact binaries in clusters: The fingerprint of the spin,"Dense stellar systems such as globular clusters and dense nuclear clusters
are the breeding ground of sources of gravitational waves for the advanced
detectors LIGO and Virgo. These systems deserve a close study to estimate rates
and parameter distribution. This is not an easy task, since the evolution of a
dense stellar cluster involves the integration of $N$ bodies with high
resolution in time and space and including hard binaries and their encounters
and, in the case of gravitational waves (GWs), one needs to take into account
important relativistic corrections. In this work we present the first
implementation of the effect of spin in mergers in a direct-summation code,
NBODY6. We employ non-spinning post-Newtonian corrections to the Newtonian
accelerations up to 3.5 post-Newtonian (PN) order as well as the spin-orbit
coupling up to next-to-lowest order and the lowest order spin-spin coupling. We
integrate spin precession and add a consistent treatment of mergers. We analyse
the implementation by running a set of two-body experiments and then we run a
set of 500 simulations of a relativistic stellar cluster. In spite of the large
number of mergers in our tests, the application of the algorithm is robust. We
find in particular the formation of a runaway star whose spin decays with the
mass it wins, independently of the initial value of the spins of the stars.
More remarkably, the subset of compact objects that do not undergo many
mergers, and hence represent a more realistic system, has a correlation between
the final absolute spin and the initial choice for the initial distribution,
which could provide us with information about the evolution of spins in dense
clusters once the first detections have started.",1302.3135v2
2015-04-13,Transverse and longitudinal angular momenta of light,"We review basic physics and novel types of optical angular momentum. We start
with a theoretical overview of momentum and angular momentum properties of
generic optical fields, and discuss methods for their experimental
measurements. In particular, we describe the well-known longitudinal (i.e.,
aligned with the mean momentum) spin and orbital angular momenta in polarized
vortex beams. Then, we focus on the transverse (i.e., orthogonal to the mean
momentum) spin and orbital angular momenta, which were recently actively
discussed in theory and observed in experiments. First, the recently-discovered
transverse spin angular momenta appear in various structured fields: evanescent
waves, interference fields, and focused beams. We show that there are several
kinds of transverse spin angular momentum, which differ strongly in their
origins and physical properties. We describe extraordinary features of the
transverse optical spins and overview recent experiments. In particular, the
helicity-independent transverse spin inherent in edge evanescent waves offers
robust spin-direction coupling at optical interfaces (the quantum spin Hall
effect of light). Second, we overview the transverse orbital angular momenta of
light, which can be both extrinsic and intrinsic. These two types of the
transverse orbital angular momentum are produced by spatial shifts of the
optical beams (e.g., in the spin Hall effect of light) and their Lorentz
boosts, respectively. Our review is underpinned by a unified theory of the
angular momentum of light based on the canonical momentum and spin densities,
which avoids complications associated with the separation of spin and orbital
angular momenta in the Poynting picture. It allows us to construct
comprehensive classification of all known optical angular momenta based on
their key parameters and main physical properties.",1504.03113v2
2015-08-21,Parameter estimation on gravitational waves from neutron-star binaries with spinning components,"Inspiraling binary neutron stars are expected to be one of the most
significant sources of gravitational-wave signals for the new generation of
advanced ground-based detectors. We investigate how well we could hope to
measure properties of these binaries using the Advanced LIGO detectors, which
began operation in September 2015. We study an astrophysically motivated
population of sources (binary components with masses
$1.2~\mathrm{M}_\odot$--$1.6~\mathrm{M}_\odot$ and spins of less than $0.05$)
using the full LIGO analysis pipeline. While this simulated population covers
the observed range of potential binary neutron-star sources, we do not exclude
the possibility of sources with parameters outside these ranges; given the
existing uncertainty in distributions of mass and spin, it is critical that
analyses account for the full range of possible mass and spin configurations.
We find that conservative prior assumptions on neutron-star mass and spin lead
to average fractional uncertainties in component masses of $\sim 16\%$, with
little constraint on spins (the median $90\%$ upper limit on the spin of the
more massive component is $\sim 0.7$). Stronger prior constraints on
neutron-star spins can further constrain mass estimates, but only marginally.
However, we find that the sky position and luminosity distance for these
sources are not influenced by the inclusion of spin; therefore, if LIGO detects
a low-spin population of BNS sources, less computationally expensive results
calculated neglecting spin will be sufficient for guiding electromagnetic
follow-up.",1508.05336v3
2016-02-10,"Implementing a search for gravitational waves from non-precessing, spinning binary black holes","Searching for gravitational waves (GWs) from binary black holes (BBHs) with
LIGO and Virgo involves matched-filtering data against a set of representative
signal waveforms --- a template bank --- chosen to cover the full signal space
of interest with as few template waveforms as possible. Although the component
black holes may have significant angular momenta (spin), previous searches for
BBHs have filtered LIGO and Virgo data using only waveforms where both
component spins are zero. This leads to a loss of signal-to-noise ratio for
signals where this is not the case. Combining the best available template
placement techniques and waveform models, we construct a template bank of GW
signals from BBHs with component spins $\chi_{1,2}\in [-0.99, 0.99]$ aligned
with the orbital angular momentum, component masses $m_{1,2}\in [2,
48]\,\mathrm{M}_\odot$, and total mass $M_\mathrm{total} \leq
50\,\mathrm{M}_\odot$. Using effective-one-body waveforms with spin effects, we
show that less than $3\%$ of the maximum signal-to-noise ratio (SNR) of these
signals is lost due to the discreetness of the bank, using the early advanced
LIGO noise curve. We use simulated advanced LIGO noise to compare the
sensitivity of this bank to a non-spinning bank covering the same parameter
space. In doing so, we consider the competing effects between improved SNR and
signal-based vetoes, and the increase in the rate of false alarms of the
aligned-spin bank due to covering a larger parameter space. We find that the
aligned-spin bank can be a factor of $1.3$ -- $5$ more sensitive than a
non-spinning bank to BBHs with dimensionless spins $> +0.6$ and component
masses $\gtrsim 20\,\mathrm{M}_\odot$. Even larger gains are obtained for
systems with equally high spins but smaller component masses.",1602.03509v2
2023-05-11,Detecting Fractionalization in Critical Spin Liquids using Color Centers,"Quantum spin liquids (QSLs) are highly entangled ground states of insulating
spin systems, in which magnetic ordering is prevented down to the lowest
temperatures due to quantum fluctuations. One of the most extraordinary
characteristics of QSL phases is their ability to support fractionalized,
low-energy quasiparticles known as spinons, which carry spin-1/2 but bear no
charge. Relaxometry based on color centers in crystalline materials -- of which
nitrogen-vacancy (NV) centers in diamond are a well-explored example --
provides an exciting new platform to probe the spin spectral functions of
magnetic materials with both energy and momentum resolution and to search for
signatures of these elusive, fractionalized excitations. In this work, we
theoretically investigate the color-center relaxometry of two archetypal QSLs:
the two-dimensional U(1) QSL with a spinon Fermi surface and the spin-1/2
antiferromagnetic spin chain. The former is characterized by a metallic,
spin-split ground state of mobile, interacting spinons, which closely resembles
a spin-polarized Fermi liquid ground state but with neutral quasiparticles. We
show that the observation of the Stoner continuum and the collective spin wave
mode in the spin spectral function would provide a strong evidence for the
existence of spinons and fractionalization. In one dimension, mobile spinons
form a Luttinger liquid ground state. We show that the spin spectral function
exhibits strong features representing the collective density and spin-wave
modes, which are broadened in an algebraic fashion with an exponent
characterized by the Luttinger parameter. The possibilities of measuring these
collective modes and detecting the power-law decay of the spectral weight using
NV relaxometry are discussed. We also examine how the transition rates are
modified by marginally irrelevant operators in the Heisenberg limit.",2305.07112v1
2011-05-18,Importance of including small body spin effects in the modelling of extreme and intermediate mass-ratio inspirals,"We explore the ability of future low-frequency gravitational wave detectors
to measure the spin of stellar mass and intermediate mass black holes that
inspiral onto super-massive Kerr black holes (SMBHs). We develop a kludge
waveform model based on the equations of motion derived by Saijo et al. [Phys
Rev D 58, 064005, 1998] for spinning BH binaries, augmented with spin-orbit and
spin-spin couplings taken from perturbative and post-Newtonian (PN)
calculations, and the associated conservative self-force corrections, derived
by comparison to PN results. We model the inspiral phase using accurate fluxes
which include perturbative corrections for the spin of the inspiralling body,
spin-spin couplings and higher-order fits to solutions of the Teukolsky
equation. We present results of Monte Carlo simulations of parameter estimation
errors and of the model errors that arise when we omit conservative corrections
from the waveform template. For a source 5000+10^6 solar mass observed with an
SNR of 1000, LISA will be able to determine the two masses to within a
fractional error of ~0.001, measure the SMBH spin magnitude, q, and the spin
magnitude of the inspiralling BH to 0.0001, 10%, respectively, and determine
the location of the source in the sky and the SMBH spin orientation to within
0.0001 steradians. For a 10+10^6 solar mass system observed with SNR of 30,
LISA will not be able to determine the spin magnitude of the inspiralling BH,
although the measurement of the other waveform parameters is not significantly
degraded by the presence of spin. The model errors which arise from ignoring
conservative corrections become significant for mass-ratios above 0.0001, but
including these corrections up to 2PN order may be sufficient to reduce these
systematic errors to an acceptable level.",1105.3567v3
2017-10-17,Accretion-induced spin-wandering effects on the neutron star in Scorpius X-1: Implications for continuous gravitational wave searches,"The LIGO's discovery of binary black hole mergers has opened up a new era of
transient gravitational wave astronomy. The potential detection of
gravitational radiation from another class of astronomical objects, rapidly
spinning non-axisymmetric neutron stars, would constitute a new area of
gravitational wave astronomy. Scorpius X-1 (Sco X-1) is one of the most
promising sources of continuous gravitational radiation to be detected with
present-generation ground-based gravitational wave detectors, such as Advanced
LIGO and Advanced Virgo. As the sensitivity of these detectors improve in the
coming years, so will power of the search algorithms being used to find
gravitational wave signals. Those searches will still require integation over
nearly year long observational spans to detect the incredibly weak signals from
rotating neutron stars. For low mass X-ray binaries such as Sco X-1 this
difficult task is compounded by neutron star ""spin wandering"" caused by
stochastic accretion fluctuations. In this paper, we analyze X-ray data from
the RXTE satellite to infer the fluctuating torque on the neutron star in Sco
X-1. We then perform a large-scale simulation to quantify the statistical
properties of spin-wandering effects on the gravitational wave signal frequency
and phase evolution. We find that there are a broad range of expected maximum
levels of frequency wandering corresponding to maximum drifts of between 0.3-50
{\mu}Hz/sec over a year at 99% confidence. These results can be cast in terms
of the maximum allowed length of a coherent signal model neglecting
spin-wandering effects as ranging between 5-80 days. This study is designed to
guide the development and evaluation of Sco X-1 search algorithms.",1710.06185v1
2021-08-16,Symmetry- and curvature effects on spin waves in vortex-state hexagonal nanotubes,"Analytic and numerical studies on curved magnetic nano-objects predict
numerous exciting effects that can be referred to as magneto-chiral effects,
which do not originate from intrinsic Dzyaloshinskii-Moriya interaction or
interface-induced anisotropies. In constrast, these chiral effects stem from
isotropic exchange or dipole-dipole interaction, present in all magnetic
materials, which acquire asymmetric contributions in case of curved geometry of
the specimen. As a result, for example, the spin-wave dispersion in round
magnetic nanotubes becomes asymmetric, namely spin waves of the same frequency
propagating in opposite directions along the nanotube exhibit different
wavelenghts. Here, using time-resolved scanning transmission X-ray microscopy
experiments, standard micromagntic simulations and a dynamic-matrix approach,
we show that the spin-wave spectrum undergoes additional drastic changes when
transitioning from a continuous to a discrete rotational symmetry, i.e. from
round to hexagonal nanotubes, which are much easier to fabricate. The polygonal
shape introduces localization of the modes both to the sharp, highly curved
corners and flat edges. Moreover, due to the discrete rotational symmetry, the
degenerate nature of the modes with azimuthal wave vectors known from round
tubes is partly lifted, resulting in singlet and duplet modes. For comparison
with our experiments, we calculate the microwave absorption from the
numerically obtained mode profiles which shows that a dedicated antenna design
is paramount for magnonic applications in 3D nano-structures. To our knowledge
these are the first experiments directly showing real space spin-wave
propagation in 3D nano objects.",2108.07103v1
2003-04-15,Large amplitude spin waves in ultra-cold gases,"We discuss the theory of spin waves in non-degenerate ultra-cold gases, and
compare various methods which can be used to obtain appropriate kinetic
equations. We then study non-hydrodynamic situations, where the amplitude of
spin waves is sufficiently large to bring the system far from local
equilibrium. In the first part of the article, we compare two general methods
which can be used to derive a kinetic equation for a dilute gas of atoms
(bosons or fermions) with two internal states (treated as a pseudo-spin 1/2).
The collisional methods are in the spirit of Boltzmann's original derivation of
his kinetic equation where, at each point of space, the effects of all sorts of
possible binary collisions are added. We discuss two different versions of
collisional methods, the Yvon-Snider approach and the S matrix approach. The
second method uses the notion of mean field, which modifies the drift term of
the kinetic equation, in the line of the Landau theory of transport in quantum
liquids. For a dilute cold gas, it turns out that all these derivations lead to
the same drift terms in the transport equation, but differ in the precise
expression of the collision integral and in higher order gradient terms. In the
second part of the article, the kinetic equation is applied to spin waves in
trapped ultra-cold gases. Numerical simulations are used to illustrate the
strongly non-hydrodynamic character of the spin waves recently observed with
trapped Rb87 atoms. The decay of the phenomenon, which takes place when the
system relaxes back towards equilibrium, is also discussed, with a short
comment on decoherence.",0304335v3
2022-01-10,Multipolar gravitational waveforms for spinning binary black holes and their impact on source characterization,"In the last five years, gravitational-wave astronomy has gone from a purely
theoretical field into a thriving experimental science. Many gravitational-wave
signals, emitted by stellar-mass binary black holes and binary neutron stars,
have been detected, and many more are expected in the future. The observation
of the gravitational-wave signals from these systems, and the characterization
of their sources, heavily relies on the precise models for the emitted
gravitational waveforms. In this thesis, I present an updated version of the
waveform models for spinning binary black holes within the effective-one-body
formalism. The novelty of the waveform models presented in this work is the
inclusion of beyond-quadupolar terms in the waveforms emitted by spinning
binary black holes. I first construct the model in the simplified case of black
holes with spins aligned with the orbital angular momentum of the binary, then
I extend it to the case of generic spin orientations. The measurement of the
source properties of a binary system emitting gravitational waves requires to
compute $\mathcal{O}(10^7-10^9)$ different waveforms. Since the waveform models
mentioned before can require $\mathcal{O}(1-10)$s to generate a single
waveform, they can be difficult to use in data-analysis studies. To overcome
this obstacle, I use the reduced-order-modeling technique to develop a faster
version of the waveform model for black holes with spins aligned to the orbital
angular momentum of the binary. The waveform models developed in this thesis
have been used by the LIGO and Virgo collaborations for the inference of the
source parameters of the gravitational-wave signals detected during the second
and third observing runs (O2 and O3) of the LIGO and Virgo detectors. Here, I
present a study on the source properties of the signals GW170729 and GW190412,
for which I have been directly involved in the analysis.",2201.03428v1
1996-02-29,Hole photoproduction in insulating copper oxide,"Basing on t-J model we calculate the k-dependence of a single hole
photoproduction probability for CuO2 plane at zero doping. We also discuss the
radiation of spin-waves which can substantially deform the shape of
photoemission spectra.",9602160v1
2001-04-12,Kane Oscillator,"The energy spectrum and wave functions for Kane oscillator describing the
spectra of electrons, light hole and spin-orbit-splitting bands in a quantum
dots with harmonic lateral confinement is found.",0104222v1
2002-09-09,Effect of a magnetic field on the spin- and charge-density wave order in La1.45Nd0.4Sr0.15CuO4,"The spin-density wave (SDW) and charge-density wave (CDW) order in
superconducting La1.45Nd0.4Sr0.15CuO4 were studied under an applied magnetic
field using neutron and X-ray diffraction techniques. In zero field,
incommensurate (IC) SDW order appears below ~ 40 K, which is characterized by
neutron diffraction peaks at (1/2 +/- 0.134, 1/2 +/- 0.134, 0). The intensity
of these IC peaks increases rapidly below T_Nd ~ 8 K due to an ordering of the
Nd^3+ spins. The application of a 1 T magnetic field parallel to the c-axis
markedly diminishes the intensity below T_Nd, while only a slight decrease in
intensity is observed at higher temperatures for fields up to 7 T. Our
interpretation is that the c-axis field suppresses the parasitic Nd^3+ spin
order at the incommensurate wave vector without disturbing the stripe order of
Cu^2+ spins. Consistent with this picture, the CDW order, which appears below
60 K, shows no change for magnetic fields up to 4 T. These results stand in
contrast to the significant field-induced enhancement of the SDW order observed
in superconducting La2-xSrxCuO4 with x ~ 0.12 and stage-4 La2CuO4+y. The
differences can be understood in terms of the relative volume fraction
exhibiting stripe order in zero field, and the collective results are
consistent with the idea that suppression of superconductivity by vortices
nucleates local patches of stripe order.",0209223v4
2004-02-25,Simultaneous existence of two spin-wave modes in ultrathin Fe/GaAs(001) films studied by Brillouin Light Scattering: experiment and theory,"A double-peaked structure was observed in the {\it in-situ} Brillouin Light
Scattering (BLS) spectra of a 6 \AA$ $ thick epitaxial Fe/GaAs(001) film for
values of an external magnetic field $H$, applied along the hard in plane
direction, lower than a critical value $H_c\simeq 0.9$ kOe. This experimental
finding is theoretically interpreted in terms of a model which assumes a
non-homogeneous magnetic ground state characterized by the presence of
perperpendicular up/down stripe domains. For such a ground state, two spin-wave
modes, namely an acoustic and an optic mode, can exist. Upon increasing the
field the magnetization tilts in the film plane, and for $H \ge H_{c}$ the
ground state is homogeneous, thus allowing the existence of just a single
spin-wave mode. The frequencies of the two spin-wave modes were calculated and
successfully compared with the experimental data. The field dependence of the
intensities of the corresponding two peaks that are present in the BLS spectra
was also estimated, providing further support to the above-mentioned
interpretation.",0402617v2
2004-04-12,Double Exchange in a Magnetically Frustrated System,"This work examines the magnetic order and spin dynamics of a double-exchange
model with competing ferromagnetic and antiferromagnetic Heisenberg
interactions between the local moments. The Heisenberg interactions are
periodically arranged in a Villain configuration in two dimensions with
nearest-neighbor, ferromagnetic coupling $J$ and antiferromagnetic coupling
$-\eta J$. This model is solved at zero temperature by performing a
$1/\sqrt{S}$ expansion in the rotated reference frame of each local moment.
When $\eta $ exceeds a critical value, the ground state is a magnetically
frustrated, canted antiferromagnet. With increasing hopping energy $t$ or
magnetic field $B$, the local moments become aligned and the ferromagnetic
phase is stabilized above critical values of $t$ or $B$. In the canted phase, a
charge-density wave forms because the electrons prefer to sit on lines of sites
that are coupled ferromagnetically. Due to a change in the topology of the
Fermi surface from closed to open, phase separation occurs in a narrow range of
parameters in the canted phase. In zero field, the long-wavelength spin waves
are isotropic in the region of phase separation. Whereas the average spin-wave
stiffness in the canted phase increases with $t$ or $\eta $, it exhibits a more
complicated dependence on field. This work strongly suggests that the jump in
the spin-wave stiffness observed in Pr$_{1-x}$Ca$_x$MnO$_3$ with $0.3 \le x \le
0.4$ at a field of 3 T is caused by the delocalization of the electrons rather
than by the alignment of the antiferromagnetic regions.",0404268v1
2004-12-08,Anisotropy and Field-Dependence of the Spin-Density-Wave Dynamics in the Quasi One-Dimensional Conductor (TMTSF)_2PF_6,"The anisotropic and non-linear transport properties of the quasi
one-dimensional organic conductor (TMTSF)_2PF_6 have been studied by dc,
radiofrequency, and microwave methods. Microwave experiments along all three
axes reveal that collective transport, which is considered to be the
fingerprint of the spin-density-wave condensate, also occurs in the
perpendicular b' direction. The pinned mode resonance is present in the $a$ and
b'-axes response, but not along the least conducting c* direction. The ac-field
threshold, above which the spin-density-wave response is non-linear, strongly
decreases as the temperature drops below 4 K. With increasing strength of the
microwave electric field and of the radiofrequency signal, the pinned mode and
the screened phason loss-peak shift to lower frequencies. In the non-linear
regime, in addition to the phason relaxation mode with Arrhenius-like resistive
decay, an additional mode with very long and temperature-independent relaxation
time appears below 4 K. We attribute the new process to short-wavelength
spin-density-wave excitations associated with discommensurations in a random
commensurate N=4 domain structure.",0412206v1
2003-05-25,On some weak-gravitational effects,"Some physically interesting weak-gravitational effects and phenomena are
reviewed and briefly discussed: particle geometric phases due to the
time-dependent spin-rotation couplings, non-inertial gravitational wave in
rotating reference of frame, hyperbolical geometric quantum phases and
topological dual mass as well.",0305094v1
2006-05-27,Higher-order spin effects in the dynamics of compact binaries II. Radiation field,"Motivated by the search for gravitational waves emitted by binary black
holes, we investigate the gravitational radiation field of point particles with
spins within the framework of the multipolar-post-Newtonian wave generation
formalism. We compute: (i) the spin-orbit (SO) coupling effects in the binary's
mass and current quadrupole moments one post-Newtonian (1PN) order beyond the
dominant effect, (ii) the SO contributions in the gravitational-wave energy
flux and (iii) the secular evolution of the binary's orbital phase up to 2.5PN
order. Crucial ingredients for obtaining the 2.5PN contribution in the orbital
phase are the binary's energy and the spin precession equations, derived in
paper I of this series. These results provide more accurate gravitational-wave
templates to be used in the data analysis of rapidly rotating Kerr-type
black-hole binaries with the ground-based detectors LIGO, Virgo, GEO 600 and
TAMA300, and the space-based detector LISA.",0605140v4
2007-07-31,Renormalized spin wave excitations in the antiferromagnetic Heisenberg-Kondo model for heavy fermions,"Recent inelastic neutron scattering experiments in CeIn3 and CePd2Si2 single
crystals, measured spin wave excitations at low temperatures. These two heavy
fermion compounds exhibit antiferromagnetic long-range order, but a strong
competition between the Ruderman-Kittel-Kasuya-Yosida(RKKY) interaction and
Kondo effect is evidenced by their nearly equal Neel and Kondo temperatures.
Our aim is to show how magnons such as measured in the antiferromagnetic phase
of these Ce compounds, can be described with a microscopic Heisenberg-Kondo
model as introduced by J.R.Iglesias, C.Lacroix and B.Coqblin, used before for
studies of the non-magnetic phase. The model includes the correlated Ce-4f
electrons hybridized with the conduction band, and we consider competing RKKY
(Heisenberg-like J_{H}) and Kondo (J_{K}) antiferromagnetic couplings. Carrying
on a series of unitary transformations, we perturbatively derive a second-order
effective Hamiltonian which, projected onto the antiferromagnetic electron
ground state, describes the spin wave excitations, renormalized by their
interaction with correlated itinerant electrons. We numerically study how the
different parameters of the model influence the renormalization of the magnons,
yielding useful information for the analysis of inelastic neutron scattering
experiments in antiferromagnetic heavy fermion compounds. We also compare our
results with available experimental data, finding good agreement with the spin
wave measurements in cubic CeIn3.",0708.0023v1
2008-04-11,Spin Waves in the Ferromagnetic Ground State of the Kagome Staircase System Co3V2O8,"Inelastic neutron scattering measurements were performed on single crystal
Co3V2O8 wherein magnetic cobalt ions reside on distinct spine and cross-tie
sites within kagome staircase planes. This system displays a rich magnetic
phase diagram which culminates in a ferromagnetic ground state below Tc~6 K. We
have studied the low-lying magnetic excitations in this phase within the kagome
plane. Despite the complexity of the system at higher temperatures, linear
spin-wave theory describes most of the quantitative detail of the inelastic
neutron measurements. Our results show two spin-wave branches, the higher
energy of which displays finite spin-wave lifetimes well below Tc, and
negligible magnetic exchange coupling between Co moments on the spine sites.",0804.1929v1
2008-07-03,Spin wave excitations in the antiferromagnetic Heisenberg-Kondo model for heavy fermions,"Recent inelastic neutron scattering experiments in CeIn$_{3}$ and
CePd$_{2}$Si$_{2}$ single crystals measured spin wave excitations at low
temperatures. These two heavy fermion compounds exhibit antiferromagnetic
long-range order, but a strong competition between the
Ruderman-Kittel-Kasuya-Yosida(RKKY) interaction and Kondo effect is evidenced
by their nearly equal N\'eel and Kondo temperatures. Our aim is to show how
magnons such as measured in the antiferromagnetic phase of these Ce compounds,
can be described with a microscopic Heisenberg-Kondo model introduced by
J.R.Iglesias, C.Lacroix and B.Coqblin, used before for studies of the
non-magnetic phase. The model includes the correlated Ce-$4 f$ electrons
hybridized with the conduction band, where we also allow for correlations, and
we consider competing
  RKKY (Heisenberg-like $J_{H} $) and Kondo ($J_{K}$) antiferromagnetic
couplings. Carrying on a series of unitary transformations, we perturbatively
derive a second-order effective Hamiltonian which, projected onto the
antiferromagnetic electron ground state, describes the spin wave excitations,
renormalized by their interaction with correlated itinerant electrons. We
numerically study how the different parameters of the model influence the
renormalization of the magnons, yielding useful information for the analysis of
inelastic neutron scattering experiments in antiferromagnetic heavy fermion
compounds. We also compare our results with the available experimental data,
finding good agreement with the spin wave measurements in cubic CeIn$_3$.",0807.1246v1
2009-03-02,Quantum electrodynamic equations for magnetic resonance- and optical spectroscopic transitions,"Quantum electrodynamic equations for magnetic resonance- and optical
spectroscopic transitions have been for the first time obtained. New phenomena
- stochastic electrical and magnetic spin wave resonances are predicted to be
the effects of EM-field quantization.",0903.0320v1
2009-05-29,Tweaking the spin-wave dispersion and suppressing the incommensurate phase in LiNiPO$_4$ by iron substitution,"Elastic and inelastic neutron scattering studies of
Li(Ni$_{1-x}$Fe$_{x}$)PO$_4$ single crystals reveal anomalous spin-wave
dispersions along the crystallographic direction parallel to the characteristic
wave vector of the magnetic incommensurate phase. The anomalous spin-wave
dispersion ({\it magnetic soft mode}) indicates the instability of the
Ising-like ground state that eventually evolves into the incommensurate phase
as the temperature is raised. The pure LiNiPO$_4$ system ($x=0$), undergoes a
first-order magnetic phase transition from a long-range incommensurate phase to
an antiferromagnetic ground state at {\it T}$_N$ = 20.8 K. At 20% Fe
concentrations, although the AFM ground state is to a large extent preserved as
that of the pure system, the phase transition is second-order, and the
incommensurate phase is completely suppressed. Analysis of the dispersion
curves using a Heisenberg spin Hamiltonian that includes inter- and in-plane
nearest and next-nearest neighbor couplings reveals frustration due to strong
competing interactions between nearest- and a next-nearest neighbor site,
consistent with the observed incommensurate structure. The Fe substitution only
slightly lowers the extent of the frustration, sufficient to suppress the IC
phase. An energy gap in the dispersion curves gradually decreases with the
increase of Fe content from $\sim$2 meV for the pure system ($x=0$) to
$\sim$0.9 meV for $x=0.2$.",0906.0033v1
2009-07-22,Quantized spin wave modes in magnetic tunnel junction nanopillars,"We present an experimental and theoretical study of the magnetic field
dependence of the mode frequency of thermally excited spin waves in rectangular
shaped nanopillars of lateral sizes 60x100, 75x150, and 105x190 nm2, patterned
from MgO-based magnetic tunnel junctions. The spin wave frequencies were
measured using spectrally resolved electrical noise measurements. In all
spectra, several independent quantized spin wave modes have been observed and
could be identified as eigenexcitations of the free layer and of the synthetic
antiferromagnet of the junction. Using a theoretical approach based on the
diagonalization of the dynamical matrix of a system of three coupled, spatially
confined magnetic layers, we have modeled the spectra for the smallest pillar
and have extracted its material parameters. The magnetization and exchange
stiffness constant of the CoFeB free layer are thereby found to be
substantially reduced compared to the corresponding thin film values. Moreover,
we could infer that the pinning of the magnetization at the lateral boundaries
must be weak. Finally, the interlayer dipolar coupling between the free layer
and the synthetic antiferromagnet causes mode anticrossings with gap openings
up to 2 GHz. At low fields and in the larger pillars, there is clear evidence
for strong non-uniformities of the layer magnetizations. In particular, at zero
field the lowest mode is not the fundamental mode, but a mode most likely
localized near the layer edges.",0907.3792v2
2010-03-02,Binary black hole merger gravitational waves and recoil in the large mass ratio limit,"Spectacular breakthroughs in numerical relativity now make it possible to
compute spacetime dynamics in almost complete generality, allowing us to model
the coalescence and merger of binary black holes with essentially no
approximations. The primary limitation of these calculations is now
computational. In particular, it is difficult to model systems with large mass
ratio and large spins, since one must accurately resolve the multiple
lengthscales which play a role in such systems. Perturbation theory can play an
important role in extending the reach of computational modeling for binary
systems. In this paper, we present first results of a code which allows us to
model the gravitational waves generated by the inspiral, merger, and ringdown
of a binary system in which one member of the binary is much more massive than
the other. This allows us to accurately calibrate binary dynamics in the large
mass ratio regime. We focus in this analysis on the recoil imparted to the
merged remnant by these waves. We closely examine the ""antikick"", an anti-phase
cancellation of the recoil arising from the plunge and ringdown waves,
described in detail by Schnittman et al. We find that, for orbits aligned with
the black hole spin, the antikick grows as a function of spin. The total recoil
is smallest for prograde coalescence into a rapidly rotating black hole, and
largest for retrograde coalescence. Amusingly, this completely reverses the
predicted trend for kick versus spin from analyses that only include inspiral
information.",1003.0485v1
2010-08-27,Magnetic Vortex Core Reversal by Excitation of Spin Waves,"Micron-sized magnetic platelets in the flux closed vortex state are
characterized by an in-plane curling magnetization and a nanometer-sized
perpendicularly magnetized vortex core. Having the simplest non-trivial
configuration, these objects are of general interest to micromagnetics and may
offer new routes for spintronics applications. Essential progress in the
understanding of nonlinear vortex dynamics was achieved when low-field core
toggling by excitation of the gyrotropic eigenmode at sub-GHz frequencies was
established. At frequencies more than an order of magnitude higher vortex state
structures possess spin wave eigenmodes arising from the magneto-static
interaction. Here we demonstrate experimentally that the unidirectional vortex
core reversal process also occurs when such azimuthal modes are excited. These
results are confirmed by micromagnetic simulations which clearly show the
selection rules for this novel reversal mechanism. Our analysis reveals that
for spin wave excitation the concept of a critical velocity as the switching
condition has to be modified.",1008.4719v5
2011-03-21,Spontaneous Magnetization of an Ideal Ferromagnet: Beyond Dyson's Analysis,"Using the low-energy effective field theory for magnons, we systematically
evaluate the partition function of the O(3) ferromagnet up to three loops.
Dyson, in his pioneering microscopic analysis of the Heisenberg model, showed
that the spin-wave interaction starts manifesting itself in the low-temperature
expansion of the spontaneous magnetization of an ideal ferromagnet only at
order $T^4$. Although several authors tried to go beyond Dyson's result, to the
best of our knowledge, a fully systematic and rigorous investigation of higher
order terms induced by the spin-wave interaction, has never been achieved. As
we demonstrate in the present paper, it is straightforward to evaluate the
partition function of an ideal ferromagnet beyond Dyson's analysis, using
effective Lagrangian techniques. In particular, we show that the
next-to-leading contribution to the spontaneous magnetization resulting from
the spin-wave interaction already sets in at order $T^{9/2}$ -- in contrast to
all claims that have appeared before in the literature. Remarkably, the
corresponding coefficient is completely determined by the leading-order
effective Lagrangian and is thus independent of the anisotropies of the cubic
lattice. We also consider even higher-order corrections and thereby solve --
once and for all -- the question of how the spin-wave interaction in an ideal
ferromagnet manifests itself in the spontaneous magnetization beyond the Dyson
term.",1103.4110v1
2011-11-14,Fermi liquid theory and ferromagnetism,"There is demonstrated that an isotropic ferromagnetic Fermi liquid reveals
instability of the ferromagnetic state in respect to the transversal
inhomogeneous deviations of magnetization from equilibrium. The result was
obtained by derivation of the spin waves spectrum by means of kinetic equation.",1111.3208v2
2015-01-23,Parameter choices and ranges for continuous gravitational wave searches for steadily spinning neutron stars,"We consider the issue of selecting parameters and their associated ranges for
carrying out searches for continuous gravitational waves from steadily rotating
neutron stars. We consider three different cases (i) the ""classic"" case of a
star spinning about a principal axis; (ii) a biaxial star, not spinning about a
principal axis; (iii) a triaxial star spinning steady, but not about a
principal axis (as described in Jones, MNRAS vol 402, 2503 (2010)). The first
of these emits only at one frequency; the other two at a pair of harmonically
related frequencies. We show that in all three cases, when written in terms of
the original ""source parameters"", there exist a number of discrete
degeneracies, with different parameter values giving rise to the same
gravitational wave signal. We show how these can be removed by suitably
restricting the source parameter ranges. In the case of the model as written
down by Jones, there is also a continuous degeneracy. We show how to remove
this through a suitable rewriting in terms of ""waveform parameters"", chosen so
as to make the specialisations to the other stellar models particularly simple.
We briefly consider the (non-trivial) relation between the assignment of prior
probabilities on one set of parameters verses the other. The results of this
paper will be of use when designing strategies for carrying out searches for
such multi-harmonic gravitational wave signals, and when performing parameter
estimation in the event of a detection.",1501.05832v2
2015-12-30,"On the ""spin connection foam"" picture of quantum gravity from precanonical quantization","Precanonical quantization is based on a generalization of the Hamiltonian
formalism to field theory, the so-called De Donder-Weyl (DW) theory, which does
not require a spacetime splitting and treats the space-time variables on an
equal footing. Quantum dynamics is described by a precanonical wave function on
the finite dimensional space of field coordinates and space-time coordinates,
which satisfies a partial derivative precanonical Schr\""odinger equation. The
standard QFT in the functional Schr\""odinger representation can be derived from
the precanonical quantization in a limiting case. An analysis of the
constraints within the DW Hamiltonian formulation of the Einstein-Palatini
vielbein formulation of GR and quantization of the generalized Dirac brackets
defined on differential forms lead to the covariant precanonical Schr\""odinger
equation for quantum gravity. The resulting dynamics of quantum gravity is
described by the wave function or transition amplitudes on the total space of
the bundle of spin connections over space-time. Thus, precanonical quantization
leads to the ""spin connection foam"" picture of quantum geometry represented by
a generally non-Gaussian random field of spin connection coefficients, whose
probability distribution is given by the precanonical wave function. The
normalizability of precanonical wave functions is argued to lead to the
quantum-gravitational avoidance of curvature singularities. Possible
connections with LQG are briefly discussed.",1512.09137v2
2016-02-10,Spin wave excitations in the tetragonal double perovskite Sr$_2$CuWO$_6$,"Sr$_2$CuWO$_6$ is a double perovskite proposed to be at the border between
two and three dimensional magnetism, with a square lattice of $S=\frac{1}{2}$
Cu$^{2+}$ ions. We have used inelastic neutron scattering to investigate the
spin wave excitations of the system, to find out how they evolve as a function
of temperature, as well as to obtain information about the magnetic exchange
interactions. We observed well defined dispersive spin wave modes at $6$~K,
which partially survive above the magnetic ordering temperature, $T_N=24$~K.
Linear spin wave theory is used to determine the exchange interactions
revealing them to be highly two-dimensional in nature. Density functional
theory calculations are presented supporting this experimental finding, which
is in contrast to a previous \emph{ab-initio} study of the magnetic
interactions. Our analysis confirms that not the nearest neighbour, but the
next nearest neighbour interactions in the tetragonal $ab$ plane are the
strongest. Low incident energy measurements reveal the opening of a
$0.6(1)$~meV gap below $T_N$, which suggests the presence of a very weak single
ion anisotropy term in the form of an easy axis along $\hat{\mathbf{a}}$.",1602.03335v2
2016-05-03,PRECESSION: Dynamics of spinning black-hole binaries with python,"We present the numerical code PRECESSION: a new open-source python module to
study the dynamics of precessing black-hole binaries in the post-Newtonian
regime. The code provides a comprehensive toolbox to (i) study the evolution of
the black-hole spins along their precession cycles, (ii) perform
gravitational-wave driven binary inspirals using both orbit-averaged and
precession-averaged integrations, and (iii) predict the properties of the
merger remnant through fitting formulae obtained from numerical-relativity
simulations. PRECESSION is a ready-to-use tool to add the black-hole spin
dynamics to larger-scale numerical studies such as gravitational-wave parameter
estimation codes, population synthesis models to predict gravitational-wave
event rates, galaxy merger trees and cosmological simulations of structure
formation. PRECESSION provides fast and reliable integration methods to
propagate statistical samples of black-hole binaries from/to large separations
where they form to/from small separations where they become detectable, thus
linking gravitational-wave observations of spinning black-hole binaries to
their astrophysical formation history. The code is also a useful tool to
compute initial parameters for numerical-relativity simulations targeting
specific precessing systems. PRECESSION can be installed from the Python
Package Index and it is freely distributed under version control on Github,
where further documentation is provided.",1605.01067v3
2016-08-29,"Comment on ""Matter-Wave Interferometry of a Levitated Thermal Nano-Oscillator Induced and Probed by a Spin""","In this comment, we agree with the formulas derived in Refs. [1,2] but show
that the results are not due to ""interference between spatially separated
states of the center of mass of a mesoscopic harmonic oscillator"".",1608.08254v1
2018-05-18,Quantum theory of spin waves for Helical ground states in Hollandite lattice,"We perform spin wave analysis of classical ground states of a model
Hamiltonian proposed earlier(Phys. Rev. B {\bf 90}, 104420(2014)) for
$\alpha-MnO_2$ compounds. It is known that the phase diagram of the Hollandite
lattice (lattice of $\alpha-MnO_2$ compounds) consists of four different
Helical phases(FH, A2H, C2H, CH phase) in the space of model parameters
$J_1,~J_2,~J_3$. The spin wave dispersion shows presence of gapless mode which
interpolates between quadratic to linear depending on phases and values of
$J_i$'s. In most cases, the 2nd lowest mode shows the existence of a roton
minima mainly from $X$ to $M$ and $M$ to $Z$ path. Few higher modes also show
roton minima. Each helical phase has its characteristic traits which can be
used to determine the phases itself. The analytical expressions of eigenmodes
at high symmetry points are obtained which can be utilized to extract the
values of $J_i$'s. Density of states, specific heat and susceptibilities at low
temperature has been studied within spin wave approximation. The specific heat
shows departure from $T^{1.5(3)}$ dependence found in three dimensional
unfrustrated ferromagnetic(anti-ferromagnetic) system which seems to be the
signature of incommensurate helical phase. The parallel susceptibility is
maximum for FH phase and minimum for CH phase at low temperature. The
perpendicular susceptibility is found to be independent of temperature at very
low temperature. Our study can be used to compare experimental results on
magnon spectrum, elastic neutron scattering, and finite temperature properties
mentioned above for clean $\alpha-MnO_2$ system",1805.07156v1
2012-09-12,Unconventional Spin Density Waves in Dipolar Fermi Gases,"The conventional spin density wave (SDW) phase (Overhauser, 1962), as found
in antiferromagnetic metal for example (Fawcett 1988), can be described as a
condensate of particle-hole pairs with zero angular momentum, $\ell=0$,
analogous to a condensate of particle-particle pairs in conventional
superconductors. While many unconventional superconductors with Cooper pairs of
finite $\ell$ have been discovered, their counterparts, density waves with
non-zero angular momenta, have only been hypothesized in two-dimensional
electron systems (Nayak, 2000). Using an unbiased functional renormalization
group analysis, we here show that spin-triplet particle-hole condensates with
$\ell=1$ emerge generically in dipolar Fermi gases of atoms (Lu, Burdick, and
Lev, 2012) or molecules (Ospelkaus et al., 2008; Wu et al.) on optical lattice.
The order parameter of these exotic SDWs is a vector quantity in spin space,
and, moreover, is defined on lattice bonds rather than on lattice sites. We
determine the rich quantum phase diagram of dipolar fermions at half-filling as
a function of the dipolar orientation, and discuss how these SDWs arise amidst
competition with superfluid and charge density wave phases.",1209.2671v2
2018-08-21,Metastable bound states of the of the interacting 2D magnetoexcitons,"The possible formation of two-dimensional (2D) magnetic bi-excitons composed
of two 2D magnetoexcitons with electrons and holes on the lowest Landau levels
(LLLs), with opposite center of- mass wave vectors k and and with antiparallel
electric dipole moments perpendicular to the corresponding wave vectors was
investigated. Two spinor structures of two electrons and of two holes were
considered. In the singlet-singlet state the spins of two electrons as well as
the effective spins of two holes create the combinations with the total spin
S=0 and its projection on the magnetic field The triplet-triplet state
corresponds to S=1. Two orbital Gaussian variational wave functions depending
on | k | and describing the relative motion of two magnetoexcitons inside the
molecule were used. It is shown that in the LLLs approximation the stable bound
states of bimagnetoexcitons do not exist. A metastable bound state for the
triplet-triplet spin configuration a metastable bound state with the orbital
wave function, having the maximum on the in-plane ring was revealed. The
metastable bound state has an energy activation barrier comparable with the
magnetoexciton ionization potential and gives rise to the new luminescence band
due to the metastable bi-exciton-para exciton conversion with the frequencies
higher than those of the para magnetoexciton luminescence line.",1808.06849v1
2020-08-04,The permanent ellipticity of the neutron star in PSR J1023+0038,"A millisecond pulsar having an ellipticity, that is an asymmetric mass
distribution around its spin-axis, could emit continuous gravitational waves,
which have not been detected so far. An indirect way to infer such waves is to
estimate the contribution of the waves to the spin-down rate of the pulsar. The
transitional pulsar PSR J1023+0038 is ideal and unique for this purpose,
because this is the only millisecond pulsar for which the spin-down rate has
been measured in both accreting and non-accreting states. Here we infer, from
our formalism based on the complete torque budget equations and the pulsar
magnetospheric origin of observed $\gamma$-rays in the two states, that PSR
J1023+0038 should emit gravitational waves due to a permanent ellipticity of
the pulsar. The formalism also explains some other main observational aspects
of this source in a self-consistent way. As an example, our formalism naturally
infers the accretion disc penetration into the pulsar magnetosphere, and
explains the observed X-ray pulsations in the accreting state using the
standard and well-accepted scenario. This, in turn, infers the larger pulsar
spin-down power in the accreting state, which, in our formalism, explains the
observed larger $\gamma$-ray emission in this state. Exploring wide ranges of
parameter values of PSR J1023+0038, and not assuming an additional source of
stellar ellipticity in the accreting state, we find the misaligned mass
quadrupole moment of the pulsar in the range of $(0.92-1.88)\times10^{36}$ g
cm$^2$, implying an ellipticity range of $(0.48-0.93)\times10^{-9}$.",2008.01716v1
2017-06-05,Spin-Projected Generalized Hartree-Fock as a Polynomial of Particle-Hole Excitations,"The past several years have seen renewed interest in the use of
symmetry-projected Hartree-Fock for the description of strong correlations.
Unfortunately, these symmetry-projected mean-field methods do not adequately
account for dynamic correlation. Presumably, this shortcoming could be
addressed if one could combine symmetry-projected Hartree-Fock with a many-body
method such as coupled cluster theory, but this is by no means straightforward
because the two techniques are formulated in very different ways. However, we
have recently shown that the singlet $S^2$-projected unrestricted Hartree-Fock
wave function can in fact be written in a coupled cluster-like wave function:
that is, the spin-projected unrestricted Hartree-Fock wave function can be
written as a polynomial of a double-excitation operator acting on some
closed-shell reference determinant. Here, we extend this result and show that
the spin-projected generalized Hartree-Fock wave function (which has both $S^2$
and $S_z$ projection) is likewise a polynomial of low-order excitation
operators acting on a closed-shell determinant, and provide a closed-form
expression for the resulting polynomial coefficients. We include a few
preliminary applications of the combination of this spin-projected Hartree-Fock
and coupled cluster theory to the Hubbard Hamiltonian, and comment on
generalizations of the methodology. Results here are not for production level,
but a similarity transformed theory that combines the two offers the promise of
being accurate for both weak and strong correlation, and particularly may offer
significant improvements in the intermediate correlation regime where neither
projected Hartree-Fock nor coupled cluster is particularly accurate.",1706.01548v2
2019-05-27,Influence of nonmagnetic dielectric spacers on the spin wave response of one-dimensional planar magnonic crystals,"The one-dimensional planar magnonic crystals are usually fabricated as a
sequence of stripes intentionally or accidentally separated by non-magnetic
spacers. The influence of spacers on shaping the spin wave spectra is complex
and still not completely clarified. We performed the detailed numerical studies
of the one-dimensional single- and bi-component magnonic crystals comprised of
a periodic array of thin ferromagnetic stripes separated by non-magnetic
spacers. We showed that the dynamic dipolar interactions between the stripes
mediated by non-magnetic spacer, even ultra-narrow, significantly shift up the
frequency of the ferromagnetic resonance and simultaneously reduce the spin
wave group velocity, which is manifested by the flattening of the magnonic
band. We attributed these changes in the spectra to the modifications of
dipolar pinning and shape anisotropy both dependent on the width of the spacers
and the thickness of the stripes, as well as to the dynamical magnetic volume
charges formed due to inhomogeneous spin wave amplitude.",1905.11016v4
2021-08-18,Dispersionless propagation of ultra-short spin-wave pulses in ultrathin yttrium iron garnet waveguides,"We study experimentally the propagation of nanosecond spin-wave pulses in
microscopic waveguides made of nanometer-thick yttrium iron garnet films. For
these studies, we use micro-focus Brillouin light scattering spectroscopy,
which provides the possibility to observe propagation of the pulses with high
spatial and temporal resolution. We show that, for most spin-wave frequencies,
dispersion leads to broadening of the pulse by several times at propagation
distances of 10 micrometers. However, for certain frequency interval, the
dispersion broadening is suppressed almost completely resulting in a
dispersionless pulse propagation. We show that the formation of the
dispersion-free region is caused by the competing effects of the dipolar and
the exchange interaction, which can be controlled by the variation of the
waveguide geometry. These conclusions are supported by micromagnetic
simulations and analytical calculations. Our findings provide a simple solution
for the implementation of high-speed magnonic systems that require undisturbed
propagation of short information-carrying spin-wave pulses.",2108.08054v1
2008-06-27,Topology and Collapse,"We show that the collapse of the wave function of an entangled state of two
spin 1/2 particles or two photons in the singlet state can be geometrically
understood as a change of fibre bundles.",0806.4428v1
2017-03-11,Constructing Gravitational Waves from Generic Spin-Precessing Compact Binary Inspirals,"The coalescence of compact objects is one of the most promising sources of
gravitational waves for ground-based interferometric detectors, such as
advanced LIGO and Virgo. Generically, com- pact objects in binaries are
expected to be spinning with spin angular momenta misaligned with the orbital
angular momentum, causing the orbital plane to precess. This precession adds
rich structure to the gravitational waves, introducing such complexity that an
analytic closed-form description has been unavailable until now. We here
construct the first closed-form frequency- domain gravitational waveforms that
are valid for generic spin-precessing quasicircular compact binary inspirals.
We first construct time-domain gravitational waves by solving the
post-Newtonian precession equations of motion with radiation reaction through
multiple scale analysis. We then Fourier transform these time-domain waveforms
with the method of shifted uniform asymptotics to obtain closed-form
expressions for frequency-domain waveforms. We study the accuracy of these
analytic, frequency-domain waveforms relative to waveforms obtained by
numerically evolving the post-Newtonian equations of motion and find that they
are suitable for unbiased parameter estimation for 99.2%(94.6%) of the binary
configurations we studied at a signal-to-noise ratio of 10(25). These new
frequency-domain waveforms could be used for detection and parameter estimation
studies due to their accuracy and low computational cost.",1703.03967v3
2019-01-17,Exciting black hole modes via misaligned coalescences: II. The mode content of late-time coalescence waveforms,"Using inspiral and plunge trajectories we construct with a generalized
Ori-Thorne algorithm, we use a time-domain black hole perturbation theory code
to compute the corresponding gravitational waves. The last cycles of these
waveforms are a superposition of Kerr quasinormal modes. In this paper, we
examine how the modes' excitations vary as a function of source parameters,
such as the larger black hole's spin and the geometry of the smaller body's
inspiral and plunge. We find that the mixture of quasinormal modes that
characterize the final gravitational waves from a coalescence is entirely
determined by the spin $a$ of the larger black hole, an angle $I$ which
characterizes the misalignment of the orbital plane from the black hole's spin
axis, a second angle $\theta_{\rm fin}$ which describes the location at which
the small body crosses the black hole's event horizon, and the direction
sgn$(\dot\theta_{\rm fin})$ of the body's final motion. If these
large-mass-ratio results hold at less extreme mass ratios, then measuring
multiple ringdown modes of binary black hole coalescence gravitational waves
may provide important information about the source's binary properties, such as
the misalignment of the orbit's angular momentum with black hole spin. This may
be particularly useful for large mass binaries, for which the early inspiral
waves are out of the detectors' most sensitive band.",1901.05902v2
2019-04-10,Testing the Wave-Particle Duality of Gravitational Wave Using the Spin-Orbital-Hall Effect of Structured Light,"Probing the polarization of gravitational waves (GWs) would provide an
evidence of graviton, indicating the quantization of gravity. Motivated by the
next generation of gravitational wave detectors, we make an attempt to study
the possible helicity coupling of structured lights to GWs. With the analogue
between of gravitational fields and the generic electromagnetic media, we
present a 4-vector optical Dirac equation based on the Maxwell theory under the
paraxial approximation. It is found that twisted lights propagating in a
gravitational field can be viewed as a non-Hermitian system with the
$\mathcal{PT}$ symmetry. We further demonstrate that the coupling effect
between angular momentums of the GWs and twisted lights may make photons
undergo both dipole and quadrupole transitions between different
orbital-angular-momentum(OAM) eigenstates and leads to some measurable optical
features, including the central intensity brightening and macroscopic rotation
of the intensity pattern for twisted lights. The former is spin-independent
while the later is spin dependent phenomena, both of which can be viewed
alternatively as the spin-orbital-Hall effect of structured lights in the GWs
and can serve as an indicator of the particle nature of GWs.",1904.05380v3
2019-04-21,Brillouin-Mandelstam Spectroscopy of Stress-Modulated Spatially Confined Spin Waves in Ni Thin Films on Piezoelectric Heterostructures,"We report results of micro-Brillouin-Mandelstam light scattering spectroscopy
of thermal magnons in the two-phase synthetic multiferroic structure consisting
of a piezoelectric (PMN-PT) substrate and a Ni thin film with the thickness of
64 nm. The experimental data reveal the first two modes of the perpendicular
standing spin waves (PSSW) spatially confined across the Ni thin film. A
theoretical analysis of the frequency dependence of the PSSW peaks on the
external magnetic field reveals the asymmetric boundary condition, i.e.
pinning, for variable magnetization at different surfaces of the Ni thin film.
The strain field induced by applying DC voltage to PMN-PT substrate leads to a
down shift of PSSW mode frequency owing to the magneto-elastic effect in Ni,
and corresponding changes in the spin wave resonance conditions. The observed
non-monotonic dependence of the PSSW frequency on DC voltage is related to an
abrupt change of the pinning parameter at certain values of the voltage. The
obtained results are important for understanding the thermal magnon spectrum in
ferromagnetic films and development of the low-power spin-wave devices.",1904.09553v1
2019-10-19,Propagation of spin-waves packets in individual nano-sized yttrium iron garnet magnonic conduits,"Modern-days CMOS-based computation technology is reaching its fundamental
limitations. The emerging field of magnonics, which utilizes spin waves for
data transport and processing, proposes a promising path to overcome these
limitations. Different devices have been demonstrated recently on the macro-
and microscale, but the feasibility of the magnonics approach essentially
relies on the scalability of the structure feature size down to an extent of a
few 10 nm, which are typical sizes for the established CMOS technology. Here,
we present a study of propagating spin-wave packets in individual yttrium iron
garnet (YIG) conduits with lateral dimensions down to 50 nm. Space and time
resolved micro-focused Brillouin-Light-Scattering (BLS) spectroscopy is used to
characterize the YIG nanostructures and measure the spin-wave decay length and
group velocity directly. The revealed magnon transport at the scale comparable
to the scale of CMOS proves the general feasibility of a magnon-based data
processing.",1910.08801v2
2020-12-08,Effective field theory for compact object evolution in binary inspirals,"Using the effective field theory framework for extended objects we describe
the evolution of spinning compact objects in the late inspiral of the
coalescence of a binary, before the plunge and merger, by including leading
order corrections due to spin, tides, dissipation and gravitational wave
radiation. Our implementation is of particular relevance for probing the
stellar structure of compact objects with gravitational wave observations. A
spinning compact object in the effective field theory framework is described as
a spinning point particle, with its finite size effects encoded in higher order
operators in the effective action, operators which have coefficients that
encapsulates the internal structure of the star. For the inspiral regime
described by non-relativistic general relativity, post-Newtonian corrections to
each term of the action can be obtained in a diagrammatic approach, including
gravitational radiation effects. Taking into account the aforementioned
ingredients of the effective theory, we solve for the dynamics of the inspiral
of binary systems using an algorithm for point particle simulations. We extract
the gravitational wave as a function of the orbital frequency, input that is
generated numerically and then evaluated in the analytic function of the
waveform. By performing illustrative numerical experiments of systems that the
LIGO-Virgo observatories have already detected, we show the role of the stellar
structure and its coefficients in the phase evolution of the waveform, as well
as the order in which they arise and the sensitivity required for the
gravitational wave observatories to measure them. If these coefficients are to
be measured, tight constraints on fundamental physics can be placed.",2012.04140v2
2021-06-01,Flat-band ferromagnetism and spin waves in the Haldane-Hubbard model,"We study the flat-band ferromagnetic phase of the Haldane-Hubbard model on a
honeycomb lattice within a bosonization scheme for flat-band Chern insulators,
focusing on the calculation of the spin-wave excitation spectrum. We consider
the Haldane-Hubbard model with the noninteracting lower bands in a nearly-flat
band limit, previously determined for the spinless model, and at 1/4-filling of
its corresponding noninteracting limit. Within the bosonization scheme, the
Haldane-Hubbard model is mapped into an effective interacting boson model,
whose quadratic term allows us to determine the spin-wave spectrum at the
harmonic approximation. We show that the excitation spectrum has two branches
with a Goldstone mode and Dirac points at center and at the K and K' points of
the first Brillouin zone, respectively. We also consider the effects on the
spin-wave spectrum due to an energy offset in the on-site Hubbard repulsion
energies and due to the presence of an staggered on-site energy term, both
quantities associated with the two triangular sublattices. In both cases, we
find that an energy gap opens at the K and K' points. Moreover, we also find
some evidences for an instability of the flat-band ferromagnetic phase in the
presence of the staggered on-site energy term. We provide some additional
results for the square lattice topological Hubbard model previous studied
within the bosonization formalism and comment on the differences between the
bosonization scheme implementation for the correlated Chern insulators on both
square and honeycomb lattices.",2106.00468v2
2021-07-01,Real-space Observation of Incommensurate Spin Density Wave and Coexisting Charge Density Wave on Cr(001) surface,"In itinerant magnetic systems, a spin density wave (SDW) state can be induced
by Fermi surface nesting and electron-electron interaction. It may intertwine
with other orders such as charge density wave (CDW), while their relation is
still yet to be understood. Here via spin-polarized scanning tunneling
microscopy, we directly observed long-range spin modulation on Cr(001) surface,
which corresponds to the well-known incommensurate SDW of bulk Cr. It displays
6.0 nm in-plane period and anti-phase behavior between adjacent (001) planes.
Meanwhile, we simultaneously observed the coexisting CDW with half the period
of SDW. Such SDW/CDW have highly correlated domain structures and are in-phase.
Surprisingly, the CDW displays a contrast inversion around a density-of-states
dip at -22 meV, indicating an anomalous CDW gap opened below EF. These
observations support that the CDW is a secondary order driven by SDW. Our work
is not only a real-space characterization of incommensurate SDW, but also
provides insights on how SDW and CDW coexist.",2107.00274v2
2021-09-11,2-output spin wave programmable logic gate,"This paper presents a 2-output Spin-Wave Programmable Logic Gate structure
able to simultaneously evaluate any pair of AND, NAND, OR, NOR, XOR, and XNOR
Boolean functions. Our proposal provides the means for fanout achievement
within the Spin Wave computation domain and energy and area savings as two
different functions can be simultaneously evaluated on the same input data. We
validate our proposal by means of Object Oriented Micromagnetic Framework
(OOMMF) simulations and demonstrate that by phase and magnetization threshold
output sensing AND, OR, NAND, NOR and XOR and XNOR functionalities can be
achieved, respectively. To get inside into the potential practical implications
of our approach we use the proposed gate to implement a 3-input Majority gate,
which we evaluate and compare with state of the art equivalent implementations
in terms of area, delay, and energy consumptions. Our estimations indicate that
the proposed gate provides 33% and 16% energy and area reduction, respectively,
when compared with spin-wave counterpart and 42% energy reduction while
consuming 12x less area when compared to a 15 nm CMOS implementation.",2109.05228v1
2022-04-04,Measuring a population of spin waves from the electrical noise of an inductively coupled antenna,"We study how a population of spin waves can be characterized from the
analysis of the electrical microwave noise delivered by an inductive antenna
placed in its vicinity. The measurements are conducted on a synthetic
antiferromagnetic thin stripe covered by a micron-sized antenna that feeds a
spectrum analyser after amplification. The antenna noise contains two
contributions. The population of incoherent spin waves generates a fluctuating
field that is sensed by the antenna: this is the ""magnon noise"". The antenna
noise also contains the contribution of the electronic fluctuations: the
Johnson-Nyquist noise. The latter depends on all impedances within the
measurement circuit, which includes the antenna self-inductance. As a result,
the electronic noise contains information about the magnetic susceptibility of
the stripe, though it does not inform on the absolute amplitude of the magnetic
fluctuations. For micrometer-sized systems at thermal equilibrium, the
electronic noise dominates and the pure magnon noise cannot be determined. If
in contrast the spinwave bath is not at thermal equilibrium with the
measurement circuit, and if the spin wave population can be changed then one
could measure a mode-resolved effective magnon temperature provided specific
precautions are implemented.",2204.01427v2
2022-07-15,The magnetic dynamics of NiPS$_3$,"Neutron spectroscopy measurements have been performed on single crystals of
the antiferromagnetic van der Waals compound NiPS$_3$. Linear spin wave theory
using a Heisenberg Hamiltonian with single-ion anisotropies has been applied to
determine the magnetic exchange parameters and the nature of the anisotropy.
The analysis reveals that NiPS$_3$ is less two-dimensional than its sister
compounds, with a relatively large ferromagnetic exchange of $J^{\prime} =
-0.3$ meV between the layered \emph{ab} planes. In-plane magnetic exchange
interactions up to the third nearest-neighbour were required to fit the data.
The nearest-neighbour exchange was ferromagnetic with $J_1 = -2.6$ meV, the
second neighbour was antiferromagnetic and small with $J_2 = 0.2$ meV, and the
dominant antiferromagnetic third neighbour exchange was $J_3 = 13.5$ meV. The
anisotropy was shown to be largely XY-like with a small uniaxial component,
leading to the appearance of two low-energy spin wave modes in the spin wave
spectrum at the Brillouin zone centre. The analysis could reproduce the spin
wave energies, however there are discrepancies with the calculated neutron
intensities hinting at more exotic phenomena.",2207.07448v2
2023-01-31,Complete identification of spin-wave eigenmodes excited by parametric pumping in YIG microdisks,"We present the parametric excitation of spin-wave modes in YIG micro-disks
via parallel pumping. Their spectroscopy is performed using magnetic resonance
force microscopy (MRFM), while their spatial profiles are determined by
micro-focus Brillouin light scattering (BLS). We observe that almost all the
fundamental eigenmodes of an in-plane magnetized YIG micro-disk, calculated
using a micromagnetic eigenmode solver, can be excited using the parallel
pumping scheme, as opposed to the transverse one. The comparison between the
MRFM and BLS data on one side, and the simulations on the other side, provides
the complete spectroscopic labeling of over 40 parametrically excited modes.
Our findings could be promising for spin-wave-based computation schemes, in
which the amplitudes of a large number of spin-wave modes have to be
controlled.",2301.13468v1
2023-03-21,On certain paradoxical properties of Einstein photon fields and Dirac electron-positron fields,"The article shows that the photons and electrons in the states with
""deinterlaced"" spins, which are isomorphic to their usual wave state ""Feynman
paths"", but also having a power to penetrate infinitely distant in arbitrarily
small time.",2305.03717v1
2023-08-03,Flavor-wave theory with quasiparticle damping at finite temperatures: Application to chiral edge modes in the Kitaev model,"We propose a theoretical framework to investigate elementary excitations at
finite temperatures within a localized electron model that describes the
interactions between multiple degrees of freedom, such as quantum spin models
and Kugel-Khomskii models. Thus far, their excitation structures have been
mainly examined using the linear flavor-wave theory, an SU($N$) generalization
of the linear spin-wave theory. These techniques introduce noninteracting
bosonic quasiparticles as elementary excitations from the ground state, thereby
elucidating numerous physical phenomena, including excitation spectra and
transport properties characterized by topologically nontrivial band structures.
Nevertheless, the interactions between quasiparticles cannot be ignored in
systems exemplified by $S=1/2$ quantum spin models, where strong quantum
fluctuations are present. Recent studies have investigated the effects of
quasiparticle damping at zero temperature in such models. In our study,
extending this approach to the flavor-wave theory for general localized
electron models, we construct a comprehensive method to calculate excitation
spectra with the quasiparticle damping at finite temperatures. We apply our
method to the Kitaev model under magnetic fields, a typical example of models
with topologically nontrivial magnon bands. Our calculations reveal that chiral
edge modes undergo significant damping in weak magnetic fields, amplifying the
damping rate by the temperature increase. This effect is caused by collisions
with thermally excited quasiparticles. Since our approach starts from a general
Hamiltonian, it will be widely applicable to other localized systems, such as
spin-orbital coupled systems derived from multi-orbital Hubbard models in the
strong correlation limit.",2308.01711v1
2023-10-03,Spatially inhomogeneous inverse Faraday effect provides tunable nonthermal excitation of exchange dominated spin waves,"We demonstrate optical nonthermal excitation of exchange dominated spin waves
of different orders in a magnetophotonic crystal. The magnetophotonic structure
consists of a thin magnetic film and a Bragg stack of nonmagnetic layers to
provide a proper nonuniform interference pattern of the inverse Faraday effect
induced by light in the magnetic layer. We found a phenomenon of the pronounced
phase slippage of the inverse Faraday effect distribution when the pump
wavelength is within the photonic band gap of the structure. It allows to tune
the interference pattern by a slight variation of light wavelength which
results in the modification of excitation efficiency of the different order
spin waves. The approach can be applied for different magnetic dielectrics
expanding their application horizons for spin-wave based devices.",2310.01984v1
2023-12-10,"Magnetoelectric Coupling in Pb(Zr,Ti)O3/CoFeB Nanoscale Waveguides Studied by Propagating Spin-Wave Spectroscopy","This study introduces a method for the characterization of the
magnetoelectric coupling in nanoscale Pb(Zr,Ti)O3/CoFeB thin film composites
based on propagating spin-wave spectroscopy. Finite element simulations of the
strain distribution in the devices indicated that the magnetoelastic effective
field in the CoFeB waveguides was maximized in the Damon - Eshbach
configuration. All-electrical broadband propagating spin-wave transmission
measurements were conducted on Pb(Zr,Ti)O3/CoFeB magnetoelectric waveguides
with lateral dimensions down to 700 nm. The results demonstrated that the
spin-wave resonance frequency can be modulated by applying a bias voltage to
Pb(Zr,Ti)O3. The modulation is hysteretic due to the ferroelastic behavior of
Pb(Zr,Ti)O3. An analytical model was then used to correlate the change in
resonance frequency to the induced magnetoelastic field in the magnetostrictive
CoFeB waveguide. We observe a hysteresis magnetoelastic field strength with
values as large as 5.61 mT, and a non-linear magnetoelectric coupling
coefficient with a maximum value of 1.69 mT/V.",2312.05819v1
2008-02-16,Competition between charge and spin order in the $t-U-V$ extended Hubbard model on the triangular lattice,"Several new classes of compounds can be modeled in first approximation by
electrons on the triangular lattice that interact through on-site repulsion $U$
as well as nearest-neighbor repulsion $V$. This extended Hubbard model on a
triangular lattice has been studied mostly in the strong coupling limit for
only a few types of instabilities. Using the extended two-particle self
consistent approach (ETPSC), that is valid at weak to intermediate coupling, we
present an unbiased study of the density and interaction dependent crossover
diagram for spin and charge density wave instabilities of the normal state at
arbitrary wave vector. When $U$ dominates over $V$ and electron filling is
large, instabilities are chiefly in the spin sector and are controlled mostly
by Fermi surface properties. Increasing $V$ eventually leads to charge
instabilities. In the latter case, it is mostly the wave vector dependence of
the vertex that determines the wave vector of the instability rather than Fermi
surface properties. At small filling, non-trivial instabilities appear only
beyond the weak coupling limit. There again, charge density wave instabilities
are favored over a wide range of dopings by large $V$ at wave vectors
corresponding to $\sqrt(3) \times \sqrt(3)$ superlattice in real space.
Commensurate fillings do not play a special role for this instability.
Increasing $U$ leads to competition with ferromagnetism. At negative values of
$U$ or $V$, neglecting superconducting fluctuations, one finds that charge
instabilities are favored. In general, the crossover diagram presents a rich
variety of instabilities. We also show that thermal charge-density wave
fluctuations in the renormalized classical regime can open a pseudogap in the
single-particle spectral weight, just as spin or superconducting fluctuations.",0802.2291v1
2019-05-01,The inertial wave activity during spin-down in a rapidly rotating penny shaped cylinder. Part I The quasi-geostrophic trigger,"In a previous paper, Oruba, Soward & Dormy (J.Fluid Mech., vol.818, 2017,
pp.205-240) considered the primary quasi-steady geostrophic (QG) motion of a
constant density fluid of viscosity $\nu$ that occurs during linear spin-down
in a cylindrical container of radius $L$ and height $H$, rotating rapidly
(angular velocity $\Omega$) about its axis of symmetry subject to mixed rigid
and stress-free boundary conditions for the case $L=H$. Here, Direct Numerical
Simulation (DNS) at large $L= 10 H$ and Ekman number $E=\nu/H^2\Omega=10^{-3}$
reveals structured inertial wave activity on the spin-down time-scale. The
analytic study, based on $E\ll 1$, builds on the results of Greenspan & Howard
(J.Fluid Mech., vol.17, 1963, pp.385-404) for an infinite plane layer
$L\to\infty$. At large but finite distance $r^\dag$ from the symmetry axis, the
meridional (QG-)flow, that causes the QG-spin down, is blocked by the lateral
boundary $r^\dag=L$, which provides a QG-trigger for inertial waves. The true
situation in the unbounded layer is complicated further by the existence of a
secondary set of maximum frequency (MF) inertial waves (a manifestation of the
transient Ekman layer) identified by Greenspan & Howard. Their blocking at
$r^\dag=L$ provides a secondary MF-trigger for yet more inertial waves that we
consider in a sequel (Part II). Here, for the QG-trigger, we solve a linear
initial value problem by Laplace transform methods. The ensuing complicated
inertial wave structure is explained analytically on approximating our
cylindrical geometry at large radius by rectangular Cartesian geometry, valid
for $L-r^\star=O(H)$ ($L\gg H$). Other than identifying small scale structure
near $r^\star=L$, our main finding is that inertial waves radiated away from
the outer boundary (but propagating towards it) reach a distance determined by
the group velocity.",1905.00478v1
2008-07-27,"Competing order, Fermi surface reconstruction, and quantum oscillations in underdoped high temperature superconductors","We consider incommensurate $d$-density wave order in underdoped high
temperature superconductors. We find that Fermi surface reconstruction can
correctly capture the phenomenology of the recent quantum oscillation
experiments that suggest incommensurate order. The predicted frequencies are a
frequency around 530 T arising from the electron pocket, a hole frequency at
around 1650 T, and a new low frequency from a smaller hole pocket at 250 T for
which there are some indications that require further investigation. The
oscillation corresponding to the electron pocket will be further split due to
bilayer coupling but the splitting is sufficiently small to require more
refined measurements. The truly incommensurate $d$-density wave breaks both
time reversal and inversion but the product of these two symmetry operations is
preserved. There is some similarity of our results with the spiral spin density
wave order, which, as pointed out by Overhauser, also breaks time reversal and
inversion. Calculations corresponding to higher order commensuration produces
results similar to anti-phase spin stripes, but appear to us to be an unlikely
explanation of the experiments. The analysis of the Gorkov equation in the
mixed state shows that the oscillation frequencies are unshifted from the
putative normal state and the additional Dingle factor arising from the
presence of the mixed state can provide a subtle distinction between the spiral
spin density wave and the $d$-density wave.",0807.4202v1
2015-09-30,Two-state Bogoliubov theory of a molecular Bose gas,"We present an analytic Bogoliubov description of a BEC of polar molecules
trapped in a quasi-2D geometry and interacting via internal state-dependent
dipole-dipole interactions. We derive the mean-field ground-state energy
functional, and we derive analytic expressions for the dispersion relations,
Bogoliubov amplitudes, and dynamic structure factors. This method can be
applied to any homogeneous, two-component system with linear coupling, and
direct, momentum-dependent interactions. The properties of the mean-field
ground state, including polarization and stability, are investigated, and we
identify three distinct instabilities: a density-wave rotonization that occurs
when the gas is fully polarized, a spin-wave rotonization that occurs near zero
polarization, and a mixed instability at intermediate fields. These
instabilities are clarified by means of the real-space density-density
correlation functions, which characterize the spontaneous fluctuations of the
ground state, and the momentum-space structure factors, which characterize the
response of the system to external perturbations. We find that the gas is
susceptible to both density-wave and spin-wave response in the polarized limit
but only a spin-wave response in the zero-polarization limit. These results are
relevant for experiments with rigid rotor molecules such as RbCs,
$\Lambda$-doublet molecules such as ThO that have an anomalously small
zero-field splitting, and doublet-$\Sigma$ molecules such as SrF where two
low-lying opposite-parity states can be tuned to zero splitting by an external
magnetic field.",1509.09268v1
2016-10-18,Correlation between opposite-helicity gravitons: Imprints on gravity-wave and microwave backgrounds,"We examine some of the roots of parity violation for gravitons and uncover a
closely related new effect: correlations between right and left handed
gravitons. Such correlators have spin 4 if they involve gravitons moving along
the same direction, and spin zero for gravitons moving with opposite
directions. In the first case, the most immediate implication would be a degree
of linear polarization for the tensor vacuum fluctuations, which could be seen
by gravity wave detectors sensitive enough to probe the primordial background,
its degree of polarization and anisotropies. Looking at the anisotropy of the
gravity waves linear polarization we identify the parity respecting and
violating components of the effect. The imprint on the CMB temperature and
polarization would be more elusive, since it averages to zero in the two-point
functions, appearing only in their cosmic variance or in fourth order
correlators. In contrast, spin zero correlations would have an effect on the
two point function of the CMB temperature and polarization, enhancing the $BB$
component if they were anti-correlations. Such correlations represent an
amplitude for the production of standing waves, as first envisaged by
Grishchuk, and could also leave an interesting signature for gravity wave
detectors.",1610.05702v2
2019-06-02,Neural Gutzwiller-projected variational wave functions,"Variational wave functions have enabled exceptional scientific breakthroughs
related to the understanding of novel phases of matter. Examples include the
Bardeen-Cooper-Schrieffer theory of superconductivity, the description of the
fractional quantum Hall effect through the Laughlin state, and Feynman's
variational understanding of large-scale quantum effects in liquid Helium. More
recently, Gutzwiller-projected wave functions, typically constructed from
fermionic degrees of freedom, have been employed to examine quantum spin models
in the presence of competing interactions, where exotic phases with no
spontaneous symmetry breaking and fractional excitations may exist. In this
work, we investigate the aforementioned fermionic wave functions supplemented
with neural networks, specifically with the so-called restricted Boltzmann
machine (RBM), to boost their accuracy and obtain reliable approximations to
the ground state of generic spin models. In particular, we apply our neural
augmented fermionic construction to the description of both magnetically
ordered and disordered phases of increasing complexity, including cases where
the ground state displays a non-trivial sign structure. Even though the RBM
state is by far more effective for N\'eel states endowed with a particularly
simple sign structure, it provides a significant improvement over the original
fermionic state in highly frustrated regimes where a complex sign structure is
anticipated, thus marking the path to an understanding of strongly-correlated
spin models on the lattice via neural Gutzwiller-projected variational wave
functions.",1906.00463v2
2020-09-13,Perfect transmission and perfect reflection of Bogoliubov quasiparticles in a dynamically unstable Bose-Einstein condensate,"The Nambu-Goldstone (NG) mode in a Bose-Einstein condensate (BEC) transmits a
potential barrier with probability 1 in the zero-energy limit, which is known
as the anomalous tunneling. In this paper, we investigate the tunneling
properties of quasiparticles in a dynamically unstable BEC. We prepare a
multi-component BEC (binary and spin-1 BEC) in a dynamically unstable state and
solve the tunneling problem of the spin-wave excitation from the condensate. We
find that the perfect transmission occurs even when the BEC is dynamically
unstable if the spin-wave is the NG mode. Here, the mode that exhibits the
perfect transmission is the dynamically unstable spin-wave mode, which is a
pure-imaginary-eigenvalue solution of the Bogoliubov-de Gennes equation. Hence,
we should take the zero-energy limit along not the real axis but the imaginary
axis. We also demonstrate the existence of the perfect reflection of a
dynamically unstable mode at the point where the imaginary part of the
eigenvalue takes its maximum. In this case, the incident and reflected waves
destructively interfere, and the amplitude of the quasiparticle wave function
is strongly suppressed. We numerically confirm that the perfect reflection is a
generic nature of dynamically unstable modes and not related to the NG mode.",2009.05998v1
2019-08-14,Asymmetric accretion and thermal `mountains' in magnetized neutron star crusts,"Accreting neutron stars are one of the main targets for continuous
gravitational wave searches, as asymmetric accretion may lead to quadrupolar
deformations, or `mountains', on the crust of the star, which source
gravitational wave emission at twice the rotation frequency. The gravitational
wave torque may also impact on the spin evolution of the star, possibly
dictating the currently observed spin periods of neutron stars in Low Mass
X-ray Binaries and leading to the increased spindown rate observed during
accretion in PSR J1023+0038. Previous studies have shown that deformed reaction
layers in the crust of the neutron star lead to thermal and compositional
gradients that can lead to gravitational wave emission. However, there are no
realistic constraints on the level of asymmetry that is expected. In this paper
we consider a natural source of asymmetry, namely the magnetic field, and
calculate the density and pressure perturbations that are expected in the crust
of accreting neutron stars. In general we find that only the outermost reaction
layers of the neutron star are strongly perturbed. The mass quadrupole that we
estimate is generally small and cannot explain the increase of spin-down rate
of PSR J1023+0038. However, if strong shallow heating sources are present at
low densities in the crust, as cooling observations suggest, these layers will
be strongly perturbed and the resulting quadrupole could explain the observed
spindown of PSR J1023+0038, and lead to observable gravitational wave signals
from systems with higher accretion rates.",1908.05038v2
2020-07-08,Constraints on ultra-low-frequency gravitational waves with statistics of pulsar spin-down rates II: Mann-Whitney U test,"We investigate gravitational waves with sub-nanoHz frequencies ($10^{-11}$ Hz
$\lesssim f_{\rm GW} \lesssim 10^{-9}$ Hz) from the spatial distribution of the
spin-down rates of milli-second pulsars. As we suggested in Yonemaru et al.
2018, gravitational waves from a single source induces the bias in the observed
spin-down rates of pulsars depending on the relative direction between the
source and pulsar. To improve the constraints on the time derivative of
gravitational-wave amplitude obtained in our previous work (Kumamoto et al.
2019), we adopt a more sophisticated statistical method called the Mann-Whitney
U test. Applying our method to the ATNF pulsar catalogue, we first found that
the current data set is consistent with no GW signal from any direction in the
sky. Then, we estimate the effective angular resolution of our method to be
$(66~{\rm deg})^2$ by studying the probability distribution of the test
statistic. Finally, we investigate gravitational-wave signal from the Galactic
Centre and M87 and, comparing simulated mock data sets with the real pulsar
data, we obtain the upper bounds on the time derivative as $\dot{h}_{\rm GC} <
8.9 \times 10^{-19} {\rm s}^{-1}$ for the Galactic Centre and $\dot{h}_{\rm
M87} < 3.3 \times 10^{-19} {\rm s}^{-1}$ for M87, which are stronger than the
ones obtained in Kumamoto et al. 2019 by factors of 7 and 25, respectively.",2007.03974v1
2020-07-27,Magnonic band structure in vertical meander-shaped CoFeB thin films,"The dispersion of spin waves in vertical meander-shaped CoFeB thin films
consisting of segments located at 90{\deg} angles with respect to each other is
investigated by Brillouin light scattering spectroscopy. We reveal the periodic
character of several dispersive branches as well as alternating frequency
ranges where spin waves are allowed or forbidden to propagate. Noteworthy is
the presence of the frequency band gaps between each couple of successive modes
only for wave numbers k=n$\pi$/a, where n is an even integer number and a is
the size of the meander unit cell, whereas the spectra show propagating modes
in the orthogonal film segments for the other wavenumbers. The micromagnetic
simulations and analytical calculations allow us to understand and explain the
results in terms of the mode spatial localization and symmetry. The obtained
results demonstrate the wave propagation in three dimensions opening the path
for multi-level magnonic architectures for signal processing.",2007.13707v2
2021-03-18,Achieving Wave Pipelining in Spin Wave Technology,"By their very nature, voltage/current excited Spin Waves (SWs) propagate
through waveguides without consuming noticeable power. If SW excitation is
performed by the continuous application of voltages/currents to the input,
which is usually the case, the overall energy consumption is determined by the
transducer power and the circuit critical path delay, which leads to high
energy consumption because of SWs slowness. However, if transducers are
operated in pulses the energy becomes circuit delay independent and it is
mainly determined by the transducer power and delay, thus pulse operation
should be targeted. In this paper, we utilize a 3-input Majority gate (MAJ) to
investigate the Continuous Mode Operation (CMO), and Pulse Mode Operation
(PMO). Moreover, we validate CMO and PMO 3-input Majority gate by means of
micromagnetic simulations. Furthermore, we evaluate and compare the CMO and PMO
Majority gate implementations in term of energy. The results indicate that PMO
diminishes MAJ gate energy consumption by a factor of 18. In addition, we
describe how PMO can open the road towards the utilization of the Wave
Pipelining (WP) concept in SW circuits. We validate the WP concept by means of
micromagnetic simulations and we evaluate its implications in term of
throughput. Our evaluation indicates that for a circuit formed by four cascaded
MAJ gates WP increases the throughput by 3.6x.",2103.10163v2
2021-07-10,Universal features of gravitational waves emitted by superkick binary black hole systems,"We use numerical relativity to study the merger and ringdown stages of
""superkick"" binary black hole systems (those with equal mass and anti-parallel
spins). We find a universal way to describe the mass and current quadrupole
gravitational waves emitted by these systems during the merger and ringdown
stage: (i) The time evolutions of these waves are insensitive to the
progenitor's parameters (spins) after being normalized by their own peak
values. (ii) The peak values, which encode all the spin information of the
progenitor, can be consistently fitted to formulas inspired by post-Newtonian
theory. We find that the universal evolution of the mass quadrupole wave can be
accurately modeled by the so-called Backwards One-Body (BOB) model. However,
the BOB model, in its present form, leads to a lower waveform match and a
significant parameter-estimation bias for the current quadrupole wave. We also
decompose the ringdown signal into seven overtones, and study the dependence of
mode amplitudes on the progenitor's parameters. Such dependence is found to be
insensitive to the overtone index (up to a scaling factor). Finally, we use the
Fisher matrix technique to investigate how the ringdown waveform can be at
least as important for parameter estimation as the inspiral stage. Assuming the
Cosmic Explorer, we find the contribution of ringdown portion dominates as the
total mass exceeds ~ 250 solar mass. For massive BBH systems, the accuracy of
parameter measurement is improved by incorporating the information of ringdown
-- the ringdown sector gives rise to a different parameter correlation from
inspiral stage, hence the overall parameter correlation is reduced in the full
signal.",2107.04890v1
2022-12-22,Spin wave dispersion of ultra-low damping hematite ($α\text{-Fe}_2\text{O}_3$) at GHz frequencies,"Low magnetic damping and high group velocity of spin waves (SWs) or magnons
are two crucial parameters for functional magnonic devices. Magnonics research
on signal processing and wave-based computation at GHz frequencies focussed on
the artificial ferrimagnetic garnet Y$_3$Fe$_5$O$_{12}$ (YIG) so far. We report
on spin-wave spectroscopy studies performed on the natural mineral hematite
($\alpha\text{-Fe}_2\text{O}_3$) which is a canted antiferromagnet. By means of
broadband GHz spectroscopy and inelastic light scattering, we determine a
damping coefficient of $1.1\times10^{-5}$ and magnon group velocities of a few
10 km/s, respectively, at room temperature. Covering a large regime of wave
vectors up to $k\approx 24~{\rm rad}/\mu$m, we find the exchange stiffness
length to be relatively short and only about 1 \r{A}. In a small magnetic field
of 30 mT, the decay length of SWs is estimated to be 1.1 cm similar to the best
YIG. Still, inelastic light scattering provides surprisingly broad and partly
asymmetric resonance peaks. Their characteristic shape is induced by the large
group velocities, low damping and distribution of incident angles inside the
laser beam. Our results promote hematite as an alternative and sustainable
basis for magnonic devices with fast speeds and low losses based on a stable
natural mineral.",2212.11887v2
1999-04-24,Quantum melting of magnetic long-range order near orbital degeneracy. Classical phases and Gaussian fluctuations,"We study the effective spin-orbital model derived for the d9 ions in a
three-dimensional perovskite lattice, as in KCuF_3, where at each site the
doubly degenerate eg orbitals contain a single hole. The model describes the
superexchange interactions that depend on the pattern of orbitals occupied. We
present the ground state properties of this model, depending on the splitting
between the eg orbitals E_z, and the Hund's rule coupling in the excited d8
states, J_H. The classical phase diagram consists of six magnetic phases which
all have different orbital ordering: two antiferromagnetic (AF) phases with
G-AF order and either x2-y2 or 3z2-r2 orbitals occupied, two phases with mixed
orbital (MO) patterns and A-AF order, and two other MO phases with either C-AF
or G-AF order. All of them become degenerate at the multicritical point
M=(E_z,J_H)=(0,0). Using a generalization of linear spin-wave theory we study
both the transverse excitations which are spin-waves and
spin-and-orbital-waves, as well as the longitudinal (orbital) excitations. The
transverse modes couple to each other, and the spin-and-orbital-wave turns into
a soft mode near the M point. Therefore, quantum corrections to the
long-range-order parameter are drastically increased near the orbital
degeneracy, and classical order is suppressed in a crossover regime between the
G-AF and A-AF phases in the (E_z,J_H) plane. This behavior is reminiscent of
that found in frustrated spin models, and we conclude that orbital degeneracy
provides a new and physically realizable mechanism which stabilizes a spin
liquid ground state due to inherent frustration of magnetic interactions. We
also point out that such a disordered magnetic phase is likely to be realized
in LiNiO_2.",9904355v1
2014-10-24,Magnetic order without tetragonal-symmetry-breaking in iron arsenides: microscopic mechanism and spin-wave spectrum,"Most iron-based superconductors undergo a transition to a magnetically
ordered state characterized by staggered stripes of parallel spins. With
ordering vectors $(\pi,0)$ or $(0,\pi)$, this magnetic state breaks the
high-temperature tetragonal symmetry of the system, which is manifested by a
splitting of the lattice Bragg peaks. Remarkably, recent experiments in
hole-doped iron arsenides reported an ordered state that displays magnetic
Bragg peaks at $(\pi,0)$ and $(0,\pi)$ but remains tetragonal. Despite being
inconsistent with a magnetic stripe configuration, this unusual magnetic phase
can be described in terms of a double-$\mathbf{Q}$ magnetic structure
consisting of an equal-weight superposition of the ordering vectors $(\pi,0)$
and $(0,\pi)$. Here we show that a non-collinear double-$\mathbf{Q}$ magnetic
configuration, dubbed \emph{orthomagnetic}, arises naturally within an
itinerant three-band microscopic model for the iron pnictides. In particular,
we find that strong deviations from perfect nesting and residual interactions
between the electron pockets favor the orthomagnetic over the stripe magnetic
state. Using an effective low-energy model, we also calculate the spin-wave
spectrum of the orthomagnetic state. In contrast to the stripe state, there are
three Goldstone modes, manifested in all diagonal and one off-diagonal
component of the spin-spin correlation function. The total magnetic structure
factor displays two anisotropic spin-wave branches emerging from both $(\pi,0)$
and $(0,\pi)$ momenta, in contrast to the case of domains of stripe order,
where only one spin-wave branch emerges from each momentum. We propose that
these unique features of the orthomagnetic state can be used to unambiguously
distinguish it from the stripe state via neutron scattering experiments, and
discuss the implications of its existence to the nature of the magnetism of the
iron arsenides.",1410.6789v2
2017-11-25,Inferring the population properties of binary neutron stars with gravitational-wave measurements of spin,"The recent LIGO-Virgo detection of gravitational waves from a binary neutron
star inspiral event GW170817 and the discovery of its accompanying
electromagnetic signals mark a new era for multimessenger astronomy. In the
coming years, advanced gravitational-wave detectors are likely to detect tens
to hundreds of similar events. Neutron stars in binaries can possess
significant spin, which is imprinted on the gravitational waveform via the
effective spin parameter $\chi_\text{eff}$. We explore the astrophysical
inferences made possible by gravitational-wave measurements of
$\chi_\text{eff}$. First, using a fiducial model informed by radio
observations, we estimate that $\approx15-30\%$ of binary neutron stars should
have spins measurable at $\gtrsim 90\%$ confidence level by advanced detectors
assuming the spin axis of the recycled neutron star aligns with the total
orbital angular momentum of the binary. Second, using Bayesian inference, we
show that it is possible to tell whether or not the spin axis of the recycled
neutron star tends to be aligned with the binary orbit using $\gtrsim 30$
detections. Finally, interesting constraints can be placed on neutron star
magnetic field decay after $\gtrsim 300$ detections, if the spin periods and
magnetic field strengths of Galactic binary neutron stars are representative of
the merging population.",1711.09226v5
2018-04-10,Control of Spin-Exchange Interaction between Alkali-Earth Atoms via Confinement-Induced Resonances in a Quasi 1+0 Dimensional System,"A nuclear-spin exchange interaction exists between two ultracold fermionic
alkali-earth (like) atoms in the electronic $^{1}{\rm S}_{0}$ state ($g$-state)
and $^{3}{\rm P}_{0}$ state ($e$-state), and is an essential ingredient for the
quantum simulation of Kondo effect. We study the control of this spin-exchange
interaction for two atoms simultaneously confined in a quasi-one-dimensional
(quasi-1D) tube, where the $g$-atom is freely moving in the axial direction
while the $e$-atom is further localized by an additional axial trap and behaves
as a quasi-zero-dimensional (quasi-0D) impurity. In this system, the two atoms
experience effective-1D spin-exchange interactions in both even and odd partial
wave channels, whose intensities can be controlled by the characteristic
lengths of the confinements via the confinement-induced-resonances (CIRs). In
current work, we go beyond that pure-1D approximation. We model the transverse
and axial confinements by harmonic traps with finite characteristic lengths
$a_\perp$ and $a_z$, respectively, and exactly solve the ""quasi-1D + quasi-0D""
scattering problem between these two atoms. Using the solutions we derive the
effective 1D spin-exchange interaction and investigate the locations and widths
of the even/odd wave CIRs for our system.
  It is found that when the ratio $a_z/a_\perp$ is larger, the CIRs can be
induced by weaker confinements, which are easier to be realized experimentally.
  The comparison between our results and the recent experiment shows that the
two experimentally observed resonance branches of the spin-exchange effect are
due to an even-wave CIR and an odd-wave CIR, respectively. Our results are
advantageous for the control and description of either the effective
spin-exchange interaction or other types of interactions between ultracold
atoms in quasi 1+0 dimensional systems.",1804.03388v3
2021-05-10,Magnon-phonon interactions enhance the gap at the Dirac point in the spin-wave spectra of CrI$_3$ two-dimensional magnets,"Recent neutron-diffraction experiments in honeycomb CrI$_3$ quasi-2D
ferromagnets have evinced the existence of a gap at the Dirac point in their
spin-wave spectra. The existence of this gap has been attributed to strong
in-plane Dzyaloshinskii-Moriya or Kitaev (DM/K) interactions and suggested to
set the stage for topologically protected edge states to sustain
non-dissipative spin transport. We perform state-of-the-art simulations of the
spin-wave spectra in monolayer CrI$_3$, based on time-dependent
density-functional perturbation theory (TDDFpT) and fully accounting for
spin-orbit couplings (SOC) from which DM/K interactions ultimately stem. While
our results are in qualitative agreement with experiments, the computed TDDFpT
magnon gap at the Dirac point is found to be 0.47~meV, roughly 6 times smaller
than the most recent experimental estimates, so questioning that intralayer
anisotropies alone can explain the observed gap. Lattice-dynamical
calculations, performed within density-functional perturbation theory (DFpT),
indicate that a substantial degeneracy and a strong coupling between
vibrational and magnetic excitations exist in this system, providing a possible
additional gap-opening mechanism in the spin-wave spectra. In order to pursue
this path, we introduce an interacting magnon-phonon Hamiltonian featuring a
linear coupling between lattice and spin fluctuations, enabled by the magnetic
anisotropy induced by SOC. Upon determination of the relevant interaction
constants by DFpT and supercell calculations, this model allows us to propose
magnon-phonon interactions as an important microscopic mechanism responsible
for the enhancement of the gap in the range of $\approx 4$~meV around the Dirac
point of the CrI$_3$ monolayer.",2105.04531v4
2023-02-02,Spin waves in a ferromagnetic topological metal,"In most metals, charges and spins can hop rapidly between atoms, yielding
strong dispersion of their energy versus momentum. There are, however, special
arrangements of atoms, such as twisted graphene bilayers or lattices which
resemble woven bamboo ""kagome"" mats, so that particle motion with strong
hopping between neighbours becomes nearly or even completely dispersionless.
Such flat bands are interesting because the interactions between the heavy
particles inhabiting them will become much more important than for strong
dispersion, resulting in novel quantum solid and liquid states, particularly
when topology enters on account of significant spin-orbit coupling for the
underlying electrons. Nonetheless, spectroscopic evidence for flat bands
engendered by lattice geometry rather than weak hopping is rare, particularly
for metallic single crystals. Here we report the discovery, using circularly
polarized X-Rays in resonant absorption and inelastic scattering (RIXS) for the
unambiguous isolation of magnetic signals, of a flat spin wave band and large
orbital moment for the metallic kagome ferromagnet Fe$_3$Sn$_2$, which has a
topologically non-trivial electronic band structure controllable by modest
external magnetic fields. The flat mode energy is consistent with the high
Curie temperature ($T_C$ ~ 640 K) as well as the strong acoustic mode
dispersion, implying, together with the substantial spin-orbit coupling
indicated by the large orbital moment, that the mode is topological. The
measured properties of the spin waves are highly unconventional, and include
very severe damping as well as the flat mode amplitude which is maximized in
the long wavelength limit where it is ordinarily expected to vanish. Our
results open the topic of interactions of topological bosons (spin waves) and
fermions (electrons) with the very specific target of explaining boson
lifetimes and amplitudes.",2302.01457v1
2003-06-23,Aspects of unconventional density waves,"Recently many people discuss unconventional density waves (i.e.
unconventional charge density waves (UCDW) and unconventional spin density
waves (USDW)). Unlike in conventional density waves, the quasiparticle spectrum
in these systems is gapless. Also these systems remain metallic. Indeed it
appears that there are many candidates for UDW. The low temperature phase of
alpha-(BEDT-TTF)_2KHg(SCN)_4, the antiferromagnetic phase in URu_2Si_2, the CDW
in transition metal dichalcogenite NbSe_2, the pseudogap phase in high T_c
cuprate superconductors, the glassy phase in organic superconductor
kappa-(BEDT-TTF)_2Cu[N(CN)_2]Br. After a brief introduction on UCDW and USDW,
we shall discuss some of the above systems, where we believe we have evidence
for unconventional density waves.",0306567v1
1999-11-09,Gravitational wave astronomy,"The first decade of the new millenium should see the first direct detections
of gravitational waves. This will be a milestone for fundamental physics and it
will open the new observational science of gravitational wave astronomy. But
gravitational waves already play an important role in the modeling of
astrophysical systems. I review here the present state of gravitational
radiation theory in relativity and astrophysics, and I then look at the
development of detector sensitivity over the next decade, both on the ground
(such as LIGO) and in space (LISA). I review the sources of gravitational waves
that are likely to play an important role in observations by first- and
second-generation interferometers, including the astrophysical information that
will come from these observations. The review covers some 10 decades of
gravitational wave frequency, from the high-frequency normal modes of neutron
stars down to the lowest frequencies observable from space. The discussion of
sources includes recent developments regarding binary black holes, spinning
neutron stars, and the stochastic background.",9911034v1
2004-11-27,Chiral symmetry and density wave in quark matter,"A density wave in quark matter is discussed at finite temperature, which
occurs along with the chiral condensation, and is described by a dual standing
wave in scalar and pseudo-scalar condensates on the chiral circle. The
mechanism is quite similar to that for the spin density wave suggested by
Overhauser, and entirely reflects many-body effects. It is found that the
chiral condensed phase with the density wave develops at a high-density region
just outside the usual chiral-transition line in phase diagram. A magnetic
property of the density wave is also elucidated.",0411350v5
1992-07-01,Ground state wave functionals for $1+1$-dimensional fermion field theories,"We use path-\-integral methods to derive the ground state wave functions of a
number of two-\-dimensional fermion field theories and related systems in
one-\-dimensional many body physics. We derive the exact wave function for the
Thirring/Luttinger and Coset fermion models and apply our results to derive the
universal behavior of the wave functions of the Heisenberg antiferromagnets and
of the Sutherland model. We find explicit forms for the wave functions in the
density and in the Grassmann representations. We show that these wave functions
always have the Jastrow factorized form and calculated the exponent. Our
results agree with the exponents derived from the Bethe Ansatz for the
Sutherland model and the Haldane-\-Shastri spin chain but apply to all the
systems in the same universality class.",9207003v1
1998-09-03,Matter Waves and Orbital Quantum Numbers,"The atom's orbital electron structure in terms of quantum numbers (principal,
azimuthal, magnetic and spin) results in space for a maximum of: 2 electrons in
the n=1 orbit, 8 electrons in the n=2 orbit, 18 electrons in the n=3 orbit, and
so on. Those dispositions are correct, but that is not because of quantum
numbers nor angular momentum nor a ""Pauli exclusion principle"".
  Matter waves were discovered in the early 20th century from their wavelength,
which was predicted by DeBroglie to be, Planck's constant divided by the
particle's momentum. But, the failure to obtain a reasonable theory for the
matter wave frequency resulted in loss of interest. That problem is resolved in
""A Reconsideration of Matter Waves"" in which a reinterpretation of Einstein's
derivation of relativistic kinetic energy [which produced his famous E = mc^2]
leads to a valid matter wave frequency and a new understanding of particle
kinetics and the atom's stable orbits.
  It is analytically shown that the orbital electron arrangement is enforced by
the necessity of accommodating the space that each orbiting electron's matter
wave occupies.",9809003v4
2006-05-16,A realist view on the treatment of identical particles,"Some basic concepts concerning systems of identical particles are discussed
in the framework of a realist interpretation, where the wave function is the
quantum object and |psi(r)|^2 d^3r is the probability that the wave function
causes an effect about the point r. The topics discussed include the role of
Hilbert-space labels, wave-function variables and wave-function parameters, the
distinction between permutation and renaming, the reason for symmetrizing the
wave function, the reason for antisymmetric wave functions, the spin-statistics
theorem, the correction term -k lnN! in the entropy, the Boltzmann limit of the
Fermi and Bose cases, and the derivation of the Fermi and Bose distributions.",0605136v5
2008-01-09,Linear Waves in the Kerr Geometry: A Mathematical Voyage to Black Hole Physics,"This paper gives a survey of wave dynamics in the Kerr space-time geometry,
the mathematical model of a rotating black hole in equilibrium. After a brief
introduction to the Kerr metric, we review the separability properties of
linear wave equations for fields of general spin $s=0, 1/2, 1, 2$,
corresponding to scalar, Dirac, electromagnetic fields and linearized
gravitational waves. We give results on the long-time dynamics of Dirac and
scalar waves, including decay rates for massive Dirac fields. For scalar waves,
we give a rigorous treatment of superradiance and describe rigorously a
mechanism of energy extraction from a rotating black hole. Finally, we discuss
the open problem of linear stability of the Kerr metric and present partial
results.",0801.1423v4
2008-08-22,"Tkachenko waves, glitches and precession in neutron star","Here I discuss possible relations between free precession of neutron stars,
Tkachenko waves inside them and glitches. I note that the proposed precession
period of the isolated neutron star RX J0720.4-3125 (Haberl et al. 2006) is
consistent with the period of Tkachenko waves for the spin period 8.4s. Based
on a possible observation of a glitch in RX J0720.4-3125 (van Kerkwijk et al.
2007), I propose a simple model, in which long period precession is powered by
Tkachenko waves generated by a glitch. The period of free precession,
determined by a NS oblateness, should be equal to the standing Tkachenko wave
period for effective energy transfer from the standing wave to the precession
motion. A similar scenario can be applicable also in the case of the PSR
B1828-11.",0808.3040v2
2010-07-18,Searching for topological density wave insulators in multi-orbital square lattice systems,"We study topological properties of density wave states with broken
translational symmetry in two-dimensional multi-orbital systems with a
particular focus on t$_{2g}$ orbitals in square lattice. Due to distinct
symmetry properties of d-orbitals, a nodal charge or spin density wave state
with Dirac points protected by lattice symmetries can be achieved. When an
additional order parameter with opposite reflection symmetry is introduced to a
nodal density wave state, the system can be fully gapped leading to a band
insulator. Among those, topological density wave (TDW) insulators can be
realized, when an effective staggered on-site potential generates a gap to a
pair of Dirac points connected by the inversion symmetry which have the same
topological winding numbers. We also present a mean-field phase diagram for
various density wave states, and discuss experimental implications of our
results.",1007.2998v1
2011-02-04,Internal wave breaking and the fate of planets around solar-type stars,"Internal gravity waves are excited at the interface of convection and
radiation zones of a solar-type star by the tidal forcing of a short-period
planet. The fate of these waves as they approach the centre of the star depends
on their amplitude. We discuss the results of numerical simulations of these
waves approaching the centre of a star, and the resulting evolution of the spin
of the central regions of the star, and the orbit of the planet. If the waves
break, we find efficient tidal dissipation, which is not present if the waves
perfectly reflect from the centre. This highlights an important amplitude
dependence of the (stellar) tidal quality factor Q', which has implications for
the survival of planets on short-period orbits around solar-type stars, with
radiative cores.",1102.0861v1
2011-09-05,Pulsars and Gravitational Waves,"The relationship between pulsar-like compact stars and gravitational waves is
briefly reviewed. Due to regular spins, pulsars could be useful tools for us to
detect ~nano-Hz low-frequency gravitational waves by pulsar-timing array
technique; besides, they would also be ~kilo-Hz high-frequency gravitational
wave radiators because of their compactness. The wave strain of an isolate
pulsar depends on the equation state of cold matter at supra-nuclear densities.
Therefore, a real detection of gravitational wave should be very meaningful in
gravity physics, micro-theory of elementary strong interaction, and astronomy.",1109.0812v2
2011-09-15,Waves of magnetic moment and generation of waves by neutron beam in quantum magnetized plasma,"This paper is devoted to studying of dispersion of waves in the magnetized
plasma with the spin and exploring of new methods of the generation wave in the
plasma. We consider the dispersion of waves, existed in the plasma in
consequence of dynamic of the magnetic moments. It is shown there are nine new
waves in the magnetized plasma because of the magnetic moments dynamic. We show
there are instabilities at propagation of the neutron beam through the plasma.
Increments of instabilities caused by neutron beam are calculated. For studying
of this effects we generalize and use the method of the many-particle quantum
hydrodynamics. Described processes can play important role at calculation of
the stability and the safeness of the nuclear reactors and the studying of the
processes in the atmosphere of the neutron stars.",1109.3335v2
2011-09-15,Gravitational Wave Astrophysics: Opening the New Frontier,"The gravitational wave window onto the universe is expected to open in ~ 5
years, when ground-based detectors make the first detections in the
high-frequency regime. Gravitational waves are ripples in spacetime produced by
the motions of massive objects such as black holes and neutron stars. Since the
universe is nearly transparent to gravitational waves, these signals carry
direct information about their sources - such as masses, spins, luminosity
distances, and orbital parameters - through dense, obscured regions across
cosmic time. This article explores gravitational waves as cosmic messengers,
highlighting key sources, detection methods, and the astrophysical payoffs
across the gravitational wave spectrum.",1109.3492v1
2018-05-16,Unconventional Superconductivity and Density Waves in Twisted Bilayer Graphene,"We study electronic ordering instabilities of twisted bilayer graphene with
$n=2$ electrons per supercell, where correlated insulator state and
superconductivity are recently observed. Motivated by the Fermi surface nesting
and the proximity to Van Hove singularity, we introduce a hot-spot model to
study the effect of various electron interactions systematically. Using
renormalization group method, we find $d$/$p$-wave superconductivity and
charge/spin density wave emerge as the two types of leading instabilities
driven by Coulomb repulsion. The density wave state has a gapped energy
spectrum at $n=2$ and yields a single doubly-degenerate pocket upon doping to
$n>2$. The intertwinement of density wave and superconductivity and the
quasiparticle spectrum in the density wave state are consistent with
experimental observations.",1805.06449v2
2018-11-12,Valley based splitting of topologically protected helical waves in elastic plates,"Topological protection offers unprecedented opportunities for wave
manipulation and energy transport in various fields of physics, including
elasticity, acoustics, quantum mechanics and electromagnetism. Distinct classes
of topological waves have been investigated by establishing analogues with the
quantum, spin and valley Hall effects. We here propose and experimentally
demonstrate the possibility of supporting multiple classes of topological modes
within a single platform. Starting from a patterned elastic plate featuring a
double Dirac cone, we create distinct topological interfaces by lifting such
degeneracy through selective breaking of symmetries across the thickness and in
the plane of the plate. We observe the propagation of a new class of
heterogeneous helical-valley edge waves capable of isolating modes on the basis
of their distinct polarization. Our results show the onset of wave splitting
resulting from the interaction of multiple topological equal-frequency wave
modes, which may have significance in applications involving elastic
beam-splitters, switches, and filters.",1811.04814v2
2019-06-14,Catching Gravitational Waves With A Galaxy-sized Net Of Pulsars,"Until recently, the only way to observe the Universe was from light received
by telescopes. But we are now able to measure gravitational waves, which are
ripples in the fabric of the Universe predicted by Albert Einstein. If two very
dense objects (like black holes) orbit each other closely, they warp space and
send out gravitational waves. For black holes that are similar in mass to the
Sun, scientists use the LIGO detector on Earth. But for the biggest black holes
in the Universe (billions of times more massive than the Sun), scientists
monitor a net of rapidly-spinning neutron stars (called pulsars) across the
Milky Way. Any gravitational wave passing by will change how long radio signals
from these pulsars take to get to Earth. The NANOGrav Collaboration monitored
34 of these pulsars over 11 years, in an attempt to detect gravitational waves
from giant black holes.",1906.07568v1
2020-12-17,Conformal partial waves in momentum space,"The decomposition of 4-point correlation functions into conformal partial
waves is a central tool in the study of conformal field theory. We compute
these partial waves for scalar operators in Minkowski momentum space, and find
a closed-form result valid in arbitrary space-time dimension $d \geq 3$
(including non-integer $d$). Each conformal partial wave is expressed as a sum
over ordinary spin partial waves, and the coefficients of this sum factorize
into a product of vertex functions that only depend on the conformal data of
the incoming, respectively outgoing operators. As a simple example, we apply
this conformal partial wave decomposition to the scalar box integral in $d = 4$
dimensions.",2012.09825v3
2021-03-31,Beta-decay formulas revisited (I): Gamow--Teller and spin-dipole contributions to allowed and first-forbidden transitions,"We propose formulas of the nuclear beta-decay rate that are useful in a
practical calculation. The decay rate is determined by the product of the
lepton and hadron current densities. A widely used formula relies upon the fact
that the low-energy lepton wave functions in a nucleus can be well approximated
by a constant and linear to the radius for the $s$-wave and $p$-wave wave
functions, respectively. We find, however, the deviation from such a simple
approximation is evident for heavy nuclei with large $Z$ by numerically solving
the Dirac equation. In our proposed formulas, the neutrino wave function is
treated exactly as a plane wave, while the electron wave function is obtained
by iteratively solving the integral equation, thus we can control the
uncertainty of the approximate wave function. The leading-order approximation
gives a formula equivalent to the conventional one and overestimates the decay
rate. We demonstrate that the next-to-leading-order formula reproduces well the
exact result for a schematic transition density as well as a microscopic one
obtained by a nuclear energy-density functional method.",2103.16815v1
2021-11-08,Phenomenological model for the electromagnetic response of a black hole binary immersed in magnetic field,"Electromagnetic counterparts of gravitational wave events usually involve
neutron stars during compact binary coalescences. On the other hand, the
community generally believes that electromagnetic emissions are hardly
generated during the mergers of binary black holes. Nevertheless, some authors
have considered the possibility of an EM counterpart signal after the GW150914,
opening the opportunity to investigate the electromagnetic emission of
stellar-mass black holes (BHs) mergers. In the case of black holes in a strong
magnetic field or with electric charges, electromagnetic emissions would appear
accompanied by gravitational waves. In this work, based on the membrane
paradigm, we consider a phenomenological model to study the electromagnetic
radiation generated by binary black holes surrounded by a uniform magnetic
field. We obtain the electromagnetic waveform detected by a far-distance
observer for varied black hole spins. By analytical Fourier transformation, we
get the chirp property of the electromagnetic waves; we found that the
power-law is 5/6, which has the opposite sign compared to gravitational waves.
The frequency of such electromagnetic waves is the same as gravitational waves.",2111.04323v1
2021-12-15,Principles of Gravitational-Wave Detection with Pulsar Timing Arrays,"Pulsar timing uses the highly stable pulsar spin period to investigate many
astrophysical topics. In particular, pulsar timing arrays make use of a set of
extremely well-timed pulsars and their time correlations as a challenging
detector of gravitational waves. It turns out that pulsar timing arrays are
particularly sensitive to ultra-low-frequency gravitational waves, which makes
them complementary to other gravitational-wave detectors. Here, we summarize
the basics, focusing especially on supermassive black-hole binaries and cosmic
strings, which have the potential to form a stochastic gravitational-wave
background in the pulsar timing array detection band, and the scientific goals
on this challenging topic. We also briefly outline the recent interesting
results of the main pulsar timing array collaborations, which have found strong
evidence of a common-spectrum process compatible with a stochastic
gravitational-wave background and mention some new perspectives that are
particularly interesting in view of the forthcoming radio observatories such as
the Five hundred-meter Aperture Spherical Telescope, the MeerKAT telescope, and
the Square Kilometer Array.",2112.08064v1
2022-02-18,The Fundamentality of Fields,"There is debate as to whether quantum field theory is, at bottom, a quantum
theory of fields or particles. One can take a field approach to the theory,
using wave functionals over field configurations, or a particle approach, using
wave functions over particle configurations. This article argues for a field
approach, presenting three advantages over a particle approach: (1) particle
wave functions are not available for photons, (2) a classical field model of
the electron gives a superior account of both spin and self-interaction as
compared to a classical particle model, and (3) the space of field wave
functionals appears to be larger than the space of particle wave functions. The
article also describes two important tasks facing proponents of a field
approach: (1) legitimize or excise the use of Grassmann numbers for fermionic
field values and in wave functional amplitudes, and (2) describe how quantum
fields give rise to particle-like behavior.",2202.09425v3
2022-10-13,Engineering Equifrequency Contours of Metasurfaces for Self-Collimated Surface Wave Steering,"Metasurfaces provide unique capability in guiding surface waves and
controlling their polarization and dispersion properties. One way to do that is
by analyzing their equifrequency contours. Equifrequency contours are the 2D
projection of the 3D dispersion diagram. Since they are a k-space map
representation of the surface, many of the wave properties can be understood
through the Equifrequency contours. In this paper, we investigate numerically
and experimentally the engineering of equifrequency contours using C-shape
metasurface design. We show the ability to provide high self-collimation as
well as spin-dependent wave splitting for the same metasurface by tuning the
frequency of operation. We also show the ability to steer the wave along a
defined curved path by rotating the C-shape which results in rotating its
equifrequency contours. This work demonstrates how engineering equifrequency
contours can be used as a powerful tool for controlling the surface wave
propagation properties.",2210.08999v1
2022-12-02,Gravitational wave from extreme mass-ratio inspirals as a probe of extra dimensions,"The field of gravitational waves is rapidly progressing due to the noticeable
advancements in the sensitivity of gravitational-wave detectors that has
enabled the detection prospects of binary black hole mergers. Extreme mass
ratio inspiral (EMRI) is one of the most compelling and captivating binary
systems in this direction, with the detection possibility by the future
space-based gravitational wave detector. In this article, we consider an EMRI
system where the primary or the central object is a spherically symmetric
static braneworld black hole that carries a \textit{tidal charge} $Q$. We
estimate the effect of the tidal charge on total gravitational wave flux and
orbital phase due to a non-spinning secondary inspiralling the primary. We
further highlight the observational implications of the tidal charge in EMRI
waveforms. We show that LISA (Laser Interferometer Space Antenna) observations
can put a much stronger constraint on this parameter than black hole shadow and
ground-based gravitational wave observations, which can potentially probe the
existence of extra dimensions.",2212.01404v2
2022-12-08,Acoustic-Driven Magnetic Skyrmion Motion,"Magnetic skyrmions have great potential for developing novel spintronic
devices. The electrical manipulation of skyrmions has mainly relied on
current-induced spin-orbit torques. A recent theoretical model suggested that
the skyrmions could be more efficiently manipulated by surface acoustic waves
(SAW), an elastic wave that can couple with magnetic moment through
magnetoelastic effect. However, the directional motion of skyrmions that is
driven by SAW is still missing. Here, we experimentally demonstrate the motion
of N\'eel-type skyrmions in Ta/CoFeB/MgO/Ta multilayers driven by propagating
SAW pulses from on-chip piezoelectric transducers. Our results reveal that the
elastic wave with longitudinal and shear vertical displacements (Rayleigh wave)
traps skyrmions, while the shear horizontal wave effectively drives the motion
of skyrmions. In particular, a longitudinal motion along the SAW propagation
direction and a transverse motion due to topological charge, are observed and
further confirmed by our micromagnetic simulations. This work demonstrates a
promising approach based on acoustic waves for manipulating skyrmions, which
could offer new opportunities for ultra-low power spintronics.",2212.04049v1
2023-07-11,Self-consistent interaction of linear gravitational and electromagnetic waves in non-magnetized plasma,"This paper explores the hybridization of linear metric perturbations with
linear electromagnetic (EM) perturbations in non-magnetized plasma for a
general background metric. The local wave properties are derived from first
principles for inhomogeneous plasma, without assuming any symmetries of the
background metric. First, we derive the effective (``oscillation-center'')
Hamiltonian that governs the average dynamics of plasma particles in a
prescribed quasimonochromatic wave that involves metric perturbations and EM
fields simultaneously. Then, using this Hamiltonian, we derive the backreaction
of plasma particles on the wave itself and obtain gauge-invariant equations
that describe the resulting self-consistent gravito-electromagnetic (GEM) waves
in a plasma. The transverse tensor modes of gravitational waves are found to
have no interaction with the plasma and the EM modes in the geometrical-optics
limit. However, for ``longitudinal"" GEM modes with large values of the
refraction index, the interplay between gravitational and EM interactions in
plasma can have a strong effect. In particular, the dispersion relation of the
Jeans mode is significantly affected by electrostatic interactions. As a
spin-off, our calculation also provides an alternative resolution of the
so-called Jeans swindle.",2307.05844v2
2023-09-16,Magneto-Acoustic Waves in antiferromagnetic CuMnAs excited by Surface Acoustic Waves,"Magnetoelastic effects in antiferromagnetic CuMnAs are investigated by
applying dynamic strain in the 0.01% range through surface acoustic waves in
the GaAs substrate. The magnetic state of the CuMnAs/GaAs is characterized by a
multitude of submicron-sized domains which we image by x-ray magnetic linear
dichroism combined with photoemission electron microscopy. Within the explored
strain range, CuMnAs shows magnetoelastic effects in the form of N\'eel vector
waves with micrometer wavelength, which corresponds to an averaged overall
spin-axis rotation up to 2.4 deg driven by the time-dependent strain from the
surface acoustic wave. Measurements at different temperatures indicate a
reduction of the wave amplitude when lowering the temperature. However, no
domain wall motion has been detected on the nanosecond timescale",2309.08893v1
2024-02-29,Quantum Bayesian Inference with Renormalization for Gravitational Waves,"Advancements in gravitational-wave interferometers, particularly the next
generation, are poised to profoundly impact gravitational wave astronomy and
multimessenger astrophysics. A hybrid quantum algorithm is proposed to carry
out quantum inference of parameters from compact binary coalescences detected
in gravitational-wave interferometers. It performs quantum Bayesian Inference
with Renormalization and Downsampling (qBIRD). We choose binary black hole
(BBH) mergers from LIGO observatories as the first case to test the algorithm,
but its application can be extended to more general instances. The quantum
algorithm is able to generate corner plots of relevant parameters such as chirp
mass, mass ratio, spins, etc. by inference of simulated gravitational waves
with known injected parameter values with zero noise, Gaussian noise and real
data, thus recovering an accuracy equivalent to that of classical Markov Chain
Monte Carlo inferences. The simulations are performed with sets of 2 and 4
parameters. These results enhance the possibilities to extend our capacity to
track signals from coalescences over longer durations and at lower frequencies
extending the accuracy and promptness of gravitational wave parameter
estimation.",2403.00846v1
1996-11-05,Low-Energy Properties of Regularly Depleted Spin Ladders,"We investigate a model for the regularly depleted two-leg spin ladder
systems. By using Lieb-Schultz-Mattis theorem, it is rigorously shown that this
model realizes massless excitations or, alternatively, a degenerate ground
state, although the original spin ladder system has a spin gap and a unique
ground state. The ground state of the depleted model is either a spin singlet
or partially ferromagnetic reflecting topological properties of the depleted
sites. In order to show that the low-energy excitations are indeed massless, we
proceed our analysis in two different ways by resorting to effective field
theories. We first investigate an effective weak-coupling model in terms of
renormalization group methods. Although the tendency to massless spin
excitations is seen in the strong coupling regime, it turns out that the model
is still massive for any finite coupling, implying that a conventional
weak-coupling approach is not efficient to describe massless modes in our
model. To overcome this difficulty, we further study low-energy properties of
the depleted spin model by mapping on the non-linear sigma model, and confirm
that the massless spin excitation indeed occur.",9611037v2
2001-12-16,Spin Coulomb drag in the two-dimensional electron liquid,"We calculate the spin-drag transresistivity $\rho_{\uparrow \downarrow}(T)$
in a two-dimensional electron gas at temperature $T$ in the random phase
approximation. In the low-temperature regime we show that, at variance with the
three-dimensional low-temperature result [$\rho_{\uparrow\downarrow}(T) \sim
T^2$], the spin transresistivity of a two-dimensional {\it spin unpolarized}
electron gas has the form $\rho_{\uparrow\downarrow}(T) \sim T^2 \ln T$. In the
spin-polarized case the familiar form $\rho_{\uparrow\downarrow}(T) =A T^2$ is
recovered, but the constant of proportionality $A$ diverges logarithmically as
the spin-polarization tends to zero. In the high-temperature regime we obtain
$\rho_{\uparrow \downarrow}(T) = -(\hbar / e^2) (\pi^2 Ry^* /k_B T)$ (where
$Ry^*$ is the effective Rydberg energy) {\it independent} of the density.
Again, this differs from the three-dimensional result, which has a logarithmic
dependence on the density. Two important differences between the spin-drag
transresistivity and the ordinary Coulomb drag transresistivity are pointed
out: (i) The $\ln T$ singularity at low temperature is smaller, in the Coulomb
drag case, by a factor $e^{-4 k_Fd}$ where $k_F$ is the Fermi wave vector and
$d$ is the separation between the layers. (ii) The collective mode contribution
to the spin-drag transresistivity is negligible at all temperatures. Moreover
the spin drag effect is, for comparable parameters, larger than the ordinary
Coulomb drag effect.",0112294v2
2005-07-22,The 5f localization/delocalization in square and hexagonal americium monolayers: A FP-LAPW electronic structure study,"The electronic and geometrical properties of bulk americium and square and
hexagonal americium monolayers have been studied with the full-potential
linearized augmented plane wave (FP-LAPW) method. The effects of several common
approximations are examined: (1) non-spin polarization (NSP) vs. spin
polarization (SP); (2) scalar-relativity (no spin-orbit coupling (NSO)) vs.
full-relativity (i.e., with spin-orbit (SO) coupling included); (3)
local-density approximation (LDA) vs. generalized-gradient approximation (GGA).
Our results indicate that both spin polarization and spin orbit coupling play
important roles in determining the geometrical and electronic properties of
americium bulk and monolayers. A compression of both americium square and
hexagonal monolayers compared to the americium bulk is also observed. In
general, the LDA is found to underestimate the equilibrium lattice constant and
give a larger total energy compared to the GGA calculations. While spin orbit
coupling shows a similar effect on both square and hexagonal monolayer
calculations regardless of the model, GGA versus LDA, an unusual spin
polarization effect on both square and hexagonal monolayers is found in the LDA
results as compared with the GGA results. The 5f delocalization transition of
americium is employed to explain our observed unusual spin polarization effect.
In addition, our results at the LDA level of theory indicate a possible 5f
delocalization could happen in the americium surface within the same Am II (fcc
crystal structure) phase, unlike the usually reported americium 5f
delocalization which is associated with crystal structure change. The
similarities and dissimilarities between the properties of an Am monolayer and
a Pu monolayer are discussed in detail.",0507536v1
2006-10-18,Frustrated impurity spins in ordered two-dimensional quantum antiferromagnets,"Dynamical properties of an impurity spin coupled symmetrically to sublattices
of ordered 2D Heisenberg quantum antiferromagnet (i.e., frustrated impurity
spin) are discussed at $T\ge0$ (existence of a small interaction stabilizing
the long range order at $T\ne0$ is implied). We continue our study on this
subject started in Phys.Rev.B 72, 174419 (2005), where spin-1/2 defect is
discussed and the host spins fluctuations are considered within the spin-wave
approximation (SWA). In the present paper we i) go beyond SWA and ii) study
impurities with spins $S\ge1/2$. It is demonstrated that in contrast to defects
coupled to sublattices asymmetrically longitudinal host spins fluctuations play
important role in the frustrated impurity dynamics. The spectral function, that
is proportional to $\omega^2$ within SWA, acquires new terms proportional to
$\omega^2$ and $\omega T^2$. It is observed that the spin-1/2 impurity
susceptibility has the same structure as that obtained within SWA: the Lorenz
peak and the non-resonant term. The difference is that the width of the peak
becomes larger being proportional to $f^2(T/J)^3$ rather than $f^4(T/J)^3$,
where $f$ is the dimensionless coupling parameter. We show that transverse
static susceptibility acquires a new negative logarithmic contribution. In
accordance with previous works we find that host spins fluctuations lead to an
effective one-ion anisotropy on the impurity site. Then defects with $S>1/2$
appears to be split. We observe strong reduction of the value of the splitting
due to longitudinal host spins fluctuations. We demonstrate that the dynamical
impurity susceptibility contains $2S$ Lorenz peaks corresponding to transitions
between the levels, and the non-resonant term.",0610506v1
2006-11-27,Spin-dependent electronic structure of transition-metal atomic chains adsorbed on single-wall carbon nanotubes,"We present a systematic study of the electronic and magnetic properties of
transition-metal (TM) atomic chains adsorbed on the zigzag single-wall carbon
nanotubes (SWNTs). We considered the adsorption on the external and internal
wall of SWNT and examined the effect of the TM coverage and geometry on the
binding energy and the spin polarization at the Fermi level. All those adsorbed
chains studied have ferromagnetic ground state, but only their specific types
and geometries demonstrated high spin polarization near the Fermi level. Their
magnetic moment and binding energy in the ground state display interesting
variation with the number of $d-$electrons of the TM atom. We also show that
specific chains of transition metal atoms adsorbed on a SWNT can lead to
semiconducting properties for the minority spin-bands, but semimetallic for the
majority spin-bands. Spin-polarization is maintained even when the underlying
SWNT is subjected to high radial strain. Spin-dependent electronic structure
becomes discretized when TM atoms are adsorbed on finite segments of SWNTs.
Once coupled with non-magnetic metal electrodes, these magnetic needles or
nanomagnets can perform as spin-dependent resonant tunnelling devices. The
electronic and magnetic properties of these nanomagnets can be engineered
depending on the type and decoration of adsorbed TM atom as well as the size
and symmetry of the tube. Our study is performed by using first-principles
pseudopotential plane wave method within spin-polarized Density Functional
Method.",0611670v1
2005-08-16,Transition from inspiral to plunge in precessing binaries of spinning black holes,"We investigate the non-adiabatic dynamics of spinning black hole binaries by
using an analytical Hamiltonian completed with a radiation-reaction force,
containing spin couplings, which matches the known rates of energy and angular
momentum losses on quasi-circular orbits. We consider both a straightforward
post-Newtonian-expanded Hamiltonian (including spin-dependent terms), and a
version of the resummed post-Newtonian Hamiltonian defined by the Effective
One-Body approach. We focus on the influence of spin terms onto the dynamics
and waveforms. We evaluate the energy and angular momentum released during the
final stage of inspiral and plunge. For an equal-mass binary the energy
released between 40Hz and the frequency beyond which our analytical treatment
becomes unreliable is found to be, when using the more reliable Effective
One-Body dynamics: 0.6% M for anti-aligned maximally spinning black holes, 5% M
for aligned maximally spinning black hole, and 1.8% M for non-spinning
configurations. In confirmation of previous results, we find that, for all
binaries considered, the dimensionless rotation parameter J/E^2 is always
smaller than unity at the end of the inspiral, so that a Kerr black hole can
form right after the inspiral phase. By matching a quasi-normal mode ringdown
to the last reliable stages of the plunge, we construct complete waveforms
approximately describing the gravitational wave signal emitted by the entire
process of coalescence of precessing binaries of spinning black holes.",0508067v1
1996-07-29,Velocity field and operator in (non relativistic) quantum mechanics,"Starting from the formal expressions of the hydrodynamical (or ``local'')
quantities employed in the applications of Clifford Algebras to quantum
mechanics, we introduce --in terms of the ordinary tensorial framework-- a new
definition for the field of a generic quantity. By translating from Clifford
into tensor algebra, we also propose a new (non-relativistic) velocity operator
for a spin 1/2 particle. This operator is the sum of the ordinary part p/m
describing the mean motion (the motion of the center-of-mass), and of a second
part associated with the so-called zitterbewegung, which is the spin
``internal'' motion observed in the center-of-mass frame. This spin component
of the velocity operator is non-zero not only in the Pauli theoretical
framework, i.e. in presence of external magnetic fields and spin precession,
but also in the Schroedinger case, when the wave-function is a spin eigenstate.
In the latter case, one gets a decomposition of the velocity field for the
Madelung fluid into two distinct parts: which constitutes the non-relativistic
analogue of the Gordon decomposition for the Dirac current. We find furthermore
that the zitterbewegung motion involves a velocity field which is solenoidal,
and that the local angular velocity is parallel to the spin vector. In presence
of a non-constant spin vector (Pauli case) we have, besides the component
normal to spin present even in the Schroedinger theory, also a component of the
local velocity which is parallel to the rotor of the spin vector.",9607214v1
2008-08-07,Quantum interference and spin-charge separation in a disordered Luttinger liquid,"We study the influence of spin on the quantum interference of interacting
electrons in a single-channel disordered quantum wire within the framework of
the Luttinger liquid (LL) model. The nature of the electron interference in a
spinful LL is particularly nontrivial because the elementary bosonic
excitations that carry charge and spin propagate with different velocities. We
extend the functional bosonization approach to treat the fermionic and bosonic
degrees of freedom in a disordered spinful LL on an equal footing. We analyze
the effect of spin-charge separation at finite temperature both on the spectral
properties of single-particle fermionic excitations and on the conductivity of
a disordered quantum wire. We demonstrate that the notion of weak localization,
related to the interference of multiple-scattered electron waves and their
decoherence due to electron-electron scattering, remains applicable to the
spin-charge separated system. The relevant dephasing length, governed by the
interplay of electron-electron interaction and spin-charge separation, is found
to be parametrically shorter than in a spinless LL. We calculate both the
quantum (weak localization) and classical (memory effect) corrections to the
conductivity of a disordered spinful LL. The classical correction is shown to
dominate in the limit of high temperature.",0808.1093v1
2009-07-09,"Artificial quantum-dot Helium molecules: Electronic spectra, spin structures, and Heisenberg clusters","Energy spectra and spin configurations of a system of N=4 electrons in
lateral double quantum dots (quantum dot Helium molecules) are investigated
using exact diagonalization (EXD), as a function of interdot separation,
applied magnetic field (B), and strength of interelectron repulsion. As a
function of the magnetic field, the energy spectra exhibit a low-energy band
consisting of a group of six states, with the number six being a consequence of
the conservation of the total spin and the ensuing spin degeneracies for four
electrons. The energies of the six states appear to cross at a single value of
the magnetic field, and with increasing Coulomb repulsion they tend to become
degenerate, with a well defined energy gap separating them from the
higher-in-energy excited states. The appearance of the low-energy band is a
consequence of the formation of a Wigner supermolecule, with the four electrons
(two in each dot) being localized at the vertices of a rectangle. Using
spin-resolved pair-correlation distributions, a method for mapping the
complicated EXD many-body wave functions onto simpler spin functions associated
with a system of four localized spins is introduced. Detailed interpretation of
the EXD spin functions and EXD spectra associated with the low-energy band via
a 4-site Heisenberg cluster (with B-dependent exchange integrals) is
demonstrated. Aspects of spin entanglement, referring to the well known N-qubit
Dicke states, are also discussed.",0907.1571v1
2009-12-22,Specific heat of stage-2 MnCl$_{2}$ graphite intercalation compound: co-existence of spin glass phase and incommensurate short-range spin order,"Stage-2 MnCl$_{2}$ GIC magnetically behaves like a quasi 2D $XY$
antiferromagnet on the triangular lattice. It shows a typical spin glass
behavior below the spin freezing temperature $T_{SG}$ (= 1.1 K). The AC
magnetic susceptibility shows a peak at $T$ = $T_{SG}$ at $H$ = 0. This peak
shifts to the low temperature side with increasing $H$, according to the de
Almeida-Thouless critical line. We have undertaken an extensive study on the
$T$ dependence of specific heat in the absence of an external field $H$ and in
the presence of $H$ along the $c$ plane. The magnetic specific heat $C_{mag}$
at $H$ = 0 shows no anomaly at $T_{SG}$, but exhibits double broad peaks around
5 K and 41 K. The magnetic specific heat $C_{mag}$ at $H$ = 0 is described by
$C_{mag} \propto (1/T^{2})\exp(-\Delta/T)$ with $\Delta = 1.41 \pm 0.03$ K,
while $C_{mag}$ at $H$ = 10 kOe is proportional to $T$. The entropy due to the
broad peak around 5 K is 1/3 of the total entropy. The residual entropy is 63 %
of the total entropy because of highly frustrated nature of the system. The
magnetic neutron scattering indicates that a short range spin order associated
with the incommensurate wave vector $| {\bf Q}_{incomm}|$ ($= 0.522 \AA^{-1}$
at 0.45 K) appears below 5 K and remains unchanged down to 63 mK. The in-plane
spin correlation length is only 18 $\AA$ at 0.45 K. The low temperature phase
below $T_{SG}$ is a kind of reentrant spin glass phase where the spin glass
phase coexists with a short range spin order associated with $| {\bf
Q}_{incomm}|$.",0912.4431v1
2013-03-19,Spectral evidence of a ghostly transition: Theory of NMR 1/T_1 relaxation in a quantum spin nematic in applied magnetic field,"There is now strong theoretical evidence that a wide range of frustrated
magnets should support quantum spin-nematic order in applied magnetic field.
Nonetheless, the fact that spin-nematic order does not break time-reversal
symmetry makes it very difficult to detect in experiment. In this article, we
continue the theme begun in [Phys. Rev. B 88, 184430 (2013)], of exploring how
spin-nematic order reveals itself in the spectrum of spin excitations. Building
on an earlier analysis of inelastic neutron scattering [Phys. Rev. B 91, 174402
(2015)], we show how the NMR 1/T_1 relaxation rate could be used to identify a
spin-nematic state. We emphasise the characteristic, universal features of
1/T_1, using a symmetry-based description of the spin-nematic order parameter
and its fluctuations.Turning to the specific case of spin-1/2 frustrated
ferromagnets, we show that the signal from competing spin-wave excitations can
be suppressed through a judicious choice of nuclear site and field direction.
As a worked example, we show how P NMR in the square-lattice frustrated
ferromagnet BaCdVO(PO_4)_2 is sensitive to spin-nematic order.",1303.4465v3
2013-11-05,Heavy quarkonium potential from Bethe-Salpeter wave function on the lattice,"We propose a novel method for the determination of the interquark potential
together with quark ""kinetic mass'' $m_Q$ from the equal-time $Q\bar{Q}$
Bethe-Salpeter (BS) amplitude in lattice QCD. Our approach allows us to
calculate spin-dependent $Q\bar{Q}$ potentials, e.g. the spin-spin potential,
as well. In order to investigate several systematic uncertainties on such
$Q\bar{Q}$ potentials, we carry out lattice QCD simulations using quenched
gauge configurations generated with the single plaquette gauge action with
three different lattice spacings, $a \approx$ 0.093, 0.068 and 0.047 fm, and
two different physical volumes, $L \approx$ 2.2 and 3.0 fm. For heavy quarks,
we employ the relativistic heavy quark (RHQ) action which can control large
discretization errors introduced by large quark mass $m_Q$. The
spin-independent central $Q\bar{Q}$ potential for the charmonium system yields
the ""Coulomb plus linear'' behavior with good scaling and small volume
dependence. We explore the quark mass dependence over the wide mass range from
the charm to beyond the bottom region, and then demonstrate that the
spin-independent central $Q\bar{Q}$ potential in the $m_Q \to \infty$ limit is
fairly consistent with the static $Q\bar{Q}$ potential obtained from Wilson
loops. The spin-spin potential at finite quark mass provides a repulsive
interaction with a finite range, which becomes narrower as the quark mass
increases. We also discuss the applicability of the $1/m_Q$ expansion approach
for the spin-spin potential.",1311.1253v1
2014-09-25,Bloch-Landau-Zener dynamics in single-particle Wannier-Zeeman systems,"Stimulated by the experimental realization of spin-dependent tunneling via
gradient magnetic field [Phys. Rev. Lett. 111, 225301 (2013); Phys. Rev. Lett.
111, 185301 (2013)], we investigate dynamics of Bloch oscillations and
Landau-Zener tunneling of single spin-half particles in a periodic potential
under the influence of a spin-dependent constant force. In analogy to the
Wannier-Stark system, we call our system as the Wannier-Zeeman system. If there
is no coupling between the two spin states, the system can be described by two
crossing Wannier-Stark ladders with opposite tilts. The spatial crossing
between two Wannier-Stark ladders becomes a spatial anti-crossing if the two
spin states are coupled by external fields. For a wave-packet away from the
spatial anti-crossing, due to the spin-dependent constant force, it will
undergo spatial Landau-Zener transitions assisted by the intrinsic intra-band
Bloch oscillations, which we call the Bloch-Landau-Zener dynamics. If the
inter-spin coupling is sufficiently strong, the system undergoes adiabatic
Bloch-Landau-Zener dynamics, in which the spin dynamics follows the local
dressed states. Otherwise, for non-strong inter-spin couplings, the system
undergoes non-adiabatic Bloch-Landau-Zener dynamics.",1409.7262v3
2015-01-30,Searches for the role of spin and polarization in gravity: a five-year update,"Searches for the role of spin in gravitation dated before the firm
establishment of the electron spin in 1925. Since mass and spin, or helicity in
the case of zero mass, are the Casimir invariants of the Poincar\'e group and
mass participates in universal gravitation, these searches are natural steps to
pursue. In this update, we report on the progress on this topic in the last
five years after our last review. We begin with how is Lorentz/Poincar\'e group
in local physics arisen from spacetime structure as seen by photon and matter
through experiments/observations. The cosmic verification of the Galileo
Equivalence Principle for photons/electromagnetic wave packets (Universality of
Propagation in spacetime independent of photon energy and polarization, i.e.
nonbirefringence) constrains the spacetime constitutive tensor to high
precision to a core metric form with an axion degree and a dilaton degree of
freedom. Hughes-Drever-type experiments then constrain this core metric to
agree with the matter metric. Thus comes the metric with axion and dilation. In
local physics this metric gives the Lorentz/Poincar\'e covariance. Constraints
on axion and dilaton from polarized/unpolarized laboratory/astrophysical/cosmic
experiments/observations are presented. In the end, we review the theoretical
progress on the issue of gyrogravitational ratio for fundamental particles and
the experimental progress on the measurements of possible long
range/intermediate range spin-spin, spin-monopole and spin-cosmos interactions.",1501.07696v1
2015-06-14,Few-second-long correlation times in a quantum dot nuclear spin bath probed by frequency-comb NMR spectroscopy,"One of the key challenges in spectroscopy is inhomogeneous broadening that
masks the homogeneous spectral lineshape and the underlying coherent dynamics.
A variety of techniques including four-wave mixing and spectral hole-burning
are used in optical spectroscopy while in nuclear magnetic resonance (NMR)
spin-echo is the most common way to counteract inhomogeneity. However, the
high-power pulses used in spin-echo and other sequences often create spurious
dynamics obscuring the subtle spin correlations that play a crucial role in
quantum information applications. Here we develop NMR techniques that allow the
correlation times of the fluctuations in a nuclear spin bath of individual
quantum dots to be probed. This is achieved with the use of frequency comb
excitation which allows the homogeneous NMR lineshapes to be measured avoiding
high-power pulses. We find nuclear spin correlation times exceeding 1 s in
self-assembled InGaAs quantum dots - four orders of magnitude longer than in
strain-free III-V semiconductors. The observed freezing of the nuclear spin
fluctuations opens the way for the design of quantum dot spin qubits with a
well-understood, highly stable nuclear spin bath.",1506.04412v1
2015-07-29,Spin dynamics and relaxation in the classical-spin Kondo-impurity model beyond the Landau-Lifschitz-Gilbert equation,"The real-time dynamics of a classical spin in an external magnetic field and
locally exchange coupled to an extended one-dimensional system of
non-interacting conduction electrons is studied numerically. Retardation
effects in the coupled electron-spin dynamics are shown to be the source for
the relaxation of the spin in the magnetic field. Total energy and spin is
conserved in the non-adiabatic process. Approaching the new local ground state
is therefore accompanied by the emission of dispersive wave packets of
excitations carrying energy and spin and propagating through the lattice with
Fermi velocity. While the spin dynamics in the regime of strong exchange
coupling J is rather complex and governed by an emergent new time scale, the
motion of the spin for weak J is regular and qualitatively well described by
the Landau-Lifschitz-Gilbert (LLG) equation. Quantitatively, however, the full
quantum-classical hybrid dynamics differs from the LLG approach. This is
understood as a breakdown of weak-coupling perturbation theory in J in the
course of time. Furthermore, it is shown that the concept of the Gilbert
damping parameter is ill-defined for the case of a one-dimensional system.",1507.08227v2
2016-01-27,Canonical Hamiltonian for an extended test body in curved spacetime: To quadratic order in spin,"We derive a Hamiltonian for an extended spinning test body in a curved
background spacetime, to quadratic order in the spin, in terms of
three-dimensional position, momentum, and spin variables having canonical
Poisson brackets. This requires a careful analysis of how changes of the spin
supplementary condition are related to shifts of the body's representative
worldline and transformations of the body's multipole moments, and we employ
bitensor calculus for a precise framing of this analysis. We apply the result
to the case of the Kerr spacetime and thereby compute an explicit canonical
Hamiltonian for the test-body limit of the spinning two-body problem in general
relativity, valid for generic orbits and spin orientations, to quadratic order
in the test spin. This fully relativistic Hamiltonian is then expanded in
post-Newtonian orders and in powers of the Kerr spin parameter, allowing
comparisons with the test-mass limits of available post-Newtonian results. Both
the fully relativistic Hamiltonian and the results of its expansion can inform
the construction of waveform models, especially effective-one-body models, for
the analysis of gravitational waves from compact binaries.",1601.07529v3
2016-05-09,Electron doping evolution of the magnetic excitations in NaFe$_{1-x}$Co$_x$As,"We use time-of-flight (ToF) inelastic neutron scattering (INS) spectroscopy
to investigate the doping dependence of magnetic excitations across the phase
diagram of NaFe$_{1-x}$Co$_x$As with $x=0, 0.0175, 0.0215, 0.05,$ and $0.11$.
The effect of electron-doping by partially substituting Fe by Co is to form
resonances that couple with superconductivity, broaden and suppress low energy
($E\le 80$ meV) spin excitations compared with spin waves in undoped NaFeAs.
However, high energy ($E> 80$ meV) spin excitations are weakly Co-doping
dependent. Integration of the local spin dynamic susceptibility
$\chi^{\prime\prime}(\omega)$ of NaFe$_{1-x}$Co$_x$As reveals a total
fluctuating moment of 3.6 $\mu_B^2$/Fe and a small but systematic reduction
with electron doping. The presence of a large spin gap in the Co-overdoped
nonsuperconducting NaFe$_{0.89}$Co$_{0.11}$As suggests that Fermi surface
nesting is responsible for low-energy spin excitations. These results parallel
Ni-doping evolution of spin excitations in BaFe$_{2-x}$Ni$_x$As$_2$, confirming
the notion that low-energy spin excitations coupling with itinerant electrons
are important for superconductivity, while weakly doping dependent high-energy
spin excitations result from localized moments.",1605.02695v1
2017-09-08,Magnetoconductance correction in zinc-blende semiconductor nanowires with spin-orbit coupling,"We study the effects of spin-orbit coupling on the magnetoconductivity in
diffusive cylindrical semiconductor nanowires. Following up on our former study
on tubular semiconductor nanowires, we focus in this paper on nanowire systems
where no surface accumulation layer is formed but instead the electron wave
function extends over the entire cross section. We take into account the
Dresselhaus spin-orbit coupling resulting from a zinc-blende lattice and the
Rashba spin-orbit coupling, which is controlled by a lateral gate electrode.
The spin relaxation rate due to Dresselhaus spin-orbit coupling is found to
depend neither on the spin density component nor on the wire growth direction
and is unaffected by the radial boundary. In contrast, the Rashba spin
relaxation rate is strongly reduced for a wire radius that is smaller than the
spin precession length. The derived model is fitted to the data of
magnetoconductance measurements of a heavily doped back-gated InAs nanowire and
transport parameters are extracted. At last, we compare our results to previous
theoretical and experimental studies and discuss the occurring discrepancies.",1709.02621v2
2012-09-08,Spin-dominated waveforms for unequal mass compact binaries,"We derive spin-dominated waveforms (SDW) for binary systems composed of
spinning black holes with unequal masses (less than 1:30). Such systems could
be formed by an astrophysical black hole with a smaller black hole or a neutron
star companion; and typically arise for supermassive black hole encounters. SDW
characterize the last stages of the inspiral, when the larger spin dominates
over the orbital angular momentum (while the spin of the smaller companion can
be neglected). They emerge as a double expansion in the post-Newtonian
parameter $\varepsilon$ and the ratio $\xi $ of the orbital angular momentum
and dominant spin. The SDW amplitudes are presented to
($\varepsilon^{3/2},\xi$) orders, while the phase of the gravitational waves to
($\varepsilon^{2},\xi$) orders (omitting the highest order mixed terms). To
this accuracy the amplitude includes the (leading order) spin-orbit
contributions, while the phase the (leading order) spin-orbit, self-spin and
mass quadrupole-monopole contributions. While the SDW hold for any mass ratio
smaller than 1:30, lower bounds for the mass ratios are derived from the best
sensitivity frequency range expected for Advanced LIGO (giving 1:140), the
Einstein Telescope ($7\times 10^{-4}$), the LAGRANGE ($7\times 10^{-7}$) and
LISA missions ($7\times 10^{-9}$), respectively.",1209.1722v2
2012-09-27,"Magnetic order, magnetic correlations and spin dynamics in the pyrochlore antiferromagnet Er2Ti2O7","Er2Ti2O7 is believed to be a realization of an XY antiferromagnet on a
frustrated lattice of corner-sharing regular tetrahedra. It is presented as an
example of the order-by-disorder mechanism in which fluctuations lift the
degeneracy of the ground state, leading to an ordered state. Here we report
detailed measurements of the low temperature magnetic properties of Er2Ti2O7,
which displays a second-order phase transition at T_N \simeq 1.2 K with
coexisting short- and long-range orders. Magnetic-susceptibility studies show
that there is no spin-glass-like irreversible effect. Heat-capacity
measurements reveal that the paramagnetic critical exponent is typical of a
3-dimensional XY magnet while the low-temperature specific heat sets an upper
limit on the possible spin-gap value and provides an estimate for the spin-wave
velocity. Muon spin relaxation measurements show the presence of spin dynamics
in the nanosecond time scale down to 21 mK. This time range is intermediate
between the shorter time characterizing the spin dynamics in Tb2Sn2O7, which
also displays long- and short-range magnetic order, and the time scale typical
of conventional magnets. Hence the ground state is characterized by exotic spin
dynamics. We determine the parameters of a symmetry-dictated Hamiltonian
restricted to the spins in a tetrahedron, by fitting the paramagnetic diffuse
neutron scattering intensity for two reciprocal lattice planes. These data are
recorded in a temperature region where the assumption that the correlations are
limited to nearest neighbors is fair.",1209.6153v1
2014-06-02,Dzyaloshinskii-Moriya interaction and chiral magnetism in 3$d$-5$d$ zig-zag chains: Tight-binding model and ab initio calculations,"We investigate the chiral magnetic order in free-standing planar 3$d$-5$d$
bi-atomic metallic chains (3$d$: Fe, Co; 5$d$: Ir, Pt, Au) using
first-principles calculations based on density functional theory. We found that
the antisymmetric exchange interaction, commonly known as Dzyaloshinskii-Moriya
interaction (DMI), contributes significantly to the energetics of the magnetic
structure. We used the full-potential linearized augmented plane wave method
and performed self-consistent calculations of homogeneous spin spirals,
calculating the DMI by treating the effect of spin-orbit interaction (SOI) in
the basis of the spin-spiral states in first-order perturbation theory. To gain
insight into the DMI results of our ab initio calculations, we develop a
minimal tight-binding model of three atoms and 4 orbitals that contains all
essential features: the spin-canting between the magnetic $3d$ atoms, the
spin-orbit interaction at the $5d$ atoms, and the structure inversion asymmetry
facilitated by the triangular geometry. We found that spin-canting can lead to
spin-orbit active eigenstates that split in energy due to the spin-orbit
interaction at the $5d$ atom. We show that, the sign and strength of the
hybridization, the bonding or antibonding character between $d$-orbitals of the
magnetic and non-magnetic sites, the bandwidth and the energy difference
between states occupied and unoccupied states of different spin projection
determine the sign and strength of the DMI. The key features observed in the
trimer model are also found in the first-principles results.",1406.0294v1
2017-03-20,Are LIGO's Black Holes Made From Smaller Black Holes?,"One proposed formation channel for stellar mass black holes (BHs) is through
hierarchical mergers of smaller BHs. Repeated mergers between comparable mass
BHs leave an imprint on the spin of the resulting BH, since the final BH spin
is largely determined by the orbital angular momentum of the binary. We find
that for stellar mass BHs forming hierarchically the distribution of spin
magnitudes is universal, with a peak at $a \sim 0.7$ and little support below
$a \sim 0.5$. We show that the spin distribution is robust against changes to
the mass ratio of the merging binaries, the initial spin distribution of the
first generation of BHs, and the number of merger generations. While we assume
an isotropic distribution of initial spin directions, spins that are
preferentially aligned or antialigned do not qualitatively change our results.
We also consider a ""cluster catastrophe"" model for BH formation in which we
allow for mergers of arbitrary mass ratios and show that this scenario predicts
a unique spin distribution that is similar to the universal distribution
derived for major majors. We explore the ability of spin measurements from
ground-based gravitational-wave (GW) detectors to constrain hierarchical merger
scenarios. We apply a hierarchical Bayesian mixture model to mock GW data and
argue that the fraction of BHs that formed through hierarchical mergers will be
constrained with $\mathcal{O}(100)$ LIGO binary black hole detections, while
with $\mathcal{O}(10)$ detections we could falsify a model in which all
component BHs form hierarchically.",1703.06869v3
2019-08-28,Interplay of spin and mass superfluidity in antiferromagnetic spin-1 BEC and bicirculation vortices,"The paper investigates the coexistence and interplay of spin and mass
superfluidity in the antiferromagnetic spin-1 BEC. The hydrodynamical theory
describes the spin degree of freedom by the equations similar to the
Landau--Lifshitz--Gilbert theory for bipartite antiferromagnetic insulator. The
variables in the spin space are two subspins with absolute value $\hbar/2$,
which play the role of two sublattice spins in the antiferromagnetic
insulators. As well as in bipartite antiferromagnetic insulators, in the
antiferromagnetic spin-1 BEC there are two spin-wave modes, one is a gapless
Goldstone mode, another is gapped. The Landau criterion shows that in limit of
small total spin (two subspins are nearly antiparallel) instability of
supercurrents starts from the gapped mode. In the opposite limit of large total
spin (two subspins are nearly parallel) the gapless modes become unstable
earlier than the gapped one. Mass and spin supercurrents decay via phase slips,
when vortices cross streamlines of supercurrent. The vortices participating in
phase slips are nonsingular bicirculation vortices. They are characterized by
two topological charges, which are winding numbers describing circulations of
two angles around the vortex axis. The winding numbers can be half-integer. A
particular example of a half-integer vortex is a half-quantum vortex with the
superfluid velocity circulation $h/2m$. But the superfluid velocity circulation
is not a topological charge, and in general the quantum of this circulation can
be continuously tuned from 0 to $h/2m$.",1908.10633v2
2020-06-04,Polarized electron-deuteron deep-inelastic scattering with spectator nucleon tagging,"Background: DIS on the polarized deuteron with detection of a proton in the
nuclear breakup region (spectator tagging) represents a unique method for
extracting the neutron spin structure functions and studying nuclear
modifications. The tagged proton momentum controls the nuclear configuration
during the DIS process and enables a differential analysis of nuclear effects.
Such measurements could be performed with the future electron-ion collider
(EIC) and forward proton detectors if deuteron beam polarization could be
achieved.
  Purpose: Develop theoretical framework for polarized deuteron DIS with
spectator tagging. Formulate procedures for neutron spin structure extraction.
  Methods: A covariant spin density matrix formalism is used to describe
general deuteron polarization in collider experiments (vector/tensor,
pure/mixed). Light-front (LF) quantum mechanics is employed to factorize
nuclear and nucleonic structure in the DIS process. A 4-dimensional
representation of LF spin structure is used to construct the polarized deuteron
LF wave function and efficiently evaluate the spin sums. Free neutron structure
is extracted using the impulse approximation and analyticity in the tagged
proton momentum (pole extrapolation).
  Results: General expressions of the polarized tagged DIS observables in
collider experiments. Analytic and numerical study of the polarized deuteron LF
spectral function and nucleon momentum distributions. Practical procedures for
neutron spin structure extraction from the tagged deuteron spin asymmetries.
  Conclusions: Spectator tagging provides new tools for precise neutron spin
structure measurements. D-wave depolarization and nuclear binding effects can
be eliminated through the tagged proton momentum dependence. The methods can be
extended to tensor-polarized observables, spin-orbit effects, and diffractive
processes.",2006.03033v1
2020-12-04,Stability of supercurrents in a superfluid phase of spin-1 bosons in an optical lattice,"We study collective modes and superfluidity of spin-1 bosons with
antiferromagnetic interactions in an optical lattice based on the
time-dependent Ginzburg-Landau (TDGL) equation derived from the spin-1
Bose-Hubbard model. Specifically, we examine the stability of supercurrents in
the polar phase in the vicinity of the Mott insulating phase with even filling
factors. Solving the linearized TDGL equation, we obtain gapless spin-nematic
modes and gapful spin-wave modes in the polar phase that arise due to the
breaking of $S^2$ symmetry in spin space. Supercurrents exhibit dynamical
instabilities induced by growing collective modes. In contrast to the
second-order phase transition, the critical momentum of mass currents is finite
at the phase boundary of the first-order superfluid-Mott insulator (SF-MI)
phase transition. Furthermore, the critical momentum remains finite throughout
the metastable SF phase and approaches zero towards the phase boundary, at
which the metastable SF state disappears. We also study the stability of spin
currents motivated by recent experiments for spinor gases. The critical
momentum of spin currents is found to be zero, where a spin-nematic mode causes
the dynamical instability. We investigate the origin of the zero critical
momentum of spin currents and find it attributed to the fact that the polar
state becomes energetically unstable even in the presence of an infinitesimal
spin current. We discuss implications of the zero critical momentum of spin
currents for the stability of the polar state.",2012.02501v2
2021-01-27,Response to Comment on: Tunneling in DNA with Spin Orbit coupling,"The comment by O. Entin-Wohlman, A. Aharony, and Y. Utsumi, on our paper S.
Varela, I. Zambrano, B. Berche, V. Mujica, and E. Medina, Phys. Rev. B 101,
241410(R) (2020) makes a few points related to the validity of our model,
especially in the light of the interpretation of Bardarson's theorem: ""in the
presence of time reversal symmetry and for half-integral spin the transmission
eigenvalues of the two terminal scattering matrix come in (Kramers) degenerate
pairs"". The authors of the comment first propose an ansatz for the wave
function in the spin active region and go on to show that the resulting
transmission does not show spin dependence, reasoning that spin dependence
would violate Bardarson's assertion. Here we clearly show that the ansatz
presented assumes spin-momentum independence from the outset and thus just
addresses the spinless particle problem. We then find the appropriate
eigenfunction contemplating spin-momentum coupling and show that the resulting
spectrum obeys Bardarson's theorem. Finally we show that the allowed
wavevectors are the ones assumed in the original paper and thus the original
conclusions follow. We recognize that the Hamiltonian in our paper written in
local coordinates on a helix was deceptively simple and offer the expressions
of how it should be written to more overtly convey the physics involved. The
relation between spin polarization and torque becomes clear, as described in
our paper. This response is a very important clarification in relation to the
implications of Bardarson's theorem concerning the possibility of spin
polarization in one dimensional systems in the linear regime.",2101.11271v1
2021-06-02,Black hole induced spins from hyperbolic encounters in dense clusters,"The black holes that have been detected via gravitational waves (GW) can have
either astrophysical or primordial origin. Some GW events show significant spin
for one of the components and have been assumed to be astrophysical, since
primordial black holes are generated with very low spins. However, it is worth
studying if they can increase their spin throughout the evolution of the
universe. Possible mechanisms that have already been explored are multiple
black hole mergers and gas accretion. We propose here a new mechanism that can
occur in dense clusters of black holes: the spin-up of primordial black holes
when they are involved in close hyperbolic encounters. We explore this effect
numerically with the Einstein Toolkit for different initial conditions,
including variable mass ratios. For equal masses, there is a maximum spin that
can be induced on the black holes, $\chi = a/m \leq 0.2$. We find however that
for large mass ratios one can attain spins up to $\chi \simeq 0.8$, where the
highest spin is induced on the most massive black hole. For small induced spins
we provide simple analytical expressions that depend on the relative velocity
and impact parameter.",2106.01436v2
2021-09-18,Spin and quadrupole correlations by three-spin interaction in the frustrated pyrochlore magnet Tb$_{2+x}$Ti$_{2-x}$O$_{7+y}$,"We have investigated the origin of the magnetic dipole correlations $\langle
\sigma_{\boldsymbol{Q}}^z \sigma_{\boldsymbol{-Q}}^z \rangle$ characterized by
the modulation wave vector $\boldsymbol{k} \sim
(\tfrac{1}{2},\tfrac{1}{2},\tfrac{1}{2})$ observed in the frustrated pyrochlore
magnet Tb$_{2+x}$Ti$_{2-x}$O$_{7+y}$. This magnetic short-range order cannot be
accounted for by adding further-neighbor exchange interactions to the
nearest-neighbor pseudospin-$\tfrac{1}{2}$ Hamiltonian for quantum pyrochlore
magnets. Using classical Monte Carlo simulation and quantum simulation based on
thermally pure quantum (TPQ) states we have shown that the spin correlations
with $\boldsymbol{k} \sim (\tfrac{1}{2},\tfrac{1}{2},\tfrac{1}{2})$ are induced
at low temperatures by a three-spin interaction of a form
$\sigma_{\boldsymbol{r}}^{\pm} \sigma_{\boldsymbol{r}^{\prime}}^z
\sigma_{\boldsymbol{r}^{\prime \prime}}^z $, which is a correction to the
Hamiltonian due to the low crystal-field excitation. Simulations using TPQ
states have shown that the spin correlations coexist with electric quadrupole
correlations $\langle \sigma_{\boldsymbol{Q}}^{\alpha}
\sigma_{\boldsymbol{-Q}}^{\beta} \rangle$ ($\alpha, \beta = x, y$) with
$\boldsymbol{k} \sim \boldsymbol{0}$. These results suggest that the putative
quantum spin liquid state of Tb$_{2+x}$Ti$_{2-x}$O$_{7+y}$ is located close to
phase boundaries of the spin-ice, quadrupole-ordered, and magnetic-ordered
states in the classical approximation, and that the three-spin interaction
brings about a quantum disordered ground state with both spin and quadrupole
correlations.",2109.08799v1
2022-01-31,Precisely computing bound orbits of spinning bodies around black holes II: Generic orbits,"In this paper, we continue our study of the motion of spinning test bodies
orbiting Kerr black holes. Non-spinning test bodies follow geodesics of the
spacetime in which they move. A test body's spin couples to the curvature of
that spacetime, introducing a ""spin-curvature force"" which pushes the body's
worldline away from a geodesic trajectory. The spin-curvature force is an
important example of a post-geodesic effect which must be modeled carefully in
order to accurately characterize the motion of bodies orbiting black holes. One
motivation for this work is to understand how to include such effects in models
of gravitational waves produced from the inspiral of stellar mass bodies into
massive black holes. In this paper's predecessor, we describe a technique for
computing bound orbits of spinning bodies around black holes with a
frequency-domain description which can be solved very precisely. In that paper,
we present an overview of our methods, as well as present results for orbits
which are eccentric and nearly equatorial (i.e., the orbit's motion is no more
than $\mathcal{O}(S)$ out of the equatorial plane). In this paper, we apply
this formulation to the fully generic case -- orbits which are inclined and
eccentric, with the small body's spin arbitrarily oriented. We compute the
trajectories which such orbits follow, and compute how the small body's spin
affects important quantities such as the observable orbital frequencies
$\Omega_r$, $\Omega_\theta$ and $\Omega_\phi$.",2201.13335v2
2022-03-04,Suspicious Siblings: The Distribution of Mass and Spin Across Component Black Holes in Isolated Binary Evolution,"The LIGO and Virgo gravitational-wave detectors have uncovered binary black
hole systems with definitively nonzero spins, as well as systems with
significant spin residing in the more massive black hole of the pair. We
investigate the ability of isolated binary evolution in forming such highly
spinning, asymmetric-mass systems through both accretion onto the first-born
black hole and tidal spin-up of the second-born black hole using a rapid
population synthesis approach with detailed considerations of spin-up through
tidal interactions. Even with the most optimistic assumptions regarding the
efficiency at which an accreting star receives material from a donor, we find
that it is difficult to form systems with significant mass asymmetry and
moderate or high spins in the primary black hole component. Assuming efficient
angular momentum transport within massive stars and Eddington-limited accretion
onto black holes, we find that $< 1.5\%$ of systems in the underlying binary
black hole population have a primary black hole spin greater than 0.2 and a
mass asymmetry of greater than 2:1 in our most optimistic models, with most
models finding that this criteria is only met in $\sim 0.01\%$ of systems. The
production of systems with significant mass asymmetries and spin in the primary
black hole component is thus an unlikely byproduct of isolated evolution unless
highly super-Eddington accretion is invoked or angular momentum transport in
massive stars is less efficient than typically assumed.",2203.02515v3
2022-03-28,Four-Vector Optical Dirac Equation and Spin-Orbit Interaction of Structured Light,"The spin-orbit interaction of light is a crucial concept for understanding
the electromagnetic properties of a material and realizing the spin-controlled
manipulation of optical fields. Achieving these goals requires a complete
description of spin-dependent optical phenomena in the context of vector-wave
mechanics. We develop an extended Dirac theory for optical fields in generic
media, which was found to be akin to a non-Hermitian chiral-extension of
massive fermions with anomalous magnetic momenta moving in an external
pseudo-magnetic field. This similarity allows us to investigate the optical
behaviors of a material by effective field theory methods and can find wide
applications in metamaterials, photonic topological insulators, etc. We
demonstrate this method by studying the spin-orbit interaction of structured
light in a spin-degenerate medium and inhomogeneous isotropic medium, which
leads to both spin-orbital-Hall effects and spin-to-orbital angular momentum
conversion. Of importance, our approach provides simple and clear physical
insight into the spin-orbit interaction of light in generic media, and could
potentially bridge our understanding of topological insulators between
electronic and photonic systems.",2203.14664v3
2022-04-07,Momentum domain polarization probing of forward and inverse spin Hall effect of leaky modes in plasmonic crystals,"Simultaneous manifestation of both forward and inverse photonic Spin Hall
effect in geometrically tailored anisotropic waveguided plasmonic crystal
system is observed through the excitation of the leaky hybridized quasiguided
modes. The quasiguided modes of the plasmonic crystal manifested in the
far-field momentum (Fourier) domain as circular ring-like intensity
distributions, and the different spin orbit interaction (SOI) effects revealed
their exclusive signature as polarization-dependent azimuthal intensity lobes
on top of it. Using a darkfield Fourier domain polarization Mueller matrix
platform, we have observed input spin (circular polarization)- dependent
trajectory of the leaky quasiguided modes in the momentum domain (forward spin
Hall effect) and its reciprocal effect as the wave vector-controlled spin
selection of quasiguided modes (inverse spin Hall effect). These effects are
separately manifested in characteristic Mueller matrix elements enabling their
interpretation as geometrical circular anisotropy effects. Resonance-enabled
enhancement and control of these effects are also demonstrated by exploiting
the spectral Fano-type resonance. The far-field manifestation of
spin-directional excitation of leaky quasiguided modes, their unique
interpretation through momentum domain Mueller matrix, regulation and control
of the SOI effects in plasmonic-photonic crystal systems, opens up exciting
avenues in spin-orbit photonic research.",2204.03699v3
2022-09-18,The causality and stability of relativistic spin-hydrodynamics,"We study the causality and stability of relativistic hydrodynamics with the
inclusion of the spin degree of freedom as a hydrodynamic field. We consider
two specific models of spin-hydrodynamics for this purpose. A linear mode
analysis for static background shows that a first-order dissipative
spin-hydrodynamics remains acausal and admits instabilities. Besides, it is
found that the inclusion of the spin field in hydrodynamics leads to new kinds
of linear modes in the system. These new modes also exhibit instability and
acausal behavior. The second model of the spin-hydrodynamics that we have
considered here is equivalent to a particular second-order conventional
hydrodynamics with no dissipative effects. For a static background, it is found
that the linear modes of this model support the sound waves only. However, when
the background has constant vorticity, then the model admits instability and
acausality in certain situations. It is found that the spin-dynamics have an
effect on the hydrodynamic response of the fluid. These findings point toward
the need for a causal and stable theory with spin as a hydrodynamic field to
describe the spin-polarized fluid.",2209.08652v2
2022-11-02,Spin pumping by a moving domain wall at the interface of an antiferromagnetic insulator and a two-dimensional metal,"A domain wall (DW) which moves parallel to a magnetically compensated
interface between an antiferromagnetic insulator (AFMI) and a two-dimensional
(2D) metal can pump spin polarization into the metal. It is assumed that
localized spins of a collinear AFMI interact with itinerant electrons through
their exchange interaction on the interface. We employed the formalism of
Keldysh Green's functions for electrons which experience potential and
spin-orbit scattering on random impurities. This formalism allows a unified
analysis of spin pumping, spin diffusion and spin relaxation effects on a 2D
electron gas. It is shown that the pumping of a nonstaggered magnetization into
the metal film takes place in the second order with respect to the interface
exchange interaction. At sufficiently weak spin relaxation this pumping effect
can be much stronger than the first-order effect of the Pauli magnetism which
is produced by the small nonstaggered exchange field of the DW. It is shown
that the pumped polarization is sensitive to the geometry of the electron's
Fermi surface and increases when the wave vector of the staggered magnetization
approaches the nesting vector of the Fermi surface. In a disordered diffusive
electron gas the induced spin polarization follows the motion of the domain
wall. It is distributed asymmetrically around the DW over a distance which can
be much larger than the DW width.",2211.01195v2
2023-04-28,Interplay of electron-magnon scattering and spin-orbit induced electronic spin-flip fcattering in a two-band Stoner model,"Magnons are one of the carriers of angular momentum that are involved in the
ultrafast magnetization dynamics in ferromagnets, but their contribution to the
electronic dynamics and their interplay with other scattering process that
occur during ultrafast demagnetization has not yet been studied in the
framework of a microscopic dynamical model. The present paper presents such an
investigation of electronic scattering dynamics in itinerant ferromagnets at
the level of Boltzmann scattering integrals for the magnon distributions and
spin-dependent electron distributions. In addition to electron-magnon
scattering, we include spin-conserving and effective Elliott-Yafet like
spin-flip electron-electron scattering processes and the influence of phonons.
In our model system, the creation or annihilation of magnons leads to
transitions between two spin-split electronic bands with energy and momentum
conservation. Due to the presence of spin-orbit coupling, Coulomb scattering
transitions between these bands are also possible, and we describe them on an
equal footing in terms of Boltzmann scattering integrals. For an instantaneous
carrier excitation process we analyze the influence of both interaction
processes on the magnon and spin-dependent electron dynamics, and show that
their interplay gives rise to an efficient creation of magnons at higher
energies and wave vectors accompanied by only a small increase of the
electronic spin polarization. These results present a microscopic dynamical
scenario that shows how non-equilibrium magnons may dominate the magnetic
response of a ferromagnet on ultrafast timescales.",2304.14978v1
2023-05-24,Flat band separation and robust spin-Berry curvature in bilayer kagome metals,"Kagome materials have emerged as a setting for emergent electronic phenomena
that encompass different aspects of symmetry and topology. It is debated
whether the XV$_6$Sn$_6$ kagome family (where X is a rare earth element), a
recently discovered family of bilayer kagome metals, hosts a topologically
non-trivial ground state resulting from the opening of spin-orbit coupling
gaps. These states would carry a finite spin-Berry curvature, and topological
surface states. Here, we investigate the spin and electronic structure of the
XV$_6$Sn$_6$ kagome family. We obtain evidence for a finite spin-Berry
curvature contribution at the center of the Brillouin zone, where the nearly
flat band detaches from the dispersing Dirac band because of spin-orbit
coupling. In addition, the spin-Berry curvature is further investigated in the
charge density wave regime of ScV$_6$Sn$_6$, and it is found to be robust
against the onset of the temperature-driven ordered phase. Utilizing the
sensitivity of angle resolved photoemission spectroscopy to the spin and
orbital angular momentum, our work unveils the spin-Berry curvature of
topological kagome metals, and helps to define its spectroscopic fingerprint.",2305.15345v1
2024-02-08,Assessing the atomic moment picture of spin dynamics: the perspective of \textit{ab initio} magnon wavefunction,"Our understanding of collective spin fluctuation in materials relies largely
on Heisenberg-type spin Hamiltonians. Implicit in these spin models is the
atomic moment picture that in transverse spin dynamics the magnetization around
an atom undergoes precessional motion as a rigid moment, which has been
challenged by emerging theoretical and experimental advances. To assess the
validity of the atomic moment picture in spin dynamics, however, necessitates
magnon wavefunctions from \textit{ab initio} methods without \textit{a priori}
spin models. To this end, we develop an efficient model-free {\it ab initio}
method for computing magnon spectrum and wavefunctions. Niu-Kleinman's
adiabatic spin-wave dynamics is reformulated using linear perturbation theory
into a generalized eigenvalue problem, which can be solved to produce magnon
spectrum and wavefunctions without assuming atomic moments. We have implemented
this method in the framework of density functional perturbation theory (DFPT).
A dynamical extension of Niu-Kleinman equation of motion is proposed to improve
inaccurate predicted magnon energies due to imperfect adiabaticity at higher
energies. Based on so-obtained {\it ab initio} magnon wavefunctions, we find
the atomic moment picture to be valid in typical ferromagnets and
antiferromagnets, but fails in the molecular orbital crystal Na$_2$IrO$_3$. Our
results suggest that the usual spin Hamiltonian approach should be taken with a
grain of salt, and possible experimental ramification on the issue is
discussed.",2402.05473v2
1998-09-02,Coexistence of charge density wave and spin-Peierls orders in quarter-filled quasi-one dimensional correlated electron systems,"Charge and spin-Peierls instabilities in quarter-filled (n=1/2) compounds
consisting of coupled ladders and/or zig-zag chains are investigated. Hubbard
and t-J models including local Holstein and/or Peierls couplings to the lattice
are studied by numerical techniques. Next nearest neighbor hopping and magnetic
exchange, and short-range Coulomb interactions are also considered. We show
that, generically, these systems undergo instabilities towards the formation of
Charge Density Waves, Bond Order Waves and (generalized) spin-Peierls modulated
structures. Moderate electron-electron and electron-lattice couplings can lead
to a coexistence of these three types of orders. In the ladder, a zig-zag
pattern is stabilized by the Holstein coupling and the nearest-neighbor Coulomb
repulsion. In the case of an isolated chain, bond-centered and site-centered
2k_F and 4k_F modulations are induced by the local Holstein coupling. In
addition, we show that, in contrast to the ladders, a small charge ordering in
the chains, strongly enhances the spin-Peierls instability. Our results are
applied to the NaV_2O_5 compound (trellis lattice) and various phases with
coexisting charge disproportionation and spin-Peierls order are proposed and
discussed in the context of recent experiments. The role of the long-range
Coulomb potential is also outlined.",9809028v1
1998-12-31,The Heisenberg antiferromagnet on an anisotropic triangular lattice: linear spin-wave theory,"We consider the effect of quantum spin fluctuations on the ground state
properties of the Heisenberg antiferromagnet on an anisotropic triangular
lattice using linear spin-wave theory. This model should describe the magnetic
properties of the insulating phase of the kappa-(BEDT-TTF)_2 X family of
superconducting molecular crystals. The ground state energy, the staggered
magnetization, magnon excitation spectra and spin-wave velocities are computed
as a function of the ratio between the second and first neighbours, J2/J1. We
find that near J2/J1 = 0.5, i.e., in the region where the classical spin
configuration changes from a Neel ordered phase to a spiral phase, the
staggered magnetization vanishes, suggesting the possibility of a quantum
disordered state. In this region, the quantum correction to the magnetization
is large but finite. This is in contrast to the frustrated Heisenberg model on
a square lattice, for which the quantum correction diverges logarithmically at
the transition from the Neel to the collinear phase. For large J2/J1, the model
becomes a set of chains with frustrated interchain coupling. For J2 > 4 J1, the
quantum correction to the magnetization, within LSW, becomes comparable to the
classical magnetization, suggesting the possibility of a quantum disordered
state. We show that, in this regime, quantum fluctuations are much larger than
for a set of weakly coupled chains with non-frustated interchain coupling.",9812429v2
1999-09-20,Tricritical Behavior in the Extended Hubbard Chains,"Phase diagrams of the one-dimensional extended Hubbard model (including
nearest-neighbor interaction $V$) at half- and quarter-filling are studied by
observing level crossings of excitation spectra using the exact
diagonalization. This method is based on the Tomonaga-Luttinger liquid theory
including logarithmic corrections which stem from the renormalization of the
Umklapp- and the backward-scattering effects.
  Using this approach, the phase boundaries are determined with high accuracy,
and then the structure of the phase diagram is clarified. At half-filling, the
phase diagram consists of two
  Berezinskii-Kosterlitz-Thouless (BKT) transition lines and one Gaussian
transition line in the charge sector, and one spin-gap transition line.
  This structure reflects the U(1) $\otimes$ SU(2) symmetry of the electron
system. Near the $U=2V$ line, the Gaussian and the spin-gap transitions take
place independently from the weak- to the intermediate-coupling region, but
these two transition lines are coupled in the strong-coupling region. This
result demonstrates existence of a tricritical point and a
bond-charge-density-wave (BCDW) phase between charge- and spin-density-wave
(CDW, SDW) phases. To clarify this mechanism of the transition, we also
investigate effect of a correlated hopping term which plays a role to enlarge
BCDW and bond-spin-density-wave (BSDW) phases. At quarter-filling, a similar
crossover phenomenon also takes place in the large-$V$ region involving
spin-gap and BKT-type metal-insulator transitions.",9909277v2
2003-06-24,First-order transition in the itinerant ferromagnet CoS$_{1.9}$Se$_{0.1}$,"Undoped CoS$_2$ is an isotropic itinerant ferromagnet with a continuous or
nearly continuous phase transition at $T_{\rm C} = 122$ K. In the doped
CoS$_{1.9}$Se$_{0.1}$ system, the Curie temperature is lowered to $T_{\rm C} =
90$ K, and the transition becomes clearly first order in nature. In particular
we find a discontinuous evolution of the spin dynamics as well as strong time
relaxation in the ferromagnetic Bragg intensity and small angle neutron
scattering in vicinity of the ferromagnetic transition. In the ordered state
the long-wavelength spin excitations were found to be conventional
ferromagnetic spin-waves with negligible spin-wave gap ($ < 0.04$ meV),
indicating that this system is also an excellent isotropic (soft) ferromagnet.
In a wide temperature range up to $0.9T_{\rm C}$, the spin-wave stiffness
$D(T)$ follows the prediction of the two-magnon interaction theory, $D(T) =
D(0)(1 - AT^{5/2})$, with $D(0) = 131.7 \pm 2.8$ meV-\AA$^{2}$. The stiffness,
however, does not collapse as $T \to T_{\rm C}$ from below. Instead a
quasielastic central peak abruptly develops in the excitation spectrum, quite
similar to results found in the colossal magnetoresistance oxides such as
(La-Ca)MnO$_3$.",0306618v1
2000-08-15,Relativistic phase shifts for Dirac particles interacting with weak gravitational fields in matter-wave interferometers,"We present a second-quantized field theory of massive spin one-half particles
or antiparticles in the presence of a weak gravitational field treated as a
spin two external field in a flat Minkowski background. We solve the
difficulties which arise from the derivative coupling and we are able to
introduce an interaction picture. We derive expressions for the scattering
amplitude and for the outgoing spinor to first-order. In several appendices,
the link with the canonical approach in General Relativity is established and a
generalized stationary phase method is used to calculate the outgoing spinor.
We show how our expressions can be used to calculate and discuss phase shifts
in the context of matter-wave interferometry (especially atom or antiatom
interferometry). In this way, many effects are introduced in a unified
relativistic framework, including spin-gravitation terms: gravitational red
shift, Thomas precession, Sagnac effect, spin-rotation effect, orbital and spin
Lense-Thirring effects, de Sitter geodetic precession and finally the effect of
gravitational waves. A new analogy with the electromagnetic interaction is
pointed out.",0008033v1
1997-04-07,Relativistic Quantum Field Theory of High-Spin Matter Fields: A Pragmatic approach for Hadronic Physics,"A consistent phenomenology of the interaction of particles of arbitrary spin
requires covariant spinors, field operators, propagators and model
interactions. Guided by an approach originally proposed by Weinberg, we
construct from group theoretical arguments the (j,0)+(0,j) covariant spinors
and the field operators for a massive particles. Specific examples are worked
out in the familiar language of the Bjorken and Drell text for the case of the
(1,0)+(0,1), (3/2,0)+(0,3/2) and (2,0)+(0,2) matter fields. The m\to 0 limit of
the covariant spinors is shown to have the expected structure. The algebra of
the \gamma^{\mu\nu} matrices associated with the (1,0)+(0,1) matter fields is
presented, and the conserved current derived. The procedure readily extends to
higher spins. The causality problem associated with the j\ge 1 wave equations
is discussed in detail and a systematic procedure to construct causal
propagators is provided. As an example a spin two wave equation satisfied by
the (2,0)+(0,2), covariant spinors is found to support not only ten correct and
causal solutions, but also thirty physically unacceptable acausal solutions.
However, we demonstrate how to construct the Feynman propagator for the higher
spin particles directly from the spinors and thus avoid the shortcomings of the
wave equation in building a phenomenology. The same exercise is repeated for
the (1,0)+(0,1) and (3/2,0)+(0,3/2) matter fields, and the same conclusions
obtained. Massless limit is discussed in detail. (Typos uncorrected, Part of
the work published and extended in several journal articles, for an important
correction see physics/9702005).",9704066v1
2007-11-26,Quantum fluctuations in high field magnetization of 2D square lattice J1-J2 antiferromagnets,"The J1-J2 square lattice Heisenberg model with spin S=1/2 has three phases
with long-range magnetic order and two unconventionally ordered phases
depending on the ratio of exchange constants. It describes a number of recently
found layered vanadium oxide compounds. A simple means of investigating the
ground state is the study of the magnetization curve and high-field
susceptibility. We discuss these quantities by using the spin-wave theory and
the exact diagonalization in the whole J1-J2 plane. We compare both results and
find good overall agreement in the sectors of the phase diagram with magnetic
order. Close to the disordered regions the magnetization curve shows strong
deviations from the classical linear behaviour caused by large quantum
fluctuations and spin-wave approximation breaks down. On the FM side (J1<0)
where one approaches the quantum gapless spin nematic ground state this region
is surprisingly large. We find that inclusion of second order spin-wave
corrections does not lead to fundamental improvement. Quantum corrections to
the tilting angle of the ordered moments are also calculated. They may have
both signs, contrary to the always negative first order quantum corrections to
the magnetization. Finally we investigate the effect of the interlayer coupling
and find that the quasi-2D picture remains valid up to |J_\perp/J1| ~ 0.3.",0711.4054v1
2009-01-23,Observation of prolonged coherence time of the collective spin wave of atomic ensemble in a paraffin coated Rb vapor cell,"We report a prolonged coherence time of the collective spin wave of a thermal
87Rb atomic ensemble in a paraffin coated cell. The spin wave is prepared
through a stimulated Raman Process. The long coherence time time is achieved by
prolonging the lifetime of the spins with paraffin coating and minimize
dephasing with optimal experimental configuration. The observation of the long
time delayed-stimulated Stokes signal in the writing process suggests the
prolonged lifetime of the prepared spins; a direct measurement of the decay of
anti-Stokes signal in the reading process shows the coherence time is up to 300
us after minimizing dephasing. This is one hundred times longer than the
reported coherence time in the similar experiments in thermal atomic ensembles
based on the Duan-Lukin-Cirac-Zoller (DLCZ) and its improved protocols. This
prolonged coherence time sets the upper limit of the memory time in quantum
repeaters based on such protocols, which is crucial for the realization of
long-distance quantum communication. The previous reported fluorescence
background in the writing process due to collision in a sample cell with buffer
gas is also reduced in a cell without buffer gas.",0901.3627v1
2012-03-29,Spin Wave Theory of Spin 1/2 XY Model with Ring Exchange on a Triangular Lattice,"We present the linear spin wave theory calculation of the superfluid phase of
a hard-core boson $J$-$K$ model with nearest neighbour exchange $J$ and
four-particle ring-exchange $K$ at half filling on the triangular lattice, as
well as the phase diagrams of the system at zero and finite temperatures. We
find that the pure $J$ model (XY model) which has a well known uniform
superfluid phase with an ordered parameter $M_x=<S_i^x>\neq 0$ at zero
temperature is quickly destroyed by the inclusion of a negative-$K$
ring-exchange interactions, favouring a state with a $(\frac{4\pi}{3}, 0)$
ordering wavevector. We further study the behaviour of the finite-temperature
Kosterlitz-Thouless phase transition ($T_{KT}$) in the uniform superfluid
phase, by forcing the universal quantum jump condition on the
finite-temperature spin wave superfluid density. We find that for $K \textless
0$, the phase boundary monotonically decreases to T=0 at $K/J = -4/3$, where a
phase transition is expected and $T_{KT}$ decreases rapidly while for positive
$K$, $T_{KT}$ reaches a maximum at some $K\neq 0$. It has been shown on a
square lattice using quantum Monte Carlo(QMC) simulations that for small
$K\textgreater 0$ away from the XY point, the zero-temperature spin stiffness
value of the XY model is decreased\cite{F}. Our result seems to agree with this
trend found in QMC simulations.",1203.6583v4
2012-12-19,Low-Temperature Properties of Ferromagnetic Spin Chains in a Magnetic Field,"The thermodynamic properties of ferromagnetic spin chains have been analyzed
with a variety of microscopic methods over the years: Bethe ansatz, spin-wave
theory, Schwinger-boson mean-field theory, Green functions and renormalization
group methods. Surprisingly, in all these different studies, to the best of our
knowledge, the manifestation of the spin-wave interaction in the
low-temperature series for the thermodynamic quantities has been ignored. In
the present work, we address this problem by following a different path, based
on the systematic effective Lagrangian method. We evaluate the partition
function up to two-loop order and derive the low-temperature expansion of the
energy density, entropy density, heat capacity, magnetization and
susceptibility in the presence of a weak external magnetic field. Remarkably,
the spin-wave interaction only manifests itself beyond two-loop order. In
particular, there is no term of order $T^2$ in the low-temperature series of
the free energy density. This is the analog of Dyson's statement that, in the
case of three-dimensional ideal ferromagnets, there is no term of order $T^4$
in the low-temperature series of the free energy density. The range of validity
of our series is critically examined in view of the Mermin-Wagner theorem. We
also compare our results with the condensed matter literature and point out
that there are some misleading statements.",1212.4774v1
2013-10-16,High-Temperature Superconductors Explained by Pairing in Spin-Density Waves,"The spin-density wave (SDW) can be considered as a pair of charge density
waves (CDWs), one composed only of electrons with up-spins and the other only
of electrons with down-spins. The high-temperature superconductivity found in
cuprates and pnictides may then be ascribed to BCS-type pairing between these
SDWs, which is then no longer simple Cooper pairing between independent singlet
electrons but rather involves collective interaction between Cooper pairs. The
pseudo-gap may also be understood to originate from this BCS-type gap of the
CDW system, in which the parameters are identical to those in the original BCS
scheme, except that the electron-electron interaction is multiplied by a factor
NCDW, which represents the number of electrons of the same spin direction that
belong to a single CDW branch that comprises half the SDW. The superconducting
gap then becomes an s dx2-y2-type gap. This gap may be calculated by assuming a
modified BCS-like scheme that takes into account the contributions of the CDWs.
These CDWs may be driven spatially into a checkerboard-shaped (or striped) form
of superconductivity, depending on whether the CDW is two- or one-dimensional.
The origin of the nodal gap may also be ascribed to the CDWs.",1310.4273v1
2015-02-25,Spin Waves and Spatially Anisotropic Exchange Interactions in the $\mathrm{S=2}$ Stripe Antiferromagnet Rb$_{0.8}$Fe$_{1.5}$S$_2$,"An inelastic neutron scattering study of the spin waves corresponding to the
stripe antiferromagnetic order in insulating Rb$_{0.8}$Fe$_{1.5}$S$_2$
throughout the Brillouin zone is reported. The spin wave spectra are well
described by a Heisenberg Hamiltonian with anisotropic in-plane exchange
interactions. Integrating the ordered moment and the spin fluctuations results
in a total moment squared of $27.6\pm4.2\mu_B^2$/Fe, consistent with $\mathrm{S
\approx 2}$. Unlike $X$Fe$_2$As$_2$ ($X=$ Ca, Sr, and Ba), where the itinerant
electrons have a significant contribution, our data suggest that this stripe
antiferromagnetically ordered phase in Rb$_{0.8}$Fe$_{1.5}$S$_2$ is a Mott-like
insulator with fully localized $3d$ electrons and a high-spin ground state
configuration. Nevertheless, the anisotropic exchange couplings appear to be
universal in the stripe phase of Fe pnictides and chalcogenides.",1502.07022v1
2015-12-21,Graphene Electrodynamics in the presence of the Extrinsic Spin Hall Effect,"We extend the electrodynamics of two dimensional electron gases to account
for the extrinsic spin Hall effect (SHE). The theory is applied to doped
graphene decorated with a random distribution of absorbates that induce
spin-orbit coupling (SOC) by proximity. The formalism extends previous
semiclassical treatments of the SHE to the non-local dynamical regime. Within a
particle-number conserving approximation, we compute the conductivity,
dielectric function, and spin Hall angle in the small frequency and wave vector
limit. The spin Hall angle is found to decrease with frequency and wave number,
but it remains comparable to its zero-frequency value around the frequency
corresponding to the Drude peak. The plasmon dispersion and linewidth are also
obtained. The extrinsic SHE affects the plasmon dispersion in the long
wavelength limit, but not at large values of the wave number. This result
suggests an explanation for the rather similar plasmonic response measured in
exfoliated graphene, which does not exhibit the SHE, and graphene grown by
chemical vapor deposition, for which a large SHE has been recently reported.
Our theory also lays the foundation for future experimental searches of SOC
effects in the electrodynamic response of two-dimensional electron gases with
SOC disorder.",1512.06481v1
2016-07-05,Heavy Electron doping-induced antiferromagnetic phase as the parent for iron-oxypnictide superconductor LaFeAsO1-xHx,"We perform transport measurements and band structure calculations of
electron-doped LaFeAsO1-xHx over a wide range of x from 0.01 to 0.66. The T^2
and sqrt(T) dependency of the resistivity are observed at x ~ 0.17 and 0.41,
respectively. The sign change of RH without opening of the spin-density-wave
gap for 0.45 < x < 0.58 and T < TN as well as the calculated non-nested Fermi
surface at x = 0.5 indicate the more localized nature of the AF2 as compared to
spin density wave phase at non-doped sample. Considering the results from band
calculations and the finite size of Hund' s rule coupling, the change of the
normal conducting state with x is reasonably explained by a strong depression
of the coherent scale owing to the increased effective Coulomb repulsion in the
narrow anti-bonding 3dxy band that approaches the half-filled regime. The
following transition from the paramagnet to AF2 is understood as the quenching
or ordering of the less-screened spins with a large entropy at low temperature.
These results suggest that the normal conducting properties over a wide doping
range for the LaFeAsO1-xHx are strongly influenced by the local spins in the
incoherent region. Thus, we conclude that the parent phase in LaFeAsO1-xHx is
not the spin-density wave but the AF2, which may be primarily responsible for
the singular superconducting properties of the 1111 type compared with other
iron pnictides.",1607.01238v1
2016-08-03,Minimal Ingredients for Orbital Texture Switches at Dirac Points in Strong Spin-Orbit Coupled Materials,"Recent angle resolved photoemission spectroscopy measurements on strong
spin-orbit coupled materials have shown an in-plane orbital texture switch at
their respective Dirac points, regardless of whether they are topological
insulators or ""trivial"" Rashba materials. This feature has also been
demonstrated in a few materials ($\text{Bi}_2\text{Se}_3$,
$\text{Bi}_2\text{Te}_3$, and $\text{BiTeI}$) though DFT calculations. Here we
present a minimal orbital-derived tight binding model to calculate the electron
wave-function in a two-dimensional crystal lattice. We show that the orbital
components of the wave-function demonstrate an orbital-texture switch in
addition to the usual spin switch seen in spin polarized bands. This orbital
texture switch is determined by the existence of three main properties: local
or global inversion symmetry breaking, strong spin-orbit coupling, and
non-local physics (the electrons are on a lattice). Using our model we
demonstrate that the orbital texture switch is ubiquitous and to be expected in
many real systems. The orbital hybridization of the bands is the key aspect for
understanding the unique wave function properties of these materials, and this
minimal model helps to establish the quantum perturbations that drive these
hybridizations.",1608.01387v1
2019-11-15,"Real wave equations, spin origin of charge, and outlook on particle physics","Radical revision on the conventional spacetime picture, illusion or emergent
phenomenon, has been the focus of the speculations on the unified frameworks
for fundamental interactions in nature. Compared to strong experimental
credence to the standard model of particle physics there is practically no
relation of these speculations with the world of real particles. In this paper
we present a new conceptual framework for particle physics in which nontrivial
geometry and topology of space and time have fundamental reality. To develop
this model we proceed with the analysis of the standard wave equations and make
them real using the transformation rule $i=\sqrt{-1} \rightarrow
C=\begin{bmatrix} 0 & 1 \\ -1 & 0 \end{bmatrix}$. Topological significance is
attached to $i$ in terms of a point defect in 1D directed line. New
interpretation of Schroedinger wave equation and $Z_2$ vortex throw light on
the nature of spin. A new meaning is also obtained on U(1) gauge symmetry and
charge. Novel properties of C-matrix and known applications are presented.
Topological origin of spin is inferred from the interpretation of Pauli algebra
that they signify 2D directed area in phase space as topological obstruction.
Electron magnetic moment decomposition in QED serves the basis for the
proposition: spin origin of charge (SOC). A dynamical logarithmic spiral
geometric structure comprising of 2+1D braids, 3 vortices with associated three
2-spinors is envisaged based on SOC. It is termed as meta-electron;
meta-neutrino has 2-vortex structure. These are the only building blocks of all
particles having the knotted vortex structures in our model. Coupling strengths
of the three fundamental interactions are related with the magnitudes of the
spin angular momentum of constituent spinors of the meta-electron.",1911.10910v1
2018-10-29,Ferromagnetism and spin excitations in topological Hubbard models with a flatband,"We study the spin-1 excitation spectra of the flatband ferromagnetic phases
in interacting topological insulators. As a paradigm, we consider a quarter
filled square lattice Hubbard model whose free part is the $\pi$ flux state
with topologically nontrivial and nearly-flat electron bands, which can realize
either the Chern or $Z_2$ Hubbard model. By using the numerical exact
diagonalization method with a projection onto the nearly-flat band, we obtain
the ferromagnetic spin-1 excitation spectra for both the Chern and $Z_2$
Hubbard models, consisting of spin waves and Stoner continuum. The spectra
exhibit quite distinct dispersions for both cases, in particular the spin wave
is gapless for the Chern Hubbard model, while gapped for the $Z_2$ Hubbard
model. Remarkably, in both cases, the nonflatness of the free electron bands
introduces dips in the lower boundary of the Stoner continuum. It significantly
renormalizes the energies of the spin waves around these dips downward and
leads to roton-like spin excitations. We elaborate that it is the softening of
the roton-like modes that destabilizes the ferromagnetic phase, and determine
the parameter region where the ferromagnetic phase is stable.",1810.11986v2
2020-04-05,Spin wave based tunable switch between superconducting flux qubits,"Quantum computing hardware has received world-wide attention and made
considerable progress recently. YIG thin film have spin wave (magnon) modes
with low dissipation and reliable control for quantum information processing.
However, the coherent coupling between a quantum device and YIG thin film has
yet been demonstrated. Here, we propose a scheme to achieve strong coupling
between superconducting flux qubits and magnon modes in YIG thin film. Unlike
the direct $\sqrt{N}$ enhancement factor in coupling to the Kittel mode or
other spin ensembles, with N the total number of spins, an additional spatial
dependent phase factor needs to be considered when the qubits are magnetically
coupled with the magnon modes of finite wavelength. To avoid undesirable
cancelation of coupling caused by the symmetrical boundary condition, a CoFeB
thin layer is added to one side of the YIG thin film to break the symmetry. Our
numerical simulation demonstrates avoided crossing and coherent transfer of
quantum information between the flux qubits and the standing spin waves in YIG
thin films. We show that the YIG thin film can be used as a tunable switch
between two flux qubits, which have modified shape with small direct inductive
coupling between them. Our results manifest that it is possible to couple flux
qubits while suppressing undesirable cross-talk.",2004.02156v1
2020-08-03,Symmetry-resolved two-magnon excitations in a strong spin-orbit-coupled bilayer antiferromagnet,"We used a combination of polarized Raman spectroscopy and spin wave
calculations to study magnetic excitations in the strong spin-orbit-coupled
(SOC) bilayer perovskite antiferromagnet $Sr_3Ir_2O_7$. We observed two broad
Raman features at ~ 800 $cm^{-1}$ and ~ 1400 $cm^{-1}$ arising from magnetic
excitations. Unconventionally, the ~ 800 $cm^{-1}$ feature is fully symmetric
($A_{1g}$) with respect to the underlying tetragonal ($D_{4h}$) crystal lattice
which, together with its broad line shape, definitively rules out the
possibility of a single magnon excitation as its origin. In contrast, the ~
1400 $cm^{-1}$ feature shows up in both the $A_{1g}$ and $B_{2g}$ channels.
From spin wave and two-magnon scattering cross-section calculations of a
tetragonal bilayer antiferromagnet, we identified the ~ 800 $cm^{-1}$ (~ 1400
$cm^{-1}$) feature as two-magnon excitations with pairs of magnons from the
zone-center $\Gamma$ point (zone-boundary van Hove singularity X point). We
further found that this zone-center two-magnon scattering is unique to bilayer
perovskite magnets which host an optical branch in addition to the acoustic
branch, as compared to their single layer counterparts. This zone-center
two-magnon mode is distinct in symmetry from the time-reversal symmetry broken
spin wave gap and phase mode proposed to explain the ~ 92 meV (742 $cm^{-1}$)
gap in RIXS magnetic excitation spectra of $Sr_3Ir_2O_7$.",2008.01052v1
2016-03-09,Extended Magnetic Exchange Interactions in the High-Temperature Ferromagnet MnBi,"The high-temperature ferromagnet MnBi continues to receive attention as a
candidate to replace rare-earth-containing permanent magnets in applications
above room temperature. This is due to a high Curie temperature, large magnetic
moments, and a coercivity that increases with temperature. The synthesis of
MnBi also allows for crystals that are free of interstitial Mn, enabling more
direct access to the key interactions underlying the physical properties of
binary Mn-based ferromagnets. In this work, we use inelastic neutron scattering
to measure the spin waves of MnBi in order to characterize the magnetic
exchange at low temperature. Consistent with the spin reorientation that occurs
below 140 K, we do not observe a spin gap in this system above our experimental
resolution. A Heisenberg model was fit to the spin wave data in order to
characterize the long-range nature of the exchange. It was found that
interactions up to sixth nearest neighbor are required to fully parameterize
the spin waves. Surprisingly, the nearest-neighbor term is antiferromagnetic,
and the realization of a ferromagnetic ground state relies on the more numerous
ferromagnetic terms beyond nearest neighbor, suggesting that the ferromagnetic
ground state arises as a consequence of the long-ranged interactions in the
system.",1603.02750v2
2017-02-16,Nonreciprocal magnons and symmetry-breaking in the noncentrosymmetric antiferromagnet,"Magnons, the spin-wave quanta, are disturbances that embody a wave
propagating through a background medium formed by ordered magnetic moments. In
an isotropic Heisenberg system, these disturbances vary in a continuous manner
around an ordered spin structure, thus requiring infinitesimal energy as a
wavevector approaches a magnetic zone centre. However, competing anisotropic
interactions arising from broken symmetry can favour a distinct static and
dynamic spin state causing a shift of the minimum point of the magnon
dispersion to a nonreciprocal wavevector. Here we report the first direct
evidence of these nonreciprocal magnons in an antiferromagnet. In the
antiferromagnet we investigated, namely, noncentrosymmetric
$\alpha$-Cu$_2$V$_2$O$_7$, they are caused by the incompatibility between
anisotropic exchange and antisymmetric Dzyaloshinskii-Moriya interactions
resulting in competing collinear and helical spin structures, respectively. The
nonreciprocity introduces the difference in the phase velocity of the
counter-rotating modes, causing the opposite spontaneous magnonic Faraday
rotation of the left- and right-propagating spin-waves. The breaking of spatial
inversion and time reversal symmetry is revealed as a magnetic-field-induced
asymmetric energy shift, which provides a test for the detailed balance
relation.",1702.04889v1
2019-05-08,"Waveform systematics for binary neutron star gravitational wave signals: Effects of spin, precession, and the observation of electromagnetic counterparts","Extracting the properties of a binary system emitting gravitational waves
relies on models describing the last stages of the compact binary coalescence.
In this article, we study potential biases inherent to current tidal waveform
approximants for spinning and precessing systems. We perform a Bayesian study
to estimate intrinsic parameters of highly spinning binary neutron star
systems. Our analysis shows that one has to include the quadrupolar deformation
of the neutron stars due to their rotation once dimensionless spins above $\chi
\sim 0.20$ are reached, otherwise the extracted intrinsic parameters are
systematically biased. We find that at design sensitivity of Advanced LIGO and
Virgo, it seems unlikely that for GW170817-like sources a clear imprint of
precession will be visible in the analysis of the signal employing current
waveform models. However, precession effects might be detectable for unequal
mass configurations with spins larger than $\chi>0.2$. We finalize our study by
investigating possible benefits of a combined gravitational wave and
electromagnetic detection. The presence of electromagnetic counterparts help in
reducing the dimensionality of the parameter space with constraints on the sky
location, source distance, and inclination. However, we note that although a
small improvement in the estimation of the tidal deformability parameter is
seen in these cases, changes in the intrinsic parameters are overall very
small.",1905.03118v1
2019-01-04,Spin-flavor oscillations of Dirac neutrinos in matter under the influence of a plane electromagnetic wave,"We study oscillations of Dirac neutrinos in background matter and a plane
electromagnetic wave. First, we find the new exact solution of the Dirac-Pauli
equation for a massive neutrino with the anomalous magnetic moment
electroweakly interacting with matter under the influence of a plane
electromagnetic wave with the circular polarization. We use this result to
describe neutrino spin oscillations in the external fields in question. Then we
consider several neutrino flavors and study neutrino spin-flavor oscillations
in this system. For this purpose we formulate the initial condition problem and
solve it accounting for the considered external fields. We derive the
analytical expressions for the transition probabilities of spin-flavor
oscillations for different types of neutrino magnetic moments. These analytical
expressions are compared with the numerical solutions of the effective
Schr\""odinger equation and with the findings of other authors. In particular,
we reveal that a resonance in neutrino spin-flavor oscillations in the
considered external fields cannot happen contrary to the previous claims.
Finally, we briefly discuss some possible astrophysical applications.",1901.01022v2
2020-07-28,Gravitational Wave Capture in Spinning Black Hole Encounters,"The orbits of two black holes which are initially unbound can be transformed
into bound orbits by emitting gravitational waves during close encounters in a
star cluster, which is called a gravitational wave (GW) capture. The effects of
spin of black holes on GW capture are investigated in the context of numerical
relativity. The radiated energy during the encounter is dependent on the
effective spin when the black holes have the equal masses as expected from
post-Newtonian approximation. The strongest emission is produced when the spins
of both black holes are anti-aligned to the orbital angular momentum in the
case of fly-by encounters. But the opposite is true in the case of direct
merging: the strongest emission comes from the black holes with aligned spins
to the orbital angular momentum. The fraction of direct merging among the GW
captures increases in proportional to $v^{4/7}$ assuming the uniform
distribution of pericenter distances in the encounters, where $v$ is the
velocity dispersion of cluster, which means about 5 % of GW capture leads to
the direct merging for star clusters with $v=150$ km s$^{-1}$.",2007.14019v1
2021-03-22,Chiral d density wave ordered pseudo gap phase of Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ bilayer. Spin texture and Dzyaloshinskii Moriya interaction,"We model Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212) bilayer system by an
inversion symmetry broken and time reversal non invariant Bloch Hamiltonian H.
The pseudo-gap phase of the bilayer is assumed to be chiral d density wave
ordered. The focal point of the paper is the theoretical study of the spin
momentum locking (SML), due to the presence of a strong spin orbit coupling in
Bi2212, reported earlier in this phase in a spin and angle resolved
photoemission spectroscopic measurement. The non trivial spin texture in k
space is found tunable by electric field and also by intercalation.The
Dzyaloshinskii Moriya interaction (DMI) coefficient, where DMI being important
energy for chiral textures like magnetic skyrmions, are calculated to set the
stage for detailed studies in a sequel. We also find that,in the nodal region,
in the presence of Zeeman field B , as in a s wave superconductor, for B
greater than or equal to B_c (a critical value) a vortex in this system becomes
a non-Abelian anyon with a Majorana zero mode required for the fault tolerant
quantum computation.",2103.12053v2
2022-08-19,Spin-orbit interactions in noncentrosymmetric plasmonic crystals probed by site-selective cathodoluminescence spectroscopy,"The study of spin-orbit coupling (SOC) of light is crucial to explore the
light-matter interactions in sub-wavelength nanostructures with broken
symmetries. In noncentrosymmetric photonic crystals, the SOC results in the
splitting of the otherwise degenerate energy bands. Herein, we explore the SOC
in a noncentrosymmetric plasmonic crystal, both theoretically and
experimentally. Cathodoluminescence (CL) spectroscopy combined with the
numerically calculated photonic band structure reveals an energy band splitting
that is ascribed to the broken symmetries in the noncentrosymmetric plasmonic
crystal. By shifting the impact position of the electron beam throughout a unit
cell of the plasmonic crystal, we show that the emergence of the energy band
splitting strongly depends on the excitation position of the surface plasmon
(SP) waves on the crystal. Moreover, we exploit angle-resolved CL and
dark-field polarimetry to demonstrate polarization-dependent scattering of SP
waves interacting with the plasmonic crystal. The scattering direction of a
given polarization is determined by the transverse spin angular momentum
inherently carried by the SP wave, which is in turn locked to the direction of
SP propagation. Our study gives insight into the design of novel plasmonic
devices with polarization-dependent directionality of the Bloch plasmons. We
expect spin-orbit plasmonics will find much more scientific interests and
potential applications with the continuous development of nanofabrication
methodologies and uncovering new aspects of spin-orbit interactions.",2208.09238v1
2022-09-14,From the gates of the abyss: Frequency- and polarization-dependent lensing of gravitational waves in strong gravitational fields,"The propagation of gravitational waves can be described in terms of null
geodesics by using the geometrical optics approximation. However, at large but
finite frequencies the propagation is affected by the spin-orbit coupling
corrections to geometrical optics, known as the gravitational spin Hall effect.
Consequently, gravitational waves follow slightly different frequency- and
polarization-dependent trajectories, leading to dispersive and birefringent
phenomena. We study the potential for detecting the gravitational spin Hall
effect in hierarchical triple black hole systems, consisting of an emitting
binary orbiting a more massive body acting as a gravitational lens. We
calculate the difference in time of arrival with respect to the geodesic
propagation and find that it follows a simple power-law dependence on frequency
with a fixed exponent. We calculate the gravitational spin Hall-corrected
waveform and its mismatch with respect to the original waveform. The waveform
carries a measurable imprint of the strong gravitational field if the source,
lens, and observer are sufficiently aligned, or for generic observers if the
source is close enough to the lens. We present constraints on dispersive time
delays from GWTC-3, translated from limits on Lorentz invariance violation.
Finally, we address the sensitivity of current and future ground detectors to
dispersive lensing. Our results demonstrate that the gravitational spin Hall
effect can be detected, providing a novel probe of general relativity and the
environments of compact binary systems.",2209.06459v2
2022-10-31,"The Bardeen-Petterson effect, disk breaking, and the spin orientations of supermassive black-hole binaries","Supermassive black-hole binaries are driven to merger by dynamical friction,
loss-cone scattering of individual stars, disk migration, and
gravitational-wave emission. Two main formation scenarios are expected.
Binaries that form in gas-poor galactic environments do not experience disk
migration and likely enter the gravitational-wave dominated phase with roughly
isotropic spin orientations. Comparatively, binaries that evolve in gas-rich
galactic environments might experience prominent phases of disk accretion,
where the Bardeen-Petterson effect acts to align the spins of the black holes
with the orbital angular momentum of the disk. However, if the accretion disk
breaks alignment is expected to be strongly suppressed -- a phenomenon that was
recently shown to occur in a large portion of the parameter space. In this
paper, we develop a semi-analytic model of joint gas-driven migration and spin
alignment of supermassive black-hole binaries taking into account the impact of
disk breaking for the first time. Our model predicts the occurrence of distinct
subpopulations of binaries depending on the efficiency of spin alignment. This
implies that future gravitational-wave observations of merging black holes
could potentially be used to (i) discriminate between gas-rich and gas-poor
hosts and (ii) constrain the dynamics of warped accretion disks.",2211.00044v2
2023-01-17,Doping-dependent charge- and spin-density wave orderings in a monolayer of Pb adatoms on Si(111),"In this work we computed the phase diagram as a function of temperature and
doping for a system of lead adatoms allocated periodically on a silicon (111)
surface. This Si(111):Pb material is characterized by a strong and long-ranged
Coulomb interaction, a relatively large value of the spin-orbit coupling, and a
structural phase transition that occurs at low temperature. In order to
describe the collective electronic behavior in the system, we perform many-body
calculations consistently taking all these important features into account. We
find that charge- and spin-density wave orderings coexist with each other in
several regions of the phase diagram. This result is in agreement with the
recent experimental observation of a chiral spin texture in the charge density
wave phase in this material. We also find that geometries of the charge and
spin textures strongly depend on the doping level. The formation of such a rich
phase diagram in the Si(111):Pb material can be explained by a combined effect
of the lattice distortion and electronic correlations.",2301.07162v3
2023-08-30,Atomic-Scale Visualization of a Cascade of Magnetic Orders in the Layered Antiferromagnet $GdTe_{3}$,"$GdTe_{3}$ is a layered antiferromagnet belonging to the family of rare-earth
square net tritellurides which has recently attracted much attention due to its
exceptionally high mobility, the presence of a novel unidirectional
incommensurate charge density wave (CDW) state, superconductivity under
pressure, and a cascade of magnetic transitions between 12 and 7 K, whose order
parameters are as yet unknown. Since the itinerant electrons and localized
moments reside on different crystalline planes in this family of compounds,
spin-charge interactions could potentially result in unexpected phases in this
system. In this work, we use spin-polarized scanning tunneling microscopy to
directly image the charge and magnetic orders in $GdTe_{3}$. Below 7 K, we find
a striped antiferromagnetic phase with twice the periodicity of the Gd lattice
and perpendicular to the CDW order. Intriguingly, between 7 and 12 K, we
discover a spin density wave which has the same periodicity as the CDW. Using a
minimal Landau free energy model we show that the spin density wave can arise
from a bulk incipient antiferromagnetic order oriented along the
$\textit{c}$-axis that couples to the CDW order. Our work reveals the order
parameters of the cascade of low temperature magnetic phases in $GdTe_{3}$ and
shows how the interplay between the charge and spin sectors can generate
multiple coexisting magnetic orders in this class of materials.",2308.15691v2
2023-10-24,Spin wave excitations in low dimensional systems with large magnetic anisotropy,"The low energy excitation spectrum of a two-dimensional ferromagnetic
material is dominated by single-magnon excitations that show a gapless
parabolic dispersion relation with the spin wave vector. This occurs as long as
magnetic anisotropy and anisotropic exchange are negligible compared to
isotropic exchange. However, to maintain magnetic order at finite temperatures,
it is necessary to have sizable anisotropy to open a gap in the spin wave
excitation spectrum. We consider four real two-dimensional systems for which
ferromagnetic order at finite temperature has been observed or predicted.
Density functional theory calculations of the total energy differences for
different spin configurations permit us to extract the relevant parameters and
connect them with a spin Hamiltonian. The corresponding values of the Curie
temperature are estimated using a simple model and found to be mostly
determined by the value of the isotropic exchange. The exchange and anisotropy
parameters are used in a toy model of finite-size periodic chains to study the
low-energy excitation spectrum, including single-magnon and two-magnon
excitations. At low energies we find that single-magnon excitations appear in
the spectrum together with two-magnon excitations. These excitations present a
gap that grows particularly for large values of the magnetic anisotropy or
anisotropic exchange, relative to the isotropic exchange.",2310.15942v1
2024-04-09,Collisions of Spin-polarized YO Molecules for Single Partial Waves,"Efficient sub-Doppler laser cooling and optical trapping of YO molecules
offer new opportunities to study collisional dynamics in the quantum regime.
Confined in a crossed optical dipole trap, we achieve the highest phase-space
density of $2.5 \times 10^{-5}$ for a bulk laser-cooled molecular sample. This
sets the stage to study YO-YO collisions in the microkelvin temperature regime,
and reveal state-dependent, single-partial-wave two-body collisional loss
rates. We determine the partial-wave contributions to specific rotational
states (first excited $N=1$ and ground $N=0$) following two strategies. First,
we measure the change of the collision rate in a spin mixture of $N=1$ by
tuning the kinetic energy with respect to the p- and d-wave centrifugal
barriers. Second, we compare loss rates between a spin mixture and a
spin-polarized state in $N=0$. Using quantum defect theory with a partially
absorbing boundary condition at short range, we show that the dependence on
temperature for $N=1$ can be reproduced in the presence of a d-wave or f-wave
resonance, and the dependence on a spin mixture for $N=0$ with a p-wave
resonance.",2404.06652v1
1995-01-16,Spin-Waves in the Mid-Infrared Spectrum of Antiferromagnetic YBa$_2$Cu$_3$O$_{6.0}$,"The mid-infrared spin-wave spectrum of antiferromagnetic
YBa$_2$Cu$_3$O$_{6.0}$\ was determined by infrared transmission and reflection
measurements ($\bbox{k} \!\! \parallel $c) at $T\!=\!10\!$~K.\@ Excitation of
single magnons of the optical branch was observed at
$E_{\text{op}}\!=\!178.0\!$~meV.\@ Two further peaks at $346\!$~meV
($\approx\!1.94\,E_{\text{op}}$) and $470\!$~meV
($\approx\!2.6\,E_{\text{op}}$) both belong to the two-magnon spectrum. Linear
spin wave theory is in good agreement with the measured two-magnon spectrum,
and allows to determine the exchange constant $J$ to be about $120\!$~meV,
whereas the intrabilayer coupling $J_{12}$ is approximately $0.55\,J$.",9501065v1
1995-11-23,Spin density wave selection in the one-dimensional Hubbard model,"The Hartree-Fock ground state phase diagram of the one-dimensional Hubbard
model is calculated, constrained to uniform phases, which have no charge
density modulation. The allowed solutions are saturated ferromagnetism (FM), a
spiral spin density wave (SSDW) and a double spin density wave} (DSDW). The
DSDW phase comprises two canted interpenetrating antiferromagnetic sublattices.
FM occurs for small filling, SSDW in most of the remainder of the phase
diagram, and DSDW in a narrow tongue near quarter (and three-quarter) filling.
Itinerant electrons lift the degeneracy with respect to canting angle in the
DSDW. The Hartree-Fock states are metallic except at multiples of a quarter
filling. Near half filling the uniform SSDW phase is unstable against phase
separation into a half-filled antiferromagnetic phase and a hole-rich SSDW
phase. The dependence of the ground state wave number on chemical potential is
conjectured to be a staircase. Comparison is made with higher dimensional
Hubbard models and the $J_{1}-J_{2}$ Heisenberg model.",9511116v1
1996-11-01,Two-hole problem in the t-J model: A canonical transformation approach,"The t-J model in the spinless-fermion representation is studied. An effective
Hamiltonian for the quasiparticles is derived using canonical transformation
approach. It is shown that the rather simple form of the transformation
generator allows to take into account effect of hole interaction with the
short-range spin waves and to describe the single-hole groundstate. Obtained
results are very close to ones of the self-consistent Born approximation.
Further accounting for the long-range spin-wave interaction is possible on the
perturbative basis. Both spin-wave exchange and an effective interaction due to
minimization of the number of broken antiferromagnetic bonds are included in
the effective quasiparticle interaction. Two-hole bound state problem is solved
using Bethe-Salpeter equation. The only d-wave bound state is found to exist in
the region of 1< (t/J) <5. Combined effect of the pairing interactions of both
types is important to its formation. Discussion of the possible relation of the
obtained results to the problem of superconductivity in real systems is
presented.",9611001v1
1997-01-23,The Quantum Hall Effect of Field Induced Spin Density Wave Phases: the Physics of the Ultra Quantum Crystal,"The Quantum Hall Effect of Field Induced Spin Density Wave Phases is
accounted for within a weak coupling theory which assumes that in the relevant
low temperature part of the phase diagram the quasi one dimensional conductor
is well described by Fermi liquid theory. Recent experimental results show that
sign inversion of the Hall Plateaux takes place all the way down from the
instability line of the normal state. The Quantum Nesting model, when it takes
into account small perturbations away from perfect nesting, describes well not
only the usual sequence of Hall plateaux, but also the anomalies connected with
sign inversion of the Hall Effect. Experimental observation of de-doubling of
sub-phase to sub-phase transition lines suggests that superposition of SDW
order parameters occurs in some parts of the phase diagram. The collective
excitations of the Ultra Quantum Crystal have a specific magneto-roton
structure. The SDW case exhibits,apart from the usual spin waves, topological
excitations which are either skyrmions or half skyrmions. It is suggested that
magneto-rotons may have been observed some years ago in specific heat
experiments.",9701174v1
1997-01-30,Various series expansions for the bilayer S=1/2 Heisenberg antiferromagnet,"Various series expansions have been developed for the two-layer, S=1/2,
square lattice Heisenberg antiferromagnet. High temperature expansions are used
to calculate the temperature dependence of the susceptibility and specific
heat. At T=0, Ising expansions are used to study the properties of the
N\'{e}el-ordered phase, while dimer expansions are used to calculate the
ground-state properties and excitation spectra of the magnetically disordered
phase. The antiferromagnetic order-disorder transition point is determined to
be $(J_2/J_1)_c=2.537(5)$. Quantities computed include the staggered
magnetization, the susceptibility, the triplet spin-wave excitation spectra,
the spin-wave velocity, and the spin-wave stiffness. We also estimates that the
ratio of the intra- and inter-layer exchange constants to be $J_2/J_1\simeq
0.07$ for cuprate superconductor $YBa_2Cu_3O_{6.2}$.",9701214v1
1997-12-17,Sign reversals of the quantum Hall effect and helicoidal magnetic-field-induced spin-density waves in quasi-one-dimensional organic conductors,"We study the effect of umklapp scattering on the magnetic-field-induced
spin-density-wave phases, which are experimentally observed in the
quasi-one-dimensional organic conductors of the Bechgaard salts family. Within
the framework of the quantized nesting model, we show that umklapp processes
may naturally explain sign reversals of the quantum Hall effect (QHE) observed
in these conductors. Moreover, umklapp scattering can change the polarization
of the spin-density wave (SDW) from linear (sinusoidal SDW) to circular
(helicoidal SDW). The QHE vanishes in the helicoidal phases, but a
magnetoelectric effect appears. These two characteristic properties may be
utilized to detect the magnetic-field-induced helicoidal SDW phases
experimentally.",9712216v1
1999-07-21,Wave-vector dependence of spin and density multipole excitations in quantum dots,"We have employed time-dependent local-spin density functional theory to
analyze the multipole spin and charge density excitations in GaAs-AlGaAs
quantum dots. The on-plane transferred momentum degree of freedom has been
taken into account, and the wave-vector dependence of the excitations is
discussed. In agreement with previous experiments, we have found that the
energies of these modes do not depend on the transferred wave-vector, although
their intensities do. Comparison with a recent resonant Raman scattering
experiment [C. Sch\""uller et al, Phys. Rev. Lett {\bf 80}, 2673 (1998)] is
made. This allows to identify the angular momentum of several of the observed
modes as well as to reproduce their energies.",9907321v1
1999-08-13,Spin Wave Theory of Double Exchange Ferromagnets,"We construct the 1/S spin-wave expansion for double exchange ferromagnets at
T=0. It is assumed that the value of Hund's rule coupling, J_H, is sufficiently
large, resulting in a fully saturated, ferromagnetic half-metallic ground
state. We evaluate corrections to the magnon dispersion law, and we also find
that, in contrast to earlier statements in the literature, magnon-electron
scattering does give rise to spin wave damping. We analyse the momentum
dependence of these quantities and discuss the experimental implications for
colossal magnetoresistance compounds.",9908202v3
1999-10-05,Collective modes in a system with two spin-density waves: the `Ribault' phase of quasi-one-dimensional organic conductors,"We study the long-wavelength collective modes in the magnetic-field-induced
spin-density-wave (FISDW) phases experimentally observed in organic conductors
of the Bechgaard salts family, focusing on phases that exhibit a sign reversal
of the quantum Hall effect (Ribault anomaly). We have recently proposed that
two SDW's coexist in the Ribault phase, as a result of Umklapp processes. When
the latter are strong enough, the two SDW's become circularly polarized
(helicoidal SDW's). In this paper, we study the collective modes which result
from the presence of two SDW's. We find two Goldstone modes, an out-of-phase
sliding mode and an in-phase spin-wave mode, and two gapped modes. The sliding
Goldstone mode carries only a fraction of the total optical spectral weight,
which is determined by the ratio of the amplitude of the two SDW's. In the
helicoidal phase, all the spectral weight is pushed up above the SDW gap. We
also point out similarities with phase modes in two-band or bilayer
superconductors. We expect our conclusions to hold for generic two-SDW systems.",9910052v2
2000-01-13,Origin of the singular Bethe ansatz solutions for the Heisenberg XXZ spin chain,"We investigate symmetry properties of the Bethe ansatz wave functions for the
Heisenberg $XXZ$ spin chain. The $XXZ$ Hamiltonian commutes simultaneously with
the shift operator $T$ and the lattice inversion operator $V$ in the space of
$\Omega=\pm 1$ with $\Omega$ the eigenvalue of $T$. We show that the Bethe
ansatz solutions with normalizable wave functions cannot be the eigenstates of
$T$ and $V$ with quantum number $(\Omega,\Upsilon)=(\pm 1,\mp 1)$ where
$\Upsilon$ is the eigenvalue of $V$. Therefore the Bethe ansatz wave functions
should be singular for nondegenerate eigenstates of the Hamiltonian with
quantum number $(\Omega,\Upsilon)=(\pm 1,\mp 1)$. It is also shown that such
states exist in any nontrivial down-spin number sector and that the number of
them diverges exponentially with the chain length.",0001175v2
2001-10-17,Magnetic field tuning of charge and spin order in the cuprate superconductors,"Recent neutron scattering, nuclear magnetic resonance, and scanning tunneling
microscopy experiments have yielded valuable new information on the interplay
between charge and spin density wave order and superconductivity in the cuprate
superconductors, by using an applied perpendicular magnetic field to tune the
ground state properties. We compare the results of these experiments with the
predictions of a theory which assumed that the ordinary superconductor was
proximate to a quantum transition to a superconductor with co-existing
spin/charge density wave order.",0110329v3
2001-11-09,Spectral properties of the Holstein double-exchange model and application to manganites,"Calculations of one-electron spectral functions, optical conductivity and
spin-wave energy in the Holstein double-exchange model are made using the
many-body coherent potential approximation. Satisfactory agreement is obtained
with angle-resolved photoemission results on La_1.2Sr_1.8Mn_2O_7 and optical
measurements on Nd_0.7Sr_0.3MnO_3. A pseudogap in the one-electron spectrum at
the Fermi level plays an important role in both systems, but a small-polaron
band is only predicted to exist in the La system. A rigorous upper bound on
spin-wave energies at T=0 is derived. The spin-wave stiffness constant D
decreases with increasing electron-phonon coupling g in a similar way to the
Curie temperature Tc, but D/(k_B Tc) increases for large g (low Tc) as observed
experimentally.",0111175v2
2001-12-20,Micromagnetism in URu2Si2 and high temperature superconductors,"It has been proposed, that unconventional density waves (UDW) are possible
candidates for systems with hidden order parameter. Unlike in conventional
density waves, no periodic modulation of either the charge-, or the
spin-density is present in UDW, in spite of a clear thermodynamic signal.
Although the unconventional spin density wave (USDW) has been suggested for the
""antiferromagnetic"" phase of URu2Si2, the micromagnetism seen by neutron
scattering has not been understood. We present here the calculation of the
local spin density due to impurities in USDW, which describes quantitatively
the neutron scattering data by Amitsuka et.al. Further, we propose that the
pseudogap phase in high temperature superconductors (HTSC) should also be USDW.
Strong evidence for this are the micromagnetism seen by Sidis et.al., and the
optical dichroism seen by Campuzano et.al.",0112387v1
2002-03-19,Magnetic contributions to the low-temperature specific heat of the ferromagnetic insulator: Pr0.8Ca0.2MnO3,"The Pr(1-x}CaxMnO3 system exhibits a ferromagnetic insulating state for the
composition range x<0.25. A metallic ferromagnetic state is never realized
because of the low hole concentration and the very small averaged A-site cation
radius. In the present study, the nature of the magnetic excitations at low
temperature has been investigated by specific heat measurements on a
Pr0.8Ca0.2MnO3 single crystal. The decrease of the specific heat under magnetic
field is qualitatively consistent with a suppression of ferromagnetic spin
waves in a magnetic field. However, at low temperature, the qualitative
agreement with the ferromagnetic spin waves picture is poor. It appears that
the large reduction of the specific heat due to the spin waves is compensated
by a Schottky-like contribution possibly arising from a Zeeman splitting of the
ground state multiplet of the Pr{3+} ions.",0203365v1
2002-07-24,"Exchange interaction parameters and adiabatic spin-wave spectra of ferromagnets: A ""renormalized magnetic force theorem""","The ``magnetic force theorem'' is frequently used to compute exchange
interaction parameters and adiabatic spin-wave spectra of ferromagnets. The
interest of this approach is that it allows to obtain these results from a
non-self-consistent calculation of the (single-electron) band energy only,
which greatly reduces the computational effort. However, as discussed by
various authors, this approach entail some systematic error. Here, a
``renormalized magnetic force theorem'' allowing to remove this systematic
error without increasing significantly the computational effort is presented.
For systems with one atom per unit cell, it amounts to a simple renormalization
of the spin-wave spectrum. This renormalization greatly improves the agreement
between calculated and experimental Curie temperatures of Fe and Ni.",0207592v2
2003-02-24,Spin-wave scattering at low temperatures in manganite films,"The temperature $T$ and magnetic field $H$ dependence of the resistivity
$\rho$ has been measured for La$_{0.8-y}$Sr$_{0.2}$MnO$_{3}$ (y=0 and 0.128)
films grown on (100) SrTiO$_{3}$ substrates. The low-temperature $\rho$ in the
ferromagnetic metallic region follows well $\rho (H,T)=\rho
_{0}(H)+A(H)\omega_{s}/\sinh (\hbar \omega_{s}/2k_{B}T)+B(H)T^{7/2}$ with $\rho
_{0}$ being the residual resistivity. We attribute the second and third term to
small-polaron and spin-wave scattering, respectively. Our analysis based on
these scattering mechanisms also gives the observed difference between the
metal-insulator transition temperatures of the films studied. Transport
measurements in applied magnetic field further indicate that spin-wave
scattering is a key transport mechanism at low temperatures.",0302486v1
2003-09-24,Anomalous behavior of spin wave resonances in Ga_{1-x}Mn_{x}As thin films,"We report ferromagnetic and spin wave resonance absorption measurements on
high quality epitaxially grown Ga_{1-x}Mn_{x}As thin films. We find that these
films exhibit robust ferromagnetic long-range order, based on the fact that up
to seven resonances are detected at low temperatures, and the resonance
structure survives to temperatures close to the ferromagnetic transition. On
the other hand, we observe a spin wave dispersion which is linear in mode
number, in qualitative contrast with the quadratic dispersion expected for
homogeneous samples. We perform a detailed numerical analysis of the
experimental data and provide analytical calculations to demonstrate that such
a linear dispersion is incompatible with uniform magnetic parameters. Our
theoretical analysis of the ferromagnetic resonance data, combined with the
knowledge that strain-induced anisotropy is definitely present in these films,
suggests that a spatially dependent magnetic anisotropy is the most likely
reason behind the anomalous behavior observed.",0309566v2
2004-06-18,Magnetic response and quantum critical behavior in the doped two-leg extended Hubbard ladder,"We have investigated quantum critical behavior in the doped two-leg extended
Hubbard ladder, by using a weak-coupling bosonization method. In the ground
state, the dominant fluctuation changes from the conventional d-wave-like
superconducting (SCd) state into density-wave states, with increasing
nearest-neighbor repulsions and/or decreasing doping rate. The competition
between the SCd state and the charge-density-wave state coexisting with the
p-density-wave state becomes noticeable on the critical point, at which the gap
for magnetic excitations vanishes. Based on the Majorana-fermion description of
the effective theory, we calculate the temperature dependence of the magnetic
response such as the spin susceptibility and the NMR relaxation rate, which
exhibit unusual properties due to two kinds of spin excitation modes. On the
quantum critical point, the spin susceptibility shows paramagnetic behavior
with logarithmic corrections and the NMR relaxation rate also exhibits
anomalous power-law behavior. We discuss the commensurability effect due to the
umklapp scattering and relevance to the two-leg ladder compounds
Sr_{14-x}Ca_xCu_{24}O_{41}.",0406430v3
2004-08-27,"Confined spin waves reveal an assembly of nanosize domains in ferromagnetic La(1-x)CaxMnO3 (x=0.17,0.2)","We report a study of spin-waves in ferromagnetic La$_{1-x}$Ca$_{x}$MnO$_3$,
at concentrations x=0.17 and x=0.2 very close to the metallic transition
(x=0.225). Below T$_C$, in the quasi-metallic state (T=150K), nearly
q-independent energy levels are observed. They are characteristic of standing
spin waves confined into finite-size ferromagnetic domains, defined in {\bf a,
b) plane for x=0.17 and in all q-directions for x=0.2. They allow an estimation
of the domain size, a few lattice spacings, and of the magnetic coupling
constants inside the domains. These constants, anisotropic, are typical of an
orbital-ordered state, allowing to characterize the domains as ""hole-poor"". The
precursor state of the CMR metallic phase appears, therefore, as an assembly of
small orbital-ordered domains.",0408611v2
2004-10-09,Magnetic ordering and spin waves in $\bf Na_{0.82}CoO_2$,"Na$_x$CoO$_2$, the parent compound of the recently synthesized superconductor
Na$_x$CoO$_2$:$y$H$_2$O, exhibits bulk antiferromagnetic order below $\sim20$ K
for 0.75 $\leq x \leq$ 0.9. We have performed neutron scattering experiments in
which we observed Bragg reflections corresponding to A-type antiferromagnetic
order in a Na$_{0.82}$CoO$_2$ single crystal and characterized the
corresponding spin-wave dispersions. The spin waves exhibit a strongly
energy-dependent linewidth. The in-plane and out-of-plane exchange constants
resulting from a fit to a nearest-neighbor Heisenberg model are similar in
magnitude, which is unexpected in view of the layered crystal structure of
Na$_{x}$CoO$_2$. Possible implications of these observations are discussed.",0410224v2
2004-11-23,The spin-wave spectrum of the Jahn-Teller system LaTiO3,"We present an analytical calculation of the spin-wave spectrum of the
Jahn-Teller system LaTiO3. The calculation includes all superexchange couplings
between nearest-neighbor Ti ions allowed by the space-group symmetries: The
isotropic Heisenberg couplings and the antisymmetric (Dzyaloshinskii-Moriya)
and symmetric anisotropies. The calculated spin-wave dispersion has four
branches, two nearly degenerate branches with small zone-center gaps and two
practically indistinguishable high-energy branches having large zone-center
gaps. The two lower-energy modes are found to be in satisfying agreement with
neutron-scattering experiments. In particular, the experimentally detected
approximate isotropy in the Brillouin zone and the small zone-center gap are
well reproduced by the calculations. The higher-energy branches have not been
detected yet by neutron scattering but their zone-center gaps are in satisfying
agreement with recent Raman data.",0411583v1
2004-12-21,Dynamics of two interacting electrons in a one-dimensional crystal with impurities,"We investigated the role that the electron-electron interaction plays on the
propagating properties of wave packets in a one-dimensional crystal with
impurities. We considered two interacting particles with opposite spins in a
band, where we treated their interaction along the Hubbard model. We have
obtained the density of states of the crystal for different values of the
interaction term, as well as solved the dynamical Schr\""{o}dinger equation by
varying the initial conditions. We have introduced a method through which we
were able to follow the time evolution of the wave packets for both spins
showed in three-dimensional plots, and have evaluated, for each particle, the
corresponding $MSD^{\prime}s $ and the centroids as function of time . These
measurements allow us to determine the influence of the interaction on
dynamical properties. We discussed the combined effect that the extension of
the initial wave packets and the interaction strength have on propagating
properties. Under certain conditions we obtained an entanglement of the two
packets associated with both spins that takes place in a small region of the
lattice.",0412596v1
2004-12-22,Spin waves and magnetic interactions in LiCu2O2,"The quasi-one-dimensional helimagnet LiCu2O2 was studied by single crystal
inelastic neutron scattering. The dispersion relation of spin wave excitations
was measured in the vicinity of the principal magnetic Bragg reflection. A spin
wave theoretical analysis of the data yields an estimate of the relevant
exchange constants and explains the mechanism of geometric frustration that
leads to helimagnetism. It is found that the simple antiferromagnetic J_1-J_2
model that was previously proposed is inadequate for LiCu2O2. The experimental
findings are generally in a qualitative agreement with first principal
calculations of [A. A. Gippius et al., Phys. Rev. B {\bf 70}, 020406 (2004)],
though certain important discrepancies remain to be explained.",0412625v1
2005-05-23,Spin-orbit coupling induced magnetism in the $d$-density wave phase of La$_{2-x}$Ba$_x$CuO$_4$ superconductors,"We study the effects of spin-orbit coupling in the $d$-density wave (DDW)
phase. In the low-temperature orthorhombic phase of La$_{2-x}$Ba$_x$CuO$_4$, we
find that spin-orbit coupling induces a ferromagnetic moment in the DDW phase,
which is polarized along the [110] direction with a considerable magnitude.
This effect does not exist in the superconducting phase. On the other hand, if
the $d$-density wave order does not exist at zero field, a magnetic field along
the [110] direction always induces such a staggered orbital current. We discuss
experimental constraints on the DDW states in light of our theoretical
predictions.",0505544v3
2005-11-21,Quantum melting of the hole crystal in the spin ladder of Sr14-xCaxCu24O41,"The ""spin ladder"" is a reduced-dimensional analogue of the high temperature
superconductors that was predicted to exhibit both superconductivity and an
electronic charge density wave or ""hole crystal"" (HC). Both phenomena have been
observed in the doped spin ladder system Sr14-xCaxCu24O41 (SCCO), which at x=0
exhibits a HC which is commensurate at all temperatures. To investigate the
effects of discommensuration we used resonant soft x-ray scattering (RSXS) to
study SCCO as a function of doped hole density, d. The HC forms only with the
commensurate wave vectors L_L = 1/5 and L_L = 1/3 and exhibits a simple
temperature scaling T_(1/3) / T_(1/5) = 5/3. For irrational wave vectors the HC
""melts"", perhaps through the motion of topological defects carrying fractional
charge.",0511524v1
2006-01-24,Coexistence of Triplet Superconductivity and Spin Density Wave,"We discuss the possibility of coexistence of spin density wave
(antiferromagnetism) and triplet superconductivity as a particular example of a
broad class of systems where the interplay of magnetism and superconductivity
is important. We focus on the case of quasi-one-dimensional metals, where it is
kown that antiferromagnetism is in close proximity to triplet superconductivity
in the pressure versus temperature phase diagram. Over a range of pressures, we
propose an intermediate non-uniform phase consisting of antiferromagnetic and
triplet superconducting orders. In the coexistence region, we propose a flop
transition in the spin density wave order parameter vector, which affects the
nature of the superconducting state.",0601551v1
2006-02-01,The metal-insulator transition of the ferromagnetic La7/8Sr1/8MnO3 probed by spin waves: a 2D stripe superstructure,"We report a study of spin waves in hole-doped ferromagnetic La7/8Sr1/8MnO3,
in the metallic state (165K) below TC (181K) and through the puzzling
metal-insulator transition which occurs at TO'O''=159K. They reveal very
unusual excitations. Propagating spin waves are observed in the small q-range
up to q=0.25 (lambda=4a), and, beyond, four dispersionless levels. Both types
of excitations have a quasi two-dimensional (2D) character. The transition is
revealed by a folding of the dispersed magnon branch at q=1/8. In the metallic
state, the dispersionless levels reveal ferromagnetic domains with 4 lattice
spacings for their size along a and b. They lead to a picture of charge
segregation with hole-poor domains surrounded with hole-rich paths. Within this
description, the transition appears as the ordering of domains, which can be
interpreted in terms of a 2D superstructure of orthogonal stripes.",0602026v1
2006-06-09,Magnetic resonance studies of the fundamental spin-wave modes in individual submicron Cu/NiFe/Cu perpendicularly magnetized disks,"Spin wave spectra of perpendicularly magnetized disks with trilayers
consisting of a 100 nm permalloy (Py) layer sandwiched by two Cu layers of 30
nm, are measured individually with a Magnetic Resonance Force Microscope
(MRFM). It is demonstrated by 3D micromagnetic simulations that in disks having
sub-micron size diameters, the lowest energy spin wave mode of the saturated
state is not spatially uniform but rather is localized at the center of the
Py/Cu interface in the region of a minimum demagnetizing field.",0606245v3
2006-09-14,Luther-Emery Phase and Atomic-Density Waves in a Trapped Fermion Gas,"The Luther-Emery liquid is a state of matter that is predicted to occur in
one-dimensional systems of interacting fermions and is characterized by a
gapless charge spectrum and a gapped spin spectrum. In this Letter we discuss a
realization of the Luther-Emery phase in a trapped cold-atom gas. We study by
means of the density-matrix renormalization-group technique a two-component
atomic Fermi gas with attractive interactions subject to parabolic trapping
inside an optical lattice. We demonstrate how this system exhibits compound
phases characterized by the coexistence of spin pairing and atomic-density
waves. A smooth crossover occurs with increasing magnitude of the atom-atom
attraction to a state in which tightly bound spin-singlet dimers occupy the
center of the trap. The existence of atomic-density waves could be detected in
the elastic contribution to the light-scattering diffraction pattern.",0609346v1
2006-10-03,Unconventional spin density wave in Bechgaard salt (TMTSF)2NO3,"Among many Bechgaard salts, TMTSF2NO3 exhibits very anomalous low temperature
properties. Unlike conventional spin density wave (SDW), TMTSF2NO3 undergoes
the SDW transition at $\T_SDW\approx 9.5$ K and the low temperature
quasiparticle excitations are gapless. Also, it is known that TMTSF2NO3 does
not exhibit superconductivity even under pressure, while FISDW is found in
TMTSF2NO3 only for P=8.5 kbar and B>20 T. Here we shall show that both the
angle dependent magnetoresistance data and the nonlinear Hall resistance of
TMTSF2NO3 at ambient pressure are interpreted satisfactory in terms of
unconventional spin density wave (USDW). Based on these facts, we propose a new
phase diagram for Bechgaards salts.",0610065v2
1999-01-06,Data analysis of gravitational-wave signals from spinning neutron stars. III. Detection statistics and computational requirements,"We develop the analytic and numerical tools for data analysis of the
gravitational-wave signals from spinning neutron stars for ground-based laser
interferometric detectors. We study in detail the statistical properties of the
optimum functional that need to be calculated in order to detect the
gravitational-wave signal from a spinning neutron star and estimate its
parameters. We derive formulae for false alarm and detection probabilities both
for the optimal and the suboptimal filters. We assess the computational
requirements needed to do the signal search. We compare a number of criteria to
build sufficiently accurate templates for our data analysis scheme. We verify
the validity of our concepts and formulae by means of the Monte Carlo
simulations. We present algorithms by which one can estimate the parameters of
the continuous signals accurately.",9901013v1
2003-05-12,Neutron Charge Radius: Relativistic Effects and the Foldy Term,"The neutron charge radius is studied within a light-front model with
different spin coupling schemes and wave functions. The cancellation of the
contributions from the Foldy term and Dirac form factor to the neutron charge
form factor is verified for large nucleon sizes and it is independent of the
detailed form of quark spin coupling and wave function. For the physical
nucleon our results for the contribution of the Dirac form factor to the
neutron radius are insensitive to the form of the wave function while they
strongly depend on the quark spin coupling scheme.",0305120v1
2003-12-22,A Naturally Narrow Positive Parity Theta^+,"We present a consistent color-flavor-spin-orbital wave function for a
positive parity Theta^+ that naturally explains the observed narrowness of the
state. The wave function is totally symmetric in its flavor-spin part and
totally antisymmetric in its color-orbital part. If flavor-spin interactions
dominate, this wave function renders the positive parity Theta^+ lighter than
its negative parity counterpart. We consider decays of the Theta^+ and compute
the overlap of this state with the kinematically allowed final states. Our
results are numerically small. We note that dynamical correlations between
quarks are not necessary to obtain narrow pentaquark widths.",0312325v4
2002-10-28,Infinite Component Relativistic Wave Equations,"We construct an infinite component relativistic wave equation which is a
linear first order differential equation identical in form to a Dirac like
equation, describing composite fields possessing multiple spin and energy
states. The main motivation for such a construction is to give a description of
Hadronic fields moving along their so called Regge Trajectories, however this
may be generalized to other composite fields. In order to construct the
equation so that it may accommodate physical states the concept of Spin Frames
is introduced, and it is found that such an equation may propagate physical
fields whose spin states differ by two units of angular momentum namely $\Delta
J=2$. The solution for the free field case is given by boosting a rest frame
spinor with the infinite dimensional Lorentz Boost which are constructed as
well. Finally we discuss the relevance of the groups GL(4R), and GL(3,1,R) and
their appearance with regards to the wave equation at hand.",0210083v1
2002-01-05,Relativistic precession and spin dynamics of an elliptic Rydberg wave packet,"Time evolution of wave packets built from the eigenstates of the Dirac
equation for a hydrogenic system is considered. We investigate the space and
spin motion of wave packets which, in the non-relativistic limit, are
stationary states with a probability density distributed uniformly along the
classical, elliptical orbit (elliptic WP). We show that the precession of such
a WP, due to relativistic corrections to the energy eigenvalues, is strongly
correlated with the spin motion. We show also that the motion is universal for
all hydrogenic systems with an arbitrary value of the atomic number Z.",0201015v2
2002-10-28,Quasi-spin wave quantum memories with dynamic symmetry,"For the two-mode exciton system formed by the quasi-spin wave collective
excitation of many $\Lambda$ atoms fixed at the lattice sites of a crystal, we
discover a dynamic symmetry depicted by the semi-direct product algebra
$SU(2)\bar{\otimes} h_2 $ in the large $N$ limit with low excitations. With the
help of the spectral generating algebra method, we obtain a larger class of
exact zero-eigenvalue states adiabatically interpolating between the initial
state of photon-type and the final state of quasi-spin wave exciton-type. The
conditions for the adiabatic passage of dark states are shown to be valid, even
with the presence of the level degeneracy. These theoretical results can lead
to propose new protocol of implementing quantum memory robust against quantum
decoherence.",0210189v2
2007-05-07,Stability of spinor Fermi gases in tight waveguides,"The two and three-body correlation functions of the ground state of an
optically trapped ultracold spin-1/2 Fermi gas (SFG) in a tight waveguide (1D
regime) are calculated in the plane of even and odd-wave coupling constants,
assuming a 1D attractive zero-range odd-wave interaction induced by a 3D p-wave
Feshbach resonance, as well as the usual repulsive zero-range even-wave
interaction stemming from 3D s-wave scattering. The calculations are based on
the exact mapping from the SFG to a ``Lieb-Liniger-Heisenberg'' model with
delta-function repulsions depending on isotropic Heisenberg spin-spin
interactions, and indicate that the SFG should be stable against three-body
recombination in a large region of the coupling constant plane encompassing
parts of both the ferromagnetic and antiferromagnetic phases. However, the
limiting case of the fermionic Tonks-Girardeau gas (FTG), a spin-aligned 1D
Fermi gas with infinitely attractive p-wave interactions, is unstable in this
sense. Effects due to the dipolar interaction and a Zeeman term due to a
resonance-generating magnetic field do not lead to shrinkage of the region of
stability of the SFG.",0705.0937v1
2007-06-08,Optical coupling to spin waves in the cycloidal multiferroic BiFeO3,"The magnon and optical phonon spectrum of an incommensurate multiferroic such
as BiFeO3 is considered in the framework of a phenomenological Landau theory.
The resulting spin wave spectrum is quite distinct from commensurate substances
due to soft mode anisotropy and magnon zone folding. The former allows
electrical control of spin wave propagation via reorientation of the
spontaneous ferroelectric moment. The latter gives rise to multiple
magneto-dielectric resonances due to the coupling of optical phonons at zero
wavevector to magnons at integer multiples of the cycloid wavevector. These
results show that the optical response of a multiferroic reveals much more
about its magnetic excitations than previously anticipated on the basis of
simpler models.",0706.1260v3
2007-07-13,Evidence for gapped spin-wave excitations in the frustrated Gd2Sn2O7 pyrochlore antiferromagnet from low-temperature specific heat measurements,"We have measured the low-temperature specific heat of the geometrically
frustrated pyrochlore Heisenberg antiferromagnet Gd2Sn2O7 in zero magnetic
field. The specific heat is found to drop exponentially below approximately 350
mK. This provides evidence for a gapped spin-wave spectrum due to an anisotropy
resulting from single ion effects and long-range dipolar interactions. The data
are well fitted by linear spin-wave theory, ruling out unconventional low
energy magnetic excitations in this system, and allowing a determination of the
pertinent exchange interactions in this material.",0707.2072v1
2007-08-03,Equilibrium Low Temperature Heat Capacity of the Spin Density Wave compound (TMTTF)2 Br: effect of a Magnetic Field,"We have investigated the effect of the magnetic field (B) on the very
low-temperature equilibrium heat capacity ceq of the quasi-1 D organic compound
(TMTTF)2Br, characterized by a commensurate Spin Density Wave (SDW) ground
state. Below 1K, ceq is dominated by a Schottky-like contribution, very
sensitive to the experimental time scale, a property that we have previously
measured in numerous DW compounds. Under applied field (in the range 0.2- 7 T),
the equilibrium dynamics, and hence ceq extracted from the time constant,
increases enormously. For B = 2-3 T, ceq varies like B2, in agreement with a
magnetic Zeeman coupling. Another specific property, common to other
Charge/Spin density wave (DW) compounds, is the occurrence of metastable
branches in ceq, induced at very low temperature by the field exceeding a
critical value. These effects are discussed within a generalization to SDWs in
a magnetic field of the available Larkin-Ovchinnikov local model of strong
pinning. A limitation of the model when compared to experiments is pointed out.",0708.0540v1
2007-08-09,Magnetic Interaction in the Geometrically Frustrated Triangular Lattice Antiferromagnet $\rm CuFeO_2$,"The spin wave excitations of the geometrically frustrated triangular lattice
antiferromagnet (TLA) $\rm CuFeO_2$ have been measured using high resolution
inelastic neutron scattering. Antiferromagnetic interactions up to third
nearest neighbors in the ab plane (J_1, J_2, J_3, with $J_2/J_1 \approx 0.44$
and $J_3/J_1 \approx 0.57$), as well as out-of-plane coupling (J_z, with
$J_z/J_1 \approx 0.29$) are required to describe the spin wave dispersion
relations, indicating a three dimensional character of the magnetic
interactions. Two energy dips in the spin wave dispersion occur at the
incommensurate wavevectors associated with multiferroic phase, and can be
interpreted as dynamic precursors to the magnetoelectric behavior in this
system.",0708.1198v2
2007-10-07,Duffin-Kemmer-Petiau formalism reexamined: non-relativistic approximation for spin 0 and spin 1 particles in a Riemannian space-time,"It is shown that the generally covariant Duffin-Kemmer-Petiau equation,
formulated in the frame of the Tetrode-Weyl-Fock-Ivanenko tetrad formalism,
allows for a non-relativistic approximation if the metric tensor is of a
special form. The Pauli equation for a vector particle involves the Riemann
curvature tensor explicitly. In analogous way, the procedure of the
non-relativistic approximation in the theory of scalar particle, charged and
neutral, is investigated in the background of Riemannian space-time. A
generalized covariant Schrodinger equation is derived when taking into account
non-minimal interaction term through scalar curvature R(x), it substantially
differs from the conventional generally covariant Schrodinger equation produced
when R(x)=0. It is demonstrated that the the non-relativistic wave function is
always complex-valued irrespective of the type of relativistic scalar particle,
charged or neutral, taken initially. The theory of vector particle proves the
same property: even if the wave function of the relativistic particle of spin 1
is taken real,the corresponding wave function in the non-relativistic
approximation is complex-valued.",0710.1423v1
2007-10-10,Gravitational-Wave Astronomy with Inspiral Signals of Spinning Compact-Object Binaries,"Inspiral signals from binary compact objects (black holes and neutron stars)
are primary targets of the ongoing searches by ground-based gravitational-wave
interferometers (LIGO, Virgo, GEO-600 and TAMA-300). We present
parameter-estimation simulations for inspirals of black-hole--neutron-star
binaries using Markov-chain Monte-Carlo methods. For the first time, we have
both estimated the parameters of a binary inspiral source with a spinning
component and determined the accuracy of the parameter estimation, for
simulated observations with ground-based gravitational-wave detectors. We
demonstrate that we can obtain the distance, sky position, and binary
orientation at a higher accuracy than previously suggested in the literature.
For an observation of an inspiral with sufficient spin and two or three
detectors we find an accuracy in the determination of the sky position of
typically a few tens of square degrees.",0710.1897v2
2008-02-22,Microwave spectral analysis by means of non-resonant parametric recovery of spin-wave signals in a thin magnetic film,"We report on the storage and non-resonant parametric recovery of microwave
signals carried by a dipolar surface spin-wave pulse in a thin ferrimagnetic
film. The information about the intensity of the spectral components of the
signal within a narrow frequency band is saved due to the excitation of a
dipolar-exchange standing spin-wave mode across the film thickness and is
afterwards restored by means of parametric amplification of this mode. The
intensity of the restored signal measured for varying shifts between the signal
carrier frequency and half of the pumping frequency, which is equal to the
frequency of the standing mode, reveals information about the entire frequency
spectrum of the input microwave signal.",0802.3302v1
2008-03-26,Superconductivity at 41 K and its competition with spin-density-wave instability in layered CeO$_{1-x}$F$_x$FeAs,"A series of layered CeO$_{1-x}$F$_x$FeAs compounds with x=0 to 0.20 are
synthesized by solid state reaction method. Similar to the LaOFeAs, the pure
CeOFeAs shows a strong resistivity anomaly near 145 K, which was ascribed to
the spin-density-wave instability. F-doping suppresses this instability and
leads to the superconducting ground state. Most surprisingly, the
superconducting transition temperature could reach as high as 41 K. The very
high superconducting transition temperature strongly challenges the classic BCS
theory based on the electron-phonon interaction. The very closeness of the
superconducting phase to the spin-density-wave instability suggests that the
magnetic fluctuations play a key role in the superconducting paring mechanism.
The study also reveals that the Ce 4f electrons form local moments and ordered
antiferromagnetically below 4 K, which could coexist with superconductivity.",0803.3790v3
2008-05-21,A Numerical Renormalization Group Study of the Superconducting and Spin Density Wave Instabilities in MFeAsO$_{1-x}$F$_x$ Compounds,"We apply the fermion renormalization group method, implemented numerically by
Honerkamp et.al., to a two-band model of FeAs-based materials. At half filling
we find the $(\pi,0)$ or $(0,\pi)$ spin density wave order and a sub-dominant
superconducting pairing tendency. Due to a topological reason, the spin density
wave gap has nodes on the fermi surfaces. Away from half filling we find an
unconventional s-wave and a sub-dominant $d_{x^2-y^2}$ pairing instability. The
former has $s$ symmetry around the hole fermi surface but exhibits
$s+d_{x^2-y^2}$ symmetry around the electron pockets where the 90 degree
rotation is broken. The pairing mechanism is inter-pocket pair hopping.
Interestingly, the same interaction also drives the antiferromagnetism.",0805.3343v3
2008-08-20,Correlation effects of exchange splitting and coexistence of spin-density-wave and superconductivity in single crystalline Sr1-xKxFe2As2,"The nature of spin-density wave and its relation with superconductivity are
crucial issues in the newly discovered Fe-based high temperature
superconductors. Particularly it is unclear whether the superconducting phase
and spin density wave (SDW) are truly exclusive from each other as suggested by
certain experiments. With angle resolved photoemission spectroscopy, we here
report exchange splittings of the band structures in Sr1-xKxFe2As2
(x=0,0.1,0.2), and the non-rigid-band behaviors of the splitting. Our data on
single crystalline superconducting samples unambiguously prove that SDW and
superconductivity could coexist in iron-pnictides.",0808.2738v1
2008-09-02,Parametrically-stimulated recovery of a microwave signal using standing spin-wave modes of a magnetic film,"The phenomenon of storage and parametrically-stimulated recovery of a
microwave signal in a ferrite film has been studied both experimentally and
theoretically. The microwave signal is stored in the form of standing spin-wave
modes existing in the film due to its finite thickness. Signal recovery is
performed by means of frequency-selective amplification of one of these
standing modes by double- requency parametric pumping process. The time of
recovery, as well as the duration and magnitude of the recovered signal, depend
on the timing and amplitudes of both the input and pumping pulses. A mean-field
theory of the recovery process based on the competitive interaction of the
signal-induced standing spin-wave mode and thermal magnons with the parametric
pumping field is developed and compared to the experimental data.",0809.0395v1
2008-10-05,Determination of exchange constants of Heusler compounds by Brillouin light scattering spectroscopy: application to Co$_2$MnSi,"Brillouin light scattering spectroscopy from so-called standing spin waves in
thin magnetic films is often used to determine the magnetic exchange constant.
The data analysis of the experimentally determined spin-wave modes requires an
unambiguous assignment to the correct spin wave mode orders. Often additional
investigations are needed to guarantee correct assignment. This is particularly
important in the case of Heusler compounds where values of the exchange
constant vary substantially between different compounds. As a showcase, we
report on the determination of the exchange constant (exchange stiffness
constant) in Co$_2$MnSi, which is found to be $A=2.35\pm0.1$ $\mu$erg/cm
($D=575\pm20$ meV \AA$^2$), a value comparable to the value of the exchange
constant of Co.",0810.0834v3
2008-11-04,Physical Origin and Generic Control of Magnonic Band Gaps of Dipole-Exchange Spin Waves in Width-Modulated-Nanostrip Waveguides,"We report, for the first time, on a novel planar structure of
magnonic-crystal waveguides, made of a single magnetic material, in which the
allowed and forbidden bands of propagating dipole-exchange spin-waves can be
manipulated by the periodic modulation of different widths in thin-film
nanostrips. The origin of the presence of several magnonic wide band gaps and
the crucial parameters for controlling those band gaps of the order of ~10 GHz
are found by micromagnetic numerical and analytical calculations. This work can
offer a route to the potential application to broad-band spin-wave filters in
the GHz frequency range.",0811.0411v3
2009-03-19,Pure quantum states of a neutrino with rotating spin in dense magnetized matter,"The problem of neutrino spin rotation in dense matter and in strong
electromagnetic fields is solved in accordance with the basic principles of
quantum mechanics. We obtain a complete system of wave functions for a massive
Dirac neutrino with an anomalous magnetic moment which are the eigenfunctions
of the kinetic momentum operator and have the form of nonspreading wave
packets. These wave functions enable one to consider the states of neutrino
with rotating spin as pure quantum states and can be used for calculating
probabilities of various processes with the neutrino in the framework of the
Furry picture.",0903.3358v3
2009-04-02,Current-controlled dynamic magnonic crystal,"We demonstrate a current-controlled, dynamic magnonic crystal. It consists of
a ferrite film whose internal magnetic field exhibits a periodic, cosine-like
variation. The field modulation is created by a direct current flowing through
an array of parallel wires placed on top of a spin-wave waveguide. A single,
pronounced rejection band in the spin-wave transmission characteristics is
formed due to spin-wave scattering from the inhomogeneous magnetic field. With
increasing current the rejection band depth and its width increase strongly.
The magnonic crystal allows a fast control of its operational characteristics
via the applied direct current. Simulations confirm the experimental results.",0904.0332v1
2009-06-04,Non-linear spin wave theory results for the frustrated S = 1/2 Heisenberg antiferromagnet on a body-centered cubic lattice,"At zero temperature the sublattice magnetization of the quantum spin-1/2
Heisenberg antiferromagnet on a body-centered cubic lattice with competing
first and second neighbor exchange (J1 and J2) is investigated using the
non-linear spin wave theory. The zero temperature phases of the model consist
of a two sublattice N\'{e}el phase for small J_2 (AF_1) and a collinear phase
at large J_2 (AF_2). We show that quartic corrections due to spin-wave
interactions enhance the sublattice magnetization in both the AF_1 and the AF_2
phase. The magnetization corrections are prominent near the classical
transition point of the model and in the J_2> J_1 regime. The ground state
energy with quartic interactions is also calculated. It is found that up to
quartic corrections the first order phase transition (previously observed in
this model) between the AF_1 and the AF_2 phase survives.",0906.0960v1
2009-07-31,Pressure-induced spin-density-wave transition in superconducting Mo3Sb7,"We report a novel pressure-induced spin-density-wave transition in the
superconductor Mo3Sb7 figured our by measurements of the electrical resistivity
and magnetization under hydrostatic pressure. The critical temperature of
superconducting Mo3Sb7 is found to increase with increasing pressure, from 2.15
K at 0.2 kbar up to 2.37 K at 22 kbar. Above 4.5 kbar, superconductivity exists
in parallel with a pressure-induced spin-density wave state, revealed by a
sharp jump in the electrical resistivity and a maximum in the magnetization at
the phase transition temperature T_SDW. The application of pressure shifts
T_SDW to lower temperatures, from 6.6 K at 4.5 kbar down to 6.15 K at 22 kbar.
A strong magnetic field dependence of T_SDW and a maximum seen in the
magnetization indicate an antiferromagnetic character of T_SDW. The pressure
dependence of T_c and T_SDW suggests a competition of the SDW and the
superconducting states in this system.",0907.5530v1
2009-08-21,Magnetic structure of EuFe2As2 determined by single crystal neutron diffraction,"Among various parent compounds of iron pnictide superconductors, EuFe2As2
stands out due to the presence of both spin density wave of Fe and
antiferromagnetic ordering (AFM) of the localized Eu2+ moment. Single crystal
neutron diffraction studies have been carried out to determine the magnetic
structure of this compound and to investigate the coupling of two magnetic
sublattices. Long range AFM ordering of Fe and Eu spins was observed below 190
K and 19 K, respectively. The ordering of Fe2+ moments is associated with the
wave vector k = (1,0,1) and it takes place at the same temperature as the
tetragonal to orthorhombic structural phase transition, which indicates the
strong coupling between structural and magnetic components. The ordering of Eu
moment is associated with the wave vector k = (0,0,1). While both Fe and Eu
spins are aligned along the long a axis as experimentally determined, our
studies suggest a weak coupling between the Fe and Eu magnetism.",0908.3142v1
2009-10-14,Electron correlation and spin density wave order in iron pnictides,"We study the correlation effects on the electronic structure and spin density
wave order in Fe-pnictides. Using the multiorbital Hubbard model and Gutzwiller
projection, we show that nonperturbative correlation effects are essential to
stabilize the metallic spin density wave phase for the intermediate correlation
strengths appropriate for pnictides. We find that the ordered moments depend
sensitively on the Hund's rule coupling $J$ but weakly on the intraorbital
Coulomb repulsion $U$, varying from $0.3\mu_B$ to $1.5\mu_B$ in the range
$J=0.3\sim0.8$ eV for $U=3\sim4$ eV. We obtain the phase diagram and discuss
the effects of orbital order and electron doping, the evolution of the Fermi
surface topology with the ordered moment, and compare to recent experiments.",0910.2707v2
2010-01-12,Dynamic pinning at a Py/Co interface measured using inductive magnetometry,"Broadband FMR responses for metallic single-layer and bi-layer magnetic films
with total thicknesses smaller than the microwave magnetic skin depth have been
studied. Two different types of microwave transducers were used to excite and
detect magnetization precession: a narrow coplanar waveguide and a wide
microstrip line. Both transducers show efficient excitation of higher-order
standing spin wave modes. The ratio of amplitudes of the first standing spin
wave to the fundamental resonant mode is independent of frequency for single
films. In contrast, we find a strong variation of the amplitudes with frequency
for bi-layers and the ratio is strongly dependent on the ordering of layers
with respect to a stripline transducer. Most importantly, cavity FMR
measurements on the same samples show considerably weaker amplitudes for the
standing spin waves. All experimental data are consistent with expected effects
due to screening by eddy currents in films with thicknesses below the microwave
magnetic skin depth. Finally, conditions for observing eddy current effects in
different types of experiments are critically examined.",1001.1837v1
2010-02-02,Role of electronic nematicity in the interplay between s- and d-wave broken-symmetry states,"To understand the role of electronic nematic order in the interplay between
s- and d-wave particle-particle or particle-hole condensate states, relations
between various s- and d-wave order parameters are studied. We find that the
nematic operator transforms two independent six-dimensional vectors. The d-wave
superconducting, d-density wave, and antiferromagnetic orders are organized
into one vector, and the s-wave superconducting, charge density wave, and
spin-triplet d-density wave orders into the other vector. Each vector acts as a
superspin and transforms under the action of SO(6) where charge, spin, eta- and
pi-pairing, spin-triplet nematic operators satisfy the SO(6) Lie algebra.
Electronic nematic order is not a part of the SO(6) group. It commutes with all
15 generators. Our findings imply that nematic order does not affect the
competition among the order parameters within the same superspin, while it
strongly interferes the interplay between two order parameters that belong to
different superspins. For example, nematicity allows a linear coupling between
d- and s-wave superconducting order parameters which modifies the
superconducting transition temperature. A generalized Ginzburg-Landau theory
and further physical implications are discussed.",1002.0586v1
2010-02-04,Magnetic excitations in ferro-pnictide materials controlled by a quantum critical point into hidden order,"The two-orbital J1-J2 model that describes a square lattice of frustrated
spin-1 iron atoms is analyzed within the linear spin-wave approximation and by
exact diagonalization over a 4x4 cluster. A quantum critical point (QCP) is
identified that separates hidden magnetic order at weak Hund's rule coupling
from a commensurate spins density wave (cSDW) at strong Hund's rule coupling.
Although the moment for cSDW order is small at the QCP, the critical linear
spin-wave spectrum shows strong low-energy excitations centered at the
wavenumbers that correspond to cSDW order. These disperse anisotropically. A
fit to the magnetic excitation spectrum of ferro-pnictide materials obtained
recently by inelastic neutron scattering measurements notably accounts for the
absence of softening at the wavenumber that corresponds to Neel order.",1002.0891v3
2010-06-21,Observation of Rabi oscillation of light assisted by atomic spin wave,"Coherent conversion between a Raman pump field and its Stokes field is
observed in a Raman process with a strong atomic spin wave initially prepared
by another Raman process operated in the stimulated emission regime. The
oscillatory behavior resembles the Rabi oscillation in atomic population in a
two-level atomic system driven by a strong light field. The Rabi-like
oscillation frequency is found to be related to the strength of the pre-built
atomic spin wave. High conversion efficiency of 40% from the Raman pump field
to the Stokes field is recorded and it is independent of the input Raman pump
field. This process can act as a photon frequency multiplexer and may find wide
applications in quantum information science.",1006.3998v1
2010-07-21,Exchange anisotropy pinning of a standing spin wave mode,"Standing spin waves in a thin film are used as sensitive probes of interface
pinning induced by an antiferromagnet through exchange anisotropy. Using
coplanar waveguide ferromagnetic resonance, pinning of the lowest energy spin
wave thickness mode in Ni(80)Fe(20)/Ir(25)Mn(75) exchange biased bilayers was
studied for a range of IrMn thicknesses. We show that pinning of the standing
mode can be used to amplify, relative to the fundamental resonance, frequency
shifts associated with exchange bias. The shifts provide a unique `fingerprint'
of the exchange bias and can be interpreted in terms of an effective
ferromagnetic film thickness and ferromagnet/antiferromagnet interface
anisotropy. Thermal effects are studied for ultra-thin antiferromagnetic
Ir(25)Mn(75) thicknesses, and the onset of bias is correlated with changes in
the pinning fields. The pinning strength magnitude is found to grow with
cooling of the sample, while the effective ferromagnetic film thickness
simultaneously decreases. These results suggest that exchange bias involves
some deformation of magnetic order in the interface region.",1007.3577v1
2010-08-13,Spin Wave Storage using Chirped Control Fields in Atomic Frequency Comb based Quantum Memory,"It has been shown that an inhomogeneously broadened optical transition shaped
into an atomic frequency comb can store a large number of temporal modes of the
electromagnetic field at the single photon level without the need to increase
the optical depth of the storage material. The readout of light modes is made
efficient thanks to the rephasing of the optical-wavelength coherence similarly
to photon echo-type techniques and the re-emission time is given by the comb
structure. For on-demand readout and long storage times, two control fields are
used to transfer back and forth the optical coherence into a spin wave. Here,
we present a detailed analysis of the spin wave storage based on chirped
adiabatic control fields. In particular, we verify that chirped fields require
significantly weaker intensities than $\pi$-pulses. The price to pay is a
reduction of the multimode storage capacity that we quantify for realistic
material parameters associated with solids doped with rare-earth-metal ions.",1008.2284v1
2010-10-18,Excitation of spin waves by tunnelling electrons in one-dimensional ferro and anti-ferromagnets,"Excitation of finite chains of magnetic atoms adsorbed on a surface by
tunnelling electrons from an STM (Scanning Tunnelling Microscope) tip is
studied using a Heisenberg Hamiltonian description of the magnetic couplings
along the chain and a strong coupling approach of inelastic tunnelling. The
excitation probability of the magnetic levels is very high and the excitation
spectra in chains of different lengths are very similar. The excitations in
finite chains can be considered as spin waves quantized in the finite object.
The energy and momentum spectra of the spin waves excited in the idealized
infinite chain by tunnelling electrons are determined from the results on the
finite chains. Both ferro- and antiferromagnetic couplings are considered,
leading to very different results. In particular, in the anti-ferromagnetic
case, excitations linked to the entanglement of the chain ground state are
evidenced.",1010.3587v1
2010-11-01,"Magnetic phase diagram of spatially anisotropic, frustrated spin-1/2 Heisenberg antiferromagnet on a stacked square lattice","Magnetic phase diagram of a spatially anisotropic, frustrated spin-1/2
Heisenberg antiferromagnet on a stacked square lattice is investigated using
second-order spin-wave expansion. The effects of interlayer coupling and the
spatial anisotropy on the magnetic ordering of two ordered ground states are
explicitly studied. It is shown that with increase in next nearest neighbor
frustration the second-order corrections play a significant role in stabilizing
the magnetization. We obtain two ordered magnetic phases (Neel and stripe)
separated by a paramagnetic disordered phase. Within second-order spin-wave
expansion we find that the width of the disordered phase diminishes with
increase in the interlayer coupling or with decrease in spatial anisotropy but
it does not disappear. Our obtained phase diagram differs significantly from
the phase diagram obtained using linear spin-wave theory.",1011.0381v2
2010-11-12,"Spin waves in the $(π,0)$ magnetically ordered iron chalcogenide Fe$_{1.05}$Te","We use inelastic neutron scattering to show that the spin waves in the iron
chalcogenide Fe$_{1.05}$Te display novel dispersion clearly different from
those in the related iron pnictide systems. By fitting the spin waves to a
Heisenberg Hamiltonian, we extract magnetic exchange couplings that are
dramatically different from both predictions by density functional calculations
and measurements on the iron pnictide CaFe$_2$As$_2$. While the
nearest-neighbor exchange couplings in CaFe$_2$As$_2$ and Fe$_{1.05}$Te are
quite different, their next-nearest-neighbor exchange couplings are similar.
These results suggest that superconductivity in the pnictides and chalcogenides
share a common magnetic origin that is intimately associated with the
next-nearest-neighbor magnetic coupling between the irons.",1011.2930v2
2011-02-22,Superconductivity mediated by the antiferromagnetic spin-wave in chalcogenide iron-base superconductors,"The ground state of K$_{0.8+x}$Fe$_{1.6+y}$Se$_2$ and other iron-based
selenide superconductors are doped antiferromagnetic semiconductors. There are
well defined iron local moments whose energies are separated from those of
conduction electrons by a large band gap in these materials. We propose that
the low energy physics of this system is governed by a model Hamiltonian of
interacting electrons with on-site ferromagnetic exchange interactions and
inter-site superexchange interactions. We have derived the effective pairing
potential of electrons under the linear spin-wave approximation and shown that
the superconductivity can be driven by mediating coherent spin wave excitations
in these materials. Our work provides a natural account for the coexistence of
superconducting and antiferromagnetic long range orders observed by neutron
scattering and other experiments.",1102.4575v1
2011-03-06,Deterministic spin-wave interferometer based on Rydberg blockade,"The spin-wave (SW) NOON state is an $N$-particle Fock state with two atomic
spin-wave modes maximally entangled. Attributed to the property that the phase
is sensitive to collective atomic motion, the SW NOON state can be utilized as
a novel atomic interferometer and has promising application in quantum enhanced
measurement. In this paper we propose an efficient protocol to
deterministically produce the atomic SW NOON state by employing Rydberg
blockade. Possible errors in practical manipulations are analyzed. A feasible
experimental scheme is suggested. Our scheme is far more efficient than the
recent experimentally demonstrated one, which only creates a heralded
second-order SW NOON state.",1103.1136v3
2011-03-07,An all-sky search algorithm for continuous gravitational waves from spinning neutron stars in binary systems,"Rapidly spinning neutron stars with non-axisymmetric mass distributions are
expected to generate quasi-monochromatic continuous gravitational waves. While
many searches for unknown, isolated spinning neutron stars have been carried
out, there have been no previous searches for unknown sources in binary
systems. Since current search methods for unknown, isolated neutron stars are
already computationally limited, expanding the parameter space searched to
include binary systems is a formidable challenge. We present a new hierarchical
binary search method called TwoSpect, which exploits the periodic orbital
modulations of the continuous waves by searching for patterns in doubly
Fourier-transformed data. We will describe the TwoSpect search pipeline,
including its mitigation of detector noise variations and corrections for
Doppler frequency modulation caused by changing detector velocity. Tests on
Gaussian noise and on a set of simulated signals will be presented.",1103.1301v2
2011-06-07,Incommensurate Spin Density Wave versus local magnetic inhomogeneities in Ba(Fe1-xNix)2As2: a 57Fe Mossbauer spectroscopy study,"We report 57Fe Mossbauer spectral results in pure and doped Ba(Fe1-xNix)2As2
with x=0.01 and 0.03. We show that all these materials present a first-order
magnetic transition towards a magnetically ordered state. In the doped
compounds, a broad distribution of Fe hyperfine fields is present in the
magnetic phase. We successfully fit the Mossbauer data in Ba(Fe1-xNix)2As2 in
the framework of two different models: 1) an incommensurate spin density wave;
2) a dopant-induced perturbation of the Fe polarization, recently proposed to
interpret 75As NMR data in Ba(Fe1-xNix)2As2, which is valid only in the very
dilute limit x=0.01. Moreover, we show here that these NMR data can also be
successfully analysed in terms of the 'incommensurate model' for all doping
contents by using the parameters obtained from the Mossbauer spectral analysis.
Therefore it is not possible to rule out the presence of an incommensurate spin
density wave on the basis of the 75As NMR data.",1106.1332v2
2012-01-02,Spin wave measurements over the full Brillouin zone of multiferroic BiFeO3,"Using inelastic neutron scattering technique, we measured the spin wave
dispersion over the entire Brillouin zone of room temperature multiferroic
BiFeO3 single crystals with magnetic excitations extending to as high as 72.5
meV. The full spin waves can be explained by a simple Heisenberg Hamiltonian
with a nearest neighbor exchange interaction (J=4.38 meV), a next nearest
neighbor exchange interaction (J'=0.15 meV), and a Dzyaloshinskii-Moriya-like
term (D=0.107 meV). This simple Hamiltonian determined, for the first time, for
BiFeO3 provides a fundamental ingredient for understanding of the novel
magnetic properties of BiFeO3.",1201.0436v2
2012-01-20,Modified Spin Wave Analysis of Low Temperature Properties of Spin-1/2 Frustrated Ferromagnetic Ladder,"Low temperature properties of the spin-1/2 frustrated ladder with
ferromagnetic rungs and legs, and two different antiferromagnetic next nearest
neighbor interaction are investigated using the modified spin wave
approximation in the region with ferromagnetic ground state. The temperature
dependence of the magnetic susceptibility and magnetic structure factors is
calculated. The results are consistent with the numerical exact diagonalization
results in the intermediate temperature range. Below this temperature range,
the finite size effect is significant in the numerical diagonalization results,
while the modified spin wave approximation gives more reliable results. The low
temperature properties near the limit of the stability of the ferromagnetic
ground state are also discussed.",1201.4242v1
2012-02-07,Spin-wave analysis of the transverse-field Ising model on the checkerboard lattice,"The ground state properties of the S=1/2 transverse-field Ising model on the
checkerboard lattice are studied using linear spin wave theory. We consider the
general case of different couplings between nearest neighbors (J1) and
next-to-nearest neighbors (J2). In zero field the system displays a large
degeneracy of the ground state, which is exponential in the system size (for
J1=J2) or in the system's linear dimensions (for J2>J1). Quantum fluctuations
induced by a transverse field are found to be unable to lift this degeneracy in
favor of a classically ordered state at the harmonic level. This remarkable
fact suggests that a quantum-disordered ground state can be instead promoted
when non-linear fluctuations are accounted for, in agreement with existing
results for the isotropic case J1=J2. Moreover spin-wave theory shows sizable
regions of instability which are further candidates for quantum-disordered
behavior.",1202.1462v1
2012-03-05,Generation of strong magnetic fields by r-modes in millisecond accreting neutron stars: induced deformations and gravitational wave emission,"Differential rotation induced by the r-mode instability can generate very
strong toroidal fields in the core of accreting, millisecond spinning neutron
stars. We introduce explicitly the magnetic damping term in the evolution
equations of the r-modes and solve them numerically in the Newtonian limit, to
follow the development and growth of the internal magnetic field. We show that
the strength of the latter can reach large values, $B \sim 10^{14} $ G, in the
core of the fastest accreting neutron stars. This is strong enough to induce a
significant quadrupole moment of the neutron star mass distribution,
corresponding to an ellipticity $|\epsilon_B}| \sim 10^{-8}$. If the symmetry
axis of the induced magnetic field is not aligned with the spin axis, the
neutron star radiates gravitational waves. We suggest that this mechanism may
explain the upper limit of the spin frequencies observed in accreting neutron
stars in Low Mass X-Ray Binaries. We discuss the relevance of our results for
the search of gravitational waves.",1203.0891v2
2012-12-06,Barkhausen-type noise in the resistance of antiferromagnetic Cr thin films,"We present an experimental study of the changes generated on the electrical
resistance $R(T)$ of epitaxial Cr thin films by the transformation of quantized
spin density wave domains as the temperature is changed. A characteristic
resistance noise appears only within the same temperature region where a
cooling-warming cycle in $R(T)$ displays hysteretic behavior. We propose an
analysis based on an analogy with the Barkhausen noise seen in ferromagnets.
There fluctuations in the magnetization $M(H)$ occur when the magnetic field
$H$ is swept. By mapping $M \rightarrow \Psi_0$ and $H \rightarrow T$, where
$\Psi_0$ corresponds to the order parameter of the spin density wave, we
generalize the Preisach model in terms of a random distribution of {\it
resistive hysterons} to explain our results. These hysterons are related to
distributions of quantized spin density wave domains with different sizes,
local energies and number of nodes.",1212.1411v1
2012-12-12,Strong fluctuations near the frustration point in cubic lattice ferromagnets with localized moments,"Thermodynamic properties of cubic Heisenberg ferromagnets with competing
exchange interactions are considered near the frustration point where the
coefficient $D$ in the spin-wave spectrum $E_{\mathbf{k}}\sim D k^{2}$
vanishes. Within the Dyson-Maleev formalism it is found that at low
temperatures thermal fluctuations stabilize ferromagnetism by increasing the
value of $D$. For not too strong frustration this leads to an unusual ""concave""
shape of the temperature dependence of magnetization, which is in agreement
with experimental data on the europium chalcogenides. The phase diagram is
constructed by means of Monte Carlo simulation, and suppression of
magnetization and Curie temperature is found in comparison with the results of
the spin-wave theory. This effect is explained by the the presence of
non-analytical corrections to the spin-wave spectrum which are represented in
the lowest order by the term $\sim (T/S)^{2} k^{2}\log{k}$.",1212.2773v2
2013-01-14,Coherent Storage of Temporally Multimode Light Using a Spin-Wave Atomic Frequency Comb Memory,"We report on coherent and multi-temporal mode storage of light using the full
atomic frequency comb memory scheme. The scheme involves the transfer of
optical atomic excitations in Pr3+:Y2SiO5 to spin-waves in the hyperfine levels
using strong single-frequency transfer pulses. Using this scheme, a total of 5
temporal modes are stored and recalled on-demand from the memory. The coherence
of the storage and retrieval is characterized using a time-bin interference
measurement resulting in visibilities higher than 80%, independent of the
storage time. This coherent and multimode spin-wave memory is promising as a
quantum memory for light.",1301.3048v1
2013-04-29,Bose glass transition and spin-wave localization for 2D bosons in a random potential,"A spin-wave approach of the zero temperature superfluid-insulator transition
for two-dimensional hard-core bosons in a random potential $\mu=\pm$ W is
developed. While at the classical level there is no intervening phase between
the Bose-condensed superfluid (SF) and the gapped disordered insulator, the
introduction of quantum fluctuations leads to a much richer physics. Upon
increasing the disorder strength W, the Bose-condensed fraction disappears
first, before the SF. Then a gapless Bose-glass phase emerges over a finite
region until the insulator appears. Furthermore, in the strongly disordered SF
regime, a mobility edge in the spin-wave excitation spectrum is found at a
finite frequency $\Omega_c$ decreasing with W, and presumably vanishing in the
Bose-glass phase.",1304.7636v2
2013-06-17,Charge and spin density waves: Quasi one dimension to two dimension,"Possibility of electronic charge and spin separation leading to charge
density wave and spin density wave is well established in one dimensional
systems in presence and absence of Coulomb interaction. We start from quasi one
dimension and show the possibility of such a transition in quasi one dimension
as well as in two dimension by going to a regime where it can be shown for free
electrons that just interact via Fermi statistics. Since Coulomb interaction
can only facilitate the phenomenon, the purpose of our work is to show the
phenomena unambiguously in the limit when Coulomb interaction can be ignored.
Finally we also comment on dimensions greater than two and inclusion of Coulomb
interactions.",1306.3781v2
2013-10-23,Singlet Mott State Simulating the Bosonic Laughlin Wave Function,"We study properties of a class of spin singlet Mott states for arbitrary spin
S bosons on a lattice, with particle number per cite n=S/l+1, where l is a
positive integer. We show that such a singlet Mott state can be mapped to a
bosonic Laughlin wave function on the sphere with a finite number of particles
at filling {\nu}=1/2l. Spin, particle and hole excitations in the Mott state
are discussed, among which the hole excitation can be mapped to the quasi-hole
of the bosonic Laughlin wave function. We show that this singlet Mott state can
be realized in a cold atom system on optical lattice, and can be identified
using Bragg spectroscopy and Stern-Gerlach techniques. This class of singlet
Mott states may be generalized to simulate bosonic Laughlin states with filling
{\nu}=q/2l.",1310.6105v2
2014-01-03,Effect of SDW fluctuations on the specific heat jump in iron pnictides at a superconducting transition,"Measurements of the specific heat jump at the onset of superconducting
transition in the iron-pnictide compounds revealed strong variation of its
magnitude as a function of doping that is peaked near the optimal doping. We
show that this behavior is direct manifestation of the coexistence between
spin-density-wave and superconducting orders and the peak originates from
thermal fluctuations of the spin-density-waves near the end point of the
coexistence phase -- a tetracritical point. Thermal fluctuations result in a
power-law dependence of the specific heat jump that is stronger than the
contribution of mass renormalization due to quantum fluctuations of
spin-density-waves in the vicinity of the putative critical point beneath the
superconducting dome.",1401.1118v1
2014-03-21,Localization of spin waves in disordered quantum rotors,"We study the dynamics of excitations in a system of $O(N)$ quantum rotors in
the presence of random fields and random anisotropies. Below the lower critical
dimension $d_{\mathrm{lc}}=4$ the system exhibits a quasi-long-range order with
a power-law decay of correlations. At zero temperature the spin waves are
localized at the length scale $L_{\mathrm{loc}}$ beyond which the quantum
tunneling is exponentially suppressed $ c \sim
e^{-(L/L_{\mathrm{loc}})^{2(\theta+1)}}$. At finite temperature $T$ the spin
waves propagate by thermal activation over energy barriers that scales as
$L^{\theta}$. Above $d_{\mathrm{lc}}$ the system undergoes an order-disorder
phase transition with activated dynamics such that the relaxation time grows
with the correlation length $\xi$ as $\tau \sim e^{C \xi^\theta/T}$ at finite
temperature and as $\tau \sim e^{C' \xi^{2(\theta+1)}/\hbar^2}$ in the vicinity
of the quantum critical point.",1403.5529v2
2014-03-24,Exchange effects in Coulomb quantum plasmas: Dispersion of waves in 2D and 3D mediums,"We describe quantum hydrodynamic equations with the Coulomb exchange
interaction for three and two dimensional plasmas. Explicit form of the force
densities are derived. We present non-linear Schrodinger equations (NLSEs) for
the Coulomb quantum plasmas with the exchange interaction. We show contribution
of the exchange interaction in the dispersion of the Langmuir, and ion-acoustic
waves. We consider influence of the spin polarization ratio on strength of the
Coulomb exchange interaction. This is important since exchange interaction
between particles with same spin direction and particles with opposite spin
directions are different. At small particle concentrations
$n_{0}<<10^{25}cm^{-3}$ and small polarization the exchange interaction gives
small decrease of the Fermi pressure. With increasing of polarization role of
the exchange interaction becomes more important, so that it can overcome the
Fermi pressure. The exchange interaction also decreases contribution of the
Langmuir frequency. Ion-acoustic waves do not exist in limit of large
polarization since the exchange interaction changes the sign of pressure. At
large particle concentrations $n_{0}>>10^{25}cm^{-3}$ the Fermi pressure
prevails over the exchange interaction for all polarizations. Similar picture
we obtain for two dimensional quantum plasmas.",1403.6075v1
2014-05-19,Mesh Size and Damped Edge Effects in Micromagnetic Spin Wave Simulation,"We have studied the dependence of spin wave dispersion on the characteristics
of the mesh used in a finite element micromagnetic simulation. It is shown that
the dispersion curve has a cut off at a frequency which is analytically
predictable. The frequency depends on the average mesh length used for the
simulation. Based on this, a recipe to effectively obtain the dispersion
relation has been suggested. In a separate study, spin wave reflections are
absorbed by introducing highly damped edges in the device. However, an abrupt
change in the damping parameter causes reflections. We compare damping profiles
and identify an exponential damping profile as causing significantly less
reflections.",1405.4615v2
2014-07-16,Phase separation and long wave-length charge instabilities in spin-orbit coupled systems,"We investigate a two-dimensional electron model with Rashba spin-orbit
interaction where the coupling constant $g=g(n)$ depends on the electronic
density. It is shown that this dependence may drive the system unstable towards
a long-wave length charge density wave (CDW) where the associated second order
instability occurs in close vicinity to global phase separation. For very low
electron densities the CDW instability is nesting-induced and the modulation
follows the Fermi momentum $k_F$. At higher density the instability criterion
becomes independent of $k_F$ and the system may become unstable in a broad
momentum range. Finally, upon filling the upper spin-orbit split band, finite
momentum instabilities disappear in favor of phase separation alone. We discuss
our results with regard to the inhomogeneous phases observed at the
LaAlO$_3$/SrTiO$_3$ or LaTiO$_3$/SrTiO$_3$ interfaces.",1407.4280v1
2014-12-12,Asymmetric spin-wave dispersion due to Dzyaloshinskii-Moriya interaction in an ultrathin Pt/CoFeB film,"Employing Brillouin spectroscopy, strong interfacial Dzyaloshinskii-Moriya
interactions have been observed in an ultrathin Pt/CoFeB film. Our
micromagnetic simulations show that spin-wave nonreciprocity due to asymmetric
surface pinning is insignificant for the 0.8nmthick CoFeB film studied. The
observed high asymmetry of the monotonic spin wave dispersion relation is thus
ascribed to strong Dzyaloshinskii-Moriya interactions present at the Pt/CoFeB
interface. Our findings should further enhance the significance of CoFeB as an
important material for magnonic, spintronic and skyrmionic applications.",1412.3907v2
2015-01-14,A spin-wave logic gate based on a width-modulated dynamic magnonic crystal,"An electric current controlled spin-wave logic gate based on a
width-modulated dynamic magnonic crystal is realized. The device utilizes a
spin-wave waveguide fabricated from a single-crystal Yttrium Iron Garnet film
and two conducting wires attached to the film surface. Application of electric
currents to the wires provides a means for dynamic control of the effective
geometry of the waveguide and results in a suppression of the magnonic band
gap. The performance of the magnonic crystal as an AND logic gate is
demonstrated.",1501.03486v2
2015-01-14,Dispersionless spin waves in Gadolinium Gallium Garnet,"We report the results of neutron scattering on a powder sample of Gd3Ga5O12
at high magnetic fields. We find that in high fields (B>1.8 T) the system is
not fully polarized, but has a small canting of the moments induced by the
dipolar interaction. We show that the degree of canting is accurately predicted
by the standard Hamiltonian which includes the dipolar interaction. The
inelastic scattering is dominated at large momentum transfers by a band of
almost dispersionless excitations. We show that these correspond to the spin
waves localized on ten site rings, expected for a system described by a nearest
neighbor interaction, and that the spectrum at high fields B>1.8 T is
well-described by a spin wave theory. The phase for fields <1.8 T is
characterized by an antiferromagnetic Bragg peak at (210) and an incommensurate
peak.",1501.03493v1
2015-02-13,Bose-Einstein condensation of magnons in atomic hydrogen gas,"We report on experimental observation of BEC-like behaviour of quantized
electron spin waves (magnons) in a dense gas of spin polarized atomic hydrogen.
The magnons are trapped and controlled with inhomogeneous magnetic fields, and
described by a Schr\""odinger-like wave equation, in analogy to the BEC
experiments with neutral atoms. We have observed the appearance of a sharp
feature in the ESR spectrum displaced from the normal spin wave spectrum. We
believe that this observation corresponds to a sudden growth of the ground
state population of the magnons and emergence of their spontaneous coherence
for hydrogen gas densities exceeding a critical value, dependent on the
trapping potential. We interpret the results as a BEC of non-equilibrium
magnons which were formed by applying the rf power.",1502.03963v1
2015-02-18,Transverse spin of light for all wavefields,"It has been known for a long time that light carries both linear and angular
momenta parallel to the direction of propagation. However, only recently it has
been pointed out that beams of light, under certain conditions, may exhibit a
transverse spin angular momentum perpendicular to the propagation direction.
When this happens, the electric field transported by the light rotates around
an axis transverse to the beam path. Such kind of fields, although deceptively
elusive, are almost ubiquitous in optics as they manifests in strongly focused
beams, plasmonic fields and evanescent waves. In this work we present a general
formalism describing all these phenomena. In particular, we demonstrate how to
mathematically generate a wave field possessing transverse spin angular
momentum density, from any arbitrarily given scalar wave field, either
propagating and evanescent.",1502.05350v2
2015-04-01,All-magnetic control of skyrmions in nanowires by a spin wave,"Magnetic skyrmions are topologically protected nanoscale objects, which are
promising building blocks for novel magnetic and spintronic devices. Here, we
investigate the dynamics of a skyrmion driven by a spin wave in a magnetic
nanowire. It is found that (i) the skyrmion is first accelerated and then
decelerated exponentially; (ii) it can turn L-corners with both right and left
turns; and (iii) it always turns left (right) when the skyrmion number is
positive (negative) in the T- and Y-junctions. Our results will be the basis of
skyrmionic devices driven by a spin wave.",1504.00409v2
2015-05-15,Graphene quantum dots probed by scanning tunneling spectroscopy and transport spectroscopy after local anodic oxidation,"Graphene quantum dots are considered as promising alternatives to quantum
dots in III-V semiconductors, e.g., for the use as spin qubits due to their
consistency made of light atoms including spin-free nuclei which both imply
relatively long spin decoherene times. However, this potential has not been
realized in experiments so far, most likely, due to a missing control of the
edge configurations of the quantum dots. Thus, a more fundamental investigation
of Graphene quantum dots appears to be necessary including a full control of
the wave function properties most favorably during transport spectroscopy
measurements. Here, we review the recent success in mapping wave functions of
graphene quantum dots supported by metals, in particular Ir(111), and show how
the goal of probing such wave functions on insulating supports during transport
spectroscopy might be achieved.",1505.04092v1
2015-09-10,Simultaneous generation of two spin-wave-photon entangled states in an atomic ensemble,"The generation and storage of entangled photons play important roles in
quantum information technique. Spontaneous Raman scattering (SRS) in atomic
ensembles provides a promising method to generate entangled photons capable of
storage. In the past experiments, a spin-wave-photon entangled state is
produced via SRS in an atomic ensemble, with which a pair of entangled photons
is obtained. Here, we report a scheme of simultaneously generating two
spin-wave-photon entangled states in an atomic ensemble by collecting Stokes
photons at two different directions. Based on the obtained two atom-photon
entangled sources, we generate a three-photon GHZ polarization-entangled state
and conditionally prepare a polarization-entangled photon pair, respectively.",1509.03159v1
2015-11-05,Perpendicular standing spin wave and magnetic anisotropic study on amorphous FeTaC films,"Magnetic anisotropy, spin wave (SW) excitation and exchange stiffness
constant of amorphous FeTaC ($d$ = 20-200 nm) films were studied as a function
of thickness using micro-strip ferromagnetic resonance (MS-FMR) technique. The
MS-FMR spectra for in-plane applied magnetic field show the presence of uniform
precessional mode ($n$ = 0) along with first perpendicular standing spin wave
(PSSW) mode ($n$ = 1) especially for $d$ = 50, 100 and 200 nm films. The
angular ($\varphi_{H}$) dependence of resonance field ($H_{r}$) and magnetic
field dependence of resonance frequencies ($f_{r}$) in planar configuration for
the uniform and PSSW modes were modeled successfully by using dispersion
relation which arises from a combination of exchange and dipolar interactions.
The relevant parameters such as saturation magnetization ($4\pi M_{S}$),
uniaxial anisotropic constant ($K_{u}$), $g$-factor, and exchange stiffness
constants ($A_{ex}$) are estimated for different FeTaC film thickness. $A_{ex}$
is found to increase from 1.52(4)$\times$10$^{-7}$ to 5.0(5)$\times$10$^{-6}$
erg/cm as the thickness of film increases from 50 to 200 nm, possibly due to
surface pinning effect or significant inhomogeneity especially at higher
thickness films.",1511.01722v2
2016-02-05,Generation of light with multimode time-delayed entanglement using storage in a solid state spin-wave quantum memory,"Here we demonstrate generating and storing entanglement in a solid state
spin-wave quantum memory with on-demand read out using the process of rephased
amplified spontaneous emission (RASE). Amplified spontaneous emission (ASE),
resulting from an inverted ensemble of Pr$^{3+}$ ions doped into a Y$_2$SiO$_5$
crystal, generates entanglement between collective states of the praseodymium
ensemble and the output light. The ensemble is then rephased using a four-level
photon echo technique. Entanglement between the ASE and its echo is confirmed
and the inseparability violation preserved when the RASE is stored as a
spin-wave for up to 5 $\mu$s. RASE is shown to be temporally multimode with
almost perfect distinguishability between two temporal modes demonstrated.
These results pave the way for the use of multimode solid state quantum
memories in scalable quantum networks.",1602.01917v2
2016-02-18,Confinement transition to density wave order in metallic doped spin liquids,"Insulating quantum spin liquids can undergo a confinement transition to a
valence bond solid state via the condensation of topological excitations of the
associated gauge theory. We extend the theory of such transitions to
fractionalized Fermi liquids (FL*): these are metallic doped spin liquids in
which the Fermi surfaces only have gauge neutral quasiparticles. Using insights
from a duality transform on a doped quantum dimer model for the U(1)-FL* state,
we show that projective symmetry group of the theory of the topological
excitations remains unmodified, but the Fermi surfaces can lead to additional
frustrating interactions. We propose a theory for the confinement transition of
$\mathbb{Z}_2$-FL* states via the condensation of visons. A variety of
confining, incommensurate density wave states are possible, including some that
are similar to the incommensurate $d$-form factor density wave order observed
in several recent experiments on the cuprate superconductors.",1602.05954v2
2016-02-19,Complete mapping of the spin-wave spectrum in vortex state nano-disk,"We report a study on the complete spin-wave spectrum inside a vortex state
nano-disk. Transformation of this spectrum is continuously monitored as the
nano-disk becomes gradually magnetized by a perpendicular magnetic field and
encouters a second order phase transition to the uniformly magnetized state.
This reveals the bijective relationship that exists between the eigen-modes in
the vortex state with the ones in the saturated state. It is found that the
gyrotropic mode can be continuously viewed as a uniform phase precession, which
uniquely softens (its frequency vanishes) at the saturation field to transform
above into the Kittel mode. By contrast the other spin-wave modes remain finite
as a function of the applied field while their character is altered by level
anti-crossing.",1602.06336v2
2016-07-22,Lattice operators for scattering of particles with spin,"We construct operators for simulating the scattering of two hadrons with spin
on the lattice. Three methods are shown to give the consistent operators for
PN, PV, VN and NN scattering, where P, V and N denote pseudoscalar, vector and
nucleon. Explicit expressions for operators are given for all irreducible
representations at lowest two relative momenta. Each hadron has a good helicity
in the first method. The hadrons are in a certain partial wave L with total
spin S in the second method. These enable the physics interpretations of the
operators obtained from the general projection method. The correct
transformation properties of the operators in all three methods are proven. The
total momentum of two hadrons is restricted to zero since parity is a good
quantum number in this case.",1607.06738v2
2016-08-31,Cavity enhanced telecom heralded single photons for spin-wave solid state quantum memories,"We report on a source of heralded narrowband (3MHz) single photons compatible
with solid-state spin-wave quantum memories based on praseodymium doped
crystals. Widely non-degenerate narrow-band photon pairs are generated using
cavity enhanced down conversion. One photon from the pair is at telecom
wavelengths and serves as heralding signal, while the heralded single photon is
at 606nm, resonant with an optical transition in Pr:YSO. The source offers a
heralding efficiency of 28% and a generation rate exceeding 2000 pairs/mW in a
single-mode. The single photon nature of the heralded field is confirmed by a
direct antibunching measurement, with a measured antibunching parameter down to
0.010(4). Moreover, we investigate in detail photon cross- and autocorrelation
functions proving non-classical correlations between the two photons. The
results presented in this paper represent significant improvement over the
state of the art and offer prospects for the demonstration of single photon
spin-wave storage in an on-demand solid state quantum memory, heralded by a
telecom photon.",1608.08943v1
2016-10-13,Spin wave excitations in the pyrovanadate alpha-Cu2V2O7,"The pyrovanadate alpha-Cu2V2O7 belongs to the orthorhombic (Fdd2) class of
crystals with noncentrosymmetric crystal structure. Recently, the compound has
been identified to be a magnetic multiferroic with a substantial electric
polarization below the magnetic transition temperature TC = 35 K. Here we
report the results of our inelastic neutron scattering (INS) studies on a
polycrystalline sample of alpha-Cu2V2O7. Our INS data clearly show the
existence of dispersive spin wave excitations below TC with a zone-boundary
energy of 11 meV at 5 K.We have analyzed the data using linear spin wave
theory, which shows good agreement between the experiment and calculation. The
analysis is consistent with the third nearest neighbor exchange interaction
playing a dominant role in the magnetism of the material.",1610.03969v1
2016-10-13,Spin wave surface states in one-dimensional planar magnonic crystals,"We have investigated surface spin wave states in one-dimensional planar
bi-component magnonic crystals, localized on the surfaces resulting from the
breaking of the periodic structure. The two systems have been considered: the
magnonic crystal with periodic changes of the anisotropy field in exchange
regime and the magnonic crystal composed of Fe and Ni stripes in dipolar regime
with exchange interactions included. We chose the symmetric unit cell for both
systems to implement the symmetry related criteria for existence of the surface
states. We investigated also the surface states induced by the presence of
perturbation of the surface areas of the magnonic crystals. We showed, that the
system with modulated anisotropy is a direct analog of the electronic crystal.
Therefore, the surface states in both systems have the same properties. For
surface states existing in magnonic crystals in dipolar regime we demonstrated
that spin waves preserve distinct differences to the electronic crystals, which
are due to long-range dynamic dipolar interactions. We found that tuning of the
strength of magnetization pinning resulting from the surface anisotropy or
dipolar effect is vitally important for existence of the surface states in
magnonic crystals.",1610.04083v1
2016-10-26,Time-resolved measurements of surface spin-wave pulses at millikelvin temperatures,"In this work, we experimentally investigate the propagation of pulsed
magnetostatic surface spin-wave (magnon) signals in an yttrium iron garnet
(YIG) waveguide at millikelvin temperatures. Our measurements are performed in
a dilution refrigerator at microwave frequencies. The excellent signal-to-noise
ratio afforded by the low-temperature environment allows the propagation of the
pulses to be observed in detail. The work gives insight both into
low-temperature magnon dynamics in YIG and the potential application of systems
of propagating magnons to solid-state quantum information processing.",1610.08402v2
2017-07-04,Spin wave dispersion just above the magnetic order-order transition in the metallic antiferromagnet Mn$_3$Pt,"Spin wave dispersion in the metallic antiferromagnet Mn$_3$Pt was
investigated just above the order-order transition temperature by using the
inelastic neutron scattering technique. The spin wave dispersion at $T = 400$ K
along [100], [110] and [111] directions was isotropic within the measurement
accuracy. The dispersion was described by $({\hbar\omega})^2 = c^2q^2 +
\Delta^2$ with $c = 190$ meV {\AA} and $\Delta = 3.3$ meV. Compared with the
dispersion at $T = 419$ K previously reported, the result demonstrates a large
reduction of the stiffness constant $c$ with increasing temperature. This is
similar to that observed in the metallic antiferromagnet FePt$_3$, and is an
indication of the itinerancy of the magnetic moments.",1707.00997v2
2017-07-04,"Absorption of electromagnetic and gravitational waves by Kerr black holes: Shadows, superradiance and the spin-helicity effect","We study the absorption of plane waves by Kerr black holes. We calculate the
absorption cross section: the area of the black hole shadow at a finite
wavelength. We present a unified picture of the absorption of all massless
bosonic fields, focussing on the on-axis incidence case. We investigate the
spin-helicity effect, arising from a coupling between dragging of frames and
the helicity of a polarized wave. We introduce and calibrate an extended sinc
approximation which provides new quantitative data on the spin-helicity effect
in strong-field gravity.",1707.01144v1
2017-07-31,Spin wave beam propagation in ferromagnetic thin film with graded refractive index: mirage effect and prospective applications,"Using analysis of iso-frequency contours of the spin-wave dispersion
relation, supported by micromagnetic simulations, we study the propagation of
spin-wave (SW) beams in thin ferromagnetic films through the areas of the
inhomogeneous refractive index. We compare the transmission and reflection of
SWs in areas with gradual and step variation of the SW refractive index. In
particular, we show the mirage effect for SWs with narrowing SW beam width, and
an application of the gradual modulation of the SWs refractive index as a
diverging lens. Furthermore, we study the propagation of SWs in ferromagnetic
stripe with modulated refractive index. We demonstrate that the system can be
considered as the graded-index waveguide, which preserves the width of the SW
beam for a long distance-the property essential for prospective applications of
magnonics.",1707.09768v4
2017-09-29,Magnetic structure and spin wave excitations in the multiferroic magnetic metal-organic framework (CD$_3$)$_2$ND$_2$[Mn(DCO$_2$)$_3$],"We report the magnetic diffraction pattern and spin wave excitations in
(CD$_3$)$_2$ND$_2$[Mn(DCO$_2$)$_3$] measured using elastic and inelastic
neutron scattering. The magnetic structure is shown to be a G-type
antiferromagnet with moments pointing along the $b$ axis. By comparison with
simulations based on linear spin wave theory, we have developed a model for the
magnetic interactions in this multiferroic metal-organic framework material.
The interactions form a three-dimensional network with antiferromagnetic
nearest-neighbour interactions along three directions of $J_1=-0.103(8)$~meV,
$J_2=-0.032(8)$~meV and $J_3=-0.035(8)$~meV.",1709.10274v1
2017-11-21,Reentrant Quantum Spin Hall States in Charge Density Wave Phase of Doped Single-Layer Transition Metal Dichalcogenides,"Using first-principles calculation methods, we reveal a series of phase
transitions as a function of electron doping in single-layer 1T$'$-MoTe$_2$ and
1T$'$-WTe$_2$ exhibiting quantum spin Hall (QSH) edge states without doping. As
increasing doping, we show that a phonon mediated superconducting phase first
realizes and is followed by a charge density wave (CDW) phase with a
nonsymmorphic lattice symmetry. The newly found CDW phase exhibits Dirac or
Weyl energy bands with a spin-orbit coupling in case of a fractional band
filling and re-enters into topological insulating phase with fully filled
bands. The robust resurgence of QSH state coexisting with the CDW phase is
shown to originate from band inversions induced by the nonsymmorphic lattice
distortion through the strong electron-phonon interaction, thus suggesting a
realization of various interfacial states between superconducting, density wave
and topological states on a two-dimensional crystal only by doping.",1711.08073v1
2018-01-17,Hartman effect for spin waves in exchange regime,"Hartman effect for spin waves tunnelling through a barrier in a thin magnetic
film is considered theoretically. The barrier is assumed to be created by a
locally increased magnetic anisotropy field. The considerations are focused on
a nanoscale system operating in the exchange-dominated regime. We derive the
formula for group delay $\tau_{gr}$ of spin wave package and show that
$\tau_{gr}$ saturates with increasing barrier width, which is a signature of
the Hartman effect predicted earlier for photonic and electronic systems. In
our calculations we consider the general boundary exchange conditions which
take into account different strength of exchange coupling between the barrier
and its surrounding. As a system suitable for experimental observation of the
Hartman effect we propose a CoFeB layer with perpendicular magnetic anisotropy
induced by a MgO overlayer.",1801.05876v3
2018-01-22,Gravitational wave bursts from long gamma-ray bursts,"One of the most luminous explosions detected, gamma-ray bursts, especially
the so-called long-duration bursts, most probably consist of an intrinsic
core-collapse to a black hole inside a super massive star. We point out that
this collapse alone will give a generic gravitational wave burst. It has been
shown that the strength of this burst depends on the dimensionless spin
parameter of the collapsing object. Under descent assumptions the gamma-ray
burst's central engine powers the explosion electromagnetically due to the
rotation of the newly formed black hole. We argue that the peak luminosity and
the isotropic energy of the gamma-ray burst can be associated with the spin of
the black hole, due to this mechanism. Since, both gravitational and
electromagnetic emission depend on the spin, they can be correlated and thus
give a straight estimate for the gravitational wave burst, when we have in hand
a gamma-ray burst with known distance. We discuss detectability limits for
present and future detectors.",1801.07079v1
2018-05-21,Gravitational Wave Beacons,"We explore spinning, precessing, unequal mass binary black holes to display
the long term orbital angular momentum, $\vec{L}$, flip dynamics. We study two
prototypical cases of binaries with mass ratios $q=1/7$ and $q=1/15$ and a
misaligned spin of the large black hole (with an intrinsic spin magnitude of
$S_2/m_2^2=0.85$). We conduct full numerical simulations, for nearly 14 and 18
orbits respectively, to evolve the binary down to merger and display a full
$L$-flip cycle. The pattern of radiation of such systems is particularly
interesting, displaying strong polarization-dependent variation of amplitudes
at precessional frequencies, leading to distinctive observational consequences
for ground, space, and pulsar timing based gravitational wave detectors. These
waveform features are strongly directional dependent and measurements of
gravitational waves polarizations can be exploited to disentangle the binary's
parameters in various astrophysical scenarios.",1805.08127v3
2018-06-05,Superconductivity in the Hubbard model and its interplay with charge stripes and next-nearest hopping t',"We report a large-scale density-matrix renormalization group study of the
lightly doped Hubbard model on 4-leg cylinders at hole doping concentration
$\delta=12.5\%$. By keeping a large number of states for long system sizes, we
are able to reveal a delicate interplay between superconductivity and charge
and spin density wave orders tunable via next-nearest neighbor hopping t'. For
finite t', the ground state is consistent with that of a Luther-Emery liquid,
having `half-filled' charge stripes with power-law superconducting and
charge-density-wave correlations of wave-length $\lambda=1/2\delta$, but
short-range spin correlations. This is in direct contrast to the case with
t'=0, where superconducting correlations fall off exponentially while charge-
and spin-density modulations are dominant. Our results indicate that a route to
robust long-range superconductivity involves destabilizing insulating charge
stripes in the doped Hubbard model.",1806.01465v2
2018-06-07,Evidence for a minimum ellipticity in millisecond pulsars,"Neutron stars spin down over time due to a number of energy-loss processes.
We provide tantalizing population-based evidence that millisecond pulsars
(MSPs) have a minimum ellipticity of $\epsilon\approx10^{-9}$ around their spin
axis and that, consequently, some spin down mostly through gravitational-wave
emission. We discuss the implications of such a minimum ellipticity in terms of
the internal magnetic field strengths and nuclear matter composition of neutron
stars and show it would result in the Advanced LIGO and Virgo
gravitational-wave detectors, or their upgrades, detecting gravitational waves
from some known MSPs in the near future.",1806.02822v2
2018-09-06,On the Rossby Wave Instability in accretion discs surrounding spinning black holes,"We have performed general relativistic hydrodynamics (GRHD) simulations of 2D
discs orbiting around spinning black holes and prone to the Rossby Wave
Instability (RWI). We show that the RWI can develop at any location in the disc
and for any spin parameter. After recovering the overall patterns of the
instability in this general relativistic context, we have analysed its
development and identified some modifications induced by the combined effects
of the relativistic rotational profile of the disc and local time dilatation
that affects the propagation of waves in the disc. We have found in particular
that the saturation level of the instability increases significantly when RWI
occurs in the very close vicinity of fast-rotating black holes where general
relativistic effects are strong. Such finding suggests that even more strongly
than in the case of Schwarzschild black-hole, it is necessary to complement
such GRHD simulations with a full GR ray-tracing processing in order to provide
synthetic observations of the disc in the distant observer frame.",1809.02080v1
2019-11-07,Electric field effect on spin waves and magnetization dynamics: role of magnetic moment current,"We show that a static electric field $E_x$ gives rise to a shift of the spin
wave dispersion relation $\omega(q_y-q_E)$ in the direction of the wavenumber
$q_y$ of the quantity $q_E=-\gamma_LE_x/c^2$. This effect is caused by the
magnetic moment current carried by the spin wave itself that generates an
additional phase proportional to the electric field, as in the Aharonov-Casher
effect. This effect is independent from the possibly present magneto-electric
effects of insulating ferromagnets and superimposes to them. By extending this
picture to arbitrary magnetization dynamics, we find that the electric field
gives rise to a dynamic interaction term which has the same chiral from of the
Dzyaloshinskii-Moriya interaction but is fully tunable with the applied
electric field.",1911.02902v1
2017-05-04,Theory of Linear Spin Wave Emission from a Bloch Domain Wall,"We report an analytical theory of linear emission of exchange spin waves from
a Bloch domain wall, excited by a uniform microwave magnetic field. The problem
is reduced to a one-dimensional Schr\""odinger-like equation with a
P\""oschl-Teller potential and a driving term of the same profile. The emission
of plane spin waves is observed at excitation frequencies above a threshold
value, as a result of a linear process. The height-to-width aspect ratio of the
P\""oschl-Teller profile for a domain wall is found to correspond to a local
maximum of the emission efficiency. Furthermore, for a tailored P\""oschl-Teller
potential with a variable aspect ratio, particular values of the latter can
lead to enhanced or even completely suppressed emission.",1705.01852v2
2017-05-17,Intertwining topological order and broken symmetry in a theory of fluctuating spin density waves,"The pseudogap metal phase of the hole-doped cuprate superconductors has two
seemingly unrelated characteristics: a gap in the electronic spectrum in the
`anti-nodal' region of the square lattice Brillouin zone, and discrete broken
symmetries. We present a SU(2) gauge theory of quantum fluctuations of
magnetically ordered states which appear in a classical theory of square
lattice antiferromagnets, in a spin density wave mean field theory of the
square lattice Hubbard model, and in a CP$^1$ theory of spinons. This theory
leads to metals with an antinodal gap, and topological order which intertwines
with precisely the observed broken symmetries.",1705.06289v3
2018-02-12,Electromagnetic wave propagating along a space curve,"Using the thin-layer approach, we derive the effective equation for the
electromagnetic wave propagating along a space curve. We find intrinsic
spin-orbit, extrinsic spin-orbit and extrinsic orbital angular momentum and
intrinsic orbital angular momentum couplings induced by torsion, which can lead
to geometric phase, spin and orbital Hall effects. And we show the helicity
inversion induced by curvature that can convert the right-handed circularly
polarized electromagnetic wave into left-handed polarized one, vice verse.
Finally, we demonstrate that the gauge invariance of the effective dynamics is
protected by the geometrically induced gauge potential.",1802.04059v1
2018-08-02,Coherent spin-wave processor of stored optical pulses,"A device being a pinnacle of development of an optical quantum memory should
combine the capabilities of storage, inter-communication and processing of
stored information. In particular, the ability to capture a train of optical
pulses, interfere them in an arbitrary way and finally perform on-demand
release would in a loose sense realize an optical analogue of a Turing Machine.
Here we demonstrate the operation of an optical quantum memory being able to
store optical pulses in the form of collective spin-wave excitations in a
multi-dimensional wavevector space. During storage, we perform complex
beamsplitter operations and demonstrate a variety of protocol implemented as
the processing stage, including interfering a pair of spin-wave modes with 95\%
visibility. By engineering the phase-matching at the readout stage we realize
the on-demand retrieval. The highly multimode structure of the presented
quantum memory lends itself both to enhancing classical optical
telecommunication as well as parallel processing of optical qubits at the
single-photon level.",1808.00927v1
2018-08-13,On the structure of the conformal higher-spin wave operators,"We study conformal higher spin (CHS) fields on constant curvature
backgrounds. By employing parent formulation technique in combination with
tractor description of GJMS operators we find a manifestly factorized form of
the CHS wave operators for symmetric fields of arbitrary integer spin $s$ and
gauge invariance of arbitrary order $t\leq s$. In the case of the usual
Fradkin-Tseytlin fields $t=1$ this gives a systematic derivation of the
factorization formulas known in the literature while for $t>1$ the explicit
formulas were not known. We also relate the gauge invariance of the CHS fields
to the partially-fixed gauge invariance of the factors and show that the
factors can be identified with (partially gauge-fixed) wave operators for
(partially)-massless or special massive fields. As a byproduct, we establish a
detailed relationship with the tractor approach and, in particular, derive the
tractor form of the CHS equations and gauge symmetries.",1808.04320v1
2019-02-11,Onset of spin wave time-domain fractals in a dynamic artificial crystal,"We report on the first observation of an exact fractal pattern in the
time-domain arising spontaneously from a dynamic artificial crystal (DAC). The
all-magnon process occurs in a passive, unlithographed magnetic waveguide. The
DAC was created by a standing spin wave of frequency $f_{\mathrm{DAC}}$ in a
region of nonlinear waveguide, resulting in a spatio-temporally periodic
potential. The interaction of travelling spin waves of frequency $f'$ with the
DAC resulted in a series of new modes appearing in a comb with intervals
$\Delta f^{(0)} = \mid f_{\mathrm{DAC}}-f'\mid$. As $H$ was increased a 1st
pre-fractal pattern was observed with frequency interval $\Delta f^{(1)}
=\Delta f^{(0)}/2$. Finally, the onset of a 2nd pre-fractal was observed with
frequency interval $\Delta f^{(2)} =\Delta f^{(1)}/2 = \Delta f^{(0)}/4$. The
magnetic field dependence of the nonlinear signals effect matched that of the
DAC. The fractal-like behavior was demonstrated for different values of $f'$.",1902.04445v2
2019-02-12,Characterization of spin wave propagation in (111) YIG thin films with large anisotropy,"We report on long-range spin wave (SW) propagation in nanometer-thick yttrium
iron garnet (YIG) film with an ultralow Gilbert damping. The knowledge of a
wavenumber value $|\vec{k}|$ is essential for designing SW devices. Although
determining the wavenumber $|\vec{k}|$ in experiments like Brillouin light
scattering spectroscopy is straightforward, quantifying the wavenumber in
all-electrical experiments has not been widely commented upon so far. We
analyze magnetostatic spin wave (SW) propagation in YIG films in order to
determine the SW wavenumber $|\vec{k}|$ excited by the coplanar waveguide. We
show that it is crucial to consider the influence of magnetic anisotropy fields
present in YIG thin films for precise determination of SW wavenumber. With the
proposed methods we find that experimentally derived values of $|\vec{k}|$ are
in perfect agreement with that obtained from electromagnetic simulation only if
anisotropy fields are included.",1902.04608v1
2020-04-06,Theory of spin waves in a hexagonal antiferromagnet,"We construct a field-theoretic description of spin waves in hexagonal
antiferromagnets with three magnetic sublattices and coplanar $120^\circ$
magnetic order. The three Goldstone modes can be separated by point-group
symmetry into a singlet $\alpha_{0}$ and a doublet $(\beta_x,\beta_y)$. The
$\alpha_0$ singlet is described by the standard theory of a free relativistic
scalar field. The field theory of the $(\beta_x,\beta_y)$ doublet is analogous
to the theory of elasticity of a two-dimensional isotropic solid with distinct
longitudinal and transverse ""speeds of sound"". The well-known Heisenberg models
on the triangular and kagome lattices with nearest-neighbour exchange turn out
to be special cases with accidental degeneracy of the spin-wave velocities. The
speeds of sound can be readily calculated for any lattice model. We apply this
approach to the compounds of the Mn$_3$X family with stacked kagome layers.",2004.02790v2
2020-04-11,Brillouin Light Scattering of Spin Waves Inaccessible with Free-Space Light,"Micro-focus Brillouin light scattering is a powerful technique for the
spectroscopic and spatial characterization of elementary excitations in
materials. However, the small momentum of light limits the accessible
excitations to the center of the Brillouin zone. Here, we utilize a metallic
nanoantenna fabricated on the archetypal ferrimagnet yttrium iron garnet to
demonstrate the possibility of Brillouin light scattering from
large-wavevector, high-frequency spin wave excitations that are inaccessible
with free-space light. The antenna facilitates sub-diffraction confinement of
electromagnetic field, which enhances the local field intensity and generates
momentum components significantly larger than those of free-space light. Our
approach provides access to high frequency spin waves important for fast
nanomagnetic devices, and can be generalized to other types of excitations and
light scattering techniques.",2004.05314v1
2020-08-13,Comparison of measured and simulated spin-wave mode spectra of magnetic nanostructures,"Motivated by the importance of magnetization dynamics in nanomagnets for the
development and optimization of magnetic devices and sensors, we measured and
modeled spin wave spectra in patterned elliptical nanomagnets. Ferromagnetic
resonance spectra for multiple nanomagnets of Ni80Fe20 , fabricated by
electron-beam lithography to have nominal short-axes of 200 nm or 100 nm, were
measured by use of heterodyne magneto-optical microwave microscopy. Scanning
electron microscope images taken of the same nanomagnets were used to define
element shapes for micromagnetic simulations. Measured spectra show significant
differences between nominally identical nanomagnets, which could be only
partially attributed to uncontrolled shape variations in the patterning
process, as evidence by the limited agreement between the measured and
simulated spectra. Agreement between measurements and simulations was improved
by including a zone of reduced magnetization and exchange at the edges of the
nanomagnets in the simulations. Our results show that the reduction of shape
variations between individual magnetic random-access memory elements can
potentially improve their performance. However, unambiguous determination of
materials parameters in nanomagnets based on analysis and modeling of spin wave
spectra remains problematic.",2008.05662v1
2016-12-20,Opening a nodal gap by fluctuating spin-density-wave in lightly doped La$_{2-x}$Sr$_x$CuO$_4$,"We investigate whether the spin or charge degrees of freedom are responsible
for the nodal gap in underdoped cuprates by performing inelastic neutron
scattering and x-ray diffraction measurements on La$_{2-x}$Sr$_x$CuO$_4$, which
is on the edge of the antiferromagnetic phase. We found that fluctuating
incommensurate spin-density-wave (SDW) with a the bottom part of an hourglass
dispersion exists even in this magnetic sample. The strongest component of
these fluctuations diminishes at the same temperature where the nodal gap
opens. X-ray scattering measurements on the same crystal show no signature of
charge-density-wave (CDW). Therefore, we suggest that the nodal gap in the
electronic band of this cuprate opens due to fluctuating SDW with no
contribution from CDW.",1612.06864v1
2016-12-30,Theoretical investigation of the magnetic dynamics in $α$-RuCl$_3$,"We study the spin-wave excitations in $\alpha$-RuCl$_3$ by the spin-wave
theory. Starting from the five-orbital Hubbard model and the perturbation
theory, we derive an effective isospin-$1/2$ model in the large Hubbard ($U$)
limit. Based on the energy-band structure calculated from the first-principle
method, we find that the effective model can be further reduced to the
$K$-$\Gamma$ model containing a ferromagnetic nearest-neighbor (NN) Kitaev
interaction ($K$) and a NN off-diagonal exchange interaction ($\Gamma$). With
the spin-wave theory, we find that the $K$-$\Gamma$ model can give magnetic
excitations which is consistent with the recent neutron scattering experiments.",1612.09515v2
2017-06-14,Broadband conversion of microwaves into propagating spin waves in patterned magnetic structures,"We have used time-resolved scanning Kerr microscopy (TRSKM) and micromagnetic
simulations to demonstrate that, when driven by spatially uniform microwave
field, the edges of patterned magnetic samples represent both efficient and
highly tunable sources of propagating spin waves. The excitation is due to the
local enhancement of the resonance frequency induced by the non-uniform dynamic
demagnetizing field generated by precessing magnetization aligned with the
edges. Our findings represent a crucial step forward in the design of nanoscale
spin-wave sources for magnonic architectures, and are also highly relevant to
the understanding and interpretation of magnetization dynamics driven by
spatially-uniform magnetic fields in patterned magnetic samples.",1706.04409v2
2017-10-07,Spin-density wave state in simple hexagonal graphite,"Simple hexagonal graphite, also known as AA graphite, is a metastable
configuration of graphite. Using tight-binding approximation it is easy to
demonstrate that AA graphite is a metal with well-defined Fermi surface. The
Fermi surface consists of two sheets, each shaped like a rugby ball. One sheet
corresponds to electron states, another corresponds to hole states. The Fermi
surface demonstrates good nesting: a suitable translation in the reciprocal
space superposes one sheet onto another. In the presence of the
electron-electron repulsion a nested Fermi surface is unstable with respect to
spin-density wave ordering. This instability is studied using the mean-field
theory at zero temperature, and the spin-density wave order parameter is
evaluated.",1710.02657v2
2018-04-16,Ultrafast destruction and recovery of the spin density wave order in iron based pnictides: a multi-pulse optical study,"We report on systematic excitation-density dependent all-optical femtosecond
time resolved study of the spin-density wave state in iron-based
superconductors. The destruction and recovery dynamics are measured by means of
the standard and a multi-pulse pump-probe technique. The experimental data are
analyzed and interpreted in the framework of an extended three temperature
model. The analysis suggests that the optical-phonons energy-relaxation plays
an important role in the recovery of almost exclusively electronically driven
spin density wave order.",1804.05769v1
2019-03-07,Interplay between intra- and inter-nanowires dynamic dipolar interactions in the spin wave band structure of Py/Cu/Py nanowires,"We have studied both experimentally and theoretically the reprogrammable spin
wave band structure in Permalloy(10nm)/Cu(5nm)/Permalloy(30nm) nanowire arrays
of width w=280 nm and inter-wire separation in the range from 80 to 280 nm. We
found that, depending on the inter-wire separation, the anti-parallel
configuration, where the magnetizations of the two Permalloy layers point in
opposite directions, is stabilized over specific magnetic field ranges thus
enabling us to directly compare the band structure with that of the parallel
alignment. We show that collective spin waves of the Bloch type propagate
through the arrays with different magnonic bandwidths as a consequence of the
interplay between the intra- and inter-nanowire dynamic dipolar interactions. A
detailed understanding, e.g. whether they have a stationary or propagating
character, is achieved by considering the phase relation (in-phase or
out-of-phase) between the dynamic magnetizations in the two ferromagnetic
layers and their average value. This work opens the path to magnetic
field-controlled reconfigurable layered magnonic crystals that can be used for
future nanoscale magnon spintronic devices.",1903.02935v1
2019-03-13,Spin wave stiffness and exchange stiffness of doped permalloy via ab-initio calculation,"The way doping affects the spin wave stiffness and the exchange stiffness of
permalloy (Py) is investigated via ab-initio calculations, using the
Korringa-Kohn-Rostoker (KKR) Green function formalism. By considering various
types of dopants of different nature (V, Gd, and Pt), we are able to draw
general conclusions. To describe the trends of the stiffness with doping is it
sufficient to account for the exchange coupling between nearest neighbors. The
polarizability of the impurities is not an important factor for the spin wave
stiffness. Rather, the decisive factor is the hybridization between the
impurity and the host states as reflected by changes in the Bloch spectral
function. Our theoretical results agree well with earlier experiments.",1903.05506v2
2019-03-22,Evanescent Gravitational Waves,"We describe the properties of evanescent gravitational waves (EGWs)---wave
solutions of Einstein equations which decay exponentially in some direction
while propagating in another. Evanescent waves are well-known in acoustics and
optics and have recently received much attention due to their extraordinary
properties such as their transverse spin and spin-momentum locking. We show
that EGWs possess similarly remarkable properties, carrying transverse spin
angular momenta and driving freely falling test masses along in elliptical
trajectories. Hence, test masses on a plane transverse to the direction of
propagation exhibit correlated vector and scalar-like
deformation---correlations which can be used to distinguish it from modified
gravity. We demonstrate that EGWs are present and dominant in the vicinity of
sub-wavelength sources such as orbiting binaries.",1903.09690v2
2020-02-29,Nonreciprocal Emergence of Hybridized Magnons in magnetic thin Films,"We investigate the transfer and control of nonreciprocity through magnons
themselves in permalloy thin films deposited on surface oxide silicon
substrate. Evidences of nonreciprocal emergence of hybridized dipole exchange
magnons (spin waves) at two permalloy surfaces are provided by studying magnon
transmission and asymmetry, via Brillouin light scattering measurements. The
dipole dominated spin wave and exchange dominated spin wave are found to be
localized near the top and bottom surfaces, respectively, and traveling along
opposite directions. The nonreciprocity and the localization are intertwined
and ca n be tuned by an in plane magnetic field. The effects are well explained
by the magnetostatic theory and can be quantitatively reproduced by the
micromagnetic simulations. Our findings provide a simple and flexible approach
to nonreciprocal all magnon logi c devices with highly compatible with silicon
based integrated circuit technology.",2003.00230v4
2020-09-07,Graded Index Confined Spin Waves in an Intermediate Domain Wall,"We propose a mathematical model for describing propagating confined modes in
domain walls of intermediate angle between domains. The proposed model is
derived from the linearised Bloch equations of motion and after reasonable
assumptions, in the scenario of a thick enough magnetic patch, are accounted.
The model shows that there is a clear dependence of the local wavenumber of the
confined spin wave on the local angle of the wall and excitation frequency
used, which leads to the definition of a local index of refraction in the wall
as a function of such angle and frequency. Therefore, the model applies to 1-D
propagating modes, although it also has physical implications for 2-D scenarios
where a domain wall merges with a saturated magnetic region. Micromagnetic
simulations are in good agreement with the predictions of the model and also
give insight on the effects of curved finite structures may have on the
propagating characteristics of spin waves in domain walls.",2009.03195v2
2021-02-01,Generation of odd-frequency surface superconductivity with spontaneous spin current due to the zero-energy Andreev bound state,"We propose that the odd-frequency $s$ wave ($s^{\rm{odd}}$ wave)
superconducting gap function, which is usually unstable in the bulk, naturally
emerges at the edge of $d$ wave superconductors. This prediction is based on
the surface spin fluctuation pairing mechanism owing to the zero-energy surface
Andreev bound state. The interference between bulk and edge gap functions
triggers the $d+s^{\rm{odd}}$ state, and the generated spin current is a useful
signal uncovering the ``hidden'' odd-frequency gap. In addition, the edge
$s^{\rm{odd}}$ gap can be determined via the proximity effect on the diffusive
normal metal. Furthermore, this study provides a decisive validation of the
``Hermite odd-frequency gap function,'' which has been an open fundamental
challenge to this field.",2102.00787v3
2021-04-22,High mass but low spin: an exclusion region to rule out hierarchical black-hole mergers as a mechanism to populate the pair-instability mass gap,"The occurrence of pair-instability supernovae is predicted to prevent the
formation of black holes with masses $\gtrsim 50 M_\odot$. Recent
gravitational-wave detections in this mass range require an explanation beyond
that of standard stellar collapse. Current modeling strategies include the
hierarchical assembly of previous generations of black-hole mergers as well as
other mechanisms of astrophysical nature (lowered nuclear-reaction rates,
envelope retention, stellar mergers, accretion, dredge-up episodes). In this
paper, we point out the occurrence of an exclusion region that cannot be easily
populated by hierarchical black-hole mergers. A future gravitational-wave
detection of a black hole with mass $\gtrsim 50M_\odot$ and spin $\lesssim 0.2$
will indicate that the pair-instability mass gap is polluted in some other way.
Such a putative outlier can be explained using hierarchical mergers only with
considerable fine-tuning of both mass ratio and spins of the preceding
black-hole merger -- an assumption that can then be cross-checked against the
bulk of the gravitational-wave catalog.",2104.11247v2
2021-10-25,Femtosecond laser comb driven perpendicular standing spin waves,"We study femtosecond laser comb driven sustained and coherent spin wave (SW)
generation in permalloy (Py) films over a thickness range of $d =$ 40--100 nm.
A simple rapid demagnetization model describes the dependence of the observed
SW intensity on laser power for all film thicknesses. In the thicker films we
observe laser comb excited perpendicular standing spin waves up to third order
and to 18 multiples of the 1 GHz laser repetition rate. Our results demonstrate
the versatility of femtosecond combs as contact-less SW point sources over a
wide range of film thickness and type of SW modes.",2110.12947v1
2004-05-18,"Topological spin transport of photons: ""magnetic monopole"" gauge field in Maxwell equations and polarization splitting of rays in periodically inhomogeneous media","Topological spin transport of electromagnetic waves (photons) in stationary
smoothly inhomogeneous isotropic medium is studied. By diagonalizing photon
kinetic energy in Maxwell equations we derive the non-Abelian pure gauge
potential in the momentum space, which in adiabatic approximation for
transverse waves takes the form of two Abelian U(1) potentials corresponding to
magnetic monopole-type fields. These fields act on circularly polarized waves
resulting in the topological spin transport of photons. We deduce general
semiclassical (geometrical optics) ray equations that take into account a
Lorentz-type force of the magnetic-monopole-like gauge field. Detailed analysis
of rays in 3D medium with 2D periodic inhomogeneity is presented. It is shown
that rays located initially in the inhomogeneity plane experience topological
deflections or splitting that move them out from this plane. The dependence of
the rays' deflection on the parameters of the medium and on the direction of
propagation is studied.",0405384v5
2016-11-04,Field-induced spin-density wave beyond hidden order in URu2Si2,"URu2Si2 is one of the most enigmatic strongly-correlated-electron systems and
offers a fertile testing ground for new concepts in condensed matter science.
In spite of >30 years of intense research, no consensus on the order parameter
of its low-temperature hidden-order phase exists. A strong magnetic field
transforms the hidden order into magnetically-ordered phases, whose order
parameter has also been defying experimental observation. Here, thanks to an
instrumentation breakthrough in high-field neutron scattering, we identify the
field-induced phases of URu2Si2 as a spin-density-wave state with wavevector k1
= (0.6 0 0). The transition to the spin-density wave represents a unique
touchstone for understanding the hidden-order phase. An intimate relationship
between this magnetic structure, the magnetic fluctuations, and the Fermi
surface is emphasized, calling for dedicated band structure calculations.",1611.01321v1
2019-08-15,Collective Excitations of Quantum Anomalous Hall Ferromagnets in Twisted Bilayer Graphene,"We present a microscopic theory for collective excitations of quantum
anomalous Hall ferromagnets (QAHF) in twisted bilayer graphene. We calculate
the spin magnon and valley magnon spectra by solving Bethe-Salpeter equations,
and verify the stability of QAHF. We extract the spin stiffness from the
gapless spin wave dispersion, and estimate the energy cost of a
skyrmion-antiskyrmion pair, which is found to be comparable in energy with the
Hartree-Fock gap. The valley wave mode is gapped, implying that the valley
polarized state is more favorable compared to the valley coherent state. Using
a nonlinear sigma model, we estimate the valley ordering temperature, which is
considerably reduced from the mean-field transition temperature due to thermal
excitations of valley waves.",1908.05417v2
2019-08-21,Signatures of coupling between spin waves and Dirac fermions in YbMnBi$_2$,"We present inelastic neutron scattering (INS) measurements of magnetic
excitations in YbMnBi$_2$, which reveal features consistent with a direct
coupling of magnetic excitations to Dirac fermions. In contrast with the large
broadening of magnetic spectra observed in antiferromagnetic metals such as the
iron pnictides, here the spin waves exhibit a small but resolvable intrinsic
width, consistent with our theoretical analysis. The subtle manifestation of
spin-fermion coupling is a consequence of the Dirac nature of the conduction
electrons, including the vanishing density of states near the Dirac points.
Accounting for the Dirac fermion dispersion specific to \ymb\ leads to
particular signatures, such as the nearly wave-vector independent damping
observed in the experiment.",1908.08114v3
2019-12-10,Multiphase Magnetism in Yb2Ti2O7,"We document the coexistence of ferro- and anti-ferromagnetism in pyrochlore
$\rm Yb_2Ti_2O_7$ using three neutron scattering techniques on stoichiometric
crystals: elastic neutron scattering shows a canted ferromagnetic ground state,
neutron scattering shows spin wave excitations from both a ferro-and an
antiferro-magnetic state, and field and temperature dependent small angle
neutron scattering reveals the corresponding anisotropic magnetic domain
structure. High-field $\langle 111 \rangle$ spin wave fits show that $\rm
Yb_2Ti_2O_7$ is extremely close to an antiferromagnetic phase boundary.
Classical Monte Carlo simulations based on the interactions inferrred from high
field spin wave measurements confirm $\psi_2$ antiferromagnetism is metastable
within the FM ground state.",1912.04913v1
2020-01-08,Assessing different approaches to ab initio calculations of spin wave stiffness,"Ab initio calculations of the spin wave stiffness constant $D$ for elemental
Fe and Ni performed by different groups in the past have led to values with a
considerable spread of 50-100 %. We present results for the stiffness constant
$D$ of Fe, Ni, and permalloy Fe$_{0.19}$Ni$_{0.81}$ obtained by three different
approaches: (i) by finding the quadratic term coefficient of the power
expansion of the spin wave energy dispersion, (ii) by a damped real-space
summation of weighted exchange coupling constants, and (iii) by integrating the
appropriate expression in reciprocal space. All approaches are implemented by
means of the same Korringa-Kohn-Rostoker (KKR) Green function formalism. We
demonstrate that if properly converged, all procedures yield comparable values,
with uncertainties of 5-10 % remaining. By a careful analysis of the influence
of various technical parameters we estimate the margin of errors for the
stiffness constants evaluated by different approaches and suggest procedures to
minimize the risk of getting incorrect results.",2001.02558v2
2020-06-01,Spin-wave spectroscopy of individual ferromagnetic nanodisks,"The increasing demand for ultrahigh data storage densities requires
development of 3D magnetic nanostructures. In this regard, focused electron
beam induced deposition (FEBID) is a technique of choice for direct-writing of
various complex nano-architectures. However, intrinsic properties of
nanomagnets are often poorly known and can hardly be assessed by local optical
probe techniques. Here, we demonstrate spatially resolved spin-wave
spectroscopy of individual circular magnetic elements with radii down to 100
nm. The key component of the setup is a microwave antenna whose microsized
central part is placed over a movable substrate with well-separated CoFe-FEBID
nanodisks. The circular symmetry of the disks gives rise to standing spin-wave
resonances and allows for the deduction of the saturation magnetization and the
exchange stiffness of the material using an analytical theory. The presented
approach is especially valuable for the characterization of direct-write
elements opening new horizons for 3D nanomagnetism and magnonics.",2006.00763v1
2020-06-03,Conformal scattering theories for tensorial wave equations on Schwarzschild spacetime,"In this paper, we establish the constructions of conformal scattering
theories for the tensorial wave equation such as the tensorial Fackerell-Ipser
and the spin $\pm 1$ Teukolsky equations on Schwarzschild spacetime. In our
strategy, we construct the conformal scattering for the tensorial
Fackerell-Ipser equations which are obtained from the Maxwell equation and spin
$\pm 1$ Teukolsky equations. Our method combines Penrose's conformal
compactification and the energy decay results of the tensorial fields
satisfying the tensorial Fackerell-Ipser equation to prove the energy equality
of the fields through the conformal boundary $\mathfrak{H}^+\cup \scri^+$
(resp. $\mathfrak{H}^-\cup \scri^-$) and the initial Cauchy hypersurface
$\Sigma_0 = \left\{ t=0 \right\}$. We will prove the well-posedness of the
Goursat problem by using a generalization of H\""ormander's results for the
tensorial wave equations. By using the results for the tensorial
Fackerell-Ipser equations we will establish the construction of conformal
scattering for the spin $\pm 1$ Teukolsky equations.",2006.02888v4
2020-06-05,Controlling the nonlinear relaxation of quantized propagating magnons in nanodevices,"Relaxation of linear magnetization dynamics is well described by the viscous
Gilbert damping processes. However, for strong excitations, nonlinear damping
processes such as the decay via magnon-magnon interactions emerge and trigger
additional relaxation channels. Here, we use space- and time-resolved
microfocused Brillouin light scattering spectroscopy and micromagnetic
simulations to investigate the nonlinear relaxation of strongly driven
propagating spin waves in yttrium iron garnet nanoconduits. We show that the
nonlinear magnon relaxation in this highly quantized system possesses
intermodal features, i.e., magnons scatter to higher-order quantized modes
through a cascade of scattering events. We further show how to control such
intermodal dissipation processes by quantization of the magnon band in
single-mode devices, where this phenomenon approaches its fundamental limit.
Our study extends the knowledge about nonlinear propagating spin waves in
nanostructures which is essential for the construction of advanced spin-wave
elements as well as the realization of Bose-Einstein condensates in scaled
systems.",2006.03400v2
2020-06-10,Long-lived and multiplexed atom-photon entanglement interface with feed-forward-controlled readouts,"The quantum interface (QI) that generates entanglement between photonic and
spin-wave (atomic memory) qubits is a basic building block for quantum
repeaters. Realizing ensemble-based repeaters in practice requires quantum
memory providing long lifetime and multimode capacity. Significant progresses
have been achieved on these separate goals. The remaining challenge is to
combine long-lived and multimode memories into a single QI. Here, by
establishing multimode, magnetic-field-insensitive and long-wavelength
spin-wave storage in laser-cooled atoms that are placed inside a
phase-passively-stabilized polarization interferometer, we constructed a
multiplexed QI that stores up to three long-lived spin-wave qubits. Using a
feed-forward-controlled system, we demonstrated that the multiplexed QI gives
rise to a 3-fold increase in the atom-photon (photon-photon)
entanglement-generation probability compared to single-mode QIs. The measured
Bell parameter is 2.5+/-0.1 combined with a memory lifetime up to 1ms. The
presented work represents a key step forward in realizing fiber-based
long-distance quantum communications.",2006.05631v1
2020-07-17,A nonlinear magnonic nano-ring resonator,"The field of magnonics, which aims at using spin waves as carriers in data
processing devices, has attracted increasing interest in recent years. We
present and study micromagnetically a nonlinear nanoscale magnonic ring
resonator device for enabling implementations of magnonic logic gates and
neuromorphic magnonic circuits. In the linear regime, this device efficiently
suppresses spin-wave transmission using the phenomenon of critical resonant
coupling, thus exhibiting the behavior of a notch filter. By increasing the
spin-wave input power, the resonance frequency is shifted leading to
transmission curves, depending on the frequency, reminiscent of the activation
functions of neurons or showing the characteristics of a power limiter. An
analytical theory is developed to describe the transmission curve of magnonic
ring resonators in the linear and nonlinear regimes and validated by a
comprehensive micromagnetic study. The proposed magnonic ring resonator
provides a multi-functional nonlinear building block for unconventional
magnonic circuits.",2007.09205v2
2020-10-14,Semi-classical quantisation of magnetic solitons in the anisotropic Heisenberg quantum chain,"Using the algebro-geometric approach, we study the structure of
semi-classical eigenstates in a weakly-anisotropic quantum Heisenberg spin
chain. We outline how classical nonlinear spin waves governed by the
anisotropic Landau-Lifshitz equation arise as coherent macroscopic low-energy
fluctuations of the ferromagnetic ground state. Special emphasis is devoted to
the simplest types of solutions, describing precessional motion and elliptic
magnetisation waves. The internal magnon structure of classical spin waves is
resolved by performing the semi-classical quantisation using the
Riemann-Hilbert problem approach. We present an expression for the overlap of
two semi-classical eigenstates and discuss how correlation functions at the
semi-classical level arise from classical phase-space averaging.",2010.07232v6
2020-12-03,Effect of strain-induced orbital splitting on the magnetic excitations in undoped cuprates,"We investigate the magnetic excitations in view of the recent reports
suggesting that the spin-wave energy may exhibit a significant dependence on
the in-plane strain of a thin film of La$_2$CuO$_4$. The nature of dependence,
as we find, can be explained naturally within a two-orbital model based on the
$d_{x^2-y^2}$ and $d_{3z^2-r^2}$ orbitals. In particular, as the
orbital-splitting energy between the $d_{x^2-y^2}$ and $d_{3z^2-r^2}$ orbitals
increases with compressive strain, the zone-boundary spin-wave energy hardens.
However, the hardening persists only until the orbital splitting reaches $\sim$
2eV, beyond which there is no significant change. The behavior of zone-boundary
spin-wave energy is explained in terms of the extent of hybridization between
one of the exchange-split $d_{x^2-y^2}$ band which is nearly half filled and
the $d_{3z^2-r^2}$ band. The role of second-order antiferromagnetic
superexchange process involving the inter-orbital hopping is also discussed.",2012.01999v1
2020-12-18,Breaking Space Inversion-Symmetry to Obtain Asymmetric Spin-Wave Excitation in Systems with Nonuniform Magnetic Exchange,"We report on the consequences of non-uniform exchange in magnetic systems.
The quantum mechanical exchange interaction between spins is responsible for
the phenomenon of magnetic order, and is generally considered to be uniform
across bulk magnetic systems. Partly inspired by the Dzyaloshinskii-Moriya
interaction--also known as antisymmetric exchange--we use a linearly varying
exchange interaction along a magnetic strip as a route to spatial inversion
symmetry-breaking. We find that, in addition to asymmetric modes and
localization, spatially-varying exchange can be used to design nonreciprocal
magnetic signal excitation at frequencies that are tunable. Moreover, our work
predicts nonreciprocity to occur across a vast range of frequencies up to
hundreds of GHz. Such spin wave engineering is a key area of ongoing research
in the fields of magnonics and spintronics, which are expected to enable the
next generation of communication technology. Analogous nonreciprocity is
expected to occur in other wave systems with gradient properties.",2012.10381v2
2020-12-29,Nonreciprocal Multi-mode and Indirect Couplings in Cavity Magnonics,"We investigate the magnon-photon couplings by employing a small magnet within
an irregular resonant cavity, which leads to a desirable nonreciprocity with a
big isolation ratio. Moreover, the higher-order couplings between the spin wave
modes with the polarized photon modes also exhibit the nonreciprocity. These
couplings between polarized photon and spin waves could be regarded as an
indirect multi-modes coupling between the ferromagnetic resonance (FMR) mode
and spin wave mode magnons mediated by the cavity mode photons. We also derive
a coupling matrix to predict the characteristics of this kind of indirect
coupling. The existence of the indirect couplings broaden the field range of
the nonreciprocity of the system. The achieved nonreciprocal multi-mode
magnon-photon couplings in a single system offer a feasible method to improve
the signal transmission quality.",2012.14765v2
2021-06-14,Mode-sensitive magnetoelastic coupling in phononic-crystal magnomechanics,"Acoustically driven spin-wave resonance in a phononic crystal cavity is
numerically investigated. The designed cavity enables confinement of gigahertz
vibrations in a wavelength-scale point-defect structure and sustains a variety
of resonance modes. Inhomogeneous strain distributions in the modes modify the
magnetostrictive coupling and the spin-wave excitation susceptible to an
external field orientation. In particular, a monopole-like mode in the cavity
having a near-symmetrical pattern shows a subwavelength-scale mode volume and
can provide a versatile acoustic excitation scheme independent on field-angle
variation. Thus, the phononic-crystal platform offers an alternative approach
to acoustically control the spin-wave dynamics with ultrasmall and
inhomogeneous mode structures, which will be a key technology to integrate and
operate large-scale magnomechanical circuits.",2106.07180v1
2021-06-24,Magnetic skyrmion generation by reflective spin-wave focusing,"We propose a method to generate magnetic skyrmions by focusing spin waves
totally reflected by a curved film edge. Based on the principle of identical
magnonic path length, we derive the edge contour that is parabolic and
frequency-independent. Micromagnetic simulations are performed to verify our
theoretical design. It is found that under proper conditions, magnetic droplet
first emerges near the focal point where the spin-wave intensity has been
significantly enhanced, and then converts to magnetic skyrmion accompanied by a
change of the topological charge. The phase diagram about the amplitude and
frequency of the driving field for skyrmion generation is obtained. Our finding
would be helpful for the designment of spintronic devices combing the advantage
of skyrmionics and magnonics.",2106.12876v1
2021-07-27,Multidimensional partial wave analysis of SIDIS dihadron beam spin asymmetries at CLAS12,"Dihadron beam spin asymmetries provide a wide range of insights into nucleon
structure and hadronization. Recent measurements at CLAS12 provide the first
empirical evidence of nonzero $G_1^\perp$, the parton helicity-dependent
dihadron fragmentation function (DiFF) encoding spin-momentum correlations in
hadronization. These measurements also allow for a point-by-point extraction of
the subleading-twist PDF $e(x)$ in a collinear framework. We observe different
behavior of the asymmetries in different invariant mass regions, motivating a
fully multidimensional study. The DiFFs also expand in terms of partial waves,
each corresponding to the interference of dihadrons of particular
polarizations. Altogether a fully multidimensional partial wave analysis is
needed, and this presentation will summarize the efforts and results obtained
thus far.",2107.12965v2
2021-09-22,Repesentation of general spin-$S$ systems using a Restricted Boltzmann Machine with Softmax Regression,"Here, we propose a novel method for representation of general spin systems
using Restricted Boltzmann Machine with Softmax Regression (SRBM) that follows
the probability distribution of the training data. SRBM training is performed
using stochastic reconfiguration method to find approximate representation of
many body wave functions. We have shown that proposed SRBM technique performs
very well and achieves the trial wave function, in a numerically more efficient
way, which is in good agreement with the theoretical prediction. We
demonstrated that the prediction of the trial wave function through SRBM
becomes more accurate as one increases the number of hidden units. We evaluated
the accuracy of our method by studying the spin-1/2 quantum systems with
softmax RBM which shows good accordance with the Exact Diagonalization(ED). We
have also compared the energies of spin chains of a few spin multiplicities($1,
3/2$ and $2$) with ED and DMRG results.",2109.10651v2
2021-11-22,Excitation and reception of magnetostatic surface spin waves in thin conducting ferromagnetic films by coplanar microwave antennas. Part II: Experiment,"We report on propagating spin-wave spectroscopy measurements carried out on
coplanar nano-antenna devices made from a Si/SiO$_2$/Ru(5nm)/Co(20)/Pt(5nm)
film. The measurements were analyzed in detail by employing newly developed
theoretical modeling and de-embedding procedures. The magnetic parameters of
the film were determined by complementary Brillouin light scattering and
ferromagnetic resonance measurements. The propagating spin wave signals could
be accounted for quantitatively for the range of externally applied magnetic
fields investigated in this study: 130-1500 Oe.",2111.11111v3
2021-12-28,Deep neural networks for solving forward and inverse problems of (2+1)-dimensional nonlinear wave equations with rational solitons,"In this paper, we investigate the forward problems on the data-driven
rational solitons for the (2+1)-dimensional KP-I equation and spin-nonlinear
Schr\""odinger (spin-NLS) equation via the deep neural networks leaning.
Moreover, the inverse problems of the (2+1)-dimensional KP-I equation and
spin-NLS equation are studied via deep learning. The main idea of the
data-driven forward and inverse problems is to use the deep neural networks
with the activation function to approximate the solutions of the considered
(2+1)-dimensional nonlinear wave equations by optimizing the chosen loss
functions related to the considered nonlinear wave equations.",2112.14040v1
2022-01-26,Nonlinear magnon polaritons,"We experimentally and theoretically demonstrate that nonlinear spin-wave
interactions suppress the hybrid magnon-photon quasiparticle or ""magnon
polariton"" in microwave spectra of an yttrium iron garnet film detected by an
on-chip split-ring resonator. We observe a strong coupling between the Kittel
and microwave cavity modes in terms of an avoided crossing as a function of
magnetic fields at low microwave input powers, but a complete closing of the
gap at high powers. The experimental results are well explained by a
theoretical model including the three-magnon decay of the Kittel magnon into
spin waves. The gap closure originates from the saturation of the ferromagnetic
resonance above the Suhl instability threshold by a coherent back reaction from
the spin waves.",2201.10889v2
2022-03-09,Exchange spin waves in thin films with gradient composition,"We report investigation of ferromagnetic resonance phenomenon in
ferromagnetic thin films with essentially non-uniform composition. Epitaxial
Pd-Fe thin film with linear distribution of Fe content across the thickness is
used as the model material. Anomalous perpendicular standing spin waves are
observed and quantified using the collective dynamic equation. Numerical
analysis yields the exchange stiffness constant for diluted Pd-Fe alloy
$D=2A/\mu_0M_s=15$~T$\cdot$nm$^2$ and the ratio of the effective magnetization
to the saturation magnetization $M_{eff}/M_s=1.16$. It is demonstrated that,
overall, engineering of thin films with non-uniform composition across the
thickness can be used for high-frequency or low-field magnonic operations using
exchange spin waves.",2203.05014v1
2022-03-30,Strain engineering and the hidden role of magnetism in monolayer VTe$_2$,"Two-dimensional transition metal dichalcogenides have attracted great
attention recently. Motivated by a recent study of crystalline bulk VTe$_2$, we
theoretically investigated the spin-charge-lattice interplay in monolayer
VTe$_2$. To understand the controversial experimental reports on several
different charge density wave ground states, we paid special attention to the
'hidden' role of antiferromagnetism as its direct experimental detection may be
challenging. Our first-principles calculations show that the 4$\times$1 charge
density wave and the corresponding lattice deformation are accompanied by the
'double-stripe' antiferromagnetic spin order in its ground state. This phase
has not only the lowest total energy but also the dynamical phonon stability,
which supports a group of previous experiments. Interestingly enough, this
ground state is stabilized only by assuming the underlying spin order. By
noticing this intriguing and previously unknown interplay between magnetism and
other degrees of freedom, we further suggest a possible strain engineering. By
applying tensile strain, monolayer VTe$_2$ exhibits phase transition first to a
different charge density wave phase and then eventually to a ferromagnetically
ordered one.",2203.16023v2
2022-04-19,Role of shape anisotropy on thermal gradient-driven domain wall dynamics in magnetic nanowires,"We investigate the magnetic domain wall (DW) dynamics in uniaxial/biaxial
nanowires under a thermal gradient (TG). The findings reveal that the DW
propagates toward the hotter region in both nanowires. The main physics of such
observations is the magnonic angular momentum transfer to the DW. The hard
(shape) anisotropy exists in biaxial nanowire, which contributes an additional
torque, hence DW speed is larger than that in uniaxial nanowire. With lower
damping, the DW velocity is smaller and DW velocity increases with damping
which is opposite to usual expectation. To explain this, it is predicted that
there is a probability to form the standing spin-waves (which do not carry net
energy/momentum) together with travelling spin-waves if the propagation length
of thermally-generated spin-waves is larger than the nanowire length. For
larger-damping, DW decreases with damping since the magnon propagation length
decreases. Therefore, the above findings might be useful in realizing the
spintronic (racetrack memory) devices.",2204.09101v2
2022-05-25,On-demand multimode optical storage in a laser-written on-chip waveguide,"Quantum memory is a fundamental building block for large-scale quantum
networks. On-demand optical storage with a large bandwidth, a high multimode
capacity and an integrated structure simultaneously is crucial for practical
application. However, this has not been demonstrated yet. Here, we fabricate an
on-chip waveguide in a $\mathrm {^{151}Eu^{3+}:Y_2SiO_5}$ crystal with
insertion losses of 0.2 dB, and propose a novel pumping scheme to enable
spin-wave atomic frequency comb (AFC) storage with a bandwidth of 11 MHz inside
the waveguide. Based on this, we demonstrate the storage of 200 temporal modes
using the AFC scheme and conditional on-demand storage of 100 temporal modes
using the spin-wave AFC scheme. The interference visibility between the readout
light field and the reference light field is $99.0\% \pm 0.6\%$ and $97\% \pm
3\%$ for AFC and spin-wave AFC storage, respectively, indicating the coherent
nature of this low-loss, multimode and integrated storage device.",2205.12762v1
2022-06-15,"Diffuse spin waves, zero modes and cluster excitations in the spin-3/2 kagomé antiferromagnet chromium jarosite, KCr$_3$(OD)$_6$(SO$_4$)$_2$","The dynamics of the S = 3=2 kagome antiferromagnet chromium jarosite,
KCr$_3$(OD)$_6$(SO$_4$)$_2$ was studied using high-resolution neutron
time-of-flight spectroscopy on a polycrystalline sample with a nearly
stoichiometric magnetic lattice (2.8(2)% Cr vacancies). Neutron spectroscopy
reveals diffuse spin wave excitations in the ordered phase with an incomplete
gap and significant finite life-time broadening as well as a pronounced zero
mode. Using linear spin wave theory, we estimate the exchange couplings, with
the leading nearest neighbor value being $J_1$ = 0:884 meV. Above $T_N$ diffuse
excitations from cooperative paramagnetism dominate. A model for
two-dimensional magnetic cluster excitations is shown to capture the essential
features of the data in the cooperative paramagnetic phase.",2206.07330v2
2022-09-07,Wideband Brillouin light scattering analysis of spin waves excited by a white-noise RF generator,"Spin waves are studied intensively for their intriguing properties and
potential use in future technology platforms for the transfer and processing of
information and microwave signals. The development of devices and materials for
spin-wave systems requires a lot of measurement time and effort, and thus
increasing the measurement throughput by extending the instrumentation
capabilities is of the essence. In this letter, we report on a new and
straightforward approach to increase the measurement throughput by fully
exploiting the wideband detection nature of the Brillouin light scattering
technique in single-shot experiments using a white-noise RF generator.",2209.03035v1
2022-09-22,Spin wave study of magnetic perpendicular surface anisotropy in single crystalline MgO$\text{/}$Fe$\text{/}$MgO films,"Broadband ferromagnetic resonance is measured in single crystalline Fe films
of varying thickness sandwiched between MgO layers. An exhaustive magnetic
characterization of the films (exchange constant, cubic, uniaxial and surface
anisotropies) is enabled by the study of the uniform and the first
perpendicular standing spin wave modes as a function of applied magnetic field
and film thickness. Additional measurements of non-reciprocal spin wave
propagation allow us to separate each of the two interface contributions to the
total surface anisotropy. The results are consistent with the model of a
quasi-bulk film interior and two magnetically different top and bottom
interfaces, a difference ascribed to different oxidation states.",2209.10906v2
2022-11-14,Spin wave diffraction model for perpendicularly magnetized films,"We present a near-field diffraction model for spin waves in perpendicularly
magnetized films applicable in any geometries of excitation fields. This model
relies on Kalinikos-Slavin formalism to express the dynamic susceptibility
tensor in k-space, and calculate the diffraction patterns via inverse
2D-Fourier transform of the response functions. We show an excellent
quantitative agreement between our model and MuMax3 micro-magnetic simulations
on two different geometries of antennas. Our method benchmarks spin wave
diffraction in perpendicularly magnetized films, and is readily applicable for
future designs of magnon beamforming and interferometric devices.",2211.07231v2
2023-01-23,Magnon-bandgap controllable artificial domain wall waveguide,"In this paper, a magnon-bandgap controllable artificial domain wall waveguide
is proposed by means of micromagnetic simulation. By the investigation of the
propagation behavior and dispersion relationship of spin waves in artificial
domain wall waveguides, it is found that the nonreciprocal propagation of spin
waves in the artificial domain walls are mainly affected by the local effective
exchange field, and the magnon bandgap can be controlled by changing the
maximum value of the effective exchange field. In addition, it is observed that
the artificial domain wall waveguides are structurally more stable than the
natural domain wall waveguides under the same spin wave injection conditions,
and the magnon bandgap of the artificial domain wall waveguides can be adjusted
by its width and magnetic anisotropy parameters. The bandgap controllable
artificial domain wall scheme is beneficial to the miniaturization and
integration of magnon devices and can be applied to future magnonic technology
as a novel frequency filter.",2301.09291v1
2023-02-16,Probing higher-spin particles with gravitational waves from compact binary inspirals,"Under the framework of gravitational effective field theory, we propose a
theory agnostic strategy of searching for higher-spin particles with
gravitational waves from compact binary inspirals. Using this strategy, we
analyze gravitational wave signals from the binary black hole merger events
GW151226 and GW170608, as well as the binary neutron star merger event
GW170817. We find that the existence of higher-spin particles with mass ranged
from $10^{-12} {\rm eV}$ to $10^{-11} {\rm eV}$ is strongly disfavored by these
events unless the particles precisely combine within a supersymmetric
supermultiplet. We argue that the gravitational effective field theory also
provides a framework to search for signals beyond GR from other GW
observations, such as extreme-mass-ratio-inspirals.",2302.08042v1
2023-05-29,Stationary and moving bright solitons in Bose-Einstein condensates with spin-orbit coupling in a Zeeman field,"With the discovery of various matter wave solitons in spin-orbit-coupled
Bose-Einstein condensates (BECs), exploring their properties has become
increasingly significant. We mainly study stationary and moving bright solitons
in spin-orbit-coupled spin-1 BECs with or without a Zeeman field. The bright
solitons correspond to the plane wave (PW) and standing wave (SW) phases. With
the assistance of single-particle energy spectrum, we obtain the existence
domains of PW and SW solitons by analytical and numerical methods. The results
indicate that the interaction between atoms is also a key factor determining
the existence of solitons. In addition, we systematically discuss the stability
domains of PW and SW solitons, and investigate the impact of different
parameters on the stability domains. We find that PW solitons are unstable when
the linear Zeeman effect reaches a certain threshold, and the threshold is
determined by other parameters. The linear Zeeman effect also leads to the
alternating distribution of stable and unstable areas of SW solitons, and makes
SW solitons stably exist in the area with stronger ferromagnetism. Finally, we
analyze the collision dynamics of different types of stable solitons.",2305.17950v1
2023-05-23,Probabilistic Spin Wave Computing with quasistatic magnetic inputs,"Spin wave computing device where an algorithm can be encoded by recording a
corresponding magnetization pattern onto a hard magnetic material was
previously proposed1 and a particular implementation of a vector-matrix
algorithm was demonstrated. In the present article we analyze the conditions
allowing for implementation of complex algorithms which can combine multiple
additive, multiplicative and conditional operators including logic expressions.
Special attention is given to how the input data is provided. Rather than
relying on a set of independent sources of the RF field as is common with the
existing spin wave computing methods we demonstrate usability of more simple
solutions using adjustable external quasistatic magnetic fields. We also show
how for the given setup probabilistic switching of magnetic elements at
elevated temperatures can be used to convert deterministic algorithms into a
probabilistic form.",2306.07976v1
2023-06-21,Triplet superconductivity and spin density wave in biased AB bilayer graphene,"We examine spin density wave and triplet superconductivity as possible ground
states of the Bernal bilayer graphene. The spin density wave is stable for the
unbiased and undoped bilayer. Both the doping and the applied bias voltage
destroy this phase. We show that, when biased and slightly doped, bilayer can
host a triplet superconducting phase. The mechanisms for both ordered phases
rely on the renormalized Coulomb interaction. Consistency of our theoretical
conclusions with recent experimental results are discussed.",2306.12312v2
2023-07-24,Cavity-enhanced and spatial-multimode spin-wave-photon quantum interface,"Practical realizations of quantum repeaters require quantum memory
simultaneously providing high retrieval efficiency, long lifetime and multimode
storages. So far, the combination of high retrieval efficiency and spatially
multiplexed storages into a single memory remains challenging. Here, we set up
a ring cavity that supports an array including 6 TEM00 modes and then
demonstrated cavity enhanced and spatially multiplexed spin wave photon quantum
interface (QI). The cavity arrangement is according to Fermat' optical theorem,
which enables the six modes to experience the same optical length per round
trip. Each mode includesn horizontal and vertical polarizations. Via DLCZ
process in a cold atomic ensemble, we create non classically correlated pairs
of spin waves and Stokes photons in the 12 modes. The retrieved fields from the
multiplexed SWs are enhanced by the cavity and the average intrinsic retrieval
efficiency reaches 70% at zero delay. The storage time for the case that
cross-correlation function of the multiplexed QI is beyond 2 reaches 0.6ms .",2307.12523v1
2023-08-18,Spin-wave dispersion and magnon chirality in multiferroic TbMnO3,"Inelastic neutron scattering experiments combining time-of-flight and
polarized techniques yield a comprehensive picture of the magnon dispersion in
multiferroic TbMnO3 including the dynamic chirality. Taking into account only
Mn3+ moments, spin-wave calculations including nearest-neighbor interactions,
frustrating next-nearest neighbor exchange as well as single-ion anisotropy and
antisymmetric terms describe the energy dispersion and the distribution of
neutron scattering intensity in the multiferroic state very well. Polarized
neutron scattering reveals strong dynamic chirality of both signs that may be
controlled by external electric fields in the multiferroic phase. Also above
the onset of long-range multiferroic order in zero electric field, a small
inelastic chiral component can be inverted by an electric field. The
microscopic spin-wave calculations fully explain also the dynamic chirality of
magnetic excitations, which is imprinted by the static chirality of the
multiferroic phase. The ordering of Tb3+ moments at lower temperature reduces
the broadening of magnons but also renders the magnon dispersion more complex.",2308.09407v1
2023-09-01,Coexistence of nematic superconductivity and spin density wave in magic-angle twisted bilayer graphene,"We argue that doped twisted bilayer graphene with magical twist angle can
become superconducting. In our theoretical scenario, the superconductivity
coexists with the spin-density-wave-like ordering. Numerical mean-field
analysis demonstrates that the spin-density-wave order, which is much stronger
than the superconductivity, leaves parts of the Fermi surface ungapped. This
Fermi surface serves as a host for the superconductivity. Since the magnetic
texture at finite doping breaks the point group of the twisted bilayer
graphene, the stabilized superconducting order parameter is nematic. We also
explore the possibility of a purely Coulomb-based mechanism of
superconductivity in the studied system. The screened Coulomb interaction is
calculated within the random phase approximation. It is shown that near the
half-filling the renormalized Coulomb repulsion indeed induces the
superconducting state, with the order parameter possessing two nodes on the
Fermi surface. We estimate the superconducting transition temperature, which
turns out to be very low. The implications of our proposal are discussed.",2309.00346v2
2023-11-10,Nonreciprocal Spin Waves in Nanoscale Domain Walls Detected by Scanning X-ray Microscopy in Perpendicular Magnetic Anisotropic Fe/Gd Multilayers,"Spin wave nonreciprocity in domain walls (DWs) allows for unidirectional
signal processing in reconfigurable magnonic circuits. Using scanning
transmission x-ray microscopy (STXM), we examined coherently-excited magnons
propagating in Bloch-like DWs in amorphous Fe/Gd multilayers with perpendicular
magnetic anisotropy (PMA). Near 1 GHz we detected magnons with short
wavelengths down to $\lambda = 281$ nm in DWs whose minimum width amounted to
$\delta_{\rm DW} = 52$ nm. Consistent with micromagnetic simulations, the STXM
data reveal their nonreciprocal magnon band structures. We identified Bloch
points which disrupted the phase evolution of magnons and induced different
$\lambda$ adjacent to the topological defects. Our observations provide direct
evidence of nonreciprocal spin waves within Bloch-like DWs, serving as
programmable waveguides in magnonic devices with directed information flow.",2311.06186v1
2023-11-22,Magneto-structural phase transitions and two-dimensional spin waves in graphite,"We have previously found experimental evidence for several quantum phenomena
in oxygen-ion implanted of hydrogenated graphite: ferromagnetism,
antiferromagnetism, paramagentism, triplet superconductivity, Andreev states,
Little-Parks oscillations, Lamb shift, Casimir effect, colossal
magnetoresistance, and topologically-protected flat-energy bands [1-6]. Triplet
superconductivity results in the formation of Josephson junctions, thus with
potential of being used for spintronics applications in the critical area of
quantum computing. In this paper, we are showing new experimental evidence for
the formation of two-dimensional (2D) spin waves in oxygen-ion enriched and in
hydrogenated highly oriented pyrolytic graphite. The temperature evolution of
the remanent magnetization Mrem(T) data confirms the formation of spin waves
that follow the 2D Heisenberg model with a weak uniaxial anisotropy. In
addition, the step-like features also found in the temperature dependence of
the electrical resistivity between insulating and metallic states suggest
several outstanding possibilities, such as a structural transition, triplet
superconductivity, and chiral properties.",2311.13116v1
2023-11-23,Exciting high-frequency short-wavelength spin waves using high harmonics of a magnonic cavity mode,"Confined spin-wave modes are a promising object for studying nonlinear
effects and future quantum technologies. Here, using micromagnetic simulations,
we use a microwave magnetic field from a coplanar waveguide (CPW) to pump a
standing spin-wave confined in the cavity of magnonic crystal. We find that the
frequency of the fundamental cavity mode is equal to the ferromagnetic
resonance frequency of the plane film and overlaps with the magnonic bandgap,
allowing high magnetic field tunability. Multi-frequency harmonics of the
cavity mode are generated once the microwave amplitude surpasses a certain
threshold. Specifically, the second and third harmonics at 0.5 T equate to 48.6
and 72.9 GHz with wavelengths of 44 and 22 nm respectively, which propagate
into the crystal. This effect reaches saturation when the CPW covers the entire
cavity, making the system feasible for realization. These processes show
potential for the advancement of magnonics at high-frequencies and very
short-wavelengths.",2311.14143v1
2023-12-08,Towards an experimental proof of the magnonic Aharonov$-$Casher effect,"Controlling the phase and amplitude of spin waves in magnetic insulators with
an electric field opens the way to fast logic circuits with ultra-low power
consumption. One way to achieve such control is to manipulate the magnetization
of the medium via magnetoelectric effects. In experiments with magnetostatic
spin waves in an yttrium iron garnet film, we have obtained the first evidence
of a theoretically predicted phenomenon: The change of the spin-wave phase due
to the magnonic Aharonov$-$Casher effect$-$the geometric accumulation of the
magnon phase as these quasiparticles propagate through an electric field
region.",2312.05113v1
2024-04-01,Non-Hermitian unidirectional routing of photonic qubits,"Efficient and tunable qubit unidirectional routers and spin-wave diodes play
an important role in both classical and quantum information processing domains.
Here, we reveal that multi-level neutral cold atoms can mediate both
dissipative and coherent couplings. Interestingly, we investigate and
practically implement this paradigm in experiments, successfully synthesizing a
system with dual functionality as both a photonic qubit unidirectional router
and a spin-wave diode. By manipulating the helicity of the field, we can
effectively balance the coherence coupling and dissipative channel, thereby
ensuring the unidirectional transfer of photonic qubits. The qubit fidelity
exceeds 97.49%, and the isolation ratio achieves $16.8\pm0.11$ dB while the
insertion loss is lower than 0.36 dB. Furthermore, we show that the spin-wave
diode can effectively achieve unidirectional information transfer by
appropriately setting the coherent coupling parameters. Our work not only
provides new ideas for the design of extensive components in quantum networks,
but also opens up new possibilities for non-Hermitian quantum physics, complex
quantum networks, and unidirectional quantum information transfer.",2404.01211v1
2024-04-02,High-energy neutrinos flavour composition as a probe of neutrino magnetic moments,"Neutrino propagation in the Galactic magnetic field is considered. To
describe neutrino flavour and spin oscillations on the galactic scale baselines
an approach using wave packets is developed. Evolution equations for the
neutrino wave packets in a uniform and non-uniform magnetic field are derived.
Analytical expressions for neutrino flavour and spin oscillations probabilities
accounting for damping due to wave packet separation are obtained for the case
of uniform magnetic field. It is shown that for oscillations on magnetic
frequencies $\omega_i^B = \mu_i B_\perp$ the coherence lengths that
characterizes the damping scale is proportional to the cube of neutrino average
momentum $p_0^3$. Probabilities of flavour and spin oscillations are calculated
numerically for neutrino interacting with the non-uniform Galactic magnetic
field. Flavour compositions of high-energy neutrino flux coming from the
Galactic centre are calculated accounting for neutrino interaction with the
magnetic field. It is shown that for neutrino magnetic moments $\sim 10^{-13}
\mu_B$ and larger these flavour compositions significantly differ from ones
predicted by the vacuum neutrino oscillations scenario.",2404.02027v1
2024-04-03,Enhancement of Magnon Transport by Superconductor Meissner Screening,"Recent experiments observe the spin-wave-Meissner-current modes in
ferromagnetic insulator-superconductor heterostructures, in which the
coherently excited spin waves seemingly do not decay as usual beneath the
superconductor strip [Borst et al., Science 382, 430 (2023)]. We interpret this
phenomenon by demonstrating that the stray magnetic field emitted by the
magnetization dynamics is reflected, focused, and enhanced inside the
ferromagnet by the supercurrent induced in the superconductor, such that the
group velocity of spin waves is strongly enhanced. Analytical and numerical
calculations based on this model predict that the coherent transport of magnons
is enhanced by close to 500% for yttrium iron garnet capped by superconducting
NbN with a decay length exceeding millimeters. Our finding may augment the
performance of magnons in quantum information and quantum transport processing.",2404.02598v1
2024-04-11,Mode-resolved micromagnetics study of parametric spin wave excitation in thin-film disks,"We present a computational study of the parametric excitation of spin waves
in thin film disks with a mode-resolved approach. The method involves
projecting out the time-dependent magnetization, computed using micromagnetics
simulations, onto the spatial profile of the eigenmodes that are obtained from
the linearization of the equations of motion. Unlike spectral analysis in the
frequency domain, the projection allows for the analysis of transient mode
dynamics under parametric excitation. We apply this method to parallel pumping
of quantized spin wave modes in in-plane magnetized thin-film disks, where
phenomena like frequency pulling, mutual phase locking, and higher-order magnon
scattering processes are identified.",2404.07561v1
2024-04-12,Nonlinear Wave-Spin Interactions in Nitrogen-Vacancy Centers,"Nonlinear phenomena represent one of the central topics in the study of
wave-matter interactions and constitute the key blocks for various applications
in optical communication, computing, sensing, and imaging. In this work, we
show that by employing the interactions between microwave photons and electron
spins of nitrogen-vacancy (NV) centers, one can realize a variety of nonlinear
effects, ranging from the resonance at the sum or difference frequency of two
or more waves to electromagnetically induced transparency from the interference
between spin transitions. We further verify the phase coherence through
two-photon Rabi-oscillation measurements. The highly sensitive, optically
detected NV-center dynamics not only provides a platform for studying
magnetically induced nonlinearities but also promises novel functionalities in
quantum control and quantum sensing.",2404.08772v1
2022-10-23,Tidally excited gravity waves in the cores of solar-type stars: resonances and critical-layer formation,"We simulate the propagation and dissipation of tidally induced nonlinear
gravity waves in the cores of solar-type stars. We perform hydrodynamical
simulations of a previously developed Boussinesq model using a spectral-element
code to study the stellar core as a wave cavity that is periodically forced at
the outer boundary with a given azimuthal wavenumber and an adjustable
frequency. For low-amplitude forcing, the system exhibits resonances with
standing g-modes at particular frequencies, corresponding to a situation in
which the tidal torque is highly frequency-dependent. For high-amplitude
forcing, the excited waves break promptly near the centre and spin up the core
so that subsequent waves are absorbed in an expanding critical layer, as found
in previous work, leading to a tidal torque with a smooth frequency-dependence.
For intermediate-amplitude forcing, we find that linear damping of the waves
gradually spins up the core such that the resonance condition can be altered
drastically. The system can evolve towards or away from g-mode resonances,
depending on the difference between the forcing frequency and the closest
eigenfrequency. Eventually, a critical layer forms and absorbs the incoming
waves, leading to a situation similar to the high-amplitude case in which the
waves break promptly. We study the dependence of this process on the forcing
amplitude and frequency, as well as on the diffusion coefficients. We emphasize
that the small Prandtl number in the centre of solar-like stars facilitates the
development of a differentially rotating core owing to the nonlinear feedback
of waves. Our simulations and analysis reveal that this important mechanism may
drastically change the phase of gravity waves and thus the classical picture of
resonance locking in solar-type stars needs to be revised.",2210.12880v2
1999-12-15,R-Mode Oscillations and Spindown of Young Rotating Magnetic Neutron Stars,"Recent work has shown that a young, rapidly rotating neutron star loses
angular momentum to gravitational waves generated by unstable r-mode
oscillations. We study the spin evolution of a young, magnetic neutron star
including both the effects of gravitational radiation and magnetic braking
(modeled as magnetic dipole radiation). Our phenomenological description of
nonlinear r-modes is similar to, but distinct from, that of Owen et al. (1998)
in that our treatment is consistent with the principle of adiabatic invariance
in the limit when direct driving and damping of the mode are absent. We show
that, while magnetic braking tends to increase the r-mode amplitude by spinning
down the neutron star, it nevertheless reduces the efficiency of gravitational
wave emission from the star. For B >= 10^14 (\nus/300 Hz)^2 G, where \nus is
the spin frequency, the spindown rate and the gravitational waveforms are
significantly modified by the effect of magnetic braking. We also estimate the
growth rate of the r-mode due to electromagnetic (fast magnetosonic) wave
emission and due to Alfven wave emission in the neutron star magnetosphere. The
Alfven wave driving of the r-mode becomes more important than the gravitational
radiation driving when B >= 10^13 (\nus/150 Hz)^3 G; the electromagnetic wave
driving of the r-mode is much weaker. Finally, we study the properties of local
Rossby-Alfven waves inside the neutron star and show that the fractional change
of the r-mode frequency due to the magnetic field is of order 0.5 (B/10^16 G)^2
(\nus/100 Hz)^-2.",9912296v2
2001-04-13,"Evolution of circular, non-equatorial orbits of Kerr black holes due to gravitational-wave emission: II. Inspiral trajectories and gravitational waveforms","The inspiral of a ``small'' ($\mu \sim 1-100 M_\odot$) compact body into a
``large'' ($M \sim 10^{5-7} M_\odot$) black hole is a key source of
gravitational radiation for the space-based gravitational-wave observatory
LISA. The waves from such inspirals will probe the extreme strong-field nature
of the Kerr metric. In this paper, I investigate the properties of a restricted
family of such inspirals (the inspiral of circular, inclined orbits) with an
eye toward understanding observable properties of the gravitational waves that
they generate. Using results previously presented to calculate the effects of
radiation reaction, I assemble the inspiral trajectories (assuming that
radiation reacts adiabatically, so that over short timescales the trajectory is
approximately geodesic) and calculate the wave generated as the compact body
spirals in. I do this analysis for several black hole spins, sampling a range
that should be indicative of what spins we will encounter in nature. The spin
has a very strong impact on the waveform. In particular, when the hole rotates
very rapidly, tidal coupling between the inspiraling body and the event horizon
has a very strong influence on the inspiral time scale, which in turn has a big
impact on the gravitational wave phasing. The gravitational waves themselves
are very usefully described as ``multi-voice chirps'': the wave is a sum of
``voices'', each corresponding to a different harmonic of the fundamental
orbital frequencies. Each voice has a rather simple phase evolution. Searching
for extreme mass ratio inspirals voice-by-voice may be more effective than
searching for the summed waveform all at once.",0104041v2
2002-10-30,The GEO600 Gravitational Wave Detector -- Pulsar Prospects,"The GEO600 laser-interferometric gravitational wave detector near Hannover,
Germany, is one of six such interferometers now close to operation worldwide.
The UK/German GEO collaboration uses advanced technologies, including
monolithic silica suspensions and signal recycling, to deliver a sensitivity
comparable with much larger detectors in their initial configurations. Here we
review the design and performance of GEO600 and consider the prospects for a
direct detection of continuous gravitational waves from spinning neutron stars.",0210649v1
1996-05-08,Many skyrmion wave functions and skyrmion statistics in quantum Hall ferromagnets,"We determine the charge and statistical angle of skyrmions in quantum Hall
ferromagnets by performing Berry phase calculations based on the microscopic
variational wave functions for many-skyrmion states. We find, in contradiction
to a recent claim by Dziarmaga, that both the charge and the statistical angle
of a skyrmion are independent of its spin (size), and are identical to those of
Laughlin quasiparticles at the same filling factor. We discuss some subtleties
in the use of these variational wave functions.",9605054v1
1998-04-01,Macroscopic Coulomb Blockade Model of Density Wave Transport,"Charge and spin density waves are highly correlated electron systems that can
transport an electric current. A model is discussed in which a field E induces
the creation, by quantum tunneling, of pairs of oppositely charged solitons and
antisolitons in a density wave. Pair creation is blocked, for fields below a
threshold value ET, because the increase in electrostatic energy would violate
energy conservation. When E > ET, this Coulomb blockade mechanism time-
correlates the pair creation and annihilation events. The model provides a
natural explanation for the extremely small phase displacements below threshold
suggested by NMR and other experiments.",9804001v1
1998-11-07,Quantum Field Theory of the Pinned Density Wave,"A model is discussed in which an electric field induces quantum nucleation of
soliton-antisoliton pairs in a pinned charge or spin density wave. Coulomb
blockade prevents pair creation until the electric field exceeds a sharp
threshold value, which can be much smaller than the classical depinning field.
We calculate the vacuum state energy and expectation value of the phase, which
is treated as a quantum scalar field. We find that the phase can also be much
smaller, below threshold, than predicted by classical ``sliding'' density wave
models.",9811103v1
1998-11-12,Quantum Theory of Atomic Four-Wave Mixing in Bose-Einstein Condensates,"We present an exact quantum mechanical analysis of collinear four-wave mixing
in a multicomponent Bose-Einstein condensate consisting of sodium atoms in the
F=1 ground state. Technically, this is achieved by taking advantage of the
conservation laws of the system to represent its Hamiltonian in terms of
angular momentum operators. We discuss explicitly the build-up of matter-wave
side-modes from noise, as well as the correlations between these modes. We show
the appearance of a strong quantum entanglement between hyperfine states. We
also demonstrate that for finite atomic numbers, the system exhibits periodic
collapses and revivals in the exchange of atoms between different spin states.",9811175v1
2001-05-17,Modulational instability of spinor condensates,"We demonstrate, analytically and numerically, that the ferromagnetic phase of
the spinor Bose-Einstein condenstate may experience modulational instability of
the ground state leading to a fragmentation of the spin domains. Together with
other nonlinear effects in the atomic optics of ultra-cold gases (such as
coherent photoassociation and four-wave mixing) this effect provides one more
analogy between coherent matter waves and light waves in nonlinear optics.",0105353v2
2003-04-29,Propagation of nonlinear waves in disordered media,"We study propagation of stationary waves in disordered non-linear media
described by the non-linear Schroedinger equation and show that for given
boundary conditions and a given coherent wave incident on a sample the number
of solutions of the equation increase exponentially with the sample size. We
also discuss the ballistic case, the sensitivity of the solutions to a change
of external parameters, the similarity of this problem to the problem of spin
glasses and time-dependent solutions.",0304673v3
2006-06-07,Ferromagnetic relaxation by magnon-induced currents,"A theory for calculating spin wave relaxation times based on the
magnon-electron interaction is developed. The theory incorporates a thin film
geometry and is valid for a large range of magnon frequencies and wave vectors.
For high conductivity metals such as permalloy, the wave vector dependent
damping constant approaches values as high as 0.2, showing the large magnitude
of the effect, and can dominate experimentally observed relaxation.",0606197v1
2006-08-09,Superconducting ground state of the two-dimensional Hubbard model: a variational study,"A trial wave function is proposed for studying the instability of the
two-dimensional Hubbard model with respect to d-wave superconductivity. Double
occupancy is reduced in a similar way as in previous variational studies, but
in addition our wave function both enhances the delocalization of holes and
induces a kinetic exchange between the electron spins. These refinements lead
to a large energy gain, while the pairing appears to be weakly affected by the
additional term in the variational wave function.",0608210v1
2001-10-23,Second post-Newtonian gravitational wave polarizations for compact binaries in elliptical orbits,"The second post-Newtonian (2PN) contribution to the `plus' and `cross'
gravitational wave polarizations associated with gravitational radiation from
non-spinning, compact binaries moving in elliptic orbits is computed. The
computation starts from our earlier results on 2PN generation, crucially
employs the 2PN accurate generalized quasi-Keplerian parametrization of
elliptic orbits by Damour, Sch\""afer and Wex and provides 2PN accurate
expressions modulo the tail terms for gravitational wave polarizations
incorporating effects of eccentricity and periastron precession.",0110100v2
2006-11-20,Gravitational waveforms from a Lense-Thirring system,"The construction of ready to use templates for gravitational waves from
spinning binaries is an important challenge in the investigation of detectable
gravitational wave signals. Here we present a method to evaluate the
gravitational wave polarization states for inspiralling compact binaries in the
extreme mass ratio limit. We discuss the effects caused by the rotation of the
central massive object for eccentric orbits in the Lense-Thirring approximation
and give the formal expressions of the polarization states including higher
order corrections. Our results are in agreement with existing calculations for
the spinless and circular orbit limits.",0611105v1
2004-11-23,The massive neutrino-like particle of the non-linear electromagnetic field theory,"A special non-linear electromagnetic field theory - the curvilinear wave
electrodynamics (CWED), whose equation in the matrix form is similar to the
equation of the Dirac lepton theory, is offered. It is shown that the solution
of this equation is the motion of the circilarly polarized electromagnetic wave
on a circular trajectory. It is also shown that such wave can be considered as
a massive neutral particle with half spin, similar to neutrino. This theory is
mathematically concurrent to the neutrino theory of Standard Model, but does
not have the contradictions of the Standard Model with last data of neutrino
experiments.",0411314v1
2005-06-01,Generalized Parton Distributions in the Impact Parameter Space with Non-zero Skewedness,"We investigate the generalized parton distributions (GPDs) with non-zero
$\xi$ and $\Delta^\perp$ for a relativistic spin-1/2 composite system, namely
for an electron dressed with a photon, in light-front framework by expressing
them in terms of overlaps of light-cone wave functions. The wave function
provides a template for the quark spin-one diquark structure of the valence
light cone wave function of the proton. We verify the inequalities among the
GPDs with different helicities and show the qualitative behaviour of the
fermion and gauge boson GPDs in the impact parameter space.",0506006v1
2007-01-11,Relativistic Green functions in a plane wave gravitational background,"We consider a massive relativistic particle in the background of a
gravitational plane wave. The corresponding Green functions for both spinless
and spin 1/2 cases, previously computed by A. Barducci and R. Giachetti
\cite{Barducci3}, are reobtained here by alternative methods, as for example,
the Fock-Schwinger proper-time method and the algebraic method. In analogy to
the electromagnetic case, we show that for a gravitational plane wave
background a semiclassical approach is also sufficient to provide the exact
result, though the lagrangian involved is far from being a quadratic one.",0701105v1
2003-11-05,Local shear waves attenuation measurements by the MR methods,"The essential feature of the method is the employment of Elasto-Magnetic
Resonance Spectroscopy (EMRS) for precise local measurements of the attenuation
of shear elastic waves introduced into a biological sample. Such a measurement
can be accomplished by combining the EMRS method with such methods, in which
collective dislocations of spins are induced by external physical factors, such
as variable electric field, strong magnetic field gradient or longitudinal
elastic wave. Theoretical bases of the method presented, related with the
external factors, are discussed in the present paper.",0311022v2
1999-06-14,Derivation of the Pauli exchange principle,"Wave functions are generally written with arguments consisting of sets of
``particle'' coordinates and quantum numbers. Pauli derived a principle
governing the exchange of pairs of sets that differ only in their spatial and
spin component $(m_s)$ coordinates. This principle states that an exchange of
two of these sets produces the same wave function except for its being
multiplied by a factor of $(-1)^{2s}$. Pauli's proof is based upon quantum
field operators and is difficult to understand. A much simpler proof, making
use of properties of wave functions, is presented here.",9906046v1
2007-07-23,Galilei invariant theories. III. Wave equations for massless fields,"Galilei invariant equations for massless fields are obtained via contractions
of relativistic wave equations. It is shown that the collection of
non-equivalent Galilei-invariant wave equations for massless fields with spin
equal 1 and 0 is very broad and describes many physically consistent systems.
In particular, there exist a huge number of such equations for massless fields
which correspond to various contractions of representations of the Lorentz
group to those of the Galilei one.",0707.3386v1
2008-12-07,Position and frequency shifts induced by massive modes of the gravitational wave background in alternative gravity,"Alternative theories of gravity predict the presence of massive scalar,
vector, and tensor gravitational wave modes in addition to the standard
massless spin~2 graviton of general relativity. The deflection and frequency
shift effects on light from distant sources propagating through a stochastic
background of gravitational waves, containing such modes, differ from their
counterparts in general relativity. Such effects are considered as a possible
signature for alternative gravity in attempts to detect deviations from
Einstein's gravity by astrophysical means.",0812.1348v2
2008-12-22,Smearing Effect in Plane-Wave Matrix Model,"Motivated by the usual D2-D0 system, we consider a configuration composed of
flat membrane and fuzzy sphere membrane in plane-wave matrix model, and
investigate the interaction between them. The configuration is shown to lead to
a non-trivial interaction potential, which indicates that the fuzzy sphere
membrane really behaves like a graviton, giant graviton. Interestingly, the
interaction is of r^{-3} type rather than r^{-5} type. We interpret it as the
interaction incorporating the smearing effect due to the fact that the
considered supersymmetric flat membrane should span and spin in four
dimensional subspace of plane-wave geometry.",0812.4112v2
2009-09-08,Theory of the Magnetic-Field-Induced Insulator in Neutral Graphene,"Recent experiments have demonstrated that neutral graphene sheets have an
insulating ground state in the presence of an external magnetic field. We
report on a $\pi$-band tight-binding-model Hartree-Fock calculation which
examines the competition between distinct candidate insulating ground states.
We conclude that for graphene sheets on substrates the ground state is most
likely a field-induced spin-density-wave, and that a charge density wave state
is possible for suspended samples. Neither of these density-wave states support
gapless edge excitations.",0909.1362v1
2009-12-30,Parameter estimation on gravitational waves from multiple coalescing binaries,"Future ground-based and space-borne interferometric gravitational-wave
detectors may capture between tens and thousands of binary coalescence events
per year. There is a significant and growing body of work on the estimation of
astrophysically relevant parameters, such as masses and spins, from the
gravitational-wave signature of a single event. This paper introduces a robust
Bayesian framework for combining the parameter estimates for multiple events
into a parameter distribution of the underlying event population. The framework
can be readily deployed as a rapid post-processing tool.",0912.5531v1
2010-03-12,The de Broglie Wave as a Localized Excitation of the Action Function,"The Hamilton-Jacobi equation of relativistic quantum mechanics is revisited.
The equation is shown to permit solutions in the form of breathers
(nondispersive oscillating/spinning solitons), displaying simultaneous
particle-like and wave-like behavior adaptable to the properties of the de
Broglie clock. Within this formalism the de Broglie wave acquires the meaning
of a localized excitation of the classical action function. The problem of
quantization in terms of the breathing action function is discussed.",1003.2542v1
2010-08-02,Zero Energy of Plane-Waves for ELKOs,"We consider the ELKO field in interaction through contorsion with its own
spin density, and we investigate the form of the consequent autointeractions;
to do so we take into account the high-density limit and find plane wave
solutions: such plane waves give rise to contorsional autointeractions for
which the Ricci metric curvature vanishes and therefore the energy density is
equal to zero identically. Consequences are discussed.",1008.0334v2
2010-10-19,Coexistence of Superconductivity and Charge Density Wave in SrPt2As2,"SrPt2As2 is a novel arsenide superconductor, which crystallizes in the
CaBe2Ge2-type structure as a different polymorphic form of the ThCr2Si2-type
structure. SrPt2As2 exhibits a charge-density-wave (CDW) ordering at about 470
K and enters into a superconducting state at Tc = 5.2 K. The coexistence of
superconductivity and CDW refers to Peierls instability with a moderately
strong electron-phonon interaction. Thus SrPt2As2 can be viewed as a
nonmagnetic analog of iron-based superconductors, such as doped BaFe2As2, in
which superconductivity emerges in close proximity to spin-density-wave
ordering.",1010.3950v2
2010-12-09,Piecewise Flat Gravitational Waves,"We examine the continuum limit of the piecewise flat locally finite gravity
model introduced by 't Hooft. In the linear weak field limit we find the
energy--momentum tensor and metric perturbation of an arbitrary configuration
of defects. The energy--momentum turns out to be restricted to satisfy certain
conditions. The metric perturbation is mostly fixed by the energy--momentum
except for its lightlike modes which reproduce linear gravitational waves,
despite no such waves being present at the microscopic level.",1012.1991v2
2011-01-04,Quantum storage via refractive index control,"Off-resonant Raman interaction of a single-photon wave packet and a classical
control field in an atomic medium with controlled refractive index is
investigated. It is shown that a continuous change of refractive index during
the interaction leads to the mapping of a single photon state to a
superposition of atomic collective excitations (spin waves) with different wave
vectors and visa versa. The suitability of refractive index control for
developing multichannel quantum memories is discussed and possible schemes of
implementation are considered.",1101.0658v1
2011-03-23,Variational study of J1-J2 Heisenberg model on Kagome lattice using projected Schwinger boson wave functions,"Motivated by the unabating interest in the spin-1/2 Heisenberg
antiferromagnetic model on the Kagome lattice, we investigate the energetics of
projected Schwinger boson (SB) wave functions in the $J_1$--$J_2$ model with
antiferromagnetic $J_2$ coupling. Our variational Monte Carlo results show that
Sachdev's $Q_1=Q_2$ SB ansatz has a lower energy than the Dirac spin liquid for
$J_2\gtrsim 0.08 J_1$ and the ${\bf q=0}$ Jastrow type magnetically ordered
state. This work demonstrates that the projected SB wave functions can be
tested on the same footing as their fermionic counterparts.",1103.4429v1
2011-07-05,Storage-recovery phenomenon in magnonic crystal,"The phenomenon of wave trapping in an artificial crystal with limited number
of periods is demonstrated experimentally using spin waves in a magnonic
crystal. The information stored in the crystal is recovered afterwards by
parametric amplification of the trapped wave. The storage process is based on
the excitation of standing internal crystal modes and differs principally from
the well-known phenomenon of deceleration of light in photonic crystals.",1107.0984v1
2011-09-23,"Green's Function Formalism of Holography with Arbitrary Mass, Spin, and Dimensionality","In this work we present a mathematical description of how one can produce and
read a thin hologram. We use different kinds of waves, such as scalar, vector
(electromagnetic field, Maxwell-Proca fields, acoustic waves, etc.). For
reading of the hologram, we use the Green's function formalism. With the help
of computer simulations, we investigate the aberrations created by this
procedure for the simplest case: 2d-scalar wave case.",1109.4996v1
2012-02-18,Measuring spectrum of spin wave using vortex dynamics,"We propose to measure the spectrum of magnetic excitation in magnetic
materials using motion of vortex lattice driven by both ac and dc current in
superconductors. When the motion of vortex lattice is resonant with oscillation
of magnetic moments, the voltage decreases at a given current. From transport
measurement, one can obtain frequency of the magnetic excitation with the wave
number determined by vortex lattice constant. By changing the lattice constant
through applied magnetic fields, one can obtains the spectrum of the magnetic
excitation up to a wave vector of order $10\rm{\ nm^{-1}}$.",1202.4048v1
2013-08-07,The gravitational wave strain in the characteristic formalism of numerical relativity,"The extraction of the gravitational wave signal, within the context of a
characteristic numerical evolution is revisited. A formula for the
gravitational wave strain is developed and tested, and is made publicly
available as part of the PITT code within the Einstein Toolkit. Using the new
strain formula, we show that artificial non-linear drifts inherent in time
integrated waveforms can be reduced for the case of a binary black hole merger
configuration. For the test case of a rapidly spinning stellar core collapse
model, however, we find that the drift must have different roots.",1308.1521v2
2014-05-19,Zero-energy Majorana states in a one-dimensional quantum wire with charge density wave instability,"One-dimensional lattice with strong spin-orbit interactions (SOI) and Zeeman
magnetic field is shown to lead to the formation of a helical charge-density
wave (CDW) state near half-filling. Interplay of the magnetic field, SOI
constants and the CDW gap seems to support Majorana bound states under
appropriate value of the external parameters. Explicit calculation of the
quasi-particles' wave functions supports a formation of the localized
zero-energy state, bounded to the sample end-points. Symmetry classification of
the system is provided. Relative value of the density of states shows a precise
zero-energy peak at the center of the band in the non-trivial topological
regime.",1405.4815v1
2014-12-02,Solitary waves in Galilean covariant Fermi field theories with self-interaction,"The generalized Levy-Leblond equation for a $(3+1)$-dimensional
self-interacting Fermi field is considered. Spin up solitary wave solutions
with space oscillations in the $x^3$-coordinate are constructed. The solutions
are shown to accumulate non-equal amounts of inertial and rest masses.",1412.1021v1
2015-04-15,Replacing the Singlet Spinor of the EPR-B Experiment in the Configuration Space with two Single-Particle Spinors in Physical Space,"Recently, for spinless non-relativistic particles, Norsen, Marian and Oriols
show that in the de Broglie-Bohm interpretation it is possible to replace the
wave function in the configuration space by single-particle wave functions in
physical space. In this paper, we show that this replacment of the wave
function in the configuration space by single-particle functions in the
3D-space is also possible for particles with spin, in particular for the
particles of the EPR-B experiment, the Bohm version of the
Einstein-Podolsky-Rosen experiment.",1504.04227v2
2016-01-04,The split-operator technique for the study of spinorial wavepacket dynamics,"The split-operator technique for wave packet propagation in quantum systems
is expanded here to the case of propagating wave functions describing
Schr\""odinger particles, namely, charge carriers in semiconductor
nanostructures within the effective mass approximation, in the presence of
Zeeman effect, as well as of Rashba and Dresselhaus spin-orbit interactions. We
also demonstrate that simple modifications to the expanded technique allow us
to calculate the time evolution of wave packets describing Dirac particles,
which are relevant for the study of transport properties in graphene.",1601.00548v1
2016-02-19,Nonlinear waves in coherently coupled Bose-Einstein condensates,"We consider a quasi-one-dimensional two-component Bose-Einstein condensate
subject to a coherent coupling between its components, such as realized in
spin-orbit coupled condensates. We study how nonlinearity modifies the dynamics
of the elementary excitations. The spectrum has two branches which are affected
in different ways. The upper branch experiences a modulational instability
which is stabilized by a long wave-short wave resonance with the lower branch.
The lower branch is stable. In the limit of weak nonlinearity and small
dispersion it is described by a Korteweg-de Vries equation or by the Gardner
equation, depending on the value of the parameters of the system.",1602.06141v1
2018-07-12,The nuclear configurational entropy approach to dynamical QCD effects,"This paper scrutinizes the dynamical QCD effects influence on mesons, namely,
the mean-square root radius of a pion in the holographic light-front wave
function setup, in the context of the AdS/QCD. The nuclear configurational
entropy, associated to mesonic holographic light-front wave functions, is shown
to have a critical point that optimizes the two parameters of the spin-improved
light-front wave function. The mean-square root pion radius and its
cross-section, computed upon these derived values, match the exact existing
experimental data to the precision of 0.14\%, below the experimental error at
the PDG.",1807.04540v1
2012-09-20,Detecting massive black hole binaries and unveiling their cosmic history with gravitational wave observations,"Space based gravitational wave astronomy will open a completely new window on
the Universe and massive black holes binaries are expected to be among the
primary actors on this upcoming stage. The New Gravitational-wave Observatory
(NGO) is a space interferometer proposal derived from the former Laser
Interferometer Space Antenna (LISA) concept. We describe here its capabilities
of observing massive black hole binaries throughout the Universe, measuring
their relevant parameters (masses, spins, distance to the observer) to high
precision. The statistical properties of the population of detected systems can
be used to constrain the massive black hole cosmic history, providing deep
insights into the faint, high redshift Universe.",1209.4671v1
2020-03-17,Synchronous whirling of spinning homogeneous elastic cylinders: linear and weakly non-linear analyses,"Stationary whirling of slender and homogeneous (continuous) elastic shafts
rotating around their axis, with pin-pin boundary condition at the ends, is
revisited by considering the complete deformations in the cross section of the
shaft. The stability against a synchronous sinusoidal disturbance of any wave
length is investigated and the analytic expression of the buckling amplitude is
derived in the weakly non-linear regime by considering both geometric and
material (hyper-elastic) non-linearities. The bifurcation is super-critical in
the long wave length domain for any elastic constitutive law, and sub-critical
in the short wave length limit for a limited range of non-linear material
parameters.",2003.07763v1
2021-04-17,Electronic instabilities of kagome metals: saddle points and Landau theory,"We study electronic instabilities of a kagome metal with a Fermi energy close
to saddle points at the hexagonal Brillouin zone face centers. Using parquet
renormalization group, we determine the leading and subleading instabilities,
finding superconducting, charge, orbital moment, and spin density waves. We
then derive and use Landau theory to discuss how different primary density wave
orders give rise to charge density wave modulations, as seen in the
AV$_3$Sb$_5$ family, with A=K,Rb,Cs. The results provide strong constraints on
the mechanism of charge ordering and how it can be further refined from
existing and future experiments.",2104.08425v2
2021-10-13,The complete control of scattering waves in multi-channel structures,"The issue of photon spin Hall effect was generalized as a universal question
of how to control all the scattering waves in a multi-channel structure
(complete control). A general theory was proposed, which provides a simple way
to achieve the complete control. This theory shows also that the necessary
condition for complete control is that the structure must contain a complete
set of sources. To demonstrate the application of the theory, the typical
scattering patterns in the two-channel and four-channel structures are achieved
theoretically. Previous this research, one could only artificially control the
scattering waves in two channels out of a four-channel structure.",2110.06861v1
2017-03-19,Localized electron wave packet description of chemical bond and excitation: Floating and breathing Gaussian with valence-bond coupling,"A model of localized electron wave packets (WPs) with variable position and
width (floating and breathing) that are spin-coupled as per the valence-bond
theory is presented. It produces accurate potential energy curves of LiH in the
ground singlet and triplet states. Quantization in a mean-field approximation
of the motion of a WP that corresponds to the Li 2s electron generates
semi-quantitative potential energy curves of low energy excited states.
Real-time semiquantal dynamics of the WP induced by an intense laser pulse
gives high-harmonic generation spectra that capture qualitative features of a
higher-level wave function calculation.",1703.06400v1
2020-01-26,Matter-wave interference originates mass-angle correlation in fusion-fission,"Mass-angle correlation of fission fragments has been understood as
manifestation of quasifission. We show that this is not so: the effect can
originate from correlation between fusion-fission amplitudes with different
total spins signifying matter-wave interference in compound nucleus processes.
This resolves the well-known puzzle with the mass-angle correlation in the
complete fusion sub-barrier reaction $^{16}$O+$^{238}$U. Our finding is
important for more reliable predictions of production cross sections for
superheavy elements. Matter-wave interference also produces quantum-classical
transition to the time-orientation localization of the coherently rotating
dinucleus in quasifission.",2001.09511v1
2020-06-29,Strong Coupling Limit of the Holstein-Hubbard Model,"We analyze the quantum phase diagram of the Holstein-Hubbard model using an
asymptotically exact strong-coupling expansion. We find all sorts of
interesting phases including a pair-density wave (PDW), a charge 4e (and even a
charge 6e) superconductor, regimes of phase separation, and a variety of
distinct charge-density-wave (CDW), spin-density-wave (SDW) and superconducting
regimes. We chart the crossovers that occur as a function of the degree of
retardation, i.e. the ratio of characteristic phonon frequency to the strength
of interactions.",2006.16253v2
2021-05-06,Long-time Markovianity of multi-level systems in the rotating wave approximation,"For the model of a multi-level system in the rotating wave approximation we
obtain the corrections for a usual weak coupling limit dynamics by means of
perturbation theory with Bogolubov-van Hove scaling. It generalizes our
previous results on a spin-boson model in the rotating wave approximation.
Additionally, in this work we take into account some dependence of the system
Hamiltonian on the small parameter. We show that the dynamics is long-time
Markovian, i.e. after the bath correlation time all the non-Markovianity could
be captured by the renormalization of initial condition and correlation
functions.",2105.02443v1
2023-04-17,Sine-square deformed mean-field theory,"We develop a theory that accurately evaluates quantum phases with any
large-scale emergent structures including incommensurate density waves or
topological textures without {\it a priori} knowing their periodicity. We
spatially deform a real-space mean-field Hamiltonian on a finite-size cluster
using a sine-squared envelope function with zero energy at system edges. The
wave functions become insensitive to the misfit of the lattice and ordering
periods. We successfully extract the ordering wave vectors by our deformed
Fourier transformation, updating the previous results for hole-doped and
spin-orbit coupled Mott insulators. The method further enables the evaluation
of a charge gap beyond the mean-field level.",2304.08200v1
2023-06-21,Gravitational waves from axions annihilation through quantum field theory,"We use the scattering method to calculate the gravitational wave from axions
annihilation in the axion cloud formed by the superradiance process around the
Kerr black hole. We consider axions annihilating to gravitons as a three-body
decay process and then calculate the corresponding decay width. In this
approach, we can simply obtain the radiation power of gravitational wave and
give the analytical approximate result with the spin effects of the Kerr black
hole. Our study can also provide a cross-check to the numerical results in the
traditional method.",2306.12375v2
2023-09-26,"Quantum Monte Carlo pair orbital wave functions for periodic systems towards the thermodynamical limit: ground states, excitations and spinors","We derive many-body single- and multi-reference wave functions for quantum
Monte Carlo of periodic systems with an anti-symmetric portion that explicitly
integrates over the Brillouin zone of one-particle Bloch states. The wave
functions are BCS-like determinants for singlets and pfaffians for polarized
states built with appropriate pair orbitals. This ab initio formalism is
broadly applicable, eg, to description of quasi-particle band gaps, optical
excitations and to systems with complicated Fermi surfaces. It generalizes to
spin-dependent interactions using two-component spinor pairs.",2309.15262v1
2024-03-13,Are Magnons just the van der Waals interaction in Disguise?,"The MBD model of the van der Waals interaction is extended to also consider
magnetic interactions, and it is demonstrated how this can be made to reproduce
the Heisenberg Hamiltonian. It is found that this leads to a weak coupling
between the charge dipole waves that are the basis for the electric-only van
der Waals interaction and the spin-dipole waves (magnons) of the Heisenberg
model. By applying the same level of theory to both simultaneously we
demonstrate that magnons and charge-dipole waves may both be considered to be a
basis for the fluctuating part of the many-body electron density.",2403.08676v1
1999-11-09,Viscous Boundary Layer Damping of R-Modes in Neutron Stars,"Recent work has raised the exciting possibility that r-modes (Rossby waves)
in rotating neutron star cores might be strong gravitational wave sources. We
estimate the effect of a solid crust on their viscous damping rate and show
that the dissipation rate in the viscous boundary layer between the oscillating
fluid and the nearly static crust is >10^5 times higher than that from the
shear throughout the interior. This increases the minimum frequency for the
onset of the gravitational r-mode instability to at least 500 Hz when the core
temperature is less than 10^10 K. It eliminates the conflict of the r-mode
instability with the accretion-driven spin-up scenario for millisecond radio
pulsars and makes it unlikely that the r-mode instability is active in
accreting neutron stars. For newborn neutron stars, the formation of a solid
crust shortly after birth affects their gravitational wave spin-down and hence
detectability by ground-based interferometric gravitational wave detectors.",9911155v1
1997-01-10,Alternating commensurate-incommensurate structures in the magnetic phase diagram of CsNiF3,"The magnetic phase diagram of the quasi one-dimensional spinchain system
CsNiF$_3$ below the N\'eel temperature is determined. For magnetic fields
perpendicular to the spin chains incommensurate phases are predicted. From
linear spin-wave theory we obtain the instability line of the paramagnetic
phase as a function of the strength and the direction of the field. The system
undergoes a transition to a commensurate or an incommensurate phase depending
on the direction of the magnetic field. In the commensurate phase the
characterizing wave vector is locked to values describing a two-sublattice
structure, whereas in the incommensurate phase the wave vector changes
continuously between the corresponding two-sublattice wave vectors.",9701064v1
2002-08-23,Wave function statistics and multifractality at the spin quantum Hall transition,"The statistical properties of wave functions at the critical point of the
spin quantum Hall transition are studied. The main emphasis is put onto
determination of the spectrum of multifractal exponents $\Delta_q$ governing
the scaling of moments $<|\psi|^{2q}>\sim L^{-qd-\Delta_q}$ with the system
size $L$ and the spatial decay of wave function correlations. Two- and
three-point correlation functions are calculated analytically by means of
mapping onto the classical percolation, yielding the values $\Delta_2=-1/4$ and
$\Delta_3=-3/4$. The multifractality spectrum obtained from numerical
simulations is given with a good accuracy by the parabolic approximation
$\Delta_q\simeq q(1-q)/8$ but shows detectable deviations. We also study
statistics of the two-point conductance $g$, in particular, the spectrum of
exponents $X_q$ characterizing the scaling of the moments $<g^q >$. Relations
between the spectra of critical exponents of wave functions ($\Delta_q$),
conductances ($X_q$), and Green functions at the localization transition with a
critical density of states are discussed.",0208451v1
2004-07-15,Large-N limit of a magnetic impurity in unconventional density waves,"We investigate the effect of unconventional density wave (UDW) condensate on
an Anderson impurity using large-N technique at T=0. In accordance with
previous treatments of a Kondo impurity in pseudogap phases, we find that Kondo
effect occurs only in a certain range of parameters. The f-electron density of
states reflects the influence of UDW at low energies and around the maximum of
the density wave gap. The static spin susceptibility diverges at the critical
coupling, indicating the transition from strong to weak coupling. In the
dynamic spin susceptibility an additional peak appears showing the presence the
UDW gap. Predictions concerning non-linear density of states are made. Our
results apply to other unconventional condensates such as d-wave
superconductors and d-density waves as well.",0407387v1
2005-06-04,Exact soliton solution of Spin Chain with a external magnetic field in linear wave background,"Employing a simple, straightforward Darboux transformation we construct exact
N-soliton solution for anisotropic spin chain driven by a external magnetic
field in linear wave background. As a special case the explicit one- and
two-soliton solution dressed by the linear wave corresponding to magnon in
quantum theory is obtained analytically and its property is discussed in
detail. The dispersion law, effective soliton mass, and the energy of each
soliton are investigated as well. Our result show that the stability criterion
of soliton is related with anisotropic parameter and the amplitude of the
linear wave.",0506104v1
2006-11-28,Strain amplification of the 4k$_F$ chain charge instability in Sr$_{14}$Cu$_{24}$O$_{41}$,"We have used resonant soft x-ray scattering (RSXS) to study the misfit strain
in Sr$_{14}$Cu$_{24}$O$_{41}$ (SCO), a cuprate that contains both doped spin
ladders and spin chains, as well as a ""control"" sample without holes,
La$_{6}$Ca$_{8}$Cu$_{24}$O$_{41}$ (LCCO). The misfit strain wave in SCO is
strongly temperature (T)-dependent and is accompanied by a substantial hole
modulation. In LCCO the strain wave is weaker, shows no hole modulation, and is
T-independent. The observed strain wave vector, $L_c=0.318$, is close to the
4k$_F$ instability of the chain. Our results indicate that the chain charge
order observed in SCO by several groups is a 4k$_F$ charge density wave (CDW)
amplified by the misfit strain in this material. This demonstrates a new
mechanism for CDW formation in condensed matter and resolves several
contraversies over the transport properties of SCO.",0611730v1
1997-12-06,A two-dimensional representation of four-dimensional gravitational waves,"The Einstein equation in D dimensions, if restricted to the class of
space-times possessing n = D - 2 commuting hypersurface-orthogonal Killing
vectors, can be equivalently written as metric-dilaton gravity in 2 dimensions
with n scalar fields. For n = 2, this results reduces to the known reduction of
certain 4-dimensional metrics which include gravitational waves. Here, we give
such a representation which leads to a new proof of the Birkhoff theorem for
plane-symmetric space--times, and which leads to an explanation, in which sense
two (spin zero-) scalar fields in 2 dimensions may incorporate the (spin two-)
gravitational waves in 4 dimensions. (This result should not be mixed up with
well--known analogous statements where, however, the 4-dimensional space-time
is supposed to be spherically symmetric, and then, of course, the equivalent
2-dimensional picture cannot mimic any gravitational waves.) Finally, remarks
on hidden symmetries in 2 dimensions are made.",9712034v1
2005-08-16,First all-sky upper limits from LIGO on the strength of periodic gravitational waves using the Hough transform,"We perform a wide parameter space search for continuous gravitational waves
over the whole sky and over a large range of values of the frequency and the
first spin-down parameter. Our search method is based on the Hough transform,
which is a semi-coherent, computationally efficient, and robust pattern
recognition technique. We apply this technique to data from the second science
run of the LIGO detectors and our final results are all-sky upper limits on the
strength of gravitational waves emitted by unknown isolated spinning neutron
stars on a set of narrow frequency bands in the range 200-$400 $Hz. The best
upper limit on the gravitational wave strain amplitude that we obtain in this
frequency range is $4.43\times 10^{-23}$.",0508065v1
2004-05-24,Dirac Particle in an Aharonov-Bohm Potential: The Structure of the First Order S-matrix,"The structure of the interaction Hamiltonian in the first order $S-$matrix
element of a Dirac particle in an Aharonov-Bohm (AB) field is analyzed and
shown to have interesting algebraic properties. It is demonstrated that as a
consequence of these properties, this interaction Hamiltonian splits both the
incident and outgoing waves in the the first order $S-$matrix into their
$\frac{\Sigma_3}{2}-$components (eigenstates of the third component of the
spin). The matrix element can then be viewed as the sum of two transitions
taking place in these two channels of the spin. At the level of partial waves,
each partial wave of the conserved total angular momentum is split into two
partial waves of the orbital angular momentum in a manner consistent with the
conservation of the total angular momentum quantum number.",0405207v4
2007-06-17,Semiclassical Dynamics of Electron Wave Packet States with Phase Vortices,"We consider semiclassical higher-order wave packet solutions of the
Schrodinger equation with phase vortices. The vortex line is aligned with the
propagation direction, and the wave packet carries a well-defined orbital
angular momentum (OAM) $\hbar l$ ($l$ is the vortex strength) along its main
linear momentum. The probability current coils around momentum in such OAM
states of electrons. In an electric field, these states evolve like massless
particles with spin $l$. The magnetic-monopole Berry curvature appears in
momentum space, which results in a spin-orbit-type interaction and a
Berry/Magnus transverse force acting on the wave packet. This brings about the
OAM Hall effect. In a magnetic field, there is a Zeeman interaction, which, can
lead to more complicated dynamics.",0706.2486v3
2007-09-06,Exact Foldy-Wouthuysen transformation for gravitational waves and magnetic field background,"We consider an exact Foldy-Wouthuysen transformation for the Dirac spinor
field on the combined background of a gravitational wave and constant uniform
magnetic field. By taking the classical limit of the spinor field Hamiltonian
we arrive at the equations of motion for the non-relativistic spinning
particle. Two different kinds of the gravitational fields are considered and in
both cases the effect of the gravitational wave on the spinor field and on the
corresponding spinning particle may be enforced by the sufficiently strong
magnetic field. This result can be relevant for the astrophysical applications
and, in principle, useful for creating the gravitational wave detectors based
on atomic physics and precise interferometry.",0709.0767v1
2008-03-06,"Effect of Inversion Symmetry on Incommensurate Order in Multiferroic RMn2O5, R=rare earth","Starting from the irreducible representations of the group of the wave vector
we construct the spin wave functions consistent with inversion symmetry,
neglected in the usual representation analysis. We obtain the relation between
the basis functions of different members of the star of the wave vector. We
introduce order parameters and determine their transformation properties under
the operations of the space group of the paramagnetic crystal. The results are
applied to construct terms in the magnetoelectric interaction which are
quadratic and quartic in the magnetic order parameters. The higher order
magnetoelectric interactions can in principle induce components of the
spontaneous polarization which are not allowed by the lowest order
magnetoelectric interaction. We also obtain the relation between the spin wave
functions of the incommensurate phase and those of the commensurate phase which
lead to analogous relations between the order parameters of these two phases.",0803.0945v1
2008-04-10,The Einstein@Home search for periodic gravitational waves in LIGO S4 data,"A search for periodic gravitational waves, from sources such as isolated
rapidly-spinning neutron stars, was carried out using 510 hours of data from
the fourth LIGO science run (S4). The search was for quasi-monochromatic waves
in the frequency range from 50 Hz to 1500 Hz, with a linear frequency drift
f-dot (measured at the solar system barycenter) in the range -f/tau < f-dot <
0.1 f/tau, where the minimum spin-down age tau was 1000 years for signals below
300 Hz and 10000 years above 300 Hz. The main computational work of the search
was distributed over approximately 100000 computers volunteered by the general
public. This large computing power allowed the use of a relatively long
coherent integration time of 30 hours, despite the large parameter space
searched. No statistically significant signals were found. The sensitivity of
the search is estimated, along with the fraction of parameter space that was
vetoed because of contamination by instrumental artifacts. In the 100 Hz to 200
Hz band, more than 90% of sources with dimensionless gravitational wave strain
amplitude greater than 1e-23 would have been detected.",0804.1747v1
2008-11-05,Ferromagnetism and orbital order in the two-orbital Hubbard model,"We investigate spin and orbital states of the two-orbital Hubbard model on a
square lattice by using a variational Monte Carlo method at quarter-filling,
i.e., the electron number per site is one. As a variational wave function, we
consider a Gutzwiller projected wave function of a mean-field type wave
function for a staggered spin and/or orbital ordered state. Then, we evaluate
expectation value of energy for the variational wave functions by using the
Monte Carlo method and determine the ground state. In the strong Coulomb
interaction region, the ground state is the perfect ferromagnetic state with
antiferro-orbital (AF-orbital) order. By decreasing the interaction, we find
that the disordered state becomes the ground state. Although we have also
considered the paramagnetic state with AF-orbital order, i.e., purely orbital
ordered state, and partial ferromagnetic states with and without AF-orbital
order, they do not become the ground state.",0811.0733v1
2009-01-12,Detecting gravitational waves from accreting neutron stars,"The gravitational waves emitted by neutron stars carry unique information
about their structure and composition. Direct detection of these gravitational
waves, however, is a formidable technical challenge. In a recent study we
quantified the hurdles facing searches for gravitational waves from the known
accreting neutron stars, given the level of uncertainty that exists regarding
spin and orbital parameters. In this paper we reflect on our conclusions, and
issue an open challenge to the theoretical community to consider how searches
should be designed to yield the most astrophysically interesting upper limits.
With this in mind we examine some more optimistic emission scenarios involving
spin-down, and show that there are technically feasible searches, particularly
for the accreting millisecond pulsars, that might place meaningful constraints
on torque mechanisms. We finish with a brief discussion of prospects for
indirect detection.",0901.1680v1
2009-02-23,Madelung Fluid Model for The Most Likely Wave Function of a Single Free Particle in Two Dimensional Space with a Given Average Energy,"We consider spatially two dimensional Madelung fluid whose irrotational
motion reduces into the Schr\""odinger equation for a single free particle. In
this respect, we regard the former as a direct generalization of the latter,
allowing a rotational quantum flow. We then ask for the most likely wave
function possessing a given average energy by maximizing the Shannon
information entropy over the quantum probability density. We show that there
exists a class of solutions in which the wave function is self-trapped,
rotationally symmetric, spatially localized with finite support, and spinning
around its center, yet stationary. The stationarity comes from the balance
between the attractive quantum force field of a trapping quantum potential
generated by quantum probability density and the repulsive centrifugal force of
a rotating velocity vector field. We further show that there is a limiting case
where the wave function is non-spinning and yet still stationary. This special
state turns out to be the lowest stationary state of the ordinary Schr\""odinger
equation for a particle in a cylindrical tube classical potential.",0902.3838v1
2009-04-29,Quantum information analysis of the phase diagram of the half-filled extended Hubbard model,"We examine the phase diagram of the half-filled one-dimensional extended
Hubbard model using quantum information entropies within the density-matrix
renormalization group. It is well known that there is a charge-density-wave
phase at large nearest-neighbor and small on-site Coloumb repulsion and a
spin-density-wave at small nearest-neighbor and large on-site Coloumb
repulsion. At intermediate Coulomb interaction strength, we find an additional
narrow region of a bond-order phase between these two phases. The phase
transition line for the transition out of the charge-density-wave phase changes
from first-order at strong coupling to second-order in a parameter regime where
all three phases are present. We present evidence that the additional
phase-transition line between the spin-density-wave and bond-order phases is
infinite order. While these results are in agreement with recent numerical
work, our study provides an independent, unbiased means of determining the
phase boundaries by using quantum information analysis, yields values for the
location of some of the phase boundaries that differ from those previously
found, and provides insight into the limitations of numerical methods in
determining phase boundaries, especially those of infinite-order transitions.",0904.4673v1
2009-05-11,Einstein@Home search for periodic gravitational waves in early S5 LIGO data,"This paper reports on an all-sky search for periodic gravitational waves from
sources such as deformed isolated rapidly-spinning neutron stars. The analysis
uses 840 hours of data from 66 days of the fifth LIGO science run (S5). The
data was searched for quasi-monochromatic waves with frequencies f in the range
from 50 Hz to 1500 Hz, with a linear frequency drift \dot{f} (measured at the
solar system barycenter) in the range -f/\tau < \dot{f} < 0.1 f/\tau, for a
minimum spin-down age \tau of 1000 years for signals below 400 Hz and 8000
years above 400 Hz. The main computational work of the search was distributed
over approximately 100000 computers volunteered by the general public. This
large computing power allowed the use of a relatively long coherent integration
time of 30 hours while searching a large parameter space. This search extends
Einstein@Home's previous search in LIGO S4 data to about three times better
sensitivity. No statistically significant signals were found. In the 125 Hz to
225 Hz band, more than 90% of sources with dimensionless gravitational-wave
strain tensor amplitude greater than 3e-24 would have been detected.",0905.1705v1
2009-05-29,Variational wave functions for frustrated magnetic models,"Variational wave functions containing electronic pairing and suppressed
charge fluctuations (i.e., projected BCS states) have been proposed as the
paradigm for disordered magnetic systems (including spin liquids). Here we
discuss the general properties of these states in one and two dimensions, and
show that different quantum phases may be described with high accuracy by the
same class of variational wave functions, including dimerized and magnetically
ordered states. In particular, phases with magnetic order may be obtained from
a straightforward generalization containing both antiferromagnetic and
superconducting order parameters, as well as suitable spin Jastrow
correlations. In summary, projected wave functions represent an extremely
flexible tool for understanding the physics of low-dimensional magnetic
systems.",0905.4854v1
2010-01-08,Phases of Augmented Hadronic Light-Front Wave Functions,"It is an important question whether the final/initial state gluonic
interactions which lead to naive-time-reversal-odd single-spin asymmetries and
diffraction at leading twist can be associated in a definite way with the
light-front wave function hadronic eigensolutions of QCD. We use light-front
time-ordered perturbation theory to obtain augmented light-front wave functions
which contain an imaginary phase which depends on the choice of advanced or
retarded boundary condition for the gauge potential in light-cone gauge. We
apply this formalism to the wave functions of the valence Fock states of
nucleons and pions, and show how this illuminates the factorization properties
of naive-time-reversal-odd transverse momentum dependent observables which
arise from rescattering. In particular, one calculates the identical
leading-twist Sivers function from the overlap of augmented light-front
wavefunctions that one obtains from explicit calculations of the single-spin
asymmetry in semi-inclusive deep inelastic lepton-polarized nucleon scattering
where the required phases come from the final-state rescattering of the struck
quark with the nucleon spectators.",1001.1163v1
2011-03-10,Light storage in an optically thick atomic ensemble under conditions of electromagnetically induced transparency and four-wave mixing,"We study the modification of a traditional electromagnetically induced
transparency (EIT) stored light technique that includes both EIT and four-wave
mixing (FWM) in an ensemble of hot Rb atoms. The standard treatment of light
storage involves the coherent and reversible mapping of one photonic mode onto
a collective spin coherence. It has been shown that unwanted, competing
processes such as four-wave mixing are enhanced by EIT and can significantly
modify the signal optical pulse propagation. We present theoretical and
experimental evidence to indicate that while a Stokes field is indeed detected
upon retrieval of the signal field, any information originally encoded in a
seeded Stokes field is not independently preserved during the storage process.
We present a simple model that describes the propagation dynamics of the fields
and the impact of FWM on the spin wave.",1103.2131v1
2011-04-13,Probing an Ultracold-Atom Crystal with Matter Waves,"Atomic quantum gases in optical lattices serve as a versatile testbed for
important concepts of modern condensed-matter physics. The availability of
methods to characterize strongly correlated phases is crucial for the study of
these systems. Diffraction techniques to reveal long-range spatial structure,
which may complement \emph{in situ} detection methods, have been largely
unexplored. Here we experimentally demonstrate that Bragg diffraction of
neutral atoms can be used for this purpose. Using a one-dimensional Bose gas as
a source of matter waves, we are able to infer the spatial ordering and on-site
localization of atoms confined to an optical lattice. We also study the
suppression of inelastic scattering between incident matter waves and the
lattice-trapped atoms, occurring for increased lattice depth. Furthermore, we
use atomic de Broglie waves to detect forced antiferromagnetic ordering in an
atomic spin mixture, demonstrating the suitability of our method for the
non-destructive detection of spin-ordered phases in strongly correlated atomic
gases.",1104.2564v2
2012-02-22,Characteristics of Quantum Magnetosonic-Wave Dispersion,"Using the quantum magnetohydrodynamics (QMHD) model, linear dispersion of
magnetosonic waves are studied in a quasineutral quantum electron-ion plasma in
two distinct regimes of nonrelativistic and relativistic degeneracies
considering also the plasma composition effect. It is shown that the
paramagnetic spin effects of the degenerated electrons plays a key role in
dynamics of magnetosonic waves. The linear wave-speed is found to have minimum
value at some degeneracy parameter in such plasmas. This is due to delicate
interplay between relativistic degeneracy and the Pauli spin-magnetization. It
is also revealed that the plasma composition has significant effect on the
linear dispersion in the relativistic degeneracy limit contrary to that of
nonrelativistic case and Zeeman energy has significant effect in
nonrelativistic degeneracy regime unlike that of relativistic one in the linear
perturbation-limit. Current findings can have important applications in both
inertial plasma confinement and astrophysical degenerate plasmas.",1202.4822v2
2012-10-02,Third post-Newtonian spin-orbit effect in the gravitational radiation flux of compact binaries,"Gravitational waves contain tail effects that are due to the backscattering
of linear waves in the curved space-time geometry around the source. The
knowledge as well as the accuracy of the two-body inspiraling post-Newtonian
(PN) dynamics and of the gravitational-wave signal has been recently improved,
notably by computing the spin-orbit (SO) terms induced by tail effects in the
gravitational-wave energy flux at the 3PN order. Here we sketch this
derivation, which yields the phasing formula including SO tail effects through
the same 3PN order. Those results can be employed to improve the accuracy of
analytical templates aimed at describing the whole process of inspiral, merger,
and ringdown.",1210.0764v1
2013-02-15,The quantum Hall hierarchy in spherical geometry,"Representative wave functions, which encode the topological properties of the
spin polarized fractional quantum Hall states in the lowest Landau level, can
be expressed in terms of correlation functions in conformal field theories.
Until now, the constructions have been restricted to flat geometries, but in
this paper we generalize to the simplest curved geometry, namely that of a
sphere. Except for being of interest for numerical studies, that usually are
performed on a sphere, the response of the FQH liquids to curvature can be used
to detect a topological quantity, the shift, which is the average orbital spin
of the constituent electrons. We give explicit expressions for representative
wave functions on the sphere, for the full Abelian FQH hierarchy, and calculate
the corresponding shifts. These microscopic results, based on wave functions,
agree with the predictions from the effective Chern-Simons field theory. The
methods we develop can also be applied to the planar case. It gives simpler
expressions for states with both quasiparticle and quasihole condensates, and
allows us to give closed form expressions for a general state in the hierarchy,
rather than finding the wave function on a case by case basis.",1302.3808v2
2013-12-19,Searching for gravitational waves from known pulsars at once and twice the spin frequency,"The existence of a superfluid core in the interior of a rotating neutron star
may have an influence on its gravitational wave emission. In addition to the
usually-assumed pure quadrupole radiation with the gravitational wave frequency
at twice the spin frequency, a frequency of rotation itself may also be present
in the gravitational wave spectrum. We study the parameters of a general model
for such emission, compare it with previously proposed, simpler models, discuss
the feasibility of the recovery of the stellar parameters and carry out the
Monte Carlo simulations to test the performance of our estimation method.",1312.5478v2
2014-05-07,On kinematical constraints in the hadrogenesis conjecture for the baryon resonance spectrum,"We consider the reaction dynamics of bosons with negative parity and spin $0$
or $1$ and fermions with positive parity and spin $\frac{1}{2}$ or
$\frac{3}{2}$. Such systems are of central importance for the computation of
the baryon resonance spectrum in the hadrogenesis conjecture. Based on a chiral
Lagrangian the coupled-channel partial-wave scattering amplitudes have to be
computed. We study the generic properties of such amplitudes. A decomposition
of the various scattering amplitudes into suitable sets of invariant functions
expected to satisfy Mandelstam's dispersion-integral representation is
presented. Sets are identified that are free from kinematical constraints and
that can be computed efficiently in terms of a novel projection algebra. From
such a representation one can deduce the analytic structure of the partial-wave
amplitudes. The helicity and the conventional angular-momentum partial-wave
amplitudes are kinematically constrained at the Kibble conditions. Therefore an
application of a dispersion-integral representation is prohibitively
cumbersome. We derive covariant partial-wave amplitudes that are free from
kinematical constraints at the Kibble conditions. They correspond to specific
polynomials in the 4-momenta and Dirac matrices that solve the various
Bethe-Salpeter equations in the presence of short-range interactions
analytically.",1405.1597v1
2015-01-28,Coexistence of charge-density-wave and pair-density-wave orders in underdoped cuprates,"We analyze incommensurate charge-density-wave (CDW) and pair-density-wave
(PDW) orders with transferred momenta $(\pm Q,0)$/$(0,\pm Q)$ in underdoped
cuprates within the spin-fermion model. Both orders appear due to exchange of
spin fluctuations before magnetic order develops.We argue that the ordered
state with the lowest energy has non-zero CDW and PDW components with the same
momentum. Such a state breaks $C_4$ lattice rotational symmetry, time-reversal
symmetry, and mirror symmetries. We argue that the feedback from CDW/PDW order
on fermionic dispersion is consistent with ARPES data. We discuss the interplay
between the CDW/PDW order and $d_{x^2-y^2}$ superconductivity and make specific
predictions for experiments.",1501.07287v2
2015-07-10,Topological septet pairing with spin-$\frac{3}{2}$ fermions -- high partial-wave channel counterpart of the $^3$He-B phase,"We systematically generalize the exotic $^3$He-B phase, which not only
exhibits unconventional symmetry but is also isotropic and topologically
non-trivial, to arbitrary partial-wave channels with multi-component fermions.
The concrete example with four-component fermions is illustrated including the
isotropic $f$, $p$ and $d$-wave pairings in the spin septet, triplet, and
quintet channels, respectively. The odd partial-wave channel pairings are
topologically non-trivial, while pairings in even partial-wave channels are
topologically trivial. The topological index reaches the largest value of $N^2$
in the $p$-wave channel ($N$ is half of the fermion component number). The
surface spectra exhibit multiple linear and even high order Dirac cones.
Applications to multi-orbital condensed matter systems and multi-component
ultra-cold large spin fermion systems are discussed.",1507.02768v3
2016-06-09,Ground state and the spin precession of the Dirac electron in counterpropagating plane electromagnetic waves,"The fundamental solution of the Dirac equation for an electron in an
electromagnetic field with harmonic dependence on space-time coordinates is
obtained. The field is composed of three standing plane harmonic waves with
mutually orthogonal phase planes and the same frequency. Each standing wave
consists of two eigenwaves with different complex amplitudes and opposite
directions of propagation. The fundamental solution is obtained in the form of
the projection operator defining the subspace of solutions to the Dirac
equation. It is illustrated by the analysis of the ground state and the spin
precession of the Dirac electron in the field of two counterpropagating plane
waves with left and right circular polarizations. Interrelations between the
fundamental solution and approximate partial solutions is discussed and a
criterion for evaluating accuracy of approximate solutions is suggested.",1606.02812v1
2018-03-13,Directional scattering from particles under evanescent wave illumination: the role of reactive power,"Study of photonic spin-orbital interactions, which involves control of the
propagation and spatial distributions of light with the polarization of
electromagnetic fields, is not only important at the fundamental level but also
has significant implications for functional photonic applications that require
active tuning of directional light propagation. Many of the experimental
demonstrations have been attributed to the spin-momentum locking characteristic
of evanescent waves. In this letter, we show another property of evanescent
waves: the polarization dependent direction of the imaginary part of the
Poynting vector, i.e. reactive power. Based on this property, we propose a
simple and robust way to tune the directional far-field scattering from
nanoparticles near a surface under evanescent wave illumination by controlling
linear polarization and direction of the incident light.",1803.04821v1
2018-05-13,Coalescence of Kerr Black Holes: Binary Systems from GW150914 to GW170814,"We investigate the energy of the gravitational wave from a binary black hole
merger by the coalescence of two Kerr black holes with an orbital angular
momentum. The coalescence is constructed to be consistent with particle
absorption in the limit in which the primary black hole is sufficiently large
compared with the secondary black hole. In this limit, we analytically obtain
an effective gravitational spin--orbit interaction dependent on the alignments
of the angular momenta. Then, binary systems with various parameters including
equal masses are numerically analyzed. According to the numerical analysis, the
energy of the gravitational wave still depends on the effective interactions,
as expected from the analytical form. In particular, we ensure that the final
black hole obtains a large portion of its spin angular momentum from the
orbital angular momentum of the initial binary black hole. To estimate the
angular momentum released by the gravitational wave in the actual binary black
hole, we apply our results to observations at the Laser Interferometer
Gravitational-Wave Observatory: GW150914, GW151226, GW170104, GW170608, and
GW170814.",1805.04900v1
2018-05-20,Absorption of electromagnetic plane waves by rotating black holes,"We study the absorption of monochromatic electromagnetic plane waves
impinging upon a Kerr black hole, in the general case that the direction of
incidence is not aligned with the black hole spin axis. We present numerical
results that are in accord with low- and high-frequency approximations. We find
that circularly-polarized waves are distinguished by the black hole spin, with
counter-rotating polarizations being more absorbed than co-rotating
polarizations. At low frequencies and moderate incidence angles, there exists a
narrow parameter window in which superradiant emission in the dipole mode can
exceed absorption in the non-superradiant modes, allowing a planar
electromagnetic wave to stimulate net emission from a black hole.",1805.07840v1
2018-05-18,Synergy between ground and space based gravitational wave detectors II: Localisation,"We study the advantage of combining measurements from future ground and space
based gravitational wave detectors in estimating the parameters of a black-hole
binary coalescence. This is an extension of our previous work (PTEP 053E01
(2016)) where we used pattern averaged waveform to study non-spinning binaries.
In this work we study the localisation and binary plane orientation, including
the (non-precessing) spin of binaries. We focus on the third generation
terrestrial detector `Einstein telescope' and a proposed space based detector
`Deci-Hertz Interferometer Gravitational wave Observatory' (DECIGO). We
consider two possible orbits for DECIGO, a heliocentric orbit and a
Sun-synchronous geocentric orbit. We demonstrate that one can obtain order of
magnitude improvement in the localisation from the space-ground combined
measurements, even with a precursor-DECIGO mission (B-DECIGO). This is
especially important for the future of gravitational wave astronomy as
improving the localisation accuracy further improves our chances of identifying
the host galaxies of these binary systems.",1805.08070v3
2017-02-03,Wave-nature and metastability of emergent crystals in chiral magnets,"Topological spin textures emerging in magnetic materials usually appear in
crystalline states. A long-standing dilemma is whether we should understand
these emergent crystals as gathering particles or coupling waves, the answer of
which affects almost every aspect of our understanding on the subject. Here we
prove that 2-D emergent crystals with long-range order in helimagnets, such as
skyrmion crystals and dipole skyrmion crystals, have a wave nature. We
systematically study their equilibrium properties, metastability, and phase
transition path when unstable. We show that the robustness of a skyrmion
crystal derives from its metastability, and that its phase transition dynamics
at low (high) magnetic field is mediated by a soft mode which breaks
(maintains) its hexagonal symmetry. Different from ordinary crystals which are
formed by. and breaks into atoms, emergent crystals have a new formation
(destruction) mechanism: they appear from (turn to) single-Q spin-density-wave
states through nonlinear mode-mode interactions.",1702.01059v4
2019-05-10,Emergent elastic waves in skyrmion crystals with finite frequencies at long wavelength limit,"A fundamental fact in solids is that the frequencies of elastic waves vanish
as the wave number approaches zero\cite{6}. Here we theoretically show that
this fact is overturned when studying the lattice vibration of skyrmion
crystals (SkX), i.e., periodic alignment of topologically nontrivial spin
solitons called magnetic skyrmions. As emergent crystals, SkX possess
collective excitations called ""emergent phonons"", which describe dynamics of
SkX caused by lattice vibration (resembling acoustical branches of ordinary
phonons) and in-lattice vibration (resembling optical branches of ordinary
phonons). We find that lattice vibration and in-lattice vibration of the
emergent phonons in SkX are coupled even at long wavelength limit, such that
multiple types of ""emergent elastic waves"" (modes causing lattice vibration of
SkX) with finite frequencies exist. This phenomenon, which originates from the
Berry phase form of kinetic energy, is generally true for emergent crystalline
states of spins. Our results show that the dynamics of magnetic emergent
crystals are intrinsically different from that of ordinary crystals.",1905.03977v1
2021-07-16,Acoustic Geometric-Phase Meta-Array,"Metasurfaces based on geometric phase acquired from the conversion of the
optical spin states provide a robust control over the wavefront of light, and
have been widely employed for construction of various types of functional
metasurface devices. However, this powerful approach cannot be readily
transferred to the manipulation of acoustic waves because acoustic waves do not
possess the spin degree of freedom. Here, we propose the concept of acoustic
geometric-phase meta-array by leveraging the conversion of orbital angular
momentum of acoustic waves, where well-defined geometric-phases can be attained
through versatile topological charge conversion processes. This work extends
the concept of geometric-phase metasurface from optics to acoustics, and
provides a new route for acoustic wave control.",2108.04688v1
2019-01-17,Transition radiation in photonic topological crystals: quasi-resonant excitation of robust edge states by a moving charge,"We demonstrate, theoretically and experimentally, that a traveling electric
charge passing from one photonic crystal into another generates edge waves --
electromagnetic modes with frequencies inside the common photonic bandgap
localized at the interface -- via a process of transition edge-wave radiation
(TER). A simple and intuitive expression for the TER spectral density is
derived and then applied to a specific structure: two interfacing photonic
topological insulators with opposite spin-Chern indices. We show that TER
breaks the time-reversal symmetry and enables valley- and spin-polarized
generation of topologically protected edge waves propagating in one or both
directions along the interface. Experimental measurements at the Argonne
Wakefield Accelerator Facility are consistent with the excitation and
localization of the edge waves. The concept of TER paves the way for novel
particle accelerators and detectors.",1901.05640v3
2019-10-16,Charge Density Waves in a Quantum Plasma,"We analyze the instability of an unpolarized uniform quantum plasma
consisting of two oppositely charged fermionic components with varying mass
ratios, against charge and spin density waves (CDWs and SDWs). Using density
functional theory, we treat each component with the local spin density
approximation and a rescaled exchange-correlation functional. Interactions
between different components are treated with a mean-field approximation. In
both two- and three-dimensions, we find leading unstable CDW modes in the
second-order expansion of the energy functional, which would induce the
transition to quantum liquid crystals. The transition point and the length of
the wave-vector are computed numerically. Discontinuous ranges of the
wave-vector are found for different mass ratios between the two components,
indicating exotic quantum phase transitions. Phase diagrams are obtained and a
scaling relation is proposed to generalize the results to two-component
fermionic plasmas with any mass scale. We discuss the implications of our
results and directions for further improvement in treating quantum plasmas.",1910.07152v1
2021-01-01,Superfluid weight and Berezinskii-Kosterlitz-Thouless transition temperature of strained graphene,"We obtain the superfluid weight and Berezinskii-Kosterlitz-Thouless (BKT)
transition temperature for highly unconventional superconducting states with
the coexistence of chiral d-wave superconductivity, charge density waves and
pair density waves in the strained graphene. Our results show that the
strain-induced flat bands can promote the superconducting transition
temperature approximately $50\%$ compared to that of the original doped
graphene, which suggests that the flat-band superconductivity is a potential
route to get superconductivity with higher critical temperatures. In
particular, we obtain the superfluid weight for the pure superconducting
pair-density-wave states from which the deduced superconducting transition
temperature is shown to be much lower than the gap-opening temperature of the
pair density wave, which is helpful to understand the phenomenon of the
pseudogap state in high-$T_c$ cuprate superconductors. Finally, we show that
the BKT transition temperature versus doping for strained graphene exhibits a
dome-like shape and it depends linearly on the spin-spin interaction strength.",2101.00192v1
2021-11-22,Excitation and reception of magnetostatic surface spin waves in thin conducting ferromagnetic films by coplanar microwave antennas. Part I: Theory,"A fully self-consistent model for the excitation and reception of
magnetostatic surface waves in thin ferromagnetic films by a set of coplanar
antennas was developed and implemented numerically. The model assumes that the
ferromagnetic film is highly conducting and is interfaced with non-magnetic
metallic films, but is also suitable for modeling magneto-insulating films.
Perpendicular magnetic anisotropy and Dzyaloshinskii-Moriya interaction can be
included at both interfaces of the ferromagnetic layer. The model calculates
the coupling impedances between the different strips constituting the coplanar
antennas. In some situations, this leads to a frequency non-reciprocity between
counter-propagating waves even in the case of no asymmetry in the spin-wave
dispersion relation. Several intermediate results of the model were checked
numerically and the final output of the model, given as the scattering
parameters, $S_{11}$, $S_{12}$, and $S_{21}$ of the antenna system, were in
good agreement with previous experimental studies.",2111.11106v3
2021-12-14,In-plane magnetic field induced density wave states near quantum spin Hall phase transitions,"We study the influence of an in-plane magnetic field and Coulomb interactions
on the physics of quantum spin Hall insulators, like those in InAs/GaSb and
HgTe/CdTe quantum wells. Using a Hartree-Fock mean-field theory approximation,
we calculate phase diagrams as functions of the band gap, band hybridization,
and magnetic field strength. We show that when the band hybridization is weak,
the system is unstable against the formation of density wave states. As the
strength of the in-plane magnetic field increases, the density-wave region of
the phase diagram expands and distinct density-wave states appear. We discuss
possible experimental implications of our results.",2112.07523v1
2022-03-21,Impact of Spin Wave Dispersion on Surface Acoustic Wave Velocity,"The dependence of the velocity of surface acoustic wave (SAW) as a function
of an external applied magnetic field is investigated in a Fe thin film
epitaxially grown on a piezoelectric GaAs substrate. The SAW velocity is
observed to strongly depend on both the amplitude and direction of the magnetic
field. To interpret the experimental data a phenomenological approach to the
relative change in SAW velocity is implemented. We find that the experimental
velocity variation can be well reproduced provided that the spin wave
dispersion is taken into account. The validity of this phenomenological model
is attested by the comparison with a quasi-exact magnetoelastic one.",2203.10994v2
2022-07-05,$T\bar T$ deformations and the pp wave correspondence,"In this paper we consider $T\bar T$ deformations in the context of pp waves
obtained from gravity duals. We propose a deformation of $AdS_5\times S^5$
similar to the deformation of the single trace $T\bar T$ deformation of
$AdS_3\times S^3\times T^4$ with NS-NS flux, and study it through the Penrose
limit, concluding that it must correspond to some dipole theory, probably
noncommutative. We $T\bar T$ deform the worldsheet string for the $AdS_5\times
S^5$ pp wave, and find a corresponding spin chain Hamiltonian. Finally,
directly $T\bar T$ deforming the spin chain Hamiltonian obtained from the pp
wave, we find that it corresponds to an equivalent BMN sector of the ${\cal
N}=4$ SYM.",2207.02257v4
2023-03-11,Mixing of one-particle-one-hole projected states with the variation after projection wave functions,"In this paper, we study the mixing of one-particle-one-hole projected states
with the variation after projection (VAP) wave functions in attempt to improve
the approximation of this method. It turns out that when minimizing only the
lowest (yrast) energy with given spin and parity, the one-particle-one-hole
projected states can not be mixed into the converged VAP wave function, which
is very similar to the situation of the Hartree-Fock method. However, if one
minimizes the sum of several lowest energies with the same spin and parity, the
one-particle-one-hole mixing can make some improvements to the VAP wave
functions. We expect such one-particle-one-hole mixing may be useful in the
calculations of the low-lying excited states in heavy nuclei with a large model
space.",2303.06518v1
2023-04-25,Predicting Angular-Momentum Waves Based on Yang-Mills Equations,"As one of the most elegant theories in physics, Yang-Mills (YM) theory not
only incorporates Maxwell's equations unifying electromagnetism, but also
underpins the standard model explaining the electroweak and strong interactions
in a succinct way. Whereas the highly nonlinear terms in YM equations involving
the interactions between potentials and fields retard the resolution for them.
In the $U(1)$ case, the solutions of Maxwell's equations are the
electromagnetic waves, which have been applied extensively in the modern
communication networks all over the world. Likewise the operator solutions of
the YM equations under the assumptions of weak-coupling and zero-coupling
predict the $SU(2)$ angular-momentum waves, which is the staple of this work.
Such angular-momentum waves are hopefully realized in the experiments through
the oscillations of spin angular momentum, such as the ``spin Zitterbewegung''
of Dirac's electron.",2304.12625v5
2023-07-28,A new approach to analyzing the spinor wave functions: Effect of strain on the electronic structure and optical transitions in bulk CdSe,"An approach to analyzing the spinor wave functions that appear in the
electronic structure calculations when taking the spin-orbit interaction into
account is developed. It is based on the projection analysis of angular parts
of wave functions onto irreducible representations of the point group and
analysis of the evolution of the energy levels upon the adiabatic turning on
the spin-orbit interaction. The technique is illustrated by an example of the
changes in the valence band structure in strained bulk CdSe with zinc-blende
structure. An analysis of the character of mixing of various branches of the
valence band supports the Luttinger-Kohn model of the valence band. It is shown
that the above calculations complemented by the Zeeman splitting in a magnetic
field make it possible to unambiguously determine the polarization of all
optical transitions. Using the spinor wave functions, matrix elements of
optical transitions between the valence subbands and the conduction band are
calculated.",2307.15534v2
2023-11-28,Coherent phonon-magnon interactions detected by micro-focused Brillouin light scattering spectroscopy,"We investigated the interaction of surface acoustic waves and spin waves with
spatial resolution by micro-focused Brillouin light scattering spectroscopy in
a Co$_{40}$Fe$_{40}$B$_{20}$ ferromagnetic layer on a LiNbO$_{3}$-piezoelectric
substrate. We experimentally demonstrate that the magnetoelastic excitation of
magnons by phonons is coherent by studying the interfering BLS-signals of the
phonons and magnons during their conversion process.We find a pronounced
spatial dependence of the phonon annihilation and magnon excitation which we
map as a function of the magnetic field. The coupling efficiency of the surface
acoustic waves (SAWs) and the spin waves (SWs) is characterized by a magnetic
field dependent decay of the SAWs amplitude.",2311.16688v1
2023-12-06,Revisiting the cosmic string origin of GW190521,"For the first time we analyse gravitational-wave strain data using waveforms
constructed from strong gravity simulations of cosmic string loops collapsing
to Schwarzschild black holes; a previously unconsidered source. Since the
expected signal is dominated by a black-hole ringdown, it can mimic the
observed gravitational waves from high-mass binary black hole mergers. To
illustrate this, we consider GW190521, a short duration gravitational-wave
event observed in the third LIGO--Virgo--KAGRA observing run. We show that
describing this event as a collapsing cosmic string loop is favoured over
previous cosmic string analyses by an approximate log Bayes factor of $22$. The
binary black hole hypothesis is still preferred, mostly because the cosmic
string remnant is non-spinning. It remains an open question whether a spinning
remnant could form from loops with angular momentum, but if possible, it would
likely bring into contention the binary black hole preference. Finally, we
suggest that searches for ringdown-only waveforms would be a viable approach
for identifying collapsing cosmic string events. This work opens up an
important new direction for the cosmic-string and gravitational-wave
communities.",2312.03860v1
2024-02-12,Parameter Estimation for Low-Mass Eccentric Black Hole Binaries,"Recent studies have shown that orbital eccentricity may indicate dynamical
assembly as a formation mechanism for binary black holes. Eccentricity leaves a
distinct signature in gravitational wave signals and it may be measured if the
binary remains eccentric when it enters the LIGO band. Although eccentricity
has not yet been confidently detected, the possibility of detecting eccentric
binaries is becoming more likely with the improved sensitivity of gravitational
wave detectors such as LIGO, Virgo, and KAGRA. It is crucial to assess the
accuracy of current search pipelines in recovering eccentricity from
gravitational wave signals if it is present. In this study, we investigate the
ability of parameter estimation pipeline RIFT to recover eccentricity in the
non-spinning and aligned-spin cases for low mass binary black holes. We use
TaylorF2Ecc and TEOBResumS to inject sets of synthetic signals and test how
well RIFT accurately recovers key binary black hole parameters. Our findings
provide valuable insights into the capability of current parameter estimation
methods to detect and measure eccentricity in gravitational wave signals.",2402.08039v1
2006-08-02,Spin Exchange Rates in Electron-Hydrogen Collisions,"The spin temperature of neutral hydrogen, which determines the 21 cm optical
depth and brightness temperature, is set by the competition between radiative
and collisional processes. In the high-redshift intergalactic medium, the
dominant collisions are typically those between hydrogen atoms. However,
collisions with electrons couple much more efficiently to the spin state of
hydrogen than do collisions with other hydrogen atoms and thus become important
once the ionized fraction exceeds ~1%. Here we compute the rate at which
electron-hydrogen collisions change the hydrogen spin. Previous calculations
included only S-wave scattering and ignored resonances near the n=2 threshold.
We provide accurate results, including all partial wave terms through the
F-wave, for the de-excitation rate at temperatures T_K < 15,000 K; beyond that
point, excitation to n>=2 hydrogen levels becomes significant. Accurate
electron-hydrogen collision rates at higher temperatures are not necessary,
because collisional excitation in this regime inevitably produces Lyman-alpha
photons, which in turn dominate spin exchange when T_K > 6200 K even in the
absence of radiative sources. Our rates differ from previous calculations by
several percent over the temperature range of interest. We also consider some
simple astrophysical examples where our spin de-excitation rates are useful.",0608067v1
1996-01-31,Berry's phase and Quantum Dynamics of Ferromagnetic Solitons,"We study spin parity effects and the quantum propagation of solitons (Bloch
walls) in quasi-one dimensional ferromagnets. Within a coherent state path
integral approach we derive a quantum field theory for nonuniform spin
configurations. The effective action for the soliton position is shown to
contain a gauge potential due to the Berry phase and a damping term caused by
the interaction between soliton and spin waves. For temperatures below the
anisotropy gap this dissipation reduces to a pure soliton mass renormalization.
The gauge potential strongly affects the quantum dynamics of the soliton in a
periodic lattice or pinning potential. For half-integer spin, destructive
interference between soliton states of opposite chirality suppresses nearest
neighbor hopping. Thus the Brillouin zone is halved, and for small mixing of
the chiralities the dispersion reveals a surprising dynamical correlation: Two
subsequent band minima belong to different chirality states of the soliton. For
integer spin, the Berry phase is inoperative and a simple tight-binding
dispersion is obtained. Finally it is shown that external fields can be used to
interpolate continuously between the Bloch wall dispersions for half-integer
and integer spin.",9601153v1
1996-08-27,Correlation functions in the three-chain Hubbard ladder,"In order to check whether odd-numbered Tomonaga-Luttinger ladders are
dominated by antiferromagnetic correlations associated with gapless spin
excitations, correlation functions of the doped three-chain Hubbard model are
obtained with the bosonization at the renormalization-group fixed point. The
correlation of the singlet superconducting pairing across the central and edge
chains is found to be dominant, reflecting two gapful spin modes, while the
intra-edge spin density wave correlation, reflecting the gapless mode, is only
subdominant. This implies that, when there are multiple spin modes, a dominant
superconductivity can arise from the presence of {\it some} spin gap(s) despite
the coexistence of power-law correlated spins.",9608126v1
1997-08-19,Possible chiral phase transition in two-dimensional solid $^3$He,"We study a spin system with two- and four-spin exchange interactions on the
triangular lattice, which is a possible model for the nuclear magnetism of
solid $^3$He layers. It is found that a novel spin structure with scalar chiral
order appears if the four-spin interaction is dominant. Ground-state properties
are studied using the spin-wave approximation. A phase transition concerning
the scalar chirality occurs at a finite temperature, even though the
dimensionality of the system is two and the interaction has isotropic spin
symmetry. Critical properties of this transition are studied with Monte Carlo
simulations in the classical limit.",9708141v1
1997-10-30,Elementary Excitations of Heisenberg Ferrimagnetic Spin Chains,"We numerically investigate elementary excitations of the Heisenberg
alternating-spin chains with two kinds of spins 1 and 1/2 antiferromagnetically
coupled to each other. Employing a recently developed efficient Monte Carlo
technique as well as an exact diagonalization method, we verify the spin-wave
argument that the model exhibits two distinct excitations from the ground state
which are gapless and gapped. The gapless branch shows a quadratic dispersion
in the small-momentum region, which is of ferromagnetic type. With the
intention of elucidating the physical mechanism of both excitations, we make a
perturbation approach from the decoupled-dimer limit. The gapless branch is
directly related to spin 1's, while the gapped branch originates from
cooperation of the two kinds of spins.",9710332v1
1998-06-30,Effects of doping on spin correlations in the periodic Anderson model,"We studied the effects of hole doping on spin correlations in the periodic
Anderson model, mainly at the full and three-quarters-full lower bands cases.
In the full lower band case, strong anti-ferromagnetic correlations develop
when the on-site repulsive interaction strength $U$ becomes comparable to the
quasi-particle band width. In the three-quarters full case, a novel kind of
spin correlation develops that is consistent with the resonance between a
$(\pi,0)$ and a $(0,\pi)$ spin-density wave. In this state the spins on
different sublattices appear uncorrelated. Hole doping away from the completely
full case rapidly destroys the long-range anti-ferromagnetic correlations, in a
manner reminiscent of the destruction of anti-ferromagnetism in the Hubbard
model. In contrast to the Hubbard model, the doping does not shift the peak in
the magnetic structure factor from the $(\pi,\pi)$ position. At dopings
intermediate to the full and three-quarters full cases, only weak spin
correlations exist.",9806374v1
1998-12-09,Spin current in ferromagnet/insulator/superconductor junctions,"A theory of spin polarized tunneling spectroscopy based on a scattering
theory is given for tunneling junctions between ferromagnets and d-wave
superconductors. The spin filtering effect of an exchange field in the
insulator is also treated. We clarify that the properties of the Andreev
reflection are largely modified due to a presence of an exchange field in the
ferromagnets, and consequently the Andreev reflected quasiparticle shows an
evanescent-wave behavior depending on the injection angle of the quasiparticle.
Conductance formulas for the spin current as well as the charge current are
given as a function of the applied voltage and the spin-polarization in the
ferromagnet for arbitrary barrier heights. It is shown that the surface bound
states do not contribute to the spin current and that the zero-bias conductance
peak expected for a d-wave superconductor splits into two peaks under the
influence of the exchange interaction in the insulator.",9812160v3
1998-12-24,Spin Dependence of the Critical Concentration for the Neel State of 2D Impure Heisenberg Antiferromagnets,"The spin-wave theory and the coherent potential approximation are applied to
a spin S Heisenberg antiferromagnet with nonmagnetic impurities on square
lattice. The impurity effects are taken into account by substituting S(1-x) for
S and using the coherent potential approximation to the exchange interaction,
where x is the impurity concentration. At T=0 for S=1/2 the critical impurity
concentration xc of the Neel state is 0.303 and the percolation threshold xp is
0.500. The ground state in xc<x<xp is the disordered state with the spin gap.
For S>=1 the long range Neel order vanishes at xp=0.500. These results explain
qualitatively the experimental results of La2Cu(1-x)Mg(x)O4 (S=1/2) and
K2Mn(1-x)Mg(x)F4 (S=5/2). The difference of xc between these materials is
caused by the decrease in the magnitude of the effective spin with impurity
doping. The spin gap is expected to be observed for La2Cu(1-x)Mg(x)O4 in
xc<x<xp at low temperatures.",9812395v2
2000-01-11,Theory of magnetic order in the three-dimensional spatially anisotropic Heisenberg model,"A spin-rotation-invariant Green's-function theory of long-range and
short-range order (SRO) in the $S=1/2$ antiferromagnetic Heisenberg model with
spatially anisotropic couplings on a simple cubic lattice is presented. The
staggered magnetization, the two-spin correlation functions, the correlation
leng spin-rotation-invariant Green's-function theory of long-range and
short-range order (SRO) in the $S=1/2$ antiferromagnetic Heisenberg model with
spatially anisotropic couplings on a simple cubic lattice is presented. The
staggered magnetization, the two-spin correlation functions, the correlation
lengths, and the static spin susceptibility are calculated self-consistently
over the whole temperature region, where the effects of spatial anisotropy are
explored. As compared with previous spin-wave approaches, the N\'{e}el
temperature is reduced by the improved description of SRO. The maximum in the
temperature dependence of the uniform static susceptibility is shifted with
anisotropy and is ascribed to the decrease of SRO with increasing temperature.
Comparing the theory with experimental data for the magnetization and
correlation length of La$_2$CuO$_4$, a good agreement in the temperature
dependences is obtained.",0001132v1
2000-11-28,Skyrmions in a ferromagnetic Bose-Einstein condensate,"The recently realized multicomponent Bose-Einstein condensates provide
opportunities to explore the rich physics brought about by the spin degrees of
freedom. For instance, we can study spin waves and phase separation,
macroscopic quantum tunneling, Rabi oscillations, the coupling between spin
gradients and superfluid flow, squeezed spin states, vortices and other
topological excitations. Theoretically, there have been already some studies of
the ground-state properties of these systems and their line-like vortex
excitations. In analogy with nuclear physics or the quantum Hall effect, we
explore here the possibility of observing point-like topological excitations or
skyrmions. These are nontrivial spin textures that in principle can exist in a
spinor Bose-Einstein condensate. In particular, we investigate the stability of
skyrmions in a fictitious spin-1/2 condensate of Rb87 atoms. We find that
skyrmions can exist in this case only as a metastable state, but with a
lifetime of the order of, or even longer than, the typical lifetime of the
condensate itself. In addition to determining the size and the lifetime of the
skyrmion, we also present its spin texture and finally briefly consider its
dynamical properties.",0011471v1
2000-12-21,Spin-stiffness and topological defects in two-dimensional frustrated spin systems,"Using a {\it collective} Monte Carlo algorithm we study the low-temperature
and long-distance properties of two systems of two-dimensional classical tops.
Both systems have the same spin-wave dynamics (low-temperature behavior) as a
large class of Heisenberg frustrated spin systems. They are constructed so that
to differ only by their topological properties. The spin-stiffnesses for the
two systems of tops are calculated for different temperatures and different
sizes of the sample. This allows to investigate the role of topological defects
in frustrated spin systems. Comparisons with Renormalization Group results
based on a Non Linear Sigma model approach and with the predictions of some
simple phenomenological model taking into account the topological excitations
are done.",0012397v2
2001-07-13,The Pseudogap in YBa$_2$Cu$_3$O$_{7-δ}$ from NMR in High Magnetic Fields,"We report $^{17}$O(2,3) and $^{63}$Cu(2) spin-lattice relaxation rates and
the $^{17}$O(2,3) spin-spin relaxation rate in different magnetic fields in
YBa$_2$Cu$_3$O$_7$ near $T_c$. Together these measurements enable us to test
the magnetic field dependence of the pseudogap effect on the spin
susceptibility in different regions of the Brillouin zone using the known form
factors for different nuclei as filters. Thus, we study the momentum dispersion
of the pseudogap behavior. We find that near the antiferromagnetic wave vector
the pseudogap is insensitive to magnetic fields up to 15 T. In the remaining
region, away from the $(\pi,\pi)$ point, the pseudogap shows a magnetic field
dependence at fields less then 10 T. The first result is indicative of the
opening of a spin-pseudogap that suppresses antiferromagnetic correlations
below a temperature $T^*$; whereas, the second result shows the effect of
pairing fluctuations on the spin susceptibility as a precursory effect of
superconductivity.",0107303v1
2002-10-29,Ferromagnetism in diluted magnetic semiconductor quantum dot arrays embedded in semiconductors,"We present an Anderson-type model Hamiltonian with exchange coupling between
the localized spins and the confined holes in the quantum dots to study the
ferromagnetism in diluted magnetic semiconductor (DMS) quantum dot arrays
embedded in semiconductors. The hybridization between the quantum-confined
holes in the DMS quantum dots and the itinerant holes in the semiconductor
valence band makes hole transfer between quantum dots, which can induce the
long range ferromagnetic order of the localized spins. In addition, it makes
the carrier spins both in the DMS quantum dots and in the semiconductors
polarized. The spontaneous magnetization of the localized spins and the spin
polarization of the holes are calculated using both the Weiss mean field
approximation and the self-consistent spin wave approximation, which are
developed for the present model.",0210643v1
2003-01-21,Optical Spin Orientation under Inter- and Intra-Subband Transitions in QWs,"It is shown that absorption of circularly polarized infrared radiation
achieved by inter-subband and intra-subband (Drude-like) transitions results in
a monopolar spin orientation of free carriers. The monopolar spin polarization
in zinc-blende-based quantum wells (QWs) is demonstrated by the observation of
the spin-galvanic and circular photogalvanic effects. It is shown that
monopolar spin orientation in n-type QWs becomes possible if an admixture of
valence band states to the conduction band wave function and the spin-orbit
splitting of the valence band are taken into account.",0301388v1
2003-01-21,Monopolar Optical Orientation of Electronic Spins in Semiconductors,"It is shown that absorption of circularly polarized infrared radiation due to
intraband (Drude-like) transitions in n-type bulk semiconductors and due to
intra-subband or inter-subband transitions in quantum well (QW) structures
results in a monopolar spin orientation of free electrons. Spin polarization in
zinc-blende-structure based QWs is demonstrated by the observation of the
spin-galvanic and the circular photogalvanic effects. The monopolar spin
orientation in n-type materials is shown to be possible if an admixture of
valence band states to the conduction band wave function and the spin-orbit
splitting of the valence band are taken into account.",0301393v1
2003-06-12,On Aharonov-Bohm oscillation in a ferromagnetic ring,"Aharonov-Bohm effect in a ferromagnetic thin ring in diffusive regime is
theoretically studied by calculating the Cooperon and Diffuson. In addition to
the spin-orbit interaction, we include the spin-wave excitation and the spin
splitting, which are expected to be dominant sources of dephasing in
ferromagnets at low temperatures. The spin splitting turns out to kill the
spin-flip channel of Cooperon but leaves the spin-conserving channel untouched.
For the experimental confirmation of interference effect (described by
Cooperons) such as weak localization and Aharonov-Bohm oscillation with period
$h/2e$, we need to suppress the dominant dephasing by orbital motion. To do
this we propose experiments on a thin film or thin ring with magnetization and
external field perpendicular to the film, in which case the effective field
inside the sample is equal to the external field (magnetization does not add
up). The field is first applied strong enough to saturate the magnetization and
then carrying out the measurement down to zero field keeping the magnetization
nearly saturated, in order to avoid domain formations (negative fields may also
be investigated if the coercive field is large enough).",0306309v1
2004-07-06,Gapped spin liquid states in a one-dimensional Hubbard model with antiferromagnetic exchange interaction,"We study the phase diagram of a one-dimensional extended Hubbard model with
antiferromagnetic exchange interaction analytically and numerically. The
bosonization and transfer-matrix renormalization group methods are used in the
corresponding coupling regimes. At half-filling, the system is a Mott insulator
with a finite spin excitation gap if the on-site Coulomb repulsion is fairly
smaller than the antiferromagnetic exchange J. This Mott-insulator is
characterized by the bond-charge-density-wave order or spontaneously
dimerization. In the weak-coupling regime where the spin-charge separation
holds approximately, the critical point separating the gapless and gapped spin
liquid phases is U_c\sim J/2. However, as J increases, the spin-charge
couplings become important and the critical point U_c is significantly
suppressed and eventually tends to zero as J\to \infty. Away from half-filling,
the charge gap completely collapses but the spin gap persists.",0407114v1
2004-08-24,Many-Polaron Effects in the Holstein Model,"We derive an effective polaronic interaction Hamiltonian, {\it exact to
second order in perturbation}, for the spinless one-dimensional Holstein model.
The small parameter is given by the ratio of the hopping term ($t$) to the
polaronic energy ($g^2 \omega_0$) in all the region of validity for our
perturbation; however, the exception being the regime of extreme
anti-adiabaticity ($t/\omega_0 \le 0.1$) and small electron-phonon coupling ($g
< 1$) where the small parameter is $t/\omega_0$. We map our polaronic
Hamiltonian onto a next-to-nearest-neighbor interaction anisotropic Heisenberg
spin model. By studying the mass gap and the power-law exponent of the
spin-spin correlation function for our Heisenberg spin model, we analyze the
Luttinger liquid to charge-density-wave transition at half-filling in the
effective polaronic Hamiltonian. We calculate the structure factor at all
fillings and find that the spin-spin correlation length decreases as one
deviates from half-filling. We also extend our derivation of polaronic
Hamiltonian to $d$-dimensions.",0408516v2
2004-11-06,"Finite-$U$ induced competing interactions, frustration, and quantum phase transition in a triangular-lattice antiferromagnet","The $120^0$ ordered antiferromagnetic state of the Hubbard model on a
triangular lattice presents an interesting case of $U$-controlled competing
interactions and frustration. The spin stiffness is found to vanish at $U^*
_{\rm stiff} \approx 6$ and the spin-wave energy $\omega_M$ at ${\bf
q}_M=(2\pi/3,0)$ etc. is found to vanish at $U_M ^* \approx 6.8$ due to
competing spin couplings generated at finite $U$. The loss of magnetic order
due to the magnetic instability at ${\bf q}_M$ yields a first-order quantum
phase transition in the insulating state at $U=U_{\rm M}^*$. Implications of
the quantum spin disordered insulator to the spin-liquid state and Mott
transition in the organic systems $\rm \kappa -(BEDT-TTF)_2 X$ are discussed.
Effects of hole and electron doping on magnetic ordering and spin stiffness are
also examined.",0411164v3
2005-02-08,Spin-Current Relaxation Time in Spin-Polarized Heisenberg Paramagnets,"We study the spatial Fourier transform of the spin correlation function
G_q(t) in paramagnetic quantum crystals by direct simulation of a 1d lattice of
atoms interacting via a nearest-neighbor Heisenberg exchange Hamiltonian. Since
it is not practical to diagonalize the s=1/2 exchange Hamiltonian for a lattice
which is of sufficient size to study long-wavelength (hydrodynamic)
fluctuations, we instead study the s -> infinity limit and treat each spin as a
vector with a classical equation of motion. The simulations give a detailed
picture of the correlation function G_q(t) and its time derivatives. At high
polarization, there seems to be a hierarchy of frequency scales: the local
exchange frequency, a wavelength-independent relaxation rate 1/tau that
vanishes at large polarization P ->1, and a wavelength-dependent spin-wave
frequency proportional to q^2. This suggests a form for the correlation
function which modifies the spin diffusion coefficients obtained in a moments
calculation by Cowan and Mullin, who used a standard Gaussian ansatz for the
second derivative of the correlation function.",0502217v1
2005-10-07,Theory of orbital state and spin interactions in ferromagnetic titanates,"A spin-orbital superexchange Hamiltonian in a Mott insulator with $t_{2g}$
orbital degeneracy is investigated. More specifically, we focus on a spin
ferromagnetic state of the model and study a collective behavior of orbital
angular momentum. Orbital order in the model occurs in a nontrivial way -- it
is stabilized exclusively by quantum effects through the order-from-disorder
mechanism. Several energetically equivalent orbital orderings are identified.
Some of them are specified by a quadrupole ordering and have no unquenched
angular momentum at low energy. Other states correspond to a noncollinear
ordering of the orbital angular momentum and show the magnetic Bragg peaks at
specific positions. Order parameters are unusually small because of strong
quantum fluctuations. Orbital contribution to the resonant x-ray scattering is
discussed. The dynamical magnetic structure factor in different ordered states
is calculated. Predictions made should help to observe elementary excitations
of orbitals and also to identify the type of the orbital order in ferromagnetic
titanates. Including further a relativistic spin-orbital coupling, we derive an
effective low-energy spin Hamiltonian and calculate a spin-wave spectrum, which
is in good agreement with recent experimental observations in YTiO$_3$.",0510175v1
2004-10-28,An expanding universe of spinning spheres,"A novel but elementary geometric construction produces on the
seven-dimensional manifold of rotated spheres in Euclidean three-space a
finslerian geometry whose geodesics are interpreted as the paths of free,
spinning, spherical particles moving through de Sitter's expanding universe. A
particle of nonzero inertial rest mass typically follows a helical track and
exhibits behavior remindful of the phenomenon of ``Zitterbewegung'' of spinning
electrons first deduced by Schroedinger from Dirac's relativistic wave
equation. Its velocity vector and its spin vector precess about the axial
direction of the helix, with their projections onto that direction at all times
parallel or at all times antiparallel. Particles of zero rest mass follow
straight tracks at the speed of light with their spin vectors parallel or
antiparallel to their velocity vectors, thereby replicating behavior of
spinning photons predicted by the quantum theory of light.",0410137v1
1998-11-24,Large - Distance Effects in QCD and Spin Asymmetries in Diffractive Reactions,"Large - distance effects in the hadron wave function for the hadron-Pomeron
vertex in the QCD -model are discussed. It is shown that they lead to the
spin-flip part of the Pomeron coupling which can reach $10 \div 20 %$ with
respect to the non-flip part. The obtained structure of the Pomeron coupling
modifies spin asymmetries in high--energy diffractive reactions where the
Pomeron structure becomes determinative. We study spin asymmetries in exclusive
reactions and in the diffractive $Q \bar Q$ and $J/\Psi$ production. We have
found that spin effects in these diffractive processes are sensitive to the
spin-flip part of the Pomeron coupling.",9811450v1
1997-01-20,Multi-parameter deformed and nonstandard $Y(gl_M)$ Yangian symmetry in a novel class of spin Calogero-Sutherland models,"It is well known through a recent work of Bernard, Gaudin, Haldane and
Pasquier (BGHP) that the usual spin Calogero-Sutherland (CS) model, containing
particles with $M$ internal degrees of freedom, respects the $Y(gl_M)$ Yangian
symmetry. By following and suitably modifying the approach of BGHP, in this
article we construct a novel class of spin CS models which exhibit
multi-parameter deformed or `nonstandard' variants of $Y(gl_M)$ Yangian
symmetry. An interesting feature of such CS Hamiltonians is that they contain
many-body spin dependent interactions, which can be calculated directly from
the associated rational solutions of Yang-Baxter equation. Moreover, these spin
dependent interactions often lead to `anyon like' representations of
permutation algebra on the combined internal space of all particles. We also
find out the general forms of conserved quantities as well as Lax pairs for the
above mentioned class of spin CS models, and describe the method of
constructing their exact wave functions.",9701097v2
2001-12-19,On the Concept of Spin,"It is substantiated that spin is a notion associated with the group of
internal symmetry that is tightly connected with the geometrical structure of
spacetime. The wave equation for the description of the particles with spin one
half is proposed. On this ground it is shown that the spin of electron is
exhibited through the quantum number and accordingly the Dirac equation
describes properties of particles with the projection of spin equal plus or
minus one half. On contrary, we put forward the conjecture that the spin of the
quark cannot be considered as a quantum number, but only as an origin of a
non-abelian gauge field. It is a deep reason for understanding quark-lepton
symmetry and such important phenomena as quark confinement.",0112172v1
2001-02-26,True energy-momentum tensors are unique. Electrodynamics spin tensor is not zero,"A true energy-momentum tensor is unique and does not admit an addition of a
term. The true electrodynamics' energy-momentum tensor is the Maxwell-Minkowski
tensor. It cannot be got with the Lagrange formalism. The canonical
energy-momentum and spin tensors are out of all relation to the physical
reality. The true electrodynamics' spin tensor is not equal to a zero. So,
electrodynamics' ponderomotive action comprises a force from the Maxwell stress
tensor and a torque from the spin tensor. A gauge non-invariant expression for
the spin tensor is presented and is used for a consideration of a circularly
polarized standing wave. A circularly polarized light beam carries a spin
angular momentum and an orbital angular momentum. So, we double the beams
angular momentum. The Beths experiment is considered.",0102084v2
2003-08-06,What is spin?,"This is a late answer to question #79 by R.I. Khrapko, ""Does plane wave not
carry a spin?,"" Am. J. Phys. /69/, 405 (2001), and a complement (on gauge
invariance, massive spin 1 and 1/2, and massless spin 2 fields) to the paper by
H.C. Ohanian, ""What is spin?,"" Am. J. Phys. /54/, 500--505 (1985). In
particular, it is confirmed that ""spin"" is a classical quantity which can be
calculated for any field using its definition, namely that it is just the
non-local part of the conserved angular momentum. This leads to explicit
expressions which are bilinear in the fields and which agree with their
standard ""quantum"" counterparts.",0308027v3
2004-03-17,Effect of electron-nuclear spin interactions on electron-spin qubits localized in self-assembled quantum dots,"The effect of electron-nuclear spin interactions on qubit operations is
investigated for a qubit represented by the spin of an electron localized in a
self-assembled quantum dot. The localized electron wave function is evaluated
within the atomistic tight-binding model. The magnetic field generated by the
nuclear spins is estimated in the presence of an inhomogeneous environment
characterized by a random nuclear spin configuration, by the dot-size
distribution, by alloy disorder, and by interface disorder. Due to these
inhomogeneities, the magnitude of the nuclear magnetic field varies from one
qubit to another by the order of 100 G, 100 G, 10 G, and 0.1 G, respectively.
The fluctuation of the magnetic field causes errors in exchange operations due
to the inequality of the Zeeman splitting between two qubits. We show that the
errors can be made lower than the quantum error threshold if an exchange energy
larger than 0.1 meV is used for the operation.",0403122v1
2005-09-28,Effective Spin Quantum Phases in Systems of Trapped Ions,"A system of trapped ions under the action of off--resonant standing--waves
can be used to simulate a variety of quantum spin models. In this work, we
describe theoretically quantum phases that can be observed in the simplest
realization of this idea: quantum Ising and XY models. Our numerical
calculations with the Density Matrix Renormalization Group method show that
experiments with ion traps should allow one to access general properties of
quantum critical systems. On the other hand, ion trap quantum spin models show
a few novel features due to the peculiarities of induced effective spin--spin
interactions which lead to interesting effects like long--range quantum
correlations and the coexistence of different spin phases.",0509197v1
2005-10-03,Understanding entangled spins in QED,"The stability of two entangled spins dressed by electrons is studied by
calculating the scattering phase shifts. The interaction between electrons is
interpreted by fully relativistic QED and the screening effect is described
phenomenologically in the Debye exponential form $e^{-\alpha r}$. Our results
show that if the (Einstein-Podolsky-Rosen-) EPR-type states are kept stable
under the interaction of QED, the spatial wave function must be
parity-dependent. The spin-singlet state $s=0$ and the polarized state $\frac
1{\sqrt{2}}(\mid +-> -\mid -+>)$ along the z-axis\QTR{bf}{\}give rise to two
different kinds of phase shifts\QTR{bf}{.} Interestingly, the interaction
between electrons in the spin-singlet pair is found to be attractive. Such an
attraction could be very useful when we extract the entangled spins from
superconductors. A mechanism to filter the entangled spins is also discussed.",0510016v5
2006-12-11,Quantum chaos with spin-chains in pulsed magnetic fields,"Recently it was found that the dynamics in a Heisenberg spin-chain subjected
to a sequence of periodic pulses from an external, parabolic, magnetic field
can have a close correspondence with the quantum kicked rotor (QKR). The QKR is
a key paradigm of quantum chaos; it has as its classical limit the well-known
Standard Map. It was found that a single spin excitation could be converted
into a pair of non-dispersive, counter-propagating spin coherent states
equivalent to the accelerator modes of the Standard Map. Here we consider how
other types of quantum chaotic systems such as a double-kicked quantum rotor or
a quantum rotor with a double-well potential might be realized with spin
chains; we discuss the possibilities regarding manipulation of the one-magnon
spin waves.",0612074v1
2007-06-07,Influence of an external magnetic field on the decoherence of a central spin coupled to an antiferromagnetic environment,"Using the spin wave approximation, we study the decoherence dynamics of a
central spin coupled to an antiferromagnetic environment under the application
of an external global magnetic field. The external magnetic field affects the
decoherence process through its effect on the antiferromagnetic environment. It
is shown explicitly that the decoherence factor which displays a Gaussian decay
with time depends on the strength of the external magnetic field and the
crystal anisotropy field in the antiferromagnetic environment. When the values
of the external magnetic field is increased to the critical field point at
which the spin-flop transition (a first-order quantum phase transition) happens
in the antiferromagnetic environment, the decoherence of the central spin
reaches its highest point. This result is consistent with several recent
quantum phase transition witness studies. The influences of the environmental
temperature on the decoherence behavior of the central spin are also
investigated.",0706.0934v1
2007-10-19,Exponential decay in a spin bath,"We show that the coherence of an electron spin interacting with a bath of
nuclear spins can exhibit a well-defined purely exponential decay for special
(`narrowed') bath initial conditions in the presence of a strong applied
magnetic field. This is in contrast to the typical case, where spin-bath
dynamics have been investigated in the non-Markovian limit, giving
super-exponential or power-law decay of correlation functions. We calculate the
relevant decoherence time T_2 explicitly for free-induction decay and find a
simple expression with dependence on bath polarization, magnetic field, the
shape of the electron wave function, dimensionality, total nuclear spin I, and
isotopic concentration for experimentally relevant heteronuclear spin systems.",0710.3762v2
2008-08-19,Spin-density induced by electromagnetic wave in two-dimensional electron gas with both Rashba and Dresselhaus spin-orbit couplings,"We consider the magnetic response of a two-dimensional electron gas (2DEG)
with both Rashba and Dresselhaus spin-orbit coupling to a microwave excitation.
We generalize the results of [A. Shnirman and I. Martin, Europhys. Lett. 78,
27001 (2007).], where pure Rashba coupling was studied. We observe that the
microwave with the in-plane electric field and the out-of-plane magnetic field
creates an out-of-plane spin polarization. The effect is more prominent in
clean systems with resolved spin-orbit-split subbands. Considered as response
to the microwave magnetic field, the spin-orbit contribution to the
magnetization far exceeds the usual Zeeman contribution in the clean limit. The
effect vanishes when the Rashba and the Dresselhaus couplings have equal
strength.",0808.2607v2
2008-11-15,Theory of Inelastic Electron Tunneling from a Localized Spin in the Impulsive Approximation,"A simple expression for the conductance steps in the inelastic electron
tunneling from spin excitations in a single magnetic atom adsorbed on a
non-magnetic metal surfaces is derived. The inelastic coupling between the
tunneling electron and the spin is via the exchange coupling and is treated in
an impulsive approximation using the Tersoff-Hamann approximation for the
tunneling between the tip and the sample. Our results for conductance steps
justify the analysis carried out by Hirjebedin et al. [Science 317, 1199
(2007)] of observed step-like conductances by inelastic electron tunneling from
spin excitations in a single magnetic adatom using a simple spin matrix
element. In addition, our result gives a simple expression for the magnitudes
of conductance steps and their lateral spatial variation with respect to the
tip position, which can be calculated directly from spin-polarized wave
functions at the Fermi level of the sample.",0811.2511v1
2008-11-18,Optical manipulation of a single Mn spin in a CdTe-based quantum dot,"A system of two coupled CdTe quantum dots, one of them containing a single Mn
ion, was studied in continuous wave and modulated photoluminescence,
photoluminescence excitation, and photon correlation experiments. Optical
writing of information in the spin state of the Mn ion has been demonstrated,
using orientation of the Mn spin by spin-polarized carriers transferred from
the neighbor quantum dot. Mn spin orientation time values from 20 ns to 100 ns
were measured, depending on the excitation power. Storage time of the
information in the Mn spin was found to be enhanced by application of a static
magnetic field of 1 T, reaching hundreds of microseconds in the dark. Simple
rate equation models were found to describe correctly static and dynamical
properties of the system.",0811.2898v1
2009-01-01,Rash spin-orbit interaction in graphene and graphene zigzag nano-ribbons,"We investigate the effects of Rashba spin-orbit interactions on the
electronic band-structure and corresponding wave-functions of graphene. By
exactly solving a tight-binding model Hamiltonian we obtain the expected
splitting of the bands -due to the SU(2) spin symmetry breaking- that is
accompanied by the appearance of additional Dirac points. These points are
originated by valence-conduction band crossings. By introducing a convenient
gauge transformation we study a model for zigzag nanoribbons with RSO
interactions. We show that the RSO interactions lifts the quasi-degeneracy of
the edge band while introducing a state-dependent spin separation in real
space. Calculation of the average magnetization perpendicular to the ribbon
plane suggest that RSO could be used to produce spin-polarized currents.
Comparisons with the intrinsic spin-orbit (I-SO) interaction proposed to exist
in graphene are also presented.",0901.0160v3
2009-04-28,Enhancement of Spin Susceptibility near Charge-Ordering Transition in a Two-Dimensional Extended Hubbard Model,"Based on the non-skeleton diagrammatic expansion satisfying the
compressibility and spin-susceptibility sum rules, we investigate static charge
and spin responses in a two-dimensional extended Hubbard model with the
nearest-neighbor Coulomb repulsion in the vicinity of its charge-ordering
transition point. In this expansion, we can calculate approximate charge and
spin response functions by systematic inclusion of vertex corrections, from
which we obtain the uniform susceptibility equal to the so-called q-limit of
the response function and the second-order transition point as a divergent
point in the same response function at some finite wave-number vector. It is
shown that the reentrant charge-ordering transition, which has already been
observed in the random-phase approximation (RPA), remains to take place even
though the vertex corrections are included beyond the RPA. As a prominent
effect of the vertex corrections, we find that the uniform spin susceptibility
is enhanced due to charge fluctuations developing toward the charge-ordering
transition. We give a qualitative comparison of this enhanced spin
susceptibility with the experimental results on the quasi-two-dimensional
organic conductors, together with its explanation in the Landau's Fermi-liquid
theory.",0904.4302v1
2009-07-04,"Quantum rings with time dependent spin-orbit coupling: Rabi oscillations, spintronic Schrodinger-cat states, and conductance properties","The strength of the (Rashba-type) spin-orbit coupling in mesoscopic
semiconductor rings can be tuned with external gate voltages. Here we consider
the case of a periodically changing spin-orbit interaction strength as induced
by sinusoidal voltages. In a closed one dimensional quantum ring with weak
spin-orbit coupling, Rabi oscillations are shown to appear. We find that the
time evolution of initially localized wave packets exhibits a series of
collapse and revival phenomena. Partial revivals -- that are typical in
nonlinear systems -- are shown to correspond to superpositions of states
localized at different spatial positions along the ring. These ""spintronic
Schrodinger-cat sates"" appear periodically, and similarly to their counterparts
in other physical systems, they are found to be sensitive to environment
induced disturbances. The time dependent spin transport problem, when leads are
attached to the ring, is also solved. We show that the ""sideband currents""
induced by the oscillating spin-orbit interaction strength can become the
dominant output channel, even in the presence of moderate thermal fluctuations
and random scattering events.",0907.0766v1
2009-08-06,Finite temperature spin-dynamics and phase transitions in spin-orbital models,"We study finite temperature properties of a generic spin-orbital model
relevant to transition metal compounds, having coupled quantum Heisenberg-spin
and Ising-orbital degrees of freedom. The model system undergoes a phase
transition, consistent with that of a 2D Ising model, to an orbitally ordered
state at a temperature set by short-range magnetic order. At low temperatures
the orbital degrees of freedom freeze-out and the model maps on to a quantum
Heisenberg model. The onset of orbital excitations causes a rapid scrambling of
the spin spectral weight away from coherent spin-waves, which leads to a sharp
increase in uniform magnetic susceptibility just below the phase transition,
reminiscent of the observed behavior in the Fe-pnictide materials.",0908.0800v2
2009-10-16,Anderson Impurity in Helical Metal,"We use a trial wave function to study the spin-1/2 Kondo effect of a helical
metal on the surface of a three-dimensional topological insulator. While the
impurity spin is quenched by conduction electrons, the spin-spin correlation of
the conduction electron and impurity is strongly anisotropic in both spin and
spatial spaces. As a result of strong spin-orbit coupling, the out-of-plane
component of the impurity spin is found to be fully screened by the orbital
angular momentum of the conduction electrons.",0910.3031v5
2009-11-03,Recovering a spinning inspiralling compact binary waveform immersed in LIGO-like noise with spinning templates,"We investigate the recovery chances of highly spinning waveforms immersed in
LIGO S5-like noise by performing a matched filtering with 10^6 randomly chosen
spinning waveforms generated with the LAL package. While the masses of the
compact binary are reasonably well recovered (slightly overestimated), the same
does not hold true for the spins. We show the best fit matches both in the
time-domain and the frequency-domain. These encompass some of the spinning
characteristics of the signal, but far less than what would be required to
identify the astrophysical parameters of the system. An improvement of the
matching method is necessary, though may be difficult due to the noisy signal.",0911.0473v3
2009-11-20,Spin Transfer Dynamics in Spin Valves with Out-of-plane Magnetized CoNi Free Layers,"We have measured spin transfer-induced dynamics in magnetic nanocontact
devices having a perpendicularly magnetized Co/Ni free layer and an in-plane
magnetized CoFe fixed layer. The frequencies and powers of the excitations
agree well with the predictions of the single-domain model and indicate that
the excited dynamics correspond to precessional orbits with angles ranging from
zero to 90 degrees as the applied current is increased at a fixed field. From
measurements of the onset current as a function of applied field strength we
estimate the magnitude of the spin torque asymmetry parameter lambda ~ 1.5. By
combining these with spin torque ferromagnetic resonance measurements, we also
estimate the spin wave radiation loss in these devices.",0911.4077v1
2010-02-19,Evolution of massive black hole spins,"Black hole spins affect the efficiency of the ""classical"" accretion
processes, hence the radiative output from quasars. Spins also determine how
much energy is extractable from the hole itself. Recently it became clear that
massive black hole spins also affect the retention of black holes in galaxies,
be cause of the impulsive ""gravitational recoil"", up to thousands km/s, due to
anisotropic emission of gravitational waves at merger. I discuss here the
evolution of massive black hole spins along the cosmic history, due to the
combination of mergers and accretion events. I describe recent simulations of
accreting black holes in merger remnants, and discuss the implication for the
spins of black holes in quasars.",1002.3827v2
2010-06-01,High cooperativity coupling of electron-spin ensembles to superconducting cavities,"Electron spins in solids are promising candidates for quantum memories for
superconducting qubits because they can have long coherence times, large
collective couplings, and many quantum bits can be encoded into the spin-waves
of a single ensemble. We demonstrate the coupling of electron spin ensembles to
a superconducting transmission-line resonator at coupling strengths greatly
exceeding the cavity decay rate and comparable to spin linewidth. We also use
the enhanced coupling afforded by the small cross-section of the transmission
line to perform broadband spectroscopy of ruby at millikelvin temperatures at
low powers. In addition, we observe hyperfine structure in diamond P1 centers
and time domain saturation-relaxation of the spins.",1006.0242v1
2010-06-08,Effects of impurities and vortices on the low-energy spin excitations in high-Tc materials,"We review a theoretical scenario for the origin of the spin-glass phase of
underdoped cuprate materials. In particular it is shown how disorder in a
correlated d-wave superconductor generates a magnetic phase by inducing local
droplets of antiferromagnetic order which eventually merge and form a
quasi-long range ordered state. When correlations are sufficiently strong,
disorder is unimportant for the generation of static magnetism but plays an
additional role of pinning disordered stripe configurations. We calculate the
spin excitations in a disordered spin-density wave phase, and show how disorder
and/or applied magnetic fields lead to a slowing down of the dynamical spin
fluctuations in agreement with neutron scattering and muon spin rotation (muSR)
experiments.",1006.1483v1
2010-07-13,Repeated measurements and nuclear spin polarization,"We study repeated (noncontinuous) measurements on the electron spin in a
quantum dot and find that the measurement technique may lead to a different
met$ or mechanism to realize nuclear spin polarization. While it may be used in
any case, the method is aimed at the further polarization, providing that
nuclear spins have been polarized by the existent electrical or optical
methods. The feasibility of the method is analyzed. The existing techniques in
electron spin measurements are applicable to this scheme. The repeated
measurements \emph{deform} the structures of the nuclear wave function and can
also serve as $\emph{gates}$ to manipulate nuclear spins.",1007.2157v3
2010-08-04,Spin relaxation due to electron-electron magnetic interaction in high Lande g-factor semiconductors,"We investigate spin transport in InSb/InAlSb heterostructure using the Monte
Carlo approach, generalized by including density matrix description of spin for
taking spin dynamics into account. In addition to the dominant Dyakonov-Perel
(DP) mechanism for spin control and relaxation, we consider magnetic
interaction between electrons which assumes importance due to high electronic
Lande g-factor in the material. It is found that while the effect of magnetic
interaction is not important at low densities, it reduces the spin relaxation
length by as much as 50% at higher densities. We also present a calculation
which elucidates the suppression of decoherence attributed to wave vector
dependent magnetic field in the DP relaxation mechanism. We note that magnetic
interaction is a general relaxation mechanism which may assume importance in
materials with high electronic Lande g-factor.",1008.0739v1
2010-12-06,Spin Susceptibility and Helical Magnetic Orders at the Edges/Surfaces of Topological Insulators Due to Fermi Surface Nesting,"We study spin susceptibility and magnetic order at the edges/surfaces of
two-dimensional and three-dimensional topological insulators when the Fermi
surface is nested. We find that due to spin-momentum locking as well as
time-reversal symmetry, spin susceptibility at the nesting wavevector has a
strong {\em helical} feature. It follows then, a {\em helical} spin density
wave (SDW) state emerges at low temperature due to Fermi surface nesting. The
helical feature of spin susceptibility also has profound impact on the magnetic
order in magnetically doped surface of three dimensional topological
insulators. In such system, from the mean field Zener theory, we predict a {\em
helical} magnetic order.",1012.1299v10
2011-01-14,Three-Body Model Calculation of Spin Distribution in Two-Nucleon Transfer Reaction,"The differential cross sections of two-nucleon transfer reactions
238U(18O,16O)240U around 10 MeV per nucleon are calculated by one-step
Born-approximation with a 16O+2n+238U three-body model. The three-body wave
function in the initial channel is obtained with the continuum-discretized
coupled-channels method, and that in the final channel is evaluated with
adiabatic approximation. The resulting cross sections have a peak around the
grazing angle, and the spin distribution, i.e., the cross section at the peak
as a function of the transferred spin, is investigated. The shape of the spin
distribution is found not sensitive to the incident energies, optical
potentials, and treatment of the breakup channels both in the initial and final
states, while it depends on the excitation energy of the residual nucleus 240U.
The peak of the spin distribution moves to the large-spin direction as the
excitation energy increases. To fulfill the condition that the peak position
should not exceeds 10 hbar, which is necessary for the surrogate ratio method
to work, it is concluded that the excitation energy of 240U must be less than
10 MeV.",1101.2732v1
2011-01-24,Identifying spin-triplet pairing in spin-orbit coupled multi-band superconductors,"We investigate the combined effect of Hund's and spin-orbit (SO) coupling on
superconductivity in multi-orbital systems. Hund's interaction leads to
orbital-singlet spin-triplet superconductivity, where the Cooper pair wave
function is antisymmetric under the exchange of two orbitals. We identify three
d-vectors describing even-parity orbital-singlet spin-triplet pairings among
t2g-orbitals, and find that the three d-vectors are mutually orthogonal to each
other. SO coupling further assists pair formation, pins the orientation of the
d-vector triad, and induces spin-singlet pairings with a relative phase
difference of \pi/2. In the band basis the pseudospin d-vectors are aligned
along the z-axis and correspond to momentum-dependent inter- and intra-band
pairings. We discuss quasiparticle dispersion, magnetic response, collective
modes, and experimental consequences in light of the superconductor Sr2RuO4.",1101.4656v3
2011-02-16,A semi-classical approach to electron spin resonance in quantum spin systems,"We develop a semi-classical approximation to electron spin resonance in
quantum spin systems, based on the rotor or non-linear sigma model. The
classical time evolution is studied using molec- ular dynamics while random
initial conditions are sampled using classical Monte Carlo methods. Although
the approximation may be especially powerful in two dimensions, we apply it
here to one- dimensional systems of large spin at intermediate temperatures, in
the presence of staggered and uniform magnetic fields. We first test the
validity of the semi-classical approximation by comparing the magnetization to
quantum Monte Carlo results on S = 2 chains. Then we calculate the ESR
spectrum, finding broad coexisting paramagnetic and spin wave resonances.",1102.3239v1
2011-03-09,Incommensurate spin Luttinger liquid phase in a model for the spin-Peierls materials TiOBr and TiOCl,"In the present work we aim to characterize the lattice configurations and the
magnetic behavior in the incommensurate phase of spin-Peierls systems. This
phase emerges when the magnetic exchange interaction is coupled to the
distortions of an underlying triangular lattice and has its experimental
realization in the quasi-one dimensional compound family TiOX (X = Cl, Br).
With a simple model of spin-1/2 chains inserted in a planar triangular geometry
which couples them elastically, we are able to obtain the
uniform-incommensurate and incommensurate-dimerized phase transitions seen in
these compounds. Moreover, we follow the evolution of the wave-vector of the
distortions with temperature inside the incommensurate phase. Finally, we
predict gapless spin excitations for the intermediate phase of TiOX compounds
along with incommensurate spin-spin correlations. This exotic Luttinger
liquid-like behavior could be observed in future experiments.",1103.1792v1
2011-04-28,Model study of dissipation in quantum phase transitions,"We consider a prototypical system of an infinite range transverse field Ising
model coupled to a bosonic bath. By integrating out the bosonic degrees, an
effective anisotropic Heisenberg model is obtained for the spin system. The
phase diagram of the latter is calculated as a function of coupling to the heat
bath and the transverse magnetic field. Collective excitations at low
temeratures are assessed within a spin-wave like analysis that exhibits a
vanishing energy gap at the quantum critical point. We also consider another
limit where the system reduces to a generalized spin-boson model of two
interacting spins. By increasing the coupling strength with the heat bath, the
two-spin wavefunction changes from an entangled state to a factorized state of
two spins which are aligned along the transverse field. We also discuss the
possible realization and application of the model to different physical
systems.",1104.5306v1
2011-05-16,Tensor network states for quantum spin ladders,"We have developed an efficient tensor network algorithm for spin ladders,
which generates ground-state wave functions for infinite-size quantum spin
ladders. The algorithm is able to efficiently compute the ground-state fidelity
per lattice site, a universal phase transition marker, thus offering a powerful
tool to unveil quantum many-body physics underlying spin ladders. To illustrate
our scheme, we consider the two-leg and three-leg Heisenberg spin ladders with
staggering dimerization. The ground-state phase diagram thus yielded is
reliable, compared with the previous studies based on the density matrix
renormalization group. Our results indicate that the ground-state fidelity per
lattice site successfully captures quantum criticalities in spin ladders.",1105.3016v1
2011-10-13,Evolution of the Kondo resonance feature and its relationship to spin-orbit coupling across the quantum critical point in Ce2Rh{1-x}CoxSi3,"We investigate the evolution of the electronic structure of Ce2Rh{1-x}CoxSi3
as a function of x employing high resolution photoemission spectroscopy. Co
substitution at the Rh sites in antiferromagnetic Ce2RhSi3 leads to a
transition from an antiferromagnetic system to a Kondo system, Ce2CoSi3 via the
Quantum Critical Point (QCP). High resolution photoemission spectra reveal
distinct signature of the Kondo resonance feature (KRF) and its spin orbit
split component (SOC) in the whole composition range indicating finite Kondo
temperature scale at the quantum critical point. We observe that the intensity
ratio of the Kondo resonance feature and its spin orbit split component,
KRF/SOC gradually increases with the decrease in temperature in the strong
hybridization limit. The scenario gets reversed if the Kondo temperature
becomes lower than the magnetic ordering temperature. While finite Kondo
temperature within the magnetically ordered phase indicates applicability of
the spin density wave picture at the approach to QCP, the dominant temperature
dependence of the spin-orbit coupled feature suggests importance of spin-orbit
interactions in this regime.",1110.2836v1
2011-12-01,Gate controlled Spin-Density Wave and Chiral FFLO Superconducting phases in interacting Quantum Spin Hall edge states,"We explore the phases exhibited by an interacting quantum spin Hall edge
state in the presence of finite chemical potential (applied gate voltage) and
spin imbalance (applied magnetic field). We find that the helical nature of the
edge state gives rise to orders that are expected to be absent in non-chiral
one-dimensional electronic systems. For repulsive interactions, the ordered
state has an oscillatory spin texture whose ordering wavevector is controlled
by the chemical potential. We analyze the manner in which a magnetic impurity
provides signatures of such oscillations. We find that finite spin imbalance
favors a finite current carrying groundstate that is not condensed in the
absence of interactions and is superconducting for attractive interactions.
This state is characterized by FFLO-type oscillations where the Cooper pairs
obtain a finite center of mass momentum.",1112.0289v1
2012-01-19,Spin and valley quantum Hall ferromagnetism in graphene,"In a graphene Landau level (LL), strong Coulomb interactions and the fourfold
spin/valley degeneracy lead to an approximate SU(4) isospin symmetry. At
partial filling, exchange interactions can spontaneously break this symmetry,
manifesting as additional integer quantum Hall plateaus outside the normal
sequence. Here we report the observation of a large number of these quantum
Hall isospin ferromagnetic (QHIFM) states, which we classify according to their
real spin structure using temperature-dependent tilted field magnetotransport.
The large measured activation gaps confirm the Coulomb origin of the broken
symmetry states, but the order is strongly dependent on LL index. In the high
energy LLs, the Zeeman effect is the dominant aligning field, leading to real
spin ferromagnets with Skyrmionic excitations at half filling, whereas in the
`relativistic' zero energy LL, lattice scale anisotropies drive the system to a
spin unpolarized state, likely a charge- or spin-density wave.",1201.4167v1
2012-02-15,Spin critical opalescence in zero temperature Bose-Einstein Condensates,"Cold atom developments suggest the prospect of measuring scaling properties
and long-range fluctuations of continuous phase transitions at
zero-temperature. We discuss the conditions for characterizing the phase
separation of Bose-Einstein condensates of boson atoms in two distinct
hyperfine spin states. The mean-field description breaks down as the system
approaches the transition from the miscible side. An effective spin description
clarifies the ferromagnetic nature of the transition. We show that a difference
in the scattering lengths for the bosons in the same spin state leads to an
effective internal magnetic field. The conditions at which the internal
magnetic field vanishes (i.e., equal values of the like-boson scattering
lengths) is a special point. We show that the long range density fluctuations
are suppressed near that point while the effective spin exhibits the long-range
fluctuations that characterize critical points. The zero-temperature system
exhibits critical opalescence with respect to long wavelength waves of impurity
atoms that interact with the bosons in a spin-dependent manner.",1202.3365v1
2012-04-05,Mott Transition and Spin Structures of Spin-1 Bosons in Two-Dimensional Optical Lattice at Unit Filling,"We study the ground state properties of spin-1 bosons in a two-dimensional
optical lattice, by applying a variational Monte Carlo method to the S=1
Bose-Hubbard model on a square lattice at unit filling. A doublon-holon binding
factor introduced in the trial state provides a noticeable improvement in the
variational energy over the conventional Gutzwiller wave function and allows us
to deal effectively with the inter-site correlations of particle densities and
spins. We systematically show how spin-dependent interactions modify the
superfluid-Mott insulator transitions in the S=1 Bose-Hubbard model due to the
interplay between the density and spin fluctuations of bosons. Furthermore,
regarding the magnetic phases in the Mott region, the calculated spin structure
factor elucidates the emergence of nematic and ferromagnetic spin orders for
antiferromagnetic ($U_2>0$) and ferromagnetic ($U_2<0$) couplings,
respectively.",1204.1175v2
2012-05-18,Theory of L-edge resonant inelastic x-ray scattering for magnetic excitations in two-leg spin ladder,"We study the magnetic excitation spectra of Cu L_{2,3}-edge resonant
inelastic x-ray scattering (RIXS) from the spin-liquid ground state in two-leg
spin ladder cuprates. Applying the projection method developed by the present
authors, we have derived the formulas of the magnetic RIXS spectra, which are
expressed by one- and two-spin correlation functions in the polarization
changing and preserving channels, respectively. The one-spin correlation
function includes both one- and two-triplon excitations and they are picked up
separately by choosing rung wave vector -q_a=\pi and 0, respectively. An
application to Sr_{14}Cu_{24}O_{41} reveals that the calculated RIXS spectrum
captures well the dispersive behavior shown by the lower boundary of
two-triplon continuum. By adjusting the geometrical configuration of the
measurement, one-triplon dispersion around the zone center could be detectable
in the RIXS experiment. The observed weak intensity in the higher energy region
might be attributed to the two-spin correlation function, which could be
detected more clearly at the M_{3}-edge RIXS spectra.",1205.4069v1
2012-07-02,Is black-hole ringdown a memory of its progenitor?,"We have performed an extensive numerical study of coalescing black-hole
binaries to understand the gravitational-wave spectrum of quasi-normal modes
excited in the merged black hole. Remarkably, we find that the masses and spins
of the progenitor are clearly encoded in the mode spectrum of the ringdown
signal. Some of the mode amplitudes carry the signature of the binary's mass
ratio, while others depend critically on the spins. Simulations of precessing
binaries suggest that our results carry over to generic systems. Using Bayesian
inference, we demonstrate that it is possible to accurately measure the mass
ratio and a proper combination of spins even when the binary is itself
invisible to a detector. Using a mapping of the binary masses and spins to the
final black hole spin, allows us to further extract the spin components of the
progenitor. Our results could have tremendous implications for gravitational
astronomy by facilitating novel tests of general relativity using merging black
holes.",1207.0399v2
2012-10-27,Collective coupling of a macroscopic number of single-molecule magnets with a microwave cavity mode,"We report the observation of strong coupling of a macroscopic ensemble of
~10^{16} Fe_8 molecular nanomagnets to the resonant mode of a microwave cavity.
We use millimeter-wave spectroscopy to measure the splitting of the system's
resonant frequency induced by the coupling between the spins and the cavity
mode. The magnitude of this splitting is found to scale with Sqrt[N], where N
is the number of collectively coupled spins. We control N by changing the
system's temperature and, thereby, the populations of the relevant spin energy
levels. Strong coupling is observed for two distinct transitions between spin
energy states. Our results indicate that at low temperatures nearly all of the
spins in the sample couple with the cavity's resonant mode even though there is
substantial inhomogeneous broadening of the Fe8 spin resonances.",1210.7330v1
2012-11-06,Indirect exchange of magnetic impurities in zigzag graphene ribbon,"We use quantum Monte Carlo method to study the indirect coupling between two
magnetic impurities on the zigzag edge of graphene ribbon, with respect to the
chemical potential $\mu$. We find that the spin-spin correlation between two
adatoms located on the nearest sites in the zigzag edge are drastically
suppressed around the zero-energy. As we switch the system away from
half-filling, the antiferromagnetic correlation is first enhanced and then
decreased. If the two adatoms are adsorbed on the sites belonging to the same
sublattice, we find similar behavior of spin-spin correlation except for a
crossover from ferromagnetic to antiferromagentic correlation in the vicinity
of zero-energy. We also calculated the weight of different components of
d-electron wave function and local magnet moment for various values of
parameters, and all the results are consistent with those of spin-spin
correlation between two magnetic impurities.",1211.1199v1
2013-05-21,Supersolid states in a spin system-phase diagram and collective excitations,"Phases analogous to supersolids can be realized in spin systems. Here we
obtain the phase diagram of a frustrated dimer spin-1/2 system on a square
lattice and study the collective excitation spectra, focusing on the supersolid
state (SS). In the phase diagram on a parameter space of the exchange
interaction and magnetic field, we find, on top of the SS phase, a phase that
has no counterpart in the Bose Hubbard model and this state becomes dominant at
the region where the enhancement of SS occurs in the bose Hubbard model. We
then investigate the excitation spectrum and spin- spin correlation, which can
be detected by neutron scattering experiments. We obtain an analytic expression
for the spin wave velocity, which agrees with hydrodynamic relations. The
intensity of excitation modes in the spin-spin correlation function is
calculated and their change in the supersolid and superfluid states is
discussed.",1305.4758v1
2013-08-08,On the transformations generated by the electromagnetic spin and orbital angular momentum operators,"We present a study of the properties of the transversal ""spin angular
momentum"" and ""orbital angular momentum"" operators. We show that the ""spin
angular momentum"" operators are generators of spatial translations which depend
on helicity and frequency and that the ""orbital angular momentum"" operators
generate transformations which are a sequence of this kind of translations and
rotations. We give some examples of the use of these operators in light matter
interaction problems. Their relationship with the helicity operator allows to
involve the electromagnetic duality symmetry in the analysis. We also find that
simultaneous eigenstates of the three ""spin"" operators and parity define a type
of standing modes which has been recently singled out for the interaction of
light with chiral molecules. With respect to the relationship between ""spin
angular momentum"", polarization, and total angular momentum, we show that,
except for the case of a single plane wave, the total angular momentum of the
field is decoupled from its vectorial degrees of freedom even in the regime
where the paraxial approximation holds. Finally, we point out a relationship
between the three ""spin"" operators and the spatial part of the Pauli-Lubanski
four vector.",1308.1729v2
2013-08-26,Spin lock composite and shaped pulses for efficient and robust pumping of dark states in magnetic resonance,"Long-lived (symmetry protected) hyperpolarized spin states offer important
new opportunities (for example, in clinical MR imaging), but existing methods
for producing these states are limited by either excess energy dissipation or
high sensitivity to inhomogeneities. We extend recent work on continuous-wave
irradiation of nearly-equivalent spins (spin-lock induced crossing) by
designing composite pulse and adiabatic shaped-pulse excitations which overcome
the limitations. These composite and adiabatic pulses differ drastically from
the traditional solutions in two-level systems. We also show this works in
chemically equivalent spin pairs, which has the advantage of allowing for
polarization transfer from and to remote spins. The approach is broadly
applicable to systems where varying excitation strength induces an avoided
crossing to a dark state, and thus to many other spectroscopic regimes.",1308.5666v1
2013-08-30,First-principles study of spin-transfer torque in Co2MnSi/Al/Co2MnSi spin-valve,"The spin-transfer torque (STT) in Co2MnSi(CMS)/Al/Co2MnSi spin-valve system
with and without interfacial disorder is studied by a first-principles
noncollinear wave-function-matching method. It is shown that in the case of
clean interface the angular dependence of STT for CoCo/Al (the asymmetry
parameter Lambda approx. 4.5) is more skewed than that for MnSi/Al (Lambda
approx. 2.9), which suggests the clean CoCo/Al architecture is much more
efficient for the application on radio frequency oscillation. We also find that
even with interfacial disorder the spin-valve of half-metallic CMS still has a
relatively large parameter Lambda compared to that of conventional ferromagnet.
In addition, for clean interface the in-plane torkance of MnSi/Al is about
twice as large as that of CoCo/Al. However, as long as the degree of
interfacial disorder is sufficiently large, the CoCo/Al and MnSi/Al will show
approximately the same magnitude of in-plane torkance. Furthermore, our results
demonstrate that CMS/Al/CMS system has very high efficiency of STT to switch
the magnetic layer of spin-valve.",1308.6703v1
2013-10-04,In-plane spin excitation anisotropy in the paramagnetic phase of NaFeAs,"We use unpolarized and polarized inelastic neutron scattering to study
low-energy spin excitations in NaFeAs, which exhibits a
tetragonal-to-orthorhombic lattice distortion at $T_s\approx 58$ K followed by
a collinear antiferromagnetic (AF) order below $T_N\approx 45$ K. In the AF
ordered state ($T<T_N$), spin waves are entirely c-axis polarized below
$\sim$10 meV, exhibiting a gap of $\sim4$ meV at the AF zone center and
disperse to $\sim$7 meV near the c-axis AF zone boundary. On warming to the
paramagnetic state with orthorhombic lattice distortion ($T_N<T<T_s$), spin
excitations become anisotropic within the FeAs plane. Upon further warming to
the paramagnetic tetragonal state ($T>T_s$), spin excitations become more
isotropic. Since similar magnetic anisotropy is also observed in the
paramagnetic tetragonal phase of superconducting
BaFe$_{1.904}$Ni$_{0.096}$As$_2$, our results suggest that the spin excitation
anisotropy in superconducting iron pnictides originates from similar anisotropy
already present in their parent compounds.",1310.1143v1
2013-10-08,Unified Dynamics of Electrons and Photons via Zitterbewegung and Spin-Orbit Interaction,"We show that when an electron or photon propagates in a cylindrically
symmetric waveguide, it experiences both a zitterbewegung effect and a
spin-orbit interaction leading to identical propagation dynamics for both
particles. Applying a unified perturbative approach to both particles
simultaneously, we find that to first-order in perturbation theory their
Hamiltonians each contain identical Darwin (zitterbewegung) and spin-orbit
terms, resulting in the unification of their dynamics. The presence of the
zitterbewegung effect may be interpreted physically as the delocalization of
the electron on the scale of its Compton wavelength, or the delocalization of
the photon on the scale of its wavelength in the waveguide. The presence of the
spin-orbit interaction leads to the prediction of several rotational effects:
the spatial or time evolution of either particle's spin/polarization vector is
controlled by the sign of its orbital angular momentum quantum number, or
conversely, its spatial wave function is controlled by its spin angular
momentum.",1310.1995v1
2013-11-11,Spin relaxation in inhomogeneous quantum dot arrays studied by electron spin resonance,"Electron states in a inhomogeneous Ge/Si quantum dot array with groups of
closely spaced quantum dots were studied by conventional continuous wave ($cw$)
ESR and spin-echo methods. We find that the existence of quantum dot groups
allows to increase the spin relaxation time in the system. Created structures
allow us to change an effective localization radius of electrons by external
magnetic field. With the localization radius close to the size of a quantum dot
group, we obtain fourfold increasing spin relaxation time $T_1$, as compared to
conventional homogeneous quantum dot arrays. This effect is attributed to
averaging of local magnetic fields related to nuclear spins $^{29}$Si and
stabilization of $S_z$-polarization during electron back-and-forth motion
within a quantum dot group.",1311.2383v1
2013-12-01,Probing evolution of binaries influenced by the spin-orbit resonances,"We evolve isolated comparable mass spinning compact binaries experiencing
Schnittman's post-Newtonian spin-orbit resonances in an inertial frame
associated with $j_0$, the initial direction of the total angular momentum. We
argue that accurate gravitational wave (GW) measurements of the initial
orientations of the two spins and orbital angular momentum from $j_0$ should
allow us to distinguish between the two possible families of spin-orbit
resonances. Therefore, these measurements have the potential to provide direct
observational evidence of possible binary formation scenarios. The above
statements should also apply for binaries that do not remain in a resonant
plane when they become detectable by GW interferometers. The resonant plane,
characterized by the vanishing scalar triple product involving the two spins
and the orbital angular momentum, naturally appears in the one parameter family
of equilibrium solutions, discovered by Schnittman. We develop a prescription
to compute the time-domain inspiral templates for binaries residing in these
resonant configurations and explore their preliminary data analysis
consequences.",1312.0217v2
2013-12-11,Interpreting the Spin-down Evolutions of Isolated Neutron Stars with Hall Effects,"The observed long-term spin-down evolution of isolated radio pulsars cannot
be explained by the standard magnetic dipole radiation with a constant braking
torque. However, how and why the torque varies still remains controversial,
which is a major issue in understanding neutron stars. Many pulsars have been
observed with significant long-term changes of their spin-down rates modulated
by quasi-periodic oscillations. Applying the phenomenological model of pulsar
timing noise we developed recently to the observed precise pulsar timing data
of isolated neutron stars, here we show that the observed long-term evolutions
of their spin-down rates and quasi-periodic modulations can be explained by
Hall effects in their crusts. Therefore the evolution of their crustal magnetic
fields, rather than that in their cores, dominates the observed long term
spin-down evolution of these young pulsars. Understanding of the nature of
pulsar timing noise not only reveals the interior physics of neutron stars, but
also allows physical modeling of pulsar spin-down and thus improves the
sensitivity of gravitational wave detections with pulsars.",1312.3049v2
2014-05-21,Spin-orbit coupled Bose-Einstein condensates in a double well,"We study the quantum dynamics of a spin-orbit (SO) coupled Bose-Einstein
condensate (BEC) in a double-well potential inspired by the experimental
protocol recently developed by NIST group. We focus on the regime where the
number of atoms is very large and perform a two-mode approximation. An
analytical solution of the two-site Bose-Hubbard-like Hamiltonian is found for
several limiting cases, which range from a strong Raman coupling to a strong
Josephson coupling, ending with the complete model in the presence of weak
nonlinear interactions. Depending on the particular limit, different approaches
are chosen: a mapping onto an SU(2) spin problem together with a
Holstein-Primakoff transformation in the first two cases and a rotating wave
approximation (RWA) when dealing with the complete model. The quantum evolution
of the number difference of bosons with equal or different spin between the two
wells is investigated in a wide range of parameters; finally the corresponding
total atomic current and the spin current are computed. We show a spin
Josephson effect which could be detected in experiments and employed to build
up realistic devices.",1405.5356v1
2014-07-17,Photonic transport control by spin-optical disordered metasurface,"Photonic metasurfaces are ultrathin electromagnetic wave-molding
metamaterials providing the missing link for the integration of nanophotonic
chips with nanoelectronic circuits. An extra twist in this field originates
from spin-optical metasurfaces providing the photon spin (polarization
helicity) as an additional degree of freedom in light-matter interactions at
the nanoscale. Here we report on a generic concept to control the photonic
transport by disordered (random) metasurfaces with a custom-tailored geometric
phase. This approach combines the peculiarity of random patterns to support
extraordinary information capacity within the intrinsic limit of speckle noise,
and the optical spin control in the geometric phase mechanism, simply
implemented in two-dimensional structured matter. By manipulating the local
orientations of anisotropic optical nanoantennas, we observe spin-dependent
near-field and free-space open channels, generating state-of-the-art
multiplexing and interconnects. Spin-optical disordered metasurfaces provide a
route for multitask wavefront shaping via a single ultrathin nanoscale photonic
device.",1407.4708v1
2014-10-24,Memory effect from spinning unbound binaries,"We present a recently developed prescription to obtain ready-to-use
gravitational wave (GW) polarization states for spinning compact binaries on
hyperbolic orbits. We include leading order spin-orbit interactions, invoking
1.5PN-accurate quasi-Keplerian parametrization for the radial part of the
orbital dynamics. We also include radiation reaction effects on $h_+$ and
$h_{\times}$ during the interaction. In the GW signals from spinning binaries
there is evidence of the memory effect in both polarizations, in contrast to
the non-spinning case, where only the cross polarizations exhibits
non-vanishing amplitudes at infinite time. We also compute 1PN-accurate GW
polarization states for non-spinning compact binaries in unbound orbits in a
fully parametric way, and compare them with existing waveforms.",1410.6605v1
2014-11-06,Gapless chiral spin liquid in a kagome Heisenberg model,"Motivated by recent experiments on the Heisenberg S=1/2 quantum spin liquid
candidate material kapellasite, we classify all possible chiral (time-reversal
symmetry breaking) spin liquids with fermionic spinons on the kagome lattice.
We obtain the phase diagram for the physically relevant extended Heisenberg
model, comparing the energies of a wide range of microscopic variational wave
functions. We propose that, at low temperature, kapellasite exhibits a gapless
chiral spin liquid phase with spinon Fermi surfaces. This two-dimensional state
inherits many properties of the nearby one-dimensional phase of decoupled
anti-ferromagnetic spin chains, but also shows some remarkable differences. We
discuss the spin structure factors and other physical properties.",1411.1622v4
2014-12-05,Hidden-Beauty Charged Tetraquarks and Heavy Quark Spin Conservation,"Assuming the dominance of the spin-spin interaction in a diquark, we point
out that the mass difference in the beauty sector M(Z_b^prime) - M(Z_b) scales
with quark masses as expected in QCD, with respect to the corresponding mass
difference M(Z_c^prime) - M(Z_c). Notably, we show that the decays
Upsilon(10890) --> Upsilon(nS) pi pi and Upsilon(10890) --> (h_b(1P), h_b(2P))
pi pi are compatible with heavy-quark spin conservation if the contributions of
Z_b,Z_b^prime intermediate states are taken into account, Upsilon(10890) being
either a Upsilon(5S) or the beauty analog of Y_c(4260). Belle results on these
decays support the quark spin wave-function of the Z states as tetraquarks. We
also consider the role of light quark spin non-conservaton in Z_b,Z_b^prime
decays into B B^* and B^* B^*. Indications of possible signatures of the still
missing X_b resonance are proposed.",1412.2049v2
2015-02-13,Spin-current injection and detection in strongly correlated organic conductor,"Spin-current injection into an organic semiconductor
$\rm{\kappa\text{-}(BEDT\text{-}TTF)_2Cu[N(CN)_2]Br}$ film induced by the spin
pumping from an yttrium iron garnet (YIG) film. When magnetization dynamics in
the YIG film is excited by ferromagnetic or spin-wave resonance, a voltage
signal was found to appear in the
$\rm{\kappa\text{-}(BEDT\text{-}TTF)_2Cu[N(CN)_2]Br}$ film.
Magnetic-field-angle dependence measurements indicate that the voltage signal
is governed by the inverse spin Hall effect in
$\rm{\kappa\text{-}(BEDT\text{-}TTF)_2Cu[N(CN)_2]Br}$. We found that the
voltage signal in the $\rm{\kappa\text{-}(BEDT\text{-}TTF)_2Cu[N(CN)_2]Br}$/YIG
system is critically suppressed around 80 K, around which magnetic and/or glass
transitions occur, implying that the efficiency of the spin-current injection
is suppressed by fluctuations which critically enhanced near the transitions.",1502.05244v1
2015-05-08,Nonreciprocal magnon propagation in a noncentrosymmetric ferromagnet,"Relativistic spin-orbit interaction drastically modifies electronic band and
endows emergent functionalities. One of the example is the Rashba effect. In
noncentrosymmetric systems such as interface and polar materials, the
electronic band is spin-splitted depending on the momentum direction owing to
the spin-orbit interaction, which is useful for the electric manipulation of
spin current. Similar relativistic band-modification is also emergent for spin
wave (magnon) in magnetic materials. The asymmetric magnon band dispersion
induced by the Dzyaloshinskii-Moriya interaction, which is antisymmetric
exchange interaction originating from the spin-orbit interaction, is
theoretically expected, and experimentally observed recently in
noncentrosymmetric ferromagnets. Here, we demonstrate that the nonreciprocal
microwave response can be induced by the asymmetric magnon band in a
noncentrosymmetric ferrimagnet LiFe$_5$O$_8$. This result may pave a new path
to designing magnonic device based on the relativistic band engineering.",1505.01942v1
2015-05-23,Variational Monte Carlo study of gapless spin liquid in the spin-$1/2$ XXZ antiferromagnetic model on the kagome lattice,"By using the variational Monte Carlo technique, we study the spin-$1/2$ XXZ
antiferromagnetic model (with easy-plane anisotropy) on the kagome lattice. A
class of Gutzwiller projected fermionic states with a spin Jastrow factor is
considered to describe either spin liquids (with $U(1)$ or $Z_2$ symmetry) or
magnetically ordered phases (with ${\bf q}=(0,0)$ or ${\bf q}=(4\pi/3,0)$). We
find that the magnetic states are not stable in the thermodynamic limit.
Moreover, there is no energy gain to break the gauge symmetry from $U(1)$ to
$Z_2$ within the spin-liquid states, as previously found in the Heisenberg
model. The best variational wave function is therefore the $U(1)$ Dirac state,
supplemented by the spin Jastrow factor. Furthermore, a vanishing $S=2$ spin
gap is obtained at the variational level, in the whole regime from the $XY$ to
the Heisenberg model.",1505.06276v2
2015-06-10,Research on the recurrence relations for the spin-weighted spheroidal harmonics,"In this paper we study the recurrence relations in the spin-weighted
spheroidal harmonics (SWSHs) through super-symmetric quantum mechanics. We use
the shape invariance property to solve the spin-weighted spheroidal wave
equations. The result shows the relation among SWSHs with a special condition
of the same parameter magnetic quantum number m but different spin-weight s.
The conclusions can be reduced to the famous recurrence relations of
spin-weighted spherical harmonics. These contents are the first investigation
of this kind recurrence relation concerning SWSHs and make it possible to
derive SWSHs from the spheroidal harmonics, so they are very important both in
theoretical background and in the astrophysical applications. Keywords:
spin-weighted spheroidal harmonics, recurrence relation, super-symmetric
quantum mechanics, shape-invariance",1506.04008v2
2015-08-10,Mechanically induced two-qubit gates and maximally entangled states for single electron spins in a carbon nanotube,"We theoretically analyze a system where two electrons are trapped separately
in two quantum dots on a suspended carbon nanotube (CNT), subject to external
ac electric driving. An indirect mechanically-induced coupling of two distant
single electron spins is induced by the interaction between the spins and the
mechanical motion of the CNT. We show that a two-qubit iSWAP gate and arbitrary
single-qubit gates can be obtained from the intrinsic spin-orbit coupling.
Combining the iSWAP gate and single-qubit gates, maximally entangled states of
two spins can be generated in a single step by varying the frequency and the
strength of the external electric driving field. The spin-phonon coupling can
be turned off by electrostatically shifting the electron wave function on the
nanotube.",1508.02107v1
2015-09-01,Spin dynamics of antiferromagnetically coupled bilayers - the case of Cr_2TeO_6,"Understanding the dynamics of interacting quantum spins has been one of the
active areas of condensed matter physics research. Recently, extensive
inelastic neutron scattering measurements have been carried out in an
interesting class of systems, Cr_2(W, Te, Mo)O_6. These systems consist of
bilayers of Cr^{3+} spins (S=3/2) with strong antiferromagnetic inter-bilayer
coupling (J) and tuneable intra-bilayer coupling (j) from ferro (for W and Mo)
to antiferro (for Te). In the limit when J>|j|, the system reduces to weakly
interacting quantum spin-3/2 dimers. In this paper we discuss the
low-temperature magnetic properties of Cr_2TeO_6 systems where both intra-layer
and inter-layer exchange couplings are antiferromagnetic, i.e. J,j>0. Using
linear spin-wave theory we obtain the magnon dispersion, sublattice
magnetization, two-magnon density of states, and longitudinal spin-spin
correlation function.",1509.00101v3
2015-09-02,Noise and current correlations in tunnel junctions of Quantum Spin Hall edge states,"The edge channels of two-dimensional topological systems are protected from
elastic reflection and are noiseless at low temperature. Yet, noise and
cross-correlations can be induced when electron waves partly transmit to the
opposite edge via tunneling through a constriction. In particular, in a quantum
spin Hall (QSH) system tunnelling occurs via both spin-preserving ($p$) and
spin-flipping ($f$) processes, each fulfilling time-reversal symmetry. We
investigate the current correlations of a four-terminal QSH setup in the
presence of a tunneling region, both at equilibrium and out-of-equilibrium. We
find that, although $p$ and $f$ processes do not commute and the generic
current correlation depends on both, under appropriate conditions a direct
detection of two types of partition noise is possible. In particular, while the
spin-preserving partitioning can be probed for any arbitrary tunnel junction
with a specific configuration of terminal biases, the spin-flipping
partitioning can be directly detected only under suitably designed setups and
conditions. We describe two setups where these conditions can be fulfilled, and
both types of partitioning can be detected and controlled.",1509.00868v2
2015-10-01,The effect of tensor interaction in splitting the energy levels of relativistic systems,"In this paper we solve analytically Dirac equation for Eckart plus Hulthen
potentials with Coulomb-like and Yukawa-like tensor interaction in the presence
of Spin and Pseudo-spin Symmetry for any k number. The Parametric
Nikiforov-Uvarov method is used to obtain the energy Eigen-values and wave
functions. We also discuss the energy Eigen-values and the Dirac spinors for
the Eckart plus Hulthen potentials for the spin and pseudo-spin symmetry with
PNU method. To show the accuracy of the present model, some numerical results
are shown in both pseudo-spin and spin symmetry limits.",1510.01636v2
2015-10-29,Spin Correlations and Topological Entanglement Entropy in a Non-Abelian Spin-1 Spin Liquid,"We analyze the properties of a non-Abelian spin-1 chiral spin liquid state
proposed by Greiter and Thomale [PRL 102, 207203 (2009)] using variational
Monte Carlo. In this state the bosonic $\nu = 1$ Moore-Read Pfaffian wave
function is used to describe a gas of bosonic spin flips on a square lattice
with one flux quantum per plaquette. For toroidal geometries there is a
three-dimensional space of these states corresponding to the topological
degeneracy of the bosonic Moore-Read state on the torus. We show that spin
correlations for different states in this space become indistinguishable for
large system size. We also calculate the Renyi entanglement entropy for
different system partitions to extract the topological entanglement entropy and
provide evidence that the topological order of the lattice spin-liquid state is
the same as that of the continuum Moore-Read state from which it is
constructed.",1510.08817v2
2015-11-06,Classification and detection of symmetry fractionalization in chiral spin liquids,"In this work we study the crystal symmetry fractionalization in chiral spin
liquids with the chiral-semion topological order. We show that if such a chiral
spin liquid is realized in a two-dimensional lattice model with odd number of
spin-$\frac12$ per unit cell and the state preserves spin rotation symmetry and
translation symmetries, the semion excitation must carry both half-integer spin
and fractional crystal quantum numbers. As a result, only a unique symmetry
enriched topological phase can be realized in chiral spin liquids in a
spin-$\frac12$ kagome lattice model. These fractional symmetry quantum numbers
are confirmed numerically using ground state wave functions obtained with the
density matrix renormalization group method.",1511.02226v2
2015-12-01,Projective symmetry group classification of chiral spin liquids,"We present a general review of the projective symmetry group classification
of fermionic quantum spin liquids for lattice models of spin $S=1/2$. We then
introduce a systematic generalization of the approach for symmetric
$\mathbb{Z}_2$ quantum spin liquids to the one of chiral phases (i.e., singlet
states that break time reversal and lattice reflection, but conserve their
product). We apply this framework to classify and discuss possible chiral spin
liquids on triangular and kagome lattices. We give a detailed prescription on
how to construct quadratic spinon Hamiltonians and microscopic wave functions
for each representation class on these lattices. Among the chiral
$\mathbb{Z}_2$ states, we study the subset of U(1) phases variationally in the
antiferromagnetic $J_1$-$J_2$-$J_d$ Heisenberg model on the kagome lattice. We
discuss static spin structure factors and symmetry constraints on the bulk
spectra of these phases.",1512.00324v3
2016-01-20,Electronic spin-triplet nematic with a twist,"We analyze a model of itinerant electrons interacting through a quadrupole
density-density repulsion in three dimensions. At the mean field level, the
interaction drives a continuous Pomeranchuk instability towards $d$-wave,
spin-triplet nematic order, which simultaneously breaks the SU(2) spin-rotation
and spatial rotational symmetries. This order results in spin antisymmetric,
elliptical deformations of the Fermi surfaces of up and down spins. We show
that the effects of quantum fluctuations are similar to those in metallic
ferromagnets, rendering the nematic transition first-order at low temperatures.
Using the fermionic quantum order-by-disorder approach to self-consistently
calculate fluctuations around possible modulated states, we show that the
first-order transition is pre-empted by the formation of a nematic state that
is intertwined with a helical modulation in spin space. Such a state is closely
related to $d$-wave bond density wave order in square-lattice systems.
Moreover, we show that it may coexist with a modulated, $p$-wave
superconducting state.",1601.05414v2
2016-01-30,Quantum Melting of Magnetic Order in an Organic Dimer-Mott Insulating System,"Quantum entanglement effects between the electronic spin and charge degrees
of freedom are examined in an organic molecular solid, termed a dimer-Mott
insulating system, in which molecular dimers are arranged in a crystal as
fundamental units. A low energy effective model includes an antisymmetric
exchange interaction, as one of the dominant magnetic interactions. This
interaction favors a 90 degree spin configuration, and competes with the
Heisenberg-type exchange interaction. Stabilities of the magnetic ordered
phases are examined by using the spin-wave theory, as well as the
Schwinger-boson theory. It is found that the spin-charge interaction promotes
an instability of the long-range magnetic ordered state around a parameter
region where two spin-spiral phases are merged. Implication for the quantum
spin liquid state observed in $\kappa$-(BEDT-TTF)$_2$Cu$_2$(CN)$_3$ is
discussed.",1602.00103v1
2016-05-12,Fredkin Spin Chain,"We introduce a new model of interacting spin 1/2. It describes interaction of
three nearest neighbors. The Hamiltonian can be expressed in terms of Fredkin
gates. The Fredkin gate (also known as the CSWAP gate) is a computational
circuit suitable for reversible computing. Our construction generalizes the
work of Ramis Movassagh and Peter Shor.
  Our model can be solved by means of Catalan combinatorics in the form of
random walks on the upper half of a square lattice [Dyck walks]. Each Dyck path
can be mapped to a wave function of the spins. The ground state is an equally
weighted superposition of Dyck walks [instead of Motzkin walks]. We can also
express it as a matrix product state. We further construct the model of
interacting spins 3/2 and greater half-integer spins. The models with higher
spins require coloring of Dyck walks. We construct SU(k) symmetric model [here
k is the number of colors]. The leading term of the entanglement entropy is
then proportional to the square root of the length of the lattice [like in
Shor-Movassagh model]. The gap closes as a high power of the length of the
lattice.",1605.03842v1
2016-06-06,Magnetic field effects in a correlated electron system with spin-state degree of freedom - Implication of an excitonic insulator -,"Magnetic field (H) effects on a correlated electron system with the
spin-state degree of freedom are examined. The effective Hamiltonian derived
from the two-orbital Hubbard model is analyzed by the mean-field approximation.
Applying H to the low-spin (LS) phase induces the excitonic insulating phase,
as well as the spin-state ordered phase where the LS and high-spin (HS) states
are ordered alternately. In the case where H is applied to the HS phase, a
reentrant transition for the HS phase appears. A rich variety of the phase
diagrams are attributed to the spin-state degree of freedom and their
combinations in the wave function as well as in the real-space configuration.",1606.01681v1
2016-06-06,Spin Nernst Effect of Magnons in Collinear Antiferromagnets,"In a collinear antiferromagnet with easy-axis anisotropy, symmetry guarantees
that the spin wave modes are doubly degenerate. The two modes carry opposite
spin angular momentum and exhibit opposite chirality. Using a honeycomb
antiferromagnet in the presence of the Dzyaloshinskii-Moriya interaction, we
show that a longitudinal temperature gradient can drive the two modes to
opposite transverse directions, realizing a spin Nernst effect of magnons with
vanishing thermal Hall current. We find that magnons around the {\Gamma}-point
and the K-point contribute oppositely to the transverse spin transport, and
their competition leads to a sign change of the spin Nernst coefficient at
finite temperature. Possible material candidates are discussed.",1606.01952v3
2016-07-31,Spin resonance peak in Fe-based superconductors with unequal gaps,"We study the spin resonance in superconducting state of iron-based materials
within multiband models with two unequal gaps, $\Delta_L$ and $\Delta_S$, on
different Fermi surface pockets. We show that due to the indirect nature of the
gap entering the spin susceptibility at the nesting wave vector $\mathbf{Q}$
the total gap $\tilde\Delta$ in the bare susceptibility is determined by the
sum of gaps on two different Fermi surface sheets connected by $\mathbf{Q}$.
For the Fermi surface geometry characteristic to the most of iron pnictides and
chalcogenides, the indirect gap is either $\tilde\Delta = \Delta_L + \Delta_S$
or $\tilde\Delta = 2\Delta_L$. In the $s_{++}$ state, spin excitations below
$\tilde\Delta$ are absent unless additional scattering mechanisms are assumed.
The spin resonance appears in the $s_\pm$ superconducting state at frequency
$\omega_R \leq \tilde\Delta$. Comparison with available inelastic neutron
scattering data confirms that what is seen is the true spin resonance and not a
peak inherent to the $s_{++}$ state.",1608.00245v2
2016-08-16,Exchange anisotropy as mechanism for spin-stripe formation in frustrated spin chains,"We investigate the spin-stripe mechanism responsible for the peculiar
nanometer modulation of the incommensurate magnetic order that emerges between
the vector-chiral and the spin-density-wave phase in the frustrated zigzag
spin-1/2 chain compound $\beta$-TeVO$_4$. A combination of magnetic-torque,
neutron-diffraction and spherical-neutron-polarimetry measurements is employed
to determine the complex magnetic structures of all three ordered phases. Based
on these results, we develop a simple phenomenological model, which exposes the
exchange anisotropy as the key ingredient for the spin-stripe formation in
frustrated spin systems.",1608.04495v2
2017-09-24,Coherent Manipulation of Spin Correlations in the Hubbard Model,"We coherently manipulate spin correlations in a two-component atomic Fermi
gas loaded into an optical lattice using spatially and time-resolved Ramsey
spectroscopy combined with high-resolution \textit{in situ} imaging. This novel
technique allows us not only to imprint spin patterns but also to probe the
static magnetic structure factor at arbitrary wave vector, in particular the
staggered structure factor. From a measurement along the diagonal of the
$1^\mathrm{st}$ Brillouin zone of the optical lattice, we determine the
magnetic correlation length and the individual spatial spin correlators. At
half filling, the staggered magnetic structure factor serves as a sensitive
thermometer for the spin temperature, which we employ to study the
thermalization of spin and density degrees of freedom during a slow quench of
the lattice depth.",1709.08231v1
2017-12-07,Fibonacci sequence and its generalizations in doped quantum spin ladders,"An interesting aspect of antiferromagnetic quantum spin ladders, with
complete dimer coverings, is that the wave function can be recursively
generated by estimating the number of coverings in the valence bond basis,
which follow the fabled Fibonacci sequence. In this work, we derive generalized
forms of this sequence for multi-legged and doped quantum spin ladders, which
allow the corresponding dimer-covered state to be recursively generated. We
show that these sequences allow for estimation of physically and
information-theoretically relevant quantities in large spin lattices without
resorting to complex numerical methods. We apply the formalism to calculate the
valence bond entanglement entropy, which is an important figure of merit for
studying cooperative phenomena in quantum spin systems with SU(2) symmetry. We
show that introduction of doping may mitigate, within the quarters of
entanglement entropy, the dichotomy between odd- and even- legged quantum spin
ladders.",1712.02726v3
2017-12-07,Orphan spins and bound in-gap states in the $S={5\over2}$ antiferromagnet CaFe$_{2}$O$_{4}$,"CaFe$_{2}$O$_{4}$ is an anisotropic $S={5\over 2}$ antiferromagnet with two
competing $A$ ($\uparrow \uparrow \downarrow \downarrow$) and $B$ ($\uparrow
\downarrow \uparrow \downarrow$) magnetic order parameters separated by static
antiphase boundaries at low temperatures. Neutron diffraction and bulk
susceptibility measurements, show that the spins near these boundaries are
weakly correlated and a carry an uncompensated ferromagnetic moment that can be
tuned with a magnetic field. Spectroscopic measurements find these spins are
bound with excitation energies less than the bulk magnetic spin-waves and
resemble the spectra from isolated spin-clusters. Localized bound orphaned
spins separate the two competing magnetic order parameters in
CaFe$_{2}$O$_{4}$.",1712.02853v1
2018-03-07,Four-Photon Kapitza-Dirac Effect as Electron Spin Filter,"We theoretically demonstrate the feasibility of producing electron beam
splitter using Kapitza-Dirac diffraction on bichromatic standing waves which
are created by the fundamental frequency and the third harmonic. The
relativistic electron in Bragg regime absorbs three photons with frequency of w
and emits a photon with frequency of 3w, four-photon Kapitza-Dirac effect. In
this four-photon Kapitza-Dirac effect distinct spin effects arise in different
polarizations of the third harmonic laser beam. It is shown that the shape of
Rabi oscillation between initial and scattered states is changed and finds two
unequal peaks. In circular polarization for fundamental and third harmonic,
despite Rabi oscillation, the spin down electron in 0.56 fs intervals maintains
its momentum and spin. Also we present an electron spin filter with combination
of a linearly polarized fundamental laser beam and a third harmonic with
circular polarization that scatters the electron beam according to its spin
state.",1803.02748v1
2018-06-06,Excitation of magnon spin photocurrents in antiferromagnetic insulators,"In the circular photogalvanic effect, circularly polarized light can produce
a direct electron photocurrent in metals and the direction of the current
depends on the polarization. We suggest that an analogous nonlinear effect
exists for antiferromagnetic insulators wherein the total spin of light and
spin waves is conserved. In consequence, a spin angular momentum is expected to
be transfered from photons to magnons so that a circularly polarized
electromagnetic field will generate a direct magnon spin current. The direction
of the current is determined by the helicity of the light. We show that this
resonant effect appears as a second order light-matter interaction. We find
also a geometric contribution to the spin photocurrent, which appears for
materials with complex lattice structures and Dzyaloshinskii-Moriya
interactions.",1806.02442v2
2018-06-13,Nature of the spin liquid in underdoped cuprate superconductors,"In the present work we address a long standing problem of the magnetic ground
state and magnetic excitations in underdoped cuprates. Modelling cuprates by
the extended $t-J$ model we show that there is a hidden dimensionless parameter
$\lambda$ which drives magnetic criticality at low doping $x$. Hence we derive
the zero temperature $\lambda-x$ phase diagram of the model. It is argued that
all underdoped cuprates are close to the quantum tricritical point $x=0$,
$\lambda=1$. The three phases ""meet"" at the tricritical point: (i) N\'eel
antiferromagnet, (ii) spin spiral with antinodal direction of the spiral wave
vector, (iii) algebraic spin liquid. We argue that underdoped cuprates belong
either to the spin liquid phase or they are on the borderline between the spin
liquid and the spin spiral. We calculate the energy position $E_{cross}$ of the
inelastic neutron scattering response maximum at ${\bm q}=(\pi,\pi)$ and
compare our results with experiments. We also explain softening of magnons in
the intermediate regime observed in inelastic neutron scattering.",1806.04855v1
2018-06-28,Electrical control of the Zeeman spin splitting in two-dimensional hole systems,"Semiconductor holes with strong spin-orbit coupling allow all-electrical spin
control, with broad applications ranging from spintronics to quantum
computation. Using a two-dimensional hole system in a GaAs quantum well, we
demonstrate a new mechanism of electrically controlling the Zeeman splitting,
which is achieved through altering the hole wave vector $k$. We find a
threefold enhancement of the in-plane $g-$factor $g_{\parallel}(k)$. We
introduce a new method for quantifying the Zeeman splitting from
magnetoresistance measurements, since the conventional tilted field approach
fails for two-dimensional systems with strong spin-orbit coupling. Finally, we
show that the Rashba spin-orbit interaction suppresses the in-plane Zeeman
interaction at low magnetic fields. The ability to control the Zeeman splitting
with electric fields opens up new possibilities for future quantum spin-based
devices, manipulating non-Abelian geometric phases, and realising Majorana
systems in $p-$type superconductor systems.",1806.10817v1
2018-07-13,Spinor self-ordering of a quantum gas in a cavity,"We observe the joint spin-spatial (spinor) self-organization of a
two-component BEC strongly coupled to an optical cavity. This unusual
nonequilibrium Hepp-Lieb-Dicke phase transition is driven by an off-resonant
two-photon Raman transition formed from a classical pump field and the emergent
quantum dynamical cavity field. This mediates a spinor-spinor interaction that,
above a critical strength, simultaneously organizes opposite spinor states of
the BEC on opposite checkerboard configurations of an emergent 2D lattice. The
resulting spinor density-wave polariton condensate is observed by directly
detecting the atomic spin and momentum state and by holographically
reconstructing the phase of the emitted cavity field. The latter provides a
direct measure of the spin state, and a spin-spatial domain wall is observed.
The photon-mediated spin interactions demonstrated here may be engineered to
create dynamical gauge fields and quantum spin glasses.",1807.04915v1
2018-10-02,Dynamical structure factor in the non-Abelian phase of the Kitaev honeycomb model in the presence of quenched disorder,"Kitaev's model of spins interacting on a honeycomb lattice describes a
quantum spin-liquid, where an emergent static $\mathbb{Z}_2$ gauge field is
coupled to Majorana fermions. In the presence of an external magnetic field and
for a range of interaction strengths, the system behaves as a gapped,
non-Abelian quantum spin-liquid. In this phase, the vortex excitations of the
emergent $\mathbb{Z}_2$ gauge field have Majorana zero modes bound to them.
Motivated by recent experimental progress in measuring and characterizing real
materials that could exhibit spin-liquid behavior, we analytically calculate
the dynamical spin structure factor in the non-Abelian phase of the Kitaev's
honeycomb model. In particular, we treat the case of quenched disorder in the
vortex configurations. Our calculations reveal a peak in the low-energy
dynamical structure factor that is a signature of the spin-liquid behavior. We
map the effective Hamiltonian to that of a chiral p-wave superconductor by
using the Jordan-Wigner transformation. Subsequently, we analytically calculate
the wave functions of the Majorana zero modes, the energy splitting for finite
separation of the vortices and finally, the dynamical structure factor in
presence of quenched disorder.",1810.01426v1
2018-10-09,Diagnosing phases of magnetic insulators via noise magnetometry with spin qubits,"Two-dimensional magnetic insulators exhibit a plethora of competing ground
states, such as ordered (anti)ferromagnets, exotic quantum spin liquid states
with topological order and anyonic excitations, and random singlet phases
emerging in highly disordered frustrated magnets. Here we show how single spin
qubits, which interact directly with the low-energy excitations of magnetic
insulators, can be used as a diagnostic of magnetic ground states.
Experimentally tunable parameters, such as qubit level splitting, sample
temperature, and qubit-sample distance, can be used to measure spin
correlations with energy and wavevector resolution. Such resolution can be
exploited, for instance, to distinguish between fractionalized excitations in
spin liquids and spin waves in magnetically ordered states, or to detect
anyonic statistics in gapped systems.",1810.04183v2
2018-02-28,Beliaev Damping in Spin-$\frac{1}{2}$ Interacting Bosons with Spin-Orbit Coupling,"Beliaev damping provides one of the most important mechanisms for dissipation
of quasiparticles through beyond-mean-field effects at zero temperature. Here
we present the first analytical result of Beliaev damping in low-energy
excitations of spin-$\frac{1}{2}$ interacting bosons with equal Rashba and
Dresslhaus spin-orbit couplings. We identify novel features of Beliaev decay
rate due to spin-orbit coupling, in particular, it shows explicit dependence on
the spin-density interaction and diverges at the interaction-modified phase
boundary between the zero-momentum and plane-wave phases. This represents a
manifestation of the effect of spin-orbit coupling in the beyond-mean-field
regime, which by breaking Galilean invariance couples excitations in the
density- and spin-channels. By describing the Beliaev damping in terms of the
observable dynamic structure factors, our results allow direct experimental
access within current facilities.",1802.10295v1
2019-02-05,Orbital-to-Spin Angular Momentum Conversion Employing Local Helicity,"Spin-orbit interactions in optics traditionally describe an influence of the
polarization degree of freedom of light on its spatial properties. The most
prominent example is the generation of a spin-dependent optical vortex upon
focusing or scattering of a circularly polarized plane-wave by a nanoparticle,
converting spin to orbital angular momentum of light. Here, we present a
mechanism of conversion of orbital-to-spin angular momentum of light upon
scattering of a linearly polarized vortex beam by a spherical silicon
nanoparticle. We show that focused linearly polarized Laguerre-Gaussian beams
of first order ($\ell = \pm 1$) exhibit an $\ell$-dependent spatial
distribution of helicity density in the focal volume. By using a dipolar
scatterer the helicity density can be manipulated locally, while influencing
globally the spin and orbital angular momentum of the beam. Specifically, the
scattered light can be purely circularly polarized with the handedness
depending on the orbital angular momentum of the incident beam. We corroborate
our findings with theoretical calculations and an experimental demonstration.
Our work sheds new light on the global and local properties of helicity
conservation laws in electromagnetism.",1902.01756v1
2019-02-20,All-electron density functional calculations for electron and nuclear spin interactions in molecules and solids,"The interaction between electronic and nuclear spins in the presence of
external magnetic fields can be described by a spin Hamiltonian, with
parameters obtained from first principles, electronic structure calculations.
We describe an approach to compute these parameters, applicable to both
molecules and solids, which is based on Density Functional Theory (DFT) and
real-space, all-electron calculations using finite elements (FE). We report
results for hyperfine tensors, zero field splitting tensors (spin-spin
component) and nuclear quadrupole tensors of a series of molecules and of the
nitrogen-vacancy center in diamond. We compare our results with those of
calculations using Gaussian orbitals and plane-wave basis sets, and we discuss
their numerical accuracy. We show that calculations based on FE can be
systematically converged with respect to the basis set, thus allowing one to
establish reference values for the spin Hamiltonian parameters, at a given
level of DFT.",1902.07377v2
2019-02-20,Green's function method for the spin and pseudospin symmetries in the single-particle resonant states,"We investigate the spin and pseudospin symmetry in the single-particle
resonant states by solving the Dirac equation containing a Woods-Saxon
potential with Green's function method. Taking double-magic nucleus $^{208}$Pb
as an example, three spin doublets $3d$, $2h$, and $1j$ and three pseudospin
doublets $3\tilde{p}$, $1\tilde{i}$, and $1\tilde{j}$ are obtained for the
single-neutron resonant states. By analyzing the energy splittings, we find
that the threshold effect plays an important role in resonant pseudospin
doubles. Besides, there is a reversed level structure of pseudospin doublets in
the continuum. Differently, all the width splittings of either the spin
doublets or the pseudospin doublets are systematically positive and the
splittings are very small except $1\tilde{j}$ doublet. Further studies show
that the splittings of the energies and widths for the resonant (pseudo)spin
doublets are independent. Besides, the similarity properties of the wave
functions of the spin and pseudospin doublets still maintain well in resonant
states.",1902.07442v1
2019-02-25,Topological spin Hall effects and tunable skyrmion Hall effects in uniaxial antiferromagnetic insulators,"Recent advances in the physics of current-driven antiferromagnetic skyrmions
have observed the absence of a Magnus force. We outline the symmetry reasons
for this phenomenon, and show that this cancellation will fail in the case of
spin polarized currents. Pairing micromagnetic simulations with semiclassical
spin wave transport theory, we demonstrate that skyrmions produce a
spin-polarized transverse magnon current, and that spin-polarized magnon
currents can in turn produce transverse motion of antiferromagnetic skyrmions.
We examine qualitative differences in the frequency dependence of the skyrmion
Hall angle between ferromagnetic and antiferromagnetic cases, and close by
proposing a simple skyrmion-based magnonic device for demultiplexing of spin
channels.",1902.09382v2
2019-02-25,Tilted Disks around Black Holes: A Numerical Parameter Survey for Spin and Inclination Angle,"We conduct a systematic study of the properties of tilted accretion flows
around spinning black holes, covering a range of tilt angles and black hole
spins, using the general-relativistic magnetohydrodynamics code Athena++. The
same initial magnetized torus is evolved around black holes with spins ranging
from 0 to 0.9, with inclinations ranging from 0 degrees to 24 degrees. The
tilted disks quickly reach a warped and twisted shape that rigidly precesses
about the black hole spin axis with deformations in shape large enough to
hinder the application of linear bending wave theory. Magnetized polar outflows
form, oriented along the disk rotation axes. At sufficiently high inclinations
a pair of standing shocks develops in the disks. These shocks dramatically
affect the flow at small radii, driving angular momentum transport. At high
spins they redirect material more effectively than they heat it, reducing the
dissipation rate relative to the mass accretion rate and lowering the radiative
efficiency of the flow.",1902.09662v1
2019-02-28,Neutrino spin oscillations in external fields in curved spacetime,"We study spin oscillations of massive Dirac neutrinos in background matter,
electromagnetic and gravitational fields. First, using the Dirac equation for a
neutrino interacting with the external fields in curved spacetime, we rederive
the quasiclassical equation for the neutrino spin evolution, which was proposed
previously basing on principles of the general covariance. Then, we apply this
result for the description of neutrino spin oscillations in nonmoving and
unpolarized matter under the influence of a constant transverse magnetic field
and a gravitational wave. We derive the effective Schr\""odinger equation for
neutrino oscillations in these external fields and solve it numerically.
Choosing realistic parameters of external fields, we show that the parametric
resonance can take place in spin oscillations of low energy neutrinos. Some
astrophysical applications are briefly discussed.",1902.11285v2
2019-06-05,Noncollinear Antiferromagnetic Order and Effect of Spin-Orbit Coupling in Spin-1 Honeycomb Lattice,"Motivated by the recently synthesized insulating nickelate Ni$_2$Mo$_3$O$_8$,
which has been reported to have an unusual non-collinear magnetic order of
Ni$^{2+}$ $S=1$ moments with a nontrivial angle between adjacent spins, we
construct an effective spin-1 model on the honeycomb lattice, with the exchange
parameters determined with the help of first principles electronic structure
calculations. The resulting bilinear-biquadratic model, supplemented with the
realistic crystal-field induced anisotropy, favors the collinear N\'eel state.
We find that the crucial key to explaining the observed noncollinear spin
structure is the inclusion of the Dzyaloshinskii--Moriya (DM) interaction
between the neighboring spins. By performing the variational mean-field and
linear spin-wave theory (LSWT) calculations, we determine that a realistic
value of the DM interaction $D\approx 2.78$ meV is sufficient to quantitatively
explain the observed angle between the neighboring spins. We furthermore
compute the spectrum of magnetic excitations within the LSWT and random-phase
approximation (RPA) which should be compared to future inelastic neutron
measurements.",1906.02215v3
2020-04-06,Transverse spinning of unpolarized light,"It is well known that spin angular momentum of light, and therefore that of
photons, is directly related to their circular polarization. Naturally, for
totally unpolarized light, polarization is undefined and the spin vanishes.
However, for nonparaxial light, the recently discovered transverse spin
component, orthogonal to the main propagation direction, is largely independent
of the polarization state of the wave. Here we demonstrate, both theoretically
and experimentally, that this transverse spin survives even in nonparaxial
fields (e.g., tightly focused or evanescent) generated from a totally
unpolarized light source. This counterintuitive phenomenon is closely related
to the fundamental difference between the degrees of polarization for 2D
paraxial and 3D nonparaxial fields. Our results open an avenue for studies of
spin-related phenomena and optical manipulation using unpolarized light.",2004.02970v1
2020-04-08,Charge-to-spin conversion efficiency in ferromagnetic nanowires by spin torque ferromagnetic resonance: Reconciling lineshape and linewidth analysis methods,"Spin orbit torques are of great interest for switching the magnetization
direction in nanostructures, moving skyrmions and exciting spin waves. The
standard method of determining their efficiency is by spin torque ferromagnetic
resonance (ST-FMR), a technique that involves analyzing the resonance linewidth
or lineshape. On microstuctures these two analysis methods are quite
consistent. Here we present ST-FMR results on permalloy (Ni$_{80}$Fe$_{20}$)
nanowires -- with widths varying from $150$ to 800 nm -- that show that the
standard model used to analyze the resonance linewidth and lineshape give
different results; the efficiency appears greatly enhanced in nanowires when
the lineshape method is used. A ST-FMR model that properly accounts for the
sample shape is presented and shows much better consistency between the two
methods. Micromagnetic simulations are used to verify the model. These results
and the more accurate nanowire model presented are of importance for
characterizing and optimizing charge-to-spin conversion efficiencies in
nanostructures.",2004.03784v1
2017-02-03,Spin qubit manipulation of acceptor bound states in group IV quantum wells,"The large spin-orbit coupling in the valence band of group IV semiconductors
provides an electric field knob for spin-qubit manipulation. This fact can be
exploited with acceptor based qubits. Spin manipulation of holes bound to
acceptors in engineered SiGe quantum wells depends very strongly on the
electric field applied and on the heterostructure parameters. The g-factor is
enhanced by the Ge content and can be tuned by shifting the hole wave-function
between the heterostructure constituent layers. The lack of inversion symmetry
induced both by the quantum well and the electric fields together with the
g-factor tunability allows the possibility of different qubit manipulation
methods such as electron spin resonance, electric dipole spin resonance and
g-tensor modulation resonance. Rabi frequencies up to hundreds of MHz can be
achieved with heavy-hole qubits, and of the order of GHz with light-hole
qubits.",1702.00960v1
2017-02-27,Frustrated Magnetism of Dipolar Molecules on a Square Optical Lattice: Prediction of a Quantum Paramagnetic Ground State,"Motivated by the experimental realization of quantum spin models of polar
molecule KRb in optical lattices, we analyze the spin 1/2 dipolar Heisenberg
model with competing anisotropic, long-range exchange interactions. We show
that, by tilting the orientation of dipoles using an external electric field,
the dipolar spin system on square lattice comes close to a maximally frustrated
region similar, but not identical, to that of the $J_1$-$J_2$ model. This
provides a simple yet powerful route to potentially realize a quantum spin
liquid without the need for a triangular or kagome lattice. The ground state
phase diagrams obtained from Schwinger-boson and spin-wave theories
consistently show a spin disordered region between the N$\acute{\textrm{e}}$el,
stripe, and spiral phase. The existence of a finite quantum paramagnetic region
is further confirmed by an unbiased variational ansatz based on tensor network
states and a tensor renormalization group.",1702.08517v3
2017-02-28,Spinning Witten Diagrams,"We develop a systematic framework to compute the conformal partial wave
expansions (CPWEs) of tree-level four-point Witten diagrams with totally
symmetric external fields of arbitrary mass and integer spin in AdS$_{d+1}$.
Employing this framework, we determine the CPWE of a generic exchange Witten
diagram with spinning exchanged field. As an intermediate step, we diagonalise
the linear map between spinning three-point conformal structures and spinning
cubic couplings in AdS. As a concrete application, we compute all exchange
diagrams in the type A higher-spin gauge theory on AdS$_{d+1}$, which is
conjectured to be dual to the free scalar $O\left(N\right)$ model. Given a
CFT$_d$, our results provide the complete holographic reconstruction of all
cubic couplings involving totally symmetric fields in the putative dual theory
on AdS$_{d+1}$.",1702.08619v2
2017-02-28,Superconducting spin valves controlled by spiral re-orientation in B20-family magnets,"We propose a superconducting spin-triplet valve, which consists of a
superconductor and an itinerant magnetic material, with the magnet showing an
intrinsic non-collinear order characterized by a wave vector that may be
aligned in a few equivalent preferred directions under control of a weak
external magnetic field. Re-orienting the spiral direction allows one to
controllably modify long-range spin-triplet superconducting correlations,
leading to spin-valve switching behavior. Our results indicate that the
spin-valve effect may be noticeable. This bilayer may be used as a magnetic
memory element for cryogenic nanoelectronics. It has the following advantages
in comparison to superconducting spin valves proposed previously: (i) it
contains only one magnetic layer, which may be more easily fabricated and
controlled, (ii) its ground states are separated by a potential barrier, which
solves the ""half-select"" problem of the addressed switch of memory elements.",1702.08828v2
2017-06-01,Spin-density fluctuations and the fluctuation-dissipation theorem in 3d ferromagnetic metals,"Spatial and time scales of spin density fluctuations (SDF) were analyzed in
3d ferromagnets using ab initio linear response calculations of complete
wavevector and energy dependence of the dynamic spin susceptibility tensor. We
demonstrate that SDF are spread continuously over the entire Brillouin zone and
while majority of them reside within the 3d bandwidth, a significant amount
comes from much higher energies. A validity of the adiabatic approximation in
spin dynamics is discussed. The SDF spectrum is shown to have two main
constituents: a minor low-energy spin wave contribution and a much larger
high-energy component from more localized excitations. Using the
fluctuation-dissipation theorem (FDT), the on-site spin correlator (SC) and the
related effective fluctuating moment were properly evaluated and their
universal dependence on the 3d band population is further discussed.",1706.00512v2
2018-04-05,Spin dynamics of the block orbital-selective Mott phase,"Iron-based superconductors display a variety of magnetic phases originating
in the competition between electronic, orbital, and spin degrees of freedom.
Previous theoretical investigations of the multi-orbital Hubbard model in one
dimension revealed the existence of an orbital-selective Mott phase (OSMP) with
block spin order. Recent inelastic neutron scattering (INS) experiments on the
BaFe$_2$Se$_3$ ladder compound confirmed the relevance of the block-OSMP.
Moreover, the powder INS spectrum reveled an unexpected structure, containing
both low-energy acoustic and high-energy optical modes. Here we present the
theoretical prediction for the dynamical spin structure factor within a
block-OSMP regime using the density-matrix renormalization group method. In
agreement with experiments we find two dominant features: low-energy dispersive
and high-energy dispersionless modes. We argue that the former represents the
spin-wave-like dynamics of the block ferromagnetic islands, while the latter is
attributed to a novel type of local on-site spin excitations controlled by the
Hund coupling.",1804.01959v2
2018-04-13,Finite-temperature properties of the extended Heisenberg model on a triangular lattice,"We present numerical results for the $J_1$-$J_2$ Heisenberg model on a
triangular lattice at finite temperatures $T>0$. In contrast to unfrustrated
lattices we reach much lower $T \sim 0.15 J_1$. In static quantities the novel
feature is a quite sharp low-$T$ maximum in the specific heat. Dynamical spin
structure factor $S({\bf q},\omega)$ allows for the extraction of the effective
spin-wave energies $\omega_{\bf q}(T)$ and their damping $\gamma_{\bf q}(T)$.
While for $J_2=0$ our results are consistent with $T=0$ spin ordering, $J_2/J_1
\sim 0.1 $ induces additional frustration with a signature of spin liquid
ground state. In the latter case, results for spin-lattice relaxation rate
indicate in the low-$T$ accesible regime on $1/T_1 \propto T^{\alpha}$ with
$\alpha \geq 1$, as observed in recent spin-liquid materials on a triangular
lattice.",1804.04819v1
2019-03-06,Honeycomb rare-earth magnets with anisotropic exchange interactions,"We study the rare-earth magnets on a honeycomb lattice, and are particularly
interested in the experimental consequences of the highly anisotropic spin
interaction due to the spin-orbit entanglement. We perform a high-temperature
series expansion using a generic nearest-neighbor Hamiltonian with anisotropic
interactions, and obtain the heat capacity, the parallel and perpendicular spin
susceptibilities, and the magnetic torque coefficients. We further examine the
electron spin resonance linewidth as an important signature of the anisotropic
spin interactions. Due to the small interaction energy scale of the rare-earth
moments, it is experimentally feasible to realize the strong-field regime.
Therefore, we perform the spin-wave analysis and study the possibility of
topological magnons when a strong field is applied to the system. The
application and relevance to the rare-earth Kitaev materials are discussed.",1903.02530v3
2019-03-25,Effect of disorder on the collective excitations of the chiral spin soliton lattice,"We assess the impact of magnetic disorder on the spin excitation spectra of
the chiral helimagnetic crystal $\mathrm{CrNb_3S_6}$ using microwave resonance
spectroscopy. The chiral spin soliton lattice phase (CSL), which is a prototype
of a noncollinear spin system that forms periodically over a macroscopic length
scale, exhibited three resonance modes over a wide frequency range. We found
that the predominance of these modes depended on the degree of magnetic
disorder and that disorder can be suppressed by sweeping the external field via
an ideal helical state at 0~T. The macroscopic coherence of the CSL can be
clearly observed through its collective dynamic behavior. Our study suggests
that magnetic disorder can be used as a mechanism to control spin wave
excitation in noncollinear spin systems.",1903.10129v1
2020-03-25,Gravitational spin-orbit coupling through third-subleading post-Newtonian order: from first-order self-force to arbitrary mass ratios,"Exploiting simple yet remarkable properties of relativistic gravitational
scattering, we use first-order self-force (linear-in-mass-ratio) results to
obtain arbitrary-mass-ratio results for the complete third-subleading
post-Newtonian (4.5PN) corrections to the spin-orbit sector of spinning-binary
conservative dynamics, for generic (bound or unbound) orbits and spin
orientations. We thereby improve important ingredients of models of
gravitational waves from spinning binaries, and we demonstrate the improvement
in accuracy by comparing against aligned-spin numerical simulations of binary
black holes.",2003.11391v2
2020-03-27,Spectral characteristics of the antiferromagnetic spin-1/2 Heisenberg model on the square lattice in a magnetic field,"We predict that spin-waves in an ordered square quantum antiferromagnet in a
transverse magnetic field (h) may demonstrate three modes of spin excitations.
Starting from the self-consistent rotation-invariant Green's function method, a
new mean-field theory is constructed for h not equal to 0. The method preserves
the translational and the axial symmetries, and provides exact fulfillment of
the single-site constraint for each of the three modes. We examine the
dynamical structure factors S(aa)(k,w), a= x, y, z. It is shown, that the
introduction of h leads to the hybridization of two degenerate spin modes due
to the appearance of a nondiagonal on a, b spin-spin Green's functions. The
comparison of the theory with the exact diagonalization study and with results
on inelastic neutron scattering experiments is discussed at T = 0. We discuss
also the correspondence of the theory to the existing theories, which allow
only two spin excitations modes for the total S(k,w).",2003.12387v1
2020-09-30,Dynamical properties of a driven dissipative dimerized $S = 1/2$ chain,"We consider the dynamical properties of a gapped quantum spin system coupled
to the electric field of a laser, which drives the resonant excitation of
specific phonon modes that modulate the magnetic interactions. We deduce the
quantum master equations governing the time-evolution of both the lattice and
spin sectors, by developing a Lindblad formalism with bath operators providing
an explicit description of their respective phonon-mediated damping terms. We
investigate the nonequilibrium steady states (NESS) of the spin system
established by a continuous driving, delineating parameter regimes in driving
frequency, damping, and spin-phonon coupling for the establishment of
physically meaningful NESS and their related non-trivial properties. Focusing
on the regime of generic weak spin-phonon coupling, we characterize the NESS by
their frequency and wave-vector content, explore their transient and relaxation
behavior, and discuss the energy flow, the system temperature, and the critical
role of the type of bath adopted. Our study lays a foundation for the
quantitative modelling of experiments currently being designed to control
coherent many-body spin states in quantum magnetic materials.",2009.14805v2
2020-11-24,Optical isolation induced by subwavelength spinning particle via spin-orbit interaction,"Optical isolation enables nonreciprocal manipulations of light with broad
applications in optical communications. Optical isolation by rotating
structures has drawn considerable attention due to its magnetic-free nature and
unprecedented performance. Conventional rotation-based optical isolation relies
on the use of bulky cavities hindering applications in subwavelength photonics.
Here, we propose a novel mechanism of optical isolation by integrating the
unique dispersion of a hyperbolic metamaterial with the transverse spin-orbit
interaction of evanescent waves. We show that rotation of a subwavelength
hyperbolic nanoparticle breaks the time-reversal symmetry and yields two
resonant chiral modes that selectively couple to the transverse spin of
waveguide modes. Remarkably, the transverse spin-orbit interaction can give
rise to unidirectional coupling and $>95\%$ isolation of infrared light at an
experimentally feasible rotation speed. Our work fuses the two important fields
of optical isolation and photonic spin-orbit interactions, leading to
magnetic-free yet compact nonreciprocal devices for novel applications in
optical communications, chiral quantum optics, and topological photonics.",2011.11973v2
2021-02-01,Magnetoelectric spectroscopy of spin excitations in LiCoPO4,"We have studied spin excitations in a single-domain crystal of
antiferromagnetic LiCoPO4 by THz absorption spectroscopy. By analyzing the
selection rules and comparing the strengths of the absorption peaks in the
different antiferromagnetic domains, we found electromagnons and
magnetoelectric spin resonances besides conventional magnetic-dipole active
spin-wave excitations. Using the sum rule for the magnetoelectric
susceptibility we determined the contribution of the spin excitations to all
the different off-diagonal elements of the static magnetoelectric
susceptibility tensor in zero as well as in finite magnetic fields. We conclude
that the magnetoelectric spin resonances are responsible for the static
magnetoelectric response of the bulk when the magnetic field is along the
x-axis, and the symmetric part of the magnetoelectric tensor with zero diagonal
elements dominates over the antisymmetric components.",2102.00994v1
2008-06-09,Hydration-induced anisotropic spin fluctuations in Na_{x}CoO_{2}\cdot1.3H_{2}O superconductor,"We report ^{59}Co NMR studies in single crystals of cobalt oxide
superconductor Na_{0.42}CoO_{2}\cdot1.3H_{2}O (T_c=4.25K) and its parent
compound Na_{0.42}CoO_{2}. We find that both the magnitude and the temperature
(T) dependence of the Knight shifts are identical in the two compounds above
T_c. The spin-lattice relaxation rate (1/T_1) is also identical above T_0
\sim60 K for both compounds. Below T_0, the unhydrated sample is found to be a
non-correlated metal that well conforms to Fermi liquid theory, while spin
fluctuations develop in the superconductor. These results indicate that water
intercalation does not change the density of states but its primary role is to
bring about spin fluctuations. Our result shows that, in the hydrated
superconducting compound, the in-plane spin fluctuation around finite wave
vector is much stronger than that along the c-axis, which indicates that the
spin correlation is quasi-two-dimensional.",0806.1412v1
2008-06-19,Coherent optical control of correlation waves of spins in semiconductors,"We calculate the dynamical fluctuation spectrum of electronic spins in a
semiconductor under a steady-state illumination by light containing
polarization squeezing correlations. Taking into account quasi-particle
lifetime and spin relaxation for this non-equilibrium situation we consider up
to fourth order optical effects which are sensitive to the squeezing phases.
  We demonstrate the possibility to control the spin fluctuations by optically
modulating these phases as a function of frequency, leading to a non-Lorentzian
spectrum which is very different from the thermal equilibrium fluctuations in
n-doped semiconductors. Specifically, in the time-domain spin-spin correlation
can exhibit time delays and sign flips originating from the phase modulations
and correlations of polarizations, respectively. For higher light intensity we
expect a regime where the squeezing correlations will dominate the spectrum.",0806.3291v1
2017-01-06,Emergence and scaling of spin turbulence in quenched antiferromagnetic spinor Bose-Einstein condensates,"We investigate the phase transition dynamics of a quasi-2D antiferromagnetic
spin-1 Bose-Einstein condensate from the easy-axis polar phase to the
easy-plane polar phase, which is initiated by suddenly changing the sign of the
quadratic Zeeman energy $q$. We observe the emergence and decay of spin
turbulence and the formation of half-quantum vortices (HQVs) in the quenched
condensate. The characteristic time and length scales of the turbulence
generation dynamics are proportional to $|q|^{-1/2}$ as inherited from the
dynamic instability of the initial state. In the evolution of the spin
turbulence, spin wave excitations develop from large to small length scales,
suggesting a direct energy cascade, and the spin population for the axial polar
domains exhibit a nonexponential decay. The final equilibrated condensate
contains HQVs, and the number is found to increase and saturate with increasing
$|q|$. Our results demonstrate the time-space scaling properties of the phase
transition dynamics near the critical point and the peculiarities of the spin
turbulence state of the antiferromagnetic spinor condensate.",1701.01559v2
2019-01-17,Spin filtering in CrI$_3$ tunnel junctions,"The recently discovered magnetism of two-dimensional (2D) van der Waals
crystals have attracted a lot of attention. Among these materials is CrI$_3$ -
a magnetic semiconductor exhibiting transitions between antiferromagnetic and
ferromagnetic orderings under the influence of an applied magnetic field. Here,
using first-principles methods based on density functional theory, we explore
spin-dependent transport in tunnel junctions formed of fcc Cu (111) electrodes
and a CrI$_3$ tunnel barrier. We find about 100% spin polarization of the
tunneling current for a ferromagnetically-ordered four-monolayer CrI$_3$ and
tunneling magnetoresistance of about 3,000% associated with a change of
magnetic ordering in CrI$_3$. This behavior is understood in terms of the spin
and wave-vector dependent evanescent states in CrI$_3$ which control the
tunneling conductance. We find a sizable charge transfer from Cu to CrI$_3$
which adds new features to the mechanism of spin-filtering in CrI$_3$-based
tunnel junctions. Our results elucidate the mechanisms of spin filtering in
CrI3 tunnel junctions and provide important insights for the design of
magnetoresistive devices based on 2D magnetic crystals.",1901.05993v1
2019-04-19,A microscopic description for polarization in particle scatterings,"We propose a microscopic description for the polarization from the first
principle through the spin-orbit coupling in particle collisions. The model is
different from previous ones based on local equilibrium assumptions for the
spin degree of freedom. It is based on scatterings of particles as wave
packets, an effective method to deal with particle scatterings at specified
impact parameters. The polarization is then the consequence of particle
collisions in a non-equilibrium state of spins. The spin-vorticity coupling
naturally emerges from the spin-orbit one encoded in polarized scattering
amplitudes of collisional integrals when one assumes local equilibrium in
momentum but not in spin.",1904.09152v1
2019-07-09,Spins of black holes in coalescing compact binaries,"Modern astrophysical methods of determination of spins of rotating
stellar-mass black hole in close binaries and of supermassive black holes in
active galactic nuclei are briefly discussed. Effective spins of coalescing
binary black holes derived from LIGO/Virgo gravitational wave observations are
specially addressed. We consider three types of coalescing binaries: double
black holes, black hole-neutron star binaries and primordial double black
holes. The effective spins of coalescing astrophysical binary black holes and
black holes with neutron stars are calculated for two plausible models of black
hole formations from stellar core collapses (without or with additional
fallback from the stellar envelope) taking into account the stellar metallicity
and star formation rate evolution in the Universe. The calculated distributions
do not contradict the reported LIGO/Virgo observations. The effective spins of
primordial coalescing stellar-mass black holes can reach a few per cent due to
accretion spin-up in the cold external medium.",1907.04218v1
2019-09-06,Spin-orbit interaction in a high-power laser irradiated micro-scale plasma waveguide,"Light carries angular momentum as spin and orbital components. The spin-orbit
interaction (SOI) of light refers to phenomena in which the spin (left or right
circular polarisation) affects the spatial degrees of freedom. Recently,
interest in SOI has surged, as it provides physical insight into the behaviour
of polarised light at subwavelength scales, and allows for spin-controlled
manipulation of light. Most studies are performed with low intensity, leaving
the role SOI plays in the relativistic laser-plasma interaction, characterised
by nonlinearity, less understood. Here, using 3D particle-in-cell simulations,
we report SOI effects in this unprecedented regime. Specifically, a circularly
polarised Gaussian laser irradiating a micro-scale plasma waveguide drives a
spin-controlled chiral surface wave, allowing the reflected harmonic photons to
gain orbital angular momentum (OAM). These effects produce intense optical
vortices in the extreme ultraviolet regime - an area of significant fundamental
and applied physics potential.",1909.02887v1
2019-09-27,Transition from inspiral to plunge into a highly spinning black hole,"We extend the Ori-Thorne-Kesden procedure to consistently describe the
non-quasi-circular transition around the ISCO from inspiral to plunge into a
black hole of arbitrary spin, including near-extremal. We identify that for
moderate or high spins the transition is governed by the Painlev\'e
transcendent equation of the first kind while for extremely high spins it is
governed by a self-similar solution to the Korteweg-de Vries equation. We match
the transition solution at leading order in the high spin limit with the
analytical quasi-circular inspiral in the near-horizon region. We also show
that the central black hole of an extreme mass ratio binary has a
near-extremality parameter that scales at least as the mass ratio due to
superradiant gravitational wave emission, which excludes extremely high spins.",1909.12848v2
2019-10-16,Acoustic spin-Chern insulator induced by synthetic spin-orbit coupling with spin conservation breaking,"Topologically protected surface modes of classical waves hold the promise to
enable a variety of applications ranging from robust transport of energy to
reliable information processing networks. The integer quantum Hall effect has
delivered on that promise in the electronic realm through high-precision
metrology devices. However, both the route of implementing an analogue of the
quantum Hall effect as well as the quantum spin Hall effect are obstructed for
acoustics by the requirement of a magnetic field, or the presence of fermionic
quantum statistics, respectively. Here, we use a two-dimensional acoustic
crystal with two layers to mimic spin-orbit coupling, a crucial ingredient of
topological insulators. In particular, our setup allows us to free ourselves of
symmetry constraints as we rely on the concept of a non-vanishing ""spin"" Chern
number. We experimentally characterize the emerging boundary states which we
show to be gapless and helical. Moreover, in an H-shaped device we demonstrate
how the transport path can be selected by tuning the geometry, enabling the
construction of complex networks.",1910.07196v1
2019-12-12,Strongly interacting spin-orbit coupled Bose-Einstein condensates in one dimension,"We theoretically study dilute superfluidity of spin-1 bosons with
antiferromagnetic interactions and synthetic spin-orbit coupling (SOC) in a
one-dimensional lattice. Employing a combination of density matrix
renormalization group and quantum field theoretical techniques we demonstrate
the appearance of a robust superfluid spin-liquid phase in which the
spin-sector of this spinor Bose-Einstein condensate remains quantum disordered
even after introducing quadratic Zeeman and helical magnetic fields. Despite
remaining disordered, the presence of these symmetry breaking fields lifts the
perfect spin-charge separation and thus the nematic correlators obey power-law
behavior. We demonstrate that, at strong coupling, the SOC induces a charge
density wave state that is not accessible in the presence of linear and
quadratic Zeeman fields alone. In addition, the SOC induces oscillations in the
spin and nematic expectation values as well as the bosonic Green's function.
These non-trivial effects of a SOC are suppressed under the application of a
large quadratic Zeeman field. We discuss how our results could be observed in
experiments on ultracold gases of $^{23}$Na in an optical lattice.",1912.06142v1
2019-12-20,Efficient Ab-initio Multiplet Calculations for Magnetic Adatoms on MgO,"Scanning probe microscopy and spectroscopy, and more recently in combination
with electron spin resonance, have allowed the direct observation of electron
dynamics on the single-atom limit. The interpretation of data is strongly
depending on model Hamiltonians. However, fitting effective spin Hamiltonians
to experimental data lacks the ability to explore a vast number of potential
systems of interest. By using plane-wave density functional theory (DFT) as
starting point, we build a multiplet Hamiltonian making use of
maximally-localized Wannier functions. The Hamiltonian contains spin-orbit and
electron-electron interactions needed to obtain the relevant spin dynamics. The
resulting reduced Hamiltonian is solved by exact diagonalization. We compare
three prototypical cases of 3d transition metals Mn (total spin $S=5/2$), Fe
($S=2$) and Co ($S=3/2$) on MgO with experimental data and find that our
calculations can accurately predict the spin orientation and anisotropy of the
magnetic adatom. Our method does not rely on experimental input and permits us
to explore and predict the fundamental magnetic properties of adatoms on
surfaces.",1912.09793v1
2020-02-09,Walker-like Domain Wall breakdown in layered Antiferromagnets driven by staggered spin-orbit fields,"Within linear continuum theory, no magnetic texture can propagate faster than
the maximum group velocity of its spin waves. Here we report a transient regime
due to the appearance of additional antiferromagnetic textures that breaks the
Lorentz translational invariance of the magnetic system by atomistic spin
dynamics simulations. This dynamical regime is akin to domain wall
Walker-breakdown in ferromagnets and involves the nucleation of an
antiferromagnetic domain wall pair. Subsequently, one of the nucleated
180$^{\circ}$ domain wall creates with the original domain wall a 360$^{\circ}$
spin-rotation which remains static even under the action of the spin-orbit
field. The other 180$^{\circ}$ domain wall becomes accelerated to
super-magnonic speeds. Under large spin-orbit fields, multiple domain wall
generation and recombination is obtained which may explain the recently
experimentally observed current pulse induce shattering of large domain
structures into small fragmented domains and the subsequent slow recreation of
large-scale domain formation prior current pulse.",2002.03332v1
2020-07-07,Heisenberg-Kitaev model in a magnetic field: $1/S$ expansion,"The exact solution of Kitaev's spin-$1/2$ honeycomb spin-liquid model has
sparked an intense search for Mott insulators hosting bond-dependent Kitaev
interactions, of which $\mathrm{Na}_{2}\mathrm{IrO}_{3}$ and
$\alpha-\mathrm{RuCl}_{3}$ are prime examples. Subsequently, it has been
proposed that also spin-$1$ and spin-$3/2$ analogs of Kitaev interactions may
occur in materials with strong spin-orbit coupling. As a minimal model to
describe these Kitaev materials, we study the Heisenberg-Kitaev Hamiltonian in
a consistent $1/S$ expansion, with $S$ being the spin size. We present a
comprehensive study of this model in the presence of an external magnetic field
applied along two different directions, [001] and [111], for which an intricate
classical phase diagram has been reported. In both settings, we employ
spin-wave theory in a number of ordered phases to compute phase boundaries at
the next-to-leading order in $1/S$ and show that quantum corrections
substantially modify the classical phase diagram. More broadly, our work
presents a consistent route to investigate the leading quantum corrections in
spin models that break spin-rotational symmetry.",2007.03717v2
2021-03-08,Excitation and Detection of THz Coherent Spin Waves in Antiferromagnetic $\mathrm{α-Fe_2O_3}$,"The efficiency of ultrafast excitation of spins in antiferromagnetic
$\mathrm{\alpha-Fe_{2}O_{3}}$ using nearly single-cycle THz pulse is studied as
a function of the polarization of the THz pulse and the sample temperature.
Above the Morin point the most efficient excitation is achieved when the
magnetic field of the THz pulse is perpendicular to the antiferromagnetically
coupled spins. Using the experimental results and equations of motion for
spins, we show that the mechanism of the spin excitation above and below the
Morin point relies on magnetic-dipole interaction of the THz magnetic field
with spins and the efficiency of the coupling is proportional to the time
derivative of the magnetic field.",2103.05083v1
2021-11-05,Photonic $\mathbb{Z}_2$ topological Anderson insulators,"That disorder can induce nontrivial topology is a surprising discovery in
topological physics. As a typical example, Chern topological Anderson
insulators (TAIs) have been realized in photonic systems, where the topological
phases exist without symmetry protection. In this work, by taking TM and TE
polarizations as pseudo-spin degrees of freedom, we theoretically propose a
scheme to realize disorder-induced symmetry-protected topological (SPT) phase
transitions in two-dimensional photonic crystals (PCs) with a combined
time-reversal, mirror and duality symmetry
$\mathcal{T}_f=\mathcal{T}M_z\mathcal{D}$. In particular, we demonstrate that
the disorder-induced SPT phase persists even without pseudo-spin conservation,
thereby realizing a photonic $\mathbb{Z}_2$ TAI, in contrast to a
$\mathbb{Z}$-classified quantum spin Hall (QSH) TAI with decoupled spins. By
formulating a new scattering approach, we show that the topology of both the
QSH and $\mathbb{Z}_2$ TAIs can be manifested by the accumulated spin rotations
of the reflected waves from the PCs. Using a transmission structure, we also
illustrate the trivialization of a disordered QSH phase with an even integer
topological index caused by spin coupling.",2111.03242v2
2021-11-08,Time evolution of spin singlet in static homogeneous exchange and magnetic fields,"Within the framework of an idealized theoretical model, we study the effect
of external static homogeneous exchange and magnetic field on the spin part of
the singlet wave function of two electrons. We begin by revising the
traditional (text- book) approach to the spin singlet. Basing our own approach
solely on the property of invariance under rotations of the coordinate system
and using the theory of spinor in- variants, we derive a generalized
representation of the spin singlet whose main feature is that the spins are in
mutually time-reversed states. We show that exactly this fea- ture
predetermines the actual form of the Hamiltonian of interaction with the
external field and stipulates time evolution of the singlet. Some applications
of these results to the theory of superconductivity and spin chemistry are
presented. In particular, it is shown that the case of ferromagnetic
superconductors constitutes a good illustration of the validity of our
quantum-mechanical consideration.",2111.04544v1
2022-01-15,Beam Spin Asymmetries of $π^+π^0$ Dihadrons from SIDIS at CLAS12,"Spin asymmetries provide a wide range of insights into nucleon structure and
hadronization. Recent measurements of beam spin asymmetries of $\pi^+\pi^-$
dihadrons from Semi-Inclusive Deep Inelastic Scattering (SIDIS) at CLAS12
provide the first empirical evidence of a nonzero $G_1^\perp$, the parton
helicity-dependent Dihadron Fragmentation Function (DiFF) encoding
spin-momentum correlations in hadronization. These measurements have been
extended to aid in the characterization of $H_1^\perp$ and
$H_1^\sphericalangle$, the DiFFs dependent on parton transverse spin, via a
multidimensional partial wave analysis, giving access to the dependence on the
interference of dihadrons of particular polarizations. Reconstruction of
$\pi^0$s allows for further extension of these measurements to $\pi^+\pi^0$ and
$\pi^-\pi^0$ dihadrons. The DiFFs describing $\pi^+\pi^-$ production differ
from those describing $\pi^+\pi^0$ and $\pi^-\pi^0$ production, which involve
different quark flavors along with a strong suppression of the exclusive
diffractive contribution. This presentation will focus on beam spin asymmetries
for $\pi^+\pi^0$ dihadrons, compared to those from $\pi^+\pi^-$ dihadrons,
which will help shed light on a more comprehensive picture of dihadron
fragmentation.",2201.05732v2
2022-06-14,"Spin-density, charge- and bond-disproportionation wave instability in hole-doped infinite-layer $R$NiO$_2$","Using \emph{ab initio} band structure methods and DFT+dynamical mean-field
theory approach we explore the possible formation of spin and charge stripes in
the Ni-O plane of hole-doped infinite-layer nickelates, $R$NiO$_2$. Our results
reveal a remarkable instability of the $C$-type $(110)$ spin state with
undistorted lattice towards the formation of the spin-density, charge- and
bond-disproportionation stripe phases accompanied by in-plane``breathing''-like
distortions of the crystal structure. Our work gives a comprehensive picture of
competing charge and spin stripe states, with possible frustration of different
stripe patterns upon doping. It suggests that the spin and charge stripe state
likely arises from strong magnetic correlations (with concomitant lattice
distortions), which play a key role for understanding the anomalous properties
of hole-doped layered nickelates.",2206.06985v2
2022-10-17,Ultrafast laser-driven topological spin textures on a 2D magnet,"Ultrafast laser excitations provide an efficient and low-power consumption
alternative since different magnetic properties and topological spin states can
be triggered and manipulated at the femtosecond (fs) regime. However, it is
largely unknown whether laser excitations already used in data information
platforms can manipulate the magnetic properties of recently discovered
two-dimensional (2D) van der Waals (vdW) materials. Here we show that
ultrashort laser pulses (30$-$85 fs) can not only manipulate magnetic domains
of 2D-XY CrCl$_3$ ferromagnets, but also induce the formation and control of
topological nontrivial meron and antimeron spin textures. We observed that
these spin quasiparticles are created within $\sim$100 ps after the excitation
displaying rich dynamics through motion, collision and annihilation with
emission of spin waves throughout the surface. Our findings highlight
substantial opportunities of using photonic driving forces for the exploration
of spin textures on 2D magnetic materials towards magneto-optical topological
applications.",2210.09210v1
2022-12-19,Discrete Laplacian Thermostat for Spin Systems with Conserved Dynamics,"A well-established numerical technique to study the dynamics of spin systems
in which symmetries and conservation laws play an important role is to
microcanonically integrate their reversible equations of motion, obtaining
thermalization through initial conditions drawn with the canonical
distribution. In order to achieve a more realistic relaxation of the magnetic
energy, numerically expensive methods that explicitly couple the spins to the
underlying lattice are normally employed. Here we introduce a stochastic
conservative thermostat that relaxes the magnetic energy while preserving the
constant of motions, thus turning microcanonical spin dynamics into a
conservative canonical dynamics, without actually simulating the lattice. We
test the thermostat on the Heisenberg antiferromagnet in d=3 and show that the
method reproduces the exact values of the static and dynamic critical
exponents, while in the low-temperature phase it yields the correct spin wave
phenomenology. Finally, we demonstrate that the relaxation coefficient of the
new thermostat is quantitatively connected to the microscopic parameters of the
spin-lattice coupling.",2212.09647v2
2023-01-18,Spin-orbit interaction in nanofiber-based Brillouin scattering,"Angular momentum is an important physical property that plays a key role in
light-matter interactions such as spin-orbit interaction. Here, we investigate
theoretically and experimentally the spin-orbit interaction between a
circularly polarized optical (spin) and a transverse vortex acoustic wave
(orbital) using Brillouin backscattering in a silica optical nanofiber. We
specifically explore the state of polarization of Brillouin backscattering
induced by the TR21 torso-radial vortex acoustic mode that carries an orbital
angular momentum. Using a full-vectorial theoretical model, we predict and
observe two operating regimes for which the backscattered Brillouin signal is
either depolarized or circularly polarized depending on the input pump
polarization. We demonstrate that when the pump is circularly polarized and
thus carries a spin angular momentum, the backscattered signal undergoes a
handedness reversal of circular polarization due to optoacoustic spin-orbit
interaction and the conservation of overall angular momentum.",2301.07592v1
2023-02-24,A Fiber-coupled Scanning Magnetometer with Nitrogen-Vacancy Spins in a Diamond Nanobeam,"Magnetic imaging with nitrogen-vacancy (NV) spins in diamond is becoming an
established tool for studying nanoscale physics in condensed matter systems.
However, the optical access required for NV spin readout remains an important
hurdle for operation in challenging environments such as millikelvin cryostats
or biological systems. Here, we demonstrate a scanning-NV sensor consisting of
a diamond nanobeam that is optically coupled to a tapered optical fiber. This
nanobeam sensor combines a natural scanning-probe geometry with high-efficiency
through-fiber optical excitation and readout of the NV spins. We demonstrate
through-fiber optically interrogated electron spin resonance and
proof-of-principle magnetometry operation by imaging spin waves in an
yttrium-iron-garnet thin film. Our scanning-nanobeam sensor can be combined
with nanophotonic structuring to control the light-matter interaction strength,
and has potential for applications that benefit from all-fiber sensor access
such as millikelvin systems.",2302.12536v1
2023-03-17,Low-energy spin excitations in optimally doped CaFe$_{0.88}$Co$_{0.12}$AsF superconductor studied with inelastic neutron scattering,"There are few inelastic neutron scattering (INS) reports on the
superconducting single crystals of FeAs-1111 system, even though it was first
discovered in 2008, due to the extreme difficulty in large single crystal
growth. In this paper, we have studied the low-energy spin excitations in the
optimally electron-doped CaFe$_{0.88}$Co$_{0.12}$AsF single crystals with
$T_\mathrm{c}$ = 21 K by INS. The resonance energy of the superconducting spin
resonant mode with $E_\mathrm{r}$ = 12 meV amounts to 6.6
$k_\mathrm{B}$$T_\mathrm{c}$, which constitutes the largest
$E_\mathrm{r}$/$k_\mathrm{B}$$T_\mathrm{c}$ ratio among iron-based
superconductors reported to date. The large ratio implies a strong coupling
between conduction electrons and magnetic excitations in
CaFe$_{0.88}$Co$_{0.12}$AsF. The resonance possesses a magnonlike upward
dispersion along transverse direction due to the anisotropy of spin-spin
correlation length within $ab$ plane in the normal-state, which points to a
spin fluctuation mediated sign-reversed ${s}\mathbf\pm$ wave pairing in
CaFe$_{0.88}$Co$_{0.12}$AsF.",2303.09787v2
2023-03-17,Third order corrections to the ground state energy of the gas of spin $s$ fermions with arbitrary densities of different spin projections,"Recently we have computed the third order corrections to the ground state
energy of the arbitrarily polarized diluted gas of spin 1/2 fermions
interacting through a spin-independent repulsive two-body potential. Here we
extend this result to the gas of spin $s$ fermions - a system the Hamiltonian
of which has an accidental $SU(2s+1)$ symmetry - with arbitrary densities of
fermions having different spin projections. The corrections are computed
semi-analytically using the effective field theory approach and are
parametrized by the $s$- and $p$- wave scattering lengths $a_0$ and $a_1$ and
the $s$-wave effective radius $r_0$, measurable in the low energy
fermion-fermion elastic scattering. The result is used to study the impact the
higher order corrections can have on the characteristics of the phase
transition (at zero temperature) to the ordered phase (on the emergence of the
itinerant ferromagnetism).",2303.09921v1
2023-05-03,One- and two-particle correlation functions in the cluster perturbation theory for cuprates,"Physics of high-$T_c$ superconducting cuprates is obscured by the effect of
strong electronic correlations. One way to overcome the problem is to seek for
an exact solution at least within the small cluster and expand it to the whole
crystal. Such an approach is in the heart of the cluster perturbation theory
(CPT). Here we develop CPT for the dynamic spin and charge susceptibilities
(spin-CPT and charge-CPT), within which the correlation effects are explicitly
taken into account by the exact diagonalization. We apply spin-CPT and
charge-CPT to the effective two-band Hubbard model for the cuprates obtained
from the three-band Emery model and calculate one- and two-particle correlation
functions, namely, spectral function and spin and charge susceptibilities.
Doping dependence of the spin susceptibility was studied within spin-CPT and
CPT-RPA that is the CPT generalization of the random phase approximation (RPA).
Both methods produce the low energy response at four incommensurate wave
vectors in qualitative agreement to the results of the inelastic neutron
scattering on overdoped cuprates.",2305.01882v1
2023-05-18,Up-down binaries are unstable and we want to know,"The relativistic spin-precession equations for black-hole binaries have four
different equilibrium solutions that correspond to systems where the two
individual black hole spins are either aligned or anti-aligned with the orbital
angular momentum. Surprisingly, it was demonstrated that only three of these
equilibrium solutions are stable. Binary systems in the up-down configuration,
where the spin of the heavier (lighter) black hole is co- (counter-) aligned
with the orbital angular momentum, might be unstable to small perturbations of
the spin directions. After the onset of the up-down instability, that occurs
after a specific critical orbital separation $r_\mathrm{UD+}$, the binary
becomes unstable to spin precession leading to large misalignment of the spins.
In this work, we present a Bayesian procedure based on the Savage-Dickey
density ratio to test the up-down origin of gravitational-wave events. We apply
this procedure to look for promising candidates among the events detected so
far during the first three observing runs performed by LIGO/Virgo.",2305.10776v1
2023-06-09,Lorentzian quantum cosmology from effective spin foams,"Effective spin foams provide the computationally most efficient spin foam
models yet and are therefore ideally suited for applications e.g. to quantum
cosmology. We provide here the first effective spin foam computations of a
finite time evolution step in a Lorentzian quantum de Sitter universe. We will
consider a set-up which computes the no-boundary wave function, as well as a
set-up describing the transition between two finite scale factors. A key
property of spin foams is that they implement discrete spectra for the areas.
We therefore study the effects that are induced by the discrete spectra.
  To perform these computations we had to identify a technique to deal with
highly oscillating and slowly converging, or even diverging sums. We illustrate
here that high order Shanks transformation work very well and are a promising
tool for the evaluation of Lorentzian (gravitational) path integrals and spin
foam sums.",2306.06012v1
2023-06-21,Eccentricity evolution of spinning binaries,"We study the evolution of the eccentricity of an eccentric orbit with
spinning components. We develop a prescription to express the evolving
eccentricity in terms of initial eccentricity and frequency. For that purpose
we considered the spins to be perpendicular to the orbital plane. Using this we
found an analytical result for the contribution of spin in eccentricity
evolution. As a result, we expressed orbital eccentricity in a series of
initial eccentricity and gravitational wave frequency. The prescription
developed here can easily be used to find arbitrarily higher-order
contributions of initial eccentricity. With the eccentricity evolution at hand,
we computed the evolving energy and angular momentum fluxes for eccentric orbit
with spinning components. This result can be used to construct the waveforms of
spinning compact objects in an eccentric orbit.",2306.12522v1
2023-07-31,Analytic solutions for the motion of spinning particles near spherically symmetric black holes and exotic compact objects,"Rapidly rotating bodies moving in curved space-time experience the so-called
spin-curvature force, which becomes important for the motion of compact objects
in gravitational-wave inspirals. In the first approximation, this effect is
captured in the motion of a spinning test particle. We solve the equations
motion of a spinning particle to leading order in spin in arbitrary static and
spherically symmetric space-times in terms of one-dimensional closed-form
integrals. This solves the problem and proves its integrability in a wide range
of modified gravities and near exotic compact objects. Then, by specializing to
the case of bound orbits in Schwarzschild space-time, we demonstrate how to
express the solution in the form of Jacobi elliptic functions.",2308.00021v2
2024-02-04,Deconstructing the spin susceptibility of a cuprate superconductor,"A major obstacle to understanding high-Tc cuprates is that superconductivity
precludes observing normal-state properties at low temperatures. One prime
example is the normal-state spin susceptibility: although its decrease upon
cooling far above Tc typifies pseudogap behavior, its behavior at low
temperatures is generally unknown. Here, our measurements in high magnetic
fields expose the spin susceptibility of YBa2Cu3Oy down to low temperatures.
Even though superconductivity is suppressed by the field, we uncover two
thermally-activated contributions alongside a residual susceptibility at T=0
due to gapless excitations. We relate these two distinct gaps to short-range
charge-density waves and to the formation of spin singlets similar to those
found in certain quantum spin systems. These phenomena thus collectively
contribute to the pseudogap in the spin susceptibility at low temperature,
supplementing short-lived antiferromagnetism known to initiate pseudogap
behavior at high temperatures. We therefore propose that the pseudogap should
be regarded as a composite property.",2402.02508v1
2024-02-26,Thermal evolution of spin excitations in honeycomb Ising antiferromagnetic FePSe3,"We use elastic and inelastic neutron scattering (INS) to study the
antiferromagnetic (AF) phase transitions and spin excitations in the
two-dimensional (2D) zig-zag antiferromagnet FePSe$_3$. By determining the
magnetic order parameter across the AF phase transition, we conclude that the
AF phase transition in FePSe$_3$ is first-order in nature. In addition, our INS
measurements reveal that the spin waves in the AF ordered state have a large
easy-axis magnetic anisotropy gap, consistent with an Ising Hamiltonian, and
possible biquadratic magnetic exchange interactions. On warming across $T_N$,
we find that dispersive spin excitations associated with three-fold rotational
symmetric AF fluctuations change into FM spin fluctuations above $T_N$. These
results suggest that the first-order AF phase transition in FePSe$_3$ may arise
from the competition between $C_3$ symmetric AF and $C_1$ symmetric FM spin
fluctuations around $T_N$, in place of a conventional second-order AF phase
transition.",2402.16983v1
2024-03-25,Detection of spin pumping free of rectification and thermal artefacts in molecular-based ferromagnetic insulator V[TCNE]x~2,"The molecular-based ferrimagnetic insulator V(TCNE)x has gained recent
interest for efficient spin-wave excitation due to its low Gilbert damping
ratio a=4E-5, and narrow ferromagnetic resonance linewidth f=1Oe. Here we
report a clean spin pumping signal detected on V(TCNE)x/metal bilayer
structures, free from spin rectification or thermal artifacts. On-chip coupling
of microwave power is achieved via a coplanar waveguide to measure the in-plane
angle-dependence of the inverse spin-Hall effect under ferromagnetic resonance
conditions with respect to a constant external magnetic field. A signature of
pure spin current from V(TCNE)x is observed in both platinum and permalloy
metal layers, demonstrating the utility of V(TCNE)x for magnon spintronics
studies in molecule/solid-state heterostructures.",2403.16429v2
2015-05-29,Microscopic Theory for Coupled Atomistic Magnetization and Lattice Dynamics,"A coupled atomistic spin and lattice dynamics approach is developed which
merges the dynamics of these two degrees of freedom into a single set of
coupled equations of motion. The underlying microscopic model comprises local
exchange interactions between the electron spin and magnetic moment and the
local couplings between the electronic charge and lattice displacements. An
effective action for the spin and lattice variables is constructed in which the
interactions among the spin and lattice components are determined by the
underlying electronic structure. In this way, expressions are obtained for the
electronically mediated couplings between the spin and lattice degrees of
freedom, besides the well known inter-atomic force constants and spin-spin
interactions. These former susceptibilities provide an atomistic ab initio
description for the coupled spin and lattice dynamics. It is important to
notice that this theory is strictly bilinear in the spin and lattice variables
and provides a minimal model for the coupled dynamics of these subsystems and
that the two subsystems are treated on the same footing. Questions concerning
time-reversal and inversion symmetry are rigorously addressed and it is shown
how these aspects are absorbed in the tensor structure of the interaction
fields. By means of these results regarding the spin-lattice coupling, simple
explanations of ionic dimerization in double anti-ferromagnetic materials, as
well as, charge density waves induced by a non-uniform spin structure are
given. In the final parts, a set of coupled equations of motion for the
combined spin and lattice dynamics are constructed, which subsequently can be
reduced to a form which is analogous to the Landau-Lifshitz-Gilbert equations
for spin dynamics and damped driven mechanical oscillator for the ...",1505.08005v3
2018-12-19,"Nonlinear-in-spin effects in effective-one-body waveform models of spin-aligned, inspiralling, neutron star binaries","Spinning neutron stars acquire a quadrupole moment due to their own rotation.
This quadratic-in-spin, self-spin effect depends on the equation of state (EOS)
and affects the orbital motion and rate of inspiral of neutron star binaries.
We incorporate the EOS-dependent self-spin (or monopole-quadrupole) terms in
the spin-aligned effective-one-body (EOB) waveform model TEOBResumS at
next-to-next-to-leading (NNLO) order, together with other (bilinear, cubic and
quartic) nonlinear-in-spin effects (at leading order, LO). The structure of the
Hamiltonian of TEOBResumS is such that it already incorporates, in the binary
black hole case, the recently computed quartic-in-spin LO term. Using the
gauge-invariant characterization of the phasing provided by the function
$Q_\omega=\omega^2/\dot{\omega}$ of $\omega=2\pi f$ , where $f$ is the
gravitational wave frequency, we study the EOS dependence of the self-spin
effects and show that: (i) the next-to-leading order (NLO) and NNLO
monopole-quadrupole corrections yield increasingly phase-accelerating effects
compared to the corresponding LO contribution; (ii) the standard TaylorF2
post-Newtonian (PN) treatment of NLO (3PN) EOS-dependent self-spin effects
makes their action stronger than the corresponding EOB description; (iii) the
addition to the standard 3PN TaylorF2 post-Newtonian phasing description of
self-spin tail effects at LO allows one to reconcile the self-spin part of the
TaylorF2 PN phasing with the corresponding TEOBResumS one up to dimensionless
frequencies $M\omega\simeq 0.04-0.06$. By generating the inspiral dynamics
using the post-adiabatic approximation, incorporated in a new implementation of
TEOBResumS, one finds that the computational time needed to obtain a typical
waveform (including all multipoles up to $\ell=8$) from 10 Hz is of the order
of 0.4 sec.",1812.07923v1
2022-07-14,Neutron Scattering Study of Fluctuating and Static Spin Correlations in the Anisotropic Spin Glass Fe$_2$TiO$_5$,"The anisotropic spin glass transition, in which spin freezing is observed
only along the c-axis in pseudobrookite Fe$_2$TiO$_5$, has long been perplexing
because the Fe$^{3+}$ moments (d$^5$) are expected to be isotropic. Recently,
neutron diffraction demonstrated that surfboard-shaped antiferromagnetic
nanoregions coalesce above the glass transition temperature, T$_g$ $\approx$ 55
K, and a model was proposed in which the freezing of the fluctuations of the
surfboards' magnetization leads to the anisotropic spin glass state. Given this
new model, we have carried out high resolution inelastic neutron scattering
measurements of the spin-spin correlations to understand the temperature
dependence of the intra-surfboard spin dynamics on neutron (picosecond)
time-scales. Here, we report on the temperature-dependence of the spin
fluctuations measured from single crystal Fe$_2$TiO$_5$. Strong quasi-elastic
magnetic scattering, arising from intra-surfboard correlations, is observed
well above T$_g$. The spin fluctuations possess a steep energy-wave vector
relation and are indicative of strong exchange interactions, consistent with
the large Curie-Weiss temperature. As the temperature approaches T$_g$ from
above, a shift in spectral weight from inelastic to elastic scattering is
observed. At various temperatures between 4 K and 300 K, a characteristic
relaxation rate of the fluctuations is determined. Despite the freezing of the
majority of the spin correlations, an inelastic contribution remains even at
base temperature, signifying the presence of fluctuating intra-surfboard spin
correlations to at least T/T$_g$ $\approx$ 0.1 consistent with a description of
Fe$_2$TiO$_5$ as a hybrid between conventional and geometrically frustrated
spin glasses.",2207.07085v1
2012-06-04,Electron doping evolution of the anisotropic spin excitations in BaFe2-xNixAs2,"We use inelastic neutron scattering to systematically investigate the
Ni-doping evolution of the low-energy spin excitations in BaFe2-xNixAs2
spanning from underdoped antiferromagnet to overdoped superconductor (0.03< x <
0.18). In the undoped state, the low-energy (<80 meV) spin waves of BaFe2As2
form transversely elongated ellipses in the [H, K] plane of the reciprocal
space. Upon Ni-doping, the c-axis magnetic exchange coupling is rapidly
suppressed and the momentum distribution of spin excitations in the [H, K]
plane is enlarged in both the transverse and longitudinal directions with
respect to the in-plane AF ordering wave vector of the parent compound. As a
function of increasing Ni-doping x, the spin excitation widths increase
linearly but with a larger rate along the transverse direction. These results
are in general agreement with calculations of dynamic susceptibility based on
the random phase approximation (RPA) in an itinerant electron picture. For
samples near optimal superconductivity at x= 0.1, a neutron spin resonance
appears in the superconducting state. Upon further increasing the
electron-doping to decrease the superconducting transition temperature Tc, the
intensity of the low-energy magnetic scattering decreases and vanishes
concurrently with vanishing superconductivity in the overdoped side of the
superconducting dome. Comparing with the low-energy spin excitations centered
at commensurate AF positions for underdoped and optimally doped materials
(x<0.1), spin excitations in the over-doped side (x=0.15) form transversely
incommensurate spin excitations, consistent with the RPA calculation.
Therefore, the itinerant electron approach provides a reasonable description to
the low-energy AF spin excitations in BaFe2-xNixAs2.",1206.0653v2
2016-06-16,Boundary-induced spin density waves in linear Heisenberg antiferromagnetic spin chains with $\mathbf{S \ge 1}$,"Linear Heisenberg antiferromagnets (HAFs) are chains of spin-$S$ sites with
isotropic exchange $J$ between neighbors. Open and periodic boundary conditions
return the same ground state energy in the thermodynamic limit, but not the
same spin $S_G$ when $S \ge 1$. The ground state of open chains of N spins has
$S_G = 0$ or $S$, respectively, for even or odd N. Density matrix
renormalization group (DMRG) calculations with different algorithms for even
and odd N are presented up to N = 500 for the energy and spin densities
$\rho(r,N)$ of edge states in HAFs with $S = 1$, 3/2 and 2. The edge states are
boundary-induced spin density waves (BI-SDWs) with $\rho(r,N)\propto(-1)^{r-1}$
for $r=1,2,\ldots N$. The SDWs are in phase when N is odd, out of phase when N
is even, and have finite excitation energy $\Gamma(N)$ that decreases
exponentially with N for integer $S$ and faster than 1/N for half integer $S$.
The spin densities and excitation energy are quantitatively modeled for integer
$S$ chains longer than $5 \xi$ spins by two parameters, the correlation length
$\xi$ and the SDW amplitude, with $\xi = 6.048$ for $S = 1$ and 49.0 for $S =
2$. The BI-SDWs of $S = 3/2$ chains are not localized and are qualitatively
different for even and odd N. Exchange between the ends for odd N is mediated
by a delocalized effective spin in the middle that increases $|\Gamma(N)|$ and
weakens the size dependence. The nonlinear sigma model (NL$\sigma$M) has been
applied the HAFs, primarily to $S = 1$ with even N, to discuss spin densities
and exchange between localized states at the ends as $\Gamma(N) \propto (-1)^N
\exp(-N/\xi)$...",1606.05054v2
2018-11-01,Spin-induced deformations and tests of binary black hole nature using third-generation detectors,"In a recent letter [N. V. Krishnendu et al., PRL 119, 091101 (2017)] we
explored the possibility of probing the binary black hole nature of coalescing
compact binaries, by measuring their spin-induced multipole moments, observed
in advanced LIGO detectors. Coefficients characterizing the spin-induced
multipole moments of Kerr black holes are predicted by the ""no-hair"" conjecture
and appear in the gravitational waveforms through quadratic and higher order
spin interactions and hence can be directly measured from gravitational wave
observations. We assess the capabilities of the third-generation gravitational
wave interferometers such as Cosmic Explorer and Einstein Telescope in carrying
out such measurements and use them to test the binary black hole nature of
observed binaries. In this paper, we extend the investigations of our previous
work, by proposing to measure (a) spin-induced quadrupole effects, (b)
simultaneous measurements of spin-induced quadrupole and octupole effects, in
the context of the third-generation detectors. We find that, using
third-generation detectors the symmetric combination of coefficients associated
with spin-induced quadrupole moment of each binary component may be constrained
to a value $\leq 1.1$ while a similar combination of coefficients for
spin-induced octupole moment may be constrained to $\leq 2$, where both
combinations take the value of 1 for a binary black hole system. Further, we
consider two different binary black hole populations, as proxies of the
population that will be observed by the third generation detectors, and obtain
the resulting distribution of the spin-induced quadrupole coefficient. These
estimates suggest that third-generation detectors can accurately constrain the
first four multipole moments of the compact objects (mass, spin, quadrupole,
and octupole) facilitating a thorough probe of their black hole nature.",1811.00317v2
2020-12-03,New effective precession spin for modeling multimodal gravitational waveforms in the strong-field regime,"Accurately modelling the complete gravitational-wave signal from precessing
binary black holes through the late inspiral, merger and ringdown remains a
challenging problem. The lack of analytic solutions for the precession dynamics
of generic double-spin systems, and the high dimensionality of the problem,
obfuscate the incorporation of strong-field spin-precession information into
semi-analytic waveform models used in gravitational-wave data analysis.
Previously, an effective precession spin, $\chi_p$, was introduced to reduce
the number of spin degrees of freedom. Here, we show that $\chi_p$ alone does
not accurately reproduce higher-order multipolar modes, in particular the ones
that carry strong imprints due to precession such as the $(2,1)$-mode. To
improve the higher-mode content, and in particular to facilitate an accurate
incorporation of precession effects in the strong-field regime into waveform
models, we introduce a new dimensional reduction through an effective
precession spin vector, $\vec{\chi}_\perp$, which takes into account precessing
spin information from both black holes. We show that this adapted effective
precession spin (i) mimics the precession dynamics of the fully precessing
configuration remarkably well, (ii) captures the signature features of
precession in higher-order modes, and (iii) reproduces the final state of the
remnant black hole with high accuracy for the overwhelming majority of
configurations. We demonstrate the efficacy of this two-dimensional precession
spin in the strong-field regime, paving the path for meaningful calibration of
the precessing sector of semi-analytic waveform models with a faithful
representation of higher-order modes through merger and the remnant black hole
spin.",2012.02209v3
2015-04-07,Generation of coherent spin-wave modes in Yttrium Iron Garnet microdiscs by spin-orbit torque,"Spin-orbit effects [1-4] have the potential of radically changing the field
of spintronics by allowing transfer of spin angular momentum to a whole new
class of materials. In a seminal letter to Nature [5], Kajiwara et al. showed
that by depositing Platinum (Pt, a normal metal) on top of a 1.3 $\mu$m thick
Yttrium Iron Garnet (YIG, a magnetic insulator), one could effectively transfer
spin angular momentum through the interface between these two different
materials. The outstanding feature was the detection of auto-oscillation of the
YIG when enough dc current was passed in the Pt. This finding has created a
great excitement in the community for two reasons: first, one could control
electronically the damping of insulators, which can offer improved properties
compared to metals, and here YIG has the lowest damping known in nature;
second, the damping compensation could be achieved on very large objects, a
particularly relevant point for the field of magnonics [6,7] whose aim is to
use spin-waves as carriers of information. However, the degree of coherence of
the observed auto-oscillations has not been addressed in ref. [5]. In this
work, we emphasize the key role of quasi-degenerate spin-wave modes, which
increase the threshold current. This requires to reduce both the thickness and
lateral size in order to reach full damping compensation [8] , and we show
clear evidence of coherent spin-orbit torque induced auto-oscillation in
micron-sized YIG discs of thickness 20 nm.",1504.01512v1
2021-07-22,Spin-orbit effects for compact binaries in scalar-tensor gravity,"Gravitational waves provide us with a new window into our Universe, and have
already been used to place strong constrains on the existence of light scalar
fields, which are a common feature in many alternative theories of gravity.
However, spin effects are still relatively unexplored in this context. In this
work, we construct an effective point-particle action for a generic spinning
body that can couple both conformally and disformally to a real scalar field,
and we show that requiring the existence of a self-consistent solution
automatically implies that if a scalar couples to the mass of a body, then it
must also couple to its spin. We then use well-established effective field
theory techniques to conduct a comprehensive study of spin-orbit effects in
binary systems to leading order in the post-Newtonian (PN) expansion. Focusing
on quasicircular nonprecessing binaries for simplicity, we systematically
compute all key quantities, including the conservative potential, the orbital
binding energy, the radiated power, and the gravitational-wave phase. We show
that depending on how strongly each member of the binary couples to the scalar,
the spin-orbit effects that are due to a conformal coupling first enter into
the phase at either 0.5PN or 1.5PN order, while those that arise from a
disformal coupling start at either 3.5PN or 4.5PN order. This suppression by
additional PN orders notwithstanding, we find that the disformal spin-orbit
terms can actually dominate over their conformal counterparts due to an
enhancement by a large prefactor. Accordingly, our results suggest that
upcoming gravitational-wave detectors could be sensitive to disformal
spin-orbit effects in double neutron star binaries if at least one of the two
bodies is sufficiently scalarised.",2107.10841v2
2022-01-10,Phase degree of freedom and topology in multiple-$Q$ spin textures,"A periodic array of topological spin textures, such as skyrmions and
hedgehogs, is called the multiple-$Q$ spin texture, as it is represented by a
superposition of multiple spin density waves. Depending on the way of
superposition, not only the magnetic but also the topological properties are
modified, leading to a variety of quantum transport and optical phenomena
caused by the emergent electromagnetic fields through the Berry phase. Among
others, the phase degree of freedom of the superposed waves is potentially
important for such modifications, but its effect has not been fully elucidated
thus far. Here we perform systematic theoretical analyses of magnetic and
topological properties of the multiple-$Q$ spin textures with the phase degree
of freedom. By introducing a hyperspace with an additional dimension
corresponding to the phase degree of freedom, we establish a generic framework
to deal with the phase shift in the multiple-$Q$ spin textures. Applying the
framework to the two-dimensional 3$Q$ spin textures, we clarify the complete
topological phase diagram while changing the phase and magnetization, which
depends on the types of the superposed waves. We also study the
three-dimensional 4$Q$ spin textures and clarify even richer topological phase
diagrams. In particular, we find novel topological phase transitions associated
with the previously unidentified Dirac strings on which the hedgehogs and
antihedgehogs cause pair creation and fusion. Moreover, we demonstrate that
phase shifts are caused by an external magnetic field in both 3$Q$ and 4$Q$
cases by analyzing the numerical data in the previous studies. Our results
illuminate the topological aspects of the skyrmion and hedgehog lattices with
the phase degree of freedom, which would be extended to other multiple-$Q$
textures and useful for the exploration of topologically nontrivial magnetic
phases and exotic quantum phenomena.",2201.03290v1
2022-02-11,Evidence for magnetic fractional excitations in a Kitaev quantum-spin-liquid candidate $α$-RuCl$_3$,"$\alpha$-RuCl$_3$ has been studied extensively because of its proximity to
the Kitaev quantum-spin-liquid (QSL) phase and the possibility of approaching
it by tuning the competing interactions. Here we present the first polarized
inelastic neutron scattering study on $\alpha$-RuCl$_3$ single crystals to
explore the scattering continuum around the $\Gamma$ point at the Brillouin
zone center, which was hypothesized to be resulting from the Kitaev QSL state
but without concrete evidence. With polarization analyses, we find that while
the spin-wave excitations around the M point vanish above the transition
temperature $T_{\rm N}$, the pure magnetic continuous excitations around the
$\Gamma$ point are robust against temperature. Furthermore, by calculating the
dynamical spin-spin correlation function using the cluster perturbation theory,
we derive magnetic dispersion spectra based on the $K$-$\Gamma$ model, which
involves with a ferromagnetic Kitaev interaction of -7.2 meV and an
off-diagonal interaction of 5.6 meV. We find this model can reproduce not only
the spin-wave excitation spectra around the M point, but also the non-spin-wave
continuous magnetic excitations around the $\Gamma$ point. These results
provide evidence for the existence of fractional excitations around the
$\Gamma$ point originating from the Kitaev QSL state, and further support the
validity of the $K$-$\Gamma$ model as the effective minimal spin model to
describe $\alpha$-RuCl$_3$.",2202.05450v1
2022-09-10,Magnetic field effects in an octupolar quantum spin liquid candidate,"Quantum spin liquid (QSL) is a disordered state of quantum-mechanically
entangled spins commonly arising from frustrated magnetic dipolar interactions.
However, QSL in some pyrochlore magnets can also come from frustrated magnetic
octupolar interactions. Although the key signature for both dipolar and
octupolar interaction-driven QSL is the presence of a spin excitation continuum
(spinons) arising from the spin quantum number fractionalization, an external
magnetic field-induced ferromagnetic order will transform the spinons into
conventional spin waves in a dipolar QSL. By contrast, in an octupole QSL, the
spin waves carry octupole moments that do not couple, in the leading order, to
the external magnetic field or to neutron moments but will contribute to the
field dependence of the heat capacity. Here we use neutron scattering to show
that the application of a large external magnetic field to Ce2Zr2O7, an
octupolar QSL candidate, induces an Anderson-Higgs transition by condensing the
spinons into a static ferromagnetic ordered state with octupolar spin waves
invisible to neutrons but contributing to the heat capacity. Our theoretical
calculations also provide a microscopic, qualitative understanding for the
presence of octupole scattering at large wavevectors in Ce2Sn2O7 pyrochlore,
and its absence in Ce2Zr2O7. Therefore, our results identify Ce2Zr2O7 as a
strong candidate for an octupolar U (1) QSL, establishing that frustrated
magnetic octupolar interactions are responsible for QSL properties in Ce-based
pyrochlore magnets.",2209.04590v1
2023-04-11,Excitation and voltage-gated modulation of single-mode dynamics in a planar nano-gap spin Hall nano-oscillator,"We experimentally study the dynamical modes excited by current-induced
spin-orbit torque and its electrostatic gating effect in a 3-terminal planar
nano-gap spin Hall nano-oscillator (SHNO) with a moderate interfacial
perpendicular magnetic anisotropy (IPMA). Both quasilinear propagating
spin-wave and localized ""bullet"" modes are achieved and controlled by varying
the applied in-plane magnetic field and driving current. The minimum linewidth
shows a linear dependence on the actual temperature of the active area,
confirming single-mode dynamics based on the nonlinear theory of spin-torque
nano-oscillation with a single mode. The observed electrostatic gating tuning
oscillation frequency arises from voltage-controlled magnetic anisotropy and
threshold current of SHNO via modification of the nonlinear damping and/or the
interfacial spin-orbit coupling of the magnetic multilayer. In contrast to
previously observed two-mode coexistence degrading the spectral purity in
Py/Pt-based SHNOs with a negligible IPMA, a single coherent spin-wave mode with
a low driven current can be achieved by selecting the ferromagnet layer with a
suitable IPMA because the nonlinear mode coupling can be diminished by bringing
in the PMA field to compensate the easy-plane shape anisotropy. Moreover, the
simulations demonstrate that the experimentally observed current and
gate-voltage modulation of auto-oscillation modes are also closely associated
with the nonlinear damping and mode coupling, which are determined by the
ellipticity of magnetization precession. The demonstrated nonlinear mode
coupling mechanism and electrical control approach of spin-wave modes could
provide the clue to facilitate the implementation of the mutual synchronization
map for neuromorphic computing applications in SHNO array networks.",2304.05026v1
2000-06-09,"R-modes in Neutron Stars with Crusts: Turbulent Saturation, Spin-down, and Crust Melting","Rossby waves (r-modes) have been suggested as a means to regulate the spin
periods of young or accreting neutron stars, and also to produce observable
gravitational wave radiation. R-modes involve primarily transverse,
incompressive motions of the star's fluid core. However, neutron stars gain
crusts early in their lives: therefore, r-modes also imply shear in the fluid
beneath the crust. We examine the criterion for this shear layer to become
turbulent, and derive the rate of dissipation in the turbulent regime. Unlike
dissipation from a viscous boundary layer, turbulent energy loss is nonlinear
in mode energy and can therefore cause the mode to saturate at amplitudes
typically much less than unity. This energy loss also reappears as heat below
the crust. We study the possibility of crust melting as well as its
implications for the spin evolution of low-mass X-ray binaries. Lastly, we
identify some universal features of the spin evolution that may have
observational consequences.",0006123v1
1995-03-06,"Phase Transition, Longitudinal Spin Fluctuations and Scaling in a Two-Layer Antiferromagnet","We consider a two-layer Heisenberg antiferromagnet which can be either in the
N\'{e}el-ordered or in the disordered phase at $T=0$, depending on the ratio of
the intra- and interlayer exchange constants. We reduce the problem to an
interacting Bose-gas and study the sublattice magnetization and the transverse
susceptibility in the ordered phase, and the spectrum of quasiparticle
excitations in both phases. We compare the results with the spin-wave theory
and argue that the longitudinal spin fluctuations, which are not included in
the spin-wave description, are small at vanishing coupling between the layers,
but increase as the system approaches the transition point. We also compute the
uniform susceptibility at the critical point to order $O(T^2)$, and show that
the corrections to scaling are numerically small, and the linear behavior of
$\chi_u$ extends to high temperatures. This is consistent with the results of
the recent Monte-Carlo simulations by Sandvik and Scalapino.",9503029v1
1997-03-02,Critical behavior and the Neel temperature of quantum quasi-two-dimensional Heisenberg antiferromagnets,"The nonlinear sigma-model and its generalization on N-component spins, the
O(N) model, are considered to describe thermodynamics of a quantum
quasi-two-dimensional (quasi-2D) Heisenberg antiferromagnet. A comparison with
standard spin-wave approaches is performed. The sublattice magnetization, Neel
temperature and spin correlation function are calculated to first order of the
1/N-expansion. A description of crossover from a 2D-like to 3D regime of
sublattice magnetization temperature dependence is obtained. The values of the
critical exponents derived are \beta =0.36, \eta =0.09. An account of the
corrections to the standard logarithmic term of the spin-wave theory modifies
considerably the value of the Neel temperature. The thermodynamic quantities
calculated are universal functions of the renormalized interlayer coupling
parameter. The renormalization of interlayer coupling parameter turns out to be
considerably temperature dependent. A good agreement with experimental data on
La2CuO4 is obtained. The application of the approach used to the case of a
ferromagnet is discussed.",9703013v1
1997-04-14,An Effective Theory for Midgap States in Doped Spin Ladder and Spin-Peierls Systems: Liouville Quantum Mechanics,"In gapped spin ladder and spin-Peierls systems the introduction of disorder,
for example by doping, leads to the appearance of low energy midgap states. The
fact that these strongly correlated systems can be mapped onto one dimensional
noninteracting fermions provides a rare opportunity to explore systems which
have both strong interactions and disorder. In this paper we show that the
statistics of the zero energy midgap wave functions in these models can be
effectively described by Liouville Quantum Mechanics. This enables us to
calculate the disorder averaged N-point correlation functions of these states
(the explicit calculation is performed for N=2,3). We find that whilst these
midgap states are typically weakly correlated, their disorder averaged
correlation are power law. This discrepancy arises because the correlations are
not self-averaging and averages of the wave functions are dominated by
anomalously strongly correlated configurations.",9704115v1
1998-01-28,Quantum Magnetism Approaches to Strongly Correlated Electrons,"Problems of strongly interacting electrons can be greatly simplified by
reducing them to effective quantum spin models. The initial step is
renormalization of the Hamiltonian into a lower energy subspace. The positive
and negative U Hubbard models are explicitely transformed into the Heisenberg
and -x-xz models respectively. Basic tools of quantum magnetism are introduced
and used: spin coherent states path integral, spin wave theory, and continuum
theory of rotators.The last lecture concerns pseudospin approaches to
superconductivity and superfluidity. The SO(3) rotator theory for the -x-xz
model describes a charge density wave to superconductor transition.
Analogously, Zhang's SO(5) rotator theory describes the antiferromagnet to
d-wave superconductor transition in high Tc cuprates. Finally the Magnus force
on the two dimensional vortices and their momentum, are derived from the Berry
phase of the spin path integral.",9801294v1
1998-04-15,Fixed-Node Monte Carlo Calculations for the 1d Kondo Lattice Model,"The effectiveness of the recently developed Fixed-Node Quantum Monte Carlo
method for lattice fermions, developed by van Leeuwen and co-workers, is tested
by applying it to the 1D Kondo lattice, an example of a one-dimensional model
with a sign problem. The principles of this method and its implementation for
the Kondo Lattice Model are discussed in detail. We compare the fixed-node
upper bound for the ground state energy at half filling with
exact-diagonalization results from the literature, and determine several spin
correlation functions. Our `best estimates' for the ground state correlation
functions do not depend sensitively on the input trial wave function of the
fixed-node projection, and are reasonably close to the exact values. We also
calculate the spin gap of the model with the Fixed-Node Monte Carlo method. For
this it is necessary to use a many-Slater-determinant trial state. The
lowest-energy spin excitation is a running spin soliton with wave number pi, in
agreement with earlier calculations.",9804147v1
1998-05-11,Spin Dynamics of the Magnetoresistive Pyrochlore Tl_2Mn_2O_7,"Neutron scattering has been used to study the magnetic order and spin
dynamics of the colossal magnetoresistive pyrochlore Tl_2Mn_2O_7. On cooling
from the paramagnetic state, magnetic correlations develop and appear to
diverge at T_C (123 K). In the ferromagnetic phase well defined spin waves are
observed, with a gapless ($\Delta <0.04$ meV) dispersion relation E=Dq^{2} as
expected for an ideal isotropic ferromagnet. As T approaches T_C from low T,
the spin waves renormalize, but no significant central diffusive component to
the fluctuation spectrum is observed in stark contrast to the
La$_{1-x}$(Ca,Ba,Sr)$_x$MnO$_3$ system. These results argue strongly that the
mechanism responsible for the magnetoresistive effect has a different origin in
these two classes of materials.",9805131v1
1998-08-27,Single hole dynamics in dimerized spin liquids,"The dynamics of a single hole in quantum antiferromagnets is influenced by
magnetic fluctuations. In the present work we consider two situations. The
first one corresponds to a single hole in the two leg t-J spin ladder. In this
case the wave function renormalization is relatively small and the
quasiparticle residue of the S=1/2 state remains close to unity. However at
large t/J there are higher spin (S=3/2,5/2,..) bound states of the hole with
the magnetic excitations, and therefore there is a crossover from
quasiparticles with S=1/2 to quasiparticles with higher spin.
  The second situation corresponds to a single hole in two coupled
antiferromagnetic planes very close to the point of antiferromagnetic
instability. In this case the hole wave function renormalization is very strong
and the quasiparticle residue vanishes at the point of instability.",9808302v1
1998-10-18,Excitation spectrum of the homogeneous spin liquid,"We discuss the excitation spectrum of a disordered, isotropic and
translationally invariant spin state in the 2D Heisenberg antiferromagnet. The
starting point is the nearest-neighbor RVB state which plays the role of the
vacuum of the theory, in a similar sense as the Neel state is the vacuum for
antiferromagnetic spin wave theory. We discuss the elementary excitations of
this state and show that these are not Fermionic spin-1/2 `spinons' but spin-1
excited dimers which must be modeled by bond Bosons. We derive an effective
Hamiltonian describing the excited dimers which is formally analogous to spin
wave theory. Condensation of the bond-Bosons at zero temperature into the state
with momentum (pi,pi) is shown to be equivalent to antiferromagnetic ordering.
The latter is a key ingredient for a microscopic interpretation of Zhang's
SO(5) theory of cuprate superconductivity",9810216v1
1999-03-15,Mechanism of CDW-SDW Transition in One Dimension,"The phase transition between charge- and spin-density-wave (CDW, SDW) phases
is studied in the one-dimensional extended Hubbard model at half-filling. We
discuss whether the transition can be described by the Gaussian and the
spin-gap transitions under charge-spin separation, or by a direct CDW-SDW
transition. We determine these phase boundaries by level crossings of
excitation spectra which are identified according to discrete symmetries of
wave functions. We conclude that the Gaussian and the spin-gap transitions take
place separately from weak- to intermediate-coupling region. This means that
the third phase exists between the CDW and the SDW states. Our results are also
consistent with those of the strong-coupling perturbative expansion and of the
direct evaluation of order parameters.",9903227v1
2000-07-07,Dimerization of Ferrimagnets on Chains and Square Lattices,"A linear spin wave analysis of dimerization of alternating Heisenberg system
with spins $s_{1}$ and $s_{2}$ on linear chain as well as square lattice is
presented. Among the several possible dimerized configurations considered in
two dimensions the plaquette configuration is found to be energetically the
most favored one. Inclusion of a variable nearest neighbor exchange coupling
$J(a)=\frac{J}{a}$ leads to a uniform power law behavior: that is to say, the
same $\delta $-dependence is found (i) in chains as well as in square lattices;
(ii) in systems consisting of different pairs of spins $s_{1}$ and $s_{2}$;
(iii) for the magnetic energy gain, the energy gap, the energy of the gapped
magnetic excitation mode as well as for the sublattice magnetization; (iv) for
all the configurations of the square lattice; and (v) in the entire range of
$\delta :$ $(0\leq \delta <1)$. The variable exchange coupling also allows \
the energy of the gapped excitation spectrum to be $\delta $-dependent even in
the linear spin wave theory.",0007133v1
2001-02-20,Spinwaves and large electron-phonon coupling near the metal-insulator transition in hole-doped high-T$_C$ oxides,"A theory for spin and lattice couplings to the electronic states in
high-T$_C$ oxides is presented, with HgBa$_2$CuO$_4$ as an example. A simple
analytical model suggests that the barrel band is sensitive to potential
perturbations with long-range Fourier components, and that gaps can be opened
at the Fermi energy. This is confirmed in self-consistent band calculations for
modulations in elongated supercells, where spin waves and phonon coupling
compete for equal q-vectors. It is argued that the wavelengths of spin-wave
modulations and of the phonon modes with large coupling, depend on the doping.
This mechanism supports the idea that pseudogaps are caused by stripe like
spin-modulations in underdoped systems, while superconductivity is attributed
to enhanced electron-phonon coupling for long wavelength phonons.",0102343v1
2001-04-19,Magnetic properties and spin waves of bilayer magnets in a uniform field,"The two-layer square lattice quantum antiferromagnet with spins 1/2 shows a
zero-field magnetic order-disorder transition at a critical ratio of the
inter-plane to intra-plane couplings. Adding a uniform magnetic field tunes the
system to canted antiferromagnetism and eventually to a fully polarized state;
similar behavior occurs for ferromagnetic intra-plane coupling. Based on a bond
operator spin representation, we propose an approximate ground state
wavefunction which covers all phases by means of a unitary transformation. The
excitations can be efficiently described as independent bosons; in the
antiferromagnetic phase these reduce to the well-known spin waves, whereas they
describe gapped spin-1 excitations in the singlet phase. We compute the spectra
of these excitations as well as the magnetizations throughout the whole phase
diagram.",0104356v3
2001-05-01,Spin-Charge Decoupling and Orthofermi Quantum Statistics,"Currently Gutzwiller projection technique and nested Bethe ansatz are two
main methods used to handle electronic systems in the $U$ infinity limit. We
demonstrate that these two approaches describe two distinct physical systems.
In the nested Bethe ansatz solutions, there is a decoupling between the spin
and charge degrees of freedom. Such a decoupling is absent in the Gutzwiller
projection technique. Whereas in the Gutzwiller approach, the usual
antisymmetry of space and spin coordinates is maintained, we show that the
Bethe ansatz wave function is compatible with a new form of quantum statistics,
viz., orthofermi statistics. In this statistics, the wave function is
antisymmetric in spatial coordinates alone. This feature ultimately leads to
spin-charge decoupling.",0105012v1
2001-09-28,Spin excitation spectra of integral and fractional quantum Hall systems,"Results are presented of detailed numerical calculations for the spin
excitation spectra of a two-dimensional electron gas confined in a quantum well
of finite width w, at magnetic fields corresponding to the fractional and
integral fillings of the lowest and of excited Landau levels. Spin waves and
skyrmions are identified, and their mutual interactions are studied at filling
factors nu=1/3, 1, 3, and 5. The smallest skyrmions at nu=1/3 are equivalent to
composite fermion charged excitons X_CF^(+/-). Bose condensates of nearly
noninteracting spin waves and Laughlin correlations between finite-size
skyrmions are found at nu=1 and 1/3 and, for w larger than about two magnetic
lengths, also at nu=3 and 5. A general criterion for the occurrence of
skyrmions at odd integral fillings and at Laughlin fractional fillings of the
lowest Landau level is given in terms of the interaction pseudopotentials. This
explains the dependence of skyrmion states on w observed in excited Landau
levels.",0109548v1
2001-10-03,Grassmannian Fields and Doubly Enhanced Skyrmions in Bilayer Quantum Hall system at $ν=2$,"At the filling factor $\nu=2$ the bilayer quantum Hall system has three
phases, the ferromagnetic phase (spin phase), the spin singlet phase (ppin
phase) and the canted antiferromagnetic phase. We analyze soft waves and
quasiparticle excitations in the spin and ppin phases. It is shown that the
dynamic field is the Grassmannian G$_{4,2}$ field carrying four complex degrees
of freedom. In each phase there are four complex soft waves (pseudo-Goldstone
modes) and one kind of skyrmion excitations (G$_{4,2}$ skyrmions) flipping
either spins or pseudospins coherently. An intriguing property is that a
quasiparticle is a G$_{4,2}$ skyrmion essentially consisting of two CP$^{3}$
skyrmions and thus possesses charge $2e$.",0110072v3
2002-01-02,Anisotropies of the Hamiltonian and the Wave Function: Inversion Phenomena in Quantum Spin Chains,"We investigate the inversion phenomenon between the XXZ anisotropies of the
Hamiltonian and the wave function in quantum spin chains, mainly focusing on
the S=1/2 trimerized XXZ model with the next-nearest-neighbor interactions. We
have obtained the ground-state phase diagram by use of the degenerate
perturbation theory and the level spectroscopy analysis of the numerical data
calculated by the Lanczos method. In some parameter regions, the spin-fluid is
realized for the Ising-like anisotropy, and the Neel state for the XY-like
anisotropy, against the ordinary situation.",0201014v1
2002-10-28,Spectral Function Analysis on Spin Dynamics in Double-Exchange Systems with Randomness,"Spin excitation spectrum is studied in the double-exchange model with
randomness. Applying the spin wave approximation and the spectral function
analysis, we examine excitation energy and linewidth using analytical as well
as numerical methods. For small wave number $q \sim 0$, the excitation energy
is cosine-like and the linewidth shows a $q$-linear behavior. This indicates
that the spin excitation becomes incoherent or localized near $q = 0$.
Crossover takes place to marginally-coherent regime where both the excitation
energy and the linewidth are proportional to $q^2$. The incoherence is due to
local fluctuations of the kinetic energy of electrons. Comparison with
experimental results in colossal magnetoresistance manganites suggests that
spatially-correlated or mesoscopic-scale fluctuations are more important in
real compounds than local or atomic-scale ones.",0210606v1
2003-01-20,Persistent spin currents in mesoscopic Heisenberg rings,"We show that at low temperatures T an inhomogeneous radial magnetic field
with magnitude B gives rise to a persistent magnetization current around a
mesoscopic ferromagnetic Heisenberg ring. Under optimal conditions this spin
current can be as large as g mu_B (T / hbar) exp [ - 2 pi (g mu_B B / Delta
)^1/2 ], as obtained from leading-order spin-wave theory. Here g is the
gyromagnetic factor, mu_B is the Bohr magneton, and Delta is the energy gap
between the ground state and the first spin-wave excitation. The magnetization
current endows the ring with an electric dipole moment.",0301351v2
2003-05-21,Disorder Effect on Spin Excitation in Double Exchange Systems,"Spin excitation spectrum is studied in the double exchange model in the
presence of disorder. Spin wave approximation is applied in the lowest order of
1/S expansion. The disorder causes anomalies in the spin excitation spectrum
such as broadening, branching, anticrossing with gap opening. The origin of the
anomalies is the Friedel oscillation, in which the perfectly polarized
electrons form the charge density wave to screen the disorder effect. Near the
zone center $q = 0$, the linewidth has a $q$ linear component while the
excitation energy scales to $q^2$, which indicates that the magnon excitation
is incoherent. As $q$ increases, there appears a crossover from this incoherent
behavior to the marginally coherent one in which both the linewidth and the
excitation energy are proportional to $q^2$. The results are compared with
experimental results in colossal magnetoresistance manganese oxides.
Quantitative comparison of the linewidth suggests that spatially-correlated or
mesoscopic-scale disorder is more relevant in real compounds than local or
atomic-scale disorder. Comparison with other theoretical proposals is also
discussed. Experimental tests are proposed for the relevance of disorder.",0305488v2
2003-08-14,The magnetic reversal in dot arrays recognized by the self-organized adaptive neural network,"The remagnetization dynamics of monolayer dot array superlattice XY 2-D spin
model with dipole-dipole interactions is simulated. Within the proposed model
of array, the square dots are described by the spatially modulated
exchange-couplings. The dipole-dipole interactions are approximated by the
hierarchical sums and spin dynamics is considered in regime of the
Landau-Lifshitz equation. The simulation of reversal for $40 000$ spins
exhibits formation of nonuniform intra-dot configurations with nonlinear
wave/anti-wave pairs developed at intra-dot and inter-dot scales. Several
geometric and parametric dependences are calculated and compared with
oversimplified four-spin model of reversal. The role of initial conditions and
the occurrence of coherent rotation mode is also investigated. The emphasis is
on the classification of intra-dot or inter-dot (interfacial) magnetic
configurations done by adaptive neural network with varying number of neurons.",0308287v1
2004-10-28,Inelastic neutron scattering study of single crystal heavy fermion YbAgGe,"Single crystals of the heavy-fermion compound YbAgGe have been studied by
neutron scattering. The magnetic ordering occurring below T1=0.5 K is
characterized by a commensurate propagation vector k=(1/3,0,1/3) and the
moments in the basal plane of the hexagonal structure. The dynamic magnetic
susceptibility is dominated by quasielastic spin fluctuations with a
characteristic energy Gamma of the order of 1 meV. The spins fluctuate
predominantly in the basal plane. No spin-wave excitations are observed in the
magnetically ordered phase. Below the Kondo temperature, TK=20 K, Gamma shows a
strong q dependence for wave vectors along the c* direction, but is
q-independent in the basal plane. Gamma shows initially a rapid increase with
temperature T at the antiferromagnetic zone center, but follows a standard
sqrt(T) law for other q values and for T>TK in general. These observations
classify YbAgGe as a well-behaved heavy-fermion compound with a particular
q-dependence of the antiferromagnetic spin fluctuations, possibly related to
the geometrical frustration of the Yb3+ ions.",0410736v1
2005-01-18,Incommensurate spin dynamics in underdoped cuprate perovskites,"The incommensurate magnetic response observed in normal-state cuprate
perovskites is interpreted based on the projection operator formalism and the
t-J model of Cu-O planes. In agreement with experiment the calculated
dispersion of maxima in the susceptibility has the shape of two parabolas with
upward and downward branches which converge at the antiferromagnetic wave
vector. The maxima are located at the momenta $({1/2},{1/2}\pm\delta)$,
$({1/2}\pm\delta,{1/2})$ and at $({1/2}\pm\delta,{1/2}\pm\delta)$,
$({1/2}\pm\delta,{1/2}\mp\delta)$ in the lower and upper parabolas,
respectively. The upper parabola reflects the dispersion of magnetic
excitations of the localized Cu spins, while the lower parabola arises due to a
dip in the spin-excitation damping at the antiferromagnetic wave vector. For
moderate doping this dip stems from the weakness of the interaction between the
spin excitations and holes near the hot spots. The frequency dependence of the
susceptibility is shown to depend strongly on the hole bandwidth and damping
and varies from the shape observed in YBa$_2$Cu$_3$O$_{7-y}$ to that inherent
in La$_{2-x}$Sr$_x$CuO$_4$.",0501418v1
2005-09-07,Doping dependence of spin excitations in the stripe phase of high-Tc superconductors,"Based on the time-dependent Gutzwiller approximation for the extended Hubbard
model we calculate the energy and momentum dependence of spin excitations for
striped ground states. Our starting point correctly reproduces the observed
doping dependence of the incommensurability in La-based cuprates and the
dispersion of magnetic modes in the insulating parent compound. This allows us
to make quantitative predictions for the doping evolution of the dispersion of
magnetic modes in the stripe phase including the energy and intensity of the
resonance peak as well as the velocity of the spin-wave like Goldstone mode. In
the underdoped regime $n_h<1/8$ we find a weak linear dependence of
$\omega_{res}$ on doping whereas the resonance energy significantly shifts to
higher values when the charge concentration in the stripes starts to deviate
from half-filling for $n_h>1/8$. The velocity $c$ is non-monotonous with a
minimum at 1/8 in coincidence with a well known anomaly in $T_c$. Our
calculations are in good agreement with available experimental data. We also
compare our results with analogous computations based on linear spin-wave
theory.",0509175v2
2005-11-08,Spin-wave interactions in quantum antiferromagnets,"We study spin-wave interactions in quantum antiferromagnets by expressing the
usual magnon annihilation and creation operators in terms of Hermitian field
operators representing transverse staggered and ferromagnetic spin
fluctuations. In this parameterization, which was anticipated by Anderson in
1952, the two-body interaction vertex between staggered spin fluctuations
vanishes at long wavelengths. We derive a new effective action for the
staggered fluctuations only by tracing out the ferromagnetic fluctuations. To
one loop order, the renormalization group flow agrees with the
nonlinear-$\sigma$-model approach.",0511199v3
2005-12-29,Ferromagnetic phase transition in spinor Bose gases,"The achievement in cooling alkali atomic gases, such as $^{87}$Rb, $^{23}$Na
and $^{7}$Li, to quantum degeneracy opens up a way to study magnetism in spinor
bosons, because these constituent atoms usually have a hyperfine spin degree of
freedom. This article reviews several basic problems related to the
ferromagnetic phase transition in spinor atomic Bose gases from a theoretical
perspective. After a brief discussion on various possible origins of the
ferromagnetic interaction, the phase diagram of the ferromagnetically coupled
spinor bosons is investigated. It is found that the ferromagnetic transition
occurs always above Bose-Einstein condensation and the Bose condensate is fully
polarized. The low-lying collective excitations of the spinor condensate,
including spin and density modes, are discussed. The spectrum of the density
mode is of the Bogliubov form and the spin wave spectrum has a $k^2$-formed
dispersion relation at long wavelengths. The spin-wave stiffness coefficient
contains contribut",0512693v1
2006-01-06,Magnetic Excitations of Stripes Near a Quantum Critical Point,"We calculate the dynamical spin structure factor of spin waves for weakly
coupled stripes. At low energy, the spin wave cone intensity is strongly peaked
on the inner branches. As energy is increased, there is a saddlepoint followed
by a square-shaped continuum rotated 45 degree from the low energy peaks. This
is reminiscent of recent high energy neutron scattering data on the cuprates.
The similarity at high energy between this semiclassical treatment and quantum
fluctuations in spin ladders may be attributed to the proximity of a quantum
critical point with a small critical exponent $\eta$.",0601128v3
2006-03-20,How spin-orbit interaction can cause electronic shot noise,"The shot noise in the electrical current through a ballistic chaotic quantum
dot with N-channel point contacts is suppressed for N --> infinity, because of
the transition from stochastic scattering of quantum wave packets to
deterministic dynamics of classical trajectories. The dynamics of the electron
spin remains quantum mechanical in this transition, and can affect the
electrical current via spin-orbit interaction. We explain how the role of the
channel number N in determining the shot noise is taken over by the ratio
l_{so}/lambda_F of spin precession length l_{so} and Fermi wave length
lambda_F, and present computer simulations in a two-dimensional billiard
geometry (Lyapunov exponent alpha, mean dwell time tau_{dwell}, point contact
width W) to demonstrate the scaling (lambda_F/l_{so})^{1/alpha tau_{dwell}} of
the shot noise in the regime lambda_F << l_{so} << W.",0603524v1
2006-04-19,High Energy Spin Excitations in Electron-Doped Superconducting Pr$_{0.88}$LaCe$_{0.12}$CuO$_{4-δ}$ with $T_c=21$ K,"We use high-resolution inelastic neutron scattering to study the
low-temperature magnetic excitations of electron-doped superconducting
Pr$_{0.88}$LaCe$_{0.12}$CuO$_{4-\delta}$ ($T_c=21\pm 1$ K) over a wide energy
range (4 meV$\le\hbar\omega\le 330$ meV). The effect of electron-doping is to
cause a wave vector ($Q$) broadening in the low-energy ($\hbar\omega\le 80$
meV) commensurate spin fluctuations at ($\pi$,$\pi$) and to suppress the
intensity of spin-wave-like excitations at high energies ($\hbar\omega\ge 100$
meV). This leads to a substantial redistribution in the spectrum of the local
dynamical spin susceptibility $\chi^{\prime\prime}(\omega)$, and reveals a new
energy scale similar to that of the lightly hole-doped YB$_2$Cu$_3$O$_{6.353}$
($T_c=18$ K).",0604449v1
2006-05-17,Tomonaga-Luttinger parameters and spin excitations in the dimerized extended Hubbard model,"We study the one-dimensional extended Hubbard model with alternating size of
the hopping integrals using the density-matrix renormalization group method. We
calculate the spin gap, the Tomonaga-Luttinger parameter, and the
charge-density-wave order parameter for various dimerizations, interaction
strengths, and band fillings. At half band-filling the spin and charge
excitations are gapped but these gaps disappear for infinitesimal hole doping.
At quarter filling, the Umklapp scattering in the half-filled lower Peierls
band generates a gap for the charge excitations but the gapless spin
excitations can be described in terms of an effective antiferromagnetic
Heisenberg model. Beyond a critical strength for the nearest-neighbor
interaction, the dimerized extended Hubbard model at quarter filling develops a
charge-density-wave ground state. The dimerization and the nearest-neighbor
Coulomb interaction strongly reduce the Tomonaga-Luttinger parameter from its
value for the bare Hubbard model. We discuss the relevance of our findings for
the Bechgaard salts.",0605433v1
2006-06-02,Effects of spin-phonon interaction on the properties of in high-T$_C$ superconductors,"The mechanism of spin-phonon coupling in high-T$_C$ copper oxides is explored
from band calculations on La$_{(2-x)}$Sr$_x$CuO$_4$ and HgBa$_2$CuO$_4$
systems. The LMTO band calculations, based on the local density approximation,
are made for cells containing frozen phonon displacements and/or spin waves
within the CuO plane. The virtual crystal approximation is used for studies of
hole doped systems. The main result is that phonons are favorable for spin
waves and vice-versa, and that pseudogaps appear naturally in the band
structures of striped materials with strong SPC. The qualitative results are
compatible with many observations showing that the properties of high-T$_C$
superconductors depend both on lattice interactions and magnetic fluctuations.
The band results are used to model various properties, mainly of the normal
state, such as isotope effects, pseudogaps, Fermi surface broadening,
T-dependence of the pseudogap, phonon softening and some aspects of
superconductivity. The possibility of perpendicular SPC is investigated, partly
by the use of a nearly free electron model.",0606066v1
1995-02-24,Gravitational waves from inspiralling compact binaries: Parameter estimation using second-post-Newtonian waveforms,"The parameters of inspiralling compact binaries can be estimated using
matched filtering of gravitational-waveform templates against the output of
laser-interferometric gravitational-wave detectors. Using a recently calculated
formula, accurate to second post-Newtonian (2PN) order [order $(v/c)^4$, where
$v$ is the orbital velocity], for the frequency sweep ($dF/dt$) induced by
gravitational radiation damping, we study the statistical errors in the
determination of such source parameters as the ``chirp mass'' $\cal M$, reduced
mass $\mu$, and spin parameters $\beta$ and $\sigma$ (related to spin-orbit and
spin-spin effects, respectively). We find that previous results using template
phasing accurate to 1.5PN order actually underestimated the errors in $\cal M$,
$\mu$, and $\beta$. For two inspiralling neutron stars, the measurement errors
increase by less than 16 percent.",9502040v1
2002-03-12,Scattering of Spinning Test Particles by Plane Gravitational and Electromagnetic Waves,"The Mathisson-Papapetrou-Dixon (MPD) equations for the motion of electrically
neutral massive spinning particles are analysed, in the pole-dipole
approximation, in an Einstein-Maxwell plane-wave background spacetime. By
exploiting the high symmetry of such spacetimes these equations are reduced to
a system of tractable ordinary differential equations. Classes of exact
solutions are given, corresponding to particular initial conditions for the
directions of the particle spin relative to the direction of the propagating
background fields. For Einstein-Maxwell pulses a scattering cross section is
defined that reduces in certain limits to those associated with the scattering
of scalar and Dirac particles based on classical and quantum field theoretic
techniques. The relative simplicity of the MPD approach and its use of
macroscopic spin distributions suggests that it may have advantages in those
astrophysical situations that involve strong classical gravitational and
electromagnetic environments.",0203038v1
2002-06-05,A mass formula for baryon resonances,"Light-baryon resonances with u,d, and s quarks only can be classified using
the non-relativistic quark model. When we assign to baryon resonances with
total angular momenta J intrinsic orbital angular momenta L and spin S we make
the following observations: plotting the squared masses of the light-baryon
resonances against these intrinsic orbital angular momenta L, Delta's with even
and odd parity can be described by the same Regge trajectory. For a given L,
nucleon resonances with spin S=3/2 are approximately degenerate in mass with
Delta resonances of same total orbital momentum L. To which total angular
momentum L and S couple has no significant impact on the baryon mass. Nucleons
with spin 1/2 are shifted in mass; the shift is - in units of squared masses -
proportional to the component in the wave function which is antisymmetric in
spin and flavor. Sequential resonances in the same partial wave are separated
in mass square by the same spacing as observed in orbital angular momentum
excitations. Based on these observations, a new baryon mass formula is proposed
which reproduces nearly all known baryon masses.",0206012v1
1994-04-21,Composite leptons and quarks constructed as triply occupied quasiparticles in quaternionic quanutm mechanics,"\noindent We propose a set of rules for constructing composite leptons and
quarks as triply occupied quasiparticles, in the quaternionic quantum mechanics
of a pair of Harari-Shupe preons $T$ and $V$. The composites fall into two
classes, those with totally antisymmetric internal wave functions, and those
with internal wave functions of mixed symmetry. The mixed symmetry states
consist of precisely the three spin 1/2 quark lepton families used in the
standard model (48 particle states, {\it not} counting the doubling arising
from antiparticles), plus one doublet of spin 3/2 quarks (24 particle states).
The antisymmetric states consist of a set of spin 3/2 leptonic states with
charges as in a standard model family (16 particle states), and a spin 1/2
leptonic fractionally charged doublet (4 particle states). We sketch ideas for
deriving our rules from a fundamental quaternionic preonic field theory.",9404134v1
2005-10-17,Long-Range GL(n) Integrable Spin Chains and Plane-Wave Matrix Theory,"Quantum spin chains arise naturally from perturbative large-N field theories
and matrix models. The Hamiltonian of such a model is a long-range deformation
of nearest-neighbor type interactions. Here, we study the most general
long-range integrable spin chain with spins transforming in the fundamental
representation of gl(n). We derive the Hamiltonian and the corresponding
asymptotic Bethe ansatz at the leading four perturbative orders with several
free parameters. Furthermore, we propose Bethe equations for all orders and
identify the moduli of the integrable system. We finally apply our results to
plane-wave matrix theory and show that the Hamiltonian in a closed sector is
not of this form and therefore not integrable beyond the first perturbative
order. This also implies that the complete model is not integrable.",0510124v2
2000-07-24,Relativistic Quark Spin Coupling Effects in the Correlations Between Nucleon Electroweak Properties,"We investigate the effect of different relativistic spin couplings of
constituent quarks on nucleon electroweak properties. Within each quark spin
coupling scheme the correlations between static electroweak observables are
found to be independent of the particular shape of the momentum part of the
nucleon light-front wave function. The neutron charge form factor is very
sensitive to different choices of spin coupling schemes once the magnetic
moment is fitted to the experimental value. However, it is found rather
insensitive to the details of the momentum part of the three-quark wave
function model.",0007055v2
2003-04-03,Total Hadron-Hadron Cross Sections at High Energies,"We calculate total hadron-hadron cross sections at high energies using the
Low-Nussinov two-gluon model of the Pomeron. The gluon exchange is represented
by a phenomenological potential including screened color-Coulomb, screened
confining, and spin-spin interactions. We use bound-state wave functions
obtained from a potential model for mesons, and a Gaussian wave function for a
proton. We evaluate total cross sections for collisions involving pion, kaon,
rho, phi, D, J/psi, psi', Upsilon, Upsilon', and the proton. We find that the
total cross sections increase with the square of the sum of the root-mean
square radii of the colliding hadrons, but there are variations arising from
the spin-spin interaction. We also calculate the total cross sections of a
mixed-color charmonium state on a pion and on a proton. The dependence of the
total cross section on the size and the color state of the charmonium is
investigated.",0304011v2
2004-11-26,Spin observables for pion photoproduction on the deuteron in the $Δ$(1232)-resonance region,"Spin observables for the three charge states of the pion for the pion
photoproduction reaction on the deuteron, $\gamma d\to\pi NN$, with polarized
photon beam and/or oriented deuteron target are predicted. For the beam-target
double-spin asymmetries, it is found that only the longitudinal asymmetries
$T_{20}^{\ell}$ and $T_{2\pm 2}^{\ell}$ do not vanish, whereas all the circular
and the other longitudinal asymmetries do vanish. The sensitivity of spin
observables to the model deuteron wave function is investigated. It has been
found that only $T_{21}$ and $T_{22}$ are sensitive to the model deuteron wave
function, in particular in the case of $\pi^0$-production above the
$\Delta$-region, and that other asymmetries are not.",0411106v1
2007-01-10,Engineering correlation and entanglement dynamics in spin systems,"We show that the correlation and entanglement dynamics of spin systems can be
understood in terms of propagation of spin waves. This gives a simple, physical
explanation of the behaviour seen in a number of recent works, in which a
localised, low-energy excitation is created and allowed to evolve. But it also
extends to the scenario of translationally invariant systems in states far from
equilibrium, which require less local control to prepare. Spin-wave evolution
is completely determined by the system's dispersion relation, and the latter
typically depends on a small number of external, physical parameters.
Therefore, this new insight into correlation dynamics opens up the possibility
not only of predicting but also of controlling the propagation velocity and
dispersion rate, by manipulating these parameters. We demonstrate this
analytically in a simple, example system.",0701053v1
2007-06-30,Causal Propagation of Spin-Cascades,"We gauge the direct product of the Proca with the Dirac equation that
describes the coupling to the electromagnetic field of the spin-cascade
(1/2,3/2) residing in the four-vector spinor and analyze propagation of its
wave fronts in terms of the Courant-Hilbert criteria. We show that the
differential equation under consideration is unconditionally hyperbolic and the
propagation of its wave fronts unconditionally causal. In this way we proof
that the irreducible spin-cascade embedded within four-vector is free from the
Velo-Zwanziger problem that plagues the Rarita-Schwinger description of
spin-3/2. The proof extends also to the direct product of two Proca equations
and implies causal propagation of the spin-cascade (0,1,2) within an
electromagnetic environment.",0707.0064v1
2007-08-06,Dynamical magnetic susceptibility in the lamellar cobaltate superconductor Na_xCoO_2$\cdot y$H_2O,"We systematically analyze the influence of the superconducting gap symmetry
and the electronic structure on the dynamical spin susceptibility in
superconducting Na_xCoO_2$\cdot y$H_2O within a three different models: the
single a_{1g}-band model with nearest-neighbor hoppings, the realistic
three-band t_{2g}-model with, and without e'_g pockets present at the Fermi
surface. We show that the magnetic response in the normal state is dominated by
the incommensurate antiferromagnetic spin density wave fluctuations at large
momenta in agreement with experimental temperature dependence of the
spin-lattice relaxation rate. Also, we demonstrate that the presence or the
absence of the e'_g-pockets at the Fermi surface does not affect significantly
this conclusion. In the superconducting state our results for d_{x^2-y^2}- or
d_{xy}-wave symmetries of the superconducting order parameter are consistent
with experimental data and exclude nodeless $d_{x^2-y^2} + id_{xy}$-wave
symmetry. We further point out that the spin-resonance peak proposed earlier is
improbable for the realistic band structure of Na_xCoO_2$\cdot y$H_2O.
Moreover, even if present the resonance peak is confined to the
antiferromagnetic wave vector and disappears away from it.",0708.0807v2
2007-08-22,Exact Solution of Strongly Interacting Quasi-One-Dimensional Spinor Bose Gases,"We present an exact analytical solution of the fundamental system of
quasi-one-dimensional spin-1 bosons with infinite delta-repulsion. The
eigenfunctions are constructed from the wave functions of non-interacting
spinless fermions, based on Girardeau's Fermi-Bose mapping, and from the wave
functions of distinguishable spins. We show that the spinor bosons behave like
a compound of non-interacting spinless fermions and non-interacting
distinguishable spins. This duality is especially reflected in the spin
densities and the energy spectrum. We find that the momentum distribution of
the eigenstates depends on the symmetry of the spin function. Furthermore, we
discuss the splitting of the ground state multiplet in the regime of large but
finite repulsion.",0708.3039v3
2007-08-23,Soliton Solution for the Spin Current in Ferromagnetic Nanowire,"We investigate the interaction of a periodic solution and one-soliton
solution for the spin-polarized current in a uniaxial ferromagnetic nanowire.
The amplitude and wave number of the periodic solution for the spin current
have the different contribution to the width, velocity, and the amplitude of
soliton solution, respectively. Moreover, we found that the soliton can be
trapped only in space with a proper condition. At last we analyze the
modulation instability and discuss dark solitary wave propagation for the spin
current on the background of a periodic solution. In some special cases the
solution can be expressed by the linear combination of periodic solution and
soliton solution.",0708.3120v1
2007-11-26,Three-Nucleon Bound State in a Spin-Isospin Dependent Three Dimensional Approach,"A spin-isospin dependent Three-Dimensional approach based on momentum vectors
for formulation of the three-nucleon bound state is presented in this paper.
The three-nucleon Faddeev equations with two-nucleon interactions are
formulated as a function of vector Jacobi momenta, specifically the magnitudes
of the momenta and the angle between them with the inclusion of the
spin-isospin quantum numbers, without employing a partial wave decomposition.
As an application the spin-isospin dependent Faddeev integral equations are
solved with Bonn-B potential. Our result for the Triton binding energy with the
value of -8.152 MeV is in good agreement with the achievements of the other
partial wave based methods.",0711.4026v2
2008-01-22,Quantum Oscillations of Tunnel Magnetoresistance Induced by Spin-Wave Excitations in Ferromagnet-Ferromagnet-Ferromagnet Double Barrier Tunnel Junctions,"The possibility of quantum oscillations of the tunnel conductance and
magnetoresistance induced by spin-wave excitations in a
ferromagnet-ferromagnet-ferromagnet double barrier tunnel junction, when the
magnetizations of the two side ferromagnets are aligned antiparallel to that of
the middle ferromagnet, is investigated in a self-consistent manner by means of
Keldysh nonequilibrium Green function method. It has been found that owing to
the s-d exchange interactions between conduction electrons and the spin density
induced by spin accumulation in the middle ferromagnet, the differential
conductance and the TMR indeed oscillate with the increase of bias voltage,
being consistent with the phenomenon that is observed recently in experiments.
The effects of magnon modes, the energy levels of electrons as well as the
molecular field in the central ferromagnet on the oscillatory transport
property of the system are also discussed.",0801.3350v1
2008-04-10,Theory of magnetic excitations in iron-based layered superconductors,"Based on the effective four-band model we analyze the spin response in the
normal and superconducting states of the Fe-pnictide superconductors. While the
normal state spin excitations are dominated by the continuum of the
interorbital antiferromagnetic fluctuations and the intraband spin density wave
fluctuations, the unconventional superconductivity yields different feedback.
The resonance peak in form of the well-defined spin exciton occurs {\it only}
for the interband scattering at the antiferromagnetic momentum ${\bf Q}_{AFM}$
for the $s_\pm$ (extended s-wave) superconducting order parameter and it
disappears rapidly for ${\bf q} < {\bf Q}_{AFM}$. The resonance feature is
extremely weak for the $d_{x^2 -y^2}$-wave order parameter due to specific
Fermi surface topology of these compounds. The essential difference between
$s_\pm$-wave and $d_{x^2 -y^2}$-wave symmetries for the magnetic excitations
can be used for experimental determination of the superconducting wave function
symmetry.",0804.1793v2
2008-04-14,Micromagnetics of single and double point contact spin torque oscillators,"In this paper we numerically conduct micromagnetic modelling to optimize
computational boundaries of magnetic thin-film elements applicable to single
and double point contact spin torque nano-oscillators. Different boundary
conditions have been introduced to compensate spin waves reflections at
boundaries that are based on extended layers, absorbing boundaries, and focal
point methods and are compared with a technique based on scattering theory. A
surface roughness boundary model is presented which is modelled according to
the Rayleigh criterion to minimize specular reflections at computational
boundaries. It is shown that the surface roughness model disperses the
reflected spin waves and improves the signal to background noise ratio. The
model is tested in comparison to conventional approaches such as extended layer
systems, variable damping constant and focal point methods for double point
contacts. The surface roughness model gives solutions that are stable in time,
in qualitative agreement with experiments and capable to reproduce phenomena
such as phase locking in double point contacts.",0804.2119v1
2008-04-28,Ising and Spin orders in Iron-based Superconductors,"Motivated by recent neutron scattering experiments, we study the ordering of
spins in the iron-based superconductors La(O_{1-x}F_x)FeAs, assuming them in
proximity to a Mott insulator in the phase diagram. The ground state of the
parent system with x = 0 is a spin density wave with ordering wave vector Q =
(0, \pi) or (\pi, 0). Upon raising the temperature, we find the system to
restore SU(2) symmetry, while an Ising symmetry remains broken, explaining the
experimentally observed lattice distortion to a monoclinic crystal structure.
Upon further temperature increase, the spins finally disorder at a second
transition. The phase transition driven by doping with charge carriers
similarly splits into an O(3) transition, and an Ising transition with z = 3 at
larger doping.",0804.4293v4
2008-07-13,Chiral spin states in the pyrochlore Heisenberg magnet: Fermionic mean-field theory and variational Monte Carlo calculations,"Fermionic mean-field theory and variational Monte Carlo calculations are
employed to shed light on the possible uniform ground states of the Heisenberg
model on the pyrochlore lattice. Among the various flux configurations, we find
the chiral spin states carrying \pm pi/2 flux through each triangular face to
be the most stable both within the mean-field theory and the projected
wave-function studies. Properties of the spin-spin correlation function and the
chirality order parameter are calculated for the projected wave functions.
Mean-field band structures are examined.",0807.2036v2
2009-02-04,Spin gap and magnetic resonance in superconducting BaFe$_{1.9}$Ni$%_{0.1}$As$_{2}$,"We use neutron spectroscopy to determine the nature of the magnetic
excitations in superconducting BaFe$_{1.9}$Ni$_{0.1}$As$_{2}$ ($T_{c}=20$ K).
Above $T_{c}$ the excitations are gapless and centered at the commensurate
antiferromagnetic wave vector of the parent compound, while the intensity
exhibits a sinusoidal modulation along the c-axis. As the superconducting state
is entered a spin gap gradually opens, whose magnitude tracks the
$T$-dependence of the superconducting gap observed by angle resolved
photoemission. Both the spin gap and magnetic resonance energies are
temperature \textit{and} wave vector dependent, but their ratio is the same
within uncertainties. These results suggest that the spin resonance is a
singlet-triplet excitation related to electron pairing and superconductivity.",0902.0813v1
2009-03-20,Quantum computing with an electron spin ensemble,"We propose to encode a register of quantum bits in different collective
electron spin wave excitations in a solid medium. Coupling to spins is enabled
by locating them in the vicinity of a superconducting transmission line cavity,
and making use of their strong collective coupling to the quantized radiation
field. The transformation between different spin waves is achieved by applying
gradient magnetic fields across the sample, while a Cooper Pair Box, resonant
with the cavity field, may be used to carry out one- and two-qubit gate
operations.",0903.3506v2
2009-05-29,A general framework for multiple scattering of polarized waves including anisotropies and Berry phase,"We develop a framework for the multiple scattering of a polarized wave. We
consider particles with spin propagating in a medium filled with scatterers. We
write the amplitudes of each spin eigenstate in a local, mobile frame. One of
the axes is in the direction of propagation of the particle. We use this
representation to define a directional Green's operator of the homogeneous
medium and also to write the spin-dependent scattering amplitudes. We show that
this representation reveals a Berry phase. We establish a generalized
Green-Dyson equation for the multiple scattering problem in this framework. We
show that the generalized Green-Dyson equation can be solved by linear algebra
if one uses a representation of the rotations based on Wigner D-matrices. The
properties of light scattering are retrieved if we use spin 1 particles. Our
theory allows to take into account several kinds of anisotropies like circular
or linear dichroism and birefringence, Faraday effects andMie scattering within
the same formalism. Several anisotropies can be present at the same time.",0905.4915v2
2009-09-02,Renormalized spin coefficients in the accumulated orbital phase for unequal mass black hole binaries,"We analyze galactic black hole mergers and their emitted gravitational waves.
Such mergers have typically unequal masses with mass ratio of the order 1/10.
The emitted gravitational waves carry the inprint of spins and mass quadrupoles
of the binary components. Among these contributions, we consider here the
quasi-precessional evolution of the spins. A method of taking into account
these third post-Newtonian (3PN) effects by renormalizing (redefining) the 1.5
PN and 2PN accurate spin contributions to the accumulated orbital phase is
developed.",0909.0487v2
2010-01-29,Spontaneous symmetry breaking in a generalized orbital compass model,"We introduce a generalized two-dimensional orbital compass model, which
interpolates continuously from the classical Ising model to the orbital compass
model with frustrated quantum interactions, and investigate it using the
multiscale entanglement renormalization ansatz (MERA). The results demonstrate
that increasing frustration of exchange interactions triggers a second order
quantum phase transition to a degenerate symmetry broken state which minimizes
one of the interactions in the orbital compass model. Using boson expansion
within the spin-wave theory we unravel the physical mechanism of the symmetry
breaking transition as promoted by weak quantum fluctuations and explain why
this transition occurs only surprisingly close to the maximally frustrated
interactions of the orbital compass model. The spin waves remain gapful at the
critical point, and both the boson expansion and MERA do not find any
algebraically decaying spin-spin correlations in the critical ground state.",1001.5457v2
2010-03-23,Investigation of the spin-glass regime between the antiferromagnetic and superconducting phases in Fe$_{1+y}$Se$_x$Te$_{1-x}$,"Using bulk magnetization along with elastic and inelastic neutron scattering
techniques, we have investigated the phase diagram of
Fe$_{1+y}$Se$_{x}$Te$_{1-x}$ and the nature of magnetic correlations in three
nonsuperconducting samples of Fe$_{1.01}$Se$_{0.1}$Te$_{0.9}$,
Fe$_{1.01}$Se$_{0.15}$Te$_{0.85}$ and Fe$_{1.02}$Se$_{0.3}$Te$_{0.7}$. A cusp
and hysteresis in the temperature dependence of the magnetization for the
$x=0.15$ and 0.3 samples indicates spin-glass (SG) ordering below $T_{\rm sg} =
23$K. Neutron scattering measurements indicate that the spin-glass behavior is
associated with short-range spin density wave (SDW) ordering characterized by a
static component and a low-energy dynamic component with a characteristic
incommensurate wave vector of ${\bf Q}_m = (0.46, 0, 0.50)$ and an anisotropy
gap of $\sim$ 2.5 meV. Our high ${\bf Q}$-resolution data also show that the
systems undergo a glassy structural distortion that coincides with the
short-range SDW order.",1003.4525v1
2010-04-14,Independent Bond Fluctuation Approximation to the Ground State of Quantum Antiferromagnets,"A simple approach to estimation of the ground state energy of quantum
antiferromagnets is developed, based on the approximation that quantum
fluctuations around different bonds are independent. The ground state energy
estimates are as good as spin wave theory or slightly better. A canonical
transformation of the spin operators to generate bond quantum fluctuations is
devised and applied to the classical ground state of the $S=\frac{1}{2}$
Heisenberg model on the square lattice. This simple picture of quantum spin
fluctuations might be useful in more complex models. The resulting nearest
neighbor and next-nearest neighbor correlations can be used in an alternative
derivation of spin waves in the Heisenberg model, giving an accurate dispersion
as well as raising and lowering operators.",1004.2330v2
2010-07-05,Spin-charge-density wave in a squircle-like Fermi surface for ultracold atoms,"We derive and discuss an experimentally realistic model describing ultracold
atoms in an optical lattice including a commensurate, but staggered, Zeeman
field. The resulting band structure is quite exotic; fermions in the third band
have an unusual rounded picture-frame Fermi surface (essentially two concentric
squircles), leading to imperfect nesting. We develop a generalized
SO(3,1)xSO(3,1) theory describing the spin and charge degrees of freedom
simultaneously, and show that the system can develop a coupled
spin-charge-density wave order. This ordering is absent in studies of the
Hubbard model that treat spin and charge density separately.",1007.0782v1
2010-07-12,Ferromagnetic Excitations in La$_{0.82}$Sr$_{0.18}$CoO$_{3}$ Observed Using Neutron Inelastic Scattering,"Polarized neutron inelastic scattering has been used to measure spin
excitations in ferromagnetic La$_{0.82}$Sr$_{0.18}$CoO$_{3}$. The magnon
spectrum of these spin excitations is well defined at low energies but becomes
heavily damped at higher energies, and can be modeled using a quadratic
dispersion. We determined a spin wave stiffness constant of $D=94\pm
3$\,meV\,\AA$^{2}$. Assuming a nearest-neighbor Heisenberg model we find
reasonable agreement between the exchange determined from D and the bulk Curie
temperature. Several possible mechanisms to account for the observed spin-wave
damping are discussed.",1007.1919v1
2010-08-31,Unusual Coupling Between Field-induced Spin Fluctuations and Spin Density Wave in Intermetallic CeAg2Ge2,"We report on the experimental evidences for an unusual coupling between the
magnetic field- induced fluctuations of correlated Ce-ions coinciding with the
discontinuous movement of the underlying spin density wave in the intermetallic
rare earth compound CeAg2Ge2. The measurements performed using neutron
scattering and magnetic Gruneisen ratio methods suggest that the coupling
onsets at H= 2.7 T, T < 3.8 K and persists to the lowest measurement
temperature T ~ 0.05 K. These measurements suggest a new mechanism behind the
spin fluctuations which can affect the intrinsic properties of the system.",1009.0037v2
2010-10-11,Parity Broken Chiral Spin Dynamics in Ba$_3$NbFe$_3$Si$_2$O$_{14}$,"The spin wave excitations emerging from the chiral helically modulated
120$^{\circ}$ magnetic order in a langasite Ba$_3$NbFe$_3$Si$_2$O$_{14}$
enantiopure crystal were investigated by unpolarized and polarized inelastic
neutron scattering. A dynamical fingerprint of the chiral ground state is
obtained, singularized by (i) spectral weight asymmetries answerable to the
structural chirality and (ii) a full chirality of the spin correlations
observed over the whole energy spectrum. The intrinsic chiral nature of the
spin waves elementary excitations is shown in absence of macroscopic time
reversal symmetry breaking.",1010.2008v2
2010-11-05,Spin-Density Wave near the Vortex Cores of Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$,"Competition with magnetism is at the heart of high temperature
superconductivity, most intensely felt near a vortex core. To investigate
vortex magnetism we have developed a spatially resolved probe using nuclear
magnetic resonance. Our spin-lattice-relaxation spectroscopy is spatially
resolved both within a conduction plane as well as from one plane to another.
With this approach we have found a spin-density wave associated with the vortex
core in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, which is expected from scanning
tunneling microscope observations of ""checkerboard"" patterns in the local
density of electronic states.[1] We determine both the spin-modulation
amplitude and decay length from the vortex core in fields up to H=30 T.",1011.1520v1
2011-01-07,A coherent triggered search for single spin compact binary coalescences in gravitational wave data,"In this paper we present a method for conducting a coherent search for single
spin compact binary coalescences in gravitational wave data and compare this
search to the existing coincidence method for single spin searches. We propose
a method to characterize the regions of the parameter space where the single
spin search, both coincident and coherent, will increase detection efficiency
over the existing non-precessing search. We also show example results of the
coherent search on a stretch of data from LIGO's fourth science run but note
that a set of signal based vetoes will be needed before this search can be run
to try to make detections.",1101.1459v1
2011-03-05,Polarized entangled Bose-Einstein condensation,"We consider a mixture of two distinct species of atoms of pseudospin-1/2 with
both intraspecies and Interspecies spin-exchange interactions, and find all the
ground stats in a general case of the parameters in the effective Hamiltonian.
In general, corresponding to the two species and two pseudo-spin states, there
are four orbital wave functions into which the atoms condense. We find that in
certain parameter regimes, the ground state is the so-called polarized
entangled Bose-Einstein condensation, i.e. in addition to condensation of
interspecies singlet pairs, there are unpaired atoms with spins polarized in
the same direction. The interspecies entanglement and polarization
significantly affect the generalized Gross-Pitaevskii equations governing the
four orbital wave functions into which the atoms condense, as an interesting
interplay between spin and orbital degrees of freedom.",1103.1021v1
2011-03-10,Suppression of Standing Spin Waves in Low-Dimensional Ferromagnets,"We examine the experimental absence of standing spin wave modes in thin
magnetic films, by means of atomistic spin dynamics simulations. Using Co on
Cu(001) as a model system, we demonstrate that by increasing the number of
layers, the ""optical"" branches predicted from adiabatic first-principles
calculations are strongly suppressed, in agreement with spin-polarized electron
energy loss spectroscopy measurements reported in the literature. Our results
suggest that a dynamical analysis of the Heisenberg model is sufficient in
order to capture the strong damping of the standing modes.",1103.1997v2
2011-04-18,Topological Spin Density Wave,"In this paper, we investigate the topological Hubbard model on honeycomb
lattice. By considering the topological properties of the magnetic state, new
types of quantum states - A-type and B-type topological spin-density-waves
(A-TSDW and B-TSDW) are explored. The low energy physics is solely determined
by its Chern-Simons-Hopf gauge field theories with different K-matrices. In the
formulism of topological field theory, we found spin-charge separated
charge-flux binding effect for A-TSDW and spin-charge synchronized charge-flux
binding effect for B-TSDW. In addition, we studied the edge states and
quantized Hall effect in different TSDWs.",1104.3601v2
2011-04-19,Antiferromagnetic spin excitations in single crystals of nonsuperconducting Li1-xFeAs,"We use neutron scattering to determine spin excitations in single crystals of
nonsuperconducting Li1-xFeAs throughout the Brillouin zone. Although angle
resolved photoemission experiments and local density approximation calculations
suggest poor Fermi surface nesting conditions for antiferromagnetic(AF) order,
spin excitations in Li1-xFeAs occur at the AF wave vectors Q = (1, 0) at low
energies, but move to wave vectors Q = (\pm 0.5, \pm0.5) near the zone boundary
with a total magnetic bandwidth comparable to that of BaFe2As2. These results
reveal that AF spin excitations still dominate the low-energy physics of these
materials and suggest both itinerancy and strong electron-electron correlations
are essential to understand the measured magnetic excitations.",1104.3653v2
2011-05-14,Anomalous tunneling of collective excitations and effects of superflow in the polar phase of a spin-1 spinor Bose-Einstein condensate,"We investigate tunneling properties of collective modes in the polar phase of
a spin-1 spinor Bose-Einstein condensate. This spinor BEC state has two kinds
of gapless modes, i.e., Bogoliubov mode and spin-wave. Within the framework of
the mean-field theory at T=0, we show that these Goldstone modes exhibit the
perfect transmission in the low-energy limit. Their anomalous tunneling
behaviors still hold in the presence of superflow, except in the critical
current state. In the critical current state, while the tunneling of Bogoliubov
mode is accompanied by finite reflection, the spin-wave still exhibit the
perfect transmission, unless the strengths of a spin-dependent and
spin-independent interactions take the same value.",1105.2857v1
2011-06-30,Spin equilibrium with or without gravitational wave emission: the case of XTE J1814-338 and SAX J1808.4-3658,"In this letter we present a new analysis of the torques acting on the
accreting millisecond X-ray pulsars SAX J1808.4-365 and XTE J1814-338, and show
how our results can be used to constrain theoretical models of the spin
evolution. In particular we find upper limits on any spin-up/down phase of XTE
J1814-338 of $|\dot{\nu}|\lesssim\,1.5\times\,10^{-14}$ Hz/s at 95% confidence
level. We examine the possibility that a gravitational wave torque may be
acting in these systems and suggest that a more likely scenario is that both
systems are close to spin equilibrium, as set by the disc/magnetosphere
interaction.",1106.6264v1
2011-08-30,Quantum criticality of dipolar spin chains,"We show that a chain of Heisenberg spins interacting with long-range dipolar
forces in a magnetic field h perpendicular to the chain exhibits a quantum
critical point belonging to the two-dimensional Ising universality class.
Within linear spin-wave theory the magnon dispersion for small momenta k is
[Delta^2 + v_k^2 k^2]^{1/2}, where Delta^2 \propto |h - h_c| and v_k^2 \propto
|ln k|. For fields close to h_c linear spin-wave theory breaks down and we
investigate the system using density-matrix and functional renormalization
group methods. The Ginzburg regime where non-Gaussian fluctuations are
important is found to be rather narrow on the ordered side of the transition,
and very broad on the disordered side.",1108.6064v3
2011-09-07,"Spin wave theory study of neutron intensity, magnetic field, and anisotropy of Type IIA FCC antiferromagnet","We study the spin dynamics in a 3D quantum antiferromagnet on a face-centered
cubic (FCC) lattice. The effects of magnetic field, single-ion anisotropy, and
biquadratic interactions are investigated using linear spin wave theory with
spins in a canted basis about the Type IIA FCC antiferromagnetic ground state
structure which is known to be stable. We calculate the expected finite
frequency neutron scattering intensity and give qualitative criteria for
typical FCC materials MnO and CoO. The magnetization reduction due to quantum
zero point fluctuations is also analyzed.",1109.1350v3
2011-09-28,Spin-polarized Dirac-cone-like surface state with $d$ character at W(110),"The surface of W(110) exhibits a Dirac-cone-like surface state with $d$
character within a spin-orbit-induced symmetry gap. As a function of wave
vector parallel to the surface, it shows nearly massless energy dispersion and
a pronounced spin polarization, which is antisymmetric with respect to the
Brillouin zone center. In addition, the observed constant energy contours are
strongly anisotropic for all energies. This discovery opens new pathways to the
study of surface spin-density waves arising from a strong Fermi surface nesting
as well as $d$-electron-based topological properties.",1109.6098v3
2011-10-03,Field-induced collective spin-exciton condensation in a quasi-2D dx2-y2-wave heavy electron superconductor,"The origin of the spin resonance observed in CeCoIn5 with Inelastic Neutron
Scattering is subject to debate. It has been shown recently that in this heavy
electron compound at low temperature an instability to a ground state with
coexisting dx2 -y2 -wave superconductivity and Spin Density Wave (SDW) order in
a magnetic field is a corollary of the consideration of a collective spin
excitation mode in a quasi-2D dx2 -y2 -wave Pauli-limited superconductor. This
provides a natural scenario for the occurence of the puzzling
high-field-low-temperature phase highlighted in CeCoIn5 . We present
perspectives on this ground state transition and propose directions for future
experiment.",1110.0387v3
2011-10-04,Two-orbital quantum spin model of magnetism in the iron pnictides,"We study a two-orbital spin model to describe (pi,0) stripe
antiferromagnetism in the iron pnictides. The ""double-spin"" model has an
on-site Hunds's coupling and inter-site interactions extending to second
neighbors (inter- and intra-orbital) on the square lattice. Using a variational
method based on a cluster decomposition, we optimize wave functions with up to
8 cluster sites (up to 2^16 variational parameters). We focus on the
anomalously small ordered moments in the stripe state of the pnictides. To
account for it, and large variations among different compounds, we show that
the second-neighbor cross-orbital exchange constant should be ferromagnetic,
which leads to ""partially hidden"" stripe order, with a moment that can be
varied over a large range by small changes in the coupling constants. In a
different parameter region, we confirm the existence of a canted state
previously found in spin-wave theory. We also identify several other phases of
the model.",1110.0761v2
2011-10-21,Magnetic properties of spin diluted iron pnictides from muSR and NMR in LaFe1-xRuxAsO,"The effect of isoelectronic substitutions on the microscopic properties of
LaFe1-xRuxAsO, for 0< x< 0.8, has been investigated by means of muSR and 139La
NMR. It was found that Ru substitution causes a progressive reduction of the
N\`eel temperature (T_N) and of the magnetic order parameter without leading to
the onset of superconductivity. The temperature dependence of 139La nuclear
spin-lattice relaxation rate 1/T_1 can be suitably described within a two-band
model. One band giving rise to the spin density wave ground-state, while the
other one is characterized by weakly correlated electrons. Fe for Ru
substitution yields to a progressive decrease of the density of states at the
Fermi level close to the one derived from band structure calculations. The
reduction of T_N with doping follows the predictions of the J_1-J_2 model on a
square lattice, which appears to be an effective framework to describe the
magnetic properties of the spin density wave ground-state.",1110.4812v1
2011-11-17,Quantum field theory from classical statistics,"An Ising-type classical statistical model is shown to describe quantum
fermions. For a suitable time-evolution law for the probability distribution of
the Ising-spins our model describes a quantum field theory for Dirac spinors in
external electromagnetic fields, corresponding to a mean field approximation to
quantum electrodynamics. All quantum features for the motion of an arbitrary
number of electrons and positrons, including the characteristic interference
effects for two-fermion states, are described by the classical statistical
model. For one-particle states in the non-relativistic approximation we derive
the Schr\""odinger equation for a particle in a potential from the time
evolution law for the probability distribution of the Ising-spins. Thus all
characteristic quantum features, as interference in a double slit experiment,
tunneling or discrete energy levels for stationary states, are derived from a
classical statistical ensemble. Concerning the particle-wave-duality of quantum
mechanics, the discreteness of particles is traced back to the discreteness of
occupation numbers or Ising-spins, while the continuity of the wave function
reflects the continuity of the probability distribution for the Ising-spins.",1111.4115v1
2012-01-01,Higher spin quaternion waves in the Klein-Gordon theory,"Electromagnetic interactions are discussed in the context of the Klein-Gordon
fermion equation. The Mott scattering amplitude is derived in leading order
perturbation theory and the result of the Dirac theory is reproduced except for
an overall factor of sixteen. The discrepancy is not resolved as the study
points into another direction. The vertex structures involved in the scattering
calculations indicate the relevance of a modified Klein-Gordon equation, which
takes into account the number of polarization states of the considered quantum
field. In this equation the d'Alembertian is acting on quaternion-like plane
waves, which can be generalized to representations of arbitrary spin. The
method provides the same relation between mass and spin that has been found
previously by Majorana, Gelfand, and Yaglom in infinite spin theories.",1201.0337v5
2012-01-16,"(PI,0) antiferromagnetic spin excitations in superconducting Rb0.82Fe1.68Se2","We use inelastic neutron scattering to show that superconducting (SC)
rubidium iron selenide Rb0.82Fe1.68Se2 exhibits antiferromagnetic (AF) spin
excitations near the in-plane wave vector Q = (PI, 0) identical to that for
iron arsenide superconductors. Moreover, we find that these excitations change
from incommensurate to commensurate with increasing energy, and occur at the
expense of spin waves associated with the coexisting sqrt(5)\timessqrt(5) block
AF phase. Since angle resolved photoemission experiments reveal no evidence for
hole-like Fermi surface at Gamma(0, 0), our results suggest that the Q = (PI,
0) excitations in SC Rb0.82Fe1.68Se2 come from localized moments and may have a
similar origin as the hourglass-like spin excitations in copper oxide
superconductors.",1201.3348v1
2012-02-06,Spin waves and revised crystal structure of honeycomb iridate Na2IrO3,"We report inelastic neutron scattering measurements on Na2IrO3, a candidate
for the Kitaev spin model on the honeycomb lattice. We observe spin-wave
excitations below 5 meV with a dispersion that can be accounted for by
including substantial further-neighbor exchanges that stabilize zig-zag
magnetic order. The onset of long-range magnetic order below 15.3 K is
confirmed via the observation of oscillations in zero-field muon-spin rotation
experiments. Combining single-crystal diffraction and density functional
calculations we propose a revised crystal structure model with significant
departures from the ideal 90 deg Ir-O-Ir bonds required for dominant Kitaev
exchange.",1202.1268v2
2012-02-20,Atomic frequency comb memory with spin wave storage in 153Eu3+:Y2SiO5,"153Eu3+:Y2SiO5 is a very attractive candidate for a long lived, multimode
quantum memory due to the long spin coherence time (~15 ms), the relatively
large hyperfine splitting (100 MHz) and the narrow optical homogeneous
linewidth (~100 Hz). Here we show an atomic frequency comb memory with spin
wave storage in a promising material 153Eu3+:Y2SiO5, reaching storage times
slightly beyond 10 {\mu}s. We analyze the efficiency of the storage process and
discuss ways of improving it. We also measure the inhomogeneous spin linewidth
of 153Eu3+:Y2SiO5, which we find to be 69 \pm 3 kHz. These results represent a
further step towards realising a long lived multi mode solid state quantum
memory.",1202.4314v1
2012-02-27,Higher spin fermions in the BTZ black hole,"Recently it has been shown that the wave equations of bosonic higher spin
fields in the BTZ background can be solved exactly. In this work we extend this
analysis to fermionic higher spin fields. We solve the wave equations for
arbitrary half-integer spin fields in the BTZ black hole background and obtain
exact expressions for their quasinormal modes. These quasinormal modes are
shown to agree precisely with the poles of the corresponding two point function
in the dual conformal field theory as predicted by the AdS/CFT correspondence.
We also obtain an expression for the 1-loop determinant in terms of the
quasinormal modes and show it agrees with that obtained by integrating the heat
kernel found by group theoretic methods.",1202.5831v1
2012-04-23,Interaction Induced Hall Response in a Spin-Orbit Coupled Bose-Einstein Condensate,"In this letter we consider the dynamic behaviors of spin-orbit coupled Bose
condensates realized in recent experiments. We show that there exists an
interaction induced ac Hall response which is absent in a non-interacting
system. This condensate has two distinct equilibrium phases known as the plane
wave phase and the stripe phase. In the plane wave phase, we show that an ac
longitudinal current will induce an ac radial current in the transverse
direction, and vice versa, as a cooperation effect of spin-velocity locking and
spin-dependent interaction. In the stripe phase, we show that the dominant
longitudinal response to a transverse radial current is sliding of the density
stripe, because it is the low-lying excitation mode originated from spontaneous
spatial translational symmetry breaking in this phase.",1204.5121v1
2012-06-12,Temperature-dependent Cross Sections for Charmonium Dissociation in Collisions with Pions and Rhos in Hadronic Matter,"Meson-charmonium dissociation reactions governed by the quark interchange are
studied with temperature-dependent quark potentials. Quark-antiquark
relative-motion wave functions and masses of charmonia and charmed mesons are
determined by the central spin-independent part of the potentials or by the
central spin-independent part and a smeared spin-spin interaction. The
prominent temperature dependence of the masses is found. Based on the
potentials, the wave functions, and the meson masses, we obtain
temperature-dependent cross sections for fifteen pion-charmonium and
rho-charmonium dissociation reactions. The numerical cross sections are
parametrized for future applications in hadronic matter. The particular
temperature dependence of the J/psi bound state leads to unusual behavior of
the cross sections for endothermic J/psi dissociation reactions. The quantum
numbers of psi' and chi_c can not make their difference in mass in the
temperature region 0.6T_c < T < T_c, but can make the psi' dissociation
different from the chi_c dissociation.",1206.2440v1
2012-07-09,Enhanced spin Hall effect in strong magnetic disorder,"We consider a two-dimensional electron gas in an inversion asymmetric layer
and in the presence of spatially distributed magnetic impurities. We
investigate the relationship between the geometrical properties of the
wave-function and the system's spin dependent transport properties. A
localization transition, arising when disorder is increased, is exhibited by
the appearance of a fractal state with finite inverse participation ratio.
Below the transition, interference effects modify the carrier's diffusion, as
revealed by the dependence on the scattering time of the power law exponents
characterizing the spreading of a wave packet. Above the transition, in the
strong disorder regime, we find that the states are spin polarized and
localized around the impurities. A significant enhancement of the spin current
develops in this regime.",1207.2100v1
2012-07-16,Spin excitations in layered antiferromagnetic metals and superconductors,"The proximity of antiferromagnetic order in high-temperature superconducting
materials is considered a possible clue to the electronic excitations which
form superconducting pairs. Here we study the transverse and longitudinal spin
excitation spectrum in a one-band model in the pure spin density wave (SDW)
state and in the coexistence state of SDW and the superconductivity. We start
from a Stoner insulator and study the evolution of the spectrum with doping,
including distinct situations with only hole pockets, with only electron
pockets and with pockets of both types. In addition to the usual spin-wave
modes, in the partially gapped cases we find significant weight of low-energy
particle-hole excitations. We discuss the implications of our findings for
neutron scattering experiments and for theories of Cooper-pairing in the
metallic SDW state.",1207.3834v1
2012-08-24,Approximate Dirac solutions of complex -symmetric Pöschl-Teller potential in view of spin and pseudospin symmetries,"By employing an exponential-type approximation scheme to replace the
centrifugal term, we have approximately solved the Dirac equation for spin-
particle subject to the complex -symmetric scalar and vector P\""oschl-Teller
(PT) potentials with arbitrary spin-orbit -wave states in view of spin and
pseudospin (p-spin) symmetries. The real bound-state energy eigenvalue equation
and the corresponding two-spinor components wave function expressible in terms
of the hypergeometric functions are obtained by means of the wave function
analysis. The spin- Dirac equation and the spin- Klein-Gordon (KG) equation
with the complex P\""oschl-Teller potentials share the same energy spectrum
under the choice of (i.e., exact spin and p-spin symmetries).",1208.4960v1
2012-10-01,Pair-density wave states through spin-orbit coupling in multilayer superconductors,"Spin singlet superconductors with quasi-two dimensional multilayer structure
are studied in high magnetic fields. Specifically we concentrate on bi- and
tri-layer systems whose layers by symmetry are subject Rashba-type spin-orbit
coupling. The combination of magnetic field and spin-orbit coupling leads to a
first order phase transition between different states of layer-dependent
superconducting order parameters upon rising the magnetic field. In this
context we distinguish the low-field Bardeen-Cooper-Schrieffer state where all
layers have order parameters of the same sign and the high-field pair-density
wave state where the layer-dependent order parameters change the sign at the
center layer. We also show that progressive paramagnetic limiting effects yield
additional features in the H-T phase diagram. As possible realizations of such
unusual superconducting phases we consider artificial superlattices of
CeCoIn_5, as well as some multilayer high-T_c cuprates.",1210.0315v1
2012-11-28,Nonlocal optical generation of spin and charge currents on the surface of magnetic insulators using total absorption and surface plasmons,"We study the nonlocal spin and charge current generation in a finite metallic
element on the surface of magnetic insulators such as \tcb{yttrium iron garnet}
due to the absorption of the magnetic surface plasmon (MSP). Whereas a surface
plasmon is completely reflected by a metal, \tcb{an} MSP \tcb{can be} absorbed
\tcb{due to the absence of backward states}. The \tcb{injection of} MSP
generates a voltage in the longitudinal direction parallel to the wave vector,
\tcb{with the voltage} proportional to input power. If the metal is a
ferromagnet, a spin current can also be \tcb{induced} in the longitudinal
direction. Our \tcb{results provide a way to improve upon} integrated circuits
of spintronics and spin wave logic devices.",1211.6716v1
2012-12-20,Gravitational waveforms for unequal mass black hole binaries detectable by KAGRA,"Gravitational waveforms generated by unequal mass black hole binaries are
expected to be common sources for future gravitational wave detectors. We
derived the waveforms emitted by such systems during the last part of the
inspiral, when the larger spin dominates over the orbital angular momentum and
the smaller spin is negligible. These Spin-Dominated Waveforms (SDW) arise as a
double expansion in the post-Newtonian parameter and another parameter
proportional to the ratio of the orbital angular momentum and the dominant
spin. The time spent by the gravitational wave as an SDW in the sensitivity
range of the KAGRA detector is presented for the first time.",1212.4973v1
2013-02-27,Anomalous Local Criticality in Heavy Fermion Metals from Holography,"We propose a holographic theory to explain numbers of anomalous critical
phenomena observed in certain heavy-fermion metals, e.g.
$\mathrm{CeCu_{5.9}Au_{0.1}}$ and $\mathrm{YbRh_{2}(Si_{0.95}Ge_{0.05}})_{2}$,
which are incompatible with any conventional spin-density-wave quantum critical
point theory. We show that the non-Gaussian nature of the fixed point from
holography plays an essential role in the physics of these materials near a
quantum critical point, which is not in the same universality class of the
spin-density-wave type fixed point. The critical spin fluctuations at the
non-Gaussian fixed point are strongly anisotropic, localized in spatial
directions and critical in temporal direction with critical exponent 2/3 in
frequency over temperature dependence at low temperature. The local critical
exponent tends to unity which leads to a constant spin relaxation rate in the
quantum critical regime at high temperature. The stability of the fixed point
is also discussed.",1302.6650v2
2013-04-23,Breakdown of Fermi liquid behavior near the hot spots in a two-dimensional model: A two-loop renormalization group analysis,"Motivated by a recent experimental observation of a nodal liquid on both
single crystals and thin films of Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ by
Chatterjee \emph{et al.} [Nature Physics \textbf{6}, 99 (2010)], we perform a
field-theoretical renormalization group (RG) analysis of a two-dimensional
model consisting of eight points located near the ""hot spots"" on the Fermi
surface which are directly connected by spin density wave ordering wave vector.
We derive RG equations up to two-loop order describing the flow of renormalized
couplings, quasiparticle weight, several order-parameter response functions,
and uniform spin and charge susceptibilities of the model. We find that while
the order-parameter susceptibilities investigated here become non-divergent at
two loops, the quasiparticle weight vanishes in the low-energy limit,
indicating a breakdown of Fermi liquid behavior at this RG level. Moreover,
both uniform spin and charge susceptibilities become suppressed in the scaling
limit which indicate gap openings in both spin and charge excitation spectra of
the model.",1304.6384v2
2013-06-27,Finding the Rashba-type spin-splitting from interband scattering in quasiparticle interference maps,"We have studied the BiCu$_2$/Cu(111) surface alloy using low-temperature
scanning tunneling microscopy and spectroscopy. We observed standing waves
caused by scattering off defects and step edges. Different from previous
studies on similar Rashba-type surfaces, we identified multiple scattering
vectors that originate from various intraband as well as interband scattering
processes. A detailed energy-dependent analysis of the standing-wave patterns
enables a quantitative determination of band dispersions, including the Rashba
splitting. The results are in good agreement with ARPES data and demonstrate
the usefulness of this strategy to determine the band structure of Rashba
systems. The lack of other possible scattering channels will be discussed in
terms of spin conservation and hybridization effects. The results open new
possibilities to study spin-dependent scattering on complex spin-orbit coupled
surfaces.",1306.6662v1
2013-10-11,Analytical theory of modulated magnetic solitons,"Droplet solitons are coherently precessing solitary waves that have been
recently realized in thin ferromagnets with perpendicular anisotropy.In the
strongly nonlinear regime, droplets can be well approximated by a slowly
precessing, circular domain wall with a hyperbolic tangent form. Utilizing this
representation, this work develops a general droplet modulation theory and
applies it to study the long range effects of the magnetostatic field and a
nanocontact spin torque oscillator (NC-STO) where spin polarized currents act
as a gain source to counteract magnetic damping. An analysis of the dynamical
equations for the droplet's center, frequency and phase demonstrates a negative
processional frequency shift due to long range dipolar interactions, dependent
on film thickness. Further analysis also demonstrates the onset of a
saddle-node bifurcation at the minimum sustaining current for the NC-STO. The
basin of attraction associated with the stable node demonstrates that spin
torque enacts a restoring force to excursions of the droplet from the
nanocontact center, observed previously in numerical simulations. Large
excursions lead to the droplet's eventual decay into spin waves.",1310.3118v1
2013-10-28,Magnetic structure and spin excitations in BaMn2Bi2,"We present a single crystal neutron scattering study of BaMn2Bi2, a recently
synthesized material with the same ThCr2Si2-type structure found in several
Fe-based unconventional superconducting materials. We show long range magnetic
order, in the form of a G-type antiferromagnetic structure, to exist up to 390
K with an indication of a structural transition at 100 K. Utilizing inelastic
neutron scattering we observe a spin-gap of 16meV, with spin-waves extending up
to 55 meV. We find these magnetic excitations to be well fit to a J1-J2-Jc
Heisenberg model and present values for the exchange interactions. The spin
wave spectrum appears to be unchanged by the 100 K structural phase transition.",1310.7317v1
2013-11-22,Black hole remnant of black hole-neutron star coalescing binaries with arbitrary black hole spin,"A model for determining the dimensionless spin parameter and mass of the
black hole remnant of black hole-neutron star mergers with arbitrary initial
black hole spin angular momentum, binary mass ratio, and neutron star mass and
cold equation of state is formulated. Tests against numerical-relativity
results are carried out, showing that both the dimensionless spin parameter and
the final mass are accurately reproduced. For the first time, the behaviour of
both quantities and of the l = 2, m = 2, n = 0 quasinormal mode frequency is
inspected throughout the parameter space. Predictions of this frequency may be
exploited to guide gravitational wave modelling and detection efforts, and to
extract physical information from detected gravitational wave signals that
would help us break degeneracies between binary black hole and black
hole-neutron star systems, improve our understanding of compact binary
formation, and constrain the neutron star equation of state.",1311.5931v2
2014-01-24,Three-electron spin states and entanglement states,"In this paper, we have given the symmetrical and antisymmetrical spin and
space wave functions of three-electron, and further given the full total
entanglement states for the three-electron, which are related to their space
and spin wave function. When we study particles entanglement we not only
consider their spin entanglement and also consider their space entanglement.
Otherwise, we find that electrons entanglement are restricted to the teeny
range, when electrons exceed the space range, their entanglement should be
broken down even disappearance, which is accordance with the experiments
results.",1401.6874v1
2014-02-17,Frequency domain reduced order models for gravitational waves from aligned-spin compact binaries,"Black-hole binary coalescences are one of the most promising sources for the
first detection of gravitational waves. Fast and accurate theoretical models of
the gravitational radiation emitted from these coalescences are highly
important for the detection and extraction of physical parameters. Spinning
effective-one-body (EOB) models for binaries with aligned spins have been shown
to be highly faithful, but are slow to generate and thus have not yet been used
for parameter estimation studies. I provide a frequency-domain singular value
decomposition (SVD)-based surrogate reduced order model that is thousands of
times faster for typical system masses and has a faithfulness mismatch of
better than $\sim 0.1\%$ with the original SEOBNRv1 model for advanced LIGO
detectors. This model enables parameter estimation studies up to
signal-to-noise ratios (SNRs) of 20 and even up to SNR 50 for total masses
below $50 M_\odot$. This article discusses various choices for approximations
and interpolation over the parameter space that can be made for reduced order
models of spinning compact binaries, provides a detailed discussion of errors
arising in the construction and assesses the fidelity of such models.",1402.4146v2
2014-03-19,Coherence rephasing combined with spin-wave storage using chirped control pulses,"Photon-echo based optical quantum memory schemes often employ intermediate
steps to transform optical coherences to spin coherences for longer storage
times. We analyze a scheme that uses three identical chirped control pulses for
coherence rephasing in an inhomogeneously broadened ensemble of three-level
$\Lambda$-systems. The pulses induce a cyclic permutation of the atomic
populations in the adiabatic regime. Optical coherences created by a signal
pulse are stored as spin coherences at an intermediate time interval, and are
rephased for echo emission when the ensemble is returned to the initial state.
Echo emission during a possible partial rephasing when the medium is inverted
can be suppressed with an appropriate choice of control pulse wavevectors. We
demonstrate that the scheme works in an optically dense ensemble, despite
control pulse distortions during propagation. It integrates conveniently the
spin-wave storage step into memory schemes based on a second rephasing of the
atomic coherences.",1403.4801v2
2014-03-25,Spin waves in the anisotropic fcc kagome antiferromagnet,"Spin wave calculations demonstrate that the macroscopic continuous degeneracy
associated with the two-dimensional kagome Heisenberg spin lattice persists in
the case of the stacked fcc structure giving rise to zero energy modes in three
dimensions. The addition of an effective local cubic anisotropy is shown to
remove this continuous degeneracy and introduce a gap in the spectrum as well
as modify the inelastic scattering function $S({\bf q},\omega)$. This scenario
supports earlier Monte Carlo simulations which indicate that the phase
transition to long range $q=0$ magnetic order is driven to be discontinuous by
critical fluctuations associated with the large degeneracy in the absence of
anisotropy, but becomes continuous with the addition of anisotropy. The results
are relevant to Ir-Mn alloys which are widely used in the magnetic storage
industry in thin film form as the antiferromagnetic pinning layer in spin-valve
structures.",1403.6352v1
2014-04-07,Small mass plunging into a Kerr black hole: Anatomy of the inspiral-merger-ringdown waveforms,"We numerically solve the Teukolsky equation in the time domain to obtain the
gravitational-wave emission of a small mass inspiraling and plunging into the
equatorial plane of a Kerr black hole. We account for the dissipation of
orbital energy using the Teukolsky frequency-domain gravitational-wave fluxes
for circular, equatorial orbits, down to the light-ring. We consider Kerr spins
$-0.99 \leq q \leq 0.99$, and compute the inspiral-merger-ringdown (2,2),
(2,1), (3,3), (3,2), (4,4), and (5,5) modes. We study the large-spin regime,
and find a great simplicity in the merger waveforms, thanks to the extremely
circular character of the plunging orbits. We also quantitatively examine the
mixing of quasinormal modes during the ringdown, which induces complicated
amplitude and frequency modulations in the waveforms. Finally, we explain how
the study of small mass-ratio black-hole binaries helps extending
effective-one-body models for comparable-mass, spinning black-hole binaries to
any mass ratio and spin magnitude.",1404.1819v1
2014-07-25,Far-from-equilibrium spin transport in Heisenberg quantum magnets,"We study experimentally the far-from-equilibrium dynamics in ferromagnetic
Heisenberg quantum magnets realized with ultracold atoms in an optical lattice.
After controlled imprinting of a spin spiral pattern with adjustable wave
vector, we measure the decay of the initial spin correlations through
single-site resolved detection. On the experimentally accessible timescale of
several exchange times we find a profound dependence of the decay rate on the
wave vector. In one-dimensional systems we observe diffusion-like spin
transport with a dimensionless diffusion coefficient of 0.22(1). We show how
this behavior emerges from the microscopic properties of the closed quantum
system. In contrast to the one-dimensional case, our transport measurements for
two-dimensional Heisenberg systems indicate anomalous super-diffusion.",1407.6934v2
2014-08-05,Imaging two-component nature of Dirac-Landau levels in the topological surface state of Bi2Se3,"Massless Dirac electrons in condensed matter have attracted considerable
attention. Unlike conventional electrons, Dirac electrons are described in the
form of two-component wave functions. In the surface state of topological
insulators, these two components are associated with the spin degrees of
freedom, hence governing the magnetic properties. Therefore, the observation of
the two-component wave function provides a useful clue for exploring the novel
spin phenomena. Here we show that the two-component nature is manifested in the
Landau levels (LLs) whose degeneracy is lifted by a Coulomb potential. Using
spectroscopic-imaging scanning tunneling microscopy, we visualize energy and
spatial structures of LLs in a topological insulator Bi2Se3. The observed
potential-induced LL splitting and internal structures of Landau orbits are
distinct from those in a conventional electron system and are well reproduced
by a two-component model Dirac Hamiltonian. Our model further predicts
non-trivial energy-dependent spin-magnetization textures in a potential
variation. This provides a way to manipulate spins in the topological surface
state.",1408.0873v1
2014-08-18,Probing the stability of the spin liquid phases in the Kitaev-Heisenberg model using tensor network algorithms,"We study the extent of the spin liquid phases in the Kitaev-Heisenberg model
using infinite Projected Entangled-Pair States tensor network ansatz wave
functions directly in the thermodynamic limit. To assess the accuracy of the
ansatz wave functions we perform benchmarks against exact results for the
Kitaev model and find very good agreement for various observables. In the case
of the Kitaev-Heisenberg model we confirm the existence of 6 different phases:
N\'eel, stripy, ferromagnetic, zigzag and two spin liquid phases. We find
finite extents for both spin liquid phases and discontinuous phase transitions
connecting them to symmetry-broken phases.",1408.4020v2
2014-10-07,Hydrodynamics of Turning Flocks,"We present a hydrodynamic model of flocking that generalizes the familiar
Toner-Tu equations to incorporate turning inertia of well-polarized flocks. The
continuum equations controlled by only two dimensionless parameters,
orientational inertia and alignment strength, are derived by coarse graining
the inertial spin model recently proposed by Cavagna et al. The interplay
between orientational inertia and bend elasticity of the flock yields
anisotropic spin waves that mediate the propagation of turning information
throughout the flock. The coupling between spin current density to the local
vorticity field through a nonlinear friction gives rise to a hydrodynamic mode
with angular-dependent propagation speed at long wavelength. This mode goes
unstable as a result of the growth of bend and splay deformations augmented by
the spin wave, signaling the transition to complex spatio-temporal patterns of
continuously turning and swirling flocks.",1410.1827v4
2014-11-02,Spin relaxation in strained graphene nanoribbons: armchair vs zigzag edges,"We study the influence of ripple waves originating from the electromechanical
effects on spin relaxation caused by electromagnetic fields in armchair and
zigzag graphene nanoribbons (GNRs). By utilizing analytical expressions
supported by numerical simulations, we show that it is possible to tune the
spin flip behaviors ON and OFF due to ripple waves in GNRs for potential
applications in straintronic devices. This finding is similar to recently made
observations on the design of spintronic devices in III-V semiconductor quantum
dots, where the sign change in the effective Land$\mathrm{\acute{e}}$
$g$-factor can be engineered with the application of gate controlled electric
fields. In particular, we show that the tuning of spin extends to larger widths
for the armchair GNRs than for the zigzag GNRs. Here we also report that the
relaxation rate vanishes like $L^5$.",1411.0195v1
2015-01-29,Controlled rephasing of single collective spin excitations in a cold atomic quantum memory,"We demonstrate active control of inhomogeneous dephasing and rephasing for
single collective atomic spin excitations (spin-waves) created by spontaneous
Raman scattering in a quantum memory based on cold $^{87}$Rb atoms. The control
is provided by a reversible external magnetic field gradient inducing an
inhomogeneous broadening of the atomic hyperfine levels. We demonstrate
experimentally that active rephasing preserves the single photon nature of the
retrieved photons. Finally, we show that the control of the inhomogeneous
dephasing enables the creation of time-separated spin-waves in a single
ensemble, followed by a selective readout in time. This is an important step
towards the implementation of a functional temporally multiplexed quantum
repeater node.",1501.07559v1
2015-03-10,Microwave-induced dynamic switching of magnetic skyrmion cores in nanodots,"The nonlinear dynamic behavior of a magnetic skyrmion in circular nanodots
was studied numerically by solving the Landau-Lifshitz-Gilbert equation with a
classical spin model. We show that a skyrmion core reversal can be achieved
within nanoseconds using a perpendicular oscillating magnetic field. Two
symmetric switching processes that correspond to excitations of the breathing
mode and the mixed mode (combination of the breathing mode and a radial
spin-wave mode) are identified. For excitation of the breathing mode, the
skyrmion core switches through nucleation of a new core from a transient
uniform state. In the mixed mode, the skyrmion core reverses with the help of
spins excited both at the edge and core regions. Unlike the magnetic vortex
core reversal, the excitation of radial spin waves does not dominate the
skyrmion core reversal process.",1503.02869v1
2015-03-17,"Topological, non topological and instanton droplets driven by spin-transfer torque in materials with perpendicular magnetic anisotropy and Dzyaloshinskii-Moriya Interaction","The interfacial Dzyaloshinskii-Moriya Interaction can modify the topology of
droplets excited by a localized spin-polarized current. Here, we show that, in
addition to the stationary droplet excitations with skyrmion number either one
(topological) or zero (non-topological), there exists, for a fixed current, an
excited mode with a non-stationary time behavior. We call this mode ""instanton
droplet"", which is characterized by time domain transitions of the skyrmion
number. These transitions are coupled to an emission of incoherent spin-waves
that can be observed in the frequency domain as a source of noise. Our results
are interesting from a fundamental point of view to study spin-wave emissions
due to a topological transition in current-driven systems, and could open the
route for experiments based on magnetoresistance effect for the design of a
further generation of nanoscale microwave oscillators.",1503.05161v2
2015-03-29,Low-non-linearity spin-torque oscillations driven by ferromagnetic nanocontacts,"Spin-torque oscillators are strong candidates as nano-scale microwave
generators and detectors. However, because of large amplitude-phase coupling
(non-linearity), phase noise is enhanced over other linear auto-oscillators.
One way to reduce nonlinearity is to use ferromagnetic layers as a resonator
and excite them at localized spots, making a resonator-excitor pair. We
investigated the excitation of oscillations in dipole-coupled ferromagnetic
layers, driven by localized current at ferromagnetic nano-contacts.
Oscillations possessed properties of optical-mode spin-waves and at low field
($\approx$200 Oe) had high frequency (15 GHz), a moderate precession amplitude
(2--3$^\circ$), and a narrow spectral linewidth ($<$3 MHz) due to localized
excitation at nano-contacts. Micromagnetic simulation showed emission of
resonator's characteristic optical-mode spin-waves from disturbances generated
by domain-wall oscillations at nano-contacts.",1503.08408v2
2015-06-30,"Nematicity, magnetic fluctuation and ferro-spin-orbital ordering in BaFe$_2$As$_2$ family","Through detailed electronic structure simulations we show that the electronic
orbital ordering (between d$_{yz}$ and d$_{xz}$ bands) takes place due to local
breaking of in-plane symmetry that generates two non-equivalent $a$, $b$
directions in 122 family of Fe-based superconductors. Orbital ordering is
strongly anisotropic and the temperature dependence of the corner zone orbital
order maps to that of the orthorhombicity parameter. Orbital anisotropy results
in two distinct spin density wave nesting wave vectors and causes inter-orbital
charge and spin fluctuations. Temperature dependence of the orbital order is
proportional to the nematic order and it sets in at a temperature where
magnetic fluctuation starts building. Magnetic fluctuations in the orthorhombic
phase is characterized through evolution of Stoner factor which reproduces
experimentalfindings very accurately. Orbital ordering becomes strongly spin
dependent in presence of magnetic interaction. Occupation probabilities of all
the Fe-d-orbitals exhibit temperature dependence indicating their possible
contribution in orbital fluctuation. This need to be contrasted with the usual
definition of nematic order parameter (n$_{d_{xz}}$-n$_{d_{yz}}$). Relationship
among orbital fluctuations, magnetic fluctuations and nematicity are
established.",1506.08948v2
2015-07-01,Dynamical spin-density waves in a spin-orbit-coupled Bose-Einstein condensate,"Synthetic spin-orbit (SO) coupling, an important ingredient for quantum
simulation of many exotic condensed matter physics, has recently attracted
considerable attention. The static and dynamic properties of a SO coupled
Bose-Einstein condensate (BEC) have been extensively studied in both theory and
experiment. Here we numerically investigate the generation and propagation of a
\textit{dynamical} spin-density wave (SDW) in a SO coupled BEC using a fast
moving Gaussian-shaped barrier. We find that the SDW wavelength is sensitive to
the barrier's velocity while varies slightly with the barrier's peak potential
or width. We qualitatively explain the generation of SDW by considering a
rectangular barrier in a one dimensional system. Our results may motivate
future experimental and theoretical investigations of rich dynamics in the SO
coupled BEC induced by a moving barrier.",1507.00318v1
2015-08-31,Near-extremal black holes as initial conditions of long GRB-supernovae and probes of their gravitational wave emission,"Long gamma-ray bursts (GRBs) associated with supernovae and short GRBs with
Extended Emission (SGRBEE) from mergers are probably powered by black holes as
a common inner engine, as their prompt GRB emission satisfies the same Amati
correlation in the $E_{p,i}-E_{iso}$ plane. We introduce modified Bardeen
equations to identify hyper-accretion driving newly formed black holes in
core-collapse supernovae to near-extremal spin as a precursor to prompt GRB
emission. Subsequent spin-down is observed in the BATSE catalog of long GRBs.
Spin-down provides a natural unification of long durations associated with the
lifetime of black hole spin for normal long GRBs and SGRBEEs, given the absence
of major fallback matter in mergers. The results point to major emissions
unseen in high frequency gravitational waves. A novel matched filtering method
is described for LIGO-Virgo and KAGRA broadband probes of nearby core-collapse
supernovae at essentially maximal sensitivity.",1509.00407v1
2015-09-28,Magnetoelectric Effects in the Spiral Magnets CuCl$_{2}$ and CuBr$_{2}$,"The nature and symmetry of the transition mechanisms in the spin-spiral
copper halides CuCl$_2$ and CuBr$_2$ are analyzed theoretically. The
magnetoelectric effects observed in the two multiferroic compounds are
described and their phase diagram at zero and applied magnetic fields are
worked out. The emergence of the electric polarization at zero field below the
paramagnetic phase is shown to result from the coupling of two distinct
spin-density waves and to be only partly related to the Dzialoshinskii-Moriya
interactions. Applying a magnetic field along the two-fold monoclinic axis of
CuCl$_2$ yields a decoupling of the spin-density waves modifying the symmetry
of the phase and the spin-spiral orientation. The remarkable periodic
dependences of the magnetic susceptibility and polarization, on rotating the
field in the monoclinic plane, are described theoretically.",1509.08410v1
2015-11-19,Spin paramagnetic deformation of a neutron star,"Quantum mechanical corrections to the hydromagnetic force balance equation,
derived from the microscopic Schr\""{o}dinger-Pauli theory of quantum plasmas,
modify the equilibrium structure and hence the mass quadrupole moment of a
neutron star. It is shown here that the dominant effect --- spin paramagnetism
--- is most significant in a magnetar, where one typically has
$\mu_{B}|\boldsymbol{B}|\gtrsim k_B T_e$, where $\mu_{B}$ is the Bohr magneton,
$\boldsymbol{B}$ is the magnetic field, and $T_e$ is the electron temperature.
The spin paramagnetic deformation of a nonbarotropic magnetar with a linked
poloidal-toroidal magnetic field is calculated to be up to ${{\sim 10}}$ times
greater than the deformation caused solely by the Lorentz force. It depends on
the degree of Pauli blocking by conduction electrons and the propensity to form
magnetic domains, processes which are incompletely modelled at magnetar field
strengths. The star becomes more oblate, as the toroidal field component
strengthens. The result implies that existing classical predictions
underestimate the maximum strength of the gravitational wave signal from
rapidly spinning magnetars at birth. Turning the argument around, future
gravitational-wave upper limits of increasing sensitivity will place
ever-stricter constraints on the physics of Pauli blocking and magnetic domain
formation under magnetar conditions.",1511.06124v1
2015-12-02,Optically tunable spin transport on the surface of a topological insulator,"The emerging field of spinoptronics has a potential to supersede the
functionality of modern electronics, while a proper description of strong
light-matter coupling pose the most intriguing questions from both fundamental
scientific and technological perspectives. In this paper we address a highly
relevant issue for such a development. We theoretically explore spin dynamics
on the surface of a 3D topological insulator (TI) irradiated with an
off-resonant high-frequency electromagnetic wave. The strong coupling between
electrons and the electromagnetic wave drastically modifies the spin properties
of TI. The effects of irradiation are shown to result in anisotropy of electron
energy spectrum near the Dirac point and suppression of spin current and are
investigated in detail in this work.",1512.00798v2
2016-01-17,Consistent quantization of massless fields of any spin and the generalized Maxwell's equations,"A simplified formalism of first quantized massless fields of any spin is
presented. The angular momentum basis for particles of zero mass and finite
spin s of the D^(s-1/2,1/2) representation of the Lorentz group is used to
describe the wavefunctions. The advantage of the formalism is that by equating
to zero the s-1 components of the wave functions, the 2s-1 subsidiary
conditions (needed to eliminate the non-forward and non-backward helicities)
are automatically satisfied. Probability currents and Lagrangians are derived
allowing a first quantized formalism. A simple procedure is derived for
connecting the wave functions with potentials and gauge conditions. The spin 1
case is of particular interest and is described with the D^(1/2,1/2) vector
representation of the well known self-dual representation of the Maxwell's
equations. This representation allows us to generalize Maxwell's equations by
adding the E_0 and B_0 components to the electric and magnetic four-vectors.
Restrictions on their existence are discussed.",1601.08223v1
2016-04-09,Interaction Corrections to Spin-Wave Theory in the Large-S Limit of the Quantum Heisenberg Ferromagnet,"The Quantum Heisenberg Ferromagnet can be naturally reformulated in terms of
interacting bosons (called spin waves or magnons) as an expansion in the
inverse spin size. We calculate the first order interaction correction to the
free energy, as an upper bound in the limit where the spin size $S \to \infty$
and $\beta S$ is fixed ($\beta$ being the inverse temperature). Our result is
valid in two and three spatial dimensions. We extrapolate our result to compare
with Dyson's low-temperature expansion. While our first-order correction has
the expected temperature dependance, in higher orders of the perturbation
theory cancellations are necessary.",1604.02548v2
2016-07-25,Damping of parametrically excited magnons in the presence of the longitudinal spin Seebeck effect,"The impact of the longitudinal spin Seebeck effect (LSSE) on the magnon
damping in magnetic-insulator/nonmagnetic-metal bilayers was recently discussed
in several reports. However, results of those experiments can be blurred by
multimode excitation within the measured linewidth. In order to avoid possible
intermodal interference, we investigated the damping of a single magnon group
in a platinum covered Yttrium Iron Garnet (YIG) film by measurement of the
threshold of its parametric excitation. Both dipolar and exchange spin-wave
branches were probed. It turned out that the LSSE-related modification of
spin-wave damping in a micrometer-thick YIG film is too weak to be observed in
the entire range of experimentally accessible wavevectors. At the same time,
the change in the mean temperature of the YIG layer, which can appear by
applying a temperature gradient, strongly modifies the damping value.",1607.07274v1
2016-07-29,Spin-polarizing interferometric beam splitter for free electrons,"A spin-polarizing electron beam splitter is described which relies on an
arrangement of linearly polarized laser waves of nonrelativistic intensity. An
incident electron beam is first coherently scattered off a bichromatic laser
field, splitting the beam into two portions, with electron spin and momentum
being entangled. Afterwards, the partial beams are coherently superposed in an
interferometric setup formed by standing laser waves. As a result, the outgoing
electron beam is separated into its spin components along the laser magnetic
field, which is shown by both analytical and numerical solutions of Pauli's
equation. The proposed laser field configuration thus exerts the same effect on
free electrons like an ordinary Stern-Gerlach magnet does on atoms.",1607.08793v2
2016-10-12,Quantum Critical Point revisited by the Dynamical Mean Field Theory,"Dynamical mean field theory is used to study the quantum critical point (QCP)
in the doped Hubbard model on a square lattice. The QCP is characterized by a
universal scaling form of the self energy and a spin density wave instability
at an incommensurate wave vector. The scaling form unifies the low energy kink
and the high energy waterfall feature in the spectral function, while the spin
dynamics includes both the critical incommensurate and high energy
antiferromagnetic paramagnons. We use the frequency dependent four-point
correlation function of spin operators to calculate the momentum dependent
correction to the electron self energy. Our results reveal a substantial
difference with the calculations based on the Spin-Fermion model which
indicates that the frequency dependence of the the quasiparitcle-paramagnon
vertices is an important factor.",1610.03720v1
2016-10-14,Electric-field tunable spin waves in PMN-PT/NiFe heterostructure: experiment and micromagnetic simulations,"We present a comprehensive theoretical and experimental study of
voltage-controlled standing spin waves resonance (SSWR) in PMN-PT/NiFe
multiferroic heterostructures patterned into microstrips. A spin-diode
technique was used to observe ferromagnetic resonance (FMR) mode and SSWR in
NiFe strip mechanically coupled with a piezoelectric substrate. Application of
an electric field to a PMNPT creates a strain in permalloy and thus shifts the
FMR and SSWR fields due to the magnetostriction effect. The experimental
results are compared with micromagnetic simulations and a good agreement
between them is found for dynamics of FMR and SSWR with and without electric
field. Moreover, micromagnetic simulations enable us to discuss the amplitude
and phase spatial distributions of FMR and SSWR modes, which are not directly
observable by means of spin diode detection technique.",1610.04500v1
2016-10-30,Remnant of binary black-hole mergers: New simulations and peak luminosity studies,"We present the results of 61 new simulations of nonprecessing spinning black
hole binaries with mass ratios $q=m_1/m_2$ in the range $1/3\leq q\leq1$ and
individual spins covering the parameter space $-0.85\leq\alpha_{1,2}\leq0.85$.
We additionally perform 10 new simulations of nonspinning black hole binaries
with mass ratios covering the range $1/6\leq q<1$. We follow the evolution for
typically the last ten orbits before merger down to the formation of the final
remnant black hole. This allows for assessment of the accuracy of our previous
empirical formulae for relating the binary parameters to the remnant final
black hole mass, spin and recoil. We use the new simulation to improve the fit
to the above remnant formulae and add a formula for the peak luminosity of
gravitational waves, produced around the merger of the two horizons into one.
We find excellent agreement (typical errors $\sim0.1-0.2\%$) for the mass and
spin, and within $\sim5\%$ for the recoil and peak luminosity. These formulae
have direct application to parameter estimation techniques applied to LIGO
observations of gravitational waves from binary black hole mergers.",1610.09713v2
2017-07-17,Indirect K-edge bimagnon resonant inelastic X-ray scattering spectrum of $α$-FeTe,"We calculate the K-edge indirect bimagnon resonant inelastic X-ray scattering
(RIXS) intensity spectra of the bicollinear antiferromagnetic order known to
occur in the $\alpha$-FeTe chalcogenide system. Utilizing linear spin wave
theory for this large-S spin system we find that the bimagnon spectrum contains
four scattering channels (two intraband and two interband). We find from our
calculations that for suitable energy-momentum combination the RIXS spectra can
exhibit a one-, two- or three- peak structure. The number of peaks provides a
clue on the various bimagnon excitation processes that can be supported both in
and within the acoustic and optical magnon branches of the bicollinear
antiferromagnet. Unlike the RIXS response of the antiferromagnetic or the
collinear antiferromagnetic spin ordering, the RIXS intensity spectrum of the
bicollinear antiferromagnet does not vanish at the magnetic ordering wave
vector $(\pi/2,-\pi/2)$. It is also sensitive to next-next nearest neighbor and
biquadratic coupling interactions. Our predicted RIXS spectrum can be utilized
to understand the role of multi-channel bimagnon spin excitations present in
the $\alpha$-FeTe chalcogenide.",1707.05057v1
2017-07-18,Solution of the spin and pseudo-spin symmetric Dirac equation in 1+1 space-time using the tridiagonal representation approach,"The aim of this work is to find exact solutions of the Dirac equation in 1+1
space-time beyond the already known class. We consider exact spin (and
pseudo-spin) symmetric Dirac equations where the scalar potential is equal to
plus (and minus) the vector potential. We also include pseudo-scalar potentials
in the interaction. The spinor wavefunction is written as a bounded sum in a
complete set of square integrable basis, which is chosen such that the matrix
representation of the Dirac wave operator is tridiagonal and symmetric. This
makes the matrix wave equation a symmetric three-term recursion relation for
the expansion coefficients of the wavefunction. We solve the recursion relation
exactly in terms of orthogonal polynomials and obtain the state functions and
corresponding relativistic energy spectrum and phase shift.",1707.05625v1
2017-08-11,Dimensional reduction by pressure in the magnetic framework material CuF$_{2}$(D$_{2}$O)$_{2}$pyz: from spin-wave to spinon excitations,"Metal organic magnets have enormous potential to host a variety of electronic
and magnetic phases that originate from a strong interplay between the spin,
orbital and lattice degrees of freedom. We control this interplay in the
quantum magnet CuF$_2$(D$_2$O)$_2$pyz by using high pressure to drive the
system through a structural and magnetic phase transition. Using neutron
scattering, we show that the low pressure state, which hosts a two-dimensional
square lattice with spin-wave excitations and a dominant exchange coupling of
0.89 meV, transforms at high pressure into a one-dimensional spin-chain
hallmarked by a spinon continuum and a reduced exchange interaction of 0.43
meV. This direct microscopic observation of a magnetic dimensional crossover as
a function of pressure opens up new possibilities for studying the evolution of
fractionalised excitations in low dimensional quantum magnets and eventually
pressure-controlled metal--insulator transitions.",1708.03586v1
2017-08-30,Signatures of gapless fermionic spinons on a strip of the kagome Heisenberg antiferromagnet,"The search for exotic quantum spin liquid states in simple yet realistic spin
models remains a central challenge in the field of frustrated quantum
magnetism. Here we consider the canonical nearest-neighbor kagome Heisenberg
antiferromagnet restricted to a quasi-1D strip consisting entirely of
corner-sharing triangles. Using large-scale density matrix renormalization
group calculations, we identify in this model an extended gapless quantum phase
characterized by central charge $c=2$ and power-law decaying spin and
bond-energy correlations which oscillate at tunably incommensurate wave
vectors. We argue that this intriguing spin liquid phase can be understood as a
marginal instability of a two-band spinon Fermi surface coupled to an emergent
U(1) gauge field, an interpretation which we substantiate via bosonization
analysis and Monte Carlo calculations on model Gutzwiller variational wave
functions. Our results represent one of the first numerical demonstrations of
emergent fermionic spinons in a simple SU(2) invariant nearest-neighbor
Heisenberg model beyond the strictly 1D (Bethe chain) limit.",1708.09397v3
2017-09-12,Direct observation of magnon-phonon coupling in yttrium iron garnet,"The magnetic insulator yttrium iron garnet (YIG) with a ferrimagnetic
transition temperature of $\sim$560 K has been widely used in microwave and
spintronic devices. Anomalous features in the spin Seeback effect (SSE)
voltages have been observed in Pt/YIG and attributed to the magnon-phonon
coupling. Here we use inelastic neutron scattering to map out low-energy spin
waves and acoustic phonons of YIG at 100 K as a function of increasing magnetic
field. By comparing the zero and 9.1 T data, we find that instead of splitting
and opening up gaps at the spin wave and acoustic phonon dispersion
intersecting points, magnon-phonon coupling in YIG enhances the hybridized
scattering intensity. These results are different from expectations of
conventional spin-lattice coupling, calling for new paradigms to understand the
scattering process of magnon-phonon interactions and the resulting
magnon-polarons.",1709.03940v1
2017-09-28,A DMRG study: Pair-density wave in spin-valley locked systems,"Interest in modulated paired states, long sought since the first proposals by
Fulde and Ferrell and by Larkin and Ovchinnikov, has grown recently in the
context of strongly coupled superconductors under the name of pair density
wave. However, there is little theoretical understanding of how such a state
might arise out of strong coupling physics in simple models. Although density
matrix renormalization group has been a powerful tool for exploring strong
coupling modulation phenomena of spin and charge stripe in the Hubbard model
and the t-J model, there has been no numerical evidence of PDW within these
models using DMRG. Here we note that a system with inversion breaking, C3v
point group symmetry may host a PDW-like state. Motivated by the fact that
spin-valley locked band structure of hole-doped group VI transition metal
dichalcogenides materializes such a setting, we use DMRG to study the
superconducting tendencies in spin-valley locked systems with strong
short-ranged repulsion. Remarkably we find robust evidence for a PDW and the
first of such evidence within DMRG studies of a simple fermionic model.",1709.10058v1
2018-01-28,Clean Os(0001) electronic surface states: a first-principle fully relativistic investigation,"We analyze the electronic structure of the Os(0001) surface by means of
first-principle calculations based on Fully Relativistic (FR) Density
Functional Theory (DFT) and a Projector Augmented-Wave (PAW) approach. We
investigate surface states and resonances analyzing their spin-orbit induced
energy splitting and their spin polarization. The results are compared with
previously studied surfaces Ir(111), Pt(111), and Au(111). We do not find any
surface state in the gap similar to the L-gap of the (111) fcc surfaces, but
find Rashba split resonances that cross the Fermi level and, as in the recently
studied Ir(111) surface, have a characteristic downward dispersion. Moreover,
for some selected surface states we study the spin polarization with respect to
${\bf k}_{\parallel}$, the wave-vector parallel to the surface. In some cases,
such as the Rashba split resonances, the spin polarization shows a smooth
behavior with slow rotations, in others the rotation is faster, due to mixing
and anti-crossing of the states.",1801.09267v1
2018-03-16,Dynamically enhanced magnetic incommensurability: Effects of local dynamics on non-local spin-correlations in a strongly correlated metal,"We compute the spin susceptibility of the two-dimensional Hubbard model away
from half-filling, and analyze the impact of frequency dependent vertex
corrections as obtained from the dynamical mean field theory (DMFT). We find
that the local dynamics captured by the DMFT vertex strongly affects non-local
spin correlations, and thus the momentum dependence of the spin susceptibility.
While the widely used random phase approximation yields commensurate
N\'eel-type antiferromagnetism as the dominant instability over a wide doping
range, the vertex corrections favor incommensurate ordering wave vectors away
from $(\pi,\pi)$. Our results indicate that the connection between the magnetic
ordering wave vector and the Fermi surface geometry, familiar for weakly
interacting systems, can hold in a strongly correlated metal, too.",1803.06175v1
2017-05-09,Low spin wave damping in the insulating chiral magnet Cu$_{2}$OSeO$_{3}$,"Chiral magnets with topologically nontrivial spin order such as Skyrmions
have generated enormous interest in both fundamental and applied sciences. We
report broadband microwave spectroscopy performed on the insulating chiral
ferrimagnet Cu$_{2}$OSeO$_{3}$. For the damping of magnetization dynamics we
find a remarkably small Gilbert damping parameter of about $1\times10^{-4}$ at
5 K. This value is only a factor of 4 larger than the one reported for the best
insulating ferrimagnet yttrium iron garnet. We detect a series of sharp
resonances and attribute them to confined spin waves in the mm-sized samples.
Considering the small damping, insulating chiral magnets turn out to be
promising candidates when exploring non-collinear spin structures for high
frequency applications.",1705.03416v1
2018-07-06,Counterroating incommensurate magnetic order and strong quantum fluctuations in the honeycomb layers of $\rm NaNi_2BiO_6$,"We report the magnetic structure and electronic properties of the honeycomb
antiferromagnet $\rm NaNi_2BiO_{5.66}$. We find magnetic order with moments
along the $c$ axis for temperatures below $T_{c1}=6.3(1)\>{\rm K}$ and then in
the honeycomb plane for $T < T_{c2}=4.8(1)\>{\rm K}$ with a counterrotating
pattern and an ordering wave vector ${\bf q}=(\frac{1}{3},\> \frac{1}{3},\>
0.15(1))$. Density functional theory and electron spin resonance indicate this
is high-spin Ni$^{3+}$ magnetism near a high to low spin transition. The
ordering wave vector, in-plane magnetic correlations, missing entropy, spin
state, and superexchange pathways are all consistent with bond-dependent
Kitaev-$\Gamma$-Heisenberg exchange interactions in $\rm NaNi_2BiO_{6-\delta}$.",1807.02528v2
2018-07-10,Spin Wave Analysis of Low-Temperature Thermal Hall Effect in the Candidate Kitaev Spin Liquid $α$-RuCl${}_3$,"Proposed effective Hamiltonians from the literature for the material
$\alpha$-RuCl${}_3$ are used to compute the magnon thermal Hall conductivity,
$\kappa_{xy}$, using linear spin wave theory for the magnetically ordered
state. No model previously proposed that was tested explains published
experimental data. Models with Kitaev interaction $K>0$ are seen to predict
$\kappa_{xy}\gtrsim 0$, which is inconsistent with the data. Fluctuations
toward a Kitaev-type spin liquid would have the wrong sign to explain the data.
However, a slight variant of a previously proposed model predicts a large
$\kappa_{xy}$, demonstrating that the low-temperature thermal Hall effect could
be generated exclusively by the Berry curvature of the magnon bands. The
experimental data of $\kappa_{xy}$ can therefore serve as another method to
constrain a proposed effective Hamiltonian.",1807.03857v1
2018-10-22,Dynamical structure factor of the three-dimensional quantum spin liquid candidate NaCaNi$_2$F$_7$,"We study the spin-1 pyrochlore material NaCaNi$_2$F$_7$ with a combination of
molecular dynamics simulations, stochastic dynamical theory and linear spin
wave theory. The dynamical structure factor from inelastic neutron scattering
is well described with a near-ideal Heisenberg Hamiltonian incorporating small
anisotropic terms {and weak second-neighbor interactions}. We find that all
three approaches reproduce remarkably well the momentum dependence of the
scattering intensity as well as its energy dependence with the exception of the
lowest energies. These results are notable in that (i) the data show a complete
lack of sharp quasiparticle excitations in momentum space over much, if not
all, of the energy range; (ii) linear spin-wave theory appears to apply in a
regime where it would be expected to fail for a number of reasons. We elucidate
what underpins these surprises, and note that basic questions about the nature
of quantum spin liquidity in such systems pose themselves as a result.",1810.09481v1
2018-02-02,Spin-orbit coupling induced magnetic anisotropy and large spin wave gap in $\rm Na Os O_3$,"The role of spin-orbit coupling and Hund's rule coupling on magnetic
ordering, anisotropy, and excitations are investigated within a minimal
three-orbital model for the $5d^3$ compound $\rm Na Os O_3$. Asymmetry between
the magnetic moments for the $xy$ and $xz,yz$ orbitals, arising from the
hopping asymmetry generated by the $\rm Os O_6$ octahedral tilting and
rotation, together with the weak correlation effect, are shown to be crucial
for the large SOC induced magnetic anisotropy and spin wave gap observed in
this compound. Due to the intrinsic SOC-induced changes in the electronic
densities under rotation of the staggered field, their coupling with the
orbital energy offset is also found to contribute significantly to the magnetic
anisotropy energy.",1802.01449v2
2018-08-22,On the Equivalence between Spin and Charge Dynamics of the Fermi Hubbard Model,"Utilizing the Fermi gas microscope, recently the MIT group has measured the
spin transport of the Fermi Hubbard model starting from a spin-density-wave
state, and the Princeton group has measured the charge transport of the Fermi
Hubbard model starting from a charge-density-wave state. Motivated by these two
experiments, we prove a theorem that shows under certain conditions, the spin
and charge transports can be equivalent to each other. The proof makes use of
the particle-hole transformation of the Fermi Hubbard model and a recently
discovered symmetry protected dynamical symmetry. Our results can be directly
verified in future cold atom experiment with the Fermi gas microscope.",1808.07225v2
2018-12-14,Non-ergodic extended phase of the Quantum Random Energy model,"The concept of non-ergodicity in quantum many body systems can be discussed
in the context of the wave functions of the many body system or as a property
of the dynamical observables, such as time-dependent spin correlators. In the
former approach the non-ergodic delocalized states is defined as the one in
which the wave functions occupy a volume that scales as a non-trivial power of
the full phase space. In this work we study the simplest spin glass model and
find that in the delocalized non-ergodic regime the spin-spin correlators decay
with the characteristic time that scales as non-trivial power of the full
Hilbert space volume. The long time limit of this correlator also scales as a
power of the full Hilbert space volume. We identify this phase with the glass
phase whilst the many body localized phase corresponds to a 'hyperglass' in
which dynamics is practically absent. We discuss the implications of these
finding to quantum information problems.",1812.06016v2
2019-06-05,The early life of millisecond magnetars,"Some neutron stars may be born spinning fast and with strong magnetic
fields---the so-called \emph{millisecond magnetars}. It is important to
understand how a star's magnetic axis moves with respect to the spin axis in
the star's early life, as this effects both electromagnetic and gravitational
wave emission. Previous studies have highlighted the importance of viscous
dissipation within the star in this process. We advance this program by
additionally considering the effect of the electromagnetic torque. We find an
interesting interplay between the viscous dissipation, which makes the magnetic
axis orthogonalise with respect to the spin, verses magnetic torques that tend
to make the magnetic axis align with the spin axis. We present some results,
and highlight areas where our model needs to be made more realistic.",1906.02610v1
2019-06-28,"Influence of anisotropy, tilt and pairing of Weyl nodes: The Weyl semimetals TaAs, TaP, NbAs and NbP","By means of $ab \ initio$ band structure methods and model Hamiltonians we
investigate the electronic, spin and topological properties of four
monopnictides crystallizing in body centered tetragonal structure. We show that
the Weyl bands around a Weyl point W1 or W2 possess a strong anisotropy and
tilt of the accompanying Dirac cones. These effects are larger for W2 nodes
than for W1 ones. The node tilts and positions in energy space significantly
influence the density of states of single-particle Weyl excitations. The node
anisotropies destroy the conventional picture of (anti)parallel spin and wave
vector of a Weyl fermion. This also holds for the Berry curvature around a
node, while the monopole charges are independent as integrated quantities. The
pairing of the nodes strongly modify the spin texture and the Berry curvature
for wave vectors in between the two nodes. Spin components may change their
orientation. Integrals over planes perpendicular to the connection line yield
finite Zak phases and winding numbers for planes between the two nodes, thereby
indicating the topological character.",1906.12231v2
2020-04-02,Spin-Dependent Charge-Carrier Recombination Processes in Tris(8-Hydroxyquinolinato) Aluminum,"We have studied the nature and dynamics of spin-dependent charge carrier
recombination in Tris(8-hydroxyquinolinato) aluminum (Alq$_3$) films in light
emitting diodes at room temperature using continuous wave and pulsed
electrically detected magnetic resonance (EDMR) spectroscopy. We found that the
EDMR signal is dominated by an electron-hole recombination process, and
another, weaker EDMR signal whose fundamental nature was investigated. From the
pulsed EDMR measurements we obtained a carrier spin relaxation time, $T_2 =
45\pm 25$ ns which is much shorter than $T_2$ in conjugated polymers, but
relatively long for a molecule containing elements with high atomic number.
Using multi-frequency continuous wave EDMR spectroscopy, we obtained the local
hyperfine field distributions for electrons and holes, as well as their
respective spin-orbit coupling induced g-factor and g-strain values.",2004.00765v1
2016-12-20,Possible excited spin density wave states in zigzag graphene nanoribbons,"We theoretically examine the possible spin ordered states in zigzag graphene
nanoribbon in a large supercell by the self-consistent mean field method as
well as the first principle calculation. In addition to the well-known
anti-ferromagnetic (AF) and ferromagnetic (FM) edge states, we find that there
are also some excited spin density wave (ESDW) states, the energy of which are
close to the AF edge state (ground state). We thus argue that these ESDW states
may coexist in experiment when the temperature is not too low. Our numerical
results indicate that the allowed ESDW are commensurate; and their dispersion
curve is plotted. This interesting feature results from the fact the there is a
flat edge band near the Fermi surface in the graphene zigzag ribbon. Finally we
use the non-equilibrium Green function theory combined with the Hubbard model
to calculate some possible spin polarization states localized in the middle and
terminal parts of graphene nanoribbons.",1612.06762v1
2017-02-03,Systematic Bias Due to Nonspinning Template Waveforms in the Gravitational Wave Parameter Estimation for Aligned-Spin Binary Black Holes,"We study the parameter estimation of gravitational waves for aligned-spin
binary black hole (BBH) signals and assess the impact of bias that can be
produced by using nonspinning template waveforms. We employ simple methods to
calculate the statistical uncertainty from an overlap distribution. For the
fiducial waveform model, we use a phenomenological model, which is designed to
generate the gravitational waveforms emitted from merging BBH systems. We show
that the mass parameters recovered by nonspinning waveform templates can be
significantly biased from the true values of aligned-spin signals. By comparing
the systematic bias with the statistical uncertainty, we examine the validity
of nonspinning templates for the parameter estimation of aligned-spin BBHs.",1702.00909v2
2017-02-28,Bulk physics entwined with a topological surface state,"For the IV-VI semiconductor family we derive an exact relation between the
microscopic gap edge wave functions of the bulk insulator and the Dirac-Weyl
topological surface state wave function, thus obtaining a fully microscopic
surface state. We find that the balance of spin-orbit interaction and crystal
field in the bulk, and the band bending at the surface, can profoundly
influence the surface state spin-momentum locking. As a manifestation of this
we predict that the spin texture of the $M$-point Dirac cones of SnTe can be
tuned through an unexpectedly rich sequence of spin textures -- warped helical
with winding number $\pm 1$, $k_x$ linear, hyperbolic, and $k_y$ linear -- e.g.
by tuning the band bending at the surface.",1702.08784v1
2019-03-19,What GW170729's exceptional mass and spin tells us about its family tree,"Gravitational-wave observations give a unique insight into the formation and
evolution of binary black holes. We use gravitational-wave measurements to
address the question of whether GW170729's source, which is (probably) the most
massive binary and the system with the highest effective inspiral spin, could
contain a black hole which is a previous merger remnant. Using the inferred
mass and spin of the system, and the empirically determined population of
binary black holes, we compute the evidence for the binary being
second-generation compared with first-generation. We find moderate evidence (a
Bayes factor of ~6-7) that the mass and spin better match a second-generation
merger, but folding in the expectation that only a small fraction of mergers
are second-generation, we conclude that there is no strong evidence that
GW170729 was the result of a second-generation merger. The results are
sensitive to the assumed mass distribution, and future detections will provide
more robust reconstructions of the binary black hole population.",1903.07813v2
2019-05-09,Measuring Spin of the Remnant Black Hole from Maximum Amplitude,"Gravitational waves emitted during the merger of two black holes carry
information about the remnant black hole, namely its mass and spin. This
information is typically found from the ringdown radiation as the black hole
settles to a final state. We find that the remnant black hole spin is already
known at the peak amplitude of the gravitational wave strain. Using this
knowledge, we present a new method for measuring the final spin that is
template independent, using only the chirp mass, the instantaneous frequency of
the strain and its derivative at maximum amplitude, all template independent.",1905.03756v2
2020-03-25,Asymmetric scattering behaviors of spin wave dependent on magnetic vortex chirality,"In this letter, an asymmetric spin wave scattering behaviors caused by vortex
chirality are investigated in cross-shaped ferromagnetic system. In the system,
four scattering behaviors are found, 1) asymmetric skew scattering, depending
on the polarity of vortex core, 2) back scattering (reflection), depending on
the vortex core stiffness, 3) side deflection scattering, depending on
structural symmetry of the vortex circulation, and 4) geometrical scattering,
depending on waveguide structure. The first and second scattering behaviors are
attributed to nonlinear topological magnon spin Hall effect related to magnon
spin-transfer torque effect, which has value for magnonic exploration and
application.",2003.11193v2
2020-09-28,Coupled dimer and bond-order-wave order in the quarter-filled one-dimensional Kondo lattice model,"Motivated by the experiments on the organic compound
$(Per)_{2}[Pt(mnt)_{2}]$, we study the ground state of the one-dimensional
Kondo lattice model at quarter filling with the density matrix renormalization
group method. We show a coupled dimer and bond-order-wave (BOW) state in the
weak coupling regime for the localized spins and itinerant electrons,
respectively. The quantum phase transitions for the dimer and the BOW orders
occur at the same critical coupling parameter $J_{c}$, with the opening of a
charge gap. The emergence of the combination of dimer and BOW order agrees with
the experimental findings of the simultaneous Peierls and spin-Peierls
transitions at low temperatures, which provides a theoretical understanding of
such phase transition. We also show that the localized spins in this insulating
state have quasi-long ranged spin correlations with collinear configurations,
which resemble the classical dimer order in the absence of a magnetic order.",2009.13089v1
2021-02-09,Spinning test body orbiting around a Kerr black hole: Eccentric equatorial orbits and their asymptotic gravitational-wave fluxes,"We use the frequency and time domain Teukolsky formalism to calculate
gravitational-wave fluxes from a spinning body on a bound eccentric equatorial
orbit around a Kerr black hole. The spinning body is represented as a point
particle following the pole-dipole approximation of the
Mathisson-Papapetrou-Dixon equations. Reformulating these equations we are not
only able to find the trajectory of a spinning particle in terms of its
constants of motion, but also to provide a method to calculate the azimuthal
and the radial frequency of this trajectory. Using these orbital quantities, we
introduce the machinery to calculate through the frequency domain Teukolsky
formalism the energy and the angular momentum fluxes at infinity, and at the
horizon, along with the gravitational strain at infinity. We crosscheck the
results obtained from the frequency domain approach with the results obtained
from a time domain Teukolsky equation solver called Teukode.",2102.04819v2
2016-11-03,Scalable synchronization of spin-Hall oscillators in out-of-plane field,"A strategy for a scalable synchronization of an array of spin-Hall
oscillators (SHOs) is illustrated. In detail, we present micromagnetic
simulations of two and five SHOs realized by means of couples of triangular
golden contacts on the top of a Pt/CoFeB/Ta trilayer. Results highlight that
the synchronization occurs for the whole current region that gives rise to the
excitation of self-oscillations. This is linked to the role of the
magnetodipolar coupling, which is the phenomenon driving the synchronization
when the distance between oscillators is not too large. Synchronization turns
out to be also robust against geometrical differences of the contacts,
simulated by considering variable distances between the tips ranging from 100nm
to 200nm. Besides, it entails an enlargement of the radiation pattern that can
be useful for the generation of spin-waves in magnonics applications.
Simulations performed to study the effect of the interfacial
Dzyaloshinskii-Moriya interaction show nonreciprocity in spatial propagation of
the synchronized spin-wave. The simplicity of the geometry and the robustness
of the achieved synchronization make this design of array of SHOs scalable for
a larger number of synchronized oscillators.",1611.01227v1
2016-11-23,Dynamics of extended bodies with spin-induced quadrupole in Kerr spacetime: generic orbits,"We discuss motions of extended bodies in Kerr spacetime by using
Mathisson-Papapetrou-Dixon equations. We firstly solve the conditions for
circular orbits, and calculate the orbital frequency shift due to the mass
quadrupoles. The results show that we need not consider the spin-induced
quadrupoles in extreme-mass-ratio inspirals for spatial gravitational wave
detectors. We quantitatively investigate the temporal variation of rotational
velocity of the extended body due to the coupling of quadrupole and background
gravitational field. For generic orbits, we numerically integrate the
Mathisson-Papapetrou-Dixon equations for evolving the motion of an extended
body orbiting a Kerr black hole. By comparing with the monopole-dipole
approximation, we reveal the influences of quadrupole moments of extended
bodies on the orbital motion and chaotic dynamics of extreme-mass-ratio
systems. We do not find any chaotic orbits for the extended bodies with
physical spins and spin-induced quadrupoles. Possible implications for
gravitational wave detection and pulsar timing observation are outlined.",1611.07602v1
2017-01-17,Dynamics of the Kitaev-Heisenberg Model,"We introduce a matrix-product state based method to efficiently obtain
dynamical response functions for two-dimensional microscopic Hamiltonians,
which we apply to different phases of the Kitaev-Heisenberg model. We find
significant broad high energy features beyond spin-wave theory even in the
ordered phases proximate to spin liquids. This includes the phase with zig-zag
order of the type observed in $\alpha$-RuCl$_3$, where we find high energy
features like those seen in inelastic neutron scattering experiments. Our
results provide an example of a natural path for proximate spin liquid features
to arise at high energies above a conventionally ordered state, as the diffuse
remnants of spin-wave bands intersect to yield a broad peak at the Brillouin
zone center.",1701.04678v1
2017-01-20,Two-magnon excitations in resonant inelastic x-ray scattering studied by spin-density-wave formalism,"We study two-magnon excitations in resonant inelastic x-ray scattering (RIXS)
at the transition-metal $K$-edge. Instead of working with effective Heisenberg
spin models, we work with a Hubbard-type model ($d$-$p$ model) for a typical
insulating cuprate La$_2$CuO$_4$. For the antiferromagnetic ground state within
the spin-density-wave (SDW) mean-field formalism, we calculate the dynamical
correlation function within the random-phase approximation (RPA), and then
obtain two-magnon excitation spectra by calculating the convolution of it.
Coupling between the $K$-shell hole and the magnons in the intermediate state
is calculated by means of diagrammatic perturbation expansion in the Coulomb
interaction. Calculated momentum dependence of RIXS spectra agrees well with
that of experiments. A notable difference from previous calculations based on
the Heisenberg spin models is that RIXS spectra have a large two-magnon weight
near the zone center, which may be confirmed by further careful high-resolution
experiments.",1701.05684v2
2017-03-06,"Spindynamics in the antiferromagnetic phases of the Dirac metals $A$MnBi$_2$ ($A=$ Sr, Ca)","The square Bi layers in $A$MnBi$_2$ ($A =$ Sr, Ca) host Dirac fermions which
coexist with antiferromagnetic order on the Mn sublattice below $T_\mathrm{N} =
290\,$K (Sr) and $270\,$K (Ca). We have measured the spin-wave dispersion in
these materials by triple-axis neutron spectroscopy. The spectra show
pronounced spin gaps of 10.2(2)$\,$meV (Sr) and 8.3(8)$\,$meV (Ca) and extend
to a maximum energy transfer of 61 - 63$\,$meV. The observed spectra can be
accurately reproduced by linear spin-wave theory from an Heisenberg effective
spin Hamiltonian. Detailed global fits of the full magnon dispersion are used
to determine the in-plane and inter-layer exchange parameters as well as on the
magnetocrystalline anisotropy constant. To within experimental error we find no
evidence that the magnetic dynamics are influenced by the Dirac fermions.",1703.01849v1
2017-03-07,Helicity locking in light emitted from a plasmonic nanotaper,"Surface plasmon waves carry an intrinsic transverse spin, which is locked to
its propagation direction. Apparently, when a singular plasmonic mode is guided
on a conic surface this spin-locking may lead to a strong circular polarization
of the far-field emission. Specifically, an adiabatically tapered gold nanocone
guides an a priori excited plasmonic vortex upwards where the mode accelerates
and finally beams out from the tip apex. The helicity of this beam is shown to
be single-handed and stems solely from the transverse spin-locking of the
helical plasmonic wave-front. We present a simple geometric model that fully
predicts the emerging light spin in our system. Finally we experimentally
demonstrate the helicity-locking phenomenon by using accurately fabricated
nanostructures and confirm the results with the model and numerical data.",1703.02278v1
2017-03-13,A model for the neutron resonance in HgBa$_{2}$CuO$_{4+δ}$,"We study the spin dynamics of the Resonant Excitonic State (RES) proposed,
within the theory of an emergent SU(2) symmetry, to explain some properties of
the pseudo-gap phase of cuprate superconductors. The RES can be described as a
proliferation of particle-hole patches with an internal modulated structure. We
model the RES modes as a charge order with multiple $2{\bf {p}}_{\text{F}}$
ordering vectors, where $2{\bf {p}}_{\text{F}}$ connects two opposite side of
the Fermi surface. This simple modelization enables us to propose a
comprehensive study of the collective mode observed at the antiferromagnetic
(AF) wave vector $\mathbf{Q}=(\pi,\pi)$ by Inelastic Neutron Scattering (INS)
in both superconducting state (SC), but also in the Pseudogap regime. In this
regime, we show that the dynamic spin susceptibility accuses a loss of
coherence terms except at special wave vectors commensurate with the lattice.
We argue that this phenomenon could explain the change of the spin response
shape around $\mathbf{Q}$. We demonstrate that the hole dependence of the RES
spin dynamics is in agreement with the experimental data in
HgBa$_{2}$CuO$_{4+\delta}$.",1703.04442v1
2017-04-22,Spin Density wave instability in a ferromagnet,"Ferromagnetic (FM) and incommensurate spin-density wave (ISDW) states are an
unusual set of competing magnetic orders that are seldom observed in the same
material without application of a polarizing magnetic field. We report, for the
first time, the discovery of an ISDW state that is derived from a FM ground
state through a Fermi surface (FS) instability in Fe$_3$Ga$_4$. This was
achieved by combining neutron scattering experiments with first principles
simulations. Neutron diffraction demonstrates that Fe$_3$Ga$_4$ is in an ISDW
state at intermediate temperatures and that there is a conspicuous re-emergence
of ferromagnetism above 360 K. First principles calculations show that the ISDW
ordering wavevector is in excellent agreement with a prominent nesting
condition in the spin-majority FS demonstrating the discovery of a novel
instability for FM metals; ISDW formation due to Fermi surface nesting in a
spin-polarized Fermi surface.",1704.06727v2
2019-04-25,Collective quantum memory activated by a driven central spin,"Coupling a qubit coherently to an ensemble is the basis for collective
quantum memories. A driven quantum dot can deterministically excite low-energy
collective modes of a nuclear spin ensemble in the presence of lattice strain.
We propose to gate a quantum state transfer between this central electron and
these low-energy excitations -- spin waves -- in the presence of a strong
magnetic field, where the nuclear coherence time is long. We develop a
microscopic theory capable of calculating the exact time evolution of the
strained electron-nuclear system. With this, we evaluate the operation of
quantum state storage and show that fidelities up to 90% can be reached with a
modest nuclear polarisation of only 50%. These findings demonstrate that
strain-enabled nuclear spin waves are a highly suitable candidate for quantum
memory.",1904.11180v2
2019-09-01,Magnetic field-dependent low-energy magnon dynamics in $α$-RuCl3,"Revealing the spin excitations of complex quantum magnets is key to
developing a minimal model that explains the underlying magnetic correlations
in the ground state. We investigate the low-energy magnons in $\alpha$-RuCl$_3$
by combining time-domain terahertz spectroscopy under an external magnetic
field and model Hamiltonian calculations. We observe two absorption peaks
around 2.0 and 2.4 meV, which we attribute to zone-center spin waves. Using
linear spin-wave theory with only nearest-neighbor terms of the exchange
couplings, we calculate the antiferromagnetic resonance frequencies and reveal
their dependence on an external field applied parallel to the nearest-neighbor
Ru-Ru bonds. We find that the magnon behavior in an applied magnetic field can
be understood only by including an off-diagonal $\Gamma$ exchange term to the
minimal Heisenberg-Kitaev model. Such an anisotropic exchange interaction that
manifests itself as a result of strong spin-orbit coupling can naturally
account for the observed mixing of the modes at higher fields strengths.",1909.00462v1
2019-09-30,Spin-dependent refraction at the interface of lateral heterostructures of 2$H$-type transition-metal dichalcogenide monolayers,"We study the refraction effect of electronic wave in hole-doped lateral
heterojunctions of metallic and semiconducting transition-metal dichalcogenide
monolayers. This effect is theoretically investigated in 2$H$-type
MoSe$_2$-NbS$_2$ and WSe$_2$-NbS$_2$ junctions by combining the
first-principles calculation and the lattice Green's function method. We show
that the electronic waves change the direction of motion at the interface and
collimate the velocity along two different directions depending on the spin. We
find that the transmission probability increases with the charge density and
that the direction of refracted electron beams is close to $\pm30^\circ$ with
respect to the perpendicular axis to the interface. The metallic
transition-metal dichalcogenide is essential for the refraction effect because
of the strong trigonal-warping effect, the large Fermi surface, and the
Zeeman-type spin-orbit coupling. The refraction effect enables to generate the
spin-polarized electronic current by using a simple fabrication of
transition-metal dichalcogenide monolayers.",1909.13401v1
2019-10-13,Theoretical Study of Spin Observables in $pd$ Elastic Scattering at Energies $T_p = 800-1000$ MeV,"Various spin observables (analyzing powers and spin-correlation parameters)
in $pd$ elastic scattering at $T_p = 800-1000$ MeV are analyzed within the
framework of the refined Glauber model. The theoretical model uses as input
spin-dependent $NN$ amplitudes obtained from the most recent partial-wave
analysis and also takes into account the deuteron $D$ wave and charge-exchange
effects. Predictions of the refined Glauber model are compared with the
existing experimental data. Reasonable agreement between the theoretical
calculations and experimental data at low momentum transfers $|t| \lesssim 0.2$
(GeV/$c)^2$ is found for all observables considered. Moderate discrepancies
found in this region are shown to be likely due to uncertainties in the input
$NN$ amplitudes. Qualitative agreement at higher momentum transfers is also
found for most observables except the tensor ones with mixed $x$ and $z$
polarization components. Possible reasons for observed deviations of the model
calculations from the data at $|t| > 0.2$ (GeV/$c)^2$ are discussed.",1910.05722v1
2019-12-03,High partial-wave Feshbach resonances in an ultracold $^6$Li-$^{133}$Cs mixture,"We measure higher partial wave Feshbach resonances in an ultracold mixture of
fermionic $^6$Li and bosonic $^{133}$Cs by magnetic field dependent atom-loss
spectroscopy. For the $p$-wave Feshbach resonances we observe triplet
structures corresponding to different projections of the pair rotation angular
momentum onto the external magnetic field axis.
  We attribute the splittings to the spin-spin and spin-rotation couplings by
modelling the observation using a full coupled-channel calculation. Comparison
with an oversimplified model, estimating the spin-rotation coupling by
describing the weakly bound close-channel molecular state with the perturbative
multipole expansion, reveals the significant contribution of the molecular
wavefunction at short internuclear distances. Our findings highlight the
potential of Feshbach resonances in providing precise information on short- and
intermediate-range molecular couplings and wavefunctions. The observed $d$-wave
Feshbach resonances allow us to refine the LiCs singlet and triplet
ground-state molecular potential curves at large internuclear separations.",1912.01264v1
2020-01-30,Neutron inelastic scattering study of rare-earth orthoferrite HoFeO$_3$,"By the single crystal inelastic neutron scattering the orthoferrite HoFeO3
was studied. We show that the spin dynamics of the Fe subsystem does not change
through the spin-reorientation transitions. The observed spectrum of magnetic
excitations was analyzed in the frames of linear spin-wave theory. Within this
approach the antiferromagnetic exchange interactions of nearest neighbors and
next nearest neighbors were obtained for Fe subsystem. Parameters of
Dzyaloshinskii-Moriya interactions at Fe subsystem were refined. The
temperature dependence of the gap in Fe spin-wave spectrum indicates the
temperature evolution of the anisotropy parameters. The estimations for the
values of Fe-Ho and Ho-Ho exchange interaction were made as well.",2001.11313v3
2020-07-07,Magnetization control by angular momentum transfer from surface acoustic wave to ferromagnetic spin moments,"The angular momentum interconversion between electron spin and other type of
angular momenta is useful to develop new spintronic functionalities. The
conversions from the angular momentum of photon and mechanical rotation to
ferromagnetic spin moment have been well studied. While the recent studies
theoretically suggested circular vibration of atoms works as angular momentum
of phonon, the direct experimental demonstration of conversion to spin moments
remains to be performed. Here we demonstrate that the phonon angular momentum
of surface acoustic wave can control the magnetization of a ferromagnetic Ni
film by means of the phononic-to-electronic conversion of angular momentum in
Ni/LiNbO$_3$ hybrid device. This result clearly shows the phonon angular
momentum is useful to further fictionalize spintronic devices.",2007.03192v1
2020-12-15,Possible Spin-Density Wave on Fermi Arc of Edge State in Single-Component Molecular Conductors [Pt(dmdt)$_2$] and [Ni(dmdt)$_2$],"We construct three-orbital tight-binding models describing single-component
molecular conductors [Pt(dmdt)$_2$] and [Ni(dmdt)$_2$] using first-principles
calculations. We show that [Ni(dmdt)$_2$] is a Dirac nodal line system with
highly one-dimensional edge states at the (001) edge, similar to
[Pt(dmdt)$_2$], as demonstrated in prior studies. To investigate possible edge
magnetism, we calculate longitudinal and transverse spin susceptibilities using
real-space-dependent random-phase approximation (RPA) in three-orbital Hubbard
models in the presence of spin--orbit coupling. We find that the edge
spin-density wave (SDW) is induced by the Coulomb repulsion and incommensurate
nestings of the Fermi arcs. We also find that the magnetic structure of the
edge SDW can be changed via extremely small carrier doping, which is
controllable in molecular conductors.",2012.08132v3
2021-05-03,First ESR Detection of Higgs Amplitude Mode and Analysis with Extended Spin-Wave Theory in Dimer System KCuCl$_3$,"KCuCl$_3$ is known to show a quantum phase transition from the disordered to
antiferromagnetically ordered phases by applying pressure. There is a
longitudinal excitation mode (Higgs amplitude mode) in the vicinity of the
quantum critical point in the ordered phase. To detect the Higgs amplitude
mode, high-pressure ESR measurements are performed in KCuCl$_3$. The
experimental data are analyzed by the extended spin-wave theory on the basis of
the vector spin chirality. We report the first ESR detection of the Higgs
amplitude mode and the important role of the electric dipole described by the
vector spin chirality.",2105.00750v1
2021-05-05,Probing the Spins of Supermassive Black Holes with Gravitational Waves from Surrounding Compact Binaries,"Merging compact black-hole (BH) binaries are likely to exist in the nuclear
star clusters around supermassive BHs (SMBHs), such as Sgr A$^\ast$. They may
also form in the accretion disks of active galactic nuclei. Such compact
binaries can emit gravitational waves (GWs) in the low-frequency band (0.001-1
Hz) that are detectable by several planned space-borne GW observatories. We
show that the orbital axis of the compact binary may experience significant
variation due to the frame-dragging effect associated with the spin of the
SMBH. The dynamical behavior of the orbital axis can be understood analytically
as a resonance phenomenon. We show that rate of change of the binary orbital
axis encodes the information on the spin of the SMBH. Therefore detecting GWs
from compact binaries around SMBHs, particularly the modulation of the waveform
associated with the variation of the binary orbital axis, can provide a new
probe on the spins of SMBHs.",2105.02230v2
2021-05-11,Helicity current generation by distorted Rashba coupling,"We theoretically study spin transport in two-or three-dimensional Rashba
systems dynamically distorted by surface acoustic waves. The spin currents in
the linear response to lattice distortion dynamics are calculated on the basis
of a microscopic theory combined with local coordinate transformations. As a
result, we find a mechanism of direct spin-current generation from lattice
distortion not associated with a charge current or spin accumulation. Moreover,
the in-plane helicity currents are generated by shear surface acoustic waves
via the present mechanism. The generated helicity currents are not parallel to
the vorticity of the lattice, and cannot be created with the conventional
methods. Thus, our findings offer an alternative functionality of the
conventional Rashba systems in the field of spintronics.",2105.04804v1
2021-11-11,Edge states in proximitized graphene ribbons and flakes in a perpendicular magnetic field: emergence of lone pseudohelical pairs and pure spin-current states,"We investigate the formation of edge states in graphene ribbons and flakes
with proximity induced valley-Zeeman and Rashba spin-orbit couplings in the
presence of a perpendicular magnetic field $B$. Two types of edges states
appear in the spin-orbit gap at the Fermi level at zero field: strongly
localized pseudohelical (intervalley) states and weakly localized intravalley
states. We show that if the magnetic field is stronger than a crossover field
$B_c$, which is a few mT for realistic systems such as graphene/WSe$_2$, only
the pseudohelical edge states remain in zigzag graphene ribbons; the
intravalley states disappear. The crossover is directly related to the closing
and reopening of the bulk gap formed between nonzero Landau levels. Remarkably,
in finite flakes the pseudohelical states undergo perfect reflection at the
armchair edges if $B > B_c$, forming standing waves at the zigzag edges. These
standing waves comprise two counterpropagating pseudohelical states, so while
they carry no charge current, they do carry (pure) spin current.",2111.06369v1
2021-11-22,Evolution of Interorbital Superconductor to Intraorbital Spin-Density Wave in Layered Ruthenates,"The ruthenate family of layered perovskites has been a topic of intense
interest with much work dedicated to understanding the superconducting state of
the single layer, Sr$_2$RuO$_4$. Another longstanding puzzle is the lack of
superconductivity in its sister compound, Sr$_3$Ru$_2$O$_7$, which constrains
the possible superconducting mechanisms of Sr$_2$RuO$_4$. Here we address a
microscopic mechanism that unifies superconducting and spin-density wave order
in this family of materials. Beginning from a model of Sr$_2$RuO$_4$ featuring
intraband pseudospin-singlet superconductivity originating from interorbital
spin-triplet pairing via Hund's and spin-orbit couplings, the addition of
bilayer coupling and staggered rotations of the oxygen octahedra are
investigated. We find that the bilayer coupling alone enhances
superconductivity, while staggered rotations destroy interorbital
superconductivity, leaving a paramagnetic metal. The magnetic field then shifts
van Hove singularities near the Fermi level, allowing intraorbital SDW order to
form in the bilayer. Our theory predicts that bilayer Sr$_3$Ru$_2$O$_7$ without
staggered rotations exhibits interorbital superconductivity with a possibly
higher transition temperature.",2111.11452v2
2021-11-27,Exploring Features in the Binary Black Hole Population,"Vamana is a mixture model framework that infers the astrophysical
distribution of chirp mass, mass ratio, and spin component aligned with the
orbital angular momentum for the binary black hole population. We extend the
mixing components in this framework to also model the redshift evolution of
merger rate and report all the major one and two-dimensional features in the
Binary Black Hole population using the 69 gravitational wave signals detected
with a false alarm rate $<1\mathrm{yr}^{-1}$ in the third Gravitational-Wave
Transient Catalog (GWTC)-3. Endorsing our previous report and a corroborating
recent report from LIGO Scientific, Virgo, and KAGRA Collaborations, we observe
the chirp mass distribution has multiple peaks and a lack of mergers with chirp
masses $10 \textrm{--} 12M_\odot$. In addition, we observe aligned spins show
mass dependence with heavier binaries exhibiting larger spins, mass ratio shows
a dependence on the chirp mass but not on the aligned spin, and the redshift
evolution of the merger rate for the peaks in the mass distribution is
disparate. These features possibly reflect the astrophysics associated with the
binary black hole formation channels. However, additional observations are
needed to improve our limited confidence in them.",2111.13991v3
2021-12-22,Neutron Scattering Studies of the Breathing Pyrochlore Antiferromagnet LiGaCr$_{4}$O$_{8}$,"We report neutron scattering measurements of the spinel oxide
LiGaCr$_{4}$O$_{8}$, in which magnetic ions Cr$^{3+}$ form a breathing
pyrochlore lattice. Our experiments reveal the coexistence of a nearly
dispersionless resonance mode and dispersive spin wave excitations in the
magnetically ordered state, which can be quantitatively described by a quantum
spin model of hexagonal loops and linear spin wave theory with the same set of
exchange parameters, respectively. Comparison to other Cr spinel oxides reveals
a linear relationship between the resonance energy and lattice constant across
all these materials, which is in agreement with our hexagonal loop
calculations. Our results suggest a unified picture for spin resonances in Cr
spinel oxides.",2112.11709v1
2022-04-22,Spin Density Wave versus Fractional Magnetization Plateau in a Triangular Antiferromagnet,"We report an excellent realization of the highly non-classical incommensurate
spin-density wave (SDW) state in the quantum frustrated antiferromagnetic
insulator Cs$_2$CoBr$_4$. In contrast to the well-known Ising spin chain case,
here the SDW is stabilized by virtue of competing planar in-chain anisotropies
and frustrated interchain exchange. Adjacent to the SDW phase is a broad $m =
1/3$ magnetization plateau that can be seen as a commensurate locking of the
SDW state into the up-up-down (UUD) spin structure. This represents the first
example of long-sought SDW-UUD transition in triangular-type quantum magnets.",2204.10682v2
2022-06-28,Geometric Origin of Intrinsic Spin Hall Effect in an Inhomogeneous Electric Field,"In recent years, the spin Hall effect has received great attention because of
its potential application in spintronics and quantum information processing and
storage. However, this effect is usually studied under the external homogeneous
electric field. Understanding how the inhomogeneous electric field affects the
spin Hall effect is still lacking. Here, we investigate a two-dimensional
two-band time-reversal symmetric system and give an expression for the
intrinsic spin Hall conductivity in the presence of the inhomogeneous electric
field, which is shown to be expressed through gauge-invariant geometric
quantities. On the other hand, when people get physical intuition on transport
phenomena from the wave packet, one issue appears. It is shown that the
conductivity obtained from the conventional wave packet approach cannot be
fully consistent with the one predicted by the Kubo-Greenwood formula. Here, we
attempt to solve this problem.",2207.01500v1
2022-09-06,Current-driven magnetization dynamics and their correlation with magnetization configurations in perpendicularly magnetized tunnel junctions,"We study spin-transfer-torque driven magnetization dynamics of a
perpendicular magnetic tunnel junction (MTJ) nanopillar. Based on the
combination of spin-torque ferromagnetic resonance and microwave spectroscopy
techniques, we demonstrate that the free layer (FL) and the weak pinned
reference layer (RL) exhibit distinct dynamic behaviors with opposite frequency
vs. field dispersion relations. The FL can support a single coherent spin-wave
(SW) mode for both parallel and antiparallel configurations, while the RL
exhibits spin-wave excitation only for the antiparallel state. These two SW
modes corresponding to the FL and RL coexist at an antiparallel state and
exhibit a crossover phenomenon of oscillation frequency with increasing the
external magnetic field, which could be helpful in the mutual synchronization
of auto-oscillations for SW-based neuromorphic computing.",2209.02271v1
2022-10-18,Dynamics of Stripe Patterns in Supersolid Spin-Orbit-Coupled Bose Gases,"Despite ground-breaking observations of supersolidity in spin-orbit-coupled
Bose-Einstein condensates, until now the dynamics of the emerging spatially
periodic density modulations has been vastly unexplored. Here, we demonstrate
the nonrigidity of the density stripes in such a supersolid condensate and
explore their dynamic behavior subject to spin perturbations. We show both
analytically in infinite systems and numerically in the presence of a harmonic
trap how spin waves affect the supersolid's density profile in the form of
crystal waves, inducing oscillations of the periodicity as well as the
orientation of the fringes. Both these features are well within reach of
present-day experiments. Our results show that this system is a paradigmatic
supersolid, featuring superfluidity in conjunction with a fully dynamic
crystalline structure.",2210.10064v2
2022-12-04,Renormalization of antiferromagnetic magnons by superconducting condensate and quasiparticles,"The ability to modify and tune the spin-wave dispersion is one of the most
important requirements for engineering of magnonic networks. In this study we
demonstrate the promise of synthetic thin-film hybrids composed of an
antiferromagnetic insulator (AF) and a normal (N) or superconducting (S) metal
for tuning and modifying the spin-wave dispersion in antiferromagnetic
insulators. The key ingredient is the uncompensated magnetic moment at the
AF/S(N) interface, which induces an effective exchange field in the adjacent
metal via the interface exchange interaction. The exchange field spin polarizes
quasiparticles in the metal and induces spinful triplet Cooper pairs screening
the magnon. The quasiparticle and Cooper pair polarization renormalizes the
magnon dispersion. The renormalization results in the splitting of the
otherwise degenerate AF magnon modes with no need to apply a magnetic field. It
is also proposed that measurements of the renormalized dispersion relations can
provide the amplitude of the effective exchange field induced by the AF in the
adjacent metal.",2212.01831v2
2022-12-14,Missing Corner in the Sky: Massless Three-Point Celestial Amplitudes,"We present the first computation of three-point celestial amplitudes in
Minkowski space of massless scalars, photons, gluons, and gravitons. Such
amplitudes were previously considered to be zero in the literature because the
corresponding scattering amplitudes in the plane wave basis vanish for finite
momenta due to momentum conservation. However, the delta function for the
momentum conservation has support in the soft and colinear regions, and
contributes to the Mellin and shadow integrals that give non-zero celestial
amplitudes. We further show that when expanding in the (shadow) conformal basis
for the incoming (outgoing) particle wave functions, the amplitudes take the
standard form of correlators in two-dimensional conformal field theory. In
particular, the three-point celestial gluon amplitudes take the form of a
three-point function of a spin-one current with two spin-one primary operators,
which strongly supports the relation between soft spinning particles and
conserved currents. Moreover, the three-point celestial amplitudes of one
graviton and two massless scalars take the form of a correlation function
involving a primary operator of conformal weight one and spin two, whose
level-one descendent is the supertranslation current.",2212.07025v2
2023-03-30,Chaotic Gas Accretion by Black Holes Embedded in AGN Discs as Cause of Low-spin Signatures in Gravitational Wave Events,"Accretion discs around super-massive black holes (SMBH) not only power active
galactic nuclei (AGNs), but also host single and binary embedded stellar-mass
black holes (EBHs) that grow rapidly from gas accretion. The merger of these
EBHs provides a promising mechanism for the excitation of some gravitational
wave events observed by LIGO-Virgo, especially those with source masses
considerably larger than isolated stellar-mass black hole binaries. In addition
to their mass and mass-ratio distribution, their hitherto enigmatic small
spin-parameters chi_effective carry important clues and stringent constraints
on their formation channels and evolutionary pathways. Here we show that,
between each coalescence, the typical rapid spin of the merged EBHs is
suppressed by their subsequent accretion of gas from a turbulent environment,
due to its ability to randomize the flow's spin orientation with respect to
that of the EBHs on an eddy-turnover timescale. This theory provides supporting
evidence for the prolificacy of EBH mergers and suggests that their mass growth
may be dominated by gas accretion rather than their coalescence in AGN discs.",2303.17097v1
2023-05-05,Magnetic excitation spectrum and Hamiltonian of the quantum spin chain BaCuTe2O6,"The magnetic excitation spectrum and Hamiltonian of the quantum magnet
BaCuTe2O6 is studied by inelastic neutron scattering (INS) and density
functional theory (DFT). INS on powder and single crystal samples reveals
overlapping spinon continuua - the spectrum of an antiferromagnetic spin-1/2
spin chain - due to equivalent chains running along the a, b, and c directions.
Long-range magnetic order onsets below TN = 6.3 K due to interchain
interactions, and is accompanied by the emergence of sharp spin-wave
excitations which replace the continuua at low energies. The spin-wave spectrum
is highly complex and was successfully modelled achieving excellent agreement
with the data. The extracted interactions reveal an intrachain interaction, J3
= 2.9 meV, while the antiferromagnetic hyperkagome interaction J2, is the
sub-leading interaction responsible for coupling the chains together in a
frustrated way. DFT calculations reveal a similar picture for BaCuTe2O6 of
dominant J3 and sub-leading J2 antiferromagnetic interactions and also indicate
a high sensitivity of the interactions to small changes of structure which
could explain the very different Hamiltonians observed in the sister compounds
SrCuTe2O6 and PbCuTe2O6.",2305.03825v1
2023-07-12,Tuning the Intrinsic Spin Hall Effect by Charge Density Wave Order in Topological Kagome Metals,"Kagome metals are topological materials with a rich phase diagram featuring
various charge density wave orders and even unconventional superconductivity.
However, little is still known about possible spin-polarized responses in these
non-magnetic compounds. Here, we perform ab-initio calculations of the
intrinsic spin Hall effect (SHE) in the kagome metals AV$_3$Sb$_5$ (A=Cs, Rb,
K), CsTi$_3$Bi$_5$ and ScV$_6$Sn$_6$. We report large spin Hall conductivities,
comparable with the Weyl semimetal TaAs. Additionally, in CsV$_3$Sb$_5$ the SHE
is strongly renormalized by the CDW order. We can understand these results
based on the topological properties of band structures, demonstrating that the
SHE is dominated by the position and shape of the Dirac nodal lines in the
kagome sublattice. Our results suggest kagome materials as a promising, tunable
platform for future spintronics applications.",2307.06230v2
2023-08-09,Interacting holes in gated WSe$_2$ quantum dots,"We develop here a theory of the electronic properties of a finite number of
valence holes in gated WSe$_2$ quantum dots, considering the influence of spin,
valley, electronic orbitals, and many-body interactions. The single-particle
wave functions are constructed by combining the spin-up and down states of the
highest valence bulk bands employing a multi-million atom ab-initio based
tight-binding model solved in the wave-vector space, allowing to study up to
100 nm radius quantum dots atomistically. The effects of the many-body
interactions are determined using the configuration interaction (CI) technique,
applied up to $N = 6$ holes occupying up to 6 electronic shells with 42
orbitals. Our results show that N=2 holes are in valley and spin
anti-ferromagnetic ground state, independent of the interaction strength and
the quantum dot size. However, we predict that higher number of holes can
undergo a transition to spontaneously broken symmetry valley and spin polarized
ferromagnetic phases, highlighting the interplay between the many-body effects
and the quantum dot lateral size and confining potential depth.",2308.05169v1
2023-11-09,Spectroscopy and Annihilation Decay Widths of Charmonium and Bottomonium Excitations,"We study the charmonium ($c\bar{c}$) and bottomonium ($b\bar{b}$) spectra,
using Cornell potential with additional constant potential term in a
non-relativistic framework, with spin-dependent corrections corresponding to
the spin-spin, spin-orbit, and tensor interactions added perturbatively. We
predict the masses of low-lying and excited states of charmonium and
bottomonium up to $n=6$ and $L=2$. We analyze the radial and orbital Regge
trajectories of both the systems and investigate their departure from
linearity. Further, we estimate the wave function at the origin and,
consequently, predict the decay widths of charmonium and bottomonium states
annihilating to leptons and photons. Also, we investigate the effect of scale
dependence of the wave function at the origin and the strong coupling constant
on the predictions of annihilation decay widths. We compare our predictions of
heavy quarkonium spectra and decay widths with experimental results and other
theoretical models.",2311.05274v2
2024-01-22,Probing the Spin-Induced Quadrupole Moment of Massive Black Holes with the Inspiral of Binary Black Holes,"One of the most important sources for the space-borne gravitational wave
detectors such as TianQin and LISA, is the merger of massivie black hole
binaries. Using the inspiral signals, we can probe the properties of the
massive black holes, such as the spin-induced multipole moments. By verifying
the relation among the mass, spin and quadrupole moment, the no-hair theoreom
can be tested. In this work, we analysed the capability on probing the
spin-induced quadrupole moment with the inspiral signal of massive black hole
binaries using space-borne gravitational wave detectors. Using the Fisher
information matrix, we find that the deviation of quadrupole moment can be
constrained to the level of $10^{-1}$, and the events with higher mass-ratio
will give a better constraint. We also find that the late inspiral part will
dominate the result of parameter estimation. The result of Bayesian analysis
shows that the capability will be improved by a few times due to the
consideration of higher modes. We also calculate the Bayes factor, and the
results indicate that the model of black hole and Boson star can be
distinguished undoubtedly.",2401.12066v1
2024-02-07,Macroscopic Magnetic Dynamics,"Ferromagnetic metals and spin-polarized $^{3}$He are spin 1/2 systems with
the same macroscopic symmetry, and thus should have macroscopic magnetic
dynamics with the same structure. Using Onsager's irreversible thermodynamics,
we develop a theory for these systems that contains two relaxation times (one
for the magnetization $\vec{M}$ and the other for the spin current
$\vec{J}_{i}$), a magnetic compressibility, and a mean-field parameter.
Currently spintronics data on metallic ferromagnets are analyzed using a
complex decay length from a theory employing a diffusion constant, a lifetime,
and a mean-field parameter. The present theory leads to a complex decay length
with the same structure. On neglecting decay of $\vec{M}$, the present theory
applies to liquids and gases. For macroscopic equations the particle statistics
is not relevant, so the theory also applies to bosons. The theory predicts a
longitudinal spin wave whose velocity we estimate for liquid $^{3}$He and for
paramagnetic metals; but such a wave should also occur for ferromagnets and for
gases.",2402.04639v1
2024-03-02,Driven charge density modulation by spin density wave and their coexistence interplay in SmFeAsO: A first-principles study,"We use density functional theory to investigate effects of spin-orbit
coupling and single-stripe-type antiferromagnetic (sAFM) ordering on the
crystal structure and electronic properties of SmFeAsO. The results indicate
that AFM ordering causes the crystal structure transition from tetragonal to
orthorhombic, along with increase in the height of As atoms from Fe layer due
to magnetostriction. It also leads to the opening of partial band gaps, the
emergence of a prominent peak near Fermi energy (EF) in the density of states
(DOS) and a reduction in Fermi surface nesting. The study finds a correlation
between the calculated area under the DOS curve, spanning from EF to the first
peak above it, and the optimal electron-doped concentration required for
inducing superconductivity in SmFeAsO. The findings suggest that spin and
charge density waves can play important roles in the superconducting mechanism
of Fe-based superconductors. Our calculations demonstrate that spin-orbit
coupling reduces electronic correlation.",2403.01111v1
2024-03-05,Magnon kinetic theory of the antiferromagnetic Hanle effect,"Motivated by the recently discovered magnonic Hanle effect in an insulating
antiferromagnet [Wimmer et al., Phys. Rev. Lett. 125, 247204 (2020)], we
develop a spin transport theory based on low-energy waves of antiferromagnetic
N\'eel order. These waves have two polarizations, which we describe in analogy
to optics using the Stokes vector on the Poincar\'e sphere. We find that the
polarization, which encodes the magnon spin angular momentum, changes
periodically with a frequency that is nonlinear in the magnetic field. This
explains the observed asymmetry in the Hanle signal as a function of the
magnetic field, along with other salient experimental features. By providing an
energy-resolved description of the spin injection, our theory combines the
kinetic transport of magnons with the coherent dynamics of their polarization
in an intuitive way. This opens a general perspective on a coherent control of
magnonic spin density in collinear antiferromagnets.",2403.03358v1
2004-09-02,Black-hole ejecta by frame-dragging along the axis of rotation,"An energy $E=\omega J$ is derived for gravitational spin-orbit coupling by
frame-dragging $\omega$ acting on angular momentum $J$. This interaction
defines a no-boundary mechanism for linear acceleration of magnetized matter
along the axis of rotation of black holes. We explain GRB030329/SN2003dh by
centered nucleation of a high-mass black hole with rapid rotation, producing
baryon-poor ejecta by gravitational spin-orbit coupling. The duration of the
burst is attributed to spin-down in the emission of gravitational-waves by a
surrounding non-axisymmetric torus.",0409062v1
1993-04-08,Disordered Boson Systems: A Perturbative Study,"A hard-core disordered boson system is mapped onto a quantum spin 1/2
XY-model with transverse random fields. It is then generalized to a system of
spins with an arbitrary magnitude S and studied through a 1/S expansion. The
first order 1/S expansion corresponds to a spin-wave theory. The effect of weak
disorder is studied perturbatively within such a first order 1/S scheme. We
compute the reduction of the speed of sound and the life time of the Bloch
phonons in the regime of weak disorder. Generalizations of the present study to
the strong disordered regime are discussed.",9304016v1
1993-11-09,Spin Excitations and Sum Rules in the Heisenberg Antiferromagnet,"Various bounds for the energy of collective excitations in the Heisenberg
antiferromagnet are presented and discussed using the formalism of sum rules.
We show that the Feynman approximation significantly overestimates (by about
30\% in the $S={1\over2}$ square lattice) the spin velocity due to the non
negligible contribution of multi magnons to the energy weighted sum rule. We
also discuss a different, Goldstone type bound depending explicitly on the
order parameter (staggered magnetization). This bound is shown to be
proportional to the dispersion of classical spin wave theory with a
q-independent normalization factor. Rigorous bounds for the excitation energies
in the anisotropic Heisenberg model are also presented.",9311020v1
1994-02-03,Exact Results for Spin and Charge Dynamics of Electrons with Supersymmetry,"Excitation spectra in the SU($\nu +1$,1) supersymmetric t-J model with
long-range exchange and transfer has quadratic dependence on spin and charge
currents for all energies. After brief review on the supersymmetry, this paper
gives a simple explanation for the spin-charge separation on the basis of a
first-quantized representation. A useful identity is derived on permutation
properties of SU($\nu$) Jastrow-type wave functions, which constitute the
ground states for a class of 1/$r^2$ interaction models.",9402009v1
1994-04-28,A microscopic approach to the dimerization in the frustrated spin-1/2 antiferromagnetic chains,"The spontaneous dimerization of the frustrated spin-$1\over2$
antiferromagnetic chains is studied by a microscopic approach based on a proper
set of composite operators (i.e., pseudo-spin operators). Two approximation
schemes are developed. Firstly, a spin-wave approximation is made by a
Dyson-Mal\'eev-like boson transformation. The ground-state properties and the
triplet excitation spectra are obtained as functions of the coupling parameter.
Secondly, based on the pseudo-spin operators, a microscopic treatment is
formulated within the framework of the powerful, systematic coupled-cluster
method (CCM). Comparison between various approximations is made. The advantage
of the CCM for the purposes of systematic improvement is emphasized.",9404090v1
1995-10-25,Spin Stiffness in the Hubbard model,"The spin stiffness $\rho_{\rm s}$ of the repulsive Hubbard model that occurs
in the hydrodynamic theory of antiferromagnetic spin waves is shown to be the
same as the thermodynamically defined stiffness involved in twisting the order
parameter. New expressions for $\rho_{\rm s}$ are derived, which enable easier
interpretation, and connections with superconducting weight and gauge
invariance are discussed.",9510144v1
1995-12-08,Ferromagnetism in the Hubbard model on the square lattice: Improved instability criterion for the Nagaoka state,"The instability of the fully polarized ferromagnetic state (Nagaoka state)
with respect to single spin flips is re-examined for the Hubbard model on the
square lattice with a large family of variational wave functions which include
correlation effects of the majority spins in the vicinity of the flipped spin.
We find a critical hole density of $\delta_{cr} = 0.251$ for $U = \infty$ and a
critical coupling of $U_{cr} = 77.7 t$. Both values improve previous
variational results considerably.",9512060v1
1995-12-08,Quantum Numbers of Textured Hall Effect Quasiparticles,"We propose a class of variational wave functions with slow variation in spin
and charge density and simple vortex structure at infinity, which properly
generalize both the Laughlin quasiparticles and baby Skyrmions. We argue that
the spin of the corresponding quasiparticle has a fractional part related in a
universal fashion to the properties of the bulk state, and propose a direct
experimental test of this claim. We show that certain spin-singlet quantum Hall
states can be understood as arising from primary polarized states by Skyrmion
condensation.",9512061v1
1996-05-01,Variational Study of the Spin-Gap Phase of the One-Dimensional t-J Model,"We propose a correlated spin-singlet-pairs wave function to describe the
spin-gap phase of the one-dimensional $t-J$ model at low density. Adding a
Jastrow factor with a variational parameter, $\nu$, first introduced by
Hellberg and Mele, is shown to correctly describe the long-range behavior
expected for the Luther-Emery phase. Using the variational Monte Carlo method
we establish a relation between $\nu$ and the Luttinger exponent $K_\rho$,
$K_\rho=\frac{1}{2\nu}$.",9604191v1
1996-06-15,Weak Localization and Negative Magnetoresistance in Wurtzite-type Crystals,"We have developed a theory of the negative magnetoresistance due to the weak
localization in uniaxial wurtzite-type crystals, in which the spin splitting of
the conduction band is linear in the wave vector, unlike the cubic ${\rm A_3
B_5}$ crystals. Unlike earlier theories, we take into account the correlation
between the electron motion in spin and co-ordinate spaces. It is shown that as
a result of this correlation the magnetoresistance depends on the orientation
of the magnetic field with respect to the main axis of the crystal even if the
effective mass is isotropic. The new theory allows to accurately determine the
value of the spin splitting constant in uniaxial crystals.",9606108v1
1996-07-17,Nagaoka State and Degeneracy in the U=infinity Hubbard Model,"The U=infinity Hubbard model on a hypercubic lattice with exactly one hole is
studied. It is seen that a degeneracy can occur in the maximal-spin sector. It
is proved variationally that the Nagaoka (maximal spin) state is not a ground
state, if degeneracy exists. We give an explicit construction of a variational
state, an incommensurate spin-wave state, with energy lower than that of the
Nagaoka state. For the case of more than one hole, a few examples are discussed
where a degeneracy exists.",9607126v1
1996-12-02,Spin dynamics of dimerized Heisenberg chains,"We study numerically the dimerized Heisenberg model with frustration
appropriate for the quasi-1D spin-Peierls compound CuGeO$_3$. We present
evidence for a bound state in the dynamical structure factor for any finite
dimerization $\delta$ and estimate the respective spectral weight. For the
homogeneous case ($\delta=0$) we show that the spin-wave velocity $v_s$ is
renormalized by the n.n.n. frustration term $\alpha$ as $v_s=\pi/2
J(1-b\alpha)$ with $b\approx1.12$",9612013v1
1997-09-24,Redistribution of the Hole Spectral Weight due to Long-Range Spin Correlations in the Three-Band Hubbard Model,"In the framework of the three-band model for CuO_2 plane in high-temperature
superconductors the spectrum of the spin-polaron hole exitation is
investigated. The problem is treated taking into account the coupling of a
local polaron with the antiferromagnetic spin wave with Q=(pi,pi). This leads
to the essential changes of the lowest polaron band E(k) and the strong
redistribution of the bare electron filling.",9709265v1
1997-10-15,Softening and Broadening of the Zone Boundary Magnons in Pr0.63Sr0.37MnO3,"We have studied the spin dynamics in Pr$_{0.63}$Sr$_{0.37}$MnO$_3$ above and
below the Curie temperature $T_C=301$ K. Three distinct new features have been
observed: a softening of the magnon dispersion at the zone boundary for
$T<T_C$, significant broadening of the zone boundary magnons as $T\to T_C$, and
no evidence for residual spin-wave like excitations just above $T_C$. The
results are inconsistent with double exchange models that have been
successfully applied to higher $T_C$ samples, indicating an evolution of the
spin system with decreasing $T_C$.",9710157v1
1997-10-24,Infinite coupling magnon theory of quantum Heisenberg magnetic models of spin s,"An infinity magnon coupling term is introduced into the Holstein-Primakoff
transformed forms of the Heisenberg ferromagnetic and antiferromagnetic models
of any spin $s$ to rigorously remove the unphysical magnon states. This term
makes the series expansion of the square root of the magnon operators become a
finite series of magnon operator products. Under a simple Hubbard-like
approximation our infinite coupling theory yields much better result than the
existing spin wave theories, especially near transition temperatures.",9710261v1
1997-10-27,Thermodynamic Properties of Heisenberg Ferrimagnetic Spin Chains: Ferromagnetic-Antiferromagnetic Crossover,"We study thermodynamic properties of the one-dimensional Heisenberg
ferrimagnet with antiferromagnetically exchange-coupled two kinds of spins 1
and 1/2. The specific heat and the magnetic susceptibility are calculated
employing a modified spin-wave theory as well as a quantum Monte Carlo method.
The specific heat is in proportion to $T^{1/2}$ at low enough temperatures but
shows a Schottky-like peak at mid temperatures. The susceptibility diverges as
$T^{-2}$. We reveal that at low temperatures the model is regarded as a
ferromagnet, while at mid temperatures it behaves like a gapped
antiferromagnet.",9710291v2
1998-01-30,Dynamical Mean-Field Theory for Doped Antiferromagnets,"We have generalized the dynamical mean-field theory to study the doping
dependence of the crossover from antiferromagnetic to short-range order
modelled by an incommensurate spin density wave in the Hubbard model. The local
selfenergy which includes spin fluctuations gives quasiparticle weights and
spectral properties in good agreement with quantum Monte Carlo and exact
diagonalization data in two dimensions. The spectra at finite doping are
characterized by a Mott-Hubbard `gap' accompanied by a pseudogap induced by the
local spin order.",9801325v1
1998-05-21,Two-Coupled Chains with Spin-Anisotropic Backward Scattering,"By applying renormalization group method to the bosonized Hamiltonian of
two-coupled chains with repulsive intrachain interaction, we have examined a
role of backward scattering with a spin-anisotropy which competes with
interchain hopping. From calculation of a dominant state in the limit of low
energy, it is found that superconducting state moves into spin density wave
state when the anisotropy becomes larger than a critical value. Further phase
diagram is shown on the plane of g-ology.",9805270v2
1998-10-13,Superconductivity and spin triplet collective mode in the t-J model close to antiferromagnetic instability,"To investigate relations between long-range antiferromagnetic (AF) order,
superconductivity and two particle triplet collective excitations we consider a
modified two dimensional t-J model at doping close to half filling. The model
includes additional hopping t'' and nearest sites Coulomb repulsion V. The
additional parameters allow us to control closeness of the system to the AF
instability. We demonstrate the possibility of co-existence of long-range AF
order and d-g-wave superconductivity. In the phase with long-range AF order we
find, analytically, superconducting gaps and spin wave renormalization. We
demonstrate that at approaching the point of the AF instability the spin
triplet collective excitation arises with energy below the superconducting gap.",9810141v1
1999-01-11,Theory of spin wave excitation in manganites,"The role of the orbital degrees of freedom is studied theoretically for the
spin dynamics of $R_{1-x}A_x$MnO$_3$. Based on the meanfield solution, an RPA
calculation has been done and it is found that the $d_{x^2-y^2}$-type orbital
is essential for the double-exchange (DE) interactions, i.e., the DE is
basically two-dimensional interaction. Based on this results compared with
experiments, we propose that the orbital wavefunction is $d_{x^2-y^2}$-type
locally even in the metallic ferromagnetic state, which fluctuate quantum
mechanically. Well agreement of the estimation with experiments suggest that
the Jahn-Teller phonon has less importance on the spin dynamics.",9901076v2
1999-02-16,Sign Rules for Anisotropic Quantum Spin Systems,"We present new and exact ``sign rules'' for various spin-s anisotropic
spin-lattice models. It is shown that, after a simple transformation which
utilizes these sign rules, the ground-state wave function of the transformed
Hamiltonian is positive-definite. Using these results exact statements for
various expectation values of off-diagonal operators are presented, and
transitions in the behavior of these expectation values are observed at
particular values of the anisotropy. Furthermore, the effects of sign rules in
variational calculations and quantum Monte Carlo calculations are considered.
They are illustrated by a simple variational treatment of a one-dimensional
anisotropic spin model.",9902219v1
1999-02-18,Spin Dynamical Properties of the Layered Perovskite La1.2Sr1.8Mn2O7,"Inelastic neutron-scattering measurements were performed on a single crystal
of the layered colossal magnetoresistance (CMR) material La1.2Sr1.8Mn2O7 (Tc ~
120K). We found that the spin wave dispersion is almost perfectly
two-dimensional with the in-plane spin stiffness constant D ~ 151meVA. The
value is similar to that of similarly doped La1-xSrxMnO3 though its Tc is three
times higher, indicating a large renormalization due to low dimensionality.
There exist two branches due to a coupling between layers within a
double-layer. The out-of-plane coupling is about 30% of the in-plane coupling
though the Mn-O bond lengths are similar.",9902253v1
1999-04-17,Tunneling Via Individual Electronic States in Ferromagnetic Nanoparticles,"We measure electron tunneling via discrete energy levels in ferromagnetic
cobalt particles less than 4 nm in diameter, using non-magnetic electrodes. Due
to magnetic anisotropy, the energy of each tunneling resonance shifts as an
applied magnetic field rotates the particle's magnetic moment. We see both
spin-increasing and decreasing tunneling transitions, but we do not observe the
spin degeneracy at small magnetic fields seen previously in non-magnetic
materials. The tunneling spectrum is denser than predicted for independent
electrons, possibly due to spin-wave excitations.",9904248v2
1999-04-22,Mixed-spin systems: coexistence of Haldane gap and antiferromagnetic long range order,"Recent experiments on the quasi-1D antiferromagnets $R_{2}BaNiO_{5}$ (R =
rare earth) have shown the existence of purely 1D Haldane gap excitations
propagating on the Ni chains. Below an ordering temperature, the gap
excitations survive and coexist with the conventional spin waves in the ordered
phase. We construct a model mixed-spin system in 2D for which the ground state
can be exactly specified. Using the Matrix Product Method, we show the
existence of Haldane gap excitations in the ordered phase. We consider
different cases of ordering to study the effect of ordering on the degeneracy
of the Haldane gap excitations.",9904311v1
1999-07-19,Edge Theories for Polarized Quantum Hall States,"Starting from recently proposed bosonic mean field theories for fully and
partially polarized quantum Hall states, we construct corresponding effective
low energy theories for the edge modes. The requirements of gauge symmetry and
invariance under global O(3) spin rotations, broken only by a Zeeman coupling,
imply boundary conditions that allow for edge spin waves. In the generic case,
these modes are chiral, and the spin stiffness differs from that in the bulk.
For the case of a fully polarized $\nu=1$ state, our results agree with
previous Hartree-Fock calculations.",9907268v2
1999-12-06,Theory of the Transition at 0.2 K in Ni-doped Bi2Sr2CaCu2O8,"A theory is put forward that the electronic phase transition at 0.2 K in
Ni-doped Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8}$ is result of the formation of a spin
density wave in the system of Ni impurities. The driving force for the
transition is the exchange interaction between the impurity spins and the spins
of the conduction electrons. This creates a small gap at two of the four nodes
of the superconducting gap. The effect is to reduce the thermal conductivity by
a factor of two, as observed.",9912078v1
2000-01-21,Theory of Diluted Magnetic Semiconductor Ferromagnetism,"We present a theory of carrier-induced ferromagnetism in diluted magnetic
semiconductors (III_{1-x} Mn_x V) which allows for arbitrary itinerant-carrier
spin polarization and dynamic correlations. Both ingredients are essential in
identifying the system's elementary excitations and describing their
properties. We find a branch of collective modes, in addition to the spin waves
and Stoner continuum which occur in metallic ferromagnets, and predict that the
low-temperature spin stiffness is independent of the strength of the exchange
coupling between magnetic ions and itinerant carriers. We discuss the
temperature dependence of the magnetization and the heat capacity.",0001320v2
2000-02-14,Effect of the Orbital Level Difference in Doped Spin-1 Chains,"Doping of a two-orbital chain with mobile S=1/2 Fermions and strong Hund's
rule couplings stabilizing the S=1 spins strongly depends on the presence of a
level difference among these orbitals. By DMRG methods we find a finite spin
gap upon doping and dominant pairing correlations without level-difference,
whereas the presence of a level difference leads to dominant charge density
wave (CDW) correlations with gapless spin-excitations. The string correlation
function also shows qualitative differences between the two models.",0002193v2
2000-06-01,High-energy magnon dispersion and multi-magnon continuum in the two-dimensional Heisenberg antiferromagnet,"We use quantum Monte Carlo simulations and numerical analytic continuation to
study high-energy spin excitations in the two-dimensional S=1/2 Heisenberg
antiferromagnet at low temperature. We present results for both the transverse
and longitudinal dynamic spin structure factor S(q,w) at q=(pi,0) and
(pi/2,pi/2). Linear spin-wave theory predicts no dispersion on the line
connecting these momenta. Our calculations show that in fact the magnon energy
at (pi,0) is 10% lower than at (pi/2,pi/2). We also discuss the transverse and
longitudinal multi-magnon continua and their relevance to neutron scattering
experiments.",0006021v1
2000-06-27,Energy separation of single-particle and continuum states in a S=1/2 weakly-coupled chains antiferromagnet,"Inelastic neutron scattering is used to study transverse-polarized magnetic
excitations in the quasi-one-dimensional S=1/2 antiferromagnet BaCu_2Si_2O_7,
where the saturation value for the N\'eel order parameter is $m_0=0.12 \mu_{\rm
B}$ per spin. At low energies the spectrum is totally dominated by
resolution-limited spin wave-like excitations. An excitation continuum sets in
above a well-defined threshold frequency. Experimental results are discussed in
the context of current theories for weakly-interacting quantum half-integer
spin chains.",0006426v1
2000-11-13,Spin Excitations in Localized and Itinerant Magnets,"Collective excitations in magnetic materials can be investigated by means of
inelastic neutron scattering. We show that this experimental method gives
access to the complete spectrum of magnetic fluctuations through the energy-
and momentum-dependence of the dynamical susceptibility. We focus on the
dynamical properties of magnets with localized spin densities and of metals.
  From such studies, microscopic parameters like exchange integrals, spin-wave
stiffness and relaxation times can be determined. This is of great help to test
current theories in magnetism.",0011220v1
2000-12-19,Significance of the direct relaxation process in the low-energy spin dynamics of a one-dimensional ferrimagnet NiCu(C_7H_6N_2O_6)(H_2O)_3 2H_2O,"In response to recent nuclear-magnetic-resonance measurements on a
ferrimagnetic chain compound NiCu(C_7H_6N_2O_6)(H_2O)_3 2H_2O [Solid State
Commun. {\bf 113} (2000) 433], we calculate the nuclear spin-lattice relaxation
rate 1/T_1 in terms of a modified spin-wave theory. Emphasizing that the
dominant relaxation mechanism arises from the direct (single-magnon) process
rather than the Raman (two-magnon) one, we explain the observed temperature and
applied-field dependences of 1/T_1. Ferrimagnetic relaxation phenomena are
generally discussed and novel ferrimagnets with extremely slow dynamics are
predicted.",0012342v1
2001-02-21,Effective interactions in the stripe state of the two-dimensional Hubbard model,"We investigate the structure of the pairing potential in the stripe phase of
the two-dimensional Hubbard model. Based on the random phase approximation we
discuss in detail the interactions in the charge- and spin channel and compare
our calculations with related considerations in commensurate antiferromagnets.
Our main finding is that due to the incommensurate charge-density wave
formation the exchange of collective modes in the charge channel is
significantly enhanced with respect to the spin bag approach whereas due to the
inhomogeneous charge distribution the coupling to transverse spin fluctuations
tends to be suppressed.",0102374v2
2001-05-10,Spin dynamics in the $S=1/2$ weakly-coupled chains antiferromagnet BaCu$_2$Si$_2$O$_7$,"Inelastic neutron scattering is used to identify single-particle and
continuum spin excitations in the quasi-one-dimensional $S=1/2$ antiferromagnet
\ba. In the data analysis, close attention is given to resolution effects. A
gap in the continuum spectrum at $\Delta_c=4.74.8$ meV is directly observed.
The gap energy is in excellent agreement with existing theoretical predictions.
Below the gap, the spectrum is dominated by sharp accoustic spin wave
excitations.",0105223v1
2001-07-18,Quantum Heisenberg Antiferromagnets versus Nonlinear $σ$ Model Without the Large S Limit,"In this letter, I develop a new topologically invariant coherent state path
integral for spin systems, and apply it to the quantum Heisenberg model on a
square lattice. As a result, the quantum nonlinear $\sigma$ model for arbitrary
values of spin can be directly obtained. The effective coupling constant and
spin wave velocity are modified by $g_s= {2\over S}\sqrt{d+{T_\Lambda\over
2SJ}}$ and $c_s=2JSa \sqrt{d+{T_\Lambda\over 2SJ}}$, where $T_\Lambda$ is a
natural temperature scale for the reliability of the theory. The formulation
can also be extended to other generalized coherent state path integrals.",0107389v1
2001-10-25,Re-examination of orbital ordering in LaMnO$_3$: Electron-electron and electron-lattice interactions,"The interactions between $e_g$ orbitals in neighboring sites are investigated
in LaMnO$_3$ by taking into account virtual exchange of electrons and phonons.
The spin and orbital ordering temperatures and the spin wave dispersion
relation are calculated. We find that the orbital ordering is mainly caused by
the electronic interactions and that the Jahn-Teller coupling is much smaller
than that reported previously. We propose that the elastic constant shows a
characteristic change at the N{\'e}el temperature by the spin and orbital
coupling and the higher-order Jahn-Teller coupling.",0110534v1
2001-12-10,An Adiabatic Quantum Pump of Spin Polarized Current,"We propose a mechanism by which an open quantum dot driven by two ac (radio
frequency) gate voltages in the presence of a moderate in-plane magnetic field
generates a spin polarized, phase coherent dc current. The idea combines
adiabatic, non-quantized (but coherent) pumping through periodically modulated
external parameters and the strong fluctuations of the electron wave function
existent in chaotic cavities. We estimate that the spin polarization of the
current can be observed for temperatures and Zeeman splitting energies of the
order of the single-particle mean level spacing.",0112157v1
2001-12-12,Quantum Phase Transition in Coupled Spin Ladders,"The ground state of an array of coupled, spin-half, antiferromagnetic ladders
is studied using spin-wave theory, exact diagonalization (up to 36 sites) and
quantum Monte Carlo techniques (up to 256 sites). Our results clearly indicate
the occurrence of a zero-temperature phase transition between a N\'eel ordered
and a non-magnetic phase at a finite value of the inter-ladder coupling
($\alpha_c\simeq0.3$). This transition is marked by remarkable changes in the
structure of the excitation spectrum.",0112206v1
2002-01-07,Two-electron quantum dot molecule: Composite particles and the spin phase diagram,"We study a two-electron quantum dot molecule in a magnetic field by the
direct diagonalization of the Hamiltonian matrix. The ground states of the
molecule with the total spin S=0 and S=1 provide a possible realization for a
qubit of a quantum computer. Switching between the states is best achieved by
changing the magnetic field. Based on an analysis of the wave function, we show
that the system consists of composite particles formed by an electron and flux
quanta attached to it. This picture can also be used to explain the spin phase
diagram.",0201076v1
2002-05-21,Transition rates via Bethe ansatz for the spin-1/2 Heisenberg chain,"We use the exact determinantal representation derived by Kitanine, Maillet,
and Terras for matrix elements of local spin operators between Bethe wave
functions of the one-dimensional s=1/2 Heisenberg model to calculate and
numerically evaluate transition rates pertaining to dynamic spin structure
factors. For real solutions z_1,...,z_r of the Bethe ansatz equations, the size
of the determinants is of order r x r. We present applications to the
zero-temperature spin fluctuations parallel and perpendicular to an external
magnetic field.",0205430v1
2002-08-29,Bose-Einstein-Young condensates,"We demonstrate a possibility to create a new state of ultracold atoms which
we call a Bose-Einstein-Young condensate. Atoms are supposed to be in different
hyperfine state of the same isotope. The wave function of such a state,
although totally symmetric with respect to simultaneous permutation of
co-ordinates and spins of any pair of atoms, has more complicated structure
than a simple product of totally symmetric co-ordinate and spin parts. Its
properties with respect to permutations of only co-ordinates or only spins are
characterized by a particular Young diagram, a symbol denoting an irreducible
representation of the permutation group.",0208581v2
2003-01-21,Hole-Doping Effects on a Two-dimensional Kondo Insulator,"We study the effects of hole doping on the two-dimensional Heisenberg-Kondo
model around the quantum critical point, where the spin liquid phase (Kondo
insulator) and the magnetically ordered phase are separated via a second-order
phase transition. By means of the self-consistent Born approximation within the
bond operator formalism as well as the standard spin wave theory, we discuss
dynamical properties of a doped hole. It is clarified that a quasi-particle
state stabilized in the spin liquid phase is gradually obscured as the system
approaches the quantum critical point. This is also the case for the
magnetically ordered phase. We argue the similarity and the difference between
these two cases.",0301401v1
2003-02-02,Universal Spin-Flip Transition in Itinerant Antiferromagnets,"We report a universal spin flip (SF) transition as a function of temperature
in spin-density-wave (SDW) systems. At low temperatures the antiferromagnetic
(AFM) polarization is parallel to the applied field and above a critical
temperature the AFM polarization {\it flips} perpendicular to the field. This
transition occurs in {\it any} SDW system and may be considered as a
qualitative probe of the itinerant character of AFM in a given material. Our SF
transition resolves the longstanding puzzle of the SF transition observed in
cromium and may be at the origin of the equally puzzling SDW-I to SDW-II
transition in Bechgaard salts for which we make experimental predictions.",0302016v1
2003-02-05,Phase diagram of the $t-t'-U$ chain at half filling,"We study the half filled Hubbard chain including next-nearest-neighbor
hopping $t'$. The model has three phases: one insulating phase with dominant
spin-density-wave correlations at large distances (SDWI), another phase with
dominant spin-dimer correlations or dimerized insulator (DI), and a third one
in which long distance correlations indicate singlet superconductivity (SS).
The boundaries of the SDWI are accurately determined numerically through a
crossing of excited energy levels equivalent to the jump in the spin Berry
phase. The DI-SS boundary is studied using several indicators like correlation
exponent $K_{\rho}$, Drude weight $D_{c}$, localization parameter $z_{L}$ and
charge gap $\Delta_{c}$.",0302106v1
2003-03-08,Transition rates via Bethe ansatz for the spin-1/2 planar XXZ antiferromagnet,"A novel determinantal representation for matrix elements of local spin
operators between Bethe wave functions of the one-dimensional s=1/2 XXZ model
is used to calculate transition rates for dynamic spin structure factors in the
planar regime. In a first application, high-precision numerical data are
presented for lineshapes and band edge singularities of the in-plane (xx)
two-spinon dynamic spin structure factor.",0303147v1
2003-04-18,Unconventional spin fluctuations in the hexagonal antiferromagnet YMnO$_3$,"We used inelastic neutron scattering to show that well below its N\'{e}el
temperature, $T_{\rm N}$, the two-dimensional (2D) XY nearly-triangular
antiferromagnet YMnO$_{3}$ has a prominent {\it central peak} associated with
2D antiferromagnetic fluctuations with a characteristic life time of 0.55(5)
ps, coexisting with the conventional long-lived spin-waves. Existence of the
two time scales suggests competition between the N\'{e}el phase favored by weak
interplane interactions, and the Kosterlitz-Thouless phase intrinsic to the 2D
XY spin system.",0304441v1
2003-05-18,New Resonances Along with Cyclotron Resonance in Heterostructures,"The usual cyclotron resonance occurs at \omega_c=eB/m*c which is independent
of spin. The new resonances depend on spin. The new resonances occur at
\omega_{c\pm}=(1/2)g_{\pm}eB/m*c where (1/2)g_{\pm}= {\it l}+(1/2)\pm s/(2{\it
l}+1). The energy in the centre of two new frequencies varies as the square
root of the 2-dimensional electrons due to spin excess in the Gaussian model.
The frequencies \omega_{c\pm} are linearly proportional to the magnetic field
except near crossing point where the linear combination of wave functions must
be made.",0305415v1
2003-06-09,Stripes and superconductivity in one-dimensional self-consistent model,"We show that many observable properties of high temperature superconductors
can be obtained in the frameworks of one-dimensional self-consistent model with
included superconducting correlations. Analytical solutions for spin, charge
and superconductivity order parameters are found.
  The ground state of the model at low hole doping is a spin-charge solitonic
superstructure. Increasing of doping leads to the phase transition to
superconducting phase. There is a region of doping where superconductivity,
spin density wave and charged stripe structure coexist.
  The charge density modulation presents in the vicinity of vortices (kinks in
the 1D model) in the superconducting state.",0306211v2
2003-10-31,Magnetic excitations in La$_{1.5}$Sr$_{0.5}$CoO$_4$,"We report magnetization and neutron scattering measurements of the half-doped
compound La$_{1.5}$Sr$_{0.5}$CoO$_4$, which exhibits a checkerboard pattern of
charge ordering below ~800K. In the antiferromagnetically-ordered phase below
\~40K the spins are found to be canted in the ab plane. The spin excitation
spectrum includes spin-wave excitations with a maximum energy of 16 meV, and
diffuse magnetic modes at energies around 30 meV.",0310778v1
2004-01-16,Magnetic field induced phase transitions in spin ladders with ferromagnetic legs,"We study the phase diagram of spin ladders with ferromagnetic legs under the
influence of a symmetry breaking magnetic field in the weak coupling effective
field theory by bosonization. For antiferromagnetic interleg coupling we
identify two phase transitions introduced by the external magnetic field. In
order to establish the universality of the phases we supplement the
bosonization approach by results from a strong coupling (rung) expansion and
from spin wave analysis.",0401301v1
2004-01-20,The spin excitation spectrum in striped bilayer compounds,"The spin dynamics of bilayer cuprate compounds are studied in a basic model.
The magnetic spectral properties are calculated in linear spin-wave theory for
several stripe configurations which differ by the relative location of the
stripes in the layers. We focus on the bilayer splitting of the magnon bands
near the incommensurate low energy peaks as well as near the $\pi$ resonance,
distinguishing between the odd and even channel. We find that a x-shaped
dispersion near the $\pi$ resonance is generic for stripes. By comparison of
our results to neutron scattering data for $\mathrm{YBa_2Cu_3O_{6+x}}$ we
conclude that the stripe model is consistent with characteristic features of
bilayer high-$T_c$ compounds.",0401354v1
2004-01-21,Non-fermi liquid behavior in itinerant antiferromagnets,"We consider a two dimensional itinerant antiferromagnet near a quantum
critical point. We show that, contrary to conventional wisdom, fermionic
excitations in the ordered state are not the usual Fermi liquid quasiparticles.
Instead, down to very low frequencies, the fermionic self energy varies as
$\omega^{2/3}$. This non-Fermi liquid behavior originates in the coupling of
fermions to the longitudinal spin susceptibility $\chi_{\parallel}(q, \Omega)$
in which the order-induced ``gap'' in the spectrum at $q=0$ dissolves into the
Landau damping term at $v_F q >\Omega$. The transverse spin fluctuations obey
$z=1$ scaling characteristic of spin waves, but remain overdamped in a finite
range near the critical point.",0401375v1
2004-02-16,Triplet superconductivity vs. easy-plane ferromagnetism in a 1D itinerant electron system with transverse spin anisotropy,"In this paper we study the ground state phase diagram of a one-dimensional
$t-U-J$ model, at half-filling. In the large-bandwidth limit and for
ferromagnetic exchange with easy-plane anisotropy, a phase with gapless charge
and massive spin excitations, characterized by the coexistence of triplet
superconducting and spin density wave instabilities is realized in the ground
state. With reduction of the bandwidth, a transition into an insulating phase
showing properties of the spin-1/2 XY model takes place.",0402405v1
2004-03-03,"Nesting, spin-fluctuations, and odd-gap superconductivity in NaxCoO2 yH2O","We have calculated the one-electron susceptibility of hydrated NaxCoO2 and
find strong nesting nearly commensurate with a 2X2 superstructure. The nesting
involves about 70% of all electrons at the Fermi level and is robust with
respect to doping. This nesting creates a tendency to a charge density wave
compatible with the charge order often seen at x approx 0.5, which is usually
ascribed to electrostatic repulsion of Na ions. In the spin channel, it gives
rise to strong spin-fluctuations, which should be important for
superconductivity. The superconducting state most compatible with this nesting
structure is an odd-gap triplet s-wave state.",0403135v1
2004-03-15,Current Induced Excitations in Cu/Co/Cu Single Ferromagnetic Layer Nanopillars,"Current-induced magnetic excitations in Cu/Co/Cu single layer nanopillars
(~50 nm in diameter) have been studied experimentally as a function of Co layer
thickness at low temperatures for large applied fields perpendicular to the
layers. For asymmetric junctions current induced excitations are observed at
high current densities for only one polarity of the current and are absent at
the same current densities in symmetric junctions. These observations confirm
recent predictions of spin-transfer torque induced spin wave excitations in
single layer junctions with a strong asymmetry in the spin accumulation in the
leads.",0403367v1
2004-03-16,Anisotropy-induced ordering in the quantum J1-J2 antiferromagnet,"We study the effect of spin anisotropies on a frustrated quantum
antiferromagnet using the J_1-J_2^{XXZ} model on the square lattice. The T=0
and finite-T phase diagrams of this model are obtained utilizing spin-wave
theory, exact diagonalization, and quantum Monte Carlo. We find that
anisotropic frustration tends to stabilize XY- and Ising-like ordered phases,
while the disordered spin-liquid phase is restricted to a small region of the
phase diagram. The ordered phases are separated by first-order transitions and
exhibit a non-trivial reentrance phenomenon.",0403375v1
2004-04-15,Magnetic groundstate and Fermi surface of bcc Eu,"Using spin-spiral technique within the full potential linearized
augmented-plane-waves (LAPW) electronic structure method we investigate the
magnon spectrum and N\'eel temperature of bcc Eu. Ground state corresponding to
an incommensurate spin-spiral is obtained in agreement with experiment and
previous calculations. We demonstrate that the magnetic coupling is primarily
through the intra-atomic $f-s$ and $f-d$ exchange and
Ruderman-Kittel-Kasuya-Yosida mechanism. We show that the existence of this
spin-spiral is closely connected to a nesting feature of the Fermi surface
which was not noticed before.",0404369v1
2004-09-13,Spin order in the one-dimensional Kondo and Hund lattices,"We study numerically the one-dimensional Kondo and Hund lattices consisting
of localized spins interacting antiferro or ferromagnetically with the
itinerant electrons, respectively. Using the Density Matrix Renormalization
Group we find, for both models and in the small coupling regime, the existence
of new magnetic phases where the local spins order forming ferromagnetic
islands coupled antiferromagnetically. Furthermore, by increasing the
interaction parameter $|J|$ we find that this order evolves toward the
ferromagnetic regime through a spiral-like phase with longer characteristic
wave lengths. These results shed new light on the zero temperature magnetic
phase diagram for these models.",0409332v1
2004-11-18,Charge and spin dynamics of interacting Fermions in a one dimensional harmonic trap,"We study an atomic Fermi gas interacting through repulsive contact forces in
a one dimensional harmonic trap. Bethe-Ansatz solutions lead to an
inhomogeneous Tomonaga-Luttinger model for the low energy excitations. The
equations of motion for charge and spin density waves are analyzed both near
the trap center and near the trap edges. While the center shows conventional
spin-charge separation the edges cause a giant increase of the separation
between these modes.",0411480v1
2005-02-10,Spin splitting of X-related donor impurity states in an AlAs barrier,"We use magnetotunneling spectroscopy to observe the spin splitting of the
ground state of an X-valley-related Si-donor impurity in an AlAs barrier. We
determine the absolute magnitude of the effective Zeeman spin splitting factors
of the impurity ground state to be g$_{I}$= 2.2 $\pm $ 0.1. We also investigate
the spatial form of the electron wave function of the donor ground state, which
is anisotropic in the growth plane.",0502266v1
2005-06-19,Anisotropic Hubbard model on a triangular lattice -- spin dynamics in Ho Mn O_3,"The recent neutron-scattering data for spin-wave dispersion in $\rm Ho Mn
O_3$ are well described by an anisotropic Hubbard model on a triangular lattice
with a planar (XY) spin anisotropy. Best fit indicates that magnetic
excitations in $\rm Ho Mn O_3$ correspond to the strong-coupling limit $U/t >
\sim 15$, with planar exchange energy $J=4t^2/U \simeq 2.5$meV and planar
anisotropy $\Delta U \simeq 0.35$meV.",0506475v3
2005-10-05,Gated Spin Transport through an Individual Single Wall Carbon Nanotube,"Hysteretic switching in the magnetoresistance of short-channel,
ferromagnetically contacted individual single wall carbon nanotubes is
observed, providing strong evidence for nanotube spin transport. By varying the
voltage on a capacitively coupled gate, the magnetoresistance can be
reproducibly modified between +10% and -15%. The results are explained in terms
of wave vector matching of the spin polarized electron states at the
ferromagnetic / nanotube interfaces.",0510112v1
2005-11-06,Dynamics of composite Haldane spin chains in IPA-CuCl3,"Magnetic excitations in the quasi-one-dimensional antiferromagnet IPA-CuCl3
are studied by cold neutron inelastic scattering. Strongly dispersive gap
excitations are observed. Contrary to previously proposed models, the system is
best described as an asymmetric quantum spin ladder. The observed spectrum is
interpreted in terms of ``composite'' Haldane spin chains. The key difference
from actual S=1 chains is a sharp cutoff of the single-magnon spectrum at a
certain critical wave vector.",0511143v1
2005-11-30,Cluster states of Fermions in the single l-shell model,"The paper concerns the ground state structure of the partly filled l-shell of
a fermionic gas of atoms of spin s in a spherically symmetric spin independent
trap potential. At particle numbers N=n(2s+1), n=1,2,...,2l+1 the basic
building blocks are clusters consisting of (2s+1) atoms, whose wave functions
are completely symmetric and antisymmetric in space and spin variables,
respectively. The creation operator of a cluster is constructed whose repeated
application to the vacuum leads to the multi-cluster state. Ground state energy
expressions are derived for the n-cluster states at different l,s values and
interpreted in simple terms.",0511734v1
2005-12-24,Low-temperature thermodynamics of one-dimensional alternating-spin Heisenberg ferromagnets,"Motivated by a novel bimetallic chain compound in which alternating magnetic
centers are ferromagnetically coupled, we investigate thermodynamic properties
of one-dimensional spin-$(S,s)$ Heisenberg ferromagnets both numerically and
analytically. On the one hand, quantum Monte Carlo calculations illuminate the
overall thermal behavior. The specific heat may exhibit a double-peaked
structure at intermediate temperatures for $S\agt 3s$ in general. On the other
hand, a modified spin-wave theory precisely describes the low-temperature
properties. Expanding the specific heat and the magnetic susceptibility, we
reveal an analogy and a contrast between mixed-spin ferromagnets and
ferrimagnets.",0512630v1
2006-05-12,Magnetic properties of spin-orbital polarons in lightly doped cobaltates,"We present a numerical treatment of a spin-orbital polaron model for
Na_xCoO_2 at small hole concentration (0.7 < x < 1). We demonstrate how the
polarons account for the peculiar magnetic properties of this layered compound:
They explain the large susceptibility; their internal degrees of freedom lead
both to a negative Curie-Weiss temperature and yet to a ferromagnetic
intra-layer interaction, thereby resolving a puzzling contradiction between
these observations. We make specific predictions on the momentum and energy
location of excitations resulting from the internal degrees of freedom of the
polaron, and discuss their impact on spin-wave damping.",0605334v1
2006-08-02,Connecting the timescales in picosecond remagnetization experiments,"In femtosecond demagnetization experiments, one gains access to the
elementary relaxation mechanisms of a magnetically ordered spin system on a
time scale of 100 fs. Following these experiments, we report a combined
micromagnetic and experimental study that connects the different regimes known
from all-optical pump-probe experiments by employing a simple micromagnetic
model. We identify spin-wave packets on the nanometer scale that contribute to
the remagnetization process on the intermediate time scale between single-spin
relaxation and collective precession.",0608063v2
2006-09-19,Solitons in a trapped spin-1 atomic condensate,"We numerically investigate a particular type of spin solitons inside a
trapped atomic spin-1 Bose-Einstein condensate (BEC) with ferromagnetic
interactions. Within the mean field theory approximation, our study of the
solitonic dynamics shows that the solitonic wave function, its center of mass
motion, and the local spin evolutions are stable and are intimately related to
the domain structures studied recently in spin-1 $^{87}$Rb condensates. We
discuss a rotating reference frame wherein the dynamics of the solitonic local
spatial spin distribution become time independent.",0609468v3
2006-10-18,A unified origin for the 3D magnetism and superconductivity in Na$_x$CoO$_2$,"We analyze the origin of the three dimensional (3D) magnetism observed in
nonhydrated Na-rich Na$_x$CoO$_2$ within an itinerant spin picture using a 3D
Hubbard model. The origin is identified as the 3D nesting between the inner and
outer portions of the Fermi surface, which arise due to the local minimum
structure of the $a_{1g}$ band at the $\Gamma$-A line. The calculated spin wave
dispersion strikingly resembles the neutron scattering result. We argue that
this 3D magnetism and the spin fluctuations responsible for superconductivity
in the hydrated systems share essentially the same origin.",0610494v1
1994-10-25,Spin dependent structure function $ g_{2}(x)$ in quark-parton model. Possible interpretation and numerical estimates,"It is shown that in the special infinite momentum frame where photon has pure
transverse components at $P\rightarrow\infty$ the spin-dependent deep inelastic
structure function $ g_{2}(x)$ has a reasonable interpretation in terms of
quark-parton wave functions, whereas in the conventional frame where photon has
pure z-component the parton model fails for $ g_{2}(x)$.The spin dependent
structure functions $ g_{1}(x)$ and $ g_{2}(x)$ have been calculated in the
relativistic quark model constructed in such frame. The results indicate
significant twist-3 contribution.",9410366v1
1995-03-15,THE PROTON SPIN PUZZLE AND DEPOLARIZATION IN $\bar{p}p\to\barΛΛ$,"We point out that the measurement of target spin depolarization $D_{nn}$ in
the $\bar{p}p\to\bar{\Lambda}\Lambda$ reaction may test dynamical mechanisms
invoked to explain the proton spin puzzle revealed by polarized deep--inelastic
scattering experiments. In particular, models with {\it negatively} polarized
$\bar{s}s$ pairs in the proton wave function predict $D_{nn}<0$, whereas models
with {\it positively} polarized gluons would predict $D_{nn}>0$.",9503333v1
1996-11-01,Problems and Prospects in Spin Physics,"This talk reviews some of the hot topics in spin physics and related
subjects, including perturbative QCD predictions for polarized parton
distributions and their possible behaviours at small x, the Bjorken and singlet
sum rules and the treatment of higher orders in perturbative QCD, different
interpretations of the EMC spin effect including chiral solitons and the axial
U(1) anomaly, other experimental indications for the presence of strange quarks
in the nucleon wave function, implications for dark matter physics, and a few
words about polarization as a tool in electroweak physics.",9611208v1
1999-09-17,Using Heavy Quark Spin Symmetry in Semileptonic $B_c$ Decays,"The form factors parameterizing the B_c semileptonic matrix elements can be
related to a few invariant functions if the decoupling of the spin of the heavy
quarks in B_c and in the mesons produced in the semileptonic decays is
exploited. We compute the form factors as overlap integral of the meson
wave-functions obtained using a QCD relativistic potential model, and give
predictions for semileptonic and non-leptonic B_c decay modes. We also discuss
possible experimental tests of the heavy quark spin symmetry in B_c decays.",9909423v1
2000-05-17,Spin structure and longitudinal polarization of hyperon in e+e- annihilation at high energies,"Longitudinal polarizations of different kinds of hyperons produced in e+e-
annihilation at LEP I and LEP II energies in different event samples are
calculated using two different pictures for the spin structure of hyperon: that
drawn from polarized deep inelastic lepton-nucleon scattering data or that
using SU(6) symmetric wave functions. The result shows that measurements of
such polarizations should provide useful information to the question of which
picture is more suitable in describing the spin effects in the fragmentation
processes.",0005172v1
2001-10-09,Soliton Models for the Nucleon and Predictions for the Nucleon Spin Structure,"In these lectures the three flavor soliton approach for baryons is reviewed.
Effects of flavor symmetry breaking in the baryon wave--functions on axial
current matrix elements are discussed. A bosonized chiral quark model is
considered to outline the computation of spin dependent nucleon structure
functions in the soliton picture.",0110128v2
1993-01-11,On the Electromagnetic Interactions of Anyons,"Using the appropriate representation of the Poincare group and a definition
of minimal coupling, we discuss some aspects of the electromagnetic
interactions of charged anyons. In a nonrelativistic expansion, we derive a
Schrodinger-type equation for the anyon wave function which includes
spin-magnetic field and spin-orbit couplings. In particular, the gyromagnetic
ratio for charged anyons is shown to be 2; this last result is essentially a
reflection of the fact that the spin is parallel to the momentum in (2+1)
dimensions.",9301037v1
1994-03-10,Symmetry Under $α\rightarrow α+ 1$ is Forbidden by Helicity Conservation,"The question as to whether helicity conservation in spin one-half Aharonov
Bohm scattering is sufficient in itself to determine uniquely the form of the
spinor wave function near the origin is examined. Although it is found that a
one parameter family of solutions is compatible with this conservation law,
there must nonetheless be singular solutions which break the symmetry $\alpha
\rightarrow \alpha +1$ required for an anyon interpretation. Thus the free
parameter which occurs does not allow one to eliminate the singular solutions
even though it does in principle mean that they can be transferred at will
between the spin up and spin down configurations.",9403065v1
1995-09-11,Quasi-Exactly Solvable Spin 1/2 Schrödinger Operators,"The algebraic structures underlying quasi-exact solvability for spin 1/2
Hamiltonians in one dimension are studied in detail. Necessary and sufficient
conditions for a matrix second-order differential operator preserving a space
of wave functions with polynomial components to be equivalent to a \sch\
operator are found. Systematic simplifications of these conditions are
analyzed, and are then applied to the construction of several new examples of
multi-parameter QES spin 1/2 Hamiltonians in one dimension.",9509057v1
2001-02-16,The Gordon decompositions of the inertial currents of the Dirac electron correspond to a Foldy-Wouthuysen transformation,"We consider Dirac's free electron theory on the first quantized level. We
decompose its canonical spin current \'a la Gordon and find a conserved
``Gordon spin'' current which turns out to be equivalent to the
Hilgevoord-Wouthuysen spin. We can conclude therefrom that the Gordon-type
decomposition mentioned above corresponds to a Foldy-Wouthuysen transformation
which transforms the Dirac wave function from the conventional Dirac-Pauli to
the Newton-Wigner representation.",0102102v1
2003-04-07,Scalar and spinning particles in a plane wave field,"We study the quantization problem of relativistic scalar and spinning
particles interacting with a radiation electromagnetic field by using the path
integral and the external source method. The spin degrees of freedom are
described in terms of Grassmann variables and the Feynman kernel is obtained
through functional integration on both Bose and Fermi variables. We provide
rigourous proof that the Feynman amplitudes are only determined by the
classical contribution and we explicitly evaluate the propagators.",0304055v1
1993-03-18,Angular Momentum Analysis of Spin 1/2 x 1/2 Scattering including Singlet-Triplet Mixing,"The angular momentum (partial wave) reduction of the Lippmann--Schwinger
equation describing the interaction of two spin 1/2 particles is extended to
the case in which the spin singlet and triplet states are coupled. A straight
forward method for obtaining the angular momentum decomposition of the general
potential is indicated. The derived formalism is needed to describe the
interaction between two nonidentical spin--1/2 particles or between two
nucleons when isospin symmetry is violated. The resulting modification of the
Stapp phase--shift analysis is given.",9303013v1
1993-10-22,Deep Inelastic Scattering of Polarized Electrons off Polarized $^3$HE: Nuclear Effects and the Neutron Spin Structure Function,"Nuclear effects in Deep Inelastic Scattering of polarized electrons off
polarized $^3$He are analyzed in terms of a spin dependent spectral function
taking into account $S'$ and $D$ waves in $^3$He, as well as Fermi motion and
binding effects. A simple and reliable equation relating the neutron and $^3$He
spin structure functions is proposed.",9310029v1
1996-03-14,Front Form Spinors in Weinberg-Soper Formalism and Melosh Transformations for any Spin,"Using the Weinberg-Soper formalism we construct the front form
$(j,0)\oplus(0,j)$ spinors. Explicit expressions for the generalised Melosh
transformations up to spin two are obtained. The formalism, without explicitly
invoking any wave equations, reproduces spin one half front-form results of
Melosh, Lepage and Brodsky, and Dziembowski.",9603019v1
1999-06-21,The short-range baryon-baryon interaction in a chiral constituent quark model,"The previous analysis of the short-range $NN$ repulsion originating from the
Goldstone boson exchange hyperfine interaction between constituent quarks is
revisited. We study in which respects the repulsion depends on the radial form
of the spin-spin quark-quark force. We show that while the radial form affects
the structure of the 6Q wave function, the short-range repulsion in the $NN$
system persists in any case. We extend our analysis to other $YN$ and $YY$
(flavor octet-octet) systems and demonstrate that the flavor-spin hyperfine
interaction implies a short-range repulsion in these B=2 systems as well.",9906058v1
2003-06-05,Understanding visual map formation through vortex dynamics of spin Hamiltonian models,"The pattern formation in orientation and ocular dominance columns is one of
the most investigated problems in the brain. From a known cortical structure,
we build spin-like Hamiltonian models with long-range interactions of the
Mexican hat type. These Hamiltonian models allow a coherent interpretation of
the diverse phenomena in the visual map formation with the help of relaxation
dynamics of spin systems. In particular, we explain various phenomena of
self-organization in orientation and ocular dominance map formation including
the pinwheel annihilation and its dependency on the columnar wave vector and
boundary conditions.",0306047v2
2004-06-04,Non-divergent pseudo-potential treatment of spin-polarized fermions under 1D and 3D harmonic confinement,"Atom-atom scattering of bosonic one-dimensional (1D) atoms has been modeled
successfully using a zero-range delta-function potential, while that of bosonic
3D atoms has been modeled successfully using Fermi-Huang's regularized s-wave
pseudo-potential. Here, we derive the eigenenergies of two spin-polarized 1D
fermions under external harmonic confinement interacting through a zero-range
potential, which only acts on odd-parity wave functions, analytically. We also
present a divergent-free zero-range potential treatment of two spin-polarized
3D fermions under harmonic confinement. Our pseudo-potential treatments are
verified through numerical calculations for short-range model potentials.",0406022v1
2005-10-07,Corrections to the energy levels of a spin-zero particle bound in a strong field,"Formulas for the corrections to the energy levels and wave functions of a
spin-zero particle bound in a strong field are derived. General case of the sum
of a Lorentz-scalar potential and zero component of a Lorentz-vector potential
is considered. The forms of the corrections differ essentially from those for
spin-1/2 particles. As an example of application of our results, we evaluated
the electric polarizability of a ground state of a spin-zero particle bound in
a strong Coulomb field.",0510056v1
2003-02-04,Einstein-Podolsky-Rosen correlations and Galilean transformations,"In this paper we calculate with full details Einstein-Podolsky-Rosen spin
correlations in the framework of nonrelativistic quantum mechanics. We consider
the following situation: two-particle state is prepared (we consider separately
distinguishable and identical particles and take into account the space part of
the wave function) and two observers in relative motion measure the spin
component of the particle along given directions. The measurements are
performed in bounded regions of space (detectors), not necessarily
simultaneously. The resulting correlation function depends not only on the
directions of spin measurements but also on the relative velocity of the
observers.",0302026v1
2004-11-09,Proposed Differential Equation for Spin 1/2,"Intimate though the connection is between orbital angular momentum and
intrinsic spin, there are differences between them the two quantities. One of
them is the fact that while orbital angular momentum has a wave-mechanics
description by courtesy of Legendre's equation, spin lacks one. In this paper,
we show that there exists a differential eigenvalue equation whose solutions
are the spin-1/2 eigenvectors.",0411060v1
2007-02-05,Sublattice addressing and spin-dependent motion of atoms in a double-well lattice,"We load atoms into every site of an optical lattice and selectively spin flip
atoms in a sublattice consisting of every other site. These selected atoms are
separated from their unselected neighbors by less than an optical wavelength.
We also show spin-dependent transport, where atomic wave packets are coherently
separated into adjacent sites according to their internal state. These tools
should be useful for quantum information processing and quantum simulation of
lattice models with neutral atoms.",0702039v2
2007-06-10,Magnon mode truncation in a rung-dimerized asymmetric spin ladder,"An exactly solvable effective model is suggested for an asymmetric spin
ladder with dimerized rungs. Magnon mode truncation originated from magnon
decay (recently observed in the 1D compound ${\rm IPA-CuCl}_3$) is naturally
described within this model. Using Bethe Ansatze we described a one-magnon
sector and obtained relations between interaction constants of the model and
experimentally observable quantities such as the gap and truncation energies,
spin velocity and the truncation wave vector. It is also shown that structure
factor turns to zero at the truncation point.",0706.1370v2
2007-10-24,Spin dynamics of a trapped spin-1 Bose Gas above the Bose-Einstein transition temperature,"We study collective spin oscillations in a spin-1 Bose gas above the
Bose-Einstein transition temperature. Starting from the Heisenberg equation of
motion, we derive a kinetic equation describing the dynamics of a thermal gas
with the spin-1 degree of freedom. Applying the moment method to the kinetic
equation, we study spin-wave collective modes with dipole symmetry. The dipole
modes in the spin-1 system are found to be classified into the three type of
modes. The frequency and damping rate are obtained as functions of the peak
density. The damping rate is characterized by three relaxation times associated
with collisions.",0710.4419v2
2008-02-01,Quantum plasma effects in the classical regime,"For quantum effects to be significant in plasmas it is often assumed that the
temperature over density ratio must be small. In this paper we challenge this
assumption by considering the contribution to the dynamics from the electron
spin properties. As a starting point we consider a multicomponent plasma model,
where electrons with spin up and spin down are regarded as different fluids. By
studying the propagation of Alfv\'{e}n wave solitons we demonstrate that
quantum effects can survive in a relatively high-temperature plasma. The
consequences of our results are discussed.",0802.0169v1
2008-08-05,Spectral functions of strongly interacting isospin-1/2 bosons in one dimension,"We study a system of one-dimensional (iso)spin-1/2 bosons in the regime of
strong repulsive interactions. We argue that the low-energy spectrum of the
system consists of acoustic density waves and the spin excitations described by
an effective ferromagnetic spin chain with a small exchange constant J. We use
this description to compute the dynamic spin structure factor and the spectral
functions of the system.",0808.0681v2
2008-09-04,Magnetic excitations in dipolar pyrochlore antiferromagnet Gd$_2$Sn$_2$O$_7$,"The spin dynamics in the geometrically frustrated pyrochlore antiferromagnet
$\rm Gd_2Sn_2O_7$ is studied by means of the electron spin resonance. In the
ordered phase ($T_N = 1$ K), we have detected three gapped resonance modes.
Their values agree well with the developed spin-wave theory which takes into
account the Heisenberg nearest-neighbor exchange, the single-ion anisotropy and
the long-range dipolar interactions. The theory also predicts a fourth
lowest-frequency gap, which lies beyond the experimental range of frequencies,
but determines the exponential decrease of the specific heat at low
temperature.",0809.0798v1
2008-10-27,Theory of the hourglass dispersion of magnetic excitations in high-T$_c$ cuprates,"A theory for the dispersion of collective magnetic excitations in
superconducting cuprates is presented with the aim to cover both high and low
doping regimes. Besides of spin fluctuations describable in the random phase
approximation (RPA) we allow for local spin rotations within a mode-coupling
theory. At low temperatures and moderately large correlation lengths we obtain
two branches of excitations which disperse up- and downwards exhibiting the
hourglass behavior observed experimentally at intermediate dopings. At large
and small dopings our theory essentially reduces to the RPA and spin wave
theory, respectively.",0810.4857v1
2008-11-08,Theory of Magnetic Order in $ Fe_{1+y}Te_{1-x}Se_x$,"We develop a local spin model to explain the rich magnetic structures in the
iron-based superconductors $Fe_{1+y}Te_{1-x}Se_x$. We show that our model
exhibits both commensurate antiferromagnetic and incommensurate magnetic order
along the crystal a-axis. The transition from the commensurate to the
incommensurate phase is induced when the concentration of excess $Fe$ atoms is
larger than a critical value. Experimentally measurable spin-wave features are
calculated, and the mean-field phase diagram of the model is obtained. Our
model also suggests the existence of a large quantum critical region due to
strong spin frustration upon increasing $Se$ concentration.",0811.1294v1
2008-12-11,Effect of a strong laser on spin precession,"The semiclassical dynamics of a charged spin-1/2 particle in an intense
electromagnetic plane wave is analyzed beyond the electric dipole approximation
and taking into account the leading relativistic corrections to the Pauli
equation. It is argued that the adiabatic spin evolution driven by a low
intensity radiation changes its character drastically as an intensity of a
laser is increasing. Particularly, it is shown that a charged particle exposes
a spin flip resonance at a certain pick value of a laser field strength, which
is determined by a particle's gyromagnetic ratio.",0812.2110v1
2009-01-08,Ultralong trapping of light using double spin coherence gratings,"Ultralong trapping of light has been observed in an optically dense
three-level solid medium interacting with a pair of counterpropagating coupling
fields. Unlike the light trapping based on standing-wave gratings excited by
the same frequency pair of counterpropagating light fields (M. Bajcsy et al.,
Nature 426, 638 (2003)), the present method uses resonant Raman optical
field-excited spin coherence gratings. The observed light trapping time is two
orders of magnitude longer than the expected value of the spin dephasing time,
where the extended storage time has potential for quantum information
processing based on nonlinear optics.",0901.1082v2
2009-02-09,Incommensurability and spin excitations of diagonal stripes in cuprates,"Based on the time-dependent Gutzwiller approximation we study the possibility
that the diagonal incommensurate spin scattering in strongly underdoped
lanthanum cuprates originates from antiferromagnetic domain walls (stripes).
Calculation of the dynamic spin response for stripes in the diagonal phase
yields the characteristic hour glass dispersion with the crossing of low energy
Goldstone and high-energy branches at a characteristic energy Ecross at the
antiferromagnetic wave-vector Q_{AF}. The high energy part is close to the
parent antiferromagnet. Our results suggest that inelastic neutron scattering
experiments on strongly underdoped lanthanum cuprates can be understood as due
to a mixture of bond centered and site centered stripe configurations with
substantial disorder.",0902.1382v1
2009-02-25,Hydrodynamic relation in 2D Heisenberg antiferromagnet in a field,"The spin-stiffness \rho_s of a 2D Heisenberg antiferromagnet depends
non-analytically on external magnetic field. We demonstrate that the
hydrodynamic relation between \rho_s, the uniform susceptibility \chi, and the
spin-wave velocity $c$ is not violated by such a behavior because similar
non-analytic terms from all three quantities mutually cancel out. In this work,
explicit expressions for the field-dependent spin stiffness and for the magnon
velocity of the 2D square lattice antiferromagnet are obtained by direct
calculation to order 1/S and in the whole range of magnetic fields.",0902.4455v1
2009-05-19,First-principles theory of magnetically induced ferroelectricity in TbMnO3,"We study the polarization induced via spin-orbit interaction by a magnetic
cycloidal order in orthorhombic TbMnO3 using first-principle methods. The case
of magnetic spiral lying in the b-c plane is analyzed, in which the pure
electronic contribution to the polarization is shown to be small. We focus our
attention on the lattice-mediated contribution, and study it's dependence on
the Coulomb interaction parameter U in the LDA+U method and on the wave-vector
of the spin spiral. The role of the spin-orbit interaction on different sites
is also analyzed.",0905.3033v1
2009-05-28,Enhanced spin Hall effect in semiconductor heterostructures with artificial potential,"We theoretically investigate an extrinsic spin Hall effect (SHE) in
semiconductor heterostructures due to the scattering by an artificial potential
created by antidot, STM tip, etc. The potential is electrically tunable. First,
we formulate the SHE in terms of phase shifts in the partial wave expansion for
two-dimensional electron gas. The effect is significantly enhanced by the
resonant scattering when the attractive potential is properly tuned. Second, we
examine a three-terminal device including an antidot, which possibly produces a
spin current with polarization of more than 50%.",0905.4551v1
2009-05-29,Is spin-charge separation observable in a transport experiment?,"We consider a one-dimensional chain consisting of an interacting area coupled
to non-interacting leads. Within the area, interaction is mediated by a local
on-site repulsion. Using real time evolution within the Density Matrix
Renormalisation Group (DMRG) scheme, we study the dynamics of wave packets in
this two-terminal transport setup. In contrast to previous works, where
excitations were created by adding potentials to the Hamiltonian, we explicitly
create left moving single particle excitations in the right lead as the
starting condition. Our simulations show that such a transport setup allows for
a clear detection of spin-charge separation using time-resolved spin-polarised
density measurements.",0905.4743v1
2009-09-11,Approximate Pseudospin and Spin Solutions of the Dirac Equation for a Class of Exponential Potentials,"Dirac equation is solved for some exponential potentials, hypergeometric-type
potential, generalized Morse potential and Poschl-Teller potential with any
spin-orbit quantum number $\kappa$ in the case of spin and pseudospin symmetry,
respectively. We have approximated for non s-waves the centrifugal term by an
exponential form. The energy eigenvalue equations, and the corresponding wave
functions are obtained by using the generalization of the Nikiforov-Uvarov
method.",0909.2086v1
2009-10-21,Parametric resonance and spin-charge separation in 1D fermionic systems,"We show that the periodic modulation of the Hamiltonian parameters for 1D
correlated fermionic systems can be used to parametrically amplify their
bosonic collective modes. Treating the problem within the Luttinger liquid
picture, we show how charge and spin density waves with different momenta are
simultaneously amplified. We discuss the implementation of our predictions for
cold atoms in 1D modulated optical lattices, showing that the fermionic
momentum distribution directly provides a clear signature of spin-charge
separation.",0910.4123v2
2009-11-16,"Infinite matrix product states, Conformal Field Theory and the Haldane-Shastry model","We generalize the Matrix Product States method using the chiral vertex
operators of Conformal Field Theory and apply it to study the ground states of
the XXZ spin chain, the J1-J2 model and random Heisenberg models. We compute
the overlap with the exact wave functions, spin-spin correlators and the Renyi
entropy, showing that critical systems can be described by this method. For
rotational invariant ansatzs we construct an inhomogenous extension of the
Haldane-Shastry model with long range exchange interactions.",0911.3029v2
2010-02-03,Paraxial spin transport using the Dirac-like paraxial wave equation,"In weakly inhomogeneous media, Maxwell equations assume a Dirac-like form
that is particularly apt for the study of paraxial propagation. Using this
form, and via the Foldy-Wouthuysen transformation technique of the Dirac
equation, we study the spin transport of paraxial light beams in weakly
inhomogeneous media. We derive the Berry effect terms and establish the spin
Hall effect and the Rytov rotation law for polarized paraxial beam transport.",1002.0647v1
2010-05-05,A Spin-Isospin Dependent 3N Scattering Formalism in a 3D Faddeev Scheme,"We have introduced a spin-isospin dependent three-dimensional approach for
formulation of the three-nucleon scattering. Faddeev equation is expressed in
terms of vector Jacobi momenta and spin-isospin quantum numbers of each
nucleon. Our formalism is based on connecting the transition amplitude $T$ to
momentum-helicity representations of the two-body $t$-matrix and the deuteron
wave function. Finally the expressions for nucleon-deuteron elastic scattering
and full breakup process amplitudes are presented.",1005.0694v2
2010-05-10,Spin-Orbit Interaction Enhanced Fractional Quantum Hall States in the Second Landau Level,"We study the fractional quantum Hall effect at filling fractions 7/3 and 5/2
in the presence of the spin-orbit interaction, using the exact diagonalization
method and the density matrix renormalization group (DMRG) method in a
spherical geometry. Trial wave functions at these fillings are the Laughlin
state and the Moore-Reed-Pfaffian state. The ground state excitation energy
gaps and pair-correlation functions at fractional filling factor 7/3 and 5/2 in
the second Landau level are calculated. We find that the spin-orbit interaction
stabilizes the fractional quantum Hall states.",1005.1446v1
2010-05-25,Systematic classical continuum limits of integrable spin chains and emerging novel dualities,"We examine certain classical continuum long wave-length limits of prototype
integrable quantum spin chains. We define the corresponding construction of
classical continuum Lax operators. Our discussion starts with the XXX chain,
the anisotropic Heisenberg model and their generalizations and extends to the
generic isotropic and anisotropic gl_n magnets. Certain classical and quantum
integrable models emerging from special ""dualities"" of quantum spin chains,
parametrized by c-number matrices, are also presented.",1005.4605v2
2010-08-13,Bound state solutions of the Dirac-Rosen-Morse potential with spin and pseudospin symmetry,"The energy spectra and the corresponding two- component spinor wavefunctions
of the Dirac equation for the Rosen-Morse potential with spin and pseudospin
symmetry are obtained. The $s-$wave ($\kappa = 0$ state) solutions for this
problem are obtained by using the basic concept of the supersymmetric quantum
mechanics approach and function analysis (standard approach) in the
calculations. Under the spin symmetry and pseudospin symmetry, the energy
equation and the corresponding two-component spinor wavefunctions for this
potential and other special types of this potential are obtained. Extension of
this result to $\kappa \neq 0$ state is suggested.",1008.2358v1
2010-09-09,Hydrodynamic equation of a spinor dipolar Bose-Einstein condensate,"We introduce equations of motion for spin dynamics in a ferromagnetic
Bose-Einstein condensate with magnetic dipole-dipole interaction, written using
a vector expressing the superfluid velocity and a complex scalar describing the
magnetization. This simple hydrodynamical description extracts the dynamics of
spin wave and affords a straightforward approach by which to investigate the
spin dynamics of the condensate. To demonstrate the advantages of the
description, we illustrate dynamical instability and magnetic fluctuation
preference, which are expressed in analytical forms.",1009.1671v3
2010-09-16,Evidence for site-centered stripes from magnetic excitations in CuO superconductors,"The success of models of coupled two-leg spin ladders in describing the
magnetic excitation spectrum of La_[2-x]Ba_xCuO_4 has been widely interpreted
as evidence for bond-centered stripes. Here, we determine the magnetic coupling
induced by the charge stripes between bond- or site-centered spin stripes
modeled by two- or three-leg ladders, respectively. We find that only the
site-centered models order. We further report excellent agreement of a fully
consistent analysis of coupled three-leg ladders using a spin wave theory of
bond operators with the experiment.",1009.3122v1
2011-02-10,Circularly Polarized Resonant Rayleigh Scattering and Skyrmions in the $ν$ = 1 Quantum Hall Ferromagnet,"We use the circularly polarized resonant Rayleigh scattering (RRS) to study
the quantum Hall ferromagnet at $\nu$ = 1. At this filling factor we observe a
right handed copolarized RRS which probes the Skyrmion spin texture of the
electrons in the photoexcited grounds state. The resonant scattering is not
present in the left handed copolarization, and this can be related to the
correlation between Skymionic effects, screening and spin wave excitations.
These results evidence that RRS is a valid method for the study of the spin
texture of the quantum Hall states.",1102.2185v2
2011-04-19,Slow Magnetic Order-Order Transition in the Spin Chain Antiferromagnet Ca3Co2O6,"Using powder neutron diffraction we have discovered an unusual magnetic
order-order transition in the Ising spin chain compound Ca3Co2O6. On lowering
the temperature an antiferromagnetic phase with propagation vector
k=(0.5,-0.5,1) emerges from a higher temperature spin density wave structure
with k=(0, 0, 1.01). This transition occurs over an unprecedented time-scale of
several hours and is never complete.",1104.3880v2
2011-06-22,Magnetic excitations in iron pnictides,"Spin wave dispersion and damping are investigated in the metallic SDW state
of different itinerant electron models including a small interlayer hopping.
Magnetic excitations in iron pnictides are shown to be well understood in terms
of physical mechanisms characteristic of metallic magnets, such as
carrier-induced ferromagnetic spin couplings, intra-band particle-hole
excitations, and the spin-charge coupling mechanism, which is also important in
ferromagnetic manganites.",1106.4421v1
2011-07-20,New eigen-mode of spin oscillations in the triplet superfluid condensate in neutron stars,"The eigen mode of spin oscillations with $\omega\simeq \sqrt{58/35}\Delta$ is
predicted to exist besides already known spin waves with $\omega \simeq\Delta
/\sqrt{5}$ in the triplet superfluid neutron condensate in the inner core of
neutron stars. The new mode is kinematically able to decay into neutrino pairs
through neutral weak currents. The problem is considered in BCS approximation
for the case of $^{3}P_{2}-^{3}F_{2}$ pairing with a projection of the total
angular momentum $m_{j}=0$ which is conventionally considered as preferable one
at supernuclear densities.",1107.4025v1
2011-07-23,Spin-plasmons in topological insulator,"Collective plasmon excitations in a helical electron liquid on the surface of
strong three-dimensional topological insulator are considered. The properties
and internal structure of these excitations are studied. Due to spin-momentum
locking in helical liquid on a surface of topological insulator, the collective
excitations should manifest themselves as coupled charge- and spin-density
waves.",1107.4695v1
2011-09-22,"Rarita--Schwinger for spin 3/2 field and separation of the variables in static coordinates of de Sitter space, Schrödinger tetrad basis","Rarita-Schwinger approach to description of a massive spin 3/2 particle is
investigated in static coordinates of the de Sitter space-time. The general
covariant system, derived from the relevant Lagrangian, is presented as a main
wave equation and additional constraints in the form of first order deferential
and algebraic relations. With the use of an extended Schr\""{o}dinger tetrad
basis and technique of Wigner D-functions the separation of the variable
performed. 16 radial equations reduce to 8 ones through diagonalization of
$P$-inversion operator for spin 3/2 field.",1109.4802v1
2011-10-09,"Liquid ground state, gap and excited states of a strongly correlated spin chain","We present an exact solution of an experimentally realizable and strongly
interacting one-dimensional spin system which is a limiting case of a quantum
Ising model with long range interaction in a transverse and longitudinal field.
Pronounced quantum fluctuations lead to a strongly correlated liquid ground
state. For open boundary conditions the ground state manifold consists of four
degenerate sectors whose quantum numbers are determined by the orientation of
the edge spins. Explicit expressions for the entanglement properties, the
excitation gap as well as the exact wave functions for a couple of excited
states are analytically derived and discussed.",1110.1815v1
2011-10-30,Correlation-driven chiral superconductivity and chiral spin order in doped kagome lattice,"We study the electronic instabilities of the Hubbard model in the 1/6
hole-doped Kagome lattice using the variational cluster approach. The 1/6 hole
doping is unique in the sense that the Fermi level is at the von Hove
singularity and the Fermi surface has a perfect nesting. In this case, a
density wave is usually realized. However, we demonstrate here that the chiral
$d_{x^{2}-y^{2}}+id_{xy}$ superconducting state is most favorable when a small
Hubbard interaction U(U<3.0t) is introduced, and a scalar chiral spin order is
realized at large U(U>5.0t). Between them, a spin-disordered insulating state
is proposed.",1110.6613v1
2011-11-26,"Evidence for a spin-quartet of nucleon resonances at 2\,GeV","Results from a multi-channel partial wave analysis of elastic and inelastic
$\pi N$ and $\gamma N$ induced reactions are presented. The analysis evidences
the existence of a spin-quartet of nucleon resonances with total angular
momenta $J^P=1/2^+,..., 7/2^+$. All states fall into a $\pm130$\,MeV mass gap
centered at 1.97\,GeV. The spin quartet is at variance with S-wave diquark
configurations required in classical di-quark models.",1111.6150v2
2011-12-20,Higher spin quasinormal modes and one-loop determinants in the BTZ black hole,"We solve the wave equations of arbitrary integer spin fields in the BTZ black
hole background and obtain exact expressions for their quasinormal modes. We
show that these quasinormal modes precisely agree with the location of the
poles of the corresponding two point function in the dual conformal field
theory as predicted by the AdS/CFT correspondence. We then use these
quasinormal modes to construct the one-loop determinant of the higher spin
field in the thermal BTZ background. This is shown to agree with that obtained
from the corresponding heat kernel constructed recently by group theoretic
methods.",1112.4619v1
2012-07-04,Y-junction splitting spin states of moving quantum dot,"The development of a working quantum computer utilizing electron spin states
as qubits is a major goal for many theorists and experimentalists. The future
applications of quantum information technology would also require a reliable
method for the transportation of quantum information. A promising such method
is the propagation of electrons by a surface acoustic wave (SAW). In this
paper, we simulate the SAW transfer of two interacting electrons through a
Y-shaped junction. Our results show that the singlet and triplet states can be
differentiated in the Y-junction by an electrostatic detuning potential, an
effect that could be used in for example measuring the state of a two-spin
qubit.",1207.1099v1
2012-08-30,Composite fermion state of spin-orbit coupled bosons,"We consider spinor Bose gas with the isotropic Rashba spin-orbit coupling in
2D. We argue that at low density its groundstate is a composite fermion state
with a Chern-Simons gauge field and filling factor one. The chemical potential
of such a state scales with the density as \mu \propto n^{3/2}. This is a lower
energy per particle than \mu \propto n for the earlier suggested groundstate
candidates: a condensate with broken time-reversal symmetry and a spin density
wave state.",1208.6266v1
2012-10-30,Approximate -state Solutions to the Dirac Mobius Square-Yukawa and Mobius Square-quasi Yukawa Problems under Pseudospin and Spin Symmetry limits with Coulomb-like Tensor Interaction,"In this paper, we present the Dirac equation for the Mobius-square-Yukawa
potentials including the tensor interaction term within the framework of
pseudospin and spin symmetry limit with arbitrary spin-orbit quantum number .
We obtained the energy eigenvalues and the corresponding wave functions using
the supersymmetry method. The limiting cases of this potential model reduce to
the Deng-Fan, Yukawa and Coulomb potentials, respectively",1210.7918v1
2012-12-08,Relativistic symmetries in the Hulthén scalar-vector-tensor interactions,"In the presence of spin and pseudospin (p-spin) symmetries, the approximate
analytical bound states of the Dirac equation for scalar-vector-tensor
Hulth\'en potentials are obtained with any arbitrary spin-orbit coupling number
using the Pekeris approximation. The Hulth\'en tensor interaction is studied
instead of the commonly used Coulomb or linear terms. The generalized
parametric Nikiforov-Uvarov (NU) method is used to obtain energy eigenvalues
and corresponding wave functions in their closed forms. We show that tensor
interaction removes degeneracies between spin and p-spin doublets. Some
numerical results are also given.",1212.1828v1
2012-12-12,Results from the spin programme at COSY-ANKE,"Some of the important results from the COSY-Juelich spin programme are
summarised. These include the measurement of the deuteron beam momentum through
the excitation of a depolarising resonance, which allowed the mass of the
eta-meson to be determined to high precision. The charge exchange of polarised
deuterons on hydrogen gave rise to a detailed study of the spin dependence of
large angle neutron-proton elastic scattering amplitudes. The measurements of
the cross section and analysing powers for pion production in both pp and pn
collisions at 353 MeV could be described very successfully in terms of a
partial wave decomposition.",1212.2771v1
2012-12-21,Approximate analytical solutions of Dirac Equation with spin and pseudo spin symmetries for the diatomic molecular potentials plus a tensor term with any angular momentum,"Approximate analytical solutions of the Dirac equation are obtained for some
diatomic molecular potentials plus a tensor interaction with spin and
pseudospin symmetries with any angular momentum. We find the energy eigenvalue
equations in the closed form and the spinor wave functions by using an
algebraic method. We also perform numerical calculations for the
P\""oschl-Teller potential to show the effect of the tensor interaction. Our
results are consistent with ones obtained before.",1212.5349v1
2013-02-08,Comparison of quantum and classical relaxation in spin dynamics,"The classical Landau-Lifshitz equation with damping term has been derived
from the time evolution of a quantum mechanical wave function under the
assumption of a non-hermitian Hamilton operator. Further, the trajectory of a
classical spin $\mathrm{S}$ has been compared with the expectation value of the
spin operator $\mathrm{\hat{S}}$. A good agreement between classical and
quantum mechanical trajectories can be found for Hamiltonians linear in
$\mathrm{\hat{S}}$ respectively $\mathrm{S}$. Quadratic or higher order terms
in the Hamiltonian result in a disagreement.",1302.1985v1
2013-02-27,Quantum Spin Hall Effect in a Three-orbital Tight-binding Hamiltonian,"We consider the quantum spin hall state in a three orbital model due to
certain loop current order induced by spin-dependent interactions. This type of
order is motivated by the loop current model which is proposed to describe the
pseudogap phase of cuprates. It is shown that this model has nontrivial Chern
parity by directly counting the zeros of the Pfaffian of time reversal
operator. By connecting to the second order Chern number, we explicitly show
the singularities of wave-functions and how they depend on gauge choices. In
this case, it is shown that the Berry phase can be mapped to Nonabelian
instanton.",1302.6656v1
2013-03-05,Model Prediction for the Transverse Single Target-Spin Asymmetry in inclusive DIS,"The single-spin asymmetry of unpolarized leptons scattering
deep-inelastically off transversely polarized nucleons is discussed. This
observable is generated by a two-photon exchange between lepton and nucleon. In
a partonic description of the asymmetry the non-perturbative part is given in
terms of multiparton correlations: quark-gluon correlation functions and
quark-photon correlation functions. Recently, a model for quark-gluon
correlation functions was presented where these objects were expressed through
non-valence light cone wave functions. Using this model, estimates for the
single-spin asymmetries for a proton and a neutron are presented.",1303.0978v1
2013-07-31,Approximate relativistic bound states of a particle in Yukawa field with Coulomb tensor interaction,"We obtain the approximate relativistic bound state of a spin-1/2 particle in
the field of the Yukawa potential and a Coulomb-like tensor interaction with
arbitrary spin-orbit coupling number k under the spin and pseudospin (p-spin)
symmetries. The asymptotic iteration method is used to obtain energy
eigenvalues and corresponding wave functions in their closed forms. Our
numerical results show that the tensor interaction removes degeneracies between
the spin and p-spin doublets and creates new degenerate doublets for various
strengths of tensor coupling.",1307.8326v1
2013-10-10,Spin-Driven Bond Order in a 1/5-Magnetization Plateau Phase in a Triangular Lattice Antiferromagnet CuFeO2,"We have investigated spin-wave excitations in a magnetic-field-induced
1/5-magnetization plateau phase in a triangular lattice antiferromagnet CuFeO2
(CFO), by means of inelastic neutron scattering measurements under applied
magnetic fields of up to 13.4 T. Comparing the observed spectra with the
calculations in which spin-lattice coupling effects for the nearest neighbor
exchange interactions are taken into account, we have determined the
Hamiltonian parameters in the field-induced 1/5- plateau phase, which directly
show that CFO exhibits a bond order associated with the magnetic structure in
this phase.",1310.2746v1
2013-10-23,Dynamics of the Dicke model close to the classical limit,"We study the dynamical properties of the Dicke model for increasing spin
length, as the system approaches the limit of a classical spin. First, we
describe the emergence of collective excitations above the groundstate that
converge to the coupled spin-oscillator oscillations found in the classical
limit. The corresponding Green functions reveal quantum dynamical signatures
close to the superradiant quantum phase transition. Second, we identify
signatures of classical quasi-periodic orbits in the quantum time evolution
using numerical time-propagation of the wave function. The resulting phase
space plots are compared to the classical trajectories. We complete our study
with the analysis of individual eigenstates close to the quasi-periodic orbits.",1310.6140v1
2014-03-14,Generation and tomography of arbitrary qubit states in a transient collective atomic excitation,"We demonstrate the generation of heralded Fock-basis qubits $(a|0\rangle +
b|1\rangle)$ from transient collective spin excitations in a hot atomic vapor.
The collective spin excitation is heralded by Raman-scattered photons in a
four-wave mixing process seeded by a weak coherent optical excitation. The
amplitude and phase of the seed field allow arbitrary control over the qubit
coefficients. The state of the ensemble is read out optically and then
characterized using balanced homodyne tomography. This work represents a step
towards quantum engineering of collective atomic spin states.",1403.3463v1
2014-11-28,Guided magnon transport in spin chains: transport speed and correcting for disorder,"High fidelity quantum information transport is necessary for most practical
models of quantum computation. By analogy with optical wave guides, a
spatio-temporally varying magnetic potential on a one dimensional spin chain
can achieve high fidelity transport of spin excitations. By comparing different
potential shapes, we establish the effects of potential shape on the fidelity
and transport speed. We incorporate disorder into our model and show methods to
minimise its effect on transport. Finally, we discuss implementations of our
scheme in several accessible systems based on hydrogenic approximations.",1411.7749v1
2015-03-11,Nature of chiral spin liquids on the kagome lattice,"We investigate the stability and the nature of the chiral spin liquids which
were recently uncovered in extended Heisenberg models on the kagome lattice.
Using a Gutzwiller projected wave function approach -- i.e. a parton
construction -- we obtain large overlaps with ground states of these extended
Heisenberg models. We further suggest that the appearance of the chiral spin
liquid in the time-reversal invariant case is linked to a classical transition
line between two magnetically ordered phases.",1503.03389v1
2015-05-12,Effect of nuclear spin symmetry in cold and ultracold reactions: D + para/ortho-H$_2$,"We report results for reaction and vibrational quenching of the collision D
with para-H$_2$($v,j=0$) and ortho-H$_2$($v,j=1$) at cold and ultracold
temperatures. We investigate the effect of nuclear spin symmetry for barrier
dominated processes ($0\le v\le 4$) and for one barrierless case ($v=5$). We
find resonant structures for energies in the range corresponding to 0.01--10 K,
which depend on the nuclear spin of H$_2$, arising from contributions of
specific partial waves. We discuss the implications on the results in this
benchmark system for ultracold chemistry.",1505.03172v1
2015-06-09,Time-domain inspiral templates for spinning compact binaries in quasi-circular orbits,"We present a prescription to compute the time-domain gravitational wave (GW)
polarization states associated with spinning compact binaries inspiraling along
quasi-circular orbits. We invoke the orbital angular momentum ${\bf L}$ rather
than its Newtonian counterpart ${\bf L_{\rm N}}$ to describe the orbits and the
two spin vectors are freely specified in the source frame associated with the
initial direction of the total angular momentum. We discuss the various
implications of our approach.",1506.02788v1
2015-08-11,"Equations of Motion of Schwarzschild, Reissner-Nordstrom and Kerr Particles","A technique for extracting from the appropriate field equations the
relativistic motion of Schwarzschild, Reissner-Nordstrom and Kerr particles
moving in external fields is motivated and illustrated. The key assumptions are
that (a) the particles are isolated and (b) near the particles the wave fronts
of the radiation generated by their motion are smoothly deformed spheres. No
divergent integrals arise in this approach. The particles are not test
particles. The formalism is used, however, to derive the Mathisson-Papapetrou
equations of motion of spinning test particles, neglecting spin-spin terms.",1508.02564v1
2016-09-21,Finite speed heat transport in a quantum spin chain after quenched local cooling,"We study the dynamics of an initially thermalized spin chain in the quantum
XY-model, after sudden coupling to a heat bath of lower temperature at one end
of the chain. In the semi-classical limit we see an exponential decay of the
system-bath heatflux by exact solution of the reduced dynamics. In the full
quantum description however, we numerically find the heatflux to reach
intermediate plateaus where it is approximately constant -- a phenomenon that
we attribute to the finite speed of heat transport via spin waves.",1609.06483v2
2017-07-28,Moving obstacle potential in a spin-orbit-coupled Bose-Einstein condensate,"We investigate the dynamics around an obstacle potential moving in the
plane-wave state of a pseudospin-$1/2$ Bose-Einstein condensate with Rashba
spin-orbit coupling. We numerically investigate the dynamics of the system and
find that it depends not only on the velocity of the obstacle but also
significantly on the direction of obstacle motion, which are verified by a
Bogoliubov analysis. The excitation diagram with respect to the velocity and
direction is obtained. The dependence of the critical velocity on the strength
of the spin-orbit coupling and the size of the obstacle is also investigated.",1707.09136v1
2017-11-10,Chiral solitons in a non-linear model of helical molecules,"In this paper an effective integrable non-linear model describing the
electron spin dynamics in a deformable helical molecule with weak spin-orbit
coupling is presented. Non-linearity arises from the electron-lattice
interaction and it enables the formation of a variety of stable solitons such
as bright solitons, breathers and rogue waves, all of them presenting well
defined spin projection onto the molecule axis. A thorough study of the soliton
solutions is presented and discussed.",1711.03794v1
2017-11-28,Spin-isospin excitation of ${}^3$He with three-proton final state,"Spin-isospin excitation of ${}^3$He nucleus by proton-induced charge-exchange
reaction, ${}^3\mathrm{He}(p,n)ppp$, at forward neutron scattering angle is
studied in a plane wave impulse approximation (PWIA). In PWIA, cross sections
of the reaction is written in terms of proton-neutron scattering amplitudes and
response functions of the transition from ${}^{3}$He to three-proton state by
spin-isospin transition operators. The response functions are calculated with
realistic nucleon-nucleon potential models using a Faddeev three-body method.
Calculated cross sections agree with available experimental data in substance.
Possible effects arising from the uncertainty of proton-neutron amplitudes and
three-nucleon interactions in three-proton system are examined.",1711.10270v1
2017-12-13,Cu hyperfine coupling constants of HgBa$_{2}$Ca$_{}$Cu$_{2}$O$_{6+δ}$,"We estimated the ratios of $^{63}$Cu hyperfine coupling constants in the
double-layer high-$T_\mathrm{c}$ superconductor HgBa$_2$CaCu$_2$O$_{6+\delta}$
from the anisotropies in Cu nuclear spin-lattice relaxation rates and spin
Knight shifts to study the nature of the ultraslow fluctuations causing the
$T_2$ anomaly in the Cu nuclear spin-echo decay. The ultraslow fluctuations may
come from uniform magnetic fluctuations spread around the wave vector $q$ = 0,
otherwise the electric origins.",1712.04656v1
2017-12-27,Finite temperature magnon spectra in yttrium iron garnet from mean field approach in tight-binding model,"We study magnon spectra at finite temperature in yttrium iron garnet from
tight-binding model with nearest neighboring exchange interaction. The spin
reduction due to thermal magnon excitation are taken into account via the mean
field approximation to the local spin and found to be different at two sets of
iron atoms. The resulting temperature dependence of the spin wave gap shows
good agreement with experiment. We find only two magnon modes are relevant to
ferromagnetic resonance.",1712.09512v1
2018-05-03,Gravity-induced geometric spin Hall effect as a probe of universality of free fall of quantum particle,"We present a novel fundamental effect that for the matter waves the
space-averaging free-fall point of quantum particles undergoes a spin-dependent
transverse shift in the gravitational field of Earth. This effect is similar to
the geometric spin Hall effect (GSHE) [Aiello et al., Phys. Rev. Lett. 103,
100401 (2009)] and can be called gravity-induced GSHE. This effect suggests
that there might be violations of the universality of free fall (UFF) or weak
equivalence principle (WEP) in the quantum domain.",1805.01263v3
2018-09-11,Effective spin-orbit models using correlated first-principles wave functions,"Diffusion Monte Carlo is one of the most accurate scalable many-body methods
for solid state systems. However, to date, spin-orbit interactions have not
been incorporated into these calcualtions at a first-principles level; only
having been applied to small systems. In this technique, we use explicitly
correlated first-principles quantum Monte Carlo calculations to derive an
effective spin-orbit model Hamiltonian. The simplified model Hamiltonian is
then solved to obtain the energetics of the system. To demonstrate this method,
benchmark studies are performed in main-group atoms and monolayer tungsten
disulfide, where high accuracy is obtained.",1809.04133v1
2019-11-04,Conformal field theory and the non-abelian $SU(2)_k$ chiral spin liquid,"We construct a family of 1D and 2D long-range SU(2) spin models as parent
Hamiltonians associated with infinite dimensional matrix product states that
arise from simple current correlation functions in $SU(2)_k$ WZW models. Our
results provide a conformal field theory foundation for recent proposals by
Greiter and coauthors regarding the realization of non-abelian chiral spin
liquids. We explain, in particular, how the symmetrization procedure for the
amplitudes of the ground state wave function suggested in Ref. arXiv:0903.4547
originates from the conformal field theory description.",1911.01505v1
2018-10-13,Spin constrained orbital angular momentum control in high-harmonic generation,"The interplay between spin and orbital angular momentum in the up-conversion
process allows us to control the macroscopic wave front of high harmonics by
manipulating the microscopic polarizations of the driving field. We demonstrate
control of orbital angular momentum in high harmonic generation from both solid
and gas phase targets using the selection rules of spin angular momentum. The
gas phase harmonics extend the control of angular momentum to
extreme-ultraviolet wavelength. We also propose a bi-color scheme to produce
spectrally separated extreme-ultraviolet radiation carrying orbital angular
momentum.",1810.05894v1
2012-09-23,On the Origin of Zigzag Magnetic Order in Iridium Oxide Na2IrO3,"We explore the phase diagram of spin-orbit Mott insulators on a honeycomb
lattice, within the Kitaev-Heisenberg model extended to its full parameter
space. Zigzag-type magnetic order is found to occupy a large part of the phase
diagram of the model, and its physical origin is explained as due to
interorbital t2g-eg hopping. Magnetic susceptibility and spin wave spectra are
calculated and compared to the experimental data, obtaining thereby the spin
coupling constants in Na2IrO3 and Li2IrO3.",1209.5100v1
2014-06-25,Rogue solitons in Heisenberg spin chain,"Following the connection of the non-linear Schr\""{o}dinger equation with the
continuum Heisenberg spin chain, we find the rogue soliton equivalent in the
spin system. The breathers are also mapped to the corresponding space or time
localized oscillatory modes, through the moving curve analogy. The
spatio-temporal evolution of the curvature and torsion of the curve, underlying
these dynamical systems, are explicated to illustrate the localization property
of the rogue waves.",1406.6524v1
2018-02-05,The Bach equations in Spin-Coefficient form,"Conformal gravity theories are defined by field equations that determine only
the conformal structure of the spacetime manifold. The Bach equations represent
an early example of such a theory, we present them here in component form in
terms of spin- and boost-weighted spin-coefficients using the compacted
spin-coefficient formalism. These equations can be used as an efficient
alternative to the standard tensor form. As a simple application we solve the
Bach equations for pp-wave and static spherically symmetric spacetimes.",1802.01537v4
2018-08-16,{\em Zitterbewegung} in Spin-Orbit Coupled Systems and Ehrenfest's Theorem,"We use Ehrenfest's theorem to provide a particularly simple derivation of the
{\em zitterbewegung} in the dynamics of initial Gaussian wave packets in a
two-dimensional electron gas. For initial packets which are very wide in the
$y$-direction, the {\em zitterbewegung} is only in the $y$-component of the
velocity. We extend our Ehrenfest theorem based calculation to the spin-orbit
coupled spinor Bose-Einstein condensate (BEC) to predict that there can be {\em
zitterbewegung} in the $x$-component of the velocity in this situation driven
by a combination of the nonlinear interaction in the condensate and the
splitting due to the spin-orbit coupling.",1808.05397v1
2019-06-14,Friedel oscillations in 2D electron gas from spin-orbit interaction in a parallel magnetic field,"Effects associated with the interference of electron waves around a magnetic
point defect in two-dimensional electron gas with combined Rashba-Dresselhaus
spin-orbit interaction in the presence of a parallel magnetic field are
theoretically investigated. The effect of a magnetic field on the anisotropic
spatial distribution of the local density of states and the local density of
magnetization is analyzed. The existence of oscillations of the density of
magnetization with scattering by a non-magnetic defect and the contribution of
magnetic scattering (accompanied by spin-flip) in the local density of electron
states are predicted.",1906.06043v1
2020-04-26,Spin Current Generation by a Surface Plasmon Polariton,"Surface plasmon polariton (SPP) is an electromagnetic wave which is tightly
localised beyond the diffraction limit at metallic surfaces. Recently, it is
theoretically proposed that the angular momentum conversion between the SPP and
electrons. In this work, we have successfully measured SPP induced spin
currents, which proves the fact that the angular momenta are interconverted.
Such conversion from light to a spin current can be used as a coupler in a next
generation spintronic computing with optical data transfer or storage.",2004.12348v1
2016-03-03,Dissipative Long-Range Entanglement Generation between Electronic Spins,"We propose a scheme for deterministic generation and long-term stabilization
of entanglement between two electronic spin qubits confined in spatially
separated quantum dots. Our approach relies on an electronic quantum bus,
consisting either of quantum Hall edge channels or surface acoustic waves, that
can mediate long-range coupling between localized spins over distances of tens
of micrometers. Since the entanglement is actively stabilized by dissipative
dynamics, our scheme is inherently robust against noise and imperfections.",1603.01130v2
2016-12-13,Theory of magnons in spin systems with Dzyaloshinskii-Moriya interaction,"We study in this paper magnetic properties of a system of quantum Heisenberg
spins interacting with each other via a ferromagnetic exchange interaction J
and an in-plane Dzyaloshinskii-Moriya interaction D. The non-collinear ground
state due to the competition between J and D is determined. We employ a
self-consistent Green'function theory to calculate the spin-wave spectrum and
the layer magnetizations at finite T in two and three dimensions as well as in
a thin film with surface effects. Analytical details and the validity of the
method are shown and discussed.",1612.04147v1
2016-12-26,Spin-selective electron transfer in quantum dot array,"We propose a spin-selective coherent electron transfer in a
silicon-quantum-dot array. Oscillating magnetic fields and temporally
controlled gate voltages are utilised to separate the electron wave function
into different quantum dots depending on the spin state. We introduce
non-adiabatic and adiabatic protocols which offer fast electron transfer and
the robustness against the error in the control-field pulse area, respectively.
We also study a shortcut-to-adiabaticity protocol which compromises these two
protocols. We show that this scheme can be extended to multi-electron systems
straightforwardly and used for non-local manipulations of the electrons.",1612.08389v2
2019-03-20,Superfield continuous spin equations of motion,"We propose a description of %manifestly supersymmetric continuous spin
representations in $4D,\mathcal{N}=1$ Minkowski superspace at the level of
equations of motions. The usual continuous spin wave function is promoted to a
chiral or a complex linear superfield which includes both the single-valued
(span integer helicities) and the double-valued (span half-integer helicities)
representations thus making their connection under supersymmetry manifest. The
set of proposed superspace constraints for both superfield generate the
expected Wigner's conditions for both representations.",1903.08631v1
2020-09-14,Tribaryons in a constituent quark model,"We calculate the matrix elements of the color-spin interaction for all
possible multi-quark states of tribaryons in flavor SU(3) broken case. For that
purpose, we construct the flavor$\otimes$color$\otimes$spin wave functions of
the tribaryons, which are taken to be antisymmetric to satisfy the Pauli
exclusion principle. Furthermore, we analyze the diquark structure of the
tribaryon configurations using the symmetric and antisymmetric basis set of
flavor, color and spin states.",2009.06220v1
2008-06-13,Gravitational waveforms for spinning compact binaries,"The rotation of the bodies and the eccentricity of the orbit have significant
effects on the emitted gravitational radiation of binary systems. This work
focuses on the evaluation of the gravitational wave polarization states for
spinning compact binaries. We consider binaries on eccentric orbits and the
spin-orbit interaction up to the 1.5 post-Newtonian order in a way which is
independent of the parameterization of the orbit. The equations of motion for
angular variables are included. The formal expressions of the polarization
states are given with the inclusion of higher order corrections to the
waveform.",0806.2273v1
2008-06-21,Spin-resolved impurity resonance states in electron-doped cuprate superconductors,"With the aim at understanding the non-monotonic $d_{x^{2}-y^{2}}$-wave gap,
we analyze the local electronic structure near impurities in the electron-doped
cuprate superconductors. We find that the local density of states near a
non-magnetic impurity in the scenario of $d_{x^{2}-y^{2}}$-wave
superconductivity with higher harmonics is qualitatively different from that
obtained from the $d_{x^{2}-y^{2}}$-wave superconductivity coexisting with
antiferromagnetic spin density wave order. We propose that spin-polarized
scanning tunneling microscopy measurements can distinguish the two scenarios
and shed light on the real physical origin of a non-monotonic
$d_{x^{2}-y^{2}}$-wave gap.",0806.3502v3
2017-03-06,Controlling topological superconductivity by magnetization dynamics,"We study theoretically a chain of precessing classical magnetic impurities in
an $s$-wave superconductor. Utilizing a rotating wave description, we derive an
effective Hamiltonian that describes the emergent Shiba band. We find that this
Hamiltonian shows non-trivial topological properties, and we obtain the
corresponding topological phase diagrams both numerically and analytically. We
show that changing the precession frequency offers a control over topological
phase transitions and the emergence of Majorana bound states. We propose
driving the magnetic impurities or magnetic texture into precession by means of
spin-transfer torque in a spin-Hall setup, and manipulate it using spin
superfluidity in the case of planar magnetic order.",1703.01870v1
2019-01-02,Massive spin zero fields in cosmology and the tail-free property,"Fields of spin $s \geq 1/2$ satisfying wave equations in a curved space obey
the Huygens principle under certain conditions clarified by a known theorem.
Here this theorem is generalized to spin zero and applied to an inflaton field
in de Sitter-like space, showing that tails of scalar radiation are an
unavoidable physical feature. Requiring the absence of tails, on the contrary,
necessarily implies an unnatural tuning between cosmological constant, scalar
field mass, and coupling constant to the curvature.",1901.00556v1
2019-12-04,Free energy asymptotics of the quantum Heisenberg spin chain,"We consider the ferromagnetic quantum Heisenberg model in one dimension, for
any spin $S\geq 1/2$. We give upper and lower bounds on the free energy,
proving that at low temperature it is asymptotically equal to the one of an
ideal Bose gas of magnons, as predicted by the spin-wave approximation. The
trial state used in the upper bound yields an analogous estimate also in the
case of two spatial dimensions, which is believed to be sharp at low
temperature.",1912.01967v2
2022-04-19,On multi-soliton solutions to the Heisenberg ferromagnetic spin chain equation in (2+1)-dimensions,"This paper concentrates on the Heisenberg ferromagnetic spin chain (HFSC)
equation in (2+1)-dimensions modelling nonlinear wave propagation in
ferromagnetic spin chain. A variable transformation is first employed to reduce
the studied equation. And then an associated matrix Riemann-Hilbert problem is
built on the real line through analyzing spectral problem of the reduced
equation. As a consequence, solving the obtained matrix Riemann-Hilbert problem
with the identity jump matrix, corresponding to the reflectionless, the general
multi-soliton solutions to the HFSC equation in (2+1)-dimensions are acquired.
Specially, the one- and two-soliton solutions are worked out and analyzed
graphically.",2204.08679v1
2022-07-18,Anomalous Hall metal and fractional Chern insulator in twisted transition metal dichalcogenides,"We predict robust Ising ferromagnetism driven by Coulomb interaction in the
metallic phase of twisted transition metal dichalcogenides homobilayers for a
range of small twist angles. Due to the presence of spin-valley locking and
Chern band, the completely spin polarized state -- a half metal -- has a spin
gap and exhibits anomalous Hall effect. We also find that near a magic angle
where the Chern band is predicted to be exceptionally flat, the anomalous Hall
metal at $1/3$ filling may become unstable at low temperature to a
$\sqrt{3}\times\sqrt{3}$ charge density wave, or a fractional Chern insulator.",2207.08895v1
2022-10-07,"Perspective: ""Relativity + Correlation + QED = Experiment''","The ultimate goal of electronic structure calculations is to make the left
and right hand sides of the titled ``equation'' as close as possible. This
requires high-precision treatment of relativistic, correlation, and quantum
electrodynamics (QED) effects simultaneously. While both relativistic and QED
effects can readily be built into the many-electron Hamiltonian, electron
correlation is more difficult to describe due to the exponential growth of the
number of parameters in the wave function. Compared with the spin-free case,
spin-orbit interaction results in the loss of spin symmetry and concomitant
complex algebra, thereby rendering the treatment of electron correlation even
more difficult. Possible solutions to these issues are highlighted here.",2210.03470v1
2022-11-22,Atomic-resolution imaging of magnetism via ptychographic phase retrieval,"Atomic-scale characterization of spin textures in solids is essential for
understanding and tuning properties of magnetic materials and devices. While
high-energy electrons are employed for atomic-scale imaging of materials, they
are insensitive to the spin textures. In general, the magnetic contribution to
the phase of high-energy electron wave is 1000 times weaker than the
electrostatic potential. Via accurate phase retrieval through electron
ptychography, here we show that the magnetic phase can be separated from the
electrostatic one, opening the door to atomic-resolution characterization of
spin textures in magnetic materials and spintronic devices.",2211.12008v2
2023-07-28,Berezinskii approach to disordered spin systems with asymmetric scattering and application to the quantum boomerang effect,"We extend the Berezinskii diagrammatic technique to one-dimensional
disordered spin systems, in which time-reversal invariance is broken due to a
spin-orbit coupling term inducing left-right asymmetric scattering. We then use
this formalism to theoretically describe the dynamics of the quantum boomerang
effect, a recently discovered manifestation of Anderson localization. The
theoretical results are confirmed by exact numerical simulations of wave-packet
dynamics in a random potential.",2307.15354v1
2024-01-29,Continuum excitations in a spin-supersolid on a triangular lattice,"Magnetic, thermodynamic, neutron diffraction and inelastic neutron scattering
are used to study spin correlations in the easy-axis XXZ triangular lattice
magnet K$_2$Co(SeO$_3$)$_2$. Despite the presence of quasi-2D ``supersolid''
magnetic order, the low-energy excitation spectrum contains no sharp modes and
is instead a broad continuum resembling that of deconfined fractional
excitations. Applying a weak magnetic field drives the system into an $m$ = 1/3
fractional magnetization plateau phase where the excitations are sharp spin
waves.",2401.16581v1
2002-04-10,Classical-Field Theory of Electron Waves as a Polarized Radiation Probe of Magnetic Surfaces,"Recently, there has been a revival of interest in mechanisms for changing the
spin polarization of an electron beam on transmission through, or reflection
from, a magnetic surface. An understanding of these mechanisms would allow the
use of an electron beam as a polarized radiation probe for magnetic
characterization, like light in MOKE and neutrons in PNR. Here, a mechanism is
described which, unlike simultaneously occurring processes proposed elsewhere,
polarizes an unpolarized incident beam without recourse to inelastic processes.
  A magnetic field leads to a Zeeman term in an electron's Hamiltonian, which
depends on the angle theta between the electron's spin vector and the magnetic
flux. As a result, when an electron wave is incident on the surface of a bulk
magnetic material (figure 1,) the wave-number of the transmitted wave depends
on theta. When the conditions of continuity of the wave-function, and of its
first spatial derivative, at the surface, and conservation of particles, are
applied, an electron reflection coefficient is obtained which also depends on
theta. Therefore, some polarizations are preferentially reflected, while others
are preferentially transmitted. The amplitude reflection and transmission
coefficients can readily be converted to intensity coefficients, and averaged
over an incoherent superposition of electron waves of different theta, e.g. an
unpolarized incident beam. The reflected polarization is P = -(2 e mu_B V B)/(3
e^2 V^2 + mu_B^2 B^2), which can take values -1/sqrt(3) <= P <= 1/sqrt(3),
depending on the balance between V and B.
  The analysis can be extended to multi-layers using the theory of Fabry-Perot
etalons.",0204231v1
2000-03-18,"New Resonant Bivacuum Mediated Interaction, as a Possible Explanation of Psi Phenomena","This paper contains development of following theories and models, related to
Psi phenomena, based on our Unified concept of Bivacuum, particles duality,
fields and time: - Theory of Virtual Replica (VR) of material objects in
Bivacuum and VR Multiplication: VRM (r,t). The VR represents a
three-dimensional (3D) superposition of Bivacuum virtual pressure waves VPW and
spin waves VirSW, modulated by pulsation of elementary particles and
translational and librational de Broglie waves of molecules of macroscopic
object (http://arxiv.org/abs/physics/0207027). The infinitive multiplication of
primary VR in space in form of 3D packets of virtual standing waves: VRM(r), is
a result of interference of all pervading external coherent basic reference
waves: (VPW) and (VirSW) with similar kinds of waves, forming VR. This
phenomena may stands for remote vision; - Theory of nonlocal Virtual Guides
(VirG) of spin, momentum and energy, with properties of quasi one-dimensional
virtual Bose condensate of bivacuum dipoles. The bundles of VirG, connecting
coherent atoms of Sender (S) and Receiver (S), are responsible for nonlocal
weak interaction; - Theory of Bivacuum Mediated Interaction (BMI) responsible
for nonlocal interaction and different Psi-phenomena without contradictions
with fundamental laws of Nature.",0003044v3
2003-07-30,Covariant Lagrangian Methods of Relativistic Plasma Theory,"We obtain a covariant decomposition of the motion of a relativistic charged
particle into parallel motion and perpendicular gyration, and transform to
guiding-center coordinates using Lie transforms. The natural guiding-center
Poisson bracket structure and Hamiltonian are derived. The guiding-center
equations of motion are presented to one order higher than the usual drifts,
and the correction to the gyromomentum is given. We then allow for eikonal wave
perturbations to the Lagrangian action. We develop a manifestly gauge-invariant
and covariant oscillation-center theory to arbitrarily high order, and thereby
derive the relativistic ponderomotive Hamiltonian.
  We sum the guiding-center action over a distribution and add the Maxwell
action to obtain the total action of a guiding-center plasma. Upon variation,
this yields self-consistent covariant relativistic kinetic and field equations;
from these we identify the guiding-center current density and the
guiding-center magnetization. Noether's theorem then yields covariant
conservation laws for the momentum-energy and the angular momentum of a
relativistic guiding-center plasma; from these we identify the guiding-center
stress-energy tensor and the guiding-center spin angular momentum tensor.
Repeating this calculation for guiding/oscillation centers, we find that
variation yields self-consistent relativistic kinetic and field equations for
the plasma in the wave field, including the wave dispersion relation; from
these we identify the wave magnetization and susceptibility. Noether's theorem
then yields conservation laws for the guiding-center plasma in the presence of
a wave field, including the wave contribution to the stress-energy and spin
angular momentum tensors.",0307148v1
2007-10-31,Localization problem of the quasiperiodic system with the spin orbit interaction,"We study one dimensional quasiperiodic system obtained from the tight-binding
model on the square lattice in a uniform magnetic field with the spin orbit
interaction. The phase diagram with respect to the Harper coupling and the
Rashba coupling are proposed from a number of numerical studies including a
multifractal analysis. There are four phases, I, II, III, and IV in this order
from weak to strong Harper coupling. In the weak coupling phase I all the wave
functions are extended, in the intermediate coupling phases II and III mobility
edges exist, and accordingly both localized and extended wave functions exist,
and in the strong Harper coupling phase IV all the wave functions are
localized. Phase I and Phase IV are related by the duality, and phases II and
III are related by the duality, as well. A localized wave function is related
to an extended wave function by the duality, and vice versa. The boundary
between phases II and III is the self-dual line on which all the wave functions
are critical. In the present model the duality does not lead to pure spectra in
contrast to the case of Harper equation.",0710.5816v2
2007-11-01,LISA sources and science,"LISA is a planned space-based gravitational-wave (GW) detector that would be
sensitive to waves from low-frequency sources, in the band of roughly (0.03 -
0.1) mHz < f < 0.1 Hz. This is expected to be an extremely rich chunk of the GW
spectrum -- observing these waves will provide a unique view of dynamical
processes in astrophysics. Here we give a quick survey of some key LISA sources
and what GWs can uniquely teach us about these sources. Particularly noteworthy
science which is highlighted here is the potential for LISA to track the
moderate to high redshift evolution of black hole masses and spins through the
measurement of GWs generated from massive black hole binaries (which in turn
form by the merger of galaxies and protogalaxies). Measurement of these binary
black hole waves has the potential to determine the masses and spins of the
constituent black holes with percent-level accuracy or better, providing a
unique high-precision probe of an aspect of early structure growth. This
article is based on the ""Astrophysics and Relativity using LISA"" talk given by
the author at the Seventh Edoardo Amaldi Conference on Gravitational Waves; it
is largely an updating of the author's writeup of a talk given at the Sixth
International LISA Symposium.",0711.0188v1
2013-02-03,Banks of templates for all-sky narrow-band searches of gravitational waves from spinning neutron stars,"We construct efficient banks of templates suitable for all-sky narrow-band
searches of almost monochromatic gravitational waves originating from spinning
neutron stars in our Galaxy in data collected by interferometric detectors. We
consider waves with one spindown parameter included and we assume that both the
position of the gravitational-wave source in the sky and the wave's frequency
together with spindown parameter are unknown. In the construction we employ
simplified model of the signal with constant amplitude and phase which is a
linear function of unknown parameters. Our template banks enable usage of the
fast Fourier transform algorithm in the computation of the maximum-likelihood
$\mathcal{F}$-statistic for nodes of the grids defining the bank and fulfill an
additional constraint needed to resample the data to barycentric time
efficiently. All these template bank features were employed in the recent
all-sky $\mathcal{F}$-statistic-based search for continuous gravitational waves
in Virgo VSR1 data [J.Aasi et al., Classical Quantum Gravity 31, 165014
(2014)]. Here we improve that template bank by constructing templates suitable
for larger range of search parameters and of smaller thicknesses for certain
values of search parameters. One of our template banks has thickness 12%
smaller than the thickness of the template bank used in the all-sky search of
Virgo VSR1 data and only 4% larger than the thickness of 4-dimensional optimal
lattice covering $A_4^\star$.",1302.0509v3
2013-06-07,Spin and the Thermal Equilibrium Distribution of Wave Functions,"Consider a quantum system $S$ weakly interacting with a very large but finite
system $B$ called the heat bath, and suppose that the composite $S\cup B$ is in
a pure state $\Psi$ with participating energies between $E$ and $E+\delta$ with
small $\delta$. Then, it is known that for most $\Psi$ the reduced density
matrix of $S$ is (approximately) equal to the canonical density matrix. That
is, the reduced density matrix is universal in the sense that it depends only
on $S$'s Hamiltonian and the temperature but not on $B$'s Hamiltonian, on the
interaction Hamiltonian, or on the details of $\Psi$. It has also been pointed
out that $S$ can also be attributed a random wave function $\psi$ whose
probability distribution is universal in the same sense. This distribution is
known as the ""Scrooge measure"" or ""Gaussian adjusted projected (GAP) measure"";
we regard it as the thermal equilibrium distribution of wave functions. The
relevant concept of the wave function of a subsystem is known as the
""conditional wave function"". In this paper, we develop analogous considerations
for particles with spin. One can either use some kind of conditional wave
function or, more naturally, the ""conditional density matrix"", which is in
general different from the reduced density matrix. We ask what the thermal
equilibrium distribution of the conditional density matrix is, and find the
answer that for most $\Psi$ the conditional density matrix is (approximately)
deterministic, in fact (approximately) equal to the canonical density matrix.",1306.1659v2
2015-08-28,$p$-orbital density wave with $d$ symmetry in high-$T_c$ cuprate superconductors predicted by the renormalization-group + constrained RPA theory,"The discovery of the charge-density-wave formation in the high-$T_c$ cuprate
superconductors has activated intensive theoretical studies for the pseudogap
states. However, the microscopic origin of the charge-density-wave state has
been unknown so far since the many-body effects beyond the mean-field-level
approximations, called the vertex corrections, are essential. Toward solving
this problem, we employ the recently developed functional renormalization-group
method, by which we can calculate the higher-order vertex corrections in a
systematic and unbiased way with high numerical accuracy. We discover the
critical development of the $p$-orbital-density-wave ($p$-ODW) instability in
the strong-spin-fluctuation region. The obtained $p$-ODW state possesses the
key characteristics of the charge ordering pattern in Bi- and Y-based
superconductors, such as the wave vector parallel to the nearest Cu-Cu
direction, and the $d$-symmetry form factor with the antiphase correlation
between $p_x$ and $p_y$ orbitals in the same unit cell. In addition, from the
observation of the beautiful scaling relation between the spin susceptibility
and the $p$-ODW susceptibility, we conclude that the main driving force of the
density wave is the Aslamazov-Larkin vertex correction that becomes very
singular near the magnetic quantum-critical point.",1508.07218v3
2017-09-12,Theory of electromagnetic wave propagation in ferromagnetic Rashba conductor,"We present a comprehensive study of various electromagnetic wave propagation
phenomena in a ferromagnetic bulk Rashba conductor from the perspective of
quantum mechanical transport. In this system, both the space inversion and time
reversal symmetries are broken, as characterized by the Rashba field $\alpha$
and magnetization $M$, respectively. First, we present a general
phenomenological analysis of electromagnetic wave propagation in media based on
the dielectric tensor. Then, we calculate the microscopic electromagnetic
response of the current and spin of conduction electrons subjected to $ \alpha$
and $M$, based on linear response theory and the Green's function method.
Firstly, it is found that a large $\alpha$ enhances the anisotropic properties
of the system and enlarges the frequency range in which the electromagnetic
waves have hyperbolic dispersion surfaces and exhibit unusual propagations
known as negative refraction and backward waves. Secondly, we consider the
electromagnetic cross-correlation effects on the wave propagation. These
effects stem from the lack of space inversion symmetry and yield $q$-linear
off-diagonal components in the dielectric tensor. This induces a Rashba-induced
birefringence. In the presence of $M$, there arises an anomalous Hall effect
and the dielectric tensor acquires off-diagonal components linear in $M$. These
components yield the Faraday effect and the Cotton-Mouton effect. When $\alpha$
and $M$ are noncollinear, $M$- and $q$-induced optical phenomena, nonreciprocal
directional dichroism is possible. In these nonreciprocal optical phenomena, a
""toroidal moment,"" $\alpha\times M$, and a ""quadrupole moment,"" $\alpha_i M_j +
\alpha_j M_i$, play central roles. These phenomena are strongly enhanced at the
spin-split transition edge in the electron band.",1709.03689v1
2014-06-10,Dynamical Tides in Compact White Dwarf Binaries: Influence of Rotation,"Tidal interactions play an important role in the evolution and ultimate fate
of compact white dwarf (WD) binaries. Not only do tides affect the pre-merger
state (such as temperature and rotation rate) of the WDs, but they may also
determine which systems merge and which undergo stable mass transfer. In this
paper, we attempt to quantify the effects of rotation on tidal angular momentum
transport in binary stars, with specific calculations applied to WD stellar
models. We incorporate the effect of rotation using the traditional
approximation, in which the dynamically excited gravity waves within the WDs
are transformed into gravito-inertial Hough waves. The Coriolis force has only
a minor effect on prograde gravity waves, and previous results predicting the
tidal spin-up and heating of inspiraling WDs are not significantly modified.
However, rotation strongly alters retrograde gravity waves and inertial waves,
with important consequences for the tidal spin-down of accreting WDs. We
identify new dynamical tidal forcing terms that arise from a proper separation
of the equilibrium and dynamical tide components; these new forcing terms are
very important for systems near synchronous rotation. Additionally, we discuss
the impact of Stokes drift currents on the wave angular momentum flux. Finally,
we speculate on how tidal interactions will affect super-synchronously rotating
WDs in accreting systems.",1406.2717v1
2018-02-18,Orbitally limited pair-density wave phase of multilayer superconductors,"We investigate the magnetic field dependence of an ideal superconducting
vortex lattice in the parity-mixed pair-density wave phase of multilayer
superconductors within a circular cell Ginzburg-Landau approach. In multilayer
systems, due to local inversion symmetry breaking, a Rashba spin-orbit coupling
is induced at the outer layers. This combined with a perpendicular paramagnetic
(Pauli) limiting magnetic field stabilizes a staggered layer dependent
pair-density wave phase in the superconducting singlet channel. The high-field
pair-density wave phase is separated from the low-field BCS phase by a
first-order phase transition. The motivating guiding question in this paper is:
what is the minimal necessary Maki parameter $\alpha_M$ for the appearance of
the pair-density wave phase of a superconducting trilayer system? To address
this problem we generalize the circular cell method for the regular flux-line
lattice of a type-II superconductor to include paramagnetic depairing effects.
Then, we apply the model to the trilayer system, where each of the layers are
characterized by Ginzburg-Landau parameter $\kappa_0$, and a Maki parameter
$\alpha_M$. We find that when the spin-orbit Rashba interaction compares to the
superconducting condensation energy, the orbitally limited pair-density wave
phase stabilizes for Maki parameters $\alpha_M> 10$.",1802.06365v1
2020-09-28,Spin-1 spin-orbit- and Rabi-coupled Bose-Einstein condensate solver,"We present OpenMP versions of FORTRAN programs for solving the
Gross-Pitaevskii equation for a harmonically trapped three-component spin-1
spinor Bose-Einstein condensate (BEC) in one (1D) and two (2D) spatial
dimensions with or without spin-orbit (SO) and Rabi couplings. Several
different forms of SO coupling are included in the programs. We use the
split-step Crank-Nicolson discretization for imaginary- and real-time
propagation to calculate stationary states and BEC dynamics, respectively. The
imaginary-time propagation programs calculate the lowest-energy stationary
state. The real-time propagation programs can be used to study the dynamics.
The simulation input parameters are provided at the beginning of each program.
The programs propagate the condensate wave function and calculate several
relevant physical quantities. Outputs of the programs include the wave
function, energy, root-mean-square sizes, different density profiles (linear
density for the 1D program, linear and surface densities for the 2D program).
The imaginary- or real-time propagation can start with an analytic wave
function or a pre-calculated numerical wave function. The imaginary-time
propagation usually starts with an analytic wave function, while the real-time
propagation is often initiated with the previously calculated converged
imaginary-time wave function.",2009.13507v3
2019-10-21,Gravitational wave signatures of ultralight vector bosons from black hole superradiance,"In the presence of an ultralight bosonic field, spinning black holes are
unstable to superradiance. The rotational energy of the black hole is converted
into a non-axisymmetric, oscillating boson cloud which dissipates through the
emission of nearly monochromatic gravitational radiation. Thus, gravitational
wave observations by ground- or space-based detectors can be used to probe the
existence of dark particles weakly coupled to the Standard Model. In this work,
we focus on massive vector bosons, which grow much faster through
superradiance, and produce significantly stronger gravitational waves compared
to the scalar case. We use techniques from black hole perturbation theory to
compute the relativistically-correct gravitational wave signal across the
parameter space of different boson masses and black hole masses and spins. This
fills in a gap in the literature between flatspace approximations, which
underestimate the gravitational wave amplitude in the non-relativistic limit,
and overestimate it in the relativistic regime, and time-domain calculations,
which have only covered a limited part of the parameter space. We also identify
parameter ranges where overtone superradiantly unstable modes will grow faster
than the lower frequency fundamental modes. Such cases will produce a distinct
gravitational wave signal due to the beating of the simultaneously populated
modes, which we compute.",1910.09476v2
2023-03-11,Removal of $K$-mixing in angular momentum projected nuclear wave functions,"Angular momentum projection plays a key role in studying nuclei and other
quantum many-body systems with rotational invariance. In this Letter, we report
a new fundamental feature of the angular momentum projection, which clearly
tells us the frequently discussed $K$-mixing in the angular momentum projected
nuclear wave function can be safely removed. At a given spin $J$, one can
generate $2J+1$ angular momentum projected states from a deformed Slater
determinant. These projected states are labeled with different $K$ numbers.
Usually, a nuclear wave function with $K$-mixing can be expressed as an
expansion in terms of all these $2J+1$ projected states. The coefficients in
this expansion can be obtained by solving the Hill-Wheeler equation.
Strikingly, we found that such nuclear wave function with $K$-mixing can always
be equivalently replaced by a single projected state generated from another
Slater determinant. Consequently, such nuclear wave function can be
significantly simplified, especially for high-spin states. This also reminds us
that the $K$-mixing in the angular momentum projected nuclear wave functions,
adopted by many present-day nuclear models, does not carry any physical
meaning, and is essentially different from that $K$-mixing caused by the
Coriolis force in the cranked shell model.",2303.06521v1
2023-12-12,Sliding Dynamics of Current-Driven Skyrmion Crystal and Helix in Chiral Magnets,"The skyrmion crystal (SkX) and helix (HL) phases, present in typical chiral
magnets, can each be considered as forms of density waves but with distinct
topologies. The SkX exhibits gyrodynamics analogous to electrons under a
magnetic field, while the HL state resembles topological trivial spin density
waves. However, unlike the charge density waves, the theoretical analysis of
the sliding motion of SkX and HL remains unclear, especially regarding the
similarities and differences in sliding dynamics between these two spin density
waves. In this work, we systematically explore the sliding dynamics of SkX and
HL in chiral magnets in the limit of large current density. We demonstrate that
the sliding dynamics of both SkX and HL can be unified within the same
theoretical framework as density waves, despite their distinct microscopic
orders. Furthermore, we highlight the significant role of gyrotropic sliding
induced by impurity effects in the SkX state, underscoring the impact of
nontrivial topology on the sliding motion of density waves. Our theoretical
analysis shows that the effect of impurity pinning is much stronger in HL
compared with SkX, i.e., $\chi^{SkX}/\chi^{HL}\sim \alpha^2$ ($\chi^{SkX}$,
$\chi^{HL}$: susceptibility to the impurity potential, $\alpha$ ($\ll 1$) is
the Gilbert damping). Moreover, the velocity correction is mostly in the
transverse direction to the current in SkX. These results are further
substantiated by realistic Landau-Lifshitz-Gilbert simulations.",2312.07116v2
2016-03-02,Air-sea interaction in tropical atmosphere: influence of ocean mixing on atmospheric processes,"One the major factors determining the development and evolution of
atmospheric convection is the sea surface temperature and its variability.
Results of this thesis show that state of atmospheric convection impacts the
diurnal distribution of thermal energy in the upper ocean. Under calm and clear
sky conditions a shallow warm layer of several meters depth develops on the
surface of the ocean. This warm layer drives an anomalous flux from the ocean
to the atmosphere. A novel Kelvin wave trajectory database based on satellite
data is introduced in this study. The investigation of its data shows that
substantial fraction of Kelvin waves is initiated as a result of interaction
with another Kelvin wave. Two distinct categories are defined and analyzed: the
two- and multiple Kelvin wave initiations, and a spin off initiation. Results
show that primary forcing of such waves are high diurnal cycle and/or increased
wind speed and latent heat flux at the ocean surface. Variability of the ocean
surface and subsurface along Kelvin wave trajectories over Indian Ocean is
investigated: wind speed and latent heat flux increase and a sea surface
temperature anomaly decreases during a wave passage. It is also shown that
Kelvin waves are longitude-diurnal cycle phase locked over the Maritime
Continent. This cycle phase locking is such that it agrees with mean, local
diurnal cycle of convection in the atmosphere. The strength of the
longitude-diurnal cycle phase locking differs between non-blocked Kelvin waves,
which make successful transition over the Maritime Continent, and blocked waves
that terminate within it. The distance between the islands of Sumatra and
Borneo agrees with the distance travelled by an average Kelvin wave in one day.
This suggests that the Maritime Continent may act as a filter, favoring
successful propagation waves, which are in phase with the local diurnal cycle
of convection.",1603.00902v1
2012-07-31,Surface Acoustic Wave-Driven Ferromagnetic Resonance in Nickel Thin Films: Theory and Experiment,"We present an extensive experimental and theoretical study of surface
acoustic wave-driven ferromagnetic resonance. In a first modeling approach
based on the Landau-Lifshitz-Gilbert equation, we derive expressions for the
magnetization dynamics upon magnetoelastic driving that are used to calculate
the absorbed microwave power upon magnetic resonance as well as the spin
current density generated by the precessing magnetization in the vicinity of a
ferromagnet/normal metal interface. In a second modeling approach, we deal with
the backaction of the magnetization dynamics on the elastic wave by solving the
elastic wave equation and the Landau-Lifshitz-Gilbert equation
selfconsistently, obtaining analytical solutions for the acoustic wave phase
shift and attenuation. We compare both modeling approaches with the complex
forward transmission of a LiNbO$_3$/Ni surface acoustic wave hybrid device
recorded experimentally as a function of the external magnetic field
orientation and magnitude, rotating the field within three different planes and
employing three different surface acoustic wave frequencies. We find
quantitative agreement of the experimentally observed power absorption and
surface acoustic wave phase shift with our modeling predictions using one set
of parameters for all field configurations and frequencies.",1208.0001v1
2013-03-09,Asymptotic behavior of Nambu-Bethe-Salpeter wave functions for multi-particles in quantum field theories,"We derive asymptotic behaviors of the Nambu-Bethe-Salpeter (NBS) wave
function at large space separations for systems with more than 2 particles in
quantum field theories. To deal with $n$-particles in the center of mass flame
coherently, we introduce the Jacob coordinates of $n$ particles and then
combine their $3(n-1)$ coordinates into the one spherical coordinate in
$D=3(n-1)$ dimensions. We parametrize on-shell $T$-matrix for $n$-particle
system of scalar fields at low energy, using the unitarity constraint of the
$S$-matrix. We then express asymptotic behaviors of the NBS wave function for
$n$ particles at low energy, in terms of parameters of $T$-matrix, and show
that the NBS wave function carry the information of $T$-matrix such as phase
shifts and mixing angles of the $n$-particle system in its own asymptotic
behavior, so that the NBS wave function can be considered as the scattering
wave of $n$-particles in quantum mechanics. This property is one of the
essential ingredients of the HAL QCD scheme to define ""potential"" from the NBS
wave function in quantum field theories such as QCD. Our results, together with
an extension to systems with spin 1/2 particles, justify the HAL QCD's
definition of potentials for 3 or more nucleons(baryons) in terms the NBS wave
functions.",1303.2210v2
2015-12-17,Symmetry analysis of translational symmetry broken density waves: application to hexagonal lattices in two dimensions,"In this work we introduce a symmetry classification for electronic density
waves which break translational symmetry due to commensurate wave vector
modulations. The symmetry classification builds on the concept of extended
point groups: symmetry groups which contain, in addition to the lattice point
group, translations that do not map the enlarged unit cell of the density wave
to itself, and become ""non-symmorphic""-like elements. Multi-dimensional
representations of the extended point group are associated with degenerate wave
vectors. Electronic properties such as (nodal) band degeneracies and
topological character can be straightforwardly addressed, and often follow
directly. To further flesh out the idea of symmetry, the classification is
constructed so as to manifestly distinguish time-reversal invariant charge
(i.e., site and bond) order, and time-reversal breaking flux order. For the
purpose of the present work we particularize to spin-rotation invariant density
waves. As a first example of the application of the classification we consider
the density waves of a simple single- and two-orbital square lattice model. The
main objective, however, is to apply the classification to two-dimensional
($2D$) hexagonal lattices, specifically the triangular and the honeycomb
lattices. The multi-component density waves corresponding to the commensurate
$M$-point ordering vectors are worked out in detail. To show that our results
generally apply to $2D$ hexagonal lattices, we develop a general low-energy
$SU(3)$ theory of (spinless) saddle point electrons.",1512.05766v3
2017-12-18,Interpolating wave packets and composite wave functions in QFT and neutrino oscillation problem,"A consistent constructive covariant description of neutrino flavour
transition amplitude in vacuum is presented. To this end a special generalized
relativistic wave packet is constructed with correct extension onto the higher
spins. This packet is uniquely defined as an `interpolating' wave packet, which
by means of relativistically invariant `width' accurately interpolates between
the states localized in momentum space and in coordinate space. The wave packet
is unambiguously determined by analytical properties of Wightman functions in
complex coordinate space naturally connected with its minimization properties.
The packet gives natural relativistic generalization of non relativistic
Gaussian wave packet but it contains covariant states of particle
(antiparticle) only with positive (negative) energy sign and propagates without
their mixing and without changing of its relativistically invariant width. For
the diagrammatic treatment of oscillation with the use of these wave packets
for external particles, the notion of covariant composite wave function for
intermediate neutrino is introduced. It strictly and naturally connects both
oscillation pictures, giving an effective language for detailed description of
this process, and resolves the problems with causality and with covariant equal
time prescription for the intermediate neutrino picture. It is closely related
to overlap function of neutrino creation/detection vertices, elucidating a
covariant meaning of the `pole integration' procedure. Their space-time
asymptotic behaviour in narrow-packets approximation naturally conforms with
such approximation of one-packet state and with the asymptotic behaviour of
oscillation amplitude. The respective overlap function is explicitly calculated
for two-packet example of pion decay vertex. Its correspondence and difference
with previous approximate calculations is analyzed.",1712.06641v3
2019-07-08,"Sub-radian-accuracy gravitational waves from coalescing binary neutron stars II: Systematic study on the equation of state, binary mass, and mass ratio","We report results of numerical relativity simulations for {\it new} 26
non-spinning binary neutron star systems with 6 grid resolutions using an
adaptive mesh refinement numerical re\ lativity code {\tt SACRA-MPI}. The
finest grid spacing is $\approx 64$--$85$ m, depending on the systems. First,
we derive long-term high-precision inspiral gravitational waveforms and show
that the accumulated gravitational-wave phase error due to the finite grid
resolution is less than $0.5$ rad during more than $200$ rad phase evolution
irrespective of the systems. We also find that the gravitational-wave phase
error for a binary system with a tabulated equation of state (EOS) is
comparable to that for a piecewise polytropic EOS. Then we validate the SACRA
inspiral gravitational waveform template, which will be used to extract tidal
deformability from gravitational wave observation, and find that accuracy of \
our waveform modeling is $\lesssim 0.1$ rad in the gravitational-wave phase and
$\lesssim 20 \%$ in the gravitational-wave amplitude up to the
gravitational-wave frequency $1000$ Hz.\
  Finally, we calibrate the proposed universal relations between a post-merger
gravitational wave signal and tidal deformability/neutron star radius in the
literature and show that th\ ey suffer from systematics and many relations
proposed as universal are not very universal. Improved fitting formulae are
also proposed.",1907.03790v2
2020-12-15,Quantum Computing without Quantum Computers: Database Search and Data Processing Using Classical Wave Superposition,"Quantum computing is an emerging field of science which will eventually lead
us to new and powerful logic devices with capabilities far beyond the limits of
current transistor-based technology. There are certain types of problems which
quantum computers can solve fundamentally faster than the tradition digital
computers. There are quantum algorithms which require both superposition and
entanglement (e.g. Shor algorithm). But neither the Grover algorithm nor the
very first quantum algorithm due to Deutsch and Jozsa need entanglement. Is it
possible to utilize classical wave superposition to speedup database search?
This interesting question was analyzed by S. Lloyd. It was concluded that
classical devices that rely on wave interference may provide the same speedup
over classical digital devices as quantum devices. There were several
experimental works using optical beam superposition for emulating Grover
algorithm. It was concluded that the use of classical wave superposition comes
with the cost of exponential increase of the resources. Since then, it is
widely believed that the use of classical wave superposition for quantum
algorithms is inevitably leading to an exponential resources overhead (number
of devices, power consumption, precision requirements). In this work, we
describe a classical Oracle machine which utilizes classical wave superposition
for database search and data processing. We present experimental data on
magnetic database search using spin wave superposition. The data show a
fundamental speedup over the digital computers without any exponential resource
overhead. We argue that in some cases the classical wave-based approach may
provide the same speedup in database search as quantum computers.",2012.08401v1
2023-09-03,Population synthesis and parameter estimation of neutron stars with continuous gravitational waves and third-generation detectors,"Precise measurement of stellar properties through the observation of
continuous gravitational waves from spinning non-axisymmetric neutron stars can
shed light onto new physics beyond terrestrial laboratories. Although hitherto
undetected, prospects for detecting continuous gravitational waves improve with
longer observation periods and more sensitive gravitational wave detectors. We
study the capability of the Advanced Laser Interferometer Gravitational-Wave
Observatory, and the Einstein Telescope to measure the physical properties of
neutron stars through continuous gravitational wave observations. We simulate a
population of Galactic neutron stars, assume continuous gravitational waves
from the stars have been detected, and perform parameter estimation of the
detected signals. Using the estimated parameters, we infer the stars' moments
of inertia, ellipticities, and the components of the magnetic dipole moment
perpendicular to the rotation axis. The estimation of the braking index proved
challenging and is responsible for the majority of the uncertainties in the
inferred parameters. Using the Einstein Telescope with an observation period of
5 yrs, point estimates using median can be made on the moments of inertia with
error of ~ 10 - 100% and on the ellipticities with error of ~ 5 - 50%, subject
to the inference of the braking index. The perpendicular magnetic dipole moment
could not be accurately inferred for neutron stars that emit mainly
gravitational waves.",2309.01133v2
1998-04-29,Gravitational Radiation and Rotation of Accreting Neutron Stars,"Recent discoveries by the Rossi X-Ray Timing Explorer indicate that most of
the rapidly accreting and weakly magnetic neutron stars in the Galaxy are
rotating at spin frequencies greater than 250 Hz. Remarkably, they all rotate
in a narrow range of frequencies. I suggest that these stars rotate fast enough
so that, on average, the angular momentum added by accretion is lost to
gravitational radiation. The strong spin frequency dependence of the angular
momentum loss rate from gravitational radiation then provides a natural reason
for similar spin frequencies. Provided that the interior temperature has a
large scale asymmetry misaligned from the spin axis, then the temperature
sensitive electron captures in the deep crust can provide the quadrupole needed
to reach this limiting situation at 300 Hz. This quadrupole is only present
during accretion and makes it difficult to form radio pulsars spinning more
rapidly than 600-800 Hz via rapid accretion. The gravity wave strength is
<10^{-26} from most neutron stars and >2 X 10^{-26} for Sco X-1. Prior
knowledge of the position, spin frequency and orbital periods will allow for
deep searches for these periodic signals with gravitational wave
interferometers (LIGO, VIRGO and the dual-recycled GEO 600 detector) and
experimenters need to take such sources into account. Sco X-1 will most likely
be detected first.",9804325v1
1995-05-23,Square-lattice Heisenberg antiferromagnet with two kinds of nearest-neighbor regular bonds,"We study the zero-temperature phase diagram of a square-lattice $S=1/2$
Heisenberg antiferromagnet with two types of regularly distributed
nearest-neighbor exchange constants, $J_1>0$ (antiferromagnetic) and $-\infty <
J_2 < \infty $, using spin-wave series based on appropriate mean-field
Hamiltonian and exact-diagonalization data for small clusters. At a
quasiclassical level, the model displays two critical points separating the
N\'eel state from (i) a helicoidal magnetic phase for relatively small
frustrating ferromagnetic couplings $J_2<0$ ($J_2/J_1<-1/3$ for classical
spins), and (ii) a finite-gap quantum paramagnetic phase for large enough
antiferromagnetic exchange constants $J_2>0$. The quantum order-disorder
transition (ii) is similar to the one recently studied in two-layer Heisenberg
antiferromagnets and is a pure result of the zero-point spin fluctuations. On
the other hand, the melting of the N\'eel state in the ferromagnetic region,
$J_2<0$, is a combined effect of the frustration and quantum spin fluctuations.
The second-order spin-wave calculations of the ground-state energy and on-site
magnetization are in accord with our exact diagonalization data in a range away
from the quantum paramagnetic phase. In approaching the phase boundary, the
theory fails due to the enhanced longitudinal spin fluctuations, as it has
recently been argued by Chubukov and Morr.",9505104v1
2005-05-05,Charge and Spin Transport in Superconducting Weak Links,"The coherent mixing of the current states in the superconducting weak link
subject to a Josephson phase difference $\phi$ and subject to an external
transport current in the banks is one of the aims of this work. At $\phi=\pi $
the nonlocal mixing of current states produces two vortices close to the
point-contact between superconducting bulks. The effect of point-contact
reflection in an impenetrable interface and effect of temperature on the
vortices have been studied. It is obtained that increasing the reflection of
the point-contact destroys the vortices while increasing the temperature
restore these vortices. The vortex state is a new version of the interference
between the macroscopic states and quantum tunnelling. Also, the weak link
between unitary triplet superconductors which have $f-$wave and $p+h-$wave
pairing symmetry has been studied from the spin and charge current-phase
relation point of view. The main result in the second part of this thesis, is
the polarization of the spin transport when a junction between triplet
superconductors is used. It is observed that the spin current is the result of
the misorientation between the gap vectors of two supercondcutors. In addition,
the weak link between two bipolar non-unitary triplet superconductors is
studied mathematically. The current-phase relations obtained in third part of
this thesis are totally different from the junctions between the unitary
spin-triplet superconductors and between the spin-singlet superconductors. The
current phase diagrams which have been obtained in this work can be used to
distinguish the symmetry of the order parameter in the crystals.",0505123v1
1996-07-29,"The spinning electron: Hidrodynamical formulation, and quantum limit, of the Barut-Zanghi theory","One of the most satisfactory pictures for spinning particles is the
Barut-Zanghi (BZ) classical theory for the relativistic extended-like electron,
that relates spin to zitterbewegung (zbw). The BZ motion equations constituted
the starting point for recent works about spin and electron structure,
co-authored by us, which adopted the Clifford algebra language. This language
results to be actually suited and fruitful for a hydrodynamical re-formulation
of the BZ theory. Working out, in such a way, a ``probabilistic fluid'', we are
allowed to re-interpret the original classical spinors as quantum
wave-functions for the electron. Thus, we can pass to ``quantize"" the BZ theory
employing this time the tensorial language, more popular in first-quantization.
``Quantizing'' the BZ theory, however, does not lead to the Dirac equation, but
rather to a non-linear, Dirac--like equation, which can be regarded as the
actual ``quantum limit'' of the BZ classical theory. Moreover, an original
variational approach to the the BZ probabilistic fluid shows that it is a
typical ``Weyssenhoff fluid'', while the Hamilton-Jacobi equation (linking
together mass, spin and zbw frequency) appears to be nothing but a special case
of de Broglie's famous energy-frequency relation. Finally, after having
discussed the remarkable correlation between the gauge transformation U(1) and
a general rotation on the spin plan, we clarify and comment on the
two-valuedness nature of the fermionic wave-function, and on the parity and
charge conjugation transformations.",9607212v1
2008-11-28,Breakdown of the rotating-wave approximation in entanglement description of spin anti-correlated states,"It is well established that an entanglement encoded in the Bell states of a
two-qubit system with correlated spins exhibits completely different evolution
properties than that encoded in states with the anti-correlated spins. A
complete and abrupt loss of the entanglement, called the entanglement sudden
death, can be found to occur for the spin correlated states, but the
entanglement evolves without any discontinuity or decays asymptotically for the
spin anti-correlated states. We consider the evolution of an initial
entanglement encoded in the spin anti-correlated states and demonstrate that
the asymptotic behavior predicted before occurs only in the weak coupling limit
or equivalently when the rotating-wave approximation (RWA) is made on the
interaction Hamiltonian of the qubits with the field. If we do not restrict
ourselves to the RWA, we find that the entanglement undergoes a discontinuity,
the sudden death phenomenon. We illustrate this behavior by employing an
efficient scheme for entanglement evolution between two cold-trapped atoms
located inside a single-mode cavity. Although only a single excitation is
initially present in the system, we find that the two-photon excited state,
which plays the key role for the discontinuity in the behavior of the
entanglement, gains a population over a short time of the evolution. When the
RWA is made on the interaction, the two-photon excited state remains
unpopulated for all times and the discontinuity is absent. We attribute this
phenomenon to the principle of complementarity between the evolution time and
energy, and the presence of the counter-rotating terms in the interaction
Hamiltonian.",0811.4633v2
2009-03-10,Interfacing nuclear spins in quantum dots to cavity or traveling-wave fields,"We show how to realize a quantum interface between optical fields and the
polarized nuclear spins in a singly charged quantum dot, which is strongly
coupled to a high-finesse optical cavity. An effective direct coupling between
cavity and nuclear spins is obtained by adiabatically eliminating the (far
detuned) excitonic and electronic states. The requirements needed to map qubit
and continuous variable states of cavity or traveling-wave fields to the
collective nuclear spin are investigated: For cavity fields, we consider
adiabatic passage processes to transfer the states. It is seen that a
significant improvement in cavity lifetimes beyond present-day technology would
be required for a quantum interface. We then turn to a scheme which couples the
nuclei to the output field of the cavity and can tolerate significantly shorter
cavity lifetimes. We show that the lifetimes reported in the literature and the
recently achieved nuclear polarization of ~90% allow both high-fidelity
read-out and write-in of quantum information between the nuclear spins and the
output field. We discuss the performance of the scheme and provide a convenient
description of the dipolar dynamics of the nuclei for highly polarized spins,
demonstrating that this process does not affect the performance of our
protocol.",0903.1727v2
2010-11-16,Nematic spin fluid in the tetragonal phase of BaFe2As2,"Magnetic interactions are generally believed to play a key role in mediating
electron pairing for superconductivity in iron arsenides; yet their character
is only partially understood. Experimentally, the antiferromagnetic (AF)
transition is always preceded by or coincident with a tetragonal to
orthorhombic structural distortion. Although it has been suggested that this
lattice distortion is driven by an electronic nematic phase, where a
spontaneously generated electronic liquid crystal state breaks the C4
rotational symmetry of the paramagnetic state, experimental evidence for
electronic anisotropy has been either in the low-temperature orthorhombic phase
or the tetragonal phase under uniaxial pressure that breaks this symmetry. Here
we use inelastic neutron scattering to demonstrate the presence of a large
in-plane spin anisotropy above TN in the unstressed tetragonal phase of
BaFe2As2. In the low-temperature orthorhombic phase, we find highly anisotropic
spin waves with a large damping along the AF a-axis direction. On warming the
system to the paramagnetic tetragonal phase, the low-energy spin waves evolve
into quasi-elastic excitations, while the anisotropic spin excitations near the
zone boundary persist. These results strongly suggest that the spin nematicity
we find in the tetragonal phase of BaFe2As2 is the source of the electronic and
orbital anisotropy observed above TN by other probes, and has profound
consequences for the physics of these materials.",1011.3771v1
2011-05-02,Projected wave function study of Z2 spin liquids on the kagome lattice for the spin-1/2 quantum Heisenberg antiferromagnet,"Motivated by recent density-matrix renormalization group (DMRG) calculations
[Yan, Huse, and White, Science 332, 1173 (2011)], which claimed that the ground
state of the nearest-neighbor spin-1/2 Heisenberg antiferromagnet on the kagome
lattice geometry is a fully gapped spin liquid with numerical signatures of Z2
gauge structure, and a further theoretical work [Lu, Ran, and Lee, Phys. Rev. B
83, 224413 (2011)], which gave a classification of all Schwinger-fermion
mean-field fully symmetric Z2 spin liquids on the kagome lattice, we have
thoroughly studied Gutzwiller-projected fermionic wave functions by using
quantum variational Monte Carlo techniques, hence implementing exactly the
constraint of one fermion per site. In particular, we investigated the
energetics of all Z2 candidates (gapped and gapless) that lie in the
neighborhood of the energetically competitive U(1) gapless spin liquids. By
using a state-of-the-art optimization method, we were able to conclusively show
that the U(1) Dirac state is remarkably stable with respect to all Z2 spin
liquids in its neighborhood, and in particular for opening a gap toward the
so-called Z2[0,{\pi}]{\beta} state, which was conjectured to describe the
ground state obtained by the DMRG method. Finally, we also considered the
addition of a small second nearest-neighbor exchange coupling of both
antiferromagnetic and ferromagnetic type, and obtained similar results, namely,
a U(1) Dirac spin-liquid ground state.",1105.0341v3
2012-04-27,Topological Sector Fluctuations and Curie Law Crossover in Spin Ice,"At low temperatures, a spin ice enters a Coulomb phase - a state with
algebraic correlations and topologically constrained spin configurations. In
Ho2Ti2O7, we have observed experimentally that this process is accompanied by a
non-standard temperature evolution of the wave vector dependent magnetic
susceptibility, as measured by neutron scattering. Analytical and numerical
approaches reveal signatures of a crossover between two Curie laws, one
characterizing the high temperature paramagnetic regime, and the other the low
temperature topologically constrained regime, which we call the spin liquid
Curie law. The theory is shown to be in excellent agreement with neutron
scattering experiments. On a more general footing, i) the existence of two
Curie laws appears to be a general property of the emergent gauge field for a
classical spin liquid, and ii) sheds light on the experimental difficulty of
measuring a precise Curie-Weiss temperature in frustrated materials; iii) the
mapping between gauge and spin degrees of freedom means that the susceptibility
at finite wave vector can be used as a local probe of fluctuations among
topological sectors.",1204.6266v1
2012-07-25,Spin-orbital quantum liquid on the honeycomb lattice,"In addition to low-energy spin fluctuations, which distinguish them from band
insulators, Mott insulators often possess orbital degrees of freedom when
crystal-field levels are partially filled. While in most situations spins and
orbitals develop long-range order, the possibility for the ground state to be a
quantum liquid opens new perspectives. In this paper, we provide clear evidence
that the SU(4) symmetric Kugel-Khomskii model on the honeycomb lattice is a
quantum spin-orbital liquid. The absence of any form of symmetry breaking -
lattice or SU(N) - is supported by a combination of semiclassical and numerical
approaches: flavor-wave theory, tensor network algorithm, and exact
diagonalizations. In addition, all properties revealed by these methods are
very accurately accounted for by a projected variational wave-function based on
the \pi-flux state of fermions on the honeycomb lattice at 1/4-filling. In that
state, correlations are algebraic because of the presence of a Dirac point at
the Fermi level, suggesting that the symmetric Kugel-Khomskii model on the
honeycomb lattice is an algebraic quantum spin-orbital liquid. This model
provides a good starting point to understand the recently discovered
spin-orbital liquid behavior of Ba_3CuSb_2O_9. The present results also suggest
to choose optical lattices with honeycomb geometry in the search for quantum
liquids in ultra-cold four-color fermionic atoms.",1207.6029v1
2013-04-09,All electrically controlled quantum gates for single heavy hole spin qubits,"In this paper, several nanodevices which realize basic single heavy hole
qubit operations are proposed and supported by time dependent self consistent
Poisson-Schr\""{o}dinger calculations using a four band heavy hole-light hole
model. In particular we propose a set of nanodevices which can act as Pauli X,
Y, Z quantum gates and as a gate that acts similar as a Hadamard gate (i.e. it
creates a balanced superposition of basis states but with an additional phase
factor) on the heavy hole spin qubit. We also present the design and simulation
of a gated semiconductor nanodevice which can realize an arbitrary sequence of
all these proposed single quantum logic gates. The proposed devices exploit the
self-focusing effect of the hole wave function which allows for guiding the
hole along a given path in the form of a stable soliton-like wave packet.
Thanks to the presence of the Dresselhaus spin orbit coupling, the motion of
the hole along a certain direction is equivalent to the application of an
effective magnetic field which induces in turn a coherent rotation of the heavy
hole spin. The hole motion and consequently the quantum logic operation is
initialized only by weak static voltages applied to the electrodes which cover
the nanodevice. The proposed gates allow for an all electric and ultrafast
(tens of picoseconds) heavy hole spin manipulation and give the possibility to
implement a scalable architecture of heavy hole spin qubits for quantum
computation applications.",1304.2674v1
2013-06-11,Null-Wave Giant Gravitons from Thermal Spinning Brane Probes,"We construct and analyze thermal spinning giant gravitons in type II/M-theory
based on spherically wrapped black branes, using the method of thermal probe
branes originating from the blackfold approach. These solutions generalize in
different directions recent work in which the case of thermal (non-spinning)
D3-brane giant gravitons was considered, and reveal a rich phase structure with
various new properties. First of all, we extend the construction to M-theory,
by constructing thermal giant graviton solutions using spherically wrapped M2-
and M5-branes. More importantly, we switch on new quantum numbers, namely
internal spins on the sphere, which are not present in the usual extremal limit
for which the brane world volume stress tensor is Lorentz invariant. We examine
the effect of this new type of excitation and in particular analyze the
physical quantities in various regimes, including that of small temperatures as
well as low/high spin. As a byproduct we find new stationary dipole-charged
black hole solutions in AdS_m X S^n backgrounds of type II/M-theory. We finally
show, via a double scaling extremal limit, that our spinning thermal giant
graviton solutions lead to a novel null-wave zero-temperature giant graviton
solution with a BPS spectrum, which does not have an analogue in terms of the
conventional weakly coupled world volume theory.",1306.2633v1
2013-11-05,Spin dynamics and an orbital-antiphase pairing symmetry in iron-based superconductors,"The symmetry of the wave function describing the Cooper pairs is one of the
most fundamental quantities in a superconductor but its measurement in the
iron-based superconductors has proved to be very difficult. The complex
multi-band nature of these materials makes the interplay of superconductivity
with spin and orbital dynamics very intriguing, leading to very material
dependent magnetic excitations, and pairing symmetries. Here we use
first-principles many-body method, including ab initio determined two-particle
vertex function, to study the spin dynamics and superconducting pairing
symmetry in a large number of iron-based superconductors. In iron compounds
with high transition temperature, we find both the dispersive high-energy spin
excitations, and very strong low energy commensurate or nearly commensurate
spin response, suggesting that these low energy spin excitations play the
dominate role in cooper pairing. We find three closely competing types of
pairing symmetries, which take a very simple form in the space of active iron
$3d$ orbitals, and differ only in the relative quantum mechanical phase of the
$xz$, $yz$ and $xy$ orbital contributions. The extensively discussed s$^{+-}$
symmetry appears when contributions from all orbitals have equal sign, while
the opposite sign in $xz$ and $yz$ orbitals leads to the $d$ wave symmetry. A
novel orbital antiphase $s^{+-}$ symmetry emerges when $xy$ orbital has
opposite sign to $xz$ and $yz$ orbitals. We propose that this orbital-antiphase
pairing symmetry explains the puzzling variation of the experimentally observed
superconducting gaps on all the Fermi surfaces of LiFeAs. This novel symmetry
of the order parameter may be realized in other iron superconductors.",1311.1188v1
2014-03-28,Pair-Density-Wave Superconducting States and Electronic Liquid Crystal Phases,"In conventional superconductors the Cooper pairs have a zero center of mass
momentum. In this paper we present a theory of superconducting states where the
Cooper pairs have a nonzero center of mass momentum, inhomogeneous
superconducting states known as a pair-density-waves (PDW) states. We show that
in a system of spin-1/2 fermions in 2 dimensions in an electronic nematic spin
triplet phase where rotational symmetry is broken both in real and in spin
space PDW phases arise naturally in a theory that can be analyzed using
controlled approximations. We show that several superfluid phases that may
arise in this phase can be treated within a controlled BCS mean field theory,
with the strength of the spin-triplet nematic order parameter playing the role
of the small parameter of this theory. We find that in a spin-triplet nematic
phase, in addition of a triplet $p$-wave and spin-singlet $d$-wave (or $s$
depending on the nematic phase) uniform superconducting states, it is also
possible to have a $d$-wave (or $s$) PDW superconductor. The PDW phases found
here can be either unidirectional, bidirectional or tridirectional depending on
the spin-triplet nematic phase and which superconducting channel is dominant.
In addition, a triple-helix state is found in a particular channel. We show
that these PDW phases are present in the weak coupling limit, in contrast to
the usual Fulde-Ferrell-Larkin-Ovchinnikov phases which require strong coupling
physics in addition to a large magnetic field (and often both).",1403.7530v2
2014-10-11,Spin wave free spectrum and magnetic field gradient of nanopatterned planes of ferromagnetic cobalt nanoparticles: key properties for magnetic resonance based quantum computing,"We present a study by ferromagnetic resonance at microwave Q band of two
sheets of cobalt nanoparticles obtained by annealing SiO2 layers implanted with
cobalt ions. This ex- perimental study is performed as a function of the
applied magnetic field orientation, tempera- ture, and dose of implanted cobalt
ions. We demonstrate that each of those magnetic sheet of cobalt nanoparticles
can be well modelled by a nearly two dimensional ferromagnetic sheet hav- ing a
reduced effective saturation magnetization, compared to a regular thin film of
cobalt. The nanoparticles are found superparamagnetic above around 210 K and
ferromagnetic below this blocking temperature. Magnetostatic calculations show
that a strong magnetic field gradient of around 0.1 G/nm could be produced by a
ferromagnetic nanostripe patterned in such magnetic sheet of cobalt
nanoparticles. Such a strong magnetic field gradient combined with electron
para- magnetic resonance may be relevant for implementing an intermediate scale
quantum computer based on arrays of coupled electron spins, as previously
reported (Eur. Phys. J. B (2014) 87, 183). However, this new approach only
works if no additional spin decoherence is introduced by the spin waves
exitations of the ferromagnetic nanostructure. We thus suggest theoretically
some possible magnetic anisotropy engineering of cobalt nanoparticles that
could allow to suppress the spin qubit decoherence induced by the unwanted
collective excitation of their spins.",1410.3005v1
2015-06-04,Spin dynamics in the presence of competing ferro- and antiferro-magnetic correlations in Yb2Ti2O7,"In this work, we show that the zero field excitation spectra in the quantum
spin ice candidate pyrochlore compound \ybti\ is a continuum characterized by a
very broad and almost flat dynamical response which extends up to $1-1.5$ meV,
coexisting or not with a quasi-elastic response depending on the wave-vector.
The spectra do not evolve between 50 mK and 2 K, indicating that the spin
dynamics is only little affected by the temperature in both the short-range
correlated and ordered regimes. Although classical spin dynamics simulations
qualitatively capture some of the experimental observations, we show that they
fail to reproduce this broad continuum. In particular, the simulations predict
an energy scale twice smaller than the experimental observations. This analysis
is based on a careful determination of the exchange couplings, able to
reproduce both the zero field diffuse scattering and the spin wave spectrum
rising in the field polarized state. According to this analysis, \ybti\ lies at
the border between a ferro and an antiferromagnetic phase. These results
suggest that the unconventional ground state of \ybti\ is governed by strong
quantum fluctuations arising from the competition between those phases. The
observed spectra may correspond to a continuum of deconfined spinons as
expected in quantum spin liquids.",1506.01729v1
2015-10-28,Competeing orders in spin-1 and spin-3/2 XXZ Kagome antiferromagnets: A series expansion study,"We study the competition between $\sqrt{3} \times \sqrt{3}$ (RT3) and $q=0$
(Q0) magnetic orders in spin-one and spin-$3/2$ Kagome-lattice XXZ
antiferromagnets with varying XY anisotropy parameter $\Delta$, using series
expansion methods. The Hamiltonian is split into two parts: an $H_0$ which
favors the classical order in the desired pattern and an $H_1$, which is
treated in perturbation theory by a series expansion. We find that the ground
state energy series for the RT3 and Q0 phases are identical up to sixth order
in the expansion, but ultimately a selection occurs, which depends on spin and
the anisotropy $\Delta$. Results for ground state energy and the magnetization
are presented. These results are compared with recent spin-wave theory and
coupled-cluster calculations. The series results for the phase diagram are
close to the predictions of spin-wave theory. For the spin-one model at the
Heisenberg point ($\Delta=1$), our results are consistent with a vanishing
order parameter, that is an absence of a magnetically ordered phase. We also
develop series expansions for the ground state energy of the spin-one
Heisenberg model in the trimerized phase. We find that the ground state energy
in this phase is lower than those of magnetically ordered ones, supporting the
existence of a spontaneously trimerized phase in this model.",1510.08518v1
2016-01-05,Quantum revivals and magnetization tunneling in effective spin systems,"Quantum mechanical objects or nanoobjects have been proposed as bits for
information storage. While time-averaged properties of magnetic,
quantum-mechanical particles have been extensively studied experimentally and
theoretically, experimental investigations of the real time evolution of
magnetization in the quantum regime were not possible until recent developments
in pump-probe techniques. Here we investigate the quantum dynamics of effective
spin systems by means of analytical and numerical treatments. Particular
attention is paid to the quantum revival time and its relation to the
magnetization tunneling. The quantum revival time has been initially defined as
the recurrence time of a total wave-function. Here we show that the quantum
revivals of wave-functions and expectation values in spin systems may be quite
different which gives rise to a more sophisticated definition of the quantum
revival within the realm of experimental research. Particularly, the revival
times for integer spins coincide which is not the case for half-integer spins.
Furthermore, the quantum revival is found to be shortest for integer ratios
between the on-site anisotropy and an external magnetic field paving the way to
novel methods of anisotropy measurements. We show that the quantum tunneling of
magnetization at avoided level crossing is coherent to the quantum revival time
of expectation values, leading to a connection between these two fundamental
properties of quantum mechanical spins.",1601.00803v1
2016-02-02,Spin liquid versus long range magnetic order in the frustrated body-centered tetragonal lattice,"An $SU({\rm n})$-symmetric generalization of the Heisenberg model for quantum
spin $S$ operators is used to investigate the geometrically frustrated
body-centered tetragonal (BCT) lattice with antiferromagnetic interlayer
coupling $J_1$ and intralayer first and second neighbor coupling $J_2$ and
$J_3$. Using complementary representations of the spin operators, we study the
phase diagram characterizing the ground state of the system. For small n, we
find that the most stable solutions correspond to four different families of
possible long range magnetic orders that are governed by $J_1$, $J_2$, and
$J_3$. First, some possible instabilities of these phases are identified for
$n=2$ in large $S$ expansions up to the linear spin-wave corrections. Then,
using a fermionic representation of the $SU({\rm n})$ spin operators for
$S=1/2$, we find that purely magnetic orders occur for ${\rm n}\le 3$ while
spin-liquid (SL) solutions are stabilized for ${\rm n}\ge 10$. The SL solution
governed by $J_1$ breaks the lattice translation symmetry. This Modulated SL is
associated to a commensurate ordering wave vector $(1,1,1)$. For $4\le {\rm
n}\le 9$, we show how competition between $J_1$, $J_2$, and $J_3$ can tune the
ground state from beeing magnetically ordered to a SL state. We discuss the
relevance of this scenario for correlated systems with BCT crystal structure.",1602.00938v1
2016-09-30,Non-collinear Order and Spin-Orbit Coupling in Sr$_3$ZnIrO$_6$,"Sr$_{3}$ZnIrO$_{6}$ is an effective spin one-half Mott insulating iridate
belonging to a family of magnets which includes a number of quasi-one
dimensional systems as well as materials exhibiting three dimensional order.
Here we present the results of an extensive investigation into the magnetism
including heat capacity, a.c. susceptibility, muon spin rotation ($\mu$SR),
neutron diffraction and inelastic neutron scattering on the same sample. It is
established that the material exhibits a transition at about $17$ K into a
three-dimensional antiferromagnetic structure with propagation vector
$\boldsymbol{k}=(0,\frac{1}{2},1)$ in the hexagonal setting of R$\bar{3}$c and
non-collinear moments of $0.87$$\mu_B$ on Ir$^{4+}$ ions. Further we have
observed a well defined powder averaged spin wave spectrum with zone boundary
energy of $\sim 5$ meV at $5$ K. We stress that a theoretical analysis shows
that the observed non-collinear magnetic structure arises from anisotropic
inter- and intra- chain exchange which has its origin in significant spin-orbit
coupling. The model can satisfactorily explain the observed spin wave
excitations.",1610.00038v2
2016-10-14,Nonlinear Dynamics of a two-level system of a single spin driven beyond the rotating-wave approximation,"Quantum systems driven by strong oscillating fields are the source of many
interesting physical phenomena. In this work, we experimentally study the
dynamics of a two-level system of a single spin driven in the strong-driving
regime where the rotating-wave approximation is not valid. This two-level
system is a subsystem of a single Nitrogen-Vacancy center coupled to a
first-shell $^{13}$C nuclear spin in diamond at a level anti-crossing point
that occurs in the $m_{s}=\pm1$ manifold when the energy level splitting
between the $m_{s}$ = $+1$ and $-1$ spin states due to the static magnetic
field is $\approx$ 127 MHz, which is roughly equal to the spectral splitting
due to the $^{13}$C hyperfine interaction. The transition frequency of this
electron spin two-level system in a static magnetic field of 28.9 G is 1.7 MHz
and it can be driven only by the $z$-component of the RF field. Electron spin
Rabi frequencies in this system can reach tens of MHz even for moderate RF
powers. The simple sinusoidal Rabi oscillations that occur when the amplitude
of the driving field is much smaller than the transition frequency become
complex when the driving field strength is comparable or greater than the
energy level splitting. We observe that the system oscillates faster than the
amplitude of the driving field and the response of the system shows multiple
frequencies.",1610.04512v2
2018-07-16,Anomalous Dimensions from Crossing Kernels,"In this note we consider the problem of extracting the corrections to CFT
data induced by the exchange of a primary operator and its descendents in the
crossed channel. We show how those corrections which are analytic in spin can
be systematically extracted from crossing kernels. To this end, we underline a
connection between: Wilson polynomials (which naturally appear when considering
the crossing kernels given recently in arXiv:1804.09334), the spectral integral
in the conformal partial wave expansion, and Wilson functions. Using this
connection, we determine closed form expressions for the OPE data when the
external operators in 4pt correlation functions have spins $J_1$-$J_2$-$0$-$0$,
and in particular the anomalous dimensions of double-twist operators of the
type $[\mathcal{O}_{J_1}\mathcal{O}_{J_2}]_{n,\ell}$ in $d$ dimensions and for
both leading and sub-leading twist. The OPE data are expressed in terms of
Wilson functions, which naturally appear as a spectral integral of a Wilson
polynomial. As a consequence, our expressions are manifestly analytic in spin
and are valid up to finite spin. We present some applications to CFTs with
slightly broken higher-spin symmetry. The Mellin Barnes integral representation
for $6j$ symbols of the conformal group in general $d$ and its relation with
the crossing kernels are also discussed.",1807.05941v5
2018-07-25,Impact of non-equilibrium fluctuations on pre-thermal dynamical phase transitions in long-range interacting spin chains,"We study the non-equilibrium phase diagram and the dynamical phase
transitions occurring during the pre-thermalization of non-integrable quantum
spin chains, subject to either quantum quenches or linear ramps of a relevant
control parameter. We consider spin systems in which long-range ferromagnetic
interactions compete with short-range, integrability-breaking terms. We capture
the pre-thermal stages of the non-equilibrium evolution via a time-dependent
spin wave expansion at leading order in the spin waves density. In order to
access regimes with strong integrability breaking, instead, we perform
numerical simulations based on the time-dependent variational principle with
matrix product states. By investigating a large class of quantum spin models,
we demonstrate that non-equilibrium fluctuations can significantly affect the
dynamics near critical points of the phase diagram, resulting in a chaotic
evolution of the collective order parameter, akin to the dynamics of a
classical particle in a multiple-well potential subject to quantum friction. We
also elucidate the signature of this novel dynamical phase on the
time-dependent correlation functions of the local order parameter. We finally
establish a connection with the notion of dynamical quantum phase transition
associated with a possible non-analytic behavior of the return probability
amplitude, or Loschmidt echo, showing that the latter displays cusps whenever
the order parameter vanishes during its real-time evolution.",1807.09797v2
2014-06-20,Spin-orbit density wave: A new phase of matter applicable to the hidden order state of URu2Si2,"We provide a brief review and detailed analysis of the spin-orbit density
wave (SODW), proposed as a possible explanation to the `hidden order' phase of
URu2Si2. Due to the interplay between inter-orbital Coulomb interaction and
spin-orbit coupling (SOC) in this compound, the SODW is shown to arise from
Fermi surface nesting instability between two spin-orbit split bands. An
effective low-energy Hamiltonian including single-particle SOC and two-particle
SODW is derived, while numerical results are calculated by using
density-functional theory (DFT) based band structure input. Computed gapped
quasiparticle spectrum, entropy loss and spin-excitation spectrum are in
detailed agreement with experiments. Interestingly, despite the fact that SODW
governs dynamical spin-excitations, the static magnetic moment is calculated to
be zero, owing to the time-reversal invariance imposed by SOC. As a
consequence, SODW can be destroyed by finite magnetic field even at zero
temperature. Our estimation of the location of the quantum critical point is
close to the experimental value of Bc ~ 35 T. Finally, we extend the idea of
SODW to other SOC systems including iridium oxides (iridates) and
two-dimensional electronic systems such as BiAg2 surface and LaAlO3/SrTiO3
interface. We show hints of quasiparticle gapping, reduction of preexisting
magnetic moment, large magneto-resistance etc. in these systems which can be
explained consistently within the SODW theory.",1406.5271v2
2018-12-03,Tidal Disruptions of Stars by Binary Black Holes: Modifying the Spin Magnitudes and Directions of LIGO Sources in Dense Stellar Environments,"Binary black holes (BBHs) appear to be widespread and are able to merge
through the emission of gravitational waves, as recently illustrated by LIGO.
The spin of the BBHs is one of the parameters that LIGO can infer from the
gravitational wave signal and can be used to constrain their production site.
If BBHs are assembled in stellar clusters they are likely to interact with
stars, which could occasionally lead to a tidal disruption event (TDE). When a
BBH tidally disrupts a star it can accrete a significant fraction of the
debris, effectively altering the spins of the BHs. Therefore, although
dynamically formed BBHs are expected to have random spin orientations, tidal
stellar interactions can significantly alter their birth spins both in
direction and magnitude. Here we investigate how TDEs by BBHs can affect the
properties of the BH members as well as exploring the characteristics of the
resulting electromagnetic signatures. We conduct hydrodynamic simulations with
a Lagrangian Smoothed Particle Hydrodynamics code of a wide range of
representative tidal interactions. We find that both spin magnitude and
orientation can be altered and temporarily aligned or anti-aligned through
accretion of stellar debris, with a significant dependence on the mass ratio of
the disrupted star and the BBH members. These tidal interactions feed material
to the BBH at very high accretion rates, with the potential to launch a
relativistic jet. The corresponding beamed emission is a beacon to an otherwise
quiescent BBH.",1812.01118v1
2019-06-25,End point of nonaxisymmetric black hole instabilities in higher dimensions,"We report on the end state of nonaxisymmetric instabilities of singly
spinning asymptotically flat Myers-Perry black holes. Starting from a singly
spinning black hole in D=5,6,7 dimensions, we introduce perturbations with
angular dependence described by m=2, m=3, or m=4 azimuthal mode numbers about
the axis of rotation. In D=5, we find that all singly spinning Myers-Perry
black holes are stable, in agreement with the results from perturbation theory.
In D=6 and 7, we find that these black holes are nonlinearly stable only for
sufficiently low spins. For intermediate spins, although the m=2 bar mode
becomes unstable and leads to large deformations, the black hole settles back
down to another member of the Myers-Perry family via gravitational wave
emission; surprisingly, we find that all such unstable black holes settle to
the same member of the Myers-Perry family. The amount of energy radiated into
gravitational waves can be very large, in some cases more than 30% of the
initial total mass of the system. For high enough spins, the m=4 mode becomes
the dominant unstable mode, leading to deformed black holes that develop local
Gregory-Laflamme instabilities, thus forming a naked singularity in finite
time, which is further evidence for the violation of the weak cosmic censorship
conjecture in asymptotically flat higher-dimensional spacetimes.",1906.10696v3
2016-03-08,Spin-wave thermal population as temperature probe in Magnetic Tunnel Junctions,"We study whether a direct measurement of the absolute temperature of a
Magnetic Tunnel Junction (MTJ) can be performed using the high frequency
electrical noise that it delivers under a finite voltage bias. Our method
includes quasi-static hysteresis loop measurements of the MTJ, together with
the field-dependence of its spin wave noise spectra. We rely on an analytical
modeling of the spectra by assuming independent fluctuations of the different
sub-systems of the tunnel junction that are described as macrospin fluctuators.
We illustrate our method on perpendicularly magnetized MgO-based MTJs patterned
in 50*100 nm2 nanopillars. We apply hard axis (in-plane) fields to let the
magnetic thermal fluctuations yield finite conductance fluctuations of the MTJ.
Instead of the free layer fluctuations that are observed to be affected by both
spin-torque and temperature, we use the magnetization fluctuations of the sole
reference layers. Their much stronger anisotropy and their much heavier damping
render them essentially immune to spin-torque. We illustrate our method by
determining current-induced heating of the perpendicularly magnetized tunnel
junction at voltages similar to those used in spin-torque memory applications.
The absolute temperature can be deduced with a precision of +/- 60 K and we can
exclude any substantial heating at the spin-torque switching voltage.",1603.02591v1
2016-03-30,Rashba-type Spin-orbit Coupling in Bilayer Bose-Einstein Condensates,"We explore a new way of producing the Rashba spin-orbit coupling (SOC) for
ultracold atoms by using a two-component (spinor) atomic Bose-Einstein
condensate (BEC) confined in a bilayer geometry. The SOC of the Rashba type is
created if the atoms pick up a {\pi} phase after completing a cyclic transition
between four combined spin-layer states composed of two spin and two layer
states. The cyclic coupling of the spin-layer states is carried out by
combining an intralayer Raman coupling and an interlayer laser assisted
tunneling. We theoretically determine the ground-state phases of the
spin-orbit-coupled BEC for various strengths of the atom-atom interaction and
the laser-assisted coupling. It is shown that the bilayer scheme provides a
diverse ground-state phase diagram. In an intermediate range of the atom-light
coupling two interlacing lattices of half- skyrmions and half-antiskyrmions are
spontaneously created. In the strong-coupling regime, where the SOC of the
Rashba-type is formed, the ground state represents plane-wave or standing-wave
phases depending on the interaction between the atoms. A variational analysis
is shown to be in a good agreement with the numerical results.",1603.09043v2
2019-05-25,Large-$S$ limit of the large-$N$ theory for the triangular antiferromagnet,"Large-$S$ and large-$N$ theories (spin value $S$ and spinor component number
$N$) are complementary, and sometimes conflicting, approaches to quantum
magnetism. While large-$S$ spin-wave theory captures the correct semiclassical
behavior, large-$N$ theories, on the other hand, emphasize the quantumness of
spin fluctuations. In order to evaluate the possibility of the non-trivial
recovery of the semiclassical magnetic excitations within a large-$N$ approach,
we compute the large-$S$ limit of the dynamic spin structure of the triangular
lattice Heisenberg antiferromagnet within a Schwinger boson spin
representation. We demonstrate that, only after the incorporation of Gaussian
($1/N$) corrections to the saddle-point ($N=\infty$) approximation, we are able
to exactly reproduce the linear spin wave theory results in the large-$S$
limit. The key observation is that the effect of $1/N$ corrections is to cancel
out exactly the main contribution of the saddle-point solution; while the
collective modes (magnons) consist of two spinon bound states arising from the
poles of the RPA propagator. This result implies that it is essential to
consider the interaction of the spinons with the emergent gauge fields and that
the magnon dispersion relation should not be identified with that of the
saddle-point spinons.",1905.10689v3
2017-01-16,Light scattering in the medium with fluctuating gyrotropy: application to spin noise spectroscopy,"The spin noise signal in the Faraday-rotation-based detection technique can
be considered equally correctly either as a manifestation of the spin-flip
Raman effect or as a result of light scattering in the medium with fluctuating
gyrotropy. In this paper, we present rigorous description of the signal
formation process upon heterodyning of the field scattered due to fluctuating
gyrotropy. Along with conventional single-beam experimental arrangement, we
consider here a more complicated, but more informative, two-beam configuration
that implies the use of an auxiliary light beam passing through the same
scattering volume and delivering additional scattered field to the detector. We
show that the signal in the spin noise spectroscopy arising due to heterodyning
of the scattered field is formed only by the scattered field components whose
wave vectors coincide with those of the probe beam. Therefore, in principle,
the detected signal in spin noise spectroscopy can be increased by increasing
overlap of the two fields in the momentum space. We also show that, in the
two-beam geometry, contribution of the auxiliary (tilted) beam to the detected
signal is represented by Fourier transform of the gyrotropy relief at the
difference of two wave vectors. This effect can be used to study spin
correlations by means of noise spectroscopy.",1701.04268v1
2017-03-22,Effective bilinear-biquadratic model for noncoplanar ordering in itinerant magnets,"Noncollinear and noncoplanar magnetic textures including skyrmions and
vortices act as emergent electromagnetic fields and give rise to novel
electronic and transport properties. We here report a unified understanding of
noncoplanar magnetic orderings emergent from the spin-charge coupling in
itinerant magnets. The mechanism has its roots in effective multiple spin
interactions beyond the conventional Ruderman-Kittel-Kasuya-Yosida (RKKY)
mechanism, which are ubiquitously generated in itinerant electron systems with
local magnetic moments. Carefully examining the higher-order perturbations in
terms of the spin-charge coupling, we construct a minimal effective spin model
composed of the bilinear and biquadratic interactions with particular wave
numbers dictated by the Fermi surface. We find that our effective model
captures the underlying physics of the instability toward noncoplanar
multiple-$Q$ states discovered recently in itinerant magnets: a single-$Q$
helical state expected from the RKKY theory is replaced by a double-$Q$ vortex
crystal with chirality density waves even for an infinitely small spin-charge
coupling on generic lattices [R. Ozawa $\mathit{et \ al.}$, J. Phys. Soc. Jpn.
$\mathbf{85}$, 103703 (2016)], and a triple-$Q$ skyrmion crystal with a high
topological number of two appears with increasing the spin-charge coupling on a
triangular lattice [R. Ozawa, S. Hayami, and Y. Motome, to appear in Phys. Rev.
Lett. (arXiv: 1703.03227)]. We find that, by introducing an external magnetic
field, our effective model exhibits a plethora of multiple-$Q$ states. Our
findings will serve as a guide for exploring further exotic magnetic orderings
in itinerant magnets.",1703.07690v1
2020-07-23,Spin-waves in 2D honeycomb lattice $XXZ$-type van der Waals antiferromagnet CoPS$_3$,"The magnetic excitations in CoPS$_3$, a two-dimensional van der Waals (vdW)
antiferromagnet with spin $S=3/2$ on a honeycomb lattice, has been measured
using powder inelastic neutron scattering. Clear dispersive spin waves are
observed with a large spin gap of ~13 meV. The magnon spectra were fitted using
an $XXZ$-type $J_1-J_2-J_3$ Heisenberg Hamiltonian with a single-ion anisotropy
assuming no magnetic exchange between the honeycomb layers. The best-fit
parameters show ferromagnetic exchange $J_1=-2.08$ meV and $J_2=-0.26$ meV for
the nearest and second-nearest neighbors and a sizeable antiferromagnetic
exchange $J_3=4.21$ meV for the third-nearest neighbor with the strong
easy-axis anisotropy $K=-2.06$ meV. The suitable fitting could only be achieved
by the anisotropic $XXZ$-type Hamiltonian, in which the exchange interaction
for the out-of-plane component is smaller than that for the in-plane one by a
ratio $\alpha=J_z/J_x=0.6$. Moreover, the absence of spin-orbit exciton around
30 meV indicates that Co$^{2+}$ ions in CoPS$_3$ have a $S=3/2$ state rather
than a spin-orbital entangled $J_\rm{eff}=1/2$ ground state. Our result
directly shows that CoPS$_3$ is an experimental realization of the $XXZ$ model
with a honeycomb lattice in 2D vdW magnets.",2007.11791v1
2021-07-19,The final twist: A model of gravitational waves from precessing black-hole binaries through merger and ringdown,"We present PhenomPNR, a frequency-domain phenomenological model of the
gravitational-wave (GW) signal from binary-black-hole mergers that is tuned to
numerical relativity (NR) simulations of precessing binaries. In many current
waveform models, e.g., the ""Phenom"" and ""EOBNR"" families that have been used
extensively to analyse LIGO-Virgo GW observations, analytic approximations are
used to add precession effects to models of non-precessing (aligned-spin)
binaries, and it is only the aligned-spin models that are fully tuned to NR
results. In PhenomPNR we incorporate precessing-binary NR results in two ways:
(i) we produce the first NR-tuned model of the signal-based precession dynamics
through merger and ringdown, and (ii) we extend a previous aligned-spin model,
PhenomD, to include the effects of misaligned spins on the signal in the
co-precessing frame. The NR calibration has been performed on 40 simulations of
binaries with mass ratios between 1:1 and 1:8, where the larger black hole has
a dimensionless spin magnitude of 0.4 or 0.8, and we choose five angles of spin
misalignment with the orbital angular momentum. PhenomPNR has a typical
mismatch accuracy within 0.1% up to mass-ratio 1:4, and within 1% up to
mass-ratio 1:8.",2107.08876v1
2022-02-11,Disorder-induced broadening of the spin waves in a triangular-lattice quantum-spin-liquid candidate YbZnGaO$_4$,"Disorder is important in the study of quantum spin liquids, but its role on
the spin dynamics remains elusive. Here, we explore the disorder effect by
investigating the magnetic-field dependence of the low-energy magnetic
excitations in a triangular-lattice frustrated magnet YbZnGaO$_4$ with
inelastic neutron scattering. With an intermediate field of 2.5 T applied along
the $c$-axis, the broad continuum at zero field becomes more smeared both in
energy and momentum. With a field up to 10 T, which fully polarizes the
magnetic moments, we observe clear spin-wave excitations with a gap of
$\sim$1.4 meV comparable to the bandwidth. However, the spectra are
significantly broadened. The excitation spectra both at zero and high fields
can be reproduced by performing classical Monte Carlo simulations which take
into account the disorder effect arising from the random site mixing of
nonmagnetic Zn$^{2+}$ and Ga$^{3+}$ ions. These results elucidate the critical
role of disorder in broadening the magnetic excitation spectra and mimicking
the spin-liquid features in frustrated quantum magnets.",2202.05462v1
2022-10-13,Superconductivity in doped triangular Mott insulators: the roles of parent spin backgrounds and charge kinetic energy,"We study the prerequisites for realizing superconductivity in doped
triangular-lattice Mott insulators by considering three distinct parent spin
backgrounds, i.e., $120^{\circ}$ antiferromagnets, quantum spin liquid, and
stripy antiferromagnets, and all possible sign combinations $(\tau_1, \tau_2)$
of nearest-neighbor hopping and next-nearest-neighbor hopping $(t_1, t_2)$.
Based on density-matrix renormalization group calculations, we find that, with
finite $t_2$ and specific sign combinations $(\tau_1, \tau_2)$, the
quasi-long-range superconductivity order can always be achieved, regardless of
the nature of the parent spin backgrounds. Besides specific hopping signs
$(\tau_1, \tau_2)$, these superconductivity phases in triangular lattices are
commonly characterized by short-ranged spin correlations and two charges per
stripe. In the robust superconductivity phase realized at larger $t_2/t_1$,
flipping the signs $\tau_2$ and $\tau_1$ gives rise to the stripe phase without
strong pairing and pseudogap-like phase without Cooper-pair phase coherence,
respectively. Interestingly, the roles of the two hopping signs are switched at
smaller $t_2/t_1$. Moreover, different sign combinations $(\tau_1, \tau_2)$
would stabilize distinct phases including superconductivity, charge density
waves, spin density waves, and pseudogap-like phases accordingly. Our findings
suggest the important role of charge kinetic energy in realizing
superconductivity in doped triangular-lattice Mott insulators.",2210.06847v2
2022-12-22,"Explicit derivation of the chiral and (generic) helical edge states for the Kane-Mele model: Closed expressions for the wave function, dispersion relation, and spin rotation","While one of the most important and intriguing features of the topological
insulators is the presence of edge states, the closed-form expressions for the
edge states of some famous topological models are still lacking. Here, we focus
on the Kane-Mele model with and without Rashba spin-orbit coupling as a
well-known model to describe a two-dimensional version of the $\mathbb{Z}_2$
topological insulator to study the properties of its edge states analytically.
By considering the tight-binding model on a honeycomb lattice with zigzag
boundaries and introducing a perturbative approach, we derive explicit
expressions for the wave functions, energy dispersion relations, and the spin
rotations of the (generic) helical edge states. To this end, we first map the
edge states of the ribbon geometry into an effective two-leg ladder model with
momentum-dependent energy parameters. Then, we split the Hamiltonian of the
system into an unperturbed part and a perturbation. The unperturbed part has a
flat-band energy spectrum and can be solved exactly which allows us to consider
the remaining part of the Hamiltonian perturbatively. The resulting energy
dispersion relation within the first-order perturbation, surprisingly, is in
excellent agreement with the numerical spectra over a very wide range of
wavenumbers. Our perturbative framework also allows deriving an explicit form
for the rotation of the spins of the momentum edge states in the absence of
axial spin symmetry due to the Rashba spin-orbit interaction.",2212.11520v1
2023-02-18,Entangling dynamics from effective rotor/spin-wave separation in U(1)-symmetric quantum spin models,"The non-equilibrium dynamics of quantum spin models is a most challenging
topic, due to the exponentiality of Hilbert space; and it is central to the
understanding of the many-body entangled states that can be generated by
state-of-the-art quantum simulators. A particularly important class of
evolutions is the one governed by U(1) symmetric Hamiltonians, initialized in a
state which breaks the U(1) symmetry -- the paradigmatic example being the
evolution of the so-called one-axis-twisting (OAT) model, featuring
infinite-range interactions between spins. In this work we show that the
dynamics of the OAT model can be closely reproduced by systems with
power-law-decaying interactions, thanks to an effective separation between the
zero-momentum degrees of freedom, associated with the so-called Anderson tower
of states, and reconstructing a OAT model; and finite-momentum ones, associated
with spin-wave excitations. This mechanism explains quantitatively the recent
numerical observation of spin squeezing and Schr\""odinger-cat generation in the
dynamics of dipolar Hamiltonians; and it paves the way for the extension of
this observation to a much larger class of models of immediate relevance for
quantum simulations.",2302.09271v1
2023-06-09,Static and dynamical properties of the spin-5/2 nearly ideal triangular lattice antiferromagnet Ba3MnSb2O9,"We study the ground state and spin excitations in Ba3MnSb2O9, an easy-plane S
= 5/2 triangular lattice antiferromagnet. By combining single-crystal neutron
scattering, electric spin resonance (ESR), and spin wave calculations, we
determine the frustrated quasi-two-dimensional spin Hamiltonian parameters
describing the material. While the material has a slight monoclinic structural
distortion, which could allow for isosceles-triangular exchanges and biaxial
anisotropy by symmetry, we observe no deviation from the behavior expected for
spin waves in the in-plane 120o state. Even the easy-plane anisotropy is so
small that it can only be detected by ESR in our study. In conjunction with the
quasi-two-dimensionality, our study establishes that Ba3MnSb2O9 is a nearly
ideal triangular lattice antiferromagnet with the quasi-classical spin S = 5/2,
which suggests that it has the potential for an experimental study of Z- or
Z2-vortex excitations.",2306.05802v2
2023-08-30,Targeted Search for Gravitational Waves from Highly Spinning Light Compact Binaries,"Searches for gravitational waves from compact-binary mergers, which to date
have reported $\sim100$ observations, have previously ignored binaries whose
components are both consistent with the mass of neutron stars $(1 M_\odot$ to $
2 M_\odot)$ and have high dimensionless spin $>0.05$. While previous searches
targeted sources that are representative of observed neutron star binaries in
the galaxy, it is already known that neutron stars can regularly be spun up to
a dimensionless spin of $\sim0.4$, and in principle reach up to $\sim0.7$
before breakup would occur. Furthermore, there may be primordial black hole
binaries or exotic formation mechanisms to produce light black holes. In these
cases, it is possible for the binary constituent to be spun up beyond that
achievable by a neutron star. A single detection of this type of source would
reveal a novel formation channel for compact-binaries. To determine if there is
evidence for any such sources, we use PyCBC to conduct a targeted search of
LIGO and Virgo data for light compact objects with high spin. Our analysis
detects previously known observations GW170817 and GW200115; however, we report
no additional mergers. The most significant candidate, not previously known, is
consistent with the noise distribution, and so we constrain the merger rate of
spinning light binaries.",2308.16173v3
2023-11-22,Triple-sinusoid hedgehog lattice in a centrosymmetric Kondo metal,"Superposed symmetry-equivalent magnetic ordering wave vectors can lead to
topologically non-trivial spin textures, such as magnetic skyrmions and
hedgehogs, and give rise to novel quantum phenomena due to fictitious magnetic
fields associated with a non-zero Berry curvature of these spin textures. To
date, all known spin textures are constructed through the superposition of
multiple spiral orders, where spins vary in directions with constant amplitude.
Recent theoretical studies have suggested that multiple sinusoidal orders,
where collinear spins vary in amplitude, can construct distinct topological
spin textures regarding chirality properties. However, such textures have yet
to be experimentally realised. In this work, we report the observation of a
zero-field magnetic hedgehog lattice from a superposition of triple sinusoidal
wave vectors in the magnetically frustrated Kondo lattice CePtAl4Ge2. Notably,
we also observe the emergence of anomalous electrical and thermodynamic
behaviours near the field-induced transition from the zero-field topological
hedgehog lattice to a non-topological sinusoidal state. These observations
highlight the role of Kondo coupling in stabilising the zero-field hedgehog
state in the Kondo lattice and warrant an expedited search for other
topological magnetic structures coupled with Kondo coupling.",2311.13405v1
2013-02-18,Resonant-plane locking and spin alignment in stellar-mass black-hole binaries: a diagnostic of compact-binary formation,"We study the influence of astrophysical formation scenarios on the
precessional dynamics of spinning black-hole binaries by the time they enter
the observational window of second- and third-generation gravitational-wave
detectors, such as Advanced LIGO/Virgo, LIGO-India, KAGRA and the Einstein
Telescope. Under the plausible assumption that tidal interactions are efficient
at aligning the spins of few-solar mass black-hole progenitors with the orbital
angular momentum, we find that black-hole spins should be expected to
preferentially lie in a plane when they become detectable by gravitational-wave
interferometers. This ""resonant plane"" is identified by the conditions
\Delta\Phi=0{\deg} or \Delta\Phi=+/-180{\deg}, where \Delta\Phi is the angle
between the components of the black-hole spins in the plane orthogonal to the
orbital angular momentum. If the angles \Delta \Phi can be accurately measured
for a large sample of gravitational-wave detections, their distribution will
constrain models of compact binary formation. In particular, it will tell us
whether tidal interactions are efficient and whether a mechanism such as mass
transfer, stellar winds, or supernovae can induce a mass-ratio reversal (so
that the heavier black hole is produced by the initially lighter stellar
progenitor). Therefore our model offers a concrete observational link between
gravitational-wave measurements and astrophysics. We also hope that it will
stimulate further studies of precessional dynamics, gravitational-wave template
placement and parameter estimation for binaries locked in the resonant plane.",1302.4442v2
2016-07-12,Understanding spin parity of $P_c(4450)$ and $Y(4274)$ in a hadronic molecular state picture,"The hidden-charmed pentaquark $P_c(4450)$ and the charmonium-like state
$Y(4274)$ are investigated as a $\bar{D}^*\Sigma_c$ and a
$D_s\bar{D}_{s0}(2317)$ molecular state, respectively. The spin parities of
these two states cannot be well understood if only S-wave $\bar{D}^*\Sigma_c$
and $D_s\bar{D}_{s0}(2317)$ interactions are considered. In this work, the
interactions are studied in a quasipotential Bethe-Salpeter equation approach
with a partial wave decomposition on spin parity $J^P$, and the contributions
of different partial waves are studied in a two-channel scattering model
including a generating channel and an observation channel. Two poles at
$4447\pm4i$ and $4392\pm46i$ MeV are produced from the $\bar{D}^*\Sigma_c$
interaction coupled with the $J/\psi p$ channel in $3/2^-$ wave and $5/2^+$
wave, respectively. The peak for the $5/2^+$ state has a comparable height as
that of the $3/2^-$ state in the $J/\psi p$ invariant mass spectrum. The
$D_s\bar{D}_{s0}(2317)$ interaction coupled with the $J/\psi\phi$ channel is
studied and a pole at $4275\pm11i$ MeV is produced in $J^{P}=1^{+}$ wave, which
corresponds to P-wave $D_s\bar{D}_{s0}(2317)$ interaction. The pole from S-wave
$D_s\bar{D}_{s0}(2317)$ interaction is far below that from P-wave interaction
even the $J/\psi\phi$ threshold, so cannot be observed in the $J/\psi\phi$
channel. The result suggests that in these cases a state carrying a spin parity
corresponding to P-wave interaction should be taken as seriously as these
carrying a spin parity corresponding to S-wave interaction in the hadronic
molecular state picture.",1607.03223v3
2018-11-12,Gauge theory for the cuprates near optimal doping,"We describe the phase diagram of a 2+1 dimensional SU(2) gauge theory of
fluctuating incommensurate spin density waves for the hole-doped cuprates. Our
primary assumption is that all low energy fermionic excitations are gauge
neutral and electron-like, while the spin density wave order is fractionalized
into Higgs fields transforming as adjoints of the gauge SU(2). The confining
phase of the gauge theory is a conventional Fermi liquid with a large Fermi
surface (and its associated $d$-wave superconductor). There is a quantum phase
transition to a Higgs phase describing the `pseudogap' at lower doping.
Depending upon the quartic terms in the Higgs potential, the Higgs phase
exhibits one or more of charge density wave, Ising-nematic, time-reversal odd
scalar spin chirality, and $\mathbb{Z}_2$ topological orders. It is notable
that the emergent broken symmetries in our theory of fluctuating spin density
waves co-incide with those observed in diverse experiments. For the
electron-doped cuprates, the spin density wave fluctuations are at wavevector
$(\pi,\pi)$, and then the corresponding SU(2) gauge theory only has a crossover
between the confining and Higgs regimes, with an exponentially large
confinement scale deep in the Higgs regime. On the Higgs side, for both the
electron- and hole-doped cases, and at scales shorter than the confinement
scale (which can be infinite when $\mathbb{Z}_2$ topological order is present),
the electron spectral function has a `fractionalized Fermi liquid (FL*)' form
with small Fermi surfaces. We also describe the deconfined quantum criticality
of the Higgs transition in the limit of a large number of Higgs flavors, and
perturbatively discuss its coupling to fermionic excitations.",1811.04930v3
2021-02-01,Strong-Magnetic-Field Magnon Transport in Monolayer Graphene,"At high magnetic fields, monolayer graphene hosts competing phases
distinguished by their breaking of the approximate SU(4) isospin symmetry.
Recent experiments have observed an even denominator fractional quantum Hall
state thought to be associated with a transition in the underlying isospin
order from a spin-singlet charge density wave at low magnetic fields to an
antiferromagnet at high magnetic fields, implying that a similar transition
must occur at charge neutrality. However, this transition does not generate
contrast in typical electrical transport or thermodynamic measurements and no
direct evidence for it has been reported, despite theoretical interest arising
from its potentially unconventional nature. Here, we measure the transmission
of ferromagnetic magnons through the two dimensional bulk of clean monolayer
graphene. Using spin polarized fractional quantum Hall states as a benchmark,
we find that magnon transmission is controlled by the detailed properties of
the low-momentum spin waves in the intervening Hall fluid, which is highly
density dependent. Remarkably, as the system is driven into the
antiferromagnetic regime, robust magnon transmission is restored across a wide
range of filling factors consistent with Pauli blocking of fractional quantum
hall spin-wave excitations and their replacement by conventional ferromagnetic
magnons confined to the minority graphene sublattice. Finally, using devices in
which spin waves are launched directly into the insulating charge-neutral bulk,
we directly detect the hidden phase transition between bulk insulating charge
density wave and a canted antiferromagnetic phases at charge neutrality,
completing the experimental map of broken-symmetry phases in monolayer
graphene.",2102.01061v1
2021-09-09,Numerical reverse engineering of general spin-wave dispersions: Bridge between numerics and analytics using a dynamic-matrix approach,"Modern problems in magnetization dynamics require more and more the numerical
determination of the spin-wave spectra and -dispersion in magnetic systems
where analytic theories are not yet available. Micromagnetic simulations can be
used to compute the spatial profiles and oscillation frequencies of spin-waves
in magnetic system with almost arbitrary geometry and different magnetic
interactions. Although numerical approaches are very versatile, they often do
not give the same insight and physical understanding as analytical theories.
For example, it is not always possible to decide whether a certain feature
(such as dispersion asymmetry, for example) is governed by one magnetic
interaction or the other. Moreover, since numerical approaches typically yield
the normal modes of the system, it is not always feasible to disentangle
hybridized modes. In this manuscript, we build a bridge between numerics and
analytics by presenting a methodology to calculate the individual contributions
to general spin-wave dispersions in a fully numerical manner. We discuss the
general form of any spin-wave dispersion in terms of the effective (stiffness)
fields produced by the modes. Based on a special type of micromagnetic
simulations, the numerical dynamic-matrix approach, we show how to calculate
each stiffness field in the respective dispersion law, separately for each
magnetic interaction. In particular, it becomes possible to disentangle
contributions of different magnetic interactions to the dispersion asymmetry in
systems where non-reciprocity is present. At the same time, dipolar-hybridized
modes can be easily disentangled. Since this method is independent of the
geometry or the involved magnetic interactions at hand, we believe it is
attractive for experimental and theoretical studies of magnetic systems where
there are no analytics yet, but also to aid the development of new analytical
theories.",2109.04521v2
2022-07-04,Finite-element dynamic-matrix approach for propagating spin waves: Extension to mono- and multilayers of arbitrary spacing and thickness,"In our recent work [AIP Adv. 11, 095006], we presented an efficient numerical
method to compute dispersions and spatial mode profiles of spin waves
propagating in waveguides with translationally invariant equilibrium
magnetization. Using a finite-element method (FEM) allowed to model
two-dimensional waveguide cross sections of arbitrary shape but only finite
size. Here, we extend our FEM propagating-wave dynamic-matrix approach from
finite waveguides to the important practical cases of infinitely-extended mono-
and multilayers of arbitrary spacing and thickness. To obtain the mode profiles
and frequencies, the linearized equation of motion of magnetization is solved
as an eigenvalue problem only on a one-dimensional line-trace mesh, defined
along the normal direction of the layers. Being an important contribution in
multilayer systems, we introduce interlayer-exchange interaction into our FEM
approach. With the calculation of dynamic dipolar fields being the main focus
of this paper, we also extend the previously presented plane-wave
Fredkin-Koehler method to calculate the dipolar potential of spin waves in
infinite layers. The major benefit of this method is that it avoids the
discretization of any non-magnetic material, such as non-magnetic spacers in
multilayers. Therefore, the computational effort becomes completely independent
on the spacer thicknesses. Furthermore, it keeps the resulting discretized
eigenvalue problem sparse, which therefore, inherits a comparably low
arithmetic complexity. As a validation of our method (implemented into the
open-source finite-element micromagnetic package TetraX), we present results
for various systems and compare them with theoretical predictions as well as
with established finite-difference numerical methods. We believe this method
offers an efficient and versatile tool to calculate spin-wave dispersions in
layered magnetic systems.",2207.01519v2
2011-05-18,Modulated Rashba interaction in a quantum wire: Spin and charge dynamics,"It was recently shown that a spatially modulated Rashba spin-orbit coupling
in a quantum wire drives a transition from a metallic to an insulating state
when the wave number of the modulation becomes commensurate with the Fermi wave
length of the electrons in the wire. It was suggested that the effect may be
put to practical use in a future spin transistor design. In the present article
we revisit the problem and present a detailed analysis of the underlying
physics. First, we explore how the build-up of charge density wave correlations
in the quantum wire due to the periodic gate configuration that produces the
Rashba modulation influences the transition to the insulating state. The
interplay between the modulations of the charge density and that of the
spin-orbit coupling turns out to be quite subtle: Depending on the relative
phase between the two modulations, the joint action of the Rashba interaction
and charge density wave correlations may either enhance or reduce the Rashba
current blockade effect. Secondly, we inquire about the role of the Dresselhaus
spin-orbit coupling that is generically present in a quantum wire embedded in
semiconductor heterostructure. While the Dresselhaus coupling is found to work
against the current blockade of the insulating state, the effect is small in
most materials. Using an effective field theory approach, we also carry out an
analysis of effects from electron- electron interactions, and show how the
single-particle gap in the insulating state can be extracted from the more
easily accessible collective charge and spin excitation thresholds. The
smallness of the single-particle gap together with the anti-phase relation
between the Rashba and chemical potential modulations pose serious difficulties
for realizing a Rashba-controlled current switch in an InAs-based device. Some
alternative designs are discussed.",1105.4141v2
2020-08-21,"Macroscopic, layered onion shell like magnetic domain structure generated in YIG film using ultrashort, megagauss magnetic pulses","Study of the formation and evolution of large scale, ordered structures is an
enduring theme in science. The generation, evolution and control of large sized
magnetic domains are intriguing and challenging tasks, given the complex nature
of competing interactions present in any magnetic system. Here, we demonstrate
large scale non-coplanar ordering of spins, driven by picosecond, megagauss
magnetic pulses derived from a high intensity, femtosecond laser. Our studies
on a specially designed Yttrium Iron Garnet (YIG)/dielectric/metal film
sandwich target, show the creation of complex, large, concentric, elliptical
shaped magnetic domains which resemble the layered shell structure of an onion.
The largest shell has a major axis of over hundreds of micrometers, in stark
contrast to conventional sub micrometer scale polygonal, striped or bubble
shaped magnetic domains found in magnetic materials, or the large dumbbell
shaped domains produced in magnetic films irradiated with accelerator based
relativistic electron beams. Through micromagnetic simulations, we show that
the giant magnetic field pulses create ultrafast terahertz (THz) spin waves. A
snapshot of these fast propagating spin waves is stored as the layered onion
shell shaped domains in the YIG film. Typically, information transport via spin
waves in magnonic devices occurs in the gigahertz (GHz) regime, where the
devices are susceptible to thermal disturbances at room temperature. Our
intense laser light pulse - YIG sandwich target combination, paves the way for
room temperature table-top THz spin wave devices, which operate just above or
in the range of the thermal noise floor. This dissipation-less device offers
ultrafast control of spin information over distances of few hundreds of
microns.",2008.09473v1
2002-06-11,LMXBs may be important LIGO sources after all,"Andersson et al. and Bildsten proposed that the spin of accreting neutron
stars is limited by removal of angular momentum by gravitational radiation
which increases dramatically with the spin frequency of the star. Both Bildsten
and Andersson et al. argued that the r-modes of the neutron star for
sufficiently quickly rotating and hot neutron stars will grow due to the
emission of gravitational radiation, thereby accounting for a time varying
quadrupole component to the neutron star's mass distribution. However, Levin
later argued that the equilibrium between spin-up due to accretion and
spin-down due to gravitational radiation is unstable, because the growth rate
of the r-modes and consequently the rate of gravitational wave emission is an
increasing function of the core temperature of the star. The system executes a
limit cycle, spinning up for several million years and spinning down in less
than a year. However, the duration of the spin-down portion of the limit cycle
depends sensitively on the amplitude at which the nonlinear coupling between
different r-modes becomes important. As the duration of the spin-down portion
increases the fraction of accreting neutron stars which may be emitting
gravitational radiation increases while the peak flux in gravitational
radiation decreases. Depending on the distribution of quickly rotating neutron
stars in the Galaxy and beyond, the number of gravitational emitters detectable
with LIGO may be large.",0206174v1
2002-04-02,"A novel spin wave expansion, finite temperature corrections and order from disorder effects in the double exchange model","The magnetic excitations of the double exchange (DE) model are usually
discussed in terms of an equivalent ferromagnetic Heisenberg model. We argue
that this equivalence is valid only at a quasi--classical level -- both quantum
and thermal corrections to the magnetic properties of DE model differ from any
effective Heisenberg model because its spin excitations interact only
indirectly, through the exchange of charge fluctuations. To demonstrate this,
we perform a novel large S expansion for the coupled spin and charge degrees of
freedom of the DE model, aimed at projecting out all electrons not locally
aligned with core spins. We generalized the Holstein--Primakoff transformation
to the case when the length of the spin is by itself an operator, and
explicitly constructed new fermionic and bosonic operators to fourth order in
1/\sqrt{S}. This procedure removes all spin variables from the Hund coupling
term, and yields an effective Hamiltonian with an overall scale of electron
hopping, for which we evaluate corrections to the magnetic and electronic
properties in 1/S expansion to order O(1/S^2). We also consider the effect of a
direct superexchange antiferromagnetic interaction between core spins. We find
that the competition between ferromagnetic double exchange and an
antiferromagnetic superexchange provides a new example of an ""order from
disorder"" phenomenon -- when the two interactions are of comparable strength,
an intermediate spin configuration (either a canted or a spiral state) is
selected by quantum and/or thermal fluctuations.",0204049v1
2003-05-22,Theory of spin response in underdoped cuprates as strongly fluctuating d-wave superconductors,"We study the spin dynamics in underdoped cuprates at low temperatures by
considering them as quasi two dimensional d-wave superconductors (dSC) with
strong phase fluctuations. An effective theory of spin degrees of freedom of
nodal quasiparticles coupled to vortex defects in the phase of the
superconducting order parameter is formulated. It represents the minimal
extension of the QED3 theory of the pseudogap phase into the superconducting
region. The theory predicts a single dSC-SDW transition, which may be
fluctuation induced first order, without the region of coexistence between the
two ordered phases. We compute the spin-spin correlator in the dSC, and explain
the evolution of the spin response with frequency as observed in neutron
scattering experiments on YBCO. We predict that at the frequencies much below
the resonance the (weak) spin response should become narrowly peaked at four
`diagonally' incommensurate wave vectors that span between the nodes of the
supercopnducting order parameter. These peaks represent an inherent collective
mode of the phase fluctuating dSC, the condensation of which would bring about
the SDW order in the pseudogap phase. Our interpretation of the resonance
suggests it should become more elusive in the superconductors with lower Tc, in
accord with its' conspicuous absence in LSCO.",0305512v1
2006-01-17,Fingerprints of spin-orbital physics in cubic Mott insulators: Magnetic exchange interactions and optical spectral weights,"The temperature dependence and anisotropy of optical spectral weights
associated with different multiplet transitions is determined by the spin and
orbital correlations. To provide a systematic basis to exploit this close
relationship between magnetism and optical spectra, we present and analyze the
spin-orbital superexchange models for a series of representative
orbital-degenerate transition metal oxides with different multiplet structure.
For each case we derive the magnetic exchange constants, which determine the
spin wave dispersions, as well as the partial optical sum rules. The magnetic
and optical properties of early transition metal oxides with degenerate
$t_{2g}$ orbitals (titanates and vanadates with perovskite structure) are shown
to depend only on two parameters, viz. the superexchange energy $J$ and the
ratio $\eta$ of Hund's exchange to the intraorbital Coulomb interaction, and on
the actual orbital state. In $e_g$ systems important corrections follow from
charge transfer excitations, and we show that KCuF$_3$ can be classified as a
charge transfer insulator, while LaMnO$_3$ is a Mott insulator with moderate
charge transfer contributions. In some cases orbital fluctuations are quenched
and decoupling of spin and orbital degrees of freedom with static orbital order
gives satisfactory results for the optical weights. On the example of cubic
vanadates we describe a case where the full quantum spin-orbital physics must
be considered. Thus information on optical excitations, their energies,
temperature dependence and anisotropy, combined with the results of magnetic
neutron scattering experiments, provides an important consistency test of the
spin-orbital models, and indicates whether orbital and/or spin fluctuations are
important in a given compound.",0601381v1
2006-09-29,Bosonization approach to charge and spin dynamics of 1D fermions with band-curvature,"We consider one-dimensional (1D) spin-1/2 fermions in a clean quantum wire,
with forward scattering interactions and a non-linear single-particle spectrum,
$\xi_k = v|k| + k^2/2m$ where $v$ is the Fermi velocity and $1/m$ is the
band-curvature. We calculate the dynamical structure factor (DSF) of the model
at small wave-vector $q$ with the help of the bosonization technique. For
spinless fermions, we show that, starting from the single-parametric spectrum:
$\om = u |q|$, bosonization emulates the 2-parametric excitation spectrum: $\om
= u |q| \pm q^2/2m^*$, where $m^*$ decreases with increasing repulsive
interactions. Moreover, away from the excitation-cone, {\it i.e.} $\om \gg u
|q|$, bosonization yields the 2-pair excitation continuum of the DSF. For
spinful fermions, we show that the spin-charge coupling (SCC) due to
band-curvature affects charge and spin DSF in an asymmetric way. For the charge
DSF, SCC manifests as a two-peak structure: a charge peak at $\om = u_\rho |q|$
but also a spin peak at $\om = u_\sigma |q|$, as charge fluctuations may decay
via chargeless spin-singlet excitations. For the magnetic DSF, SCC manifests as
a continuous transfer of magnetic spectral weight to frequencies $\om >
u_\sigma |q|$, as spin fluctuations decay via pairs of chargeless spin and
spinless charge-neutral excitations.",0609754v2
2001-03-07,Coalescence of Two Spinning Black Holes: An Effective One-Body Approach,"We generalize to the case of spinning black holes a recently introduced
``effective one-body'' approach to the general relativistic dynamics of binary
systems. The combination of the effective one-body approach, and of a Pad\'e
definition of some crucial effective radial functions, is shown to define a
dynamics with much improved post-Newtonian convergence properties, even for
black hole separations of the order of $6 GM / c^2$. We discuss the approximate
existence of a two-parameter family of ``spherical orbits'' (with constant
radius), and, of a corresponding one-parameter family of ``last stable
spherical orbits'' (LSSO). These orbits are of special interest for forthcoming
LIGO/VIRGO/GEO gravitational wave observations. It is argued that for most (but
not all) of the parameter space of two spinning holes the effective one-body
approach gives a reliable analytical tool for describing the dynamics of the
last orbits before coalescence. This tool predicts, in a quantitative way, how
certain spin orientations increase the binding energy of the LSSO. This leads
to a detection bias, in LIGO/VIRGO/GEO observations, favouring spinning black
hole systems, and makes it urgent to complete the conservative effective
one-body dynamics given here by adding (resummed) radiation reaction effects,
and by constructing gravitational waveform templates that include spin effects.
Finally, our approach predicts that the spin of the final hole formed by the
coalescence of two arbitrarily spinning holes never approaches extremality.",0103018v2
2002-02-13,Conserved currents of massless fields of spin s>0,"A complete and explicit classification of all locally constructed conserved
currents and underlying conserved tensors is obtained for massless linear
symmetric spinor fields of any spin s>0 in four dimensional flat spacetime.
These results generalize the recent classification in the spin s=1 case of all
conserved currents locally constructed from the electromagnetic spinor field.
The present classification yields spin s>0 analogs of the well-known
electromagnetic stress-energy tensor and Lipkin's zilch tensor, as well as a
spin s>0 analog of a novel chiral tensor found in the spin s=1 case. The chiral
tensor possesses odd parity under a duality symmetry (i.e., a phase rotation)
on the spin s field, in contrast to the even parity of the stress-energy and
zilch tensors. As a main result, it is shown that every locally constructed
conserved current for each s>0 is equivalent to a sum of elementary linear
conserved currents, quadratic conserved currents associated to the
stress-energy, zilch, and chiral tensors, and higher derivative extensions of
these currents in which the spin s field is replaced by its repeated
conformally-weighted Lie derivatives with respect to conformal Killing vectors
of flat spacetime. Moreover, all of the currents have a direct, unified
characterization in terms of Killing spinors. The cases s=2, s=1/2 and s=3/2
provide a complete set of conserved quantities for propagation of gravitons
(i.e., linearized gravity waves), neutrinos and gravitinos, respectively, on
flat spacetime. The physical meaning of the zilch and chiral quantities is
discussed.",0202019v2
1999-03-19,"Two-Step Contribution to Intermediate Energy (p,p') and (p,n) Reactions","We calculate the two-step contribution to (p,p') and (p,n) reactions at
intermediate energy. We describe the motion of the incident nucleon with plane
wave and compare the contribution from the two-step processes with that from
the one-step processes. To describe the two-step processes, we extende the
response functions into the nondiagonal ones with respect to the momentum
transfer q.
  We performed a numerical calculation for the cross sections of the $^{12}$C,
$^{40}$Ca(p,p') scatterings and the spin longitudinal and the spin transverse
cross sections of the $^{12}$C,$^{40}$Ca(p,n) reactions at 346 MeV and 494 MeV.
We found that the two-step contribution is appreciable in comparison with the
one-step processes in higher energy transfer region for the spin longitudinal
and the spin transverse (p,n) reactions. We also found that the two-step
processes give larger contribution to the spin transverse (p,n) reaction than
to the spin longitudinal reaction. This finding is very encouraging to
interpret the discrepancy between the DWIA calculation and the experimental
results of the spin longitudinal and the spin transverse cross sections.",9903049v2
2001-01-07,Formation and Dynamics of a Schrödinger-Cat State in Continuous Quantum Measurement,"We consider the process of a single-spin measurement using magnetic resonance
force microscopy (MRFM) as an example of a truly continuous measurement in
quantum mechanics. This technique is also important for different applications,
including a measurement of a qubit state in quantum computation. The
measurement takes place through the interaction of a single spin with a
quasi-classical cantilever, modeled by a quantum oscillator in a coherent state
in a quasi-classical region of parameters. The entire system is treated
rigorously within the framework of the Schr\""odinger equation, without any
artificial assumptions. Computer simulations of the spin-cantilever dynamics,
where the spin is continuously rotated by means of cyclic adiabatic inversion,
show that the cantilever evolves into a Schr\""odinger-cat state: the
probability distribution for the cantilever position develops two asymmetric
peaks that quasi-periodically appear and vanish. For a many-spin system our
equations reduce to the classical equations of motion, and we accurately
describe conventional MRFM experiments involving cyclic adiabatic inversion of
the spin system. We surmise that the interaction of the cantilever with the
environment would lead to a collapse of the wave function; however, we show
that in such a case the spin does not jump into a spin eigenstate.",0101035v1
2009-01-24,Orbital angular momentum is dependent on polarization,"It is shown that the momentum density of free electromagnetic field splits
into two parts. One has no contribution to the net momentum due to the
transversality condition. The other yields all the momentum. The angular
momentum that originates from the former part is spin, and the angular momentum
that originates from the latter part is orbital angular momentum. Expressions
for the spin and orbital angular momentum are given in terms of the electric
vector in reciprocal space. The spin and orbital angular momentum defined this
way are used to investigate the angular momentum of nonparaxial beams that are
described in a recently published paper [Phys. Rev. A 78, 063831 (2008)]. It is
found that the orbital angular momentum depends, apart from an $l$-dependent
term, on two global quantities, the polarization represented by a generalized
Jones vector and a new characteristic represented by a unit vector
$\mathbf{I}$, though the spin depends only on the polarization. The
polarization dependence of orbital angular momentum through the effect of
$\mathbf{I}$ is obtained and discussed. Some applications of the result
obtained here are also made. The fact that the spin originates from the part of
momentum density that has no contribution to the net momentum is used to show
that there does not exist the paradox on the spin of circularly polarized plane
wave. The polarization dependence of both spin and orbital angular momentum is
shown to be the origin of conversion from the spin of a paraxial
Laguerre-Gaussian beam into the orbital angular momentum of the focused beam
through a high numerical aperture.",0901.3813v3
2009-09-12,Angular momentum of non-paraxial light beam: Dependence of orbital angular momentum on polarization,"It is shown that the momentum density of free electromagnetic field splits
into two parts. One has no contribution to the net momentum due to the
transversality condition. The other yields all the momentum. The angular
momentum that is associated with the former part is spin, and the angular
momentum that is associated with the latter part is orbital angular momentum.
Expressions for the spin and orbital angular momentum are given in terms of the
electric vector in reciprocal space. The spin and orbital angular momentum
defined this way are used to investigate the angular momentum of nonparaxial
beams that are described in a recently published paper [Phys. Rev. A 78, 063831
(2008)]. It is found that the orbital angular momentum depends, apart from an
$l$-dependent term, on two global quantities, the polarization represented by a
generalized Jones vector and a new characteristic represented by a unit vector
$\mathbf{I}$, though the spin depends only on the polarization. The
polarization dependence of orbital angular momentum through the impact of
$\mathbf{I}$ is obtained and discussed. Some applications of the result
obtained here are also made. The fact that the spin originates from the
momentum density that has no contribution to the net momentum is used to show
that there does not exist the paradox on the spin of circularly polarized plane
wave. The polarization dependence of both spin and orbital angular momentum is
shown to be the origin of conversion from the spin of a paraxial
Laguerre-Gaussian beam into the orbital angular momentum of the focused beam
through a high numerical aperture.",0909.2306v1
2010-06-08,Dynamic spin susceptibility of superconducting cuprates: A microscopic theory of the magnetic resonance mode,"A microscopic theory of the dynamic spin susceptibility (DSS) in the
superconducting state within the t-J model is presented. It is based on an
exact representation for the DSS obtained by applying the Mori-type projection
technique for the relaxation function in terms of Hubbard operators. The static
spin susceptibility is evaluated by a sum-rule-conserving generalized
mean-field approximation, while the self-energy is calculated in the
mode-coupling approximation. The spectrum of spin excitations is studied in the
underdoped and optimally doped regions. The DSS reveals a resonance mode (RM)
at the antiferromagnetic wave vector Q = \pi(1,1) at low temperatures due to a
strong suppression of the damping of spin excitations. This is explained by an
involvement of spin excitations in the decay process besides the particle-hole
continuum usually considered in random-phase-type approximations. The spin gap
in the spin-excitation spectrum at Q plays a dominant role in limiting the
decay in comparison with the superconducting gap which results in the
observation of the RM even above $T_c$ in the underdoped region. A good
agreement with inelastic neutron-scattering experiments on the RM in YBCO
compounds is found.",1006.1525v2
2010-07-09,The spin states of Co ions in La1.5Ca0.5CoO4 from first-principles,"The spin states and electronic structure of layered perovskite La1.5Ca0.5CoO4
are investigated using fullpotential linearized augmented plane-wave method.
All the computational results indicate that the Co2+ ion is in a high-spin
state and the Co3+ in a low-spin state. The Co2+ t2g orbitals with a small
crystal-field splitting are mixed by spin-orbit coupling, which accounts for
the observed easy in-plane magnetism. The nonmagnetic LS-Co3+ state, which is
stabilized by a strong crystal field, provides a natural explanation for the
observed low magnetic ordering temperature and a spin-blockade phenomenon of
the electron hopping. Furthermore, we find that the intermediate-spin state of
Co3+ has a large multiplet splitting. But the lowest-lying IS state of Co3+ is
still higher in energy than the LS ground state by a few hundred millielectron
volts and the HS state of Co3+ is even less stable, both in sharp contrast to a
recent experimental study which suggested the HS+IS mixed Co3+ ground state. We
note that either the IS-Co3+ or HS-Co3+ states or their mixture would produce a
wrong out-of-plane magnetic anisotropy and a much higher magneticordering
temperature than observed. Thus, the present work sheds light on this material
concerning its electronic and magnetic structure, and it would stimulate
different experiments to settle this intriguing spin-state issue.",1007.1494v2
2010-12-07,Reducing orbital eccentricity of precessing black-hole binaries,"Building initial conditions for generic binary black-hole evolutions without
initial spurious eccentricity remains a challenge for numerical-relativity
simulations. This problem can be overcome by applying an eccentricity-removal
procedure which consists in evolving the binary for a couple of orbits,
estimating the eccentricity, and then correcting the initial conditions. The
presence of spins can complicate this procedure. As predicted by post-Newtonian
theory, spin-spin interactions and precession prevent the binary from moving
along an adiabatic sequence of spherical orbits, inducing oscillations in the
radial separation and in the orbital frequency. However, spin-induced
oscillations occur at approximately twice the orbital frequency, therefore they
can be distinguished from the initial spurious eccentricity, which occurs at
approximately the orbital frequency. We develop a new removal procedure based
on the derivative of the orbital frequency and find that it is successful in
reducing the eccentricity measured in the orbital frequency to less than 0.0001
when moderate spins are present. We test this new procedure using
numerical-relativity simulations of binary black holes with mass ratios 1.5 and
3, spin magnitude 0.5 and various spin orientations. The numerical simulations
exhibit spin-induced oscillations in the dynamics at approximately twice the
orbital frequency. Oscillations of similar frequency are also visible in the
gravitational-wave phase and frequency of the dominant mode.",1012.1549v2
2011-11-10,Chiral symmetry breaking and the spin content of hadrons,"From the parton distributions in the infinite momentum frame one finds that
only about 30% of the nucleon spin is carried by spins of the valence quarks,
which gave rise to the term ""spin crisis"". Similar results hold for the lowest
mesons, as it follows from the lattice simulations. We define the spin content
of a meson in the rest frame and use a complete and orthogonal $\bar q q$
chiral basis and a unitary transformation from the chiral basis to the (2S+1)LJ
basis. Then, given a mixture of different allowed chiral representations in the
meson wave function at a given resolution scale, one can obtain its spin
content at this scale. To obtain the mixture of the chiral representations in
the meson we measure in dynamical lattice simulations a ratio of couplings of
interpolarors with different chiral structure. For the rho meson we obtain
practically the 3S1 state with no trace of the spin crisis. Then a natural
question arises: which definition does reflect the spin content of a hadron?",1111.2562v1
2013-08-03,A possibility of high spin hole states in doped CoO$_2$ layered systems,"We introduce and investigate an effective five-band model for $t_{2g}$ and
$e_g$ electrons to describe doped cobalt oxides with Co$^{3+}$ and Co$^{4+}$
ions in two-dimensional CoO$_2$ triangular lattice layers, as in
Na$_{1-x}$CoO$_2$. The effective Hamiltonian includes anisotropic kinetic
energy (due to both direct Co-Co and indirect Co-O-Co hoppings), on-site
Coulomb interactions parameterized by intraorbital Hubbard repulsion $U$ and
full Hund's exchange tensor, crystal-field terms and Jahn-Teller static
distortions. We study it using correlated wave functions on $6\times 6$
clusters with periodic boundary conditions. The computations indicate low S=0
spin to high S=2 spin abrupt transition in the undoped systems when increasing
strength of the crystal field, while intermediate S=1 spins are not found.
Surprisingly, for the investigated realistic Hamiltonian parameters describing
low spin states in CoO$_2$ planes, doping generates high $S=\frac{5}{2}$ spins
at Co$^{4+}$ ions that are pairwise bound into singlets, seen here as pairs of
up and down spins. It is found that such singlet pairs self-organize at higher
doping into lines of spins with coexisting antiferromagnetic and ferromagnetic
bonds, forming stripe-like structures. The ground states are insulating within
the investigated range of doping because computed HOMO-LUMO gaps are never
small enough.",1308.0705v1
2014-08-18,The Masses and Spins of Neutron Stars and Stellar-Mass Black Holes,"Stellar-mass black holes and neutron stars represent extremes in gravity,
density, and magnetic fields. They therefore serve as key objects in the study
of multiple frontiers of physics. In addition, their origin (mainly in
core-collapse supernovae) and evolution (via accretion or, for neutron stars,
magnetic spindown and reconfiguration) touch upon multiple open issues in
astrophysics.
  In this review, we discuss current mass and spin measurements and their
reliability for neutron stars and stellar-mass black holes, as well as the
overall importance of spins and masses for compact object astrophysics. Current
masses are obtained primarily through electromagnetic observations of binaries,
although future microlensing observations promise to enhance our understanding
substantially. The spins of neutron stars are straightforward to measure for
pulsars, but the birth spins of neutron stars are more difficult to determine.
In contrast, even the current spins of stellar-mass black holes are challenging
to measure. As we discuss, major inroads have been made in black hole spin
estimates via analysis of iron lines and continuum emission, with reasonable
agreement when both types of estimate are possible for individual objects, and
future X-ray polarization measurements may provide additional independent
information. We conclude by exploring the exciting prospects for mass and spin
measurements from future gravitational wave detections, which are expected to
revolutionize our understanding of strong gravity and compact objects.",1408.4145v1
2015-10-14,Angstrom-resolution magnetic resonance imaging of single molecules via wavefunction fingerprints of nuclear spins,"Single-molecule sensitivity of nuclear magnetic resonance (NMR) and angstrom
resolution of magnetic resonance imaging (MRI) are the highest challenges in
magnetic microscopy. Recent development in dynamical-decoupling- (DD) enhanced
diamond quantum sensing has enabled single-nucleus NMR and nanoscale NMR.
Similar to conventional NMR and MRI, current DD-based quantum sensing utilizes
the frequency fingerprints of target nuclear spins. The frequency fingerprints
by their nature cannot resolve different nuclear spins that have the same noise
frequency or differentiate different types of correlations in nuclear-spin
clusters, which limit the resolution of single-molecule MRI. Here we show that
this limitation can be overcome by using wave-function fingerprints of target
nuclear spins, which is much more sensitive than the frequency fingerprints to
the weak hyperfine interaction between the targets and a sensor under resonant
DD control. We demonstrate a scheme of angstrom-resolution MRI that is capable
of counting and individually localizing single nuclear spins of the same
frequency and characterizing the correlations in nuclear-spin clusters. A
nitrogen-vacancy-center spin sensor near a diamond surface, provided that the
coherence time is improved by surface engineering in the near future, may be
employed to determine with angstrom resolution the positions and conformation
of single molecules that are isotope labeled. The scheme in this work offers an
approach to breaking the resolution limit set by the frequency gradients in
conventional MRI and to reaching the angstrom-scale resolution.",1510.04081v3
2015-12-02,Spin-dependent transport through a chiral molecule in the presence of spin-orbit interaction and non-unitary effects,"Recent experiments have demonstrated the efficacy of chiral helically shaped
molecules in polarizing the scattered electron spin, an effect termed as
chiral-induced spin selectivity (CISS). Here we solve a simple tight-binding
model for electron transport through a single helical molecule, with spin-orbit
interactions on the bonds along the helix. Quantum interference is introduced
via additional electron hopping between neighboring sites in the direction of
the helix axis. When the helix is connected to two one-dimensional single-mode
leads, time-reversal symmetry prevents spin polarization of the outgoing
electrons. One possible way to retrieve such a polarization is to allow leakage
of electrons from the helix to the environment, via additional outgoing leads.
Technically, the leakage generates complex site self-energies, which break
unitarity. As a result, the electron waves in the helix become evanescent, with
different decay lengths for different spin polarizations, yielding a net spin
polarization of the outgoing electrons, which increases with the length of the
helix (as observed experimentally). A maximal polarization can be measured at a
finite angle away from the helix axis.",1512.00793v2
2016-07-14,Complete conservative dynamics for inspiralling compact binaries with spins at the fourth post-Newtonian order,"In this work we complete the spin-dependent conservative dynamics of
inspiralling compact binaries at the fourth post-Newtonian order, and in
particular the derivation of the next-to-next-to-leading order spin-squared
interaction potential. We derive the physical equations of motion of the
position and the spin from a direct variation of the action. Further, we derive
the quadratic-in-spin Hamiltonians, as well as their expressions in the
center-of-mass frame. We construct the conserved integrals of motion, which
form the Poincar\'e algebra. This construction provided a consistency check for
the validity of our result, which is crucial in particular in the current
absence of another independent derivation of the next-to-next-to-leading order
spin-squared interaction. Finally, we provide here the complete gauge-invariant
relations among the binding energy, angular momentum, and orbital frequency of
an inspiralling binary with generic compact spinning components to the fourth
post-Newtonian order. These high post-Newtonian orders, in particular taking
into account the spins of the binary constituents, will enable to gain more
accurate information on the constituents from even more sensitive
gravitational-wave detections to come.",1607.04252v2
2016-08-18,Phase diagram and spin correlations of the Kitaev-Heisenberg model: Importance of quantum effects,"We explore the phase diagram of the Kitaev-Heisenberg model with nearest
neighbor interactions on the honeycomb lattice using the exact diagonalization
of finite systems combined with the cluster mean field approximation, and
supplemented by the insights from the linear spin-wave and second--order
perturbation theories. This study confirms that by varying the balance between
the Heisenberg and Kitaev term, frustrated exchange interactions stabilize in
this model four phases with magnetic long range order: N\'eel phase,
ferromagnetic phase, and two other phases with coexisting antiferromagnetic and
ferromagnetic bonds, zigzag and stripy phases. They are separated by two
disordered quantum spin-liquid phases, and the one with ferromagnetic Kitaev
interactions has a substantially broader range of stability as the neighboring
competing ordered phases, ferromagnetic and stripy, have very weak quantum
fluctuations. Focusing on the quantum spin-liquid phases, we study spatial spin
correlations and dynamic spin structure factor of the model by the exact
diagonalization technique, and discuss the evolution of gapped low-energy spin
response across the quantum phase transitions between the disordered spin
liquid and magnetic phases with long range order.",1608.05333v1
2016-10-28,Insulating nanomagnets driven by spin torque,"Magnetic insulators, such as yttrium iron garnet (Y$_3$Fe$_5$O$_{12}$), are
ideal materials for ultra-low power spintronics applications due to their low
energy dissipation and efficient spin current generation and transmission.
Recently, it has been realized that spin dynamics can be driven very
effectively in micrometer-sized Y$_3$Fe$_5$O$_{12}$/Pt heterostructures by
spin-Hall effects. We demonstrate here the excitation and detection of spin
dynamics in Y$_3$Fe$_5$O$_{12}$/Pt nanowires by spin-torque ferromagnetic
resonance. The nanowires defined via electron-beam lithography are fabricated
by conventional room temperature sputtering deposition on Gd$_3$Ga$_5$O$_{12 }$
substrates and lift-off. We observe field-like and anti-damping-like torques
acting on the magnetization precession, which are due to simultaneous
excitation by Oersted fields and spin-Hall torques. The Y$_3$Fe$_5$O$_{12}$/Pt
nanowires are thoroughly examined over a wide frequency and power range. We
observe a large change in the resonance field at high microwave powers, which
is attributed to a decreasing effective magnetization due to microwave
absorption. These heating effects are much more pronounced in the investigated
nanostructures than in comparable micron-sized samples. By comparing different
nanowire widths, the importance of geometrical confinements for magnetization
dynamics becomes evident: quantized spin-wave modes across the width of the
wires are observed in the spectra. Our results are the first stepping stones
toward the realization of integrated magnonic logic devices based on
insulators, where nanomagnets play an essential role.",1610.09360v1
2017-07-27,Correlations and confinement of excitations in an asymmetric Hubbard ladder,"Correlation functions and low-energy excitations are investigated in the
asymmetric two-leg ladder consisting of a Hubbard chain and a noninteracting
tight-binding (Fermi) chain using the density matrix renormalization group
method. The behavior of charge, spin and pairing correlations is discussed for
the four phases found at half filling, namely, Luttinger liquid, Kondo-Mott
insulator, spin-gapped Mott insulator and correlated band insulator.
Quasi-long-range antiferromagnetic spin correlations are found in the Hubbard
leg in the Luttinger liquid phase only. Pair-density-wave correlations are
studied to understand the structure of bound pairs found in the Fermi leg of
the spin-gapped Mott phase at half filling and at light doping but we find no
enhanced pairing correlations. Low-energy excitations cause variations of spin
and charge densities on both legs that demonstrate the confinement of the
lowest charge excitations on the Fermi leg while the lowest spin excitations
are localized on the Hubbard leg in the three insulating phases. The velocities
of charge, spin, and single-particle excitations are investigated to clarify
the confinement of elementary excitations in the Luttinger liquid phase. The
observed spatial separation of elementary spin and charge excitations could
facilitate the coexistence of different (quasi-)long-range orders in
higher-dimensional extensions of the asymmetric Hubbard ladder.",1707.08780v1
2018-09-24,"High-accuracy mass, spin, and recoil predictions of generic black-hole merger remnants","We present accurate fits for the remnant properties of generically precessing
binary black holes, trained on large banks of numerical-relativity simulations.
We use Gaussian process regression to interpolate the remnant mass, spin, and
recoil velocity in the 7-dimensional parameter space of precessing black-hole
binaries with mass ratios $q\leq2$, and spin magnitudes $\chi_1,\chi_2\leq0.8$.
For precessing systems, our errors in estimating the remnant mass, spin
magnitude, and kick magnitude are lower than those of existing fitting formulae
by at least an order of magnitude (improvement is also reported in the
extrapolated region at high mass ratios and spins). In addition, we also model
the remnant spin and kick directions. Being trained directly on precessing
simulations, our fits are free from ambiguities regarding the initial frequency
at which precessing quantities are defined. We also construct a model for
remnant properties of aligned-spin systems with mass ratios $q\leq8$, and spin
magnitudes $\chi_1,\chi_2\leq0.8$. As a byproduct, we also provide error
estimates for all fitted quantities, which can be consistently incorporated
into current and future gravitational-wave parameter-estimation analyses. Our
model(s) are made publicly available through a fast and easy-to-use Python
module called surfinBH.",1809.09125v2
2017-05-10,Post-Newtonian templates for binary black-hole inspirals: the effect of the horizon fluxes and the secular change in the black-hole masses and spins,"Black holes (BHs) in an inspiraling compact binary system absorb the
gravitational-wave (GW) energy and angular-momentum fluxes across their event
horizons and this leads to the secular change in their masses and spins during
the inspiral phase. The goal of this paper is to present ready-to-use, 3.5
post-Newtonian (PN) template families for spinning, non-precessing, binary BH
inspirals in quasicircular orbits, including the 2.5PN and 3.5PN horizon flux
contributions as well as the correction due to the secular change in the BH
masses and spins through 3.5PN order, respectively, in phase. We show that, for
binary BHs observable by Advanced LIGO with high mass ratio (larger than ~10)
and large aligned-spins (larger than ~0.7), the mismatch between the
frequency-domain template with and without the horizon-flux contribution is
typically above the 3% mark. For (supermassive) binary BHs observed by LISA,
even a moderate mass-ratios and spins can produce a similar level of the
mismatch. Meanwhile, the mismatch due to the secular time variations of the BH
masses and spins is well below the 1% mark in both cases, hence this is truly
negligible. We also point out that neglecting the cubic-in-spin, point-particle
phase term at 3.5PN order would deteriorate the effect of BH absorption in the
template.",1705.03869v4
2018-07-03,Who Ordered That? On The Origin of LIGO's Merging Binary Black Holes,"LIGO's detection of gravitational waves from binary black hole mergers was an
unexpected surprise that immediately raised the question - what is the origin
of these black hole binaries? The ""simplest"" scenario is evolution of field
massive stellar binaries. However, other possibilities involving capture have
been proposed. We explore here one of the more interesting clues on this
puzzle: the relatively modest spins of the resulting black holes that imply
that the progenitor black holes were not spinning rapidly. More specifically we
consider the implication of observed distribution of, $\chi_{\rm eff}$, the
mass weighted projected (along the orbital axis) spins on the field evolution
scenario. In all cases $\chi_{\rm eff}$ is small and in two of the cases the
best fit value is negative. Only in one event the spin is positive at 90\%
credible. These observations are puzzling within the field binary scenario in
which positive higher spins ($\chi_{\rm eff} \ge 0.5$) are expected. At first
sight one may expect that this rules out the field evolutionary scenario.
Indeed we show that with typical parameters a significant fraction ($\ge 25\%$)
of the mergers should have high effective spin values. However, uncertainties
in the outcome of the common envelope phase (the typical separation and whether
the stars are rotating or not) and in the late stages of massive star evolution
(the strength of the winds) make it impossible to rule out, at present, these
scenarios. While observations of mergers with high effective spin will support
this scenario, future observations of negative spin mergers would rule it out.",1807.01336v1
2018-10-24,High-fidelity spin and optical control of single silicon vacancy centres in silicon carbide,"Optically interfaced spins in the solid promise scalable quantum networks.
Robust and reliable optical properties have so far been restricted to systems
with inversion symmetry. Here, we release this stringent constraint by
demonstrating outstanding optical and spin properties of single silicon vacancy
centres in silicon carbide. Despite the lack of inversion symmetry, the
system's particular wave function symmetry decouples its optical properties
from magnetic and electric fields, as well as from local strain. This provides
a high-fidelity spin-to-photon interface with exceptionally stable and narrow
optical transitions, low inhomogeneous broadening, and a large fraction of
resonantly emitted photons. Further, the weak spin-phonon coupling results in
electron spin coherence times comparable with nitrogen-vacancy centres in
diamond. This allows us to demonstrate coherent hyperfine coupling to single
nuclear spins, which can be exploited as qubit memories. Our findings promise
quantum network applications using integrated semiconductor-based
spin-to-photon interfaces.",1810.10296v1
2018-10-23,Long term evolution of CFS-unstable neutron stars and role of differential rotation on short time-scales,"I consider differential rotation, associated with radiation-driven
Chandrasekhar-Friedman-Schutz (CFS) instability and its possible observational
evidences. I focus on the evolution of the apparent spin frequency, which is
typically associated with the motion of a specific point on the stellar surface
(e.g., polar cap). I start from long-term evolution (on the timescale when
instability significantly changes the spin frequency). For this case, I reduce
evolution equations to one differential equation and demonstrate that it can be
directly derived from energy conservation law. This equation governs evolution
rate through sequence of thermally equilibrium states and provides linear
coupling for the cooling power and rotation energy losses via gravitational
wave emission. In particular, it shows that differential rotation do not affect
long-term spin-down. On the contrary, on the short timescales, differential
rotation can significantly modify the apparent spin-down, if one examines a
strongly unstable star with very small initial amplitude of unstable mode. This
statement is confirmed by consideration of Newtonian non-magnetized perfect
fluid and dissipative stellar models as well as magnetized stellar model. For
example, despite that widely applied evolution equations predict effective spin
to be constant in absence of dissipation, the CFS-unstable star should be
observed as spinning-down. However, effects of differential rotation on
apparent spin-down are negligible for realistic models of neutron star
recycling, unless: (1) the neutron star is not magnetized, and (2) r-mode
amplitude is modulated faster than the shear viscosity dissipation timescale,
being large enough that spin-down can be measured on modulation timescale.",1810.10379v1
2018-08-20,Hamiltonians and canonical coordinates for spinning particles in curved space-time,"The spin-curvature coupling as captured by the so-called
Mathisson-Papapetrou-Dixon (MPD) equations is the leading order effect of the
finite size of a rapidly rotating compact astrophysical object moving in a
curved background. It is also a next-to-leading order effect in the phase of
gravitational waves emitted by extreme-mass-ratio inspirals (EMRIs), which are
expected to become observable by the LISA space mission. Additionally,
exploring the Hamiltonian formalism for spinning bodies is important for the
construction of the so-called Effective-One-Body waveform models that should
eventually cover all mass ratios.
  The MPD equations require supplementary conditions determining the frame in
which the moments of the body are computed. We review various choices of these
supplementary spin conditions and their properties. Then, we give Hamiltonians
either in proper-time or coordinate-time parametrization for the
Tulczyjew-Dixon, Mathisson-Pirani, and Kyrian-Semer\'ak conditions. Finally, we
also give canonical phase-space coordinates parametrizing the spin tensor. We
demonstrate the usefulness of the canonical coordinates for symplectic
integration by constructing Poincar\'e surfaces of section for spinning bodies
moving in the equatorial plane in Schwarzschild space-time. We observe the
motion to be essentially regular for EMRI-ranges of the spin, but for larger
values the Poincar\'e surfaces of section exhibit the typical structure of a
weakly chaotic system. A possible future application of the numerical
integration method is the inclusion of spin effects in EMRIs at the precision
requirements of LISA.",1808.06582v2
2017-02-17,Spin conductance of YIG thin films driven from thermal to subthermal magnons regime by large spin-orbit torque,"We report a study on spin conductance in ultra-thin films of Yttrium Iron
Garnet (YIG), where spin transport is provided by propagating spin waves, that
are generated and detected by direct and inverse spin Hall effects in two Pt
wires deposited on top. While at low current the spin conductance is dominated
by transport of thermal magnons, at high current, the spin conductance is
dominated by low-damping non-equilibrium magnons thermalized near the spectral
bottom by magnon-magnon interaction, with consequent a sensitivity to the
applied magnetic field and a longer decay length. This picture is supported by
microfocus Brillouin Light Scattering spectroscopy.",1702.05226v3
2020-03-10,Fourth post-Newtonian effective-one-body Hamiltonians with generic spins,"In a compact binary coalescence, the spins of the compact objects can have a
significant effect on the orbital motion and gravitational-wave (GW) emission.
For generic spin orientations, the orbital plane precesses, leading to
characteristic modulations of the GW signal. The observation of precession
effects is crucial to discriminate among different binary formation scenarios,
and to carry out precise tests of General Relativity. Here, we work toward an
improved description of spin effects in binary inspirals, within the
effective-one-body (EOB) formalism, which is commonly used to build waveform
models for LIGO and Virgo data analysis. We derive EOB Hamiltonians including
the complete fourth post-Newtonian (4PN) conservative dynamics, which is the
current state of the art. We place no restrictions on the spin orientations or
magnitudes, or on the type of compact object (e.g., black hole or neutron
star), and we produce the first generic-spin EOB Hamiltonians complete at 4PN
order. We consider multiple spinning EOB Hamiltonians, which are more or less
direct extensions of the varieties found in previous literature, and we suggest
another simplified variant. Finally, we compare the circular-orbit,
aligned-spin binding-energy functions derived from the EOB Hamiltonians to
numerical-relativity simulations of the late inspiral. While finding that all
proposed Hamiltonians perform reasonably well, we point out some interesting
differences, which could guide the selection of a simpler, and thus
faster-to-evolve EOB Hamiltonian to be used in future LIGO and Virgo inference
studies.",2003.04469v2
2020-09-22,Magnon-mediated spin currents in Tm3Fe5O12/Pt with perpendicular magnetic anisotropy,"The control of pure spin currents carried by magnons in magnetic insulator
(MI) garnet films with a robust perpendicular magnetic anisotropy (PMA) is of
great interest to spintronic technology as they can be used to carry, transport
and process information. Garnet films with PMA present labyrinth domain
magnetic structures that enrich the magnetization dynamics, and could be
employed in more efficient wave-based logic and memory computing devices. In
MI/NM bilayers, where NM being a normal metal providing a strong spin-orbit
coupling, the PMA benefits the spin-orbit torque (SOT) driven magnetization's
switching by lowering the needed current and rendering the process faster,
crucial for developing magnetic random-access memories (SOT-MRAM). In this
work, we investigated the magnetic anisotropies in thulium iron garnet (TIG)
films with PMA via ferromagnetic resonance measurements, followed by the
excitation and detection of magnon-mediated pure spin currents in TIG/Pt driven
by microwaves and heat currents. TIG films presented a Gilbert damping constant
{\alpha}~0.01, with resonance fields above 3.5 kOe and half linewidths broader
than 60 Oe, at 300 K and 9.5 GHz. The spin-to-charge current conversion through
TIG/Pt was observed as a micro-voltage generated at the edges of the Pt film.
The obtained spin Seebeck coefficient was 0.54 {\mu}V/K, confirming also the
high interfacial spin transparency.",2009.10299v1
2020-11-17,Implications of recoil kicks for black hole mergers from LIGO/Virgo catalogs,"The first and second Gravitational Wave Transient Catalogs by the LIGO/Virgo
Collaboration include $50$ confirmed merger events from the first, second, and
first half of the third observational runs. We compute the distribution of
recoil kicks imparted to the merger remnants and estimate their retention
probability within various astrophysical environments as a function of the
maximum progenitor spin ($\chi_{\rm max}$), assuming that the LIGO/Virgo binary
black hole (BBH) mergers were catalyzed by dynamical assembly in a dense star
cluster. We find that the distributions of average recoil kicks are peaked at
about $150$ km s$^{-1}$, $250$ km s$^{-1}$, $350$ km s$^{-1}$, $600$ km
s$^{-1}$, for maximum progenitor spins of $0.1$, $0.3$, $0.5$, $0.8$,
respectively. Only environments with escape speed $\gtrsim 100$ km s$^{-1}$, as
found in galactic nuclear star clusters as well as in the most massive globular
clusters and super star clusters, could efficiently retain the merger remnants
of the LIGO/Virgo BBH population even for low progenitor spins ($\chi_{\rm
max}=0.1$). In the case of high progenitor spins ($\chi_{\rm max}\gtrsim 0.5$),
only the most massive nuclear star clusters can retain the merger products. We
also show that the estimated values of the effective spin and of the remnant
spin of GW170729, GW190412, GW190519, and GW190620 can be reproduced if their
progenitors were moderately spinning ($\chi_{\rm max}\gtrsim 0.3$), while for
GW190517 if the progenitors were rapidly spinning ($\chi_{\rm max}\gtrsim
0.8$). Alternatively, some of these events could be explained if at least one
of the progenitors is already a second-generation BH, originated from a
previous merger.",2011.08935v2
2021-10-07,Relativistic scattering of a fast spinning neutron star by a massive black hole,"The orbital dynamics of fast spinning neutron stars encountering a massive
Black Hole (BH) with unbounded orbits are investigated using the
quadratic-in-spin Mathisson-Papapetrou- Dixon (MPD) formulation. We consider
the motion of the spinning neutron stars with astrophysically relevant speed in
the gravity field of the BH. For such slow-speed scattering, the hyperbolic
orbits followed by these neutron stars all have near the e = 1 eccentricity,
and have distinct properties compared with those of e >> 1. We have found that
compared with geodesic motion, the spin-orbit and spin-spin coupling will lead
to a variation of scattering angles at spatial infinity, and this variation is
more prominent for slow-speed scattering than fast-speed scattering. Such a
variation leads to an observable difference in pulse-arrival-time within a few
hours of observation, and up to a few days or months for larger BH masses or
longer spinning periods. Such a relativistic pulsar-BH system also emits a
burst of gravitational waves (GWs) in the sensitivity band of LISA, and for
optimal settings, can be seen up to 100 Mpc away. A radio follow up of such a
GW burst with SKA or FAST will allow for measuring the orbital parameters with
high accuracy and testing the predictions of General Relativity (GR).",2110.03494v1
2019-07-26,Optical spin-wave storage in a solid-state hybridized electron-nuclear spin ensemble,"Solid-state impurity spins with optical control are currently investigated
for quantum networks and repeaters. Among these, rare-earth-ion doped crystals
are promising as quantum memories for light, with potentially long storage
time, high multimode capacity, and high bandwidth. However, with spins there is
often a tradeoff between bandwidth, which favors electronic spin, and memory
time, which favors nuclear spins. Here, we present optical storage experiments
using highly hybridized electron-nuclear hyperfine states in
$^{171}$Yb$^{3+}$:Y$_2$SiO$_5$, where the hybridization can potentially offer
both long storage time and high bandwidth. We reach a storage time of 1.2 ms
and an optical storage bandwidth of 10 MHz that is currently only limited by
the Rabi frequency of the optical control pulses. The memory efficiency in this
proof-of-principle demonstration was about 3%. The experiment constitutes the
first optical storage using spin states in any rare-earth ion with electronic
spin. These results pave the way for rare-earth based quantum memories with
high bandwidth, long storage time and high multimode capacity, a key resource
for quantum repeaters.",1907.11571v2
2019-07-31,Spin-spiral formalism based on the multiple scattering Green's function technique with applications to ultrathin magnetic films and multilayers,"Based on the Korringa-Kohn-Rostoker Green's function technique we present a
computational scheme for calculating the electronic structure of layered
systems with homogeneous spin-spiral magnetic state. From the self-consistent
non-relativistic calculations the total energy of the spin-spiral states is
determined as a function of the wave vector, while a relativistic extension of
the formalism in first order of the spin-orbit coupling gives an access to the
effect of the Dzyaloshinskii-Moriya interactions. We demonstrate that the newly
developed method properly describes the magnetic ground state of a Mn monolayer
on W(001) and that of a Co monolayer on Pt(111). The obtained spin-spiral
energies are mapped to a classical spin model, the parameters of which are
compared to those calculated directly from the relativistic torque method. In
case of the Co/Pt(111) system we find that the isotropic interaction between
the Co atoms is reduced and the Dzyaloshinskii-Moriya interaction is increased
when capped by a Ru layer. In addition, we perform spin-spiral calculations on
Ir/Fe/Co/Pt and Ir/Co/Fe/Pt multilayer systems and find a spin-spiral ground
state with very long wavelength due to the frustrated isotropic couplings
between the Fe atoms, whereas the Dzyaloshinskii-Moriya interaction strongly
depends on the sequence of the Fe and Co layers.",1907.13328v1
2019-08-08,"The Pauli and $\text{Lévy-Leblond}$ Equations, and the Spin Current Density","We review the literature on the Pauli equation and its current density,
discussing the progression from the original phenomenological version of Pauli
to its derivation by $\text{L\'{e}vy-Leblond}$ from a linearization of the
$\text{Schr\""{o}dinger}$ equation. It was established conclusively by
$\text{L\'{e}vy-Leblond}$'s work that the spin of a spin-1/2 particle such as
an electron is non-relativistic in nature, contrary to what was often stated
following Dirac's derivation of a relativistic wave equation, and his
subsequent demonstration that Pauli's spin interaction term appeared in the
non-relativistic limit. In this limit, the Gordon decomposition of the
associated probability current density was found to contain a spin-dependent
term. Such a term does not follow, however, from the usual derivation of the
current density from the Pauli equation, although various physically motivated
but otherwise ad hoc explanations were put forward to account for it. We
comment on the only exception to these of which we are aware implying the spin
term in the current was in fact non-relativistic in nature. However, the
earlier work of $\text{L\'{e}vy-Leblond}$ had already shown, with no additional
assumptions, that this term was a prominent feature of the current density
derived from his equation. Hence, just as with the spin itself, the spin
current was non-relativistic, claims to the contrary notwithstanding. We
present a somewhat simplified derivation of the $\text{L\'{e}vy-Leblond}$
equation and its current density, commenting on possibilities for experimental
work that might indicate measurable consequences of the spin term in the
current density.",1908.03276v2
2020-09-30,Pathways for producing binary black holes with large misaligned spins in the isolated formation channel,"Binary black holes (BBHs) can form from the collapsed cores of isolated
high-mass binary stars. The masses and spins of these BBHs are determined by
the complicated interplay of phenomena such as tides, winds, accretion,
common-envelope evolution (CEE), supernova natal kicks, and stellar
core-envelope coupling. The gravitational waves emitted during the mergers of
BBHs depend on their masses and spins and can thus constrain these phenomena.
We present a simplified model of binary stellar evolution and identify regions
of the parameter space that produce BBHs with large spins misaligned with their
orbital angular momentum. In Scenario A (B) of our model, stable mass transfer
(SMT) occurs after Roche-lobe overflow (RLOF) of the more (less) massive star,
while CEE follows RLOF of the less (more) massive star. Each scenario is
further divided into Pathways 1 and 2 depending on whether the core of the more
massive star collapses before or after RLOF of the less massive star,
respectively. If the stellar cores are coupled weakly to their envelopes,
highly spinning BBHs can be produced if natal spins greater than $10\%$ of the
breakup value are inherited from the stellar progenitors. BBHs can
alternatively acquire large spins by tidal synchronization during the
Wolf-Rayet stage in Scenario A or by accretion onto the initially more massive
star during SMT in Scenario B. BBH spins can be highly misaligned if the kicks
are comparable to the orbital velocity, which is more easily achieved in
Pathway A1 where the kick of the more massive star precedes CEE.",2010.00078v2
2021-07-13,Quantum spins and hybridization in artificially-constructed chains of magnetic adatoms on a superconductor,"Magnetic adatom chains on surfaces constitute fascinating quantum spin
systems. Superconducting substrates suppress interactions with bulk electronic
excitations but couple the adatom spins to a chain of subgap Yu-Shiba-Rusinov
(YSR) quasiparticles. Using a scanning tunneling microscope, we investigate
such correlated spin-fermion systems by constructing Fe chains adatom by adatom
on superconducting NbSe$_2$. The adatoms couple entirely via the substrate,
retaining their quantum spin nature. In dimers, we observe that the deepest YSR
state undergoes a quantum phase transition due to Ruderman-Kittel-Kasuya-Yosida
interactions, a distinct signature of quantum spins. Chains exhibit coherent
hybridization and band formation of the YSR excitations, indicating
ferromagnetic coupling. Longer chains develop separate domains due to
coexisting charge-density-wave order of NbSe$_2$. Despite the
spin-orbit-coupled substrate, we find no signatures of Majoranas, possibly
because quantum spins reduce the parameter range for topological
superconductivity. We suggest that adatom chains are versatile systems for
investigating correlated-electron physics and its interplay with topological
superconductivity.",2107.06361v2
2021-07-20,Hints of spin-orbit resonances in the binary black hole population,"Binary black hole spin measurements from gravitational wave observations can
reveal the binary's evolutionary history. In particular, the spin orientations
of the component black holes within the orbital plane, $\phi_1$ and $\phi_2$,
can be used to identify binaries caught in the so-called spin-orbit resonances.
In a companion paper, we demonstrate that $\phi_1$ and $\phi_2$ are best
measured near the merger of the two black holes. In this work, we use these
spin measurements to provide the first constraints on the full six-dimensional
spin distribution of merging binary black holes. In particular, we find that
there is a preference for $\Delta \phi = \phi_1 - \phi_2 \sim \pm \pi$ in the
population, which can be a signature of spin-orbit resonances. We also find a
preference for $\phi_1 \sim -\pi/4$ with respect to the line of separation near
merger, which has not been predicted for any astrophysical formation channel.
However, the strength of these preferences depends on our prior choices, and we
are unable to constrain the widths of the $\phi_1$ and $\Delta \phi$
distributions. Therefore, more observations are necessary to confirm the
features we find. Finally, we derive constraints on the distribution of recoil
kicks in the population, and use this to estimate the fraction of merger
remnants retained by globular and nuclear star clusters. We make our spin and
kick population constraints publicly available.",2107.09693v4
2021-07-30,Compton Black-Hole Scattering for $s \leq 5/2$,"Quantum scattering amplitudes for massive matter have received new attention
in connection to classical calculations relevant to gravitational-wave physics.
Amplitude methods and insights are now employed for precision computations of
observables needed for describing the gravitational dynamics of bound massive
objects such as black holes. An important direction is the inclusion of spin
effects needed to accurately describe rotating (Kerr) black holes. Higher-spin
amplitudes introduced by Arkani-Hamed, Huang and Huang at three points have by
now a firm connection to the effective description of Kerr black-hole physics.
The corresponding Compton higher-spin amplitudes remain however an elusive open
problem. Here we draw from results of the higher-spin literature and show that
physical insights can be used to uniquely fix the Compton amplitudes up to spin
5/2, by imposing a constraint on a three-point higher-spin current that is a
necessary condition for the existence of an underlying unitary theory. We give
the unique effective Lagrangians up to spin $5/2$, and show that they reproduce
the previously-known amplitudes. For the multi-graviton amplitudes analogous to
the Compton amplitude, no further corrections to our Lagrangians are expected,
and hence such amplitudes are uniquely predicted. As an essential tool, we
introduce a modified version of the massive spinor-helicity formalism which
allows us to conveniently obtain higher-spin states, propagators and compact
expressions for the amplitudes.",2107.14779v2
2022-02-05,Full-zone Persistent Spin Textures with Giant Spin Splitting in Two-dimensional Group IV-V Compounds,"Persistent spin texture (PST), a property of solid-state materials
maintaining unidirectional spin polarization in the momentum $k$-space, offers
a route to deliver the necessary long carrier spin lifetimes through the
persistent spin helix (PSH) mechanism. However, most of the discovered PST
locally occurred in the small part around certain high symmetry $k$-points or
lines in the first Brillouin zone (FBZ), thus limiting the stability of the PSH
state. Herein, by symmetry analysis and first-principles calculations, we
report the emergence of full-zone PST (FZPST), a phenomenon displaying the PST
in the whole FBZ, in the two-dimensional group IV-V $A_{2}B_{2}$ ($A$ = Si, Sn,
Ge; $B$ = Bi, Sb) compounds. Due to the existence of the in-plane mirror
symmetry operation in the wave vector point group symmetry for the arbitrary
$\vec{k}$ in the whole FBZ, fully out-of-plane spin polarization is observed in
the $k$-space, thus maintaining the FZPST. Importantly, we observed giant spin
splitting in which the PST sustains, supporting large SOC parameters and small
wavelengths of the PSH states. Our $\vec{k}\cdot\vec{p}$ analysis demonstrated
that the FZPST is robust for the non-degenerate bands, which can be effectively
controlled by the application of an external electric field, thus offering a
promising platform for future spintronic applications.",2202.02558v3
2022-02-22,Wide-angle giant photonic spin Hall effect,"Photonic spin Hall effect is a manifestation of spin-orbit interaction of
light and can be measured by a transverse shift \lambda of photons with
opposite spins. The precise measurement of transverse shifts can enable many
spin-related applications, such as precise metrology and optical sensing.
However, this transverse shift is generally small (i.e. \delta /\lambda
<{10}^{-1}, \lambda is the wavelength), which impedes its precise measurement.
To-date proposals to generate giant spin Hall effect (namely with \delta
/\lambda >{10}^{2}) have severe limitations, particularly its occurrence only
over a narrow angular cone (with a width of \Delta \theta <{1}^{\circ}). Here
we propose a universal scheme to realize the wide-angle giant photonic spin
Hall effect with \Delta \theta >{70}^{\circ} by exploiting the interface
between free space and uniaxial epsilon-near-zero media. The underlying
mechanism is ascribed to the almost-perfect polarization splitting between s
and p polarized waves at the designed interface. Remarkably, this
almost-perfect polarization splitting does not resort to the interference
effect and is insensitive to the incident angle, which then gives rise to the
wide-angle giant photonic spin Hall effect.",2202.10732v4
2022-04-27,The linear mode analysis and spin relaxation,"In this paper, a detailed analysis on normal modes of the linearized Hermite
collision operator is presented, which follows from linearizing spin Boltzmann
equation for massive fermions proposed in \cite{Weickgenannt:2021cuo} with the
non-diagonal part of the transition rate neglected and approximating what we
got with a mutilated operator. With the assumption of total angular momentum
conservation, the collision term is proved to well describe the equilibrium
state and gives proper interpretation for collisional invariants, thus is
relevant for the research on local spin polarization. Following the familiar
fashion as used in quantum mechanics, we treat the problem of solving normal
modes as a degenerate perturbation problem and calculate the dispersion
relations for intriguing eleven zero modes, which form one-to-one
correspondence to all collisional invariants. We find that the results of
spinless modes appearing in ordinary hydrodynamics are consistent with
available conclusions in textbooks. As for spin-related modes, we obtain the
frequencies up to second order in wave vector and relate them with the
dissipation of spin density fluctuation. In addition, the ratio of two
relaxation time scales for spin and momentum is shown as a function of reduced
mass, which reads that based on present framework spin equilibration is almost
as slow as momentum equilibration as far as the strange quark spins in quark
gluon plasma (QGP) are concerned.",2204.12946v2
2022-05-05,Tossing Black Hole Spin Axes,"The detection of double black hole (BH+BH) mergers provides a unique
possibility to understand their physical properties and origin. To date, the
LIGO-Virgo-KAGRA network of high-frequency gravitational wave observatories
have announced the detection of more than 85 BH+BH merger events (Abbott et al.
2022a). An important diagnostic feature that can be extracted from the data is
the distribution of effective inspiral spins of the BHs. This distribution is
in clear tension with theoretical expectations from both an isolated binary
star origin, which traditionally predicts close-to aligned BH component spins
(Kalogera 2000; Farr et al. 2017), and formation via dynamical interactions in
dense stellar environments that predicts a symmetric distribution of effective
inspiral spins (Mandel & O'Shaughnessy 2010; Rodriguez et al. 2016b). Here it
is demonstrated that isolated binary evolution can convincingly explain the
observed data if BHs have their spin axis tossed during their formation process
in the core collapse of a massive star, similarly to the process evidently
acting in newborn neutron stars. BH formation without spin-axis tossing,
however, has difficulties reproducing the observed data - even if alignment of
spins prior to the second core collapse is disregarded. Based on simulations
with only a minimum of assumptions, constrains from empirical data can be made
on the spin magnitudes of the first- and second-born BHs, thereby serving to
better understand massive binary star evolution prior to the formation of BHs.",2205.02541v3
2022-07-11,Magnetic structure and spin dynamics of the quasi-2D antiferromagnet Zn-doped copper pyrovanadate,"Magnetic properties of the antiferromagnet Zn$_{0.15}$Cu$_{1.85}$V$_2$O$_7$
(ZnCVO) have been thoroughly investigated on powder and single-crystal samples.
The crystal structure determination using powder x-ray and neutron diffraction
confirms that ZnCVO with Zn = 0.15 is isostructural with
$\beta$-Cu$_{2}$V$_2$O$_7$ ($\beta$-CVO) with small deviation in the lattice
parameters. Macroscopic magnetic properties measurements also confirm the
similarity between the two compounds. The Cu$^{2+}$ spins were found to align
along the crystallographic $c$-axis, antiparallel to their nearest neighbors
connected by the leading exchange interaction $J_1$. Spin dynamics reveals a
typical symmetric spin-wave dispersion with strong interactions in the
$bc$-plane and weak interplane coupling. The exchange interaction analysis
indicates that the spin network of ZnCVO is topologically consistent with the
previous DFT prediction but the values of leading exchange interactions are
contradictory. Furthermore, rather than the predicted 2D honeycomb structure,
the spin network in ZnCVO could be better described by the anisotropic 2D spin
network composing of $J_1$, $J_5$, and $J_6$ interactions, four bonds per one
spin site, coupled by weak interplane interactions.",2207.04618v2
2022-10-21,Calculation of molecular g-tensors by sampling spin orientations of generalised Hartree-Fock states,"The variational inclusion of spin-orbit coupling in self-consistent field
(SCF) calculations requires a generalised two-component framework, which
permits the single-determinant wave function to completely break spin symmetry.
The individual components of the molecular g-tensor are commonly obtained from
separate SCF solutions that align the magnetic moment along one of the three
principal tensor axes. However, this strategy raises the question if energy
differences between solutions are relevant, or how convergence is achieved if
the principal axis system is not determined by molecular symmetry. The present
work resolves these issues by a simple two-step procedure akin to the generator
coordinate method (GCM). First, a few generalised Hartree Fock (GHF) solutions
are converged, applying, where needed, a constraint to the orientation of the
magnetic-moment or spin vector. Then, superpositions of GHF determinants are
formed through non-orthogonal configuration interaction. This procedure yields
a Kramers doublet for the calculation of the complete g-tensor. Alternatively,
for systems with weak spin-orbit effects, diagonalisation in a basis spanned by
spin rotations of a single GHF determinant affords qualitatively correct
g-tensors by eliminating errors related to spin contamination. For small
first-row molecules, these approaches are evaluated against experimental data
and full configuration interaction results. It is further demonstrated for two
systems (a fictitious tetrahedral CH4+ species, and a CuF4(2-) complex) that a
GCM strategy, in contrast to alternative mean-field methods, can correctly
describe the spin-orbit splitting of orbitally-degenerate ground states, which
causes large g-shifts and may lead to negative g-values.",2210.12009v1
2023-04-09,Dynamics for Super-Extremal Kerr Binary Systems at ${\cal O}(G^2)$,"Using the recently derived higher spin gravitational Compton amplitude from
low-energy analytically continued ($a/Gm\gg1$) solutions of the Teukolsky
equation for the scattering of a gravitational wave off the Kerr black hole,
observables for non-radiating super-extremal Kerr binary systems at second
post-Minkowskian (PM) order and up to sixth order in spin are computed. The
relevant 2PM amplitude is obtained from the triangle-leading singularity in
conjunction with a generalization of the holomorphic classical limit for
massive particles with spin oriented in generic directions. Explicit results
for the 2PM eikonal phase written for both Covariant and Canonical spin
supplementary conditions -- CovSSC and CanSSC respectively -- as well as the
2PM linear impulses and individual spin kicks in the CanSSC are presented. The
observables reported in this letter are expressed in terms of generic contact
deformations of the gravitational Compton amplitude, which can then be
specialized to Teukolsky solutions. In the latter case, the resulting 2PM
observables break the newly proposed spin-shift symmetry of the 2PM amplitude
starting at the fifth order in spin. Aligned spin checks as well as the high
energy behavior of the computed observables are discussed.",2304.04287v3
2023-09-11,Quantum control and Berry phase of electron spins in rotating levitated diamonds in high vacuum,"Levitated diamond particles in high vacuum with internal spin qubits have
been proposed for exploring macroscopic quantum mechanics, quantum gravity, and
precision measurements. The coupling between spins and particle rotation can be
utilized to study quantum geometric phase, create gyroscopes and rotational
matter-wave interferometers. However, previous efforts in levitated diamonds
struggled with vacuum level or spin state readouts. To address these gaps, we
fabricate an integrated surface ion trap with multiple stabilization
electrodes. This facilitates on-chip levitation and, for the first time,
optically detected magnetic resonance measurements of a nanodiamond levitated
in high vacuum. The internal temperature of our levitated nanodiamond remains
moderate below $10^{-5}$ Torr. Impressively, we have driven a nanodiamond to
rotate up to 20 MHz ($1.2 \times 10^{9}$ rpm), surpassing typical
nitrogen-vacancy (NV) center electron spin dephasing rates. Using these NV
spins, we observe the effect of the Berry phase arising from particle rotation.
In addition, we demonstrate quantum control of spins in a rotating nanodiamond.
These results mark an important development in interfacing mechanical rotation
with spin qubits, expanding our capacity to study quantum phenomena.",2309.05821v2
2023-10-05,Intervalley coherence and intrinsic spin-orbit coupling in rhombohedral trilayer graphene,"Rhombohedral graphene multilayers provide a clean and highly reproducible
platform to explore the emergence of superconductivity and magnetism in a
strongly interacting electron system. Here, we use electronic compressibility
and local magnetometry to explore the phase diagram of this material class in
unprecedented detail. We focus on rhombohedral trilayer in the quarter metal
regime, where the electronic ground state is characterized by the occupation of
a single spin and valley isospin flavor. Our measurements reveal a subtle
competition between valley imbalanced (VI) orbital ferromagnets and intervalley
coherent (IVC) states in which electron wave functions in the two momentum
space valleys develop a macroscopically coherent relative phase. Contrasting
the in-plane spin susceptibility of the IVC and VI phases reveals the influence
of graphene's intrinsic spin-orbit coupling, which drives the emergence of a
distinct correlated phase with hybrid VI and IVC character. Spin-orbit also
suppresses the in-plane magnetic susceptibility of the VI phase, which allows
us to extract the spin-orbit coupling strength of $\lambda \approx 50\mu$eV for
our hexagonal boron nitride-encapsulated graphene system. We discuss the
implications of finite spin-orbit coupling on the spin-triplet superconductors
observed in both rhombohedral and twisted graphene multilayers.",2310.03781v2
2023-11-16,Spin-phonon interactions on the kagome lattice: Dirac spin liquid versus valence-bond solids,"We investigate the impact of the spin-phonon coupling on the S=1/2 Heisenberg
model on the kagome lattice. For the pure spin model, there is increasing
evidence that the low-energy properties can be correctly described by a Dirac
spin liquid, in which spinons with a conical dispersion are coupled to emergent
gauge fields. Within this scenario, the ground-state wave function is well
approximated by a Gutzwiller-projected fermionic state [Y. Ran, M. Hermele,
P.A. Lee, and X.-G. Wen, Phys. Rev. Lett. 98, 117205 (2007)]. However, the
existence of U(1) gauge fields may naturally lead to instabilities when small
perturbations are included. Since phonons are ubiquitous in real materials,
they may play a relevant role in the determination of the actual physical
properties of the kagome antiferromagnet. We perform a step forward in this
direction, including phonon degrees of freedom (at the quantum level) and
applying a variational approach based upon Gutzwiller-projected fermionic
Ans\""atze. Our results suggest that the Dirac spin liquid is stable for small
spin-phonon couplings, while valence-bond solids are obtained at large
couplings. Even though different distortions can be induced by the spin-phonon
interaction, the general aspect is that the energy is lowered by maximizing the
density of perfect hexagons in the dimerization pattern.",2311.09823v2
2023-12-16,Topological phase transitions and thermal Hall effect in a noncollinear spin texture,"The noncollinear spin textures provide promising avenues to stabilize exotic
magnetic phases and excitations. They have attracted vast attention owning to
their nontrivial band topology in the past decades. Distinct from the
conventional route of involving the Dzyaloshinskii-Moriya interaction in a
honeycomb magnet, the interplay of bond-dependent Kitaev and $\Gamma$
interactions, originating from the spin-orbit coupling and octahedra crystal
field in real materials, has demonstrated to be another source to generate
noncollinear spin textures with multiple spins in a magnetic unit cell.
Notably, earlier works have revealed a triple-meron crystal (TmX) consisting of
eighteen spins in the frustrated Kitaev-$\Gamma$ model. Aligning with previous
efforts, here we attempt to identity that the TmX hosts several peculiar
features with the help of the linear spin-wave theory. To begin with, the
symmetric anisotropic exchanges are beneficial for the existence of
nonreciprocal magnons, which are stabilized by an external magnetic field.
Further, within the regime of TmX, successive topological phase transitions
occur, accompanied by the changes of Chern number in value and thermal Hall
conductivity in sign. In addition, topological nature of magnons is also
verified by the onset of chiral edge modes in a nanoribbon geometry. Our
findings pave the way to study topological phenomena of noncollinear spin
textures in potential Kitaev materials.",2312.10473v1
2007-03-26,Apparent horizon formation in the head-on collision of gyratons,"The gyraton model describes a gravitational field of an object moving with
the velocity of light which has finite energy and spin distributed during some
finite time interval $L$. A gyraton may be considered as a classical toy model
for a quantum wave packet of high-energy particles with spin. In this paper we
study a head-on collision of two gyratons and black hole formation in this
process. The goal of this study is to understand the role of the gravitational
spin-spin interaction in the process of mini-black-hole formation in particle
collisions. To simplify the problem we consider several gyraton models with
special profiles of the energy and spin density distribution. For these models
we study the apparent horizon (AH) formation on the future edge of a spacetime
region before interaction. We demonstrate that the AH forms only if the energy
duration and the spin are smaller than some critical values, while the length
of the spin distribution should be at least of the order of the system
gravitational radius. We also study gravitational spin-spin interaction in the
head-on collision of two gyratons under the assumption that the values of
gyraton spins are small. We demonstrate that the metric in the interaction
region for such gyratons depends on the relative helicities of incoming
gyratons, and the collision of gyratons with oppositely directed spins allows
the AH formation in a larger parameter region than in the collision of the
gyratons with the same direction of spins. Some applications of the obtained
results to the mini-black-hole production at the Large Hadron Collider in TeV
gravity scenarios are briefly discussed.",0703127v3
2013-05-24,Realizing a lattice spin model with polar molecules,"With the recent production of polar molecules in the quantum regime,
long-range dipolar interactions are expected to facilitate the understanding of
strongly interacting many-body quantum systems and to realize lattice spin
models for exploring quantum magnetism. In atomic systems, where interactions
require wave function overlap, effective spin interactions on a lattice can be
realized via superexchange; however, the coupling is weak and limited to
nearest-neighbor interactions. In contrast, dipolar interactions exist in the
absence of tunneling and extend beyond nearest neighbors. This allows coherent
spin dynamics to persist even at high entropy and low lattice filling. Effects
of dipolar interactions in ultracold molecular gases have so far been limited
to the modification of chemical reactions. We now report the observation of
dipolar interactions of polar molecules pinned in a 3D optical lattice. We
realize a lattice spin model with spin encoded in rotational states, prepared
and probed by microwaves. This spin-exchange interaction arises from the
resonant exchange of rotational angular momentum between two molecules. We
observe clear oscillations in the evolution of the spin coherence in addition
to an overall decay. The frequency of these oscillations, the strong dependence
of the spin coherence time on the lattice filling, and the effect of a
multi-pulse sequence designed to reverse dynamics due to two-body exchange
interactions all provide evidence of dipolar interactions. We also demonstrate
suppression of loss in weak lattices due to a quantum Zeno mechanism.
Measurements of these tunneling-induced losses allow us to independently
determine the lattice filling factor. These results comprise an initial
exploration of the behavior of many-body spin models with direct, long-range
spin interactions and lay the groundwork for future studies of many-body
dynamics in spin lattices.",1305.5598v1
2016-07-08,Morphology effects on spin-dependent transport and recombination in polyfluorene thin films,"We have studied the role of spin-dependent processes on conductivity in
polyfluorene (PFO) thin films by conducting continuous wave (c.w.) electrically
detected magnetic resonance (EDMR) spectroscopy at temperatures between 10 K
and 293 K using microwave frequencies between about 100 MHz and 20 GHz as well
as pulsed EDMR at X-band. Variable frequency EDMR allows us to establish the
role of spin-orbit coupling in spin-dependent processes, pulsed EDMR probes
coherent spin motion effects. We used PFO for this study in order to allow for
the investigation of the effects of microscopic morphological ordering since
this material can adopt two distinct intrachain morphologies: an amorphous
(glassy) phase, and an ordered (beta) phase. In thin films of organic
light-emitting diodes (OLEDs) the appearance of a particular phase can be
controlled by deposition parameters, and is verified by electroluminescence
spectroscopy. We conducted multi-frequency c.w. EDMR, electrically detected
Rabi spinbeat experiments, Hahn-echo and inversion-recovery measurements.
Coherent echo spectroscopy reveals electrically detected electron spin-echo
envelope modulation (ESEEM) due to the precession of the carrier spins around
the protons. Our results demonstrate that while conformational disorder can
influence the observed EDMR signals, including the sign of the current changes
on resonance as well as the magnitudes of local hyperfine fields and charge
carrier spin-orbit interactions, it does not qualitatively affect the nature of
spin-dependent transitions in this material. At 293 K and 10 K, polaron-pair
recombination through weakly spin-spin coupled intermediate charge carrier pair
states is dominant, while at low temperatures, additional signatures of
spin-dependent charge transport through the interaction of polarons with
triplet excitons are seen in the half-field resonance of a triplet spin-1
species.",1607.02462v1
2019-12-19,Magnon-driven chiral charge and spin pumping and electron-magnon scattering from time-dependent quantum transport combined with atomistic spin dynamics theory,"Using newly developed quantum-classical hybrid framework, we investigate
interaction between spin-polarized conduction electrons and a single spin wave
(SW) coherently excited within a metallic ferromagnetic nanowire. When the
nanowire hosting SW is attached to two normal metal (NM) leads, with no dc bias
voltage applied between them, the SW pumps chiral electronic charge and spin
currents into the leads---their direction is tied to the direction of SW
propagation and they scale linearly with the frequency of the precession. This
is in contrast to: standard pumping by the uniform precession mode with
identical spin currents flowing in both directions and no accompanying charge
current; or experimentally observed [C.~Ciccarelli et al., Nat. Nanotech. 10,
50 (2014); M.~Evelt et al., Phys. Rev. B 95, 024408 (2017)] magnonic charge
pumping which requires spin-orbit coupling spin-orbit coupling. The mechanism
behind our prediction is nonadiabaticity due to time-retardation
effects---motion of localized magnetic moment affects conduction electron spin
in a retarded way, so that it takes a finite time until the electron spin
reacts to the motion of the classical vector. Upon injecting dc spin-polarized
charge current from the left NM lead, electrons interact with SW where
outflowing charge and spin current into the right NM lead are changed due to
both scattering off time-dependent potential generated by the SW and
superposition with the currents pumped by the SW itself. Using Lorentzian
voltage pulse to excite leviton out of the Fermi sea, which carries one
electron charge with no accompanying electron-hole pairs and behaves as
soliton-like quasiparticle, we describe how a single electron interacts with a
single SW.",1912.09452v2
2022-06-01,Spin symmetry energy and equation of state of spin-polarized neutron star matter,"Equation of states (EOS) of the spin-polarized nuclear matter (NM) is studied
within the Hartree-Fock (HF) formalism using the realistic density dependent
nucleon-nucleon interaction. With a nonzero fraction $\Delta$ of spin-polarized
baryons in NM, the spin- and spin-isospin dependent parts of the HF energy
density give rise to the \emph{spin symmetry} energy that behaves in about the
same manner as the \emph{isospin symmetry} energy, widely discussed in
literature as the nuclear symmetry energy. The present HF study shows a strong
correlation between the spin symmetry energy and nuclear symmetry energy over
the whole range of baryon densities. The important contribution of the spin
symmetry energy to the EOS of the spin-polarized NM is found to be comparable
with that of the nuclear symmetry energy to the EOS of the isospin-polarized or
asymmetric (neutron-rich) NM. Based on the HF energy density, the EOS of the
spin-polarized ($\beta$-stable) np$e\mu$ matter is obtained for the
determination of the macroscopic properties of neutron star (NS). A realistic
density dependence of the spin-polarized fraction $\Delta$ have been suggested
to explore the impact of the spin symmetry energy to the gravitational mass $M$
and radius $R$, as well as the tidal deformability of NS. Given the empirical
constrains inferred from a coherent Bayesian analysis of gravitational wave
signals of the NS merger GW170817 and the observed masses of the heaviest
pulsars, the strong impacts of the spin symmetry energy $W$, nuclear symmetry
energy $S$, and nuclear incompressibility $K$ to the EOS of nucleonic matter in
magnetar were revealed.",2206.00218v1
2010-09-16,Evolution of Spin Direction of Accreting Magnetic Protostars and Spin-Orbit Misalignment in Exoplanetary Systems: II. Warped Discs,"Magnetic interactions between a protostar and its accretion disc tend to
induce warping in the disc and produce secular changes in the stellar spin
direction, so that the spin axis may not always be perpendicular to the disc.
This may help explain the recently observed spin-orbit misalignment in a number
of exoplanetary systems. We study the dynamics of warped protoplanetary discs
under the combined effects of magnetic warping/precession torques and internal
stresses in the disc, including viscous damping of warps and propagation of
bending waves. We show that when the outer disc axis is misaligned with the
stellar spin axis, the disc evolves towards a warped steady-state on a
timescale that depends on the disc viscosity or the bending wave propagation
speed, but in all cases is much shorter than the timescale for the spin
evolution (of order of a million years). Moreover, for the most likely physical
parameters characterizing magnetic protostars, circumstellar discs and their
interactions, the steady-state disc has a rather small warp, such that the
whole disc lies approximately in a single plane determined by the outer disc
boundary conditions, although more extreme parameters may give rise to larger
disc warps. In agreement with our recent analysis (Lai et al. 2010) based on
flat discs, we find that the back-reaction magnetic torques of the slightly
warped disc on the star can either align the stellar spin axis with the disc
axis or push it towards misalignment, depending on the parameters of the
star-disc system. This implies that newly formed planetary systems may have a
range of inclination angles between the stellar spin axis and the symmetry axis
of the planetary orbits.",1009.3233v2
2011-08-04,Gravitational waves from spinning black hole-neutron star binaries: dependence on black hole spins and on neutron star equations of state,"We study the merger of black hole (BH)-neutron star (NS) binaries with a
variety of BH spins aligned or anti-aligned with the orbital angular momentum,
and with the mass ratio in the range MBH/MNS = 2--5, where MBH and MNS are the
mass of the BH and NS, respectively. We model NS matter by systematically
parametrized piecewise polytropic equations of state. The initial condition is
computed in the puncture framework adopting an isolated horizon framework to
estimate the BH spin and assuming an irrotational velocity field for the fluid
inside the NS. Dynamical simulations are performed in full general relativity
by an adaptive mesh refinement code, SACRA. The treatment of hydrodynamic
equations and estimation of the disk mass are improved. We find that the NS is
tidally disrupted irrespective of the mass ratio when the BH has a moderately
large prograde spin, whereas only binaries with low mass ratios, MBH/MNS <~ 3
or small compactnesses of the NSs, bring the tidal disruption when the BH spin
is zero or retrograde. The mass of the remnant disk is accordingly large as >~
0.1 Msun, which is required by central engines of short gamma-ray bursts, if
the BH spin is prograde. Information of the tidal disruption is reflected in a
clear relation between the compactness of the NS and an appropriately defined
""cutoff frequency"" in the gravitational-wave spectrum, above which the spectrum
damps exponentially. We find that the tidal disruption of the NS and excitation
of the quasinormal mode of the remnant BH occur in a compatible manner in high
mass-ratio binaries with the prograde BH spin. The correlation between the
compactness and the cutoff frequency still holds for such cases. It is also
suggested by extrapolation that the merger of an extremely spinning BH and an
irrotational NS binary does not lead to formation of an overspinning BH.",1108.1189v2
2018-12-15,Motion deviation of test body induced by spin and cosmological constant in extreme mass ratio inspiral binary system,"The future space-borne detectors will provide the possibility to detect
gravitational waves emitted from extreme mass ratio inspirals of stellar-mass
compact objects into supermassive black holes. It is natural to expect that the
spin of the compact object and cosmological constant will affect the orbit of
the inspiral process and hence lead to the considerable phase shift of the
corresponding gravitational waves. In this paper, we investigate the motion of
a spinning test particle in the spinning black hole background with a
cosmological constant and give the order of motion deviation induced by the
particle's spin and the cosmological constant by considering the corresponding
innermost stable circular orbit. By taking the neutron star or kerr black hole
as the small body, the deviations of the innermost stable circular orbit
parameters induced by the particle's spin and cosmological constant are given.
Our results show that the deviation induced by particle's spin is much larger
than that induced by cosmological constant when the test particle locates not
very far away from the black hole, the accumulation of phase shift during the
inspiral from the cosmological constant can be ignored when compared to the one
induced by the particle's spin. However when the test particle locates very far
away from the black hole, the impact from the cosmological constant will
increase dramatically. Therefore the accumulation of phase shift for the whole
process of inspiral induced by the cosmological constant and the particle's
spin should be handled with caution.",1812.06345v2
2020-08-04,General-relativistic spin system,"The models of spin systems defined on Euclidean space provide powerful
machinery for studying a broad range of condensed matter phenomena. While the
non-relativistic effective description is sufficient for most of the
applications, it is interesting to consider special and general relativistic
extensions of such models. Here, we introduce a framework that allows us to
construct theories of continuous spin variables on a curved spacetime. Our
approach takes advantage of the results of the non-linear field space theory,
which shows how to construct compact phase space models, in particular for the
spherical phase space of spin. Following the methodology corresponding to a
bosonization of spin systems into the spin wave representations, we postulate a
representation having the form of the Klein-Gordon field. This representation
is equivalent to the semi-classical version of the well-known
Holstein-Primakoff transformation. The general-relativistic extension of the
spin wave representation is then performed, leading to the
general-relativistically motivated modifications of the Ising model coupled to
a transversal magnetic field. The advantage of our approach is its off-shell
construction, while the popular methods of coupling fermions to general
relativity usually depend on the form of Einstein field equations with matter.
Furthermore, we show equivalence between the considered spin system and the
Dirac-Born-Infeld type scalar field theory with a specific potential, which is
also an example of k-essence theory. Based on this, the cosmological
consequences of the introduced spin field matter content are preliminarily
investigated.",2008.01729v2
2020-03-21,First-principles perspective on magnetic second sound,"The fluctuations of the magnetic order parameter, or longitudinal spin
excitations, are investigated theoretically in the ferromagnetic Fe and Ni as
well as in the antiferromagnetic phase of the pnictide superconductor FeSe. The
charge and spin dynamics of these systems is described by evaluating the
generalized charge and spin density response function calculated from
first-principles linear response time dependent density functional theory
within adiabatic local spin density approximation. We observe that the formally
non-interacting Kohn-Sham system features strong coupling between the
magnetization and charge dynamics in the longitudinal channel and that the
coupling is effectively removed upon the inclusion of the Coulomb interaction
in the charge channel and the resulting appearance of plasmons. The
longitudinal spin fluctuations acquire a collective character without the
emergence of the Goldstone boson, similar to the case of paramagnon excitations
in non-magnetic metals like Pd. In ferromagnetic Fe and Ni the longitudinal
spin dynamics is governed by interactions between low-energy intraband
electron-hole pairs while in quasi two dimensional antiferromagnet FeSe it is
dominated by the interband transitions with energies of the order of exchange
splitting. In the later material, the collective longitudinal magnetization
fluctuations feature well defined energies and long life times for small
momenta and appear below the particle-hole continuum. The modes become strongly
Landau-damped for growing wave-vectors. We relate our theoretical findings to
existing experimental spin-polarized electron energy loss spectroscopy results.
In bulk bcc Fe, the longitudinal magnetic modes appear above the typical
energies of transverse spin-waves, have energies comparable with the Stoner
spin-flip excitation continuum, and are order of magnitude less energetic than
the charge dynamics.",2003.09735v3
2021-04-27,Prospects for estimating parameters from gravitational waves of superspinar binaries,"To date, close to fifty presumed black hole binary mergers were observed by
the LIGO and Virgo detectors. The analyses have been done with an assumption
that these objects are black holes by limiting the spin prior to the Kerr
bound. However, the above assumption is not valid for superspinars, which have
the Kerr geometry but rotate beyond the Kerr bound. In this study, we
investigate whether and how the limited spin prior range causes a bias in
parameter estimation for superspinars if they are detected. To this end, we
estimate binary parameters of the simulated inspiral signals of the
gravitational waves of compact binaries by assuming that at least one component
of them is a superspinar. We have found that when the primary is a superspinar,
both mass and spin parameters are biased in parameter estimation due to the
limited spin prior range. In this case, the extended prior range is strongly
favored compared to the limited one. On the other hand, when the primary is a
black hole, we do not see much bias in parameter estimation due to the limited
spin prior range, even though the secondary is a superspinar. We also apply the
analysis to black hole binary merger events GW170608 and GW190814, which have a
long and loud inspiral signal. We do not see any preference of superspinars
from the model selection for both events. We conclude that the extension of the
spin prior range is necessary for accurate parameter estimation if highly
spinning primary objects are found, while it is difficult to identify
superspinars if they are only the secondary objects. Nevertheless, the bias in
parameter estimation of spin for the limited spin prior range can be a clue of
the existence of superspinars.",2104.12968v2
2014-03-27,Distinguishing black-hole spin-orbit resonances by their gravitational-wave signatures,"If binary black holes form following the successive core collapses of
sufficiently massive binary stars, precessional dynamics may align their spins
$\mathbf S_1$ and $\mathbf S_2$ and the orbital angular momentum $\mathbf L$
into a plane in which they jointly precess about the total angular momentum
$\mathbf J$. These spin orientations are known as spin-orbit resonances since
$\mathbf S_1$, $\mathbf S_2$, and $\mathbf L$ all precess at the same frequency
to maintain their planar configuration. Two families of such spin-orbit
resonances exist, alike in dignity but differentiated by whether the components
of the two spins in the orbital plane are either aligned or antialigned. The
fraction of binary black holes in each family is determined by the stellar
evolution of their progenitors, so if gravitational-wave detectors could
measure this fraction they could provide important insights into astrophysical
formation scenarios for binary black holes. In this paper, we show that even
under the conservative assumption that binary black holes are observed along
the direction of $\mathbf J$ (where precession-induced modulations to the
gravitational waveforms are minimized), the waveforms of many members of each
resonant family can be distinguished from all members of the opposing family in
events with signal-to-noise ratios $\rho \simeq 10$, typical of those expected
for the first detections with Advanced LIGO/Virgo. We hope that our preliminary
findings inspire a greater appreciation of the capability of gravitational-wave
detectors to constrain stellar astrophysics and stimulate further studies of
the distinguishability of spin-orbit resonant families in more expanded regions
of binary black-hole parameter space.",1403.7147v2
2016-10-20,Magnetic excitations in quasi-one dimensional helimagnets: Magnon decays and in uence of the inter-chain interactions,"We present a comprehensive study of the magnetic properties of the long-range
ordered quasi-one dimensional $J_{1}$-$J_{2}$ systems with a newly developed
torque equilibrium spin-wave expansion approach, which can describe the spin
Casimir and magnon decay effects in a unified framework. While the framework
does not lose the generality, our discussion will be restricted to two
representative types of inter-chain coupling systems: $J_{3}$- or
$J_{4}$-system respectively. In spite of the long-range spiral order, the
dynamical properties of these systems turn out to be highly nontrivial due to
the incommensurate noncollinear spin configuration and the strong quantum
fluctuation effects enhanced by the frustration and low-dimensionality. Both
the systems show prominent spin Casimir effects induced by the vacuum
fluctuation of the spin waves and related modification of the ordering vector,
Lifshitz point's position and sublattice magnetization. Significant and
spontaneous magnon decay effects are manifested in the quantum corrections to
the excitation spectrum. By adjusting the strength of magnetic anisotropy and
varying the approximation scheme, it is revealed that these striking distinct
features are quite robust and have deep connection with both the spin Casimir
and the magnon decay effects. Thus these special consequences of the
inter-chain coupling on the spin wave dynamics may be served as a set of probes
for different types of inter-chain couplings in experiments. At last, to guide
experimental measurements such as inelastic neutron scattering in realistic
materials and complement our theoretical framework, we develop the analytical
theory of the dynamical structure factor within the torque equilibrium
formulism and provide the explicit results of the quasi-one dimensional
$J_{1}$-$J_{2}$ systems.",1610.06365v2
2017-08-04,"Identification of spin wave resonances and crystal field transitions in simple chromites RCrO3 (R=Pr, Sm, Er) at ultralow temperatures in the THz spectral region","We report on THz absorption spectroscopy combined with high magnetic fields
of polycrystalline RCrO3 (R= Pr, Sm, Er) aiming understanding spin wave
resonances at their low temperature magnetic phases. Our measurements show that
the temperature, and the implicit anisotropies at which the Cr3+ spin
reorientation at TSR takes place, are determinant on the ferromagnetic-like
(FM) and the antiferromagnetic-like (AFM) spin modes being optically active. It
is found that they are dependent on Rare Earth 4f moment and ion size. We also
studied temperature and field dependence of crystal field levels in the same
spectroscopic region. Pr3+ non-Kramers emerges at 100 K and Zeeman splits. An
observed absence of spin wave resonances in PrCrO3 is attributed to Pr3+
remaining paramagnetic. In SmCrO3 near cancelation of the spin and orbital
moments is proposed as the possible reason for not detecting Sm3+ ground state
transitions. Here, the FM and AFM resonant modes harden when the temperature
decreases and split linearly on applied fields at 5 K and below. In ErCrO3 the
Er3+ Kramers doublet becomes active at about the TSR onset. Each line further
experiences Zeeman splitting under magnetic fields while an spin reversal
induced by a 2.5 T field, back to the Gamma4 (Fz) from the Gamma1 phase at 2 K,
produces a secondary splitting. The 5 K AFM and FM excitations in ErCrO3 have a
concerted frequency-intensity temperature dependence and a shoulder pointing to
the Er3+ smaller ion size also disrupting the two magnetic sublattice
approximation . Both resonances reduce to one when the temperature is lowered
to 2 K in the Gamma1 representation.",1708.01497v1
2021-03-23,Spin Wave Based Approximate Computing,"Spin Waves(SWs) enable the realization of energy efficient circuits as they
propagate and interfere within waveguides without consuming noticeable energy.
However, SW computing can be even more energy efficient by taking advantage of
the approximate computing paradigm as many applications are error-tolerant like
multimedia and social media. In this paper we propose an ultra-low energy novel
Approximate Full Adder(AFA) and a 2-bit inputs Multiplier(AMUL). We validate
the correct functionality of our proposal by means of micromagnetic simulations
and evaluate the approximate FA figure of merit against state-of-the-art
accurate SW, 7nmCMOS, Spin Hall Effect(SHE), Domain Wall Motion(DWM), accurate
and approximate 45nmCMOS, Magnetic Tunnel Junction(MTJ), and Spin-CMOS FA
implementations. Our results indicate that AFA consumes 43% and 33% less energy
than state-of-the-art accurate SW and 7nmCMOS FA, respectively, and saves 69%
and 44% when compared with accurate and approximate 45nm CMOS, respectively,
and provides a 2 orders of magnitude energy reduction when compared with
accurate SHE, accurate and approximate DWM, MTJ, and Spin-CMOS, counterparts.
In addition, it achieves the same error rate as approximate 45nmCMOS and
Spin-CMOS FA whereas it exhibits 50% less error rate than the approximate DWM
FA. Furthermore, it outperforms its contenders in terms of area by saving at
least 29% chip real-estate. AMUL is evaluated and compared with
state-of-the-art accurate SW and 16nm CMOS accurate and approximate
state-of-the-art designs. The evaluation results indicate that it saves at
least 2x and 5x energy in comparison with the state-of-the-art SW designs and
16nm CMOS accurate and approximate designs, respectively, and has an average
error rate of 10%, while the approximate CMOS MUL has an average error rate of
13%, and requires at least 64% less chip real-estate.",2103.12869v3
2023-02-22,Phenomenological relationship between eccentric and quasi-circular orbital binary black hole waveform,"Eccentricity, an important parameter of gravitational waves, has been paid
more and more attention because it can reflect the dynamics of compact object
mergers. Obtaining an accurate and fast gravitational waveform template is of
great significance for the estimation of gravitational wave parameters. This
paper aims to do an extended study of the phenomenological fitting model
proposed by Setyawati and Ohme for adding eccentricity to quasi-circular
orbital waveforms. It can be applied to higher eccentricity up to e = 0.4. But
the higher the eccentricity, the less the accuracy. For e in [0, 0.1], it gives
an overlap of more than 99.99%. For e in [0.1, 0.2], it gives an overlap of
more than 99.9%. For e in [0.2, 0.3], it gives an overlap of more than 99%. For
e in [0.3, 0.4], it gives an overlap of more than 90%. The reason for these
phenomena is that the larger the eccentricity, the larger the deviation of the
eccentricity estimator from the cosine function due to the large change in the
morphology of the eccentric waveform, and the worse the fitting effect of the
model. It can be applied to higher-order modes and gives the same overlap
behavior. After adding a shift parameter, it can be applied to spin-aligned or
spin-antialigned waveforms. After obtaining spin-precessing effect, it can be
applied to the spin-precessing case. In summary, non-spining, spin-aligned,
spin-antialigned or spin-precessing waveforms with eccentricity can be
constructed from quasi-circular non-spining waveforms by the phenomenological
model, which is not only helpful for us to quickly construct phenomenological
gravitational wave templates, but also reveals a phenomenological and universal
relationship between eccentric waveform and quasi-circular orbital waveform.",2302.11227v1
2008-03-04,Octonic relativistic quantum mechanics,"In this paper we represent the generalization of relativistic quantum
mechanics on the base of eght-component values ""octons"", generating associative
noncommutative spatial algebra. It is shown that the octonic second-order
equation for the eight-component octonic wave function, obtained from the
Einshtein relation for energy and momentum, describes particles with spin of
1/2. It is established that the octonic wave function of a particle in the
state with defined spin projection has the specific spatial structure in the
form of octonic oscillator with two spatial polarizations: longitudinal linear
and transversal circular. The relations between bispinor and octonic
descriptions of relativistic particles are established. We propose the
eight-component spinors, which are octonic generalisation of two-component
Pauli spinors and four-component Dirac bispinors. It is shown that proposed
eight-component spinors separate the states with different spin projection,
different particle-antiparticle state as well as different polarization of the
octonic oscillator. We demonstrate that in the frames of octonic relativistic
quantum mechanics the second-order equation for octonic wave function can be
reformulated in the form of the system of first-order equations for quantum
fields, which is analogous to the system of Maxwell equations for the
electromagnetic field. It is established that for the special type of wave
functions the second-order equation can be reduced to the single first-order
equation, which is analogous to the Dirac equation. At the same time it is
shown that this first-order equation describes particles, which do not create
quantum fields.",0803.0375v2
2013-04-11,A single-spin precessing gravitational wave in closed form,"In coming years, gravitational wave detectors should find black hole-neutron
star binaries, potentially coincident with astronomical phenomena like short
GRBs. These binaries are expected to precess. Gravitational wave science
requires a tractable model for precessing binaries, to disentangle precession
physics from other phenomena like modified strong field gravity, tidal
deformability, or Hubble flow; and to measure compact object masses, spins, and
alignments. Moreover, current searches for gravitational waves from compact
binaries use templates where the binary does not precess and are ill-suited for
detection of generic precessing sources. In this paper we provide a closed-form
representation of the single-spin precessing waveform in the frequency domain
by reorganizing the signal as a sum over harmonics, each of which resembles a
nonprecessing waveform. This form enables simple analytic calculations (e.g., a
Fisher matrix) with easily-interpreted results. We have verified that for
generic BH-NS binaries, our model agress with the time-domain waveform to 2\%.
Straightforward extensions of the derivations outlined here [and provided in
full online] allow higher accuracy and error estimates.",1304.3332v2
2014-04-10,"Competing charge-density-wave, magnetic and topological ground states at and near Dirac points in graphene in axial magnetic fields","In the presence of axial magnetic fields that can be realized in deliberately
buckled monolayer graphene, quasi-relativistic Dirac fermions may find
themselves in a variety of broken symmetry phases even for weak interactions.
Through a detailed Hartree self-consistent numerical calculation in finite
strained graphene with cylindrical and open boundaries we establish the
possibility of realizing a charge-density-wave order for the spinless fermions
in the presence of weak nearest-neighbor repulsion. Such an instability gives
rise to a staggered pattern of average fermionic density between bulk and
boundary of the system as well as among two sublattices of graphene, due to the
spatial separation of the zero energy states localized on opposite sublattices.
Although with fermions spin restored, an unconventional magnetic order driven
by the onsite repulsion, possibly leads to the dominant instability at the
Dirac point, the proposed charge-density-wave order can nevertheless be
realized at finite doping, which is always accompanied by a finite
ferromagnetic moment. Additionally, the charge-density-wave phase supports a
quantized charge or spin Hall conductivity when its formation away from the
Dirac point is further preceded by the appearance of topological anomalous or
spin Hall insulator respectively. The topological orders in strained graphene
can be supported by weak second neighbor repulsion, for example. Therefore,
depending on the relative strength of various short-range components of the
Coulomb interaction a number of broken symmetry phases can be realized within
the zero energy manifold in strained graphene.",1404.2926v2
2014-12-02,Exploring intertwined orders in cuprate superconductors,"The concept of intertwined orders has been introduced to describe the
cooperative relationship between antiferromagnetic spin correlations and
electron (or hole) pair correlations that develop in copper-oxide
superconductors. This contrasts with systems in which, for example,
charge-density-wave (CDW) order competes for Fermi surface area with
superconductivity. La$_{2-x}$Ba$_x$CuO$_4$ with $x=0.125$ provides an example
in which the ordering of spin stripes coincides with the onset of
two-dimensional superconducting correlations. The apparent frustration of the
interlayer Josephson coupling has motivated the concept of the
pair-density-wave superconductor, a state that theoretical calculations show to
be energetically competitive with the uniform $d$-wave superconductor. Even at
$x=0.095$, where there is robust superconductivity below 32~K in zero field,
the coexistence of strong, low-energy, incommensurate spin excitations implies
a spatially modulated and intertwined pair wave function. Recent observations
of CDW order in YBa$_2$Cu$_3$O$_{6+x}$ and other cuprate families have raised
interesting questions regarding the general role of charge modulations and the
relation to superconductivity. While there are differences in the doping
dependence of the modulation wave vectors in YBa$_2$Cu$_3$O$_{6+x}$ and
La$_{2-x}$Ba$_x$CuO$_4$, the maximum ordering strength is peaked at the hole
concentration of 1/8 in both cases. There are also possible connections with
the quantum oscillations that have been detected about the same hole
concentration but at high magnetic fields. Resolving these relationships
remains a research challenge.",1412.1011v1
2014-12-12,Dual parametrization of generalized parton distributions in two equivalent representations,"The dual parametrization and the Mellin-Barnes integral approach represent
two frameworks for handling the double partial wave expansion of generalized
parton distributions (GPDs) in the conformal partial waves and in the
$t$-channel ${\rm SO}(3)$ partial waves. Within the dual parametrization
framework, GPDs are represented as integral convolutions of forward-like
functions whose Mellin moments generate the conformal moments of GPDs. The
Mellin-Barnes integral approach is based on the analytic continuation of the
GPD conformal moments to the complex values of the conformal spin. GPDs are
then represented as the Mellin-Barnes-type integrals in the complex conformal
spin plane. In this paper we explicitly show the equivalence of these two
independently developed GPD representations. Furthermore, we clarify the
notions of the $J=0$ fixed pole and the $D$-form factor. We also provide some
insight into GPD modeling and map the phenomenologically successful
Kumeri\v{c}ki-M\""uller GPD model to the dual parametrization framework by
presenting the set of the corresponding forward-like functions. We also build
up the reparametrization procedure allowing to recast the double distribution
representation of GPDs in the Mellin-Barnes integral framework and present the
explicit formula for mapping double distributions into the space of double
partial wave amplitudes with complex conformal spin.",1412.4165v1
2015-03-14,Use of gravitational waves to probe the formation channels of compact binaries,"With the discovery of the binary black hole coalescence GW150914, the era of
gravitational-wave astrophysics has started. Gravitational-wave signals emitted
by compact binary coalescences will be detected in large number by LIGO and
Virgo in the coming months and years. Much about compact binaries is still
uncertain, including some key details about their formation channels. The two
scenarios which are typically considered, common envelope evolution and
dynamical capture, result in different distributions for the orientation of the
black hole spins. In particular, common envelope evolution is expected to be
highly efficient in aligning spins with the orbital angular momentum. In this
paper we simulate catalogs of gravitational-wave signals in which a given
fraction of events comes from common envelop evolution, and has spins nearly
aligned with the orbital angular momentum. We show how the fraction of aligned
systems can be accurately estimated using Bayesian parameter estimation, with 1
$\sigma$ uncertainties of the order of 10% after 100-200 sources are detected.",1503.04307v2
2016-02-24,Eddy-current effects on ferromagnetic resonance: Spin wave excitations and microwave screening effects,"We investigate how controlling induced eddy currents in thin film
ferromagnet-normal metal (FM/NM) structures can be used to tailor the local
microwave (MW) fields in ferromagnetic resonance (FMR) experiments. The MW
fields produced by eddy currents will in general have a relative phase shift
with respect to the applied MW field which depends on the sample geometry. The
induced fields can thus partially compensate the applied MW field, effectively
screening the FM in selected parts of the sample. The highly localized fields
produced by eddy currents enable the excitation of spin wave modes with
non-zero wave vectors, in contrast to the uniform k = 0 mode normally excited
in FMR experiments. We find that the orientation of the applied MW field is one
of the key parameters controlling the eddy-current effects. The induced
currents are maximized when the applied MW field is oriented perpendicular to
the sample plane. Increasing the magnitude of the eddy currents results in a
stronger induced MW field, enabling a more effective screening of the applied
MW field as well as an enhanced excitation of spin wave modes. This
investigation underlines that eddy currents can be used to control the
magnitude and phase of the local MW fields in thin film structures.",1602.07463v2
2017-12-12,Microwave to optical photon conversion by means of travelling-wave magnons in YIG films,"In this work we study theoretically the efficiency of a travelling magnon
based microwave to optical photon converter for applications in Quantum
Information (QI). The converter employs an epitaxially grown yttrium iron
garnet (YIG) film as the medium for propagation of travelling magnons (spin
waves). The conversion is achieved through coupling of magnons to guided
optical modes of the film. The total microwave to optical photon conversion
efficiency is found to be larger than in a similar process employing a YIG
sphere by at least 4 orders of magnitude. By creating an optical resonator of a
large length from the film (such that the traveling magnon decays before
forming a standing wave over the resonator length) one will be able to further
increase the efficiency by several orders of magnitude, potentially reaching a
value similar to achieved with opto-mechanical resonators. Also, as a spin-off
result, it is shown that isolation of more that 20 dB with direct insertion
losses about 5 dBm can be achieved with YIG film based microwave isolators for
applications in Quantum Information.
  An important advantage of the suggested concept of the QI devices based on
travelling spin waves is a perfectly planar geometry and a possibility of
implementing a the device as a hybrid opto-microwave chip.",1712.04304v2
2018-05-07,Quantum depletion and superfluid density of a supersolid in Raman spin-orbit coupled Bose gases,"We theoretically investigate a three-dimensional weakly interacting Bose gas
with one-dimensional Raman-type spin-orbit coupling at zero temperature. By
employing an improved ansatz, including high-order harmonics in the stripe
phase, we show that the critical transition from the stripe to the plane-wave
phases is shifted to a relatively larger Rabi frequency compared to the
prediction by previous work [Li $\textit{et al.}$, Phys. Rev. Lett.
$\textbf{108}$, 225301 (2012)] using a first-order stripe ansatz. We also
determine the quantum depletion and superfluid density over a large range of
Rabi frequency in different phases. The depletion exhibits an intriguing
behavior with a discontinuous jump at the transition between the stripe and
plane-wave phases, and a maximum at the transition between the plane-wave and
zero-momentum phases. The superfluid density is derived through a phase-twist
method. In the plane-wave and zero-momentum phases, it is significantly
suppressed along the spin-orbit-coupling direction and vanishes at the
transition, consistent with a recent work [Zhang $\textit{et al.}$, Phys. Rev.
A $\textbf{94}$, 033635 (2016)], while in the stripe phase, it smoothly
decreases with increasing Rabi frequency. Our predictions would be useful for
further theoretical and experimental studies of the exotic supersolid stripe
phase.",1805.02320v2
2018-06-20,Anchoring and Binning the Coordinate Bethe Ansatz,"The Coordinate Bethe Ansatz (CBA) expresses, as a sum over permutations, the
matrix element of an XXX Heisenberg spin chain Hamiltonian eigenstate with a
state with fixed spins. These matrix elements comprise the wave functions of
the Hamiltonian eigenstates. However, as the complexity of the sum grows
rapidly with the length N of the spin chain, the exact wave function in the
continuum limit is too cumbersome to be exploited. In this note we provide an
approximation to the CBA whose complexity does not directly depend upon N. This
consists of two steps. First, we add an anchor to the argument of the
exponential in the CBA. The anchor is a permutation-dependent integral multiple
of 2 pi. Once anchored, the distribution of these arguments simplifies,
becoming approximately Gaussian. The wave function is given by the Fourier
transform of this distribution and so the calculation of the wave function
reduces to the calculation of the moments of the distribution. Second, we
parametrize the permutation group as a map between integers and we bin these
maps. The calculation of the moments then reduces to a combinatorial exercise
on the partitioning into bins. As an example we consider the matrix element
between the classical and quantum ground states.",1806.07768v2
2020-08-31,Extreme mass ratio inspirals on the equatorial plane in the adiabatic order,"We compute gravitational waves from inspiraling stellar-mass compact objects
on the equatorial plane of a massive spinning black hole (BH). Our inspiral
orbits are computed by taking into account the adiabatic change of orbital
parameters due to gravitational radiation in the lowest order in mass ratio. We
employ an interpolation method to compute the adiabatic change at arbitrary
points inside the region of orbital parameter space computed in advance. Using
the obtained inspiral orbits and associated gravitational waves, we compute
power spectra of gravitational waves and the signal-to-noise ratio (SNR) for
several values of the BH spin, the masses of the binary, and the initial
orbital eccentricity during a hypothetical three-yrs LISA observation before
final plunge. We find that (i) the SNR increases as the BH spin and the mass of
the compact object increase for the BH mass $M \agt 10^6M_\odot$, (ii) the SNR
has a maximum for $M \approx 10^6M_\odot$, and (iii) the SNR increases as the
initial eccentricity increases for $M=10^6M_\odot$. We also show that
incorporating the contribution from the higher multipole modes of gravitational
waves is crucial for enhancing the detection rate.",2008.13554v2
2016-11-18,"Description of the $^{11}$Li$(p,d){^{10}}$Li transfer reaction using structure overlaps from a full three-body model","Recent data on the differential angular distribution for the transfer
reaction $^{11}$Li(p,d)$^{10}$Li at $E/A=5.7$ MeV in inverse kinematics are
analysed within the DWBA reaction framework, using the overlap functions
calculated within a three-body model of $^{11}$Li. The weight of the different
$^{10}$Li configurations in the system's ground state is obtained from the
structure calculations unambiguously. The effect of the $^{9}$Li spin in the
calculated observables is also investigated. We find that, although all the
considered models succeed in reproducing the shape of the data, the magnitude
is very sensitive to the content of $p_{1/2}$ wave in the $^{11}$Li
ground-state wave function. Among the considered models, the best agreement
with the data is obtained when the $^{11}$Li ground state contains a $\sim$31\%
of $p_{1/2}$ wave in the $n$-$^9$Li subsystem. Although this model takes into
account explicitly the splitting of the $1^+$ and $2^+$ resonances due to the
coupling of the $p_{1/2}$ wave to the $3/2^-$ spin of the core, a similar
degree of agreement can be achieved with a model in which the $^{9}$Li spin is
ignored, provided that it contains a similar p-wave content.",1611.06000v3
2016-11-19,"Frustrated Heisenberg Antiferromagnets on Cubic Lattices: Magnetic Structures, Exchange Gaps, and Non-Conventional Critical Behaviour","We have studied the Heisenberg antiferromagnets characterized by the magnetic
structures with the periods being two times larger than the lattice period. We
have considered all the types of the Bravais lattices (simple cubic, bcc and
fcc) and divided all these antiferromagnets into 7 classes i.e. 3 plus 4
classes denoted with symbols A and B correspondingly. The order parameter
characterizing the degeneracies of the magnetic structures is an ordinary Neel
vector for A classes and so-called 4-complex for B classes. We have taken into
account the fluctuation corrections for these states within the spin-wave and
large-N expansions ($N$ is the number of spin components). Below the Neel
temperature $T_{\rm{N}}$ quantum and thermal fluctuations lift the degeneracy
making simple one-wave vector collinear structure preferable for all the
classes. A satellite of this effect is opening of the exchange gaps at certain
wave vectors in the spin wave spectrum (there is an analogous effect for the
nonuniform static transverse susceptibility). However, as the temperature
approaches $T_{\rm{N}}$, the exchange gaps are closing. We have calculated the
critical indices $\eta$ and $\nu$ to order of $1/N$ and found that they differ
for A and B classes.",1611.06305v2
2019-04-29,Experimental Realization of a Passive GHz Frequency-Division Demultiplexer for Magnonic Logic Networks,"The emerging field of magnonics employs spin waves and their quanta, magnons,
to implement wave-based computing on the micro- and nanoscale. Multi-frequency
magnon networks would allow for parallel data processing within single logic
elements whereas this is not the case with conventional transistor-based
electronic logic. However, a lack of experimentally proven solutions to
efficiently combine and separate magnons of different frequencies has impeded
the intensive use of this concept. In this Letter, the experimental realization
of a spin-wave demultiplexer enabling frequency-dependent separation of
magnonic signals in the GHz range is demonstrated. The device is based on
two-dimensional magnon transport in the form of spin-wave beams in unpatterned
magnetic films. The intrinsic frequency-dependence of the beam direction is
exploited to realize a passive functioning obviating an external control and
additional power consumption. This approach paves the way to magnonic
multiplexing circuits enabling simultaneous information transport and
processing.",1904.12744v2
2019-10-05,Geometric control of collective spontaneous emission,"Dipole spin-wave states of atomic ensembles with wave vector ${\bf
k}(\omega)$ mismatched from the dispersion relation of light are difficult to
access by far-field excitation but may support rich phenomena beyond the
traditional phase-matched scenario in quantum optics. We propose and
demonstrate an optical technique to efficiently access these states. In
particular, subnanosecond laser pulses shaped by a home-developed wideband
modulation method are applied to shift the spin wave in ${\bf k}$ space with
state-dependent geometric phase patterning, in an error-resilient fashion and
on timescales much faster than spontaneous emission. We verify this control
through the redirection, switch off, and recall of collectively enhanced
emission from a $^{87}$Rb gas with $\sim 75\%$ single-step efficiency. Our work
represents a first step toward efficient control of electric dipole spin waves
for studying many-body dissipative dynamics of excited gases, as well as for
numerous quantum optical applications.",1910.02289v4
2020-10-29,Deep Learning Ensemble for Real-time Gravitational Wave Detection of Spinning Binary Black Hole Mergers,"We introduce the use of deep learning ensembles for real-time, gravitational
wave detection of spinning binary black hole mergers. This analysis consists of
training independent neural networks that simultaneously process strain data
from multiple detectors. The output of these networks is then combined and
processed to identify significant noise triggers. We have applied this
methodology in O2 and O3 data finding that deep learning ensembles clearly
identify binary black hole mergers in open source data available at the
Gravitational-Wave Open Science Center. We have also benchmarked the
performance of this new methodology by processing 200 hours of open source,
advanced LIGO noise from August 2017. Our findings indicate that our approach
identifies real gravitational wave sources in advanced LIGO data with a false
positive rate of 1 misclassification for every 2.7 days of searched data. A
follow up of these misclassifications identified them as glitches. Our deep
learning ensemble represents the first class of neural network classifiers that
are trained with millions of modeled waveforms that describe quasi-circular,
spinning, non-precessing, binary black hole mergers. Once fully trained, our
deep learning ensemble processes advanced LIGO strain data faster than
real-time using 4 NVIDIA V100 GPUs.",2010.15845v1
2020-12-02,"Fast, flexible, and accurate evaluation of gravitational-wave Malmquist bias with machine learning","Many astronomical surveys are limited by the brightness of the sources, and
gravitational-wave searches are no exception. The detectability of
gravitational waves from merging binaries is affected by the mass and spin of
the constituent compact objects. To perform unbiased inference on the
distribution of compact binaries, it is necessary to account for this selection
effect, which is known as Malmquist bias. Since systematic error from selection
effects grows with the number of events, it will be increasingly important over
the coming years to accurately estimate the observational selection function
for gravitational-wave astronomy. We employ density estimation methods to
accurately and efficiently compute the compact binary coalescence selection
function. We introduce a simple pre-processing method, which significantly
reduces the complexity of the required machine learning models. We demonstrate
that our method has smaller statistical errors at comparable computational cost
than the method currently most widely used allowing us to probe narrower
distributions of spin magnitudes. The currently used method leaves $10-50\%$ of
the interesting black hole spin models inaccessible; our new method can probe
$>99\%$ of the models and has a lower uncertainty for $>80\%$ of the models.",2012.01317v3
2021-06-17,Gravitational-wave constraints on the GWTC-2 events by measuring the tidal deformability and the spin-induced quadrupole moment,"Gravitational waves from compact binary coalescences provide a unique
laboratory to test properties of compact objects. As alternatives to the
ordinary black holes in general relativity, various exotic compact objects have
been proposed. Some of them have largely different values of the tidal
deformability and spin-induced quadrupole moment from those of black holes, and
their binaries could be distinguished from the binary black hole by using
gravitational waves emitted during their inspiral regime, excluding the highly
model-dependent merger and ringdown regimes. We reanalyze gravitational waves
from low-mass merger events in the GWTC-2, detected by the Advanced LIGO and
Advanced Virgo. Focusing on the influence of tidal deformability and
spin-induced quadrupole moment in the inspiral waveform, we provide
model-independent constraints on deviations from the standard binary black hole
case. We find that all events that we have analyzed are consistent with the
waveform of the binary black hole in general relativity. Bayesian model
selection shows that the hypothesis that the binary is composed of exotic
compact objects is disfavored by all events.",2106.09193v4
2021-11-23,Resonant dynamics of skyrmion lattices in thin film multilayers: Localised modes and spin wave emission,"The spectral signatures of magnetic skyrmions under microwave field
excitation are of fundamental interest and can be an asset for high frequency
applications. These topological solitons can be tailored in multilayered thin
films, but the experimental observation of their spin wave dynamics remains
elusive, in particular due to large damping. Here, we study Pt/FeCoB/AlO$_x$
multilayers hosting dense and robust skyrmion lattices at room temperature with
Gilbert damping of $\sim 0.02$. We use magnetic force microscopy to
characterise their static magnetic phases and broadband ferromagnetic resonance
to probe their high frequency response. Micromagnetic simulations reproduce the
experiments with accuracy and allow us to identify distinct resonant modes
detected in the skyrmion lattice phase. Low ($<$ 2 GHz) and intermediate
frequency ($2-8$ GHz) modes involve excitations localised to skyrmion edges in
conjunction with precession of the uniform background magnetisation, while a
high frequency ($>$ 12 GHz) mode corresponds to in-phase skyrmion core
precession emitting spin waves into uniform background with wavelengths in the
50--80 nm range commensurate with the lattice structure. These findings could
be instrumental in the investigation of room temperature wave scattering and
the implementation of novel microwave processing schemes in reconfigurable
arrays of solitons.",2111.11797v2
2022-04-29,"Temperature-sensitive spin-wave nonreciprocity induced by interlayer dipolar coupling in ferromagnet/X (X=paramagnet, superconductor) hybrid systems","Spin-wave (SW) spectra have theoretically been studied in a thin film of a
ferromagnet (FM) on a substrate from a paramagnet (PM) (an FM above the
critical temperature) or from superconductor (SC). A spin wave propagating in
the FM induces the dynamic magnetization and superconducting current in the
underlying PM and SC, respectively, which affect the SW propagation by their
magnetic fields. As a result of this interaction, the SW spectrum becomes
nonreciprocal to depend on the sign of the SW wave vector q. We show that the
nonreciprocal contribution to the SW spectra in FM/PM and FM/SC systems is
given by the frequency shift of
{\Delta}{\omega}(q)={\omega}(q)-{\omega}(-q)=a(T)({\tau}{\cdot}q) with
{\tau}=(n{\times}M) being the toroidal magnetic moment, M the FM magnetization,
n the unit vector normal to the FM/PM(SC) interface, and a(T) the
temperature-dependent constant of a dipole nature, whose sign depends on the
substrate type. As the {\Delta}{\omega}(T) dependence is strong at temperatures
T close to the critical temperature Tc for the FM-PM or normal metal-SC
transition, one gets a possibility to control the frequency SW nonreciprocity
with temperature variation near Tc. The dipolar mechanism we propose for SW
frequency nonreciprocity is promising for introducing this property of SW
propagation into functional devices.",2204.13938v1
2023-05-10,Wave function and spatial structure of polarons in an antiferromagnetic bilayer,"Adding a dopant to an antiferromagnetic spin background disturbs the magnetic
order and leads to the formation of a quasiparticle coined the magnetic
polaron, which plays a central role in understanding strongly correlated
materials. Recently, remarkably detailed insights into the spatial properties
of such polarons have been obtained using atoms in optical lattices. Motivated
by this we develop a nonperturbative scheme for calculating the wave function
of the magnetic polaron in a bilayer antiferromagnet using the self-consistent
Born approximation. The scheme includes an infinite number of spin waves, which
is crucial for an accurate description of the most interesting regime of strong
correlations. Utilizing the developed wave function, we explore the spatial
structure of the polaron dressing cloud consisting of magnetically frustrated
spins surrounding the hole. Mimicking the nonmonotonic behavior of the
antiferromagnetic order, we find that the dressing cloud first decreases and
then increases in size with increasing interlayer hopping. The increase
reflects the decrease in the magnetic order as a quantum phase transition to a
disordered state is approached for large interlayer hopping. We, furthermore,
find that the symmetry of the ground state dressing cloud changes as the
interlayer coupling increases. Our results should be experimentally accessible
using quantum simulation with optical lattices.",2305.05980v2
2023-12-28,"Microscopic Mechanism of Pair-, Charge- and Spin-Density-Wave Instabilities in Interacting D-Dimensional Fermi Liquids","We present an analytic theory unraveling the microscopic mechanism of
instabilities within interacting $D$-dimensional Fermi liquid. Our model
consists of a $D$-dimensional electron gas subject to an instantaneous
electron-electron interaction of a finite range exceeding the average
inter-particle distance. Pair, charge and spin susceptibilities are evaluated
via the one-loop renormalization group theory and via the bosonization
approach, giving identical results. In case of a repulsive interaction, we
identify an intrinsic Fermi liquid instability towards insulating spin/charge
density wave order when the interaction coupling strength reaches a universal
critical value. If both electron and hole pockets of the same size are present,
the ground state is an excitonic insulator at arbitrarily small repulsive
interaction. If the interaction is attractive, the ground state is a singlet
non-BCS superconductor with a uniform condensate. In case if both electron and
hole Fermi surfaces are present, we predict an instability towards the
inter-pocket pair-density-wave ordering at the critical coupling. This
prediction lends strong theoretical support to the pair-density-wave scenario
of superconductivity in cuprate materials. Due to its simple and universal
nature, presented microscopic mechanism of intrinsic instabilities of
interacting $D$-dimensional Fermi liquids constitutes a solid theoretical
ground for understanding quantum phase transitions in a variety of quantum
materials, from ultraclean semiconductor quantum wells to high-temperature
superconductors.",2312.17208v2
1993-07-19,Evolution of Magnetic Properties of Lightly Doped Copper Oxides,"We study how doping destroys the AF order in the layered cuprates within the
framework of the charge--transfer insulator concept. We use the criterion of
stability of the AF background to show that the stability problem is one of the
main issues in any correspondence between results for the $t-J$ model and, say,
the three--band model for the lightly--doped layered oxides. Provided a
phenomenological conduction band is chosen to satisfy the criterion of
stability, a detailed picture of how dopants influence the spin wave spectrum
at $T=0$ is presented. The critical concentration $x_c$ for the destruction of
the AF long range order is due to the Cherenkov effect when the Fermi velocity
first exceeds the spin wave velocity. We then discuss the overall spectrum of
spin excitations and find that the spin wave attenuation for $x < x_c$, $T=0$
due to Landau damping appears in the range of magnon momenta $k(x) = 2 m^* s
\pm \alpha \sqrt{x}$. We also argue that in the presence of superconductivity,
the Cherenkov effect is eliminated due to the gap in the spectrum. This may
restore the role of the AF fluctuations as the main source of dissipation at
the lowest temperatures.",9307040v1
1995-05-17,Magnetic Behavior of the Cuprate Superconductors,"I review recent work on magnetic dynamics of the high temperature
superconductors using a model that combines two weakly interacting species of
low-energy excitations: the antiferromagnetic spin waves which carry spin-1 and
no charge, and Fermi-liquid-like quasiparticles which carry spin-1/2 and charge
e. The model allows conversion of spin waves into electron-hole pairs; however,
the low-energy spin waves are not collective modes of the quasiparticles near
the Fermi surface, but rather are a separate branch of the low-energy spectrum.
With certain experimentally justified assumptions, this theory is remarkably
universal: the dependence on the detailed microscopic Hamiltonian and on doping
can be absorbed into several experimentally measurable parameters. The z=1
theory of the insulators and z=2 theory of the overdoped materials, are both
reproduced as limiting cases of the theory described here, which predicts that
the underdoped materials remain in z=1 universality class at sufficiently high
temperature. This theory provides a framework for understanding both the
experimental results and microscopic calculations, and in particular yields a
possible explanation of the spin gap phenomenon. I also discuss some of the
important unresolved issues.",9505070v1
1995-11-06,Theory of a single Oxygen hole propagating in Sr_2CuO_2Cl_2: the spin of the quasiparticles in CuO_2 planes,"Recent photoemission experiments have measured E vs. k for a single hole
propa- gating in antiferromagnetically aligned Sr_2CuO_2Cl_2. Comparisons with
(i) the t - t' - J model, for which the carrier is a spinless vacancy, and (ii)
a strong-coupling version of the three-band Emery model, for which the carrier
is a S = 1/2 hole moving on the Oxygen sublattice, have demonstrated that if
one wishes to describe the quasiparticle throughout the entire first Brillouin
zone the three-band model is superior. Here we present a new variational wave
func- tion for a single Oxygen hole in the three-band model: it utilizes a
classical representation of the antiferromagnetically ordered Cu-spin
background but explicitly includes the quantum fluctuations of the lowest
energy doublet of the Cu-O-Cu bond containing the Oxygen hole. We find that
this wave function leads to a quasiparticle dispersion for physical exchange
and hopping parame- ters that is in excellent agreement with the measured ARPES
data. We also obtain the average spin of the Oxygen hole, and thus deduce that
this spin is only quenched to zero at certain wave vectors, helping to explain
the inadequacy of the t - t' - J model to match the experimentally observed
disper- sion relation everywhere in the first Brillouin zone.",9511030v1
2008-05-22,Intrinsic and non-local Gilbert damping in polycrystalline nickel studied by Ti:Sapphire laser fs spectroscopy,"The use of femtosecond laser pulses generated by a Ti:Sapphire laser system
allows us to gain an insight into the magnetization dynamics on time scales
from sub-picosecond up to 1 ns directly in the time domain. This experimental
technique is used to excite a polycrystalline nickel (Ni) film optically and
probe the dynamics afterwards. Different spin wave modes (the Kittel mode,
perpendicular standing spin-wave modes (PSSW) and dipolar spin-wave modes
(Damon-Eshbach modes)) are identified as the Ni thickness is increased. The
Kittel mode allows determination of the Gilbert damping parameter alpha
extracted from the magnetization relaxation time tau_alpha. The non-local
damping by spin currents emitted into a non-magnetic metallic layer of vanadium
(V), palladium (Pd) and the rare earth dysprosium (Dy) are studied for
wedge-shaped Ni films 1 nm-30 nm. The damping parameter increases from
alpha=0.045 intrinsic for nickel to alpha>0.10 for the heavy materials, such as
Pd and Dy, for the thinnest Ni films below 10 nm thickness. Also, for the
thinnest reference Ni film thickness, an increased magnetic damping below 4 nm
is observed. The origin of this increase is discussed within the framework of
line broadening by locally different precessional frequencies within the laser
spot region.",0805.3495v1
2009-03-03,Effects of the magnetic orderings on the dynamical conductivity: optical investigations of EuFe$_2$As$_2$ single crystals,"The magnetic, transport and optical properties of EuFe$_2$As$_2$ single
crystals have been investigated parallel and perpendicular to the $ab$-plane.
The anisotropy $\rho_c/\rho_{ab}\approx 8$ depends only slightly on
temperature. In both orientations, the spin-density wave transition at $T_{\rm
SDW}=189$ K shows up as a considerable increase in the dc resistivity.
Susceptibility measurements evidence the magnetic order of the Eu$^{2+}$
moments at $T_N=19$ K with little influence on the electronic transport taking
place in the FeAs layers. Polarization-dependent infrared spectroscopy reveals
strongly anisotropic optical properties and yields a carrier density of only
$4.2\times 10^{21} {\rm cm}^{-3}$ and a bandmass of $m_b=2m_0$. A sizeable
Drude contribution is present at all temperatures and narrows upon cooling.
Below $T_{\rm SDW}$, the spin-density-wave gap develops in the in-plane optical
conductivity; no appreciable change is detected for the perpendicular
polarization. Modifications in the phonon features are associated with changes
of the electronic properties at $T_{\rm SDW}$. The extended Drude analysis
yields a linear behavior of the frequency-dependent scattering rate below
$T_{\rm SDW}$, indicating an interaction between the charge carriers and spin
fluctuations in the spin-density-wave state.",0903.0575v1
2011-07-13,Controlling the pair momentum of the FFLO state in a 3D Fermi gas through a 1D periodic potential,"The question whether a spin-imbalanced Fermi gas can accommodate the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state has been the subject of intense
study. This state, in which Cooper pairs obtain a nonzero momentum, has
hitherto eluded experimental observation. Recently, we demonstrated that the
FFLO state can be stabilized in a 3D Fermi gas, by adding a 1D periodic
potential. Until now it was assumed that the FFLO wave vector always lies
parallel to this periodic potential (FFLO-P). In this contribution we show
that, surprisingly, the FFLO wave vector can also lie skewed with respect to
the potential (FFLO-S). Starting from the partition sum, the saddle-point free
energy of the system is derived within the path-integral formalism. Minimizing
this free energy allows us to study the different competing ground states of
the system. To qualitatively understand the underlying pairing mechanism, we
visualize the Fermi surfaces of the spin up and spin down particles. From this
visualization, we find that tilting the FFLO wave vector with respect to the
direction of the periodic potential, can result in a larger overlap between the
pairing bands of both spin species. This skewed FFLO state can provide an
additional experimental signature for observing FFLO superfluidity in a 3D
Fermi gas.",1107.2613v2
2011-09-27,Dispersion and damping of zone-boundary magnons in the noncentrosymmetric superconductor CePt3Si,"Inelastic neutron scattering (INS) is employed to study damped spin-wave
excitations in the noncentrosymmetric heavy-fermion superconductor CePt3Si
along the antiferromagnetic Brillouin-zone boundary in the low-temperature
magnetically ordered state. Measurements along the (1/2 1/2 L) and (H H 1/2-H)
reciprocal-space directions reveal deviations in the spin-wave dispersion from
the previously reported model. Broad asymmetric shape of the peaks in energy
signifies strong spin-wave damping by interactions with the particle-hole
continuum. Their energy width exhibits no evident anomalies as a function of
momentum along the (1/2 1/2 L) direction, which could be attributed to
Fermi-surface nesting effects, implying the absence of pronounced commensurate
nesting vectors at the magnetic zone boundary. In agreement with a previous
study, we find no signatures of the superconducting transition in the magnetic
excitation spectrum, such as a magnetic resonant mode or a superconducting spin
gap, either at the magnetic ordering wavevector (0 0 1/2) or at the zone
boundary. However, the low superconducting transition temperature in this
material still leaves the possibility of such features being weak and therefore
hidden below the incoherent background at energies ~0.1 meV, precluding their
detection by INS.",1109.5784v1
2011-10-10,"Ab-initio calculation of effective exchange interactions, spin waves, and Curie temperature in L2_1- and L1_2-type local moment ferromagnets","Employing first-principles electronic structure calculations in conjunction
with the frozen-magnon method we study the effective exchange interactions and
spin waves in local moment ferromagnets. As prototypes we have chosen three
L2$_1$-type full Heusler alloys Cu$_2$MnAl, Ni$_2$MnSn and Pd$_2$MnSn, and the
L1$_2$-type XPt$_3$ compounds with X= V, Cr and Mn. We have also included
CoPt$_3$ which is a usual ferromagnet. In all compounds due to the large
spatial separation ($\sim 4$ \AA) of the magnetic transition metal atoms, the
3\textit{d} states belonging to different atoms overlap weakly and as a
consequence the exchange coupling is indirect, mediated by the \textit{sp}
electrons. Calculated effective exchange parameters are long range and show
RKKY-type oscillations. The spin-wave dispersion curves are in reasonable
agreement with available experimental data. Using the calculated exchange
parameters we have estimated the Curie temperatures within both the mean-field
and the random-phase approximations. In local moment ferromagents deviations of
the estimated Curie temperature with respect to the available experimental data
occur when the ground-state electronic structure calculations overestimate the
values of the spin magnetic moments as in VPt$_3$.",1110.2156v1
2012-02-19,Spin fluctuations and superconductivity in powders of Fe_1+xTe_0.7Se_0.3 as a function of interstitial iron concentration,"Using neutron inelastic scattering, we investigate the role of interstitial
iron on the low-energy spin fluctuations in powder samples of
Fe_{1+x}Te_{0.7}Se_{0.3}. We demonstrate how combining the principle of
detailed balance along with measurements at several temperatures allows us to
subtract both temperature-independent and phonon backgrounds from S(Q,\omega)
to obtain purely magnetic scattering. For small values of interstitial iron
(x=0.009(3)), the sample is superconducting (T_{c}=14 K) and displays a spin
gap of 7 meV peaked in momentum at wave vector q_{0}=(\pi,\pi) consistent with
single crystal results. On populating the interstitial iron sites, the
superconducting volume fraction decreases and we observe a filling in of the
low-energy magnetic fluctuations and a decrease of the characteristic wave
vector of the magnetic fluctuations. For large concentrations of interstitial
iron (x=0.048(2)) where the superconducting volume fraction is minimal, we
observe the presence of gapless spin fluctuations at a wave vector of
q_{0}=(\pi,0). We estimate the absolute total moment for the various samples
and find that the amount of interstitial iron does not change the total
magnetic spectral weight significantly, but rather has the effect of shifting
the spectral weight in Q and energy. These results show that the
superconducting and magnetic properties can be tuned by doping small amounts of
iron and are suggestive that interstitial iron concentration is also a
controlling dopant in the Fe_{1+x}Te_{1-y}Se_{y} phase diagram in addition to
the Te/Se ratio.",1202.4152v1
2014-03-11,A Local Description of Dark Energy in Terms of Classical Two-Component Massive Spin-One Uncharged Fields on Spacetimes with Torsionful Affinities,"It is assumed that the two-component spinor formalisms for curved spacetimes
that are endowed with torsionful affine connexions can supply a local
description of dark energy in terms of classical massive spin-one uncharged
fields. The relevant wave functions are related to torsional affine potentials
which bear invariance under the action of the generalized Weyl gauge group.
Such potentials are thus taken to carry an observable character and emerge from
contracted spin affinities whose patterns are chosen in a suitable way. New
covariant calculational techniques are then developed towards deriving
explicitly the wave equations that supposedly control the propagation in
spacetime of the dark energy background. What immediately comes out of this
derivation is a presumably natural display of interactions between the fields
and both spin torsion and curvatures. The physical properties that may arise
directly from the solutions to the wave equations are not brought out.",1403.2984v9
2014-11-05,Spin Wave Neuroanalog of von Neumann's Microwave Computer,"Frequency and phase of neural activity play important roles in the behaving
brain. The emerging understanding of these roles has been informed by the
design of analog devices that have been important to neuroscience, among them
the neuroanalog computer developed by O. Schmitt in the 1930's. In the 1950's,
J. von Neumann, in a search for high performance computing using microwaves,
invented a logic machine based on similar devices, that can perform logic
functions including binary arithmetic. Described here is a novel embodiment of
his machine using nano-magnetics. The embodiment is based on properties of
ferromagnetic thin films that are governed by a nonlinear Schrodinger equation
for magnetization in a film. Electrical currents through point contacts on a
film create spin torque nano oscillators (STNO) that define the oscillator
elements of the system. These oscillators may communicate through directed
graphs of electrical connections or by radiation in the form of spin waves. It
is shown here how to construct a logic machine using STNO, that this machine
can perform several computations simultaneously using multiplexing of inputs,
that this system can evaluate iterated logic functions, and that spin waves can
communicate frequency, phase and binary information. Neural tissue and the
Schmitt, von Neumann and STNO devices share a common bifurcation structure,
although these systems operate on vastly different space and time scales. This
suggests that neural circuits may be capable of computational functionality
described here.",1411.1401v1
2015-06-19,Rapid gravitational wave parameter estimation with a single spin: Systematic uncertainties in parameter estimation with the SpinTaylorF2 approximation,"Reliable low-latency gravitational wave parameter estimation is essential to
target limited electromagnetic followup facilities toward astrophysically
interesting and electromagnetically relevant sources of gravitational waves. In
this study, we examine the tradeoff between speed and accuracy. Specifically,
we estimate the astrophysical relevance of systematic errors in the posterior
parameter distributions derived using a fast-but-approximate waveform model,
SpinTaylorF2 (STF2), in parameter estimation with lalinference_mcmc. Though
efficient, the STF2 approximation to compact binary inspiral employs
approximate kinematics (e.g., a single spin) and an approximate waveform (e.g.,
frequency domain versus time domain). More broadly, using a large
astrophysically-motivated population of generic compact binary merger signals,
we report on the effectualness and limitations of this single-spin
approximation as a method to infer parameters of generic compact binary
sources. For most low-mass compact binary sources, we find that the STF2
approximation estimates compact binary parameters with biases comparable to
systematic uncertainties in the waveform. We illustrate by example the effect
these systematic errors have on posterior probabilities most relevant to
low-latency electromagnetic followup: whether the secondary is has a mass
consistent with a neutron star; whether the masses, spins, and orbit are
consistent with that neutron star's tidal disruption; and whether the binary's
angular momentum axis is oriented along the line of sight.",1506.06032v1
2015-12-21,On the accuracy and precision of numerical waveforms: Effect of waveform extraction methodology,"We present a new set of 95 numerical relativity simulations of non-precessing
binary black holes (BBHs). The simulations sample comprehensively both
black-hole spins up to spin magnitude of 0.9, and cover mass ratios 1 to 3. The
simulations cover on average 24 inspiral orbits, plus merger and ringdown, with
low initial orbital eccentricities $e<10^{-4}$. A subset of the simulations
extends the coverage of non-spinning BBHs up to mass ratio $q=10$.
Gravitational waveforms at asymptotic infinity are computed with two
independent techniques, extrapolation, and Cauchy characteristic extraction. An
error analysis based on noise-weighted inner products is performed. We find
that numerical truncation error, error due to gravitational wave extraction,
and errors due to the finite length of the numerical waveforms are of similar
magnitude, with gravitational wave extraction errors somewhat dominating at
noise-weighted mismatches of $\sim 3\times 10^{-4}$. This set of waveforms will
serve to validate and improve aligned-spin waveform models for gravitational
wave science.",1512.06800v2
2016-04-05,Homodyne-detected ferromagnetic resonance of in-plane magnetized nano-contacts: composite spin wave resonances and their excitation mechanism,"This work provides a detailed investigation of the measured in-plane
field-swept homodyne-detected ferromagnetic resonance (FMR) spectra of an
extended Co/Cu/NiFe pseudo spin valve stack using a nanocontact (NC) geometry.
The magnetodynamics are generated by a pulse-modulated microwave current and
the resulting rectified dc mixing voltage, which appears across the NC at
resonance, is detected using a lock-in amplifier. Most notably, we find that
the measured spectra of the NiFe layer are composite in nature and highly
asymmetric, consistent with the broadband excitation of multiple modes.
Additionally, the data must be fit with two Lorentzian functions in order to
extract a reasonable value for the Gilbert damping of the NiFe. Aided by
micromagnetic simulations, we conclude that (i) for in-plane fields the rf
Oersted field in the vicinity of the NC plays the dominant role in generating
the observed spectra, (ii) in addition to the FMR mode, exchange dominated spin
waves are also generated, and (iii) the NC diameter sets the mean wavevector of
the exchange dominated spin wave, in good agreement with the dispersion
relation.",1604.01389v1
2018-05-02,Pseudo-Goldstone gaps and order-by-quantum-disorder in frustrated magnets,"In systems with competing interactions, continuous degeneracies can appear
which are accidental, in that they are not related to any symmetry of the
Hamiltonian. Accordingly, the pseudo-Goldstone modes associated with these
degeneracies are also unprotected. Indeed, through a process known as
""order-by-quantum-disorder"", quantum zero-point fluctuations can lift the
degeneracy and induce a gap for these modes. We show that this gap can be
exactly computed at leading order in $1/S$ in spin-wave theory from the mean
curvature of the classical and quantum zero-point energies - without the need
to consider any spin-wave interactions. We confirm this equivalence through
direct calculations of the spin-wave spectrum to $O(1/S^2)$ in a wide variety
of theoretically and experimentally relevant quantum spin models. We prove this
equivalence through the use of an exact sum rule that provides the required
mixing of different orders of $1/S$. Finally, we discuss some implications for
several leading order-by-quantum-disorder candidate materials, clarifying the
expected pseudo-Goldstone gap sizes in Er$_2$Ti$_2$O$_7$ and
Ca$_3$Fe$_2$Ge$_3$O$_{12}$.",1805.00947v2
2018-07-15,K-matrix formulation of two-particle scattering in a wave guide in the presence of one-dimensional spin-orbit coupling,"The creation of artificial gauge fields in neutral ultracold atom systems has
opened the possibility to study the effects of spin-orbit coupling terms in
clean environments. This work considers the multi-channel scattering properties
of two atoms confined by a wave guide in the presence of spin-orbit coupling
terms within a K-matrix scattering framework. The tunability of resonances,
induced by the interplay of the external wave guide geometry, the interactions,
and the spin-orbit coupling terms, is demonstrated. Our results for the
K-matrix elements as well as partial and total reflection coefficients for two
identical fermions interacting through a finite-range interaction potential in
the singlet channel only are compared with those obtained for a strictly
one-dimensional effective low- energy Hamiltonian, which uses the effective
coupling constant derived in Zhang et al. [Scientific Reports 4, 1 (2014)] and
Zhang et al. [Phys. Rev. A 88, 053605 (2013)] as input. In the regime where the
effective Hamiltonian is applicable, good agreement is obtained, provided the
energy- dependence of the coupling constant is accounted for. Our approach
naturally describes the energy regime in which the bands associated with
excited transverse modes lie below a subset of the bands associated with the
lowest transverse modes. The threshold behavior is discussed and scattering
observables are linked to bound state properties.",1807.05564v2
2018-10-02,The Discrete Noise of Magnons,"Magnonics is a rapidly developing subfield of spintronics, which deals with
devices and circuits that utilize spin currents carried by magnons - quanta of
spin waves. Magnon current, i.e. spin waves, can be used for information
processing, sensing, and other applications. A possibility of using the
amplitude and phase of magnons for sending signals via electrical insulators
creates conditions for avoiding Ohmic losses, and achieving ultra-low power
dissipation. Most of the envisioned magnonic logic devices are based on spin
wave interference, where the minimum energy per operation is limited by the
noise level. The sensitivity and selectivity of magnonic sensors is also
limited by the low frequency noise. However, the fundamental question ""do
magnons make noise?"" has not been answered yet. It is not known how noisy
magnonic devices are compared to their electronic counterparts. Here we show
that the low-frequency noise of magnonic devices is dominated by the random
telegraph signal noise rather than 1/f noise - a striking contrast to
electronic devices (f is a frequency). We found that the noise level of surface
magnons depends strongly on the power level, increasing sharply at the on-set
of nonlinear dissipation. The presence of the random telegraph signal noise
indicates that the current fluctuations involve random discrete macro events.
We anticipate that our results will help in developing the next generation of
magnonic devices for information processing and sensing.",1810.01500v1
2014-06-23,Propulsion of a domain wall in an antiferromagnet by magnons,"We analyze the dynamics of a domain wall in an easy-axis antiferromagnet
driven by circularly polarized magnons. Magnons pass through a stationary
domain wall without reflection and thus exert no force on it. However, they
reverse their spin upon transmission, thereby transferring two quanta of
angular momentum to the domain wall and causing it to precess. A precessing
domain wall partially reflects magnons back to the source. The reflection of
spin waves creates a previously identified reactive force. We point out a
second mechanism of propulsion, which we term redshift: magnons passing through
a precessing domain wall lower their frequency by twice the angular velocity of
the domain wall; the concomitant reduction of magnons' linear momentum
indicates momentum transfer to the domain wall. We solve the equations of
motion for spin waves in the background of a uniformly precessing domain wall
with the aid of supersymmetric quantum mechanics and compute the net force and
torque applied by magnons to the domain wall. Redshift is the dominant
mechanism of propulsion at low spin-wave intensities; reflection dominates at
higher intensities. We derive a set of coupled algebraic equations to determine
the linear velocity and angular frequency of the domain wall in a steady state.
The theory agrees well with numerical micromagnetic simulations.",1406.6051v1
2018-12-29,Dzyaloshinskii-Moriya Interaction in Magneto-Ferroelectric Superlattices: Spin Waves and Skyrmions,"We study in this paper effects of Dzyaloshinskii-Moriya (DM) magnetoelectric
coupling between ferroelectric and magnetic layers in a superlattice formed by
alternate magnetic and ferroelectric films.Magnetic films are films of simple
cubic lattice with Heisenberg spins interacting with each other via an exchange
$J$ and a DM interaction with the ferroelectric interface. Electrical
polarizations of $\pm{1}$ are assigned at simple cubic lattice sites in the
ferroelectric films.We determine the ground-state (GS) spin configuration in
the magnetic film. In zero field, the GS is periodically non collinear and in
an applied field $\mathbf H$ perpendicular to the layers, it shows the
existence of skyrmions at the interface. Using the Green's function method we
study the spin waves (SW) excited in a monolayer and also in a bilayer
sandwiched between ferroelectric films, in zero field. We show that the DM
interaction strongly affects the long-wave length SW mode. We calculate also
the magnetization at low temperature $T$. We use next Monte Carlo simulations
to calculate various physical quantities at finite temperatures such as the
critical temperature, the layer magnetization and the layer polarization, as
functions of the magnetoelectric DM coupling and the applied magnetic
field.Phase transition to the disordered phase is studied in detail.",1812.11344v1
2019-02-21,Effects of the removal of Ta capping layer on the magnetization dynamics of Permalloy thin films,"We have investigated the spin wave dynamics of Permalloy (Py) thin films with
and without a Ta capping layer for varying Py thickness (15 nm, 20 nm and 30
nm) using all optical time-resolved magneto-optical Kerr effect measurements.
XPS measurements confirm the oxidation of the originally-prepared samples and
also that the removal of the Ta capping layer is achievable by a few sputtering
cycles. The magnetic field strength dependencies of the spin wave modes with
the variation of the Py film thickness for the samples are studied. We observe
that the presence of the Ta capping layer reduces the precessional frequencies
of the samples while the samples without a Ta capping layer enhance the role of
Py thickness. We also observe that the decay time of spin waves is highly
dependent on the top layer of the samples. The decay time increases with
increasing Py thicknesses for Ta/Py/Ta samples implying that the enhancement of
decay time is caused by the Ta/Py/Ta interfaces. Whereas, for Ta/Py samples the
decay time decreases with increasing Py thickness. The results of this work
extend the knowledge on the magnetization dynamics of Py thin films giving
information on how to resume and even enhance the spin mobility after a
deleterious oxidation process. This can open new scenarios on the building
process and on the maintenance of fast magnetic switching devices.",1902.07832v1
2019-03-27,Theory of standing spin waves in finite-size chiral spin soliton lattice,"We present a theory of standing spin wave (SSW) in a monoaxial chiral
helimagnet. Motivated by experimental findings on the magnetic field-dependence
of the resonance frequency in thin films of Cr${}$Nb$_{3} $S${}_{6}$[Goncalves
et al., Phys. Rev. B95, 104415 (2017)], we examine the SSW over a chiral
soliton lattice (CSL) excited by an ac magnetic field applied parallel and
perpendicular to the chiral axis. For this purpose, we generalize Kittel-Pincus
theories of the SSW in ferromagnetic thin films to the case of non-collinear
helimagnet with the surface end spins which are softly pinned by an anisotropy
field. Consequently, we found there appear two types of modes. One is a Pincus
mode which is composed of a long-period Bloch wave and a short-period ripple
originated from the periodic structure of the CSL. Another is a short-period
Kittel ripple excited by space-periodic perturbation which exists only in the
case where the ac field is applied perpendicular the chiral axis. We
demonstrate that the existence of the Pincus mode and the Kittel ripple is
consistent with experimentally found double resonance profile.",1903.11675v1
2020-03-10,Gravitational spin Hall effect of light,"The propagation of electromagnetic waves in vacuum is often described within
the geometrical optics approximation, which predicts that wave rays follow null
geodesics. However, this model is valid only in the limit of infinitely high
frequencies. At large but finite frequencies, diffraction can still be
negligible, but the ray dynamics becomes affected by the evolution of the wave
polarization. Hence, rays can deviate from null geodesics, which is known as
the gravitational spin Hall effect of light. In the literature, this effect has
been calculated ad hoc for a number of special cases, but no general
description has been proposed. Here, we present a covariant
Wentzel-Kramers-Brillouin analysis from first principles for the propagation of
light in arbitrary curved spacetimes. We obtain polarization-dependent ray
equations describing the gravitational spin Hall effect of light. We also
present numerical examples of polarization-dependent ray dynamics in the
Schwarzschild spacetime, and the magnitude of the effect is briefly discussed.
The analysis reported here is analogous to that of the spin Hall effect of
light in inhomogeneous media, which has been experimentally verified.",2003.04553v2
2020-03-18,A cold atom temporally multiplexed quantum memory with cavity-enhanced noise suppression,"Future quantum repeater architectures, capable of efficiently distributing
information encoded in quantum states of light over large distances, will
benefit from multiplexed photonic quantum memories. In this work we demonstrate
a temporally multiplexed quantum repeater node in a laser-cooled cloud of
$^{87}$Rb atoms. We employ the DLCZ protocol where pairs of photons and single
collective spin excitations (so called spin waves) are created in several
temporal modes using a train of write pulses. To make the spin waves created in
different temporal modes distinguishable and enable selective readout, we
control the dephasing and rephasing of the spin waves by a magnetic field
gradient, which induces a controlled reversible inhomogeneous broadening of the
involved atomic hyperfine levels. We demonstrate that by embedding the atomic
ensemble inside a low finesse optical cavity, the additional noise generated in
multi-mode operation is strongly suppressed. By employing feed forward readout,
we demonstrate distinguishable retrieval of up to 10 temporal modes. For each
mode, we prove non-classical correlations between the first and second photon.
Furthermore, an enhancement in rates of correlated photon pairs is observed as
we increase the number of temporal modes stored in the memory. The reported
capability is a key element of a quantum repeater architecture based on
multiplexed quantum memories.",2003.08418v1
2020-03-26,Gravitational waves and mass ejecta from binary neutron star mergers: Effect of the spin orientation,"We continue our study of the binary neutron star parameter space by
investigating the effect of the spin orientation on the dynamics, gravitational
wave emission, and mass ejection during the binary neutron star coalescence. We
simulate seven different configurations using multiple resolutions to allow a
reasonable error assessment. Due to the particular choice of the setups, five
configurations show precession effects, from which two show a precession
(""wobbling"") of the orbital plane, while three show a ""bobbing"" motion, i.e.,
the orbital angular momentum does not precess, while the orbital plane moves
along the orbital angular momentum axis. Considering the ejection of mass, we
find that precessing systems can have an anisotropic mass ejection, which could
lead to a final remnant kick of $\sim 40 \rm km/s$ for the studied systems.
Furthermore, for the chosen configurations, antialigned spins lead to larger
mass ejecta than aligned spins, so that brighter electromagnetic counterparts
could be expected for these configurations. Finally, we compare our simulations
with the precessing, tidal waveform approximant IMRPhenomPv2_NRTidalv2 and find
good agreement between the approximant and our numerical relativity waveforms
with phase differences below 1.2 rad accumulated over the last $\sim$ 16
gravitational wave cycles.",2003.11901v3
2017-04-06,Polarizations of Gravitational Waves in Horndeski Theory,"We analyze the polarization content of gravitational waves in Horndeski
theory. Besides the familiar plus and cross polarizations in Einstein's General
Relativity, there is one more polarization state which is the mixture of the
transverse breathing and longitudinal polarizations.The additional mode is
excited by the massive scalar field. In the massless limit, the longitudinal
polarization disappears, while the breathing one persists. The upper bound on
the graviton mass severely constrains the amplitude of the longitudinal
polarization, which makes its detection highly unlikely by the ground-based or
space-borne interferometers in the near future. However, pulsar timing arrays
might be able to detect the polarization excited by the massive scalar field.
Since additional polarization states appear in alternative theories of gravity,
the measurement of the polarizations of gravitational waves can be used to
probe the nature of gravity. In addition to the plus and cross states, the
detection of the breathing polarization means that gravitation is mediated by
massless spin 2 and spin 0 fields, and the detection of both the breathing and
longitudinal states means that gravitation is propagated by the massless spin 2
and massive spin 0 fields.",1704.01899v4
2019-04-09,Effect of exchange interaction on electronic instabilities in the honeycomb lattice: A functional renormalization group study,"The impact of local and nonlocal density-density interactions on the
electronic instabilities in the honeycomb lattice is widely investigated. Some
early studies proposed the emergence of interaction-induced topologically
nontrivial phases, but recently, it was denied in several works including
renormalization group calculations with refined momentum resolution. We use the
truncated unity functional renormalization group to study the many-body
instabilities of electrons on the half-filled honeycomb lattice, focusing on
the effect of the exchange interaction. We show that varying the
next-nearest-neighbor repulsion and nearest-neighbor exchange integral can lead
to diverse ordered phases, namely, the quantum spin Hall, the spin-Kekul\'e,
and some spin- and charge-density-wave phases. The quantum spin Hall phase can
be induced by a combination of the ferromagnetic exchange and pair hopping
interactions. Another exotic phase, the spin-Kekul\'e phase, develops in a very
small region of the parameter space considered. We encounter the
three-sublattice charge-density-wave phase in a large part of the parameter
space. It is replaced by the incommensurate charge density wave when increasing
the exchange integral. In order to reduce the computational effort, we derive
the explicit symmetry relations for the bosonic propagators of the effective
interaction and propose a linear-response-based approach for identifying the
form factor of order parameter. Their efficiencies are confirmed by numerical
calculations in our work.",1904.04482v2
2019-10-14,Spectroscopy and decay properties of bottomonium using instanton induced potential from QCD vacuum,"Ground state and radial excitation mass spectra of bottomonium states are
computed using the Instanton Induced $q \bar{q}$ Potential obtained from
Instanton Liquid Model for QCD vacuum. The Schrodinger equation is solved for
two body problem using variational method. Hyperfine interactions are
incorporated to remove the degeneracy between spin singlet and spin triplet
states of $S$ wave masses. Spin-orbit and tensor interactions through one gluon
exchange has been added to the spin average masses of P and D wave states. The
vector decay constants and pseudoscalar decay constants are also estimated
using the Van Royan Weiskopff formula within non-relativistic limit. The
di-leptonic, di-gamma, di-gluon decays of the bottomonium states are predicted
without and with QCD corrections up to the lowest order using numerical values
of the wave function at origin. Tri-gluon decays of respective $S$, $P$ and $D$
states are also studied. Other annihilation decay channels of bottomonium
states into $\gamma gg$ , $\gamma \gamma \gamma$ , $q\bar{q} + g $ are also
computed. The radiative transitions of first order like electric dipole
transitions (E1) and magnetic dipole transitions (M1) are estimated. Our
estimations of the mass spectra and decay properties for bottomonium found to
be in excellent agreement with the average experimental values reported by
particle data group.",1910.06111v1
2020-06-04,Heisenberg Exchange and Dzyaloshinskii-Moriya Interaction in Ultrathin CoFeB Single and Multilayers,"We present results of the analysis of Brillouin Light Scattering (BLS)
measurements of spin waves performed on ultrathin single and multirepeat CoFeB
layers with adjacent heavy metal layers. From a detailed study of the spin-wave
dispersion relation, we independently extract the Heisenberg exchange
interaction (also referred to as symmetric exchange interaction), the
Dzyaloshinskii-Moriya interaction (DMI, also referred to as antisymmetric
exchange interaction), and the anisotropy field. We find a large DMI in CoFeB
thin films adjacent to a Pt layer and nearly vanishing DMI for CoFeB films
adjacent to a W layer. Furthermore, the residual influence of the dipolar
interaction on the dispersion relation and on the evaluation of the Heisenberg
exchange parameter is demonstrated. In addition, an experimental analysis of
the DMI on the spin-wave lifetime is presented. All these parameters play a
crucial role in designing skyrmionic or spin-orbitronic devices.",2006.02690v1
2022-03-22,Spin precession in the gravity wave analogue black hole spacetime,"It was predicted that the spin precession frequency of a stationary gyroscope
shows various anomalies in the strong gravity regime if its orbit shrinks, and
eventually its precession frequency becomes arbitrarily high very close to the
horizon of a rotating black hole. Considering the gravity waves of a flowing
fluid with vortex in a shallow basin, that acts as a rotating analogue black
hole, one can observe the predicted strong gravity effect on the spin
precession in the laboratory. Attaching a thread with the buoyant particles and
anchored it to the bottom of the fluid container with a short length of
miniature chain, one can construct a simple local test gyroscope to measure the
spin precession frequency in the vicinity of the gravity wave analogue black
hole. The thread acts as the axis of the gyroscope. By regulating the orbital
frequency of the test gyroscope, one can also be able to measure the strong
gravity Lense-Thirring effect and geodetic/de-Sitter effect with this
experimental set-up, as the special cases. For example, to measure the
Lense-Thirring effect, the length of the miniature chain can be set to zero, so
that the gyroscope becomes static. One can also measure the geodetic precession
with this system by orbiting the test gyroscope in the so-called Keplerian
frequency around the non-rotating analogue black hole that can be constructed
by making the rotation of the fluid/vortex negligible compared to its radial
velocity.",2203.11459v1
2022-09-22,Detection of a Pair Density Wave State in UTe$_2$,"Spin-triplet topological superconductors should exhibit many unprecedented
electronic properties including fractionalized electronic states relevant to
quantum information processing. Although UTe$_2$ may embody such bulk
topological superconductivity, its superconductive order-parameter
$\Delta(\mathbf{k})$ remains unknown. Many diverse forms for
$\Delta(\mathbf{k})$ are physically possible in such heavy fermion materials.
Moreover, intertwined density waves of spin (SDW), charge (CDW) and pairs (PDW)
may interpose, with the latter state exhibiting spatially modulating
superconductive order-parameter $\Delta(\mathbf{r})$, electron pair density and
pairing energy-gap. Hence, the newly discovered CDW state in UTe$_2$ motivates
the prospect that a PDW state may exist in this material. To search for it, we
visualize the pairing energy-gap with $\mu$$eV$-scale energy-resolution using
superconductive STM tips. We detect three PDWs, each with peak-peak gap
modulations circa 10 $\mu$$eV$ and at incommensurate wavevectors
$\mathbf{P}_{i=1,2,3}$ that are indistinguishable from the wavevectors
$\mathbf{Q}_{i=1,2,3}$ of the prevenient CDW. Concurrent visualization of the
UTe$_2$ superconductive PDWs and the non-superconductive CDWs reveals that
every $\mathbf{P}_i$ : $\mathbf{Q}_i$ pair exhibits a relative phase
$\delta\phi \approx \pi$. From these observations, and given UTe$_2$ as a
spin-triplet superconductor, this PDW state should be a spin-triplet pair
density wave. While such states do exist in superfluid $^{3}$He, for
superconductors they are unprecedented.",2209.10859v3
2023-01-15,Metastable supersolid in spin-orbit coupled Bose-Einstein condensates,"Supersolid is a special state of matter with both superfluid properties and
spontaneous modulation of particle density. In this paper, we focus on the
supersolid stripe phase realized in a spin-orbit coupled Bose-Einstein
condensate and explore the properties of a class of metastable supersolids. In
particular, we study a one-dimensional supersolid whose characteristic wave
number $k$ (magnitude of wave vector) deviates from $k_{m}$, i.e., the one at
ground state. In other words, the period of density modulation is shorter or
longer than the one at ground state. We find that this class of supersolids can
still be stable if their wave numbers fall in the range $k_{c1}<k<k_{c2}$, with
two thresholds $k_{c1}$ and $k_{c2}$. Stripes with $k$ outside this range
suffer from dynamical instability with complex Bogoliubov excitation spectrum
at long wavelength. Experimentally, these stripes with $k$ away from $k_m$ are
accessible by exciting the longitudinal spin dipole mode, resulting in temporal
oscillation of stripe period as well as $k$. Within the mean-field
Gross-Pitaevskii theory, we numerically confirm that for a large enough
amplitude of spin dipole oscillation, the stripe states become unstable through
breaking periodicity, in qualitative agreement with the existence of thresholds
of $k$ for stable stripes. Our work extends the concept of supersolid and
uncovers a new class of metastable supersolids to explore.",2301.06094v1
2023-12-01,A continuous-wave and pulsed X-band electron spin resonance spectrometer operating in ultra-high vacuum for the study of low dimensional spin ensembles,"We report the development of a continuous-wave and pulsed X-band electron
spin resonance (ESR) spectrometer for the study of spins on ordered surfaces
down to cryogenic temperatures. The spectrometer operates in ultra-high vacuum
and utilizes a half-wavelength microstrip line resonator realized using
epitaxially grown copper films on single crystal Al$_2$O$_3$ substrates. The
one-dimensional microstrip line resonator exhibits a quality factor of more
than 200 at room temperature, close to the upper limit determined by radiation
losses. The surface characterizations of the copper strip of the resonator by
atomic force microscope, low-energy electron diffraction, and scanning
tunneling microscope show that the surface is atomically clean, flat, and
single crystalline. Measuring the ESR spectrum at 15 K from a few nm thick
molecular film of YPc$_2$, we find a continuous-wave ESR sensitivity of $2.6
\cdot 10^{11}~\text{spins}/\text{G} \cdot \text{Hz}^{1/2}$ indicating that a
signal-to-noise ratio of $3.9~\text{G} \cdot \text{Hz}^{1/2}$ is expected from
a monolayer of YPc$_2$ molecules. Advanced pulsed ESR experimental capabilities
including dynamical decoupling and electron-nuclear double resonance are
demonstrated using free radicals diluted in a glassy matrix.",2312.00459v2
2024-01-05,Spin-1/2 kagome Heisenberg antiferromagnet: Machine learning discovery of the spinon pair density wave ground state,"Spin-1/2 kagome antiferromagnet (AFM) is one of the most studied models in
frustrated magnetism since it is a promising candidate to host exotic spin
liquid states. However, despite numerous studies using both analytical and
numerical approaches, the nature of the ground state and low-energy excitations
in this system remain elusive. This is related to the difficulty in determining
the spin gap in various calculations. We present the results of our
investigation of the Kagome AFM using the recently developed group equivariant
convolutional neural networks - an advanced machine learning technique for
studying strongly frustrated models. The approach, combined with variational
Monte Carlo, introduces significant improvement of the achievable results
accuracy in comparison with approaches based on other neural network
architectures that lack generalization quality for frustrated spin systems.
Contrary to the results obtained previously with various methods, that
predicted Z_2 or U(1) Dirac spin liquid states, our results strongly indicate
that the ground state of the kagome lattice antiferromagnet is a spinon pair
density wave that does not break time-reversal symmetry or any of the lattice
symmetries. The found state appears due to the spinon Cooper pairing
instability close to two Dirac points in the spinon energy spectrum and
resembles the pair density wave state studied previously in the context of
underdoped cuprate superconductors in connection with the pseudogap phase. The
state has significantly lower energy than the lowest energy states found by the
SU(2) symmetric density matrix renormalization group calculations and other
methods.",2401.02866v1
2002-09-09,A note on gravitational wave lensing,"In a recent paper [Ruffa] it was proposed that the massive black hole at the
Galactic center may act as a gravitational lens focusing gravitational wave
energy to the Earth. Considering the gravitational wave signal emitted by
galactic spinning pulsars, an enhancement in the gravitational wave intensity
by a factor of a few thousand is found. For galactic and extra-galactic sources
the intensity enhancement can be as high as 4,000 and 17,000, respectively. In
this note we consider the probability of significant signal enhancement from
galactic and extra-galactic pulsars by the proposed mechanism and find that it
is actually negligible. The lensing effect due to a possible companion object
(a star or the galactic center black hole) of the gravitational wave source is
also investigated in the framework of the classical microlensing theory.",0209149v1
2005-05-11,"Hydrodynamical stellar models including rotation, internal gravity waves and atomic diffusion. I. Formalism and tests on Pop I dwarfs","In this paper, we develop a formalism in order to incorporate the
contribution of internal gravity waves to the transport of angular momentum and
chemicals over long time-scales in stars. We show that the development of a
double peaked shear layer acts as a filter for waves, and how the asymmetry of
this filter produces momentum extraction from the core when it is rotating
faster than the surface. Using only this filtered flux, it is possible to
follow the contribution of internal waves over long (evolutionary) time-scales.
  We then present the evolution of the internal rotation profile using this
formalism for stars which are spun down via magnetic torquing. We show that
waves tend to slow down the core, creating a ""slow"" front that may then
propagate from the core to the surface. Further spin down of the surface leads
to the formation of a new front. Finally we show how this momentum transport
reduces rotational mixing in a 1.2Msun, Z=0.02 model, leading to a surface
lithium abundance in agreement with observations in the Hyades.",0505229v1
1993-07-19,Comparison of Variational Approaches for the Exactly Solvable 1/r-Hubbard Chain,"We study Hartree-Fock, Gutzwiller, Baeriswyl, and combined
Gutzwiller-Baeriswyl wave functions for the exactly solvable one-dimensional
$1/r$-Hubbard model. We find that none of these variational wave functions is
able to correctly reproduce the physics of the metal-to-insulator transition
which occurs in the model for half-filled bands when the interaction strength
equals the bandwidth. The many-particle problem to calculate the variational
ground state energy for the Baeriswyl and combined Gutzwiller-Baeriswyl wave
function is exactly solved for the~$1/r$-Hubbard model. The latter wave
function becomes exact both for small and large interaction strength, but it
incorrectly predicts the metal-to-insulator transition to happen at infinitely
strong interactions. We conclude that neither Hartree-Fock nor Jastrow-type
wave functions yield reliable predictions on zero temperature phase transitions
in low-dimensional, i.e., charge-spin separated systems.",9307036v1
1997-12-19,On solitary waves in classical anisotropic Heisenberg chains with generalized boundary conditions,"We examine solitary waves in classical Heisenberg chains with an uniaxial
anisotropy and a parallel magnetic field in a continuum approach. The boundary
conditions commonly used are generalized to nonlinear spin wave states, which
themselves turn out to be stable only for an anisotropy of the easy-plane type.
In this case we obtain two different branches of one-soliton solutions which
can be mapped onto each other by a formal time inversion. Moreover, they show
some remarkable similarity to dark solitons of the Nonlinear Schr\""odinger
equation. Numerical simulations for the discrete Heisenberg chain show that
these solitary waves are highly, but not absolutely stable under interaction
with linear excitations and as well under scattering with each other. The
possible significance of these solitary waves in a phenomenological theory of
one-dimensional magnets is briefly addressed.",9712241v1
2005-09-26,Correlation Effect on the Two-Dimensional Peierls Phase,"The effect of the electron-electron (e-e) interaction on the Peierls lattice
distortions due to the electron-lattice (e-l) interaction is studied in the
two-dimensional Peierls-Hubbard model, treating the fluctuation of e-e
interaction around the Hartree-Fock solution within the 2nd order perturbation
theory. In our previous work, using the Hartree-Fock approximation, we found
multimode Peierls lattice distortions with wave vectors, the nesting vector
$\mathbf{Q}$ and those parallel to it, are not affected by an e-e interaction
if it is weak compared with the e-l coupling. The phase transition between the
BOW (bond order wave) with multimode lattice distortions and the SDW (spin
density wave) with the wave vector $\mathbf{Q}$ behaves as the 1st order
transition. The property of the multimode BOW is found to change drastically
when we consider the fluctuation effect within the 2nd order perturbation
theory. The Fourier components of the multimode BOW increase gradually as the
e-e interaction parameter is increased. Especially the Fourier component with
the wave vector equal to the smallest reciprocal lattice vector in the presence
of the multimode BOW is most strongly affected by the fluctuation effect.",0509634v1
2006-03-30,Unconventional Density Waves in Organic Conductors and in Superconductors,"Unconventional density waves (UDW) are one of the ground states in metallic
crystalline solids and have been speculated already in 1968. However, more
focused studies on UDW started only recently, perhaps after the identification
of the low temperature phase in alpha-(BEDT-TTF)_2KHg(SCN)_4 as unconventional
charge density wave (UCDW) in 2002. More recently, the metallic phase of
Bechgaard salts (TMTSF)_2X with X=PF_6 and ReO_4 under both pressure and
magnetic field appears to be unconventional spin density wave (USDW). The
pseudogap regime of high T_c superconductors LSCO, YBCO, Bi2212 and the one in
CeCoIn_5 belong to d-wave density waves (d-DW).
  In these identifications, the angular dependent magnetoresistance and the
giant Nernst effect have played the crucial role. These are the simplest
manifestations of the Landau quantization of quasiparticle energy in UDW in the
presence of magnetic field (the Nersesyan effect). Also we speculate that UDW
will be most likely found in alpha$-(BEDT-TTF)_2I_3, alpha-(BEDT-TTF)_2I_2Br,
kappa-(BEDT-TTF)_2Cu(NCS)_2, kappa-(BEDT-TTF)_2Cu(CN)_2Br,
lambda-(BEDT)_2GaCl_4 and in many other organic compounds.",0603806v1
1999-05-08,The Detection of Gravitational Waves with LIGO,"Gravitational wave emission is expected to arise from a variety of
astrophysical phenomena. A new generation of detectors with sensitivity
consistent with expectation from such sources is being developed. The Laser
Interferometer Gravitational-Wave Observatory (LIGO), one of these ambitious
undertakings, is being developed by a Caltech-MIT collaboration. It consists of
two widely separated interferometers, which will be used in coincidence to
search for sources from compact binary systems, spinning neutron stars,
supernovae and other astrophysical or cosmological phenomena that emit
gravitational waves. The construction of LIGO is well underway and preparations
are being made for the commissioning phase. In this lecture, I review the
underlying physics of gravitational waves, review possible astrophysical and
cosmological sources and discuss the LIGO interferometer status and plans.",9905026v1
2000-12-04,The gravitational wave symphony of the Universe,"The new millennium will see the upcoming of several ground-based
interferometric gravitational wave antennas. Within the next decade a
space-based antenna may also begin to observe the distant Universe. These
gravitational wave detectors will together operate as a network taking data
continuously for several years, watching the transient and continuous phenomena
occurring in the deep cores of astronomical objects and dense environs of the
early Universe where gravity was extremely strong and highly non-linear. The
network will listen to the waves from rapidly spinning non-axisymmetric neutron
stars, normal modes of black holes, binary black hole inspiral and merger,
phase transitions in the early Universe, quantum fluctuations resulting in a
characteristic background in the early Universe. The gravitational wave
antennas will open a new window to observe the dark Universe unreachable via
other channels of astronomical observations.",0012014v2
2001-11-02,Gravitational waves from rotating neutron stars,"In this review we examine the dynamics and gravitational wave detectability
of rotating strained neutron stars. The discussion is divided into two halves:
triaxial stars, and precessing stars. We summarise recent work on how crustal
strains and magnetic fields can sustain triaxiality, and suggest that Magnus
forces connected with pinned superfluid vortices might contribute to
deformation also. The conclusions that could be drawn following the successful
gravitational wave detection of a triaxial star are discussed, and areas
requiring further study identified. The latest ideas regarding free precession
are then outlined, and the recent suggestion of Middleditch et al (2000a,b)
that the remnant of SN1987A contains a freely precessing star, spinning-down by
gravitational wave energy loss, is examined critically. We describe what we
would learn about neutron stars should the gravitational wave detectors prove
this hypothesis to be correct.",0111007v1
2002-03-21,Teukolsky Master Equation: De Rham wave equation for the gravitational and electromagnetic fields in vacuum,"A new version of the Teukolksy Master Equation, describing any massless field
of different spin $s=1/2,1,3/2,2$ in the Kerr black hole, is presented here in
the form of a wave equation containing additional curvature terms. These
results suggest a relation between curvature perturbation theory in general
relativity and the exact wave equations satisfied by the Weyl and the Maxwell
tensors, known in the literature as the de Rham-Lichnerowicz Laplacian
equations. We discuss these Laplacians both in the Newman-Penrose formalism and
in the Geroch-Held-Penrose variant for an arbitrary vacuum spacetime.
Perturbative expansion of these wave equations results in a recursive scheme
valid for higher orders. This approach, apart from the obvious implications for
the gravitational and electromagnetic wave propagation on a curved spacetime,
explains and extends the results in the literature for perturbative analysis by
clarifying their true origins in the exact theory.",0203069v1
2003-06-23,Mode coupling in the nonlinear response of black holes,"We study the properties of the outgoing gravitational wave produced when a
non-spinning black hole is excited by an ingoing gravitational wave.
Simulations using a numerical code for solving Einstein's equations allow the
study to be extended from the linearized approximation, where the system is
treated as a perturbed Schwarzschild black hole, to the fully nonlinear regime.
Several nonlinear features are found which bear importance to the data analysis
of gravitational waves. When compared to the results obtained in the linearized
approximation, we observe large phase shifts, a stronger than linear generation
of gravitational wave output and considerable generation of radiation in
polarization states which are not found in the linearized approximation. In
terms of a spherical harmonic decomposition, the nonlinear properties of the
harmonic amplitudes have simple scaling properties which offer an economical
way to catalog the details of the waves produced in such black hole processes.",0306098v2
2006-01-13,Helicity-Rotation-Gravity Coupling for Gravitational Waves,"The consequences of spin-rotation-gravity coupling are worked out for linear
gravitational waves. The coupling of helicity of the wave with the rotation of
a gravitational-wave antenna is investigated and the resulting modifications in
the Doppler effect and aberration are pointed out for incident high-frequency
gravitational radiation. Extending these results to the case of a
gravitomagnetic field via the gravitational Larmor theorem, the rotation of
linear polarization of gravitational radiation propagating in the field of a
rotating mass is studied. It is shown that in this case the linear polarization
state rotates by twice the Skrotskii angle as a consequence of the spin-2
character of linear gravitational waves.",0601054v2
2000-04-12,Entropy generation and inflation in wave collision induced pre-big-bang cosmology,"We study inflation and entropy generation in a recently proposed pre-big-bang
model universe produced in a collision of gravitational and dilaton waves. It
is shown that enough inflation occurs provided the incoming waves are
sufficiently weak. We also find that entropy in this model is dynamically
generated as the result of the nonlinear interaction of the incoming waves,
before the universe enters the phase of dilaton driven inflation. In
particular, we give the scaling of the entropy produced in the collision in
terms of the focusing lengths of the incoming waves.",0004094v2
2002-08-05,Type IIA String and Matrix String on PP-wave,"We study type IIA string theories on the pp-waves with 24 supercharges. The
type IIA pp-wave backgrounds are derived from the maximally supersymmetric
pp-wave solution in eleven dimensions through the toroidal compactification on
the spatial isometry directions. The associated actions of type IIA strings are
obtained by using these metrics and other background fields of the type IIA
supergravities on the one hand. On the other hand, we derive these theories
from D=11 supermembrane on the pp-wave via double dimensional reduction for the
spatial isometry directions. The resulting actions agree with those of type IIA
strings obtained in the study of the supergravities. Also, the action of the
matrix string is written down. Moreover, the quantization of closed and open
strings is discussed. In particular, we study Dp-branes allowed in one of the
type IIA theories.",0208029v4
2002-07-10,Description of 8Be as Deformed Gas-like Two-Alpha-Paricle States,"In order to study non-zero spin excitations of the recently proposed
alpha-cluster condensation in the self-conjugate 4n nuclei, spatial deformation
is introduced into the model wave function of the alpha-cluster condensate. The
rotational band states of 8Be are investigated as a first step of a test case
for the study of the deformation of the alpha-cluster condensate. Calculations
reproduce well the binding energy of the 0+ ground state and also the
excitation energy of the 2+ state. Our 0+ wave function is found to be almost
exactly equal to the 0+ wave function obtained by the generator coordinate
method using Brink's 2 alpha wave function. The study shows that both the 0+
ground and 2+ excited states can be considered as having a gas-like (i.e.
weakly bound) 2 alpha-cluster structure. As for the 0+ ground state, the change
of the wave function, due to the introduction of the deformation, is found to
be very small.",0207022v1
2005-06-28,Einstein's Photon Concept Quantified by the Bohr Model of the Photon,"The photon is modeled as a monochromatic solution of Maxwell's equations
confined as a soliton wave by the principle of causality of special relativity.
The soliton travels rectilinearly at the speed of light. The solution can
represent any of the known polarization (spin) states of the photon. For
circularly polarized states the soliton's envelope is a circular ellipsoid
whose length is the observed wavelength ($\lambda$), and whose diameter is
$\lambda/\pi$; this envelope contains the electromagnetic energy of the wave
($h\nu=hc/\lambda$). The predicted size and shape is confirmed by experimental
measurements: of the sub-picosecond time delay of the photo-electric effect, of
the attenuation of undiffracted transmission through slits narrower than the
soliton's diameter of $\lambda/\pi$, and by the threshold intensity required
for the onset of multiphoton absorption in focussed laser beams. Inside the
envelope the wave's amplitude increases linearly with the radial distance from
the axis of propagation, being zero on the axis. Outside the envelope the wave
is evanescent with an amplitude that decreases inversely with the radial
distance from the axis. The evanescent wave is responsible for the observed
double-slit interference phenomenon.",0506231v1
2006-03-08,Wave-Particle Duality and the Coherent Quantum Domain Picture,"It is proposed that the paradox of wave-particle duality in quantum mechanics
may be resolved using a physical picture analogous to magnetic domains. Within
this picture, a quantum particle represents a coherent region of a quantum wave
with characteristic total energy, momentum, and spin. The dynamics of such a
state are described by the usual linear quantum wave equations. But the
coherence is maintained by a nonlinear self-interaction term that is evident
only during transitions from one quantum state to another. This is analogous to
the self-organizing property of domains in a ferromagnetic material, in which a
single domain may appear as a stable macro-particle, but with rapid transitions
between different domain configurations also possible. For the quantum case,
this implies that the ""collapse of the wave function"" is a real dynamical
physical process that occurs continuously in spacetime. This picture may also
permit the resolution of apparent paradoxes associated with quantum measurement
and entangled states.",0603070v1
2007-05-22,Photon wave mechanics and position eigenvectors,"One and two photon wave functions are derived by projecting the quantum state
vector onto simultaneous eigenvectors of the number operator and a recently
constructed photon position operator [Phys. Rev A 59, 954 (1999)] that couples
spin and orbital angular momentum. While only the Landau-Peierls wave function
defines a positive definite photon density, a similarity transformation to a
biorthogonal field-potential pair of positive frequency solutions of Maxwell's
equations preserves eigenvalues and expectation values. We show that this real
space description of photons is compatible with all of the usual rules of
quantum mechanics and provides a framework for understanding the relationships
amongst different forms of the photon wave function in the literature. It also
gives a quantum picture of the optical angular momentum of beams that applies
to both one photon and coherent states. According to the rules of qunatum
mechanics, this wave function gives the probability to count a photon at any
position in space.",0705.3196v1
2007-06-03,Coherent Lattice Vibrations in Superconductors,"A recent analysis by Kadin has noted that the superconducting wavefunction
within the BCS theory may be represented in real-space as a spherical
electronic orbital (on the scale of the coherence length) coupled to a
standing-wave lattice vibration. This lattice vibration, effectively a bound
phonon, has wavevector 2kf and a near-resonant frequency (on the order of the
Debye frequency) that maximizes the attractive electrostatic interaction energy
with the electronic orbital. The present paper extends this picture to a
coherent standing-wave pattern of electron and phonon waves that traverses the
entire superconductor on the macroscopic scale. These parallel planes form a
diffractive waveguide for electron waves traveling parallel to the planes,
permitting lossless supercurrent. A similar picture may be extended to
unconventional superconductors such as the cuprates, with an array of standing
spin waves rather than phonons. Such coherent lattice vibrations should be
universal and distinctive indicators of the superconducting state, and should
be observable below Tc using standard x-ray and neutron diffraction techniques.
Further implications of this picture are discussed.",0706.0338v1
2007-06-06,Resonant Scattering of Ultracold Atoms in Low Dimensions,"Low energy scattering amplitudes for two atoms in one- and two-dimensional
atomic wave guides are derived for short range isotropic and resonant
interactions in high partial wave channels. Taking into account the finite
width of the resonance which was neglected in previous works is shown to have
important implications in the properties of the confinement induced resonances.
For spin polarized fermions in quasi-1D wave guides it imposes a strong
constraint on the atomic density for achieving the Fermi Tonks Girardeau gas.
For a planar wave guide, the charateristics of the 2D induced scattering
resonances in $p$- and d-wave are determined as a function of the 3D scattering
parameters and of the wave guide frequency.",0706.0834v3
2007-08-13,"Two-particle scattering on the lattice: Phase shifts, spin-orbit coupling, and mixing angles","We determine two-particle scattering phase shifts and mixing angles for
quantum theories defined with lattice regularization. The method is suitable
for any nonrelativistic effective theory of point particles on the lattice. In
the center-of-mass frame of the two-particle system we impose a hard spherical
wall at some fixed large radius. For channels without partial-wave mixing the
partial-wave phase shifts are determined from the energies of the
nearly-spherical standing waves. For channels with partial-wave mixing further
information is extracted by decomposing the standing wave at the wall boundary
into spherical harmonics, and we solve coupled-channels equations to extract
the phase shifts and mixing angles. The method is illustrated and tested by
computing phase shifts and mixing angles on the lattice for spin-1/2 particles
with an attractive Gaussian potential containing both central and tensor force
parts.",0708.1780v2
2008-03-11,On an excitation mechanism for trapped inertial waves in discs around black holes,"According to one model, high-frequency quasi-periodic oscillations (QPOs) can
be identified with inertial waves, trapped in the inner regions of accretion
discs around black holes due to relativistic effects. In order to be detected,
their amplitudes need to reach large enough values via some excitation
mechanism. We work out in detail a non-linear coupling mechanism suggested by
Kato, in which a global warping or eccentricity of the disc has a fundamental
role. These large-scale deformations combine with trapped modes to generate
`intermediate' waves of negative energy that are damped as they approach either
their corotation resonance or the inner edge of the disc, resulting in
amplification of the trapped waves. We determine the growth rates of the
inertial modes, as well as their dependence on the spin of the black hole and
the properties of the disc. Our results indicate that this coupling mechanism
can provide an efficient excitation of trapped inertial waves, provided the
global deformations reach the inner part of the disc with non-negligible
amplitude.",0803.1671v1
2009-07-14,GRB afterglow plateaus and Gravitational Waves: multi-messenger signature of a millisecond magnetar?,"The existence of a shallow decay phase in the early X-ray afterglows of
gamma-ray bursts is a common feature. Here we investigate the possibility that
this is connected to the formation of a highly magnetized millisecond pulsar,
pumping energy into the fireball on timescales longer than the prompt emission.
In this scenario the nascent neutron star could undergo a secular bar-mode
instability, leading to gravitational wave losses which would affect the
neutron star spin-down. In this case, nearby gamma-ray bursts with isotropic
energies of the order of 1e50 ergs would produce a detectable gravitational
wave signal emitted in association with an observed X-ray light-curve plateau,
over relatively long timescales of minutes to about an hour. The peak amplitude
of the gravitational wave signal would be delayed with respect to the gamma-ray
burst trigger, offering gravitational wave interferometers such as the advanced
LIGO and Virgo the challenging possibility of catching its signature on the
fly.",0907.2290v2
2009-09-22,Gravitational wave emission from rotating superfluid neutron stars,"In this paper we investigate the effect of a pinned superfluid component on
the gravitational wave emission of a steadily rotating deformed neutron star.
We show that the superfluid pinning allows the possibility for there to be
gravitational wave emission at both the stellar spin frequency $\Omega$ and its
first harmonic, $2\Omega$. This contrasts with the conventional case where
there is no pinned superfluidity, where either only the $2\Omega$ harmonic is
present, or else the star undergoes precession, a feature which is not believed
to be common in the known pulsar population. This work motivates the carrying
out of gravitational wave searches where both the $\Omega$ and $2\Omega$
harmonics are searched for, even in targeted searches for waves from known
pulsars which aren't observed to precess. Observation of such a two-component
signal would provide evidence in favour of pinned superfluidity inside the
star.",0909.4035v2
2010-01-24,Electromagnetic Waves in the De Sitter Space,"5-Dimensional wave equation for a massive particle of spin 1 in the
background of de Sitter space-time model is solved in static coordinates. The
spherical 5-dimensional vectors $A_{a}, a= 1,...,5$ of three types, $j,j+1,
j-1$ are constructed. In massless case they give electromagnetic wave
solutions, obeying the Lorentz condition. 5-form of equations in massless case
is used to produce recipe to build electromagnetic wave solutions of the types
$\Pi, E,M$; the first is trivial and can be removed by a gauge ransformation.
The recipe is specified to produce spherical $\Pi, E, M$ solutions in static
coordinates.",1001.4253v1
2011-04-22,A new approach to investigate dineutron correlation and its application to $^{10}$Be,"We propose a new framework by means of the dineutron condensate (DC) wave
function to describe the dineutron correlation, which is characterized by the
spatially strong correlation of a spin-zero neutron-neutron pair, in
neutron-rich nuclei with an active deformed core surrounded by valence
neutrons. Using the DC wave function for a 2$\alpha$+2n system, which
corresponds to a toy model for the $^{10}$Be system, we investigate the
neutron-neutron correlation around the $2\alpha$ core and discuss the mechanism
of the dineutron formation at the surface of finite nuclei. To investigate
dineutron correlations in realistic nuclear systems, we superpose the
antisymmetrized molecular dynamics (AMD) wave functions and the DC wave
functions. Applying the AMD+DC method to $^{10}$Be, we show effects of the DC
wave functions in the ground and excited $0^+$ states of $^{10}$Be and discuss
the dineutron correlation in them.",1104.4397v1
2011-06-30,"Dispersions, weights, and widths of the single-particle spectral function in the normal phase of a Fermi gas","The dispersions, weights, and widths of the peaks of the single-particle
spectral function in the presence of pair correlations, for a Fermi gas with
either attractive or repulsive short-range inter-particle interaction, are
determined in the normal phase over a wide range of wave vectors, with a
twofold purpose. The first one is to determine how these dispersions identify
both an energy scale known as the pseudo-gap near the Fermi wave vector, as
well as an additional energy scale related to the contact C at large wave
vectors. The second one is to differentiate the behaviors of the repulsive gas
from the attractive one in terms of crossing versus avoided crossing of the
dispersions near the Fermi wave vector. An analogy will also be drawn between
the occurrence of the pseudo-gap physics in a Fermi gas subject to pair
fluctuations and the persistence of local spin waves in the normal phase of
magnetic materials.",1106.6193v2
2011-08-31,Conformal Partial Waves: Further Mathematical Results,"Further results for conformal partial waves for four point functions for
conformal primary scalar fields in conformally invariant theories are obtained.
They are defined as eigenfunctions of the differential Casimir operators for
the conformal group acting on two variable functions subject to appropriate
boundary conditions. As well as the scale dimension $\Delta$ and spin $\ell$
the conformal partial waves depend on two parameters $a,b$ related to the
dimensions of the operators in the four point function. Expressions for the
Mellin transform of conformal partial waves are obtained in terms of
polynomials of the Mellin transform variables given in terms of finite sums.
Differential operators which change $a,b$ by $\pm 1$, shift the dimension $d$
by $\pm 2$ and also change $\Delta,\ell$ are found. Previous results for
$d=2,4,6$ are recovered. The trivial case of $d=1$ and also $d=3$ are also
discussed. For $d=3$ formulae for the conformal partial waves in some
restricted cases as a single variable integral representation based on the
Bateman transform are found.",1108.6194v2
2013-12-16,Black Hole Superradiance in Dynamical Spacetime,"We study the superradiant scattering of gravitational waves by a nearly
extremal black hole (dimensionless spin $a=0.99$) by numerically solving the
full Einstein field equations, thus including backreaction effects. This allows
us to study the dynamics of the black hole as it loses energy and angular
momentum during the scattering process. To explore the nonlinear phase of the
interaction, we consider gravitational wave packets with initial energies up to
$10%$ of the mass of the black hole. We find that as the incident wave energy
increases, the amplification of the scattered waves, as well as the energy
extraction efficiency from the black hole, is reduced. During the interaction
the apparent horizon geometry undergoes sizable nonaxisymmetric oscillations.
The largest amplitude excitations occur when the peak frequency of the incident
wave packet is above where superradiance occurs, but close to the dominant
quasinormal mode frequency of the black hole.",1312.4529v2
2014-02-24,Gas Model of Gravitons with Light Speed,"We first review some aspects of gravitational wave and the thermodynamic
expression of Einstein field equations, these achieved conclusions allow people
to think of Einstein's gravitational wave as a kind of sound wave in ordinary
gas which propagates as an adiabatic compression wave. In the following, using
the properties of photon gas in ""white wall box"", we find an analogous
relationship between ordinary gas and photon gas through sound velocity
formula. At last, by taking the ordinary gas as an intermediary, we find that
gravitational wave is analogous to photon gas, or equally, gravitons are
analogous to photons although they are different in some ways such as spins and
coupling strengths, and these different properties don't affect their
propagation speeds. Utilizing this analogous relationship, we achieve the gas
model of gravitons and this model naturally gives out the light speed of
gravitons",1402.5767v2
2014-03-28,Gravitational wave emission from oscillating millisecond pulsars,"Neutron stars undergoing r-mode oscillation emit gravitational radiation that
might be detected on earth. For known millisecond pulsars the observed spindown
rate imposes an upper limit on the possible gravitational wave signal of these
sources. Taking into account the physics of r-mode evolution, we show that only
sources spinning at frequencies above a few hundred Hertz can be unstable to
r-modes, and we derive a more stringent universal r-mode spindown limit on
their gravitational wave signal, exploiting the fact that the r-mode saturation
amplitude is insensitive to the structural properties of individual sources. We
find that this refined bound limits the gravitational wave strain from
millisecond pulsars to values below the detection sensitivity of
next-generation detectors. Young sources are therefore a more promising option
for the detection of gravitational waves emitted by r-modes and to probe the
interior composition of compact stars in the near future.",1403.7500v1
2014-04-28,A more effective coordinate system for parameter estimation of precessing compact binaries from gravitational waves,"Ground-based gravitational wave detectors are sensitive to a narrow range of
frequencies, effectively taking a snapshot of merging compact-object binary
dynamics just before merger. We demonstrate that by adopting analysis
parameters that naturally characterize this 'picture', the physical parameters
of the system can be extracted more efficiently from the gravitational wave
data, and interpreted more easily. We assess the performance of MCMC parameter
estimation in this physically intuitive coordinate system, defined by (a) a
frame anchored on the binary's spins and orbital angular momentum and (b) a
time at which the detectors are most sensitive to the binary's gravitational
wave emission. Using anticipated noise curves for the advanced-generation LIGO
and Virgo gravitational wave detectors, we find that this careful choice of
reference frame and reference time significantly improves parameter estimation
efficiency for BNS, NS-BH, and BBH signals.",1404.7070v1
2014-07-18,Roles of Hund's rule coupling in excitonic density-wave states,"Excitonic density-wave states realized by the quantum condensation of
electron-hole pairs (or excitons) are studied in the two-band Hubbard model
with Hund's rule coupling and the pair hopping term. Using the variational
cluster approximation, we calculate the grand potential of the system and
demonstrate that Hund's rule coupling always stabilizes the excitonic
spin-density-wave state and destabilizes the excitonic charge-density-wave
state and that the pair hopping term enhances these effects. The
characteristics of these excitonic density-wave states are discussed using the
calculated single-particle spectral function, density of states, condensation
amplitude, and pair coherence length. Implications of our results in the
materials' aspects are also discussed.",1407.4872v2
2014-08-07,Gravitational waves from the collision of tidally disrupted stars with massive black holes,"We use simulations of hydrodynamics coupled with full general relativity to
investigate the gravitational waves produced by a star colliding with a massive
black hole when the star's tidal disruption radius lies far outside of the
black hole horizon. We consider both main-sequence and white-dwarf compaction
stars, and nonspinning black holes, as well as those with near-extremal spin.
We study the regime in between where the star can be accurately modeled by a
point particle, and where tidal effects completely suppress the gravitational
wave signal. We find that nonnegligible gravitational waves can be produced
even when the star is strongly affected by tidal forces, as well as when it
collides with large angular momentum. We discuss the implications that these
results have for the potential observation of gravitational waves from these
sources with future detectors.",1408.1695v2
2014-11-13,Visualizing molecular unidirectional rotation,"A molecule can be optically accelerated to rotate unidirectionally at a
frequency of a few terahertzes which is many orders higher than the classical
mechanical rotor. Such a photon-induced ultrafast molecular unidirectional
rotation has been well explored as a controllable spin of the molecular nuclear
wave packet. Although it has been observed for more than 10 years, a complete
imaging of the unidirectional rotating nuclear wave packet is still missing,
which is essentially the cornerstone of all the exploring applications. Here,
for the first time, we experimentally visualize the time-dependent evolution of
the double-pulse excited molecular unidirectional rotation by Coulomb explosion
imaging the rotational nuclear wave packet. Our results reveal comprehensive
details undiscovered in pioneering measurements, which exhibits as a joint of
the quantum revival of the impulsively aligned rotational wave packet and its
unidirectional rotation following the angular momentum conservation. The
numerical simulations well reproduce the experimental observations and
intuitively revivify the thoroughgoing evolution of the rotational wave packet.",1411.3523v1
2015-01-09,Post-Minkowskian Limit and Gravitational Waves solutions of Fourth Order Gravity: a complete study,"The post-Minkowskian limit and gravitational wave solutions for general
fourth-order gravity theories are discussed. Specifically, we consider a
Lagrangian with a generic function of curvature invariants $f(R,
R_{\alpha\beta}R^{\alpha\beta},
R_{\alpha\beta\gamma\delta}R^{\alpha\beta\gamma\delta})$. It is well known that
when dealing with General Relativity such an approach provides massless
spin-two waves as propagating degree of freedom of the gravitational field
while this theory implies other additional propagating modes in the gravity
spectra. We show that, in general, fourth order gravity, besides the standard
massless graviton is characterized by two further massive modes with a
finite-distance interaction. We find out the most general gravitational wave
solutions in terms of Green functions in vacuum and in presence of matter
sources. If an electromagnetic source is chosen, only the modes induced by
$R_{\alpha\beta}R^{\alpha\beta}$ are present, otherwise, for any $f(R)$ gravity
model, we have the complete analogy with tensor modes of General Relativity.
Polarizations and helicity states are classified in the hypothesis of plane
wave.",1501.02187v2
2015-05-07,Formation of Bright Solitons from Wave Packets with Repulsive Nonlinearity,"Formation of bright envelope solitons from wave packets with a repulsive
nonlinearity was observed for the first time. The experiments used surface
spin-wave packets in magnetic yttrium iron garnet (YIG) thin film strips. When
the wave packets are narrow and have low power, they undergo self-broadening
during the propagation. When the wave packets are relatively wide or their
power is relatively high, they can experience self-narrowing or even evolve
into bright solitons. The experimental results were reproduced by numerical
simulations based on a modified nonlinear Schr\""odinger equation model.",1505.01882v1
2015-07-21,First-principle variational formulation of polarization effects in geometrical optics,"The propagation of electromagnetic waves in isotropic dielectric media with
local dispersion is studied under the assumption of small but nonvanishing
$\lambda/l$, where $\lambda$ is the wavelength, and $l$ is the characteristic
inhomogeneity scale. It is commonly known that, due to nonzero $\lambda/l$,
such waves can experience polarization-driven bending of ray trajectories and
polarization dynamics that can be interpreted as the precession of the wave
""spin"". The present work reports how Lagrangians describing these effects can
be deduced, rather than guessed, within a strictly classical theory. In
addition to the commonly known ray Lagrangian featuring the Berry connection, a
simple alternative Lagrangian is proposed that naturally has a canonical form.
The presented theory captures not only eigenray dynamics but also the dynamics
of continuous wave fields and rays with mixed polarization, or ""entangled""
waves. The calculation assumes stationary lossless media with isotropic local
dispersion, but generalizations to other media are straightforward to do.",1507.05863v2
2016-05-28,Trapping neutral particles endowed with a magnetic moment by an electromagnetic wave carrying orbital angular momentum: Semiclassical theory,"The motion of a neutral atom endowed with a magnetic moment interacting with
the magnetic field is determined from the Ehrenfest-like equations of motion.
These equations for the average values of the translational and spin degrees of
freedom are derived from the Schr\""odinger-Pauli wave equation and they form a
set of nine coupled nonlinear evolution equations. The numerical and analytic
solutions of these equations are obtained for the combination of the rotating
magnetic field of a wave carrying orbital angular momentum and a static
magnetic field. The running wave traps the atom only in the transverse
direction while the standing wave traps the atom also in the direction of the
beam.",1605.08894v1
2016-07-07,Completeness of general pp-wave spacetimes and their impulsive limit,"We investigate geodesic completeness in the full family of pp-wave or
Brinkmann spacetimes in their extended as well as in their impulsive form. This
class of geometries contains the recently studied gyratonic pp-waves, modelling
the exterior field of a spinning beam of null particles, as well as NPWs, which
generalise classical pp-waves by allowing for a general wave surface. The
problem of geodesic completeness reduces to the question of completeness of
trajectories on a Riemannian manifold under an external force field. Building
upon respective recent results we derive completeness criteria in terms of the
spatial asymptotics of the profile function in the extended case. In the
impulsive case we use a fixed point argument to show that irrespective of the
behaviour of the profile function all geometries in the class are complete.",1607.01934v3
2016-09-09,A nonorthogonal state-interaction approach for matrix product state wave functions,"We present a state-interaction approach for matrix product state (MPS) wave
functions in a nonorthogonal molecular orbital basis. Our approach allows us to
calculate for example transition and spin-orbit coupling matrix elements
between arbitrary electronic states provided that they share the same
one-electron basis functions and active orbital space, respectively. The key
element is the transformation of the MPS wave functions of different states
from a nonorthogonal to a biorthonormal molecular orbital basis representation
exploiting a sequence of non-unitary transformations following a proposal by
Malmqvist (Int. J. Quantum Chem. 30, 479 (1986)). This is well-known for
traditional wave-function parametrizations but has not yet been exploited for
MPS wave functions.",1609.02684v1
2018-08-28,Recent progress in the partial-wave analysis of the diffractively produced $π^-π^+π^-$ final state at COMPASS,"The COMPASS spectrometer at CERN has collected a large data set for
diffractive three-pion production of $46\times10^6$ exclusive events. Based on
previous conventional Partial-Wave Analyses (PWA), we performed a `freed-isobar
PWA' on the same data, removing model assumptions on the dynamic isobar
amplitudes for dominating waves. In this analysis, we encountered continuous
mathematical ambiguities, which we were able to identify and resolve. This
analysis gives an unprecedented insight in the interplay of $2\pi$ and $3\pi$
dynamics in the process. As an example we show results for a spin-exotic wave
$J^{PC}_{X^-}=1^{-+}$ wave.",1808.09207v1
2019-06-04,Non-reciprocal Wave Phenomena in Energy Self-reliant Gyric Metamaterials,"This work presents a mechanism by which non-reciprocal wave transmission is
achieved in a class of gyric metamaterial lattices with embedded rotating
elements. A modulation of the device's angular momentum is obtained via
prescribed rotations of a set of locally housed spinning motors and are then
used to induce space-periodic, time-periodic, as well as space-time-periodic
variations which influence wave propagation in distinct ways. Owing to their
dependence on gyroscopic effects, such systems are able to break reciprocal
wave symmetry without stiffness perturbations rendering them consistently
stable as well as energy self-reliant. Dispersion patterns, band gap emergence,
as well as non-reciprocal wave transmission in the space-time-periodic gyric
metamaterials are predicted both analytically from the gyroscopic system
dynamics as well as numerically via time-transient simulations. In addition to
breaking reciprocity, we show that the energy content of a frictionless gyric
metamaterial is conserved over one temporal modulation cycle enabling it to
exhibit a stable response irrespective of the pumping frequency.",1906.01690v1
2017-10-10,Surface plasmon oscillations in a semi-bounded semiconductor plasma,"We study the dispersion properties of surface plasmon oscillations in a
semi-bounded semiconductor plasma with the effects of the Coulomb exchange
force associated with the spin polarization of electrons and holes as well as
the effects of the Fermi degenerate pressure and the quantum Bohm potential.
Starting from a quantum hydrodynamic (QHD) model coupled to the Poisson
equation, we derive the general dispersion relation for surface plasma waves.
Previous results in this context are recovered. The dispersion properties of
the surface waves are analyzed in some particular cases of interest and the
relative influence of the quantum forces on these waves are also studied for a
nano-sized GaAs semiconductor plasma. It is found that the Coulomb exchange
effects significantly modify the behaviors of the surface plasmon waves. The
present results are applicable to understand the propagation characteristics of
surface waves in solid density plasmas.",1710.03405v1
2020-09-29,PyROQ: a Python-based Reduced Order Quadrature Building Code for Fast Gravitational Wave Inference,"The next generation of gravitational-wave observatories will reach low
frequency limits on the orders of a few Hz, thus enabling the detection of
gravitational wave signals of very long duration. The run time of standard
parameter estimation techniques with these long waveforms can be months or even
years, making it impractical with existing Bayesian inference pipelines.
Reduced order modeling and reduced order quadrature integration rule have
recently been exploited as promising techniques that can greatly reduce
parameter estimation computational costs. We describe a Python-based reduced
order quadrature building code, PyROQ, which builds the reduced order
quadrature data needed to accelerate parameter estimation of gravitational
waves. We present the first bases for the IMRPhenomXPHM waveform model of
binary-black-hole coalescences, including subdominant harmonic modes and
precessing spins effects. Furthermore, the code infrastructure makes it
directly applicable to the gravitational wave inference for space-borne
detectors such as the Laser Interferometer Space Antenna (LISA).",2009.13812v3
2021-04-01,Modeling the Galactic Neutron Star Population for Use in Continuous Gravitational Wave Searches,"Searches for continuous gravitational waves from \textit{unknown} Galactic
neutron stars provide limits on the shapes of neutron stars. A rotating neutron
star will produce gravitational waves if asymmetric deformations exist in its
structure that are characterized by the star's ellipticity. In this study, we
use a simple model of the spatial and spin distribution of Galactic neutron
stars to estimate the total number of neutron stars probed, using gravitational
waves, to a given upper limit on the ellipticity. This may help optimize future
searches with improved sensitivity. The improved sensitivity of
third-generation gravitational wave detectors may increase the number of
neutron stars probed, to a given ellipticity, by factors of 100 to 1000.",2104.00771v2
2019-01-08,Tail-free self-accelerating solitons and vortices,"Self-accelerating waves in conservative systems, which usually feature slowly
decaying tails, such as Airy waves, have drawn great interest in studies of
quantum and classical wave dynamics. They typically appear in linear media,
while nonlinearities tend to deform and eventually destroy them. We
demonstrate, by means of analytical and numerical methods, the existence of
robust one- and two-dimensional (1D and 2D) self-accelerating tailless solitons
and solitary vortices in a model of two-component Bose-Einstein condensates,
dressed by a microwave (MW) field, whose magnetic component mediates long-range
interaction between the matter-wave constituents, with the feedback of the
matter waves on the MW field taken into account. In particular,
self-accelerating 2D solitons may move along a curved trajectory in the
coordinate plane. The system may also include the spin-orbit coupling between
the components, leading to similar results for the self-acceleration. The
effect persists if the contact cubic nonlinearity is included. A similar
mechanism may generate 1D and 2D self-accelerating solitons in optical media
with thermal nonlinearity.",1901.02325v1
2019-01-25,Axisymmetric density waves in Saturn's rings,"Density waves in Saturn's rings are usually tightly wrapped spiral patterns
generated by resonances with either Saturn's moons or structures inside the
planet. However, between the Barnard and Bessel Gaps in the Cassini Division
(i.e. between 120,240 and 120,300 km from Saturn's spin axis), there are
density variations that appear to form an axisymmetric density wave consisting
of concentric zones of varying densities that propagate radially through the
rings. Axisymmetric waves cannot be generated directly by a satellite
resonance, but instead appear to be excited by interference between a nearby
satellite resonance and normal mode oscillations on the inner edge of the
Barnard Gap. Similar axisymmetric waves may exist just interior to other
resonantly confined edges that exhibit a large number of normal modes,
including the Dawes ringlet in the outer C ring and the outermost part of the B
ring.",1901.09104v1
2019-12-25,A re-formulization of the transfer matrix method for calculating wave-functions in higher dimensional disordered open systems,"We present a numerically stable re-formulization of the transfer matrix
method (TMM). The iteration form of the traditional TMM is transformed into
solving a set of linear equations. Our method gains the new ability of
calculating accurate wave-functions of higher dimensional disordered systems.
It also shows higher efficiency than the traditional TMM when treating finite
systems. In contrast to the diagonalization method, our method not only
provides a new route for calculating the wave-function corresponding to the
boundary conditions of open systems in realistic transport experiments, but
also has advantages that the calculating wave energy/frequency can be tuned
continuously and the efficiency is much higher. Our new method is further used
to identify the necklace state in the two dimensional disordered Anderson
model, where it shows advantage in cooperating the wave-functions with the
continuous transmission spectrum of open systems. The new formulization is very
simple to implement and can be readily generalized to various systems such as
spin-orbit coupling systems or optical systems.",1912.11672v1
2021-01-29,Scattering on Quasi-Spherical Black-Holes: Features and Beyond,"Recent developments in the gravitational waves interferometry require more
pertinent theoretical models of gravitational waves generation and propagation.
Untouched possible mechanisms of spin-2 spacetime perturbations production, we
will consider their subsequent scattering on other black holes (BHs).
Specifically, we consider a generalization of the Regge-Wheeler-Zerilli
equations for the case of distorted BHs (BHs surrounded with matter) in
Minkowski and Anti-de Sitter spacetimes, the metric potential of which obeys
the Liouville equation. We establish significant differences in scattering
characteristics of waves of different spins and angular momenta, including the
gravitational waves, caused by losing the spherical symmetry of their
propagation background. In particular, we demonstrate the strong impact of the
background geometry deformation on the grey-body factors, hence on the
absorption cross-sections of scattering waves, and explore the issue of
stability of the background geometry upon changing the deformation degree
parameters.",2101.12488v1
2021-05-28,Deep searches for X-ray pulsations from Scorpius X-1 and Cygnus X-2 in support of continuous gravitational wave searches,"Neutron stars in low mass X-ray binaries are hypothesised to emit continuous
gravitational waves that may be detectable by ground-based observatories. The
torque balance model predicts that a higher accretion rate produces
larger-amplitude gravitational waves, hence low mass X-ray binaries with high
X-ray flux are promising targets for gravitational wave searches. The detection
of X-ray pulsations would identify the spin frequency of these neutron stars,
and thereby improve the sensitivity of continuous gravitational-wave searches
by reducing the volume of the search parameter space. We perform a
semi-coherent search for pulsations in the two low mass X-ray binaries Scorpius
X-1 and Cygnus X-2 using X-ray data from the \textit{ Rossi X-ray Timing
Explorer} Proportional Counter Array. We find no clear evidence for pulsations,
and obtain upper limits (at $90\%$ confidence) on the fractional pulse
amplitude, with the most stringent being $0.034\%$ for Scorpius X-1 and
$0.23\%$ for Cygnus X-2. These upper limits improve upon those of Vaughan et
al. (1994) by factors of $\sim 8.2$ and $\sim 1.6$ respectively.",2105.13803v1
2022-02-21,Density-wave tendency from a topological nodal-line perspective,"The understanding of density waves is a vital component of our insight into
electronic quantum matters. Here, we propose an additional mosaic to the
existing mechanisms such as Fermi-surface nesting, electron-phonon coupling,
and exciton condensation. In particular, we find that certain 2D spin
density-wave systems are equivalent to 3D Dirac nodal-line systems in the
presence of a magnetic field, whose electronic structure takes the form of
Dirac-fermion Landau levels and allows a straightforward analysis of its
optimal filling. The subsequent minimum-energy wave vector varies over a
continuous range and shows no direct connection to the original Fermi surfaces
in 2D. Also, we carry out numerical calculations where the results on model
examples support our theory. Our study points out that we have yet to attain a
complete understanding of the emergent density wave formalism.",2202.10151v2
2022-04-15,Celestial insights into the S-matrix bootstrap,"We consider 2-2 scattering in four spacetime dimensions in Celestial
variables. Using the crossing symmetric dispersion relation (CSDR), we recast
the Celestial amplitudes in terms of crossing symmetric partial waves. These
partial waves have spurious singularities in the complex Celestial variable,
which need to be removed in local theories. The locality constraints (null
constraints) admit closed form expressions, which lead to novel bounds on
partial wave moments. These bounds allow us to quantify the degree of low spin
dominance(LSD) for scalar theories. We study a new kind of positivity that
seems to be present in a wide class of theories. We prove that this positivity
arises only in theories with a spin-0 dominance. The crossing symmetric partial
waves with spurious singularities removed, dubbed as Feynman blocks, have
remarkable properties in the Celestial variable, namely typically realness, in
the sense of Geometric Function Theory (GFT). Using GFT techniques we derive
non-projective bounds on Wilson coefficients in terms of partial wave moments.",2204.07617v3
2022-06-01,Charge density wave and superconductivity in 6R-TaS2,"The layered transition metal dichalcogenide compounds 1T-TaS2 and 4H-TaS2 are
well known for their exotic properties, which include charge density wave,
superconductivity, Mott transition, etc., and lately quantum spin liquid. Here,
we report the magnetic, transport and transmission electron microscopy study of
the charge density wave and superconductivity in 6R-TaS2 which is a relatively
less studied polymorph of this dichalcogenide TaS2. Our high temperature
electron microscopy reveals multiple charge density wave transitions between
room temperature and 650K. Magnetization, and the electrical resistivity
measurements in the temperature range of 2-400 K reveal that 6R-TaS2 undergoes
a charge density wave transition around 305 K and is followed by a transition
to a superconducting state around 3.5 K. The low temperature specific heat
measurement exhibits anomaly associated with the superconducting transition
around 2.4 K. The estimated Ginzburg Landau parameter suggests that this
compound lies at the extreme limit of type-II superconductivity.",2206.00281v3
2022-06-06,Observability of lensing of gravitational waves from massive black hole binaries with LISA,"The gravitational waves emitted by massive black hole binaries in the LISA
band can be lensed. Wave-optics effects in the lensed signal are crucial when
the Schwarzschild radius of the lens is smaller than the wavelength of the
radiation. These frequency-dependent effects can enable us to infer the lens
parameters, possibly with a single detection alone. In this work, we assess the
observability of wave-optics effects with LISA by performing an
information-matrix analysis using analytical solutions for both point-mass and
singular isothermal sphere lenses. We use gravitational-waveform models that
include the merger, ringdown, higher harmonics, and aligned spins to study how
waveform models and source parameters affect the measurement errors in the lens
parameters. We find that previous work underestimated the observability of
wave-optics effects and that LISA can detect lensed signals with higher impact
parameters and lower lens masses.",2206.02803v2
2022-10-08,Observation of polarization singularities and topological textures in sound waves,"Polarization singularities and topological polarization structures are
generic features of inhomogeneous vector wave fields of any nature. However,
their experimental studies mostly remain restricted to optical waves. Here we
report observation of polarization singularities, topological Mobius-strip
structures and skyrmionic textures in 3D polarization fields of inhomogeneous
sound waves. Our experiments are made in the ultrasonic domain using
nonparaxial propagating fields generated by space-variant 2D acoustic sources.
We also retrieve distributions of the 3D spin density in these fields. Our
results open the avenue to investigations and applications of topological
features and nontrivial 3D vector properties of structured sound waves.",2210.03976v1
2023-01-29,Spin vector deviation and the gravitational wave memory effect between two free-falling gyroscopes in the plane wave spacetime,"In the plane wave spacetime, we find that there will be a precession angle
deviation between two free-falling gyroscopes when gravitational waves passed
through. This kind of angle deviation is closely related to the well-known
standard velocity memory effect. Initial conditions such as the separation
velocity or displacement between the two gyroscopes will affect this angle
deviation. The evolutions of the angle deviation are calculated for different
cases. We find that in some extreme circumstance, the angle deviation's order
of magnitude produced by a rotating compact binary source could be $10^{-14}$
rads. Therefore, this memory effect caused by the gravitational wave is likely
to be detected in the future.",2301.12341v1
2023-03-10,Potential energy surfaces for electron dynamics from a model of localized Gaussian wave packets with valence-bond spin-coupling: high-harmonic generation spectra from H and He atoms,"Potential energy surfaces of electron dynamics (ePES) are constructed from a
model of localized electron wave packets (eWP) with non-orthogonal valence-bond
(VB) spin coupling and applied to quantum dynamics simulations of high harmonic
generation (HHG) spectra of hydrogen and helium atoms induced by intense laser
pulses. The dynamics of the single electron on the ePES is calculated by
numerically solving the time-dependent Schrodinger equation. The results
reasonably reproduce previous studies. The dynamics of the electron wave
function, dipole moment and dipole acceleration were analyzed by comparing one-
and two-dimensional calculations. It was found that the main part of the wave
function remains within a few Bohrs of the nuclear position, while the part of
the wave function that is several orders of magnitude smaller in probability
density, which escapes the laser-induced potential barrier by quantum tunneling
effect, mainly contributes to the HHG.",2303.05794v2
2023-06-16,Short-term evolution of electron wave packet in a constant crossed field with radiative corrections,"We study the dynamics of an electron wave packet in a strong constant crossed
electromagnetic field with account for radiative corrections due to interaction
of the electron with the vacuum fluctuations. We evaluate a wave packet
composed of the solutions to the Dyson-Schwinger equation, which describes
electron propagation without emission of real photons. Spacetime dependence of
the wave packet is obtained analytically for a short time interval, the more
restricted from above the wider is the packet in momentum space. The radiative
corrections alter the electron wavefunction, resulting in particular in a
damping of the wave packet. The expectation value of the Dirac spin operator
also gets modified.",2306.09932v1
2023-08-22,"Pair density wave, unconventional superconductivity, and non-Fermi liquid quantum critical phase in frustrated Kondo lattice","Motivated by the recent discovery of an intermediate quantum critical phase
between the antiferromagnetic order and the Fermi liquid in the frustrated
Kondo lattice CePdAl, we study here a Kondo-Heisenberg chain with frustrated
$J_1$-$J_2$ XXZ interactions among local spins using the density matrix
renormalization group method. Our simulations reveal a global phase diagram
with rich ground states including the antiferromagnetic order, the
valence-bond-solid and bond-order-wave orders, the pair density wave state, the
uniform superconducting state, and the Luttinger liquid state. We show that
both the pair density wave and uniform superconductivity belong to the family
of Luther-Emery liquids and may arise from pair instability of an intermediate
quantum critical phase with medium Fermi volume in the presence of strong
quantum fluctuations, while the Luttinger liquid has a large Fermi volume. This
suggests a deep connection between the pair density wave, the unconventional
superconductivity, and the non-Fermi liquid quantum critical phase.",2308.11414v2
2023-11-08,Parametrized multipolar gravitational waveform for testing general relativity: Amplitude corrections upto 2PN order,"A parametrized multipolar gravitational wave phasing within multipolar
post-Minkowskian and post-Newtonian formalism was developed in earlier works
[S. Kastha et al., PRD 98, 124033 (2018) & S. Kastha et al., PRD 100, 044007
(2019)]. This facilitates the model-agnostic tests for the multipolar structure
of compact binaries using gravitational wave observations. In this paper, we
derive a parametrized multipolar amplitude of the gravitational wave signal in
terms of mass and current-type radiative multipole moments within the
post-Newtonian approximation to general relativity. We assume the compact
binary to be moving in quasi-circular orbits, with component spins (anti-)
aligned with respect to the binary's orbital angular momentum. We report a
closed-form expression for the parameterized multipolar amplitude of the
waveform at second post-Newtonian order both in time and frequency domains.
This includes the contribution from the leading five mass-type and the leading
four current-type radiative moments. This framework of constructing a
parametrized waveform accomplishes a generic parametrization of both
gravitational wave phase and amplitude with the same set of phenomenological
parameters. Hence, it should significantly enhance the precision of the
multipole tests in the context of present and future gravitational wave
detectors.",2311.04672v1
2024-02-14,Slow-Wave Hybrid Magnonics,"Cavity magnonics is an emerging research area focusing on the coupling
between magnons and photons. Despite its great potential for coherent
information processing, it has been long restricted by the narrow interaction
bandwidth. In this work, we theoretically propose and experimentally
demonstrate a novel approach to achieve broadband photon-magnon coupling by
adopting slow waves on engineered microwave waveguides. To the best of our
knowledge, this is the first time that slow wave is combined with hybrid
magnonics. Its unique properties promise great potentials for both fundamental
research and practical applications, for instance, by deepening our
understanding of the light-matter interaction in the slow wave regime and
providing high-efficiency spin wave transducers. The device concept can be
extended to other systems such as optomagnonics and magnomechanics, opening up
new directions for hybrid magnonics.",2402.08872v1
2003-05-19,The anapole moments in disk-form MS-wave ferrite particle,"The anapole moments describe the parity-violating parity-odd,
time-reversal-even couplings between elementary particles and the
electromagnetic (EM) field. Surprisingly, the anapole-like moment properties
can be found in certain artificially engineered physical systems. In
microwaves, ferrite resonators with multi-resonance magnetostatic-wave
(MS-wave) oscillations may have sizes two-four orders less than the free-space
EM wavelength at the same frequency. MS-wave oscillations in a ferrite sample
occupy a special place between the pure electromagnetic and spin-wave
(exchange) processes. The energy density of MS-wave oscillations is not the
electromagnetic-wave density of energy and not the exchange energy density as
well. These microscopic oscillating objects -- the particles -- may interact
with the external EM fields by a very specific way, forbidden for the classical
description. To describe such interactions, the quantum mechanical analysis
should be used. The presence of surface magnetic currents is one of the
features of MS oscillations in a normally magnetized ferrite disk resonator.
Because of such magnetic currents, MS oscillations in ferrite disk resonators
become parity violating. The parity-violating couplings between disk-form
ferrite particles and the external EM field should be analyzed based on the
notion of an anapole moment.",0305431v1
2004-10-13,Model wave functions and dynamic correlations in light-medium nuclei,"The nuclei $^4$He, $^8$Be, $^{12}$C and $^{16}$O have been studied starting
from nucleon-nucleon interactions of $v_4$ type. The wave function is built as
the product of three terms, a Jastrow correlation factor, a linear correlation
factor and a model wave function. The correlation factors account for both the
short range repulsive and the spin and isospin dependence of the nuclear
potential. The model wave function is antisymmetric and has the values of the
angular momentum and parity of the state under description. For the model wave
function we have used two different schemes. The first one is based on a
Harmonic Oscillator shell model with and without deformation, and the second
one is based on the Margenau-Brink model of alpha clustering. Projection
operators of parity and total angular momentum are used. The performance of
these two models is studied and compared systematically. Wave functions for the
ground state and some members of its rotational band and some other bound
states of these nuclei have been obtained. Binding energies, root mean square
radius and the expectation value of the kinetic energy and the different
channels of the nuclear interactions and the one-- and two-- body densities are
reported. The two different model wave functions and the effects of the
different nucleon-nucleon correlations have been evaluated on those quantities.
All the results here presented have been obtained by using the Variational
Monte Carlo method.",0410058v1
2007-12-15,A gravitational-wave probe of effective quantum gravity,"The Green-Schwarz anomaly-cancelling mechanism in string theories requires a
Chern-Simons term in the Einstein-Hilbert action, which leads to an amplitude
birefringence of spacetime for the propagation of gravitational waves. While
the degree of birefringence may be intrinsically small, its effects on a
gravitational wave will accumulate as the wave propagates. The proposed Laser
Interferometer Space Antenna (LISA) will be sensitive enough to observe the
gravitational waves from sources at cosmological distances great enough that
interesting bounds on the Chern-Simons may be found. Here we evaluate the
effect of a Chern-Simons induced spacetime birefringence to the propagation of
gravitational waves from such systems. We find that gravitational waves from in
coalescing binary black hole system are imprinted with a signature of
Chern-Simons gravity. This signature appears as a time-dependent change in the
apparent orientation of the binary's orbital angular momentum with respect to
the observer line-of-sight, with the change magnitude reflecting the integrated
history of the Chern-Simons coupling over the worldline of a radiation
wavefront. While spin-orbit coupling in the binary system will also lead to an
evolution of the system's orbital angular momentum, the time dependence and
other details of this \emph{real} effect are different than the \emph{apparent}
effect produced by Chern-Simons birefringence, allowing the two effects to be
separately identified.",0712.2542v1
2014-12-12,Projected Constraints on Lorentz-Violating Gravity with Gravitational Waves,"Gravitational waves are excellent tools to probe the foundations of General
Relativity in the strongly dynamical and non-linear regime. One such foundation
is Lorentz symmetry, which can be broken in the gravitational sector by the
existence of a preferred time direction, and thus, a preferred frame at each
spacetime point. This leads to a modification in the orbital decay rate of
binary systems, and also in the generation and chirping of their associated
gravitational waves. We here study whether waves emitted in the late,
quasi-circular inspiral of non-spinning, neutron star binaries can place
competitive constraints on two proxies of gravitational Lorentz-violation:
Einstein-\AE{}ther theory and khronometric gravity. We model the waves in the
small-coupling (or decoupling) limit and in the post-Newtonian approximation,
by perturbatively solving the field equations in small deformations from
General Relativity and in the small-velocity/weak-gravity approximation. We
assume a gravitational wave consistent with General Relativity has been
detected with second- and third-generation, ground-based detectors, and with
the proposed space-based mission, DECIGO, with and without coincident
electromagnetic counterparts. Without a counterpart, a detection consistent
with General Relativity of neutron star binaries can only place competitive
constraints on gravitational Lorentz violation when using future,
third-generation or space-based instruments. On the other hand, a single
counterpart is enough to place constraints that are 10 orders of magnitude more
stringent than current binary pulsar bounds, even when using second-generation
detectors. This is because Lorentz violation forces the group velocity of
gravitational waves to be different from that of light, and this difference can
be very accurately constrained with coincident observations.",1412.4132v1
2018-01-15,Fluctuation effects at the onset of $\bf 2k_F$ density wave order with one pair of hot spots in two-dimensional metals,"We analyze quantum fluctuation effects at the onset of charge or spin density
wave order in two-dimensional metals with an incommensurate $2k_F$ wave vector
connecting a single pair of hot spots on the Fermi surface. We compute the
momentum and frequency dependence of the fermion self-energy near the hot spots
to leading order in a fluctuation expansion (one loop). Non-Fermi liquid
behavior with anomalous frequency scaling and a vanishing quasi particle weight
is obtained. The momentum dependence yields a divergent renormalization of the
Fermi velocity and a flattening of the Fermi surface near the hot spots. Going
beyond the leading order calculation we find that the one-loop result is not
self-consistent. We show that any momentum-independent self-energy with a
non-Fermi liquid frequency exponent wipes out the peak of the polarization
function at the $2k_F$ wave vector, and thus destroys the mechanism favoring
$2k_F$ density waves over those with generic wave vectors. However, a $2k_F$
density wave quantum critical point might survive in presence of a sufficiently
flat renormalized Fermi surface.",1801.04885v3
2018-08-30,Optimizing Pulsar Timing Arrays Observations for Detection and Characterization of Low-Frequency Gravitational Wave Sources,"Observations of low-frequency gravitational waves will require the highest
possible timing precision from an array of the most spin-stable pulsars. We can
improve the sensitivity of a pulsar timing array (PTA) to different
gravitational-wave sources by observing pulsars with low timing noise over
years to decades and distributed across the sky. We discuss observing
strategies for a PTA focused on a stochastic gravitational-wave background such
as from unresolved supermassive black hole binaries as well as focused on
single continuous-wave sources. First we describe the method to calculate a
PTA's sensitivity to different gravitational-wave-source classes. We then apply
our method to the 45 pulsars presented in the North American Nanohertz
Observatory for Gravitational Waves (NANOGrav) 11-year data set. For expected
amplitudes of the stochastic background, we find that all pulsars contribute
significantly over the timescale of decades; the exception is for very
pessimistic values of the stochastic background amplitude. For individual
single sources, we find that a number of pulsars contribute to the sensitivity
of a given source but that which pulsars contribute are different depending on
the source, or versus an all-sky metric. Our results seem robust to the
presence of temporally-correlated red noise in pulsar arrival times. It is
critical to obtain more robust pulsar-noise parameters as they heavily affect
our results. Our results show that it is also imperative to locate and time as
many high-precision pulsars as possible, as quickly as possible, to maximize
the sensitivity of next-generation PTA detectors.",1808.10071v1
2020-08-07,Tidal dissipation in evolving low-mass and solar-type stars with predictions for planetary orbital decay,"We study tidal dissipation in stars with masses in the range $0.1-1.6
M_\odot$ throughout their evolution, including turbulent effective viscosity
acting on equilibrium tides and inertial waves in convection zones, and
internal gravity waves in radiation zones. We consider a range of stellar
evolutionary models and incorporate the frequency-dependent effective viscosity
acting on equilibrium tides based on the latest simulations. We compare the
tidal flow and dissipation obtained with the conventional equilibrium tide,
which is strictly invalid in convection zones, finding that the latter
typically over-predicts the dissipation by a factor of 2-3. Dissipation of
inertial waves is computed using a frequency-averaged formalism accounting for
realistic stellar structure for the first time, and is the dominant mechanism
for binary circularization and synchronization on the main sequence.
Dissipation of gravity waves in the radiation zone assumes these waves to be
fully damped (e.g.~by wave breaking), and is the dominant mechanism for
planetary orbital decay. We calculate the critical planetary mass required for
wave breaking as a function of stellar mass and age, and show that this
mechanism predicts destruction of many hot Jupiters but probably not Earth-mass
planets on the main sequence. We apply our results to compute tidal quality
factors following stellar evolution, and tidal evolutionary timescales, for the
orbital decay of hot Jupiters, and the spin synchronization and circularization
of binary stars. We also provide predictions for shifts in transit arrival
times due to tidally-driven orbital decay of hot Jupiters that may be detected
with NGTS, TESS or PLATO.",2008.03262v1
2019-01-03,Gravitational Wave Denoising of Binary Black Hole Mergers with Deep Learning,"Gravitational wave detection requires an in-depth understanding of the
physical properties of gravitational wave signals, and the noise from which
they are extracted. Understanding the statistical properties of noise is a
complex endeavor, particularly in realistic detection scenarios. In this
article we demonstrate that deep learning can handle the non-Gaussian and
non-stationary nature of gravitational wave data, and showcase its application
to denoise the gravitational wave signals generated by the binary black hole
mergers GW150914, GW170104, GW170608 and GW170814 from advanced LIGO noise. To
exhibit the accuracy of this methodology, we compute the overlap between the
time-series signals produced by our denoising algorithm, and the numerical
relativity templates that are expected to describe these gravitational wave
sources, finding overlaps ${\cal{O}}\gtrsim0.99$. We also show that our deep
learning algorithm is capable of removing noise anomalies from numerical
relativity signals that we inject in real advanced LIGO data. We discuss the
implications of these results for the characterization of gravitational wave
signals.",1901.00869v2
2020-12-27,Searching for spin-2 ULDM with gravitational waves interferometers,"The detection of gravitational waves from merging binaries has ushered in the
era of gravitational wave interferometer astronomy. Besides these strong,
transient, calamitous events, much weaker signals can be detected if the
oscillations are nearly monochromatic and ""continuous"", that is, coherent over
a long time. In this work we show that ultra-light dark matter of spin two,
owing to its universal coupling $\alpha$ to Standard Model fields, generates a
signal that is akin to but distinct from a continuous gravitational wave. We
show that this signal could be detected with current and planned gravitational
wave interferometers. In the event of a null detection, current facilities
could constrain the coupling to be below $\alpha\sim10^{-7}$ for frequencies of
tens of Hz, corresponding to dark matter masses around the $10^{-13}$ eV mark.
Future facilities could further lower these upper limits and extend them to
smaller masses down to $10^{-18}$ eV. These limits would be the most stringent
bounds on the spin-2 Yukawa fifth force strength, parametrised by $\alpha$, in
the frequency ranges accessible by gravitational wave interferometers. The
implementation of this type of searches for gravitational wave interferometers
would therefore further our grasp of both dark matter and gravity.",2012.13997v2
2021-07-20,New searches for continuous gravitational waves from seven fast pulsars,"We conduct searches for continuous gravitational waves from seven pulsars,
that have not been targeted in continuous wave searches of Advanced LIGO data
before. We target emission at exactly twice the rotation frequency of the
pulsars and in a small band around such frequency. The former search assumes
that the gravitational wave quadrupole is changing phase-locked with the
rotation of the pulsar. The search over a range of frequencies allows for
differential rotation between the component emitting the radio signal and the
component emitting the gravitational waves, for example the crust or
magnetosphere versus the core. Timing solutions derived from the Arecibo
327-MHz Drift-Scan Pulsar Survey (AO327) observations are used. No evidence of
a signal is found and upper limits are set on the gravitational wave amplitude.
For one of the pulsars we probe gravitational wave intrinsic amplitudes just a
factor of 3.8 higher than the spin-down limit, assuming a canonical moment of
inertia of $10^{38}$ kg m$^2$. Our tightest ellipticity constraint is $1.5
\times 10^{-8}$, which is a value well within the range of what a neutron star
crust could support.",2107.09727v3
2022-01-10,Continuous gravitational waves in the lab: recovering audio signals with a table-top optical microphone,"Gravitational-wave observatories around the world are searching for
continuous waves: persistent signals from sources such as spinning neutron
stars. These searches use sophisticated statistical techniques to look for weak
signals in noisy data. In this paper, we demonstrate these techniques using a
table-top model gravitational-wave detector: a Michelson interferometer where
sound is used as an analog for gravitational waves. Using signal processing
techniques from continuous-wave searches, we demonstrate the recovery of tones
with constant and wandering frequencies. We also explore the use of the
interferometer as a teaching tool for educators in physics and electrical
engineering by using it as an ""optical microphone"" to capture music and speech.
A range of filtering techniques used to recover signals from noisy data are
detailed in the Supplementary Material. Here, we present highlights of our
results using a combined notch plus Wiener filter and the statistical log
minimum mean-square error (logMMSE) estimator. Using these techniques, we
easily recover recordings of simple chords and drums, but complex music and
speech are more challenging. This demonstration can be used by educators in
undergraduate laboratories and can be adapted for communicating
gravitational-wave and signal-processing topics to non-specialist audiences.",2201.03683v1
2022-09-08,Extracting ultralight boson properties from boson clouds around post-merger remnants,"Ultralight bosons are a class of hypothetical particles that could
potentially solve critical problems in fields ranging from cosmology to
astrophysics and fundamental physics. If ultralight bosons exist, they form
clouds around spinning black holes with sizes comparable to their particle
Compton wavelength through superradiance, a well-understood classical wave
amplification process that has been studied for decades. After these clouds
form, they dissipate and emit continuous gravitational waves through the
annihilation of ultralight bosons into gravitons. These gravitons could be
detected with ground-based gravitational-wave detectors using continuous-wave
searches. However, it is conceivable for other continuous-wave sources to mimic
the emission from the clouds, which could lead to false detections. Here we
investigate how one can use continuous waves from clouds formed around known
merger remnants to alleviate this problem. In particular, we simulate a
catalogue of merger remnants that form clouds around them and demonstrate with
select ""golden"" merger remnants how one can perform a Bayesian
cross-verification of the ultralight boson hypothesis that has the potential to
rule out alternative explanations. Our proof-of-concept study suggest that, in
the future, there is a possibility that a merger remnant exists close enough
for us to perform the analysis and test the boson hypothesis if the bosons
exist in the relevant mass range. Future research will focus on building more
sophisticated continuous-wave tools to perform this analysis in practice.",2209.03536v2
2022-09-22,Inferring neutron star properties with continuous gravitational waves,"Detection of continuous gravitational waves from rapidly-spinning neutron
stars opens up the possibility of examining their internal physics. We develop
a framework that leverages a future continuous gravitational wave detection to
infer a neutron star's moment of inertia, equatorial ellipticity, and the
component of the magnetic dipole moment perpendicular to its rotation axis. We
assume that the neutron star loses rotational kinetic energy through both
gravitational wave and electromagnetic radiation, and that the distance to the
neutron star can be measured, but do not assume electromagnetic pulsations are
observable or a particular neutron star equation of state. We use the Fisher
information matrix and Monte Carlo simulations to estimate errors in the
inferred parameters, assuming a population of gravitational-wave-emitting
neutron stars consistent with the typical parameter domains of continuous
gravitational wave searches. After an observation time of one year, the
inferred errors for many neutron stars are limited chiefly by the error in the
distance to the star. The techniques developed here will be useful if
continuous gravitational waves are detected from a radio, X-ray, or gamma-ray
pulsar, or else from a compact object with known distance, such as a supernova
remnant.",2209.10981v2
2023-09-12,Open Quantum System Approach to the Gravitational Decoherence of Spin-1/2 Particles,"This paper investigates the decoherence effect resulting from the interaction
of squeezed gravitational waves with a system of massive particles in spatial
superposition. This paper investigates the decoherence effect resulting from
the interaction of squeezed gravitational waves with a system of massive
particles in spatial superposition. We first employ the open quantum system
approach to obtain the established decoherence in a spatial superposition of
massive objects induced by squeezed gravitational waves. Subsequently, we focus
on the spin-1/2 particle system, and our analysis reveals that the decoherence
rate depends on both the squeezing strength and the squeezing angle of the
gravitational waves. Our results demonstrate that squeezed gravitational waves
with squeezing strengths of $r_p\geq1.2$ and a squeezing angle of
$\varphi_p=\pi/2$ can induce a 1 % decoherence within 1 s free falling of a
cloud of spin-1/2 particles. This investigation sheds light on the relationship
between squeezed gravitational waves and the coherence of spatial superposition
states in systems of massive particles and their spin. The dependence of
decoherence on squeezing strength and, in the case of spin-$1/2$ particles, on
the squeezing angle paves the way for further exploration and understanding of
the quantum-gravity connection. We suggest that such an experimental setup
could also be employed to eventually investigate the level of squeezing effect
(and hence quantum-related properties) of gravitational waves produced in the
early universe from inflation.",2309.07236v2
1995-08-04,Thermally-driven Neutron Star Glitches,"We examine the thermal and dynamical response of a neutron star to a sudden
perturbation of the inner crust temperature. During the star's evolution,
starquakes and other processes may deposit $\gap 10^{42}$ ergs, causing
significant internal heating and increased frictional coupling between the
crust and the more rapidly rotating neutron superfluid the star is expected to
contain. Through numerical simulation we study the propagation of the thermal
wave created by the energy deposition, the induced motion of the interior
superfluid, and the resulting spin evolution of the crust. We find that energy
depositions of $\sim 10^{40}$ ergs produce gradual spin-ups above the timing
noise level, while larger energy depositions produce sudden spin jumps
resembling pulsar glitches. For a star with a temperature in the observed range
of the Vela pulsar, an energy deposition of $\sim 10^{42}$ ergs produces a
large spin-up taking place over minutes, similar to the Vela ``Christmas''
glitch. Comparable energy deposition in a younger and hotter ``Crab-like'' star
produces a smaller spin-up taking place over $\sim 1$ day, similar to that seen
during the partially time-resolved Crab glitch of 1989.",9508021v1
2000-02-04,R-mode runaway and rapidly rotating neutron stars,"We present a simple spin evolution model that predicts that rapidly rotating
accreting neutron stars will mainly be confined to a narrow range of
spin-frequencies; P= 1.5-5 ms. This is in agreement with current observations
of both neutron stars in the Low-Mass X-ray Binaries and millisecond
radiopulsars. The main ingredients in the model are; i) the instability of
r-modes above a critical spin rate, ii) thermal runaway due to heat released as
viscous damping mechanisms counteract the r-mode growth, and iii) a revised
estimate of the strength of dissipation due to the presence of a viscous
boundary layer at the base of the crust in an old and relatively cold neutron
star. We discuss the gravitational waves that are radiated during the brief
r-mode driven spin-down phase. We also briefly touch on how the new estimates
affects the predicted initial spin periods of hot young neutron stars.",0002114v2
2002-02-01,Spin--Down Power in Astrophysics,"While the accretion power in astrophysics has been studied in many
astronomical environments, the ``spin--down power'' is often neglected. In this
essay I demonstrate that the spin--down power alone may drive a rotating system
from sub-critical condition to critical condition with a small but finite
probability. In the case of an isolated spinning-down neutron star, the star
may undergo a quark--hadron phase transition in its center and become
observable as a soft gamma repeater or a cosmological gamma--ray burst. For a
spinning--down white dwarf, its Chandrasekhar mass limit will decrease and may
reach the stellar mass, then the star explodes to a type Ia supernova.
Gravitational wave detectors may be able to test these models.",0202040v1
1993-08-23,The Quartet State of the Two-Dimensional Heisenberg Model with Spin 1/2 on a Square Lattice,"The low-energy properties of the two-dimensional Heisenberg model with
spin-$\frac{1}{2}$ on a square lattice are investigated on the basis of the
local dimer order. The lattice is divided into square blocks consisting of the
quartet of spins. The spin variables and the Heisenberg Hamiltonian are
expressed in terms of the low-energy quartet variables. On the basis of the
Dyson-Maleev representation the spin-wave theory of the quartet state is
developed. The spectrum of the lower magnon excitations consists of three
degenerate modes with the energy gap $\Delta =0.17J$. The ground state energy
per spin $E/N =-0.6J$. This preprint repeats in the main the previous one but
it contains calculations of the basic corrections and therefore has complete
character.",9308030v1
1994-12-01,Chiral Anomaly and Spin Gap in One-Dimensional Interacting Fermions,"Semiclassical approach has been developed for the one-dimensional interacting
fermion systems. Starting from the incommensurate spin density wave (SDW) mean
field state for the repulsive Hubbard model in 1D, the non-Abelian bosonized
Lagrangian describing the spin-charge separation is obtained. The Berry phase
term is derived from the chiral anomaly, and we obtain the massless
Tomonaga-Luttinger liquid in the single chain case while the spin gap opens in
the double-chain system. This approach offers a new method to identify the
strong-coupling fixed point, and its relation to the Abelian bosonization
formalism is discussed on the spin gap state. The generalization to higher
dimensions is also discussed.",9412003v2
1995-06-24,Enhanced Charge and Spin Currents in the One-Dimensional Disordered Mesoscopic Hubbard Ring,"We consider a one-dimensional mesoscopic Hubbard ring with and without
disorder and compute charge and spin stiffness as a measure of the permanent
currents. For finite disorder we identify critical disorder strength beyond
which the charge currents in a system with repulsive interactions are {\em
larger} than those for a free system. The spin currents in the disordered
repulsive Hubbard model are enhanced only for small $U$, where the magnetic
state of the system corresponds to a charge density wave pinned to the
impurities. For large $U$, the state of the system corresponds to localized
isolated spins and the spin currents are found to be suppressed. For the
attractive Hubbard model we find that the charge currents are always suppressed
compared to the free system at all length scales.",9505110v1
1995-08-01,Numerical evidence for the spin-Peierls state in the frustrated quantum antiferromagnet,"We study the spin-$1\over2$ Heisenberg antiferromagnet with an
antiferromagnetic $J_3$ (third nearest neighbor) interaction on a square
lattice. We numerically diagonalize this ``$J_1$-$J_3$'' model on clusters up
to 32-sites and search for novel ground state properties as the frustration
parameter $J_3/J_1$ changes. For ``larger'' $J_3/J_1$ we find enhancement of
incommensurate spin order, in agreement with spin-wave, large-$N$ expansions,
and other predictions. But for intermediate $J_3/J_1$, the low lying excitation
energy spectrum suggests that this incommensurate order is short-range. In the
same region, the first excited state has the symmetries of the columnar dimer
(spin-Peierls) state. The columnar dimer order parameter suggests the presence
of long-range columnar dimer order. Hence, this spin-Peierls state is the best
candidate for the ground state of the $J_1$-$J_3$ model in an intermediate
$J_3/J_1$ region.",9508002v1
1995-12-11,Statistics of skyrmions in Quantum Hall systems,"We analyze statistical interactions of skyrmions in the quantum Hall system
near a critical filling fraction in the framework of the Ginzburg-Landau model.
The phase picked up by the wave-function during an exchange of two skyrmions
close to $\nu=1/(2n+1)$ is $\pi[S+1/2(2n+1)]$, where $S$ is the skyrmion's
spin. In the same setting an exchange of two fully polarized vortices gives
rise to the phase $\pi/(2n+1)$. Skyrmions with odd and even numbers of reversed
spins have different quantum statistics. Condensation of skyrmions with an even
number of reversed spins leads to filling fractions with odd denominators,
while condensation of those with an odd number of reversed spins gives rise to
filling fractions with even denominators.",9512077v2
1996-01-30,Origin of spin-gap in CaV$_4$O$_9$: effect of frustration and lattice distortion,"We study the origin of spin-gap in recently discovered material CaV$_4$O$_9$.
We analyze the spin-$1/2$ Heisenberg model on the $1/5$ depleted square lattice
with nearest neighbor (nn) and next nearest neighbor (nnn) interactions, in
terms of the singlet and triplet states of the 4-spin plaquettes and 2-spin
dimers. Phase diagram of the model is obtained within a linear
``spin-wave""-like approximation, and is shown to agree well with the earlier
results of QMC simulations for nn interactions. We further propose that the
special lattice structure of CaV$_4$O$_9$ naturally leads to lattice
distortions, which enhances the spin-gap via a spin-Peierls mechanism.",9601145v1
1997-05-05,Dynamical properties of low dimensional CuGeO3 and NaV2O5 systems,"Properties of low-dimensional spin-Peierls systems are described by using a
one dimensional S=1/2 antiferromagnetic Heisenberg chain linearly coupled to a
single phonon mode of wave vector pi (whose contribution is expected to be
dominant). By exact diagonalizations of small rings with up to 24 sites
supplemented by a finite size scaling analysis, static and dynamical properties
are investigated. Numerical evidences are given for a spontaneous discrete
symmetry breaking towards a spin gapped phase with a frozen lattice
dimerization. Special emphasis is put on the comparative study of the two
inorganic spin-Peierls compounds CuGeO3 and NaV2O5 and the model parameters are
determined from a fit of the experimental spin gaps. We predict that the
spin-phonon coupling is 2 or 3 times larger in NaV2O5 than in CuGeO3. Inelastic
neutron scattering spectra are calculated and similar results are found in the
single phonon mode approximation and in the model including a static
dimerization. In particular, the magnon S=1 branch is clearly separated from
the continuum of triplet excitations by a finite gap.",9705032v2
1997-05-26,One Spin-Polaron Problem in the Two-Dimensional Kondo-Lattice,"Within the frameworks of spin-polaron concept and the spherically symmetric
state for the antiferromagnetic spin background, the one-particle motion is
studied for two-dimensional Kondo-lattice. The elemetary excitations are
represented as a Bloch superposition of four one-site electron states: two
local states- a bare electron state and a local spin-polaron of small radius,
and two states of delocalized polarons which correspond to the coupling of
local states to the antiferromagnetic spin wave with momentum Q=(pi,pi), so
called Q-polarons. As a remarkable result we show that the lowest band of
elementary excitations is essentially determined by Q-polaron states in
strongly coupled regime. The account of Q-polarons shifts the band bottom from
(pi,pi) to (0,0). The spectral weight of a bare particle in the lowest band
states can greatly differ from 1. This may lead to a large Fermi surface for
relatively small particle concentration.",9705255v1
1997-11-11,Accurate mapping of quantum Heisenberg magnetic models of spin $s$ on strong-coupling magnon systems,"An infinite-$U$ term is introduced into the Holstein-Primakoff-transformed
magnon hamiltonian of quantum Heisenberg magnetic models of spin $s$. This term
removes the unphysical spin wave states on every site and truncates
automatically the expansion in powers of the magnon occupation operator. The
resultant strong-coupling magnon hamiltonians are accurately equivalent to the
original spin hamiltonians. The on-site $U$ levels and their implications are
studied. Within a simple decoupling approximation for our strong-coupling
magnon models we can easily reproduce the results for the (sublattice)
magnetizations obtained previously for the original spin model. But our bosonic
hamiltonians without any unphysical states allow for substantially improved
values for the spectral weight in the ground state and for lower ground-state
energies than those obtained within previous approximations.",9711086v1
1998-04-03,Self-Consistent Gaussian Approximation for Classical Spin Systems: Thermodynamics,"The self-consistent Gaussian approximation (SCGA) for classical spin systems
described by a completely anisotropic D-component vector model is proposed,
which takes into account fluctuations of the molecular field and thus is a next
step beyond the molecular field approximation. The SCGA is sensitive to the
lattice dimension and structure and to the form of spin interactions and yields
rather accurate values of the field-dependent magnetization m(H,T) and other
thermodynamic functions in the whole plane (H,T) excluding the vicinity of the
critical point (0,T_c), where the SCGA breaks down, showing a first-order phase
transition. The values of T_c themselves can be determined in the SCGA with an
accuracy better than 1% for actual 3-dimensional structures. At low and high
temperatures the SCGA recovers the leading terms of the spin-wave theory, the
low- and high-temperature series expansions, respectively. The accuracy of the
SCGA increases with the increase of the spin dimension D, and in the limit D
\to \infty the exact solution for the spherical model is recovered.",9804040v2
1999-01-28,Doped bilayer antiferromagnets: Hole dynamics on both sides of a magnetic ordering transition,"The two-layer square lattice quantum antiferromagnet with spins 1/2 shows a
magnetic order-disorder transition at a critical ratio of the interplane to
intraplane couplings. We investigate the dynamics of a single hole in a bilayer
antiferromagnet described by a t-J Hamiltonian. To model the spin background we
propose a ground-state wave function for the undoped system which covers both
magnetic phases and includes transverse as well as longitudinal spin
fluctuations. The photoemission spectrum is calculated using the spin-polaron
picture for the whole range of the ratio of the magnetic couplings. This allows
for the study of the hole dynamics of both sides of the magnetic order-disorder
transition. For small interplane coupling we find a quasiparticle with
properties known from the single-layer antiferromagnet, e.g., the dispersion
minimum is at (pi/2,pi/2). For large interplane coupling the hole dispersion is
similar to that of a free fermion (with reduced bandwidth). The cross-over
between these two scenarios occurs inside the antiferromagnetic phase which
indicates that the hole dynamics is governed by the local environment of the
hole.",9901326v2
1999-06-05,Direct observation of the multiple spin gap excitations in two-dimensional dimer system SrCu2(BO3)2,"Various spin gap excitations have been observed in the two-dimensional dimer
system SrCu_2(BO_3)_2 by means of submillimeter wave ESR. The zero-field energy
gap of the lowest spin gap excitation shows a splitting into two triplet modes
and the energy splitting clearly depends on the magnetic field orientation when
a field is rotated in the {\mib {ac}}-plane. A zero-field splitting is also
found between the S(_z)=+1 and S(_z)=-1 branches of each triplet. These
behaviors are qualitatively explained by considering the anisotropic exchange
coupling of inter-dimer and intra-dimer, respectively. The averaged value of
the lowest spin gap energy is determined to be 722 \pm 2 GHz(34.7 K). We have
also found the second spin gap excitation at 1140 GHz(54.7 K), which indicates
that the inter-dimer coupling is significantly strong. Besides these modes, a
number of gapped ESR absorption are found and we propose that these multiple
magnetic excitations are caused by the localized nature of the excited state in
the present system.",9906072v1
1999-06-25,Sound and Heat Absorption by a 2D Electron Gas in an Odd-Integer Quantized-Hall Regime,"The absorption of bulk acoustic phonons in a two-dimensional (2D) GaAs/AlGaAs
heterostructure is studied (in the clean limit) where the 2D electron-gas
(2DEG), being in an odd-integer quantum-Hall state, is in fact a spin
dielectric. Of the two channels of phonon absorption associated with excitation
of spin waves, one, which is due to the spin-orbit (SO) coupling of electrons,
involves a change of the spin state of the system and the other does not. We
show that the phonon-absorption rate corresponding to the former channel (in
the paper designated as the second absorption channel) is finite at zero
temperature ($T$), whereas that corresponding to the latter (designated as the
first channel) vanishes for $T\to 0$. The long-wavelength limit, being the
special case of the first absorption channel, corresponds to sound (bulk and
surface) attenuation by the 2DEG. At the same time, the ballistic phonon
propagation and heat absorption are determined by both channels. The 2DEG
overheat and the attendant spin-state change are found under the conditions of
permanent nonequilibrium phonon pumping.",9906396v3
1999-09-14,Oscillation of the tunnel splitting in nanospin systems within the particle mapping formalism,"The oscillation of tunnel splitting in the biaxial spin system within
magnetic field along the anisotropy axis is analyzed within the particle
mapping approach, rather than in the (\theta-\phi) spin coherent-state
representation. In our mapping procedure, the spin system is transformed into a
particle moving in the restricted $S^1$ geometry whose wave function subjects
to the boundary condition involving additional phase shift. We obtain the new
topological phase that plays the same role as the Wess-Zumino action in spin
coherent-state representation. Considering the interference of two possible
trajectories, instanton and anti-instanton, we get the identical condition for
the field at which tunneling is quenched, with the previous result within spin
coherent-state representation.",9909195v2
2000-02-25,Mechanical detection of nuclear spin relaxation in a micron-size crystal,"A room temperature nuclear magnetic resonance force microscope (MRFM), fitted
in a $^1$Tesla electromagnet, is used to measure the nuclear spin relaxation of
$^1$H in a micron-size (70ng) crystal of ammonium sulfate. NMR sequences,
combining both pulsed and continuous wave r.f. fields, have allowed us to
measure mechanically $T_2$ and $T_1$, the transverse and longitudinal spin
relaxation times. Because two spin species with different $T_1$ values are
measured in our $7\mu{\rm m}$ thick crystal, magnetic resonance imaging of
their spatial distribution inside the sample section are performed. To
understand quantitatively the measured signal, we carefully study the influence
of the spin-lattice relaxation and the non-adiabaticity of the c.w. sequence on
the intensity and time dependence of the detected signal.",0002404v1
2000-03-23,XPS and NMR as Complementary Probes of Pseudogaps and Spin-charge Separation,"The possibility that strongly correlated many-electron systems may exhibit
spin-charge separation has generated great excitement, particularly in the
light of recent experiments on low dimensional conductors and high temperature
superconductors. However, finding experimental support for this hypothesis has
been made difficult by the fact that most commonly used probes couple
simultaneously to spin and charge excitations. We argue that core hole
photoemission (XPS)/nuclear magnetic resonance (NMR) couple independently and
in exactly comparable ways to the local charge/spin susceptibilities of the
system being measured. The explicit comparison of XPS and NMR data,
particularly in systems which exhibit a pseudogap, may therefore yield fresh
evidence for the existence (or non-existence) of spin-charge separation.
Application of these ideas to the normal state of high temperature
superconductors is discussed, and the application is further illustrated in
some detail for quasi one-dimensional systems with charge density waves.",0003385v2
2001-02-27,Exact Bond-Located Spin Ground State in the Hubbard Chain with Off-Diagonal Coulomb Interactions,"We show the existence of an exact ground state in certain parameter regimes
of one-dimensional half-filled extended Hubbard model with site-off-diagonal
interactions. In this ground state, the bond-located spin correlation exhibits
a long-range order. In the case when the spin space is SU(2) symmetric, this
ground state degenerates with higher spin states including a fully
ferromagnetic state. We also discuss the relation between the exact
bond-ordered ground state and the critical bond-spin-density-wave phase.",0102497v1
2001-09-06,A dimerized spin fluid in a one-dimensional electron system,"The ground state of a one-dimensional Hubbard model with a bond-charge
attraction W term at half-filling is investigated by the density matrix
renormalization group method. It is confirmed that the spin gap will be closed
at U>8W. But the long-range bond order wave survives even when the spin gap is
closed. It indicates that the ground state is a novel dimerized spin fluid at
U>8W. By a charge-spin transformation, it is shown that there should be a
dimerized metallic phase at U<-8W. Furthermore, it is found that the Hubbard
interaction U enhances initially the dimerization for a weak bond charge
attraction W whereas it reduces monotonously the dimerization for a stronger
bond charge attraction W.",0109101v1
2001-11-30,"Localization, Dirac Fermions and Onsager Universality","Disordered systems exhibiting exponential localization are mapped to
anisotropic spin chains with localization length being related to the
anisotropy of the spin model. This relates localization phenomenon in fermions
to the rotational symmetry breaking in the critical spin chains. One of the
intriguing consequence is that the statement of Onsager universality in spin
chains implies universality of the localized fermions where the fluctuations in
localized wave functions are universal. We further show that the fluctuations
about localized nonrelativistic fermions describe relativistic fermions. This
provides a new approach to understand the absence of localization in disordered
Dirac fermions. We investigate how disorder affects well known universality of
the spin chains by examining the multifractal exponents. Finally, we examine
the effects of correlations on the localization characteristics of relativistic
fermions.",0111583v1
2002-01-17,Electron spin decoherence in quantum dots due to interaction with nuclei,"We study the decoherence of a single electron spin in an isolated quantum dot
induced by hyperfine interaction with nuclei for times smaller than the nuclear
spin relaxation time. The decay is caused by the spatial variation of the
electron envelope wave function within the dot, leading to a non-uniform
hyperfine coupling.
  We evaluate the spin correlation function with and without magnetic fields
and find that the decay of the spin precession amplitude is not exponential but
rather power (inverse logarithm) law-like. For fully polarized nuclei we find
an exact solution and show that the precession amplitude and the decay behavior
can be tuned by the magnetic field.
  The corresponding decay time is given by $\hbar N/A$, where $A$ is a
hyperfine interaction constant and $N$ the number of nuclei inside the dot. The
amplitude of precession, reached as a result of the decay, is finite. We show
that there is a striking difference between the decoherence time for a single
dot and the dephasing time for an ensemble of dots.",0201303v1
2002-06-27,Spin dynamics in stripe-ordered La5/3Sr1/3NiO4,"Polarized and unpolarized neutron inelastic scattering has been used to
measure the spin excitations in the spin-charge-ordered stripe phase of
La5/3Sr1/3NiO4. At high energies, sharp magnetic modes are observed
characteristic of a static stripe lattice. The energy spectrum is described
well by a linear spin wave model with intra- and inter-stripe exchange
interactions between neighbouring Ni spins given by J = 15 +/- 1.5 meV and J' =
7.5 +/- 1.5 meV respectively. A pronounced broadening of the magnetic
fluctuations in a band between 10 meV and 25 meV is suggestive of coupling to
collective motions of the stripe domain walls.",0206536v1
2002-11-19,Theory of phase fluctuating d-wave superconductors and the spin response in underdoped cuprates,"The minimal theory of spin of gapless quasiparticles coupled to fluctuating
vortex defects in the phase of the d-wave superconducting order parameter at
T=0 is studied. With the proliferation of the vortex loops the theory reduces
to the previuosly studied QED3, with its concomitant spin-density-wave (chiral)
instability. We find a single superconductor-insulator phase transition, which
may be fluctuation induced first-order, at which vortices condense and the
chiral symmetry for fermions dynamically breaks. We compute the spin-spin
correlation function deep in the fluctuating superconducting state, and discuss
some prominent trends in the neutron scattering data on underdoped cuprates in
light of our results.",0211418v4
2002-11-28,Electron spin evolution induced by interaction with nuclei in a quantum dot,"We study the decoherence of a single electron spin in an isolated quantum dot
induced by hyperfine interaction with nuclei for times smaller than the nuclear
spin relaxation time. The decay is caused by the spatial variation of the
electron envelope wave function within the dot, leading to a non-uniform
hyperfine coupling $A$. We show that the usual treatment of the problem based
on the Markovian approximation is impossible because the correlation time for
the nuclear magnetic field seen by the electron spin is itself determined by
the flip-flop processes.
  The decay of the electron spin correlation function is not exponential but
rather power (inverse logarithm) law-like. For polarized nuclei we find an
exact solution and show that the precession amplitude and the decay behavior
can be tuned by the magnetic field. The decay time is given by $\hbar N/A$,
where $N$ is the number of nuclei inside the dot. The amplitude of precession,
reached as a result of the decay, is finite. We show that there is a striking
difference between the decoherence time for a single dot and the dephasing time
for an ensemble of dots.",0211678v1
2002-12-12,Spin Precession and Oscillations in Mesoscopic Systems,"We compare and contrast magneto-transport oscillations in the fully quantum
(single-electron coherent) and classical limits for a simple but illustrative
model. In particular, we study the induced magnetization and spin current in a
two-terminal double-barrier structure with an applied Zeeman field between the
barriers and spin disequilibrium in the contacts. Classically, the spin current
shows strong tunneling resonances due to spin precession in the region between
the two barriers. However, these oscillations are distinguishable from those in
the fully coherent case, for which a proper treatment of the electron phase is
required. We explain the differences in terms of the presence or absence of
coherent multiple wave reflections.",0212308v1
2003-03-31,Spin-lattice models: inhomogeneity and diffusion,"In spin-lattice models with order parameter conserved, we generalize the idea
of spin diffusion incorporating a variety factors as possible driving forces,
including the external field and the temperature. The Kawasaki dynamics in the
Gaussian model and the one-dimensional Ising model are studied. The Gaussian
model is rigorously treated and the critical exponent $\gamma =1$ is obtained.
The competition of the internal and the external inhomogeneities may lead to
interesting and rich dynamic behavior. The diffusion induced by the
inhomogeneity of the magnetization itself is believed to vanish near the
critical point, meanwhile the nonvanishing diffusion induced by the
inhomogeneity of the environment may be coupled to the spin configuration and
weakened by thermal noise. Several interesting examples are visualized, and the
concept of local hysteresis is proposed in this spin-conserved dynamics. A
dynamic phase transition is observed in the one-dimensional Ising model subject
to an electromagnetic wave.",0303638v2
2003-06-16,Gate control of spin dynamics in III-V semiconductor quantum dots,"We show that the g-factor and the spin-flip time T_{1} of a heterojunction
quantum dot is very sensitive to the band-bending interface electric field even
in the absence of wave function penetration into the barrier. When this
electric field is of the order of 10^{5} V/cm, g and T_{1} show high
sensitivity to dot radius and magnetic field arising from the interplay between
Rashba and Dresselhaus spin-orbit interactions. This result opens new
possibilities for the design of a quantum dot spin quantum computer where
g-factor and T_{1} can be engineered by manipulating the spin-orbit coupling
through external gates.",0306417v2
2003-06-17,Low-energy spectra in the t-J type models at light doping,"Based on a variational approach, we propose that there are two kinds of low
energy states in the t-J type models at low doping. In a quasi-particle state
an unpaired spin bound to a hole with a well-defined momentum can be excited
with spin waves. The resulting state shows a suppression of antiferromagnetic
order around the hole with the profile of a {\em spin bag}. These spin-bag
states with spin and charge or hole separated form a continuum of low-energy
excitations. Very different properties predicted by these two kinds of states
explain a number of anomalous results observed in the exact diagonalization
studies on small clusters up to 32 sites.",0306424v1
2003-08-20,Novel excitonic states and photoluminescence in quantum hall systems,"The formation and possible decay processes of neutral and charged excitonic
complexes in electronic integral and fractional quantum Hall systems are
discussed. The excitonic complexes are bound states of a small number of the
relevant negatively and positively charged quasiparticles (e.g., conduction
electrons and valence holes, reversed-spin electrons and spin holes, Laughlin
quasielectrons and quasiholes, composite Fermions) that can occur in a 2D
electron in the presence of a strong magnetic field. Examples of such bound
states are interband neutral and charged excitons, fractionally charged ""anyon
excitons"", spin waves, skyrmions, or ""skyrmion excitons"". Possible decay
processes include radiative recombination, experimentally observed in
photoluminescence or spin transitions, important in the context of nuclear spin
relaxation.",0308410v1
2003-08-20,Excitonic complexes in quantum Hall systems,"The formation and various possible decay processes of neutral and charged
excitonic complexes in electronic integral and fractional quantum Hall systems
are discussed. The excitonic complexes are bound states of a small number of
the relevant negatively and positively charged quasiparticles (e.g., conduction
electrons and valence holes, reversed-spin electrons and spin holes, Laughlin
quasielectrons and quasiholes, composite fermions) that occur in an electron
system under specific conditions (e.g., electron density, well width, electric
and magnetic fields, or hydrostatic pressure). The examples of such bound
states are interband neutral and charged excitons, fractionally charged ""anyon
excitons"", spin waves, skyrmions, or ""skyrmion excitons"". Their possible decay
processes include radiative recombination, experimentally observed in
photoluminescence or far infrared emission, or spin transitions, important in
the context of nuclear spin relaxation.",0308411v1
2004-01-21,Landau Fermi Liquid Picture of Spin Density Functional Theory: Strutinsky Approach to Quantum Dots,"We analyze the ground state energy and spin of quantum dots obtained from
spin density functional theory (SDFT) calculations. First, we introduce a
Strutinsky-type approximation, in which quantum interference is treated as a
correction to a smooth Thomas-Fermi description. For large irregular dots, we
find that the second-order Strutinsky expressions have an accuracy of about 5
percent compared to the full SDFT and capture all the qualitative features.
Second, we perform a random matrix theory/random plane wave analysis of the
Strutinsky SDFT expressions. The results are statistically similar to the SDFT
quantum dot statistics. Finally, we note that the second-order Strutinsky
approximation provides, in essence, a Landau Fermi liquid picture of spin
density functional theory. For instance, the leading term in the spin channel
is simply the familiar exchange constant. A direct comparison between SDFT and
the perturbation theory derived ``universal Hamiltonian'' is thus made
possible.",0401389v1
2004-07-09,Magnetically Stabilized Nematic Order I: Three-Dimensional Bipartite Optical Lattices,"We study magnetically stabilized nematic order for spin-one bosons in optical
lattices. We show that the Zeeman field-driven quantum transitions between
non-nematic Mott states and quantum spin nematic states in the weak hopping
limit are in the universality class of the ferromagnetic XXZ (S=1/2) spin
model. We further discuss these transitions as condensation of interacting
magnons. The development of O(2) nematic order when external fields are applied
corresponds to condensation of magnons, which breaks a U(1) symmetry.
Microscopically, this results from a coherent superposition of two non-nematic
states at each individual site. Nematic order and spin wave excitations around
critical points are studied and critical behaviors are obtained in a dilute gas
approximation. We also find that spin singlet states are unstable with respect
to quadratic Zeeman effects and Ising nematic order appears in the presence of
any finite quadratic Zeeman coupling. All discussions are carried out for
states in three dimensional bipartite lattices.",0407259v1
2004-10-15,Matter-Wave Solitons in an F=1 Spinor Bose-Einstein Condensate,"Following our previous work [J. Ieda, T. Miyakawa, M. Wadati,
cond-mat/0404569] on a novel integrable model describing soliton dynamics of an
F=1 spinor Bose--Einstein condensate, we discuss in detail the properties of
the multi-component system with spin-exchange interactions. The exact multiple
bright soliton solutions are obtained for the system where the mean-field
interaction is attractive (c_0 < 0) and the spin-exchange interaction is
ferromagnetic (c_2 < 0). A complete classification of the one-soliton solution
with respect to the spin states and an explicit formula of the two-soliton
solution are presented. For solitons in polar state, there exists a variety of
different shaped solutions including twin peaks. We show that a ""singlet pair""
density can be used to distinguish those energetically degenerate solitons. We
also analyze collisional effects between solitons in the same or different spin
state(s) by computing the asymptotic forms of their initial and final states.
The result reveals that it is possible to manipulate the spin dynamics by
controlling the parameters of colliding solitons.",0410384v1
2004-12-21,Variational study of triangular lattice spin-1/2 model with ring exchanges and spin liquid state in κ-(ET)_2 Cu_2 (CN)_3,"We study triangular lattice spin-1/2 system with antiferromagnetic Heisenberg
and ring exchanges using variational approach focusing on possible realization
of spin liquid states. Trial spin liquid wave functions are obtained by
Gutzwiller projection of fermionic mean field states and their energetics is
compared against magnetically ordered trial states. We find that in a range of
the ring exchange coupling upon destroying the antiferromagnetic order, the
best such spin liquid state is essentially a Gutzwiller-projected Fermi sea
state. We propose this spin liquid with spinon Fermi surface as a candidate for
the nonmagnetic insulating phase observed in the organic compound \kappa-(ET)_2
Cu_2 (CN)_3, and describe some experimental consequences of this proposal.",0412556v1
2005-02-07,Incommensurate magnetism in the coupled spin tetrahedra system Cu2Te2O5Cl2,"Neutron scattering studies on powder and single crystals have provided new
evidences for unconventional magnetism in Cu2Te2O5Cl2. The compound is built
from tetrahedral clusters of S=1/2 Cu2+ spins located on a tetragonal lattice.
Magnetic ordering, emerging at TN=18.2 K, leads to a very complex multi-domain,
most likely degenerate, ground state, which is characterized by an
incommensurate (ICM) wave vector k ~ [0.15, 0.42,1/2]. The Cu2+ ions carry a
magnetic moment of 0.67(1) mB/ Cu2+ at 1.5 K and form a four helices spin
arrangement with two canted pairs within the tetrahedra. A domain
redistribution is observed when a magnetic field is applied in the tetragonal
plane (Hc&#8776;0.5 T), but not for H||c up to 4 T. The excitation spectrum is
characterized by two well-defined modes, one completely dispersionless at 6.0
meV, the other strongly dispersing to a gap of 2 meV. The reason for such
complex ground state and spin excitations may be geometrical frustration of the
Cu2+ spins within the tetrahedra, intra- and inter-tetrahedral couplings having
similar strengths and strong Dzyaloshinski-Moriya anisotropy. Candidates for
the dominant intra- and inter-tetrahedral interactions are proposed.",0502165v1
2005-04-14,Optical pumping of the electron spin polarization in bulk CuCl,"In CuCl bulk crystal negatively charged excitons (trions $X^-$) can be
induced by the resonant optical excitation of extra electrons in conduction
band minimum. In the case of light polarization and due to the top valence band
structure of CuCl only the electrons with spin antiparallel to the direction of
the light propagation contribute to the formation of $X^-$, while the emerging
$X^-$ can recombine into both possible electron states, with spin parallel and
antiparallel to the direction of light propagation. We propose to use this
mechanism for optical electronic spin pumping. We describe the dynamics of
pumping in terms of density matrix formalism. The coherent pumping laser pulse
propagating through the sample is described by Maxwell wave equation coupled to
the density matrix evolution equations. The results of our approximate simple
model calculations suggest that spin polarization close to 100% can be achieved
in time shorter than 100ps.",0504368v2
2005-07-12,Symplectic integrators for classical spin systems,"We suggest a numerical integration procedure for solving the equations of
motion of certain classical spin systems which preserves the underlying
symplectic structure of the phase space. Such symplectic integrators have been
successfully utilized for other Hamiltonian systems, e. g. for molecular
dynamics or non-linear wave equations. Our procedure rests on a decomposition
of the spin Hamiltonian into a sum of two completely integrable Hamiltonians
and on the corresponding Lie-Trotter decomposition of the time evolution
operator. In order to make this method widely applicable we provide a large
class of integrable spin systems whose time evolution consists of a sequence of
rotations about fixed axes. We test the proposed symplectic integrator for
small spin systems, including the model of a recently synthesized magnetic
molecule, and compare the results for variants of different order.",0507262v1
2005-10-03,Spin polarization of edge states and magnetosubband structure in quantum wires,"We provide a quantitative description of the structure of edge states in
split-gate quantum wires in the integer quantum Hall regime. We develop an
effective numerical approach based on the Green's function technique for the
self-consistent solution of Schrodinger equation where electron- and spin
interactions are included within the density functional theory in the local
spin density approximation. The major advantage of this technique is that it
can be directly incorporated into magnetotransport calculations, because it
provides the self-consistent eigenstates and wave vectors at a given energy,
not at a given wavevector (as conventional methods do). We use the developed
method to calculate the subband structure and propagating states in the quantum
wires in perpendicular magnetic field starting with a geometrical layout of the
wire. We discuss how the spin-resolved subband structure, the current
densities, the confining potentials, as well as the spin polarization of the
electron and current densities evolve when an applied magnetic field varies. We
demonstrate that the exchange and correlation interactions dramatically affect
the magnetosubbands in quantum wires bringing qualitatively new features in
comparison to a widely used model of spinless electrons in Hartree
approximation.",0510048v1
2005-10-13,Spin gaps and magnetic structure of NaxCoO2,"We present two experiments that provide information on spin anisotropy and
the magnetic structure of NaxCoO2. First, we report low-energy neutron
inelastic scattering measurements of the zone-center magnetic excitations in
the magnetically ordered phase of Na0.75CoO2. The energy spectra suggest the
existence of two gaps, and are very well fitted by a spin-wave model with both
in-plane and out-of-plane anisotropy terms. The gap energies decrease with
increasing temperature and both gaps are found to have closed when the
temperature exceeds the magnetic ordering temperature T_m~22 K. Secondly, we
present neutron diffraction studies of Na0.85CoO2 with a magnetic field applied
approximately parallel to the c axis. For fields in excess of ~8T a magnetic
Bragg peak was observed at the (0,0,3) position in reciprocal space. We
interpret this as a spin-flop transition of the A-type antiferromagnetic
structure, and we show that the spin-flop field is consistent with the size of
the anisotropy gap.",0510360v1
2005-10-13,Statics and dynamics of an incommensurate spin order in a geometrically frustrated antiferromagnet CdCr$_2$O$_4$,"Using elastic and inelastic neutron scattering we show that a cubic spinel,
CdCr$_2$O$_4$, undergoes an elongation along the c-axis ($c > a = b$) at its
spin-Peierls-like phase transition at $T_N$ = 7.8 K. The N\'{e}el phase ($T <
T_N$) has an incommesurate spin structure with a characteristic wave vector
\textbf{Q}$_M$ = (0,$\delta$,1) with $\delta \sim$ 0.09 and with spins lying on
the $ac$-plane. This is in stark contrast to another well-known Cr-based
spinel, ZnCr$_2$O$_4$, that undergoes a c-axis contraction and a commensurate
spin order. The magnetic excitations of the incommensurate N\'{e}el state has a
weak anisotropy gap of 0.6 meV and it consists of at least three bands
extending up to 5 meV.",0510363v1
2006-01-23,Spin and valley-orbit splittings in SiGe/Si heterostructures,"Spin and valley-orbit splittings are calculated in SiGe/Si/SiGe quantum wells
(QWs) by using the tight-binding approach. In accordance with the symmetry
considerations an existence of spin splitting of electronic states in perfect
QWs with an odd number of Si atomic planes is microscopically demonstrated. The
spin splitting oscillates with QW width and these oscillations related to the
inter-valley reflection of an electron wave from the interfaces. It is shown
that the splittings under study can efficiently be described by an extended
envelope-function approach taking into account the spin- and valley-dependent
interface mixing. The obtained results provide a theoretical base to the
experimentally observed electron spin relaxation times in SiGe/Si/SiGe QWs.",0601520v1
2006-05-23,Role of covalency in the ground state properties of perovskite ruthenates: A first principle study using local spin density approximations,"We investigate the electronic structure of SrRuO3 and CaRuO3 using full
potential linearized augmented plane wave method within the local spin density
approximations. The ferromagnetic ground state in SrRuO3 could exactly be
described in these calculations and the calculated spin magnetic moment is
found to be close to the experimentally observed values. Interestingly, the
spin polarized calculations for CaRuO3 exhibit large spin moment as observed in
the experiments but the magnetic ground state has higher energy than that in
the non-magnetic solution. Various calculations for different structural
configurations indicate that Ca-O covalency plays the key role in determining
the electronic structure and thereby the magnetic ground state in this system.",0605553v1
2006-07-10,Classifying Novel Phases of Spinor Atoms,"We consider many-body states of bosonic spinor atoms which, at the mean-field
level, can be characterized by a single-particle wave function. Such states
include BEC phases and insulating Mott states with one atom per site. We
describe and apply a classification scheme that makes explicit spin symmetries
of such states and enables one to naturally analyze their collective modes and
topological excitations. Quite generally, the method allows classification of a
spin F system as a polyhedron with 2F vertices. After discussing the general
formalism we apply it to the many-body states of bosons with hyperfine spins
two and three. For spin-two atoms we find the ferromagnetic state, a continuum
of nematic states, and a state having the symmetry of the point group of the
regular tetrahedron. For spin-three atoms we obtain similar ferromagnetic and
nematic phases as well as states having symmetries of various types of
polyhedra with six vertices: the hexagon, the pyramid with pentagonal base, the
prism, and the octahedron.",0607253v4
2006-09-15,Random 3D Spin System Under the External Field and Dielectric Permittivity Superlattice Formation,"A dielectric medium consisting of roughly polarized molecules is treated as a
3D disordered spin system (spin glass). A microscopic approach for the study of
statistical properties of this system on micrometer space scale and nanosecond
time scale of standing electromagnetic wave is developed. Using ergodic
hypothesis the initial 3D spin problem is reduced to two separate 1D problems
along external field propagation. The first problem describes the disordered
spin chain system while the second one describes a disordered N-particle
quantum system with relaxation in the framework of Langevin-Schroedinger
(L-Sch) type equation. Statistical properties of both systems are investigated
in detail. Basing on these constructions, the coefficient of polarizability,
related to collective orientational effects, is calculated. Clausius-Mossotti
formula for dielectric constant is generalized. For dielectric permittivity
function generalized equation is found taking into account Clausius-Mossotti
generalized formula.",0609366v1
2006-11-16,Quantum Description of Nuclear Spin Cooling in a Quantum Dot,"We study theoretically the cooling of an ensemble of nuclear spins coupled to
the spin of a localized electron in a quantum dot. We obtain a master equation
for the state of the nuclear spins interacting with a sequence of polarized
electrons that allows us to study quantitatively the cooling process including
the effect of nuclear spin coherences, which can lead to ``dark states'' of the
nuclear system in which further cooling is inhibited. We show that the
inhomogeneous Knight field mitigates this effect strongly and that the
remaining dark state limitations can be overcome by very few shifts of the
electron wave function, allowing for cooling far beyond the dark state limit.
Numerical integration of the master equation indicates, that polarizations
larger than 90% can be achieved within a millisecond timescale.",0611438v2
2006-11-23,Heavy-fermion spin liquid in the strong hybridization limit of the finite-U Anderson lattice model,"Studying the finite-U Anderson lattice model in the strong hybridization
limit, we find a heavy-fermion spin liquid phase, where both conduction and
localized fermions are strongly hybridized to form heavy fermions but this
heavy-fermion phase corresponds to a symmetric Mott insulating state owing to
the presence of charge gap, resulting from large Hubbard-U interactions in
localized fermions. We show that this heavy-fermion spin liquid phase differs
from the ""fractionalized"" Fermi liquid state, where the latter corresponds to a
metallic state with a small Fermi surface of conduction electrons while
localized fermions decouple from conduction electrons to form a spin liquid
state. We discuss the stability of this anomalous spin liquid phase against
antiferromagnetic ordering and gauge fluctuations, in particular, instanton
effects associated with confinement of slave particles. Furthermore, we propose
a variational wave function to check its existence from the microscopic model.",0611601v3
2007-01-23,Density functional approach to study structural properties and Electric Field Gradients in rare earth materials,"We investigated the effect of spin polarization on the structural properties
and gradient of electric field (EFG) on Sn, In, and Cd impurity in RSn$_3$
(R=Sm, Eu, Gd) and RIn$_3$ (R=Tm, Yb, Lu) compounds. The calculations were
performed self-consistently using the scalar-relativistic full potential
linearized augmented plane wave method. The local density approximations (LDA)
and generalized gradient approximation without spin polarization (GGA) and with
spin polarization (GGA+SP) to density functional theory were applied. In
addition to that we performed some calculations within open core treatment
(GGA+open core). It is clearly seen that GGA+SP is successful in predicting the
larger lattice parameter and the dramatic drop of EFG for R=(Eu, Yb) relative
to other rare earth compounds. This is an indication that spin splitting
generated by spin polarization without any modification, is capable of treating
properly the highly correlated f electrons in these systems.",0701557v2
2007-02-07,Anomalous magnetic phase in an undistorted pyrochlore oxide Cd2Os2O7 induced by geometrical frustration,"We report on the muon spin rotation/relaxation study of a pyrochlore oxide,
Cd2Os2O7, which exhibits a metal-insulator (MI) transition at T_{MI}~225 K
without structural phase transition. It reveals strong spin fluctuation
(>10^8/s) below the MI transition, suggesting a predominant role of geometrical
spin frustration amongst Os^{5+} ions. Meanwhile, upon further cooling, a
static spin density wave discontinuously develops below T_{SDW}~150 K. These
observations strongly suggest the occurrence of an anomalous magnetic
transition and associated change in the local spin dynamics in undistorted
pyrochlore antiferromagnet.",0702164v2
2007-02-10,Spin-dependent Rotating Wigner Molecules in Quantum dots,"The spin-dependent trial wave functions with rotational symmetry are
introduced to describe rotating Wigner molecular states with spin degree of
freedom in four- and five-electron quantum dots under magnetic fields. The
functions are constructed with unrestricted Hartree-Fock orbits and projection
technique in long-range interaction limit. They highly overlap with the
exact-diagonalized ones and give the accurate energies in strong fields. The
zero points, i.e. vortices of the functions have straightforward relations to
the angular momenta of the states. The functions with different total spins
automatically satisfy the angular momentum transition rules with the increase
of magnetic fields and explicitly show magnetic couplings and characteristic
oscillations with respect to the angular momenta. Based on the functions, it is
demonstrated that the entanglement entropies of electrons depend on the
z-component of total spin and rise with the increase of angular momenta.",0702256v2
1995-09-01,Absorption Probability of De Sitter Horizon for Massless Fields with Spin,"The evaluation of the absorption coefficients are important for particle
emission caused by Hawking radiation. In the case of cosmological particle
emission from the event horizon in De Sitter space, it is known that the scalar
wave functions are solved in terms of Legendre functions. For fields with
higher spin, the solution has been examined with low frequency approximation.
We shows that the radial equations of the fields with spin $0,1/2,1$ and $2$
can be solved analytically in terms of the hypergeometric functions. We
calculate the absorption probability using asymptotic expansion for high
frequency limit. It turns out that the absorption coefficients are universal to
all bosonic fields; They depend only on the angular momentum and not spin. In
the case of spin $1/2$ fermions, we can also find non-vanishing absorption
probability in contrast to the previously known result.",9508068v1
1999-06-19,On dilaton solutions of de Sitter inflation and primordial spin-torsion density fluctuations,"Four classes of exact solutions of Einstein-Cartan dilatonic inflationary de
Sitter cosmology are given.The first is obtained from the equation of state of
massless dilaton instead of an unpolarized fermion fluid used previously by
Gasperini.Repulsive gravity is found in the case where dilatons are constraint
by the presence of spin-torsion effects.The second and third solutions
represent respectively massive dilatons in the radiation era with the massive
potential and torsion kinks and finally the dust of spinning
particles.Primordial spin-density fluctuations are also computed based on
Primordial fluctuations of temperature obtained from COBE data.The temperature
fluctuation can also be computed from the nearly flat spectrum of the
gravitational waves produced during inflation and by the result that the
dilaton mass would be proportional to the Hubble constant.This result agrees
with the COBE data.This idea is also used to compute the spin-torsion density
in the inflation era.",9906085v1
2000-10-04,Gravitational field and equations of motion of spinning compact binaries to 2.5 post-Newtonian order,"We derive spin-orbit coupling effects on the gravitational field and
equations of motion of compact binaries in the 2.5 post-Newtonian approximation
to general relativity, one PN order beyond where spin effects first appear. Our
method is based on that of Blanchet, Faye, and Ponsot, who use a post-Newtonian
metric valid for general (continuous) fluids and represent pointlike compact
objects with a delta-function stress-energy tensor, regularizing divergent
terms by taking the Hadamard finite part. To obtain post-Newtonian spin
effects, we use a different delta-function stress-energy tensor introduced by
Bailey and Israel. In a future paper we will use the 2.5PN equations of motion
for spinning bodies to derive the gravitational-wave luminosity and phase
evolution of binary inspirals, which will be useful in constructing matched
filters for signal analysis. The gravitational field derived here may help in
posing initial data for numerical evolutions of binary black hole mergers.",0010014v1
2001-07-25,Ruling Out Chaos in Compact Binary Systems,"We investigate the orbits of compact binary systems during the final inspiral
period before coalescence by integrating numerically the second-order
post-Newtonian equations of motion. We include spin-orbit and spin-spin
coupling terms, which, according to a recent study by Levin [J. Levin, Phys.
Rev. Lett. 84, 3515 (2000)], may cause the orbits to become chaotic. To examine
this claim, we study the divergence of initially nearby phase-space
trajectories and attempt to measure the Lyapunov exponent gamma. Even for
systems with maximally spinning objects and large spin-orbit misalignment
angles, we find no chaotic behavior. For all the systems we consider, we can
place a strict lower limit on the divergence time t_L=1/gamma that is many
times greater than the typical inspiral time, suggesting that chaos should not
adversely affect the detection of inspiral events by upcoming
gravitational-wave detectors.",0107082v1
2002-12-16,High Spin Glueballs from the Lattice,"We discuss the principles underlying higher spin glueball calculations on the
lattice. For that purpose, we develop numerical techniques to rotate Wilson
loops by arbitrary angles in lattice gauge theories close to the continuum. As
a first application, we compute the glueball spectrum of the SU(2) gauge theory
in 2+1 dimensions for both parities and for spins ranging from 0 up to 4
inclusive. We measure glueball angular wave functions directly, decomposing
them in Fourier modes and extrapolating the Fourier coefficients to the
continuum. This allows a reliable labelling of the continuum states and gives
insight into the way rotation symmetry is recovered. As one of our results, we
demonstrate that the D=2+1 SU(2) glueball conventionally labelled as J^P = 0^-
is in fact 4^- and that the lightest ``J=1'' state has, in fact, spin 3.",0212026v2
2001-03-25,Spin transfer in high energy fragmentation processes,"We point out that measuring longitudinal polarizations of different hyperons
produced in lepton induced reactions are ideal to study the spin transfer of
the fragtmenting quark to produced hadron in high energy hadronization
processes. We briefly summarize the method used in calculating the hyperon
polarizations in these processes, then present some of the results for e+e- and
e-p or \nu p reactions obtained using two different pictures for the spin
structure of hyperon: that drawn from polarized deep inelastic lepton-nucleon
scattering data or that using SU(6) symmetric wave functions. The results show
in particular that measurements of such polarizations should provide useful
information to the question of which picture is more suitable in describing the
spin effects in the fragmentation processes.",0103266v1
1998-07-20,Massive spinning particles and the geometry of null curves,"We study the simplest geometrical particle model associated with null paths
in four-dimensional Minkowski space-time. The action is given by the
pseudo-arclength of the particle worldline. We show that the reduced classical
phase space of this system coincides with that of a massive spinning particle
of spin $s=\alpha^2/M$, where $M$ is the particle mass, and $\alpha$ is the
coupling constant in front of the action. Consistency of the associated quantum
theory requires the spin $s$ to be an integer or half integer number, thus
implying a quantization condition on the physical mass $M$ of the particle.
Then, standard quantization techniques show that the corresponding Hilbert
spaces are solution spaces of the standard relativistic massive wave equations.
Therefore this geometrical particle model provides us with an unified
description of Dirac fermions ($s=1/2$) and massive higher spin fields.",9807143v1
2001-03-27,Spin ordering of nuclear spectra from random interactions,"Recent developments in many-body quantum chaos have raised the issue of
correlations between different families of levels in the spectra of random
fermionic systems. It seems that rotational invariance is sufficient to force
an otherwise random system to have statistically ordered spectra where the
ground state can have zero spin or the maximum spin allowed a huge portion of
the time. We have tackled this question and have characterized the role of
``geometric chaoticity'' and pairing in random systems. We have shown how the
geometry gives rise to such a distribution of ground state spins and examined
the coexistence of these regularities with chaotic wave functions.",0103069v1
2000-01-14,Spin dynamics of wave packets evolving with the Dirac Hamiltonian in atoms with high Z,"The motion of circular WP for one electron in central Coulomb field with high
Z is calculated. The WP is defined in terms of solutions of the Dirac equation
in order to take into account all possible relevant effects in particular the
spin-orbit potential. A time scale is defined within which spin dynamics must
be taken into account mainly in the atoms with high Z. Within this time scale
there exists a mechanism of collapses and revivals of the spin already shown by
the authors for harmonic oscillator potential and called the 'spin-orbit
pendulum'. However this effect has not the exact periodicity of the simpler
model, but the WP's spatial motion is nevertheless quite similar.",0001051v2
2002-05-29,Quantum Entanglement of Moving Bodies,"We study the properties of quantum information and quantum entanglement in
moving frames. We show that the entanglement between the spins and the momenta
of two particles can be interchanged under a Lorentz transformation, so that a
pair of particles that is entangled in spin but not momentum in one reference
frame, may, in another frame, be entangled in momentum at the expense of
spin-entanglement. Similarly, entanglement between momenta may be transferred
to spin under a Lorentz transformation. While spin and momentum entanglement
each is not Lorentz invariant, the joint entanglement of the wave function is.",0205179v4
2006-11-02,Electron Fabry-Perot interferometer with two entangled magnetic impurities,"We consider a one-dimensional (1D) wire along which single conduction
electrons can propagate in the presence of two spin-1/2 magnetic impurities.
The electron may be scattered by each impurity via a contact-exchange
interaction and thus a spin-flip generally occurs at each scattering event.
Adopting a quantum waveguide theory approach, we derive the stationary states
of the system at all orders in the electron-impurity exchange coupling
constant. This allows us to investigate electron transmission for arbitrary
initial states of the two impurity spins. We show that for suitable electron
wave vectors, the triplet and singlet maximally entangled spin states of the
impurities can respectively largely inhibit the electron transport or make the
wire completely transparent for any electron spin state. In the latter case, a
resonance condition can always be found, representing an anomalous behaviour
compared to typical decoherence induced by magnetic impurities. We provide an
explanation for these phenomena in terms of the Hamiltonian symmetries.
Finally, a scheme to generate maximally entangled spin states of the two
impurities via electron scattering is proposed.",0611025v2
2007-06-02,Magnetic impurities in a superconductor: Effect of domain walls and interference,"We consider the effect of magnetic impurities, modeled by classical spins, in
a conventional superconductor. We study their effect on the quasiparticles,
specifically on the spin density and local density of states (LDOS). As
previously emphasized, the impurities induce multiple scatterings of the
quasiparticle wave functions leading to complex interference phenomena. Also,
the impurities induce quantum phase transitions in the many-body system.
Previous authors studied the effect of either a small number of impurities
(from one to three) or a finite concentration of impurities, typically in a
disordered distribution. In this work we assume a regular set of spins
distributed inside the superconductor in such a way that the spins are
oriented, forming different types of domain walls, assumed stable. This
situation may be particularly interesting in the context of spin transfer due
to polarized currents traversing the material.",0706.0269v1
2007-09-06,Half-metallic graphene nanodots,"A comprehensive first-principles theoretical study of the electronic
properties and half-metallic nature of finite rectangular graphene nanoribbons
is presented. We identify the bisanthrene isomer of the C28H14 molecule to be
the smallest polycyclic aromatic hydrocarbon to present a spin polarized ground
state. Even at this quantum dot level, the spins are predicted to be aligned
antiferromagnetically at the two zigzag edges of the molecule. As a rule of
thumb, we find that zigzag edges that are at least three consecutive units
long, will present spin polarization if the width of the system is 1 nm or
wider. Room temperature detectability of the magnetic ordering is predicted for
molecules with zigzag edges 1 nm and longer. For the longer systems studied,
spin wave structures appear in some high spin multiplicity states. Energy gap
oscillations with the length of the zigzag edge are observed. The amplitude of
these oscillations is found to be smaller than that predicted for infinite
ribbons. The half-metallic nature of the ribbons under an external in-plane
electric field is found to be preserved even for finite and extremely short
systems.",0709.0938v2
2007-10-30,Spin polaron in the J1-J2 Heisenberg model,"We have studied the validity of the spin polaron picture in the frustrated
J1-J2 Heisenberg model. For this purpose, we have computed the hole spectral
functions for the Neel, collinear, and disordered phases of this model, by
means of the self-consistent Born approximation and Lanczos exact
diagonalization on finite-size clusters. We have found that the spin polaron
quasiparticle excitation is always well defined for the magnetically ordered
Neel and collinear phases, even in the vicinity of the magnetic quantum
critical points, where the local magnetization vanishes. As a general feature,
the effect of frustration is to increase the amplitude of the multimagnon
states that build up the spin polaron wave function, leading to the reduction
of the quasiparticle coherence. Based on Lanczos results, we discuss the
validity of the spin polaron picture in the disordered phase.",0710.5720v1
2007-12-11,Quantum Monte Carlo study of small pure and mixed spin-polarized tritium clusters,"We have investigated the stability limits of small spin-polarized clusters
consisting of up to ten spin-polarized tritium T$\downarrow$ atoms and the
mixtures of T$\downarrow$ with spin-polarized deuterium D$\downarrow$ and
hydrogen H$\downarrow$ atoms. All of our calculations have been performed using
the variational and diffusion Monte Carlo methods. For clusters with
D$\downarrow$ atoms, the released node procedure is used in cases where the
wave function has nodes. In addition to the energy, we have also calculated the
structure of small clusters using unbiased estimators. Results obtained for
pure T$\downarrow$ clusters are in good accordance with previous calculations,
confirming that the trimer is the smallest spin-polarized tritium cluster. Our
results show that mixed T$\downarrow$-H$\downarrow$ clusters having up to ten
atoms are unstable and that it takes at least three tritium atoms to bind one,
two or three D$\downarrow$ atoms. Among all the considered clusters, we have
found no other Borromean states except the ground state of the T$\downarrow$
trimer.",0712.1730v1
2007-12-21,Comparison between numerical-relativity and post-Newtonian waveforms from spinning binaries: the orbital hang-up case,"We compare results from numerical simulations of spinning binaries in the
""orbital hangup"" case, where the binary completes at least nine orbits before
merger, with post-Newtonian results using the approximants TaylorT1, T4 and Et.
We find that, over the ten cycles before the gravitational-wave frequency
reaches $M\omega = 0.1$, the accumulated phase disagreement between NR and
2.5PN results is less than three radians, and is less than 2.5 radians when
using 3.5PN results. The amplitude disagreement between NR and restricted PN
results increases with the black holes' spin, from about 6% in the equal-mass
case to 12% when the black holes' spins are $S_i/M_i^2 = 0.85$. Finally, our
results suggest that the merger waveform will play an important role in
estimating the spin from such inspiral waveforms.",0712.3787v3
2008-02-07,Spin-transfer switching and low-field precession in exchange-biased spin valve nano-pillars,"Using a three-dimensional focused-ion beam lithography process we have
fabricated nanopillar devices which show spin transfer torque switching at zero
external magnetic fields. Under a small in-plane external bias field, a
field-dependent peak in the differential resistance versus current is observed
similar to that reported in asymmetrical nanopillar devices. This is
interpreted as evidence for the low-field excitation of spin waves which in our
case is attributed to a spin-scattering asymmetry enhanced by the IrMn exchange
bias layer coupled to a relatively thin CoFe fixed layer.",0802.1003v1
2008-03-19,Resonant Spin-Transfer-Driven Switching of Magnetic Devices Assisted by Microwave Current Pulses,"The torque generated by the transfer of spin angular momentum from a
spin-polarized current to a nanoscale ferromagnet can switch the orientation of
the nanomagnet much more efficiently than a current-generated magnetic field,
and is therefore in development for use in next-generation magnetic random
access memory (MRAM). Up to now, only DC currents and square-wave current
pulses have been investigated in spin-torque switching experiments. Here we
present measurements showing that spin transfer from a microwave-frequency
pulse can produce a resonant excitation of a nanomagnet and lead to improved
switching characteristics in combination with a square current pulse. With the
assistance of a microwave-frequency pulse, the switching time is reduced and
achieves a narrower distribution than when driven by a square current pulse
alone, and this can permit significant reductions in the integrated power
required for switching. Resonantly excited switching may also enable
alternative, more compact MRAM circuit architectures.",0803.2880v1
2008-03-21,Intrinsic electric polarization in spin-orbit coupled semiconductor heterostructures,"We present Maxwell equations with source terms for the electromagnetic field
interacting with a moving electron in a spin-orbit coupled semiconductor
heterostructure. We start with the eight--band ${\bm k}{\bm p}$ model and
derive the electric and magnetic polarization vectors using the Gordon--like
decomposition method. Next, we present the ${\bm k}{\bm p}$ effective
Lagrangian for the nonparabolic conduction band electrons interacting with
electromagnetic field in semiconductor heterostructures with abrupt interfaces.
This Lagrangian gives rise to the Maxwell equations with source terms and
boundary conditions at heterointerfaces as well as equations for the electron
envelope wave function in the external electromagnetic field together with
appropriate boundary conditions. As an example, we consider spin--orbit effects
caused by the structure inversion asymmetry for the conduction electron states.
We compute the intrinsic contribution to the electric polarization of the
steady state electron gas in asymmetric quantum well in equilibrium and in the
spin Hall regime. We argue that this contribution, as well as the intrinsic
spin Hall current, are not cancelled by the elastic scattering processes.",0803.3193v1
2008-03-26,Quantum Phase Transitions beyond the Landau's Paradigm in Sp(4) Spin System,"We propose quantum phase transitions beyond the Landau's paradigm of Sp(4)
spin Heisenberg models on the triangular and square lattices, motivated by the
exact Sp(4)$\simeq$ SO(5) symmetry of spin-3/2 fermionic cold atomic system
with only $s-$wave scattering. On the triangular lattice, we study a phase
transition between the $\sqrt{3}\times\sqrt{3}$ spin ordered phase and a $Z_2$
spin liquid phase, this phase transition is described by an O(8) sigma model in
terms of fractionalized spinon fields, with significant anomalous scaling
dimensions of spin order parameters. On the square lattice, we propose a
deconfined critical point between the Neel order and the VBS order, which is
described by the CP(3) model, and the monopole effect of the compact U(1) gauge
field is expected to be suppressed at the critical point.",0803.3822v4
2008-08-26,Superconducting state of quasiparticles with spin dependent mass and their distinguishability for Cooper-pair state,"Spin dependence of quasiparticle mass has been observed recently in CeCoIn5
and other systems. It emerges from strong electronic correlations in a
magnetically polarized state and was predicted earlier. Additionally, the
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)phase has also been discovered in
CeCoIn5 and therefore, the question arises as to what extent these two basic
phenomena are interconnected, as it appears in theory. Here we show that the
appearance of the spin-split masses essentially extends the regime of
temperature and applied magnetic field, in which FFLO state is stable, and
thus, it is claimed to be very important for the phase detectability.
Furthermore, in the situation when the value of the spin z-component \sigma
differentiates masses of the particles, the fundamental question is to what
extent the two mutually bound particles are indistinguishable quantum
mechanically? By considering first the Cooper-pair state we show explicitly
that the antisymmetry of the spin-pair wave function in the ground state may be
broken when the magnetic field is applied.",0808.3542v1
2008-09-18,Evaluation of new spin foam vertex amplitudes,"The Christensen-Egan algorithm is extended and generalized to efficiently
evaluate new spin foam vertex amplitudes proposed by Engle, Pereira & Rovelli
and Freidel & Krasnov, with or without (factored) boundary states. A concrete
pragmatic proposal is made for comparing the different models using uniform
methodologies, applicable to the behavior of large spin asymptotics and of
expectation values of specific semiclassical observables. The asymptotics of
the new models exhibit non-oscillatory, power-law decay similar to that of the
Barrett-Crane model, though with different exponents. Also, an analysis of the
semiclassical wave packet propagation problem indicates that the Magliaro,
Rovelli and Perini's conjecture of good semiclassical behavior of the new
models does not hold for generic factored states, which neglect spin-spin
correlations.",0809.3190v3
2008-11-26,Critical Slowing Down of Triangular Lattice Spin-3/2 Heisenberg Antiferromagnet Li7RuO6 via 7Li NMR,"We report 7Li NMR studies of single crystals of triangular-lattice Heisenberg
antiferromagnet Li7RuO6. Slow critical divergence with a wide critical region
of |T/TN - 1|< 7 was observed in 7Li nuclear spin-lattice relaxation rate. The
slowing down of staggered spin fluctuations was analyzed in a renormalized
classical region of a two-dimensional triangular-lattice non-linear sigma
model. A spin stiffness constant was found to reduce to about 20 % from the
value in a spin-wave approximation. The effect of spin frustration, e.g., Z2
vortex excitations on the critical phenomena is suggested.",0811.4226v2
2009-01-12,Non-thermal transient sources from rotating black holes,"Rotating black holes can power the most extreme non-thermal transient
sources. They have a long-duration viscous time-scale of spin-down and produce
non-thermal emissions along their spin-axis, powered by a relativistic
capillary effect. We report on the discovery of exponential decay in BATSE
light curves of long GRBs by matched filtering, consistent with a viscous
time-scale, and identify UHECRs energies about the GZK threshold in linear
acceleration of ion contaminants along the black hole spin-axis, consistent
with black hole masses and lifetimes of FR II AGN. We explain the absence of
UHECRs from BL Lac objects due to UHECR emissions preferably at appreciable
angles away from the black hole spin-axis. Black hole spin may be key to
unification of GRBs and their host environments, and to AGN and their host
galaxies. Our model points to long duration bursts in radio from long GRBs
without supernovae and gravitational-waves from all long GRBs.",0901.1674v1
2009-02-27,Monte Carlo Determination of the Low-Energy Constants of a Spin 1/2 Heisenberg Model with Spatial Anisotropy,"Motivated by the possible mechanism for the pinning of the electronic liquid
crystal direction in YBCO as proposed in \cite{Pardini08}, we use the first
principles Monte Carlo method to study the spin 1/2 Heisenberg model with
antiferromagnetic couplings $J_{1}$ and $J_{2}$ on the square lattice. The
corresponding low-energy constants, namely the spin stiffness $\rho_s$, the
staggered magnetization density ${\cal M}_s$, the spin wave velocity $c$, as
well as the ground state energy density $e_0$ are determined by fitting the
Monte Carlo data to the predictions of magnon chiral perturbation theory. In
particular, the spin stiffnesses $\rho_{s1}$ and $\rho_{s2}$ are investigated
as a function of the ratio $J_{2}/J_{1}$ of the couplings. Although we find a
good agreement between our results with those obtained by the series expansion
method in the weakly anisotropic regime, for strong anisotropy we observe
discrepancies.",0902.4861v3
2009-04-22,Nonstationary theory of magnetic field induced current for molecular spin nanojunction,"For the study of molecular spin junctions, we take into account two types of
couplings between the molecule and the metal leads: (i) electron transfer that
gives rise to net current in the biased junction and (ii) energy transfer
between the molecule and the leads. Using a rotating wave approximation in the
Heisenberg representation, we derive a set of differential equations for the
expectation values of relevant variables: electron and phonon populations and
molecular polarization. A magnetic field control method to enhance the charge
transfer at spin nanojunctions, which characterizes the molecule feature, is
discussed. An approximate analytical solution of the resulting dynamical
equation is supported by numerical solution. The magnetic control by charge
transfer is described by transient pseudo-fermions of electrons interacting
with spins. The rapid adiabatic passage of the energy between the molecule and
the leads is taken into account. The current for molecular spin nanojunctions
is derived.",0904.3461v1
2009-04-24,Effect of electron-doping on spin excitations of underdoped BaFe$_{1.96}$Ni$_{0.04}$As$_{2}$,"We use neutron scattering to study magnetic order and spin excitations in
BaFe$_{1.96}$Ni$_{0.04}$As$_{2}$. On cooling, the system first changes the
lattice symmetry from tetragonal to orthoromhbic near $\sim$97 K, and then
orders antiferromagnetically at $T_N=91$ K before developing weak
superconductivity below $\sim$15 K. Although superconductivity appears to
co-exist with static antiferromagnetic order from transport and neutron
diffraction measurement, inelastic neutron scattering experiments reveal that
magnetic excitations do not respond to superconductivity. Instead, the effect
of electron-doping is to reduce the c-axis exchange coupling in BaFe$_2$As$_2$
and induce quasi two-dimensional spin excitations. These results suggest that
transition from three-dimensional spin waves to two-dimensional spin
excitations by electron-doping is important for the separated
structural/magnetic phase transitions and high-temperature superconductivity in
iron arsenides.",0904.3775v1
2009-04-24,Magnon BEC and Spin Superfluidity: a 3He primer,"Bose-Einstein condensation (BEC) is a quantum phenomenon of formation of the
collective quantum state, in which the macroscopic number of particles occupies
the lowest energy state and thus is governed by a single wave function. Here we
highlight the BEC in a magnetic subsystem -- the BEC of magnons, elementary
magnetic excitations. Magnon BEC is manifested as the spontaneously emerging
state of the precessing spins, in which all spins precess with the same
frequency and phase even in the inhomogeneous magnetic field. We consider this
phenomenon on example of spin precession in superfluid phases of $^3$He. The
magnon BEC in these phases has all the properties of spin superfluidity. The
states of the phase-coherent precession belong to the class of the coherent
quantum states, which manifest themselves by superfluidity, superconductivity,
quantum Hall effect, Josephson effect and many other macroscopic quantum
phenomena.",0904.3889v1
2009-05-12,Strong-coupling Spin-singlet Superconductivity with Multiple Full Gaps in Hole-doped Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ Probed by Fe-NMR,"We present $^{57}$Fe-NMR measurements of the novel normal and
superconducting-state characteristics of the iron-arsenide superconductor
Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ ($T_c$ = 38 K). In the normal state, the
measured Knight shift and nuclear spin-lattice relaxation rate $(1/T_1)$
demonstrate the development of wave-number ($q$)-dependent spin fluctuations,
except at $q$ = 0, which may originate from the nesting across the disconnected
Fermi surfaces. In the superconducting state, the spin component in the
$^{57}$Fe-Knight shift decreases to almost zero at low temperatures, evidencing
a spin-singlet superconducting state. The $^{57}$Fe-$1/T_1$ results are totally
consistent with a $s^\pm$-wave model with multiple full gaps, regardless of
doping with either electrons or holes.",0905.1896v1
2009-07-17,Spin-order driven Fermi surface revealed by quantum oscillations in an underdoped high Tc superconductor,"We use quantum oscillation measurements to distinguish between spin and
orbital components of the lowest energy quasiparticle excitations in
YBa2Cu3O6.54, each of which couple differently to a magnetic field. Our
measurements reveal the phase of the observed quantum oscillations to remain
uninverted over a wide angular range, indicating that the twofold spin
degeneracy of the Landau levels is virtually unaltered by the magnetic field.
The inferred suppression of the spin degrees of freedom indicates a spin
density-wave is responsible for creation of the small Fermi surface pockets in
underdoped YBa2Cu3O6+x - further suggesting that excitations of this phase are
important contributors to the unconventional superconducting pairing mechanism.",0907.2958v1
2009-09-10,Coupling of localized moments and itinerant electrons in EuFe2As2 single crystals studied by Electron Spin Resonance,"Electron spin resonance measurements in EuFe2As2 single crystals revealed an
absorption spectrum of a single resonance with Dysonian lineshape. Above the
spin-density wave transition at T_SDW = 190 K the spectra are isotropic and the
spin relaxation is strongly coupled to the CEs resulting in a Korringa-like
increase of the linewidth. Below T_SDW, a distinct anisotropy develops and the
relaxation behavior of the Eu spins changes drastically into one with
characteristic properties of a magnetic insulating system, where dipolar and
crystal-field interactions dominate. This indicates a spatial confinement of
the conduction electrons to the FeAs layers in the SDW state.",0909.2054v1
2009-10-02,Field-induced coupled superconductivity and spin density wave order in the Heavy Fermion compound CeCoIn5,"The high field superconducting state in CeCoIn5 has been studied by
transverse field muon spin rotation measurements with an applied field parallel
to the crystallographic c-axis close to the upper critical field Hc2 = 4.97 T.
At magnetic fields >= 4.8 T the muon Knight shift is enhanced and the
superconducting transition changes from second order towards first order as
predicted for Pauli-limited superconductors. The field and temperature
dependence of the transverse muon spin relaxation rate sigma reveal
paramagnetic spin fluctuations in the field regime from 2 T < H < 4.8 T. In the
normal state close to Hc2 correlated spin fluctuations as described by the self
consistent renormalization theory are observed. The results support the
formation of a mode-coupled superconducting and antiferromagnetically ordered
phase in CeCoIn5 for H directed parallel to the c-axis.",0910.0353v1
2009-10-06,Canonical formulation of gravitating spinning objects at 3.5 post-Newtonian order,"The 3.5 post-Newtonian (PN) order is tackled by extending the canonical
formalism of Arnowitt, Deser, and Misner to spinning objects. This extension is
constructed order by order in the PN setting by utilizing the global Poincare
invariance as the important consistency condition. The formalism is valid to
linear order in the single spin variables. Agreement with a recent action
approach is found. A general formula for the interaction Hamiltonian between
matter and transverse-traceless part of the metric at 3.5PN is derived. The
wave equation resulting from this Hamiltonian is considered in the case of the
constructed formalism for spinning objects. Agreement with the Einstein
equations is found in this case. The energy flux at the spin-orbit level is
computed.",0910.1008v2
2010-02-08,Coulomb-induced Rashba spin-orbit coupling in semiconductor quantum wells,"In the absence of an external field, the Rashba spin-orbit interaction (SOI)
in a two-dimensional electron gas in a semiconductor quantum well arises
entirely from the screened electrostatic potential of ionized donors. We adjust
the wave functions of a quantum well so that electrons occupying the first
(lowest) subband conserve their spin projection along the growth axis (Sz),
while the electrons occupying the second subband precess due to Rashba SOI.
Such a specially designed quantum well may be used as a spin relaxation
trigger: electrons conserve Sz when the applied voltage (or current) is lower
than a certain threshold V*; higher voltage switches on the Dyakonov-Perel spin
relaxation.",1002.1510v2
2010-03-12,Spin dynamics in electron-doped pnictide superconductors,"The doping dependence of spin excitations in
Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$ is studied based on a two-orbital model
under RPA approximation. The interplay between the spin-density-wave (SDW) and
superconductivity (SC) is considered in our calculation. Our results for the
spin susceptibility are in good agreement with neutron scattering (NS)
experiments in various doping ranges at temperatures (T) above and below the
superconducting transition temperature T$_{c}$. For the overdoped sample where
one of the two hole pockets around $\Gamma$ point disappears according to
ARPES, we show that the imaginary part of the spin susceptibility in both SC
and normal phases exhibits a gap-like behavior. This feature is consistent with
the ""pseudogap"" as observed by recent NMR and NS experiments.",1003.2609v1
2010-03-30,Quantum and pseudoclassical descriptions of nonrelativistic spinning particles in noncommutative space,"We construct a nonrelativistic wave equation for spinning particles in the
noncommutative space (in a sense, a $\theta$-modification of the Pauli
equation). To this end, we consider the nonrelativistic limit of the
$\theta$-modified Dirac equation. To complete the consideration, we present a
pseudoclassical model (\`a la Berezin-Marinov) for the corresponding
nonrelativistic particle in the noncommutative space. To justify the latter
model, we demonstrate that its quantization leads to the $\theta$-modified
Pauli equation. Then, we extract $\theta$-modified interaction between a
nonrelativistic spin and a magnetic field from the $\theta$-modified Pauli
equation and construct a $\theta$-modification of the Heisenberg model for two
coupled spins placed in an external magnetic field. In the framework of such a
model, we calculate the probability transition between two orthogonal EPR
(Einstein-Podolsky-Rosen) states for a pair of spins in an oscillatory magnetic
field and show that some of such transitions, which are forbidden in the
commutative space, are possible due to the space noncommutativity.",1003.5902v3
2010-04-01,Angle-dependence of quantum oscillations in YBa2Cu3O6.59 shows free spin behaviour of quasiparticles,"Measurements of quantum oscillations in the cuprate superconductors afford a
new opportunity to assess the extent to which the electronic properties of
these materials yield to a description rooted in Fermi liquid theory. However,
such an analysis is hampered by the small number of oscillatory periods
observed. Here we employ a genetic algorithm to globally model the field,
angular, and temperature dependence of the quantum oscillations observed in the
resistivity of YBa2Cu3O6.59. This approach successfully fits an entire data set
to a Fermi surface comprised of two small, quasi-2-dimensional cylinders. A key
feature of the data is the first identification of the effect of Zeeman
splitting, which separates spin-up and spin-down contributions, indicating that
the quasiparticles in the cuprates behave as nearly free spins, constraining
the source of the Fermi surface reconstruction to something other than a
conventional spin density wave with moments parallel to the CuO2 planes.",1004.0260v2
2010-06-18,On the Meissner Effect of the Odd-Frequency Superconductivity with Critical Spin Fluctuations: Possibility of Zero Field FFLO pairing,"We investigate the influence of critical spin fluctuations on electromagnetic
responses in the odd-frequency superconductivity. It is shown that the Meissner
kernel of the odd-frequency superconductivity is strongly reduced by the
critical spin fluctuation or the massless spin wave mode in the
antiferromagnetic phase. These results imply that the superfluid density is
reduced, and the London penetration depth is lengthened for the odd-frequency
pairing. It is also shown that the zero field Flude-Ferrell-Larkin-Ovchinnikov
pairing is spontaneously realized both for even- and odd-frequency in the case
of sufficiently strong coupling with low lying spin-modes.",1006.3722v2
2010-07-07,Spin Zeros and the Origin of Fermi Surface Reconstruction in the Cuprates,"Two recent quantum oscillation studies find contradictory results concerning
the existence of spin zeros - zeros of the oscillatory signal induced by Zeeman
splitting of the Landau levels. We discuss these experiments in light of
calculations of the oscillations assuming a spin density wave state. We find
that the lack of spin zeros reported in one of the experiments is consistent
with either hole or electron pockets in such a state, if the staggered moment
is perpendicular to the external field. An analysis for field directions near
the planes might be able to differentiate between the two. On the other hand,
if spin zeros exist as reported in the other experiment, then the staggered
moment would have to have a substantial longitudinal component. We suggest
several experiments to test whether this is indeed the case.",1007.1047v1
2010-08-27,Optical orientation and spin-dependent recombination in GaAsN alloys under continuous-wave pumping,"We present a systematic theoretical study of spin-dependent recombination and
its effect on optical orientation of photoelectron spins in semiconductors with
deep paramagnetic centers. For this aim we generalize the Shockley-Read theory
of recombination of electrons and holes through the deep centers with allowance
for optically-induced spin polarization of free and bound electrons. Starting
from consideration of defects with three charge states we turn to the
two-charge-state model possessing nine parameters and show that it is
compatible with available experimental data on undoped GaAsN alloys. In the
weak- and strong-pumping limits, we derive simple analytic equations which are
useful in prediction and interpretation of experimental results. Experimental
and theoretical dependencies of the spin-dependent-recombination ratio and
degree of photoluminescence circular polarization on the pumping intensity and
the transverse magnetic field are compared and discussed.",1008.4755v1
2010-08-28,Quantum and pseudoclassical descriptions of nonrelativistic spinning particles in noncommutative space,"We construct a nonrelativistic wave equation for spinning particles in the
noncommutative space (in a sense, a $\theta$-modification of the Pauli
equation). To this end, we consider the nonrelativistic limit of the
$\theta$-modified Dirac equation. To complete the consideration, we present a
pseudoclassical model (\`a la Berezin-Marinov) for the corresponding
nonrelativistic particle in the noncommutative space. To justify the latter
model, we demonstrate that its quantization leads to the $\theta$-modified
Pauli equation. We extract $\theta$-modified interaction between a
nonrelativistic spin and a magnetic field from such a Pauli equation and
construct a $\theta$-modification of the Heisenberg model for two coupled spins
placed in an external magnetic field. In the framework of such a model, we
calculate the probability transition between two orthogonal EPR
(Einstein-Podolsky-Rosen) states for a pair of spins in an oscillatory magnetic
field and show that some of such transitions, which are forbidden in the
commutative space, are possible due to the space noncommutativity. This allows
us to estimate an upper bound on the noncommutativity parameter.",1008.4890v2
2010-10-21,Controlling spin motion and interactions in a one-dimensional Bose gas,"Experiments on ultracold gases offer unparalleled opportunities to explore
quantum many-body physics, with excellent control over key parameters including
temperature, density, interactions and even dimensionality. In some systems,
atomic interactions can be adjusted by means of magnetic Feshbach resonances,
which have played a crucial role in realizing new many-body phenomena. However,
suitable Feshbach resonances are not always available, and they offer limited
freedom since the magnetic field strength is the only control parameter. Here
we show a new way to tune interactions in one-dimensional quantum gases using
state-dependent dressed potentials, enabling control over non-equilibrium spin
motion in a two-component gas of 87Rb. The accessible range includes the point
of spin-independent interactions where exact quantum many-body solutions are
available and the point where spin motion is frozen. This versatility opens a
new route to experiments on spin waves, spin-""charge"" separation and the
relation between superfluidity and magnetism in low-dimensional quantum gases.",1010.4545v1
2010-11-16,Development in the Scattering Matrix Theory: From Spin-Orbit-Coupling Affected Shot Noise to Quantum Pumping,"The review chapter starts by a pedagogical introduction to the general
concept of the scattering theory: from the fundamental wave-function picture to
the second-quantization language, with the aim to clear possible ambiguity in
conventional textbooks. Recent progress in applying the method to current
fluctuations and oscillating-parameter driven quantum pumping processes is
presented with inclusion of contributions by B\""{u}ttiker, Brouwer, Moskalets,
Zhu, etc. In particular, the spin-orbit-coupling affected shot noise can be
dealt with by taking into account the spin-dependent scattering processes. A
large shot noise suppression with the Fano factor below 0.5 observed
experimentally can be illustrated by effective repulsion between electrons with
antiparallel spin induced by the Dresselhaus spin-orbit coupling effect. A
Floquet scattering theory for quantum-mechanical pumping in mesoscopic
conductors is developed by Moskalets et al., which gives a general picture of
quantum pumping phenomenon, from adiabatic to non-adiabatic and from weak
pumping to strong pumping.",1011.3603v1
2011-01-07,Spinning super-massive objects in galactic nuclei up to $a_* > 1$,"Nowadays we believe that a typical galaxy contains about $10^7$ stellar-mass
black holes and a single super-massive black hole at its center. According to
general relativity, these objects are characterized solely by their mass $M$
and by their spin parameter $a_*$. A fundamental limit for a black hole in
general relativity is the Kerr bound $|a_*| \le 1$, but the accretion process
can spin it up to $a_* \approx 0.998$. If a compact object is not a black hole,
the Kerr bound does not hold and in this letter I provide some evidences
suggesting that the accretion process could spin the body up to $a_* > 1$.
While this fact should be negligible for stellar-mass objects, some of the
super-massive objects at the center of galaxies may actually be super-spinning
bodies exceeding the Kerr bound. Such a possibility can be tested by
gravitational wave detectors like LISA or by sub-millimeter very long baseline
interferometry facilities.",1101.1364v2
2011-01-25,Manifestation of New Interference Effects in Superconductor/Ferromagnet Spin Valve,"Superconductor/ferromagnet (S/F) spin valve effect theories based on the S/F
proximity phenomenon assume that the superconducting transition temperature Tc
of F1/F2/S or F1/S/F2 trilayers for parallel magnetizations of the F1- and
F2-layers (TcP) are smaller than for the antiparallel orientations (TcAP).
Here, we report for CoOx/Fe1/Cu/Fe2/In multilayered systems with varying
Fe2-layer thickness the sign-changing oscillating behavior of the spin valve
effect \Delta Tc=TcAP-TcP. Our measurements revealed the full direct spin valve
effect with TcAP>TcP for Fe2-layer thickness dFe2<1 nm and the full inverse
(TcAP<TcAP) spin valve effect for dFe2>=1 nm. Interference of Cooper pair wave
functions reflected from both surfaces of the Fe2-layer appear as the most
probable reason for the observed behavior of \Delta Tc.",1101.4817v2
2011-03-11,Signatures of spin-orbit interaction in transport properties of finite carbon nanotubes in a parallel magnetic field,"The transport properties of finite nanotubes placed in a magnetic field
parallel to their axes are investigated. Upon including spin-orbit coupling and
curvature effects, two main phenomena are analyzed which crucially depend on
the tube's chirality: i) Finite carbon nanotubes in a parallel magnetic field
may present a suppression of current due to the localization at the edges of
otherwise conducting states. This phenomenon occurs due to the magnetic-field
dependent open boundary conditions obeyed by the carbon nanotube's wave
functions. The transport is fully suppressed above threshold values of the
magnetic field which depend on the nanotube chirality, length and on the
spin-orbit coupling. ii) Reversible spin polarized currents can be obtained
upon tuning the magnetic field, exploiting the curvature-induced spin-orbit
splitting.",1103.2308v1
2011-06-08,Quantum Magnetism with Polar Alkali Dimers,"We show that dipolar interactions between ultracold polar alkali dimers in
optical lattices can be used to realize a highly tunable generalization of the
t-J model, which we refer to as the t-J-V-W model. The model features
long-range spin-spin interactions J_z and J_perp of XXZ type, long-range
density-density interaction V, and long-range density-spin interaction W, all
of which can be controlled in both magnitude and sign independently of each
other and of the tunneling t. The ""spin"" is encoded in the rotational degree of
freedom of the molecules, while the interactions are controlled by applied
static electric and continuous-wave microwave fields. Furthermore, we show that
nuclear spins of the molecules can be used to implement an additional (orbital)
degree of freedom that is coupled to the original rotational degree of freedom
in a tunable way. The presented system is expected to exhibit exotic physics
and to provide insights into strongly correlated phenomena in condensed matter
systems. Realistic experimental imperfections are discussed.",1106.1655v1
2011-07-11,Elementary excitations in dipolar spin-1 Bose-Einstein condensates,"We have numerically solved the low-energy excitation spectra of ferromagnetic
Bose-Einstein condensates subject to dipolar interparticle interactions. The
system is assumed to be harmonically confined by purely optical means, thereby
maintaining the spin degree of freedom of the condensate order parameter. Using
a zero-temperature spin-1 model, we solve the Bogoliubov excitations for
different spin textures, including a spin-vortex state in the absence of
external magnetic fields and a rapidly rotating polarized spin texture in a
finite homogeneous field. In particular, we consider the effect of dipolar
interactions on excitations characteristic of ferromagnetic condensates. The
energies of spin waves and magnetic quadrupole modes are found to increase
rapidly with the dipolar coupling strength, whereas the energies of density
oscillations change only slightly.",1107.2061v2
2011-10-10,Neutrino emissivity of $^{3}P_{2}$-$^{3}F_{2}$ superfluid cores in neutron stars,"The influence of the admixture of the $^{3}F_{2}$ state onto collective spin
oscillations and neutrino emission processes in the triplet superfluid neutron
liquid is studied in the BCS approximation. The eigen mode of spin oscillations
with $\omega\simeq\sqrt{58/35}\Delta$ is predicted to exist in the triplet
superfluid neutron condensate besides the already known mode
$\omega\simeq\Delta/\sqrt{5}$. Excitation of the high-frequency spin
oscillations in the condensate occurs through the tensor interactions between
quasiparticles.
  Neutrino energy losses through neutral weak currents are found to consist of
three separate contributions caused by a recombination of broken Cooper pairs
and by weak decays of the collective modes of spin oscillations. Neutrino
decays of the low-frequency spin waves can play an important role in the
cooling scenario of neutron stars. Weak decays of the high-frequency
oscillations that occur only if the tensor forces are taken into account in the
pairing interactions does not modify substantially the total energy losses.
Simple expressions are suggested for the total neutrino emissivity.",1110.2145v1
2011-11-16,Spin-spin correlation function of the 2D XY model with weak site or bond dilution,"The spin-spin correlation function of the 2D XY model decays as a power law
at all temperatures below the Berezinskii-Kosterlitz-Thouless transition point
with a temperature dependent exponent $\eta=\eta(T/J)$ ($J$ is the
ferromagnetic coupling strength). It is known from computer experiments that in
the 2D XY model with site or bond dilution this exponent depends on
concentration $p$ of removed sites/bonds as well. Knowing the slope
$\partial\eta/\partial p$ at point $p=0$, one can predict the value of the
exponent for small dilution concentrations:
$\eta(p)\simeq\eta(0)+p(\partial\eta/\partial p)|_{p=0}$. As it is shown in
this paper, the spin-wave Hamiltonian allows to obtain exact results for this
slope: $(\partial\eta/\partial p)|_{p=0} = T/(2J) + O((T/J)^2)$ and $T/(\pi J)
+ O((T/J)^2)$ for site and for bond dilution, respectively.",1111.3939v2
2012-01-09,Externally driven one-dimensional Ising model,"A one dimensional kinetic Ising model at a finite temperature on a
semi-infinite lattice with time varying boundary spins is considered. Exact
expressions for the expectation values of the spin at each site are obtained,
in terms of the time dependent boundary condition and the initial conditions.
The solution consists of a transient part which is due to the initial
condition, and a part driven by the boundary. The latter is an evanescent wave
when the boundary spin is oscillating harmonically. Low- and high-frequency
limits are investigated with greater detail. The total magnetization of the
lattice is also obtained. It is seen that for any arbitrary rapidly varying
boundary conditions, this total magnetization is equal to the the boundary spin
itself, plus essentially the time integral of the boundary spin. A nonuniform
model is also investigated.",1201.1836v1
2012-02-07,Electrical activation and electron spin resonance measurements of implanted bismuth in isotopically enriched silicon-28,"We have performed continuous wave and pulsed electron spin resonance
measurements of implanted bismuth donors in isotopically enriched silicon-28.
Donors are electrically activated via thermal annealing with minimal diffusion.
Damage from bismuth ion implantation is repaired during thermal annealing as
evidenced by narrow spin resonance linewidths (B_pp=12uT and long spin
coherence times T_2=0.7ms, at temperature T=8K). The results qualify ion
implanted bismuth as a promising candidate for spin qubit integration in
silicon.",1202.1560v2
2012-02-17,Growth of Interaction Between Antiprotons (Negative Hyperons) and Nuclei in Polarized Matter: The Possibility to Study the Spin-Dependent Part of the Forward Scattering Amplitude in the Range of Low-Energies,"The influence of Coulomb interaction on the phenomenon of ""optical"" spin
rotation of negatively charged particles (antiprotons, etc.) moving in matter
with polarized nuclei is considered. It is shown that because the density of
the antiproton (negative hyperon) wave function on the nucleus increases, the
spin precession frequency grows as the particle decelerates. As a result, spin
rotation of negatively charged particles becomes observable despite their rapid
deceleration. This provides information about the spin--dependent part of the
amplitude of coherent elastic zero--angle scattering in the range of low
energies, where scattering experiments are practically impossible to perform.",1202.3897v2
2012-02-22,Temperature dependence of the resonance and low energy spin excitations in superconducting FeTe$_{0.6}$Se$_{0.4}$,"We use inelastic neutron scattering to study the temperature dependence of
the low-energy spin excitations in single crystals of superconducting
FeTe$_{0.6}$Se$_{0.4}$ ($T_c=14$ K). In the low-temperature superconducting
state, the imaginary part of the dynamic susceptibility at the electron and
hole Fermi surfaces nesting wave vector $Q=(0.5,0.5)$,
$\chi^{\prime\prime}(Q,\omega)$, has a small spin gap, a two-dimensional
neutron spin resonance above the spin gap, and increases linearly with
increasing $\hbar\omega$ for energies above the resonance. While the intensity
of the resonance decreases like an order parameter with increasing temperature
and disappears at temperature slightly above $T_c$, the energy of the mode is
weakly temperature dependent and vanishes concurrently above $T_c$. This
suggests that in spite of its similarities with the resonance in electron-doped
superconducting BaFe$_{2-x}$(Co,Ni)$_x$As$_2$, the mode in
FeTe$_{0.6}$Se$_{0.4}$ is not directly associated with the superconducting
electronic gap.",1202.5015v1
2012-03-29,Correlation functions in SU(2)-invariant RVB spin liquids on nonbipartite lattices,"We introduce a Monte Carlo scheme based on sampling of Pfaffians to
investigate Anderson's resonating-valence-bond (RVB) spin liquid wave function
on the kagome and the triangular lattice. This eliminates a sign problem that
prevents utilization of the valence bond basis in Monte Carlo studies for
non-bipartite lattices. Studying lattice sizes of up to 600 sites, we calculate
singlet-singlet and spin-spin correlations, and demonstrate how the lattice
symmetry is restored within each topological sector as the system size is
increased. Our findings are consistent with the expectation that the nearest
neighbor RVB states describe a topological spin liquid on these non-bipartite
lattices.",1203.6621v2
2012-03-31,Spin Squeezing under Non-Markovian Channels by Hierarchy Equation Method,"We study spin squeezing under non-Markovian channels, and consider an
ensemble of $N$ independent spin-1/2 particles with exchange symmetry. Each
spin interacts with its own bath, and the baths are independent and identical.
For this kind of open system, the spin squeezing under decoherence can be
investigated from the dynamics of the local expectations, and the multi-qubit
dynamics can be reduced into the two-qubit one. The reduced dynamics is
obtained by the hierarchy equation method, which is a exact without
rotating-wave and Born-Markov approximation. The numerical results show that
the spin squeezing displays multiple sudden vanishing and revival with lower
bath temperature, and it can also vanish asymptotically.",1204.0093v1
2012-05-31,Effect of spin-orbit coupling on magnetic and orbital order in MgV$_2$O$_4$,"Recent measurements on MgV$_2$O$_4$ single crystal have reignited the debate
on the role of spin-orbit (SO) coupling in dictating the orbital order in
Vanadium spinel systems. Density functional theory calculations were performed
using the full-potential linearized augmented-plane-wave method within the
local spin density approximation (LSDA), Coulomb correlated LSDA+U, and with SO
interaction (LSDA+U+SO) to study the magnetic and orbital ordering in low
temperature phase of MgV$_2$O$_4$. It is observed that the spin-orbit coupling
in the experimentally observed antiferromagnetic phase, affects the orbital
order differently in alternate V-atom chains along c-axis. This observation is
found to be consistent with the experimental prediction that the effect of
spin-orbit coupling is intermediate between that in case of ZnV$_2$O$_4$ and
MnV$_2$O$_4$.",1205.6950v1
2012-07-25,Multipole Analysis of Radio-Frequency Reactions in Ultra-Cold Atoms,"Using the multipole expansion we analyze photo induced reactions in an
ultra-cold atomic gas composed of identical neutral bosons. While the
Frank-Condon factor dominates the photo induced spin-flip reactions, we have
found that for frozen-spin process where the atomic spins are conserved the
reaction rate is governed by the monopole $r^2$ and the quadrupole terms.
Consequently, the dependence of the frozen-spin reaction rate on the photon
wave number $k$ acquires an extra $k^4$ factor in comparison to the spin-flip
process. Comparing the relative strength of the $r^2$ and quadrupole modes in
dimer photoassociation we predict that the mutual importance of these two modes
changes with temperature and scattering length.",1207.5936v2
2012-08-14,Field induced spin exciton doublet splitting in d_{x^2-y^2}-wave 115-heavy electron superconductors,"We investigate the spin-exciton modes in the superconducting d_{x^2-y^2}
state of CeMIn_5 heavy fermion compounds found at the antiferromagnetic wave
vector by inelastic neutron scattering. We present a theoretical model that
explains the field dependence for both field directions. We show that the
recently observed splitting of the spin exciton doublet in CeCoIn_5 into two
non-degenerate modes for in-plane field appears naturally in this model. This
is due to the spin anisotropy of g- factors and quasiparticle interactions
which lead to different resonant conditions for the dynamic susceptibility
components. We predict that the splitting of the spin resonance doublet becomes
strongly nonlinear for larger fields when the energy of both split components
decreases. For field along the tetragonal axis no splitting but only a
broadening of the resonance is found in agreement with experiment.",1208.2897v1
2012-11-02,Degeneracy between mass and spin in black-hole-binary waveforms,"We explore the degeneracy between mass and spin in gravitational waveforms
emitted by black-hole binary coalescences. We focus on spin-aligned waveforms
and obtain our results using phenomenological models that were tuned to
numerical-relativity simulations. A degeneracy is known for low-mass binaries
(particularly neutron-star binaries), where gravitational-wave detectors are
sensitive to only the inspiral phase, and the waveform can be modelled by
post-Newtonian theory. Here, we consider black-hole binaries, where detectors
will also be sensitive to the merger and ringdown, and demonstrate that the
degeneracy persists across a broad mass range. At low masses, the degeneracy is
between mass ratio and total spin, with chirp mass accurately determined. At
higher masses, the degeneracy persists but is not so clearly characterised by
constant chirp mass as the merger and ringdown become more significant. We
consider the importance of this degeneracy both for performing searches
(including searches where only non-spinning templates are used) and in
parameter extraction from observed systems. We compare observational
capabilities between the early (~2015) and final (2018 onwards) versions of the
Advanced LIGO detector.",1211.0546v1
2012-11-23,Extrinsic Spin Hall Effect Due to Transition-Metal Impurities,"We investigate the extrinsic spin Hall effect in the electron gas model due
to transition-metal impurities based on the single-impurity Anderson model with
orbital degrees of freedom. Both the skew scattering and side jump mechanisms
are analyzed in a unified way, and the significant role of orbital degrees of
freedom are clarified. The obtained spin Hall conductivities are in proportion
to the spin-orbit polarization at the Fermi level ($R = <l \cdot s>$) as is the
case with the intrinsic spin Hall effect: skew scattering term $\sigma^{ss} ~ R
\delta_1/\rho$, and side jump term $\sigma^{sj} ~ R$, where $\delta_1$ is the
phase shift for $p$ ($l=1$) partial wave. Furthermore, the present study
indicates the existence of a nontrivial close relationship between the
intrinsic term $\sigma^{int}$ and the extrinsic side jump term $\sigma^{sj}$.",1211.5549v1
2012-12-09,Single Mode Approximation for sub-Ohmic Spin-Boson Model: Adiabatic Limit and Critical Properties,"In this work, the quantum phase transition in the sub-Ohmic spin-boson model
is studied using a single-mode approximation, by combining the rotating wave
transformation and the transformations used in the numerical renormalization
group (NRG). Analytical results for the critical coupling strength $\alpha_c$,
the magnetic susceptibility $\chi(T)$, and the spin-spin correlation function
$C(\omega)$ at finite temperatures are obtained and further confirmed by
numerical results. We obtain the same $\alpha_c$ as the mean-field
approximation. The critical exponents are classical: $\beta=1/2$, $\delta=3$,
$\gamma=1$, $x=1/2$, $y_t^{*}=1/2$, in agreement with the spin-boson model in
$0<s<1/2$ regime. $C(\omega)$ has nontrivial behavior reflecting coherent
oscillation with temperature dependent damping effects due to the environment.
We point out the original NRG has problem with the crossover temperature
$T^{*}$, and propose a chain Hamiltonian possibly suitable for implementing NRG
without boson state truncation error.",1212.1889v1
2012-12-10,Antiferromagnetic Spatial Ordering in a Quenched One-dimensional Spinor Gas,"We have experimentally observed the emergence of spontaneous
antiferromagnetic spatial order in a sodium spinor Bose-Einstein condensate
that was quenched through a magnetic phase transition. For negative values of
the quadratic Zeeman shift, a gas initially prepared in the F = 1, mF = 0 state
collapsed into a dynamically evolving superposition of all 3 spin projections,
mF = 0, +/-1. The quench gave rise to rich, nonequilibrium behavior where both
nematic and magnetic spin waves were generated. We characterized the
spatiotemporal evolution through two particle correlations between atoms in
each pair of spin states. These revealed dramatic differences between the
dynamics of the spin correlations and those of the spin populations.",1212.2233v1
2013-01-11,"Neutron Scattering Study on Spin Dynamics in Superconducting (Tl,Rb)2Fe4Se5","We observed in superconducting (Tl,Rb)2Fe4Se5 spin-wave branches that span an
energy range from 6.5 to 209 meV. Spin dynamics are successfully described by a
Heisenberg localized spin model whose dominant in-plane interactions include
only the nearest (J1 and J1') and next nearest neighbor (J2 and J2') exchange
terms within and between the tetramer spin blocks, respectively. These
experimentally determined exchange constants would crucially constrain the
theoretical viewpoints on magnetism and superconductivity in the Fe-based
materials.",1301.2413v1
2013-01-11,Spin-filtering efficiency of ferrimagnetic spinels CoFe2O4 and NiFe2O4,"We assess the potential of the ferrimagnetic spinel ferrites CoFe2O4 and
NiFe2O4 to act as spin filtering barriers in magnetic tunnel junctions. Our
study is based on the electronic structure calculated by means of
first-principles density functional theory within different approximations for
the exchange correlation energy. We show that, in agreement with previous
calculations, the densities of states suggest a lower tunneling barrier for
minority spin electrons, and thus a negative spin-filter effect. However, a
more detailed analysis based on the complex band-structure reveals that both
signs for the spin-filtering efficiency are possible, depending on the band
alignment between the electrode and the barrier materials and depending on the
specific wave-function symmetry of the relevant bands within the electrode.",1301.2541v1
2013-02-19,Spin effects in electron vortex states,"The recent experimental realization of electron vortex beams opens up a wide
research domain previously unexplored. The present paper explores the
relativistic properties of these electron vortex beams, and quantifies
deviations from scalar wave theory. It is common in electron optics to use the
Schr\""odinger equation neglecting spin. The present paper investigates the role
of spin and the total angular momentum Jz and how it pertains to the vortex
states. As an application, we also investigate if it is possible to use
holographic reconstruction to create novel total angular momentum eigenstates
in a Transmission Electron Microscope. It is demonstrated that relativistic
spin coupling effects disappear in the paraxial limit, and spin effects in
holographically created electron vortex beams can only be exploited by using
specialized magnetic apertures.",1302.4547v2
2013-03-21,Relaxation of flying spin qubits in quantum wires by hyperfine interaction,"We consider the relaxation of a spin qubit in a quantum dot propagating as a
whole in a one-dimensional semiconductor with hyperfine coupling. We show that
this motion leads to qualitatively new features in this process compared to
static quantum dots. For a fast straightforward motion, the initial spin
density decreases to zero with the relaxation rate independent of the spatial
spread of the electron wave function and inversely proportional to the electron
speed. However, for the oscillatory motion, the qubit acquires memory, and the
dephasing becomes Gaussian rather than exponential. After some time, one third
of the initial spin polarization is restored, as it happens for static qubits.
This revival can occur either through periodic peaks or through a monotonous
increase in the polarization, after a minimum, until a plateau has been
reached. Our results can be useful for the understanding of the spin dynamics
and decoherence in quantum wires.",1303.5273v1
2013-04-08,Spin states of iron impurities in magnesium oxide under pressure: A possible intermediate state,"Ferropericlase (Mg,Fe)O is a major lower mantle mineral, and studying its
properties is a fundamental step toward understanding the Earth's interior.
Here, we performed a first-principles investigation on the properties of iron
as an isolated impurity in magnesium oxide, which is the condition of
ferropericlase under which iron-iron interactions could be neglected. The
calculations were carried using the all-electron full-potential linearized
augmented plane wave method within the density functional theory in the
generalized gradient approximation plus the on-site Hubbard correction. We
present the electronic and magnetic properties, electric and magnetic hyperfine
splitting of this impurity in high and low spin states for several charge
states at zero pressure, which were then extended to high pressures. For the
impurity in the neutral charge state, our results indicated that there is a
metastable intermediate spin state (S=1), in addition to the high (S=2) and low
(S=0) spin states. Those results were discussed in the context of an
intermediate spin state, experimentally identified in ferrosilicate perovskite.",1304.2227v1
2013-04-09,Ground-state phase diagram and critical temperature of two-component Bose gases with Rashba spin-orbit coupling,"Ground-state phase diagram of two-component Bose gases with Rashba spin-orbit
coupling is determined via a variational approach. A phase in which the fully
polarized condensate occupies zero momentum is identified. This zero-momentum
phase competes with the spin density wave phase when interspecies interaction
is stronger than intraspecies interaction, and the former one is always the
ground state for weak spin-orbit coupling. When the energies of these two
phases are close, there is a phase separation between them. At finite
temperature, such a zero-momentum condensation can be induced by a
ferromagnetic phase transition in normal state. The spontaneous spin
polarization removes the degeneracy of quasiparticles' energy minima, and
consequently the modified density of state accommodates a Bose condensation to
appear below a critical temperature.",1304.2690v2
2013-05-09,Competing superfluid orders in spin-orbit coupled fermionic cold atom optical lattices,"The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase, a superconducting state
with non-zero total momentum Cooper pairs in a large magnetic field, was first
predicted about 50 years ago, and since then became an important concept in
many branches of physics. Despite intensive search in various materials,
unambiguous experimental evidence for the FFLO phase is still lacking in
experiments. In this paper, we show that both FF (uniform order parameter with
plane-wave phase) and LO phase (spatially varying order parameter amplitude)
can be observed using fermionic cold atoms in spin-orbit coupled optical
lattices. The increasing spin-orbit coupling enhances the FF phase over the LO
phase. The coexistence of superfluid and magnetic orders is also found in the
normal BCS phase. The pairing mechanism for different phases is understood by
visualizing superfluid pairing densities in different spin-orbit bands. The
possibility of observing similar physics using spin-orbit coupled
superconducting ultra-thin films is also discussed.",1305.2152v2
2013-05-14,Quasiclassical Treatment and Odd-parity/Triplet Correspondence in Topological Superconductors,"We construct a quasiclassical framework for topological superconductors with
the strong spin-orbit coupling such as CuxBi2Se3. In the manner of the
quasiclassical treatment, decomposing the slowly varying component from the
total quasi-particle wave function, the original massive Dirac Bogoliubov-de
Gennes (BdG) Hamiltonian derived from the tight-binding model represented by 8
x 8 matrix is reduced to 4 x 4 one. The resultant equations are equivalent to
Andreev-type equations of singlet or triplet superconductors, in which the
apparent spin-orbit coupling vanishes. Using this formalism, we find a fact
that the odd-parity superconductivity in topological superconductors turns to
the spin-triplet one. % without the spin-orbit coupling through the
quasiclassical treatment. Moreover, in terms of the quasiclassical treatment,
we show that the topologically-protected zero-energy states in topological
superconductors has the correspondence to the Andreev bound states established
in a long history of studies for the unconventional superconductors. This
clearly indicates that low-energy non-trivial superconducting properties in the
topological superconductors can be analyzed by the established theoretical
descriptions on the spin-triplet superconductors.",1305.3025v2
2013-06-06,Spin Magnetic Moment and Persistent Orbital Currents in Cylindrical Nanolayer,"Densities of persistent orbital and spin magnetic moment currents of an
electron in a cylindrical nanolayer in the presence of external axial magnetic
field are considered. For the mentioned current densities analytical
expressions are obtained. The conditions when in the system only spin magnetic
moment current is present are defined. Dependencies of orbital and spin
magnetic moment currents on geometrical parameters of nanolayer are derived. It
is shown that in the case of layered geometry the dependence of spin magnetic
moment current on radial coordinate has a non-monotonic behavior. This is the
peculiarity of layered geometry of nanostructure and it is due to the behavior
of wave function of the system along the radial direction. Dependent on the
directions of the field and orbital rotation of the electron there are defined
values of radial coordinates when the orbital current disappears. The
transition to the case of cylindrical quantum dot is discussed as well.",1306.1396v2
2013-06-27,Matter Wave Interferometry of a Levitated Thermal Nano-Oscillator Induced and Probed by a Spin,"We show how the interference between spatially separated states of the center
of mass (COM) of a mesoscopic harmonic oscillator can be evidenced by coupling
it to a spin and performing solely spin manipulations and measurements (Ramsey
Interferometry). We propose to use an optically levitated diamond bead
containing an NV center spin. The nano-scale size of the bead makes the
motional decoherence due to levitation negligible. The form of the spin-motion
coupling ensures that the scheme works for thermal states so that moderate
feedback cooling suffices. No separate control or observation of the COM state
is required and thereby one dispenses with cavities, spatially resolved
detection and low mass-dispersion ensembles. The controllable relative phase in
the Ramsey interferometry stems from a gravitational potential difference so
that it uniquely evidences coherence between states which involve the whole
nano-crystal being in spatially distinct locations.",1306.6579v2
2013-07-17,Electron-Phonon Coupling on the Surface of Topological Insulators,"Topological insulators (TIs) are materials that have a bulk electronic band
gap like an ordinary insulator but have protected conducting states on their
surface. One of the most interesting properties of TIs is their spin helicity,
whereby the spin is locked normal to the wave vector of the surface electronic
state. The topological surface states should be very stable in TIs, since these
spin-textured surface states are robust against spin-independent
backscattering. Scattering from defects and other lattice imperfections is
possible provided the spin is not completely flipped. However, the quality of
TI crystals can be controlled by careful growth, whereas phonons will exist in
even the most perfect crystals. Consequently, electron-phonon coupling (EPC)
should be the dominant scattering mechanism for surface electronic states at
finite temperatures. Hence, the study of EPC in TIs is of exceptional
importance in assessing any potential applications. In this article both
experimental and theoretical studies of the EPC on the surface of TIs are
reviewed, with the contents mainly focused on the typical strong three
dimensional TIs, such as Bi2Se3 and Bi2Te3.",1307.4559v1
2013-07-22,Quantum Monte Carlo study of the three-dimensional spin-polarized homogeneous electron gas,"We have studied the spin-polarized three-dimensional homogeneous electron gas
using the diffusion quantum Monte Carlo method, with trial wave functions
including backflow and three-body correlations in the Jastrow factor, and we
have used twist averaging to reduce finite-size effects. Calculations of the
pair correlation function, including the on-top pair density, as well as the
structure factor and the total energy, are reported for systems of 118
electrons in the density range $r_\text{s}=0.5$--20 a.u., and for spin
polarizations of 0, 0.34, 0.66, and 1. We consider the spin resolution of the
pair correlation function and structure factor, and the energy of spin
polarization. We show that a control variate method can reduce the variance
when twist-averaging, and we have achieved higher accuracy and lower noise than
earlier quantum Monte Carlo studies.",1307.5794v1
2013-08-01,Spin effects in strong-field laser-electron interactions,"The electron spin degree of freedom can play a significant role in
relativistic scattering processes involving intense laser fields. In this
contribution we discuss the influence of the electron spin on (i) Kapitza-Dirac
scattering in an x-ray laser field of high intensity, (ii) photo-induced
electron-positron pair production in a strong laser wave and (iii) multiphoton
electron-positron pair production on an atomic nucleus. We show that in all
cases under consideration the electron spin can have a characteristic impact on
the process properties and their total probabilities. To this end,
spin-resolved calculations based on the Dirac equation in the presence of an
intense laser field are performed. The predictions from Dirac theory are also
compared with the corresponding results from the Klein-Gordon equation.",1308.0231v2
2013-08-27,Soft confinement in a 3-d spin system,"We consider a 1+3 dimensional spin system. The spin-wave (magnon) field is
described by the O(3) non-linear sigma model with a symmetry-breaking
potential. This interacts with a slow spin SU(2) doublet Schrodinger fermion.
The interaction is described by a generalized nonperturbative Yukawa coupling,
and the self-consistency condition is solved with the aid of a non-relativistic
Gribov equation. When the Yukawa coupling is sufficiently strong, the solution
exhibits supercriticality and soft confinement, in a way that is quite
analogous to Gribov's light-quark confinement theory.
  The solution corresponds to a new type of spin polaron, whose condensation
may lead to exotic superconductivity.",1308.5731v1
2013-10-07,Double magnetic resonance and spin anisotropy in Fe-based superconductors due to static and fluctuating antiferromagnetic orders,"Motivated by recent neutron scattering experiments in Fe-based
superconductors, we study how the magnetic resonance in the superconducting
state is affected by the simultaneous presence of either static or fluctuating
magnetic orders using the random phase approximation. We find that for the
underdoped materials with coexisting superconducting and antiferromagnetic
orders, spin rotational symmetry is explicitly broken at the ordering momentum
$Q_1 = (\pi,0)$. Only the longitudinal susceptibility exhibits the resonance
mode, whereas a spin-wave Goldstone mode develops in the transverse component.
Meanwhile, at the frustrated momentum $Q_2 = (0,\pi)$, the susceptibility
becomes isotropic in spin space and the magnetic resonance exists for both
components. Furthermore, the resonance energies at $Q_1$ and $Q_2$ have
distinct scales, which provides a natural explanation for the recently observed
double resonance peaks. In addition, we show that near optimal doping the
existence of strong magnetic fluctuations, which are modeled here via a
Gaussian mode, can still induce the spin anisotropy in the magnetic
susceptibility.",1310.1657v2
2013-10-28,Maximal Rabi frequency of an electrically driven spin in a disordered magnetic field,"We present a theoretical study of the spin dynamics of a single electron
confined in a quantum dot. Spin dynamics is induced by the interplay of
electrical driving and the presence of a spatially disordered magnetic field,
the latter being transverse to a homogeneous magnetic field. We focus on the
case of strong driving, i.e., when the oscillation amplitude $A$ of the
electron's wave packet is comparable to the quantum dot length $L$. We show
that electrically driven spin resonance can be induced in this system by
subharmonic driving, i.e., if the excitation frequency is an integer fraction
(1/2, 1/3, etc) of the Larmor frequency. At strong driving we find that (i) the
Rabi frequencies at the subharmonic resonances are comparable to the Rabi
frequency at the fundamental resonance, and (ii) at each subharmonic resonance,
the Rabi frequency can be maximized by setting the drive strength to an
optimal, finite value. Our simple model is applied to describe electrical
control of a spin-valley qubit in a weakly disordered carbon nanotube.",1310.7350v2
2013-10-31,Two distinct spin liquid states in a layered cubic lattice,"We construct a family of short-range resonating-valence-bond wave functions
on a layered cubic lattice, allowing for a tunable anisotropy in the amplitudes
assigned to nearest-neighbour valence bonds along one axis. Monte Carlo
simulations reveal that four phases are stabilized over the full range of the
anisotropy parameter. They are separated from one another by a sequence of
continuous quantum phase transitions. An antiferromagnetic phase, centred on
the perfect isotropy point, intervenes between two distinct quantum spin liquid
states. One of them is continuously deformable to the two-dimensional U(1) spin
liquid, which is known to exhibit critical bond correlations. The other has
both spin and bond correlations that decay exponentially. The existence of this
second phase is proof that, contrary to expectations, neither a bipartite
lattice structure nor a conventional Marshall sign rule is an impediment to
realizing a fully gapped quantum spin liquid.",1311.0004v1
2013-11-06,Quantum Spin Hall Effect as $\mathbb{Z}_2$ Global Gauge Anomaly,"We study the relation between the quantum spin Hall effect(QSHE) and the
$\mathbb{Z}_2$ global gauge anomaly and discover that there exists an
one-to-one correspondence between them. By constructing a two dimensional
non-abelian gauge theory whose non-abelian gauge field is the Berry connection
induced by the Bloch wave function of the quantum spin Hall system, we prove
that if the quantum spin Hall system is topologically nontrivial, the
corresponding 2D gauge theory has a global gauge anomaly. We further generalize
our discussion of the zero modes of the Dirac operator which play a central
role in our analysis. We find that the classical ""spin"" Hall effect also
contains a $\mathbb{Z}_2$ topological invariant which is not noticed before as
far as we know.",1311.1416v2
2013-12-22,Dynamical Skyrmion State in a Spin Current Nano-Oscillator with Perpendicular Magnetic Anisotropy,"We study the spectral characteristics of spin current nano-oscillators based
on the Pt/[Co/Ni] magnetic multilayer with perpendicular magnetic anisotropy.
By varying the applied magnetic field and current, both localized and
propagating spin wave modes of the oscillation are achieved. At small fields,
we observe an abrupt onset of the modulation sidebands. We use micromagnetic
simulations to identify this state as a dynamical magnetic skyrmion stabilized
in the active device region by spin current injection, whose current-induced
dynamics is accompanied by the gyrotropic motion of the core due to the skew
deflection. Our results demonstrate a practical route for controllable skyrmion
manipulation by spin current in magnetic thin films.",1312.6343v2
2014-01-07,Experimental investigation of the optical spin selection rules in bulk Si and Ge/Si quantum dots,"We study the relationship between the circular polarization of
photoluminescence and the magnetic field-induced spin-polarization of the
recombining charge carriers in bulk Si and Ge/Si quantum dots. First, we
quantitatively compare experimental results on the degree of circular
polarization of photons resulting from phonon-assisted radiative transitions in
intrinsic and doped bulk Si with calculations which we adapt from recently
predicted spin-dependent phonon-assisted transition probabilities in Si. The
excellent agreement of our experiments and calculations quantitatively verifies
these spin-dependent transition probabilities and extends their validity to
weak magnetic fields. Such magnetic fields can induce a luminescence
polarization of up to 3%/T. We then investigate phononless transitions in Ge/Si
quantum dots as well as in degenerately doped Si. Our experiments
systematically show that the sign of the degree of circular polarization of
luminescence resulting from phononless transitions is opposite to the one
associated with phonon-assisted transitions in Si and with phononless
transitions in direct band gap semiconductors. This observation implies
qualitatively different spin-dependent selection rules for phononless
transitions, which seem to be related to the confined character of the electron
wave function.",1401.1515v1
2014-07-01,Parity mixing of pair at nuclear surface due to spin-orbit potential in $^{18}$F,"We investigate the structure of $^{18}$F with the microscopic wave function
based on the three-body $^{16}$O+$p$+$n$ model. In the calculation of the
generator coordinate method (GCM) of the three-body model, $T=0$ energy spectra
of $J^\pi=1^+$, $3^+$, and $5^+$ states and $T=1$ spectra of $J^\pi=0^+$, $2^+$
states in $^{18}$F are described reasonably. Based on the dinucleon picture,
the effect of the spin-orbit force on the $T=0$ and $T=1$ $pn$ pairs around the
$^{16}$O core is discussed. The $T=1$ pair in the $J^\pi=0^+$ state gains the
spin-orbit potential energy involving the odd-parity mixing in the pair. The
spin-orbit potential energy gain with the parity mixing is not so efficient for
the $T=0$ pair in the $J^\pi=1^+$ state. The parity mixing in the pair is
regarded as the internal symmetry breaking of the pair in the spin-orbit
potential at the nuclear surface.",1407.0151v1
2014-07-10,NMR investigation of spin correlations in BaCo2As2,"We use NMR techniques to investigate the magnetic properties of BaCo2As2
single crystals, the non-superconducting end member of the Co-substituted
iron-pnictide high Tc superconductor Ba(Fe1-xCox)2As2 with x = 1. We present
75As NMR evidence for enhancement of low frequency spin fluctuations below ~
100 K. This enhancement is accompanied by that of static uniform spin
susceptibility at the wave vector q = 0, suggesting that the primary channel of
the spin correlations is ferromagnetic rather than antiferromagnetic.
Comparison between the NMR Knight shift 75K and bulk susceptibility chi(bulk)
data uncovers the presence of two separate components of spin susceptibility
with distinct temperature dependences, presumably because multiple electronic
bands crossing the Fermi energy play different roles in the electronic
properties of BaCo2As2.",1407.2750v1
2014-07-15,Transverse Spin and Classical Gluon Fields: Combining Two Perspectives on Hadronic Structure,"In recent decades, the spin and transverse momentum of quarks and gluons were
found to play integral roles in the structure of the nucleon. Simultaneously,
the onset of gluon saturation in hadrons and nuclei at high energies was
predicted to result in a new state of matter dominated by classical gluon
fields. Understanding both of these contributions to hadronic structure is
essential for current and future collider phenomenology. In this Dissertation,
we study the combined effects of transverse spin and gluon saturation using the
Glauber-Gribov-Mueller / McLerran-Venugopalan model of a heavy nucleus in the
quasi-classical approximation. We investigate the use of a
transversely-polarized projectile as a probe of the saturated gluon fields in
the nucleus, finding that the transverse spin asymmetry of produced particles
couples to the component of the gluon fields which is antisymmetric under both
time reversal and charge conjugation. We also analyze the effects of saturation
on the transverse spin asymmetry (Sivers function) of quarks within the wave
function of the nucleus, finding that gluon saturation preferentially generates
the asymmetry through the orbital angular momentum of the nucleons, together
with nuclear shadowing.",1407.4047v1
2014-08-02,Crossover from Room-temperature Double-channel Ballistic Transport to Single-channel Ballistic Transport in Zigzag Graphene Nanoribbons,"Very recently, it was demonstrated explicitly that a zigzag graphene
nanoribbon (GNR) exhibits a crossover of conductance from G0 to G0/2 with
increasing the length (G0 = 2e2/h is the quantum of conductance) even at
room-temperature [Baringhaus, et al. Nature 506, 349 (2014)]. Such a result is
puzzling as none of previous theories seem to match the experimental
observations. Here, we propose a model to explain the crossover from
double-channel to single-channel ballistic transport in zigzag GNR. The sp3
distortion of carbon atoms at the GNR edges induces a large spin-orbit coupling
on the edges atoms, which enhances spin-flip scattering of edge states of the
zigzag GNR. With sufficient spin-flip scattering, the wave-function of edge
states becomes a superposition of the spin-up and spin-down components. Then
the coupling of the two edges becomes important. This removes the edge degree
of freedom in the zigzag GNR and results in the evolution of the conductance
from G0 to G0/2 with increasing the length.",1408.0327v3
2014-10-17,Coexistence of ferromagnetism and superconductivity in iron based pnictides: a time resolved magnetooptical study,"Ferromagnetism and superconductivity are antagonistic phenomena. Their
coexistence implies either a modulated ferromagnetic order parameter on a
lengthscale shorter than the superconducting coherence length or a weak
exchange coupling between the itinerant superconducting electrons and the
localized ordered spins. In some iron based pnictide superconductors the
coexistence of ferromagnetism and superconductivity has been clearly
demonstrated. The nature of the coexistence, however, remains elusive since no
clear understanding of the spin structure in the superconducting state has been
reached and the reports on the coupling strength are controversial. We show, by
a direct optical pump-probe experiment, that the coupling is weak, since the
transfer of the excess energy from the itinerant electrons to ordered localized
spins is much slower than the electron-phonon relaxation, implying the
coexistence without the short-lengthscale ferromagnetic order parameter
modulation. Remarkably, the polarization analysis of the coherently excited
spin wave response points towards a simple ferromagnetic ordering of spins with
two distinct types of ferromagnetic domains.",1410.4651v1
2014-10-24,"The remains of a spinning, hyperbolic encounter","We review a recently proposed approach to construct gravitational wave (GW)
polarization states of unbound spinning compact binaries. Through this rather
simple method, we are able to include corrections due to the dominant order
spin-orbit interactions, in the quadrupolar approximation and in a
semi-analytic way. We invoke the 1.5 post-Newtonian (PN) accurate
quasi-Keplerian parametrization for the radial part of the dynamics and impose
its temporal evolution in the PN accurate polarization states equations.
Further, we compute 1PN accurate amplitude corrections for the polarization
states of non-spinning compact binaries on hyperbolic orbits. As an interesting
application, we perform comparisons with previously available results for both
the GW signals in the case of non-spinning binaries and the theoretical
prediction for the amplitude of the memory effect on the metric after the
hyperbolic passage.",1410.6606v1
2014-10-27,Spin-$\frac{1}{2}$ Heisenberg $J_1$-$J_2$ antiferromagnet on the kagome lattice,"We report variational Monte Carlo calculations for the spin-$\frac{1}{2}$
Heisenberg model on the kagome lattice in the presence of both nearest-neighbor
$J_1$ and next-nearest-neighbor $J_2$ antiferromagnetic superexchange
couplings. Our approach is based upon Gutzwiller projected fermionic states
that represent a flexible tool to describe quantum spin liquids with different
properties (e.g., gapless and gapped). We show that, on finite clusters, a
gapped $\mathbb{Z}_{2}$ spin liquid can be stabilized in the presence of a
finite $J_2$ superexchange, with a substantial energy gain with respect to the
gapless $U(1)$ Dirac spin liquid. However, this energy gain vanishes in the
thermodynamic limit, implying that, at least within this approach, the $U(1)$
Dirac spin liquid remains stable in a relatively large region of the phase
diagram. For $J_2/J_1 \gtrsim 0.3$, we find that a magnetically ordered state
with ${\bf q}={\bf 0}$ overcomes the magnetically disordered wave functions,
suggesting the end of the putative gapless spin-liquid phase.",1410.7359v2
2014-12-06,From Spin Vertex to String Vertex,"In the recent publication arXiv:1410.8860 the spin vertex was introduced as a
new approach for computing three-point functions in N = 4 SYM. In this note we
consider the BMN limit of the spin vertex for scalar excitations and show that
it reproduces the string vertex in the light-cone string field theory which
describes the string interactions in the pp-wave background at the leading
order of BMN expansion. This is achieved by introducing a polynomial
representation for the spin vertex. We derive the Neumann coefficients from the
spin vertex at weak coupling and show they match with the Neumann coefficients
from the string field theory.",1412.2256v3
2015-01-14,CW and pulsed electrically detected magnetic resonance spectroscopy at 263 GHz/12 T on operating amorphous silicon solar cells,"Here we describe a new high frequency/high field continuous wave and pulsed
electrically detected magnetic resonance (CW EDMR and pEDMR) setup, operating
at 263 GHz and resonance fields between 0 and 12 T. Spin dependent transport in
illuminated hydrogenated amorphous silicon p-i-n solar cells at 5 K and 90 K
was studied by in operando 263 GHz CW and pEDMR alongside with complementary
X-band CW EDMR. Benefiting from the superior resolution at 263 GHz, we were
able to better resolve EDMR signals originating from spin dependent hopping and
recombination processes. 5 K EDMR spectra were found to be dominated by
conduction and valence band tale states involved in spin dependent hopping,
with additional contributions from triplet exciton states. 90 K EDMR spectra
could be assigned to spin pair recombination involving conduction band tail
states and dangling bonds as dominating spin dependent transport process, with
additional contributions from valence band tail and triplet exciton states.",1501.03485v1
2015-02-18,Spectral shape deformation in inverse spin Hall voltage in Y3Fe5O12|Pt bilayers at high microwave power levels,"We report on the deformation of microwave absorption spectra and of the
inverse spin Hall voltage signals in thin film bilayers of yttrium iron garnet
(YIG) and platinum at high microwave power levels in a 9.45-GHz TE011 cavity.
As the microwave power increases from 0.15 to 200 mW, the resonance field
shifts to higher values, and the initially Lorentzian spectra of the microwave
absorption intensity as well as the inverse spin Hall voltage signals become
asymmetric. The contributions from opening of the magnetization precession cone
and heating of YIG cannot well reproduce the data. Control measurements of
inverse spin Hall voltages on thin-film YIG|Pt systems with a range of line
widths underscore the role of spin-wave excitations in spectral deformation.",1502.05198v1
2015-02-20,Oscillating spin-orbit interaction in two-dimensional superlattices: sharp transmission resonances and time-dependent spin polarized currents,"We consider ballistic transport through a lateral, two-dimensional
superlattice with experimentally realizable, sinusoidally oscillating
Rashba-type spin-orbit interaction. The periodic structure of the rectangular
lattice produces a spin-dependent miniband structure for static SOI. Using
Floquet theory, transmission peaks are shown to appear in the mini-bandgaps as
a consequence of the additional, time-dependent SOI. A detailed analysis shows
that this effect is due to the generation of harmonics of the driving
frequency, via which e.g., resonances that cannot be excited in the case of
static SOI become available. Additionally, the transmitted current shows space
and time-dependent partial spin-polarization, in other words, polarization
waves propagate through the superlattice.",1502.05798v1
2015-03-23,Local dynamics of topological magnetic defects in the itinerant helimagnet FeGe,"Chiral magnetic interactions induce complex spin textures including helical
and conical spin waves, as well as particle-like objects such as magnetic
skyrmions and merons. These spin textures are the basis for innovative device
paradigms and give rise to exotic topological phenomena, thus being of interest
for both applied and fundamental sciences. Present key questions address the
dynamics of the spin system and emergent topological defects. Here we analyze
the micromagnetic dynamics in the helimagnetic phase of FeGe. By combining
magnetic force microscopy, single-spin magnetometry, and
Landau-Lifschitz-Gilbert simulations we show that the nanoscale dynamics are
governed by the depinning and subsequent motion of magnetic edge dislocations.
The motion of these topologically stable objects triggers perturbations that
can propagate over mesoscopic length scales. The observation of stochastic
instabilities in the micromagnetic structure provides new insight to the
spatio-temporal dynamics of itinerant helimagnets and topological defects, and
discloses novel challenges regarding their technological usage.",1503.06622v2
2015-06-11,Efficient Synchronization of Dipolarly Coupled Vortex-Based Spin Transfer Nano-Oscillators,"Due to their nonlinear properties, spin transfer nano-oscillators can easily
adapt their frequency to external stimuli. This makes them interesting model
systems to study the effects of synchronization and brings some opportunities
to improve their microwave characteristics in view of their applications in
information and communication technologies and to design innovative computing
architectures. So far, mutual synchronization of spin transfer nano-oscillators
through propagating spin-waves and exchange coupling in a common magnetic layer
has been demonstrated. Here we show that the dipolar interaction is also an
efficient mechanism to synchronize neighbouring oscillators. We experimentally
study a pair of vortex-based spin-transfer nano-oscillators, in which mutual
synchronization can be achieved despite a significant frequency mismatch
between oscillators. Importantly, the coupling efficiency is controlled by the
magnetic configuration of the vortices, as confirmed by an analytical model
highlighting the physics at play in the synchronization process as well as by
micromagnetic simulations.",1506.03603v2
2015-06-30,Anomalous Spin Response and Virtual-Carrier-Mediated Magnetism in a Topological Insulator,"We present a comprehensive theoretical study of the static spin response in
HgTe quantum wells, revealing distinctive behavior for the topologically
nontrivial inverted structure. Most strikingly, the q=0 (long-wave-length) spin
susceptibility of the undoped topological-insulator system is constant and
equal to the value found for the gapless Dirac-like structure, whereas the same
quantity shows the typical decrease with increasing band gap in the
normal-insulator regime. We discuss ramifications for the ordering of localized
magnetic moments present in the quantum well, both in the insulating and
electron-doped situations. The spin response of edge states is also considered,
and we extract effective Lande g-factors for the bulk and edge electrons. The
variety of counter-intuitive spin-response properties revealed in our study
arises from the system's versatility in accessing situations where the
charge-carrier dynamics can be governed by ordinary Schrodinger-type physics,
mimics the behavior of chiral Dirac fermions, or reflects the material's
symmetry-protected topological order.",1506.08913v2
2015-09-01,Driving spin excitations by hydrostatic pressure in BiFeO3,"Optical spectroscopy has been combined with computational and theoretical
techniques to show how the spin dynamics in the model multiferroic BiFeO3
responds to the application of hydrostatic pressure and its corresponding
series of structural phase transitions from R3c to the Pnma phases. As pressure
increases, multiple spin excitations associated with non-collinear cycloidal
magnetism collapse into two excitations, which show jump discontinuities at
some of the ensuing crystal phase transitions. Effective Hamiltonian approach
provides information on the electrical polarization and structural changes of
the oxygen octahedra through the successive structural phases. The extracted
parameters are then used in a Ginzburg-Landau model to reproduce the evolution
with pressure of the spin waves excitations observed at low energy and we
demonstrate that the structural phases and the magnetic anisotropy drive and
control the spin excitations.",1509.00284v1
2015-09-15,Dynamical current-induced ferromagnetic and antiferromagnetic resonances,"We demonstrate that ferromagnetic and antiferromagnetic excitations can be
triggered by the dynamical spin accumulations induced by the bulk and surface
contributions of the spin Hall effect. Due to the spin-orbit interaction, a
time-dependent spin density is generated by an oscillatory electric field
applied parallel to the atomic planes of Fe/W(110) multilayers. For symmetric
trilayers of Fe/W/Fe in which the Fe layers are ferromagnetically coupled, we
demonstrate that only the collective out-of-phase precession mode is excited,
while the uniform (in-phase) mode remains silent. When they are
antiferromagnetically coupled, the oscillatory electric field sets the Fe
magnetizations into elliptical precession motions with opposite angular
velocities. The manipulation of different collective spin-wave dynamical modes
through the engineering of the multilayers and their thicknesses may be used to
develop ultrafast spintronics devices. Our work provides a general framework
that probes the realistic responses of materials in the time or frequency
domain.",1509.04599v2
2015-11-27,Spin Decomposition of Electron in QED,"We perform a systematic study on the spin decomposition of an electron in QED
at one-loop order. It is found that the electron orbital angular momentum
defined in Jaffe-Manohar and Ji spin sum rules agrees with each other, and the
so-called potential angular momentum vanishes at this order. The calculations
are performed in both dimensional regularization and Pauli-Villars
regularization for the ultraviolet divergences, and they lead to consistent
results. We further investigate the calculations in terms of light-front wave
functions, and find a missing contribution from the instantaneous interaction
in light-front quantization. This clarifies the confusing issues raised
recently in the literature on the spin decomposition of an electron, and will
help to consolidate the spin physics program for nucleons in QCD.",1511.08817v1
2015-12-04,Kondo screening in two-dimensional $p$-type transition-metal dichalcogenides,"Systems with strong spin orbit coupling support a number of new phases of
matter and novel phenomena. This work focuses on the interplay of spin orbit
coupling and interactions in yielding correlated phenomena in two dimensional
transition metal dichalcogenides. In particular we explore the physics of Kondo
screening resulting from the lack of centro-symmetry, large spin splitting and
spin valley locking in hole doped systems. The key ingredients are i) valley
dependent spin-momentum locking perpendicular to the two dimensional crystal;
ii) single nondegenerate Fermi surface per valley, and iii) nontrivial Berry
curvature associated with the low energy bands. The resulting Kondo resonance
has a finite triplet component and nontrivial momentum space structure which
facilitates new approaches to both probe and manipulate the correlated state.
Using a variational wave function and the numerical renormalization group
approaches we study the nature of the Kondo resonance both in the absence and
presence of circularly polarized light. The latter induces an imbalance in the
population of the two valleys leading to novel magnetic phenomena in the
correlated state.",1512.01590v2
2015-12-21,Quantum antiferromagnetic Heisenberg half-odd integer spin model as the entanglement Hamiltonian of the integer spin Affleck-Kennedy-Lieb-Tasaki states,"Applying a symmetric bulk bipartition to one-dimensional
Affleck-Kennedy-Lieb-Tasaki valence bond solid (VBS) states for the integer
spin-S Haldane gapped phase, we can create an array of fractionalized spin-S/2
edge states with the super unit cell $l$ in the reduced bulk system, and the
topological properties encoded in the VBS wave functions can be revealed. The
entanglement Hamiltonian (EH) with $l=even$ corresponds to the quantum
antiferromagnetic Heisenberg spin-S/2 model. For the even integer spins, the EH
still describes the Haldane gapped phase. For the odd integer spins, however,
the EH just corresponds to the quantum antiferromagnetic Heisenberg half-odd
integer spin model with spinon excitations, characterizing the critical point
separating the topological Haldane phase from the trivial gapped phase. Our
results thus demonstrate that the topological bulk property not only determines
its fractionalized edge states, but also the quantum criticality associated
with the topological phase, where the elementary excitations are precisely
those fractionalized edge degrees of freedom confined in the bulk of the
topological phase.",1512.06550v2
2015-12-21,Spin effects on the dynamics of compact binaries,"Compact binaries are the most promising source for the advanced gravitational
wave detectors, which will start operating this year. The influence of spin on
the binary evolution is an important consequence of general relativity and can
be large. It is argued that the spin supplementary condition, which is related
to the observer dependence of the center, gives rise to a gauge symmetry in the
action principle of spinning point-particles. These spinning point-particles
serve as an analytic model for extended bodies. The internal structure can be
modelled by augmenting the point-particle with higher-order multipole moments.
Consequences of the recently discovered universal (equation of state
independent) relations between the multipole moments of neutron stars are
discussed.",1512.06768v2
2016-01-21,Spin pumping in strongly coupled magnon-photon systems,"We experimentally investigate magnon-polaritons, arising in ferrimagnetic
resonance experiments in a microwave cavity with a tuneable quality factor. To
his end, we simultaneously measure the electrically detected spin pumping
signal and microwave reflection (the ferrimagnetic resonance signal) of a
yttrium iron garnet (YIG) / platinum (Pt) bilayer in the microwave cavity. The
coupling strength of the fundamental magnetic resonance mode and the cavity is
determined from the microwave reflection data. All features of the magnetic
resonance spectra predicted by first principle calculations and an input-output
formalism agree with our experimental observations. By changing the decay rate
of the cavity at constant magnon-photon coupling rate, we experimentally tune
in and out of the strong coupling regime and successfully model the
corresponding change of the spin pumping signal. Furthermore, we observe the
coupling and spin pumping of several spin wave modes and provide a quantitative
analysis of their coupling rates to the cavity.",1601.05681v1
2016-04-05,Triplet Superfluidity on a triangular ladder with dipolar fermions,"Motivated by recent experimental progress in the field of dipolar-Fermi
gases, we investigate the quantum phases of dipolar fermions, on a triangular
ladder at half filling. Using density matrix renormalization group method, in
presence of onsite repulsion and intersite attractive interaction, we find
exotic spin-triplet superfluid phase in addition to the usual spin-density and
charge-density waves. We examine the stability of spin-triplet superfluid phase
by varying hopping along the rungs of the triangle. Possibility of fermionic
supersolidity has also been discussed, by considering three- body interaction
in the Hamiltonian. We also study the effect of spin-dependent hopping on the
stability of spin-triplet superfluid phase.",1604.01225v3
2016-04-05,Conductance measurement of spin-orbit coupling in the two-dimensional electron systems with in-plane magnetic field,"We consider determination of spin-orbit (SO) coupling constants for the
two-dimensional electron gas from measurements of electric properties in
rotated in-plane magnetic field. %Due to the interplay Due to the SO coupling
the electron backscattering is accompanied by spin precession and spin mixing
of the incident and reflected electron waves. The competition of the external
and SO-related magnetic fields produces a characteristic conductance dependence
on the in-plane magnetic field value and orientation which, in turn, allows for
determination of the absolute value of the effective spin-orbit coupling
constant as well as the ratio of the Rashba and Dresselhaus SO contributions.",1604.01270v2
2016-04-28,Large-scale Ising spin network based on degenerate optical parametric oscillators,"Simulating a network of Ising spins with physical systems is now emerging as
a promising approach for solving mathematically intractable problems. Here we
report a large-scale network of artificial spins based on degenerate optical
parametric oscillators (DOPO), paving the way towards a photonic Ising machine
capable of solving difficult combinatorial optimization problems. We generated
>10,000 time-division-multiplexed DOPOs using dual-pump four-wave mixing (FWM)
in a highly nonlinear fibre (HNLF) placed in a fibre cavity. Using those DOPOs,
a one-dimensional (1D) Ising model was simulated by introducing
nearest-neighbour optical coupling. We observed the formation of spin domains
and found that the domain size diverged near the DOPO threshold, which suggests
that the DOPO network can simulate the behavior of low-temperature Ising spins.",1604.08288v1
2016-06-16,Spin dynamics of counterrotating Kitaev spirals via duality,"Incommensurate spiral order is a common occurrence in frustrated magnetic
insulators. Typically, all magnetic moments rotate uniformly, through the same
wavevector. However the honeycomb iridates family Li2IrO3 shows an
incommensurate order where spirals on neighboring sublattices are
counter-rotating, giving each moment a different local environment.
Theoretically describing its spin dynamics has remained a challenge: the Kitaev
interactions proposed to stabilize this state, which arise from strong
spin-orbit effects, induce magnon umklapp scattering processes in spin-wave
theory. Here we propose an approach via a (Klein) duality transformation into a
conventional spiral of a frustrated Heisenberg model, allowing a direct
derivation of the dynamical structure factor. We analyze both Kitaev and
Dzyaloshinskii-Moriya based models, both of which can stabilize counterrotating
spirals, but with different spin dynamics, and we propose experimental tests to
identify the origin of counterrotation.",1606.05356v2
2016-07-06,High-Fidelity Hot Gates for Generic Spin-Resonator Systems,"We propose and analyze a high-fidelity hot gate for generic spin-resonator
systems which allows for coherent spin-spin coupling, in the presence of a
thermally populated resonator mode. Our scheme is non-perturbative, applies to
a broad class of physical systems, including for example spins coupled to
circuit-QED and surface acoustic wave resonators as well as nanomechanical
oscillators, and can be implemented readily with state-of-the-art experimental
setups. We provide and numerically verify simple expressions for the fidelity
of creating maximally entangled states under realistic conditions.",1607.01614v2
2016-07-10,Crossover from collisionless to collisional spin dynamics of polarized fermions,"We study the transverse spin dynamics of trapped polarized Fermi gases in the
high temperature limit. In the non-interacting collisionless regime, a magnetic
field gradient induces collective spin wave oscillations. In the strongly
interacting collisional regime, the dynamics are governed by spin diffusion.
These two limits have been extensively studied both experimentally and
theoretically, but the crossover between them has received less attention. In
this paper, we use a quantum Boltzmann equation to study transverse spin
dynamics and show how the excitations evolve from dispersive to diffusive in
the high temperature limit. We provide analytical solutions in the two limiting
regimes, which agree well with our numerical results.",1607.02764v4
2016-08-07,An electrically driven spin qubit based on valley mixing,"The electrical control of single spin qubits based on semiconductor quantum
dots is of great interest for scalable quantum computing since electric fields
provide an alternative mechanism for qubit control compared with magnetic
fields and can also be easier to produce. Here we outline the mechanism for a
drastic enhancement in the electrically-driven spin rotation frequency for
silicon quantum dot qubits in the presence of a step at a hetero-interface. The
enhancement is due to the strong coupling between the ground and excited states
which occurs when the electron wave-function overcomes the potential barrier
induced by the interface step. We theoretically calculate single qubit gate
times of 170ns for a quantum dot confined at a silicon/silicon-dioxide
interface. The engineering of such steps could be used to achieve fast
electrical rotation and entanglement of spin qubits despite the weak spin-orbit
coupling in silicon.",1608.02189v2
2016-08-19,Competing Exchange Interactions in the Multiferroic and Ferrimagnetic CaBaCo$_4$O$_7$,"Competing exchange interactions can produce complex magnetic states together
with spin-induced electric polarizations. With competing interactions on
alternating triangular and kagome layers, the swedenborgite CBO may have one of
the largest measured spin-induced polarizations of about 1700 nC/cm$^2$ below
its ferrimagnetic transition temperature at 70 K. Powder neutron-diffraction
data, magnetization measurements, and spin-wave resonance frequencies in the
THz range reveal that the complex spin order of multiferroic CBO can be
described as a triangular array of c-axis chains ferrimagnetically coupled to
each other in the ab plane. Magnetostriction on bonds that couple those chains
produces the large spin-induced polarization of CBO.",1608.05628v3
2016-08-24,Spin mixing in Cs ultralong-range Rydberg molecules: a case study,"We calculate vibrational spectra of ultralong-range Cs(32p) Rydberg molecules
which form in an ultracold gas of Cs atoms. We account for the partial-wave
scattering of the Rydberg electrons from the ground Cs perturber atoms by
including the full set of spin-resolved ${}^{1,3}S_J$ and ${}^{1,3}P_J$
scattering phase shifts, and allow for the mixing of singlet (S=0) and triplet
(S=1) spin states through Rydberg electron spin-orbit and ground electron
hyperfine interactions. Excellent agreement with observed data in
Sa{\ss}mannshausen et al. [Phys. Rev. Lett. 113, 133201(2015)] in line
positions and profiles is obtained. We also determine the spin-dependent
permanent electric dipole moments for these molecules. This is the first such
calculation of ultralong-range Rydberg molecules in which all of the
relativistic contributions are accounted for.",1608.06939v1
2016-09-25,Effects of Spin-Orbit Coupling on Jaynes-Cummings and Tavis-Cummings Models,"We consider ultracold atoms inside a ring optical cavity that supports a
single plane-wave mode. The cavity field, together with an external coherent
laser field, drives a two-photon Raman transition between two internal
pseudo-spin states of the atom. This gives rise to an effective coupling
between atom's pseudo-spin and external center-of-mass (COM) motion. For the
case of a single atom inside the cavity, We show how the spin-orbit coupling
modifies the static and dynamic properties of the Jaynes-Cummings (JC) model.
In the case of many atoms in thermodynamic limit, we show that the spin-orbit
coupling modifies the Dicke superradiance phase transition boundary and the
non-superradiant normal phase may become reentrant in some regimes.",1609.07815v2
2016-10-01,Pancharatnam-Berry phase induced spin-selective transmission in herringbone dielectric metamaterials,"Manipulating the polarisation of light is crucial for sensing and imaging
applications. One such aspect in particular is selective transmission of one
circular polarisation (spin) when light is transmitted through a medium or a
device. However, most present methods of achieving this have relatively low
efficiency and selectivity, whilst high selectivity examples rely on lossy and
complex three-dimensional helical or multilayer structures. Here, we propose a
dielectric metamaterial approach for achieving spin-selective transmission of
electromagnetic waves, utilizing spin-controlled constructive or destructive
interference between two Pancharatnam-Berry (PB) phases in conjunction with
propagative dynamic phase. The dielectric metamaterial, consisting of
monolithic silicon herringbone structures, exhibits a broadband operation in
the terahertz regime whilst obtaining a spin-selective efficiency upwards of
60%. Such a device is robust and is not easily degraded by errors in
fabrication.",1610.00196v1
2016-10-05,Interactions in Higher-Spin Gravity: a Holographic Perspective,"This thesis is an elaboration of recent results on the holographic
re-construction of metric-like interactions in higher-spin gauge theories on
anti-de Sitter space (AdS), employing their conjectured holographic duality
with free conformal field theories (CFTs). After reviewing the general approach
and establishing the necessary intermediate results, we extract explicit
expressions for the complete cubic action on AdS$_{d+1}$ and the quartic
self-interaction of the scalar on AdS$_4$ for the type A minimal bosonic
higher-spin theory from the three- and four- point correlation functions of
single-trace operators in the free scalar $O\left(N\right)$ vector model. For
this purpose tools were developed to evaluate tree-level three-point Witten
diagrams involving fields of arbitrary integer spin and the conformal partial
wave expansions of tree-level four-point Witten diagrams, which are underpinned
by the ambient space formulation of AdS space and CFT. We also discuss the
implications of the holographic duality on the locality properties of
interactions in higher-spin gauge theories.",1610.01318v2
2016-10-17,Spin-orbit coupling in quasi-one-dimensional Wigner crystals,"We study the effect of Rashba spin-orbit coupling (SOC) on the charge and
spin degrees of freedom of a quasi-one-dimensional (quasi-1D) Wigner crystal.
As electrons in a quasi-1D Wigner crystal can move in the transverse direction,
SOC cannot be gauged away in contrast to the pure 1D case. We show that for
weak SOC, a partial gap in the spectrum opens at certain ratios between density
of electrons and the inverse Rashba length. We present how the low-energy
branch of charge degrees of freedom deviates due to SOC from its usual linear
dependence at small wave vectors. In the case of strong SOC, we show that spin
sector of a Wigner crystal cannot be described by an isotropic
antiferromagnetic Heisenberg Hamiltonian any more, and that instead the ground
state of neighboring electrons is mostly a triplet state. We present a new spin
sector Hamiltonian and discuss the spectrum of Wigner crystal in this limit.",1610.05241v2
2017-07-25,Frustrated spin-1/2 ladder with ferro- and antiferromagnetic legs,"Two-leg spin-1/2 ladder systems consisting of a ferromagnetic leg and an
antiferromagnetic leg are considered where the spins on the legs interact
through antiferromagnetic rung couplings $J_1$. These ladders can have two
geometrical arrangements either zigzag or normal ladder and these systems are
frustrated irrespective of their geometry. This frustration gives rise to
incommensurate spin density wave, dimer and spin fluid phases in the ground
state. The magnetization in the systems decreases linearly with $J^2_1$, and
the systems show an incommensurate phase for $0.0<J_1<1.0$. The spin-spin
correlation functions in the incommensurate phase follow power law decay which
is very similar to Heisenberg antiferromagnetic chain in external magnetic
field. In large $J_1$ limit, the normal ladder behaves like a collection of
singlet dimers, whereas the zigzag ladder behaves as a one dimensional spin-1/2
antiferromagnetic chain.",1707.07826v1
2017-08-03,Spin Resonance in the New-Structure-Type Iron-Based Superconductor CaKFe4As4,"The dynamical spin susceptibility in the new-structure-type iron-based
superconductor CaKFe$_4$As$_4$ was investigated by using a combination of
inelastic neutron scattering (INS) measurements and random phase approximation
(RPA) calculations. Powder INS measurements show that the spin resonance at
$Q_\text{res}=1.17(1)$~$\text{\AA}^{-1}$, corresponding to the $(\pi,\pi)$
nesting wave vector in tetragonal notation, evolves below $T_\text{c}$. The
characteristic energy of the spin resonance $E_\text{res}=12.5$~meV is smaller
than twice the size of the superconducting gap ($2\Delta$). The broad energy
feature of the dynamical susceptibility of the spin resonance can be explained
by the RPA calculations, in which the different superconducting gaps on
different Fermi surfaces are taken into account. Our INS and PRA studies
demonstrate that the superconducting pairing nature in CaKFe$_4$As$_4$ is the
$s_\pm$ symmetry.",1708.01006v2
2017-08-25,Magnetic fluctuations and spin-spirals in single-layer FeSe,"The magnetic properties of monolayer FeSe films are investigated via
first-principles spin-spiral calculations. Although the (pi,pi) collinear
antiferromagnetic (CL-AFM) mode is lowest in energy, the spin-wave energy E(q)
- which exhibits intrinsic non-Heisenberg behavior - is found to be extremely
very flat over a large region of the two-dimensional Brillouin zone centered at
the checkerboard antiferromagnetic (CB-AFM) q=0 configuration, giving rise to a
sharp peak in the spin density of states. Considering the paramagnetic state as
an incoherent average over spin-spiral states, we find that resulting
electronic band states around the Fermi level closely resemble the bands of the
CB-AFM configuration - not the CL-AFM one - and thus providing a natural
explanation of the angle-resolved photoemission observations. The presence of
the SrTiO3(001) substrate, both with and without interfacial oxygen vacancies,
is found to reduce the energy difference between the CB-AFM and CL-AFM states
and hence enhancing the CB-AFM-like fluctuations.",1708.07868v2
2017-11-27,Characterization of Spin-Transfer-Torque effect induced magnetization dynamics driven by short current pulses,"We present a time-resolved study of the magnetization dynamics in a
microstructured Cr$|$Heusler$|$Pt waveguide driven by the Spin-Hall-Effect and
the Spin-Transfer-Torque effect via short current pulses. In particular, we
focus on the determination of the threshold current at which the spin-wave
damping is compensated. We have developed a novel method based on the temporal
evolution of the magnon density at the beginning of an applied current pulse at
which the magnon density deviates from the thermal level. Since this method
does not depend on the signal-to-noise ratio, it allows for a robust and
reliable determination of the threshold current which is important for the
characterization of any future application based on the Spin-Transfer-Torque
effect.",1711.09647v1
2017-11-29,Relativistic interpretation on the nature of nuclear tensor force,"The spin-dependent nature of the nuclear tensor force is studied in details
within the relativistic Hartree-Fock approach. The relativistic formalism for
the tensor force is supplemented with an additional Lorentz-invariant tensor
formalism in $\sigma$-scalar channel, so as to take into account almost fully
the nature of the tensor force brought about by the Fock diagrams in realistic
nuclei. Specifically, the tensor sum rules are tested for the spin and
pseudo-spin partners with/without nodes, to further understand the tensor force
nature within relativistic model. It is shown that the interference between two
components of nucleon spinors brings distinct violations on the tensor sum
rules in realistic nuclei , which is mainly due to the opposite sign on
$\kappa$ quantities of the upper and lower components as well as the nodal
difference. Even though, the sum rules can be precisely reproduced if taking
the same radial wave functions for the spin/pseudo-spin partners in addition to
neglecting the lower/upper components, revealing clearly the nature of tensor
force.",1711.10950v1
2017-12-13,"Post-Newtonian Dynamics in Dense Star Clusters: Highly-Eccentric, Highly-Spinning, and Repeated Binary Black Hole Mergers","We present models of realistic globular clusters with post-Newtonian dynamics
for black holes. By modeling the relativistic accelerations and
gravitational-wave emission in isolated binaries and during three- and
four-body encounters, we find that nearly half of all binary black hole mergers
occur inside the cluster, with about 10% of those mergers entering the
LIGO/Virgo band with eccentricities greater than 0.1. In-cluster mergers lead
to the birth of a second generation of black holes with larger masses and high
spins, which, depending on the black hole natal spins, can sometimes be
retained in the cluster and merge again. As a result, globular clusters can
produce merging binaries with detectable spins regardless of the birth spins of
black holes formed from massive stars. These second-generation black holes
would also populate any upper mass gap created by pair-instability supernovae.",1712.04937v3
2017-12-22,Structure of the first order Reduced Density Matrix in three electron systems: A Generalized Pauli Constraints assisted study,"We investigate the structure of the one-body Reduced Density Matrix (1RDM) of
three electron systems, i.e. doublet and quadruplet spin configurations,
corresponding to the smallest interacting system with an open-shell ground
state. To this end, we use Configuration Interaction (CI) expansions of the
exact wave function in Slater determinants built from natural orbitals in a
finite dimensional Hilbert space. With the exception of maximally polarized
systems, the natural orbitals of spin eigenstates are generally spin dependent,
i.e. the spatial parts of the up and down natural orbitals form two different
sets. A measure to quantify this spin dependence is introduced and it is shown
that it varies by several orders of magnitude depending on the system. We also
study the ordering issue of the spin-dependent occupation numbers which has
practical implications in Reduced Density Matrix Functional Theory minimization
schemes when Generalized Pauli Constraints are imposed and in the form of the
CI expansion in terms of the natural orbitals. Finally, we discuss the
aforementioned CI expansion when there are GPCs that are almost ""pinned"".",1712.08670v2
2018-01-30,Magnetic phase diagram of the quantum spin chain compound SrCo$_{2}$V$_{2}$O$_{8}$: a single-crystal neutron diffraction study in magnetic field,"We explore the spin states in the quantum spin chain compound
SrCo$_{2}$V$_{2}$O$_{8}$ up to 14.9 T and down to 50 mK, using single-crystal
neutron diffraction. Upon cooling in zero-field, antiferromagnetic (AFM) order
of N\'eel type develops at $T_\mathrm{{N}}$ $\simeq$ 5.0 K. Applying an
external magnetic field ($H$ $\parallel$ $c$-axis) destabilizes the N\'eel
order, leading to an order-disorder transition when applying a field between
$T_\mathrm{{N}}$ and $\sim$ 1.5 K. Below 1.5 K, we observe a N\'eel to
longitudinal spin density wave (LSDW) order transition at 3.9 T, and a LSDW to
emergent AFM order transition at 7.0 T. Our results also reveal several unique
signatures for the states of the spins that are not present in the
isostructural counterpart BaCo$_{2}$V$_{2}$O$_{8}$.",1801.10237v2
2018-03-06,Methods for preparation and detection of neutron spin-orbit states,"The generation and control of neutron orbital angular momentum (OAM) states
and spin correlated OAM (spin-orbit) states provides a powerful probe of
materials with unique penetrating abilities and magnetic sensitivity. We
describe techniques to prepare and characterize neutron spin-orbit states, and
provide a quantitative comparison to known procedures. The proposed detection
method directly measures the correlations of spin state and transverse
momentum, and overcomes the major challenges associated with neutrons, which
are low flux and small spatial coherence length. Our preparation techniques,
utilizing special geometries of magnetic fields, are based on coherent
averaging and spatial control methods borrowed from nuclear magnetic resonance.
The described procedures may be extended to other probes such as electrons and
electromagnetic waves.",1803.02295v1
2018-06-05,Multi-orbital nature of the spin fluctuations in Sr$_2$RuO$_4$,"The spin susceptibility of strongly correlated Sr$_2$RuO$_4$ is known to
display a rich structure in reciprocal space, with a prominent peak at ${\bf
Q}_i$=$(0.3,0.3,0)$. It is still debated if the resulting incommensurate
spin-density-wave fluctuations foster unconventional superconductivity at low
temperature or compete therewith. By means of density functional theory
combined with dynamical mean-field theory, we reveal the realistic
multi-orbital signature of the (dynamic) spin susceptibility beyond existing
weak-coupling approaches. The experimental fluctuation spectrum up to 80 meV is
confirmed by theory. Furthermore, the peak at ${\bf Q}_i$ is shown to carry
nearly equal contributions from each of the Ru$(4d)$-$t_\mathrm{2g}$ orbitals,
pointing to a cooperative effect resulting in the dominant spin fluctuations.",1806.01511v2
2018-06-11,Spin dynamics of coupled spin ladders near quantum criticality in Ba2CuTeO6,"We report inelastic neutron scattering measurements of the magnetic
excitations in Ba2CuTeO6, proposed by ab initio calculations to magnetically
realize weakly coupled antiferromagnetic two-leg spin-1/2 ladders. Isolated
ladders are expected to have a singlet ground state protected by a spin gap.
Ba2CuTeO6 orders magnetically, but with a small Neel temperature relative to
the exchange strength, suggesting that the interladder couplings are relatively
small and only just able to stabilize magnetic order, placing Ba2CuTeO6 close
in parameter space to the critical point separating the gapped phase and Neel
order. Through comparison of the observed spin dynamics with linear spin wave
theory and quantum Monte Carlo calculations, we propose values for all relevant
intra- and interladder exchange parameters, which place the system on the
ordered side of the phase diagram in proximity to the critical point. We also
compare high field magnetization data with quantum Monte Carlo predictions for
the proposed model of coupled ladders.",1806.04052v2
2018-09-07,Quantum interferometry with a g-factor-tunable spin qubit,"We study quantum interference effects of a qubit whose energy levels are
continuously modulated. The qubit is formed by an impurity electron spin in a
silicon tunneling field-effect transistor, and it is read out by spin blockade
in a double-dot configuration. The qubit energy levels are modulated via its
gate-voltage-dependent g-factors, with either rectangular, sinusoidal, or ramp
radio-frequency waves. The energy-modulated qubit is probed by the electron
spin resonance. Our results demonstrate the potential of spin qubit
interferometry implemented in a silicon device and operated at a relatively
high temperature.",1809.02326v2
2018-09-17,Chiral and helical $p$-wave superconductivity in doped bilayer BiH,"We investigate the superconductivity (SC) driven by correlation effects in
electron-doped bilayer BiH near a type-II van Hove singularity (vHS). By
functional renormalization group, we find triplet $p$-wave pairing prevails in
the interaction parameter space, except for spin density wave (SDW) closer to
the vHS or when the interaction is too strong. Because of the large atomic
spin-orbital coupling (SOC), the $p$-wave pairing occurs between equal-spin
electrons, and is chiral and two-fold degenerate. The chiral state supports
in-gap edge states, even though the low energy bands in the SC state are
topologically trivial. The absence of mirror symmetry allows Rashba SOC that
couples unequal spins, but we find its effect is of very high order, and can
only drive the chiral $p$-wave into helical $p$-wave deep in the SC state.
Interestingly, there is a six-fold degeneracy in the helical states, reflected
by the relative phase angle $\theta=n\pi/3$ (for integer $n$) between the spin
components of the helical pairing function. The phase angle is shown to be
stable in the vortex state.",1809.06103v1
2018-11-30,Spin and orbital ordering in bilayer Sr$_3$Cr$_2$O$_7$,"Using maximally localized Wannier functions obtained from DFT calculations,
we derive an effective Hubbard Hamiltonian for a bilayer of Sr$_3$Cr$_2$O$_7$,
the $n=2$ member of the Ruddlesden-Popper Sr$_{n+1}$Cr$_n$O$_{3n+1}$ system.
The model consists of effective $t_{2g}$ orbitals of Cr in two square lattices,
one above the other. The model is further reduced at low energies and two
electrons per site, to an effective Kugel-Khomskii Hamiltonian that describes
interacting spins 1 and pseudospins 1/2 at each site describing spin and
orbitals degrees of freedom respectively. We solve this Hamiltonian at zero
temperature using pseudospin bond operators and spin waves. Our results confirm
a previous experimental and theoretical study that proposes spin ordering
antiferromagnetic in the planes and ferromagnetic between planes, while
pseudospins form vertical singlets, although the interplane separation is
larger than the nearest-neighbor distance in the plane. We explain the physics
behind this rather unexpected behavior.",1811.12749v2
2018-07-04,Spin Waves in Detwinned BaFe$_2$As$_2$,"Understanding magnetic interactions in the parent compounds of
high-temperature superconductors forms the basis for determining their role for
the mechanism of superconductivity. For parent compounds of iron pnictide
superconductors such as $A$Fe$_2$As$_2$ ($A=$ Ba, Ca, Sr), although spin
excitations have been mapped out throughout the entire Brillouin zone (BZ),
measurements were carried out on twinned samples and did not allow for a
conclusive determination of the spin dynamics. Here we use inelastic neutron
scattering to completely map out spin excitations of $\sim$100\% detwinned
BaFe$_2$As$_2$. By comparing observed spectra with theoretical calculations, we
conclude that the spin excitations can be well described by an itinerant model
with important contributions from electronic correlations.",1807.01471v1
2018-10-26,Matrix-element induced spin polarization of photoelectrons from bulk bands,"Angular- or $k$-resolved photoelectron spectroscopy in the soft X-ray range
gives access to the bulk electronic structure of materials. Here this technique
is extended to the spin degree of freedom. A non-magnetic material (tungsten)
was chosen, in order to exclude any initial-state spin polarization from
exchange-split bands. By measurement of two spin-polarizations for different
light helicity, one can distinguish between contributions of optical
spin-orientation by circularly-polarized X-rays (Fano componen) and a second
component originating from interference of final-state partial waves. Both
phenomena have so far only been observed at low photon energies. Their
detection in the X-ray range is a milestone on the way to the ""complete
experiment"" in bulk photoemission.",1810.11403v2
2012-09-27,Temperature dependence of the paramagnetic spin excitations in BaFe$_2$As$_2$,"We use inelastic neutron scattering to study temperature dependence of the
paramagnetic spin excitations in iron pnictide BaFe$_2$As$_2$ throughout the
Brillouin zone. In contrast to a conventional local moment Heisenberg system,
where paramagnetic spin excitations are expected to have a Lorentzian function
centered at zero energy transfer, the high-energy ($\hbar\omega>100$ meV)
paramagnetic spin excitations in BaFe$_2$As$_2$ exhibit spin-wave-like features
up to at least 290 K ($T= 2.1T_N$). Furthermore, we find that the sizes of the
fluctuating magnetic moments $<m^2>\approx 3.6\ \mu^2_B$ per Fe are essentially
temperature independent from the AF ordered state at $0.05T_N$ to $2.1T_N$,
which differs considerably from the temperature dependent fluctuating moment
observed in the iron chalcogenide Fe$_{1.1}$Te [I. A. Zaliznyak {\it et al.},
Phys. Rev. Lett. {\bf 107}, 216403 (2011).]. These results suggest
unconventional magnetism and strong electron correlation effects in
BaFe$_2$As$_2$.",1209.6271v1
2018-08-01,The generalized gradient approximation kernel in time-dependent density functional theory,"A complete understanding of a material requires both knowledge of the excited
states as well as of the ground state. In particular, the low energy
excitations are of utmost importance while studying the electronic, magnetic,
dynamical, and thermodynamical properties of the material. Time-Dependent
Density Functional Theory (TDDFT), within the linear regime, is a successful
\textit{ab-initio} method to access the electronic charge and spin excitations.
However, it requires an approximation to the exchange-correlation (XC) kernel
which encapsulates the effect of electron-electron interactions in the
many-body system. In this work we derive and implement the spin-polarized XC
kernel for semi-local approximations such as the adiabatic Generalized Gradient
Approximation (AGGA). This kernel has a quadratic dependence on the wavevector,
{\bf q}, of the perturbation, however the impact of this on the electron energy
loss spectra (EELS) is small. Although the GGA functional is good in predicting
structural properties, it generality overestimates the exchange spin-splitting.
This leads to higher magnon energies, as compared to both ALDA and experiment.
In addition, interaction with the Stoner spin-flip continuum is enhanced by
AGGA, which strongly suppresses the intensity of spin-waves.",1808.00215v1
2018-08-17,"Magnetism and superconductivity in Eu(Fe$_{1-x}$Ni$_{x}$)As$_2$ ($x$ = 0, 0.04)","We report Eu-local-spin magnetism and Ni-doping-induced superconductivity
(SC) in a 112-type ferroarsenide system Eu(Fe$_{1-x}$Ni$_{x}$)As$_2$. The
non-doped EuFeAs$_2$ exhibits two primary magnetic transitions at $\sim$100 and
$\sim$ 40 K, probably associated with a spin-density-wave (SDW) transition and
an antiferromagnetic ordering in the Fe and Eu sublattices, respectively. Two
additional successive transitions possibly related to Eu-spin modulations
appear at 15.5 and 6.5 K. For the Ni-doped sample with $x$ = 0.04, the SDW
transition disappears, and SC emerges at $T_\mathrm{c}$ = 17.5 K. The Eu-spin
ordering remains at around 40 K, followed by the possible reentrant magnetic
modulations with enhanced spin canting. Consequently, SC coexists with a weak
spontaneous magnetization below 6.2 K in Eu(Fe$_{0.96}$Ni$_{0.04}$)As$_2$,
which provides a complementary playground for the study of the interplay
between SC and magnetism.",1808.05813v1
2018-12-18,Quantum Interface of an Electron and a Nuclear Ensemble,"Coherent excitation of an ensemble of quantum objects underpins quantum
many-body phenomena, and offers the opportunity to realize a quantum memory to
store information from a qubit. Thus far, a deterministic and coherent
interface between a single quantum system, e.g. a qubit, and such an ensemble
has remained elusive. We first use an electron to cool the mesoscopic
nuclear-spin ensemble of a semiconductor quantum dot to the nuclear
sideband-resolved regime. We then implement an all-optical approach to access
these individual quantized electronic-nuclear spin transitions. Finally, we
perform coherent optical rotations of a single collective nuclear spin
excitation corresponding to a spin wave called a nuclear magnon. These results
constitute the building blocks of a dedicated local memory per quantum-dot spin
qubit and promise a solid-state platform for quantum-state engineering of
isolated many-body systems.",1812.07540v1
2019-06-18,Indirect Chiral Magnetic Exchange through Dzyaloshinskii-Moriya--Enhanced RKKY Interactions in Manganese Oxide Chains on Ir(100),"Ruderman-Kittel-Kasuya-Yosida interaction even if their wave functions lack
direct overlap. Theory predicts that spin-orbit scattering leads to a
Dzyaloshinskii-Moriya type enhancement of this indirect exchange interaction,
giving rise to chiral exchange terms. Here we present a combined spin-polarized
scanning tunneling microscopy, angle-resolved photoemission, and density
functional theory study of MnO$_2$ chains on Ir(100). Whereas we find
antiferromagnetic Mn--Mn coupling along the chain, the inter-chain coupling
across the non-magnetic Ir substrate turns out to be chiral with a
$120^{\circ}$ rotation between adjacent MnO$_2$ chains. Calculations reveal
that the Dzyaloshinskii-Moriya interaction results in spin spirals with a
periodicity in agreement with experiment. Our findings confirm the existence of
indirect chiral magnetic exchange, potentially giving rise to exotic phenomena,
such as chiral spin-liquid states in spin ice systems or the emergence of new
quasiparticles.",1906.07703v1
2019-06-26,Possible glass-like random singlet magnetic state in 1T-TaS2,"Two-dimensional layered transition-metal-dichalcogenide compound 1T-TaS2
shows the rare coexistence of charge density wave (CDW) and electron
correlation driven Mott transition. In addition, atomic-cluster spins on the
triangular lattice of the CDW state of 1T-TaS2 give rise to the possibility of
the exotic spin-singlet state in which quantum fluctuations of spins are strong
enough to prevent any long range magnetic ordering down to absolute zero ( 0
K). We present here the evidences of a glass-like random singlet magnetic state
in 1T-TaS2 at low temperatures through a study of temperature and time
dependence of magnetization. Comparing the experimental results with a
representative canonical spin-glass system Au(1.8%Mn), we show that this
glass-like state is distinctly different from the well established canonical
spin-glass state.",1906.10914v2
2020-04-01,"The mass gap, the spin gap, and the origin of merging binary black holes","Two of the dominant channels to produce the black-hole binary mergers
observed by LIGO and Virgo are believed to be the isolated evolution of stellar
binaries in the field and dynamical formation in star clusters. Their relative
efficiency can be characterized by a ""mixing fraction."" Pair instabilities
prevent stellar collapse from generating black holes more massive than about
$45 M_\odot$. This ""mass gap"" only applies to the field formation scenario, and
it can be filled by repeated mergers in clusters. A similar reasoning applies
to the binary's effective spin. If black holes are born slowly rotating, the
high-spin portion of the parameter space (the ""spin gap"") can only be populated
by black hole binaries that were assembled dynamically. Using a semianalytical
cluster model, we show that future gravitational-wave events in either the mass
gap, the spin gap, or both can be leveraged to infer the mixing fraction
between the field and cluster formation channels.",2004.00650v2
2020-04-28,Enhancement of acoustic spin pumping by acoustic distributed Bragg reflector cavity,"Surface acoustic waves (SAWs) in the GHz frequency range can inject spin
currents dynamically into adjacent nonmagnetic layers via spin pumping effect
associated with ferromagnetic resonance. Here, we demonstrate an enhancement of
acoustic ferromagnetic resonance and spin current generation by a pair of SAW
reflector gratings, which form an acoustic analogue of the distributed Bragg
reflector cavity. In the experiment, we confirmed 2.04 $\pm$ 0.02 times larger
SAW power absorption in a device with cavity than in case of no acoustic
cavity. We confirmed up to 2.96 $\pm$ 0.02 times larger spin current generation
by measuring electric voltages generated by the inverse Edelstein effect (IEE)
at the interface between Cu and Bi$_2$O$_3$. The results suggest that acoustic
cavities would be useful to enhance the conversion efficiency in SAW driven
coupled magnon-phonon dynamics.",2004.13885v3
2020-08-25,Electron Spin Resonance of Defects in Spin Chains. o-(DMTTF)2X : a versatile system behaving like molecular magnet,"The paper presents the Electron Paramagnetic Resonance study of defects in
the spin chain o- (DMTTF)2X family using continuous wave and pulsed techniques.
The defects in spin chains are strongly correlated and present similar
microscopic structure as a molecular magnet. By means of 2D-HYSCORE and DFT
calculations we show a strong reduction of hyperfine coupling between the
defects and the nuclear spin bath. We assume that the reduction is due to the
Heisenberg exchange interaction which screens the effect of the nuclei.",2008.10897v1
2016-12-02,Observation of quantum-limited spin transport in strongly interacting two-dimensional Fermi gases,"We measure the transport properties of two-dimensional ultracold Fermi gases
during transverse demagnetization in a magnetic field gradient. Using a
phase-coherent spin-echo sequence, we are able to distinguish bare spin
diffusion from the Leggett-Rice effect, in which demagnetization is slowed by
the precession of spin current around the local magnetization. When the
two-dimensional scattering length is tuned to be comparable to the inverse
Fermi wave vector $k_F^{-1}$, we find that the bare transverse spin diffusivity
reaches a minimum of $1.7(6)\hbar/m$, where $m$ is the bare particle mass. The
rate of demagnetization is also reflected in the growth rate of the s-wave
contact, observed using time-resolved spectroscopy. At unitarity, the contact
rises to $0.28(3) k_F^2$ per particle, measuring the breaking of scaling
symmetry. Our observations support the conjecture that in systems with strong
scattering, the local relaxation rate is bounded from above by $k_B T/\hbar$.",1612.00815v2
2017-02-01,Ab initio dynamical exchange interactions in frustrated anti-ferromagnets,"The ultrafast response to an optical pulse excitation of the spin-spin
exchange interaction in transition metal anti-ferromagnets is studied within
the framework of the time-dependent spin-density functional theory. We propose
a formulation for the purely dynamical exchange interaction, which is non-local
in space, and it is derived starting from {\it ab initio} arguments. Then, we
investigate the effect of the laser pulse on the onset of the dynamical
process. It is found that we can distinguish two types of excitations, both
activated immediately after the action of the laser pulse. While the first one
can be associated to a Stoner-like excitation and involves the transfer of spin
from one site to another, the second one is related to the ultrafast
modification of a Heisenberg-like exchange interaction and can trigger the
formation of spin waves in the first few hundred femtoseconds of the time
evolution.",1702.00375v1
2017-02-02,Strong spin-orbit interaction of light on the surface of atomically thin crystals,"The photonic spin Hall effect (SHE) can be regarded as a direct optical
analogy of the SHE in electronic systems where a refractive index gradient
plays the role of electric potential. However, it has been demonstrated that
the effective refractive index fails to adequately explain the lightmatter
interaction in atomically thin crystals. In this paper, we examine the
spin-orbit interaction on the surface of the freestanding atomically thin
crystals. We find that it is not necessary to involve the effective refractive
index to describe the spin-orbit interaction and the photonic SHE in the
atomically thin crystals. The strong spin-orbit interaction and giant photonic
SHE have been predicted, which can be explained as the large polarization
rotation of plane-wave components in order to satisfy the transversality of
photon.",1702.00531v1
2017-02-13,Origins of bond and spin order in rare-earth nickelate bulk and heterostructures,"We analyze the charge- and spin response functions of rare-earth nickelates
RNiO3 and their heterostructures using random-phase approximation in a two-band
Hubbard model. The inter-orbital charge fluctuation is found to be the driving
mechanism for the rock-salt type bond order in bulk RNiO3, and good agreement
of the ordering temperature with experimental values is achieved for all RNiO3
using realistic crystal structures and interaction parameters. We further show
that magnetic ordering in bulk is not driven by the spin fluctuation and should
be instead explained as ordering of localized moments. This picture changes for
low-dimensional heterostructures, where the charge fluctuation is suppressed
and overtaken by the enhanced spin instability, which results in a
spin-density-wave ground state observed in recent experiments. Predictions for
spectroscopy allow for further experimental testing of our claims.",1702.03677v1
2017-06-06,Spin Seebeck effect and magnon-magnon drag in Pt/YIG/Pt structures,"The formation of the two: injected (""coherent"") and ""thermally"" excited,
different in energies magnon subsystems and the influence of its interaction
with phonons and between on drag effect under spin Seebeck effect conditions in
the magnetic insulator part of the metal/ferromagnetic insulator/metal
structure is studied. An approximation of the effective parameters, when each
of the interacting subsystems (""injected"", ""thermal"" magnons, and phonons) is
characterized by its own effective temperature and drift velocities have been
considered. The analysis of the macroscopic momentum balance equations of the
systems of interest conducted for different ratios of the drift velocities of
the magnon and phonon currents show that the ""injected"" magnons relaxation on
the ""thermal"" ones is possible to be dominant over its relaxation on phonons.
This interaction will be the defining in the forming of the temperature
dependence of the spin-wave current under spin Seebeck effect conditions, and
inelastic part of the magnon-magnon interaction is the dominant spin relaxation
mechanism.",1706.02154v1
2017-06-19,Chiral Spin Mode on the Surface of a Topological Insulator,"Using polarization-resolved resonant Raman spectroscopy, we explore
collective spin excitations of the chiral surface states in a three dimensional
topological insulator, Bi$_2$Se$_3$. We observe a sharp peak at 150 meV in the
pseudovector $A_2$ symmetry channel of the Raman spectra. By comparing the data
with calculations, we identify this peak as the transverse collective spin mode
of surface Dirac fermions. This mode, unlike a Dirac plasmon or a surface
plasmon in the charge sector of excitations, is analogous to a spin wave in a
partially polarized Fermi liquid, with spin-orbit coupling playing the role of
an effective magnetic field.",1706.05776v3
2019-03-13,Linear and non-linear coherent coupling in a Bell-Bloom magnetometer,"Spin-exchange collisions in hot vapours are generally regarded as a
decoherence mechanism. In contrast, we show that linear and non-linear
spin-exchange coupling can lead to the generation of atomic coherence in a
Bell-Bloom magnetometer. In particular, we theoretically and experimentally
demonstrate that non-linear spin exchange coupling, acting in an analogous way
to a wave-mixing mechanism, can create new modes of coherent excitation which
inherit the magnetic properties of the natural Larmor coherence. The generated
coherences further couple via linear spin-exchange interaction, leading to an
increase of the natural coherence lifetime of the system. Notably, the
measurements are performed in a low-density caesium vapour and for non-zero
magnetic field, outside the standard conditions for collisional coherence
transfer. The strategies discussed are important for the development of
spin-exchange coupling into a resource for an improved measurement platform
based on room-temperature alkali-metal vapours.",1903.05605v1
2019-03-20,Investigating ultrafast quantum magnetism with machine learning,"We investigate the efficiency of the recently proposed Restricted Boltzmann
Machine (RBM) representation of quantum many-body states to study both the
static properties and quantum spin dynamics in the two-dimensional Heisenberg
model on a square lattice. For static properties we find close agreement with
numerically exact Quantum Monte Carlo results in the thermodynamical limit. For
dynamics and small systems, we find excellent agreement with exact
diagonalization, while for systems up to N=256 spins close consistency with
interacting spin-wave theory is obtained. In all cases the accuracy converges
fast with the number of network parameters, giving access to much bigger
systems than feasible before. This suggests great potential to investigate the
quantum many-body dynamics of large scale spin systems relevant for the
description of magnetic materials strongly out of equilibrium.",1903.08482v3
2019-05-23,Unraveling the origin of black holes from effective spin measurements with LIGO-Virgo,"We investigate how to use information on the effective spin parameter of
binary black hole mergers from the LIGO-Virgo gravitational wave detections to
discriminate the origin of the merging black holes. We calculate the expected
probability distribution function for the effective spin parameter for
primordial black holes. Using LIGO-Virgo observations, we then calculate odds
ratios for different models for the distribution of black holes' spin magnitude
and alignment. We evaluate the posterior probability density for a possible
mixture of astrophysical and primordial black holes as emerging from current
data, and calculate the number of future merger events needed to discriminate
different spin and alignment models at a given level of statistical
significance.",1905.13019v2
2020-03-25,Two-photon driven magnon-pair resonance as a signature of spin-nematic order,"We theoretically study the nonlinear magnetic resonance driven by intense
laser or electromagnetic wave in a fully polarized frustrated magnet near a
less-visible spin-nematic ordered phase. In general, both magnons and magnon
pairs (two-magnon bound state) appear as the low-energy excitation in the
saturated state of spin-nematic magnets. Their excitation energies are usually
in terahertz (THz) or gigahertz range. Magnon pairs with angular momentum
2$\hbar$ can be excited by the simultaneous absorption of two photons, and such
multi-photon processes occur if the applied THz laser is strong enough. We
compute laser-driven magnetic dynamics of a frustrated four-spin system with
both magnon ($\hbar$) and magnon-pair (2$\hbar$) like excitations which is
analogous to a macroscopic frustrated magnet with a spin nematic phase. We
estimate the required strength of magnetic field of laser for the realization
of two photon absorption, taking into account dissipation effects with the
Lindblad equation. We show that intense THz laser with ac magnetic field of
0.1-1.0 Tesla is enough to observe magnon-pair resonance.",2003.11240v2
2020-03-26,Possible occurrence of superconductivity by the $π$-flux Dirac string formation due to spin-twisting itinerant motion of electrons,"We show that the Rashba spin-orbit interaction causes spin-twisting itinerant
motion of electrons in metals and realizes the quantized cyclotron motion of
conduction electrons without an external magnetic field. From the view point of
the Berry connection, the cause of this {quantized} motion is the appearance of
a non-trivial Berry connection ${\bf A}^{\rm fic}=-{\hbar \over {2e}}\nabla
\chi$ ($\chi$ is an angular variable with period $2\pi$ that generates $\pi$
flux (in the units of $\hbar=1, e=1,c=1$) inside the nodal singularities of the
wave function (a ""Dirac string"") along the centers of spin-twisting.
  Since it has been shown in our previous work[Ref.1]that the collective mode
of $\nabla \chi$ is stabilized by the electron-pairing and generates
supercurrent, the $\pi$-flux Dirac string created by the spin-twisting
itinerant motion will be stabilized by the electron-pairing and produce
supercurrent.",2003.11742v1
2020-09-06,Spin and Entanglement in General Relativity,"In a previous paper, we have shown that the classical and quantum
relativistic dynamics of the Stueckelberg-Horwitz-Piron [SHP] theory can be
embedded in general relativity (GR). We briefly review the SHP theory here,
and, in particular, the formulation of the theory of spin in the framework of
relativistic quantum theory. We show here how the quantum theory of
relativistic spin can be embedded, using a theorem of Abraham, Marsden and
Ratiu, and also explicit derivation, into the framework of GR by constructing a
local induced representation. The relation to the work of Fock and Ivanenko is
also discussed. We show that in a gravitational field there is s highly complex
structure for the spin distribution in the support of the wave function. We
then discuss entanglement for the spins of a two body system.",2009.02744v3
2020-09-27,Dynamical spin susceptibility in La2CuO4 studied by resonant inelastic x-ray scattering,"Resonant inelastic X-ray scattering (RIXS) is a powerful probe of elementary
excitations in solids. It is now widely applied to study magnetic excitations.
However, its complex cross-section means that RIXS has been more difficult to
interpret than inelastic neutron scattering (INS). Here we report
high-resolution RIXS measurements of magnetic excitations of La2CuO4, the
antiferromagnetic parent of one system of high-temperature superconductors. At
high energies (~2 eV), the RIXS spectra show angular-dependent dd orbital
excitations which are found to be in good agreement with single-site multiplet
calculations. At lower energies (<0.3 eV), we show that the
wavevector-dependent RIXS intensities are proportional to the product of the
single-ion spin-flip cross section and the dynamical susceptibility of the
spin-wave excitations. When the spin-flip crosssection is dividing out, the
RIXS magnon intensities show a remarkable resemblance to INS data. Our results
show that RIXS is a quantitative probe the dynamical spin susceptibility in
cuprate and therefore should be used for quantitative investigation of other
correlated electron materials.",2009.12925v1
2021-02-11,Magnonics in collinear magnetic insulating systems,"In the last decades, collinear magnetic insulating systems have emerged as
promising energy-saving information carriers. Their elementary collective spin
excitations, i.e., magnons, can propagate for long distances bypassing the
Joule heating effects that arise from electron scattering in metal-based
devices. This tutorial article provides an introduction to theoretical and
experimental advances in the study of magnonics in collinear magnetic
insulating systems. We start by outlining the quantum theory of spin waves in
ferromagnetic and antiferromagnetic systems and we discuss their quantum
statistics. We review the phenomenology of spin and heat transport of the
coupled coherent and incoherent spin dynamics and the interplay between
magnetic excitations and lattice degrees of freedom. Finally, we introduce the
reader to the key ingredients of two experimental probes of magnetization
dynamics, spin transport and NV-center relaxometry setups, and discuss
experimental findings relevant to the outlined theory.",2102.08829v1
2021-04-09,Non-thermal breaking of magnetic order via photo-generated spin defects,"In Mott insulators the evolution of antiferromagnetic order to
superconducting or charge-density-wave-like states upon chemical doping
underpins the control of quantum phases. Photo-doping can induce similar
transitions on the ultrafast timescale, however the response of the spin system
has remained elusive. Here, we use 4D-ultrafast optical spectroscopy to extract
quantitative magnetic dynamics in the spin-orbit coupled Mott insulator
Sr3Ir2O7. We demonstrate that light can non-thermally melt long-range spin
order. At low fluences magnetic order recovers within 1 ps despite
demagnetization of roughly 50%. However, high fluences induce a crossover to a
long-lived demagnetized state without increasing the lattice temperature. We
show that the generation of photo-induced spin defects enables a mechanism that
stabilizes the demagnetized state which could help expose new transient phases.",2104.04294v2
2021-04-19,Unconventional quantum sound-matter interactions in spin-optomechanical-crystal hybrid systems,"We predict a set of unusual quantum acoustic phenomena resulting from
sound-matter interactions in a fully tunable solid-state platform, in which an
array of solid-state spins in diamond are coupled to quantized acoustic waves
in a one-dimensional (1D) optomechanical crystal. We find that, by a spatially
varying laser drive that introduces a position-dependent phase in the
optomechanical interaction, the mechanical band structure can be tuned in situ,
consequently leading to unconventional quantum sound-matter interactions. We
show that quasi-chiral sound-matter interactions can occur, with tunable ranges
from bidirectional to quasi-unidirectional, when the spins are resonant with
the bands. When the solid-state spins'frequency lies within the acoustic
band-gap, we demonstrate the emergence of an exotic polariton bound state,
which can mediate long-range tunable, odd-neighbor and complex spin-spin
interactions. This work expands the present exploration of quantum phononics
and can have wide applications in quantum simulation and quantum information
processing.",2104.09101v1
2021-08-04,Spin interactions and topological magnonics in chromium trihalide CrClBrI,"The discovery of spontaneous magnetism in van der Waal (vdW) magnetic
monolayers has opened up an unprecedented platform for investigating magnetism
in purely two-dimensional systems. Recently, it has been shown that the
magnetic properties of vdW magnets can be easily tuned by adjusting the
relative composition of halides. Motivated by these experimental advances, here
we derive a model for a trihalide CrClBrI monolayer from symmetry principles
and we find that, in contrast to its single-halide counterparts, it can display
highly anisotropic nearest- and next-to-nearest neighbor Dzyaloshinskii-Moriya
and Heisenberg interactions. Depending on the parameters, the DM interactions
are responsible for the formation of exotic chiral spin states, such as
skyrmions and spin cycloids, as shown by our Monte Carlo simulations. Focusing
on a ground state with a two-sublattice unit cell, we find spin-wave bands with
nonvanishing Chern numbers. The resulting magnon edge states yield a magnon
thermal Hall conductivity that changes sign as function of temperature and
magnetic field, suggesting chromium trihalides as a candidate for testing
topological magnon transport in two-dimensional noncollinear spin systems.",2108.02165v4
2021-08-28,Rolling spinners on the water surface,"Angular momentum of spinning bodies leads to their remarkable interactions
with fields, waves, fluids, and solids. Orbiting celestial bodies, balls in
sports, liquid droplets above a hot plate, nanoparticles in optical fields, and
spinning quantum particles exhibit nontrivial rotational dynamics. Here, we
report self-guided propulsion of magnetic fast-spinning particles on a liquid
surface in the presence of a solid boundary. Above some critical spinning
frequency (higher rotational Reynolds numbers), such particles generate
localized 3D vortices and form composite 'spinner-vortex' quasi-particles with
nontrivial, yet robust dynamics. Such spinner-vortices are attracted and
dynamically trapped near the boundaries, propagating along the wall of any
shape similarly to 'liquid wheels'. The propulsion velocity and the distance to
the wall are controlled by the angular velocity of the spinner via the balance
between the Magnus and wall-repulsion forces. Our results offer a new type of
surface vehicles and provide a powerful tool to manipulate spinning objects in
fluids.",2108.12578v1
2021-10-12,The non-chiral intermediate Heisenberg ferromagnet equation,"We present and solve a soliton equation which we call the non-chiral
intermediate Heisenberg ferromagnet (ncIHF) equation. This equation, which
depends on a parameter $\delta >0$, describes the time evolution of two coupled
spin densities propagating on the real line, and in the limit $\delta \to
\infty$ it reduces to two decoupled half-wave maps (HWM) equations of opposite
chirality. We show that the ncIHF equation is related to the A-type hyperbolic
spin Calogero-Moser (CM) system in two distinct ways: (i) it is obtained as a
particular continuum limit of a Inozemtsev-type spin chain related to this CM
system, (ii) it has multi-soliton solutions obtained by a spin-pole ansatz and
with parameters satisfying the equations of motion of a complexified version of
this CM system. The integrability of the ncIHF equation is shown by
constructing a Lax pair. We also propose a periodic variant of the ncIHF
equation related to the A-type elliptic spin CM system.",2110.06239v1
2021-10-20,Spin Fluctuations Yield zT Enhancement in Ferromagnets,"Thermal fluctuation of local magnetization in magnetic metals intercoupled
with charge carriers and phonons offers a path to enhance thermoelectric
performance. The thermopower enhancement by spin fluctuations (SF) has been
observed before. However, the crucial evidence for enhancing
thermoelectric-figure-of-merit (zT) by SF has not been reported until now. Here
we report evidence for such enhancement in the ferromagnetic CrTe. The SF leads
to nearly 80% zT enhancement in ferromagnetic CrTe near and below TC~335 K. The
ferromagnetism in CrTe is originated from the collective electronic and
localized magnetic moments. The field-dependent transport properties
demonstrate the profound impact of SF on the electrons and phonons. The SF
simultaneously enhances the thermopower and reduces the thermal conductivity.
Under an external magnetic field, the enhancement in thermopower is suppressed,
and the thermal conductivity is enhanced, evidencing the existence of a strong
SF near and below TC. The anomalous thermoelectric transport properties are
analyzed based on theoretical models, and a good agreement with experimental
data is found. Furthermore, the detailed analysis proves an insignificant
impact from spin-wave contribution to the transport properties. This study
contributes to the fundamental understanding of spin fluctuation for designing
high-performance spin-driven thermoelectric materials.",2110.10798v1
2003-12-10,Tunable spin polarization in III-V quantum wells with a ferromagnetic barrier,"We demonstrate the epitaxial growth of optical-quality electrically-gated
III-V ferromagnetic quantum structures. Photoluminescence spectroscopy reveals
that initially unpolarized photoexcited holes in a GaAs quantum well become
spin-polarized opposite to the magnetization of an adjacent digital
ferromagnetic layer in the AlGaAs barrier. A vertical bias is used to tune the
spin polarization from -0.4 to 6.3 percent at T = 5 K and B = 1 kG during which
the luminescence becomes quenched, indicating that the polarization is mediated
by wave function overlap between heavy holes in the quantum well and Mn-ions in
the barrier. Polarization is observed under negligible current flow and is
insensitive to the initial spin orientation of the carriers, differentiating
the effect from both electrical and optical spin injection.",0312240v1
2016-11-03,Exact results for polaron and molecule in one-dimensional spin-1/2 Fermi gas,"Using exact Bethe ansatz (BA) solutions, we show that a spin-down fermion
immersed into a fully polarized spin-up Fermi sea with a weak attraction is
dressed by the surrounding spin-up fermions to form the one-dimensional analog
of a polaron. As the attraction becomes strong, the spin-down fermion binds
with one spin-up fermion to form a tightly bound molecule. Throughout the whole
interaction regime, a crossover from the polaron to a molecule state is fully
demonstrated through exact results of the excitation spectrum, the effective
mass, binding energy and kinetic energy. Furthermore, a clear distinction
between the polaron and molecule is conceived by the probability distribution,
single particle reduced density matrix and density-density correlations, which
are calculated directly from the Bethe ansatz wave function. Such a
polaron-molecule crossover presents a universal nature of an impurity immersed
into a fermionic medium with an attraction in one dimension.",1611.01073v1
2016-11-18,Temporal evolution of auto-oscillations in a YIG/Pt microdisc driven by pulsed spin Hall effect-induced spin-transfer torque,"The temporal evolution of pulsed Spin Hall Effect - Spin Transfer Torque
(SHE-STT) driven auto-oscillations in a Yttrium Iron Garnet (YIG) / platinum
(Pt) microdisc is studied experimentally using time-resolved Brillouin Light
Scattering (BLS) spectroscopy. It is demonstrated that the frequency of the
auto-oscillations is different in the center and at the edge of the
investigated disc that is related to the simultaneous STT excitation of a
bullet and a non-localized spin-wave mode. Furthermore, the magnetization
precession intensity is found to saturate on a time scale of 20 ns or longer,
depending on the current density. For this reason, our findings suggest that a
proper ratio between the current and the pulse duration is of crucial
importance for future STT-based devices.",1611.06054v1
2017-01-16,Quantum Hall Spin Diode,"Double layer two-dimensional electron systems at high perpendicular magnetic
field are used to realize magnetic tunnel junctions in which the electrons at
the Fermi level in the two layers have either parallel or anti-parallel spin
magnetizations. In the anti-parallel case the tunnel junction, at low
temperatures, behaves as a nearly ideal spin diode. At elevated temperatures
the diode character degrades as long-wavelength spin waves are thermally
excited. These tunnel junctions provide a demonstration that the spin
polarization of the electrons in the $N=1$ Landau level at filling factors $\nu
= 5/2$ and 7/2 is essentially complete, and, with the aid of an in-plane
magnetic field component, that Landau level mixing at these filling factors is
weak in the samples studied.",1701.04463v1
2017-01-21,Controlling electron spin dynamics in bichromatic Kapitza-Dirac scattering by the laser field polarization,"Spin-dependent Kapitza-Dirac scattering of electron beams from
counterpropagating bichromatic laser waves in various polarization geometries
is studied. The corresponding scattering probabilities are obtained by
analytical and numerical solutions of the time-dependent Dirac equation,
assuming a field frequency ratio of 2. When the fundamental field mode is
circular-polarized, we show that spin dynamics are generally suppressed at low
intensities, but can become distinct at high intensities. Conversely, when a
linearly or elliptically polarized fundamental mode is combined with a second
harmonic of circular polarization, strong spin effects arise already at low
field intensities. In particular, a polarization configuration is identified
which acts as a spin filter for free electrons.",1701.05951v2
2017-01-30,Quark Wigner distributions and spin-spin correlations,"We investigate the Wigner distributions for $u$ and $d$ quarks in a
light-front quark-diquark model of a proton to unravel the spatial and spin
structure. The light-front wave functions are modeled from the soft-wall
AdS/QCD prediction. We consider the contributions from both the scalar and the
axial vector diquarks. The Wigner distributions for unpolarized, longitudinally
polarized, and transversely polarized protons are presented in the transverse
momentum plane as well as in the transverse impact parameter plane. The Wigner
distributions satisfy a Soffer-bound-type inequality. We also evaluate all the
leading twist GTMDs and show their scale evolution. The spin-spin correlations
between the quark and the proton are investigated",1701.08551v2
2017-03-11,Spin-orbit interaction driven dimerization in one dimensional frustrated magnets,"We study the effect of spin-orbit interaction on one-dimensional
U(1)-invariant frustrated magnets with dominant critical nematic fluctuations.
The spin-orbit coupling explicitly breaks the U(1) symmetry of arbitrary global
spin rotations about the high-symmetry axis down to $Z_2$ (invariance under a
$\pi$-rotation). Given that the nematic order parameter is invariant under a
$\pi$-rotation, it is relevant to ask if other discrete symmetries can be
spontaneously broken. Here we demonstrate that the spin-orbit coupling induces
a bond density wave that spontaneously breaks the translational symmetry and
opens a gap in the excitation spectrum.",1703.03881v2
2017-04-03,Spin-orbit-coupling induced localization in the expansion of an interacting Bose-Einstein condensate,"By developing a hydrodynamic formalism, we investigate the expansion dynamics
of the single-minimum phase of a binary spin-orbit coupled Bose-Einstein
condensate, after releasing from an external harmonic trap. We find that the
expansion of the condensate along the direction of the spin-orbit coupling is
dramatically slowed down near the transition between the single-minimum phase
and the plane-wave phase. Such a slow expansion, resembling a form of an
effective localization, is due to the quenching of the superfluid motion which
results in a strong increase of the effective mass. In the single-minimum phase
the anisotropic expansion of the Bose gas, which is spin balanced at
equilibrium, is accompanied by the emergence of a local spin polarization. Our
analytic scaling solutions emerging from hydrodynamic picture are compared with
a full numerical simulation based on the coupled Gross-Pitaevskii equations.",1704.00677v1
2019-01-17,Spin of Primordial Black Holes,"Primordial black holes, formed from rare peaks in the primordial fluctuations
$\zeta$, are non-rotating at zeroth order in $\zeta_{\rm rms}$. We show that
the spin also vanishes at first order in $\zeta_{\rm rms}$, suggesting the
dimensionless spin parameter $a_{\rm rms} \sim \zeta_{\rm rms}^2$. We identify
one quadratic contribution to the spin by calculating (and extrapolating to the
formation time) the torque on a black hole due to ambient acoustic waves. For a
reasonable density of primordial black holes this implies a percent level spin
parameter.",1901.05963v3
2019-01-31,Direct Observation of Unusual Interfacial Dzyaloshinskii-Moriya Interaction in Graphene/NiFe/Ta Heterostructure,"Graphene/ferromagnet interface promises a plethora of new science and
technology. The interfacial Dzyaloshinskii Moriya interaction (iDMI) is
essential for stabilizing chiral spin textures, which are important for future
spintronic devices. Here, we report direct observation of iDMI in
graphene/Ni80Fe20/Ta heterostructure from non-reciprocity in spin-wave
dispersion using Brillouin light scattering (BLS) technique. Linear scaling of
iDMI with the inverse of Ni80Fe20 thicknesses suggests primarily interfacial
origin of iDMI. Both iDMI and spin-mixing conductance increase with the
increase in defect density of graphene obtained by varying argon pressure
during sputter deposition of Ni80Fe20. This suggests that the observed iDMI
originates from defect-induced extrinsic spin-orbit coupling at the interface.
The direct observation of iDMI at graphene/ferromagnet interface without
perpendicular magnetic anisotropy opens new route in designing thin film
heterostructures based on 2-D materials for controlling chiral spin structure
such as skyrmions and bubbles, and magnetic domain-wall-based storage and
memory devices.",1901.11287v1
2019-04-06,Eccentric Binary Black Holes with Spin via the Direct Integration of the Post-Newtonian Equations of Motion,"We integrate the third and a half post-Newtonian equations of motion for a
fully generic binary black hole system, allowing both for non-circular orbits,
and for one or both of the black holes to spin, in any orientation. Using the
second post-Newtonian order expression beyond the leading order quadrupole
formula, we study the gravitational waveforms produced from such systems. Our
results are validated by comparing to Taylor T4 in the aligned-spin circular
cases, and the additional effects and modulations introduced by the
eccentricity and the spins are analyzed. We use the framework to evaluate the
evolution of eccentricity, and trace its contributions to source terms
corresponding to the different definitions. Finally, we discuss how this direct
integration equations-of-motion code may be relevant to existing and upcoming
gravitational wave detectors, showing fully generic, precessing, eccentric
gravitational waveforms from a fiducial binary system with the orbital plane
and spin precession, and the eccentricity reduction.",1904.03443v2
2019-08-25,Variational study of two-impurity spin-boson model with a common Ohmic bath: Ground-state phase transitions,"By means of a trial wave function, the multi-D$_1$ ansatz, extensive
variational calculations with more than ten thousand parameters have been
carried out to study quantum phase transitions in the ground states of a
two-impurity system embedded in a common Ohmic bath of bosons. Quantum
criticality in both the impurity system and the Ohmic bosonic bath is
investigated with relevant transition points and critical exponents determined
accurately. With the linear grid of the Ohmic spectral density, our numerical
calculations produce a much better description of the ground states with lower
energies than other calculations employing a logarithmic grid with a
discretization factor far greater than unity. It offers a possible solution to
the considerable controversy on the critical coupling in the literature.
Moreover, the ground-state phase transition is inferred to be of first order in
the presence of strong antiferromagnetic spin-spin couplin}, at variance with
that in the ferromagnetic regime or in the absence of spin-spin coupling where
the transition belongs to the Kosterlitz-Thouless universality class.",1908.09245v1
2019-08-28,Spin functional renormalization group for quantum Heisenberg ferromagnets: Magnetization and magnon damping in two dimensions,"We use the spin functional renormalization group recently developed by two of
us [J. Krieg and P. Kopietz, Phys. Rev. B $\bf{99}$, 060403(R) (2019)] to
calculate the magnetization $M ( H , T )$ and the damping of magnons due to
classical longitudinal fluctuations of quantum Heisenberg ferromagnets. In
order to guarantee that for vanishing magnetic field $H \rightarrow 0$ the
magnon spectrum is gapless when the spin rotational invariance is spontaneously
broken, we use a Ward identity to express the magnon self-energy in terms of
the magnetization. In two dimensions our approach correctly predicts the
absence of long-range magnetic order for $H=0$ at finite temperature $T$. The
magnon spectrum then exhibits a gap from which we obtain the transverse
correlation length. We also calculate the wave-function renormalization factor
of the magnons. As a mathematical by-product, we derive a recursive form of the
generalized Wick theorem for spin operators in frequency space which
facilitates the calculation of arbitrary time-ordered connected correlation
functions of an isolated spin in a magnetic field.",1908.10753v2
2019-09-02,Second-order perturbation theory with spin-symmetry projected Hartree-Fock,"We propose two different schemes for second-order perturbation theory with
spin-projected Hartree-Fock. Both schemes employ the same ansatz for the
first-order wave function, which is a linear combination of spin-projected
configurations. The first scheme is based on the normal-ordered projected
Hamiltonian, which is partitioned into the Fock-like component and the
remaining two-particle-like contribution. In the second scheme, the generalized
Fock operator is used to construct a spin-free zeroth-order Hamiltonian. To
avoid the intruder state problem, we adopt the level-shift techniques
frequently used in other multi-reference perturbation theories. We describe
both real and imaginary shift schemes and compare their performances on small
systems. Our results clearly demonstrate the superiority of the second
perturbation scheme with an imaginary shift over other proposed approaches in
various aspects, giving accurate potential energy curves, spectroscopic
constants, and singlet-triplet splitting energies. We also apply these methods
to the calculation of spin gaps of transition metal complexes as well as the
potential energy curve of the chromium dimer.",1909.00644v2
2019-09-27,Effective spin distribution of black hole mergers in triples,"Many astrophysical scenarios have been proposed to explain the several black
hole (BH) and neutron star binary mergers observed via gravitational waves
(GWs) by the LIGO-Virgo collaboration. Contributions from various channels can
be statistically disentangled by mass, spin, eccentricity and redshift
distributions of merging binaries. In this paper, we investigate the signatures
of BH-BH binary mergers induced by a third companion through the Lidov-Kozai
mechanism in triple systems. We adopt different prescriptions for the
supernovae natal kicks and consider different progenitor metallicities and
initial orbital parameters. We show that the typical eccentricity in the LIGO
band is $0.01$-$0.1$ and that the merger rate is in the range $0.008-9 \
\mathrm{Gpc}^{-3}\ \mathrm{yr}^{-1}$, depending on the natal kick prescriptions
and progenitor metallicity. Furthermore, we find that the typical distribution
of effective projected spin is peaked at $\chi_{\rm eff}\sim 0$ with
significant tails. We show that the triple scenario could reproduce the
distribution of $\chi_{\rm eff}$. We find that the triple channel may be
strongly constrained by the misalignment angle between the binary component
spins in future detections with spin precession.",1910.00407v2
2020-01-10,Bound fermion states in pinned vortices in the surface states of a superconducting topological insulator: The Majorana bound state,"By analytically solving the Bogoliubov-de Gennes equations we study the
fermion bound states at the center of the core of a vortex in a two-dimensional
superconductor. We consider three kinds of 2D superconducting models: (a) a
standard type II superconductor in the mixed state with low density of vortex
lines, (b) a superconductor with strong spin-orbit coupling locking the spin
parallel to the momentum and (c) a superconductor with strong spin-orbit
coupling locking the spin perpendicular to the momentum. The 2D superconducting
states are induced via proximity effect between an $s$-wave superconductor and
the surface states of a strong topological insulator. In case (a) the energy
gap for the excitations is of order $\Delta_{\infty}^2/(2E_F)$, while for cases
(b) and (c) a zero-energy Majorana state arises together with an equally spaced
($\Delta^2_{\infty}/E_F$) sequence of fermion excitations. The spin-momentum
locking is key to the formation of the Majorana state. We present analytical
expressions for the energy spectrum and the wave functions.",2001.03666v2
2020-02-26,Magnon dispersion and dynamic spin response in three-dimensional spin models for $α$-RuCl$_3$,"In the search for experimental realizations of bond-anisotropic Kitaev
interactions and resulting spin-liquid phases, the layered magnet
$\alpha$-RuCl$_3$ is a prime candidate. Its modelling typically involves
Heisenberg, Kitaev, and symmetric off-diagonal $\Gamma$ interactions on the
two-dimensional honeycomb lattice. However, recent neutron-scattering
experiments point towards a sizeable magnetic interlayer coupling. Here we
study three-dimensional exchange models for $\alpha$-RuCl$_3$, for both
possible $R\bar{3}$ and $C2/m$ crystal structures. We discuss the symmetry
constraints on the interlayer couplings, construct minimal models, and use them
to compute the magnetic mode dispersion and the dynamical spin structure
factor, in both the zero-field zigzag phase and the paramagnetic high-field
phase. Our predictions for the interlayer mode dispersion shall guide future
experiments; they also call for a reevaluation of the quantitative model
parameters relevant for $\alpha$-RuCl$_3$.",2002.11727v2
2020-02-27,Electric control of spin orbit coupling in graphene-based nanostructures with broken rotational symmetry,"Spin and angular momenta of light are important degrees of freedom in
nanophotonics which control light propagation, optical forces and information
encoding. Typically, optical angular momentum is generated using q-plates or
spatial light modulators. Here, we show that graphene-supported plasmonic
nanostructures with broken rotational symmetry provide a surprising spin to
orbital angular momentum conversion, which can be continuously controlled by
changing the electrochemical potential of graphene. Upon resonant illumination
by a circularly polarized plane wave, a polygonal array of indium-tin-oxide
nanoparticles on a graphene sheet generates scattered field carrying
electrically-tunable orbital angular momentum. This unique photonic spin-orbit
coupling occurs due to the strong coupling of graphene plasmon polaritons and
localised surface plasmons of the nanoparticles and leads to the controlled
directional excitation of graphene plasmons. The tuneable spin-orbit conversion
pave the way to high-rate information encoding in optical communications,
electric steering functionalities in optical tweezers, and nanorouting of
higher-dimensional entangled photon states.",2002.12058v1
2020-07-24,Quantum point particle approximation of spinning black holes and compact stars,"Gravitational wave observatories targeted for compact binary coalescence,
such as LIGO and VIRGO, require various theoretical inputs for their efficient
detection. One of such inputs are analytical description of binary dynamics at
sufficiently separated orbital scales, commonly known as post-Newtonian
dynamics. One approach for determining such two-body effective Hamiltonians is
to use quantum scattering amplitudes.
  This dissertation aims at an improved understanding of classical physics of
spinning bodies in quantum scattering amplitudes, for application to the
problem of effective two-body Hamiltonians. The main focus will be on
spin-induced higher-order multipole moments. In this dissertation results for
the first post-Minkowskian order (linear in Newton's constant $G$ and to all
orders in relative momentum $p^2$) Hamiltonian that is valid for arbitrary
compact spinning bodies to all orders in spin is presented. Next, obstruction
and prospects for the formulation's extension to second post-Minkowskian order
is discussed, based on an equivalent loop order quantum field theory
computations.
  This dissertation is based on the works [1-4].",2007.12398v1
2020-10-26,Bayesian analysis of the spin distribution of LIGO/Virgo black holes,"Gravitational wave detection from binary black hole (BBH) inspirals has
become routine thanks to the LIGO/Virgo interferometers. The nature of these
back holes remains uncertain. We study here the spin distributions of
LIGO/Virgo black holes from the first catalogue GWTC-1 and the first four
published BBH events from run O3. We compute the Bayes evidence for several
independent priors: flat, isotropic, spin-aligned and anti-aligned. We find
strong evidence for low spins in all of the cases, and significant evidence for
small isotropic spins versus any other distribution. When considered as a
homogeneous population of black holes, these results give support to the idea
that LIGO/Virgo BBH are primordial.",2010.13811v2
2020-12-11,Off-shell higher-spin fields in $AdS_{4}$ and external currents,"We construct an unfolded system for off-shell fields of arbitrary integer
spin in 4d anti-de Sitter space. To this end we couple an on-shell system,
encoding Fronsdal equations, to external Fronsdal currents for which we find an
unfolded formulation. We present a reduction of the Fronsdal current system
which brings it to the unfolded Fierz-Pauli system describing massive fields of
arbitrary integer spin. Reformulating off-shell higher-spin system as the set
of Schwinger-Dyson equations we compute propagators of higher-spin fields in
the de Donder gauge directly from the unfolded equations. We discover operators
that significantly simplify this computation, allowing a straightforward
extraction of wave equations from an unfolded system.",2012.06570v4
2021-03-05,A taxonomy of black-hole binary spin precession and nutation,"Binary black holes with misaligned spins will generically induce both
precession and nutation of the orbital angular momentum $\bf{L}$ about the
total angular momentum $\bf{J}$. These phenomena modulate the phase and
amplitude of the gravitational waves emitted as the binary inspirals to merger.
We introduce a ""taxonomy"" of binary black-hole spin precession that encompasses
all the known phenomenology, then present five new phenomenological parameters
that describe generic precession and constitute potential building blocks for
future gravitational waveform models. These are the precession amplitude
$\langle\theta_L\rangle$, the precession frequency $\langle \Omega_L\rangle$,
the nutation amplitude $\Delta\theta_L$, the nutation frequency $\omega$, and
the precession-frequency variation $\Delta\Omega_L$. We investigate the
evolution of these five parameters during the inspiral and explore their
statistical properties for sources with isotropic spins. In particular, we find
that nutation of $\bf{L}$ is most prominent for binaries with high spins ($\chi
\gtrsim 0.5$) and moderate mass ratios ($q \sim 0.6$).",2103.03894v2
2021-03-18,Engineering spin-spin interactions with optical tweezers in trapped ions,"We propose a new method for generating programmable interactions in one- and
two-dimensional trapped-ion quantum simulators. Here we consider the use of
optical tweezers to engineer the sound-wave spectrum of trapped ion crystals.
We show that this approach allows us to tune the interactions and connectivity
of the ion qubits beyond the power-law interactions accessible in current
setups. We demonstrate the experimental feasibility of our proposal using
realistic tweezer settings and experimentally relevant trap parameters to
generate the optimal tweezer patterns to create target spin-spin interaction
patterns in both one- and two-dimensional crystals. Our approach will advance
quantum simulation in trapped-ion platforms as it allows them to realize a
broader family of quantum spin Hamiltonians.",2103.10425v3
2021-06-06,Spins of primordial black holes formed in different cosmological scenarios,"Primordial black holes (PBHs) could account for all or part of dark matter,
as well as for some LIGO events. We discuss the spins of primordial black holes
produced in different cosmological scenarios, with the emphasis on recently
discovered possibilities. PBHs produced as a horizon-size collapse of density
perturbations are known to have very small spins. In contrast, PBHs resulting
from assembly of matterlike objects (particles, Q-balls, oscillons, etc.) can
have large or small spins depending on their formation history and the
efficiency of radiative cooling. We show that scalar radiation can remove the
angular momentum very efficiently, leading to slowly rotating PBHs in those
scenarios for which the radiative cooling is important. Gravitational waves
astronomy offers an opportunity to determine the spins of black holes, opening
a new window on the early Universe if, indeed, some black holes have primordial
origin.",2106.03237v2
2021-07-01,Novel elementary excitations in spin-1/2 antiferromagnets on the triangular lattice,"We discuss spin-$\frac12$ Heisenberg antiferromagnet on the triangular
lattice using the recently proposed bond-operator technique (BOT). We use the
variant of the BOT which takes into account all spin degrees of freedom in the
magnetic unit cell containing three spins. Apart from conventional magnons
known from the spin-wave theory (SWT), there are novel high-energy collective
excitations in the BOT which are built from high-energy excitations of the
magnetic unit cell. We obtain also another novel high-energy quasiparticle
which has no counterpart not only in the SWT but also in the harmonic
approximation of the BOT. All observed elementary excitations produce visible
anomalies in dynamical spin correlators. We show that quantum fluctuations
considerably change properties of conventional magnons predicted by the SWT.
The effect of a small easy-plane anisotropy is discussed. The anomalous spin
dynamics with multiple peaks in the dynamical structure factor is explained
that was observed recently experimentally in $\rm Ba_3CoSb_2O_9$ and which the
SWT could not describe even qualitatively.",2107.00256v5
2021-07-08,Spatial entanglement of fermions in one-dimensional quantum dots,"The time dependent quantum Monte Carlo method for fermions is introduced and
applied for calculation of entanglement of electrons in one-dimensional quantum
dots with several spin-polarized and spin-compensated electron configurations.
The rich statistics of wave functions provided by the method allows one to
build reduced density matrices for each electron and to quantify the spatial
entanglement using measures such as quantum entropy by treating the electrons
as identical or distinguishable particles. Our results indicate that the
spatial entanglement in parallel-spin configurations is rather small and it is
determined mostly by the quantum nonlocality introduced by the ground state. By
contrast, in the spin-compensated case the outermost opposite-spin electrons
interact like bosons which prevails their entanglement, while the inner shell
electrons remain largely at their Hartree-Fock geometry. Our findings are in a
close correspondence with the numerically exact results, wherever such
comparison is possible.",2107.03834v1
2021-07-14,Diffusive and Fluid-like Motion of Homochiral Domain Walls in Easy-Plane Magnetic Strips,"Propagation of easy-plane magnetic precession can enable more efficient spin
transport than conventional spin waves. Such easy-plane spin transport is
typically understood in terms of a hydrodynamic model, partially analogous to
superfluids. Here, using micromagnetic simulations, we examine easy-plane spin
transport in magnetic strips as the motion of a train of domain walls rather
than as hydrodynamic flow. We observe that the motion transitions from
diffusive to fluid-like as the density of domain walls is increased. This
transition is most evident in notched nanostrips, where the the domain walls
are pinned by the notch defect in the diffusive regime but propagate
essentially unimpeded in the fluid-like regime. Our findings suggest that spin
transport via easy-plane precession, robust against defects, is achievable in
strips based on realistic metallic ferromagnets and hence amenable to practical
device applications.",2107.07025v2
2021-07-16,Dynamic mean-field theory for dense spin systems at infinite temperature,"A dynamic mean-field theory for spin ensembles (spinDMFT) at infinite
temperatures on arbitrary lattices is established. The approach is introduced
for an isotropic Heisenberg model with $S = \tfrac12$ and external field. For
large coordination numbers, it is shown that the effect of the environment of
each spin is captured by a classical time-dependent random mean-field which is
normally distributed. Expectation values are calculated by averaging over these
mean-fields, i.e., by a path integral over the normal distributions. A
self-consistency condition is derived by linking the moments defining the
normal distributions to spin autocorrelations. In this framework, we explicitly
show how the rotating wave approximation becomes a valid description for
increasing magnetic field. We also demonstrate that the approach can easily be
extended. Exemplarily, we employ it to reach a quantitative understanding of a
dense ensemble of spins with dipolar interaction which are distributed randomly
on a plane including static Gaussian noise as well.",2107.07821v2
2021-09-02,Terahertz Nonlinear Optics in Two-dimensional Semi-Hydrogenated SiB,"Phase transition and current of planar clusters with loops of Josephson $\pi$
junction is of great importance for application in the adiabatic quantum
computation devices (AQC). Each $\pi$-ring possesses an orbital moment with a
current. The orientation of these orbital moments is altered by
self-interactions and controlled with a bias current. In the current research,
we construct the phase diagram of semi-hydrogenated SiB (H-SiB) semiconductor
using a two-dimensional (2D) Ising model with considering nearest-neighbor and
diagonal interactions of spin planes on the on the hexagonal lattice. Our
findings reveal that by decreasing temperature, two phase transitions of order
and disorder occur and at low temperatures a glassy state appears, where this
model maps to spin qubit. We theoretically study the magnetostriction effect by
considering of laser electromagnetic field coupled to the spin planes of
electric polarization of magnetic insulator for both unstrained and strained
H-SiB monolayers. The dynamic of laser-spin coupling and spin current shows
nonlinear optical effects and high-harmonic generation (HHG) under both
terahertz (THz) and gigahertz (GHz) electromagnetic waves. The findings of this
research open an avenue for experimentalists how to detect HHG in the
topological insulators, Dirac systems, Mott insulators, and superconducting
memories.",2109.00858v1
2021-09-09,SUSY in the Sky with Gravitons,"Picture yourself in the wave zone of a gravitational scattering event of two
massive, spinning compact bodies (black holes, neutron stars or stars). We show
that this system of genuine astrophysical interest enjoys a hidden
$\mathcal{N}=2$ supersymmetry, at least to the order of spin-squared
(quadrupole) interactions in arbitrary $D$ spacetime dimensions. Using the
${\mathcal N}=2$ supersymmetric worldline action, augmented by finite-size
corrections for the non-Kerr black hole case, we build a quadratic-in-spin
extension to the worldline quantum field theory (WQFT) formalism introduced in
our previous work, and calculate the two bodies' deflection and spin kick to
sub-leading order in the post-Minkowskian expansion in Newton's constant $G$.
For spins aligned to the normal vector of the scattering plane we also obtain
the scattering angle. All $D$-dimensional observables are derived from an
eikonal phase given as the free energy of the WQFT, that is invariant under the
$\mathcal{N}=2$ supersymmetry transformations.",2109.04465v3
2021-09-27,Designing spin-textured flat bands in twisted graphene multilayers via helimagnet encapsulation,"Twisted graphene multilayers provide tunable platforms to engineer flat bands
and exploit the associated strongly correlated physics. The two-dimensional
nature of these systems makes them suitable for encapsulation by materials that
break specific symmetries. In this context, recently discovered two-dimensional
helimagnets, such as the multiferroic monolayer NiI$_2$, are specially
appealing for breaking time-reversal and inversion symmetries due to their
nontrivial spin textures. Here we show that this spin texture can be imprinted
on the electronic structure of twisted bilayer graphene by proximity effect. We
discuss the dependence of the imprinted spin texture on the wave-vector of the
helical structure, and on the strength of the effective local exchange field.
Based on these results we discuss the nature of the superconducting
instabilities that can take place in helimagnet encapsulated twisted bilayer
graphene. Our results put forward helimagnetic encapsulation as a powerful way
of designing spin-textured flat band systems, providing a starting point to
engineer a new family of correlated moire states.",2109.13130v2
2021-09-28,Spin oscillations of a single-mode polariton system driven by a plane wave,"Theoretical study is performed of a single-mode polariton system with linear
coupling of spin components. When combined with an ordinary two-particle
interaction, the spin coupling involves a spontaneous symmetry breaking
accompanied by a switch from linear to circular polarization under resonant
driving. The asymmetric steady states can also lose stability, giving way to
oscillatory and chaotic dynamics. Here, we explore a continuous transformation
between the multistable regime, where the system is steady and locked in phase
to the pump but has a broken spin symmetry, and full-span oscillations of the
circular-polarization degree, owing to which the symmetry is effectively
reestablished. Such oscillations are analogous to the intrinsic Josephson
effect and prove to be robust against arbitrarily strong perturbations.
Transitional phenomena include the Hopf bifurcation, spin bistability of limit
cycles, and continuous transitions to and from dynamical chaos through series
of period doubling/halving events.",2109.13775v3
2021-09-29,GW200115: a non-spinning black hole -- neutron star merger,"GW200115 was the second merger of a black hole and a neutron star confidently
detected through gravitational waves. Inference on the signal allows for a
large black hole spin misaligned with the orbital angular momentum, but shows
little support for aligned spin values. We show that this is a natural
consequence of measuring the parameters of a black hole -- neutron star binary
with non-spinning components while assuming the priors used in the
LIGO-Virgo-KAGRA analysis. We suggest that, a priori, a non-spinning binary is
more consistent with current astrophysical understanding.",2109.14759v2
2021-11-22,Spin-charge separation in a 1D Fermi gas with tunable interactions,"Ultracold atoms confined to periodic potentials have proven to be a powerful
tool for quantum simulation of complex many-body systems. We confine fermions
to one-dimension to realize the Tomonaga-Luttinger liquid model describing the
highly collective nature of their low-energy excitations. We use Bragg
spectroscopy to directly excite either the spin or charge wave for various
strength of repulsive interaction. We observe that the velocity of the spin and
charge excitations shift in opposite directions with increasing interaction, a
hallmark of spin-charge separation. The excitation spectra are in quantitative
agreement with the Tomonaga-Luttinger liquid theory, and furthermore, we find
that the spin excitations become dispersive at large interaction, signaling the
onset of the nonlinear Luttinger liquid regime.",2111.11545v2
2021-12-17,Triplet character of 2D-fermion dimers arising from $s$-wave attraction via spin-orbit coupling and Zeeman splitting,"We theoretically study spin-$1/2$ fermions confined to two spatial dimensions
and experiencing isotropic short-range attraction in the presence of both
spin-orbit coupling and Zeeman spin splitting - a prototypical system for
developing topological superfluidity in the many-body sector. Exact solutions
for two-particle bound states are found to have a triplet contribution that
dominates over the singlet part in an extended region of parameter space where
the combined Zeeman- and center-of-mass-motion-induced spin-splitting energy is
large. The triplet character of dimers is purest in the regime of weak $s$-wave
interaction strength. Center-of-mass momentum is one of the parameters
determining the existence of bound states, which we map out for both two- and
one-dimensional types of spin-orbit coupling. Distinctive features emerging in
the orbital part of the bound-state wave function, including but not limited to
its $p$-wave character, provide observable signatures of unconventional
pairing.",2112.09336v2
2022-01-25,Moiré Engineering of Spin-Orbit Coupling in Twisted Platinum Diselenide,"We study the electronic structure and correlated phases of twisted bilayers
of platinum diselenide using large-scale ab initio simulations combined with
the functional renormalization group. PtSe$_2$ is a group-X transition metal
dichalcogenide, which hosts emergent flat bands at small twist angles in the
twisted bilayer. Remarkably, we find that moir\'e engineering can be used to
tune the strength of Rashba spin-orbit interactions, altering the electronic
behavior in a novel manner. We reveal that an effective triangular lattice with
a twist-controlled ratio between kinetic and spin-orbit coupling scales can be
realized. Even dominant spin-orbit coupling can be accessed in this way and we
discuss consequences for the interaction driven phase diagram, which features
pronounced exotic superconducting and entangled spin-charge density waves.",2201.10615v1
2022-04-04,The binary black hole spin distribution likely broadens with redshift,"The population-level distributions of the masses, spins, and redshifts of
binary black holes (BBHs) observed using gravitational waves can shed light on
how these systems form and evolve. Because of the complex astrophysical
processes shaping the inferred BBH population, models allowing for correlations
among these parameters will be necessary to fully characterize these sources.
We hierarchically analyze the BBH population detected by LIGO and Virgo with a
model allowing for correlations between the effective aligned spin and the
primary mass and redshift. We find that the width of the effective spin
distribution grows with redshift at 98.6% credibility. We determine this trend
to be robust under the application of several alternative models and
additionally verify that such a correlation is unlikely to be spuriously
introduced using a simulated population. We discuss the possibility that this
correlation could be due to a change in the natal black hole spin distribution
with redshift.",2204.01578v2
2022-04-06,Muon spin rotation and relaxation study on Nb$_{1-y}$Fe$_{2+y}$,"We present a detailed study of the magnetic properties of weakly
ferromagnetic/quantum critical Nb$_{1-y}$Fe$_{2+y}$ using muon spin rotation
and relaxation ($\mu$SR). By means of an angular dependent study of the muon
spin rotation signal in applied magnetic fields on a single crystal in the
paramagnetic state we establish the muon stopping site in the crystallographic
lattice of NbFe$_2$. With this knowledge we develop models to describe the muon
spin rotation and relaxation signals in the weakly ferromagnetic, spin density
wave and quantum critical phases of Nb$_{1-y}$Fe$_{2+y}$ and fit the
corresponding experimental data. In particular, we quantify the $\mu$SR
response for quantum critical behavior in Nb$_{1.0117}$Fe$_{1.9883}$ and
extract the influence of residual weak structural disorder. From our analysis,
Nb$_{1-y}$Fe$_{2+y}$ emerges to be uniquely suited to study quantum criticality
close to weak itinerant ferromagnetic order.",2204.02852v3
2022-04-23,Nonreciprocal light propagation induced by a subwavelength spinning cylinder,"Nonreciprocal optical devices have broad applications in light manipulations
for communications and sensing. Non-magnetic mechanisms of optical
nonreciprocity are highly desired for high-frequency on-chip applications.
Here, we investigate the nonreciprocal properties of light propagation in a
dielectric waveguide induced by a subwavelength spinning cylinder. We find that
the chiral modes of the cylinder can give rise to unidirectional coupling with
the waveguide via the transverse spin-orbit interaction, leading to different
transmissions for guided wave propagating in opposite directions and thus
optical isolation. We reveal the dependence of the nonreciprocal properties on
various system parameters including mode order, spinning speed, and coupling
distance. The results show that higher-order chiral modes and larger spinning
speed generally give rise to stronger nonreciprocity, and there exists an
optimal cylinder-waveguide coupling distance where the optical isolation
reaches the maximum. Our work contributes to the understanding of
nonreciprocity in subwavelength moving structures and can find applications in
integrated photonic circuits, topological photonics, and novel metasurfaces.",2204.11093v1
2022-04-27,Refining magnetic interactions from the magnetic field dependence of spin-wave excitations in magnetoelectric LiFePO$_4$,"We investigated the spin excitations of magnetoelectric $\text{LiFePO}_4$ by
THz absorption spectroscopy in magnetic fields up to 33$\,$T. By studying their
selection rules, we found not only magnetic-dipole, but also electric-dipole
active (electromagnons) and magnetoelectric resonances. The magnetic field
dependence of four strong low-energy modes is reproduced well by our
four-sublattice spin model for fields applied along the three orthorhombic
axes. From the fit, we refined the exchange couplings, single-ion anisotropies,
and the Dzyaloshinskii-Moriya interaction parameters. Additional spin
excitations not described by the mean-field model are observed at higher
frequencies. Some of them shows a strong shift with magnetic field, up to
4$\,\text{cm}^{-1}/\text{T}$, when the field is applied along the easy axis.
Based on this field dependence, we attribute these high frequency resonances to
excitation of higher spin multipoles and of two magnons, which become
THz-active due to the low symmetry of the magnetically ordered state.",2204.12967v1
2022-05-20,Microscopic analysis of spin-momentum locking on a geometric phase metasurface,"We revisit spin-orbit coupling in a plasmonic Berry metasurface comprised of
rotated nanoapertures, which is known to imprint a robust far-field
polarization response. We present a scattering formalism that shows how that
spin-momentum locking emerges from the geometry of the unit cell without
requiring global rotation symmetries. We find and confirm with Mueller
polarimetry measurements that spin-momentum locking is an approximate symmetry.
The symmetry breakdown is ascribed to the elliptical projection of circularly
polarized light into the planar surface. This breakdown is maximal when surface
waves are excited, and a new set of spin-momentum locking rules is presented
for this case.",2205.10245v2
2022-05-24,Universal scattering phase shift in the presence of spin-orbit coupling,"Scattering phase shift, as a key parameter in scattering theory, plays an
important role in characterizing low-energy collisions between ultracold atoms.
In this work, we theoretically investigate the universal low-energy behavior of
the scattering phase shifts for cold atoms in the presence of spin-orbit
coupling. We first construct the asymptotic form of the two-body wave function
when two fermions get as close as the interaction range, and consider
perturbatively the correction of the spin-orbit coupling up to the second
order, in which new scattering parameters are introduced. Then for elastic
collisions, the scattering phase shifts are defined according to the unitary
scattering $S$ matrix. We show how the low-energy behavior of the scattering
phase shifts is modified by these new scattering parameters introduced by
spin-orbit coupling. The universality of the scattering phase shifts is
manifested as the independence of the specific form of the interatomic
potential. The explicit forms of the new scattering parameters are analytically
derived within a model of the spherical-square-well potential. Our method
provides a unified description of the low-energy properties of scattering phase
shifts in the presence of spin-orbit coupling.",2205.11732v1
2022-05-31,Spin-Acoustic Control of Silicon Vacancies in 4H Silicon Carbide,"We demonstrate direct, acoustically mediated spin control of naturally
occurring negatively charged silicon monovacancies (V$_{Si}^-$) in a high
quality factor Lateral Overtone Bulk Acoustic Resonator fabricated out of high
purity semi-insulating 4H-Silicon Carbide. We compare the frequency response of
silicon monovacancies to a radio-frequency magnetic drive via
optically-detected magnetic resonance and the resonator's own radio-frequency
acoustic drive via optically-detected spin acoustic resonance and observe a
narrowing of the spin transition to nearly the linewidth of the driving
acoustic resonance. We show that acoustic driving can be used at room
temperature to induce coherent population oscillations. Spin acoustic resonance
is then leveraged to perform stress metrology of the lateral overtone bulk
acoustic resonator, showing for the first time the stress distribution inside a
bulk acoustic wave resonator. Our work can be applied to the characterization
of high quality-factor micro-electro-mechanical systems and has the potential
to be extended to a mechanically addressable quantum memory.",2205.15488v1
2022-07-18,Geometry and topology of spin random fields,"Spin (spherical) random fields are very important in many physical
applications, in particular they play a key role in Cosmology, especially in
connection with the analysis of the Cosmic Microwave Background radiation.
These objects can be viewed as random sections of the s-th complex tensor power
of the tangent bundle of the 2-sphere. In this paper, we discuss how to
characterize their expected geometry and topology. In particular, we
investigate the asymptotic behaviour, under scaling assumptions, of general
classes of geometric and topological functionals including Lipschitz-Killing
Curvatures and Betti numbers for (properly defined) excursion sets; we cover
both the cases of fixed and diverging spin parameters s. In the special case of
monochromatic fields (i.e., spin random eigenfunctions) our results are
particularly explicit; we show how their asymptotic behaviour is non-universal
and we can obtain in particular complex versions of Berry's random waves and of
Bargmann-Fock's models as subcases of a new generalized model, depending on the
rate of divergence of the spin parameter s.",2207.08413v1
2022-08-08,Temperature and Field Dependence of Ferromagnetic Magnon in Monolayer Honeycomb Spin Lattice,"Temperature and field dependence of collective spin excitations or magnon in
monolayer honeycomb spin lattices is investigated using an anisotropic exchange
XZ-Heisenberg model in an external field. Magnetic phase transition in the
presence of the transverse field is the spin reorientation (SR) transition with
magnon intensity existing above the SR temperature. The transverse field either
decreases or sustains the spin-wave intensity in the temperature region below
or above the SR temperature, respectively. The gap of the zero-momentum
low-energy magnon branch closes at the SR transverse field, which is the
critical quantum phase transition field at zero temperature. The application of
the model to a two-dimensional CrI$_3$ explains the existence of the
zero-momentum magnon mode above the Curie temperature and shows the suitable
values of the exchange parameters compared with the DFT calculations. The
estimated magnon velocity near the Dirac point in this material is about 1.74
km/s.",2208.03913v1
2022-12-02,From fermionic spin-Calogero-Sutherland models to the Haldane-Shastry chain by freezing,"The Haldane-Shastry spin chain has a myriad of remarkable properties,
including Yangian symmetry and, for spin $1/2$, explicit highest-weight
eigenvectors featuring (the case $\alpha = 1/2$ of) Jack polynomials. This
stems from the spin-Calogero-Sutherland model, which reduces to Haldane-Shastry
in a special `freezing' limit.
  In this work we clarify various points that, to the best of our knowledge,
were missing in the literature. We have two main results. First, we show that
freezing the $\mathit{fermionic}$ spin-1/2 Calogero-Sutherland model naturally
accounts for the precise form of the Haldane-Shastry wave functions, including
the Vandermonde factor squared. Second, we use the fermionic framework to prove
the claim of Bernard-Gaudin-Haldane-Pasquier that the Yangian highest-weight
eigenvectors of the $SU(r)$-version of the Haldane-Shastry chain arise by
freezing $SU(r-1)$ spin-Calogero-Sutherland eigenvectors at $\alpha = 1/2$.",2212.01373v2
2023-01-15,Spin-Flavor SU(6) Symmetry for Baryon-Baryon Interactions,"Short-range parts of the baryon-baryon ($BB$) interactions are analyzed from
the spin-flavor $SU(6)_{sf}\supset SU(3)_f \times SU(2)_s$ symmetry viewpoint.
Due to the Pauli principle of quarks, the symmetry structure of the wave
functions is restricted at short distances. Consequently, the $BB$ states with
the same spin-flavor quantum numbers may be reduced into one or a few
spin-flavor states. Such reduction causes repulsion and/or suppression of
transitions at short distances. We show that the observed suppression of the
$\Xi N \to \Lambda\Lambda$ conversion can be explained following the above
argument. It is also applied to the suppression of the $\Sigma N$ to $\Lambda
N$ conversion in the spin 1 and isospin 1/2 channel. Furthermore, the effects
of the color-magnetic interaction (CMI), which prefers flavor antisymmetric
states, to the Pauli-allowed states are discussed.",2301.06026v1
2023-02-10,Spin-controlled photonics via temporal anisotropy,"Temporal metamaterials, based on time-varying constitutive properties, offer
new exciting possibilities for advanced field manipulations. In this study, we
explore the capabilities of anisotropic temporal slabs, which rely on abrupt
changes in time from isotropic to anisotropic response (and vice versa). Our
findings show that these platforms can effectively manipulate the wave-spin
dimension, allowing for a range of intriguing spin-controlled photonic
operations. We demonstrate these capabilities through examples of
spin-dependent analog computing and spin-orbit interaction effects for vortex
generation. These results provide new insights into the field of temporal
metamaterials, and suggest potential applications in communications, optical
processing and quantum technologies.",2302.05153v2
2023-02-22,A spin-energy operator inequality for Heisenberg-coupled qubits,"We slightly strengthen an operator inequality identified by Correggi et al.
that lower bounds the energy of a Heisenberg-coupled graph of $s=1/2$ spins
using the total spin. In particular, $\Delta H \ge C \Delta\vec{S}^2$ for a
graph-dependent constant $C$, where $\Delta H$ is the energy above the ground
state and $\Delta\vec{S}^2$ is the amount by which the square of the total spin
$\vec{S} = \sum_i \vec{\sigma}_i/2$ falls below its maximum possible value. We
obtain explicit constants in the special case of a cubic lattice. We briefly
discuss the interpretation of this bound in terms of low-energy, approximately
non-interacting magnons in spin wave theory and contrast it with another
inequality found by B\""arwinkel et al.",2302.11267v1
2023-02-22,Compressing the atomic cloud in a matter-wave stripe soliton,"We consider an attractive quasi-one dimensional spin-orbit coupled
Bose-Einstein condensate (SOC BEC) confined in a periodic potential produced by
the combination of linear and nonlinear optical lattices, and study the effects
of squeezing a stripe soliton by varying the inter-atomic interaction in the
nonlinear lattice. It is observed that the nodes on the soliton arising
entirely due to the effect of spin-orbit coupling tend to disappear as we
increase the squeezing effect to finally get a stable fundamental soliton. This
leads us to conclude that external pressure can reduce the effect of spin-orbit
coupling in the SOC BEC and even convert the system to a traditional BEC
without spin-orbit coupling. We make use of an information theoretic measure to
visualize how does the atomic density distribution in the condensate respond to
continual reduction in the spin-orbit coupling effect.",2302.11626v2
2023-03-15,Instability of magnetic skyrmion strings induced by longitudinal spin currents,"It is well established that spin-transfer torques exerted by in-plane spin
currents give rise to a motion of magnetic skyrmions resulting in a skyrmion
Hall effect. In films of finite thickness or in three-dimensional bulk samples
the skyrmions extend in the third direction forming a string. We demonstrate
that a spin current flowing longitudinally along the skyrmion string instead
induces a Goldstone spin wave instability. Our analytical results are confirmed
by micromagnetic simulations of both a single string as well as string lattices
suggesting that the instability eventually breaks the strings. A longitudinal
current is thus able to melt the skyrmion string lattice via a dynamical phase
transition. For films of finite thickness or in the presence of disorder a
threshold current will be required, and we estimate the latter assuming weak
collective pinning.",2303.08532v1
2023-03-20,Acoustic frequency atomic spin oscillator in the quantum regime,"We experimentally demonstrate quantum behavior of a macroscopic atomic spin
oscillator in the acoustic frequency range. Quantum back-action of the spin
measurement, ponderomotive squeezing of light, and oscillator spring softening
are observed at spin oscillation frequencies down to 6 kHz. Quantum noise
sources characteristic of spin oscillators operating in the near-DC frequency
range are identified and means for their mitigation are presented. These
results constitute an important step towards quantum noise reduction and
entanglement-enhanced sensing in the acoustic range using a negative-mass
reference frame. In particular, the results are relevant for broadband noise
reduction in gravitational wave detectors.",2303.11029v3
2023-04-09,Extraordinary coupled spin and chirality of electromagnetic guided waves,"Optical spin and chirality play key roles in the interaction between light
and chiral materials. The propagating guided modes by optical waveguides hardly
produce optical chirality because of the broken symmetry between electric and
magnetic components. Here for the first time we discover that the directional
coupling of spatially guided modes can create polarization helicity, and thus
generate optical spin and chirality. They are originated from the intrinsic
phase retardation of {\pi}/2 between two directionally coupled spatial modes.We
show that these near-field coupled spin and chirality manifests as
odd-symmetric density distribution in the cross-section of symmetric
waveguides, and especially this odd-symmetric distribution is intrinsically
locked to coupling paths regardless of the propagation direction of light.
Furthermore, such odd-symmetric chirality could produce a considerable chiral
gradient force that can be used to separate chiral nanoparticles. These
extraordinary electromagnetic properties may further prosper spin photonics and
chiral light-matter interaction on nanophotonic platforms.",2304.04764v1
2023-05-03,An overview of the spin dynamics of antiferromagnetic Mn$_5$Si$_3$,"The metallic compound Mn$_5$Si$_3$ hosts a series of antiferromagnetic phases
which can be controlled by external stimuli such as temperature and magnetic
field. In this work, we investigate the spin-excitation spectrum of bulk
Mn$_5$Si$_3$ by combining inelastic neutron scattering measurements and density
functional theory calculations. We study the evolution of the dynamical
response under external parameters and demonstrate that the spin dynamics of
each phase is robust against any combination of temperature and magnetic field.
In particular, the high-energy spin dynamics is very characteristic of the
different phases consisting of either spin waves or broad fluctuations
patterns.",2305.02409v2
2023-05-15,Long-time relaxation of a finite spin bath linearly coupled to a qubit,"We discuss the long-time relaxation of a qubit linearly coupled to a finite
bath of $N$ spins (two-level systems, TLSs), with the interaction Hamiltonian
in rotating wave approximation. We focus on the regime $N\gg 1$, assuming that
the qubit-bath coupling is weak, that the range of spin frequencies is
sufficiently broad, and that all the spins are initialized in the ground state.
Despite the model being perfectly integrable, we make two interesting
observations about the effective system relaxation. First, as one would expect,
the qubit relaxes exponentially towards its zero-temperature state at a well
characterized rate. Second, the bath spins, even when mutually coupled, do not
relax towards a thermal distribution, but rather form a Lorentzian distribution
peaked at the frequency of the initially excited qubit. This behavior is
captured by an analytical approximation that makes use of the property $N\gg 1$
to treat the TLS frequencies as a continuum and is confirmed by our numerical
simulations.",2305.08692v2
2023-07-20,NeoSySPArtaN: A Neuro-Symbolic Spin Prediction Architecture for higher-order multipole waveforms from eccentric Binary Black Hole mergers using Numerical Relativity,"The prediction of spin magnitudes in binary black hole and neutron star
mergers is crucial for understanding the astrophysical processes and
gravitational wave (GW) signals emitted during these cataclysmic events. In
this paper, we present a novel Neuro-Symbolic Architecture (NSA) that combines
the power of neural networks and symbolic regression to accurately predict spin
magnitudes of black hole and neutron star mergers. Our approach utilizes GW
waveform data obtained from numerical relativity simulations in the SXS
Waveform catalog. By combining these two approaches, we leverage the strengths
of both paradigms, enabling a comprehensive and accurate prediction of spin
magnitudes. Our experiments demonstrate that the proposed architecture achieves
an impressive root-mean-squared-error (RMSE) of 0.05 and mean-squared-error
(MSE) of 0.03 for the NSA model and an RMSE of 0.12 for the symbolic regression
model alone. We train this model to handle higher-order multipole waveforms,
with a specific focus on eccentric candidates, which are known to exhibit
unique characteristics. Our results provide a robust and interpretable
framework for predicting spin magnitudes in mergers. This has implications for
understanding the astrophysical properties of black holes and deciphering the
physics underlying the GW signals.",2307.11003v1
2023-08-25,Parameter space investigation for spin-dependent electron diffraction in the Kapitza-Dirac effect,"We demonstrate that spin-dependent electron diffraction is possible for a
smooth range of transverse electron momenta in a two-photon Bragg scattering
scenario of the Kapitza-Dirac effect. Our analysis is rendered possible by
introducing a generalized specification for quantifying spin-dependent
diffraction, yielding an optimization problem which is solved by making use of
a Newton gradient iteration scheme. With this procedure, we investigate the
spin-dependent effect for different transverse electron momenta and different
laser polarizations of the standing light wave Kapitza-Dirac scattering. The
possibility for using arbitrarily low transverse electron momenta, when setting
up a spin-dependent Kapitza-Dirac experiment allows longer interaction times of
the electron with the laser and therefore enables less constraining parameters
for an implementation of the effect.",2308.13200v2
2023-09-15,Super Slowly Spinning Stars in Close Binaries,"Stars in short-period binaries typically have spins that are aligned and
synchronized with the orbit of their companion. In triple systems, however, the
combination of spin and orbital precession can cause the star's rotation to
evolve to a highly misaligned and sub-synchronous equilibrium known as a
Cassini state. We identify a population of recently discovered stars that
exhibit these characteristics and which are already known to have tertiary
companions. These third bodies have a suitable orbital period to allow the
inner binary to evolve into the sub-synchronous Cassini state, which we confirm
with orbital evolution models. We also compute the expected stellar obliquity
and spin period, showing that the observed rotation rates are often slower than
expected from equilibrium tidal models. However, we show that tidal dissipation
via inertial waves can alter the expected spin-orbit misalignment angle and
rotation rate, potentially creating the very slow rotation rates in some
systems. Finally, we show how additional discoveries of such systems can be
used to constrain the tidal physics and orbital evolution histories of stellar
systems.",2309.08505v1
2023-12-04,Anisotropic skyrmion crystal on a centrosymmetric square lattice under an in-plane magnetic field,"We investigate the instability toward a skyrmion crystal under an in-plane
magnetic field in centrosymmetric tetragonal magnets. By performing the
simulated annealing for a spin model on the square lattice, we find that the
interplay among the easy-plane two-spin anisotropic interaction, positive
biquadratic interaction, and high-harmonic wave-vector interaction plays an
important role in stabilizing the skyrmion crystal in the in-plane external
magnetic field. The obtained skyrmion crystal consists of a pair of vortex and
antivortex with opposite polarization in terms of the out-of-plane spin
component. We also show that various multiple-$Q$ states emerge depending on
the model parameters. Our results indicate the possibility of topological spin
textures in centrosymmetric tetragonal magnets with easy-plane magnetic
anisotropy when the ground-state spin configuration at zero field is
characterized by a single-$Q$ in-plane cycloidal spiral state.",2312.01542v1
2023-12-15,Mutual synchronization in spin torque and spin Hall nano-oscillators,"This chapter reviews the state of the art in mutually synchronized
spin-torque and spin Hall nano-oscillator (STNO and SHNO) arrays. After briefly
introducing the underlying physics, we discuss different nano-oscillator
implementations and their functional properties with respect to frequency
range, output power, phase noise, and modulation rates. We then introduce the
concepts and the theory of mutual synchronization and discuss the possible
coupling mechanisms in spintronic nano-oscillators, such as dipolar,
electrical, and spin-wave coupling. We review the experimental literature on
mutually synchronized STNOs and SHNOs in one- and two-dimensional arrays and
discuss ways to increase the number of mutually synchronized nano-oscillators.
Finally, the potential for applications ranging from microwave signal
sources/detectors and ultrafast spectrum analyzers to neuromorphic computing
elements and Ising machines is discussed together with the specific electronic
circuitry that has been designed so far to harness this potential.",2312.09656v1
2023-12-20,Heisenberg spin chain with random-sign couplings,"We study the 1D quantum Heisenberg chain with randomly ferromagnetic or
antiferromagnetic couplings (a model previously studied by approximate
strong-disorder renormalization group). We find that, at least for sufficiently
large spin $S$, the ground state has ""spin glass"" order. The spin waves on top
of this state have the dynamical exponent ${z=3/2}$, intermediate between the
values $z=1$ of the antiferromagnet and ${z=2}$ of the ferromagnet. DMRG
simulations are in good agreement with the analytical results for spins ${S=1}$
and ${S=3/2}$. The case ${S=1/2}$ shows large finite size effects: we suggest
that this case is also ordered, but with a small ordered moment.",2312.13452v1
2024-01-26,Rotational evolution of young-to-old stars with data-driven three-dimensional wind models,"Solar-type stars form with a wide range of rotation rates. A wide range
persists until a stellar age of 0.6 Gyr, after which solar-type stars exhibit
Skumanich spin-down. Rotational evolution models incorporating polytropic
stellar winds struggle to simultaneously reproduce these two regimes, namely
the initially wide range and the Skumanich spin-down without imposing an
a-priori cap on the wind mass-loss rate. We show that a three-dimensional wind
model driven by Alfv\'en waves and observational data yields wind torques that
agree with the observed age distribution of rotation rates. In our models of
the Sun and twenty-seven open cluster stars aged from 0.04 to 0.6 Gyr that have
observationally derived surface magnetic maps and rotation rates, we find
evidence of exponential spin-down in young stars that are rapid rotators and
Skumanich spin-down for slow rotators. The two spin-down regimes emerge
naturally from our data-driven models. Our modelling suggests that the observed
age distribution of stellar rotation rates arises as a consequence of magnetic
field strength saturation in rapid rotators.",2401.14747v1
2024-02-06,On-chip optical wavefront shaping by transverse spin induced Pancharatanam-Berry phase,"Pancharatnam-Berry (PB) metasurfaces can be applied to manipulate the phase
and polarization of light within subwavelength thickness. The underlying
mechanism is attributed to the geometric phase originating from the
longitudinal spin of light. Here, we demonstrate a new type of PB geometric
phase derived from the intrinsic transverse spin of guided light. Using
full-wave numerical simulations, we show that the rotation of a metallic nano
bar sitting on a metal substrate can induce a geometric phase covering 2$\pi$
full range for the surface plasmons carrying intrinsic transverse spin.
Specially, the geometric phase is different for the surface plasmons
propagating in opposite directions due to spin-momentum locking. We apply the
geometric phase to design metasurfaces to manipulate the wavefront of surface
plasmons to achieve steering and focusing. Our work provides a new mechanism
for on-chip light manipulations with potential applications in designing
ultra-compact optical devices for imaging and sensing.",2402.03650v1
2024-02-07,Are magnetic monopoles at the origin of magneto-electricity in spin ices?,"The possibilities of combining several degrees of freedom inside a unique
material have recently been highlighted in their dynamics and proposed as
information carriers in quantum devices where their cross-manipulation by
external parameters such as electric and magnetic fields could enhance their
functionalities. An emblematic example is that of electromagnons, spin-waves
dressed with electric dipoles, that are fingerprints of multiferroics.
Point-like objects have also been identified, which may take the form of
excited quasiparticles. This is the case for magnetic monopoles, the exotic
excitations of spin ices, that have been recently proposed to carry an electric
dipole although experimental evidences remain elusive. Presently, we
investigate the electrical signature of a classical spin ice and a related
compound that supports quantum fluctuations. Our in-depth study clearly
attributes magnetoelectricity to the correlated spin ice phase distinguishing
it from extrinsic and single-ion effects. Our calculations show that the
proposed model conferring magnetoelectricity to monopoles is not sufficient,
calling for higher order contributions.",2402.05260v2
2024-02-09,g-factor symmetry and topology in semiconductor band states,"The $\bf{g}$ tensor, which determines the reaction of Kramers-degenerate
states to an applied magnetic field, is of increasing importance in the current
design of spin qubits. It is affected by details of heterostructure
composition, disorder, and electric fields, but it inherits much of its
structure from the effect of the spin-orbit interaction working at the
crystal-lattice level. Here we uncover new symmetry and topological features of
$\bf{g}=\bf{g}_L+\bf{g}_S$ for important valence and conduction bands in
silicon, germanium, and gallium arsenide. For all crystals with high (cubic)
symmetry, we show that large departures from the nonrelativistic value $g=2$
are {\em guaranteed} by symmetry. In particular, considering the spin part
$\bf{g}_S(\bf{k})$, we prove that the scalar function $det(\bf{g}_S(\bf{k}))$
must go to zero on closed surfaces in the Brillouin zone, no matter how weak
the spin-orbit coupling is. We also prove that for wave vectors $\bf{k}$ on
these surfaces, the Bloch states $|u_{n\bf{k}}\rangle$ have maximal
spin-orbital entanglement. Using tight-binding calculations, we observe that
the surfaces $det(\bf{g}(\bf{k}))=0$ exhibit many interesting topological
features, exhibiting Lifshitz critical points as understood in Fermi-surface
theory.",2402.06310v1
2024-03-09,Hybrid Spin-Orbit Exciton-Magnon Excitations in FePS$_3$,"FePS$_3$ is a layered van der Waals (vdW) Ising antiferromagnet that has
recently been studied in the context of true 2D magnetism, and emerged as an
ideal material platform for investigating strong spin-phonon coupling, and
non-linear magneto-optical phenomena. In this work, we demonstrate an important
unresolved role of spin-orbit coupling (SOC) in the ground state and
excitations of this compound. Combining first principles calculations with
Linear Flavor Wave Theory (LFWT), we find strong mixing and spectral overlap of
different spin-orbital single-ion states. As such, the low-lying excitations
form complex mixtures of local degrees of freedom most accurately viewed as
hybrid spin-orbit exciton-magnon modes. Complete parameterization of the
resulting low-energy model including all such degrees of freedom requires
nearly half a million coupling constants. Despite this complexity, we show that
such a model can be inexpensively derived using local many-body-based
approaches, which yield quantitative agreement with recent experiments. The
results highlight the importance of SOC even in first row transition metals,
and provide essential insight into the properties of 2D magnets with unquenched
orbital moments.",2403.05958v1
2024-03-14,Topological responses from gapped Weyl points in 2D altermagnets,"Altermagnetism combines aspects of both ferromagnetism and
antiferromagnetism, breaking spin degeneracy while possessing no net
magnetization. In this work, we study the symmetry requirements for
topologically protected Weyl points in 2D altermagnets, involving bands with
the same spin quantum number. We classify all spin-wallpaper groups whose
symmetries protect 2D Weyl points and show that their nontrivial topology is
charactrized by a quantized $\pi$-Berry phase. Representative electronic
tight-binding and magnonic linear spin-wave models are constructed to
investigate the unusual transport characteristics of these 2D Weyl points.
Different mass terms, induced for example through strain or via coupling to
light or a substrate, gap out the Weyl points leading to emerging gapped
topological phases. Depending on the mass terms, these phases carry finite
Chern and/or spin Chern numbers and exhibit protected edge states as well as
anomalous electronic and thermal Hall responses. We calculate these Hall
currents for the different topological phases.",2403.09520v1
2024-03-27,Bridging hadronic and vacuum structure by heavy quarkonia,"We discuss the central and, mostly, spin-dependent potentials in heavy
quarkonia $\bar b b, \bar c c$, with two goals in mind. The first is
phenomenological: using the splitting between the 1S and 2S pairs, as well as
the 1P and 2P quartet masses, we obtain very accurate values of all matrix
elements of the spin-depepdent potentials. The second is theoretical: using
standard wave functions, we compute these matrix elements, from perturbative,
nonperturbative and ``string"" contributions. The model for nonperturbative
effects is a ``dense instanton liquid model"", in which the QCD vacuum is made
of (strongly color correlated) instanton-antiinstanton pairs or ""molecules"". We
calcuate their effect via standard Wilson lines, with or without extra powers
of gauge fields. We find that this model provides a reasonable description of
all central, spin-spin and spin-orbit forces at distances $r= 0-0.7 \, fm $,
relevant for $\bar b b $ and $\bar c c$ quarkonia.",2403.18700v1
2024-04-17,Self-Ordered Supersolid in Spinor Condensates with Cavity-Mediated Spin-Momentum-Mixing Interactions,"Ultracold atoms with cavity-mediated long-range interactions offer a
promising platform for investing novel quantum phenomena. Exploiting recent
experimental advancements, we propose an experimental scheme to create
self-ordered supersolid in spin-$1/2$ condensates confined within an optical
cavity. The interplay of cavity and pump fields gives rise to supersolid square
and plane wave phases, comprehensively described by the two-component
Tavis-Cummings model. We show that the self-ordered supersolid phase exhibits
an undamped gapless Goldstone mode over a wide parameter range. This proposal,
achievable with current experimental setups utilizing identical laser
configurations, is in contrast to the realization of checkerboard
supersolidity, which hinges on constructing a $U(1)$ symmetry by utilizing two
${\cal Z}_2$ symmetries with precisely matched atom-cavity coupling in
multimode resonators. By employing the superradiant photon-exchange process, we
realize for the first time cavity-mediated spin-momentum-mixing interactions
between highly correlated spin and momentum modes, analogous to that observed
spin-mixing in spin-1 condensates. Our scheme provides a unique platform for
realizing spin-momentum squeezing and spatially distributed multipartite
entanglement.",2404.11157v1
2024-04-17,$SO(4)$ Symmetry in Hydrogen Atom with Spin,"As the simplest atom in nature, the hydrogen atom has been explored
thoroughly from the perspective of non-relativistic quantum mechanics to
relativistic quantum mechanics. Among the research on hydrogen atom, its energy
level is the most basic, which can be obtained more conveniently predicated on
the $SO(4)$ symmetry than the wave-equation resolution. Moreover, ``spin'' is
another indispensable topic in quantum mechanics, appearing as an intrinsic
degree of freedom. In this work, we generalize the quantum Runge-Lenz vector to
a spin-dependent one, and then extract a novel Hamiltonian of hydrogen atom
with spin based on the requirement of $SO(4)$ symmetry. Furthermore, the energy
spectrum of hydrogen atom with spin potentials is also determined by the
remarkable approach of $SO(4)$ symmetry. Our findings extend the ground of
hydrogen atom, and may contribute to other complicated models based on hydrogen
atom.",2404.11437v1
2011-11-30,Theory of spin-orbit coupling in bilayer graphene,"Theory of spin-orbit coupling in bilayer graphene is presented. The
electronic band structure of the AB bilayer in the presence of spin-orbit
coupling and a transverse electric field is calculated from first-principles
using the linearized augmented plane wave method implemented in the WIEN2k
code. The first-principles results around the K points are fitted to a
tight-binding model. The main conclusion is that the spin-orbit effects in
bilayer graphene derive essentially from the single-layer spin-orbit coupling
which comes almost solely from the d orbitals. The intrinsic spin-orbit
splitting (anticrossing) around the K points is about 24\mu eV for the
low-energy valence and conduction bands, which are closest to the Fermi level,
similarly as in the single layer graphene. An applied transverse electric field
breaks space inversion symmetry and leads to an extrinsic (also called
Bychkov-Rashba) spin-orbit splitting. This splitting is usually linearly
proportional to the electric field. The peculiarity of graphene bilayer is that
the low-energy bands remain split by 24\mu eV independently of the applied
external field. The electric field, instead, opens a semiconducting band gap
separating these low-energy bands. The remaining two high-energy bands are
spin-split in proportion to the electric field; the proportionality coefficient
is given by the second intrinsic spin-orbit coupling, whose value is 20\mu eV.
All the band-structure effects and their spin splittings can be explained by
our tight-binding model, in which the spin-orbit Hamiltonian is derived from
symmetry considerations. The magnitudes of intra- and interlayer
couplings---their values are similar to the single-layer graphene ones---are
determined by fitting to first-principles results.",1111.7223v2
2018-01-08,Factorization and resummation: A new paradigm to improve gravitational wave amplitudes. II: the higher multipolar modes,"The factorization and resummation approach of Nagar and Shah~[Phys.~Rev.~D~94
(2016), 104017], designed to improve the strong-field behavior of the
post-Newtonian (PN) residual waveform amplitudes $f_{\ell m}$'s entering the
effective-one-body, circularized, gravitational waveform for spinning
coalescing binaries, is here improved and generalized to all multipoles up to
$\ell=6$. For a test-particle orbiting a Kerr black hole, each multipolar
amplitude is truncated at relative 6~post Newtonian (PN) order, both for the
orbital (nonspinning) and spin factors. By taking a certain Pad\'e approximant
(typically the $P^4_2$ one) of the orbital factor in conjuction with the
inverse Taylor (iResum) representation of the spin factor, it is possible to
push the analytical/numerical agreement of the energy fluxe at the level of
$5\%$ at the last-stable-orbit for a quasi-maximally spinning black hole with
dimensionless spin parameter $+0.99$. When the procedure is generalized to
comparable-mass binaries, each orbital factor is kept at relative $3^{+3}$PN
order, i.e. the 3PN comparable-mass terms are hybridized with higher PN
test-particle terms up to 6PN relative order. The same Pad\'e resummation is
used for continuity. By contrast, the spin factor is only kept at the highest
comparable-mass PN-order currently available. We illustrate that the
consistency between different truncations in the spin content of the waveform
amplitudes is stronger in the resummed case than when using the standard
Taylor-expanded form of Pan et al.~[Phys.~Rev.~D~83 (2011) 064003]. We finally
introduce a method to consistently hybridize comparable-mass and test-particle
information {\it also} in the presence of spin (including the spin of the
particle), discussing it explicitly for the $\ell=m=2$ spin-orbit and
spin-square terms.",1801.02366v1
2018-02-19,Spin-orbit coupling effects in zinc-blende InSb and wurtzite InAs nanowires: Realistic calculations with multiband $\vec{k} \cdot \vec{p}$ method,"A systematic numerical investigation of spin-orbit fields in the conduction
bands of III-V semiconductor nanowires is performed. Zinc-blende InSb nanowires
are considered along [001], [011], and [111] directions, while wurtzite InAs
nanowires are studied along [0001] and [10$\overline{1}$0] or
[11$\overline{2}$0] directions. Realistic multiband $\vec{k} \cdot \vec{p}\,$
Hamiltonians are solved by using plane-wave expansions of real-space
parameters. In all cases the linear and cubic spin-orbit coupling parameters
are extracted for nanowire widths from 30 to 100 nm. Typical spin-orbit
energies are on the $\mu$eV scale, except for InAs wurtzite nanowires grown
along [10$\overline{1}$0] or [11$\overline{2}$0], in which the spin-orbit
energy is about meV, largely independent of the wire diameter. Significant
spin-orbit coupling is obtained by applying a transverse electric field,
causing the Rashba effect. For an electric field of about 4 mV/nm the obtained
spin-orbit energies are about 1 meV for both materials in all investigated
growth directions. The most favorable system, in which the spin-orbit effects
are maximal, are InAs WZ nanowires grown along [1010] or [11$\overline{2}$0],
since here spin-orbit energies are giant (meV) already in the absence of
electric field. The least favorable are InAs WZ nanowires grown along [0001],
since here even the electric field does not increase the spin-orbit energies
beyond 0.1 meV. The presented results should be useful for investigations of
optical orientation, spin transport, weak localization, and superconducting
proximity effects in semiconductor nanowires.",1802.06734v2
2020-10-22,Spin-Orbit Misalignments in Tertiary-Induced Black-Hole Binary Mergers: Theoretical Analysis,"Black-hole (BH) binary mergers driven by gravitational perturbations of
tertiary companions constitute an important class of dynamical formation
channels for compact binaries detected by LIGO/VIRGO. Recent works have
examined numerically the combined orbital and spin dynamics of BH binaries that
undergo large Lidov-Kozai (LK) eccentricity oscillations induced by a highly
inclined companion and merge via gravitational wave radiation. However, the
extreme eccentricity variations make such systems difficult to characterize
analytically. In this paper, we develop an analytical formalism for
understanding the spin dynamics of binary BHs undergoing LK-induced mergers. We
show that, under certain conditions, the eccentricity oscillations of the
binary can be averaged over to determine the long-term behavior of the BH spin
in a smooth way. In particular, we demonstrate that the final spin-orbit
misalignment angle $\theta_{\rm sl}$ is often related to the binary's
primordial spin orientation through an approximate adiabatic invariant. Our
theory explains the ""$90^\circ$ attractor"" (as found in recent numerical
studies) for the evolution of $\theta_{\rm sl}$ when the initial BH spin is
aligned with the orbital axis and the octupole LK effects are negligible --
such a ""$90^\circ$ attractor"" would lead to a small binary effective spin
parameter $\chi_{\rm eff}\sim 0$ even for large intrinsic BH spins. We
calculate the deviation from adiabaticity in closed form as a function of the
initial conditions. We also place accurate constraints on when this adiabatic
invariant breaks down due to resonant spin-orbit interactions. We consider both
stellar-mass and supermassive BH tertiary companions, and provide simple
prescriptions for determining analytically the final spin-orbit misalignment
angles of the merging BH binaries.",2010.11951v2
2022-10-31,From the EFT of Spinning Gravitating Objects to Poincaré and Gauge Invariance at the 4.5PN Precision Frontier,"We confirm the generalized actions of the complete NLO cubic-in-spin
interactions for generic compact binaries which were first tackled via an
extension of the EFT of spinning gravitating objects. We first reduce these
generalized actions to standard actions with spins, where the interaction
potentials are found to consist of $6$ independent sectors, including a new
unique sector that is proportional to the square of the quadrupolar deformation
parameter, $C_{\text{ES}^2}$. We derive the general Hamiltonians in an
arbitrary reference frame, and for generic kinematic configurations. With these
most general Hamiltonians we construct the full Poincar\'e algebra of all the
sectors at the fourth and a half post-Newtonian (4.5PN) order, including the
third subleading spin-orbit sector, recently accomplished uniquely via our
framework, thus proving the Poincar\'e invariance of all relevant sectors. We
then derive the binding energies with gauge-invariant relations useful for
gravitational-wave applications. Finally, we also derive the extrapolated
scattering angles in the aligned-spins configuration for the scattering
problem. Yet, as made clear already as of quadratic-in-spin sectors, the
aligned-spins simplification inherent to the scattering-angle observable,
entails a great loss of physical information, that is only growing with
higher-spin sectors. Our completion of the full Poincar\'e algebra at the
present $4.5$PN order provides strong confidence that this new precision
frontier in PN theory has now been established.",2210.17538v2
2022-12-05,Spin excitation continuum to topological magnon crossover and thermal Hall conductivity in Kitaev magnets,"There has been great interest in identifying a Kitaev quantum spin liquid
state in frustrated magnets with bond-dependent interactions. In particular,
the experimental report of a half-quantized thermal Hall conductivity in
$\alpha$-RuCl$_3$ in the presence of a magnetic field has generated excitement
as it could be strong evidence for a field-induced chiral spin liquid. More
recent experiments, however, provide a conflicting interpretation advocating
for topological magnons in the field-polarized state as the origin of the
non-quantized thermal Hall conductivity observed in their experiments. An
inherent difficulty in distinguishing between the two scenarios is the phase
transition between a putative two-dimensional spin liquid and the
field-polarized state exists only at zero temperature, while the behaviour at
finite temperature is mostly crossover phenomena. In this work, we provide
insights into the finite temperature crossover behavior between the spin
excitation continuum in a quantum spin liquid and topological magnons in the
field-polarized state in three different theoretical models with large Kitaev
interactions. These models allow for a field-induced phase transition from a
spin liquid (or an intermediate field-induced spin liquid) to the
field-polarized state in the quantum model. We obtain the dynamical spin
structure factor as a function of magnetic field using molecular dynamics
simulations and compute thermal Hall conductivity in the field-polarized
regime. We demonstrate the gradual evolution of the dynamical spin structure
factor exhibiting crossover behaviour near magnetic fields where
zero-temperature phase transitions occur in the quantum model. We also examine
nonlinear effects on topological magnons and the validity of thermal Hall
conductivity computed using linear spin wave theory. We discuss the
implications of our results to existing and future experiments.",2212.02516v1
1999-07-05,"Rotation Representations and e, $pi$, p Masses","Mass is proportional to phase gain per unit time; for e, $\pi$, and p the
quantum frequencies are 0.124, 32.6, and 227 Zhz, respectively. By explaining
how these particles acquire phase at different rates, we explain why these
particles have different masses. Any free particle spin 1/2 wave function is a
sum of plane waves with spin parallel to velocity. Each plane wave, a pair of
2-component rotation eigenvectors, can be associated with a 2x2 matrix
representation of rotations in a Euclidean space without disturbing the plane
wave's space-time properties. In a space with more than four dimensions, only
rotations in a 4d subspace can be represented. So far all is well known. Now
consider that unrepresented rotations do not have eigenvectors, do not make
plane waves, and do not contribute phase. The particles e, $\pi,$ and p are
assigned rotations in a 4d subspace of 16d, rotations in an 8d subspace of 12d,
and rotations in a 12d subspace of 12d, respectively. The electron 4d subspace,
assumed to be as likely to align with any one 4d subspace as with any other,
produces phase when aligned with the represented 4d subspace in 16d. Similarly,
we calculate the likelihood that a 4d subspace of the pion's 8d space aligns
with the represented 4d subspace in 12d. The represented 4d subspace is
contained in the proton's 12d space, so the proton always acquires phase. By
the relationship between mass and phase, the resulting particle phase ratios
are the particle mass ratios and these are coincident with the measured mass
ratios, within about one percent. 1999 PACS number(s): 03.65.Fd
Keywords:Algebraic methods; particle masses; rotation group",9907012v1
2010-10-14,Banks of templates for directed searches of gravitational waves from spinning neutron stars,"We construct efficient banks of templates suitable for directed searches of
almost monochromatic gravitational waves originating from spinning nuetron
stars in our Galaxy in data being collected by currently operating
interferometric detectors. We thus assume that the position of the
gravitational-wave source in the sky is known, but we do not assume that the
wave's frequency and its derivatives are a priori known. In the construction we
employ simplified model of the signal with constant amplitude and phase which
is a polynomial function of time. All our template banks enable usage of the
fast Fourier transform algorithm in the computation of the maximum-likelihood
F-statistic for nodes of the grids defining the bank. We study and employ the
dependence of the grid's construction on the choice of the position of the
observational interval with respect to the origin of time axis. We also study
the usage of the fast Fourier transform algorithms with non-standard frequency
resolutions achieved by zero padding or folding the data. In the case of the
gravitational-wave signal with one spindown parameter included we have found
grids with covering thicknesses which are only 0.1%--16% larger than the
thickness of the optimal two-dimensional hexagonal covering.",1010.2879v1
2012-01-16,Searches for continuous gravitational wave signals and stochastic backgrounds in LIGO and Virgo data,"We present results from searches of recent LIGO and Virgo data for continuous
gravitational wave signals (CW) from spinning neutron stars and for a
stochastic gravitational wave background (SGWB). The first part of the talk is
devoted to CW analysis with a focus on two types of searches. In the targeted
search of known neutron stars a precise knowledge of the star parameters is
used to apply optimal filtering methods. In the absence of a signal detection,
in a few cases, an upper limit on strain amplitude can be set that beats the
spindown limit derived from attributing spin-down energy loss to the emission
of gravitational waves. In contrast, blind all-sky searches are not directed at
specific sources, but rather explore as large a portion of the parameter space
as possible. Fully coherent methods cannot be used for these kind of searches
which pose a non trivial computational challenge. The second part of the talk
is focused on SGWB searches. A stochastic background of gravitational waves is
expected to be produced by the superposition of many incoherent sources of
cosmological or astrophysical origin. Given the random nature of this kind of
signal, it is not possible to distinguish it from noise using a single
detector. A typical data analysis strategy relies on cross-correlating the data
from a pair or several pairs of detectors, which allows discriminating the
searched signal from instrumental noise. Expected sensitivities and prospects
for detection from the next generation of interferometers are also discussed
for both kind of sources.",1201.3176v1
2012-03-20,Gravitational-wave bursts and stochastic background from superfluid vortex avalanches during pulsar glitches,"The current-quadrupole gravitational-wave signal emitted during the spin-up
phase of a pulsar glitch is calculated from first principles by modeling the
vortex dynamics observed in recent Gross-Pitaevskii simulations of pinned,
decelerating quantum condensates. Homogeneous and inhomogeneous unpinning
geometries, representing creep- and avalanche-like glitches, provide lower and
upper bounds on the gravitational wave signal strength respectively. The signal
arising from homogeneous glitches is found to scale with the square root of
glitch size, whereas the signal from inhomogeneous glitches scales proportional
to glitch size. The signal is also computed as a function of vortex travel
distance and stellar angular velocity. Convenient amplitude scalings are
derived as functions of these parameters. For the typical astrophysical
situation, where the glitch duration (in units of the spin period) is large
compared to the vortex travel distance (in units of the stellar radius), an
individual glitch from an object $1\,\rm{kpc}$ from Earth generates a wave
strain of $10^{-24} [(\Delta\omega/\omega) / 10^{-7}] (\omega/10^2 \rm{rad
s}^{-1})^3 (\Delta r / 10^{-2} \rm{m})^{-1}$, where $\Delta r$ is the average
distance travelled by a vortex during a glitch, $\Delta\omega/\omega$ is the
fractional glitch size, and $\omega$ is the pulsar angular velocity. The
non-detection of a signal from the 2006 Vela glitch in data from the fifth
science run conducted by the Laser Interferometer Gravitational-Wave
Observatory implies that the glitch duration exceeds $\sim 10^{-4}\,\rm{ms}$.
This represents the first observational lower bound on glitch duration to be
obtained.",1203.4466v1
2012-10-23,Gravitational wave emission and spindown of young pulsars,"The rotation frequencies of young pulsars are systematically below their
theoretical Kepler limit. R-modes have been suggested as a possible explanation
for this observation. With the help of semi-analytic expressions that make it
possible to assess the uncertainties of the r-mode scenario due to the impact
of uncertainties in underlying microphysics, we perform a quantitative analysis
of the spin-down and the emitted gravitational waves of young pulsars. We find
that the frequency to which r-modes spin down a young neutron star is
surprisingly insensitive both to the microscopic details and the saturation
amplitude. Comparing our result to astrophysical data, we show that for a range
of sufficiently large saturation amplitudes r-modes provide a viable spindown
scenario and that all observed young pulsars are very likely already outside
the r-mode instability region. Therefore the most promising sources for
gravitational wave detection are unobserved neutron stars associated with
recent supernovae, and we find that advanced LIGO should be able to see several
of them. We find the remarkable result that the gravitational wave strain
amplitude is completely independent of both the r-mode saturation amplitude and
the microphysics, and depends on the saturation mechanism only within some tens
of per cent. However, the gravitational wave frequency depends on the amplitude
and we provide the required expected timing parameter ranges to look for
promising sources in future searches.",1210.6091v2
2013-06-21,Study of ambiguities in $π^-p\to ΛK^0$ scattering amplitudes,"Amplitudes for the reaction $\pi^-p\to \Lambda K^0$ are reconstructed from
data on the differential cross section $d\sigma/d\Omega$, the recoil
polarization $P$, and on the spin rotation parameter $\beta$. At low energies,
no data on $\beta$ exist, resulting in ambiguities. An approximation using $S$
and $P$ waves leads only to a fair description of the data on $d\sigma/d\Omega$
and $P$; in this case, there are two sets of amplitudes. Including $D$ waves,
the data on $d\sigma/d\Omega$ and $P$ are well reproduced by the fit but now,
there are several distinct solutions which describe the data with identical
precision. In the range where the spin rotation parameter $\beta$ was measured,
a full and unambiguous reconstruction of the partial wave amplitudes is
possible. The energy-independent amplitudes are compared to the energy
dependent amplitudes which resulted from a coupled channel fit (BnGa2011-02) to
a large data set including both pion and photo-induced reactions. Significant
deviations are observed. Consistency between energy dependent and energy
independent solutions by choosing the energy independent solution which is
closest to the energy dependent solution. In a second step, the {\it known}
energy dependent solution for low (or high) partial waves is imposed and only
the high (or low) partial waves are fitted leading to smaller uncertainties.",1306.5126v2
2014-09-02,The Riemann Geometry of Space and Gravitational Waves With The Spin $s=1$,"It is taken into account that not the Ricci tensor ${R_{il}}$ (Einstein
equation), but the Riemann tensor ${R_{iklm}}$ provides the most general
description of the space geometry. If ${{R_{il}}=0}$ (the space empty with
matter, but it can be occupied by gravitational waves) then
${{R_{iklm}}={C_{iklm}}} $ . The tensor ${C_{iklm}}$ is the Weyl tensor, which
disappears by conversion:${{R_{il}}={g^{km}}{R_{iklm}}}$ and we lose all
information about the space structure, which is described by ${C_{iklm}}$ .The
symmetry of ${R_{il}}$ provides the existents of gravitational waves with the
spin s=2. We show that ${C_{iklm}}$ describes gravitational waves with s=1.
Such gravitational waves can be created in inhomogeneous media, where the
selected directions are determined by derivates of the energy-momentum tensor
${T^m}_{i,k}$ of matter. It is taken into account that gravitation is described
not only by the metric tensor $g^{ik} = (1/2)(\gamma^i \gamma^k + \gamma^k
\gamma^i)$, but also by the anti-symmetric tensor $\sigma^{ik} =
(i/2)({\gamma^i}{\gamma^k} - {\gamma^k}{\gamma^i})$, where ${\gamma^k}(x)$ are
Clifford matrices. We show that the tensor ${K_{ik}} = (1/4){\sigma^{lm}}
{R_{iklm}}$, is the anty-simmetric analog to the Ricci tensor. The ${K_{lm}}$
describes various kinds of space metrics, not described by the Ricci tensor. It
includes the Weyl tensor ${C_{iklm}}$, because $\sigma^{lm} {C_{lmik}}$ is not
zero.",1410.2781v1
2015-04-14,Magnetic Untwisting in Solar Jets that Go into the Outer Corona in Polar Coronal Holes,"We study 14 large solar jets observed in polar coronal holes. In EUV movies
from SDO/AIA, each jet appears similar to most X-ray jets and EUV jets that
erupt in coronal holes, but each is exceptional in that it goes higher than
most, so high that it is observed in the outer corona beyond 2.2 RSun in images
from the SOHO/LASCO/C2 coronagraph. From AIA He II 304 {\AA} movies and
LASCO/C2 running-difference images of these high-reaching jets, we find: (1)
the front of the jet transits the corona below 2.2 RSun at a speed typically
several times the sound speed; (2) each jet displays an exceptionally large
amount of spin as it erupts; (3) in the outer corona, most of the jets display
measureable swaying and bending of a few degrees in amplitude; in three jets
the swaying is discernibly oscillatory with a period of order 1 hour. These
characteristics suggest that the driver in these jets is a magnetic-untwisting
wave that is basically a large-amplitude (i.e., non-linear) torsional Alfven
wave that is put into the reconnected open field in the jet by interchange
reconnection as the jet erupts. From the measured spinning and swaying we
estimate that the magnetic-untwisting wave loses most of its energy in the
inner corona below 2.2 RSun. We point out that the torsional waves observed in
Type-II spicules might dissipate in the corona in the same way as the
magnetic-untwisting waves in our big jets and thereby power much of the coronal
heating in coronal holes.",1504.03700v1
2015-07-14,Triggering Collapse of the Presolar Dense Cloud Core and Injecting Short-Lived Radioisotopes with a Shock Wave. IV. Effects of Rotational Axis Orientation,"Both astronomical observations of the interaction of Type II supernova
remnants (SNR) with dense interstellar clouds as well as cosmochemical studies
of the abundances of daughter products of short-lived radioisotopes (SLRIs)
formed by supernova nucleosynthesis support the hypothesis that the Solar
Systems SLRIs may have been derived from a supernova. This paper continues a
series devoted to examining whether such a shock wave could have triggered the
dynamical collapse of a dense, presolar cloud core and simultaneously injected
sufficient abundances of SLRIs to explain the cosmochemical evidence. Here we
examine the effects of shock waves striking clouds whose spin axes are oriented
perpendicular, rather than parallel, to the direction of propagation of the
shock front. The models start with 2.2 solar mass cloud cores and shock speeds
of 20 or 40 km/sec. Central protostars and protoplanetary disks form in all
models, though with disk spin axes aligned somewhat randomly. The disks derive
most of their angular momentum not from the initial cloud rotation, but from
the Rayleigh-Taylor fingers that also inject shock wave SLRIs. Injection
efficiencies, fi, the fraction of the incident shock wave material injected
into the collapsing cloud core, are 0.04 - 0.1 in these models, similar to when
the rotation axis is parallel to the shock propagation direction. Evidently
altering the rotation axis orientation has only a minor effect on the outcome,
strengthening the case for this scenario as an explanation for the Solar
Systems SLRIs.",1507.03956v1
2018-06-28,Tracking black hole kicks from gravitational wave observations,"Coalescing binary black holes emit anisotropic gravitational radiation. This
causes a net emission of linear momentum that produces a gradual acceleration
of the source. As a result, the final remnant black hole acquires a
characteristic velocity known as recoil velocity or gravitational kick. The
symmetries of gravitational wave emission are reflected in the interactions of
the gravitational wave modes emitted by the binary. In this work we make use of
the rich information encoded in the higher-order modes of the gravitational
wave emission to infer the component of the kick along the line-of-sight (or
\textit{radial kick}). We do this by performing parameter inference on
simulated signals given by numerical relativity waveforms for non-spinning
binaries using numerical relativity templates of aligned-spin (non-precessing)
binary black holes. We find that for suitable sources, namely those with mass
ratio $q\geq 2$ and total mass $M \sim 100M_\odot$, and for modest radial kicks
of $120km/s$, the $90\%$ credible intervals of our posterior probability
distributions can exclude a zero kick at a signal-to-noise ratio of $15$; using
a single Advanced LIGO detector working at its early sensitivity. The
measurement of a non-zero radial kick component would provide the first
observational signature of net transport of linear momentum by gravitational
waves away from their source.",1806.11160v2
2020-03-06,Superconducting properties of the hole-doped three-band \emph{d-p} model studied with minimal-size real-space \emph{d}-wave pairing operators,"The three-band \emph{d-p} model is investigated by means of Variational
Monte-Carlo (VMC) method with the BCS-like wave-function supplemented by the
Gutzwiller and Jastrow correlators. The VMC optimization leads to $d$-$wave$
superconducting state with a characteristic dome-like shape of the order
parameter for hole doping $\delta \lesssim 0.4$, in a good agreement with the
experimental observations. Also, the off-diagonal pair-pair correlation
functions, calculated within VMC, vindicates the results obtained very recently
within the diagrammatic expansion of the Gutzwiller wave function method
(DE-GWF) [cf. Phys. Rev. B \textbf{99}, 104511 (2019)]. Subsequently, the
nature of the $d$-$wave$ pairing is investigated by means of recently proposed
\emph{minimal-size real-space d-wave pairing operators} [Phys. Rev. B
\textbf{100}, 214502 (2019)]. An emergence of the long-range superconducting
ordering for both $d$ and $p$ orbitals is reported by analysing the
corresponding off-diagonal pair-pair correlation functions. The dominant
character of \emph{d-wave} pairing on $d$ orbitals is confirmed. Additionally,
the trial wave-function is used to investigate the magnetic properties of the
system. The analysis of spin-spin correlation functions is carried out and
shows antiferromagnetic $\mathbf{q}=(\pi,\pi)$, short-range order, as expected.
For the sake of completeness, the charge gap has been estimated, which for the
parent compound takes the value $\Delta_{CG}\approx1.78\pm0.51\text{ eV}$, and
agrees with values reported experimentally for the cuprates.",2003.03117v3
2021-08-23,Revealing the Primordial Irreducible Inflationary Gravitational-Wave Background with a Spinning Peccei-Quinn Axion,"The primordial irreducible gravitational-wave background due to quantum
vacuum tensor fluctuations produced during inflation spans a large range of
frequencies with an almost scale-invariant spectrum but is too low to be
detected by the next generation of gravitational-wave interferometers. We show
how this signal is enhanced by a short temporary kination era in the
cosmological history (less than 10 e-folds), that can arise at any energy scale
between a GeV and the inflationary scale $10^{16}$ GeV. We argue that such
kination era is naturally generated by a spinning axion before it gets trapped
by its potential. It is usually assumed that the axion starts oscillating
around its minimum from its initially frozen position. However, the early
dynamics of the Peccei-Quinn field can induce a large kinetic energy in the
axion field, triggering a kination era, either before or after the axion
acquires its mass, leading to a characteristic peak in the primordial
gravitational-wave background. This represents a smoking-gun signature of axion
physics as no other scalar field dynamics is expected to trigger such a
sequence of equations of state in the early universe. We derive the resulting
gravitational-wave spectrum, and present the parameter space that leads to such
a signal as well as the detectability prospects, in particular at LISA,
Einstein Telescope, Cosmic Explorer and Big Bang Observer. We show both
model-independent predictions and present as well results for two specific
well-motivated UV completions for the QCD axion dark matter where this dynamics
is built-in.",2108.10328v1
2017-03-10,An improved algorithm for narrow-band searches of continuous gravitational waves,"Continuous gravitational waves signals, emitted by asymmetric spinning
neutron stars, are among the main targets of current detectors like Advanced
LIGO and Virgo. In the case of sources, like pulsars, which rotational
parameters are measured through electromagnetic observations, typical searches
assume that the gravitational wave frequency is at a given known fixed ratio
with respect to the star rotational frequency. For instance, for a neutron star
rotating around one of its principal axis of inertia the gravitational signal
frequency would be exactly two times the rotational frequency of the star. It
is possible, however, that this assumption is wrong. This is why search
algorithms able to take into account a possible small mismatch between the
gravitational waves frequency and the frequency inferred from electromagnetic
observations have been developed. In this paper we present an improved pipeline
to perform such narrow-band searches for continuous gravitational waves from
neutron stars, about three orders of magnitude faster than previous
implementations. The algorithm that we have developed is based on the {\it
5-vectors} framework and is able to perform a fully coherent search over a
frequency band of width $\mathcal{O}$(Hertz) and for hundreds of spin-down
values running a few hours on a standard workstation. This new algorithm opens
the possibility of long coherence time searches for objects which rotational
parameters are highly uncertain.",1703.03493v1
2019-10-11,Directed search for continuous gravitational-wave signals from the Galactic Center in the Advanced LIGO second observing run,"In this work we present the results of a search for continuous gravitational
waves from the Galactic Center using LIGO O2 data. The search uses the
Band-Sampled-Data directed search pipeline, which performs a semi-coherent
wide-parameter-space search, exploiting the robustness of the FrequencyHough
transform algorithm. The search targets signals emitted by isolated asymmetric
spinning neutron stars, located within 25-150 parsecs from the Galactic Center.
The frequencies covered in this search range between 10 and 710 Hz with a
spin-down range from $-1.8\times10^{-9}$ to $3.7\times10^{-11}$ Hz/s. No
continuous wave signal has been detected and upper limits on the gravitational
wave amplitude are presented. The most stringent upper limit at $95\%$
confidence level, for the Livingston detector, is $\sim 1.4 \times 10^{-25}$ at
frequencies near 160 Hz. To date, this is the most sensitive directed search
for continuous gravitational-wave signals from the Galactic Center and the
first search of this kind using the LIGO second observing run.",1910.05097v3
2020-02-14,Single-electron quantum dynamics in high-harmonic generation spectrum from LiH molecule: analysis of potential energy surfaces for electrons constructed from a model of localized Gaussian wave packets with valence-bond spin-coupling,"High-harmonic generation (HHG) spectrum from a LiH molecule induced by an
intense laser pulse is computed and analyzed with potential energy surfaces for
electron motion (ePES) constructed from a model of localized electron wave
packets (EWP) with valence-bond spin-coupling. The molecule has two valence
ePES with binding energies of 0.39 hartree and 1.1 hartree. The HHG spectrum
from an electron dynamics on the weaker bound valence ePES, virtually assigned
to Li 2s, exhibits a dominant peak at the first harmonic without plateau and
cut-off. This compares with the free electron spectrum under oscillating laser
field and is comprehensive with the shape and depth of the ePES. The other
valence ePES, assingned to H 1s, is deeper bound such that the overall profile
of the wave function is well approximated by a Gaussian of the width comparable
to the Li-H bond length. However, a small fraction, less than $10^{-3}$, of the
probability density amplitude tunnels out from the bound potential with high
wave number, and spreads over tens of nm's with parts recombining to the
molecule due to the laser field oscillation. This minor portion of the
electronic wave function is the major origin of the HHG extending up to 50
harmonic orders. Nonlinear dynamics within the potential well induced by the
laser field oscillation also contributes to the HHG up to 30 harmonic orders.",2002.05908v1
2020-12-02,Symmetry of the Magnetoelastic Interaction of Rayleigh and Shear Horizontal Magnetoacoustic Waves in Nickel Thin Films on LiTaO$_3$,"We study the interaction of Rayleigh and shear horizontal surface acoustic
waves (SAWs) with spin waves in thin Ni films on a piezoelectric LiTaO$_3$
substrate, which supports both SAW modes simultaneously. Because Rayleigh and
shear horizontal modes induce different strain components in the Ni thin films,
the symmetries of the magnetoelastic driving fields, of the magnetoelastic
response, and of the transmission nonreciprocity differ for both SAW modes. Our
experimental findings are well explained by a theoretical model based on a
modified Landau--Lifshitz--Gilbert approach. We show that the symmetries of the
magnetoelastic response driven by Rayleigh- and shear horizontal SAWs
complement each other, which makes it possible to excite spin waves for any
relative orientation of magnetization and SAW propagation direction and,
moreover, can be utilized to characterize surface strain components of unknown
acoustic wave modes.",2012.01055v2
2021-11-19,On the applicability of single-spacecraft interferometry methods using electric field probes,"When analyzing plasma waves, a key parameter to determine is the phase
velocity. It enables us to, for example, compute wavelengths, wave potentials,
and determine the energy of resonant particles. The phase velocity of a wave,
observed by a single spacecraft equipped with electric field probes, can be
determined using interferometry techniques. While several methods have been
developed to do this, they have not been documented in detail. In this study,
we use an analytical model to analyze and compare three interferometry methods
applied on the probe geometry of the Magnetospheric Multiscale spacecraft. One
method relies on measured probe potentials, whereas the other two use different
E-field measurements: one by reconstructing the E-field between two probes and
the spacecraft, the other by constructing four pairwise parallel E-field
components in the spacecraft spin-plane. We find that the potential method is
sensitive both to how planar the wave is, and to spacecraft potential changes
due to the wave. The E-field methods are less affected by the spacecraft
potential, and while the reconstructed E-field method is applicable in some
cases, the second E-field method is almost always preferable. We conclude that
the potential based interferometry method is useful when spacecraft potential
effects are negligible and the signals of the different probes are very well
correlated. The method using two pairs of parallel E-fields is practically
always preferable to the reconstructed E-field method and produces the correct
velocity in the spin-plane, but it requires knowledge of the propagation
direction to provide the full velocity.",2111.10288v2
2022-03-08,Tidal dissipation due to inertial waves can explain the circularization periods of solar-type binaries,"Tidal dissipation is responsible for circularizing the orbits and
synchronizing the spins of solar-type close binary stars, but the mechanisms
responsible are not fully understood. Previous work has indicated that
significant enhancements to the theoretically-predicted tidal dissipation rates
are required to explain the observed circularization periods
($P_\mathrm{circ}$) in various stellar populations, and their evolution with
age. This was based partly on the common belief that the dominant mechanism of
tidal dissipation in solar-type stars is turbulent viscosity acting on
equilibrium tides in convective envelopes. In this paper we study tidal
dissipation in both convection and radiation zones of rotating solar-type stars
following their evolution. We study equilibrium tide dissipation, incorporating
a frequency-dependent effective viscosity motivated by the latest
hydrodynamical simulations, and inertial wave (dynamical tide) dissipation,
adopting a frequency-averaged formalism that accounts for the realistic
structure of the star. We demonstrate that the observed binary circularization
periods can be explained by inertial wave (dynamical tide) dissipation in
convective envelopes. This mechanism is particularly efficient during pre-main
sequence phases, but it also operates on the main sequence if the spin is close
to synchronism. The predicted $P_\mathrm{circ}$ due to this mechanism increases
with main-sequence age in accord with observations. We also demonstrate that
both equilibrium tide and internal gravity wave dissipation are unlikely to
explain the observed $P_\mathrm{circ}$, even during the pre-main sequence,
based on our best current understanding of these mechanisms. Finally, we
advocate more realistic dynamical studies of stellar populations that employ
tidal dissipation due to inertial waves.",2203.03950v1
2022-08-10,Forward volume magnetoacoustic spin wave excitation with micron-scale spatial resolution,"The interaction between surface acoustic waves (SAWs) and spin waves (SWs) in
a piezoelectric-magnetic thin film heterostructure yields potential for the
realization of novel microwave devices and applications in magnonics. In the
present work, we characterize magnetoacoustic waves in three adjacent magnetic
micro-stripes made from CoFe+Ga, CoFe, and CoFe+Pt with a single pair of
tapered interdigital transducers (TIDTs). The magnetic micro-stripes were
deposited by focused electron beam-induced deposition (FEBID) and focused ion
beam-induced deposition (FIBID) direct-writing techniques. The transmission
characteristics of the TIDTs are leveraged to selectively address the
individual micro-stripes. Here, the external magnetic field is continuously
rotated out of the plane of the magnetic thin film and the forward volume SW
geometry is probed with the external magnetic field along the film normal. Our
experimental findings are well explained by an extended phenomenological model
based on a modified Landau-Lifshitz-Gilbert approach that considers SWs with
nonzero wave vectors. Magnetoelastic excitation of forward volume SWs is
possible because of the vertical shear strain $\varepsilon_{xz}$ of the
Rayleigh-type SAW.",2208.05205v1
2022-11-07,SuperRad: Modeling the black hole superradiance gravitational waveform,"Gravitational signatures of black hole superradiance are a unique probe of
ultralight particles that are weakly-coupled to ordinary matter. The existence
of an ultralight boson would lead spinning black holes with size comparable to
the Compton wavelength of the boson to become superradiantly unstable to
forming an oscillating cloud, spinning down the black hole, and radiating
gravitational waves in the process. However, maximizing the chance of observing
such signals or, in their absence, placing the strongest constraints on the
existence of such particles, requires accurate theoretical predictions. In this
work, we introduce a new gravitational waveform model, SuperRad, that models
the dynamics, oscillation frequency, and gravitational wave signals of these
clouds by combining numerical results in the relativistic regime with fits
calibrated to analytical estimates, covering the entire parameter space of
ultralight scalar and vector clouds with the lowest two azimuthal numbers ($m =
1$ and $2$). We present new calculations of the gravitational wave frequency
evolution as the boson cloud dissipates, including using fully
general-relativistic methods to quantify the error in more approximate
treatments. Finally, as a first application, we assess the viability of
conducting follow-up gravitational wave searches for ultralight vector clouds
around massive black hole binary merger remnants. We show that LISA may be able
to probe vector masses in the range from $1\times 10^{-16}$ eV to $6\times
10^{-16}$ eV using follow-up gravitational wave searches.",2211.03845v2
1998-05-17,Gravitational radiation limit on the spin of young neutron stars,"A newly discovered instability in rotating neutron stars, driven by
gravitational radiation reaction acting on the stars' $r$-modes, is shown here
to set an upper limit on the spin rate of young neutron stars. We calculate the
timescales for growth of linear perturbations due to gravitational radiation
reaction, and for dissipation by shear and bulk viscosity, working to second
order in a slow-rotation expansion within a Newtonian polytropic stellar model.
The results are very temperature-sensitive: in hot neutron stars ($T>10^9$ K),
the lowest-order $r$-modes are unstable, while in colder stars they are damped
by viscosity. These calculations have a number of interesting astrophysical
implications. First, the $r$-mode instability will spin down a newly born
neutron star to a period close to the initial period inferred for the Crab
pulsar, probably between 10 and 20 ms. Second, as an initially rapidly rotating
star star spins down, an energy equivalent to roughly 1% of a solar mass is
radiated as gravitational waves, which makes the process an interesting source
for detectable gravitational waves. Third, the $r$-mode instability rules out
the scenario whereby millisecond pulsars are formed by accretion-induced
collapse of a white dwarf: the new star would be hot enough to spin down to
much slower rates.",9805225v1
2005-07-20,Astrophysical Unipolar Inductors Powered by Gravitational Wave Emission,"We consider the Unipolar Inductor Model (Goldreich & Lynden-Bell 1969)
applied to Double Degenerate Binaries (DDBs) with ultrashort periods (Wu et al.
2002). In this model a magnetized primary white dwarf has a slight asynchronism
between its spin and orbital motion, so that the (non-magnetic) secondary
experiences a motional electric field when moving through the primary field
lines. This induces a current flow between the two stars and provides an
electric spin-orbit coupling mechanism for the primary. We study the combined
effect of Gravitational Wave emission and electric spin-orbit coupling on the
evolution of the primary degree of asynchronism and the associated rate of
electric current dissipation in such systems, assuming that the primary's spin
is not affected by any other mechanisms. In particular, we show that in
ultrashort period binaries the emission of GW pumps energy in the electric
circuit as to keep it steadily active. This happens despite the fact that
spin-orbit coupling can rapidly synchronize the primary, because GW represent a
slow desynchronizing mechanism steadily substracting orbital angular momentum
to the system. A slightly asynchronous steady-state is thus achieved,
determined by the balance between these two competing effects. This can be
shown to correspond to a condition where the total available electric energy is
conserved, because of GW emission, while dissipation, synchronization and
orbital shrinking continue.",0507474v1
1999-10-07,Interaction of surface acoustic waves with a two-dimensional electron gas in the presence of spin splitting of the Landau bands,"The absorption and variation of the velocity of a surface acoustic wave of
frequency $f$= 30 MHz interacting with two-dimensional electrons are
investigated in GaAs/AlGaAs heterostructures with an electron density $n=(1.3 -
2.8) \times 10^{11} cm^{-2}$ at $T$=1.5 - 4.2 K in magnetic fields up to 7 T.
Characteristic features associated with spin splitting of the Landau level are
observed. The effective g factor and the width of the spin-split Landau bands
are determined: $g^* \simeq 5$ and $A$=0.6 meV. The greater width of the
orbital-split Landau bands (2 meV) relative to the spin-split bands is
attributed to different shielding of the random fluctuation potential of
charged impurities by 2D electrons. The mechanisms of the nonlinearities
manifested in the dependence of the absorption and the velocity increment of
the SAW on the SAW power in the presence of spin splitting of the Landau levels
are investigated.",9910096v2
2003-11-02,Stripe phase: analytical results for weakly coupled repulsive Hubbard model,"Motivated by the stripe developments in cuprates, we review some analytical
results of our studies of the charge- and spin density modulations (CDW and
SDW) in a weakly coupled one dimensional repulsive electron system on a
lattice. It is shown that close to half filling, in the high temperature regime
above the mean field transition temperature, short range repulsions favor
charge density fluctuations with wave vectors bearing special relations with
those of the spin density fluctuations. In the low temperature regime, not only
the wave vectors, but also the mutual phases of the CDW and SDW become coupled
due to a quantum interference phenomenon, leading to the stripe phase
instability in a quasi one-dimensional repulsive electron system. It is shown
that away from half filling periodic lattice potential causes cooperative
condensation of the spin and charge superlattices. ""Switching off"" this
potential causes vanishing of the stripe order. The leading spin-charge
coupling term in the effective Landau functional is derived microscopically.
Results of the 1D renormalization group (parquet) analysis away from half
filling are also presented, which indicate transient-scale correlations
resembling the mean-field pattern. Farther, the self-consistent solution for
the spin-charge solitonic superstructure in a quasi-one-dimensional electron
system is obtained in the framework of the Hubbard model as a function of hole
doping and temperature. Possible relationship with the stripe phase
correlations observed in high T_c cuprates is discussed.",0311019v1
2005-12-15,Ferromagnetic Resonance Linewidths in Ultrathin Structures: Theoretical Studies of Spin Pumping,"We present theoretical studies of the spin pumping contribution to the
ferromagnetic resonance linewidth for various ultrathin film ferromagnetic
structures. We consider the isolated film on a substrate, with Fe on Au(100)
and Fe on W(110) as examples. We explore as well the linewidth from this
mechanism for the optical and acoustical collective modes of FM/Cu$_{\rm
N}$/FM/Cu(100) structures. The calculations employ a realistic electronic
structure, with self consistent ground states generated from the empirical
tight binding method, with nine bands for each material in the structure. The
spin excitations are generated through use of the random phase approximation
applied to the system, including the semi infinite substrate on which the
structure is grown. We calculate the frequency response of the system directly
by examining the spectral density associated with collective modes whose wave
vector parallel to the surface is zero. Linewidths with origin in leakage of
spin angular momentum from the adsorbed structure to the semi infinite
substrate may be extracted from these results. We discuss a number of issues,
including the relationship between the interfilm coupling calculated
adiabatically for trilayers, and that extracted from the (dynamical) spin wave
spectrum. We obtain excellent agreement with experimental data, within the
framework of calculations with no adjustable parameters.",0512333v1
2006-05-23,Electronic structure of BaIrO3: A first principle study using local spin-density approximations,"We investigate the electronic structure of BaIrO3, an interesting compound
exhibiting charge density wave transition in its insulating phase and
ferromagnetic transition at the same temperature, using full potential
linearized augmented plane wave method within the local spin density
approximations. The ferromagnetic ground state could exactly be described in
these calculations and the calculated spin magnetic moment is found to be small
as observed in the magnetic measurements. Interestingly, no signature of
exchange splitting is observed in the density of states corresponding to Ir 5d
and/or any other electronic states. The small spin moment appears essentially
due to unequal population of the up- and down-spin Ir 5d bands. Comparison of
the valence band density of states with the experimental spectral functions
suggests that a rigid shift of the Fermi level towards higher energies in the
calculated density of states provides a good description of the experimental
spectra. This indicates that the intrinsic oxygen non-stoichiometry leads to
electron doping in the system and plays the primary role in determining the
electronic structure rather than the electron correlation effects as often
observed in other systems. The calculated results for Ba 5p core levels show
that the Madelung potential of one of the three non-equivalent Ba atoms is
different from that of other two as predicted in the recent experiments.",0605555v1
2003-12-18,"Searching for Gravitational Waves from the Inspiral of Precessing Binary Systems: Astrophysical Expectations and Detection Efficiency of ""Spiky'' Templates","Relativistic spin-orbit and spin-spin couplings has been shown to modify the
gravitational waveforms expected from inspiraling binaries with a black hole
and a neutron star. As a result inspiral signals may be missed due to
significant losses in signal-to-noise ratio, if precession effects are ignored
in gravitational-wave searches. We examine the sensitivity of the anticipated
loss of signal-to-noise ratio on two factors: the accuracy of the precessing
waveforms adopted as the true signals and the expected distributions of
spin-orbit tilt angles, given the current understanding of their physical
origin. We find that the results obtained using signals generated by
approximate techniques are in good agreement with the ones obtained by
integrating the 2PN equations. This shows that a complete account of all
high-order post-Newtonian effects is usually not necessary for the
determination of detection efficiencies. Based on our current astrophysical
expectations, large tilt angles are not favored and as a result the decrease in
detection rate varies rather slowly with respect to the black hole spin
magnitude and is within 20--30% of the maximum possible values.",0312084v2
2007-09-14,^{17}O and ^{51}V NMR for the zigzag spin-1 chain compound CaV2O4,"$^{51}$V NMR studies on CaV2O4 single crystals and $^{17}$O NMR studies on
$^{17}$O-enriched powder samples are reported. The temperature dependences of
the $^{17}$O NMR line width and nuclear spin-lattice relaxation rate give
strong evidence for a long-range antiferromagnetic transition at Tn = 78 K in
the powder. Magnetic susceptibility measurements show that Tn = 69 K in the
crystals. A zero-field $^{51}$V NMR signal was observed at low temperatures (f
$\approx$ 237 MHz at 4.2 K) in the crystals. The field swept spectra with the
field in different directions suggest the presence of two antiferromagnetic
substructures. Each substructure is collinear, with the easy axes of the two
substructures separated by an angle of 19(1) degree, and with their average
direction pointing approximately along the b-axis of the crystal structure. The
two spin substructures contain equal number of spins. The temperature
dependence of the ordered moment, measured up to 45 K, shows the presence of an
energy gap Eg in the antiferromagnetic spin wave excitation spectrum.
Antiferromagnetic spin wave theory suggests that Eg lies between 64 and 98 K.",0709.2379v2
2008-09-16,Gravitational Radiation from Plunging Orbits - Perturbative Study -,"Numerical relativity has recently yielded a plethora of results about kicks
from spinning mergers which has, in turn, vastly increased our knowledge about
the spin interactions of black hole systems. In this work we use black hole
perturbation theory to calculate accurately the gravitational waves emanating
from the end of the plunging stage of an extreme mass ratio merger in order to
further understand this phenomenon. This study focuses primarily on spin
induced effects with emphasis on the maximally spinning limit and the
identification of possible causes of generic behavior.
  We find that gravitational waves emitted during the plunging phase exhibit
damped oscillatory behavior, corresponding to a coherent excitation of
quasi-normal modes by the test particle. This feature is universal in the sense
that the frequencies and damping time do not depend on the orbital parameters
of the plunging particle. Furthermore, the observed frequencies are distinct
from those associated with the usual free quasi-normal ringing. Our calculation
suggests that a maximum in radiated energy and momentum occurs at spin
parameters equal to $a/M=0.86$ and $a/M=0.81$, respectively for the plunge
stage of a polar orbit. The dependence of linear momentum emission on the angle
at which a polar orbit impacts the horizon is quantified. One of the advantages
of the perturbation approach adopted here is that insight into the actual
mechanism of radiation emission and its relationship to black hole ringing is
obtained by carefully identifying the dominant terms in the expansions used.",0809.2814v1
2009-02-04,Spin dynamics of frustrated easy-axis triangular antiferromagnet 2H-AgNiO2 explored by inelastic neutron scattering,"We report inelastic neutron scattering measurements of the spin dynamics in
the layered hexagonal magnet 2H-AgNiO2 which has stacked triangular layers of
antiferromagnetically-coupled Ni2+ spins (S=1) ordered in a collinear
alternating stripe pattern. We observe a broad band of magnetic excitations
above a small gap of 1.8 meV and extending up to 7.5 meV, indicating strongly
dispersive excitations. The measured dispersions of the boundaries of the
powder-averaged spectrum can be quantitatively explained by a linear spin-wave
dispersion for triangular layers with antiferromagnetic nearest- and weak
next-nearest neighbor couplings, a strong easy-axis anisotropy and additional
weak inter-layer couplings. The resulting dispersion relation has global minima
not at magnetic Bragg wavevectors but at symmetry-related soft points and we
attribute this anomalous feature to the strong competition between the
easy-axis anisotropy and the frustrated antiferromagnetic couplings. We have
also calculated the quantum corrections to the dispersion relation to order 1/S
in spin-wave theory by extending the work of Chubukov and Jolicoeur [Phys. Rev.
B v46, 11137 (1992)] and find that the presence of easy-axis anisotropy
significantly reduces the quantum renormalizations predicted for the isotropic
model.",0902.0676v1
2009-05-08,Parameter estimation for signals from compact binary inspirals injected into LIGO data,"During the fifth science run of the Laser Interferometer Gravitational-wave
Observatory (LIGO), signals modelling the gravitational waves emitted by
coalescing non-spinning compact-object binaries were injected into the LIGO
data stream. We analysed the data segments into which such injections were made
using a Bayesian approach, implemented as a Markov-chain Monte-Carlo technique
in our code SPINspiral. This technique enables us to determine the physical
parameters of such a binary inspiral, including masses and spin, following a
possible detection trigger. For the first time, we publish the results of a
realistic parameter-estimation analysis of waveforms embedded in real detector
noise. We used both spinning and non-spinning waveform templates for the data
analysis and demonstrate that the intrinsic source parameters can be estimated
with an accuracy of better than 1-3% in the chirp mass and 0.02-0.05 (8-20%) in
the symmetric mass ratio if non-spinning waveforms are used. We also find a
bias between the injected and recovered parameters, and attribute it to the
difference in the post-Newtonian orders of the waveforms used for injection and
analysis.",0905.1323v1
2009-06-11,Lagrangian higher spin field theories from the O(N) extended supersymmetric particle,"The wave function in the quantum theory of the O(N) extended supersymmetric
particle model describes a massless free field with spin N/2. This quantum
theory is here exactly solved in terms of gauge fields in arbitrary even
dimensions using only the basic quantum operators which include graded external
differentials, trace operators, index structure operators and their duals. The
resulting equations for the gauge fields are of first (N odd) or second order
(N even) and are shown to be generalized (Fang)-Fronsdal equations which are
fully gauge invariant since they include compensator fields in a natural way.
Local gauge invariant actions are first derived in analogy with the derivation
by Francia and Sagnotti in the symmetric case. Then a minimal formulation is
given within which it is easy to set up gauge invariant actions and here
appropriate actions for the above equations are proposed.
  In a second part it is shown that there exist projection operators from the
states of the field strengths (wave functions) to Weyl states (Weyl tensors)
expressed only in terms of the trace operators and their duals for integer
spins or in terms of the gamma trace operators and their duals for half-integer
spins. These Weyl states are not just fully gauge invariant but also invariant
under generalized Weyl transformations. If one lets the equations be determined
by the actions defined to be the squares of these Weyl tensors then the theory
is conformally invariant and the equations are of order N for the gauge fields
defined as in the exact theory. In d=4 this higher order conformal theory fits
into the framework for conformal higher spin theories set up by Fradkin,
Tseytlin and Linetski.",0906.2084v1
2010-05-13,Gravitational-wave spin-down and stalling lower limits on the electrical resistivity of the accreted mountain in a millisecond pulsar,"The electrical resistivity of the accreted mountain in a millisecond pulsar
is limited by the observed spin-down rate of binary radio millisecond pulsars
(BRMSPs) and the spins and X-ray fluxes of accreting millisecond pulsars
(AMSPs). We find $\eta \ge 10^{-28}\,\mathrm{s}\,
(\tau_\mathrm{SD}/1\,\mathrm{Gyr})^{-0.8}$ (where $\tau_\mathrm{SD}$ is the
spin-down age) for BRMSPs and $\eta \ge
10^{-25}\,\mathrm{s}\,(\dot{M}_\mathrm{a}/\dot{M}_\mathrm{E})^{0.6}$ (where
$\dot{M}_\mathrm{a}$ and $\dot{M}_\mathrm{E}$ are the actual and Eddington
accretion rates) for AMSPs. These limits are inferred assuming that the
mountain attains a steady state, where matter diffuses resistively across
magnetic flux surfaces but is replenished at an equal rate by infalling
material. The mountain then relaxes further resistively after accretion ceases.
The BRMSP spin-down limit approaches the theoretical electron-impurity
resistivity at temperatures $\ga 10^5$ K for an impurity concentration of $\sim
0.1$, while the AMSP stalling limit falls two orders of magnitude below the
theoretical electron-phonon resistivity for temperatures above $10^8$ K. Hence
BRMSP observations are already challenging theoretical resistivity calculations
in a useful way. Next-generation gravitational-wave interferometers will
constrain $\eta$ at a level that will be competitive with electromagnetic
observations.",1005.2257v1
2010-09-13,"Inspiral of Generic Black Hole Binaries: Spin, Precession, and Eccentricity","Given the absence of observations of black hole binaries, it is critical that
the full range of accessible parameter space be explored in anticipation of
future observation with gravitational wave detectors. To this end, we compile
the Hamiltonian equations of motion describing the conservative dynamics of the
most general black hole binaries, as computed by Will and collaborators, and
incorporate an effective treatment of dissipation through gravitational
radiation. We evolve these equations for systems with orbital eccentricity and
precessing spins. We find that, while spin-spin coupling corrections can
destroy constant radius orbits in principle, the effect is so small that orbits
will reliably tend to quasi-spherical orbits as angular momentum and energy are
lost to gravitational radiation. Still, binaries that are initially highly
eccentric may retain eccentricity as they pass into the detectable bandwidth of
ground-based gravitational wave detectors. We also show that a useful set of
natural frequencies for an orbit demonstrating both spin precession and
periastron precession is comprised of (1) the frequency of angular motion in
the orbital plane, (2) the frequency of the plane precession, and (3) the
frequency of radial oscillations. These three natural harmonics shape the
observed waveform.",1009.2533v3
2011-01-17,"Shape of spin density wave versus temperature in AFe2As2 (A=Ca, Ba, Eu): A Mössbauer study","Parent compounds AFe2As2 (A=Ca, Ba, Eu) of the 122 family of the iron-based
superconductors have been studied by 57Fe Moessbauer spectroscopy in the
temperature range 4.2 K - ~300 K. Spin density waves (SDW) have been found with
some confidence. They are either incommensurate with the lattice period or the
ratio of the respective periods is far away from ratio of small integers. SDW
shape is very unconventional i.e. differs from the sinusoidal shape. Magnetic
order starts with lowered temperature as narrow sheets of the significant
electron spin density separated by areas with very small spin density. Magnetic
sheets are likely to be ordered in the alternate anti-ferromagnetic fashion as
the material as whole behaves similarly to collinear anti-ferromagnet. Further
lowering of temperature simply expands sheet thickness leading to the near
triangular SDW. Finally, sheets fill the whole available space and almost
rectangular shape of SDW is reached. Substantial maximum amplitude of SDW
appears at the temperature just below the magnetic onset temperature, and this
maximum amplitude increases slightly with lowering temperature. The square root
from the mean squared hyperfine field behaves versus temperature according to
the universality class (1, 2), i.e., with the electronic spin space having
dimensionality equal unity and the real space having dimensionality equal two.
The more or less pronounced tail above transition temperature due to the
development of incoherent SDW is seen.",1101.3225v2
2011-01-31,"Stripes, spin resonance and $d_{x^2-y^2}-$pairing symmetry in FeSe-based layered superconductors","We calculate RPA-BCS based spin resonance spectra of newly discovered
iron-selenide superconductor using two orbitals tight-binding (TB) model. The
slightly squarish electron pocket Fermi surfaces (FSs) at
$(\pi,0)/(0,\pi)-$momenta produce leading interpocket nesting instability at
incommensurate vector $q\sim(\pi,0.5\pi)$ in the normal state static
susceptibility, pinning a strong stripe-like spin-density wave (SDW) or
antiferromagnetic (AFM) order at some critical value of $U$. The same nesting
also induces $d_{x^2-y^2}-$pairing. The superconducting (SC) gap is nodeless
and isotropic on the FSs as they are concentric to the four-fold symmetry point
of the $d-$wave gap maxima, in agreement with various measurements. This
induces an slightly incommensurate spin resonance with `hour-glass'-like
dispersion feature, in close agreement with neutron data of chalcogenides. We
also calculate $T$ pendence of the SC gap solving BCS gap equations and find
that the spin resonance follows the same $T$ evolution of $\Delta(T)$ both in
energy and intensity, suggesting that an itinerant weak or intermediate pair
coupling theory is relevant in this system.",1101.6056v3
2013-08-08,Imprints of spin-orbit density wave in the hidden order state of URu2Si2,"The mysterious second order quantum phase transition, commonly attributed to
the `hidden-order' (HO) state, in heavy-fermion metal URu2Si2 exhibits a number
of paradoxical electronic and magnetic properties which cannot be associated
with any conventional order parameter. We characterize and reconcile these
exotic properties of the HO state based on a spin-orbit density wave order
(SODW), constructed on the basis of a realistic density-functional theory (DFT)
band structure. We quantify the nature of the gapped electronic and magnetic
excitation spectrum, in agreement with measurements, while the magnetic moment
is calculated to be zero owing to the spin-orbit coupling induced time-reversal
invariance. Furthermore, a new collective mode in the spin-1 excitation
spectrum is predicted to localize at zero momentum transfer in the HO state
which can be visualized, for example, by electron spin resonance (ESR) at zero
magnetic field or polarized inelastic neutron scattering measurements. The
results demonstrate that the concomitant broken and invariant symmetries
protected SODW order not only provides insights into numerous nontrivial
hidden-order phenomena, but also offers a parallel laboratory to the formation
of a topologically protected quantum state beyond the quantum spin-Hall state
and Weyl semimetals.",1308.1992v2
2015-03-19,Measuring intermediate mass black hole binaries with advanced gravitational wave detectors,"We perform a systematic study to explore the accuracy with which the
parameters of intermediate-mass black-hole binary systems can be measured from
their gravitational wave (GW) signatures using second-generation GW detectors.
We make use of the most recent reduced-order models containing inspiral, merger
and ringdown signals of aligned-spin effective-one-body waveforms (SEOBNR) to
significantly speed up the calculations. We explore the phenomenology of the
measurement accuracies for binaries with total masses between 50 and 500
$M_\odot$ and mass ratios between 0.1 and 1. We find that (i) at total masses
below ~200 $M_\odot$, where the signal-to-noise-ratio is dominated by the
inspiral portion of the signal, the chirp mass parameter can be accurately
measured; (ii) at higher masses, the information content is dominated by the
ringdown, and total mass is measured more accurately; (iii) the mass of the
lower-mass companion is poorly estimated, especially at high total mass and
more extreme mass ratios; (iv) spin cannot be accurately measured for our
injection set with non-spinning components. Most importantly, we find that for
binaries with non-spinning components at all values of the mass ratio in the
considered range and at network signal-to-noise ratio of 15, analyzed with
spin-aligned templates, the presence of an intermediate-mass black hole with
mass >100 $M_\odot$ can be confirmed with 95% confidence in any binary that
includes a component with a mass of 130 $M_\odot$ or greater.",1503.05953v2
2016-04-01,Structural and magnetic field effects on spin fluctuations in Sr$_{3}$Ru$_2$O$_7$,"We investigate the evolution of magnetic excitations in Sr$_3$Ru$_2$O$_7$
using a three band tight binding model that takes into account the influence of
Mn and Ti dopant ions. The effect of dopant ions on the Sr$_3$Ru$_2$O$_7$ band
structure has been included by taking into account the dopant induced
suppression of the oxygen octahedral rotation in the tight binding band
structure and changes in electron occupation. We find that the low energy spin
fluctuations are dominated by three wave vectors around
Q=$((0,0),(\pi/2,\pi/2))$, and $(\pi,0)$ which compete with each other. As the
octahedral rotation is suppressed with increasing doping, the three wave
vectors evolve differently. In particular, the undoped compound has dominant
wavevectors at Q=$((0,0),(\pi/2,\pi/2))$, but doping Sr$_3$Ru$_2$O$_7$ leads to
a significant enhancement in the spin susceptibility at the Q=$(\pi,0)$
wavevector bringing the system closer to a magnetic instability. All the
features calculated from our model are in agreement with neutron scattering
experiments. We have also studied the effect of a c-axis Zeeman field on the
low energy spin fluctuations. We find that an increasing magnetic field
suppresses the AFM fluctuations and leads to stronger competition between the
AFM and FM spin fluctuations. The magnetic field dependence observed in our
calculations therefore supports the scenario that the observed nematic phase in
the metamagnetic region in Sr$_3$Ru$_2$O$_7$ is intimately related to the
presence of a competing ferromagnetic instability.",1604.00286v1
2016-07-25,Accuracy in Measuring the Neutron Star Mass in Gravitational Wave Parameter Estimation for Black Hole-Neutron Star Binaries,"Recently, two gravitational wave (GW) signals, named as GW150914 and
GW151226, have been detected by the two LIGO detectors. Although both signals
were identified as originating from merging black hole (BH) binaries, GWs from
systems containing neutron stars (NSs) are also expected to be detected in the
near future by the Advanced detector network. In this work, we assess the
accuracy in measuring the NS mass ($M_{ns}$) for the GWs from BH-NS binaries
adopting the Advanced LIGO sensitivity with a signal-to-noise ratio of 10. By
using the Fisher matrix method, we calculate the measurement errors ($\sigma$)
in $M_{ns}$ assuming the NS mass of $1 \leq M_{ns}/M_{\odot} \leq 2$ and low
mass BHs with the range of $4 \leq M_{bh}/M_{\odot} \leq 10$. We used the
TaylorF2 waveform model where the spins are aligned with the orbital angular
momentum, but here we only consider the BH spins. We find that the fractional
errors ($\sigma/M_{ns} \times 100$) are in the range of $10\% - 50\%$ in our
mass region for a given dimensionless BH spin as $\chi_{bh} = 0$. The errors
tend to increase as the BH spin increases, and this tendency is stronger for
higher NS masses (or higher total masses). In particular, for the highest mass
NSs ($M_{ns}=2~M_{\odot}$), the errors $\sigma$ can be larger than the true
value of $M_{ns}$ if the dimensionless BH spin exceeds $\sim 0.6$.",1607.07118v1
2016-09-29,Multiscale Model Approach for Magnetization Dynamics Simulations,"Simulations of magnetization dynamics in a multiscale environment enable
rapid evaluation of the Landau-Lifshitz-Gilbert equation in a mesoscopic sample
with nanoscopic accuracy in areas where such accuracy is required. We have
developed a multiscale magnetization dynamics simulation approach that can be
applied to large systems with spin structures that vary locally on small length
scales. To implement this, the conventional micromagnetic simulation framework
has been expanded to include a multiscale solving routine. The software
selectively simulates different regions of a ferromagnetic sample according to
the spin structures located within in order to employ a suitable discretization
and use either a micromagnetic or an atomistic model. To demonstrate the
validity of the multiscale approach, we simulate the spin wave transmission
across the regions simulated with the two different models and different
discretizations. We find that the interface between the regions is fully
transparent for spin waves with frequency lower than a certain threshold set by
the coarse scale micromagnetic model with no noticeable attenuation due to the
interface between the models. As a comparison to exact analytical theory, we
show that in a system with Dzyaloshinskii-Moriya interaction leading to spin
spiral, the simulated multiscale result is in good quantitative agreement with
the analytical calculation.",1609.09295v1
2017-08-01,"Coupling between Charge, Lattice, Orbital, and Spin in a Charge Density Wave of 1$T$-TaS$_2$","Two-dimensional layered transition metal dichalcogenide (TMDC) materials
often exhibit exotic quantum matter phases due to the delicate coupling and
competitions between the charge, lattice, orbital, and spin degrees of freedom.
Surprisingly, we here present, based on first-principles density-functional
theory calculations, the incorporation of all such degrees of freedom in a
charge density wave (CDW) of monolayer (ML) TMDC 1$T$-TaS$_2$. We reveal that
the CDW formed via the electron-phonon coupling is significantly stabilized by
the orbital hybridization. The resulting lattice distortion to the ""David-star""
superstructure constituted of one cental, six nearest-neighbor, and six
next-nearest-neighbor Ta atoms is accompanied by the formation of
quasimolecular orbitals due to a strong hybridization of the Ta $t_{\rm 2g}$
orbitals. Furthermore, the flat band of the quasimolecular orbital at the Fermi
level has a spin splitting caused by an intramolecular exchange, yielding a
full spin polarization with a band-gap opening. Our finding of the intricate
charge-lattice-orbital-spin coupling in ML 1$T$-TaS$_2$ provides a framework
for the exploration of various CDW phases observed in few-layer or bulk
1$T$-TaS$_2$.",1708.00213v1
2018-05-10,"Magnetic excitations in bulk multiferroic two-dimensional triangular lattice antiferromagnet (Lu,Sc)FeO$_3$","Non-collinear two-dimensional triangular lattice antiferromagnets (2D TLAF)
are currently an area of very active research due to their unique magnetic
properties, which lead to non-trivial quantum effects that experimentally
manifest themselves in the spin excitation spectra. Recent examples of such
insulating 2D TLAF include (Y,Lu)MnO$_3$, LiCrO$_2$, and CuCrO$_2$. Hexagonal
LuFeO3 is a recently synthesized 2D TLAF which exhibits properties of an ideal
multiferroic material, partially because of the high spin ($S=5/2$) and strong
magnetic super-exchange interactions. We report the full range of spin dynamics
in a bulk single crystal of (Lu$_{0.6}$Sc$_{0.4}$)FeO$_3$ (Sc doping to
stabilize the hexagonal structure) measured via time-of-flight inelastic
neutron scattering. Modeling with linear spin wave theory yields a nearest
neighbor exchange coupling of $J$ = 4.0(2) meV (DFT calculations for
$h$-LuFeO$_3$ predicted a value of 6.31 meV) and anisotropy values of $K_D$ =
0.17(1) meV (easy plane) and $K_A$~=~-0.05(1)~meV (local easy axis). It is
observed that the magnon bandwidth of the spin wave spectra is twice as large
for $h$-(Lu,Sc)FeO$_3$ as it is for $h$-LuMnO$_3$.",1805.03912v2
2018-06-07,Fractional topological insulator precursors in spin-orbit fermion ladders,"We study precursor states of fractional topological insulators (FTIs) in
interacting fermionic ladders with spin-orbit coupling. Within a
microscopically motivated bosonization approach, we investigate different
competing phases depending on same-spin and interspin interactions at
fractional effective filling $\nu=1/3$ per spin. In the spin-decoupled limit,
we find that strong repulsive interactions of already moderate range may lead
to a partially gapped state with two time-reversed copies of a quasi-one
dimensional Laughlin phase. This FTI precursor competes with an interleg
partially gapped phase displaying quasi long-range density wave order, however
it may be stabilized if interactions have suitable anisotropy, or are
sufficiently near SU($2$) symmetry, in leg space. When the FTI phase is
present, it is moderately robust to small interspin interactions; these
introduce competing partially gapped phases of orbital antiferromagnetic and
bond density wave character. Performing a strong coupling analysis of the FTI
precursor regime, we find that the main effect of interspin interactions is to
induce correlated quasiparticle backscattering between the precursor FTI edge
modes. Although this process competes with the topological phase, we show, by
considering an array of ladders, that its influence may disappear upon
approaching the two dimensional case. Considering time-reversal symmetry
breaking perturbations, we also describe a protocol that adiabatically pumps
$1/6$ charge per half-cycle, thus providing a quantized FTI signature arising
already in the single ladder regime.",1806.02874v3
2019-02-27,Coexistence of ferromagnetic and stripe antiferromagnetic spin fluctuations in SrCo$_2$As$_2$,"We use inelastic neutron scattering to study energy and wave vector
dependence of spin fluctuations in SrCo$_2$As$_2$, derived from
SrFe$_{2-x}$Co$_x$As$_2$ iron pnictide superconductors. Our data reveals the
coexistence of antiferromagnetic (AF) and ferromagnetic (FM) spin fluctuations
at wave vectors $\textbf{Q}_{\rm AF}$=(1,0) and $\textbf{Q}_{\rm
FM}$=(0,0)/(2,0), respectively. By comparing neutron scattering results with
those of dynamic mean field theory calculation and angle-resolved photoemission
spectroscopy experiments, we conclude that both AF and FM spin fluctuations in
SrCo$_2$As$_2$ are closely associated with a flat band of the $e_g$ orbitals
near the Fermi level, different from the $t_{2g}$ orbitals in superconducting
SrFe$_{2-x}$Co$_x$As$_2$. Therefore, Co-substitution in
SrFe$_{2-x}$Co$_x$As$_2$ induces a $t_{2g}$ to $e_g$ orbital switching, and is
responsible for FM spin fluctuations detrimental to the singlet pairing
superconductivity.",1902.10621v1
2020-04-06,Extreme mass ratio inspirals with spinning secondary: a detailed study of equatorial circular motion,"Extreme mass-ratio inspirals detectable by the future Laser Interferometer
Space Antenna provide a unique way to test general relativity and fundamental
physics. Motivated by this possibility, here we study in detail the EMRI
dynamics in the presence of a spinning secondary, collecting and extending
various results that appeared in previous work and also providing useful
intermediate steps and new relations for the first time. We present the results
of a frequency-domain code that computes gravitational-wave fluxes and the
adiabatic orbital evolution for the case of circular, equatorial orbits with
(anti)aligned spins. The spin of the secondary starts affecting the
gravitational-wave phase at the same post-adiabatic order as the leading-order
self-force terms and introduces a detectable dephasing, which can be used to
measure it at $5-25\%$ level, depending on individual spins. In a companion
paper we discuss the implication of this effect for tests of the Kerr bound.",2004.02654v2
2016-03-11,Instability of three-band Tomonaga-Luttinger liquid: renormalization group analysis and possible application to K2Cr3As3,"Motivated by recently discovered quasi-one-dimensional superconductor
K$_{2}$Cr$_{3}$As$_{3}$ with $D_{3h}$ lattice symmetry, we study
one-dimensional three-orbital Hubbard model with generic electron repulsive
interaction described by intra-orbital repulsion $U$, inter-orbital repulsion,
and Hund's coupling $J$. As extracted from density functional theory
calculation, two of the three atomic orbitals are degenerate ($E^{\prime}$
states) and the third one is non-degenerate ($A^{\prime}_1$), and the system is
presumed to be at an incommensurate filling. With the help of bosonization, we
have usual three-band Tomonaga-Luttinger liquid for the normal state. Possible
charge density wave (CDW), spin density wave (SDW) and superconducting (SC)
instabilities are analyzed by renormalization group. The ground state depends
on the ratio $J/U$ and is sensitive to the degeneracy of $E^{\prime}$ bands. At
$0<J<U/3$, spin-singlet SC state is favored, while spin-triplet
superconductivity will be favored in the region $U/3<J<U/2$. The SDW state has
the lowest energy only in the unphysical parameter region $J>U/2$. When the
two-fold degeneracy of $E^{\prime}$ bands is lifted, SDW instability has the
tendency to dominate over the spin-singlet SC state at $0<J<U/3$, while the
order parameter of the spin-triplet SC state will be modulated by a phase
factor $2\Delta k_F x$ at $U/3<J<U/2$. Possible experimental consequences and
applications to K$_{2}$Cr$_{3}$As$_{3}$ are discussed.",1603.03651v3
2017-02-16,Spin-wave excitations evidencing the Kitaev interaction in single crystalline $α$-RuCl$_3$,"Kitaev interactions underlying a quantum spin liquid have been long sought,
but experimental data from which their strengths can be determined directly is
still lacking. Here, by carrying out inelastic neutron scattering measurements
on high-quality single crystals of $\alpha$-RuCl$_3$, we observe spin-wave
spectra with a gap of $\sim$2 meV around the M point of the two-dimensional
Brillouin zone. We derive an effective-spin model in the strong-coupling limit
based on energy bands obtained from first-principle calculations, and find that
the anisotropic Kitaev interaction $K$ term and the isotropic antiferromagentic
off-diagonal exchange interaction $\Gamma$ term are significantly larger than
the Heisenberg exchange coupling $J$ term. Our experimental data can be well
fit using an effective-spin model with $K=-6.8$ meV and $\Gamma=9.5$ meV. These
results demonstrate explicitly that Kitaev physics is realized in real
materials.",1702.04920v1
2017-06-20,Dynamical characteristics of electromagnetic field under conditions of total reflection,"The dynamical characteristics of electromagnetic fields include energy,
momentum, angular momentum (spin) and helicity. We analyze their spatial
distributions near the planar interface between two transparent and
non-dispersive media, when the incident monochromatic plane wave with arbitrary
polarization is totally reflected, and an evanescent wave is formed in the
medium with lower optical density. Based on the recent arguments in favor of
the Minkowski definition of the electromagnetic momentum in a material medium
[Phys. Rev. A 83, 013823 (2011); 86, 055802 (2012); Phys. Rev. Lett. 119,
073901 (2017)], we derive the explicit expressions for the dynamical
characteristics in both media, with special attention to their behavior at the
interface. Especially, the ""extraordinary"" spin and momentum components
orthogonal to the plane of incidence are described, and the canonical (spin -
orbital) momentum decomposition is performed that contains no singular terms.
The field energy, helicity, the spin momentum and orbital momentum components
are everywhere regular but experience discontinuities at the interface; the
spin components parallel to the interface appear to be continuous, which
testifies for the consistency of the adopted Minkowski picture. The results
supply a meaningful example of the electromagnetic momentum decomposition, with
separation of spatial and polarization degrees of freedom, in inhomogeneous
media, and can be used in engineering the structured fields designed for
optical sorting, dispatching and micromanipulation.",1706.06263v4
2019-03-04,Constraints on ultra-low-frequency gravitational waves with statistics of pulsar spin-down rates,"We probe ultra-low-frequency gravitational waves (GWs) with statistics of
spin-down rates of milli-second pulsars (MSPs) by a method proposed in our
prevous work (Yonemaru et al. 2016). The considered frequency range is
$10^{-12}{\rm Hz} \lesssim f_{\rm GW} \lesssim 10^{-10}$Hz, which cannot be
accessed by the conventional pulsar timing array. The effect of such
low-frequency GWs appears as a bias to spin-down rates which has a quadrupole
pattern in the sky. We use the skewness of the spin-down rate distribution and
the number of MSPs with negative spin-down rates to search for the bias induced
by GWs. Applying this method to 149 MSPs selected from the ATNF pulsar catalog,
we derive upper bounds on the time derivative of the GW amplitudes of $\dot{h}
< 6.2 \times 10^{-18}~{\rm sec}^{-1}$ and $\dot{h} < 8.1 \times 10^{-18}~{\rm
sec}^{-1}$ in the directions of the Galactic Center and M87, respectively.
Approximating the GW amplitude as $\dot{h} \sim 2 \pi f_{\rm GW} h$, the bounds
translate into $h < 3 \times 10^{-9}$ and $h < 4 \times 10^{-9}$, respectively,
for $f_{\rm GW} = 1/(100~{\rm yr})$. Finally, we give the implications to
possible super-massive black hole binaries at these sites.",1903.01129v2
2021-10-24,Post-Newtonian Waveforms from Spinning Scattering Amplitudes,"We derive the classical gravitational radiation from an aligned spin binary
black hole on \textit{closed} orbits, using a dictionary built from the 5-point
QFT scattering amplitude of two massive particles exchanging and emitting a
graviton. We show explicitly the agreement of the transverse-traceless
components of the radiative linear metric perturbations -- and the
corresponding gravitational wave energy flux -- at future null infinity,
derived from the scattering amplitude and those derived utilizing an effective
worldline action in conjunction with multipolar post-Minkowskian matching. At
the tree-level, this result holds at leading orders in the black holes'
velocities and up to quadratic order in their spins. At sub-leading order in
black holes' velocities, we demonstrate a matching of the radiation field for
quasi-circular orbits in the no-spin limit. At the level of the radiation
field, and to leading order in the velocities, there exists a one-to-one
correspondence between the binary black hole mass and current quadrupole
moments, and the scalar and linear-in-spin scattering amplitudes, respectively.
Therefore, we show explicitly that waveforms, needed to detect gravitational
waves from \textit{inspiraling} binary black holes, can be derived
consistently, to the orders considered, from the classical limit of quantum
\textit{scattering} amplitudes.",2110.12537v3
2004-05-19,Auxiliary-Fermion Approach to Critical Fluctuations in the 2D Quantum AF Heisenberg Model,"The nearest-neighbor quantum-antiferromagnetic (AF) Heisenberg model for spin
1/2 on a two-dimensional square lattice is studied in the auxiliary-fermion
representation. Expressing spin operators by canonical fermionic particles
requires a constraint on the fermion charge Q=1 on each lattice site, which is
imposed approximately through the thermal average. The resulting interacting
fermion system is first treated in mean-field theory (MFT), which yields an AF
ordered ground state and spin waves in quantitative agreement with conventional
spin-wave theory. At finite temperature a self-consistent approximation beyond
mean field is required in order to fulfill the Mermin-Wagner theorem. We first
discuss a fully self-consistent approximation, where fermions are renormalized
due to fluctuations of their spin density, in close analogy to FLEX. While
static properties like the correlation length come out correctly, the dynamical
response lacks the magnon-like peaks which would reflect the appearance of
short-range order at low T. This drawback, which is caused by overdamping, is
overcome in a `minimal self-consistent approximation' (MSCA), which we derive
from the equations of motion. The MSCA features dynamical scaling at small
energy and temperature and is qualitatively correct both in the regime of
order-parameter relaxation at long wavelengths and in the short-range-order
regime. We also discuss the impact of vertex corrections and the problem of
pseudo-gap formation in the single-particle density of states due to long-range
fluctuations. Finally we show that the (short-range) magnetic order in MFT and
MSCA helps to fulfill the constraint on the local fermion occupancy.",0405438v2
2017-01-10,Effective lattice model for collective modes in a Fermi liquid with spin-orbit coupling,"A Fermi-liquid (FL) with spin-orbit coupling (SOC) supports a special type of
collective modes--chiral spin waves--which are oscillations of magnetization
even in the absence of the external magnetic field. We study the chiral spin
waves of a two-dimensional FL in the presence of both the Rashba and
Dresselhaus types of SOC and also subject to the in-plane magnetic field. We
map the system of coupled kinetic equations for the angular harmonics of the
occupation number onto an effective one-dimensional tight-binding model, in
which the lattice sites correspond to angular-momentum channels.
Linear-in-momentum SOC ensures that the effective tight-binding model has only
nearest-neighbor hopping on a bipartite lattice. In this language, the
continuum of spin-flip particle-hole excitations becomes a conduction band of
the lattice model, whereas electron-electron interaction, parameterized by the
harmonics of the Landau function, is mapped onto lattice defects of both
on-site and bond type. Collective modes correspond to bound states formed by
such defects. All the features of the collective-mode spectrum receive natural
explanation in the lattice picture as resulting from the competition between
on-site and bond defects.",1701.02781v3
2019-09-03,"Spectral Lines of Quantized, Spinning Black Holes and their Astrophysical Relevance","In this Letter, we study black hole area quantization in the context of
gravitational wave physics. It was recently argued that black hole area
quantization could be a mechanism to produce so-called echoes as well as
characteristic absorption lines in gravitational wave observations of merging
black holes. One can match the spontaneous decay of these quantum black holes
to Hawking radiation calculations. Using some assumptions, one can then
estimate the natural widths of these states. As can be seen from a classical
paper by Bekenstein and Mukhanov, the ratio between width and spacing of
nonspinning black hole states approaches a small constant, which seems to
confirm the claim. However, we find that, including the effect of black hole
spin, the natural widths increase. To properly address any claim about
astrophysical black holes, one should examine the spinning case, as real black
holes spin. Thus, the word spinning is key to the question of whether or not
black holes should have an observable spectrum in nature. Our results suggest
that it should be possible to distinguish between any scenarios for which the
answer to this question is yes. However, for all of the commonly discussed
scenarios, our answer is almost certainly no.",1909.01254v2
2020-07-16,Characterizing Astrophysical Binary Neutron Stars with Gravitational Waves,"Merging binary neutron stars are thought to be formed predominantly via
isolated binary evolution. In this standard formation scenario, the first-born
neutron star goes through a recycling process and might be rapidly spinning
during the final inspiral, whereas the second-born star is expected to have
effectively zero spin at merger. Based on this feature, we propose a new
framework for the astrophysical characterization of binary neutron stars
observed from their gravitational wave emission. We further propose a prior for
the dimensionless spins of recycled neutron stars, given by a gamma
distribution with a shape parameter of 2 and a scale parameter of 0.012,
extrapolated from radio pulsar observations of Galactic binary neutron stars.
Interpreting GW170817 and GW190425 in the context of the standard formation
scenario and adopting the gamma-distribution prior, we find positive support
(with a Bayes factor of 6, over the nonspinning hypothesis) for a spinning
recycled neutron star in GW190425, whereas the spin of the recycled neutron
star in GW170817 is small and consistent with our prior. We measure the masses
of the recycled (slow) neutron stars in GW170817 and GW190425 to be
$1.34_{-0.09}^{+0.12}$ $(1.38_{-0.11}^{+0.11})$ $M_{\odot}$ and
$1.64_{-0.11}^{+0.13}$ $(1.66_{-0.12}^{+0.12})$ $M_{\odot}$, with $68\%$
credibility, respectively. We discuss implications for the astrophysical
origins of these two events and outline future prospects of studying binary
neutron stars using our framework.",2007.08198v5
2020-10-02,Averaging of thermoacoustic azimuthal instabilities,"We consider the acoustic flow field of rotationally symmetric systems, like
an annular combustor and the flow in a round duct, in absence of a mean
azimuthal flow field. We focus on azimuthal instabilities, which manifest as
either spinning (rotating) waves or standing waves, or a linear combination of
the two. These instabilities are often excited by some level of background
noise that makes the system randomly change between spinning and standing
states, undergo amplitude variations and changes to the azimuthal orientation
of the solution. To account for this random change, we make use of a novel
ansatz to track as a function of time the amplitude, orientation, nature
(standing/spinning) and temporal phase of these instabilities. To capture the
effect of the background noise, we apply stochastic averaging on the governing
equations and obtain a novel differential equation. The equation allows to
study the effects of acoustic sources and sinks on the statistics of the
solution, and of explicit and spontaneous symmetry breaking and noise
intensity. We focus on this last effect and show how the noise intensity
affects the system preference for spinning and/or standing states. We find for
example that, when present, background noise pushes the system away from
spinning states and towards standing states, consistently with experiments and
numerical simulations.",2010.00800v1
2021-03-10,Spin effects on neutron star fundamental-mode dynamical tides: phenomenology and comparison to numerical simulations,"Gravitational waves from neutron star binary inspirals contain information on
strongly-interacting matter in unexplored, extreme regimes. Extracting this
requires robust theoretical models of the signatures of matter in the
gravitational-wave signals due to spin and tidal effects. In fact, spins can
have a significant impact on the tidal excitation of the quasi-normal modes of
a neutron star, which is not included in current state-of-the-art waveform
models. We develop a simple approximate description that accounts for the
Coriolis effect of spin on the tidal excitation of the neutron star's
quadrupolar and octupolar fundamental quasi-normal modes and incorporate it in
the SEOBNRv4T waveform model. We show that the Coriolis effect introduces only
one new interaction term in an effective action in the co-rotating frame of the
star, and fix the coefficient by considering the spin-induced shift in the
resonance frequencies that has been computed numerically for the mode
frequencies of rotating neutron stars in the literature. We investigate the
impact of relativistic corrections due to the gravitational redshift and
frame-dragging effects, and identify important directions where more detailed
theoretical developments are needed in the future. Comparisons of our new model
to numerical relativity simulations of double neutron star and neutron
star-black hole binaries show improved consistency in the agreement compared to
current models used in data analysis",2103.06100v2
2021-05-25,Looking for the parents of LIGO's black holes,"Solutions to the two-body problem in general relativity allow us to predict
the mass, spin and recoil velocity of a black-hole merger remnant given the
masses and spins of its binary progenitors. In this paper we address the
inverse problem: given a binary black-hole merger, can we use the parameters
measured by gravitational-wave interferometers to tell if the binary components
are of hierarchical origin, i.e. if they are themselves remnants of previous
mergers? If so, can we determine at least some of the properties of their
parents? This inverse problem is in general overdetermined. We show that
hierarchical mergers occupy a characteristic region in the plane composed of
the effective spin parameters $\chi_{\rm eff}$ and $\chi_{\rm p}$, and
therefore a measurement of these parameters can add weight to the
hierarchical-merger interpretation of some gravitational-wave events, including
GW190521. If one of the binary components has hierarchical origin and its spin
magnitude is well measured, we derive exclusion regions on the properties of
its parents: for example we infer that the parents of GW190412 (if
hierarchical) must have had unequal masses and low spins. Our formalism is
quite general, and it can be used to infer constraints on the astrophysical
environment producing hierarchical mergers.",2105.12140v2
2021-12-13,"AI and extreme scale computing to learn and infer the physics of higher order gravitational wave modes of quasi-circular, spinning, non-precessing binary black hole mergers","We use artificial intelligence (AI) to learn and infer the physics of higher
order gravitational wave modes of quasi-circular, spinning, non precessing
binary black hole mergers. We trained AI models using 14 million waveforms,
produced with the surrogate model NRHybSur3dq8, that include modes up to $\ell
\leq 4$ and $(5,5)$, except for $(4,0)$ and $(4,1)$, that describe binaries
with mass-ratios $q\leq8$, individual spins $s^z_{\{1,2\}}\in[-0.8, 0.8]$, and
inclination angle $\theta\in[0,\pi]$.Our probabilistic AI surrogates can
accurately constrain the mass-ratio, individual spins, effective spin, and
inclination angle of numerical relativity waveforms that describe such signal
manifold. We compared the predictions of our AI models with Gaussian process
regression, random forest, k-nearest neighbors, and linear regression, and with
traditional Bayesian inference methods through the PyCBC Inference toolkit,
finding that AI outperforms all these approaches in terms of accuracy, and are
between three to four orders of magnitude faster than traditional Bayesian
inference methods. Our AI surrogates were trained within 3.4 hours using
distributed training on 1,536 NVIDIA V100 GPUs in the Summit supercomputer.",2112.07669v2
2021-12-27,Prospects for determining the nature of the secondaries of extreme mass-ratio inspirals using the spin-induced quadrupole deformation,"The measurement of multipole moments of astrophysical objects through
gravitational wave (GW) observations provides a novel way to distinguish black
holes from other astrophysical objects. This paper studies the gravitational
wave radiation from an extreme mass ratio inspiral (EMRI) system consisting of
a supermassive Kerr black hole (the primary object) and a spinning stellar-mass
compact object (the secondary object). The quadrupolar deformation induced by
the spin of the secondary is different for different astrophysical objects. We
compute the effect of the quadrupolar deformation on the GW phase and provide
an order of magnitude estimate of whether LISA can distinguish different
astrophysical objects through GW phase measurement. We find that although LISA
can not distinguish between a black hole and a neutron star, it can distinguish
black holes from a large variety of highly spinning astrophysical objects like
superspinars and highly deformable exotic compact objects like boson stars for
EMRI systems with relatively large mass ratio ($q\sim 10^{-4}$). Furthermore,
we show that the effect of spin-induced quadrupolar deformation on the GW phase
for white dwarf and brown dwarf-EMRI systems can be quite significant even for
small values of mass ratio ($q\lesssim 10^{-6}$).",2112.13869v3
2022-01-21,Momentum Signatures of Site Percolation in Disordered 2D Ferromagnets,"In this work, we consider a two-dimensional square lattice of pinned magnetic
spins with nearest-neighbour interactions and we randomly replace a fixed
proportion of spins with nonmagnetic defects carrying no spin. We focus on the
linear spin-wave regime and address the propagation of a spin-wave excitation
with initial momentum $k_0$. We compute the disorder-averaged momentum
distribution obtained at time $t$ and show that the system exhibits two
regimes. At low defect density, typical disorder configurations only involve a
single percolating magnetic cluster interspersed with single defects
essentially and the physics is driven by Anderson localization. In this case,
the momentum distribution features the emergence of two known emblematic
signatures of coherent transport, namely the coherent backscattering (CBS) peak
located at $-k_0$ and the coherent forward scattering (CFS) peak located at
$k_0$. At long times, the momentum distribution becomes stationary. However,
when increasing the defect density, site percolation starts to set in and
typical disorder configurations display more and more disconnected clusters of
different sizes and shapes. At the same time, the CFS peak starts to oscillate
in time with well defined frequencies. These oscillation frequencies represent
eigenenergy differences in the regular, disorder-immune, part of the
Hamiltonian spectrum. This regular spectrum originates from the small-size
magnetic clusters and its weight grows as the system undergoes site percolation
and small clusters proliferate. Our system offers a unique spectroscopic
signature of cluster formation in site percolation problems.",2201.08752v2
2022-03-04,Exchange interactions and spin dynamics in the layered honeycomb ferromagnet CrI$_3$,"We derive the microscopic spin Hamiltonian for rhombohedral CrI$_3$ using
extensive first-principles density functional theory (DFT) calculations which
incorporate spin-orbit coupling and Hubbard U. Our calculations indicate a
dominant nearest-neighbor ferromagnetic Heisenberg exchange with weaker
further-neighbor Heisenberg terms. In addition, we find a Dzyaloshinskii-Moriya
interaction which primarily drives a topological gap in the spin-wave spectrum
at the Dirac point, and uncover a non-negligible antiferromagnetic Kitaev
coupling between the S=3/2 Cr moments. The out-of-plane magnetic moment is
stabilized by weak symmetric bond-dependent terms and a local single-ion
anisotropy. Using linear spin wave theory, we find that our exchange parameters
are in reasonably good agreement with inelastic neutron scattering (INS)
experiments. Employing classical Monte Carlo simulations, we study the magnetic
phase transition temperature $T_c$ and its evolution with an applied in-plane
magnetic field. We further demonstrate how future high-resolution INS
experiments on the magnon dispersion of single crystals in an in-plane magnetic
field may be used to quantitatively extract the strength of the
antiferromagnetic Kitaev exchange coupling.",2203.02567v1
2022-03-06,Superfluidity of a Raman spin-orbit-coupled Bose gas at finite temperature,"We investigate the superfluidity of a three-dimensional weakly interacting
Bose gas with a one-dimensional Raman-type spin-orbit coupling at both zero and
finite temperatures. Using the imaginary-time Green's function within the
Bogoliubov approximation, we explicitly derive analytic expressions of the
current-current response functions in the plane-wave and zero-momentum phases,
from which we extract the superfluid density in the limits of long wavelength
and zero frequency. At zero temperature, we check that the resultant superfluid
density agrees exactly with our previous analytic prediction obtained from a
phase-twist approach. Both results also satisfy a generalized Josephson
relation in the presence of spin-orbit coupling. At finite temperature, we find
a significant non-monotonic temperature dependence of superfluid density near
the transition from the plane-wave phase to the zero-momentum phase. We show
that this non-trivial behavior might be understood from the sound velocity,
which has a similar temperature dependence. The non-monotonic temperature
dependence is also shared by Landau critical velocity, above which the
spin-orbit-coupled Bose gas loses its superfluidity. Our results would be
useful for further theoretical and experimental studies of superfluidity in
exotic spin-orbit coupled quantum gases.",2203.02921v1
2022-03-16,Nuclear Magnetic Resonance for Arbitrary Spin Values in the Rotating Wave Approximation,"In order to probe the transitions of a nuclear spin $s$ from one of its
substate quantum numbers $m$ to another substate $m'$, the experimenter applies
a magnetic field ${\bm B}_0$ in some particular direction, such along $\hat{\bm
z}$, and then applies an weaker field ${\bm B}_1(t)$ that is oscillatory in
time with the angular frequency $\omega$, and is normally perpendicular to
${\bm B}_0$, such as ${\bm B}_1(t)=B_1\hat{\bm x}\cos(\omega t)$. In the
rotating wave approximation, ${\bm B}_1(t)=B_1[\hat{\bm x}\cos(\omega
t)+\hat{\bm y}\sin(\omega t)]$. Although this problem is solved for spin
$\frac{1}{2}$ in every quantum mechanics textbook, for the general spin $s$
case, its general solution has been published only for the overall probability
of a transition between the states, but the time dependence of the probability
of finding the nucleus in each of the substates has not previously been
published. Here we present an elementary method to solve this problem exactly,
and present figures for the time dependencies of the various substates states
for a variety of initial substate probabilities for a variety of $s$ values. We
found a new result: unlike the $s=\frac{1}{2}$ case, for which if the initial
probability of finding the particle in one of the substates was 1, and the time
dependence of the probabilities of each of the substates oscillates between 0
and 1, for higher spin values, the time dependencies of the probabilities
finding the particle in each of its substates, which periodic, is considerably
more complicated.",2203.08755v1
2022-05-03,Signatures of mass ratio reversal in gravitational waves from merging binary black holes,"The spins of merging binary black holes offer insights into their formation
history. Recently it has been argued that in isolated binary evolution of two
massive stars the firstborn black hole is slowly rotating, whilst the
progenitor of the second-born black hole can be tidally spun up if the binary
is tight enough. Naively, one might therefore expect that only the less massive
black hole in merging binaries exhibits non-negligible spin. However, if the
mass ratio of the binary is ""reversed"" (typically during the first mass
transfer episode), it is possible for the tidally spun up second-born to become
the more massive black hole. We study the properties of such mass-ratio
reversed (MRR) binary black hole mergers using a large set of 560 population
synthesis models. We find that the more massive black hole is formed second in
$\gtrsim 70\%$ of binary black holes observable by LIGO, Virgo, and KAGRA for
most model variations we consider, with typical total masses $\gtrsim 20$
M$_{\odot}$ and mass ratios $q = m_2 / m_1 \sim 0.7$ (where $m_1 > m_2$). The
formation history of these systems typically involves only stable mass transfer
episodes. The second-born black hole has non-negligible spin ($\chi > 0.05$) in
up to $25\%$ of binary black holes, with among those the more (less) massive
black hole spinning in $0\%$--$80\%$ ($20\%$--$100\%$) of cases, varying
greatly in our models. We discuss our models in the context of several observed
gravitational-wave events and the observed mass ratio - effective spin
correlation.",2205.01693v1
2022-09-02,Recognizing the constitution of small bodies in extreme-mass-ratio inspirals by gravitational waves,"The extreme mass ratio inspirals(EMRIs) are promising gravitational wave(GW)
sources for space-borne GW detectors. The signals of EMRIs usually have long
timescales, ranging from several months to several years, and their detection
requires accurate GW signal templates. In most waveform models, the compact
objects in EMRIs are considered test particles, which do not consider the small
bodies' spin, mass distribution, and tidal deformation. In this work, we
simulate the GW signals of EMRIs by considering the compact objects' spin and
mass quadrupole. We find that a compact object's spin can significantly
influence the GW signals, and the tidal-induced and spin-induced quadrupoles
matter only if the compact objects are white dwarfs, especially EMRIs of a
higher symmetric mass ratio. We can distinguish white dwarfs from other compact
objects in this case. The structures of black holes and neutron stars in EMRIs
do not have detectable effects on GW signals. Furthermore, compared with the GW
signals that use test particle approximation, the signal-to-noise ratios(SNRs)
of GW signals that consider extended bodies decrease slightly, which hints that
we can omit the spin and quadrupole of the compact object in the detection of
EMRIs.",2209.01110v1
2022-09-09,"Self-gravitating disks around rapidly spinning, tilted black holes: General relativistic simulations","We perform general relativistic simulations of self-gravitating black
hole-disks in which the spin of the black hole is significantly tilted
($45^\circ$ and $90^\circ$) with respect to the angular momentum of the disk
and the disk-to-black hole mass ratio is $16\%-28\%$. The black holes are
rapidly spinning with dimensionless spins up to $\sim 0.97$. These are the
first self-consistent hydrodynamic simulations of such systems, which can be
prime sources for multimessenger astronomy. In particular tilted black
hole-disk systems lead to: i) black hole precession; ii) disk precession and
warping around the black hole; iii) earlier saturation of the
Papaloizou-Pringle instability compared to aligned/antialigned systems,
although with a shorter mode growth timescale; iv) acquisition of a small
black-hole kick velocity; v) significant gravitational wave emission via
various modes beyond, but as strong as, the typical $(2,2)$ mode; and vi) the
possibility of a broad alignment of the angular momentum of the disk with the
black hole spin. This alignment is not related to the Bardeen-Petterson effect
and resembles a solid body rotation. Our simulations suggest that any
electromagnetic luminosity from our models may power relativistic jets, such as
those characterizing short gamma-ray bursts. Depending on the black hole-disk
system scale the gravitational waves may be detected by LIGO/Virgo, LISA and/or
other laser interferometers.",2209.04454v1
2022-10-14,Jordan-Wigner fermionization of quantum spin systems on arbitrary 2D lattices: A mutual Chern-Simons approach,"A variety of analytical approaches have been developed for the study of
quantum spin systems in two dimensions, the notable ones being spin-waves,
slave boson/fermion parton constructions, and for lattices with one-to-one
local correspondence of faces and vertices, the 2D Jordan-Wigner (JW)
fermionization. Field-theoretically, JW fermionization is implemented through
Chern-Simons (CS) flux attachment. For a correct fermionization of lattice
quantum spin-$1/2$ magnets, it is necessary that the fermions obey mutual
bosonic (anyonic) statistics under exchange - this is not possible to implement
on arbitrary 2D lattices if fermionic matter couples only to the lattice gauge
fields. Enlarging the gauge degrees of freedom to include the dual lattice
allows the construction of consistent mutual Chern-Simons field theories. Here
we propose a mutual CS theory where the microscopic (spin) degrees of freedom
are represented as lattice fermionic matter additionally coupled to specific
combinations of dual lattice gauge fields that depend on the local geometry. We
illustrate the use of this method for understanding the properties of a
honeycomb Kitaev model subjected to a strong Zeeman field in the $z$-direction.
Our CS gauge theory framework provides an understanding why the topological
phase is degraded at lower (higher) critical fields for the ferro- (antiferro-)
magnetic Kitaev interaction. Additionally, we observe an effectively
one-dimensional character of the low-excitations at higher fields in the
$z$-direction which we also confirm by spin-wave calculations.",2210.07718v2
2023-04-10,Efficient multi-timescale dynamics of precessing black-hole binaries,"We present analytical and numerical progress on black-hole binary spin
precession at second post-Newtonian order using multi-timescale methods. In
addition to the commonly used effective spin which acts as a constant of
motion, we exploit the weighted spin difference and show that such
reparametrization cures the coordinate singularity that affected the previous
formulation for the case of equal-mass binaries. The dynamics on the precession
timescale is written down in closed form in both coprecessing and inertial
frames. Radiation reaction can then be introduced in a quasi-adiabatic fashion
such that, at least for binaries on quasi-circular orbits, gravitational
inspirals reduce to solving a single ordinary differential equation. We provide
a broad review of the resulting phenomenology and rewrite the relevant physics
in terms of the newly adopted parametrization. This includes the spin-orbit
resonances, the up-down instability, spin propagation at past time infinity,
and new precession estimators to be used in gravitational-wave astronomy. Our
findings are implemented in version 2 of the public Python module PRECESSION.
Performing a precession-averaged post-Newtonian evolution from/to arbitrarily
large separation takes $\lesssim 0.1$ s on a single off-the-shelf processor - a
50x speedup compared to our previous implementation. This allows for a wide
variety of applications including propagating gravitational-wave posterior
samples as well as population-synthesis predictions of astrophysical nature.",2304.04801v2
2023-07-28,Evidence for a correlation between binary black hole mass ratio and black-hole spins,"The astrophysical origins of the binary black hole systems seen with
gravitational waves are still not well understood. However, features in the
distribution of black-hole masses, spins, redshifts, and eccentricities provide
clues into how these systems form. Much has been learned by investigating these
distributions one parameter at a time. However, we can extract additional
information by studying the covariance between pairs of parameters. Previous
work has shown preliminary support for an anti-correlation between mass ratio
$q \equiv m_2/m_1$ and effective inspiral spin $\chi_\mathrm{eff}$ in the
binary black hole population. In this study, we test for the existence of this
anti-correlation using updated data from the third gravitational wave transient
catalogue (GWTC-3) and improve our copula-based framework to employ a more
robust model for black-hole spins. We find evidence for an anti-correlation in
$(q, \chi_\mathrm{eff})$ with 99.7% credibility. This may imply high
common-envelope efficiencies, stages of super-Eddington accretion, or a
tendency for binary black hole systems to undergo mass-ratio reversal during
isolated evolution. Covariance in $(q,\chi_\mathrm{eff})$ may also be used to
investigate the physics of tidal spin-up as well as the properties of
binary-black-hole-forming active galactic nuclei.",2307.15278v2
2023-08-18,A fresh view on Frenkel excitons: Electron-hole pair exchange and many-body formalism,"We here present a fresh approach to Frenkel excitons in cubic semiconductor
crystals, with a special focus on the spin and spatial degeneracies of the
electronic states. This approach uses a second quantization formulation of the
problem in terms of creation operators for electronic states on all lattice
sites -- their creation operators being true fermion operators in the
tight-binding limit valid for semiconductors hosting Frenkel excitons. This
operator formalism avoids using cumbersome ($6N_s$ x $6N_s$) Slater
determinants -- 2 for spin, 3 for spatial degeneracy and $N_s$ for the number
of lattice sites -- to represent state wave functions out of which the Frenkel
exciton eigenstates are derived. A deep understanding of the tricky Coulomb
physics that takes place in the Frenkel exciton problem, is a prerequisite for
possibly diagonalizing this very large matrix analytically. This is done in
three steps: (i) the first diagonalization, with respect to lattice sites,
follows from transforming excitations on the $N_s$ lattice sites
$\mathbf{R}_\ell$ into $N_s$ exciton waves $\mathbf{K}_n$, by using appropriate
phase prefactors; (ii) the second diagonalization, with respect to spin,
follows from the introduction of spin-singlet and spin-triplet electron-hole
pair states, through the commonly missed sign change when transforming
electron-absence operators into hole operators; (iii) the third
diagonalization, with respect to threefold spatial degeneracy, leads to the
splitting of the exciton level into one longitudinal and two transverse modes,
that result from the singular interlevel Coulomb scattering in the small
$\mathbf{K}_n$ limit.",2308.09299v1
2013-10-06,Post-Newtonian Theory for Gravitational Waves,"To be observed and analyzed by the network of current gravitational wave
detectors (LIGO, Virgo, KAGRA), and in anticipation of future third generation
ground based (Einstein Telescope, Cosmic Explorer) and space borne (LISA)
detectors, inspiralling compact binaries -- binary star systems composed of
neutron stars and/or black holes in their late stage of evolution prior the
final coalescence -- require high-accuracy predictions from general relativity.
The orbital dynamics and emitted gravitational waves of these very relativistic
systems can be accurately modelled using state-of-the-art post-Newtonian
theory. In this article we review the Multipolar-Post-Minkowskian approximation
scheme, merged to the standard Post-Newtonian expansion into a single formalism
valid for general isolated matter system. This cocktail of approximation
methods (called MPM-PN) has been successfully applied to compact binary
systems, producing equations of motion up to the fourth-post-Newtonian (4PN)
level, and gravitational waveform and flux to 4.5PN order beyond the Einstein
quadrupole formula. We describe the dimensional regularization at work in such
high post-Newtonian calculations, for curing both ultra-violet and infra-red
divergences. Several landmark results are detailed: the definition of multipole
moments, the gravitational radiation reaction, the conservative dynamics of
circular orbits, the first law of compact binary mechanics, and the non-linear
effects in the gravitational wave propagation (tails, iterated tails and
non-linear memory). We also discuss the case of compact binaries moving on
eccentric orbits, and the effects of spins (both spin-orbit and spin-spin) on
the equations of motion and gravitational wave energy flux and waveform.",1310.1528v5
2022-10-28,Outlook for detecting the gravitational wave displacement and spin memory effects with current and future gravitational wave detectors,"Gravitational wave memory effects arise from non-oscillatory components of
gravitational wave signals, and they are predictions of general relativity in
the nonlinear regime that have close connections to the asymptotic properties
of isolated gravitating systems. There are many types of memory effects that
have been studied in the literature. In this paper we focus on the
""displacement"" and ""spin"" memories, which are expected to be the largest of
these effects from sources such as the binary black hole mergers which have
already been detected by LIGO and Virgo. The displacement memory is a change in
the relative separation of two initially comoving observers due to a burst of
gravitational waves, whereas the spin memory is a portion of the change in
relative separation of observers with initial relative velocity. As both of
these effects are small, LIGO, Virgo, and KAGRA can only detect memory effects
from individual events that are much louder (and thus rarer) than those that
have been detected so far. By combining data from multiple events, however,
these effects could be detected in a population of binary mergers. In this
paper, we present new forecasts for how long current and future detectors will
need to operate in order to measure these effects from populations of binary
black hole systems that are consistent with the populations inferred from the
detections from LIGO and Virgo's first three observing runs. We find that a
second-generation detector network of LIGO, Virgo, and KAGRA operating at the
O4 (""design"") sensitivity for 1.5 years and then operating at the O5 (""plus"")
sensitivity for an additional year can detect the displacement memory. For
Cosmic Explorer, we find that displacement memory could be detected for
individual loud events, and that the spin memory could be detected in a
population within 2 years of observation time.",2210.16266v3
2004-08-03,From incommensurate to dispersive spin-fluctuations: The high-energy inelastic spectrum in superconducting YBa2Cu3O6.5,"We have investigated the spin fluctuations at energy transfers up to ~110
meV, well above the resonance energy (33 meV) in the YBa2Cu3O6.5 ortho-II
superconductor using neutron time-of-flight and triple-axis techniques. The
spectrum at high energies differs from the low-energy incommensurate
modulations previously reported where the incommensurate wave vector is largely
independent of energy. Well above the resonance the peak of the spin response
lies at wave vectors that increase with energy. Within error the excitations at
all energies above the resonance are best described by a ring around the (pi,
pi) position. The isotropic wave-vector pattern differs from a recently
reported square pattern in different but related systems. The spin spectral
weight at high-energies is similar to that in the insulator but the
characteristic velocity is ~40% lower. We introduce a method of extracting the
acoustic and optic weights at all energies from time-of-flight data. We find
that the optic spectral weight extends to surprisingly low-energies of ~25 meV,
and infer that the bilayer spin correlations weaken with increase in hole
doping. When the low-energy optic excitations are taken into account we measure
the total integrated weight around (pi, pi), for energies below 120 meV, to
agree with that expected from the insulator. As a qualitative guide, we compare
spin-wave calculations for an ordered and a disordered stripe model and
describe the inadequacy of this and other stripe models for the high-energy
fluctuations.",0408071v2
2019-11-26,Antiferromagnetic chiral spin density wave and strain-induced Chern insulator in the square lattice Hubbard model with frustration,"We employ the Hartree-Fock approximation to identify the magnetic ground
state of the Hubbard model on a frustrated square lattice. We investigate the
phase diagram as a function of the Coulomb repulsion's strength $U$, and the
ratio $t'/t$ between the nearest and next nearest neighbor hoppings $t$ and
$t'$. At half-filling and for a sufficiently large $U$, an antiferromagnetic
chiral spin density wave order with nonzero spin chirality emerges as the
ground state in a wide regime of the phase diagram near $t'/t=1/\sqrt{2}$,
where the Fermi surface is well-nested for both $(\pi,\pi)$ and
$(\pi,0)/(0,\pi)$ wave vectors. This triple-${\bf Q}$ chiral phase is
sandwiched by a single-${\bf Q}$ N\'{e}el phase and a double-${\bf Q}$ coplanar
spin-vortex crystal phase, at smaller and larger $t'/t$, respectively. The
energy spectrum in the chiral spin density wave phase consists of four pairs of
degenerate bands. These give rise to two pairs of Dirac cones with the same
chirality at the point $({\pi \over 2},{\pi\over 2})$ of the Brillouin zone. We
demonstrate that the application of a diagonal strain induces a $d_{xy}$-wave
next nearest neighbor hopping which, in turn, opens gaps in the two Dirac cones
with opposite masses. As a result, four pairs of well-separated
topologically-nontrivial bands emerge, and each pair of those contributes with
a Chern number $\pm1$. At half-filling, this leads to a zero total Chern number
and renders the topologically-notrivial properties observable only in the ac
response regime. Instead, we show that at $3/4$ filling, the triple-${\bf Q}$
chiral phase yields a Chern insulator exhibiting the quantum anomalous Hall
effect.",1911.11499v2
2017-06-17,Optical momentum and angular momentum in complex media: From the Abraham-Minkowski debate to unusual properties of surface plasmon-polaritons,"We examine the momentum and angular-momentum (AM) properties of monochromatic
optical fields in dispersive and inhomogeneous isotropic media, using the
Abraham- and Minkowski-type approaches, as well as the kinetic (Poynting-like)
and canonical (with separate spin and orbital degrees of freedom) pictures.
While the kinetic Abraham-Poynting momentum describes the energy flux and the
group velocity of the wave, the Minkowski-type quantities, with proper
dispersion corrections, describe the actual momentum and angular momentum
carried by the wave. The kinetic Minkowski-type momentum and AM densities agree
with phenomenological results derived by Philbin. Using the canonical
spin-orbital decomposition, previously used for free-space fields, we find the
corresponding canonical momentum, spin and orbital AM of light in a dispersive
inhomogeneous medium. These acquire a very natural form analogous to the
Brillouin energy density and are valid for arbitrary structured fields. The
general theory is applied to a non-trivial example of a surface
plasmon-polariton (SPP) wave at a metal-vacuum interface. We show that the
integral momentum of the SPP per particle corresponds to the SPP wave vector,
and hence exceeds the momentum of a photon in the vacuum. We also provide the
first accurate calculation of the transverse spin and orbital AM of the SPP.
While the intrinsic orbital AM vanishes, the transverse spin can change its
sign depending on the SPP frequency. Importantly, we present both macroscopic
and microscopic calculations, thereby proving the validity of the general
phenomenological results. The microscopic theory also predicts a transverse
magnetization in the metal (i.e., a magnetic moment for the SPP) as well as the
corresponding direct magnetization current, which explains the difference
between the Abraham and Minkowski momenta.",1706.05493v3
2019-01-17,"Exciting black hole modes via misaligned coalescences: I. Inspiral, transition, and plunge trajectories using a generalized Ori-Thorne procedure","The last gravitational waves emitted in the coalescence of two black holes
are quasi-normal ringing modes of the merged remnant. In general relativity,
the mass and the spin of the remnant black hole uniquely determine the
frequency and damping time of each radiated mode. The amplitudes of these modes
are determined by the mass ratio of the system and the geometry of the
coalescence. This paper is part I of an analysis that aims to compute the
""excitation factors"" associated with misaligned binary black hole coalescence.
To simplify the analysis, we consider a large mass ratio system consisting of a
non-spinning body of mass $\mu$ that inspirals on a quasi-circular trajectory
into a Kerr black hole of mass $M$ and spin parameter $a$, with $\mu/M \ll 1$.
Our goal is to understand how different modes are excited as a function of the
black hole spin $a$ and an angle $I$ which characterizes the misalignment of
the orbit with the black hole's spin axis. Though the large mass ratio limit
does not describe the binaries that are being observed by gravitational-wave
detectors today, this limit makes it possible to quickly and easily explore the
binary parameter space, and to develop insight into how the system's late
ringing waves depend on the binary's geometry. In this first analysis, we
develop the worldline which the small body follows as it inspirals and then
plunges into the large black hole. Our analysis generalizes earlier work by Ori
and Thorne to describe how a non-equatorial circular inspiral transitions into
a plunging trajectory that falls into the black hole. The worldlines which we
develop here are used in part II as input to a time-domain black hole
perturbation solver. This solver computes the gravitational waves generated by
such inspirals and plunges, making it possible to characterize the modes which
the coalescence excites.",1901.05901v2
2022-03-29,Flat-band ferromagnetism in a correlated topological insulator on a honeycomb lattice,"We study the flat-band ferromagnetic phase of a spinfull and time-reversal
symmetric Haldane-Hubbard model on a honeycomb lattice within a bosonization
formalism for flat-band Z$_2$ topological insulators. Such a study extend our
previous one [L. S. G. Leite and R. L. Doretto, Phys. Rev. B {\bf 104}, 155129
(2021)] concerning the flat-band ferromagnetic phase of a correlated Chern
insulator described by a Haldane-Hubbard model. We consider the topological
Hubbard model at $1/4$ filling of its corresponding noninteracting limit and in
the nearly flat band limit of its lower free-electronic bands. We show that it
is possible to define boson operators associated with two distinct spin-flip
excitations, one that changes (mixed-lattice excitations) and a second one that
preserves (same-lattice excitations) the index related with the two triangular
sublattices. Within the bosonization scheme, the fermionic model is mapped into
an effective interacting boson model, whose quadratic term is considered at the
harmonic approximation in order to determine the spin-wave excitation spectrum.
For both mixed and same-lattice excitations, we find that the spin-wave
spectrum is gapped and has two branches, with an energy gap between the lower
and the upper bands at the $K$ and $K'$ points of the first Brillouin zone.
Such a behavior is distinct from the one of the corresponding correlated Chern
insulator, whose spin-wave spectrum has a Goldstone mode at the center of the
first Brillouin zone and Dirac points at $K$ and $K'$ points. We also find some
evidences that the spin-wave bands for the same-lattice excitations might be
topologically nontrivial even in the completely flat band limit.",2203.15573v2
2023-01-24,Distinguishing binary black hole precessional morphologies with gravitational wave observations,"The precessional motion of binary black holes can be classified into one of
three morphologies, based on the evolution of the angle between the components
of the spins in the orbital plane: Circulating, librating around 0, and
librating around $\pi$. These different morphologies can be related to the
binary's formation channel and are imprinted in the binary's gravitational wave
signal. In this paper, we develop a Bayesian model selection method to
determine the preferred spin morphology of a detected binary black hole. The
method involves a fast calculation of the morphology which allows us to
restrict to a specific morphology in the Bayesian stochastic sampling. We
investigate the prospects for distinguishing between the different morphologies
using gravitational waves in the Advanced LIGO/Advanced Virgo network with
their plus-era sensitivities. For this, we consider fiducial high- and low-mass
binaries having different spin magnitudes and signal-to-noise ratios (SNRs). We
find that in the cases with high spin and high SNR, the true morphology is
strongly favored with $\log_{10}$ Bayes factors $\gtrsim 4$ compared to both
alternative morphologies when the binary's parameters are not close to the
boundary between morphologies. However, when the binary parameters are close to
the boundary between morphologies, only one alternative morphology is strongly
disfavored. In the low-spin, high-SNR cases, the true morphology is still
favored with a $\log_{10}$ Bayes factor $\sim 2$ compared to one alternative
morphology. We also consider the gravitational wave signal from GW200129_065458
that has some evidence for precession (modulo data quality issues) and find
that there is no preference for a specific morphology. Our method for
restricting the prior to a given morphology is publicly available through an
easy-to-use Python package called bbh_spin_morphology_prior. (Abridged)",2301.10125v2
2023-05-02,Weyl geometric effects on the propagation of light in gravitational fields,"We consider the effects of Weyl geometry on the propagation of
electromagnetic waves and on the gravitational spin Hall effect of light. It is
usually assumed that in vacuum the electromagnetic waves propagate along null
geodesics, a result which follows from the geometrical optics approximation.
However, this model is valid only in the limit of infinitely high frequencies.
At large but finite frequencies, the ray dynamics is affected by the wave
polarization. Therefore, the propagation of the electromagnetic waves can
deviate from null geodesics, and this phenomenon is known as the gravitational
spin Hall effect of light. On the other hand, Maxwell's equations have the
remarkable property of conformal invariance. This property is a cornerstone of
Weyl geometry and the corresponding gravitational theories. As a first step in
our study, we obtain the polarization-dependent ray equations in Weyl geometry,
describing the gravitational spin Hall effect of light in the presence of
nonmetricity. As a specific example of the spin Hall effect of light in Weyl
geometry, we consider the case of the simplest conformally invariant action,
constructed from the square of the Weyl scalar, and the strength of the Weyl
vector only. The action is linearized in the Weyl scalar by introducing an
auxiliary scalar field. In static spherical symmetry, this theory admits an
exact black hole solution, which generalizes the standard Schwarzschild
solution through the presence of two new terms in the metric, having a linear
and a quadratic dependence on the radial coordinate. We numerically study the
polarization-dependent propagation of light rays in this exact Weyl geometric
metric, and the effects of the presence of the Weyl vector on the magnitude of
the spin Hall effect are estimated.",2305.01313v2
1998-04-29,"Magnetic correlations and quantum criticality in the insulating antiferromagnetic, insulating spin liquid, renormalized Fermi liquid, and metallic antiferromagnetic phases of the Mott system V_2O_3","Magnetic correlations in all four phases of pure and doped vanadium
sesquioxide V_2O_3 have been examined by magnetic thermal neutron scattering.
While the antiferromagnetic insulator can be accounted for by a Heisenberg
localized spin model, the long range order in the antiferromagnetic metal is an
incommensurate spin-density-wave, resulting from a Fermi surface nesting
instability. Spin dynamics in the strongly correlated metal are dominated by
spin fluctuations in the Stoner electron-hole continuum. Furthermore, our
results in metallic V_2O_3 represent an unprecedentedly complete
characterization of the spin fluctuations near a metallic quantum critical
point, and provide quantitative support for the SCR theory for itinerant
antiferromagnets in the small moment limit. Dynamic magnetic correlations for
energy smaller than k_BT in the paramagnetic insulator carry substantial
magnetic spectral weight. However, the correlation length extends only to the
nearest neighbor distance. The phase transition to the antiferromagnetic
insulator introduces a sudden switching of magnetic correlations to a different
spatial periodicity which indicates a sudden change in the underlying spin
Hamiltonian. To describe this phase transition and also the unusual short range
order in the paramagnetic state, it seems necessary to take into account the
orbital degrees of freedom associated with the degenerate d-orbitals at the
Fermi level in V_2O_3.",9804320v3
2003-08-29,Landau Expansion for the Kugel-Khomskii $t_{2g}$ Hamiltonian,"The Kugel-Khomskii (KK) Hamiltonian for the titanates describes spin and
orbital superexchange interactions between $d^1$ ions in an ideal perovskite
structure in which the three $t_{2g}$ orbitals are degenerate in energy and
electron hopping is constrained by cubic site symmetry. In this paper we
implement a variational approach to mean-field theory in which each site, $i$,
has its own $n \times n$ single-site density matrix $\rhov(i)$, where $n$, the
number of allowed single-particle states, is 6 (3 orbital times 2 spin states).
The variational free energy from this 35 parameter density matrix is shown to
exhibit the unusual symmetries noted previously which lead to a
wavevector-dependent susceptibility for spins in $\alpha$ orbitals which is
dispersionless in the $q_\alpha$-direction. Thus, for the cubic KK model
itself, mean-field theory does not provide wavevector `selection', in agreement
with rigorous symmetry arguments. We consider the effect of including various
perturbations. When spin-orbit interactions are introduced, the susceptibility
has dispersion in all directions in ${\bf q}$-space, but the resulting
antiferromagnetic mean-field state is degenerate with respect to global
rotation of the staggered spin, implying that the spin-wave spectrum is
gapless. This possibly surprising conclusion is also consistent with rigorous
symmetry arguments. When next-nearest-neighbor hopping is included, staggered
moments of all orbitals appear, but the sum of these moments is zero, yielding
an exotic state with long-range order without long-range spin order. The effect
of a Hund's rule coupling of sufficient strength is to produce a state with
orbital order.",0308608v1
2005-10-19,Electron spin echo relaxation and envelope modulation of phosphorus shallow donors in silicon,"Spins of single donor atoms are attractive candidates for large scale quantum
information processing in silicon, since quantum computation can be realized
through the manipulation of electron and/or nuclear spins. We here report on
two-pulse electron spin echo experiments on phosphorus shallow donors in
natural and 28Si-enriched silicon epilayers doped with 10^16 cm-3 P donors. The
experiments address the spin-spin relaxation times and mechanisms and provide,
through the electron spin echo envelope modulation (ESEEM) effect, information
on the donor electron wave function. Experiments performed as a function of the
pulse turning angle allowed us to measure the exponential relaxation and
spectral diffusion times depurated by instantaneous diffusion. According to
these results, isotopically purified samples are necessary to reduce the
spectral diffusion contribution and the P shallow donors concentration plays a
fundamental role in determining the intrinsic phase memory time. ESEEM peaks
have been assigned to hyperfine-coupled silicon-29 nuclei at specific
crystallographic positions on the basis of a spectral fit procedure including
instrumental distortions.",0510497v1
2004-07-25,The dynamics of precessing binary black holes using the post-Newtonian approximation,"We investigate the (conservative) dynamics of binary black holes using the
Hamiltonian formulation of the post-Newtonian (PN) equations of motion. The
Hamiltonian we use includes spin-orbit coupling, spin-spin coupling, and mass
monopole/spin-induced quadrupole interaction terms. In the case of both
quasi-circular and eccentric orbits, we search for the presence of chaos (using
the method of Lyapunov exponents) for a large variety of initial conditions.
For quasi-circular orbits, we find no chaotic behavior for black holes with
total mass 10 - 40 solar masses when initially at a separation corresponding to
a Newtonian gravitational-wave frequency less than 150 Hz. Only for rather
small initial radial distances, for which spin-spin induced oscillations in the
radial separation are rather important, do we find chaotic solutions, and even
then they are rare. Moreover, these chaotic quasi-circular orbits are of
questionable astrophysical significance, since they originate from direct
parametrization of the equations of motion rather than from widely separated
binaries evolving to small separations under gravitational radiation reaction.
In the case of highly eccentric orbits, which for ground-based interferometers
are not astrophysically favored, we again find chaotic solutions, but only at
pericenters so small that higher order PN corrections, especially higher spin
PN corrections, should also be taken into account.",0407091v2
1999-07-26,Masses and Internal Structure of Mesons in the String Quark Model,"The relativistic quantum string quark model, proposed earlier, is applied to
all mesons, from pion to $\Upsilon$, lying on the leading Regge trajectories
(i.e., to the lowest radial excitations in terms of the potential quark
models). The model describes the meson mass spectrum, and comparison with
measured meson masses allows one to determine the parameters of the model:
current quark masses, universal string tension, and phenomenological constants
describing nonstring short-range interaction. The meson Regge trajectories are
in general nonlinear; practically linear are only trajectories for light-quark
mesons with non-zero lowest spins. The model predicts masses of many new
higher-spin mesons. A new $K^*(1^-)$ meson is predicted with mass 1910 Mev. In
some cases the masses of new low-spin mesons are predicted by extrapolation of
the phenomenological short-range parameters in the quark masses. In this way
the model predicts the mass of $\eta_b(1S)(0^{-+})$ to be $9500\pm 30$ MeV, and
the mass of $B_c(0^-)$ to be $6400\pm 30$ MeV (the potential model predictions
are 100 Mev lower). The relativistic wave functions of the composite mesons
allow one to calculate the energy and spin structure of mesons. The average
quark-spin projections in polarized $\rho$-meson are twice as small as the
nonrelativistic quark model predictions. The spin structure of $K^*$ reveals an
80% violation of the flavour SU(3). These results may be relevant to
understanding the ``spin crises'' for nucleons.",9907486v1
2005-10-19,Massive relativistic particle model with spin from free two-twistor dynamics and its quantization,"We consider a relativistic particle model in an enlarged relativistic phase
space M^{18} = (X_\mu, P_\mu, \eta_\alpha, \oeta_\dalpha, \sigma_\alpha,
\osigma_\dalpha, e, \phi), which is derived from the free two-twistor dynamics.
The spin sector variables (\eta_\alpha, \oeta_\dalpha, \sigma_\alpha,\
osigma_\dalpha) satisfy two second class constraints and account for the
relativistic spin structure, and the pair (e,\phi) describes the electric
charge sector. After introducing the Liouville one-form on M^{18}, derived by a
non-linear transformation of the canonical Liouville one-form on the
two-twistor space, we analyze the dynamics described by the first and second
class constraints. We use a composite orthogonal basis in four-momentum space
to obtain the scalars defining the invariant spin projections. The
first-quantized theory provides a consistent set of wave equations, determining
the mass, spin, invariant spin projection and electric charge of the
relativistic particle. The wavefunction provides a generating functional for
free, massive higher spin fields.",0510161v2
2002-03-01,Baryon resonances and strong QCD,"Light-baryon resonances (with u,d, and s quarks in the SU(3) classification)
fall on Regge trajectories. When their squared masses are plotted against the
intrinsic orbital angular momenta {\rm L}, $\Delta^*$'s with even and odd
parity can be described by the same Regge trajectory. For a given {\rm L},
nucleon resonances with spin {\rm S}=3/2 are approximately degenerate in mass
with $\Delta$ resonances. To which total angular momentum {\rm L} and {\rm S}
couple has no significant impact on the baryon mass. Nucleons with spin 1/2 are
shifted in mass; the shift is - in units of squared masses - proportional to
the component in the wave function which is antisymmetric in spin and flavor.
Based on these observations, a new baryon mass formula is proposed which
reproduces nearly all known baryon masses. It is shown that the masses are
compatible with a quark-diquark picture while the richness of the
experimentally known states require three particles to participate in the
dynamics. This conflict is resolved by proposing that quarks polarize the QCD
condensates and are surrounded by a polarization cloud shielding the color. A
new interpretation of constituent quarks as colored quark clusters emerges;
their interaction is responsible for the mass spectrum. Fast flavor exchange
between the colored quark clusters exhausts the dynamical richness of the
three-particle dynamics. The colored-quark-cluster model provides a mechanism
in which the linear confinement potential can be traced to the increase of the
volume in which the condensates are polarized. The quark-spin magnetic moment
induces currents in the polarized condensates which absorb the quark-spin
angular momentum: the proton spin is not carried by quark spins. The model
provides a new picture of hybrids and glueballs.",0203002v1
1997-08-30,Nuclear magnetic resonance spectroscopy: An experimentally accessible paradigm for quantum computing,"We present experimental results which demonstrate that nuclear magnetic
resonance spectroscopy is capable of efficiently emulating many of the
capabilities of quantum computers, including unitary evolution and coherent
superpositions, but without attendant wave-function collapse. Specifically, we
have: (1) Implemented the quantum XOR gate in two different ways, one using
Pound-Overhauser double resonance, and the other using a spin-coherence double
resonance pulse sequence; (2) Demonstrated that the square root of the
Pound-Overhauser XOR corresponds to a conditional rotation, thus obtaining a
universal set of gates; (3) Devised a spin-coherence implementation of the
Toffoli gate, and confirmed that it transforms the equilibrium state of a
four-spin system as expected; (4) Used standard gradient-pulse techniques in
NMR to equalize all but one of the populations in a two-spin system, so
obtaining the pseudo-pure state that corresponds to |00>; (5) Validated that
one can identify which basic pseudo-pure state is present by transforming it
into one-spin superpositions, whose associated spectra jointly characterize the
state; (6) Applied the spin-coherence XOR gate to a one-spin superposition to
create an entangled state, and confirmed its existence by detecting the
associated double-quantum coherence via gradient-echo methods.",9709001v2
2008-01-17,Towards the theory of ferrimagnetism,"Two-sublattice ferrimagnet, with spin-$s_1$ operators $\bf{S_{1i}}$ at the
sublattice $A$ site and spin-$s_2$ operators $\bf{S_{2i}}$ at the sublattice
$B$ site, is considered. The magnon of the system, the transversal fluctuation
of the total magnetization, is a complicate mixture of the transversal
fluctuations of the sublattice $A$ and $B$ spins. As a result, the magnons'
fluctuations suppress in a different way the magnetic orders of the $A$ and $B$
sublattices and one obtains two phases. At low temperature $(0,T^*)$ the
magnetic orders of the $A$ and $B$ spins contribute to the magnetization of the
system, while at the high temperature $(T^*,T_N)$, the magnetic order of the
spins with a weaker intra-sublattice exchange is suppressed by magnon
fluctuations, and only the spins with stronger intra-sublattice exchange has
non-zero spontaneous magnetization. The $T^*$ transition is a transition
between two spin-ordered phases in contrast to the transition from spin-ordered
state to disordered state ($T_N$-transition). There is no additional symmetry
breaking, and the Goldstone boson has a ferromagnetic dispersion in both
phases. A modified spin-wave theory is developed to describe the two phases.
All known Neel's anomalous $M(T)$ curves are reproduced, in particular that
with ""compensation point"". The theoretical curves are compared with
experimental ones for sulpho-spinel $MnCr2S_{4-x}Se_{x}$ and rare earth iron
garnets.",0801.2651v1
2009-10-08,Side-jumps in the spin-Hall effect: construction of the Boltzmann collision integral,"We present a systematic derivation of the side-jump contribution to the
spin-Hall current in systems without band structure spin-orbit interactions,
focusing on the construction of the collision integral for the Boltzmann
equation. Starting from the quantum Liouville equation for the density operator
we derive an equation describing the dynamics of the density matrix in the
first Born approximation and to first order in the driving electric field.
Elastic scattering requires conservation of the total energy, including the
spin-orbit interaction energy with the electric field: this results in a first
correction to the customary collision integral found in the Born approximation.
A second correction is due to the change in the carrier position during
collisions. It stems from the part of the density matrix off-diagonal in wave
vector. The two corrections to the collision integral add up and are
responsible for the total side-jump contribution to the spin-Hall current. The
spin-orbit-induced correction to the velocity operator also contains terms
diagonal and off-diagonal in momentum space, which together involve the total
force acting on the system. This force is explicitly shown to vanish (on the
average) in the steady state: thus the total contribution to the spin-Hall
current due to the additional terms in the velocity operator is zero.",0910.1596v2
2009-11-13,Competing quantum paramagnetic ground states of the Heisenberg antiferromagnet on the star lattice,"We investigate various competing paramagnetic ground states of the Heisenberg
antiferromagnet on the two dimensional star lattice which exhibits geometric
frustration. Using slave particle mean field theory combined with a projective
symmetry group analysis, we examine a variety of candidate spin liquid states
on this lattice, including chiral spin liquids, spin liquids with Fermi
surfaces of spinons, and nematic spin liquids which break lattice rotational
symmetry. Motivated by connection to large-N SU(N) theory as well as numerical
exact diagonalization studies, we also examine various valence bond solid (VBS)
states on this lattice. Based on a study of energetics using Gutzwiller
projected states, we find that a fully gapped spin liquid state is the lowest
energy spin liquid candidate for this model. We also find, from a study of
energetics using Gutzwiller projected wave functions and bond operator
approaches, that this spin liquid is unstable towards two different VBS states
-- a VBS state which respects all the Hamitonian symmetries and a VBS state
which exhibits $\sqrt{3}\times\sqrt{3}$ order -- depending on the ratio of the
Heisenberg exchange couplings on the two inequivalent bonds of the lattice. We
compute the triplon dispersion in both VBS states within the bond operator
approach and discuss possible implications of our work for future experiments
on candidate materials.",0911.2702v1
2011-01-01,Signature effects of spin clustering and distribution of spin couplings on magnetization behaviour in Ni-Fe-Mo and Ni-Fe-W alloys,"The spontaneous magnetization as a function of temperature is investigated
for a number of disordered Ni-Fe-Mo and Ni-Fe-W alloys using superconducting
quantum interference device magnetometry, with a focus on the low-T behavior as
well as the critical exponents associated with the magnetic phase transition.
While the low-T magnetization is found to be well described by Bloch's T^{3/2}
law, an extraordinary enhancement of the spin-wave parameter B and the reduced
coefficient B_{3/2}=BT_C ^{3/2} are observed with increasing Fe dilution as
compared to conventional 3d ferromagnets, whereas the critical amplitudes are
found to decrease systematically. Recent locally self-consistent calculations
of finite-temperature spin dynamics in a generic diluted magnet provide an
understanding in terms of two distinct energy scales associated with weakly
coupled bulk spins in the FM matrix and strongly coupled cluster spins. In view
of similar behaviour observed in diluted magnetic semiconductors and other
ferromagnetic alloys, it is proposed that these distinctive features
corresponding to the three important temperature regimes provide macroscopic
indicators of signature effects of spin clustering on magnetization behaviour
in disordered ferromagnets.",1101.0343v2
2011-03-25,Unconventional temperature enhanced magnetism in iron telluride,"Highly energetic magnetic fluctuations, discovered in high-temperature
superconductors (HTSC) by inelastic neutron scattering (INS), are now widely
believed to be vital for the superconductivity. In two competing scenarios,
they either originate from local atomic spins, or are a property of cooperative
spin-density-wave (SDW) behavior of conduction electrons. Both assume clear
partition into localized electrons, giving rise to local spins, and itinerant
ones, occupying well-defined, rigid conduction bands. Here, by performing an
INS study of spin dynamics in iron telluride, a parent material of one of the
iron-based HTSC families, we have discovered that this very assumption fails,
and that conduction and localized electrons are fundamentally entangled. We
find that the real-space structure of magnetic correlations can be explained by
a simple local-spin plaquette model. However, the effective spin implicated in
such a model, appears to increase with the increasing temperature. Thus, we
observe a remarkable redistribution of magnetism between the two groups of
electrons, which occurs in the temperature range relevant for the
superconductivity. The analysis of magnetic spectral weight shows that the
effective spin per Fe at T \approx 10 K, in the antiferromagnetic phase,
corresponds to S \approx 1, consistent with the recent analyses that emphasize
importance of Hund's intra-atomic exchange. However, it grows to S \approx 3/2
in the disordered phase, a result that profoundly challenges the picture of
rigid bands, broadly accepted for HTSC.",1103.5073v1
2011-03-26,Evolution of the spin parameter of accreting compact objects with non-Kerr quadrupole moment,"There is robust observational evidence supporting the existence of $5 - 20$
$M_\odot$ compact bodies in X-ray binary systems and of $10^5 - 10^9$ $M_\odot$
bodies at the center of many galaxies. All these objects are commonly
interpreted as black holes, even is there is no direct evidence that they have
an event horizon. A fundamental limit for a black hole in 4-dimensional general
relativity is the Kerr bound $|a_*| \le 1$, where $a_*$ is the spin parameter.
This is just the condition for the existence of the event horizon. The
accretion process can spin a black hole up to $a_* \approx 0.998$ and some
super-massive objects in galactic nuclei could be rapidly rotating black holes
with spin parameter close to this limit. However, if these super-massive
objects are not black holes, the Kerr bound does not hold and the accretion
process can spin them up to $a_* > 1$. In this paper, I consider compact bodies
with non-Kerr quadrupole moment. I study the evolution of the spin parameter
due to accretion and I find its equilibrium value. Future experiments like the
gravitational wave detector LISA will be able to test if the super-massive
objects at the center of galaxies are the black holes predicted by general
relativity. If they are not black holes, some of them may be super-spinning
objects with $a_* > 1$.",1103.5135v2
2011-09-26,Quantum spin Hamiltonians for the SU(2)_k WZW model,"We propose to use null vectors in conformal field theories to derive model
Hamiltonians of quantum spin chains and corresponding ground state wave
function(s). The approach is quite general, and we illustrate it by
constructing a family of Hamiltonians whose ground states are the chiral
correlators of the SU(2)_k WZW model for integer values of the level k. The
simplest example corresponds to k=1 and is essentially a nonuniform
generalization of the Haldane-Shastry model with long-range exchange couplings.
At level k=2, we analyze the model for N spin 1 fields. We find that the Renyi
entropy and the two-point spin correlator show, respectively, logarithmic
growth and algebraic decay. Furthermore, we use the null vectors to derive a
set of algebraic, linear equations relating spin correlators within each model.
At level k=1, these equations allow us to compute the two-point spin
correlators analytically for the finite chain uniform Haldane-Shastry model and
to obtain numerical results for the nonuniform case and for higher-point spin
correlators in a very simple way and without resorting to Monte Carlo
techniques.",1109.5470v2
2011-11-09,On Relativistic Quantum Information Properties of Entangled Wave Vectors of Massive Fermions,"We study special relativistic effects on the entanglement between either
spins or momenta of composite quantum systems of two spin-1/2 massive
particles, either indistinguishable or distinguishable, in inertial reference
frames in relative motion. For the case of indistinguishable particles, we
consider a balanced scenario where the momenta of the pair are well-defined but
not maximally entangled in the rest frame while the spins of the pair are
described by a one-parameter ($\eta$) family of entangled bipartite states. For
the case of distinguishable particles, we consider an unbalanced scenario where
the momenta of the pair are well-defined and maximally entangled in the rest
frame while the spins of the pair are described by a one-parameter ($\xi$)
family of non-maximally entangled bipartite states. In both cases, we show that
neither the spin-spin ($ss$) nor the momentum-momentum ($mm$) entanglements
quantified by means of Wootters' concurrence are Lorentz invariant quantities:
the total amount of entanglement regarded as the sum of these entanglements is
not the same in different inertial moving frames. In particular, for any value
of the entangling parameters, both $ss$ and $mm$-entanglements are attenuated
by Lorentz transformations and their parametric rates of change with respect to
the entanglements observed in a rest frame have the same monotonic behavior.
However, for indistinguishable (distinguishable) particles, the change in
entanglement for the momenta is (is not) the same as the change in entanglement
for spins. As a consequence, in both cases, no entanglement compensation
between spin and momentum degrees of freedom occurs.",1111.2348v1
2012-03-13,Effects of post-Newtonian Spin Alignment on the Distribution of Black-Hole Recoils,"Recent numerical relativity simulations have shown that the final black hole
produced in a binary merger can recoil with a velocity as large as 5,000 km/s.
Because of enhanced gravitational-wave emission in the so-called ""hang-up""
configurations, this maximum recoil occurs when the black-hole spins are
partially aligned with the orbital angular momentum. We revisit our previous
statistical analysis of post-Newtonian evolutions of black-hole binaries in the
light of these new findings. We demonstrate that despite these new
configurations with enhanced recoil velocities, spin alignment during the
post-Newtonian stage of the inspiral will still significantly suppress (or
enhance) kick magnitudes when the initial spin of the more massive black hole
is more (or less) closely aligned with the orbital angular momentum than that
of the smaller hole. We present a preliminary study of how this post-Newtonian
spin alignment affects the ejection probabilities of supermassive black holes
from their host galaxies with astrophysically motivated mass ratio and initial
spin distributions. We find that spin alignment suppresses (enhances) ejection
probabilities by ~ 40% (20%) for an observationally motivated mass-dependent
galactic escape velocity, and by an even greater amount for a constant escape
velocity of 1,000 km/s. Kick suppression is thus at least a factor two more
efficient than enhancement.",1203.2920v2
2012-07-31,Spin excitations in a single La$_2$CuO$_4$ layer,"The dynamics of S=1/2 quantum spins on a 2D square lattice lie at the heart
of the mystery of the cuprates
\cite{Hayden2004,Vignolle2007,Li2010,LeTacon2011,Coldea2001,Headings2010,Braicovich2010}.
In bulk cuprates such as \LCO{}, the presence of a weak interlayer coupling
stabilizes 3D N\'{e}el order up to high temperatures. In a truly 2D system
however, thermal spin fluctuations melt long range order at any finite
temperature \cite{Mermin1966}. Further, quantum spin fluctuations transfer
magnetic spectral weight out of a well-defined magnon excitation into a
magnetic continuum, the nature of which remains controversial
\cite{Sandvik2001,Ho2001,Christensen2007,Headings2010}. Here, we measure the
spin response of \emph{isolated one-unit-cell thick layers} of \LCO{}. We show
that coherent magnons persist even in a single layer of \LCO{} despite the loss
of magnetic order, with no evidence for resonating valence bond (RVB)-like spin
correlations \cite{Anderson1987,Hsu1990,Christensen2007}. Thus these
excitations are well described by linear spin wave theory (LSWT). We also
observe a high-energy magnetic continuum in the isotropic magnetic response.
This high-energy continuum is not well described by 2 magnon LSWT, or indeed
any existing theories.",1208.0018v1
2012-10-01,51V-NMR study of antiferromagnetic state and spin dynamics in the quasi-one-dimensional BaCo2V2O8,"We report on our 51V-NMR study of static and dynamical magnetic properties in
the quasi-one-dimensional antiferromagnet BaCo2V2O8. Although the NMR spectrum
shows well-defined antiferromagnetic (AF) order in the N\'eel ground state, the
AF characteristic from the NMR spectrum is incomplete between 3.5 K and TN= 5.4
K, which could be affected by quantum spin fluctuations. The AF NMR spectrum
indicates two V sites experiencing different magnetic field magnitudes, HA1=2.1
kOe and HA2=3.8 kOe. These internal fields could be explained by accounting for
the classical and the pseudo-dipolar fields from Co2+ spins with a proposed
magnetic structure based on the neutron diffraction measurements. In the
paramagnetic state, the nuclear spin relaxation is dominated by AF spin
fluctuations through the dipolar-type coupling between V and surrounding Co2+
ions. The linear relation between the nuclear spin-lattice relaxation rate
1/T1T and the magnetic susceptibility chi indicates that the Q component of
magnetic susceptibility chi(Q) is roughly proportional to chi, where Q is the
AF wave number. A change in slope of 1/T1T with respect to \chi around 150 K
suggests a change in the AF spin fluctuation spectrum.",1210.0272v1
2013-08-16,Theory of metallic double perovskites with spin orbit coupling and strong correlations; application to ferrimagnetic Ba2FeReO6,"We consider a model of the double perovskite Ba2FeReO6, a room temperature
ferrimagnet with correlated and spin-orbit coupled Re t2g electrons moving in
the background of Fe moments stabilized by Hund's coupling. We show that for
such 3d/5d double perovskites, strong correlations on the 5d-element (Re) are
essential in driving a half-metallic ground state. Incorporating both strong
spin-orbit coupling and the Hubbard repulsion on Re leads to a band structure
consistent with ab initio calculations. Using our model, we find a large spin
polarization at the Fermi level, and obtain a semi-quantitative understanding
of the saturation magnetization of Ba2FeReO6, as well as X-ray magnetic
circular dichroism data indicating a significant orbital magnetization. Based
on the orbital populations obtained in our theory, we predict a specific doping
dependence to the tetragonal distortion accompanying ferrimagnetic order.
Finally, the combination of a net magnetization and spin-orbit interactions is
shown to induce Weyl nodes in the band structure, and we predict a significant
intrinsic anomalous Hall effect in hole-doped Ba2FeReO6. The uncovered
interplay of strong correlations and spin-orbit coupling lends partial support
to our previous work, which used a local moment description to capture the spin
wave dispersion found in neutron scattering measurements. Our work is of broad
interest for understanding metallic 4d-based and 5d-based double perovskites
which are of fundamental interest and of possible relevance to spintronic
applications.",1308.3701v2
2013-11-18,Mergers of binary neutron stars with realistic spin,"Simulations of binary neutron stars have seen great advances in terms of
physical detail and numerical quality. However, the spin of the neutron stars,
one of the simplest global parameters of binaries, remains mostly unstudied. We
present the first, fully nonlinear general relativistic dynamical evolutions of
the last three orbits for constraint satisfying initial data of spinning
neutron star binaries, with astrophysically realistic spins aligned and
anti-aligned to the orbital angular momentum. The initial data is computed with
the constant rotational velocity approach. The dynamics of the systems is
analyzed in terms of gauge-invariant binding energy vs. orbital angular
momentum curves. By comparing to a binary black hole configuration we can
estimate the different tidal and spin contributions to the binding energy for
the first time. First results on the gravitational wave forms are presented.
The phase evolution during the orbital motion is significantly affected by
spin-orbit interactions, leading to delayed or early mergers. Furthermore, a
frequency shift in the main emission mode of the hyper massive neutron star is
observed. Our results suggest that a detailed modeling of merger waveforms
requires the inclusion of spin, even for the moderate magnitudes observed in
binary neutron star systems.",1311.4443v2
2014-02-05,Spatial and temporal propagation of Kondo correlations,"We address the fundamental question how the spatial Kondo correlations are
building up in time assuming an initially decoupled impurity spin $\vec{S}_{\rm
imp}$. We investigate the time-dependent spin-correlation function
$\chi(\vec{r},t) = \langle \vec{S}_\mathrm{imp} \vec{s}(\vec{r}) \rangle (t)$
in the Kondo model with antiferromagnetic and ferromagnetic couplings where $
\vec{s}(\vec{r})$ denotes the spin density of the conduction electrons after
switching on the Kondo coupling at time $t=0$. We present data obtained from a
time-dependent numerical renormalisation group (TD-NRG) calculation. We gauge
the accuracy of our two-band NRG by the spatial sum-rules of the equilibrium
correlation functions and the reproduction of the analytically exactly known
spin-correlation function of the decoupled Fermi sea. We find a remarkable
building up of Kondo-correlation outside of the light cone defined by the Fermi
velocity of the host metal. By employing a perturbative approach exact in
second-order of the Kondo coupling, we connect these surprising correlations to
the intrinsic spin-density entanglement of the Fermi sea. The thermal wave
length supplies a cutoff scale at finite temperatures beyond which correlations
are exponentially suppressed. We present data for the frequency dependent
retarded spin-spin susceptibility and use the results to calculate the
real-time response of a weak perturbation in linear response: within the
spatial resolution no response outside of the light cone is found.",1402.1028v2
2014-07-29,Formation of magnetic skyrmions with tunable properties in PdFe bilayer deposited on Ir(111),"We perform an extensive study of the spin-configurations in a PdFe bilayer on
Ir(111) in terms of ab initio and spin-model calculations. We use the
spin-cluster expansion technique to obtain spin model parameters, and solve the
Landau-Lifshitz-Gilbert equations at zero temperature. In particular, we focus
on effects of layer relaxations and the evolution of the magnetic ground state
in external magnetic field. In the absence of magnetic field, we find a
spin-spiral ground state, while applying external magnetic field skyrmions are
generated in the system. Based on energy calculations of frozen spin
configurations with varying magnetic field we obtain excellent agreement for
the phase boundaries with available experiments. We find that the wave length
of spin-spirals and the diameter of skyrmions decrease with increasing inward
Fe layer relaxation which is correlated with the increasing ratio of the
nearest-neighbor Dzyaloshinskii-Moriya interaction and the isotropic exchange
coupling, $D/J$. Our results also indicate that the applied field needed to
stabilize the skyrmion lattice increases when the diameter of individual
skyrmions decreases. Based on our observations, we suggest that the formation
of the skyrmion lattice can be tuned by small structural modification of the
thin film.",1407.7718v2
2014-10-23,Spectroscopic confirmation of linear relation between Heisenberg- and interfacial Dzyaloshinskii-Moriya-exchange in polycrystalline metal films,"Proposals for novel spin-orbitronic logic1 and memory devices2 are often
predicated on assumptions as to how materials with large spin-orbit coupling
interact with ferromagnets when in contact. Such interactions give rise to a
host of novel phenomena, such as spin-orbit torques3,4 , chiral
spin-structures5,6 and chiral spin-torques. These chiral properties are related
to the anti-symmetric exchange, also referred to as the interfacial
Dzyaloshinskii-Moriya interaction (DMI)9,10. For numerous phenomena, the
relative strengths of the symmetric Heisenberg exchange and the DMI is of great
importance. Here, we use optical spin-wave spectroscopy (Brillouin light
scattering) to directly determine the DMI vector for a series of Ni80Fe20/Pt
samples, and then compare the nearest-neighbor DMI coupling energy with the
independently measured Heisenberg exchange integral. We find that the
Ni80Fe20-thickness-dependencies of both the microscopic symmetric- and
antisymmetric-exchange are identical, consistent with the notion that the basic
mechanisms of the DMI and Heisenberg exchange essentially share the same
underlying physics, as was originally proposed by Moriya11. While of
significant fundamental importance, this result also leads us to a deeper
understanding of DMI and how it could be optimized for spin-orbitronic
applications.",1410.6243v1
2015-07-06,Spontaneous polarization of composite fermions in the $n=1$ Landau level of graphene,"Motivated by recent experiments that reveal expansive fractional quantum Hall
states in the $n=1$ graphene Landau level and suggest a nontrivial role of the
spin degree of freedom [Amet {\em et al.}, Nat. Common. {\bf 6}, 5838 (2014)],
we perform accurate quantitative study of the the competition between
fractional quantum Hall states with different spin polarizations. We find that
the fractional quantum Hall effect is well described in terms of composite
fermions, but the spin physics is qualitatively different from that in the
$n=0$ Landau level. In particular, for the states at filling factors $n/(2n\pm
1)$, both exact diagonalization and the composite fermion theory show that the
ground state is fully spin polarized and supports a robust spin wave mode even
in the limit of vanishing Zeeman coupling. Thus, even though composite fermions
are formed, a mean field description that treats them as weakly interacting
particles breaks down, and the exchange interaction between them is strong
enough to cause a qualitative change in the behavior by inducing full spin
polarization. We also verify that the fully spin polarized composite fermion
Fermi sea has lower energy than the paired Pfaffian state at the relevant half
fillings in the $n=1$ graphene Landau level, indicating a lack of fractional
quantum Hall effect at half filling in the $n=1$ graphene Landau level.",1507.01334v3
2016-06-02,Orbital selective spin excitations and their impact on superconductivity of LiFe1-xCoxAs,"We use neutron scattering to study spin excitations in single crystals of
LiFe$_{0.88}$Co$_{0.12}$As, which is located near the boundary of the
superconducting phase of LiFe$_{1-x}$Co$_{x}$As and exhibits non-Fermi-liquid
behavior indicative of a quantum critical point. By comparing spin excitations
of LiFe$_{0.88}$Co$_{0.12}$As with a combined density functional theory (DFT)
and dynamical mean field theory (DMFT) calculation, we conclude that
wave-vector correlated low energy spin excitations are mostly from the $d_{xy}$
orbitals, while high-energy spin excitations arise from the $d_{yz}$ and
$d_{xz}$ orbitals. Unlike most iron pnictides, the strong orbital selective
spin excitations in LiFeAs family cannot be described by anisotropic Heisenberg
Hamiltonian. While the evolution of low-energy spin excitations of
LiFe$_{1-x}$Co$_x$As are consistent with electron-hole Fermi surface nesting
condition for the $d_{xy}$ orbital, the reduced superconductivity in
LiFe$_{0.88}$Co$_{0.12}$As suggests that Fermi surface nesting conditions for
the $d_{yz}$ and $d_{xz}$ orbitals are also important for superconductivity in
iron pnictides.",1606.00727v1
2016-08-03,Real space mean-field theory of a spin-1 Bose gas in synthetic dimensions,"The internal degrees of freedom provided by ultracold atoms give a route for
realizing higher dimensional physics in systems with limited spatial
dimensions. Non-spatial degrees of freedom in these systems are dubbed
""synthetic dimensions"". This connection is useful from an experimental
standpoint but complicated by the fact that interactions alter the condensate
ground state. Here we use the Gross-Pitaevskii equation to study ground state
properties of a spin-1 Bose gas under the combined influence of an optical
lattice, spin-orbit coupling, and interactions at the mean field level. The
associated phases depend on the sign of the spin-dependent interaction
parameter and the strength of the optical lattice potential. We find ""charge""
and spin density wave phases which are directly related to helical spin order
in real space and affect the behavior of edge currents in the synthetic
dimension. We determine the resulting phase diagram as a function of the
spin-orbit coupling and spin-dependent interaction strength, considering both
attractive (ferromagnetic) and repulsive (polar) spin-dependent interactions.
Our results are applicable to current and future experiments, specifically with
$^{87}$Rb, $^{7}$Li, $^{41}$K, and $^{23}$Na.",1608.01346v2
2017-07-18,Spin and valley polarized one-way Klein tunneling in photonic topological insulators,"Advances of condensed matter physics in exploiting the spin degree of freedom
of electrons led to the emergence of the field of spintronics, which envisions
new and more efficient approaches to data transfer, computing, and storage
[1-3]. These ideas have been inspiring analogous approaches in photonics, where
the manipulation of an artificially engineered pseudo-spin degrees of freedom
is enabled by synthetic gauge fields acting on light [4,5,6]. The ability to
control these additional degrees of freedom can significantly expand the
landscape of available optical responses, which may revolutionize optical
computing and the basic means of controlling light in photonic devices across
the entire electromagnetic spectrum. Here we demonstrate a new class of
photonic systems, described by effective Hamiltonians in which competing
synthetic gauge fields engineered in pseudo-spin, chirality/sublattice and
valley subspaces result in band gap opening at one of the valleys, while the
other valley exhibits Dirac-like conical dispersion. It is shown that such
effective response has dramatic implications on photon transport, among which:
(i) spin-polarized and valley-polarized one-way Klein tunneling and (ii)
topological edge states that coexist within the Dirac continuum for opposite
valley and spin polarizations. These phenomena offer new ways to control light
in photonics, in particular for on-chip optical isolation, filtering and
wave-division multiplexing by selective action on their pseudo-spin and valley
degrees of freedom.",1707.05802v1
2017-08-24,Black Hole Spin Axis in Numerical Relativity,"Colliding black holes are systems of profound interest in both gravitational
wave astronomy and in gravitation theory, and a variety of methods have been
developed for modeling their dynamics in detail. The features of these dynamics
are determined by the masses of the holes and by the magnitudes and axes of
their spins. While masses and spin magnitudes can be defined in reasonably
unambiguous ways, the spin axis is a concept which despite great physical
importance is seriously undermined by the coordinate freedom of general
relativity. Despite a great wealth of detailed numerical simulations of generic
spinning black hole collisions, very little attention has gone into defining or
justifying the definitions of the spin axis used in the numerical relativity
literature. In this paper, we summarize and contrast the various spin direction
measures available in the SpEC code, including a comparison with a method
common in other codes, we explain why these measures have shown qualitatively
different nutation features than one would expect from post-Newtonian theory,
and we derive and implement new measures that give much better agreement.",1708.07325v2
2018-01-24,The hangup effect in unequal mass binary black hole mergers and further studies of their gravitational radiation and remnant properties,"We present the results of 74 new simulations of nonprecessing spinning black
hole binaries with mass ratios $q=m_1/m_2$ in the range $1/7\leq q\leq1$ and
individual spins covering the parameter space $-0.95\leq\alpha_{1,2}\leq0.95$
with one runs with spins of $\pm0.95$. We supplement those runs with 107
previous simulations to study the hangup effect in black hole mergers, i.e. the
delay or prompt merger of spinning holes with respect to non spinning binaries.
We perform the numerical evolution for typically the last ten orbits before the
merger and down to the formation of the final remnant black hole. This allows
us to study the hangup effect for unequal mass binaries leading us to identify
the spin variable that controls the number of orbits before merger as
$\vec{S}_{hu}\cdot{\hat{L}},$ where
$\vec{S}_{hu}=(1+\frac12\frac{m_2}{m_1})\vec{S}_1+(1+\frac12\frac{m_1}{m_2})\vec{S}_2$.
We also combine the total results of those 181 simulations to obtain improved
fitting formulae for the remnant final black hole mass, spin and recoil
velocity as well as for the peak luminosity and peak frequency of the
gravitational strain, and find new correlations among them. This accurate new
set of simulations enhances the number of available numerical relativity
waveforms available for parameter estimation of gravitational wave
observations.",1801.08162v1
2018-03-30,Dynamical DMRG study of spin and charge excitations in the four-leg t-t'-J ladder,"The ground state of the t-t'-J ladder with four legs favors a striped charge
distribution for the parameters corresponding to hole-doped cuprate
superconductors. We investigate the dynamical spin and charge structure factors
of the model by using the dynamical density matrix renormalization group (DMRG)
and clarify the influence of the stripe on the structure factors. The dynamical
charge structure factor along the momentum direction from q=(0,0) to (pi,0)
clearly shows low-energy excitations corresponding to the stripe order in hole
doping. On the other hand, the stripe order weakens in electron doping,
resulting in fewer low-energy excitations in the charge channel. In the spin
channel, we find incommensurate spin excitations near q=(pi,pi) forming an
hourglass behavior in hole doping, while in electron doping we find clearly
spin-wave-like dispersions starting from q=(pi,pi). Along the (0,0)-(pi,0)
direction, the spin excitations are strongly influenced by the stripes in hole
doping, resulting in two branches that form a discontinuous behavior in the
dispersion. In contrast, the electron-doped systems show a downward shift in
energy toward (pi,0). These behaviors along the (0,0)-(pi,0) direction are
qualitatively similar to momentum-dependent spin excitations recently observed
by resonant inelastic x-ray scattering experiments in hole- and electron-doped
cuprate superconductors.",1803.11342v2
2018-05-03,Unravelling the complex magnetic structure of multiferroic pyroxene NaFeGe2O6: A combined experimental and theoretical study,"Magnetic order and the underlying magnetic model of the multiferroic pyroxene
NaFeGe2O6 are systematically investigated by neutron powder diffraction,
thermodynamic measurements, density-functional bandstructure calculations, and
Monte-Carlo simulations. Upon cooling, NaFeGe2O6 first reveals one-dimensional
spin-spin correlations in the paramagnetic state below about 50 K, revealed by
magnetic diffuse scattering. The sinusoidal spin-density wave with spins along
the a-direction sets in at 13 K, followed by the cycloidal configuration with
spins lying in the (ac) plane below 11.6 K. Microscopically, the strongest
magnetic coupling runs along the structural chains, J1 ' 12 K, which is likely
related to the one-dimensional spin-spin correlations. The interchain couplings
J2 ' 3:8K and J3 ' 2:1K are energetically well balanced and compete, thus
giving rise to the incommensurate order in sharp contrast to other
transition-metal pyroxenes, where one type of the interchain couplings
prevails. The magnetic model of NaFeGe2O6 is further completed by the weak
single-ion anisotropy along the a-direction. Our results resolve the earlier
controversies regarding the magnetic order in NaFeGe2O6 and establish relevant
symmetries of the magnetic structures. These results, combined with symmetry
analysis, enable us to identify the possible mechanisms of the magnetoelectric
coupling in this compound. We also elucidate microscopic conditions for the
formation of incommensurate magnetic order in pyroxenes.",1805.01436v2
2018-05-03,Post-Newtonian spin-tidal couplings for compact binaries,"We compute the spin-tidal couplings that affect the dynamics of two orbiting
bodies at the leading order in the post-Newtonian (PN) framework and to linear
order in the spin. These corrections belong to two classes: (i) terms arising
from the coupling between the ordinary tidal terms and the point-particle
terms, which depend on the standard tidal Love numbers of order $l$ and affect
the gravitational-wave (GW) phase at $(2l+5/2)$PN order and (ii) terms
depending on the rotational tidal Love numbers, recently introduced in previous
work, that affect the GW phase at $(2l+1/2+\delta_{2l})$PN order. For circular
orbits and spins orthogonal to the orbital plane, all leading-order spin-tidal
terms enter the GW phase at $1.5$PN order relative to the standard,
quadrupolar, tidal deformability term (and, thus, before the standard octupolar
tidal deformability terms). We present the GW phase that includes all tidal
terms up to $6.5$PN order and to linear order in the spin. We comment on a
conceptual issue related to the inclusion of the rotational tidal Love numbers
in a Lagrangian formulation and on the relevance of spin-tidal couplings for
parameter estimation in coalescing neutron-star binaries and for tests of
gravity.",1805.01487v3
2018-11-14,Wide nutation: binary black-hole spins repeatedly oscillating from full alignment to full anti-alignment,"Within the framework of 2PN black-hole binary spin precession, we explore
configurations where one of the two spins oscillates from being completely
aligned with the orbital angular momentum to being completely anti-aligned with
it during a single precession cycle. This ""wide nutation"" is the extreme limit
of the generic phenomenon of spin nutation in black-hole binaries. Crucially,
wide nutation happens on the short precession time scale and it is not a
secular effect due to gravitational-wave radiation reaction. The spins of these
binaries, therefore, flip repeatedly as one of these special configurations is
entered. Binaries with total mass $M$, mass ratio $q$, and dimensionless spin
$\chi_1$ ($\chi_2$) of the more (less) massive black hole are allowed to
undergo wide nutation at binary separations $r \leq r_{\rm wide} \equiv [(q
\chi_2 - \chi_1)/(1-q)]^2 M$. Sources that are more likely to nutate widely
have similar masses and effective spins close to zero.",1811.05979v2
2019-11-25,Quantum field theory of topological spin dynamics,"We develop a field theory of quantum magnets and magnetic (semi)metals, which
is suitable for the analysis of their universal and topological properties. The
systems of interest include collinear, coplanar and general non-coplanar
magnets. At the basic level, we describe the dynamics of magnetic moments using
smooth vector fields in the continuum limit. Dzyaloshinskii-Moriya interaction
is captured by a non-Abelian vector gauge field, and chiral spin couplings
related to topological defects appear as higher-rank antisymmetric tensor gauge
fields. We distinguish type-I and type-II magnets by their equilibrium response
to the non-Abelian gauge flux, and characterize the resulting lattices of
skyrmions and hedgehogs, the spectra of spin waves, and the chiral response to
external perturbations. The general spin-orbit coupling of electrons is
similarly described by non-Abelian gauge fields, including higher-rank tensors
related to the electronic Berry flux. Itinerant electrons and local moments
exchange their gauge fluxes through Kondo and Hund interactions. Hence, by
utilizing gauge fields, this theory provides a unifying physical picture of
``intrinsic'' and ``topological'' anomalous Hall effects, spin-Hall effects,
and other correlations between the topological properties of electrons and
moments. We predict ``topological'' magnetoelectric effect in materials prone
to hosting hedgehogs. Links to experiments and model calculations are provided
by deriving the couplings and gauge fields from generic microscopic models,
including the Hubbard model with spin-orbit interactions. We establish the
possible existence of novel quantum spin liquids that exhibit a fractional
magnetoelectric effect, and discuss a few applications to topological magnetic
conductors like Mn$_3$Sn and Pr$_2$Ir$_2$O$_7$.",1911.11155v2
2018-11-29,Electric-Dipole Spin Resonances,"Resonance phenomena in solids generally fall into two distinct classes,
electric and magnetic, driven, respectively, by the $E$ and $H$ components of
the electromagnetic wave incident on the solid. The canonical examples of the
two types of resonances are the electron cyclotron resonance (CR) and the
electron paramagnetic resonance (EPR), originating from the electron orbital
and spin degrees of freedom, respectively. The behavior becomes considerably
more interesting (and more complicated) in the presence of the spin-orbital
interaction. In this case, a more general type of resonance may occur, which is
driven by the electric excitation mechanism and involves the spin degrees of
freedom. Such electric-dipole spin resonance (EDSR) may occur at the spin
excitation frequency or at a combination of the orbital and spin frequencies,
spanning a wide bandwidth. The EDSR phenomenon, first predicted by Rashba
(1960), has been probed experimentally in 3D solids with different crystal
symmetries, as well as in low-dimensional systems (heterojunctions, inversion
layers, dislocations and impurity states). Due to its electric dipole origin,
the EDSR features a relatively high intensity, which may exceed by orders of
magnitude the EPR intensity. This review summarizes the work on EDSR prior to
1991, laying out the theoretical framework and discussing different
experimental systems in which the EDSR-related physics can be realized and
explored.",1812.01721v1
2016-03-10,Variational Monte Carlo study of chiral spin liquid in quantum antiferromagnet on the triangular lattice,"By using Gutzwiller projected fermionic wave functions and variational Monte
Carlo technique, we study the spin-$1/2$ Heisenberg model with the
first-neighbor ($J_1$), second-neighbor ($J_2$), and additional scalar chiral
interaction $J_{\chi}{\bf S}_i \cdot ({\bf S}_j \times {\bf S}_k)$ on the
triangular lattice. In the non-magnetic phase of the $J_1-J_2$ triangular model
with $0.08 \lesssim J_2/J_1 \lesssim 0.16$, recent density-matrix
renormalization group (DMRG) studies [Zhu and White, Phys. Rev. B {\bf 92},
041105 (2015); Hu, Gong, Zhu, and Sheng, Phys. Rev. B {\bf 92}, 140403 (2015)]
find a possible gapped spin liquid with the signal of a competition between a
chiral and a $Z_2$ spin liquid. Motivated by the DMRG results, we consider the
chiral interaction $J_{\chi}{\bf S}_i \cdot ({\bf S}_j \times {\bf S}_k)$ as a
pertubation for this non-magnetic phase. We find that with growing $J_{\chi}$,
the gapless U(1) Dirac spin liquid, which has the best variational energy for
$J_{\chi}=0$, exhibits the energy instability towards a gapped spin liquid with
non-trivial magnetic fluxes and nonzero chiral order. We calculate topological
Chern number and ground-state degeneracy, both of which identify this flux
state as the chiral spin liquid with fractionalized Chern number $C=1/2$ and
two-fold topological degeneracy. Our results indicate a positive direction to
stabilize a chiral spin liquid near the non-magnetic phase of the $J_1-J_2$
triangular model.",1603.03365v2
2018-04-29,Probing spin-phonon interactions in silicon carbide with Gaussian acoustics,"Hybrid spin-mechanical systems provide a platform for integrating quantum
registers and transducers. Efficient creation and control of such systems
require a comprehensive understanding of the individual spin and mechanical
components as well as their mutual interactions. Point defects in silicon
carbide (SiC) offer long-lived, optically addressable spin registers in a
wafer-scale material with low acoustic losses, making them natural candidates
for integration with high quality factor mechanical resonators. Here, we show
Gaussian focusing of a surface acoustic wave in SiC, characterized by a novel
stroboscopic X-ray diffraction imaging technique, which delivers direct, strain
amplitude information at nanoscale spatial resolution. Using ab initio
calculations, we provide a more complete picture of spin-strain coupling for
various defects in SiC with C3v symmetry. This reveals the importance of shear
for future device engineering and enhanced spin-mechanical coupling. We
demonstrate all-optical detection of acoustic paramagnetic resonance without
microwave magnetic fields, relevant to sensing applications. Finally, we show
mechanically driven Autler-Townes splittings and magnetically forbidden Rabi
oscillations. These results offer a basis for full strain control of
three-level spin systems.",1804.10996v2
2019-05-07,Thermal spin photonics in the near-field of nonreciprocal media,"The interplay of spin angular momentum and thermal radiation is a frontier
area of interest to nanophotonics as well as topological physics. Here, we show
that a thick planar slab of a nonreciprocal material, despite being at thermal
equilibrium with its environment, can exhibit nonzero photon spin angular
momentum and nonzero radiative heat flux in its vicinity. We identify them as
the persistent thermal photon spin (PTPS) and the persistent planar heat
current (PPHC) respectively. With a practical example system, we reveal that
the fundamental origin of these phenomena is connected to spin-momentum locking
of thermally excited evanescent waves. We also discover spin magnetic moment of
surface polaritons in nonreciprocal photonics that further clarifies these
features. We then propose a novel thermal photonic imaging experiment based on
Brownian motion that allows one to witness these surprising features by
directly looking at them using a lab microscope. We further demonstrate the
universal behavior of these near-field thermal radiation phenomena through a
comprehensive analysis of gyroelectric, gyromagnetic and magneto-electric
nonreciprocal materials. Together, these results expose a surprisingly little
explored research area of thermal spin photonics with prospects for new avenues
related to non-Hermitian topological photonics and radiative heat transport.",1905.02745v2
2020-09-11,"Next-to-leading order spin-orbit effects in the equations of motion, energy loss and phase evolution of binaries of compact bodies in the effective field theory approach","We compute spin-orbit effects in the equations of motion, binding energy and
energy loss of binary systems of compact objects at the next-to-leading order
in the post-Newtonian (PN) approximation in the effective field theory (EFT)
framework. We then use these quantities to compute the evolution of the orbital
frequency and accumulated orbital phase including spin-orbit effects beyond the
dominant order. To obtain the results presented in this paper, we make use of
known ingredients in the EFT literature, such as the potential and the
multipole moments with spin effects at next-to-leading order, and which are
given in the linearized harmonic gauge and with the spins in the locally flat
frame. We also obtain the correction to the center-of-mass frame caused by
spin-orbit effects at next-to-leading order. We demonstrate the equivalence
between our EFT results and those which were obtained elsewhere using different
formalisms. The results presented in this paper provide us with the final
ingredients for the construction of theoretical templates for gravitational
waves including next-to-leading order spin-orbit effects, which will be
presented in a future publication.",2009.05628v1
2021-08-26,Spin-orbit misalignment from triple-star common envelope evolution,"I study a triple star common envelope evolution (CEE) of a tight binary
system that is spiraling-in inside a giant envelope and launches jets that
spin-up the envelope with an angular momentum component perpendicular to the
orbital angular momentum of the triple star system. This occurs when the
orbital plane of the tight binary system and that of the triple star system are
inclined to each other, so the jets are not along the triple star orbital
angular momentum. The merger of the tight binary stars also tilts the envelope
spin direction. If the giant is a red supergiant (RSG) star that later
collapses to form a black hole (BH) the BH final spin is misaligned with the
orbital angular momentum. Therefore, CEE of neutron star (NS) or BH tight
binaries with each other or with one main sequence star (MSS) inside the
envelope of an RSG, where the jets power a common envelope jets supernova
(CEJSN) event, might end with a NS/BH-NS/BH close binary system with spin-orbit
misalignment. Such binaries can later merge to be gravitational waves sources.
I list five triple star scenarios that might lead to spin-orbit misalignments
of NS/BH-NS/BH binary systems, two of which predict that the two spins be
parallel to each other. In the case of a tight binary system of two MSSs inside
an asymptotic giant branch star the outcome is an additional non-spherical
component to the mass loss with the formation of a messy planetary nebula.",2108.11876v2
2021-08-30,On the large apparent black hole spin-orbit misalignment angle in GW200115,"GW200115 is one of the first two confidently detected gravitational-wave
events of neutron star-black hole mergers. An interesting property of this
merger is that the black hole, if spinning rapidly, has its spin axis
negatively aligned (with a misalignment angle $> 90^{\circ}$) with the binary
orbital angular momentum vector. Although such a large spin-orbit misalignment
angle naturally points toward a dynamical origin, the measured neutron
star-black hole merger rate exceeds theoretical predictions of the dynamical
formation channel. In the canonical isolated binary formation scenario, the
immediate progenitor of GW200115 is likely to be a binary consisting of a black
hole and a helium star, with the latter forming a neutron star during a
supernova explosion. Since the black hole is generally expected to spin along
the pre-supernova binary orbital angular momentum axis, a large neutron star
natal kick is required to produce the observed misalignment angle. Using simple
kinematic arguments, we find that a misalignment angle $> 90^{\circ}$ in
GW200115-like systems implies a kick velocity $\sim 600\, \text{km/s}$ and a
kick direction within $\approx 30 ^{\circ}$ of the pre-supernova orbital plane.
We discuss different interpretations of the large apparent black hole
spin-orbit misalignment angle, including a non-spinning black hole.",2108.13540v2
2003-12-19,The 2-matrix of the spin-polarized electron gas: contraction sum rules and spectral resolutions,"The spin-polarized homogeneous electron gas with densities $\rho_\uparrow$
and $\rho_\downarrow$ for electrons with spin `up' ($\uparrow$) and spin `down'
($\downarrow$), respectively, is systematically analyzed with respect to its
lowest-order reduced densities and density matrices and their mutual relations.
The three 2-body reduced density matrices $\gamma_{\uparrow\uparrow}$,
$\gamma_{\downarrow\downarrow}$, $\gamma_a$ are 4-point functions for electron
pairs with spins $\uparrow\uparrow$, $\downarrow\downarrow$, and antiparallel,
respectively. From them, three functions $G_{\uparrow\uparrow}(x,y)$,
$G_{\downarrow\downarrow}(x,y)$, $G_a(x,y)$, depending on only two variables,
are derived. These functions contain not only the pair densities but also the
1-body reduced density matrices. The contraction properties of the 2-body
reduced density matrices lead to three sum rules to be obeyed by the three key
functions $G_{ss}$, $G_a$. These contraction sum rules contain corresponding
normalization sum rules as special cases. The momentum distributions
$n_\uparrow(k)$ and $n_\downarrow(k)$, following from $f_\uparrow(r)$ and
$f_\downarrow(r)$ by Fourier transform, are correctly normalized through
$f_s(0)=1$. In addition to the non-negativity conditions
$n_s(k),g_{ss}(r),g_a(r)\geq 0$ [these quantities are probabilities], it holds
$n_s(k)\leq 1$ and $g_{ss}(0)=0$ due to the Pauli principle and $g_a(0)\leq 1$
due to the Coulomb repulsion. Recent parametrizations of the pair densities of
the spin-unpolarized homogeneous electron gas in terms of 2-body wave functions
(geminals) and corresponding occupancies are generalized (i) to the
spin-polarized case and (ii) to the 2-body reduced density matrix giving thus
its spectral resolutions.",0312519v1
2019-09-30,"High-harmonic generation by electric polarization, spin current, and magnetization","High-harmonic generation (HHG), a typical nonlinear optical effect, has been
actively studied in electron systems such as semiconductors and
superconductors. As a natural extension, we theoretically study HHG from
electric polarization, spin current and magnetization in magnetic insulators
under terahertz (THz) or gigahertz (GHz) electromagnetic waves. We use simple
one-dimensional spin chain models with or without multiferroic coupling between
spins and the electric polarization, and study the dynamics of the spin chain
coupled to an external ac electric or magnetic field. We map spin chains to
two-band fermions and invoke an analogy of semiconductors and superconductors.
With a quantum master equation and Lindblad approximation, we compute the time
evolution of the electric polarization, spin current, and magnetization,
showing that they exhibit clear harmonic peaks. We also show that the
even-order HHG by magnetization dynamics can be controlled by static magnetic
fields in a wide class of magnetic insulators. We propose experimental setups
to observe these HHG, and estimate the required strength of the ac electric
field $E_0$ for detection as $E_0\sim100$kV/cm--1MV/cm, which corresponds to
the magnetic field $B_0\sim0.1$T--1T. The estimated strength would be relevant
also for experimental realizations of other theoretically-proposed nonlinear
optical effects in magnetic insulators such as Floquet engineering of magnets.",1910.00146v3
2019-12-16,Neutron Spin Resonance in the Heavily Hole-doped KFe$_{2}$As$_{2}$ Superconductor,"We report high-resolution neutron scattering measurements of the low energy
spin fluctuations of KFe$_{2}$As$_{2}$, the end member of the hole-doped
Ba$_{1-x}$K$_x$Fe$_2$As$_2$ family with only hole pockets, above and below its
superconducting transition temperature $T_c$ ($\sim$ 3.5 K). Our data reveals
clear spin fluctuations at the incommensurate wave vector ($0.5\pm\delta$, 0,
$L$), ($\delta$ = 0.2)(1-Fe unit cell), which exhibit $L$-modulation peaking at
$L=0.5$. Upon cooling to the superconducting state, the incommensurate spin
fluctuations gradually open a spin-gap and form a sharp spin resonance mode.
The incommensurability ($2\delta$ = 0.4) of the resonance mode ($\sim1.2$ meV)
is considerably larger than the previously reported value ($2\delta$
$\approx0.32$) at higher energies ($\ge\sim6$ meV). The determination of the
momentum structure of spin fluctuation in the low energy limit allows a direct
comparison with the realistic Fermi surface and superconducting gap structure.
Our results point to an $s$-wave pairing with a reversed sign between the hole
pockets near the zone center in KFe$_{2}$As$_{2}$.",1912.07220v1
2020-01-15,Photocurrent measurements in topological insulator $\text{Bi}_2\text{Se}_3$ nanowires,"Circular photogalvanic currents are a promising new approach for
spin-optoelectronics. To date, such currents have only been induced in
topological insulator flakes or extended films. It is not clear whether they
can be generated in nanodevices. In this paper, we demonstrate the generation
of circular photogalvanic currents in $\text{Bi}_2\text{Se}_3$ nanowires. Each
nanowire shows topological surface states. Here, we generate and distinguish
the different photocurrent contributions via the driving light wave. We
separate the circular photogalvanic currents from those due to thermal Seebeck
effects, through controlling the laser light polarization. The results reveal a
spin-polarized surface-Dirac electron flow in the nanowires arising from
spin-momentum locking and spin-orbit effects. The second photocurrent
contribution described in this letter is caused by the thermal Seebeck effect.
By scanning the photocurrent, it can be spatially resolved; upon reversing the
gradient direction along the nanowire, the photocurrent changes its sign, and
close to the gold contacts, the amplitudes of the different photocurrent
contributions are affected by the proximity to the contacts. In the center of
the nanowires, where the effects from the gold contact/ topological insulator
stacks vanish, the spin-polarized current remains constant along the nanowires.
This opens up a new method of all-optical spin current generation in
topological insulator nanowires and hybrid structures for nanoscale
spin-orbitronics.",2001.05249v2
2020-06-30,Spin and density self-ordering in dynamic polarization gradients fields,"We study the zero-temperature quantum phase diagram for a two-component
Bose-Einstein condensate in an optical cavity. The two atomic spin states are
Raman coupled by two transverse orthogonally-polarized, blue detuned plane-wave
lasers inducing a repulsive cavity potential. For weak pump the lasers favor a
state with homogeneous density and predefined uniform spin direction. When one
pump laser is polarized parallel to the cavity mode polarization, the photons
coherently scattered into the resonator induce a polarization gradient along
the cavity axis, which mediates long-range density-density, spin-density, and
spin-spin interactions. We show that the coupled atom-cavity system implements
central aspects of the $t$-$J$-$V$-$W$ model with a rich phase diagram. At the
mean-field limit we identify at least four qualitatively distinct density- and
spin-ordered phases including ferro- and anti-ferromagnetic order along the
cavity axis, which can be controlled via the pump strength and detuning. A real
time observation of amplitude and phase of the emitted fields bears strong
signatures of the realized phase and allows for real-time determination of
phase transition lines. Together with measurements of the population imbalance
most properties of the phase diagram can be reconstructed.",2006.16582v2
2020-07-16,Majorana end states in an interacting quantum wire,"We propose and investigate a simple one-dimensional model for a
single-channel quantum wire hosting electrons that interact repulsively and are
subject to a significant spin-orbit interaction. We show that an external
Zeeman magnetic field, applied at the right angle to the Rashba spin-orbit
axis, drives the wire into a correlated spin-density wave state with gapped
spin and gapless charge excitations. By computing the ground-state degeneracies
of the model with either (anti-)periodic or open boundary conditions, we
conclude that the correlated spin-density state realizes a gapless
symmetry-protected topological phase, as the ground state is unique in the ring
geometry while it is two-fold degenerate in the wire with open boundaries.
Microscopically the two-fold degeneracy is found to be protected by the
conservation of the magnetization parity. Open boundaries induce localized
zero-energy (midgap) states which are described, at the special Luther-Emery
point of the model, by Majorana fermions. We find that spin densities at the
open ends of the wire exhibit unusual long-ranged correlations despite the fact
that all correlations in the bulk of the wire decay in a power-law or
exponential fashion. Our study exposes the crucial importance of the
long-ranged string operator needed to implement the correct commutation
relations between spin densities at different points in the wire. Along the way
we rederive the low-energy theory of Galilean-invariant electron systems in
terms of current operators.",2007.08482v3
2021-01-17,Experimental determination of the magnetic interactions of frustrated Cairo pentagon lattice materials,"We present inelastic neutron scattering measurements of the Cairo pentagon
lattice magnets Bi$_2$Fe$_4$O$_9$ and Bi$_4$Fe$_5$O$_{13}$F, supported by high
field magnetisation measurements of Bi$_2$Fe$_4$O$_9$. Using linear spin wave
theory and mean field analyses we determine the spin exchange interactions and
single-ion anisotropy in these materials. The Cairo lattice is geometrically
frustrated and consists of two inequivalent magnetic sites, both occupied by
Fe$^{3+}$ ions and connected by two competing nearest neighbour interactions.
We found that one of these interactions, coupling nearest neighbour spins on
the three-fold symmetric sites, is extremely strong and antiferromagnetic.
These strongly coupled dimers are then weakly coupled to a framework formed
from spins occupying the other inequivalent site. In addition we found that the
Fe$^{3+}$ $S=5/2$ spins have a non-negligible single-ion anisotropy, which
manifests as a spin anisotropy gap in the neutron spectrum and a spin-flop
transition in high field magnetisation measurements.",2101.06786v1
2021-07-02,Quantum spin solver near saturation: QS$^3_{~}$,"We develop a program package named QS$^{3}$ [\textipa{kj\'u:-\'es-kj\'u:b}]
based on the (thick-restart) Lanczos method for analyzing spin-1/2 XXZ-type
quantum spin models on spatially uniform/non-uniform lattices near fully
polarized states, which can be mapped to dilute hardcore Bose systems. All
calculations in QS$^{3}$, including eigenvalue problems, expectation values for
one/two-point spin operators, and static/dynamical spin structure factors, are
performed in the symmetry-adapted bases specified by the number
$N_{\downarrow}$ of down spins and the wave number $\boldsymbol{k}$ associated
with the translational symmetry without using the bit representation for
specifying spin configurations. Because of these treatments, QS$^{3}$ can
support large-scale quantum systems containing more than 1000 sites with dilute
$N_{\downarrow}$. We show the benchmark results of QS$^{3}$ for the low-energy
excitation dispersion of the isotropic Heisenberg model on the
$10\times10\times10$ cubic lattice, the static and dynamical spin structure
factors of the isotropic Heisenberg model on the $10\times10$ square lattice,
and the open-MP parallelization efficiency on the supercomputer (Ohtaka) based
on AMD Epyc 7702 installed at the Institute for the Solid State Physics (ISSP).
Theoretical backgrounds and the user interface of QS$^{3}$ are also described.",2107.00872v1
2021-09-24,Analysis of Different Sets of Spin-Adapted Substitution Operators in Open-Shell Coupled Cluster Theory,"In spin-adapted open-shell coupled cluster (CC) theory, the choice of
spin-free spatial substitution operators is generally not unique. Due to an
increasing linear dependence of the cluster operator (with increasing
substitution level), the options to span identical linear spaces increase
rapidly. In this work several sets of non-orthogonal as well as orthogonal
spin-adapted substitution operators are generated and used in consecutive
Configuration Interaction (CI) and CC calculations. All (full) operator sets
were generated to span the same linear space. The results are analyzed in terms
of the produced wave function quality and the amount of recovered correlation
energy w.r.t. full CI. In particular, the influence of different amounts of
spectators, the influence of orthogonality as well as the effect of spin
incompleteness was investigated. It was found that CC calculations involving
fewer spectators lead to more accurate results in general. Here correlation
energy differences of up to 0.32\% for minimal to maximal spectating sets were
obtained. As expected, all conducted calculations led to identical results for
non-orthogonal and orthogonal operator sets. Spin completeness on the other
hand was found to be of great importance. Spin-incomplete Cluster operators led
to significant errors in both the correlation energies and the FCI overlap.",2109.12214v1
2022-01-25,Frustration model and spin excitations in the helimagnet FeP,"The metallic compound FeP belongs to the class of materials that feature a
complex noncollinear spin order driven by magnetic frustration. While its
double-helix magnetic structure with a period $\lambda_{\text{s}} \approx 5c$,
where $c$ is the lattice constant, was previously well determined, the relevant
spin-spin interactions that lead to that ground state remain unknown. By
performing extensive inelastic neutron scattering measurements, we obtained the
spin-excitation spectra in a large part of the momentum-energy space. The
spectra show that the magnons are gapped with a gap energy of $\sim$5 meV.
Despite the 3D crystal structure, the magnon modes display strongly anisotropic
dispersions, revealing a quasi-one-dimensional character of the magnetic
interactions in FeP. The physics of the material, however, is not determined by
the dominating exchange, which is ferromagnetic. Instead, the weaker
two-dimensional antiferromagnetic interactions between the rigid ferromagnetic
spin chains drive the magnetic frustration. Using linear spin-wave theory, we
were able to construct an effective Heisenberg Hamiltonian with an anisotropy
term capable of reproducing the observed spectra. This enabled us to quantify
the exchange interactions in FeP and determine the mechanism of its magnetic
frustration.",2201.10358v2
2022-08-29,Spin-statistics relation and the Abelian braiding phase for anyons in fractional quantum Hall effect,"Quasihole excitations in fractional quantum Hall (FQH) systems exhibit
fractional statistics and fractional spin, but how the spin-statistics relation
emerges from many-body physics remains poorly understood. Here we prove a
spin-statistics relation using only FQH wave functions, on both the sphere and
disk geometry. In particular, the proof on the disk generalizes to all
quasiholes in realistic systems, which have a finite size and could be deformed
into arbitrary shapes. Different components of the quasihole spins are linked
to different conformal Hilbert spaces (CHS), which are nullspaces of model
Hamiltonians that host the respective FQH ground states and quasihole states.
Understanding how the intrinsic spin of the quasiholes is linked to different
CHS is crucial for the generalized spin-statistics relation that takes into
account the effect of metric deformation. In terms of the experimental
relevance, this enables us to study the effect of deformation and disorder that
introduces an additional source of Berry curvature, an aspect of anyon braiding
that has been largely neglected in previous literature.",2208.13786v3
2022-12-04,Superradiant Masing with Solid-state Spins at Room Temperature,"Steady-state superradiance and superradiant lasing attract significant
attentions in the field of optical lattice clocks, but have not been achieved
so far due to the technical challenges and atom loss problem. In this article,
we propose that their counter-part may be observed in the microwave domain with
solid-state spins-microwave resonator systems at room temperature with
realistic technical restrictions. To validate our proposal, we investigate
systematically the system dynamics and steady-state by solving quantum master
equations for the multi-level and multi-process dynamic of trillions of spins.
To this end, we employ a mean-field approach, and convert the mean-field
dynamics of the spin ensemble into the one in a more intuitive Dicke state
picture. Our calculations show that for systems with nitrogen vacancy center
spins and pentacene molecular spins the superradiant Rabi oscillations occur
firstly due to transitions among different Dicke states, and the subsequent
continuous-wave superradiant masing can achieve a linewidth well below
millihertz. Our work may guide further exploration of transient and
steady-state superradiant masing with the mentioned and other solid-state spins
systems, such as silicon vacancy centers in silicon carbide and boron vacancy
centers in hexagonal boron nitride, where the coherent radiation with
ultra-narrow linewidth may find applications in deep-space communications,
radio astronomy and high-precision metrology.",2212.01864v1
2023-07-06,Spin-Polarized Majorana Zero Modes in Proximitized Superconducting Penta-Silicene Nanoribbons,"We theoretically investigate the possibility of obtaining Majorana zero modes
(MZMs) in penta-silicene nanoribbons (p-SiNRs) with induced \textit{p}-wave
superconductivity. The model explicitly considers an external magnetic field
perpendicularly applied to the nanoribbon plane, as well as an extrinsic Rashba
spin-orbit coupling (RSOC), in addition to the first nearest neighbor hopping
term and \textit{p}-wave superconducting pairing. By analyzing the dispersion
relation profiles, we observe the successive closing and reopening of the
induced superconducting gap with a single spin component, indicating a
spin-polarized topological phase transition (TPT). Correspondingly, the plots
of the energy spectrum versus the chemical potential reveal the existence of
zero-energy states with a preferential spin orientation characterized by
nonoverlapping wave functions localized at opposite ends of the superconducting
p-SiNRs. These findings strongly suggest the emergence of topologically
protected, spin-polarized MZMs at the ends of the p-SiNRs with induced
\textit{p}-wave superconducting pairing, which can be realized by proximitizing
the nanoribbon with an \textit{s}-wave superconductor, such as lead. The
proposal paves the way for silicene-based Majorana devices hosting multiple
MZMs with a well-defined spin orientation, with possible applications in
fault-tolerant quantum computing platforms and Majorana spintronics.",2307.03185v1
2023-08-14,Systematic determination of coupling constants in spin clusters from broken-symmetry mean-field solutions,"Quantum-chemical calculations aimed at deriving magnetic coupling constants
in exchange-coupled spin clusters commonly utilize a broken-symmetry (BS)
approach. This involves calculating several distinct collinear spin
configurations, predominantly by density-functional theory (DFT). The energies
of these configurations are interpreted in terms of the Heisenberg model to
determine coupling constants for spin pairs. However, this energy-based
procedure has inherent limitations, primarily in its inability to provide
information on isotropic spin interactions beyond those included in the
Heisenberg model. Biquadratic exchange or multi-center terms, for example, are
usually inaccessible and hence assumed to be negligible. The present work
introduces a novel approach employing BS mean-field solutions, specifically
Hartree-Fock wave functions, for the construction of effective spin
Hamiltonians. This expanded method facilitates the extraction of a broader
range of coupling parameters by considering not only the energies, but also
Hamiltonian and overlap elements between different BS states. We demonstrate
how comprehensive s = 1/2 Hamiltonians, including multi-center terms, can be
straightforwardly constructed from a complete set of BS solutions. The approach
is exemplified for small clusters within the context of the half-filled
single-band Hubbard model. This allows to contrast the current strategy against
exact results, thereby offering an enriched understanding of the
spin-Hamiltonian construction from BS solutions.",2308.07484v1
2023-08-25,Spin effects in gravitational waveforms and fluxes for binaries on eccentric orbits to the third post-Newtonian order,"Compact binaries can have non-negligible orbital eccentricities in the
frequency band of ground-based gravitational-wave detectors, depending on their
astrophysical formation channels. To accurately determine the parameters of
such systems, waveform models need to incorporate eccentricity effects. In this
paper, we consider an eccentric binary of spinning nonprecessing compact
objects, and derive the energy and angular momentum fluxes at infinity, as well
as the gravitational waveform modes to the third post-Newtonian order. The
novel results of this paper include the next-to-leading order instantaneous
spin-orbit and spin-spin contributions to the waveform modes, in addition to
the hereditary (tail and memory) contributions to the modes and fluxes for
eccentric orbits. The instantaneous contributions are derived for generic
motion, while the hereditary contributions are computed in a small-eccentricity
expansion, but we consider a resummation that makes them valid for large
eccentricities. We employ a quasi-Keplerian parametrization of the motion using
harmonic coordinates and the covariant spin-supplementary condition, which
complements some results in the literature in other coordinates. Our results
can be useful in improving the accuracy of waveform models for spinning
binaries on eccentric orbits.",2308.13606v2
2023-11-05,A variational Monte Carlo approach to the SU(4) spin-orbital model on the triangular lattice,"Previous investigations have suggested that the simplest spin-orbital model
on the simplest frustrated lattice can host a nematic quantum spin-orbital
liquid state. Namely, the orbital degeneracy of the SU(4) Kugel-Khomskii (KK)
model tends to enhance quantum fluctuations and stabilize a quantum
spin-orbital liquid exhibiting stripy features on the triangular lattice, as
revealed by the state-of-the-art method of the density matrix renormalization
group boosted by Gutzwiller projected wave functions. In this work, using the
variational quantum Monte Carlo method, we have studied several spin-orbital
liquid states, including a uniform $\pi$ flux state, three stripy states, and a
plaquette state, on the $L\times{}L$ torus up to $L=24$. It turns out that one
of these stripy states, called the ""stripe-II"" state, is energetically favored.
This ground state breaks the $C_6$ symmetry of the lattice, resulting in a
reduced $C_2$ symmetry and doubled unit cells, while preserving the SU(4)
spin-orbital rotation symmetry. Such a nematic quantum spin-orbital liquid
state can be characterized by a parton Fermi surface (FS) consisting of open
orbits in the Brillouin zone, in contrast to the circular FS of the uniform
$\pi$-flux state.",2311.02639v2
2023-12-12,Dzyaloshinskii-Moriya interaction inducing weak ferromagnetism in centrosymmetric altermagnets and weak ferrimagnetism in noncentrosymmetric altermagnets,"The Dzyaloshinskii-Moriya interaction (DMI) has explained successfully the
weak ferromagnetism in some centrosymmetric antiferromagnets. However, in the
last years, it was generally claimed that the DMI is not effective in
centrosymmetric systems. We reconciled these views by separating the
conventional antiferromagnets and altermagnets. Altermagnets represent
collinear antiferromagnetic compounds with spin-up and spin-down sublattices
connected only by mirror and roto-translational symmetries. Consequently, the
system shows even-parity wave spin order in the k-space lifting the Kramer's
degeneracy in the non-relativistic band structure. We emphasize that the DMI
can create weak ferromagnetism in centrosymmetric altermagnets while it is not
effective in centrosymmetric conventional antiferromagnets. Additionally, DMI
can create weak ferromagnetism or weak ferrimagnetism in noncentrosymmetric
altermagnets. Once the spin-orbit coupling is included in an altermagnetic
system without time-reversal symmetry, the components of spin moments of the
two sublattices along the Neel vector are antiparallel but the other two spin
components orthogonal to the N\'eel vector can be either parallel or
antiparallel for centrosymetric systems. For noncentrosymmetric systems, we can
have different bands showing parallel or antiparallel spin components resulting
in weak ferrimagnetism. We can divide the altermagnetic compounds into classes
based on the weak ferromagnetism or weak ferrimagnetism properties. The weak
ferromagnetism and weak ferrimagnetism induced by DMI is a property exclusively
of the altermagnets, not present in either ferromagnets or conventional
antiferromagnets so we propose that altermagnets should be classified based on
this property.",2312.07678v2
2024-02-12,Gravitational Magnus effect from scalar dark matter,"In fluid dynamics, the Magnus effect is the force perpendicular to the motion
of a spinning object as it moves through a medium. In general relativity, an
analogous effect exists for a spinning compact object moving through matter,
purely as a result of gravitational interactions. In this work we consider a
Kerr black hole moving at relativistic velocities through scalar dark matter
that is at rest. We simulate the system numerically and extract the total
spin-curvature force on the black hole perpendicular to its motion. We confirm
that the force scales linearly with the dimensionless spin parameter $a/M$ of
the black hole up to $a/M = 0.99$, and measure its dependence on the speed $v$
of the black hole in the range $0.1 \le v \le 0.55$ for a fixed spin. Compared
to previous analytic work applicable at small $v$, higher-order corrections in
the velocity are found to be important: the total force is nonzero, and the
dependence is not linear in $v$. We find that in all cases the total force is
in the opposite direction to the hydrodynamical analogue, although at low
speeds it appears to approach the expectation that the Weyl and Magnus
components cancel. Spin-curvature effects may leave an imprint on gravitational
wave signals from extreme mass-ratio inspirals, where the secondary black hole
has a nonnegligible spin and moves in the presence of a dark matter cloud. We
hope that our simulations can be used to support and extend the limits of
analytic results, which are necessary to better quantify such effects in the
relativistic regime.",2402.07977v1
2024-03-12,Discrete Laplacian thermostat for flocks and swarms: the fully conserved Inertial Spin Model,"Experiments on bird flocks and midge swarms reveal that these natural systems
are well described by an active theory in which conservation laws play a
crucial role. By building a symplectic structure that couples the particles'
velocities to the generator of their internal rotations (spin), the Inertial
Spin Model (ISM) reinstates a second-order temporal dynamics that captures many
phenomenological traits of flocks and swarms. The reversible structure of the
ISM predicts that the total spin is a constant of motion, the central
conservation law responsible for all the novel dynamical features of the model.
However, fluctuations and dissipation introduced in the original model to make
it relax, violate the spin conservation law, so that the ISM aligns with the
biophysical phenomenology only within finite-size regimes, beyond which the
overdamped dynamics characteristic of the Vicsek model takes over. Here, we
introduce a novel version of the ISM, in which the irreversible terms needed to
relax the dynamics strictly respect the conservation of the spin. We perform a
numerical investigation of the fully conservative model, exploring both the
fixed-network case, which belongs to the equilibrium class of Model G, and the
active case, characterized by self-propulsion of the agents and an
out-of-equilibrium reshuffling of the underlying interaction network. Our
simulations not only capture the correct spin wave phenomenology of the ordered
phase, but they also yield dynamical critical exponents in the near-ordering
phase that agree very well with the theoretical predictions.",2403.07644v1
2006-10-24,Non-dissipative tidal synchronization in accreting binary white dwarf systems,"We study a non-dissipative hydrodynamical mechanism that can stabilize the
spin of the accretor in an ultra-compact double white dwarf binary. This novel
synchronization mechanism relies on a nonlinear wave interaction spinning down
the background star. The essential physics of the synchronization mechanism is
summarized as follows. As the compact binary coalesces due to gravitational
wave emission, the largest star eventually fills its Roche lobe and accretion
starts. The accretor then spins up due to infalling material and eventually
reaches a spin frequency where a normal mode of the star is resonantly driven
by the gravitational tidal field of the companion. If the resonating mode
satisfies a set of specific criteria, which we elucidate in this paper, it
exchanges angular momentum with the background star at a rate such that the
spin of the accretor locks at this resonant frequency, even though accretion is
ongoing. Some of the accreted angular momentum that would otherwise spin up the
accretor is fed back into the orbit through this resonant tidal interaction.
  Two modes capable of stabilizing the accretor's spin are the l=4,m=2 and
l=5,m=3 CFS unstable hybrid r-modes, which stabilize the spin of the accretor
at frequency 2.6 and 1.5 times the binary's orbital frequency respectively.
Since the stabilization mechanism relies on continuously driving a mode at
resonance, its lifetime is limited since eventually the mode amplitude
saturates due to non-linear mode-mode coupling. Rough estimates of the lifetime
of the effect lie from a few orbits to millions of years.",0610692v2
2007-03-06,Black Hole Spin Evolution: Implications for Short-hard Gamma Ray Bursts and Gravitational Wave Detection,"The evolution of the spin and tilt of black holes in compact black hole -
neutron star and black hole - black hole binary systems is investigated within
the framework of the coalescing compact star binary model for short gamma ray
bursts via the population synthesis method. Based on recent results on
accretion at super critical rates in slim disk models, estimates of natal
kicks, and the results regarding fallback in supernova models, we obtain the
black hole spin and misalignment. It is found that the spin parameter, a_spin},
is less than 0.5 for initially non rotating black holes and the tilt angle,
i_tilt, is less than 45 deg for 50% of the systems in black hole - neutron star
binaries. Upon comparison with the results of black hole - neutron star merger
calculations we estimate that only a small fraction (~ 0.01) of these systems
can lead to the formation of a torus surrounding the coalesced binary
potentially producing a short-hard gamma ray burst. On the other hand, for high
initial black hole spin parameters (a_spin>0.6) this fraction can be
significant (~ 0.4). It is found that the predicted gravitational radiation
signal for our simulated population does not significantly differ from that for
non rotating black holes. Due to the (i) insensitivity of signal detection
techniques to the black hole spin and the (ii) predicted overall low
contribution of black hole binaries to the signal we find that the detection of
gravitational waves are not greatly inhibited by current searches with non
spinning templates. It is pointed out that the detection of a black hole -
black hole binary inspiral system with LIGO or VIRGO may provide a direct
measurement of the initial spin of a black hole.",0703131v2
2006-08-11,Measuring coalescing massive binary black holes with gravitational waves: The impact of spin-induced precession,"The coalescence of massive black holes generates gravitational waves (GWs)
that will be measurable by space-based detectors such as LISA to large
redshifts. The spins of a binary's black holes have an important impact on its
waveform. Specifically, geodetic and gravitomagnetic effects cause the spins to
precess; this precession then modulates the waveform, adding periodic structure
which encodes useful information about the binary's members. Following
pioneering work by Vecchio, we examine the impact upon GW measurements of
including these precession-induced modulations in the waveform model. We find
that the additional periodicity due to spin precession breaks degeneracies
among certain parameters, greatly improving the accuracy with which they may be
measured. In particular, mass measurements are improved tremendously, by one to
several orders of magnitude. Localization of the source on the sky is also
improved, though not as much -- low redshift systems can be localized to an
ellipse which is roughly ${a few} \times 10$ arcminutes in the long direction
and a factor of 2-4 smaller in the short direction. Though not a drastic
improvement relative to analyses which neglect spin precession, even modest
gains in source localization will greatly facilitate searches for
electromagnetic counterparts to GW events. Determination of distance to the
source is likewise improved: We find that relative error in measured luminosity
distance is commonly $\sim 0.2%-0.7%$ at $z \sim 1$. Finally, with the
inclusion of precession, we find that the magnitude of the spins themselves can
typically be determined for low redshift systems with an accuracy of about
$0.1%-10 %$, depending on the spin value, allowing accurate surveys of mass and
spin evolution over cosmic time.",0608062v5
2013-02-26,Massive disk formation in the tidal disruption of a neutron star by a nearly extremal black hole,"Black hole-neutron star (BHNS) binaries are important sources of
gravitational waves for second-generation interferometers, and BHNS mergers are
also a proposed engine for short, hard gamma-ray bursts. The behavior of both
the spacetime (and thus the emitted gravitational waves) and the neutron star
matter in a BHNS merger depend strongly and nonlinearly on the black hole's
spin. While there is a significant possibility that astrophysical black holes
could have spins that are nearly extremal (i.e. near the theoretical maximum),
to date fully relativistic simulations of BHNS binaries have included
black-hole spins only up to $S/M^2$=0.9, which corresponds to the black hole
having approximately half as much rotational energy as possible, given the
black hole's mass. In this paper, we present a new simulation of a BHNS binary
with a mass ratio $q=3$ and black-hole spin $S/M^2$=0.97, the highest simulated
to date. We find that the black hole's large spin leads to the most massive
accretion disk and the largest tidal tail outflow of any fully relativistic
BHNS simulations to date, even exceeding the results implied by extrapolating
results from simulations with lower black-hole spin. The disk appears to be
remarkably stable. We also find that the high black-hole spin persists until
shortly before the time of merger; afterwards, both merger and accretion spin
down the black hole.",1302.6297v2
2015-11-03,Relativistic Simulations of Eccentric Binary Neutron Star Mergers: One-arm Spiral Instability and Effects of Neutron Star Spin,"We perform general-relativistic hydrodynamical simulations of dynamical
capture binary neutron star mergers, emphasizing the role played by the neutron
star spin. Dynamical capture mergers may take place in globular clusters, as
well as other dense stellar systems, where most neutron stars have large spins.
We find significant variability in the merger outcome as a function of initial
neutron star spin. For cases where the spin is aligned with the orbital angular
momentum, the additional centrifugal support in the remnant hypermassive
neutron star can prevent the prompt collapse to a black hole, while for
antialigned cases the decreased total angular momentum can facilitate the
collapse to a black hole. We show that even moderate spins can significantly
increase the amount of ejected material, including the amount unbound with
velocities greater than half the speed of light, leading to brighter
electromagnetic signatures associated with kilonovae and interaction of the
ejecta with the interstellar medium. Furthermore, we find that the initial
neutron star spin can strongly affect the already rich phenomenology in the
postmerger gravitational wave signatures that arise from the oscillation modes
of the hypermassive neutron star. In several of our simulations, the resulting
hypermassive neutron star develops the one-arm ($m=1$) spiral instability, the
most pronounced cases being those with small but non-negligible neutron star
spins. For long-lived hypermassive neutron stars, the presence of this
instability leads to improved prospects for detecting these events through
gravitational waves, and thus may give information about the neutron star
equation of state.",1511.01093v2
2018-02-15,The spin of the second-born black hole in coalescing binary black holes,"Various binary black hole formation channels have been proposed since the
first gravitational event GW150914 was discovered by the Advanced Laser
Interferometer Gravitational-Wave Observatory (AdLIGO). For all evolutionary
channels based on the evolution of isolated binaries, the immediate progenitor
of the binary black hole is a close binary system composed of a black hole and
a helium star. We perform detailed binary evolution and systematically explore
the parameter space of initial binary properties, including initial black hole
and helium star masses, initial rotation of the helium star as well as
metallicity. We argue that the spin of the first-born black hole at its birth
is negligible ($\lesssim 0.1$), hence the second-born black hole's spin
dominates the measured effective spin, $\chi_{\rm eff}$, from gravitational
wave events of double black hole mergers. We find that tides can be important
only when orbital periods are shorter than 2 days. Upon core collapse, the
helium star produces a black hole (the second-born black hole in the system)
with a spin that can span the entire range from zero to maximally spinning. We
show that the bimodal distribution of the spin of the second-born black hole
obtained in recent papers is mainly due to oversimplifying assumptions. We find
an anti-correlation between the merging timescale of the two black holes,
T$_{\rm merger}$, and the effective spin $\chi_{\rm eff}$. Finally, we provide
new prescriptions for the tidal coefficient E$_2$ for both H-rich and the
helium-rich stars. We predict that, with future improvements to AdLIGO's
sensitivity, the sample of merging binary black hole systems will show an
overdensity of sources with positive but small $\chi_{\rm eff}$. originating
from lower mass black hole mergers born at low redshift.",1802.05738v1
2008-06-10,"Spin-S Kitaev model: Classical Ground States, Order by Disorder and Exact Correlation Functions","In the first part of this paper, we study the spin-S Kitaev model using spin
wave theory. We discover a remarkable geometry of the minimum energy surface in
the N-spin space. The classical ground states, called Cartesian or CN-ground
states, whose number grows exponentially with the number of spins N, form a set
of points in the N-spin space. These points are connected by a network of flat
valleys in the N-spin space, giving rise to a continuous family of classical
ground states. Further, the CN-ground states have a correspondence with dimer
coverings and with self avoiding walks on a honeycomb lattice. The zero point
energy of our spin wave theory picks out a subset from a continuous family of
classically degenerate states as the quantum ground states; the number of these
states also grows exponentially with N. In the second part, we present some
exact results. For arbitrary spin-S, we show that localized Z_2 flux
excitations are present by constructing plaquette operators with eigenvalues
\pm 1 which commute with the Hamiltonian. This set of commuting plaquette
operators leads to an exact vanishing of the spin-spin correlation functions,
beyond nearest neighbor separation, found earlier for the spin-1/2 model [G.
Baskaran, S. Mandal and R. Shankar, Phys. Rev. Lett. 98, 247201 (2007)]. We
introduce a generalized Jordan-Wigner transformation for the case of general
spin-S, and find a complete set of commuting link operators, similar to the
spin-1/2 model, thereby making the Z_2 gauge structure more manifest. The
Jordan-Wigner construction also leads, in a natural fashion, to Majorana
fermion operators for half-integer spin cases and hard-core boson operators for
integer spin cases, strongly suggesting the presence of Majorana fermion and
boson excitations in the respective low energy sectors.",0806.1588v2
2019-08-08,Annihilation of topological solitons in magnetism with spin wave burst finale: The role of nonequilibrium electrons causing nonlocal damping and spin pumping over ultrabroadband frequency range,"We not only reproduce burst of short-wavelength spin waves (SWs) observed in
recent experiment [S. Woo et al., Nat. Phys. 13, 448 (2017)] on
magnetic-field-driven annihilation of two magnetic domain walls (DWs) but,
furthermore, we predict that this setup additionally generates highly unusual}
pumping of electronic spin currents in the absence of any bias voltage. Prior
to the instant of annihilation, their power spectrum is ultrabroadband, so they
can be converted into rapidly changing in time charge currents, via the inverse
spin Hall effect, as a source of THz radiation of bandwidth $\simeq 27$ THz
where the lowest frequency is controlled by the applied magnetic field. The
spin pumping stems from time-dependent fields introduced into the quantum
Hamiltonian of electrons by the classical dynamics of localized magnetic
moments (LMMs) comprising the domains. The pumped currents carry spin-polarized
electrons which, in turn, exert backaction on LMMs in the form of nonlocal
damping which is more than twice as large as conventional local Gilbert
damping. The nonlocal damping can substantially modify the spectrum of emitted
SWs when compared to widely-used micromagnetic simulations where conduction
electrons are completely absent. Since we use fully microscopic (i.e.,
Hamiltonian-based) framework, self-consistently combining time-dependent
electronic nonequilibrium Green functions with the Landau-Lifshitz-Gilbert
equation, we also demonstrate that previously derived phenomenological formulas
miss ultrabroadband spin pumping while underestimating the magnitude of
nonlocal damping due to nonequilibrium electrons.",1908.03194v5
2021-01-22,Spin dynamics in NaFeAs and NaFe$_{0.53}$Cu$_{0.47}$As probed by resonant inelastic X-ray scattering,"The parent compounds of iron-based superconductors are magnetically-ordered
bad metals, with superconductivity appearing near a putative magnetic quantum
critical point. The presence of both Hubbard repulsion and Hund's coupling
leads to rich physics in these multiorbital systems, and motivated descriptions
of magnetism in terms of itinerant electrons or localized spins. The
NaFe$_{1-x}$Cu$_x$As series consists of magnetically-ordered bad metal ($x=0$),
superconducting ($x\approx0.02$) and magnetically-ordered
semiconducing/insulating ($x\approx0.5$) phases, providing a platform to
investigate the connection between superconductivity, magnetism and electronic
correlations. Here we use X-ray absorption spectroscopy and resonant inelastic
X-ray scattering to study the valence state of Fe and spin dynamics in two
NaFe$_{1-x}$Cu$_x$As compounds ($x=0$ and 0.47). We find that magnetism in both
compounds arises from Fe$^{2+}$ atoms, and exhibits underdamped dispersive spin
waves in their respective ordered states. The dispersion of spin excitations in
NaFe$_{0.53}$Cu$_{0.47}$As is consistent with being quasi-one-dimensional.
Compared to NaFeAs, the band top of spin waves in NaFe$_{0.53}$Cu$_{0.47}$As is
slightly softened with significantly more spectral weight of the spin
excitations. Our results indicate the spin dynamics in
NaFe$_{0.53}$Cu$_{0.47}$As arise from localized magnetic moments and suggest
the iron-based superconductors are proximate to a correlated insulating state
with localized iron moments.",2101.08948v1
2023-10-12,Extreme mass-ratio inspiral and waveforms for a spinning body into a Kerr black hole via osculating geodesics and near-identity transformations,"Understanding the orbits of spinning bodies in curved spacetime is important
for modeling binary black hole systems with small mass ratios. At zeroth order
in mass ratio, the smaller body moves on a geodesic. Post-geodesic effects are
needed to model the system accurately. One very important post-geodesic effect
is the gravitational self-force, which describes the small body's interaction
with its own contribution to a binary's spacetime. Another post-geodesic
effect, the spin-curvature force, is due to the smaller body's spin coupling to
spacetime curvature. In this paper, we combine the leading orbit-averaged
backreaction of point-particle gravitational-wave emission with the
spin-curvature force to construct the worldline and gravitational waveform for
a spinning body spiraling into a Kerr black hole. We use an osculating geodesic
integrator, which treats the worldline as evolution through a sequence of
geodesic orbits, as well as near-identity transformations, which eliminate
dependence on orbital phases, allowing for fast computation of inspirals. The
resulting inspirals and waveforms include all critical dynamical effects which
govern such systems (orbit and precession frequencies, inspiral, strong-field
gravitational-wave amplitudes), and as such form an effective first model for
the inspiral of spinning bodies into Kerr black holes. We emphasize that our
present calculation is not self consistent, since we neglect effects which
enter at the same order as effects we include. However, our analysis
demonstrates that the impact of spin-curvature forces can be incorporated into
EMRI waveform tools with relative ease. The calculation is sufficiently modular
that it should not be difficult to include neglected post-geodesic effects as
efficient tools for computing them become available. (Abridged)",2310.08438v1
2023-10-30,Dynamical renormalisation of a spin Hamiltonian via high-order nonlinear magnonics,"The macroscopic magnetic order in the ground state of solids is determined by
the spin-dependent Hamiltonian of the system. In the absence of external
magnetic fields, this Hamiltonian contains the exchange interaction, which is
of electrostatic origin, and the spin-orbit coupling, whose magnitude depends
on the atomic charge. Spin-wave theory provides a representation of the entire
spectrum of collective magnetic excitations, called magnons, assuming the
interactions to be constant and the number of magnons in the system negligible.
However, the electric field component of light is able to perturb electrostatic
interactions, charge distributions and, at the same time, can create a magnon
population. A fundamental open question therefore concerns the possibility to
optically renormalise the spin Hamiltonian. Here, we test this hypothesis by
using femtosecond laser pulses to resonantly pump electric-dipole-active pairs
of high-energy magnons near the edges of the Brillouin zone. The transient spin
dynamics reveals the activation and a surprising amplification of coherent
low-energy zone-centre magnons, which are not directly driven. Strikingly, the
spectrum of these low-energy magnons differs from the one observed in thermal
equilibrium, the latter being consistent with spin-wave theory. The light-spin
interaction thus results in a room-temperature renormalisation of the magnetic
Hamiltonian, with an estimated modification of the magnetic interactions by 10%
of their ground-state values. We rationalise the observation in terms of a
novel resonant scattering mechanism, in which zone-edge magnons couple
nonlinearly to the zone-centre modes. In a quantum mechanical model, we
analytically derive the corrections to the spectrum due to the photo-induced
magnon population, which are consistent with our experiments. Our results
present a milestone for an all-optical engineering of Hamiltonians.",2310.19667v1
1997-06-12,Unstable waves in winds of magnetic massive stars,"We use a luminous fast magnetic rotator model to analyze the influence of a
magnetic field on the linear waves induced in the wind of a massive star by the
radiative instability. We show that a twisted magnetic field can drive a strong
wind with a wind efficiency $(\dot{M}v_\infty)/(L/c)>1$ even without multiple
scattering. The radiation amplified waves in the wind are modified by the
twisted magnetic field so that they can enhance the wind and lead to
overestimates for $\dot{M}$ and $v_\infty$. Finally we argue that the spin down
time might be consistent with the lifetime derived from the mass loss rate
within the uncertainties regarding the stellar structure. Therefore our model
may help to explain high, observed values for $\dot{M}$ and $v_\infty$ without
being ruled out by the spin down problem.",9706117v1
2005-06-17,Radio-quiet neutron star 1E 1207.4-5209: a possible strong Gravitational-wave source,"There are four puzzles on 1E 1207.4-5209: (1) the characteristic age of the
pulsar is much higher than the estimated age of the supernova remnant; (2) the
magnetic field inferred from spin-down is significantly different from the
value obtained from the cyclotron absorption lines; (3) the spinning down of
the pulsar is non-monotonic; (4) the magnitude of the frequency's first
derivative varies significantly and its sign is also variable. The third puzzle
can be explained by a wide binary system, with orbital period from 0.2 to 6 yr.
This letter proposes that all four puzzles can be explained naturally by an
ultra-compact binary with orbital period of between 0.5 and 3.3 min. With the
shortest orbital period and a close distance of 2 kpc, the characteristic
amplitude of gravitational waves is $h\sim3\times10^{-21}$. It would be an
excellent source of gravitational-wave detectors such as the Laser
Interferometer Space Antenna.",0506431v2
1997-09-18,Magneto-Roton Modes in the Ultra Quantum Crystal: Life and Death at Large Magnetic Field,"The Ultra Quantum Crystal (UQC) phases observed in quasi-one-dimensional
conductors of the Bechgaard salts family under magnetic field exhibit both Spin
Density Wave order and a Quantized Hall Effect, which may exhibit sign
reversals. We examine the case with no sign reversals. Collective modes in the
UQC have been shown to have a rich spectrum, with local Magneto-Roton like
minima. As the field increases, Magneto-Roton modes, which have minima at
quantized wave vectors, merge, or not, in the single particle excitation
continuum. In the high field phase, the Hall conductivity at zero temperature
is zero; at the transition from the N=1 phase, it has two Magneto-Roton modes,
the energies of which increase rapidly with magnetic field. The modes survive
until a critical field above which the high field phase looks more like a
perfect nesting insulating Spin Density Wave.",9709210v1
1998-12-08,Orbital dynamics in ferromagnetic transition metal oxides,"We consider a model of strongly correlated $e_g$ electrons interacting by
superexchange orbital interactions in the ferromagnetic phase of LaMnO$_3$. It
is found that the classical orbital order with alternating occupied $e_g$
orbitals has a full rotational symmetry at orbital degeneracy, and the
excitation spectrum derived using the linear spin-wave theory is gapless. The
quantum (fluctuation) corrections to the order parameter and to the ground
state energy restore the cubic symmetry of the model. By applying a uniaxial
pressure orbital degeneracy is lifted in a tetragonal field and one finds an
orbital-flop phase with a gap in the excitation spectrum. In two dimensions the
classical order is more robust near the orbital degeneracy point and quantum
effects are suppressed. The orbital excitation spectra obtained using finite
temperature diagonalization of two-dimensional clusters consist of a
quasiparticle accompanied by satellite structures. The orbital waves found
within the linear spin-wave theory provide an excellent description of the
dominant pole of these spectra.",9812123v1
1999-10-27,Effect of the spin-orbit interaction on the band structure and conductance of quasi-one-dimensional systems,"We discuss the effect of the spin-orbit interaction on the band structure,
wave functions and low temperature conductance of long quasi-one-dimensional
electron systems patterned in two-dimensional electron gases (2DEG). Our model
for these systems consists of a linear (Rashba) potential confinement in the
direction perpendicular to the 2DEG and a parabolic confinement transverse to
the 2DEG. We find that these two terms can significantly affect the band
structure introducing a wave vector dependence to subband energies, producing
additional subband minima and inducing anticrossings between subbands. We
discuss the origin of these effects in the symmetries of the subband wave
functions.",9910466v1
2001-07-17,Competition between charge/spin-density-wave orders and superconductivity in La$_{1.875}$Ba$_{0.125-x}$Sr$_{x}$CuO$_{4}$,"We have performed a series of elastic neutron scattering measurements on
1/8-hole doped La$_{1.875}$Ba$_{0.125-x}$Sr$_{x}$CuO$_{4}$ single crystals with
{\it x} = 0.05, 0.06, 0.075 and 0.085. % Both charge-density-wave (CDW) and
spin-density-wave (SDW) orders are found to develop simultaneously below the
structural transition temperature between the low-temperature orthorhombic
(LTO) and low-temperature tetragonal (LTT) or low-temperature less-orthorhombic
(LTLO) phases. % In the ground state the CDW order is observed only in the
LTT/LTLO phase and drastically degrades towards the LTO boundary. The {\it
x}-dependence of {\it T}$_{c}$ strongly suggests a direct effect of the CDW
order on the suppression of superconductivity. % Results are discussed in
comparison with those from the La$_{1.6-x}$Nd$_{0.4}$Sr$_{x}$CuO$_{4}$ system
within the framework of the stripe model.",0107355v3
2001-12-20,Theory of Magnetic Field Induced Spin Density Wave in High Temperature Superconductors,"The induction of spin density wave (SDW) and charge density wave (CDW)
orderings in the mixed state of high $T_c$ superconductors (HTS) is
investigated by using the self-consistent Bogoliubov-de Gennes equations based
upon an effective model Hamiltonian with competing SDW and d-wave
superconductivity interactions. For optimized doping sample, the modulation of
the induced SDW and its associated CDW is determined by the vortex lattice and
their patterns obey the four-fold symmetry. By deceasing doping level, both SDW
and CDW show quasi-one dimensional like behavior, and the CDW has a period just
half that of the SDW along one direction. From the calculation of the local
density of states (LDOS), we found that the majority of the quasi-particles
inside the vortex core are localized. All these results are consistent with
several recent experiments on HTS.",0112369v2
2003-02-07,Field-induced spin-density-wave phases in TMTSF organic conductors: quantization versus non-quantization,"We study the magnetic-field-induced spin-density-wave (FISDW) phases in TMTSF
organic conductors in the framework of the quantized nesting model. In
agreement with recent suggestions, we find that the SDW wave-vector ${\bf Q}$
deviates from its quantized value near the transition temperature $T_c$ for all
phases with quantum numbers $N>0$. Deviations from quantization are more
pronounced at low pressure and higher $N$ and may lead to a suppression of the
first-order transitions $N+1\to N$ for $N\ge 5$. Below a critical pressure, we
find that the N=0 phase invades the entire phase diagram in accordance with
earlier experiments. We also show that at T=0, the quantization of ${\bf Q}$
and hence the Hall conductance is always exact. Our results suggest a novel
phase transition/crossover at intermediate temperatures between phases with
quantized and non-quantized ${\bf Q}$.",0302142v1
2005-01-09,First-principles calculations of the magnetism of Fe$_2$O$_2$H$_2$,"By expanding the wave function in plane waves, we use the pseudopotential
method of density functional theory within the generalized gradient
approximation to calculate the effective magnetic coupling energies of the
S=5/2 spins in the Fe2 dimer, approximated as Fe$_2$O$_2$H$_2$. Setting the
Fe-O bond length at the value corresponding to the minimum total energy, we
find the difference in antiferromagnetic and ferromagnetic exchange energies as
a function of the Fe-O-Fe bond angle $\theta$. The effective interaction is
antiferromagnetic for 63$^{\circ}<\theta<105^{\circ}$, and is ferromagnetic
otherwise. Full potential augmented plane wave calculations were also performed
at $\theta=100,105^{\circ}$, confirming these results, and providing
information relevant to the local anisotropy of the spin interactions.",0501178v1
2005-05-16,Renormalization Group calculations with k|| dependent couplings in a ladder,"We calculate the phase diagram of a ladder system, with a Hubbard interaction
and an interchain coupling $t_\perp$. We use a Renormalization Group method, in
a one loop expansion, introducing an original method to include $k_{||}$
dependence of couplings. We also classify the order parameters corresponding to
ladder instabilities. We obtain different results, depending on whether we
include $k_{||}$ dependence or not. When we do so, we observe a region with
large antiferromagnetic fluctuations, in the vicinity of small $t_\perp$,
followed by a superconducting region with a simultaneous divergence of the Spin
Density Waves channel. We also investigate the effect of a non local backward
interchain scattering : we observe, on one hand, the suppression of singlet
superconductivity and of Spin Density Waves, and, on the other hand, the
increase of Charge Density Waves and, for some values of $t_\perp$, of triplet
superconductivity. Our results eventually show that $k_{||}$ is an influential
variable in the Renormalization Group flow, for this kind of systems.",0505385v1
2005-09-30,Resonating-valence-bond structure of Gutzwiller-projected superconducting wave functions,"Gutzwiller-projected (GP) wave functions have been widely used for describing
spin-liquid physics in frustrated magnets and in high-temperature
superconductors. Such wave functions are known to represent states of the
resonating-valence-bond (RVB) type. In the present work I discuss the RVB
structure of a GP singlet superconducting state with nodes in the spectrum. The
resulting state for the undoped spin system may be described in terms of the
""path integral"" over loop coverings of the lattice, thus extending the known
construction for RVB states. The problem of the topological order in GP states
may be reformulated in terms of the statistical behavior of loops. The simple
example of the projected d-wave state on the square lattice demonstrates that
the statistical behavior of loops is renormalized in a nontrivial manner by the
projection.",0509791v2
2005-12-07,Rashba spin splitting in biased semiconductor quantum wells,"Rashba spin splitting (RSS) in biased semiconductor quantum wells is
investigated theoretically based on the eight-band envelope function model. We
find that at large wave vectors, RSS is both nonmonotonic and anisotropic as a
function of in-plane wave vector, in contrast to the widely used linear and
isotropic model. We derive an analytical expression for RSS, which can
correctly reproduce such nonmonotonic behavior at large wave vectors. We also
investigate numerically the dependence of RSS on the various band parameters
and find that RSS increases with decreasing band gap and subband index,
increasing valence band offset, external electric field, and well width. Our
analytical expression for RSS provides a satisfactory explanation to all these
features.",0512141v2
2005-12-21,Entanglement Properties Of Quantum Many-Body Wave Functions,"Entanglement properties of the trial many-body wave functions in variational
treatments of the transverse Ising model in two, three, and four dimensions are
investigated. Based on data for magnetizations and correlation functions
generated by for symmetry-breaking Hartree-Jastrow trial ground states, results
are presented for several measures of bipartite entanglement, including the von
Neumann entropy of a single spin in the lattice, the concurrence between two
spins, and a lower bound on the localizable entanglement, as functions of
coupling strength. A simple relation is established between the Hartree-Jastrow
states and the nilpotent polynomial representation of multipartite
entanglement. In addition, some general comments are made on the entanglement
properties of classes of many-body wave functions commonly adopted in theories
of strongly correlated quantum systems.",0512558v1
2006-07-27,Magnon Bose condensation in symmetry breaking magnetic field,"Magnon Bose condensation (BC)in the symmetry breaking magnetic field is a
result of unusual form of the Zeeman energy, which has terms linear in the
spin-wave operators and terms mixing excitations differ in the Wave-vector of
the magnetic structure. The following examples are considered: simple
easy-plane tetragonal antiferromagnets (AF), frustrated AF family$R_2Cu O_4$
where $R=Pr,Nd$ etc. and cubic magnets with the Dzyaloshinskii-Moriya
interaction ($Mn Si$ etc.). In all cases the BC becomes important when the
magnetic field becomes comparable with the spin-wave gap. The theory is
illustrated by existing experimental results.",0607711v2
2006-08-01,Excitation spectra of the spin-1/2 triangular-lattice Heisenberg antiferromagnet,"We use series expansion methods to calculate the dispersion relation of the
one-magnon excitations for the spin-1/2 triangular-lattice nearest-neighbor
Heisenberg antiferromagnet above a three-sublattice ordered ground state.
Several striking features are observed compared to the classical (large-S)
spin-wave spectra. Whereas at low energies the dispersion is only weakly
renormalized by quantum fluctuations, significant anomalies are observed at
high energies. In particular, we find roton-like minima at special wave-vectors
and strong downward renormalization in large parts of the Brillouin zone,
leading to very flat or dispersionless modes. We present detailed comparison of
our calculated excitation energies in the Brillouin zone with the spin-wave
dispersion to order 1/S calculated recently by Starykh, Chubukov, and Abanov
[cond-mat/0608002]. We find many common features but also some quantitative and
qualitative differences. We show that at temperatures as low as 0.1J the
thermally excited rotons make a significant contribution to the entropy.
Consequently, unlike for the square lattice model, a non-linear sigma model
description of the finite-temperature properties is only applicable at
extremely low temperatures.",0608008v1
1995-11-22,Open-Flux Solutions to the Constraints for Plane Gravity Waves,"The metric for plane gravitational waves is quantized using the Ashtekar
field variables. The z axis (direction of travel of the waves) is taken to be
the entire real line. Solutions to the constraints are proposed; they involve
open-ended flux lines running along the entire z axis. These solutions are
annihilated by the constraints except at the two boundary points, where the
Gauss constraint does not annihilate the solutions. This result is in sharp
contrast to the situation in the general, 3+1 dimensional case without planar
symmetry, where the Gauss constraints do not contribute at boundaries because
the Lagrange multipliers for the Gauss constraints vanish there. The
constraints annihilate the solutions if classical matter is included (so that
flux lines are terminated on the matter). The SU(2) holonomy matrices used in
the solutions are (2j+1) dimensional, where j may be any spin, not necessarily
j = 1/2. In this respect the solutions resemble the spin network states
recently constructed by Rovelli and Smolin in loop space.",9511061v1
1999-01-28,Search techniques for gravitational waves from black-hole ringdowns,"Of all the astronomical sources of gravitational radiation, the ringdown
waveform arising from a small perturbation of a spinning black hole is perhaps
the best understood: for the late stages of such a perturbation, the waveform
is simply an exponentially-damped sinusoid. Searching interferometric
gravitational wave antenna data for these should be relatively easy. In this
paper, I present the results of a single-filter search for ringdown waveforms
arising from a 50 solar mass black hole with 98% of its maximum spin angular
momentum using data from the Caltech 40-meter prototype interferometer. This
search illustrates the techniques that may be used in analyzing data from
future kilometer-scale interferometers and describes some of the difficulties
present in the analysis of interferometer data. Most importantly, it
illustrates the use of coincident events in the output of two independent
interferometers (here simulated by 40-meter data at two different times) to
substantially reduce the spurious event rate. Such coincidences will be
essential tools in future gravitational wave searches in kilometer-scale
interferometers.",9901084v1
2003-04-30,All-sky upper limit for gravitational radiation from spinning neutron stars,"We present results of the all-sky search for gravitational-wave signals from
spinning neutron stars in the data of the EXPLORER resonant bar detector. Our
data analysis technique was based on the maximum likelihood detection method.
We briefly describe the theoretical methods that we used in our search. The
main result of our analysis is an upper limit of ${\bf 2\times10^{-23}}$ for
the dimensionless amplitude of the continuous gravitational-wave signals coming
from any direction in the sky and in the narrow frequency band from 921.00 Hz
to 921.76 Hz.",0304107v1
1993-12-18,"Complex wave function, Chiral spin order parameter and Phase Problem","We study the two dimensional Hubbard model by use of the ground state
algorithm in the Monte Carlo simulation. We employ complex wave functions as
trial function in order to have a close look at properties such as chiral spin
order ($\chi$SO) and flux phase. For half filling, a particle-hole
transformation leads to sum rules with respect to the Green's functions for a
certain choice of a set of wave functions. It is then analytically shown that
the sum rules lead to the absence of the $\chi$SO. Upon doping, we are
confronted with the sign problem, which in our case %ch appears as a ``phase
problem"" due to the phase of the Monte Carlo weights. The average of the phase
shows an exponential decay as a function of inverse temperature similarly to
that of sign by Loh Jr. et. al. . We compare the numerical results with those
of exact numerical calculations.",9312073v1
2006-06-22,Instanton contribution to the Sivers function,"We study the Sivers function for valence u and d quarks in the proton within
the instanton model for QCD vacuum, adopting the MIT bag model wave functions
for quarks. Within approaches based on perturbative one-gluon final state
interactions a non-zero value of the Sivers function is related to the presence
of both S and P wave components in quark wave functions. We show that the
instanton-induced chromomagnetic, nonperturbative interaction leads to very
specific spin-spin correlations between the struck and spectator quarks,
resulting in a non-trivial flavour dependence of the Sivers function.
Comparison of the obtained Sivers functions with phenomenological
parameterizations is discussed.",0606238v2
2001-02-05,"Wave Functionals, Gauge Invariant Equations for Massive Modes and the Born-Infeld Equation in the Loop Variable Approach to String Theory","In earlier papers on the loop variable approach to gauge invariant
interactions in string theory, a ``wave functional'' with some specific
properties was invoked.
  It had the purpose of converting the generalized momenta to space time
fields. In this paper we describe this object in detail and give some explicit
examples. We also work out the interacting equations of the massive mode of the
bosonic string, interacting with electromagnetism, and discuss in detail the
gauge invariance. This is naturally described in this approach as a massless
spin two field interacting with a massless spin one field in a higher
dimension. Dimensional reduction gives the massive system. We also show that in
addition to describing fields perturbatively, as is required for reproducing
the perturbative equations, the wave functional can be chosen to reproduce the
Born-Infeld equations, which are non-perturbative in field strengths. This
makes contact with the sigma model approach.",0102017v1
2004-08-23,Spin 1/2 and Invariant Coefficients II. Massless,"A `covariant' field that transforms like a relativistic field operator is
required to be a linear combination of `canonical' fields that transform like
annihilation and creation operators and with invariant coefficients. The
Invariant Coefficient Hypothesis contends that this familiar construction by
itself yields useful results. Thus, just the transformation properties are
considered here, not the specific properties of annihilation or creation
operators. The results include Weyl wave equations for some massless fields
and, for other fields, Weyl-like noncovariant wave equations that are allowed
here because no assumptions are made to exclude them. The hypothesis produces
wave equations for translation-matrix-invariant fields while
translation-matrix-dependent coefficient functions have currents that are the
vector potentials of the coefficient functions of those
translation-matrix-invariant fields. The statement is proven by showing that
Maxwell equations are satisfied, though in keeping with the hypothesis they are
not assumed to hold. The underlying mechanism is the same for the massless
class here as it is for the massive class in a previous paper, suggesting that
spin 1/2 particles may have a universal electromagnetic-type charge whether
they are massive or massless.
  Keywords: Relativistic quantum fields; neutrino; Poincare transformations",0408176v1
2004-12-10,Velocity in Lorentz-Violating Fermion Theories,"We consider the role of the velocity in Lorentz-violating fermionic quantum
theory, especially emphasizing the nonrelativistic regime. Information about
the velocity will be important for the kinematical analysis of scattering and
other problems. Working within the minimal standard model extension, we derive
new expressions for the velocity. We find that generic momentum and spin
eigenstates may not have well-defined velocities. We also demonstrate how
several different techniques may be used to shed light on different aspects of
the problem. A relativistic operator analysis allows us to study the behavior
of the Lorentz-violating Zitterbewegung. Alternatively, by studying the time
evolution of Gaussian wave packets, we find that there are Lorentz-violating
modifications to the wave packet spreading and the spin structure of the wave
function.",0412112v2
1998-10-09,Structure of the ^3He in Backward Elastic p ^3He-Scattering,"Backward elastic $p ^3He$-scattering at incident proton kinetic energies
$T_p>1$ GeV is investigated in the framework of the np-pair transfer mechanism
and triangular diagram of one-pion exchange with a subprocess $pd\to ^3He\pi^0$
using a realistic three-body wave function of the $^3He$ nucleus.
  It is found that the $np-$pair transfer mechanism dominates owing to a rich
high momentum component of the $^3He$ wave function.
  We show that the experimental cross section of this process is defined mainly
by the values of the Faddeev component of the $^3He$ wave function, $\phi
^{23}({\bf q}_{23}, {\bf p}_1)$, at high relative momenta $q_{23}> 0.6 GeV/c$
of the NN-pair in the $^1S_0$-state and at low spectator momenta $p_1\leq 0.1$
GeV/c. The spin-spin correlation parameter is calculated in the framework of
the dominating mechanism for the case of polarized target and beam.
Rescatterings in the initial and final states are taken into account.
Comparison with the $pd\to dp$ process is performed.",9810028v2
2007-01-08,Subtleties of Lorentz Invariance in Relativistic Constituent Quark Models of the Nucleon and the Spin-Dependent Quark Density,"We study the effects of a barely perceivable violation of Lorentz invariance
on results computed using a relativistic constituent quark model wave function.
The model nucleon wave function of Gross {\it et al.} is constructed such
thatthere is no orbital angular momentum and that the spin-dependent density is
spherical. This model wave function is claimed to be manifestly covariant, but
we show that this is not so. In particular,the seeming covariance of the matrix
elements of the electromagnetic current arises from using the Breit frame.
Matrix elements have a different appearance in any other frame.",0701017v3
2004-08-22,Novel Gravity Probe B Gravitational Wave Detection,"The Gravity Probe B (GP-B) satellite experiment will measure the precession
of on-board gyroscopes to extraordinary accuracy. Such precessions are
predicted by General Relativity (GR), and one component of this precession is
the `frame-dragging' or Lense-Thirring effect, which is caused by the rotation
of the earth, and the other is the geodetic effect. A new theory of gravity
predicts, however, a second and much larger `frame-dragging' or vorticity
induced spin precession. This spin precession component will also display the
effects of novel gravitational waves which are predicted by the new theory of
gravity, and which have already been seen in several experiments. The magnitude
and signature of these gravitational wave induced precession effects is given
for comparison with the GP-B experimental data.",0408097v1
2005-01-09,"Modified Kaluza-Klein Theory, Quantum Hidden Variables and 3-Dimensional Time","In this paper, the basic quantum field equations of free particle with
0-spin, 1-spin (for case of massless and mass $>$ 0) and 1/2 spin are derived
from Einstein equations under modified Kaluza-Klein metric, it shows that the
equations of quantum fields can be interpreted as pure geometry properties of
curved higher-dimensional time-space . One will find that if we interpret the
5th and 6th dimension as ``extra'' time dimension, the particle's wave-function
can be naturally interpreted as a single particle moving along geodesic path in
6-dimensional modified Kaluza-Klein time-space. As the result, the fundamental
physical effect of quantum theory such as double-slit interference of single
particle, statistical effect of wave-function, wave-packet collapse, spin,
Bose-Einstein condensation, Pauli exclusive principle can be interpreted as
``classical'' behavior in new time-space. In the last part of this paper, we
will coupling field equations of 0-spin, 1-spin and 1/2-spin particles with
gravity equations.",0501034v2
2007-08-30,Gravitational waves from black-hole mergers,"Coalescing black-hole binaries are expected to be the strongest sources of
gravitational waves for ground-based interferometers as well as the space-based
interferometer LISA. Recent progress in numerical relativity now makes it
possible to calculate the waveforms from the strong-field dynamical merger and
is revolutionizing our understanding of these systems. We review these dramatic
developments, emphasizing applications to issues in gravitational wave
observations. These new capabilities also make possible accurate calculations
of the recoil or kick imparted to the final remnant black hole when the merging
components have unequal masses, or unequal or unaligned spins. We highlight
recent work in this area, focusing on results of interest to astrophysics.",0708.4202v2
2007-09-07,A template bank to search for gravitational waves from inspiralling compact binaries: II. Phenomenological model,"Matched filtering is used to search for gravitational waves emitted by
inspiralling compact binaries in data from ground-based interferometers. One of
the key aspects of the detection process is the deployment of a set of
templates, also called a template bank, to cover the astrophysically
interesting region of the parameter space. In a companion paper, we described
the template-bank algorithm used in the analysis of LIGO data to search for
signals from non-spinning binaries made of neutron star and/or stellar-mass
black holes; this template bank is based upon physical template families. In
this paper, we describe the phenomenological template bank that was used to
search for gravitational waves from non-spinning black hole binaries (from
stellar mass formation) in the second, third and fourth LIGO science runs. We
briefly explain the design of the bank, whose templates are based on a
phenomenological detection template family. We show that this template bank
gives matches greater than 95% with the physical template families that are
expected to be captured by the phenomenological templates.",0709.1050v1
2007-10-02,Phase diagram of the one-dimensional half-filled extended Hubbard model,"We study the ground state of the one-dimensional half-filled Hubbard model
with on-site (nearest-neighbor) repulsive interaction $U$ ($V$) and
nearest-neighbor hopping $t$. In order to obtain an accurate phase diagram, we
consider various physical quantities such as the charge gap, spin gap,
Luttinger-liquid exponents, and bond-order-wave (BOW) order parameter using the
density-matrix renormalization group technique. We confirm that the BOW phase
appears in a substantial region between the charge-density-wave (CDW) and
spin-density-wave phases. Each phase boundary is determined by multiple means
and it allows us to do a cross-check to demonstrate the validity of our
estimations. Thus, our results agree quantitatively with the renormalization
group results in the weak-coupling regime ($U \lesssim 2t$), with the
perturbation results in the strong-coupling regime ($U \gtrsim 6t$), and with
the quantum Monte Carlo results in the intermediate-coupling regime. We also
find that the BOW-CDW transition changes from continuous to first order at the
tricritical point $(U_{\rm t}, V_{\rm t}) \approx (5.89t, 3.10t)$ and the BOW
phase vanishes at the critical end point $(U_{\rm c}, V_{\rm c}) \approx
(9.25t, 4.76t)$.",0710.0673v1
2007-10-23,"Complex Kerr Geometry, Twistors and the Dirac Electron","The Kerr-Newman spinning particle displays some remarkable relations to the
Dirac electron and has a reach spinor structure which is based on a twistorial
description of the Kerr congruence determined by the Kerr theorem. We consider
the relation between this spinor-twistorial structure and spinors of the Dirac
equation, and show that the Dirac equation may naturally be incorporated into
Kerr-Schild formalism as a master equation controlling the twistorial structure
of Kerr geometry. As a result, the Dirac electron acquires an extended
space-time structure having clear coordinate description with natural
incorporation of a gravitational field. The relation between the Dirac wave
function and Kerr geometry is realized via a chain of links: {\it Dirac wave
function $ \Rightarrow $ Complex Kerr-Newman Source $ \Rightarrow $ Kerr
Theorem $ \Rightarrow $ Real Kerr geometry.} As a result, the wave function
acquires the role of an ``order parameter'' which controls spin, dynamics, and
twistorial polarization of Kerr-Newman space-time.",0710.4249v2
2008-07-23,Neutron diffraction in a model itinerant metal near a quantum critical point,"Neutron diffraction measurements on single crystals of Cr1-xVx (x=0, 0.02,
0.037) show that the ordering moment and the Neel temperature are continuously
suppressed as x approaches 0.037, a proposed Quantum Critical Point (QCP). The
wave vector Q of the spin density wave (SDW) becomes more incommensurate as x
increases in accordance with the two band model. At xc=0.037 we have found
temperature dependent, resolution limited elastic scattering at 4
incommensurate wave vectors Q=(1+/-delta_1,2, 0, 0)*2pi/a, which correspond to
2 SDWs with Neel temperatures of 19 K and 300 K. Our neutron diffraction
measurements indicate that the electronic structure of Cr is robust, and that
tuning Cr to its QCP results not in the suppression of antiferromagnetism, but
instead enables new spin ordering due to novel nesting of the Fermi surface of
Cr.",0807.3586v2
2008-10-17,Pnictides as frustrated quantum antiferromagnet close to a quantum phase transition,"We present a detailed description of the dynamics of the magnetic modes in
the recently discovered superconducting pnictides using reliable
self-consistent spin-wave theory and series expansion. Contrary to linear
spin-wave theory, no gapless mode occurs at the N\'eel wave vector. We discuss
the scenario that the static magnetic moment is strongly reduced by magnetic
fluctuations arising from the vicinity to a quantum phase transition. Smoking
gun experiments to verify this scenario are proposed and possible results are
predicted. Intriguingly in this scenario, the structural transition at finite
temperature would be driven by an Ising transition in directional degrees of
freedom.",0810.3068v2
2008-12-22,Degeneracies in Sky Localisation Determination from a Spinning Coalescing Binary through Gravitational Wave Observations: a Markov-Chain Monte-Carlo Analysis for two Detectors,"Gravitational-wave signals from inspirals of binary compact objects (black
holes and neutron stars) are primary targets of the ongoing searches by
ground-based gravitational-wave interferometers (LIGO, Virgo, and GEO-600). We
present parameter-estimation simulations for inspirals of
black-hole--neutron-star binaries using Markov-chain Monte-Carlo methods. As a
specific example of the power of these methods, we consider source localisation
in the sky and analyse the degeneracy in it when data from only two detectors
are used. We focus on the effect that the black-hole spin has on the
localisation estimation. We also report on a comparative Markov-chain
Monte-Carlo analysis with two different waveform families, at 1.5 and 3.5
post-Newtonian order.",0812.4302v2
2009-03-31,Gigantic Impact of Magnetic Impurity on Stripe Order in La$_{2-x}$Sr$_{x}$CuO$_4$ ($x$$\sim$1/8),"Precise neutron-scattering experiments on
La$_{1.88-y}$Sr$_{0.12+y}$Cu$_{0.99}$R$_{0.01}$O$_4$ ($y$=0 for R=Cu, Zn and
$y$=0.01 for R=Ga, Fe) were performed to examine the stability of stripe order
in cuprate oxides through impurity substitution effects. For all the
impurity-substituted samples a static charge-density-wave order similar to that
reported in the low-temperature-tetragonal phase (LTT) was discovered in the
low-temperature-orthorhombic (LTO) phase for the first time. Fe substitution
significantly enhanced both the charge- and spin-density-wave orders. These
results indicate that dynamical charge stripes can be stabilized into static
ones around the Cu-site defects regardless of the type of crystal structure.
Additionally, large magnetic moments at the Cu-site may induce a decrease in
the Cu spin fluctuations around the defects, which in turn, enhances the static
charge-density-wave order.",0903.5391v1
2009-09-04,"Unconventional electronic reconstruction in undoped (Ba,Sr)Fe$_2$As$_2$ across the spin density wave transition","Through a systematic high resolution angle-resolved photoemission study of
the iron pnictide compounds (Ba,Sr)Fe$_2$As$_2$, we show that the electronic
structures of these compounds are significantly reconstructed across the spin
density wave ordering, which cannot be described by a simple folding scenario
of conventional density wave ordering. Moreover, we find that LDA calculations
with an incorporated suppressed magnetic moment of 0.5$\mu_{\tiny{\textrm{B}}}$
can match well the details in the reconstructed electronic structure,
suggesting that the nature of magnetism in the pnictides is more itinerant than
local, while the origin of suppressed magnetic moment remains an important
issue for future investigations.",0909.0831v1
2009-11-03,Secular momentum transport by gravitational waves from spinning compact binaries,"We present a closed system of coupled first order differential equations
governing the secular linear momentum loss of a compact binary due to emitted
gravitational waves, with the leading order relativistic and spin-orbit
perturbations included. In order to close the system, the secular evolution
equations of the linear momentum derived from the dissipative dynamics are
supplemented with the secular evolutions of the coupled angular variables, as
derived from the conservative dynamics.",0911.0477v2
2010-01-27,Scanning tunneling spectroscopy of a dilute two-dimensional electron system exhibiting Rashba spin splitting,"Using scanning tunneling spectroscopy (STS) at 5 K in B-fields up to 7 T, we
investigate the local density of states of a two-dimensional electron system
(2DES) created by Cs adsorption on p-type InSb(110). The 2DES, which in
contrast to previous STS studies exhibits a 2D Fermi level, shows standing
waves at B = 0 T with corrugations decreasing with energy and with wave numbers
in accordance with theory. In magnetic field percolating drift states are
observed within the disorder broadened Landau levels. Due to the large electric
field perpendicular to the surface, a beating pattern of the Landau levels is
found and explained quantitatively by Rashba spin splitting within the lowest
2DES subband. The Rashba splitting does not contribute significantly to the
standing wave patterns in accordance with theory.",1001.4957v1
2010-02-04,Incommensurate spin density wave in Co-doped BaFe2As2,"57Fe Mossbauer spectroscopy measurements are presented in the underdoped
Ba(Fe{1-x}Cox)2As2 series for x=0.014 (T_c < 1.4K) and x=0.03 and 0.045 (T_c ~
2 and 12K respectively). The spectral shapes in the so-called spin-density wave
(SDW) phase are interpreted in terms of incommensurate modulation of the
magnetic structure, and allow the shape of the modulation to be determined. In
undoped BaFe2As2, the magnetic structure is commensurate, and we find that
incommensurability is present at the lowest doping level (x=0.014). As Co
doping increases, the low temperature modulation progressively loses its
""squaredness"" and tends to a sine-wave. The same trend occurs for a given
doping level, as temperature increases. We find that a magnetic hyperfine
component persists far above the SDW transition, its intensity being
progressively tranferred to a paramagnetic component on heating.",1002.0931v2
2011-08-12,A model of the T-dependent pseudogap and its competition with superconductivity in copp er oxides,"Results for pseudogaps are obtained from a band model, where the stability of
the gap depends on the amplitudes of vibrational displacements, or magnetic
moments, and their coupling to electrons. A one-particle gap is favored by
normal thermal excitations of phonons or spin waves. Another gap can be
generated by spontaneous waves at lower temperature, if the electronic energy
gain overcomes the elastic/magnetic energy needed for increased amplitudes of
the oscillations. This state is characterized by charge or spin density waves.
The pseudogap has many features in common with the superconducting gap, and the
model lends support to the interpretation that the pseudogap is a precursor of,
and competes with, superconducting pairing.",1108.2626v1
2011-09-13,Competing many-body instabilities and unconventional superconductivity in graphene,"The band structure of graphene exhibits van Hove singularities (VHS) at
doping x=+- 1/8 away from the Dirac point. Near the VHS, interactions effects,
enhanced due to the large density of states, can give rise to various many-body
phases at experimentally accessible temperatures. We study the competition
between different many-body instabilities in graphene using functional
renormalization group (FRG). We predict a rich phase diagram, which, depending
on long range hopping as well as screening strength and absolute scale of the
Coulomb interaction, contains a d+id-wave superconducting (SC) phase, or a spin
density wave phase at the VHS. The d+id state is expected to exhibit quantized
charge and spin Hall response, as well as Majorana modes bound to vortices. In
the vicinity of the VHS, we find singlet d+id-wave as well as triplet f-wave SC
phases.",1109.2953v1
2011-12-05,Mixed partial-wave scattering with spin-orbit coupling and validity of pseudo-potentials,"We present exact solutions of two-body problem for spin-1/2 fermions with
isotropic spin-orbit(SO) coupling and interacting with an arbitrary short-range
potential. We find that in each partial-wave scattering channel, the
parametrization of two-body wavefunction at short inter-particle distance
depends on the scattering amplitudes of all channels. This reveals the mixed
partial-wave scattering induced by SO couplings. By comparing with results from
a square-well potential, we investigate the validity of original
pseudo-potential models in the presence of SO coupling. We find the s-wave
pseudo-potential provides a good approximation for low-energy solutions near
s-wave resonances, given the length scale of SO coupling much longer than the
potential range. However, near p-wave resonance the p-wave pseudo-potential
gives low-energy solutions that are qualitatively different from exact ones,
based on which we conclude that the p-wave model can not be applied to the
fermion system if the SO coupling strength is larger or comparable to the Fermi
momentum.",1112.1122v2
2012-04-14,Coexistence of long-range and algebraic correlations for short-range valence-bond wave functions in three dimensions,"We investigate nearest-neighbor valence-bond wave functions on bipartite
three-dimensional lattices. By performing large-scale Monte Carlo simulations,
we find that long-range magnetic order coexists with dipolar four-spin
correlations on the cubic lattice, this latter feature being reminiscent of the
Coulomb phase for classical dimers on the same lattice. Similar properties are
found for the lower-coordination diamond lattice. While this suggests that the
coexistence of magnetic order and dipolar four-spin correlations is generic for
bipartite three-dimensional lattices, we show that simple generalizations of
these wave functions can encode different ordering behaviors.",1204.3195v2
2012-05-26,Spin and Orbital Angular Momenta of Electromagnetic Waves in Free Space,"We derive exact expressions, in the form of Fourier integrals over the (k,w)
domain, for the energy, momentum, and angular momentum of a light pulse
propagating in free space. The angular momentum is seen to split naturally into
two parts. The spin contribution of each plane-wave constituent of the pulse,
representing the difference between its right- and left-circular polarization
content, is aligned with the corresponding k-vector. In contrast, the orbital
angular momentum associated with each plane-wave is orthogonal to its k-vector.
In general, the orbital angular momentum content of the wavepacket is the sum
of an intrinsic part, due, for example, to phase vorticity, and an extrinsic
part, r_CM x p, produced by the linear motion of the center-of-mass r_CM of the
light pulse in the direction of its linear momentum p.",1205.5900v1
2013-04-16,On pair functions for strong correlations,"The UHF wave function may be written as a spin-contaminated \textit{pair}
wave function of the APSG form, and the overlap of the alpha and beta
corresponding orbitals of the UHF solution can be taken as a proxy for the
strength of the correlation captured by breaking symmetry. We demonstrate this
with calculations on one- and two-dimensional hydrogen clusters and make
contact with the well studied Hubbard model. The UHF corresponding orbitals
pair in a manner that allows a smooth evolution from doubly occupied orbitals
at small distance to one in which wave function breaks symmetry, segregating
the $\alpha$ and $\beta$ electrons onto distinct sublattices at large
distances. By performing spin projection on these UHF solutions, we address
strong correlations that are difficult to capture at intermediate distances
using a single determinant. Approved for public release: LA-UR-13-22691.",1304.4457v1
2013-07-15,On the Instabilities of the Walker Propagating Domain Wall Solution,"A powerful mathematical method for front instability analysis that was
recently developed in the field of nonlinear dynamics is applied to the 1+1
(spatial and time) dimensional Landau-Lifshitz-Gilbert (LLG) equation. From the
essential spectrum of the LLG equation, it is shown that the famous Walker
rigid body propagating domain wall (DW) is not stable against the spin wave
emission. In the low field region only stern spin waves are emitted while both
stern and bow waves are generated under high fields. By using the properties of
the absolute spectrum of the LLG equation, it is concluded that in a high
enough field, but below the Walker breakdown field, the Walker solution could
be convective/absolute unstable if the transverse magnetic anisotropy is larger
than a critical value, corresponding to a significant modification of the DW
profile and DW propagating speed. Since the Walker solution of 1+1 dimensional
LLG equation can be realized in experiments, our results could be also used to
test the mathematical method in a controlled manner.",1307.3825v3
2013-11-12,On the Possibility of Reversible Magnonic Logic Gates,"We propose and develop a concept of magnonic logic gates enabling reversible
computing. The gates consist of passive elements: waveguides, cross-junctions
and phase shifters. Logical 0 and 1 are encoded in the relative phase of the
propagating spin wave packets (0 or {\pi}). The gates contain several possible
trajectories for each packet to propagate from the input to the output.
Re-direction of the spin wave packets among the possible trajectories is due to
the interference in the magnetic cross-junctions. Two wave packets coming to
the cross-junction in-phase propagate through the junction without reflection.
Two packets coming out-of-phase to the junction are completely reflected back.
The operation of the cross-junction is illustrated by numerical modeling. We
estimate the power dissipation in the proposed circuits and the feasibility of
cascading such magnetic devices in large circuits. The proposed gates may
potentially provide a route to magnetic reversible logic circuitry with power
dissipation less than kT per operation.",1311.2918v1
2014-02-17,Existence of Travelling Wave Solutions to the Maxwell-Pauli and Maxwell-Schrödinger Systems,"We study two mathematical descriptions of a charged particle interacting with
it's self-generated electromagnetic field. The first model is the one-body
Maxwell-Schr\""odinger system where the interaction of the spin with the
magnetic field is neglected and the second model is the related one-body
Maxwell-Pauli system where the spin-field interaction is included. We prove
that there exist travelling wave solutions to both of these systems provided
that the speed $|v|$ of the wave is not too large. Moreover, we observe that
the energies of these solutions behave like $\frac{mv^2}{2}$ for small
velocities of the particle, which may be interpreted as saying that the
effective mass of the particle is the same as it's bare mass.",1402.3936v1
2014-05-17,Generation and delayed retrieval of spatially multimode Raman scattering in warm rubidium vapors,"We apply collective Raman scattering to create, store and retrieve spatially
multimode light in warm rubidium-87 vapors. The light is created in a
spontaneous Stokes scattering process. This is accompanied by the creation of
counterpart collective excitations in the atomic ensemble -- the spin waves.
After a certain storage time we coherently convert the spin waves into the
light in deterministic anti-Stokes scattering. The whole process can be
regarded as a delayed four-wave mixing which produces pairs of correlated,
delayed random images. Storage of higher order spatial modes up to microseconds
is possible owing to usage of a buffer gas. We study the performance of the
Raman scattering, storage and retrieval of collective excitations focusing on
spatial effects and the influence of decoherence caused by diffusion of
rubidium atoms in different buffer gases. We quantify the number of modes
created and retrieved by analyzing statistical correlations of intensity
fluctuations between portions of the light scattered in the far field.",1405.4404v1
2014-08-05,Detecting compact binary coalescences with seedless clustering,"Compact binary coalescences are a promising source of gravitational waves for
second-generation interferometric gravitational-wave detectors. Although
matched filtering is the optimal search method for well-modeled systems,
alternative detection strategies can be used to guard against theoretical
errors (e.g., involving new physics and/or assumptions about spin/eccentricity)
while providing a measure of redundancy. In previous work, we showed how
""seedless clustering"" can be used to detect long-lived gravitational-wave
transients in both targeted and all-sky searches. In this paper, we apply
seedless clustering to the problem of low-mass ($M_\text{total}\leq10M_\odot$)
compact binary coalescences for both spinning and eccentric systems. We show
that seedless clustering provides a robust and computationally efficient method
for detecting low-mass compact binaries.",1408.0840v1
2014-09-11,Spin Wave Emission in Field-Driven Domain Wall Motion,"A domain wall (DW) in a nanowire can propagate under a longitudinal magnetic
field by emitting spin waves (SWs). We numerically investigated the properties
of SWs emitted by the DW motion, such as frequency and wavenumber, and their
relation with the DW motion. For a wire with a low transverse anisotropy and in
a field above a critical value, a DW emits SWs to both sides (bow and stern),
while it oscillates and propagates at a low average speed. For a wire with a
high transverse anisotropy and in a weak field, the DW emits mostly stern
waves, while the DW distorts itself and DW center propagates forward like a
drill at a relative high speed.",1409.3286v2
2014-10-16,Goos-Hänchen shifts in spin-orbit-coupled cold atoms,"We consider a matter wave packet of cold atom gas impinging upon a step
potential created by the optical light field. In the presence of spin-orbit
(SO) coupling, the atomic eigenstates contain two types of evanescent states,
one of which is the ordinary evanescent state with pure imaginary wave vector
while the other possesses complex wave vector and is recognized as oscillating
evanescent state. We show that the presence and interplay of these two types of
evanescent states can give rise to two different mechanisms for total internal
reflection (TIR), and thus lead to unusual Goos-H\""anchen (GH) effect. As a
result, not only large positive but also large negative GH shift can be
observed in the reflected atomic beam. The dependence of the GH shift on the
incident angle, energy and height of the step potential is studied numerically.",1410.4283v2
2014-12-02,Dynamical generation of dark solitons in spin-orbit-coupled Bose-Einstein condensates,"We numerically investigate the ground state, the Raman-driving dynamics and
the nonlinear excitations of a realized spin-orbit-coupled Bose-Einstein
condensate in a one-dimensional harmonic trap. Depending on the Raman coupling
and the interatomic interactions, three ground-state phases are identified:
stripe, plane wave and zero-momentum phases. A narrow parameter regime with
coexistence of stripe and zero-momentum or plane wave phases in real space is
found. Several sweep progresses across different phases by driving the Raman
coupling linearly in time is simulated and the non-equilibrium dynamics of the
system in these sweeps are studied. We find kinds of nonlinear excitations,
with the particular dark solitons excited in the sweep from the stripe phase to
the plane wave or zero-momentum phase within the trap. Moreover, the number and
the stability of the dark solitons can be controlled in the driving, which
provide a direct and easy way to generate dark solitons and study their
dynamics and interaction properties.",1412.0800v2
2015-08-21,Radiative damping in wave guide based FMR measured via analysis of perpendicular standing spin waves in sputtered Permalloy films,"The damping $\alpha$ of the spinwave resonances in 75 nm, 120 nm, and 200nm
-thick Permalloy films is measured via vector-network-analyzer
ferromagnetic-resonance (VNA-FMR) in the out-of-plane geometry. Inductive
coupling between the sample and the waveguide leads to an additional radiative
damping term. The radiative contribution to the over-all damping is determined
by measuring perpendicular standing spin waves (PSSWs) in the Permalloy films,
and the results are compared to a simple analytical model. The damping of the
PSSWs can be fully explained by three contributions to the damping: The
intrinsic damping, the eddy-current damping, and the radiative damping. No
other contributions were observed. Furthermore, a method to determine the
radiative damping in FMR measurements with a single resonance is suggested.",1508.05265v1
2015-09-05,Foldy-Wouthuysen transformation of the generalised Dirac Hamiltonian in a gravitational-wave background,"Goncalves et al. derived a non-relativistic limit of the generalised Dirac
Hamiltonian in the presence of a gravitational wave, using the exact
Foldy-Wouthuysen transformation. This gave rise to the intriguing notion that
spin-precession may occur even in the absence of a magnetic field. We argue
that this effect is not physical as it is the result of a gauge-variant term
that was an artefact of a flawed application of the exact Foldy-Wouthuysen
transformation. In this paper we derive the correct non-relativistic limit of
the generalised Dirac Hamiltonian in the presence of a gravitational wave,
using both the exact and standard Foldy-Wouthuysen transformation. We show that
both transformations consistently produce a Hamiltonian where all terms are
gauge-invariant. Unfortunately however, we also show that this means the novel
spin-precession effect does not exist.",1509.01671v1
2015-11-07,Quantum triangular ice in the easy-axis ferromagnetic phase,"We use spin wave theory to investigate the ground state properties of the
$Z_2$-invariant quantum XXZ model on the triangular lattice in the
ferromagnetic phase. The Hamiltonian comprises nearest and
next-nearest-neighbour Ising couplings, external magnetic fields, and a
$Z_2$-invariant ferromagnetic coupling. We show that quantum fluctuations are
suppressed in this system, hence linear spin wave theory gives reasonable
estimates of the ground state thermodynamic properties. Our results show that,
at half-filling (zero magnetic fields), the spontaneous breaking of $Z_2$
symmetry leads to a ferromagnetic phase whose energy spectrum is gapped at all
excitations with a maxon dispersion at $\mathbf{k}=0$. This is in sharp
contrast to rotational invariant systems with a vanishing phonon dispersion. We
show that the $\mathbf{k}=0$ mode enhances the estimated values of the
thermodynamic quantities. We obtain the trends of the particle density and the
condensate fraction. The density of states and the dynamical structure factors
exhibit fascinating peaks at unusual wave vectors, which should be of interest.",1511.02311v3
2015-12-15,Bilayer honeycomb lattice with ultracold atoms: Multiple Fermi surfaces and incommensurate spin density wave instability,"We propose an experimental setup using ultracold atoms to implement a bilayer
honeycomb lattice with Bernal stacking. In presence of a potential bias between
the layers and at low densities, Fermions placed in this lattice form an
annular Fermi sea. The presence of two Fermi surfaces leads to interesting
patterns in Friedel oscillations and RKKY interactions in presence of
impurities. Furthermore, a repulsive fermion-fermion interaction leads to a
Stoner instability towards an incommensurate spin-density-wave order with a
wave vector equal to the thickness of the Fermi sea. The instability occurs at
a critical interaction strength which goes down with the density of the
fermions. We find that the instability survives interaction renormalization due
to vertex corrections and discuss how this can be seen in experiments. We also
track the renormalization group flows of the different couplings between the
fermionic degrees of freedom, and find that there are no perturbative
instabilities, and that Stoner instability is the strongest instability which
occurs at a critical threshold value of the interaction. The critical
interaction goes to zero as the chemical potential is tuned towards the band
bottom.",1512.04685v2
2016-01-04,Breakdown of the Bloch-wave behavior for a single hole in a gapped antiferromagnet,"Whether a doped hole propagates as a Bloch wave or not is an important issue
of doped Mott physics. Here we examine this problem based on the quasiparticle
spectral weight $Z$ distribution, calculated by density matrix renormalization
group (DMRG). By tuning the anisotropy of a two-leg $t$-$J$ ladder without
closing the background spin gap, the $Z$ distribution unambiguously reveals a
transition of the single hole state from a Bloch wave to a novel one with
spontaneous translational symmetry breaking. We further establish a direct
connection of such a transition with a nonlocal phase string entanglement
between the hole and quantum spins, which explains numerical observations.",1601.00655v1
2016-04-13,Ultrafast spin density wave transition in Chromium governed by thermalized electron gas,"The energy and momentum selectivity of time- and angle-resolved photoemission
spectroscopy is exploited to address the ultrafast dynamics of the
antiferromagnetic spin density wave (SDW) transition photoexcited in epitaxial
thin films of chromium. We are able to quantitatively extract the evolution of
the SDW order parameter $\Delta$ through the ultrafast phase transition.
$\Delta$ is defined by the transient temperature of the thermalized electron
gas. The complete destruction of SDW order on a sub-100~fs time scale is
observed, much faster than for conventional charge density wave materials. Our
results reveal that equilibrium concepts for phase transitions such as the
order parameter may be utilized even in the strongly non-adiabatic regime of
ultrafast photo-excitation.",1604.03697v2
2016-06-24,"Spin density wave order, topological order, and Fermi surface reconstruction","In the conventional theory of density wave ordering in metals, the onset of
spin density wave (SDW) order co-incides with the reconstruction of the Fermi
surfaces into small 'pockets'. We present models which display this transition,
while also displaying an alternative route between these phases via an
intermediate phase with topological order, no broken symmetry, and pocket Fermi
surfaces. The models involve coupling emergent gauge fields to a fractionalized
SDW order, but retain the canonical electron operator in the underlying
Hamiltonian. We establish an intimate connection between the suppression of
certain defects in the SDW order, and the presence of Fermi surface sizes
distinct from the Luttinger value in Fermi liquids. We discuss the relevance of
such models to the physics of the hole-doped cuprates near optimal doping.",1606.07813v3
2016-07-11,Low loss spin wave resonances in organic-based ferrimagnet vanadium tetracyanoethylene thin films,"We experimentally demonstrate high quality factor spin wave resonances in an
encapsulated thin film of the organic-based ferrimagnet vanadium
tetracyanoethylene (V[TCNE]$_\textit{x~2}$) coated on an a-plane sapphire
substrate by low temperature chemical vapor deposition. The thickness standing
wave modes are observed in a broad frequency range (1 GHz ~ 5 GHz) with high
quality factor exceeding 3,200 in ambient air at room temperature, rivaling
those of inorganic magnetic materials. The exchange constant of
V[TCNE]$_\textit{x~2}$, a crucial material parameter for future study and
device design of the V[TCNE]$_\textit{x~2}$, is extracted from the measurement
with a value of $(4.61\pm 0.35)\times 10^{-16} \mathrm{\: m^{2}}$. Our result
establishes the feasibility of using organic-based materials for building
hybrid magnonic devices and circuits.",1607.03041v2
2016-08-07,Gravitational waves from a plunge into a nearly extremal Kerr black hole,"We study numerically in the time domain the linearized gravitational waves
emitted from a plunge into a nearly extremal Kerr black hole by solving the
inhomogeneous Teukolsky equation. We consider spinning black holes for which
the specific spin angular momentum $a/M=1-\epsilon$, and we consider values of
$\epsilon\geq 10^{-6}$. We find an effective transient behavior for the
quasi-normal ringdown: the early phase of the quasi-normal ringdown is governed
by a decay according to inverse time, with frequency equaling twice the black
hole's horizon frequency. The smaller $\epsilon$ the later the transition from
this transient inverse time decay to exponential decay. Such sources, if exist,
may be interesting potential sources for terrestrial or space borne
gravitational wave observatories.",1608.02244v1
2016-08-11,Chiral magnetic excitations in FeGe films,"Although chiral magnetic materials have emerged as a potential ingredient in
future spintronic memory devices, there are few comprehensive studies of
magnetic properties in scalably-grown thin films. We present growth, systematic
physical and magnetic characterization, and microwave absorption spectroscopy
of B20 FeGe thin films. We also perform micromagnetic simulations and
analytical theory to understand the dynamical magnetic behavior of this
material. We find magnetic resonance features in both the helical and
field-polarized magnetic states that are well explained by micromagnetic
simulations and analytical calculations. In particular, we show the resonant
enhancement of spin waves along the FeGe film thickness that has a wave vector
matching the helical vector. Using our analytic model, we also describe the
resonance frequency of a helical magnetic state, which depends solely on its
untwisting field. Our results pave the way for understanding and manipulating
high frequency spin waves in thin-film chiral-magnet FeGe near room
temperature.",1608.03582v1
2016-08-22,Spatially Homogeneous Entanglement for Matter-Wave Interferometry Created with Time-Averaged Measurements,"We demonstrate a method to generate spatially homogeneous entangled,
spin-squeezed states of atoms appropriate for maintaining a large amount of
squeezing even after release into the arm of a matter-wave interferometer or
other free space quantum sensor. Using an effective intracavity dipole trap, we
allow atoms to move along the cavity axis and time average their coupling to
the standing wave used to generate entanglement via collective measurements,
demonstrating 11(1) dB of directly observed spin squeezing. Our results show
that time averaging in collective measurements can greatly reduce the impact of
spatially inhomogeneous coupling to the measurement apparatus.",1608.06234v1
2016-10-12,Relaxation time spectrum of low-energy excitations in one- and two-dimensional materials with charge or spin density waves,"The long-time thermal relaxation of (TMTTF)$_2$Br, Sr$_{14}$Cu$_{24}$O$_{41}$
and Sr$_2$Ca$_{12}$Cu$_{24}$O$_{41}$ single crystals at temperatures below 1 K
and magnetic field up to 10 T is investigated. The data allow us to determine
the relaxation time spectrum of the low energy excitations caused by the
charge-density wave (CDW) or spin-density wave (SDW). The relaxation time is
mainly determined by a thermal activated process for all investigated
materials. The maximum relaxation time increases with increasing magnetic
field. The distribution of barrier heights corresponds to one or two Gaussian
functions. The doping of Sr$_{14-x}$Ca$_{x}$Cu$_{24}$O$_{41}$ with Ca leads to
a drastic shift of the relaxation time spectrum to longer time. The maximum
relaxation time changes from 50 s (x = 0) to 3000 s (x = 12) at 0.1 K and 10 T.
The observed thermal relaxation at x=12 clearly indicates the formation of the
SDW ground state at low temperatures.",1610.03683v2
2016-10-13,Spin-wave spectra in periodically surface-modulated ferromagnetic thin films,"This article presents theoretical results for the dynamic response of
periodically surface-modulated ferromagnetic thin films. For such system, the
role of the periodic dipolar field induced by the modulation is addressed by
using the plane-wave method. By controlling the geometry of the modulated
volumes within the film, the frequency modes and spatial profiles of spin waves
can be manipulated. The angular dependence of the frequency band-gaps unveils
the influence of both dynamic and static magnetic charges, which reside in the
edges of the etching periodic zones, and it is stablished that band-gap widths
created by static magnetic charges are broader than the one created by dynamic
magnetic charges. To corroborate the validity of the model, the theoretical
results are compared with ferromagnetic resonance simulations, where a very
good agreement is achieved between both methods. The theoretical model allows
for a detailed understanding of the physics underlying these kind of systems,
thereby providing an outlook to potential applications associated with magnonic
crystals-based devices.",1610.04176v1
2016-10-12,Astrophysical Prior Information and Gravitational-wave Parameter Estimation,"The detection of electromagnetic counterparts to gravitational waves has
great promise for the investigation of many scientific questions. It has long
been hoped that in addition to providing extra, non-gravitational information
about the sources of these signals, the detection of an electromagnetic signal
in conjunction with a gravitational wave could aid in the analysis of the
gravitational signal itself. That is, knowledge of the sky location,
inclination, and redshift of a binary could break degeneracies between these
extrinsic, coordinate-dependent parameters and the physical parameters, such as
mass and spin, that are intrinsic to the binary. In this paper, we investigate
this issue by assuming a perfect knowledge of extrinsic parameters, and
assessing the maximal impact of this knowledge on our ability to extract
intrinsic parameters. However, we find only modest improvements in a few
parameters --- namely the primary component's spin --- and conclude that, even
in the best case, the use of additional information from electromagnetic
observations does not improve the measurement of the intrinsic parameters
significantly.",1610.05633v2
2016-10-21,Analog rotating black holes in a magnetohydrodynamic inflow,"We present a model of the analog geometry in a magnetohydrodynamic (MHD)
flow. For the MHD flow with magnetic pressure-dominated and gas
pressure-dominated conditions, we obtain the magnetoacoustic metric for the
fast MHD mode. For the slow MHD mode, on the other hand, the wave is governed
by the advective-type equation without an isotropic dispersion term. Thus, the
""distance"" perpendicular to the wave propagation is not defined and the
magnetoacoustic metric cannot be introduced. To investigate the properties of
the magnetoacoustic geometry for the fast mode, we prepare a two-dimensional
axisymmetric inflow and examine the behavior of magnetoacoustic rays which is a
counterpart of the MHD waves in the eikonal limit. We find that the
magnetoacoustic geometry is classified into three types depending on two
parameters characterizing the background flow:~analog spacetimes of rotating
black holes, ultra spinning stars with ergoregions, and spinning stars without
ergoregions. We address the effects of the magnetic pressure on the effective
geometries.",1610.06690v4
2017-09-26,"Observation of ""broad"" d-wave Feshbach resonances with a triplet structure","High partial-wave ($l\ge2$) Feshbach resonance (FR) in an ultracold mixture
of $^{85}$Rb-$^{87}$Rb atoms is investigated experimentally aided by a
partial-wave insensitive analytic multichannel quantum-defect theory (MQDT).
Two ""broad"" resonances from coupling between d-waves in both the open and
closed channels are observed and characterized. One of them shows a fully
resolved triplet structure with splitting ratio well explained by the
perturbation to the closed channel due to interatomic spin-spin interaction.
These tunable ""broad"" d-wave resonances, especially the one in the
lowest-energy open channel, could find important applications in simulating
d-wave coupling dominated many-body systems. In addition, we find that there is
generally a time and temperature requirement, associated with tunneling through
the angular momentum barrier, to establish and observe resonant coupling in
nonzero partial waves.",1709.08794v2
2017-12-21,Reducing the number of templates for aligned-spin compact binary coalescence gravitational wave searches using metric-agnostic template nudging,"Efficient multi-dimensional template placement is crucial in computationally
intensive matched-filtering searches for Gravitational Waves (GWs). Here, we
implement the Neighboring Cell Algorithm (NCA) to improve the detection volume
of an existing Compact Binary Coalescence (CBC) template bank. This algorithm
has already been successfully applied for a binary millisecond pulsar search in
data from the Fermi satellite. It repositions templates from over-dense regions
to under-dense regions and reduces the number of templates that would have been
required by a stochastic method to achieve the same detection volume. Our
method is readily generalizable to other CBC parameter spaces. Here we apply
this method to the aligned--single-spin neutron-star--black-hole binary
coalescence inspiral-merger-ringdown gravitational wave parameter space. We
show that the template nudging algorithm can attain the equivalent
effectualness of the stochastic method with 12% fewer templates.",1712.07869v2
2018-01-31,Non-Fermi surface nesting driven commensurate magnetic ordering in Fe-doped Sr$_2$RuO$_4$,"Sr$_2$RuO$_4$, an unconventional superconductor, is known to possess an
incommensurate spin density wave instability driven by Fermi surface nesting.
Here we report a static spin density wave ordering with a commensurate
propagation vector $q_c$ = (0.25 0.25 0) in Fe-doped Sr$_2$RuO$_4$, despite the
magnetic fluctuations persisting at the incommensurate wave vectors $q_{ic}$ =
(0.3 0.3 L) as in the parent compound. The latter feature is corroborated by
the first principles calculations, which show that Fe substitution barely
changes the nesting vector of the Fermi surface. These results suggest that in
addition to the known incommensurate magnetic instability, Sr$_2$RuO$_4$ is
also in proximity to a commensurate magnetic tendency that can be stabilized
via Fe doping.",1801.10514v1
2018-05-01,Spontaneous Exact Spin-Wave Fractals in Magnonic Crystals,"Exact fractals of nonlinear waves that rely on strong dispersion and
nonlinearity and arise spontaneously out of magnetic media were observed for
the first time. The experiments make use of a microwave to excite a spin wave
in a quasi-one-dimensional magnonic crystal. When the power of the input
microwave (Pin) is low, the output signal has a power-frequency spectrum that
consists of a single peak. When Pin is increased to a certain level, the new
side modes are generated through modulational instability (MI), resulting in a
comb-like frequency spectrum. With a further increase in Pin, each peak in the
frequency comb can evolve into its own, finer comb through the MI. As Pin is
increased further, one can observe yet another set of finer frequency combs.
Such a frequency-domain fractal manifests itself as multiple layers of
amplitude modulation in the time-domain signal.",1805.00517v2
2018-09-14,Can a Magnetic Field Destroy a Spin-Density-Wave Phase in a Quasi-One-Dimensional Conductor?,"It is known that, in a pure one-dimensional case, Charge-Density-Wave (CDW)
phase is destroyed by a magnetic field, whereas Spin-Density-Wave (SDW) one
does not feel the field. In reality, SDW phase is often observed in
quasi-one-dimensional (Q1D) conductors due to the so-called ""nesting"" property
of their electron spectra. We show that, in the latter case, a high magnetic
field generates some ""anti-nesting"" term in a Q1D electron spectrum, which
destroys SDW phase. We suggest to perform the corresponding experiments in SDW
phases of the real Q1D organic conductors with chemical formula (TMTSF)$_2$X
(X=PF$_6$, ClO$_4$, etc.).",1809.05597v1
2018-02-02,Charge and current orders in the spin-fermion model with overlapping hot spots,"Experiments carried over the last years on the underdoped cuprates have
revealed a variety of symmetry-breaking phenomena in the pseudogap state.
Charge-density waves, breaking of $C_{4}$ rotational symmetry as well as
time-reversal symmetry breaking have all been observed in several cuprate
families. In this regard, theoretical models where multiple non-superconducting
orders emerge are of particular interest. We consider the recently introduced
(Phys. Rev. B 93, 085131 (2016)) spin-fermion model with overlapping 'hot
spots' on the Fermi surface. Focusing on the particle-hole instabilities we
obtain a rich phase diagram with the chemical potential relative to the
dispersion at $(0,\pi);\;(\pi,0)$ and the Fermi surface curvature in the
antinodal regions being the control parameters. We find evidence for d-wave
Pomeranchuk instability, d-form factor charge density waves as well as
commensurate and incommensurate staggered bond current phases similar to the
d-density wave state. The current orders are found to be promoted by the
curvature. Considering the appropriate parameter range for the hole-doped
cuprates, we discuss the relation of our results to the pseudogap state and
incommensurate magnetic phases of the cuprates.",1802.00694v2
2018-08-15,Collective excitations in two-component one-dimensional massless Dirac plasma,"We study spectra of long wavelength plasma oscillations in a system of two
energy splitted one-dimensional (1D) massless Dirac fermion subbands coupled by
spin-orbit interaction. Such a system may be formed by edge subbands in
semiconducting transition metal dichalcogenide monolayers. Intrasubband
transitions of massless Dirac fermions give rise to optical and acoustic
gapless branches of intrasubband 1D plasmons. We reveal that the optical branch
is of quantum character with group velocity being inverse proportional to
square root of the Planck constant, whereas the acoustic branch is classical
one with group velocity proportional to geometric mean of the edge subband
velocities. Spin-orbit interaction, allowing intersubband transitions in the
system, results in emergence of two branches of intersubband 1D plasmons: upper
and lower ones. The upper and lower branches are gapped at small wave vectors
and evolve with positive and negative group velocities, respectively, from
energy splitting of the edge subbands at Fermi-level. The both intersubband
branches adjoin intersubband single particle excitation continuum from above,
while in case of the edge subbands with unequal velocities the lower one
experiences Landau damping at small wave vectors. In addition, the lower
branch, attaining zero frequency at a non-zero wave vector, alters its group
velocity from negative to positive one.",1808.05180v1
2019-06-05,Braiding properties of paired spin-singlet and non-abelian hierarchy states,"We study explicit model wave functions describing the fundamental quasiholes
in a class of non-abelian fractional quantum Hall states. This class is a
family of paired spin-singlet states with $n\geq1$ internal degrees of freedom.
We determine the braid statistics of the quasiholes by determining the
monodromy of the explicit quasihole wave functions, that is how they transform
under exchanges of quasihole coordinates. The statistics is shown to be the
same as that of the quasiholes in the Read-Rezayi states, up to a phase. We
also discuss the application of this result to a class of non-abelian hierarchy
wave functions.",1906.01919v2
2020-08-05,Torque equilibrium spin wave theory of Raman scattering in an anisotropic triangular lattice antiferromagnet with Dzyaloshinskii-Moriya interaction,"We apply torque equilibrium spin wave theory (TESWT) to investigate an
anisotropic XXZ antiferromagnetic model with Dzyaloshinskii-Moriya (DM)
interaction in a triangular lattice. Considering the quasiparticle vacuum as
our reference, we provide an accurate analysis of the non-collinear ground
state of a frustrated triangular lattice magnet using the TESWT formalism. We
elucidate the effects of quantum fluctuations on the ordering wave vector based
on model system parameters. We study the single magnon dispersion, the
two-magnon continuum using the spectral function, and the Raman spectrum of
bimagnon and trimagnon excitations. We present our results for the $HH, VV$,
and the $HV$ polarization Raman geometry dependence of the bimagnon and the
trimagnon excitation spectrum where $H (V)$ represents horizontal (vertical)
polarization. Our calculations show that both the $HH$ and the $HV$
polarization spectrum can be used to determine the degree of anisotropy of our
system. We calculate the Raman spectra of Ba$_3$CoSb$_2$O$_9$ and
Cs$_2$CuCl$_4$.",2008.02287v2
2016-12-18,Bottleneck accumulation of hybrid magneto-elastic bosons,"It is known that an ensemble of magnons, quanta of spin waves, can be
prepared as a Bose gas of weakly interacting quasiparticles with conservation
of the particle number. Furthermore, the thermalization of the overpopulated
magnon gas can lead to the formation of a Bose-Einstein condensate at the
bottom of a spin-wave spectrum. However, magnon-phonon scattering processes can
significantly modify this scenario and new quasiparticles are formed -
magneto-elastic bosons. Our observations of a parametrically populated magnon
gas in a single-crystal film of Yttrium Iron Garnet by means of
wavevector-resolved Brillouin light scattering spectroscopy including
magneto-elastic coupling resulted in the discovery of a novel condensation
phenomenon: A spontaneous accumulation of hybrid magneto-elastic bosonic
quasiparticles at the intersection of the lowest magnon mode and a transversal
acoustic wave.",1612.05925v1
2019-03-21,Cascaded Rotational Doppler Effect,"We propose and substantiate experimentally the cascaded rotational Doppler
effect for interactions of spinning objects with light carrying angular
momentum. Based on the law of parity conservation for electromagnetic
interactions, we reveal that the frequency shift can be doubled through
cascading two rotational Doppler processes which are mirror-imaged to each
other. This effect is further experimentally verified with a rotating half-wave
plate, and the mirror-imaging process is achieved by reflecting the
frequency-shifted circularly polarized wave upon a mirror with a quarter-wave
plate in front of it. The mirror symmetry and thus parity conservation
guarantees that this doubled frequency shift can be further multiplied with
more successive mirror-imaging conjugations, with photons carrying spin and/or
orbital angular momentum, which could be widely applied for detection of
rotating systems ranging from molecules to celestial bodies with high precision
and sensitivity.",1903.08868v1
2019-05-03,Spinors in Supersymmetric dS/CFT,"We study fermionic bulk fields in the dS/CFT dualities relating ${\cal N}=2$
supersymmetric Euclidean vector models with reversed spin-statistics in three
dimensions to supersymmetric Vasiliev theories in four-dimensional de Sitter
space. These dualities specify the Hartle - Hawking wave function in terms of
the partition function of deformations of the vector models. We evaluate this
wave function in homogeneous minisuperspace models consisting of
supersymmetry-breaking combinations of a half-integer spin field with either a
scalar, a pseudoscalar or a metric squashing. The wave function appears to be
well-behaved and globally peaked at or near the supersymmetric de Sitter
vacuum, with a low amplitude for large deformations. Its behavior in the
semiclassical limit qualitatively agrees with earlier bulk computations both
for massless and massive fermionic fields.",1905.01322v2
2019-05-08,Calculating ground state properties of correlated fermionic systems with BCS trial wave functions in Slater determinant path-integral approaches,"We introduce an efficient and numerically stable technique to make use of a
BCS trial wave function in the computation of correlation functions of strongly
correlated quantum fermion systems. The technique is applicable to any
projection approach involving paths of independent-fermion propagators, for
example in mean-field or auxiliary-field quantum Monte Carlo (AFQMC)
calculations. Within AFQMC, in the absence of the sign problem, the methodology
allows the use of a BCS reference state which can greatly reduce the required
imaginary time of projection, and improves Monte Carlo sampling efficiency and
statistical accuracy for systems where pairing correlations are important. When
the sign problem is present, the approach provides a powerful generalization of
the constrained-path AFQMC technique which usually uses Slater determinant
trial wave functions. As a demonstration of the capability of the methodology,
we present benchmark results for the attractive Hubbard model, both
spin-balanced (no sign problem) and with a finite spin polarization (with sign
problem).",1905.05012v1
2020-11-10,High efficient metasurface quarter-wave plate with wavefront engineering,"Metasurfaces with local phase tuning by subwavelength elements promise
unprecedented possibilities for ultra-thin and multifunctional optical devices,
in which geometric phase design is widely used due to its resonant-free and
large tolerance in fabrications. By arranging the orientations of anisotropic
nano-antennas, the geometric phase-based metasurfaces can convert the incident
spin light to its orthogonal state, and enable flexible wavefront engineering
together with the function of a half-wave plate. Here, by incorporating the
propagation phase, we realize another important optical device of quarter-wave
plate together with the wavefront engineering as well, which is implemented by
controlling both the cross- and co-polarized light simultaneously with a
singlet metasurface. Highly efficient conversion of the spin light to a variety
of linearly polarized light are obtained for meta-holograms, metalens focusing
and imaging in blue light region. Our work provides a new strategy for
efficient metasurfaces with both phase and polarization control, and enriches
the functionalities of metasurface devices for wider application scenarios.",2011.05116v1
2021-08-31,Quantum unidirectional magnetoresistance,"We predict unidirectional magnetoresistance effects arising in a bilayer
composed of a nonmagnetic metal and a ferromagnetic insulator, whereby both
longitudinal and transverse resistances vary when the direction of the applied
electric field is reversed or the magnetization of the ferromagnetic layer is
rotated. In the presence of spin-orbit coupling, an electron wave incident on
the interface of the bilayer undergoes a spin rotation and a momentum-dependent
phase shift. Quantum interference between the incident and reflected waves
furnishes the electron with an additional velocity that is even in the in-plane
component of the electron's wavevector, giving rise to quadratic
magnetotransport that is rooted in the wave nature of electrons. The
corresponding unidirectional magnetoresistances exhibit decay lengths at the
scale of the Fermi wavelength$-$distinctive signatures of the quantum nonlinear
magnetotransport effect.",2108.13711v2
2016-11-02,Determining the dominant partial wave contributions from angular distributions of single- and double-polarization observables in pseudoscalar meson photoproduction,"This work presents a simple method to determine the significant partial wave
contributions to experimentally determined observables in pseudoscalar meson
photoproduction. First, fits to angular distributions are presented and the
maximum orbital angular momentum $\text{L}_{\mathrm{max}}$ needed to achieve a
good fit is determined. Then, recent polarization measurements for $\gamma p
\rightarrow \pi^{0} p$ from ELSA, GRAAL, JLab and MAMI are investigated
according to the proposed method. This method allows us to project high-spin
partial wave contributions to any observable as long as the measurement has the
necessary statistical accuracy. We show, that high precision and large angular
coverage in the polarization data are needed in order to be sensitive to
high-spin resonance-states and thereby also for the finding of small resonance
contributions. This task can be achieved via interference of these resonances
with the well-known states. For the channel $\gamma p \rightarrow \pi^{0} p$,
those are the $N(1680)\frac{5}{2}^{+}$ and $\Delta(1950)\frac{7}{2}^{+}$,
contributing to the $F$-waves.",1611.01031v2
2019-09-12,Searching for Eccentricity: Signatures of Dynamical Formation in the First Gravitational-Wave Transient Catalogue of LIGO and Virgo,"Binary black holes are thought to form primarily via two channels: isolated
evolution and dynamical formation. The component masses, spins, and
eccentricity of a binary black hole system provide clues to its formation
history. We focus on eccentricity, which can be a signature of dynamical
formation. Employing the spin-aligned eccentric waveform model SEOBNRE, we
perform Bayesian inference to measure the eccentricity of binary black hole
merger events in the first Gravitational-Wave Transient Catalogue of LIGO and
Virgo. We find that all of these events are consistent with zero eccentricity.
We set upper limits on eccentricity ranging from 0.02 to 0.05 with 90%
confidence at a reference frequency of 10 Hz. These upper limits do not
significantly constrain the fraction of LIGO-Virgo events formed dynamically in
globular clusters, because only ~ 5% are expected to merge with measurable
eccentricity. However, with the Gravitational-Wave Transient Catalogue set to
expand dramatically over the coming months, it may soon be possible to
significantly constrain the fraction of mergers taking place in globular
clusters using eccentricity measurements.",1909.05466v2
2019-12-12,Topological $\mathbb{Z}_2$ RVB quantum spin liquid on the ruby lattice,"We construct a short-range resonating valence-bond state (RVB) on the ruby
lattice, using projected entangled-pair states (PEPS) with bond dimension
$D=3$. By introducing non-local moves to the dimer patterns on the torus, we
distinguish four distinct sectors in the space of dimer coverings, which is a
signature of the topological nature of the RVB wave function. Furthermore, by
calculating the reduced density matrix of a bipartition of the RVB state on an
infinite cylinder and exploring its entanglement entropy, we confirm the
topological nature of the RVB wave function by obtaining non-zero topological
contribution, $\gamma=-\rm{ln}\ 2$, consistent with that of a $\mathbb{Z}_2$
topological quantum spin liquid. We also calculate the ground-state energy of
the spin-$\frac{1}{2}$ antiferromagnetic Heisenberg model on the ruby lattice
and compare it with the RVB energy. Finally, we construct a quantum-dimer model
for the ruby lattice and discuss it as a possible parent Hamiltonian for the
RVB wave function.",1912.06215v1
2019-12-20,Theory of Four-Wave Mixing of Cylindrical Vector Beams in Optical Fibers,"Cylindrical vector (CV) beams are a set of transverse spatial modes that
exhibit a cylindrically symmetric intensity profile and a variable polarization
about the beam axis. They are composed of a non-separable superposition of
orbital and spin angular momentum. Critically, CV beams are also the eigenmodes
of optical fiber and, as such, are of wide-spread practical importance in
photonics and have the potential to increase communications bandwidth through
spatial multiplexing. Here, we derive the coupled amplitude equations that
describe the four-wave mixing (FWM) of CV beams in optical fibers. These
equations allow us to determine the selection rules that govern the
interconversion of CV modes in FWM processes. With these selection rules, we
show that FWM conserves the total angular momentum, the sum of orbital and spin
angular momentum, in the conversion of two input photons to two output photons.
When applied to spontaneous four-wave mixing, the selection rules show that
photon pairs can be generated in CV modes directly and can be entangled in
those modes. Such quantum states of light in CV modes could benefit
technologies such as quantum key distribution with satellites.",1912.10109v1
2020-02-07,Charge carrier drop at the onset of pseudogap behavior in the two-dimensional Hubbard model,"We show that antiferromagnetic spin-density wave order in the two-dimensional
Hubbard model yields a drop of the charge carrier density as observed in recent
transport measurements for cuprate superconductors in high magnetic fields upon
entering the pseudogap regime. The amplitude and the (generally incommensurate)
wave vector of the spin-density wave is obtained from dynamical mean-field
theory (DMFT). An extrapolation of the finite temperature results to zero
temperature yields an approximately linear doping dependence of the magnetic
gap $\Delta(p) \propto p^*-p$ in a broad doping range below the critical doping
$p^*$. The magnetic order leads to a Fermi surface reconstruction with electron
and hole pockets, where electron pockets exist only in a restricted doping
range below $p^*$. DC charge transport properties are computed by combining the
renormalized band structure as obtained from the DMFT with a doping-independent
phenomenological scattering rate. A pronounced drop of the longitudinal
conductivity and the Hall number in a narrow doping range below $p^*$ is
obtained.",2002.02786v1
2020-05-21,Cooperative Ru(4d)-Ho(4f) magnetic orderings and phase coexistence in the 6H-perovskite multiferroic Ba3HoRu2O9,"We report cooperative magnetic orderings in a 6H-perovskite multiferroic
system, Ba3HoRu2O9, via comprehensive neutron powder diffraction measurements.
This system undergoes long-range antiferromagnetic ordering at TN1 ~ 50 K with
a propagation wave vector of K1 = (0.5 0 0), a transition temperature much
higher than the previously reported one at ~10 K (TN2). Both Ru and Ho-moments
order simultaneously below TN1, followed by spin-reorientations at lower
temperatures, demonstrating strong Ru(4d)-Ho(4f) magnetic correlation. Below
TN1 another magnetic phase with a propagation wave vector K2 = (0.25 0.25 0)
emerges and coexists with the one associated with K1, which is rarely observed
and suggests complex magnetism due to phase competition in the magnetic ground
state. We argue that the exchange-striction arising from the up-up-down-down
spin structure associated with K2-wave vector below TN2 may be responsible for
the small ferroelectric polarization reported previously in this compound.",2005.10861v2
2020-06-12,Search for gravitational waves from five low mass X-ray binaries in the second Advanced LIGO observing run with an improved hidden Markov model,"Low mass X-ray binaries are prime targets for continuous gravitational wave
searches by ground-based interferometers. Results are presented from a search
for five low-mass X-ray binaries whose spin frequencies and orbital elements
are measured accurately from X-ray pulsations: HETE J1900.1-2455, IGR
J00291+5934, SAX J1808.4-3658, XTE J0929-314, and XTE J1814-338. Data are
analysed from Observing Run 2 of the Advanced Laser Interferometer
Gravitational-wave Observatory (LIGO). The search algorithm uses a hidden
Markov model to track spin wandering, the $\mathcal{J}$-statistic maximum
likelihood matched filter to track orbital phase, and a suite of five vetoes to
reject artefacts from non-Gaussian noise. The search yields a number of
low-significance, above threshold candidates consistent with the selected
false-alarm probability. The candidates will be followed up in subsequent
observing runs.",2006.06907v2
2020-07-23,Interpretations of ground-state symmetry breaking and strong correlation in wavefunction and density functional theories,"Strong correlations within a symmetry-unbroken ground-state wavefunction can
show up in approximate density functional theory as symmetry-broken
spin-densities or total densities, which are sometimes observable. They can
arise from soft modes of fluctuations (sometimes collective excitations) such
as spin-density or charge-density waves at non-zero wavevector. In this sense,
an approximate density functional for exchange and correlation that breaks
symmetry can be more revealing (albeit less accurate) than an exact functional
that does not. The examples discussed here include the stretched H$_2$
molecule, antiferromagnetic solids, and the static charge-density wave/Wigner
crystal phase of a low-density jellium. It is shown that (and in what sense)
the static charge density wave is a soft plasmon.",2007.12052v1
2020-07-30,Coherent multi-mode conversion from microwave to optical wave via a magnon-cavity hybrid system,"Coherent conversion from microwave to optical wave opens new research avenues
towards long distant quantum network covering quantum communication, computing,
and sensing out of the laboratory. Especially multi-mode enabled system is
essential for practical applications. Here we experimentally demonstrate
coherent multi-mode conversion from the microwave to optical wave via
collective spin excitation in a single crystal yttrium iron garnet (YIG,
Y3Fe5O12) which is strongly coupled to a microwave cavity mode in a
three-dimensional rectangular cavity. Expanding collective spin excitation mode
of our magnon-cavity hybrid system from Kittel to multi magnetostatic modes, we
verify that the size of YIG sphere predominantly plays a crucial role for the
microwave-to-optical multi-mode conversion efficiency at resonant conditions.
We also find that the coupling strength between multi magnetostatic modes and a
cavity mode is manipulated by the position of a YIG inside the cavity. It is
expected to be valuable for designing a magnon hybrid system that can be used
for coherent conversion between microwave and optical photons.",2007.15299v1
2020-12-06,A Fundamental Equation for Gravitational Wave and Its Analogues in Type D Spacetimes,"It is well known that Teukolsky equation of gravitational perturbations
provides a powerful tool for the investigation of the ringdown phase of a
binary black hole merger, but it is applicable only for final configurations in
the Kerr cases. Here we introduce a new concept: the spin-coefficient
connection. Employing it and a new transformation function, we find that the
gravitational perturbations can be written as a single equation. Each
coefficients of this equation has explicit physical significance. More
importantly, the equation is universally applied to virtually any black hole
since it does not depend on specific metrics and coordinate system. We also
find that any massless field of nonzero spin $s<2$ obeys the gravitational
wave-like equation, which shows that the fields can be used as the analogue
models of gravitational wave.",2012.03203v1
2020-12-22,Emergent criticality and universality class of spin and charge density wave transitions of two-component lattice Bose gases in optical cavities at finite temperature,"We investigate the finite temperature spin density wave (SDW) and charge
density wave (CDW) transition of two-component lattice spinor Bose gases in
optical lattices in the Mott-insulator limit. At the temperature scale around
half of the on-site interaction energy, we find a new critical regime emerges
and features, in particular, a new bicritical line and two critical lines
associated with the finite temperature SDW-CDW, homogeneous-SDW, and
homogeneous-CDW transition, respectively. Direct calculation of the critical
exponents for the scaling behavior and investigating on the effective theory in
this critical regime show that they belong to the five-dimensional Ising
universality class, clearly manifesting the long-range character of the
system's interaction. Our prediction of the emergent criticality can be readily
observed by current experimental setups operated at the intermediate
temperature scale around half the on-site interaction energy.",2012.11894v1
2020-12-29,Topological turbulence in spin-orbit-coupled driven-dissipative quantum fluids of light generates high angular momentum states,"We demonstrate the formation of a high angular momentum turbulent state in an
exciton-polariton quantum fluid with TE-TM Spin-Orbit Coupling (SOC). The
transfer of particles from quasi-resonantly cw pumped \spl component to \sm
component is accompanied with the generation of a turbulent gas of quantum
vortices by inhomogeneities. We show that this system is unstable with respect
to the formation of bogolons at a finite wave vector, controlled by the laser
detuning. In a finite-size cavity, the domains with this wave vector form a
ring-like structure along the border of a cavity, with a gas of mostly
same-sign vortices in the center. The total angular momentum is imposed by the
sign of TE-TM SOC, the wave vector of instability, and the cavity size. This
effect can be detected experimentally via local dispersion measurements or by
interference. The proposed configuration thus allows simultaneous experimental
studies of quantum turbulence and high-angular momentum states in
continuously-pumped exciton-polariton condensates.",2012.14814v1
2021-03-17,Ultra-compact X-ray binaries as dual-line gravitational-wave sources,"By virtue of their sub-hour orbital periods, ultra-compact X-ray binaries are
promising sources for the space-borne gravitational-wave interferometers LISA,
Taiji, and TianQin. Some of these systems contain a neutron star primary, whose
spin period can be measured directly via pulse timing, or indirectly through
rotational modulations of burst phenomena. It is pointed out here that since
actively accreting stars, with spin frequencies in the hundreds of Hz, may
continuously emit appreciable gravitational waves due to the presence of
accretion-built mountains, toroidal magnetic fields, and/or $r$-mode
oscillations, such binaries are also candidate sources for ground-based
interferometers. Two Galactic systems (4U 1728-34 and 4U 1820-30) are
identified as being potentially detectable by both LISA and aLIGO
simultaneously: a dual-line detection of this sort could provide percent-level
constraints on the mass, radius, and internal magnetic field strength of the
neutron star. With the Einstein Telescope, we find that at least four of the
known ultra-compact binaries become dual-line visible.",2103.09858v2
2021-03-18,Binary black hole mergers from young massive and open clusters: comparison to GWTC-2 gravitational wave data,"Several astrophysical scenarios have been proposed to explain the origin of
the population of binary black hole (BBH) mergers detected in gravitational
waves (GWs) by the LIGO/Virgo Collaboration. Among them, BBH mergers assembled
dynamically in young massive and open clusters have been shown to produce
merger rate densities consistent with LIGO/Virgo estimated rates. We use the
results of a suite of direct, high-precision $N$-body evolutionary models of
young massive and open clusters and build the population of BBH mergers, by
accounting for both a cosmologically-motivated model for the formation of young
massive and open clusters and the detection probability of LIGO/Virgo. We show
that our models produce dynamically-paired BBH mergers that are well consistent
with the observed masses, mass ratios, effective spin parameters, and final
spins of the second Gravitational Wave Transient Catalog (GWTC-2).",2103.10447v2
2021-06-04,Ladder resummation of spin 1/2 fermion many-body systems with arbitrary partial-wave content,"We resum the ladder diagrams for the calculation of the energy density
$\cal{E}$ of a spin 1/2 fermion many-body system in terms of arbitrary vacuum
two-body scattering amplitudes. The partial-wave decomposition of the in-medium
two-body scattering amplitudes is developed, and the expression for calculating
$\cal{E}$ in a partial-wave amplitude expansion is also given. The case of
contact interactions is completely solved and is shown to provide renormalized
results, expressed directly in terms of scattering data parameters, within
cutoff regularization in a wide class of schemes. $S$- and $P$-wave
interactions are considered up to including the first three-terms in the
effective-range expansion, paying special attention to the parametric region
around the unitary limit.",2106.02652v2
2021-06-22,Room And Cryogenic Temperature Behaviour of Magnetic Sensors Based on Gan/Si Single Saw Resonators,"This work analyzes resonance frequency shift vs. the applied magnetic field
strength for GHz operating GaN/Si SAW single resonators. Magnetostrictive
elements (Ni and CoFeB) were deposited in the proximity of the interdigitated
transducers (IDTs) of the resonators (A-type structures) and also over the
IDTs, after covering them with a BCB layer to avoid short circuits with IDTs
metal (B-type structures). This work targets emerging applications of SAW
resonators in driving spin wave pumping and in coupling of surface acoustic
waves (SAW) with superconducting Q-bits. Magnetic sensitivity of the SAWs was
analyzed at room temperature (RT) and at cryogenic temperatures, obtaining high
magnetic sensitivities at 16 K. According to our knowledge, GaN based SAWs are
first time used in magnetic applications; also, cryogenic behavior of magnetic
SAW sensors is first time analyzed.",2106.11605v1
2021-07-27,Normal Approximate Likelihoods to Gravitational Wave Events,"Gravitational wave observations of quasicircular compact binary mergers in
principle provide an arbitrarily complex likelihood over eight independent
intrinsic parameters: the masses and spins of the two merging objects. In this
work, we demonstrate by example that a simple normal approximation over fewer
(usually, three) effective dimensions provides a very accurate representation
of the likelihood, and allows us to replicate the eight-dimensional posterior
over the mass and spin degrees of freedom. Alongside this paper, we provide the
parameters for multivariate normal fits for each event published in GWTC-1 and
GWTC-2, using the posterior samples from the catalog for each associated
release. These normal approximations provide a highly efficient way to
characterize gravitational wave observations when combining large numbers of
events.",2107.13082v2
2021-09-03,First-post-Newtonian generation of gravitational waves in Einstein-Cartan theory,"In this paper we investigate the gravitational-wave generation problem at the
first post-Newtonian order in the context of Einstein-Cartan theory by
exploiting the Blanchet-Damour formalism. The quantum intrinsic spin carried by
slowly moving, weakly stressed, weakly self-gravitating sources is described
geometrically by means of the torsion tensor. We obtain the expression of the
source multipole moments with the required accuracy. The analysis of the
physical meaning of the lowest-order non-radiative moments and of the
asymptotic gravitational waveform is also performed. Eventually, we draw our
conclusions and estimate the order of magnitude of the spin contributions in
the gravitational-wave signal.",2109.01384v2
2021-10-31,Generation of entanglement between a highly wave-packet-tunable photon and a spin-wave memory in cold atoms,"Controls of waveforms (pulse durations) of single photons are important tasks
for effectively interconnecting disparate atomic memories in hybrid quantum
networks. So far, the waveform control of single photon that is entangled with
an atomic memory remains unexplored. Here, we demonstrated control of waveform
length of the photon that is entangled with an atomic spin-wave memory by
varying light-atom interaction time in cold atoms. The Bell parameter S as a
function of the duration of photon pulse is measured, which shows that
violations of Bell equality can be achieved for the photon pulse in the
duration range from 40 ns to 50 us, where, S=2.64+/-0.02 and S=2.26+/-0.05 for
the 40-ns and 50-{\mu}s durations, respectively. The measured results show that
S parameter decreases with the increase in the pulse duration. We confirm that
the increase in photon noise probability per pulse with the pulse-duration is
responsible for the S decrease.",2111.00387v1
2021-11-03,Observation of Dirac Charge Density Waves in Bi$_2$Te$_2$Se,"While parallel segments in the Fermi level contours, often found at the
surfaces of topological insulators (TIs) would imply ""strong"" nesting
conditions, the existence of charge density waves (CDWs) - periodic modulations
of the electron density - has not been verified up to now. Here, we report the
observation of a CDW at the surface of the Bi$_2$Te$_2$Se(111), below $\approx
350\,$K by helium atom scattering, and thus experimental evidence of a CDW
involving Dirac topological electrons. Deviations of the order parameter
observed below $180\,$K and a low temperature break of time reversal symmetry
suggest the onset of a spin density wave with the same period as the CDW in
presence of a prominent electron-phonon interaction originating from the Rashba
spin-orbit coupling.",2111.02323v4
2021-12-08,Gyroscopic Gravitational Memory,"We study the motion of a gyroscope located far away from an isolated
gravitational source in an asymptotically flat spacetime. As seen from a local
frame tied to distant stars, the gyroscope precesses when gravitational waves
cross its path, resulting in a net ""orientation memory"" that carries
information on the wave profile. At leading order in the inverse distance to
the source, the memory consists of two terms: the first is linear in the metric
perturbation and coincides with the spin memory effect, while the second is
quadratic and measures the net helicity of the wave burst. Both are closely
related to symmetries of the gravitational radiative phase space at null
infinity: spin memory probes superrotation charges, while helicity is the
canonical generator of local electric-magnetic duality on the celestial sphere.",2112.04535v3
2021-12-27,Skyrmion based energy efficient straintronic physical reservoir computing,"Physical Reservoir Computing (PRC) is an unconventional computing paradigm,
which exploits nonlinear dynamics of reservoir blocks to perform recognition
and classification tasks. Here we show with simulations that patterned thin
films hosting several skyrmions, particularly one, two, four and nine
skyrmions, can implement energy efficient reservoir computing. This reservoir
computing (RC) block is based on nonlinear breathing dynamics of skyrmions,
which are coupled to each other through dipole interaction and spin waves, in
response to a voltage generated strain. This nonlinear and coupled
magnetization dynamics is exploited to perform temporal pattern recognition.
Two performance metrics, namely Short-Term Memory (STM) and Parity Check (PC)
capacity are studied to demonstrate the potential of such skyrmion based PRC in
addition to showing it can classify sine and square waves with 100% accuracy.
Furthermore, our study demonstrates that nonlinear magnetization dynamics and
interaction through spin waves and dipole coupling have a strong influence on
STM and PC capacity, thus explaining the role of physical interactions in a
dynamical system on its ability to perform Reservoir Computing (RC).",2112.13527v2
2022-01-12,The angular dependence of magnetization dynamics induced by a GHz range strain pulse,"The dynamics of magnetization is important in spintronics, where the coupling
between phonon and magnon attracts much attention. In this work, we study the
angular dependence of the coupling between longitudinal-wave phonon and magnon.
We investigated the magnetization dynamics using the time-resolved
magneto-optical Kerr effect, which allows measuring spin-wave resonances and
the magnetic echo signal. The frequency, mode number, and amplitude of the
spin-wave resonance change with the out-of-plane angle of the external magnetic
field. The amplitude of the magnetic echo signal caused by the strain pulse
also changes with the angle. We calculate these angular dependences based on
the Landau-Lifshitz-Gilbert equation and find that the angles of the external
field and magnetic moment are important factors for the phonon-magnon coupling
when phonon propagates in the thickness direction under the out-of-plane
magnetic field.",2201.04396v1
2022-01-25,Atomistic simulations of magnetoelastic effects on sound velocity,"In this work, we leverage atomistic spin-lattice simulations to examine how
magnetic interactions impact the propagation of sound waves through a
ferromagnetic material. To achieve this, we characterize the sound wave
velocity in BCC iron, a prototypical ferromagnetic material, using three
different approaches that are based on the oscillations of kinetic energy,
finite-displacement derived forces, and corrections to the elastic constants,
respectively. Successfully applying these methods within the spin-lattice
framework, we find good agreement with the Simon effect including high order
terms. In analogy to experiments, morphic coefficients associated with the
transverse and longitudinal waves propagating along the [001] direction are
extracted from fits to the fractional change in velocity data. The present
efforts represent an advancement in magnetoelastic modelling capabilities which
can expedite the design of future magneto-acoustic devices.",2201.10368v3
2022-02-17,Intense high-harmonic optical vortices generated from a micro-plasma-waveguide irradiated by a circularly polarized laser pulse,"A scheme for generating intense high-harmonic optical vortices is proposed.
It relies on spin-orbit interaction of light when a relativistically-strong
circularly polarized laser pulse irradiates a micro-plasma-waveguide. The
intense laser field drives a strong surface wave at the inner boundary of the
waveguide, which leads to high-order harmonic generation as the laser traveling
inside. For a circularly polarized drive laser, the optical chirality is
imprinted to the surface wave, which facilitates conversion of spin angular
momentum of the fundamental light into orbital angular momenta of the
harmonics. A ""shaken waveguide"" model is developed showing that the
aforementioned phenomena arises due to nonlinear plasma response that modifies
electromagnetic mode at high intensities. We further show the phase velocities
of all the harmonic beams are automatically matched to the driving laser, so
that the harmonic intensities increase with propagation distance. The
efficiency of harmonic production are related to the surface wave breaking
effect, which can be significantly enhanced using a tightly focused laser. Our
simulation suggests an overall conversion efficiency $\sim5\%$ can be achieved.",2202.08561v1
2022-04-26,Impact and detectability of spin-tidal couplings in neutron star inspirals,"The gravitational wave signal from a binary neutron star merger carries the
imprint of the deformability properties of the coalescing bodies, and then of
the equation of state of neutron stars. In current models of the waveforms
emitted in these events, the contribution of tidal deformation is encoded in a
set of parameters, the tidal Love numbers. More refined models include
tidal-rotation couplings, described by an additional set of parameters, the
rotational tidal Love numbers, which appear in the waveform at $6.5$
post-Newtonian order. For neutron stars with spins as large as $\sim0.1$, we
show that neglecting tidal-rotation couplings may lead to a significant error
in the parameter estimation by third-generation gravitational wave detectors.
By performing a Fisher matrix analysis we assess the measurability of
rotational tidal Love numbers, showing that their contribution in the waveform
could be measured by third-generation detectors. Our results suggest that
current models of tidal deformation in late inspiral should be improved in
order to avoid waveform systematics and extract reliable information from
gravitational wave signals observed by next generation detectors.",2204.12510v1
2022-08-08,Search for continuous gravitational waves from PSR J0437$-$4715 with a hidden Markov model in O3 LIGO data,"Results are presented for a semi-coherent search for continuous gravitational
waves from the millisecond pulsar PSR J0437$-$4715, using a hidden Markov model
to track spin wandering, in LIGO data from the third LIGO-Virgo observing run.
This is the first search for PSR J0437$-$4715 to cover a wide frequency range
from $60$ Hz to $500$ Hz and simultanously accommodate random spin deviations
from the secular radio ephemeris. Two searches are performed with plausible
coherence times of $10$ days and $30$ days, as the frequency wandering
time-scale of the gravitational-wave-emitting quadrupole is unknown. The former
analysis yields no surviving candidates, while the latter yields five
candidates after the veto procedure. The detection statistic of each of the
five survivors is mapped as a function of sky position, in preparation for
follow-up analyses in the future, e.g. during LIGO-Virgo-KAGRA fourth observing
run.",2208.03932v1
2022-09-07,Acoustic attenuation in magnetic insulator films: effects of magnon polaron formation,"A magnon and a phonon are the quanta of spin wave and lattice wave,
respectively, and they can hybridize into a magnon polaron when their
frequencies and wavenumbers match close enough the values at the exceptional
point. Guided by an analytically calculated magnon polaron dispersion,
dynamical phase-field simulations are performed to investigate the effects of
magnon polaron formation on the attenuation of a bulk acoustic wave in a
magnetic insulator film. It is shown that a stronger magnon-phonon coupling
leads to a larger attenuation. The simulations also demonstrate the existence
of a minimum magnon-phonon interaction time required for the magnon polaron
formation, which is found to decrease with the magnetoelastic coupling
coefficient but increase with the magnetic damping coefficient. These results
deepen the understanding of the mechanisms of acoustic attenuation in magnetic
crystals and provide insights into the design of new-concept spin interconnects
that operate based on acoustically driven magnon propagation.",2209.03481v2
2022-10-24,Fractional Dynamics and Modulational Instability in Long-Range Heisenberg Chains,"We study the effective dynamics of ferromagnetic spin chains in presence of
long-range interactions. We consider the Heisenberg Hamiltonian in one
dimension for which the spins are coupled through power-law long-range exchange
interactions with exponent $\alpha$. We add to the Hamiltonian an anisotropy in
the $z$-direction. In the framework of a semiclassical approach, we use the
Holstein-Primakoff transformation to derive an effective long-range discrete
nonlinear Schr\""odinger equation. We then perform the continuum limit and we
obtain a fractional nonlinear Schr\""odinger-like equation. Finally, we study
the modulational instability of plane-waves in the continuum limit and we prove
that, at variance with the short-range case, plane waves are modulationally
unstable for $\alpha < 3$. We also study the dependence of the modulation
instability growth rate and critical wave-number on the parameters of the
Hamiltonian and on the exponent $\alpha$.",2210.13201v1
2022-12-25,Stationary solitons in F=1 spin-orbit coupled Bose-Einstein condensates,"We consider solitary wave excitations above the ground state of $F=1$
spin-orbit coupled Bose-Einstein condensates (SOBECs). The low energy
properties of SOBECs in any of the three branches of the single particle
dispersion relation can be described by suitable scalar nonlinear Schr\""odinger
(NLS) equations which we obtain using multiple-scale expansions. This enables
us to examine a variety of different configurations, such as dark solitary
waves associated with higher energy branches, as well as dark and bright
structures in the lowest branch. The lowest branch can also exhibit a
``superstripe'' phase that supports solitary waves. In all cases, we provide
explicit expressions for the NLS coefficients, and confirm their validity with
full numerical simulations of the SOBEC system including a harmonic confining
potential.",2212.12966v2
2023-02-08,Non Fermi liquid behavior at flat hot spots from quantum critical fluctuations at the onset of charge- or spin-density wave order,"We analyze quantum fluctuation effects at the onset of charge or spin density
wave order with a $2k_F$ wave vector $\mathbf{Q}$ in two-dimensional metals --
for the special case where $\mathbf{Q}$ connects a pair of hot spots situated
at high symmetry points of the Fermi surface with a vanishing Fermi surface
curvature. We compute the order parameter susceptibility and the fermion
self-energy in one-loop approximation. The susceptibility has a pronounced peak
at $\mathbf{Q}$, and the self-energy displays non-Fermi liquid behavior at the
hot spots, with a linear frequency dependence of its imaginary part. The real
part of the one-loop self-energy exhibits logarithmic divergences with
universal prefactors as a function of both frequency and momentum, which may be
interpreted as perturbative signatures of power laws with universal anomalous
dimensions. As a result, one obtains a non-Fermi liquid metal with a vanishing
quasiparticle weight at the hot spots, and a renormalized dispersion relation
with anomalous algebraic momentum dependencies near the hot spots.",2302.04172v1
2023-04-16,Competing charge and magnetic order in the candidate centrosymmetric skyrmion host EuGa$_2$Al$_2$,"Eu(Ga$_{1-x}$Al$_x$)$_4$ are centrosymmetric systems that have recently been
identified as candidates to stabilise topologically non-trivial magnetic
phases, such as skyrmion lattices. In this Letter, we present a high-resolution
resonant x-ray and neutron scattering study on EuAl2Ga2 that provides new
details of the complex coupling between the electronic ordering phenomena. Our
results unambiguously demonstrate that the system orders to form a spin density
wave with moments aligned perpendicular to the direction of the propagation
vector, and upon further cooling, a cycloid with moments in the ab plane, in
contrast to what has been reported in the literature. We show that concomitant
with the onset of the spin density wave is the suppression of the charge order,
indicative of a coupling between the localised 4$f$ electrons and itinerant
electron density. Furthermore we demonstrate that the charge density wave order
breaks the four-fold symmetry present in the I4/mmm crystal structure, thus
declassifying these systems as square-net magnets.",2304.07903v2
2023-06-20,Kramers' degenerate magnetism and superconductivity,"Motivated by the recent discovery of odd-parity multipolar antiferromagnetic
order in CeRh$_2$As$_2$, we examine the coexistence of such translation
invariant Kramers' degenerate magnetic states and superconductivity. We show
that the presence of such magnetic states generically suppresses
superconductivity, whether it be spin-singlet or spin-triplet, unless the
magnetic state drives a symmetry-required pair density wave (PDW)
superconducting order. We apply our results to CeRh$_2$As$_2$, where no pair
density wave order appears; and to the loop current order in the cuprates,
where such pair density wave superconductivity must appear together with
Bogoliubov Fermi surfaces. In the former case, we explain why superconductivity
is not suppressed.",2306.11218v3
2023-09-15,Slowly Rotating Close Binary Stars in Cassini States,"Recent asteroseismic measurements have revealed a small population of stars
in close binaries, containing primaries with extremely slow rotation rates.
Such stars defy the standard expectation of tidal synchronization in such
systems, but they can potentially be explained if they are trapped in a
spin-orbit equilibrium known as Cassini state 2 (CS2). This state is maintained
by orbital precession due to an outer tertiary star, and it typically results
in a very sub-synchronous rotation rate and high degree of spin-orbit
misalignment. We examine how CS2 is affected by magnetic braking and different
types of tidal dissipation. Magnetic braking results in a slower equilibrium
rotation rate, while tidal dissipation via gravity waves can result in a
slightly higher rotation rate than predicted by equilibrium tidal theory, and
dissipation via inertial waves can result in much slower rotation rates. For
seven binary systems with slowly rotating primaries, we predict the location of
the outer tertiary predicted by the CS2 theory. In five of these systems, a
tertiary companion has already been detected, although it closer than expected
in three of these, potentially indicating tidal dissipation via inertial waves.
We also identify a few new candidate systems among a population of eclipsing
binaries with rotation measurements via spot modulation.",2309.08506v1
2023-09-18,Terahertz magnon frequency comb,"Magnon frequency comb (MFC), the spin-wave spectra composing of equidistant
coherent peaks, is attracting much attention in magnonics. A terahertz (THz)
MFC, combining the advantages of the THz and MFC technologies, is highly
desired because it would significantly advance the MFC applications in
ultrafast magnonic metrology, sensing, and communications. Here, we show that
the THz MFC can be generated by nonlinear interactions between spin waves and
skyrmions in antiferromagnets [Z. Jin \emph{et al}.,
\href{https://doi.org/10.48550/arXiv.2301.03211}{arXiv:2301.03211}]. It is
found that the strength of the three-wave mixing between propagating magnons
and breathing skyrmions follows a linear dependence on the driving frequency
and the MFC signal can be observed over a broad driving frequency range. Our
results extend the working frequency of MFC to the THz regime, which would have
potential applications in ultrafast spintronic devices and promote the
development of nonlinear magnonics in antiferromagnets.",2309.09475v1
2023-10-20,A Study on the Well-Posedness of 1D Energy-Critical Half-Wave Maps Equations,"In this article, we study the well-posedness of the energy-critical half-wave
maps equation (HWM) in dimension $1$. The half-wave maps equation emerges from
the continuum limit of the Haldane Shastry spin chains and has been shown to
arise as the continuum limit of Calogero-Moser classical spin systems. In
higher dimension $d\geq 5$, it has been shown that (HWM) is well-posed by
Krieger and Sire. This result has been improved by Krieger and Kiesenhofer to
$d = 4$ but the Strichartz estimate on which the argument is built no longer
holds for smaller dimensions. A Lax-pair structure has been revealed for this
equation by Lenzmann and G\'erard, indicating complete integrability and the
fact that rational solutions stay rational for all time. The well-posedness of
the (HWM) equation in lower dimensions remains an open problem. Here, we show
the well-posedness of (HWM) in the rational case for finite times with
separated poles, and for large and infinite times with distinct speeds of
propagation.",2310.13442v3
2023-11-08,Glitching pulsars as gravitational wave sources,"Spinning neutron stars, when observed as pulsars, are seen to undergo
occasional spin-up events known as glitches. Despite several decades of study,
the physical mechanisms responsible for glitches are still not well understood,
but probably involve an interplay between the star's outer elastic crust, and
the superfluid and superconducting core that lies within. Glitches will be
accompanied by some level of gravitational wave emission. In this article we
review proposed models that link gravitational wave emission to glitches,
exploring both short duration burst-like emission, and longer-lived signals. We
illustrate how detections (and in some cases, non-detections) of gravitational
signals probe both the glitch mechanism, and, by extension, the behaviour of
matter at high densities.",2311.04586v2
2023-11-30,Torsion waves in Covariant Canonical Gauge Theory of Gravity,"In the framework of Covariant Canonical Gauge Theory of Gravity (CCGG), the
dynamics of the arising torsion field is analyzed. Since the action is
quadratic in the Riemann tensor and therefore also in the derivative of the
torsion, torsion is no longer identical to spin density as in the
Einstein-Cartan theory but propagates dynamically. It is shown in this paper,
that in the weak torsion limit, the torsion axial vector field obeys a wave
equation with an effective mass term, which is partially dependent on the
scalar curvature. It is also shown, that its source is given by the fermion
axial current, which is the net fermionic spin of the system. Possible
measurable effects and approaches to experimental analysis are discussed. For
example, neutron star mergers could act as a dipole or quadrupole for torsional
radiation and an analysis of radiation of pulsars could lead to a detection of
torsional wave background radiation.",2311.18602v1
2023-12-03,Flavor asymmetry of light sea quarks in proton : A light-front spectator model,"We formulate a light-front spectator model for the proton that incorporates
the presence of light sea quarks. In this particular model, the sea quarks are
seen as active partons, whereas the remaining components of the proton are
treated as spectators. The proposed model relies on the formulation of the
light-front wave function constructed by the soft wall AdS/QCD. The model wave
functions are parameterized by fitting the unpolarized parton distribution
functions of light sea quarks from the CTEQ18 global analysis. We then employ
the light-front wave functions to obtain the sea quarks generalized parton
distribution functions, transverse momentum dependent parton distributions, and
their asymmetries, which are accessible in the upcoming Electron-Ion-Colliders.
We investigate sea quarks' spin and orbital angular momentum contributions to
the proton spin.",2312.01484v1
2023-12-07,Ringdown of a dynamical spacetime,"The gravitational waves emitted (some time) after two black holes merge are
well described by the theory of linear perturbations on a spacetime
characterized by the mass and spin of the remnant. However, in the very early
stages right after merger, both the mass and spin are changing. In this work we
explore, in a set up based on Vaidya's spacetime, the dynamical consequences of
a change of mass in the spacetime due to the accretion of null matter (for
example, gravitational waves). We show that accretion imprints time-dependent
frequencies and amplitude to a ringdown waveform, and we show how to model
accurately this effect in certain regimes. We also comment on the direct
emission of gravitational waves due to perturbations in the in--falling matter,
which is of relevance for black holes embedded in astrophysical environments.",2312.04633v1
2023-12-14,Magnetization Reversal of 50-nm-wide Ni81Fe19 Nanostripes by Ultrashort Magnons in Yttrium Iron Garnet for Memory-Enhanced Magnonic Circuits,"Spin waves (magnons) can enable wave-based neuromorphic computing by which
one aims at overcoming limitations inherent to conventional electronics and the
von Neumann architecture. In this study, we explore the storage of magnon
signals and the magnetization switching of periodic and aperiodic arrays of
Ni81Fe19 (Py) nanostripes with widths (w) between 50 nm and 200 nm. Spin waves
excited with low microwave power in yttrium iron garnet induce the reversal of
the nanostripes of different w in a small opposing field. Exploiting
microwave-to-magnon transducers for magnon modes with ultrashort wavelengths,
we demonstrate the reversal of 50-nm-wide Py nanostripes by magnons with
wavelength ~ 100 nm after they have propagated over 25 micrometer in YIG. The
findings are important for designing a magnon-based in-memory computing device.",2312.09177v1
2024-01-08,Hybrid skyrmion and anti-skyrmion phases in polar $C_{\rm 4v}$ systems,"We investigate the stability of the skyrmion crystal phase in a tetragonal
polar system with the Dzyaloshinskii-Moriya interaction by focusing on the
symmetry of ordering wave vectors forming the skyrmion crystal. Our analysis is
based on numerical simulations for an effective spin model, which is derived
from the weak-coupling regime in the Kondo lattice model on a polar square
lattice. We show that a hybrid square skyrmion crystal consisting of Bloch and
N\'eel spin textures emerges even under polar $C_{\rm 4v}$ symmetries when the
ordering wave vectors correspond to low-symmetric wave vectors in momentum
space, which is in contrast to the expectation from the Lifshitz invariants. We
also show the instability toward the anti-skyrmion crystal and rhombic skyrmion
crystal depending on the direction of the Dzyaloshinskii-Moriya vector in
momentum space. Furthermore, we show that the regions of the skyrmion crystal
phases are affected by taking into account the symmetric anisotropic exchange
interaction. Our results open the potential direction of engineering the hybrid
skyrmion crystal and anti-skyrmion crystal phases in polar magnets.",2401.04245v1
2024-01-12,Spin squeezed states and wobbling motion in collective Hamiltonian,"A semiclassical approach is proposed to calculate the collective potential
and mass parameters to formulate a collective Hamiltonian capable of describing
the wobbling motion in both even-even and odd-mass systems. By diagonalizing
the resulting collective Hamiltonian (CH), one can obtain the energies and wave
functions associated with the wobbling states. Furthermore, a novel technique
called spin squeezed state (SSS) maps is introduced based on the derived wave
functions. To validate the results obtained from the collective Hamiltonian, a
comparative analysis is conducted against predictions from the triaxial rotor
model (TRM) and particle triaxial rotor (PTR) model. Notably, the SSS plots
determined using the TRM and PTR models exhibit a strong correlation with the
probability density distributions of the wave functions obtained from the CH.
This correlation highlights the consistency and coherence between the different
theoretical approaches when describing the wobbling phenomenon and associated
rotational dynamics.",2401.06460v1
2024-02-05,Spinning $Q$-ball Superradiance in 3+1D,"Recently, it has been found that a $Q$-ball can amplify waves incident upon
it, due to rotation in the internal space and the interaction of the two modes
in the complex scalar field. While the spherically symmetric 3D case has been
investigated previously, here we explore the 3D axi-symmetric case, which is
numerically much more challenging. The difficulty comes because a partial wave
expansion is needed, and the different partial waves can not be separated, for
either the background spinning Q-ball solution or the perturbative scattering
on top of it. A relaxation method and a high dimensional shooting method are
applied to compute the Q-ball solutions and the amplification factors
respectively. We also classify the behavior of the amplification factors and we
discuss their bounds and the superradiance criteria.",2402.03193v2
2024-02-24,"Phase diagram of the one dimensional $t_1-t_2-J$ model: Ferromagnetism, triplet pairing, charge and pair density waves","We present a density matrix renormalization group (DMRG) study of an extended
$t-J$ model with hopping to the first and second neighbors -- the one
dimensional $t_1-t_2-J$ model. The full phase diagram as a function of the
density $n$ and exchange strength $J$, for both positive and negative values of
$t_2$, is obtained. For $t_2=-0.5$ we observe that, in the strongly interacting
region, Nagaoka Ferromagnetism (FM) is accompanied by a triplet pair density
wave (PDW) upon doping. As the spin exchange $J$ increases, a charge density
wave (CDW) phase emerges and then gives way to singlet superconductivity (SC).
This phase behaves as a singlet PDW with vanishing spacial average of the order
parameter and a spin gap. When $t_2=0.5$, the physics is basically reminiscent
of the conventional $t-J$ model, undergoing a transition from a metallic to a
SC phase as a function of $J$.",2402.15927v1
2011-02-04,Three-dimensional simulations of internal wave breaking and the fate of planets around solar-type stars,"We study the fate of internal gravity waves approaching the centre of a
non-rotating solar-type star, by performing 3D numerical simulations using a
Boussinesq-type model. These waves are excited at the top of the radiation zone
by the tidal forcing of a short-period planet on a circular, coplanar orbit.
This extends previous work done in 2D by Barker & Ogilvie. We first derive a
linear wave solution, which is not exact in 3D; however, the reflection of
ingoing waves from the centre is close to perfect for moderate amplitude waves.
Waves with sufficient amplitude to cause isentropic overturning break, and
deposit their angular momentum near the centre. This forms a critical layer, at
which the angular velocity of the flow matches the orbital angular frequency of
the planet. This efficiently absorbs ingoing waves, and spins up the star from
the inside out, while the planet spirals into the star. We also perform
numerical integrations to determine the linearised adiabatic tidal response
throughout the star, for solar-type stellar models with masses in the range 0.5
< m_star/M_sun < 1.1, throughout their main sequence lifetimes. The aim is to
study the launching region for these waves at the top of the radiation zone in
more detail, and to determine the accuracy of a semi-analytic approximation for
the tidal torque on the star, that was derived under the assumption that all
ingoing wave angular momentum is absorbed in a critical layer. The main
conclusions are that this nonlinear mechanism of tidal dissipation could
provide an explanation for the survival of all short-period extrasolar planets
observed around FGK stars, while it predicts the destruction of more massive
planets. This work provides further support for the model outlined in a
previous paper by Barker & Ogilvie, and makes predictions that will be tested
by ongoing observational studies, such as WASP and Kepler.",1102.0857v1
2000-07-28,"Gravitational Waves from a Compact Star in a Circular, Inspiral Orbit, in the Equatorial Plane of a Massive, Spinning Black Hole, as Observed by LISA","Results are presented from high-precision computations of the orbital
evolution and emitted gravitational waves for a stellar-mass object spiraling
into a massive black hole in a slowly shrinking, circular, equatorial orbit.
The focus of these computations is inspiral near the innermost stable circular
orbit (isco)---more particularly, on orbits for which the angular velocity
Omega is 0.03 < Omega/Omega_{isco} < 1. The computations are based on the
Teukolsky-Sasaki-Nakamura formalism, and the results are tabulated in a set of
functions that are of order unity and represent relativistic corrections to
low-orbital-velocity formulas. These tables can form a foundation for future
design studies for the LISA space-based gravitational-wave mission. A first
survey of applications to LISA is presented: Signal to noise ratios S/N are
computed and graphed as functions of the time-evolving gravitational-wave
frequency for representative values of the hole's mass M and spin a and the
inspiraling object's mass \mu, with the distance to Earth chosen to be r_o = 1
Gpc. These S/N's show a very strong dependence on the black-hole spin, as well
as on M and \mu. A comparison with predicted event rates shows strong promise
for detecting these waves, but not beyond about 1Gpc if the inspiraling object
is a white dwarf or neutron star. This argues for a modest lowering of LISA's
noise floor. A brief discussion is given of the prospects for extracting
information from the observed waves",0007074v1
2014-09-15,Gravitational-wave modes from precessing black-hole binaries,"Gravitational waves from precessing black-hole binaries exhibit features that
are absent in nonprecessing systems. The most prominent of these is a
parity-violating asymmetry that beams energy and linear momentum preferentially
along or opposite to the orbital angular momentum, leading to recoil of the
binary. The asymmetry will appear as amplitude and phase modulations at the
orbital frequency. For strongly precessing systems, it accounts for at least 3%
amplitude modulation for binaries in the sensitivity band of ground-based
gravitational-wave detectors, and can exceed 50% for massive systems. Such
asymmetric features are also clearly visible when the waves are decomposed into
modes of spin-weighted spherical harmonics, and are inherent in the waves
themselves---rather than resulting from residual eccentricity in numerical
simulations, or from mode-mixing due to precession. In particular, there is
generically no instantaneous frame for which the mode decomposition will have
any symmetry. We introduce a method to simplify the expressions for waveforms
given in analytical relativity, which can be used to combine existing
high-order waveforms for nonprecessing systems with expressions for the
precessing contributions, leading to improved accuracy and a unified treatment
of precessing and nonprecessing binaries. Using this method, it is possible to
clarify the nature and the origins of the asymmetries and show the effects of
asymmetry on recoils more clearly. We present post-Newtonian (PN) expressions
for the waveform modes that include these terms, complete to the relative 2PN
level in spin (proportional to $v^4/c^4$ times a certain combination of the
spins). Comparing the results of those expressions to numerical results, we
find good qualitative agreement. We also demonstrate how these expressions can
be used to efficiently calculate waveforms for gravitational-wave astronomy.",1409.4431v2
2018-07-31,Quantifying wave-function overlaps in inhomogeneous Majorana nanowires,"A key property of Majorana zero modes is their protection against local
perturbations. In the standard picture, this protection is guaranteed by a high
degree of spatial nonlocality of the Majoranas, namely a suppressed
wave-function overlap, in the topological phase. However, a careful
characterisation of resilience to local noise goes beyond mere spatial
separation, and must also take into account the projection of wave-function
spin. By considering the susceptibility of a given zero mode to different local
perturbations, we find the relevant forms of spin-resolved wave-function
overlaps that measure its resilience. We quantify these overlaps and study
their dependence with nanowire parameters in several classes of experimentally
relevant configurations. These include nanowires with inhomogeneous depletion
and induced pairing, barriers and quantum dots. Smooth inhomogeneities have
been shown to produce near-zero modes, so-called pseudo-Majoranas, below the
critical Zeeman field in the bulk. Surprisingly, their resilience is found to
be comparable or better than that of topological Majoranas in realistic
systems. We further study how accurately their overlaps can be estimated using
a purely local measurement on one end of the nanowire, accessible through
conventional transport experiments. In uniform nanowires this local estimator
is remarkably accurate. In inhomogeneous cases it is less accurate but can
still provide reasonable estimates for potential inhomogeneities of the order
of the superconducting gap. We further analyse the zero mode wave-function
structure, spin texture and spectral features associated with each type of
inhomogeneity. All our results highlight the strong connection between internal
wave-function degrees of freedom, nonlocality and protection in smoothly
inhomogeneous nanowires.",1807.11924v3
2022-06-29,Prospects for detecting and localizing short-duration transient gravitational waves from glitching neutron stars without electromagnetic counterparts,"Neutron stars are known to show accelerated spin-up of their rotational
frequency called a glitch. Highly magnetized rotating neutron stars (pulsars)
are frequently observed by radio telescopes (and in other frequencies), where
the glitch is observed as irregular arrival times of pulses which are otherwise
very regular. A glitch in an isolated neutron star can excite the fundamental
(f)-mode oscillations which can lead to gravitational wave generation.
Electromagnetic observations of pulsars (and hence pulsar glitches) require the
pulsar to be oriented so that the jet is pointed toward the detector, but this
is not a requirement for gravitational wave emission which is more isotropic
and not jetlike. Hence, gravitational wave observations have the potential to
uncover nearby neutron stars where the jet is not pointed towards the Earth. In
this work, we study the prospects of finding glitching neutron stars using a
generic all-sky search for short-duration gravitational wave transients. The
analysis covers the high-frequency range from $1-4$ kHz of LIGO-Virgo detectors
for signals up to a few seconds. We set upper limits for the third observing
run of the LIGO-Virgo detectors and present the prospects for upcoming
observing runs of LIGO, Virgo, KAGRA, and LIGO India. We find the detectable
glitch size will be around $10^{-5}$ Hz for the fifth observing run for pulsars
with spin frequencies and distances comparable to the Vela pulsar. We also
present the prospects of localizing the direction in the sky of these sources
with gravitational waves alone, which can facilitate electromagnetic follow-up.
We find that for the five detector configuration, the localization capability
for a glitch size of $10^{-5}$ Hz is around $132\,\mathrm{deg}^{2}$ at
$1\sigma$ confidence for $50\%$ of events with distance and spin frequency as
that of Vela.",2206.14515v3
2024-02-05,Convolutional restricted Boltzmann machine (CRBM) correlated variational wave function for the Hubbard model on a square lattice: Mott metal-insulator transition,"We use a convolutional restricted Boltzmann machine (CRBM) neural network to
construct a variational wave function (WF) for the Hubbard model on a square
lattice and study it using the variational Monte Carlo (VMC) method. In the
wave function, the CRBM acts as a correlation factor to a mean-field BCS state.
The number of variational parameters in the WF does not grow automatically with
the lattice size and it is computationally much more efficient compared to
other neural network based WFs. We find that in the intermediate to strong
coupling regime of the model at half-filling, the wave function outperforms
even the highly accurate long range backflow-Jastrow correlated wave function.
Using the WF, we study the ground state of the half-filled model as a function
of onsite Coulomb repulsion $U$. We consider two cases for the
next-nearest-neighbor hopping parameter, e.g., $t'=0$ as well as a frustrated
model case with $t'\neq 0$. By examining several quantities, e.g., double
occupancy, charge gap, momentum distribution, and spin-spin correlations, we
find that the weekly correlated phase in both cases is paramagnetic metallic
(PM). As $U$ is increased, the system undergoes a first-order Mott transition
to an insulating state at a critical $U_c$, the value of which depends upon
$t'$. The Mott state in both cases is spin gapped with long range
antiferromagnetic (AF) order. Remarkably, the AF order emerges spontaneously
from the wave function which does not have any explicitly broken symmetry in
it. Apart from some quantitative differences in the results for the two values
of $t'$, we find some interesting qualitative differences in the way the Mott
transition takes place in the two cases.",2402.02794v1
2001-01-10,X-ray Observations of Neutron Star Binaries: Evidence for Millisecond Spins,"High amplitude X-ray brightness oscillations during thermonuclear X-ray
bursts were discovered with the Rossi X-ray Timing Explorer (RXTE) in early
1996. Spectral and timing evidence strongly supports the conclusion that these
oscillations are caused by rotational modulation of the burst emission and that
they reveal the spin frequency of neutron stars in low mass X-ray binaries
(LMXB), a long sought goal of X-ray astronomy. I briefly review the status of
our knowledge of these oscillations. So far 10 neutron star systems have been
observed to produce burst oscillations, interestingly, the observed frequencies
cluster in a fairly narrow range from about 300 - 600 Hz, well below the
break-up frequency for most modern neutron star equations of state (EOS). This
has led to suggestions that their spin frequencies may be limited by the loss
of angular momentum due to gravitational wave emission. Connections with
gravity wave rotational instabilities will be briefly described.",0101160v1
2005-04-25,Self-interaction spin effects in inspiralling compact binaries,"Gravitational radiation drives compact binaries through an inspiral phase
towards a final coalescence. For binaries with\textit{spin, mass quadrupole and
magnetic dipole moments}, various contributions add to this process, which is
characterized by the rate of increase $df/dt$ of the gravitational wave
frequency and the accumulated number $\mathcal{N}$ of gravitational wave
cycles. We present here all contributions to $df/dt$ and $% \mathcal{N}$ up to
the second post-Newtonian order. Among them we give for the first time the
contributions due to the \textit{self-interaction of individual spins}. These
are shown to be commensurable with the proper spin-spin contributions for the
recently discovered J0737-3039 double pulsar, and argued to represent the first
corrections to the radiation reaction in the Lense-Thirring approach.",0504538v2
1995-03-30,Charge and spin density wave ordering transitions in strongly correlated metals,"We study the quantum transition from a strongly correlated metal, with heavy
fermionic quasiparticles, to a metal with commensurate charge or spin density
wave order. To this end, we introduce and numerically analyze a large
dimensionality model of Ising spins in a transverse field, coupled to two
species of fermions; the analysis borrows heavily from recent progress in the
solution of the Hubbard model in large dimensions. At low energies, the Ising
order parameter fluctuations are characterized by the critical exponent $z \nu
= 1$, while above an energy scale, $\Gamma$, there is a crossover to $z\nu =
1/2$ criticality. We show that $\Gamma$ is of the order of the width of the
heavy quasiparticle band, and can be made arbitrarily small for a correlated
metal close to a Mott-Hubbard insulator. Therefore, such a correlated metal has
a significant intermediate energy range of $z\nu=1/2$ behavior, a single
particle spectrum with a narrow quasiparticle band, and well-formed analogs of
the lower and upper Hubbard bands; we suggest that these features are
intimately related in general.",9503158v1
1995-11-01,Theory of Phonon-Assisted Multimagnon Optical Absorption and Bimagnon States in Quantum Antiferromagnets,"We calculate the effective charge for multimagnon infrared (IR) absorption
assisted by phonons in a perovskite like antiferromagnet and we compute the
spectra for two magnon absorption using interacting spin-wave theory. The full
set of equations for the interacting two magnon problem is presented in the
random phase approximation for arbitrary total momentum of the magnon pair. The
spin wave theory results fit very well the primary peak of recent measured
bands in the parent insulating compounds of cuprate superconductors. The line
shape is explained as being due to the absorption of one phonon plus a new
quasiparticle excitation of the Heisenberg Hamiltonian that consists off a long
lived virtual bound state of two magnons (bimagnon). The bimagnon states have
well defined energy and momentum in a substantial portion of the Brillouin
zone. The higher energy bands are explained as one phonon plus higher
multimagnon absorption processes. Other possible experiments for observing
bimagnons are proposed. In addition we predict the line shape for the spin one
system La$_2$NiO$_4$.",9511005v1
1996-09-17,Spin-density wave versus superconducting fluctuations for quasi-one-dimensional electrons in two chains of Tomonaga-Luttinger liquids,"We study possible states at low temperatures by applying the
renormalization-group method to two chains of Tomonaga-Luttinger liquids with
both repulsive intrachain interactions and interchain hopping. As the energy
decreases below the hopping energy, three distinct regions I, III, and II
appear successively depending on properties of fluctuations. The crossover from
the spin-density wave (SDW) state to superconducting (SC) state takes place in
region III where there are the excitation gaps of transverse charge and spin
fluctuations. The competition between SDW and SC states in region III is
crucial to understanding the phase diagram in the quasi-one-dimensional organic
conductors.",9609154v1
1996-11-14,Heisenberg model with Dzyaloshinskii-Moriya interaction: A Schwinger boson study,"We present a Schwinger-boson approach to the Heisenberg model with
Dzyaloshinskii-Moriya interaction. We write the anisotropic interactions in
terms of Schwinger bosons keeping the correct symmetries present in the spin
representation, which allows us to perform a conserving mean-field
approximation. Unlike previous studies of this model by linear spin-wave
theory, our approach takes into account magnon-magnon interactions and includes
the effects of three-boson terms characteristic of noncollinear phases. The
results reproduce the linear spin-wave predictions in the semiclassical large-S
limit, and show a small renormalization in the strong quantum limit S=1/2. For
the sake of definiteness, we specialize the calculations for the pattern of
Moriya vectors corresponding to the orthorhombic phase in La_2CuO_4, and give a
fairly detailed account of the behavior of ground-state energy, anisotropy gap,
and net ferromagnetic moment. In the last part of this work we generalize our
approach to describe the geometry of the intermediate phase in
La_{2-x}Nd_xCuO_4, and discuss the effects of including nondegenerate 2p_z
oxygen orbitals in the calculations.",9611116v1
1997-05-27,Incommensurate phases in ferromagnetic spin-chains with weak antiferromagnetic interchain interaction,"We study planar ferromagnetic spin-chain systems with weak antiferromagnetic
inter-chain interaction and dipole-dipole interaction. The ground state depends
sensitively on the relative strengths of antiferromagnetic exchange and dipole
energies kappa=J'a^2c/(g_L\mu_B)^2. For increasing values of \kappa, the ground
state changes from a ferromagnetic via a collinear antiferromagnetic and an
incommensurate phase to a 120^o structure for very large antiferromagnetic
energy. Investigation of the magnetic phase diagram of the collinear phase, as
realized in CsNiF_3, shows that the structure of the spin order depends
sensitivly on the direction of the magnetic field in the hexagonal plane. For
certain angular domains of the field incommensurate phases appear which are
separated by commensurate phases. When rotating the field, the wave vector
characterizing the structure changes continuously in the incommensurate phase,
whereas in the commensurate phase the wave vector is locked to a fixed value
describing a two-sublattice structure. This is a result of the competition
between the exchange and the dipole-dipole interaction.",9705280v1
1997-09-26,Effective Field Theory Approach to Ferromagnets and Antiferromagnets in Crystaline Solids,"We present a systematic construction of effective lagrangians for the low
energy and momentum region of ferromagnetic and antiferromagnetic spin waves in
crystalline solids. We fully exploit the spontaneous symmetry breaking pattern
$SU(2)\to U(1)$, the fact that spin waves are its associated Goldstone modes,
the crystallographic space group and time reversal symmetries. We show how to
include explicit SU(2) breaking terms due to spin-orbit and magnetic dipole
interactions. The coupling to electromagnetic fields is also discussed in
detail. For definiteness we work with the space group $R\bar 3 c$ and present
our results to next to leading order.",9709298v3
1997-10-01,"Magnetic ordering, spin waves, and Haldane gap excitations in (Nd_x Y_{1-x})_2 Ba Ni O_5 linear-chain mixed-spin antiferromagnets","Linear-chain nickelates with the composition (Nd_x Y_{1-x})_2 Ba Ni O_5 (x=1,
x=0.75, x=0.5, and x=0.25) are studied in a series of neutron scattering
experiments. Powder diffraction is used to determine the temperature dependence
of the magnetic structure in all four systems. Single-crystal inelastic neutron
scattering is employed to investigate the temperature dependence of the
Haldane-gap excitations and low-energy spin waves in the x=1 compound Nd_2 Ba
Ni O_5. The results of these experiments are discussed in the context of the
``Haldane chain in a staggered field'' model for R_2 Ba Ni O_5 systems, and
quantitative agreement with theory is obtained.",9710015v2
1998-05-12,Collective excitation spectrum of a disordered Hubbard model,"We study the collective excitation spectrum of a d=3 site-disordered
Anderson-Hubbard model at half-filling, via a random-phase approximation (RPA)
about broken-symmetry, inhomogeneous unrestricted Hartree-Fock (UHF) ground
states. We focus in particular on the density and character of low-frequency
collective excitations in the transverse spin channel. In the absence of
disorder, these are found to be spin-wave-like for all but very weak
interaction strengths, extending down to zero frequency and separated from a
Stoner-like band, to which there is a gap. With disorder present, a prominent
spin-wave-like band is found to persist over a wide region of the
disorder-interaction phase plane in which the mean-field ground state is a
disordered antiferromagnet, despite the closure of the UHF single-particle gap.
Site resolution of the RPA excitations leads to a microscopic rationalization
of the evolution of the spectrum with disorder and interaction strength, and
enables the observed localization properties to be interpreted in terms of the
fraction of strong local moments and their site-differential distribution.",9805132v1
1998-09-28,Bruekner approach to the spin-wave gap critical index for the two-layer Heisenberg antiferromagnet,"We consider the two-layer Heisenberg antiferromagnet near a zero temperature
quantum phase transition from a disordered dimer phase to a collinear Neel
state. At approaching the transition point the spin-wave gap vanishes as
$\Delta \propto (J_\perp-J_{\perp c})^{\nu}$. To account for strong
correlations between the S=1 elementary excitations we apply the Brueckner
diagram approach which gives the critical index $\nu\approx 0.5$. We
demonstrate also that the linearized in density Brueckner equations give the
mean field result $\nu=1$. Finally an expansion of the Brueckner equations in
powers of the density, combined with the scaling hypothesis, give $\nu\approx
0.67$. This value reasonably agrees with that of the nonlinear O(3)
$\sigma$-model. Our approach demonstrates that for other quantum spin models
the critical index can be different from that in the nonlinear $\sigma$-model.
We discuss the conditions for this to occur.",9809368v1
1998-09-30,Exact diagonalization of the S=1/2 Heisenberg antiferromagnet on finite bcc lattices to estimate properties on the infinite lattice,"Here we generate finite bipartite body-centred cubic lattices up to 32
vertices. We have studied the spin one half Heisenberg antiferromagnet by
diagonalizing its Hamiltonian on each of the finite lattices and hence
computing its ground state properties. By extrapolation of these data we obtain
estimates of the T = 0 properties on the infinite bcc lattice. Our estimate of
the T = 0 energy agrees to five parts in ten thousand with third order spin
wave and series expansion method estimates, while our estimate of the staggered
magnetization agrees with the spin wave estimate to within a quarter of one
percent.",9809405v1
1998-10-09,Magnetic anisotropy and low-energy spin waves in the Dzyaloshinskii-Moriya spiral magnet Ba_2 Cu Ge_2 O_7,"New neutron diffraction and inelastic scattering experiments are used to
investigate in detail the field dependence of the magnetic structure and
low-energy spin wave spectrum of the Dzyaloshinskii-Moriya helimagnet Ba_2 Cu
Ge_2 O_7. The results suggest that the previously proposed model for the
magnetism of this compound (an ideal sinusoidal spin spiral, stabilized by
isotropic exchange and Dzyaloshinskii-Moriya interactions) needs to be refined.
Both new and previously published data can be quantitatively explained by
taking into account the Kaplan-Shekhtman-Entin-Wohlman-Aharony (KSEA) term, a
special magnetic anisotropy term that was predicted to always accompany
Dzyaloshinskii-Moriya interactions in insulators.",9810122v1
1998-12-17,Spin wave analysis to the spatially-anisotropic Heisenberg antiferromagnet on triangular lattice,"We study the phase diagram at T=0 of the antiferromagnetic Heisenberg model
on the triangular lattice with spatially-anisotropic interactions. For values
of the anisotropy very close to J_alpha/J_beta=0.50, conventional spin wave
theory predicts that quantum fluctuations melt the classical structures, for
S=1/2. For the regime J_beta<J_alpha, it is shown that the incommensurate
spiral phases survive until J_beta/J_alpha=0.27, leaving a wide region where
the ground state is disordered. The existence of such nonmagnetic states
suggests the possibility of spin liquid behavior for intermediate values of the
anisotropy.",9812311v2
1999-06-10,Hall-like effect induced by spin-orbit interaction,"The effect of spin-orbit interaction on electron transport properties of a
cross-junction structure is studied. It is shown that it results in spin
polarization of left and right outgoing electron waves. Consequently, incoming
electron wave of a proper polarization induces voltage drop perpendicularly to
the direct current flow between source and drain of the considered
four-terminal cross-structure. The resulting Hall-like resistance is estimated
to be of the order of 10^-3 - 10^-2 h/e^2 for technologically available
structures. The effect becomes more pronounced in the vicinity of resonances
where Hall-like resistance changes its sign as function of the Fermi energy.",9906151v1
2000-02-01,Spin Dynamics and Orbital State in LaTiO_3,"A neutron scattering study of the Mott-Hubbard insulator LaTiO$_{3}$
(T$_{{\rm N}}=132$ K) reveals a spin wave spectrum that is well described by a
nearest-neighbor superexchange constant $J=15.5$ meV and a small
Dzyaloshinskii-Moriya interaction ($D=1.1$ meV). The nearly isotropic spin wave
spectrum is surprising in view of the absence of a static Jahn-Teller
distortion that could quench the orbital angular momentum, and it may indicate
strong orbital fluctuations. A resonant x-ray scattering study has uncovered no
evidence of orbital order in LaTiO$_{3}$.",0002014v2
2000-03-31,Two Kinds of the Coexistent States in One-Dimensional Quarter -Filled Systems under Magnetic Fields,"The coexistent state of the spin density wave (SDW) and the charge density
wave (CDW) in the one-dimensional quarter-filled system and with the Coulomb
interaction up to the next-nearest sites under magnetic fields is studied. It
is found that, in the coexistent state of $2k_{\rm F}$-SDW and $2k_{\rm
F}$-CDW, the charge order is suppressed and $2k_{\rm F}$-SDW changes to
$2k_{\rm F}$-SDW having the different alignment of spin under high magnetic
fields, whereas, in the coexistent state of $2k_{\rm F}$-SDW and $4k_{\rm
F}$-CDW, $4k_{\rm F}$-CDW still remains and $2k_{\rm F}$-SDW is suppressed. The
critical temperature of the charge order is higher than that of the spin order
when the inter-site Coulomb interaction is strong. These will be observed in
experiments such as the X-ray scattering measurement and NMR.",0003502v1
2000-07-04,"Spin-triplet superconducting pairing due to local (Hund's rule, Dirac) exchange","We discuss general implications of the local spin-triplet pairing among
fermions induced by local ferromagnetic exchange, example of which is the
Hund's rule coupling. The quasiparticle energy and their wave function are
determined for the three principal phases with the gap, which is momentum
independent. We utilize the Bogolyubov-Nambu-De Gennes approach, which in the
case of triplet pairing in the two-band case leads to the four-components wave
function. Both gapless modes and those with an isotropic gap appear in the
quasiparticle spectrum. A striking analogy with the Dirac equation is briefly
explored. This type of pairing is relevant to relativistic fermions as well,
since it reflects the fundamental discrete symmetry-particle interchange. A
comparison with the local interband spin-singlet pairing is also made.",0007060v1
2000-07-27,"Ab-initio calculations of exchange interactions, spin-wave stiffness constants, and Curie temperatures of Fe, Co, and Ni","We have calculated Heisenberg exchange parameters for bcc-Fe, fcc-Co, and
fcc-Ni using the scalar-relativistic spin-polarized Green function technique
within the tight-binding linear muffin-tin orbital method and by employing the
magnetic force theorem to calculate total energy changes associated with a
local rotation of magnetization directions. We have also determined spin-wave
stiffness constants and found the dispersion curves for metals in question
employing the Fourier transform of calculated Heisenberg exchange parameters.
Curie temperatures were calculated both in the mean-field approximation and
within the Green function random phase approximation. The latter results were
found to be in a better agreement with available experimental data.",0007441v2
2000-08-10,Combined effect of frustration and dimerization in ferrimagnetic chains and square lattice,"Within the zero-temperature linear spin-wave theory we have investigated the
effect of frustration and dimerization of a Heisenberg system with alternating
spins $s_{1}$ and $s_{2}$ on one- and two-dimensional lattices. The combined
effect most visibly appears in the elementary excitation spectra. In contrast
to the ground state energy that decreases with dimerization and increases with
frustration, the excitation energies are shown to be suppressed in energy by
both dimerization and frustration. The threshold value of frustration that
signals a transition from a classical ferrimagnetic state to a spiral state,
decreases with dimerization, showing that dimerization further helps in the
phase transition. The correlation length and sublattice magnetization decrease
with both dimerization and frustration indicating the destruction of the
long-range classical ferrimagnetic. The linear spin wave theory shows that in
the case of a square lattice, dimerization initially opposes the
frustration-led transition to a spiral magnetic state, but then higher
magnitudes of lattice deformation facilitate the transition. It also shows that
the transition to spiral state is inhibited in a square lattice beyond a
certain value of dimerization.",0008165v1
2000-11-01,Onset of antiferromagnetism in heavy fermion metals,"There are two views of antiferromagnets. The first proceeds from atomic
physics, which predicts that atoms with unpaired electrons develop magnetic
moments. In a solid, the coupling between moments on nearby ions then yields
antiferromagnetic order at low temperatures. The second, based on the physics
of electron fluids or 'Fermi liquids', states that Coulomb interactions can
drive the fluid to adopt a more stable configuration by developing a spin
density wave. It is presently unknown which view is appropriate at a `quantum
critical point', where the antiferromagnetic transition temperature vanishes.
Here we describe an atomically local contribution to the magnetic correlations
which develops in the metal CeCu$_{6-x}$Au$_{x}$ at the critical gold
concentration ($x_c=0.1$) where the magnetic ordering temperature is tuned to
zero. This contribution implies that a Fermi-liquid destroying spin-localizing
transition, unanticipated for the spin density wave description, coincides with
the antiferromagnetic quantum critical point.",0011002v1
2001-02-22,Low-Temperature Properties of Quasi-One-Dimensional Molecule-Based Ferromagnets,"Quantum and thermal behaviors of low-dimensional mixed-spin systems are
investigated with particular emphasis on the design of molecule-based
ferromagnets. One can obtain a molecular ferromagnet by assembling molecular
bricks so as to construct a low-dimensional system with a magnetic ground state
and then coupling the chains or the layers again in a ferromagnetic fashion.
Two of thus-constructed quasi-one-dimensional bimetallic compounds are
qualitatively viewed within the spin-wave treatment, one of which successfully
grows into a bulk magnet, while the other of which ends in a singlet ground
state. Then, concentrating on the ferrimagnetic arrangement on a two-leg ladder
which is well indicative of general coupled-chain ferrimagnets, we develop the
spin-wave theory and fully reveal its low-energy structure. We inquire further
into the ferromagnetic aspect of the ferrimagnetic ladder numerically
calculating the sublattice magnetization and the magnetic susceptibility. There
exists a moderate coupling strength between the chains in order to obtain the
most ferromagnetic ferrimagnet.",0102417v2
2003-02-20,Electronic structure of rectangular quantum dots,"We study the ground state properties of rectangular quantum dots by using the
spin-density-functional theory and quantum Monte Carlo methods. The dot
geometry is determined by an infinite hard-wall potential to enable comparison
to manufactured, rectangular-shaped quantum dots. We show that the electronic
structure is very sensitive to the deformation, and at realistic sizes the
non-interacting picture determines the general behavior. However, close to the
degenerate points where Hund's rule applies, we find spin-density-wave-like
solutions bracketing the partially polarized states. In the
quasi-one-dimensional limit we find permanent charge-density waves, and at a
sufficiently large deformation or low density, there are strongly localized
stable states with a broken spin-symmetry.",0302410v1
2003-10-07,Local enhancement of spin and orbital antiferromagnetism around a single vortex in high-Tc superconductors,"In a simple model we investigate three competing orders: d-wave
superconductivity, spin and orbital antiferromagnetism (AF) in the vicinity of
a single vortex in a cuprate superconductor. We find that when the potential
for the orbital AF $V_{d}$ is comparatively small, the spin-density-wave (SDW)
order has an enhancement at the vortex core center, and the ''d-density-wave''
(DDW) order exhibits a rather weak behavior around the core and vanishing small
away from the core. However, when $V_{d}$ becomes large, globally, the SDW
order decreases and the DDW order increases; locally, not only the peak of the
SDW order around the core still exists, though relatively suppressed, but also
a local peak for the DDW order finally appears. Similar effects are also
revealed for the features when varying doping. Comparisons with experiments are
discussed.",0310134v1
2004-01-24,Bosonic representation of one-dimensional Heisenberg ferrimagnets,"The energy structure and the thermodynamics of ferrimagnetic Heisenberg
chains of alternating spins S and s are described in terms of the Schwinger
bosons and modified spin waves. In the Schwinger representation, we average the
local constraints on the bosons and diagonalize the Hamiltonian at the
Hartree-Fock level. In the Holstein-Primakoff representation, we optimize the
free energy in two different ways introducing an additional constraint on the
staggered magnetization. A new modified spin-wave scheme, which employs a
Lagrange multiplier keeping the native energy structure free from temperature
and thus differs from the original Takahashi Scheme, is particularly stressed
as an excellent language to interpret one-dimensional quantum ferrimagnetism.
Other types of one-dimensional ferrimagnets and the antiferromagnetic limit S=s
are also mentioned.",0401476v1
2004-04-20,Strong spin-orbit splitting on Bi surfaces,"Using first-principles calculations and angle-resolved photoemission, we show
that the spin-orbit interaction leads to a strong splitting of the surface
state bands on low-index surfaces of Bi. The dispersion of the states and the
corresponding Fermi surfaces are profoundly modified in the whole surface
Brillouin zone. We discuss the implications of these findings with respect to a
proposed surface charge density wave on Bi(111) as well as to the surface
screening, surface spin-density waves, electron (hole) dynamics in surface
states, and to possible applications to the spintronics.",0404461v2
2004-06-20,Effects of the On-Site Coulomb Repulsion in Double Exchange Magnets,"We investigate the zero-temperature phase diagram and spin-wave properties of
a double exchange magnet with on-site Hubbard repulsion. It is shown that even
within a simple Hartree -- Fock approach this interaction (which is often
omitted in theoretical treatments) leads to qualitatively important effects
which are highly relevant in the context of experimental data for the colossal
magnetoresistance compounds. These include the asymmetry of the doping
dependence of spin stiffness, and the zone-boundary ``softening'' of spin wave
dispersion. Effects of Hubbard repulsion on phase separation are analyzed as
well. We also show that in the ferromagnetic phase, an unusual
temperature-dependent effective electron-electron interaction arises at finite
T. The mean-field scheme, however, does not yield the experimentally observed
density of states depletion near the Fermi level. We speculate that proper
treatment of electron-electron interactions may be necessary for understanding
both this important feature and more generally the physics of colossal
magnetoresistance phenomenon.",0406431v4
2004-08-27,Long-range dynamics of magnetic impurities coupled to a two-dimensional Heisenberg antiferromagnet,"We consider a two-dimensional Heisenberg antiferromagnet on a square lattice
with weakly coupled impurities, i.e. additional spins interacting with the host
magnet by a small dimensionless coupling constant g<<1. Using linear spin-wave
theory, we find that the magnetization disturbance at distance r from a single
impurity behaves as g/r for 1<<r<<1/g and as 1/(gr^3) for r>>1/g. Surprisingly
the disturbance is inversely proportional to the coupling constant! The
interaction between two impurities separated by a distance r is proportional to
g^2/r for 1<<r<<1/g and to 1/r^3 for r>>1/g. Hence at large distances, the
interaction is universal and independent of the coupling constant. We also find
that the frequency of Rabi oscillations between two impurities is proportional
to g^2 ln(gr) at 1<<r<<1/g, logarithmically enhanced compared to the spin-wave
width. This leads to a new mechanism for NMR, NQR and EPR line broadening. All
these astonishing results are due to the gapless spectrum of the magnetic
excitations in the quantum antiferromagnet.",0408598v2
2004-09-12,Quantum Versus Jahn-Teller Orbital Physics in YVO$_3$ and LaVO$_3$,"We argue that the large Jahn-Teller (JT) distortions in YVO$_3$ and LaVO$_3$
should suppress the quantum orbital fluctuation. The unusual magnetic
properties can be well explained based on LDA+$U$ calculations using
experimental structures, in terms of the JT orbital. The observed splitting of
the spin-wave dispersions for YVO$_3$ in C-type antiferromagnetic state is
attributed to the inequivalent VO$_2$ layers in the crystal structure, instead
of the ``orbital Peierls state''. Alternative stacking of $ab$-plane exchange
couplings produces the c-axis spin-wave splitting, thus the spin system is
highly three dimensional rather than quasi-one-dimensional. Similar splitting
is also predicted for LaVO$_3$, although it is weak.",0409299v1
2004-09-28,Ordering and Spin Waves in NaNiO2 : A Stacked Quantum Ferromagnet,"Neutron scattering measurements on powder NaNiO2 reveal magnetic Bragg peaks
and spin waves characteristic of strongly correlated s=1/2 magnetic moments
arranged in ferromagnetic layers which are stacked antiferromagnetically. This
structure lends itself to stacking sequence frustration in the presence of
mixing between nickel and alkali metal sites, possibly providing a natural
explanation for the enigmatic spin glass state of the isostructural compound,
LiNiO2.",0409727v2
2004-12-22,Duality relations and exotic orders in electronic ladder systems,"We discuss duality relations in correlated electronic ladder systems to
clarify mutual relations between various conventional and unconventional
phases. For the generalized two-leg Hubbard ladder, we find two exact duality
relations, and also one asymptotic relation which holds in the low-energy
regime. These duality relations show that unconventional (exotic) density-wave
orders such as staggered flux or circulating spin-current are directly mapped
to conventional density-wave orders, which establishes the appearance of
various exotic states with time-reversal and/or spin symmetry breaking. We also
study duality relations in the SO(5) symmetry that was proposed to unify
antiferromagnetism and d-wave superconductivity. We show that the same SO(5)
symmetry also unifies circulating spin current order and s-wave
superconductivity.",0412610v1
2005-01-04,Incommensurate magnetic response in cuprate perovskites,"The incommensurate magnetic response of the normal-state cuprate perovskites
is interpreted based on Mori's memory function approach and the t-J model of
Cu-O planes. In agreement with experiment the calculated dispersion of the
susceptibility maxima has the shape of two parabolas with upward and downward
branches which converge at the antiferromagnetic wave vector. The maxima are
located at $({1/2},{1/2}\pm\delta)$, $({1/2}\pm\delta,{1/2})$ and at
$({1/2}\pm\delta,{1/2}\pm\delta)$, $({1/2}\pm\delta,{1/2}\mp\delta)$ in the
lower and upper parabolas, respectively. The upper parabola reflects the
dispersion of magnetic excitations of the localized Cu spins, while the lower
parabola arises due to a dip in the spin-excitation damping at the
antiferromagnetic wave vector. For moderate doping this dip stems from the
weakness of the interaction between the spin excitations and holes near the hot
spots.",0501040v1
2005-03-03,Quantum Phase Transitions of Frustrated Heisenberg Antiferromagnets: a Comprehensive Renormalization Approach,"We develop a novel renormalization approach for frustrated quantum
antiferromagnets. It is designed to consistently treat spin-wave interactions
all over the magnetic Brillouin zone, including high-energy modes in outer
regions as well as low energy modes in the center. Focusing on the paradigmatic
$J_1$-$J_2$ model, we find a unifying description of the second-order
transition between the N\'eel phase and the paramagnetic phase and the
first-order transition between the N\'eel phase and the columnar phase. Our
approach provides explicit results for the renormalized values of the spin
stiffness and spin-wave velocity characterizing the low-energy magnons in the
N\'eel phase.",0503076v2
2005-08-03,Effects of an external magnetic field on the gaps and quantum corrections in an ordered Heisenberg antiferromagnet with Dzyaloshinskii-Moriya anisotropy,"We study the effects of external magnetic field on the properties of an
ordered Heisenberg antiferromagnet with the Dzyaloshinskii-Moriya (DM)
interaction. Using the spin-wave theory quantum correction to the energy,
on-site magnetization, and uniform magnetization are calculated as a function
of the field H and the DM anisotropy constant D. It is shown that the spin-wave
excitations exhibit an unusual field-evolution of the gaps. This leads to
various non-analytic dependencies of the quantum corrections on H and D. It is
also demonstrated that, quite generally, the DM interaction suppresses quantum
fluctuations, thus driving the system to a more classical ground state. Most of
the discussion is devoted to the spin-S, two-dimensional square lattice
antiferromagnet, whose S=1/2 case is closely realized in K2V3O8 where at H=0
the DM anisotropy is hidden by the easy-axis anisotropy but is revealed in a
finite field. The theoretical results for the field-dependence of the
spin-excitation gaps in this material are presented and the implications for
other systems are discussed.",0508114v2
2005-09-10,Theory of Magnetodynamics Induced by Spin Torque in Perpendicularly Magnetized Thin Films,"A nonlinear model of spin wave excitation using a point contact in a thin
ferromagnetic film is introduced. Large-amplitude magnetic solitary waves are
computed, which help explain recent spin-torque experiments. Numerical
simulations of the fully nonlinear model predict excitation frequencies in
excess of 0.2 THz for contact diameters smaller than 6 nm. Simulations also
predict a saturation and red shift of the frequency at currents large enough to
invert the magnetization under the point contact. The theory is approximated by
a cubic complex Ginzburg-Landau type equation. The mode's nonlinear frequency
shift is found by use of perturbation techniques, whose results agree with
those of direct numerical simulations.",0509265v1
2005-12-16,Evolution of spin-wave excitations in ferromagnetic metallic manganites,"Neutron scattering results are presented for spin-wave excitations of three
ferromagnetic metallic $A_{1-x}A^{\prime}_{x}$MnO$_3$ manganites (where $A$ and
$A^\prime$ are rare- and alkaline-earth ions), which when combined with
previous work elucidate systematics of the interactions as a function of
carrier concentration $x$, on-site disorder, and strength of the lattice
distortion. The long wavelength spin dynamics show only a very weak dependence
across the series. The ratio of fourth to first neighbor exchange ($J_4/J_1$)
that controls the zone boundary magnon softening changes systematically with
$x$, but does not depend on the other parameters. None of the prevailing models
can account for these behaviors.",0512368v1
2006-06-26,Finite compressibility in the low-doping region of the two-dimensional $t{-}J$ model,"We revisit the important issue of charge fluctuations in the two-dimensional
$t{-}J$ model by using an improved variational method based on a wave function
that contains both the antiferromagnetic and the d-wave superconducting order
parameters. In particular, we generalize the wave function introduced some time
ago by J.P. Bouchaud, A. Georges, and C. Lhuillier [J. de Physique {\bf 49},
553 (1988)] by considering also a {\it long-range} spin-spin Jastrow factor, in
order to correctly reproduce the small-$q$ behavior of the spin fluctuations.
We mainly focus our attention on the physically relevant region $J/t \sim 0.4$
and find that, contrary to previous variational ansatz, this state is stable
against phase separation for small hole doping. Moreover, by performing
projection Monte Carlo methods based on the so-called fixed-node approach, we
obtain a clear evidence that the $t{-}J$ model does not phase separate for $J/t
\lesssim 0.7$ and that the compressibility remains finite close to the
antiferromagnetic insulating state.",0606659v1
2006-11-17,Effective Hamiltonians for large-S pyrochlore antiferromagnet,"The pyrochlore lattice Heisenberg antiferromagnet has a massive classical
ground state degeneracy. We summarize three approximation schemes, valid for
large spin length $S$, to capture the (partial) lifting of this degeneracy when
zero-point quantum fluctuations are taken into account; all three are related
to analytic loop expansions. The first is harmonic order spin waves; at this
order, there remains an infinite manifold of degenerate collinear ground
states, related by a gauge-like symmetry. The second is anharmonic (quartic
order) spin waves, using a self-consistent approximation; the harmonic-order
degeneracy is split, but (within numerical precision) some degeneracy may
remain, with entropy still of order $L$ in a system of $L^3$ sites. The third
is a large-N approximation, a standard and convenient approach for frustrated
antiferromagnets; however, the large-N result contradicts the harmonic order at
$O(S)$ hence must be wrong (for large $S$).",0611481v1
2007-03-26,Origin of charge density wave in the coupled spin ladders in Sr$_{14-x}$Ca$_x$Cu$_{24}$O$_{41}$,"We formulate a d-p multiband charge transfer model for Cu$_2$O$_5$ coupled
spin ladders, relevant for Cu$_2$O$_3$ plane of
Sr$_{14-x}$Ca$_x$Cu$_{24}$O$_{41}$, and solve it using Hartree-Fock
approximation. The results explain that (i) the charge density wave (CDW) with
its periodicity dependent on doping is stabilized by purely electronic
many-body interactions in a single spin ladder and (ii) the inclusion of the
interladder interactions favors (disfavors) the stability of the CDW with odd
(even) periodicity, respectively. This stays in agreement with recent
experimental results and suggests the structure of the minimal microscopic
model which should be considered in future more sophisticated studies.",0703669v2
2005-05-17,Improved Stack-Slide Searches for Gravitational-Wave Pulsars,"We formulate and optimize a computational search strategy for detecting
gravitational waves from isolated, previously-unknown neutron stars (that is,
neutron stars with unknown sky positions, spin frequencies, and spin-down
parameters). It is well known that fully coherent searches over the relevant
parameter-space volumes are not computationally feasible, and so more
computationally efficient methods are called for. The first step in this
direction was taken by Brady & Creighton (2000), who proposed and optimized a
two-stage, stack-slide search algorithm. We generalize and otherwise improve
upon the Brady-Creighton scheme in several ways. Like Brady & Creighton, we
consider a stack-slide scheme, but here with an arbitrary number of
semi-coherent stages and with a coherent follow-up stage at the end. We find
that searches with three semi-coherent stages are significantly more efficient
than two-stage searches (requiring about 2-5 times less computational power for
the same sensitivity) and are only slightly less efficient than searches with
four or more stages. We calculate the signal-to-noise ratio required for
detection, as a function of computing power and neutron star spin-down-age,
using our optimized searches.",0505082v1
2007-03-12,Interactions between Multipolar Nuclear Transitions and Gravitational Waves,"Interactions between multipolar nuclear transitions and gravitational waves
(GWs) are theoretically investigated. Two nonclassical scenarios of the GW
detection are suggested. We demonstrate in this report that the long-lived
Moessbauer nuclides of multipolar transitions are suitable transducers to
detect the impinging GWs. Shape deformation and spin flip of nucleus are
derived from the Hamiltonian with gravity interaction. The GWs generate a
nuclear quadrupole deformation in analogy with the Stark effect, of which the
electric field generates the dipole deformation of electron orbits. Likewise in
analogy with the nuclear magnetic resonance that the rotating radio-frequency
field flips the nuclear spin, the GWs flip the nuclear spin by the resonant
helicity-rotation-gravity coupling. The high energy states of the quadrupole
deformation in heavy nuclides can dramatically speed up the multipolar
transitions, which may be important for the GW detection particularly in the
low frequency band, ranging from 100 nHz to 1 Hz.",0703066v2
2001-03-15,Neutrino kinetics in a magnetized dense plasma,"The relativistic kinetic equations (RKE) for lepton plasma in the presence of
a strong external magnetic field are derived in Vlasov approximation. The new
RKE for the electron spin distribution function includes the weak interaction
with neutrinos originated by the axial vector current ($\sim c_A$) and provided
by the parity nonconservation. In a polarized electron gas Bloch equation
describing the evolution of the magnetization density perturbation is derived
from the electron spin RKE being modified in the presence of neutrino fluxes.
Such modified hydrodynamical equation allows to obtain the new dispersion
equation in a magnetized plasma from which the neutrino driven instability of
spin waves can be found. It is shown that this instability is more efficient
e.g. in a magnetized supernova than the analogous one for Langmuir waves
enhanced in an isotropic plasma.",0103176v2
2002-12-27,Analysis of dynamical corrections to baryon magnetic moments,"We present and analyze QCD corrections to the baryon magnetic moments in
terms of the one-, two-, and three-body operators which appear in the effective
field theory developed in our recent papers. The main corrections are extended
Thomas-type corrections associated with the confining interactions in the
baryon. We investigate the contributions of low-lying angular excitations to
the moments quantitatively and show that they are completely negligible. When
the QCD corrections are combined with the non-quark model contributions of the
meson loops, we obtain a model which describes the moments within a mean
deviation of 0.04 $\mu_N$. The nontrivial interplay of the two types of
corrections to the quark-model moments is analyzed in detail, and explains why
the quark model is so successful. In the course of these calculations, we
parametrize the general spin structure of the $j={1/2}^+$ baryon wave functions
in a form which clearly displays the symmetry properties and the internal
angular momentum content of the wave functions, and allows us to use spin-trace
methods to calculate the many spin matrix elements which appear in the
expressions for the moments. This representation may be useful elsewhere.",0212381v1
1998-02-16,Spinning Particle as a Super Black Hole,"A natural combined model of the Kerr spinning particle and superparticle is
obtained leading to a non-trivial super black hole solution. By analogue with
complex structure of the Kerr solution we perform a supershift on the Kerr
geometry, and then select a ""body""-submanifold of superspace that yields a
non-trivial supergeneralization of the Kerr metric with a nonlinear realization
of (2,0)-supersymmetry. For the known parameters of spinning particles this
""black hole"" is to be in a specific state without horizons and very far from
extreme. The naked Kerr singular ring has to be hidden inside a rotating
superconducting disk, built of a supermultiplet of matter fields. Stringy wave
excitations of the Kerr singular ring (traveling waves) yield an extra axial
singular line modulated by de Broglie periodicity.",9802110v2
2004-06-07,Twistorial Analyticity and Three Stringy Systems of the Kerr Spinning Particle,"The Kerr spinning particle has a remarkable analytical twistorial structure.
Analyzing electromagnetic excitations of the Kerr circular string which are
aligned to this structure, we obtain a simple stringy skeleton of the spinning
particle which is formed by a topological coupling of the Kerr circular
singular string and by an axial singular stringy system.
  We show that the chiral traveling waves, related to an orientifold
world-sheet of the axial stringy system, are described by the massive Dirac
equation, so we argue that the axial string may play the part of a stringy
carrier of wave function and play also a dominant role in the scattering
processes.
  A key role of the third, {\it complex} Kerr string is discussed. We
conjecture that it may be one more alternative to the Witten twistor string,
and a relation to the spinor helicity formalism is also discussed.",0406063v4
2001-10-19,Spin Representations of the q-Poincare Algebra,"The spin of particles on a non-commutative geometry is investigated within
the framework of the representation theory of the q-deformed Poincare algebra.
An overview of the q-Lorentz algebra is given, including its representation
theory with explicit formulas for the q-Clebsch-Gordan coefficients. The
vectorial form of the q-Lorentz algebra (Wess), the quantum double form
(Woronowicz), and the dual of the q-Lorentz group (Majid) are shown to be
essentially isomorphic. The construction of q-Minkowski space and the
q-Poincare algebra is reviewed. The q-Euclidean sub-algebra, generated by
rotations and translations, is studied in detail. The results allow for the
construction of the q-Pauli-Lubanski vector, which, in turn, is used to
determine the q-spin Casimir and the q-little algebras for both the massive and
the massless case. Irreducible spin representations of the q-Poincare algebra
are constructed in an angular momentum basis, accessible to physical
interpretation. It is shown how representations can be constructed,
alternatively, by the method of induction. Reducible representations by
q-Lorentz spinor wave functions are considered. Wave equations on these spaces
are found, demanding that the spaces of solutions reproduce the irreducible
representations. As generic examples the q-Dirac equation and the q-Maxwell
equations are computed explicitly and their uniqueness is shown.",0110219v1
1999-07-26,Measurement of Partial-Wave Contributions in pp --> pp pi^0,"We report a measurement of the spin-dependent total cross section ratios
delta_sigma_T/sigma_tot and delta_sigma_L/sigma_tot of the pp --> pp pi^0
reaction between 325 MeV and 400 MeV. The experiment was carried out with a
polarized internal target in a storage ring. Non-vertical beam polarization was
obtained by the use of solenoidal spin rotators. Near threshold, the knowledge
of both spin-dependent total cross sections is sufficient to deduce the
strength of certain participating partial waves, free of any model.",9907017v2
1997-03-19,Covariant equations for the three-body bound state,"The covariant spectator (or Gross) equations for the bound state of three
identical spin 1/2 particles, in which two of the three interacting particles
are always on shell, are developed and reduced to a form suitable for numerical
solution. The equations are first written in operator form and compared to the
Bethe-Salpeter equation, then expanded into plane wave momentum states, and
finally expanded into partial waves using the three-body helicity formalism
first introduced by Wick. In order to solve the equations, the two-body
scattering amplitudes must be boosted from the overall three-body rest frame to
their individual two-body rest frames, and all effects which arise from these
boosts, including the Wigner rotations and rho-spin decomposition of the
off-shell particle, are treated exactly. In their final form, the equations
reduce to a coupled set of Faddeev-like double integral equations with
additional channels arising from the negative rho-spin states of the off-shell
particle.",9703043v1
1999-05-20,"(j,0)+(0,j) Covariant spinors and causal propagators based on Weinberg formalism","A pragmatic approach to constructing a covariant phenomenology of the
interactions of composite, high-spin hadrons is proposed. Because there are no
known wave equations without significant problems, we propose to construct the
phenomenology without explicit reference to a wave equation. This is done by
constructing the individual pieces of a perturbation theory and then utilizing
the perturbation theory as the definition of the phenomenology. The covariant
spinors for a particle of spin $j$ are constructed directly from Lorentz
invariance and the basic precepts of quantum mechanics following the logic put
forth originally by Wigner and developed by Weinberg. Explicit expressions for
the spinors are derived for j=1, 3/2 and 2. Field operators are constructed
from the spinors and the free-particle propagator is derived from the vacuum
expectation value of the time-order product of the field operators. A few
simple examples of model interactions are given. This provides all the
necessary ingredients to treat at a phenomenological level and in a covariant
manner particles of arbitrary spin.",9905047v1
2005-08-15,"Conservation of Angular Momentum, Transverse Shift, and Spin Hall Effect in Reflection and Refraction of Electromagnetic Wave Packet","We present a solution to the problem of reflection/refraction of a polarized
Gaussian beam on the interface between two transparent media. The transverse
shifts of the beams' centers of gravity are calculated. They always satisfy the
total angular momentum conservation law for beams, however, in general, do not
satisfy the conservation laws for individual photons in consequence of the lack
of the ``which path'' information in a two-channel wave scattering. The field
structure for the reflected/refracted beam is analyzed. In the scattering of a
linearly-polarized beam, photons of opposite helicities are accumulated at the
opposite edges of the beam: this is the spin Hall effect for photons, which can
be registered in the cross-polarized component of the scattered beam.",0508093v4
1999-09-07,Spin-orbit pendulum - Relativistic extension,"We discuss an extension of the theory of {\em spin-orbit pendulum} phenomenon
given in [1] to relativistic approach. It is done within the so called Dirac
Oscillator. Our first results, focusing on circular wave packet motion have
been published recently [2]. The scope of this paper is motion of a linear wave
packet. In relativistic approach we found {\em Zitterbewegung} in spin-orbit
motion (in Dirac representation) due to coupling to negative energy states.
This effect is washed out in the Foldy-Wouthuysen representation. Another
important change with respect to non-relativistic case is the loss of
periodicity. The phenomenon reminds the time evolution of population inversion
in Jaynes-Cummings model.",9909023v1
2007-04-01,Matter-Wave Bright Solitons with a Finite Background in Spinor Bose-Einstein Condensates,"We investigate dynamical properties of bright solitons with a finite
background in the F=1 spinor Bose-Einstein condensate (BEC), based on an
integrable spinor model which is equivalent to the matrix nonlinear
Schr\""{o}dinger equation with a self-focusing nonlineality. We apply the
inverse scattering method formulated for nonvanishing boundary conditions. The
resulting soliton solutions can be regarded as a generalization of those under
vanishing boundary conditions. One-soliton solutions are derived in an explicit
manner. According to the behaviors at the infinity, they are classified into
two kinds, domain-wall (DW) type and phase-shift (PS) type. The DW-type implies
the ferromagnetic state with nonzero total spin and the PS-type implies the
polar state, where the total spin amounts to zero. We also discuss two-soliton
collisions. In particular, the spin-mixing phenomenon is confirmed in a
collision involving the DW-type. The results are consistent with those of the
previous studies for bright solitons under vanishing boundary conditions and
dark solitons. As a result, we establish the robustness and the usefulness of
the multiple matter-wave solitons in the spinor BECs.",0704.0082v1
2007-07-02,Exploring black hole superkicks,"Recent calculations of the recoil velocity in black-hole binary mergers have
found kick velocities of $\approx2500 $km/s for equal-mass binaries with
anti-aligned initial spins in the orbital plane. In general the dynamics of
spinning black holes can be extremely complicated and are difficult to analyze
and understand. In contrast, the ``superkick'' configuration is an example with
a high degree of symmetry that also exhibits exciting physics. We exploit the
simplicity of this ``test case'' to study more closely the role of spin in
black-hole recoil and find that: the recoil is with good accuracy proportional
to the difference between the $(l = 2, m = \pm 2)$ modes of $\Psi_4$, the major
contribution to the recoil occurs within $30M$ before and after the merger, and
that this is after the time at which a standard post-Newtonian treatment breaks
down. We also discuss consequences of the $(l = 2, m = \pm 2)$ asymmetry in the
gravitational wave signal for the angular dependence of the SNR and the
mismatch of the gravitational wave signals corresponding to the north and south
poles.",0707.0135v1
2007-10-29,Eikonal Methods in AdS/CFT: Regge Theory and Multi-Reggeon Exchange,"We analyze conformal field theory 4-point functions of the form A ~ O_1(x_1)
O_2(x_2) O_1(x_3) O_2(x_4), where the operators O_i are scalar primaries. We
show that, in the Lorentzian regime, the limit x_1 -> x_3 is dominated by the
exchange of conformal partial waves of highest spin. When partial waves of
arbitrary spin contribute to A, the behavior of the Lorentzian amplitude for
x_1 -> x_3 must be analyzed using complex-spin techniques, leading to a
generalized Regge theory for CFT's. Whenever the CFT is dual to a string
theory, the string tree-level contribution A_tree to the amplitude A presents a
Regge pole corresponding the a gravi-reggeon exchange. In this case, we apply
the impact parameter representation for CFT amplitudes, previously developed,
to analyze multiple reggeon exchanges in the eikonal limit. As an example, we
apply these general techniques to N=4 super-Yang-Mills theory in d=4 in the
limit of large 't Hooft coupling, including the leading string corrections to
pure graviton exchange.",0710.5480v3
2008-03-10,Boundary criticality and multifractality at the 2D spin quantum Hall transition,"Multifractal scaling of critical wave functions at a disorder-driven
(Anderson) localization transition is modified near boundaries of a sample.
Here this effect is studied for the example of the spin quantum Hall plateau
transition using the supersymmetry technique for disorder averaging. Upon
mapping of the spin quantum Hall transition to the classical percolation
problem with reflecting boundaries, a number of multifractal exponents
governing wave function scaling near a boundary are obtained exactly. Moreover,
additional exact boundary scaling exponents of the localization problem are
extracted, and the problem is analyzed in other geometries.",0803.1343v2
2008-03-24,Competing Orders and Spin-Density-Wave Instability in La(O$_{1-x}$F$_x$)FeAs,"The interplay between different ordered phases, such as superconducting,
charge or spin ordered phases, is of central interest in condensed matter
physics. The very recent discovery of superconductivity with a remarkable
T$_c$= 26 K in Fe-based oxypnictide La(O$_{1-x}$F$_x$)FeAs is a surprise to the
scientific community\cite{Kamihara08}. The pure LaOFeAs itself is not
superconducting but shows an anomaly near 150 K in both resistivity and dc
magnetic susceptibility. Here we provide combined experimental and theoretical
evidences showing that the anomaly is caused by the spin-density-wave (SDW)
instability, and electron-doping by F suppresses the SDW instability and
recovers the superconductivity. Therefore, the La(O$_{1-x}$F$_x$)FeAs offers an
exciting new system showing competing orders in layered compounds.",0803.3426v1
2008-05-02,Commensurate Spin Density Wave in LaOFeAs: A Local Probe Study,"We present a detailed study on the magnetic order in the undoped mother
compound LaOFeAs of the recently discovered Fe-based superconductor
LaO$_{1-x}$F$_x$FeAs. In particular, we present local probe measurements of the
magnetic properties of LaOFeAs by means of $^{57}$Fe M\""ossbauer spectroscopy
and muon spin relaxation in zero external field along with magnetization and
resistivity studies. These experiments prove a commensurate static magnetic
order with a strongly reduced ordered moment of 0.25(5) $\mu_B$ at the iron
site below T_N = 138 K, well separated from a structural phase transition at
T_N = 156 K. The temperature dependence of the sublattice magnetization is
determined and compared to theory. Using a four-band spin density wave model
both, the size of the order parameter and the quick saturation below T_N are
reproduced.",0805.0264v2
2008-08-09,Enhanced spin density wave in LaOFeSb,"We predict atomic, electronic, and magnetic structures of a hypothetical
compound LaOFeSb by first-principles density-functional calculations. It is
shown that LaOFeSb prefers a stripe-type antiferromagnetic phase (i.e., spin
density wave (SDW) phase) to the non-magnetic (NM) phase, with a larger Fe spin
moment and greater SDW-NM energy difference than those of LaOFeAs. The SDW
phase is found to favor the orthorhombic structure while the tetragonal
structure is more stable in the NM phase. In the NM-phase LaOFeSb, the
electronic bandwidth near the Fermi energy is reduced compared with LaOFeAs,
indicating smaller orbital overlap between Fe $d$ states and subsequently
enhanced intra-atomic exchange coupling. The calculated Fermi surface in the NM
phase consists of three hole and two electron sheets, and shows increased
nesting between two hole and two electron sheets compared with LaOFeAs.
Monotonous changes found in our calculated material properties of LaOFePn
(Pn=P, As, and Sb), along with reported superconducting properties of doped
LaOFeP and LaOFeAs, suggest that doped LaOFeSb may have a higher
superconducting transition temperature.",0808.1348v1
2008-09-14,Effects of the $g$-factor in semi-classical kinetic plasma theory,"A kinetic theory for spin plasmas is put forward, generalizing those of
previous authors. In the model, the ordinary phase space is extended to include
the spin degrees of freedom. Together with Maxwell's equations, the system is
shown to be energy conserving. Analysing the linear properties, it is found
that new types of wave-particle resonances are possible, that depend directly
on the anomalous magnetic moment of the electron. As a result new wave modes,
not present in the absence of spin, appear. The implications of our results are
discussed.",0809.2382v2
2008-11-03,Anharmonic Ground state selection in the pyrochlore antiferromagnet,"In the pyrochlore lattice Heisenberg antiferromagnet, for large spin length
$S$, the massive classical ground state degeneracy is partly lifted by the
zero-point energy of quantum fluctuations at harmonic order in spin-waves.
However, there remains an infinite manifold of degenerate collinear ground
states, related by a gaugelike symmetry. We have extended the spin-wave
calculation to quartic order, assuming a Gaussian variational wavefunction
(equivalent to Hartree-Fock approximation). Quartic calculations \emph{do}
break the harmonic-order degeneracy of periodic ground states. The form of the
effective Hamiltonian describing this splitting, which depends on loops, was
fitted numerically and also rationalized analytically. We find a family of
states that are still almost degenerate, being split by the term from loops of
length 26. We also calculated the anharmonic terms for the checkerboard
lattice, and discuss why it (as well as the kagom\'e lattice) behave
differently than the pyrochlore at anharmonic orders.",0811.0395v4
2008-11-17,Anomalous Hall voltage rectification and quantized spin-wave excitation induced by the simultaneous dc- and rf-current application in Ni81Fe19 wire,"An anomalous Hall effect and rectification of a Hall voltage are observed by
applying a radio-frequency (rf) current through a single-layered ferromagnetic
wire located on a coplanar waveguide. The components of the magnetization
precession, both in and perpendicular to the plane, can be detected via the
Hall voltage rectification of the rf current by incorporating an additional
direct (dc) current. In this paper, we propose a phenomenological model, which
describes the time-dependent anisotropic magnetoresistance and time-dependent
planer Hall effect. The nonlinearity of the spin dynamics accompanied by
spin-waves as functions of rf and dc currents is also studied, as well as those
of the magnitude and orientation of the external magnetic field.",0811.2618v2
2008-12-02,Hybridization of Spin and Plasma Waves in Josephson Tunnel Junctions Containing a Ferromagnetic Layer,"We study dynamics of tunnel Josephson junctions with a thin ferromagnetic
layer F [superconductor-insulator-ferromagnet-superconductor (SIFS) junctions].
On the basis of derived equations relating the superconducting phase and
magnetic moment to each other we analyze collective excitations in the system
and find a new mode which is a hybrid of plasmalike and spin waves. The latter
are coupled together in a broad range of parameters characterizing the system.
Using the solution describing the collective modes we demonstrate that besides
the Fiske steps new peaks appear on the I-V characteristics due to oscillations
of the magnetic moment M in the ferromagnetic layer. Thus, by measuring the I-V
curve of the SIFS junctions, one can extract information about the spectrum of
spin excitations in the ferromagnet F.",0812.0512v3
2008-12-12,Spiky strings in AdS_3 x S^1 and their AdS-pp-wave limits,"We study a class of classical solutions for closed strings moving in AdS_3 x
S^1 part of AdS_5 x S^5 with energy E and spin S in AdS_3 and angular momentum
J and winding m in S^1. They have rigid shape with n spikes in AdS_3. We find
that when J or m are non-zero, the spikes do not end in cusps. We consider in
detail a special large n limit in which S ~ n^2, J ~ n, i.e. S >> J >> 1, with
(E+S)/ n^2, (E-S)/ n, J/n, m/n staying finite. In that limit the spiky spinning
string approaches the boundary of AdS_5. We show that the corresponding
solution can be interpreted as describing a periodic-spike string moving in
AdS_3 --pp-wave x S^1 background. The resulting expression for the string
energy should represent a strong-coupling prediction for anomalous dimension of
a class of dual gauge theory states in a particular thermodynamic limit of the
SL(2) spin chain.",0812.2431v3
2009-01-28,A phason disordered two dimensional quantum antiferromagnet,"We examine a novel type of disorder in quantum antiferromagnets. Our model
consists of localized spins with antiferromagnetic exchanges on a bipartite
quasiperiodic structure, which is geometrically disordered in such a way that
no frustration is introduced. In the limit of zero disorder, the structure is
the perfect Penrose rhombus tiling. This tiling is progressively disordered by
augmenting the number of random ""phason flips"" or local tile-reshuffling
operations. The ground state remains N\'eel ordered, and we have studied its
properties as a function of increasing disorder using linear spin wave theory
and quantum Monte Carlo. We find that the ground state energy decreases,
indicating enhanced quantum fluctuations with increasing disorder. The magnon
spectrum is progressively smoothed, and the effective spin wave velocity of low
energy magnons increases with disorder. For large disorder, the ground state
energy as well as the average staggered magnetization tend towards limiting
values characteristic of this type of randomized tilings.",0901.4441v1
2009-02-28,Spinning Dilaton Black Holes in 2 +1 Dimensions: Quasi-normal Modes and the Area Spectrum,"We have studied the perturbation of a spinning dilaton black hole in 2 +1
dimensions by a massless scalar field. The wave equations of a massless scalar
field is shown to be exactly solvable in terms of hypergeometric functions. The
quasinormal frequencies are computed for slowly spinning black holes. The
stability of the black hole is discussed. The asymptotic form of the
quasinormal frequencies are evaluated. The area spectrum of the quantum black
holes are evaluated by using the asymptotic quasi-normal frequencies and is
shown to be equally-spaced.",0903.0088v3
2009-03-10,A geometrical approach to the dynamics of spinor condensates II: Collective modes,"In this paper we study the linearized dynamics of spinor condensates using
the spin-node formalism developed in arXiv:0812.3403. We provide a general
method to linearize the equations of motion based on the symmetry of the
mean-field ground state using the local stereographic projection of the spin
nodes. We also provide a simple construction to extract the collective modes
from symmetry considerations alone akin to the analysis of vibrational
excitations of polyatomic molecules. Finally, we will present a mapping between
the spin-wave modes, and the wave functions of electrons in atoms, where the
spherical symmetry is degraded by a crystal field.",0903.1863v2
2009-03-11,Geometrodynamics of polarized light: Berry phase and spin Hall effect in a gradient-index medium,"We review the geometrical-optics evolution of an electromagnetic wave
propagating along a curved ray trajectory in a gradient-index dielectric
medium. A Coriolis-type term appears in Maxwell equations under transition to
the rotating coordinate system accompanying the ray. This term describes the
spin-orbit coupling of light which consists of (i) the Berry phase responsible
for a trajectory-dependent polarization variations and (ii) the spin Hall
effect representing polarization-dependent trajectory perturbations. These
mutual phenomena are described within universal geometrical structures
underlying the problem and are explained by the dynamics of the intrinsic
angular momentum carried by the wave. Such close geometro-dynamical
interrelations illuminate a dual physical nature of the phenomena.",0903.1910v1
2009-03-20,Population synthesis of double neutron stars,"Using the StarTrack binary population synthesis code we model the population
of double neutron stars in the Galaxy. We include a detailed treatment of the
spin evolution of each pulsar due to processes such as spin-down and spin-up
during accretion events as well as magnetic field decay. We also model the
spatial distribution of double neutron stars by including their natal kicks and
subsequent propagation in the Galactic gravitational potential. This synthetic
pulsar population is compared to the observed sample of double neutron stars
taking into account the selection effects of detection in the radio band, to
determine the most likely evolutionary parameters. With these parameters we
determine the properties of the double neutron star binaries detectable in
gravitational waves by the high frequency interferometers LIGO and VIRGO. In
particular, we discuss the distributions of chirp masses and mass ratios in
samples selected by their radio or gravitational wave emission.",0903.3538v2
2009-08-04,Pressure-induced Spin-Peierls to Incommensurate Charge-Density-Wave Transition in the Ground State of TiOCl,"The ground state of the spin-Peierls system TiOCl was probed using
synchrotron x-ray diffraction on a single-crystal sample at T = 6 K. We tracked
the evolution of the structural superlattice peaks associated with the
dimerized ground state as a function of pressure. The dimerization along the b
axis is rapidly suppressed in the vicinity of a first-order structural phase
transition at Pc = 13.1(1) GPa. The high-pressure phase is characterized by an
incommensurate charge density wave perpendicular to the original spin chain
direction. These results show that the electronic ground state undergoes a
fundamental change in symmetry, indicating a significant change in the
principal interactions.",0908.0518v1
2009-09-11,"The double life of electrons in magnetic iron pnictides, as revealed by NMR","We present a phenomenological, two-fluid approach to understanding the
magnetic excitations in Fe pnictides, in which a paramagnetic fluid with
gapless, incoherent particle-hole excitations coexists with an
antiferromagnetic fluid with gapped, coherent spin wave excitations. We show
that this two-fluid phenomenology provides an excellent quantitative
description of NMR data for magnetic ""122"" pnictides, and argue that it finds a
natural justification in LSDA and spin density wave calculations. We further
use this phenomenology to estimate the maximum renormalisation of the ordered
moment that can follow from low-energy spin fluctuations in Fe pnictides. We
find that this is too small to account for the discrepancy between ab intio
calculations and neutron scattering measurements.",0909.2207v4
2009-09-28,Entangled Superfluids,"We study the condensate dynamics of the so-called entangled Bose-Einstein
condensation (EBEC), which is the ground state of a mixture of two species of
pseudospin-$\frac{1}{2}$ atoms with interspecies spin-exchange scattering in
certain parameter regimes. EBEC leads to four inter-dependent superfluid
components, each corresponding to the orbital wave function associated with a
spin component of a species. The four superflows have various
counter-relations, and altogether lead to a conserved total supercurrent and a
conserved total spin supercurrent. In the homogenous case, we also obtain the
elementary excitations due to variations of the single-particle orbital wave
functions, by exactly solving the generalized time-dependent Bogoliubov
equations. There are three gapless Bogoliubov modes and one Klein-Gordon-like
gapped mode. The origin of these excitations are also discussed from the
perspective of spontaneous breaking of the symmetries possessed by the system.",0909.4990v2
2009-10-05,Spin and charge order in doped Hubbard model: long-wavelength collective modes,"Determining the ground state properties of the two-dimensional Hubbard model
has remained an outstanding problem. Applying recent advances in constrained
path auxiliary-field quantum Monte Carlo techniques and simulating large
rectangular periodic lattices, we calculate the long-range spin and charge
correlations in the ground state as a function of doping. At intermediate
interaction strengths, an incommensurate spin density wave (SDW) state is
found, with antiferromagnetic order and essentially homogeneous charge
correlation. The wavelength of the collective mode decreases with doping, as
does its magnitude. The SDW order vanishes beyond a critical doping. As the
interaction is increased, the holes go from a wave-like to a particle-like
state, and charge ordering develops which eventually evolves into stripe-like
states.",0910.0712v1
2009-10-18,Inward dispersion of the spin excitation spectrum of stripe-ordered La2NiO4+d,"Polarized- and unpolarized-neutron scattering measurements of the spin
excitation spectrum in the stripe-ordered phase of La2NiO4+d (d = 0.11) are
presented. At low energies, the magnetic spectral weight is found to shift
anomalously towards the two-dimensional antiferromagnetic wave vector, similar
to the low-energy dispersions observed in cuprate superconductors. While
spin-wave spectra in stripe phases can exhibit an apparent inward dispersion,
we find that the peak shifts measured here cannot be accounted for by this
effect. Possible extensions of the model are discussed.",0910.3418v1
2009-12-17,Magnetic non-collinear neutron wave resonator,"Equations for the neutron reflection amplitude from a magnetic non-collinear
wave resonator (NWR) are obtained. It is shown that resonances of the same
reflection order of neutrons experiencing spin-flip (spin-flip neutrons) appear
in pairs. Conditions under which in the resonator square enhancement of the
spin-flip neutron reflection intensity with respect to growth of the portion of
scattered and absorbed neutrons takes place, are determined.",0912.3557v2
2009-12-19,Temperature dependence of uniform static magnetic susceptibility in a two-dimensional quantum Heisenberg antiferromagnetic model,"A perturbation spin-wave theory for the quantum Heisenberg antiferromagnets
on a square lattice is proposed to calculate the uniform static magnetic
susceptibility at finite temperatures, where a divergence in the previous
theories due to an artificial phase transition has been removed. To the zeroth
order, the main features of the uniform static susceptibility are produced: a
linear temperature dependence at low temperatures and a smooth crossover in the
intermediate range and the Curie law at high temperatures. When the leading
corrections from the spin-wave interactions are included, the resulting spin
susceptibility in the full temperature range is in agreement with the numerical
quantum Monte Carlo simulations and high-temperature series expansions.",0912.3859v1
2010-01-19,Ground-state phase diagram of the two-dimensional t-J model,"The ground-state phase diagram of the two-dimensional t-J model is
investigated in the context of the tensor network algorithm in terms of the
graded Projected Entangled-Pair State representation of the ground-state wave
functions. There is a line of phase separation between the Heisenberg
anti-ferromagnetic state without hole and a hole-rich state. For both J=0.4t
and J=0.8t, a systematic computation is performed to identify all the competing
ground states for various dopings. It is found that, besides a possible
Nagaoka's ferromagnetic state, the homogeneous regime consists of four
different phases: one phase with charge and spin density wave order coexisting
with a p_x (p_y)-wave superconducting state, one phase with the symmetry mixing
of d+s-wave superconductivity in the spin-singlet channel and p_x (p_y)-wave
superconductivity in the spin-triplet channel in the presence of an
anti-ferromagnetic background, one superconducting phase with extended s-wave
symmetry, and one superconducting phase with p_x (p_y)-wave symmetry in a
ferromagnetic background.",1001.3343v1
2010-01-29,Strong correlation and massive spectral-weight redistribution induced spin density wave in a-Fe1.06Te,"The electronic structure of a-Fe1.06Te is studied with angle-resolved
photoemission spectroscopy. We show that there is substantial spectral weight
around Gamma and X, and lineshapes are intrinsically incoherent in the
paramagnetic state. The magnetic transition is characterized by a massive
spectral-weight transfer over an energy range as large as the band width, which
even exhibits a hysteresis loop that marks the strong first order transition.
Coherent quasiparticles emerge in the magnetically ordered state due to
decreased spin fluctuations, which account for the change of transport
properties from insulating behavior to metallic behavior. Our observation
demonstrates that Fe1.06Te distinguishes itself from other iron-based systems
with more local characters and much stronger interactions among different
degrees of freedom, and how a spin density wave is formed in the presence of
strong correlation.",1001.5327v1
2010-02-08,Theory of itinerant magnetic excitations in the SDW phase of iron-based superconductors,"We argue that salient experimental features of the magnetic excitations in
the SDW phase of iron-based superconductors can be understood within an
itinerant model. We identify a minimal itinerant model and use a multi-band RPA
treatment of the dynamical spin susceptibility. Weakly-damped spin-waves are
found near the ordering momentum and it is shown how they dissolve into the
particle-hole continuum. We show that ellipticity of the electron bands
accounts for the anisotropy of the spin waves along different crystallographic
directions and the gap at the momentum conjugated to the ordering one. We argue
that our theory agrees well with the neutron scattering data.",1002.1668v2
2010-03-03,Field Theory for a Deuteron Quantum Liquid,"Based on general symmetry principles we study an effective Lagrangian for a
neutral system of condensed spin-1 deuteron nuclei and electrons, at
greater-than-atomic but less-than-nuclear densities. We expect such matter to
be present in thin layers within certain low-mass brown dwarfs. It may also be
produced in future shock-wave-compression experiments as an effective fuel for
laser induced nuclear fusion. We find a background solution of the effective
theory describing a net spin zero condensate of deuterons with their spins
aligned and anti-aligned in a certain spontaneously emerged preferred
direction. The spectrum of low energy collective excitations contains two spin
waves with linear dispersions -- like in antiferromagnets -- as well as gapped
longitudinal and transverse modes related to the Meissner effect -- like in
superconductors. We show that counting of the Nambu-Goldstone modes of
spontaneously broken internal and space-time symmetries obeys, in a nontrivial
way, the rules of the Goldstone theorem for Lorentz non-invariant systems. We
discuss thermodynamic properties of the condensate, and its potential
manifestation in the low-mass brown dwarfs.",1003.0865v2
2010-05-22,Spin dynamics and domain formation of a spinor Bose-Einstein condensate in an optical cavity,"We consider a ferromagnetic spin-1 Bose-Einstein condensate (BEC)
dispersively coupled to a unidirectional ring cavity. We show that the ability
of a cavity to modify, in a highly nonlinear fashion, matter-wave phase shifts
adds a new dimension to the study of spinor condensates both within and beyond
the single-mode approximation. In addition to demonstrating strong matter-wave
bistability as in our earlier publication [L. Zhou et al., Phys. Rev. Lett.
103, 160403 (2009)], we show that the interplay between atomic and cavity
fields can greatly enrich both the physics of critical slowing down in spin
mixing dynamics and the physics of spin-domain formation in spinor condensates.",1005.4121v1
2010-06-29,1:1 alkali-TCNQ salts and the bond order wave (BOW) phase of half-filled linear Hubbard-type models,"The bond order wave (BOW) phase of half-filled linear Hubbard-type models is
narrow and difficult to characterize aside from a few ground state properties.
The BOW phase of a frustrated Heisenberg spin chain is wide and tractable. It
has broken inversion symmetry C_i in a regular array and finite gap E_m to the
lowest triplet state. The spin-BOW is exact in finite systems at a special
point. Its elementary excitations are spin-1/2 solitons that connect BOWs with
opposite phase. The same patterns of spin densities and bond orders appear in
the BOW phase of Hubbard-type models. Infrared (IR) active lattice phonons or
molecular vibrations are derivatives of P, the polarization along the stack.
Molecular vibrations that are forbidden in regular arrays become IR active when
C_i symmetry is broken. 1:1 alkali-TCNQ salts contain half-filled regular TCNQ-
stacks at high temperature, down to 100 K in the Rb-TCNQ(II) polymorph whose
magnetic susceptibility and polarized IR spectra indicate a BOW phase. More
complete modeling will require explicit electronic coupling to phonons and
molecular vibrations.",1006.5637v1
2010-07-09,Space-time evolution of Dirac wave packets,"In this work we study the dynamics of free 3D relativistic Gaussian wave
packets with different spin polarization. We analyze the connection between the
symmetry of initial state and the dynamical characteristics of moving particle.
The corresponding solutions of Dirac equation having different types of
symmetry were evaluated analytically and numerically and after that the
electron probability densities, as well as, the spin densities were visualized.
The average values of velocity of the packet center and the average spin were
calculated analytically, and the parameters of transient Zitterbewegung in
different directions were obtained. These results can be useful for the
interpretation of future experiments with trapped ions.",1007.1566v2
2010-07-23,"Helical spin-waves, magnetic order, and fluctuations in the langasite compound Ba3NbFe3Si2O14","We have investigated the spin fluctuations in the langasite compound
Ba3NbFe3Si2O14 in both the ordered state and as a function of temperature. The
low temperature magnetic structure is defined by a spiral phase characterized
by magnetic Bragg peaks at q=(0,0,tau ~ 1/7) onset at TN=27 K as previously
reported by Marty et al. The nature of the fluctuations and temperature
dependence of the order parameter is consistent with a classical second order
phase transition for a two dimensional triangular antiferromagnet. We will show
that the physical properties and energy scales including the ordering
wavevector, Curie-Weiss temperature, and the spin-waves can be explained
through the use of only symmetric exchange constants without the need for the
Dzyaloshinskii-Moriya interaction. This is accomplished through a set of
``helical"" exchange pathways along the c direction imposed by the chiral
crystal structure and naturally explains the magnetic diffuse scattering which
displays a strong vector chirality up to high temperatures well above the
ordering temperature. This illustrates a strong coupling between magnetic and
crystalline chirality in this compound.",1007.4216v1
2010-08-26,Two- and three-dimensional magnetic correlations in the spin-1/2 square-lattice system Zn2VO(PO4)2,"The magnetic correlations in the quasi-two dimensional spin-1/2
square-lattice system Zn2VO(PO4)2 have been investigated by neutron diffraction
technique. A long-range antiferromagnetic (AFM) ordering below 3.75 K (TN) has
been observed with a reduced moment of 0.66(2) {\mu}B per V ion at 1.5 K. In a
given ab plane, the AFM spin arrangement is N\'eel type and the AFM layers are
coupled ferromagnetically along the c axis. Remarkably, we have observed a pure
2D short-range AFM ordering in the ab plane above TN. Interestingly, the
coexistence of diffuse magnetic scattering and three dimensional
antiferromagnetic Bragg peaks has been found below TN, indicating the presence
of spin-waves as confirmed by our calculation using the linear spin-wave
theory. The observed results are discussed in the light of existing theory for
a two-dimensional spin-1/2 square-lattice system.",1008.4481v1
2010-09-29,Magnetic spectrum of the two-dimensional antiferromagnet La2CoO4 studied by inelastic neutron scattering,"We report measurements of the magnetic excitation spectrum of the layered
antiferromagnet La2CoO4 by time-of-flight neutron inelastic scattering. In the
energy range probed in our experiments (0-250 meV) the magnetic spectrum
consists of spin-wave modes with strong in-plane dispersion extending up to 60
meV, and a nearly dispersionless peak at 190 meV. The spin-wave modes exhibit a
small (~1 meV) dispersion along the magnetic zone boundary. We show that the
magnetic spectrum can be described very well by a model of a Heisenberg
antiferromagnet that includes the full spin and orbital degrees of freedom of
Co2+ in an axially-distorted crystal field. The collective magnetic dynamics
are found to be controlled by dominant nearest-neighbour exchange interactions,
strong XY-like single-ion anisotropy and a substantial unquenched orbital
angular momentum.",1009.5913v2
2010-11-01,Multi-stability in an optomechanical system with two-component Bose-Einstein condensate,"We investigate a system consisting of a two-component Bose-Einstein
condensate interacting dispersively with a Fabry-Perot optical cavity where the
two components of the condensate are resonantly coupled to each other by
another classical field. The key feature of this system is that the atomic
motional degrees of freedom and the internal pseudo-spin degrees of freedom are
coupled to the cavity field simultaneously, hence an effective spin-orbital
coupling within the condensate is induced by the cavity. The interplay among
the atomic center- of-mass motion, the atomic collective spin and the cavity
field leads to a strong nonlinearity, resulting in multi- stable behavior in
both matter wave and light wave at the few-photon level.",1011.0394v2
2010-11-05,Incommensurate spin-density wave and multiband superconductivity in Na$_{x}$FeAs as revealed by nuclear magnetic resonance,"We report a $^{23}$Na and $^{75}$As nuclear magnetic resonance (NMR)
investigation of Na$_{x}$FeAs series ($x=1$, 0.9, 0.8) exhibiting a
spin-density wave (SDW) order below $T_{\rm SDW}=45$, 50 and 43 K for $x=1$,
0.9, 0.8, respectively, and a bulk superconductivity below $T_c\approx 12$ K
for x=0.9. Below $T_{\rm SDW}$, a spin-lattice relaxation reveals the presence
of gapless particle-hole excitations in the whole $x$ range, meaning that a
portion of the Fermi surface remains gapless. The superconducting fraction as
deduced from the bulk susceptibility scales with this portion, while the SDW
order parameter as deduced from the NMR linewidth scales inversely with it. The
NMR lineshape can only be reproduced assuming an incommensurate (IC) SDW. These
findings qualitatively correspond to the mean-field models of competing
interband magnetism and intraband superconductivity, which lead to an IC SDW
order coexisting with superconductivity in part of the phase diagram.",1011.1387v2
2010-11-11,The Spin-weighted Spheroidal Wave functions in the Case of s=1/2,"The spin-weighted spheroidal equations in the case s=1/2 is thoroughly
studied in the paper by means of the perturbation method in supersymmetry
quantum mechanics. The first-five terms of the super-potential in the series of
the parameter beta are given. The general form of the nth term of the
superpotential is also obtained, which could derived from the previous terms
W_{k}, k<n. From the results, it is easy to give the ground eigenfunction of
the equation. Furthermore, the shape-invariance property is investigated in the
series form of the parameter beta and is proven kept in this series form for
the equations. This nice property guarantee one could obtain the excited
eigenfunctions in the series form from the ground eigenfunctions by the method
in supersymmetry quantum mechanics. This shows the perturbation method method
in supersymmetry quantum mechanics could solve the spin-weight spheroidal wave
equations completely in the series form of the small parameter beta.",1011.2579v1
2011-01-05,The Fascinating World of Landau-Lifshitz-Gilbert Equation: An Overview,"The Landau-Lifshitz-Gilbert (LLG) equation is a fascinating nonlinear
evolution equation both from mathematical and physical points of view. It is
related to the dynamics of several important physical systems such as
ferromagnets, vortex filaments, moving space curves, etc. and has intimate
connections with many of the well known integrable soliton equations, including
nonlinear Schr\""odinger and sine-Gordon equations. It can admit very many
dynamical structures including spin waves, elliptic function waves, solitons,
dromions, vortices, spatio-temporal patterns, chaos, etc. depending on the
physical and spin dimensions and the nature of interactions. An exciting recent
development is that the spin torque effect in nanoferromagnets is described by
a generalization of the LLG equation which forms a basic dynamical equation in
the field of spintronics. This article will briefly review these developments
as a tribute to Robin Bullough who was a great admirer of the LLG equation.",1101.1005v1
2011-04-28,Spin-density-wave instability in graphene doped near the van Hove singularity,"We study the instability of the metallic state towards the formation of a new
ground state in graphene doped near the van Hove singularity. The system is
described by the Hubbard model and a field theoretical approach is used to
calculate the charge and spin susceptibility. We find that for repulsive
interactions, within the random phase approximation, there is a competition
between ferromagnetism and spin-density wave (SDW). It turns out that a SDW
with a triangular geometry is more favorable when the Hubbard parameter is
above the critical value U_c(T), which depends on the temperature T, even if
there are small variations in the doping. Our results can be verified by ARPES
or neutron scattering experiments in highly doped graphene.",1104.5334v2
2011-05-12,"Complete set of polarization transfer observables for the ${}^{16}{\rm O}(\vec{p},\vec{n}){}^{16}{\rm F}$ reaction at 296 MeV and 0 degrees","We report measurements of the cross section and a complete set of
polarization transfer observables for the ${}^{16}{\rm
O}(\vec{p},\vec{n}){}^{16}{\rm F}$ reaction at a bombarding energy of $T_p$ =
296 MeV and a reaction angle of $\theta_{\rm lab}$ = $0^{\circ}$.
  The data are compared with distorted-wave impulse approximation calculations
employing the large configuration-space shell-model (SM) wave functions.
  The well-known Gamow-Teller and spin-dipole (SD) states at excitation
energies of $E_x$ $\lesssim$ 8 MeV have been reasonably reproduced by the
calculations except for the spin--parity $J^{\pi}$ = $2^-$ state at $E_x$ =
5.86 MeV.
  The SD resonance at $E_x$ $\simeq$ 9.5 MeV appears to have more $J^{\pi}$ =
$2^-$ strength than $J^{\pi}$ = $1^-$ strength, consistent with the
calculations.
  The data show significant strength in the spin-longitudinal polarized cross
section $ID_L(0^{\circ})$ at $E_x$ $\simeq$ 15 MeV, which indicates existence
of the $J^{\pi}$ = $0^-$ SD resonance as predicted in the SM calculations.",1105.2449v2
2011-05-31,"Role of Hund's coupling in stabilization of the (0,pi) ordered SDW state within the minimal two-band model for iron pnictides","Spin wave excitations and stability of the (0,pi) ordered SDW state are
investigated within the minimal two-band model for iron pnictides including a
Hund's coupling term. The SDW state is shown to be stable in two distinct
doping regimes --- finite hole doping in the lower SDW band for small second
neighbour hoppings, and small electron doping in the upper SDW band for
comparable first and second neighbour hoppings. In both cases, Hund's coupling
strongly stabilizes the SDW state due to generation of additional ferromagnetic
spin couplings involving the inter-orbital part of the particle-hole
propagator. Spin wave energies for the two-band model are very similar to the
one-band t-t' Hubbard model results obtained earlier, and are in agreement with
inelastic neutron scattering studies of iron pnictides.",1105.6191v1
2011-05-31,Quantum critical response at the onset of spin density wave order in two-dimensional metals,"We study the frequency dependence of the electron self energy and the optical
conductivity in a recently developed field theory of the spin density wave
quantum phase transition in two dimensional metals. We focus on the interplay
between the Fermi surface `hot spots' and the remainder of the `cold' Fermi
surface. Scattering of electrons off the fluctuations of the spin density order
parameter, \phi, is strongest at the hot spots; we compute the conductivity due
to this scattering in a rainbow approximation. We point out the importance of
composite operators, built out of products of the primary electron or $\phi$
fields: these have important effects also away from the hot spots. The simplest
composite operator, \phi^2, leads to non-Fermi liquid behavior on the entire
Fermi surface. We also find an intermediate frequency window in which the cold
electrons loose their quasiparticle form due to effectively one-dimensional
scattering processes. The latter processes are part of umklapp scattering which
leads to singular contributions to the optical conductivity at the lowest
frequencies at zero temperature.",1106.0001v1
2011-09-18,Particle with spin S=3/2 in Riemannian space-time,"Equations for 16-component vector-bispinor field, originated from
Rarita-Schwinger Lagrangian for spin 3/2 field extended to Riemannian
space-time are investigated. Additional general covariant constrains for the
field are produced, which for some space-time models greatly simplify original
wave equation.
  Peculiarities in description of the massless spin 3/2 field are specified. In
the flat Minkowski space for massless case there exist gauge invariance of the
main wave equation, which reduces to possibility to produce a whole class of
trivial solutions in the the form of 4-gradient of arbitrary (gauge) bispinor
function, \Psi ^{0}_{c} = \partial_{c} \psi. Generalization of that property
for Riemannian model is performed; it is shown that in general covariant case
solutions of the gradient type \Psi^{0}_{\beta} = (\nabla_{\beta} +
\Gamma_{\beta})\Psi exist in space-time regions where the Ricci tensor obeys an
identity R_{\alpha \beta} - {1 \over 2} R g_{\alpha \beta} = 0.",1109.3871v1
2011-12-15,"Selective spin wave excitation in ferromagnetic (Ga,Mn)As layers by picosecond strain pulses","We demonstrate selective excitation of a spin wave mode in a ferromagnetic
(Ga,Mn)As film by picosecond strain pulses. For a certain range of magnetic
fields applied in the layer plane only a single frequency is detected for the
magnetization precession. We explain this selectivity of spin mode excitation
by the necessity of spatial matching of magnon and phonon eigenfunctions, which
represents a selection rule analogous to momentum conservation for
magnon-phonon interaction in bulk ferromagnetic materials.",1112.3394v1
2012-01-11,Spin-orbit density wave induced hidden topological order in URu2Si2,"The conventional order parameters in quantum matters are often characterized
by 'spontaneous' broken symmetries. However, sometimes the broken symmetries
may blend with the invariant symmetries to lead to mysterious emergent phases.
The heavy fermion metal URu2Si2 is one such example, where the order parameter
responsible for a second-order phase transition at Th = 17.5 K has remained a
long-standing mystery. Here we propose via ab-initio calculation and effective
model that a novel spin-orbit density wave in the f-states is responsible for
the hidden-order phase in URu2Si2. The staggered spin-orbit order 'spontaneous'
breaks rotational, and translational symmetries while time-reversal symmetry
remains intact. Thus it is immune to pressure, but can be destroyed by magnetic
field even at T = 0 K, that means at a quantum critical point. We compute
topological index of the order parameter to show that the hidden order is
topologically invariant. Finally, some verifiable predictions are presented.",1201.2246v2
2012-03-05,Hidden and antiferromagnetic order as a rank-5 superspin in URu2Si2,"We propose a candidate for the hidden order in URu2Si2: a rank-5 E type spin
density wave between Uranium 5f crystal field doublets breaking time reversal
and lattice tetragonal symmetry in a manner consistent with recent torque
measurements [R. Okazaki et al, Science 331, 439 (2011)]. We argue that
coupling of this order parameter to magnetic probes can be hidden by crystal
field effects, while still having significant effects on transport,
thermodynamics and magnetic susceptibilities. In a simple tight-binding model
for the heavy quasiparticles, we show the connection between the hidden order
and antiferromagnetic phases arises since they form different components of
this single rank-5 pseudo-spin vector. Using a phenomenological theory, we show
the experimental pressure-temperature phase diagram can be qualitatively
reproduced by tuning terms which break pseudo-spin rotational symmetry. As a
test of our proposal, we predict the presence of small magnetic moments in the
basal plane oriented in the [110] direction ordered at the wave-vector (0,0,1).",1203.1047v2
2012-04-05,Spin waves and Collisional Frequency Shifts of a Trapped-Atom Clock,"We excite spin-waves with spatially inhomogeneous pulses and study the
resulting frequency shifts of a chip-scale atomic clock of trapped $^{87}$Rb.
The density-dependent frequency shifts of the hyperfine transition simulate the
s-wave collisional frequency shifts of fermions, including those of optical
lattice clocks. As the spin polarizations oscillate in the trap, the frequency
shift reverses and it depends on the area of the second Ramsey pulse,
exhibiting a predicted beyond mean-field frequency shift. Numerical and
analytic models illustrate the observed behaviors.",1204.1150v4
2012-04-19,Field-induced quantum fluctuations in the heavy fermion superconductor CeCu2Ge2,"Quantum-mechanical fluctuations in strongly correlated electron systems cause
unconventional phenomena such as non-Fermi liquid behavior, and arguably high
temperature superconductivity. Here we report the discovery of a field-tuned
quantum critical phenomenon in stoichiometric CeCu2Ge2, a spin density wave
ordered heavy fermion metal that exhibits unconventional superconductivity
under ~ 10 GPa of applied pressure. Our finding of the associated quantum
critical spin fluctuations of the antiferromagnetic spin density wave order,
dominating the local fluctuations due to single-site Kondo effect, provide new
information about the underlying mechanism that can be important in
understanding superconductivity in this novel compound.",1204.4375v1
2012-04-20,Experimental evidence of low-lying gapped excitations in the quantum fluid at nu=5/2,"The low-lying neutral excitation spectrum of the incompressible quantum Hall
fluid at $\nu=5/2$ is investigated by inelastic light scattering. Gapped modes
are observable only in a very narrow filling factor range centered at 5/2 at
energies that overlap estimates from transport activation gaps. The modes are
interpreted as critical points in the wave-vector dispersion of excitations
that preserve spin orientation. For very small changes $|\delta\nu|\lesssim
0.01$ the gapped modes disappear and a continuum of low-lying excitations takes
over indicating the transition from an incompressible fluid at 5/2 to a
compressible state. Observations of spin wave modes indicate spin polarization
of the 5/2 and 2+1/3 quantum Hall fluids.",1204.4759v1
2012-05-18,Helimagnons in a chiral ground state of the pyrochlore antiferromagnets,"The Goldstone mode in a helical magnetic phase, also known as the helimagnon,
is a propagating mode with a highly anisotropic dispersion relation. Here we
study theoretically the helimagnon excitations in a complex chiral ground state
of pyrochlore antiferromagnets such as spinel CdCr2O4 and itinerant magnet
YMn2. We show that the effective theory of the soft modes in the helical state
possesses a symmetry similar to that of smectic liquid crystals. We compute the
low-energy spin-wave spectrum based on a microscopic spin Hamiltonian and find
a dispersion relation characteristic of the helimagnons. By performing dynamics
simulations with realistic model parameters, we also obtain an overall
agreement between experiment and the numerical spin-wave spectrum. Our work
thus also clarifies the mechanisms that relive the magnetic frustration in
these compounds.",1205.4225v2
2012-07-17,The Free Energy of the Quantum Heisenberg Ferromagnet at Large Spin,"We consider the spin-S ferromagnetic Heisenberg model in three dimensions, in
the absence of an external field. Spin wave theory suggests that in a suitable
temperature regime the system behaves effectively as a system of
non-interacting bosons (magnons). We prove this fact at the level of the
specific free energy: if $ S \to \infty $ and the inverse temperature $ \beta
\to 0 $ in such a way that $ \beta S $ stays constant, we rigorously show that
the free energy per unit volume converges to the one suggested by spin wave
theory. The proof is based on the localization of the system in small boxes and
on upper and lower bounds on the local free energy, and it also provides
explicit error bounds on the remainder.",1207.4050v1
2012-08-28,Modulation frequency dependence of continuous-wave optically/electrically detected magnetic resonance,"Continuous wave optically and electrically detected magnetic resonance
spectroscopy (cwODMR/cwEDMR) allow the investigation of paramagnetic states
involved in spin-dependent transitions, like recombination and transport.
Although experimentally similar to conventional electron spin resonance (ESR),
there exist limitations when applying models originally developed for ESR to
observables (luminescence and electric current) of cwODMR and cwEDMR. Here we
present closed-form solutions for the modulation frequency dependence of cwODMR
and cwEDMR based on an intermediate pair recombination model and discuss
ambiguities which arise when attempting to distinguish the dominant
spin-dependent processes underlying experimental data. These include: 1) a
large number of quantitatively different models cannot be differentiated, 2)
signs of signals are determined not only by recombination, but also by other
processes like dissociation, intersystem-crossing, pair generation, and even
experimental parameter such as, modulation frequency, microwave power, and
temperature, 3) radiative and non-radiative recombination cannot be
distinguished due to the observed signs of cwODMR and cwEDMR experiments.",1208.5573v1
2012-08-28,d+id' Chiral Superconductivity in Bilayer Silicene,"We investigate the structure and physical properties of the undoped bilayer
silicene through first-principles calculations and find the system is
intrinsically metallic with sizable pocket Fermi surfaces. When realistic
electron-electron interaction turns on, the system is identified as a chiral
d+id' topological superconductor mediated by the strong spin fluctuation on the
border of the antiferromagnetic spin density wave order. Moreover, the tunable
Fermi pocket area via strain makes it possible to adjust the spin density wave
critical interaction strength near the real one and enables a high
superconducting critical temperature.",1208.5596v3
2012-10-18,Magnetic excitation spectra in pyrochlore iridates,"Metal-insulator transitions in pyrochlore iridates (A2Ir2O7) are believed to
occur due to subtle interplay of spin-orbit coupling, geometric frustration,
and electron interactions. In particular, the nature of magnetic ordering of
iridium ions in the insulating phase is crucial for understanding of several
exotic phases recently proposed for these materials. We study the spectrum of
magnetic excitations in the intermediate-coupling regime for the so-called
all-in/all-out magnetic state in pyrochlore iridates with non-magnetic A-site
ions (A=Eu,Y), which is found to be preferred in previous theoretical studies.
We find that the effect of charge fluctuations on the spin-waves in this regime
leads to strong departure from the lowest-order spin-wave calculations based on
models obtained in strong-coupling calculations. We discuss the characteristic
features of the magnetic excitation spectrum that can lead to conclusive
identification of the magnetic order in future resonant inelastic x-ray (or
neutron) scattering experiments. Knowledge of the nature of magnetic order and
its low-energy features may also provide useful information on the accompanying
metal-insulator transition.",1210.5242v2
2012-10-26,Ground state in a half-doped manganite distinguished by neutron spectroscopy,"We have measured the spin-wave spectrum of the half-doped bilayer manganite
Pr(Ca,Sr)2Mn2O7 in its spin, charge, and orbital ordered phase. The
measurements, which extend throughout the Brillouin zone and cover the entire
one-magnon spectrum, are compared critically with spin-wave calculations for
different models of the electronic ground state. The data are described very
well by the Goodenough model, which has weakly interacting ferromagnetic
zig-zag chains in the CE-type arrangement. A model that allows ferromagnetic
dimers to form within the zigzags is inconsistent with the data. The analysis
conclusively rules out the strongly bound dimer (Zener polaron) model.",1210.7108v2
2012-11-01,Matter-wave bright solitons in spin-orbit coupled Bose-Einstein condensates,"We study matter-wave bright solitons in spin-orbit (SO) coupled Bose-Einstein
condensates (BECs) with attractive interatomic interactions. We use a
multiscale expansion method to identify solution families for chemical
potentials in the semi-infinite gap of the linear energy spectrum. Depending on
the linear and spin-orbit coupling strengths, the solitons may resemble either
standard bright nonlinear Schr\""{o}dinger solitons or exhibit a modulated
density profile, reminiscent of the stripe phase of SO-coupled repulsive BECs.
Our numerical results are in excellent agreement with our analytical findings,
and demonstrate the potential robustness of such solitons for experimentally
relevant conditions through stability analysis and direct numerical
simulations.",1211.0199v1
2013-01-25,Driven skyrmions and dynamical transitions in chiral magnets,"We study the dynamics of skyrmions in chiral magnets in the presence of a
spin polarized current. The motion of skyrmions in the ferromagnetic background
excites spin waves and contributes to additional damping. At a large current,
the spin wave spectrum becomes gapless and skyrmions are created dynamically
from the ferromagnetic state. At an even higher current, these skyrmions are
strongly deformed due to the damping and become unstable at a threshold
current, leading to a chiral liquid. We show how skyrmions can be created by
increasing the current in the magnetic spiral state. We then construct a
dynamic phase diagram for a chiral magnet with a current. The instability
transitions between different states can be observed as experimentally clear
signatures in the transport measurements, such as jumps and hysteresis.",1301.5963v2
2013-04-16,Sending classical information through relativistic quantum channels,"We investigate how special relativity influences the transmission of
classical information through quantum channels by evaluating the Holevo bound
when the sender and the receiver are in (relativistic) relative motion. By
using the spin degrees of freedom of spin-1/2 fermions to encode the classical
information we show that, for some configurations, the accessible information
in the receiver can be increased when the spin detector moves fast enough. This
is possible by allowing the momentum wave packet of one of the particles to be
wide enough while the momentum wave packets of other particles are kept
relatively narrow. In this way, one can take advantage of the fact that boosts
entangle the spin and momentum degrees of freedom of spin-1/2 fermions to
increase the accessible information in the former. We close the paper with a
discussion of how this relativistic quantum channel cannot in general be
described by completely positive quantum maps.",1304.4607v1
2013-06-16,Two-dimensional p-wave superconducting states with magnetic moments on a conventional s-wave superconductor,"Unconventional superconductivity induced by the magnetic moments in a
conventional spin-singlet s-wave superconductor is theoretically studied. By
choosing the spin directions of these moments, one can design spinless pairing
states appearing within the s-wave superconducting energy gap. It is found that
the helix spins produce px + py-wave state while the skyrmion crystal
configuration px + ipy-wave like state. Nodes in the energy gap and the zero
energy flat band of Majorana edge states exist in the former one, while the
chiral Majorana channels along edges of the sample and the zero energy Majorana
bound state at the core of the vortex appear in the latter case.",1306.3686v2
2013-06-27,Quantum computing through electron propagation in the edge states of quantum spin Hall systems,"We propose to implement quantum computing based on electronic spin qubits by
controlling the propagation of the electron wave packets through the helical
edge states of quantum spin Hall systems (QSHs). Specfically, two
non-commutative single-qubit gates, which rotate a qubit around z and y axes,
can be realized by utilizing gate voltages either on a single QSH edge channel
or on a quantum point contact structure. The more challenging two-qubit
controlled phase gate can be implemented through the on-demand capacitive
Coulomb interaction between two adjacent edge channels from two parallel QSHs.
As a result, a universal set of quantum gates can be achieved in an
all-electrical way. The fidelity and purity of the two-qubit gate are
calculated with both time delay and finite width of the wave packets taken into
consideration, which can reach high values with the existing high-quality
single electron source.",1306.6522v2
2013-07-09,Spin-Density-Wave-Type Ordering of LaCoGe Revealed by ^{59}Co- and ^{139}La-Nuclear Magnetic Resonance Measurements,"The low-temperature magnetic properties of LaCoGe with the tetragonal
CeFeSi-type structure were investigated by ^{59}Co- and ^{139}La-nuclear
magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements.
The nuclear spin-lattice relaxation rate divided by the temperature, 1/(T_1 T),
gradually increases with decreasing temperature and shows a kink at
approximately 18 K, below which an inhomogeneous internal field appears at the
Co nuclear site. These results indicate that antiferromagnetic ordering occurs
below T_N ~ 18 K. However, an internal field was not observed at the La nuclear
site below T_N. Taking all NMR results into account, we conclude that
spin-density-wave (SDW)-type ordering occurs, where magnetic correlations are
of the checkerboard type in the ab-plane and have a long periodicity along the
c-axis with inhomogeneous ordered moments pointing to the c-axis.",1307.2412v1
2013-07-20,Microscopic coexistence of a two-component incommensurate spin density wave with superconductivity in underdoped NaFe$_{0.983}$Co$_{0.017}$As,"We have performed $^{75}$As and $^{23}$Na nuclear magnetic resonance (NMR)
measurements on a single crystal of NaFe$_{0.9835}$Co$_{0.0165}$As and found
microscopic coexistence of superconductivity with a two-component spin density
wave (SDW). Using $^{23}$Na NMR we measured the spatial distribution of local
magnetic fields. The SDW was found to be incommensurate with a major component
having magnetic moment ($\sim0.2\,\mu_B$/Fe) and a smaller component with
magnetic moment ($\sim0.02\,\mu_B$/Fe). Spin lattice relaxation experiments
reveal that this coexistence occurs at a microscopic level.",1307.5366v1
2013-12-30,Validity of the spin-wave approximation for the free energy of the Heisenberg ferromagnet,"We consider the quantum ferromagnetic Heisenberg model in three dimensions,
for all spins $S\geq 1/2$. We rigorously prove the validity of the spin-wave
approximation for the excitation spectrum, at the level of the first
non-trivial contribution to the free energy at low temperatures. Our proof
comes with explicit, constructive upper and lower bounds on the error term. It
uses in an essential way the bosonic formulation of the model in terms of the
Holstein-Primakoff representation. In this language, the model describes
interacting bosons with a hard-core on-site repulsion and a nearest-neighbor
attraction. This attractive interaction makes the lower bound on the free
energy particularly tricky: the key idea there is to prove a differential
inequality for the two-particle density, which is thereby shown to be smaller
than the probability density of a suitably weighted two-particle random process
on the lattice.",1312.7873v2
2014-01-20,On the theory of inhomogeneous Bose-Einstein condensation of magnons in yttrium garnet,"The Bose-Einstein condensation (BEC) of magnons created by a strong pumping
in ferromagnetic thin films of yttrium iron garnet used as systems of finite
size is considered analytically. Such a peculiarity, typical for this magnetic
material, as the presence of a minimum in the spectrum of spin waves at a
finite value of the wave vector is taken into account. The definition of
hightemperature BEC is introduced and its characteristics are discussed. A role
of boundary conditions for spin variables is analyzed, and it is shown that in
the case of free spins on the boundary the magnon lattice can form in the
system. The factors responsible for its appearance are discussed.",1401.4854v1
2014-05-09,Spin wave spectrum of the quantum ferromagnet on the pyrochlore lattice Lu2V2O7,"Neutron inelastic scattering has been used to probe the spin dynamics of the
quantum (S=1/2) ferromagnet on the pyrochlore lattice Lu2V2O7. Well-defined
spin waves are observed at all energies and wavevectors, allowing us to
determine the parameters of the Hamiltonian of the system. The data are found
to be in excellent overall agreement with a minimal model that includes a
nearest- neighbour Heisenberg exchange J = 8:22(2) meV and a
Dzyaloshinskii-Moriya interaction (DMI) D =1:5(1) meV. The large DMI term
revealed by our study is broadly consistent with the model developed by Onose
et al. to explain the magnon Hall effect they observed in Lu2V2O7 [1], although
our ratio of D=J = 0:18(1) is roughly half of their value and three times
larger than calculated by ab initio methods [2].",1405.2284v1
2014-05-13,Spin oscillations of relativistic fermions in the field of a traveling circularly polarized electromagnetic wave and a constant magnetic field,"The Dirac equation, in the field of a traveling circularly polarized
electromagnetic wave and a constant magnetic field, has singular solutions,
corresponding the expansion of energy in vicinity of some singular point. These
solutions described relativistic fermions. States relating to these solutions
are not stationary. The temporal change of average energy, momentum and spin
for single and mixed states is studied in the paper. A distinctive feature of
the states is the disappearance of the longitudinal component of the average
spin. Another feature is the equivalence of the condition of fermion minimal
energy and the classical condition of the magnetic resonance. Finding such
solutions assumes the use of a transformation for rotating and co-moving frames
of references. Comparison studies of solutions obtained with the Galilean and
non-Galilean transformation shown that some parameters of the non-Galilean
transformation may be measured in high-energy physics.",1405.3613v1
2014-05-28,Electronic control of the spin-wave damping in a magnetic insulator,"It is demonstrated that the decay time of spin-wave modes existing in a
magnetic insulator can be reduced or enhanced by injecting an in-plane dc
current, $I_\text{dc}$, in an adjacent normal metal with strong spin-orbit
interaction. The demonstration rests upon the measurement of the ferromagnetic
resonance linewidth as a function of $I_\text{dc}$ in a 5~$\mu$m diameter
YIG(20nm){\textbar}Pt(7nm) disk using a magnetic resonance force microscope
(MRFM). Complete compensation of the damping of the fundamental mode is
obtained for a current density of $\sim 3 \cdot 10^{11}\text{A.m}^{-2}$, in
agreement with theoretical predictions. At this critical threshold the MRFM
detects a small change of static magnetization, a behavior consistent with the
onset of an auto-oscillation regime.",1405.7415v1
2014-07-31,Method for all-sky searches of continuous gravitational wave signals using the frequency-Hough transform,"In this paper we present a hierarchical data analysis pipeline for all-sky
searches of continuous gravitational wave signals, like those emitted by
spinning neutron stars asymmetric with respect to the rotation axis, with
unknown position, rotational frequency and spin-down. The core of the pipeline
is an incoherent step based on a particularly efficient implementation of the
Hough transform, that we call frequency-Hough, that maps the data
time-frequency plane to the source frequency/spin-down plane for each fixed
direction in the sky. Theoretical ROCs and sensitivity curves are computed and
the dependency on various thresholds is discussed. A comparison of the
sensitivity loss with respect to an ""optimal"" method is also presented. Several
other novelties, with respect to other wide-parameter analysis pipelines, are
also outlined. They concern, in particular, the construction of the grid in the
parameter space, with over-resolution in frequency and parameter refinement,
candidate selection and various data cleaning steps which are introduced to
improve search sensitivity and rejection of false candidates.",1407.8333v1
2014-08-20,Magnetic spiral induced by strong correlations in MnAu$_2$,"The compound MnAu$_2$ is one of the oldest known spin-spiral materials, yet
the nature of the spiral state is still not clear. The spiral cannot be
explained via relativistic effects due to the short pitch of the spiral and the
weakness of the spin-orbit interaction in Mn, and another common mechanism,
nesting, is ruled out as direct calculations show no features at the relevant
wave vector. We propose that the spiral state is induced by a competition
between the short-range antiferromagnetic exchange and a long-range interaction
induced by the polarization of Au bands, similar to double exchange. We find
that, contrary to earlier reports, the ground state in standard density
functional theory is ferromagnetic, \emph{i.e.}, the latter interaction
dominates. However, an accounting for Coulomb correlations via a Hubbard $U$
suppresses the Schrieffer-Wolff type $s-d$ magnetic interaction between Mn and
Au faster than the superexchange interaction, favoring a spin-spiral state. For
realistic values of $U$ the resulting spiral wave vector is in close agreement
with experiment.",1408.4719v1
2014-08-27,The magnitude of the magnetic exchange interaction in the heavy fermion antiferromagnet CeRhIn$_5$,"We have used high-resolution neutron spectroscopy experiments to determine
the complete spin wave spectrum of the heavy fermion antiferromagnet
CeRhIn$_5$. The spin wave dispersion can be quantitatively reproduced with a
simple $J_1$-$J_2$ model that also naturally explains the magnetic spin-spiral
ground state of CeRhIn$_5$ and yields a dominant in-plane nearest-neighbor
magnetic exchange constant $J_0$ = 0.74 meV. Our results pave the way to a
quantitative understanding of the rich low-temperature phase diagram of the
prominent Ce$T$In$_5$ ($T$ = Co, Rh, Ir) class of heavy fermion materials.",1408.6585v1
2014-10-02,Investigation of the temperature-dependence of ferromagnetic resonance and spin waves in Co2FeAl0.5Si0.5,"Co2FeAl0.5Si0.5 (CFAS) is a Heusler compound that is of interest for
spintronics applications, due to its high spin polarization and relatively low
Gilbert damping constant. In this study, the behavior of ferromagnetic
resonance as a function of temperature was investigated in CFAS, yielding a
decreasing trend of damping constant as the temperature was increased from 13
to 300 K. Furthermore, we studied spin waves in CFAS using both frequency
domain and time domain techniques, obtaining group velocities and attenuation
lengths as high as 26 km/s and 23.3 um, respectively, at room temperature.",1410.0439v1
2014-12-18,Exchange Magnon-Polaritons in Microwave Cavities,"We formulate a scattering theory to study magnetic films in microwave
cavities beyond the independent-spin and rotating wave approximations of the
Tavis-Cummings model. We demonstrate that strong coupling can be realized not
only for the ferromagnetic resonance (FMR) mode, but also for spin wave
resonances (SWRs); the coupling strengths are mode dependent and decrease with
increasing mode index. The strong coupling regime can be also accessed
electrically by spin pumping into a metal contact.",1412.5809v3
2015-01-14,Hydrodynamic spin fluctuations in the antiferromagnetic Heisenberg chain,"We study the finite temperature, low energy, long wave-length spectrum of the
dynamic structure factor of the spin-$1/2$ antiferromagnetic Heisenberg chain
in the presence of exchange anisotropy and external magnetic fields. Using
imaginary-time quantum Monte-Carlo we extract parameters, relevant to
characterize a {\it renormalized} Luttinger liquid. For small momentum our
results are consistent with a change from propagating spinon density waves to
spin diffusion, described by a finite-frequency spin-current relaxation rate.
Results for this relaxation rate as well as other Luttinger liquid parameters
are presented versus temperature, momentum, magnetic field, and anisotropy,
including finite-size analysis, and checks for anomalous diffusion. Our results
are consistent with exact diagonalization and Bethe Ansatz, where available,
and with corroborate findings of other previous studies using bosonization,
transfer matrix renormalization group, and quantum Monte-Carlo.",1501.03447v1
2015-02-05,Comparing Post-Newtonian and Numerical-Relativity Precession Dynamics,"Binary black-hole systems are expected to be important sources of
gravitational waves for upcoming gravitational-wave detectors. If the spins are
not colinear with each other or with the orbital angular momentum, these
systems exhibit complicated precession dynamics that are imprinted on the
gravitational waveform. We develop a new procedure to match the precession
dynamics computed by post-Newtonian (PN) theory to those of numerical binary
black-hole simulations in full general relativity. For numerical relativity NR)
simulations lasting approximately two precession cycles, we find that the PN
and NR predictions for the directions of the orbital angular momentum and the
spins agree to better than $\sim 1^{\circ}$ with NR during the inspiral,
increasing to $5^{\circ}$ near merger. Nutation of the orbital plane on the
orbital time-scale agrees well between NR and PN, whereas nutation of the spin
direction shows qualitatively different behavior in PN and NR. We also examine
how the PN equations for precession and orbital-phase evolution converge with
PN order, and we quantify the impact of various choices for handling partially
known PN terms.",1502.01747v1
2015-02-23,Torsion induced effects in magnetic nanowires,"Magnetic helix wire is one of the most simple magnetic systems which manifest
properties of both curvature and torsion. There exist two equilibrium states in
the helix wire with easy-tangential anisotropy: a quasi-tangential
magnetization distribution in case of relatively small curvatures and torsions,
and an onion state in opposite case. In the last case the magnetization is
close to tangential one, deviations are caused by the torsion and curvature.
Possible equilibrium magnetization states in the helix magnet with different
anisotropy directions are studied theoretically. The torsion also essentially
influences the spin-wave dynamics, acting as an effective magnetic field.
Originated from the curvature induced effective Dzyaloshinskii interaction,
this magnetic field leads to the coupling between the helix chirality and the
magnetochirality, it breaks mirror symmetry in spin-wave spectrum. All
analytical predictions on magnetization statics an dynamics are well confirmed
by the direct spin lattice simulations.",1502.06482v3
2015-04-28,Large and Small Fermi-Surface Spin Density Waves in the Kondo Lattice Model,"We demonstrate the existence of metallic spin density waves (SDWs) in the
Kondo lattice model on a square lattice for a wide range of parameters by means
of real space dynamical mean field theory. In these SDWs, the spin polarization
as well as the charge density depend on the lattice site and are modulated
along one direction of the square lattice. We show that within this phase of
metallic SDWs the Fermi surface changes from small to large, when the coupling
strength is increased. Furthermore, the transition between the large
Fermi-surface SDW phase and the paramagnetic phase is of second order, while
the transition between the small Fermi-surface SDW phase and the paramagnetic
phase is of first order. A local quantum critical point is thus avoided in our
calculations by undergoing a first order phase transition.",1504.07338v2
2015-04-28,"Multicriticality, Metastability, and Roton Feature in Bose-Einstein Condensates with Three-Dimensional Spin-Orbit Coupling","We theoretically study homogeneously trapped atomic Bose-Einstein condensates
where all three momentum components couple to a pseudo-spin-$1/2$ degree of
freedom. Tuning the anisotropies of spin-orbit coupling and the spin-dependent
interactions is shown to provide access to a rich phase diagram with a
tetracritical point, first-order phase transitions, and multiple metastable
phases of stripe and plane-wave character. The elementary excitation spectrum
of the axial plane-wave phase features an anisotropic roton feature and can be
used to probe the phase diagram. In addition to providing a versatile
laboratory for studying fundamental concepts in statistical physics, the
emergence of metastable phases creates new opportunities for observing
false-vacuum decay and bubble nucleation in ultra-cold-atom experiments.",1504.07370v1
2015-07-11,Entanglement of magnetic impurities through electron scattering in an electric field,"We show that the entanglement between two distant magnetic impurities,
generated via electron scattering, can be easily modulated by controlling the
magnitude of an applied external electric field. We assume that the two
magnetic impurities are fixed and located on an one-dimensional quantum wire. A
ballistic electron moving through the wire is scattered off by both impurities,
so the electron spin can be seen as a mediator between the spins of the
impurities. Heisenberg operators are used to describe the interactions between
electron and impurities spins. We use a wave guide formalism to model the
ballistic electron wave-function. Entanglement control is shown to be possible
for three different protocols of entanglement detection. The effect of
detection protocols on the entanglement extraction is discussed.",1507.03120v1
2015-07-22,Dynamical properties of the honeycomb-lattice Iridates ${\rm Na_2IrO_3}$,"We investigate the dynamical properties of ${\rm Na_2IrO_3}$. For five
effective models proposed for ${\rm Na_2IrO_3}$, we numerically calculate
dynamical structure factors (DSFs) with an exact diagonalization method. An
effective model obtained from $ab$ $initio$ calculations explains inelastic
neutron scattering experiments adequately. We further calculate excitation
modes based on linearized spin-wave theory. The spin-wave excitation of the
effective models obtained by $ab$ $initio$ calculations disagrees with the
low-lying excitation of DSFs. We attribute this discrepancy to the location of
${\rm Na_2IrO_3}$ in a parameter space close to the phase boundary with the
Kitaev spin-liquid phase.",1507.06044v2
2015-07-30,General Relativity and Compact Objects,"Starting with the conceptual foundation of general relativity (GR) -
equivalence principle, space-time geometry and special relativity, I train
cross hairs on two characteristic predictions of GR - black holes and
gravitational waves. These two consequences of GR have played a significant
role in relativistic astrophysics, e.g. compact X-ray sources, GRBs, quasars,
blazars, coalescing binary pulsars, etc.
  With quantum theory wedded to GR, particle production from vacuum becomes a
generic feature whenever event horizons are present. In this paper, I shall
briefly discuss the fate of a `black hole atom' when Hawking radiation is taken
into account. In the context of gravitational waves, I shall focus on the
possible consequences of gravitational and electromagnetic radiation from
highly magnetized and rapidly spinning white dwarfs. The discovery of RX
J0648.0-4418 system - a WD in a binary with mass slightly over 1.2 $
M_{\odot}$, and rotating with spin period as short as 13.2 s, provides an
impetus to revisit the problem of WD spin evolution due to energy loss.",1507.08511v2
2015-07-30,Quasi-soliton scattering in quantum spin chains,"The quantum scattering of magnon bound states in the anisotropic Heisenberg
spin chain is shown to display features similar to the scattering of solitons
in classical exactly solvable models. Localized colliding Gaussian wave packets
of bound magnons are constructed from string solutions of the Bethe equations
and subsequently evolved in time, relying on an algebraic Bethe ansatz based
framework for the computation of local expectation values in real space-time.
The local magnetization profile shows the trajectories of colliding wave
packets of bound magnons, which obtain a spatial displacement upon scattering.
Analytic predictions on the displacements for various values of anisotropy and
string lengths are derived from scattering theory and Bethe ansatz phase
shifts, matching time evolution fits on the displacements. The time evolved
block decimation (TEBD) algorithm allows for the study of scattering
displacements from spin-block states, showing similar scattering displacement
features.",1507.08624v2
2015-08-06,Molecular orbital polarization in Na2Ti2Sb2O: microscopic route to metal-metal transition without spontaneous symmetry breaking,"Ordered phases such as charge- and spin-density wave state accompany either
full or partial gapping of Fermi surface (FS) leading a metal-insulator or
metal-metal transition (MMT). However, there are examples of MMT without any
signatures of symmetry breaking. One example is Na$_2$Ti$_2$Sb$_2$O, where a
partial gapping of FS is observed but a density wave ordering has not been
found. Here we propose a microscopic mechanism of such a MMT which occurs due
to a momentum dependent spin-orbit coupled molecular orbital polarization.
Since a molecular $d$ orbital polarization is present due to a small spin-orbit
coupling of Ti, there is no spontaneous symmetry breaking involved. However, a
sharp increase of polarization happens above a critical electron interaction
which gaps out the $d$ orbtial FS and reduces the density of states
significantly, while the rest of FS associated with Sb $p$ orbtials is almost
intact across MMT. Experimental implications to test our proposal and
applications to other systems are also discussed.",1508.01519v1
2015-12-15,Optical emission spectroscopy study of competing phases of electrons in the second Landau level,"Quantum phases of electrons in the filling factor range $2 \leq\nu\leq 3$ are
probed by the weak optical emission from the partially populated second Landau
level and spin wave measurements. Observations of optical emission include a
multiplet of sharp peaks that exhibit a strong filling factor dependence. Spin
wave measurements by resonant inelastic light scattering probe breaking of spin
rotational invariance and are used to link this optical emission with
collective phases of electrons. A remarkably rapid interplay between emission
peak intensities manifests phase competition in the second Landau level.",1512.04914v1
2016-01-28,Spin-Cherenkov effect in a magnetic nanostrip with interfacial Dzyaloshinskii-Moriya interaction,"Spin-Cherenkov effect enables strong excitations of spin waves (SWs) with
nonlinear wave dispersions. The Dzyaloshinskii-Moriya interaction (DMI) results
in anisotropy and nonreciprocity of SWs propagation. In this work, we study the
effect of the interfacial DMI on SW Cherenkov excitations in permalloy
thin-film strips within the framework of micromagnetism. By performing
micromagnetic simulations, it is shown that coherent SWs are excited when the
velocity of a moving magnetic source exceeds the propagation velocity of the
SWs. Moreover, the threshold velocity of the moving magnetic source with finite
DMI can be reduced compared to the case of zero DMI. It thereby provides a
promising route towards efficient SW generation and propagation, with potential
applications in spintronic and magnonic devices.",1601.07755v2
2016-02-07,The Inward Dispersion of the Neutron Scattering Experiments in HTSC Cuprates,"The theory of the high temperature superconducting cuprates, which is based
on the condensation of holes into strings in checker-board geometry, was
successful to explain the elastically scattered Neutrons by spin waves. Here it
is extended to analyze the inward dispersion curve of its inelastic
counterpart, up to the resonance energy- . This extension is done by applying
the perturbation theory of the linear response to the condensed strings. The
approximated susceptibility is derived by means of the ring diagram. The
dispersion relation is obtained from the dispersion of the poles of the
susceptibility integral. It is found that the particle anti-particle pair that
yields the susceptibility is the time reversal pair where the particle momentum
is in phase A, and the anti-particle momentum is in phase B. The dispersion is
found to be in agreement with experiment, subject to some suggested
corrections. The weak intensity by the resonance energy, as well as the
dispersion, is speculated to be modified due to interference with spin waves
that are caused by direct spin flip, as in the mother undoped materials.",1602.05089v3
2016-02-18,"Zitterbewegung, internal momentum and spin of the circular travelling wave electromagnetic electron","The study of this paper demonstrates that electron has Dirac delta like
internal momentum (u,p_{{\theta}}), going round in a circle of radius equal to
half the reduced Compton wavelength of electron with tangential velocity c. The
circular momentum p_{{\theta}} and energy u emanate from circular Dirac delta
type rotating monochromatic electromagnetic (EM) wave that itself travels in
another circle having radius equal to the reduced Compton wavelength of
electron. The phenomenon of Zitterbewegung and the spin of electron are the
natural consequences of the model. The spin is associated with the internal
circulating momentum of electron in terms of four component spinor, which leads
to the Dirac equation linking the EM electron model with quantum mechanical
theory. Our model accurately explains the experimental results of electron
channelling experiment, [P. Catillon et al., Found.Phys. 38, 659 (2008)], in
which the momentum resonance is observed at 161.784MeV/c corresponding to
Zitterbewegung frequency of 80.874MeV/c electron beam.",1602.07534v1
2016-04-05,Ising tricriticality in the extended Hubbard model with bond dimerization,"We explore the quantum phase transition between Peierls and
charge-density-wave insulating states in the one-dimensional, half-filled,
extended Hubbard model with explicit bond dimerization. We show that the
critical line of the continuous Ising transition terminates at a tricritical
point, belonging to the universality class of the tricritical Ising model with
central charge $c=7/10$. Above this point, the quantum phase transition becomes
first order. Employing a numerical matrix-product-state based (infinite)
density-matrix renormalization group method we determine the ground-state phase
diagram, the spin and two-particle charge excitations gaps, and the
entanglement properties of the model with high precision. Performing a
bosonization analysis we can derive a field description of the transition
region in terms of a triple sine-Gordon model. This allows us to derive field
theory predictions for the power-law (exponential) decay of the density-density
(spin-spin) and bond-order-wave correlation functions, which are found to be in
excellent agreement with our numerical results.",1604.01228v2
2016-04-16,Classical electrodynamics in a space with spin noncommutativity of coordinates,"We propose a new relativistic Lorentz-invariant spin-noncommutative algebra.
Using the Weyl ordering of noncommutative position operators, we build an
analogue of the Moyal-Groenewald product for the proposed algebra. The Lagrange
function of an electromagnetic field in the space with spin noncommutativity is
constructed. In such a space electromagnetic field becomes non-abelian. A gauge
transformation law of this field is also obtained. Exact nonlinear field
equations of noncommutative electromagnetic field are derived from the least
action principle. Within the perturbative approach we consider field of a point
charge in a constant magnetic field and interaction of two plane waves. An
exact solution of a plane wave propagation in a constant magnetic and electric
fields is found.",1604.07448v1
2016-05-12,Fixed-node and fixed-phase approximations and their relationship to variable spins in quantum Monte Carlo,"We compare the fixed-phase approximation with the better known, but closely
related fixed-node approximation on several testing examples. We found that
both approximations behave very similarly with the fixed-phase results being
very close to the fixed-node method whenever nodes/phase were of high and
comparable accuracy. The fixed-phase exhibited larger biases when the trial
wave functions errors in the nodes/phase were intentionally driven to
unrealistically large values. We also present a formalism that enables to
describe wave functions with the full antisymmetry in spin-spatial degrees of
freedom using our recently developed method for systems with spins as fully
quantum variables. This opens new possibilities for simulations of fermionic
systems in the fixed-phase approximation formalism.",1605.03813v1
2016-06-22,Self-consistent spin-wave analysis of the 1/3 magnetization plateau in the kagome antiferromagnet,"We propose a modified spin-wave theory to study the 1/3 magnetization plateau
of the antiferromagnetic Heisenberg model on the kagome lattice. By the
self-consistent inclusion of quantum corrections, the 1/3 plateau is stabilized
over a broad range of magnetic fields for all spin quantum numbers, S. The
values of the critical magnetic fields and the widths of the magnetization
plateaus are fully consistent with recent numerical results from exact
diagonalization and infinite projected entangled paired states.",1606.06924v1
2016-07-04,Infinite matter properties and zero-range limit of nonrelativistic finite-range interactions,"We discuss some infinite matter properties of two finite-range interactions
widely used for nuclear structure calculations, namely Gogny and M3Y
interactions. We show that some useful informations can be deduced for the
central, tensor and spin-orbit terms from the spin-isospin channels and the
partial wave decomposition of the symmetric nuclear matter equation of state.
We show in particular that the central part of the Gogny interaction should
benefit from the introduction of a third Gaussian and the tensor parameters of
both interactions can be deduced from special combinations of partial waves. We
also discuss the fact that the spin-orbit of the M3Y interaction is not
compatible with local gauge invariance. Finally, we show that the zero-range
limit of both families of interactions coincides with the specific form of the
zero-range N3LO Skyrme interaction and we emphasize from this analogy the
benefits of N3LO.",1607.00835v2
2016-07-19,Spin resonance in the superconducting state of Li$_{1-x}$Fe$_{x}$ODFe$_{1-y}$Se observed by neutron spectroscopy,"We have performed inelastic neutron scattering measurements on a powder
sample of the superconductor lithium iron selenide hydroxide
Li$_{1-x}$Fe$_{x}$ODFe$_{1-y}$Se ($x \simeq 0.16, y \simeq 0.02$, $T_{\rm c} =
41$\,K). The spectrum shows an enhanced intensity below $T_{\rm c}$ over an
energy range $0.64\times2\Delta < E < 2\Delta$, where $\Delta$ is the
superconducting gap, with maxima at the wave vectors $Q_1 \simeq
1.46$\,\AA$^{-1}$ and $Q_2 \simeq 1.97$\,\AA$^{-1}$. The behavior of this
feature is consistent with the spin resonance mode found in other
unconventional superconductors, and strongly resembles the spin resonance
observed in the spectrum of the molecular-intercalated iron selenide,
Li$_{0.6}$(ND$_{2}$)$_{0.2}$(ND$_{3}$)$_{0.8}$Fe$_{2}$Se$_{2}$. The signal can
be described with a characteristic two-dimensional wave vector $(\pi, 0.67\pi)$
in the Brillouin zone of the iron square lattice, consistent with the nesting
vector between electron Fermi sheets.",1607.05588v2
2016-08-29,Order parameter fluctuation and ordering competition in $\mathrm{Ba_{1-x}K_xFe_2As_2}$,"The competition among superconductivity, stripe-type magnetic order, and a
new type of $C_4$ symmetric magnetic order in $\mathrm{Ba_{1-x}K_xFe_2As_2}$ is
theoretically studied, focusing on its impact on the global phase diagram. By
carrying out a renormalization group analysis of an effective field theory, we
obtain the energy-scale dependent flows of all the model parameters, and then
apply the results to understand the observed phase diagram. On the basis of the
renormalization group analysis, we show that the critical line of nematic order
has a negative slope in the superconducting dome and superconductivity is
suppressed near the magnetic quantum critical point, which are both consistent
with recent experiments. Moreover, we find that, although the observed $C_4$
symmetric magnetic state could be a charge-spin density wave or a spin-vortex
crystal at high temperatures, charge-spin density wave is the only stable $C_4$
magnetic state in the low-temperature regime. Therefore, ordering competition
provides a method to distinguish these two candidate $C_4$ magnetic states.",1608.07935v2
2016-09-06,Chiral charge pumping in graphene deposited on a magnetic insulator,"We demonstrate that a sizable chiral charge pumping can be achieved at room
temperature in graphene/Yttrium Iron Garnet (YIG) bilayer systems. The effect,
which cannot be attributed to the ordinary spin pumping, reveals itself in the
creation of a dc electric field/voltage in graphene as a response to the
dynamic magnetic excitations (spin waves) in an adjacent out-of-plane
magnetized YIG film. We show that the induced voltage changes its sign when the
orientation of the static magnetization is reversed, clearly indicating the
broken spatial inversion symmetry in the studied system. The strength of effect
shows a non-monotonous dependence on the spin-wave frequency, in agreement with
the proposed theoretical model.",1609.01613v2
2016-08-21,The Unusual Nature of Confined Modes in a Chiral System,"Nonreciprocity of spin wave propagation is a well-known consequence of
antisymmetric exchange contributions possible in magnetic spin systems that
lack inversion symmetry. In this case, it is possible for the energy of a state
to depend on the sign of its momentum as {\omega}(k) ${\neq}$ {\omega}(-k). We
discuss here the consequences of this nonreciprocity on counterpropagating
travelling spin wave states. In a confined geometry we find states with
well-defined nodes but with amplitudes that are modulated such that inversion
symmetry of the mode profile is lost. This feature leads to the suggestion that
additional features may become visible in, for example, ferromagnetic resonance
studies of ferromagnetic micro-elements with DMI, allowing a quantification of
the amplitude and direction of the DMI. Moreover, this interference between
nonreciprocal modes forms the basis for a generalized concept of mode
confinement.",1609.03417v1
2016-10-11,Magnetic gap opening in rhombohedral-stacked multilayer graphene from first principles,"We investigate the occurrence of magnetic and charge density wave
instabilities in rhombohedral-stacked multilayer (three to eight layers)
graphene by first principles calculations including exact exchange. Neglecting
spin-polarization, an extremely flat surface band centered at the special point
${\bf K}$ of the Brillouin zone occurs at the Fermi level. Spin polarization
opens a gap in the surface state by stabilizing an antiferromagnetic state. The
top and the bottom surface layers are weakly ferrimagnetic in-plane (net
magnetization smaller than $10^{-3}\mu_B$), and are antiferromagnetic coupled
to each other. This coupling is propagated by the out-of-plane
antiferromagnetic coupling between the nearest neighbors. The gap is very small
in a spin-polarized generalized gradient approximation, while it is
proportional to the amount of exact exchange in hybrid functionals. For
trilayer rhombohedral graphene it is $38.6$ meV in PBE0, in agreement with the
$42$ meV gap found in experiments. We study the temperature and doping
dependence of the magnetic gap. At electron doping of $n \sim 7 \times 10^{11}$
cm$^{-2}$ the gap closes. Charge density wave instabilities with
$\sqrt{3}\times\sqrt{3}$ periodicity do not occur.",1610.03445v2
2017-09-18,Supersymmetric dS/CFT,"We put forward new explicit realisations of dS/CFT that relate ${\cal N}=2$
supersymmetric Euclidean vector models with reversed spin-statistics in three
dimensions to specific supersymmetric Vasiliev theories in four-dimensional de
Sitter space. The partition function of the free supersymmetric vector model
deformed by a range of low spin deformations that preserve supersymmetry
appears to specify a well-defined wave function with asymptotic de Sitter
boundary conditions in the bulk. In particular we find the wave function is
globally peaked at undeformed de Sitter space, with a low amplitude for strong
deformations. This suggests that supersymmetric de Sitter space is stable in
higher-spin gravity and in particular free from ghosts. We speculate this is a
limiting case of the de Sitter realizations in exotic string theories.",1709.06024v2
2018-01-22,Localization of magnon modes in a curved magnetic nanowire,"Spin waves in magnetic nanowires can be bound by a local bending of the wire.
The eigenfrequency of a truly local magnon mode is determined by the curvature:
a general analytical expression is established for any infinitesimally weak
localized curvature of the wire. The interaction of the local mode with spin
waves, propagating through the bend, results in scattering features, which is
well confirmed by spin-lattice simulations.",1801.06945v3
2018-05-21,Inverse Edelstein effect induced by magnon - phonon coupling,"We demonstrate a spin to charge current conversion via magnon-phonon coupling
and inverse Edelstein effect on the hybrid device Ni/Cu(Ag)/Bi$_{2}$O$_{3}$.
The generation of spin current ($J_{s}\approx 10^{8}A/m^{2}$) due to magnon -
phonon coupling reveals the viability of acoustic spin pumping as mechanism for
the development of spintronic devices. A full in-plane magnetic field angle
dependence of the power absorption and a combination of longitudinal and
transverse voltage detection reveals the symmetric and asymmetric components of
the inverse Edelstein effect voltage induced by Rayleigh type surface acoustic
waves. While the symmetric components are well studied, asymmetric components
are widely unexplored. We assign the asymmetric contributions to the
interference between longitudinal and shear waves and an anisotropic charge
distribution in our hybrid device.",1805.07900v1
2018-06-07,Triangular antiferromagnetism on the honeycomb lattice of twisted bilayer graphene,"We present the electronic band structures of states with the same symmetry as
the three-sublattice planar antiferromagnetic order of the triangular lattice.
Such states can also be defined on the honeycomb lattice provided the spin
density waves lie on the bonds. We identify cases which are consistent with
observations on twisted bilayer graphene: a correlated insulator with an energy
gap, yielding a single doubly-degenerate Fermi surface upon hole doping. We
also discuss extensions to metallic states which preserve spin rotation
invariance, with fluctuating spin density waves and bulk $\mathbb{Z}_2$
topological order.",1806.02837v2
2018-11-06,Electrically-Tunable High Curie Temperature Two-Dimensional Ferromagnetism in Van der Waals Layered Crystals,"Identifying intrinsic low-dimensional ferromagnets with high transition
temperature and electrically tunable magnetism is crucial for the development
of miniaturized spintronics and magnetoelectrics. Recently long-range 2D
ferromagnetism was observed in van der Waals crystals CrI$_3$ and
Cr$_2$Ge$_2$Te$_6$, however their Curie temperature is significantly lowered
when reducing down to monolayer/few layers. Herein, using renormalized
spin-wave theory and first-principles electronic structure theory, we present a
theoretical study of electrically tunable 2D ferromagnetism in van der Waals
layered CrSBr and CrSeBr semiconductors with high Curie temperature of ~150K
and sizable band gap. High transition temperature is attributed to strong
anion-mediated superexchange interaction and a sizable spin-wave excitation gap
due to large exchange and single-ion anisotropy. Remarkably, hole and electron
doping can switch magnetization easy axis from in-plane to out-of-plane
direction. These unique characteristics establish monolayer CrSBr and CrSeBr as
promising platform for realizing 2D spintronics and magnetoelectrics such as 2D
spin field effect transistor.",1811.02674v2
2018-11-21,The high-frequency dynamics of domain walls with strong Dzyaloshinskii-Moriya interaction,"Domain walls (DWs) in perpendicularly magnetized nanotracks (PMNTs) with
interfacial Dzyaloshinskii-Moriya interaction (DMI) have become the primary
objects of theoretical and experimental interest due to their technological
suitability in spintronic nanodevices. Chiral DWs in PMNTs can be driven
efficiently by the spin-orbit torque. However, the high-frequency dynamic
behavior of the chiral DW has not been explored. In this work, using
micromagnetic calculation, we have discovered a novel dynamic mode, the sway
mode, of DWs under an out-of-plane high-frequency alternating current (AC)
magnetic field in a PMNT with strong DMI. This dynamic phenomenon is strictly
related with DMI-related boundary effect and can be understood in terms of the
propagation of an amplitude-tuned spin wave in the DW plane. The spin wave
exhibits some characteristic frequencies due to the space-confinement of DW.
This work offers the possibility of a visual route for characterizing DMI.",1811.08590v1
2019-11-11,Excitonic density wave and spin-valley superfluid in bilayer transition metal dichalcogenide,"Artificial moir\'e superlattices in 2d van der Waals heterostructure is a new
venue for realizing and controlling correlated electronic phenomena. Recently,
twisted bilayer WSe$_2$ emerged as a new robust moir\'e system hosting a
correlated insulator at moir\'e half-filling over a range of twist angle. In
this work, we present a theory of this insulating state as an excitonic density
wave due to intervalley electron-hole pairing. We show that exciton
condensation is strongly enhanced by a van Hove singularity near the Fermi
level. Our theory explains the remarkable sensitivity of the insulating gap to
the vertical electric field. In contrast, the gap is weakly reduced by a
perpendicular magnetic field, with quadratic dependence at low field. The
different responses to electric and magnetic field can be understood in terms
of pair-breaking versus non-pair-breaking effects in a BCS analog of the
system. We further predict superfluid spin transport in this electrical
insulator, which can be detected by optical spin injection and spatial-temporal
imaging.",1911.04493v3
2017-05-08,Spin-dependent coupling between quantum dots and topological quantum wires,"Considering Rashba quantum wires with a proximity-induced superconducting gap
as physical realizations of Majorana fermions and quantum dots, we calculate
the overlap of the Majorana wave functions with the local wave functions on the
dot. We determine the spin-dependent tunneling amplitudes between these two
localized states and show that we can tune into a fully spin polarized
tunneling regime by changing the distance between dot and Majorana fermion.
Upon directly applying this to the tunneling model Hamiltonian, we calculate
the effective magnetic field on the quantum dot flanked by two Majorana
fermions. The direction of the induced magnetic field on the dot depends on the
occupation of the nonlocal fermion formed from the two Majorana end states
which can be used as a readout for such a Majorana qubit.",1705.03002v1
2018-07-13,Magnon band topology in spin-orbital coupled magnets: classification and application to $α$-RuCl$_3$,"In spite of flourishing studies on the topology of spin waves, a generic
framework to classify and compute magnon band topology in non-collinear magnets
is still missing. In this work we provide such a theory framework, by mapping
an arbitrary linear spin wave into a local free-fermion Hamiltonian with
exactly the same spectrum, symmetry implementation and band topology, which
allows for a full classification and calculation on any topological properties
of magnon bands. We apply this fermionization approach to honeycomb Kitaev
magnet $\alpha$-RuCl$_3$, and show the existence of topologically protected
magnon band crossings, and field-induced magnon Chern bands under small
magnetic fields.",1807.05232v2
2018-10-15,Localized spin waves in isolated $kπ$ skyrmions,"The localized magnon modes of isolated $k\pi$ skyrmions on a field-polarized
background are analyzed based on the Landau-Lifshitz-Gilbert equation within
the terms of an atomistic classical spin model, with system parameters based on
the Pd/Fe biatomic layer on Ir(111). For increasing skyrmion order $k$ a higher
number of excitation modes are found, including modes with nodes in the radial
eigenfunctions. It is shown that at low fields $2\pi$ and $3\pi$ skyrmions are
destroyed via a burst instability connected to a breathing mode, while $1\pi$
skyrmions undergo an elliptic instability. At high fields all $k\pi$ skyrmions
collapse due to the instability of a breathing mode. The effective damping
parameters of the spin waves are calculated in the low Gilbert damping limit,
and they are found to diverge in the case of the lowest-lying modes at the
burst and collapse instabilities, but not at the elliptic instability. It is
shown that the breathing modes of $k\pi$ skyrmions may become overdamped at
higher Gilbert damping values.",1810.06471v1
2018-10-31,Spin-wave stiffness and micromagnetic exchange interactions expressed by means of the KKR Green function approach,"We represent an approach to calculate micromagnetic model parameters such as
the tensor of exchange stiffness, Dzyaloshinskii-Moriya interaction (DMI) as
well as spin-wave stiffness. The scheme is based on the fully relativistic
Korringa-Kohn-Rostoker Green function (KKR-GF) technique and can be seen as a
relativistic extension of the work of Lichtenstein {\em et al.} The expression
for $D^{z\alpha}$ elements of DMI differ from the expressions for $D^{x\alpha}$
and $D^{y\alpha}$ elements as the former are derived via second-order
perturbation term of the energy caused by spin-spiral while the latter are
associated with the first-order term. Corresponding numerical results are
compared with those obtained using other schemes reported in the literature.",1810.13175v1
2018-02-12,Topological Magnons in Kitaev Magnets at High Fields,"We study the Kitaev-Heisenberg-$\Gamma$-$\Gamma'$ model that describes the
magnetism in strong spin-orbit coupled honeycomb lattice Mott insulators. In
strong $[111]$ magnetic fields that bring the system into the fully polarized
paramagnetic phase, we find that the spin wave bands carry nontrivial Chern
numbers over large regions of the phase diagram implying the presence of chiral
magnon edge states. In contrast to other topological magnon systems, the
topological nontriviality of these systems results from the presence of magnon
number non-conserving terms in the Hamiltonian. Since the effects of
interactions are suppressed by $J/h$, the validity of the single particle
picture is tunable making paramagnetic phases particularly suitable for the
exploration of this physics. Using time dependent DMRG and interacting spin
wave theory, we demonstrate the presence of the chiral edge mode and its
evolution with field.",1802.04283v1
2018-08-15,Spin density wave as a superposition of two magnetic states of opposite chirality and its implications,"A magnetic solid with weak spin frustration tends to adopt a noncollinear
magnetic structure such as cycloidal structure below a certain temperature and
a spin density wave (SDW) slightly above this temperature. The causes for these
observa-tions were explored by studying the magnetic structures of BaYFeO4,
which undergoes an SDW and a cycloidal phase transi-tion below 48 and 36 K,
respectively, in terms of density func-tional theory calculations. We show that
an SDW structure aris-es from a superposition of two magnetic states of
opposite chi-rality, an SDW state precedes a chiral magnetic state due to the
lattice relaxation, and whether an SDW is transversal or longitudinal is
governed by the magnetic anisotropy of magnetic ions.",1808.05044v1
2018-08-16,Angular momentum-dependent topological transport and its experimental realization using a transmission line network,"Novel classical wave phenomenon analogs of the quantum spin Hall effect are
mostly based on the construction of pseudo-spins. Here we show that the
non-trivial topology of a system can also be realized using orbital angular
momentum through angular-momentum-orbital coupling. The idea is illustrated
with a tight-binding model and experimentally demonstrated with a transmission
line network. We show experimentally that even a very small network cluster
exhibits one-way topological edge states, and their properties can be described
in terms of local Chern numbers. Our work provides a new mechanism to realize
counterparts of the quantum spin Hall effect in classical waves and may offer
insights for other systems.",1808.05413v1
2018-12-06,Transverse profile and 3D spin canting of a Majorana state in carbon nanotubes,"The full spatial 3D profile of Majorana bound states (MBS) in a nanowire-like
setup featuring a semiconducting carbon nanotube (CNT) as the central element
is discussed. By accurate tight-binding calculations we show that the chiral
nature of the CNT lattice is imprinted in the MBS wave function which has a
helical structure, anisotropic in the transverse direction. The local spin
canting angle displays a similar spiral pattern, varying around the CNT
circumference. We reconstruct the intricate 3D profile of the MBS wave function
analytically, using an effective low energy Hamiltonian accounting both for the
electronic spin and valley degrees of freedom of the CNT. We find that the four
components of the Majorana spinor are related by the three symmetries of our
Bogoliubov-de Gennes (BdG) Hamiltonian, reducing the number of independent
components to one. A Fourier transform analysis uncovers the presence of three
contributions to the MBS, one from the $\Gamma$-point and one from each of the
Fermi points, with further complexity added by the presence of two valley
states in each contribution.",1812.02796v2
2018-12-10,Quantum phase transitions in the spin-boson model without the counterrotating terms,"We study the spin-boson model without the counterrotating terms by a
numerically exact method based on variational matrix product states.
Surprisingly, the second-order quantum phase transition (QPT) is observed for
the sub-Ohmic bath in the rotating-wave approximations. Moreover, first-order
QPTs can also appear before the critical points. With the decrease of the bath
exponents, these first-order QPTs disappear successively, while the
second-order QPT remains robust. The second-order QPT is further confirmed by
multi-coherent-states variational studies, while the first-order QPT is
corroborated with the exact diagonalization in the truncated Hilbert space.
Extension to the Ohmic bath is also performed, and many first-order QPTs appear
successively in a wide coupling regime, in contrast to previous findings. The
previous pictures for many physical phenomena for the spin-boson model in the
rotating-wave approximation have to be modified at least at the strong
coupling.",1812.03758v2
2019-02-08,Hybrid quantum systems based on magnonics,"Engineered quantum systems enabling novel capabilities for communication,
computation, and sensing have blossomed in the last decade. Architectures
benefiting from combining distinct and complementary physical quantum systems
have emerged as promising platforms for developing quantum technologies. A new
class of hybrid quantum systems based on collective spin excitations in
ferromagnetic materials has led to the diverse set of experimental platforms
which are outlined in this review article. The coherent interaction between
microwave cavity modes and collective spin-wave modes is presented as the
backbone of the development of more complex hybrid quantum systems. Indeed,
quanta of excitation of the spin-wave modes, called magnons, can also interact
coherently with optical photons, phonons, and superconducting qubits in the
fields of cavity optomagnonics, cavity magnomechanics, and quantum magnonics,
respectively. Notably, quantum magnonics provides a promising platform for
performing quantum optics experiments in magnetically-ordered solid-state
systems. Applications of hybrid quantum systems based on magnonics for quantum
information processing and quantum sensing are also outlined briefly.",1902.03024v2
2019-02-19,Spin-wave mediated interactions for Majority Computation using Skyrmions and Spin-torque Nano-oscillators,"Recent progress in all-electrical nucleation, detection and manipulation of
magnetic skyrmions has unlocked the tremendous potential of skyrmion-based
spintronic devices. Here, we show via micromagnetic simulations that the stable
magnetic oscillations of STNO radiate spin waves (SWs) that can be scattered in
the presence of skyrmions in the near vicinity. Interference between SWs
emitted by the STNO and SWs scattered by the skyrmion gives rise to interesting
dynamics that leads to amplification or attenuation of STNO's magnetic
oscillations. In the presence of strong Dzyaloshinskii-Moriya interaction
(DMI), the amplified magnetic oscillations evolve into a new skyrmion. These
interactions between skyrmions and STNOs are found to be identical for both
Neel-type and Bloch-type skyrmions, and are not observed between domain walls
and STNOs. These findings offer a novel perspective in processing information
using single skyrmions and we propose a 3-bit majority gate for logic
applications.",1902.06925v2
2019-02-21,Inspiral of a Spinning Black Hole--Magnetized Neutron Star Binary: Increasing Charge and Electromagnetic Emission,"The mergers of black hole (BH)--neutron star (NS) binaries have been one of
the most interesting topics in astrophysics, because such events have been
thought to possibly produce multimessenger signals including gravitational
waves and broadband electromagnetic (EM) waves. In this paper, we investigate
EM emission from the inspiral of a binary composed of a spinning BH and a
magnetized NS. Observationally, the BH is usually more massive than
$\sim7M_\odot$ and the NS has a mass $\simeq 1.4M_\odot$. During the inspiral
of such a binary, the BH will accumulate more and more charges based on the
charging scenario of Wald, even though the BH will eventually swallow the NS
whole inevitably. We calculate the emission luminosities and energies through
three energy dissipation mechanisms: magnetic dipole radiation, electric dipole
radiation, and magnetic reconnection. We show that magnetic dipole radiation
due to the spin of the increasingly charged BH and magnetic reconnection in
between the BH and the NS could be most significant at the final inspiral
stage. We find that if the BH is rapidly rotating and the NS is strongly
magnetized, these mechanisms would lead to a detectable EM signal (e.g., a
short-duration X-ray transient).",1902.07939v2
2020-04-23,Damping of gravitational waves in 2-2-holes,"A 2-2-hole is an explicit realization of a horizonless object that can still
very closely resemble a BH. An ordinary relativistic gas can serve as the
matter source for the 2-2-hole solution of quadratic gravity, and this leads to
a calculable area-law entropy. Here we show that it also leads to an estimate
of the damping of a gravitational wave as it travels to the center of the
2-2-hole and back out again. We identify two frequency dependent effects that
greatly diminish the damping. Spinning 2-2-hole solutions are not known, but we
are still able to consider some spin dependent effects. The frequency and spin
dependence of the damping helps to determine the possible echo resonance signal
from the rotating remnants of merger events. It also controls the fate of the
ergoregion instability.",2004.11285v3
2016-03-29,Quantum phase diagram of $J_1-J_2$ Heisenberg $S=1/2$ antiferromagnet in honeycomb lattice: a modified spin wave study,"Using modified spin wave (MSW) method, we study the $J_1-J_2$ Heisenberg
model with first and second neighbor antiferromagnetic exchange interactions.
For symmetric $S=1/2$ model, with the same couplings for all the equivalent
neighbors, we find three phase in terms of frustration parameter
${\bar\alpha=J_2/J_1}$: (1) a commensurate collinear ordering with staggered
magnetization (N{\'e}el.I state) for $0\leq{\bar\alpha}\lesssim 0.207$ , (2) a
magnetically gapped disordered state for $0.207\lesssim{\bar\alpha}\lesssim
0.369$, preserving all the symmetries of the Hamiltonian and lattice, hence by
definition is a quantum spin liquid (QSL) state and (3) a commensurate
collinear ordering in which two out of three nearest neighbor magnetizations
are antiparallel and the remaining pair are parallel (N{\'e}el.II state), for
$0.396\lesssim{\bar\alpha}\leq 1$. We also explore the phase diagram of
distorted $J_1-J_2$ model with $S=1/2$. Distortion is introduced as an
inequality of one nearest neighbor coupling with the other two. This yields a
richer phase diagram by the appearance of a new gapped QSL, a gapless QSL and
also a valence bond crystal (VBC) phase in addition to the previously three
phases found for undistorted model.",1603.08896v1
2017-02-01,$P_c(4380)$ in a constituent quark model,"The constituent quark model with color-spin hyperfine potential is used to
investigate the property of a compact pentaquark configuration with
$J^p$=$3/2^-$ and isospin=1/2, which is the most likely quantum number of one
of the recently observed exotic baryon states at LHCb. Starting from the
characterization of the isospin, color, and spin states for the pentaquark
configuration, we construct the total wave function composed of the spatial
wave function, which we take to be symmetric and in S-wave, and the four
orthogonal isospin $\otimes$ color $\otimes$ spin states that satisfy the Pauli
principle. We then use the variational method to find a compact stable
configuration. While there are compact configurations where the hyperfine
potential is more attractive than the sum of $p$ and $J/\psi$ hyperfine
potentials, we find that the ground state is the isolated $p$ and $J/\psi$
state. Furthermore, the mass of the excited state lies far above the observed
pentaquark state leading us to conclude that the observed states can not be a
compact multiquark configuration with $J^p$=$3/2^-$.",1702.00381v1
2017-02-26,Progenitors of binary black hole mergers detected by LIGO,"Possible formation mechanisms of massive close binary black holes that can
merge in the Hubble time to produce powerful gravitational wave bursts detected
during advanced LIGO O1 science run are briefly discussed. The pathways include
the evolution from field low-metallicity massive binaries, the dynamical
formation in globular clusters and primordial black holes. Low effective black
hole spins inferred for LIGO GW150914 and LTV151012 events are discussed.
Population synthesis calculations of the expected spin and chirp mass
distributions from the standard field massive binary formation channel are
presented for different metallicities (from zero-metal Population III stars up
to solar metal abundance). We conclude that that merging binary black holes can
contain systems from different formation channels, discrimination between which
can be made with increasing statistics of mass and spin measurements from
ongoing and future gravitational wave observations.",1702.08056v1
2018-04-06,Quantum-impurity relaxometry of magnetization dynamics,"Prototypes of quantum impurities (QI), such as NV and SiV centers in diamond,
have been recently growing in popularity due to their minimally invasive and
high-resolution magnetic field sensing. Here, we focus on quantum-impurity
relaxometry as a method to probe collective excitations in magnetic insulators.
We develop a general framework that relates the experimentally-measurable
quantum-impurity relaxation rates to the properties of a magnetic system via
the noise emitted by the latter. We suggest that, when the quantum-impurity
frequency lies within the spin-wave gap, quantum-impurity relaxometry can be
effectively deployed to detect signatures of the coherent spin dynamics, such
as magnon condensation, both in ferromagnetic and antiferromagnetic systems, as
well as open prospects to nonintrusively probe spin-wave transport regimes in
magnetic insulators.",1804.02417v1
2019-03-07,Unconventional Field-Induced Spin-Density-Wave Phases in Quasi-One-Dimensional Conductors in High Magnetic Fields,"It is known that the Field-Induced Spin-Density-Wave (FISDW) phases are
experimentally observed in the quasi-one-dimensional (Q1D) organic conductors
with chemical formula (TMTSF)$_2$X (X=PF$_6$, ClO$_4$, etc.) and some others in
moderate magnetic fields. From a theoretical point of view, they appear as a
result of ""one-dimensionalization"" of the Q1D electron spectra due to the
orbital electron effect in a magnetic field. We predict that the novel FISDW
phases with different physical meaning have to appear in inclined high magnetic
fields in Q1D conductors as a result of combination of the spin-splitting and
orbital electron effects. We suggest performing the corresponding experiments
in the (TMTSF)$_2$X materials.",1903.03184v1
2018-12-18,Bound State Solutions of the Dirac-Shifted Tietz-Wei Potential Plus a Generalized Ring-Shaped Potential with Spin and Pseudospin symmetry,"In this study, approximate bound state solutions of the Dirac equation with
the newly proposed shifted Tietz-Wei (sTW) potential were obtained for any
arbitrary quantum number. Using Generalized Parametric Nikiforov Methods, the
eigenenergy equations as well as the upper and lower spinors of the wave
function corresponding to spin and pseudospin symmetric solutions were obtained
by solving the radial equation. The Pekeris approximation scheme in terms of
the parameters of the shifted Tietz-Wei potential was used to deal with the
spin-orbit coupling potential term k(k+1)/r^2. The solutions obtained for the
radial and polar angular parts of the wave functions were written in terms of
the well-known Jacobi polynomial.",1903.10277v1
2019-05-04,Identification and time-resolved study of YIG spin wave modes in a MW cavity in strong coupling regime,"Recently, the hybridization of microwave-frequency cavity modes with
collective spin excitations attracted large interest for the implementation of
quantum computation protocols, which exploit the transfer of information among
these two physical systems. Here, we investigate the interaction among the
magnetization precession modes of a small YIG sphere and the MW electromagnetic
modes, resonating in a tridimensional aluminum cavity. In the strong coupling
regime, anti-crossing features were observed in correspondence of various
magnetostatic modes, which were excited in a magnetically saturated sample.
Time-resolved studies show evidence of Rabi oscillations, demonstrating
coherent exchange of energy among photons and magnons modes. To facilitate the
analysis of the standing spin-wave patterns, we propose here a new procedure,
based on the introduction of a novel functional variable. The resulting easier
identification of magnetostatic modes can be exploited to investigate, control
and compare many-levels hybrid systems in cavity- and opto-magnonics research.",1905.01522v2
2019-05-14,Single-photon-level light storage in cold atoms using the Autler-Townes splitting protocol,"Broadband spin-photon interfaces for long-lived storage of photonic quantum
states are key elements for quantum information technologies. Yet, reliable
operation of such memories in the quantum regime is challenging due to photonic
noise arising from technical and/or fundamental limitations in the
storage-and-recall processes controlled by strong electromagnetic fields. Here,
we experimentally implement a single-photon-level spin-wave memory in a
laser-cooled Rubidium gas, based on the recently proposed Autler-Townes
splitting (ATS) protocol. We demonstrate storage of 20-ns-long laser pulses,
each containing an average of 0.1 photons, for 200 ns with an efficiency of
$12.5\%$ and signal-to-noise ratio above 30. Notably, the robustness of ATS
spin-wave memory against motional dephasing allows for an all-spatial filtering
of the control-field noise, yielding an ultra-low unconditional noise
probability of $3.3\times10^{-4}$, without the complexity of spectral
filtering. These results highlight that broadband ATS memory in ultracold atoms
is a preeminent option for storing quantum light.",1905.05856v1
2019-05-17,Spin-valley density wave in moiré materials,"We introduce and study a minimum two-orbital Hubbard model on a triangular
lattice, which captures the key features of both the trilayer ABC-stacked
graphene-boron nitride heterostructure and twisted transition metal
dichalcogenides in a broad parameter range. Our model comprises first- and
second-nearest neighbor hoppings with valley-contrasting flux that accounts for
trigonal warping in the band structure. For the strong-coupling regime with one
electron per site, we derive a spin-orbital exchange Hamiltonian and find the
semiclassical ground state to be a spin-valley density wave. We show that a
relatively small second-neighbor exchange interaction is sufficient to
stabilize the ordered state against quantum fluctuations. Effects of spin- and
valley Zeeman fields as well as thermal fluctuations are also examined.",1905.07401v1
2019-05-29,Acoustic Radiation Force and Torque on Small Particles as Measures of the Canonical Momentum and Spin Densities,"We examine acoustic radiation force and torque on a small (subwavelength)
absorbing isotropic particle immersed in a monochromatic (but generally
inhomogeneous) sound-wave field. We show that by introducing the monopole and
dipole polarizabilities of the particle, the problem can be treated in a way
similar to the well-studied optical forces and torques on dipole Rayleigh
particles. We derive simple analytical expressions for the acoustic force
(including both the gradient and scattering forces) and torque. Importantly,
these expressions reveal intimate relations to the fundamental field properties
introduced recently for acoustic fields: the canonical momentum and spin
angular momentum densities. We compare our analytical results with previous
calculations and exact numerical simulations. We also consider an important
example of a particle in an evanescent acoustic wave, which exhibits the
mutually-orthogonal scattering (radiation-pressure) force, gradient force, and
torque from the transverse spin of the field.",1905.12216v2
2020-09-03,Nature of Partial Magnetic Order in the Frustrated Antiferromagnet Gd2Ti2O7,"Partially-ordered magnets are distinct from both spin liquids and
conventional ordered magnets because order and disorder coexist in the same
magnetic phase. Here, we determine the nature of partial order in the canonical
frustrated pyrochlore antiferromagnet Gd$_2$Ti$_{2}$O$_{7}$. Using
single-crystal neutron-diffraction measurements in applied magnetic field,
magnetic symmetry analysis, inelastic neutron-scattering measurements, and
spin-wave modeling, we show that its low-temperature magnetic structure
involves two propagation vectors (2-$\mathbf{k}$ structure) with suppressed
ordered magnetic moments and enhanced spin-wave fluctuations. Our experimental
results support theoretical predictions of thermal fluctuation-driven order in
Gd$_{2}$Ti$_{2}$O$_{7}$.",2009.01670v1
2020-11-10,Spin-waves in the collinear antiferromagnetic phase of Mn$_\bf{5}$Si$_\bf{3}$,"By combining two independent approaches, inelastic neutron scattering
measurements and density functional theory calculations, we study the
spin-waves in the high-temperature collinear antiferromagnetic phase (AFM2) of
Mn$_5$Si$_3$. We obtain its magnetic ground-state properties and electronic
structure. This study allowed us to determine the dominant magnetic exchange
interactions and magnetocrystalline anisotropy in the AFM2 phase of
Mn$_5$Si$_3$. Moreover, the evolution of the spin excitation spectrum is
investigated under the influence of an external magnetic field perpendicular to
the anisotropy easy-axis. The low energy magnon modes show a different magnetic
field dependence which is a direct consequence of their different precessional
nature. Finally, possible effects related to the Dzyaloshinskii-Moriya
interaction are also considered.",2011.05455v3
2021-02-08,Variation after projection calculations for high-spin states,"In this paper, an improvement has been made on the variation after projection
(VAP) method, which is crucial in the calculations of high-spin states. It
turns out that, the form of the trial VAP wave function with spin $J$ can be
simplified by adopting just one projected state rather than previously adopting
all $(2J+1)$ angular momentum projected states for each selected reference
state, $|\Phi\rangle$. The present calculations show that such simplification
still minimizes the angular momentum projected energy up to a very good
approximation. In this simplified VAP scheme, one can obtain almost equivalent
VAP wave functions starting from different sets of the projected basis states.
This clearly shows that a nuclear state can not be identified with a single
intrinsic state, while in the traditional nuclear collective models, an
intrinsic state is usually assigned to a well deformed rotational band.",2102.04044v2
2021-02-16,Locallized Magnetism in Low-Dimensional Systems,"The current theoretical and experimental situation is reviewed for
low-dimensional (layered and chain-like) insulating systems. Such systems
possess a low magnetic transition temperature $T_M$ and pronounced short-range
magnetic order above this temperature. Both the standard and self-consistent
spin-wave theories are shown to be insufficient to quantitatively describe the
experimental data on these systems. Field-theoretical approaches taking into
account the contribution of the spin-fluctuation excitations (neglected in the
spin-wave theories) to the thermodynamic properties of ferro- and
antiferromagnets are discussed. Analytical expressions for $T_M$ and
temperature dependences of long-range order paramenters are obtained, which are
in a fair agreement with experimental data.",2102.08130v1
2021-10-21,Massless Dirac magnons in the two dimensional van der Waals honeycomb magnet CrCl3,"Two dimensional van der Waals ferromagnets with honeycomb structures are
expected to host the bosonic version of Dirac particles in their magnon
excitation spectra. Using inelastic neutron scattering, we study spin wave
excitations in polycrystalline CrCl$_3$, which exhibits ferromagnetic honeycomb
layers with antiferromagnetic stackings along the $c$-axis. For comparison,
polycrystal samples of CrI$_3$ with different grain sizes are also studied. We
find that the powder-averaged spin wave spectrum of CrCl$_3$ at $T$ = 2 K can
be adequately explained by the two dimensional spin Hamiltonian including
in-plane Heisenberg exchanges only. The observed excitation does not exhibit
noticeable broadening in energy, which is in remarkable contrast to the
substantial broadening observed in CrI$_3$. Based on these results, we conclude
that the ferromagnetic phase of CrCl$_3$ hosts massless Dirac magnons and is
thus not topological.",2110.10894v1
2021-10-22,$π$-Phase shift across stripes in a charge density wave system,"Many strongly correlated materials are characterized by deeply intertwined
charge and spin order. Besides their high superconducting transition
temperatures, one of the central features of these complex patterns in cuprates
is a phase shift which occurs across lines of decreased hole density. That is,
when doped away from their AF phase, the additional charge is not distributed
uniformly, but rather in `stripes'. The sublattices preferentially occupied by
up and down spin are reversed across these stripes, a phenomonenon referred to
as a `$\pi$-phase shift'. Many of the spin-charge patterns, including the
$\pi$-phase shift, are reproduced by Density Matrix Renormalization Group and
Quantum Monte Carlo calculations of simplified tight binding (repulsive
Hubbard) models. In this paper we demonstrate that this sublattice reversal is
generic by considering the corresponding phenomenon in the attractive Hubbard
Hamiltonian, where a charge density wave phase forms at half-filling. We
introduce charge stripes via an appropriate local chemical potential;
measurements of charge correlation across the resulting lines of lowered
density reveal a clear $\pi$ phase.",2110.11639v2
2016-11-21,Coherence and stiffness of spin waves in diluted ferromagnets,"We present results of a numerical analysis of magnon spectra in supercells
simulating two-dimensional and bulk random diluted ferromagnets with
long-ranged pair exchange interactions. We show that low-energy spectral
regions for these strongly disordered systems contain a coherent component
leading to interference phenomena manifested by a pronounced sensitivity of the
lowest excitation energies to the adopted boundary conditions. The dependence
of configuration averages of these excitation energies on the supercell size
can be used for an efficient determination of the spin-wave stiffness D. The
developed formalism is applied to the ferromagnetic Mn-doped GaAs semiconductor
with optional incorporation of phosphorus; the obtained concentration trends of
D are found in reasonable agreement with recent experiments. Moreover, a
relation of the spin stiffness to the Curie temperature Tc has been studied for
Mn-doped GaAs and GaN semiconductors. It is found that the ratio Tc/D exhibits
qualitatively the same dependence on Mn concentration in both systems.",1611.06691v1
2017-01-03,First-principles modeling of the Invar effect in Fe65Ni35 by the spin-wave method,"Thermal lattice expansion of the Invar Fe65Ni35 alloy is investigated in
first-principles calculations using the spin-wave method, which is generalized
here for the ferromagnetic state with short range order. It is shown that
magnetic short-range order effects make substantial contribution to the
equilibrium lattice constant and cannot be neglected in the accurate ab initio
modeling of the thermal expansion in Fe-Ni alloys. We also demonstrate that at
high temperatures, close and above the magnetic transition, magnetic entropy
associated with transverse and longitudinal spin fluctuations yields a
noticeable contribution to the equilibrium lattice constant. The obtained
theoretical results for the temperature dependent lattice constant are in
semiquantitative agreement with the experimental data apart from the region
close the magnetic transition.",1701.00618v5
2017-03-02,Competing magnetic orders in the superconducting state of Nd-doped CeRhIn$_{5}$ under pressure,"Applied pressure drives the heavy-fermion antiferromagnet CeRhIn$_{5}$
towards a quantum critical point that becomes hidden by a dome of
unconventional superconductivity. Magnetic fields suppress this superconducting
dome, unveiling the quantum phase transition of local character. Here, we show
that $5\%$ magnetic substitution at the Ce site in CeRhIn$_{5}$, either by Nd
or Gd, induces a zero-field magnetic instability inside the superconducting
state. This magnetic state not only should have a different ordering vector
than the high-field local-moment magnetic state, but it also competes with the
latter, suggesting that a spin-density-wave phase is stabilized in zero field
by Nd and Gd impurities - similarly to the case of
Ce$_{0.95}$Nd$_{0.05}$CoIn$_{5}$. Supported by model calculations, we attribute
this spin-density wave instability to a magnetic-impurity driven condensation
of the spin excitons that form inside the unconventional superconducting state.",1703.00562v1
2017-03-27,Anisotropic exchange and spin-wave damping in pure and electron-doped Sr$_2$IrO$_4$,"The collective magnetic excitations in the spin-orbit Mott insulator
(Sr$_{1-x}$La$_x$)$_2$IrO$_4$ ($x=0,\,0.01,\,0.04,\, 0.1$) were investigated by
means of resonant inelastic x-ray scattering. We report significant magnon
energy gaps at both the crystallographic and antiferromagnetic zone centers at
all doping levels, along with a remarkably pronounced momentum-dependent
lifetime broadening. The spin-wave gap is accounted for by a significant
anisotropy in the interactions between $J_\text{eff}=1/2$ isospins, thus
marking the departure of Sr$_2$IrO$_4$ from the essentially isotropic
Heisenberg model appropriate for the superconducting cuprates.",1703.09051v4
2017-04-17,Solution of the $κ$-deformed Dirac equation with vector and scalar interactions in the context of spin and pseudospin symmetries,"The deformed Dirac equation invariant under the $\kappa$-Poincar\'{e}-Hopf
quantum algebra in the context of minimal and scalar couplings under spin and
pseudospin symmetries limits is considered. The $\kappa$-deformed Pauli-Dirac
Hamiltonian allows us to study effects of quantum deformation in a class of
physical systems, such as an Zeeman-like effect, Aharonov-Bohm effect and an
anomalous-like contribution to the electron magnetic moment, between others. In
our analysis, we consider the motion of an electron in a uniform magnetic field
and interacting with (i) a planar harmonic oscillator and (ii) a linear
potential. We verify that the particular choice of a linear potential induces a
Coulomb-type term in the equation of motion. Expressions for the energy
eigenvalues and wave functions are determined taking into account both
symmetries limits. We verify that the energies and wave functions of the
particle are modified by the deformation parameter as well as by the element of
spin.",1704.04847v2
2018-12-31,Developing Tools for Multimessenger Gravitational Wave Astronomy,"We present work in progress to craft open-sourced numerical tools that will
enable the calculation of electromagnetic counterparts to gravitational
waveforms: the {\tt GiRaFFE} (General Relativistic Force-Free Electrodynamics)
code. {\tt GiRaFFE} numerically solves the general relativistic
magnetohydrodynamics system of equations in the force-free limit, to model the
magnetospheres surrounding compact binaries, in order (1) to characterize the
nonlinear interaction between the source and its surrounding magnetosphere, and
(2) to evaluate the electromagnetic counterparts of gravitational waves,
including the production of collimated jets. We apply this code to various
configurations of spinning black holes immersed in external magnetic field, in
order to both test our implementation, and to explore the effect of strong
gravitational field, high spins and of misalignment between the magnetic field
lines an black hole spin, on the electromagnetic output and the collimation of
Poynting jets.
  We will extend our work to collisions of black holes immersed in external
magnetic field, which are prime candidates for coincident detection in both
gravitational and electromagnetic spectra.",1901.00025v2
2019-01-22,Magnetic stripe soliton and localized stripe wave in spin-1 Bose-Einstein condensates,"The recent experimental realization of spin-orbit coupling for ultracold
atomic gases opens a new avenue for engineering solitons with internal spatial
structures through tuning atomic band dispersions. However, the types of the
resulting stripe solitons in a spin-1/2 Bose-Einstein condensate (BEC) have
been limited to dark-dark or bright-bright with the same density profiles for
different spins. Here we propose that general types of stripe solitons,
including magnetic stripe (e.g., dark-bright) and localized stripe waves
(neither bright nor dark), could be realized in a spin-1 BEC with widely
tunable band dispersions through modulating the coupling between three spin
states and the linear momentum of atoms. \ Surprisingly, a moving magnetic
stripe soliton can possess both negative and positive effective masses at
different velocities, leading to a zero mass soliton at certain velocity. Our
work showcases the great potential of realizing novel types of solitons through
band dispersion engineering, which may provide a new approach for exploring
soliton physics in many physical branches.",1901.07631v2
2019-07-04,Resonant Acoustic Wave Assisted Spin-Transfer-Torque Switching of Nanomagnets,"We report the possibility of achieving an order of magnitude reduction in the
energy dissipation needed to write bits in perpendicular magnetic tunnel
junctions (p-MTJs) by simulating the magnetization dynamics under a combination
of resonant surface acoustic waves (r-SAW) and spin-transfer-torque (STT). The
magnetization dynamics were simulated using the Landau-Lifshitz-Gilbert
equation under macrospin assumption with the inclusion of thermal noise. The
resonant magnetization dynamics in the magnetostrictive nanomagnet build over
few 10s of cycles of SAW application that drives the magnetization to precess
in a cone with a deflection of ~45 degrees from the perpendicular direction.
This reduces the STT current density required to switch the magnetization
direction without increasing the STT application time or degrading the
switching probability in the presence of room temperature thermal noise. This
could lead to a pathway to achieve energy efficient switching of spin transfer
torque random access memory (STTRAM) whose lateral dimensions can be scaled
aggressively despite using materials with low magnetostriction by employing
resonant excitation.",1907.02255v1
2019-07-24,Observation of Two Sound Modes in a Binary Superfluid Gas,"We study the propagation of sound waves in a binary superfluid gas with two
symmetric components. The binary superfluid is constituted using a
Bose-Einstein condensate of $^{23}$Na in an equal mixture of two hyperfine
ground states. Sound waves are excited in the condensate by applying a local
spin-dependent perturbation with a focused laser beam. We identify two distinct
sound modes, referred to as density sound and spin sound, where the densities
of the two spin components oscillate in phase and out of phase, respectively.
The observed sound propagation is explained well by the two-fluid hydrodynamics
of the binary superfluid. The ratio of the two sound velocities is precisely
measured with no need for absolute density calibration, and we find it in
quantitatively good agreement with known interaction properties of the binary
system.",1907.10289v1
2019-09-06,Gravitational-wave-driven tidal secular instability in neutron star binaries,"We report the existence of a gravitational-wave-driven secular instability in
neutron star binaries, acting on the equilibrium tide. The instability is
similar to the classic Chandrasekhar-Friedman-Schutz (CFS) instability of
normal modes and is active when the spin of the primary star exceeds the
orbital frequency of the companion. Modeling the neutron star as a Newtonian
n=1 polytrope, we calculate the instability time scale, which can be as low as
a few seconds at small orbital separations but still larger than the inspiral
time scale. The implications for orbital and spin evolution are also briefly
explored, where it is found that the instability slows down the inspiral and
decreases the stellar spin.",1909.04490v1
2019-10-03,Neutrino oscillations in gravitational waves,"We study spin and flavor oscillations of neutrinos under the influence of
gravitational waves (GWs). We rederive the quasiclassical equation for the
evolution of the neutrino spin in various external fields in curved spacetime
starting from the Dirac equation for a massive neutrino. Then, we consider
neutrino spin oscillations in nonmoving and unpolarized matter, a transverse
magnetic field, and a plane GW. We show that a parametric resonance can take
place in this system. We also study neutrino flavor oscillations in GWs. The
equation for the density matrix of flavor neutrinos is solved when we discuss
the neutrino interaction with stochastic GWs emitted by coalescing supermassive
black holes. We find the fluxes of cosmic neutrinos, undergoing flavor
oscillations in such a gravitational background, which can be potentially
measured by a terrestrial detector. Some astrophysical applications of our
results are considered.",1910.01415v1
2020-05-15,Multiple magnon modes in spin-1/2 Heisenberg antiferromagnet on simple square lattice in strong magnetic field,"We discuss spin-$\frac12$ Heisenberg antiferromagnet on simple square lattice
in magnetic field $H$ using recently proposed bond-operator technique. It is
well known that magnetically ordered phases of quantum magnets are well
described at least qualitatively by the conventional spin-wave theory that only
introduces quantum corrections into the classical solution of the problem. We
observe that quantum fluctuations change drastically dynamical properties of
the considered model at $H$ close to its saturation value: the dynamical
structure factor shows anomalies corresponding to Green's function poles which
have no counterparts in the spin-wave theory. That is, quantum fluctuations
produce multiple short-wavelength magnon modes not changing qualitatively the
long-wavelength spin dynamics. Our results are in agreement with previous
quantum Monte-Carlo simulations and exact diagonalization of finite clusters.",2005.07537v3
2020-06-11,Light-wave Control of Non-equilibrium Correlated States using Quantum Femtosecond Magnetism and Time-Periodic Modulation of Coherent Transport,"Lightwave quantum electronics utilizes the oscillating carrier wave of
intense laser fields to control quantum materials properties. Using quantum
kinetic equations of motion, we describe lightwave-driven nonlinear quantum
transport of electronic spin and charge with simultaneous quantum fluctuations
of non-collinear local spins. During cycles of field oscillations, spin-charge
inter-atomic quantum excitations trigger non-adiabatic time evolution of an
antiferromagnetic insulator state into a metallic non-equilibrium state with
transient magnetization. Lightwave modulation of electronic hopping changes the
energy landscape and establishes a non-thermal pathway to laser-induced
transitions in correlated systems with strong local magnetic exchange
interactions.",2006.06718v1
2020-07-03,Interplay of spin waves and vortices in the 2D XY model at small vortex-core energy,"The Berezinskii-Kosterlitz-Thouless (BKT) mechanism describes universal
vortex unbinding in many two-dimensional systems, including the paradigmatic XY
model. However, most of these systems present a complex interplay between
excitations at different length scales that complicates theoretical
calculations of nonuniversal thermodynamic quantities. These difficulties may
be overcome by suitably modifying the initial conditions of the BKT flow
equations to account for noncritical fluctuations at small length scales. In
this work, we perform a systematic study of the validity and limits of this
two-step approach by constructing optimised initial conditions for the BKT
flow. We find that the two-step approach can accurately reproduce the results
of Monte-Carlo simulations of the traditional XY model. In order to
systematically study the interplay between vortices and spin-wave excitations,
we introduce a modified XY model with increased vortex fugacity. We present
large-scale Monte-Carlo simulations of the spin stiffness and vortex density
for this modified XY model and show that even at large vortex fugacity, vortex
unbinding is accurately described by the nonperturbative functional
renormalisation group.",2007.01526v2
2020-07-08,Analytic Property of Vortex-Type Spin Structures in Itinerant Electron System with Inversion Symmetry,"Analytic properties of the multiple spin density waves showing vortex
structures, which have recently been found in the fcc Hubbard model using the
generalized Hartree-Fock (GHF) approximation, have been investigated. It is
shown that the 2Q multiple helical spin density waves (SDW) consist of two
types of half-skyrmion vortices and two types of antivortices. In the 3Q
multiple helical SDW, the half-skyrmion vortex structures with the ""westerlies""
are shown to be twisted along the axis perpendicular to the vortex plane. The
12Q multiple SDW (12QMSDW) are analyzed as a superposition of the 2-4QMSDW on
the (001) plane and the remaining 4QMSDW. It is shown analytically that the
2-4QMSDW forms the planar vortices and antivortices with zero core
polarization, so that the 12QMSDW forms the same types of vortices with
additional SDW polarization in the [001] direction. These results are in good
agreement with the visualization image data based on the GHF calculations.",2007.03863v1
2020-09-30,Gravitational wave peak luminosity model for precessing binary black holes,"When two black holes merge, a tremendous amount of energy is released in the
form of gravitational radiation in a short span of time, making such events
among the most luminous phenomenon in the universe. Models that predict the
peak luminosity of black hole mergers are of interest to the gravitational wave
community, with potential applications in tests of general relativity. We
present a surrogate model for the peak luminosity that is directly trained on
numerical relativity simulations of precessing binary black holes. Using
Gaussian process regression, we interpolate the peak luminosity in the
7-dimensional parameter space of precessing binaries with mass ratios $q\leq4$,
and spin magnitudes $\chi_1,\chi_2\leq0.8$. We demonstrate that our errors in
estimating the peak luminosity are lower than those of existing fitting
formulae by about an order of magnitude. In addition, we construct a model for
the peak luminosity of aligned-spin binaries with mass ratios $q\leq8$, and
spin magnitudes $|\chi_{1z}|,|\chi_{2z}|\leq0.8$. We apply our precessing model
to infer the peak luminosity of the GW event GW190521, and find the results to
be consistent with previous predictions.",2010.00120v2
2020-10-22,Effects of optical lattices on bright solitons in spin-orbit coupled Bose-Einstein condensates,"The stationary bright solitons that appear in the ground state of the
spin-orbit coupled Bose-Einstein condensate (SOC-BEC) exhibit nodes. We
consider SOC-BEC in combined linear and nonlinear optical lattices and study
their effects on the matter-wave bright soliton and find that the parameters of
the nonlinear lattice or atomic scattering length can be judiciously
manipulated to have useful control over the nodes of the soliton. It is seen
that the soliton with large number of nodes is less stable compared to one
having fewer number of nodes. We infer that that the synthetic spin-orbit
coupling induces instability in the ordinary matter-wave soliton.",2010.11888v2
2020-12-14,Non-collinear ground state from a four-spin chiral exchange in a tetrahedral magnet,"We propose a quartic chiral term $m_x m_y m_z \nabla \cdot \mathbf{m}$ for
the energy density of a cubic ferromagnet with broken parity symmetry (point
group $T_d$). We demonstrate that this interaction causes a phase transition
from a collinear ferromagnetic state to a non-collinear magnetic cone ground
state provided its strength exceeds the geometric mean of magnetic exchange and
cubic anisotropy. The corresponding non-collinear ground state may also be
additionally stabilized by an external magnetic field pointing along certain
crystallographic directions. The four-spin chiral exchange does also manifest
itself in peculiar magnon spectra and favors spin waves with the wave vector
that is perpendicular to the average magnetization direction.",2012.07666v1
2020-12-29,Skyrmions as quasiparticles: free energy and entropy,"The free energy and the entropy of magnetic skyrmions with respect to the
collinear state are calculated for a (Pt$_{0.95}$Ir$_{0.05}$)/Fe bilayer on
Pd(111) via atomistic spin model simulations. The simulations are carried out
starting from very low temperatures where the skyrmion number is conserved up
to the range where skyrmions are constantly created and destroyed by thermal
fluctuations, highlighting their quasiparticle nature. The higher entropy of
the skyrmions at low temperature leads to a reduced free energy, such that the
skyrmions become energetically preferred over the collinear state due to
entropic stabilization as predicted by linear spin-wave theory. Going beyond
the linear spin-wave approximation, a sign change is shown to occur in the free
energy as well as the entropy at elevated temperature.",2012.14688v2
2021-01-29,Parameter estimation of a two-component neutron star model with spin wandering,"It is an open challenge to estimate systematically the physical parameters of
neutron star interiors from pulsar timing data while separating spin wandering
intrinsic to the pulsar (achromatic timing noise) from measurement noise and
chromatic timing noise (due to propagation effects). In this paper we formulate
the classic two-component, crust-superfluid model of neutron star interiors as
a noise-driven, linear dynamical system and use a state-space-based
expectation-maximization method to estimate the system parameters using
gravitational-wave and electromagnetic timing data. Monte Carlo simulations
show that we can accurately estimate all six parameters of the two-component
model provided that electromagnetic measurements of the crust angular velocity,
and gravitational-wave measurements of the core angular velocity, are both
available. When only electromagnetic data are available we can recover the
overall relaxation time-scale, the ensemble-averaged spin-down rate, and the
strength of the white-noise torque on the crust. However, the estimates of the
secular torques on the two components and white noise torque on the superfluid
are biased significantly.",2101.12421v1
2021-03-08,"Characterising a tunable, pulsed atomic beam using matter-wave interferometry","We describe the creation and characterisation of a velocity tunable,
spin-polarized beam of slow metastable argon atoms. We show that beam velocity
can be determined with a precision below 1 \% using matter-wave interferometry.
The profile of the interference pattern was also used to determine the velocity
spread of the beam, as well as Van der Waals co-efficient for the interaction
between the metastable atoms and the multi-slit silicon nitride grating. The
Van der Waals co-efficient was determined to be $C_3$=1.84$\pm$0.17\,a.u., in
good agreement with values derived from spectroscopic data. Finally, the spin
polarization of the beam produced during acceleration of the beam was also
measured, demonstrating a spatially uniform spin polarization of 96 \% in the
m=+2 state.",2103.04756v1
2021-03-15,Photon echo from lensing of fractional excitations in Tomonaga-Luttinger spin liquid,"We study theoretically the nonlinear optical response of Tomonaga-Luttinger
spin liquid in the context of terahertz (THz) two-dimensional coherent
spectroscopy (2DCS). Using the gapless phase of the XXZ-type spin chain as an
example, we show that its third-order nonlinear magnetic susceptibilities
$\chi^{(3)}_{+--+}$ and $\chi^{(3)}_{-++-}$ exhibit photon echo, where $\pm$
refers to the left/right-hand circular polarization with respect to the $S^z$
axis. The photon echo arises from a ``lensing'' phenomenon in which the wave
packets of fractional excitations move apart and then come back toward each
other, amounting to a refocusing of the excitations' world lines.
Renormalization group irrelevant corrections to the fixed point Hamiltonian
result in dispersion and/or damping of the wave packets, which can be
sensitively detected by lensing and consequently the photon echo. Our results
thus unveil the strength of THz-2DCS in probing the dynamical properties of the
collective excitations in a prototypical gapless many-body system.",2103.08122v2
2021-03-15,Loop Quantum Gravity's Boundary Maps,"In canonical quantum gravity, the presence of spatial boundaries naturally
leads to a boundary quantum states, representing quantum boundary conditions
for the bulk fields. As a consequence, quantum states of the bulk geometry
needs to be upgraded to wave-functions valued in the boundary Hilbert space:
the bulk become quantum operator acting on boundary states. We apply this to
loop quantum gravity and describe spin networks with 2d boundary as
wave-functions mapping bulk holonomies to spin states on the boundary. This
sets the bulk-boundary relation in a clear mathematical framework, which allows
to define the boundary density matrix induced by a bulk spin network states
after tracing out the bulk degrees of freedom. We ask the question of the bulk
reconstruction and prove a boundary-to-bulk universal reconstruction procedure,
to be understood as a purification of the mixed boundary state into a pure bulk
state. We further perform a first investigation in the algebraic structure of
induced boundary density matrices and show how correlations between bulk
excitations, i.e. quanta of 3d geometry, get reflected into the boundary
density matrix.",2103.08409v1
2021-03-19,Millisecond Magnetars,"Two classes of X-ray/$\gamma$-ray sources, the Soft Gamma Repeaters and the
Anomalous X-ray Pulsars have been identified with isolated, slowly spinning
magnetars, neutron stars whose emission draws energy from their extremely
strong magnetic field ($\sim 10^{15}-10^{16}$ G). Magnetars are believed to
form with millisecond spin period and to represent an important fraction of the
whole population of young neutron stars. Newborn magnetars can convert very
quickly their rotational energy into electromagnetic and/or gravitational
waves, by virtue of their strong magnetic fields and fast spins. This chapter
provides a brief summary of astrophysical problems and scenarios in which
millisecond magnetars are believed to play a key role: these include Gamma Ray
Bursts, Supernovae, Gravitational Wave events and Fast Radio Bursts.",2103.10878v1
2021-05-04,Non-local magnon transport in a magnetic domain wall wave guide,"Magnetic domain walls function as a wave guide for low energy magnons. In
this paper we develop the theory for the non-local transport of these bound
magnons through a ferromagnetic insulator that are injected and detected
electrically in adjacent normal metal leads by spin-flip scatting processes and
the (inverse) spin-Hall effect. Our set-up requires a twofold degeneracy of the
magnetic ground state, which we realize by an easy axis and hard axis
anisotropy, in the ferromagnetic insulator. This is readily provided by a broad
range of materials. The domain wall is a a topologically protected feature of
the system and we obtain the non-local spin transport through it. Thereby we
provide a framework for reconfigureable magnonic devices.",2105.01694v1
2021-05-26,Examination of orbital evolution and gravitational waves of OJ 287 in the 4PN order,"We computed the orbital evolution and the emitted gravitational radiation of
the supermassive black hole binary OJ 287. Here we used the initial data
provided by the outburst structure of the system. We considered the spin-spin,
spin-orbit, and the next-to-next leading order fourth post-Newtonian (4PN)
corrections in our analysis. In this way, we could make an accurate examination
of unstable orbits ($3M < r <6M$) of the secondary black hole. We tested the
4PN terms by analyzing the total and radiated energy, compared the
post-Newtonian parameters and the separation of the two black holes for 3PN and
4PN. In conclusion, the 4PN corrections provided a significantly more accurate
tool for analyzing unstable orbits than earlier 3PN terms. Furthermore, in this
paper, we show the gravitational waves emitted by OJ 287 during its complete
orbital evolution including unstable orbits.",2105.12496v2
2021-06-15,Frustrated mixed-spin ladders: Evidence for a bond order wave phase between rung-singlet and Haldane phases,"In frustrated spin ladders the interplay of frustration and correlations
leads to the familiar Haldane (H) and rung-singlet (RS) phases. The nature of
the transition between these two phases is still under debate. In this paper we
tackle this issue using tools of quantum information theory. We consider
frustrated mixed-spin-(1, 1/2) ladders with antiferromagnetic leg, rung and
diagonal couplings, and calculate various quantities, such as the entanglement
entropy (EE), the Schmidt gap, and the level degeneracy of the entanglement
spectrum (ES). We use two numerical techniques, the infinite time-evolving
block decimation (iTEBD) and the density matrix renormalization group (DMRG).
We demonstrate that there exists an intermediate phase in which the ES levels
do not exhibit the characteristic degeneracies of the H and RS phases. To
understand the underlying physics in this phase, we investigate short-range
spin correlations along legs, rungs and diagonals and show that in this
intermediate phase long-wavelength modulations occur, akin to bond order waves.",2106.07940v2
2021-06-23,Dancing Synchronization in Coupled Spin-Torque Nano-Oscillators,"We are reporting a new type of synchronization, termed dancing
synchronization, between two spin-torque nano-oscillators (STNOs) coupled
through spin waves. Different from the known synchronizations in which two
STNOs are locked with various fixed relative phases, in this new synchronized
state two STNOs have the same frequency, but their relative phase varies
periodically within the common period, resulting in a dynamic waving pattern.
The amplitude of the oscillating relative phase depends on the coupling
strength of two STNOs, as well as the driven currents. The dancing
synchronization turns out to be universal, and can exist in two nonlinear Van
der Pol oscillators coupled both reactively and dissipativly. Our findings open
doors for new functional STNO-based devices.",2106.12197v1
2021-07-29,Exact closed-form analytic wave functions in two dimensions: Contact-interacting fermionic spinful ultracold atoms in a rapidly rotating trap,"Exact two-dimensional analytic wave functions for an arbitrary number $N$ of
contact-interacting lowest-Landau-level (LLL) spinful fermions are derived with
the use of combined numerical and symbolic computational approaches via
analysis of exact Hamiltonian numerical diagonalization data. Closed-form
analytic expressions are presented for two families of zero-interaction-energy
states at given total angular momentum and total spin $0 \leq S \leq N/2$ in
the neighborhood of the $\nu=1$ filling, covering the range from the maximum
density droplet to the first quasihole. Our theoretical predictions for
higher-order spatial and momentum correlations reveal intrinsic polygonal,
multi-ring crystalline-type structures, which can be tested with ultracold-atom
experiments in rapidly rotating traps, simulating quantum Hall physics
(including quantum LLL skyrmions).",2107.14098v1
2021-09-30,Interaction of magnons with plasmons in a system of antiferromagnetic insulators coupled to a superconductor microwave cavity through the interfacial exchange interaction,"A superconductor can interact with magnets through the magnetic field which
is induced by the supercurrent. However, this interaction is rather weak and
requires relatively large magnets to reach a sizable hybridization of microwave
electromagnetic modes with magnons. The size of the device can be drastically
reduced by means of the large interfacial exchange interaction between spins in
a magnet and a superconductor. In the spin-orbit coupled superconductor this
interaction can be transmitted to the s-wave condensate through a mixing of
triplet and singlet Cooper pairs. In this paper we theoretically consider thin
antiferromagnetic films, which make a spin compensated contact to a
superconducting wire, which forms a cavity for Mooij-Sch\""{o}n plasma waves.
The effective Lagrangian is derived where the interaction of these waves with
magnons is taken into account. Frequencies of hybrid magnon-plasmon modes are
calculated. A system of two micromagnets placed far apart are also considered
and their mutual coupling through the cavity mode is calculated.",2109.14973v1
2022-01-18,Spin-polarizing electron beam splitter from crossed graphene nanoribbons,"Junctions composed of two crossed graphene nanoribbons (GNRs) have been
theoretically proposed as electron beam splitters where incoming electron waves
in one GNR can be split coherently into propagating waves in \emph{two}
outgoing terminals with nearly equal amplitude and zero back-scattering. Here
we scrutinize this effect for devices composed of narrow zigzag GNRs taking
explicitly into account the role of Coulomb repulsion that leads to
spin-polarized edge states within mean-field theory. We show that the
beam-splitting effect survives the opening of the well-known correlation gap
and, more strikingly, that a \emph{spin-dependent} scattering potential emerges
which spin-polarizes the transmitted electrons in the two outputs. A
near-perfect polarization can be achieved by joining several junctions in
series. Our findings suggest that GNRs are interesting building blocks in
spintronics and quantum technologies with applications for interferometry and
entanglement.",2201.07147v2
2022-01-24,Hund's coupling and electronic anisotropy in the spin-density wave state of iron pnictides,"In the multiband systems, Hund's coupling ($J$) plays a significant role in
the spin and charge excitations. We study the dependence of electronic
anisotropy on $J$ in terms of Drude-weight along different directions as well
as the orbital order in the four-fold symmetry broken spin-density wave state
of iron pnictides. A robust behavior of the Drude-weight anisotropy within a
small window around $J \sim 0.25U$ with $U$ as intraorbital Coulomb interaction
is described in terms of orbital-weight distribution along the reconstructed
Fermi surfaces. We also find that the ferro-orbital order increases with $J$ in
the widely accepted regime for the latter, which is explained as a consequence
of rising exchange field with an increase in magnetization.",2201.09808v1
2022-02-08,Breakdown of Linear Spin-wave Theory and Existence of Spinon Bound States in the Frustrated Kagome Lattice Antiferromagnet,"Spin dynamics of the spin-1/2 kagome lattice antiferromagnet
Cs$_2$Cu$_3$SnF$_{12}$ was studied using high-resolution, time-of-flight
inelastic neutron scattering. The flat mode, a characteristic of the frustrated
kagome antiferromagnet, and the low-energy dispersive mode, which is dominated
by magnons, can be well described by the linear spin-wave theory. However, the
theory fails to describe three weakly dispersive modes between 9 and 14 meV.
These modes could be attributed to two-spinon bound states, which decay into
free spinons away from the zone center and at a high temperature, giving rise
to continuum scattering.",2202.03681v1
2022-03-18,"Interplay of charge density waves, disorder, and superconductivity in 2$H$-TaSe$_2$ elucidated by NMR","Single crystals of pristine and 6% Pd-intercalated 2H-TaSe$_2$ have been
studied by means of $^{77}$Se nuclear magnetic resonance (NMR). The temperature
dependence of the $^{77}$Se spectrum, with an unexpected line narrowing upon Pd
intercalation, unravels the presence of correlated local lattice distortions
far above the transition temperature of the charge density wave (CDW) order,
thereby supporting a strong-coupling CDW mechanism in 2H-TaSe$_2$. While, the
Knight shift data suggest that the incommensurate CDW transition involves a
partial Fermi surface gap opening. As for spin dynamics, the $^{77}$Se
spin-lattice relaxation rate $T_1^{-1}$ as a function of temperature shows that
a pseudogap behavior dominates the low-energy spin excitations even within the
CDW phase, and gets stronger along with superconductivity in the Pd-6% sample.
We discuss that CDW fluctuations may be responsible for the pseudogap as well
as superconductivity, although the two phenomena are unlikely to be directly
linked each other.",2203.09662v1
2022-04-07,Domain wall formation and magnon localization in twisted chromium trihalides,"The rise of twistronics has revolutionized the field of condensed matter
physics, and more specifically the future applications of two-dimensional
materials. At small twist angles, the microscopic world becomes strongly
correlated, and unexpected physical phenomena such as superconductivity emerge.
For magnetic layers, stacking plays a crucial role in the magnetic exchange
coupling between the layers leading to non-trivial spin configurations and flat
spin-wave dispersion when twisted. In this work, we give a short overview of
the most recent theoretical and experimental works reporting the effect of
twist angles on two-dimensional magnets. Besides, we discuss the effect of the
twist angle and the local antiferromagnetic interlayer exchange coupling on the
formation of antiferromagnetic domains in chromium trihalides. Finally, we show
some preliminary results on the effect of the stacking and the twist angle on
the spin-wave dispersion of bilayer CrI$_3$",2204.03244v1
2022-04-21,Effect of Wigner rotation on estimating unitary-shift parameter of relativistic spin-1/2 particle,"We obtain the accuracy limit for estimating the expectation value of the
position of a relativistic particle for an observer moving along one direction
at a constant velocity. We use a specific model of a relativistic spin-1/2
particle described by a gaussian wave function with a spin down in the rest
frame. To derive the state vector of the particle for the moving observer, we
use the Wigner rotation that entangles the spin and the momentum of the
particle. Based on this wave function for the moving frame, we obtain the
symmetric logarithmic derivative (SLD) Cramer-Rao bound that sets the
estimation accuracy limit for an arbitrary moving observer. It is shown that
estimation accuracy decreases monotonically in the velocity of the observer
when the moving observer does not measure the spin degree of freedom. This
implies that the estimation accuracy limit worsens with increasing the
observer's velocity, but it is finite even in the relativistic limit. We derive
the amount of this information loss by the exact calculation of the SLD Fisher
information matrix in an arbitrary moving frame.",2204.10395v2
2022-04-24,Generating Two-dimensional Ferromagnetic Charge Density Waves via External Fields,"Two-dimensional (2D) ferromagnetic charge density wave (CDW), an exotic
quantum state for exploring the intertwining effect between correlated charge
and spin orders in 2D limit, has not been discovered in the experiments yet.
Here, we propose a feasible strategy to realize 2D ferromagnetic CDWs under
external fields, which is demonstrated in monolayer VSe$_2$ using
first-principles calculations. Under external tensile strain, two novel
ferromagnetic CDWs ($\sqrt{3}$$\times$$\sqrt{3}$ and 2$\times2\sqrt{3}$ CDWs)
can be generated, accompanied by distinguishable lattice reconstructions of
magnetic V atoms. Remarkably, because the driving forces for generating these
two ferromagnetic CDWs are strongly spin-dependent, fundamentally different
from that in conventional CDWs, the $\sqrt{3}$$\times$$\sqrt{3}$ and
2$\times2\sqrt{3}$ CDWs can exhibit two dramatically different half-metallic
phases under a large strain range, along with either a flat band or a Dirac
cone around Fermi level. Our proposed strategy and material demonstration may
open a door to generate and manipulate correlation effect between collective
charge and spin orders via external fields.",2204.11179v1
2022-04-26,Spin waves and magnetic exchange Hamiltonian in CrSBr,"CrSBr is an air-stable 2D van der Waals semiconducting magnet with great
technological promise, but its atomic-scale magnetic interactions -- crucial
information for high-frequency switching -- are poorly understood. We present
an experimental study to determine the CrSBr magnetic exchange Hamiltonian and
bulk magnon spectrum. We confirm the $A$-type antiferromagnetic order using
single crystal neutron diffraction. We also measure the magnon dispersions
using inelastic neutron scattering and rigorously fit the excitation modes to a
spin wave model. The magnon spectrum is well described by an intra-plane
ferromagnetic Heisenberg exchange model with seven nearest in-plane exchanges.
This fitted exchange Hamiltonian enables theoretical predictions of CrSBr
behavior: as one example, we use the fitted Hamiltonian to predict the presence
of chiral magnon edge modes with a spin-orbit enhanced CrSBr heterostructure.",2204.12461v2
2022-05-05,Scattering Hypervolume of Fermions in Two Dimensions,"We define the three-body scattering hypervolume $D_F$ for identical
spin-polarized fermions in two dimensions, by considering the wave function of
three such fermions colliding at zero energy and zero orbital angular momentum.
We derive the asymptotic expansions of such a wave function when three fermions
are far apart or one pair and the third fermion are far apart, and $D_F$
appears in the coefficients of such expansions. For weak interaction
potentials, we derive an approximate formula of $D_F$ by using the Born
expansion. We then study the shift of energy of three such fermions in a large
periodic area due to $D_F$. This shift is proportional to $D_F$ times the
square of the area of the triangle formed by the momenta of the fermions. We
also calculate the shifts of energy and of pressure of spin-polarized
two-dimensional Fermi gases due to a nonzero $D_F$ and the three-body
recombination rate of spin-polarized ultracold atomic Fermi gases in two
dimensions.",2205.02658v2
2022-05-24,Competing spin-fluctuations in Sr$_2$RuO$_4$ and their tuning through epitaxial strain,"In this study, we report the magnetic energy landscape of Sr2RuO4 employing
the generalized Bloch approach within density functional theory. We identify
the two dominant magnetic instabilities, ferromagnetic and spin-density-wave,
together with other predominant instabilities. We show that epitaxial strain
can change the overall magnetic tendency of the system, and tune the relative
weight of the various magnetic instabilities in the system. Especially, the
balance between spin-density wave and ferromagnetic instabilities can be
controlled by the strain, and, eventually can lead to the new magnetic phases
as well as superconducting phases with possibly altered pairing channels. Our
findings are compared with previous theoretical models and experimental reports
for the various magnetic features of the system and offer a first-principles
explanation to them.",2205.11711v1
2022-06-02,First Constraining Upper Limits on Gravitational Wave Emission from NS 1987A in SNR 1987A,"We report on a search for continuous gravitational waves (GWs) from NS 1987A,
the neutron star born in SN 1987A. The search covered a frequency band of
75-275 Hz, included a wide range of spin-down parameters for the first time,
and coherently integrated 12.8 days of data below 125 Hz and 8.7 days of data
above 125 Hz from the second Advanced LIGO observing run. We found no
astrophysical signal. We set upper limits on GW emission as tight as an
intrinsic strain of $2\times10^{-25}$ at 90\% confidence. The large spin-down
parameter space makes this search the first astrophysically consistent one for
continuous GWs from NS 1987A. Our upper limits are the first consistent ones to
beat an analog of the spin-down limit based on the age of the neutron star, and
hence are the first GW observations to put new constraints on NS 1987A.",2206.01168v1
2022-06-21,Dipolar spin-waves and tunable band gap at the Dirac points in the 2D magnet ErBr3,"Topological magnon insulators constitute a growing field of research for
their potential use as information carriers without heat dissipation. We report
an experimental and theoretical study of the magnetic ground-state and
excitations in the van der Waals two-dimensional honeycomb magnet ErBr3. We
show that the magnetic properties of this compound are entirely governed by the
dipolar interactions which generate a continuously degenerate non-collinear
ground-state on the honeycomb lattice with spins confined in the plane. We find
that the magnon dispersion exhibits Dirac-like cones when the magnetic moments
in the ground-state are related by time-reversal and inversion symmetries
associated with a Berry phase \pi as in single-layer graphene. A magnon band
gap opens when the dipoles are rotated away from this state, entailing a finite
Berry curvature in the vicinity of the K and K' Dirac points. Our results
illustrate that the spin-wave dispersion of dipoles on the honeycomb lattice
can be reversibly controlled from a magnetic phase with Dirac cones to a
topological antiferromagnetic insulator with non-trivial valley Chern number.",2206.10168v1
2022-08-01,Scattering Amplitude Techniques in Classical Gauge Theories and Gravity,"In this thesis we present a study of the computation of classical observables
in gauge theories and gravity directly from scattering amplitudes. In
particular, we discuss the direct application of modern amplitude techniques in
the one, and two-body problems for both, scattering and bounded scenarios, and
in both, classical electrodynamics and gravity, with particular emphasis on
spin effects in general, and in four spacetime dimensions. Among these
observables we have the conservative linear impulse and the radiated waveform
in the two-body problem, and the differential cross section for the scattering
of waves off classical spinning compact objects. Implications of classical soft
theorems in the computation of classical radiation are also discussed.
Furthermore, formal aspects of the double copy for massive spinning matter, and
its application in a classical two-body context are considered. Finally, the
relation between the minimal coupling gravitational Compton amplitude and the
scattering of gravitational waves off the Kerr black hole is presented.",2208.00832v1
2022-10-19,Competing ferromagnetic superconducting states in europium-based iron pnictides,"In europium-based iron pnictides superconducting Fe-planes can be influenced
by a Zeeman field originated from the neighboring Eu-planes. The field tends to
induce spin-density waves with a ferromagnetic average which coexists with the
superconducting order by forming complementary patterns of the superconducting
and magnetic order parameters in a Fulde-Ferrell-Larkin-Ovchinnikov phase and a
two-dimensional textured-superconducting phase. The hard gap around the Fermi
energy disappears in these fragile inhomogeneous superconducting states, which
features, instead, V-shaped spin-resolved local density of states. The
inhomogeneous states are also competing with either a homogeneous
superconducting or a homogeneous ferromagnetic state, manifesting the
intertwining influences of the magnetic orders in Fe and Eu planes, the
spin-density wave band structure, and the superconducting pairing order.",2210.10312v1
2022-12-12,Pair density wave characterized by a hidden string order parameter,"A composite pairing structure of superconducting state is revealed by density
matrix renormalization group study in a two-leg $t$-$J$ model. The pairing
order parameter is composed of a pairing amplitude and a phase factor, in which
the latter explicitly depends on the spin background with an analytic form
identified in the anisotropic limit as the interchain hopping integral
$t_{\perp}\rightarrow 0$. Such a string-like phase factor is responsible for a
pair density wave (PDW) induced by spin polarization with a wavevector
$Q_{\mathrm {PDW}}=2\pi m$ ($m$ the magnetization). By contrast, the pairing
amplitude remains smooth, unchanged by the PDW. In particular, a local spin
polarization can give rise to a sign change of the order parameter across the
local defect. Unlike in an Fulde-Ferrell-Larkin-Ovchinnikov state, the nonlocal
phase factor here plays a role as the new order parameter characterizing the
PDW, whose origin can be traced back to the essential sign structure of the
doped Mott insulator.",2212.06170v1
2022-12-28,Search for manifestations of spin-torsion coupling,"We investigate the axial vector torsion-spin coupling effects in the
framework of the Poincar\'e gauge theory of gravity with the general Yang-Mills
type Lagrangian. The dynamical equations for the ``electric'' and ``magnetic''
components of the torsion field variable are obtained in the general form and
it is shown that the helicity density and the spin density of the
electromagnetic field appear as the physical sources. The modified Maxwell's
equations for the electromagnetic field are derived, and the electromagnetic
wave propagation under the action of the uniform homogeneous torsion field is
considered. We demonstrate the Faraday effect of rotation of the polarization
for such a wave, and establish the strong bound on the possible cosmic axial
torsion field from the astrophysical data.",2212.13871v2
2023-01-03,Numerical study of magneto-optical binding between two dipolar particles under illumination by two counter-propagating waves,"The formation of a stable magneto plasmonic dimer with THz resonances is
theoretically studied for the principal directions of the system. Unlike a
recent report, our work provides a complete description of the full photonic
coupling for arbitrary magnetic fields as, for instance, unbalanced particle
spins. As an illustration, we consider two small, n-doped InSb nanoparticles
under illumination by two counter-propagating plane waves. Remarkably, when an
external magnetic field exists, the symmetry in the system is broken, and a
resonant radiation pressure for the dimer appears. Similarly, tunable
inter-particle forces and spins are exerted on the non-reciprocal dimer. The
system is also characterized when the magnetic field is absent. Moreover, we
show how the mechanical observables truly characterize the dimer since their
resonance dependency contains detailed information about the system. Unlike
far-field observables like absorption, mechanical magnitudes depend on the
system's near-field. In addition, the nature of the particle spins is
originally explained by the energy flow's behavior around the dimer. This work
constitutes a generalization of any previous approach to optical binding
between small nanoparticles. It paves the way for fully controlling optical
matter and nano factory designs based on surface plasmon polaritons.",2301.01213v1
2023-04-18,Dispersion engineering in spin-orbit coupled spinor $F=1$ condensates driven by negative masses,"In this paper, we bring out several potential signatures of negative mass
regimes while investigating an expanding spin-orbit (SO) coupled spinor $F=1$
Bose-Einstein condensates by analyzing the dispersion relation of the
single-particle quantum system. In SO-coupled spinor condensates, a negative
mass parameter generates a wave packet that propagates in the opposite
direction of the momentum. We analyze the dynamics of spin waves analytically
and present a simple approach to investigate the expansion of spinor
condensates. In particular, we examine the dynamics when both masses are
negative, which results in the spinor condensates splitting into two
counter-propagating self-interfering packets (SIPs). Using numerical
simulations of the coupled Gross-Pitaevskii equations, we demonstrate the
density expansion and self-interference patterns with and without magnetization
for repulsive and attractive interactions with different coupling parameters.
The highlight of our investigation is that we are able to unearth several
phenomena observed in experiments, such as self-interfering packets, pileup,
modulation instability, slow down, self-trapping, and gap solitons. In
particular, the gap soliton exists at the gap created by the intersection of
two negative masses.",2304.08844v2
2023-07-09,Dzyaloshinskii-Moriya torque-driven resonance in antiferromagnetic α-Fe2O3,"We examine the high-frequency optical mode of {\alpha}-Fe2O3 and report that
Dzyaloshinskii-Moriya (DM) interaction generates a new type of torque on the
magnetic resonance. Using a continuous-wave terahertz interferometer, we
measure the optical mode spectra, where the asymmetric absorption with a large
amplitude and broad linewidth is observed near the magnetic transition point,
Morin temperature (TM ~ 254.3 K). Based on the spin wave model, the spectral
anomaly is attributed to the DM interaction-induced torque, enabling to extract
the strength of DM interaction field of 4 T. Our work opens a new avenue to
characterize the spin resonance behaviors at an antiferromagnetic singular
point for next-generation and high-frequency spin-based information
technologies.",2307.04135v1
2023-09-09,"Anisotropic neutron star crust, solar system mountains, and gravitational waves","Mountains or non-axisymmetric deformations of rotating neutron stars (NS)
efficiently radiate gravitational waves (GW). We consider analogies between NS
mountains and surface features of solar system bodies. Both NS and moons such
as Europa or Enceladus have thin crusts over deep oceans while Mercury has a
thin crust over a large metallic core. Thin sheets may wrinkle in universal
ways. Europa has linear features, Enceladus has ``Tiger"" stripes, and Mercury
has lobate scarps. NS may have analogous features. The innermost inner core of
the Earth is anisotropic with a shear modulus that depends on direction. If NS
crust material is also anisotropic this will produce an ellipticity, when the
crust is stressed, that grows with spin frequency. This yields a breaking index
(log derivative of spin down rate) very different from $n=5$ and could explain
the maximum spin observed for neutron stars and a possible minimum ellipticity
of millisecond pulsars.",2309.04855v1
2023-09-27,Emergent Quantum Phenomena of Noncentrosymmetric Charge-Density Wave in 1T-Transition Metal Dichalcogenides,"1T-transition metal dichalcogenides (TMD) have been an exciting platform for
exploring the intertwinement of charge density waves and strong correlation
phenomena. While the David star structure has been conventionally considered as
the underlying charge order in the literature, recent scanning tunneling probe
experiments on several monolayer 1T-TMD materials have motivated a new,
alternative structure, namely the anion-centered David star structure. In this
paper, we show that this novel anion-centered David star structure manifestly
breaks inversion symmetry, resulting in flat bands with pronounced Rashba
spin-orbit couplings. These distinctive features unlock novel possibilities and
functionalities for 1T-TMDs, including the giant spin Hall effect, the
emergence of Chern bands, and spin liquid that spontaneously breaks crystalline
rotational symmetry. Our findings establish promising avenues for exploring
emerging quantum phenomena of monolayer 1T-TMDs with this novel
noncentrosymmetric structure.",2309.15916v1
2023-10-16,Exploring spin of ultralight dark matter with gravitational wave detectors,"We propose a novel method for distinguishing the spin of ultralight dark
matter (ULDM) using interferometric gravitational wave detectors. ULDM can be a
bosonic field of spin-0, 1, or 2, and each induces distinctive signatures in
signals. We find that the finite-time traveling effect causes a dominant signal
for spin-0 and spin-1 ULDM, while not for spin-2. By using overlap reduction
functions (ORF) of multiple detectors, we can differentiate between the spins
of ULDM. Furthermore, we point out that the current constraint on the coupling
constant of spin-1 ULDM to baryons becomes 30 times weaker when the finite-time
light-travel effect on the ORF is taken into account.",2310.10646v1
2023-11-20,Spectroscopy of elementary excitations from quench dynamics in a dipolar XY Rydberg simulator,"We use a Rydberg quantum simulator to demonstrate a new form of spectroscopy,
called quench spectroscopy, which probes the low-energy excitations of a
many-body system. We illustrate the method on a two-dimensional simulation of
the spin-1/2 dipolar XY model. Through microscopic measurements of the spatial
spin correlation dynamics following a quench, we extract the dispersion
relation of the elementary excitations for both ferro- and anti-ferromagnetic
couplings. We observe qualitatively different behaviors between the two cases
that result from the long-range nature of the interactions, and the frustration
inherent in the antiferromagnet. In particular, the ferromagnet exhibits
elementary excitations behaving as linear spin waves. In the anti-ferromagnet,
spin waves appear to decay, suggesting the presence of strong nonlinearities.
Our demonstration highlights the importance of power-law interactions on the
excitation spectrum of a many-body system.",2311.11726v1
2023-12-14,Temperature-induced supersolidity in spin-orbit-coupled Bose gases,"Close to the superfluid plane-wave (PW) - supersolid stripe (ST) phase
transition point of a zero temperature quasi-one-dimensional spin-orbit-coupled
Bose gas, we find that an increase in temperature induces a phase transition to
the supersolid phase with a broken translational symmetry from the superfluid
plane-wave phase. We use the Hartree-Fock-Bogoliubov theory with the Popov
approximation to investigate the effect of thermal fluctuations on the
collective excitation spectrum and investigate the softening of the spin-dipole
mode corresponding to the shift in the quantum critical point. This is in stark
contrast to the PW-ST phase transition in a homogeneous system where non-zero
temperatures facilitate the melting of the stripe phase.",2312.08719v2
2024-01-02,Compact Binary Foreground Subtraction for Detecting the Stochastic Gravitational-wave Background in Ground-based Detectors,"Stochastic gravitational-wave (GW) background (SGWB) contains information
about the early Universe and astrophysical processes. The recent evidence of
SGWB by pulsar timing arrays in the nanohertz band is a breakthrough in the GW
astronomy. For ground-based GW detectors, while unfortunately in data analysis
the SGWB can be masked by loud GW events from compact binary coalescences
(CBCs). Assuming a next-generation ground-based GW detector network, we
investigate the potential for detecting the astrophysical and cosmological SGWB
with non-CBC origins by subtracting recovered foreground signals of loud CBC
events. As an extension of the studies by Sachdev et al. (2020) and Zhou et al.
(2023), we incorporate aligned spin parameters in our waveform model. Because
of the inclusion of spins, we obtain significantly more pessimistic results
than the previous work, where the residual energy density of foreground is even
larger than the original background. The degeneracy between the spin parameters
and symmetric mass ratio is strong in the parameter estimation process and it
contributes most to the imperfect foreground subtraction. Our results have
important implications for assessing the detectability of SGWB from non-CBC
origins for ground-based GW detectors.",2401.00984v1
2024-02-23,Spinning Black Hole in a Fluid,"In this paper, we propose a new Analogue Gravity example - a spinning (or
Kerr) Black Hole in an extended fluid model. The fluid model receives Berry
curvature contributions and applies to electron dynamics in Condensed Matter
lattice systems in the hydrodynamic limit. We construct the acoustic metric for
sonic fluctuations that obey a structurally relativistic wave equation in an
effective curved background. In a novel approach of dimensional analysis, we
have derived explicit expressions for effective mass and angular momentum per
unit mass in the acoustic metric (in terms of fluid parameters), to identify
with corresponding parameters of the Kerr metric. The spin is a manifestation
of the Berry curvature-induced effective noncommutative structure in the fluid.
Finally we put the Kerr Black Hole analogy in a robust setting by revealing
explicitly the presence of horizon and ergo-region for a specific background
fluid velocity profile. We also show that near horizon behavior of the
phase-space trajectory of a probe particle agrees with Kerr Black Hole analogy.
In fluid dynamics perspective, presence of a horizon signifies the wave
blocking phenomenon.",2402.15540v1
2024-03-04,Theory of collective excitations in the quadruple-$Q$ magnetic hedgehog lattices,"Hedgehog and antihedgehog spin textures in magnets behave as emergent
monopoles and antimonopoles, which give rise to astonishing transport and
electromagnetic phenomena. Using the Kondo-lattice model in three dimensions,
we theoretically study collective spin-wave excitation modes of magnetic
hedgehog lattices which have recently been discovered in itinerant magnets such
as MnSi$_{1-x}$Ge$_{x}$ and SrFeO$_3$. It is revealed that the spin-wave modes,
which appear in the sub-terahertz regime, have dominant amplitudes localized at
Dirac strings connecting hedgehog-antihedgehog pairs and are characterized by
their translational oscillations. It is found that their spectral features
sensitively depend on the number and configuration of the Dirac strings and,
thus, can be exploited for identifying the topological phase transitions
associated with the monopole-antimonopole pair annihilations.",2403.01765v1
2024-03-27,Extreme Terahertz Magnon Multiplication Induced by Resonant Magnetic Pulse Pairs,"Nonlinear interactions of spin-waves and their quanta, magnons, have emerged
as prominent candidates for interference-based technology, ranging from quantum
transduction to antiferromagnetic spintronics. Yet magnon multiplication in the
terahertz (THz) spectral region represents a major challenge. Intense, resonant
magnetic fields from THz pulse-pairs with controllable phases and amplitudes
enable high order THz magnon multiplication, distinct from non-resonant
nonlinearities such as the high harmonic generation by below-band gap electric
fields. Here, we demonstrate exceptionally high-order THz nonlinear magnonics.
It manifests as 7$^\text{th}$-order spin-wave-mixing and 6$^\text{th}$ harmonic
magnon generation in an antiferromagnetic orthoferrite. We use THz
multi-dimensional coherent spectroscopy to achieve high-sensitivity detection
of nonlinear magnon interactions up to six-magnon quanta in strongly-driven
many-magnon correlated states. The high-order magnon multiplication, supported
by classical and quantum spin simulations, elucidates the significance of
four-fold magnetic anisotropy and Dzyaloshinskii-Moriya symmetry breaking.
Moreover, our results shed light on the potential quantum fluctuation
properties inherent in nonlinear magnons.",2403.18168v1
2024-04-17,Exact Demonstration of pair-density-wave superconductivity in the $σ_z$-Hubbard model,"Describing and achieving `unconventional' superconductivity remains a
forefront challenge in quantum many-body physics. Here we use a unitary
mapping, combined with the well-established properties of the attractive
Hubbard model to demonstrate rigorously a Hamiltonian with a low temperature
pair-density-wave (PDW) phase. We also show that the same mapping, when applied
to the widely accepted properties of the repulsive Hubbard model, leads to a
Hamiltonian exhibiting triplet $d$-wave PDW superconductivity and an unusual
combination of ferro- and antiferro-magnetic spin correlations. We then
demonstrate the persistence of the $d$-wave PDW in a Hamiltonian derived from
the mapping of the extended $t$-$J$ model in the large-$U$ limit. Furthermore,
through strategic manipulation of the nearest-neighbor hopping signs of
spin-down electrons, we illustrate the attainability of PDW superconductivity
at other momenta. The intertwining of different magnetic and exotic pairing
correlations noted here may have connections to experimental observations in
spin-triplet candidates like UTe$_2$.",2404.11043v1
2002-07-03,Temperature dependence and mechanism of electrically detected ESR at the n=1 filling factor of a two-dimensional electron system in GaAs quantum wells,"Electrically detected electron spin resonance (EDESR) signals were acquired
as a function of temperature in the 0.3-4.2 K temperature range in a
AlGaAs/GaAs multiple quantum well sample at the filling factor at 5.7 T. In the
particular sample studied, the line width is approximately temperature
independent, while the amplitude exhibits a maximum at about 2.2 K and vanishes
with increased or decreased temperature. To explain the observed temperature
dependence of the signal amplitude, the signal amplitude temperature dependence
is calculated assuming a model based on heating. The model ascribes the
resonant absorption of microwave power of the 2DES to the uniform mode of the
electron spin magnetization where the elementary spin excitations at filling
factor are taken to be spin waves, while the short wavelength spin wave modes
serve as a heat sink for the absorbed energy. Due to the finite thermal
conductance to the surroundings, the temperature of the 2DES spin wave system
is increased, resulting in a thermal activation of the longitudinal
magnetoconductance. The proposed heating model correctly predicts the location
of the maximum in the experimentally observed temperature dependence of the
EDESR amplitude. It also correctly predicts that the signal should vanish as
the temperature is increased or decreased. The results of the present study
demonstrate how experimental EDESR studies can, under appropriate conditions,
provide data that can be used to discriminate between competing theories for
the magnetic ordering and magnetic excitations of a 2DES in the regime of the
quantum Hall effect.",0207108v1
2009-12-29,Modified spin-wave theory with ordering vector optimization I: frustrated bosons on the spatially anisotropic triangular lattice,"We investigate a system of frustrated hardcore bosons, modeled by an XY
antiferromagnet on the spatially anisotropic triangular lattice, using
Takahashi's modified spin-wave (MSW) theory. In particular we implement
ordering vector optimization on the ordered reference state of MSW theory,
which leads to significant improvement of the theory and accounts for quantum
corrections to the classically ordered state. The MSW results at zero
temperature compare favorably to exact diagonalization (ED) and projected
entangled-pair state (PEPS) calculations. The resulting zero-temperature phase
diagram includes a 1D quasi-ordered phase, a 2D Neel ordered phase, and a 2D
spiraling ordered phase. We have strong indications that the various ordered or
quasi-ordered phases are separated by spin-liquid phases with short-range
correlations, in analogy to what has been predicted for the Heisenberg model on
the same lattice. Within MSW theory we also explore the finite-temperature
phase diagram. We find that the zero-temperature long-range-ordered phases turn
into quasi-ordered phases (up to a Berezinskii-Kosterlitz-Thouless
temperature), while zero-temperature quasi-ordered phases become short-range
correlated at finite temperature. These results show that modified spin-wave
theory is very well suited for describing ordered and quasi-ordered phases of
frustrated XY spins (or, equivalently, of frustrated lattice bosons) both at
zero and finite temperatures. While MSW theory, just as other theoretical
methods, cannot describe spin-liquid phases, its breakdown provides a fast
method for singling out Hamiltonians which may feature these intriguing quantum
phases. We thus suggest a tool for guiding our search for interesting systems
whose properties are necessarily studied with a physical quantum simulator.",0912.5213v1
2011-09-22,Tidal Dissipation in Planet-Hosting Stars: Damping of Spin-Orbit Misalignment and Survival of Hot Jupiters,"Observations of hot Jupiters around solar-type stars with very short orbital
periods (~day) suggest that tidal dissipation in such stars is not too
efficient so that these planets can survive against rapid orbital decay. This
is consistent with recent theoretical works, which indicate that the tidal Q of
planet-hosting stars can indeed be much larger than the values inferred from
stellar binaries. On the other hand, recent measurements of Rossiter-McLaughlin
effects in transiting hot Jupiter systems not only reveal that many such
systems have misaligned stellar spin with respect to the orbital axis, but also
show that systems with cooler host stars tend to have aligned spin and orbital
axes. Winn et al. suggested that this obliquity - temperature correlation may
be explained by efficient damping of stellar obliquity due to tidal dissipation
in the star. This explanation, however, is in apparent contradiction with the
survival of these short-period hot Jupiters. We show that in the solar-type
parent stars of close-in exoplanetary systems, the effective tidal Q governing
the damping of stellar obliquity can be much smaller than that governing
orbital decay. This is because for misaligned systems, the tidal potential
contains a Fourier component with frequency equal to the stellar spin frequency
(in the rotating frame of the star). This component can excite inertial waves
in the convective envelope of the star, and the dissipation of inertial waves
then leads to a spin-orbit alignment torque, but not orbital decay. By
contrast, for aligned systems, such inertial wave excitation is forbidden since
the tidal forcing frequency is much larger than the stellar spin frequency. We
derive a general effective tidal evolution theory for misaligned binaries,
taking account of different tidal responses and dissipation rates for different
tidal forcing components.",1109.4703v2
2015-07-20,Distinguishing black-hole spin-orbit resonances by their gravitational wave signatures. II: Full parameter estimation,"Gravitational waves from coalescing binary black holes encode the evolution
of their spins prior to merger. In the post-Newtonian regime and on the
precession timescale, this evolution has one of three morphologies, with the
spins either librating around one of two fixed points (""resonances"") or
circulating freely. In this work we perform full parameter estimation on
resonant binaries with fixed masses and spin magnitudes, changing three
parameters: a conserved ""projected effective spin"" $\xi$ and resonant family
$\Delta\Phi=0,\pi$ (which uniquely label the source), the inclination
$\theta_{JN}$ of the binary's total angular momentum with respect to the line
of sight (which determines the strength of precessional effects in the
waveform), and the signal amplitude. We demonstrate that resonances can be
distinguished for a wide range of binaries, except for highly symmetric
configurations where precessional effects are suppressed. Motivated by new
insight into double-spin evolution, we introduce new variables to characterize
precessing black hole binaries which naturally reflects the timescale
separation of the system and therefore better encode the dynamical information
carried by gravitational waves.",1507.05587v3
2018-05-04,Gravitational-wave astrophysics with effective-spin measurements: asymmetries and selection biases,"Gravitational waves emitted by coalescing compact objects carry information
about the spin of the individual bodies. However, with present detectors only
the mass-weighted combination of the components of the spin along the orbital
angular momentum can be measured accurately. This quantity, the effective spin
$\chi_{\mathrm{eff}}$, is conserved up to at least the second post-Newtonian
order. The measured distribution of $\chi_{\mathrm{eff}}$ values from a
population of detected binaries, and in particular whether this distribution is
symmetric about zero, encodes valuable information about the underlying
compact-binary formation channels. In this paper we focus on two important
complications of using the effective spin to study astrophysical population
properties: (i) an astrophysical distribution for $\chi_{\mathrm{eff}}$ values
which is symmetric does not necessarily lead to a symmetric distribution for
the detected effective spin values, leading to a \emph{selection bias}; and
(ii) the posterior distribution of $\chi_{\mathrm{eff}}$ for individual events
is \emph{asymmetric} and it cannot usually be treated as a Gaussian. We find
that the posterior distributions for $\chi_{\mathrm{eff}}$ systematically show
fatter tails toward larger positive values, unless the total mass is large or
the mass ratio $m_2/m_1$ is smaller than $\sim 1/2$. Finally we show that
uncertainties in the measurement of $\chi_{\mathrm{eff}}$ are systematically
larger when the true value is negative than when it is positive. All these
factors can bias astrophysical inference about the population when we have more
than $\sim 100$ events and should be taken into account when using
gravitational-wave measurements to characterize astrophysical populations.",1805.03046v2
2016-03-07,Spin polarization of Majorana zero modes and topological quantum phase transition in semiconductor Majorana nanowires,"A number of recent works have discussed the issue of spin polarization of a
Majorana zero mode in condensed matter systems. Here we show that the spin
polarization density of a Majorana zero mode, computed as an average of the
spin operator over its wave function, vanishes everywhere. A single
non-degenerate Majorana zero mode, therefore, does not couple to an applied
magnetic field, except via hybridization with higher energy excited states (if
present), which may perturb its wave function. If `spin' is defined by
considering only the particle components of the wave function, as has been done
in some recent works, Majorana zero modes do have a non-zero spatial profile of
this quantity, measurable in scanning tunneling microscopy (STM) experiments.
However, if such a quantity is measured in spin-resolved tunneling experiments
(without spatial resolution), we show that it cannot be used as a unique
signature of Majorana zero modes in the topologically non-trivial
superconducting phase. As a byproduct, we show that in spatially inhomogeneous
systems, accidental zero energy modes, which for all practical purposes behave
as Majorana zero modes (including giving rise to a zero bias conductance peak
of height 2e^2/h), can appear with increasing magnetic field even in the
absence of a topological quantum phase transition (TQPT). But only after gap
closing and the associated TQPT, the modes are localized near the system edges,
resulting in the maximum topological protection. In the light of these
considerations, demonstrating the nonlocal character of the
topologically-protected Majorana pair and its emergence {\em after} the systems
undergo a TQPT, become critical tasks for the ongoing experimental search for
Majorana bound states in condensed matter systems.",1603.02255v1
2021-11-17,Common origin of black holes in high mass X-ray binaries and in gravitation-wave sources,"Black hole (BH) high mass X-ray binary (HMXB) systems are likely the
progenitors of the BH-BH mergers detected in gravitational waves by
LIGO/Virgo/KAGRA (LVK). Yet BHs in the gravitational wave sources reach higher
masses (100Msun) than BHs in HMXBs (20Msun), and have typically lower spins
(a<0.25 with tail extending to larger values) than the published values for BHs
in HMXBs (a>0.9). This could suggest that these two classes of systems belong
to different populations (apples and oranges) but we show here that it does not
have to be the case. The difference in masses is easily explained as the known
HMXB-BHs are in galaxies with relatively high-metallicity, so their progenitor
stars are subject to strong mass loss from winds which leads to relatively low
mass BH at core collapse. Conversely, LVK allows for detection of BHs from
low-metallicity galaxies that naturally produce more massive stellar-origin
BHs. The explanation of the difference in BH spins is not as straightforward,
but we show that in HMXBs the BH spin value derivation depends strongly on how
the HMXB accretion disk emission is modeled. We demonstrate this explicitly for
the case of Cyg X-1, showing excellent spectral fits with low spin (a=0.1) when
taking into account the Comptonization of the disk photosphere. Similar results
have recently been shown for LMC X-1 (allowing for a=0.1). We suggest that such
low BH spins are generic for all three HMXB BHs. Hence we conclude that current
observations are consistent with LVK BHs and HMXB BHs belonging to the same
population (all apples).",2111.09401v2
2023-12-11,Stroboscopic X-ray Diffraction Microscopy of Dynamic Strain in Diamond Thin-film Bulk Acoustic Resonators for Quantum Control of Nitrogen Vacancy Centers,"Bulk-mode acoustic waves in a crystalline material exert lattice strain
through the thickness of the sample, which couples to the spin Hamiltonian of
defect-based qubits such as the nitrogen-vacancy (NV) center defect in diamond.
This mechanism has been previously harnessed for unconventional quantum spin
control, spin decoherence protection, and quantum sensing. Bulk-mode acoustic
wave devices are also important in the microelectronics industry as microwave
filters. A key challenge in both applications is a lack of appropriate operando
microscopy tools for quantifying and visualizing gigahertz-frequency dynamic
strain. In this work, we directly image acoustic strain within NV
center-coupled diamond thin-film bulk acoustic wave resonators using
stroboscopic scanning hard X-ray diffraction microscopy at the Advanced Photon
Source. The far-field scattering patterns of the nano-focused X-ray diffraction
encode strain information entirely through the illuminated thickness of the
resonator. These patterns have a real-space spatial variation that is
consistent with the bulk strain's expected modal distribution and a
momentum-space angular variation from which the strain amplitude can be
quantitatively deduced. We also perform optical measurements of strain-driven
Rabi precession of the NV center spin ensemble, providing an additional
quantitative measurement of the strain amplitude. As a result, we directly
measure the NV spin-stress coupling parameter $b = 2.73(2)$ MHz/GPa by
correlating these measurements at the same spatial position and applied
microwave power. Our results demonstrate a unique technique for directly
imaging AC lattice strain in micromechanical structures and provide a direct
measurement of a fundamental constant for the NV center defect spin
Hamiltonian.",2312.06862v1
2007-11-27,Kondo Effect in Spin Chains,"The free electron Kondo problem can be described by a one-dimensional (1D)
model because only the s-wave part of the electronic wave-function is affected
by the Kondo coupling. Since only the spin degrees of freedom are involved in
the Kondo interaction, and due to spin-charge separation in 1D, the universal
low energy long distance physics of the Kondo model also arises when a magnetic
impurity is coupled to the end of a gap-less antiferromagnetic J_1-J_2 spin-1/2
chain, where J_1(J_2) is the (next-)nearest neighbor coupling. Experimental
realizations of such spin chain models are possible and using various
analytical and numerical techniques, we present a detailed and quantitative
comparison between the usual free electron Kondo model and such spin chain
versions of the Kondo problem. For the gap-less J_1-J_2 spin chain two cases
are studied, with zero next nearest neighbor coupling, J_2=0, and with a
critical second neighbor coupling, J_2=J_2c. We first focus on the spin chain
impurity model at J_2c~0.2412 where a bulk marginal coupling present in the
spin chain model for J_2<J_2c vanishes. At J_2c, the usual Kondo physics is
recovered in the spin chain model in the low energy regime. We then analyze the
nearest-neighbor model (J_2=0) where a new kind of Kondo effect occurs due to
the presence of the bulk marginal coupling. This marginal coupling leads to a
slower variation of the Kondo temperature T_K with the bare Kondo coupling. In
the exact Bethe ansatz solution of this spin chain impurity model (J_2=0) Frahm
and Zvyagin noted this relation as well as the connection to the Kondo problem.
Here, we provide further evidence for the connection to Kondo physics and
present low temperature QMC results for the impurity susceptibility that
further support this connection.",0711.4350v1
2011-10-10,Accurate gravitational waveforms for binary-black-hole mergers with nearly extremal spins,"Motivated by the possibility of observing gravitational waves from merging
black holes whose spins are nearly extremal (i.e., 1 in dimensionless units),
we present numerical waveforms from simulations of merging black holes with the
highest spins simulated to date: (1) a 25.5-orbit inspiral, merger, and
ringdown of two holes with equal masses and spins of magnitude 0.97 aligned
with the orbital angular momentum; and (2) a previously reported 12.5-orbit
inspiral, merger, and ringdown of two holes with equal masses and spins of
magnitude 0.95 anti-aligned with the orbital angular momentum. First, we
consider the horizon mass and spin evolution of the new aligned-spin
simulation. During the inspiral, the horizon area and spin evolve in remarkably
close agreement with Alvi's analytic predictions, and the remnant hole's final
spin agrees reasonably well with several analytic predictions. We also find
that the total energy emitted by a real astrophysical system with these
parameters---almost all of which is radiated during the time included in this
simulation---would be 10.952% of the initial mass at infinite separation.
Second, we consider the gravitational waveforms for both simulations. After
estimating their uncertainties, we compare the waveforms to several
post-Newtonian approximants, finding significant disagreement well before
merger, although the phase of the TaylorT4 approximant happens to agree
remarkably well with the numerical prediction in the aligned-spin case. We find
that the post-Newtonian waveforms have sufficient uncertainty that hybridized
waveforms will require far longer numerical simulations (in the absence of
improved post-Newtonian waveforms) for accurate parameter estimation of
low-mass binary systems.",1110.2229v1
2012-04-13,Spin parity and broken symmetry in finite spin-1/2 chains with frustrated exchange: quantum transition from high to low spin,"Exact diagonalization of finite spin-1/2 chains with periodic boundary
conditions is applied to the ground state (gs) of chains with ferromagnetic (F)
exchange $J_1 < 0$between first neighbors, antiferromagnetic (AF) exchange $J_2
= \alpha J_1 > 0$between second neighbors, and axial anisotropy $0 \le \Delta
\le 1$. In zero field, the gs is in the $S_z = 0$ sector for the relevant
parameters and is doubly degenerate at multiple points $\gamma_m = (\alpha_m,
\Delta_m)$ in the $\alpha$, $\Delta$ plane. Degeneracy under inversion at sites
or spin parity or both leads, respectively, to a bond order wave (BOW), to
staggered magnetization or to vector chiral (VC) order. Exact results up to $N
= 28$ spins directly yield order parameters and spin correlation functions
whose weak N dependencies allow inferences about infinite chains. The high-spin
gs at $J_2 = 0$ changes discontinuously at $\gamma_1 = (-1/4, 1)$ to a singlet
in the isotropic ($\Delta = 1$) chain. The transition from high to low spin
$S(\alpha, \Delta)$ is continuous for $ \Delta < \Delta_B = 0.95 \pm 0.01$ on
the degeneracy line $\alpha_1(\Delta)$. The gs has staggered magnetization
between $\Delta_A = 0.72$ and $\Delta_B$, and a BOW for $\Delta < \Delta_A$.
When both inversion and spin parity are reversed at $\gamma_m$, the correlation
functions $C(p)$ for spins separated by $p$ sites are identical. $C(p)$ minima
are shifted by $\pi/2$ from the minima of VC order parameters at separation
$p$, consistent with right and left-handed helices along the z axis and spins
in the xy plane. Degenerate gs of finite chains are related to quantum phase
diagrams of extended $\alpha$, $\Delta$ chains, with good agreement for order
parameters along the line $\alpha_1(\Delta)$.",1204.2862v1
2013-12-21,Lagrangian for Frenkel electron and position's non-commutativity due to spin,"We construct relativistic-invariant spinning-particle Lagrangian without
auxiliary variables. Spin is considered as a composed quantity constructed on
the base of non-Grassmann vector-like variable. The variational problem
guarantees both fixed value of spin and Frenkel condition on spin-tensor.
Taking into account the Frenkel condition, we obtain, inevitably, relativistic
corrections to the algebra of position variables: their classical brackets
became noncommutative, with the ""parameter of non-commutativity"" proportional
to the spin-tensor. This leads to a number of interesting consequences in
quantum theory. We construct the relativistic quantum mechanics in canonical
formalism (in physical-time parametrization) and in covariant formalism (in
arbitrary parametrization). We show how state-vectors and operators of
covariant formulation can be used to compute mean values of physical operators
of position and spin. This proves relativistic covariance of canonical
formalism. Various candidates for position and spin operators of an electron
acquire clear meaning and interpretation in the Lagrangian model of Frenkel
electron. We also establish the relation between Frenkel electron and
positive-energy sector of Dirac equation, this allowed us to turn to the
long-standing problem on spin and position operators of Dirac theory. Contrary
to widely assumed opinion, our results argue in favor of Pryce's (d)-type
operators. This implies that effects of non-commutativity could be presented at
the Compton wave length, in contrast to conventional expectations at the Planck
length. At last, we present the manifestly covariant form of spin and position
operators of Dirac equation.",1312.6247v3
2016-02-02,Carrier-impurity spin transfer dynamics in paramagnetic II-VI diluted magnetic semiconductors in the presence of a wave-vector-dependent magnetic field,"Quantum kinetic equations of motion for carrier and impurity spins in
paramagnetic II-VI diluted magnetic semiconductors in a $\mathbf{k}$-dependent
effective magnetic field are derived, where the carrier-impurity correlations
are taken into account. In the Markov limit, rates for the electron-impurity
spin transfer can be derived for electron spins parallel and perpendicular to
the impurity spins corresponding to measurable decay rates in Kerr experiments
in Faraday and Voigt geometry. Our rigorous microscopic quantum kinetic
treatment automatically accounts for the fact that, in an individual spin
flip-flop scattering process, a spin flip of an electron is necessarily
accompanied by a flop of an impurity spin in the opposite direction and the
corresponding change of the impurity Zeeman energy influences the final energy
of the electron after the scattering event. This shift in the electron energies
after a spin flip-flop scattering processes, which usually has been overlooked
in the literature, turns out to be especially important in the case of
extremely diluted magnetic semiconductors in an external magnetic field. As a
specific example for a $\mathbf{k}$-dependent effective magnetic field the
effects of a Rashba field on the dynamics of the carrier-impurity correlations
in a Hg$_{1-x-y}$Cd$_y$Mn$_x$Te quantum well are described. It is found that,
although accounting for the Rashba interaction in the dynamics of the
correlations leads to a modified $\mathbf{k}$-space dynamics, the time
evolution of the total carrier spin is not significantly influenced.
Furthermore, a connection between the present theory and the description of
collective carrier-impurity precession modes is presented.",1602.00911v2
2018-03-28,"Electronic structure of the Co(0001)/MoS2 interface, and its possible use for electrical spin injection in a single MoS2 layer","The ability to perform efficient electrical spin injection from ferromagnetic
metals into two-dimensional semiconductor crystals based on transition metal
dichalcogenide monolayers is a prerequisite for spintronic and valleytronic
devices using these materials. Here, the hcp Co(0001)/MoS2 interface electronic
structure is investigated by first-principles calculations based on the density
functional theory. In the lowest energy configuration of the hybrid system
after optimization of the atomic coordinates, we show that interface sulfur
atoms are covalently bound to one, two or three cobalt atoms. A decrease of the
Co atom spin magnetic moment is observed at the interface, together with a
small magnetization of S atoms. Mo atoms also hold small magnetic moments which
can take positive as well as negative values. The charge transfers due to
covalent bonding between S and Co atoms at the interface have been calculated
for majority and minority spin electrons and the connections between these
interface charge transfers and the induced magnetic properties of the MoS2
layer are discussed. Band structure and density of states of the hybrid system
are calculated for minority and majority spin electrons, taking into account
spin-orbit coupling. We demonstrate that MoS2 bound to the Co contact becomes
metallic due to hybridization between Co d and S p orbitals. For this metallic
phase of MoS2, a spin polarization at the Fermi level of 16 % in absolute value
is calculated, that could allow spin injection into the semiconducting MoS2
monolayer channel. Finally, the symmetry of the majority and minority spin
electron wave functions at the Fermi level in the Co-bound metallic phase of
MoS2 and the orientation of the border between the metallic and semiconducting
phases of MoS2 are investigated, and their impact on spin injection into the
MoS2 channel is discussed.",1803.10612v1
2018-08-07,Spin orientations of merging black holes formed from the evolution of stellar binaries,"We study the expected spin misalignments of merging binary black holes (BHs)
formed in isolation by combining state-of-the-art population-synthesis models
with efficient post-Newtonian evolutions, thus tracking sources from stellar
formation to gravitational-wave detection. We present extensive predictions of
the properties of sources detectable by both current and future
interferometers. We account for the fact that detectors are more sensitive to
spinning BH binaries with suitable spin orientations and find that this
significantly impacts the population of sources detectable by LIGO, while this
is not the case for 3rd-generation detectors. We find that three formation
pathways, differentiated by the order of core collapse and common-envelope
phases, dominate the observed population, and that their relative importance
critically depends on the recoils imparted to BHs at birth. Our models suggest
that measurements of the ""effective-spin"" parameter $\chi_{\rm eff}$ will allow
for powerful constraints. For instance, we find that the role of spin
magnitudes and spin directions in $\chi_{\rm eff}$ can be largely disentangled,
and that the symmetry of the effective-spin distribution is a robust indicator
of the binary's formation history. Our predictions for individual spin
directions and their precessional morphologies confirm and extend early toy
models, while exploring substantially more realistic and broader sets of
initial conditions. Our main conclusion is that specific subpopulations of BH
binaries will exhibit distinctive precessional dynamics: these classes include
(but are not limited to) sources where stellar tidal interactions act on
sufficiently short timescales, and massive binaries produced in pulsational
pair-instability supernovae. Measurements of BH spin orientations have enormous
potential to constrain specific evolutionary processes in the lives of massive
binary stars.",1808.02491v2
2018-12-17,Electron spin relaxation of single phosphorus donors in metal-oxide-semiconductor nanoscale devices,"We analyze the electron spin relaxation rate $1/T_1$ of individual
ion-implanted $^{31}$P donors, in a large set of metal-oxide-semiconductor
(MOS) silicon nanoscale devices, with the aim of identifying spin relaxation
mechanisms peculiar to the environment of the spins. The measurements are
conducted at low temperatures ($T\approx 100$~mK), as a function of external
magnetic field $B_0$ and donor electrochemical potential $\mu_{\rm D}$. We
observe a magnetic field dependence of the form $1/T_1\propto B_0^5$ for
$B_0\gtrsim 3\,$ T, corresponding to the phonon-induced relaxation typical of
donors in the bulk. However, the relaxation rate varies by up to two orders of
magnitude between different devices. We attribute these differences to
variations in lattice strain at the location of the donor. For $B_0\lesssim
3\,$T, the relaxation rate changes to $1/T_1\propto B_0$ for two devices. This
is consistent with relaxation induced by evanescent-wave Johnson noise created
by the metal structures fabricated above the donors. At such low fields, where
$T_1>1\,$s, we also observe and quantify the spurious increase of $1/T_1$ when
the electrochemical potential of the spin excited state $|\uparrow\rangle$
comes in proximity to empty states in the charge reservoir, leading to
spin-dependent tunneling that resets the spin to $|\downarrow\rangle$. These
results give precious insights into the microscopic phenomena that affect spin
relaxation in MOS nanoscale devices, and provide strategies for engineering
spin qubits with improved spin lifetimes.",1812.06644v2
2021-04-15,Supernova Fallback as Origin of Neutron Star Spins and Spin-kick Alignment,"Natal kicks and spins are characteristic properties of neutron stars (NSs)
and black holes (BHs). Both offer valuable clues to dynamical processes during
stellar core collapse and explosion. Moreover, they influence the evolution of
stellar multiple systems and the gravitational-wave signals from their inspiral
and merger. Observational evidence of possibly generic spin-kick alignment has
been interpreted as indication that NS spins are either induced with the NS
kicks or inherited from progenitor rotation, which thus might play a
dynamically important role during stellar collapse. Current three-dimensional
supernova simulations suggest that NS kicks are transferred in the first
seconds of the explosion, mainly by anisotropic mass ejection and, on a
secondary level, anisotropic neutrino emission. In contrast, the NS spins are
only determined minutes to hours later by angular momentum associated with
fallback of matter that does not become gravitationally unbound in the
supernova. Here, we propose a novel scenario to explain spin-kick alignment as
a consequence of tangential vortex flows in the fallback matter that is
accreted mostly from the direction of the NS's motion. For this effect the
initial NS kick is crucial, because it produces a growing offset of the NS away
from the explosion center, thus promoting onesided accretion. In this new
scenario conclusions based on traditional concepts are reversed. For example,
pre-kick NS spins are not required, and rapid progenitor-core rotation can
hamper spin-kick alignment. We also discuss implications for natal BH kicks and
the possibility of tossing the BH's spin axis during its formation.",2104.07493v2
2019-07-26,Universal relations for spin-orbit-coupled Fermi gases in two and three dimensions,"We present a comprehensive derivation of a set of universal relations for
spin-orbit-coupled Fermi gases in three or two dimension, which follow from the
short-range behavior of the two-body physics. Besides the adiabatic energy
relations, the large-momentum distribution, the grand canonical potential and
pressure relation derived in our previous work for three-dimensional systems
{[}Phys. Rev. Lett. 120, 060408 (2018){]}, we further derive high-frequency
tail of the radio-frequency spectroscopy and the short-range behavior of the
pair correlation function. In addition, we also extend the derivation to
two-dimensional systems with Rashba type of spin-orbit coupling. To simply
demonstrate how the spin-orbit-coupling effect modifies the two-body
short-range behavior, we solve the two-body problem in the sub-Hilbert space of
zero center-of-mass momentum and zero total angular momentum, and
perturbatively take the spin-orbit-coupling effect into account at short
distance, since the strength of the spin-orbit coupling should be much smaller
than the corresponding scale of the finite range of interatomic interactions.
The universal asymptotic forms of the two-body wave function at short distance
are then derived, which do not depend on the short-range details of interatomic
potentials. We find that new scattering parameters need to be introduced
because of spin-orbit coupling, besides the traditional $s$- and $p$-wave
scattering length (volume) and effective ranges. This is a general and unique
feature for spin-orbit-coupled systems. We show how these two-body parameters
characterize the universal relations in the presence of spin-orbit coupling.
This work probably shed light for understanding the profound properties of the
many-body quantum systems in the presence of the spin-orbit coupling.",1907.11433v1
2022-01-31,Inferring the neutron star maximum mass and lower mass gap in neutron star-black hole systems with spin,"Gravitational-wave (GW) detections of merging neutron star-black hole (NSBH)
systems probe astrophysical neutron star (NS) and black hole (BH) mass
distributions, especially at the transition between NS and BH masses. Of
particular interest are the maximum NS mass, minimum BH mass, and potential
mass gap between them. While previous GW population analyses assumed all NSs
obey the same maximum mass, if rapidly spinning NSs exist, they can extend to
larger maximum masses than nonspinning NSs. In fact, several authors have
proposed that the $\sim2.6\,M_\odot$ object in the event GW190814 -- either the
most massive NS or least massive BH observed to date -- is a rapidly spinning
NS. We therefore infer the NSBH mass distribution jointly with the NS spin
distribution, modeling the NS maximum mass as a function of spin. Using 4
LIGO-Virgo NSBH events including GW190814, if we assume that the NS spin
distribution is uniformly distributed up to the maximum (breakup) spin, we
infer the maximum non-spinning NS mass is $2.7^{+0.5}_{-0.4}\,M_\odot$ (90\%
credibility), while assuming only nonspinning NSs, the NS maximum mass must be
$>2.53 M_\odot$ (90\% credibility). The data support the mass gap's existence,
with a minimum BH mass at $5.4^{+0.7}_{-1.0} M_\odot$. With future
observations, under simplified assumptions, 150 NSBH events may constrain the
maximum nonspinning NS mass to $\pm0.02\,M_\odot$, and we may even measure the
relation between the NS spin and maximum mass entirely from GW data. If rapidly
rotating NSs exist, their spins and masses must be modeled simultaneously to
avoid biasing the NS maximum mass.",2202.05164v2
2022-06-23,The curious case of GW200129: interplay between spin-precession inference and data-quality issues,"Measurement of spin-precession in black hole binary mergers observed with
gravitational waves is an exciting milestone as it relates to both general
relativistic dynamics and astrophysical binary formation scenarios. In this
study, we revisit the evidence for spin-precession in GW200129 and localize its
origin to data in LIGO Livingston in the 20--50\,Hz frequency range where the
signal amplitude is lower than expected from a non-precessing binary given all
the other data. These data are subject to known data quality issues as a glitch
was subtracted from the detector's strain data. The lack of evidence for
spin-precession in LIGO Hanford leads to a noticeable inconsistency between the
inferred binary mass ratio and precessing spin in the two LIGO detectors,
something not expected from solely different Gaussian noise realizations. We
revisit the LIGO Livingston glitch mitigation and show that the difference
between a spin-precessing and a non-precessing interpretation for GW200129 is
smaller than the statistical and systematic uncertainty of the glitch
subtraction, finding that the support for spin-precession depends sensitively
on the glitch modeling. We also investigate the signal-to-noise ratio $\sim7$
trigger in the less sensitive Virgo detector. Though not influencing the
spin-precession studies, the Virgo trigger is grossly inconsistent with the
ones in LIGO Hanford and LIGO Livingston as it points to a much heavier system.
We interpret the Virgo data in the context of further data quality issues.
While our results do not disprove the presence of spin-precession in GW200129,
we argue that any such inference is contingent upon the statistical and
systematic uncertainty of the glitch mitigation. Our study highlights the role
of data quality investigations when inferring subtle effects such as
spin-precession for short signals such as the ones produced by high-mass
systems.",2206.11932v2
2022-09-19,Andreev bound states at boundaries of polarized 2D Fermi superfluids with s-wave pairing and spin-orbit coupling,"A topological superfluid phase characterized by an emergent chiral-p-wave
pair potential is expected to form in a two-dimensional Fermi superfluid
subject to s-wave pairing, spin-orbit coupling and a large-enough Zeeman
splitting. Andreev bound states appear at phase boundaries, including Majorana
zero modes whose existence is assured by the bulk-boundary correspondence
principle. Here we study the physical properties of these subgap-energy bound
states at step-like interfaces using the spin-resolved Bogoliubov-deGennes
mean-field formalism and assuming small spin-orbit coupling. Extending a
recently developed spin-projection technique based on Feshbach partitioning
[SciPost Phys. 5, 016 (2018)] combined with the Andreev approximation allows us
to obtain remarkably simple analytical expressions for the bound-state energies
as well as the majority and minority spin components of their wave functions.
Besides the vacuum boundary, where a majority-spin Majorana excitation is
encountered, we also consider the boundary between the topological and a
nontopological superfluid phase that can appear in a coexistence scenario due
to the first-order topological phase transition predicted for this system. At
this superfluid-superfluid interface, we find a localized chiral Majorana mode
hosted by the minority-spin sector. Our theory further predicts majority-spin
subgap-energy bound states similar to those found at a Josephson junction
between same-chirality p-wave superfluids. Their presence affects the Majorana
mode due to a coupling of minority and majority spin sectors only in the small
energy range where their spectra overlap. Our results may inform experimental
efforts aimed at realizing and characterizing unconventional Majorana
quasiparticles.",2209.08766v2
2023-02-14,Collapsar Black Holes are Likely Born Slowly Spinning,"Collapsing stars constitute the main black hole (BH) formation channel, and
are occasionally associated with the launch of relativistic jets that power $
\gamma $-ray bursts (GRBs). Thus, collapsars offer an opportunity to infer the
natal (before spin-up/down by accretion) BH spin directly from observations. We
show that once the BH saturates with large-scale magnetic flux, the jet power
is dictated by the BH spin and mass accretion rate. Core-collapse simulations
by Halevi et al. 2023 and GRB observations favor stellar density profiles that
yield an accretion rate $ \dot{m} \approx 10^{-2} M_\odot~{\rm s^{-1}} $,
weakly dependent on time. This leaves the spin as the main factor that governs
the jet power. By comparing the jet power to characteristic GRB luminosities,
we find that the majority of BHs associated with jets are likely born slowly
spinning with a dimensionless spin $ a \simeq 0.2 $, or $ a \lesssim 0.5 $ for
wobbling jets, with the main uncertainty originating in the unknown $ \gamma
$-ray radiative efficiency. This result could be applied to the entire
core-collapse BH population, unless an anti-correlation between the stellar
magnetic field and angular momentum is present. In a companion paper,
Jacquemin-Ide et al. 2023, we show that regardless of the natal spin, the
extraction of BH rotational energy leads to spin-down to $ a \lesssim 0.2 $,
consistent with gravitational-wave observations. We verify our results by
performing the first 3D general relativistic magnetohydrodynamic simulations of
collapsar jets with characteristic GRB energies, powered by slowly spinning
BHs. We find that jets of typical GRB power struggle to escape from the star,
providing the first numerical indication that many jets fail to generate a GRB.",2302.07271v2
2006-05-23,Fermion nodes and nodal cells of noninteracting and interacting fermions,"A fermion node is subset of fermionic configurations for which a real wave
function vanishes due to the antisymmetry and the node divides the
configurations space into compact nodal cells (domains). We analyze the
properties of fermion nodes of fermionic ground state wave functions for a
number of systems. For several models we demonstrate that noninteracting
spin-polarized fermions in dimension two and higher have closed-shell ground
state wave functions with the minimal two nodal cells for any system size and
we formulate a theorem which sumarizes this result. The models include periodic
fermion gas, fermions on the surface of a sphere, fermions in a box. We prove
the same property for atomic states with up to 3d half-filled shells. Under
rather general assumptions we then derive that the same is true for unpolarized
systems with arbitrarily weak interactions using Bardeen-Cooper-Schrieffer
(BCS) variational wave function. We further show that pair correlations
included in the BCS wave function enable singlet pairs of particles to wind
around the periodic box without crossing the node pointing towards the
relationship of nodes to transport and many-body phases such as
superconductivity. Finally, we point out that the arguments extend also to
fermionic temperature dependent/imaginary-time density matrices. The results
reveal fundamental properties of fermion nodal structures and provide new
insights for accurate constructions of wave functions and density matrices in
quantum and path integral Monte Carlo methods.",0605550v1
2006-12-16,Learning about compact binary merger: the interplay between numerical relativity and gravitational-wave astronomy,"Activities in data analysis and numerical simulation of gravitational waves
have to date largely proceeded independently. In this work we study how
waveforms obtained from numerical simulations could be effectively used within
the data analysis effort to search for gravitational waves from black hole
binaries. We propose measures to quantify the accuracy of numerical waveforms
for the purpose of data analysis and study how sensitive the analysis is to
errors in the waveforms. We estimate that ~100 templates (and ~10 simulations
with different mass ratios) are needed to detect waves from non-spinning binary
black holes with total masses in the range 100 Msun < M < 400 Msun using
initial LIGO. Of course, many more simulation runs will be needed to confirm
that the correct physics is captured in the numerical evolutions. From this
perspective, we also discuss sources of systematic errors in numerical waveform
extraction and provide order of magnitude estimates for the computational cost
of simulations that could be used to estimate the cost of parameter space
surveys. Finally, we discuss what information from near-future numerical
simulations of compact binary systems would be most useful for enhancing the
detectability of such events with contemporary gravitational wave detectors and
emphasize the role of numerical simulations for the interpretation of eventual
gravitational-wave observations.",0612100v1
2009-08-21,Effect of coexisting order of various form and wave vector on low-temperature thermal conductivity in d-wave superconductors,"In light of recent experimental evidence of density wave order in the
cuprates, we consider a phenomenological model of a d-wave superconductor with
coexisting charge, spin or pair density wave order of various form and wave
vector. We study the evolution of the nodal structure of the quasiparticle
energy spectrum as a function of the amplitude of the coexisting order and
perform diagrammatic linear response calculations of the low-temperature
(universal-limit) thermal conductivity. The work described herein expands upon
our past studies, which focused on a particular unit-cell-doubling charge
density wave, generalizing our techniques to a wider class of coexisting order.
We find that the question of whether the nodes of the d-wave superconductor
survive amidst a reasonable level of coexisting order is sensitive to the form
and wave vector of the order. However, in cases where the nodes do become
gapped, we identify a signature of the approach to this nodal transition, in
the low-temperature thermal conductivity, that appears to be quite general. The
amplitude of this signature is found to be disorder-dependent, which suggests a
connection between the presence of coexisting order in the underdoped cuprates
and recent observations of deviations from universal (disorder-independent)
thermal conductivity in the underdoped regime.",0908.3168v1
2010-06-07,Simulations of Detonation Wave Propagation in Rectangular Ducts Using a Three-Dimensional WENO Scheme,"This paper reports high resolution simulations using a fifth-order weighted
essentially non-oscillatory (WENO) scheme with a third order TVD Runge-Kutta
time stepping method to examine the features of detonation front and physics in
square ducts. The simulations suggest that two and three-dimensional detonation
wave front formations are greatly enhanced by the presence of transverse waves.
The motion of transverse waves generates triple points (zones of high pressure
and large velocity coupled together), which cause the detonation front to
become locally overdriven and thus form ""hot spots"". The transversal motion of
these hot spots maintains the detonation to continuously occur along the whole
front in two and three-dimensions. The present simulations indicate that the
influence of the transverse waves on detonation is more profound in three
dimensions and the pattern of quasi-steady detonation fronts also depends on
the duct size. For a narrow duct (4LX4L where L is the half reaction length),
the detonation front displays a distinctive ""spinning"" motion about the axial
direction with a well-defined period. For a wider duct (20LX20L), the
detonation front exhibits a ""rectangular mode"" periodically, with the front
displaying ""convex"" and ""concave"" shapes one following the other and the
transverse waves on the four walls being partly out-of-phase with each other.",1006.1218v1
2013-07-30,Corotation resonance and overstable oscillations in black-hole accretion discs: general-relativistic calculations,"We study the dynamics of spiral waves and oscillation modes in relativistic
rotating discs around black holes. Generalizing the Newtonian theory, we show
that wave absorption can take place at the corotation resonance, where the
pattern frequency of the wave matches the background disc rotation rate. We
derive the general relativistic expression for the disc vortensity (vorticity
divided by surface density), which governs the behaviour of density
perturbation near corotation. Depending on the gradient of the generalized disc
vortensity, corotational wave absorption can lead to the amplification or
damping of the spiral wave. We apply our general theory of relativistic wave
dynamics to calculate the non-axisymmetric inertial-acoustic modes (also called
p-modes) trapped in the inner-most region of a black hole accretion disc.
Because general relativity changes the profiles of the radial epicyclic
frequency and disc vortensity near the inner disc edge close to the black hole,
these p-modes can become overstable under appropriate conditions. We present
the numerical results of the frequencies and growth rates of p-modes for
various black hole spin and model disc parameters (the surface density profile
and sound speed), and discuss their implications for understanding the
enigmatic high-frequency quasi-periodic oscillations observed in black hole
X-ray binaries.",1307.8077v1
2013-12-20,Hall Viscosity of Hierarchical Quantum Hall States,"Using methods based on conformal field theory, we construct model wave
functions on a torus with arbitrary flat metric for all chiral states in the
abelian quantum Hall hierarchy. These functions have no variational parameters,
and they transform under the modular group in the same way as the
multicomponent generalizations of the Laughlin wave functions. Assuming the
absence of Berry phases upon adiabatic variations of the modular parameter
$\tau$, we calculate the quantum Hall viscosity and find it to be in agreement
with the formula, given by Read, which relates the viscosity to the average
orbital spin of the electrons. For the filling factor $\nu=2/5$ Jain state,
which is at the second level in the hierarchy, we compare our model wave
function with the numerically obtained ground state of the Coulomb interaction
Hamiltonian in the lowest Landau level, and find very good agreement in a large
region of the complex $\tau$-plane. For the same example, we also numerically
compute the Hall viscosity and find good agreement with the analytical result
for both the model wave function and the numerically obtained Coulomb wave
function. We argue that this supports the notion of a generalized plasma
analogy that would ensure that wave functions obtained using the conformal
field theory methods do not acquire Berry phases upon adiabatic evolution.",1312.6038v2
2014-07-31,Gravitational waves from rapidly rotating neutron stars,"Rapidly rotating neutron stars in Low Mass X-ray Binaries have been proposed
as an interesting source of gravitational waves. In this chapter we present
estimates of the gravitational wave emission for various scenarios, given the
(electromagnetically) observed characteristics of these systems. First of all
we focus on the r-mode instability and show that a 'minimal' neutron star model
(which does not incorporate exotica in the core, dynamically important magnetic
fields or superfluid degrees of freedom), is not consistent with observations.
We then present estimates of both thermally induced and magnetically sustained
mountains in the crust. In general magnetic mountains are likely to be
detectable only if the buried magnetic field of the star is of the order of
$B\approx 10^{12}$ G. In the thermal mountain case we find that gravitational
wave emission from persistent systems may be detected by ground based
interferometers. Finally we re-asses the idea that gravitational wave emission
may be balancing the accretion torque in these systems, and show that in most
cases the disc/magnetosphere interaction can account for the observed spin
periods.",1407.8254v1
2014-08-12,Fermions and gravitational gyrotropy,"In conventional general relativity without torsion, high-frequency
gravitational waves couple to the chiral number density of spin one-half
quanta: the polarization of the waves is rotated by $2\pi N_5 {\ell_{\rm
Pl}^2}$, where $N_5$ is the chiral column density and $\ell_{\rm Pl}$ is the
Planck length. This means that if a primordial distribution of gravitational
waves with E-E or B-B correlations passed through a chiral density of fermions
in the very early Universe, an E-B correlation will be generated. This in turn
will give rise to E-B and T-B correlations in the cosmic microwave background
(CMB). Less obviously but more primitively, the condition Albrecht called
""cosmic coherence"" would be violated, changing the restrictions on the class of
admissible cosmological gravitational waves. This altered class of waves would,
generally speaking, probe earlier physics than do the conventional waves; their
effects on the CMB would be most pronounced for low ($\lesssim 100$)
multipoles. Rough estimates indicate that if the tensor-to-scalar ratio is less
than about $10^{-2}$, it will be hard to constrain a spatially homogeneous
primordial $N_5$ by present data.",1408.2729v2
2016-04-27,Fast and Accurate Inference on Gravitational Waves from Precessing Compact Binaries,"Inferring astrophysical information from gravitational waves emitted by
compact binaries is one of the key science goals of gravitational-wave
astronomy. In order to reach the full scientific potential of
gravitational-wave experiments we require techniques to mitigate the cost of
Bayesian inference, especially as gravitational-wave signal models and analyses
become increasingly sophisticated and detailed. Reduced order models (ROMs) of
gravitational waveforms can significantly reduce the computational cost of
inference by removing redundant computations. In this paper we construct the
first reduced order models of gravitational-wave signals that include the
effects of spin-precession, inspiral, merger, and ringdown in compact object
binaries, and which are valid for component masses describing binary neutron
star, binary black hole and mixed binary systems. This work utilizes the
waveform model known as ""IMRPhenomPv2"". Our ROM enables the use of a fast
reduced order quadrature (ROQ) integration rule which allows us to approximate
Bayesian probability density functions at a greatly reduced computational cost.
We find that the ROQ rule can be used to speed up inference by factors as high
as 300 without introducing systematic bias. This corresponds to a reduction in
computational time from around half a year to a half a day, for the longest
duration/lowest mass signals. The ROM and ROQ rule are available with the main
inference library of the LIGO Scientific Collaboration, LALInference.",1604.08253v2
2016-06-29,Orbital angular momentum of scalar field generated by gravitational scatterings,"It has been expected that astronomical observations to detect the orbital
angular momenta of electromagnetic waves may give us a new insight into
astrophysics. Previous works pointed out the possibility that a rotating black
hole can produce orbital angular momenta of electromagnetic waves through
gravitational scattering, and the spin parameter of the black hole can be
measured by observing them. However, the mechanism how the orbital angular
momentum of the electromagnetic wave is generated by the gravitational
scattering has not been clarified sufficiently. In this paper, in order to
understand it from a point of view of gravitational lensing effects, we
consider an emitter which radiates a spherical wave of the real massless scalar
field and study the deformation of the scalar wave by the gravitational
scattering due to a black hole by invoking the geometrical optics
approximation. We show that the frame dragging caused by the rotating black
hole is not a necessary condition for generating the orbital angular momentum
of the scalar wave. However, its components parallel to the direction cosines
of images appear only if the black hole is rotating.",1606.09217v2
2018-06-04,Towards a systematically improvable many-body description of antiferromagnetic iron oxide,"We report variational and fixed-node diffusion quantum Monte Carlo (QMC)
calculations of anti-ferromagnetic iron oxide (FeO) in the ground state B1
crystal structure. The goal of this study was a systematic investigation of the
sensitivity of several ground state properties to a variety of QMC wave
function generation techniques including advanced wave functions such as
multi-determinant expansions and backflow transformations. We found that the
predicted lattice distortion was largely controlled by the choice of single
particle orbitals used to construct the wave function, rather than by
subsequent wave function optimization techniques within QMC. However, the
absolute magnetic moment was remarkably insensitive to the method of wave
function construction. QMC estimates of total spin density indicate that in
addition to strong electronic correlation of the Fe $3d$ states, charge
transfer may be an important but challenging piece of physics to accurately
capture within existing QMC methods. Finally, we highlight the need for
advanced and systematically improvable many-body wave functions suitable for
accurately describing challenging real systems.",1806.01383v2
2018-07-17,Probing the formation of the seeds of supermassive black holes with gravitational waves,"The existence of black holes in the intermediate mass interval between one
hundred and ten thousand solar masses, filling the gap between the stellar and
the supermassive black holes is a key prediction to explain the origin of
luminous QSOs at redshifts as large as seven. There is a sheer difficulty in
forming giant black holes of billion suns in less than one billion years. This
has led to the concept of seed black holes. They are high redshift intermediate
mass black holes that formed during cosmic dawn. Seeds are a transient
population, which later grew massive through episodes of accretion and mergers.
In this chapter we explore the possibility of discovering seed black holes and
track their growth across all cosmic epoch, by detecting the gravitational wave
signal they emit at the time of their coalescence, when they pair to form close
binaries. We show that the ESA LISA mission for the detection of low frequency
gravitational waves will be paramount in granting this insight. Gravitational
waves travel unimpeded through the cosmos and carry exquisite information on
the masses and spins of the merging black holes. To this purpose we introduce
key concepts on the gravitational wave emission from binaries, describing
briefly their formation pathway during halo mergers and galaxy collisions.",1807.06967v1
2018-10-09,Experimental observation of hybrid TE-TM polarized surface waves supported by hyperbolic metasurface,"Hyperbolic metasurfaces have gained significant attention due to their
extraordinary electromagnetic properties to control propagating plane waves,
but the excitation and propagation of the surface plasmon-polaritons at
hyperbolic metasurfaces, called hyperbolic plasmons, have been experimentally
observed just recently. However, the advantages of the hyperbolic plasmons,
such as hybrid TE-TM polarization discussed below, are not yet fully revealed
and analyzed. In this paper we focus on the numerical and experimental
characterization of surface waves in the frequency range from 2 to 8 GHz
supported by a hyperbolic metasurface composed of anisotropic metallic
Jerusalem crosses printed on a thin dielectric substrate. We show different
shapes of equal frequency contours, which correspond to a plethora of
excitation and propagation regimes of surface waves. The principal novelty of
this work consists in the experimental demonstration of the surface waves with
a hybrid, i.e. mixed TE-TM, polarization. Surface waves with a hybrid
polarization are the promising tool in a number of applications and phenomena
including polarization converters, plasmonic sensors, plasmon steering over a
surface, optical forces, spin-orbit photonics, and highlight the impact for the
on-chip and planar networks.",1810.03910v1
2020-03-13,"Semi-relativistic (e,2e) study with twisted electron beam on Cu and Ag","In this communication, we report our calculations of Triple Differential
Cross-Section (TDCS) for the relativistic (e,2e) process with a twisted
electron beam on Cu and Ag atomic targets in coplanar asymmetric geometry mode.
The theoretical formalism has been developed in the first Born approximation
(FBA) in which we use the Dirac plane wave as well as the twisted electron wave
for the incident electron beam to study the effect of various parameters of the
twisted electron beam on the (e,2e) process. We use Dirac plane wave, semi
relativistic Coulomb wave and Darwin wave function for the scattered, ejected
and K-shell electron respectively. We compare the angular profiles of the TDCS
of the twisted electron impact (e,2e) process with that of the plane wave. We
segregate the TDCS for charge-charge interaction and current-current
interaction with their interference term and study the effect of different
parameters of the twisted electron beam on them. The study is also extended to
the macroscopic Cu and Ag targets to further investigate the effect of the
opening angle of the twisted electron beam on TDCS. The spin asymmetry in TDCS
caused by polarized incident electron beam is also studied to elucidate the
effects of the twisted electron beam on the (e,2e) process.",2003.06459v2
2003-12-05,High magnetic field induced charge density wave states in a quasi-one dimensional organic conductor,"We have measured the high field magnetoresistence and magnetization of
quasi-one- dimensional (Q1D) organic conductor (Per)2Pt(mnt)2 (where Per =
perylene and mnt = maleonitriledithiolate), which has a charge density wave
(CDW) ground state at zero magnetic field below 8 K. We find that the CDW
ground state is suppressed with moderate magnetic fields of order 20 T, as
expected from a mean field theory treatment of Pauli effects[W. Dieterich and
P. Fulde, Z. Physik 265, 239 - 243 (1973)]. At higher magnetic fields, a new,
density wave state with sub-phases is observed in the range 20 to 50 T, which
is reminiscent of the cascade of field induced, quantized, spin density wave
phases (FISDW) observed in the Bechgaard salts. The new density wave state,
which we tenatively identify as a field induced charge density wave state
(FICDW), is re-entrant to a low resistance state at even higher fields, of
order 50 T and above. Unlike the FISDW ground state, the FICDW state is only
weakly orbital, and appears for all directions of magnetic field. Our findings
are substantiated by electrical resistivity, magnetization, thermoelectric, and
Hall measurements. We discuss our results in light of theoretical work
involving magnetic field dependent Q1D CDW ground states in high magnetic
fields [D. Zanchi, A. Bjelis, and G. Montambaux, Phys. Rev. B 53, (1996)1240;
A. Lebed, JETP Lett. 78,138(2003)].",0312172v1
2019-01-25,Gravitational waves from dynamical tides in white dwarf binaries,"We study the effect of tidal forcing on gravitational wave signals from
tidally relaxed white dwarf pairs in the LISA, DECIGO and BBO frequency band
($0.1-100\,{\rm mHz}$). We show that for stars not in hydrostatic equilibrium
(in their own rotating frames), tidal forcing will result in energy and angular
momentum exchange between the orbit and the stars, thereby deforming the orbit
and producing gravitational wave power in harmonics not excited in perfectly
circular synchronous binaries. This effect is not present in the usual
orbit-averaged treatment of the equilibrium tide, and is analogous to transit
timing variations in multiplanet systems. It should be present for all LISA
white dwarf pairs since gravitational waves carry away angular momentum faster
than tidal torques can act to synchronize the spins, and when mass transfer
occurs as it does for at least eight LISA verification binaries. With the
strain amplitudes of the excited harmonics depending directly on the density
profiles of the stars, gravitational wave astronomy offers the possibility of
studying the internal structure of white dwarfs, complimenting information
obtained from asteroseismology of pulsating white dwarfs. Since the vast
majority of white-dwarf pairs in this frequency band are expected to be in the
quasi-circular state, we focus here on these binaries, providing general
analytic expressions for the dependence of the induced eccentricity and strain
amplitudes on the stellar apsidal motion constants and their radius and mass
ratios. Tidal dissipation and gravitation wave damping will affect the results
presented here and will be considered elsewhere.",1901.09045v2
2019-12-31,Persistent gravitational wave observables: Nonlinear plane wave spacetimes,"In the first paper in this series, we introduced ""persistent gravitational
wave observables"" as a framework for generalizing the gravitational wave memory
effect. These observables are nonlocal in time and nonzero in the presence of
gravitational radiation. We defined three specific examples of persistent
observables: a generalization of geodesic deviation that allowed for arbitrary
acceleration, a holonomy observable involving a closed curve, and an observable
that can be measured using a spinning test particle. For linearized plane
waves, we showed that our observables could be determined just from one, two,
and three time integrals of the Riemann tensor along a central worldline, when
the observers follow geodesics. In this paper, we compute these three
persistent observables in nonlinear plane wave spacetimes, and we find that the
fully nonlinear observables contain effects that differ qualitatively from the
effects present in the observables at linear order. Many parts of these
observables can be determined from two functions, the transverse Jacobi
propagators, and their derivatives (for geodesic observers). These functions,
at linear order in the spacetime curvature, reduce to the one, two, and three
time integrals of the Riemann tensor mentioned above.",1912.13449v2
2021-01-20,Protected Long-Distance Guiding of Hypersound Underneath a Nano-Corrugated Surface,"Within a new paradigm for communications on the nanoscale, high-frequency
surface acoustic waves are becoming effective data carrier and encoder. On-chip
communications require acoustic wave propagation along nano-corrugated surfaces
which strongly scatter traditional Rayleigh waves. Here we propose the delivery
of information using subsurface acoustic waves with hypersound frequencies ~20
GHz, which is a nanoscale analogue of subsurface sound waves in the ocean. A
bunch of subsurface hypersound modes is generated by pulsed optical excitation
in a multilayer semiconductor structure with a metallic nanograting on top. The
guided hypersound modes propagate coherently beneath the nanograting, retaining
the surface imprinted information, on a distance of more than 50 {\mu}m which
essentially exceeds the propagation length of Rayleigh waves. The concept is
suitable for interfacing single photon emitters, such as buried quantum dots,
carrying coherent spin excitations in magnonic devices, and encoding the
signals for optical communications at the nanoscale.",2101.08189v1
2021-01-27,Modeling Solar Wind Variations over an 11-yr Cycle with Alfvén Wave Dissipation: a Parameter Study,"We study the behaviour and properties of the solar wind using a 2.5D Alfv\'en
wave driven wind model. We first systematically compare the results of an
Alfv\'en wave (AW) driven wind model with a polytropic approach. Polytropic
magnetohydrodynamic wind models are thermally driven, while Alfv\'en waves act
as additional acceleration and heating mechanisms in the Alfv\'en wave driven
model. We confirm that an AW-driven model is required to reproduce the observed
bimodality of slow and fast solar winds. We are also able to reproduce the
observed anti-correlation between the terminal wind velocity and the coronal
source temperature with the AW-driven wind model. We also show that the wind
properties along an eleven-year cycle differ significantly from one model to
the other. The AW-driven model again shows the best agreement with
observational data. Indeed, solar surface magnetic field topology plays an
important role in the Alfv\'en wave driven wind model, as it enters directly
into the input energy sources via the Poynting flux. On the other hand, the
polytropic wind model is driven by an assumed pressure gradient; thus it is
relatively less sensitive to the surface magnetic field topology. Finally, we
note that the net torque spinning down the Sun exhibits the same trends in the
two models, showing that the polytropic approach still captures correctly the
essence of stellar winds.",2101.11511v1
2021-12-21,"Mass spectra, wave functions and mixing effects of the $(bcq)$ baryon","Mass spectra and wave functions of the $J^P=\frac{1}{2}^+$ $(bcq)$ baryons
are calculated by the relativistic Bethe-Salpeter equation\,(BSE) with
considering the mixing effects between the $1^+$ and $0^+$ $(bc)$-diquarks
inside. Based on the diquark picture, the three-body problem of baryons is
transformed into two two-body problems. The BSE and wave functions of the $0^+$
diquark are given, and then solved numerically to obtain the effective mass
spectra and form factors. Also we present the wave functions at zero point for
the $(bc)$-diquark. Considering the obtained diquark form factors, the $(bcq)$
baryons are then described by the BSE as the bound state of a diquark and a
light quark, where the interaction kernel includes the inner transitions
between the $0^+$ and $1^+$ diquarks. The general wave function of the
$\frac{1}{2}^+$ $(bcq)$ baryons is constructed and solved to obtain the
corresponding mass spectra. Especially, by using the obtained wave functions,
the mixing effects between $\Xi_{bc}(\Omega_{bc})$ and
$\Xi_{bc}'(\Omega'_{bc})$ in ground states are computed and determined to be
small ($\sim \!1\%$). The numerical results indicate that it is a good choice
to take $\Xi_{bc}$ and $\Xi'_{bc}$ as the baryon states with the inside
$(bc)$-diquarks occupying the definite spin.",2112.10966v1
2022-01-21,Quasilinear theory for inhomogeneous plasma,"This paper presents quasilinear theory (QLT) for classical plasma interacting
with inhomogeneous turbulence. The particle Hamiltonian is kept general; for
example, relativistic, electromagnetic, and gravitational effects are subsumed.
A Fokker--Planck equation for the dressed 'oscillation-center' distribution is
derived from the Klimontovich equation and captures quasilinear diffusion,
interaction with the background fields, and ponderomotive effects
simultaneously. The local diffusion coefficient is manifestly
positive-semidefinite. Waves are allowed to be off-shell (i.e. not constrained
by a dispersion relation), and a collision integral of the Balescu--Lenard type
emerges in a form that is not restricted to any particular Hamiltonian. This
operator conserves particles, momentum, and energy, and it also satisfies the
H-theorem, as usual. As a spin-off, a general expression for the spectrum of
microscopic fluctuations is derived. For on-shell waves, which satisfy a
quasilinear wave-kinetic equation, the theory conserves the momentum and energy
of the wave--plasma system. The action of nonresonant waves is also conserved,
unlike in the standard version of QLT. Dewar's oscillation-center QLT of
electrostatic turbulence (1973, Phys. Fluids 16, 1102) is proven formally as a
particular case and given a concise formulation. Also discussed as examples are
relativistic electromagnetic and gravitational interactions, and QLT for
gravitational waves is proposed.",2201.08562v5
2022-07-26,The effects of nonlinearities on tidal flows in the convective envelopes of rotating stars and planets in exoplanetary systems,"In close exoplanetary systems, tidal interactions drive orbital and spin
evolution of planets and stars over long timescales. Tidally-forced inertial
waves (restored by the Coriolis acceleration) in the convective envelopes of
low-mass stars and giant gaseous planets contribute greatly to the tidal
dissipation when they are excited and subsequently damped (e.g. through viscous
friction), especially early in the life of a system. These waves are known to
be subject to nonlinear effects, including triggering differential rotation in
the form of zonal flows. In this study, we use a realistic tidal body forcing
to excite inertial waves through the residual action of the equilibrium tide in
the momentum equation for the waves. By performing 3D nonlinear hydrodynamical
simulations in adiabatic and incompressible convective shells, we investigate
how the addition of nonlinear terms affects the tidal flow properties, and the
energy and angular momentum redistribution. In particular, we identify and
justify the removal of terms responsible for unphysical angular momentum
evolution observed in a previous numerical study. Within our new set-up, we
observe the establishment of strong cylindrically-sheared zonal flows, which
modify the tidal dissipation rates from prior linear theoretical predictions.
We demonstrate that the effects of this differential rotation on the waves
neatly explains the discrepancies between linear and nonlinear dissipation
rates in many of our simulations. We also highlight the major role of both
corotation resonances and parametric instabilities of inertial waves, which are
observed for sufficiently high tidal forcing amplitudes or low viscosities, in
affecting the tidal flow response.",2207.12780v1
2022-08-24,Impact of the wave-like nature of Proca stars on their gravitational-wave emission,"We present a systematic study of the dynamics and gravitational-wave emission
of head-on collisions of spinning vector boson stars, known as Proca stars. To
this aim we build a catalogue of about 800 numerical-relativity simulations of
such systems. We find that the wave-like nature of bosonic stars has a large
impact on the gravitational-wave emission. In particular, we show that the
initial relative phase $\Delta \epsilon =\epsilon_1-\epsilon_2$ of the two
complex fields forming the stars (or equivalently, the relative phase at
merger) strongly impacts both the emitted gravitational-wave energy and the
corresponding mode structure. This leads to a non-monotonic dependence of the
emission on the frequency of the secondary star $\omega_2$, for fixed frequency
$\omega_1$ of the primary. This phenomenology, which has not been found for the
case of black-hole mergers, reflects the distinct ability of the Proca field to
interact with itself in both constructive and destructive manners. We postulate
this may serve as a smoking gun to shed light on the possible existence of
these objects.",2208.11717v3
2023-02-08,Controlled non-autonomous matter-wave solitons in spinor Bose-Einstein condensates with spatiotemporal modulation,"To study controlled evolution of non-autonomous matter-wave solitons in
spinor Bose-Einstein condensates with spatiotemporal modulation, we focus on a
system of three coupled Gross-Pitaevskii (GP) equations with
space-time-dependent external potentials and temporally modulated gain/loss
distributions. An integrability condition and a non-isospectral Lax pair for
the coupled GP equations are obtained. Using it, we derive an infinite set of
dynamical invariants, the first two of which are the mass and momentum. The
Darboux transform is used to generate one- and two-soliton solutions. Under the
action of different external potentials and gain/loss distributions, various
solutions for controlled non-autonomous matter-wave solitons of both
ferromagnetic and polar types are obtained, such as self-compressed, snake-like
and stepwise solitons, and as well as breathers. In particular, the formation
of states resembling rogue waves, under the action of a sign-reversible
gain-loss distribution, is demonstrated too. Shape-preserving and changing
interactions between two non-autonomous matter-wave solitons and bound states
of solitons are addressed too. In this context, spin switching arises in the
polar-ferromagnetic interaction. Stability of the non-autonomous matter-wave
solitons is verified by means of systematic simulations of their perturbed
evolution.",2302.04146v1
2023-03-02,VARAHA: A Fast Non-Markovian sampler for estimating Gravitational-Wave posteriors,"This article introduces VARAHA, an open-source, fast, non-Markovian sampler
for estimating gravitational-wave posteriors. VARAHA differs from existing
Nested sampling algorithms by gradually discarding regions of low likelihood,
rather than gradually sampling regions of high likelihood. This alternative
mindset enables VARAHA to freely draw samples from anywhere within the
high-likelihood region of the parameter space, allowing for analyses to
complete in significantly fewer cycles. This means that VARAHA can
significantly reduce both the wall and CPU time of all analyses. VARAHA offers
many benefits, particularly for gravitational-wave astronomy where Bayesian
inference can take many days, if not weeks, to complete. For instance, VARAHA
can be used to estimate accurate sky locations, astrophysical probabilities and
source classifications within minutes, which is particularly useful for
multi-messenger follow-up of binary neutron star observations; VARAHA localises
GW170817 $\sim 30$ times faster than LALInference. Although only aligned-spin,
dominant multipole waveform models can be used for gravitational-wave analyses,
it is trivial to extend this algorithm to include additional physics without
hindering performance. We envision VARAHA being used for gravitational-wave
studies, particularly estimating parameters using expensive waveform models,
analysing subthreshold gravitational-wave candidates, generating simulated data
for population studies, and rapid posterior estimation for binary neutron star
mergers.",2303.01463v2
2023-10-20,Perturbing the Stable Accretion Disk in Kerr and 4-D Einstein-Gauss-Bonnet Gravities:Comprehensive Analysis of Instabilities and Dynamics,"The study of a disturbed accretion disk holds great significance in the realm
of astrophysics. This is because such events play a crucial role in revealing
the nature of disk structure, the release of energy, and the generated shock
waves. Thus, they can help explain the causes of X-ray emissions observed in
black hole accretion disk systems. In this paper, we perturb the stable disk
formed by spherical accretion around Kerr and EGB black holes. This
perturbation reveals one- and two-armed spiral shock waves on the disk's
surface. We find a strong connection between these waves and the black hole's
spin parameter (a/M) and the EGB coupling constant ($\alpha$). Specifically, we
found that as alpha increases in the negative direction, the dynamics of the
disk and the waves become more chaotic. Additionally, we observe that the
angular momentum of the perturbing matter significantly affects mass accretion
and the oscillation of the arising shock waves. This allows us to observe
changes in QPOs frequencies. Particularly, perturbations with angular momentum
matches the observed C-type QPOs frequencies of GRS 1915 + 105 source. Thus, we
conclude that the possibility of the shock waves occurring within the vicinity
of GRS 1915 + 105 is substantial.",2310.13847v1
1998-02-02,First Principles Calculations of Charge and Spin Density Waves of sqr3-Adsorbates on Semiconductors,"We present ab-initio electronic structure results on the surface of sqr3
adsorbates. In particular, we address the issue of metal-insulator
instabilities, charge-density-waves (CDWs) or spin-density-waves (SDWs), driven
by partly filled surface states and their 2D Fermi surface, and/or by the onset
of magnetic instabilities. The focus is both on the newly discovered
commensurate CDW transitions in the Pb/Ge(111) and Sn/Ge(111) structures, and
on the puzzling semiconducting behavior of the Pb/Ge(111), K/Si(111):B and
SiC(0001) surfaces. In all cases, the main factor driving the instability
appears to be an extremely narrow surface state band. We have carried out so
far preliminary calculations for the Si/Si(111) surface, chosen as our model
system, within the gradient corrected local density (LDA+GC) and local spin
density (LSD+GC) approximations, with the aim of understanding the possible
interplay between 2D Fermi surface and electron correlations in the surface +
adsorbate system. Our spin- unrestricted results show that the sqr3
paramagnetic surface is unstable towards a commensurate SDW with periodicity
3x3 and magnetization 1/3.",9802017v1
1998-11-19,The Magnetic Origin of d-Wave High-Tc Superconductivity from Tunneling Spectroscopy Measurements on Bi2212 Single Crystals,"The complete scenario of high-Tc superconductivity based on experimental data
from electron-tunneling spectroscopy on underdoped, overdoped and Ni-doped
Bi2212 single crystals using a break-junction technique is presented. There are
two different types of superconductivity in cuprates: superconductivity due to
pairing of spinons on charged stripes and magnetic superconductivity mediated
by spin-waves. The coherent state of the spinon superconductivity is
established via the magnetic superconductivity. In NCCO, there is only the
spinon superconductivity and the coherent state is established due to the
Josephson coupling between charged stripes. Below Tc, we observe four different
gaps, namely, (i) a SDW gap due to antiferromagnetic correlations; (ii) a
superconducting gap due to spinon pairing; (iii) a d-wave magnetic
superconducting gap, and (iv) a small superconducting gap most likely having
g-wave symmetry. We show that the d-wave superconductivity is mediated by
spin-waves and the magnitude of the superconducting gap due to pairing of
spinons is larger than the magnitude of the d-wave gap, however, the d-wave gap
is more intense. The superconducting gap due to pairing of spinons most likely
has a s-wave symmetry. The maximum magnitudes of the SDW, the spinon and d-wave
gaps are located at (p/2, p/2), (p/2, p/2) and (p, 0) on the Fermi surface,
respectively. The d-g-wave superconductivity mediated by spin-waves can be
considered as a pairing of magnetic polarons. We formulate a theorem for
cuprates by analogy with the Anderson's theorem for classical superconductors.
The presented model of high-Tc superconductivity naturally explains other
experimental data.",9811284v3
2000-09-20,Neutron Scattering study of Sr_2Cu_3O_4Cl_2,"We report a neutron scattering study on the tetragonal compound
Sr_2Cu_3O_4Cl_2, which has two-dimensional (2D) interpenetrating Cu_I and
Cu_{II} subsystems, each forming a S=1/2 square lattice quantum Heisenberg
antiferromagnet (SLQHA). The mean-field ground state is degenerate, since the
inter-subsystem interactions are geometrically frustrated. Magnetic neutron
scattering experiments show that quantum fluctuations lift the degeneracy and
cause a 2D Ising ordering of the Cu_{II} subsystem. Due to quantum fluctuations
a dramatic increase of the Cu_I out-of-plane spin-wave gap is also observed.
The temperature dependence and the dispersion of the spin-wave energy are
quantitatively explained by spin-wave calculations which include quantum
fluctuations explicitly. The values for the nearest-neighbor superexchange
interactions between the Cu_I and Cu_{II} ions and between the Cu_{II} ions are
determined experimentally to be J_{I-II} = -10(2)meV and J_{II}= 10.5(5)meV,
respectively. Due to its small exchange interaction, J_{II}, the 2D dispersion
of the Cu_{II} SLQHA can be measured over the whole Brillouin zone with thermal
neutrons, and a novel dispersion at the zone boundary, predicted by theory, is
confirmed. The instantaneous magnetic correlation length of the Cu_{II} SLQHA
is obtained up to a very high temperature, T/J_{II}\approx 0.75. This result is
compared with several theoretical predictions as well as recent experiments on
the S=1/2 SLQHA.",0009314v2
2001-08-17,Magnetic and charge structures in itinerant-electron magnets: Coexistence of multiple SDW and CDW,"A theory of Kondo lattices is applied to studying possible magnetic and
charge structures of itinerant-electron antiferromagnets. Even helical spin
structures can be stabilized when the nesting of the Fermi surface is not sharp
and the superexchange interaction, which arises from the virtual exchange of
pair excitations across the Mott-Hubbard gap, is mainly responsible for
magnetic instability. Sinusoidal spin structures or spin density waves (SDW)
are only stabilized when the nesting of the Fermi surface is sharp enough and a
novel exchange interaction arising from that of pair excitations of
quasi-particles is mainly responsible for magnetic instability. In particular,
multiple SDW are stabilized when their incommensurate ordering wave-numbers
$\pm{\bf Q}$ are multiple; magnetizations of different $\pm{\bf Q}$ components
are orthogonal to each other in double and triple SDW when magnetic anisotropy
is weak enough. Unless $\pm 2{\bf Q}$ are commensurate, charge density waves
(CDW) with $\pm 2{\bf Q}$ coexist with SDW with $\pm{\bf Q}$. Because the
quenching of magnetic moments by the Kondo effect depends on local numbers of
electrons, the phase of CDW or electron densities is such that magnetic moments
are large where the quenching is weak. It is proposed that the so called stipe
order in cuprate-oxide high-temperature superconductors must be the coexisting
state of double incommensurate SDW and CDW.",0108270v1
2001-12-11,Slow relaxation experiments in disordered charge and spin density waves: collective dynamics of randomly distributed solitons,"We show that the dynamics of disordered charge density waves (CDWs) and spin
density waves (SDWs) is a collective phenomenon. The very low temperature
specific heat relaxation experiments are characterized by: (i) ``interrupted''
ageing (meaning that there is a maximal relaxation time); and (ii) a broad
power-law spectrum of relaxation times which is the signature of a collective
phenomenon. We propose a random energy model that can reproduce these two
observations and from which it is possible to obtain an estimate of the glass
cross-over temperature (typically $T_g \simeq 100 - 200$ mK). The broad
relaxation time spectrum can also be obtained from the solutions of two
microscopic models involving randomly distributed solitons. The collective
behavior is similar to domain growth dynamics in the presence of disorder and
can be described by the dynamical renormalization group that was proposed
recently for the one dimensional random field Ising model [D.S. Fisher, P. Le
Doussal and C. Monthus, Phys. Rev. Lett. {\bf 80}, 3539 (1998)]. The typical
relaxation time scales like $\tau^{\rm typ} \sim \tau_0 \exp{(T_g/T)}$. The
glass cross-over temperature $T_g$ related to correlations among solitons is
equal to the average energy barrier and scales like $T_g \sim 2 x \xi_0
\Delta$. $x$ is the concentration of defects, $\xi_0$ the correlation length of
the CDW or SDW and $\Delta$ the charge or spin gap.",0112182v2
2005-12-09,Molecular orbital calculations of two-electron states for P donor solid-state spin qubits,"We theoretically study the Hilbert space structure of two neighbouring P
donor electrons in silicon-based quantum computer architectures. To use
electron spins as qubits, a crucial condition is the isolation of the electron
spins from their environment, including the electronic orbital degrees of
freedom. We provide detailed electronic structure calculations of both the
single donor electron wave function and the two-electron pair wave function. We
adopted a molecular orbital method for the two-electron problem, forming a
basis with the calculated single donor electron orbitals. Our two-electron
basis contains many singlet and triplet orbital excited states, in addition to
the two simple ground state singlet and triplet orbitals usually used in the
Heitler-London approximation to describe the two-electron donor pair wave
function. We determined the excitation spectrum of the two-donor system, and
study its dependence on strain, lattice position and inter donor separation.
This allows us to determine how isolated the ground state singlet and triplet
orbitals are from the rest of the excited state Hilbert space. In addition to
calculating the energy spectrum, we are also able to evaluate the exchange
coupling between the two donor electrons, and the double occupancy probability
that both electrons will reside on the same P donor. These two quantities are
very important for logical operations in solid-state quantum computing devices,
as a large exchange coupling achieves faster gating times, whilst the magnitude
of the double occupancy probability can affect the error rate.",0512200v1
2006-03-31,Magnetic Excitations of Stripes and Checkerboards in the Cuprates,"We discuss the magnetic excitations of well-ordered stripe and checkerboard
phases, including the high energy magnetic excitations of recent interest and
possible connections to the ""resonance peak"" in cuprate superconductors. Using
a suitably parametrized Heisenberg model and spin wave theory, we study a
variety of magnetically ordered configurations, including vertical and diagonal
site- and bond-centered stripes and simple checkerboards. We calculate the
expected neutron scattering intensities as a function of energy and momentum.
At zero frequency, the satellite peaks of even square-wave stripes are
suppressed by as much as a factor of 34 below the intensity of the main
incommensurate peaks. We further find that at low energy, spin wave cones may
not always be resolvable experimentally. Rather, the intensity as a function of
position around the cone depends strongly on the coupling across the stripe
domain walls. At intermediate energy, we find a saddlepoint at $(\pi,\pi)$ for
a range of couplings, and discuss its possible connection to the ""resonance
peak"" observed in neutron scattering experiments on cuprate superconductors. At
high energy, various structures are possible as a function of coupling strength
and configuration, including a high energy square-shaped continuum originally
attributed to the quantum excitations of spin ladders. On the other hand, we
find that simple checkerboard patterns are inconsistent with experimental
results from neutron scattering.",0603829v3
1994-02-04,Gravitational Waves from Mergin Compact Binaries: How Accurately Can One Extract the Binary's Parameters from the Inspiral Waveform?,"The most promising source of gravitational waves for the planned detectors
LIGO and VIRGO are merging compact binaries, i.e., neutron star/neutron star
(NS/NS), neutron star/black hole (NS/BH), and black hole/black-hole (BH/BH)
binaries. We investigate how accurately the distance to the source and the
masses and spins of the two bodies will be measured from the gravitational wave
signals by the three detector LIGO/VIRGO network using ``advanced detectors''
(those present a few years after initial operation). The combination ${\cal M}
\equiv (M_1 M_2)^{3/5}(M_1 +M_2)^{-1/5}$ of the masses of the two bodies is
measurable with an accuracy $\approx 0.1\%-1\%$. The reduced mass is measurable
to $\sim 10\%-15\%$ for NS/NS and NS/BH binaries, and $\sim 50\%$ for BH/BH
binaries (assuming $10M_\odot$ BH's). Measurements of the masses and spins are
strongly correlated; there is a combination of $\mu$ and the spin angular
momenta that is measured to within $\sim 1\%$. We also estimate that distance
measurement accuracies will be $\le 15\%$ for $\sim 8\%$ of the detected
signals, and $\le 30\%$ for $\sim 60\%$ of the signals, for the LIGO/VIRGO
3-detector network.",9402014v1
2009-02-03,Optical and Raman spectroscopy studies on Fe-based superconductors,"A brief review of optical and Raman studies on the Fe-based superconductors
is given, with special emphasis on the competing phenomenon in this system.
Optical investigations on ReFeAsO (Re=rare-earth element) and AFe$_2$As$_2$
(A=alkaline-earth metal) families provide clear evidence for the gap formation
in the broken symmetry states, including the partial gaps in the spin-density
wave states of parent compounds, and the pairing gaps in the superconducting
states for doped compounds. Especially, the superconducting gap has an s-wave
pairing lineshape in hole-doped BaFe$_2$As$_2$. Optical phonons at zone center
detected by Raman and infrared techniques are classified for several Fe-based
compounds. Related issues, such as the electron-phonon coupling and the effect
of spin-density wave and superconducting transitions on phonons, are also
discussed. Meanwhile, open questions including the \emph{T}-dependent
mid-infrared peak at 0.6-0.7 eV, electronic correlation, and the
similarities/differences between high-\Tc cuprates and Fe-based superconductors
are also briefly discussed. Important results from other experimental probes
are compared with optical data to better understand the spin-density wave
properties, the superconductivity, and the multi-band character in Fe-based
compounds.",0902.0435v1
2009-03-16,Spin Waves and Magnetic Exchange Interactions in CaFe2As2,"Antiferromagnetism is relevant to high temperature (high-Tc)
superconductivity because copper oxide and iron arsenide high-Tc
superconductors arise from electron- or hole-doping of their antiferromagnetic
(AF) ordered parent compounds. There are two broad classes of explanation for
the phenomenon of antiferromagnetism: in the local moment picture, appropriate
for the insulating copper oxides, AF interactions are well described by a
Heisenberg Hamiltonian; while in the itinerant model, suitable for metallic
chromium, AF order arises from quasiparticle excitations of a nested Fermi
surface. There has been contradictory evidence regarding the microscopic origin
of the AF order in iron arsenide materials, with some favoring a localized
picture while others supporting an itinerant point of view. More importantly,
there has not even been agreement about the simplest effective ground state
Hamiltonian necessary to describe the AF order. Here we report inelastic
neutron scattering mapping of spin-wave excitations in CaFe2As2, a parent
compound of the iron arsenide family of superconductors. We find that the spin
waves in the entire Brillouin zone can be described by an effective
three-dimensional local moment Heisenberg Hamiltonian, but the large in-plane
anisotropy cannot. Therefore, magnetism in the parent compounds of iron
arsenide superconductors is neither purely local nor purely itinerant; rather
it is a complicated mix of the two.",0903.2686v1
2010-05-07,Quantum phase transitions of metals in two spatial dimensions: II. Spin density wave order,"We present a field-theoretic renormalization group analysis of Abanov and
Chubukov's model of the spin density wave transition in two dimensional metals.
We identify the independent field scale and coupling constant renormalizations
in a local field theory, and argue that the damping constant of spin density
wave fluctuations tracks the renormalization of the local couplings. The
divergences at two-loop order overdetermine the renormalization constants, and
are shown to be consistent with our renormalization scheme. We describe the
physical consequences of our renormalization group equations, including the
breakdown of Fermi liquid behavior near the ""hot spots"" on the Fermi surface.
In particular, we find that the dynamical critical exponent z receives
corrections to its mean-field value z = 2. At higher orders in the loop
expansion, we find infrared singularities similar to those found by S.-S. Lee
for the problem of a Fermi surface coupled to a gauge field. A treatment of
these singularities implies that an expansion in 1/N, (where N is the number of
fermion flavors) fails for the present problem. We also discuss the
renormalization of the pairing vertex, and find an enhancement which scales as
logarithm-squared of the energy scale. A similar enhancement is also found for
a modulated bond order which is locally an Ising-nematic order.",1005.1288v2
2010-06-06,Surface and bulk electronic structures of LaOFeAs studied by angle resolved photoemission spectroscopy,"The electronic structure of LaOFeAs, a parent compound of iron-arsenic
superconductors, is studied by angleresolved photoemission spectroscopy. By
examining its dependence on photon energy, polarization, sodium dosing and the
counting of Fermi surface volume, both the bulk and the surface contributions
are identified. We find that a bulk band moves toward high binding energies
below structural transition, and shifts smoothly across the spin density wave
transition by about 25 meV. Our data suggest the band reconstruction may play a
crucial role in the spin density wave transition, and the structural transition
is driven by the short range magnetic order. For the surface states, both the
LaO-terminated and FeAs-terminated components are revealed. Certain small band
shifts are verified for the FeAs-terminated surface states in the spin density
wave state, which is a reflection of the bulk electronic structure
reconstruction. Moreover, sharp quasiparticle peaks quickly rise at low
temperatures, indicating of drastic reduction of the scattering rate. A kink
structure in one of the surface band is shown to be possibly related to the
electron-phonon interactions.",1006.1107v1
2010-10-27,Three dimensional generalization of the $J_1$-$J_2$ Heisenberg model on a square lattice and role of the interlayer coupling $J_c$,"A possibility to describe magnetism in the iron pnictide parent compounds in
terms of the two-dimensional frustrated Heisenberg $J_1$-$J_2$ model has been
actively discussed recently. However, recent neutron scattering data has shown
that the pnictides have a relatively large spin wave dispersion in the
direction perpendicular to the planes. This indicates that the third dimension
is very important. Motivated by this observation we study the $J_1$-$J_2$-$J_c$
model that is the three dimensional generalization of the $J_1$-$J_2$
Heisenberg model for $S = 1/2$ and S = 1. Using self-consistent spin wave
theory we present a detailed description of the staggered magnetization and
magnetic excitations in the collinear state. We find that the introduction of
the interlayer coupling $J_c$ suppresses the quantum fluctuations and
strengthens the long range ordering. In the $J_1$-$J_2$-$J_c$ model, we find
two qualitatively distinct scenarios for how the collinear phase becomes
unstable upon increasing $J_1$. Either the magnetization or one of the spin
wave velocities vanishes. For $S = 1/2$ renormalization due to quantum
fluctuations is significantly stronger than for S=1, in particular close to the
quantum phase transition. Our findings for the $J_1$-$J_2$-$J_c$ model are of
general theoretical interest, however, the results show that it is unlikely
that the model is relevant to undoped pnictides.",1010.5551v2
2011-07-28,Identification and selection rules of the spin-wave eigen-modes in a normally magnetized nano-pillar,"We report on a spectroscopic study of the spin-wave eigen-modes inside an
individual normally magnetized two layers circular nano-pillar
(Permalloy$|$Copper$|$Permalloy) by means of a Magnetic Resonance Force
Microscope (MRFM). We demonstrate that the observed spin-wave spectrum
critically depends on the method of excitation. While the spatially uniform
radio-frequency (RF) magnetic field excites only the axially symmetric modes
having azimuthal index $\ell=0$, the RF current flowing through the
nano-pillar, creating a circular RF Oersted field, excites only the modes
having azimuthal index $\ell=+1$. Breaking the axial symmetry of the
nano-pillar, either by tilting the bias magnetic field or by making the pillar
shape elliptical, mixes different $\ell$-index symmetries, which can be excited
simultaneously by the RF current. Experimental spectra are compared to
theoretical prediction using both analytical and numerical calculations. An
analysis of the influence of the static and dynamic dipolar coupling between
the nano-pillar magnetic layers on the mode spectrum is performed.",1107.5699v2
2011-12-08,200 ps Vortex Core Reversal by Azimuthal Spin Waves,"Spin wave mediated vortex core reversal has been investigated by
time-resolved scanning transmission X-ray microscopy (STXM). Movies showing the
development of the spin wave and vortex core magnetization dynamics during
unidirectional vortex core reversal could be taken in Permalloy discs, 1.6 \mu
m in diameter and 50 nm thick, during excitation with rotating ac field bursts
of one period duration at 4.5 GHz and with amplitudes up to 4 mT.
Unidirectional switching is achieved by taking advantage of an asymmetry for CW
or CCW excitation caused by the gyrofield. The differences in the magnetization
dynamics due to this asymmetry could be imaged during continuous excitation
with multi-GHz rotating fields. All our experimental results are in good
agreement with micromagnetic simulations.
  In addition, for the sample geometry given above, simulations reveal a lower
limit of about 200 ps for the time of unidirectional vortex core switching,
which cannot be overcome by shortening the excitation length or by increasing
the excitation amplitude. We explain this limitation by the finite time needed
for an energy transfer of the global excitation towards the center of the
sample. Thus smaller samples will allow for much shorter vortex core reversal
times.",1112.1903v1
2012-04-10,The Out-of-Equilibrium Time-Dependent Gutzwiller Approximation,"We review the recently proposed extension of the Gutzwiller approximation, M.
Schiro' and M. Fabrizio, Phys. Rev. Lett. 105, 076401 (2010), designed to
describe the out-of-equilibrium time-evolution of a Gutzwiller-type variational
wave function for correlated electrons. The method, which is strictly
variational in the limit of infinite lattice-coordination, is quite general and
flexible, and it is applicable to generic non-equilibrium conditions, even far
beyond the linear response regime. As an application, we discuss the quench
dynamics of a single-band Hubbard model at half-filling, where the method
predicts a dynamical phase transition above a critical quench that resembles
the sharp crossover observed by time-dependent dynamical mean field theory. We
next show that one can actually define in some cases a multi-configurational
wave function combination of a whole set of mutually orthogonal Gutzwiller wave
functions. The Hamiltonian projected in that subspace can be exactly evaluated
and is equivalent to a model of auxiliary spins coupled to non-interacting
electrons, closely related to the slave-spin theories for correlated electron
models. The Gutzwiller approximation turns out to be nothing but the mean-field
approximation applied to that spin-fermion model, which displays, for any
number of bands and integer fillings, a spontaneous $Z_2$ symmetry breaking
that can be identified as the Mott insulator-to-metal transition.",1204.2175v1
2012-08-02,"Observation of a $J^{PC}=1^{-+}$ exotic signal in the $π^{-}π^{0}π^{0}$ system diffractively produced at COMPASS, and comparison to the charged decay mode","The COMPASS experiment at the CERN SPS features good charged particle
tracking and coverage by electromagnetic calorimetry, and our data provide
excellent opportunity for simultaneous observation of new states in two
different decay modes within the same experiment. The existence of the
spin-exotic $\pi_1(1600)$ resonance in the $\rho\pi$ decay channel is studied
for the first time in COMPASS in both decay modes of the diffractively produced
$(3\pi)^{-}$ system: $\pi^{-}p \rightarrow \pi^{-}\pi^{0}\pi^{0}p$ and
$\pi^{-}p \rightarrow \pi^{-}\pi^{+}\pi^{-}p$. A preliminary partial-wave
analysis (PWA) performed on the 2008 proton target data allows for a first
conclusive comparison of both $(3\pi)^{-}$ decay modes not only for main waves
but also for small ones, including the spin-exotic $1^{-+}$ wave. We find the
neutral versus charged mode results in good agreement with expectations from
isospin symmetry. Both, the intensities and the relative phases to well-known
resonances, are consistent for the neutral and the charged decay modes of the
$(3\pi)^{-}$ system. The status on the search for the spin-exotic $\pi_1(1600)$
resonance produced on a proton target is discussed.",1208.0474v1
2012-08-19,Visualizing the microscopic coexistence of spin density wave and superconductivity in underdoped NaFe1-xCoxAs,"Although the origin of high temperature superconductivity in the iron
pnictides is still under debate, it is widely believed that magnetic
interactions or fluctuations play an important role in triggering Cooper
pairing. Because of the relevance of magnetism to pairing, the question of
whether long range spin magnetic order can coexist with superconductivity
microscopically has attracted strong interests. The available experimental
methods used to answer this question are either bulk probes or local ones
without control of probing position, thus the answers range from mutual
exclusion to homogeneous coexistence. To definitively answer this question,
here we use scanning tunneling microscopy to investigate the local electronic
structure of an underdoped NaFe1-xCoxAs near the spin density wave (SDW) and
superconducting (SC) phase boundary. Spatially resolved spectroscopy directly
reveal both the SDW and SC gap features at the same atomic location, providing
compelling evidence for the microscopic coexistence of the two phases. The
strengths of the SDW and SC features are shown to anti correlate with each
other, indicating the competition of the two orders. The microscopic
coexistence clearly indicates that Cooper pairing occurs when portions of the
Fermi surface (FS) are already gapped by the SDW order. The regime TC < T <
TSDW thus show a strong resemblance to the pseudogap phase of the cuprates
where growing experimental evidences suggest a FS reconstruction due to certain
density wave order. In this phase of the pnictides, the residual FS has a
favorable topology for magnetically mediated pairing when the ordering moment
of the SDW is small.",1208.3842v1
2013-03-06,"I-Love-Q Relations in Neutron Stars and their Applications to Astrophysics, Gravitational Waves and Fundamental Physics","The exterior gravitational field of a slowly-rotating neutron star can be
characterized by its multipole moments, the first few being the neutron star
mass, moment of inertia, and quadrupole moment to quadratic order in spin. In
principle, all of these quantities depend on the neutron star's internal
structure, and thus, on unknown nuclear physics at supra-nuclear energy
densities. We here find relations between the moment of inertia, the Love
numbers and the quadrupole moment (I-Love-Q relations) that do not depend
sensitively on the neutron star's internal structure. Three important
consequences derive from these I-Love-Q relations. On an observational
astrophysics front, the measurement of a single member of the I-Love-Q trio
would automatically provide information about the other two, even when the
latter may not be observationally accessible. On a gravitational wave front,
the I-Love-Q relations break the degeneracy between the quadrupole moment and
the neutron-star spins in binary inspiral waveforms, allowing second-generation
ground-based detectors to determine the (dimensionless) averaged spin to
$\mathcal{O}(10)%$, given a sufficiently large signal-to-noise ratio detection.
On a fundamental physics front, the I-Love-Q relations allow for tests of
General Relativity in the neutron-star strong-field that are both theory- and
internal structure-independent. As an example, by combining gravitational-wave
and electromagnetic observations, one may constrain dynamical Chern-Simons
gravity in the future by more than 6 orders of magnitude more stringently than
Solar System and table-top constraints.",1303.1528v3
2014-05-03,Unidirectional sub-100 ps magnetic vortex core reversal,"The magnetic vortex structure, an important ground state configuration in
micron and sub-micron sized ferromagnetic thin film platelets, is characterized
by a curling in-plane magnetization and, in the center, a minuscule region with
out-of-plane magnetization, the vortex core, which points either up or down. It
has already been demonstrated that the vortex core polarity can be reversed
with external AC magnetic fields, frequency-tuned to the (sub-GHz) gyrotropic
eigenmode or to (multi-GHz) azimuthal spin wave modes, where reversal times in
the sub-ns regime can be realized. This fast vortex core switching may also be
of technological interest as the vortex core polarity can be regarded as one
data bit. Here we experimentally demonstrate that unidirectional vortex core
reversal by excitation with sub-100 ps long orthogonal monopolar magnetic pulse
sequences is possible in a wide range of pulse lengths and amplitudes. The
application of such short digital pulses is the favourable excitation scheme
for technological applications. Measured phase diagrams of this unidirectional,
spin wave mediated vortex core reversal are in good qualitative agreement with
phase diagrams obtained from micromagnetic simulations. The time dependence of
the reversal process, observed by time-resolved scanning transmission X-ray
microscopy indicates a switching time of 100 ps and fits well with our
simulations. The origin of the asymmetric response to clockwise and counter
clockwise excitation which is a prerequisite for reliable unidirectional
switching is discussed, based on the gyromode - spin wave coupling.",1405.0590v1
2014-08-21,Magnonic band structure of domain wall magnonic crystals,"Magnonic crystals are prototype magnetic metamaterials designed for the
control of spin wave propagation. Conventional magnonic crystals are composed
of single domain elements. If magnetization textures, such as domain walls,
vortices and skyrmions, are included in the building blocks of magnonic
crystals, additional degrees of freedom over the control of the magnonic band
structure can be achieved. We theoretically investigate the influence of domain
walls on the spin wave propagation and the corresponding magnonic band
structure. It is found that the rotation of magnetization inside a domain wall
introduces a geometric vector potential for the spin wave excitation. The
corresponding Berry phase has quantized value $4 n_w \pi$, where $n_w$ is the
winding number of the domain wall. Due to the topological vector potential, the
magnonic band structure of magnonic crystals with domain walls as comprising
elements differs significantly from an identical magnonic crystal composed of
only magnetic domains. This difference can be utilized to realize dynamic
reconfiguration of magnonic band structure by a sole nucleation or annihilation
of domain walls in magnonic crystals.",1408.4889v3
2015-07-21,Hyperscaling at the spin density wave quantum critical point in two dimensional metals,"The hyperscaling property implies that spatially isotropic critical quantum
states in $d$ spatial dimensions have a specific heat which scales with
temperature as $T^{d/z}$, and an optical conductivity which scales with
frequency as $\omega^{(d-2)/z}$ for $\omega \gg T$, where $z$ is the dynamic
critical exponent. We examine the spin-density-wave critical fixed point of
metals in $d=2$ found by Sur and Lee (Phys. Rev. B 91, 125136 (2015)) in an
expansion in $\epsilon = 3-d$. We find that the contributions of the ""hot
spots"" on the Fermi surface to the optical conductivity and specific heat obey
hyperscaling (up to logarithms), and agree with the results of the large $N$
analysis of the optical conductivity by Hartnoll et al. (Phys. Rev. B 84,
125115 (2011)). With a small bare velocity of the boson associated with the
spin density wave order, there is an intermediate energy regime where
hyperscaling is violated with $d \rightarrow d_t$, where $d_t = 1$ is the
number of dimensions transverse to the Fermi surface. We also present a
Boltzmann equation analysis which indicates that the hot spot contribution to
the DC conductivity has the same scaling as the optical conductivity, with $T$
replacing $\omega$.",1507.05962v2
2015-08-24,Topologically protected acoustic helical edge states and interface states in strongly coupled metamaterial ring lattices,"Time reversal (T) invariant topological insulator is widely recognized as one
of the fundamental discoveries in condensed matter physics, for which the most
fascinating hallmark is perhaps a spin based topological protection, the total
cancellation of scattering of conduction electrons with certain spins on matter
surface. Recently, it has created a paradigm shift for topological insulators,
from electronics to photonics, phononics as well as mechanics, bringing about
not only involved new physics but also potential applications in robust wave
transport. Despite the growing interests in realizing topologically protected
acoustic wave transport, T-invariant acoustic topological insulator has not yet
been achieved. Here, we report the first demonstration of acoustic topological
insulator: a strongly coupled metamaterial ring lattice that supports one-way
propagation of helical edge states under T-symmetry, backscattering immune to
boundary abrupt variations. The very unique thing is the formation of
spin-filtered interface states due to lattice dislocations. The mechanism
underlying the formation of topologically protected edge states and interface
states is applicable in various other wave systems or higher dimensions.",1508.06243v1
2015-11-26,Theoretical formalism for collective spin-wave edge excitations in arrays of dipolarly interacting magnetic nanodots,"A general theory of edge spin wave excitations in semi-infinite and finite
periodic arrays of magnetic nanodots existing in a spatially uniform
magnetization ground state is developed. The theory is formulated using a
formalism of multi-vectors of magnetization dynamics, which allows one to study
edge excitations in arrays having arbitrary complex primitive cells and lattice
geometry. The developed formalism can describe edge excitations localized both
at the physical edges of the array and at the internal ""domain walls""
separating array regions existing in different static magnetization states.
Using a perturbation theory in the framework of the developed formalism it is
possible to calculate damping of edge modes and their excitation by external
variable magnetic fields. The theory is illustrated on the following
practically important examples: (i) calculation of the FMR absorption in a
finite nanodot array having the shape of a right triangle, (ii) calculation of
nonreciprocal spin wave spectra of edge modes, including modes at the physical
edges of an array and modes at the domain walls inside an array, (iii) study of
the influence of the domain wall modes on the FMR spectrum of an array existing
in a non-ideal chessboard antiferromagnetic ground state.",1511.08483v3
2015-12-14,Electronic structures of [111]-oriented free-standing InAs and InP nanowires,"We report on a theoretical study of the electronic structures of the
[111]-oriented, free-standing, zincblende InAs and InP nanowires with hexagonal
cross sections by means of an atomistic $sp^{3}s^{*} $, spin-orbit interaction
included, nearest-neighbor, tight-binding method. The band structures and the
band state wave functions of these nanowires are calculated and the symmetry
properties of the bands and band states are analyzed based on the $C_{3v}$
double point group. It is shown that all bands of these nanowires are doubly
degenerate at the $\Gamma$-point and some of these bands will split into
non-degenerate bands when the wave vector $k$ moves away from the
$\Gamma$-point as a manifestation of spin-splitting due to spin-orbit
interaction. It is also shown that the lower conduction bands of these
nanowires all show simple parabolic dispersion relations, while the top valence
bands show complex dispersion relations and band crossings. The band state wave
functions are presented by the spatial probability distributions and it is
found that all the band states show $2\pi/3$-rotation symmetric probability
distributions. The effects of quantum confinement on the band structures of the
[111]-oriented InAs and InP nanowires are also examined and an empirical
formula for the description of quantization energies of the lowest conduction
band and the highest valence band is presented. The formula can simply be used
to estimate the enhancement of the band gaps of the nanowires at different
sizes as a result of quantum confinement.",1512.04206v1
2016-01-26,Cluster-shell competition and its effect on the $E0$ transition probability in $^{20}$Ne,"$^{20}$Ne has been known as a typical example of a nucleus with $\alpha$
cluster structure ($^{16}$O+$\alpha$ structure). However according to the
spherical shell model, the spin-orbit interaction acts attractively for four
nucleons outside of the $^{16}$O core, and this spin-orbit effect cannot be
taken into account in the simple $\alpha$ cluster models. We investigate how
the $\alpha$ cluster structure competes with independent particle motions of
these four nucleons. The antisymmetrized quasi-cluster model (AQCM) is a method
to describe a transition from the $\alpha$ cluster wave function to the
$jj$-coupling shell model wave function. In this model, the cluster-shell
transition is characterized by only two parameters; $R$ representing the
distance between clusters and $\Lambda$ describing the breaking of $\alpha$
clusters, and the contribution of the spin-orbit interaction, very important in
the $jj$-coupling shell model, can be taken into account by changing $\alpha$
clusters to quasi clusters. In this article, based on AQCM, we apply $^{16}$O
plus one quasi cluster model for $^{20}$Ne. Here we focus on the $E0$
transition matrix element, which has been known as the quantity characterizing
the cluster structure. The $E0$ transition matrix elements are sensitive to the
change of the wave functions from $\alpha$ cluster to $jj$-coupling shell
model.",1601.06900v1
2017-07-07,Interplay between the edge-state magnetism and long-range Coulomb interaction in zigzag graphene nanoribbons: quantum Monte Carlo study,"We perform projective quantum Monte Carlo simulations of zigzag graphene
nanoribbons within a realistic model with long-range Coulomb interactions.
Increasing the relative strength of nonlocal interactions with respect to the
on-site repulsion does not generate a phase transition but has a number of
nontrivial effects. At the single-particle level we observe a marked
enhancement of the Fermi velocity at the Dirac points. At the two-particle
level, spin- and charge-density-wave fluctuations compete. As a consequence,
the edge magnetic moment is reduced but the edge dispersion relation increases
in the sense that the single-particle gap at momentum $q=\pi/|{\pmb a}_1|$
grows. We attribute this to nonlocal charge fluctuations which assist the spin
fluctuations to generate the aforementioned gap. In contrast, the net result of
the interaction-induced renormalization of different energy scales is a
constant spin-wave velocity of the edge modes. However, since the particle-hole
continuum is shifted to higher energies---due to the renormalization of the
Fermi velocity---Landau damping is reduced. As a result, a roughly linear
spin-wave-like mode at the edge spreads out through a larger part of the
Brillouin zone.",1707.02065v2
2017-07-16,A Monolithic Topologically Protected Phononic Circuit,"Precise control of elastic waves in modes and coherences is of great use in
reinforcing nowadays elastic energy harvesting/storage, nondestructive testing,
wave-mater interaction, high sensitivity sensing and information processing,
etc. All these implementations are expected to have elastic transmission with
lower transmission losses and higher degree of freedom in transmission path.
Inspired by topological states of quantum matters, especially quantum spin Hall
effects (QSHEs) providing passive solutions of unique disorder-immune surface
states protected by underlying nontrivial topological invariants of the bulk,
thus solving severe performance trade-offs in experimentally realizable
topologically ordered states. Here, we demonstrate experimentally the first
elastic analogue of QSHE, by a concise phononic crystal plate with only
perforated holes. Strong elastic spin-orbit coupling is realized accompanied by
the first topologically-protected phononic circuits with both robustness and
negligible propagation loss overcoming many circuit- and system-level
performance limits induced by scattering. This elegant approach in a monolithic
substrate opens up the possibility of realizing topological materials for
phonons in both static and time-dependent regimes, can be immediately applied
to multifarious chip-scale devices with both topological protection and massive
integration, such as on-chip elastic wave-guiding, elastic splitter, elastic
resonator with high quality factor, and even (pseudo-)spin filter.",1707.04901v1
2018-09-07,Electron-magnon scattering in elementary ferromagnets from first principles: lifetime broadening and band anomalies,"We study the electron-magnon scattering in bulk Fe, Co, and Ni within the
framework of many-body perturbation theory implemented in the full-potential
linearized augmented-plane-wave method. To this end, a $\mathbf{k}$-dependent
self-energy ($GT$ self-energy) describing the scattering of electrons and
magnons is constructed from the solution of a Bethe-Salpeter equation for the
two-particle (electron-hole) Green function, in which single-particle Stoner
and collective spin-wave excitations (magnons) are treated on the same footing.
Partial self-consistency is achieved by the alignment of the chemical
potentials. The resulting renormalized electronic band structures exhibit
strong spin-dependent lifetime effects close to the Fermi energy, which are
strongest in Fe. The renormalization can give rise to a loss of quasiparticle
character close to the Fermi energy, which we attribute to electron scattering
with spatially extended spin waves. This scattering is also responsible for
dispersion anomalies in conduction bands of iron and for the formation of
satellite bands in nickel. Furthermore, we find a band anomaly at a binding
energy of 1.5~eV in iron, which results from a coupling of the quasihole with
single-particle excitations that form a peak in the Stoner continuum. This band
anomaly was recently observed in photoemission experiments. On the theory side,
we show that the contribution of the Goldstone mode to the $GT$ self-energy is
expected to (nearly) vanish in the long-wavelength limit. We also present an
in-depth discussion about the possible violation of causality when an
incomplete subset of self-energy diagrams is chosen.",1809.02395v2
2018-11-27,Hybrid magneto-dynamical modes in a single magnetostrictive nanomagnet on a piezoelectric substrate arising from magneto-elastic modulation of precessional dynamics,"Magneto-elastic (or ""straintronic"") switching has emerged as an extremely
energy-efficient mechanism for switching the magnetization of magnetostrictive
nanomagnets in magnetic memory, logic and non-Boolean circuits. Here, we
investigate the ultrafast magneto-dynamics associated with straintronic
switching in a single quasi-elliptical magnetostrictive Co nanomagnet deposited
on a piezoelectric PMN-PT substrate using time-resolved magneto-optical Kerr
effect (TR-MOKE) measurements. The pulsed laser pump beam in the TR-MOKE plays
a dual role: it causes precession of the nanomagnet's magnetization about an
applied bias magnetic field and it also generates surface acoustic waves (SAWs)
in the piezoelectric substrate that produce periodic strains in the
magnetostrictive nanomagnet and modulate the precessional dynamics. This
modulation gives rise to intriguing hybrid magneto-dynamical modes in the
nanomagnet, with rich spin wave texture. The characteristic frequencies of
these modes are 5-15 GHz, indicating that strain can affect magnetization in a
magnetostrictive nanomagnet in time scales much smaller than 1 ns (~100 ps).
This can enable ~10 GHz-range magneto-elastic nano-oscillators that are
actuated by strain instead of a spin-polarized current, as well as ultrafast
magneto-electric generation of spin waves for magnonic logic circuits,
holograms, etc.",1811.11297v1
2017-05-12,Switching dynamics of the spin density wave in superconducting CeCoIn5,"The ordering wave vector $\mathbf{Q}$ of a spin density wave (SDW),
stabilized within the superconducting state of $\mathrm{CeCoIn_5}$ in a high
magnetic field, has been shown to be hypersensitive to the direction of the
field. $\mathbf{Q}$ can be switched from a nodal direction of the $d$-wave
superconducting order parameter to a perpendicular node by rotating the
in-plane magnetic field through the antinodal direction within a fraction of a
degree. Here, we address the dynamics of the switching of $\mathbf{Q}$. We use
a free energy functional based on the magnetization density, which describes
the condensation of magnetic fluctuations of nodal quasiparticles, and show
that the switching process includes closing of the SDW gap at one $\mathbf{Q}$
and then reopening the SDW gap at another $\mathbf{Q}$ perpendicular to the
first one. The magnetic field couples to $\mathbf{Q}$ through the spin-orbit
interaction. Our calculations show that the width of the hysteretic region of
switching depends linearly on the deviation of magnetic field from the critical
field associated with the SDW transition, consistent with our thermal
conductivity measurements. The agreement between theory and experiment supports
our scenario of the hypersensitivity of the $Q$ phase on the direction of
magnetic field, as well as the magnon condensation as the origin of the SDW
phase in $\mathrm{CeCoIn_5}$.",1705.04655v1
2018-07-20,Impact of high-order tidal terms on binary neutron-star waveforms,"GW170817, the milestone gravitational-wave event originated from a binary
neutron star merger, has allowed scientific community to place a constraint on
the equation of state of neutron stars by extracting the leading-order,
tidal-deformability term from the gravitational waveform. Here we incorporate
tidal corrections to the gravitational-wave phase at next-to-leading and
next-to-next-to-leading order, including the magnetic tidal Love numbers, tail
effects, and the spin-tidal couplings recently computed in Tiziano Abdelsalhin
[Phys. Rev. D 98, 104046 (2018)]. These effects have not yet been included in
the waveform approximants for the analysis of GW170817. We provide a
qualitative and quantitative analysis of the impact of these new terms by
studying the parameter bias induced on events compatible with GW170817 assuming
second-generation (advanced LIGO) and third-generation (Einstein Telescope)
ground-based gravitational-wave interferometers. We find that including the
tidal-tail term deteriorates the convergence properties of the post-Newtonian
expansion in the relevant frequency range. We also find that the effect of
magnetic tidal Love numbers could be measurable for an optimal GW170817 event
with signal-to-noise ratio $\rho \approx 1750$ detected with the Einstein
Telescope. On the same line, spin-tidal couplings may be relevant if mildly
high-spin $\chi \gtrsim 0.1$ neutron star binaries exist in nature.",1807.08016v3
2012-09-04,Single spin asymmetry in high energy QCD,"We present the first steps in an effort to incorporate the physics of
transverse spin asymmetries into the saturation formalism of high energy QCD.
We consider a simple model in which a transversely polarized quark scatters on
a proton or nuclear target. Using the light-cone perturbation theory the hadron
production cross section can be written as a convolution of the light-cone wave
function squared and the interaction with the target. To generate the single
transverse spin asymmetry (STSA) either the wave function squared or the
interaction with the target has to be T-odd. In this work we use the
lowest-order q->qG wave function squared, which is T-even, generating the STSA
from the T-odd interaction with the target mediated by an odderon exchange. We
study the properties of the obtained STSA, some of which are in qualitative
agreement with experiment: STSA increases with increasing projectile x_F and is
a non-monotonic function of the transverse momentum k_T. Our mechanism predicts
that the quark STSA in polarized proton--nucleus collisions should be much
smaller than in polarized proton--proton collisions. We also observe that the
STSA for prompt photons due to our mechanism is zero within the accuracy of the
approximation.",1209.0727v1
2018-02-09,Monocrystalline free standing 3D yttrium iron garnet magnon nano resonators,"Nano resonators in which mechanical vibrations and spin waves can be coupled
are an intriguing concept that can be used in quantum information processing to
transfer information between different states of excitation. Until now, the
fabrication of free standing magnetic nanostructures which host long lived spin
wave excitatons and may be suitable as mechanical resonators seemed elusive. We
demonstrate the fabrication of free standing monocrystalline yttrium iron
garnet (YIG) 3D nanoresonators with nearly ideal magnetic properties. The
freestanding 3D structures are obtained using a complex lithography process
including room temperature deposition and lift-off of amorphous YIG and
subsequent crystallization by annealing. The crystallization nucleates from the
substrate and propagates across the structure even around bends over distances
of several micrometers to form e.g. monocrystalline resonators as shown by
transmission electron microscopy. Spin wave excitations in individual
nanostructures are imaged by time resolved scanning Kerr microscopy. The narrow
linewidth of the magnetic excitations indicates a Gilbert damping constant of
only $\alpha = 2.6 \times 10^{-4}$ rivalling the best values obtained for
epitaxial YIG thin film material. The new fabrication process represents a leap
forward in magnonics and magnon mechanics as it provides 3D YIG structures of
unprecedented quality. At the same time it demonstrates a completely new route
towards the fabrication of free standing crystalline nano structures which may
be applicable also to other material systems.",1802.03176v2
2019-02-03,Bose-Einstein condensate in Bloch bands with off-diagonal periodic potential,"We report the Bose-Einstein condensate (BEC) in the Bloch bands with
off-diagonal periodic potential (ODPP), which simultaneously plays the role of
spin-orbit coupling (SOC) and Zeeman field. This model can be realized using
two independent Raman couplings in the same three level system, in which the
time-reversal symmetry ensures the energy degeneracy between the two states
with opposite momenta. We find that these two Raman couplings can be used to
tune the spin polarization in momentum space, thus greatly modifies the
effective scatterings over the Bloch bands. We observe a transition from the
Bloch plane wave phase with condensate at one wave vector to the Bloch stripe
phase with condensates at the two Bloch states with opposite wave vectors.
These two phases will exhibit totally different spin textures and density
modulations in real space, which are totally different from that in free space.
In momentum space multiple peaks differ by some reciprocal lattice vectors can
be observed, reflecting the periodic structure of the ODPP. A three-band
effective model is proposed to understand these observations. This system can
provide a new platform in investigating of various physics, such as collective
excitations, polaron and topological superlfuids, over the Bloch bands.",1902.00830v1
2020-04-02,Shock Waves in a Superfluid with Higher-Order Dispersion,"Higher-order dispersion can lead to intriguing dynamics that are becoming a
focus of modern hydrodynamics research. Such systems occur naturally, for
example in shallow water waves and nonlinear optics, for which several types of
novel dispersive shocks structures have been identified. Here we introduce
ultracold atoms as a tunable quantum simulations platform for higher-order
systems. Degenerate quantum gases are well controlled model systems for the
experimental study of dispersive hydrodynamics in superfluids and have been
used to investigate phenomena such as vortices, solitons, dispersive shock
waves and quantum turbulence. With the advent of Raman-induced spin-orbit
coupling, the dispersion of a dilute gas Bose-Einstein condensate can be
modified in a flexible way, allowing for detailed investigations of
higher-order dispersion dynamics. Here we present a combined experimental and
theoretical study of shock structures generated in such a system. The breaking
of Galilean invariance by the spin-orbit coupling allows two different types of
shock structures to emerge simultaneously in a single system. Numerical
simulations suggest that the behavior of these shock structures is affected by
interactions with vortices in a manner reminiscent of emerging viscous
hydrodynamics due to an underlying quantum turbulence in the system. This
result suggests that spin-orbit coupling can be used as a powerful means to tun
the effective viscosity in cold-atom experiments serving as quantum simulators
of turbulent hydrodynamics, with applications from condensed matter and optics
to quantum simulations of neutron stars.",2004.00832v1
2020-04-27,Nonlinear interaction of acoustic waves with a spheroidal particle: radiation force and torque effects,"The nonlinear interaction of a time-harmonic acoustic wave with an
anisotropic particle gives rise to the radiation force and torque effects.
These phenomena are at the heart of the acoustofluidics technology, where
microparticles such as cells and microorganisms are acoustically manipulated.
We present a theoretical model considering a generic acoustic beam interacting
with a subwavelength spheroidal particle in a nonviscous fluid. Concise
analytical expressions of the radiation force and torque are obtained in the
scattering dipole approximation. The radiation force is given in terms of a
gradient and scattering force; while the radiation torque has two fundamental
contributions, namely, the momentum arm and acoustic spin (spin-torque effect).
As a practical example, we use the theory to describe the interaction of two
crossed plane waves and a prolate spheroidal particle. The results reveal the
particle is transversely trapped in a pressure node and is axially pushed by
the radiation force. Also, the momentum arm aligns the particle in the axial
direction. At certain specific positions, only the spin-torque occurs. Our
findings are remarkably consistent with finite-element simulations. The success
of our model enables its use as an investigation tool for the manipulation of
anisotropic microparticles in acoustofluidics.",2004.12980v1
2017-02-15,Spin waves in periodic antidot waveguide of complex base,"We consider the planar magnonic waveguide with a periodic sequence of
antidots forming zig-zag pattern, where two neighboring antidots are shifted
towards the opposite edges of the waveguide. This system has a complex base
with two antidots in one unit cell. The Brillouin zone is here two-times
narrower than the Brillouin zone for the waveguide without displacement of
antidots. We have shown that for dispersion relation folded into narrower
Brillouin zone, new frequency gap can be opened and their width can be
controlled by the shift of the antidots. We found that, the different strength
of spin wave pinning at the edges of the periodic waveguide (and their
antidots)determines the dependence of the width of gap on the shift of
antidots. For the systems with completely free or ideally pinned magnetization,
these dependencies are qualitatively different. We have found an optimum shift
of antidot for maximzing the width of the gap for the system with pinned
magnetization. More interestingly, we notice that for this kind of geometry of
the structure, majority of the modes are doubly degenerate at the edge of
Brillouin zone and have a finite group velocity at the very close vicinity of
the edge of Brillouin zone, for larger values of antidot shift. This empowers
us to design magnonic waveguide to steer the spin waves.",1702.04667v2
2017-02-15,Resonant properties of dipole skyrmions in amorphous Fe/Gd multilayers,"The dynamic response of dipole skyrmions in Fe/Gd multilayer films is
investigated by ferromagnetic resonance measurements and compared to
micromagnetic simulations. We detail thickness and temperature dependent
studies of the observed modes as well as the effects of magnetic field history
on the resonant spectra. Correlation between the modes and the magnetic phase
maps constructed from real-space imaging and scattering patterns allows us to
conclude the resonant modes arise from local topological features such as
dipole skyrmions but does not depend on the collective response of a closed
packed lattice of these chiral textures. Using, micromagnetic modeling, we are
able to quantitatively reproduce our experimental observations which suggests
the existence of localized spin-wave modes that are dependent on the helicity
of the dipole skyrmion. We identify four localized spin wave excitations for
the skyrmions that are excited under either in-plane or out-of-plane r.f.
fields. Lastly we show that dipole skyrmions and non-chiral bubble domains
exhibit qualitatively different localized spin wave modes.",1702.04691v2
2017-06-05,Quantum and thermal fluctuations in a Raman spin-orbit coupled Bose gas,"We theoretically study a three-dimensional weakly-interacting Bose gas with
Raman-induced spin-orbit coupling at finite temperature. By employing a
generalized Hartree-Fock-Bogoliubov theory with Popov approximation, we
determine a complete finite-temperature phase diagram of three exotic
condensation phases (i.e., the stripe, plane-wave and zero-momentum phases),
against both quantum and thermal fluctuations. We find that the plane-wave
phase is significantly broadened by thermal fluctuations. The phonon mode and
sound velocity at the transition from the plane-wave phase to the zero-momentum
phase are thoughtfully analyzed. At zero temperature, we find that quantum
fluctuations open an unexpected gap in sound velocity at the phase transition,
in stark contrast to the previous theoretical prediction of a vanishing sound
velocity. At finite temperature, thermal fluctuations continue to significantly
enlarge the gap, and simultaneously shift the critical minimum. For a Bose gas
of $^{87}$Rb atoms at the typical experimental temperature, $T=0.3T_{0}$, where
$T_{0}$ is the critical temperature of an ideal Bose gas without spin-orbit
coupling, our results of gap opening and critical minimum shifting in the sound
velocity, are qualitatively consistent with the recent experimental observation
{[}S.-C. Ji \textit{et al.}, Phys. Rev. Lett. \textbf{114}, 105301 (2015){]}.",1706.01170v1
2019-03-15,The Krein-Schrödinger Formalism of Bosonic BdG and Certain Classical Systems and Their Topological Classification,"To understand recent works on classical and quantum spin equations and their
topological classification, we develop a unified mathematical framework for
bosonic BdG systems and associated classical wave equations; it applies not
just to equations that describe quantized spin excitations in magnonic crystals
but more broadly to other systems that are described by a BdG hamiltonian.
Because here the generator of dynamics, the analog of the hamiltonian, is
para-, aka Krein-, hermitian but not hermitian, the theory of Krein spaces
plays a crucial role. For systems which are thermodynamically stable, the
classical equations can be expressed as a Schr\""odinger equation with a
hermitian hamiltonian. We then proceed to apply the Cartan-Altland-Zirnbauer
classification scheme: to properly understand what topological class these
equations belong to, we need to conceptually distinguish between symmetries and
constraints. Complex conjugation enters as a particle-hole constraint (as
opposed to a symmetry), since classical waves are necessarily real-valued.
Because of this distinction only commuting symmetries enter in the topological
classification. Our arguments show that the equations for spin waves in
magnonic crystals are a system of class A, the same topological class as
quantum hamiltonians describing the Integer Quantum Hall Effect. Consequently,
the magnonic edge modes first predicted by Shindou et al. are indeed analogs of
the Quantum Hall Effect, and their net number is topologically protected.",1903.06354v1
2020-11-24,A generalized precession parameter $χ_\mathrm{p}$ to interpret gravitational-wave data,"Originally designed for waveform approximants, the effective precession
parameter $\chi_\mathrm{p}$ is the most commonly used quantity to characterize
spin-precession effects in gravitational-wave observations of black-hole binary
coalescences. We point out that the current definition of $\chi_\mathrm{p}$
retains some, but not all, variations taking place on the precession timescale.
We rectify this inconsistency and propose more general definitions that either
fully consider or fully average those oscillations. Our generalized parameter
$\chi_\mathrm{p}\in[0,2]$ presents an exclusive region $\chi_\mathrm{p}>1$ that
can only be populated by binaries with two precessing spins. We apply our
prescriptions to current LIGO/Virgo events and find that posterior
distributions of $\chi_\mathrm{p}$ tend to show longer tails at larger values.
This appears to be a generic feature, implying that (i) current
$\chi_\mathrm{p}$ measurement errors might be underestimated, but also that
(ii) evidence for spin precession in current data might be stronger than
previously inferred. Among the gravitational-wave events released to date, that
which shows the most striking behavior is GW190521.",2011.11948v2
2017-01-02,A Surrogate Model of Gravitational Waveforms from Numerical Relativity Simulations of Precessing Binary Black Hole Mergers,"We present the first surrogate model for gravitational waveforms from the
coalescence of precessing binary black holes. We call this surrogate model
NRSur4d2s. Our methodology significantly extends recently introduced
reduced-order and surrogate modeling techniques, and is capable of directly
modeling numerical relativity waveforms without introducing phenomenological
assumptions or approximations to general relativity. Motivated by GW150914,
LIGO's first detection of gravitational waves from merging black holes, the
model is built from a set of $276$ numerical relativity (NR) simulations with
mass ratios $q \leq 2$, dimensionless spin magnitudes up to $0.8$, and the
restriction that the initial spin of the smaller black hole lies along the axis
of orbital angular momentum. It produces waveforms which begin $\sim 30$
gravitational wave cycles before merger and continue through ringdown, and
which contain the effects of precession as well as all $\ell \in \{2, 3\}$
spin-weighted spherical-harmonic modes. We perform cross-validation studies to
compare the model to NR waveforms \emph{not} used to build the model, and find
a better agreement within the parameter range of the model than other,
state-of-the-art precessing waveform models, with typical mismatches of
$10^{-3}$. We also construct a frequency domain surrogate model (called
NRSur4d2s_FDROM) which can be evaluated in $50\, \mathrm{ms}$ and is suitable
for performing parameter estimation studies on gravitational wave detections
similar to GW150914.",1701.00550v2
2017-01-18,Excitation of magnon accumulation by laser clocking as a source of long-range spin waves in transparent magnetic films,"Optical tools are of great promise for generation of spin waves due to the
possibility to manipulate on ultrashort time scales and to provide local
excitation. However, a single laser pulse can inject spin waves only with a
broad frequency spectrum, resulting in a short propagation distance and low
amplitude. Here we excite a magnetic garnet film by a train of fs-laser pulses
with 1 GHz repetition rate so that pulse separation is smaller than decay time
of the magnetic modes which allows to achieve collective photonic impact on
magnetization. It establishes a quasi-stationary source of SWs, namely a
coherent magnon accumulation (""magnon cloud""). This approach has several
appealing features: (i) the source is tunable; (ii) the SW amplitude can be
significantly enhanced; (iii) the spectrum of the generated SWs is quite narrow
that provides longer propagation distance; (iv) the periodic pumping results in
almost constant in time SW amplitude up to 100 um away from the source; and (v)
the SW emission shows a pronounced directionality. These results expand the
capabilities of ultrafast coherent optical control of magnetization and pave a
way for applications in data processing, including the quantum regime. The
quasi-stationary magnon accumulation might be also of interest for the problem
of magnon Bose-Einstein condensate.",1701.05109v1
2017-03-11,Spin-wave dynamics in Permalloy/Cobalt magnonic crystals in the presence of a non-magnetic spacer,"In this paper, we theoretically study the influence of a non-magnetic spacer
between ferromagnetic dots and ferromagnetic matrix on the frequency dispersion
of the spin wave excitations in two-dimensional bi-component magnonic crystals.
By means of the dynamical matrix method we investigate structures inhomogeneous
across the thickness represented by square arrays of Cobalt or Permalloy dots
in a Permalloy matrix. We show that the introduction of a non-magnetic spacer
significantly modifies the total internal magnetic field especially at the
edges of the grooves and dots. This permits the manipulation of the magnonic
band structure of spin waves localized either at the edges of the dots or in
matrix material at the edges of grooves. According to the micromagnetic
simulations two types of end modes were found. The corresponding frequencies
are significantly influenced by the end modes localization region. We also show
that, with the use of a single ferromagnetic material, it is possible to design
a magnonic crystal preserving properties of bi-component magnonic crystals and
magnonic antidot lattices. Finally, the influence of the non-magnetic spacers
on the technologically relevant parameters like group velocity and magnonic
band width are discussed.",1703.03978v1
2019-01-26,Effects of Nanodots Shape and Lattice Constants on the Spin Wave Dynamics of Patterned Permalloy Dots,"Micromagnetic simulations studies on Permalloy (Ni80Fe20) nanodot with
different shape and edge-to-edge separation (s) down to 25nm arranged in square
lattice are reported. We observe the significant variation of spin-wave (SW)
dynamics of nanodots of different shapes (triangular, diamond and hexagon) and
of fixed dot diameter 100nm with varying s. Modes for single dot are
transformed in an array into multiple quantized, edge and centre modes for
different shapes and edge-to-edge separations, with different spin wave
frequencies and peak intensities. Specifically, in the triangular dot sample, a
broad range of mode frequencies is observed with highest SW frequency 14.7 GHz.
For separation less than 100nm, the SW frequencies undergoes significant
modification due to the varying nature of the magnetostatic and dipolar
interaction in the array while for separation above 100nm, the SW frequency
mostly remain constant. The power profiles confirm the nature of the observed
modes. The spatial profiles of magnetostatic field are determined by a
combination of internal magnetic-field profiles within the nanodots and the
magnetostatic fields within the lattice. The inter-dots interaction of
magnetostatic field shows dipolar and quadrupole contributions for all the
shapes. Interestingly, vortex states with shifted core and polarity are
observed in the array for all the shapes at Hbias = 0. Our results provide
important understanding about the tunability of SW spectra in the array of
triangular, diamond and hexagon shaped nanoelements.",1901.09155v1
2019-07-05,Tunability of domain structure and magnonic spectra in antidot arrays of Heusler alloy,"Materials suitable for magnonic crystals demand low magnetic damping and long
spin wave (SW) propagation distance. In this context Co based Heusler compounds
are ideal candidates for magnonic based applications. In this work, antidot
arrays (with different shapes) of epitaxial
$\mathrm{Co}_2\mathrm{Fe}_{0.4}\mathrm{Mn}_{0.6}\mathrm{Si}$ (CFMS) Heusler
alloy thin films have been prepared using e-beam lithography and sputtering
technique. Magneto-optic Kerr effect and ferromagnetic resonance analysis have
confirmed the presence of dominant cubic and moderate uniaxial magnetic
anisotropies in the thin films. Domain imaging via x-ray photoemission electron
microscopy on the antidot arrays reveals chain like switching or correlated
bigger domains for different shape of the antidots. Time-resolved MOKE
microscopy has been performed to study the precessional dynamics and magnonic
modes of the antidots with different shapes. We show that the optically induced
spin-wave spectra in such antidot arrays can be tuned by changing the shape of
the holes. The variation in internal field profiles, pinning energy barrier,
and anisotropy modifies the spin-wave spectra dramatically within the antidot
arrays with different shapes. We further show that by combining the
magnetocrystalline anisotropy with the shape anisotropy, an extra degree of
freedom can be achieved to control the magnonic modes in such antidot lattices.",1907.02746v1
2020-05-06,Nonlinear dynamical tides in white dwarf binaries,"Compact white dwarf (WD) binaries are important sources for space-based
gravitational-wave (GW) observatories, and an increasing number of them are
being identified by surveys like ZTF. We study the effects of nonlinear
dynamical tides in such binaries. We focus on the global three-mode parametric
instability and show that it has a much lower threshold energy than the local
wave-breaking condition studied previously. By integrating networks of coupled
modes, we calculate the tidal dissipation rate as a function of orbital period.
We construct phenomenological models that match these numerical results and use
them to evaluate the spin and luminosity evolution of a WD binary. While in
linear theory the WD's spin frequency can lock to the orbital frequency, we
find that such a lock cannot be maintained when nonlinear effects are taken
into account. Instead, as the orbit decays, the spin and orbit go in and out of
synchronization. Each time they go out of synchronization, there is a brief but
significant dip in the tidal heating rate. While most WDs in compact binaries
should have luminosities that are similar to previous traveling-wave estimates,
a few percent should be about ten times dimmer because they reside in heating
rate dips. This offers a potential explanation for the low luminosity of the CO
WD in J0651. Lastly, we consider the impact of tides on the GW signal and show
that LISA and TianGO can constrain the WD's moment of inertia to better than 1%
for deci-Hz systems.",2005.03058v1
2020-06-29,Measuring precession in asymmetric compact binaries,"Gravitational-wave observations of merging compact binaries hold the key to
precision measurements of the objects' masses and spins. General-relativistic
precession, caused by spins misaligned with the orbital angular momentum, is
considered a crucial tracer for determining the binary's formation history and
environment, and it also improves mass estimates -- its measurement is
therefore of particular interest with wide-ranging implications. Precession
leaves a characteristic signature in the emitted gravitational-wave signal that
is even more pronounced in binaries with highly unequal masses. The recent
observations of GW190412 and GW190814 have confirmed the existence of such
asymmetric compact binaries. Here, we perform a systematic study to assess the
confidence in measuring precession in gravitational-wave observations of high
mass ratio binaries and, our ability to measure the mass of the lighter
companion in neutron star -- black hole type systems. Using Bayesian model
selection, we show that precession can be decisively identified for low-mass
binaries with mass ratios as low as $1:3$ and mildly precessing spins with
magnitudes $\lesssim 0.4$, even in the presence of systematic waveform errors.",2006.16153v2
2021-07-30,Effective chirp mass captures the inspiral frequency evolution of the non-spinning eccentric compact binary,"Compact binary systems with black holes are the primary sources of
interferometric advanced gravitational wave detectors. Astrophysical models
suggest finite possibility of binary systems with appreciable non-zero
eccentricity in the dense stellar environment like globular clusters and
galactic nuclei. While most of the compact binary measurements have not shown
appreciable eccentricity, constrains on the eccentricity have been placed on
few detected events. With increasing sensitivity of the gravitational wave
detectors, the eccentric binaries are plausible sources in the gravitational
wave window. Nevertheless, the challenges in the waveform modelling for high
values of eccentricity constrain both the search methodologies of eccentric
system as well as parameter estimation of the eccentricity. Waveform
independent approaches are being investigated. In this work, we demonstrate
that a new effective chirp mass $\mathcal{M}_e$ parameter can be defined which
governs the dynamics of the non-spinning eccentric compact binary system. We
obtain the phenomenological model of the same for low to moderate eccentricity
values. One direct implication is its application in the unmodelled searches
and as an another implication, we demonstrate that this model can be used to
constrain the eccentricity of the non-spinning eccentric binaries in the
advanced detector era in the waveform model-independent way.",2107.14736v2
2021-12-10,Impact of the interfacial Dzyaloshinskii-Moriya interaction on the band structure of one-dimensional artificial magnonic crystals: a micromagnetic study,"We present the results of a systematic micromagnetic study of the effect of
the Dzyaloshinskii-Moriya interaction (DMI) on the spin wave band structure of
two one-dimensional magnonic crystals (MCs), both with the same periodicity
p=300 nm, but different implementation of the DMI modulation. In the first
system the artificial periodicity was achieved by modulating the interfacial
DMI constant D, while in the second system also the sample morphology was
modulated. Due to the folding property of the band structure in the dispersion
relations of the magnonic crystals it is possible to extend the sensitivity of
Brillouin light scattering towards weak DMI strength (D in the range from 0 to
0.5 mJ/m2), by measuring the frequency splitting of folded modes in high-order
artificial Brillouin zones, since the splitting increases almost linearly with
the band index. For relatively large values of the DMI (D in the range from 1.0
to 2.0 mJ/m2) the spin waves dispersion relations present flat modes for
positive wavevectors, separated by forbidden frequency gaps whose amplitude
depend on the value of D. These frequency gaps are more pronounced for the
sample with morphology modulation. The non-reciprocal, localised, spatial
profiles of these modes in both MCs are discussed with reference to spin waves
in plain films and in isolated stripes of the same thickness.",2112.05360v1
2022-02-02,Pair-density-wave superconductor from doping Haldane chain and rung-singlet ladder,"We report the numerical discovery of a pair-density-wave (PDW) superconductor
from doping either (i) a spin-one Haldane chain or (ii) a two-leg ladder in the
rung singlet phase in which the doped charges occupy a single leg. We model
these systems using a generalized Kondo model. The itinerant electrons are
correlated and described by the $t-J$ model, and are further coupled to a spin
$1/2$ Heisenberg model through the Kondo coupling $J_K$. When the density of
electrons $x$ is one, the Mott insulator is in a Haldane phase or in a rung
singlet phase depending on whether $J_K$ is negative or positive. Upon doping,
a pair-density-wave with $\mathbf Q=\pi$ can emerge for both signs of $J_K$. In
the $J_K \rightarrow -\infty$ limit, the model reduces to the recently proposed
type II t-J model and we observes a continuous transition between the PDW
superconductor and an unconventional Luttinger liquid phase with doping. We
also identify a composite order parameter for the superconductor, which can be
understood as a Cooper pair formed by two nearby fermionic spin-polarons. Our
model and the predicted PDW phase can be experimentally realized by doping S=1
chains formed by Ni$^{2+}$ in a solid state system or a two-leg ladder of
fermionic cold atoms with a potential bias between legs, which preferentially
dopes carriers into a single leg.",2202.01224v1
2022-06-21,Perturbations of spinning black holes beyond General Relativity: Modified Teukolsky equation,"The detection of gravitational waves from compact binary mergers by the
LIGO/Virgo collaboration has, for the first time, allowed for tests of
relativistic gravity in the strong, dynamical and nonlinear regime. Outside
Einstein's relativity, spinning black holes may be different from their general
relativistic counterparts, and their merger may then lead to a modified
ringdown. We study the latter and, for the first time, derive a modified
Teukolsky equation, i.e., a set of linear, decoupled differential equations
that describe dynamical perturbations of non-Kerr black holes for the radiative
Newman-Penrose scalars $\Psi_0$ and $\Psi_4$. We first focus on non-Ricci-flat,
Petrov type D black hole backgrounds in modified gravity, and derive the
modified Teukolsky equation through direct decoupling and through a new
approach, proposed by Chandrasekhar, that uses certain gauge conditions. We
then extend this analysis to non-Ricci-flat, Petrov type I black hole
backgrounds in modified gravity, assuming they can be treated as a linear
perturbation of Petrov type D, black hole backgrounds in GR by generalizing
Chandrasekhar's approach, and derive the decoupled modified Teukolsky equation.
Our work lays the foundation to study the gravitational waves emitted in the
ringdown phase of black hole coalescence in modified gravity for black holes of
any spin. Our work can also be extended to compute gravitational waves emitted
by extreme mass-ratio binary inspirals in modified gravity.",2206.10652v2
2022-06-22,Spin wave stiffness and damping in a frustrated chiral helimagnet Co$_8$Zn$_8$Mn$_4$ as measured by small-angle neutron scattering,"Multiple intriguing low temperature phenomena have recently been discovered
in the family of chiral cubic Co-Zn-Mn compounds with $\beta-$Mn-type
structure. In particular, Co$_8$Zn$_8$Mn$_4$ displays a reduction of the
helical spiral pitch on cooling, along with lattice shape transformations of
metastable skyrmions and the manifestation of peculiar magnetic textures due to
strong magnetocrystalline anisotropy. Here we report on temperature-dependent
measurements of helimagnon excitations in the field polarized regime
Co$_8$Zn$_8$Mn$_4$ using the spin wave small-angle neutron scattering (SWSANS)
technique. By applying a new analytical expression to interpret the data,
quantitative estimates for both spin wave stiffness and damping are extracted
across a wide temperature range between 70 K and 250 K. We speculate that their
non-trivial temperature-dependencies arise due to the effects of magnetic
frustration arising from Mn magnetic moments, which is further reflected in
continuous variations of both exchange and Dzyaloshinskii-Moriya interactions.",2206.11006v1
2022-09-01,Magnon dynamics in parity-time-symmetric dipolarly coupled waveguides and magnonic crystals,"We consider the magnonic properties of two dipolarly coupled magnetic
stripes, both deposited on a normal conductive substrate with strong spin-orbit
coupling. A charge current in the substrate acts on the adjacent magnets with
spin-orbit torques, which result in magnonic damping or antidamping of the spin
waves, and hence a gain-loss coupling of the two magnetic stripes. The whole
setup is demonstrated to exhibit features typical for parity-time (PT)
symmetric systems. Phenomena are demonstrated that can be functionalized in
magnonic devices, including reconfigurable magnonic diodes and logic devices.
Alternative stripes designs and PT-symmetric, periodic, coupled magnonic
textures are studied. Analytical and full numerical analysis identify the
conditions for the appearance of exceptional points (EPs), where magnonic gain
and loss are balanced and evidence nonreciprocal magnon propagation and
enhanced magnon excitation around EPs. Furthermore, the dipolar coupling is
shown to bring in a wave vector-dependent PT-symmetric behavior. Proposing and
simulating a PT-symmetric magnonic crystal, we show how EPs and hence
associated phenomena can be steered to a particular wave vector in a gaped
spectrum via material design. The phenomena offer additional tools for
magnonic-based communication and computational devices.",2209.00180v1
2022-09-26,Phononic Skyrmions,"Skyrmions with topologically stable configurations have shown a promising
route toward magnetic and photonic materials for information processing due to
their defect-immune and low-driven energy. However, the practical application
of magnetic skyrmions is severely hindered by their harsh cryogenic environment
and complex carriers. In addition, the narrowband nature of magnetic and
photonic skyrmions leads to lower data rate transmissions, restricting the
development of high-speed information processing technologies. Here, we
introduce and demonstrate the concept of phononic skyrmion as new topological
structures to break the above barriers. The phononic skyrmion can be produced
in any solid structure at room temperature, including chip-scale structures,
with high robustness and ultra-bandwidth, which could pave a new path for
high-speed and topological information processing technologies. We
experimentally demonstrate the existence of phononic skyrmion formed by
breaking the rotational symmetry of the three-dimensional hybrid spin of
elastic waves. The frequency-independent spin configuration leads to the
remarkable ultra-broadband and tunable feature of phononic skyrmions. We
further experimentally show the excellent robustness of the flexibly movable
phononic skyrmion lattices against local defects of disorder, sharp corners,
and even rectangular holes. Our research also opens a vibrant horizon towards
an unprecedented way for elastic wave manipulation and structuration by spin
configuration, and offers a promising lever for alternative phononic
technologies, including quantum information, biomedical testing, and wave
engineering.",2209.12706v1
2022-09-27,Tailoring crosstalk between localized 1D spin-wave nanochannels using focused ion beams,"1D spin-wave conduits are envisioned as nanoscale components of
magnonics-based logic and computing schemes for future generation electronics.
`A-la-carte methods of versatile control of the local magnetization dynamics in
such nanochannels are highly desired for efficient steering of the spin waves
in magnonic devices. Here, we present a study of localized dynamical modes in
1-$\mu$m-wide Permalloy conduits probed by microresonator ferromagnetic
resonance technique. We clearly observe the lowest-energy edge mode in the
microstrip after its edges were finely trimmed by means of focused Ne$^+$ ion
irradiation. Furthermore, after milling the microstrip along its long axis by
focused ion beams, creating consecutively $\sim$50 and $\sim$100 nm gaps,
additional resonances emerge and are attributed to modes localized at the inner
edges of the separated strips. To visualize the mode distribution, spatially
resolved Brillouin light scattering microscopy was used showing an excellent
agreement with the ferromagnetic resonance data and confirming the mode
localization at the outer/inner edges of the strips depending on the magnitude
of the applied magnetic field. Micromagnetic simulations confirm that the
lowest-energy modes are localized within $\sim$15-nm-wide regions at the edges
of the strips and their frequencies can be tuned in a wide range (up to 5 GHz)
by changing the magnetostatic coupling (i.e. spatial separation) between the
microstrips.",2209.13180v2
2022-11-03,Performance of different correction maps in the extended phase-space method for spinning compact binaries,"Since the first detection of gravitational waves by the LIGO/VIRGO team, the
related research field has attracted more attention. The spinning compact
binaries system, as one of the gravitational-wave sources for broadband laser
interferometers, has been widely studied by related researchers. In order to
analyze the gravitational wave signals using matched filtering techniques,
reliable numerical algorithms are needed. Spinning compact binaries systems in
Post-Newtonian (PN) celestial mechanics have an inseparable Hamiltonian. The
extended phase-space algorithm is an effective solution for the problem of this
system. We have developed correction maps for the extended phase-space method
in our previous work, which significantly improves the accuracy and stability
of the method with only a momentum scale factor. In this paper, we will add
more scale factors to modify the numerical solution in order to minimize the
errors in the constants of motion. However, we find that these correction maps
will result in a large energy bias in the subterms of the Hamiltonian in
chaotic orbits, whose potential and kinetic energy, etc. are calculated
inaccurately. We develop new correction maps to reduce the energy bias of the
subterms of the Hamiltonian, which can instead improve the accuracy of the
numerical solution and also provides a new idea for the application of the
manifold correction in other algorithms.",2211.01880v1
2022-11-04,Exchange energies in CoFeB/Ru/CoFeB Synthetic Antiferromagnets,"The interlayer exchange coupling confers specific properties to Synthetic
Antiferromagnets that make them suitable for several applications of
spintronics. The efficient use of this magnetic configuration requires an
in-depth understanding of the magnetic properties and their correlation with
the material structure. Here we establish a reliable procedure to quantify the
interlayer exchange coupling and the intralayer exchange stiffness in synthetic
antiferromagnets; we apply it to the ultrasmooth and amorphous
Co$_{40}$Fe$_{40}$B$_{20}$ (5-40 nm)/Ru/ Co$_{40}$Fe$_{40}$B$_{20}$ material
platform. The complex interplay between the two exchange interactions results
in a gradient of the magnetization orientation across the thickness of the
stack which alters the hysteresis and the spin wave eigenmodes of the stack in
a non trivial way. We measured the field-dependence of the frequencies of the
first four spin waves confined within the thickness of the stack. We modeled
these frequencies and the corresponding thickness profiles of these spin waves
using micromagnetic simulations. The comparison with the experimental results
allows to deduce the magnetic parameters that best account for the sample
behavior. The exchange stiffness is established to be 16 $\pm$ 2 pJ/m,
independently of the Co$_{40}$Fe$_{40}$B$_{20}$ thickness. The interlayer
exchange coupling starts from -1.7 mJ/m$^2$ for the thinnest layers and it can
be maintained above -1.3 mJ/m$^2$ for CoFeB layers as thick as 40 nm. The
comparison of our method with earlier characterizations using the sole
saturation fields argues for a need to revisit the tabulated values of
interlayer exchange coupling in thick synthetic antiferromagnets.",2211.02497v1
2022-11-18,"Spin density wave, Fermi liquid, and fractionalized phases in a theory of antiferromagnetic metals using paramagnons and bosonic spinons","The pseudogap metal phase of the hole-doped cuprates can be described by
small Fermi surfaces of electron-like quasiparticles, which enclose a volume
violating the Luttinger relation. This violation requires the existence of
additional fractionalized excitations which can be viewed as fractionalized
remnants of the paramagnon. We fractionalize the paramagnon into bosonic
spinons, and present a gauge theory of bosonic spinons, a Higgs field, and an
ancilla layer of fermions coupled to the original electrons. Along with the
small Fermi surface metal, this theory displays conventional phases: the Fermi
liquid with a low-energy paramagnon mode, and phases with spin density wave
order. We follow the evolution of the electronic photoemission spectrum across
these quantum phase transitions. We consider both the two-sublattice N\'eel and
incommensurate spin density wave phases.",2211.10452v6
2022-12-12,"Spin, charge and $η$-spin separation in one-dimensional photo-doped Mott insulators","We show that effectively cold metastable states in one-dimensional
photo-doped Mott insulators described by the extended Hubbard model exhibit
spin, charge and $\eta$-spin separation. Namely, their wave functions in the
large on-site Coulomb interaction limit can be expressed as $|\Psi\rangle
=|\Psi_{\rm charge}\rangle|\Psi_{\rm spin}\rangle |\Psi_{\rm
\eta-spin}\rangle$, which is analogous to the Ogata-Shiba states of the doped
Hubbard model in equilibrium. Here $\eta$-spin represents the type of the
photo-generated pseudeparticles (doublon or holon). $|\Psi_{\rm charge}\rangle$
is determined by spinless free fermions, $|\Psi_{\rm spin}\rangle$ by the
isotropic Heisenberg model in the squeezed spin space, and $|\Psi_{\rm
\eta-spin}\rangle$ by the XXZ model in the squeezed $\eta$-spin space. In
particular, the metastable $\eta$-pairing and charge-density-wave (CDW) states
correspond to the gapless and gapful states of the XXZ model. The specific form
of the wave function allows us to accurately determine the exponents of
correlation functions. The form also suggests that the central charge of the
$\eta$-pairing state is 3 and that of the CDW phase is 2, which we numerically
confirm. Our study provides analytic and intuitive insights into the
correlations between active degrees of freedom in photo-doped strongly
correlated systems.",2212.06263v2
2022-12-14,Gravitational radiation from thermal mountains on accreting neutron stars: sources of temperature non-axisymmetry,"The spin-distribution of accreting neutron stars in low-mass X-ray binary
(LMXB) systems shows a concentration of pulsars well below the Keplarian
break-up limit. It has been suggested that their spin frequencies may be
limited by the emission of gravitational waves, due to the presence of
large-scale asymmetries in the internal temperature profile of the star. These
temperature asymmetries have been demonstrated to lead to a non-axisymmetric
mass-distribution, or `mountain', that generates gravitational waves at twice
the spin frequency. The presence of a toroidal magnetic field in the interior
of accreting neutron stars has been shown to introduce such anisotropies in the
star's thermal conductivity, by restricting the flow of heat orthogonal to the
magnetic field and establishing a non-axisymmetric temperature distribution
within the star. We revisit this mechanism, extending the computational domain
from (only) the crust to the entire star, incorporating more realistic
microphysics, and exploring different choices of outer boundary condition. By
allowing a magnetic field to permeate the core of the neutron star, we find
that the likely level of temperature asymmetry in the inner crust ($\rho \sim
10^{13}$ g cm$^{-3}$) can be up to 3 orders of magnitude greater than the
previous estimate, improving prospects for one day detecting continuous
gravitational radiation. We also show that temperature asymmetries sufficiently
large to be interesting for gravitational wave emission can be generated in
strongly accreting neutron stars if crustal magnetic fields can reach $\sim
10^{12}$ G.",2212.07452v2
2023-04-03,Observation of spin-wave moiré edge and cavity modes in twisted magnetic lattices,"We report the experimental observation of the spin-wave moir\'e edge and
cavity modes using Brillouin light scattering spectro-microscopy in a
nanostructured magnetic moir\'e lattice consisting of two twisted triangle
antidot lattices based on an yttrium iron garnet thin film. Spin-wave moir\'e
edge modes are detected at an optimal twist angle and with a selective
excitation frequency. At a given twist angle, the magnetic field acts as an
additional degree of freedom for tuning the chiral behavior of the magnon edge
modes. Micromagnetic simulations indicate that the edge modes emerge within the
original magnonic band gap and at the intersection between a mini-flatband and
a propagation magnon branch. Our theoretical estimate for the Berry curvature
of the magnon-magnon coupling suggests a non-trivial topology for the chiral
edge modes and confirms the key role played by the dipolar interaction. Our
findings shed light on the topological nature of the magnon edge mode for
emergent moir\'e magnonics.",2304.01001v1
2023-11-29,Nonlinear erasing of propagating spin-wave pulses in thin-film Ga:YIG,"Nonlinear phenomena are key for magnon-based information processing, but the
nonlinear interaction between two spin-wave signals requires their
spatio-temporal overlap which can be challenging for directional processing
devices. Our study focuses on a gallium-substituted yttrium iron garnet film,
which exhibits an exchange-dominated dispersion relation and thus provides a
particularly broad range of group velocities compared to pure YIG. Using time-
and space-resolved Brillouin light scattering spectroscopy, we demonstrate the
excitation of time-separated spin-wave pulses at different frequencies from the
same source, where the delayed pulse catches up with the previously excited
pulse and outruns it due to its higher group velocity. By varying the
excitation power of the faster pulse, the outcome can be finely tuned from a
linear superposition to a nonlinear interaction of both pulses, resulting in a
full attenuation of the slower pulse. Therefore, our findings demonstrate the
all-magnonic erasing process of a propagating magnonic signal, which enables
the realization of complex temporal logic operations with potential
application, e.g., in inhibitory neuromorphic functionalities.",2311.17821v2
2024-02-15,Standing spin waves in Permalloy-NiO bilayers as a probe of the interfacial exchange coupling,"Ferromagnetic/Antiferromagnetic (FM/AFM) bilayers dynamics have been a recent
topic of interest due to the interaction occurring at the interface, where the
magnetic moments of the AFM can be imprinted into the FM, and the exchange bias
field can affect these dynamics. Here, we investigate Permalloy (Py) and NiO
(Py/NiO) hybrids and for comparison single Py films in the broad Py thickness
range varied from few nm to 200 nm by using static (Kerr effect) and dynamic
(spin waves) measurements along with micromagnetic simulations. We observe
hybrid modes between uniform (ferromagnetic resonance FMR, n=0) and
perpendicular standing spin waves (PSSWs, n=1, 2) and a clear enhancement of
the PSSWs modes frequencies upon interfacing Py with NiO both from experiments
and simulations. This enhancement becomes less pronounced as the thickness of
the film increases, demonstrating its interfacial origin rooted in the exchange
coupling between the FM and AFM layers. Besides, through micromagnetic
simulations, we investigate and correlate changes in spatial profiles of the
PSSWs with the interfacial exchange coupling. As the thickness is increased, we
see that the n=1 and n=2 modes begin to couple with the fundamental FMR mode,
resulting in asymmetric (with respect the Py layer center) modes. Our results
suggest that PSSWs detection in a ferromagnet offers a means of probing the
interfacial exchange coupling with the adjacent AFM layer. Furthermore, the
controlled spatial symmetry breaking by the AFM layer enables engineering of
PSSWs with different spatial profiles in the FM.",2402.10292v1
2024-02-21,Non-nucleonic degrees of freedom and the spin structure of the deuteron,"Electro-disintegration of the deuteron at large $Q^2$ currently represents on
of the most promising reactions which allows to probe the bound nuclear state
at internal momenta comparable to the rest mass of the nucleon. Large internal
momentum in this case makes non-nuncleonic states energetically more feasible
and the question that we address is what are the signatures that will indicate
the existence of such states in the ground state of the nuclear wave function.
  To probe such states we developed a light-front formalism for relativistic
description of a composite pseudo-vector system in which emerging proton and
neutron are observed in electro-disintegration reaction. In leading high energy
approximation our calculations show the possibility of the existence of a new
``incomplete"" P-state-like structure in the deuteron at extremely large
internal momenta. The incompleteness of the observed P-state violates the
angular condition for the momentum distribution, which can happen only if the
deuteron contains non-nucleonic structures, such as $\Delta\Delta$, $N^*N$ or
hidden color components. Because such states have distinctive angular momentum
($l=1$) they significantly modify the polarization properties of the deuteron
wave function. As a result in addition to angular anisotropy of the LF momentum
distribution of the nucleon in the deuteron one predicts strong modification of
the tensor polarization asymmetry of the deuteron beyond the S- and D- wave
predictions at large internal momenta in the deuteron.",2402.13458v1
2004-07-01,Spin structure and magnetic phase transitions in TbBaCo2O5.5,"Spin ordering in TbBaCo2O5.5 and its temperature transformation is studied.
Polymorphism due to the oxygen ordering with the average content close to 5.5
is investigated. One of ceramic samples (I), in addition to the main phase ap x
2ap x 2ap, Pmmm, (Z=2), contained about 25% of the phase ap x ap x 2ap, Pmmm,
(Z=1), with statistical distribution of oxygen over the apical sites, where ap
is parameter of perovskite cell. The other sample (II) contained only a main
phase with well defined octahedral and pyramidal sublattices. Treatment of
neutron diffraction patterns of the sample I itself gives a sophisticated spin
structure. Knowing the structure of sample II, one can chose only proper
magnetic lines, which give exactly the same results as for sample II. Above the
Neel temperature TN ~ 290K, there is a structural transition to the phase 2ap x
2ap x 2ap, Pmma. At TN, the spins order with the wave vector k19 = 0 (Phase 1).
At T1 ~ 255K, a magnetic transition takes place to the phase 2 with k22 = b3/2.
At T2 ~ 170K, the crystal structure changes to 2ap x 2ap x 4ap, Pcca (Z=4). The
wave vector of the spin structure becomes again k19 = 0 (Phase 3). The basis
functions of irreducible representations of the group Gk have been found. Using
results of this analysis, the magnetic structure in all phases is determined.
The spins are always parallel to the x axis, and the difference is in the
values and mutual orientation of the moments in the ordered non-equivalent
pyramidal or octahedral positions. Spontaneous moment at T = 260 K is due to
ferrimagnetic ordering of the moments in pyramidal sites.
(Dzyaloshinskii-Moriya canting is forbidden by symmetry.) The moment values
together with the ligand displacements are used to analyze the picture of
spin-state/orbital ordering in each phase.",0407010v3
2003-10-06,A physical template family for gravitational waves from precessing binaries of spinning compact objects: Application to single-spin binaries,"The detection of the gravitational waves (GWs) emitted by precessing binaries
of spinning compact objects is complicated by the large number of parameters
(such as the magnitudes and initial directions of the spins, and the position
and orientation of the binary with respect to the detector) that are required
to model accurately the precession-induced modulations of the GW signal. In
this paper we describe a fast matched-filtering search scheme for precessing
binaries, and we adopt the physical template family proposed by Buonanno, Chen,
and Vallisneri [Phys.Rev.D 67, 104025 (2003)] for ground-based interferometers.
This family provides essentially exact waveforms, written directly in terms of
the physical parameters, for binaries with a single significant spin, and for
which the observed GW signal is emitted during the phase of adiabatic inspiral
(for LIGO-I and VIRGO, this corresponds to a total mass M < 15Msun). We show
how the detection statistic can be maximized automatically over all the
parameters (including the position and orientation of the binary with respect
to the detector), except four (the two masses, the magnitude of the single
spin, and the opening angle between the spin and the orbital angular momentum),
so the template bank used in the search is only four-dimensional; this
technique is relevant also to the searches for GW from extreme--mass-ratio
inspirals and supermassive blackhole inspirals to be performed using the
space-borne detector LISA. Using the LIGO-I design sensitivity, we compute the
detection threshold (~10) required for a false-alarm probability of
10^(-3)/year, and the number of templates (~76,000) required for a minimum
match of 0.97, for the mass range (m1,m2)=[7,12]Msun*[1,3]Msun.",0310034v3
2010-04-15,Schwinger Boson Mean Field Theories of Spin Liquid States on Honeycomb Lattice: Projective Symmetry Group Analysis and Critical Field Theory,"Motivated by the recent numerical evidence[1] of a short-range resonating
valence bond state in the honeycomb lattice Hubbard model, we consider
Schwinger boson mean field theories of possible spin liquid states on honeycomb
lattice. From general stability considerations the possible spin liquids will
have gapped spinons coupled to Z$_2$ gauge field. We apply the projective
symmetry group(PSG) method to classify possible Z$_2$ spin liquid states within
this formalism on honeycomb lattice. It is found that there are only two
relevant Z$_2$ states, differed by the value of gauge flux, zero or $\pi$, in
the elementary hexagon. The zero-flux state is a promising candidate for the
observed spin liquid and continuous phase transition into commensurate N\'eel
order. We also derive the critical field theory for this transition, which is
the well-studied O(4) invariant theory[2-4], and has an irrelevant coupling
between Higgs and boson fields with cubic power of spatial derivatives as
required by lattice symmetry. This is in sharp contrast to the conventional
theory[5], where such transition generically leads to non-colinear
incommensurate magnetic order. In this scenario the Z$_2$ spin liquid could be
close to a tricritical point. Soft boson modes will exist at seven different
wave vectors. This will show up as low frequency dynamical spin susceptibility
peaks not only at the $\Gamma$ point (the N\'eel order wave vector) but also at
Brillouin zone edge center $M$ points and twelve other points. Some simple
properties of the $\pi$-flux state are studies as well. Symmetry allowed
further neighbor mean field ansatz are derived in Appendix which can be used in
future theoretical works along this direction.",1004.2693v3
2011-04-01,Supernova Fallback onto Magnetars and Propeller-Powered Supernovae,"We explore fallback accretion onto newly born magnetars during the supernova
of massive stars. Strong magnetic fields (~10^{15} G) and short spin periods
(~1-10 ms) have an important influence on how the magnetar interacts with the
infalling material. At long spin periods, weak magnetic fields, and high
accretion rates, sufficient material is accreted to form a black hole, as is
commonly found for massive progenitor stars. When B<5*10^{14} G, accretion
causes the magnetar to spin sufficiently rapidly to deform triaxially and
produce gravitational waves, but only for ~50-200 s until it collapses to a
black hole. Conversely, at short spin periods, strong magnetic fields, and low
accretion rates, the magnetar is in the ""propeller regime"" and avoids becoming
a black hole by expelling incoming material. This process spins down the
magnetar, so that gravitational waves are only expected if the initial
protoneutron star is spinning rapidly. Even when the magnetar survives, it
accretes at least ~0.3 solar masses, so we expect magnetars born within these
types of environments to be more massive than the 1.4 solar masses typically
associated with neutron stars. The propeller mechanism converts the ~10^{52}
ergs of spin energy in the magnetar into the kinetic energy of an outflow,
which shock heats the outgoing supernova ejecta during the first ~10-30 s. For
a small ~5 solar mass hydrogen-poor envelope, this energy creates a brighter,
faster evolving supernova with high ejecta velocities ~(1-3)*10^4 km/s and may
appear as a broad-lined Type Ib/c supernova. For a large >10 solar mass
hydrogen-rich envelope, the result is a bright Type IIP supernova with a
plateau luminosity of ~10^{43} ergs/s lasting for a timescale of ~60-80 days.",1104.0252v1
2012-02-08,Antiferromagnetic order in systems with doublet $S_{\rm tot}=1/2$ ground states,"We use projector Quantum Monte-Carlo methods to study the $S_{\rm tot}=1/2$
doublet ground states of two dimensional $S=1/2$ antiferromagnets on a $L
\times L$ square lattice with an odd number of sites $N_{\rm tot}=L^2$. We
compute the ground state spin texture $\Phi^z(\vec{r}) =
<S^z(\vec{r})>_{\uparrow}$ in $|G>_{\uparrow}$, the $S^z_{\rm tot}=1/2$
component of this doublet, and investigate the relationship between $n^z$, the
thermodynamic limit of the staggered component of this ground state spin
texture, and $m$, the thermodynamic limit of the magnitude of the staggered
magnetization vector of the same system in the singlet ground state that
obtains for even $N_{\rm tot}$. We find a univeral relationship between the
two, that is independent of the microscopic details of the lattice level
Hamiltonian and can be well approximated by a polynomial interpolation formula:
$n^z \approx (1/3 - \frac{a}{2} -\frac{b}{4}) m + am^2+bm^3$, with $a \approx
0.288$ and $b\approx -0.306$. We also find that the full spin texture
$\Phi^z(\vec{r})$ is itself dominated by Fourier modes near the
antiferromagnetic wavevector in a universal way. On the analytical side, we
explore this question using spin-wave theory, a simple mean field model written
in terms of the total spin of each sublattice, and a rotor model for the
dynamics of $\vec{n}$. We find that spin-wave theory reproduces this
universality of $\Phi^z(\vec{r})$ and gives $n^z = (1-\alpha -\beta/S)m +
(\alpha/S)m^2 +{\mathcal O}(S^{-2})$ with $\alpha \approx 0.013$ and $\beta
\approx 1.003$ for spin-$S$ antiferromagnets, while the sublattice-spin mean
field theory and the rotor model both give $n^z = 1/3 m$ for $S=1/2$
antiferromagnets. We argue that this latter relationship becomes asymptotically
exact in the limit of infinitely long-range {\em unfrustrated} exchange
interactions.",1202.1687v1
2014-03-13,Magnetic transitions in the spin S=5/2 frustrated magnet BiMn2PO6 and strong lattice softening in BiMn2PO6 and BiZn2PO6 below 200 K,"The crystallographic, magnetic and thermal properties of BiMn2PO6 and
BiZn2PO6 were investigated by x-ray diffraction, magnetic susceptibility \chi,
heat capacity Cp, and 31P NMR measurements as well as by density-functional
band-theory calculations. Both compounds show a strong monotonic lattice
softening on cooling, where the Debye temperature decreases by a factor of two
from \Theta_D=650K at T=300K to \Theta_D=300K at T=2K. The \chi(T) data for
BiMn2PO6 above 150K follow a Curie-Weiss law with a Curie constant consistent
with a S=5/2 with g=2 and an antiferromagnetic (AFM) Weiss temperature
\theta_CW= -78K. The \chi data indicate long-range AFM ordering below TN=30K,
confirmed by a sharp lambda-type peak in Cp(T) at 28.8K. The band-theory
calculations indicate that BiMn2PO6 is an AFM compound with dominant
interactions J1/kB= 6.7K and J3/kB= 5.6K along the legs and rungs of a two-leg
spin-ladder, respectively. In addition to the long-range AFM ordering at
TN=30K, a second transition at 10 K is observed from the \chi and NMR
measurements but is not evident in the Cp data. The Cp data at low T suggest a
significant contribution from AFM spin waves moving in three dimensions and the
absence of a spin-wave gap. A detailed analysis of the NMR spectra indicates
commensurate magnetic order between 10K and 30K and a possible incommensurate
modulation and/or spin canting below 10K. The commensurate order is consistent
with microscopic simulations that yield a collinear Neel-type AFM spin
arrangement both within and between the ladders, despite the presence of
multiple weak interactions frustrating this magnetic structure. Frustration for
AFM ordering and 1D spatial anisotropy of the 3D spin interactions are
manifested in the frustration ratio f=|{\theta}CW|/TN=2.6, indicating a
suppression of TN from 68K in the absence of these effects to 30K in BiMn2PO6.",1403.3146v2
2015-02-03,Static and Dynamic Properties of Interacting Spin-1 Bosons in an Optical Lattice,"We study the physics of interacting spin-$1$ bosons in an optical lattice
using a variational Gutzwiller technique. We compute the mean-field ground
state wave-function and discuss the evolution of the condensate, spin, nematic,
and singlet order parameters across the superfluid-Mott transition. We then
extend the Gutzwiller method to derive the equations governing the dynamics of
low energy excitations in the lattice. Linearizing these equations, we compute
the excitation spectra in the superfluid and Mott phases for both ferromagnetic
and antiferromagnetic spin-spin interactions. In the superfluid phase, we
recover the known excitation spectrum obtained from Bogoliubov theory. In the
nematic Mott phase, we obtain gapped, quadratically dispersing particle and
hole-like collective modes, whereas in the singlet Mott phase, we obtain a
non-dispersive gapped mode, corresponding to the breaking of a singlet pair.
For the ferromagnetic Mott insulator, the Gutzwiller mean-field theory only
yields particle-hole like modes but no Goldstone mode associated with long
range spin order. To overcome this limitation, we supplement the Gutzwiller
theory with a Schwinger boson mean-field theory which captures super-exchange
driven fluctuations. In addition to the gapped particle-hole-like modes, we
obtain a gapless quadratically dispersing ferromagnetic spin-wave Goldstone
mode. We discuss the evolution of the singlet gap, particle-hole gap, and the
effective mass of the ferromagnetic Goldstone mode as the superfluid-Mott phase
boundary is approached from the insulating side. We discuss the relevance and
validity of Gutzwiller mean-field theories to spinful systems, and potential
extensions of this framework to include more exotic physics which appears in
the presence of spin-orbit coupling or artificial gauge fields.",1502.01041v1
2015-02-26,The spin rate of pre-collapse stellar cores: wave-driven angular momentum transport in massive stars,"The core rotation rates of massive stars have a substantial impact on the
nature of core-collapse supernovae and their compact remnants. We demonstrate
that internal gravity waves (IGW), excited via envelope convection during a red
supergiant phase or during vigorous late time burning phases, can have a
significant impact on the rotation rate of the pre-SN core. In typical ($10 \,
M_\odot \lesssim M \lesssim 20 \, M_\odot$) supernova progenitors, IGW may
substantially spin down the core, leading to iron core rotation periods $P_{\rm
min,Fe} \gtrsim 30 \, {\rm s}$. Angular momentum (AM) conservation during the
supernova would entail minimum NS rotation periods of $P_{\rm min,NS} \gtrsim 3
\, {\rm ms}$. In most cases, the combined effects of magnetic torques and IGW
AM transport likely lead to substantially longer rotation periods. However, the
stochastic influx of AM delivered by IGW during shell burning phases inevitably
spin up a slowly rotating stellar core, leading to a maximum possible core
rotation period. We estimate maximum iron core rotation periods of $P_{\rm
max,Fe} \lesssim 5 \times 10^3 \, {\rm s}$ in typical core-collapse supernova
progenitors, and a corresponding spin period of $P_{\rm max, NS} \lesssim 500
\, {\rm ms}$ for newborn neutron stars. This is comparable to the typical birth
spin periods of most radio pulsars. Stochastic spin-up via IGW during shell
O/Si burning may thus determine the initial rotation rate of most neutron
stars. For a given progenitor, this theory predicts a Maxwellian distribution
in pre-collapse core rotation frequency that is uncorrelated with the spin of
the overlying envelope.",1502.07779v3
2015-11-06,Impact of gravitational radiation higher order modes on single aligned-spin gravitational wave searches for binary black holes,"Current template-based gravitational wave searches for compact binary
coalescences (CBC) use waveform models that neglect the higher order modes
content of the gravitational radiation emitted, considering only the
quadrupolar $(\ell,|m|)=(2,2)$ modes. We study the effect of such a neglection
for the case of aligned-spin CBC searches for equal-spin (and non-spinning)
binary black holes in the context of two versions of Advanced LIGO: the
upcoming 2015 version, known as early Advanced LIGO (eaLIGO) and its
Zero-Detuned High Energy Power version, that we will refer to as Advanced LIGO
(AdvLIGO). In addition, we study the case of a non-spinning search for initial
LIGO (iLIGO). We do this via computing the effectualness of the aligned-spin
SEOBNRv1 ROM waveform family, which only considers quadrupolar modes, towards
hybrid post-Newtonian/Numerical Relativity waveforms which contain higher order
modes. We find that for all LIGO versions, losses of more than $10\%$ of events
occur for mass ratio $q\geq6$ and $M \geq 100M_\odot$ due to the neglection of
higher modes. Moreover, for iLIGO and eaLIGO, losses notably increase up to
$(39,23)\%$ respectively for the highest mass $(220M_\odot)$ and mass ratio
($q=8$) studied. For the case of early AdvLIGO, losses of $10\%$ occur for
$M>50M_\odot$ and $q\geq6$. Neglection of higher modes leads to
observation-averaged systematic parameter biases towards lower spin, total mass
and chirp mass. For completeness, we perform a preliminar, non-exhaustive
comparison of systematic biases to statistical errors. We find that, for a
given SNR, systematic biases dominate over statistical errors at much lower
total mass for eaLIGO than for AdvLIGO.",1511.02060v2
2018-05-26,"Spin gaps in the ordered states of La$_2$LiXO$_6$ (X = Ru, Os) and their relation to distortion of the cubic double perovskite structure in 4$d^3$ and 5$d^3$ magnets","Time-of-flight inelastic neutron scattering measurements have been carried
out on polycrystalline samples of the 4$d^3$ and 5$d^3$ double pervoskite
antiferromagnets La$_2$LiRuO$_6$ and La$_2$LiOsO$_6$. These reveal the
development of an inelastic spin gap in La$_2$LiRuO$_6$ and La$_2$LiOsO$_6$ of
$\sim$ 1.8(8) meV and 6(1) meV, below their respective ordering temperatures,
$T_N$, $\sim$ 23.8 K and 30 K. The bandwidth of the spin excitations is shown
to be $\sim$ 5.7(9) to 12(1) meV, respectively, at low temperatures. Spin gaps
are surprising in such magnets as the t$_{2g}$ levels of Ru$^{5+}$ or Os$^{5+}$
are expected to be half-filled, resulting in an anticipated orbital singlet for
both materials. We compare these results in monoclinic double perovskites
La$_2$LiRuO$_6$ and La$_2$LiOsO$_6$ with those in cubic Ba$_2$YRuO$_6$ and
Ba$_2$YOsO$_6$, as well as with those in the more strongly monoclinic
La$_2$NaRuO$_6$, La$_2$NaOsO$_6$, and Sr$_2$ScOsO$_6$, and model the inelastic
magnetic scattering with linear spin wave theory using minimal anisotropic
exchange interactions. We discuss the possible role of the distortion of the
face-centered cubic, double perovskite structure on the spin gap formation and
geometric frustration in these materials, and show that $T_N$ scales with the
top of the spin wave band in all members of these families that display long
range order.",1805.10467v1
2021-02-04,Magnon-spinon dichotomy in the Kitaev hyperhoneycomb $β$-Li$_2$IrO$_3$,"The family of edge-sharing tri-coordinated iridates and ruthenates has
emerged in recent years as a major platform for Kitaev spin liquid physics,
where spins fractionalize into emergent magnetic fluxes and Majorana fermions
with Dirac-like dispersions. While such exotic states are usually pre-empted by
long-range magnetic order at low temperatures, signatures of Majorana fermions
with long coherent times have been predicted to manifest at intermediate and
higher energy scales, similar to the observation of spinons in quasi-1D spin
chains. Here we present a Resonant Inelastic X-ray Scattering study of the
magnetic excitations of the hyperhoneycomb iridate $\beta$-Li$_2$IrO$_3$ under
a magnetic field with a record-high-resolution spectrometer. At
low-temperatures, dispersing spin waves can be resolved around the predicted
intertwined incommensurate spiral and field-induced zigzag orders, whose
excitation energy reaches a maximum of 16meV. A 2T magnetic field softens the
dispersion around ${\bf Q}=0$. The behavior of the spin waves under magnetic
field is consistent with our semiclassical calculations for the ground state
and the dynamical spin structure factor, which further predicts that the ensued
intertwined uniform states remain robust up to very high fields (100 T). Most
saliently, the low-energy magnon-like mode is superimposed by a broad continuum
of excitations, centered around 35meV and extending up to 100meV. This
high-energy continuum survives up to at least 300K -- well above the ordering
temperature of 38K -- and gives evidence for pairs of long-lived Majorana
fermions of the proximate Kitaev spin liquid.",2102.02714v2
2021-09-02,Survey of gravitational wave memory in intermediate mass ratio binaries,"The non-linear gravitational wave (GW) memory effect is a distinct prediction
in general relativity. While the effect has been well studied for comparable
mass binaries, it has mostly been overlooked for intermediate mass ratio
inspirals (IMRIs). We offer a comprehensive analysis of the phenomenology and
detectability of memory effects, including contributions from subdominant
harmonic modes, in heavy IMRIs consisting of a stellar mass black hole and an
intermediate mass black hole. When formed through hierarchical mergers, for
example when a GW190521-like remnant captures a stellar mass black hole, IMRI
systems have a large total mass, large spin on the primary, and possibly
residual eccentricity; features that potentially raise the prospect for memory
detection. We compute both the displacement and spin non-linear GW memory from
the $m \neq 0$ gravitational waveforms computed within a black hole
perturbation theory framework that is partially calibrated to numerical
relativity waveforms. We probe the dependence of memory effects on mass ratio,
spin, and eccentricity and consider the detectability of a memory signal from
IMRIs using current and future GW detectors. We find that (i) while
eccentricity introduces additional features in both displacement and spin
memory, it does not appreciatively change the prospects of detectability, (ii)
including higher modes into the memory computation can increase singal-to-noise
(SNR) values by about 7\% in some cases, (iii) the SNR from displacement memory
dramatically increases as the spin approaches large, positive values, (iv) spin
memory from heavy IMRIs would, however, be difficult to detect with future
generation detectors even from highly spinning systems. Our results suggest
that hierarchical binary black hole mergers may be a promising source for
detecting memory and could favorably impact memory forecasts.",2109.00754v2
2005-03-01,Relativistic SPH Calculations of Compact Binary Mergers,"We review recent progress in understanding the hydrodynamics of compact
binary mergers using relativistic smoothed particle hydrodynamics (SPH) codes.
Recent results are discussed for both double neutron stars and black hole -
neutron star binaries. The gravitational wave signals from these mergers
contain a lot of information about the masses and radii of the stars and the
equation of state of the neutron star fluid. For black hole - neutron star
mergers, the final fate of the fluid and the gravitational wave emission depend
strongly on the mass ratio and the black hole spin.",0503007v1
2006-05-01,Searching for sub-millisecond pulsars: A theoretical view,"Sub-millisecond pulsars should be triaxial (Jacobi ellipsoids), which may not
spin down to super-millisecond periods via gravitation wave radiation during
their lifetimes if they are extremely low mass bare strange quark stars. It is
addressed that the spindown of sub-millisecond pulsars would be torqued
dominantly by gravitational wave radiation (with braking index n ~ 5). The
radio luminosity of sub-millisecond pulsars could be high enough to be detected
in advanced radio telescopes. Sub-millisecond pulsars, if detected, should be
very likely quark stars with low masses and/or small equatorial ellipticities.",0605028v2
1996-10-15,On the Convergence to Ergodic Behaviour of Quantum Wave Functions,"We study the decrease of fluctuations of diagonal matrix elements of
observables and of Husimi densities of quantum mechanical wave functions around
their mean value upon approaching the semi-classical regime ($\hbar \rightarrow
0$). The model studied is a spin (SU(2)) one in a classically strongly chaotic
regime. We show that the fluctuations are Gaussian distributed, with a width
$\sigma^2$ decreasing as the square root of Planck's constant. This is
consistent with Random Matrix Theory (RMT) predictions, and previous studies on
these fluctuations. We further study the width of the probability distribution
of $\hbar$-dependent fluctuations and compare it to the Gaussian Orthogonal
Ensemble (GOE) of RMT.",9610014v1
1993-02-06,Phase diagram of the one-dimensional extended Hubbard model at quarter filling,"We used exact diagonalization of small clusters and exact results in various
limits to determine the phase diagram and the critical exponents of the one
dimensional (1D) $U-V$ model at quarter-filling. We found an instability of the
Luttinger liquid to a charge-density wave (CDW) insulator across a boundary
going from ($U$,$V$) =($+\infty$,$2t$) to ($4t$,$+\infty$). In the metallic
phase, the dominant fluctuations are superconducting if $V$ is large enough and
spin-density wave (SDW) otherwise. In the latter case, the critical exponent
$\alpha$ of the momentum distribution does not exceed 9/16. The relevance of
these results to 1D organic conductors is discussed.",9302010v1
1994-03-11,Large size two-hole bound states in t-J model,"Several series of shallow large-size ($l \gg lattice~ spacing$) two-hole
bound states are found in the two-dimensional t-J model. Their binding energies
depend exponentially on the inverse value of the hole-spin-wave coupling
constant. Their parity is connected with the angular wave function in a
nonstandard way. The possible role of these states in the formation of
superconducting pairing is considered.",9403044v1
1994-04-28,t-J model Studied by the New Lanczos-Power Method,"The initial trial wave function used in a simple ground-state projection
method, the power method, is systematically improved by using Lanczos
algorithm. Much faster convergence to the ground state achieved by using these
wave functions significantly reduces the effect of the fermion sign problem.
The energy, spin and charge correlation functions are calculated for the ground
states of the two-dimensional $t-J$ model. Results for an $8\times8$ cluster
with 42 and 26 electrons are presented. The density correlation function for
the $t-J$ model at small J shows a surprisingly good agreement with that of a
system of non-interacting hard-core bosons.",9404095v1
1994-12-14,Theory of Electronic Raman Scattering in Disordered $d-$wave Superconductors,"A theory for the effect of impurity scattering on electronic Raman scattering
in unconventional superconductors is presented. The impurity dependence of the
the spectra can be used to to distinguish between conventional (anisotropic
$s-$wave) or unconventional ($d$-wave) energy gaps, and excellent agreement
with the data on three cuprate superconductors is shown for $d_{x^{2}-y^{2}}$
pairing. The full frequency dependence of the spectra can be reproduced by
including inelastic scattering due to spin fluctuations and/or Coulomb
scattering on a partially nested Fermi surface.",9412065v1
1995-09-19,An Alternative Route to D-wave Superconductivity: the Charge Channel,"We demonstrate that a $d_{x^2-y^2}$ superconducting pairing is naturally
associated with the screened Coulomb interaction $V_{eff}({\bf q},\omega)$
within the $CuO_2$ plane of high $T_c$ superconductors. This pairing
instability arises (via the dielectric constant) from wave-vector structure in
$V_{eff}({\bf q},\omega )$ at ${\bf q}=(\pi,\pi)$, which is associated with 2D
Van Hove and local field effects. Our results, which are independent of the
bandstructure, suggest that direct Coulomb intereactions are significant (when
compared to the spin channel) and will, at the least, enhance any other
underlying mechanism for $d_{x^2-y^2}$ wave pairing.",9509119v1
1995-11-22,Diffusion of electrons in two-dimensional disordered symplectic systems,"Diffusion of electrons in two-dimensional disordered systems with spin-orbit
interactions is investigated numerically. Asymptotic behaviors of the second
moment of the wave packet and of the temporal auto-correlation function are
examined. At the critical point, the auto-correlation function exhibits the
power-law decay with a non-conventional exponent $\alpha$ which is related to
the fractal structure in the energy spectrum and in the wave functions. In the
metallic regime, the present results imply that transport properties can be
described by the diffusion equation for normal metals.",9511108v1
1997-12-20,Collective Excitations in High-Temperature Superconductors,"Collective, low-energy excitations in quasi-two-dimensional d-wave
superconductors are analyzed. While the long-range Coulomb interaction shifts
the charge-density-wave and phase modes up to the plasma energy, the
spin-density-wave excitation that arises due to a strong local
electron-electron repulsion can propagate as a damped collective mode within
the superconducting energy gap. It is suggested that these excitations are
relevant to high-Tc superconductors, close to the antiferromagnetic phase
boundary, and may explain some of the exotic features of the experimentally
observed spectral-density and neutron-scattering data.",9712255v1
1998-10-08,Density Matrix Renormalization Group of Gapless Systems,"We investigate convergence of the density matrix renormalization group (DMRG)
in the thermodynamic limit for gapless systems. Although the DMRG correlations
always decay exponentially in the thermodynamic limit, the correlation length
at the DMRG fixed-point scales as $\xi \sim m^{1.3}$, where $m$ is the number
of kept states, indicating the existence of algebraic order for the exact
system. The single-particle excitation spectrum is calculated, using a
Bloch-wave ansatz, and we prove that the Bloch-wave ansatz leads to the
symmetry $E(k)=E(\pi -k)$ for translationally invariant half-integer
spin-systems with local interactions. Finally, we provide a method to compute
overlaps between ground states obtained from different DMRG calculations.",9810093v1
1999-02-02,Instabilities at [110] Surfaces of d_{x^2-y^2} Superconductors,"We compare different scenarios for the low temperature splitting of the
zero-energy peak in the local density of states at (110) surfaces of
d_{x^2-y^2}-wave superconductors, observed by Covington et al.
(Phys.Rev.Lett.79 (1997), 277). Using a tight binding model in the
Bogolyubov-de Gennes treatment we find a surface phase transition towards a
time-reversal symmetry breaking surface state carrying spontaneous currents and
an s+id-wave state. Alternatively, we show that electron correlation leads to a
surface phase transition towards a magnetic state corresponding to a local spin
density wave state.",9902026v1
1999-11-07,Nonlinear conduction of sliding electronic crystals: Charge and Spin Density Waves,"A model of local metastable states due to the pinning induces plastic
deformations allows to describe the nonlinear I-V curves in sliding density
waves -DW. With increasing the DW velocity v, the metastable states of
decreasing lifetimes ~1/v are accessed. The characteristic second threshold
field is reached when configurations of shortest life time are accessed by the
fast moving DW. Thus the DW works as a kind of a ``linear accelerator'' testing
virtual states.",9911100v1
2001-01-15,Neutron Scattering Signature of d-density Wave Order in the Cuprates,"An ordered $d$-density wave (DDW) state has been proposed as an explanation
of the pseudogap phase in underdoped high-temperature superconductors. The
staggered currents associated with this order have signatures which are
qualitatively different from those of ordered spins. We apply the order
parameter theory to an orthorhombic bilayer system and show that the expected
magnitude as well as the momentum, energy, and polarization dependence of the
consequent neutron scattering is consistent with the findings of a recent
experiment.",0101204v2
2001-01-16,Optical excitations of a self assembled artificial ion,"By use of magneto-photoluminescence spectroscopy we demonstrate bias
controlled single-electron charging of a single quantum dot. Neutral, single,
and double charged excitons are identified in the optical spectra. At high
magnetic fields one Zeeman component of the single charged exciton is found to
be quenched, which is attributed to the competing effects of tunneling and
spin-flip processes. Our experimental data are in good agreement with
theoretical model calculations for situations where the spatial extent of the
hole wave functions is smaller as compared to the electron wave functions.",0101240v1
2001-04-09,Phase diagram regions deduced for strongly correlated systems via unitary transformation,"From known phase diagram regions of different model Hamiltonians describing
strongly correlated systems we deduced new domains of the ground state phase
diagram of the same model by an unitary transformation. Different types of
extended Hubbard Hamiltonians were used for the starting point and the
existence of new stable spin-density wave, charge-density wave, ferromagnetic
state and a paramagnetic insulator is demonstrated. The used procedure itself
is dimension independent.",0104143v1
2002-02-27,One-dimensional Disordered Density Waves and Superfluids: The Role of Quantum Phase Slips and Thermal Fluctuations,"The low temperature phase diagram of 1D disordered quantum systems like
charge or spin density waves, superfluids and related systems is considered by
a full finite T renormalization group approach, presented here for the first
time. At zero temperature the consideration of quantum phase slips leads to a
new scenario for the unpinning (delocalization) transition. At finite T a rich
cross-over diagram is found which reflects the zero temperature quantum
critical behavior.",0202507v1
2002-05-09,Accurate hyperfine couplings for C59N,"We identify the shortcomings of existing ab initio quantum chemistry
calculations for the hyperfine couplings in the recently characterized
azafullerene, C59N. Standard gaussian basis sets in the context of
all--electron calculations are insufficient to resolve the spin density near
the cores of the atoms. Using the Projector Augmented Wave method implemented
on top of a standard pseudopotential plane--wave density--functional framework,
we compute significantly more accurate values for the Fermi contact
interaction.",0205198v1
2002-08-15,Orbital-singlet pairing and order parameter symmetry in Sr_2RuO_4,"Based on the degeneracy of the d_{zx} and d_{yz} orbitals in Sr_2RuO_4 it is
argued that the Cooper pairs condense in orbital singlets. Together with the
spin-triplet wave functions the real-space wave function then is symmetric.
Considering interaction effects the order parameter is found to have A_{1g}
symmetry consistent with a number of experimental observations. The sensitivity
of the material on non-magnetic impurities follows in a straightforward manner
from the orbital-singlet configuration.",0208301v1
2003-04-22,Nanoscopic Filters as the Origin of d Wave Energy Gaps,"A ferroelastic nanoscopic checkerboard pattern of pseudo- and superconductive
gaps has been resolved by scanning tunneling microscopy on BSCCO. Using this
pattern one can derive [not assume] a macroscopic anisotropic d wave
superconductive energy gap that agrees well with angle-resolved photoemission
and Fourier transform scanning tunneling microscopy data. The derivation is
orbital only [no spins], it explains chemical trends in Raman scattering peak
positions and strengths, and it predicts an unexpected reversal of anisotropic
Raman gap signatures between BSCCO and LSCO, in good agreement with experiment.",0304501v1
2003-07-08,"Superconductivity, d Charge-Density Wave and Electronic Raman Scattering in High-T$_c$ Superconductors","The competition of superconductivity and a d charge-density wave (CDW) is
studied in the t-J model as a function of temperature at large N where N is the
number of spin components. Applying the theory to electronic Raman scattering
the temperature dependence of the $B_{1g}$ and the $A_{1g}$ spectra are
discussed for a slightly underdoped case.",0307177v1
2003-10-24,Exact duality relations in correlated electron systems,"Using gauge transformations on electron bond operators, we derive exact
duality relations between various order parameters for correlated electron
systems. Applying these transformations, we find two duality relations in the
generalized two-leg Hubbard ladder at arbitrary filling. The relations show
that unconventional density-wave orders such as staggered flux or circulating
spin-current are dual to conventional density-wave orders and there are direct
mappings between dual phases. Several exact results on the phase diagram are
also concluded.",0310574v2
2004-02-20,Low-frequency incommensurate magnetic response in strongly correlated systems,"It is shown that in the t-J model of Cu-O planes at low frequencies the
dynamic spin structure factor is peaked at incommensurate wave vectors
(1/2+-delta,1/2)$, (1/2,1/2+-delta). The incommensurability is connected with
the momentum dependencies of the magnon frequency and damping near the
antiferromagnetic wave vector. The behavior of the incommensurate peaks is
similar to that observed in La_{2-x}(Ba,Sr)_xCuO_{4+y} and YBa_2Cu_3O_{7-y}:
for hole concentrations 0.02<x<=0.12 we find that delta is nearly proportional
to x, while for x>0.12 it tends to saturation. The incommensurability
disappears with increasing temperature. Generally the incommensurate magnetic
response is not accompanied by an inhomogeneity of the carrier density.",0402512v1
2004-10-13,Zitterbewegung of electronic wave packets in semiconductor nanostructures,"We study the zitterbewegung of electronic wave packets in III-V zinc-blende
semiconductor quantum wells due to spin-orbit coupling. Our results suggest a
direct experimental proof of this fundamental effect, confirming a
long-standing theoretical prediction. For electron motion in a harmonic quantum
wire, we numerically and analytically find a resonance condition maximizing the
zitterbewegung.",0410321v2
2005-06-27,Spin-lattice coupling in the ferrimagnetic semiconductor FeCr2S4 probed by surface acoustic waves,"Using surface acoustic waves, the elastomagnetic coupling could be studied in
thin single crystalline plates of the ferrimagnetic semiconductor FeCr2S4 by
measuring the attenuation and the frequency tracking in the temperature range
4.2 K to 200 K. The data clearly display the anomalies found in low-field
magnetization measurements.",0506702v1
2006-05-22,Many-body wavefunctions for normal liquid $^3$He,"We present new trial wave-functions which include 3-body correlations into
the backflow coordinates and a 4-body symmetric potential. We show that our
wavefunctions lower the energy enough to stabilize the ground state energies of
normal liquid $^3$He in the unpolarized state at all pressures in agreement
with experiment; however, quantitative discrepancies remain. Further, we
include strong spin coupling into the Fermi liquid by adapting pairing wave
functions. We demonstrate a new, numerically stable method to evaluate pairing
functions which is also useful for Path Integrals calculations at low, but
non-zero temperatures.",0605513v2
2006-05-30,A modified triplet-wave expansion method applied to the alternating Heisenberg chain,"An alternative triplet-wave expansion formalism for dimerized spin systems is
presented, a modification of the 'bond operator' formalism of Sachdev and
Bhatt. Projection operators are used to confine the system to the physical
subspace, rather than constraint equations. The method is illustrated for the
case of the alternating Heisenberg chain, and comparisons are made with the
results of dimer series expansions and exact diagonalization. Some discussion
is included of the phenomenon of 'quasiparticle breakdown', as it applies to
the two-triplon bound states in this model.",0605724v4
2006-09-25,"Light-Induced Magnetic Precession in (Ga,Mn)As Slabs: Hybrid Standing-Wave Damon-Eshbach Modes","Coherent oscillations associated with spin precessions were observed in
ultrafast optical experiments on ferromagnetic (Ga,Mn)As films. Using a
complete theoretical description of the processes by which light couples to the
magnetization, values for the exchange and anisotropy constants were obtained
from the field-dependence of the magnon frequencies and the
oscillation-amplitude ratios. Results reveal a relatively large negative
contribution to the energy due to surface anisotropy leading to excitations
that are a mixture of bulk waves and surface modes.",0609646v1
2006-09-27,Ballistic side jump motion of electrons and holes in semiconductor quantum wells,"We investigate the ballistic motion of electrons and holes in III-V
semiconductor quantum wells with spin-orbit coupling and a homogeneous in-plane
electric field. As a result of a non-perturbative treatment of both of these
influences, particle wave packets undergo a pronounced side jump perpendicular
to the field direction. For wave packets of sufficient width the amplitude of
this motion can be estimated analytically and increases with decreasing field
strength. We discuss the scaling behavior of the effect and some if its
experimental implications",0609686v1
2007-01-26,Analysis of a SU(4) generalization of Halperin's wave function as an approach towards a SU(4) fractional quantum Hall effect in graphene sheets,"Inspired by the four-fold spin-valley symmetry of relativistic electrons in
graphene, we investigate a possible SU(4) fractional quantum Hall effect, which
may also arise in bilayer semiconductor quantum Hall systems with small Zeeman
gap. SU(4) generalizations of Halperin's wave functions [Helv. Phys. Acta 56,
75 (1983)], which may break differently the original SU(4) symmetry, are
studied analytically and compared, at nu=2/3, to exact-diagonalization studies.",0701661v2
2007-03-28,Characteristic frequency of the magnetic radiation of spinor condensates,"The magnetic radiation of the fully-condensed states of $^{23}$Na condensates
have been studied. A narrow characteristic spectral line with a wave length
proportional to N^(-2/5) (N is the number of particles) and with a probability
of transition proportional to N^(17/5) emitted (absorbed) by the condensate was
found. It implies that short wave radiation with a huge probability of
transition can be obtained if numerous atoms are trapped. A new technique
developed by the authors, namely, the analytical forms of the fractional
parentage coefficients, was used to calculate analytically the matrix elements
between the total spin-states.",0703739v1
1996-04-12,Testing Theories of Gravity with a Spherical Gravitational Wave Detector,"We consider the possibility of discriminating different theories of gravity
using a recently proposed gravitational wave detector of spherical shape. We
argue that the spin content of different theories can be extracted relating the
measurements of the excited spheroidal vibrational eigenmodes to the
Newman-Penrose parameters. The sphere toroidal modes cannot be excited by any
metric GW and can be thus used as a veto.",9604026v1
1999-08-31,Gravitational-wave driven instability of rotating relativistic stars,"A brief review of the stability of rotating relativistic stars is followed by
a more detailed discussion of recent work on an instability of r-modes, modes
of rotating stars that have axial parity in the slow-rotation limit. These
modes may dominate the spin-down of neutron stars that are rapidly rotating at
birth, and the gravitational waves they emit may be detectable.",9908083v1
1999-09-30,Does a dynamical system lose energy by emitting gravitational waves?,"We note that Eddington's radiation damping calculation of a spinning rod
fails to account for the complete mass integral as given by Tolman. The missing
stress contributions precisely cancel the standard rate given by the
'quadrupole formula'. This indicates that while the usual 'kinetic' term can
properly account for dynamical changes in the source, the actual mass is
conserved. Hence gravity waves are not carriers of energy in vacuum. This
supports the hypothesis that energy including the gravitational contribution is
confined to regions of non-vanishing energy-momentum tensor $T_{ik}$.
  PACS numbers: 04.20.Cv, 04.30.-w",9909095v1
2000-05-16,LISA observations of massive black holes binaries using post-Newtonian wave-forms,"We consider LISA observations of in-spiral signals emitted by massive black
hole binary systems in circular orbit and with negligible spins. We study the
accuracy with which the source parameters can be extracted from the data
stream. We show that the use of waveforms retaining post-Newtonian corrections
not only to the phase but also the amplitude can drastically improve the
estimation of some parameters.",0005059v1
2001-07-13,Detecting torsion from LISA and teleparallel gravity,"Torsion detection from totally skew symmetric torsion waves in the context of
teleparallel gravity is discussed. A gedanken experiment to detect Cartan's
contortion based on a circle of particles not necessarily spinning is proposed.
It is shown that by making use of previous value of contortion at the surface
of the Earth computed by Nitsch of $10^{-24} s^{-1}$ a relative displacement of
$10^{-21}$ is obtained which is of the order of the gravitational wave of
$10^{-3}Hz$. Since LISA has been designed to work in the mHz regime this GW
detector could be used for an indirect detection of torsion in $T_{4}$.",0107048v2
2001-08-09,Dual Metrics and Non-Generic Supersymmetries for a Class of Siklos Spacetimes,"The presence of Killing-Yano tensors implies the existence of non-generic
supercharges in spinning point particle theories on curved backgrounds. Dual
metrics are defined through their associated non-degenerate Killing tensors of
valence two. Siklos spacetimes, which are the only non-trivial Einstein spaces
conformal to non-flat pp-waves are investigated in regards to the existence of
their corresponding Killing and Killing-Yano tensors. It is found that under
some restrictions, pp-wave metrics and Siklos spacetimes admit dual metrics and
non-generic supercharges. Possible significance of those dual spacetimes are
discussed.",0108029v1
2002-05-22,Solution of Massless Spin One Wave Equation in Robertson-Walker Space-time,"We generalize the quantum spinor wave equation for photon into the curved
space-time and discuss the solutions of this equation in Robertson-Walker
space-time and compare them with the solution of the Maxwell equations in the
same space-time.",0205097v2
2002-07-30,Data analysis of continuous gravitational wave: Fourier transform-II,"In this paper we obtain the Fourier Transform of a continuous gravitational
wave. We have analysed the data set for (i) one year observation time and (ii)
arbitrary observation time, for arbitrary location of detector and source
taking into account the effects arising due to rotational as well as orbital
motion of the earth. As an application of the transform we considered spin down
and N-component signal analysis.",0207119v1
2003-02-12,Analytical solution of the neutrino wave equation in Kerr geometry with Vaidya-Patel coordinates,"Analytical solution of Weyl neutrino wave equation in Kerr geometry is
presented by making use of the two-spinor component spin-coefficient
Newman-Penrose (NP) calculus. So far only asymptotic or approximate solutions
have been found for the Weyl equation in this background. It is shown that
neutrino current asymmetry is also present in this solution.",0302042v1
2003-04-20,Electromagnetic Waves in a Rotating Frame of Reference,"We discuss the electromagnetic measurements of rotating observers and study
the propagation of electromagnetic waves in a uniformly rotating frame of
reference. The phenomenon of helicity-rotation coupling is elucidated and some
of the observational consequences of the coupling of the spin of a particle
with the rotation of a gravitational source are briefly examined.",0304069v2
2003-05-27,"Pseudoenergy, Superenergy, and Energy Radiation via Gravitational Waves in General Relativity","For slowly spinning matter the rate of energy loss via radiation of
gravitational waves is estimated in General Relativity (GR) within a generally
covariant superenergy approach. This estimation differs from Einstein's
Quadrupole Formula (EQF) by a suppression factor ($\Pi\ll1$). For a symmetric
two-body-like distribution of scalar matter $\Pi$ is estimated to be
$\ll(v/c)^2(r/R)^2$, where $v$ is orbital velocity of the bodies, $c$ -
velocity of light, $r$ - radius of each body, and $R$ -- the inter-body
distance. This contradiction with EQF is briefly discussed.",0305100v1
2004-02-06,A Metropolis-Hastings algorithm for extracting periodic gravitational wave signals from laser interferometric detector data,"The Markov chain Monte Carlo methods offer practical procedures for detecting
signals characterized by a large number of parameters and under conditions of
low signal-to-noise ratio. We present a Metropolis-Hastings algorithm capable
of inferring the spin and orientation parameters of a neutron star from its
periodic gravitational wave signature seen by laser interferometric detectors",0402038v1
2006-05-31,The influence of differential rotation on the detectability of gravitational waves from the r-mode instability,"Recently, it was shown that differential rotation is an unavoidable feature
of nonlinear r-modes. We investigate the influence of this differential
rotation on the detectability of gravitational waves emitted by a newly born,
hot, rapidly-rotating neutron star, as it spins down due to the r-mode
instability. We conclude that gravitational radiation may be detected by the
advanced laser interferometer detector LIGO if the amount of differential
rotation at the time the r-mode instability becomes active is not very high.",0606001v1
2004-01-13,Representations of the discrete inhomogeneous Lorentz group and Dirac wave equation on the lattice,"We propose the fundamental and two dimensional representation of the Lorentz
groups on a (3+1)-dimensional hypercubic lattice, from which representations of
higher dimensions can be constructed. For the unitary representation of the
discrete translation group we use the kernel of the Fourier transform. From the
Dirac representation of the Lorentz group (including reflections) we derive in
a natural way the wave equation on the lattice for spin 1/2 particles. Finally
the induced representation of the discrete inhomogeneous Lorentz group is
constructed by standard methods and its connection with the continuous case is
discussed.",0401019v1
1998-05-26,Renormalization of Chiral-Even Twist-3 Light-cone Wave Functions for Vector Mesons in QCD,"We present the one-loop anomalous dimension matrices for the chiral-even
twist-3 (nonsinglet) conformal operators, which govern the scale-dependence of
the vector meson light-cone wave functions through the conformal expansion. It
is clarified that the constraints from the charge-conjugation invariance and
the chirality conservation allow only one independent anomalous dimension
matrix for each conformal spin.",9805460v3
1999-01-11,Diffractive S and D-wave vector mesons in deep inelastic scattering,"We derive helicity amplitudes for diffractive leptoproduction of the S and D
wave states of vector mesons. We predict a dramatically different spin
dependence for production of the S and D wave vector mesons. We find very small
$R=\sigma_{L}/\sigma_{T}$ and abnormally large higher twist effects in
production of longitudinally polarized D-wave vector mesons.",9901267v2
1999-04-12,The polarization of a final electron in the field of intensive electromagnetic wave,"The polarization properties of the Compton effect in the field of a
circularly polarized electromagnetic wave are discussed. In the case of
nonlinear Compton effect the behavior of spin is analyzed. The transformation
of the longitudinal polarization in the transverse polarization is showed. We
obtained the total formulas describing the polarization of the final electron
in the nonlinear case.",9904300v1
2000-06-10,Diffractive Vector Meson Production In A Unified $κ$-Factorization Approach,"In the framework of the $\kappa$-factorization approach and on the basis of
recently determined DGSF, we calculated the production rates of ground and
excited (2S and D wave) states of vector mesons and investigated their various
kinematical and spin dependencies. We also addressed the issue of S/D wave
mixing in quarkonia.",0006101v1
2000-08-14,The use of configuration interaction method for describing fine- splitting effects in the bound two- quark system,"The screened quasi-relativistic potential is used for describing spin-orbit
splitting in $^{3}P_{J}$ waves of quark-antiquark system. Fermi-Breit equation
is solved numerically in configuration interaction approximation. This
approximation takes into account the mixing of wave functions up to fifth order
and corrects substantially perturbation calculations. The nature of potentials
Lorenz transformation property is elucidated. Very good quantitative results
for $b\bar{b}$ and $c\bar{c}$ quarkonia and quite acceptable qualitative
characteristics as well as for systems with unequal masses are obtained for
$u\bar{u}$.",0008128v1
2001-02-08,Parametric Resonance of Neutrino Oscillations in Electromagnetic Wave,"Within the Lorentz invariant formalizm for description of neutrino evolution
in electromagnetic fields and matter we consider neutrino spin oscillations in
the circular polarized electromagnetic wave, the amplitude of which is a
modulated function of time. It is shown for the first time that the parametric
resonance of neutrino oscillations can occur in such a system.",0102099v3
2001-12-06,The interplay of soft and hard contributions in the electromagnetic pion form factor,"We consider various relativistic models for the valence Fock-state wave
function of the pion. These models are obtained from simple instant-form wave
functions by applying a Melosh rotation to the spin part and by imposing
physical constraints on the parameters. We discuss how the soft and the hard
(perturbative) parts of the electromagnetic form factor are affected by the
choice of the model and by the Melosh rotation.",0112099v1
2002-07-10,Exclusive Semileptonic Decays of B Mesons to Orbitally and Radial Excited D,"In this paper we compute, within in the context of a relativistic quark
model, the Isgur-Wise functions for exclusive semileptonic $\bar B \to X_c$
decays, where $X_c$ is any charmed mesons with total spin $J=0,1,2$ or one of
their first excited states. The relevant matrix elements are computed by a
direct numerical integration, in coordinate space, of the convolution of the
wave function of the $B$ meson at rest and the wave function of the $X_c$
meson, boosted according with its recoil factor. Our results are compared with
other predictions found in the existing literature.",0207134v1
2005-04-18,Strong decays of P wave baryons in the $1/N_c$ expansion,"The hadronic decays of non-strange negative parity baryons are analyzed in
the framework of the 1/Nc expansion. A complete basis of spin-flavor operators
for the pseudoscalar meson S and D partial wave amplitudes is established to
order 1/Nc and the unknown effective coefficients are determined by fitting to
the empirically known widths. A set of relations between widths that result at
the leading order, i.e. order Nc^0, is given and tested with the available
data.",0504150v1
2005-09-30,P-wave Pentaquark and its Decay in the Quark Model with Instanton Induced Interaction,"P-wave pentaquarks with strangeness +1, I=0 and J^P=1/2^+ are studied in the
non-relativistic quark model with instanton induced interaction (III). We
present their mass splittings and orbital-spin-isospin-color structures. It is
found that decompositions of the wave functions are sensitive to III, while the
mass splittings are insensitive. The decay of the lowest energy pentaquark,
\Theta^+, is found to be suppressed when the contribution of III is increased.
Its wave function is dominated by Jaffe-Wilczek-type configuration at large
III.",0510001v1
1995-07-13,Generalization of a result of Matsuo and Cherednik to the Calogero-Sutherland- Moser integrable models with exchange terms,"A few years ago, Matsuo and Cherednik proved that from some solutions of the
Knizhnik-Zamolodchikov (KZ) equations, which first appeared in conformal field
theory, one can obtain wave functions for the Calogero integrable system. In
the present communication, it is shown that from some solutions of generalized
KZ equations, one can construct wave functions, characterized by any given
permutational symmetry, for some Calogero-Sutherland-Moser integrable models
with exchange terms. Such models include the spin generalizations of the
original Calogero and Sutherland ones, as well as that with $\delta$-function
interaction.",9507078v1
1999-04-27,Asymptotic Form of Zero Energy Wave Functions in Supersymmetric Matrix Models,"We derive the power law decay, and asymptotic form, of SU(2) x Spin(d)
invariant wave-functions which are zero-modes of all s_d=2(d-1) supercharges of
reduced (d+1)-dimensional supersymmetric SU(2) Yang Mills theory, resp. of the
SU(2)-matrix model related to supermembranes in d+2 dimensions.",9904182v2
2002-12-02,Remarks on type IIB pp waves with Ramond-Ramond fluxes and massive two dimensional nonlinear sigma models,"We continue the study of supersymmetric type IIB pp wave solutions by
Maldacena and Maoz (hep-th/0207284), who showed Ramond-Ramond five-forms can
induce potential terms in the light cone string actions which are nonlinear
sigma models with special holonomy target spaces. We show nonvanishing
Ramond-Ramond three-forms provide extra potential terms involving Killing
vectors in the string action and identify the supersymmetry requirements. In
particular, in solutions with (1,1) worldsheet supersymmetry, the Killing
vectors are required to be self-dual in Spin(7).",0212017v2
2002-12-16,Open strings in the plane wave background II: Superalgebras and Spectra,"In hep-th/0211011 we started a systematic investigation of open strings in
the plane wave background. In this paper we continue the analysis by discussing
the superalgebras of conserved charges, the spectra of open strings, and the
spectra of DBI fluctuations around D-brane embeddings. We also derive the
gluing conditions for corresponding boundary states and analyze their
symmetries. All results are consistent with each other, and confirm the
existence of additional supersymmetries as previously discussed. We further
show that for every symmetry current one can construct a (countably) infinite
number of related currents that contain more worldsheet derivatives, and
discuss non-local symmetries.",0212184v1
2003-01-27,An overview of branes in the plane wave background,"We give an overview of D-branes in the maximally supersymmetric plane wave
background of IIB supergravity. We start by reviewing the results of the probe
analysis. We then present the open string analysis and show how certain
spacetime symmetries are restored using worldsheet symmetries. We discuss the
construction of these branes as boundary states and summarize what is known
about the dual gauge theory description.",0301221v1
2003-08-25,Perturbative calculation of quasi-normal modes of Schwarzschild black holes,"We discuss a systematic method of analytically calculating the asymptotic
form of quasi-normal frequencies of a four-dimensional Schwarzschild black hole
by expanding around the zeroth-order approximation to the wave equation
proposed by Motl and Neitzke. We obtain an explicit expression for the
first-order correction and arbitrary spin. Our results are in agreement with
the results from WKB and numerical analyses in the case of gravitational waves.",0308168v2
2003-09-24,On quasi-normal modes of Kerr black holes,"We calculate analytically asymptotic values of quasi-normal frequencies of
four-dimensional Kerr black holes by solving the Teukolsky wave equation. We
obtain an expression for arbitrary spin of the wave in agreement with Hod's
proposal which is based on Bohr's correspondence principle. However, the range
of frequencies is bounded from above by $1/a$, where $a$ is the angular
momentum per unit mass of the black hole. Our argument is only valid in the
small-$a$ limit which includes the Schwarzschild case.",0309227v1
2004-09-17,Quantum integrable multi atom matter-radiation models with and without rotating wave approximation,"New integrable multi-atom matter-radiation models with and without rotating
wave approximation (RWA) are constructed and exactly solved through algebraic
Bethe ansatz. The models with RWA are generated through ancestor model approach
in an unified way. The rational case yields the standard type of
matter-radiaton models, while the trigonometric case corresponds to their
q-deformations. The models without RWA are obtained from the elliptic case at
the Gaudin and high spin limit.",0409032v1
1993-11-23,Coherent Pion Radiation From Nucleon Antinucleon Annihilation,"A unified picture of nucleon antinucleon annihilation into pions emerges from
a classical description of the pion wave produced in annihilation and the
subsequent quantization of that wave as a coherent state. When the constraints
of energy-momentum and iso-spin conservation are imposed on the coherent state,
the pion number distribution and charge ratios are found to be in excellent
agreement with experiment.",9311020v1
2000-09-25,Effective Field Theory for Neutron-Deuteron Scattering: Higher Partial Waves,"The phase shifts for the higher partial waves in the spin quartet and doublet
channel of nd scattering are presented at next-to-leading and
next-to-next-to-leading order in an effective field theory in which pions are
integrated out. The results agree with both phase shift analyses and potential
model calculations.",0009072v1
2002-01-10,On the relation between the long-wave instability and the pion condensation in nuclear matter,"The solutions to the zero-sound frequency equation and pion dispersion
equation are considered for the different values of the parameters of the
effective particle-hole interaction. The branches of solutions, responsible for
the long-wave instability [Pomeranchuk] of the nuclear matter \omega_P(k) are
presented for the both equations. It is shown that in the pion dispersion
equation the solutions \omega_P(k) result in the instability not only for
values of the spin-isospin constant g'\leq -1/2, violating stability criteria,
but for all g' < g'_p (|g'_p|\ll 1 and g'_p < 0). At g' > g'_p the branches
\omega_P(k) turn into the solutions responsible for pion condensation.",0201023v1
2000-12-27,Evaporative cooling of cesium atoms in the gravito-optical surface trap,"We report on cooling of an atomic cesium gas closely above an
evanescent-wave. Our first evaporation experiments show a temperature reduction
from 10muK down to 300nK along with a gain in phase-space density of almost two
orders of magnitude. In a series of measurements of heating and spin
depolarization an incoherent background of resonant photons in the
evanescent-wave diode laser light was found to be the limiting factor at this
stage.",0012058v1
2006-08-03,Derivation of the paraxial form of the angular momentum of the electromagnetic field from the general form,"It is shown how the standard forms for the spin and orbital components of the
angular momentum of a paraxial wave of electromagnetic radiation are obtained
from the general expressions for the angular momentum that have been derived
recently. This result will enable the general expressions for angular momentum
to be applied with confidence to the many configurations of electromagnetic
fields that are more complicated than plane or paraxial waves.",0608029v2
2005-01-04,Thermodynamical Versus Optical Complementarity,"We establish correspondence between macroscopic thermodynamical quantities
and complementarity in wave interference. The well known visibility and
predictability in a double slit--like experiment are shown to be connected to
magnetic susceptibility and magnetization of a general interacting spin chain.
This gives us the ability to analyze the tradeoff between thermodynamical
quantities in the same information--theoretic way that is used in analyzing the
wave--particle duality. We thus obtain new physical insights into usually
complicated thermodynamical models, such as viewing a phase transition simply
as a change from an effective single slit diffraction to a double slit
interference.",0501015v1
2005-07-19,Pseudopotential method for higher partial wave scattering,"We present a zero-range pseudopotential applicable for all partial wave
interactions between neutral atoms. For p- and d-waves we derive effective
pseudopotentials, which are useful for problems involving anisotropic external
potentials. Finally, we consider two nontrivial applications of the p-wave
pseudopotential: we solve analytically the problem of two interacting
spin-polarized fermions confined in a harmonic trap, and analyze the scattering
of p-wave interacting particles in a quasi-two-dimensional system.",0507186v2
2005-11-02,Observation of dark state polariton collapses and revivals,"By time-dependent variation of a control field, both coherent and single
photon states of light are stored in, and retrieved from, a cold atomic gas.
The efficiency of retrieval is studied as a function of the storage time in an
applied magnetic field. A series of collapses and revivals is observed, in very
good agreement with theoretical predictions. The observations are interpreted
in terms of the time evolution of the collective excitation of atomic spin wave
and light wave, known as the dark-state polariton.",0511015v1
2006-04-26,Atomic entanglement generation with reduced decoherence via four-wave mixing,"In most proposals for the generation of entanglement in large ensembles of
atoms via projective measurements, the interaction with the vacuum is
responsible for both the generation of the signal that is detected and the spin
depolarization or decoherence. In consequence, one has to usually work in a
regime where the information aquisition via detection is sufficiently slow
(weak measurement regime) such as not to strongly disturb the system. We
propose here a four-wave mixing scheme where, owing to the pumping of the
atomic system into a dark state, the polarization of the ensemble is not
critically affected by spontaneous emission, thus allowing one to work in a
strong measurement regime.",0604192v1
2007-04-16,Magnetosonic solitons in a Fermionic quantum plasma,"Starting from the governing equations for a quantum magnetoplasma including
the quantum Bohm potential and electron spin-1/2 effects, we show that the
system of quantum magnetohydrodynamic (QMHD) equations admit rarefactive
solitons due to the balance between nonlinearities and quantum
diffraction/tunneling effects. It is found that the electron spin-1/2 effect
introduces a pressure-like term with negative sign in the QMHD equations, which
modifies the shape of the solitary magnetosonic waves and makes them wider and
shallower. Numerical simulations of the time-dependent system shows the
development of rarefactive QMHD solitary waves that are modified by the spin
effects.",0704.2049v2
2007-05-11,The Plasma Emission Model of RX J1856.5-3754,"A spectral analysis of the nearby isolated neutron star RX J1856.5-3754 is
presented. Applying the kinetic approach, the distribution functions of
emitting electrons are derived and the entire spectra is fitted. It is found
that waves excited by the cyclotron mechanism, come in the radio domain. We
confirm that the cyclotron instability is quite efficient, since the
estimations show that the time of wave-particle interaction is long enough for
particles to acquire perpendicular momentum and generate observed radiation.
The lack of rotational modulation is discussed and the pulsar spin period is
estimated.",0705.1628v1
2007-06-14,Generalized rotating-wave approximation for arbitrarily large coupling,"A generalized version of the rotating-wave approximation for the single-mode
spin-boson Hamiltonian is presented. It is shown that performing a simple
change of basis prior to eliminating the off-resonant terms results in a
significantly more accurate expression for the energy levels of the system. The
generalized approximation works for all values of the coupling strength and for
a wide range of detuning values, and may find applications in solid-state
experiments.",0706.2087v1
2007-06-25,Coulomb effects in polarization transfer in elastic antiproton and proton electron scattering at low energies,"The influence of Coulomb distortion on the polarization transfer in elastic
proton and antiproton electron scattering at low energies is calculated in a
distorted wave Born approximation. For antiproton electron scattering Coulomb
effects reduce substantially the spin transfer cross section compared to the
plane wave Born approximation whereas for proton electron scattering they lead
to a dramatic increase for kinetic proton lab energies below about 20 keV.",0706.3576v3
2007-07-23,Galilei invariant theories. II. Wave equations for massive fields,"Galilei invariant equations for massive fields with various spins are found
and classified. They have been obtained directly, i.e., by using requirement of
Galilei invariance and the facts on representations of the Galilei group
deduced in our previous paper de Montigny M, Niederle J and Nikitin A G, J.
Phys. A {\bf 39}, 1-21, 2006 . It is shown that the collection of
non-equivalent Galilei-invariant wave equations for vector and scalar fields is
very broad and describes many physically consistent systems.",0707.3286v1
2007-07-24,Baryon resonances and polarization transfer in hyperon photoproduction,"A partial wave analysis is presented of data on photoproduction of hyperons
including single and double polarization observables. The large spin transfer
probability reported by the CLAS collaboration can be successfully described
with an isobar partial wave analysis.",0707.3596v2
2007-09-13,Drift Wave Model of Rotating Radio Transients,"During the last few years there were discovered and deeply examined several
transient neutron stars (Rotating Radio Transients). It is already well
accepted that these objects are rotating neutron stars. But their extraordinary
features (burst-like behavior) made necessary revision of well accepted models
of pulsar interior structure. Nowadays most popular model for RRATs is
precessing pulsar model, which is the subject of big discussion. We assume that
these objects are pulsars with specific spin parameters. An important feature
of our model, naturally explaining most of the properties of these neutron
stars, is presence of very low frequency, nearly transverse drift waves
propagating across the magnetic field and encircling the open field lines
region of the pulsar magnetosphere.",0709.2019v1
2007-10-16,Friedel oscillations of Density of States in a one-dimensional Mott insulator and Incommensurate Charge Density Wave/Superconductor,"Oscillations of local density of states generated by a single scalar impurity
potential are calculated for one-dimensional systems with dynamically generated
charge or spin gap. At zero temperature the oscillations develop at finite wave
vector ($\pi$ for the Mott insulator and $2k_F$ for ICDW/SC) and at frequencies
larger than the soliton spectral gap $m$. Their amplitude has a broad maximum
at $\omega \approx 3m$, where $m$ is the gap magnitude.",0710.3131v2
2007-11-29,On the question of ferromagnetism in alkali metal thin films,"Electronic and magnetic structure of $(100)$ films of K and Cs are calculated
within the plane-wave projector augmented wave (PAW) formalism of the density
functional theory (DFT) using both local spin density approximation (LSDA) and
the PW91 generalized gradient approximation (GGA). Only a 6 layer Cs film is
found to have a ferromagnetic (FM) state which is degenerate with a
paramagnetic (PM) state within the accuracy of these calculations. This is at
variance with the results obtained from a finite thickness uniform jellium
model (UJM). Implications of these results for the experiments on transition
metal doped alkali metal thin films and bulk hosts are discussed.",0711.4744v1
2008-03-07,Transport in open spin chains: A Monte Carlo wave-function approach,"We investigate energy transport in several two-level atom or spin-1/2 models
by a direct coupling to heat baths of different temperatures. The analysis is
carried out on the basis of a recently derived quantum master equation which
describes the nonequilibrium properties of internally weakly coupled systems
appropriately. For the computation of the stationary state of the dynamical
equations, we employ a Monte Carlo wave-function approach. The analysis
directly indicates normal diffusive or ballistic transport in finite models and
hints toward an extrapolation of the transport behavior of infinite models.",0803.1128v1
2008-09-25,Gravitational radiation from pulsar glitches,"The nonaxisymmetric Ekman flow excited inside a neutron star following a
rotational glitch is calculated analytically including stratification and
compressibility. For the largest glitches, the gravitational wave strain
produced by the hydrodynamic mass quadrupole moment approaches the sensitivity
range of advanced long-baseline interferometers. It is shown that the
viscosity, compressibility, and orientation of the star can be inferred in
principle from the width and amplitude ratios of the Fourier peaks (at the spin
frequency and its first harmonic) observed in the gravitational wave spectrum
in the plus and cross polarizations. These transport coefficients constrain the
equation of state of bulk nuclear matter, because they depend sensitively on
the degree of superfluidity.",0809.4352v1
2008-10-10,Galilean equations for massless fields,"Galilei-invariant equations for massless fields are obtained via contractions
of relativistic wave equations. It is shown that the collection of
non-equivalent Galilei-invariant wave equations for massless fields with spin
equal 1 and 0 is very reach and corresponds to various contractions of the
representations of the Lorentz group to those of the Galilei one. It describes
many physically consistent systems, e.g., those of electromagnetic fields in
various media or Galilean Chern-Simon models. Finally, classification of all
linear and a big group of non-linear Galilei-invariant equations for massless
fields is presented.",0810.1894v2
2009-01-16,Magnetic Moment Coupling to Circularly Polarized Photons,"Exact stationary solutions of the wave equation are obtained to describe the
interaction between magnetic moment of elementary particle and circularly
polarized photons. The obtained solutions substantially modify the conventional
model of field-matter interaction. It follows from them that magnetic moment
couples to photons, and this coupling leads to bound particle-photon states
with different energies for different orientations of magnetic moment. As a
consequence, the interaction splits particle states differing by directions of
total angular momentum. Stationary spin splitting, induced by photons, and
concomitant effects can be observed for particles exposed to a laser-generated
circularly polarized electromagnetic wave.",0901.2501v3
2009-02-09,Integrability of scattering amplitudes in N=4 SUSY,"We argue, that the multi-particle scattering amplitudes in N=4 SUSY at large
$N_c$ and in the multi-Regge kinematics for some physical regions have the high
energy behavior appearing from the contribution of the Mandelstam cuts in the
corresponding $t$-channel partial waves. The Mandelstam cuts correspond to
gluon composite states in the adjoint representation of the gauge group
$SU(N_c)$. The hamiltonian for these states in the leading logarithmic
approximation coincides with the local hamiltonian of an integrable open spin
chain. We construct the corresponding wave functions using the integrals of
motion and the Baxter-Sklyanin approach.",0902.1444v1
2009-03-19,Natural optical activity of metals,"We derive the current response of noncentrosymmetric metal in normal and in
superconducting states to the electromagnetic field with finite frequency and
wave vector. The conductivity tensor is found contains the linear in wave
vector off diagonal part generating natural optical activity. The Kerr rotation
of polarization of light reflected from the metal surface is calculated. Its
value is expressed through the fine-structure constant and the ratio of light
frequency to the band splitting due to the spin-orbit interaction.",0903.3306v1
2009-05-05,Statistics at the tip of a branching random walk and the delay of traveling waves,"We study the limiting distribution of particles at the frontier of a
branching random walk. The positions of these particles can be viewed as the
lowest energies of a directed polymer in a random medium in the mean-field
case. We show that the average distances between these leading particles can be
computed as the delay of a traveling wave evolving according to the Fisher-KPP
front equation. These average distances exhibit universal behaviors, different
from those of the probability cascades studied recently in the context of mean
field spin-glasses.",0905.0613v1
2009-06-04,Detecting d-wave superfluid and d-density wave states of ultracold Fermions on optical lattices,"We propose a pump probe experiment for detecting the d-wave superfluid and
d-density wave phases of ultracold Fermions on an optical lattice. The pump
consists of periodic modulations of the optical lattice intensity which creates
quasiparticle pairs in these systems. The changes in the momentum distribution
under the drive can be used to measure quasiparticle dispersion and gap
anisotropy. Further, we show that the pattern of peaks and dips in the spin
selective density-density correlation function provides a phase sensitive probe
of the symmetry of the order parameter in these systems.",0906.0931v1
2009-07-01,Negative Refraction Gives Rise to the Klein Paradox,"Electromagnetic negative refraction in metamaterials has attracted
increasingly great interest, since its first experimental verification in 2001.
It potentially leads to the applications superior to conventional devices
including compact antennas for mobile stations, imaging beyond the diffraction
limit, and high-resolution radars, not to mention the anamolous wave
propagation in fundamental optics. Here, we report how metamaterials could be
used to simulate the ""negative refraction of spin-zero particles interacting
with a strong potential barrier"", which gives rise to the Klein paradox--a
counterintuitive relativistic process. We address the underlying physics of
analogous wave propagation behaviours in those two entirely different domains
of quantum and classical.",0907.0265v1
2009-09-22,Pure Phase Decoherence in a Ring Geometry,"We study the dynamics of pure phase decoherence for a particle hopping around
an N-site ring, coupled both to a spin bath and to an Aharonov-Bohm flux which
threads the ring. Analytic results are found for the dynamics of the influence
functional and of the reduced density matrix of the particle, both for initial
single wave-packet states, and for states split initially into 2 separate
wave-packets moving at different velocities. We also give results for the
dynamics of the current as a function of time.",0909.4098v3
2009-10-14,Bipolaron Density-Wave Driven By Antiferromagnetic Correlations and Frustration in Organic Superconductors,"We describe the Paired Electron Crystal (PEC) which occurs in the interacting
frustrated two-dimensional 1/4-filled band. The PEC is a charge-ordered state
with nearest-neighbor spin singlets separated by pairs of vacant sites, and can
be thought of as a bipolaron density wave. The PEC has been experimentally
observed in the insulating state proximate to superconductivity in the organic
charge-transfer solids. Increased frustration drives a PEC-to-superconductor
transition in these systems.",0910.2728v1
2009-11-23,Fluctuation-driven first order behavior near the T=0 two dimensional stripe to fermi liquid transition,"The possibility is investigated that competition between fluctuations at
different symmetry-related ordering wave vectors may affect the quantum phase
transition between a fermi liquid and a longitudinal spin density wave state,
in particular giving rise to an intermediate 'nematic' state with broken
rotational symmetry but unbroken translational symmetry. At the marginal
dimension the nematic transition is found to be preempted by a first order
transition but a weak symmetry breaking field restores a second order magnetic
transition with an intermediate regime in which correlations substantially
enhance the broken rotational symmetry. Comparison to recent experiments is
made.",0911.4486v1
2009-12-14,Long Range orders in multiferroics,"We proposed that in multiferroics there exists a third long range order
besides the electric polarization and magnetic order. This long range order
reduces the symmetry of the spatial part of the wave functions of electrons.
Thus the cancellation in the spin current"" model can be avoided. As a result,
the expectation value of electric polarization will be larger by an order of
magnitude. We have derived a new form of electric polarization \vec{P}
-\vec{Q}\times(\vec{s_i}\times\vec{s_{j+1}}) where \vec{Q} is the wave vector
of this long range order",0912.2617v2
2009-12-14,Configuration mixing of angular-momentum projected triaxial relativistic mean-field wave functions,"The framework of relativistic energy density functionals is extended to
include correlations related to the restoration of broken symmetries and to
fluctuations of collective variables. The generator coordinate method is used
to perform configuration mixing of angular-momentum projected wave functions,
generated by constrained self-consistent relativistic mean-field calculations
for triaxial shapes. The effects of triaxial deformation and of $K$-mixing is
illustrated in a study of spectroscopic properties of low-spin states in
$^{24}$Mg.",0912.2650v2
2010-01-03,Photodisintegration of $^3H$ in a three dimensional Faddeev approach,"An interaction of a photon with $^3H$ is invstigated based on a three
dimensional Faddeev approach. In this approach the three-nucleon Faddeev
equations with two-nucleon interactions are formulated with consideration of
the magnitude of the vector Jacobi momenta and the angle between them with the
inclusion of the spin-isospin quantum numbers, without employing a partial wave
decomposition. In this formulation the two body t-matrices and triton wave
function are calculated in the three dimensional approach using AV18 potential.
In the first step we use the standard single nucleon current in this article.",1001.0362v1
2010-03-01,Effective Mass Dirac-Morse Problem with any kappa-value,"The Dirac-Morse problem are investigated within the framework of an
approximation to the term proportional to $1/r^2$ in the view of the
position-dependent mass formalism. The energy eigenvalues and corresponding
wave functions are obtained by using the parametric generalization of the
Nikiforov-Uvarov method for any $\kappa$-value. It is also studied the
approximate energy eigenvalues, and corresponding wave functions in the case of
the constant-mass for pseudospin, and spin cases, respectively.",1003.0269v1
2010-03-19,A formulation without partial wave decomposition for scattering of spin-1/2 and spin-0 particles,"A new technique has been developed to calculate scattering of spin-1/2 and
spin-0 particles. The so called momentum-helicity basis states are constructed
from the helicity and the momentum states, which are not expanded in the
angular momentum states. Thus, all angular momentum states are taken into
account. Compared with the partial-wave approach this technique will then give
more benefit especially in calculations for higher energies. Taking as input a
simple spin-orbit potential, the Lippman-Schwinger equations for the T-matrix
elements are solved and some observables are calculated.",1003.3711v1
2010-03-22,Calculating the Fine Structure of a Fabry-Perot Resonator using Spheroidal Wave Functions,"A new set of vector solutions to Maxwell's equations based on solutions to
the wave equation in spheroidal coordinates allows laser beams to be described
beyond the paraxial approximation. Using these solutions allows us to calculate
the complete first-order corrections in the short-wavelength limit to
eigenmodes and eigenfrequencies in a Fabry-Perot resonator with perfectly
conducting mirrors. Experimentally relevant effects are predicted. Modes which
are degenerate according to the paraxial approximation are split according to
their total angular momentum. This includes a splitting due to coupling between
orbital angular momentum and spin angular momentum.",1003.4168v1
2010-04-22,Wien2wannier: From linearized augmented plane waves to maximally localized Wannier functions,"We present an implementaion of interface between the full-potential
linearized augmented plane wave package Wien2k and the wannier90 code for the
construction of maximally localized Wannier functions. The FORTRAN code and a
documentation is made available and results are discussed for SrVO$_3$,
Sr$_2$IrO$_4$ (including spin-orbit coupling), LaFeAsO, and FeSb$_2$.",1004.3934v1
2010-07-16,Double-valuedness of the electron wave function and rotational zero-point motion of electrons in rings,"I propose that the phase of an electron's wave function changes by $\pi$ when
the electron goes around a loop maintaining phase coherence. Equivalently, that
the minimum orbital angular momentum of an electron in a ring is $\hbar/2$
rather than zero as generally assumed, hence that the electron in a ring has
azimuthal zero point motion. This proposal provides a physical explanation for
the origin of electronic `quantum pressure', it implies that a spin current
exists in the ground state of aromatic ring molecules, and it suggests an
explanation for the ubiquitousness of persistent currents observed in
mesoscopic rings.",1007.2834v1
2010-08-23,Vortex states in hole-doped iron-pnictide superconductors,"Based on a phenomenological model with competing spin-density-wave (SDW) and
extended $s-$wave superconductivity, the vortex states in
Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$ are investigated by solving Bogoliubov-de
Gennes equations. Our result for the optimally doped compound without induced
SDW is in qualitative agreement with recent scanning tunneling microscopy
experiment. We also propose that the main effect of the SDW on the vortex
states is to reduce the intensity of the in-gap peak in the local density of
states and transfer the spectral weight to form additional peaks outside the
gap.",1008.3885v1
2010-09-11,Nonlinear optical response of hole-trion systems in quantum dots in tilted magnetic fields,"We discuss, from a theoretical point of view, the four wave mixing
spectroscopy on an ensemble of p-doped quantum dots in a magnetic field
slightly tilted from the in-plane configuration. We describe the system
evolution in the density matrix formalism. In the limit of coherent ultrafast
optical driving, we obtain analytical formulas for the single system dynamics
and for the response of an inhomogeneously broadened ensemble. The results are
compared to the previously studied time-resolved Kerr rotation spectroscopy on
the same system. We show that the Kerr rotation and four wave mixing spectra
yield complementary information on the spin dynamics (precession and damping).",1009.2202v1
2011-01-28,Study of the eta meson production with the polarised proton beam,"The azimuthally symmetric WASA detector and the polarised proton beam of
COSY, enable investigations of energy and angular dependence of the beam
analysing power in the pp --> ppeta reaction. The aim of the studies is the
determination of the partial wave contributions via interference terms which
are inaccessible from spin averaged observables. The partial wave decomposition
is mandatory for the understanding of the reaction dynamics and for the
determination of the eta-proton interaction, independently of the theoretical
paradigm used.",1101.5486v1
2011-02-21,Equivalence Principle and Gravitational Redshift,"We investigate leading order deviations from general relativity that violate
the Einstein equivalence principle in the gravitational standard model
extension. We show that redshift experiments based on matter waves and clock
comparisons are equivalent to one another. Consideration of torsion balance
tests, along with matter wave, microwave, optical, and M\""ossbauer clock tests,
yields comprehensive limits on spin-independent Einstein equivalence
principle-violating standard model extension terms at the $10^{-6}$ level.",1102.4362v2
2011-05-27,Broadband time-reversal of optical pulses using a switchable photonic-crystal mirror,"Recently, Chumak et al. have demonstrated experimentally the time-reversal of
microwave spin pulses based on non-adiabatically tuning the wave speed in a
spatially-periodic manner. Here, we solve the associated wave equations
analytically, and give an explicit formula for the reversal efficiency. We then
discuss the implementation for short optical electromagnetic pulses and show
that the new scheme may lead to their accurate time-reversal with efficiency
higher than before.",1105.5670v1
2011-06-28,On kinematical constraints in fermion-antifermion systems,"We consider the scattering of fermions off antifermions with spin 1/2 and
3/2. Starting from helicity partial-wave scattering amplitudes we derive
transformations that eliminate all kinematical constraints. Such amplitudes are
expected to satisfy partial-wave dispersion relations and therefore provide a
suitable basis for data analysis and the construction of effective field
theories. Our derivation relies on a decomposition of the various scattering
amplitudes into suitable sets of invariant functions.",1106.5619v1
2011-11-08,On kinematical constraints in boson-boson systems,"We consider the scattering of two-bosons with negative parity and spin 0 or
1. Starting from helicity partial-wave scattering amplitudes we derive
transformations that eliminate all kinematical constraints. Such amplitudes are
expected to satisfy partial-wave dispersion relations and therefore provide a
suitable basis for data analysis and the construction of effective field
theories. Our derivation relies on a decomposition of the various scattering
amplitudes into suitable sets of invariant functions. A novel algebra was
developed that permits the efficient computation of such functions in terms of
computer algebra codes.",1111.1838v1
2012-06-01,Berry Effect in Unmagnetized Inhomogeneous Cold Plasmas,"The propagation of electromagnetic waves in an unmagnetized weakly
inhomogeneous cold plasma is examined. We show that the inhomogeneity induces a
gauge connection term in wave equation, which gives rise to Berry effects in
the dynamics of polarized rays in the post geometric optics approximation. The
polarization plane of a plane polarized ray rotates as a result of the
geometric Berry phase, which is the Rytov rotation. Also, the Berry curvature
causes the optical Hall effect, according to which, rays of left/right circular
polarization deflect oppositely to produce a spin current directed across the
direction of propagation.",1206.0106v1
2012-07-24,The relativistic Pauli equation,"After discussing the way that C2 and the algebra of complex 2x2 matrices can
be used for the representation of both non-relativistic rotations and Lorentz
transformations, we show that Dirac bispinors can be more advantageously
represented as 2x2 complex matrices. One can then give the Dirac equation a
form for such matrix-valued wave functions that no longer necessitates the
introduction of gamma matrices or a choice for their representation. The
minimally-coupled Dirac equation for a charged spinning particle in an external
electromagnetic field then implies a second order equation in the matrix-valued
wave functions that is of Klein-Gordon type and represents the relativistic
analogue of the Pauli equation. We conclude by presenting the Lagrangian form
for the relativistic Pauli equation.",1207.5752v1
2012-08-13,Density Waves Instability and a Skyrmion Lattice on the Surface of Strong Topological Insulators,"In this work we analyze the instability conditions for spin-density-waves
(SDW) formation on the surface of strong topological insulators. We find that
for a certain range of Fermi-energies and strength of interactions the SDW
state is favored compared to the unmagnetized and the uniform-magnetization
states. We also find that the SDW are of spiral nature and for a certain range
of parameters a Skyrmion-lattice may form on the surface. We show that this
phase may have a non trivial Chern-number even in the absence of an external
magnetic field.",1208.2576v1
2012-11-01,Localization of Matter Fields in the 6D Standing Wave Braneworld,"We introduce new 6D standing wave braneworld model generated by gravity
coupled to a phantom-like scalar field and investigate the problem of pure
gravitational localization of matter fields. We show that in the case of
increasing warp factor spin 0, 1, 1/2 and 2 fields are localized on the brane.",1211.0206v2
2012-11-29,Color and Isospin Waves from Tetrahedral Shubnikov Groups,"This note supplements a recent article in which it was pointed out that the
observed spectrum of quarks and leptons can arise as quasi-particle excitations
in a discrete internal space. The paper concentrated on internal vibrational
modes and it was only noted in the end that internal spin waves ('mignons')
might do the same job. Here it will be shown how the mignon-mechanism works in
detail. In particular the Shubnikov group $A_4 + S (S_4 - A_4)$ will be used to
describe the spectrum, and the mignetic ground state is explicitly given.",1212.0753v2
2012-12-25,2kF-Friedel to 4kF-Wigner oscillations in one-dimensional Fermi gases under confinement,"Density oscillations of confined one-dimensional Fermi gases of contact
repulsive interactions in a continuous space are discussed within
Bethe-ansatz-based spin-density-functional theory. The results are compared
against the exact analytical and the exact diagonalization method. For an
unpolarized system, the number of peaks in the density profiles is doubled,
signaling the crossover of the 2k_F-Friedel to 4k_F-Wigner oscillations (with
kF being the Fermi wave vector). For both unpolarized and polarized systems, a
threshold of the short-range interaction strength can be found where Nf-peak
Wigner oscillations of a 4k_F wave vector appear in the density profile (N_f is
the total particle number).",1212.6081v1
2013-04-22,Numerical Solutions in 5D Standing Wave Braneworld,"Within the 5D standing wave braneworld model numerical solutions of the
equations for matter fields with various spins are found. It is shown that
corresponding action integrals are factorizable and convergent over the extra
coordinate, i.e. 4D fields are localized on the brane. We find that only left
massless fermions are localized on the brane, while the right fermions are
localized in the bulk. We demonstrate also quantization of Kaluza-Klein excited
modes in our model.",1304.6079v1
2013-05-07,"Spin observables in 71A MeV 6,8He-hydrogen scattering","Predictions of cross sections and analyzing powers using g-folding optical
potentials for the scattering of 71A MeV 6,8He ions from (polarized) hydrogen
are compared with data. A g-folding model in which exchange amplitudes are
evaluated explicitly was used with wave functions of 6,8He specified from a
no-core shell model that used a complete (0+2+4)hw basis. The analyzing powers
reveal some sensitivities to the details of the wave functions, especially in
the case of halo nuclei.",1305.1445v1
2013-06-28,Three-Body Bound State Calculations by Using Three-Dimensional Low Momentum Interaction $V_{low-k}$,"Three-dimensional (3D) Faddeev integral equations are solved for three-body
(3B) bound state problem without using the partial wave (PW) form of low
momentum two-body (2B) interaction $V_{low-k}$ which is constructed from spin
independent Malfliet-Tjon V (MT-V) potential. The dependence of 3B binding
energy on the cutoff momentum of $V_{low-k}$ is investigated for a wide range
of $\Lambda$ from $1.0$ to $7.0\, fm^{-1}$. The properties of Faddeev
components and 3B wave function are displayed and the effect of number of grid
points for momentum and angle variables on the accuracy and the stability of
numerical results is studied by calculation of the expectation value of total
Hamiltonian.",1306.6683v2
2013-09-07,Supermassive black hole mergers as dual sources for electromagnetic flares in the jet emission and gravitational waves,"We present a new type of observation relating the gravitational wave emission
of supermassive black hole mergers to their electromagnetic counterparts. This
dual emission involves variability of a relativistic jet arising from the
spin-orbit precession of the supermassive black hole binary at its base.",1309.1831v1
2013-09-19,A tossed coin as quantum mechanical object,"Comprehensive and physically consistent model of a tossed coin is presented
in terms of geometric algebra. The model clearly shows that there is nothing
elementary particle specific in the half-spin quantum mechanical formalism. It
also demonstrates what really is behind this formalism, feasibly reveals the
probabilistic meaning of wave function and shows that arithmetic of packed
objects, namely wave functions and Pauli matrices, reduces the amount of
available information.",1309.5002v4
2013-11-04,Kicked Dirac particle in a box,"We study quantum dynamics of a kicked relativistic spin-half particle in a
one dimensional box. Time-dependence of the average kinetic energy and
evolution of the wave packet are explored. Kicking potential is introduced as
the Lorentz-scalar, i.e., through the mass-term in the Dirac equation. It is
found that depending on the values of the kicking parameters E(t) can be
periodic, monotonically growing and non-periodic function of time. Particle
transport in the system is studied by considering spatio-temporal evolution of
the Gaussian wave packet.Splitting of the packet into two symmetric parts and
restoration of the profile of the packet is found.",1311.0799v1
2013-11-20,Spin Waves and Dielectric Softening of Polar Molecule Condensates,"We consider an oblate Bose-Einstein condensate of heteronuclear polar
molecules in a weak applied electric field. This system supports a rich
quasiparticle spectrum that plays a critical role in determining its bulk
dielectric properties. In particular, in sufficiently weak fields the system
undergoes a polarization wave rotonization, leading to the development of
textured electronic structure and a dielectric instability that is
characteristic of the onset of a negative static dielectric function.",1311.5110v2
2013-12-12,"Modelling gravitational waves from precessing black-hole binaries: Progress, challenges and prospects","The inspiral and merger of two orbiting black holes is among the most
promising sources for the first (hopefully imminent) direct detection of
gravitational waves (GWs), and measurements of these signals could provide a
wealth of information about astrophysics, fundamental physics and cosmology.
Detection and measurement require a theoretical description of the GW signals
from all possible black-hole-binary configurations, which can include
complicated precession effects due to the black-hole spins. Modelling the GW
signal from generic precessing binaries is therefore one of the most urgent
theoretical challenges facing GW astronomy. This article briefly reviews the
phenomenology of generic-binary dynamics and waveforms, and recent advances in
modelling them.",1312.3641v1
2014-03-11,Long-range interaction induced phases in Weyl semimetals,"The interplay of spin orbit coupling and electron electron interaction
condensing new phases of matter is an important new phenomena in solid state
physics. In this paper we explore the nature of excitonic phases induced in
Weyl semimetals by long range Coulomb repulsion. Its has been previously shown
that short range repulsion leads to a ferromagnetic insulator while short range
attraction results in a charge density wave state. Here we show the the charge
density wave is the energetically favored state in the presence of long range
repulsion.",1403.2456v1
2014-05-09,The Legacy of M. P. Bronstein: on relativistic wave equations for spin 2 fields and some comments,"We briefly give a very simple picture about one of the most remarkable
results of Matvej Petrovich Bronstein concerning the quantization of the
gravitational waves showing also that the linearized Einstein equations of the
paper: Phys.Rev. D65 (2002) 104005 are the same Bronstein's equations given 66
years before.",1405.2334v2
2014-12-05,Partial wave decomposition of the N3LO equation of state,"By means of a partial wave decomposition, we separate their contributions to
the equation of state of symmetric nuclear matter for the N3LO
pseudo-potential. In particular, we show that although both the tensor and the
spin-orbit terms do not contribute to the equation of state, they give a
non-vanishing contribution to the separate (JLS) channels.",1412.1934v1
2015-01-13,A note on gravitational wave extraction from binary simulations,"In previous works, we developed a perturbative extrapolation formula to
obtain gravitational waves at infinity from binary black hole simulations,
based on the Regge-Wheeler-Zerilli formalism. In practice, this formula was
basically derived in a background flat spacetime. We derive here an estimation
of errors and an improved extrapolation formula by using the Teukolsky
perturbative equation for a background Kerr spacetime. The improved formula
requires knowledge about a mass and spin of the background spacetime.",1501.02890v2
2015-02-07,Sound emission from the gas of molecular superrotors,"We use an optical centrifuge to deposit a controllable amount of rotational
energy into dense molecular ensembles. Subsequent rotation-translation energy
transfer, mediated by thermal collisions, results in the localized heating of
the gas and generates strong sound wave, clearly audible to the unaided ear.
For the first time, the amplitude of the sound signal is analyzed as a function
of the experimentally measured rotational energy. The proportionality between
the two experimental observables confirms that rotational excitation is the
main source of the detected sound wave. As virtually all molecules, including
the main constituents of the atmosphere, are amenable to laser spinning by the
centrifuge, we anticipate this work to stimulate further development in the
area of photo-acoustic control and spectroscopy.",1502.02654v1
2015-04-03,Plane Wave Density Functional Theory Studies of the Structural and the Electronic Properties of Amino Acids Attached to Graphene Oxide via Peptide Bonding,"We studied the electronic and the structural properties of amino acids
(alanine, glycine, and histidine) attached to graphene oxide (GO) by peptide
bonding, via plane wave pseudopotential total-energy calculations within the
local spin density approximation (LSDA). The HOMO-LUMO gap, the Hirshfeld
charges, and the equilibrium geometrical structures exhibit keen variations
depending on the species of the attached amino acid. The GO-amino acid system
appears to be a good candidate as a biosensor.",1504.00741v1
2015-04-16,Cracking the invisible cloak by using the temporal steering inequality,"Invisible cloaks provide a way to hide an object under the detection of
waves. A perfect cloak guides the incident waves through the cloaking shell
without any distortion. In most cases, some important quantum degrees of
freedom, e.g. electron spin or photon polarization, are not taken into account
when designing a cloak. Here, we propose to use the temporal steering
inequality of these degrees of freedom to detect the existence of an invisible
cloak.",1504.04142v1
2015-12-15,Vector Laguerre-Gauss beams with polarization-OAM entanglement in a graded-index medium,"It is shown that the vector-vortex Laguerre-Gauss modes with
polarization-orbital angular momentum (OAM) entanglement are the vector
solutions of the Maxwell equations in a graded-index medium. Focusing of
linearly and circularly polarized vortex light beams with nonzero azimuthal and
radial indices in a cylindrical graded-index medium is investigated. The wave
shape variation with distance taking into account the spin-orbit and
nonparaxial effects is analyzed. Effect of long-term periodical revival of wave
packets due to mode interference in a graded-index cylindrical optical
waveguide is demonstrated. High efficiency transfer of a strongly focused spot
through an optical waveguide over large distances takes place with a period of
revival.",1512.04712v1
2016-08-25,Hybrid surface waves in two-dimensional Rashba-Dresselhaus materials,"We address the electromagnetic properties of two-dimensional electron gas
confined by a dielectric environment in the presence of both Rashba and
Dresselhaus spin-orbit interactions. It is demonstrated that off-diagonal
components of the conductivity tensor resulting from a delicate interplay
between Rashba and Dresselhaus couplings lead to the hybridization of
transverse electric and transverse magnetic surface electromagnetic modes
localized at the interface. We show that the characteristics of these hybrid
surface waves can be controlled by additional intense external off-resonant
coherent pumping.",1608.07128v2
2017-12-05,Inclusive breakup calculations in angular momentum basis: application to $^7$Li+$^{58}$Ni,"The angular momentum basis method is introduced to solve the inclusive
breakup within the model proposed by Ichimura, Austern, and Vincent [Phys. Rev.
C 32, 431 (1985)]. This method is based on the geometric transformation between
Jacobi coordinates, thus it is easy to corporate with particle spins. To test
the validity of this partial wave expansion method, a benchmark calculation is
done comparing with the one given in [Phys. Rev. C 92, 044616 (2015)]. Using
the distorted-wave Born approximation (DWBA) version of IAV model, some
applications to $^7$Li reactions are presented and compared with available
data.",1712.01433v1
2018-05-08,A semicoherent glitch-robust continuous gravitational wave search,"Continuous gravitational-wave signals from isolated non-axisymmetric rotating
neutron stars may undergo episodic spin-up events known as glitches. If
unmodelled by a search, these can result in missed or misidentified detections.
We outline a semicoherent glitch-robust search method that allows
identification of glitching signal candidates and inference about the model
parameters.",1805.03314v1
2018-05-15,Atomic-scale detection of magnetic impurity interactions in bulk semiconductors,"We demonstrate on the basis of ab initio simulations how passivated
semiconductor surfaces can be exploited to study bulklike interaction
properties and wave functions of magnetic impurities on the atomic scale with
conventional and spin-polarized scanning tunneling microscopy. By applying our
approach to the case of $3d$ transition metal impurities close to the
H/Si$(111)$ surface, we show exemplarily that their wave functions in Si are
less extended than for Mn in GaAs, thus obstructing ferromagnetism in Si.
Finally, we discuss possible applications of this method to other dilute
magnetic semiconductors.",1805.05745v1
2018-07-06,Gravitational waves from compact binaries in post-Newtonian accurate hyperbolic orbits,"We derive from first principles third post-Newtonian (3PN) accurate
Keplerian-type parametric solution to describe PN-accurate dynamics of
non-spinning compact binaries in hyperbolic orbits. Orbital elements and
functions of the parametric solution are obtained in terms of the conserved
orbital energy and angular momentum in both Arnowitt-Deser-Misner type and
modified harmonic coordinates. Elegant checks are provided that include a
modified analytic continuation prescription to obtain our independent
hyperbolic parametric solution from its eccentric version. A prescription to
model gravitational wave polarization states for hyperbolic compact binaries
experiencing 3.5PN-accurate orbital motion is presented that employs our
3PN-accurate parametric solution.",1807.02380v1
2018-09-30,Quartetting Wave Function Approach to $^{20}$Ne: Shell Model and Local Density Approximation,"We investigate $\alpha$-like correlations in $^{20}$Ne. A quartet of nucleons
(different spin/isospin) is moving in a mean field produced by the $^{16}$O
core nucleus. Improving the Thomas-Fermi model (local density approach), a
shell model is considered for the core nucleus. The effective potential of the
$\alpha$-like quartet and the wave function for the center-of-mass (c.o.m.)
motion are calculated and compared with other approaches.",1810.01274v1
2018-02-12,Zitterbewegung of exciton-polaritons,"Macroscopic wave packets of spin-polarized exciton-polaritons in
two-dimensional microcavities experience the zitterbewegung, the effect
manifested by the appearance of the oscillatory motion of polaritons in the
direction normal to the initial propagation direction. The oscillating
trajectories of exciton-polaritons are adjustable by the control parameters:
the splitting of the longitudinal and transverse exciton-polariton modes, the
wave vector and the width of the resonant cw pump. Our theoretical analysis
supported by the numerical calculations allowed to optimize values of the
control parameters suitable for a direct experimental observation of the
zitterbewegung effect.",1802.04049v1
2018-02-26,$S$ wave hidden charm - hidden strangeness production in $e^+e^-$ annihilation,"It is suggested that the recently observed enhancement of the relative yield
in $e^+e^-$ annihilation of states with hidden charm and hidden strangeness
above 4.43\,GeV is associated with the $S$ wave production of the charmed
strange meson pairs $D_{s0}(2317) \bar D_s^* + {\rm c.c.}$ and $D_{s1}^*(2460)
\bar D_s+ {\rm c.c.}$. This mechanism implies a pattern of breaking of the
Heavy Quark Spin Symmetry (HQSS) that can be tested in the final channels such
as $\eta_c(1S) \phi$, $h_c(1P) \eta $, $h_c(1P) \eta' $ produced in the same
energy range.",1802.09492v1
2018-12-24,Matter-wave interferometry using a levitated magnetic nanoparticle,"The superposition principle is one of the bizarre predictions of quantum
mechanics. Nevertheless, it has been experimentally verified using electrons,
photons, atoms, and molecules. In this article, using a $20~$nm levitated
ferromagnetic FePt nanoparticle, an exotic all optical spin polarization
technique and the matter-wave interferometry, we show that a mesoscopic spatial
Schrodinger cat can be created. Additionally, we argue that the maximum spatial
separation between the delocalized wavepackets can be $25~\mu m$ and is
significantly larger than the object itself.",1812.09948v5
2020-04-30,High frequency gravitational waves from spin-3/2 fields,"We point out the peculiar form of the gravitational wave signal expected from
a gas of particles carry spin 3/2 produced during preheating. Given the very
few ways that gravitinos can manifest themselves in an experimentally
observable way, we stress the importance of improving the sensitivity of
ultra-high frequency detectors in the future. This review is based on work that
appeared in [arXiv:1811.11774 [hep-ph]].",2004.14770v1
2020-08-24,"Energy, linear momentum, and spin and orbital angular momenta of circularly polarized Laguerre-Gaussian wave-packets","We derive expressions for the energy, linear momentum, and angular momentum
content of circularly polarized Laguerre-Gaussian wave-packets propagating in
free space. The vectorial nature of the electromagnetic field is taken into
account, and the various consequences of paraxial approximation, which is
typically invoked in theoretical treatments of the Laguerre-Gaussian beams, are
examined.",2008.10694v1
2016-12-19,Electrically driven magnetic antenna based on multiferroic composites,"We suggest and demonstrate via large scale numerical simulations an
electrically operated spin- wave inducer based on composite multiferroic
junctions. Specifcally, we consider an interfacially coupled
ferromagnetic/ferroelectric structure that emits controllably spin waves in the
ferromagnets if the ferroelectric polarization is poled by an external electric
field. The roles of geometry and material properties are discussed.",1612.06326v1
2017-10-11,Scattering from finite-volume energies including higher partial waves and multiple decay channels,"A new implementation of estimating the two-to-two $K$-matrix from
finite-volume energies based on the Luescher formalism is described. The method
includes higher partial waves and multiple decay channels, and the fitting
procedure properly includes all covariances and statistical uncertainties. The
method is also simpler than previously used procedures. Formulas and software
for handling total spins up to $S=2$ and orbital angular momenta up to $L=6$
are presented.",1710.04169v1
2020-03-31,Integral representation of finite temperature non-Markovian evolution of some RWA systems,"We introduce the Friedrichs model at finite temperature which is one- and
zero-particle restriction of spin-boson in the rotating wave approximation and
obtain the population of the excited state for this model. We also consider the
oscillator interacting with bosonic thermal bath in the rotating wave
approximation and obtain dynamics of mean excitation number for this
oscillator. Both solutions are expressed in terms of integrals of
zero-temperature solutions with correspondent correlation functions.",2003.13993v1
2021-10-03,Gravitational effects on neutrino decoherence in Lense-Thirring metric,"We analyze gravity effects on neutrino wave packet decoherence. As a specific
example, we consider the gravitational field of a spinning spherical body
described by the Lense-Thirring metric. By working in the weak-field limit and
employing Gaussian wave packets, we show that the characteristic coherence
length of neutrino oscillation processes is nontrivially affected, the
corrections being dependent on the mass and angular velocity of the gravity
source. Possible experimental implications are finally discussed.",2110.00971v1
2004-05-07,Hall Effect of Light,"We derive the semiclassical equation of motion for the wave-packet of light
taking into account the Berry curvature in the momentum space. This equation
naturally describes the interplay between the orbital and spin angular momenta,
i.e., the conservation of the total angular momentum of light. This leads to
the shift of the wave-packet motion perpendicular to the gradient of the
dielectric constant, i.e., the polarization-dependent Hall effect of light. An
enhancement of this effect in the photonic crystal is also proposed.",0405129v3
2008-06-13,Bounding the greybody factors for Schwarzschild black holes,"Greybody factors in black hole physics modify the naive Planckian spectrum
that is predicted for Hawking radiation when working in the limit of
geometrical optics. We consider the Schwarzschild geometry in (3+1) dimensions,
and analyze the Regge-Wheeler equation for arbitrary particle spin S and
wave-mode angular momentum L, deriving rigourous bounds on the greybody factors
as a function of S, L, wave frequency (omega), and the black hole mass, m.",0806.2209v2
2017-01-23,Is there a narrow $N(1685)$?,"The helicity-dependent observable $E$ for the reaction $\gamma d\to \eta n
(p)$ with a spectator proton was recently measured by the A2 Collaboration at
MAMI in Mainz. The data were interpreted as further evidence for a narrow
resonance with spin and parity $J^P=1/2^+$ ($P_{11}$ wave). However, a full
partial wave analysis without any narrow resonance leads to an excellent
description of the data, imposing a narrow resonance with the properties
suggested by the A2 Collaboration leads to a significant deterioration of the
fit quality: there is no need for a narrow resonance.",1701.06387v2
2017-04-02,Density wave like transport anomalies in surface doped Na$_{2}$IrO$_3$,"We report that the surface conductivity of Na$_{2}$IrO$_3$ crystal is
extremely tunable by high energy Ar plasma etching and can be tuned from
insulating to metallic with increasing etching time. Temperature dependent
electrical transport for the metallic samples show signatures of first order
phase transitions which are consistent with charge or spin density wave like
phase transitions recently predicted theoretically. Additionally,
grazing-incidence small-angle x-ray scattering (GISAXS) reveal that the room
temperature surface structure of Na$_{2}$IrO$_3$ does not change after plasma
etching.",1704.00263v2
2019-01-17,Charge Density Wave in a Doped Kondo Chain,"We report the existence of the charge density wave (CDW) in the ground state
of 1D Kondo lattice model at the filling of n=0.75 in the weak coupling region.
The CDW is driven by the effective Coulomb repulsion mediated by the localized
spins. Based on our numerical results using the density matrix renormalization
group method, we show that the CDW phase appears in the paramagnetic region
previously known as the Tomonaga-Luttinger liquid. The emergence of this phase
serves as an example of CDW phase induced without bare repulsive interactions,
and enriches the phase diagram of the 1D Kondo lattice model.",1901.05643v1
2019-04-25,Gravitational Plane Waves in a Non-Riemannian Description of Brans-Dicke Gravity,"The variational field equations of Brans-Dicke scalar-tensor theory of
gravitation are given in a non-Riemannian setting in the language of exterior
differential forms over 4-dimensional spacetime. The class of pp-wave metrics
together with the Brans-Dicke scalar field are used to derive the geodesic and
autoparallel equations of motion for non-spinning test masses in Brinkmann and
Rosen coordinates. The effects of the gradient of the scalar field on the
auto-parallel equations of motion and Jacobi deviation equation are discussed.",1904.11209v2
2019-07-12,Deuteron wave function for Reid93 potential and polarization observables in elastic lepton-deuteron scattering,"Elastic lepton-deuteron scattering was considered within the limit of zero
lepton mass. The deuteron wave function in the coordinate representation for
the Reid93 potential was applied to numerical calculations. The
angular-momentum dependence of values spin correlation coefficients
$C_{xz}^{(0)}$, $C_{zz}^{(0)}$ and tensor asymmetries $A_{xx}^{(0)}$,
$A_{xz}^{(0)}$, $A_{zz}^{(0)}$ have been evaluated in 3D format for Reid93
potential. These polarization observables are analyzed for different energies
and scattering angles. Application of the obtained values allows better
explanation and illustration of the laws of elastic lepton-deuteron scattering.",1907.05726v1
2019-07-30,Gravitational Wave Signals of Pseudo-Goldstone Dark Matter in the $\mathbb{Z}_{3}$ Complex Singlet Model,"We study pseudo-Goldstone dark matter in the $\mathbb{Z}_{3}$ complex scalar
singlet model. Because the direct detection spin-independent cross section is
suppressed, such dark matter is allowed in a large mass range. Unlike in the
original model stabilized by a parity, due to the cubic coupling of the singlet
the $\mathbb{Z}_{3}$ model can accommodate first-order phase transitions that
give rise to a stochastic gravitational wave signal potentially observable in
future space-based detectors.",1907.13136v2
2020-01-12,Cosmological Collider Signatures of Massive Vectors from Non-Gaussian Gravitational Waves,"The cosmological collider provides a model-independent probe of particle
physics during inflation. We extend the study of cosmological collider physics
to much smaller scales through gravitational wave (GW) probes. With a
Chern-Simons interaction, a massive vector field can obtain a chemical
potential and its particle production can cause significant non-Gaussian GW
signals. We calculate the mass and spin dependences of the induced GW 3-point
correlation function in the squeezed limit, and estimate its amplitude. Such
signals may be detectable in the current and upcoming GW interferometer
experiments.",2001.03879v1
2020-01-21,Field Tensor Network States,"We define a class of tensor network states for spin systems where the
individual tensors are functionals of fields. The construction is based on the
path integral representation of correlators of operators in quantum field
theory. These tensor network states are infinite dimensional versions of matrix
product states and projected entangled pair states. We find the field-tensor
that generates the Haldane-Shastry wave function and extend it to two
dimensions. We give evidence that the latter underlies the topological chiral
state described by the Kalmeyer-Laughlin wave function.",2001.07723v2
2020-06-21,The nature of short-ranged correlations in nuclear systems,"We apply ideas of the parquet-diagram and optimized Fermi-hypernetted chain
methods to determine the short-range structure of the pair wave function in
neutron matter and compare these with Bethe-Goldstone results and those of
low-order variational calculations. It is shown that the induced interaction,
describing the exchange of density, spin, and tensor fluctuations, has a
profound influence on the short-ranged structure of the pair wave function and,
hence, on effective interactions in neutron matter.",2006.11849v1
2020-06-28,Surface-acoustic-wave-induced unconventional superconducting pairing,"Unconventional superconductivity is usually associated with symmetry breaking
in the system. Here we consider a simple setup consisting of a solid state
material with conduction electrons and an applied surface acoustic wave (SAW),
that can break time and spatial translation symmetries. We study the symmetries
of the possible SAW-induced order parameters, showing that even-frequency
spin-triplet odd-parity order parameter can occur. We suggest different methods
of how to engineer the symmetries of the order parameters using SAWs and the
applications of such setups.",2006.15589v4
2020-12-20,Strong coupling antiferromagnetic resonance with sub-THz cavity fields,"Strong coupling of electromagnetic cavity fields with antiferromagnetic spin
waves in hematite ($\alpha$-Fe$_2$O$_3$) was achieved above room temperature. A
cube of hematite was placed in a metallic tube and transmission was measured,
using a continuous-wave THz spectrometer. Spectra, collected as a function of
temperature, reveal the formation of magnetic polaritons.",2012.10910v2
2021-01-12,Gravitational wave templates from Extreme Mass Ratio Inspirals,"An extreme mass ratio inspiral takes place when a compact stellar object is
inspiraling into a supermassive black hole due to gravitational radiation
reaction. Gravitational waves (GWs) from this system can be calculated using
the Teukolsky equation (TE). In our case, we compute the asymptotic GW fluxes
of a spinning body orbiting a Kerr black hole by solving numerically the TE
both in time and frequency domain. Our ultimate goal is to produce GW templates
for space-based detectors such as LISA.",2101.04533v1
2021-03-19,Exact solution for wave scattering from black holes: Formulation,"We establish an exact formulation for wave scattering of a massless field
with spin and charge by a Kerr-Newman-de Sitter black hole. Our formulation is
based on the exact solution of the Teukolsky equation in terms of the local
Heun function, and does not require any approximation. It serves as simple
exact formulae with arbitrary high precision, which realize fast calculation
without restrictions on model parameters. We highlight several applications
including quasinormal modes, cross section, reflection/absorption rate, and
Green function.",2103.10802v2
2022-01-04,Klein-Gordon equation in $q$-deformed Euclidean space,"We introduce $q$-versions of the Klein-Gordon equation in the
three-dimensional $q$-deformed Euclidean space. We determine plane wave
solutions to our $q$-deformed Klein-Gordon equations. We show that these plane
wave solutions form a complete orthogonal system. We discuss the propagators of
our $q$-deformed Klein-Gordon equations. We derive continuity equations for the
charge density, the energy density, and the momentum density of a $q$-deformed
spin-zero particle.",2201.01292v1
2022-03-04,Circularly polarized periodic gravitational wave and the Pais-Uhlenbeck oscillator,"The ""Bargmann framework"" allows us to prove the equivalence of the
Pais-Uhlenbeck oscillator with a spin-zero particle in a circularly polarized
periodic gravitational wave. Pushing forward the symmetries (which include
Carroll symmetry) of the latter, we derive conserved charges for the
Pais-Uhlenbeck oscillator.",2203.02338v3
2022-04-28,$Z_n$ symmetry in the vortex muon decay,"Polarization of a vortex state fermion has rich structure due to the
nontrivial momentum distribution of wave function. This larger freedom provides
an unique opportunity to prepare fermions in exotic polarized states, which do
not exist for plane-wave state fermions. Based on the so called spin-orbit
state which was studied both theoretically and experimentally, we put forward a
peculiar vortex muon whose polarization exhibits $Z_n$ symmetry and study its
decay. We investigate the azimuthal distribution of the emitted electrons and
find that it exhibits the same symmetry ($Z_n$) as the initial state.",2204.13351v2
2022-09-21,Numerical Test and Analysis of the 2nd Law of Black Hole Thermodynamics with Gravitational-Wave Data from Binary Black Hole Merger Events,"Gravitational-wave detections of black hole mergers in binary systems offer
an excellent opportunity to test the 2nd law of black hole thermodynamics. In
this paper, we review how the entropy of any astrophysical black hole is
calculated and we use LIGO and VIRGO's mass and spin data measurements from
black hole merger events detected over the past years to perform entropy
calculations and numerically test the generalized 2nd law of thermodynamics.
Besides, we analyze the mathematical correlation between the black hole merger
event's initial parameters to prove and conclude that the theorem will always
hold.",2209.11683v1
2022-12-01,On unitarity of the Coon amplitude,"The Coon amplitude is a one-parameter deformation of the Veneziano amplitude.
We explore the unitarity of the Coon amplitude through its partial wave
expansion using tools from $q$-calculus. Our analysis establishes manifest
positivity on the leading and sub-leading Regge trajectories in arbitrary
spacetime dimensions $D$, while revealing a violation of unitarity in a certain
region of $(q,D)$ parameter space starting at the sub-sub-leading Regge order.
A combination of numerical studies and analytic arguments allows us to argue
for the manifest positivity of the partial wave coefficients in fixed spin and
Regge asymptotics.",2212.00764v2
2023-04-06,Constrains on s and d components of electron boson coupling constants in one band d wave Eliashberg theory for high Tc superconductors,"The phenomenology of overdoped high Tc superconductors can be described by a
one band d wave Eliashberg theory where the mechanism of superconducting
coupling is mediated by antiferromagnetic spin fluctuations and whose
characteristic energy Omega0 scales with Tc according to the empirical law
Omega0 = 5.8 kBTc. This model presents universal characteristics that are
independent of the critical temperature such as the link between the s and d
components of electron boson coupling constants and the invariance of the ratio
2Delta/kBTc.",2304.03231v2
2023-04-24,QCD bound states in motion,"I consider the frame dependence of QCD bound states in the presence of a
confining, spatially constant gluon field energy density. The states are
quantized at equal time in $A^0=0$ (temporal) gauge. I derive the frame
dependence of the wave functions, and demonstrate the Lorentz covariance of the
electromagnetic (transition) form factors for states of any spin. The wave
functions of $J^{PC}=0^{-+}$ states with CM momentum $P \neq 0$ are considered
in some detail, verifying their local normalizability and the expected frame
dependence of the bound state energy.",2304.11903v2
2023-12-02,Spin interaction of non-relativistic neutrons with an ultrashort laser pulse,"The non-relativistic Pauli equation is used to study the interaction of slow
neutrons with a short magnetic pulse. In the extreme limit, the pulse is acting
on the magnetic moment of the neutron only at one instant of time. We obtain
the scattering amplitude by deriving the junction conditions for the Pauli wave
function across the pulse. Explicit expressions are given for a beam of
polarized plane wave neutrons subjected to a pulse of spatially constant
magnetic field strength. Assuming that the magnetic field is generated by an
ultrashort laser pulse, we provide crude numerical estimates.",2312.01079v1
2023-12-31,Generalization of the Bargmann-Wigner approach to constructing relativistic fields,"We review the method for constructing local relativistic fields corresponding
to the Bargmann-Wigner wave functions that describe the unitary irreducible
representations of the $4D$ Poincar\'{e} group. The method is based on the use
of the generalized Wigner operator connecting the wave functions of induced
representations and local relativistic fields. Applications of this operator
for constructing massive local relativistic fields as well as massless helicity
local fields and massless local infinite spin fields are considered.",2401.00494v1
2024-01-23,Curvature effect induce topological phase transitions in two dimensional topological superconductor,"Recently, topological superconductor is one of the important topics in
condensed matter physics due to the exotic features of quasiparticles resided
on the edge, surface and vortex core. In our work, we analyze the two
dimensional s+p wave noncentrosymmetric superconductor(NCS) with Rashba
spin-orbit coupling in 2D cylindrical coordinate to find the relationship
between the topological phase transition and the curvature. With analytical
calculation and numerical analyze, we confirm that the topological phase
transition in s+p wave NCS in 2D cylindrical coordinate is related to the
curvature from band theory perspective.",2401.12705v1
2024-03-19,A relativistic position--dependent mass system of bosonic field in cosmic string space--time background,"In this work, we investigate the relativistic quantum motions of spin--zero
scalar bosons via the Duffin--Kemmer--Petiau (DKP) equation with a
position--dependent mass (PDM) system in the background of the topological
defect space--time produced by a cosmic string. We determine the radial wave
equation and obtain the exact analytical solutions of the wave equation for the
linear and Cornell--type potential through the Bi--Confluent Heun differential
equation. In fact, we have obtained the ground state energy for both
potentials.",2403.13095v1
2003-09-11,Components of the gravitational force in the field of a gravitational wave,"Gravitational waves bring about the relative motion of free test masses. The
detailed knowledge of this motion is important conceptually and practically,
because the mirrors of laser interferometric detectors of gravitational waves
are essentially free test masses. There exists an analogy between the motion of
free masses in the field of a gravitational wave and the motion of free charges
in the field of an electromagnetic wave. In particular, a gravitational wave
drives the masses in the plane of the wave-front and also, to a smaller extent,
back and forth in the direction of the wave's propagation. To describe this
motion, we introduce the notion of `electric' and `magnetic' components of the
gravitational force. This analogy is not perfect, but it reflects some
important features of the phenomenon. Using different methods, we demonstrate
the presence and importance of what we call the `magnetic' component of motion
of free masses. It contributes to the variation of distance between a pair of
particles. We explicitely derive the full response function of a 2-arm laser
interferometer to a gravitational wave of arbitrary polarization. We give a
convenient description of the response function in terms of the spin-weighted
spherical harmonics. We show that the previously ignored `magnetic' component
may provide a correction of up to 10 %, or so, to the usual `electric'
component of the response function. The `magnetic' contribution must be taken
into account in the data analysis, if the parameters of the radiating system
are not to be mis-estimated.",0309058v2
2019-06-05,Partial wave decomposition on the lattice and its applications to the HAL QCD method,"The approximated partial wave decomposition method to the discrete data on a
cubic lattice, developed by C. W. Misner, is applied to the calculation of
$S$-wave hadron-hadron scatterings by the HAL QCD method in lattice QCD. We
consider the Nambu-Bethe-Salpeter (NBS) wave function for the spin-singlet
$\Lambda_c N$ system calculated in the $(2+1)$-flavor QCD on a
$(32a~\mathrm{fm})^3$ lattice at the lattice spacing $a\simeq0.0907$ fm and
$m_\pi \simeq 700$ MeV. We find that the $l=0$ component can be successfully
extracted by Misner's method from the NBS wave function projected to $A_1^+$
representation of the cubic group, which contains small $l\ge 4$ components.
Furthermore, while the higher partial wave components are enhanced so as to
produce significant comb-like structures in the conventional HAL QCD potential
if the Laplacian approximated by the usual second order difference is applied
to the NBS wave function, such structures are found to be absent in the
potential extracted by Misner's method, where the Laplacian can be evaluated
analytically for each partial wave component. Despite the difference in the
potentials, two methods give almost identical results on the central values and
on the magnitude of statistical errors for the fits of the potentials, and
consequently on the scattering phase shifts. This indicates not only that
Misner's method works well in lattice QCD with the HAL QCD method but also that
the contaminations from higher partial waves in the study of $S$-wave
scatterings are well under control even in the conventional HAL QCD method. It
will be of interest to study interactions in higher partial wave channels in
the HAL QCD method with Misner's decomposition, where the utility of this new
technique may become clearer.",1906.01987v2
2023-06-13,Oxygen isotope effect on the superfluid density within the $d-$wave and $s-$wave pairing channels of YBa$_2$Cu$_4$O$_8$,"We report on measurements of the oxygen isotope ($^{16}$O/$^{18}$O) effect
(OIE) on the transition temperature $T_{\rm c}$ and the zero-temperature
in-plane magnetic penetration depth $\lambda_{\rm ab}(0)$ in the stoichiometric
cuprate superconductor YBa$_2$Cu$_4$O$_8$ by means of muon-spin
rotation/relaxation. An analysis of the temperature evolution of
$\lambda^{-2}_{\rm ab}$ in terms of coexisting $s+d-$wave order parameters
reveals that the OIE on the superfluid density $\rho_{\rm
s}(0)\propto\lambda^{-2}_{\rm ab}(0)$ stems predominantly from the $d-$wave
component while the contribution of the $s-$wave one is almost zero. The OIE on
the transition temperature $T_{\rm c}$ is found to be rather small: $\delta
T_{\rm c}/T_{\rm c}= -0.32(7)$%, compared to the total OIE on the superfluid
density $\rho_{\rm s}(0)$: $\delta \rho_{\rm s}(0)/\rho_{\rm s}(0)=
-2.8(1.0)$%. The partial OIE's on the corresponding $d-$wave and $s-$wave
components of $\rho_{\rm s}(0)$ are $\delta \rho_{\rm s,d}(0)/\rho_{\rm s}(0)=
-3.0(1.2)$%, and $\delta \rho_{\rm s,s}(0)/\rho_{\rm s}(0)= 0.2(1.2)$%,
respectively. Our results demonstrate that polaron formation in the CuO$_2$
planes is the origin of the observed OIE in the $d-$wave channel. In the much
weaker $s-$wave channel, fermionic quasiparticles are present, which do not
contribute to the OIE on $\rho_{\rm s}(0)$. Our results support the original
idea of K. Alex M\""{u}ller on the polaronic nature of the supercarries in
high-temperature cuprate superconductors.",2306.08112v1
2023-08-03,Continuous gravitational waves from trapped magnetar ejecta and the connection to glitches and antiglitches,"Gravitational waves from isolated sources have eluded detection so far. The
upper limit of long-lasting continuous gravitational wave emission can now
probe physically-motivated models with the most optimistic being strongly
constrained. Naturally, one might want to relax the assumption of the
gravitational wave being quasi-infinite in duration, leading to the idea of
transient continuous gravitational waves. In this paper, we outline how to get
transient continuous waves from magnetars (or strongly-magnetised neutron
stars) that exhibit glitches and/or antiglitches and apply the model to
magnetar SGR J1935+2154. The toy model hypothesizes that at a glitch or
antiglitch, mass is ejected from the magnetar but becomes trapped on its
outward journey through the magnetosphere. Depending on the height of the
trapped ejecta and the magnetic inclination angle, we are able to reproduce
both glitches and antiglitches from simple angular momentum arguments. The
trapped ejecta causes the magnetar to precess leading to gravitational wave
emission at once and twice the magnetar's spin frequency, for a duration equal
to however long the ejecta is trapped for. We find that the gravitational waves
are more detectable when the magnetar is: closer, rotating faster, or has
larger glitches/antiglitches. The detectability also improves when the ejecta
height and magnetic inclination angle have values near their critical values,
though this requires more mass to be ejected to remain consistent with the
observed glitch/antiglitch. We find it unlikely that gravitational waves will
be detected from SGR J1935+2154 when using the trapped ejecta model.",2308.01588v2
2004-06-25,Propagation and Transmission of Alfven Waves in Rotating Magnetars,"We study the propagation and transmission of Alfven waves in the context of
cylindrical geometry. This approximates the polar cap region of aligned pulsar
with strong magnetic fields. Non-propagating region appears in the presence of
rotation. The displacement current further prevents the low frequency modes
from propagating near the stellar surface. The transmission rates to the
exterior through the surface are calculated. The rates increase with the
frequency and the magnetic field strength. The transmission also depends on the
helicity states of the waves, but the difference becomes small in the high
frequency regime. We also point out the possibility of the spin-up by outgoing
wave emission in the low frequency regime, if a certain condition holds.",0406572v1
2005-07-04,The gravitational-wave spectrum of a non-axisymmetric torus around a rapidly spinning black hole,"The gravitational-wave spectrum emitted by a non-axisymmetric torus rotating
at an angular velocity $\Omega_T$, is derived in terms of a structure function
representing a combination of sausage-tilt modes in the torus in the limit of
an incompressible fluid. The analysis of the gravitational-wave spectrum is
then applied to a model proposed recently, in which a highly magnetized torus
interacts with a stellar mass, Kerr black hole via poloidal field lines that
connect the torus and the horizon. The deformation of the torus results from
global magnetic instabilities when the magnetic field strength inside the torus
exceeds a few times $10^{15}$ Gauss. The dynamics of the system is illustrated
using a non-MHD toy model. It is found that, quite generally, most of the
gravitational-wave energy emitted is in the frequency range of sensitivity of
LIGO and Virgo.",0507078v1
1995-08-06,Sound propagation in density wave conductors and the effect of long-range Coulomb interaction,"We study theoretically the sound propagation in charge- and spin-density
waves in the hydrodynamic regime. First, making use of the method of comoving
frame, we construct the stress tensor appropriate for quasi-one dimensional
systems within tight-binding approximation. Taking into account the screening
effect of the long-range Coulomb interaction, we find that the increase of the
sound velocity below the critical temperature is about two orders of magnitude
less for longitudinal sound than for transverse one. It is shown that only the
transverse sound wave with displacement vector parallel to the chain direction
couples to the phason of the density wave, therefore we expect significant
electromechanical effect only in this case.",9508019v1
1995-10-23,A First-Landau-Level Laughlin/Jain Wave Function for the Fractional Quantum Hall Effect,"We show that the introduction of a more general closed-shell operator allows
one to extend Laughlin's wave function to account for the richer hierarchies
(1/3, 2/5, 3/7 ...; 1/5, 2/9, 3/13, ..., etc.) found experimentally. The
construction identifies the special hierarchy states with condensates of
correlated electron clusters. This clustering implies a single-particle (ls)j
algebra within the first Landau level (LL) identical to that of multiply filled
LLs in the integer quantum Hall effect. The end result is a simple generalized
wave function that reproduces the results of both Laughlin and Jain, without
reference to higher LLs or projection.",9510133v2
1996-05-01,Statistics of skyrmions and the 5/2 puzzle,"1) For the hard core interaction there is some freedom left in the choice of
the exact multiskyrmionic wave function's topology. The statistics of textured
quasiholes, analyzed by calculation of the Berry phase, depends on this choice
of topology.
  2) We find a class of textured two-hole eigenstates of the Coulomb
interaction. There is no definite quantum statistics but there is a definite
rule of how to construct Coulomb eigenstates out of the hard core wave
functions.
  3) A wave function for the 5/2 state is constructed according to this rule.",9605003v3
1998-06-30,Wave Function of the Largest Skyrmion on a Sphere,"It has been clarified that charged excitation known as a skyrmion exists
around the ferromagnetic ground state at the Landau level filling factor
$\nu=1/q$, where $q$ is an odd integer. An infinite sized skyrmion is realized
in the absence of the spin-Zeeman splitting or for double-layered systems.
Analytical form of the wave function is identified at $\nu=1$ and $\nu=1/3$
through exact diagonalization of the Hamiltonian for finite sized spherical
systems. It is clarified that the skyrmion wave functions at $\nu=1$ and
$\nu=1/3$ are qualitatively different: they are not related by the composite
fermion transformation. Long-range behavior of the skyrmion wave function
around $\nu=1$ is shown to be consistent with the semiclassical picture of the
skyrmion.",9806363v2
1999-11-17,Instabilities Toward Charge Density Wave and Paired Quantum Hall State of Half-Filled Landau Levels,"We study the stability of spin-resolved Landau levels at electron filling
factor $\nu=n+1/2$, where n is a positive integer. Representing the half-filled
topmost Landau level by fermions and the n filled inner Landau levels by n
bosons, coupled to the Chern-Simons gauge fields, we show that the ground
states exhibit charge density wave order for $n(n+1/2)>15.54 \pi(a_B^*)^2 n_e$,
where $n_e$ is the 2D carrier density and $a_B^*$ is the effective Bohr radius.
We find that the pairing interaction mediated by the fluctuating gauge field is
enhanced near the charge density wave instability such that p-wave pairing of
the Chern-Simons fermions prevails for
$3.49(\pi{\ab}^2)n_e<n^2(n+1/2)<20.22\pi(a_B^*)^2 n_e$. The competition between
charge density wave order and paired quantum Hall state is discussed in
connection to recent experiments.",9911265v1
2003-02-28,A Luttinger Liquid in Box,"We study a Luttinger Liquid in a finite one-dimensional wire with box-like
boundary conditions by considering the local distribution of the single
particle spectral weight. This corresponds to the experimental probability of
extracting a single electron at a given place and energy, which can be
interpreted as the square of an electron wave-function. For the non-interacting
case, this is given by a standing wave at the Fermi wave-vector. In the
presence of interactions, however, the wave-functions obtain additional
structure with a sharp depletion near the edges and modulations throughout the
wire. In the spinful case, these modulations correspond to the separate spin-
and charge-like excitations in the system.",0302625v2
2004-11-30,Real Space Imaging of One-Dimensional Standing Waves: Direct Evidence for a Luttinger Liquid,"Electronic standing waves with two different wavelengths were directly mapped
near one end of a single-wall carbon nanotube as a function of the tip position
and the sample bias voltage with highresolution position-resolved scanning
tunneling spectroscopy. The observed two standing waves caused by separate spin
and charge bosonic excitations are found to constitute direct evidence for a
Luttinger liquid. The increased group velocity of the charge excitation, the
power-law decay of their amplitudes away from the scattering boundary, and the
suppression of the density of states near the Fermi level were also directly
observed or calculated from the two different standing waves.",0412001v1
2006-06-14,Dephasing of Andreev pairs entering a charge density wave,"An Andreev pair from a s-wave superconductor (S) entering a conventional
gapless charge density wave (CDW) below the Peierls gap dephases on the Fermi
wavelength while one particle states are localized on the CDW coherence length.
The paths following different sequences of impurities interfere destructively,
due to the different electron and hole densities in the CDW. The same
conclusion holds for averaging over the conduction channels in the ballistic
system. We apply two microscopic approaches to this phenomenon: i) a Blonder,
Tinkham, Klapwijk (BTK) approach for a single highly transparent S-CDW
interface; and ii) the Hamiltonian approach for the Josephson effect in a clean
CDW and a CDW with non magnetic disorder. The Josephson effect through a spin
density wave (SDW) is limited by the coherence length, not by the Fermi
wave-length.",0606382v4
1994-09-27,Gravitational Waves from a Particle Orbiting Around a Rotating Black Holes: Post-Newtonian Expansion,"Using the Teukolsky and Sasaki-Nakamura equations for the gravitational
perturbation of the Kerr spacetime, we calculate the post-Newtonian expansion
of the energy and angular momentum luminosities of gravitational waves from a
test particle orbiting around a rotating black hole up through ${\rm P^{5/2}N}$
order beyond the quadrupole formula. We apply a method recently developed by
Sasaki to the case of a rotating black hole. We take into account a small
inclination of the orbital plane to the lowest order of the Carter constant.
The result to $ P^{3/2}N}$ order is in agreement with a similar calculation by
Poisson as well as with the standard post-Newtonian calculation by Kidder et
al. Using our result, we calculate the integrated phase of gravitational waves
from a neutron star-neutron star binary and a black hole-neutron star binary
during their inspiral stage. We find that, in both cases, spin-dependent terms
in the P$^2$N and P$^{5/2}$N corrections are important to construct effective
template waveforms which will be used for future laser-interferometric
gravitational wave detectors.",9409054v1
1995-06-30,Gravitational Waves from Compact Bodies,"A review is given of recent research on gravitational waves from compact
bodies and its relevance to the LIGO/VIRGO international network of
high-frequency (10 to 10,000 Hz) gravitational-wave detectors, and to the
proposed LISA system of low-frequency (0.1 to 0.0001 Hz) detectors. The sources
that are reviewed are ordinary binary star systems, binaries made from compact
bodies (black holes and neutron stars), the final inspiral and coalescence of
compact-body binaries, the inspiral of stars and small black holes into massive
black holes, the stellar core collapse that triggers supernovae, and the spin
of neutron stars. This paper is adapted from a longer review article entitled
``Gravitational Waves'' (GRP-411) that the author has written for the
Proceedings of the Snowmass '94 Summer Study on Particle and Nuclear
Astrophysics and Cosmology.",9506084v1
1995-12-30,Exact Gravitational Shock Wave Solution of Higher Order Theories,"We find an {\it exact} pp--gravitational wave solution of the fourth order
gravity field equations. Outside the (delta--like) source this {\it not} a
vacuum solution of General Relativity. It represents the contribution of the
massive, $m=(-\beta)^{-1/2}$, spin--two field associated to the Ricci squared
term in the gravitational Lagrangian. The fourth order terms tend to make
milder the singularity of the curvature at the point where the particle is
located. We generalize this analysis to $D$--dimensions, extended sources, and
higher than fourth order theories. We also briefly discuss the scattering of
fields by this kind of plane gravitational waves.",9512050v2
1998-03-27,Group Theoretical Examination of the Relativistic Wave Equations on Curved Spaces. II. De Sitter and Anti-de Sitter Spaces,"The group theoretical approach to the relativistic wave equations in the de
Sitter and Anti-de Sitter spaces for spin~0 and 1/2 massive particles is
considered. The invariant wave equations which determines the appropriate
irreducible representations are constructed. The explicit solutions of these
equations possessing a simplicity and physical transparency are obtained
without use of the separation of variables method. The connection with the
general-covariant approach to wave equations in a curved space is established.
It is shown that the Anti-de Sitter space is the solution of the Einstein-Dirac
equations. The geometrical meaning of the mass quantization in the Anti-de
Sitter space and of the particle creation in de Sitter space is shown.",9803092v3
2003-12-10,Searching for gravitational waves from the Crab pulsar - the problem of timing noise,"Of the current known pulsars, the Crab pulsar (B0531+21) is one of the most
promising sources of gravitational waves. The relatively large timing noise of
the Crab causes its phase evolution to depart from a simple spin-down model.
This effect needs to be taken in to account when performing time domain
searches for the Crab pulsar in order to avoid severely degrading the search
efficiency. The Jodrell Bank Crab pulsar ephemeris is examined to see if it can
be used for tracking the phase evolution of any gravitational wave signal from
the pulsar, and we present a method of heterodyning the data that takes account
of the phase wander. The possibility of obtaining physical information about
the pulsar from comparisons of the electromagnetically and a gravitationally
observed timing noise is discussed. Finally, additional problems caused by
pulsar glitches are discussed.",0312057v1
2004-07-30,Propagation of Dirac Wave Functions in Accelerated Frames of Reference,"The first-order gravity effects of Dirac wave functions are found from the
inertial effects in the accelerated frames of reference. Derivations and
discussions about Lense-Thirring effect and the gyrogravitational ratio for
intrinsic spin are presented. We use coordinate transformations among reference
frames to study and understand the Lense-Thirring effect of a scalar particle.
For a Dirac particle, the wave-function transformation operator from an
inertial frame to a moving accelerated frame is obtained. From this, the Dirac
wave function is solved and its change of polarization gives the
gyrogravitational ratio 1 for the first-order gravitational effects. The
eikonal approach to this problem is presented in the end for ready extension to
investigations involving curvature terms.",0407115v1
2006-06-20,The search for continuous gravitational waves: metric of the multi-detector F-statistic,"We develop a general formalism for the parameter-space metric of the
multi-detector F-statistic, which is a matched-filtering detection statistic
for continuous gravitational waves. We find that there exists a whole family of
F-statistic metrics, parametrized by the (unknown) amplitude parameters of the
gravitational wave. The multi-detector metric is shown to be expressible in
terms of noise-weighted averages of single-detector contributions, which
implies that the number of templates required to cover the parameter space does
not scale with the number of detectors. Contrary to using a longer observation
time, combining detectors of similar sensitivity is therefore the
computationally cheapest way to improve the sensitivity of coherent
wide-parameter searches for continuous gravitational waves.
  We explicitly compute the F-statistic metric family for signals from isolated
spinning neutron stars, and we numerically evaluate the quality of different
metric approximations in a Monte-Carlo study. The metric predictions are tested
against the measured mismatches and we identify regimes in which the local
metric is no longer a good description of the parameter-space structure.",0606088v2
1992-11-16,Relativistic Constituent Quark Model for Baryons,"The electroweak properties of nucleons and hyperons are calculated in a
relativistic constituent quark model. The baryons are treated as three quark
bound states, and the diagrams of perturbation theory are considered on the
light front. The electroweak properties of the baryons are of nonperturbative
nature and can be represented by one-loop diagrams. We consider different
extensions of the simplest model: quark form factors, configuration mixing of
the wave function, asymmetric wave function, wave function different from the
one of a harmonic oscillator valid up to energies of more than 30 GeV$^2$. A
comprehensive study of various baryonic properties is given: elastic form
factors of the nucleon, magnetic moments of the baryon octet, semileptonic weak
form factors. This analysis also gives the Kobayashi-Maskawa matrix element
$V_{us}$ and a sound symmetry breaking scheme for the Cabibbo theory. A
consistent physical picture appears in this work. The nucleon consists of an
unmixed, symmetric three quark state, the wave function of the hyperons is
however asymmetric with a spin-isospin-0 diquark. Only for the
strangeness-changing weak decay do we need nontrivial form factors.",9211255v1
2004-08-03,Three-Quark Wave Function of Nucleon in the Quasipotential Approach,"The structure of the nucleon wave function as a bound system of the
constituent quarks was considered in framework of the quasipotential method of
description of the bound states with a fixed number of particles.
  In the impulse approximation the wave function is reduced to the three-quark
component of the vector state in the Fock-momentum space.
  Spin structure of the wave function was studied by the decomposition method
of the irreducible representations product of inhomogeneous Lorentz group.
  Physical distinction of SU(6) symmetric solution is determined by uniqueness
of this solution in the nonrelativistic limit.
  The effective mass approximation for the relativistic theory was numerically
studied, in which dispersion of the average quark momentum is small as compare
to a big average quark momentum.
  Relativistic generalization of the nonrelativistic three-particle oscillator
was proposed.",0408037v2
2003-03-13,Relativistic Top Deviation Equation and Gravitational Waves,"By using the relativistic top theory, we derive a relativistic top deviation
equation. This equation turns out to be a generalization of the geodesic
deviation equation for a pair of nearby point particles. In fact, we show that
when the spin angular momentum tensor associated to the top vanishes, such a
relativistic top deviation equation reduces to the geodesic deviation equation
for spinless point particles. Just as the geodesic deviation equation for
spinless particles can be used to investigate the detection of gravitational
waves, our generalized formula for a relativistic top can be used to study the
gravitational wave background. Our formulation may be of special interest to
detect the inflationary gravitational waves via the polarization of the cosmic
background radiation.",0303123v2
2003-09-18,Conformal Partial Waves and the Operator Product Expansion,"By solving the two variable differential equations which arise from finding
the eigenfunctions for the Casimir operator for $O(d,2)$ succinct expressions
are found for the functions, conformal partial waves, representing the
contribution of an operator of arbitrary scale dimension $\Delta$ and spin
$\ell$ together with its descendants to conformal four point functions for
$d=4$, recovering old results, and also for $d=6$. The results are expressed in
terms of ordinary hypergeometric functions of variables $x,z$ which are simply
related to the usual conformal invariants. An expression for the conformal
partial wave amplitude valid for any dimension is also found in terms of a sum
over two variable symmetric Jack polynomials which is used to derive relations
for the conformal partial waves.",0309180v2
2006-09-12,Galloping instability of viscous shock waves,"Motivated by physical and numerical observations of time oscillatory
``galloping'', ``spinning'', and ``cellular'' instabilities of detonation
waves, we study Poincar\'e--Hopf bifurcation of traveling-wave solutions of
viscous conservation laws. The main difficulty is the absence of a spectral gap
between oscillatory modes and essential spectrum, preventing standard reduction
to a finite-dimensional center manifold. We overcome this by direct
Lyapunov--Schmidt reduction, using detailed pointwise bounds on the linearized
solution operator to carry out a nonstandard implicit function construction in
the absence of a spectral gap. The key computation is a space-time stability
estimate on the transverse linearized solution operator reminiscent of Duhamel
estimates carried out on the full solution operator in the study of nonlinear
stability of spectrally stable traveling waves.",0609331v6
1999-03-03,Relativistic Quantum States of an Electron with Anomalous Magnetic Moment in an Electromagnetic Wave Field and a Homogeneous Magnetic Field,"The exact solution of the Dirac equation and the spectrum of electron
quasi-energies in a superposition of the field of a circularly polarized
electromagnetic wave and a homogeneous magnetic field parallel to the direction
of wave propagation, are found taking into account the anomalous magnetic
moment. It is found that taking account of the anomalous magnetic moment
removes the spin degeneracy and that for intense fields the levels change
radically. The shift of the radiation frequency due to the intensity of the
wave field is found. This shift can be considerable.",9903007v1
2007-01-18,Non-Abelian evolution of electromagnetic waves in a weakly anisotropic inhomogeneous medium,"A theory of electromagnetic wave propagation in a weakly anisotropic smoothly
inhomogeneous medium is developed, based on the quantum-mechanical
diagonalization procedure applied to Maxwell equations. The equations of motion
for the translational (ray) and intrinsic (polarization) degrees of freedom are
derived ab initio. The ray equations take into account the optical Magnus
effect (spin Hall effect of photons) as well as trajectory variations owing to
the medium anisotropy. Polarization evolution is described by the precession
equation for the Stokes vector. In generic case, the evolution of waves turns
out to be non-Abelian: it is accompanied by mutual conversion of the normal
modes and periodic oscillations of the ray trajectories analogous to electron
zitterbewegung. The general theory is applied to examples of wave evolution in
media with circular and linear birefringence.",0701213v2
2005-11-24,Quantum-Classical Dynamics of Wave Fields,"An approach to the quantum-classical mechanics of phase space dependent
operators, which has been proposed recently, is remodeled as a formalism for
wave fields. Such wave fields obey a system of coupled non-linear equations
that can be written by means of a suitable non-Hamiltonian bracket. As an
example, the theory is applied to the relaxation dynamics of the spin-boson
model. In the adiabatic limit, a good agreement with calculations performed by
the operator approach is obtained. Moreover, the theory proposed in this paper
can take nonadiabatic effects into account without resorting to surface-hopping
approximations. Hence, the results obtained follow qualitatively those of
previous surface-hopping calculations and increase by a factor of (at least)
two the time length over which nonadiabatic dynamics can be propagated with
small statistical errors. Moreover, it is worth to note that the dynamics of
quantum-classical wave fields here proposed is a straightforward
non-Hamiltonian generalization of the formalism for non-linear quantum
mechanics that Weinberg introduced recently.",0511229v5
2007-06-07,Deconstructing triplet nucleon-nucleon scattering,"Nucleon-nucleon scattering in spin-triplet channels is analysed within an
effective field theory where one-pion exchange is treated nonperturbatively.
Justifying this requires the identification of an additional low-energy scale
in the strength of that potential. Short-range interactions are organised
according to the resulting power counting, in which the leading term is
promoted to significantly lower order than in the usual perturbative counting.
In each channel there is a critical momentum above which the waves probe the
singular core of the tensor potential and the new counting is necessary. When
the effects of one- and two-pion exchange have been removed using a
distorted-wave Born approximation, the residual scattering in waves with L<=2
is well described by the first three terms in the new counting. In contrast,
the scattering in waves with L>=3 is consistent with the perturbative counting,
at least for energies up to 300 MeV. This pattern is in agreement with
estimates of the critical momenta in these channels.",0706.0984v2
2008-04-11,Dirac neutrino magnetic moment and the shock wave revival in a supernova explosion,"The process of the two-step conversion of the neutrino helicity, $\nu_L \to
\nu_R \to \nu_L$, is analysed in the supernova conditions, where the first
stage is realized due to the interaction of the neutrino magnetic moment with
the plasma electrons and protons in the supernova core. The second stage is
caused by the neutrino resonant spin-flip in a magnetic field of the supernova
envelope. Given the neutrino magnetic moment within the interval $10^{-13}
\mu_{\rm B} < \mu_\nu < 10^{-12} \mu_{\rm B}$, and with the existence of the
magnetic field at the scale $\sim 10^{13}$ G between the neutrinosphere and the
shock-wave stagnation region, it is shown that an additional energy of the
order of $10^{51}$ erg can be injected into this region during the typical time
of the shock-wave stagnation. This energy could be sufficient for stumulation
of the damped shock wave.",0804.1916v2
2008-05-08,Polarization of Long-Wavelength Gravitational Waves by Rotating Black Holes,"The scattering cross section for a long-wavelength planar gravitational wave
impinging upon a rotating black hole is calculated, for the special case in
which the direction of incidence is aligned with the rotation axis. We show
that black hole rotation leads to a term in the cross section that is
proportional to $a\omega$. Hence, contrary to some claims, co-rotating and
counter-rotating helicities are scattered differently, and a partial
polarization is induced in an unpolarized incident wave.
  The scattering amplitudes are found via partial wave series. To compute the
series, two ingredients are required: phase shifts and spin-weighted spheroidal
harmonics. We show that the phase shifts may be found from low-frequency
solutions of the radial Teukolsky equation derived by Mano, Suzuki and
Takasugi. The spheroidal harmonics may be expanded in spherical harmonics; we
present expansions accurate to second order in $a \omega$. The two ingredients
are combined to give explicit expressions for the helicity-conserving and
helicity-reversing amplitudes, valid in the long-wavelength limit.",0805.1236v2
2008-07-25,Source Tracking for Sco X-1,"Sco X-1, the brightest low mass X-ray binary, is likely to be a source for
gravitational wave emission. In one mechanism, emission of a gravitational wave
arrests the increase in spin frequency due to the accretion torque in a low
mass X-ray binary. Since the gravitational waveform is unknown, a detection
method assuming no apriori knowledge of the signal is preferable. In this
paper, we propose to search for a gravitational wave from Sco X-1 using a {{\it
source tracking}} method based on a coherent network analysis. In the method,
we combine data from several interferometric gravitational wave detectors
taking into account of the direction to Sco X-1, and reconstruct two
polarization waveforms at the location of Sco X-1 in the sky as Sco X-1 is
moving. The source tracking method opens up the possibility of searching for a
wide variety of signals. We perform Monte Carlo simulations and show results
for bursts, modeled, short duration periodic sources using a simple excess
power and a matched filter method on the reconstructed signals.",0807.4171v1
2008-07-28,Assigning confidence to inspiral gravitational wave candidates with Bayesian model selection,"Bayesian model selection provides a powerful and mathematically transparent
framework to tackle hypothesis testing, such as detection tests of
gravitational waves emitted during the coalescence of binary systems using
ground-based laser interferometers. Although its implementation is
computationally intensive, we have developed an efficient probabilistic
algorithm based on a technique known as nested sampling that makes Bayesian
model selection applicable to follow-up studies of candidate signals produced
by on-going searches of inspiralling compact binaries. We discuss the
performance of this approach, in terms of ""false alarm rate"" and ""detection
probability"" of restricted second post-Newtonian inspiral waveforms from
non-spinning compact objects in binary systems. The results confirm that this
approach is a viable tool for detection tests in current searches for
gravitational wave signals.",0807.4483v1
2009-01-22,Diurnal Thermal Tides in a Non-synchronized Hot Jupiter,"We perform a linear analysis to investigate the dynamical response of a
non-synchronized hot Jupiter to stellar irradiation. In this work, we consider
the diurnal Fourier harmonic of the stellar irradiation acting at the top of a
radiative layer of a hot Jupiter with no clouds and winds. In the absence of
the Coriolis force, the diurnal thermal forcing can excite internal waves
propagating into the planet's interior when the thermal forcing period is
longer than the sound crossing time of the planet's surface. When the Coriolis
effect is taken into consideration, the latitude-dependent stellar heating can
excite weak internal waves (g modes) and/or strong baroclinic Rossby waves
(buoyant r modes) depending on the asynchrony of the planet. When the planet
spins faster than its orbital motion (i.e. retrograde thermal forcing), these
waves carry negative angular momentum and are damped by radiative loss as they
propagate downwards from the upper layer of the radiative zone. As a result,
angular momentum is transferred from the lower layer of the radiative zone to
the upper layer and generates a vertical shear. We estimate the resulting
internal torques for different rotation periods based on the parameters of HD
209458b.",0901.3401v1
2009-02-04,Dislocations and vortices in pair density wave superconductors,"With the ground breaking work of the Fulde, Ferell, Larkin, and Ovchinnikov
(FFLO), it was realized that superconducting order can also break translational
invariance; leading to a phase in which the Cooper pairs develop a coherent
periodic spatially oscillating structure. Such pair density wave (PDW)
superconductivity has become relevant in a diverse range of systems, including
cuprates, organic superconductors, heavy fermion superconductors, cold atoms,
and high density quark matter. Here we show that, in addition to charge density
wave (CDW) order, there are PDW ground states that induce spin density wave
(SDW) order when there is no applied magnetic field. Furthermore, we show that
PDW phases support topological defects that combine dislocations in the induced
CDW/SDW order with a fractional vortex in the usual superconducting order.
These defects provide a mechanism for fluctuation driven non-superconducting
CDW/SDW phases and conventional vortices with CDW/SDW order in the core.",0902.0805v1
2010-08-30,"The general theory of porcupines, perfect and imperfect","Porcupines are networks of gravitational wave detectors in which the
detectors and the distances between them are short relative to the
gravitational wavelengths of interest. Perfect porcupines are special
configurations whose sensitivity to a gravitational plane wave is independent
of the propagation direction or polarization of the wave. I develop the theory
of porcupines, including the optimal estimator \hat{h}^{ij} for the
gravitational wave field; useful formulae for the spin-averaged and
rotationally-averaged SNR^{2}; and a simple derivation of the properties of
perfect porcupines. I apply these results to the interesting class of
``simple'' porcupines, and mention some open problems.",1008.4997v2
2011-02-09,Variational study of the quantum phase transition in bilayer Heisenberg model with Bosonic RVB wave function,"We study the ground state phase diagram of the bilayer Heisenberg model on
square lattice with a Bosonic RVB wave function. The wave function has the form
of a Gutzwiller projected Schwinger Boson mean field ground state and involves
two variational parameters. We find the wave function provides an accurate
description of the system on both sides of the quantum phase transition.
Especially, through the analysis of the spin structure factor, ground state
fidelity susceptibility and the Binder moment ratio $Q_{2}$, a continuous
transition from the antiferromagnetic ordered state to the quantum disordered
state is found at the critical coupling of
$\alpha_{c}=J_{\perp}/J_{\parallel}\approx2.62$, in good agreement with the
result of quantum Monte Carlo simulation. The critical exponent estimated from
the finite size scaling analysis($1/\nu\approx1.4$) is consistent with that of
the classical 3D Heisenberg universality class.",1102.1819v1
2012-08-28,Alternative route to charge density wave formation in multiband systems,"Charge and spin density waves, periodic modulations of the electron and
magnetization densities, respectively, are among the most abundant and
non-trivial low-temperature ordered phases in condensed matter. The ordering
direction is widely believed to result from the Fermi surface topology.
However, several recent studies indicate that this common view needs to be
supplemented. Here, we show how an enhanced electron-lattice interaction can
contribute to or even determine the selection of the ordering vector in the
model charge density wave system ErTe3. Our joint experimental and theoretical
study allows us to establish a relation between the selection rules of the
electronic light scattering spectra and the enhanced electron-phonon coupling
in the vicinity of band degeneracy points. This alternative proposal for charge
density wave formation may be of general relevance for driving phase
transitions into other broken-symmetry ground states, particularly in multiband
systems such as the iron based superconductors.",1208.5701v2
2012-10-08,"Post-Newtonian prediction for the (2,2) mode of the gravitational wave emitted by compact binaries","We present our 3.5PN computation of the (2,2) mode of the gravitational wave
amplitude emitted by compact binaries, on quasi-circular orbits and in the
absence of spins. We use the multipolar post-Newtonian wave generation
formalism, extending and building on previous works which computed the 3PN
order. This calculation required the extension of the multipolar
post-Minkowskian algorithm, as well as the computation of the mass source
quadrupole at 3.5PN order. Our result will allow more accurate comparisons to
numerical relativity, and is a first step towards the computation of the full
3.5PN waveform amplitude, which would improve the estimation of the source
parameters by gravitational wave detectors.",1210.2339v1
2014-01-21,Magnonic Holographic Memory,"Holography is a technique based on the wave nature of light which allows us
to utilize wave interference between the object beam and the coherent
background. Holography is usually associated with images being made from light,
however, this is only a narrow field of holography. The first holograms were
designed for use with electron microscopes and it was not until a decade later
with the advent of the laser that optical holographic images were popularized.
Multiple other fields have had major contributions made by using wave
interference to produce holograms, including acoustic holograms used in seismic
applications, and microwave holography used in radar systems. Holography has
been also recognized as a future data storing technology with unprecedented
data storage capacity and ability to write and read a large number of data in a
highly parallel manner. Here, we present a magnonic holographic memory device
exploiting spin wave interference.",1401.5133v1
2014-07-05,Orbital density wave order and electronic correlation driven insulating 1T-TaS2 monolayer,"We present the orbital resolved electronic properties of structurally
distorted 1T-TaS2 monolayers. After optimizing the crystal structures, we
obtain the lattice parameters and atomic positions in the star-of-David
structure, and show the low-temperature band structures of distorted bulk are
consistent with recent angle resolved photoemission spectroscopy (ARPES) data.
We further clearly demonstrate that $5d$ electrons of Ta form ordered
orbital-density-wave (ODW) state with dominant $5d_{3{z}^2-{r}^2}$ character in
central Ta, driving the one-dimensional metallic state in paramagnetic bulk and
half-filled insulator in monolayer. Meanwhile, the star-of-David distortion in
monolayers favors charge density wave and the flat band stabilizes
ferromagnetic density wave of Ta spins with the same wavevector of ODW 4/13
b_1+1/13 b2. We propose that $1$T-TaS$_{2}$ monolayer may pave a new way to
study the exciton physics, exciton-polaron coupling, and potential applications
for its exciton luminescence.",1407.1407v1
2014-09-18,Modular matrices from universal wave function overlaps in Gutzwiller-projected parton wave functions,"We implement the universal wave function overlap (UWFO) method to extract
modular $S$ and $T$ matrices for topological orders in Gutzwiller-projected
parton wave functions (GPWFs). The modular $S$ and $T$ matrices generate a
projective representation of $SL(2,\mathbb{Z})$ on the degenerate-ground-state
Hilbert space on a torus and may fully characterize the 2+1D topological
orders, i.e. the quasi-particle statistics and chiral central charge (up to
$E_8$ bosonic quantum Hall states). We used the variational Monte Carlo method
to computed the $S$ and $T$ matrices of the chiral spin liquid (CSL)
constructed by the GPWF on the square lattice, and confirm that the CSL carries
the same topological order as the $\nu=\frac{1}{2}$ bosonic Laughlin state. We
find that the non-universal exponents in UWFO can be small and direct numerical
computation is able to be applied on relatively large systems. We also discuss
the UWFO method for GPWFs on other Bravais lattices in two and three dimensions
by using the Monte Carlo method. UWFO may be a powerful method to calculate the
topological order in GPWFs.",1409.5427v1
2015-01-28,Odd Frequency Density Waves,"A new type of hidden order in many body systems is explored. This order
appears in states which are analogues to charge density waves, or spin density
waves, but involve anomalous particle-hole correlations that are odd in
relative time and frequency. These states are shown to be inherently different
from the usual states of density waves. We discuss two methods to
experimentally observe the new type of pairing where a clear distinction
between odd and even correlations can be detected: (i) by measuring the
density-density correlation, both in time and space and (ii) via the
conductivity which, according to the Kubo formula, is given by the
current-current correlation. An order parameter for these states is defined and
calculated for a simple model, illuminating the physical nature of this order.",1501.07049v1
2015-02-04,Klein tunneling and supercollimation of pseudospin-1 electromagnetic waves,"Pseudospin plays a central role in many novel physical properties of graphene
and other artificial systems which have pseudospins of 1/2. Here we show that
in certain photonic crystals (PCs) exhibiting conical dispersions at k = 0, the
eigenmodes near the ""Dirac-like point"" can be described by an effective
spin-orbit Hamiltonian with a pseudospin of 1, treating wave propagations in
the upper cone, the lower cone and a flat band (corresponding to zero
refractive index) within a unified framework. The 3-component spinor gives rise
to boundary conditions distinct from those of pseudospin-1/2, leading to new
wave transport behaviors as manifested in Klein tunneling and supercollimation.
For example, collimation can be realized more easily with pseudospin-1 than
pseudospin-1/2. The special wave scattering properties of pseudospin-1 photons,
coupled with the discovery that the effective photonic ""potential"" can be
varied by a simple change of length scale, may offer new ways to control photon
transport.",1502.01127v2
2015-03-06,The Abundance of X-Shaped Radio Sources: Implications for the Gravitational Wave Background,"Coalescence of super massive black holes (SMBH's) in galaxy mergers is
potentially the dominant contributor to the low frequency gravitational wave
background (GWB). IIt was proposed by Merritt and Ekers (2002) that X-shaped
radio galaxies are signposts of such coalescences, and that their abundance
might be used to predict the magnitude of the gravitational wave background. In
Roberts et al. (2015) we present radio images of all 52 X-shaped radio source
candidates out of the sample of 100 selected by Cheung (2007) for which
archival VLA data were available. These images indicate that at most 21% of the
candidates might be genuine X-shaped radio sources that were formed by a
restarting of beams in a new direction following a major merger. This suggests
that fewer than 1.3% of extended radio sources appear to be candidates for
genuine axis reorientations (""spin flips""), much smaller than the 7% suggested
by Leahy and Parma (1992). Thus the associated gravitational wave background
may be substantially smaller than previous estimates. These results can be used
to normalize detailed calculations of the SMBH coalescence rate and the GWB.",1503.02021v3
2015-07-09,General transformation of alpha cluster model wave function to jj-coupling shell model in various 4N nuclei,"The antisymmetrized quasi-cluster model (AQCM) is a method to describe a
transition from the alpha-cluster wave function to the jj-coupling shell model
wave function. In this model, the cluster-shell transition is characterized by
only two parameters; R representing the distance between alpha clusters and
Lambda describing the breaking of alpha clusters, and the contribution of the
spin-orbit interaction, very important in the jj-coupling shell model, can be
taken into account starting with the alpha cluster model wave function. In this
article we show the generality of AQCM by extending the application to heavier
region; various 4N nuclei from 4He to 52Fe. We show and compare the energy
curves for the alpha+40Ca cluster configuration calculated with and without
alpha breaking effect in 44Ti.",1507.02400v1
2015-11-05,Was Einstein Wrong on Quantum Physics?,"Einstein is considered by many as the father of quantum physics in some
sense. Yet there is an unshakable view that he was wrong on quantum physics.
Although it may be a subject of considerable debate, the core of his allegedly
wrong demurral was the insistence on finding an objective reality underlying
the manifestly bizarre behavior of quantum objects. The uncanny wave-particle
duality of a quantum particle is a prime example. In view of the latest
developments, particularly in quantum field theory, objections of Einstein are
substantially corroborated. Careful investigation suggests that a travelling
quantum particle is a holistic wave packet consisting of an assemblage of
irregular disturbances in quantum fields. It acts as a particle because only
the totality of all the disturbances in the wave packet yields the energy
momentum with the mass of a particle, along with its other conserved quantities
such as charge and spin. Thus the wave function representing a particle is not
just a fictitious mathematical construct but embodies a reality of nature as
asserted by Einstein.",1511.05098v2
2015-12-08,The stochastic background of gravitational waves due to the f-mode instability in neutron stars,"This paper presents an estimate for the spectral properties of the stochastic
background of gravitational waves emitted by a population of hot, young,
rapidly rotating neutron stars throughout the Universe undergoing $f$-mode
instabilities, formed through either core-collapse supernova explosions or the
merger of binary neutron star systems. Their formation rate, from which the
gravitational wave event rate is obtained, is deduced from observation-based
determinations of the cosmic star formation rate. The gravitational wave
emission occurs during the spin-down phase of the $f$-mode instability. For low
magnetized neutron stars and assuming 10\% of supernova events lead to $f$-mode
unstable neutron stars, the background from supernova-derived neutron stars
peaks at $\Omega_{\text{gw}} \sim 10^{-9}$ for the $l=m=2$ $f$-mode, which
should be detectable by cross-correlating a pair of second generation
interferometers (e.g. Advanced LIGO/Virgo) with an upper estimate for the
signal-to-noise ratio of $\approx$ 9.8. The background from supramassive
neutron stars formed from binary mergers peaks at $\Omega_{\text{gw}} \sim
10^{-10}$ and should not be detectable, even with third generation
interferometers (e.g. Einstein Telescope).",1512.02502v1
2016-01-06,Experimental Realization of a Reflections-Free Compact Delay Line Based on a Photonic Topological Insulator,"Electromagnetic (EM) waves propagating through an inhomogeneous medium
inevitably scatter whenever electromagnetic properties of the medium change on
the scale of a single wavelength. This fundamental phenomenon constrains how
optical structures are designed and interfaced with each other. Recent
theoretical work indicates that electromagnetic structures collectively known
as photonic topological insulators (PTIs) can be employed to overcome this
fundamental limitation, thereby paving the way for ultra-compact photonic
structures that no longer have to be wavelength-scale smooth. Here we present
the first experimental demonstration of a photonic delay line based on
topologically protected surface electromagnetic waves (TPSWs) between two PTIs
which are the EM counterparts of the quantum spin-Hall topological insulators
in condensed matter. Unlike conventional guided EM waves that do not benefit
from topological protection, TPSWs are shown to experience multi-wavelength
reflection-free time delays when detoured around sharply-curved paths, thus
offering a unique paradigm for compact and efficient wave buffers and other
devices.",1601.01311v2
2017-07-17,A Lax Pair Structure for the Half-Wave Maps Equation,"We consider the half-wave maps equation $$ \partial_t \vec{S} = \vec{S}
\wedge |\nabla| \vec{S}, $$ where $\vec{S}= \vec{S}(t,x)$ takes values on the
two-dimensional unit sphere $\mathbb{S}^2$ and $x \in \mathbb{R}$ (real line
case) or $x \in \mathbb{T}$ (periodic case). This an energy-critical
Hamiltonian evolution equation recently introduced in \cite{LS,Zh}, which
formally arises as an effective evolution equation in the classical and
continuum limit of Haldane-Shastry quantum spin chains. We prove that the
half-wave maps equation admits a Lax pair and we discuss some analytic
consequences of this finding. As a variant of our arguments, we also obtain a
Lax pair for the half-wave maps equation with target $\mathbb{H}^2$ (hyperbolic
plane).",1707.05028v2
2017-07-18,Estimating the two-particle $K$-matrix for multiple partial waves and decay channels from finite-volume energies,"An implementation of estimating the two-to-two $K$-matrix from finite-volume
energies based on the L\""uscher formalism and involving a Hermitian matrix
known as the ""box matrix"" is described. The method includes higher partial
waves and multiple decay channels. Two fitting procedures for estimating the
$K$-matrix parameters, which properly incorporate all statistical covariances,
are discussed. Formulas and software for handling total spins up to $S=2$ and
orbital angular momenta up to $L=6$ are obtained for total momenta in several
directions. First tests involving $\rho$-meson decay to two pions include the
$L=3$ and $L=5$ partial waves, and the contributions from these higher waves
are found to be negligible in the elastic energy range.",1707.05817v1
2017-09-06,Primordial gravitational waves amplification from causal fluids,"We consider the evolution of the gravitational wave spectrum for super-Hubble
modes in interaction with a relativistic fluid, which is regarded as an
effective description of fluctuations in a light scalar minimally coupled
field, during the earliest epoch of the radiation dominated era after the end
of inflation. We obtain the initial conditions for gravitons and fluid from
quantum fluctuations at the end of inflation, and assume instantaneous
reheating. We model the fluid by using relativistic causal hydrodynamics. There
are two dimensionful parameters, the relaxation time $\tau$ and temperature. In
particular we study the interaction between gravitational waves and the non
trivial tensor (spin 2) part of the fluid energy-momentum tensor. Our main
result is that the new dimensionful parameter $\tau$ introduces a new relevant
scale which distinguishes two kinds of super-Hubble modes. For modes with
$H^{-1}<\lambda<\tau$ the fluid-graviton interaction increases the amplitude of
the primordial gravitational wave spectrum at the electroweak transition by a
factor of about $1.3$ with respect to the usual scale invariant spectrum.",1709.01661v3
2018-01-06,Smeared nematic quantum phase transitions due to rare-region effects in inhomogeneous systems,"The concept of a vestigial nematic order emerging from a ""mother"" spin or
charge density-wave state has been applied to describe the phase diagrams of
several systems, including unconventional superconductors. In a perfectly clean
system, the two orders appear simultaneously via a first-order quantum phase
transition, implying the absence of quantum criticality. Here, we investigate
how this behavior is affected by impurity-free droplets that are naturally
present in inhomogeneous systems. Due to their quantum dynamics, finite-size
droplets sustain long-range nematic order but not long-range density-wave
order. Interestingly, rare droplets with moderately large sizes undergo a
second-order nematic transition even before the first-order quantum transition
of the clean system. This gives rise to an extended regime of inhomogeneous
nematic order, which is followed by a density-wave quantum Griffiths phase. As
a result, a smeared quantum nematic transition, separated from the density-wave
quantum transition, emerges in moderately disordered systems.",1801.01988v1
2018-04-28,Self-ordering induces multiple topological transitions for elastic waves in phononic crystals,"Topological defects with symmetry-breaking phase transitions have captured
much attention. Vortex generated by topological defects exhibits exotic
properties and its flow direction can be switched by altering the spin
configurations. Contrary to electromagnetic and acoustic domains, the
topological transport of elastic waves in periodic structures with topological
defects is not well explored due to the mode conversion between the
longitudinal and transverse modes. Here, we propose an elastic topological
insulator with spontaneously broken symmetry based on the topological theory of
defects and homotopy theory. Multiple topological transitions for elastic waves
are achieved by topologically modifying the ellipse orientation in a triangular
lattice of elliptical cylinders. The solid system, independent of the number of
molecules in order parameter space, breaks through the limit of the point-group
symmetry to emulate elastic pseudospin-orbit coupling. The transport robustness
of the edge states is experimentally demonstrated. Our approach provides new
possibilities for controlling and transporting elastic waves.",1805.01061v1
2018-05-30,Magnonic band gap and mode hybridization in continuous Permalloy film induced by vertical coupling with an array of Permalloy ellipses,"We investigate magnonic band structure in thin homogeneous permalloy film
decorated with periodic array of elliptically shaped permalloy dots and
separated by non-magnetic Pt spacer. We demonstrated experimentally formation
of the magnonic band structure for Damon-Eshbach wave propagating in permalloy
film with the band gap opened at the Brillouin zone border and band splitting
at smaller wavenumbers, due to the Bragg interference and interaction of
propagating wave of the continuous film with a standing resonant mode of the
nano-ellipses, respectively. The shape anisotropy of the permalloy nanodots
allows to control the spin wave dynamics through the switch between two states
of the magnetization with respect to the underneath film magnetization, thus
enabling magnonic band structure reprogrammability. With numerical analysis we
show, that predominant role in formation of the magnonic band structure is
played by a vertical dynamic coupling between propagating wave in the film and
magnetization oscillations in the nanodots.",1805.12178v2
2018-06-29,Complex-angle analysis of electromagnetic waves on interfaces,"Electromagnetic wave is reflected and refracted at interfaces, satisfying
Fresnel-Snell law which is required by conservations of energy and momentum. If
the incident angle is lower than the critical angle, we can use this
Fresnel-Snell law, but the Fresnel-Snell law is modified in the case of
existence of dissipation ($\tilde{n} = n + i\kappa, \kappa > 0$) or in the
condition of total internal reflection. In the cases, we have to extend the
angle of refraction from real number to complex number ($\theta \rightarrow
\tilde{\theta} = \theta + i\psi, \psi \neq 0$). In this paper, by using
complex-angle approach, we analyse the behaviour of electromagnetic waves in
various kind of interfaces: dielectric - dielectric system, dissipative
dielectric - dielectric system, and metal - dielectric system. We show that
iso-frequency curves in wavenumber space is opened in the case where $n, \kappa
> 0$, and closed either when $n \rightarrow 0$ or when $\kappa \rightarrow 0$
(""Lifshitz transition"" of electromagnetic waves). Excess momentum (wavenumber)
and anomalous spin (circular polarization) emerging with the transition are
also discussed.",1806.11482v1
2018-11-05,Signatures of pair-density wave order in phase-sensitive measurements of La$_{2-x}$Ba$_x$CuO$_4$-Nb Josephson junctions and SQUIDs,"The interplay of charge order, spin order, and superconductivity in
La$_{2-x}$Ba$_x$CuO$_4$ creates a complex physical system that hosts several
interesting phases, such as two-dimensional superconductivity within the
CuO$_2$ planes and the ordered pair-density wave state in which charge ordering
is intertwined with superconductivity. Using Josephson interferometry
techniques, we measure the current-phase relation of junctions and SQUIDs
incorporating this material and observe a significant sin($2\phi$)-component
indicative of closely-spaced alternations of the sign of the Josephson coupling
predicted by the pair-density wave model. We find that the ratio of the
sin(2$\phi$)-component to the conventional sin($\phi$)-component to be largest
near x=1/8 doping, where the pair-density wave state is believed to be the
strongest, and that it increases with increasing temperature as the Josephson
coupling in the junction weakens.",1811.02048v1
2018-11-24,Angular-Momentum Selectivity and Asymmetry in Highly Confined Wave Propagation Along Sheath-Helical Metasurface Tubes,"Highly confined surface waves present unique opportunities to enhance light
interactions with localized emitters or molecules. Hyperbolic dispersion in
metasurfaces allows us to tailor and manipulate surface waves, enhancing the
local density of states over broad bandwidths. So far, propagation on this
platform was mainly studied in planar geometries, which facilitates the
analysis but somehow limits the realm of possibilities. Here we show that
""wrapping"" hyperbolic metasurfaces into tubes may greatly enrich the wave
propagation dynamics along their axis. This system shows strong interaction
with fields and sources carrying optical angular momentum, pronounced field
asymmetries, and opens pathways to valley-specific excitation and routing. In
addition, we demonstrate that various parameter regimes enable strong spin and
helicity to momentum locking.",1811.09761v3
2018-11-28,Stochastic gravitational waves from spin-3/2 fields -- Hunting SUSY in the sky,"Stochastic gravitational waves can be produced during the preheating when
out-of-equilibrium particles are produced with an anisotropic stress-tensor. We
discuss the case where these particles carry spin 3/2. We compute the spectrum
of the gravitational waves generated by the transverse and longitudinal
components. We find a different scaling of the spectrum near the peak and the
longitudinal components lead to an enhancement when compared to spin-1/2
fermions with Yukawa couplings. We note, as expected, that the corresponding
typical frequency is too high for the current observation and calls for
ultra-high frequency gravitational wave detectors in the future.",1811.11774v3
2018-07-24,Excitation and control of large amplitude standing magnetization waves,"A robust approach to excitation and control of large amplitude standing
magnetization waves in an easy axis ferromagnetic by starting from a ground
state and passage through resonances with chirped frequency microwave or spin
torque drives is proposed. The formation of these waves involves two stages,
where in the first stage, a spatially uniform, precessing magnetization is
created via passage through a resonance followed by a self-phase-locking
(autoresonance) with a constant amplitude drive. In the second stage, the
passage trough an additional resonance with a spatial modulation of the driving
amplitude yields transformation of the uniform solution into a doubly
phase-locked standing wave, whose amplitude is controlled by the variation of
the driving frequency. The stability of this excitation process is analyzed
both numerically and via Whitham's averaged variational principle.",1807.09033v1
2019-02-26,Analyzing Gravitational Waves with General Relativity,"After a short review of prominent properties of gravitational waves and the
newly born gravitational astronomy, we focus on theoretical aspects. Analytic
approximation methods in general relativity have played a crucial role in the
recent discoveries of gravitational waves. They are used to build theoretical
template banks for searching and analyzing the signals in the ground-based
detectors LIGO and Virgo, and, further ahead, space-based LISA-like detectors.
In particular, the post-Newtonian approximation describes with high accuracy
the early inspiral of compact binary systems, made of black holes or neutron
stars. It mainly consists of extending the Einstein quadrupole formula by a
series of relativistic corrections up to high order. The compact objects are
modelled by point masses with spins. The practical calculations face difficult
problems of divergences, which have been solved thanks to the dimensional
regularization. In the last rotations before the merger, the finite size
effects and the internal structure of neutron stars (notably the internal
equation of state) affect the evolution of the orbit and the emission of
gravitational waves. We describe these effects within a simple Newtonian model.",1902.09801v1
2020-04-20,Explicit Triangular Decoupling of the Separated Lichnerowicz Tensor Wave Equation on Schwarzschild into Scalar Regge-Wheeler Equations,"We consider the vector and the Lichnerowicz wave equations on the
Schwarzschild spacetime, which correspond to the Maxwell and linearized
Einstein equations in harmonic gauges (or, respectively, in Lorenz and de
Donder gauges). After a complete separation of variables, the radial mode
equations form complicated systems of coupled linear ODEs. We outline a precise
abstract strategy to decouple these systems into sparse triangular form, where
the diagonal blocks consist of spin-$s$ scalar Regge-Wheeler equations (for
spins $s=0,1,2$). Building on the example of the vector wave equation, which we
have treated previously, we complete a successful implementation of our
strategy for the Lichnerowicz wave equation. Our results go a step further than
previous more ad-hoc attempts in the literature by presenting a full and
maximally simplified final triangular form. These results have important
applications to the quantum field theory of and the classical stability
analysis of electromagnetic and gravitational perturbations of the
Schwarzschild black hole in harmonic gauges.",2004.09651v2
2016-03-06,Gauss' Law and Non-Linear Plane Waves for Yang-Mills Theory,"We investigate Non-Linear Plane-Wave solutions of the classical Minkowskian
Yang-Mills (YM) equations of motion. By imposing a suitable ansatz which solves
Gauss' law for the $SU(3)$ theory, we derive solutions which consist of Jacobi
elliptic functions depending on an enumerable set of elliptic modulus values.
The solutions represent periodic anharmonic plane waves which possess arbitrary
non-zero mass and are exact extrema of the non-linear YM action. Among them, a
unique harmonic plane wave with a non-trivial pattern in phase, spin and color
is identified. Similar solutions are present in the $SU(4)$ case while are
absent from the $SU(2)$ theory.",1603.01858v1
2019-03-29,Formation of nonlinear X-waves in condensed matter systems,"X-waves are an example of a localized wave packet solution of the homogeneous
wave equation, and can potentially arise in any area of physics relating to
wave phenomena, such as acoustics, electromagnetism, or quantum mechanics. They
have been predicted in condensed matter systems such as atomic Bose-Einstein
condensates in optical lattices, and were recently observed in
exciton-polariton condensates. Here we show that polariton X-waves result from
an interference between two separating wave packets that arise from the
combination of a locally hyperbolic dispersion relation and nonlinear
interactions. We show that similar X-wave structures could also be observed in
expanding spin-orbit coupled Bose-Einstein condensates.",1903.12357v2
2020-11-12,Early warning of precessing compact binary merger with third-generation gravitational-wave detectors,"Rapid localization of gravitational-wave events is important for the success
of the multi-messenger observations. The forthcoming improvements and
constructions of gravitational-wave detectors will enable detecting and
localizing compact-binary coalescence events even before mergers, which is
called early warning. The performance of early warning can be improved by
considering modulation of gravitational wave signal amplitude due to the Earth
rotation and the precession of a binary orbital plane caused by the misaligned
spins of compact objects. In this paper, for the first time we estimate
localization precision in the early warning quantitatively, taking into account
an orbital precession. We find that a neutron star-black hole binary at $z=0.1$
can typically be localized to $100\,\mathrm{deg}^2$ and $10\,\mathrm{deg^2}$ at
the time of $12$ -- $15 \,\mathrm{minutes}$ and $50$ -- $300\,\mathrm{seconds}$
before merger, respectively, which cannot be achieved without the precession
effect.",2011.06130v1
2003-12-03,Electronic Raman scattering in unconventional density waves,"We investigate the electronic Raman scattering in pure, quasi-one dimensional
conductors with density wave ground state. In particular, we develop the theory
of light-scattering on spin and charge density waves, both conventional and
unconventional. We calculate the electronic Raman response of the interacting
electron system with a single, highly anisotropic conduction band. The
calculation is carried out in the mean field approximation. Beside the
quasiparticle contribution, the electron-electron interaction is also included
on RPA level. The contribution of collective modes and the effect of Coulomb
screening are investigated. In analogy with unconventional superconductivity,
the obtained Raman spectra - which are finite in the low temperature phase
possessing a gap, and vanish identically in the normal state - show unique and
strong dependence on the polarization of the incoming and scattered light. We
have found distinct, characteristic lineshapes, especially in the
unconventional situation, depending on the various scattering geometries and
the particular momentum dependence of the density wave order parameter.",0312093v2
2008-06-24,Reconstruction of the Fermi surface in the pseudogap state of cuprates,"Reconstruction of the Fermi surface of high-temperature superconducting
cuprates in the pseudogap state is analyzed within nearly exactly solvable
model of the pseudogap state, induced by short-range order fluctuations of
antiferromagnetic (AFM, spin density wave (SDW), or similar charge density wave
(CDW)) order parameter, competing with superconductivity. We explicitly
demonstrate the evolution from ""Fermi arcs"" (on the ""large"" Fermi surface)
observed in ARPES experiments at relatively high temperatures (when both the
amplitude and phase of density waves fluctuate randomly) towards formation of
typical ""small"" electron and hole ""pockets"", which are apparently observed in
de Haas - van Alfen and Hall resistance oscillation experiments at low
temperatures (when only the phase of density waves fluctuate, and correlation
length of the short-range order is large enough). A qualitative criterion for
quantum oscillations in high magnetic fields to be observable in the pseudogap
state is formulated in terms of cyclotron frequency, correlation length of
fluctuations and Fermi velocity.",0806.3826v1
2017-04-01,Interpretation of the newly observed $Ω_c^0$ resonances,"We study the charmed and bottomed doubly strange baryons within the
heavy-quark-light-diquark framework. The two strange quarks are assumed to lie
in $S$ wave and thus their total spin is 1. We calculate the mass spectra of
the $S$ and $P$ wave orbitally excited states and find the $\Omega_c^0 (2695)$
and $\Omega_c^0 (2770)$ fit well as the $S$ wave states of charmed doubly
strange baryons. The five newly $\Omega_c^0(X)$ resonances observed by the LHCb
Collaboration, i.e. $\Omega_c^0(3000)$, $\Omega_c^0(3050)$, $\Omega_c^0(3066)$,
$\Omega_c^0(3090)$, and $\Omega_c^0(3119)$, can be interpreted as the $P$ wave
orbitally excited states. In heavy quark effective theory, we analyze their
decays into the $\Xi^+_c K^-$ and $\Xi_c'^+ K^-$, and point out that decays of
the five P-wave $\Omega_c^0$ states into the $\Xi_c^+ K^-$ and $\Xi_c'^+K^-$
are suppressed by either heavy quark symmetry or phase space. The narrowness of
the five newly observed $\Omega_c^0(X)$ states can then be naturally
interpreted with heavy quark symmetry.",1704.00179v2
2019-04-23,R-mode instability in compact stars,"R-mode oscillations have been identified as viable and promising targets for
continuous gravitational wave searches, meanwhile, it would allow us to probe
the interior of compact stars directly. As well as emitting gravitational wave,
r-modes would strongly affect the thermal and spin evolution of compact stars.
In this paper, we reviewed the theory behind the gravitational wave driven
r-mode instability in a rapidly rotating compact star. In particular, we will
focus on r-mode instability window, r-mode evolution and detectability of
r-mode.",1904.10957v1
2019-09-19,Direct constraints on ultra-light boson mass from searches for continuous gravitational waves,"\textit{Superradiance} can trigger the formation of an ultra-light boson
cloud around a spinning black hole. Once formed, the boson cloud is expected to
emit a nearly periodic, long-duration, gravitational-wave signal. For boson
masses in the range $(10^{-13}-10^{-11})$ eV, and stellar mass black holes,
such signals are potentially detectable by gravitational wave detectors, like
Advanced LIGO and Virgo. In this {\it Letter} we present full band upper limits
for a generic all-sky search for periodic gravitational waves in LIGO O2 data,
and use them to derive - for the first time - direct constraints on the
ultra-light scalar boson field mass.",1909.08854v1
2020-01-21,First search for r-mode gravitational waves from J0537-6910,"We report results of the first search to date for continuous gravitational
waves from unstable r-modes from the pulsar J0537-6910. We use data from the
first two observing runs of the Advanced LIGO network. We find no significant
signal candidate and set upper limits on the amplitude of gravitational wave
signals, which are within an order of magnitude of the spin-down values. We
highlight the importance of having timing information at the time of the
gravitational wave observations, i.e. rotation frequency and
frequency-derivative values, and glitch occurrence times, such as those that a
NICER campaign could provide.",2001.07605v4
2020-05-28,Black Hole Gravitational Waves in the Effective Field Theory of Gravity,"We investigate the propagation of gravitational waves on a black hole
background within the low energy effective field theory of gravity, where
effects from heavy fields are captured by higher dimensional curvature
operators. Depending on the spin of the particles integrated out, the speed of
gravitational waves at low energy can be either superluminal or subluminal as
compared to the causal structure observed by other species. Interestingly
however, gravitational waves are always exactly luminal at the black hole
horizon, implying that the horizon is identically defined for all species. We
further compute the corrections on quasinormal frequencies caused by the higher
dimensional curvature operators and highlight the corrections arising from the
low energy effective field.",2005.13923v3
2020-07-13,Gravitational-wave selection effects using neural-network classifiers,"We present a novel machine-learning approach to estimate selection effects in
gravitational-wave observations. Using techniques similar to those commonly
employed in image classification and pattern recognition, we train a series of
neural-network classifiers to predict the LIGO/Virgo detectability of
gravitational-wave signals from compact-binary mergers. We include the effect
of spin precession, higher-order modes, and multiple detectors and show that
their omission, as it is common in large population studies, tends to
overestimate the inferred merger rate in selected regions of the parameter
space. Although here we train our classifiers using a simple signal-to-noise
ratio threshold, our approach is ready to be used in conjunction with full
pipeline injections, thus paving the way toward including actual distributions
of astrophysical and noise triggers into gravitational-wave population
analyses.",2007.06585v2
2020-07-17,The Sound of Clearing the Throat: Gravitational Waves from a Black Hole Orbiting in a Wormhole Geometry,"Current ground-based gravitational wave detectors are tuned to capture the
collision of compact objects such as stellar origin black holes and neutron
stars; over 20 such events have been published to date. Theoretically, however,
more exotic compact objects may exist, collisions of which should also generate
copious gravitational waves. In this paper, we model the inspiral of a stellar
mass black hole into a stable, non-spinning, traversable wormhole, and find a
characteristic waveform -- an anti-chirp and/or burst -- as the black hole
emerges, i.e., outspirals, into our region of the Universe. This novel waveform
signature may be useful in searches for wormholes in future gravitational wave
data or used to constrain possible wormhole geometries in our Universe.",2007.09135v1
2021-03-29,Wave-encoding and Shuffling Enables Rapid Time Resolved Structural Imaging,"T2-Shuffling reconstructs multiple sharp T2-weighted images from a single
volumetric fast spin-echo (3D-FSE) scan. Wave-CAIPI is a parallel imaging
technique that achieves good reconstruction at high accelerations through
additional sinusoidal gradients that induce a voxel spreading effect in the
readout direction to better take advantage of coil-sensitivity information. In
this work, the Shuffling model in T2-Shuffling is augmented with wave-encoding
to achieve higher acceleration capability. The resulting ""Wave-Shuffling""
approach is applied to 3D-FSE and Magnetization-Prepared Rapid Gradient-Echo
(MPRAGE) to achieve rapid, 1 mm-isotropic resolution, time-resolved structural
imaging.",2103.15881v2
2021-05-24,Imprint of black hole area quantization and Hawking radiation on inspiraling binary,"We study the potential of gravitational wave astronomy to observe the quantum
aspects of black holes. According to Bekenstein's quantization, we find that
black hole area discretization can have observable imprints on the
gravitational wave signal from an inspiraling binary black hole. We study the
impact of quantization on tidal heating. We model the absorption lines and
compute gravitational wave flux due to tidal heating in such a case. By
including the quantization we find the dephasing of the gravitational wave, to
our knowledge it has never been done before. We discuss the observability of
the phenomena in different parameter ranges of the binary. We show that in the
inspiral, it leads to vanishing tidal heating for the high spin values.
Therefore measuring non-zero tidal heating can rule out area quantization. We
also argue that if area quantization is present in nature then our current
modeling with reflectivity can possibly probe the Hawking radiation which may
bring important information regarding the quantum nature of gravity.",2105.11140v3
2021-07-22,The ${\bar K}N$ interaction in higher partial waves,"We present a chiral ${\bar K}N$ interaction model that has been developed and
optimized in order to account for the experimental data of inelastic ${\bar
K}N$ reaction channels that open at higher energies. In particular, we study
the effect of the higher partial waves which originate directly from the chiral
Lagrangian, as they could supersede the role of high-spin resonances employed
in earlier phenomenological models to describe meson-baryon cross sections in
the 2~GeV region. We present a detailed derivation of the partial wave
amplitudes that emerge from the chiral SU(3) meson-baryon Lagrangian up to the
d-waves and next-to-leading order in the chiral expansion. We implement a
nonperturbative unitarization in coupled channels and optimize the model
parameters to a large pool of experimental data in the relevant energy range
where these new contributions are expected to be important. The obtained
results are encouraging. They indicate the ability of the chiral higher partial
waves to extend the description of the scattering data to higher energies and
to account for structures in the reaction cross sections that cannot be
accommodated by theoretical models limited to the s-waves.",2107.10560v1
2021-11-01,"Topological Phases in AB-Stacked MoTe$_2$/WSe$_2$: $\mathbb{Z}_2$ Topological Insulators, Chern Insulators, and Topological Charge Density Waves","We present a theory on the quantum phase diagram of AB-stacked
MoTe$_2$/WSe$_2$ using a self-consistent Hartree-Fock calculation performed in
the plane-wave basis, motivated by the observation of topological states in
this system. At filling factor $\nu=2$ (two holes per moir\'e unit cell),
Coulomb interaction can stabilize a $\mathbb{Z}_2$ topological insulator by
opening a charge gap. At $\nu=1$, the interaction induces three classes of
competing states, spin density wave states, an in-plane ferromagnetic state,
and a valley polarized state, which undergo first-order phase transitions tuned
by an out-of-plane displacement field. The valley polarized state becomes a
Chern insulator for certain displacement fields. Moreover, we predict a
topological charge density wave forming a honeycomb lattice with ferromagnetism
at $\nu=2/3$. Future directions on this versatile system hosting a rich set of
quantum phases are discussed.",2111.01152v3
2021-11-24,Search methods for continuous gravitational-wave signals from unknown sources in the advanced-detector era,"Continuous gravitational waves are long-lasting forms of gravitational
radiation produced by persistent quadrupolar variations of matter. Standard
expected sources for ground-based interferometric detectors are neutron stars
presenting non-axisymmetries such as crustal deformations, r-modes or free
precession. More exotic sources could include decaying ultralight boson clouds
around spinning black holes. A rich suite of data-analysis methods spanning a
wide bracket of thresholds between sensitivity and computational efficiency has
been developed during the last decades to search for these signals. In this
work, we review the current state of searches for continuous gravitational
waves using ground-based interferometer data, focusing on searches for unknown
sources. These searches typically consist of a main stage followed by several
post-processing steps to rule out outliers produced by detector noise. So far,
no continuous gravitational wave signal has been confidently detected, although
tighter upper limits are placed as detectors and search methods are further
developed.",2111.12575v2
2022-02-02,Status and perspectives of Continuous Gravitational Wave searches,"The birth of gravitational wave astronomy was triggered by the first
detection of a signal produced by the merger of two compact objects (also known
as a compact binary coalescence event). The following detections made by the
Earth-based network of advanced interferometers had a significant impact in
many fields of science: astrophysics, cosmology, nuclear physics and
fundamental physics. However, compact binary coalescence signals are not the
only type of gravitational waves potentially detectable by LIGO, Virgo, and
KAGRA. An interesting family of still undetected signals, and the ones that are
considered in this review, are the so-called continuous waves, paradigmatically
exemplified by the gravitational radiation emitted by galactic, fast-spinning
isolated neutron stars with a certain degree of asymmetry in their mass
distribution. In this work, I will review the status and the latest results
from the analyses of advanced detector data, including searches for dark matter
signatures.",2202.01088v3
2022-09-06,Gravitational Waves by the Perturbation of a Rotating Axisymmetric Rigid Body,"Precession is one of the important mechanisms of gravitational wave
generation in astrophysics. In general, free precession of a rigid body can be
caused by the rotation of a triaxial body. In the case of symmetric body, if
only the principal axis does not coincide with the axis of rotation, then there
is the precession. When a symmetric body rotates around one of its principal
axes, the body cannot move with precession. However, when there is a
perturbation in angular velocity of the symmetric body spinning around the
principal axis of the largest moment, the body can have a precession motion. In
this paper, the wave forms and their characteristics of gravitational waves by
the perturbation of a rotating axisymmetric rigid body are studied.",2209.02269v1
2022-09-09,"Excitonic density-waves, bi-excitons and orbital selective pairing in two-orbital correlated chains","We present a comprehensive study of a one-dimensional two-orbital model at
and below quarter-filling that realizes a number of unconventional phases. In
particular, we find an excitonic density wave in which excitons quasi-condense
with finite center of mass momentum and an order parameter that changes phase
with wave-vector $Q$. In this phase, excitons behave as hard-core bosons
without charge order. In addition, excitons can pair to form bi-excitons in a
state that is close to a charge density-wave instability. When pairing
dominates over the inter-orbital repulsion, we encounter a regime in which one
orbital is metallic, while the other forms a spin gapped superconductor, a
genuine orbital selective paired state. All these results are supported by
both, analytical and numerical calculations. By assuming a quasi-classical
approximation, we solve the three-body hole-electron-spinon problem and show
that excitons are held together by forming a bound state with spinons. In order
to preserve the antiferromagnetic background, excitons acquire a dispersion
that has a minimum away from $k=0$. The full characterization of the different
phases is obtained by means of extensive density matrix renormalization group
calculations.",2209.04094v1
2023-01-18,Gravitational waves or X-ray counterpart? No need to choose,"Binary black holes emit gravitational waves as they inspiral towards
coalescence. Searches for electromagnetic counterparts to these gravitational
waves rely on looking for common sources producing both signals. In this paper,
we take a different approach: we investigate the impact of radiation zone
effects, including retardation effects and gravitational wave propagation onto
the circumbinary disk around stellar-mass, spinning black holes, using general
relativistic hydrodynamical simulations. Then we used a general relativistic
ray-tracing code to extract its X-ray spectrum and lightcurve. This allowed us
to show that radiation zone effects leave an imprint onto the disk, leading to
quasi-periodic patterns in the X-ray lightcurve. The amplitude of the
modulation is weak (<1%) but increases with time and is strongly dependent on
the inclination angle.",2301.07376v1
2023-01-28,Photoinduced pseudospin-wave emission from charge-density-wave domain wall with superconductivity,"We study photoinduced dynamics triggered by an inhomogeneity due to
competition between charge density waves (CDWs) and superconductivity. As a
simple example, we consider the superconducting (SC) interface between two CDW
domains with opposite signs. The real-time dynamics are calculated within the
time-dependent Hartree--Fock--Bogoliubov framework, where the order parameter
dynamics and the nonequilibrium quasiparticle distribution functions are
studied. We also calculate the various dynamical response functions within a
generalized random phase approximation. Through comparisons between the real
time dynamics and the analysis of the response functions, it is found that the
photo-driven SC interface can emit collective modes of the SC order parameter.
This is analogous to the spin wave emission from the magnetic domain wall in an
antiferromagnet, particularly in the case of a low driving frequency, where the
order parameters can be mapped onto the pseudospin picture. In the
high-frequency case, we find a domain wall melting caused by changes in the
quasiparticle distribution, which induces superconductivity in the whole
system.",2301.12049v1
2023-03-13,Wave function dependent Form Factors and Radii of Mesons,"In this work, meson wave functions are selected to investigate the properties
of charmonium, bottomonium, and charmed-bottom mesons. To find the masses of
the ground, radial and orbital excited states of mesons, variational method is
applied on the selected meson wave functions. In addition, mesons are treated
non-relativistically by considering the chromodynamic potential model in the
linear plus coulombic form along with the incorporation of spin. Our mass
predictions show good agreement with the available experimental data and the
theoretical predictions found by different methods. Moreover, RMS radii, form
factors and charged radii are calculated by using the selected trial wave
functions. Momentum dependance of the form factors is shown graphically.
Predicted RMS radii and charged radii are compared with the theoretical
results, wherever available. Results show that RMS radii and charged radii have
inverse relation with the masses of mesons, i.e., heavier mesons have smaller
radii and vice versa.",2303.07394v3
2023-05-05,Breaking the entangling gate speed limit for trapped-ion qubits using a phase-stable standing wave,"All laser-driven entangling operations for trapped-ion qubits have hitherto
been performed without control of the optical phase of the light field, which
precludes independent tuning of the carrier and motional coupling. By placing
$^{88}$Sr$^+$ ions in a $\lambda=674$ nm standing wave, whose relative position
is controlled to $\approx\lambda/100$, we suppress the carrier coupling by a
factor of $18$, while coherently enhancing the spin-motion coupling. We
experimentally demonstrate that the off-resonant carrier coupling imposes a
speed limit for conventional traveling-wave M{\o}lmer-S{\o}rensen gates; we use
the standing wave to surpass this limit and achieve a gate duration of $15\
\mu$s, restricted by the available laser power.",2305.03450v2
2023-05-11,What are neutron stars made of? Gravitational waves may reveal the answer,"Neutron stars are one of the most mysterious wonders in the Universe. Their
extreme densities hint at new and exotic physics at work within. Gravitational
waves could be the key to unlocking their secrets. In particular, a first
detection of gravitational waves from rapidly-spinning, deformed neutron stars
could yield new insights into the physics of matter at extreme densities and
under strong gravity. Once a first detection is made, a critical challenge will
be to robustly extract physically interesting information from the detected
signals. In this essay, we describe initial research towards answering this
challenge, and thereby unleashing the full power of gravitational waves as an
engine for the discovery of new physics.",2305.06606v1
2023-06-23,Robust Coherent Control of Bimolecular Collisions beyond the Ultracold Regime,"Quantum coherent control of bimolecular collisions beyond the ultracold
regime can face a major challenge due to the incoherent addition of different
partial wave contributions to the total scattering cross section. These
contributions become increasingly numerous as the collision energy increases,
leading to a loss of overall control. Here, we overcome this limitation by
leveraging the recently discovered Partial Wave Phase Locking (PWPL) effect,
which synchronizes the oscillations of all partial wave contributions. By using
rigorous quantum scattering calculations, we demonstrate that PWPL enables
coherent control of spin exchange in ion-atom collisions, far outside the
ultracold regime, even with as many as 5000 partial wave contributions. The
predicted extent of control is sufficient to be measurable in cold atom-ion
hybrid experiments.",2306.13470v1
2023-08-02,"Arbitrariness and Usefulness of the Expressions of Elastic wave's Energy, Momentum and Angular Momentum","Elastic angular momentum is an emerging field, with some controversies on the
correct field-theory expressions and the decomposition of longitudinal and
transverse components. Motivated by the recent two papers [Phys.Rev.Lett. 128,
064301(2022), Phys.Rev.Lett. 129, 204303(2022)] on this issue, we
systematically analyze by Noether's theorem the canonical and Belinfante
energy-momentem and angular momentum, then explain why the two familiar
expressions, together with other various conservered currents, are all correct
for elastic wave. Remarkbly, to illustrate the usefullness of different
expressions, we give an example on earthquake energy measurement with a new
energy density expression which is more advantageous in practical measurement.
Moreover, since the elastic wave is distinct from a quantum one, we suggest
that the decomposition of longitudinal and transverse components, in fact,
makes sense and can be clearly expressed by the observable displacement field.
We hope that this paper would clarify the controversies, and finally we give
prospect of future work on the Geometric Spin Hall Effect of elastic wave,
where the various expressions of conserved currents would exhibit different
applications.",2308.05109v1
2023-10-09,Spatial asymmetry of optically excited spin waves in anisotropic ferromagnetic film,"We analytically discuss and micromagnetically prove the ways to tune the
spatial asymmetry of the initial phase, amplitude, and wavevectors of
magnetostatic waves driven by ultrafast laser excitation. We consider that the
optical pulse heats a thin ferromagnetic metallic film and abruptly decreases
the saturation magnetization and the parameter of uniaxial anisotropy. The two
corresponding terms of laser-induced torque have different azimuthal
symmetries, with the 4-fold symmetry of the demagnetization-related term, and
the isotropic distribution of the anisotropy-related term. As a result, the
initial phase and amplitude of excited magnetostatic waves have a non-trivial
azimuthal distribution tunable with the angle between the external magnetic
field and anisotropy axis, and the laser spot diameter. Moreover, the variation
of these parameters tunes the distribution of wavevectors, resulting in
additional asymmetry between the spectral components of the waves propagating
in different directions.",2310.05895v1
2023-10-29,Search for gravitational waves from Scorpius X-1 with a hidden Markov model in O3 LIGO data with a corrected orbital ephemeris,"Results are presented for a semi-coherent search for gravitational waves from
the low-mass X-ray binary Scorpius X-1 in Observing Run 3 (O3) data from the
Laser Interferometer Gravitational Wave Observatory, using an updated orbital
parameter ephemeris and a hidden Markov model (HMM) to allow for spin
wandering. The new orbital ephemeris corrects errors in previously published
orbital measurements and implies a new search domain. This search domain does
not overlap with the one used in the original Scorpius X-1 HMM O3 search. The
corrected domain is approximately three times smaller by area in the $T_{\rm
asc}$--$P$ plane than the original domain, where $T_{\rm asc}$ and $P$ denote
the time of passage through the ascending node and the orbital period
respectively, reducing the trials factor and computing time. No evidence is
found for gravitational radiation in the search band from 60 Hz to 500 Hz.
Upper limits are computed for the characteristic gravitational wave strain.
They are consistent with the values from the original Scorpius X-1 HMM O3
search.",2310.19183v1
2023-10-30,BHPWAVE: An adiabatic gravitational waveform model for compact objects undergoing quasi-circular inspirals into rotating massive black holes,"We present {bhpwave}: a new Python-based, open-source tool for generating the
gravitational waveforms of stellar-mass compact objects undergoing
quasi-circular inspirals into rotating massive black holes. These binaries,
known as extreme-mass-ratio inspirals (EMRIs), are exciting mHz gravitational
wave sources for future space-based detectors such as the Laser Interferometer
Space Antenna (LISA). Relativistic models of EMRI gravitational wave signals
are necessary to unlock the full scientific potential of mHz detectors, yet few
open-source EMRI waveform models exist. Thus we built {bhpwave}, which uses the
adiabatic approximation from black hole perturbation theory to rapidly
construct gravitational waveforms based on the leading-order inspiral dynamics
of the binary. In this work, we present the theoretical and numerical
foundations underpinning {bhpwave}. We also demonstrate how {bhpwave} can be
used to assess the impact of EMRI modeling errors on LISA gravitational wave
data analysis. In particular, we find that for retrograde orbits and
slowly-spinning black holes we can mismodel the gravitational wave phasing by
as much as $\sim 10$ radians without significantly biasing EMRI parameter
estimation.",2310.19706v2
2007-03-19,Quark core formation in spinning-down pulsars,"Pulsars spin-down due to magnetic torque reducing its radius and increasing
the central energy density. Some pulsar which are born with central densities
close to the critical value of quark deconfinement may undergo a phase
transition and structural re-arrengement. This process may excite oscillation
modes and emmit gravitational waves. We determine the rate of quark core
formation in neutron stars using a realistic population synthesis code.",0703507v1
1995-01-27,Fractal Spectrum of a Quasi_periodically Driven Spin System,"We numerically perform a spectral analysis of a quasi-periodically driven
spin 1/2 system, the spectrum of which is Singular Continuous. We compute
fractal dimensions of spectral measures and discuss their connections with the
time behaviour of various dynamical quantities, such as the moments of the
distribution of the wave packet. Our data suggest a close similarity between
the information dimension of the spectrum and the exponent ruling the algebraic
growth of the 'entropic width' of wavepackets.",9501013v1
1998-05-22,WKB for a damped spin,"The master equation for a damped spin well known from the theory of
superradiance, is written as a finite-difference equation and solved by a
WKB-like method. The propagator thus obtained looks like the van Vleck
propagator of a certain classical Hamiltonian system with one degree of
freedom. A new interpretation is provided of the temporal broadening of
initially sharp probability distributions as the analogue of the spreading of
the quantum mechanical wave packet.",9805018v1
1993-05-17,Anyons on Higher Genus Surfaces - a Constructive Approach,"We reconsider the problem of anyons on higher genus surfaces by embedding
them in three dimensional space. From a concrete realization based on three
dimensional flux tubes bound to charges moving on the surface, we explicitly
derive all the representations of the spinning braid group. The component
structure of the wave functions arises from winding the flux tubes around the
handles. We also argue that the anyons in our construction must fulfil the
generalized spin-statistics relation.",9305015v2
1993-06-02,Toward a Unified Magnetic Phase Diagram of the Cuprate Superconductors,"We propose a unified magnetic phase diagram of cuprate superconductors. A new
feature of this phase diagram is a broad intermediate doping region of
quantum-critical, $z=1$, behavior, characterized by temperature independent
$T_1T/T_{\rm 2G}$ and linear $T_1T$, where the spin waves are not completely
absorbed by the electron-hole continuum. The spin gap in the moderately doped
materials is related to the suppression of the low-energy spectral weight in
the quantum disordered, $z=1$, regime. The crossover to the $z=2$ regime, where
$T_1T/T_{\rm 2G}^2 \simeq \mbox{const}$, occurs only in the fully doped
materials.",9306007v1
1993-08-03,Realization of a Spin liquid in a Two Dimensional Quantum Antiferromagnet,"The ground state properties of the two dimensional spatially anisotropic
Heisenberg model are investigated by use of field theory mappings, spin-wave
expansion and Lanczos technique. Evidence for a disorder transition induced by
anisotropy at about $J_y/J_x < 0.1$ is shown. We argue that the disordered
phase is gapless and its long wavelength properties can be interpreted in terms
of decoupled one dimensional chains.",9308002v1
1993-10-27,Frustrated Honeycomb Heisenberg Antiferromagnet: A Schwinger Boson Approach,"We analyze the frustrated Heisenberg antiferromagnet defined on a honeycomb
lattice using a Schwinger-boson mean-field theory. The spin-wave velocity and
the susceptibility are presented as functions of the strength of the
frustrating interaction for spin S=1/2, and the dynamic structure factor is
calculated for various temperatures and frustrations. For large S, we find an
increased Neel stability with respect to the classical case.",9310063v1
1994-01-26,Hartree Fock and RPA studies of the Hubbard model,"The applicability of the Hartree-Fock and random phase approximations to
models of strongly correlated electrons is discussed. The 2D Hubbard model is
analyzed. An antiferromagnetic phase (at half filling) and Fermi liquid
behavior (at low electron densities) are found. In addition, the system shows
an unconventional regime near half filling. It is characterized by the
formation of spin and charge textures. Local magnetic moments and spin waves
are also present, and the quasiparticle pole at the Fermi energy vanishes. The
charge excitation spectrum is gapless. The overall features resemble those of
the 1D Luttinger liquid.",9401057v1
1994-10-06,Phase Transitions of Frustrated XY spins in Two Dimensions,"The row model is used to study the commensurate-incommensurate (C-IC) an
isotropic (FFTXY) transitions of the frustrated 2D XY model on the triangular
lattice. New relevant variables clarify the physics of these transitions: phase
and chiral variables are coupled so that spin waves generate long range polar
interactions. The resulting dielectric constan diverges at the transition. A
single transition occurs for the FFTXY model; in the C-IC regime the Lifshitz
point is at T=0 and the C phase i a Smectic-A like phase which disorders via a
2D nematic-smectic-A transition.",9410016v1
1995-01-13,Enhancement of superconducting correlation due to interlayer tunneling.,"Interlayer single particle tunneling between the $Cu-O$ layers suppress the
in-plane short range magnetic order (which is modeled as spin density wave
(SDW) insulator). Doping over the SDW state kills perfect nesting of the Fermi
surface (FS) in certain directions and hence SDW gap reduces to zero in those
directions of the FS. Coupling between the planes through interlayer tunneling
($t_{\perp}$) further suppresses the in-plane magnetic SDW-gap and hence
becomes anisotropic. Superconductivity arises in the gapless regions of the FS
under the `modified spin bag' mechanism. We show that the highest $T_c$ can
only be obtained for non-zero $t_{\perp}$ based on this mechanism.",9501053v1
1995-05-18,Quantum Numbers of Hall Effect Skyrmions,"By carefully considering a family of wave functions for Skyrmions in simple
quantum Hall states, whose members are labelled by a non-negative integer and
which properly generalizes the traditional Laughlin quasiparticle, we argue
that the spin of this particle has a fractional part related in a universal
fashion to the properties of the bulk state, and propose a direct experimental
test of this claim. We argue directly also for the fractional charge and
fractional quantum statistics of these particles. We show that certain
spin-singlet quantum Hall states can be understood as arising from primary
polarized states by Skyrmion condensation.",9505081v1
1995-06-19,A note on inverse-square exchange models,"The su(1$|$1) symmetric version of the Haldane-Shastry spin chain is
diagonalized by means of a linear transformation. The same transformation
applied to the original su(2) model yields simple expressions for the
Hamiltonian and the generators of the Yangian symmetry of the model in terms of
spin wave operators.",9506077v2
1995-07-22,Ising Expansion for the Hubbard Model,"We develop series expansions for the ground state properties of the Hubbard
model, by introducing an Ising anisotropy into the Hamiltonian. For the
two-dimensional (2D) square lattice half-filled Hubbard model, the ground state
energy, local moment, sublattice magnetization, uniform magnetic susceptibility
and spin stiffness are calculated as a function of $U/t$, where $U$ is the
Coulomb constant and $t$ is the hopping parameter. Magnetic susceptibility data
indicate a crossover around $U\approx 4$ between spin density wave
antiferromagnetism and Heisenberg antiferromagnetism. Comparisons with Monte
Carlo simulations, RPA result and mean field solutions are also made.",9507096v2
1996-04-23,Two-dimensional S=1/2 antiferromagnet on a plaquette lattice,"We consider a simplified model of the magnetic structure of the
two-dimensional compound $CaV_4O_9$ in terms of interacting square plaquettes
of spins with two distinct antiferromagnetic exchange constants. We analyze the
competition between two types of singlet ground states and the Neel ordered one
in terms of respectively, numerical cluster expansion and nonlinear spin wave
theory. The resulting phase diagram agrees well with known Quantum Monte Carlo
results and suggests a first order transition between ordered and singlet
ground states as a function of the exchange constants.",9604145v1
1996-05-11,The end of c=1 CFT,"Conformal field theory (CFT) with the central charge c=1 is important both in
the field theory and in the condensed matter physics, since it has the
continuous internal symmetry (U(1) or SU(2)) and a marginal operator, and it is
an effective theory of many 1D quantum spin and 1D electron systems. So it is
valuable to understand how the c=1 CFT models become unstable. In this paper we
discuss an instability of the c=1 CFT, that is, the transition to the
ferromagnetic state. For the U(1) CFT case, we find that the spin wave velocity
$v$ and the critical dimension $K$ behave $v, 1/K \propto \sqrt{\Delta_c
-\Delta}$ under reasonable assumptions.",9605070v1
1996-05-15,Internal Excitations and Dissipative Damping of Quantum Hall Skyrmions,"We propose an intrinsic maximum speed for dissipationless E cross B drift of
Skyrmion quasiparticles in quantum Hall ferromagnets. When this speed is
exceeded, Skyrmions can radiate spin-waves by making internal excitations which
allow total spin to be conserved. Our proposal is illustrated by a
time-dependent Hartree-Fock approximation calculation of the excitation
spectrum for a Skyrmion bound to an impurity.",9605091v1
1996-07-30,Superfluids and Supersolids on Frustrated 2D Lattices,"We study the ground state of hard-core bosons with nearest-neighbor hopping
and nearest-neighbor interactions on the triangular and Kagom\'e lattices by
mapping to a system of spins ($S={1\over2}$), which we analyze using spin-wave
theory. We find that the both lattices display superfluid and supersolid (a
coexistence of superfluid and solid) order as the parameters and filling are
varied. Quantum fluctuations seem large enough in the Kagom\'e system to raise
the interesting possibility of a disordered ground state.",9607217v1
1997-03-06,Ferromagnetic spin fluctuation induced superconductivity in Sr_2RuO_4,"We propose a quantitative model for triplet superconductivity in Sr_2RuO_4
based on first principles calculations for the electronic structure and
magnetic susceptibility. The superconductivity is due to ferromagnetic spin
fluctuations, that are strong at small wave vectors. The calculated effective
mass renormalization, renormalized susceptibility, and superconducting critical
temperature are all in good agreement with experiment. The most stable
superconducting solution has order parameters of comparable magnitude on all
three sheets of the Fermi surface. We also propose an explanation of the
discrepancy between the Fermi surface topology observed in the photoemission
and in de Haas-van Alphen experiments.",9703068v2
1997-11-02,Studies of a 2-Chain Spin Ladder with Frustrating Second Neighbor Interactions,"The Heisenberg model on a 2-chain spin-1/2 ladder with frustrating second
neighbor interactions is studied by using series expansions about the Ising and
dimer limits, numerical diagonalization, and by Abelian bosonization analysis.
The phase diagram is determined, and pair correlations and the complete
dispersion relations for the triplet spin-wave excitations are also computed.",9711006v2
1997-12-16,"""Superconductor""-insulator transitions in a Hubbard chain with nearest- neighbor and bond-charge interactions","We consider a half-filled generalized Hubbard chain with electron-hole
symmetric correlated hopping and on-site and nearest-neighbor repulsions U and
V respectively. In addition to the insulating charge- and spin-density wave
phases for large V and U respectively, we identify a phase with dominant
superconducting correlations at large distances for small U and V. Using two
Berry phases (one associated to the charge and the other to the spin degrees of
freedom) as discrete order parameters, we construct a phase diagram for the
three thermodynamic phases.",9712190v1
1997-12-29,Pseudogap and incommensurate magnetic fluctuations in YBa_2Cu_3O_{6. 6},"Unpolarized inelastic neutron scattering is used to study the temperature and
wave vector dependence of the dynamical magnetic susceptibility,
$\chi''(q,\omega)$, of a well characterized single crystal $YBa_2Cu_3O_{6.6}$
($T_c=62.7$ K). We find that a pseudogap opens in the spin fluctuation spectrum
at temperatures well above $T_c$. We speculate that the appearance of the low
frequency incommensurate fluctuations is associated with the opening of the
pseudogap. To within the error of the measurements, a gap in the spin
fluctuation spectrum is found in the superconducting state.",9712311v1
1998-03-13,Bose-Einstein condensation with internal degrees of freedom in alkali atom gases,"The Bogoliubov theory is extended to a Bose-Einstein condensation with
internal degrees of freedom, realized recently in $^{23}$Na gases where several
hyperfine states are simultaneously cooled optically. Starting with a
Hamiltonian constructed from general gauge and spin rotation symmetry
principles fundamental equations for condensate are derived. The ground state
where time reversal symmetry is broken in some case and low-lying collective
modes, e.g. spin and density wave modes, are discussed. Novel vortex as a
topological defect can be created experimentally.",9803160v1
1998-06-28,Combination of Ferromagnetic and Antiferromagnetic Features in Heisenberg Ferrimagnets,"We investigate the thermodynamic properties of Heisenberg ferrimagnetic
mixed-spin chains both numerically and analytically with particular emphasis on
the combination of ferromagnetic and antiferromagnetic features. Employing a
new density-matrix renormalization-group technique as well as a quantum Monte
Carlo method, we reveal the overall thermal behavior: At very low temperatures,
the specific heat and the magnetic susceptibility times temperature behave like
$T^{1/2}$ and $T^{-1}$, respectively, whereas at intermediate temperatures,
they exhibit a Schottky-like peak and a minimum, respectively. Developing the
modified spin-wave theory, we complement the numerical findings and give a
precise estimate of the low-temperature behavior.",9806344v1
1998-08-19,Collective Modes in High-Temperature Superconductors,"The role of collective modes in various experiments on the cuprates is
investigated. We calculate the neutron scattering, photoemission (ARPES), and
Raman scattering intensities below $T_c$ within the fluctuation-exchange (FLEX)
approximation for the two-dimensional Hubbard model. It is shown that the large
peak in the dynamical spin susceptibility arises from a weakly damped
spin-density-wave collective mode. This gives rise to a dip between the sharp
low energy peak and the higher binding energy hump in the ARPES spectrum.
Furthermore, we show that the collective mode of the amplitude fluctuation of
the d-wave gap yields a broad peak above the pair-breaking threshold in the
$B_{1g}$ Raman spectrum.",9808210v1
1998-08-20,Collinear Néel-type ordering in partially frustrated lattices,"We consider two partially frustrated S = 1/2 antiferromagnetic spin systems
on the triangular and pentagonal lattices. In an elementary plaquette of the
two lattices, one bond has exchange interaction strength $\alpha$ ($\alpha \leq
1$) whereas all other bonds have exchange interaction strength unity. We show
that for $\alpha$ less than a critical value $\alpha_{c}$, collinear
N\'eel-type ordering is possible in the ground state. The ground state energy
and the excitation spectrum have been determined using linear spin wave theory
based on the Holstein-Primakoff transformation.",9808222v1
1999-01-26,"Linear dependence of peak width in $χ(\bq, ω)$ vs T_c for YBCO superconductors","It is shown that the momentum space width of the peak in the spin
susceptibility, Im$\chi(q,\omega)$, is linearly proportional to the
superconducting $T_c$: $T_c = \hbar v^*\Delta q$ with $\hbar v^* \simeq 35
meV$\AA. This relation is similar to the linear relation between incommensurate
peak splitting and $T_c$ in LaSrCuO superconductors, as first proposed by
Yamada et al. (Phys. Rev. B 57, 6165, (1998)). The velocity $\hbar v^*$ is
smaller than Fermi velocity or the spin-wave velocity of the parent compound
and remains the same for a wide doping range. This result points towards strong
similarities in magnetic state of YBCO and LaSrCuO.",9901294v1
1999-01-30,The correlation length of the Heisenberg antiferromagnet with arbitrary spin S,"Experiments and numerical data on the correlation length for large S disagree
strongly with the theoretical prediction based on the effective field theory
prescription of the magnon physics. The reason is that for large S, at any
accessible correlation lengths, the cut-off effects from the non-magnon scales
become large and can not be treated by an effective field theory. We study
these effects in a spin-wave expansion. The corrected prediction connects the
renormalized classical and the classical scaling regions smoothly and comes
close to the data.",9901355v1
1999-07-07,Spin symmetry breaking in bilayer quantum Hall systems,"Based on the construction of generalized Halperin wave functions, we predict
the possible existence of a large class of broken spin symmetry states in
bilayer quantum Hall structures, generalizing the recently suggested canted
antiferromgnetic phase to many fractional fillings. We develop the appropriate
Chern-Simons theory, and establish explicitly that the low-lying neutral
excitation is a Goldstone mode and that the charged excitations are bimerons
with continuously tunable (through the canted antiferromagnetic order
parameter) electric charge on the individual merons.",9907107v1
1999-07-27,Triplet superconductivity in a one-dimensional ferromagnetic t-J model,"In this paper we study the ground state phase diagram of a one-dimensional
$t-U-J$ model, at half-filling. In the large-bandwidth limit and for
ferromagnetic exchange with easy-plane anisotropy, a phase with gapless charge
and massive spin excitations, characterized by the coexistence of triplet
superconducting ($TS$) and spin density wave ($SDW^{z}$) instabilities is
realized in the ground state. With reduction of the bandwidth, a transition
into an insulating phase showing properties of the spin-1/2 XY model takes
place. In the case of weakly anisotropic antiferromagnetic exchange the system
shows a long range dimerized (Peierls) ordering in the ground state. The
complete weak-coupling phase diagram of the model, including effects of the
on-site Hubbard interaction, is obtained.",9907415v1
1999-08-13,Single-Particle Pseudogap in Two-Dimensional Electron Systems,"We investigate pseudogap phenomena in the 2D electron system.
  Based on the mode-mode coupling theory of antiferromagnetic (AFM) and
$d_{x^2-y^2}$-wave superconducting ($d$SC) fluctuations, single-particle
dynamics is analyzed. For the parameter values of underdoped cuprates,
pseudogap structure grows in the single-particle spectral weight $A(k,\omega)$
around the wave vector $(\pi,0)$ and $(0,\pi)$ below the pseudo-spin-gap
temperature $\TPG$ signaled by the reduction of dynamical spin correlations in
qualitative agreement with the experimental data. The calculated results for
the overdoped cuprates also reproduce the absence of the pseudogap in the
experiments. We also discuss limitations of our weak-coupling approach.",9908195v1
1999-08-20,How large can be SDW and CDW apmlitudes in underdoped cuprates,"Self-consistent calculation of spin (charge) density wave order (SDW/CDW)
parameters have been performed for bilayered cuprates on the basis of a singlet
correlated band model. Evolution of the Fermi surface in the strongly
underdoped regime is described by using a two-band approach. The smooth
development of the pseudogap formation temperature is explained from underdoped
to overdoped states and the Fourier amplitudes <s_q> (spin) and <e_q> (charge)
modulations have been calculated. We have found a maximum of the
incommensurability for doping 0.09-0.11 holes per copper site.",9908297v1
1999-09-01,Normal Fermi Liquid Behavior of Quasiholes in the Spin-Polaron Model for Copper Oxides,"Based on the t-J model and the self-consistent Born approximation, the
damping of quasiparticle hole states near the Fermi surface is calculated in a
low doping regime. Renormalization of spin-wave excitations due to hole doping
is taken into account. The damping is shown to be described by a familiar form
$\text{Im}\Sigma({\bf k}^{\prime},\epsilon)\propto (\epsilon^{2}/
\epsilon_{F})\ln(\epsilon/ \epsilon_{F})$ characteristic of the 2-dimensional
Fermi liquid, in contrast with the earlier statement reported by Li and Gong
[Phys. Rev. B {\bf 51}, 6343 (1995)] on the marginal Fermi liquid behavior of
quasiholes.",9909020v1
1999-10-27,A Novel Longitudinal Mode in the Coupled Quantum Chain Compound KCuF3,"Inelastic neutron scattering measurements are reported that show a new
longitudinal mode in the antiferromagnetically ordered phase of the spin-1/2
quasi-one-dimensional antiferromagnet KCuF3. This mode signals the cross-over
from one-dimensional to three-dimensional behavior and indicates a reduction in
the ordered spin moment of a spin-1/2 antiferromagnet. The measurements are
compared with recent quantum field theory results and are found to be in
excellent agreement. A feature of the data not predicted by theory is a damping
of the mode by decay processes to the transverse spin-wave branches.",9910459v1
1999-11-25,Monte Carlo Study of the Anisotropic Heisenberg Antiferromagnet on the Triangular Lattice,"We report a Monte Carlo study of the classical antiferromagnetic Heisenberg
model with easy axis anisotropy on the triangular lattice. Both the free energy
cost for long wavelength spin waves as well as for the formation of free
vortices are obtained from the spin stiffness and vorticity modulus
respectively. Evidence for two distinct Kosterlitz-Thouless types of
defect-mediated phase transitions at finite temperatures is presented.",9911403v1
1999-12-01,Exact ground states for a class of one-dimensional frustrated quantum spin models,"We have found the exact ground state for two frustrated quantum spin-1/2
models on a linear chain. The first model describes ferromagnet-
antiferromagnet transition point. The singlet state at this point has
double-spiral ordering. The second model is equivalent to special case of the
spin-1/2 ladder. It has non-degenerate singlet ground state with exponentially
decaying spin correlations and there is an energy gap. The exact ground state
wave function of these models is presented in a special recurrent form and
recurrence technics of expectation value calculations is developed.",9912010v1
1999-12-02,Scenario of Superconducting Transition for quasi-2D HTS,"We discuss the scenario of superconducing transition for quasi two dimension
HTS with spin fluctuation pairing mechanism. At mean field temperature of 2D
superconducting transition the interaction of fluctuation spin waves with holes
in copper-oxigen planes leads to the pairing of holes and to the fluctuation
generation of superconducting regions, and also to the essential temperature
dependence of the strength of the interlayer coupling. At decreasing
temperature and sufficiently small interlayer coupling the transition of the
sample to coherent superconducting state occurs.",9912042v1
2000-05-15,Low Temperature Anomaly in Mesoscopic Kondo Wires,"We report the observation of an anomalous magnetoresistance in extremely
dilute quasi-one-dimensional AuFe wires at low temperatures, along with a
hysteretic background at low fields. The Kondo resistivity does not show the
unitarity limit down to the lowest temperature, implying uncompensated spin
states. We suggest that the anomalous magnetoresistance may be understood as
the interference correction from the accumulation of geometric phase in the
conduction electron wave function around the localized impurity spin.",0005234v1
2000-06-13,Coherent dipolar correlations in the ground-state of Kagome frustrated antiferromagnets,"We propose a new model for the nature of the low temperature phase of a
geometrically frustrated antiferromgnet (AFM) with a Kagome lattice,
SrCr$_{8-x}$Ga$_{4+x}$O$_{19}$. We propose that the long-range dipolar
interaction between the magnetic Cr$^{3+}$ ions introduces correlations in
their dynamics. The dipolar ground-state has the spins performing correlated
zero-point oscillations in a coherent state with a well defined global phase
and a complex order-parameter (i.e. Off-Diagonal Long Range Order). We
calculate the magnon excitations of such a dipolar array and we find good
agreement with the spin-wave velocities infered from measurements of the
specific-heat. Various experimental properties of these materials are naturally
explained by such a model.",0006215v1
2000-09-07,Intermediate spin approach to the tunneling of nano-magnets,"The theory for the quantum tunneling of nano-magnets is developed within the
intermediate spin framework. Periodic magnetic effects are seen to reflect that
associated with a change of flux by a single flux quantum $\Phi_{0}$. Essential
are Schr\""odinger cat wave functions which involve superpositions of different
magnitudes of the applied magnetic field. For systems in which the tunneling
paths are not co-planar the theory leads to essentially complex magnetic fields
although the expectation values of the fields remain real. In general the
ground states correspond to minimal uncertainty squeezed states. The degree of
squeezing depends on the anisotropy parameters.",0009098v1
2000-12-15,Phase transition in a magnetic field in V2-yO3 (y=0 and 0.04),"The effect of a magnetic field on the two long-range-ordered magnetic phases,
the collinear insulating antiferromagnetic (AFI) and the incommensurate
metallic transverse spin density wave (SDW), is investigated for the vanadium
sesquioxide system. A field of 18 T has little effect on the AFI phase of a
nominal V2O3 sample. The transverse SDW phase of V1.96O3 can be suppressed by a
4.6(3)-T magnetic field applied in the plane of spiraling spins, while the same
magnetic field applied along the spiral axis has little effect on the SDW
phase.",0012297v1
2001-02-27,Spin polarization and magneto-luminescence of confined electron-hole systems,"A BCS-like variational wave-function, which is exact in the infinite field
limit, is used to study the interplay among Zeeman energies, lateral
confinement and particle correlations induced by the Coulomb interactions in
strongly pumped neutral quantum dots. Band mixing effects are partially
incorporated by means of field-dependent masses and g-factors. The spin
polarization and the magneto-luminescence are computed as functions of the
number of electron-hole pairs present in the dot and the applied magnetic
field.",0102504v1
2001-07-03,Random phase approximation for multi-band Hubbard models,"We derive the random-phase approximation for spin excitations in general
multi-band Hubbard models, starting from a collinear ferromagnetic Hartree-Fock
ground state. The results are compared with those of a recently introduced
variational many-body approach to spin-waves in itinerant ferromagnets. As we
exemplify for Hubbard models with one and two bands, the two approaches lead to
qualitatively different results. The discrepancies can be traced back to the
fact that the Hartree-Fock theory fails to describe properly the local moments
which naturally arise in a correlated-electron theory.",0107050v1
2001-08-13,Stripes and spin-incommensurabilities are favored by lattice anisotropies,"Structural distortions in cuprate materials give a natural origin for
anisotropies in electron properties. We study a modified one-band t-J model in
which we allow for different hoppings and antiferromagnetic couplings in the
two spatial directions ($t_x \ne t_y$ and $J_x \ne J_y$). Incommensurate peaks
in the spin structure factor show up only in the presence of a lattice
anisotropy, whereas charge correlations, indicating enhanced fluctuations at
incommensurate wave vectors, are almost unaffected with respect to the
isotropic case.",0108198v1
2001-09-28,Skyrmions in integral and fractional quantum Hall systems,"Numerical results are presented for the spin excitations of a two-dimensional
electron gas confined to a quantum well of width w. Spin waves and charged
skyrmion excitations are studied for filling factors nu=1, 3, and 1/3. Phase
diagrams for the occurrence of skyrmions of different size as a function of w
and the Zeeman energy are calculated. For nu=3, skyrmions occur only if w is
larger than about twice the magnetic length. A general necessary condition on
the interaction pseudopotential for the occurrence of stable skyrmion states is
proposed.",0109549v1
2001-10-07,Anomalous Spin Excitation Spectrum of the Heisenberg Model in a Magnetic Field,"Making the assumption that high energy fermions exist in the two dimensional
spin-1/2 Heisenberg antiferromagnet we present predictions based on the pi-flux
ansatz for the dynamic structure factor when the antiferromagnet is subject to
a uniform magnetic field. The main result is the presence of gapped excitations
in a momentum region near (pi,pi) with energy lower than that at (pi,pi). This
is qualitatively different from spin wave theory predictions and may be tested
by experiments or by quantum Monte Carlo.",0110133v2
2002-05-15,Quantum Interference between Impurities: Creating Novel Many-Body States in s-wave Superconductors,"We demonstrate that quantum interference of electronic waves that are
scattered by multiple magnetic impurities in an s-wave superconductor gives
rise to novel bound states. We predict that by varying the inter-impurity
distance or the relative angle between the impurity spins, the states' quantum
numbers, as well as their distinct frequency and spatial dependencies, can be
altered. Finally, we show that the superconductor can be driven through
multiple local crossovers in which its spin polarization, $<s_z >$, changes
between $<s_z >=0, 1/2$ and 1.",0205328v1
2002-06-29,Solvable Kinetic Gaussian Model in External Field,"In this paper, the single-spin transition dynamics is used to investigate the
kinetic Gaussian model in a periodic external field. We first derive the
fundamental dynamic equations, and then treat an isotropic d-dimensional
hypercubic lattice Gaussian spin system with Fourier's transformation method.
We obtain exactly the local magnetization and the equal-time pair correlation
function. The critical characteristics of the dynamical, the complex
susceptibility, and the dynamical response are discussed. The results show that
the time evolution of the dynamical quantities and the dynamical responses of
the system strongly depend on the frequency and the wave vector of the external
field.",0207007v1
2002-07-12,Transport properties and electronic states of the thermoelectric oxide NaCo_2O_4,"Physical properties of the thermoelectric oxide NaCo_2O_4 are briefly
reviewed. The high thermoelectric properties of this material are attributed to
the substantially enhanced effective mass, which comes from the large entropy
of Co$^{4+}$ in the low spin state. The large entropy confined in the CoO_2
block causes a spin-density-wave transition at 22 K upon Cu substitution for
Co, which can be regarded as ``order from disorder''.",0207315v1
2002-11-19,The Electron-Gas Pair Densities and their Normalization Sum Rules in Terms of Overhauser Geminals and Corresponding Scattering Phase Shifts,"It is shown, how the normalization sum rules of the spin-parallel and
spin-antiparallel pair densities of the homogeneous electron gas become sum
rules for the scattering phase shifts of the Overhauser two-body wave functions
(geminals), with which the pair densities have been successfully parametrized
recently. These new sum rules relate two-body quantities to a one-body
quantity, namely the asymptotics of the Overhauser geminals to the momentum
distribution.",0211408v2
2003-06-04,The Orbital Order Parameter in La0.95Sr0.05MnO3 probed by Electron Spin Resonance,"The temperature dependence of the electron-spin resonance linewidth in
La0.95Sr0.05MnO3 has been determined and analyzed in the paramagnetic regime
across the orbital ordering transition. From the temperature dependence and the
anisotropy of linewidth and $g$-value the orbital order can be unambiguously
determined via the mixing angle of the wave functions of the $e_{\rm
g}$-doublet. The linewidth shows a similar evolution with temperature as
resonant x-ray scattering results.",0306088v1
2003-08-06,Charge dynamics in the Mott insulating phase of the ionic Hubbard model,"We extend to charge and bond operators the transformation that maps the ionic
Hubbard model at half filling onto an effective spin Hamiltonian. Using these
operators we calculate the amplitude of the charge density wave in different
dimensions. In one dimension, the charge-charge correlations at large distance
d decay as 1/(d^3 ln^{3/2}d), in spite of the presence of a charge gap, as a
consequence of remaining charge-spin coupling. Bond-bond correlations decay as
(-1)^d 1/(d ln^{3/2}d) as in the usual Hubbard model.",0308120v2
2004-01-24,Nuclear Magnetic Relaxation in the Haldane-Gap Antiferromagnet Ni(C_2_H_8_N_2_)_2_NO_2_(ClO_4_),"A new theory is proposed to interpret nuclear spin-lattice relaxation-time
(T_1_) measurements on the spin-1 quasi-one-dimensional Heisenberg
antiferromagnet Ni(C_2_H_8_N_2_)_2_NO_2_(ClO_4_) (NENP). While Sagi and Affleck
pioneeringly discussed this subject in terms of field-theoretical languages,
there is no theoretical attempt yet to explicitly simulate the novel
observations of 1/T_1_ reported by Fujiwara et al.. By means of modified spin
waves, we solve the minimum of 1/T_1_ as a function of an applied field,
pending for the past decade.",0401478v1
2004-01-28,Microscopic mechanisms of magnetization reversal,"Two principal scenarios of magnetization reversal are considered. In the
first scenario all spins perform coherent motion and an excess of magnetic
energy directly goes to a nonmagnetic thermal bath. A general dynamic equation
is derived which includes a tensor damping term similar to the
Bloch-Bloembergen form but the magnetization magnitude remains constant for any
deviation from equilibrium. In the second reversal scenario, the absolute value
of the averaged sample magnetization is decreased by a rapid excitation of
nonlinear spin-wave resonances by uniform magnetization precession. We have
developed an analytic k-space micromagnetic approach that describes this entire
reversal process in an ultra-thin soft ferromagnetic film for up to 90^{o}
deviation from equilibrium. Conditions for the occurrence of the two scenarios
are discussed.",0401590v1
2004-03-17,Variational description of Mott insulators,"The Gutzwiller wave function for a strongly correlated model can, if
supplemented with a long-range Jastrow factor, provide a proper variational
description of Mott insulators, so far unavailable. We demonstrate this concept
in the prototypical one-dimensional $t-t^\prime$ Hubbard model, where at half
filling we reproduce all known phases, namely the ordinary Mott undimerized
insulator with power-law spin correlations at small $t^\prime/t$, the
spin-gapped metal above a critical $t^\prime/t$ and small $U$, and the
dimerized Mott insulator at large repulsion.",0403430v2
2004-08-20,Magnetoresistance of a semiconducting magnetic wire with domain wall,"We investigate theoretically the influence of the spin-orbit interaction of
Rashba type on the magnetoresistance of a semiconducting ferromagnetic
nanostructure with a laterally constrained domain wall. The domain wall is
assumed sharp (on the scale of the Fermi wave length of the charge carriers).
It is shown that the magnetoresistance in such a case can be considerably
large, which is in a qualitative agreement with recent experimental
observations. It is also shown that spin-orbit interaction may result in an
increase of the magnetoresistance. The role of localization corrections is also
briefly discussed.",0408456v1
2004-12-09,Entanglement distillation by adiabatic passage in coupled quantum dots,"Adiabatic passage of two correlated electrons in three coupled quantum dots
is shown to provide a robust and controlled way of distilling, transporting and
detecting spin entanglement, as well as of measuring the rate of spin
disentanglement. Employing tunable interdot coupling the scheme creates, from
an unentangled two-electron state, a superposition of spatially separated
singlet and triplet states. A single measurement of a dot population (charge)
collapses the wave function to either of these states, realizing entanglement
to charge conversion. The scheme is robust, with the efficiency close to 100%,
for a large range of realistic spectral parameters.",0412229v1
2004-12-15,Zero-temperature criticality in the two-dimensional gauge glass model,"The zero-temperature critical state of the two-dimensional gauge glass model
is investigated. It is found that low-energy vortex configurations afford a
simple description in terms of gapless, weakly interacting vortex-antivortex
pair excitations. A linear dielectric screening calculation is presented in a
renormalization group setting that yields a power-law decay of spin-wave
stiffness with distance. These properties are in agreement with low-temperature
specific heat and spin-glass susceptibility data obtained in large-scale
multi-canonical Monte Carlo simulations.",0412415v1
2004-12-22,Influence of Ni doping on the electronic structure of Ni_2MnGa,"The modifications in the electronic structure of Ni_{2+x}Mn_{1-x}Ga by Ni
doping have been studied using full potential linearized augmented plane wave
method and ultra-violet photoemission spectroscopy. Ni 3d related electron
states appear due to formation of Ni clusters. We show the possibility of
changing the minority-spin DOS with Ni doping, while the majority-spin DOS
remains almost unchanged. The total magnetic moment decreases with excess Ni.
The total energy calculations corroborate the experimentally reported changes
in the Curie temperature and the martensitic transition temperature with x.",0412611v2
2005-01-09,Consequences of the local spin self-energy approximation on the heavy Fermion quantum phase transition,"We show, using the periodic Anderson model, that the local spin self-energy
approximation, as implemented in the extended dynamical mean field theory
(EDMFT), results in a first order phase transition which persists to T=0.
Around the transition, there is a finite coexistence region of the paramagnetic
and antiferromagnetic (AFM) phases. The region is bounded by two critical
transition lines which differ by an electron-hole bubble at the AFM ordering
wave vector.",0501175v2
2005-03-04,17-O NMR studies of a triangular-lattice superconductor Na{x}CoO{2}yH{2}O,"We report the first 17-O NMR studies of a triangular-lattice superconductor
Na{1/3}CoO{2}-[4/3]H{2}O and the host material Na{x}CoO{2} (x=0.35 and 0.72).
Knight shift measurements reveal that p-d hybridization induces sizable spin
polarization in the O triangular-lattice layers. Water-intercalation makes
CoO{2} planes homogeneous, and enhances low frequency spin fluctuations near
T{c}=4.5 K at some finite wave-vectors different from both the ferromagnetic
and ``120 degree'' modes.",0503116v2
2005-03-09,Spin fluctuations in the stacked-triangular antiferromagnet YMnO3,"The spectrum of spin fluctuations in the stacked-triangular antiferromagnet
YMnO3 was studied above the Neel temperature using both unpolarized and
polarized inelastic neutron scattering. We find an in-plane and an out-of-plane
excitation. The in-plane mode has two components just above TN, a
resolution-limited central peak and a Debye-like contribution. The
quasi-elastic fluctuations have a line-width that increases with q like Dq^z
and the dynamical exponent z=2.3. The out-of-plane fluctuations have a gap at
the magnetic zone center and do not show any appreciable q-dependence at small
wave-vectors.",0503209v1
2005-06-22,Semiclassical ordering in the large-N pyrochlore antiferromagnet,"We study the semiclassical limit of the $Sp(N)$ generalization of the
pyrochlore lattice Heisenberg antiferromagnet by expanding about the $N \to
\infty$ saddlepoint in powers of a generalized inverse spin. To leading order,
we write down an effective Hamiltonian as a series in loops on the lattice.
Using this as a formula for calculating the energy of any classical ground
state, we perform Monte-Carlo simulations and find a unique collinear ground
state. This state is not a ground state of linear spin-wave theory, and can
therefore not be a physical (N=1) semiclassical ground state.",0506574v2
2005-06-28,Topological transition in a two-dimensional model of liquid crystal,"Simulations of nematic-isotropic transition of liquid crystals in two
dimensions are performed using an O(2) vector model characterised by non linear
nearest neighbour spin interaction governed by the fourth Legendre polynomial
$P\_4$. The system is studied through standard Finite-Size Scaling and
conformal rescaling of density profiles of correlation functions. A topological
transition between a paramagnetic phase at high temperature and a critical
phase at low temperature is observed. The low temperature limit is discussed in
the spin wave approximation and confirms the numerical results.",0506736v1
2005-10-03,Low energy electronic states and triplet pairing in layered cobaltates,"The structure of the low-energy electronic states in layered cobaltates is
considered starting from the Mott insulating limit. We argue that the coherent
part of the wave-functions and the Fermi-surface topology at low doping are
strongly influenced by spin-orbit coupling of the correlated electrons on the
$t_{2g}$ level. An effective t-J model based on mixed spin-orbital states is
radically different from that for the cuprates, and supports unconventional,
pseudospin-triplet pairing.",0510051v1
2005-10-31,Magnetic properties of antiferromagnetic quantum Heisenberg spin systems with a strict single particle site occupation,"We work out the magnetization and susceptibility of Heisenberg- and
  XXZ-model antiferromagnet spin-1/2 systems in $D$ dimensions under a rigorous
constraint of single particle site occupancy. Quantum fluctuations are taken
into account up to the first order in a loop expansion beyond the N\'eel state
mean field solution. We discuss the results, their validity in the vicinity of
the critical point and compare them with the results obtained by means of a
spin wave approach.",0510832v1
2005-11-02,Current-induced vortex displacement and annihilation in a single Permalloy disk,"The induced motion of a magnetic vortex in a micron-sized ferromagnetic disk
due to the DC current injection is studied by measuring planar Hall effect. The
DC current injection is found to induce the spin torque that sweeps the vortex
out of the disk at the critical current while bias magnetic field are applied.
The current-induced vortex core displacement deduced from the change in planar
Hall resistance is quantitatively consistent with theoretical prediction. Peak
structures similar to those originated from spin wave excitations are observed
in the differential planar Hall resistance curve.",0511040v1
2005-12-09,Nematic phase transitions in two-dimensional systems,"Simulations of nematic-isotropic transition of liquid crystals in two
dimensions are performed using an O(2) vector model characterised by non linear
nearest neighbour spin interaction governed by the fourth Legendre polynomial
$P\_4$. The system is studied through standard Finite-Size Scaling and
conformal rescaling of density profiles or correlation functions. The low
temperature limit is discussed in the spin wave approximation and confirms the
numerical results, while the value of the correlation function exponent at the
deconfining transition seems controversial.",0512194v1
2006-04-20,Magnetic phase diagram of a frustrated ferrimagnetic ladder: Relation to the one-dimensional boson Hubbard model,"We study the magnetic phase diagram of two coupled mixed-spin $(1,{1/2})$
Heisenberg chains as a function of the frustration parameter related to
diagonal exchange couplings. The analysis is performed by using spin-wave
series and exact numerical diagonalization techniques. The obtained phase
diagram--containing the Luttinger liquid phase, the plateau phase with a
magnetization per rung $M=1/2$, and the fully polarized phase--is closely
related to the generic $(J/U,\mu/U)$ phase diagram of the one-dimensional boson
Hubbard model.",0604495v1
2006-05-25,Time Quantified Monte Carlo Algorithm for Interacting Spin Array Micromagnetic Dynamics,"In this paper, we reexamine the validity of using time quantified Monte Carlo
(TQMC) method [Phys. Rev. Lett. 84, 163 (2000); Phys. Rev. Lett. 96, 067208
(2006)] in simulating the stochastic dynamics of interacting magnetic
nanoparticles. The Fokker-Planck coefficients corresponding to both TQMC and
Langevin dynamical equation (Landau-Lifshitz-Gilbert, LLG) are derived and
compared in the presence of interparticle interactions. The time quantification
factor is obtained and justified. Numerical verification is shown by using TQMC
and Langevin methods in analyzing spin-wave dispersion in a linear array of
magnetic nanoparticles.",0605621v1
2006-07-13,The SU(3) bosons and the spin nematic state on the spin-1 bilinear-biquadratic triangular lattice,"A bond-operator mean-field theory in the SU(3) bosons representation is
developed to describe the antiferro-nematic phase of the spin-1
bilinear-biquadratic model. The calculated static structure factors reveal
delicately that the antiferro-nematic state may exhibit both the ferro- and
antiferro-quadruple long-range orders, which is reminiscent of the ferrimagnets
or the canted antiferromagnets. This result may influence the spin wave theory
concerned with this phase. Possible relevance of this unconventional state to
the quasi-two-dimensional triangular material NiGa2S4 is addressed.",0607330v1
2006-08-10,Spin Dynamics of a Magnetic Antivortex,"We report on a study of the dynamics of a magnetic antivortex in a submicron,
asteroid shaped, permalloy ferromagnet using micromagnetic simulations. As with
vortex states in disk and square geometries, a gyrotropic mode was found in
which a shifted antivortex core orbits about the center of the asteroid. Pulsed
magnetic fields were used to generate azimuthal or radial spin wave modes,
depending on the field orientation. The degeneracy of low frequency azimuthal
mode frequencies is lifted by gyrotropic motion of the antivortex core, and
restored by inserting a hole in the center of the particle to suppress this
motion. We briefly compare the dynamics of the vortex state of the asteroid to
the antivortex. The size dependence of the antivortex modes is reported.",0608245v1
2006-12-21,Sound propagation in a Fermi gas near a Feshbach resonance,"Sound waves are observed and studied in an optically trapped degenerate Fermi
gas of spin-up and spin-down atoms with magnetically tunable interactions.
Measurements are made throughout the crossover region, from a
weakly-interacting Fermi gas through the resonant Fermi superfluid regime to a
Bose condensate of dimer molecules. The measured sound velocities test the
equation of state and confirm the universal hypothesis.",0612567v1
2006-12-22,E-band excitations in the magnetic Keplerate molecule Fe30,"The low-temperature excitations in the magnetic Keplerate molecule Fe30 as
calculated by linear spin-wave theory (SWT), modified linear SWT, and
spin-level mean-field theory (SLMFT) are compared to the recent inelastic
neutron scattering results by Garlea et al. [Phys. Rev. B 73, 024414 (2006)].
SLMFT reproduces a part of the experimental spectrum rather well, but not all
of it. SWTs yield a fraction of the E-band excitations and hence are not
capable of a complete description of the excitation spectrum.",0612580v1
2007-01-12,Momentum dependent light scattering in insulating cuprates,"We investigate the problem of inelastic x-ray scattering in the spin$-{1/2}$
Heisenberg model on the square lattice. We first derive a momentum dependent
scattering operator for the $A_{1g}$ and $B_{1g}$ polarization geometries. On
the basis of a spin-wave analysis, including magnon-magnon interactions and
exact-diagonalizations, we determine the qualitative shape of the spectra. We
argue that our results may be relevant to help interpret inelastic x-ray
scattering experiments in the antiferromagnetic phase of the cuprates.",0701289v1
1994-11-08,Maximally Symmetric Spin-Two Bitensors on $S^3$ and $H^3$,"The transverse traceless spin-two tensor harmonics on $S^3$ and $H^3$ may be
denoted by $T^{(kl)}{}_{ab}$. The index $k$ labels the (degenerate) eigenvalues
of the Laplacian $\square$ and $l$ the other indices. We compute the bitensor
$\sum_l T^{(kl)}{}_{ab}(x) T^{(kl)}{}_{a'b'}(x')^*$ where $x,x'$ are distinct
points on a sphere or hyperboloid of unit radius. These quantities may be used
to find the correlation function of a stochastic background of gravitational
waves in spatially open or closed Friedman-Robertson-Walker cosmologies.",9411023v2
2002-12-09,Gravitational Acceleration of Spinning Bodies From Lunar Laser Ranging Measurements,"The Sun's relativistic gravitational gradient accelerations of Earth and
Moon, dependent on the motions of the latter bodies, act upon the system's
internal angular momentum. This spin-orbit force (which plays a part in
determining the gravity wave signal templates for astrophysical sources)
slightly accelerates the Earth-Moon system as a whole, but it more robustly
perturbs that system's internal dynamics with a 5 cm, synodically oscillating
range contribution which is presently measured to 4 mm precision by more than
three decades of lunar laser ranging.",0212043v1
2003-02-10,Propagation of perturbations in non-linear spin-2 theories,"In this communication I analyze the problem of complete exceptionality of
wave propagation in a class of spin 2 field theories. I show that, under the
imposition of the good weak-field limit, only two Lagrangians are completely
exceptional. These are the linear Fierz Lagrangian, and a Born-Infeld-like
Lagrangian. As a byproduct, I reobtain the result that in a nonlinear theory,
spin 2 particles follow an effective metric that depends on the nonlinearities
of the Lagrangian.",0302031v1
2003-10-14,The wave equation on the Schwarzschild metric II: Local decay for the spin 2 Regge Wheeler equation,"Odd-type spin 2 perturbations of Einstein's equation can be reduced to the
scalar Regge-Wheeler equation. We show that the weighted norms of solutions are
in L^2 of time and space. This result uses commutator methods and applies
uniformly to all relevant spherical harmonics.",0310066v2
1992-12-18,Finite size and temperature effects in the AF Heisenberg model,"The low temperature and large volume effects in the d=2+1 antiferromagnetic
quantum Heisenberg model are dominated by magnon excitations. The leading and
next-to-leading corrections are fully controlled by three physical constants,
the spin stiffness, the spin wave velocity and the staggered magnetization.
Among others, the free energy, the ground state energy, the low lying
excitations, staggered magnetization, staggered and uniform susceptibilities
are studied here. The special limits of very low temperature and infinite
volume are considered also.",9212022v1
1993-08-20,Relativistic Covariant Equal-Time Equation For Quark-Diquark System,"Relativistic three-dimensional quasipotential (equal-time) equations are
considered, which describe bound states of fermion and boson of spin S=0 or
S=1. The spin structure of the interaction quasipotentials in such systems is
studied, and corresponding partial-wave equation for the simplest case is
obtained. Such equations can be used in calculations of energy spectra, decay
rates and structure functions of quark-diquark systems (nucleons and their
resonances) as well as for description of ($\pi\mu$)- atom.",9308305v1
1994-05-31,"Single spin asymmetry in inclusive pion production, Collins effect and the string model","We calculate the single spin asymmetry in the inclusive pion production in
proton-proton collisions. We generate the asymmetry at the level of
fragmentation function (Collins effect) by the Lund coloured string mechanism.
We compare our results with the Fermilab E704 data from polarized proton-proton
collisions at 200 GeV. We show that the transversely polarized quark densities
at high Bjorken x strongly differ from these predicted by the SU(6) proton wave
function.",9405426v1
1999-06-03,Ruling out a higher spin field solution to the cosmological constant problem,"We consider the modification of Newton's gravity law in Dolgov's higher spin
models designed to compensate the cosmological constant. We find that the
effective Planck mass is unacceptably large in these models. We also point out
that the properties of gravitational waves are entirely different in these
models as compared to general relativity.",9906239v1
2000-10-11,Strongly Distorted Baryon Wave-Functions: Hyperon Beta-Decay and the Spin of the Lambda and the Nucleon,"Within the collective coordinate approach to chiral soliton models we suggest
that breaking of SU(3) flavor symmetry mainly resides in the baryon
wave-functions while the charge operators have no (or only small) symmetry
breaking components. In this framework we study the $g_A/g_V$ ratios for
hyperon beta-decay as well as the various quark flavor components of the axial
charge of the nucleon and the $\Lambda$-hyperon.",0010110v1
2001-10-17,The Spin of the Nucleon in Effective Models,"The three flavor soliton approach for baryons is utilized to discuss effects
of flavor symmetry breaking in the baryon wave--functions on axial current
matrix elements. The flavor content of the singlet axial current matrix
elements, that parameterizes the quark spin contribution to the total angular
momentum, is disentangled and studied as a function of the effective flavor
symmetry breaking. Here the nucleon and the Lambda--hyperon are considered.",0110236v1
2004-02-06,Pair Production of Arbitrary Spin Particles by Electromagnetic Fields,"The exact solutions of the wave equation for arbitrary spin particles in the
field of the soliton-like electric impulse were obtained. The differential
probability of pair production of particles by electromagnetic fields has been
evaluated on the basis of the exact solutions. As a particular case, the
particle pair producing in the constant and uniform electric field were
studied.",0402067v1
2005-02-22,Origin of magnetic field in compact stars and magnetic properties of quark matter,"Microscopic origin of the magnetic field observed in compact stars is studied
in quark matter. Spontaneous spin polarization appears in high-density region
due to the Fock exchange term. On the other hand, quark matter becomes unstable
to form spin density wave in the moderate density region, where restoration of
chiral symmetry plays an important role. Coexistence of the magnetism and color
superconductivity is briefly discussed.",0502201v3
2005-06-01,Magnetism and superconductivity in quark matter,"Magnetic properties of quark matter and its relation to the microscopic
origin of the magnetic field observed in compact stars are studied. Spontaneous
spin polarization appears in high-density region due to the Fock exchange term,
which may provide a scenario for the behaviors of magnetars. On the other hand,
quark matter becomes unstable to form spin density wave in the moderate density
region, where restoration of chiral symmetry plays an important role.
Coexistence of magnetism and color superconductivity is also discussed.",0506002v1
2005-10-07,Quantization of Fermionic Fields with Two Mass States in the First Order Formalism,"The relativistic 20-component wave equation, describing particles with spin
1/2 and two mass states, is analyzed. The projection operators extracting
states with definite energy and spin projections, and density matrix are
obtained. The canonical quantization of the field with two mass states in the
formalism of the first order is performed and the chronological pairing of the
20-component operators was found.",0510103v1
2006-04-14,"Determination of $χ_b$ spin in the decays $χ_{b0,2}\toψψ$ and $χ_{b0,2}\to\JP\JP\to 2(μ^+μ^-)$","The decays $\chi_{b0,2}\to\psi\psi$ and
$\chi_{b0,2}\to\psi\psi\to2(\mu^+\mu^-)$ are considered. It is shown that with
the help of $\psi$-meson angular distributions and the distributions by final
muon kinematical variables it is possible to determine the spin of the decaying
$\chi_b$-meson. These distributions can also give an additional information
about $\psi$-meson wave functions.",0604129v1
2006-11-13,Neutrino spin-flavor oscillations in rapidly varying magnetic fields,"The general formalism for the description of neutrino oscillations in
arbitrary rapidly varying external fields is elaborated. We obtain the new
effective Hamiltonian which determines the evolution of the averaged neutrino
wave function. The general technique is applied to the neutrino oscillations in
rapidly varying magnetic fields. We evaluate the transition probabilities of
the neutrino spin-flavor oscillations in magnetic fields of the Sun and compare
them with the numerical solutions of the Schroedinger equation with the exact
Hamiltonian.",0611167v1
2007-03-20,Baryon-baryon and baryon-antibaryon interaction amplitudes in the spin--momentum operator expansion method,"Partial wave scattering amplitudes in baryon-baryon and baryon-antibaryon
collisions and amplitudes for the production and decay of baryon resonances are
constructed in the framework of the spin-momentum operator expansion method.
The approach is relativistically invariant and it allows us to perform combined
analyses of different reactions imposing analyticity and unitarity directly.
The role of final state interactions (triangle and box diagrams) is discussed.",0703216v2
1993-11-02,"A One Dimensional Ideal Gas of Spinons, or Some Exact Results on the XXX Spin Chain with Long Range Interaction","We describe a few properties of the XXX spin chain with long range
interaction. The plan of these notes is:
  1. The Hamiltonian
  2. Symmetry of the model
  3. The irreducible multiplets
  4. The spectrum
  5. Wave functions and statistics
  6. The spinon description
  7. The thermodynamics",9311013v1
1996-09-17,Spinning Particle Dynamics on Six-Dimensional Minkowski Space,"Massive spinning particle in $6d$-Minkowski space is described as a
mechanical system with the configuration space $R^{5,1} \times CP^3$. The
action functional of the model is unambiguously determined by the requirement
of identical (off-shell) conservation for the phase-space counterparts of three
Casimir operators of Poincar\'e group. The model proves to be completely
solvable. Its generalization to the constant curvature background is presented.
Canonical quantization of the theory leads to the relativistic wave equations
for the irreducible $6d$ fields.",9609133v1
1998-10-28,Arbitrary spin massless bosonic fields in d-dimensional anti-de Sitter space,"Arbitrary spin free massless bosonic fields propagating in even $d$ -
dimensional anti-de Sitter spacetime are investigated. Free wave equations of
motion, subsidiary conditions and the corresponding gauge transformations for
such fields are proposed. The lowest eigenvalues of the energy operator for the
massless fields and the gauge parameter fields are derived. The results are
formulated in $SO(d-1,2)$ covariant form as well as in terms of intrinsic
coordinates. An inter-relation of two definitions of masslessness based on
gauge invariance and conformal invariance is discussed.",9810231v1
1999-04-15,Massless fields over $R^1 \times H^3$ space-time and coherent states for the Lorentz group,"The solutions of the arbitrary-spin massless wave equations over ${\bf R}^1
\times H^3$ space are obtained using the generalized coherent states for the
Lorentz group. The use of these solutions for the construction of invariant
propagators of quantized massless fields with an arbitrary spin over the ${\bf
R}^1 \times H^3$ space is considered. The expression for the scalar propagator
is obtained in the explicit form.",9904108v2
2001-03-26,On the Generalized Exclusion Statistics,"We review the principal steps leading to drive the wave function $\psi
_{\{k_1,k_2,...,k_N \}}(1,2,...,N)$ of a gaz of $N$ identical particle states
with exotic statistics. For spins $s=1/M$ $mod(1)$, we show that the
quasideterminant conjectured in [19], by using $2d$ conformal field theoretical
methods, is indeed related to the quantum determinant of noncommutative
geometry. The q-number $[N]!=\prod_{n=1}^N(\sum_{j=0}^{N-1} q^j)$ carrying the
effect of the generalized Pauli exclusion principle, according to which no more
than $(M-1)$ identical particles of spin $s=1/M$ $mod(1)$ can live altogether
on the same quantum state, is rederived in rigourous from the q-antisymmetry.
Other features are also given.",0103212v1
2002-06-26,Spin-isospin rotation dynamics,"The equations for the solitons arbitrarily rotating in the ordinary and
isotopic space are obtained. The wave functions of the corresponding dynamic
states in the quantum case are found. The generalized matrix of the moments of
inertia is degenerate for the O(2)-invariant configurations characteristic for
the nucleon and delta-isobar. The equation for such configurations is
established. It is shown that the spin-isospin rotation prevents the collapse
of the soliton states in the SU(2) sigma-model. The entire consideration is
based on the variational approach to the method of collective variables.",0206230v3
2004-01-07,Integrable Open Spin Chains in Defect Conformal Field Theory,"We demonstrate that the one-loop dilatation generator for the scalar sector
of a certain perturbation of N=4 Super Yang-Mills with fundamentals is the
Hamiltonian of an integrable spin chain with open boundary conditions. The
theory is a supersymmetric defect conformal field theory (dCFT) with the
fundamentals in hypermultiplets confined to a codimension one defect. We obtain
a K-matrix satisfying a suitably generalized form of the boundary Yang-Baxter
equation, study the Bethe ansatz equations and demonstrate how Dirichlet and
Neumann boundary conditions arise in field theory, and match to existing
results in the plane wave limit.",0401041v2
2006-02-20,Galilean Exotic Planar Supersymmetries and Nonrelativistic Supersymmetric Wave Equations,"We describe the general class of $N$-extended $D=(2+1)$ Galilean
supersymmetries obtained, respectively, from the $N$-extended D=3 Poincar\'{e}
superalgebras with maximal sets of central charges. We confirm the consistency
of supersymmetry with the presence of the `exotic' second central charge
$\theta$. We show further how to introduce a N=2 Galilean superfield equation
describing nonrelativistic spin 0 and spin 1/2 free particles.",0602198v2
2003-03-19,"Single Site Spin Expectation for the Imaginary Time Heisenberg Ferromagnet Wave Function, Numerical Approximation and Theoretical Argument","Certain approximations for the spin expectations have been studied both
numerically and theoretically. Approximations are constructed using solutions
of the lattice heat equation. The most interesting idea is a certain randomness
assumption for a theoretically derived quantity, that leads directly to a given
approximation. We are betting the randomness assumption is rigorously correct.",0303046v3
2003-09-30,Group Structure of an Extended Lorentz Group,"In a previous paper we extended the Lorentz group to include a set of Dirac
boosts that give a direct correspondence with a set of generators which for
spin 1/2 systems are proportional to the Dirac matrices. The group is
particularly useful for developing general linear wave equations beyond spin
1/2 systems. In this paper we develop explicit group properties of this
extended Lorentz group to obtain group parameters that will be useful for
physical calculations for systems which might manifest the group properties.
This group is a subgroup of an extended Poincare group, whose structure will be
developed in a subsequent paper.",0309060v1
2003-11-25,Group Structure of an Extended Poincare Group,"In previous papers we extended the Lorentz and Poincare groups to include a
set of Dirac boosts that give a direct correspondence with a set of generators
which for spin 1/2 systems are proportional to the Dirac matrices. The groups
are particularly useful for developing general linear wave equations beyond
spin 1/2 systems. In this paper we develop explicit group properties of the
extended Poincare group to obtain group parameters that will be useful for
physical calculations in systems which manifest the group properties. The
inclusion of space-time translations will allow future explorations of the
gauge properties inherent in the group structure.",0311044v1
1999-08-13,"Neutron Electric Form Factor from 3He(pol)(e(pol),e'n)","In a double polarised electron scattering experiment data have been taken
from which $G_E^n$ can be extracted for $Q^2=0.2{GeV}^2/c^2$. We have measured
asymmetries corresponding to the spin-spin correlation functions $A'_x$ and
$A'_z$ and to the target analyzing power $A_y^0$. In order to investigate the
influence of the reaction mechanisms and the different components of the
$^3{He}$ wave function, also the $(e,e'p)$ and $(e,e'd)$ channels have been
measured simultaneously. Some preliminary results are presented.",9908003v1
1993-03-18,Nuclear effects in Deep Inelastic Scattering of polarized electrons off polarized 3He and the neutron spin structure functions,"It is shown that the nuclear effects playing a relevant role in Deep
Inelastic Scattering of polarized electrons by polarized $^3$He are mainly
those arising from the effective proton and neutron polarizations generated by
the $S'$ and $D$ waves in $^3$He. A simple and reliable equation relating the
neutron, $g_1^n$, and $^3$He, $g_1^3$, spin structure functions is proposed. It
is shown that the measurement of the first moment of the $^3$He structure
function can provide a significant check of the Bjorken Sum Rule.",9303016v1
1993-10-14,"Quasi-Elastic $d(\vec{p},\vec{n})2p$ Reaction and Spin Response Functions of the Deuteron","We calculated response functions of the deuteron for charge exchange
processes, including the final state interaction between two protons. Using
them we evaluated the double differential cross section and polarization
observables of $d(\vec{p},\vec{n})2p$ by means of plane wave impulse
approximation with an optimal factorization. Calculation well reproduced the
shape of the energy spectra of the cross section, though somewhat overestimated
the magnitude. It also reproduced the spin observables well.",9310015v1
1998-04-09,Relativistic Spin-Flavor States in Light Front Dynamics,"Orthonormal spin-flavor wave functions of Lorentz covariant quark models of
the Bakamjian-Thomas type are constructed for nucleon resonances. Three
different bases are presented. The manifestly Lorentz covariant Dirac-Melosh
basis is related to the Pauli-Melosh basis and the symmetrized Bargmann-Wigner
basis that are manifestly orthogonal.",9804021v1
2000-08-30,E1 transitions between spin-dipole and Gamow-Teller giant resonances,"The branching ratios for E1 transitions between the spin-dipole (SD) and
Gamow-Teller (GT) giant resonances in $^{90}$Nb and $^{208}$Pb are evaluated.
Assuming the main GT-state has the wave function close to that for the ""ideal""
GT-state, we reduced the problem to calculate the SD and GT strength functions.
These strength functions are evaluated within an extended continuum-RPA
approach.",0008061v1
2003-08-27,Spin asymmetries for confined Dirac particles,"We study the Bjorken `x' (or equivalently Nachtmann `xi') dependence of the
virtual photon spin asymmetry in polarized deep inelastic scattering of
electrons from hadrons. We use an exactly solved relativistic potential model
of the hadron, treating the constituents as independent massless Dirac
particles confined to an infinitely massive force center. The importance of
including the p-wave components of the Dirac wave function is demonstrated.
Comparisons are made to the observed data on the proton by taking into account
the observed flavor dependence of the valence quark distribution functions.",0308078v1
2005-02-21,Spin-dependent neutrino-induced nucleon knockout,"We study neutrino-induced nucleon knockout off atomic nuclei and examine the
polarization properties of the ejectile. A detailed study of the spin
dependence of the outgoing nucleon is presented. The numerical results are
derived within a non-relativistic plane-wave impulse-approximation approach.
Our calculations reveal large polarization asymmetries, and clear
dissimilarities between neutrino- and antineutrino-induced reactions. They
reflect the fact that neutrino-induced nucleon knockout is dominated by the
transverse axial current and gains its major contributions from forward nucleon
emission and backward lepton scattering.",0502061v1
2007-02-06,Demonstration of the spin-statistics connection in elementary quantum mechanics,"A simple demonstration of the spin-statistics connection is presented. The
effect of exchange and space inversion operators on two-particle states is
reviewed. The connection follows directly from successive application of these
operations to the two-particle wave function for identical particles in an
s-state, evaluated at spatial coordinates $\pm x$, but at equal time,
\emph{i.e.}, at spacelike interval.",0702058v2
1998-09-22,Reconstruction of spin states and its conceptual implications,"State reconstruction for quantum spins is reviewed. Emphasis is on
non-tomographic approaches which are based on measurements performed with a
Stern-Gerlach apparatus. Two consequences of successfully implemented state
reconstruction are pointed out. First, it allows one to determine
experimentally the expectation value of an arbitrary operator without a device
measuring it. Second, state reconstruction suggests a reformulation of
Schroedinger's equation in terms of expectation values only, without explicit
reference to a wave function or a density operator.",9809065v1
2000-07-28,Raman Excited Spin Coherences in N-V Diamond,"Raman excited spin coherences were experimentally observed in N-V diamond
color centers via nondegenerate four-wave mixing (NDFWM) and
electromagnetically induced transparency (EIT). The maximal absorption
suppression was found to be 17%, which corresponds to 70% of what is possible
given the random geometric orientation of the N-V center in diamond. In the
context of quantum computing in solids, this level of transparency represents
the efficient preparation of quantum bits (qubits), as well as ability to
perform arbitrary single qubit rotations.",0007114v1
2002-06-21,On a motion equation for two particles in relativistic quantum mechanics,"The purpose of the present note is to propose, in the framework of
relativistic quantum mechanics, a new Poincare-invariant equation for two
particles with masses m_1, m_2 and spin s_1=s_2=1/2. It is a first-order linear
differential equation for the eight-component wave function. With the help of
this equation the description of the motion of two-particle systems is reduced
to the description of one-particle systems in the (1+6)-dimensional Minkowski
space which can be in two spin states (s=0 or s=1).",0206154v1
2002-06-21,Poincare-invariant equations with a rising mass spectrum,"In this note we shall construct, in the framework of relativistic quantum
mechanics, the Poincare-invariant motion equations with realistic mass spectra.
These equations describe a system with mass spectra of the form $m^2=a^2+b^2
s(s+1)$, where a and b are arbitrary parameters. Such equations are obtained by
a reduction of the motion equation for two particles to a one-particle equation
which describes the particle in various mass and spin states. It we impose a
certain condition on the wave function of the derived equation, such an
equation describes the free motion of a fixed-mass particle with arbitrary (but
fixed) spin s.",0206156v1
2004-02-17,"Reply to ""Non-relativistic proofs of the spin-statistics connection,"" by Shaji and Sudarshan","I earlier proved under stated assumptions of nonrelativistic quantum
mechanics, that identical spin-zero particles with no internal degrees of
freedom must be bosons. Shaji and Sudarshan have criticized that proof,
asserting that it is ""based on single-valuedness under rotation of the wave
functions of systems of identical particles."" No such assumption was used.
Here, to remove all doubt, I exclude the fermion possibility through a proof in
which even the existence of rotation is not used. Following that, I assume that
the Hilbert space is invariant under rotation to exclude other symmetries which
correspond neither to bosons nor to fermions. In that proof no issue of
single-valuedness can arise.",0402118v1
2005-09-26,Spacetime algebra and electron physics,"This paper surveys the application of geometric algebra to the physics of
electrons. It first appeared in 1996 and is reproduced here with only minor
modifications. Subjects covered include non-relativistic and relativistic
spinors, the Dirac equation, operators and monogenics, the Hydrogen atom,
propagators and scattering theory, spin precession, tunnelling times, spin
measurement, multiparticle quantum mechanics, relativistic multiparticle wave
equations, and semiclassical mechanics.",0509178v1
2006-02-28,Entanglement properties of quantum spin chains,"We investigate the entanglement properties of a finite size 1+1 dimensional
Ising spin chain, and show how these properties scale and can be utilized to
reconstruct the ground state wave function. Even at the critical point, few
terms in a Schmidt decomposition contribute to the exact ground state, and to
physical properties such as the entropy. Nevertheless the entanglement here is
prominent due to the lower-lying states in the Schmidt decomposition.",0602233v2
2006-09-26,Energy momentum flows for the massive vector field,"We present a causal trajectory interpretation for the massive vector field,
based on the flows of rest energy and a conserved density defined using the
time-like eigenvectors and eigenvalues of the stress-energy-momentum tensor.
This work extends our previous work which used a similar procedure for the
scalar field. The massive, spin-one, complex vector field is discussed in
detail and solutions are classified using the Pauli-Lubanski spin vector. The
flows of energy-momentum are illustrated in a simple example of standing waves
in a plane.",0609198v1
2007-04-05,Correlation functions and excitation spectrum of the frustrated ferromagnetic spin-1/2 chain in an external magnetic field,"Magnetic field effects on the one-dimensional frustrated ferromagnetic chain
are studied by means of effective field theory approaches in combination with
numerical calculations utilizing Lanczos diagonalization and the density matrix
renormalization group method. The nature of the ground state is shown to change
from a spin-density-wave region to a nematic-like one upon approaching the
saturation magnetization. The excitation spectrum is analyzed and the behavior
of the single spin-flip excitation gap is studied in detail, including the
emergent finite-size corrections.",0704.0764v2
2007-05-23,Gravitational waveforms for finite mass binaries,"One of the promising sources of gravitational radiation is a binary system
composed of compact stars. It is an important question how the rotation of the
bodies and the eccentricity of the orbit affect the detectable signal. Here we
present a method to evaluate the gravitational wave polarization states for
inspiralling compact binaries with comparable mass. We consider eccentric
orbits and the spin-orbit contribution in the case of one spinning object up to
1.5 post-Newtonian order. For circular orbits our results are in agreement with
existing calculations.",0705.3481v2
2007-06-28,Variational Principles for Constrained Electromagnetic Field and Papapetrou Equation,"In our previous article [4] an approach to derive Papapetrou equations for
constrained electromagnetic field was demonstrated by use of field variational
principles. The aim of current work is to present more universal technique of
deduction of the equations which could be applied to another types of
non-scalar fields. It is based on Noether theorem formulated in terms of
Cartan' formalism of orthonormal frames. Under infinitesimal coordinate
transformation the one leads to equation which includes volume force of
spin-gravitational interaction. Papapetrou equation for vector of propagation
of the wave is derived on base of the equation. Such manner of deduction allows
to formulate more accurately the constraints and clarify equations for the
potential and for spin.",0706.4163v1
2007-08-16,Gauge invariance in fractional field theories,"The principle of local gauge invariance is applied to fractional wave
equations and the interaction term is determined up to order $o(\bar{g})$ in
the coupling constant $\bar{g}$. As a first application, based on the
Riemann-Liouville fractional derivative definition, the fractional Zeeman
effect is used to reproduce the baryon spectrum accurately.
  The transformation properties of the non relativistic fractional
Schr\""odinger-equation under spatial rotations are investigated and an internal
fractional spin is deduced.",0708.2262v2
2007-12-04,Diffractive vector meson electroproduction at small Bjorken $x$ within GPD approach,"We study light vector meson electroproduction at small $x$ within the
generalized parton distributions (GPDs) model. The modified perturbative
approach is used, where the quark transverse degrees of freedom in the vector
meson wave function and hard subprocess are considered. Our results on the
cross section and spin observables are in good agreement with experiment",0712.0490v1
2007-12-21,Elliptic constructions of hyperkaehler metrics II: The quantum mechanics of a Swann bundle,"The generalized Legendre transform method of Lindstrom and Rocek yields
hyperkaehler metrics from holomorphic functions. Its main ingredients are
sections of ${\cal O}(2j)$ bundles over the twistor space satisfying a reality
condition with respect to antipodal conjugation on the hyperkaehler sphere of
complex structures. Formally, the structure of the real ${\cal O}(2j)$ sections
is identical to that of quantum-mechanical wave functions describing the states
of a particle with spin $j$ in the spin coherent representation. We analyze
these sections and their SO(3) invariants and illustrate our findings with two
Swann bundle constructions.",0712.3600v1
2007-12-28,Entanglement propagation through spin chains in the presence of a staggered magnetic field,"We study the dynamics of entanglement in the XY spin chain subject to a
staggered magnetic field and contrast it to the previously studied uniform
field case. We find that, depending on parameter values, a staggered field can
provide better conditions for a perfect entanglement transfer, while even a
modest amount of exchange anisotropy appears to have a strong detrimental
effect. We also study interactions between different waves of entanglement and
assess the possibility of simultaneous transmission of multiple bits of quantum
information.",0712.4349v1
2008-01-15,Magnetic Excitations of the Diagonal Incommensurate Phase in Lightly-Doped La2-xSrxCuO4,"We present inelastic neutron scattering experiments on a single-domain
crystal of lightly-doped La1.96Sr0.04CuO4. We find that the magnetic excitation
spectrum in this insulating phase with a diagonal incommensurate spin
modulation is remarkably similar to that in the superconducting regime, where
the spin modulation is bond parallel. In particular, we find that the
dispersion slope at low energy is essentially independent of doping and
temperature over a significant range. The energy at which the excitations cross
the commensurate antiferromagnetic wave vector increases roughly linearly with
doping through the underdoped regime.",0801.2254v1
2008-01-30,Long-range magnetic order and spin-lattice coupling in the delafossite CuFeO2,"The electronic and magnetic properties of the delafossite CuFeO2 are
investigated by means of electronic structure calculations. They are performed
using density functional theory in the generalized gradient approximation as
well as the new full-potential augmented spherical wave method. The
calculations reveal three different spin states at the iron sites. Taking into
account the correct crystal structure, we find long-range antiferromagnetic
ordering in agreement with experiment. Contrasting previous work, our
calculations show that non-local exchange interactions lead to a semiconducting
ground state.",0801.4787v1
2008-02-22,"Negative-Parity States and beta-decays in odd Ho and Dy Nuclei with A=151,153","We have investigated the negative-parity states and electromagnetic
transitions in $^{151,153}$Ho and $^{151,153}$Dy within the framework of the
interacting boson fermion model 2 (IBFM-2). Spin assignments for some states
with uncertain spin are made based on this calculation. Calculated excitation
energies, electromagnetic transitions and branching ratios are compared with
available experimental data and a good agreement is obtained. The model wave
functions have been used to study $\beta$-decays from Ho to Dy isotones, and
the calculated $\log ft$ values are close to the experimental data.",0802.3316v1
2008-03-17,The influence of spin-dependent phases of tunneling electrons on the conductance of a point ferromagnet/isolator/superconductor contact,"The Andreev reflection probability for a ferromagnet/isolator/superconductor
(FIS) contact at the arbitrary spin-dependent amplitudes of the electron waves
transmitted through and reflected from the potential barrier is found. It is
shown that Andreev reflection probabilities of electron and hole excitations in
the FIS contact are different. The energy levels of Andreev bound states are
found. The ballistic conductance of the point FIS contact is calculated.",0803.2499v2
2008-05-09,Quantum Phase Transition in the Itinerant Antiferromagnet (V0.9Ti0.1)2O3,"Quantum-critical behavior of the itinerant electron antiferromagnet
(V0.9Ti0.1)2O3 has been studied by single-crystal neutron scattering. By
directly observing antiferromagnetic spin fluctuations in the paramagnetic
phase, we have shown that the characteristic energy depends on temperature as
c_1 + c_2 T^{3/2}, where c_1 and c_2 are constants. This T^{3/2} dependence
demonstrates that the present strongly correlated d-electron antiferromagnet
clearly shows the criticality of the spin-density-wave quantum phase transition
in three space dimensions.",0805.1363v3
2008-07-07,On the Classical Limit of Spin Network Gravity: Two Conjectures,"Estimates are given of the time scales which govern spreading of a coherent
state wave packet. The estimates, based on dimensional analysis, suggest that
spreading should be small for coherent states with average angular momentum of
order 100 or larger. It is conjectured that in the classical limit, terms in
the Hamiltonian which add a new vertex will be suppressed, compared to terms
which modify the existing spin network without changing the number of vertices.",0807.1043v1
2008-07-24,The Collinear Magnetic Phases of the Geometrically-Frustrated Antiferromagnet CuFeO$_2$: The Importance of Stacking,"The correct stacking of hexagonal layers is used to obtain accurate estimates
for the exchange and anisotropy parameters of the geometrically-frustrated
antiferromagnet CuFeO$_2$. Those parameters are highly constrained by the
stability of a collinear metamagnetic phase between fields of 13.5 and 20 T.
Constrained fits of the spin-wave frequencies of the collinear $\uudd $ phase
below 7 T are used to identify the magnetic unit cell of the metamagnetic
$\uuudd $ phase, which contains two hexagonal layers and 10 Fe$^{3+}$ spins.",0807.3948v1
2008-07-28,High Field ESR in the Two-Dimensional Triangular Lattice Antiferromagnet NiGa2S4,"In this Letter, we report the results of ESR measurements in high magnetic
fields up to about 53 T on single crystals of NiGa2S4 to clarify the spin
dynamics in more detail. We have found that the dynamics of Z2 vortices affects
the temperature dependence of the ESR absorption linewidth and the frequency
dependence of the ESR resonance fields at 1.3 K is well explained by a
conventional spin wave theory. These results suggest an occurrence of Z2
vortex-induced topological transition.",0807.4438v2
2008-08-27,Polygonal excitations of spinning and levitating droplets,"The shape of a weightless spinning liquid droplet is governed by the balance
between the surface tension and centrifugal forces. The axisymmetric shape for
slow rotation becomes unstable to a non-axisymmetric distortion above a
critical angular velocity, beyond which the droplet progresses through a series
of 2-lobed shapes. Theory predicts the existence of a family of 3- and 4-lobed
equilibrium shapes at higher angular velocity. We investigate the formation of
a triangular-shaped magnetically levitated water droplet, driven to rotate by
the Lorentz force on an ionic current within the droplet. We also study
equatorial traveling waves which give the droplet 3, 4 and 5-fold symmetry.",0808.3704v1
2008-09-09,Pair correlations of a spin-imbalanced Fermi gas on two-leg ladders,"We study the pair correlations of a spin-imbalanced two-leg ladder with
attractive interactions, using the density matrix renormalization group method
(DMRG). We identify regions in the phase diagram spanned by the chemical
potential and the magnetic field that can harbor
Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)-like physics. Results for the pair
structure factor, exhibiting multiple pairing wave-vectors, substantiate the
presence of FFLO-like correlations. We further discuss phase separation
scenarios induced by a harmonic trap, which differ from the case of isolated
chains.",0809.1539v2
2008-10-10,The magnetohydrodynamics model of twin kilohertz QPOs in LMXBs,"We suggest an explanation for the twin kilohertz quasi-periodic oscillations
(kHz QPOs) in low-mass X-ray binaries (LMXBs) based on magnetohydrodynamics
(MHD) oscillation modes in neutron star magnetospheres. Including the effect of
the neutron star spin, we derive several MHD wave modes by solving the
dispersion equations, and propose that the coupling of the two resonant MHD
modes may lead to the twin kHz QPOs. This model naturally relates the upper,
lower kHz QPO frequencies with the spin frequencies of the neutron stars, and
can well account for the measured data of six LMXBs.",0810.1797v1
2008-10-24,A quantum interface between light and nuclear spins in quantum dots,"The coherent coupling of flying photonic qubits to stationary matter-based
qubits is an essential building block for quantum communication networks. We
show how such a quantum interface can be realized between a traveling-wave
optical field and the polarized nuclear spins in a singly charged quantum dot
strongly coupled to a high-finesse optical cavity. By adiabatically eliminating
the electron a direct effective coupling is achieved. Depending on the laser
field applied, interactions that enable either write-in or read-out are
obtained.",0810.4488v3
2008-11-13,Zero-field superfluid density in d-wave superconductor evaluated from the results of muon-spin-rotation experiments in the mixed state,"We report on measurements of the in-plane magnetic penetration \lambda_{ab}
in the optimally doped cuprate superconductor (BiPb)_2(SrLa)_2CuO_6+\delta (OP
Bi2201) by means of muon-spin rotation (\muSR). We show that in unconventional
$d-$wave superconductors (like OP Bi2201), \muSR experiments conducted in
various magnetic fields allow to evaluate the zero-field magnetic penetration
depth \lambda_0, which relates to the zero-field superfluid density in terms of
\rho_s\propto\lambda_0^-2.",0811.2077v1
2008-11-19,Unscreening Effect on Fe-Pnictide Superconductor,"We study a microscopic mechanism of Fe-pnictide superconductor, considering
the screening effects of Coulomb interaction in addition to the conventional
spin-fluctuation mechanism. It is shown that, by electron doping, the
transition temperature of superconductivity increases due to the ""unscreening""
effect even though the density of states decrease, while that of spin-density
wave rapidly decreases due to breaking of nesting conditions. Our results give
a clear interpretation to the mystery of interrelation between T_c and the
density of states observed in the Fe-pnictide superconductors.",0811.3052v1
2009-01-12,The influence of spin-dependent phases of tunneling electrons on the conductance of a point ferromagnet/isolator/d-wave superconductor contact,"The influence of phase shifts of electron waves passing through and reflected
by the potential barrier on the Andreev reflection in a
ferromagnet/isolator/d-wave superconductor (FIS) contact is studied. It is
found that in a superconductor the surface spin-dependent Andreev bound states
inside the superconducting gap are formed as a result of the interference of
electron-like and hole-like quasiparticles due to repeated Andreev reflections.
The peak in the conductance of the FIS contact at the zero potential for the
(110)-oriented superconductor disappears rapidly as the polarization of a
ferromagnet increases, whereas for the (100)-oriented superconductor it
appears. The physical reason for this behavior of conductance is discussed.",0901.1558v1
2009-01-19,Possible Kondo effect in the iron arsenides,"The normal state of the iron arsenides shows the poor metallic behavior mixed
with strong magnetic fluctuations. In particular, some FeAs-1111 and FeAs-122
compounds show the linear-T dependence of susceptibility above the spin-density
wave (SDW) transition and the logarithmic upturn of resistivity at low
temperatures. We suggest that this is due to the spin-flip scattering between
the charge carriers and the local moments in the undoped FeAs layer where Kondo
effect coexists with the SDW. This scenario is also accounted for the change of
the magnetoresistance from positive to negative in the Sr3Sc2O5Fe2As2 compound.",0901.2787v2
2009-02-02,Hawking temperature and higher order calculations,"Hawking radiation has recently been explained by using solutions of wave
equations across black hole horizons in a WKB approximation. Higher order
calculations using both usual and non-singular coordinates are found to change
the solution for zero spin, but this change is not an alteration of the Hawking
temperature. For spin 1/2, there is no correction to the simplest form of the
solution.",0902.0230v4
2009-02-05,Spin and angular momentum operators and their conservation,"Lorentz's reciprocity lemma and Feld-Tai reciprocity theorem show the effect
of interchanging the action and reaction in Maxwell's equations. We derive a
free-space version of these reciprocity relations which generalizes the
conservation of the momentum-energy tensor. This relation corresponds to the
interference conservation of electromagnetic waves. We show that for any
transformation or symmetry that leaves Maxwell's equations invariant, we can
modify the reciprocity relation to introduce a conserving density, optical flux
and stress tensor extending Noether's theorem to a different context. We apply
this method to transformations that can be expressed as Hermitian operators and
more specifically we define the operators associated with the optical energy,
spin, linear and angular momentum.",0902.0938v1
2009-03-25,Exchange Constants and Neutron Spectra of Iron Pnictide Materials,"We show that the neutron scattering spectra observed in CaFe$_2$As$_2$ by
Zhao et al (arXiv:0903.2686v1) and the highly unusual spatially anisotropic
exchange constants in the iron pnictides derived by Han et al (Phys. Rev. Lett.
102, 107003 (2009)), using electronic structure calculations, can be explained
by assuming a role for orbital order in these materials. We write down a simple
model Hamiltonian with tertagonal symmetry, whose spin-wave spectra describes
the observed dispersion relations. We further argue that these materials have
orbital selective Mott transition, which is driven by superexchange between
neighboring iron atoms. We suggest that reduced spin and quasi-one
dimensionality and not frustration are responsible for the reduced moments in
these materials.",0903.4408v1
2009-03-27,Quantum transport through a Tonks-Girardeau gas,"We investigate the propagation of spin impurity atoms through a strongly
interacting one-dimensional Bose gas. The initially well localized impurities
are accelerated by a constant force, very much analogous to electrons subject
to a bias voltage, and propagate as a one-dimensional impurity spin wave
packet. We follow the motion of the impurities in situ and characterize the
interaction induced dynamics. We observe a very complex non-equilibrium
dynamics, including the emergence of large density fluctuations in the
remaining Bose gas, and multiple scattering events leading to dissipation of
the impurity's motion.",0903.4823v2
2009-04-24,Magnetic response of the J1-J2 spin Hamiltonian from classical Monte Carlo and Schwinger boson mean field theory,"Magnetic susceptibilities at several potential ordering wave vectors (0,0),
(\pi,0), and (\pi,\pi) are analyzed for the antiferromagnetic J1-J2 spin
Hamiltonian by classical Monte Carlo and Schwinger boson mean field theories
over the parameter range 0 \le 2J_2/J_1 \le 2. We find a nearly linear-T
behavior of the uniform susceptibility that extends up to the temperature scale
of J_1 within both calculation schemes when 2J_2/J_1 is sufficiently removed
from the critical point 2J_2/J_1=1. The window of linear temperature dependence
diminishes as the critical point is approached.",0904.3809v1
2009-05-01,The DSUB$m$ Approximation Scheme for the Coupled Cluster Method and Applications to Quantum Magnets,"A new approximate scheme, DSUB$m$, is described for the coupled cluster
method. We then apply it to two well-studied (spin-1/2 Heisenberg
antiferromagnet) spin-lattice models, namely: the $XXZ$ and the $XY$ models on
the square lattice in two dimensions. Results are obtained in each case for the
ground-state energy, the sublattice magnetization and the quantum critical
point. They are in good agreement with those from such alternative methods as
spin-wave theory, series expansions, quantum Monte Carlo methods and those from
the CCM using the LSUB$m$ scheme.",0905.0078v1
2009-05-29,"Spin-lattice coupling, frustration and magnetic order in multiferroic RMnO3","We have performed high resolution neutron diffraction and inelastic neutron
scattering experiments in the frustrated multiferroic hexagonal compounds RMnO3
(R=Ho, Yb, Sc, Y), which provide evidence of a strong magneto-elastic coupling
in the the whole family. We can correlate the atomic positions, the type of
magnetic structure and the nature of the spin waves whatever the R ion and
temperature. The key parameter is the position of the Mn ions in the unit cell
with respect to a critical threshold of 1/3, which determines the sign of the
coupling between Mn triangular planes.",0905.4824v1
2009-06-04,Integrable and superintegrable systems with spin in three-dimensional Euclidean space,"A systematic search for superintegrable quantum Hamiltonians describing the
interaction between two particles with spin 0 and 1/2, is performed. We
restrict to integrals of motion that are first-order (matrix) polynomials in
the components of linear momentum. Several such systems are found and for one
non-trivial example we show how superintegrability leads to exact solvability:
we obtain exact (nonperturbative) bound state energy formulas and exact
expressions for the wave functions in terms of products of Laguerre and Jacobi
polynomials.",0906.1021v2
2009-10-09,On the Geometry of the Berry-Robbins Approach to Spin-Statistics,"Within a geometric and algebraic framework, the structures which are related
to the spin-statistics connection are discussed. A comparison with the
Berry-Robbins approach is made. The underlying geometric structure constitutes
an additional support for this approach. In our work, a geometric approach to
quantum indistinguishability is introduced which allows the treatment of
singlevaluedness of wave functions in a global, model independent way.",0910.1659v1
2009-10-24,Integral Formula for the Characteristic Cauchy Problem on a curved Background,"We give a local integral formula, valid on general curved space-times, for
the characteristic Cauchy problem for the Dirac equation with arbitrary spin
using the method developed by Friedlander in his book ""the wave equation on a
curved spacetime"" (1975). The results obtained by Penrose in the flat case in
""Null hypersurface initial data for classical fields of arbitrary spin for
general relativity"" (Gen. Rel. Grav 1980) are recovered directly. It is
expected that this method can be used to obtain sharp estimates for the
characteristic Cauchy problem for the Dirac equation.",0910.4620v1
2009-10-26,Creation and detection of skyrmions in a Bose-Einstein condensate,"We present the first experimental realization and characterization of
two-dimensional skyrmions and half-skyrmions in a spin-2 Bose-Einstein
condensate. The continuous rotation of the local spin of the skyrmion through
an angle of pi (and half-skyrmion through an angle of pi/2) across the cloud is
confirmed by the spatial distribution of the three spin states as parameterized
by the bending angle of the ell-vector. The winding number, w = (0, 1, 2), of
the skyrmions is confirmed through matter-wave interference.",0910.4918v1
2009-11-06,Transversity in exclusive meson electroproduction,"In this talk various spin effects in hard exclusive electroproduction of
mesons are briefly reviewed and the data discussed in the light of recent
theoretical calculations within the frame work of the handbag approach. For
electroproduction of positively charged pions it is shown that there is a
strong contribution from photon-pion transitions which can be modeled by the
transversity GPD H_T accompanied by the twist-3 pion wave function.",0911.1231v1
2009-11-13,Constituent Quark Rest Energy and Wave Function Across the Light Cone,"It is shown that for a constituent quark in the intra-nucleon self-consistent
field the spin-orbit interaction lowers the quark rest energy to values
$\sim100$ MeV, which agrees with the DIS momentum sum rule. The possibility of
violation of the spectral condition for the light-cone momentum component of a
bound quark is discussed.",0911.2669v1
2009-12-01,Properties of a diagonal 2-orbital ladder model of the Fe-pnictide superconductors,"We study a diagonal 2-orbital ladder model of the Fe based superconductors
using the density matrix renormalization group method. At half filling, we find
a close competition between a ""spin-striped"" state and a non-collinear
""spin-checkerboard"" state, as well as significant nematic correlations. Upon
finite hole or electron doping, the dominant pairing correlations are found to
have A$_{1,g}$ ($S-$wave) symmetry.",0912.0277v2
2009-12-17,Non-Fermi liquid fixed point for an imbalanced gas of fermions in $1+ε$ dimensions,"We consider a gas of two species of fermions with population imbalance. Using
the renormalization group in $d=1+\epsilon$ dimensions, we show that for
spinless fermions and $\epsilon > 0$ a fixed point appears at finite attractive
coupling where the quasiparticle residue vanishes, and identify this with the
transition to Larkin--Ovchinnikov--Fulde--Ferrell order (inhomogeneous
superconductivity). When the two species of fermions also carry spin degrees of
freedom we find a fixed point indicating a transition to spin density wave
order.",0912.3544v2
2010-01-08,The Two-Nucleon System in Three Dimensions,"A recently developed formulation for treating two- and three-nucleon bound
states in a three-dimensional formulation based on spin-momentum operators is
extended to nucleon-nucleon scattering. Here the nucleon-nucleon t-matrix is
represented by six spin-momentum operators accompanied by six scalar functions
of momentum vectors. We present the formulation and provide numerical examples
for the deuteron and nucleon-nucleon scattering observables. A comparison to
results from a standard partial wave decomposition establishes the reliability
of this new formulation.",1001.1264v1
2010-03-10,Electronic Structure Calculations of Magnetic Exchange Interactions in Europium Monochalcogenides,"Using a combination of local spin density and Hubbard 1 approximations we
study the mechansim of exchange interacion in EuX (X=O, S, Se and Te). We
reproduce known experimental results about bulk modulus, critical pressure for
structural phase transition, magnetic ordering temperature, spin--wave
dispersions as well as momentum-- and tempearuture--dependent band shift. Our
numerical results show pressure induced competition between the hybirization
enhanced exchange interaction and Kondo--like coupling in EuO. Possible ways to
enhance T_{c} are discussed.",1003.2039v1
2010-03-13,Muon-spin-spectroscopy study of the penetration depth of FeTe0.5Se0.5,"Muon spin spectroscopy measurements have been used to study the
superconducting state of FeTe0.5Se0.5. The temperature dependence of the
in-plane magnetic penetration depth, lambda_ab(T), is found to be compatible
with either a two gap s+s wave or an anisotropic s-wave model. The value for
lambda_ab(T) at T=0 K is estimated to be lambda_ab(0)=534(2)nm.",1003.2726v2
2010-04-21,Quasihole condensates in quantum Hall liquids,"We develop a formalism to describe quasihole condensates in quantum Hall
liquids and thereby extend the conformal field theory approach to the full
hierarchy of spin-polarized Abelian states, and to several classes of
non-Abelian hierarchical states. Most previously proposed spin-polarized
quantum Hall wave functions appear as special cases. In this paper we explain
the physical motivations for the approach, and exemplify it by explicitly
constructing the level-two quasihole condensate state at filling fraction 2/3,
and the two level-three states at 5/13 and 5/7 which are built from
combinations of quasielectron and quasihole condensates.",1004.3657v1
2010-05-04,Subleading Spin-Orbit Correction to the Newtonian Potential in Effective Field Theory Formalism,"We study the gravitational dynamics in the early inspiral phase of coalescing
compact binaries using Non-Relativistic General Relativity (NRGR) - an
effective field theory formalism based on the post-newtonian expansion, but
which provides a consistent lagrangian framework and a systematic way in which
to study binary dynamics and gravitational wave emission. We calculate in this
framework the spin-orbit correction to the newtonian potential at 2.5 PN.",1005.0634v2
2010-06-24,Field-induced decay dynamics in square-lattice antiferromagnet,"Dynamical properties of the square-lattice Heisenberg antiferromagnet in
applied magnetic field are studied for arbitrary value S of the spin. Above the
threshold field for two-particle decays, the standard spin-wave theory yields
singular corrections to the excitation spectrum with logarithmic divergences
for certain momenta. We develop a self-consistent approximation applicable for
S >= 1, which avoids such singularities and provides regularized magnon decay
rates. Results for the dynamical structure factor obtained in this approach are
presented for S = 1 and S = 5/2.",1006.4838v2
2010-07-02,Spin-polarizing properties of heterostructures with magnetic nano elements,"The problem of electron resonant and non-resonant scatterings on two
magnetized barriers is studied in the one-dimension. The transfer-matrix is
built up to exactly calculate the coefficient of the electron transmittance
through the system of two magnetic barriers with non-collinear magnetizations.
The polarization of the transmitted electron wave for resonance and
non-resonance transmittances is calculated. The transmittance coefficient and
spin polarization can be drastically enhanced and controlled by the angle
between the barrier magnetizations",1007.0421v1
2010-07-16,Exclusive pion electroproduction and transversity,"In this talk it is reported on an analysis of hard exclusive pion
electroproduction within the handbag approach. Particular emphasis is laid on
single-spin asymmetries. It is argued that a recent HERMES measurement of
asymmetries measured with a transversely polarized target clearly indicate the
occurrence of strong contributions from transversely polarized photons. Within
the handbag approach such gamma_T --> pion transitions are described by the
transversity GPDs accompanied by a twist-3 pion wave function. It is shown that
this approach leads to results on cross sections and single-spin asymmetries in
fair agreement with experiment.",1007.2717v1
2010-07-28,Temporally multiplexed quantum repeaters with atomic gases,"We propose a temporally multiplexed version of the Duan-Lukin-Cirac-Zoller
(DLCZ) quantum repeater protocol using controlled inhomogeneous spin broadening
in atomic gases. A first analysis suggests that the advantage of multiplexing
is negated by noise due to spin wave excitations corresponding to unobserved
directions of Stokes photon emission. However, this problem can be overcome
with the help of a moderate-finesse cavity which is in resonance with Stokes
photons, but invisible to the anti-Stokes photons. Our proposal promises
greatly enhanced quantum repeater performance with atomic gases.",1007.5028v1
2010-07-31,Interferometry with Two Pairs of Spin Correlated Photons,"We propose a new experiment employing two independent sources of spin
correlated photon pairs. Two photons from different unpolarized sources each
pass through a polarizer to a detector. Although their trajectories never mix
or cross they exhibit 4th-order-interference-like correlations when the other
two photons interfere on a beam splitter even when the latter two do not pass
any polarizers at all. A wave packet calculation shows that the experiment
permits a very discriminatory test of hidden variable theories.",1008.0078v2
2010-08-10,ROHF Theory Made Simple,"Restricted open-shell Hartree-Fock (ROHF) theory is formulated as a projected
self-consistent unrestricted HF (UHF) model by mathematically constraining spin
density eigenvalues. The resulting constrained UHF (CUHF) wave function is
identical to that obtained from Roothaan's effective Fock operator. Our
$\alpha$ and $\beta$ CUHF Fock operators are parameter-free and have canonical
orbitals and orbital energies that are physically meaningful as in UHF, except
for eliminating spin contamination. The present approach removes ambiguities in
ROHF orbital energies and the non-uniqueness of methods that build upon them.
We present benchmarks to demonstrate CUHF physical correctness and good
agreement with experimental results.",1008.1607v1
2010-08-31,NMR evidence of strong-correlated superconductivity in LiFeAs: tuning toward an SDW ordering,"In this letter, we reported the results of NMR study on LiFeAs single
crystals. We find a strong evidence of the low temperature spin fluctuations;
by changing sample preparation conditions, the system can be tuned toward an
spin-density-wave (SDW) quantum-critical point. The detection of an
interstitial Li(2) ion, possibly locating in the tetrahedral hole, suggests
that the off-stoichiometry and/or lattice defect can probably account for the
absence of the SDW ordering in LiFeAs. These facts show that LiFeAs is a
strongly correlated system and the superconductivity is likely originated from
the SDW fluctuations.",1008.5199v1
2010-10-28,Vortex Collapse for the L2-Critical Nonlinear Schrödinger Equation,"The focusing cubic nonlinear Schr\""odinger equation in two dimensions admits
vortex solitons, standing wave solutions with spatial structure, Qm(r,theta) =
e^{i m theta} Rm(r). In the case of spin m = 1, we prove there exists a class
of data that collapse with the vortex soliton profile at the log-log rate. This
extends the work of Merle and Rapha\""el, (the case m = 0,) and suggests that
the L2 mass that may be concentrated at a point during generic collapse may be
unbounded. Difficulties with m >= 2 or when breaking the spin symmetry are
discussed.",1010.5864v1
2010-11-11,Heavy Quark Spin Symmetry and Heavy Baryons: Electroweak Decays,"Heavy quark spin symmetry is discussed in the context of single and doubly
heavy baryons. A special attention is paid to the constraints/simplifications
that this symmetry imposes on the non-relativistic constituent quark model wave
functions and on the b->c semileptonic decays of these hadrons.",1011.2596v1
2010-12-08,Optically erasing disorder in semiconductor microcavities with dynamic nuclear polarization,"The mean squared value of the photonic disorder is found to be reduced by a
factor of 100 in a typical GaAs based microcavity, when exposed to a circularly
polarized continuous wave optical pump without any special spatial patterning.
Resonant excitation of the cavity mode excites a spatially non-uniform
distribution of spin-polarized electrons, which depends on the photonic
disorder profile. Electrons transfer spin to nuclei via the hyperfine contact
interaction, inducing a long-living Overhauser magnetic field able to modify
the potential of exciton-polaritons.",1012.1732v2
2011-01-18,Temperature-dependent spin resonance energy in iron pnictides and multiband s\pm Eliashberg theory,"The phenomenology of iron-pnictides superconductors can be explained in the
framework of a three bands s\pm wave Eliashberg theory with only two free
parameters plus a feedback effect i.e. the effect of the condensate on the
antiferromagnetic spin fluctuactions responsible of the superconductivity in
these compounds. I have examined the experimental data of four materials:
LaFeAsO1-xFx, SmFeAsO1-xFx, Ba1-xKxFe2As2, and Ba(FexCo1-x)2As2 and I have
found that it is possible to reproduce the experimental critical temperature
and gap values in a moderate strong-coupling regime: ltot about 1.7-2.0.",1101.3473v2
2011-02-02,Integrable quantum spin chains and their classical continuous counterparts,"We present certain classical continuum long wave-length limits of prototype
integrable quantum spin chains, and define the corresponding construction of
classical continuum Lax operators. We also provide two specific examples, i.e.
the isotropic and anisotropic Heisenberg models.",1102.0425v1
2011-02-08,Coupling of replicate order-parameters in incommensurate multiferroics,"The specific properties of incommensurate multiferroic phases resulting from
the coupling of order-parameter replicates are worked out using the
illustrative example of iron vanadate. The dephasing between the
order-parameter copies induces an additional broken symmetry phase
corresponding to the lowest symmetry of the system and varies critically at the
transition to the multiferroic phase. It reflects the temperature dependence of
the angle between paired spins in the antiferromagnetic spiral structure.
Expressing the transition order-parameters in terms of spin-density waves
allows showing that isotropic exchange interactions contribute to the
stabilization of the ferroelectric phase.",1102.1575v1
2011-02-22,Quantum optomechanics of a Bose-Einstein Antiferromagnet,"We investigate the cavity optomechanical properties of an antiferromagnetic
Bose-Einstein con- densate, where the role of the mechanical element is played
by spin-wave excitations. We show how this system can be described by a single
rotor that can be prepared deep in the quantum regime under realizable
experimental conditions. This system provides a bottom-up realization of
dispersive rotational optomechanics, and opens the door to the direct
observation of quantum spin fluctuations.",1102.4583v2
2011-04-14,Chirality waves in two-dimensional magnets,"We theoretically show that moderate interaction between electrons confined to
move in a plane and localized magnetic moments leads to formation of a
noncoplanar magnetic state. The state is similar to the skyrmion crystal
recently observed in cubic systems with the Dzyaloshinskii-Moriya interaction;
however, it does not require spin-orbit interaction. The non-coplanar magnetism
is accompanied by the ground-state electrical and spin currents, generated via
the real-space Berry phase mechanism. We examine the stability of the state
with respect to lattice discreteness effects and the magnitude of magnetic
exchange interaction. The state can be realized in a number of transition metal
and magnetic semiconductor systems.",1104.2673v2
2011-04-15,The ground state energy of the frustrated ferromagnetic spin chain near the transition point,"The one-dimensional quantum spin-1/2 model with nearest-neighbor
ferromagnetic and next-nearest-neighbor antiferromagnetic interaction is
considered. The Hamiltonian is first bosonized by using the linear spin wave
approximation, and then is treated by using the Green's function approach. An
integral expression of the quantum correction to the classical ground state
energy is derived. The critical behavior of the ground state energy in the
vicinity of the transition point from the ferromagnetic to the singlet ground
state is analyzed by numerical calculation, and the result is $-8\gamma^2$.",1104.2946v1
2011-05-12,Double-$\it q$ Order in a Frustrated Random Spin System,"We use the three-dimensional Heisenberg model with site randomness as an
effective model of the compound Sr(Fe$_{1-x}$Mn$_x$)O$_2$. The model consists
of two types of ions that correspond to Fe and Mn ions. The nearest-neighbor
interactions in the ab-plane are antiferromagnetic. The nearest-neighbor
interactions along the c-axis between Fe ions are assumed to be
antiferromagnetic, whereas other interactions are assumed to be ferromagnetic.
From Monte Carlo simulations, we confirm the existence of the
double-$\boldsymbol{q}$ ordered phase characterized by two wave numbers,
$(\pi\pi\pi)$ and $(\pi\pi0)$. We also identify the spin ordering pattern in
the double-$\boldsymbol{q}$ ordered phase.",1105.2455v1
2011-06-08,Thermal spin-transfer in Fe-MgO-Fe tunnel junctions,"We compute thermal spin transfer torques (TST) in Fe-MgO-Fe tunnel junctions
using a first principles wave function-matching method. At room temperature,
the TST in a junction with 3 MgO monolayers amounts to 10^-7J/m^2/K, which is
estimated to cause magnetization reversal for temperature differences over the
barrier of the order of 10 K. The large TST can be explained by multiple
scattering between interface states through ultrathin barriers. The angular
dependence of the TST can be very skewed, possibly leading to thermally induced
high-frequency generation.",1106.1572v2
2011-07-04,Coupled-cluster calculations for the ground- and excited-states of the spin-half XXZ model,"The coupled-cluster method is applied to the spin-1/2 antiferromagnetic XXZ
model on a square lattice by employing an approximation which contains two-body
long-range correlations and high-order four-body local correlations.
Improvement is found for the ground-state energy, sublattice magnetization, and
the critical anisotropy when comparing with the approximation including the
two-body correlations alone. We also obtain the full excitation spectrum which
is in good agreement with the quantum Monte Carlo results and the high-order
spin-wave theory.",1107.0599v3
2011-07-18,Molecular-spin dynamics study of electromagnons in multiferroic RMn$_2$O$_5$,"We investigate the electromagnon in magnetoferroelectrics RMn$_2$O$_5$ using
combined molecular-spin dynamics simulations. We identify the origin of the
electromagnon modes observed in the optical spectra and reproduce the most
salient features of the electromagnon in these compounds. We find that the
electromagnon frequencies are very sensitive to the magnetic wave vector along
the $a$ direction. We further investigate the electromagnon in magnetic field.
Although the modes frequencies change significant under magnetic field, the
static dielectric constant electromagnon does not change much in the magnetic
field.",1107.3349v1
2011-08-09,Superconductivity and antiferromagnetism as interfering orders in organic conductors,"Superconductivity in the Bechgaard salts series of quasi-one-dimensional
organic conductors occurs on the verge of spin-density-wave ordering when
hydrostatic pressure is applied. The sequence of instabilities is intimately
connected to normal state anomalies in various quantities like the temperature
dependence of electrical transport and nuclear spin-lattice relaxation rate. We
discuss how such a connection takes its origin in the interference between the
different pairing mechanisms responsible for antiferromagnetism and
superconductivity, a duo that can be comprehended in terms of a weak coupling
renormalization group theory. The recent developments along this line of though
are presented in relation to experiments.",1108.1842v1
2011-09-08,Particle with spin 2 and anomalous magnetic moment in external electromagnetic and gravitational fields,"Tensor 50-component form of the first order relativistic wave equation for a
particle with spin 2 and anomalous magnetic moment is extended to the case of
an arbitrary curved space-time geometry. An additional parameter considered in
the presence of only electromagnetic field as related to anomalous magnetic
moment, turns to determine additional interaction terms with external
geometrical background through Ricci R_{kl} and Riemann R_{klmn} tensors.",1109.1715v1
2011-09-15,Propagation of local excitations through strongly correlated quantum chains,"The propagation of an external transverse magnetic signal acting locally on a
1d chain of spins generates a disturbance which runs through the system. This
quantum effect can be interpreted as a classical traveling wave which contains
a superposition of a large set of frequencies depending on the size of the
chain. Its local amplitude fixes the size of the z-component of the spins at
any location in the chain. The average and maximum value of the group velocity
are determined and compared with the transmission velocity fixed by the
Lieb-Robinson upper bound inequality.",1109.3392v1
2011-10-09,Spin 1/2 Particle in the Field of the Dirac String on the background of Anti de Sitter Space-Time,"The Dirac monopole string is specified for anti de Sitter cosmological model.
Dirac equation for spin 1/2 particle in presence of this monopole has been
examined on the background of anti de Sitter space-time in static coordinates.
Instead of spinor monopole harmonics, the technique of Wigner D-functions is
used. After separation of the variables radial equations have been solved
exactly in terms of hypergeometric functions. The complete set of spinor wave
solutions has been constructed, the most attention is given to treating the
states of minimal values for total moment quantum number j_{min}. At all values
of j, the energy spectrum is discrete.",1110.1806v1
2011-10-18,Momentum dependent ultrafast electron dynamics in antiferromagnetic EuFe2As2,"Employing the momentum-sensitivity of time- and angle-resolved photoemission
spectroscopy we demonstrate the analysis of ultrafast single- and many-particle
dynamics in antiferromagnetic EuFe2As2. Their separation is based on a
temperature-dependent difference of photo-excited hole and electron relaxation
times probing the single particle band and the spin density wave gap,
respectively. Reformation of the magnetic order occurs at 800 fs, which is four
times slower compared to electron-phonon equilibration due to a smaller
spin-dependent relaxation phase space.",1110.3938v2
2011-11-04,Rashba diamond in an Aharonov-Casher ring,"Spin interference due to Rashba spin-orbit interaction (SOI) in a ballistic
two-dimensional electron gas (2DEG) ring conductor submitted to a bias voltage
is investigated theoretically. We calculate the scattering matrices and
differential conductance with lead-ring junction coupling as an adjustable
parameter. Due to the interference of electronic waves traversing the ring, the
differential conductance modulated by both bias voltage and SOI exhibits a
diamond-shaped pattern, thus termed as \ti{Rashba diamond}. This feature offers
a supplementary degree of freedom to manipulate phase interference.",1111.1244v1
2011-11-17,Stripes and superconductivity in the two-dimensional self-consistent model,"We found solutions of the Bogoliubov-de Gennes equations for the
two-dimensional self-consistent model of superconductors with $d_{x^2-y^2}$
symmetry of the order parameter, taking into account spin and charge
distributions. Analytical solutions for spin-charge density wave phases in the
absence of the superconductivity (""stripe"" and ""checkerboard"" structures) are
presented. Analytical solutions for coexisting superconductivity and stripes
are found.",1111.4139v2
2011-11-23,Dark solitons in ferromagnetic chains with first- and second-neighbor interactions,"We study the ferromagnetic spin chain with both first- and second-neighbor
interactions. We obtained the condition for the appearance and stability of
bright and dark solitons for arbitrary wave number inside the Brillouin zone.
The influence of the second-neighbor interaction and the anisotropy on the
soliton properties is considered. The scattering of dark solitons from point
defects in the discrete spin chain is investigated numerically.",1111.5477v1
2011-12-24,Time-dependent density functional theory for open spin chains,"The application of methods of time-dependent density functional theory
(TDDFT) to systems of qubits provided the interesting possibility of simulating
an assigned Hamiltonian evolution by means of an auxiliary Hamiltonian having
different two-qubit interactions and hence a possibly simpler wave function
evolution. In this note we extend these methods to some instances of Lindblad
evolution of a spin chain.",1112.5731v1
2012-01-11,Frequency domain studies of current-induced magnetization dynamics in single magnetic-layer nanopillars,"Spin transfer torque-induced high-frequency dynamics of single thin
cobalt-layer nanopillars of circular and elliptical shape have been observed
directly. Two types of precessional modes can be identified as a function of
magnetic field perpendicular to the layer plane, excited for negative current
polarity only. They are assigned to vortex-core and transverse spin-wave
excitations, which corroborate recent model predictions. The observed narrow
linewidth of 4 MHz at room temperature indicates the high coherence of the
magnetic excitations.",1201.2268v1
2012-04-04,Calculation of the phase of hidden rotating antiferromagnetic order,"The phase of the rotating order parameter in rotating antiferromagnetism is
calculated using a combination of mean-field theory and Heisenberg equation.
This phase shows a linear time dependence, which allows us to interpret
rotating antiferromagnetism as a synchronized Larmor-like precession of all the
spins in the system or as an unusual ${\bf q}=(\pi,\pi)$ spin-wave around a
zero local magnetization. We discuss implications for the pseudogap state of
high-$T_C$ superconducting materials. Rotating antiferromagnetism has been
proposed to model the pseudogap state in these materials.",1204.0977v1
2012-04-18,Collective excitations and marginal stability of quantum Ising spin glasses,"We solve the Sherrington-Kirkpatrick (SK) model in a transverse field \Gamma
deep in its quantum glass phase at zero temperature. We show that the glass
phase is critical everywhere, exhibiting collective excitations with a gapless
Ohmic spectral function. Using an effective potential approach, we interpret
the latter as being due to disordered spin waves which behave as weakly
coupled, underdamped harmonic oscillators. In the limit of small transverse
field the low frequency tail of the spectrum tends to a universal,
\Gamma-independent limit.",1204.4156v2
2012-05-01,Quasi-plane waves for spin 1 field in Lobachevsky space and a generalized helicity operator,"Spin 1 particle is investigated in 3-dimensional curved space of constant
negative curvature. An extended helicity operator is defined and the variables
are separated in a tetrad-based 10-dimensional Duffin--Kemmer equation in quasi
Cartesian coordinates. The problem is solved exactly in hypergeometric
functions, the quantum states are determined by three quantum numbers. It is
shown that Lobachevsky geometry acts effectively as a medium with simple
reflecting properties. Transition to a massless case of electromagnetic field
is performed.",1205.0150v1
2012-05-06,Nonrelativistic approximation for quasi-planes waves of a spin 1 particle in Lobachevsky space,"Spin 1 particle in Pauli approximation is investigated on the background of
the curved space of constant negative curvature, Lobachevsky space.
Nonrelativistic approximation is performed in the system of 10 equations
resulted from separating the variables in Duffin-Kemmer equation specified in
quasi-cartesian coordinates. The problem is solved exactly in Bessel functions,
the quantum states are determined by four quantum numbers. The treatment is
substantially based on the use of a generalized helicity operator in
Lobachevsky space model.",1205.1224v1
2012-07-30,Half-metallic magnetization plateaux,"We propose a novel interaction-based route to half-metal state for
interacting electrons on two-dimensional lattices. Magnetic field applied
parallel to the lattice is used to tune one of the spin densities to a
particular commensurate with the lattice value in which the system
spontaneously `locks in' via van Hove enhanced density wave state. Electrons of
opposite spin polarization retain their metallic character and provide for the
half-metal state which, in addition, supports magnetization plateau in a finite
interval of external magnetic field. Similar half-metal state is realized in
the finite-U Hubbard model on a triangular lattice at 1/3 of the maximum
magnetization.",1207.7124v1
2012-10-11,Decays and productions via bottomonium for Z_b resonances and other B anti-B molecules,"We discuss decays and productions for the possible molecular states formed by
bottom mesons B (B*) and anti-B (anti-B*). The twin resonances found by Belle,
Zb(10610) and Zb(10650), are such candidates. The spin wave functions of the
molecular states are rearranged into those of heavy and light spin degrees of
freedom by using the re-coupling formulae of angular momentum. By applying the
heavy quark symmetry we derive model independent relations among various decay
and production rates, which can be tested in experiments.",1210.3170v2
2012-12-05,Rashba spin-orbit interaction in a circular quantum ring in the presence of a magnetic field,"Exact wave functions and energy levels are obtained for an electron in a
two-dimensional semiconductor circular quantum ring with a confining potential
of finite depth in the presence of both an external magnetic field and the
Rashba spin-orbit interaction.",1212.1014v1
2013-01-08,Normal and superconducting properties of LiFeAs explained in the framework of four-band Eliashberg Theory,"In this paper we propose a model to reproduce superconductive and normal
properties of the iron pnictide LiFeAs in the framework of the four-band spm
wave Eliashberg theory. A confirmation of the multiband nature of the system
rises from the experimental measurements of the superconductive gaps and
resistivity as function of temperature. We found that the most plausible
mechanism is the antiferromagnetic spin fluctuation and the estimated values of
the total antiferromagnetic spin fluctuation coupling constant in the
superconductive and normal state are lambda{tot}=2.00 and lambda{tot,tr}=0.77.",1301.1542v1
2013-01-15,Manipulation of Ferromagnets via the Spin-Selective Optical Stark Effect,"We investigate the non-resonant all-optical switching of magnetization. We
treat the inverse Faraday effect (IFE) theoretically in terms of the
spin-selective optical Stark effect for linearly or circularly polarized light.
In the dilute magnetic semiconductors (Ga,Mn)As, strong laser pulses below the
band gap induce effective magnetic fields of several teslas in a direction
which depends on the magnetization and light wave vectors. Our theory
demonstrates that the polarized light catalyzes the angular momentum transfer
between lattice and the magnetization.",1301.3481v2
2013-03-07,On Integrating the Left-Flat Vacuum Einstein Equations,"Considering the spin-coefficient version of the left-flat vacuum Einstein
equations, all but one of the fifty equations can be explicitly integrated via
the introduction of five spin-weight s=-2 complex potentials. The final
equation is a non-linear wave equation for the last of the potentials.
Solutions to this equation determine solutions for the entire system. Solutions
for several special cases are obtained",1303.1807v2
2013-03-22,"Electronic properties of AlN crystal doped with Cr, Mn and Fe","The spin-resolved electronic energy band spectra, as well as partial and
total density of electronic states of the crystal AlN, doped with Cr, Mn and
Fe, have been evaluated within the projector augmented waves (PAW) approach by
means of the ABINIT code. The Hartree-Fock exchange for correlated electrons is
used to describe the correlated orbitals in the PAW framework. The calculated
one-electron energies for electrons of spin up and down are very different. We
have found that all the considered crystals are ferromagnetic.",1303.5544v1
2013-04-12,Metaspin and dirishonic dark matter,"The antisymmetry requirement of rishon bound state wave functions suggests a
new rishon quantum number called M spin. From M spin conservation and the
Nussinov-Weingarten-Witten theorem we predict the existence of a stable
pseudoscalar dirishonic meson, called zeta, that is lighter than the lightest
neutrino. Its mass is estimated as m(zeta) = 10^{-9} eV. This particle could
make up the major part of cold dark matter in the Universe.",1304.3685v1
2013-04-25,Properties of Odd-Frequency Superconductivity in Antiferromagnetic Ordered State,"We investigate properties below T_c of odd-frequency pairing which is
realized by antiferromagnetic critical spin fluctuations or spin wave modes. It
is shown that \Delta(\epsilon_n) becomes maximum at finite \epsilon_n, and
\Delta(\pi T) becomes maximum at finite T. Implications of the present results
to the experimental results of CeCu_2Si_2 and CeRhIn_5 are given.",1304.6837v1
2013-07-25,Vector boson excitations near deconfined quantum critical points,"We show that the N\'eel states of two-dimensional antiferromagnets have low
energy vector boson excitations in the vicinity of deconfined quantum critical
points. We compute the universal damping of these excitations arising from
spin-wave emission. Detection of such a vector boson will demonstrate the
existence of emergent topological gauge excitations in a quantum spin system.",1307.6860v1
2013-08-06,A toy model for the pseudogap state of cuprates,"A toy model is developed to capture ""dance of pre-formed pairs"" in the
pseudogap state of high temperature cuprate superconductors. The model is a
crude description of a hypothetical situation in which spin-driven spatial
organization of the pre-formed pairs is analyzed. Within a mean-field theory (a
slight generalization of Bragg-Williams theory) we examined the behaviour of
heat capacity and an ""order parameter"" which captures the short range
correlations between the pre-formed pairs. Below a transition temperature these
short range correlations enhance and leads to a long range order (spin-density
wave). This is examined through the breakdown of statistical independence.",1308.1189v1
2013-10-04,What do kets represent?,"It is usually assumed that a ket represents the state of an actually existing
particle. But one can show there is no evidence for particles. The
particle-like properties of mass, spin and charge, as well as particle-like
trajectories, the photoelectric effect, and localized effects from spread-out
wave functions can be explained using quantum mechanics alone. It is therefore
proposed instead that kets represent particle-like solutions to a
pre-representational linear partial differential equation which has Poincar\'e
and internal symmetries. This equation underlies the completely
representational character, including mass, spin, charge, internal symmetries,
and symmetric and antisymmetric statistics, of current quantum mechanics.",1310.1295v1
2013-10-05,Transversity in exclusive vector-meson leptoproduction,"The role of transversity or helicity-flip generalized parton distributions
(GPDs) in leptoproduction of vector mesons is investigated within the framework
of the handbag approach. The transversity GPDs in combination with twist-3
meson wave functions, occur in the amplitudes for transitions from a
transversely polarized virtual photon to a longitudinal polarized vector meson.
The importance of the transversity GPDs can be examined in some of the spin
density matrix elements and in transverse target spin asymmetries. Using
suitable parametrizations of both helicity-flip and non-flip GPDs, which are
essentially taken from our previous papers, we estimate these observables and
compare the results with available data.",1310.1472v1
2013-10-25,Microscopic origin of the relativistic splitting of surface states,"Spin-orbit splitting of surface states is analyzed within and beyond the
Rashba model using as examples the (111) surfaces of noble metals, Ag2Bi
surface alloy, and topological insulator Bi2Se3. The ab initio analysis of
relativistic velocity proves the Rashba model to be fundamentally inapplicable
to real crystals. The splitting is found to be primarily due to a spin-orbit
induced in-plane modification of the wave function, namely to its effect on the
nonrelativistic Hamiltonian. The usual Rashba splitting -- given by charge
distribution asymmetry -- is an order of magnitude smaller.",1310.6893v2
2013-11-27,A new representation for two- and three-point correlators of operators from sl(2) sector,"We construct a new representation for two- and three-point correlators of
operators from sl(2) sector of planar N = 4 SYM. The spin and twist of
operators are arbitrary. We start with the correlation function of light-ray
operators and carry out a projection to particular local operators using the
method of Separated Variables. With the same calculation we obtain polynomials
which are dual to wave functions of sl(2,R) spin-chain.",1311.6957v2
2014-01-02,Relativistic spinor equation of photon,"In this paper, we have proposed the spiron equation of free and non-free
photon, and give the spin operator and spin wave function of photon. We
calculate the helicity of photon and prove there are left-handed and
right-handed photon. By the spiron equation of non-free photon, we can study
the quantum property of photon in medium, which can be used in quantum optics,
photonic crystals and so on.",1401.0555v1
2014-03-27,"Pseudospin and Spin Symmetric Solutions of Dirac Equation: Hellmann Potential, Wei Hua Potential, Varshni Potential","Approximate analytical solutions of the Dirac equation are obtained for the
Hellmann potential, Wei Hua potential and Varshni potential with any
$\kappa$-value for the cases having the Dirac equation pseudospin and spin
symmetries. Closed forms of the energy eigenvalue equations and the spinor wave
functions are obtained by using the Nikiforov-Uvarov method and some tables are
given to see the dependence of the energy eigenvalues on different quantum
number pairs ($n, \kappa$).",1403.6936v1
2014-04-21,Nuclear tetrahedral states and high-spin states studied using quantum number projection method,"We have recently developed an efficient method of performing the full quantum
number projection from the most general mean-field (HFB type) wave functions
including the angular momentum, parity as well as the proton and neutron
particle numbers. With this method, we have been investigating several nuclear
structure mechanisms. In this report, we discuss the obtained quantum
rotational spectra of the tetrahedral nuclear states formulating certain
experimentally verifiable criteria, of the high-spin states, focussing on the
wobbling- and chiral-bands, and of the drip-line nuclei as illustrative
examples.",1404.5090v1
2014-05-18,Spin light of electron in dense neutrino fluxes,"An electron motion in a dense neutrino flux is investigated. The Dirac
equation exact solutions for the electron energy and wave function in this
external environment are obtained. On this basis we predict the existence of an
electromagnetic radiation that can be emitted by electrons in dense neutrino
fluxes. We term this phenomenon ""the spin light of electron in dense neutrino
flux"" ($SLe_{\nu}$). The main properties of the $SLe_{\nu}$ are studied. We
argue that the $SLe_{\nu}$ in dense neutrino fluxes should have important
consequences in astrophysics and for supernovae processes in particular.",1405.6598v1
2014-08-20,Vortex Core Structure in Multilayered Rashba Superconductors,"We numerically study the electronic structure of a single vortex in two
dimensional superconducting bilayer systems within the range of the mean-field
theory. The lack of local inversion symmetry in the system is taken into
account through the layer dependent Rashba spin-orbit coupling. The spatial
profiles of the pair potential and the local quasiparticle density of states
are calculated in the clean spin-singlet superconductor on the basis of the
quasiclassical theory. In particular, we discuss the characteristic core
structure in the pair-density wave state, which is spatially modulated exotic
superconducting phase in a high magnetic field.",1408.4550v1
2014-10-03,Dynamics of a vortex dipole across a magnetic phase boundary in a spinor Bose-Einstein condensate,"Dynamics of a vortex dipole in a spin-1 Bose-Einstein condensate in which
magnetic phases are spatially distributed is investigated. When a vortex dipole
travels from the ferromagnetic phase to the polar phase, or vice versa, it
penetrates the phase boundary and transforms into one of the various spin
vortex dipoles, such as a leapfrogging ferromagnetic-core vortex dipole and a
half-quantum vortex dipole. Topological connections of spin wave functions
across the phase boundary are discussed.",1410.0743v1
2015-01-19,Wigner translations and the observer-dependence of the position of masslesss spinning particles,"The Wigner little group for massless particles is isomorphic to the Euclidean
group ${\rm SE}(2)$. Applied to momentum eigenstates, or to infinite plane
waves, the Euclidean ""Wigner translations"" act as the identity. We show that
when applied to finite wavepackets the translation generators move the packet
trajectory parallel to itself through a distance proportional to the particle's
helicity. We relate this effect to the Hall effect of light and to the
Lorentz-frame dependence of the position of a massless spinning particle.",1501.04586v1
2015-02-02,Quantum Pairwise Symmetry: Applications in 2D Shape Analysis,"A pair of rooted tangents -- defining a quantum triangle -- with an
associated quantum wave of spin 1/2 is proposed as the primitive to represent
and compute symmetry. Measures of the spin characterize how ""isosceles"" or how
""degenerate"" these triangles are -- which corresponds to their mirror or
parallel symmetry. We also introduce a complex-valued kernel to model
probability errors in the parameter space, which is more robust to noise and
clutter than the classical model.",1502.00561v2
2015-02-17,Direct Exchange versus the indirect Exchange of the t-J Hamiltonian in HTSC Cuprates,"The direct exchange integral and the transfer integral are calculated for the
anti-bonding wave-function of the HTSC cuprates. The direct exchange integral
yields a value three times larger than the indirect exchange of the t-J
Hamiltonian. It also predicts positive exchange energy for neighboring parallel
spins, contrary to the prediction of zero energy by the t-J Hamiltonian. A
modified t-J Hamiltonian is proposed, and the implications of the results are
discussed.",1502.05353v3
2015-04-24,Non-equilibrium quasi-long-range order of driven random field O(N) model,"We investigate three-dimensional O(N) spin models driven with a uniform
velocity over a random field. Within a spin-wave approximation, it is shown
that in the strong driving regime the model with N=2 exhibits a
quasi-long-range order in which the spatial correlation function decays in a
power-law form. Furthermore, for the cases that N=2 and 3, we numerically
demonstrate a non-equilibrium phase transition between the quasi-long-range
order phase and the disordered phase, which turns out to resemble the
Kosterlitz-Thouless transition in the two-dimensional pure XY model in
equilibrium.",1504.06411v2
2015-05-24,3D transformation for rotating frames and temporal behavior of spin in rotating electromagnetic fields,"The Dirac equation is invariant under rotations with a constant frequency and
invariable cylindrical radius. 3D transformation for rotating frames is found
with help of this invariance. Exact localized solutions of the Dirac equation
in the field of a traveling circularly polarized electromagnetic wave and
constant magnetic field exist and possess unusual properties. Temporal changes
of spin pertaining to the solutions are studied.",1505.07064v2
2015-06-30,Spin-wave localization in disordered magnets,"The effect of disorder on magnonic transport in low-dimensional magnetic
materials is studied in the framework of a classical spin model. Numerical
investigations give insight into scattering properties of the systems and show
the existence of Anderson localization in 1D and weak localization in 2D,
potentially affecting the functionality of magnonic devices.",1506.09045v2
2015-07-19,Scattering-Free Optical Edge States between Heterogeneous Photonic Topological Insulators,"We propose a set of three simple photonic platforms capable of emulating
quantum topologically insulating phases corresponding to Hall, spin-Hall, and
valley-Hall effects. It is shown that an interface between any two of these
heterogeneous photonic topological insulators supports scattering-free surface
states. Spin and valley degrees of freedom characterizing such topologically
protected surface waves determine their unique pathways through complex
photonic circuits comprised of multiple heterogeneous interfaces.",1507.05256v1
2015-08-17,Evidence for resonant scattering of electrons by spin fluctuations in $LaNiO_3/LaAlO_3$ heterostructures grown by pulsed laser deposition,"We present measurements of resistivity $\rho$ in highly oriented $LaNiO_3$
films grown on $LaAlO_3$ substrates by using a pulsed laser deposition
technique. The experimental data are found to follow a universal $\rho (T)
\propto T^{3/2}$ dependence for the entire temperature interval ($20K<T<300K$).
The observed behavior has been attributed to a resonant scattering of electrons
on antiferromagnetic fluctuations (with a characteristic energy $\hbar \omega
_{sf}\simeq 2.1meV$) triggered by spin-density wave propagating through the
interface boundary of $LaNiO_3/LaAlO_3$ sandwich.",1508.04063v1
2015-08-26,"Phase diagram of one-, two-, and three-dimensional quantum spin systems derived from entanglement properties","We study the bipartite entanglement per bond to determine characteristic
features of the phase diagram of various quantum spin models in different
spatial dimensions. The bipartite entanglement is obtained from a tensor
network representation of the ground state wave-function. Three spin-1/2 models
(Ising, XY, XXZ, all in a transverse field) are investigated. Imaginary-time
evolution (TEBD in 1D, `simple update' in 2D and 3D) is used to determine the
ground states of these models. The phase structure of the models is discussed
for all three dimensions.",1508.06508v1
2015-11-16,Analysis of half-spin particle motion in Reissner-Nordstroem and Schwarzschild fields by means of the method of effective potentials,"The paper presents the analysis of effective potentials of Dirac equations in
Schwarzschild and Reissner-Nordstroem fields. It is shown that in the majority
of the explored cases the condition of a particle ""fall"" to appropriate event
horizons is fulfilled. The exception is one of the solutions with normalizable
wave functions for the Reissner-Nordstroem extreme field, for which the
existence of the stationary bound state of half-spin particles is possible
inside the event horizon.",1511.05058v1
2015-11-17,A Corpuscular Picture of Electrons in Chemical Bond,"We introduce a theory of chemical bond with a corpuscular picture of
electrons. It employs a minimal set of localized electron wave packets with
'floating and breathing' degrees of freedom and the spin-coupling of
non-orthogonal valence-bond theory. It accurately describes chemical bonds in
ground and excited states of spin singlet and triplet, in a distinct manner
from conventional theories, indicating potential for establishing a dynamical
theory of electrons in chemical bonds.",1511.05331v1
2016-01-13,Wigner distributions and orbital angular momentum of a proton,"The Wigner distributions for u and d quarks in a proton are calculated using
the light front wave functions (LFWFs) of the scalar quark-diquark model for
nucleon constructed from the soft-wall AdS/QCD correspondence. We present a
detail study of the quark orbital angular momentum(OAM) and its correlation
with quark spin and proton spin. The quark density distributions, considering
the different polarizations of quarks and proton, in transverse momentum plane
as well as in transverse impact parameter plane are presented for both u and d
quarks.",1601.03217v2
2016-02-05,Magnetic order and spin excitations in the Kitaev--Heisenberg model on the honeycomb lattice,"We consider the quasi-two-dimensional pseudo-spin-1/2 Kitaev - Heisenberg
model proposed for A2IrO3 (A=Li, Na) compounds. The spin-wave excitation
spectrum, the sublattice magnetization, and the transition temperatures are
calculated in the random phase approximation (RPA) for four different ordered
phases, observed in the parameter space of the model: antiferomagnetic, stripe,
ferromagnetic, and zigzag phases. The N\'{e}el temperature and temperature
dependence of the sublattice magnetization are compared with the experimental
data on Na2IrO3.",1602.01961v1
2016-04-28,Energy repartition in the nonequilibrium steady state,"The concept of temperature in nonequilibrium thermodynamics is an outstanding
theoretical issue. We propose an energy repartition principle that leads to a
spectral (mode-dependent) temperature in steady-state nonequilibrium systems.
The general concepts are illustrated by analytic solutions of the classical
Heisenberg spin chain connected to Langevin heat reservoirs with arbitrary
temperature profiles. Gradients of external magnetic fields are shown to
localize spin waves in a Wannier-Zeemann fashion, while magnon interactions
renormalize the spectral temperature. Our generic results are applicable to
other thermodynamic systems such as Newtonian liquids, elastic solids, and
Josephson junctions.",1604.08369v2
2016-10-07,Magnonic black holes,"We show that the interaction between spin-polarized current and magnetization
dynamics can be used to implement black-hole and white-hole horizons for
magnons - the quanta of oscillations in the magnetization direction in magnets.
We consider three different systems: easy-plane ferromagnetic metals, isotropic
antiferromagnetic metals, and easy-plane magnetic insulators. Based on
available experimental data, we estimate that the Hawking temperature can be as
large as 1 K. We comment on the implications of magnonic horizons for spin-wave
scattering and transport experiments, and for magnon entanglement.",1610.02313v1
2017-07-14,Analytic approach to pion-kaon scattering and strange resonances,"We review our analysis of $\pi K$ scattering using forward dispersion
relations. The method yields a set of simple parameterizations that are
compatible with forward dispersion relations up to 1.6 GeV while still
describing the data. Once the partial waves are obtained, we calculate the
poles in the complex plane by means of Pad\'e approximants, thus avoiding a
particular model for the pole parameterization. The resonances calculated below
1.8 GeV are the much debated scalar $\kappa$-meson, nowadays known as
$K_0^*(800)$, the scalar $K_0^*(1430)$, the $K^*(892)$ and $K_1^*(1410)$
vectors, the spin-two $K_2^*(1430)$ as well as the spin-three $K^*_3(1780)$.",1707.04534v1
2017-07-27,Ultrafast nanoscale magnetic switching via intense picosecond electron bunches,"The magnetic field associated with a picosecond intense electron pulse is
shown to switch locally the magnetization of extended films and nanostructures
and to ignite locally spin waves excitations. Also, topologically protected
magnetic textures such as skyrmions can be imprinted swiftly in a sample with a
residual Dzyaloshinskii-Moriya spin-orbital coupling. Characteristics of the
created excitations such as the topological charge or the width of the magnon
spectrum can be steered via the duration and the strength of the electron
pulses. The study points to a possible way for a spatiotemporally controlled
generation of magnetic and skyrmionic excitations.",1707.08838v1
2017-08-01,Expanding the Bethe/Gauge Dictionary,"We expand the Bethe/Gauge dictionary between the XXX Heisenberg spin chain
and 2d N = (2,2) supersymmetric gauge theories to include aspects of the
algebraic Bethe ansatz. We construct the wave functions of off-shell Bethe
states as orbifold defects in the A-twisted supersymmetric gauge theory and
study their correlation functions. We also present an alternative description
of off-shell Bethe states as boundary conditions in an effective N = 4
supersymmetric quantum mechanics. Finally, we interpret spin chain R-matrices
as correlation functions of Janus interfaces for mass parameters in the
supersymmetric quantum mechanics.",1708.00445v1
2017-12-18,Multipole Stability of Spinning M2-branes in the Classical Limit of the BMN Matrix Model,"We explore the stability of a recently found class of spinning dielectric
M2-branes in the 11-dimensional maximally supersymmetric plane-wave background.
We find two small windows of instabilities in the dipole (j=1) and quadrupole
(j = 2) sector of linear multipole perturbations.",1712.06544v2
2018-01-25,First-order differential equations for a particle with spin $S = 1$,"A system of first-order differential equations for a particle with nonzero
mass and spin $S = 1$ is constructed. As distinct from the Proca-Duffin-Kemmer
(PDK) equations, the system has the form of the dynamical equation
$i\hbar\partial_t\hat{\Psi}=\hat{\mathrm{H}}\hat{\Psi}$ (with constraints) with
a Hamiltonian linear in momentum. The six-component wave function yields the
positive-definite probability density $\hat{\Psi}^{\dagger}\hat{\Psi}\geq 0$.
The system of equations has much in common with the Dirac and Maxwell
equations.",1801.08414v1
2018-01-26,Neutrino motion and spin oscillations in magnetic field and matter currents,"A brief review of a neutrino oscillations effect in an external magnetic
field and matter currents is given. An ultra-relativistic neutrino propagation
in moving external media is investigated. We have found a new spin operator
which commutes with the corresponding Hamiltonian, exact wave functions and
energy spectrum are obtained.",1801.08911v1
2018-05-22,Dark Matter in Quantum Gravity,"We show that quantum gravity, whatever its ultra-violet completion might be,
could account for dark matter. Indeed, besides the massless gravitational field
recently observed in the form of gravitational waves, the spectrum of quantum
gravity contains two massive fields respectively of spin 2 and spin 0. If these
fields are long-lived, they could easily account for dark matter. In that case,
dark matter would be very light and only gravitationally coupled to the
standard model particles.",1805.08552v1
2018-06-26,Scalar charge of black holes in Einstein-Maxwell-dilaton theory,"We show that the monopole scalar charge of black holes in
Einstein--Maxwell--dilaton theory is proportional to the electric potential at
the event horizon, with a proportionality factor given by (minus) the scalar
coupling constant. We also show that the scalar charge, in the weak electric
charge limit, does not depend on the black hole spin. This result can be very
useful to circumvent spin degeneracy issues when testing the theory against
gravitational waves observations.",1806.10238v2
2018-09-17,Lorentz-violating extension of the spin-one Duffin-Kemmer-Petiau equation,"We investigate the breaking of Lorentz symmetry caused by the inclusion of an
external four-vector via a Chern-Simons-like term in the Duffin-Kemmer-Petiau
Lagrangian for massless and massive spin-one fields. The resulting equations of
motion lead to the appearance of birefringence, where the corresponding photons
are split into two propagation modes. We discuss the gauge invariance of the
extended Lagrangian. Throughout the paper, we utilize projection operators to
reduce the wave-functions to their physical components, and we provide many new
properties of these projection operators.",1809.06400v1
2012-09-19,Linear and nonlinear wave propagation in weakly relativistic quantum plasmas,"We consider a recently derived kinetic model for weakly relativistic quantum
plasmas. We find that that the effects of spin-orbit interaction and Thomas
precession may alter the linear dispersion relation for a magnetized plasma in
case of high plasma densities and/or strong magnetic fields. Furthermore, the
ponderomotive force induced by an electromagnetic pulse is studied for an
unmagnetized plasma. It turns out that for this case the spin-orbit interaction
always give a significant contribution to the quantum part of the ponderomotive
force.",1209.4213v2
2014-06-12,Multiple-Q Instability by (d-2)-dimensional Connections of Fermi Surfaces,"We propose a general mechanism of multiple-Q ordering with noncollinear and
noncoplanar spin textures in itinerant magnets. By analyzing the fourth-order
perturbation with respect to the spin-charge coupling, we find that the
instability toward multiple-Q ordering is caused by (d-2)-dimensional
connections of the Fermi surfaces in the extended Brillouin zone by the
multiple-Q wave vectors: zero(one)-dimensional point (line) connections in the
two(three)-dimensional systems. The instabilities are obtained as the ""fixed
points"" in the two-parameter flow diagram, irrespective of lattice structures.
The hidden Fermi surface instability provides a universal origin of
noncollinear and noncoplanar instabilities common to frustrated and
unfrustrated lattice systems.",1406.3119v1
2014-06-20,"""Nodal gap"" induced by the incommensurate diagonal spin density modulation in underdoped high-$T_c$ superconductors","Recently it was revealed that the whole Fermi surface is fully gapped for
several families of underdoped cuprates. The existence of the finite energy gap
along the $d$-wave nodal lines (""nodal gap"") contrasts the common understanding
of the $d$-wave pairing symmetry, which challenges the present theories for the
high-$T_c$ superconductors. Here we propose that the incommensurate diagonal
spin-density-wave order can account for the above experimental observation. The
Fermi surface and the local density of states are also studied. Our results are
in good agreement with many important experiments in high-$T_c$
superconductors.",1406.5408v1
2018-08-03,Modulated Continuous Wave Control for Energy-efficient Electron-nuclear Spin Coupling,"We develop energy efficient, continuous microwave schemes to couple electron
and nuclear spins, using phase or amplitude modulation to bridge their
frequency difference. These controls have promising applications in biological
systems, where microwave power should be limited, as well as in situations with
high Larmor frequencies due to large magnetic fields and nuclear magnetic
moments. These include nanoscale NMR where high magnetic fields achieves
enhanced thermal nuclear polarisation and larger chemical shifts. Our controls
are also suitable for quantum information processors and nuclear polarisation
schemes.",1808.01209v2
2020-04-02,Numerical evaluation of two-time correlation functions in open quantum systems with matrix product state methods: a comparison,"We compare the efficiency of different matrix product state (MPS) based
methods for the calculation of two-time correlation functions in open quantum
systems. The methods are the purification approach [1] and two approaches [2,3]
based on the Monte-Carlo wave function (MCWF) sampling of stochastic quantum
trajectories using MPS techniques. We consider a XXZ spin chain either exposed
to dephasing noise or to a dissipative local spin flip. We find that the
preference for one of the approaches in terms of numerical efficiency depends
strongly on the specific form of dissipation.",2004.01133v2
2020-08-26,One- and two-magnon excitations in antiferromagnet PbFeBO4,"The linear spin-wave theory study of PbFeBO4 spin dynamics is presented. It
is shown that the modes observed in Raman scattering experiments below Neel
temperature are optical magnon and two-magnon excitations. Based on the magnon
energy, two-magnon band lineshape, and Weiss temperature, the consistent set of
the exchange coupling constants up the third neighbor is derived and compared
with the results of ab initio calculations. The small deviation of the observed
two-magnon band from the one-magnon density of states suggests a surprisingly
negligible role of magnon-magnon interactions.",2008.11530v2
2017-10-10,Flipping-shuttle oscillations of bright one- and two-dimensional solitons in spin-orbit-coupled Bose-Einstein condensates with Rabi mixing,"We analyze a possibility of macroscopic quantum effects in the form of
coupled structural oscillations and shuttle motion of bright two-component
spin-orbit-coupled striped (one-dimensional, 1D) and semi-vortex
(two-dimensional, 2D) matter-wave solitons, under the action of linear mixing
(Rabi coupling) between the components. In 1D, the intrinsic oscillations
manifest themselves as flippings between spatially even and odd components of
striped solitons, while in 2D the system features periodic transitions between
zero-vorticity and vortical components of semi-vortex solitons. The
consideration is performed by means of a combination of analytical and
numerical methods.",1710.03664v1
2018-04-10,Crust breaking and the limiting rotational frequency of neutron stars,"The limiting rotational frequency of neutron stars may be determined by the
strength of their crusts. As a star spins up from accretion, centrifugal forces
will cause the crust to fail. If the crust breaks unevenly, a rotating mass
quadrupole moment will radiate gravitational waves (GW). This radiation can
prevent further spin up and may be a promising source for continuous GW
searches. We calculate that for a breaking strain (strength) of neutron star
crust that is consistent with molecular dynamics simulations, the crust may
fail at rotational frequencies in agreement with observations.",1804.04952v1
2019-03-01,Recurrence analysis of spinning particles in the Schwarzschild background,"In this work the dynamics of a spinning particle moving in the Schwarzschild
background is studied. In particular, the methods of Poincar\'{e} section and
recurrence analysis are employed to discern chaos from order. It is shown that
the chaotic or regular nature of the orbital motion is reflected on the
gravitational waves.",1903.00360v1
2019-03-09,Atoms trapped by a spin-dependent optical lattice potential: realization of a ground state quantum rotor,"In a cold atom gas subject to a 2D spin-dependent optical lattice potential
with hexagonal symmetry, trapped atoms undergo orbital motion around the
potential minima. Such atoms are elementary quantum rotors. We develop the
theory of such quantum rotors. Wave functions, energies, and degeneracies are
determined for both bosonic and fermionic atoms, and magnetic dipole
transitions between the states are elucidated. Quantum rotors in optical
lattices with precisely one atom per unit cell can be used as high precision
rotation sensors, accelerometers, and magnetometers.",1903.03847v2
2019-03-21,Spin-zero system of DKP equation in the background of a flat class of Gödel-type space-time,"In this paper, we investigate the Duffin-Kemmer-Petiau (DKP) equation for
spin-zero system of charge-free particles in the background of a flat class of
G\""{o}del-type space-times, and evaluate the individual energy levels and
corresponding wave-functions, in details.",1903.09311v2
2019-05-29,Affine lattice construction of spiral surfaces in classical Heisenberg models,"Frustration in classical spin models can lead to degenerate ground states
without long range order. In reciprocal space, these degeneracies appear as
manifolds of wave vectors, their dimensionality increasing with the degree of
frustration and the robustness of the disordered spin-liquid state. Here, we
present a recipe to explicitly construct Heisenberg models on Bravais lattices
with codimension-one manifolds, i.e., lines in two-dimensions and surfaces with
different Euler characteristics in three-dimensions. Furthermore, we discuss
the role of thermal and quantum fluctuations in stabilizing ordered states.",1905.12504v3
2020-03-10,Fundamental Properties of the Proton in Light-Front Zero Modes,"For a proton in the infinite momentum frame, its wave function contains a
zero-momentum part (light-front zero-modes) originated from the modification of
the QCD vacuum in the presence of the valence quarks, exhibiting a light-front
long-range order in the quantum state. This ``non-travelling'' component of the
proton contributes to its fundamental properties, including the mass and spin,
as well as the naive-time-reversal-odd correlations between transverse momentum
and spin. The large momentum effective theory (LaMET) provides a theoretical
approach to study the physical properties of the proton's zero-mode
``condensate'' through lattice simulations.",2003.04478v1
2020-03-23,Scattering Theory and Spectral Stability under a Ricci Flow for Dirac Operators,"Given a noncompact spin manifold $M$ with a fixed topological spin structure
and two complete Riemannian metrics $g$ and $h$ on $M$ with bounded sectional
curvatures, we prove a criterion for the existence and completeness of the wave
operators $\mathscr{W}_{\pm}(D_h, D_g, I_{g,h})$ and $\mathscr{W}_{\pm}(D_h^2,
D^2_g, I_{g,h})$, where $I_{g,h}$ is the canonically given unitary map between
the underlying $L^2$-spaces of spinors. This criterion does not involve any
injectivity radius assumptions and leads to a criterion for the stability of
the absolutely continuous spectrum of a Dirac operator and its square under a
Ricci flow.",2003.10204v1
2016-11-19,Spatially-indirect Exciton Condensate Phases in Double Bilayer Graphene,"We present a theory of spatially indirect exciton condensate states in
systems composed of a pair of electrically isolated Bernal graphene bilayers.
The ground state phase diagram in a two-dimensional
displacement-field/inter-bilayer-bias space includes layer-polarized
semiconductors, spin-density-wave states, exciton condensates, and states with
mixed excitonic and spin order. We find that two different condensate states,
distinguished by a chirality index, are stable under different electrical
control conditions.",1611.06410v1
2017-02-16,Physics of Cold Atomic Fermi Gases,"We consider a cold two-species atomic Fermi gas confined in a trap. We
combine the Hermitian coupling between the states (we assume them to be the
states with different spins) with the Cooper pairing of atoms with these
different spins. This opens up a new prospect for investigation of interplay
between various phenomena involving Raman coupling (e.g., atom lasers,
dark-state polaritons) and effects caused by Cooper pairing of particles (e.g.,
superfluidity). We have obtained a threshold of transition from oscillatory to
amplifying behavior of matter waves.",1703.00813v2
2019-01-10,The Marolf-Ori singularity inside fast spinning black holes,"The effective shock wave singularity at the outgoing leg of the inner horizon
of a linearly perturbed fast spinning black hole is studied numerically for
either scalar field, or vacuum, gravitational perturbations. We demonstrate the
occurrence of the Marolf-Ori singularity, including changes of order unity in
the scalar field $\phi$ for the scalar field model, and in the Weyl scalars
$\psi_0$ and $\psi_4$ (rescaled appropriately by the horizon function $\Delta$)
and the Kretschmann curvature scalar $K$ for the vacuum, gravitational
perturbations model for both null and timelike geodesic observers. We quantify
the shock sharpening effect and show that in all cases its rate agrees with
expectations.",1901.03413v1
2019-07-05,Rashba cavity QED: a route towards the superradiant quantum phase transition,"We develop a theory of cavity quantum electrodynamics for a 2D electron gas
in the presence of Rashba spin-orbit coupling and perpendicular static magnetic
field, coupled to spatially nonuniform multimode quantum cavity photon fields.
We demonstrate that the lowest polaritonic frequency of the full Hamiltonian
can vanish for realistic parameters, achieving the Dicke superradiant quantum
phase transition. This singular behaviour originates from soft spin-flip
transitions possessing a non-vanishing dipole moment at non-zero wave vectors
and can be viewed as a magnetostatic instability.",1907.02938v1
2019-07-29,Magnetization Dynamics in Holographic Ferromagnets: Landau-Lifshitz Equation from Yang-Mills Fields,"We introduce a new approach to understand magnetization dynamics in
ferromagnets based on the holographic realization of ferromagnets. A
Landau-Lifshitz equation describing the magnetization dynamics is derived from
a Yang-Mills equation in the dual gravitational theory, and temperature
dependences of the spin-wave stiffness and spin transfer torque appearing in
the holographic Landau-Lifshitz equation are investigated by the holographic
approach. The results are consistent with the known properties of magnetization
dynamics in ferromagnets with conduction electrons.",1907.12306v1
2019-10-11,Shift current from electromagnon excitations in multiferroics,"Electromagnon is the spin wave in multiferroic materials and is known to
accompany electric polarization due to the cross correlation between the charge
and spin. Here, we theoretically show that the electromagnons also induce dc
current upon their photoexcitations. The proposed dc current response
originates from the shift current mechanism which is characterized by the so
called shift vector, a geometric quantity of the Bloch wavefunctions.",1910.05182v2
2020-01-19,Chiral Coupling to Magnetodipolar Radiation,"We review and extend the theory of chiral pumping of spin waves by
magnetodipolar stray fields that generate unidirectional spin currents and
asymmetric magnon densities. We illustrate the physical principles by two kinds
of chiral excitations of magnetic films, i.e., by the evanescent Oersted field
of a narrow metallic stripline with an AC current bias and a magnetic nanowire
under ferromagnetic resonance.",2001.06821v2
2020-01-21,Bound states in ultrastrong waveguide QED,"We discuss the properties of bound states in finite-bandwidth waveguide QED
beyond the Rotating Wave Approximation or excitation number conserving
light-matter coupling models. Therefore, we extend the \emph{standard}
calculations to a broader range of light-matter strengths, in particular, in
the so-called ultrastrong coupling regime. We do this using the Polaron
technique. Our main results are as follows. We compute the spontaneous emission
rate, which is renormalized as compared to the Fermi Golden Rule formula. We
generalise the existence criteria for bound states, their properties and their
role in the qubits thermalization. We discuss effective spin-spin interactions
through both vacuum fluctuations and bound states. Finally, we sketch a perfect
state-transfer protocol among distant emitters.",2001.07643v1
2020-02-07,Massless Phases for the Villain model in $d\geq 3$,"We consider the classical Villain rotator model in $\mathbb{Z}^d, d\geq 3$ at
sufficiently low temperature, and prove that the truncated two-point function
decays asymptotically as $|x|^{2-d}$, with an algebraic rate of convergence. We
also obtain the same asymptotic decay separately for the transversal two-point
functions. This quantifies the spontaneous magnetization result for the Villain
model at low temperature, and rigorously establishes the Gaussian spin-wave
conjecture in dimension $d\ge 3$. We believe that our method extends to finite
range interactions and to other abelian spin systems and abelian gauge theory
in $d\geq 3$.",2002.02946v1
2020-07-23,Spin and polarisation dependent LCFA rates for nonlinear Compton and Breit-Wheeler processes,"In this paper we derive and discuss the completely spin- and
photon-polarisation dependent probability rates for nonlinear Compton
scattering and nonlinear Breit-Wheeler pair production. The locally constant
field approximation, which is essential for applications in plasma-QED
simulation codes, is rigorously derived from the strong-field QED matrix
elements in the Furry picture for a general plane-wave background field. We
discuss important polarisation correlation effects in the spectra of both
processes. Asymptotic limits for both small and large values of $\chi$ are
derived and their spin/polarisation dependence is discussed.",2007.11837v2
2021-01-21,Analysis of the Dirac equation with the Killingbeck potential in non-commutative space,"In this paper, we investigate the Dirac equation with the Killingbeck
potential under the external magnetic field in non-commutative space.
Corresponding to the expressions of the energy level and wave functions in spin
symmetry limit and pseudo-spin symmetry limit are derived by using the Bethe
ansatz method. The parameter B associated with the external magnetic field and
non-commutative parameter {\theta} make to modify the energy level for
considered systems.",2101.08406v1
2021-06-10,Duffin-Kemmer-Petiau particles in the presence of the spiral dislocation,"In this study, we investigated the influence of the topological defects
space-time with a spiral dislocation on a spin-zero boson field by using the
Duffin-Kemmer-Petiau (DKP) equation. To be more specific, we solved the
generalized spin-zero DKP equation in the presence of a spiral dislocation
exactly. We derived the wave function and corresponding energy eigenvalues for
two cases, in the absence and presence of a static potential by using
analytical methods. We numerically demonstrated the effect of the spiral
dislocation on the solutions.",2106.05791v1
2021-11-29,On the ground-state energy of a mixture of two different oppositely polarized fermionic gases,"We report the results of the computation of the order $(k_{\rm F}a_0)^2$
correction, where $k_{\rm F}=3\pi^2\rho$ is the Fermi wave vector and $a_0$ the
$s$-wave scattering length of the repulsive interaction, to the ground-state
energy of a mixture of oppositely polarized $N_a$ spin $1/2$ fermions $a$ of
masses $m_a$ and $N_b$ spin $1/2$ fermions $b$ of masses $m_b$ ($\rho=N/V$,
$N=N_a+N_b$). It is shown that the results of the paper \cite{FraPil} in which
the same correction has been computed entirely numerically, using a more
traditional approach, can be easily and semianalytically reproduced using the
effective field theory technique.",2111.14927v1
2022-03-11,Self-interfering dynamics in Bose-Einstein condensates with engineered dispersions,"Optical lattice and spin-orbit coupling are typical experimental approaches
to engineer dispersion. We reveal a self-interfering dynamics in a
noninteracting Bose-Einstein condensate with the engineered dispersion by
optical lattice or spin-orbit coupling. The self-interference results from the
co-occupation of positive and negative effect mass regimes in the engineered
dispersion. The physical origination of the self-interference is explained by
the Wigner distribution function of the self-interfering wave-packet. We
characterize detail features of the self-interference pattern.",2203.05722v1
2022-04-21,Detection of roton and phonon excitations in a spin-orbit coupled Bose-Einstein condensate with a moving barrier,"We propose to detect phonon and roton excitations in a two-dimensional
Bose-Einstein condensate with Raman-induced spin-orbit coupling by perturbing
the atomic cloud with a weak barrier. The two excitation modes can be observed
by moving the barrier along different directions in appropriate parameter
regimes. Phonon excitations are identified by the appearance of solitary waves,
while roton excitations lead to distinctive spatial density modulations. We
show that this method can also be used to determine the anisotropic critical
velocities of superfluid.",2204.09865v2
2022-07-11,Resummation of the $α$ expansion for nonlinear pair production,"We show how to resum the Furry-picture $\alpha$ expansion in order to take
quantum radiation reaction and spin transition into account in the nonlinear
trident process in (pulsed) plane-wave background fields. The results are
therefore nontrivial functions of both the background field strength, $eE$, and
the coupling to the quantized photon field, $\alpha=e^2/4\pi$. The effective
expansion parameter, $T$, is $\alpha$ times $eE/m\omega\gg1$, which makes
higher orders important. We show that they can change the sign of the spin
dependent part already at $T<1$, which will be experimentally accessible.",2207.05031v1
2022-07-25,Broken-symmetry self-consistent GW approach: degree of spin contamination and evaluation of effective exchange couplings in solid antiferromagnets,"We adopt a broken-symmetry strategy for evaluating effective magnetic
constants $J$ within the fully self-consistent GW method. To understand the
degree of spin contamination present in broken-symmetry periodic solutions, we
propose several size-extensive quantities that demonstrate that the
unrestricted self-consistent GW preserves well the broken-symmetry character of
the unrestricted Hartree--Fock solutions. The extracted $J$ are close to the
ones obtained from multireference wave-function calculations. In this paper, we
establish a robust computational procedure for finding magnetic coupling
constants from self-consistent GW calculations and apply it to solid
antiferromagnetic nickel and manganese oxides.",2207.12064v1
2023-04-13,Magnon squeezing in conical spin spirals,"We investigate squeezing of magnons in a conical spin spiral configuration.
We find that while the energy of magnons propagating along the $\boldsymbol{k}$
and the $-\boldsymbol{k}$ directions can be different due to the non-reciprocal
dispersion, these two modes are connected by the squeezing, hence can be
described by the same squeezing parameter. The squeezing parameter diverges at
the center of the Brillouin zone due to the translational Goldstone mode of the
system, but the squeezing also vanishes for certain wave vectors. We discuss
possible ways of detecting the squeezing.",2304.06338v2
2023-07-18,Flat-band spin density wave in twisted bilayer materials,"Twisting is a novel technique for creating strongly correlated effects in
two-dimensional bilayered materials, and can tunably generate nontrivial
topological properties, magnetism, and superconductivity. Magnetism is
particularly significant as it can both compete with superconductivity and lead
to the emergence of nontrivial topological states. However, the origin of
magnetism in twisted structures remains a subject of controversy. Using
self-developed large-scale electronic structure calculations, we propose the
magnetism in these twisted bilayer systems originates from spin splitting
induced by the enhanced ratio of the exchange interaction to band dispersion.",2307.09506v1
2023-09-07,Electric Analog of Magnons in Order-Disorder Ferroelectrics,"We analyze the ``ferron"" excitations in order-disorder ferroelectrics by a
microscopic pseudo-spin model. We demonstrate that analogous to magnons, the
quanta of spin waves in magnetic materials, ferrons carry both static and
oscillating electric dipole moments, exhibit a Stark effect, and may be
parametrically excited by THz radiation. The anti-crossing gap of the
ferron-photon hybrid depends strongly on propagation direction and an applied
static electric field. We predict ferron diffusion lengths that can reach
centimeters, which implies efficient transport of electric polarization by
temperature gradients. These properties suggest that ferroelectric materials
may be useful for information technology beyond data storage applications.",2309.03691v1
2023-10-13,Thermal Phase Diagram of the Square Lattice Ferro-antiferromagnetic $J_1-J_2$ Heisenberg Model,"Using state of the art tensor network computations combined with spin wave
theory, we compute the finite temperature phase diagram of the spin 1/2
$J_1-J_2$ Heisenberg model on the square lattice with ferromagnetic $J_1 < 0$
and antiferromagnetic $J_2 > 0$. We localize the first order line originating
from the first order zero temperature point as well as the second order thermal
transition at large $J_2$ associated with spontaneous lattice rotation symmetry
breaking. This second order line terminates at a critical end point where it
meets the first order line. We found no evidence for an intermediate phase.",2310.09344v1
2023-12-25,Field-induced transformation between triangular and square skyrmion crystals in a tetragonal polar magnet,"Magnetic skyrmions with topologically nontrivial spin textures form a variety
of periodic structures depending on microscopic interactions and lattice
symmetry. We theoretically investigate a transformation between triangular and
square skyrmion crystals against an external magnetic field in a polar
tetragonal magnet. By performing the simulated annealing for a classical spin
model, we show that the competition of the Dzyaloshinskii-Moriya interaction at
multiple wave vectors is a key ingredient in inducing the structural transition
in terms of the skyrmion crystals. The present results indicate the importance
of magnetic frustration in momentum space as the origin of exotic topological
phase transitions.",2312.15587v1
2024-02-28,Polarized-deuteron scattering by spin-zero target nuclei at intermediate energies,"General analytical expressions for the observables in $dA$-scattering
reaction have been derived in the diffraction approximation. The resulting
formulas describe the cross section and polarization states of the deuteron
when it scattering by nuclei with zero spin in the ground state. The tabulated
distributions of the target nucleus density and the realistic deuteron wave
functions calculated on the basis of Nijmegen nucleon-nucleon potentials were
used. The nucleon-nucleus phases were calculated in the framework of Glauber
formalism and making use of the double-folding potential. The calculated cross
sections and analyzing powers in elastic scattering of deuterons by
$^{16}\text{O}$ and $^{40}\text{Ca}$ nuclei at 700 MeV are compared with the
corresponding experimental data.",2402.18521v1
2024-03-13,Nuclear coherent $π^0$ photoproduction with charge-exchange and spin-flip rescattering,"In this work, we present an updated model for nuclear $\pi^0$
photoproduction, which incorporates pion second-order rescattering on
intermediate excited nuclear states. Our approach is based on the distorted
wave impulse approximation in momentum space. The many-body medium effects are
incorporated in the complex effective $\Delta$ self-energy, employing the
results of the recently developed second-order pion-nucleus scattering
potential. The experimental data for ${}^{12}$C and ${}^{40}$Ca are
successfully described without the need to fit the model parameters of the
photoproduction amplitude as a result of incorporating the second-order part of
nuclear photoproduction potential, which involves intermediate nucleon
spin-flip and charge exchange.",2403.08608v1
1993-10-21,Neel Temperature for Quasi-Two-Dimensional Dipolar Antiferromagnets,"We calculate the N\'eel temperature $T_N$ for two-dimensional isotropic
dipolar Heisenberg antiferromagnets via linear spin-wave theory and a high
temperature expansion, employing the method of Callen. The theoretical
predictions for $T_N$ for K$_2$MnF$_4$, Rb$_2$MnF$_4$, Rb$_2$MnCl$_4$ and
(CH$_3$NH$_3$)$_2$MnCl$_4$ are in good agreement with the measured values.",9310049v1
1995-02-06,Superconducting Instability in a 1D lattice of Berry Phase Molecules,"We study the 1D model of conduction electrons interacting with local vibronic
modes. States in the conduction band are two-fold degenerate both in orbital
index and spin. It is shown that such 1D system has a strong tendency to
superconductivity. The superconducting pairing originates from coupling of two
charge density waves; the scaling dimension of the order parameter is close to
1/4.",9502023v1
1997-06-18,"Renormalization-group approach to the metal-insulator transitions in (DCNQI)_2M (DCNQI is N,N'-dicyanoquinonediimine and M=Ag, Cu)","Metal-insulator transitions and different ground-state phases in quasi-one-
dimensional materials, (R_1R_2-DCNQI)_2M (R_1=R_2=CH_3, I and M=Ag, Cu), are
studied with a renormalization-group method. We use one-dimensional continuum
models with backward scatterings, umklapp processes and couplings with 2k_F and
4k_F phonons (not static lattice distortion). We take a quarter- filled band
for M=Ag and a sixth-filled band coupled with a third-filled band for M=Cu.
Depending on electron-electron and electron-phonon coupling strengths, the
ground-state phase becomes a Tomonaga-Luttinger liquid or a state with a
gap(s). For M=Ag, there appear a spin-gap state with a dominant 2k_F
charge-density-wave correlation, a Mott insulator with a dominant 4k_F
charge-density-wave correlation, or a spin-Peierls state with different
magnitudes of spin and charge gaps. Three-dimensionality is taken into account
by cutting off the logarithmic singularity in either the particle-particle
channel or the particle-hole channel. The difference between the ground-state
phase of the R_1=R_2=CH_3 salt (spin-Peierls state) and that of the R_1=R_2=I
salt (antiferromagnetic state) is qualitatively explained by a difference in
the cutoff energy in the particle-particle channel. For M=Cu, there appear a
Mott insulator with a charge density wave of period 3 and a Peierls insulator
with a charge density wave of period 6. The conditions for the experimentally
observed, Mott insulator phase are strong correlation in the sixth-filled band,
moderate electron-phonon couplings, and finite electron-4k_F phonon coupling.
Resistance is calculated as a function of temperature with a memory-function
approximation in both cases above. It qualitatively reproduces the differences
among the M=Ag and M=Cu cases as well as the R_1=R_2=CH_3 and R_1=R_2=I cases.",9706183v1
1999-04-18,Orientational phase transitions in anisotropic rare-earth magnets at low temperatures,"Orientational phase transitions are investigated within the Heisenberg model
with single-site anisotropy. The temperature dependence of the cone angle is
calculated within the spin-wave theory. The role of the quantum
renormalizations of anisotropy constants is discussed. A comparison with the
experimental data on the cone-plane orientational transition in holmium is
performed.",9904251v1
1999-12-03,Overlap integral for quantum skyrmions,"We made use a simplified form for the quantum skyrmion wave function based on
the spin coherent states to obtain the analytical expression for appropriate
overlap integral.",9912048v3
2000-03-16,Effects of spin-elastic interactions in frustrated Heisenberg antiferromagnets,"The Heisenberg antiferromagnet on a compressible triangular lattice in the
spin- wave approximation is considered. It is shown that the interaction
between quantum fluctuations and elastic degrees of freedom stabilizes the low
symmetric L-phase with a collinear Neel magnetic ordering. Multi-stability in
the dependence of the on-site magnetization on an unaxial pressure is found.",0003280v1
2001-10-19,Very low-frequency excitations in frustrated two-dimensional $S=1/2$ Heisenberg antiferromagnets,"muSR and 7Li NMR relaxation measurements in frustrated two-dimensional S=1/2
Heisenberg antiferromagnets on a square lattice are presented. It is found that
both in Li2VOSiO4 and Li2VOGeO4, spin dynamics at frequencies well below the
Heisenberg exchange frequency are present. These dynamics are associated with
the motions of walls separating coexisting collinear domains with a magnetic
wave vector rotated by 90 degrees.",0110398v1
2003-03-02,Long Range Dynamics Related to Magnetic Impurity in the 2D Heisenberg Antiferromagnet,"We consider a magnetic impurity in the two-dimensional Heisenberg
antifferomagnet with long range antiferromagnetic order. At low temperature the
impurity magnetic susceptibility has a Curie term ($\propto 1/T$) and a
logarithmic correction ($\propto \ln(T)$). We calculate the correction and
derive related Ward identity for the impurity-spin-wave vertex.",0303016v1
2004-06-01,A suggested 4 x 4 structure in underdoped cuprate superconductors: a Wigner supersolid,"A wave function is proposed for the ""$4\times 4$"" inhomogeneous structures
observed on cuprate superconductors. It is based on the Gutzwiller-RVB
technique proposed in recent papers, and consists of a Wigner solid of hole
pairs embedded in a sea of d-wave spin singlet pairs. Arguments are given that
the nodal quasiparticles may remain unscattered and even superconducting on
such a structure.",0406038v1
2004-09-27,Electronic Structure and Magnetic Properties of Solids,"We review basic computational techniques for simulations of various magnetic
properties of solids. Several applications to compute magnetic anisotropy
energy, spin wave spectra, magnetic susceptibilities and temperature dependent
magnetisations for a number of real systems are presented for illustrative
purposes.",0409704v1
2005-10-26,Ferroelectricity in spiral magnets,"It was recently observed that materials showing most striking multiferroic
phenomena are frustrated spin-density-wave magnets. We present a simple
phenomenological theory, which describes the orientation of the induced
electric polarization for various incommensurate magnetic states, its
dependence on temperature and magnetic field, and anomalies of dielectric
susceptibility at magnetic transitions. We show that electric polarization can
be induced at domain walls and that magnetic vortices carry electric charge.",0510692v1
2005-11-04,Ultrafast laser excitation of spin waves by permanent modification of the exchange bias interaction in IrMn/Co,"This paper has been withdrawn by the authors due to a critical error
discovered in Figures 1, 2 and 4.",0511112v2
1994-06-21,A Cosmological No-Hair Theorem,"A generalisation of Price's theorem is given for application to Inflationary
Cosmologies. Namely, we show that on a Schwarzschild--de Sitter background
there are no static solutions to the wave or gravitational perturbation
equations for modes with angular momentum greater than their intrinsic spin.",9406036v1
2001-10-04,Optimum Placement of Post-1PN GW Chirp Templates Made Simple at any Match Level via Tanaka-Tagoshi Coordinates,"A simple recipe is given for constructing a maximally sparse regular lattice
of spin-free post-1PN gravitational wave chirp templates subject to a given
minimal match constraint, using Tanaka-Tagoshi coordinates.",0110024v2
2004-05-17,Exotic Meson Decay to $ωπ^{0}π^{-}$,"A partial-wave analysis of the mesons from the reaction $\pi^{-}%
p\to\pi^{+}\pi^{-}\pi^{-}\pi^{0}\pi^{0}p$ has been performed. The data show
$b_{1}\pi$ decay of the spin-exotic states $\pi_{1}(1600)$ and \
$\pi_{1}(2000)$. Three isovector $2^{-+}$ states were seen in the
$\omega\rho^{-}$ decay channel. In addition to the well known $\pi_{2}(1670)$,
signals were also observed for $\pi_{2}(1880)$ and $\pi_{2}(1970)$.",0405044v1
1998-06-15,Light-Cone Meson-Baryon Fluctuations and Single-Spin Asymmetries,"We show that energetically favored meson-baryon fluctuations present in the
light-cone wave function of a transversely polarized proton can account for the
left-right asymmetries measured in inclusive meson production processes.",9806364v3
2000-12-22,On the $σ_L/σ_T$ Ratio in Polarized Vector Meson Photoproduction,"We study the spin-dependent cross-sections of vector meson photoproduction
for longitudinally and transversely polarized photons within a QCD- model. The
dependence of the $\sigma_T/\sigma_L$ ratio on the photon virtuality and on the
meson wave function is analysed.",0012307v1
2005-10-06,Ferromagnetism in quark matter and origin of the magnetic field in compact stars,"Two magnetic aspects of quark matter, ferromagnetism and spin density wave,
are discussed in the temperature-density plane. Some implications of
ferromagnetism are suggested on relativistic heavy-ion collisions and compact
stars.",0510068v1
2005-12-29,Particle escape into extra space,"We focus on escape of a spin integer particle the challenge for which is of
course that the corresponding field equation contains the second order time
derivative and, in general, may be problematic for interpreting the
extra-dimensional part of the field as a wave function for the KK modes as it
is usually regarded.",0512362v2
2006-02-08,Bose-Einstein Condensates as a Probe for Lorentz Violation,"The effects of small Lorentz-violating terms on Bose-Einstein condensates are
analyzed. We find that there are changes to the phase and shape of the
ground-state wave function that vary with the orientation of the trap. In
addition, spin-couplings can act as a source for spontaneous symmetry breaking
in ferromagnetic condensates making them sensitive probes for fundamental
symmetry violation.",0602071v1
1994-12-29,Dynamical Supersymmetry of a Vortex System with $1/r^{2}$ Potential,"The Pauli Hamiltonian for a spin $\frac{1}{2}$ charged particle interacting
with a point magnetic vortex and $1/r^{2}$ potential exhibits a dynamical
supersymmetry $Osp(1,1)$ on the plane except at the origin. Using this
symmetry, the spectrum and the wave functions have been obtained. And, the
dynamical supersymmetry could be imported to the case when an external harmonic
potential is added.",9412225v1
1996-12-05,Whirling Waves and the Aharonov-Bohm Effect for Relativistic Spinning Particles,"The formulation of Berry for the Aharonov-Bohm effect is generalized to the
relativistic regime. Then, the problem of finding the self-adjoint extensions
of the (2+1)-dimensional Dirac Hamiltonian, in an Aharonov-Bohm background
potential, is solved in a novel way. The same treatment also solves the problem
of finding the self-adjoint extensions of the Dirac Hamiltonian in a background
Aharonov-Casher.",9612058v1
2001-04-03,Covariant Quantum Green's Function for an Accelerated Particle,"Covariant relativistic quantum theory is used to study the covariant Green's
function, which can be used to determine the proper time evolved wave functions
that are solutions to the covariant Schr\""odinger type equation for a massive
spin zero particle. The concept of covariant action is used to obtain the
Green's function for an accelerated relativistic particle.",0104030v1
2002-04-20,Noncommutative gravity in three dimensions coupled to spinning sources,"Noncommutative gravity in three dimensions with vanishing cosmological
constant is examined. We find a solution which describes a spacetime in the
presence of a torsional source. We estimate the phase shift for each partial
wave of a scalar field in the spacetime by the Born approximation.",0204173v1
2002-10-11,Calculation of Expectation Values of S$_{z}$ and S$^{2}$ operators for spin-1 and spin-3/2 particles,"In the present article we calculate the expectation values of of S$_{z}$ and
S$^{2}$ operators for spin-1 and spin-3/2 particles by expanding a general wave
function which includes all spin values. The results are same as in the
stantard quantum mechanics.",0210106v1
2003-02-14,Chiral Symmetry and Vertex Symmetry in the Extended Moeller-Rosenfeld Model,"Vertex symmetry for interacting fermions will be shown to lead to a
Lagrangian exhibiting $SU(2N)_W$ invariance associated with the subgroup
$SU(2N)_q \times SU(2N)_{\bar{q}}$ generated by $C$-odd and $C$-even spin
operators. Approximate $SU(6)_W$ vertex symmetry as well as chiral invariance
will then be shown to follow from a principle of maximum smoothness
(M\""oller-Rosenfeld) of the bound state quark wave function.",0302102v1
2006-03-17,Charge Conjugation in the Galilean Limit,"Strictly working in the framework of the nonrelativistic quantum mechanics of
a spin 1/2 particle coupled to an external electromagnetic field, we show, by
explicit construction, the existence of a charge conjugation operator matrix
which defines the corresponding antiparticle wave function and leads to the
galilean and gauge invariant Schroedinger-Pauli equation satisfied by it.",0603137v1
2003-02-20,Counting nodal domains,"We consider the nodal domains of Gaussian random waves in two dimensions. We
present a method to calculate the distribution of the number of nodal domains
and the average connectivity with the help of auxiliary Potts-spins. An
analytical approach could be helpful to decide whether the pattern of nodal
domains belongs to the universality class of short-ranged percolation. This is
not completely evident since we find (weak) long-ranged correlations between
distant avoided nodal intersections.",0302049v1
2002-04-09,Numerical Implementation of Three-Body Forces in Bound State Faddeev Calculations in Three Dimensions,"The Faddeev equations for the three-body bound state are solved directly as
thre e-dimensional integral equations without employing partial wave
decomposition. Two-body forces of the Malfliet-Tjon type and simple spin
independent genuine three-body forces are considered for the calculation of the
three-body binding energy.",0204027v1
2005-04-12,Angular momentum of light,"By means of the Helmholtz theorem on the decomposition of vector fields, the
angular momentum of the classical electromagnetic field is decomposed, in a
general and manifestly gauge invariant manner, into a spin component and an
orbital component. The method is applied to linearly and circularly polarized
plane waves in their classical and quantum forms.",0504078v2
1997-02-10,Quantum Interference of Polarized Electrons in the Presence of Magnetic Strings,"This work analyzes the effects of shielding on the Aharonov-Bohm scattering
of electrons endowed with spin. The interaction of polarized electrons with
bare and shielded magnetic strings is studied with the aid of the Dirac
equation. It is found that the difference between the amplitudes for the
scattering by bare and shielded strings of incident wave packets of width
$\delta$ and impact parameter $d$ is proportional to $\exp(-d^2/2\delta^2)$.",9702025v1
2000-05-16,The Pauli Equation for Probability Distributions,"The ""marginal"" distributions for measurable coordinate and spin projection is
introduced. Then, the analog of the Pauli equation for spin-1/2 particle is
obtained for such probability distributions instead of the usual wave
functions. That allows a classical-like approach to quantum mechanics. Some
illuminating examples are presented.",0005058v1
2001-05-07,Electron State Entanglement at Double Ionization,"Electron wave function entanglement and spin reconfiguration as source of
electron correlation are investigated. Properties of correlation function are
shown to have the best concordance with experimental data under supposition
that probability of change of electron state to triplet state is about 0.5 or
more.",0105025v2
2003-07-25,There is no first quantization - except in the de Broglie-Bohm interpretation,"The relativistic effects of the integer-spin quantum field theory imply that
the wave functions describing a fixed number of particles do not admit the
usual probabilistic interpretation. Among several most popular interpretations
of quantum mechanics applied to first quantization, the only interpretation for
which this fact does not lead to a serious problem, and therefore the only
consistent interpretation of first quantization, is the de Broglie-Bohm
interpretation.",0307179v1
2005-02-07,When the macroscopic game is the quantum game?,"An example of the macroscopic game of two partners consisting of two
classical games played simultaneously with special dependence of strategies is
considered. The average profit of each partner is equal to the average profit
obtained in the quantum game with two noncommuting operators for the spin one
half system with strategies defined by the wave function. Nash equilibria in
the macroscopic game coincide with Nash equilibria of the quantum game.",0502038v1
2007-10-12,Dynamical instability of the XY spiral state of ferromagnetic condensates,"We calculate the spectrum of collective excitations of the XY spiral state
prepared adiabatically or suddenly from a uniform ferromagnetic F=1 condensate.
For spiral wavevectors past a critical value, spin wave excitation energies
become imaginary indicating a dynamical instability. We construct phase
diagrams as functions of spiral wavevector and quadratic Zeeman energy.",0710.2499v1
2007-11-21,Ferromagnetism in QCD phase diagram,"A possibility and properties of spontaneous magnetization in quark matter are
investigated. Magnetic susceptibility is evaluated within Fermi liquid theory,
taking into account of the screening effect of gluons. Spin wave in the
polarized quark matter, as the Nambu-Goldstone mode, is formulated by way of
the coherent-state path integral.",0711.3349v1
2008-07-11,Numerical evidence for unstable magnons at high fields in the Heisenberg antiferromagnet on the square lattice,"We find evidence for decaying magnons at strong magnetic field in the square
lattice spin-1/2 Heisenberg antiferromagnet. The results are obtained using
Quantum Monte Carlo simulations combined with a Bayesian inference technique to
obtain dynamics and are consistent with predictions from spin wave theory.",0807.1837v2
2008-08-07,Solutions of Dirac Equation for Symmetric Generalized Woods-Saxon Potential by the Hypergeometric Method,"The Dirac equation is solved approximately for the Hulthen potential with the
pseudospin symmetry for any spin-orbit quantum number $\kappa$ in the
position-dependent mass background. Solutions are obtained reducing the Dirac
equation into a Schr\""{o}dinger-like differential equation by using an
appropriate coordinate transformation. The Nikiforov-Uvarov method is used in
the calculations to get energy eigenvalues and the corresponding wave
functions.",0808.1002v1
2009-01-29,"Spin-waves in triangular lattice antiferromagnet: decays, spectrum renormalization, and singularities","We present a comprehensive study of the dynamical properties of the quantum
Heisenberg antiferromagnet on a triangular lattice within the framework of
spin-wave theory. The distinct features of spin-wave excitations in the
triangular-lattice antiferromagnet are (i) finite lifetime at zero temperature
due to spontaneous two-magnon decays, (ii) strong renormalization of magnon
energies with respect to the harmonic result, and (iii) logarithmic
singularities in the decay rate Gamma_k. Quantum corrections to the magnon
spectrum are obtained using both the on-shell and off-shell solutions of the
Dyson equation with the lowest-order magnon self-energy. At low-energies magnon
excitations remain well-defined albeit with the anomalous decay rate Gamma_k ~
k^2 at k->0 and Gamma_k ~ |k-Q_AF|^7/2 at k->Q_AF. At high energies, magnons
are heavily damped with the decay rate reaching (2 Gamma_k/E_k) ~ 0.3 for the
case S=1/2. The on-shell solution shows logarithmic singularities in Gamma_k
with the concomitant jump-like discontinuities in E_k along certain contours in
the momentum space. Such singularities are even more prominent in the magnon
spectral function A(k,w). Although the off-shell solution removes such
log-singularities, the decay rates remain strongly enhanced. We also discuss
the role of higher-order corrections and show that such singularities may lead
to complete disappearance of the spectrum in the vicinity of certain k-points.
The kinematic conditions for two-magnon decays are analyzed for various
generalizations of the triangular-lattice antiferromagnet as well as for the
XXZ model on a kagome lattice. Our results suggest that decays and
singularities in the spin-wave spectra must be ubiquitous in all these systems.",0901.4803v3
2009-02-09,Chiral Odd Generalized Parton Distributions in Position Space,"We report on a calculation of the chiral odd generalized parton distributions
(GPDs) for non-zero skewness $\zeta$ in transverse and longitudinal position
spaces by taking Fourier transform with respect to the transverse and
longitudinal momentum transfer respectively using overlaps of light-front wave
functions (LFWFs).",0902.1461v1
2009-04-13,The Pauli exclusion principle and beyond,"The Pauli exclusion principle can be stated as inequality
$<\psi|\rho|\psi>\le 1$ for the electron density matrix $\rho$. Nowadays it is
replaced by skew symmetry of the multi-electron wave function. The replacement
leads to numerous additional constraints on $\rho$, which are discussed in this
letter together with their physical implications, in particular for spin
magnetic moment of a multi-electron system.",0904.2009v1
2009-04-27,The Fate of the Two-Magnon Bound State in the Heisenberg Antiferromagnet,"The energy spectrum of the two-magnon bound states in the Heisenberg-Ising
antiferromagnet on the square lattice are calculated using series expansion
methods. The results confirm an earlier spin-wave prediction of Oguchi and
Ishikawa, that the bound states vanish into the continuum before the isotropic
Heisenberg limit is reached.",0904.4085v1
2009-08-03,The imbalanced antiferromagnet in an optical lattice,"We study the rich properties of the imbalanced antiferromagnet in an optical
lattice. We present its phase diagram, discuss spin waves and explore the
emergence of topological excitations in two dimensions, known as merons, which
are responsible for a Kosterlitz-Thouless transition that has never
unambiguously been observed.",0908.0236v1
2010-04-07,Spiral order by disorder and lattice nematic order in a frustrated Heisenberg antiferromagnet on the honeycomb lattice,"Motivated by recent experiments on Bi$_3$Mn$_4$O$_{12}$(NO$_3$), we study a
frustrated $J_1$-$J_2$ Heisenberg model on the two dimensional (2D) honeycomb
lattice. The classical $J_1$-$J_2$ Heisenberg model on the two dimensional (2D)
honeycomb lattice has N\'eel order for $J_2 < J_1/6$. For $J_2 > J_1/6$, it
exhibits a one-parameter family of degenerate incommensurate spin spiral ground
states where the spiral wave vector can point in any direction. Spin wave
fluctuations at leading order lift this accidental degeneracy in favor of
specific wave vectors, leading to spiral order by disorder. For spin $S=1/2$,
quantum fluctuations are, however, likely to be strong enough to melt the
spiral order parameter over a wide range of $J_2/J_1$. Over a part of this
range, we argue that the resulting state is a valence bond solid (VBS) with
staggered dimer order - this VBS is a nematic which breaks lattice rotational
symmetry. Our arguments are supported by comparing the spin wave energy with
the energy of the dimer solid obtained using a bond operator formalism. Turning
to the effect of thermal fluctuations on the spiral ordered state, any nonzero
temperature destroys the magnetic order, but the discrete rotational symmetry
of the lattice remains broken resulting in a thermal analogue of the nematic
VBS. We present arguments, supported by classical Monte Carlo simulations, that
this nematic transforms into the high temperature symmetric paramagnet via a
thermal phase transition which is in the universality class of the classical
3-state Potts (clock) model in 2D. We discuss the possible relevance of our
results for honeycomb magnets, such as Bi$_3$M$_4$O$_{12}$(NO$_3$) (with
M=Mn,V,Cr), and bilayer triangular lattice magnets.",1004.1119v2
2010-07-02,"Reply to Comment on ""Unconventional s-wave superconductivity in Fe(Se,Te)""","Mazin and Singh comment that the peaks in the Fourier-transformed
spectroscopic maps of Fe(Se,Te) are not related to the
quasi-particle-interference (QPI) but may be Bragg peaks associated with
chalcogen lattice and possible surface reconstruction which would be triggered
by surface-induced spin-density wave. We show that the peaks are too broad to
be assigned as Bragg peaks and are consistent with QPI.",1007.0307v1
2010-11-29,How to complete light meson spectroscopy to M = 2410 MeV/c^2,"A measurement of transverse polarisation in pbar-p -> all-neutral final
states would almost certainly determine a complete set of partial wave
amplitudes over the mass range 1910 to 2410 MeV. This should identify all
resonances in this mass range. The experiment is technically straightforward
and cheap by present standards.",1011.6237v1
2011-02-01,QCD Origin of Strong Magnetic Field in Compact Stars,"Some magnetic properties of quark matter and a microscopic origin of the
strong magnetic field in compact stars are discussed; ferromagnetic order is
discussed with the Fermi liquid theory and possible appearance of spin density
wave is suggested within the NJL model. Implications of these magnetic
properties are briefly discussed for compact stars.",1102.0064v1
2011-06-27,A New Expression for 3N Bound State Faddeev Equation in a 3D Approach,"A spin-isospin dependent three-dimensional approach has been applied for
formulation of the three-nucleon bound state and a new expression for Faddeev
equation based on three-nucleon free basis state has been obtained. Then the
three-nucleon wave function has been obtained as a function of five independent
variables.",1106.5319v1
2011-11-02,Phase transitions in dipolar gases in optical lattices,"We investigate the phase diagrams of two-dimensional lattice dipole systems
with variable geometry. For bipartite square and triangular lattices with
tunable vertical sublattice separation, we find rich phase diagrams featuring a
sequence of easy-plane magnetically ordered phases separated by incommensurate
spin-wave states.",1111.0550v2
2012-08-07,Vortex dynamics and skyrmions in four to six dimensions: Coherence vortices in Bose-Einstein condensates,"I point out how coherence vortices, i.e., topological defects in a
correlation function, could help explore new physics if they are created in
matter waves. Vortex dynamics could be studied in up to six dimensions, and
spin topological defects unseen in lower dimensions could be created. A
rudimentary proof-of-principle experiment is sketched and simulated, in which
three Bose-Einstein condensates are used to create and detect coherence
vortices.",1208.1489v1
2013-07-23,Calculation of multifractal dimensions in spin chains,"It was demonstrated in [Phys. Rev. E 86, 021104, (2012)], that the
ground-state wave functions for a large variety of one-dimensional spin-1/2
models are multifractals in the natural spin-z basis. We present here the
details of analytical derivations and numerical confirmations of these results.",1307.6016v1
2014-02-14,Extremely high-resolution measurements of microwave magnetisation dynamics in magnetic thin films and nanostructures,"In this work we discuss the use of interferometric measurement technique to
study microwave magnetization dynamics on ferromagnetic nanostructures. We
demonstrate that in this way one can resolve features which are impossible to
resolve with broadband ferromagnetic resonance and traveling spin wave
spectroscopy otherwise.",1402.3459v1
2014-11-09,Discovering the QCD Axion with Black Holes and Gravitational Waves,"Advanced LIGO may be the first experiment to detect gravitational waves.
Through superradiance of stellar black holes, it may also be the first
experiment to discover the QCD axion with decay constant above the GUT scale.
When an axion's Compton wavelength is comparable to the size of a black hole,
the axion binds to the black hole, forming a ""gravitational atom."" Through the
superradiance process, the number of axions occupying the bound levels grows
exponentially, extracting energy and angular momentum from the black hole.
Axions transitioning between levels of the gravitational atom and axions
annihilating to gravitons can produce observable gravitational wave signals.
The signals are long-lasting, monochromatic, and can be distinguished from
ordinary astrophysical sources. We estimate up to O(1) transition events at
aLIGO for an axion between 10^-11 and 10^-10 eV and up to 10^4 annihilation
events for an axion between 10^-13 and 10^-11 eV. In the event of a null
search, aLIGO can constrain the axion mass for a range of rapidly spinning
black hole formation rates. Axion annihilations are also promising for much
lighter masses at future lower-frequency gravitational wave observatories; the
rates have large uncertainties, dominated by supermassive black hole spin
distributions. Our projections for aLIGO are robust against perturbations from
the black hole environment and account for our updated exclusion on the QCD
axion of 6*10^-13 eV < ma < 2*10^-11 eV suggested by stellar black hole spin
measurements.",1411.2263v3
2015-05-13,Magnetic Solitons for Non Heisenberg Anisotropic Hamiltonians in Linear Quadrupole Excitations,"We discuss system with non-isotropic non-Heisenberg Hamiltonian with nearest
neighbor exchange within a mean field approximation process. We drive equations
describing non-Heisenberg non-isotropic model using coherent states in real
parameters and then obtain dispersion equations of spin wave of dipole and
quadrupole branches for a small linear excitation from the ground state. In
final, soliton solution for quadrupole branches for these linear equations
obtained.",1505.03244v1
2015-07-01,Accuracy and precision of gravitational-wave models of inspiraling neutron star -- black hole binaries with spin: comparison with numerical relativity in the low-frequency regime,"Coalescing binaries of neutron stars (NS) and black holes (BH) are one of the
most important sources of gravitational waves for the upcoming network of
ground based detectors. Detection and extraction of astrophysical information
from gravitational-wave signals requires accurate waveform models. The
Effective-One-Body and other phenomenological models interpolate between
analytic results and $10-30$ orbit numerical relativity (NR) merger
simulations. In this paper we study the accuracy of these models using new NR
simulations that span $36-88$ orbits, with mass-ratios and black hole spins
$(q,\chi_{BH}) = (7, \pm 0.4), (7, \pm 0.6)$, and $(5, -0.9)$. We find that:
(i) the recently published SEOBNRv1 and SEOBNRv2 models of the
Effective-One-Body family disagree with each other (mismatches of a few
percent) for black hole spins $\geq 0.5$ or $\leq -0.3$, with waveform mismatch
accumulating during early inspiral; (ii) comparison with numerical waveforms
indicate that this disagreement is due to phasing errors of SEOBNRv1, with
SEOBNRv2 in good agreement with all of our simulations; (iii) Phenomenological
waveforms disagree with SEOBNRv2 over most of the NSBH binary parameter space;
(iv) comparison with NR waveforms shows that most of the model's dephasing
accumulates near the frequency interval where it switches to a phenomenological
phasing prescription; and finally (v) both SEOBNR and post-Newtonian (PN)
models are effectual for NSBH systems, but PN waveforms will give a significant
bias in parameter recovery. Our results suggest that future gravitational-wave
detection searches and parameter estimation efforts targeted at NSBH systems
with $q\lesssim 7$ and $\chi_\mathrm{BH} \approx [-0.9, +0.6]$ will benefit
from using SEOBNRv2 templates. For larger black hole spins and/or binary
mass-ratios, we recommend the models be further investigated as suitable NR
simulations become available.",1507.00103v1
2015-12-09,Wigner function of a qubit,"We show that real polarization method can be effectively used to
geometrically quantize physical systems with compact phase space, like the
spin. Our method enables us to construct a wave function of a qubit in both
position and momentum representations and also its Wigner function. These
results can be used in quantum informatics.",1512.02867v1
2016-05-11,Solving the two dimensional Schrödinger equation using basis truncation: a controversial case,"Solutions of the Schr\""odinger equation by spanning the wave function is a
complete basis is a common practice is many-body interacting systems. We shall
study the case of a two-dimensional quantum system composed by two interacting
spin-less electrons and see that the correctness of the matrix approach depends
inexplicably on the type of interaction existing between particles.",1605.03343v1
2018-03-11,"Classical ground states, spin-wave and PCUT analysis of $\rm H_2SQ$ system","We study an organic Hydrogen bonded material $\rm{H_2SQ}$ analytically and
map out the phase diagram as well as low energy excitations in the relevant
parameter space. At zeroth order the dynamics is governed by plaquette
interaction (product of $\sigma_z$ over a plaquette) which defines a $Z_2$
gauge theory and a deconfinement phase satisfying ""ice rules"". The system is
studied under additional interactions such as an external Zeeman field (with
strength $K$) in $x$-direction, a inter-molecular interaction (with strength
$J_1$) and a dipole-dipole interaction with strength $J_2$ such that
$K>J_1>J_2$. The effect of dipole-dipole interaction removes the local $Z_2$
symmetry and gives rise to four global degenerate states with Ferroeletric
order. Using meanfield analysis we chart out the phase diagram for classical
version of the model and find $K_c$ which defines the transition from
disordered phase to ordered phase in $J_1, K$ plane for various values of
$J_2$. We find that presence of $J_1$ and $J_2$ tends to stabilize the
deconfined phases. Over the classical ground states we perform spin-wave
analysis and surprisingly find that quantum fluctuations does not remove the
classical degeneracy at all at quadratic level. The spin-wave spectrum is found
for the four global degenerate ground states which shows both gapped spectrum
and gapless spectrum (near the vicinity of CDT transition) for $J_2=0$. However
for $J_2$ finite, the spectrum is always gapped. We perform PCUT analysis to
improve the results of spin-wave analysis and calculate ground state energy and
one particle dispersion and gap at high symmetry point. Using this we draw the
phase boundary between confined and deconfined phase in the $K-J_1$ plane. The
effect of $J_2$ is also discussed in the resulting phase boundary.",1803.03989v1
2018-09-04,Symmetries in subatomic multi-quark systems,"We discus the role of QCD (Quantum Chromodynamics) to low energy phenomena
involving the color-spin symmetry of the quark model. We then combine it with
orbital and isospin symmetry to obtain wave functions with the proper
permutation symmetry, focusing on multi quark systems.",1809.00799v2
2020-08-27,Multi-frequency Data Parallel Spin Wave Logic Gates,"By their very nature, Spin Waves (SWs) with different frequencies can
propagate through the same waveguide without affecting each other, while only
interfering with their own species. Therefore, more SW encoded data sets can
coexist, propagate, and interact in parallel, which opens the road towards
hardware replication free parallel data processing. In this paper, we take
advantage of these features and propose a novel data parallel spin wave based
computing approach. To explain and validate the proposed concept, byte-wide
2-input XOR and 3-input Majority gates are implemented and validated by means
of Object Oriented MicroMagnetic Framework (OOMMF) simulations. Furthermore, we
introduce an optimization algorithm meant to minimize the area overhead
associated with multifrequency operation and demonstrate that it diminishes the
byte-wide gate area by 30% and 41% for XOR and Majority implementations,
respectively. To get inside on the practical implications of our proposal we
compare the byte-wide gates with conventional functionally equivalent scalar SW
gate based implementations in terms of area, delay, and power consumption. Our
results indicate that the area optimized 8-bit 2-input XOR and 3-input Majority
gates require 4.47x and 4.16x less area, respectively, at the expense of 5% and
7% delay increase, respectively, without inducing any power consumption
overhead. Finally, we discuss factors that are limiting the currently
achievable parallelism to 8 for phase based gate output detection and
demonstrate by means of OOMMF simulations that this can be increased 16 for
threshold based detection based gates.",2008.12220v2
2017-06-05,Effect of the Constant Potential in the Bethe-Salpeter Equation for Proton-Neutron Elastic Scattering,"Nucleon-nucleon potential is given in coordinate space starting from the
Bethe-Salpeter equation appropriate to elastic scattering at the intermediate
energy region. The next order in the potential is added to construct the
scattering wave for ${}^3S_1$ state. The constant terms have an effect on the
spin observables particularly at the center of mass angle $\theta=90^{\circ}$",1706.01229v1
2019-01-02,Magnetic properties of the multi-walled nanotubes constituted by localized magnetic moments: spin-1/2 case,"Magnetic properties of the multi-walled nanotubes have been investigated.
Heisenberg model, which is a suitable model for the system consist of atoms
with localized wave functions has been used. Effective field theory in two spin
cluster for spin-1/2 has been numerically solved and critical properties such
as phase diagrams as well as the behavior of the order parameter and hysteresis
loops obtained.",1901.00328v1
2019-04-27,Critical Behavior and Anisotropy in Single Crystal SrRuO$_3$,"The magnetization of single crystal SrRuO3 is studied as a function of
temperature along different crystallographic directions. The magnetocrystalline
anisotropy and behavior near the critical transition temperature are analyzed
in detail. The magnetization vs temperature is found to vary more like $T^2$
rather than $T^{3/2}$ expected for spin waves.",1904.12193v1
2019-07-06,Analytical model for gravitational-wave echoes from spinning remnants,"Gravitational-wave echoes in the post-merger signal of a binary coalescence
are predicted in various scenarios, including near-horizon quantum structures,
exotic states of matter in ultracompact stars, and certain deviations from
general relativity. The amplitude and frequency of each echo is modulated by
the photon-sphere barrier of the remnant, which acts as a spin- and
frequency-dependent high-pass filter, decreasing the frequency content of each
subsequent echo. Furthermore, a major fraction of the energy of the echo signal
is contained in low-frequency resonances corresponding to the quasi-normal
modes of the remnant. Motivated by these features, in this work we provide an
analytical gravitational-wave template in the low-frequency approximation
describing the post-merger ringdown and the echo signal of a spinning
ultracompact object. Besides the standard ringdown parameters, the template is
parametrized in terms of only two physical quantities: the reflectivity
coefficient and the compactness of the remnant. We discuss novel effects
related to the spin and to the complex reflectivity, such as a more involved
modulation of subsequent echoes, the mixing of two polarizations, and the
ergoregion instability in case of perfectly-reflecting spinning remnants.
Finally, we compute the errors in the estimation of the template parameters
with current and future gravitational-wave detectors using a Fisher matrix
framework. Our analysis suggests that models with almost perfect reflectivity
can be excluded/detected with current instruments, whereas probing values of
the reflectivity smaller than $80\%$ at $3\sigma$ confidence level requires
future detectors (Einstein Telescope, Cosmic Explorer, LISA). The template
developed in this work can be easily implemented to perform a matched-filter
based search for echoes and to constrain models of exotic compact objects.",1907.03091v3
2020-12-09,Partial decay widths of baryons in the spin-momentum operator expansion method,"The covariant operator expansion method used by the Bonn-Gatchina group for
the analysis of the meson photoproduction data is extended on the case of meson
electro-production reactions. The angular dependence of the partial waves is
deduced and the obtained amplitudes are compared with those used in other
analyses of the electro-production reactions",2012.05305v1
2022-12-22,Matrix Approach to Helicity States of Dirac Free Particles,"We derive the free wave solutions of the Dirac equation from the viewpoint of
matrix algebra. The concept of spin and the corresponding helicity states are
analyzed in detail. This consideration may help the readers to study
mathematical methods of relativistic quantum mechanics.",2212.11994v2
2023-10-28,A thousand fermions in a 3D harmonic trap via Monte Carlo simulations,"By use of a special wave function derived from similarly transformed
propagators, this work shows that the energy of a thousand spin-balanced
fermions in a three-dimensional harmonic potential can be accurately computed
using the Monte Carlo method.",2310.18818v1
2005-11-09,Morphological analysis of the cm-wave continuum in the dark cloud LDN1622,"The spectral energy distribution of the dark cloud LDN1622, as measured by
Finkbeiner using WMAP data, drops above 30GHz and is suggestive of a Boltzmann
cutoff in grain rotation frequencies, characteristic of spinning dust emission.
  LDN1622 is conspicuous in the 31 GHz image we obtained with the Cosmic
Background Imager, which is the first cm-wave resolved image of a dark cloud.
The 31GHz emission follows the emission traced by the four IRAS bands. The
normalised cross-correlation of the 31 GHz image with the IRAS images is higher
by 6.6sigma for the 12um and 25um bands than for the 60um and 100um bands:
C(12+25) = 0.76+/-0.02 and C(60+100) = 0.64+/-0.01.
  The mid-IR -- cm-wave correlation in LDN 1622 is evidence for very small
grain (VSG) or continuum emission at 26-36GHz from a hot molecular phase. In
dark clouds and their photon-dominated regions (PDRs) the 12um and 25um
emission is attributed to stochastic heating of the VSGs. The mid-IR and
cm-wave dust emissions arise in a limb-brightened shell coincident with the PDR
of LDN1622, where the incident UV radiation from the Ori OB1b association heats
and charges the grains, as required for spinning dust.",0511283v1
2007-02-19,Tidal dissipation in rotating solar-type stars,"We calculate the excitation and dissipation of low-frequency tidal
oscillations in uniformly rotating solar-type stars. For tidal frequencies
smaller than twice the spin frequency, inertial waves are excited in the
convective envelope and are dissipated by turbulent viscosity. Enhanced
dissipation occurs over the entire frequency range rather than in a series of
very narrow resonant peaks, and is relatively insensitive to the effective
viscosity. Hough waves are excited at the base of the convective zone and
propagate into the radiative interior. We calculate the associated dissipation
rate under the assumption that they do not reflect coherently from the center
of the star. Tidal dissipation in a model based on the present Sun is
significantly enhanced through the inclusion of the Coriolis force but may
still fall short of that required to explain the circularization of close
binary stars. However, the dependence of the results on the spin frequency,
tidal frequency, and stellar model indicate that a more detailed evolutionary
study including inertial and Hough waves is required. We also discuss the case
of higher tidal frequencies appropriate to stars with very close planetary
companions. The survival of even the closest hot Jupiters can be plausibly
explained provided that the Hough waves they generate are not damped at the
center of the star. We argue that this is the case because the tide excited by
a hot Jupiter in the present Sun would marginally fail to achieve nonlinearity.
As conditions at the center of the star evolve, nonlinearity may set in at a
critical age, resulting in a relatively rapid inspiral of the hot Jupiter.",0702492v1
1998-09-15,Data analysis of gravitational-wave signals from spinning neutron stars. II. Accuracy of estimation of parameters,"We examine the accuracy of estimation of parameters of the gravitational-wave
signals from spinning neutron stars that can be achieved from observations by
Earth-based laser interferometers. We consider a model of the signal consisting
of two narrowband components and including both phase and amplitude modulation.
We calculate approximate values of the rms errors of the parameter estimators
using the Fisher information matrix. We carry out extensive Monte Carlo
simulations and obtain cumulative distribution functions of rms errors of
astrophysically interesting parameters: amplitude of the signal, wobble angle,
position of the source in the sky, frequency, and spindown coefficients. We
consider both all-sky searches and directed searches. We also examine the
possibility of determination of neutron star proper motion. We perform
simulations for all laser-interferometric detectors that are currently under
construction and for several possible lengths of the observation time and sizes
of the parameter space. We find that observations of continuous
gravitational-wave signals from neutron stars by laser-interferometric
detectors will provide a very accurate information about their astrophysical
properties. We derive several simplified models of the signal that can be used
in the theoretical investigations of the data analysis schemes independently of
the physical mechanisms generating the gravitational-wave signal.",9809046v1
2000-06-22,"Post-Newtonian SPH calculations of binary neutron star coalescence. II. Binary mass ratio, equation of state, and spin dependence","Using our new Post-Newtonian SPH (smoothed particle hydrodynamics) code, we
study the final coalescence and merging of neutron star (NS) binaries. We vary
the stiffness of the equation of state (EOS) as well as the initial binary mass
ratio and stellar spins. Results are compared to those of Newtonian
calculations, with and without the inclusion of the gravitational radiation
reaction. We find a much steeper decrease in the gravity wave peak strain and
luminosity with decreasing mass ratio than would be predicted by simple
point-mass formulae. For NS with softer EOS (which we model as simple
$\Gamma=2$ polytropes) we find a stronger gravity wave emission, with a
different morphology than for stiffer EOS (modeled as $\Gamma=3$ polytropes as
in our previous work). We also calculate the coalescence of NS binaries with an
irrotational initial condition, and find that the gravity wave signal is
relatively suppressed compared to the synchronized case, but shows a very
significant second peak of emission. Mass shedding is also greatly reduced, and
occurs via a different mechanism than in the synchronized case. We discuss the
implications of our results for gravity wave astronomy with laser
interferometers such as LIGO, and for theoretical models of gamma-ray bursts
(GRBs) based on NS mergers.",0006078v2
2004-11-30,Quasi-local holography and quasi-local mass of classical fields in Minkowski spacetime,"The 2-surface characterization of special classical radiative Higgs-,
Yang-Mills and linear zero-rest-mass (l.z.r.m) fields with any spin is
investigated. We determine all the zero quasi-local mass Higgs- and Yang-Mills
field configurations with compact semisimple gauge groups, and show that they
are plane waves (provided the Higgs field is massless and linear) and
appropriate generalizations of plane waves (`Yang-Mills pp-waves'),
respectively. A tensor field (generalizing the energy-momentum tensor for the
Maxwell field and of the Bel-Robinson tensor for the linearized gravitational
field) is found by means of which the pp-wave nature of the solutions of the
l.z.r.m. field equations with any spin can be characterized equivalently. It is
shown that these radiative Yang-Mills and l.z.r.m. fields, given on a finite
globally hyperbolic domain D, are determined completely by certain
unconstrained data set on a closed spacelike 2-surface, the `edge of D'. These
pure radiative solutions are shown to determine a dense subset in the set of
solutions of various (Yang-Mills and l.z.r.m.) field equations. Thus for these
field configurations some `classical quasi-local holography' holds.",0411148v2
2006-04-10,A template bank to search for gravitational waves from inspiralling compact binaries I: physical models,"Gravitational waves from coalescing compact binaries are searched using the
matched filtering technique. As the model waveform depends on a number of
parameters, it is necessary to filter the data through a template bank covering
the astrophysically interesting region of the parameter space. The choice of
templates is defined by the maximum allowed drop in signal-to-noise ratio due
to the discreteness of the template bank. In this paper we describe the
template-bank algorithm that was used in the analysis of data from the Laser
Interferometer Gravitational Wave Observatory (LIGO) and GEO 600 detectors to
search for signals from binaries consisting of non-spinning compact objects.
Using Monte-Carlo simulations, we study the efficiency of the bank and show
that its performance is satisfactory for the design sensitivity curves of
ground-based interferometric gravitational wave detectors GEO 600, initial
LIGO, advanced LIGO and Virgo. The bank is efficient to search for various
compact binaries such as binary primordial black holes, binary neutron stars,
binary black holes, as well as a mixed binary consisting of a non-spinning
black hole and a neutron star.",0604037v5
2006-09-07,A brief survey of LISA sources and science,"LISA is a planned space-based gravitational-wave (GW) detector that would be
sensitive to waves from low-frequency sources, in the band of roughly $(0.03 -
0.1) {\rm mHz} \lesssim f \lesssim 0.1 {\rm Hz}$. This is expected to be an
extremely rich chunk of the GW spectrum -- observing these waves will provide a
unique view of dynamical processes in astrophysics. Here we give a quick survey
of some key LISA sources and what GWs can uniquely teach us about these
sources. Particularly noteworthy science which is highlighted here is the
potential for LISA to track the moderate to high redshift evolution of black
hole masses and spins through the measurement of GWs generated from massive
black hole binaries (which in turn form by the merger of galaxies and
protogalaxies). Measurement of these binary black hole waves has the potential
to determine the masses and spins of the constituent black holes with
percent-level accuracy or better, providing a unique high-precision probe of an
aspect of early structure growth. This article is based on the ``Astrophysics
Tutorial'' talk given by the author at the Sixth International LISA Symposium.",0609028v2
2001-03-29,Nonlinear and spin effects in two-photon annihilation of a fermion pair in an intensive laser wave,"The pattern of calculation of amplitudes of a series of processes in the
field of an intensive laser wave, in which two fermions $(p; p')$ and two real
photons $(k_1; k_2)$ participate, is considered. In relation to one-photon
processes, these processes are of the second order on $\alpha$, if the wave
intensity $\xi \ll 1$ (i.e., actually absorption from the wave only one
quantum). Otherwise, they are competing and essentially nonlinear. One-photon
processes have a number of the important physical applications. For example,
${\gamma}e$ and ${\gamma}{\gamma}$ colliders work on their basis.
  In DSB the calculation is conducted at the level of reaction amplitudes. It
essentially simplifies both the calculation and the form of obtained results;
those combinations of amplitudes which describe the spin effects are easy to
calculate. And these effects are especially essential in nonlinear processes.
The calculations are conducted in covariant form. Besides compactness, this
provides independence of the frames of reference and energy modes. The masses
of fermions are taken into account precisely and are not assumed equal each
other (heavy leptons, modes of various decays). The pattern of calculation is
given in the channel indicated in the title. The amplitudes of this channel are
also applicable for calculating of induced decay of orthopositronium into two
photons. And in this approach there is no necessity to assume the relative
momentum equal to zero.",0103323v1
2009-01-12,Electrodynamics in Iron and Steel,"In order to calculate the reflected EM fields at low amplitudes in iron and
steel, more must be understood about the nature of long wavelength excitations
in these metals. A bulk piece of iron is a very complex material with
microstructure, a split band structure, magnetic domains and crystallographic
textures that affect domain orientation. Probing iron and other bulk
ferromagnetic materials with weak reflected and transmitted inductive low
frequency fields is an easy operation to perform but the responses are
difficult to interpret because of the complexity and variety of the structures
affected by the fields. First starting with a simple single coil induction
measurement and classical EM calculation to show the error is grossly under
estimating the measured response. Extending this experiment to measuring the
transmission of the induced fields allows the extraction of three dispersion
curves which define these internal fields. One dispersion curve yielded an
exceedingly small effective mass of 1.8 10^{-39}kg (1.3 10^{-9} m_e) for those
spin waves. There is a second distinct dispersion curve more representative of
the density function of a zero momentum bound state rather than a propagating
wave. The third dispersion curve describes a magneto-elastic coupling to a very
long wave length propagating mode. These experiments taken together display the
characteristics of a high temperature Bose-Einstein like condensation that can
be initiated by pumping two different states. A weak time dependent field
drives the formation of coupled J=0 spin wave pairs with the reduced effective
mass reflecting the increased size of the coherent state. These field can
dominate induction measurements well past the Curie temperature.",0901.1631v2
2009-10-10,Excitation of Trapped Waves in Simulations of Tilted Black Hole Accretion Disks with Magnetorotational Turbulence,"We analyze the time dependence of fluid variables in general relativistic,
magnetohydrodynamic simulations of accretion flows onto a black hole with
dimensionless spin parameter a/M=0.9. We consider both the case where the
angular momentum of the accretion material is aligned with the black hole spin
axis (an untilted flow) and where it is misaligned by 15 degrees (a tilted
flow). In comparison to the untilted simulation, the tilted simulation exhibits
a clear excess of inertial variability, that is, variability at frequencies
below the local radial epicyclic frequency. We further study the radial
structure of this inertial-like power by focusing on a radially extended band
at 118 (M/10Msol)^-1 Hz found in each of the three analyzed fluid variables.
The three dimensional density structure at this frequency suggests that the
power is a composite oscillation whose dominant components are an over dense
clump corotating with the background flow, a low order inertial wave, and a low
order inertial-acoustic wave. Our results provide preliminary confirmation of
earlier suggestions that disk tilt can be an important excitation mechanism for
inertial waves.",0910.1882v1
2010-09-07,Stochastic background of gravitational waves emitted by magnetars,"Two classes of high energy sources in our galaxy are believed to host
magnetars, neutron stars whose emission results from the dissipation of their
magnetic field. The extremely high magnetic field of magnetars distorts their
shape, and causes the emission of a conspicuous gravitational waves signal if
rotation is fast and takes place around a different axis than the symmetry axis
of the magnetic distortion. Based on a numerical model of the cosmic star
formation history, we derive the cosmological background of gravitational waves
produced by magnetars, when they are very young and fast spinning. We adopt
different models for the configuration and strength of the internal magnetic
field (which determines the distortion) as well as different values of the
external dipole field strength (which governs the spin evolution of magnetars
over a wide range of parameters). We find that the expected gravitational wave
background differs considerably from one model to another. The strongest
signals are generated for magnetars with very intense toroidal internal fields
($\sim 10^{16}$ G range) and external dipole fields of $\sim 10^{14}$, as
envisaged in models aimed at explaining the properties of the Dec 2004 giant
flare from SGR 1806-20. Such signals should be easily detectable with third
generation ground based interferometers such as the Einstein Telescope.",1009.1240v2
2010-09-27,Colloquium: Nonlinear collective interactions in quantum plasmas with degenerate electron fluids,"The current understanding of some important nonlinear collective processes in
quantum plasmas with degenerate electrons is presented. After reviewing the
basic properties of quantum plasmas, we present model equations (e.g. the
quantum hydrodynamic and effective nonlinear Schr\""odinger-Poisson equations)
that describe collective nonlinear phenomena at nanoscales. The effects of the
electron degeneracy arise due to Heisenberg's uncertainty principle and Pauli's
exclusion principle for overlapping electron wavefunctions that result in
tunneling of electrons and the electron degeneracy pressure. Since electrons
are Fermions (spin-1/2), there also appears an electron spin current and a spin
force acting on electrons due to the Bohr magnetization. The quantum effects
produce new aspects of electrostatic (ES) and electromagnetic (EM) waves in a
quantum plasma that are summarized in here. Furthermore, we discuss nonlinear
features of ES ion waves and electron plasma oscillations (ESOs), as well as
the trapping of intense EM waves in quantum electron density cavities.
Specifically, simulation studies of the coupled nonlinear Schr\""odinger (NLS)
and Poisson equations reveal the formation and dynamics of localized ES
structures at nanoscales in a quantum plasma. We also discuss the effect of an
external magnetic field on the plasma wave spectra and develop quantum
magnetohydrodynamic (Q-MHD) equations. The results are useful for understanding
numerous collective phenomena in quantum plasmas, such as those in compact
astrophysical objects, in plasma-assisted nanotechnology, and in the
next-generation of intense laser-solid density plasma interaction experiments.",1009.5215v2
2010-10-25,Exploring the Use of Numerical Relativity Waveforms in Burst Analysis of Precessing Black Hole Mergers,"Recent years have witnessed tremendous progress in numerical relativity and
an ever improving performance of ground-based interferometric gravitational
wave detectors. In preparation for Advanced LIGO and a new era in gravitational
wave astronomy, the numerical relativity and gravitational wave data analysis
communities are collaborating to ascertain the most useful role for numerical
relativity waveforms in the detection and characterization of binary black hole
coalescences. In this paper, we explore the detectability of equal mass,
merging black hole binaries with precessing spins and total mass M_T in
[80,350]Msol, using numerical relativity waveforms and template-less search
algorithms designed for gravitational wave bursts. In particular, we present a
systematic study using waveforms produced by the MAYAKRANC code that are added
to colored, Gaussian noise and analyzed with the Omega burst search algorithm.
Detection efficiency is weighed against the orientation of one of the
black-hole's spin axes. We find a strong correlation between the detection
efficiency and the radiated energy and angular momentum, and that the inclusion
of the l=2, m=+/-1,0 modes, at a minimum, is necessary to account for the full
dynamics of precessing systems.",1010.5200v1
2011-07-05,Spin- and charge-density waves in the Hartree-Fock ground state of the two-dimensional Hubbard model,"The ground states of the two-dimensional repulsive Hubbard model are studied
within the unrestricted Hartree-Fock (UHF) theory. Magnetic and charge
properties are determined by systematic, large-scale, exact numerical
calculations, and quantified as a function of electron doping $h$. In the
solution of the self-consistent UHF equations, multiple initial configurations
and simulated annealing are used to facilitate convergence to the global
minimum. New approaches are employed to minimize finite-size effects in order
to reach the thermodynamic limit. At low to moderate interacting strengths and
low doping, the UHF ground state is a linear spin-density wave (l-SDW), with
antiferromagnetic order and a modulating wave. The wavelength of the modulating
wave is $2/h$. Corresponding charge order exists but is substantially weaker
than the spin order, hence holes are mobile. As the interaction is increased,
the l-SDW states evolves into several different phases, with the holes
eventually becoming localized. A simple pairing model is presented with
analytic calculations for low interaction strength and small doping, to help
understand the numerical results and provide a physical picture for the
properties of the SDW ground state. By comparison with recent many-body
calculations, it is shown that, for intermediate interactions, the UHF solution
provides a good description of the magnetic correlations in the true ground
state of the Hubbard model.",1107.0976v3
2011-07-13,Coulomb singularities in scattering wave functions of spin-orbit-coupled states,"We report on our analysis of the Coulomb singularity problem in the frame of
the coupled channel scattering theory including spin-orbit interaction. We
assume that the coupling between the partial wave components involves orbital
angular momenta such that $\Delta l = 0, \pm 2$. In these conditions, the two
radial functions, components of a partial wave associated to two values of the
angular momentum $l$, satisfy a system of two second-order ordinary
differential equations. We examine the difficulties arising in the analysis of
the behavior of the regular solutions near the origin because of this coupling.
First, we demonstrate that for a singularity of the first kind in the
potential, one of the solutions is not amenable to a power series expansion.
The use of the Lippmann-Schwinger equations confirms this fact: a logarithmic
divergence arises at the second iteration. To overcome this difficulty, we
introduce two auxilliary functions which, together with the two radial
functions, satisfy a system of four first-order differential equations. The
reduction of the order of the differential system enables us to use a
matrix-based approach, which generalizes the standard Frobenius method. We
illustrate our analysis with numerical calculations of coupled scattering wave
functions in a solid-state system.",1107.2643v1
2011-09-06,Quadrupole moment of a magnetically confined mountain on an accreting neutron star: effect of the equation of state,"Magnetically confined mountains on accreting neutron stars are promising
sources of continuous-wave gravitational radiation and are currently the
targets of directed searches with long-baseline detectors like the Laser
Interferometer Gravitational Wave Observatory (LIGO). In this paper, previous
ideal-magnetohydrodynamic models of isothermal mountains are generalized to a
range of physically motivated, adiabatic equations of state. It is found that
the mass ellipticity drops substantially, from \epsilon ~ 3e-4 (isothermal) to
\epsilon ~ 9e-7 (non-relativistic degenerate neutrons), 6e-8 (relativistic
degenerate electrons) and 1e-8 (non-relativistic degenerate electrons)
(assuming a magnetic field of 3e12 G at birth). The characteristic mass M_{c}
at which the magnetic dipole moment halves from its initial value is also
modified, from M_{c}/M_{\sun} ~ 5e-4 (isothermal) to M_{c}/M_{\sun} ~ 2e-6,
1e-7, and 3e-8 for the above three equations of state, respectively. Similar
results are obtained for a realistic, piecewise-polytropic nuclear equation of
state. The adiabatic models are consistent with current LIGO upper limits,
unlike the isothermal models. Updated estimates of gravitational-wave
detectability are made. Monte Carlo simulations of the spin distribution of
accreting millisecond pulsars including gravitational-wave stalling agree
better with observations for certain adiabatic equations of state, implying
that X-ray spin measurements can probe the equation of state when coupled with
magnetic mountain models.",1109.1040v1
2011-12-07,Updated gravitational-wave upper limits on the internal magnetic field strength of recycled pulsars,"Recent calculations of the hydromagnetic deformation of a stratified,
non-barotropic neutron star are generalized to describe objects with
superconducting interiors, whose magnetic permeability \mu is much smaller than
the vacuum value \mu_0. It is found that the star remains oblate if the
poloidal magnetic field energy is \gtrsim 40% of total magnetic field energy,
that the toroidal field is confined to a torus which shrinks as \mu decreases,
and that the deformation is much larger (by a factor \sim \mu_0/\mu) than in a
non-superconducting object. The results are applied to the latest direct and
indirect upper limits on gravitational-wave emission from Laser Interferometer
Gravitational Wave Observatory (LIGO) and radio pulse timing (spin-down)
observations of 81 millisecond pulsars, to show how one can use these
observations to infer the internal field strength. It is found that the
indirect spin-down limits already imply astrophysically interesting constraints
on the poloidal-toroidal field ratio and diamagnetic shielding factor (by which
accretion reduces the observable external magnetic field, e.g. by burial).
These constraints will improve following gravitational-wave detections, with
implications for accretion-driven magnetic field evolution in recycled pulsars
and the hydromagnetic stability of these objects' interiors.",1112.1542v1
2012-06-26,Super Tonks-Girardeau state in an attractive one-dimensional dipolar gas,"The ground state of a one-dimensional (1D) quantum gas of dipoles oriented
perpendicular to the longitudinal axis, with a strong 1/x^3 repulsive
potential, is studied at low 1D densities $n$. Near contact the dependence of
the many-body wave function on the separation x_{jl} of two particles reduces
to a two-body wave function \Psi_{rel}(x_{jl}). Immediately after a sudden
rotation of the dipoles so that they are parallel to the longitudinal axis,
this wave function will still be that of the repulsive potential, but since the
potential is now that of the attractive potential, it will not be stationary.
It is shown that as nd^2 -> 0 the rate of change of this wave function
approaches zero. It follows that for small values of nd^2, this state is
metastable and is an analog of the super Tonks-Girardeau state of bosons with a
strong zero-range attraction. The dipolar system is equivalent to a spinor
Fermi gas with spin $z$ components \sigma_{\uparrow}=\perp (perpendicular to
the longitudinal axis) and \sigma_{\downarrow}=|| (parallel to the longitudinal
axis). A Fermi-Fermi mapping from spinor to spinless Fermi gas followed by the
standard 1960 Fermi-Bose mapping reduces the Fermi system to a Bose gas.
Potential experiments realizing the sudden spin rotation with ultracold dipolar
gases are discussed, and a few salient properties of these states are
accurately evaluated by a Monte Carlo method.",1206.6042v3
2013-12-16,Spiral antiferromagnets beyond the spin-wave approximation: frustrated $XY$ and Heisenberg models in the honeycomb lattice,"We examine the stability of classical states with a generic incommensurate
spiral order against quantum fluctuations. Specifically, we focus on the
frustrated spin-1/2 $XY$ and Heisenberg models on the honeycomb lattice with
nearest-neighbor $J_1$ and next-nearest-neighbor $J_2$ antiferromagnetic
couplings. Our variational approach is based on the Jastrow wave functions,
which include quantum correlations on top of classical spin waves. We perform a
systematic optimization of wave vectors and Jastrow pseudo-potentials within
this class of variational states and find that quantum fluctuations favor
collinear states over generic coplanar spirals. The N\'eel state with ${\bf
Q}=(0,0)$ extends its stability well beyond the classical value $J_2/J_1=1/6$.
Most importantly, the collinear states with ${\bf Q}=(0,2\pi/\sqrt{3})$ (and
the two symmetry-related states) are found to be stable in a large regime with
intermediate frustration, while at the classical level they are limited to the
point $J_2/J_1=0.5$. For large frustration, the $120^\circ$ state is stabilized
for finite values of $J_2/J_1$ in both models.",1312.4558v2
2014-08-05,Four-quark structure of the excited states of heavy mesons,"We propose a four-quark structure for some of the excited states of heavy
mesons containing a single charm or bottom quark. The four-quark wave functions
are constructed based on a diquark-antidiquark form under the constraint that
they form an antitriplet $\bar{\bf{3}}_f$ in $\mbox{SU(3)}_f$, which seems to
be realized in some of the excited states listed in Particle Data Group.
Depending on the structure of antidiquark, we construct two possible models for
its wave functions: Model I) the antidiquark is symmetric in flavor
($\bar{\bf{6}}_f$) and antisymmetric in color ($\bf{3}_c$) and Model II) the
antidiquark is antisymmetric in flavor ($\bf{3}_f$) and symmetric in color
($\bar{\bf{6}}_c$). To test phenomenological relevance of these wave functions,
we calculate the mass differences among the excited states of spin $J=0,1,2$
using color-spin interactions. The four-quark wave functions based on Model~I
is found to reproduce the observed mass of the excited states of heavy mesons.
Also, our four-quark model provides an interesting phenomenology relating to
the decay widths of the excited states. To further pursue the possibility of
the four-quark structure, we make a few predictions for open charm and open
bottom states that may be discovered in future experiments. Most of them are
expected to have broad widths, which would make them difficult to be identified
experimentally. However, one resonance with $J=1$ containing bottom and strange
quarks is expected to appear as a sharp peak with its mass around $B^{\bar
s}_{1N} \sim 5753$~MeV. Confirmation of the existence of such states in future
experiments will shed light on our understanding of the structure of heavy
meson excited states.",1408.1139v1
2015-04-05,Decay rates of charmonia within a quark-antiquark confining potentials,"In this work, we investigate the spectroscopy and decay rates of charmonia
within the framework of non-relativistic Schr\""{o}dinger equation by employing
an approximate inter quark-antiquark potential. The spin hyperfine, spin-orbit
and tensor components of the one gluon exchange interaction are employed to
compute the spectroscopy of the excited S states and few low-lying P and D
waves. The resultant wave functions at zero inter quark separation as well as
some finite separation are employed to predict the di-gamma, di-leptonic and
di-gluon decay rates of charmonia states by using the conventional Van
Royen-Weisskopf formula. The di-gamma and di-leptonic decay widths are also
computed by incorporating the relativistic corrections of order $v^4$ within
the NRQCD formalism. We have observed that the NRQCD predictions with their
matrix elements computed at finite radial separation yielded results which are
found to be in better agreement with experimental value for both di-gamma and
di-leptonic decays. The same scenario is seen in the case when di-gamma and
di-leptonic decay widths are computed with Van Royen-Weisskopf formula. It is
also observed that the di-gluon decay width with the inclusion of binding
energy effects are in better agreement with the experimental data available for
1S-2S and 1P. The di-gluon decay width of 3S and 2P waves waves are also
predicted. Thus, the present study of decay rates clearly indicates the
importance of binding energy effects.",1504.01103v3
2016-05-07,Prime Factorization Using Magnonic Holographic Device,"Determining the prime factors of a given number N is a problem, which
requires super-polynomial time for conventional digital computers. A
polynomial-time algorithm was invented by P. Shor for quantum computers.
However, the realization of quantum computers is associated with significant
technological challenges in achieving and preserving quantum entanglement.
Prime factorization can be also solved by using classical wave interference
without quantum entanglement. In this work, we present experimental data
showing prime factorization by utilizing spin wave interference. The prime
factorization includes three major steps. First, general type computer
calculates the sequence of numbers mkmod(N), where N is the number to be
factorized, m is a randomly chosen positive integer, and k=0,1,2,3,4,5,6 .. .
Next, the period of calculated sequence r is determined by exploiting spin wave
interference. Finally, the general type computer finds the primes based on the
obtained r. The experiment on the period finding was accomplished on the
6-terminal Y3Fe2(FeO4)3 device. We chose number 15 for a test and found its
primes in a sequence of measurements. The obtained data demonstrate an example
of solving a prime factorization problem using classical wave interference. We
discuss the physical and technological limitations of this approach, which
define the maximum size of N and the computational speed. Though this classical
approach cannot compete with the quantum algorithm in efficiency, magnonic
holographic devices can be potentially utilized as complementary logic units
aimed to speed up prime factorization with classical computers.",1605.02127v1
2016-06-27,Blume-Capel ferromagnet driven by propagating and standing magnetic field wave: Dynamical modes and nonequilibrium phase transition,"The dynamical responses of Blume-Capel (S=1) ferromagnet to the plane
propagating (with fixed frequency and wavelength) and standing magnetic field
waves are studied sepa- rately in two dimensions by extensive Monte Carlo
simulation. Depending on the values of temperature, amplitude of the
propagating magnetic field and the strength of anisotropy, two different
dynamical phases are observed. For a fixed value of anisotropy and the
amplitude of the propagating magnetic field, the system undergoes a dynamical
phase transition from a driven spin wave propagating phase to a pinned or spin
frozen state as the system is cooled down. The time averaged magnetisation over
a full cycle of the propagating magnetic field plays the role of the dynamic
order parameter. A comprehensive phase diagram is plotted in the plane formed
by the amplitude of the propagating wave and the temperature of the system. It
is found that the phase boundary shrinks inward as the anisotropy increases.
The phase boundary, in the plane described by the strength of the anisotropy
and temperature, is also drawn. This phase boundary was observed to shrink
inward as the field amplitude increases.",1606.08155v3
2016-09-06,Photoexcitation of electron wave packets in quantum spin Hall edge states: effects of chiral anomaly from a localised electric pulse,"We show that, when a spatially localised electric pulse is applied at the
edge of a quantum spin Hall system, electron wavepackets of the helical states
can be photoexcited by purely intra-branch electrical transitions, without
invoking the bulk states or the magnetic Zeeman coupling. In particular, as
long as the electric pulse remains applied, the photoexcited densities lose
their character of right- and left-movers, whereas after the ending of the
pulse they propagate in opposite directions without dispersion, i.e.
maintaining their space profile unaltered. Notably we find that, while the
momentum distribution of the photoexcited wave packets depends on the
temperature $T$ and the chemical potential $\mu$ of the initial equilibrium
state and displays a non-linear behavior on the amplitude of the applied pulse,
in the mesoscopic regime the space profile of the wave packets is independent
of $T$ and $\mu$. Instead, it depends purely on the applied electric pulse, in
a linear manner, as a signature of the chiral anomaly characterising massless
Dirac electrons. We also discuss how the photoexcited wave packets can be
tailored with the electric pulse parameters, for both low and finite
frequencies.",1609.01478v2
2018-01-24,"On Small Beams with Large Topological Charge II: Photons, Electrons and Gravitational Waves","Beams of light with a large topological charge significantly change their
spatial structure when they are focused strongly. Physically, it can be
explained by an emerging electromagnetic field component in the direction of
propagation, which is neglected in the simplified scalar wave picture in
optics. Here we ask: Is this a specific photonic behavior, or can similar
phenomena also be predicted for other species of particles? We show that the
same modification of the spatial structure exists for relativistic electrons as
well as for focused gravitational waves. However, this is for different
physical reasons: For electrons, which are described by the Dirac equation, the
spatial structure changes due to a Spin-Orbit coupling in the relativistic
regime. In gravitational waves described with linearized general relativity,
the curvature of space-time between the transverse and propagation direction
leads to the modification of the spatial structure. Thus, this universal
phenomenon exists for both massive and massless elementary particles with Spin
1/2, 1 and 2. It would be very interesting whether other types of particles
such as composite systems (neutrons or C$_{60}$) or neutrinos show a similar
behaviour and how this phenomenon can be explained in a unified physical way.",1801.07825v3
2018-09-04,Propagation and attenuation of sound in one-dimensional quantum liquids,"At low temperatures, elementary excitations of a one-dimensional quantum
liquid form a gas that can move as a whole with respect to the center of mass
of the system. This internal motion attenuates at exponentially long time
scales. As a result, in a broad range of frequencies the liquid is described by
two-fluid hydrodynamics, and the system supports two sound modes. The physical
nature of the two sounds depends on whether the particles forming the quantum
liquid have a spin degree of freedom. For particles with spin, the modes are
analogous to the first and second sound modes in superfluid $^4$He, which are
the waves of density and entropy, respectively. When dissipative processes are
taken into account, we find that at low frequencies the second sound is
transformed into heat diffusion, while the first sound mode remains weakly
damped and becomes the ordinary sound. In a spinless liquid the entropy and
density oscillations are strongly coupled, and the resulting sound modes are
hybrids of the first and second sound. As the frequency is lowered and
dissipation processes become important, the crossover to single-fluid regime
occurs in two steps. First the hybrid modes transform into predominantly
density and entropy waves, similar to the first and second sound, and then the
density wave transforms to the ordinary sound and the entropy wave becomes a
heat diffusion mode. Finally, we account for the dissipation due to viscosity
and intrinsic thermal conductivity of the gas of excitations, which controls
attenuation of the sound modes at high frequencies.",1809.01099v1
2018-09-19,A semi-coherent analysis method to search for continuous gravitational waves emitted by ultra-light boson clouds around spinning black holes,"As a consequence of superradiant instability induced in Kerr black holes,
ultra-light boson clouds can be a source of persistent gravitational waves,
potentially detectable by current and future gravitational-wave detectors.
These signals have been predicted to be nearly monochromatic, with a small
steady frequency increase (spin-up), but given the several assumptions and
simplifications done at theoretical level, it is wise to consider, from the
data analysis point of view, a broader class of gravitational signals in which
the phase (or the frequency) slightly wander in time. Also other types of
sources, e.g. neutron stars in which a torque balance equilibrium exists
between matter accretion and emission of persistent gravitational waves, would
fit in this category. In this paper we present a robust and computationally
cheap analysis pipeline devoted to the search of such kind of signals. We
provide a full characterization of the method, through both a theoretical
sensitivity estimation and through the analysis of syntethic data in which
simulated signals have been injected. The search setup for both all-sky
searches and higher sensitivity directed searches is discussed.",1809.07202v1
2019-11-07,Symmetry breaking of azimuthal waves: Slow-flow dynamics on the Bloch Sphere,"Depending on the reflectional and rotational symmetries of annular combustors
for aeroengines and gas turbines, self-sustained azimuthal thermoacoustic
eigenmodes can be standing, spinning or mix of these two types of waves. These
thermoacoustic limit cycles are unwanted because the resulting intense acoustic
fields induce high-cycle fatigue of the combustor components. This paper
presents a new theoretical framework for describing, in an idealized annular
combustor, the dynamics of the slow-flow variables, which define the state of
an eigenmode, i.e. if the latter is standing, spinning or mixed. The acoustic
pressure is expressed as a hypercomplex field and this ansatz is inserted into
a one dimensional wave equation that describes the thermoacoustics of a thin
annulus. Slow-flow averaging of this wave equation is performed by adapting the
classic Krylov-Bogoliubov method to the quaternion field in order to derive a
system of coupled first order differential equations for the four slow-flow
variables, i.e. the amplitude, the nature angle, the preferential direction and
the temporal phase of the azimuthal thermoacoustic mode. The state of the mode
can be conveniently depicted by using the first three slow-flow variables as
spherical coordinates for a Bloch sphere representation. Stochastic forcing
from the turbulence in annular combustors is also accounted for. This new
analytical model describes both rotational and reflectional symmetry breaking
bifurcations induced by the non-uniform distribution of thermoacoustic sources
along the annulus circumference and by the presence of a mean swirl.",1911.02830v4
2019-11-29,Real space observation of magnon interaction with driven space-time crystals,"The concept of Space-Time Crystals (STC), i.e. translational symmetry
breaking in time and space, was recently proposed and experimentally
demonstrated for quantum systems. Here, we transfer this concept to magnons and
experimentally demonstrate a driven STC at room temperature. The STC is
realized by strong homogeneous micro-wave pumping of a micron-sized permalloy
(Py) stripe and is directly imaged by Scanning Transmission X-ray Microscopy
(STXM). For a fundamental understanding of the formation of the STC,
micromagnetic simulations are carefully adapted to model the experimental
findings. Beyond the mere generation of a STC, we observe the formation of a
magnonic band structure due to back folding of modes at the STC's Brillouin
zone boundaries. We show interactions of magnons with the STC that appear as
lattice scattering. This results in the generation of ultra short spin waves
down to 100 nm wavelength that cannot be described by classical dispersion
relations for linear spin wave excitations. We expect that room temperature
STCs will be a useful tool to investigate non-linear wave physics, as they can
be easily generated and manipulated to control their spatial and temporal band
structure.",1911.13192v1
2020-08-21,Critical couplings in topological-insulator waveguide-resonator systems observed in elastic waves,"Waveguides and resonators are core components in the large-scale integration
of electronics, photonics, and phononics, both in existing and future
scenarios. In certain situations, there is critical coupling of the two
components; i.e., no energy passes through the waveguide after the incoming
wave couples into the resonator. The transmission spectral characteristics
resulting from this phenomenon are highly advantageous for signal filtering,
switching, multiplexing, and sensing. In the present study, adopting an
elastic-wave platform, we introduce topological insulator (TI), a remarkable
achievement in condensed matter physics over the past decade, into a classical
waveguide-ring-resonator configuration. Along with basic similarities with
classical systems, a TI system has important differences and advantages, mostly
owing to the spin-momentum locked transmission states at the TI boundaries. As
an example, a two-port TI waveguide resonator can fundamentally eliminate
upstream reflections while completely retaining useful transmission spectral
characteristics, and maximize the energy in the resonator, with possible
applications being novel signal processing, gyro/sensing, lasering, energy
harvesting, and intense wave-matter interactions, using phonons, photons, or
even electrons. The present work further enhances the confidence of using
topological protection for practical device performance and functionalities,
especially considering the crucial advantage of introducing (pseudo)spins to
existing conventional configurations. More in-depth research on advancing
phononics/photonics, especially on-chip, is foreseen.",2008.09547v1
2017-10-19,Hidden Markov model tracking of continuous gravitational waves from a binary neutron star with wandering spin. II. Binary orbital phase tracking,"A hidden Markov model (HMM) scheme for tracking continuous-wave gravitational
radiation from neutron stars in low-mass X-ray binaries (LMXBs) with wandering
spin is extended by introducing a frequency-domain matched filter, called the
J-statistic, which sums the signal power in orbital sidebands coherently. The
J-statistic is similar but not identical to the binary-modulated F-statistic
computed by demodulation or resampling. By injecting synthetic LMXB signals
into Gaussian noise characteristic of the Advanced Laser Interferometer
Gravitational-wave Observatory (Advanced LIGO), it is shown that the
J-statistic HMM tracker detects signals with characteristic wave strain $h_0
\geq 2 \times 10^{-26}$ in 370 d of data from two interferometers, divided into
37 coherent blocks of equal length. When applied to data from Stage I of the
Scorpius X-1 Mock Data Challenge organised by the LIGO Scientific
Collaboration, the tracker detects all 50 closed injections ($h_0 \geq 6.84
\times 10^{-26}$), recovering the frequency with a root-mean-square accuracy of
$\leq 1.95\times10^{-5}$ Hz. Of the 50 injections, 43 (with $h_0 \geq 1.09
\times 10^{-25}$) are detected in a single, coherent 10-d block of data. The
tracker employs an efficient, recursive HMM solver based on the Viterbi
algorithm, which requires $\sim 10^5$ CPU-hours for a typical, broadband
(0.5-kHz), LMXB search.",1710.07092v1
2017-10-28,Overcoming the SQL in gravitational wave detectors using spin systems with negative effective mass,"Quantum back action (QBA) of a measurement limits the precision of
observation of the motion of a free mass. This profound effect dabbed the
""Heisenberg microscope"" in the early days of quantum mechanics, leads to the
standard quantum limit (SQL) stemming from the balance between the measurement
sensitivity and the QBA. Here we consider the measurement of motion of a free
mass performed in a quantum reference frame with an effective negative mass
which is not limited by QBA. As a result, the disturbance on the motion of a
free mass can be measured beyond SQL. QBA-limited detection of motion for a
free mass is extremely challenging, but there are devices where this effect is
expected to play an essential role, namely, gravitational wave detectors (GWD)
such as LIGO and VIRGO. Recent reports on observation of gravitational waves
have opened new horizons in cosmology and astrophysics. Here we present a
general idea and a detailed numerical analysis for QBA-evading measurement of
the gravitational wave effect on the GWD mirrors which can be considered free
masses under relevant conditions. The measurement is performed by two entangled
beams of light probing the GWD and an auxiliary atomic spin ensemble,
respectively. The latter plays a role of a free negative mass. We show that
under realistic conditions the sensitivity of the GWD can be significantly
increased over the entire frequency band of interest.",1710.10405v1
2021-02-15,Exchange-Mediated Mutual Correlation and Dephasing in Free-Electron and Light Interactions,"The quantum world distinguishes itself from the classical world by being
governed by probability amplitudes rather than probabilities. On a
single-particle level, quantum phases can be manipulated leading to observable
interference patterns that can be used as a probe e.g. in matter wave
microscopy. But the quantum world bears even more fascinating effects when it
comes to the interplay between more than one particle. Correlations between
quantum particles such as entanglement can be exploited to speed up
computational algorithms or enable secure cryptography. Here, we propose and
numerically explore a thought experiment to address the question whether
quantum correlations between particles can be used in matter wave microscopy.
Specifically, we address the following questions: How can information be
transferred between two mutually spin-correlated free-electron wavepackets? Can
Coulomb and exchange correlations be linked to the decoherence mechanism of
matter waves? Using a time-dependent Hartree-Fock algorithm, we will show that
the exchange term has a substantial role in transferring the information
between two mutually spin-correlated electrons, whereas the Hartree potential
(or mean-field Coulomb potential) dominates the dephasing on a single-particle
level. Our findings might facilitate fermionic matter-wave interferometry
experiments in which it is possible to retrieve information about non-classical
correlations and the mechanism of decoherence in open versus closed quantum
systems.",2102.07439v2
2021-10-06,Parameterised population models of transient non-Gaussian noise in the LIGO gravitational-wave detectors,"The two interferometric LIGO gravitational-wave observatories provide the
most sensitive data to date to study the gravitational-wave Universe. As part
of a global network, they have just completed their third observing run in
which they observed many tens of signals from merging compact binary systems.
It has long been known that a limiting factor in identifying transient
gravitational-wave signals is the presence of transient non-Gaussian noise,
which reduce the ability of astrophysical searches to detect signals
confidently. Significant efforts are taken to identify and mitigate this noise
at the source, but its presence persists, leading to the need for software
solutions. Taking a set of transient noise artefacts categorised by the
GravitySpy software during the O3a observing era, we produce parameterised
population models of the noise projected into the space of astrophysical model
parameters of merging binary systems. We compare the inferred population
properties of transient noise artefacts with observed astrophysical systems
from the GWTC2.1 catalogue. We find that while the population of astrophysical
systems tend to have near equal masses and moderate spins, transient noise
artefacts are typically characterised by extreme mass ratios and large spins.
This work provides a new method to calculate the consistency of an observed
candidate with a given class of noise artefacts. This approach could be used in
assessing the consistency of candidates found by astrophysical searches (i.e.
determining if they are consistent with a known glitch class). Furthermore, the
approach could be incorporated into astrophysical searches directly,
potentially improving the reach of the detectors, though only a detailed study
would verify this.",2110.02689v1
2017-03-10,Variational Monte Carlo method for fermionic models combined with tensor networks and applications to the hole-doped two-dimensional Hubbard model,"The conventional tensor-network states employ real-space product states as
reference wave functions. Here, we propose a many-variable variational Monte
Carlo (mVMC) method combined with tensor networks by taking advantages of both
to study fermionic models. The variational wave function is composed of a pair
product wave function operated by real space correlation factors and tensor
networks. Moreover, we can apply quantum number projections, such as spin,
momentum and lattice symmetry projections, to recover the symmetry of the wave
function to further improve the accuracy. We benchmark our method for one- and
two-dimensional Hubbard models, which show significant improvement over the
results obtained individually either by mVMC or by tensor network. We have
applied the present method to hole doped Hubbard model on the square lattice,
which indicates the stripe charge/spin order coexisting with a weak $d$-wave
superconducting order in the ground state for the doping concentration less
than 0.3, where the stripe oscillation period gets longer with increasing hole
concentration. The charge homogeneous and highly superconducting state also
exists as a metastable excited state for the doping concentration less than
0.25.",1703.03537v2
2019-04-09,Pseudogap and weak multifractality in disordered Mott charge-density-wave insulator,"The competition, coexistence and cooperation of various orders in
low-dimensional materials like spin, charge, topological orders and
charge-density-wave has been one of the most intriguing issues in condensed
matter physics. In particular, layered transition metal dichalcogenides provide
an ideal platform for studying such an interplay with a notable case of
1${T}$-TaS$_{2}$ featuring Mott-insulating ground state, charge-density-wave,
spin frustration and emerging superconductivity together. We investigated local
electronic states of Se-substituted 1${T}$-TaS$_{2}$ by scanning tunneling
microscopy/spectroscopy (STM/STS), where superconductivity emerges from the
unique Mott-CDW state. Spatially resolved STS measurements reveal that an
apparent V-shape pseudogap forms at the Fermi Level (E$_{F}$), with the origin
of the electronic states splitting and transformation from the Mott states, and
the CDW gaps are largely preserved. The formation of the pseudogap has little
correlation to the variation of local Se concentration, but appears to be a
global characteristics. Furthermore, the correlation length of local density of
states (LDOS) diverges at the Fermi energy and decays rapidly at high energies.
The spatial correlation shows a power-law decay close to the Fermi energy. Our
statistics analysis of the LDOS indicates that our system exhibits weak
multifractal behavior of the wave functions. These findings strongly support a
correlated metallic state induced by disorder in our system, which provides an
new insight into the novel mechanism of emerging superconductivity in the
two-dimensional correlated electronic systems.",1904.04508v1
2019-09-02,The Speed of Gravity,"Within the standard effective field theory of General Relativity, we show
that the speed of gravitational waves deviates, ever so slightly, from
luminality on cosmological and other spontaneously Lorentz-breaking
backgrounds. This effect results from loop contributions from massive fields of
any spin, including Standard Model fields, or from tree level effects from
massive higher spins $s \ge 2$. We show that for the choice of interaction
signs implied by S-matrix and spectral density positivity bounds suggested by
analyticity and causality, the speed of gravitational waves is in general
superluminal at low-energies on NEC preserving backgrounds, meaning
gravitational waves travel faster than allowed by the metric to which photons
and Standard Model fields are minimally coupled. We show that departure of the
speed from unity increases in the IR and argue that the speed inevitably
returns to luminal at high energies as required by Lorentz invariance.
Performing a special tuning of the EFT so that renormalization sensitive
curvature-squared terms are set to zero, we find that finite loop corrections
from Standard Model fields still lead to an epoch dependent modification of the
speed of gravitational waves which is determined by the precise field content
of the lightest particles with masses larger than the Hubble parameter today.
Depending on interpretation, such considerations could potentially have
far-reaching implications on light scalar models, such as axionic or fuzzy cold
dark matter.",1909.00881v2
2021-01-14,Alternative possibility of GW190521: Gravitational waves from high-mass black hole-disk systems,"We evolve high-mass disks of mass $15$-$50M_\odot$ orbiting a $50M_\odot$
spinning black hole in the framework of numerical relativity. Such high-mass
systems could be an outcome during the collapse of rapidly-rotating
very-massive stars. The massive disks are dynamically unstable to the so-called
one-armed spiral-shape deformation with the maximum fractional
density-perturbation of $\delta \rho/\rho \gtrsim 0.1$, and hence,
high-amplitude gravitational waves are emitted. The waveforms are characterized
by an initial high-amplitude burst with the frequency of $\sim 40$-$50$ Hz and
the maximum amplitude of $(1$-$10)\times 10^{-22}$ at the hypothetical distance
of 100 Mpc and by a subsequent low-amplitude quasi-periodic oscillation. We
illustrate that the waveforms in our models with a wide range of the disk mass
resemble that of GW190521. We also point out that gravitational waves from
rapidly-rotating very-massive stars can be the source for 3rd-generation
gravitational-wave detectors for exploring the formation process of
rapidly-spinning high-mass black holes of mass $\sim 50$-$100M_\odot$ in an
early universe.",2101.05440v2
2021-11-01,Spectrum evolution and chirping of laser-induced spin wave packets in thin iron films,"We present the experimental study of ultrafast optical excitation of
magnetostatic surface spin wave (MSSW) packets and their spectral properties in
thin films of pure iron. As the packets leave the excitation area and propagate
in space, their spectra evolve non-trivially. Particularly, low or high
frequency components are suppressed at the border of the excitation area
depending on the orientation of the external magnetic field with respect to the
magnetocrystolline anisotropy axes of the film. The effect is ascribed to the
ultrafast local heating of the film. Further, the time resolution of the
implemented all-optical technique allows us to extract the chirp of the MSSW
packet in the time domain via wavelet analysis. The chirp is a result of the
group velocity dispersion of the MSSW and, thus, is controlled by the film
magnetic parameters, magnetization and anisotropy, and external field
orientation. The demonstrated tunable modulation of MSSW wave packets with
femtosecond laser pulses may find application in future magnonic-photonic
hybrid devices for wave-based data processing.",2111.00983v2
2021-11-11,Enhanced charge density wave with mobile superconducting vortices in La$_{1.885}$Sr$_{0.115}$CuO$_4$,"Superconductivity in the cuprates is found to be intertwined with charge and
spin density waves. Determining the interactions between the different types of
order is crucial for understanding these important materials. Here, we
elucidate the role of the charge density wave (CDW) in the prototypical cuprate
La$_{1.885}$Sr$_{0.115}$CuO$_4$, by studying the effects of large magnetic
fields ($H$) up to 24 Tesla. At low temperatures ($T$), the observed CDW peaks
reveal two distinct regions in the material: a majority phase with short-range
CDW coexisting with superconductivity, and a minority phase with longer-range
CDW coexisting with static spin density wave (SDW). With increasing magnetic
field, the CDW first grows smoothly in a manner similar to the SDW. However, at
high fields we discover a sudden increase in the CDW amplitude upon entering
the vortex-liquid state. Our results signify strong coupling of the CDW to
mobile superconducting vortices and link enhanced CDW amplitude with local
superconducting pairing across the $H-T$ phase diagram.",2111.06422v1
2021-12-13,Transformation of an energy spectrum and wave functions in the crossover from two- to three-dimensional topological insulator in HgTe quantum wells: long and thorny way,"A magnetotransport and quantum capacitance of the two-dimensional electron
gas in HgTe/Cd$_x$Hg$_{1-x}$Te quantum wells of a width ($20.2-46.0$)~nm are
experimentally investigated. It is shown that the first energy subband of
spatial quantization is split due to the spin-orbit interaction and the split
branches are single-spin, therewith the splitting strength increases with the
increase of the quantum well width. The electron effective masses in the
branches are close to each other within the actual density range.
Magneto-intersubband oscillations (MISO) observed in the structures under study
exhibit the growing amplitude with the increasing electron density that
contradicts to the expected decrease of wave function overlap for the
rectangular quantum well. To interpret the data obtained, we have used a
self-consistent approach to calculate the electron energy spectrum and the wave
function within framework of the \emph{kP}-model. It has been in particular
shown that the MISO amplitude increase results from the increasing overlap of
the wave functions due to their shift from the gate electrode with the gate
voltage increase known as phenomenon of the negative electron polarizability.
The results obtained from the transport experiments are supported by quantum
capacitance measurements.",2112.06838v1
2022-03-25,Deep follow-up for gravitational-wave inference: a case study with GW151226,"New analyses of gravitational wave events raise questions about the nature of
some events. For example, LIGO--Virgo--KAGRA initially determined GW151226 to
be a merger with a mass-ratio $q\approx0.5$ and effective inspiral spin
$\chi_{\text{eff}}\approx 0.2$. However, recent works offer an alternative
picture: GW151226 is a lower-mass-ratio event $q \approx 0.3$ with slightly
higher spin $\chi_{\text{eff}}\approx 0.3$. This discrepancy has been
challenging to resolve as a wide range of differences are employed for each
analysis. This work introduces a ``deep follow-up'' framework to efficiently
compute the posterior odds between two different peaks in parameter space. In
doing so, we aim to help resolve disputes about the true nature of
gravitational-wave events associated with conflicting astrophysical
interpretations. Our proposal is not a replacement for standard inference
techniques; instead, our method provides a diagnostic tool to understand
discrepancies between conflicting results. We demonstrate this method by
studying three {$q$-$\chi_{\text{eff}}$} peaks proposed for GW151226. We find
the $(q\sim0.5, \chi_{\text{eff}}\sim0.2)$ interpretation is only slightly
preferred over the $(q\sim0.3, \chi_{\text{eff}}\sim0.3)$ hypothesis with a
posterior odds of $\sim1.7\pm0.4$, suggesting that neither of the two peaks can
be ruled out. We discuss strategies to produce more reliable parameter
estimation studies in gravitational-wave astronomy.",2203.13406v2
2022-05-28,Spectral Evidence for Unidirectional Charge Density Wave in Detwinned BaNi$_2$As$_2$,"The emergence of unconventional superconductivity in proximity to intertwined
electronic orders is especially relevant in the case of iron-based
superconductors. Such order consists of an electronic nematic order and a spin
density wave in these systems. BaNi$_2$As$_2$, like its well-known iron-based
analog BaFe$_2$As$_2$, also hosts a symmetry-breaking structural transition
that is coupled to a unidirectional charge density wave (CDW), providing a
novel platform to study intertwined orders. Here, through a systematic
angle-resolved photoemission spectroscopy study combined with a detwinning
$B_1g$ uniaxial strain, we identify distinct spectral evidence of band
evolution due to the structural transition as well as CDW-induced band folding.
In contrast to the nematicity and spin density wave in BaFe$_2$As$_2$, the
structural and CDW order parameters in BaNi$_2$As$_2$ are observed to be
strongly coupled and do not separate in the presence of uniaxial strain. Our
measurements point to a likely lattice origin of the CDW in BaNi$_2$As$_2$.",2205.14339v1
2022-06-29,Four eccentric mergers increase the evidence that LIGO--Virgo--KAGRA's binary black holes form dynamically,"The growing population of compact binary mergers detected with gravitational
waves contains multiple events that are challenging to explain through isolated
binary evolution. Such events have higher masses than are expected in isolated
binaries, component spin-tilt angles that are misaligned, and/or non-negligible
orbital eccentricities. We investigate the orbital eccentricities of 62 binary
black hole candidates from the third gravitational-wave transient catalogue of
the LIGO-Virgo-KAGRA Collaboration with an aligned-spin, moderate-eccentricity
waveform model. Within this framework, we find that at least four of these
events show significant support for eccentricity $e_{10} \geq 0.1$ at a
gravitational-wave frequency of $10$~Hz ($> 60\%$ credibility, under a
log-uniform eccentricity prior that spans the range $10^{-4} < e_{10} < 0.2$).
Two of these events are new additions to the population: GW191109 and
GW200208\_22. If the four eccentric candidates are truly eccentric, our results
suggest that densely-populated star clusters may produce 100\% of the observed
mergers. However, it remains likely that other formation environments with
higher yields of eccentric mergers -- for example, active galactic nuclei --
also contribute. We estimate that we will be able to confidently distinguish
which formation channel dominates the eccentric merger rate after $\gtrsim 80$
detections of events with $e_{10} \geq 0.05$ at LIGO--Virgo sensitivity, with
only $\sim 5$ detectably-eccentric events required to distinguish formation
channels with third-generation gravitational-wave detectors.",2206.14695v2
2022-11-25,"On thermal fluctuations and quantum regularities of $\mathcal{F}(R,\mathcal{G})$ gravity black holes with constant topological Euler density in nonlinear electrodynamics","We discuss the corrected thermodynamics and naked singularity structure of
the topological static spherically symmetric solution in
$\mathcal{F}(R,\mathcal{G})$ - gravity coupled with Born-Infeld - like
nonlinear electrodynamics. Solutions admitting black holes with constant
topological Euler density is analyzed in view of various thermodynamical
variables. The inclusion of logarithmic correction to the entropy is extended
to the other thermodynamical variables and the contribution of corrected
variables are displayed on various plots. The stability of black hole under the
effect of thermal variables is also studied. As a second scope of this study,
solutions admitting timelike naked singularity are probed with bosonic and
fermionic quantum wave packets to see if the singularity is quantum
mechanically regular or not. In this context, the evolution of these probes
remains well-defined if the corresponding spatial Hamiltonian operator is
essentially self-adjoint. Our calculations reveal that when the singularity is
probed with specific wave modes involving spin - $0$ and spin - $1/2$ quantum
wave packets, the corresponding wave operators turn out to be essentially
self-adjoint, which in turn implies unique well-defined time evolution.",2211.14294v2
2023-04-07,Simple parameter estimation using observable features of gravitational-wave signals,"Using simple, intuitive arguments, we discuss the expected accuracy with
which astrophysical parameters can be extracted from an observed gravitational
wave signal. The observation of a chirp like signal in the data allows for
measurement of the component masses and aligned spins, while measurement in
three or more detectors enables good localization. The ability to measure
additional features in the observed signal -- the existence or absence of power
in i) the second gravitational wave polarization, ii) higher gravitational wave
multipoles or iii) spin-induced orbital precession -- provide new information
which can be used to significantly improve the accuracy of parameter
measurement. We introduce the simple-pe algorithm which uses these methods to
generate rapid parameter estimation results for binary mergers. We present
results from a set of simulations, to illustrate the method, and compare
results from simple-pe with measurements from full parameter estimation
routines. The simple-pe routine is able to provide initial parameter estimates
in a matter of CPU minutes, which could be used in real-time alerts and also as
input to significantly accelerate detailed parameter estimation routines.",2304.03731v2
2023-04-18,Chaos and fast scrambling delays of dyonic Kerr-Sen-AdS$_4$ black hole and its ultra-spinning version,"The scrambling time and its delay are calculated using holography in an
asymptotically AdS black hole solution of the gauged
Einstein-Maxwell-Dilaton-Axion (EMDA) theory, the dyonic Kerr-Sen-AdS$_4$ black
hole, perturbed by rotating and charged shock waves along the equator. The
leading term of the scrambling time for a black hole with large entropy is
logarithmic in the entropy and hence supports the fast scrambling conjecture
for this black hole solution, which implies that the system under consideration
is chaotic. We also find that the instantaneous minimal Lyapunov index is
bounded by $\kappa=2\pi T_H/(1-\mu\mathcal{L})$, which is analogous to the
surface gravity but for the rotating shock waves, and becomes closer to
equality for the near extremal black hole. For a small value of the AdS scale,
we found that the Lyapunov exponent can exceed the bound for a large value of
$\mathcal{L}$. Due to the presence of the electric and magnetic charge of the
shock waves, we also show that the scrambling process of this holographic
system is delayed by a time scale that depends on the charges of the shock
waves. The calculations also hold for the ultra-spinning version of this black
hole. The result of this paper generalizes the holographic calculations of
chaotic systems which are described by an EMDA theory in the bulk.",2304.08751v3
2023-05-15,Scattering of magnetostatic surface modes of ferromagnetic films by geometric defects,"Magnonics, an emerging field of Magnetism, studies spin waves (SWs) in
nano-structures, with an aim towards possible applications. As information may
be eventually transmitted with efficiency stored in the phase and amplitude of
spin waves, a topic of interest within Magnonics is the propagation of SW
modes. Thus, understanding mechanisms that may influence SW propagation is of
interest. Here the effect of localized surface geometric defects on
magnetostatic surface modes propagation is studied in ferromagnetic films and
semi-infinite media. Theoretical results are developed that allow to calculate
the scattering of these surface or Damon-Eshbach (DE) modes. A Green-Extinction
theorem is used to determine the scattering of incident surface modes, through
the determination of phase shifts of associated modes that are symmetric and
anti-symmetric under inversion in the same geometry with geometric defects.
Choosing localized symmetric depressions as geometric defects, scattering
transmission coefficients are determined that show perfect transmission at
specific frequencies or wave-lengths, that we associate with resonances in the
system. Interestingly the system shows the appearance of localized modes in the
depression regions, with associated discrete frequencies immersed in the
continuum spectrum of these surface DE modes. These localized modes have a
short wave-length content, and appear similarly in semi-infinite surfaces with
depressions. The latter indicates that these types of scattering effects should
appear in all surfaces with roughness or more pronounced geometric defects.",2305.08749v1
2023-06-22,Inclusive probability to record an electron in elastic electromagnetic scattering by a spin one-half hadron wave packet,"The inclusive probability to record an electron in elastic electromagnetic
scattering of an electron by a spin one-half hadron is obtained, the initial
quantum states of the electron and the hadron being described by the density
matrices of a general form. Contrary to the Rosenbluth formula for the
differential cross-section for this process, the first nontrivial contribution
to the inclusive probability turns out to be of order $\alpha$ and not
$\alpha^2$. This contribution describes the interference between the trivial
contribution to the $S$-matrix and the leading contribution to its connected
part. The explicit expression for this interference terms is derived. For
example, for Gaussian wave packets the interference contribution to the
inclusive probability is of relative order $2\times 10^{-2}$ in comparison with
the contribution of the free passed particle for the nonrelativistic proton and
the $10$ MeV electron with the normal deviation of momenta in the electron and
hadron wave packets of order $10$ keV. It is shown that the same interference
term arises when the electron is scattered by the classical electromagnetic
field produced by the hadron electromagnetic current averaged with respect to
the free evolving density matrix of the hadron, even in the case of a single
hadron. The interference term describes coherent scattering of the electron by
the hadron wave packet and is immune to the quantum recoil experienced by a
hadron due to scattering. The effective electron mass operator is found on the
mass-shell.",2306.12987v2
1998-10-29,Runaway Heating By R-modes of Neutron Stars in Low Mass X-ray Binaries,"Recently Andersson et. al., and Bildsten have independently suggested that an
r-mode instability might be responsible for stalling the neutron-star spin-up
in strongly accreting, Low Mass X-ray Binaries (LMXBs). We show that if this
does occur, then there are two possibilities for the resulting neutron-star
evolution:
  If the r-mode damping is a decreasing function of temperature, then the star
undergoes a cyclic evolution: (i) accretional spin-up triggers the instability
near the observed maximum spin rate; (ii) the r-modes become highly excited
through gravitational-radiation reaction, and in a fraction of a year they
viscously heat the star; (iii) r-mode gravitational-radiation reaction then
spins the star down in a fraction of a year to some limiting rotational
frequency; (iv) the r-mode instability shuts off; (v) the neutron star slowly
cools and is spun up by accretion, until it once again reaches the instability
point, closing the cycle. The shortness of the epoch of r-mode activity makes
it unlikely that r-modes are currently excited in the neutron star of any
galactic LMXBs. Nevertheless, this cyclic evolution could be responsible for
keeping the rotational frequencies within the observed LMXB frequency range.
  If, on the other hand, the r-mode damping is temperature independent, then a
steady state with constant angular velocity and $T_{\rm core}\simeq 4\times
10^8$K is reached, in which r-mode viscous heating is balanced by neutrino
cooling and accretional spin-up torque is balanced by
gravitational-radiation-reaction spin-down torque. In this case the neutron
stars in LMXBs could be potential sources of periodic gravitational waves,
detectable by enhanced LIGO interferometers.",9810471v1
2005-07-05,Orbital and spin variability of the Intermediate Polar BG CMi,"Results of a CCD study of the variability of the cataclysmic variable BG CMi
obtained at the Korean 1.8m telescope in 2002-2005 are presented. The
""multi-comparison star"" method had been applied for better accuracy estimates.
The linear ephemeris based on 19 mean maxima for 2002--2005 is HJD
2453105.31448(6)+0.01057257716(198)(E-764707). The period differs from that
predicted by the quadratic ephemeris by Pych et al. (1996) leading to a
possible cycle miscount. The statistically optimal ephemeris is a fourth-order
polynomial, as a quadratic or even a cubic ephemeris leads to unaceptably large
residuals: Min.HJD=$ 2445020.28095(28)+0.0105729609(57)E
-1.58(32)\cdot10^{-13}E^2-5.81(64)\cdot10^{-19}E^3+4.92(41)\cdot10^{-25}E^4.$
Thus the rate of the spin-up of the white dwarf is decreasing. An alternative
explanation is that the spin-up has been stopped during recent years. The
deviations between the amplutudes of the spin variability in V and R, as well
as between phases are not statistically significant. However, the orbital light
curves exhibit distinct difference; the corresponding color index shows a
nearly sinusoidal shape with a maximum at orbital phase $\sim0.2.$ The
variations of the amplitude of spin waves shows a short maximum at the phase of
the orbital dip. The corrected ephemeris for orbital minima is
Min.HJD=$2448368.7225(12)+0\fd13474841(6)\cdot(E-24849)$ with a narrow dip
occuring 0.07P later. The rate of the spin period variation seems to be
changed, justifying the necessity of regular observations of intermediate
polars.",0507086v1
2007-02-02,Newborn Magnetars as sources of Gravitational Radiation: constraints from High Energy observations of Magnetar Candidates,"Soft Gamma Repeaters and the Anomalous X-ray Pulsars are believed to contain
slowly spinning ""magnetars"". The enormous energy liberated in the 2004 Dece 27
giant flare from SGR 1806-20, together with the likely recurrence time of such
events, points to an internal magnetic field strength ~ 10^{16} G. Such strong
fields are expected to be generated by a coherent alpha-Omega dynamo in the
early seconds after the Neutron Star formation, if its spin period is of a few
milliseconds at most. A substantial deformation of the NS is caused by such
fields and a newborn millisecond-spinning magnetar would thus radiate for a few
days a strong gravitational wave signal. Such a signal may be detected with
Advanced LIGO-class detectors up to the distance of the Virgo cluster, where ~
1 magnetar per year are expected to form. Recent X-ray observations reveal that
SNRs around magnetar candidates do not show evidence for a larger energy
content than standard SNRs (Vink & Kuiper 2006). This is at variance with what
would be expected if the spin energy of the young, millisecond NS were radiated
away as electromagnetic radiation andd/or relativistic particle winds and,
thus, transferred quickly to the expanding gas shell. We show here that these
recent findings can be reconciled with the idea of magnetars being formed with
fast spins, if most of their initial spin energy is radiated thorugh GWs. In
particular, we find that this occurs for essentially the same parameter range
that would make such objects detectable by Advanced LIGO-class detectors up to
the Virgo Cluster.",0702075v1
1996-02-12,Weak Antilocalization and Spin Precession in Quantum Wells,"The results of magnetoconductivity measurements in GaInAs quantum wells are
presented. The observed magnetoconductivity appears due to the quantum
interference, which lead to the weak localization effect. It is established
that the details of the weak localization are controlled by the spin splitting
of electron spectra. A theory is developed which takes into account both linear
and cubic in electron wave vector terms in spin splitting, which arise due to
the lack of inversion center in the crystal, as well as the linear terms which
appear when the well itself is asymmetric. It is established that, unlike spin
relaxation rate, contributions of different terms into magnetoconductivity are
not additive. It is demonstrated that in the interval of electron densities
under investigation (0.98-1.85)*10^(12) 1/cm^2 all three contribution are
comparable and have to be taken into account to achieve a good agreement
between the theory and experiment. The results obtained from comparison of the
experiment and the theory have allowed us to determine what mechanisms dominate
the spin relaxation in quantum wells and to improve the accuracy of
determination of spin splitting parameters in A3B5 crystals and 2D structures.",9602068v1
1998-03-09,Metal-insulator transition in the one-dimensional Kondo lattice model,"We study the usual one-dimensional Kondo lattice model (1D KLM) using the
non-Abelian bosonization formalism. At half-filling, we obtain a Kondo
insulator with a gap in both charge and spin excitations which varies quite
linearly with the Kondo exchange $J_K$. It consists of a Spin Density Glass
state, or a $q=\pi$ spin density wave weakly pinned by a nearly
antiferromagnetically ordered spin array. We will analyze the stability of the
SDG state in presence of randomness. We will compare these results with those
obtained in the one-dimensional Heisenberg-Kondo lattice model (1D HKLM) where
the spins are coupled through a large Heisenberg exchange. Away from
half-filling, the system is metallic and yields a very small spin gap which is
equal to the one-impurity Kondo gap $T_k^{(imp)}$. Unlike the one-impurity
Kondo model, we will show why this Kondo phase cannot rule the fixed point of
the 1D KLM, away from half-filling. We will rather obtain a normal
heavy-fermion state controlled by the energy scale $T_{coh}\sim
(T_k^{(imp)})^2/t$ (t is the hopping term) with a quite long-range
antiferromagnetic polarization. It is important to notice that both the SDG
state and the normal heavy-fermion state are susceptible to occur near a
magnetic instability.",9803099v2
1999-02-17,Quantum Monte Carlo Study of Weakly Coupled Spin Ladders,"We report a quantum Monte Carlo study of the thermodynamic properties of
arrays of spin ladders with various widths ($n$), coupled via a weak
inter-ladder exchange coupling $\alpha J$, where $J$ is the intra-ladder
coupling both along and between the chains. This coupled ladder system serves
as a simplified model for the magnetism of presumed ordered spin and charge
stripes in the two-dimensional CuO$_2$ planes of hole-doped copper oxides. Our
results for $n=3$ with weak inter-ladder coupling $\alpha=0.05$, estimated from
the $t-t'-t''-J$ model, show good agreement with the ordering temperature of
the recently observed spin density wave condensation in La$_2$CuO$_{4+y}$. We
show that there exists a quantum critical point at $\alpha_c \simeq 0.07$ for
$n=4$, and determine the phase diagram. Our data at this quantum critical point
agree quantitatively with the universal scaling predicted by the quantum
nonlinear $\sigma$ model. We also report results on random mixtures of $n=2$
and $n=3$ ladders, which correspond to the doping region near but above 1/8.
Our study on the magnetic static structure factor reveals a saturation of the
incommensurability of the spin correlations around 1/8, while the
incommensurability of the charge stripes grows linearly with hole
concentration. The implications of this result for the interpretation of
neutron scattering experiments on the dynamic spin fluctuations in
La$_{2-x}$Sr$_x$CuO$_4$ are discussed.",9902248v1
2000-11-01,Evolution of the resonance and incommensurate spin fluctuations in superconducting YBa$_2$Cu$_3$O$_{6+x}$,"Polarized and unpolarized neutron triple-axis spectrometry was used to study
the dynamical magnetic susceptibility $\chi^{\prime\prime}({\bf q},\omega)$ as
a function of energy ($\hbar\omega$) and wave vector (${\bf q}$) in a wide
temperature range for the bilayer superconductor YBa$_2$Cu$_3$O$_{6+x}$ with
oxygen concentrations, $x$, of 0.45, 0.5, 0.6, 0.7, 0.8, 0.93, and 0.95. The
most prominent features in the magnetic spectra include a spin gap in the
superconducting state, a pseudogap in the normal state, the much-discussed
resonance, and incommensurate spin fluctuations below the resonance. We
establish the doping dependence of the spin gap in the superconducting state,
the resonance energy, and the incommensurability of the spin fluctuations. We
discuss in detail the procedure used for separating the magnetic scattering
from phonon and other spurious effects. In the comparison of our experimental
results with various microscopic theoretical models, particular emphasis was
made to address the similarities and differences in the spin fluctuations of
YBa$_2$Cu$_3$O$_{6+x}$ and La$_{2-x}$Sr$_x$CuO$_4$.",0011019v1
2001-07-03,Quantum Orders and Symmetric Spin Liquids,"A concept -- quantum order -- is introduced to describe a new kind of orders
that generally appear in quantum states at zero temperature. Quantum orders
that characterize universality classes of quantum states (described by {\em
complex} ground state wave-functions) is much richer then classical orders that
characterize universality classes of finite temperature classical states
(described by {\em positive} probability distribution functions). The Landau's
theory for orders and phase transitions does not apply to quantum orders since
they cannot be described by broken symmetries and the associated order
parameters. We find projective representations of symmetry groups (which will
be called projective symmetry groups) can be used to characterize quantum
orders. With the help of quantum orders and the projective symmetry groups, we
construct hundreds of symmetric spin liquids, which have SU(2), U(1) or $Z_2$
gauge structures at low energies. Remarkably, some of the stable quantum phases
support gapless excitations even without any spontaneous symmetry breaking. We
propose that it is the quantum orders (instead of symmetries) that protect the
gapless excitations and make algebraic spin liquids and Fermi spin liquids
stable. Since high $T_c$ superconductors are likely to be described by a
gapless spin liquid, the quantum orders and their projective symmetry group
descriptions lay the foundation for spin liquid approach to high $T_c$
superconductors.",0107071v2
2002-09-30,"Disorder-induced noncollinear ferromagnetism in models for (III,Mn)V semiconductors","We study the ground state properties of kinetic-exchange models for (III,Mn)V
semiconductors with randomly distributed Mn ions. Our method is embedded in a
path integral spin-wave type formalism leading to an effective action for Mn
spins only with full Matsubara frequency dependence. The zero-frequency
contribution to this action is equivalent to static perturbation theory and
characterizes the stabilty of a given spin configuration, while the component
linear in frequency can be interpreted as the joint Berry phase of the Mn and
carrier system. For simple parabolic-band carriers the collinear ferromagnetic
state with all Mn spins in parallel is always stationary but generically
unstable. This instability can be characterized in terms of inverse
participation ratios and is due to long-ranged nonlocal spin fluctuations. We
also present results for the ground state magnetization as a function of an
external field. For carrier dispersions involving anisotropy induced by
spin-orbit coupling the collinear state is not even stationary and therefore
also not the ground state. This interplay between the anisotropy in the carrier
system and the disorder in the Mn positions reflects recent findings by Zarand
and Janko (Phys. Rev. Lett. 89, 047201 (2002)) obtained within the RKKY
approximation. The stationarity of the collinear state (with the magnetization
pointing in one of the cubic symmetry directions) is restored in the continuum
or virtual crystal approximation where disorder is neglected.",0209675v2
2005-10-07,"Collective Spin and Charge Excitations in (Sr,La)_{14-x}Ca_xCu_{24}O_{41} Quantum Spin Ladders","We study magnetic and electronic properties of two-leg ladder materials. We
observed a two-magnon (2M) resonance which we analyze in terms of symmetry,
relaxation and resonance properties. Our findings were contrasted to 2M Raman
measurements in other magnetic crystals. This comparison made us suggest that
the spin-spin correlations in a self-doped two leg ladder may have a modulated
component besides the exponential decay characteristic of a spin liquid ground
state. We found that the 2M intensity resonates at the Mott gap energy.
Interplane Sr substitution for Ca introduces strong disorder leading to
inhomogeneous broadening of the 2M resonance. The doped holes in the spin
liquid ground state further dilute the magnetic correlations, suppressing the
spectral weight of this excitation. At high Ca concentrations are
superconducting under pressure and hole pairing was proposed to be a robust
feature of doped ladders. The measured dielectric response in the microwave
region, the low energy Raman data, the non-linear transport properties along
with soft x-ray scattering allowed us to conclude that the ground state for a
wide range of Ca concentrations (x < 12) is characterized by charge density
wave correlations. This state seems to be driven not by phonons but by Coulomb
forces and many-body effects. We highlighted the similarity in the finite
frequency Raman response as opposed to the very different behavior of the DC
resistivity between undoped and doped ladders. We found that at high Ca
concentrations the carrier relaxation is characterized by the same large
activation energy (~2000 K) as in the self-doped compound. This observation
prompted us to suggest an unconventional metallic transport driven by
collective electronic response.",0510193v1
2006-04-29,Magnetosubband and edge state structure in cleaved-edge overgrown quantum wires,"We provide a systematic quantitative description of the structure of edge
states and magnetosubband evolution in hard wall quantum wires in the integer
quantum Hall regime. Our calculations are based on the self-consistent Green's
function technique where the electron- and spin interactions are included
within the density functional theory in the local spin density approximation.
We analyze the evolution of the magnetosubband structure as magnetic field
varies and show that it exhibits different features as compared to the case of
a smooth confinement. In particularly, in the hard-wall wire a deep and narrow
triangular potential well (of the width of magnetic length $l_B$) is formed in
the vicinity of the wire boundary. The wave functions are strongly localized in
this well which leads to the increase of the electron density near the edges.
Because of the presence of this well, the subbands start to depopulate from the
central region of the wire and remain pinned in the well region until they are
eventually pushed up by increasing magnetic field. We also demonstrate that the
spin polarization of electron density as a function of magnetic field shows a
pronounced double-loop pattern that can be related to the successive
depopulation of the magnetosubbands. In contrast to the case of a smooth
confinement, in hard-wall wires the compressible strips do not form in the
vicinity of wire boundaries and spatial spin separation between spin-up and
spin-down states near edges is absent.",0605008v1
2006-06-02,The Coupled Cluster Method Applied to the {\it XXZ} Model on the Square Lattice,"A review of the coupled cluster method (CCM) applied to lattice quantum spin
systems is presented here. The CCM formalism is explained and an application to
the spin-half {\it XXZ} model on the square lattice is presented. Low orders of
approximation are carried out analytically and a high-order CCM formulation is
presented. Results for the SUB2 approximation are carried out numerically for
SUB2-$m$ and analytically for SUB2. It is found that SUB2-$m$ results converge
rapidly to the full SUB2 solution, including new results for the SUB2-$m$
limiting points compared to the SUB2 critical point. Results for the
ground-state energy and the sublattice magnetisation are presented. A study of
the excitation spectrum of this model at the SUB2 critical point is given.
Indeed, the shape of the excitation spectrum at the SUB2 critical point is
identical to that predicted by spin-wave theory for the isotropic model, albeit
with a multiplicative factor of 1.1672. This result compares very well to
results of cumulant series expansions and Monte Carlo simulation that again
predict a similar shape for the excitation spectrum, but with multiplicative
factors of 1.18 and 1.21$\pm$0.03, respectively. Results for the isotropic
Heisenberg model on the square lattice for the spin-one antiferromagnet and the
spin-one/spin-half ferrimagnet are also given.",0606060v1
2006-12-06,The 2D XY model on a finite lattice with structural disorder: quasi-long-range ordering under realistic conditions,"We present an analytic approach to study concurrent influence of quenched
non-magnetic site-dilution and finiteness of the lattice on the 2D XY model.
Two significant deeply connected features of this spin model are: a special
type of ordering (quasi-long-range order) below a certain temperature and a
size-dependent mean value of magnetisation in the low-temperature phase that
goes to zero (according to the Mermin-Wagner-Hohenberg theorem) in the
thermodynamic limit. We focus our attention on the asymptotic behaviour of the
spin-spin correlation function and the probability distribution of
magnetisation. The analytic approach is based on the spin-wave approximation
valid for the low-temperature regime and an expansion in the parameters which
characterise the deviation from completely homogeneous configuration of
impurities. We further support the analytic considerations by Monte Carlo
simulations performed for different concentrations of impurities and compare
analytic and MC results. We present as the main quantitative result of the work
the exponent of the spin-spin correlation function power law decay. It is non
universal depending not only on temperature as in the pure model but also on
concentration of magnetic sites. This exponent characterises also the vanishing
of magnetisation with increasing lattice size.",0612147v1
2007-06-01,Strongly modulated transmission of a spin-split quantum wire with local Rashba interaction,"We investigate the transport properties of ballistic quantum wires in the
presence of Zeeman spin splittings and a spatially inhomogeneous Rashba
interaction. The Zeeman interaction is extended along the wire and produces
gaps in the energy spectrum which allow electron propagation only for spinors
lying along a certain direction. For spins in the opposite direction the waves
are evanescent far away from the Rashba region, which plays the role of the
scattering center. The most interesting case occurs when the magnetic field is
perpendicular to the Rashba field. Then, the spins of the asymptotic
wavefunctions are not eigenfunctions of the Rashba Hamiltonian and the
resulting coupling between spins in the Rashba region gives rise to sudden
changes of the transmission probability when the Fermi energy is swept along
the gap. After briefly examining the energy spectrum and eigenfunctions of a
wire with extended Rashba coupling, we analyze the transmission through a
region of localized Rashba interaction, in which a double interface separates a
region of constant Rashba interaction from wire leads free from spin-orbit
coupling. For energies slightly above the propagation threshold, we find the
ubiquitous occurrence of transmission zeros (antiresonances) which are analyzed
by matching methods in the one-dimensional limit. We find that a a minimal
tight-binding model yields analytical transmission lineshapes of Fano
antiresonance type. More general angular dependences of the external magnetic
field is treated within projected Schroedinger equations with Hamiltonian
matrix elements mixing wavefunction components. Finally, we consider a
realistic quantum wire where the energy subbands are coupled via the Rashba
intersubband coupling term and discuss its effect on the transmission zeros.",0706.0107v1
2007-06-08,Measuring the spin polarization and Zeeman energy of a spin-polarized electron gas: Comparison between Raman scattering and photoluminescence,"We compare resonant electronic Raman scattering and photoluminescence
measurements for the characterization of a spin-polarized two-dimensional
electron gas embedded in $\text{Cd}_{1-x}\text{Mn}_x\text{Te}$ single quantum
wells. From Raman scattering by single-particle excitations in a zero magnetic
field, we measure the Fermi velocity and then obtain the Fermi energy (as well
as the electron density), which is comparable to that extracted from
photoluminescence for moderate electron densities, assuming a bare band-edge
mass. At large electron densities, the Fermi energies derived from Raman
scattering and photoluminescence differ. For an applied in-plane magnetic field
and zero wave vector transferred to the electron gas, Raman scattering spectra
show peaks at both the Zeeman energy $Z$, resulting from collective excitations
of the spin-polarized electron gas, and the one electron spin-flip energy
$Z^*$. Magneto-photoluminescence spectra show conduction band splitting that
are equivalent to $Z$, suggesting that collective effects are present in the
photoluminescence spectra. Assuming (as before) an uncorrected mass, the degree
of spin polarization $\zeta$ determined from the magneto-photoluminescence
lineshape is found to differ from that derived from the magnetic field
dependent Raman scattering measurements for large electron densities. We
attribute the discrepancy in measuring $\zeta$ and the Fermi energy to the
renormalized mass resulting from many-body electron-electron interactions.",0706.1255v1
2008-03-31,Chern-number spin Hamiltonians for magnetic nano-clusters by DFT methods,"Combining field-theoretical methods and ab-initio calculations, we construct
an effective Hamiltonian with a single giant-spin degree of freedom, capable of
the describing the low-energy spin dynamics of ferromagnetic metal nanoclusters
consisting of up to a few tens of atoms. In our procedure, the magnetic moment
direction of the Kohn-Sham SDFT wave-function is constrained by means of a
penalty functional, allowing us to explore the entire parameter space of
directions, and to extract the magnetic anisotropy energy and Berry curvature
functionals. The average of the Berry curvature over all magnetization
directions is a Chern number - a topological invariant that can only take on
values equal to multiples of one half, representing the dimension of the
Hilbert space of the effective spin system. The spin Hamiltonian is obtained by
quantizing the classical anisotropy energy functional, after performing a
change of variables to a constant Berry curvature space. The purpose of this
article is to examine the impact of the topological effect from the Berry
curvature on the low-energy total-spin-system dynamics. To this end, we study
small transition metal clusters: Co$_{n}$ ($n=2,...,5$), Rh$_{2}$, Ni$_{2}$,
Pd$_{2}$, Mn$_{x}$N$_{y}$, Co$_{3}$Fe$_{2}$.",0803.4430v1
2008-04-06,Fermionization for charge degrees of freedom and bosonization of spin degrees of freedom in the SU(2) slave-boson theory,"Fermionizing the charge sector and bosonizing the spin part in the SU(2)
slave-boson theory, we derive an effective field theory for dynamics of doped
holes in the antiferromagnetically correlated spin background, where spin
fluctuations are described by an SO(5) Wess-Zumino-Witten (WZW) theory while
dynamics of doped holes is characterized by QED$_{3}$ with a chemical potential
term. An important feature of our effective field theory is the coupling term
between valance bond fluctuations and doped holes. Considering that valance
bond fluctuations are deeply related with monopole excitations of staggered
U(1) gauge fields in the bosonic field theory for spin fluctuations, we
demonstrate that hole dynamics helps deconfinement of bosonic spinons near the
quantum critical point of the SO(5) WZW theory. We solve this effective field
theory in the Eliashberg framework, and find non-Fermi liquid physics in
thermodynamics and transport, where $z = 3$ criticality with dynamical exponent
$z$ plays an important role for hole dynamics. We discuss validity of our field
theory, applying it to a doped spin chain and comparing it with the
slave-fermion framework. Furthermore, we discuss instability of the anomalous
metallic phase against superconductivity and density waves of doped holes,
resulting from competition between gauge and valance bond fluctuations.",0804.0895v3
2009-03-02,"Ferromagnetic properties of p-(Cd,Mn)Te quantum wells: Interpretation of magneto-optical measurements by Monte Carlo simulations","In order to single out dominant phenomena that account for carrier-controlled
magnetism in p-(Cd,Mn)Te quantum wells we have carried out magneto-optical
measurements and Monte Carlo simulations of time dependent magnetization. The
experimental results show that magnetization relaxation is faster than 20 ns in
the paramagnetic state. Decreasing temperature below the Curie temperature Tc
results in an increase of the relaxation time but to less than 10 micro
seconds. This fast relaxation may explain why the spontaneous spin splitting of
electronic states is not accompanied by the presence of non-zero macroscopic
magnetization below Tc. Our Monte Carlo results reproduce the relative change
of the relaxation time on decreasing temperature. At the same time, the
numerical calculations demonstrate that antiferromagnetic spin-spin
interactions, which compete with the hole-mediated long-range ferromagnetic
coupling, play an important role in magnetization relaxation of the system. We
find, in particular, that magnetization dynamics is largely accelerated by the
presence of antiferromagnetic couplings to the Mn spins located outside the
region, where the holes reside. This suggests that macroscopic spontaneous
magnetization should be observable if the thickness of the layer containing
localized spins will be smaller than the extension of the hole wave function.
Furthermore, we study how a spin-independent part of the Mn potential affects
Tc. Our findings show that the alloy disorder potential tends to reduce Tc, the
effect being particularly strong for the attractive potential that leads to
hole localization.",0903.0406v1
2009-11-06,The importance of precession in modelling the direction of the final spin from a black-hole merger,"The prediction of the spin of the black hole resulting from the merger of a
generic black-hole binary system is of great importance to study the
cosmological evolution of supermassive black holes. Several attempts have been
recently made to model the spin via simple expressions exploiting the results
of numerical-relativity simulations. Here, I first review the derivation of a
formula, proposed in Barausse & Rezzolla, Apj 704 L40, which accurately
predicts the final spin magnitude and direction when applied to binaries with
separations of hundred or thousands of gravitational radii. This makes my
formula particularly suitable for cosmological merger-trees and N-body
simulations, which provide the spins and angular momentum of the two black
holes when their separation is of thousands of gravitational radii. More
importantly, I investigate the physical reason behind the good agreement
between my formula and numerical relativity simulations, and nail it down to
the fact that my formula takes into account the post-Newtonian precession of
the spins and angular momentum in a consistent manner.",0911.1274v2
2010-04-12,Magnetism in Fe-based superconductors,"In this review, we present a summary of experimental studies of magnetism in
Fe-based superconductors. The doping dependent phase diagram shows strong
similarities to the generic phase diagram of the cuprates. Parent compounds
exhibit magnetic order together with a structural phase transition both of
which are progressively suppressed with doping allowing superconductivity to
emerge. The stripe-like spin arrangement of Fe moments in the magnetically
ordered state shows the identical in-plane structure for the RFeAsO (R=rare
earth) and AFe2As2 (A=Sr, Ca, Ba, Eu and K) parent compounds, notably different
than the spin configuration of the cuprates. Interestingly, Fe1+yTe orders with
a different spin order despite very similar Fermi surface topology. Studies of
the spin dynamics in the parent compounds shows that the interactions are best
characterized as anisotropic three-dimensional (3D) interactions. Despite the
room temperature tetragonal structure, analysis of the low temperature spin
waves under the assumption of a Heisenberg Hamiltonian indicates strong
in-plane anisotropy with a significant next-near neighbor interaction. In the
superconducting state, a resonance, localized in both wavevector and energy is
observed in the spin excitation spectrum as in the cuprates. This resonance is
observed at a wavevector compatible with a Fermi surface nesting instability
independent of the magnetic ordering of the relevant parent compound. The
resonance energy (Er) scales with superconducting transition temperature (TC)
as Er ~4.9 kBTC consistent with the canonical value of ~5 kBTC observed in the
cuprates. Moreover, the relationship between the resonance energy and the
superconducting gap, \Delta, is similar to that observed in many unconventional
superconductors (Er/2\Delta ~ 0.64).",1004.1969v1
2010-06-07,"""Alice"" String as Source of the Kerr Spinning Particle","Kerr geometry has twofoldedness which can be cured by a truncation of the
`negative' sheet of metric. It leads to the models of disk-like sources of the
Kerr solution and to a class of disk-like or bag-like models of the Kerr
spinning particle. There is an alternative way: to retain the `negative' sheet
as the sheet of advanced fields. In this case the source of spinning particle
is the Kerr singular ring which can be considered as a twofold ""Alice"" string.
This string can have electromagnetic excitations in the form of traveling waves
generating spin and mass of the particle. Model of this sort was suggested in
1974 as a ""microgeon with spin"". Recent progress in the obtaining of the
nonstationary and radiating Kerr solutions enforces us to return to this model
and to consider it as a model for the light spinning particles. We discuss here
the real and complex Kerr geometry and some unusual properties of the
oscillating solutions in the model of ""Alice"" string source.",1006.1274v1
2010-10-13,Simulating merging binary black holes with nearly extremal spins,"Astrophysically realistic black holes may have spins that are nearly extremal
(i.e., close to 1 in dimensionless units). Numerical simulations of binary
black holes are important tools both for calibrating analytical templates for
gravitational-wave detection and for exploring the nonlinear dynamics of curved
spacetime. However, all previous simulations of binary-black-hole inspiral,
merger, and ringdown have been limited by an apparently insurmountable barrier:
the merging holes' spins could not exceed 0.93, which is still a long way from
the maximum possible value in terms of the physical effects of the spin. In
this paper, we surpass this limit for the first time, opening the way to
explore numerically the behavior of merging, nearly extremal black holes.
Specifically, using an improved initial-data method suitable for binary black
holes with nearly extremal spins, we simulate the inspiral (through 12.5
orbits), merger and ringdown of two equal-mass black holes with equal spins of
magnitude 0.95 antialigned with the orbital angular momentum.",1010.2777v3
2011-03-30,Spin liquid in a single crystal of the frustrated diamond lattice antiferromagnet CoAl2O4,"We study spin liquid in the frustrated diamond lattice antiferromagnet
CoAl2O4 by means of single crystal neutron scattering in zero and applied
magnetic field. The magnetically ordered phase appearing below TN=8 K remains
nonconventional down to 1.5 K. The magnetic Bragg peaks at the q=0 positions
remain broad and their profiles have strong Lorentzian contribution.
Additionally, they are connected by weak diffuse streaks along the <111>
directions. These observations are explained within the spiral spin liquid
model as short-range magnetic correlations of spirals populated at these finite
temperatures, as the energy minimum around q=0 is flat and the energy of
excited states with q=(111) is low. The agreement is only qualitative, leading
us to suspect that microstructure effects are also important. Magnetic field
significantly perturbs spin correlations. The 1.5 K static magnetic moment
increases from 1.58 mB/Co at zero field to 2.08 mB/Co at 10 T, while the
magnetic peaks, being still broad, acquire almost Gaussian profile. Spin
excitations are rather conventional spin waves at zero field, resulting in the
exchange parameters J1=0.92(1) meV, J2=0.101(2) meV and the anisotropy term
D=-0.0089(2) meV for CoAl2O4. The application of a magnetic field leads to a
pronounced broadening of the excitations at the zone center, which at 10 T
appear gapless and nearly featureless.",1103.5799v2
2012-10-30,Large Stark Effect for Li Donor Spins in Si,"We study the effect of a static electric field on lithium donor spins in
silicon. The anisotropy of the effective mass leads to the anisotropy of the
quadratic Stark susceptibility, which we determined using the Dalgarno-Lewis
exact summation method. The theory is asymptotically exact in the field domain
below Li-donor ionization threshold, relevant to the Stark-tuning electron spin
resonance experiments. To obtain the generalized Stark susceptibilities at
arbitrary fields, we propose a new variational wave function which reproduces
the exact results in the low-field limit. With the calculated susceptibilities
at hand, we are able to predict and analyze several important physical effects.
First, we observe that the energy level shifts due to the quadratic Stark
effect for Li donors in Si are equivalent to, and can be mapped onto, those
produced by an external stress.
  Second, we demonstrate that the Stark effect anisotropy, combined with the
unique valley-orbit splitting of a Li donor in Si, spin-orbit interaction and
specially tuned external stress, may lead to a very strong modulation of the
donor spin $g$-factor by the electric field. Third, we investigate the
influence of random strains on the $g$-factor shifts and quantify the random
strain limits and requirements to Si material purity necessary to observe the
$g$-factor Stark shifts experimentally. Finally, we discuss possible
implications of our results for quantum information processing with Li spin
qubits in Si.",1210.8164v1
2013-04-29,"Dynamics of spin-1 bosons in an optical lattice: spin mixing, quantum phase revival spectroscopy and effective three-body interactions","We study the dynamics of spin-1 atoms in a periodic optical-lattice potential
and an external magnetic field in a quantum quench scenario where we start from
a superfluid ground state in a shallow lattice potential and suddenly raise the
lattice depth. The time evolution of the non-equilibrium state, thus created,
shows collective collapse-and-revival oscillations of matter-wave coherence as
well as oscillations in the spin populations. We show that the complex pattern
of these two types of oscillations reveals details about the superfluid and
magnetic properties of the initial many-body ground state. Furthermore, we show
that the strengths of the spin-dependent and spin-independent atom-atom
interactions can be deduced from the observations. The Hamiltonian that
describes the physics of the final deep lattice not only contains two-body
interactions but also effective multi-body interactions, which arise due to
virtual excitations to higher bands. We derive these effective spin-dependent
three-body interaction parameters for spin-1 atoms and describe how spin-mixing
is affected. Spinor atoms are unique in the sense that multi-body interactions
are directly evident in the in-situ number densities in addition to the
momentum distributions. We treat both antiferromagnetic (e.g. $^{23}$Na atoms)
and ferromagnetic (e.g. $^{87}$Rb and $^{41}$K) condensates.",1304.7565v1
2013-05-10,Open spin chains for giant gravitons and relativity,"We study open spin chains for strings stretched between giant graviton states
in the N=4 SYM field theory in the collective coordinate approach. We study the
boundary conditions and the effective Hamiltonian of the corresponding spin
chain to two loop order.
  The ground states of the spin chain have energies that match the relativistic
dispersion relation characteristic of massive W boson particles on the
worldvolume of the giant graviton configurations, up to second order in the
limit where the momentum is much larger than the mass. We find evidence for a
non-renormalization theorem for the ground state wave function of this spin
chain system. We also conjecture a generalization of this result to all loop
orders which makes it compatible with a fully relativistic dispersion relation.
We show that the conjecture follows if one assumes that the spin chain admits a
central charge extension that is sourced by the giant gravitons, generalizing
the giant magnon dispersion relation for closed string excitations. This
provides evidence for ten dimensional local physics mixing AdS directions and
the five-sphere emerging from an N=4 SYM computation in the presence of a
non-trivial background (made of D-branes) that break the conformal field theory
of the system.",1305.2394v2
2013-05-28,Microscopic observation of magnon bound states and their dynamics,"More than eighty years ago, H. Bethe pointed out the existence of bound
states of elementary spin waves in one-dimensional quantum magnets. To date,
identifying signatures of such magnon bound states has remained a subject of
intense theoretical research while their detection has proved challenging for
experiments. Ultracold atoms offer an ideal setting to reveal such bound states
by tracking the spin dynamics after a local quantum quench with single-spin and
single-site resolution. Here we report on the direct observation of two-magnon
bound states using in-situ correlation measurements in a one-dimensional
Heisenberg spin chain realized with ultracold bosonic atoms in an optical
lattice. We observe the quantum walk of free and bound magnon states through
time-resolved measurements of the two spin impurities. The increased effective
mass of the compound magnon state results in slower spin dynamics as compared
to single magnon excitations. In our measurements, we also determine the decay
time of bound magnons, which is most likely limited by scattering on thermal
fluctuations in the system. Our results open a new pathway for studying
fundamental properties of quantum magnets and, more generally, properties of
interacting impurities in quantum many-body systems.",1305.6598v2
2013-08-13,Continuous phase transition from Néel state to Z_2 spin liquid state on a square lattice,"Recent numerical studies of the $J_1$-$J_2$ model on a square lattice suggest
a possible continuous phase transition between the N\'eel state and a gapped
spin-liquid state with Z$_2$ topological order. We show that such a phase
transition can be realized through two steps: First bring the N\'eel state to
the U(1) deconfined quantum critical point, which has been studied in the
context of N\'eel -- valence bond solid (VBS) state phase transition. Then
condense the spinon pair -- skyrmion/antiskyrmion bound state, which carries
both gauge charge and flux of the U(1) gauge field emerging at the deconfined
quantum critical point. We also propose a Schwinger boson projective wave
function to realize such a Z$_2$ spin liquid state and find that it has a
relatively low variational energy ($-0.4893J_1$/site) for the $J_1$-$J_2$ model
at $J_2=0.5J_1$. The spin liquid state we obtain breaks the fourfold rotational
symmetry of the square lattice and therefore is a nematic spin liquid state.
This direct continuous phase transition from the N\'eel state to a spin liquid
state may be realized in the $J_1$-$J_2$ model, or the anisotropic
$J_{1x}$-$J_{1y}$-$J_2$ model.",1308.2759v2
2013-09-29,Decoupled phase of frustrated spin-1/2 antiferromagnetic chains with and without long range order in the ground state,"The quantum phases of one-dimensional spin $s= 1/2$ chains are discussed for
models with two parameters, frustrating exchange $g = J_2 > 0$ between second
neighbors and normalized nonfrustrating power-law exchange with exponent
$\alpha$ and distance dependence $r^{-\alpha}$. The ground state (GS) at $g =
0$ has long-range order (LRO) for $\alpha < 2$, long-range spin fluctuations
for $\alpha > 2$. The models conserve total spin $S = S_A + S_B$, have singlet
GS for any $g$, $\alpha \ge 0$ and decouple at $1/g = 0$ to linear Heisenberg
antiferromagnets on sublattices $A$ and $B$ of odd and even-numbered sites.
Exact diagonalization of finite chains gives the sublattice spin $ \ < S^2_A \
>$, the magnetic gap $E_m$ to the lowest triplet state and the excitation
$E_{\sigma}$ to the lowest singlet with opposite inversion symmetry to the GS.
An analytical model that conserves sublattice spin has a first order quantum
transition at $g_c = 1/4{\rm ln2}$ from a GS with perfect LRO to a decoupled
phase with $S_A = S_B = 0$ for $g \ge 4/\pi^2$ and no correlation between spins
in different sublattices. The model with $\alpha = 1$ has a first order
transition to a decoupled phase that closely resembles the analytical model.
The bond order wave (BOW) phase and continuous quantum phase transitions of
finite models with $\alpha \ge 2$ are discussed in terms of GS degeneracy where
$E_{\sigma}(g) = 0$, excited state degeneracy where $E_{\sigma}(g) = E_m(g)$,
and $\ < S^2_A \ >$. The decoupled phase at large frustration has nondegenerate
GS for any exponent $\alpha$ and excited states related to sublattice
excitations.",1309.7542v1
2013-12-03,Temperature and Magnetic Field Dependence of Spin Ice Correlations in the Pyrochlore Magnet Tb2Ti2O7,"We present a parametric study of the diffuse magnetic scattering at
(1/2,1/2,1/2) positions in reciprocal space, ascribed to a frozen
antiferromagnetic spin ice state in single crystalline Tb2Ti2O7. Our
high-resolution neutron scattering measurements show that the elastic (-0.02
meV < E < 0.02 meV) (1/2,1/2,1/2) scattering develops strongly below ~275 mK,
and correlates with the opening of a spin gap of ~0.06-0.08 meV over most of
the Brillouin zone. The concomitant low-lying magnetic spin excitations are
weakly dispersive and appear to soften near the (1/2,1/2,1/2) wave vector at 80
mK. The nature of the transition at 275 mK has many characteristics of spin
glass behavior, consistent with ac-susceptibility measurements. The application
of a magnetic field of 0.075 T applied along the [1-10] direction destroys the
(1/2,1/2,1/2) elastic scattering, revealing the fragility of this short-range
ordered ground state. We construct a refined H-T phase diagram for Tb2Ti2O7 and
[1-10] fields which incorporates this frozen spin ice regime and the
antiferromagnetic long-range order previously known to be induced in relatively
large fields. Specific heat measurements on the same crystal reveal a sharp
anomaly at Tc~450 mK and no indication of a transition near ~275 mK. We
conclude that the higher temperature specific heat peak is not related to the
magnetic ordering but is likely a signal of other, nonmagnetic, correlations.",1312.0847v1
2014-08-14,Ultrafast reduction in exchange interaction by a laser pulse: Alternative path to femtomagnetism,"Since the beginning of femtomagnetism, it has been hotly debated how an
ultrafast laser pulse can demagnetize a sample and switch its spins within a
few hundred femtoseconds, but no consensus has been reached. In this paper, we
propose that an ultrafast reduction in the exchange interaction by a
femtosecond laser pulse is mainly responsible for demagnetization and spin
switching. The key physics is that the dipole selection rule demands two
distinctive electron configurations for the ground and excited states and
consequently changes the exchange interaction. Although the exchange
interaction change is almost instantaneous, its effect on the spin is delayed
by the finite spin wave propagation. Consistent with the experimental
observation, the delay becomes longer with a stronger exchange interaction
pulse. In spin-frustrated systems, the effect of the exchange interaction
change is even more dramatic, where the spin can be directly switched from one
direction to the other. Therefore, our theory has the potential to explain the
essence of major observations in rare-earth transition metal compounds for the
last seven years. Our findings are likely to motivate further research in the
quest of the origin of femtomagnetism.",1408.3433v1
2014-08-19,Polyradical character and spin frustration in fullerene molecules: An ab initio non-collinear Hartree--Fock study,"Most {\em ab initio} calculations on fullerene molecules have been carried
out based on the paradigm of the H\""uckel model. This is consistent with the
restricted nature of the independent-particle model underlying such
calculations, even in single-reference-based correlated approaches. On the
other hand, previous works on some of these molecules using model Hamiltonians
have clearly indicated the importance of short-range inter-atomic spin-spin
correlations. In this work, we consider {\em ab initio} non-collinear
Hartree--Fock (HF) solutions for representative fullerene systems: the bowl,
cage, ring, and pentagon isomers of C$_{20}$, and the larger C$_{30}$,
C$_{36}$, C$_{60}$, C$_{70}$, and C$_{84}$ fullerene cages. In all cases but
the ring we find that the HF minimum corresponds to a truly non-collinear
solution with a torsional spin density wave. Optimized geometries at the
generalized HF (GHF) level lead to fully symmetric structures, even in those
cases where Jahn-Teller distortions have been previously considered. The nature
of the GHF solutions is consistent with the $\pi$-electron space becoming
polyradical in nature: each $p$-orbital remains effectively singly occupied.
The spin frustration, induced by the pentagon rings in an otherwise
anti-ferromagnetic background, is minimized at the HF level by aligning the
spins in non-collinear arrangements. The long-range magnetic ordering observed
is reminiscent of the character of broken symmetry HF solutions in polyacene
systems.",1408.4386v1
2014-12-29,Structural properties and spin-phonon coupling in orthorhombic Y-substituted GdMnO$_{3}$,"We present a systematic study of the structure and lattice dynamics at room
temperature, and the phonon behavior at low temperatures in orthorhombic
Gd$_{1-x}$Y$_{x}$MnO$_{3}$ manganites, with 0 $\leq$ x $\leq$ 0.4, using powder
x-ray diffraction and Raman scattering. A thorough analysis towards the
correlation between both structural and Raman modes parameters was undertaken.
The data obtained at room temperature reveal structural distortions arising
from the Jahn-Teller distortion and octahedra tilting. The Jahn-Teller
distortion is apparently x-independent, while an increase of Mn-O1-Mn bond
angle of about 0.5{\deg} could be ascertain when x changes from 0 to 0.4.
Spin-phonon coupling was evidenced from the Raman results. The temperature
dependence of the B1g in-plane O2 stretching mode of the MnO6 octahedron has
revealed either a positive or negative shift regarding the pure anharmonic
temperature dependence of the phonon frequency, which strongly depends on the
Y-concentration. The frequency renormalization is explained in terms of a
competition between ferro and antiferromagnetic interactions. The ratio between
the spin-phonon coupling constant and the effective magnetic exchange integral
per spin was determined from the renormalized wave number of the in-plane O2
stretching mode, associated with the spin-spin correlation function.",1412.8350v2
2015-02-28,Symmetry protected skyrmions in 3D spin-orbit coupled Bose gases,"We present a variational study of pseudo-spin $1/2$ Bose gases in a harmonic
trap with weak 3D spin-orbit coupling of $\bmsigma\cdot\mathbf{p}$ type. This
spin-orbit coupling mixes states with different parities, which inspires us to
approximate the single particle state with the eigenstates of the total angular
momentum, i.e. superposition of harmonic $s$-wave and $p$-wave states. As the
time reversal symmetry is protected by two-body interaction, we set the
variational order parameter as the combination of two mutually time reversal
symmetric eigenstates of the total angular momentum. The variational results
essentially reproduce the 3D skyrmion-like ground state recently identified by
Kawakami {\it et al.}. We show that these skyrmion-like ground states emerging
in this model are primarily caused by $p$ wave spatial mode involving in the
variational order parameter that drives two spin components spatially
separated. We find the ground state of this system falls into two phases with
different density distribution symmetries depending on the relative magnitude
of intraspecies and interspecies interaction: Phase I has parity symmetric and
axisymmetric density distributions, while Phase II is featured with special
joint symmetries of discrete rotational and time reversal symmetry. With the
increasing interaction strength the transition occurs between two phases with
distinct density distributions, while the topological 3D skyrmion-like spin
texture is symmetry protected.",1503.00128v1
2015-06-01,$1/f^α$ noise and generalized diffusion in random Heisenberg spin systems,"We study the `flux noise' spectrum of random-bond quantum Heisenberg spin
systems using a real-space renormalization group (RSRG) procedure that accounts
for both the renormalization of the system Hamiltonian and of a generic probe
that measures the noise. For spin chains, we find that the dynamical structure
factor $S_q(f)$, at finite wave-vector $q$, exhibits a power-law behavior both
at high and low frequencies $f$, with exponents that are connected to one
another and to an anomalous dynamical exponent through relations that differ at
$T = 0$ and $T = \infty$. The low-frequency power-law behavior of the structure
factor is inherited by any generic probe with a finite band-width and is of the
form $1/f^\alpha$ with $0.5 < \alpha < 1$. An analytical calculation of the
structure factor, assuming a limiting distribution of the RG flow parameters
(spin size, length, bond strength) confirms numerical findings. More generally,
we demonstrate that this form of the structure factor, at high temperatures, is
a manifestation of anomalous diffusion which directly follows from a
generalized spin-diffusion propagator. We also argue that $1/f$-noise is
intimately connected to many-body-localization at finite temperatures. In two
dimensions, the RG procedure is less reliable; however, it becomes convergent
for quasi-one-dimensional geometries where we find that one-dimensional
$1/f^\alpha$ behavior is recovered at low frequencies; the latter
configurations are likely representative of paramagnetic spin networks that
produce $1/f^\alpha$ noise in SQUIDs.",1506.00643v1
2015-07-17,Silicon vacancy center in 4H-SiC: Electronic structure and spin-photon interfaces,"Defects in silicon carbide are of intense and increasing interest for
quantum-based applications due to this material's properties and technological
maturity. We calculate the multi-particle symmetry adapted wave functions of
the negatively charged silicon vacancy defect in hexagonal silicon carbide via
use of group theory and density functional theory and find the effects of
spin-orbit and spin-spin interactions on these states. Although we focused on
$\textrm{V}_{\textrm{Si}}^-$ in 4H-SiC, because of its unique fine structure
due to odd number of active electrons, our methods can be easily applied to
other defect centers of different polytpes, especially to the 6H-SiC. Based on
these results we identify the mechanism that polarizes the spin under optical
drive, obtain the ordering of its dark doublet states, point out a path for
electric field or strain sensing, and find the theoretical value of its
ground-state zero field splitting to be 68 MHz, in good agreement with
experiment. Moreover, we present two distinct protocols of a spin-photon
interface based on this defect. Our results pave the way toward novel quantum
information and quantum metrology applications with silicon carbide.",1507.05091v2
2015-08-31,Dynamical structure factors and excitation modes of the bilayer Heisenberg model,"Using quantum Monte Carlo simulations along with higher-order spin-wave
theory, bond-operator and strong-coupling expansions, we analyse the dynamical
spin structure factor of the spin-half Heisenberg model on the square-lattice
bilayer. We identify distinct contributions from the low-energy Goldstone modes
in the magnetically ordered phase and the gapped triplon modes in the quantum
disordered phase. In the antisymmetric (with respect to layer inversion)
channel, the dynamical spin structure factor exhibits a continuous evolution of
spectral features across the quantum phase transition, connecting the two types
of modes. Instead, in the symmetric channel we find a depletion of the spectral
weight when moving from the ordered to the disordered phase. While the
dynamical spin structure factor does not exhibit a well-defined distinct
contribution from the amplitude (or Higgs) mode in the ordered phase, we
identify an only marginally-damped amplitude mode in the dynamical singlet
structure factor, obtained from interlayer bond correlations, in the vicinity
of the quantum critical point. These findings provide quantitative information
in direct relation to possible neutron or light scattering experiments in a
fundamental two-dimensional quantum-critical spin system.",1508.07816v1
2015-09-08,New insights on the spin-up of a neutron star during core-collapse,"The spin of a neutron star at birth may be impacted by the asymmetric
character of the explosion of its massive progenitor. During the first second
after bounce, the spiral mode of the Standing Accretion Shock Instability
(SASI) is able to redistribute angular momentum and spin-up a neutron star born
from a non-rotating progenitor. Our aim is to assess the robustness of this
process. We perform 2D numerical simulations of a simplified setup in
cylindrical geometry to investigate the timescale over which the dynamics is
dominated by a spiral or a sloshing mode. We observe that the spiral mode
prevails only if the ratio of the initial shock radius to the neutron star
radius exceeds a critical value. In that regime, both the degree of asymmetry
and the average expansion of the shock induced by the spiral mode increase
monotonously with this ratio, exceeding the values obtained when a sloshing
mode is artificially imposed. With a timescale of 2-3 SASI oscillations, the
dynamics of SASI takes place fast enough to affect the spin of the neutron star
before the explosion. The spin periods deduced from the simulations are
compared favorably to analytical estimates evaluated from the measured
saturation amplitude of the SASI wave. Despite the simplicity of our setup,
numerical simulations revealed unexpected stochastic variations, including a
reversal of the direction of rotation of the shock. Our results show that the
spin up of neutron stars by SASI spiral modes is a viable mechanism even though
it is not systematic.",1509.02828v2
2015-10-14,Field-induced dynamical properties of the $XXZ$ model on a honeycomb lattice,"We present a comprehensive $1/S$ study of the field-induced dynamical
properties of the nearest-neighbor $XXZ$ antiferromagnet on a honeycomb lattice
using the formalism of the nonlinear spin-wave theory developed for this model.
The external magnetic field controls spin frustration in the system and induces
non-collinearity of the spin structure, which is essential for the two-magnon
decay processes. Our results include an intriguing field-evolution of the
regions of the Brillouin zone wherein decays of spin excitations are prominent,
a detailed classification of the decay channels involving magnons from both
excitation branches, and a thorough analysis of the singularities in the magnon
spectra due to coupling to the two magnon continuum, all of which are
illustrated for several field and anisotropy values. We highlight a number of
features related to either the non-Bravais nature of the lattice, or the
existence of the Dirac-like points in the spectrum. In addition, the asymptotic
behavior of the decay rates near high-symmetry points is analyzed in detail.
The inelastic neutron-scattering spin-spin structure factor is obtained in the
leading $1/S$ order and is shown to exhibit qualitatively distinct fingerprints
of the decay-induced magnon dynamics such as quasiparticle peaks broadened by
decays and strong spectral weight redistribution.",1510.04275v2
2016-01-07,Hubbard model with Rashba or Dresselhaus spin-orbit coupling and Rotated Anti-ferromagnetic Heisenberg Model,"In this work, we investigate the possible dramatic effects of Rashba or
Dresselhaus spin-orbit coupling (SOC) on fermionic Hubbard model in a 2d square
lattice. In the strong coupling limit, it leads to the Rotated
Anti-ferromagnetic Heisenberg model which is a new class of quantum spin model.
For a special equivalent class, we identify a new spin-orbital entangled
commensurate ground ( Y-y ) state subject to strong quantum fluctuations at
$T=0$. We evaluate the quantum fluctuations by the spin wave expansion up to
order $ 1/S^2 $. In some SOC parameter regime, the Y-y state supports a massive
relativistic in-commensurate magnon ( C-IC ) with its two gap minima positions
continuously tuned by the SOC parameters. The C-IC magnons dominate all the low
temperature thermodynamic quantities and also lead to the separation of the
peak positions between the longitudinal and the transverse spin structure
factors. In the weak coupling limit, any weak repulsive interaction also leads
to a weak Y-y state. There is only a crossover from the weak to the strong
coupling. High temperature expansions of the specific heats in both weak and
strong coupling are presented. The dramatic roles to be played by these C-IC
magnons at generic SOC parameters or under various external probes are hinted.
Experimental applications to both layered noncentrosymmetric materials and cold
atom are discussed.",1601.01642v2
2016-01-16,Gauge Covariance and Spin Current Conservation in the Gauge Field Formulation of Systems with Spin-Orbit Coupling,"The question of gauge-covariance in the non-Abelian gauge-field formulation
of two space-dimensional systems with spin-orbit coupling relevant to
spintronics is investigated. Although, these are generally gauge-fixed models,
it is found that for the class of gauge fields that are space-time independent
and satisfy a U(1) algebra, thus having a vanishing field strength, there is a
residual gauge freedom in the Hamiltonian. The gauge transformations assume the
form of a space-dependent rotation of the transformed wave functions with
rotation angles and axes determined by the specific form of the gauge-field,
i.e., the spin-orbit coupling. The fields can be gauged away, reducing the
Hamiltonian to one which is isospectral to the free-particle Hamiltonian, and
giving rise to the phenomenon of persistent spin helix reported first by
B.~A.~Bernevig \emph{et al.} [Phys.~Rev.~Lett. \textbf{97}, 236601 (2006)]. The
investigation of the global gauge transformations leads to the derivation of a
continuity equation where the component of the spin-density along given
directions, again fixed by the specific form of the gauge field, is conserved.",1601.04158v1
2016-05-17,Spin-lattice coupling mediated multiferroicity in (ND4)2FeCl5D2O,"We report a neutron diffraction study of the multiferroic mechanism in
(ND4)2FeCl5D2O, a molecular compound that exhibits magnetically induced
ferroelectricity. This material exhibits two successive magnetic transitions on
cooling: a long-range order transition to an incommensurate (IC) collinear
sinusoidal spin state at TN=7.3 K, followed by a second transition to an IC
cycloidal spin state at TFE=6.8 K, the later of which is accompanied by
spontaneous ferroelectric polarization. The cycloid structure is strongly
distorted by spin-lattice coupling as evidenced by the observations of both odd
and even higher-order harmonics associated with the cycloid wave vector, and a
weak commensurate phase that coexists with the IC phase. The appearance of the
2nd-order harmonic coincides with the onset of the electric polarization,
thereby providing unambiguous evidence that the induced electric polarization
is mediated by the spin-lattice interaction. Our results for this system, in
which the orbital angular momentum is expected to be quenched, are remarkably
similar to those of the prototypical TbMnO3, in which the magnetoelectric
effect is attributed to spin-orbit coupling.",1605.05214v1
2016-06-28,Perspective: Ultrafast magnetism and THz spintronics,"This year the discovery of femtosecond demagnetization by laser pulses is 20
years old. For the first time this milestone work by Bigot and coworkers gave
insight in a very direct way into the time scales of microscopic interactions
that connect the spin and electron system. While intense discussions in the
field were fueled by the complexity of the processes in the past, it now became
evident that it is a puzzle of many different parts. Rather than giving an
overview that has been presented in previous reviews on ultrafast processes in
ferromagnets, this perspective will show that with our current depth of
knowledge the first real applications are on their way: THz spintronics and
all-optical spin manipulation are becoming more and more feasible. The aim of
this perspective is to point out where we can connect the different puzzle
pieces of understanding gathered over 20 years to develop novel applications.
based on many observations in a large number of experiments. Differences in the
theoretical models arise from the localized and delocalized nature of
ferromagnetism. Transport effects are intrinsically non-local in spintronic
devices and at interfaces. We review the need for multiscale modeling to
address processes starting from electronic excitation of the spin system on the
picometer length scale and sub-femtosecond time scale, to spin wave generation,
and towards the modeling of ultrafast phase transitions that altogether
determine the response time of the ferromagnetic system. Today, our current
understanding gives rise to the first real applications of ultrafast spin
physics for ultrafast magnetism control: THz spintronic devices. This makes the
field of ultrafast spin-dynamics an emerging topic open for many researchers
right now.",1606.08725v1
2016-10-18,Symmetry protected topological phases of 1D interacting fermions with spin-charge separation,"The low energy behavior of a huge variety of one-dimensional interacting
spinful fermionic systems exhibits spin-charge separation, described in the
continuum limit by two sine-Gordon models decoupled in the charge and spin
channels. Interaction is known to induce, besides the gapless Luttinger liquid
phase, eight possible gapped phases, among which are the Mott, Haldane,
charge-/spin-density, and bond-ordered wave insulators, and the Luther Emery
liquid. Here we prove that some of these physically distinct phases have
nontrivial topological properties, notably the presence of degenerate protected
edge modes with fractionalized charge/spin. Moreover, we show that the eight
gapped phases are in one-to-one correspondence with the symmetry-protected
topological (SPT) phases classified by group cohomology theory in the presence
of particle-hole symmetry P. The latter result is also exploited to
characterize SPT phases by measurable nonlocal order parameters which follow
the system evolution to the quantum phase transition. The implications on the
appearance of exotic orders in the class of microscopic Hubbard Hamiltonians,
possibly without P symmetry at higher energies, are discussed.",1610.05706v3
2017-07-16,First Principles Study of the Giant Magnetic Anisotropy Energy in Bulk Na4IrO4,"In 5d transition metal oxides, novel properties arise from the interplay of
electron correlations and spin--orbit interactions. Na4IrO4, where 5d
transition-metal Ir atom occupies the center of the square-planar coordination
environment, is synthesized. Based on density functional theory, we calculate
its electronic and magnetic properties. Our numerical results show that the
Ir-5d bands are quite narrow, and the bands around the Fermi level are mainly
contributed by d_{xy},d_{yz} and d_{zx} orbitals. The magnetic easy-axis is
perpendicular to the IrO4 plane, and the magnetic anisotropy energy (MAE) of
Na4IrO4 is found to be very giant. We estimate the magnetic parameters by
mapping the calculated total energy for different spin configurations onto a
spin model. The next nearest neighbor exchange interaction J2 is much larger
than other intersite exchange interactions and results in the magnetic ground
state configuration. Our study clearly demonstrates that the huge MAE comes
from the single-ion anisotropy rather than the anisotropic interatomic spin
exchange. This compound has a large spin gap but very narrow spin-wave
dispersion, due to the large single-ion anisotropy and relatively small
exchange couplings. Noticing this remarkable magnetic feature originated from
its highly isolated IrO4 moiety, we also explore the possiblity to further
enhance the MAE.",1707.04865v1
2017-12-03,Competing phases and topological excitations of spin-one pyrochlore antiferromagnets,"Most works on pyrochlore magnets deal with the interacting spin-1/2 local
moments. We here study the spin-one local moments on the pyrochlore lattice,
and propose a generic interacting spin model on a pyrochlore lattice. Our spin
model includes the antiferromagnetic Heisenberg interaction, the
Dzyaloshinskii-Moriya interaction and the single-ion spin anisotropy. We
develop a flavor wave theory and combine with a mean-field approach to study
the global phase diagram of this model and establish the relation between
different phases in the phase diagram. We find the regime of the quantum
paramagnetic phase where a degenerate line of the magnetic excitations emerges
in the momentum space. We further predict the critical properties of the
transition out of the quantum paramagnet to the proximate orders. The presence
of quantum order by disorder in the parts of the ordered phases is then
suggested. We point out the existence of degenerate and topological excitations
in various phases. We discuss the relevance with fluoride pyrochlore material
NaCaNi$_2$F$_7$ and explain the role of the spin-orbit coupling and the
magnetic structures of the Ru-based pyrochlore A$_2$Ru$_2$O$_7$ and the
Mo-based pyrochlore A$_2$Mo$_2$O$_7$.",1712.00740v1
2018-05-10,"Angular momenta, helicity, and other properties of dielectric-fiber and metallic-wire modes","Spin and orbital angular momenta (AM) of light are well studied for
free-space electromagnetic fields, even nonparaxial. One of the important
applications of these concepts is the information transfer using AM modes,
often via optical fibers and other guiding systems. However, the
self-consistent description of the spin and orbital AM of light in optical
media (including dispersive and metallic cases) was provided only recently
[K.Y. Bliokh et al., Phys. Rev. Lett. 119, 073901 (2017)]. Here we present the
first accurate calculations, both analytical and numerical, of the spin and
orbital AM, as well as the helicity and other properties, for the full-vector
eigenmodes of cylindrical dielectric and metallic (nanowire) waveguides. We
find remarkable fundamental relations, such as the quantization of the
canonical total AM of cylindrical guided modes in the general nonparaxial case.
This quantization, as well as the noninteger values of the spin and orbital AM,
are determined by the generalized geometric and dynamical phases in the mode
fields. Moreover, we show that the spin AM of metallic-wire modes is
determined, in the geometrical-optics approximation, by the transverse spin of
surface plasmon-polaritons propagating along helical trajectories on the wire
surface. Our work provides a solid platform for future studies and applications
of the AM and helicity properties of guided optical and plasmonic waves.",1805.03820v2
2018-11-01,"Hidden $SU(2)$ Symmetries, the Symmetry Hierarchy and the Emergent Eight-Fold Way in Spin-1 Quantum Magnets","The largest allowed symmetry in a spin-1 quantum system is an $SU(3)$
symmetry rather than the $SO(3)$ spin rotation. In this work, we reveal some
$SU(2)$ symmetries as subgroups of $SU(3)$ that, to the best of our knowledge,
have not previously been recognized. Then, we construct $SU(2)$ symmetric
Hamiltonians and explore the ground-state phase diagram in accordance with the
$SU(3)\supset SU(2)\times U(1)$ symmetry hierarchy. It is natural to treat the
eight generators of the $SU(3)$ symmetry on an equal footing; this approach is
called the eight-fold way. We find that the spin spectral functions and spin
quadrupole spectral functions share the same structure, provided that the
elementary excitations are flavor waves at low energies, which serves as a clue
to the eight-fold way. An emergent $S=1/2$ quantum spin liquid is proposed to
coexist with gapful spin nematic order in one of the ground states. In analogy
to quantum chromodynamics, we find the gap relation for hydrodynamic modes in
quantum spin-orbital liquid states, which is nothing but the Gell-Mann-Okubo
formula.",1811.00474v3
2019-11-01,Growth of resonances and chaos for a spinning test particle in the Schwarzschild background,"Inspirals of stellar mass compact objects into supermassive black holes are
known as extreme mass ratio inspirals. In the simplest approximation, the
motion of the compact object is modeled as a geodesic in the space-time of the
massive black hole with the orbit decaying due to radiated energy and angular
momentum, thus yielding a highly regular inspiral. However, once the spin of
the secondary compact body is taken into account, integrability is broken and
prolonged resonances along with chaotic motion appear.
  We numerically integrate the motion of a spinning test body in the field of a
non-spinning black hole and analyse it using various methods. We show for the
first time that resonances and chaos can be found even for astrophysical values
of spin. On the other hand, we devise a method to analyse the growth of the
resonances, and we conclude that the resonances we observe are only caused by
terms quadratic in spin and will generally stay very small in the
small-mass-ratio limit. Last but not least, we compute gravitational waveforms
by solving numerically the Teukolsky equations in the time-domain and establish
that they carry information on the motion's dynamics. In particular, we show
that the time series of the gravitational wave strain can be used to discern
regular from chaotic motion of the source.",1911.00414v1
2019-02-27,Intertwined spin-orbital coupled orders in the iron-based superconductors,"The underdoped phase diagram of the iron-based superconductors exemplifies
the complexity common to many correlated materials. Indeed, multiple ordered
states that break different symmetries but display comparable transition
temperatures are present. Here, we argue that such a complexity can be
understood within a simple unifying framework. This framework, built to respect
the symmetries of the non-symmorphic space group of the FeAs/Se layer, consists
of primary magnetically-ordered states and their vestigial phases that
intertwine spin and orbital degrees of freedom. All vestigial phases have
Ising-like and zero wave-vector order parameters, described in terms of
composite spin order and exotic orbital-order patterns such as spin-orbital
loop-currents, staggered atomic spin-orbit coupling, and emergent Rashba- and
Dresselhaus-type spin-orbit interactions. Moreover, they host unusual
phenomena, such as the electro-nematic effect, by which electric fields acts as
transverse fields to the nematic order parameter, and the ferro-N\'eel effect,
by which a uniform magnetic field induces N\'eel order. We discuss the
experimental implications of our findings to iron-based superconductors and
possible extensions to other correlated compounds with similar space groups.",1902.10831v2
2020-08-06,Constraining the ellipticity of millisecond pulsars with observed spin-down rates,"A spinning neutron star (NS) that is asymmetric with respect to its spin axis
can emit continuous gravitational wave (GW) signals. The spin frequencies and
their distribution of radio millisecond pulsars (MSPs) and accreting MSPs
provide some evidences of GW radiation, and MSPs are ideal probes detecting
high frequency GW signals. It is generally thought that MSPs originate from the
recycled process, in which the NS accretes the material and angular momentum
from the donor star. The accreted matter would be confined at the polar cap
zone by an equatorial belt of compressed magnetic field fixed in the deep crust
of the NS, and yields ""magnetic mountain"". Based on an assumption that the
spin-down rates of three transitional MSPs including PSR J1023+0038 are the
combinational contribution of the accretion torque, the propeller torque, and
the GW radiation torque, in this work we attempt to constrain the ellipticities
of MSPs with observed spin-down rates. Assuming some canonical parameters of
NSs, the ellipticities of three transitional MSPs and ten redbacks are
estimated to be $\epsilon=(0.9-23.4)\times 10^{-9}$. The electrical
resistivities of three transitional MSPs are also derived to be in the range
$\eta=(1.2-15.3)\times 10^{-31}~\rm s$, which display an ideal power law
relation with the accretion rate. The characteristic strains ($h_{\rm
c}=(0.6-2.5)\times10^{-27}$) of GW signals emitting by these sources are
obviously beyond the sensitivity scope of the aLIGO. We expect that the
third-generation GW detectors like the Einstein Telescope can seize the GW
signals from these sources in the future.",2008.02444v2
2020-08-13,Magnetization Dynamics of Nanoscale Magnetic Materials: A Perspective,"Nanomagnets form the building blocks for a gamut of miniaturized
energy-efficient devices including data storage, memory, wave-based computing,
sensors and biomedical devices. They also offer a span of exotic phenomena and
stern challenges. The progress in the magnetization dynamics of single
nanomagnets and one- and two-dimensional arrays of nanostructures in the form
of dots, antidots, nanoparticles, binary and bicomponent structures and
patterned multilayers have been presented. Progress in unconventional and new
structures like artificial spin ice and three-dimensional nanomagnets and spin
textures like domain walls, vortex and skyrmions have been presented.
Furthermore, a huge variety of new topics in the magnetization dynamics of
magnetic nanostructures are rapidly emerging. An overview of the steadily
evolving topics like spatio-temporal imaging of fast dynamics of
nanostructures, dynamics of spin textures, artificial spin ice have been
discussed. In addition, dynamics of contemporary and newly transpired magnetic
architectures such as nanomagnet arrays with complex basis and symmetry,
magnonic quasicrystals, fractals, defect structures, novel three-dimensional
structures have been introduced. Effects of various spin-orbit coupling and
ensuing spin textures as well as quantum hybrid systems comprising of
magnon-photon, magnon-phonon and magnon-magnon coupling, antiferromagnetic
nanostructures are rapidly growing and are expected to dominate this research
field in the coming years. Finally, associated topics like nutation dynamics
and nanomagnet antenna are briefly discussed. Despite showing a great progress,
only a small fraction of nanomagnetism and its ancillary topics have been
explored so far and huge efforts are envisaged in this evergrowing research
area in the generations to come.",2008.05819v1
2020-08-23,Multispinon excitations in the spin S=1/2 antiferromagnetic Heisenberg model,"With the commutation relations of the spin operators, we first write out the
equations of motion of the spin susceptibility and related correlation
functions that have a hierarchical structure, then under the ""soft cut-off""
approximation, we give a set of equations of motion of spin susceptibilities
for a spin S=1/2 antiferromagnetic Heisenberg model, that is independent of
whether or not the system has a long range order in the low energy/temperature
limit. Applying for a chain, a square lattice and a honeycomb lattice,
respectively, we obtain the upper and the lowest boundaries of the low-lying
excitations by solving this set of equations. For a chain, the upper and the
lowest boundaries of the low-lying excitations are the same as that of the
exact ones obtained by the Bethe ansatz, where the elementary excitations are
the spinon pairs. For a square lattice, the spin wave excitation (magnons)
resides in the region close to the lowest boundary of the low-lying
excitations, and the multispinon excitations take place in the high energy
region close to the upper boundary of the low-lying excitations. For a
honeycomb lattice, we have one kind of ""mode"" of the low-lying excitation. The
present results obey the Lieb-Schultz-Mattis theorem, and they are also
consistent with recent neutron scattering observations and numerical
simulations for a square lattice.",2008.09974v1
2016-12-22,Cross-over from an incommensurate singlet spiral state with a vanishingly small spin-gap to a valence bond solid state in dimerized frustrated ferromagnetic spin-chains,"Motivated by the magnetic properties of the spin-chain compounds
LiCuSbO$_4$$\equiv$LiSbCuO$_4$ and Rb$_2$Cu$_2$Mo$_3$O$_{12}$, we study the
ground state of the Heisenberg chain with dimerized nearest-neighbor
ferromagnetic (FM)($J_1, J_1^\prime<0$) and next-nearest-neighbor
antiferromagnetic ($J_2>0$) couplings. Using the density-matrix renormalization
group technique and spin-wave theory we find a first-order transition between a
fully-polarized FM and an incommensurate spiral state at
$2\alpha=\beta/(1+\beta)$, where $\alpha$ is the frustration ratio $J_2/|J_1|$
and $\beta$ the degree of dimerization $J_1^\prime/J_1$.In the singlet spiral
state the spin-gap is vanishingly small in the vicinity of the FM transition,
corresponding to a situation of LiCuSbO$_4$. For larger $\alpha$, corresponding
to Rb$_2$Cu$_2$Mo$_3$O$_{12}$, and smaller $\beta$ there is a crossover from
this frustration induced incommensurate state to an
Affleck-Lieb-Kennedy-Tasaki-type valence bond solid state with substantial
spin-gaps.",1612.07609v2
2017-06-19,Spin order and dynamics in the diamond-lattice Heisenberg antiferromagnets CuRh2O4 and CoRh2O4,"Antiferromagnetic insulators on the diamond lattice are candidate materials
to host exotic magnetic phenomena ranging from spin-orbital entanglement to
degenerate spiral ground-states and topological paramagnetism. Compared to
other three-dimensional networks of magnetic ions, such as the geometrically
frustrated pyrochlore lattice, the investigation of diamond-lattice magnetism
in real materials is less mature. In this work, we characterize the magnetic
properties of model A-site spinels CoRh2O4 (cobalt rhodite) and CuRh2O4 (copper
rhodite) by means of thermo-magnetic and neutron scattering measurements and
perform group theory analysis, Rietveld refinement, mean-field theory, and spin
wave theory calculations to analyze the experimental results. Our investigation
reveals that cubic CoRh2O4 is a canonical S=3/2 diamond-lattice Heisenberg
antiferromagnet with a nearest neighbor exchange J = 0.63 meV and a Neel
ordered ground-state below a temperature of 25 K. In tetragonally distorted
CuRh2O4, competiting exchange interactions between up to third nearest-neighbor
spins lead to the development of an incommensurate spin helix at 24 K with a
magnetic propagation vector k = (0,0,0.79). Strong reduction of the ordered
moment is observed for the S=1/2 spins in CuRh2O4 and captured by our 1/S
corrections to the staggered magnetization. Our work identifies CoRh2O4 and
CuRh2O4 as reference materials to guide future work searching for exotic
quantum behavior in diamond-lattice antiferromagnets.",1706.05881v1
2017-06-20,Symmetry-enriched Bose-Einstein condensates in spin-orbit coupled bilayer system,"We consider the fate of Bose-Einstein condensation (BEC) with time-reversal
symmetry and inversion symmetry in a spin-orbit coupled bilayer system. When
these two symmetry operators commute, all the single particle bands are exactly
two-fold degenerate in the momentum space. The scattering in the two-fold
degenerate rings can relax the spin-momentum locking effect resulting from
spin-orbit coupling, thus we can realize the spin polarized plane wave phase
even when the inter-particle interaction dominates. When these two operators
anti-commute, the lowest two bands may have the same minimal energy, which have
totally different spin structures. As a result, the competition between
different condensates in these two energetically degenerate rings can give rise
to interesting stripe phases with atoms condensed at two or four colinear
momenta. We find that the crossover between these two cases is accompanied by
the excited band condensation when the interference energy can overcome the
increased single particle energy in the excited band. This effect is not based
on strong interaction, thus can be realized even with moderate interaction
strength.",1706.06234v1
2017-10-07,High pressure x-ray study of spin-Peierls physics in the quantum spin chain material TiOCl,"The application of pressure can induce transitions between unconventional
quantum phases in correlated materials. The inorganic compound TiOCl, composed
of chains of S=1/2 Ti ions, is an ideal realization of a spin-Peierls system
with a relatively simple unit cell. At ambient pressure, it is an insulator due
to strong electronic interactions (a Mott insulator). Its resistivity shows a
sudden decrease with increasing pressure, indicating a transition to a more
metallic state which may coincide with the emergence of charge density wave
order. Therefore, high pressure studies of the structure with x-rays are
crucial in determining the ground-state physics in this quantum magnet. In
ambient pressure, TiOCl exhibits a transition to an incommensurate nearly
dimerized state at $T_{c2}=92$ K and to a commensurate dimerized state at
$T_{c1}=66$ K. Here, we discover a rich phase diagram as a function of
temperature and pressure using x-ray diffraction on a single crystal in a
diamond anvil cell down to $T=4$ K and pressures up to 14.5 GPa. Remarkably,
the magnetic interaction scale increases dramatically with increasing pressure,
as indicated by the high onset temperature of the spin-Peierls phase. At
$\sim$7 GPa, the extrapolated onset of the spin-Peierls phase occurs above
$T=300$ K, indicating a quantum singlet state exists at room temperature.
Further comparisons are made with the phase diagrams of related spin-Peierls
systems that display metallicity and superconductivity under pressure.",1710.02632v1
2017-10-13,Possible quadrupolar nematic phase in the frustrated spin chain LiCuSbO$_4$: an NMR investigation,"The frustrated one-dimensional (1D) quantum magnet LiCuSbO$_4$ is one rare
realization of the $J_1-J_2$ spin chain model with an easily accessible
saturation field, formerly estimated to 12~T. Exotic multipolar nematic phases
were theoretically predicted in such compounds just below the saturation field,
but without unambiguous experimental observation so far. In this paper we
present extensive experimental research of the compound in the wide temperature
(30mK$-$300K) and field (0$-$13.3T) range by muon spin rotation ($\mu$SR),
$^7$Li nuclear magnetic resonance (NMR) and magnetic susceptibility (SQUID).
$\mu$SR experiments in zero magnetic field demonstrate the absence of long
range 3D ordering down to 30mK. Together with former heat capacity data [S.E.
Dutton \emph{et al}, Phys. Rev. Lett. 108, 187206 (2012)], magnetic
susceptibility measurements suggest short range correlated vector chiral phase
in the field range $0-4$T. In the intermediate field values (5$-$12T), the
system enters in a 3D ordered spin density wave phase with 0.75$\mu_B$ per
copper site at lowest temperatures (125mK), estimated by NMR. At still higher
field, the magnetization is found to be saturated above 13T where the spin
lattice $T_1^{-1}$ relaxation reveals a spin gap estimated to 3.2(2)K. We
narrow down the possibility of observing a multipolar nematic phase to the
range 12.5$-$13T.",1710.05004v1
2020-11-08,"Meron, skyrmion, and vortex crystals in centrosymmetric tetragonal magnets","The recent experimental confirmation of a transformation between meron and
skyrmion topological spin textures in the chiral magnet Co$_8$Zn$_9$Mn$_3$
[S.-Z. Lin et al., Phys. Rev. B 91, 224407 (2015); X. Z. Yu et al., Nature 564,
95 (2018)] confirms that the skyrmion crystals discovered in 2009 [S.
M\""{u}hlbauer et al., Science 323, 915 (2009)] are just the tip of the iceberg.
Crystals of topological textures, including skyrmions, merons, vortices, and
monopoles, can be stabilized by combining simple physical ingredients, such as
lattice symmetry, frustration, and spin anisotropy. The current challenge is to
find the combinations of these ingredients that produce specific topological
spin textures. Here we report a simple mechanism for the stabilization of
meron, skyrmion, and vortex crystals in centrosymmetric tetragonal magnets. In
particular, the meron/skyrmion crystals can form even in absence of magnetic
field. The application of magnetic field leads to a rich variety of topological
spin textures that survive in the long wavelength limit of the theory. When
conduction electrons are coupled to the spins, these topological spin textures
twist the electronic wave functions to induce Chern insulators and Weyl
semimetals for specific band filling fractions.",2011.04033v3
2021-02-02,Detecting spins with a microwave photon counter,"Quantum emitters respond to resonant illumination by radiating
electromagnetic fields. A component of these fields is phase-coherent with the
driving tone, while another one is incoherent, consisting of spontaneously
emitted photons and forming the fluorescence signal. Atoms and molecules are
routinely detected by their fluorescence at optical frequencies, with important
applications in quantum technology and microscopy. Spins, on the other hand,
are usually detected by {their coherent response} at radio- or microwave
frequencies, either in continuous-wave or pulsed magnetic resonance. Indeed,
fluorescence detection of spins is hampered {by their low spontaneous emission
rate} and by the lack of single-photon detectors in this frequency range. Here,
using superconducting quantum devices, we demonstrate the detection of a small
ensemble of donor spins in silicon by their fluorescence at microwave frequency
and millikelvin temperatures. We enhance the spin radiative decay rate by
coupling them to a high-quality-factor and small-mode-volume superconducting
resonator, and we connect the device output to a newly-developed microwave
single-photon counter based on a superconducting qubit. We discuss the
potential of fluorescence detection as a novel method for magnetic resonance
spectroscopy of small numbers of spins.",2102.01415v1
2021-02-02,Spin misalignment of black hole binaries from young star clusters: implications for the origin of gravitational waves events,"Recent studies indicate that the progenitors of merging black hole (BH)
binaries from young star clusters can undergo a common envelope phase just like
isolated binaries. If the stars emerge from the common envelope as naked cores,
tidal interactions can efficiently synchronize their spins before they collapse
into BHs. Contrary to the isolated case, these binary BHs can also undergo
dynamical interactions with other BHs in the cluster before merging. The
interactions can tilt the binary orbital plane, leading to spin-orbit
misalignment. We estimate the spin properties of merging binary BHs undergoing
this scenario by combining up-to-date binary population synthesis and accurate
few-body simulations. We show that post-common envelope binary BHs are likely
to undergo only a single encounter, due to the high binary recoil velocity and
short coalescence times. Adopting conservative limits on the binary-single
encounter rates, we obtain a local BH merger rate density of ~6.6 yr^-1 Gpc^-3.
Assuming low (<0.2) natal BH spins, this scenario reproduces the trends in the
distributions of effective spin Xeff and precession parameters Xp inferred from
GWTC-2, including the peaks at (Xeff, Xp) ~ (0.1, 0.2) and the tail at negative
Xeff values.",2102.01689v2
2021-04-25,Staggered spin-orbit interaction in a nanoscale device,"The coupling of the spin and the motion of charge carriers stems directly
from the atomic structure of a conductor. It has become an important ingredient
for the emergence of topological matter, and, in particular, topological
superconductivity which could host non-abelian excitations such as Majorana
modes or parafermions. These modes are sought after mostly in semiconducting
platforms which are made of heavy atoms and therefore exhibit naturally a large
spin-orbit interaction. Creating domain walls in the spin orbit interaction at
the nanoscale may turn out to be a crucial resource for engineering topological
excitations suitable for universal topological quantum computing. For example,
it has been proposed for exploring exotic electronic states or for creating
hinge states. Realizing this in natural platforms remains a challenge. In this
work, we show how this can be alternatively implemented by using a synthetic
spin orbit interaction induced by two lithographically patterned magnetically
textured gates. By using a double quantum dot in a light material -- a carbon
nanotube -- embedded in a microwave cavity, we trigger hopping between two
adjacent orbitals with the microwave photons and directly compare the wave
functions separated by the domain wall via the light-matter coupling. We show
that we can achieve an engineered staggered spin-orbit interaction with a
change of strength larger than the hopping energy between the two sites.",2104.12181v1
2017-01-05,Phase diagram of weakly coupled Heisenberg spin chains subject to a uniform Dzyaloshinskii-Moriya interaction,"Motivated by recent experiments on spin chain materials K$_2$CuSO$_4$Cl$_2$
and K$_2$CuSO$_4$Br$_2$, we theoretically investigate the problem of weakly
coupled spin chains (chain exchange $J$, interchain $J'$) subject to a
$\textit{staggered between chains}$, but $\textit{uniform}$ within a given
chain, Dzyaloshinskii-Moriya (DM) interaction of magnitude $D$. In the
experimentally relevant limit $J' \ll D \ll J$ of strong DM interaction the
spins on the neighboring chains are forced to rotate in opposite directions,
effectively resulting in a cancelation of the interchain interaction between
components of spins in the plane normal to the vector ${\pmb D}$. This has the
effect of promoting two-dimensional collinear spin density wave (SDW) state,
which preserves U(1) symmetry of rotations about the $\pmb D$-axis. We also
investigate response of this interesting system to an external magnetic field
${\pmb h}$ and obtain the $h-D$ phase diagrams for the two important
configurations, ${\pmb h} \parallel {\pmb D}$ and ${\pmb h} \perp {\pmb D}$.",1701.01465v3
2017-01-23,Testing the binary black hole nature of a compact binary coalescence,"We propose a novel method to test the binary black hole (BBH) nature of
compact binaries detectable by gravitational wave (GW) interferometers and
hence constrain the parameter space of other exotic compact objects. The spirit
of the test lies in the ""no-hair"" conjecture for black holes where all
properties of a black hole are characterised by the mass and the spin of the
black hole. The method relies on observationally measuring the quadrupole
moments of the compact binary constituents induced due to their spins. If the
compact object is a Kerr black hole (BH), its quadrupole moment is expressible
solely in terms of its mass and spin. Otherwise, the quadrupole moment can
depend on additional parameters (such as equation of state of the object). The
higher order spin effects in phase and amplitude of a gravitational waveform,
which explicitly contains the spin-induced quadrupole moments of compact
objects, hence uniquely encodes the nature of the compact binary. Thus we argue
that an independent measurement of the spin-induced quadrupole moment of the
compact binaries from GW observations can provide a unique way to distinguish
binary BH systems from binaries consisting of exotic compact objects.",1701.06318v2
2017-04-26,Determining the population properties of spinning black holes,"There are at least two formation scenarios consistent with the first
gravitational-wave observations of binary black hole mergers. In field models,
black hole binaries are formed from stellar binaries that may undergo common
envelope evolution. In dynamic models, black hole binaries are formed through
capture events in globular clusters. Both classes of models are subject to
significant theoretical uncertainties. Nonetheless, the conventional wisdom
holds that the distribution of spin orientations of dynamically merging black
holes is nearly isotropic while field-model black holes prefer to spin in
alignment with the orbital angular momentum. We present a framework in which
observations of black hole mergers can be used to measure ensemble properties
of black hole spin such as the typical black hole spin misalignment. We show
how to obtain constraints on population hyperparameters using minimal
assumptions so that the results are not strongly dependent on the uncertain
physics of formation models. These data-driven constraints will facilitate
tests of theoretical models and help determine the formation history of binary
black holes using information encoded in their observed spins. We demonstrate
that the ensemble properties of binary detections can be used to search for and
characterize the properties of two distinct populations of black hole mergers.",1704.08370v2
2019-10-04,Spin fluctuation anisotropy as a probe of orbital-selective hole-electron quasiparticle excitations in detwinned Ba(Fe1-xCox)2As2,"We use inelastic neutron scattering to study spin excitation anisotropy in
mechanically detwinned Ba(Fe1-xCox)2As2 with x = 0.048 and 0.054. Both samples
exhibit a tetragonal-to-orthorhombic structural transition at Ts, a collinear
static antiferromagnetic (AF) order at wave vector Q1 = QAF = (1, 0) below the
Neel temperature TN, and superconductivity below Tc (Ts > TN > Tc). In the high
temperature paramagnetic tetragonal phase (T > Ts), spin excitations centered
at Q1 and Q2 = (0, 1) are gapless and have four-fold (C4) rotational symmetry.
On cooling to below TN but above Tc, spin excitations become highly
anisotropic, developing a gap at Q2 but still are gapless at Q1. Upon entering
into the superconducting state, a neutron spin resonance appears at Q1 with no
magnetic scattering at Q2. By comparing these results with those from angle
resolved photoemission spectroscopy experiments, we conclude that the
anisotropic shift of the dyz and dxz bands in detwinned Ba(Fe1-xCox)2As2 below
Ts is associated with the spin excitation anisotropy, and the
superconductivity-induced resonance arises from the electron-hole Fermi surface
nesting of quasiparticles with the dyz orbital characters.",1910.01871v1
2020-01-03,The spin rates of O stars in WR + O Magellanic Cloud binaries,"Some massive, merging black holes (BH) may be descendants of binary O stars.
The evolution and mass transfer between these O stars determines the spins of
their progeny BH. These will be measurable with future gravitational wave
detectors, incentivizing the measurement of the spins of O stars in binaries.
We previously measured the spins of O stars in Galactic Wolf-Rayet (WR) + O
binaries. Here we measure the vsini of four LMC and two SMC O stars in WR + O
binaries to determine whether lower metallicity might affect the spin rates. We
find that the O stars in Galactic and Magellanic WR + O binaries display
average vsini = 258 +/- 18 km/s and 270 +/- 15 km/s, respectively. Two LMC O
stars measured on successive nights show significant line width variability,
possibly due to differing orbital phases exhibiting different parts of the O
stars illuminated differently by their WR companions. Despite this variability,
the vsini are highly super-synchronous but distinctly subcritical for the O
stars in all these binaries; thus we conclude that an efficient mechanism for
shedding angular momentum from O stars in WR + O binaries must exist. This
mechanism, probably related to Roche lobe overflow-created dynamo magnetic
fields, prevents nearly 100% breakup spin rates, as expected when RLOF
operates, as it must, in these stars. A Spruit-Tayler dynamo and O star wind
might be that mechanism.",2001.01012v1
2020-01-22,The dynamics of a domain wall in ferrimagnets driven by spin-transfer torque,"The spin-transfer-torque-driven (STT-driven) dynamics of a domain wall in an
easy-axis rare-earth transition-metal ferrimagnet is investigated theoretically
and numerically in the vicinity of the angular momentum compensation point
$T_A$, where the net spin density vanishes. The particular focus is given on
the unusual interaction of the antiferromagnetic dynamics of a ferrimagnetic
domain wall and the adiabatic component of STT, which is absent in
antiferromagnets but exists in the ferrimagnets due to the dominant coupling of
conduction electrons to transition-metal spins. Specifically, we first show
that the STT-induced domain-wall velocity changes its sign across $T_A$ due to
the sign change of the net spin density, giving rise to a phenomenon unique to
ferrimagnets that can be used to characterize $T_A$ electrically. It is also
shown that the frequency of the STT-induced domain-wall precession exhibits its
maximum at $T_A$ and it can approach the spin-wave gap at sufficiently high
currents. Lastly, we report a numerical observation that, as the current
density increases, the domain-wall velocity starts to deviate from the
linear-response result, calling for a more comprehensive theory for the
domain-wall dynamics in ferrimagnets driven by a strong current.",2001.08037v1
2020-06-23,Imaging non-collinear antiferromagnetic textures via single spin relaxometry,"Antiferromagnetic materials are promising platforms for next-generation
spintronics owing to their fast dynamics and high robustness against parasitic
magnetic fields. However, nanoscale imaging of the magnetic order in such
materials with zero net magnetization remains a major experimental challenge.
Here we show that non-collinear antiferromagnetic spin textures can be imaged
by probing the magnetic noise they locally produce via thermal populations of
magnons. To this end, we perform nanoscale, all-optical relaxometry with a
scanning quantum sensor based on a single nitrogen-vacancy (NV) defect in
diamond. Magnetic noise is detected through an increase of the spin relaxation
rate of the NV defect, which results in an overall reduction of its
photoluminescence signal under continuous laser illumination. As a
proof-of-concept, the efficiency of the method is demonstrated by imaging
various spin textures in synthetic antiferromagnets, including domain walls,
spin spirals and antiferromagnetic skyrmions. This imaging procedure could be
extended to a large class of intrinsic antiferromagnets and opens up new
opportunities for studying the physics of localized spin wave modes for
magnonics.",2006.13130v1
2020-07-02,The impact of metallic contacts on spin-polarized photocurrents in topological insulator $\text{Bi}_2\text{Se}_3$ nanowires,"Recently, a new quantum phase, the topological insulator, has been vividly
investigated in a variety of materials. Its unique bandstructure allows for
optical generation and control of spin-polarized currents based on the circular
photogalvanic effect. In this paper, we generate and distinguish the different
photocurrent contributions via the the polarization of the driving light wave.
We discuss the helicity-dependent spin-polarized current and the polarization
independent thermoelectric current as spatially resolved maps, focusing on the
influence of the topological insulator/metallic contact interface. We observe
for both current contributions a significant enhancement of the current values
at the topological insulator/metallic contact interface and moreover a
dipole-like distribution of the spin-polarized current close to the contacts.
We discuss the general behavior of the thermovoltage as a three-material
Seebeck effect and explain the enhanced values by the acceleration of the
photoelectrons generated in the space charge region of the topological
insulator/metallic contact interface. Furthermore, we interpret the temperature
gradient together with the spin Nernst effect as a possible origin for the
enhancement and dipole-like distribution of the spin-polarized current.",2007.00993v2
2020-10-12,Constraining the spin parameter of near-extremal black holes using LISA,"We describe a model that generates first order adiabatic EMRI waveforms for
quasi-circular equatorial inspirals of compact objects into rapidly rotating
(near-extremal) black holes. Using our model, we show that LISA could measure
the spin parameter of near-extremal black holes (for $a \gtrsim 0.9999$) with
extraordinary precision, $\sim$ 3-4 orders of magnitude better than for
moderate spins, $a \sim 0.9$. Such spin measurements would be one of the
tightest measurements of an astrophysical parameter within a gravitational wave
context. Our results are primarily based off a Fisher matrix analysis, but are
verified using both frequentest and Bayesian techniques. We present analytical
arguments that explain these high spin precision measurements. The high
precision arises from the spin dependence of the radial inspiral evolution,
which is dominated by geodesic properties of the secondary orbit, rather than
radiation reaction. High precision measurements are only possible if we observe
the exponential damping of the signal that is characteristic of the
near-horizon regime of near-extremal inspirals. Our results demonstrate that,
if such black holes exist, LISA would be able to successfully identify rapidly
rotating black holes up to $a = 1-10^{-9}$ , far past the Thorne limit of $a =
0.998$.",2010.05932v2
2020-10-19,Geometrical Hall effect and momentum-space Berry curvature from spin-reversed band pairs,"When nanometric, noncoplanar spin textures with scalar spin chirality (SSC)
are coupled to itinerant electrons, they endow the quasiparticle wavefunctions
with a gauge field, termed Berry curvature, in a way that bears analogy to
relativistic spin-orbit coupling (SOC). The resulting deflection of moving
charge carriers is termed geometrical (or topological) Hall effect. Previous
experimental studies modeled this signal as a real-space motion of wavepackets
under the influence of a quantum-mechanical phase. In contrast, we here compare
the modification of Bloch waves themselves, and of their energy dispersion, due
to SOC and SSC. Using the canted pyrochlore ferromagnet Nd$_2$Mo$_2$O$_7$ as a
model compound, our transport experiments and first-principle calculations show
that SOC impartially mixes electronic bands with equal or opposite spin, while
SSC is much more effective for opposite spin band pairs.",2010.09537v4
2021-01-02,Spin evolution of neutron stars in two modes: implication for millisecond pulsars,"An understanding of spin frequency ($\nu$) evolution of neutron stars in the
low-mass X-ray binary (LMXB) phase is essential to explain the observed
$\nu$-distribution of millisecond pulsars (MSPs), and to probe the stellar and
binary physics, including the possibility of continuous gravitational wave
emission. Here, using numerical computations we conclude that $\nu$ can evolve
in two distinctly different modes, as $\nu$ may approach a lower spin
equilibrium value ($\nu_{\rm eq,per}$) for persistent accretion for a long-term
average accretion rate ($\dot{M}_{\rm av}$) greater than a critical limit
($\dot{M}_{\rm av,crit}$), and may approach a higher effective spin equilibrium
value ($\nu_{\rm eq,eff}$) for transient accretion for $\dot{M}_{\rm av} <
\dot{M}_{\rm av,crit}$. For example, when $\dot{M}_{\rm av}$ falls below
$\dot{M}_{\rm av,crit}$ for an initially persistent source, $\nu$ increases
considerably due to transient accretion, which is counterintuitive. We also
find that, contrary to what was suggested, a fast or sudden decrease of
$\dot{M}_{\rm av}$ to zero in the last part of the LMXB phase is not essential
for the genesis of spin-powered MSPs, and neutron stars could spin up in this
$\dot{M}_{\rm av}$-decreasing phase. Our findings imply that the traditional
way of $\nu$-evolution computation is inadequate in most cases, even for
initially persistent sources, and may not even correctly estimate whether $\nu$
increases or decreases.",2101.00518v1
2021-05-03,The Hubbard model on triangular $N$-leg cylinders: chiral and non-chiral spin liquids,"The existence of a gapped chiral spin liquid has been recently suggested in
the vicinity of the metal-insulator transition of the Hubbard model on the
triangular lattice, by intensive density-matrix renormalization group (DMRG)
simulations [A. Szasz, J. Motruk, M.P. Zaletel, and J.E. Moore, Phys. Rev. X
{\bf 10}, 021042 (2020)]. Here, we report the results obtained within the
variational Monte Carlo technique based upon Jastrow-Slater wave functions,
implemented with backflow correlations. As in DMRG calculations, we consider
$N$-leg cylinders. For $N=4$ and in the presence of a next-nearest neighbor
hopping, a chiral spin liquid emerges between the metal and the insulator with
magnetic quasi-long-range order. Within our approach, the chiral state is
gapped and breaks the reflection symmetry. By contrast, for both $N=5$ and
$N=6$, the chiral spin liquid is not the state with the lowest variational
energy: in the former case a nematic spin liquid is found in the entire
insulating regime, while for the less frustrated case with $N=6$ the results
are very similar to the one obtained on two-dimensional clusters [L.F. Tocchio,
A. Montorsi, and F. Becca, Phys. Rev. B {\bf 102}, 115150 (2020)], with an
antiferromagnetic phase close to the metal-insulator transition and a nematic
spin liquid in the strong-coupling regime.",2105.00920v2
2021-06-23,Field-Induced Spin Excitations in the Spin-1/2 Triangular-Lattice Antiferromagnet CsYbSe$_2$,"A layered triangular lattice with spin-1/2 ions is an ideal platform to
explore highly entangled exotic states like quantum spin liquid (QSL). Here, we
report a systematic in-field neutron scattering study on a perfect
two-dimensional triangular-lattice antiferromagnet, CsYbSe$_2$, a member of the
large QSL candidate family rare-earth chalcogenides. The elastic neutron
scattering measured down to 70 mK shows that there is a short-range
120$^{\circ}$ magnetic order at zero field. In the field-induced ordered
states, the spin-spin correlation lengths along the $c$ axis are relatively
short, although the heat capacity results indicate long-range magnetic orders
at 3 T $-$ 5 T. The inelastic neutron scattering spectra evolve from highly
damped continuum-like excitations at zero field to relatively sharp spin wave
modes at the plateau phase. Our extensive large-cluster density-matrix
renormalization group calculations with a Heisenberg triangular-lattice
nearest-neighbor antiferromagnetic model reproduce the essential features of
the experimental spectra, including continuum-like excitations at zero field,
series of sharp magnons at the plateau phase as well as two-magnon excitations
at high energy. This work presents comprehensive experimental and theoretical
overview of the unconventional field-induced spin dynamics in
triangular-lattice Heisenberg antiferromagnet and thus provides valuable
insight into quantum many-body phenomena.",2106.12451v2
2021-07-21,Magnetic and superconducting phase diagram of Eu(Fe$_{1-x}$Ni$_{x}$)As$_{2}$,"We report the Ni-doping effect on magnetism and superconductivity (SC) in an
Eu-containing 112-type system Eu(Fe$_{1-x}$Ni$_{x})$As$_{2}$ ($0\leq x\leq
0.15$) by the measurements of resistivity, magnetization, and specific heat.
The undoped EuFeAs$_2$ undergoes a spin-density-wave (SDW) transition at
$T_\mathrm{SDW}\sim$ 105 K in the Fe sublattice and a magnetic ordering at
$T_\mathrm{m}\sim$ 40 K in the Eu sublattice. Complex Eu-spin magnetism is
manifested by a spin-glass reentrance at $T_\mathrm{SG}\sim$ 15 K and an
additional spin reorientation at $T_\mathrm{SR}\sim$ 7 K. With Ni doping, the
SDW order is rapidly suppressed, and SC emerges in the Ni-doping range of 0.01
$\leq x\leq$ 0.1 where a maximum of the superconducting transition temperature
$T_\mathrm{c}^{\mathrm{max}}=$ 17.6 K shows up at $x$ = 0.04. On the other
hand, $T_\mathrm{m}$ decreases very slowly, yet $T_\mathrm{SG}$ and
$T_\mathrm{SR}$ hardly change with the Ni doping. The phase diagram has been
established, which suggests a very weak coupling between SC and Eu spins. The
complex Eu-spin magnetism is discussed in terms of the
Ruderman-Kittel-Kasuya-Yosida interactions mediated by the conduction electrons
from both layers of FeAs and As surrounding Eu$^{2+}$ ions.",2107.09855v1
2021-11-05,Quadrupolar magnetic excitations in an isotropic spin-1 antiferromagnet,"The microscopic origins of emergent behaviours in condensed matter systems
are encoded in their excitations. In ordinary magnetic materials, single
spin-flips give rise to collective dipolar magnetic excitations called magnons.
Likewise, multiple spin-flips can give rise to multipolar magnetic excitations
in magnetic materials with spin $\mathbf{S} \boldsymbol{\ge} \mathbf{1}$.
Unfortunately, since most experimental probes are governed by dipolar selection
rules, collective multipolar excitations have generally remained elusive. For
instance, only dipolar magnetic excitations have been observed in isotropic
$\mathbf{S}\boldsymbol{=}\mathbf{1}$ Haldane spin systems. Here, we unveil a
hidden quadrupolar constituent of the spin dynamics in antiferromagnetic
$\mathbf{S}\boldsymbol{=}\mathbf{1}$ Haldane chain material
Y$_\mathbf{2}$BaNiO$_\mathbf{5}$ using Ni $\mathbf{L_3}$-edge resonant
inelastic x-ray scattering. Our results demonstrate that pure quadrupolar
magnetic excitations can be probed without direct interactions with dipolar
excitations or anisotropic perturbations. Originating from on-site double
spin-flip processes, the quadrupolar magnetic excitations in
Y$_\mathbf{2}$BaNiO$_\mathbf{5}$ show a remarkable dual nature of collective
dispersion. While one component propagates as non-interacting entities, the
other behaves as a bound quadrupolar magnetic wave. This result highlights the
rich and largely unexplored physics of higher-order magnetic excitations.",2111.03625v1
2022-02-23,Temperature Dependence of Spin and Charge Orders in the Doped Two-Dimensional Hubbard Model,"Competing and intertwined orders including inhomogeneous patterns of spin and
charge are observed in many correlated electron materials, such as
high-temperature superconductors. Introducing a new development of the
constrained-path auxiliary-field quantum Monte Carlo (AFQMC) method, we study
the interplay between thermal and quantum fluctuations in the two-dimensional
Hubbard model. We obtain an accurate and systematic characterization of the
evolution of the spin and charge correlations as a function of temperature $T$
and how it connects to the ground state, at three representative doping levels
$\delta = 1/5$, $1/8$, and $1/10$. We find increasing short-range commensurate
antiferromagnetic correlations as $T$ is lowered. As the correlation length
grows sufficiently large, a modulated spin-density-wave (SDW) appears. At
$\delta = 1/5$, the SDW saturates and remains short-ranged as $T \rightarrow
0$. In contrast, at $\delta = 1/8$ and $1/10$ this evolves into a ground-state
stripe phase. We study the relation between spin and charge orders and find
that formation of charge order appears to be driven by that of the spin order.
We identify a finite-temperature phase transition below which charge ordering
sets in and discuss the implications of our results for the nature of this
transition.",2202.11741v3
2022-04-08,Manipulating the transverse spin angular momentum and Belinfante momentum of spin-polarized light by a tilted stratified medium in optical tweezers,"In the recent past, optical tweezers incorporating a stratified medium have
been exploited to generate complex translational and rotational dynamics in
mesoscopic particles due to the coupling between the spin and orbital angular
momentum of the light, generated as a consequence of the tight focusing of
light by a high numerical aperture objective lens into the stratified medium.
Here, we consider an optical tweezers system with a tilted stratified medium
(direction of stratification at an angle with the axis of the incident beam),
and show that for input circularly polarized Gaussian beams, the resulting
spin-orbit interaction deeply influences the generation of transverse spin
angular momentum (TSAM) and Belinfante momentum of light, and allows additional
control on their magnitude. Importantly, the TSAM generated in our system
consists of both the orthogonal components, which is in sharp contrast to the
case of evanescent waves and surface plasmons, where only one of the TSAM
components are generated. The broken symmetry due to the tilt ensures that,
depending upon the helicity of the input beam, the magnitude of the mutually
orthogonal components of the TSAM depend entirely on the tilt angle. This may
prove to be an effective handle in exotic spin-controlled manipulation of
particles in experiments.",2204.04316v2
2022-04-28,"Low-energy spin excitations of the frustrated ferromagnetic $J_1$-$J_2$ chain material linarite, PbCuSO$_4$(OH)$_2$, in applied magnetic fields $\mathbf{H} \parallel b$ axis","We report a study of the spin dynamics of the frustrated ferromagnetic
$J_1$-$J_2$ chain compound linarite, PbCuSO$_4$(OH)$_2$, in applied magnetic
fields up to field polarization. By means of an extreme-environment inelastic
neutron scattering experiment, we have measured the low-energy spin excitations
of linarite in fields up to 8.8 T for $\mathbf{H} \parallel b$ axis. We have
recorded the spin excitation spectra along $h$, $k$ and $l$ for the
field-induced magnetic phases IV, V and the field polarized state close to
saturation. By employing first-principles calculations, we estimate the leading
magnetic exchanges out of the $bc$ plane and model the dispersion relations
using linear spin-wave theory. In this way, we find evidence for a (very weak)
residual magnetic exchange coupling out of the $bc$ plane. Together with the
previously established dominant intrachain couplings $J_1$ and $J_2$ and the
interchain coupling $J_3$, we derive an effective set of exchange couplings for
a microscopic description of linarite. Further, we find that the peculiar
character of phase V manifests itself in the measured spin dynamics.",2204.13482v2
2022-05-09,Fragment-orbital-dependent spin fluctuations in the single-component molecular conductor [Ni(dmdt)$_2$],"Motivated by recent nuclear magnetic resonance experiments, we calculated the
spin susceptibility, Knight shift, and spin-lattice relaxation rate
($1/T_{1}T$) of the single-component molecular conductor [Ni(dmdt)$_2$] using
the random phase approximation in a multi-orbital Hubbard model describing the
Dirac nodal line electronic system in this compound. This Hubbard model is
composed of three fragment orbitals and on-site repulsive interactions obtained
using ab initio many-body perturbation theory calculations. We found
fragment-orbital-dependent spin fluctuations with the momentum
$\textbf{q}$=$\textbf{0}$ and an incommensurate value of the wavenumber
$\textbf{q}$=$\textbf{Q}$ at which a diagonal element of the spin
susceptibility is maximum. The $\textbf{q}$=$\textbf{0}$ and $\textbf{Q}$
responses become dominant at low and high temperatures, respectively, with the
Fermi-pocket energy scale as the boundary. We show that $1/T_{1}T$ decreases
with decreasing temperature but starts to increase at low temperature owing to
the $\textbf{q}$=$\textbf{0}$ spin fluctuations, while the Knight shift keeps
monotonically decreasing. These properties are due to the intra-molecular
antiferromagnetic fluctuations caused by the characteristic wave functions of
this Dirac nodal line system, which is described by an $n$-band ($n\geq 3$)
model. We show that the fragment orbitals play important roles in the magnetic
properties of [Ni(dmdt)$_2$].",2205.04020v4
2022-05-24,Emission of coherent THz magnons in an antiferromagnetic insulator triggered by ultrafast spin-phonon interactions,"Antiferromagnetic materials have been proposed as new types of narrowband THz
spintronic devices owing to their ultrafast spin dynamics. Manipulating
coherently their spin dynamics, however, remains a key challenge that is
envisioned to be accomplished by spin-orbit torques or direct optical
excitations. Here, we demonstrate the combined generation of broadband THz
(incoherent) magnons and narrowband (coherent) magnons at 1 THz in low damping
thin films of NiO/Pt. We evidence, experimentally and through modelling, two
excitation processes of magnetization dynamics in NiO, an off-resonant
instantaneous optical spin torque and a strain-wave-induced THz torque induced
by ultrafast Pt excitation. Both phenomena lead to the emission of a THz signal
through the inverse spin Hall effect in the adjacent heavy metal layer. We
unravel the characteristic timescales of the two excitation processes found to
be < 50 fs and > 300 fs, respectively, and thus open new routes towards the
development of fast opto-spintronic devices based on antiferromagnetic
materials.",2205.11965v1
2022-06-06,Probing spin dynamics of ultra-thin van der Waals magnets via photon-magnon coupling,"Layered van der Waals (vdW) magnets can maintain a magnetic order even down
to the single-layer regime and hold promise for integrated spintronic devices.
While the magnetic ground state of vdW magnets was extensively studied, key
parameters of spin dynamics, like the Gilbert damping, crucial for designing
ultra-fast spintronic devices, remains largely unexplored. Despite recent
studies by optical excitation and detection, achieving spin wave control with
microwaves is highly desirable, as modern integrated information technologies
predominantly are operated with these. The intrinsically small numbers of
spins, however, poses a major challenge to this.
  Here, we present a hybrid approach to detect spin dynamics mediated by
photon-magnon coupling between high-Q superconducting resonators and ultra-thin
flakes of Cr$_2$Ge$_2$Te$_6$ (CGT) as thin as 11\,nm. We test and benchmark our
technique with 23 individual CGT flakes and extract an upper limit for the
Gilbert damping parameter. These results are crucial in designing on-chip
integrated circuits using vdW magnets and offer prospects for probing spin
dynamics of monolayer vdW magnets.",2206.02460v2
2022-06-13,Charge and spin correlations in insulating and incoherent metal states of twisted bilayer graphene,"We study electronic, charge, and magnetic properties of twisted bilayer
graphene with fillings $2\leq n\leq 6$ per moire unit cell within the recently
introduced formulation of extended dynamical mean-field theory (E-DMFT) for
two-sublattice systems. We use previously obtained hopping parameters between
the states, described by Wannier functions, centered at the lattice spots of AB
and BA stacking, and the long-range Coulomb interaction, obtained within cRPA
analysis. We show that account of spin exchange between AB and BA nearest
neighbour spots is crucial to introduce charge and spin correlations between
these spots. Account of this exchange yields preferable concentration of
electrons in the same valley, with the tendency of parallel spin alignment of
electrons in AB and BA spots, in agreement with earlier results of the strong
coupling analysis, suggested SU(2)$\times$SU(2) emergent spin-valley symmetry.
The local spectral functions show almost gapped state at the fillings
$n=2,4,6$, and incoherent metal state for the other fillings. We find that in
both cases the local states of electrons have rather long lifetime. At the same
time, the non-local charge- and spin susceptibilities, obtained within the
ladder approximation, are peaked at incommensurate wave vectors, which implies
that the above discussed ordering tendencies are characterised by an
incommensurate pattern.",2206.06231v3
2022-06-29,SgrA$^{*}$ spin and mass estimates through the detection of an extremely large mass-ratio inspiral,"Estimating the spin of ${\rm SgrA^\ast}$ is one of the current challenges we
face in understanding the center of our Galaxy. In the present work, we show
that detecting the gravitational waves (GWs) emitted by a brown dwarf
inspiraling around ${\rm SgrA^\ast}$ will allow us to measure the mass and the
spin of ${\rm SgrA^\ast}$ with unprecedented accuracy. Such systems are known
as extremely large mass-ratio inspirals (XMRIs) and are expected to be abundant
and loud sources in our galactic center. We consider XMRIs with a fixed orbital
inclination and different spins of ${\rm SgrA^\ast}$ ($s$) between 0.1 and 0.9.
For both cases, we obtain the number of circular and eccentric XMRIs expected
to be detected by space-borne GW detectors like LISA and TianQin. We find that
if the orbit is eccentric, then we expect to always have several XMRIs in band
while for almost circular XMRIs, we only expect to have one source in band if
${\rm SgrA^\ast}$ is highly spinning. We later perform a Fisher matrix analysis
to show that by detecting a single XMRI the mass of ${\rm SgrA^\ast}$ can be
determined with an accuracy of the order $10^{-2}\,\text{M}_{\odot}$, while the
spin can be measured with an accuracy between $10^{-7}$ and $10^{-4}$ depending
on the orbital parameters of the XMRI.",2206.14399v2
2022-06-30,Tailoring phase transition from topological superconductor to trivial superconductor induced by magnetic textures of a spin-chain on a $p$-wave superconductor,"We theoretically investigate the phase transition from a non-trivial
topological $p$-wave superconductor to a trivial $s$-wave like superconducting
phase through a gapless phase, driven by different magnetic textures as an
one-dimensional spin-chain impurity, e.g. Bloch-type, in-plane and out-of-plane
N\'eel-type spin-chains etc. In our proposal, the chain of magnetic impurities
is placed on a spin-triplet $p$-wave superconductor where we obtain numerically
as well as analytically an effective $s$-wave like pairing due to spin
rotation, resulting in gradual destruction of the Majorana zero modes present
in the topological superconducting phase. In particular, when the impurity
spins are antiferromagnetically aligned i.e. spiral wave vector $G_{s}=\pi$,
the system becomes an effective $s$-wave superconductor without Majorana zero
modes in the local density of states. The Shiba bands, on the other hand,
formed due to the overlapping of Yu-Shiba-Rusinov states play a crucial role in
this topological to trivial superconductor phase transition, confirmed by the
sign change in the minigap within the Shiba bands. We also characterize this
topological phase transition via gap closing and winding number analysis.
Moreover, interference of the Shiba bands exhibiting oscillatory behavior
within the superconducting gap, $-\Delta_{p}$ to $\Delta_{p}$, as a function of
$G_{s}$, also reflects an important evidence for the formation of an effective
$s$-wave pairing. Such oscillation is absent in the $p$-wave regime.",2206.15196v2
2022-07-28,Do high-spin high-mass X-ray binaries contribute to the population of merging binary black holes?,"Gravitational-wave observations of binary black hole (BBH) systems point to
black hole spin magnitudes being relatively low. These measurements appear in
tension with high spin measurements for high-mass X-ray binaries (HMXBs). We
use grids of MESA simulations combined with the rapid population-synthesis code
COSMIC to examine the origin of these two binary populations. It has been
suggested that Case-A mass transfer while both stars are on the main sequence
can form high-spin BHs in HMXBs. Assuming this formation channel, we show that
depending on critical mass ratios for the stability of mass transfer, 48-100%
of these Case-A HMXBs merge during the common-envelope phase and up to 42%
result in binaries too wide to merge within a Hubble time. Both MESA and COSMIC
show that high-spin HMXBs formed through Case-A mass transfer can only form
merging BBHs within a small parameter space where mass transfer can lead to
enough orbital shrinkage to merge within a Hubble time. We find that only up to
11% of these Case-A HMXBs result in BBH mergers, and at most 20% of BBH mergers
came from Case-A HMXBs. Therefore, it is not surprising that these two spin
distributions are observed to be different.",2207.14290v2
2022-09-16,On a heuristic point of view concerning the optical activity,"Motivated by a recent finding that Fresnel's phenomenological description of
the optical activity in the chiral medium is not self-consistent, we conduct a
thorough investigation into the nature of the polarization of a plane light
wave. We demonstrate that the polarization of light is the reflection of one of
its quantum-mechanical properties, called the quasi-spin. Unexpectedly, the
quasi-spin is not an observable with respect to the laboratory coordinate
system. Instead, it is with respect to the momentum-dependent local coordinate
system. The representative operators for the quasi-spin are the Pauli matrices.
The wavefunction is the Jones vector. In order to completely determine a state
of polarization, two different kinds of degrees of freedom are needed. One is
the degrees of freedom to characterize the state of quasi-spin. They are the
Stokes parameters, the expectation values of the Pauli matrices in the state
described by the Jones vector. The other is the degrees of freedom to specify
the local coordinate system, including the propagation direction and an angle
of rotation about it. Accordingly, there are two independent mechanisms to
change the state of polarization. One is to change the state of quasi-spin in a
fixed local coordinate system. This is the traditional mechanism that can be
expressed as an SU(2) rotation of the Jones vector. The other is to change the
local coordinate system with the state of quasi-spin remaining fixed in it. At
last, we show that it is the newly-identified mechanism that accounts for the
optical activity.",2209.07982v1
2022-11-01,Trimer quantum spin liquid in a honeycomb array of Rydberg atoms,"Quantum spin liquids are elusive but paradigmatic examples of strongly
correlated quantum states that are characterized by long-range quantum
entanglement. Recently, the direct signatures of a gapped topological
$\mathbb{Z}_2$ spin liquid have been observed in a system of Rydberg atoms
arrayed on the ruby lattice. Here, we illustrate the concrete realization of a
fundamentally different class of spin liquids in a honeycomb array of Rydberg
atoms. Exploring the quantum phase diagram of this system using both
density-matrix renormalization group and exact diagonalization simulations,
several density-wave-ordered phases are characterized and their origins
explained. More interestingly, in the regime where third-nearest-neighbor atoms
lie within the Rydberg blockade radius, we find a novel ground state -- with an
emergent $\mathrm{U}(1)\times \mathrm{U}(1)$ local symmetry -- formed from
superpositions of classical {\it trimer} configurations on the dual triangular
lattice. The fidelity of this trimer spin liquid state can be enhanced via
dynamical preparation, which we explain by a Rydberg-blockade-based projection
mechanism associated with the smooth turnoff of the laser drive. Finally, we
discuss the robustness of the trimer spin liquid phase under realistic
experimental parameters and demonstrate that our proposal can be readily
implemented in current Rydberg atom quantum simulators.",2211.00653v1
2022-11-20,Nodes and Spin Windings for Topological Transitions in Light-Matter Interactions: \\ Anisotropic Quantum Rabi Model as a Born Abstract Artist,"By extracting different levels of topological information a new light is shed
on the energy spectrum of the anisotropic quantum Rabi model (QRM) which is the
fundamental model of light-matter interactions with indispensable
counter-rotating terms in ultra-strong couplings. Besides conventional
topological transitions (TTs) at gap closing, abundant unconventional TTs
including a particular one universal for different energy levels are unveiled
underlying level anticrossings without gap closing by tracking the
wave-function nodes. On the other hand, it is found that the nodes have a
correspondence to spin windings, which not only endows the nodes a more
explicit topological character in supporting single-qubit TTs but also turns
the topological information physically detectable. Furthermore, hidden
small-spin-knot transitions are exposed for the ground state, while more kinds
of spin-knot transitions emerge in excited states including unmatched node
numbers and spin winding numbers. As a surprise, frequently the spin windings
produce portraits in high spiritual similarity with abstract artistic works,
which demonstrates that the anisotropic QRM may be the Picasso of physical
models. This signifies that art is joining the dialogue between mathematics and
physics which was triggered by the milestone work of revealing integrability of
the QRM.",2211.11072v1
2022-11-30,Unconventional spin dynamics in the non-collinear phase of a ferrimagnet,"Ferrimagnets containing several partially compensated magnetic sublattices
are considered the most promising materials for all-optical data storage and
for ultrafast communications based on spin waves. There are two magnetic phases
of the ferrimagnets: collinear and non-collinear ones. Up to now spin dynamics
in ferrimagnets has been studied mostly in the collinear state without paying
much attention to the kind of the magnetic phase. Here we investigate laser
induced ultrafast spin dynamics in a rare-earth iron garnet film in the
noncollinear phase as well. We identify a crucial influence of the magnetic
phase on the excited spin modes which allowed us to discover several prominent
effects previously overlooked. In particular, the non-collinearity makes the
quasi-antiferromagnetic mode sensitive to the external magnetic field and
brings its frequency close to the frequency of the quasiferromagnetic mode. The
latter maximizes near the magnetization compensation point and vanishes towards
the collinear phase. Spectacularly, at the phase transition the
quasiferromagnetic mode becomes soft and its amplitude significantly increases
reaching 7{\deg}. This opens new opportunities for the ultrafast control of
spins in ferrimagnets for nonthermal data storage and data processing.",2212.00085v2
2022-12-06,Giant gate-tunable renormalization of spin-correlated flat-band states and bandgap in a 2D magnetic insulator,"Emergent quantum phenomena in two-dimensional van der Waal (vdW) magnets are
largely governed by the interplay between the exchange and Coulomb
interactions. The ability to tune the Coulomb interaction in such strongly
correlated materials enables the precise control of spin-correlated flat-band
states, bandgap (Eg) and unconventional magnetism, all of which are crucial for
next-generation spintronics and magnonics applications. Here, we demonstrate a
giant gate-tunable renormalization of spin-correlated flat-band states and
bandgap in magnetic chromium tribromide (CrBr3) monolayers grown on graphene.
Our gate-dependent scanning tunneling spectroscopy (STS) studies reveal that
the inter-flat-band spacing and bandgap of CrBr3 can be continuously tuned by
120 meV and 240 meV respectively via electrostatic injection of carriers into
the hybrid CrBr3/graphene system, equivalent to the modulation of the Cr
on-site Coulomb repulsion energy by 500 meV. This can be attributed to the
self-screening of CrBr3 arising from the gate-induced carriers injected into
CrBr3, which dominates over the opposite trend from the remote screening of the
graphene substrate. Precise tuning of the spin-correlated flat-band states and
bandgap in 2D magnets via electrostatic modulation of Coulomb interactions not
only provides new strategies for optimizing the spin transport channels but
also may exert a crucial influence on the exchange energy and spin-wave gap,
which could raise the critical temperature for magnetic order.",2212.02772v1
2022-12-26,Modeling horizon absorption in spinning binary black holes using effective worldline theory,"The mass and spin of black holes (BHs) in binary systems may change due to
the infall of gravitational-wave (GW) energy down the horizons. For spinning
BHs, this effect enters at 2.5 post-Newtonian (PN) order relative to the
leading-order energy flux at infinity. There is currently a discrepancy in the
literature in the expressions of these horizon fluxes in the test-body limit at
4PN order (relative 1.5PN order). Here, we model the horizon absorption as
tidal heating in an effective worldline theory of a spinning particle equipped
with tidally-induced quadrupole and octupole moments. We match the tidal
response to analytic solutions of the Teukolsky equation in a scattering
scenario, and obtain general formulae for the evolution of mass and spin. We
then specialize to the case of aligned-spin--quasi-circular binaries, obtaining
the corresponding contributions to the GW phasing through 4PN order.
Importantly, we find that the number of GW cycles due to horizon fluxes with
masses observed by LIGO-Virgo-KAGRA detectors is about 2-3 orders of magnitude
smaller than the other contributions to the phasing at the same PN order.
Furthermore, in the test-body limit, we find full agreement with results
obtained earlier from BH perturbation theory, with a small mass in an
equatorial circular orbit treated as a source perturbing the Kerr metric. Thus,
we weigh in on one side of the previous discrepancy.",2212.13095v2
2023-01-10,Magnetic anisotropy and low-energy spin dynamics in the van der Waals compounds Mn$_{2}$P$_{2}$S$_{6}$ and MnNiP$_{2}$S$_{6}$,"We report the detailed high-field and high-frequency electron spin resonance
(HF-ESR) spectroscopic study of the single-crystalline van der Waals compounds
Mn$_{2}$P$_{2}$S$_{6}$ and MnNiP$_{2}$S$_{6}$. Analysis of magnetic excitations
shows that in comparison to Mn$_{2}$P$_{2}$S$_{6}$ increasing the Ni content
yields a larger magnon gap in the ordered state and a larger g-factor value and
its anisotropy in the paramagnetic state. The studied compounds are found to be
strongly anisotropic having each the unique ground state and type of magnetic
order. Stronger deviation of the g-factor from the free electron value in the
samples containing Ni suggests that the anisotropy of the exchange is an
important contributor to the stabilization of a certain type of magnetic order
with particular anisotropy. At temperatures above the magnetic order, we have
analyzed the spin-spin correlations resulting in a development of slowly
fluctuating short-range order. They are much stronger pronounced in
MnNiP$_{2}$S$_{6}$ compared to Mn$_{2}$P$_{2}$S$_{6}$. The enhanced spin
fluctuations in MnNiP$_{2}$S$_{6}$ are attributed to the competition of
different types of magnetic order. Finally, the analysis of the temperature
dependent critical behavior of the magnon gaps below the ordering temperature
in Mn$_{2}$P$_{2}$S$_{6}$ suggests that the character of the spin wave
excitations in this compound undergoes a field induced crossover from a 3D-like
towards 2D XY regime.",2301.04239v2
2023-03-29,Continuous spin excitations in the three-dimensional frustrated magnet K2Ni2(SO4)3,"Continuous spin excitations are widely recognized as one of the hallmarks of
novel spin states in quantum magnets, such as quantum spin liquids (QSLs).
Here, we report the observation of such kind of excitations in K2Ni2(SO4)3,
which consists of two sets of intersected spin-1 Ni2+ trillium lattices. Our
inelastic neutron scattering measurement on single crystals clearly shows a
dominant excitation continuum, which exhibits a distinct temperature-dependent
behavior from that of spin waves, and is rooted in strong quantum spin
fluctuations. Further using the self-consistent-gaussian-approximation method,
we determined the fourth- and fifth-nearest neighbor exchange interactions are
dominant. These two bonds together form a unique three-dimensional network of
corner-sharing tetrahedra, which we name as ''hyper-trillium'' lattice. Our
results provide direct evidence for the existence of QSL features in
K2Ni2(SO4)3 and highlight the potential for the hyper-trillium lattice to host
frustrated quantum magnetism.",2303.16384v1
2023-03-30,Spin and Orbital Angular Momentum of Coherent Photons in a Waveguide,"Spin angular momentum of a photon corresponds to a polarisation degree of
freedom of lights, and such that various polarisation properties are coming
from macroscopic manifestation of quantum-mechanical properties of lights. An
orbital degree of freedom of lights is also manipulated to form a vortex of
lights with orbital angular momentum, which is also quantised. However, it is
considered that spin and orbital angular momentum of a photon cannot be split
from the total orbital angular momentum in a gauge-invariant way. Here, we
revisit this issue for a coherent monochromatic ray from a laser source,
propagating in a waveguide. We obtained the helical components of spin and
orbital angular momentum by the correspondence with the classical Ponyting
vector. By applying a standard quantum field theory using a coherent state, we
obtained the gauge-independent expressions of spin and orbital angular momentum
operators. During the derivations, it was essential to take a finite
cross-sectional area into account, which leads the finite longitudinal
component along the direction of the propagation, which allows the splitting.
Therefore, the finite mode profile was responsible to justify the splitting,
which was not possible as far as we are using plane-wave expansions in a
standard theory of quantum-electrodynamics (QED). Our results suggest spin and
orbital angular momentum are well-defined quantum-mechanical freedoms at least
for coherent photons propagating in a waveguide and in a vacuum with a finite
mode profile.",2303.17129v1
2023-03-31,Theoretical groundwork supporting the precessing-spin two-body dynamics of the effective-one-body waveform models SEOBNRv5,"Waveform models are essential for gravitational-wave (GW) detection and
parameter estimation of coalescing compact-object binaries. More accurate
models are required for the increasing sensitivity of current and future GW
detectors. The effective-one-body (EOB) formalism combines the post-Newtonian
(PN) and small mass-ratio approximations with numerical-relativity results, and
produces highly accurate inspiral-merger-ringdown waveforms. In this paper, we
derive the analytical precessing-spin two-body dynamics for the SEOBNRv5
waveform model, which has been developed for the upcoming LIGO-Virgo-KAGRA
observing run. We obtain an EOB Hamiltonian that reduces to the exact Kerr
Hamiltonian in the test-mass limit. It includes the full 4PN precessing-spin
information, and is valid for generic compact objects (i.e., for black holes or
neutron stars). We also build an efficient and accurate EOB Hamiltonian that
includes partial precessional effects, notably orbit-averaged in-plane spin
effects for circular orbits, and derive 4PN-expanded precessing-spin equations
of motion, consistent with such an EOB Hamiltonian. The results were used to
build the computationally-efficient precessing-spin multipolar SEOBNRv5PHM
waveform model.",2303.18143v2
2023-04-05,Representation Theory and Topology of Coherent Photons with Angular Momentum,"Photons are elementary particles of lights, which have both spin and orbital
angular momentum as internal degrees of freedom. Nature of spin is known as
polarisation, which is widely used for sunglasses, liquid-crystal displays,
digital-coherent communications, while orbital angular momentum is useful for
optical tweezers, laser-patterning, and quantum optics. However, spin and
orbital angular momentum of photons are considered to be impossible for
splitting into two independent degrees of freedom in a proper gauge invariant
way, proved by plane wave expansions in a free space. Here, we show these
degrees of freedom are well-defined quantum observables in a waveguide and a
free space as far as the propagation mode is sufficiently confined in the core.
We found Stokes parameters are spin expectation values of coherent photons,
which exhibit non-trivial topological features like a torus, a M\""obius strip,
and a bosonic Dirac cone. We have applied an SU(N) representation theory to
describe both spin and orbital angular momentum of photons, and experimentally
demonstrated their controls over a full Poincar\'e sphere to show a fullerene
C$_{60}$ and the earth by qubits. We have also ascribed topological colour
charge to photonic orbital angular momentum, whose SU(3) states are shown on a
proposed Gell-Mann hypersphere in SO(8), whose parameters could be embedded in
SO(5). We have also realised photonic SU(4) states of singlet and triplet
states, which were successfully projected into SU(2)$\times$SU(2) states by a
rotated polariser. Our results indicate that our platform of manipulating spin
and orbital angular momentum is useful for exploring a photonic quantum
chromodynamics and a higher order macroscopic quantum state.",2304.02178v1
2023-05-16,Magnon Hall effect in antiferromagnetic lattices,"Topology applied to condensed matter is an important area of research and
technology, and topological magnetic excitations have recently become an active
field of study. This paper presents a general discussion of magnon Hall
transport in two-dimensional antiferromagnets. Although the Chern number is
zero for a collinear antiferromagnet, we offer a general discussion that can be
used in the more general case. First, we study the Union Jack lattice, where an
effective time-reversal symmetry is broken, making the system display the
magnon Hall effect. Then, we investigate the brick-wall lattice where such
symmetry is present. Consequently, we have a phenomenon similar to the quantum
spin Hall effect in electronic systems. Both lattices have not yet been studied
from the topological point of view. The coexistence of opposite spin
polarization in an antiferromagnet resembles the electron spin in various
transport phenomena. We study magnon transport in the lattices mentioned above
with Dzyaloshinskii-Moriya interaction and easy-axis single-ion anisotropy. We
calculate the Berry curvature from the eigenvalues of the Hamiltonian. From
that, we plot the spin Hall and thermal Hall conductivities, as well as the
spin Nernst coefficient, as functions of the temperature. In the Union Jack
lattice, we treat the effect of anharmonic interactions using a mean-field spin
wave theory where the Hamiltonian becomes implicitly temperature-dependent. We
determine self-consistently the renormalized dispersion and the staggered
magnetization as a function of temperature. Our calculations can be applied to
other antiferromagnetic lattices.",2305.09077v2
2023-05-25,Dzyaloshinskii-Moriya interaction in strongly spin-orbit-coupled systems: General formula and application to topological and Rashba materials,"We theoretically study the Dzyaloshinskii-Moriya interaction (DMI) mediated
by band electrons with strong spin-orbit coupling (SOC). We first derive a
general formula for the coefficient ${\bm D}_i$ of the DMI in free energy in
terms of Green's functions, and examine its variations in relation to physical
quantities. In general, the DMI coefficient can vary depending on physical
quantities, i.e., whether one is looking at equilibrium spin structure (${\bm
D}_i$) or spin-wave dispersion (${\bm D}_i^{(2)}$), and the obtained formula
helps to elucidate their relations. By explicit evaluations for a magnetic
topological insulator and a Rashba ferromagnet with perpendicular
magnetization, we observe ${\bm D}_i^{(2)} \ne {\bm D}_i$ in general. In the
latter model, or more generally, when the magnetization and the spin-orbit
field are mutually orthogonal, ${\bm D}_i$ is exactly related to the
equilibrium spin current for arbitrary strength of SOC, generalizing the
similar relation for systems with weak SOC. Among various systems with strong
SOC, magnetic Weyl semimetals are special in that ${\bm D}_i^{(2)} = {\bm
D}_i$, and in fact, the DMI in this system arises as the chiral anomaly.",2305.16083v2
2023-05-31,Realization of U(1) Dirac Quantum Spin Liquid in YbZn2GaO5,"The emergence of a quantum spin liquid (QSL), a state of matter that can
result when electron spins are highly correlated but do not become ordered, has
been the subject of a considerable body of research in condensed matter
physics. Spin liquid states have been proposed as hosts for high-temperature
superconductivity and can host topological properties with potential
applications in quantum information science. The excitations of most quantum
spin liquids are not conventional spin waves but rather quasiparticles known as
spinons, whose existence is well established experimentally only in
one-dimensional systems; the unambiguous experimental realization of QSL
behavior in higher dimensions remains challenging. Here we investigate the
novel compound YbZn2GaO5, which hosts an ideal triangular lattice of effective
spin-1/2 moments with no inherent chemical disorder. Thermodynamic and
inelastic neutron scattering (INS) measurements performed on high-quality
single crystal samples of YbZn2GaO5 exclude the possibility of long-range
magnetic ordering down to 60 mK, demonstrate a quadratic power law for the heat
capacity and reveal a continuum of magnetic excitations in parts of the
Brillouin zone. Both low-temperature thermodynamics and INS spectra suggest
that YbZn2GaO5 is a U(1) Dirac QSL with gapless spinon excitations concentrated
at certain points in the Brillouin zone, and additional features in INS are
also consistent with theoretical expectations for a Dirac QSL on the triangular
lattice.",2305.20040v1
2023-09-06,Quantifying the limits of controllability for the nitrogen-vacancy electron spin defect,"Solid-state electron spin qubits, like the nitrogen-vacancy center in
diamond, rely on control sequences of population inversion to enhance
sensitivity and improve device coherence. But even for this paradigmatic
system, the fundamental limits of population inversion and potential impacts on
applications like quantum sensing have not been assessed quantitatively. Here,
we perform high accuracy simulations beyond the rotating wave approximation,
including explicit unitary simulation of neighboring nuclear spins. Using
quantum optimal control, we identify analytical pulses for the control of a
qubit subspace within the spin-1 ground state and quantify the relationship
between pulse complexity, control duration, and fidelity. We find exponentially
increasing amplitude and bandwidth requirements with reduced control duration
and further quantify the emergence of non-Markovian effects for multipulse
sequences using sub-nanosecond population inversion. From this, we determine
that the reduced fidelity and non-Markovianity is due to coherent interactions
of the electron spin with the nuclear spin environment. Ultimately, we identify
a potentially realizable regime of nanosecond control duration for
high-fidelity multipulse sequences. These results provide key insights into the
fundamental limits of quantum information processing using electron spin
defects in diamond.",2309.03120v1
2023-09-06,Universal spin wavepacket transport in van der Waals antiferromagnets,"Antiferromagnets (AFMs) are promising platforms for the transmission of
quantum information via magnons (the quanta of spin waves), offering advantages
over ferromagnets with regard to dissipation, speed of response, and immunity
to external fields. Recently, it was shown that in the insulating van der Waals
(vdW) semiconductor, CrSBr, strong spin-exciton coupling enables readout of
magnon density and propagation using photons of visible light. This exciting
observation came with a puzzle: photogenerated magnons were observed to
propagate 10$^3$ times faster than the velocity inferred from neutron
scattering, leading to a conjecture that spin wavepackets are carried along by
coupling to much faster elastic modes. Here we show, through a combination of
theory and experiment, that the propagation mechanism is, instead, coupling
within the magnetic degrees of freedom through long range dipole-dipole
coupling. This mechanism is an inevitable consequence of Maxwell's equations,
and as such, will dominate the propagation of spin at long wavelengths in the
entire class of vdW magnets currently under intense investigation. Moreover,
identifying the mechanism of spin propagation provides a set of optimization
rules, as well as caveats, that are essential for any future applications of
these promising systems.",2309.03278v1
2023-10-23,Approximate symmetries of long-range Rydberg molecules including spin effects,"An operator that generates an approximate symmetry of long-range Rydberg
molecules (LRRMs) formed by two alkali atoms, one in a Rydberg state and the
other in the ground state, is identified. This is first done by evaluating the
natural orbitals associated to a variational calculation of the binding wave
function within the Born-Oppenheimer description of the molecule including $s-$
and $p-$ Fermi pseudopotential and the hyperfine structure energy terms. The
resulting orbitals with highest occupation number are shown to be identical to
those obtained by a perturbative model for high angular momentum -- trilobite
and butterfly -- LRRMs. Whenever the slight dependence of the quantum defects
of the Rydberg electron on its total momentum $\vec j = \vec \ell +\vec s_1$
can be neglected, the symmetry operator of the high angular momentum LRRMs
orbitals is identified as the sum of the spin of the Rydberg electron $\vec
s_1$, spin of the valence electron $\vec s_2$ and the spin of nucleus $\vec i$
of the ground state atom, $\vec {N} =\vec {s_1} + \vec {s_2} + \vec {i}$. The
spin-orbitals that diagonize $\vec{N}$ define compact basis sets for the
description of LRRMs beyond the aforementioned approximations. The matrix
elements of the Hamitonian in these basis sets have simple expressions, so that
the relevance of triplet and singlet contributions can be directly estimated.
The expected consequences of this approximate spin-symmetry on the spectra of
LRRMs are briefly described.",2310.15095v2
2023-11-22,Quantum spin dynamics due to strong Kitaev interactions in the triangular-lattice antiferromagnet CsCeSe$_2$,"The extraordinary properties of the Kitaev model have motivated an intense
search for new physics in materials that combine geometrical and bond
frustration. In this work, we employ inelastic neutron scattering, spin wave
theory, and exact diagonalization to study the spin dynamics in the perfect
triangular-lattice antiferromagnet (TLAF) CsCeSe$_2$. This material orders into
a stripe phase, which is demonstrated to arise as a consequence of the
off-diagonal bond-dependent terms in the spin Hamiltonian. By studying the spin
dynamics at intermediate fields, we identify an interaction between the
single-magnon state and the two-magnon continuum that causes decay of coherent
magnon excitations, level repulsion, and transfer of spectral weight to the
continuum that are controlled by the strength of the magnetic field. Our
results provide a microscopic mechanism for the stabilization of the stripe
phase in TLAF and show how complex many-body physics can be present in the spin
dynamics in a magnet with strong Kitaev coupling even in an ordered ground
state.",2311.13146v2
2023-12-11,Static magnetic order with strong quantum fluctuations in spin-1/2 honeycomb magnet Na2Co2TeO6,"Kitaev interactions, arising from the interplay of frustration and bond
anisotropy, can lead to strong quantum fluctuations and, in an ideal case, to a
quantum-spin-liquid state. However, in many nonideal materials, spurious
non-Kitaev interactions typically promote a zigzag antiferromagnetic order in
the d-orbital transition metal compounds. By combining neutron scattering with
muon-spin rotation and relaxation techniques, we provide new insights into the
exotic properties of Na2Co2TeO6, a candidate Kitaev material. Below TN, the
zero-field muon-spin relaxation rate becomes almost constant (at 0.45 us-1). We
attribute this temperature-independent muon-spin relaxation rate to the strong
quantum fluctuations, as well as to the frustrated Kitaev interactions. As the
magnetic field increases, neutron scattering data indicate a much broader
spin-wave-excitation gap at the K-point. Therefore, quantum fluctuations seem
not only robust, but are even enhanced by the applied magnetic field. Our
findings provide valuable hints for understanding the onset of the
quantum-spin-liquid state in Kitaev materials.",2312.06284v2
2023-12-16,The effect of stellar rotation on black hole mass and spin,"The gravitational wave signature of a binary black hole (BBH) merger is
dependent on its component mass and spin. If such black holes originate from
rapidly rotating progenitors, the large angular momentum reserve in the star
could drive a collapsar-like supernova explosion, hence substantially impacting
these characteristics of the black holes in the binary. To examine the effect
of stellar rotation on the resulting black hole mass and spin, we conduct a 1D
general relativistic study of the end phase of the collapse. We find that the
resulting black hole mass at times differ significantly from the previously
assumed values. We quantify the dependence of the black hole spin magnitude on
the hydrodynamics of the accretion flow, providing analytical relations for
calculating the mass and spin based on the progenitor's pre-collapse
properties. Depending on the nature of the accretion flow, our findings have
implications for the black hole upper mass gap resulting from pair-instability
supernovae, the maximum mass of a maximally rotating stellar black hole
($M_{\rm BH, max} \approx 35M_\odot$), and the maximum effective spin of a BBH
formed in tidally locked helium star - black hole binary ($\chi_{\rm eff, max}
\approx 0.325$).",2312.10400v2
2011-03-22,On the role of the magnetic dipolar interaction in cold and ultracold collisions: Numerical and analytical results for NH($^3Σ^-$) + NH($^3Σ^-$),"We present a detailed analysis of the role of the magnetic dipole-dipole
interaction in cold and ultracold collisions. We focus on collisions between
magnetically trapped NH molecules, but the theory is general for any two
paramagnetic species for which the electronic spin and its space-fixed
projection are (approximately) good quantum numbers. It is shown that dipolar
spin relaxation is directly associated with magnetic-dipole induced avoided
crossings that occur between different adiabatic potential curves. For a given
collision energy and magnetic field strength, the cross-section contributions
from different scattering channels depend strongly on whether or not the
corresponding avoided crossings are energetically accessible. We find that the
crossings become lower in energy as the magnetic field decreases, so that
higher partial-wave scattering becomes increasingly important \textit{below} a
certain magnetic field strength. In addition, we derive analytical
cross-section expressions for dipolar spin relaxation based on the Born
approximation and distorted-wave Born approximation. The validity regions of
these analytical expressions are determined by comparison with the NH + NH
cross sections obtained from full coupled-channel calculations. We find that
the Born approximation is accurate over a wide range of energies and field
strengths, but breaks down at high energies and high magnetic fields. The
analytical distorted-wave Born approximation gives more accurate results in the
case of s-wave scattering, but shows some significant discrepancies for the
higher partial-wave channels. We thus conclude that the Born approximation
gives generally more meaningful results than the distorted-wave Born
approximation at the collision energies and fields considered in this work.",1103.4274v1
2011-11-28,Pair-Density-Wave Superconducting Order in Two-Leg Ladders,"We show using bosonization methods that extended Hubbard-Heisenberg models on
two types of two leg ladders (without flux and with flux $\pi$ per plaquette)
have commensurate pair-density wave (PDW) phases. In the case of the
conventional (flux-less) ladder the PDW arises when certain filling fractions
for which commensurability conditions are met.
  For the flux $\pi$ ladder the PDW phase is generally present. The PDW phase
is characterized by a finite spin gap and a superconducting order parameter
with a finite (commensurate in this case) wave vector and power-law
superconducting correlations. In this phase the uniform superconducting order
parameter, the $2k_F$ charge-density-wave (CDW) order parameter and the
spin-density- wave N\'eel order parameter exhibit short range (exponentially
decaying) correlations. We discuss in detail the case in which the bonding band
of the ladder is half filled for which the PDW phase appears even at weak
coupling. The PDW phase is shown to be dual to a uniform superconducting (SC)
phase with quasi long range order. By making use of bosonization and the
renormalization group we determine the phase diagram of the spin-gapped regime
and study the quantum phase transition. The phase boundary between PDW and the
uniform SC ordered phases is found to be in the Ising universality class. We
generalize the analysis to the case of other commensurate fillings of the
bonding band, where we find higher order commensurate PDW states for which we
determine the form of the effective bosonized field theory and discuss the
phase diagram. We compare our results with recent findings in the
Kondo-Heisenberg chain. We show that the formation of PDW order in the ladder
embodies the notion of intertwined orders.",1111.6320v2
2017-09-07,Radiation driven instability of rapidly rotating relativistic stars: criterion and evolution equations via multipolar expansion of gravitational waves,"I suggest a novel approach for deriving evolution equations for rapidly
rotating relativistic stars affected by radiation-driven
Chandrasekhar-Friedman-Schutz (CFS) instability. This approach is based on the
multipolar expansion of gravitational wave emission and appeals to the global
physical properties of the star (energy, angular momentum, and thermal state),
but not to canonical energy and angular momentum, which is traditional. It
leads to simple derivation of the CFS instability criterion for normal modes
and the evolution equations for a star, affected by this instability. The
approach also gives a precise form to simple explanation of the CFS
instability: it occurs when two conditions met: (a) gravitational wave emission
removes angular momentum from the rotating star (thus releasing the rotation
energy) and (b) gravitational waves carry less energy, than the released amount
of the rotation energy. Results are illustrated by r-mode instability in slowly
rotating Newtonian stars. In resulting evolution equations emission of
gravitational waves directly affects the spin frequency, being in line with the
arguments by Levin & Ushomirsky (2001), but in contrast to widely accepted
equations by Lindblom et al. (1998); Ho & Lai (2000), there effective spin
frequency decrease is coupled with dissipation of unstable mode. This problem,
initially stressed by Levin & Ushomirsky (2001), is shown to be superficial,
and arises as a result of definition of the effective spin frequency by
Lindblom et al. (1998); Ho & Lai (2000). Namely, it is shown, that if this
definition is taken into account properly, the evolution equations coincide
with obtained here in the leading order in mode amplitude. I also argue that
the next-to-leading order terms in evolution equations (which differ for Owen
et al. 1998 and Ho & Lai 2000) require clarification and thus it would be more
self-consistent to omit them.",1709.02446v1
2019-03-09,Tracking continuous gravitational waves from a neutron star at once and twice the spin frequency with a hidden Markov model,"Searches for continuous gravitational waves from rapidly spinning neutron
stars normally assume that the star rotates about one of its principal axes of
moment of inertia, and hence the gravitational radiation emits only at twice
the spin frequency of the star, $2f_*$. The superfluid interior of a star
pinned to the crust along an axis nonaligned with any of its principal axes
allows the star to emit gravitational waves at both $f_*$ and $2f_*$, even
without free precession, a phenomenon not clearly observed in known pulsars.
The dual-harmonic emission mechanism motivates searches combining the two
frequency components of a signal to improve signal-to-noise ratio. We describe
an economical, semicoherent, dual-harmonic search method, combined with a
maximum likelihood coherent matched filter, F-statistic, and improved from an
existing hidden Markov model (HMM) tracking scheme to track two frequency
components simultaneously. We validate the method and demonstrate its
performance through Monte Carlo simulations. We find that for sources emitting
gravitational waves at both $f_*$ and $2f_*$, the rate of correctly recovering
synthetic signals (i.e., detection efficiency), at a given false alarm
probability, can be improved by $\sim 10$%-70% by tracking two frequencies
simultaneously compared to tracking a single component only. For sources
emitting at $2f_*$ only, dual-harmonic tracking only leads to minor sensitivity
loss, producing $\lesssim 10\%$ lower detection efficiency than tracking a
single component. In directed continuous-wave searches where $f_*$ is unknown
and hence the full frequency band is searched, the computationally efficient
HMM tracking algorithm provides an option of conducting both the dual-harmonic
search and the conventional single frequency tracking to obtain optimal
sensitivity, with a typical run time of $\sim 10^3$ core-hr for one year's
observation.",1903.03866v2
2022-07-04,Population properties and multimessenger prospects of neutron star-black hole mergers following GWTC-3,"Neutron star-black hole (NSBH) mergers detected in gravitational waves have
the potential to shed light on supernova physics, the dense matter equation of
state, and the astrophysical processes that power their potential
electromagnetic counterparts. We use the population of four candidate NSBH
events detected in gravitational waves so far with a false alarm rate $\leq
1~\mathrm{yr}^{-1}$ to constrain the mass and spin distributions and
multimessenger prospects of these systems. We find that the black holes in
NSBHs are both less massive and have smaller dimensionless spins than those in
black hole binaries. We also find evidence for a mass gap between the most
massive neutron stars and least massive black holes in NSBHs at 98.6%
credibility. Using an approach driven by gravitational-wave data rather than
binary simulations, we find that fewer than 14% of NSBH mergers detectable in
gravitational waves will have an electromagnetic counterpart. While the
inferred presence of a mass gap and fraction of sources with a counterpart
depend on the event selection and prior knowledge of source classification, the
conclusion that the black holes in NSBHs have lower masses and smaller spin
parameters than those in black hole binaries is robust. Finally, we propose a
method for the multimessenger analysis of NSBH mergers based on the
nondetection of an electromagnetic counterpart and conclude that, even in the
most optimistic case, the constraints on the neutron star equation of state
that can be obtained with multimessenger NSBH detections are not competitive
with those from gravitational-wave measurements of tides in binary neutron star
mergers and radio and X-ray pulsar observations.",2207.01568v4
2022-07-21,Inferring eccentricity evolution from observations of coalescing binary black holes,"The origin and formation of stellar-mass binary black holes remains an open
question that can be addressed by precise measurements of the binary and
orbital parameters from their gravitational-wave signal. Such binaries are
expected to circularize due to the emission of gravitational waves as they
approach merger. However, depending on their formation channel, some binaries
could have a non-negligible eccentricity when entering the frequency band of
current gravitational-wave detectors. In order to measure eccentricity in an
observed gravitational-wave signal, accurate waveform models that describe
binaries in eccentric orbits are necessary. In this work we demonstrate the
efficacy of the improved TEOBResumS waveform model for eccentric coalescing
binaries with aligned spins. We first validate the model against mock signals
of aligned-spin binary black hole mergers and quantify the impact of
eccentricity on the estimation of other intrinsic binary parameters. We then
perform a fully Bayesian reanalysis of GW150914 with the eccentric waveform
model. We find (i) that the model is reliable for aligned-spin binary black
holes and (ii) that GW150914 is consistent with a non-eccentric merger although
we cannot rule out small values of initial eccentricity at a reference
frequency of $20$ Hz. Finally, we present a systematic method to measure the
eccentricity and its evolution directly from the gravitational-wave posterior
samples. Such an estimator is useful when comparing results from different
analyses as the definition of eccentricity may differ between models. Our
scheme can be applied even in the case of small eccentricities and can be
adopted straightforwardly in post-processing to allow for direct comparison
between models.",2207.10474v2
2004-08-17,Neutron spin polarization in strong magnetic fields,"The effects of strong magnetic fields on the inner crust of neutron stars are
investigated after taking into account the anomalous magnetic moments of
nucleons. Energy spectra and wave functions for protons and neutrons in a
uniform magnetic field are provided. The particle spin polarizations and the
yields of protons and neutrons are calculated in a free Fermi gas model.
Obvious spin polarization occurs when $B\geq10^{14}$G for protons and
$B\geq10^{17}$G for neutrons, respectively. It is shown that the neutron spin
polarization depends solely on the magnetic field strength.",0408299v5
2004-09-07,Spin-Orbit Resonance and the Evolution of Compact Binary Systems,"Starting with a post-Newtonian description of compact binary systems, we
derive a set of equations that describes the evolution of the orbital angular
momentum and both spin vectors during inspiral. We find regions of phase space
that exhibit resonance behavior, characterized by small librations of the spin
vectors around a fixed orientation. Due to the loss of energy and orbital
angular momentum through radiation reaction, systems can eventually be captured
into these resonance orientations. By investigating the long-term evolution of
compact binaries with a variety of initial conditions, we find that the
distribution in parameter space can be strongly affected by resonance captures.
This has the effect of significantly reducing the size of search space for
gravitational wave sources, in turn improving the chances of detecting such
sources through methods of template matching. Furthermore, by calculating the
expected spin distribution at the end of the inspiral phase, we can predict
what are the most likely initial conditions for the plunge phase, a result of
great interest for numerical relativity calculations.",0409174v1
2004-11-28,Modelling the spin equilibrium of neutron stars in LMXBs without gravitational radiation,"In this paper we discuss the spin-equilibrium of accreting neutron stars in
LMXBs. We demonstrate that, when combined with a naive spin-up torque, the
observed data leads to inferred magnetic fields which are at variance with
those of galactic millisecond radiopulsars. This indicates the need for either
additional spin-down torques (eg. gravitational radiation) or an improved
accretion model. We show that a simple consistent accretion model can be
arrived at by accounting for radiation pressure in rapidly accreting systems
(above a few percent of the Eddington accretion rate). In our model the inner
disk region is thick and significantly sub-Keplerian, and the estimated
equilibrium periods are such that the LMXB neutron stars have properties that
accord well with the galactic millisecond radiopulsar sample. The implications
for future gravitational-wave observations are also discussed briefly.",0411747v2
1992-10-14,Generalized spin density wave state of the Hubbard model on the C12 and C60 clusters,"The one-band Hubbard model at half-filling on a truncated tetrahedron
(C$_{12}$), and on the C$_{60}$ molecule is studied. Within the Hartree-Fock
approximation, we find a magnetic-like instability of the `Fermi sea' towards a
spin-ordered phase for an intermediate value of the coupling ${\rm
(U/t)_c}\approx 2.6$. The ordered phase presents a spin arrangement similar to
that of the classical Heisenberg model defined on the same clusters. We study
the linear excitations around the Hartree-Fock ground states using the
random-phase approximation. On a finite cluster, we expect that these results
signal the presence of a $rapid$ $crossover$ between a paramagnetic region and
a regime where spin correlations are important. The relationship with the
Heisenberg limit (large ${\rm U/t}$) is discussed. Finally, we comment on
implications of our results for purely repulsive models of superconductivity in
alkali-metal-doped fullerenes.",9210011v1
1992-12-09,Theory of Anisotropic Superexchange in Insulating Cuprates,"Spin-orbit corrections to superexchange are calculated using the method of
Moriya [T.\ Moriya, {\it Phys.\ Rev.}~{\bf 120} 91, (1960)] for two of the
insulating parent compounds of the cuprate superconductors: (1)
La$_{2-x}$Nd$_x$CuO$_4$ where the CuO$_6$ octahedra forming each Cu-O layer are
tilted in staggered fashion about an axis which depends on $x$ and temperature;
and (2) YBa$_2$Cu$_3$O$_{6+x}$ ($x \alt 0.4$) where the Cu-O layers form
CuO$_2$-Y-CuO$_2$ bilayers in which the in-plane O$^{2-}$ ions are displaced
uniformly towards the Y$^{3+}$ layer. For (1) a simple formula is derived for
the weak ferromagnetic moment in each Cu-O layer as a function of the tilting
axis and magnitude. For (2) it is shown that the anisotropic corrections to
superexchange are different from what has previously been assumed. For the
correct spin Hamiltonian a classical N\'eel state in which the Cu spins are
lying in the plane is unstable in a single Cu-O layer, but when a bilayer is
considered there is a critical value of the interlayer exchange coupling which
stabilizes this state. For both cases (1) and (2) spin-wave spectra are
calculated and shown to compare favorably with experiment.",9212015v1
1994-02-24,Functional Integrals for Correlated Electrons,"The application of functional integral methods and the Hubbard--Stratonovich
transformation to the Hubbard model is discussed. For the attractive case,
using a simple gauge transformation of the superconducting order parameter
field, the effective action for the low-energy phase excitations is derived.
Inclusion of the electromagnetic field is straightforward. For the repulsive
case at half--filling use of a fluctuating spin reference frame allows a
derivation of the effective nonlinear sigma model for arbitrary coupling
strength U. Results for the spin-wave velocity and the spin stiffness are
obtained for arbitrary U. Away from half--filling, at large U an effective
action for doped fermions and the spins is found which is related to the slave
fermion formulation of the correlated fermion problem. The formalism is
generalized to include the full SU(2)xSU(2) symmetry of the Hubbard model. This
allows the derivation of a Ginzburg-Landau like theory that includes both
particle-hole and particle-particle excitations. (paper at the NATO workshop on
the Hubbard model, San Sebastian, Spain, oct. 1993)",9402103v1
1994-07-06,"Exact spectra, spin susceptibilities and order parameter of the quantum Heisenberg antiferromagnet on the triangular lattice","Exact spectra of periodic samples are computed up to $ N=36 $.
  Evidence of an extensive set of low lying levels, lower than the softest
magnons, is exhibited.
  These low lying quantum states are degenerated in the thermodynamic limit;
their symmetries and dynamics as well as their finite-size scaling are strong
arguments in favor of N\'eel order.
  It is shown that the N\'eel order parameter agrees with first-order spin-wave
calculations. A simple explanation of the low energy dynamics is given as well
as the numerical determinations of the energies, order parameter and spin
susceptibilities of the studied samples. It is shown how suitable boundary
conditions, which do not frustrate N\'eel order, allow the study of samples
with $ N=3p+1 $ spins.
  A thorough study of these situations is done in parallel with the more
conventional case $ N=3p $.",9407028v1
1995-01-10,Magnetic Phases of the 2D Hubbard Model at Low Doping,"We study the equilibrium spin configuration of the 2D Hubbard model at low
doping, when a long-range magnetic order is still present. We use the
spin-density-wave formalism and examine the two suggested candidates for a
ground state: the planar spiral $(\pi,Q)$ and $(Q,Q)$ states. In a mean-field
theory, each of these two states is a ground state in a certain range of
parameters. We however show that both states have negative bosonic modes in a
transverse channel which implies that the spiral states are in fact unstable
(the $(Q,Q)$ state, in addition, has a negative longitudinal stiffness). We
searched for a ground state in a parameter range which on a mean-field level
favored the $(\pi,Q)$ phase, and found that the equilibrium spin configuration
is noncoplanar. These findings lead to a novel scenario of spin reorientation
upon doping in Hubbard antiferromagnets.",9501036v1
1995-07-14,Skyrmion Excitations in Quantum Hall Systems,"Using finite size calculations on the surface of a sphere we study the
topological (skyrmion) excitation in quantum Hall system with spin degree of
freedom at filling factors around $\nu=1$. In the absence of Zeeman energy, we
find, in systems with one quasi-particle or one quasi-hole, the lowest energy
band consists of states with $L=S$, where $L$ and $S$ are the total orbital and
spin angular momentum. These different spin states are almost degenerate in the
thermodynamic limit and their symmetry-breaking ground state is the state with
one skyrmion of infinite size. In the presence of Zeeman energy, the skyrmion
size is determined by the interplay of the Zeeman energy and electron-electron
interaction and the skyrmion shrinks to a spin texture of finite size. We have
calculated the energy gap of the system at infinite wave vector limit as a
function of the Zeeman energy and find there are kinks in the energy gap
associated with the shrinking of the size of the skyrmion. breaking ground
state is the state with one skyrmion of infinite size. In the presence of
Zeeman energy, the skyrmion size is determined by the interplay of the Zeeman
energy and electron-electron",9507054v1
1996-01-14,The ground state of the two-leg Hubbard ladder: a density--matrix renormalization group study,"We present density-matrix renormalization group results for the ground state
properties of two-leg Hubbard ladders. The half-filled Hubbard ladder is an
insulating spin-gapped system, exhibiting a crossover from a spin-liquid to a
band-insulator as a function of the interchain hopping matrix element. When the
system is doped, there is a parameter range in which the spin gap remains. In
this phase, the doped holes form singlet pairs and the pair-field and the ""$4
k_F$"" density correlations associated with pair density fluctuations decay as
power laws, while the ""$2 k_F$"" charge density wave correlations decay
exponentially. We discuss the behavior of the exponents of the pairing and
density correlations within this spin gapped phase. Additional one-band
Luttinger liquid phases which occur in the large interband hopping regime are
also discussed.",9601047v1
1996-08-09,Chiral Metal as a Ferromagnetic Super Spin Chain,"The electrons on the surface of a disordered multi-layer integer quantum Hall
system constitute an unusual chiral metal with ballistic motion transverse to
the field, and diffusive motion parallel to it. We present a non-perturbative
analytic treatment of an appropriate model, consisting of disordered chiral
Fermions in two dimensions. A supersymmetric generating functional is set up
for the correlation functions of this system. The strong disorder limit is
mapped into a supersymmetric spin chain, with ferromagnetic exchange coupling,
reflecting the electron's chiral motion. The ferromagnetic ground state and the
spin wave excitations, corresponding to the diffusion modes of the chiral
metal, are found exactly. The parametric density of states correlator in the
ergodic limit is computed from a Boltzmann-weighted sum over low energy spin
states. The result is of a universal form and coincides with that for a
Hermitian random matrix.",9608049v2
1996-12-18,The Spin Gap in the Context of the Boson-Fermion Model for High $T_c$ Superconductivity,"The issue of the spin gap in the magnetic susceptibility $\chi''(q,\omega)$
in high T_c superconductors is discussed within a scenario of a mixture of
localized tightly bound electron pairs in singlet states (bi-polarons) and
itinerant electrons. Due to a local exchange between the two species of charge
carriers, antiferromagnetic correlations are induced amongst the itinerant
electrons in the vicinity of the sites containing the bound electron pairs. As
the temperature is lowered these exchange processes become spatially correlated
leading to a spin wave-like spectrum in the subsystem of the itinerant
electrons. The onset of such coherence is accompanied by the opening of a
pseudo gap in the density of states of the electron subsystem whose temperature
dependence is reflected in that of $\chi'' (q,\omega)$ near $q =(\pi,\pi)$
where a ``spin gap'' is observed by inelastic neutron scattering and NMR.",9612171v1
1997-04-28,Phase transition in the one-dimensional Kondo lattice model with attractive electron-electron interaction,"The one-dimensional Kondo lattice model with attractive interaction among the
conduction electrons is analyzed in the case of half-filling. It is shown that
there are three distinct phases depending on the coupling constants of the
model. Two phases have a spin and charge gap. While one shows a clear
separation of the spin and charge excitation spectrum the other phase may be
characterized as a band insulator type where both excitations are due to
two-particle states. The third phase is gapless in both channels and has quasi
long-range order in the spin and charge density wave correlation. In this phase
the spin and charge excitations have again a clearly separated spectrum. For
the analysis we discuss first two limiting cases. Then a density matrix
renormalization group calculation on finite systems is applied to determine the
phase diagram and the correlation functions in the gapped and gapless phase for
general couplding constants.",9704226v1
1997-08-14,The effect of valley-spin degeneracy on the screening of charged impurity centers in two- and three-dimensional electronic devices,"Accurate characterization of charged impurity centers is of importance for
the electronic devices and materials. The role of valley-spin degeneracy on the
screening of an attractive ion by the mobile carriers is assessed within a
range of systems from spin-polarized single-valley to six-valley. The screening
is treated using the self-consistent local-field correction of
  Singwi and co-workers known as STLS. The bound electron wave function is
formulated in the form of an integral equation. Friedel oscillations are seen
to be influential especially in two-dimensions which cannot be adequately
accounted for by the hydrogenic variational approaches. Our results show
appreciable differences at certain densities with respect to simplified
techniques, resulting mainly in the enhancement of the impurity binding
energies. The calculated Mott constants are provided where available. The main
conclusion of the paper is the substantial dependence of the charged impurity
binding energy on the valley-spin degeneracy in the presence of screening.",9708103v1
1997-10-08,Spin susceptibility and the pi-excitation in underdoped cuprates,"The dynamical spin susceptibility chi'' at wave vector (pi, pi) and the
spectrum pi'' of the spin-triplet particle--particle excitation with center of
mass momentum (pi, pi) (pi-excitation) are considered in the slave-boson
formulation of the t--J-model. Propagators are calculated in a diagrammatic
t-matrix approximation in the d-wave superconducting state for a wide doping
range. The resulting spectra chi'' and pi'' both show a resonance at a doping
dependent energy, in qualitative agreement with recent numerical cluster
calculations. In underdoped systems, the peak position is comparable to that
found in neutron scattering experiments. The peak in chi'' as well as pi'' is
at low doping entirely caused by spin fluctuations, whereas the triplet
particle--particle channel does not contribute as a collective mode.",9710065v1
1997-12-11,Spatial Structure of Spin Polarons in the t-J Model,"The deformation of the quantum Neel state induced by a spin polaron is
analyzed in a slave fermion approach. Our method is based on the selfconsistent
Born approximation for Green's and the wave function for the quasiparticle. The
results of various spin-correlation functions relative to the position of the
moving hole are discussed and shown to agree with those available from small
cluster calculations. Antiferromagnetic correlations in the direct neighborhood
of the hole are reduced, but they remain antiferromagnetic even for J as small
as 0.1 t. These correlation functions exhibit dipolar distortions in the spin
structure, which sensitively depend on the momentum of the quasiparticle. Their
asymptotic decay with the distance from the hole is governed by power laws, yet
the spectral weight of the quasiparticles does not vanish.",9712119v1
1997-12-14,Properties of Quantum Hall Skyrmions from Anomalies,"It is well known that the Fractional Quantum Hall Effect (FQHE) may be
effectively represented by a Chern-Simons theory. In order to incorporate QH
Skyrmions, we couple this theory to the topological spin current, and include
the Hopf term. The cancellation of anomalies for chiral edge states, and the
proviso that Skyrmions may be created and destroyed at the edge, fixes the
coefficients of these new terms. Consequently, the charge and the spin of the
Skyrmion are uniquely determined. For those two quantities we find the values
$e\nu N_{Sky}$ and $\nu N_{Sky}/2$, respectively, where $e$ is electron charge,
$\nu$ is the filling fraction and $N_{Sky}$ is the Skyrmion winding number. We
also add terms to the action so that the classical spin fluctuations in the
bulk satisfy the standard equations of a ferromagnet, with spin waves that
propagate with the classical drift velocity of the electron.",9712151v2
1998-09-30,Vortices in Quantum Spin Systems,"We examine spin vortices in ferromagnetic quantum Heisenberg models with
planar anisotropy on two-dimensional lattices. The symmetry properties and the
time evolution of vortices built up from spin-coherent states are studied in
detail. Although these states show a dispersion typical for wave packets,
important features of classical vortices are conserved. Moreover, the results
on symmetry properties provide a construction scheme for vortex-like
excitations from exact eigenstates, which have a well-controlled time
evolution. Our approach works for arbitrary spin length both on triangular and
square lattices.",9809401v2
1998-11-17,Dual Order Parameter for the Nodal Liquid,"The guiding conception of vortex-condensation-driven Mott insulating behavior
is central to the theory of the nodal liquid. We amplify our earlier
description of this idea and show how vortex condensation in 2D electronic
systems is a natural extension of 1D Mott insulating and 2D bosonic Mott
insulating behavior. For vortices in an underlying superconducting pair field,
there is an important distinction between the condensation of flux hc/2e and
flux hc/e vortices. The former case leads to spin-charge confinement,
exemplified by the band insulator and the charge-density-wave. In the latter
case, spin and charge are liberated leading directly to a 2D Mott insulator
exhibiting *spin-charge separation*. Possible upshots include not only the
nodal liquid, but also a novel undoped antiferromagnetic insulating phase with
gapped excitations exhibiting spin-charge separation.",9811236v1
1999-03-02,"Crystal Field, Magnetic Anisotropy and Excitations in Rare-Earth Hexaborides","We clarify the role of crystalline electric field (CEF) induced magnetic
anisotropy in the ground state and spin-wave spectrum of cubic rare-earth
materials with dominating isotropic magnetic exchange interactions. In
particular we study the hexaboride NdB_6 which is shown to exhibit strong
spin-quadrupolar coupling. The CEF scheme is analyzed and a non-collinear
magnetization response is found. The spin orientation in the
antiferromagnetically ordered ground-state is identified. Moreover, the spin
excitations are evaluated and in agreement with inelastic neutron scattering a
suppression of one of the two magnetic modes in the strong-coupling regime is
predicted.",9903039v1
1999-05-07,Renormalized Bosonic Interaction of Excitons,"An effective bosonic Hamiltonian of $1s$ excitons with ``spin'' degrees of
freedom in two dimension is obtained through a projection procedure, starting
from a conventional electron-hole Hamiltonian ${\cal H}_{eh}$. We first
demonstrate that a straightforward transformation of ${\cal H}_{eh}$ into a
Hamiltonian of bosonic excitons does not give the two-body interaction between
an ``up-spin'' exciton and a ``down-spin'' exciton, which are created by the
left- and right-circularly polarized light beams, respectively. We then show
that this interaction is generated through a projection procedure onto the
subspace spanned by $1s$ excitons, as a renormalization effect coming from
higher exciton states. The projection also renormalizes the interaction between
$1s$ excitons with the same spins by a large amount. These renormalization
effects are crucial for the polarization dependence of the optical responses
from semiconductors. The present theory gives the microscopic foundation of the
phenomenology that was successfully applied to the analysis of four-wave mixing
experiments in GaAs quantum wells strongly coupled to the radiation field in a
high-Q micro cavity.",9905085v1
1999-05-26,Spontaneous symmetry breaking in single and molecular quantum dots,"Classes of spontaneous symmetry breaking at zero and low magnetic fields in
single quantum dots (QD's) and quantum dot molecules (QDM's) are discussed in
relation to the ratio R_W between the interelectron Coulomb repulsion and the
harmonic confinement, using spin-and-Space unrestricted Hartree-Fock
calculations. These include: Wigner crystallization for R_W > 1, and formation
of non-crystallized electron puddles localized on the individual dots in QDM's,
as well as spin-density waves in single QD's, for R_W < 1.
  Erratum:
  Subsequent to the the publication of our Letter, we have performed further
systematic spin-and-space unrestricted Hartree-Fock calculations. While the
behavior and magnitudes of the addition energies shown in our Letter are
maintained, as well as our finding pertaining to the prevalent violation of
Hund's first rule, our improved calculations yield in certain instances
different spin polarizations.",9905383v2
1999-11-07,ESR investigation on the Breather mode and the Spinon-Breather dynamical crossover in Cu Benzoate,"A new elementary-excitation, the so called ""breather excitation"", is observed
directly by millimeter-submillimeter wave electron spin resonance (ESR) in the
Heisenberg quantum spin-chain Cu benzoate, in which a field-induced gap is
found recently by specific heat and neutron scattering measurements. Distinct
anomalies were found in line width and in resonance field around the ""dynamical
crossover"" regime between the gap-less spinon-regime and the gapped
breather-regime. When the temperature becomes sufficiently lower than the
energy gap, a new ESR-line with very narrow line-width is found, which is the
manifestation of the breather excitation. The non-linear field dependence of
the resonance field agrees well with the theoretical formula of the first
breather-excitation proposed by Oshikawa and Affleck. The present work
establishes experimentally for the first time that a sine-Gordon model is
applicable to explain spin dynamics in a S=1/2 Heisenberg spin chain subjected
to staggered field even in high fields.",9911094v2
2000-02-25,Does Giant Magnetoresistance Survive in Presence of Superconducting Contact?,"The giant magnetoresistance (GMR) of ferromagnetic bilayers with a
superconducting contact (F1/F2/S) is calculated in ballistic and diffusive
regimes. As in spin-valve, it is assumed that the magnetization in the two
ferromagnetic layers F1 and F2 can be changed from parallel to antiparallel. It
is shown that the GMR defined as the change of conductance between the two
magnetic configurations is an oscillatory function of the thickness of F2 layer
and tends to an asymptotic positive value at large thickness. This is due to
the formation of quantum well states in F2 induced by Andreev reflection at the
F2/S interface and reflection at F1/F2 interface in antiparallel configuration.
In the diffusive regime, if only spin-dependent scattering rates in the
magnetic layers are considered (no difference in Fermi wave-vectors between
spin up and down electrons) then the GMR is supressed due to the mixing of spin
up and down electron-hole channels by Andreev reflection.",0002411v1
2000-06-10,On the interpretation of spin-polarized electron energy loss spectra,"We study the origin of the structure in the spin-polarized electron energy
loss spectroscopy (SPEELS) spectra of ferromagnetic crystals. Our study is
based on a 3d tight-binding Fe model, with constant onsite Coulomb repulsion U
between electrons of opposite spin. We find it is not the total density of
Stoner states as a function of energy loss which determines the response of the
system in the Stoner region, as usually thought, but the densities of Stoner
states for only a few interband transitions. Which transitions are important
depends ultimately on how strongly umklapp processes couple the corresponding
bands. This allows us to show, in particular, that the Stoner peak in SPEELS
spectra does not necessarily indicate the value of the exchange splitting
energy. Thus, the common assumption that this peak allows us to estimate the
magnetic moment through its correlation with exchange splitting should be
reconsidered, both in bulk and surface studies. Furthermore, we are able to
show that the above mechanism is one of the main causes for the typical
broadness of experimental spectra. Finally, our model predicts that optical
spin waves should be excited in SPEELS experiments.",0006177v1
2000-06-28,"Doped two orbital chains with strong Hund's rule couplings - ferromagnetism, spin gap, singlet and triplet pairings","Different models for doping of two-orbital chains with mobile $S=1/2$
fermions and strong, ferromagnetic (FM) Hund's rule couplings stabilizing the
S=1 spins are investigated by density matrix renormalization group (DMRG)
methods. The competition between antiferromagnetic (AF) and FM order leads to a
rich phase diagram with a narrow FM region for weak AF couplings and strongly
enhanced triplet pairing correlations. Without a level difference between the
orbitals, the spin gap persists upon doping, whereas gapless spin excitations
are generated by interactions among itinerant polarons in the presence of a
level difference. In the charge sector we find dominant singlet pairing
correlations without a level difference, whereas upon the inclusion of a
Coulomb repulsion between the orbitals or with a level difference, charge
density wave (CDW) correlations decay slowest. The string correlation functions
remain finite upon doping for all models.",0006439v1
2000-10-26,Spintronics and Quantum Computing: Switching Mechanisms for Qubits,"Quantum computing and quantum communication are remarkable examples of new
information processing technologies that arise from the coherent manipulation
of spins in nanostructures. We review our theoretical proposal for using
electron spins in quantum-confined nanostructures as qubits. We present single-
and two-qubit gate mechanisms in laterally as well as vertically coupled
quantum dots and discuss the possibility to couple spins in quantum dots via
exchange or superexchange. In addition, we propose a new stationary wave
switch, which allows to perform quantum operations with quantum dots or
spin-1/2 molecules placed on a 1D or 2D lattice.",0010434v1
2000-11-22,Collective excitations in ferrimagnetic Heisenberg ladders,"We study ground-state properties and the low-lying excitations of Heisenberg
spin ladders composed of two ferrimagnetic chains with alternating site spins
$(S_1>S_2)$ by using the bosonic Dyson-Maleev formalism and Lanczos numerical
techniques. The emphasis is on properties of the ferrimagnetic phase which is
stable for antiferromagnetic interchain couplings $J_{\perp}\geq 0$. There are
two basic implications of the underlying lattice structure: (i) the spin-wave
excitations form folded acoustic and optical branches in the extended Brillouin
zone and (ii) the ground state parameters (such as the on-site magnetizations
and spin-stiffness constant) show a crossover behavior in the weak-coupling
region $0<J_{\perp}<1$. The above peculiarities of the ladder ferrimagnetic
state are studied up to second order in the quasiparticle interaction and by a
numerical diagonalization of ladders containing up to N=12 rungs. The presented
results for the ground-state parameters and the excitation spectrum can be used
in studies on the low-temperature thermodynamics of ferrimagnetic ladders.",0011388v1
2000-12-22,The magnetic ordering in the mixed valence compound beta-Na0.33V2O5,"The low-temperature electron spin resonance (ESR) spectra and the static
magnetization data obtained for the stoichiometric single crystals of
$\beta$-Na$_{0.33}$V$_2$O$_5$ indicate that this quasi-one-dimensional mixed
valence (V4+/V5+) compound demonstrates at $T_N=22$ K the phase transition into
the canted antiferromagnetically ordered state. The spontaneous magnetization
of $3.4\times 10^{-3}$ $\mu_B$ per V$^{4+}$ ion was found to be oriented along
the two-fold $b$ axis of the monoclinic structure, the vector of
antiferromagnetism is aligned with the $a$ axis and the Dzyaloshinsky vector is
parallel to the $c$-axis. The experimental data were successfully described in
the frame of the macroscopic spin dynamics and the following values for the
macroscopic parameters of the spin system were obtained: the Dzyaloshinsky
field $H_D=6$ kOe, the energy gaps of two branches of the spin wave spectrum
$\Delta_1=48$ GHz and $\Delta_2=24$ GHz.",0012434v1
2001-03-09,Spin ordering quantum transitions of superconductors in a magnetic field,"We argue that recent neutron scattering measurements by Lake et. al. (Science
291, 1759 (2001)) of the spin excitation spectrum of LSCO in a magnetic field
can be understood in terms of proximity to a phase with co-existing
superconductivity and spin density wave order. We present a general theory for
such quantum transitions, and argue that their low energy spin fluctuations are
controlled by a singular correction from the superflow kinetic energy, acting
in the region outside the vortex cores. We propose numerous experimental tests
of our theory.",0103192v4
2001-05-15,Exact ground state of one- and two-dimensional frustrated quantum spin systems,"We outline the recent results on the ground state for a class of one- and
two-dimensional frustrated quantum spin models with competing ferro(F)- and
antiferromagnetic (AF) interactions. Frustrated spin systems are known to have
many interesting properties due to large quantum fluctuations. As a result of
these fluctuations usual mean-field approach gives quite crude (if not false)
description of these systems. Therefore, exactly solvable models are very
instructive at investigations of such systems. The exact ground state wave
function of proposed models has a structure of the valence-bond state (VBS)
type. One of the 1D model describes the transition line between the F and AF
phase. The exact singlet ground state on this line has a double-spiral
ordering. Using different approximation methods we study the magnetization
curve in the AF phase. The second considered set of the 1D and 2D models has an
exact non-degenerate ground state with exponentially decaying spin
correlations. We also proposed the 1D and 2D electronic models with exact
ground state represented in terms of singlet bond functions which are the
generalization of the RVB functions including ionic states.",0105295v1
2001-05-20,Ab Initio Calculations of the Spin-Half XY Model,"In this article, the correlated basis-function (CBF) method is applied for
the first time to the quantum spin-half {\it XY} model on the linear chain, the
square lattice, and the simple cubic lattice. In this treatment of the quantum
spin-half {\it XY} model a Jastrow ansatz is utilised to approximate the
ground-state wave function. Results for the ground-state energy and the
sublattice magnetisation are presented, and evidence that the CBF detects the
quantum phase transition point in this model is also presented. The CBF results
are compared to previous coupled cluster method (CCM) results for the spin-half
{\it XY} model, and the two formalisms are then compared and contrasted.",0105386v1
2001-08-31,Inversion Phenomena of the Anisotropies of the Hamiltonian and the Wave-Function in the Distorted Diamond Type Spin Chain,"We investigate the ground-sate phase diagram of the XXZ version of the S=1/2
distorted diamond chain by use of the degenerate perturbation theory near the
truncation point. In case of the XY-like interaction anisotropy, the phase
diagram consists of the Neel phase and the spin-fluid phase. For the Ising-like
interaction anisotropy case, it consists of three phases: the ferrimagnetic
phase, the Neel phase and the spin-fluid phase. The magnetization in the
ferrimagnetic phase is 1/3 of the saturation magnetization. The remarkable
nature of the phase diagram is the existence of the Neel phase, although the
interaction anisotropy is XY-like. And also, the spin-fluid phase appears in
spite of the Ising-like interaction anisotropy. We call these regions
""inversion regions"".",0108528v1
2001-09-18,Self-consistent Ornstein-Zernike approximation for three-dimensional spins,"An Ornstein-Zernike approximation for the two-body correlation function
embodying thermodynamic consistency is applied to a system of classical
Heisenberg spins on a three-dimensional lattice. The consistency condition
determined in a previous work is supplemented by introducing a simplified
expression for the mean-square fluctuations of the spin on each lattice site.
The thermodynamics and the correlations obtained by this closure are then
compared with approximants based on extrapolation of series expansions and with
Monte Carlo simulations. The comparison reveals that many properties of the
model, including the critical temperature, are very well reproduced by this
simple version of the theory, but that it shows substantial quantitative error
in the critical region, both above the critical temperature and with respect to
its rendering of the spontaneous magnetization curve. A less simple but
conceptually more satisfactory version of the SCOZA is then developed, but not
solved, in which the effects of transverse correlations on the longitudinal
susceptibility is included, yielding a more complete and accurate description
of the spin-wave properties of the model.",0109315v1
2001-11-28,Spin instabilities and quantum phase transitions in integral and fractional quantum Hall states,"The inter-Landau-level spin excitations of quantum Hall states at filling
factors nu=2 and 4/3 are investigated by exact numerical diagonalization for
the situation in which the cyclotron (hbar*omega_c) and Zeeman (E_Z) splittings
are comparable. The relevant quasiparticles and their interactions are studied,
including stable spin wave and skyrmion bound states. For nu=2, a spin
instability at a finite value of epsilon=hbar*omega_c-E_Z leads to an abrupt
paramagnetic to ferromagnetic transition, in agreement with the mean-field
approximation. However, for nu=4/3 a new and unexpected quantum phase
transition is found which involves a gradual change from paramagnetic to
ferromagnetic occupancy of the partially filled Landau level as epsilon is
decreased.",0111532v1
2002-03-03,Anomaly in Spin Excitation Spectrum of Double-Exchange Systems with Randomness,"Spin excitation spectrum of the double-exchange model is studied in the
presence of randomness. Spin wave approximation in the ground state shows that
the randomness significantly modifies the spectrum from the cosine-like one in
the pure system to that with anomalies such as broadening, anti-crossing and
gap opening. The origin of anomalies is speculated to be modulation of
effective ferromagnetic coupling by the Friedel oscillation. These anomalies
qualitatively reproduce the spin excitation spectrum in colossal
magnetoresistance manganites whose Curie temperatures are relatively low. Our
results suggest that randomness control is an important notion to understand
effects of the A-site substitution which has previously been understood as the
bandwidth control.",0203041v1
2002-06-15,Spin and charge dynamics of stripes in doped Mott insulators,"We study spin and charge dynamics of stripes in doped Mott insulators by
considering a two-dimensional Hubbard model with N fermion flavors. For N =2 we
recover the normal one-band model while for N -> infty a spin density wave
mean-field solution. For all band fillings, lattice topologies and N= 4 n the
model may be solved by means of Monte Carlo methods without encountering the
sign problem. At N=4 and in the vicinity of the Mott insulator, the single
particle density of states shows a gap. Within this gap and on rectangular
topologies of sizes up to 30 X 12 we find gapless spin collective modes
centered around q = (\pi \pm \epsilon_x,\pi \pm \epsilon_y) as well as charge
modes centered around q = (\pm 2 \epsilon_x, \pm 2 \epsilon_y), q = (\pm
\epsilon_x, \pm \epsilon_y) and q = (0,0). \epsilon_{x,y} depends on the
lattice topology and doping.",0206287v2
2002-07-08,Strongly coupled quantum criticality with a Fermi surface in two dimensions: fractionalization of spin and charge collective modes,"We describe two dimensional models with a metallic Fermi surface which
display quantum phase transitions controlled by strongly interacting critical
field theories below their upper critical dimension. The primary examples
involve transitions with a topological order parameter associated with
dislocations in collinear spin density wave (""stripe"") correlations: the
gapping of the order parameter fluctuations leads to a fractionalization of
spin and charge collective modes, and this transition has been proposed as a
candidate for the cuprates near optimal doping. The coupling between the order
parameter and long-wavelength volume and shape deformations of the Fermi
surface is analyzed by the renormalization group, and a runaway flow to a
non-perturbative regime is found in most cases. A phenomenological scaling
analysis of simple observable properties of possible second order quantum
critical points is presented, with results quite similar to those near quantum
spin glass transitions and to phenomenological forms proposed by Schroeder et
al. (cond-mat/0011002).",0207167v2
2002-08-07,Magnetic-field dependence of electron spin relaxation in n-type semiconductors,"We present a theoretical investigation of the magnetic field dependence of
the longitudinal ($T_1$) and transverse ($T_2$) spin relaxation times of
conduction band electrons in n-type III-V semiconductors. In particular, we
find that the interplay between the Dyakonov-Perel process and an additional
spin relaxation channel, which originates from the electron wave vector
dependence of the electron $g$-factor, yields a maximal $T_2$ at a finite
magnetic field. We compare our results with existing experimental data on
n-type GaAs and make specific additional predictions for the magnetic field
dependence of electron spin lifetimes.",0208139v2
2002-12-12,Low-energy spin fluctuations of the heavy-Fermion compound CeNi_2Ge_2: origin of non-Fermi liquid behavior,"Neutron scattering shows that non-Fermi-liquid behavior of the heavy-Fermion
compound CeNi_2Ge_2 is brought about by development of low-energy spin
fluctuations with an energy scale of 0.6 meV. They appear around
antiferromagnetic wave vectors $({1/2} {1/2} 0)$ and $(0 0 {3/4})$ at low
temperatures, and coexist with high-energy spin fluctuations with an energy
scale of 4 meV and a modulation vector $(0.23, 0.23, {1/2})$. The energy
dependence of the spin fluctuations is a peculiar character of CeNi_2Ge_2 which
differs from typical heavy-Fermion compounds, and suggests importance of
low-energy structures of quasiparticle bands.",0212265v1
2002-12-19,The Wave Functions for the Free-Fermion Part of the Spectrum of the $SU_q(N)$ Quantum Spin Models,"We conjecture that the free-fermion part of the eigenspectrum observed
recently for the $SU_q(N)$ Perk-Schultz spin chain Hamiltonian in a finite
lattice with $q=\exp (i\pi (N-1)/N)$ is a consequence of the existence of a
special simple eigenvalue for the transfer matrix of the auxiliary
inhomogeneous $SU_q(N-1)$ vertex model which appears in the nested Bethe ansatz
approach. We prove that this conjecture is valid for the case of the SU(3) spin
chain with periodic boundary condition. In this case we obtain a formula for
the components of the eigenvector of the auxiliary inhomogeneous 6-vertex model
($q=\exp (2 i \pi/3)$), which permit us to find one by one all components of
this eigenvector and consequently to find the eigenvectors of the free-fermion
part of the eigenspectrum of the SU(3) spin chain. Similarly as in the known
case of the $SU_q(2)$ case at $q=\exp(i2\pi/3)$ our numerical and analytical
studies induce some conjectures for special rates of correlation functions.",0212475v1
2003-04-12,Ground State of a Heisenberg Chain with Next-Nearest-Neighbor Bond Alternation,"We investigate the ground-state properties of the spin-half $J_1{-}J_2$
Heisenberg chain with a next-nearest-neighbor spin-Peierls dimerization using
conformal field theory and Lanczos exact diagonalizations. In agreement with
the results of a recent bosonization analysis by Sarkar and Sen, we find that
for small frustration ($J_2/J_1$) the system is in a Luttinger spin-fluid
phase, with gapless excitations, and a finite spin-wave velocity. In the regime
of strong frustration the ground state is spontaneously dimerized and the bond
alternation reduces the triplet gap, leading to a slight enhancement of the
critical point separating the Luttinger phase from the gapped one. An accurate
determination of the phase boundary is obtained numerically from the study of
the excitation spectrum.",0304302v1
2003-06-13,Modification of the classical Heisenberg helimagnet by weak uniaxial anisotropy and magnetic field,"Classical ground state of the isotropic Heisenberg spin Hamiltonian on a
primitive Bravais lattice is known to be a single-Q planar spin spiral. A
uniaxial anisotropy and external magnetic field distort this structure by
generating the higher-order Fourier harmonics at wave-vectors nQ in the spatial
spin configuration. These features are not captured in the formalism based on
the Luttinger-Tisza theorem, where the classical ground state energy is
minimized under the ``weak'' condition on the length of the spins. We discuss
why the correct solution is lost in that approach and present an alternative
microscopic treatment of the problem. It allows to find the classical ground
state for general Q for both easy-axis and easy-plane uniaxial second-order
anisotropy, and for any orientation of the magnetic field, by treating the
effect of anisotropy (but not the field) as a perturbation to the exchange
structure. As a result, the classical ground state energy, the uniform
magnetization, and the magnetic Bragg peak intensities that are measured in
experiment, are calculated.",0306370v1
2003-09-11,Theory of Current-Induced Magnetization Precession,"We solve appropriate drift-diffusion and Landau-Lifshitz-Gilbert equations to
demonstrate that unpolarized current flow from a non-magnet into a ferromagnet
can produce a precession-type instability of the magnetization. The fundamental
origin of the instability is the difference in conductivity between majority
spins and minority spins in the ferromagnet. This leads to spin accumulation
and spin currents that carry angular momentum across the interface. The
component of this angular momentum perpendicular to the magnetization drives
precessional motion that is opposed by Gilbert damping. Neglecting magnetic
anisotropy and magnetostatics, our approximate analytic and exact numerical
solutions using realistic values for the material parameters show (for both
semi-infinite and thin film geometries) that a linear instability occurs when
both the current density and the excitation wave vector parallel to the
interface are neither too small nor too large. For many aspects of the problem,
the variation of the magnetization in the direction of the current flows makes
an important contribution.",0309289v1
2003-09-11,Lightly doped dimerized spin chain in the one-dimensional t-J-J' model,"We study the one-dimensional t-J-J'-model in the limit of small hole doping
$x$ and small $J/t$, $J'/t$. Special emphasis is put on the regime $J'/J
\approx .5$ where a spin gap is present at small doping and the undoped spin
chain is strongly dimerized. Using a perturbative approach and Luttinger liquid
arguments, we demonstrate for this non-integrable class of models that the
charge degrees of freedom behave as non-interacting spinless solitons in the
dilute hole limit. Our approach is also used to evaluate the energy and mass
renormalization of a single hole. Interestingly, the corrections of these
quantities are in powers of $\sqrt{J/t}$. At $J'/J=.5$ we construct a
variational spin-polaron wave function for the hole and find good agreement
with our perturbative results.",0309296v2
2004-01-15,Ferrimagnetic mixed-spin ladders in weak and strong coupling limits,"We study two similar spin ladder systems with the ferromagnetic leg coupling.
First model includes two sorts of spins, s= 1/2 and s= 1, and the second model
comprises only s=1/2 legs coupled by a ""triangular"" rung exchange. The
antiferromagnetic (AF) rung coupling destroys the long-range order and
eventually makes the systems equivalent to the AF s=1/2 Heisenberg chain. We
investigate the situation by different methods in weak and strong rung coupling
limits. Particularly we compare the spin-wave theory and the bosonization
method in the weak coupling regime of the second model. We analyze the spectra
and correlations, and discuss the order parameter of these ladder systems.",0401264v2
2004-01-26,Spin dynamics in lightly doped La$_{2-x}$Sr$_x$CuO$_4$: Relaxation function within the $t - J$ model,"The relaxation function theory of doped two-dimensional $S=1/2$ Heisenberg
antiferromagnetic (AF) system in the paramagnetic state is presented taking
into account the hole subsystem as well as both the electron and AF
correlations. The expression for fourth frequency moment of relaxation shape
function is derived within the $t-J$ model. The presentation obeys rotational
symmetry of the spin correlation functions and is valid for all wave vectors
through the Brillouin zone. The spin diffusion contribution to relaxation rates
is evaluated and is shown to play a significant role in carrier free and doped
antiferromagnet in agreement with exact diagonalization calculations. At low
temperatures the main contribution to the nuclear spin-lattice relaxation rate,
$^{63}(1/T_1)$, of plane $^{63}$Cu arises from the AF fluctuations, and
$^{17}(1/T_1)$, of plane $^{17}$O, has the contributions from the wavevectors
in the vicinity of $(\pi,\pi)$ and small $q \sim 0$. It is shown that the
theory is able to explain the main features of experimental data on temperature
and doping dependence of $^{63}(1/T_1)$ in the paramagnetic state of both
carrier free La$_2$CuO$_4$ and doped La$_{2-x}$Sr$_x$CuO$_4$ compounds.",0401514v1
2004-06-08,Gauge Theory Pairing and Spin Fluctuations Near the Quantum Critical Point,"We develop a new theory of pairing and magnetic spin fluctuation effect near
the quantum critical point. Several novel properties are predicted: 1) based on
a spin fermion model, we derive two new interactions, a) a spin deformational
potential $H_{sdp}$ proportional to the bandwidth $W$ (as opposed to the
considerably smaller exchange coupling $J$ of the nearly antiferromagnetic
Fermi liquid theory) and b) a diamagnetic potential $H_{dia}$, quadratic in a
gauge potential $\vec{A}$. A dramatic increase of $T_C$ is predicted for $0.01
W\leq J\leq 10 W$. This should have immense technological impact in electric
energy production, storage and transmission, as well as for medical
electronics, microwave electronics, computer memory and information storage,
separations technology and maglev, amongst others. The striking prediction to
be confirmed by experiment is that the pairing order parameter
$\Delta(\vec{k})$ is predicted to be $p-$wave, i.e., $l=1$, S=1, as compared to
$l=2$ and S=1 for conventional HTS materials. In addition a novel collective
model is predicted whose frequency, $\omega_L$ is in the optical range and is
determined by $H_{sdp}$.",0406200v1
2004-06-11,Electron correlations in two-dimensional small quantum dots,"We consider circular and elliptic quantum dots with parabolic external
confinement, containing 0 - 22 electrons and with values of r_s in the range 0
< r_s < 3. We perform restricted and unrestricted Hartree-Fock calculations,
and further take into account electron correlations using second-order
perturbation theory. We demonstrate that in many cases correlations
qualitatively change the spin structure of the ground state from that obtained
under Hartree-Fock and spin-density-functional calculations. In some cases the
correlation effects destroy Hund's rule. We also demonstrate that the
correlations destroy static spin-density waves observed in Hartree-Fock and
spin-density-functional calculations.",0406258v4
2004-06-24,Resonant magnetic X-ray scattering spectra in SDW Cr -- ab initio study -----,"Using ab-initio band structure calculation based on the local density
approximation, Cr K-edge resonant X-ray magnetic scattering spectra are
analyzed in the spin density wave (SDW) state of chromium. We perform band
structure calculation, assuming an ideal bcc lattice structure with the lattice
constant observed at the spin-flip temperature T_{SF} and a commensurate SDW
state with the propagation vector close to the observed value at T_{SF}. Taking
account of the spin-orbit interaction, we obtain the orbital moment on each Cr
site induced in proportion to the local spin moment, which is quite small, at
most a tenth of those in nickel or iron. In spite of the tiny 3d orbital
moment, the orbital polarization is found to have large fluctuations as a
function of energy. We obtain the scattering intensity at the Cr K-edge on the
SDW magnetic Bragg spot, which shows resonant enhancement in good agreement
with the experiment. The 3d orbital polarization is found to be highly
correlated with the intensity of the resonant main peak, indicating that the 4p
orbital polarization is mainly induced by the 3d orbital polarization through
the p-d hybridization.",0406576v1
2004-07-20,Spin-dependent transmission through a chain of rings: influence of a periodically modulated spin-orbit interaction strength or ring radius,"We study ballistic electron transport through a finite chain of quantum
circular rings in the presence of spin-orbit interaction of strength \alpha.
For a single ring the transmission and reflection coefficients are obtained
analytically and from them the conductance for a chain of rings as a function
of \alpha and of the wave vector k of the incident electron. We show that due
to destructive spin interferences the chain can be totaly opaque for certain
ranges of k the width of which depends on the value of \alpha. A periodic
modulation of the strength \alpha or of the ring radius widens up the gaps
considerably and produces a nearly binary conductance output.",0407536v1
2004-08-06,Ultrafast initialization and QND-readout of a spin qubit via control of nanodot-vacuum coupling,"Ultrafast initialization enables fault-tolerant processing of quantum
information while QND readout enables scalable quantum computation. By
spatially assembling photon resonators and wave-guides around an n-doped
nanodot and by temporally designing optical pump pulses, an efficient quantum
pathway can be established from an electron spin to a charged exciton to a
cavity photon and finally to a flying photon in the waveguide. Such control of
vacuum-nanodot coupling can be exploited for ultrafast initialization and QND
readout of the spin, which are particularly compatible with the optically
driven spin quantum computers.",0408148v2
2004-10-07,Quantum Fluctuations and Excitations in Antiferromagnetic Quasicrystals,"We study the effects of quantum fluctuations and the excitation spectrum for
the antiferromagnetic Heisenberg model on a two-dimensional quasicrystal, by
numerically solving linear spin-wave theory on finite approximants of the
octagonal tiling. Previous quantum Monte Carlo results for the distribution of
local staggered magnetic moments and the static spin structure factor are
reproduced well within this approximate scheme. Furthermore, the magnetic
excitation spectrum consists of magnon-like low-energy modes, as well as
dispersionless high-energy states of multifractal nature. The dynamical spin
structure factor, accessible to inelastic neutron scattering, exhibits
linear-soft modes at low energies, self-similar structures with bifurcations
emerging at intermediate energies, and flat bands in high-energy regions. We
find that the distribution of local staggered moments stemming from the
inhomogeneity of the quasiperiodic structure leads to a characteristic energy
spread in the local dynamical spin susceptibility, implying distinct nuclear
magnetic resonance spectra, specific for different local environments.",0410180v1
2004-11-15,Current induced Spin Torque in a nanomagnet,"In a nanomagnet (whose total spin S< 1000), very small polarized currents can
lead to magnetic reversal. Treating on the same footing the transport and
magnetic properties of a nanomagnet connected to magnetic leads via tunneling
barriers, we derive a closed equation for the time evolution of the
magnetization. The interplay between Coulomb blockade phenomena and magnetism
gives some additional structure to the current induced spin torque. In addition
to the possibility of stabilizing uniform spin waves, we find that the system
is highly hysteretic: up to three different magnetic states can be
simultaneously stable in one region of the parameter (magnetic field and bias
voltage) space.",0411375v2
2005-02-18,Rashba effect in quantum networks,"We present a formalism to study quantum networks made up by single-channel
quantum wires in the presence of Rashba spin-orbit coupling and magnetic field.
In particular, linear transport through one-dimensional and two-dimensional
finite-size networks is studied by means of the scattering formalism. In some
particular quantum networks, the action of the magnetic field or of the Rashba
spin-orbit coupling induces localization of the electron wave function. This
phenomenon, which relies on both the quantum-mechanical interference and the
geometry of the network, is manifested through the suppression of the
conductance for specific values of the spin-orbit-coupling strength or of the
magnetic field. Furthermore, the interplay of the Aharonov-Bohm phases and of
the non-Abelian phases introduced by spin-orbit coupling, is discussed in a
number of cases.",0502455v2
2005-04-12,Spin and orbital ferromagnetism in strongly correlated itinerant electron systems,"Spectra of one-electron and collective excitations in narrow-band
ferromagnets with unquenched orbital moments are calculated in various
theoretical models. The interaction of spin and orbital excitations with
conduction electrons results in the damping of the former which, however, turns
out to be rather small; therefore, apart from usual spin waves, well-defined
orbitons can exist. Non-quasiparticle states occur in the electron energy
spectrum near the Fermi energy due to this interaction. The criteria of
stability of the saturated spin and orbital ferromagnetic ordering are
considered. Possible effects of orbital ordering in magnetite and in colossal
magnetoresistance manganites are discussed.",0504280v2
2005-04-13,Transport of Charge and Spin in the Weak Link between Misoriented $PrOs_4Sb_{12}$ Superconductors,"Recently, the ``$(p+h)-$wave'' form of pairing symmetry has been proposed for
the superconductivity in $PrOs_{4}Sb_{12}$ compound [Parker D, Maki K and Haas
S, \textbf{cond-mat/0407254}]. In the present paper, a stationary Josephson
junction as a weak-link between $PrOs_{4}Sb_{12}$ triplet superconductors is
theoretically investigated. The quasiclassical Eilenberger equations are
analytically solved. The spin and charge current-phase diagrams are plotted and
the effect of misorientation between crystals on the spin current, and
spontaneous and Josephson currents is studied. It is found that such
experimental investigations of the current-phase diagrams can be used to test
the pairing symmetry in the above-mentioned superconductors. It is shown that
this apparatus can be applied as a polarizer for the spin current.",0504319v1
2005-05-07,Nuclear Magnetic Orderings and Frustration in Bcc 3He in High Magnetic Fields,"We studied phase transitions and thermodynamic properties of the
field-induced antiferromagnetic nuclear-spin ordered phase in bcc solid 3He by
measuring the melting pressure at temperatures down to 0.4 mK in magnetic
fields up to 15 T. The transition temperature from the paramagnetic phase is
reentrant with increasing field with a maximum at 10 T. This indicates that the
system is highly frustrated by the competing multiple-spin exchanges and
excludes other mechanisms related to the zero-point vacancies. The upper
critical field was estimated as 19.7 T, which reveals non-negligible
contributions from higher order exchanges beyond six spins. A considerable
softening of the spin waves in the ordered phase in low fields also suggests
the strong frustration.",0505177v1
2005-07-22,Multiple Scattering Theory for Two-dimensional Electron Gases in the Presence of Spin-Orbit Coupling,"In order to model the phase-coherent scattering of electrons in
two-dimensional electron gases in the presence of Rashba spin-orbit coupling, a
general partial-wave expansion is developed for scattering from a cylindrically
symmetric potential. The theory is applied to possible electron flow imaging
experiments using a moveable scanning probe microscope tip. In such
experiments, it is demonstrated theoretically that the Rashba spin-orbit
coupling can give rise to spin interference effects, even for unpolarized
electrons at nonzero temperature and no magnetic field.",0507528v2
2005-08-04,Electron and Spin Correlations in Semiconductor Heterostructures: Quantum Singwi-Tosi-Land-Sjolander Theory,"We apply the quantum Singwi-Tosi-Land-Sjolander (QSTLS) theory for a study of
many-body effects in the quasi-two-dimensional (Q2D) electron liquid (EL) in
GaAs/AlxGa1-xAs heterojunctions. The effect of the layer thickness is included
through a variational approach. We have calculated the density, spin-density
static structure factors, spin-dependent pair distribution functions (PDF) and
compared our results with those of two-dimensional (2D) EL given in earlier
papers. Using the static structure factors (SSF) we have calculated various
dynamic correlation functions such as spin-dependent local-field factors (LFF)
and effective potentials of the Q2D EL. We have also calculated the inverse
static dielectric function of the 2D and Q2D EL using different approximations.
We find that the effect of finite thickness on the dielectric function is
remarkable and at the intermediate values of wave number q there is a
significant difference between the QSTLS and STLS results.",0508121v1
2005-11-16,"Spin Hamiltonian, Competing Small Energy Scales and Incommensurate Long Range Order in the Highly Frustrated Gd3Ga5O12 Garnet Antiferromagnet","Despite the availability of a spin Hamiltonian for the Gd3Ga5O12 garnet (GGG)
for over twenty five years, there has so far been little theoretical insight
regarding the many unusual low temperature properties of GGG. Here we
investigate GGG in zero magnetic field using mean-field theory. We reproduce
the spin liquid-like correlations and, most importantly, explain the positions
of the sharp peaks seen in powder neutron diffraction experiments. We show that
it is crucial to treat accurately the long-range nature of the magnetic dipolar
interactions to allow for a determination of the small exchange energy scales
involved in the selection of the experimental ordering wave vector. Our results
show that the incommensurate order in GGG is classical in nature, intrinsic to
the microscopic spin Hamiltonian and not caused by weak disorder.",0511403v2
2006-01-07,Fermi Surface and Anisotropic Spin-Orbit Coupling of Sb(111) studied by Angle-Resolved Photoemission Spectroscopy,"High-resolution angle-resolved photoemission spectroscopy has been performed
on Sb(111) to elucidate the origin of anomalous electronic properties in
group-V semimetal surfaces. The surface was found to be metallic despite the
semimetallic character of bulk. We clearly observed two surface-derived Fermi
surfaces which are likely spin split, demonstrating that the spin-orbit
interaction plays a dominant role in characterising the surface electronic
states of group-V semimetals. Universality/disimilarity of the electronic
structure in Bi and Sb is discussed in relation to the granular
superconductivity, electron-phonon coupling, and surface charge/spin density
wave.",0601133v1
2006-02-22,Theory of the helical spin crystal: a candidate for the partially ordered state of MnSi,"MnSi is an itinerant magnet which at low temperatures develops a helical spin
density wave. Under pressure it undergoes a transition into an unusual
partially ordered state whose nature is debated. Here we propose that the
helical spin crystal (the magnetic analog of a solid) is a useful starting
point to understand partial order in MnSi. We consider different helical spin
crystals and determine conditions under which they may be energetically
favored. The most promising candidate has bcc structure and is reminiscent of
the blue phase of liquid-crystals in that it has line-nodes of magnetization
protected by symmetry. We introduce a Landau theory to study the properties of
these states, in particular the effect of crystal anisotropy, magnetic field
and disorder. These results compare favorably with existing data on MnSi from
neutron scattering and magnetic field studies. Future experiments to test this
scenario are also proposed.",0602529v3
2006-07-14,In-plane Anisotropy of the Magnetic Fluctuations in NaxCoO2-yH2O,"We report the $^{59}$Co NMR studies of the in-plane anisotropy of bilayer
hydrated Na$_{x}\mathrm{CoO_{2}} \cdot$$y\mathrm{H_{2}O}$ using a oriented
powder sample by a magnetic field in Fluorinert FC70. We found for the first
time the $ab$-plane anisotropy of the $^{59}$Co NMR Knight shift $K$, the
nuclear spin-lattice relaxation rate 1/$T_{1}$ and the nuclear spin-spin
relaxation rate 1/$T_{2}$ at a magnetic field $H \sim$ 7.5 T up to 200K. Below
75 K, the anisotropy of $K$ is large compared with that at high temperatures.
The hyperfine coupling constants seem to change around the temperature 150 K,
in which the bulk susceptibility $\chi$ shows broad minimum, suggesting a
change of the electronic state of CoO$_{2}$ plane. 1/$T_{1}$ also shows a
significant anisotropy, which cannot be explained only by the anisotropy of the
hyperfine coupling constants nor the anisotropic uniform spin susceptibility.
The difference in the in-plane anisotropy of $T_{1}$ from that of $K$ indicates
that the magnetic fluctuation at a finite wave vector $\vec{q} \neq 0$ is also
anisotropic and the anisotropy is different from that at $\vec{q} = 0$.",0607368v1
2006-09-01,Spin momentum transfer and Oersted field induce a vortex nano-oscillator in thin ferromagnetic film devices,"A nonlinear model of spin-wave excitation involving a point contact in a thin
ferromagnetic film that includes the Oersted magnetic field contribution is
presented. We consider the case of an external dc field applied perpendicular
to the film plane. The two-dimensional vectorial model reduces to an exact
one-dimensional equation of motion. Large-amplitude vortex modes are computed,
which represent a fundamental shift in the geometrical understanding of spin
transfer nano-oscillators. Odd symmetry forces the magnetization to be pinned
in the center of the point contact. Using the spin transfer efficiency as a
single fitting parameter, the calculated dependence of frequency on current and
contact size is in good agreement with recent experimental data. These vortex
states are geometrically very different from previously computed cylindrical
modes that exhibit even symmetry when the Oersted field is ignored.",0609030v2
2006-10-24,Scattering on the lateral one-dimensional superlattice with spin-orbit coupling,"The problem of scattering of the two-dimensional electron gas on the lateral
one-dimensional superlattice both having different strengths of Rashba
spin-orbit coupling is investigated. The scattering is considered for all the
electron states on a given Fermi level. The distribution of spin density
components along the superlattice is studied for the transmitted states where
the formation of standing waves is observed. It is found that the shape of spin
density distribution is robust against the variations of the Rashba coupling
constants, the superlattice potential strength, and the Fermi level in the
electron gas.",0610657v3
2006-11-03,Rashba Spin Interferometer,"A spin interferometer utilizing the Rashba effect is proposed. The novel
design is composed of a one-dimensional (1D) straight wire and a 1D half-ring.
By calculating the norm of the superposed wave function, we derive analytical
expressions to describe the spin interference spectrum as a function of the
Rashba coupling strength. Presented spin interference results are identified to
include (i) the quantum-mechanical 4pi rotation effect, (ii) geometric effect,
and (iii) Shubnikov-de Haas-like beating effect.",0611077v2
2006-11-28,Effect of Spin Fluctuations on Phonon-Mediated Superconductivity in the Vicinity of a Quantum Critical Point,"We consider an s-wave superconductor in the vicinity of a second-order
ferromagnetic (FM) or spin-density-wave (SDW) quantum critical point (QCP),
where the superconductivity and magnetism arise from separate mechanisms. The
quantum critical spin fluctuations reduce the superconducting T_c. Near a FM
QCP, we find that T_c falls to zero as 1/|ln kappa| in 3D and as kappa in 2D,
where kappa ~ |J-J_c|^nu is the inverse correlation length of the spin
fluctuations, and measures the distance |J-J_c| from the quantum critical
point. SDW quantum critical fluctuations, on the other hand, suppress T_c to
zero as sqrt(kappa) in 2D, and suppress T_c only to a finite value in 3D,
producing a cusp of the form (const + |J-J_c|^nu).",0611718v1
2007-01-09,Twenty years of magnon Bose condensation and spin current superfluidity in 3He-B,"20 years ago a new quantum state of matter was discovered and identified. The
observed dynamic quantum state of spin precession in superfluid 3He-B bears the
properties of spin current superfluidity, Bose condensation of spin waves --
magnons, off-diagonal long-range order and related phenomena of quantum
coherence",0701180v13
2007-01-10,Correlations and entanglements in a few-electron quantum dot without Zeeman splitting,"We explore the correlations and entanglements of exact-diagonalized
few-electron wave functions in a quantum dot in magnetic fields without the
Zeeman splitting. With the increase of the field, the lowest states with
different spins gradually form a narrow band and the electronic states undergo
a transition from liquids to rotating Wigner molecules which are accompanied by
different characters of charge correlations. For both the liquid and crystal
states, the spin conditional probability densities show magnetic couplings
between the particles which depend on the particle numbers, the total spins and
the angular momenta of the states. The von Neumann entropies show the
spin-dependent entanglements between electrons. The regular magnetic-coupling
oscillations and converging entanglement entropies emerge in the rotating
Wigner molecular states.",0701189v1
2007-01-22,Fractional Spin Hall Effect in Atomic Bose Gases,"We propose fractional spin hall effect (FSHE) by coupling pseudospin states
of cold bosonic atoms to optical fields. The present scheme is an extension to
interacting bosonic system of the recent work \cite{liu,zhu} on optically
induced spin hall effect in non-interacting atomic system. The system has two
different types of ground states. The 1st type of ground state is a 1/3-factor
Laughlin function, and has the property of chiral - anti-chiral interchange
antisymmetry, while the 2nd type is shown to be a 1/4-factor wave function with
chiral - anti-chiral symmetry. The fractional statistics corresponding to the
fractional spin Hall states are studied in detail, and are discovered to be
different from that corresponding to the fractional quantum Hall (FQH) states.
Therefore the present FSHE can be distinguished from FQH regime in the
measurement.",0701506v3
2007-02-01,Quantum Magnetism and Superconductivity,"The spin of the neutron allows neutron scattering to reveal the magnetic
structure and dynamics of materials over nanometre length scales and picosecond
timescales. Neutron scattering is particularly in demand in order to understand
high-temperature superconductors, which lie close to magnetically ordered
phases, and highly correlated metals with giant effective fermion masses, which
lie close to magnetic order or pass through a mysterious phase of hidden order
before becoming superconducting. Neutron scattering also is the probe of choice
for revealing new phases of matter and new particles, as seen in the surprising
behaviour of quantum spin chains and ladders where mass gaps and excited
triplons replace conventional spin waves. Examples are given of quantum
phenomena where neutron scattering has played a defining role that challenges
current understanding of condensed matter.",0702024v1
2007-03-11,Non-Perturbative Treatment of Charge and Spin Fluctuations in the Two-Dimensional Extended Hubbard Model: Extended Two-Particle Self-Consistent Approach,"We study the spin and charge fluctuations of the extended Hubbard model (EHM)
with on-site interaction U and first neighbor interaction V on the
two-dimensional square lattice in the weak to intermediate coupling regime. We
propose an extension of the two-particle self-consistent (ETPSC) approximation
that includes the effect of functional derivatives of the pair correlation
functions on irreducible spin and charge vertices. These functional derivatives
were ignored in our previous work. We evaluate them assuming particle-hole
symmetry. The resulting theory satisfies conservations laws and the
Mermin-Wagner theorem. Our current results are in much better agreement with
benchmark Quantum Monte-Carlo (QMC) results. As a function of U and V, we can
determine the crossover temperatures towards renormalized classical regimes
where either spin or charge fluctuations dominate. The dominant wave vector is
self-determined by the approach.",0703270v1
1996-09-28,A Spin-Statistics Theorem for Certain Topological Geons,"We review the mechanism in quantum gravity whereby topological geons,
particles made from non-trivial spatial topology, are endowed with nontrivial
spin and statistics. In a theory without topology change there is no
obstruction to ``anomalous'' spin-statistics pairings for geons. However, in a
sum-over-histories formulation including topology change, we show that
non-chiral abelian geons do satisfy a spin-statistics correlation if they are
described by a wave function which is given by a functional integral over
metrics on a particular four-manifold. This manifold describes a topology
changing process which creates a pair of geons from $R^3$.",9609064v1
1997-11-03,Two Kerr black holes with axisymmetric spins: An improved Newtonian model for the head-on collision and gravitational radiation,"We present a semi-analytical approach to the interaction of two (originally)
Kerr black holes through a head-on collision process. An expression for the
rate of emission of gravitational radiation is derived from an exact solution
to the Einstein's field equations. The total amount of gravitational radiation
emitted in the process is calculated and compared to current numerical
investigations. We find that the spin-spin interaction increases the emission
of gravitational wave energy up to 0.2% of the total rest mass. We discuss also
the possibility of spin-exchange between the holes.",9711005v1
1998-08-27,Observable frequency shifts via spin-rotation coupling,"The phase perturbation arising from spin-rotation coupling is developed as a
natural extension of the celebrated Sagnac effect. Experimental evidence in
support of this phase shift, however, has yet to be realized due to the
exceptional sensitivity required. We draw attention to the relevance of a
series of experiments establishing that circularly polarized light, upon
passing through a rotating half-wave plate, is changed in frequency by twice
the rotation rate. These experiments may be interpreted as demonstrating the
role of spin-rotation coupling in inducing this frequency shift, thus providing
direct empirical verification of the coupling of the photon helicity to
rotation. A neutron interferometry experiment is proposed which would be
sensitive to an analogous frequency shift for fermions. In this arrangement,
polarized neutrons enter an interferometer containing two spin flippers, one of
which is rotating while the other is held stationary. An observable beating in
the transmitted neutron beam intensity is predicted.",9808077v1
2005-11-01,The volume operator for spin networks with planar or cylindrical symmetry,"This paper constructs a kinematic basis for spin networks with planar or
cylindrical symmetry, by exploiting the fact that the basis elements are
representations of an O(3) subgroup of O(4). The action of the volume operator
on this basis gives a difference equation for the eigenvalues and eigenvectors
of the volume operator. For basis elements of low spin, the difference equation
can be solved readily on a computer. For higher spins, I solve for the
eigenvalues using a WKBJ method. This paper considers only the case where the
gravitational wave can have both polarizations. The single polarization case is
considered in a spearate paper.",0511005v2
2006-03-03,"Reconstructing Quantum Geometry from Quantum Information: Area Renormalisation, Coarse-Graining and Entanglement on Spin Networks","After a brief review of spin networks and their interpretation as wave
functions for the (space) geometry, we discuss the renormalisation of the area
operator in loop quantum gravity. In such a background independent framework,
we propose to probe the structure of a surface through the analysis of the
coarse-graining and renormalisation flow(s) of its area. We further introduce a
procedure to coarse-grain spin network states and we quantitatively study the
decrease in the number of degrees of freedom during this process. Finally, we
use these coarse-graining tools to define the correlation and entanglement
between parts of a spin network and discuss their potential interpretation as a
natural measure of distance in such a state of quantum geometry.",0603008v1
1992-10-01,Natural Hadronic Degrees of Freedom for an Effective QCD Action in the Front Form,"On the one hand any effective action of the QCD,
$S[\pi,\,\rho,\,\omega,\ldots,N,\,\overline N,\,\Delta^{3/2},\ldots]$, would
involve, at least in principle, a tower of hadronic fields of all spins; on the
other hand the front form of the field theory has emerged as an appropriate
framework to investigate the high energy behaviour of many systems. Motivated
by these simple considerations we present a systematic formalism which
explicitly provides the front form fields appropriate for constructing a
$S[\pi,\,\rho,\,\omega,\ldots,N,\,\overline N,\,\Delta^{3/2},\ldots]$. Further,
a transformation matrix $\Omega(j)$ is constructed which determines how the
front form hadronic fields superimpose to yield the more familiar instant form
fields. Explicit results for the front form hadronic fields up to spin two are
catalogued in appendixes. For spin one half, the $\Omega(1/2)$ coincides with
the celebrated ``Melosh transformation.'' The formalism, without explicitly
invoking any wave equations, reproduces spin one half front-form results of
Lepage and Brodsky, and Dziembowski.",9210204v1
1993-09-23,Physics of Polarized pp Collisions,"I will summarize the physics that can be investigated with polarized pp
collisions. It is technically feasible to use the RHIC collider for
accelerating highly polarized protons to a center-of-mass energy of about 400
GeV, with high luminosity. Such collisions can be used to probe the
spin-dependence of hard collisions and of partons in a hadron, including the
gluons. There are interesting twist 3 phenomena that are likely to be
significant in view of the large transverse spin asymmetries at lower energies;
this will have important implications for the spin structure of the proton wave
function. Recent theoretical developments include the possibility of probing
the spin of transversely polarized quarks via asymmetries in the jets they
make.",9309317v1
2005-01-08,Azimuthal asymmetries in unpolarized Drell-Yan events on nuclear targets,"We show that for Drell-Yan events by unpolarized hadronic projectiles and
nuclear targets, azimuthal asymmetries can arise from the nuclear distortion of
the hadronic projectile wave function, typically a spin-orbit effect occurring
on the nuclear surface. The asymmetry depends on quantities that enter also the
spin asymmetry in the corresponding Drell-Yan event on polarized free nucleonic
targets. Hence, this study can be of help in exploring the spin structure of
the nucleon, in particular the transverse spin distribution of partons inside
the proton. All arguments can be extended also to antinucleon projectiles and,
consequently, apply to possible future measurements involving nuclear targets
at the foreseen HESR ring at GSI.",0501055v2
1994-03-29,A Field Theory Approach to the $t$-$J$ Model and the Spin-Charge Separation,"We analyze the $t$-$J$ model using the ${\rm CP}^1$ representation for the
slave operators (holons and spinons) which is particularly suited to study the
phenomenon of the spin-charge separation in strongly correlated electron
systems. In particular, we show that for the one-dimensional $t$-$J$ model
below half-filling the low energy effective dynamics of the spin and charge
degrees of freedom is represented in the continuum limit by a ${\rm CP}^1$
model with a topological term, minimally coupled to a massless Dirac field with
a four-fermion interaction. The bosonic term of this action describes the spin
waves produced by the spinons, while the fermionic term represents the low
energy charge excitations. This theory exhibits explicitly a local abelian
gauge invariance.",9403176v1
1996-03-26,A Universal Model of D=4 Spinning Particle,"A universal model for D=4 spinning particle is constructed with the
configuration space chosen as ${\bf R}^{3,1}\times S^2$, where the sphere
corresponds to the spinning degrees of freedom. The Lagrangian includes all the
possible world--line first order invariants of the manifold. Each combination
of the four constant parameters entering the Lagrangian gives the model, which
describes the proper irreducible Poincar\'e dynamics both at the classical and
quantum levels, and thereby the construction uniformly embodies the massive,
massless and continuous helicity cases depending upon the special choice of the
parameters. For the massive case, the connection with the Souriau approach to
elementary systems is established. Constrained Hamiltonian formulation is built
and Dirac canonical quantization is performed for the model in the covariant
form. An explicit realization is given for the physical wave functions in terms
of smooth tensor fields on ${\bf R}^{3,1}\times S^2$. One-parametric family of
consistent interactions with general electromagnetic and gravitational fields
is introduced in the massive case. The spin tensor is shown to satisfy the
Frenkel-Nyborg equation with arbitrary fixed gyromagnetic ratio in a limit of
weakly varying electromagnetic field.",9603174v1
1998-07-17,Classical and quantum theories of spin,"A great effort has been devoted to formulate a classical relativistic theory
of spin compatible with quantum relativistic wave equations. The main
difficulty in order to connect classical and quantum theories rests in finding
a parameter which plays the role of proper time at a purely quantum level. We
present a partial review of several proposals of classical and quantum spin
theories from the pioneer works of Thomas and Frenkel, revisited in the
classical BMT work, to the semiclassical model of Barut and Zanghi [Phys. Rev.
Lett. 52, 2009 (1984)]. We show that the last model can be obtained from a
semiclassical limit of the Feynman proper time parametrization of the Dirac
equation. At the quantum level we derive spin precession equations in the
Heisenberg picture. Analogies and differences with respect to classical
theories are discussed in detail.",9807131v1
1999-10-06,"Structure of Spinning Particle Suggested by Gravity, Supergravity and Low Energy String Theory","The structure of spinning particle suggested by the rotating Kerr-Newman
(black hole) solution, super-Kerr-Newman solution and the Kerr-Sen solution to
low energy string theory is considered. Main peculiarities of the Kerr spinning
particle are discussed: a vortex of twisting principal null congruence,
singular ring and the Kerr source representing a rotating relativistic disk of
the Compton size. A few stringy structures can be found in the real and complex
Kerr geometry.
  Low-energy string theory predicts the existence of a heterotic string placed
on the sharp boundary of this disk. The obtained recently supergeneralization
of the Kerr-Newman solution suggests the existence of extra axial singular line
and fermionic traveling waves concentrating near these singularities.
  We discuss briefly a possibility of experimental test of these predictions.",9910045v1
2005-10-31,Extension of the Shirafuji model for Massive Particles with Spin,"We extend the Shirafuji model for massless particles with primary spacetime
coordinates and composite four-momenta to a model for massive particles with
spin and electric charge. The primary variables in the model are the spacetime
four-vector, four scalars describing spin and charge degrees of freedom as well
as a pair of Weyl spinors. The geometric description proposed in this paper
provides an intermediate step between the free purely twistorial model in
two-twistor space in which both spacetime and four-momenta vectors are
composite, and the standard particle model, where both spacetime and
four-momenta vectors are elementary. We quantize the model and find explicitly
the first-quantized wavefunctions describing relativistic particles with mass,
spin and electric charge. The spacetime coordinates in the model are not
commutative; this leads to a wavefunction that depends only on one covariant
projection of the spacetime four-vector (covariantized time coordinate)
defining plane wave solutions.",0510266v1
2007-02-07,Massive Particle Model with Spin from a Hybrid (spacetime-twistorial) Phase Space Geometry and Its Quantization,"We extend the Shirafuji model for massless particles with primary spacetime
coordinates and composite four-momenta to a model for massive particles with
spin and electric charge. The primary variables in the model are the spacetime
four-vector, four scalars describing spin and charge degrees of freedom as well
as a pair of Weyl spinors. The geometric description proposed in this paper
provides an intermediate step between the free purely twistorial model in
two-twistor space in which both spacetime and four-momenta vectors are
composite, and the standard particle model, where both spacetime and
four-momenta vectors are elementary. We quantize the model and find explicitly
the first-quantized wavefunctions describing relativistic particles with mass,
spin and electric charge. The spacetime coordinates in the model are not
commutative; this leads to a wavefunction that depends only on one covariant
projection of the spacetime four-vector defining plane wave solutions.",0702050v1
2003-04-23,Shapes of the Proton,"A model proton wave function, constructed using Poincare invariance, and
constrained by recent electromagnetic form factor data, is used to study the
shape of the proton. Spin-dependent quark densities are defined as matrix
elements of density operators in proton states of definite spin-polarization,
and shown to have an infinite variety of non-spherical shapes. For high
momentum quarks with spin parallel to that of the proton, the shape resembles
that of a peanut, but for quarks with anti-parallel spin the shape is that of a
bagel.",0304076v2
2004-10-22,"Virtual photon asymmetry for confined, interacting Dirac particles with spin symmetry","We study the Bjorken x dependence of the virtual photon spin asymmetry in
polarized deep inelastic scattering of electrons from hadrons. We use an
exactly solved relativistic potential model of the hadron, treating the
constituents as independent massless Dirac particles bound to an infinitely
massive force center. The potential is chosen to have spin symmetry and a
linear radial dependence with spherical symmetry. The effect of interactions of
the struck constituent with the remainder of the target on the longitudinal
photon asymmetry is demonstrated. In particular, the small-x suppression of the
photon asymmetry observed in polarized deep inelastic scattering from the
proton is shown to be a consequence of these interactions. The effect of
p--wave components of the Dirac wave function, long known to give an important
contribution to the spin of hadrons, is explicitly demonstrated through their
interference with the s--wave term.",0410093v1
2006-10-10,Nucleon-Nucleon Potential: Drift Effects,"In the rest frame of a many-body system, used in the calculation of its
static and scattering properties, the center of mass of a two-body subsystem is
allowed to drift. We show, in a model independent way, that drift corrections
to the nucleon-nucleon potential are relatively large and arise from both one-
and two-pion exchange processes. As far as chiral symmetry is concerned,
corrections to these processes begin respectively at $\cO(q^2)$ and $\cO(q^4)$.
The two-pion exchange interaction also yields a new spin structure, that
promotes the presence of $P$ waves in trinuclei and is associated with profile
functions which do not coincide with neither central nor spin-orbit ones. In
principle, the new spin terms should be smaller than the $\cO(q^3)$ spin-orbit
components. However, in the isospin even channel, a large contribution reverts
this expectation and gives rise to the prediction of important drift effects.",0610046v1
2001-06-25,A theory of electromagnetism with uniquely defined potential and covariant conserved spin,"A theory of electromagnetism is proposed that is based on the Fermi
Lagrangian, which is symmetric under electromagnetic spin rotation. Its
features are: - the four-potential is unambiguously determined by the
inhomogeneous wave equation and boundary conditions at infinity. - the Lorenz
condition and minimal coupling then follow from charge conservation. -
electromagnetic spin is conserved and spin operators can be defined without
sacrificing covariance. - quantisation is fully covariant, without redefining
the metric. - all experimental predictions are the same as in the standard
theory. This result proves that electromagnetic gauge invariance is redundant
as a fundamental principle of physics.",0106078v1
1999-03-22,The Dirac Oscillator. A relativistic version of the Jaynes--Cummings model,"The dynamics of wave packets in a relativistic Dirac oscillator is compared
to that of the Jaynes-Cummings model. The strong spin-orbit coupling of the
Dirac oscillator produces the entanglement of the spin with the orbital motion
similar to what is observed in the model of quantum optics. The collapses and
revivals of the spin which result extend to a relativistic theory our previous
findings on nonrelativistic oscillator where they were known under the name of
`spin-orbit pendulum'. There are important relativistic effects (lack of
periodicity, zitterbewegung, negative energy states). Many of them disappear
after a Foldy-Wouthuysen transformation.",9903073v1
2000-07-30,Relativistic Aharonov-Casher Phase in Spin One,"The Aharonov-Casher (AC) phase is calculated in relativistic wave equations
of spin one. The AC phase has previously been calculated from the Dirac-Pauli
equation using a gauge-like technique \cite{MK1,MK2}. In the spin-one case, we
use Kemmer theory (a Dirac-like particle theory) to calculate the phase in a
similar manner. However the vector formalism, the Proca theory, is more widely
known and used. In the presence of an electromagnetic field, the two theories
are `equivalent' and may be transformed into one another. We adapt these
transformations to show that the Kemmer theory results apply to the Proca
theory. Then we calculate the Aharonov-Casher phase for spin-one particles
directly in the Proca formalism.",0007118v2
2002-07-17,Torus quantization for spinning particles,"We derive semiclassical quantization conditions for systems with spin. To
this end one has to define the notion of integrability for the corresponding
classical system which is given by a combination of the translational motion
and classical spin precession. We determine the geometry of the invariant
manifolds of this product dynamics which support semiclassical solutions of the
wave equation. The semiclassical quantization conditions contain a new term,
which is of the same order as the Maslov correction. This term is identified as
a rotation angle for a classical spin vector. Applied to the relativistic
Kepler problem the procedure sheds some light on the amazing success of
Sommerfeld's theory of fine structure [Ann. Phys. (Leipzig) 51 (1916) 1-94].",0207095v1
2003-06-04,Non-relativistic proofs of the spin-statistics connection,"A recent paper by Peshkin [1] has drawn attention again to the problem of
understanding the spin statistics connection in non-relativistic quantum
mechanics. Allen and Mondragon [2] has pointed out correctly some of the flaws
in Peshkin's arguments which are based on the single valuedness under rotation
of the wave functions of systems of identical particles. We examine carefully
the claim that is made in the title of [2] that there can be ``no
spin-statistics connection in non-relativistic quantum mechanics''. We show
that we can derive the spin statistics connection for non-relativistic quantum
field theories which have equations of motion of the Hamiltonian type based on
SU(2) invariance of the Lagrangian. The formalism and machinary of
non-relativistic quantum field theory as opposed to usual quantum mechanics is
necessary for constructing our proof.",0306033v2
2007-04-03,Fabrication of half metallicity in a ferromagnetic metal,"We investigate the growth of half metallic phase in a ferromagnetic material
using state-of-the-art full potential linearized augmented plane wave method.
To address the issue, we have substituted Ti at the Ru-sites in SrRuO3, where
SrRuO3 is a ferromagnetic material. Calculated results establish Ti4+ valence
states (similar to SrTiO3), which was predicted experimentally. Thus, Ti
substitution dilutes the Ru-O-Ru connectivity, which is manifested in the
calculated results in the form of significant band narrowing leading to finite
gap between t2g and eg bands. At 75% substitution, a large gap (> 2 eV) appears
at the Fermi level, e_F in the up spin density of states, while the down spin
states contributes at e_F characterizing the system a half-metallic
ferromagnet. The t2g - eg gap can be tailored judiciously by tuning Ti
concentrations to minimize thermal effects, which is often the major bottleneck
to achieve high spin polarization at elevated temperatures in other materials.
This study, thus, provides a novel but simple way to fabricate half-metallicity
in ferromagnetic materials, which are potential candidates for spin-based
technology.",0704.0321v1
2007-05-03,"On the Dynamical Ferromagnetic, Quantum Hall, and Relativistic Effects on the Carbon Nanotubes Nucleation and Growth Mechanism","The mechanism of carbon nanotube (CNT) nucleation and growth has been a
mystery for over 15 years. Prior models have attempted the extension of older
classical transport mechanisms. In July 2000, a more detailed and accurate
nonclassical, relativistic mechanism was formulated considering the detailed
dynamics of the electronics of spin and orbital rehybridization between the
carbon and catalyst via novel mesoscopic phenomena and quantum dynamics.
Ferromagnetic carbon was demonstrated. Here, quantum (Hall) effects and
relativistic effects of intense many body spin-orbital interactions for novel
orbital rehybridization dynamics (Little Effect) are proposed in this new
dynamical magnetic mechanism. This dynamic ferromagnetic mechanism is proven by
imposing dynamic and static magnetic fields during CNT syntheses and observing
the different influence of these external magnetic environments on the
catalyzing spin currents and spin waves and the resulting CNT formation.",0705.0407v1
2007-05-25,Tuning phase transition between quantum spin Hall and ordinary insulating phases,"An effective theory is constructed for analyzing a generic phase transition
between the quantum spin Hall and the insulator phases. Occurrence of
degeneracies due to closing of the gap at the transition are carefully
elucidated. For systems without inversion symmetry the gap-closing occurs at
\pm k_0(\neq G/2) while for systems with inversion symmetry, the gap can close
only at wave-numbers k=G/2, where G is a reciprocal lattice vector. In both
cases, following a unitary transformation which mixes spins, the system is
represented by two decoupled effective theories of massive two-component
fermions having masses of opposite signs. Existence of gapless helical modes at
a domain wall between the two phases directly follows from this formalism. This
theory provides an elementary and comprehensive phenomenology of the quantum
spin Hall system.",0705.3696v2
2007-05-31,X-ray Microdiffraction Images of Antiferromagnetic Domain Evolution in Chromium,"Magnetic x-ray diffraction combined with x-ray focusing optics is used to
image individual antiferromagnetic spin density wave domains in a chromium
single crystal at the micron scale. The cross section for non-resonant magnetic
x-ray scattering depends on the antiferromagnetic modulation vector and spin
polarization direction and allows these quantities to be extracted
independently. The technique is used to show that the broadening of the
nominally first order ""spin-flip"" transition at 123 K, at which the spins
rotate by 90 deg., originates at the walls between domains with orthogonal
modulation vectors. During cooling the transition begins at these walls and
progresses inwards. The modulation-vector domains are themselves unchanged.",0705.4636v1
2007-06-01,Nanocrystals in silicon photonic crystal standing-wave cavities as spin-photon phase gates for quantum information processing,"By virtue of a silicon high-Q photonic crystal nanocavity, we propose and
examine theoretically interactions between a stationary electron spin qubit of
a semiconductor nanocrystal and a flying photon qubit. Firstly, we introduce,
derive and demonstrate for the first time the explicit conditions towards
realization of a spin-photon two-qubit phase gate, and propose these
interactions as a generalized quantum interface for quantum information
processing. Secondly, we examine novel single-spin-induced reflections as
direct evidence of intrinsic bare and dressed modes in our coupled
nanocrystal-cavity system. The excellent physical integration of this silicon
system provides tremendous potential for large-scale quantum information
processing.",0706.0064v2
2007-09-23,Quantum dynamics and entanglement of spins on a square lattice,"Bulk magnetism in solids is fundamentally quantum mechanical in nature. Yet
in many situations, including our everyday encounters with magnetic materials,
quantum effects are masked, and it often suffices to think of magnetism in
terms of the interaction between classical dipole moments. Whereas this
intuition generally holds for ferromagnets, even as the size of the magnetic
moment is reduced to that of a single electron spin (the quantum limit), it
breaks down spectacularly for antiferromagnets, particularly in low dimensions.
Considerable theoretical and experimental progress has been made in
understanding quantum effects in one-dimensional quantum antiferromagnets, but
a complete experimental description of even simple two-dimensional
antiferromagnets is lacking. Here we describe a comprehensive set of neutron
scattering measurements that reveal a non-spin-wave continuum and strong
quantum effects, suggesting entanglement of spins at short distances in the
simplest of all two-dimensional quantum antiferromagnets, the square lattice
Heisenberg system.",0709.3632v1
2007-10-09,Long wavelength spin dynamics of ferromagnetic condensates,"We obtain the equations of motion for a ferromagnetic Bose condensate of
arbitrary spin in the long wavelength limit. We find that the magnetization of
the condensate is described by a non-trivial modification of the
Landau-Lifshitz equation, in which the magnetization is advected by the
superfluid velocity. This hydrodynamic description, valid when the condensate
wavefunction varies on scales much longer than either the density or spin
healing lengths, is physically more transparent than the corresponding
time-dependent Gross-Pitaevskii equation. We discuss the conservation laws of
the theory and its application to the analysis of the stability of magnetic
helices and Larmor precession. Precessional instabilities in particular provide
a novel physical signature of dipolar forces. Finally, we discuss the
anisotropic spin wave instability observed in the recent experiment of
Vengalattore et. al. (Phys. Rev. Lett. 100, 170403, (2008)).",0710.1848v2
2007-10-16,Quantum/Classical Interface: Fermion Spin,"Although intrinsic spin is usually viewed as a purely quantum property with
no classical analog, we present evidence here that fermion spin has a classical
origin rooted in the geometry of three-dimensional physical space. Our approach
to the quantum/classical interface is based on a formulation of relativistic
classical mechanics that uses spinors. Spinors and projectors arise naturally
in the Clifford's geometric algebra of physical space and not only provide
powerful tools for solving problems in classical electrodynamics, but also
reproduce a number of quantum results. In particular, many properites of
elementary fermions, as spin-1/2 particles, are obtained classically and relate
spin, the associated g-factor, its coupling to an external magnetic field, and
its magnetic moment to Zitterbewegung and de Broglie waves. The relationship is
further strengthened by the fact that physical space and its geometric algebra
can be derived from fermion annihilation and creation operators. The approach
resolves Pauli's argument against treating time as an operator by recognizing
phase factors as projected rotation operators.",0710.3144v2
2007-10-26,Mesoscopic Spin-Boson Models of Trapped Ions,"Trapped ions arranged in Coulomb crystals provide us with the elements to
study the physics of a single spin coupled to a boson bath. In this work we
show that optical forces allow us to realize a variety of spin-boson models,
depending on the crystal geometry and the laser configuration. We study in
detail the Ohmic case, which can be implemented by illuminating a single ion
with a travelling wave. The mesoscopic character of the phonon bath in trapped
ions induces new effects like the appearance of quantum revivals in the spin
evolution.",0710.5145v2
2007-10-26,Circularization and Final Spin in Eccentric Binary Black Hole Inspirals,"We present results from numerical relativity simulations of equal mass,
non-spinning binary black hole inspirals and mergers with initial
eccentricities e <= 0.8 and coordinate separations D >= 12 M of up to 9 orbits
(18 gravitational wave cycles). We extract the mass M_f and spin a_f of the
final black hole and find, for eccentricities e < 0.4, that a_f/M_f = 0.69 and
M_f/M_adm = 0.96 are independent of the initial eccentricity, suggesting that
the binary has circularized by the merger time. For e > 0.5, the black holes
plunge rather than orbit, and we obtain a maximum spin parameter a_f/M_f = 0.72
around e = 0.5.",0710.5167v2
2007-10-29,Disordered loops in the two-dimensional antiferromagnetic spin-fermion model,"The spin-fermion model has long been used to describe the quantum-critical
behavior of 2d electron systems near an antiferromagnetic (AFM) instability.
Recently, the standard procedure to integrate out the fermions to obtain an
effective action for spin waves has been questioned in the clean case. We show
that in the presence of disorder, the single fermion loops display two
crossover scales: upon lowering the energy, the singularities of the clean
fermionic loops are first cut off, but below a second scale new singularities
arise that lead again to marginal scaling. In addition, impurity lines between
different fermion loops generate new relevant couplings which dominate at low
energies. We outline a non-linear sigma model formulation of the single-loop
problem, which allows to control the higher singularities and provides an
effective model in terms of low-energy diffusive as well as spin modes.",0710.5458v1
2007-11-29,"First principles study of Sc, Ti and V doped Na$_n$(n =4, 5, 6) clusters: Enhanced magnetic moments","Theoretical studies on the geometry, electronic structure and spin
multiplicity of Sc, Ti and V doped Na$_n$ (n = 4, 5, 6) clusters have been
carried out within a gradient corrected density functional approach. Two
complementary approaches including all-electron calculations on free clusters,
and supercell calculations using planewave pseudopotential and projector
augmented wave formalisms have been carried out. It is shown that spin magnetic
moments of the transition metal atoms, the magnitude of host polarization, and
the sign of the host polarization all change with the number of alkali atoms.
In particular the transition metal atoms are shown to attain spin moments that
are higher than their atomic values. The role of hybridization between the
transition atom d-states and the alkali $sp$-states is highlighted to account
for the evolutions in the spin moments and host polarization.",0711.4660v1
2007-12-03,Finite size effects on spin-torque driven ferromagnetic resonance in spin-valves with a Co/Ni synthetic free layer,"Spin-torque driven ferromagnetic resonance (ST-FMR) is used to study magnetic
excitations in Co/Ni synthetic layers confined in nanojunctions. Field swept
ST-FMR measurements were conducted with a magnetic field applied perpendicular
to the layer surface. The resonance lines were measured under low amplitude
excitation in a linear response regime. The resulting resonance fields were
compared with those obtained using conventional rf field driven FMR on extended
films with the same Co/Ni layer structure. A lower resonance field is found in
confined structures. The effect of both dipolar fields acting on the Co/Ni
layer emanating from other magnetic layers in the device and finite size
effects on the spin wave spectrum are discussed.",0712.0404v2
2007-12-12,Electric field effect on electron spin splitting in SiGe/Si quantum wells,"Effect of electric field on spin splitting in SiGe quantum wells (QWs) has
been studied theoretically. Microscopical calculations of valley and spin
splittings are performed in the effective $sp^3d^5s^*$ tight-binding model. The
splittings oscillate as a function of the QW width due to inter-valley
reflection of the electron wave off the interfaces. In accordance with the
symmetry considerations additional electric-field-induced terms appear in the
electron spin-dependent Hamiltonian. The oscillations of splitting are
suppressed in rather low electric fields. The tight-binding calculations have
been analyzed by using the envelope function approach extended to asymmetrical
QWs.",0712.1955v2
2007-12-14,Spin-orbit coupled Bose-Einstein condensates,"We consider a many-body system of pseudo-spin-1/2 bosons with spin-orbit
interactions, which couple the momentum and the internal pseudo-spin degree of
freedom created by spatially varying laser fields. The corresponding single-
particle spectrum is generally anisotropic and contains two degenerate minima
at finite momenta. At low temperatures, the many-body system condenses into
these minima generating a new type of entangled Bose-Einstein condensate. We
show that in the presence of weak density-density interactions the many-body
ground state is characterized by a twofold degeneracy. The corresponding
many-body wave function describes a condensate of ``left-'' and
``right-moving'' bosons. By fine-tuning the parameters of the laser field, one
can obtain a bosonic version of the spin-orbit coupled Rashba model. In this
symmetric case, the degeneracy of the ground state is very large, which may
lead to phases with nontrivial topological properties. We argue that the
predicted new type of Bose-Einstein condensates can be observed experimentally
via time-of-flight imaging, which will show characteristic multipeak structures
in momentum distribution.",0712.2256v3
2007-12-20,Fulde-Ferrell-Larkin-Ovchinnikov superfluidity in one-dimensional optical lattices,"Spin-polarized attractive Fermi gases in one-dimensional (1D) optical
lattices are expected to be remarkably good candidates for the observation of
the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase. We model these systems with
an attractive Hubbard model with population imbalance. By means of the
density-matrix renormalization-group method we compute the pairing correlations
as well as the static spin and charge structure factors in the whole range from
weak to strong coupling. We demonstrate that pairing correlations exhibit
quasi-long range order and oscillations at the wave number expected from FFLO
theory. However, we also show by numerically computing the mixed spin-charge
static structure factor that charge and spin degrees of freedom appear to be
coupled already for small imbalance. We discuss the consequences of this
coupling for the observation of the FFLO phase, as well as for the
stabilization of the quasi-long range order into long-range order by coupling
many identical 1D systems, as in quasi-1D optical lattices.",0712.3364v1
2008-01-11,Spin-orbit effects on two-electron states in nanowhisker double quantum dots,"We investigate theoretically the combined effects of the electron-electron
and the Rashba spin-orbit interactions on two electrons confined in
quasi-one-dimensional AlInSb-based double quantum dots. We calculate the
two-electron wave functions and explore the interplay between these two
interactions on the energy levels and the spin of the states. The energy
spectrum as a function of an applied magnetic field shows crossings and
anticrossings between triplet and singlet states, associated with level mixing
induced by the spin-orbit coupling. We find that the fields at which these
crossings occur can be naturally controlled by the interdot barrier width,
which controls the exchange integral in the structure.",0801.1808v1
2008-02-11,Local density of states of 1D Mott insulators and CDW states with a boundary,"We determine the local density of states (LDOS) of one-dimensional
incommensurate charge density wave (CDW) states in the presence of a strong
impurity potential, which is modeled by a boundary. We find that the CDW gets
pinned at the impurity, which results in a singularity in the Fourier transform
of the LDOS at momentum 2k_F. At energies above the spin gap we observe
dispersing features associated with the spin and charge degrees of freedom
respectively. In the presence of an impurity magnetic field we observe the
formation of a bound state localized at the impurity. All of our results carry
over to the case of one dimensional Mott insulators by exchanging the roles of
spin and charge degrees of freedom. We discuss the implications of our result
for scanning tunneling microscopy experiments on spin-gap systems such as
two-leg ladder cuprates and 1D Mott insulators.",0802.1544v2
2008-02-12,Controlling soliton excitations in Heisenberg spin chain through magic angle,"We study the nonlinear dynamics of collective excitation in a $N$-site $XXZ$
quantum spin chain, which is manipulated by an oblique magnetic field. We show
that, when the tilted field is applied along the magic angle $\theta_{0}
=\pm\arccos \sqrt{1/3}$, the anisotropic Heisenberg spin chain becomes
isotropic and thus an free propagating spin wave is stimulated. And in the
regime of the tilted angle larger and smaller then the magic angle, two types
of nonlinear excitations appear, which are bright soliton and dark soliton.",0802.1610v4
2008-03-05,Micromagnetic study of a spin-torque oscillator based on a magnetic nano-contact magnetized at an arbitrary angle,"The nature of spin wave modes excited by spin-polarized direct current in a
spin-torque auto-oscillator based on a magnetic nanocontact was studied by a
micromagnetic simulation in the case when the external bias magnetic field was
rotated from the in-plane to perpendicular-to-plane orientation. In qualitative
agreement with the weakly-nonlinear analytical theory it was found, that at a
certain critical angle, an abrupt switching from the self-localized nonlinear
""bullet"" mode to a propagating quasi-linear Slonczewski mode takes place, and
is accompanied by an upward jump in generated microwave frequency. It was,
also, found that the analytical theory overestimates the magnitude of a
critical magnetization angle, corresponding to the mode switching, and that the
magnitude of the frequency jump caused by the mode switching is inversely
proportional to the nanocontact radius.",0803.0704v1
2008-03-08,Spin structure factors and valence-bond-solid states of the trimerized Heisenberg chains in a magnetic field,"By means of the density matrix renormalization group (DMRG) method, the
static spin structure factors and the magnetization plateaus of the trimerized
Heisenberg ferromagnet-ferromagnet-antiferromagnet and
antiferromagnet-antiferromagnet-ferromagnet spin chains in the presence of a
magnetic field are elaborately studied. It is found that in the plateau states,
the static structure factor with three peaks does not vary with the external
magnetic field as well as the exchange couplings; the spin correlation function
behaves as a perfect sequence and has a simple relation with the magnetization
per site. An approximate wave function for the plateau states is proposed, and
a picture based on the valence-bond-solid states is presented in order to
understand the origin and the total number of the magnetization plateaus, which
are shown to be in agreement with the DMRG results.",0803.1238v1
2008-05-05,"Orbital degeneracy, Hund's coupling, and band ferromagnetism: effective quantum parameter, suppression of quantum corrections, and enhanced stability","An effective quantum parameter is obtained for the band ferromagnet in terms
of orbital degeneracy and Hund's coupling. This quantum parameter determines,
in analogy with 1/N for the generalized Hubbard model and 1/S for quantum spin
systems, the strength of quantum corrections to spin stiffness and spin-wave
energies. Quantum corrections are obtained by incorporating correlation effects
in the form of self-energy and vertex corrections within a
spin-rotationally-symmetric approach in which the Goldstone mode is explicitly
preserved order by order. It is shown that even a relatively small Hund's
coupling is rather efficient in strongly suppressing quantum corrections,
especially for large N, resulting in strongly enhanced stability of the
ferromagnetic state. This mechanism for the enhancement of ferromagnetism by
Hund's coupling implicitly involves a subtle interplay of lattice,
dimensionality, band dispersion, spectral distribution, and band filling
effects.",0805.0470v1
2008-05-28,Dynamic nuclear polarization with simultaneous excitation of electronic and nuclear transitions,"Dynamic nuclear polarization transfers spin polarization from electrons to
nuclei. We have achieved this by a new method, simultaneously exciting
transitions of electronic and nuclear spins. The efficiency of this technique
improves with increasing magnetic field. Experimental results are shown for
N@C60 with continuous-wave microwaves, which can be expected to produce even
higher polarization than the corresponding pulsed techniques for electron spins
greater than 1/2. The degree of nuclear polarization in this case can be easily
monitored through the intensities of the well resolved hyperfine components in
the EPR spectrum. The nuclear spin-lattice relaxation time is orders of
magnitude longer than that of the electrons.",0805.4357v1
2008-08-11,Giant Extrinsic Spin Hall Effect due to Rare-Earth Impurities,"We investigate the extrinsic spin Hall effect in the electron gas model due
to magnetic impurities, by focusing on Ce- and Yb-impurities. In the dilute
limit, the skew scattering term dominates the side jump term. For
Ce-impurities, the spin Hall angle $\alpha_{\rm SH}$ due to skew scattering is
given by $-8\pi\sin\delta_2/7$, where $\delta_2 (\ll 1)$ is the phase shift
for$d (l=2)$ partial wave. Since $\alpha_{\rm SH}$ reaches $O(10^{-1})$ if
$\delta_2 \simge 0.03$, the spin Hall effect is anticipated to be considerable
in metals with rare-earth impurities. The giant extrinsic SHE originates from
the large orbital angular momentum, which is also significant for the intrinsic
SHE.",0808.1459v2
2008-08-18,Dilution effect in correlated electron system with orbital degeneracy,"Theory of dilution effect in orbital ordered system is presented. The $e_g$
orbital model without spin degree of freedom and the spin-orbital coupled model
in a three-dimensional simple-cubic lattice are analyzed by the Monte-Carlo
simulation and the cluster expansion method. In the $e_g$ orbital model without
spin degree of freedom, reduction of the orbital ordering temperature due to
dilution is steeper than that in the dilute magnet. This is attributed to a
modification of the orbital wave-function around vacant sites. In the
spin-orbital coupled model, it is found that magnetic structure is changed from
the A-type antiferromagnetic order into the ferromagnetic one. Orbital
dependent exchange interaction and a sign change of this interaction around
vacant sites bring about this novel phenomena. Present results explain the
recent experiments in transition-metal compounds with orbital dilution.",0808.2372v1
2008-09-12,Spin-squared Hamiltonian of next-to-leading order gravitational interaction,"The static, i.e., linear momentum independent, part of the next-to-leading
order (NLO) gravitational spin(1)-spin(1) interaction Hamiltonian within the
post-Newtonian (PN) approximation is calculated from a 3-dim. covariant ansatz
for the Hamilton constraint. All coefficients in this ansatz can be uniquely
fixed for black holes. The resulting Hamiltonian fits into the canonical
formalism of Arnowitt, Deser, and Misner (ADM) and is given in their
transverse-traceless (ADMTT) gauge. This completes the recent result for the
momentum dependent part of the NLO spin(1)-spin(1) ADM Hamiltonian for binary
black holes (BBH). Thus, all PN NLO effects up to quadratic order in spin for
BBH are now given in Hamiltonian form in the ADMTT gauge. The equations of
motion resulting from this Hamiltonian are an important step toward more
accurate calculations of templates for gravitational waves.",0809.2200v3
2008-09-22,Entanglement Resonance in Driven Spin Chains,"We consider a spin-1/2 anisotropic XY model with time-dependent spin-spin
coupling as means of creating long-distance entanglement. We predict the
emergence of significant entanglement between the first and the last spin
whenever the ac part of the coupling has a frequency matching the Zeeman
splitting. In particular, we find that the concurrence assumes its maximum with
a vanishing dc part. Mapping the time-dependent Hamiltonian within a
rotating-wave approximation to an effective static model provides qualitative
and quantitative understanding of this entanglement resonance. Numerical
results for the duration of the entanglement creation and its length dependence
substantiate the effective static picture.",0809.3712v2
2008-10-09,Electrical rectification effect in single domain magnetic microstrips: a micromagnetics-based analysis,"Upon passing an a.c. electrical current along magnetic micro- or nanostrips,
the measurement of a d.c. voltage that depends sensitively on current frequency
and applied field has been recently reported by A. Yamaguchi and coworkers. It
was attributed to the excitation of spin waves by the spin transfer torque,
leading to a time-varying anisotropic magnetoresistance and, by mixing of a.c.
current and resistance, to a d.c. voltage. We have performed a quantitative
analysis by micromagnetics, including the spin transfer torque terms considered
usually, of this situation. The signals found from the spin transfer torque
effect are several orders of magnitude below the experimental values, even if a
static inhomogeneity of magnetization (the so-called ripple) is taken into
account. On the other hand, the presence of a small non-zero average Oersted
field is shown to be consistent with the full set of experimental results, both
qualitatively and quantitatively. We examine, quantitatively, several sources
for this average field and point to the contacts to the sample as a likely
origin.",0810.1588v1
2008-10-24,Spin Dynamics in the Magnetoelectric Effect LiCoPO$_4$ Compound,"Inelastic neutron scattering (INS) experiments were performed to investigate
the spin dynamics in magnetoelectric effect (ME) LiCoPO$_4$ single crystals.
Weak dispersion was detected in the magnetic excitation spectra along the three
principal crystallographic axes measured around the (0 1 0) magnetic
reflection. Analysis of the data using linear spin-wave theory indicate that
single-ion anisotropy in LiCoPO$_4$ is as important as the strongest
nearest-neighbor exchange coupling. Our results suggest that Co$^{2+}$
single-ion anisotropy plays an important role in the spin dynamics of
LiCoPO$_4$ and must be taken into account in understanding its physical
properties. High resolution INS measurements reveal an anomalous low energy
excitation that we hypothesize may be related to the magnetoelectric effect of
LiCoPO$_4$.",0810.4471v1
2008-11-04,Chiral odd GPDs in transverse and longitudinal impact parameter spaces,"We investigate the chiral odd generalized parton distributions (GPDs) for
non-zero skewness $\zeta$ in transverse and longitudinal position spaces by
taking Fourier transform with respect to the transverse and longitudinal
momentum transfer respectively. We present overlap formulas for the chiral-odd
GPDs in terms of light-front wave functions (LFWFs) of the proton both in the
ERBL and DGLAP regions. We calculate them in a field theory inspired model of a
relativistic spin 1/2 composite state with the correct correlation between the
different LFWFs in Fock space, namely that of the quantum fluctuations of an
electron in a generalized form of QED. We show the spin-orbit correlation
effect of the two-particle LFWF as well as the correlation between the
constituent spin and the transverse spin of the target.",0811.0521v2
2008-11-17,Dynamical properties of the one-dimensional spin-1/2 Bose-Hubbard model near Mott-insulator to ferromagnetic liquid transition,"We investigate the dynamics of the one-dimensional strongly repulsive
spin-1/2 Bose-Hubbard model for filling $\nu\le1.$ While at $\nu=1$ the system
is a Hubbard-Mott insulator exhibiting dynamical properties of the Heisenberg
ferromagnet, at $\nu<1$ it is a ferromagnetic liquid with complex spin
dynamics. We find that close to the insulator-liquid transition the system
admits for a complete separation of spin and density degrees of freedom valid
at {\it all} energy and momentum scales within the $t-J$ approximation. This
allows us to derive the propagator of transverse spin waves and the shape of
the magnon peak in the dynamic spin structure factor.",0811.2676v2
2008-12-05,Theory of Tunneling Spectroscopy in a Mn$_{12}$ Single-Electron Transistor by Density-Functional Theory Methods,"We consider tunneling transport through a Mn$_{12}$ molecular magnet using
spin density functional theory. A tractable methodology for constructing
many-body wavefunctions from Kohn-Sham orbitals allows for the determination of
spin-dependent matrix elements for use in transport calculations. The tunneling
conductance at finite bias is characterized by peaks representing transitions
between spin multiplets, separated by an energy on the order of the magnetic
anisotropy. The energy splitting of the spin multiplets and the spatial part of
their many-body wave functions, describing the orbital degrees of freedom of
the excess charge, strongly affect the electronic transport, and can lead to
negative differential conductance.",0812.1058v2
2009-01-14,Charge and spin transport in strongly correlated one-dimensional quantum systems driven far from equilibrium,"We study the charge conductivity in one-dimensional prototype models of
interacting particles, such as the Hubbard and the t-V spinless fermion model,
when coupled to some external baths injecting and extracting particles at the
boundaries. We show that, if these systems are driven far from equilibrium, a
negative differential conductivity regime can arise. The above electronic
models can be mapped into Heisenberg-like spin ladders coupled to two magnetic
baths, so that charge transport mechanisms are explained in terms of quantum
spin transport. The negative differential conductivity is due to oppositely
polarized ferromagnetic domains which arise at the edges of the chain, and
therefore inhibit spin transport: we propose a qualitative understanding of the
phenomenon by analyzing the localization of one-magnon excitations created at
the borders of a ferromagnetic region. We also show that negative differential
conductivity is stable against breaking of integrability. Numerical simulations
of non-equilibrium time evolution have been performed by employing a
Monte-Carlo wave function approach and a matrix product operator formalism.",0901.2032v3
2009-07-31,Magnetism and superconductivity in single crystals $Eu_{1-x}Sr_xFe_{2-y}Co_{y}As_2$,"We systematically studied the transport properties of single crystals of
$Eu_{1-x}Sr_xFe_{2-y}$Co$_{y}As_2$. Co doping can suppress the spin-density
wave (SDW) ordering and induces a superconducting transition, but a resistivity
reentrance due to the antiferromagnetic ordering of $Eu^{2+}$ spins is
observed, indicating the competition between antiferromagnetism (AFM) and
superconductivity. It is striking that the resistivity reentrance can be
completely suppressed by external magnetic field (H) because a metamagnetic
transition from antiferromagnetism to ferromagnetism for $Eu^{2+}$ spins is
induced by magnetic field. Superconductivity without resistivity reentrance
shows up by partial substitution of Eu$^{2+}$ with non-magnetic Sr$^{2+}$ to
completely destroy the AFM ordering of $Eu^{2+}$ spins. These results suggest
that the antiferromagnetism destroys the superconductivity, while the
ferromagnetism can coexist with the superconductivity in the iron-based
high-$T_c$ superconductors.",0907.5547v1
2009-08-19,Polarized neutron scattering studies of the kagome lattice antiferromagnet KFe3(OH)6(SO4)2,"We report polarized neutron scattering studies of spin-wave excitations and
spin fluctuations in the S=5/2 kagome lattice antiferromagnet KFe3(OH)6(SO4)2
(jarosite). Inelastic polarized neutron scattering measurements at 10 K on a
single crystal sample reveal two spin gaps, associated with in-plane and
out-of-plane excitations. The polarization analysis of quasi-elastic scattering
at 67 K shows in-plane spin fluctuations with XY symmetry, consistent with the
disappearance of the in-plane gap above the Neel temperature T_N = 65 K. Our
results suggest that jarosite is a promising candidate for studying the 2D XY
universality class in magnetic systems.",0908.2670v1
2009-09-21,The spin-1/2 J1-J2 Heisenberg antiferromagnet on the square lattice: Exact diagonalization for N=40 spins,"We present numerical exact results for the ground state and the low-lying
excitations for the spin-1/2 J1-J2 Heisenberg antiferromagnet on finite square
lattices of up to N=40 sites. Using finite-size extrapolation we determine the
ground-state energy, the magnetic order parameters, the spin gap, the uniform
susceptibility, as well as the spin-wave velocity and the spin stiffness as
functions of the frustration parameter J2/J1. In agreement with the generally
excepted scenario we find semiclassical magnetically ordered phases for J2 <
J2^{c1} and J2 > J2^{c2} separated by a gapful quantum paramagnetic phase. We
estimate J2^{c1} \approx 0.35J1 and J2^{c2} \approx 0.66J1.",0909.3723v1
2009-11-24,Origin of adiabatic and non-adiabatic spin transfer torques in current-driven magnetic domain wall motion,"A consistent theory to describe the correlated dynamics of quantum mechanical
itinerant spins and semiclassical local magnetization is given. We consider the
itinerant spins as quantum mechanical operators, whereas local moments are
considered within classical Lagrangian formalism. By appropriately treating
fluctuation space spanned by basis functions, including a zero-mode wave
function, we construct coupled equations of motion for the collective
coordinate of the center-of-mass motion and the localized zero-mode coordinate
perpendicular to the domain wall plane. By solving them, we demonstrate that
the correlated dynamics is understood through a hierarchy of two time scales:
Boltzmann relaxation time when a non-adiabatic part of the spin-transfer torque
appears, and Gilbert damping time when adiabatic part comes up.",0911.4628v1
2009-12-21,Dispersive Spin Fluctuations in the near optimally-doped superconductor Ba(Fe1-xCox)2As2 ($x$=0.065),"Inelastic neutron scattering is used to probe the collective spin excitations
of the near optimally-doped superconductor Ba(Fe1-xCox)2As2 ($x$=0.065).
Previous measurements on the antiferromagnetically ordered parents of this
material show a strongly anisotropic spin-wave velocity. Here we measure the
magnetic excitations up to 80 meV and show that a similar anisotropy persists
for superconducting compositions. The dispersive mode measured here connects
directly with the spin resonance previously observed in this compound. When
placed on an absolute scale, our measurements show that the local- or
wavevector- integrated susceptibility is larger in magnitude than that of the
ordered parents over the energy range probed.",0912.4134v3
2009-12-23,Current-induced torques in continuous antiferromagnetic textures,"We study the influence of an electric current on a continuous non-collinear
antiferromagnetic texture. Despite the lack of a net magnetic moment we find
that the exchange interaction between conduction electrons and local
magnetization generally results in current-induced torques that are similar in
phenomenology to spin transfer torques in ferromagnets. We present the
generalization of the non-linear sigma model equation of motion for the
N\'{e}\`{e}l vector that includes these current-induced torques, and briefly
discuss the resulting current-induced antiferromagnetic domain wall motion and
spin-wave Doppler shift. We give an interpretation of our results using a
unifying picture of current-induced torques in ferromagnets and
antiferromagnets in which they are viewed as due to the current-induced spin
polarization resulting from an effective spin-orbit coupling.",0912.4519v1
2010-01-11,Magnon softening in a ferromagnetic monolayer: a first-principles spin dynamics study,"We study the Fe/W(110) monolayer system through a combination of first
principles calculations and atomistic spin dynamics simulations. We focus on
the dispersion of the spin waves parallel to the [001] direction. Our results
compare favorably with the experimental data of Prokop et al. [Phys. Rev. Lett.
102, 177206], and correctly capture a drastic softening of the magnon spectrum,
with respect to bulk bcc Fe. The suggested shortcoming of the itinerant
electron model, in particular that given by density functional theory, is
refuted. We also demonstrate that finite temperature effects are significant,
and that atomistic spin dynamics simulations represent a powerful tool with
which to include these.",1001.1669v2
2010-01-29,The search for spinning black hole binaries in mock LISA data using a genetic algorithm,"Coalescing massive Black Hole binaries are the strongest and probably the
most important gravitational wave sources in the LISA band. The spin and
orbital precessions bring complexity in the waveform and make the likelihood
surface richer in structure as compared to the non-spinning case. We introduce
an extended multimodal genetic algorithm which utilizes the properties of the
signal and the detector response function to analyze the data from the third
round of mock LISA data challenge (MLDC 3.2). The performance of this method is
comparable, if not better, to already existing algorithms. We have found all
five sources present in MLDC 3.2 and recovered the coalescence time, chirp
mass, mass ratio and sky location with reasonable accuracy. As for the orbital
angular momentum and two spins of the Black Holes, we have found a large number
of widely separated modes in the parameter space with similar maximum
likelihood values.",1001.5380v1
2010-02-04,Coherent Manipulation of Individual Electron Spin in a Double Quantum Dot Integrated with a Micro-Magnet,"We report the coherent manipulation of electron spins in a double quantum dot
integrated with a micro-magnet. We performed electric dipole spin resonance
experiments in the continuous wave (CW) and pump-and-probe modes. We observed
two resonant CW peaks and two Rabi oscillations of the quantum dot current by
sweeping an external magnetic field at a fixed frequency. Two peaks and
oscillations are measured at different resonant magnetic field, which reflects
the fact that the local magnetic fields at each quantum dot are modulated by
the stray field of a micro-magnet. As predicted with a density matrix approach,
the CW current is quadratic with respect to microwave (MW) voltage while the
Rabi frequency (\nu_Rabi) is linear. The difference between the \nu_Rabi values
of two Rabi oscillations directly reflects the MW electric field across the two
dots. These results show that the spins on each dot can be manipulated
coherently at will by tuning the micro-magnet alignment and MW electric field.",1002.0897v1
2010-03-01,Magneto-electric photocurrent generated by direct inter-band transitions in InGaAs/InAlAs two-dimensional electron gas,"We report observation of magneto-electric photocurrent generated via direct
inter-band transitions in an InGaAs/InAlAs two-dimensional electron gas excited
by a linearly polarized incident light.The electric current is proportional to
the in-plane magnetic field which unbalances the velocities of the photoexcited
carriers with opposite spins and consequently generates electric current from a
spin photocurrent. The observed light polarization dependence of the electric
current is explained microscopically by taking into account of the anisotropy
of the photoexcited carrier density in wave vector space. The spin photocurrent
can be extracted from the measured current and the conversion coefficient of
spin photocurrent to electric current is estimated to be
$10^{-3}$$\sim$$10^{-2}$ per Tesla.",1003.0276v2
2010-03-05,Geometric phase of a central spin coupled to an antiferromagnetic environment,"Using the spin-wave approximation, we study the geometric phase (GP) of a
central spin (signal qubit) coupled to an antiferromagnetic (AF) environment
under the application of an external global magnetic field. The external
magnetic field affects the GP of the qubit directly and also indirectly through
its effect on the AF environment. We find that when the applied magnetic field
is increased to the critical magnetic field point, the AF environment undergoes
a spin-flop transition, a first-order phase transition, and at the same time
the GP of the qubit changes abruptly to zero. This sensitive change of the GP
of a signal qubit to the parameter change of a many-body environment near its
critical point may serve as another efficient tool or witness to study the
many-body phase transition. The influences of the AF environment temperature
and crystal anisotropy field on the GP are also investigated.",1003.1300v1
2010-03-17,Supersolid phases in a realistic three-dimensional spin model,"Supersolid phases, in which a superfluid component coexists with conventional
crystalline long range order, have recently attracted a great deal of attention
in the context of both solid helium and quantum spin systems. Motivated by
recent experiments on 2H-AgNiO$_2$, we study the magnetic phase diagram of a
realistic three-dimensional spin model with single-ion anisotropy and competing
interactions on a layered triangular lattice, using classical Monte Carlo
simulation techniques, complemented by spin-wave calculations. For parameters
relevant to experiment, we find a cascade of different phases as a function of
magnetic field, including three phases which are supersolids in the sense of
Liu and Fisher. One of these phases is continuously connected with the
collinear ground state of AgNiO$_2$, and is accessible at relatively low values
of magnetic field. The nature of this low-field transition, and the possibility
of observing this new supersolid phase in AgNiO$_2$, are discussed.",1003.3430v3
2010-04-14,Tensor coupling effects on spin symmetry in anti-Lambda spectrum of hypernuclei,"The effects of $\bar\Lambda\bar\Lambda\omega$-tensor coupling on the spin
symmetry of $\bar{\Lambda}$ spectra in $\bar{\Lambda}$-nucleus systems have
been studied with the relativistic mean-field theory. Taking
$^{12}$C+$\bar{\Lambda}$ as an example, it is found that the tensor coupling
enlarges the spin-orbit splittings of $\bar\Lambda$ by an order of magnitude
although its effects on the wave functions of $\bar{\Lambda}$ are negligible.
Similar conclusions has been observed in $\bar{\Lambda}$-nucleus of different
mass regions, including $^{16}$O+$\bar{\Lambda}$, $^{40}$Ca+$\bar{\Lambda}$ and
$^{208}$Pb+$\bar{\Lambda}$. It indicates that the spin symmetry in
anti-lambda-nucleus systems is still good irrespective of the tensor coupling.",1004.2313v1
2010-04-16,Edge Dynamics in a Quantum Spin Hall State: Effects from Rashba Spin-Orbit Interaction,"We analyze the dynamics of the helical edge modes of a quantum spin Hall
state in the presence of a spatially non-uniform Rashba spin-orbit (SO)
interaction. A randomly fluctuating Rashba SO coupling is found to open a
scattering channel which causes localization of the edge modes for a weakly
screened electron-electron (e-e) interaction. A periodic modulation of the SO
coupling, with a wave number commensurate with the Fermi momentum, makes the
edge insulating already at intermediate strengths of the e-e interaction. We
discuss implications for experiments on edge state transport in a HgTe quantum
well.",1004.2777v2
2010-04-20,23Na and 75As NMR Study of Antiferromagnetism and Spin Fluctuations on NaFeAs Single Crystals,"We report the $^{23}$Na and $^{75}$As NMR studies on NaFeAs single crystals.
The structure transition temperature $T_S$ (55 K) and the spin density wave
(SDW) transition temperature $T_{SDW}$ (40.5 K) are determined by the NMR line
splits. The spin-lattice relaxation rates indicate that the spin fluctuations
are strongly enhanced just below $T_S$ and drive a second order SDW transition.
A fluctuating feature of the SDW ordering is also seen below the $T_{SDW}$. We
further performed high-pressure NMR studies on NaFeAs, and found that the
$T_{SDW}$ increases by $\sim$7 K and the magnetic moment increases by 30% under
2.5 GPa pressure.",1004.3581v2
2010-04-23,Gravitational memory in binary black hole mergers,"In addition to the dominant oscillatory gravitational wave signals produced
during binary inspirals, a non-oscillatory component arises from the nonlinear
""memory"" effect, sourced by the emitted gravitational radiation. The memory
grows significantly during the late inspiral and merger, modifying the signal
by an almost step-function profile, and making it difficult to model by
approximate methods. We use numerical evolutions of binary black holes to
evaluate the nonlinear memory during late-inspiral, merger and ringdown. We
identify two main components of the signal: the monotonically growing portion
corresponding to the memory, and an oscillatory part which sets in roughly at
the time of merger and is due to the black hole ringdown. Counter-intuitively,
the ringdown is most prominent for models with the lowest total spin. Thus, the
case of maximally spinning black holes anti-aligned to the orbital angular
momentum exhibits the highest signal-to-noise (SNR) for interferometric
detectors. The largest memory offset, however, occurs for highly spinning black
holes, with an estimated value of h^tot_20 \approx 0.24 in the maximally
spinning case. These results are central to determining the detectability of
nonlinear memory through pulsar timing array measurements.",1004.4209v2
2010-05-04,Disorder-induced freezing of dynamical spin fluctuations in underdoped cuprates,"We study the dynamical spin susceptibility of a correlated d-wave
superconductor (dSC) in the presence of disorder, using an unrestricted
Hartree-Fock approach. This model provides a concrete realization of the notion
that disorder slows down spin fluctuations, which eventually ""freeze out"". The
evolution of disorder-induced spectral weight transfer agrees qualitatively
with experimental observations on underdoped cuprate superconductors. For
sufficiently large disorder concentrations, static spin density wave (SDW)
order is created when droplets of magnetism nucleated by impurities overlap. We
also study the disordered stripe state coexisting with a dSC and compare its
magnetic fluctuation spectrum to that of the disorder-generated SDW phase.",1005.0520v2
2010-05-04,Complete phenomenological gravitational waveforms from spinning coalescing binaries,"The quest for gravitational waves from coalescing binaries is customarily
performed by the LIGO-Virgo collaboration via matched filtering, which requires
a detailed knowledge of the signal. Complete analytical coalescence waveforms
are currently available only for the non-precessing binary systems. In this
paper we introduce complete phenomenological waveforms for the dominant
quadrupolar mode of generically spinning systems. These waveforms are
constructed by bridging the gap between the analytically known inspiral phase,
described by spin Taylor (T4) approximants in the restricted waveform
approximation, and the ring-down phase through a phenomenological intermediate
phase, calibrated by comparison with specific, numerically generated waveforms,
describing equal mass systems with dimension-less spin magnitudes equal to 0.6.
The overlap integral between numerical and phenomenological waveforms ranges
between 0.95 and 0.99.",1005.0551v2
2010-05-05,Valence bond entanglement entropy of frustrated spin chains,"We extend the definition of the recently introduced valence bond entanglement
entropy to arbitrary SU(2) wave functions of S=1/2 spin systems. Thanks to a
reformulation of this entanglement measure in terms of a projection, we are
able to compute it with various numerical techniques for frustrated spin
models. We provide extensive numerical data for the one-dimensional J1-J2 spin
chain where we are able to locate the quantum phase transition by using the
scaling of this entropy with the block size. We also systematically compare
with the scaling of the von Neumann entanglement entropy. We finally underline
that the valence-bond entropy definition does depend on the choice of
bipartition so that, for frustrated models, a ""good"" bipartition should be
chosen, for instance according to the Marshall sign.",1005.0787v2
2010-05-29,Direct evidence of spin-split one-dimensional metallic surface state on Si(557)-Au,"We report unprecedented evidence of a spin split one-dimensional metallic
surface state for the system of Si(557)-Au obtained by means of high-resolution
spin- and angle-resolved photoelectron spectroscopy combined with first
principles calculations. The surface state shows double parabolic energy
dispersions along the Au chain structure together with a reversal of the spin
polarization with respect to the time-reversal symmetry point as is
characteristic from the Rashba effect. Moreover, we have observed a
considerably large out-of-plane spin polarization which we attribute to the
highly anisotropic wave function of the gold chains.",1005.5450v1
2010-07-05,Itinerant-Electron Magnetism in the Heisenberg Limit,"The Hubbard model in the Heisenberg limit is studied by Kondo-lattice theory.
The Kondo temperature T_K or k_BT_K, which is an energy scale of low-energy
local quantum spin fluctuations, is enhanced by the resonating valence bond
(RVB) mechanism, so that T_K\simeq T_MF/(2D), where T_MF is the Neel
temperature in the mean-field approximation of the corresponding Heisenberg
model and D is the spatial dimensionality. Electrons certainly behave as
localized spins at T\gg T_K, but they are still itinerant at T\ll T_K unless an
antiferromagnetic complete gap opens. When the Neel temperature T_N is so high
that T_N\gg T_MF/(2D), magnetism is prototypic local-moment magnetism. When T_N
is so low that T_N \ll T_MF/(2D) because of low dimensionality or frustration,
magnetism is itinerant-electron magnetism of an almost spin liquid, i.e., a
normal Fermi liquid or a Tomonaga-Luttinger liquid in which the spectral weight
of single-particle excitations is almost vanishing. The spin susceptibility has
a temperature and wave-number dependence characteristic of itinerant-electron
magnetism. This type of itinerant-electron magnetism must also be possible in
the Heisenberg model.",1007.0764v1
2010-08-09,Observation of the Magnon Hall Effect,"The Hall effect usually occurs when the Lorentz force acts on a charge
current in a conductor in the presence of perpendicular magnetic field. On the
other hand, neutral quasi-particles such as phonons and spins can carry heat
current and potentially show the Hall effect without resorting to the Lorentz
force. We report experimental evidence for the anomalous thermal Hall effect
caused by spin excitations (magnons) in an insulating ferromagnet with a
pyrochlore lattice structure. Our theoretical analysis indicates that the
propagation of the spin wave is influenced by the Dzyaloshinskii-Moriya
spin-orbit interaction, which plays the role of the vector potential as in the
intrinsic anomalous Hall effect in metallic ferromagnets.",1008.1564v1
2010-08-11,Theory for a dissipative droplet soliton excited by a spin torque nanocontact,"A novel type of solitary wave is predicted to form in spin torque oscillators
when the free layer has a sufficiently large perpendicular anisotropy. In this
structure, which is a dissipative version of the conservative droplet soliton
originally studied in 1977 by Ivanov and Kosevich, spin torque counteracts the
damping that would otherwise destroy the mode. Asymptotic methods are used to
derive conditions on perpendicular anisotropy strength and applied current
under which a dissipative droplet can be nucleated and sustained. Numerical
methods are used to confirm the stability of the droplet against various
perturbations that are likely in experiments, including tilting of the applied
field, non-zero spin torque asymmetry, and non-trivial Oersted fields. Under
certain conditions, the droplet experiences a drift instability in which it
propagates away from the nanocontact and is then destroyed by damping.",1008.1898v1
2010-08-18,Spin-flavor oscillations of Dirac neutrinos described by relativistic quantum mechanics,"Spin-flavor oscillations of Dirac neutrinos in matter and a magnetic field
are studied using the method of relativistic quantum mechanics. Using the exact
solution of the wave equation for a massive neutrino, taking into account
external fields, the effective Hamiltonian governing neutrino spin-flavor
oscillations is derived. Then the The consistency of our approach with the
commonly used quantum mechanical method is demonstrated. The obtained
correction to the usual effective Hamiltonian results in the appearance of the
new resonance in neutrino oscillations. Applications to spin-flavor neutrino
oscillations in an expanding envelope of a supernova are discussed. In
particular, transitions between right-polarized electron neutrinos and
additional sterile neutrinos are studied for realistic background matter and
magnetic field distributions. The influence of other factors such as the
longitudinal magnetic field, the matter polarization, and the non-standard
contributions to the neutrino effective potential, is also analyzed.",1008.3115v3
2010-09-06,Spin Dynamics of a $J_1-J_2$ Antiferromagnet and its Implications for Iron Pnictides,"Motivated by the recent observation of antiferromagnetic correlations in the
paramagnetic phase of iron pnictides, we study the finite-temperature spin
dynamics of a two-dimensional $J_1-J_2$ antiferromagnet. We consider the
paramagnetic phase in the $J_2>J_1$ regime of a $(\pi,0)$ collinear ground
state, using the modified spin wave theory. Below the mean-field Ising
transition temperature, we identify short-range anisotropic antiferromagnetic
correlations. We show that the dynamical structure factor
$\mathcal{S}(\mathbf{q},\omega)$ contains elliptic features in the momentum
space, and determine its variation with temperature and energy. Implications
for the spin-dynamical experiments in the iron pnictides are discussed.",1009.1111v3
2010-09-21,Realtime magnetic field sensing and imaging using a single spin in diamond,"The Zeeman splitting of a localized single spin can be used to construct a
magnetometer allowing high precision measurements of magnetic fields with
almost atomic spatial resolution. While sub-{\mu}T sensitivity can in principle
be obtained using pulsed techniques and long measurement times, a fast and
easy-to-use method without laborious data post-processing is desirable for a
scanning-probe approach with high spatial resolution. In order to measure the
resonance frequency in realtime, we applied a field-frequency lock to the
continuous wave ODMR signal of a single electron spin in a nanodiamond. In our
experiment, we achieved a sampling rate of up to 100 readings per second with a
sensitivity of 6 {\mu}T/$\sqrt{Hz}$. Using this method we have imaged the
microscopic field distribution around a magnetic wire. Images with \sim 30
{\mu}T resolution and 4096 sub-micron sized pixels were acquired in 10 minutes.
By measuring the field response of multiple spins on the same object we were
able to partly reconstruct the orientation of the field.",1009.4138v2
2010-11-09,Observation of exchange Coulomb interactions in the quantum Hall state at nu=3,"Coulomb exchange interactions of electrons in the nu=3 quantum Hall state are
determined from two inter-Landau level spin-flip excitations measured by
resonant inelastic light scattering. The two coupled collective excitations are
linked to inter-Landau level spin-flip transitions arising from the N=0 and N=1
Landau levels. The strong repulsion between the two spin-flip modes in the
long-wave limit is clearly manifested in spectra displaying Coulomb exchange
contributions that are comparable to the exchange energy for the quantum Hall
state at nu=1. Theoretical calculations within the Hartree-Fock approximation
are in a good agreement with measured energies of spin-flip collective
excitations.",1011.2022v1
2011-01-06,Ordered moment in the anisotropic and frustrated square lattice Heisenberg model,"The two-dimensional frustrated next nearest neighbor Heisenberg model on the
square lattice is a prime example for a spin system where quantum fluctuations
can either destroy or stabilize magnetic order. The phase boundaries and
staggered moment dependence on the frustration ratio J_2/J_1 of the exchange
constants are fairly well understood both from approximate analytical and
numerical methods. In this work we use exact diagonalization for finite
clusters for an extensive investigation of the more general J_1a,b-J_2 model
which includes a spatial exchange anisotropy between next-neighbor spins. We
introduce a systematic way of tiling the square lattice and, for this low
symmetry model, define a controlled procedure for the finite size scaling that
is compatible with the possible magnetic phases. We obtain ground state
energies, structure factors and ordered moments and compare with the results of
spin wave calculations. We conclude that J_1a,b exchange anisotropy strongly
stabilizes the columnar antiferromagnetic phase for all frustration parameters,
in particular in the region of the spin nematic phase of the isotropic model.",1101.1181v2
2011-02-02,Entanglement entropy of critical spin liquids,"Quantum spin liquids are phases of matter whose internal structure is not
captured by a local order parameter. Particularly intriguing are critical spin
liquids, where strongly interacting excitations control low energy properties.
Here we calculate their bipartite entanglement entropy that characterize their
quantum structure. In particular we calculate the Renyi entropy $S_2$, on model
wavefunctions obtained by Gutzwiller projection of a Fermi sea. Although the
wavefunctions are not sign positive, $S_2$ can be calculated on relatively
large systems (>324 spins), using the variational Monte Carlo technique. On the
triangular lattice we find that entanglement entropy of the projected Fermi-sea
state violates the boundary law, with $S_2$ enhanced by a logarithmic factor.
This is an unusual result for a bosonic wave-function reflecting the presence
of emergent fermions. These techniques can be extended to study a wide class of
other phases.",1102.0350v2
2011-03-01,Spin excitations in K$_{0.84}$Fe$_{1.99}$Se$_2$ superconductor as studied by Mössbauer spectroscopy,"M\""ossbauer spectroscopy was used to probe the site specific information of
the $K_{0.84}Fe_{1.99}Se_2$ superconductor. Possibility of coexistence of
superconductivity and magnetism is discussed. A spin excitation gap, $\Delta E
\approx$5\,meV, is observed by analyzing the temperature dependence of the
hyperfine magnetic field (HMF) at the iron site within the spin wave theory.
Using a simple model suggested in the literature, the temperature dependence of
the HMF is well reproduced, suggesting that, below room temperature, the
iron-selenide superconductors can be regarded as ferromagnetically coupled spin
blocks that interact with each other antiferromagnetically to form the observed
checkerboard-like magnetic structure.",1103.0098v5
2011-04-14,Long-Range Magnetic Interactions in the Multiferroic Antiferromagnet $\rm MnWO_4$,"The spin-wave excitations of the multiferroic $\rm MnWO_4$ have been measured
in its low-temperature collinear commensurate phase using high-resolution
inelastic neutron scattering. These excitations can be well described by a
Heisenberg model with competing long-range exchange interactions and a
single-ion anisotropy term. The magnetic interactions are strongly frustrated
within the zigzag spin chain along c axis and between chains along the a axis,
while the coupling between spin along the b axis is much weaker. The balance of
these interactions results in the noncollinear incommensurate spin structure
associated with the magnetoelectric effect, and the perturbation of the
magnetic interactions leads to the observed rich phase diagrams of the
chemically-doped materials. This delicate balance can also be tuned by the
application of external electric or magnetic fields to achieve magnetoelectric
control of this type of materials.",1104.2867v1
2011-04-18,Acoustic phonons and spin relaxation in graphene nanoribbons,"Phonons are responsible for limiting both the electron mobility and the spin
relaxation time in solids and provide a mechanism for thermal transport. In
view of a possible transistor function as well as spintronics applications in
graphene nanoribbons, we present a theoretical study of acoustic phonons in
these nanostructures. Using a two-dimensional continuum model which takes into
account the monatomic thickness of graphene, we derive Hermitian wave equations
and infer phonon creation and annihilation operators. We elaborate on two types
of boundary configuration, which we believe can be realized in experiment: (i)
fixed and (ii) free boundaries. The former leads to a gapped phonon dispersion
relation, which is beneficial for high electron mobilites and long spin
lifetimes. The latter exhibits an ungapped dispersion and a finite sound
velocity of out-of-plane modes at the center of the Brillouin zone. In the
limit of negligible boundary effects, bulk-like behavior is restored. We also
discuss the deformation potential, which in some cases gives the dominant
contribution to the spin relaxation rate T_1^{-1}.",1104.3520v2
2011-05-18,Control of ferroelectric polarization via uniaxial pressure in the spin-lattice-coupled multiferroic CuFe1-xGaxO2,"We have demonstrated that ferroelectric polarization in a spin-driven
multiferroic CuFe1-xGaxO2 with x = 0.035 can be controlled by the application
of uniaxial pressure. Our neutron diffraction and in-situ ferroelectric
polarization measurements have revealed that the pressure dependence of the
ferroelectric polarization is explained by repopulation of three types of
magnetic domains originating from the trigonal symmetry of the crystal. We
conclude that the spin-driven anisotropic lattice distortion and the fixed
relationship between the directions of the magnetic modulation wave vector and
the ferroelectric polarization are the keys to this spin-mediated piezoelectric
effect.",1105.3525v1
2011-05-28,Paired Superfluidity and Fractionalized Vortices in Spin-orbit Coupled Bosons,"In this letter we study finite temperature properties of spin-1/2 interacting
bosons with spin-orbit coupling in two dimensions. When the ground state has
stripe order, we show that thermal fluctuations will first melt the stripe
order and lead to a superfluid of boson pairs if the spin-orbit coupling is
isotropic or nearly isotropic. Such a phase supports fractionalized quantum
vortices. The Kosterlize-Thouless transition from superfluid to normal state is
driven by proliferation of half vortices. When the ground state is a plane wave
state, the transition to normal state is driven by conventional
Kosterlize-Thouless transition. However, the critical temperature will drop to
zero for isotropic spin-orbit coupling.",1105.5700v1
2011-06-01,Remarkable paramagnetic features of Fermi-Dirac plasmas,"In this paper by using the relativistic magnetic susceptibility of a
Fermi-Dirac (relativistically degenerate) plasma, quantum magnetohydrodynamics
(QMHD) model is used to investigate the propagation of spin-induced (SI)
magnetosonic nonlinear excitations in a normally and relativistically
degenerate dense electron-ion plasma in the presence of the spin magnetization
effect. Based on the conventional pseudopotential method the matching criterion
for the evolution of SI solitary structures is evaluated. It is found that, the
plasma mass density and strength of the magnetic field have significant effects
on excitation and evolution of magnetosonic nonlinear structures in Fermi-Dirac
plasmas. Only rarefactive SI magnetosonic solitary structures are found to
excite in such plasmas. Furthermore, fundamental differences are shown to exist
in magnetosonic soliton dynamics in the two distinct plasma degeneracy regimes,
which is due to interplay between the negative spin paramagnetism pressure-like
and positive relativistic degeneracy pressure of electrons. Current
investigation can help better understand the electron spin effects on nonlinear
wave propagations in strongly magnetized dense astrophysical objects such as
white dwarfs and pulsar magnetospheres.",1106.0226v1
2011-09-01,Diffractive dissociation into $K_sK^{\pm}π^{\mp}π^{-}$ final states,"The COMPASS fixed-target experiment at CERN/SPS is dedicated to the study of
hadron structure and spectroscopy, especially the search for spin-exotic
states. After having started to study the existence of the spin-exotic
$\pi_1(1600)$ resonance in the 2004 pilot-run data, the new 2008/09 data will
enable us to further clarify the situation. Apart from the $\pi_1(1600)$
resonance, also a spin-exotic $\pi_1(2000)$ was reported in the past in the
$f_1(1285)\pi$ decay channel by the E852/BNL experiment, however, this state
still lacks confirmation. We present a first event selection of the
diffractively produced $(K\bar{K}\pi\pi)^{-}$ system showing clean $f_1(1285)$
and $f_1(1420)$ resonances at competing statistics. A partial-wave analysis
started on $f_1(1285)\pi$ and $f_1(1420)\pi$ decay channels will further
complete the search for spin-exotics in the 2008/09 COMPASS data.",1109.0219v1
2011-09-12,Stabilizing the spiral order with spin-orbit coupling in an anisotropic triangular antiferromagnet,"We study the effects of spin-orbit coupling (SOC) on the large-U Hubbard
model on anisotropic triangular lattice at half-filling using the
Schwinger-boson method. We find that the SOC will in general lead to a zero
temperature condensation of the Schwinger bosons with a single condensation
momentum. As a consequence, the spin-spin correlation vanishes along the z-axis
but develops in the $x$-$y$ plane, with the ordering wave vector being
dramatically dependent on the SOC. Moreover, the phase boundary of the magnetic
ordered state extends to the region of large spatial anisotropy with increased
condensation density, demonstrating that the spiral order is always stabilized
by the SOC.",1109.2364v1
2011-09-22,Ground-state phases of ultracold bosons with Rashba-Dresselhaus spin-orbit coupling,"We study ultracold bosons in three dimensions with an anisotropic
Rashba-Dresselhaus spin-orbit coupling. We first carry out the exact summation
of ladder diagrams for the two-boson t-matrix at zero energy. Then, with the
t-matrix as the effective interaction, we find the ground-state phase diagrams
of bosons in mean field as a function of the spin-orbit coupling, the
anisotropy, and the scattering lengths between particles in the same and in
different pseudospin states. The resulting phase diagrams have much richer
structures than those obtained using mean-field couplings, exhibiting three
different phases: a plane-wave condensate, a striped condensate, and an
unstable phase. The differences between the present approach using the t-matrix
compared to using mean-field couplings is significant for large scattering
lengths, large spin-orbit-coupling strength, or small anisotropy.",1109.4954v2
2011-09-23,Spin polarization versus lifetime effects at point contacts between superconducting niobium and normal metals,"Point-contact Andreev reflection spectroscopy is used to measure the spin
polarization of metals but analysis of the spectra has encountered a number of
serious challenges, one of which is the difficulty to distinguish the effects
of spin polarization from those of the finite lifetime of Cooper pairs. We have
recently confirmed the polarization-lifetime ambiguity for Nb-Co and Nb-Cu
contacts and suggested to use Fermi surface mismatch, the normal reflection due
to the difference of Fermi wave vectors of the two electrodes, to solve this
dilemma. Here we present further experiments on contacts between
superconducting Nb and the ferromagnets Fe and Ni as well as the noble metals
Ag and Pt that support our previous results. Our data indicate that the Nb -
normal metal interfaces have a transparency of up to about 80 per cent and a
small, if not negligible, spin polarization.",1109.5039v1
2011-10-02,Metastable magnetic domain wall dynamics,"The dynamics of metastable magnetic domain walls in straight ferromagnetic
nanowires under spin waves, external magnetic fields, and current induced spin
transfer torque are studied by micromagnetic simulations. It is found that in
contrast to a stable wall, it is possible to displace a metastable domain wall
in the absence of any external excitation. In addition, independent of the
domain wall excitation method, the velocity of a metastable wall is much
smaller than a stable wall and their displacement direction could be different
from the stable wall depending on the structure of metastable walls. Under the
current induced spin transfer torque excitation, the direction of domain wall
displacement is directly related to the intensity of nonadiabatic spin transfer
torque. In a rough nanowire, it is found that the displacement of a metastable
wall could happen much below the critical excitation of a stable wall.
Furthermore, we show that it is possible to have either a forward or backward
displacement of a metastable domain wall by changing the pulse width of the
excitation.",1110.0175v1
2011-10-06,Incommensurate correlations in the anisotropic triangular Heisenberg lattice,"We study the anisotropic spin-half antiferromagnetic triangular Heisenberg
lattice in two dimensions, seen as a set of chains with couplings J (J') along
(in between) chains, respectively. Our focus is on the incommensurate
correlation that emerges in this system in a wide parameter range due to the
intrinsic frustration of the spins. We study this system with traditional DMRG
using cylindrical boundary conditions to least constrain possible
incommensurate order. Despite that the limit of essentially decoupled chains
J'/J < 0.5 is not very accessible numerically, it appears that the spin-spin
correlations remain incommensurate for any finite 0 < J' < Jc', where Jc'/J >
1. The incommensurate wave vector q_J, however, approaches the commensurate
value corresponding to the antiferromagnetic correlation of a single chain very
rapidly with decreasing J'/J, roughly as q_J ~ pi - c_1 (J'/J)^n exp(-c_2
J/J').",1110.1406v1
2011-11-09,Low-density molecular gas of tightly-bound Rashba-Dresselhaus fermions,"We study interacting Rashba-Dresselhaus fermions in two spatial dimensions.
First, we present a new exact solution to the two-particle pairing problem of
spin-orbit-coupled fermions for arbitrary Rashba and Dresselhaus spin-orbit
interactions. An exact molecular wave function and the Green function are
explicitly derived along with the binding energy and the spectrum of the
molecular state. In the second part, we consider a thermal Boltzmann gas of
fermionic molecules and compute the time-of-flight velocity and spin
distributions for a single fermion in the gas. We show that the pairing
signatures can be observed already in the first-moment expectation values, such
as time-of-flight density and spin profiles.",1111.2340v2
2011-12-04,Zn-induced spin dynamics in overdoped La$_{2-x}$Sr$_x$Cu$_{1-y}$Zn$_y$O$_4$,"Spin fluctuations and the local spin susceptibility in isovalently
Zn-substituted La$_{2-x}$Sr$_{x}$Cu$_{1-y}$Zn$_y$O$_4$ ($x=0.25$,
$y\approx0.01$) are measured via inelastic neutron scattering techniques. As
Zn$^{2+}$ is substituted onto the Cu$^{2+}$-sites, an anomalous enhancement of
the local spin susceptibility $\chi^{\prime\prime}(\omega)$ appears due to the
emergence of a commensurate antiferromagnetic excitation centered at wave
vector \textbf{Q}$=(\pi, \pi, 0)$ that coexists with the known incommensurate
SDW excitations at \textbf{Q}$_{HK}=(\pi\pm\delta,\pi), (\pi,\pi\pm\delta)$.
Our results support a picture of Zn-induced antiferromagnetic (AF) fluctuations
appearing through a local staggered polarization of Cu$^{2+}$-spins, and the
simultaneous suppression of T$_c$ as AF fluctuations are slowed in proximity to
Zn-impurities suggests the continued importance of high energy AF fluctuations
at the far overdoped edge of superconductivity in the cuprates.",1112.0775v2
2012-01-04,Energy of Stable Half-Quantum Vortex in Equal-Spin-Pairing,"In the triplet equal-spin-pairing states of both 3He-A phase and Sr2RuO4
superconductor, existence of Half-Quantum Vortices HQVs are possible. The
vortices carry half-integer multiples of magnetic quantum flux (hc/2e). To
obtain equilibrium condition for such systems, one has to take into account not
only weak interaction energy but also effects of Landau Fermi liquid. Our
method is based on the explanation of the HQV in terms of a BCS-like wave
function with a spin-dependent boots. We have considered l=2 order effects of
the Landau Fermi liquid. We have shown that the effects of Landau Fermi liquid
interaction with l=2 are negligible. In stable HQV, an effective Zeeman field
exists. In the thermodynamic stability state, the effective Zeeman field
produces a non-zero spin polarization in addition to the polarization of
external magnetic field.",1201.0821v1
2012-01-27,First-principles investigation of hyperfine interactions for nuclear spin entanglement in photo-excited fullerenes,"The study of hyperfine interactions in optically excited fullerenes has
recently acquired importance within the context of nuclear spin entanglement
for quantum information technology. We here report a first-principles
pseudopotential study of the hyperfine coupling parameters of optically excited
fullerene derivatives as well as small organic radicals. The calculations are
performed within the gauge-invariant projector-augmented wave method [C.
Pickard and F. Mauri, Phys. Rev. B. 63, 245101 (2001)]. In order to establish
the accuracy of this methodology we compare our results with all-electron
calculations and with experiment. In the case of fullerene derivatives we study
the hyperfine coupling in the spin-triplet exciton state and compare our
calculations with recent electron paramagnetic resonance measurements [M.
Schaffry et al., Phys. Rev. Lett. 104, 200501 (2010)]. We discuss our results
in light of a recent proposal for entangling remote nuclear spins in
photo-excited chromophores.",1201.5849v1
2012-01-30,Quantitative MRFM characterization of the autonomous and forced dynamics in a spin transfer nano-oscillator,"Using a magnetic resonance force microscope (MRFM), the power emitted by a
spin transfer nano-oscillator consisting of a normally magnetized Py$|$Cu$|$Py
circular nanopillar is measured both in the autonomous and forced regimes. From
the power behavior in the subcritical region of the autonomous dynamics, one
obtains a quantitative measurement of the threshold current and of the noise
level. Their field dependence directly yields both the spin torque efficiency
acting on the thin layer and the nature of the mode which first
auto-oscillates: the lowest energy, spatially most uniform spin-wave mode. From
the MRFM behavior in the forced dynamics, it is then demonstrated that in order
to phase-lock this auto-oscillating mode, the external source must have the
same spatial symmetry as the mode profile, i.e., a uniform microwave field must
be used rather than a microwave current flowing through the nanopillar.",1201.6344v1
2012-01-31,Nonreciprocal Directional Dichroism and Toroidalmagnons in Helical Magnets,"We investigate a dynamical magnetoelectric effect due to a magnetic resonance
in helical spin structures through the coupling between magnetization and
electric polarization via a spin current mechanism. We show that the magnon has
both the dynamical magnetic moment $\Delta M^\omega$ and the electric moment
$\Delta P^\omega$ ($\perp \Delta M^\omega$), i.e., a dynamical toroidal moment,
under external magnetic fields, and thus it is named the {\em toroidalmagnon}.
The toroidalmagnon exists in most conical spin structures owing to the
generality of the spin current mechanism. In the absorption of electromagnetic
waves, the toroidalmagnon excitation process generally induces a nonreciprocal
directional dichroism as a consequence of an interference of the magnetic and
electric responses.",1201.6458v1
2012-02-26,Non-Grassmann mechanical model of the Dirac equation,"We construct a new example of the spinning-particle model without Grassmann
variables. The spin degrees of freedom are described on the base of an inner
anti-de Sitter space. This produces both $\Gamma^\mu$ and
$\Gamma^{\mu\nu}$\,-matrices in the course of quantization. Canonical
quantization of the model implies the Dirac equation. We present the detailed
analysis of both the Lagrangian and the Hamiltonian formulations of the model
and obtain the general solution to the classical equations of motion. Comparing
{\it Zitterbewegung} of the spatial coordinate with the evolution of spin, we
ask on the possibility of space-time interpretation for the inner space of
spin. We enumerate similarities between our analogous model of the Dirac
equation and the two-body system subject to confining potential which admits
only the elliptic orbits of the order of de Broglie wave-length. The Dirac
equation dictates the perpendicularity of the elliptic orbits to the direction
of center-of-mass motion.",1202.5757v3
2012-04-11,Magneto-Electric Coupling in Single Crystal Cu2OSeO3 Studied by a Novel Electron Spin Resonance Technique,"The magneto-electric (ME) coupling on spin-wave resonances in single-crystal
Cu2OSeO3 was studied by a novel technique using electron spin resonance
combined with electric field modulation. An external electric field E induces a
magnetic field component \mu_0 H^i = \gamma E along the applied magnetic field
H with \gamma=0.7(1) \mu T/(V/mm) at 10 K. We found that ME coupling strength
\gamma is temperature dependent and highly anisotropic. \gamma(T) nearly
follows that of spin susceptibility J(T) and rapidly decreases above the Curie
temperature Tc. The ratio \gamma/J monotonically decreases with increasing
temperature without an anomaly at Tc.",1204.2481v2
2012-04-23,Low-energy Spin Excitation in Coexistent Phase of Antiferromagnetism and d-wave Superconductivity,"Nuclear quadrupole resonance measurements have shown evidences that the heavy
fermion compound CeRhIn$_5$ exhibits a coexistent phase with commensurate
antiferromagnetism and d-wave superconductivity. In order to clarify the nature
of the spin-excitations in the coexistent phase, we have applied the RPA method
to an itinerant model, where the effective interaction is given by two
mean-field terms of commensurate antiferromagnetism and d-wave
superconductivity. It is shown that, around the transition line between the
antiferromagnetic and the coexistent states, a low-energy incommensurate
spin-excitation is found to develop due to Fermi surface nesting. This feature
reminds of the switching of magnetic ordering wave vector observed in the
neutron diffraction. Further, we also calculate spin relaxation rate, which
gives a reasonable explanation of the temperature dependence of NQR relaxation
rate in the system with the coexistent ground state.",1204.5032v3
2012-04-27,Spin and holographic metals,"In this paper we discuss two-dimensional holographic metals from a condensed
matter physics perspective. We examine the spin structure of the Green's
function of the holographic metal, demonstrating that the excitations of the
holographic metal are ""chiral"", lacking the inversion symmetry of a
conventional Fermi surface, with only one spin orientation for each point on
the Fermi surface, aligned parallel to the momentum. While the presence of a
Kramer's degeneracy across the Fermi surface permits the formation of a singlet
superconductor, it also implies that ferromagnetic spin fluctuations are absent
from the holographic metal, leading to a complete absence of Pauli
paramgnetism. In addition, we show how the Green's function of the holographic
metal can be regarded as a reflection coefficient in anti-de-Sitter space,
relating the ingoing and outgoing waves created by a particle moving on the
external surface.",1204.6310v2
2012-04-27,"Disorder, cluster spin glass, and hour-glass spectra in striped magnetic insulators","Hour-glass-shaped magnetic excitation spectra have been detected in a variety
of doped transition-metal oxides with stripe-like charge order. Compared to the
predictions of spin-wave theory, these spectra display a different intensity
distribution and anomalous broadening. Here we show, based on a comprehensive
modelling of these phenomena for La5/3Sr1/3CoO4, how quenched disorder in the
charge sector causes frustration, and consequently cluster-glass behavior at
low temperatures, in the spin sector. This spin-glass physics, which is
insensitive to the detailed nature of the charge disorder, but sensitive to the
relative strength of the magnetic inter-stripe coupling, ultimately determines
the distribution of magnetic spectral weight and thus causes the hour-glass
spectrum.",1204.6323v2
2012-04-27,Prediction of polaron-like vortices and dissociation depinning transition in magnetic superconductors: The example of ErNi2B2C,"In borocarbide ErNi$_2$B$_2$C the phase transition to the commensurate spin
density wave at 2.3 K leaves 1/20 part of Ising-like Er spins practically free.
Vortices polarize these spins nonuniformly and repolarize them when moving. At
a low spin relaxation rate and at low bias currents vortices carrying magnetic
polarization clouds become polaron-like and their velocities are determined by
the effective drag coefficient which is significantly bigger than the
Bardeen-Stephen (BS) one. As current increases, at a critical current $J_c$
vortices release polarization clouds and the velocity as well as the voltage in
the I-V characteristics jump to values corresponding to the BS drag
coefficient. The nonuniform components of the magnetic field and magnetization
drop as velocity increases resulting in weaker polarization and discontinuous
dynamic dissociation depinning transition. As current decreases, on the way
back, vortices are retrapped by polarization clouds at the current $J_r<J_c$.",1204.6348v2
2012-04-28,Frustrated RVB states in 2D: classifications and short-range correlations,"Resonating valence bond (RVB) states are of crucial importance in our
intuitive understanding of quantum spin liquids in 2D. We systematically
classify short-range bosonic RVB states into symmetric or nematic spin liquids
by examining their flux patterns. We further map short-range bosonic RVB states
into projected BCS wave functions, on which we perform large-scale Monte Carlo
simulations without the minus sign problem. Our results clearly show that both
spin and dimer correlations decay exponentially in all the short-range
frustrated (non-bipartite or $Z_2$) bosonic RVB states we studied, indicating
that they are gapped $Z_2$ quantum spin liquids. Generically, we conjecture
that all short-range frustrated bosonic RVB states in 2D have only short-range
correlations.",1204.6381v4
2012-05-15,Spin-stripe density varies linearly with hole content in single-layer Bi2201 cuprate,"We have performed inelastic neutron scattering measurements on the
single-layer cuprate Bi2+xSr2-xCuO6+y (Bi2201) with x=0.2, 0.3, 0.4 and 0.5, a
doping range that spans the spin-glass (SG) to superconducting (SC) phase
boundary. The doping evolution of low energy spin fluctuations was found to be
characterized by a change of incommensurate modulation wave vector from the
tetragonal [110] to [100]/[010] directions, while maintaining a linear relation
between the incommensurability and the hole concentration, delta p. In the SC
regime, the spectral weight is strongly suppressed below 4 meV. Similarities
and differences in the spin correlations between Bi2201 and the prototypical
single-layer system La2-xSrxCuO4 are discussed.",1205.3301v2
2012-06-04,Quantitative cw Overhauser DNP Analysis of Hydration Dynamics,"Liquid state Overhauser Effect Dynamic Nuclear Polarization (ODNP) has
experienced a recent resurgence of interest. In particular, a new manifestation
of the ODNP measurement measures the translational mobility of water within
5-10 \AA\ of an ESR-active spin probe (i.e. the local translational diffusivity
D_{local} near an electron spin resonance active molecule). Such spin probes,
typically stable nitroxide radicals, have been attached to the surface or
interior of macromolecules, including proteins, polymers, and membrane
vesicles. Despite the unique specificity of this measurement, it requires only
a standard X-band (~10 GHz) continuous wave (cw) electron spin resonance (ESR)
spectrometer, coupled with a standard nuclear magnetic resonance (NMR)
spectrometer. Here, we present a set of developments and corrections that allow
us to improve the accuracy of quantitative ODNP and apply it to samples more
than two orders of magnitude lower than were previously feasible.",1206.0510v1
2012-06-19,Spin hydrodynamics in the S = 1/2 anisotropic Heisenberg chain,"We study the finite-temperature dynamical spin susceptibility of the
one-dimensional (generalized) anisotropic Heisenberg model within the
hydrodynamic regime of small wave vectors and frequencies. Numerical results
are analyzed using the memory function formalism with the central quantity
being the spin-current decay rate gamma(q,omega). It is shown that in a generic
nonintegrable model the decay rate is finite in the hydrodynamic limit,
consistent with normal spin diffusion modes. On the other hand, in the gapless
integrable model within the XY regime of anisotropy Delta < 1 the behavior is
anomalous with vanishing gamma(q,omega=0) proportional to |q|, in agreement
with dissipationless uniform transport. Furthermore, in the integrable system
the finite-temperature q = 0 dynamical conductivity sigma(q=0,omega) reveals
besides the dissipationless component a regular part with vanishing
sigma_{reg}(q=0,omega to 0) to 0.",1206.4248v2
2012-07-03,Approximate relativistic bound state solutions of the Tietz-Hua rotating oscillator for any -state,"Approximate analytic solutions of the Dirac equation with Tietz-Hua (TH)
potential are obtained for arbitrary spin-orbit quantum number using the
Pekeris approximation scheme to deal with the spin-orbit coupling terms In the
presence of exact spin and pseudo-spin (pspin) symmetric limitation, the bound
state energy eigenvalues and associated two-component wave functions of the
Dirac particle moving in the field of attractive and repulsive TH potential are
obtained using the parametric generalization of the Nikiforov-Uvarov (NU)
method. The cases of the Morse potential, the generalized Morse potential and
non-relativistic limits are studied.",1207.0675v1
2012-08-28,Spin-orbit coupling induced separation and hidden spin textures in spin-1 Bose-Einstein condensates,"We analytically and numerically investigate the ground state of the
spin-orbit coupled spin-1 Bose-Einstein condensates in an external parabolic
potential. When the spin-orbit coupling strength $\kappa$ is comparable with
that of the trapping potential, the density distribution centers of different
components of the spinor condensate deviate evidently from the trap center in
the plane wave and stripe phases. When $\kappa\gg1$, the magnitude of this
deviation decreases as $\kappa$ is getting larger and larger. Correspondingly,
periphery half-skyrmions textures arise. This deviation can be reflected by the
non-uniform magnetic moment in the $z$ direction, $\mathcal{F}_z$. With the
manipulation of the external trap, the local magnitude of $\mathcal{F}_z$ can
be increased evidently. This kind of increase of $\mathcal{F}_z$ is also
observed in the square vortex lattice phase of the condensate.",1208.5591v3
2012-08-28,NMR Search for the Spin Nematic State in LaFeAsO Single Crystal,"We report a 75-As single crystal NMR investigation of LaFeAsO, the parent
phase of a pnictide high Tc superconductor. We demonstrate that spin dynamics
develop a strong two-fold anisotropy within each orthorhombic domain below the
tetragonal-orthorhombic structural phase transition at T[TO]~156 K. This
intermediate state with a dynamical breaking of the rotational symmetry freezes
progressively into a spin density wave (SDW) below T[SDW]~142 K. Our findings
are consistent with the presence of a spin nematic state below T[TO] with an
incipient magnetic order.",1208.5652v2
2012-12-07,Exact solutions of a spatially-dependent mass Dirac equation for Coulomb field plus tensor interaction via Laplace transformation method,"The spatially-dependent mass Dirac equation is solved exactly for attractive
scalar and repulsive vector Coulomb potentials including a tensor interaction
potential under the spin and pseudospin (p-spin) symmetric limits by using the
Laplace transformation method (LTM). Closed forms of the energy eigenvalue
equation and wave functions are obtained for arbitrary spin-orbit quantum
number Some numerical results are given too. The effect of the tensor
interaction on the bound states is presented. It is shown that the tensor
interaction removes the degeneracy between two states in the spin doublets. We
also investigate the effects of the spatially-dependent mass on the bound
states under the conditions of the spin symmetric limit and in the absence of
tensor interaction",1212.1566v2
2013-01-08,Kinematical and Dynamical Aspects of Higher-Spin Bound-State Equations in Holographic QCD,"In this paper we derive holographic wave equations for hadrons with arbitrary
spin starting from an effective action in a higher-dimensional space asymptotic
to anti-de Sitter (AdS) space. Our procedure takes advantage of the local
tangent frame, and it applies to all spins, including half-integer spins. An
essential element is the mapping of the higher-dimensional equations of motion
to the light-front Hamiltonian, thus allowing a clear distinction between the
kinematical and dynamical aspects of the holographic approach to hadron
physics. Accordingly, the non-trivial geometry of pure AdS space encodes the
kinematics, and the additional deformations of AdS space encode the dynamics,
including confinement. It thus becomes possible to identify the features of
holographic QCD which are independent of the specific mechanisms of conformal
symmetry breaking. In particular, we account for some aspects of the striking
similarities and differences observed in the systematics of the meson and
baryon spectra.",1301.1651v1
2013-01-25,Chiral magnetism and helimagnons in a pyrochlore antiferromagnet,"Recent neutron scattering measurements on the spinel CdCr2O4 revealed a rare
example of helical magnetic order in geometrically frustrated pyrochlore
antiferromagnet. The spin spiral characterized by an incommensurate wavevector
Q = 2pi (0, delta, 1) with delta ~0.09 is accompanied by a tetragonal
distortion. Here we conduct a systematic study on the magnetic ground state
resulting from the interplay between the Dzyaloshinskii-Moriya interaction and
further neighbor exchange couplings, two of the most important mechanisms for
stabilizing incommensurate spin orders. We compute the low-energy spin-wave
spectrum based on a microscopic spin Hamiltonian and find a dispersion relation
characteristic of the helimagnons. By numerically integrating the
Landau-Lifshitz-Gilbert equation with realistic model parameters, an overall
agreement between experiment and the numerical spectrum, lending further
support to the view that a softened optical phonon triggers the magnetic
transition and endows the lattice a chirality.",1301.5958v1
2013-02-11,De Donder-Weyl Hamiltonian formulation and precanonical quantization of vielbein gravity,"The De Donder-Weyl (DW) covariant Hamiltonian formulation of Palatini
first-order Lagrangian of vielbein (tetrad) gravity and its precanonical
quantization are presented. No splitting into the space and time is required in
this formulation. Our recent generalization of Dirac brackets is used to treat
the second class primary constraints appearing in the DW Hamiltonian
formulation and to find the fundamental brackets. Quantization of the latter
yields the representation of vielbeins as differential operators with respect
to the spin connection coefficients, and the Dirac-like precanonical
Schr\""odinger equation on the space of spin connection coefficients and
space-time variables. The transition amplitudes on this space describe the
quantum geometry of space-time. We also discuss the Hilbert space of the
theory, the invariant measure on the spin connection coefficients, and point to
the possible quantum singularity avoidance built in in the natural choice of
the boundary conditions of the wave functions on the space of spin connection
coefficients.",1302.2610v2
2013-03-15,Strong coupling theory of heavy fermion criticality,"We present a theory of the scaling behavior of the thermodynamic, transport
and dynamical properties of a three-dimensional metal at an antiferromagnetic
critical point. We show how the critical spin fluctuations at the AFM
wavevector q=Q induce energy fluctuations at small q, giving rise to a
diverging quasiparticle effective mass over the whole Fermi surface. The
coupling of the fermionic and bosonic degrees of freedom leads to a
self-consistent relation for the effective mass, which has a strong coupling
solution in addition to the well-known weak-coupling, spin-density-wave
solution. We thereby use the recently-introduced concept of critical
quasiparticles, employing a scale-dependent effective mass ratio m*/m and
quasiparticle weight factor Z. As a consequence of the diverging effective mass
the Landau Fermi liquid interaction is found to diverge in all channels except
the critical one, causing important vertex corrections. The ensuing spin
fluctuation spectrum obeys omega/T scaling. Our results are in good agreement
with experimental data on the heavy fermion compounds YbRh2Si2$ and
CeCu(6-x)Au(x) assuming 3D and 2D spin fluctuations, respectively.",1303.3926v2
2013-03-25,Spin stiffness calculation in anisotropic XY model with Ring exchange interaction,"We present the spin wave theory of XY model with anisotropic nearest
neighbour (NN) interactions $J(J^{\prime})$ along the $x(y)$ directions, next
nearest (NNN) neighbour interaction $J_D$ and the ring exchange interaction $K$
on the square lattice. We calculate the thermodynamic quantities: Zero
temperature spin stiffness, internal energy, specific heat and the
magnetization. Using the diagonalized Hamiltonian, we show that no soft modes
develop when $\eta + \lambda >0 $, where $\eta = J^{\prime}/J$ and $\lambda =
K/J$. We further show that anisotropy ($\eta =2$) decreases the spin stiffness
by 5.7% of its isotropic ($\eta =1$) maximum value for some values of $\lambda$
and $\delta = J_D/J$. A similar reduction shows up in the magnetization. The
plot of the stiffness against $\eta (\lambda)$ reaches a maximum at
$\eta=0(\lambda =0)$ for specific values of $\delta$ and decreases rapidly as
it approaches $\eta + \lambda + 1=0$. In general, the supersolid phase
transition suggested earlier\cite{H} will occur in the regime $\eta + \lambda
+1 <0$.",1303.6209v2
2013-04-17,Black-hole perturbation theory: The asymptotic spectrum of the prolate spin-weighted spheroidal harmonics,"Prolate spin-weighted spheroidal harmonics play a key role in black-hole
perturbation theory. In particular, the highly damped quasinormal resonances of
rotating Kerr black holes are closely related to the asymptotic eigenvalues of
these important functions. We here present a novel and compact derivation of
the asymptotic eigenvalues of the prolate spin-weighted spheroidal harmonics.
Our analysis is based on a simple trick which transforms the corresponding
spin-weighted spheroidal angular equation into a Schr\""odinger-like wave
equation which is amenable to a standard WKB analysis. Our analytical results
for the prolate asymptotic spectrum agree with previous numerical computations
of the eigenvalues which appear in the literature.",1304.4683v1
2013-05-10,Spin-Orbit Force from Lattice QCD,"We present a first attempt to determine nucleon-nucleon potentials in the
parity-odd sector, which appear in 1P1, 3P0, 3P1, 3P2-3F2 channels, in Nf=2
lattice QCD simulations. These potentials are constructed from the
Nambu-Bethe-Salpeter wave functions for J^P=0^-, 1^- and 2^-, which correspond
to A1^-, T1^- and T2^- + E^- representation of the cubic group, respectively.
We have found a large and attractive spin-orbit potential VLS(r) in the
isospin-triplet channel, which is qualitatively consistent with the
phenomenological determination from the experimental scattering phase shifts.
The potentials obtained from lattice QCD are used to calculate the scattering
phase shifts in 1P1, 3P0, 3P1 and 3P2-3F2 channels. The strong attractive
spin-orbit force and a weak repulsive central force in spin-triplet P-wave
channels lead to an attraction in the 3P2 channel, which is related to the
P-wave neutron paring in neutron stars.",1305.2293v2
2013-05-21,On the high energy spin excitations in the high temperature superconductors: an RVB theory,"The high energy spin excitation in the high T$_{c}$ cuprates is studied in
the single mode approximation for the $t-t'-J$ model. An exact form for the
mode dispersion is derived. When the Gutzwiller projected BCS state is used as
the variational ground state, a spin-wave-like dispersion of about 2.2$J$ is
uncovered along the $\Gamma=(0,0)$ to $\mathrm{M}=(\pi,0)$ line. Both the mode
energy and the integrated intensity of the spin fluctuation spectrum are found
to be almost doping independent in large doping range, which agrees very well
with the observations of recent RIXS measurements. Together with previous
studies on the quasiparticle properties of the Gutzwiiler projected BCS state,
our results indicate that such a Fermionic RVB theory can provide a consistent
description of both the itinerant and the local aspect of electronic
excitations in the high T$_{c}$ cuprates.",1305.4834v1
2013-06-17,Magnetic excitations in the spin-1/2 triangular-lattice antiferromagnet Cs$_2$CuBr$_4$,"We report on high-field electron spin resonance (ESR) studies of magnetic
excitations in the spin-1/2 triangular-lattice antiferromagnet Cs$_2$CuBr$_4$.
Frequency-field diagrams of ESR excitations are measured for different
orientations of magnetic fields up to 25 T. We show that the substantial
zero-field energy gap, $\Delta\approx9.5$ K, observed in the low-temperature
excitation spectrum of Cs$_2$CuBr$_4$ [Zvyagin $et~al.$, Phys. Rev. Lett. 112,
077206 (2014)], is present well above $T_N$. Noticeably, the transition into
the long-range magnetically ordered phase does not significantly affect the
size of the gap, suggesting that even below $T_N$ the high-energy spin dynamics
in Cs$_2$CuBr$_4$ is determined by short-range-order spin correlations. The
experimental data are compared with results of model spin-wave-theory
calculations for spin-1/2 triangle-lattice antiferromagnet.",1306.3887v3
2013-06-29,First-principles calculations of current-induced spin-transfer torques in magnetic domain walls,"Current-induced spin-transfer torques (STTs) have been studied in Fe, Co and
Ni domain walls (DWs) by the method based on the first-principles noncollinear
calculations of scattering wave functions expanded in the tight-binding
linearized muffin-tin orbital (TB-LMTO) basis. The results show that the
out-of-plane component of nonadiabatic STT in Fe DW has localized form, which
is in contrast to the typical nonlocal oscillating nonadiabatic torques
obtained in Co and Ni DWs. Meanwhile, the degree of nonadiabaticity in STT is
also much greater for Fe DW. Further, our results demonstrate that compared to
the well-known first-order nonadiabatic STT, the torque in the third-order
spatial derivative of local spin can better describe the distribution of
localized nonadiabatic STT in Fe DW. The dynamics of local spin driven by this
third-order torques in Fe DW have been investigated by the
Landau-Lifshitz-Gilbert (LLG) equation. The calculated results show that with
the same amplitude of STTs the DW velocity induced by this third-order term is
about half of the wall speed for the case of the first-order nonadiabatic STT.",1307.0062v1
2013-06-30,Graphene Enabled Low-Control Quantum Gates between Static and Mobile Spins,"We show that the feature of Klein tunneling makes graphene a unique interface
for implementing low control quantum gates between static and mobile qubits. A
ballistic electron spin is considered as the mobile qubit, while the static
qubit is the electronic spin of a quantum dot fixed in a graphene nanoribbon.
Scattering is the low control mechanism of the gate, which, in other systems,
is really difficult to exploit because of both back-scattering and the momentum
dependence of scattering. We find that Klein tunneling enables the
implementation of quasi-deterministic quantum gates regardless of the momenta
or the shape of the wave function of the incident electron. The Dirac equation
is used to describe the system in the one particle approximation with the
interaction between the static and the mobile spins modelled by a Heisenberg
Hamiltonian. Furthermore, we discuss an application of this model to generate
entanglement between two well separated static qubits.",1307.0217v1
2013-07-16,"Gravitational Waveforms for Precessing, Quasicircular Compact Binaries with Multiple Scale Analysis: Small Spin Expansion","We obtain analytical gravitational waveforms in the frequency-domain for
precessing, quasi-circular compact binaries with small spins, applicable, for
example, to binary neutron star inspirals. We begin by calculating an analytic
solution to the precession equations, obtained by expanding in the
dimensionless spin parameters and using multiple-scale analysis to separate
timescales. We proceed by analytically computing the Fourier transform of
time-domain waveform through the stationary phase approximation. We show that
the latter is valid for systems with small spins. Finally, we show that these
waveforms have a high overlap with numerical waveforms obtained through direct
integration of the precession equations and discrete Fourier transformations.
The resulting, analytic waveform family is ideal for detection and parameter
estimation of gravitational waves emitted by inspiraling binary neutron stars
with ground-based detectors.",1307.4418v2
2013-07-31,Relativistic symmetries in trigonometric Poschl-Teller potential plus tensor interaction,"The Dirac equation is solved to obtain its approximate bound states for a
spin-1/2 particle in the presence of trigonometric Poschl-Teller (tPT)
potential including a Coulomb-like tensor interaction with arbitrary spin-orbit
quantum number $\kappa$ using an approximation scheme to substitute the
centrifugal terms k(k+1)/r^2. In view of spin and pseudo-spin (p-spin)
symmetries, the relativistic energy eigenvalues and the corresponding
two-component wave functions of a particle moving in the field of attractive
and repulsive tPT potentials are obtained using the asymptotic iteration method
(AIM). We present numerical results in the absence and presence of tensor
coupling $A$ and for various values of spin and p-spin constants and quantum
numbers n and k. The non-relativistic limit is also obtained.",1308.0008v1
2013-08-01,Inverse Spin Hall Effect in nanometer-thick YIG/Pt system,"High quality nanometer-thick (20 nm, 7 nm and 4 nm) epitaxial YIG films have
been grown on GGG substrates using pulsed laser deposition. The Gilbert damping
coefficient for the 20 nm thick films is 2.3 x 10-4 which is the lowest value
reported for sub-micrometric thick films. We demonstrate Inverse spin Hall
effect (ISHE) detection of propagating spin waves using Pt. The amplitude and
the lineshape of the ISHE voltage correlate well to the increase of the Gilbert
damping when decreasing thickness of YIG. Spin Hall effect based
loss-compensation experiments have been conducted but no change in the
magnetization dynamics could be detected.",1308.0192v1
2013-08-02,Stretched exponential spin relaxation in organic superconductors,"Proton NMR measurements on the organic superconductor
$\kappa-(ET)_2Cu[N(CN)_2]Br$ ($T_C = 11.6$ K) exhibit stretched exponential
spin-lattice relaxation below $T\approx 25$ K, suggestive of an inhomogeneous
magnetic phase that develops in the normal state and coexists with
superconductivity. The onset of this phase coincides approximately with a large
normal state Nernst signal reported previously. By contrast, the closely
related superconductor $\kappa-(ET)_2Cu[(NCS)_2]Br$ ($T_C = 10.5$ K) shows
single exponential spin-lattice relaxation and a conventional Nernst effect.
The temperature range $T_C < T < 30$ K encompasses several phenomena in the
$\kappa-(ET)_2X$ conductors, including changes in conduction electron spin
resonance, electronic phase separation and the onset of antiferromagnetic
order. Analogous behavior in $La_{2-x}Sr_xCuO_4$ suggests that a density wave
may develop in $\kappa-(ET)_2Cu[N(CN)_2]Br$.",1308.0614v1
2013-08-06,Time-domain inspiral templates for spinning compact binaries in quasi-circular orbits described by their orbital angular momenta,"We present a prescription to compute the time-domain gravitational wave (GW)
polarization states associated with spinning compact binaries inspiraling along
quasi-circular orbits. We invoke the orbital angular momentum $\vek L$ rather
than its Newtonian counterpart $\vek L_{\rm N}$ to describe the binary orbits
while the two spin vectors are freely specified in an inertial frame associated
with the initial direction of the total angular momentum. We show that the use
of $\vek L$ to describe the orbits leads to additional 1.5PN order amplitude
contributions to the two GW polarization states compared to the $\vek L_{\rm
N}$-based approach and discuss few implications of our approach. Further, we
provide a plausible prescription for GW phasing based on few theoretical
considerations and which may be treated as the natural circular limit to GW
phasing for spinning compact binaries in inspiraling eccentric orbits
[Gopakumar A and Sch{\""a}fer G 2011 {\em Phys. Rev. D} {\bf 84} 124007].",1308.1315v2
2013-08-28,Re-entrant magnetic field induced charge and spin gaps in the coupled dual-chain quasi-one dimensional organic conductor Perylene$_2$[Pt(mnt)$_2$],"An inductive method is used to follow the magnetic field-dependent
susceptibility of the coupled charge density wave (CDW) and spin-Peierls (SP)
ordered state behavior in the dual chain organic conductor
Perylene$_2$[Pt(mnt)$_2$]. In addition to the coexisting SP-CDW state phase
below 8 K and 20 T, the measurements show that a second spin-gapped phase
appears above 20 T that coincides with a field-induced insulating phase. The
results support a strong coupling of the CDW and SP order parameters even in
high magnetic fields, and provide new insight into the nature of the magnetic
susceptibility of dual-chain spin and charge systems.",1308.6271v1
2013-09-09,The quantum and Klein-Gordon oscillators in a non-commutative complex space and the thermodynamic functions,"In this work we study the quantum and Klein-Gordon oscillators in
non-commutative complex space. We show that the quantum oscillator in
non-commutative complex space obeys an equation similar to the equation of
motion of an electron with spin in a commutative space in an external uniform
magnetic field. Therefore the wave function ${\psi}(z,\bar{z}) $ takes values
in $C^{4}$, spin up, spin down, particle, antiparticle, a result which is
obtained by the Dirac theory. We derive the thermodynamic functions associated
to the partition function. We show that the non-commutativity affects energy at
the high temperature limit. The Klein Gordon oscillator in non-commutative
complex space also has a similar equation of motion to that a fermions with
spin 1/2 in a commutative space in a constant magnetic field. The energy levels
could be obtained by exact solution.",1309.2064v2
2013-10-30,Systematic parameter errors in inspiraling neutron star binaries,"The coalescence of two neutron stars is an important gravitational wave
source for LIGO and other detectors. Numerous studies have considered the
precision with which binary parameters (masses, spins, Love numbers) can be
measured. Here I consider the accuracy with which these parameters can be
determined in the presence of systematic errors due to waveform approximations.
These approximations include truncation of the post-Newtonian (PN) series and
neglect of neutron star (NS) spin, tidal deformation, or orbital eccentricity.
All of these effects can yield systematic errors that exceed statistical errors
for plausible parameter values. In particular, neglecting spin, eccentricity,
or high-order PN terms causes a significant bias in the NS Love number. Tidal
effects will not be measurable with PN inspiral waveforms if these systematic
errors are not controlled.",1310.8288v2
2013-11-29,Generation linewidth of mode-hopping spin torque oscillators,"Experiments on spin torque oscillators commonly observe multi-mode signals.
Recent theoretical works have ascribed the multi-mode signal generation to
coupling between energy-separated spin wave modes. Here, we analyze in detail
the dynamics generated by such mode coupling. We show analytically that the
mode-hopping dynamics broaden the generation linewidth and makes it generally
well described by a Voigt lineshape. Furthermore, we show that the mode-hopping
contribution to the linewidth can dominate in which case it provides a direct
measure of the mode-hopping rate. Due to the thermal drive of mode-hopping
events, the mode-hopping rate also provides information on the energy barrier
separating modes and temperature-dependent linewidth broadening. Our results
are in good agreement with experiments, revealing the physical mechanism behind
the linewidth broadening in multi-mode spin torque oscillators.",1311.7660v1
2013-12-03,Gravitational self-torque and spin precession in compact binaries,"We calculate the effect of self-interaction on the ""geodetic"" spin precession
of a compact body in a strong-field orbit around a black hole. Specifically, we
consider the spin precession angle $\psi$ per radian of orbital revolution for
a particle carrying mass $\mu$ and spin $s \ll (G/c) \mu^2$ in a circular orbit
around a Schwarzschild black hole of mass $M \gg \mu$. We compute $\psi$
through $O(\mu/M)$ in perturbation theory, i.e, including the correction
$\delta\psi$ (obtained numerically) due to the torque exerted by the
conservative piece of the gravitational self-field. Comparison with a
post-Newtonian (PN) expression for $\delta\psi$, derived here through 3PN
order, shows good agreement but also reveals strong-field features which are
not captured by the latter approximation. Our results can inform
semi-analytical models of the strong-field dynamics in astrophysical binaries,
important for ongoing and future gravitational-wave searches.",1312.0775v2
2014-02-09,Site specific spin dynamics in BaFe2As2: tuning the ground state by orbital differentiation,"The role of orbital differentiation on the emergence of superconductivity in
the Fe-based superconductors remains an open question to the scientific
community. In this investigation, we employ a suitable microscopic spin probe
technique, namely Electron Spin Resonance (ESR), to investigate this issue on
selected chemically substituted BaFe$_{2}$As$_{2}$ single crystals. As the
spin-density wave (SDW) phase is suppressed, we observe a clear increase of the
Fe 3$d$ bands anisotropy along with their localization at the FeAs plane. Such
an increase of the planar orbital content interestingly occurs independently on
the chemical substitution responsible for suppressing the SDW phase. As a
consequence, the magnetic fluctuations combined with the resultant particular
symmetry of the Fe 3$d$ bands are propitious ingredients to the emergence of
superconductivity in this class of materials.",1402.2001v1
2014-02-21,Heavy quark symmetry in multi-hadron systems,"We discuss the properties of hadronic systems containing one heavy quark in
the heavy quark limit. The heavy quark symmetry guarantees the mass degeneracy
of the states with total spin and parity $(j-1/2)^{P}$ and $(j+1/2)^{P}$ with
$j \geq 1/2$, because the heavy-quark spin is decoupled from the total spin $j$
of the light components called brown muck. We apply this idea to heavy
multi-hadron systems, and formulate the general framework to analyze their
properties. We demonstrate explicitly the spin degeneracy and the decomposition
of the wave functions in exotic heavy hadron systems generated by the one boson
exchange potential. The masses of the brown muck can be extracted from
theoretical and experimental hadron spectra, leading to the color non-singlet
spectroscopy.",1402.5222v1
2014-02-24,Spin-dependent recombination involving oxygen-vacancy complexes in silicon,"Spin-dependent relaxation and recombination processes in $\gamma$-irradiated
$n$-type Czochralski-grown silicon are studied using continuous wave (cw) and
pulsed electrically detected magnetic resonance (EDMR). Two processes involving
the SL1 center, the neutral excited triplet state of the oxygen-vacancy
complex, are observed which can be separated by their different dynamics. One
of the processes is the relaxation of the excited SL1 state to the ground state
of the oxygen-vacancy complex, the other a charge transfer between $^{31}$P
donors and SL1 centers forming close pairs, as indicated by electrically
detected electron double resonance. For both processes, the recombination
dynamics are studied with pulsed EDMR techniques. We demonstrate the
feasibility of true zero-field cw and pulsed EDMR for spin 1 systems and use
this to measure the lifetimes of the different spin states of SL1 also at
vanishing external magnetic field.",1402.5957v2
2014-03-20,$D$ and $D^{\ast}$ meson mixing in spin-isospin correlated cold nuclear matter,"We propose to study the mass spectrum of the heavy-light mesons to probe the
structure of the spin-isospin correlation in the nuclear medium. We point out
that the spin-isospin correlation in the nuclear medium generates a mixing
among the heavy-light mesons carrying different spins and isospins such as
$D^+$, $D^0$, $D^{\ast +}$, and $D^{\ast 0}$ mesons. We use two types of
correlations motivated by the skyrmion crystal and the chiral density wave as
typical examples to obtain the mass splitting caused by the mixing. Our result
shows that the structure of the mixing reflects the pattern of the correlation,
i.e., the remaining symmetry. Furthermore, the magnitude of the mass
modification provides information of the strength of the correlation.",1403.5140v2
2014-04-10,Macroscopic Quantum Coherence of the Spin Triplet in the Spin-Ladder Compound Sr14Cu24O41,"We report the direct observation by inelastic neutron scattering experiments
of a spin triplet of magnetic excitations in the response associated with the
ladders in the composite cuprate Sr14Cu24O41. This appears as a peak at
q_{Q1D}=\pi and energy \Delta_1=32.5 meV, and we conjecture that all the
triplets making up this conspicuous peak have the same phase and therefore
interpret it as the signature of the occurrence of quantum coherence along the
ladder direction between entangled spin pairs. From the comparison with
previous neutron and x-ray data, we conclude that the temperature evolution of
this mode is driven by the crystallization of holes into a charge density wave
in the ladder sublattice",1404.2890v1
2014-04-24,Strong driving of a single spin using arbitrarily polarized fields,"The strong driving regime occurs when a quantum two-level system is driven
with an external field whose amplitude is greater or equal to the energy
splitting between the system's states, and is typically identified with the
breaking of the rotating wave approximation (RWA). We report an experimental
study, in which the spin of a single nitrogen-vacancy (NV) center in diamond is
strongly driven with microwave (MW) fields of arbitrary polarization. We
measure the NV center spin dynamics beyond the RWA, and characterize the
limitations of this technique for generating high-fidelity quantum gates. Using
circularly polarized MW fields, the NV spin can be harmonically driven in its
rotating frame regardless of the field amplitude, thus allowing rotations
around arbitrary axes. Our approach can effectively remove the RWA limit in
quantum-sensing schemes, and assist in increasing the number of operations in
QIP protocols.",1404.6282v1
2014-05-13,The emergence of classical behavior in magnetic adatoms,"A wide class of nanomagnets shows striking quantum behavior, known as quantum
spin tunneling (QST): instead of two degenerate ground states with opposite
magnetizations, a bonding-antibonding pair forms, resulting in a splitting of
the ground state doublet with wave functions linear combination of two
classically opposite magnetic states, leading to the quenching of their
magnetic moment. Here we study how QST is destroyed and classical behavior
emerges in the case of magnetic adatoms, as the strength of their coupling,
either to the substrate or to each other, is increased. Both spin-substrate and
spin-spin coupling renormalize the QST splitting to zero allowing the
environmental decoherence to eliminate superpositions between classical states,
leading to the emergence of spontaneous magnetization.",1405.3304v1
2014-05-23,Spin Order by Quantum Frustration in Triangular Lattice Mott Insulator NaCrO2 : A Neutron Scattering Study,"We report high resolution neutron scattering measurements on the triangular
lattice Mott insulator Na$_x$CrO$_2$ ($x$=1) which has recently been shown to
exhibit an unusually broad fluctuating crossover regime extending far below the
onset of spin freezing ($T_c\sim$41K). Our results show that below some
crossover temperature ($T\sim0.75T_c$) a small incommensuration develops which
helps resolve the spin frustration and drives three-dimensional magnetic order
supporting coherent spin wave modes. This incommensuration assisted dimensional
crossover suggests that inter-layer frustration is responsible for stabilizing
the rare 2D correlated phase above 0.75$T_c$. In contrast to the host compound
of 2D cobaltate superconductor such as Na$_x$CoO$_2$ ($\xi_c>50$\AA), no
magnetic long-range order is observed down to 1.5K ($\xi_c<16$\AA).",1405.6184v1
2014-07-02,Short-range cluster spin glass near optimal superconductivity in BaFe$_{2-x}$Ni$_{x}$As$_{2}$,"High-temperature superconductivity in iron pnictides occurs when electrons
are doped into their antiferromagnetic (AF) parent compounds. In addition to
inducing superconductivity, electron-doping also changes the static
commensurate AF order in the undoped parent compounds into short-range
incommensurate AF order near optimal superconductivity. Here we use neutron
scattering to demonstrate that the incommensurate AF order in
BaFe$_{2-x}$Ni$_{x}$As$_{2}$ is not a spin-density-wave arising from the
itinerant electrons in nested Fermi surfaces, but consistent with a cluster
spin glass in the matrix of the superconducting phase. Therefore, optimal
superconductivity in iron pnictides coexists and competes with a mesoscopically
separated cluster spin glass phase, much different from the homogeneous
coexisting AF and superconducting phases in the underdoped regime.",1407.0568v1
2014-07-21,Causality Constraints on Corrections to the Graviton Three-Point Coupling,"We consider higher derivative corrections to the graviton three-point
coupling within a weakly coupled theory of gravity. Lorentz invariance allows
further structures beyond the one present in the Einstein theory. We argue that
these are constrained by causality. We devise a thought experiment involving a
high energy scattering process which leads to causality violation if the
graviton three-point vertex contains the additional structures. This violation
cannot be fixed by adding conventional particles with spins $J \leq 2$. But, it
can be fixed by adding an infinite tower of extra massive particles with higher
spins, $J > 2$. In AdS theories this implies a constraint on the conformal
anomaly coefficients $\left|{a - c \over c} \right| \lesssim {1 \over
\Delta_{gap}^2}$ in terms of $\Delta_{gap}$, the dimension of the lightest
single particle operator with spin $J > 2$. For inflation, or de Sitter-like
solutions, it indicates the existence of massive higher spin particles if the
gravity wave non-gaussianity deviates significantly from the one computed in
the Einstein theory.",1407.5597v1
2014-08-30,Identifying a bath-induced Bose liquid in interacting spin-boson models,"We study the ground state phase diagram of a one-dimensional hard-core
bosonic model with nearest-neighbor interactions (XXZ model) where every site
is coupled Ohmically to an independent but identical reservoir, hereby
generalizing spin-boson models to interacting spin-boson systems. We show that
a bath-induced Bose metal phase can occur in the ground state phase diagram
away from half filling. This phase is compressible, gapless, and conducting but
not superfluid. At haf-filling, only a Luttinger liquid and a charge density
wave are found. The phase transition between them is of Kosterlitz-Thouless
type where the Luttinger parameter takes a non-universal value.The applied
quantum Monte Carlo method can be used for all open bosonic and unfrustrated
spin systems, regardless of their dimension, filling factor and spectrum of the
dissipation as long as the quantum system couples to the bath via the density
operators.",1409.0142v3
2014-11-28,Towards holographic higher-spin interactions: Four-point functions and higher-spin exchange,"Within holography, we calculate the contribution of an arbitrary spin-s gauge
boson exchange in $AdS_{d+1}$ to the four-point function with scalar operators
on the boundary. As an important ingredient, we first compute the complete
bulk-to-bulk propagators for massless bosonic higher-spin fields in the
metric-like formulation, in any dimension and in various gauges. The split
representation of the bulk-to-bulk propagators in terms of bulk-to-boundary
propagators allows to present the higher-spin exchange diagram in the form of a
conformal partial wave expansion. Our results provide a step towards the larger
goal of the holographic reconstruction of bulk interactions, and of clarifying
bulk locality.",1412.0016v2
2014-12-03,Spin dynamics of the bilinear-biquadratic $S=1$ Heisenberg model on the triangular lattice: a quantum Monte Carlo study,"We study thermodynamic properties as well as the dynamical spin and
quadrupolar structure factors of the O(3)-symmetric spin-1 Heisenberg model
with bilinear-biquadratic exchange interactions on the triangular lattice.
Based on a sign-problem-free quantum Monte Carlo approach, we access both the
ferromagnetic and the ferroquadrupolar ordered, spin nematic phase as well as
the SU(3)-symmetric point which separates these phases. Signatures of Goldstone
soft-modes in the dynamical spin and the quadrupolar structure factors are
identified, and the properties of the low-energy excitations are compared to
the thermodynamic behavior observed at finite temperatures as well as to
Schwinger-boson flavor-wave theory.",1412.1225v1
2014-12-29,Unusual ordered phases of highly frustrated magnets: a review,"We review ground states and excitations of a quantum antiferromagnet on
triangular and other frustrated lattices. We pay special attention to the
combined effects of magnetic field h, spatial anisotropy R, and spin magnitude
S. The focus of the review is on the novel collinear spin density wave and spin
nematic states, which are characterized by fully gapped transverse spin
excitations with $S^z = \pm 1$. We discuss extensively R-h phase diagram of the
antiferromagnet, both in the large-S semiclassical limit and the quantum S=1/2
limit. When possible, we point out connections with experimental findings.",1412.8482v1
2015-01-09,First-principles theory of electron-spin fluctuation coupling and superconducting instabilities in iron selenide,"We present first-principles calculations of the coupling of quasiparticles to
spin fluctuations in iron selenide and discuss which types of superconducting
instabilities this coupling gives rise to. We find that strong
antiferromagnetic stripe-phase spin fluctuations lead to large coupling
constants for superconducting gaps with $s_\pm$-symmetry, but these coupling
constants are significantly reduced by other spin fluctuations with small wave
vectors. An accurate description of this competition and an inclusion of band
structure and Stoner parameter renormalization effects lead to a value of the
coupling constant for an $s_\pm$-symmetric gap which can produce a
superconducting transition temperature consistent with experimental
measurements.",1501.02200v1
2015-01-23,Giant gap in the magnon excitations of the quasi-1D chain compound Sr3NiIrO6,"Inelastic neutron scattering on the spin-chain compound Sr$_3$NiIrO$_6$
reveals gapped quasi-1D magnetic excitations. The observed one-magnon band
between 29.5 and 39 meV consists of two dispersive modes. The spin wave
spectrum could be well fitted with an antiferromagnetic anisotropic exchange
model and single ion anisotropy on the Ni site. The extracted dominant
anisotropic antiferromagnetic intra-chain exchange interaction between Ir and
Ni ions are $J_z=19.5$ meV and $J_{xy}=12.1$ meV. These values justify previous
electronic structure calculations, showing the importance of Ir spin orbit
coupling on the electron correlations. The magnetic excitations survive up to
200 K well above the magnetic ordering temperature of $T_N \sim 70$ K, also
indicating a quasi-1D nature of the magnetic interactions in Sr$_3$NiIrO$_6$.
Our results not only support the idea of the existence of a new temperature
scale well above $T_N$, but also emphasize the need to consider new exchange
paths complicated by the SOC, resulting in additional characteristic
temperatures in such spin-chain systems.",1501.05735v1
2015-01-26,Dynamics of magnon fluid in Dzyaloshinskii-Moriya magnet and its manifestation in magnon-Skyrmion scattering,"We construct Holstein-Primakoff Hamiltonian for magnons in arbitrary slowly
varying spin background, for a microscopic spin Hamiltonian consisting of
ferromagnetic spin exchange,Dzyaloshinskii-Moriya exchange, and the Zeeman
term. The Gross-Pitaevskii-type equation for magnon dynamics contains several
background gauge fields pertaining to local spin chirality, inhomogeneous
potential, and anomalous scattering that violates the boson number
conservation. Non-trivial corrections to previous formulas derived in the
literature are given. Subsequent mapping to hydrodynamic fields yields the
continuity equation and the Euler equation of the magnon fluid dynamics. Magnon
wave scattering off a localized Skyrmion is examined numerically based on our
Gross-Pitaevskii formulation. Dependence of the effective flux experienced by
the impinging magnon on the Skyrmion radius is pointed out, and compared with
analysis of the same problem using the Landau-Lifshitz-Gilbert equation.",1501.06467v1
2015-02-06,Quantum fluctuations stabilize Skyrmion textures,"Here we show that the zero point energy associated to the quantum spin
fluctuations of a non- collinear spin texture produce Casimir-like magnetic
fields. We study the effect of these Casimir fields on the topologically
protected non-collinear spin textures known as skyrmions. We calculate the zero
point energy, to the lowest order in the spin wave expansion, in a Heisenberg
model with Dzyalonshinkii-Moriya interactions chosen so that the classical
ground state displays skyrmion textures, that disappear upon application of a
strong enough magnetic field. Our calculations show that the Casimir magnetic
field contributes a 10 percent of the total Zeeman energy necessary to delete
the skyrmion texture with an applied field, and is thereby an observable
effect.",1502.01950v1
2015-02-10,Spin Andreev-like reflection in metal-Mott insulator heterostructures,"Using the time-dependent density-matrix renormalization group (tDMRG), we
study the time evolution of electron wave packets in one-dimensional (1D)
metal-superconductor heterostructures. The results show Andreev reflection at
the interface, as expected. By combining these results with the well-known
single-spin-species electron-hole transformation in the Hubbard model, we
predict an analogous spin Andreev reflection in metal-Mott insulator
heterostructures. This effect is numerically confirmed using 1D tDMRG, but it
is expected to be present also in higher dimensions, as well as in more general
Hamiltonians. We present an intuitive picture of the spin reflection, analogous
to that of Andreev reflection at metal-superconductors interfaces. This allows
us to discuss a novel antiferromagnetic proximity effect. Possible experimental
realizations are discussed.",1502.03006v1
2015-02-19,The thermal Hall effect of spin excitations in a Kagome magnet,"At low temperatures, the thermal conductivity of spin excitations in a
magnetic insulator can exceed that of phonons. However, because they are charge
neutral, the spin waves are not expected to display a thermal Hall effect in a
magnetic field. Recently, this semiclassical notion has been upended in quantum
magnets in which the spin texture has a finite chirality. In the Kagome
lattice, the chiral term generates a Berry curvature. This results in a thermal
Hall conductivity $\kappa_{xy}$ that is topological in origin. Here we report
observation of a large $\kappa_{xy}$ in the Kagome magnet Cu(1-3, bdc) which
orders magnetically at 1.8 K. The observed $\kappa_{xy}$ undergoes a remarkable
sign-reversal with changes in temperature or magnetic field, associated with
sign alternation of the Chern flux between magnon bands. We show that thermal
Hall experiments probe incisively the effect of Berry curvature on heat
transport.",1502.05688v1
2015-03-21,Transfer of high-dimensional quantum state through an XXZ-Heisenberg quantum spin chain,"We propose and analyze an efficient high-dimensional quantum state transfer
scheme through an $XXZ$-Heisenberg spin chain in an inhomogeneous magnetic
field. By the use of a combination of coherent quantum coupling and free
spin-wave approximation, pure unitary evolution results in a perfect
high-dimensional swap operation between two remote quantum registers mediated
by a uniform quantum data bus, and the feasibility is confirmed by numerical
simulations. Also, we observe that either the strong $z$-directional coupling
or high quantum spin number can partly suppress the thermal excitations and
protect quantum information from the thermal noises when the quantum data bus
is in the thermal equilibrium state.",1503.06274v2
2015-03-24,Eccentric mergers of black holes with spinning neutron stars,"We study dynamical capture binary black hole-neutron star (BH-NS) mergers
focusing on the effects of the neutron star spin. These events may arise in
dense stellar regions, such as globular clusters, where the majority of neutron
stars are expected to be rapidly rotating. We initialize the BH-NS systems with
positions and velocities corresponding to marginally unbound Newtonian orbits,
and evolve them using general-relativistic hydrodynamical simulations. We find
that even moderate spins can significantly increase the amount of mass in
unbound material. In some of the more extreme cases, there can be up to a third
of a solar mass in unbound matter. Similarly, large amounts of tidally stripped
material can remain bound and eventually accrete onto the BH---as much as a
tenth of a solar mass in some cases. These simulations demonstrate that it is
important to treat neutron star spin in order to make reliable predictions of
the gravitational wave and electromagnetic transient signals accompanying these
sources.",1503.07171v3
2015-04-06,Quantum order by disorder in the Kitaev model on a triangular lattice,"We identify and discuss the ground state of a quantum magnet on a triangular
lattice with bond-dependent Ising-type spin couplings, that is, a triangular
analog of the Kitaev honeycomb model. The classical ground-state manifold of
the model is spanned by decoupled Ising-type chains, and its accidental
degeneracy is due to the frustrated nature of the anisotropic spin couplings.
We show how this subextensive degeneracy is lifted by a quantum
order-by-disorder mechanism and study the quantum selection of the ground state
by treating short-wavelength fluctuations within the linked cluster expansion
and by using the complementary spin-wave theory. We find that quantum
fluctuations couple next-nearest-neighbor chains through an emergent four-spin
interaction, while nearest-neighbor chains remain decoupled. The remaining
discrete degeneracy of the ground state is shown to be protected by a hidden
symmetry of the model.",1504.01435v3
2015-04-19,Motion of free spins and NMR imaging without a radio-frequency magnetic field,"NMR imaging without any radio-frequency magnetic field is explained by a
quantum treatment of independent spin~$\tfrac 12$. The total magnetization is
determined by means of their individual wave function. The theoretical
treatment, based on fundamental axioms of quantum mechanics and solving
explicitly the Schr\""{o}dinger equation with the kinetic energy part which
gives the motion of free spins, is recalled. It explains the phase shift of the
spin noise spectrum with its amplitude compared to the conventional NMR
spectrum. Moreover it explains also the relatively good signal to noise ratio
of NMR images obtained without a RF pulse. This derivation should be helpful
for new magnetic resonance imaging sequences or for developing quantum
computing by NMR.",1504.04882v1
2015-05-21,Isofrequency pairing of spinning particles in Schwarzschild-de Sitter spacetime,"It has been established in Schwarzschild spacetime (and more generally in
Kerr spacetime) that pairs of geometrically different timelike geodesics with
the same radial and azimuthal frequencies exist in the strong field regime. The
occurrence of this socalled isofrequency pairing is of relevance in view of
gravitational-wave observations. In this paper we generalize the results on
isofrequency pairing in two directions. Firstly, we allow for a (positive)
cosmological constant, i.e., we replace the Schwarzschild spacetime with the
Schwarzschild-de Sitter spacetime. Secondly, we consider not only spinless
test-particles (i.e., timelike geodesics) but also test-particles with spin. In
the latter case we restrict to the case that the motion is in the equatorial
plane with the spin perpendicular to this plane. We find that the cosmological
constant as well as the spin have distinct impacts on the description of bound
motion in the frequency domain.",1505.05728v1
2015-06-03,Dibaryons in a constituent quark model,"We investigate the properties of dibaryons containing u and d quarks in the
constituent quark model. In constructing the ground state wave function, we
choose the spatial part to be fully symmetric and the remaining color, isospin
and spin part to be antisymmetric so as to satisfy the the Pauli principle. By
adapting the IS coupling scheme that combine the isospin basis function with
the spin basis function, and subsequently coupling this to the color singlet
basis function, we construct the color $\otimes$ isospin $\otimes$ spin states
compatible with the physical states of the dibaryon. By using the variational
method, we then calculate the mass of the dibaryon in a nonrelativistic
potential model, involving Coulomb, color confinement and color-spin hyperfine
interaction. In particular, to asses the stability for different types of the
confinement potential, we introduce one that is linearly proportional to the
interquark distance and another to its square root. For all cases considered,
we find that there are no compact bound states against the strong decay.",1506.01123v1
2015-06-19,Charge-spin-orbital Fluctuations in Mixed Valence Spinels: Comparative Study of AlV2O4 and LiV2O4,"Mixed valence spinels provide a fertile playground for the interplay between
charge, spin, and orbital degrees of freedom in strongly correlated electrons
on a geometrically frustrated lattice. Among them, AlV$_2$O$_4$ and
LiV$_2$O$_4$ exhibit contrasting and puzzling behavior: self-organization of
seven-site clusters and heavy fermion behavior. We theoretically perform a
comparative study of charge-spin-orbital fluctuations in these two compounds,
on the basis of the multiband Hubbard models constructed by using the
maximally-localized Wannier functions obtained from the ab initio band
calculations. Performing the eigenmode analysis of the generalized
susceptibility, we find that, in AlV$_2$O$_4$, the relevant fluctuation appears
in the charge sector in $\sigma$-bonding type orbitals. In contrast, in
LiV$_2$O$_4$, optical-type spin fluctuations in the $a_{\rm 1g}$ orbital are
enhanced at an incommensurate wave number at low temperature. Implications from
the comparative study are discussed for the contrasting behavior, including the
metal-insulator transition under pressure in LiV$_2$O$_4$.",1506.06023v2
2015-07-14,"Level crossing, spin structure factor and quantum phases of the frustrated spin-1/2 chain with first and second neighbor exchange","The spin-1/2 chain with isotropic Heisenberg exchange $J_1$, $J_2 > 0$
between first and second neighbors is frustrated for either sign of J1. Its
quantum phase diagram has critical points at fixed $J_1/J_2$ between gapless
phases with nondegenerate ground state (GS) and quasi-long-range order (QLRO)
and gapped phases with doubly degenerate GS and spin correlation functions of
finite range. In finite chains, exact diagonalization (ED) estimates critical
points as level crossing of excited states. GS spin correlations enter in the
spin structure factor $S(q)$ that diverges at wave vector $q_m$ in QLRO($q_m$)
phases with periodicity $2\pi/q_m$ but remains finite in gapped phases.
$S(q_m)$ is evaluated using ED and density matrix renormalization group (DMRG)
calculations. Level crossing and the magnitude of $S(q_m)$ are independent and
complementary probes of quantum phases, based respectively on excited and
ground states. Both indicate a gapless QLRO($\pi/2$) phase between $-1.2 <
J_1/|J_2| < 0.45$. Numerical results and field theory agree well for quantum
critical points at small frustration $J_2$ but disagree in the sector of weak
exchange $J_1$ between Heisenberg antiferromagnetic chains on sublattices of
odd and even-numbered sites.",1507.03720v1
2015-08-06,Odd-parity superconductivity by competing spin-orbit coupling and orbital effect in artificial heterostructures,"We show that odd-parity superconductivity occurs in multilayer Rashba systems
without requiring spin-triplet Cooper pairs. A pairing interaction in the
spin-singlet channel stabilizes the odd-parity pair-density-wave (PDW) state in
the magnetic field parallel to the two-dimensional conducting plane. It is
shown that the layer-dependent Rashba spin-orbit coupling and the orbital
effect play essential roles for the PDW state in binary and tricolor
heterostructures. We demonstrate that the odd-parity PDW state is a
symmetry-protected topological superconducting state characterized by the
one-dimensional winding number in the symmetry class BDI. The superconductivity
in the artificial heavy-fermion superlattice CeCoIn_5/YbCoIn_5 and bilayer
interface SrTiO_3/LaAlO_3 is discussed.",1508.01333v2
2015-09-10,Variation after full projection with triaxially deformed nuclear mean field,"We implemented a variation after projection (VAP) algorithm based on a
triaxially deformed Hartree-Fock-Bogoliubov vacuum state. This is the first
projected mean field study that includes all the quantum numbers (except
parity), i.e., spin ($J$), isospin ($T$) and mass number ($A$). Systematic VAP
calculations with $JTA$-projection have been performed for the even-even
$sd$-shell nuclei with the USDB Hamiltonian. All the VAP ground state energies
are within 500 keV above the exact shell model values. Our VAP calculations
show that the spin projection has two important effects: (1) the spin
projection is crucial in achieving good approximation of the full shell model
calculation. (2) the intrinsic shapes of the VAP wavefunctions with spin
projection are always triaxial, while the Hartree-Fock-Bogoliubov methods
likely provide axial intrinsic shapes. Finally, our analysis suggests that one
may not be possible to associate an intrinsic shape to an exact shell model
wave function.",1509.03058v1
2015-09-14,Spectral characteristics of time resolved magnonic spin Seebeck effect,"Spin Seebeck effect (SSE) holds promise for new spintronic devices with
low-energy consumption. The underlying physics, essential for a further
progress, is yet to be fully clarified. This study of the time resolved
longitudinal SSE in the magnetic insulator yttrium iron garnet (YIG) concludes
that a substantial contribution to the spin current stems from small
wave-vector subthermal exchange magnons. Our finding is in line with the recent
experiment by S. R. Boona and J. P. Heremans, Phys. Rev. B 90, 064421 (2014).
Technically, the spin-current dynamics is treated based on the
Landau-Lifshitz-Gilbert (LLG) equation also including magnons back-action on
thermal bath, while the formation of the time dependent thermal gradient is
described self-consistently via the heat equation coupled to the magnetization
dynamics",1509.04018v1
2015-09-14,Transverse Chiral Optical Forces by Chiral Surface Plasmon Polaritons,"Recently the new concepts of transverse spin angular momentum and Belinfante
spin momentum of evanescent waves have drawn considerable attention. Here, we
investigate these novel physical properties of electromagnetic fields in the
context of locally excited surface plasmon polaritons. We demonstrate, both
analytically and numerically, that locally excited surface plasmon polaritons
possess transverse spin angular momentum and Belinfante momentum with rich and
non-trivial characteristics. We also show that the transverse spin angular
momentum of locally excited surface plasmon polaritons leads to the emergence
of transverse chiral forces in opposite directions for chiral objects of
different handedness. The magnitude of such a transverse force is comparable to
the optical gradient force and scattering forces. This finding may pave the way
for realization of optical separation of chiral biomolecules.",1509.04270v2
2015-09-16,Antiferromagnetic order in CeCoIn5 oriented by spin-orbital coupling,"An incommensurate spin density wave ($Q$ phase) confined inside the
superconducting state at high basal plane magnetic field is an unique property
of the heavy fermion metal CeCoIn$_5$. The neutron scattering experiments and
the theoretical studies point out that this state come out from the soft mode
condensation of magnetic resonance excitations. We show that the fixation of
direction of antiferromagnetic modulations by a magnetic field reported by
Gerber et al., Nat. Phys. {\bf 10}, 126 (2014) is explained by spin-orbit
coupling. This result, obtained on the basis of quite general phenomenological
arguments, is supported by the microscopic derivation of the $\chi_{zz}$
susceptibility dependence on the mutual orientation of the basal plane magnetic
field and the direction of modulation of spin polarization in a multi-band
metal.",1509.04915v4
2015-09-24,Self-Organized Topological Superconductivity in a Yu-Shiba-Rusinov Chain,"We study a chain of magnetic moments exchange coupled to a conventional three
dimensional superconductor. In the normal state the chain orders into a
collinear configuration, while in the superconducting phase we find that
ferromagnetism is unstable to the formation of a magnetic spiral state. Beyond
weak exchange coupling the spiral wavevector greatly exceeds the inverse
superconducting coherence length as a result of the strong spin-spin
interaction mediated through the subgap band of Yu-Shiba-Rusinov states.
Moreover, the simple spin-spin exchange description breaks down as the subgap
band crosses the Fermi energy, wherein the spiral phase becomes stabilized by
the spontaneous opening of a $p-$wave superconducting gap within the band. This
leads to the possibility of electron-driven topological superconductivity with
Majorana boundary modes using magnetic atoms on superconducting surfaces.",1509.07399v2
2015-10-02,On the Extraction of Exchange Parameters in Transition-Metal Perovskites,"The extraction of exchange parameters from measured spin-wave dispersion
relations has severe limitations particularly for magnetic compounds such as
the transition-metal perovskites, where the nearest-neighbor exchange parameter
usually dominates the couplings between the further-distant-neighbor spins.
Very precise exchange parameters beyond the nearest-neighbor spins can be
obtained by neutron spectroscopic investigations of the magnetic excitation
spectra of isolated multimers in magnetically diluted compounds. This is
exemplified for manganese trimers in the mixed three- and two-dimensional
perovskite compounds KMnxZn1-xF3 and K2MnxZn1-xF4, respectively. It is shown
that the small exchange couplings between the second-nearest and the
third-nearest neighboring spins can be determined unambiguously and with equal
precision as the dominating nearest-neighbor exchange coupling.",1510.00569v1
2015-11-29,Single to multi quasiparticle excitations in the itinerant helical magnet CeRhIn$_{5}$,"CeRhIn$_{5}$ is an itinerant magnet where the Ce$^{3+}$ spins order in a
simple helical phase. We investigate the spin excitations and observe sharp
spin-waves parameterized by a nearest neighbor exchange $J_{RKKY}$=0.88 $\pm$
0.05 meV. At higher energies, the spin fluctuations are heavily damped where
single quasiparticle excitations are replaced by a momentum and energy
broadened continuum constrained by kinematics of energy and momentum
conservation. The delicate energy balance between localized and itinerant
characters results in the breakdown of the single quasiparticle picture in
CeRhIn$_{5}$.",1511.09003v1
2015-11-30,Tricriticalities and Quantum Phases in Spin-Orbit-Coupled Spin-$1$ Bose Gases,"We study the zero-temperature phase diagram of a spin-orbit-coupled
Bose-Einstein condensate of spin $1$, with equally weighted Rashba and
Dresselhaus couplings. Depending on the antiferromagnetic or ferromagnetic
nature of the interactions, we find three kinds of striped phases with
qualitatively different behaviors in the modulations of the density profiles.
Phase transitions to the zero-momentum and the plane-wave phases can be induced
in experiments by independently varying the Raman coupling strength and the
quadratic Zeeman field. The properties of these transitions are investigated in
detail, and the emergence of tricritical points, which are the direct
consequence of the spin-dependent interactions, is explicitly discussed.",1511.09225v2
2015-12-17,Role of vibrations on decoherence in molecular spin qubits: The case of [Cu(mnt)$_2$]$^{2-}$,"Herein we develop a simple first-principles methodology to determine the
modulation that vibrations exert on spin energy levels, a key for the rational
design of high-temperature molecular spin qubits and single-molecule magnets.
This methodology is demonstrated by applying it to [Cu(mnt)$_2$]$^{2-}$
(mnt$^{2-}$ = 1,2-dicyanoethylene-1,2-dithiolate), a highly coherent complex,
using DFT to calculate the normal vibrational modes and wave-function based
theory calculations to estimate the spin energy level structure. By
theoretically identifying the most relevant vibrational modes, we are able to
offer general strategies to chemically design more resilient magnetic
molecules, where the qubit energy is not coupled to local vibrations.",1512.05690v2
2015-12-22,Observation of Unusual Magnetoelastic Effects in a Quasi-1D Spiral Magnet,"We present a systematic study of spin and lattice dynamics in the
quasi-one-dimensional spiral magnet CuBr2, using Raman scattering in
conjunction with infrared and neutron spectroscopy. Along with the development
of spin correlations upon cooling, we observe a rich set of broad Raman bands
at energies that correspond to phonon-dispersion energies near the
one-dimensional magnetic wave vector. The low-energy bands further exhibit a
distinct intensity maximum at the spiral magnetic ordering temperature. We
attribute these unusual observations to two possible underlying mechanisms: (1)
formation of hybrid spin-lattice excitations, and/or (2) ""quadrumerization"" of
the lattice caused by spin-singlet entanglement in competition with the spiral
magnetism.",1512.07120v2
2015-12-23,Bose-Einstein condensate in an optical lattice with Raman-assisted two-dimensional spin-orbit coupling,"In a recent experiment by Wu {\textit et al.} (arXiv:1511.08170), a
Raman-assisted two-dimensional spin-orbit coupling has been realized for a
Bose-Einstein condensate in an optical lattice potential. In light of this
exciting progress, we study in detail key properties of the system. As the
Raman lasers inevitably couple atoms to high-lying bands, the behaviors of the
system in both the single- and many-particle sectors are significantly
affected. In particular, the high-band effects enhance the plane-wave phase and
lead to the emergence of ""roton"" gaps at low Zeeman fields. Furthermore, we
identify high-band-induced topological phase boundaries in both the
single-particle and the quasi-particle spectra. We then derive an effective
two-band model, which captures the high-band physics in the experimentally
relevant regime. Our results not only offer valuable insights into the novel
two-dimensional lattice spin-orbit coupling, but also provide a systematic
formalism to model high-band effects in lattice systems with Raman-assisted
spin-orbit couplings.",1512.07448v3
2016-01-26,Jahn-Teller effect in systems with strong on-site spin-orbit coupling,"When strong spin-orbit coupling removes orbital degeneracy, it would at the
same time appear to render the Jahn-Teller mechanism ineffective. We discuss
such a situation, the t_2g manifold of iridates, and show that, while the
Jahn-Teller effect does indeed not affect the j_eff=1/2 antiferromagnetically
ordered ground state, it leads to distinctive signatures in the j_eff=3/2
spin-orbit exciton. It allows for a hopping of the spin-orbit exciton between
the nearest neighbor sites without producing defects in the j_eff=1/2
antiferromagnet. This arises because the lattice-driven Jahn-Teller mechanism
only couples to the orbital degree of freedom, but is not sensitive to the
phase of the wave function that defines isospin j_z. This contrasts sharply
with purely electronic propagation, which conserves isospin, and presence of
Jahn-Teller coupling can explain some of the peculiar features of measured
resonant inelastic x-ray scattering spectra of Sr_2IrO_4.",1601.07069v1
2016-02-05,Generalized Surface Polaritons and their quantum spin Hall effect,"Surface polaritons, e.g., surface plasmon polaritons, are invaluable tools in
nanophotonics. However, considerable plasmon loss narrows the application
regime of plasmonic devices. Here we reveal some general conditions for
lossless surface polaritons to emerge at the interface of a gain and a loss
media. The gain medium does not only compensate the energy loss, but also
modifies surface wave oscillation mechanisms. A new type of surface polaritons
induced by the sign switch of the imaginary part of the permittivity across the
interface is discovered. The surface polaritons exhibit spin Hall effect due to
spin-momentum locking and unique Berry phase. The spin Hall coefficient changes
the sign across the parity-time symmetric limit and becomes quantized for
perfect metal-dielectric interface and for dielectric-dielectric interface with
very large permittivity contrast, carrying opposite topological numbers. Our
study opens a new direction for manipulating light with surface polaritons in
non-Hermitian optical systems.",1602.01926v1
2016-05-14,Coherent perfect absorption mediated enhancement of transverse spin in a gap plasmon guide,"We consider a symmetric gap plasmon guide (a folded Kretschmann
configuration) supporting both symmeric and antisymmetric coupled surface
plasmons. We calculate the transverse spin under illumination from both the
sides like in coherent perfect absorption (CPA), whereby all the incident light
can be absorbed to excite one of the modes of the structure. Significant
enhancement in the transverse spin is shown to be possible when the CPA dip and
the mode excitation are at the same frequency. The enhancement results from
CPA-mediated total transfer of the incident light to either of the coupled
modes and the associated large local fields. The transverse spin is localized
in the structure since in the ambient dielectric there are only incident plane
waves lacking any structure.",1605.04401v5
2016-05-27,Spin-Hall effect and circular birefringence of a uniaxial crystal plate,"The linear birefringence of uniaxial crystal plates is known since the 17th
century, and it is widely used in numerous optical setups and devices. Here we
demonstrate, both theoretically and experimentally, a fine lateral circular
birefringence of such crystal plates. This effect is a novel example of the
spin-Hall effect of light, i.e., a transverse spin-dependent shift of the
paraxial light beam transmitted through the plate. The well-known linear
birefringence and the new circular birefringence form an interesting analogy
with the Goos-H\""anchen and Imbert-Fedorov beam shifts that appear in the light
reflection at a dielectric interface. We report the experimental observation of
the effect in a remarkably simple system of a tilted half-wave plate and
polarizers using polarimetric and quantum-weak-measurement techniques for the
beam-shift measurements. In view of great recent interest in spin-orbit
interaction phenomena, our results could find applications in modern
polarization optics and nano-photonics.",1605.08505v2
2016-06-15,Spin dynamics in Kapitza-Dirac scattering of electrons from bichromatic laser fields,"Kapitza-Dirac scattering of nonrelativistic electrons from counterpropagating
bichromatic laser waves of linear polarization is studied. The focus lies on
the electronic spin dynamics in the Bragg regime when the laser fields possess
a frequency ratio of two. To this end, the time-dependent Pauli equation is
solved numerically, both in coordinate space and momentum space. Our numerical
results are corroborated by analytical derivations. We demonstrate that, for
certain incident electron momenta, the scattering crucially relies on the
electron spin which undergoes characteristic Rabi-like oscillations. A
parameter regime is identified where the Rabi oscillations reach maximum
amplitude. We also briefly discuss spin-dependent Kapitza-Dirac scattering of
protons.",1606.04813v2
2016-07-15,"Honeycomb-lattice Heisenberg-Kitaev model in a magnetic field: Spin canting, metamagnetism, and vortex crystals","The Heisenberg-Kitaev model is a paradigmatic model to describe the magnetism
in honeycomb-lattice Mott insulators with strong spin-orbit coupling, such as
A$_2$IrO$_3$ (A = Na, Li) and $\alpha$-RuCl$_3$. Here we study in detail the
physics of the Heisenberg-Kitaev model in an external magnetic field. Using a
combination of Monte-Carlo simulations and spin-wave theory we map out the
classical phase diagram for different directions of the magnetic field. Broken
SU(2) spin symmetry renders the magnetization process rather complex, with
sequences of phases and metamagnetic transitions. In particular, we find
various large-unit-cell and multi-Q phases including a vortex-crystal phase for
a field in the [111] direction. We also discuss quantum corrections in the
high-field phase.",1607.04640v2
2016-07-18,Unified Spin Model for Magnetic Excitations in Iron Chalcogenides,"Recent inelastic neutron scattering (INS) measurements on FeSe and
Fe(Te$_{1-x}$Se$_x$), have sparked intense debate over the nature of the ground
state in these materials. Here we propose an effective bilinear-biquadratic
spin model which is shown to consistently describe the evolution of low-energy
spin excitations in FeSe, both under applied pressure and upon Se/Te
substitution. The phase diagram, studied using a combination of variational
mean-field, flavor-wave calculations, and density-matrix renormalization group
(DMRG), exhibits a sequence of transitions between the columnar antiferromagnet
common to the iron pnictides, the non-magnetic ferroquadrupolar phase
attributed to FeSe, and the double-stripe antiferromagnetic order known to
exist in Fe$_{1+y}$Te. The calculated spin structure factor in these phases
mimics closely that observed with INS in the Fe(Te$_{1-x}$Se$_x$), series. In
addition to the experimentally established phases, the possibility of
incommensurate magnetic order is also predicted.",1607.05295v3
2016-08-21,Electric transport in three-dimensional Skyrmion/monopole crystal,"We study theoretically the transport properties of a three-dimensional spin
texture made from three orthogonal helices, which is essentially a lattice of
monopole-antimonopole pairs connected by Skyrmion strings. This spin structure
is proposed for MnGe based on the neutron scattering experiment as well as the
Lorentz transmission electron microscopy observation. Equipped with a
sophisticated spectral analysis method, we adopt finite temperature Green's
function technique to calculate the longitudinal dc electric transport in such
system. We consider conduction electrons interacting with spin waves of the
topologically nontrivial spin texture, wherein fluctuations of monopolar
emergent magnetic field enter. We study in detail the behavior of electric
resistivity under the influence of temperature, external magnetic field and a
characteristic monopole motion, especially a novel magnetoresistivity effect
describing the latest experimental observations in MnGe, wherein a topological
phase transition signifying strong correlation is identified.",1608.05902v2
2016-08-24,Anisotropic spin fluctuations in Sr$_2$RuO$_4$: role of spin-orbit coupling and induced strain,"We analyze the spin anisotropy of the magnetic susceptibility of Sr$_2$RuO$4$
in presence of spin-orbit coupling and anisotropic strain using
quasi-two-dimensional tight-binding parametrization fitted to the ARPES
results. Similar to the previous observations we find the in-plane polarization
of the low ${\bf q}$ magnetic fluctuations and the out-of-plane polarization of
the incommensurate magnetic fluctuation at the nesting wave vector ${\bf Q}_1 =
(2/3 \pi ,2/3 \pi)$ but also nearly isotropic fluctuations near ${\bf
Q}_2=(\pi/6,\pi/6)$. Furthermore, one finds that apart from the high-symmetry
direction of the tetragonal Brillouin zone the magnetic anisotropy is maximal,
i.e. $\chi^{xx} \neq \chi^{yy} \neq \chi^{zz}$. This is the consequence of the
orbital anisotropy of the $xz$ and $yz$ orbitals in the momentum space. We also
study how the magnetic anisotropy evolves in the presence of the strain and
find strong Ising-like ferromagnetic fluctuations near the Lifshitz transition
for the $xy$-band.",1608.06786v1
2016-08-29,Impurity effects on spin dynamics in magnetic and superconducting iron pnictides and chalcogenides,"In this paper we summarize the effects of magnetic and nonmagnetic impurities
on the spin dynamics in Febased superconductors and their parent compounds. The
effects of chemical substitution, vacancies, and disorder on the suppression or
stabilization of superconductivity and spin-density-wave phases are reviewed in
the context of recent neutron-spectroscopy measurements of spin excitations. We
also present new results on the structure of magnetic fluctuations in BaFe2As2
single crystals doped with Mn local moments and discuss them in relationship to
the previously reported (pi, pi) branch of checkerboard magnetic excitations.",1608.08123v4
2016-08-31,Relativistic Killingbeck Energy States Under an External Magnetic Fields,"We address the behavior of the Dirac equation with the Killingbeck radial
potential including the external magnetic and Aharonov-Bohm (AB) flux fields.
The spin and pseudo-spin symmetries are considered. The correct bound state
spectra and their corresponding wave functions are obtained. We seek such a
solution using the biconfluent Heun differential equation method. Further, we
give some of our results at the end of this study. Our final results can be
reduced to their non-relativistic forms by simply using some appropriate
transformations. The spectra, in the spin and pseudo-spin symmetries, are very
similar with a slight difference in energy spacing between different states.",1609.00315v1
2016-09-10,Role of correlations on spin-polarized neutron matter,"Using the Hellmann--Feynman theorem we analyze the contribution of the
different terms of the nucleon-nucleon interaction to the spin symmetry energy
of neutron matter. The analysis is performed within the microscopic
Brueckner--Hartree--Fock approach using the Argonne V18 realistic potential
plus the Urbana IX three-body force. The main contribution to the spin-symmetry
energy of neutron matter comes from the S=0 channel, acting only in the
non-polarized neutron matter, in particular the $^1S_0$ and the $^1D_2$ partial
waves. The importance of correlations in spin-polarized neutron matter is
estimated by evaluating the kinetic energy difference between the correlated
system and the underlying Fermi sea.",1609.03005v2
2016-09-12,Equations for spinning test particles in equatorial orbits when they are orbiting in a weak rotating field,"This paper formulates, via the Mathisson - Papapetrou - Dixon equations, the
system of equations for a test particle with spin when it is orbiting a weak
Kerr metric. We shall restrict ourselves to the case of circular orbits with
the purpose of comparing our results with the results of the literature. In
particular, we solve the set of equations of motion for the case of circular
trajectories both spinless and spinning test particles around rotating bodies
in equatorial plane. The results obtained are an important guideline for the
study of the effects of the particles with spin in rotating gravitational
fields such as Gravitomagnetics Effects or gravitational waves.",1609.03630v1
2016-09-15,Diffused vorticity and moment of inertia of a spin-orbit coupled Bose-Einstein condensate,"By developing the hydrodynamic theory of spinor superfluids we calculate the
moment of inertia of a harmonically trapped Bose-Einstein condensate with
spin-orbit coupling. We show that the velocity field associated with the
rotation of the fluid exhibits diffused vorticity, in contrast to the
irrotational behavior characterizing a superfluid. Both Raman-induced and
Rashba spin-orbit couplings are considered. In the first case the moment of
inertia takes the rigid value at the transition between the plane wave and the
single minimum phase, while in the latter case the rigid value is achieved in
the limit of isotropic Rashba coupling. A procedure to generate the rigid
rotation of the fluid and to measure the moment of inertia is proposed. The
quenching of the quantum of circulation $h/m$, caused by Raman induced
spin-orbit coupling in a toroidal geometry, is also discussed.",1609.04694v2
2016-09-19,Illuminating Black Hole Binary Formation Channels with Spins in Advanced LIGO,"The recent detections of the binary black hole mergers GW150914 and GW151226
have inaugurated the field of gravitational-wave astronomy. For the two main
formation channels that have been proposed for these sources, isolated binary
evolution in galactic fields and dynamical formation in dense star clusters,
the predicted masses and merger rates overlap significantly, complicating any
astrophysical claims that rely on measured masses alone. Here, we examine the
distribution of spin- orbit misalignments expected for binaries from the field
and from dense star clusters. Under standard assumptions for black-hole natal
kicks, we find that black-hole binaries similar to GW150914 could be formed
with significant spin-orbit misalignment only through dynamical processes. In
particular, these heavy-black-hole binaries can only form with a significant
spin-orbit anti-alignment in the dynamical channel. Our results suggest that
future detections of merging black hole binaries with measurable spins will
allow us to identify the main formation channel for these systems.",1609.05916v2
2016-09-22,Triplet $p$-wave pairing correlation in low doped zigzag graphene nanoribbons,"We reveal an edge spin triplet $p-$wave superconducting pairing correlation
in slightly doped zigzag graphene nanoribbons. By employing a method that
combines random-phase approximation, the finite-temperature determinant quantum
Monte Carlo approach, and the ground-state constrained-path quantum Monte Carlo
method, it is shown that such a spin-triplet pairing is mediated by the
ferromagnetic fluctuations caused by the flat band at the edge. The spin
susceptibility and effective pairing interactions at the edge strongly increase
as the on-site Coulomb interaction increases, indicating the importance of
electron-electron correlations. It is also found that the doping-dependent
ground-state $p$-wave pairing correlation bears some similarity to the famous
superconducting dome in the phase diagram of a high-temperature superconductor,
while the spin correlation at the edge is weakened as the system is doped away
from half filling.",1609.06858v3
2016-10-04,Effect of temperature on spin-transfer torque induced magnetic solitons,"Spin-transfer torques in a nanocontact to an extended magnetic film can
create spin waves that condense to form dissipative droplet solitons. Here we
report an experimental study of the temperature dependence of the current and
applied field thresholds for droplet soliton formation, as well as the
nanocontact's electrical characteristics associated with droplet dynamics.
Nucleation of droplet solitons requires higher current densities at higher
temperatures, in contrast to typical spin-transfer torque induced switching
between static magnetic states. Magnetoresistance and electrical noise
measurements show that soliton instabilities become more pronounced with
increasing temperature. These results are of fundamental interest in
understanding the influence of thermal noise on droplet solitons, and in
controlling their dynamics.",1610.00931v1
2017-07-10,Theory of ground states for classical Heisenberg spin systems II,"We apply the theory of ground states for classical, finite, Heisenberg spin
systems previously published to a couple of spin systems that can be considered
as finite models $K_{12},\,K_{15}$ and $K_{18}$ of the AF Kagome lattice. The
model $K_{12}$ is isomorphic to the cuboctahedron. In particular, we find
three-dimensional ground states that cannot be viewed as resulting from the
well-known independent rotation of subsets of spin vectors. For a couple of
ground states with translational symmetry we calculate the corresponding wave
numbers. Finally we study the model $K_{12w}$ without boundary conditions which
exhibits new phenomena as, e.~g., two-dimensional families of three-dimensional
ground states.",1707.02859v2
2017-08-11,Accurate inspiral-merger-ringdown gravitational waveforms for non-spinning black-hole binaries including the effect of subdominant modes,"We present an analytical waveform family describing gravitational waves (GWs)
from the inspiral, merger and ringdown of non-spinning black-hole binaries
including the effect of several non-quadrupole modes [($\ell = 2, m = \pm 1),
(\ell = 3, m = \pm 3), (\ell = 4, m = \pm 4)$ apart from $(\ell = 2, m=\pm2)$].
We first construct spin-weighted spherical harmonics modes of hybrid waveforms
by matching numerical-relativity simulations (with mass ratio $1-10$)
describing the late inspiral, merger and ringdown of the binary with
post-Newtonian/effective-one-body waveforms describing the early inspiral. An
analytical waveform family is constructed in frequency domain by modeling the
Fourier transform of the hybrid waveforms making use of analytical functions
inspired by perturbative calculations. The resulting highly accurate,
ready-to-use waveforms are highly faithful (unfaithfulness $\simeq 10^{-4} -
10^{-2}$) for observation of GWs from non-spinning black hole binaries and are
extremely inexpensive to generate.",1708.03501v1
2017-08-23,Uniform energy bound and Morawetz estimate for extreme components of spin fields in the exterior of a slowly rotating Kerr black hole II: linearized gravity,"This second part of the series treats spin $\pm2$ components (or extreme
components), that satisfy the Teukolsky master equation, of the linearized
gravity in the exterior of a slowly rotating Kerr black hole. For each of these
two components, after performing a first-order differential operator once and
twice, the resulting equations together with the Teukolsky master equation
itself constitute a linear spin-weighted wave system. An energy and Morawetz
estimate for spin $\pm 2$ components is proved by treating this system. This is
a first step in a joint work (Andersson et al. in Stability for linearized
gravity on the Kerr spacetime, arXiv:1903.03859, 2019) in addressing the linear
stability of slowly rotating Kerr metrics.",1708.07385v3
2017-09-06,An oscillating Casimir potential between two impurities in a spin-orbit coupled Bose-Einstein condensate,"We study the Casimir potential between two impurities immersed in a
spin-orbit coupled BoseEinstein condensate (BEC) with plane-wave order. We find
that, by exchanging the virtual phonons/excitations, a remarkable anisotropic
oscillating potential with both positive and negative parts can be induced
between the impurities, with the period of the oscillation depending on the
spin-orbit coupling strength. As a consequence, this would inevitably lead to a
non-central Casimir force, which can be tuned by varying the strength of
spin-orbit coupling . These results are elucidated for BECs with
one-dimensional Raman-induced and two-dimensional Rashba-type SOC.",1709.01978v1
2017-09-21,Electrically controllable spin filtering based on superconducting helical states,"The magnetoelectric effects in the surface states of the 3D TI are extremely
strong due to the full spin-momentum locking. Here the microscopic theory of
S/3D TI bilayer structures in terms of quasiclassical Green's functions is
developed. On the basis of the developed formalism it is shown that the DOS in
the S/TI bilayer manifests giant magnetoelectric behavior and, as a result,
S/3D TI heterostructures can work as non-magnetic fully electrically
controllable spin filters. It is shown that due to the full spin-momentum
locking the amplitudes of the odd-frequency singlet and triplet components of
the consensate wave function are equal. The same is valid for the even
frequency singlet and triplet components. We unveil the connection between the
odd-frequency pairing in S/3D TI heterostructures and magnetoelectric effects
in the DOS.",1709.07505v1
2017-10-31,Nuclear Magnetic Resonance in High Magnetic Field: Application to Condensed Matter Physics,"In this review, we describe the potentialities offered by the nuclear
magnetic resonance (NMR) technique to explore at a microscopic level new
quantum states of condensed matter induced by high magnetic fields. We focus on
experiments realised in resistive (up to 34~T) or hybrid (up to 45~T) magnets,
which open a large access to these quantum phase transitions. After an
introduction on NMR observable, we consider several topics: quantum spin
systems (spin-Peierls transition, spin ladders, spin nematic phases,
magnetisation plateaus and Bose-Einstein condensation of triplet excitations),
the field-induced charge density wave (CDW) in high $T_c$~superconductors, and
exotic superconductivity including the Fulde-Ferrel-Larkin-Ovchinnikov
superconducting state and the field-induced superconductivity due to the
Jaccarino-Peter mechanism.",1711.00033v2
2017-11-23,Magnetic and Electronic Properties of Spin-Orbit Coupled Dirac Electrons on a $(001)$ Thin Film of Double Perovskite Sr$_2$FeMoO$_6$,"We present an interacting model for the electronic and magnetic behavior of a
strained $(001)$ atomic layer of Sr$_2$FeMoO$_6,$ which shows room-temperature
ferrimagnetism and magnetoresistance with potential spintronics application in
the bulk. We find that the strong spin-orbit coupling in the molybdenum 4$d$
shell gives rise to a robust ferrimagnetic state with an emergent
spin-polarized electronic structure consisting of flat bands and four massive
or massless Dirac dispersions. Based on the spin-wave theory, we demonstrate
that the magnetic order remains intact for a wide range of doping, leading to
the possibility of exploring flat band physics, such as Wigner crystallization
in electron-doped Sr$_{2-x}$La$_{x}$FeMoO$_6.$",1711.08674v3
2018-01-09,Majorana zero energy modes in silicene,"Zero energy modes are shown to exist in silicene under suitably chosen
magnetic as well as electric fields. Two Majorana modes are found on the
application of opposite local magnetization on the silicene sub-lattices. We
identify a non-Majorana zero energy mode carrying pure spin current under the
influence of inhomogeneous gate electric field. In both cases, wave functions
reveal subtle interference pattern in phase space, showing structures finer
than the Planck constant $\hbar$. A spin system coupled through spin-spin
($\sigma_{z}\otimes\sigma_{z}$) interaction with the Majorana modes exhibits
periodic revival of coherence with a minimum period $\sim $1/n. The same system
shows decoherence-free evolution in the case of gate electric field. Under a
momentum dependent interaction, one Majorana mode having a bound state in the
continuum character is found to be more robust as compared to the other. The
mode arising on application of electric field shows rapid loss of coherence for
such an interaction.",1801.02900v1
2017-12-19,The Three-Dimensionality of Momentum as a Property of Photons,"In the theory of modern physics, such as in relativity and quantum mechanics,
the three-dimensionality of space is introduced as a presupposed fact. The
three-dimensionality of particle motion, that is, the three-dimensionality of
particle momentum, is a result of this fact. In this paper, I make two
assumptions on the spin properties of photons, and then deduce a relation
between the direction of photon momentum and the spin plane to which the photon
spin state belongs. Based on this relation, the three-dimensionality of photon
momentum is taken as the photon's own property. Moreover, this relation allows
us to better understand some of the well-known theoretical results, such as the
change rules of the spin states of spin-1 particles under space rotation as
well as the relation between the momentum direction of the classical
electromagnetic wave and the directions of the electric and magnetic fields.",1801.03766v1
2018-01-12,Control of oxidation and spin state in a single-molecule junction,"The oxidation and spin state of a metal-organic molecule determine its
chemical reactivity and magnetic properties. Here, we demonstrate the
reversible control of the oxidation and spin state in a single Fe-porphyrin
molecule in the force field of the tip of a scanning tunneling microscope.
Within the regimes of half-integer and integer spin state, we can further track
the evolution of the magnetocrystalline anisotropy. Our experimental results
are corroborated by density functional theory and wave function theory. This
combined analysis allows us to draw a complete picture of the molecular states
over a large range of intramolecular deformations.",1801.04162v1
2018-01-15,Transverse spin in scattering of focused radially and azimuthally polarized vector beams,"We study the effect of focusing of the radially and azimuthally polarized
vector beams on the spin angular momentum (SAM) density and Poynting vector of
scattered waves from a Mie particle. Remarkably, the study reveals that the SAM
density of the scattered field is solely transverse in nature for radially and
azimuthally polarized incident vector beams; however the Poynting vector shows
usual longitudinal character. We also demonstrate that the transverse SAM
density can further be tuned with wavelength and focusing of the incident beam
by exploiting the interference of different scattering modes. These results may
stimulate further experimental technique of detecting the transverse spin and
Belinfante's spin-momentum densities.",1801.04832v2
2018-01-26,Enhancement of Superconducting $T_c$ due to the Spin-orbit Interaction,"We calculate the superconducting $T_c$ for a system which experiences Rashba
spin-orbit interactions. Contrary to the usual case where the electron-electron
interaction is assumed to be wave vector-independent, where superconductivity
is suppressed by the spin-orbit interaction (except for a small region at low
electron or hole densities), we find an enhancement of the superconducting
transition temperature when we include a correlated hopping interaction between
electrons. This interaction originates in the expansion of atomic orbitals due
to electron-electron repulsion and gives rise to superconductivity only at high
electron (low hole) densities. When superconductivity results from this
interaction it is enhanced by spin-orbit coupling, in spite of a suppression of
the density of states. The degree of electron-hole asymmetry about the Fermi
surface is also enhanced.",1801.08988v2
2018-03-03,Stable spin domains in a non-degenerate ultra-cold gas,"We study the stability of two-domain spin structures in an ultra-cold gas of
magnetically trapped $^{87}$Rb atoms above quantum degeneracy. Adding a small
effective magnetic field gradient stabilizes the domains via coherent
collective spin rotation effects, despite negligibly perturbing the potential
energy relative to the thermal energy. We demonstrate that domain stabilization
is accomplished through decoupling the dynamics of longitudinal magnetization,
which remains in time-independent domains, from transverse magnetization, which
undergoes a purely transverse spin wave trapped within the domain wall. We
explore the effect of temperature and density on the steady-state domains, and
compare our results to a hydrodynamic solution to a quantum Boltzmann equation.",1803.01096v1
2018-03-06,Refrigeration beyond weak internal coupling,"We investigate the performance of a three-spin quantum absorption
refrigerator using a refined open quantum system model valid across all
inter-spin coupling strengths. It describes the transition between previous
approximate models for the weak and the ultrastrong coupling limit, and it
predicts optimal refrigeration for moderately strong coupling, where both
approximations are inaccurate. Two effects impede a more effective cooling: the
coupling between the spins no longer reduces to a simple resonant energy
exchange (the rotating wave approximation fails), and the interactions with the
thermal baths become sensitive to the level splitting, thus opening additional
heat channels between the reservoirs. We identify the modified conditions of
refrigeration as a function of the inter-spin coupling strength, and we show
that, contrary to intuition, a high-temperature work reservoir thwarts
refrigeration in the strong coupling regime.",1803.02002v2
2018-03-06,Gravitational radiation from the classical spinning double copy,"We establish a correspondence between perturbative classical gluon and
gravitational radiation emitted by spinning sources, to linear order in spin.
This is an extension of the non-spinning classical perturbative double copy and
uses the same color-to-kinematic replacements. The gravitational theory has a
scalar (dilaton) and a 2-form field (the Kalb-Ramon axion) in addition to the
graviton. In arXiv:1712.09250, we computed axion radiation in the gravitational
theory to show that the correspondence fixes its action. Here, we present
complete details of the gravitational computation. In particular, we also
calculate the graviton and dilaton amplitudes in this theory and find that they
precisely match with the predictions of the double copy. This constitutes a
non-trivial check of the classical double copy correspondence, and brings us
closer to the goal of simplifying the calculation of gravitational wave
observables for astrophysically relevant sources.",1803.02405v1
2018-03-09,Phase Transition and Field Effect Topological Quantum Transistor made of monolayer MoS2,"We study topological phase transitions and topological quantum field effect
transistor in monolayer Molybdenum Disulfide (MoS2) using a two-band
Hamiltonian model. Without considering the quadratic (q^2) diagonal term in the
Hamiltonian, we show that the phase diagram includes quantum anomalous Hall
(QAH), quantum spin Hall (QSH), and spin quantum anomalous Hall effect (SQAH)
regions such that the topological Kirchhoff law is satisfied in the plane. By
considering the q^2 diagonal term and including one valley, it is shown that
MoS2 has a non-trivial topology, and the valley Chern number is non-zero for
each spin. We show that the wave function is (is not) localized at the edges
when the q^2 diagonal term is added (deleted) to (from) the spin-valley Dirac
mass equation. We calculate the quantum conductance of zigzag MoS2 nanoribbons
by using the nonequilibrium Green function method and show how this device
works as a field effect topological quantum transistor.",1803.03390v1
2018-03-13,Fast electron spin flips via strong subcycle electric excitation,"An important goal in quantum information processing is to reduce the duration
of quantum-logical operations. Motivated by this, we provide a theoretical
analysis of electrically induced fast dynamics of a single-electron spin-orbit
qubit. We study the example of a one-dimensional quantum dot with Rashba
spin-orbit interaction and harmonic driving, and focus on the case of strong
driving, when the real-space oscillation amplitude of the driven electron is
comparable to the width of its wave function. We provide simple approximate
analytical relations between the qubit Larmor frequency, the shortest
achievable qubit-flip time, and the driving amplitude required for the shortest
achievable qubit flip. We find that these relations compare well with results
obtained from numerical simulations of the qubit dynamics. Based on our
results, we discuss practical guidelines to maximize speed and quality of
electric single-qubit operations on spin-orbit qubits.",1803.04677v1
2018-03-26,Rigorous Results for the Ground States of the Spin-2 Bose-Hubbard Model,"We present rigorous and universal results for the ground states of the $f=2$
spinor Bose-Hubbard model. The model includes three two-body on site
interaction terms, two of which are spin dependent while the other one is spin
independent. We prove that, depending only on the coefficients of the two spin
dependent terms, the ground state exhibits maximum or minimum total spin or
SU(5) ferromagnetism. Exact ground-state degeneracies and the forms of
ground-state wave function are also determined in each case. All these results
are valid regardless of dimension, lattice structure, or particle number. Our
approach takes advantage of the symmetry of the Hamiltonian and employs
mathematical tools including the Perron-Frobenius theorem and the Lie algebra
$\mathfrak{so}(5)$.",1803.09441v2
2018-05-08,Decomposition of Abraham momentum into complex orbital and spin momenta in evanescent wave,"The Abraham momentum of electromagnetic field represents the decomposition
property into real-valued orbital and spin contributions. However, we found
that the orbital and spin momenta of evanescent electromagnetic fields are
inherently complex. Consequently, the decomposition of Abraham momentum was
reexamined and the exact expressions of orbital and spin momenta were obtained,
which are applicable to both propagating and evanescent electromagnetic fields.
Furthermore, we also justified the newly-derived decomposition of Abraham
momentum for lossy media, which was further demonstrated by a concrete example
of surface polariton of metal. In addition, by means of the complex orbital
momentum of surface polariton the complex group velocity was tentatively put
forward with its real part representing the energy flux velocity and its
imaginary part denoting the osmotic velocity of energy penetrating the
corresponding media",1805.02846v1
2018-05-10,"Lattice distortion effects on the frustrated spin-1 triangular-antiferromagnet A3NiNb2O9 (A = Ba, Sr and Ca)","In the geometrically frustrated materials with the low-dimensional and small
spin moment, the quantum fluctuation could interfere with the complicated
interplay of the spin, electron, lattice and orbital interactions, and host
exotic ground states such as nematic spin-state and chiral liquid phase. While
the quantum phases of the one-dimensional chain and S - 1/2 two-dimensional
triangular-lattice antiferromagnet (TLAF) had been more thoroughly investigated
by both theorists and experimentalists, the work on S = 1 TLAF has been
limited. We induced the lattice distortion into the TLAFs, A3NiNb2O9 (A = Ba,
Sr, and Ca) with S (Ni2+) = 1, and applied the thermodynamic, magnetic and
neutron scattering measurements. Although A3NiNb2O9 kept the non-collinear
120{\deg} antiferromagnetic phase as the ground state, the Ni2+-lattice changed
from the equilateral triangle (A = Ba) into isosceles triangle (A = Sr and Ca).
The inelastic neutron scattering data were simulated by the linear spin-wave
theory, and the competition between the single-ion anisotropy and the exchange
anisotropy from the distorted lattice was discussed.",1805.03986v1
2018-05-14,The relativistic center of mass in field theory with spin,"In order to unravel the origin of the nucleon spin, one has to study in
detail the question of orbital angular momentum, and in particular the
reference point about which it is defined. With this in mind, we review the
concept of relativistic center of mass, generalize the discussion to the case
of asymmetric energy-momentum tensors, and establish the link with the
light-front formalism. We find that the $p$-wave in the Dirac plane-wave
solutions arises from a relativistic quantum-mechanical effect which forces the
canonical reference point to depend on the observer. This explains why
longitudinal spin is much simpler to study than transverse spin. It is also the
reason behind the observation of induced shifts and distortions in the parton
distributions defined within the light-front formalism.",1805.05284v2
2018-05-18,Simple Unfolded Equations for Massive Higher Spins in AdS$_3$,"We propose a simple unfolded description of free massive higher spin
particles in anti-de-Sitter spacetime. While our unfolded equation of motion
has the standard form of a covariant constancy condition, our formulation
differs from the standard one in that our field takes values in a different
internal space, which for us is simply a unitary irreducible representation of
the symmetry group. Our main result is the explicit construction, for the case
of AdS$_3$, of a map from our formulation to the standard wave equations for
massive higher spin particles, as well as to the unfolded description prevalent
in the literature. It is hoped that our formulation may be used to clarify the
group-theoretic content of interactions in higher spin theories.",1805.07279v2
2018-05-24,Model of massless relativistic particle with continuous spin and its twistorial description,"We propose a new world-line Lagrangian model of the D=4 massless relativistic
particle with continuous spin and develop its twistorial formulation. The
description uses two Penrose twistors subjected to four first class
constraints. After the first quantization of the world-line twistorial model,
the wave function is defined by an unconstrained function on the
two-dimensional complex affine plane. We find the twistor transform that
determines the space-time field of the continuous spin particle through the
corresponding twistor one, which plays the role of a prepotential. It is shown
that this space-time field is an exact solution of the space-time constraints
defining the irreducible massless representation of the Poincare group with
continuous spin.",1805.09706v3
2018-06-28,Orbital Motion From Optical Spin: The Extraordinary Momentum Of Circularly Polarized Light Beams,"We provide a vivid demonstration of the mechanical effect of transverse spin
momentum in an optical beam in free space. This component of the Poynting
momentum was previously thought to be virtual, and unmeasurable. Here, its
effect is revealed in the inertial motion of a probe particle in a circularly
polarized Gaussian trap, in vacuum. Transverse spin forces combine with thermal
fluctuations to induce a striking range of non-equilibrium phenomena. With
increasing beam power we observe (i) growing departures from energy
equipartition, (ii) the formation of coherent, thermally excited orbits and,
ultimately, (iii) the ejection of the particle from the trap. Our results
complement and corroborate recent measurements of spin momentum in evanescent
waves, and extend them to a new geometry, in free space. In doing so, we
exhibit fundamental, generic features of the mechanical interaction of
circularly polarized light with matter. The work also shows how observations of
the under-damped motion of probe particles can provide detailed information
about the nature and morphology of momentum flows in arbitrarily structured
light fields as well as providing a test bed for elementary non-equilibrium
statistical mechanics.",1806.10922v1
2018-09-18,Externally controlled high degree of spin polarization and spin inversion in a conducting junction: Two new approaches,"We propose two new approaches for regulating spin polarization and spin
inversion in a conducting junction within a tight-binding framework based on
wave-guide theory. The system comprises a magnetic quantum ring with finite
modulation in site potential is coupled to two non-magnetic electrodes. Due to
close proximity an additional tunneling is established between the electrodes
which regulates electronic transmission significantly. At the same time the
phase associated with site potential, which can be tuned externally yields
controlled transmission probabilities. Our results are valid for a wide range
of parameter values which demonstrates the robustness of our proposition. We
strongly believe that the proposed model can be realized in the laboratory.",1809.06544v1
2019-11-04,Predicting the properties of black holes merger remnants with Deep Neural Networks,"We present the first estimation of the mass and spin magnitude of Kerr black
holes resulting from the coalescence of binary black holes using a deep neural
network. The network is trained on a dataset containing 80\% of the full
publicly available catalog of numerical simulations of gravitational waves
emission by binary black hole systems, including full precession effects for
spinning binaries. The network predicts the remnant black holes mass and spin
with an error less than 0.04\% and 0.3\% respectively for 90\% of the values in
the non-precessing test dataset, it is 0.1\% and 0.3\% respectively in the
precessing test dataset. When compared to existing fits in the LIGO algorithm
software library, the network enables to reduce the remnant mass root mean
square error to one half in the non-precessing case. In the precessing case,
both remnant mass and spin mean square errors are decreased to one half, and
the network corrects the bias observed in available fits.",1911.01496v2
2019-11-21,The nature of the chemical bond in the dicarbon molecule,"The molecular dissociation energy has often been explained and discussed in
terms of singlet bonds, formed by bounded pairs of valence electrons. In this
work we use a highly correlated resonating valence bond ansatz, providing a
consistent paradigm for the chemical bond, where spin fluctuations are shown to
play a crucial role. Spin fluctuations are known to be important in magnetic
systems and correspond to the zero point motion of the spin waves emerging from
a magnetic broken symmetry state. Recently, in order to explain the excitation
spectrum of the carbon dimer, an unusual quadruple bond has been proposed.
Within our ansatz, a satisfactory description of the carbon dimer is determined
by the magnetic interaction of two Carbon atoms with antiferromagnetically
ordered S = 1 magnetic moments. This is a first step that, thanks to the highly
scalable and efficient quantum Monte Carlo technique, may open the way for
understanding challenging complex systems containing atoms with large spins
(e.g. transition metals).",1911.09748v4
2019-11-29,Relativistic quantum mechanics description of neutrino spin-flavor oscillations in various external fields,"We review the application of the relativistic quantum mechanics method for
the description of neutrino oscillations for the studies of spin-flavor
oscillations in background matter under the influence of a plane
electromagnetic wave. Basing on the new exact solution of the Dirac-Pauli
equation for a massive neutrino in the given external fields, we derive the
transition probabilities for spin and spin-flavor oscillations. The obtained
expressions are analyzed for different types of the neutrino magnetic moments.
Our results are compared with findings of other authors.",1911.13261v1
2017-05-01,Finite energy spin fluctuation as a pairing glue in systems with coexisting electron and hole bands,"We study, within the fluctuation exchange approximation, the
spin-fluctuation-mediated superconductivity in Hubbard-type models possessing
electron and hole bands, and compare them with a model on a square lattice with
a large Fermi surface. In the square lattice model, superconductivity is more
enhanced for better nesting for a fixed band filling. By contrast, in the
models with electron and hole bands, superconductivity is optimized when the
Fermi surface nesting is degraded to some extent, where finite energy spin
fluctuation around the nesting vector develops. The difference lies in the
robustness of the nesting vector, namely, in models with electron and hole
bands, the wave vector at which the spin susceptibility is maximized is fixed
even when the nesting is degraded, whereas when the Fermi surface is large, the
nesting vector varies with the deformation of the Fermi surface. We also
discuss the possibility of realizing in actual materials the bilayer Hubbard
model, which is a simple model with electron and hole bands, and is expected to
have a very high T_c.",1705.00421v1
2017-05-18,Classical Emergence of Intrinsic Spin-Orbit Interaction of Light at the Nanoscale,"Traditionally, in macroscopic geometrical optics intrinsic polarization and
spatial degrees of freedom of light can be treated independently. However, at
the subwavelength scale these properties appear to be coupled together, giving
rise to the spin-orbit interaction (SOI) of light. In this work we address
theoretically the classical emergence of the optical SOI at the nanoscale. By
means of a full-vector analysis involving spherical vector waves we show that
the spin-orbit factorizability condition, accounting the mutual influence
between the amplitude (spin) and phase (orbit), is fulfilled only in the
far-field limit. On the other side, in the near-field region, an additional
relative phase introduces an extra term that hinders the factorization and
reveals an intricate dynamical behavior according to the SOI regime. As a
result, we find a suitable theoretical framework able to capture analytically
the main features of intrinsic SOI of light. Besides allowing for a better
understanding into the mechanism leading to its classical emergence at the
nanoscale, our approach may be useful in order to design experimental setups
that enhance the response of SOI-based effects.",1705.06501v3
2017-05-20,Multipolar phase in frustrated spin-1/2 and 1 chains,"The $J_1-J_2$ spin chain model with nearest neighbor $J_1$ and next nearest
neighbor anti-ferromagnetic $J_2$ interaction is one of the most popular
frustrated magnetic models. This model system has been extensively studied
theoretically and applied to explain the magnetic properties of the real
low-dimensional materials. However, existence of different phases for the
$J_1-J_2$ model in an axial magnetic field $h$ is either not understood or has
been controversial. In this paper we show the existence of higher order $p>4$
multipolar phase near the critical point $(J_2/J_1)_c=-0.25$. The criterion to
detect the quadrupolar or spin nematic (SN)/spin density wave of type two
(SDW$_2$) phase using the inelastic neutron scattering (INS) experiment data is
also discussed, and INS data of LiCuVO$_4$ compound is modelled. We discuss the
dimerized and degenerate ground state in the quadrupolar phase. The major
contribution of binding energy in the spin-1/2 system comes from the
longitudinal component of the nearest neighbor bonds. We also study spin
nematic/SDW$_2$ phase in spin-1 system in large $J_2/J_1$ limit.",1705.07292v1
2017-05-26,"Low-energy spin dynamics of orthoferrites AFeO$_3$ (A = Y, La, Bi)","YFeO$_3$ and LaFeO$_3$ are members of the rare-earth orthoferrites family
with \textit{Pbnm} space group. Using inelastic neutron scattering, the
low-energy spin excitations have been measured around magnetic Brillouin zone
center. Splitting of magnon branches and non-zero magnon gap is observed for
both compounds, which is similar to the behavior observed in multiferroic
BiFeO$_3$. Spin wave calculations which include both Dzyaloshinsky-Moriya
interactions and single-ion anisotropy in the spin-Hamiltonian comprehensively
accounts for all the experimentally observed features. Our results offer
insight into the unifying physics underlying the Fe$^{3+}$-based perovskites as
well as their distinguishing characteristics.",1705.09441v3
2018-07-08,Hybrid quantum system with nitrogen-vacancy centers in diamond coupled to surface phonon polaritons in piezomagnetic superlattices,"We investigate a hybrid quantum system where an ensemble of nitrogen-vacancy
(NV) centers in diamond is interfaced with a piezomagnetic superlattice that
supports surface phonon polaritons (SPhPs). We show that the strong magnetic
coupling between the collective spin waves in the NV spin ensemble and the
quantized SPhPs can be realized, thanks to the subwavelength nature of the
SPhPs and relatively long spin coherence times. The magnon-polariton coupling
allows different modes of the SPhPs to be mapped and orthogonally stored in
different spatial modes of excitation in the solid medium. Because of its easy
implementation and high tunability, the proposed hybrid structure with NV spins
and piezoactive superlattices could be used for quantum memory and quantum
computation.",1807.02750v1
2012-09-09,Gapless spin-liquid phase in the kagome spin-1/2 Heisenberg antiferromagnet,"We study the energy and the static spin structure factor of the ground state
of the spin-1/2 quantum Heisenberg antiferromagnetic model on the kagome
lattice. By the iterative application of a few Lanczos steps on accurate
projected fermionic wave functions and the Green's function Monte Carlo
technique, we find that a gapless (algebraic) U(1) Dirac spin liquid is
competitive with previously proposed gapped (topological) Z2 spin liquids. By
performing a finite-size extrapolation of the ground-state energy, we obtain an
energy per site E/J=-0.4365(2), which is equal, within three error bars, to the
estimates given by the density-matrix renormalization group (DMRG). Our
estimate is obtained for a translationally invariant system, and, therefore,
does not suffer from boundary effects, like in DMRG. Moreover, on finite toric
clusters at the pure variational level, our energies are lower compared to
those from DMRG calculations.",1209.1858v4
2012-09-21,Theory of spin-orbit coupling at LaAlO3/SrTiO3 interfaces and SrTiO3 surfaces,"The theoretical understanding of the spin-orbit coupling (SOC) effects at
LaAlO$_{3}$/SrTiO$_{3}$ interfaces and SrTiO$_{3}$ surfaces is still in its
infancy. We perform first-principles density-functional-theory calculations and
derive from these a simple tight-binding Hamiltonian, through a Wannier
function projection and group theoretical analysis. We find striking
differences to the standard Rashba theory for spin-orbit coupling in
semiconductor heterostructures due to multi-orbital effects: by far the biggest
SOC effect is at the crossing point of the $xy$ and $yz$ (or $zx$) orbitals;
and around the $\Gamma$ point a Rashba spin splitting with a cubic dependence
on the wave vector $\vec{k}$ is possible.",1209.4705v2
2014-06-10,Coherent spin-rotational dynamics of oxygen super rotors,"We use state- and time-resolved coherent Raman spectroscopy to study the
rotational dynamics of oxygen molecules in ultra-high rotational states. While
it is possible to reach rotational quantum numbers up to $N \approx 50$ by
increasing the gas temperature to 1500 K, low population levels and gas
densities result in correspondingly weak optical response. By spinning O$_2$
molecules with an optical centrifuge, we efficiently excite extreme rotational
states with $N\leqslant 109$ in high-density room temperature ensembles. Fast
molecular rotation results in the enhanced robustness of the created rotational
wave packets against collisions, enabling us to observe the effects of weak
spin-rotation coupling in the coherent rotational dynamics of oxygen. The decay
rate of spin-rotation coherence due to collisions is measured as a function of
the molecular angular momentum and explained in terms of the general scaling
law. We find that at high values of $N$, the rotational decoherence of oxygen
is much faster than that of the previously studied non-magnetic nitrogen
molecules. This may suggest a different mechanism of rotational relaxation in
paramagnetic gases.",1406.2668v1
2018-02-28,Relativistic positron scattering from heavy ground-state nuclei,"Cross sections and spin asymmetries for elastic positron scattering and for
the emission of positron bremsstrahlung in collision with nuclei of zero and
half-integer spin are calculated within the relativistic partial-wave theory.
For elastic scattering, comparison is made with the respective results from
electron scattering by 208Pb, 89Y and 23Na nuclei at high energies (up to 400
MeV). It is found that the difference between electron and positron intensities
diminishes with energy, although the diffraction oscillations, which differ in
phase for the two species, prevail up to the highest energies considered.
Magnetic scattering strongly reduces the spin asymmetries for nuclei with spin,
both for positrons and electrons. For the elementary process of bremsstrahlung
the cross section, which is studied for the 197Au and 208Pb targets at low
energies (1-30 MeV), increases with photon frequency for large scattering
angles and small photon emission angles, in contrast to the usual behaviour of
the doubly differential cross section, or of the triply differential cross
section at small scattering angles.",1802.10362v1
2018-12-07,Flat bands and dynamical localization of spin-orbit coupled Bose-Einstein condensates,"Flat bands and dynamical localization of binary mixtures of Bose-Einstein
condensates, with spin-orbit coupling subjected to a deep optical lattice which
is shaking in time and to a periodic time modulation of the Zeeman field, are
investigated. In contrast with usual dynamical localization in the absence of
spin-orbit coupling, we find that to fully suppress the tunneling in the system
the optical lattice shaking is not enough, and a proper tuning of the
spin-orbit term, achievable via the Zeeman field modulation, is also required.
This leads to a sequence of Zeeman parameter values where energy bands become
flat, the tunneling in the system is suppressed, and the dynamical localization
phenomenon occurs. Exact wave functions at the dynamical localization points
show that the binary mixture localizes on a dimer with the two components
occupying different sites. This type of localization occurs in exact form also
for the ground state of the system at the dynamical localization points in the
presence of nonlinearity and remains valid, although in approximate form, for a
wide range of the Zeeman parameter around these points. The possibility of
observing the above phenomena in real experiments is also briefly discussed.",1812.03164v1
2018-12-27,Thermodynamics of delta-chain with ferro- and antiferromagnetic interactions,"Motivated by a novel cyclic compound $Fe_{10}Gd_{10}$ with record ground
state spin in which the arrangement of magnetic ions with $s=\frac{5}{2}$ and
$s=\frac{7}{2}$ corresponds to a saw-tooth chain we investigate the
thermodynamics of the delta-chain with competing ferro- and antiferromagnetic
interactions. We study both classical and quantum versions of the model. The
classical model is exactly solved and quantum effects are studied using full
diagonalization and a finite temperature Lanczos technique for finite
delta-chains as well as modified spin wave theory. It is shown that the main
features of the magnetic susceptibility of the quantum spin delta chain are
correctly described by the classical spin model, while quantum effects
significantly change the low-temperature behavior of the specific heat. The
relation of the obtained results to the $Fe_{10}Gd_{10}$ system is discussed.",1812.10760v1
2019-02-22,Quantum solitons in spin-orbit-coupled Bose-Bose mixtures,"Recent experimental and theoretical results show that weakly interacting
atomic Bose-Bose mixtures with attractive interspecies interaction are
stabilized by beyond-mean-field effects. Here we consider the peculiar
properties of these systems in a strictly one-dimensional configuration, taking
also into account the nontrivial role of spin-orbit and Rabi couplings. We show
that when the value of inter- and intraspecies interaction strengths are such
that mean-field contributions to the energy cancel, a self-bound bright soliton
fully governed by quantum fluctuations exists. We derive the phase diagram of
the phase transition between a single-peak soliton and a multipeak (striped)
soliton, produced by the interplay between spin-orbit, Rabi couplings and
beyond-mean-field effects, which also affect the breathing mode frequency of
the atomic cloud. Finally, we prove that a phase imprinting of the single-peak
soliton leads to a self-confined propagating solitary wave even in the presence
of spin-orbit coupling.",1902.08603v2
2019-06-18,Non uniform superconductivity in wires with strong spin-orbit coupling,"We study theoretically the onset of nonuniform superconductivity in a
one-dimensional single wire in presence of Zeeman (or exchange field) and
spin-orbit coupling. Using the Green's function formalism, we show that the
spin-orbit coupling stabilizes modulated superconductivity in a broad range of
temperatures and Zeeman fields. We investigate the anisotropy of the
temperature-Zeeman field phase diagram, which is related to the orientation of
the Zeeman field. In particular, the inhomogeneous superconducting state
disappears if this latter field is aligned or perpendicular to the wire
direction. We identify two regimes corresponding to weak and strong spin-orbit
coupling respectively. The wave-vector of the modulated phase is evaluated in
both regimes. The results also pertain for quasi-1D superconductors made of
weakly coupled 1D chains.",1906.07572v3
2020-04-08,Anisotropic magnetic excitations from single-chirality antiferromagnetic state in Ca-kapellasite,"We present a $^{35}$Cl NMR study for spin $S=1/2$ perfect kagome
antiferromagnet Ca-kapellasite (CaCu$_{3}$(OH)$_{6}$Cl$_{2}\cdot$0.6H$_{2}$O)
with a magnetic transition at $T^{\ast}=7.2$ K. The static magnetic structure
in the ground state has been determined to be a chirality-ordered $Q=0$ state,
which is selected by a finite Dzyaloshinskii-Moriya interaction. The low-energy
magnetic excitations in the ordered state are investigated by the nuclear
spin-lattice relaxation rate measurement. We detect a weakly temperature
dependent contribution in the magnetic fluctuations perpendicular to the kagome
plane in addition to the dispersive spin-wave contribution in the kagome plane.
The low-energy magnetic excitations from the coplanar spin structure are
attributed to the zero mode originating from the flat band in this kagome
antiferromagnet.",2004.03827v1
2020-04-09,First-Principles Calculation of Spin and Orbital Contributions to Magnetically Ordered Moments in Sr$_{2}$IrO$_{4}$,"We show how an accurate first-principles treatment of the
canted-antiferromagnetic ground state of Sr$_2$IrO$_4$, a prototypical $5d$
correlated spin-orbit coupled material, can be obtained without invoking any
free parameters such as the Hubbard U or tuning the spin-orbit coupling
strength. Our theoretically predicted iridium magnetic moment of 0.250 $\mu_B$,
canted by 12.6$^{\circ}$ off the a-axis, is in accord with experimental
results. By resolving the magnetic moments into their spin and orbital
components, we show that our theoretically obtained variation of the magnetic
scattering amplitude $<M_{m}>$ as a function of the polarization angle is
consistent with recent non-resonant magnetic x-ray scattering measurements. The
computed value of the band gap (55 meV) is also in line with the corresponding
experimental values. A comparison of the band structure to that of the cuprates
suggests the presence of incommensurate charge-density wave phases in
Sr$_{2}$IrO$_{4}$.",2004.04759v1
2020-08-13,Interpreting the X-ray afterglows of gamma-ray bursts with radiative losses and millisecond magnetars,"The spin-down energy of millisecond magnetars has been invoked to explain
X-ray afterglow observations of a significant fraction of short and long
gamma-ray bursts. Here, we extend models previously introduced in the
literature, incorporating radiative losses with the spin down of a magnetar
central engine through an arbitrary braking index. Combining this with a model
for the tail of the prompt emission, we show that our model can better explain
the data than millisecond-magnetar models without radiative losses or those
that invoke spin down solely through vacuum dipole radiation. We find that our
model predicts a subset of X-ray flares seen in some gamma-ray bursts. We can
further explain the diversity of X-ray plateaus by altering the radiative
efficiency and measure the braking index of newly-born millisecond magnetars.
We measure the braking index of GRB061121 as $n=4.85^{+0.11}_{-0.15}$
suggesting the millisecond-magnetar born in this gamma-ray burst spins down
predominantly through gravitational-wave emission.",2008.05745v2
2016-03-11,Separating hyperfine from spin-orbit interactions in organic semiconductors by multi-octave magnetic resonance using coplanar waveguide microresonators,"Separating the influence of hyperfine from spin-orbit interactions in
spin-dependent carrier recombination and dissociation processes necessitates
magnetic resonance spectroscopy over a wide range of frequencies. We have
designed compact and versatile coplanar waveguide resonators for
continuous-wave electrically detected magnetic resonance, and tested these on
organic light-emitting diodes. By exploiting both the fundamental and
higher-harmonic modes of the resonators we cover almost five octaves in
resonance frequency within a single setup. The measurements with a common
pi-conjugated polymer as the active material reveal small but non-negligible
effects of spin-orbit interactions, which give rise to a broadening of the
magnetic resonance spectrum with increasing frequency.",1603.03807v1
2017-02-08,Measuring Majorana non-locality and spin structure with a quantum dot,"Robust zero bias transport anomalies in semiconducting nanowires with
proximity-induced superconductivity have been convincingly demonstrated in
various experiments. While these are compatible with the existence of Majorana
zero modes at the ends of the nanowire, a direct proof of their non-locality
and topological protection is now needed. Here we show that a quantum dot at
the end of the nanowire may be used as a powerful spectroscopic tool to
quantify the degree of Majorana non-locality through a local transport
measurement. Moreover, the spin polarization of dot sub-gap states at
singlet-doublet transitions in the Coulomb blockade regime allows the dot to
directly probe the spin structure of the Majorana wave function, and indirectly
measure the spin-orbit coupling of the nanowire.",1702.02525v3
2017-02-15,Bosons with incommensurate potential and spin-orbit coupling,"We chart out the phase diagram of ultracold `spin-half' bosons in a
one-dimensional optical lattice in the presence of Aubry-Andr\'e (AA) potential
and with spin-orbit (SO) and Raman couplings investigating the transition from
superfluid (SF) to localized phases and the existence of density wave phase for
nearest-neighbor interaction (NNI). We show that the presence of SO coupling
and AA potential leads to a novel spin-split momentum distribution of the
bosons in the localized phase near the boundary with the SF phase, which can
act as a signature of such a transition. We also obtain the level statistics of
the bosons in the superfluid phase with finite NNI and demonstrate its change
from Gaussian Unitary Ensemble (GUE) to Gaussian Orthogonal Ensemble (GOE) as a
function of the Raman coupling. We discuss experiments which can test our
theory.",1702.04714v1
2017-02-27,Dynamics of Bound Magnon Pairs in the Quasi-One-Dimensional Frustrated Magnet LiCuVO_4,"We report on the dynamics of the spin-1/2 quasi-one-dimensional frustrated
magnet LiCuVO$\mathrm{_4}$ measured by nuclear spin relaxation in high magnetic
fields 10--34 T, in which the ground state has spin-density-wave order. The
spin fluctuations in the paramagnetic phase exhibit striking anisotropy with
respect to the magnetic field. The transverse excitation spectrum probed by
$^{51}$V nuclei has an excitation gap, which increases with field. On the other
hand, the gapless longitudinal fluctuations sensed by $^7$Li nuclei grow with
lowering temperature, but tend to be suppressed with increasing field. Such
anisotropic spin dynamics and its field dependence agree with the theoretical
predictions and are ascribed to the formation of bound magnon pairs, a
remarkable consequence of the frustration between ferromagnetic nearest
neighbor and antiferromagnetic next-nearest-neighbor interactions.",1702.08573v2
2017-06-13,Asymmetric splitting of an antiferromagnetic resonance via quartic exchange interactions in multiferroic hexagonal HoMnO$_3$,"The symmetric splitting of two spin-wave branches in an antiferromagnetic
resonance (AFR) experiment has been an essential measurement of
antiferromagnets for over half a century. In this work, circularly polarized
time-domain THz spectroscopy experiments performed on the low symmetry
multiferroic h-HoMnO$_3$ reveal an AFR of the Mn sublattice to split
asymmetrically in applied magnetic field, with an $\approx$ 50\% difference in
$g$-factors between the high and low energy branches of this excitation. The
temperature dependence of the $g$-factors, including a drastic renormalization
at the Ho spin ordering temperature, reveals this asymmetry to unambiguously
stem from Ho-Mn interactions. Theoretical calculations demonstrate the AFR
asymmetry is not explained by conventional Ho-Mn exchange mechanisms alone and
are only reproduced if quartic spin interactions are also included in the spin
Hamiltonian. Our results provide a paradigm for the optical study of such novel
interactions in hexagonal manganites and low symmetry antiferromagnets in
general.",1706.04141v2
2017-09-30,The impacts of the quantum-dot confining potential on the spin-orbit effect,"For a nanowire quantum dot with the confining potential modeled by both the
infinite and the finite square wells, we obtain exactly the energy spectrum and
the wave functions in the strong spin-orbit coupling regime. We find that
regardless of how small the well height is, there are at least two bound states
in the finite square well: one has the $\sigma^{x}\mathcal{P}=-1$ symmetry and
the other has the $\sigma^{x}\mathcal{P}=1$ symmetry. When the well height is
slowly tuned from large to small, the position of the maximal probability
density of the first excited state moves from the center to $x\ne0$, while the
position of the maximal probability density of the ground state is always at
the center. A strong enhancement of the spin-orbit effect is demonstrated by
tuning the well height. In particular, there exists a critical height
$V^{c}_{0}$, at which the spin-orbit effect is enhanced to maximal.",1710.00816v3
2018-04-25,Magnon thermal Hall effect in kagome antiferromagnets with Dzyaloshinskii-Moriya interactions,"We theoretically study magnetic and topological properties of
antiferromagnetic kagome spin systems in the presence of both in- and
out-of-plane Dzyaloshinskii-Moriya interactions. In materials such as the iron
jarosites, the in-plane interactions stabilize a canted noncollinear ""umbrella""
magnetic configuration with finite scalar spin chirality. We derive expressions
for the canting angle, and use the resulting order as a starting point for a
spin-wave analysis. We find topological magnon bands, characterized by non-zero
Chern numbers. We calculate the magnon thermal Hall conductivity, and propose
the iron jarosites as a promising candidate system for observing the magnon
thermal Hall effect in a noncollinear spin configuration. We also show that the
thermal conductivity can be tuned by varying an applied magnetic field, or the
in-plane Dzyaloshinskii-Moriya strength. In contrast with previous studies of
topological magnon bands, the effect is found to be large even in the limit of
small canting.",1804.09783v2
2019-03-06,Anomalous Magnetic Behavior in Ba2CoO4 with Isolated CoO4 Tetrahedra,"The dimensionality of the electronic and magnetic structure of a given
material is generally predetermined by its crystal structure. Here, using
elastic and inelastic neutron scattering combined with magnetization
measurements, we find unusual magnetic behavior in three-dimensional (3D)
Ba2CoO4. In spite of isolated CoO4 tetrahedra, the system exhibits a 3D
noncollinear antiferromagnetic order in the ground state with an anomalously
large Curie-Weiss temperature of 110 K compared to TN = 26 K. More
unexpectedly, spin dynamics displays quasi-2D spin wave dispersion with an
unusually large spin gap, and 1D magnetoelastic coupling. Our results indicate
that Ba2CoO4 is a unique system for exploring the interplay between isolated
polyhedra, low-dimensional magnetism, and novel spin states in oxides.",1903.02490v1
2019-05-20,Double ionization of a three-electron atom: Spin correlation effects,"We study the effects of spin degrees of freedom and wave function symmetries
on double ionization in three-electron systems. Each electron is assigned one
spatial degree of freedom. The resulting three-dimensional Schr\""odinger
equation is integrated numerically using grid-based Fourier transforms. We
reveal three-electron effects on the double ionization yield by comparing
signals for different ionization channels. We explain our findings by the
existence of fundamental differences between three-electronic and truly
two-electronic spin-resolved ionization schemes. We find, for instance, that
double ionization from a three-electron system is dominated by electrons that
have the opposite spin.",1905.08357v2
2020-03-05,The branching ratio of LIGO binary black holes,"Formation of binary black holes (BBHs) detected by gravitational-wave (GW)
observations could be broadly divided into two categories: those formed through
field binary evolution and those assembled dynamically in dense stellar
systems. The branching ratio of the BBHs refers to the contribution of each
channel. The dynamical assembly channel would predict a symmetric distribution
in the effective spins of the BBHs while field formation predicts BBHs to have
positive effective spins. By modeling these two populations based on their
effective spin distribution we show that in the 10 BBHs detected by LIGO/Virgo
the contribution of the dynamically assembled BBHs to be more than about 50\%
with 90\% confidence. This result is based on the assumption that the field
binaries are born with positive effective spins not restricted to have small
values.",2003.02764v1
2020-03-29,Hypergiant spin polarons photogenerated in ferromagnetic europium chalcogenides,"We find that in the ferromagnetic semiconductor EuS, near its Curie
temperature, a single band-edge photon generates a spin polaron (SP), whose
magnetic moment approaches 20,000 Bohr magnetons. This is much larger than the
supergiant photoinduced SPs in antiferromagnetic europium chalcogenides,
reported previously. The larger SP in ferromagnetic EuS, and still larger
expected for EuO, is explained by a larger Bohr radius of the photoexcited
electron state, which encircles and polarizes a greater number of lattice
spins. However, because the wave function of the photoexcited electron spreads
over a greater volume, the photoexcited electron exchange interaction with
individual lattice spins weakens, which makes the SP more easily quenched
thermally.",2003.12956v1
2020-03-30,Formation mechanism of helical Q structure in Gd-based skyrmion materials,"Using the ab initio local force method, we investigate the formation
mechanism of the helical spin structure in GdRu$_2$Si$_2$ and Gd$_2$PdSi$_3$.
We calculate the paramagnetic spin susceptibility and find that the Fermi
surface nesting is not the origin of the incommensurate modulation, in contrast
to the naive scenario based on the Ruderman-Kittel-Kasuya-Yosida mechanism. We
then decompose the exchange interactions between the Gd spins into each orbital
component, and show that spin-density-wave type interaction between the Gd-5$d$
orbitals is ferromagnetic, but the interaction between the Gd-4$f$ orbitals is
antiferromagnetic. We conclude that the competition of these two interactions,
namely, the inter-orbital frustration, stabilizes the finite-Q structure.",2003.13167v1
2020-09-23,The Spin Orbit term in the Nuclear Shell Model,"Quasi-nuclear systems, representing nuclei with variable size, are studied to
investigate the occurrence of the spin-orbit term in the nuclear mean field in
the transition from infinite nuclear matter to finite nuclei. Relativistic as
well as non-relativistic mean field calculations based on models for the
nucleon-nucleon ($NN$) interaction, which fit the $NN$ scattering data, are
considered. A very strong correlation between the strength of the spin-orbit
term and radius of the nuclear system is observed. The origin of the spin-orbit
term is analyzed by inspecting the contributions of the different partial waves
and various mesons in a One-Boson-Exchange model of the $NN$ interaction. The
influence of correlation effects and the enhancement of the small component of
Dirac spinors for nucleons in the nuclear medium is discussed.",2009.11214v2
2020-09-25,Efficient matrix-product-state preparation of highly entangled trial states: Weak Mott insulators on the triangular lattice revisited,"Using tensor network states to unravel the physics of quantum spin liquids in
minimal, yet generic microscopic spin or electronic models remains notoriously
challenging. A prominent open question concerns the nature of the insulating
ground state of two-dimensional half-filled Hubbard-type models on the
triangular lattice in the vicinity of the Mott metal-insulator transition, a
regime which can be approximated microscopically by a spin-1/2 Heisenberg model
supplemented with additional ""ring-exchange"" interactions. Using a novel and
efficient state preparation technique whereby we initialize full density matrix
renormalization group (DMRG) calculations with highly entangled
Gutzwiller-projected Fermi surface trial wave functions, we show -- contrary to
previous works -- that the simplest triangular lattice $J$-$K$ spin model with
four-site ring exchange likely does not harbor a fully gapless U(1) spinon
Fermi surface (spin Bose metal) phase on four- and six-leg wide ladders. Our
methodology paves the way to fully resolve with DMRG other controversial
problems in the fields of frustrated quantum magnetism and strongly correlated
electrons.",2009.12435v2
2020-11-25,Spin-polarized vortices with reversed circulation,"We present the analysis of the structure of fermionic vortices with the
spin-polarized core from a weak coupling limit to the unitary regime. We show
the mechanism for the generation of the {\it reversed circulation} in the
vortex core induced by an excess of majority spin particles. We introduce the
classification of the polarized vortices based on the number of Fermi circles
where the minigap vanishes. This provides a unique description of the vortex as
one cannot smoothly map wave functions into one another corresponding to
vortices differing by the number of Fermi circles. The effective mass of
quasiparticles along the vortex core is analyzed and its role in the
propagation of spin-polarization along the vortex line is discussed.",2011.13021v2
2021-02-21,Spin excitations in the heavily overdoped monolayer graphene superconductor: an analog to the cuprates,"Recently it was reported experimentally that the monolayer graphene can be
doped to beyond the Van Hove singularity. We study theoretically the possible
superconductivity and the corresponding spin excitations of the monolayer
graphene in this doping region. A static spin-density-wave state is favorable
due to the nested Fermi surface as the Fermi level is doped to the Van Hove
singularity point. Superconductivity may be realized upon further doping. The
spin excitations in the superconducting state are studied theoretically based
on the random phase approximation. The overall features are qualitatively the
same with those in cuprate superconductors. Thus we have proposed an exciting
possibility, namely, the heavily overdoped monolayer graphene can become a
novel platform to study the unconventional superconductivity.",2102.10625v2
2021-02-23,2D Relativistic Oscillators with a Uniform Magnetic Field in Anti-deSitter Space,"We study analytically the two dimensional deformed bosonic oscillator
equations for charged particles (both spin 0 and spin 1 particles) subject to
the effect of a uniform magnetic field. We consider the presence of a minimal
uncertainty in momentum caused by the Anti-deSitter model and we use the
Nikiforov-Uvarov method to solve the system. The exact energy eigenvalues and
the corresponding wave functions are analytically obtained for both
Klein-Gordon and scalar Duffin-Kemmer-Petiau cases. For spin 1 DKP case, we
deduce the behaviour of the DKP equation and write the non-relativistic
energies where we show the fundamental role of the spin in this case. Finally,
we study the thermodynamic properties of the system.",2102.11718v1
2021-02-26,Angle Locking of a Levitating Diamond using Spin-Diamagnetism,"The negatively charged nitrogen-vacancy (NV) center in nano- or micro-
diamonds has emerged as a promising magnetic field sensor, as a candidate for
hyper-polarizing paramagnetic species, as well as a tool for spin-mechanics at
the nanoscale. However, NV-doped diamonds are presently not straightforwardly
employable for these applications in a liquid or when levitating under
atmospheric pressures due to the random angular Brownian motion which tends to
rotate the NV quantization axis over the course of the measurments. Here, we
report on angle locking of the crystalline axis of a trapped micro-diamond
along an external magnetic field. Specifically, we use spin population
inversion after a ground state level crossing of the NV center to turn the
diamond into a diamagnet. The diamond crystalline axis naturally aligns to the
magnetic field with high precision and in the absence of micro-wave, offering
bright prospects for applications in biology and spin-mechanical platforms.",2102.13637v3
2021-04-08,Robust d-wave superconductivity in the square-lattice $t$-$J$ model,"Unravelling competing orders emergent in doped Mott insulators and their
interplay with unconventional superconductivity is one of the major challenges
in condensed matter physics. To explore possible superconductivity state in the
doped Mott insulator, we study a square-lattice $t$-$J$ model with both the
nearest and next-nearest-neighbor electron hoppings and spin Heisenberg
interactions. By using the state-of-the-art density matrix renormalization
group simulations with imposing charge $U(1)$ and spin $SU(2)$ symmetries on
the large-scale six-leg cylinders, we establish a quantum phase diagram
including three phases: a stripe charge density wave phase, a superconducting
phase without static charge order, and a superconducting phase coexistent with
a weak charge stripe order. Crucially, we demonstrate that the superconducting
phase has a power-law pairing correlation decaying much slower than the charge
density and spin correlations, which is a quasi-1D descendant of the uniform
d-wave superconductor in two dimensions. These findings reveal that enhanced
charge and spin fluctuations with optimal doping is able to produce robust
d-wave superconductivity in doped Mott insulators, providing a foundation for
connecting theories of superconductivity to models of strongly correlated
systems.",2104.03758v2
2021-10-08,Inverse-Faraday effect from the orbital angular momentum of light,"It is usually admitted that the inverse Faraday effect (IFE) originates from
the spin angular momentum (SAM) of light. In this paper, we evidence that part
of the IFE in a metal is induced by the orbital angular momentum (OAM) of
light. On the basis of a hydrodynamic model of the conduction electron gas, we
describe the dependence of the IFE on the spin and orbital angular momenta as
well as spin-orbit interaction in a non-paraxial light beam. We also
numerically quantify the relative contributions of the SAM and OAM of light to
the IFE in a thin gold film illuminated by different focused beams carrying SAM
and/or OAM. The OAM of light provides a new degree of freedom in the control of
the IFE and resulting optomagnetic field, thus potentially impacting various
research fields including all-optical magnetization switching and spin-wave
excitation.",2110.04198v1
2021-10-20,Gapless Dirac magnons in CrCl$_{3}$,"Bosonic Dirac materials are testbeds for dissipationless spin-based
electronics. In the quasi two-dimensional honeycomb lattice of CrX$_{3}$ (X=Cl,
Br, I), Dirac magnons have been predicted at the crossing of acoustical and
optical spin waves, analogous to Dirac fermions in graphene. Here we show that,
distinct from CrBr$_{3}$ and CrI$_{3}$, gapless Dirac magnons are present in
bulk CrCl$_{3}$, with inelastic neutron scattering intensity at low
temperatures approaching zero at the Dirac $K$ point. Upon warming,
magnon-magnon interactions induce strong renormalization and decreased
lifetimes, with a ~25% softening of the upper magnon branch intensity from 5 to
50 K, though magnon features persist well above T$_{N}$. Moreover, an unusual
negative thermal expansion (NTE) of the $a$-axis lattice constant and anomalous
phonon behavior are observed below 50 K, indicating magnetoelastic and
spin-phonon coupling arising from an increase in the in-plane spin correlations
that begins tens of Kelvin above T$_{N}$.",2110.10771v1
2008-06-17,Magnetoconductance properties of rectangular arrays of spintronic quantum rings,"Electron transport through multi-terminal rectangular arrays of quantum rings
is studied in the presence of Rashba-type spin-orbit interaction (SOI) and of a
perpendicular magnetic field. Using the analytic expressions for the
transmission and reflection coefficients for single rings we obtain the
conductance through such arrays as a function of the SOI strength, the magnetic
flux, and of the wave vector $k$ of the incident electron. Due to destructive
or constructive spin interferences caused by the SOI, the array can be totally
opaque for certain ranges of $k$, while there are parameter values where it is
completely transparent. Spin resolved transmission probabilities show
nontrivial spin transformations at the outputs of the arrays. When point-like
random scattering centers are placed between the rings, the Aharonov-Bohm peaks
split, and an oscillatory behavior of the conductance emerges as a function of
the SOI strength.",0806.2734v1
2008-06-18,Selective Heating Mechanism of Magnetic Metal Oxides by Alternating Magnetic Field in Microwave Sintering Process,"The mechanism of rapid and selective heating of magnetic metal oxides under
the magnetic field of microwaves which continues beyond the Curie temperature $
T_{c} $ is identified by using the Heisenberg model. Monte Carlo calculations
based on the energy principle show that such heating is caused by non-resonant
response of electron spins in the unfilled 3d shell to the wave magnetic field.
Small spin reorientation thus generated leads to a large internal energy change
through the exchange interactions between spins, which becomes maximal around $
T_{c} $ for magnetite $ {\rm Fe}_{3}{\rm O}_{4} $. The dissipative spin
dynamics simulation yields the imaginary part of the magnetic susceptibility,
which becomes largest around $ T_{c} $ and for the microwave frequency around 2
GHz. Hematite $ {\rm Fe}_{2}{\rm O}_{3} $ with weak spontaneous magnetization
responds much less to microwaves as observed in experiments. The heating of
titanium oxide by microwave magnetic field only when oxygen defects are present
is also explained by our theory in terms of the absence of spontaneous
magnetization.",0806.3055v3
2016-11-29,Dynamical Shiba states by precessing magnetic moments in an s-wave superconductor,"We study theoretically the dynamics of a Shiba state forming around
precessing classical spin in an s-wave superconductor. Utilizing a rotating
wave description for the precessing magnetic impurity, we find the resulting
Shiba bound state quasi-energy and the spatial extension of the Shiba
wavefunction. We show that such a precession pertains to dc charge and spin
currents flowing through a normal STM tip tunnel coupled to the superconductor
in the vicinity of the impurity. We calculate these currents and find that they
strongly depend on the magnetic impurity precession frequency, precession
angle, and on the position of the Shiba energy level in the superconducting
gap. The resulting charge current is found to be proportional to the difference
between the electron and hole wavefunctions of the Shiba state, being a direct
measure for such an asymmetry. By dynamically driving the impurity one can
infer the spin dependence of the Shiba states in the absence of a
spin-polarized STM tip",1611.09722v1
2017-03-08,Spin dynamics of antiferromagnets in the presence of a homogeneous magnetization,"We use general hydrodynamic equations to determine the long-wavelength spin
excitations in isotropic antiferromagnets in the presence of a homogeneous
magnetization. The latter may be induced, such as in antiferromagnets in an
external magnetic field, or spontaneous, such as in ferrimagnetic or canted
phases that are characterized by the coexistence of antiferromagnetic and
ferromagnetic order. Depending on the physical situation, we find propagating
spin waves that are gapped in some cases and gapless in others, diffusive
modes, or relaxational modes. The excitation spectra turn out to be
qualitatively different depending on whether or not the homogeneous
magnetization is a conserved quantity. The results lay the foundation for a
description of a variety of quantum phase transitions, including the transition
from a ferromagnetic metal to an antiferromagnetic one, and the spin-flop
transitions that are observed in some antiferromagnets. They also are crucial
for incorporating weak-localization and Altshuler-Aronov effects into the
descriptions of quantum phases in both clean and disordered magnetic metals.",1703.03009v1
2017-04-03,Spin dynamics and spin-dependent recombination of a polaron pair under a strong ac drive,"We study theoretically the recombination within a pair of two polarons in
magnetic field subject to a strong linearly polarized ac drive. Strong drive
implies that the Zeeman frequencies of the pair-partners are much smaller than
the Rabi frequency, so that the rotating wave approximation does not apply.
What makes the recombination dynamics nontrivial, is that the partners
recombine only when they form a singlet, S. By admixing singlet to triplets,
the drive induces the triplet recombination as well. We calculate the effective
decay rate of all four spin modes. Our main finding is that, under the strong
drive, the major contribution to the decay of the modes comes from short time
intervals when the driving field passes through zero. When the recombination
time in the absence of drive is short, fast recombination from S leads to
anomalously slow recombination from the other spin states of the pair. We show
that, with strong drive, this recombination becomes even slower. The
corresponding decay rate falls off as a power law with the amplitude of the
drive.",1704.00392v1
2017-04-06,Density inhomogeneities and Rashba spin-orbit coupling interplay in oxide interfaces,"There is steadily increasing evidence that the two-dimensional electron gas
(2DEG) formed at the interface of some insulating oxides like LaAlO3/SrTiO3 and
LaTiO3/SrTiO3 is strongly inhomogeneous. The inhomogeneous distribution of
electron density is accompanied by an inhomogeneous distribution of the
(self-consistent) electric field confining the electrons at the interface. In
turn this inhomogeneous transverse electric field induces an inhomogeneous
Rashba spin-orbit coupling (RSOC). After an introductory summary on two
mechanisms possibly giving rise to an electronic phase separation accounting
for the above inhomogeneity,we introduce a phenomenological model to describe
the density-dependent RSOC and its consequences. Besides being itself a
possible source of inhomogeneity or charge-density waves, the density-dependent
RSOC gives rise to interesting physical effects like the occurrence of
inhomogeneous spin-current distributions and inhomogeneous quantum-Hall states
with chiral ""edge"" states taking place in the bulk of the 2DEG. The
inhomogeneous RSOC can also be exploited for spintronic devices since it can be
used to produce a disorder-robust spin Hall effect.",1704.01852v1
2017-04-11,Long range interactions in antiferromagnetic quantum spin chains,"We study the role of long range dipolar interactions on antiferromagnetic
spin chains, from the classical $S\to \infty$ limit to the deep quantum case
$S=1/2$, including a transverse magnetic field. To this end, we combine
different techniques such as classical energy minima, classical Monte Carlo,
linear spin waves, bosonization and DMRG. We find a phase transition from the
already reported dipolar ferromagnetic region to an antiferromagnetic region
for high enough antiferromagnetic exchange. Thermal and quantum fluctuations
destabilize the classical order before reaching magnetic saturation in both
phases, and also close to zero field in the antiferromagnetic phase. In the
extreme quantum limit $S=1/2$, extensive DMRG computations show that the main
phases remain present with transition lines to saturation significatively
shifted to lower fields, in agreement with the bosonization analysis. The
overall picture keeps close analogy with the phase diagram of the anisotropic
XXZ spin chain in a transverse field.",1704.03420v3
2017-04-18,Spin-polarized quasi 1D state with finite bandgap on the Bi/InSb(001) surface,"One-dimensional (1D) electronic states were discovered on 1D surface atomic
structure of Bi fabricated on semiconductor InSb(001) substrates by
angle-resolved photoelectron spectroscopy (ARPES). The 1D state showed steep,
Dirac-cone-like dispersion along the 1D atomic structure with a finite direct
bandgap opening as large as 150 meV. Moreover, spin-resolved ARPES revealed the
spin polarization of the 1D unoccupied states as well as that of the occupied
states, the orientation of which inverted depending on the wave vector
direction parallel to the 1D array on the surface. These results reveal that a
spin-polarized quasi-1D carrier was realized on the surface of 1D Bi with
highly efficient backscattering suppression, showing promise for use in future
spintronic and energy-saving devices.",1704.05258v2
2017-04-18,Gate controlled spin-valley locking of resident carriers in WSe2 monolayers,"Using time-resolved Kerr rotation, we measure the spin/valley dynamics of
resident electrons and holes in single charge-tunable monolayers of the
archetypal transition-metal dichalcogenide (TMD) semiconductor WSe2. In the
n-type regime, we observe long (70 ns) polarization relaxation of electrons
that is sensitive to in-plane magnetic fields $B_y$, indicating spin
relaxation. In marked contrast, extraordinarily long (2 microsecond)
polarization relaxation of holes is revealed in the p-type regime, that is
unaffected by $B_y$, directly confirming long-standing expectations of strong
spin-valley locking of holes in the valence band of monolayer TMDs. Supported
by continuous-wave Kerr spectroscopy and Hanle measurements, these studies
provide a unified picture of carrier polarization dynamics in monolayer TMDs,
which can guide design principles for future valleytronic devices.",1704.05448v1
2017-04-21,Distribution of eigenstate populations and dissipative beating dynamics in uniaxial single-spin magnets,"Numerical simulations of magnetization reversal of a quantum uniaxial magnet
under a swept magnetic field [Hatomura, \textit{et al}., \textit{Quantum
Stoner-Wohlfarth Model}, Phys. Rev. Lett. \textbf{116}, 037203 (2016)] are
extended. In particular, how the ""wave packet"" describing the time-evolution of
the system is scattered in the successive avoided level crossings is
investigated from the viewpoint of the distribution of the eigenstate
populations. It is found that the peak of the distribution as a function of the
magnetic field does not depend on spin-size $S$, which indicates that the delay
of magnetization reversal due to the finite sweeping rate is the same in both
the quantum and classical cases. The peculiar synchronized oscillations of all
the spin components result in the beating of the spin-length. Here, dissipative
effects on this beating are studied by making use of the generalized
Lindblad-type master equation. The corresponding experimental situations are
also discussed in order to find conditions for experimental observations.",1704.06466v1
2019-04-02,Theory of Tunneling Effect in 1D AIII-class Topological Insulator (Nanowire) Proximity Coupled with a Superconductor,"We study the tunneling effect in an AIII-class insulator proximity coupled
with a spin-singlet $s$-wave superconductor, in which three phases are
characterized by the integer topological invariant $\mathcal{N}$. By solving
the Bogoliubov-de Gennes equation explicitly, we analytically obtain a normal
reflection coefficient $R_{\sigma\sigma'}$ and an Andreev reflection
coefficient $A_{\sigma\sigma'}$, and derive a charge conductance formula,where
$\sigma(\sigma')$ is the spin index of a reflected (injected) wave. The
resulting conductance indicates a wide variety of line shapes: (i)gap structure
without coherence peaks for $\mathcal{N}=0$, (ii)quantized zero-bias
conductance peak (ZBCP) with height $2e^{2}/h$ for $\mathcal{N}=1$, and
(iii)ZBCP spitting for $\mathcal{N}=2$. At zero bias voltage $eV=0$,
$\sum_{\sigma\sigma'} R_{\sigma\sigma'} = \sum_{\sigma\sigma'}
A_{\sigma\sigma'}$ is satisfied and the spin direction of an injected electron
is rotated at approximately $90^\circ$ for the $\mathcal{N}=1$ state.
Meanwhile, $A_{\sigma\sigma'}=0$ is satisfied for the $\mathcal{N}=2$ state,
and the spin rotation angle can become $180^\circ$.",1904.01586v2
2019-04-11,Strain tuning and anisotropic spin correlations in iron-based systems,"Nematic order in the iron-based superconductors is closely tied to a lattice
distortion and a structural transition from tetragonal to orthorhombic
symmetry. External stress of the appropriate symmetry acts as a conjugate field
of the nematic order parameter and can be utilized to detwin nematic domains
but also smears an otherwise sharp nematic transition. On the other hand,
applying stress in proper symmetry channels allows one to tune the nematic
phase transition. Recent experiments analyzed the stress-induced changes of the
nematic and magnetic phase transition temperature. Here we show that the
observed trends can be understood in terms of spin-induced nematicity. The
strain sensitivity is shown to be a fluctuation effect. The strong sensitivity
to antisymmetric strain is a consequence of the anisotropic nature of the
magnetic excitation spectrum. The formalism presented here can be naturally
generalized to determine the strain-sensitivity of vestigial phases related to
other magnetic states that have been observed in the iron-based systems, such
as e.g.\ the spin-charge density wave and the spin-vortex crystals.",1904.05583v2
2019-07-02,Bias-free reconfigurable magnonic phase shifter based on a spin-current controlled ferromagnetic resonator,"Controllable phase modulation plays a pivotal role in the researches of
magnonic logic gates. Here we propose a reconfigurable spin-current controlled
magnonic phase shifter based on a ferromagnetic resonator. The proposed phase
shifter requires no magnetic bias field during operation. The device is
directly configured over the waveguide while keeping the original structure of
the waveguide unaffected. Numerical micromagnetic simulations show that the
phase shifter could yield either a {\pi}-phase or no shift depending on the
magnetization status of the resonator, which can be controlled by a current
pulse. Moreover, the phase-shifting operation could be affected by spin
current. At different input current density, the device could be either used as
a dynamic controlled phase shifter or a spin-wave valve. Finally, a XNOR
magnonic logic gate is demonstrated using the proposed phase shifter. Our work
can be a beneficial step to enhance the functionality and compatibility of the
magnonic logic circuits.",1907.01303v1
2019-08-22,Phase diagram and quantum criticality of Heisenberg spin chains with Ising-like interchain couplings -- Implication to YbAlO$_3$,"Motivated by recent progress on field-induced phase transitions in
quasi-one-dimensional quantum antiferromagnets, we study the phase diagram of
$S=1/2$ antiferromagnetic Heisenberg chains with Ising anisotropic interchain
couplings under a longitudinal magnetic field via large-scale quantum Monte
Carlo simulations. The interchain interactions is shown to enhance longitudinal
spin correlations to stabilize an incommensurate longitudinal spin density wave
order at low temperatures. With increasing field the ground state changes to a
canted antiferromagnetic order until the magnetization fully saturates above a
quantum critical point controlled by the $(3+2)$D XY universality. Increasing
temperature in the quantum critical regime the system experiences a fascinating
dimension crossover to a universal Tomonaga-Luttinger liquid. The calculated
NMR relaxation rate $1/T_1$ indicates this Luttinger liquid behavior survives a
broad field and temperature regime. Our results determine the global phase
diagram and quantitative features of quantum criticality of a general model for
quasi-one-dimensional spin chain compounds, and thus lay down a concrete ground
to the study on these materials.",1908.08467v1
2019-09-16,Nature and impact of stripe freezing in La$_{1.67}$Sr$_{0.33}$NiO$_4$,"La$_{1.67}$Sr$_{0.33}$NiO$_4$ develops charge and spin stripe orders at
temperatures of roughly 200 K, with modulation wave vectors that are
temperature independent. Various probes of spin and charge response have
provided independent evidence for some sort of change below $\sim50$ K. In
combination with a new set of neutron scattering measurements, we propose a
unified interpretation of all of these observations in terms of a freezing of
Ni-centered charges stripes, together with a glassy ordering of the spin
stripes that shows up in neutron scattering as a slight rotation of the average
spin direction.",1909.07411v2
2019-09-20,Dimer Physics in the Frustrated Cairo Pentagonal Antiferromagnet Bi2Fe4O9,"The research field of magnetic frustration is dominated by triangle-based
lattices but exotic phenomena can also be observed in pentagonal networks. A
peculiar noncollinear magnetic order is indeed known to be stabilized in
Bi2Fe4O9 materializing a Cairo pentagonal lattice. We present the spin wave
excitations in the magnetically ordered state, obtained by inelastic neutron
scattering. They reveal an unconventional excited state related to local
precession of pairs of spins. The magnetic excitations are then modeled to
determine the superexchange interactions for which the frustration is indeed at
the origin of the spin arrangement. This analysis unveils a hierarchy in the
interactions, leading to a paramagnetic state (close to the N\'eel temperature)
constituted of strongly coupled dimers separated by much less correlated spins.
This produces two types of response to an applied magnetic field associated
with the two nonequivalent Fe sites, as observed in the magnetization
distributions obtained using polarized neutrons.",1909.09573v2
2019-10-08,Orbital Nernst Effect of Magnons,"In the past, magnons have been shown to mediate thermal transport of spin in
various systems. Here, we reveal that the fundamental coupling of scalar spin
chirality, inherent to magnons, to the electronic degrees of freedom in the
system can result in the generation of sizeable orbital magnetization and
thermal transport of orbital angular momentum. We demonstrate the emergence of
the latter phenomenon of orbital Nernst effect by referring to the spin-wave
Hamiltonian of kagome ferromagnets, predicting that in a wide range of systems
the transverse current of orbital angular momentum carried by magnons in
response to an applied temperature gradient can overshadow the accompanying
spin current. We suggest that the discovered effect fundamentally correlates
with the topological Hall effect of fluctuating magnets, and it can be utilized
in magnonic devices for generating magnonic orbital torques.",1910.03317v2
2019-10-31,Coherent spin pumping in a strongly coupled magnon-magnon hybrid system,"We experimentally identify coherent spin pumping in the magnon-magnon hybrid
modes of permalloy/yttrium iron garnet (Py/YIG) bilayers. Using broadband
ferromagnetic resonance, an ""avoided crossing"" is observed between the uniform
mode of Py and the spin wave mode of YIG due to the fieldlike interfacial
exchange coupling. We also identify additional linewidth suppression and
enhancement for the in-phase and out-of-phase hybrid modes, respectively,
\textcolor{black}{which can be interpreted as concerted dampinglike torque from
spin pumping}. Our analysis predicts inverse proportionality of both fieldlike
and dampinglike torques to the square root of the Py thickness, which
quantitatively agrees with experiments.",1910.14470v2
2019-12-12,Weak-coupling Mean-field Theory of Magnetic Properties of NiGa$_2$S$_4$,"We report a mean-field theoretical study of a triangular lattice magnet
NiGa$_2$S$_4$. Specifically, spiral mean-field theory is applied to a 17-band
$d$-$p$ model constructed from the maximally localized Wannier functions. Our
itinerant-model approach shows that the most stable spiral magnetic state has
an ordering vector near ${\bf Q}=(0.15,0.15,0)$, consistent with neutron
scattering experiments, when we assume the Ni-site Coulomb interaction is not
so strong ($U \approx 2$ eV). To map onto a classical Heisenberg spin model, we
estimate spin exchange interactions from the mean-field results, and find that
the nearest-neighbor exchange is ferromagnetic and the largest (larger than the
third nearest-neighbor exchange, in contrast to early studies). We also
calculate the dynamical spin correlation function $S({\bf q}, \omega)$, using
the same model within the random-phase approximation (RPA). Calculated $S({\bf
q}, \omega)$ has a spectral structure quite different from that of conventional
spin-wave excitations.",1912.05720v2
2020-01-28,Magnetic oscillation modes in square lattice artificial spin ice,"Small amplitude dipolar oscillations are considered in artificial spin ice on
a square lattice in two dimensions. The net magnetic moment of each elongated
magnetic island in the spin ice is assumed to have Heisenberg-like dynamics.
Each island's magnetic moment is assumed to be influenced by shape anisotropies
and by the dipolar interactions with its nearest neighbors. The magnetic
dynamics is linearized around one of the ground states, leading to an $8\times
8$ matrix to be diagonalized for the magnetic spin wave modes. Analytic
solutions are found and classified as antisymmetric and symmetric with regard
to their in-plane dynamic fluctuations. Although only the leading dipolar
interactions are included, modes similar to these may be observable
experimentally.",2001.10409v1
2020-02-11,Topological superconductivity in the doped chiral spin liquid on the triangular lattice,"It has long been proposed that doping a chiral spin liquid (CSL) or
fractional quantum Hall state can give rise to topological superconductivity.
Despite of intensive effort, definitive evidences still remain lacking. We
address this problem by studying the $t$-$J$ model supplemented by
time-reversal symmetry breaking chiral interaction $J_\chi$ on the triangular
lattice using density-matrix renormalization group with a finite concentration
$\delta$ of doped holes. It has been established that the undoped, i.e.,
$\delta$=0, system has a CSL ground state in the parameter region $0.32\le
J_\chi/J \le 0.56$. Upon light doping, we find that the ground state of the
system is consistent with a Luther-Emery liquid with power-law superconducting
and charge-density-wave correlations but short-range spin-spin correlations. In
particular, the superconducting correlations, whose pairing symmetry is
consistent with $d\pm id$-wave, are dominant at all hole doping concentrations.
Our results provide direct evidences that doping the CSL on the triangular
lattice can naturally give rise to topological superconductivity.",2002.04686v2
2020-02-14,Low energy magnons in the chiral ferrimagnet $\text{Cu}_2\text{OSeO}_3$: a coarse-grained approach,"We report a comprehensive neutron scattering study of low energy magnetic
excitations in the breathing pyrochlore helimagnetic
$\text{Cu}_2\text{OSeO}_3$. Fully documenting the four lowest energy magnetic
modes that leave the ferrimagnetic configuration of the ""strong tetrahedra""
intact ($|\hbar\omega|<13$ meV), we find gapless quadratic dispersion at the
$\Gamma$ point for energies above 0.2 meV, two doublets separated by 1.6(2) meV
at the $R$ point, and a bounded continuum at the $X$ point. Our constrained
rigid spin cluster model relates these features to Dzyaloshinskii-Moriya (DM)
interactions and the incommensurate helical ground state. Combining
conventional spin wave theory with a spin cluster form-factor accurately
reproduces the measured equal time structure factor through multiple Brillouin
zones. An effective spin Hamiltonian describing the complex anisotropic
inter-cluster interactions is obtained.",2002.06283v2
2020-02-27,"Separation of variables for rational gl(n) spin chains in any compact representation, via fusion, embedding morphism and Backlund flow","We propose a way to separate variables in a rational integrable
$\mathfrak{gl}(n)$ spin chain with an arbitrary finite-dimensional irreducible
representation at each site and with generic twisted periodic boundary
conditions. Firstly, we construct a basis that diagonalises a higher-rank
version of the Sklyanin B-operator; the construction is based on recursive
usage of an embedding of a $\mathfrak{gl}(k)$ spin chain into a
$\mathfrak{gl}(k+1)$ spin chain which is induced from a Yangian homomorphism
and controlled by dual diagonals of Gelfand-Tsetlin patterns. Then, we show
that the same basis can be equivalently constructed by action of
Backlund-transformed fused transfer matricies, whence the Bethe wave functions
factorise into a product of ascending Slater determinants in Baxter
Q-functions. Finally, we construct raising and lowering operators -- the
conjugate momenta -- as normal-ordered Wronskian expressions in Baxter
Q-operators evaluated at zeros of B -- the separated variables. It is an
immediate consequence of the proposed construction that the Bethe algebra
comprises the maximal possible number of mutually commuting charges -- a
necessary property for Bethe equations to be complete.",2002.12341v2
2020-05-08,Staggered-flux state for rectangular-lattice spin 1/2 Heisenberg antiferromagnet,"We investigate the spin-1/2 Heisenberg model on a rectangular lattice, using
the Gutzwiller projected variational wave function known as the staggered flux
state. Using Monte Carlo techniques, the variational parameters and static
spin-structure factor for different coupling anisotropies $\gamma=J_y/J_x$ are
calculated. We observe a gradual evolution of the ground state energy towards a
value which is very close to the 1D estimate provided by the Bethe ansatz and a
good agreement between the finite size scaling of the energies. The spin-spin
correlation functions exhibit a power-law decay with varying exponents for
different anisotropies. Though the lack of N\'eel order makes the staggered
flux state energetically unfavorable in the symmetric case $\gamma=1$, it
appears to capture the essence of the system close to 1D. Hence we believe that
the staggered flux state provides an interesting starting point to explore the
crossover from quantum disordered chains to the N\'eel ordered 2D square
lattices.",2005.03928v1
2020-05-08,Electrical detection of magnon-photon interaction via auxiliary spin wave mode,"We report on the electrical detection of a hybrid magnon-photon system, which
is comprised of a magnetic sample coupled to a planar cavity. While the uniform
Kittel mode has the largest coupling strength among all the magnon modes, it
only generates a modest voltage signal by means of inverse spin-Hall effect. We
have found that the generated voltage can be significantly enhanced by
introducing a higher order magnon mode, which possesses a much higher spin
pumping efficiency and furthermore, it is nearly degenerated with the Kittel
mode. The experimental results can be explained by our theoretical model, and
suggest that the use of an auxiliary magnon mode can realize the configuration
of a magnon-photon system with both strong coupling and large spin current.",2005.04161v1
2020-05-11,Universal relations for hybridized $s$- and $p$-wave interactions from spin-orbital coupling,"In this work, we study the universal relations for one-dimensional
spin-orbital-coupled fermions near both $s$- and $p$-wave resonances using
effective field theory. Since the spin-orbital coupling mixes different partial
waves, a contact matrix is introduced to capture the non-trivial correlation
between dimers. We find the signature of the spin-orbital coupling appears at
the leading order for the off-diagonal components of the momentum distribution
matrix, which is proportional to $1/q^{3}$ ($q$ is the relative momentum). We
further derive the large frequency behavior of the Raman spectroscopy, which
serves as an independent measurable quantity for contacts. Finally, we give an
explicit example of contacts by considering a two-body problem.",2005.04997v2
2020-05-15,Off-axis dipole forces in optical tweezers by an optical analog of the {Magnus} effect,"It is shown that a circular dipole can deflect the focused laser beam that
induces it, and will experience a corresponding transverse force. Quantitative
expressions are derived for Gaussian and angular tophat beams, while the
effects vanish in the plane-wave limit. The phenomena are analogous to the
Magnus effect pushing a spinning ball onto a curved trajectory. The optical
case originates in the coupling of spin and orbital angular momentum of the
dipole and the light. In optical tweezers the force causes off-axis
displacement of the trapping position of an atom by a spin-dependent amount up
to $\lambda/2\pi$, set by the direction of a magnetic field. This suggests
direct methods to demonstrate and explore these effects, for instance to induce
spin-dependent motion.",2005.07790v3
2020-06-24,Localization of 5f-electrons and pressure effects on magnetism in U intermetallics in the light of spin-fluctuation theory,"UCoGa and URhGa, two isostructural compounds show opposite signs of the
initial response of Curie temperature to applied hydrostatic premenssure. To
determine the physical origin of this contradiction the magnetization data
measured with respect to temperature, magnetic field and hydrostatic pressure
were analyzed in the framework of the Takahashi's spin-fluctuation theory. The
parameters T0 and TA characterizing the distribution widths of the
spin-fluctuation spectrum in the energy and wave vector space, respectively,
and TC/T0, the degree of the 5f-electron localization have been determined.
Examination of available experimental data for the other UTX (T = a transition
metal, X = Al, Ga) ferromagnets having the ZrNiAl-type structure revealed some
correlations between the degree of the 5f-electron localization represented by
the spin-fluctuation parameters and the response of Curie-temperature on the
applied pressure. These observations may be applied more generally to describe
the localization and magnetic behaviors of the majority of the uranium
ferromagnetic compounds.",2006.13683v2
2020-07-01,Spinning Black Holes Fall in Love,"The open question of whether a black hole can become tidally deformed by an
external gravitational field has profound implications for fundamental physics,
astrophysics and gravitational-wave astronomy. Love tensors characterize the
tidal deformability of compact objects such as astrophysical (Kerr) black holes
under an external static tidal field. We prove that all Love tensors vanish
identically for a Kerr black hole in the nonspinning limit or for an
axisymmetric tidal perturbation. In contrast to this result, we show that Love
tensors are generically nonzero for a spinning black hole. Specifically, to
linear order in the Kerr black hole spin and the weak perturbing tidal field,
we compute in closed form the Love tensors that couple the mass-type and
current-type quadrupole moments to the electric-type and magnetic-type
quadrupolar tidal fields. For a dimensionless spin ~ 0.1, the nonvanishing
quadrupolar Love tensors are ~ 0.002, thus showing that black holes are
particularly ""rigid"" compact objects.",2007.00214v2
2020-07-02,Wave-particle duality of electrons with spin-momentum locking,"We investigate the effects of spin-momentum locking on the interference and
diffraction patterns due to a double- or single-slit in an electronic
\emph{Gedankenexperiment}. We show that the inclusion of the
spin-degree-of-freedom, when coupled to the motion direction of the carrier --
a typical situation that occurs in systems with spin-orbit interaction -- leads
to a modification of the interference and diffraction patterns that depend on
the geometrical parameters of the system.",2007.01021v3
2020-07-06,"Triplons, Magnons, and Spinons in a Single Quantum Spin System: SeCuO3","Quantum spin systems exhibit an enormous range of collective excitations, but
their spin waves, gapped triplons, fractional spinons, or yet other modes are
generally held to be mutually exclusive. Here we show by neutron spectroscopy
on SeCuO$_3$ that magnons, triplons, and spinons are present simultaneously. We
demonstrate that this is a consequence of a structure consisting of two coupled
subsystems and identify all the interactions of a minimal magnetic model. Our
results serve qualitatively to open the field of multi-excitation spin systems
and quantitatively to constrain the complete theoretical description of one
member of this class of materials.",2007.02972v2
2020-06-24,Proper relativistic position operators in 1+1 and 2+1 dimensions,"We have revisited the Dirac theory in 1+1 and 2+1 dimensions by using the
covariant representation of the parity-extended Poincar\'e group in their
native dimensions. The parity operator plays a crucial role in deriving wave
equations in both theories. We studied two position operators, a canonical one
and a covariant one that becomes the particle position operator projected onto
the particle subspace. In 1+1 dimensions the particle position operator, not
the canonical position operator, provides the conserved Lorentz generator. The
mass moment defined by the canonical position operator needs an additional
unphysical spin-like operator to become the conserved Lorentz generator in 1+1
dimensions. In 2+1 dimensions, the sum of the orbital angular momentum given by
the canonical position operator and the spin angular momentum becomes a
constant of motion. However, orbital and spin angular momentum do not conserve
separately. On the other hand the orbital angular momentum given by the
particle position operator and its corresponding spin angular momentum become a
constant of motion separately.",2007.04770v1
2020-07-10,Nuclear Surface Acoustic Resonance with Spin-Rotation Coupling,"We show that, under an appropriate out-of-plane static magnetic field,
nuclear spins in a thin specimen on a surface acoustic wave (SAW) cavity can be
resonantly excited and detected through spin-rotation coupling. Since such a
SAW cavity can have the quality factor as high as $10^{4}$ and the mode volume
as small as $10^{-2}$ mm$^{3}$ the signal-to-noise ratio in detecting the
resonance is estimated to be quite high. We argue that detecting nuclear spin
resonance of a single flake of an atomically-thin layer of two-dimensional
semiconductor, which has so far been beyond hope with the conventional
inductive method, can be a realistic target with the proposed scheme.",2007.05645v1
2020-07-12,Density Dependent Spin-Orbit Coupling in Degenerate Quantum Gases,"In this letter we propose a method to realize a kind of spin-orbit coupling
in ultracold Bose and Fermi gases whose format and strength depend on density
of atoms. Our method combines two-photon Raman transition and periodical
modulation of spin-dependent interaction, which gives rise to the direct Raman
process and the interaction assisted Raman process, and the latter depends on
density of atoms. These two processes have opposite effects in term of
spin-momentum locking and compete with each other. As the interaction
modulation increases, the system undergoes a crossover from the direct Raman
process dominated regime to the interaction assisted Raman process dominated
regime. For this crossover, we show that for bosons, both the condensate
momentum and the chirality of condensate wave function change sign, and for
fermions, the Fermi surface distortion is inverted. We highlight that there
exists an emergent spatial reflection symmetry in the crossover regime, which
can manifest itself universally in both Bose and Fermi gases. Our method paves
a way to novel phenomena in a non-abelian gauge field with intrinsic dynamics.",2007.05999v2
2020-07-31,Quantum Phases and Spin Liquid Properties of 1T-TaS2,"Quantum materials exhibiting magnetic frustration are connected to diverse
phenomena including high-Tc superconductivity, topological order and quantum
spin liquids (QSLs). A QSL is a quantum phase (QP) related to a
quantum-entangled fluid-like state of matter. Previous experiments on QSL
candidate materials are usually interpreted in terms of a single QP, although
theories indicate that many distinct QPs are closely competing in typical
frustrated spin models. Here we report on combined temperature-dependent muon
spin relaxation and specific heat measurements for the triangular-lattice QSL
candidate material 1T-TaS2 that provide evidence for competing QPs. The
measured properties are assigned to arrays of individual QSL layers within the
layered charge density wave structure of 1T-TaS2 and their characteristic
parameters can be interpreted as those of distinct Z2 QSL phases. The present
results reveal that a QSL description can extend beyond the lowest
temperatures, offering a new perspective in the search for novel quantum
materials.",2007.15905v2
2020-09-30,Breathing kagome XY quantum magnet with four-site ring exchange,"We study the impact of trimerization (breathing) of the nearest-neighbor (NN)
exchange on the planar XY spin-1/2 ferromagnet on the kagome lattice, including
additional four-site ring exchange. For uniform NN exchange, this model has
previously been shown to transit from a long-range ordered ferromagnet into a
Z2 quantum spin liquid by virtue of the ring exchange. Using quantum
Monte-Carlo calculations, based on the stochastic series expansion, we present
results for the spin stiffness, the quantum phase diagram, the longitudinal
static, as well as the transverse dynamic structure factor. Our results
corroborate 3D XY universality also at finite trimerization and suggest a
simple continuation of the quantum critical point of the uniform case into a
line in terms of rescaled exchange parameters. Moreover, at any trimerization
and in the ordered phase the elementary excitations can be understood very well
in terms of linear spin wave theory, while beyond the critical line, in the
spin liquid phase we find signatures of spinon continua.",2010.00014v2
2020-10-29,"""Tiny galaxies"" from ""little bang""","We show, by solving the linearized Vlasov equations, that in the presence of
an attractive density-dependent vector, or tensor, mean field potential, under
a portion of the spinodal unstable phase region where the attractions among the
quarks are more dominant, the transverse modes, i.e., the fluctuations of the
current densities perpendicular to the wave vector, are activated due to
relativity. In particular, the current densities in both the transverse
directions oscillate with the same frequency, indicating the existence of the
spontaneous rotations of the dense clusters. These rotating clusters would
certainly create a local vortical flow field which, according to chiral (or
spin) vortical effect, leads to the macroscopic separation of the axial charges
or spins due to the spin-orbital interactions. Hence, for the first time, the
connection between the axial charge or spin in-homogeneity and the first-order
phase transition is proposed.",2010.15752v1
2020-12-01,Nonreciprocal optical solitons in a spinning Kerr resonator,"We propose a spinning nonlinear resonator as an experimentally accessible
platform to achieve nonreciprocal control of optical solitons. Nonreciprocity
here results from the relativistic Sagnac-Fizeau optical drag effect, which is
different for pump fields propagating in the spinning direction or in the
direction opposite to it. We show that in a spinning Kerr resonator, different
soliton states appear for the input fields in different directions. These
nonreciprocal solitons are more stable against losses induced by inter-modal
coupling between clockwise and counterclockwise modes of the resonator. Our
work builds a bridge between nonreciprocal physics and soliton science,
providing a promising route towards achieving soliton-wave optical isolators
and one-way soliton communications.",2012.00225v4
2020-12-02,Measuring correlated electron motion in atoms with the momentum-balance density,"Three new measures of relative electron motion are introduced: equimomentum,
antimomentum, and momentum-balance. The equimomentum is the probability that
two electrons have the exact same momentum, whereas the antimomentum is the
probability their momenta are the exact opposite. Momentum-balance (MB) is the
difference between the equimomentum and antimomentum, and therefore indicates
if equal or opposite momentum is more probably in a system of electrons. The
equimomentum, antimomentum and MB densities are also introduced, which are the
local contribution to each quantity. The MB and MB density of the
extrapolated-Full Configuration Interaction wave functions of atoms of the
first three rows of the periodic table are analyzed, with a particular focus on
contrasting the correlated motion of electrons with opposite and parallel spin.
Coulomb correlation between opposite-spin electrons leads to a higher
probability of equimomentum, whereas Fermi correlation between parallel-spin
electrons leads to a higher probability of antimomentum. The local contribution
to MB, given an electron is present, is a minimum at the nucleus and generally
increases as the distance from the nucleus increases. There are also
interesting similarities between the effects of Fermi correlation and Coulomb
correlation (of opposite-spin electrons) on MB.",2012.01543v1
2020-12-16,The Magnetoelastic Distortion of Multiferroic BiFeO$_3$ in the Canted Antiferromagnetic State,"Using THz spectroscopy, we show that the spin-wave spectrum of multiferroic
BiFeO$_3$ in its high-field canted antiferromagnetic state is well described by
a spin model that violates rhombohedral symmetry. We demonstrate that the
monoclinic distortion of the canted antiferromagnetic state is induced by the
single-ion magnetoelastic coupling between the lattice and the two nearly
anti-parallel spins. The revised spin model for BiFeO$_3$ contains two new
single-ion anisotropy terms that violate rhombohedral symmetry and depend on
the direction of the magnetic field.",2012.09178v1
2021-03-22,Properties of white dwarf in the binary system AR Scorpii and its observed features,"The binary system AR Scorpii hosts an M-type main sequence cool star orbiting
around a magnetic white dwarf in the Milky Way Galaxy. The broadband
non-thermal emission over radio, optical and X-ray wavebands observed from AR
Scorpii indicates strong modulations on the spin frequency of the white dwarf
as well as the spin-orbit beat frequency of the system. Therefore, AR Scorpii
is also referred to as a white dwarf pulsar wherein a fast spinning white dwarf
star plays very crucial role in the broadband non-thermal emission. Several
interpretations for the observed features of AR Scorpii appear in the
literature without firm conclusions. In this work, we investigate connection
between some of the important physical properties like spin-down power, surface
magnetic field, equation of state, temperature and gravity associated with the
white dwarf in the binary system AR Scorpii and its observational
characteristics. We explore the plausible effects of white dwarf surface
magentic field on the absence of substantial accretion in this binary system
and also discuss the gravitational wave emission due to magnetic deformation
mechanism.",2103.11602v1
2021-03-22,Calibration of Spin-Light Coupling by Coherently Induced Faraday Rotation,"Calibrating the strength of the light-matter interaction is an important
experimental task in quantum information and quantum state engineering
protocols. The strength of the off-resonant light-matter interaction in
multi-atom spin oscillators can be characterized by the coupling rate
$\Gamma_\text{S}$. Here we utilize the Coherently Induced Faraday Rotation
(CIFAR) signal for determining the coupling rate. The method is suited for both
continuous and pulsed readout of the spin oscillator, relying only on applying
a known polarization modulation to the probe laser beam and detecting a known
optical polarization component. Importantly, the method does not require
changes to the optical and magnetic fields performing the state preparation and
probing. The CIFAR signal is also independent of the probe beam photo-detection
quantum efficiency, and allows direct extraction of other parameters of the
interaction, such as the tensor coupling $\zeta_\text{S}$, and the damping rate
$\gamma_\text{S}$. We verify this method in the continuous wave regime, probing
a strongly coupled spin oscillator prepared in a warm cesium atomic vapour.",2103.11729v1
2021-03-26,"A Unified Approach to Scalar, Vector, and Tensor Slepian Functions on the Sphere and Their Construction by a Commuting Operator","We present a unified approach for constructing Slepian functions - also known
as prolate spheroidal wave functions - on the sphere for arbitrary tensor ranks
including scalar, vectorial, and rank 2 tensorial Slepian functions, using
spin-weighted spherical harmonics. For the special case of spherical cap
regions, we derived commuting operators, allowing for a numerically stable and
computationally efficient construction of the spin-weighted
spherical-harmonic-based Slepian functions. Linear relationships between the
spin-weighted and the classical scalar, vectorial, tensorial, and higher-rank
spherical harmonics allow the construction of classical
spherical-harmonic-based Slepian functions from their spin-weighted
counterparts, effectively rendering the construction of spherical-cap Slepian
functions for any tensorial rank a computationally fast and numerically stable
task.",2103.14650v1
2021-05-01,Towards Kitaev Spin Liquid in 3d Transition Metal Compounds,"This paper reviews the current progress on searching the Kitaev spin liquid
state in 3d electron systems. Honeycomb cobaltates were recently proposed as
promising candidates to realize the Kitaev spin liquid state, due to the more
localized wave functions of 3d ions compared with that of 4d and 5d ions, and
also the easy tunability of the exchange Hamiltonian in favor of Kitaev
interaction. Several key parameters that have large impacts on the exchange
constants, such as the charge-transfer gap and the trigonal crystal field, are
identified and discussed. Specifically, tuning crystal field effect by means of
strain or pressure is emphasized as an efficient phase control method driving
the magnetically ordered cobaltates into the spin liquid state. Experimental
results suggesting the existence of strong Kitaev interactions in layered
honeycomb cobaltates are discussed. Finally, the future research directions are
briefly outlined.",2105.00168v3
2021-05-11,Spin/Valley pumping of resident electrons in WSe2 and WS2 monolayers,"Monolayers of transition metal dichalcogenides are ideal materials to control
both spin and valley degrees of freedom either electrically or optically.
Nevertheless, optical excitation mostly generates excitons species with
inherently short lifetime and spin/valley relaxation time. Here we demonstrate
a very efficient spin/valley optical pumping of resident electrons in n-doped
WSe2 and WS2 monolayers. We observe that, using a continuous wave laser and
appropriate doping and excitation densities, negative trion doublet lines
exhibit circular polarization of opposite sign and the photoluminescence
intensity of the triplet trion is more than four times larger with circular
excitation than with linear excitation. We interpret our results as a
consequence of a large dynamic polarization of resident electrons using
circular light.",2105.04861v1
2021-05-20,Coexistence of ferromagnetism and spin-orbit coupling by incorporation of platinum in two-dimensional VSe$_2$,"We report on a novel material, namely two-dimensional (2D)
V$_{1-x}$Pt$_x$Se$_2$ alloy, exhibiting simultaneously ferromagnetic order and
Rashba spin-orbit coupling. While ferromagnetism is absent in 1T-VSe$_2$ due to
the competition with the charge density wave phase, we demonstrate
theoretically and experimentally that the substitution of vanadium by platinum
in VSe$_2$ (10-50 %) to form an homogeneous 2D alloy restores ferromagnetic
order with Curie temperatures of 6 K for 5 monolayers and 25 K for one
monolayer of V$_{0.65}$Pt$_{0.35}$Se$_2$. Moreover, the presence of platinum
atoms gives rise to Rashba spin-orbit coupling in (V,Pt)Se$_2$ providing an
original platform to study the interplay between ferromagnetism and spin-orbit
coupling in the 2D limit.",2105.10022v1
2021-06-30,Magnetic-field-controlled spin fluctuations and quantum criticality in Sr3Ru2O7,"When the transition temperature of a continuous phase transition is tuned to
absolute zero, new ordered phases and physical behaviour emerge in the vicinity
of the resulting quantum critical point. Sr3Ru2O7 can be tuned through quantum
criticality with magnetic field at low temperature. Near its critical field Bc
it displays the hallmark T-linear resistivity and a T log(1/T) electronic heat
capacity behaviour of strange metals. However, these behaviours have not been
related to any critical fluctuations. Here we use inelastic neutron scattering
to reveal the presence of collective spin fluctuations whose relaxation time
and strength show a nearly singular variation with magnetic field as Bc is
approached. The large increase in the electronic heat capacity and entropy near
Bc can be understood quantitatively in terms of the scattering of conduction
electrons by these spin-fluctuations. On entering the spin density wave (SDW)
phase present near Bc, the fluctuations become stronger suggesting that the SDW
order is stabilised through an ""order-by-disorder"" mechanism.",2106.15854v2
2021-06-30,Design and realization of topological Dirac fermions on a triangular lattice,"Large-gap quantum spin Hall insulators are promising materials for
room-temperature applications based on Dirac fermions. Key to engineer the
topologically non-trivial band ordering and sizable band gaps is strong
spin-orbit interaction. Following Kane and Mele's original suggestion, one
approach is to synthesize monolayers of heavy atoms with honeycomb coordination
accommodated on templates with hexagonal symmetry. Yet, in the majority of
cases, this recipe leads to triangular lattices, typically hosting metals or
trivial insulators. Here, we conceive and realize ""indenene"", a triangular
monolayer of indium on SiC exhibiting non-trivial valley physics driven by
local spin-orbit coupling, which prevails over inversion-symmetry breaking
terms. By means of tunneling microscopy of the 2D bulk we identify the quantum
spin Hall phase of this triangular lattice and unveil how a hidden honeycomb
connectivity emerges from interference patterns in Bloch $p_x \pm ip_y$-derived
wave functions.",2106.16025v1
2021-07-12,Scattering Hypervolume of Spin-Polarized Fermions,"We analyze the collision of three identical spin-polarized fermions at zero
collision energy, assuming arbitrary finite-range potentials, and define the
corresponding three-body scattering hypervolume $D_F$. The scattering
hypervolume $D$ was first defined for identical bosons in 2008 by one of us. It
is the three-body analog of the two-body scattering length. We solve the
three-body Schr\""{o}dinger equation asymptotically when the three fermions are
far apart or one pair and the third fermion are far apart, deriving two
asymptotic expansions of the wave function. Unlike the case of bosons for which
$D$ has the dimension of length to the fourth power, here the $D_F$ we define
has the dimension of length to the eighth power. We then analyze the
interaction energy of three such fermions with momenta $\hbar\mathbf{k}_1$,
$\hbar\mathbf{k}_2$ and $\hbar\mathbf{k}_3$ in a large periodic cubic box. The
energy shift due to $D_F$ is proportional to $D_F/\Omega^2$, where $\Omega$ is
the volume of the box. We also calculate the shifts of energy and pressure of
spin-polarized Fermi gases due to a nonzero $D_F$ and the three-body
recombination rate of spin-polarized ultracold atomic Fermi gases at finite
temperatures.",2107.05309v2
2021-11-05,Temperature-driven transition from skyrmion to bubble crystals in centrosymmetric itinerant magnets,"Interplay between itinerant electrons and localized spins in itinerant
magnets gives rise to a variety of noncoplanar multiple-$Q$ spin textures, such
as the skyrmion, hedgehog, meron, and vortex. We elucidate that another type of
multiple-$Q$ state consisting of collinear sinusoidal waves, a magnetic bubble
crystal, appears at finite temperatures in a centrosymmetric itinerant electron
system. The results are obtained for the classical Kondo lattice model with
easy-axis single-ion anisotropy on a triangular lattice by a large-scale
numerical simulation. We find that a finite-temperature topological phase
transition between the skyrmion crystal and the bubble crystal occurs by
changing the temperature. We obtain the minimal key ingredients for inducing
the finite-temperature transition by analyzing an effective spin model where it
is shown that the synergy between the multiple-spin interaction and magnetic
anisotropy plays a significant role.",2111.03202v1
2021-11-22,Insights into the Anisotropic Spin-$S$ Kitaev Chain,"Recently there has been a renewed interest in properties of the higher-spin
Kitaev models, especially their low-dimensional analogues with additional
interactions. These quasi-1D systems exhibit rich phase diagrams with
symmetry-protected topological phases, Luttinger liquids, hidden order, and
higher-rank magnetism. However, the nature of the pure spin-$S$ Kitaev chains
are not yet fully understood. Earlier works found a unique ground state with
short-ranged correlations for $S = 1$, and an intriguing double-peak structure
in the heat capacity associated with an entropy plateau. To understand the
low-energy excitations and thermodynamics for general $S$ we study the
anisotropic spin-$S$ Kitaev chain. Starting from the dimerized limit we derive
an effective low-energy Hamiltonian at finite anisotropy. For half-integer
spins we find a trivial effective model, reflecting a non-local symmetry
protecting the degeneracy, while for integer $S$ we find interactions among the
flux degrees of freedom that select a unique ground state. The effective model
for integer spins is used to predict the low-energy excitations and
thermodynamics, and we make a comparison with the semiclassical limit through
linear spin wave theory. Finally, we speculate on the nature of the isotropic
limit.",2111.11457v1
2021-11-22,Stability of ordered and disordered phases in the Heisenberg-Kitaev model in a magnetic field,"The $S=1/2$ Kitaev honeycomb model has attracted significant attention as an
exactly solvable example with a quantum spin liquid ground state. In a properly
oriented external magnetic field, chiral Majorana edge modes associated with a
quantized thermal Hall conductance emerge, and a distinct spin-disordered phase
appears at intermediate field strengths, below the polarized phase. However,
since material realizations of Kitaev magnetism invariably display competing
exchange interactions, the stability of these exotic phases with respect to
additional couplings is a key issue. Here, we report a 24-site exact
diagonalization study of the Heisenberg-Kitaev model in a magnetic field
applied in the [001] and [111] directions. By mapping the full phase diagram of
the model and contrasting the results to recent nonlinear spin-wave
calculations, we show that both methods agree well, thus establishing that
quantum corrections substantially modify the classical phase diagram.
Furthermore, we find that, in a [111] field, the intermediate-field
spin-disordered phase is remarkably stable to Heisenberg interactions and may
potentially end in a novel quantum tricritical point.",2111.11474v1
2021-11-23,On the group theoretical approach to relativistic wave equations for arbitrary spin,"Formulating a relativistic equation for particles with arbitrary spin remains
an open challenge in theoretical physics. In this study, the main algebraic
approaches used to generalize the Dirac and Kemmer Duffin equations for
particles of arbitrary spin are investigated. It is proved that an irreducible
relativistic equation formulated using spin matrices satisfying the commutation
relations of the anti-de Sitter group leads to inconsistent results, mainly as
a consequence of violation of unitarity and the appearance of a mass spectrum
that does not reflect the physical reality of elementary particles. However,
the introduction of subsidiary conditions resolves the problem of unitarity and
restores the physical meaning of the mass spectrum. The equations obtained by
these approaches are solved and the physical nature of the solutions is
discussed.",2111.12554v1
2021-11-29,Element selective ultrafast magnetization dynamics of hybrid Stoner-Heisenberg magnets,"Stoner and Heisenberg excitations in magnetic materials are inherently
different. The former involves an effective reduction of the exchange
splitting, whereas the latter comprises excitation of spin-waves. In this work,
we test the impact of these two excitations in the hybrid Stoner-Heisenberg
system FePd. We present a microscopic picture of ultrafast demagnetization
dynamics in this alloy, which represents both components of strong local
exchange splitting in Fe, and induced polarization in Pd. We identify
spin-orbit coupling and optical inter-site spin transfer as the two dominant
factors for demagnetization at ultrashort timescales. By tuning the external
laser pulse, the extrinsic inter-site spin transfer can be manipulated for site
selective demagnetization on femtosecond time scales providing the fastest way
for optical and selective control of the magnetization dynamics in alloys.
Remarkably, the drastic difference in origin of the magnetic moment of the Fe
and Pd species is not deciding the initial magnetization dynamics in this
alloy.",2111.14607v1
2021-12-03,Dissipation-Induced Order: The $S=1/2$ Quantum Spin Chain Coupled to an Ohmic Bath,"We consider an $S=1/2$ antiferromagnetic quantum Heisenberg chain where each
site is coupled to an independent bosonic bath with ohmic dissipation. The
coupling to the bath preserves the global SO(3) spin symmetry. Using
large-scale, approximation-free quantum Monte Carlo simulations, we show that
any finite coupling to the bath suffices to stabilize long-range
antiferromagnetic order. This is in stark contrast to the isolated Heisenberg
chain where spontaneous breaking of the SO(3) symmetry is forbidden by the
Mermin-Wagner theorem. A linear spin-wave theory analysis confirms that the
memory of the bath and the concomitant retarded interaction stabilize the
order. For the Heisenberg chain, the ohmic bath is a marginal perturbation so
that exponentially large system sizes are required to observe long-range order
at small couplings. Below this length scale, our numerics is dominated by a
crossover regime where spin correlations show different power-law behaviors in
space and time. We discuss the experimental relevance of this crossover
phenomena.",2112.02124v2
2021-12-15,Efficient Simulation of Dynamics in Two-Dimensional Quantum Spin Systems with Isometric Tensor Networks,"We investigate the computational power of the recently introduced class of
isometric tensor network states (isoTNSs), which generalizes the isometric
conditions of the canonical form of one-dimensional matrix-product states to
tensor networks in higher dimensions. We discuss several technical details
regarding the implementation of isoTNSs-based algorithms and compare different
disentanglers -- which are essential for an efficient handling of isoTNSs. We
then revisit the time evolving block decimation for isoTNSs ($\text{TEBD}^2$)
and explore its power for real time evolution of two-dimensional (2D) lattice
systems. Moreover, we introduce a density matrix renormalization group
algorithm for isoTNSs ($\text{DMRG}^2$) that allows to variationally find
ground states of 2D lattice systems. As a demonstration and benchmark, we
compute the dynamical spin structure factor of 2D quantum spin systems for two
paradigmatic models: First, we compare our results for the transverse field
Ising model on a square lattice with the prediction of the spin-wave theory.
Second, we consider the Kitaev model on the honeycomb lattice and compare it to
the result from the exact solution.",2112.08394v2
2021-12-29,Dzyaloshinskii-Moriya Induced Spin-Transfer Torques in Kagome Antiferromagnets,"In recent years antiferromagnets (AFMs) have become very promising for
nanoscale spintronic applications due to their unique properties such as THz
dynamics and absence of stray fields. Manipulating antiferromagnetic textures
is currently, however, limited to very few exceptional material symmetry
classes allowing for staggered torques on the magnetic sublattices. In this
work, we predict for kagome AFMs with broken mirror symmetry a new coupling
mechanism between antiferromagnetic domain walls (DWs) and spin currents,
produced by the relativistic Dzyaloshinskii-Moriya interaction (DMI). We
microscopically derive the DMI's free energy contribution for the kagome AFMs.
Unlike ferromagnets and collinear AFMs, the DMI does not lead to terms linear
in the spatial derivatives but instead renormalizes the spin-wave stiffness and
anisotropy energies. Importantly, we show that the DMI induces a highly
nontrivial twisted DW profile that is controllable via two linearly independent
components of the spin accumulation. This texture manipulation mechanism goes
beyond the concept of staggered torques and implies a higher degree of
tunability for the current-driven DW motion compared to conventional
ferromagnets and collinear AFMs.",2112.14504v2
2021-12-31,"Meson structure on the light-front III : The Hamiltonian, heavy quarkonia, spin and orbit mixing","This is the third paper on hadronic light front wave functions (LFWFs). We
derive a light front Hamiltonian from first principles using the key features
of the QCD vacuum at low resolution. In the first approximation, it gives
transverse oscillator and longitudinal harmonic modes and yields the correct
Regge trajectories. For heavy quarkonia, we compare its spectrum to that
obtained from the usual Schroedinger equation in the rest frame. We use the
same approach for light quarks, and investigate the role of confinement and
chiral symmetry breaking in the quark-antiquark sector. We then study spin-spin
and spin-orbit mixing, resulting in e.g. quadrupole moments of vector mesons.
For the light mesons, we show how to extend the famed t$^\prime$Hooft
interaction to the light front, which solves the U(1) problem and helps produce
a light pion. We use the ensuing light front wavefunctions, to derive the
pertinent parton distribution functions, parton amplitudes and low energy
constants.",2112.15586v2
2022-02-17,Fluctuating intertwined stripes in the strange metal regime of the Hubbard model,"Strongly correlated electron systems host a variety of poorly understood
correlations in their high temperature normal state. Unlike ordered phases
defined by order parameters, these normal state phases are often defined
through unconventional properties such as strange metallic transport or
spectroscopic pseudogaps. Characterizing the microscopic correlations in the
normal state is necessary to elucidate mechanisms that lead to these properties
and their connection to ground state orders. Here we establish the presence of
intertwined charge and spin stripes in the strange metal normal state of the
Hubbard model using determinant quantum Monte Carlo calculations. The charge
and spin density waves constituting the stripes are fluctuating and
short-ranged, yet they obey a mutual commensurability relation and remain
microscopically interlocked, as evidenced through measurements of three-point
spin-spin-hole correlation functions. Our findings demonstrate the ability of
many-body numerical simulations to unravel the microscopic correlations that
define quantum states of matter.",2202.08845v1
2022-03-06,Elongated Skyrmion as Spin Torque Nano-Oscillator and Magnonic Waveguide,"Spin torque nano-oscillator has been extensively studied both theoretically
and experimentally in recent decades due to its potential applications in
future microwave communication technology and neuromorphic computing. In this
work, we present a skyrmion-based spin torque nano-oscillator driven by a
spatially uniform direct current, where the skyrmion is confined by two pinning
sites. Different from other skyrmion-based oscillators that arise from the
circular motion or the breathing mode of a skyrmion, the steady-state
oscillatory motions are produced by the periodic deformation of an elongated
skyrmion. Through micromagnetic simulations, we find that the oscillation
frequency depends on the driving current, the damping constant as well as the
characteristics of pinning sites. This nonlinear response to direct current
turns out to be universal and can also appear in the case of antiskyrmions,
skyrmioniums and domain walls. Furthermore, the elongated skyrmion possesses a
rectangle-like domain wall, which could also serve as a magnonic waveguide.
Utilizing the propagation of spin waves in this waveguide, we propose a device
design of logic gate and demonstrate its performance.",2203.02969v2
2022-05-30,Gravitational bremsstrahlung from spinning binaries in the post-Minkowskian expansion,"We present a novel calculation of the four-momentum that is radiated into
gravitational waves during the scattering of two arbitrarily spinning bodies.
Our result, which is accurate to leading order in $G$, to quadratic order in
the spins, and to all orders in the velocity, is derived by using a
Routhian-based worldline effective field theory formalism in concert with a
battery of analytic techniques for evaluating loop integrals. While nonspinning
binaries radiate momentum only along the direction of their relative velocity,
we show that the inclusion of spins generically allows for momentum loss in all
three spatial directions. We also verify that our expression for the radiated
energy agrees with the overlapping terms from state-of-the-art calculations in
post-Newtonian theory.",2205.15295v2
2022-06-24,Elementary excitations in a spin-orbit-coupled spin-1 Bose-Einstein condensate,"While a spin-orbit-coupled spin-1 Bose-Einstein condensate has been
experimentally observed, its elementary excitations remain unclear in the
stripe phase. Here, we systematically study the elementary excitations in three
distinct phases of a spin-orbit-coupled spin-1 Bose-Einstein condensate. We
find that the excitation spectrum as well as the corresponding static response
function and structure factor depend strongly on spin-orbit coupling parameters
such as the quadratic Zeeman field and the Rabi frequency. In the stripe phase,
besides two gapless Goldstone modes, we show the existence of roton
excitations. Finally, we demonstrate that quantum phase transitions between
these different phases including the zero-momentum, plane wave and stripe
phases are characterized by the sound velocities and the quantum depletion.",2206.12053v1
2022-07-05,Twisting the Dirac cones of the SU(4) spin-orbital liquid on the honeycomb lattice,"By combining the density matrix renormalization group (DMRG) method with
Gutzwiller projected wave functions, we study the SU(4) symmetric spin-orbital
model on the honeycomb lattice. We find that the ground states can be well
described by a Gutzwiller projected $\pi$-flux state with Dirac-type gapless
excitations at one quarter filling. Although these Dirac points are gapped by
emergent gauge fluxes on finite cylinders, they govern the critical behavior in
the thermodynamic limit. By inserting a $\theta=\pi$ spin flux to twist the
boundary condition, we can shift the gapless sector to the ground state, which
provides compelling evidence for the presence of a gapless Dirac spin-orbital
liquid.",2207.02239v1
2022-08-09,Modelling of planar germanium hole qubits in electric and magnetic fields,"Hole-based spin qubits in strained planar germanium quantum wells have
received considerable attention due to their favourable properties and
remarkable experimental progress. The sizeable spin-orbit interaction in this
structure allows for efficient electric qubit operations. However, it also
couples the qubit to electrical noise. In this work we perform simulations of a
heterostructure hosting these hole spin qubits. We solve the effective mass
equations for a realistic heterostructure, provide a set of analytical basis
wave functions, and compute the effective g-factor of the heavy-hole
ground-state. Our investigations reveal a strong impact of highly excited light
hole states located outside the quantum well on the g-factor. Consequently,
contrary to recent predictions, we find that sweet spots in out-of-plane
magnetic fields are shifted to impractically large electric fields. However,
for magnetic fields close to in-plane alignment, sweet spots at low electric
fields are recovered. This work will be helpful in understanding and improving
coherence of germanium hole spin qubits.",2208.04795v1
2022-09-09,A spinwave Ising machine,"We demonstrate a spin-wave-based time-multiplexed Ising Machine (SWIM),
implemented using a 5 $\mu$m thick Yttrium Iron Garnet (YIG) film and
off-the-shelf microwave components. The artificial Ising spins consist of
34--68 ns long 3.125 GHz spinwave RF pulses with their phase binarized using a
phase-sensitive microwave amplifier. Thanks to the very low spinwave group
velocity, the 7 mm long YIG waveguide can host an 8-spin MAX-CUT problem and
solve it in less than 4 $\mu$s while consuming only 7 $\mu$J. Using a real-time
oscilloscope, we follow the temporal evolution of each spin as the SWIM
minimizes its energy and find both uniform and domain-propagation-like
switching of the spin state. The SWIM has the potential for substantial further
miniaturization, scalability, speed, and reduced power consumption, and may
become a versatile platform for commercially feasible optimization problem
solvers with high performance.",2209.04291v1
2022-10-12,Quantum amplification of spin currents in cavity magnonics by a parametric drive induced long-lived mode,"Cavity-mediated magnon-magnon coupling can lead to a transfer of spin-wave
excitations between two spatially separated magnetic samples. We enunciate how
the application of a two-photon parametric drive to the cavity can lead to
stark amplification in this transfer efficiency. The recurrent multiphoton
absorption by the cavity opens up an infinite ladder of accessible energy
levels, which can induce higher-order transitions within the magnon Fock space.
This is reflected in a heightened spin-current response from one of the
magnetic samples when the neighboring sample is coherently pumped. The
enhancement induced by the parametric drive can be considerably high within the
stable dynamical region. Specifically, near the periphery of the stability
boundary, the spin current is amplified by several orders of magnitude. Such
striking enhancement factors are attributed to the emergence of parametrically
induced strong coherences precipitated by a long-lived mode. While
contextualized in magnonics, the generality of the principle would allow
applications to energy transfer between systems contained in parametric
cavities.",2210.05898v1
2022-12-06,Spin wavepacket propagation in quasi-2D antiferromagnets,"Antiferromagnets are attractive platforms for the propagation of information
via spin waves, offering advantages over ferromagnets in speed of response and
immunity to external fields. A recent study of the quasi-2D antiferromagnet
CrSBr reported that spin wavepackets propagate with group velocities that are
orders of magnitude higher than expected from the magnon dispersion obtained by
inelastic neutron scattering [1,2]. Here we show that the anomalous magnitude
and anisotropy of the group velocity, v_g, are naturally explained by
considering the long-range magnetic dipole-dipole interaction. We also
demonstrate that v_g can be tuned over orders of magnitude by applying an
external magnetic field or varying the sample thickness. Beyond spin wavepacket
propagation, the dipolar interaction creates the possibility of non-equilibrium
Bose-Einstein condensation in antiferromagnets, previously thought to be a
property unique to ferromagnets.",2212.03261v1
2022-12-07,Evaporation of Primordial Black Holes in the Early Universe: Mass and Spin Distributions,"Many cosmological phenomena lead to the production of primordial black holes
in the early Universe. These phenomena often create a population of black holes
with extended mass and spin distributions. As these black holes evaporate via
Hawking radiation, they can modify various cosmological observables, lead to
the production of dark matter, modify the number of effective relativistic
degrees of freedom, $N_{\rm eff}$, source a stochastic gravitational wave
background and alter the dynamics of baryogenesis. We consider the Hawking
evaporation of primordial black holes that feature non-trivial mass and spin
distributions in the early Universe. We demonstrate that the shape of such a
distribution can strongly affect most of the aforementioned cosmological
observables. We outline the numerical machinery we use to undertake this task.
We also release a new version of FRISBHEE that handles the evaporation of
primordial black holes with an arbitrary mass and spin distribution throughout
cosmic history.",2212.03878v2
2023-01-14,A Chiral Inverse Faraday Effect Mediated by an Inversely Designed Plasmonic Antenna,"The inverse Faraday effect is a magneto-optical process allowing the
magnetization of matter by an optical excitation carrying a non-zero spin or
orbital moment of light. This phenomenon was considered until now as symmetric;
right or left circular polarizations generate magnetic fields oriented in the
direction of light propagation or in the counter-propagating direction. Here,
we demonstrate that by manipulating the spin density of light in a plasmonic
nanostructure, we generate a chiral inverse Faraday effect, creating a strong
magnetic field of 500 mT only for one helicity of the light, the opposite
helicity producing this effect only for the mirror structure. This new optical
concept opens the way to the generation of magnetic fields with unpolarized
light, finding application in the ultrafast manipulation of magnetic domains
and processes, such as spin precession, spin currents and waves, magnetic
skyrmion or magnetic circular dichroism, with direct applications in data
storage and data processing technologies.",2301.05971v1
2023-02-23,Ultrafast laser-induced spin-lattice dynamics in the van der Waals antiferromagnet CoPS3,"CoPS3 stands out in the family of the van der Waals antiferromagnets XPS3
(X=Mn, Ni, Fe, Co) due to the unquenched orbital momentum of the magnetic Co2+
ions which is known to facilitate the coupling of spins to both electromagnetic
waves and lattice vibrations. Here, using a time-resolved magneto-optical
pump-probe technique we experimentally study the ultrafast laser-induced
dynamics of mutually correlated spins and lattice. It is shown that a
femtosecond laser pulse acts as an ultrafast heater and thus results in the
melting of the antiferromagnetic order. At the same time, the resonant pumping
of the 4T1g - 4T2g electronic transition in Co2+ ions effectively changes their
orbital momentum, giving rise to a mechanical force that moves the ions in the
direction parallel to the orientation of their spins, thus generating a
coherent Bg phonon mode at the frequency of about 4.7 THz.",2302.12104v1
2023-03-27,Ground state phase diagram and superconductivity of the doped Hubbard model on six-leg square cylinders,"We have studied the ground state properties of Hubbard model on long six-leg
square cylinders with doped hole concentration per site $5.55\% \leq \delta\leq
12.5\%$ using density-matrix renormalization group. By keeping a large number
of states for long system sizes, we find that the nature of the ground state is
remarkably sensitive to the presence of next-nearest-neighbor electron hopping
$t'$. In the positive $t'$ side, we find a robust $d$-wave superconducting (SC)
phase characterized by coexisting quasi-long-range SC and charge density wave
(CDW) correlations. Without $t'$ the ground state forms an insulating stripe
phase with long-range CDW order but short-range spin-spin and SC correlations.
In stark contrast to four-leg cylinders, our results show that the lightly
doped Hubbard model on six-leg cylinders remains insulating in the negative
$t'$ side where the SC correlations decay exponentially with short correlation
lengths. In the larger negative $t'$ side, the doped holes form a novel holon
Wigner crystal with one doped hole per emergent unit cell and short-range
spin-spin correlations.",2303.15541v1
2023-03-27,Refined Spin Wave Model and Multi-magnon Bound States in $Li_{2}CuO_{2}$,"Here we report a study of the spin dynamics in the ferromagnetic chain
compound $Li_{2}CuO_{2}$. Inelastic neutron scattering measurements allow for
the spin Hamiltonian to be determined using a $J_{1}-J_{2}$ $XXZ$-Heisenberg
spin chain model with weak interchain interactions. The primary exchange
parameters determined from our data are qualitatively consistent with those of
Lorenz $et$ $al.$ [Europhys. Lett. 88, 37002 (2009)], and our data allow for
the resolution of additional interchain exchange interactions. We also observe
the formation of two- and, potentially, three-magnon bound states. The
two-magnon bound state exists only in the magnetically ordered phase of this
material, consistent with stabilization by the weak, Ising-like exchange
anisotropy of the nearest-neighbor intrachain interaction. In contrast, the
potential three-magnon state persists in a finite temperature regime above
$T_{N}$, indicating an unconventional character. Our results establish
$Li_{2}CuO_{2}$ as an experimental platform for the study of exchange
anisotropy-stabilized bound states in a ferromagnetic chain.",2303.15639v2
2023-04-07,A two-color dual-comb system for time-resolved measurements of ultrafast magnetization dynamics using triggerless asynchronous optical sampling,"We report on an Er-doped fiber (EDF)-laser-based dual-comb system that allows
us to perform triggerless asynchronous optical sampling (ASOPS) pump-probe
measurements of ultrafast demagnetization and spin precession in magnetic
materials. Because the oscillation frequencies of the two frequency-comb light
sources are highly stabilized, the pulse-to-pulse timing jitter is sufficiently
suppressed and data accumulation without any trigger signals is possible. To
effectively induce spin precession in ferromagnetic thin films, the spectral
bandwidth of the output of one of the EDF frequency comb sources is broadened
by a highly nonlinear fiber and then amplified at a wavelength of about 1030 nm
by a Yb-doped fiber amplifier. The output of the other frequency comb source is
converted to about 775 nm by second harmonic generation. We used this system to
observe the ultrafast demagnetization and spin precession dynamics on the
picosecond and nanosecond time scales in a permalloy thin film. This
time-domain spectroscopy system is promising for the rapid characterization of
spin-wave generation and propagation dynamics in magnetic materials.",2304.03666v1
2023-05-05,Self-consistent effective-one-body theory for spinning binaries based on post-Minkowskian approximation,"This paper extends the research on the self-consistent effective-one-body
theory of a real spinless two-body system based on the post-Minkowskian
approximation (Science China, 65, 100411, (2022)) to the case of a binary
system for the spinning black holes. An effective rotating metric and an
improved Hamiltonian for the spinning black hole binaries were constructed. The
decoupled equation for the null tetrad component of the gravitational perturbed
Weyl tensor $\psi^B_{4}$ in the effective rotating spacetime is found with the
help of the gauge transform characteristics of the Weyl tensors. The decoupled
equation is then separated between radial and angular variables in the slowly
rotating background spacetime, and a formal solution of $\psi^B_{4}$ is
obtained. On this basis, the formal expressions of the radiation reaction force
and the waveform for the ``plus'' and ``cross'' modes of the gravitational wave
are presented. These results, obtained in the same effective spacetime,
constitute a self-consistent effective-one-body theory for the spinning black
hole binaries based on the post-Minkowskian approximation.",2305.03225v2
2023-05-22,Quark distribution functions and spin-flavor structures in $N \to Δ$ transitions,"Transition generalized parton distributions have emerged as a novel tool for
studying the quantum chromodynamics (QCD) structure of resonances. They provide
an integrated picture of the transition form factors and the transition parton
distribution functions. In this study, we delve into the angular momentum (AM)
properties for the $N\to \Delta$ transition and its decomposition into the
orbital angular momentum and the intrinsic spin in the context of the quark
distribution functions. First, we explore the spin-flavor structures within the
framework of both the overlap representations of the three-quark light-cone
wave functions and the large $N_c$ limit of QCD. We then estimate the AM quark
distribution functions for the $N\to \Delta$ transition. Our analysis reveals a
substantial flavor asymmetry present in both the orbital angular momentum and
intrinsic spin components.",2305.12714v2
2023-05-23,A Reversed Inverse Faraday Effect,"The inverse Faraday effect is a magneto-optical process allowing the
magnetization of matter by an optical excitation carrying a non-zero spin of
light. In particular, a right circular polarization generates a magnetization
in the direction of light propagation and a left circular polarization in the
opposite direction to this propagation. We demonstrate here that by
manipulating the spin density of light, i.e., its polarization, in a plasmonic
nanostructure, we generate a reversed inverse Faraday effect. A right circular
polarization will generate a magnetization in the opposite direction of the
light propagation, a left circular polarization in the direction of
propagation. Also, we demonstrate that this new physical phenomenon is chiral,
generating a strong magnetic field only for one helicity of the light, the
opposite helicity producing this effect only for the mirror structure. This new
optical concept opens the way to the generation of magnetic fields with
unpolarized light, finding application in the ultrafast manipulation of
magnetic domains and processes, such as spin precession, spin currents, and
waves, magnetic skyrmion or magnetic circular dichroism, with direct
applications in data storage and processing technologies.",2305.14469v1
2023-05-25,Crystallization dynamics of magnetic skyrmions in a frustrated itinerant magnet,"We investigate the phase ordering kinetics of skyrmion lattice (SkL) in a
metallic magnet. The SkL can be viewed as a superposition of magnetic stripes
whose periods are determined by the quasi-nesting wave vectors of the
underlying Fermi surface. An effective magnetic Hamiltonian that describes the
electron-mediated spin-spin interaction is obtained for a two-dimensional s-d
model with the Rashba spin-orbit coupling. Large-scale Landau-Lifshitz-Gilbert
dynamics simulations based on the effective spin Hamiltonian reveal a two-stage
phase ordering of the SkL phase after a thermal quench. The initial fast
crystallization of skyrmions is followed by a slow relaxation dominated by the
annihilation dynamics of dislocations, which are topological defects of the
constituent magnetic stripe orders. The late-stage phase ordering also exhibits
a dynamical scaling symmetry. We further show that the annihilation of
dislocations follows a power-law time dependence with a logarithmic correction
that depends on magnetic fields. Implications of our results for SkL phases in
magnetic materials are also discussed.",2305.16182v1
2023-07-07,10-GHz-clock time-multiplexed non-degenerate optical parametric oscillator network with a variable planar lightwave circuit interferometer,"A coherent XY machine (CXYM) is a physical spin simulator that can simulate
the XY model by mapping XY spins onto the continuous phases of non-degenerate
optical parametric oscillators (NOPOs). Here, we demonstrated a large-scale
CXYM with >47,000 spins by generating 10-GHz-clock time-multiplexed NOPO pulses
via four-wave mixing in a highly nonlinear fiber inside a fiber ring cavity. By
implementing a unidirectional coupling from the i-th pulse to the (i+1)-th
pulse with a variable 1-pulse delay planar lightwave circuit interferometer, we
successfully controlled the effective temperature of a one-dimensional XY spin
network within two orders of magnitude.",2307.03333v2
2023-07-13,Strong-field scattering of two spinning black holes: Numerical Relativity versus post-Minkowskian gravity,"Highly accurate models of the gravitational-wave signal from coalescing
compact binaries are built by completing analytical computations of the binary
dynamics with non-perturbative information from numerical relativity (NR)
simulations. In this paper we present four sets of NR simulations of equal-mass
black hole binaries that undergo strong-field scattering: (i) we reproduce and
extend the nonspinning simulations first presented in [Damour \textit{et al.},
Phys.Rev.D 89 (2014) 8, 081503], (ii) we compute two suites of nonspinning
simulations at higher energies, probing stronger field interactions, (iii) we
present a series of \textit{spinning} simulations including, for the first
time, unequal-spin configurations. When comparing the NR scattering angles to
analytical predictions based on state-of-the-art post-Minkowskian (PM)
calculations, we find that PM-expanded scattering angles show poor convergence
towards NR data. By contrast, a resummed computation of scattering angles via a
spin-dependent, radiation-reacted, effective-one-body potential shows excellent
agreement for both nonspinning and spinning configurations.",2307.06999v2
2023-08-07,Frustration relief and reorientation transition in the kagome-like dolerophanite Cu$_2$OSO$_4$,"We present a theoretical study of dolerophanite Cu$_2$OSO$_4$, a layered
kagome-like spin-$\frac{1}{2}$ magnetic insulator that can be described either
as a system of chains coupled through dimers or as a kagome lattice where every
third spin is replaced by a ferromagnetic spin dimer. Building on insights from
ab initio calculations, classical numerical minimizations, and semiclassical
expansions, we arrive at a minimal microscopic description that accounts for
the experimental data reported so far, including the nature of the magnetic
order, the reported spin length, and the observed anisotropy. The latter arises
by a peculiar competition between the antisymmetric (Dzyaloshinskii-Moriya) and
the symmetric part of the exchange anisotropy, which gives rise to a two-step
re-orientation process involving two successive continuous phase transitions.
Our work uncovers mechanisms stabilizing canted ferrimagnetic order in kagome
systems, and highlights strong magnetic anisotropy in the presence if
dissimilar magnetic orbitals on crystallographically nonequivalent Cu sites. We
also show how these anisotropy terms affect the spin-wave spectrum and how they
can be tracked experimentally.",2308.03599v2
2023-08-15,Global biasing using a Hardware-based artificial Zeeman term in Spinwave Ising Machines,"A spinwave Ising machine (SWIM) is a newly proposed type of time-multiplexed
hardware solver for combinatorial optimization that employs feedback coupling
and phase sensitive amplification to map an Ising Hamiltonian into
phase-binarized propagating spin-wave RF pulses in an Yttrium-Iron-Garnet (YIG)
film. In this work, we increase the mathematical complexity of the SWIM by
adding a global Zeeman term to a 4-spin MAX-CUT Hamiltonian using a continuous
external electrical signal with the same frequency as the spin pulses and phase
locked with with one of the two possible states. We are able to induce
ferromagnetic ordering in both directions of the spin states despite
antiferromagnetic pairwise coupling. Embedding a planar antiferromagnetic spin
system in a magnetic field has been proven to increase the complexity of the
graph associated to its Hamiltonian and thus this straightforward
implementation helps explore higher degrees of complexity in this evolving
solver.",2308.07718v1
2023-08-16,Dimensional reduction of Kitaev spin liquid at quantum criticality,"We investigate the fate of the Kitaev spin liquid (KSL) under the influence
of an external magnetic field $h$ in the [001] direction and upon tuning bond
anisotropy of the Kitaev coupling $K_z$ keeping $K_x = K_y = K$. Guided by
density matrix renormalization group, exact diagonalization, and with insights
from parton mean field theory, we uncover a field-induced gapless-to-gapless
Lifshitz transition from the nodal KSL to an intermediate gapless phase. The
intermediate phase sandwiched between $h_{c1}$ and $h_{c2}$, which persists for
a wide range of anisotropy $K_z/K > 0$, is composed of weakly coupled
one-dimensional quantum critical chains. This intermediate phase is a
dimensional crossover which asymptotically leads to the one-dimensional quantum
Ising criticality characterized by the (1+1)D conformal field theory as the
field reaches the phase transition at $h_{c2}$. Beyond $h_{c2}$ the system
enters a partially polarized phase describable as effectively decoupled bosonic
chains in which spin waves propagate along the one-dimensional zigzag
direction. Our findings provide a comprehensive phase diagram and offer
insights into the unusual physics of dimensional reduction generated by a
uniform magnetic field in an otherwise two-dimensional quantum spin liquid.",2308.08116v2
2023-08-18,Chiral spin-transfer torque induced by curvature gradient,"This work analyzes the propagation of a transverse domain wall (DW) motion
under the action of an electric current along a nanowire (NW) with a curvature
gradient. Our results evidence that the curvature gradient induces a chiral
spin-transfer torque (CSTT) whose effect on the DW motion depends on the
direction along which the DW points. The origin of the CSTT is explained in
terms of a position and phase-dependent effective field associated with the DW
profile and the electric current direction. Finally, our results reveal that
this chiral mechanism can also affect the behavior of other magnetization
collective modes, such as spin waves. This work shows the emergence of
curvature-induced chiral spin transport and highlights a new phenomenon to be
considered for designing spintronic devices.",2308.09276v1
2023-08-28,Hadronic structure on the light-front IX . Orbital-spin-isospin wave functions of baryons,"This paper which is part of a series, is devoted to several technical issues.
In the first part of the paper, we discuss the usual wavefunctions in the CM
frame for baryons, by clarifying the representations of the three-quark
permutation group $S_3$. We extend the analysis for up to five ``spinors"" with
$\rho,\lambda$-symmetry, and derive explicitly the totally symmetric
wavefunctions modulo color. They are explicitly used to describe the excited
nucleons $N^*$ states, in the P- and D-shell. We also show how to use symbolic
operations in Mathematica, in spin-tensor notations to make explicit these
states. For the S- and P-shells, the totally antisymmetric wavefunctions are
given, and the pertinent matrix elements for the spin-dependent operators
calculated, including the mixing between states with different total spin $S$.
In the second part of the paper we turn to the light front wavefunctions, with
an emphasis on the longitudinal wavefunctions, with a novel basis set. We also
discuss their symmetries under permutations, and select the proper combinations
for the transverse and longitudinal excitations for $N^*$ on the light front.",2308.14694v1
2023-09-08,Hubbard Bands and Exotic States in Doped and Undoped Mott Systems: The Kotliar-Ruckenstein Representation,"The slave-particle representation is a promising method to treat the
properties of exotic strongly correlated systems. We develop a unified approach
to describe both the paramagnetic state with possible spin-liquid features and
states with strong long-range or short-range magnetic order. Combining the
Kotliar-Ruckenstein representation and fractionalized spin-liquid deconfinement
picture, the Mott transition and Hubbard subbands are considered. The spectrum
in the insulating state is significantly affected by the presence of the spinon
spin-liquid spectrum and a hidden Fermi surface. Presenting a modification of
the Kotliar-Ruckenstein representation in the spin-wave region, we treat the
case of magnetic order, with special attention being paid to the half-metallic
ferromagnetic state. The formation of small and large Fermi surfaces for doped
current carriers in the antiferromagnetic state is also discussed.",2309.04304v1
2023-09-14,Phase control of magnons in the van der Waals antiferromagnet NiPS$_3$,"We demonstrate phase control of magnons in the van der Waals antiferromagnet
NiPS$_3$ using optical excitation by polarized light. The sign of the coherent
precession of spin amplitude changes upon (1) reversing the helicity of a
circularly polarized pump beam, or (2) rotating the polarization of a linearly
polarized pump by $\pi/2$. Because these two excitation pathways have
comparable generation efficiency, the phase of spin precession can be
continuously tuned from 0 to $2\pi$ by controlling the polarization state of
the pump pulse. The ability to excite magnons with a desired phase has
potential applications in the design of a spin-wave phased array and ultrafast
spin information processing.",2309.07451v1
2023-09-26,Spin-orbit excitons in a correlated metal: Raman scattering study of Sr2RhO4,"Using Raman spectroscopy to study the correlated 4$d$-electron metal
Sr$_2$RhO$_4$, we observe pronounced excitations at 220 meV and 240 meV with
$A_\mathrm{1g}$ and $B_\mathrm{1g}$ symmetries, respectively. We identify them
as transitions between the spin-orbit multiplets of the Rh ions, in close
analogy to the spin-orbit excitons in the Mott insulators Sr$_2$IrO$_4$ and
$\alpha$-RuCl$_3$. This observation provides direct evidence for the unquenched
spin-orbit coupling in Sr$_2$RhO$_4$. A quantitative analysis of the data
reveals that the tetragonal crystal field $\Delta$ in Sr$_2$RhO$_4$ has a sign
opposite to that in insulating Sr$_2$IrO$_4$, which enhances the planar $xy$
orbital character of the effective $J=1/2$ wave function. This supports a
metallic ground state, and suggests that $c$-axis compression of Sr$_2$RhO$_4$
may transform it into a quasi-two-dimensional antiferromagnetic insulator.",2309.15299v2
2023-10-03,Optical excitation of multiple standing spin modes in 3D optomagnonic nanocavities,"We report the first experimental observation of multiple standing spin modes
in 3D optomagnonic nanocavity formed by nanometer-sized iron-garnet
nanocylinder. We show that launching of standing spin modes is achieved due to
a high confinement of the optically generated effective magnetic field caused
by the localized optical resonance. Quantization and spin-wave mode
inhomogeneity is achieved in each of the three spatial dimensions. The
presented approach opens new horizons of 3D optomagnonics by combining
nanophotonic and magnonic functionalities within a single nanocavity.",2310.01974v1
2023-11-06,Bottomonia in quark-antiquark confining potential,"In this paper, we comprehensively explore bottomonia mass spectra and their
decay properties by solving the non-relativistic Schrodinger wave equation
numerically with approximate quark-antiquark potential form. We also
incorporate spin-dependent terms - spin-spin, spin-orbit, and tensor terms to
remove mass degeneracy and to obtain excited states ($nS, nP, nD, nF, n = 1, 2,
3, 4, 5$) mass spectra. By using Van Royen - Weisskopf formula, we investigate
leptonic decay constants, di-leptonic, di-gamma, tri-gamma, di-gluon decay
widths and also incorporate first-order radiative corrections. We also computed
radiative transition widths, which give a better insight into the
non-perturbative aspects of QCD. The present results for mass spectroscopy and
decay properties are in tune with available experimental values and other
theoretical predictions. Our results may provide better insight to upcoming
experimental information in the near future.",2311.02857v1
2023-11-10,Relaxation to persistent currents in a Hubbard trimer coupled to fermionic baths,"We consider a ring of fermionic quantum sites, modeled by the Fermi-Hubbard
Hamiltonian, in which electrons can move and interact strongly via the Coulomb
repulsion. The system is coupled to fermionic cold baths which by the exchange
of particles and energy induce relaxation in the system. We eliminate the baths
and describe the system effectively by the Lindblad master equations in various
versions valid for different coupling parameter regimes. The early relaxation
phase proceeds in a universal way, irrespective of the relative couplings and
approximations. The system settles down to its low-energy sector and is
consecutively well approximated by the Heisenberg model. In the late
relaxation, different Lindblad approaches push the system towards different
final states with opposite, extreme spin orders, from ferromagenetic to
antiferromagnetic. Due to spin frustration in the trimer (a three site ring),
degenerate ground states are formed by spin waves (magnons). The system
described by the global coherent version of the Lindblad operators relaxes
towards the final states carrying directed persistent spin currents. We
numerically confirm these predictions.",2311.06331v1
2023-12-17,Spontaneous Formation of Altermagnetism from Orbital Ordering,"Altermagnetism has emerged as a third type of collinear magnetism. In
contrast to standard ferromagnets and antiferromagnets, altermagnets exhibit
extra even-parity wave spin order parameters resulting in a spin-splitting of
electronic bands in momentum space. In real space, sublattices of opposite spin
polarization are anisotropic and related by rotational symmetry. In the
hitherto identified altermagnetic candidate materials the anisotropies arise
from the local crystallographic symmetry. Here, we show that altermagnetism can
also form as an interaction-induced electronic instability in a lattice without
the crystallographic sublattice anisotropy. We provide a microscopic example of
a two-orbital model showing that the coexistence of staggered antiferromagnetic
and orbital order can realize robust altermagnetism. We quantify the
spin-splitter conductivity as a key experimental observable and discuss
material candidates for the interaction-induced realization of altermagnetism.",2312.10839v1
2023-12-19,Near-field Spin Chern Number Quantized by Real-Space Topology of Optical Structures,"The concept of Chern number has been widely used to describe the topological
properties of periodic condensed matter and classical wave systems. It is
typically defined in the momentum space and is closely related to the geometric
phase of dispersion bands. Here, we introduce a new type of spin Chern number
defined in the real space for optical near fields of finite-sized structures.
This real-space spin Chern number is derived from the geometric phase of the
near fields and exhibits an intrinsic relationship with the topology of the
optical structures: the spin Chern number of optical near fields is quantized
and equal to the Euler characteristic of the optical structures. This
relationship is robust under continuous deformation of the structure's geometry
and is independent of the specific material constituents or external
excitation. Our work enriches topological physics by extending the concept of
Chern number from the momentum space to the real space and opens exciting
possibilities for manipulating light based on the topology of optical
structures, with potential applications in high-precision optical metrology,
optical sensing and imaging.",2312.11771v1
2024-01-25,Universal collective Larmor-Silin mode emerging in magnetized correlated Dirac fermions,"Employing large-scale quantum Monte Carlo simulations, we find in magnetized
interacting Dirac fermion model, there emerges a new and universal collective
Larmor-Silin spin wave mode in the transverse dynamical spin susceptibility.
Such mode purely originates from the interaction among Dirac fermions and
distinguishes itself from the usual particle-hole continuum with finite
lifetime and clear dispersion, both at small and large momenta in a large
portion of the Brillouin zone. Our unbiased numerical results offer the dynamic
signature of this new collective excitations in interacting Dirac fermion
systems, and provide experimental guidance for inelastic neutron scattering,
electron spin resonance and other spectroscopic approaches in the investigation
of such universal collective modes in quantum Moire materials, topological
insulators and quantum spin liquid materials under magnetic field, with
quintessential interaction nature beyond the commonly assumed noninteracting
Dirac fermion or spinon approximations.",2401.14358v2
2024-02-08,Absence of breakdown of ferrodark solitons exhibiting snake instability,"We investigate the dynamical stability and real time dynamics of the
two-types of ferrodark solitons (FDSs) which occur as topological magnetic
domain walls in the easy-plane phase of a quasi-two-dimensional (2D)
ferromagnetic spin-1 Bose-Einstein condensate. The type-I FDS has positive
inertial mass and exhibits a single dynamical instability that generates in
plane spin winding, causing polar-core spin vortex dipoles. The positive
inertial mass leads to the elastic oscillations of the soliton under transverse
perturbations. The type-II FDS has negative inertial mass and exhibits a snake
instability and a spin-twist instability, with the latter involving the
generation of out of plane spin winding. Distinct from the normal dynamics of
negative mass solitons under long wave length transverse perturbations, the
snake instability does not lead to the type-II FDS breaking down. Instead,
segments of the type-II FDS convert to type-I and mass vortex dipoles are
produced. The resulting hybridized-chain of the two soliton types and vortices
exhibits complex 2D soliton dynamics at long times while the vortices remain
confined and the topological structure of a magnetic domain wall is preserved.",2402.05351v1
2024-02-16,M1 Radiative and spin-nonflip $ππ$ transitions of $B_c$ states in the Cornell potential model,"In this paper, we mainly predict the rates of M1 radiative and spin-nonflip
$\pi\pi$ transitions of $B_{c}$-meson under the non-relativistic Cornell
potential model with a screening potential effect. We employ the numerical wave
function to determine the M1 radiative transition widths of $B_c$ excited
states and utilize the Kuang-Yan proposed method for the spin-nonflip $\pi\pi$
transitions among $B_c$ states. Our theoretical results are valuable for
studying the M1 radiative and spin-nonflip $\pi\pi$ transition processes of
$B_c$ states in experiments.",2402.10629v1
2024-02-22,Impact of Magnon Interactions on Transport in Honeycomb Antiferromagnets,"The thermal transport of magnons has attracted substantial attention as an
energy-efficient alternative to the transport of electrons. Most theoretical
studies so far have been carried out within the frame of the linear spin-wave
theory, which dramatically fails upon increasing the temperature and in the
presence of competing interactions. In this work, we consider the impact of
three- and four-magnon interactions in a honeycomb antiferromagnet, where such
interactions are remarkably strong even at zero temperature. Using a
combination of quantum field theory and mean-field theory, we compute the band
structure of the interacting magnons and investigate the spin Nernst effect. We
find that in the presence of in-plane Dzyaloshinskii-Moriya Interaction, the
three-magnon interaction induces a non-reciprocal band splitting, even at zero
temperature, leading to an enhancement of the spin Nernst conductivity. In
contrast, the four-magnon interaction renormalizes the magnon spectrum at high
temperatures, leading to a reduction of the overall magnon spin Nernst effect.
These results suggest that interactions can massively influence the transport
properties of magnons in antiferromagnets, even at zero temperature, and should
be taken into account for predictive modeling.",2402.14572v1
2024-03-01,Investigation of spin excitations and charge order in bulk crystals of the infinite-layer nickelate LaNiO$_2$,"Recent x-ray spectroscopic studies have revealed spin excitations and charge
density waves in thin films of infinite-layer (IL) nickelates. However,
clarifying whether the origin of these phenomena is intrinsic to the material
class or attributable to impurity phases in the films has presented a major
challenge. Here we utilize topotactic methods to synthesize bulk crystals of
the IL nickelate LaNiO$_2$ with crystallographically oriented surfaces. We
examine these crystals using resonant inelastic x-ray scattering (RIXS) at the
Ni $L_3$-edge to elucidate the spin and charge correlations in the bulk of the
material. While we detect the presence of prominent spin excitations in the
crystals, fingerprints of charge order are absent at the ordering vectors
identified in previous in thin-film studies. These results contribute to the
understanding of the bulk properties of LaNiO$_2$ and establish topotactically
synthesized crystals as viable complementary specimens for spectroscopic
investigations.",2403.00493v1
2024-03-01,Chiral Spin Liquid on a Shastry-Sutherland Heisenberg Antiferromagnet,"We demonstrate the existence of a topological chiral spin liquid in the
frustrated Shastry-Sutherland Heisenberg model with an additional spin
chirality interaction, using numerically unbiased exact diagonalization and
density matrix renormalization group methods. We establish a quantum phase
diagram where conventional phases, including dimer singlet, plaquette singlet,
N{\' e}el and collinear phase, can be clearly identified by suitable local
order parameters. Among them a $SU(2)_1$ chiral spin liquid emerges in the
highly frustrated region, which is unambiguously identified by two
topologically degenerate ground states, modular matrix, and characteristic
level counting in entanglement spectrum, featuring the same topological order
of $\nu=1/2$ bosonic Laughlin state. The phase boundaries among the different
orders are determined by the energy level crossing analysis and wave function
fidelity susceptibility.",2403.00597v2
2024-03-13,Dielectric microwave resonator with large optical apertures for spin-based quantum devices,"Towards a spin-based quantum microwave-optical photon transducer, we
demonstrate a low-loss dielectric microwave resonator with an internal quality
factor of $2.30\times10^4$ while accommodating optical apertures with a
diameter of $8\, \mathrm{mm}$. The two seemingly conflicting requirements, high
quality factor and large optical apertures, are satisfied thanks to the large
dielectric constant of rutile ($\mathrm{TiO_2}$). The quality factor is limited
by radiation loss, and we confirmed by numerical simulation that this
dielectric resonator can achieve a quality factor exceeding $10^6$ by extending
the height of the resonator enclosure. Using this resonator, we performed both
continuous-wave (cw) and pulse electron spin resonance (ESR) spectroscopy on
2,2-diphenyl-1-picrylhydrazyl (DPPH) crystalline powder and P1 centers in a
diamond crystal in a dilution refrigerator. The cw ESR spectroscopy
demonstrated high-cooperativity and strong spin-resonator coupling with the
DPPH and P1 centers respectively, while the pulse ESR spectroscopy successfully
measured longitudinal and transverse relaxation times.",2403.08458v1
2024-04-02,Are Doppler Velocity Measurements Useful for Spinning Radar Odometry?,"Spinning, frequency-modulated continuous-wave (FMCW) radar has been gaining
popularity for autonomous vehicle navigation. The spinning radar is chosen over
the more classic automotive `fixed' radar as it is able to capture the full 360
degree field of view without requiring multiple sensors and extensive
calibration. However, commercially available spinning radar systems have not
previously had the ability to extract radial velocities due to the lack of
repeated measurements in the same direction and fundamental hardware setup. A
new firmware upgrade now makes it possible to alternate the modulation of the
radar signal between azimuths. In this paper, we first present a way to use
this alternating modulation to extract radial Doppler velocity measurements
from single raw radar intensity scans. We then incorporate these measurements
in two different modern odometry pipelines and evaluate them in progressively
challenging autonomous driving environments. We show that using Doppler
velocity measurements enables our odometry to continue functioning at
state-of-the-art even in severely geometrically degenerate environments.",2404.01537v1
2024-04-16,Azimuthal spin asymmetries in pion-polarized proton induced Drell-Yan process at COMPASS using holographic light-front QCD,"We compute all the leading-twist azimuthal spin asymmetries in the
pion-proton induced Drell-Yan process. These spin asymmetries arise from
convolutions of the leading-twist transverse-momentum-dependent parton
distributions (TMDs) of both the incoming pion and the target proton. We employ
the holographic light-front pion wave functions for the pion TMDs, while for
the proton TMDs, we utilize a light-front quark-diquark model constructed by
the soft-wall AdS/QCD. The gluon rescattering is crucial to predict nonzero
time-reversal odd TMDs. We study the utility of a nonperturbative SU$(3)$ gluon
rescattering kernel, which extends beyond the typical assumption of
perturbative U$(1)$ gluons. Subsequently, we employ Collins-Soper scale
evolution at Next-to-Leading Logarithmic precision for the TMDs evolution. Our
predictions for the spin asymmetries are consistent with the available
experimental data from COMPASS and other phenomenological studies.",2404.10623v1
2005-11-02,Gravitational Radiation from Newborn Magnetars,"There is growing evidence that two classes of high-energy sources, the Soft
Gamma Repeaters and the Anomalous X-ray Pulsars contain slowly spinning
``magnetars'', i.e. neutron stars whose emission is powered by the release of
energy from their extremely strong magnetic fields (>10^15 G. We show here that
the enormous energy liberated in the 2004 December 27 giant flare from
SGR1806-20 (~5 10^46 erg), together with the likely recurrence time of such
events, requires an internal field strength of > 10^16 G. Toroidal magnetic
fields of this strength are within an order of magnitude of the maximum fields
that can be generated in the core of differentially-rotating neutron stars
immediately after their formation, if their initial spin period is of a few
milliseconds. A substantial deformation of the neutron star is induced by these
magnetic fields and, provided the deformation axis is offset from the spin
axis, a newborn fast-spinning magnetar would radiate for a few weeks a strong
gravitational wave signal the frequency of which (0.5-2 kHz range) decreases in
time. The signal from a newborn magnetar with internal field > 10^16.5 G could
be detected with Advanced LIGO-class detectors up to the distance of the Virgo
cluster (characteristic amplitude h_c about 10^-21). Magnetars are expected to
form in Virgo at a rate approx. 1/yr. If a fraction of these have sufficiently
high internal magnetic field, then newborn magnetars constitute a promising new
class of gravitational wave emitters.",0511068v2
1996-07-01,"Theory of Photoluminescence of the $ν=1$ Quantum Hall State: Excitons, Spin-Waves and Spin-Textures","We study the theory of intrinsic photoluminescence of two-dimensional
electron systems in the vicinity of the $\nu=1$ quantum Hall state. We focus
predominantly on the recombination of a band of initial ``excitonic states''
that are the low-lying energy states of our model at $\nu=1$. It is shown that
the recombination of excitonic states can account for recent observations of
the polarization-resolved spectra of a high-mobility GaAs quantum well. The
asymmetric broadening of the spectral line in the $\sigma_-$ polarization is
explained to be the result of the ``shake-up'' of spin-waves upon radiative
recombination of excitonic states. We derive line shapes for the recombination
of excitonic states in the presence of long-range disorder that compare
favourably with the experimental observations. We also discuss the stabilities
and recombination spectra of other (``charged'') initial states of our model.
An additional high-energy line observed in experiment is shown to be consistent
with the recombination of a positively-charged state. The recombination
spectrum of a negatively-charged initial state, predicted by our model but not
observed in the present experiments, is shown to provide a direct measure of
the formation energy of the smallest ``charged spin-texture'' of the $\nu=1$
state.",9607002v2
1998-02-04,"Addition spectrum, persistent current, and spin polarization in coupled quantum dot arrays: coherence, correlation, and disorder","The ground state persistent current and electron addition spectrum in
two-dimensional quantum dot arrays and one-dimensional quantum dot rings,
pierced by an external magnetic flux, are investigated using the extended
Hubbard model. The collective multidot problem is shown to map exactly into the
strong field noninteracting finite-size Hofstadter butterfly problem at the
spin polarization transition. The finite size Hofstadter problem is discussed,
and an analytical solution for limiting values of flux is obtained. In weak
fields we predict novel flux periodic oscillations in the spin component along
the quantization axis with a periodicity given by $\nu h/e$ ($\nu \le 1$). The
sensitivity of the calculated persistent current to interaction and disorder is
shown to reflect the intricacies of various Mott-Hubbard quantum phase
transitions in two- dimensional systems: the persistent current is suppressed
in the antiferromagnetic Mott-insulating phase governed by intradot Coulomb
interactions; the persistent current is maximized at the spin density wave -
charge density wave transition driven by the nearest neighbor interdot
interaction; the Mott-insulating phase persistent current is enhanced by the
long-range interdot interactions to its noninteracting value; the strong
suppression of the noninteracting current in the presence of random disorder is
seen only at large disorder strengths; at half filling even a relatively weak
intradot Coulomb interaction enhances the disordered noninteracting system
persistent current; in general, the suppression of the persistent current by
disorder is less significant in the presence of the long-range interdot Coulomb
interaction.",9802057v1
2000-01-24,"Ordering Dynamics of Heisenberg Spins with Torque: Crossover, Spinwaves and Defects","We study the effect of a torque induced by the local molecular field on the
phase ordering dynamics of the Heisenberg model when the total magnetization is
conserved. The torque drives the zero-temperature ordering dynamics to a new
fixed point, characterized by exponents $z=2$ and $\lambda \approx 5$. This
`torque-driven' fixed point is approached at times such that $g^2 t\gg 1$,
where $g$ is the strength of the torque. All physical quantities, like the
domain size $L(t)$ and the equal and unequal time correlation functions obey a
crossover scaling form over the entire range of $g$. An attempt to understand
this crossover behavior from the approximate Gaussian Closure Scheme fails
completely, implying that the dynamics at late times cannot be understood from
the dynamics of defects alone. We provide convincing arguments that the spin
configurations can be decomposed in terms of defects and spin-waves which
interact with each other even at late times. In the absence of the torque term,
the spin waves decay faster, but even so we find that the Gaussian closure
scheme is inconsistent. In the latter case the inconsistency may be remedied by
including corrections to a simple gaussian distribution. For completeness we
include a discussion of the ordering dynamics at $T_c$, where the torque is
shown to be relevant, with exponents $z=4-\epsilon/2$ and $\lambda = d$ (where
$\epsilon = 6-d$). We show to all orders in perturbation theory that
$\lambda=d$ as a consequence of the conservation law.",0001340v1
2003-05-19,Theory of Kondo lattices and its application to high-temperature superconductivity and pseudo-gaps in cuprate oxides,"A theory of Kondo lattices is developed for the t-J model on a square
lattice. The spin susceptibility is described in a form consistent with a
physical picture of Kondo lattices: Local spin fluctuations at different sites
interact with each other by a bare intersite exchange interaction, which is
mainly composed of two terms such as the superexchange interaction, which
arises from the virtual exchange of spin-channel pair excitations of electrons
across the Mott-Hubbard gap, and an exchange interaction arising from that of
Gutzwiller's quasi-particles. The bare exchange interaction is enhanced by
intersite spin fluctuations developed because of itself. The enhanced exchange
interaction is responsible for the development of superconducting fluctuations
as well as the Cooper pairing between Gutzwiller's quasi-particles. On the
basis of the microscopic theory, we develop a phenomenological theory of
low-temperature superconductivity and pseudo-gaps in the under-doped region as
well as high-temperature superconductivity in the optimal-doped region.
Anisotropic pseudo-gaps open mainly because of d\gamma-wave superconducting
low-energy fluctuations: Quasi-particle spectra around (\pm\pi/a,0) and
(0,\pm\pi/a), with a the lattice constant, or X points at the chemical
potential are swept away by strong inelastic scatterings, and quasi-particles
are well defined only around (\pm\pi/2a,\pm\pi/2a) on the Fermi surface or
line. As temperatures decrease in the vicinity of superconducting critical
temperatures, pseudo-gaps become smaller and the well-defined region is
extending toward X points. The condensation of d\gamma-wave Cooper pairs
eventually occurs at low enough temperatures when the pair breaking by
inelastic scatterings becomes small enough.",0305422v1
2004-03-16,"Stripe order, depinning, and fluctuations in La$_{1.875}$Ba$_{0.125}$CuO$_{4}$ and La$_{1.875}$Ba$_{0.075}$Sr$_{0.050}$CuO$_{4}$","We present a neutron scattering study of stripe correlations measured on a
single crystal of La$_{1.875}$Ba$_{0.125}$CuO$_{4}$. Within the
low-temperature-tetragonal (LTT) phase, superlattice peaks indicative of spin
and charge stripe order are observed below 50 K. For excitation energies
$\hbar\omega\le12$ meV, we have characterized the magnetic excitations that
emerge from the incommensurate magnetic superlattice peaks. In the ordered
state, these excitations are similar to spin waves. Following these excitations
as a function of temperature, we find that there is relatively little change in
the {\bf Q}-integrated dynamical spin susceptibility for $\hbar\omega\sim10$
meV as stripe order disappears and then as the structure transforms from LTT to
the low-temperature-orthorhombic (LTO) phase. The {\bf Q}-integrated signal at
lower energies changes more dramatically through these transitions, as it must
in a transformation from an ordered to a disordered state. We argue that the
continuous evolution through the transitions provides direct evidence that the
incommensurate spin excitations in the disordered state are an indicator of
dynamical charge stripes. An interesting feature of the thermal evolution is a
variation in the incommensurability of the magnetic scattering. Similar
behavior is observed in measurements on a single crystal of
La$_{1.875}$Ba$_{0.075}$Sr$_{0.050}$CuO$_{4}$; maps of the scattered intensity
in a region centered on the antiferromagnetic wave vector and measured at
$\hbar\omega=4$ meV are well reproduced by a model of disordered stripes with a
temperature-dependent mixture of stripe spacings. We discuss the relevance of
our results to understanding the magnetic excitations in cuprate
superconductors.",0403396v1
2001-08-20,Spin correlations in $\vec{p}\vec{p}\to pnπ^{+}$ pion production near threshold,"A first measurement of longitudinal as well as transverse spin correlation
coefficients for the reaction $\vec{p}\vec{p}\to pn\pi^+$ was made using a
polarized proton target and a polarized proton beam. We report kinematically
complete measurements for this reaction at 325, 350, 375 and 400 MeV beam
energy. The spin correlation coefficients $A_{xx}+A_{yy}, A_{xx}-A_{yy},
A_{zz}, A_{xz},$ and the analyzing power $A_{y},$ as well as angular
distributions for $\sigma(\theta_{\pi})$ and the polarization observables
$A_{ij}(\theta_{\pi})$ were extracted. Partial wave cross sections for dominant
transition channels were obtained from a partial wave analysis that included
the transitions with final state angular momenta of $l\leq 1$. The measurements
of the ${\vec{p}\vec{p}\to pn\pi^{+}}$ polarization observables are compared
with the predictions from the J\""ulich meson exchange model. The agreement is
very good at 325 MeV, but it deteriorates increasingly for the higher energies.
At all energies agreement with the model is better than for the reaction
${\vec{p}\vec{p}\to pp\pi^{0}}$.",0108021v1
2002-02-14,"Polarization transfer in the $^{16}$O$(p,p')$ reaction at forward angles and structure of the spin-dipole resonances","Cross sections and polarization transfer observables in the $^{16}$O$(p,p')$
reactions at 392 MeV were measured at several angles between $\theta_{lab}=$
0$^\circ$ and 14$^\circ$. The non-spin-flip (${\Delta}S=0$) and spin-flip
(${\Delta}S=1$) strengths in transitions to several discrete states and broad
resonances in $^{16}$O were extracted using a model-independent method. The
giant resonances in the energy region of $E_x=19-$27 MeV were found to be
predominantly excited by ${\Delta}L=1$ transitions. The strength distribution
of spin-dipole transitions with ${\Delta}S=1$ and ${\Delta}L=1$ were deduced.
The obtained distribution was compared with a recent shell model calculation.
Experimental results are reasonably explained by distorted-wave impulse
approximation calculations with the shell model wave functions.",0202015v2
2001-05-11,Violation of the gauge equivalence,"F. V. Gubarev et al. (``On the significance of the vector potential
squared'', Phys. Rev. Lett. 86, 2220) have argued that the vector potential
itself may have physical meaning, in defiance of the gauge equivalence
principle. Earlier R. I. Khrapko proposed a gauge noninvariant electrodynamics
spin tensor (``Spin density of electromagnetic waves''). The standard
electrodynamics spin tensor is zero.
  Here we point out that the Biot-Savarat formula uniquely results in a
preferred, ""true"" vector potential field which is generated from a given
magnetic field. A similar integral formula uniquely permits to find a ""true""
scalar potential field generated from a given electric field even in the case
of a nonpotential electric field.
  A conception of differential forms is used. We say that an exterior
derivative of a form is the boundary of this form and the integration of a form
by the Biot-Savarat-type formula results in a new form named the generation.
Generating from a generation yields zero. The boundary of a boundary is zero. A
boundary is closed. A generation is sterile. A conjugation is considered. The
conjugation converts closed forms to sterile forms and back. It permits to
construct chains of forms. The conjunction differs from the Hodge star
operation: the conjugation does not imply the dualization. A circularly
polarized wave is considered in view of the electrodynamics spin tensor
problem.
  A new anthropic principle is presented.",0105031v3
2007-04-20,Evidence for decay of spin-waves above the pseudogap in underdoped YBa2Cu3O6.35,"The magnetic spectrum at high-energies in heavily underdoped
YBa$_{2}$Cu$_{3}$O$_{6.35}$ (T$_{c}$=18 K) has been determined throughout the
Brillouin zone. At low-energy the scattering forms a cone of spin excitations
emanating from the antiferromagnetic (0.5, 0.5) wave vector with an acoustic
velocity similar to that of insulating cuprates. At high energy transfers,
below the maximum energy of 270 meV at (0.5, 0), we observe zone boundary
dispersion much larger and spectral weight loss more extensive than in
insulating antiferromagnets. Moreover we report phenomena not found in
insulators, an overall lowering of the zone-boundary energies and a large
damping of $\sim$ 100 meV of the spin excitations at high-energies. The energy
above which the damping occurs coincides approximately with the gap determined
from transport measurements. We propose that as the energy is raised the spin
excitations encounter an extra channel of decay into particle-hole pairs of a
continuum that we associate with the pseudogap.",0704.2739v1
2007-08-06,X-ray Scattering Study of the spin-Peierls transition and soft phonon behavior in TiOCl,"We have studied the S=1/2 quasi-one-dimensional antiferromagnet TiOCl using
single crystal x-ray diffraction and inelastic x-ray scattering techniques. The
Ti ions form staggered spin chains which dimerize below Tc1 = 66 K and have an
incommensurate lattice distortion between Tc1 and Tc2 = 92 K. Based on our
measurements of the intensities, wave vectors, and harmonics of the
incommensurate superlattice peaks, we construct a model for the incommensurate
modulation. The results are in good agreement with a soliton lattice model,
though some quantitative discrepancies exist near Tc2. The behavior of the
phonons has been studied using inelastic x-ray scattering with ~2 meV energy
resolution. For the first time, a zone boundary phonon which softens at the
spin-Peierls temperature Tsp has been observed. Our results show reasonably
good quantitative agreement with the Cross-Fisher theory for the phonon
dynamics at wave vectors near the zone boundary and temperatures near Tsp.
However, not all aspects of the data can be described, such as the strong
overdamping of the soft mode above Tsp. Overall, our results show that TiOCl is
a good realization of a spin-Peierls system, where the phonon softening allows
us to identify the transition temperature as Tsp=Tc2=92 K",0708.0717v1
2008-04-11,Destruction of Neel order in the cuprates by electron-doping,"Motivated by the evidence in PCCO and NCCO of a magnetic quantum critical
point at which Neel order is destroyed, we study the evolution with doping of
the T=0 quantum phases of the electron doped cuprates. At low doping, there is
a metallic Neel state with small electron Fermi pockets, and this yields a
fully gapped d_{x^2-y^2} superconductor with co-existing Neel order at low
temperatures. We analyze the routes by which the spin-rotation symmetry can be
restored in these metallic and superconducting states. In the metal, the loss
of Neel order leads to a topologically ordered `doublon metal' across a
deconfined critical point with global O(4) symmetry. In the superconductor, in
addition to the conventional spin density wave transition, we find a variety of
unconventional possibilities, including transitions to a nematic superconductor
and to valence bond supersolids. Measurements of the spin correlation length
and of the anomalous dimension of the Neel order by neutron scattering or NMR
should discriminate these unconventional transitions from spin density wave
theory.",0804.1794v4
2009-09-07,High accuracy simulations of black hole binaries:spins anti-aligned with the orbital angular momentum,"High-accuracy binary black hole simulations are presented for black holes
with spins anti-aligned with the orbital angular momentum. The particular case
studied represents an equal-mass binary with spins of equal magnitude
S/m^2=0.43757 \pm 0.00001. The system has initial orbital eccentricity ~4e-5,
and is evolved through 10.6 orbits plus merger and ringdown. The remnant mass
and spin are M_f=(0.961109 \pm 0.000003)M and S_f/M_f^2=0.54781 \pm 0.00001,
respectively, where M is the mass during early inspiral. The gravitational
waveforms have accumulated numerical phase errors of <~ 0.1 radians without any
time or phase shifts, and <~ 0.01 radians when the waveforms are aligned with
suitable time and phase shifts. The waveform is extrapolated to infinity using
a procedure accurate to <~ 0.01 radians in phase, and the extrapolated waveform
differs by up to 0.13 radians in phase and about one percent in amplitude from
the waveform extracted at finite radius r=350M. The simulations employ
different choices for the constraint damping parameters in the wave zone; this
greatly reduces the effects of junk radiation, allowing the extraction of a
clean gravitational wave signal even very early in the simulation.",0909.1313v1
2010-09-28,Boundary effects on the local density of states of one-dimensional Mott insulators and charge density wave states,"We determine the local density of states (LDOS) for spin-gapped
one-dimensional charge density wave (CDW) states and Mott insulators in the
presence of a hard-wall boundary. We calculate the boundary contribution to the
single-particle Green function in the low-energy limit using field theory
techniques and analyze it in terms of its Fourier transform in both time and
space. The boundary LDOS in the CDW case exhibits a singularity at momentum
2kF, which is indicative of the pinning of the CDW order at the impurity. We
further observe several dispersing features at frequencies above the spin gap,
which provide a characteristic signature of spin-charge separation. This
demonstrates that the boundary LDOS can be used to infer properties of the
underlying bulk system. In presence of a boundary magnetic field mid-gap states
localized at the boundary emerge. We investigate the signature of such bound
states in the LDOS. We discuss implications of our results on STM experiments
on quasi-1D systems such as two-leg ladder materials like Sr14Cu24O41. By
exchanging the roles of charge and spin sectors, all our results directly carry
over to the case of one-dimensional Mott insulators.",1009.5587v3
2011-02-25,Quasiclassical description of a superconductor with a spin density wave,"We derive equations for the quasiclassical Green's functions $\check{g}$
within a simple model of a two-band superconductor with a spin-density-wave
(SDW). The elements of the matrix $\check{g}$ are the retarded, advanced, and
Keldysh functions each of which is an $8\times 8$ matrix in the Gor'kov-Nambu,
the spin and the band space. In equilibrium, these equations are a
generalization of the Eilenberger equation. On the basis of the derived
equations we analyze the Knight shift, the proximity and the dc Josephson
effects in the superconductors under consideration. The Knight shift is shown
to depend on the orientation of the external magnetic field with respect to the
direction of the vector of the magnetization of the SDW. The proximity effect
is analyzed for an interface between a superconductor with the SDW and a normal
metal. The function describing both superconducting and magnetic correlations
is shown to penetrate the normal metal or a metal with the SDW due to the
proximity effect. The dc Josephson current in an $S_{SDW}/N/S_{SDW}$ junction
is also calculated as a function of the phase difference $\phi$. It is shown
that in our model the Josephson current does not depend on the mutual
orientation of the magnetic moments in the superconductors $S_{SDW}$ and is
proportional to $ \sin \phi$. The dissipationless spin current $j_{sp}$ depends
on the angle $\alpha $ between the magnetization vectors in the same way
($j_{sp} \sim \sin \alpha $) and is not zero above the superconducting
transition temperature.",1102.5272v2
2011-03-10,"Phase diagram of the XXZ ferrimagnetic spin-(1/2, 1) chain in the presence of transverse magnetic field","We investigate the phase diagram of an anisotropic ferrimagnet spin-(1/2, 1)
in the presence of a non-commuting (transverse) magnetic field. We find a
magnetization plateau for the isotropic case while there is no plateau for the
anisotropic ferrimagnet. The magnetization plateau can appear only when the
Hamiltonian has the U(1) symmetry in the presence of the magnetic field. The
anisotropic model is driven by the magnetic field from the N\'{e}el phase for
low fields to the spin-flop phase for intermediate fields and then to the
paramagnetic phase for high fields. We find the quantum critical points and
their dependence on the anisotropy of the aforementioned field-induced quantum
phase transitions. The spin-flop phase corresponds to the spontaneous breaking
of Z2 symmetry. We use the numerical density matrix renormalization group and
analytic spin wave theory to find the phase diagram of the model. The energy
gap, sublattice magnetization, and total magnetization parallel and
perpendicular to the magnetic field are also calculated. The elementary
excitation spectrums of the model are obtained via the spin wave theory in the
three different regimes depending on the strength of the magnetic field.",1103.1967v2
2012-06-08,Weak Spin Fluctuation with Finite Wave Vector and Superconducting Gap Symmetry in KxFe2-ySe2: 77Se Nuclear Magnetic Resonance,"We report $^{77}$Se-nuclear magnetic resonance (NMR) results down to
sufficiently low temperatures under magnetic fields parallel to both the
$ab$-plane and the c-axis in a paramagnetic/superconducting (PM/SC) phase of
K$_x$Fe$_{2-y}$Se$_2$. The observation of anisotropy in the orbital part of the
Knight shift results in the anisotropy of its spin part increasing on
approaching the transition temperature. The anisotropy of the Korringa relation
suggests the presence of the weak spin fluctuations with a finite wave vector
$\bm{q}$, which induce the magnetic fluctuations along the ab-plane at the Se
site. Such fluctuations do not correspond to the stripe $(\pi,0)$ correlation
of the Fe moment observed in many Fe-based superconductors, and are not
contradictory to weak $(\pi,\pi)$ correlations. The nuclear spin-lattice
relaxation rate $1/T_1$ shows a field-independent $T_1T \sim const.$ behavior
at low temperatures for $H \parallel ab$, which is attributed to the nonzero
density of states at the Fermi level and can be explained by the sign-changing
order parameter even for nodeless gaps. The temperature dependence of $1/T_1$
is reproduced well by nodeless models with two isotropic gaps or a single
anisotropic gap. The obtained gap magnitude in the isotropic two-gap model is
comparable to those obtained in the angle-resolved photoemission spectroscopy
experiments.",1206.1756v2
2012-11-16,Relaxation in quantum dots due to evanescent-wave Johnson noise from a metallic backgate,"We present our study of decoherence in charge (spin) qubits due to
evanescent-wave Johnson noise (EWJN) in a laterally coupled double quantum dot
(single quantum dot). The high density of evanescent modes in the vicinity of
metallic gates causes energy relaxation and a loss of phase coherence of
electrons trapped in quantum dots. We derive expressions for the resultant
energy relaxation rates of charge and spin qubits in a variety of dot
geometries, and EWJN is shown to be a dominant source of decoherence for spin
qubits held at low magnetic fields. Previous studies in this field approximated
the charge or spin qubit as a point dipole. Ignoring the finite size of the
quantum dot in this way leads to a spurious divergence in the relaxation rate
as the qubit approaches the metal. Our approach goes beyond the dipole
approximation and remedies this unphysical divergence by taking into account
the finite size of the quantum dot. Additionally, we derive an enhancement of
EWJN that occurs outside a thin metallic film, relative to the field
surrounding a conducting half-space.",1211.3983v3
2012-12-12,Topological entanglement entropy in Gutzwiller projected spin liquids,"The topological entanglement entropy(TEE) of Gutzwiller projected RVB state
is studied with Monte Carlo simulation. New tricks are proposed to improve the
convergence of TEE, which enable us to show that the spin liquid state studied
in Ref.\cite{Vishwanath} actually does not support $Z_{2}$ topological order, a
conclusion that is consistent with the information drawn from the inspection of
the topological degeneracy on the same state. We find both a long ranged RVB
amplitude and an approximate Marshall sign structure are at the origin of the
suppression of vison gap in this spin liquid state. On the other hand, robust
signature of $Z_{2}$ topological order, i.e., a TEE of $\ln2$, is clearly
demonstrated for a Gutzwiiler projected RVB state on triangular lattice which
is evolved from the RVB state proposed originally by Anderson\cite{Sorella}. We
also find that it is the sign, rather than the amplitude of the RVB wave
function, that dominates the TEE and is responsible for a positive value of
TEE, which implies that the nonlocal entanglement in the RVB state is mainly
encoded in the sign of the RVB wave function. Our results indicate that some
information that is important for the topological property of a RVB state is
missed in the effective field theory description and that a $Z_{2}$ gauge
structure in the saddle point action is not enough for the RVB state to exhibit
topological order, even if its spin correlation is extremely short ranged.",1212.2703v1
2013-05-08,High-bandwidth quantum memory protocol for storing single photons in rare-earth doped crystals,"We present a detailed analysis of a high-bandwidth quantum memory protocol
for storing single photons in a rare-earth-ion doped crystal. The basic idea is
to benefit from a coherent free-induced decay type re-emission which occurs
naturally when a photon with a broadband spectrum is absorbed by a narrow
atomic transition in an optically dense ensemble. This allows for a
high-bandwidth memory for realistic material parameters. Long storage time and
on-demand readout are obtained by means of spins states in a lambda-type
configuration, through the transfer of the optical coherence to a spin
coherence (so-called spin-wave storage). We give explicit formulas and show
numerical results which make it possible to gain insight into the dependence of
the memory efficiency on the optical depth and on the width and the shape of
stored photons. We present a feasibility study in rare-earth doped crystals and
show that high efficiencies and high bandwidth can be obtained with realistic
parameters. High-bandwidth memories using spin-wave storage offers the
possibility of very high time-bandwidth products, which is important for
experiment where high repetition rates are needed.",1305.1863v2
2013-11-11,Effective-one-body model for black-hole binaries with generic mass ratios and spins,"Gravitational waves emitted by black-hole binary systems have the highest
signal-to-noise ratio in LIGO and Virgo detectors when black-hole spins are
aligned with the orbital angular momentum and extremal. For such systems, we
extend the effective-one-body inspiral-merger-ringdown waveforms to generic
mass ratios and spins calibrating them to 38 numerical-relativity nonprecessing
waveforms produced by the SXS Collaboration. The numerical-relativity
simulations span mass ratios from 1 to 8, spin magnitudes up to 98% of
extremality, and last for 40 to 60 gravitational-wave cycles. When the total
mass of the binary is between 20Msun and 200Msun, the effective-one-body
nonprecessing (dominant mode) waveforms have overlaps above 99% (using the
advanced-LIGO design noise spectral density) with all of the 38 nonprecessing
numerical waveforms, when maximizing only on initial phase and time. This
implies a negligible loss in event rate due to modeling. Moreover, without
further calibration, we show that the precessing effective-one-body (dominant
mode) waveforms have overlaps above 97% with two very long, strongly precessing
numerical-relativity waveforms, when maximizing only on the initial phase and
time.",1311.2544v1
2014-03-03,The honeycomb lattice with multi-orbital structure: topological and quantum anomalous Hall insulators with large gaps,"We construct a minimal four-band model for the two-dimensional (2D)
topological insulators and quantum anomalous Hall insulators based on the
$p_x$- and $p_y$-orbital bands in the honeycomb lattice. The multiorbital
structure allows the atomic spin-orbit coupling which lifts the degeneracy
between two sets of on-site Kramers doublets $j_z=\pm\frac{3}{2}$ and
$j_z=\pm\frac{1}{2}$. Because of the orbital angular momentum structure of
Bloch-wave states at $\Gamma$ and $K(K^\prime)$ points, topological gaps are
equal to the atomic spin-orbit coupling strengths, which are much larger than
those based on the mechanism of the $s$-$p$ band inversion. In the weak and
intermediate regime of spin-orbit coupling strength, topological gaps are the
global gap. The energy spectra and eigen wave functions are solved analytically
based on Clifford algebra. The competition among spin-orbit coupling $\lambda$,
sublattice asymmetry $m$ and the N\'eel exchange field $n$ results in band
crossings at $\Gamma$ and $K (K^\prime)$ points, which leads to various
topological band structure transitions. The quantum anomalous Hall state is
reached under the condition that three gap parameters $\lambda$, $m$, and $n$
satisfy the triangle inequality. Flat bands also naturally arise which allow a
local construction of eigenstates. The above mechanism is related to several
classes of solid state semiconducting materials.",1403.0563v6
2014-05-21,Singular spin-wave theory and scattering continua in the cone state of Cs_2CuCl_4,"For temperatures below 0.6 K the geometrically frustrated layered quantum
antiferromagnet Cs$_2$CuCl$_4$ in a magnetic field perpendicular to the layers
orders magnetically in a so-called cone state, where the magnetic moments have
a finite component in the field direction while their projection onto the
layers forms a spiral. Modeling this system by a two-dimensional spatially
anisotropic quantum Heisenberg antiferromagnet with Dzyaloshinskii-Moriya
interaction, we find that even for vanishing temperature the usual spin-wave
expansion is plagued by infrared divergencies which are due to the coupling
between longitudinal and transverse spin fluctuations in the cone state.
Similar divergencies appear also in the ground state of the interacting Bose
gas in two and three dimensions. Using known results for the correlation
functions of the interacting Bose gas, we present a non-perturbative expression
for the dynamic structure factor in the cone state of Cs$_2$CuCl$_4$. We show
that in this state the spectral line shape of spin fluctuations exhibits
singular scattering continua which can be understood in terms of the well-known
anomalous longitudinal fluctuations in the ground state of the two-dimensional
Bose gas.",1405.5539v2
2014-12-08,Quasi-Two Dimensional Spin and Phonon Excitations in $La_{1.965}Ba_{0.035}CuO_{4}$,"We present time-of-flight inelastic neutron scattering measurements of
$La_{1.965}Ba_{0.035}CuO_{4}$ (LBCO), a lightly doped member of the high
temperature superconducting La-based cuprate family. By using time-of-flight
neutron instrumentation coupled with single crystal sample rotation we obtain a
four-dimensional data set (three {\bf Q} and one energy) that is both
comprehensive and spans a large region of reciprocal space. Our measurements
identify rich structure in the energy dependence of the highly dispersive spin
excitations, which are centered at equivalent ($\frac{1}{2},\frac{1}{2}, L$)
wave-vectors. These structures correlate strongly with several crossings of the
spin excitations with the lightly dispersive phonons found in this system.
These effects are significant and account for on the order of 25$\%$ of the
total inelastic scattering for energies between $\sim$5 and 40 meV at low
$|{\bf Q}|$. Interestingly, this scattering also presents little or no
$L$-dependence. As the phonons and dispersive spin excitations centered at
equivalent ($\frac{1}{2},\frac{1}{2}, L$) wave-vectors are common to all
members of La-based 214 copper oxides, we conclude such strong quasi-two
dimensional scattering enhancements are likely to occur in all such 214
families of materials, including those concentrations corresponding to
superconducting ground states. Such a phenomenon appears to be a fundamental
characteristic of these materials and is potentially related to superconducting
pairing.",1412.2706v1
2015-03-23,Neutron spin resonance as a probe of superconducting gap anisotropy in partially detwinned electron underdoped NaFe$_{0.985}$Co$_{0.015}$As,"We use inelastic neutron scattering (INS) to study the spin excitations in
partially detwinned NaFe$_{0.985}$Co$_{0.015}$As which has coexisting static
antiferromagnetic (AF) order and superconductivity ($T_c=15$ K, $T_N=30$ K). In
previous INS work on a twinned sample, spin excitations form a dispersive sharp
resonance near $E_{r1}=3.25$ meV and a broad dispersionless mode at $E_{r1}=6$
meV at the AF ordering wave vector ${\bf Q}_{\rm AF}={\bf Q}_1=(1,0)$ and its
twinned domain ${\bf Q}_2=(0,1)$. For partially detwinned
NaFe$_{0.985}$Co$_{0.015}$As with the static AF order mostly occurring at ${\bf
Q}_{\rm AF}=(1,0)$, we still find a double resonance at both wave vectors with
similar intensity. Since ${\bf Q}_1=(1,0)$ characterizes the explicit breaking
of the spin rotational symmetry associated with the AF order, these results
indicate that the double resonance cannot be due to the static and fluctuating
AF orders, but originate from the superconducting gap anisotropy.",1503.06737v3
2015-05-22,Double-Q spin-density wave in iron arsenide superconductors,"Elucidating the nature of the magnetic ground state of iron-based
superconductors is of paramount importance in unveiling the mechanism behind
their high temperature superconductivity. Until recently, it was thought that
superconductivity emerges only from an orthorhombic antiferromagnetic stripe
phase, which can in principle be described in terms of either localized or
itinerant spins. However, we recently reported that tetragonal symmetry is
restored inside the magnetically ordered state of a hole-doped BaFe2As2. This
observation was interpreted as indirect evidence of a new double-Q magnetic
structure, but alternative models of orbital order could not be ruled out.
Here, we present Mossbauer data that show unambiguously that half of the iron
sites in this tetragonal phase are non-magnetic, establishing conclusively the
existence of a novel magnetic ground state with a non-uniform magnetization
that is inconsistent with localized spins. We show that this state is naturally
explained as the interference between two spin-density waves, demonstrating the
itinerant character of the magnetism of these materials and the primary role
played by magnetic over orbital degrees of freedom.",1505.06175v1
2015-07-10,Topologically protected elastic waves in phononic metamaterials,"Topological states of quantum matter exhibit unique disorder-immune surface
states protected by underlying nontrivial topological invariants of the bulk.
Such immunity from backscattering makes topological surface or edge states
ideal carriers for both classical and quantum information. So far, topological
matters have been explored only in the realms of electronics and photonics,
with limited range of bulk properties and largely immutable materials. These
constraints thus impose severe performance trade-offs in experimentally
realizable topologically ordered states. In contrast, phononic metamaterials
not only provide access to a much wider range of material properties, but also
allow temporal modulation in the non-adiabatic regime. Here, from the
first-principles we demonstrate numerically the first phononic topological
metamaterial in an elastic-wave analogue of the quantum spin Hall effect. A
dual-scale phononic crystal slab is used to support two effective spins of
phonon over a broad bandwidth, and strong spin-orbit coupling is realized by
breaking spatial mirror symmetry. By preserving the spin polarization with an
external load or spatial symmetry, phononic edge states are shown to be robust
against scattering from discrete defects as well as disorders in the continuum.
Our system opens up the possibility of realizing topological materials for
phonons in both static and time-dependent regimes.",1507.03002v1
2015-12-10,Variational wave functions for the $S=1/2$ Heisenberg model on the anisotropic triangular lattice: Spin liquids and spiral orders,"By using variational wave functions and quantum Monte Carlo techniques, we
investigate the complete phase diagram of the Heisenberg model on the
anisotropic triangular lattice, where two out of three bonds have
super-exchange couplings $J$ and the third one has instead $J^\prime$. This
model interpolates between the square lattice and the isotropic triangular one,
for $J^\prime/J \le 1$, and between the isotropic triangular lattice and a set
of decoupled chains, for $J/J^\prime \le 1$. We consider all the
fully-symmetric spin liquids that can be constructed with the fermionic
projective-symmetry group classification [Y. Zhou and X.-G. Wen,
arXiv:cond-mat/0210662] and we compare them with the spiral magnetic orders
that can be accommodated on finite clusters. Our results show that, for
$J^\prime/J \le 1$, the phase diagram is dominated by magnetic orderings, even
though a spin-liquid state may be possible in a small parameter window, i.e.,
$0.7 \lesssim J^\prime/J \lesssim 0.8$. In contrast, for $J/J^\prime \le 1$, a
large spin-liquid region appears close to the limit of decoupled chains, i.e.,
for $J/J^\prime \lesssim 0.6$, while magnetically ordered phases with spiral
order are stabilized close to the isotropic point.",1512.03356v2
2016-01-08,Magnons and Phonons Optically Driven Out of Local Equilibrium in a Magnetic Insulator,"Magnons are the energy quanta of fundamental spin excitations, namely spin
waves, and they can make a considerable contribution to energy transport in
some magnetic materials in a similar manner as lattice vibration waves or
phonons. The coupling and possible non-equilibrium between magnons and other
energy carriers have been used to explain several recently discovered thermally
driven spin transport and energy conversion phenomena. Here, we report
experiments in which local non-equilibrium between magnons and phonons in a
single crystalline bulk magnetic insulator, Y3Fe5O12 (yttrium iron garnet, or
YIG), has been created optically within a focused laser spot and probed
directly with the use of micro-Brillouin light scattering (BLS). By analyzing
the experimental results with a thermally induced magnon diffusion model, we
obtain the magnon diffusion length of thermal magnons. By explicitly
establishing non-equilibrium between magnons and phonons, our studies represent
an important step toward a quantitative understanding of various spin-heat
coupling phenomena.",1601.01982v3
2016-01-20,Gapless quantum excitations from an Ice-like Splayed Ferromagnetic ground state in stoichiometric Yb2Ti2O7,"The ground state of the quantum spin ice candidate magnet Yb2Ti2O7 is known
to be sensitive to weak disorder at the 1 percent level which occurs in single
crystals grown from the melt. Powders produced by solid state synthesis tend to
be stoichiometric and display large and sharp heat capacity anomalies at
relatively high temperatures, with Tc about 0.26 K. We have carried out neutron
elastic and inelastic measurements on well characterized and equilibrated
stoichiometric powder samples of Yb2Ti2O7 which show resolution-limited Bragg
peaks to appear at low temperatures, but whose onset correlates with
temperatures much higher than Tc. The corresponding magnetic structure is best
described as an ice-like splayed ferromagnet. The spin dynamics in Yb2Ti2O7 are
shown to be gapless on an energy scale smaller than 0.09 meV at all
temperatures, and organized into a continuum of scattering with vestiges of
highly overdamped ferromagnetic spin waves present. These excitations differ
greatly from conventional spin waves predicted for Yb2Ti2O7 s mean field
ordered state, but appear robust to weak disorder as they are largely
consistent with those displayed by non stoichiometric crushed single crystals
and single crystals, as well as by powder samples of Yb2Ti2O7 s sister quantum
magnet Yb2Sn2O7.",1601.05139v1
2016-05-20,Semiclassical theory of the magnetization process of the triangular lattice Heisenberg model,"Motivated by the numerous examples of 1/3 magnetization plateaux in the
triangular lattice Heisenberg an- tiferromagnet with spins ranging from 1/2 to
5/2, we revisit the semiclassical calculation of the magnetization curve of
that model, with the aim of coming up with a simple method that allows one to
calculate the full mag- netization curve, and not just the critical fields of
the 1/3 plateau. We show that it is actually possible to calculate the
magnetization curve including the first quantum corrections and the appearance
of the 1/3 plateau entirely within linear spin-wave theory, with predictions
for the critical fields that agree to order 1/S with those derived a long-time
ago on the basis of arguments that required to go beyond linear spin-wave
theory. This calculation relies on the central observation that there is a kink
in the semiclassical energy at the field where the classical ground state is
the collinear up-up-down structure, and that this kink gives rise to a locally
linear behavior of the energy with the field when all semiclassical ground
states are compared to each other for all fields. The magnetization curves
calculated in this way for spin 1/2, 1 and 5/2 are shown to be in good
agreement with available experimental data.",1605.06347v4
2016-06-08,"Breaking the rotating wave approximation for a strongly-driven, dressed, single electron spin","We investigate the dynamics of a strongly-driven, microwave-dressed,
donor-bound electron spin qubit in silicon. A resonant oscillating magnetic
field $B_1$ is used to dress the electron spin and create a new quantum system
with a level splitting proportional to $B_1$. The dressed two-level system can
then be driven by modulating the detuning $\Delta\nu$ between the microwave
source frequency $\nu_{\rm MW}$ and the electron spin transition frequency
$\nu_e$ at the frequency of the level splitting. The resulting dressed qubit
Rabi frequency $\Omega_{R\rho}$ is defined by the modulation amplitude, which
can be made comparable to the level splitting using frequency modulation on the
microwave source. This allows us to investigate the regime where the rotating
wave approximation breaks down, without requiring microwave power levels that
would be incompatible with a cryogenic environment. We observe clear deviations
from normal Rabi oscillations and can numerically simulate the time evolution
of the states in excellent agreement with the experimental data.",1606.02380v2
2016-09-20,Bouncing Dirac particles: compatibility between MIT boundary conditions and Thomas precession,"We consider the reflection of a Dirac plane wave on a perfectly reflecting
plane described by chiral MIT boundary conditions and determine the rotation of
the spin in the reflected component of the wave. We solve the analogous problem
for a classical particle using the evolution of the spin defined by the Thomas
precession and make a comparison with the quantum result. We find that the
rotation axes of the spin in the two problems coincide only for a vanishing
chiral angle, in which case the rotation angles coincide in the nonrelativistic
limit, and also remain remarkably close in the relativistic regime. The result
shows that in the nonrelativistic limit the interaction between the spin and a
reflecting surface with nonchiral boundary conditions is completely contained
in the Thomas precession effect, in conformity with the fact that these
boundary conditions are equivalent to an infinite repulsive scalar potential
outside the boundary. By contrast, in the ultrarelativistic limit the rotation
angle in the quantum problem remains finite, while in the classical one the
rotation angle diverges. We comment on the possible implications of this
discrepancy on the validity of the Mathisson-Papapetrou-Dixon equations at
large accelerations.",1609.06249v2
2017-07-27,Proposed physical explanation for the electron spin and related antisymmetry,"We offer a possible physical explanation for the origin of the electron spin
and the related antisymmetry of the wave function for a two-electron system, in
the framework of nonrelativistic quantum mechanics as provided by linear
stochastic electrodynamics. A consideration of the separate coupling of the
electron to circularly polarized modes of the random electromagnetic vacuum
field, allows to disclose the spin angular momentum and the associated magnetic
moment with a $g$-factor 2, and to establish the connection with the usual
operator formalism. The spin operator turns out to be the generator of internal
rotations, in the corresponding coordinate representation. In a bipartite
system, the distinction between exchange of particle coordinates (which include
the internal rotation angle) and exchange of states becomes crucial. Following
the analysis of the respective symmetry properties, the electrons are shown to
couple in antiphase to the same vacuum field modes. This finding, encoded in
the antisymmetry of the wave function, provides a physical rationale for the
Pauli principle. The extension of our results to a multipartite system is
briefly discussed.",1707.08674v2
2017-05-10,Sensitivity of new detection method for ultra-low frequency gravitational waves with pulsar spin-down rate statistics,"A new detection method for ultra-low frequency gravitational waves (GWs) with
a frequency much lower than the observational range of pulsar timing arrays
(PTAs) was suggested in Yonemaru et al. (2016). In the PTA analysis, ultra-low
frequency GWs ($\lesssim 10^{-10}$ Hz) which evolve just linearly during the
observation time span are absorbed by the pulsar spin-down rates since both
have the same effect on the pulse arrival time. Therefore, such GWs cannot be
detected by the conventional method of PTAs. However, the bias on the observed
spin-down rates depends on relative direction of a pulsar and GW source and
shows a quadrupole pattern in the sky. Thus, if we divide the pulsars according
to the position in the sky and see the difference in the statistics of the
spin-down rates, ultra-low frequency GWs from a single source can be detected.
In this paper, we evaluate the potential of this method by Monte-Carlo
simulations and estimate the sensitivity, considering only the ""Earth term""
while the ""pulsar term"" acts like random noise for GW frequencies
$10^{-13}-10^{-10}$ Hz. We find that with 3,000 milli-second pulsars, which are
expected to be discovered by a future survey with the Square Kilometre Array,
GWs with the derivative of amplitude of about $3 \times 10^{-19}~\rm{s}^{-1}$
can in principle be detected. Implications for possible supermassive binary
black holes in Sgr${}^*$ and M87 are also given.",1705.04733v2
2019-06-20,Numerical binary black hole collisions in dynamical Chern-Simons gravity,"We produce the first numerical relativity binary black hole gravitational
waveforms in a higher-curvature theory beyond general relativity. In
particular, we study head-on collisions of binary black holes in order-reduced
dynamical Chern-Simons gravity. This is a precursor to producing
beyond-general-relativity waveforms for inspiraling binary black hole systems
that are useful for gravitational wave detection. Head-on collisions are
interesting in their own right, however, as they cleanly probe the quasi-normal
mode spectrum of the final black hole. We thus compute the leading-order
dynamical Chern-Simons modifications to the complex frequencies of the
post-merger gravitational radiation. We consider equal-mass systems, with equal
spins oriented along the axis of collision, resulting in remnant black holes
with spin. We find modifications to the complex frequencies of the quasi-normal
mode spectrum that behave as a power law with the spin of the remnant, and that
are not degenerate with the frequencies associated with a Kerr black hole of
any mass and spin. We discuss these results in the context of testing general
relativity with gravitational wave observations.",1906.08789v2
2017-06-04,Hedgehog spin-vortex crystal stabilized in a hole-doped iron-based superconductor,"Magnetism is widely considered to be a key ingredient of unconventional
superconductivity. In contrast to cuprate high-temperature superconductors,
antiferromagnetism in Fe-based superconductors (FeSCs) is characterized by a
pair of magnetic propagation vectors. Consequently, three different types of
magnetic order are possible. Of theses, only stripe-type spin-density wave
(SSDW) and spin-charge-density wave (SCDW) orders have been observed. A
realization of the proposed spin-vortex crystal (SVC) order is noticeably
absent. We report a magnetic phase consistent with the hedgehog variation of
SVC order in Ni- and Co-doped CaKFe4As4 based on thermodynamic, transport,
structural and local magnetic probes combined with symmetry analysis. The
exotic SVC phase is stabilized by the reduced symmetry of the CaKFe4As4
structure. Our results suggest that the possible magnetic ground states in
FeSCs have very similar energies, providing an enlarged configuration space for
magnetic fluctuations to promote high-temperature superconductivity.",1706.01067v2
2020-03-18,Model independent tests of the Kerr bound with extreme mass ratio inspirals,"An outstanding prediction of general relativity is the fact that the angular
momentum $S$ of an isolated black hole with mass $\mu$ is limited by the Kerr
bound, $S\leq G\mu^2/c$. Testing this cornerstone is challenging due to the
difficulty in modelling spinning compact objects that violate this bound. We
argue that precise, model-independent tests can be achieved by measuring
gravitational waves from an extreme mass ratio inspiral around a supermassive
object, one of the main targets of the future LISA mission. In the extreme mass
ratio limit, the dynamics of the small compact object depends only on its
multipole moments, which are free parameters. At variance with the
comparable-mass case, accurate waveforms are valid also when the spin of the
small object greatly exceeds the Kerr bound. By computing the orbital dephasing
and the gravitational-wave signal emitted by a spinning point particle in
circular, nonprecessing, equatorial motion around a Kerr black hole, we
estimate that LISA will be able to measure the spin of the small compact object
at the level of $10\%$. Together with mass measurements, this will allow for
theory-agnostic, unprecedented constraints on string-theory inspired objects
such as ""superspinars"", almost in their entire parameter space.",2003.08448v2
2021-08-10,On the Angular Momentum Transport Efficiency within the Star Constrained from Gravitational-wave Observations,"The LIGO Scientific Collaboration and Virgo Collaboration (LVC) have recently
reported in GWTC-2.1 eight additional candidate events with a probability of
astrophysical origin greater than 0.5 in the LVC deeper search on O3a running.
In GWTC-2.1, the majority of the effective inspiral spins ($\chi_{\rm eff}$)
show magnitudes consistent with zero, while two (GW190403$_{-}$051519 and
GW190805$_{-}$211137) of the eight new events have $\chi_{\rm eff}$ $> 0$ (at
90% credibility). We note that GW190403$_{-}$051519 was reported with
$\chi_{\rm eff}$ = $0.70^{+0.15}_{-0.27}$ and mass ratio $q$ =
$0.25^{+0.54}_{-0.11}$, respectively. Assuming a uniform prior probability
between 0 and 1 for each black hole's dimensionless spin magnitude,
GW190403$_{-}$051519 was reported with the dimensionless spin of the more
massive black hole, $\chi_1$ = $0.92^{+0.07}_{-0.22}$. This is the fastest
first-born black hole ever measured in all current gravitational-wave events.
If GW190403$_{-}$051519 is formed through isolated binary evolution channel,
this extremely high spin challenges, at least in that case, the existence of
efficient angular momentum transport mechanism between the stellar core and the
radiative envelope of massive stars, as for instance predicted by the
Tayler-Spruit dynamo (Spruit 2002) or its revised version by Fuller et al.
2019.",2108.04821v3
2017-01-25,Hybrid nanodiamond-YIG systems for efficient quantum information processing and nanoscale sensing,"The nitrogen-vacancy (NV) center in diamond has been extensively studied in
recent years for its remarkable quantum coherence properties that make it an
ideal candidate for room temperature quantum computing and quantum sensing
schemes. However, these schemes rely on spin-spin dipolar interactions, which
require the NV centers to be within a few nanometers from each other while
still separately addressable, or to be in close proximity of the diamond
surface, where their coherence properties significantly degrade. Here we
demonstrate a method for overcoming these limitations using a hybrid yttrium
iron garnet (YIG)-nanodiamond quantum system constructed with the help of
directed assembly and transfer printing techniques. We show that YIG spin-waves
can amplify the oscillating field of a microwave source by more than two orders
of magnitude and efficiently mediate its coherent interactions with an NV
center ensemble. These results demonstrate that spin-waves in ferromagnets can
be used as quantum buses for enhanced, long-range qubit interactions, paving
the way to ultra-efficient manipulation and coupling of solid state defects in
hybrid quantum networks and sensing devices.",1701.07401v1
2017-03-15,"Symmetry analysis of strain, electric and magnetic fields in the $\text{Bi}_2\text{Se}_3$-class of topological insulators","Based on group theoretical arguments we derive the most general Hamiltonian
for the $\text{Bi}_2\text{Se}_3$-class of materials including terms to third
order in the wave vector, first order in electric and magnetic fields, first
order in strain and first order in both strain and wave vector. We determine
analytically the effects of strain on the electronic structure of
$\text{Bi}_2\text{Se}_3$. For the most experimentally relevant surface
termination we analytically derive the surface state spectrum, revealing an
anisotropic Dirac cone with elliptical constant energy counturs giving rise to
different velocities in different in-plane directions. The spin-momentum
locking of strained $\text{Bi}_2\text{Se}_3$ is shown to be modified and for
some strain configurations we see a non-zero spin component perpendicular to
the surface. Hence, strain control can be used to manipulate the spin degree of
freedom via the spin-orbit coupling. We show that for a thin film of
$\text{Bi}_2\text{Se}_3$ the surface state band gap induced by coupling between
the opposite surfaces changes opposite to the bulk band gap under strain.
Tuning the surface state band gap by strain, gives new possibilities for the
experimental investigation of the thickness dependent gap and optimization of
optical properties relevant for, e.g., photodetector and energy harvesting
applications. We finally derive analytical expressions for the effective mass
tensor of the Bi$_2$Se$_3$ class of materials as a function of strain and
electric field.",1703.05259v2
2017-03-24,Are gravitational waves spinning down PSR J1023+0038?,"The pulsar J1203+0038 rotates with a frequency $\nu\approx 592$ Hz and has
been observed to transition between a radio state, during which it is visible
as a millisecond radio pulsar, and and a Low Mass X-ray Binary state, during
which accretion powered X-ray pulsations are visible. Timing during the two
phases reveals that during the LMXB phase the neutron star is spinning down at
a rate of $\dot{\nu}\approx -3 \times 10^{-15}$ Hz/s, which is approximately
27\% faster than the rate measured during the radio phase, $\dot{\nu}\approx
-2.4 \times 10^{-15}$ Hz/s, and at odds with the predictions of accretion
models. In this letter we suggest that the increase in spin-down rate is
compatible with gravitational wave emission, and in particular to the creation
of a `mountain' during the accretion phase. We show that asymmetries in
pycno-nuclear reaction rates in the crust can lead to a large enough mass
quadrupole to explain the observed spin-down rate, which so far has no other
self-consistent explanation, and that radio timing at the onset of the next
millisecond radio pulsar phase can test this scenario. Another possibility is
that an unstable $r$-mode with amplitude $\alpha\approx 5\times10^{-8}$ may be
present in the system.",1703.08374v1
2017-04-18,Superradiance in rotating stars and pulsar-timing constraints on dark photons,"In the presence of massive bosonic degrees of freedom, rotational
superradiance can trigger an instability that spins down black holes. This
leads to peculiar gravitational-wave signatures and distribution in the
spin-mass plane, which in turn can impose stringent constraints on ultralight
fields. Here, we demonstrate that there is an analogous spindown effect for
conducting stars. We show that rotating stars amplify low frequency
electromagnetic waves, and that this effect is largest when the time scale for
conduction within the star is of the order of a light crossing time. This has
interesting consequences for dark photons, as massive dark photons would cause
stars to spin down due to superradiant instabilities. The time scale of the
spindown depends on the mass of the dark photon, and on the rotation rate,
compactness, and conductivity of the star. Existing measurements of the
spindown rate of pulsars place direct constraints on models of dark sectors.
Our analysis suggests that dark photons of mass $m_V \sim 10^{-12}$ eV are
excluded by pulsar-timing observations. These constraints also exclude
superradiant instabilities triggered by dark photons as an explanation for the
spin limit of observed pulsars.",1704.06151v1
2019-04-29,Testing the Kerr nature of intermediate-mass and supermassive black hole binaries using spin-induced multipole moment measurements,"The gravitational wave measurements of spin-induced multipole moment
coefficients of a binary black hole system can be used to distinguish black
holes from other compact objects [N. V. Krishnendu et al., PRL 119, 091101
(2017)]. Here, we apply the idea proposed in [N. V. Krishnendu et al., PRL 119,
091101 (2017)] to binary systems composed of intermediate-mass and supermassive
black holes and derive the expected bounds on their Kerr nature using future
space-based gravitational wave detectors. Using astrophysical models of binary
black hole population, we study the measurability of the spin-induced
quadrupole and octupole moment coefficients using LISA and DECIGO. The errors
on spin-induced quadrupole moment parameter of the binary system are found to
be { $\leq 0.1$ for almost $3\%$ of the total supermassive binary black hole
population which is detectable by LISA whereas it is $\sim 46\%$ for the
intermediate-mass black hole binaries observable by DECIGO at its design
sensitivity.} We find that { errors on} {\it both} the quadrupole and octupole
moment parameters can be estimated to { be} $\leq 1$ for $\sim 2\%$ and $\sim
50\%$ {of the population} respectively for LISA and DECIGO detectors. { Our
findings suggest that a subpopulation of binary black hole events, with the
signal to noise ratio thresholds greater than 200 and 100 respectively for LISA
and DECIGO detectors, would permit tests of black hole nature to 10\%
precision.}",1904.12712v2
2019-08-09,Gravitational wave detection beyond the standard quantum limit using a negative-mass spin system and virtual rigidity,"Gravitational wave detectors (GWDs), which have brought about a new era in
astronomy, have reached such a level of maturity that further improvement
necessitates quantum-noise-evading techniques. Numerous proposals to this end
have been discussed in the literature, e.g., invoking frequency-dependent
squeezing or replacing the current Michelson interferometer topology by that of
the quantum speedmeter. Recently, a proposal based on the linking of a standard
interferometer to a negative-mass spin system via entangled light has offered
an unintrusive and small-scale new approach to quantum noise evasion in GWDs
[Phys. Rev. Lett. $\mathbf{121}$, 031101 (2018)]. The solution proposed therein
does not require modifications to the highly refined core optics of the present
GWD design and, when compared to previous proposals, is less prone to losses
and imperfections of the interferometer. In the present article, we refine this
scheme to an extent that the requirements on the auxiliary spin system are
feasible with state-of-the-art implementations. This is accomplished by
matching the effective (rather than intrinsic) susceptibilities of the
interferometer and spin system using the virtual rigidity concept, which, in
terms of implementation, requires only suitable choices of the various
homodyne, probe, and squeezing phases.",1908.03416v2
2020-05-15,Spin density wave and electron nematicity in magic-angle twisted bilayer graphene,"We study theoretically many-body properties of magic-angle twisted bilayer
graphene for different doping levels. Our investigation is focused on the
emergence, stability, and manifestations of nematicity of the ordered
low-temperature electronic state. It is known that, at vanishing interactions,
the low-energy spectrum of the system studied consists of four almost-flat
almost-degenerate bands. Electron-electron repulsion lifts this degeneracy. To
account for such an interaction effect, a numerical mean-field theory is used.
Assuming that the ground state has spin-density-wave-like order, we introduce a
multicomponent order parameter describing spin magnetization. Our simulations
show that the order parameter structure depends on the doping level. In
particular, doping away from the charge neutrality point reduces the rotational
symmetry of the ordered state, indicating the appearance of an electron nematic
state. Manifestations of the nematicity can be observed in the spatial
distribution of the spin magnetization within a moir{\'e} cell, as well as in
the single-electron band structure. The nematicity is strongest at half-filling
(two extra electron or holes per supercell). We argue that nematic symmetry
breaking is a robust feature of the system ground state, stable against model
parameters variations. Specifically, it is shown that, away from the charge
neutrality point, it persists for all three parametrizations of the interlayer
hopping amplitudes discussed in the paper. Obtained theoretical results are
consistent with the available experimental data.",2005.07749v3
2020-10-06,"Bond-bond correlations, gap relations and thermodynamics of spin-$1/2$ chains with spin-Peierls transitions and bond-order-wave phases","The spin-$1/2$ chain with antiferromagnetic exchange $J_1$ and $J_2 = \alpha
J_1$ between first and second neighbors, respectively, has both gapless and
gapped ($\Delta(\alpha) > 0$) quantum phases at frustration $0 \le \alpha \le
3/4$. The ground state instability of regular ($\delta = 0$) chains to
dimerization ($\delta > 0$) drives a spin-Peierls transition at
$T_{SP}(\alpha)$ that varies with $\alpha$ in these strongly correlated
systems. The thermodynamic limit of correlated states is obtained by exact
treatment of short chains followed by density matrix renormalization
calculations of progressively longer chains. The doubly degenerate ground
states of the gapped regular phase are bond order waves (BOWs) with long-range
bond-bond correlations and electronic dimerization $\delta_e(\alpha)$. The $T$
dependence of $\delta_e(T,\alpha)$ is found using four-spin correlation
functions and contrasted to structural dimerization $\delta(T,\alpha)$ at $T
\le T_{SP}(\alpha)$. The relation between $T_{SP}(\alpha)$ and the $T = 0$ gap
$\Delta(\delta(0),\alpha)$ varies with frustration in both gapless and gapped
phases. The magnetic susceptibility $\chi(T,\alpha)$ at $T > T_{SP}$ can be
used to identify physical realizations of spin-Peierls systems. The $\alpha =
1/2$ chain illustrates the characteristic BOW features of a regular chain with
a large singlet-triplet gap and electronic dimerization.",2010.02999v1
2021-03-17,Quasinormal modes of slowly-rotating black holes in dynamical Chern-Simons gravity,"The detection of gravitational waves from compact binary mergers by the
LIGO/Virgo collaboration has, for the first time, allowed us to test
relativistic gravity in its strong, dynamical and nonlinear regime, thus
opening a new arena to confront general relativity (and modifications thereof)
against observations. We consider a theory which modifies general relativity by
introducing a scalar field coupled to a parity-violating curvature term known
as dynamical Chern-Simons gravity. In this theory, spinning black holes are
different from their general relativistic counterparts and can thus serve as
probes to this theory. We study linear gravito-scalar perturbations of black
holes in dynamical Chern-Simons gravity at leading-order in spin and (i) obtain
the perturbed field equations describing the evolution of the perturbed
gravitational and scalar fields, (ii) numerically solve these equations by
direct integration to calculate the quasinormal mode frequencies for the
dominant and higher multipoles and tabulate them, (iii) find strong evidence
that these rotating black holes are linearly stable, and (iv) present general
fitting functions for different multipoles for gravitational and scalar
quasinormal mode frequencies in terms of spin and Chern-Simons coupling
parameter. Our results can be used to validate the ringdown of small-spin
remnants of numerical relativity simulations of black hole binaries in
dynamical Chern-Simons gravity and pave the way towards future tests of this
theory with gravitational wave ringdown observations.",2103.09913v3
2021-06-09,Entanglement between a telecom photon and an on-demand multimode solid-state quantum memory,"Entanglement between photons at telecommunication wavelengths and long-lived
quantum memories is one of the fundamental requirements of long-distance
quantum communication. Quantum memories featuring on-demand read-out and
multimode operation are additional precious assets that will benefit the
communication rate. In this work we report the first demonstration of
entanglement between a telecom photon and a collective spin excitation in a
multimode solid-state quantum memory. Photon pairs are generated through widely
non-degenerate parametric down-conversion, featuring energy-time entanglement
between the telecom-wavelength idler and a visible signal photon. The latter is
stored in a Pr$^{3+}$:Y$_2$SiO$_5$ crystal as a spin wave using the full Atomic
Frequency Comb scheme. We then recall the stored signal photon and analyze the
entanglement using the Franson scheme. We measure conditional fidelities of
$92(2)\%$ for excited-state storage, enough to violate a CHSH inequality, and
$77(2)\%$ for spin-wave storage. Taking advantage of the on-demand read-out
from the spin state, we extend the entanglement storage in the quantum memory
for up to 47.7~$\mu$s, which could allow for the distribution of entanglement
between quantum nodes separated by distances of up to 10 km.",2106.05079v3
2021-07-06,The relative contribution to heavy metals production from binary neutron star mergers and neutron star-black hole mergers,"The origin of the heavy elements in the Universe is not fully determined.
Neutron star-black hole (NSBH) and {binary neutron star} (BNS) mergers may both
produce heavy elements via rapid neutron-capture (r-process). We use the recent
detection of gravitational waves from NSBHs, improved measurements of the
neutron star equation-of-state, and the most modern numerical simulations of
ejected material from binary collisions to measure the relative contribution of
NSBHs and BNSs to the production of heavy elements. As the amount of r-process
ejecta depends on the mass and spin distribution of the compact objects, as
well as on the equation-of-state of the neutron stars, we consider various
models for these quantities, informed by gravitational-wave and pulsar data. We
find that in most scenarios, BNSs have produced more r-process elements than
NSBHs over the past 2.5 billion years. If black holes have preferentially small
spins, BNSs can produce at least twice of the amount of r-process elements than
NSBHs. If black hole spins are small and there is a dearth of low mass
($<5M_{\odot}$) black holes within NSBH binaries, BNSs can account for the near
totality of the r-process elements from binaries. For NSBH to produce large
fraction of r-process elements, black holes in NSBHs must have small masses and
large aligned spins, which is disfavored by current data.",2107.02714v2
2021-09-20,Spin Wave Based 4-2 Compressor,"By their very nature, Spin Waves (SWs) consume ultra-low amounts of energy,
which makes them suitable for ultra-low energy consumption applications. In
addition, a compressor can be utilized to further reduce the energy consumption
and enhance the speed of a multiplier. Therefore, we propose a novel energy
efficient SW based 4-2 compressor consisting of 4 XOR gates and 2 Majority
gates. The proposed compressor is validated by means of micromagnetic
simulations and compared with the state-of-the-art SW, 22nm CMOS, Magnetic
Tunnel Junction (MTJ), Domain Wall Motion (DWM), and Spin-CMOS technologies.
The performance evaluation shows that the proposed compressor consumes 2.5x
less and 1.25x less energy than the 22nm CMOS and the conventional SW
compressor, respectively, whereas it consumes at least 3 orders of magnitude
less energy than the MTJ, DWM, and Spin-CMOS designs. Furthermore, the
compressor achieves the smallest chip real-estate. In summary, the performance
evaluation of our proposed compressor shows that the SW technology has the
potential to progress the state-of-the-art circuit design in terms of energy
consumption and scalability.",2109.09516v1
2021-12-05,Population Properties of Gravitational-Wave Neutron Star--Black Hole Mergers,"Over the course of the third observing run of LIGO-Virgo-KAGRA Collaboration,
several gravitational-wave (GW) neutron star--black hole (NSBH) candidates have
been announced. By assuming these candidates are real signals and of
astrophysical origins, we analyze the population properties of the mass and
spin distributions for GW NSBH mergers. We find that the primary BH mass
distribution of NSBH systems, whose shape is consistent with that inferred from
the GW binary BH (BBH) primaries, can be well described as a power-law with an
index of $\alpha = 4.8^{+4.5}_{-2.8}$ plus a high-mass Gaussian component
peaking at $\sim33^{+14}_{-9}\,M_\odot$. The NS mass spectrum could be shaped
as a near flat distribution between $\sim1.0-2.1\,M_\odot$. The constrained NS
maximum mass agrees with that inferred from NSs in our Galaxy. If GW190814 and
GW200210 are NSBH mergers, the posterior results of the NS maximum mass would
be always larger than $\sim2.5\,M_\odot$ and significantly deviate from that
inferred in the Galactic NSs. The effective inspiral spin and effective
precession spin of GW NSBH mergers are measured to potentially have near-zero
distributions. The negligible spins for GW NSBH mergers imply that most events
in the universe should be plunging events, which supports the standard isolated
formation channel of NSBH binaries. More NSBH mergers to be discovered in the
fourth observing run would help to more precisely model the population
properties of cosmological NSBH mergers.",2112.02605v2
2022-01-03,Coherent dynamics of a single Mn-doped quantum dot revealed by four-wave mixing spectroscopy,"For future quantum technologies the combination of a long quantum state
lifetime and an efficient interface with external optical excitation are
required. In solids, the former is for example achieved by individual spins,
while the latter is found in semiconducting artificial atoms combined with
modern photonic structures. One possible combination of the two aspects is
reached by doping a single quantum dot, providing a strong excitonic dipole,
with a magnetic ion, that incorporates a characteristic spin texture. Here, we
perform four-wave mixing spectroscopy to study the system's quantum coherence
properties. We characterize the optical properties of the undoped CdTe quantum
dot and find a strong photon echo formation which demonstrates a significant
inhomogeneous spectral broadening. Incorporating the Mn$^{2+}$ ion introduces
its spin-5/2 texture to the optical spectra via the exchange interaction,
manifesting as six individual spectral lines in the coherent response. The
random flips of the Mn-spin result in a special type of spectral wandering
between the six transition energies, which is fundamentally different from the
quasi-continuous spectral wandering that results in the Gaussian inhomogeneous
broadening. Here, the discrete spin-ensemble manifests in additional dephasing
and oscillation dynamics.",2201.00792v1
2022-02-16,Misaligned Spinning Binary Black Hole Mergers in Hot Magnetized Plasma,"We present general relativistic magneto-hydrodynamical simulations of
equal-mass spinning black hole binary mergers embedded in a magnetized gas
cloud. We focus on the effect of the spin orientation relative to the orbital
angular momentum on the flow dynamics, mass accretion rate and Poynting
luminosity. We find that, across the inspiral, the gas accreting onto the
individual black holes concentrates into disk-like overdensities, whose angular
momenta are oriented towards the spin axes and which persist until merger. We
identify quasi-periodic modulations occurring in the mass accretion rate at the
level of 1-20%, evolving in parallel with the gravitational wave chirp. The
similarity between the accretion rate time-series and the gravitational strain
is a consequence of the interplay between strong, dynamical gravitational
fields and magnetic fields in the vicinity of the inspiralling black holes.
This result suggests that quasi-periodicity in the pre-merger accretion rate of
massive binaries is not exclusive of environments in which the black holes are
embedded in a circumbinary accretion disk, and could provide an additional
useful signature of electromagnetic emission concurrent to low-frequency
gravitational wave detection.",2202.08282v2
2022-09-13,Spin-wave dynamics in the KCeS2 delafossite: A theoretical description of powder inelastic neutron-scattering data,"Layered rare-earth delafossites $ARX_2$ with $R$ = Yb(III) or Ce(III) have
received a lot of interest as potential hosts for a quantum spin-liquid ground
state. Some systems of this family that show no long-range order down to the
lowest measured temperatures, such as NaYbO$_2$, NaYbS$_2$, and NaYbSe$_2$, are
presumed to be in a quantum spin-liquid state. However, other isostructural
compounds are known to order antiferromagnetically at subkelvin temperatures.
Among them, KCeS$_2$ exhibits stripe-$yz$ magnetic order in the
triangular-lattice planes that sets in below 400 mK. Here we investigate the
spin-wave spectrum of this ordered phase with powder inelastic neutron
scattering and describe it using a model Hamiltonian obtained from
first-principles calculations based on the complete $|J,m_J\rangle$ multiplet
description of the Ce sites with an anisotropic nearest-neighbor exchange
interaction. Combing the current understanding of the exchange interaction in
the systems with the effects of texturing in the powder, we have been able to
model the inelastic neutron scattering spectrum with high fidelity.",2209.06092v2
2022-10-04,"Numerical relativity higher order gravitational waveforms of eccentric, spinning, non-precessing binary black hole mergers","We use the open source, community-driven, numerical relativity software, the
Einstein Toolkit to study the physics of eccentric, spinning, nonprecessing
binary black hole mergers with mass-ratios $q=\{2, 4, 6\}$, individual
dimensionless spin parameters $\chi_{1z}=\pm0.6$, $\chi_{2z}=\pm0.3$, that
include higher order gravitational wave modes $\ell\leq4$, except for memory
modes. Assuming stellar mass binary black hole mergers that may be detectable
by the advanced LIGO detectors, we find that including modes up to $\ell=4$
increases the signal-to-noise of compact binaries between $3.5\%$ to $35\%$,
compared to signals that only include the $\ell=|m|=2$ mode. We use two
waveform models, TEOBResumS and SEOBNRE, which incorporate spin and
eccentricity corrections in the waveform dynamics, to quantify the orbital
eccentricity of our numerical relativity catalog in a gauge-invariant manner
through fitting factor calculations. Our findings indicate that the inclusion
of higher order wave modes has a measurable effect in the recovery of
moderately and highly eccentric black hole mergers, and thus it is essential to
develop waveform models and signal processing tools that accurately describe
the physics of these astrophysical sources.",2210.01852v2
2022-10-04,Total angular momentum of water molecule and magnetic field interaction,"One of the must important non-invasive techniques in medicine is the Magnetic
Resonance Imaging (MRI), it is used to obtain information of the structure of
the human body parts using three dimensional images. The technique to obtain
these images is based by the emission of radio waves produced by the protons of
the hydrogen atoms in water molecules when placed in a constant magnetic field
after they interact with a pulsed radio frequency (RF) current, the spin of the
protons are in a spin excited state. When the RF field is turned off, the MRI
sensors are able to detect the energy released (RF waves) as the protons
realign their spins with the magnetic field.
  We used a three particles model for the water molecule: the two protons from
the hydrogen atoms move around the doubly negatively charged oxygen
(unstructured), to describe the total angular momentum. The energy levels from
the water molecule are studied in presence of an uniform external magnetic
field, which interacts with the proton's spin and orbital angular momentum. The
energy is shifted and the degeneration is lifted. To illustrate the results, we
provide numerical results for a magnetic field strength commonly used in MRI
devices.",2210.01867v1
2022-10-12,Spin-phonon coupling driven Charge density wave in a Kagome Magnet,"The intertwining between spin, charge, and lattice degrees of freedom can
give rise to unusual macroscopic quantum states, including high-temperature
superconductivity and quantum anomalous Hall effects. Recently, a charge
density wave (CDW) is observed in the kagome antiferromagnet FeGe, indicative
of possible intertwining physics. An outstanding question is that whether
magnetic correlation is fundamental for the spontaneous spatial symmetry
breaking orders. Here, utilizing elastic and high-resolution inelastic x-ray
scattering, we discover a charge dimerization superlattice that coexists with
the 2$\times$2$\times$1 CDW in the kagome sublattice. Most interestingly,
between the magnetic and CDW transition temperature, the phonon dynamical
structure factor shows a giant phonon-energy hardening and a substantial phonon
linewidth broadening near the charge-dimerization wavevectors, both signaling
the spin-phonon coupling. By first principles calculations, we show that both
the static and dynamic spin excitations intertwine with the phonon to drive the
spatial symmetry breaking.",2210.06359v2
2023-01-30,Charge density wave-templated spin cycloid in topological semimetal $NdSb_{x}Te_{2-x-δ}$,"Magnetic topological semimetals present open questions regarding the
interplay of crystal symmetry, magnetism, band topology, and electron
correlations. $LnSb_{x}Te_{2-x-\delta}$ (Ln= lanthanide) is a family of
square-net-derived topological semimetals that allows compositional control of
band filling, and access to different topological states via an evolving charge
density wave (CDW) distortion. Previously studied Gd and Ce members containing
a CDW have shown complex magnetic phase diagrams, which implied that spins
localized on Ln interact with the CDW, but to this date, no magnetic structures
have been solved within the CDW regime of this family of compounds. Here, we
report on the interplay of the CDW with magnetism in $NdSb_{x}Te_{2-x-\delta}$,
by comparing the undistorted square net member $NdSb_{0.94}Te_{0.92}$ with the
CDW-distorted phase $NdSb_{0.48}Te_{1.37}$, via single-crystal x-ray
diffraction, magnetometry, heat capacity, and neutron powder diffraction.
$NdSb_{0.94}Te_{0.92}$ is a collinear antiferromagnet with $T_N$ $\sim$ 2.7 K,
where spins align antiparallel to each other, but parallel to the square net of
the nuclear structure. $NdSb_{0.48}Te_{1.37}$ exhibits a nearly five-fold
modulated CDW ($q_{CDW}=0.18b^*$), isostructural to other
$LnSb_{x}Te_{2-x-\delta}$ at similar x. $NdSb_{0.48}Te_{1.37}$ displays more
complex magnetism with $T_N = 2.3 K$, additional metamagnetic transitions, and
an elliptical cycloid magnetic structure with $q_{mag}=-0.41b^*$.The magnitudes
of $q_{CDW}$ and $q_{mag}$ exhibit a integer relationship,
$1+2q_{mag}=q_{CDW}$, implying a coupling between the CDW and magnetic
structure. Given that the CDW is localized within the nonmagnetic distorted
square net, we propose that conduction electrons ""template"" the spin modulation
via the Ruderman-Kittel-Kasuya-Yosida interaction.",2301.13102v1
2023-03-02,Relativistic cosmology and intrinsic spin of matter: Results and theorems in Einstein-Cartan theory,"We start by presenting the general set of structure equations for the 1+3
threading spacetime decomposition in 4 spacetime dimensions, valid for any
theory of gravitation based on a metric compatible affine connection. We then
apply these equations to the study of cosmological solutions of the
Einstein-Cartan theory in which the matter is modeled by a perfect fluid with
intrinsic spin. It is shown that the metric tensor can be described by a
generic FLRW solution. However, due to the presence of torsion the Weyl tensors
might not vanish. The coupling between the torsion and Weyl tensors leads to
the conclusion that, in this cosmological model, the universe must either be
flat or open, excluding definitely the possibility of a closed universe. In the
open case, we derive a wave equation for the traceless part of the magnetic
part of the Weyl tensor and show how the intrinsic spin of matter in a dynamic
universe leads to the generation and emission of gravitational waves. Lastly,
in this cosmological model, it is found that the torsion tensor, which has an
intrinsic spin as its source, contributes to a positive accelerated expansion
of the universe. Comparing the theoretical predictions of the model with the
current experimental data, we conclude that torsion cannot completely replace
the role of a cosmological constant.",2303.03104v1
2023-04-03,Cosmic Cousins: Identification of a Subpopulation of Binary Black Holes Consistent with Isolated Binary Evolution,"Observations of gravitational waves (GWs) from merging compact binaries have
become a regular occurrence. The continued advancement of the LIGO-Virgo-KAGRA
(LVK) Collaboration detectors have now produced a catalog of over 90 such
mergers, from which we can begin to uncover the formation history of merging
compact binaries. In this work, we search for subpopulations in the LVK's third
gravitational wave transient catalog (GWTC-3) by incorporating discrete latent
variables in the hierarchical Bayesian inference framework to probabilistically
assign each BBH observation into separate categories associated with distinctly
different population distributions. By incorporating formation channel
knowledge within the mass and spin correlations found in each category, we find
an over density of mergers with a primary mass of $\sim10 M_\odot$, consistent
with isolated binary formation. This low-mass subpopulation has a spin
magnitude distribution peaking at $a_\mathrm{peak}=0.16^{0.19}_{-0.16}$,
exhibits spins preferentially aligned with the binary's orbital angular
momentum, is constrained by $15^{+0.0}_{-1.0}$ of our observations, and
contributes $82\%^{+8.0\%}_{-16\%}$ to the overall population of BBHs.
Additionally, we find that the component of the mass distribution containing
the previously identified $35M_\odot$ peak has spins consistent with the
$10M_\odot$ events, with $99\%$ of primary masses less than $m_{1,99\%} =
49^{+25}_{-8.1} M_\odot$, providing an estimate of the lower edge of the
theorized pair instability mass gap. This work is a first step in gaining a
deeper understanding of compact binary formation and evolution, and will
provide more robust conclusions as the catalog of observations becomes larger.",2304.01288v2
2023-04-17,Spin Fluctuations in Sr$_{1.8}$La$_{0.2}$RuO$_4$,"We use inelastic neutron scattering to study spin fluctuations in
Sr$_{1.8}$La$_{0.2}$RuO$_4$, where Lanthanum doping triggers a Lifshitz
transition by pushing the van Hove singularity in the $\gamma$ band to the
Fermi energy. Strong spin fluctuations emerge at an incommensurate wave vector
$\mathbf{Q}_{ic} = (0.3,0.3)$, corresponding to the nesting vector between
$\alpha$ and $\beta$ Fermi sheets. The incommensurate antiferromagnetic
fluctuations shift toward $(0.25,0.25)$ with increasing energy up to
${\sim}110$ meV. By contrast, scatterings near the ferromagnetic wave vectors
$\mathbf{Q} = (1,0)$ and $(1,1)$ remain featureless at all energies. This
contradicts the weak-coupling perspective that suggests a sharp enhancement of
ferromagnetic susceptibility due to the divergence of density of states in the
associated $\gamma$ band. Our findings imply that ferromagnetic fluctuations in
Sr$_2$RuO$_4$ and related materials do not fit into the weak-coupling paradigm,
but instead are quasi-local fluctuations induced by Hund's coupling. This
imposes significant constraints for the pairing mechanism involving spin
fluctuations.",2304.08214v2
2023-10-25,First frequency-domain phenomenological model of the multipole asymmetry in gravitational-wave signals from binary-black-hole coalescence,"Gravitational-wave signals from binaries that contain spinning black holes in
general include an asymmetry between the $+m$ and $-m$ multipoles that is not
included in most signal models used in LIGO-Virgo-KAGRA (LVK) analysis to date.
This asymmetry manifests itself in out-of-plane recoil of the final black hole
and its inclusion in signal models is necessary both to measure this recoil,
but also to accurately measure the full spin information of each black hole. We
present the first model of the anti-symmetric contribution to the dominant
co-precessing-frame signal multipole throughout inspiral, merger and ringdown.
We model the anti-symmetric contribution in the frequency domain, and take
advantage of the approximations that the anti-symmetric amplitude can be
modelled as a ratio of the (already modelled) symmetric amplitude, and analytic
relationships between the symmetric and anti-symmetric phases during the
inspiral and ringdown. The model is tuned to single-spin numerical-relativity
simulations up to mass-ratio 8 and spin magnitudes of 0.8, and has been
implemented in a recent phenomenological model for use in the fourth LVK
observing run. However, the procedure described here can be easily applied to
other time- or frequency-domain models.",2310.16980v1
2023-12-14,"Nonlocal damping of spin waves in a magnetic insulator induced by normal, heavy, or altermagnetic metallic overlayer: a Schwinger-Keldysh field theory approach","Understanding spin wave (SW) damping, and how to control it to the point of
being able to amplify SW-mediated signals, is one of the key requirements to
bring the envisaged magnonic technologies to fruition. Even widely used
magnetic insulators with low magnetization damping in their bulk, such as
yttrium iron garnet, exhibit 100-fold increase in SW damping due to inevitable
contact with metallic layers in magnonic circuits, as observed in very recent
experiments [I. Bertelli et al., Adv. Quantum Technol. 4, 2100094 (2021)]
mapping SW damping in spatially-resolved fashion. Here, we provide microscopic
and rigorous understanding of wavevector-dependent SW damping using extended
Landau-Lifshitz-Gilbert equation with nonlocal damping tensor, instead of
conventional local scalar Gilbert damping, as derived from Schwinger-Keldysh
nonequilibrium quantum field theory. In this picture, the origin of nonlocal
magnetization damping and thereby induced wavevector-dependent SW damping is
interaction of localized magnetic moments of magnetic insulator with conduction
electrons from the examined three different types of metallic overlayers --
normal, heavy, and altermagnetic. Due to spin-split energy-momentum dispersion
of conduction electrons in the latter two cases, the nonlocal damping is
anisotropic in spin and space, and it can be dramatically reduced by changing
the relative orientation of the two layers when compared to the usage of normal
metal overlayer.",2312.09140v1
2024-01-16,Control of charge-spin interconversion in van der Waals heterostructures with chiral charge density waves,"A charge density wave (CDW) represents an exotic state in which electrons are
arranged in a long range ordered pattern in low-dimensional materials. Although
our understanding of the fundamental character of CDW has been enriched after
extensive studies, its relationship with functional phenomena remains
relatively limited. Here, we show an unprecedented demonstration of a tunable
charge-spin interconversion (CSI) in graphene/1T-TaS$_2$ van der Waals
heterostructures by manipulating the distinct CDW phases in 1T-TaS$_2$. Whereas
CSI from spins polarized in all three directions are observed in the
heterostructure when the CDW phase does not show commensurability, the output
of one of the components disappears and the other two are enhanced when the CDW
phase becomes commensurate. The experimental observation is supported by
first-principles calculations, which evidence that chiral CDW multidomains are
at the origin of the switching of CSI. Our results uncover a new approach for
on-demand CSI in low-dimensional systems, paving the way for advanced
spin-orbitronic devices.",2401.08817v1
2024-04-09,High-Fidelity CZ Gates in Double Quantum Dot -- Circuit QED Systems Beyond the Rotating-Wave Approximation,"Semiconductor double quantum dot (DQD) qubits coupled via superconducting
microwave resonators provide a powerful means of long-range manipulation of the
qubits' spin and charge degrees of freedom. Quantum gates can be implemented by
parametrically driving the qubits while their transition frequencies are
detuned from the resonator frequency. Long-range two-qubit CZ gates have been
proposed for the DQD spin qubit within the rotating-wave approximation (RWA).
Rapid gates demand strong coupling, but RWA breaks down when coupling strengths
become significant relative to system frequencies. Therefore, understanding the
detrimental impact of time-dependent terms ignored by RWA is critical for
high-fidelity operation. Here, we go beyond RWA to study CZ gate fidelity for
both DQD spin and charge qubits. We propose a novel parametric drive on the
charge qubit that produces fewer time-dependent terms and show that it
outperforms its spin counterpart. We find that drive amplitude - a parameter
dropped in RWA - is critical for optimizing fidelity and map out high-fidelity
regimes. Our results demonstrate the necessity of going beyond RWA in
understanding how long-range gates can be realized in DQD qubits, with charge
qubits offering considerable advantages in high-fidelity operation.",2404.06187v1
2011-01-19,Measuring parameters of massive black hole binaries with partially aligned spins,"The future space-based gravitational wave detector LISA will be able to
measure parameters of coalescing massive black hole binaries, often to
extremely high accuracy. Previous work has demonstrated that the black hole
spins can have a strong impact on the accuracy of parameter measurement.
Relativistic spin-induced precession modulates the waveform in a manner which
can break degeneracies between parameters, in principle significantly improving
how well they are measured. Recent studies have indicated, however, that spin
precession may be weak for an important subset of astrophysical binary black
holes: those in which the spins are aligned due to interactions with gas. In
this paper, we examine how well a binary's parameters can be measured when its
spins are partially aligned and compare results using waveforms that include
higher post-Newtonian harmonics to those that are truncated at leading
quadrupole order. We find that the weakened precession can substantially
degrade parameter estimation. This degradation is particularly devastating for
the extrinsic parameters sky position and distance. Absent higher harmonics,
LISA typically localizes the sky position of a nearly aligned binary a factor
of $\sim 6$ less accurately than for one in which the spin orientations are
random. Our knowledge of a source's sky position will thus be worst for the
gas-rich systems which are most likely to produce electromagnetic counterparts.
Fortunately, higher harmonics of the waveform can make up for this degradation.
By including harmonics beyond the quadrupole in our waveform model, we find
that the accuracy with which most of the binary's parameters are measured can
be substantially improved. In some cases, parameters can be measured as well in
partially aligned binaries as they can be when the binary spins are random.",1101.3591v2
2013-06-02,Competing 4f-electron dynamics in Ce(Ru1-xFex)2Al10 (x=0 to 1): magnetic ordering emerging from the Kondo semiconducting state,"We have carried out muon spin relaxation (muSR), neutron diffraction and
inelastic neutron scattering (INS) investigations on polycrystalline samples of
Ce(Ru1-xFex)2Al10 (x=0, 0.3, 0.5, 0.8 and 1) to investigate the nature of the
ground state (magnetic ordered versus paramagnetic) and the origin of the spin
gap formation as evident from the bulk measurements in the end members. Our
zero-field muSR spectra clearly reveal coherent two-frequency oscillations at
low temperature in x=0, 0.3 and 0.5 samples, which confirms the long-range
magnetic ordering of the Ce-moment with TN=27, 26 and 21 K respectively. On the
other hand the muSR spectra of x=0.8 and x=1 down to 1.4 K and 0.045 K,
respectively exhibit a temperature independent Kubo-Toyabe term confirming a
paramagnetic ground state. The long-range magnetic ordering in x=0.5 below 21 K
has been confirmed through the neutron diffraction study. INS measurements of
x=0 clearly reveal the presence of a sharp inelastic excitation near 8 meV
between 5 K and 26 K, due to an opening of a gap in the spin excitation
spectrum, which transforms into a broad response at and above 30 K.
Interestingly, at 4.5 K the spin gap excitation broadens in x=0.3 and exhibits
two clear peaks at 8.4(3) and 12.0(5) meV in x=0.5. In the x=0.8 sample, which
remains paramagnetic down to 1.2 K, there is a clear signature of a spin gap of
10-12 meV at 7 K, with a strong Q-dependent intensity. Evidence of a spin gap
of 12.5(5) meV has also been found in x=1. The observation of a spin gap in the
paramagnetic samples (x=0.8 and 1) is an interesting finding in this study and
it challenges our understanding of the origin of the semiconducting gap in
CeT2Al10 (T=Ru and Os) compounds in terms of hybridization gap opening only a
small part of the Fermi surface, gapped spin waves, or a spin-dimer gap.",1306.0223v1
2017-07-10,Revisit of Antiferromagnetism in Hubbard Model by A Cluster Slave-Spin Method,"The cluster slave-spin method is introduced to systematically investigate the
solutions of the Hubbard model including the symmetry-broken phases. In this
method, the electron operator is factorized into a fermioninc spinon describing
the physical spin and a slave-spin describing the charge fluctuations.
Following the $U(1)$ formalism derived by Yu and Si [Phys. Rev. B 86, 085104
(2012)], it is shown that the self-consistent equations to explore various
symmetry-broken density wave states can be constructed in general with a
cluster of multiple slave-spin sites. We employ this method to study the
antiferromagnetic (AFM) state in the single band Hubbard model with the two and
four-site clusters of slave spins. While the Hubbard gap, the charge gap due to
the doubly-occupied states, scales with the Hubbard interaction $U$ as
expected, the AFM gap $\Delta$, the gap in the spinon dispersion in the AFM
state, exhibits a crossover from the weak to strong-coupling behaviors as $U$
increases. Our cluster slave-spin method reproduces not only the traditional
mean-field behavior of $\Delta \sim U$ in the weak-coupling limit, but also the
behavior of $\Delta \sim t^2/U$ predicted by the superexchange mechanism in the
strong coupling limit. In addition, the holon-doublon correlator as functions
of $U$ and doping $x$ is also computed, which exhibits a strong tendency toward
the holon-doublon binding in the strong coupling regime. We further show that
the quasiparticle weight obtained by the cluster slave-spin method is in a good
agreement with the generalized Gutzwiller approximation in both AFM and
paramagnetic states, and the results can be improved beyond the generalized
Gutzwiller approximation as the cluster is enlarged from a single site to 4
sites. Our results demonstrate that the cluster slave-spin method can be a
powerful tool to systematically investigate the strongly correlated system.",1707.03042v1
2017-09-06,Explaining LIGO's observations via isolated binary evolution with natal kicks,"We compare binary evolution models with different assumptions about
black-hole natal kicks to the first gravitational-wave observations performed
by the LIGO detectors. Our comparisons attempt to reconcile merger rate,
masses, spins, and spin-orbit misalignments of all current observations with
state-of-the-art formation scenarios of binary black holes formed in isolation.
We estimate that black holes (BHs) should receive natal kicks at birth of the
order of $\sigma\simeq 200$ (50) km/s if tidal processes do (not) realign
stellar spins. Our estimate is driven by two simple factors. The natal kick
dispersion $\sigma$ is bounded from above because large kicks disrupt too many
binaries (reducing the merger rate below the observed value). Conversely, the
natal kick distribution is bounded from below because modest kicks are needed
to produce a range of spin-orbit misalignments. A distribution of misalignments
increases our models' compatibility with LIGO's observations, if all BHs are
likely to have natal spins. Unlike related work which adopts a concrete BH
natal spin prescription, we explore a range of possible BH natal spin
distributions. Within the context of our models, for all of the choices of
$\sigma$ used here and within the context of one simple fiducial parameterized
spin distribution, observations favor low BH natal spin.",1709.01943v3
2020-07-09,Magnetic resonance of collective paramagnets with gapped excitations spectrum,"Some magnets due to particular geometry of the exchange bonds do not undergo
transition to the conventional magnetically ordered state despite of the
presence of significant exchange couplings. Instead, a collective paramagnetic
state is formed. The later state can remain stable down to $T=0$ if the ground
state of this magnet turns out to be nonmagnetic singlet separated from the
excited triplet states by an energy gap. Low-temperature spin dynamics of the
collective paramagnets with gapped excitations spectrum (or spin-gap magnets)
can be described in terms of a dilute gas of the triplet excitations. Applied
magnetic field can suppress the energy gap, resulting in the formation of the
gapless spin-liquid state or even leading to the unusual phenomenon of
field-induced antiferromagnetic order. Introduction of defects in the
crystallographic structure of the spin-gap magnet can result either in the
formation of multi-spin paramagnetic center or in the formation of randomly
distributed modified exchange bonds in the crystal. This review includes
results of electron spin resonance (ESR) spectroscopy study of several
representative quantum paramagnets with gapped excitations spectrum:
quasy-two-dimensional magnet \phcc{}, quasy-one-dimensional magnets of
""spin-tube"" type \sul{} and ""spin-ladder"" type \dimpy{}. We will demonstrate
that ESR absorption spectra reveal common features of these systems: ESR
spectroscopy allows to observe and characterize fine structure if the triplet
energy levels, to identify many-particles relaxation processes in the gas of
triplet excitations and to observe collective spin-wave oscillations in the
field induced antiferromagnetically ordered state, as well as to observe some
individual features of the studied systems.",2007.04885v1
2022-02-20,Non-Abelian Landau-Ginzburg Theory of Ferromagnetic Superconductivity and Photon-Spinon Mixing,"We propose an effective theory of non-Abelian superconductivity, an
SU(2)xU(1) extension of the Abelian Landau-Ginzburg theory, which could be
viewed as an effective theory of ferromagnetic superconductivity made of
spin-up and spin-down doublet Cooper pair. Just like the Abelian
Landau-Ginzburg theory it has the U(1) electromagnetic interaction, but the new
ingredient is the non-Abelian SU(2) gauge interaction between the spin doublet
Cooper pair. A remarkable feature of the theory is the mixing between the
photon and the diagonal part of the SU(2) gauge boson. After the mixing it has
massless gauge boson (the massless non-Abelian spinon) and massive gauge boson
(the massive photon), in addition to the massive off-diagonal gauge bosons (the
massive non-Abelian spinons) which induces the spin-flip interaction between
the spin up and down components of the Cooper pair. So, unlike the ordinary
Landau-Ginzburg theory it has a long range interaction mediated by the massless
non-Abelian spinon, which could be responsible for the long range magnetic
order and spin waves observed in ferromagnetic superconductors. The theory is
characterized by three scales. In addition to the correlation length fixed by
the mass of the Higgs field it has two different penetration lengths, the one
fixed by the mass of the photon (which generates the well known Meissner
effect) and the other fixed by the mass of the off-diagonal spinons (which
determines the scale of the spin flip interaction). The non-Abelian structure
of the theory naturally accommodates new topological objects, the non-Abrikosov
quantized spin vortex (as well as the well known Abrikosov vortex) and
non-Abelian spin monopole. We discuss the physical implications of the
non-Abelian Landau-Ginzburg theory.",2202.09775v4
2023-03-07,The Spin of a Newborn Black Hole: Swift J1728.9-3613,"The origin and distribution of stellar-mass black hole spins are a rare
window into the progenitor stars and supernova events that create them. Swift
J1728.9-3613 is an X-ray binary, likely associated with the supernova remnant
G351.9-0.9 (Balakrishnan et al. 2023). A NuSTAR X-ray spectrum of this source
during its 2019 outburst reveals reflection from an accretion disk extending to
the innermost stable circular orbit. Modeling of the relativistic Doppler
shifts and gravitational redshifts imprinted on the spectrum measures a
dimensionless spin parameter of $a=0.86\pm0.02$ ($1\sigma$ confidence), a small
inclination angle of the inner accretion disk $\theta<10$ degrees, and a
sub-solar iron abundance in the disk $A_{\rm Fe}<0.84$. This high spin value
rules out a neutron star primary at the $5\;\sigma$ level of confidence. If the
black hole is located in a still visible supernova remnant, it must be young.
Therefore, we place a lower limit on the natal black hole spin of $a>0.82$,
concluding that the black hole must have formed with a high spin. This
demonstrates that black hole formation channels that leave a supernova remnant,
and those that do not (e.g. Cyg X-1), can both lead to high natal spin with no
requirement for subsequent accretion within the binary system. Emerging
disparities between the population of high-spin black holes in X-ray binaries
and the low-spin black holes that merge in gravitational wave events may
therefore be explained in terms of different stellar conditions prior to
collapse, rather than different environmental factors after formation.",2303.04164v1
2023-07-03,Effects of spin-orbit coupling on gravitational waveforms from a triaxial non-aligned neutron star in a binary system,"Spinning neutron stars (NSs) can emit continuous gravitational waves (GWs)
that carry a wealth of information about the compact object. If such a signal
is detected, it will provide us with new insight into the physical properties
of matter under extreme conditions. Future space-based GW detectors, such as
LISA and TianQin, can potentially detect some double NSs in tight binaries with
orbital periods shorter than 10 minutes. The possibility of a successful
directed search for continuous GWs from the spinning NS in such a binary system
identified by LISA/TianQin will be significantly increased with the proposed
next-generation ground-based GW observatories, such as Cosmic Explorer and
Einstein Telescope. Searching for continuous GWs from such a tight binary
system requires highly accurate waveform templates that account for the
interaction of the NS with its companion. In this spirit, we derive analytic
approximations that describe the GWs emitted by a triaxial non-aligned NS in a
binary system in which the effects of spin-orbit coupling have been
incorporated. The difference with the widely used waveform for the isolated NS
is estimated and the parameter estimation accuracy of an example signal using
Cosmic Explorer is calculated. For a typical tight double NS system with a
6~min orbital period, the angular frequency correction of the spinning NS in
this binary due to spin precession is $\sim 10^{-6}~{\rm Hz}$, which is in the
same order of magnitude as the angular frequency of orbital precession. The
fitting factor between the waveforms with and without spin precession will drop
to less than 0.97 after a few days ($\sim 10^5~{\rm s}$). We find that
spin-orbit coupling has the potential to improve the accuracy of parameter
estimation, especially for the binary inclination angle and spin precession
cone opening angle, by up to 3 orders of magnitude. (Abridged)",2307.01055v2
2023-11-23,An upper limit on the spins of merging binary black holes formed through binary evolution,"As gravitational wave detectors improve, observations of black hole (BH)
mergers will provide the joint distribution of their masses and spins. This
will be a critical benchmark to validate formation scenarios. Merging binary
BHs formed through isolated binary evolution require both components to be
stripped of their hydrogen envelopes before core-collapse. The rotation rates
of such stripped stars are constrained by their surface critical rotation,
restricting their angular momentum content at core-collapse. We use stripped
star models at low metallicities ($Z_\odot/10$, $Z_\odot/50$ and $Z_\odot/250$)
to determine the spins of BHs produced by critically rotating stellar
progenitors. To study how such progenitors can arise, we consider their
formation through chemically homogeneous evolution (CHE). We use a
semianalytical model to study the final spins of CHE binaries, and compare our
results against available detailed population synthesis models. We find that
above BH masses of $\simeq 25M_\odot$, the dimensionless spin of critically
rotating stripped stars ($a = Jc/(GM^2$)) is below unity. This results in an
exclusion region at high chirp masses and effective spins that cannot be
populated by binary evolution. CHE can produce binaries where both BHs hit this
limit, producing a pile-up at the boundary of the excluded region. Highly
spinning BHs arise from very low-metallicity CHE systems with short delay
times, which merge at higher redshifts. On the other hand, the contribution of
CHE to merging binary BHs in the third observing run of the LVK collaboration
is expected to be dominated by systems with low spins ($\chi_\mathrm{eff}<0.5$)
which merge near redshift zero. Owing to its higher projected sensitivity and
runtime, the fourth observing run of the LVK collaboration can potentially
place constraints on the high spin population and the existence of a limit set
by critical rotation.",2311.14041v1
2006-01-21,New interpretation of the atomic spectra and other quantum phenomena: A mixed mechanism of classical $LC$ circuits and quantum wave-particle duality,"We study the energy conversion laws of the macroscopic harmonic $LC $
oscillator, the electromagnetic wave (photon) and the hydrogen atom. As our
analysis indicates that the energies of these apparently different systems obey
exactly the same energy conversion law. Based on our results and the
wave-particle duality of electron, we find that the atom in fact is a natural
microscopic $LC$ oscillator. In the framework of classical electromagnetic
field theory we analytically obtain, for the hydrogen atom, the quantized
electron orbit radius. Without the adaptation of any other fundamental
principles of quantum mechanics, we present a reasonable explanation of the
polarization of photon, the Zeeman effect, Selection rules and Pauli exclusion
principle. Particularly, it is found that a pairing Pauli electron can move
closely and steadily in a DNA-like double helical electron orbit. Our results
also reveal an essential connection between electron spin and the intrinsic
helical movement of electron and indicate that the spin itself is the effect of
quantum confinement. In addition, a possible physical mechanism of
superconductivity and the deeper physical understandings of the electron mass,
zero point energy, and the hardness property of electron are also provided.
Finally, we show analytically that the Dirac's quantization of magnetic
monopole is merely a special handed electron at absolute zero-temperature,
which strongly suggests that any efforts to seek for the magneticmonopole in
real space will be entirely in vain. Furthermore, it appears that the
electron's spin and the magnetic monopole are actually two different concepts
for one possible physical phenomenon.",0601169v7
2012-03-27,Nonspinning searches for spinning binaries in ground-based detector data: Amplitude and mismatch predictions in the constant precession cone approximation,"Current searches for compact binary mergers by ground-based
gravitational-wave detectors assume for simplicity the two bodies are not
spinning. If the binary contains compact objects with significant spin, then
this can reduce the sensitivity of these searches, particularly for black
hole--neutron star binaries. In this paper we investigate the effect of
neglecting precession on the sensitivity of searches for spinning binaries
using non-spinning waveform models. We demonstrate that in the sensitive band
of Advanced LIGO, the angle between the binary's orbital angular momentum and
its total angular momentum is approximately constant. Under this \emph{constant
precession cone} approximation, we show that the gravitational-wave phasing is
modulated in two ways: a secular increase of the gravitational-wave phase due
to precession and an oscillation around this secular increase. We show that
this secular evolution occurs in precisely three ways, corresponding to
physically different apparent evolutions of the binary's precession about the
line of sight. We estimate the best possible fitting factor between \emph{any}
non-precessing template model and a single precessing signal, in the limit of a
constant precession cone. Our closed form estimate of the fitting-factor
depends only the geometry of the in-band precession cone; it does not depend
explicitly on binary parameters, detector response, or details of either signal
model. The precessing black hole--neutron star waveforms least accurately
matched by nonspinning waveforms correspond to viewing geometries where the
precession cone sweeps the orbital plane repeatedly across the line of sight,
in an unfavorable polarization alignment.",1203.6060v3
2012-12-19,Black hole-neutron star mergers at realistic mass ratios: Equation of state and spin orientation effects,"Black hole-neutron star mergers resulting in the disruption of the neutron
star and the formation of an accretion disk and/or the ejection of unbound
material are prime candidates for the joint detection of gravitational-wave and
electromagnetic signals when the next generation of gravitational-wave
detectors comes online. However, the disruption of the neutron star and the
properties of the post-merger remnant are very sensitive to the parameters of
the binary. In this paper, we study the impact of the radius of the neutron
star and the alignment of the black hole spin for systems within the range of
mass ratio currently deemed most likely for field binaries (M_BH ~ 7 M_NS) and
for black hole spins large enough for the neutron star to disrupt (J/M^2=0.9).
We find that: (i) In this regime, the merger is particularly sensitive to the
radius of the neutron star, with remnant masses varying from 0.3M_NS to 0.1M_NS
for changes of only 2 km in the NS radius; (ii) 0.01-0.05M_sun of unbound
material can be ejected with kinetic energy >10^51 ergs, a significant increase
compared to low mass ratio, low spin binaries. This ejecta could power
detectable optical and radio afterglows. (iii) Only a small fraction (<3%) of
the Advanced LIGO events in this parameter range have gravitational-wave
signals which could offer constraints on the equation of state of the neutron
star. (iv) A misaligned black hole spin works against disk formation, with less
neutron star material remaining outside of the black hole after merger, and a
larger fraction of that material remaining in the tidal tail instead of the
forming accretion disk. (v) Large kicks (v>300 km/s) can be given to the final
black hole as a result of a precessing BHNS merger, when the disruption of the
neutron star occurs just outside or within the innermost stable spherical
orbit.",1212.4810v2
2014-02-28,Excitations in the quantum paramagnetic phase of the quasi-one-dimensional Ising magnet CoNb$_2$O$_6$ in a transverse field: Geometric frustration and quantum renormalization effects,"The quasi-one-dimensional (1D) Ising ferromagnet CoNb$_2$O$_6$ has recently
been driven via applied transverse magnetic fields through a continuous quantum
phase transition from spontaneous magnetic order to a quantum paramagnet, and
dramatic changes were observed in the spin dynamics, characteristic of weakly
perturbed 1D Ising quantum criticality. We report here extensive single-crystal
inelastic neutron scattering measurements of the magnetic excitations
throughout the three-dimensional (3D) Brillouin zone in the quantum
paramagnetic phase just above the critical field to characterize the effects of
the finite interchain couplings. In this phase, we observe that excitations
have a sharp, resolution-limited line shape at low energies and over most of
the dispersion bandwidth, as expected for spin-flip quasiparticles. We map the
full bandwidth along the strongly dispersive chain direction and resolve clear
modulations of the dispersions in the plane normal to the chains,
characteristic of frustrated interchain couplings in an antiferromagnetic
isosceles triangular lattice. The dispersions can be well parametrized using a
linear spin-wave model that includes interchain couplings and further neighbor
exchanges. The observed dispersion bandwidth along the chain direction is
smaller than that predicted by a linear spin-wave model using exchange values
determined at zero field, and this effect is attributed to quantum
renormalization of the dispersion beyond the spin-wave approximation in fields
slightly above the critical field, where quantum fluctuations are still
significant.",1402.7355v2
2015-08-28,Frequency-domain gravitational waves from non-precessing black-hole binaries. II. A phenomenological model for the advanced detector era,"We present a new frequency-domain phenomenological model of the
gravitational-wave signal from the inspiral, merger and ringdown of
non-precessing (aligned-spin) black-hole binaries. The model is calibrated to
19 hybrid effective-one-body--numerical-relativity waveforms up to mass ratios
of 1:18 and black-hole spins of $|a/m| \sim 0.85$ ($0.98$ for equal-mass
systems). The inspiral part of the model consists of an extension of
frequency-domain post-Newtonian expressions, using higher-order terms fit to
the hybrids. The merger-ringdown is based on a phenomenological ansatz that has
been significantly improved over previous models. The model exhibits mismatches
of typically less than 1\% against all 19 calibration hybrids, and an
additional 29 verification hybrids, which provide strong evidence that, over
the calibration region, the model is sufficiently accurate for all relevant
gravitational-wave astronomy applications with the Advanced LIGO and Virgo
detectors. Beyond the calibration region the model produces physically
reasonable results, although we recommend caution in assuming that \emph{any}
merger-ringdown waveform model is accurate outside its calibration region. As
an example, we note that an alternative non-precessing model, SEOBNRv2
(calibrated up to spins of only 0.5 for unequal-mass systems), exhibits
mismatch errors of up to 10\% for high spins outside its calibration region. We
conclude that waveform models would benefit most from a larger number of
numerical-relativity simulations of high-aligned-spin unequal-mass binaries.",1508.07253v2
2015-10-19,Asymptotic gravitational wave fluxes from a spinning particle in circular equatorial orbits around a rotating black hole,"We present a new computation of the asymptotic gravitational wave energy
fluxes emitted by a {\it spinning} particle in circular equatorial orbits about
a Kerr black hole. The particle dynamics is computed in the pole-dipole
approximation, solving the Mathisson-Papapetrou equations with the Tulczyjew
spin-supplementary-condition. The fluxes are computed, for the first time, by
solving the 2+1 Teukolsky equation in the time-domain using hyperboloidal and
horizon-penetrating coordinates. Denoting by $M$ the black hole mass and by
$\mu$ the particle mass, we cover dimensionless background spins
$a/M=(0,\pm0.9)$ and dimensionless particle spins $-0.9\leq S/\mu^2 \leq +0.9$.
Our results span orbits of Boyer-Lindquist coordinate radii $4\leq r/M \leq
30$; notably, we investigate the strong-field regime, in some cases even beyond
the last-stable-orbit. We confirm, numerically, the Tanaka {\it et al.} [Phys.\
Rev.\ D 54, 3762] 2.5th order accurate Post-Newtonian (PN) predictions for the
gravitational wave fluxes of a spinning particle in circular equatorial orbit:
we find an unambiguos trend of the PN-prediction towards the numerical results
when $r$ is large. At $r/M=30$ the fractional agreement between the full
numerical flux, approximated as the sum over the modes $m=1,2,3$, and the PN
prediction is $\lesssim0.5\%$ in all cases tested. This is close to our
fractional numerical accuracy ($\sim 0.2\%$). For smaller radii, the agreement
between the 2.5PN prediction and the numerical result progressively
deteriorates. Our numerical data will be essential to develop suitably resummed
expressions of the 2.5PN analytical fluxes in order to improve their accuracy
in the strong-field regime.",1510.05548v3
2018-03-05,Manifolds of magnetic ordered states and excitations in the almost Heisenberg pyrochlore antiferromagnet MgCr2O4,"In spinels ACr2O4 (A=Mg, Zn) realisation of the classical pyrochlore
Heisenberg antiferromagnet model is complicated by a strong spin-lattice
coupling: the extensive degeneracy of the ground state is lifted by a
magneto-structural transition at TN=12.5 K. We study the resulting
low-temperature low-symmetry crystal structure by synchrotron x-ray
diffraction. The consistent features of x-ray low-temperature patterns are
explained by the tetragonal model of Ehrenberg et. al (Pow. Diff. 17, 230(
2002)), while other features depend on sample or cooling protocol. Complex
partially ordered magnetic state is studied by neutron diffraction and
spherical neutron polarimetry. Multiple magnetic domains of configuration arms
of the propagation vectors k1=(1/2 1/2 0), k2=(1 0 1/2) appear. The ordered
moment reaches 1.94(3) muB/Cr3+ for k1 and 2.08(3) muB/Cr3+ for k2, if equal
amount of the k1 and k2 phases is assumed. The magnetic arrangements have the
dominant components along the [110] and [1-10] diagonals and a smaller
c-component. By inelastic neutron scattering we investigate the spin
excitations, which comprise a mixture of dispersive spin waves propagating from
the magnetic Bragg peaks and resonance modes centered at equal energy steps of
4.5 meV. We interpret these as acoustic and optical spin wave branches, but
show that the neutron scattering cross sections of transitions within a unit of
two corner-sharing tetrahedra match the observed intensity distribution of the
resonances. The distinctive fingerprint of cluster-like excitations in the
optical spin wave branches suggests that propagating excitations are localized
by the complex crystal structure and magnetic orders.",1803.01703v1
2019-08-29,Pushing down the lateral dimension of single and coupled magnetic dots to the nanometric scale: characteristics and evolution of the spin-wave eigenmodes,"Planar magnetic nanoelements, either single- or multi-layered, are exploited
in a variety of current or forthcoming spintronic and/or ICT devices, such as
read heads, magnetic memory cells, spin-torque nano-oscillators, nanomagnetic
logic circuits, magnonic crystals and artificial spin-ices. The lateral
dimensions of the elemental magnetic components have been squeezed down during
the last decade to a few tens of nanometers, but they are still an order of
magnitude larger that the exchange correlation length of the constituent
materials. This means that the spectrum of spin-wave eigenmodes, occurring in
the GHz range, is relatively complex and cannot be described within a simple
macrospin approximation. On the other hand, a detailed knowledge of the
dynamical spectrum is needed to understand or to predict crucial
characteristics of the devices. With this focused review we aim at the analysis
and the rationalization of the characteristics of the eigenmodes spectrum of
magnetic nanodots, paying special attention to the following key points: (i)
Consider and compare the case of in-plane and out of-plane orientation of the
magnetization, as well as of single- and multi-layered dots, putting in
evidence similarities and diversities, and proposing a unifying nomenclature
and labelling scheme; (ii) Underline the evolution of the spectrum when the
lateral size of magnetic dots is squeezed down from hundreds to tens of
nanometers, as in current devices, with emphasis given to the occurrence of
soft modes and to the change of spatial localization of the fundamental mode
for in-plane magnetized dots; (iii) Extend the analysis from isolated elements
to twins of dots, as well as to dense arrays of dipolarly interacting dots,
showing how the discretized eigenmodes distinctive of the single element
transform in finite-width frequency bands of spin waves propagating through the
array.",1908.11098v1
2020-04-30,Black hole genealogy: Identifying hierarchical mergers with gravitational waves,"In dense stellar environments, the merger products of binary black hole
mergers may undergo additional mergers. These hierarchical mergers are
predicted to have higher masses than the first generation of black holes made
from stars. The components of hierarchical mergers are expected to have
significant characteristic spins $\chi\sim 0.7$. However, since the population
properties of first-generation black holes are uncertain, it is difficult to
know if any given merger is first-generation or hierarchical. We use
observations of gravitational waves to reconstruct the binary black hole mass
and spin spectrum of a population containing hierarchical merger events. We
employ a phenomenological model that captures the properties of merging binary
black holes from simulations of dense stellar environments. Inspired by recent
work on the isolated formation of low-spin black holes, we include a zero-spin
subpopulation. We analyze binary black holes from LIGO and Virgo's first two
observing runs, and find that this catalog is consistent with having no
hierarchical mergers. We find that the most massive system in this catalog,
GW170729, is mostly likely a first-generation merger, having a $4\%$
probability of being a hierarchical merger assuming a $5 \times 10^5 M_{\odot}$
globular cluster mass. Using our model, we find that $99\%$ of first-generation
black holes in coalescing binaries have masses below 44 $M_{\odot}$, and the
fraction of binaries with near-zero spin is $0.051^{+0.156}_{-0.048}$ ($90\%$
credible interval). Upcoming observations will determine if hierarchical
mergers are a common source of gravitational waves.",2005.00023v3
2020-06-28,Avoided quasiparticle decay and enhanced excitation continuum in the spin-1/2 near-Heisenberg triangular antiferromagnet Ba3CoSb2O9,"We explore the magnetic excitations of the spin-1/2 triangular
antiferromagnet Ba3CoSb2O9 in its 120 degree ordered phase using single-crystal
high-resolution inelastic neutron scattering. Sharp magnons with no decay are
observed throughout reciprocal space, with a strongly renormalized dispersion
and multiple soft modes compared to linear spin wave theory. We propose an
empirical parametrization that can quantitatively capture the complete
dispersions in the three-dimensional Brillouin zone and explicitly show that
the dispersion renormalizations have the direct consequence that one to two
magnon decays are avoided throughout reciprocal space, whereas such decays
would be allowed for the unrenormalized dispersions. At higher energies, we
observe a very strong continuum of excitations with highly-structured intensity
modulations extending up at least 4x the maximum one-magnon energy. The
one-magnon intensities decrease much faster upon increasing energy than
predicted by linear spin wave theory and the higher-energy continuum contains
much more intensity than can be accounted for by a two-magnon cross-section,
suggesting a significant transfer of spectral weight from the high-energy
magnons into the higher-energy continuum states. We attribute the strong
dispersion renormalizations and substantial transfer of spectral weight to
continuum states to the effect of quantum fluctuations and interactions beyond
the spin wave approximation, and make connections to theoretical approaches
that might capture such effects. Finally, through measurements in a strong
applied magnetic field, we find evidence for magnetic domains with opposite
senses for the spin rotation in the 120 degree ordered ground state, as
expected in the absence of Dzyaloshinskii-Moriya interactions, when the sense
of spin rotation is selected via spontaneous symmetry breaking.",2006.15554v1
2020-12-11,Antiferromagnetic Kitaev interaction in $J_\rm{eff}=1/2$ cobalt honeycomb materials Na$_3$Co$_2$SbO$_6$ and Na$_2$Co$_2$TeO$_6$,"Finding new materials with antiferromagnetic (AFM) Kitaev interaction is an
urgent issue to broaden and enrich the quantum magnetism research
significantly. By carrying out inelastic neutron scattering experiments and
subsequent analysis, we conclude that Na$_3$Co$_2$SbO$_6$ and
Na$_2$Co$_2$TeO$_6$ are new honeycomb cobalt-based AFM Kitaev systems. The
spin-orbit excitons at 20-28~meV in both compounds strongly supports the idea
that Co$^{2+}$ ions of both compounds have a spin-orbital entangled
$J_\rm{eff}=1/2$ state. Furthermore, we found that a generalized
Kitaev-Heisenberg Hamiltonian can well describe the spin-wave excitations of
both compounds with additional 3rd nearest-neighbor interaction. Our best-fit
parameters show large AFM Kitaev terms and off-diagonal symmetric anisotropy
terms of a similar magnitude in both compounds. We should stress that our
parameters' optimized magnetic structures are consistent with the magnetic
structures reported from neutron diffraction studies. Moreover, there is also
the magnon-damping effect at the higher energy part of the spin waves, as
usually observed in other Kitaev magnets. We demonstrate that
Na$_3$Co$_2$SbO$_6$ and Na$_2$Co$_2$TeO$_6$ are the first experimental
realization of AFM Kitaev magnets based on the systematic studies of the spin
waves and analysis.",2012.06167v3
2021-09-01,Influence of Rashba spin-orbit and Rabi couplings on the miscibility and ground state phases of binary Bose-Einstein condensates,"We study the miscibility properties and ground state phases of two-component
spin-orbit (SO) coupled Bose-Einstein condensates (BECs) in a harmonic trap
with strong axial confinement. By numerically solving the coupled
Gross-Pitaevskii equations in the two-dimensional setting, we analyze the
SO-coupled BECs for two possible permutations of the intra- and interspecies
interactions, namely (i) weak intra- and weak interspecies interactions (W-W)
and (ii) weak intra- and strong interspecies interactions (W-S). Considering
the density overlap integral as a miscibility order parameter, we investigate
the miscible-immiscible transition by varying the coupling parameters. We
obtain various ground state phases, including plane wave, half quantum vortex,
elongated plane wave, and different stripe wave patterns for W-W interactions.
For finite Rabi coupling, an increase in SO coupling strength leads to the
transition from the fully miscible to the partially miscible state. We also
characterize different ground states in the coupling parameter space using the
root mean square sizes of the condensate. The spin density vector for the
ground state phases exhibits density, quadrupole and dipole like spin
polarizations. For the W-S interaction, in addition to that observed in the W-W
case, we witness semi vortex, mixed mode, and shell-like immiscible phases. We
notice a wide variety of spin polarizations, such as density, dipole,
quadrupole, symbiotic, necklace, and stripe-like patterns for the W-S case. A
detailed investigation in the coupling parameter space indicates immiscible to
miscible state phase transition upon varying the Rabi coupling for a fixed
Rashba SO coupling. The critical Rabi coupling for the immiscible-miscible
phase transition decreases upon increasing the SO coupling strength.",2109.00491v1
2023-04-21,Operators of quantum theory of Dirac's free field,"The quantum theory of free Dirac's massive fermions is reconstructed around
the new conserved spin operator and its corresponding position one proposed
initially by Pryce long time ago and re-defined recently with the help of a new
spin symmetry and suitable spectral representations. [I. I. Cot\u{a}escu, Eur.
Phys. J. C (2022) 82:1073]. This approach is generalized here defining the
operator action in passive mode, associating to any integral operator in
configuration representation a pair of integral operators acting directly on
particle and antiparticle wave spinors in momentum representation instead on
the mode spinors. This framework allows an effective quantization procedure
giving a large set of one-particle operators with physical meaning as the spin
and orbital parts of the isometry generators, the Pauli-Lubanski and position
operators or other spin-type operators proposed so far. A special attention is
paid to the operators which mix the particle and antiparticle sectors whose
off-diagonal associated operators have oscillating terms producing
zitterbevegung. The principal operators of this type including the usual
coordinate operator are derived here for the first time. As an application, it
is shown that an apparatus measuring these new observables may prepare and
detect one-particle wave-packets moving uniformly without zitterbewegung or
spin dynamics, spreading in time normally as any other relativistic even
non-relativistic wave-packet.",2304.12182v7
2020-03-06,Characterizing the continuous gravitational-wave signal from boson clouds around Galactic isolated black holes,"Ultralight bosons can form large clouds around stellar-mass black holes via
the superradiance instability. Through processes such as annihilation, these
bosons can source continuous gravitational wave signals with frequencies within
the range of LIGO and Virgo. If boson annihilation occurs, then the Galactic
black hole population will give rise to many gravitational signals; we refer to
this as the ensemble signal. We characterize the ensemble signal as observed by
the gravitational-wave detectors; this is important because the ensemble signal
carries the primary signature that a continuous wave signal has a boson
annihilation origin. We explore how a broad set of black hole population
parameters affects the resulting spin-0 boson annihilation signal and consider
its detectability by recent searches for continuous gravitational waves. A
population of $10^8$ black holes with masses up to $30\mathrm{M}_\odot$ and a
flat dimensionless initial spin distribution between zero and unity produces up
to a thousand signals loud enough to be in principle detected by these
searches. For a more moderately spinning population the number of signals drops
by about an order of magnitude, still yielding up to a hundred detectable
signals for some boson masses. A non-detection of annihilation signals at
frequencies between 100 and 1200 Hz disfavors the existence of scalar bosons
with rest energies between $2\times10^{-13}$ and $2.5\times10^{-12}$ eV.
Finally we show that, depending on the black hole population parameters, care
must be taken in assuming that the continuous wave upper limits from searches
for isolated signals are still valid for signals that are part of a dense
ensemble: Between 200 and 300 Hz, we urge caution when interpreting a null
result for bosons between 4 and $6\times10^{-13}$ eV.",2003.03359v2
2021-09-08,Persistent gravitational wave observables: Curve deviation in asymptotically flat spacetimes,"In the first paper in this series, a class of observables that generalized
the gravitational wave memory effect were introduced and given the name
""persistent gravitational wave observables."" These observables are all nonlocal
in time, nonzero in spacetimes with gravitational radiation, and have an
observable effect that persists after the gravitational waves have passed. In
this paper, we focus on the persistent observable known as ""curve deviation,""
and we compute the observable using the Bondi-Sachs approach to asymptotically
flat spacetimes at the leading, nontrivial order in inverse Bondi radius. The
curve deviation is related to the final separation of two observers who have an
initial separation, initial relative velocity, and relative acceleration. The
displacement gravitational wave memory effect is the part of the curve
deviation that depends on the initial separation and is the entire contribution
for initially comoving, inertial observers at large Bondi radius. The spin and
center-of-mass memory effects are contained within the dependence of the curve
deviation on the initial relative velocity, and the dependence of the curve
deviation on relative acceleration contains observables distinct from these
known memory effects. We find that the full curve deviation observable can be
written in terms of differences in nonradiative data before and after the
radiation (which we call the ""charge"" contribution), along with a nonlinear
""flux"" contribution that vanishes in the absence of gravitational radiation.
This splitting generalizes the notion of ""ordinary"" and ""null"" memory that
exists for the displacement, spin, and center-of-mass gravitational wave memory
effects to the full curve deviation observable.",2109.03832v3
2021-09-16,Gravitational waves from deformed neutron stars: mountains and tides,"With the remarkable advent of gravitational-wave astronomy, we have shed
light on previously shrouded events: compact binary coalescences. Neutron stars
are promising (and confirmed) sources of gravitational radiation and it proves
timely to consider the ways in which these stars can be deformed. Gravitational
waves provide a unique window through which to examine neutron-star interiors
and learn more about the equation of state of ultra-dense nuclear matter. In
this work, we study two relevant scenarios for gravitational-wave emission:
neutron stars that host (non-axially symmetric) mountains and neutron stars
deformed by the tidal field of a binary partner. Although they have yet to be
seen with gravitational waves, rotating neutron stars have long been considered
potential sources. By considering the observed spin distribution of accreting
neutron stars with a phenomenological model for the spin evolution, we find
evidence for gravitational radiation in these systems. We study how mountains
are modelled in both Newtonian and relativistic gravity and introduce a new
scheme to resolve issues with previous approaches to this problem. The crucial
component of this scheme is the deforming force that gives the star its
non-spherical shape. We find that the force (which is a proxy for the star's
formation history), as well as the equation of state, plays a pivotal role in
supporting the mountains. Considering a scenario that has been observed with
gravitational waves, we calculate the structure of tidally deformed neutron
stars, focusing on the impact of the crust. We find that the effect on the
tidal deformability is negligible, but the crust will remain largely intact up
until merger.",2109.07858v2
2023-04-30,Methods and prospects for gravitational wave searches targeting ultralight vector boson clouds around known black holes,"Ultralight bosons are predicted in many extensions to the Standard Model and
are popular dark matter candidates. The black hole superradiance mechanism
allows for these particles to be probed using only their gravitational
interaction. In this scenario, an ultralight boson cloud may form spontaneously
around a spinning black hole and extract a non-negligible fraction of the black
hole's mass. These oscillating clouds produce quasi-monochromatic,
long-duration gravitational waves that may be detectable by ground-based or
space-based gravitational wave detectors. We discuss the capability of a new
long-duration signal tracking method, based on a hidden Markov model, to detect
gravitational wave signals generated by ultralight vector boson clouds,
including cases where the signal frequency evolution timescale is much shorter
than that of a typical continuous wave signal. We quantify the detection
horizon distances for vector boson clouds with current- and next-generation
ground-based detectors. We demonstrate that vector clouds hosted by black holes
with mass $\gtrsim 60 M_{\odot}$ and spin $\gtrsim 0.6$ are within the reach of
current-generation detectors up to a luminosity distance of $\sim 1$ Gpc. This
search method enables one to target vector boson clouds around remnant black
holes from compact binary mergers detected by gravitational-wave detectors. We
discuss the impact of the sky localization of the merger events and demonstrate
that a typical remnant black hole reasonably well-localized by the current
generation detector network is accessible in a follow-up search.",2305.00401v2
2023-06-27,Physics-inspired spatiotemporal-graph AI ensemble for gravitational wave detection,"We introduce a novel method for gravitational wave detection that combines:
1) hybrid dilated convolution neural networks to accurately model both short-
and long-range temporal sequential information of gravitational wave signals;
and 2) graph neural networks to capture spatial correlations among
gravitational wave observatories to consistently describe and identify the
presence of a signal in a detector network. These spatiotemporal-graph AI
models are tested for signal detection of gravitational waves emitted by
quasi-circular, non-spinning and quasi-circular, spinning, non-precessing
binary black hole mergers. For the latter case, we needed a dataset of 1.2
million modeled waveforms to densely sample this signal manifold. Thus, we
reduced time-to-solution by training several AI models in the Polaris
supercomputer at the Argonne Leadership Supercomputing Facility within 1.7
hours by distributing the training over 256 NVIDIA A100 GPUs, achieving optimal
classification performance. This approach also exhibits strong scaling up to
512 NVIDIA A100 GPUs. We then created ensembles of AI models to process data
from a three detector network, namely, the advanced LIGO Hanford and Livingston
detectors, and the advanced Virgo detector. An ensemble of 2 AI models achieves
state-of-the-art performance for signal detection, and reports seven
misclassifications per decade of searched data, whereas an ensemble of 4 AI
models achieves optimal performance for signal detection with two
misclassifications for every decade of searched data. Finally, when we
distributed AI inference over 128 GPUs in the Polaris supercomputer and 128
nodes in the Theta supercomputer, our AI ensemble is capable of processing a
decade of gravitational wave data from a three detector network within 3.5
hours.",2306.15728v1
2016-03-22,Meaning of the nuclear wave function,"Background The intense current experimental interest in studying the
structure of the deuteron and using it to enable accurate studies of neutron
structure motivate us to examine the four-dimensional space-time nature of the
nuclear wave function, and the various approximations used to reduce it to an
object that depends only on three spatial variables.
  Purpose: The aim is to determine if the ability to understand and analyze
measured experimental cross sections is compromised by making the reduction
from four to three dimensions.
  Method: Simple, exactly-calculable, covariant models of a bound-state wave
state wave function (a scalar boson made of two constituent-scalar bosons) with
parameters chosen to represent a deuteron are used to investigate the accuracy
of using different approximations to the nuclear wave function to compute the
quasi-elastic scattering cross section. Four different versions of the wave
function are defined (light-front spectator, light-front, light-front with
scaling and non-relativistic) and used to compute the cross sections as a
function of how far off the mass-shell (how virtual) is the struck constituent.
  Results: We show that making an exact calculation of the quasi-elastic
scattering cross section involves using the light-front spectator wave
function. All of the other approaches fail to reproduce the model exact
calculation if the value of Bjorken $x$ differs from unity. The model is
extended to consider an essential effect of spin to show that constituent
nucleons cannot be treated as being on their mass shell even when taking the
matrix element of a `good' current.
  Conclusions: It is necessary to develop realistic light-front spectator wave
functions to meet the needs of current and planned experiments.",1603.07032v1
2016-12-23,Validating gravitational-wave detections: The Advanced LIGO hardware injection system,"Hardware injections are simulated gravitational-wave signals added to the
Laser Interferometer Gravitational-wave Observatory (LIGO). The detectors' test
masses are physically displaced by an actuator in order to simulate the effects
of a gravitational wave. The simulated signal initiates a control-system
response which mimics that of a true gravitational wave. This provides an
end-to-end test of LIGO's ability to observe gravitational waves. The
gravitational-wave analyses used to detect and characterize signals are
exercised with hardware injections. By looking for discrepancies between the
injected and recovered signals, we are able to characterize the performance of
analyses and the coupling of instrumental subsystems to the detectors' output
channels. This paper describes the hardware injection system and the recovery
of injected signals representing binary black hole mergers, a stochastic
gravitational wave background, spinning neutron stars, and sine-Gaussians.",1612.07864v1
2020-02-02,A millimeter-wave Bell Test using a ferrite parametric amplifier and a homodyne interferometer,"A combined ferrite parametric amplifier and millimeter-wave homodyne
interferometer are proposed as an ambient temperature Bell Test. It is shown
that the non-linear magnetic susceptibility of the yttrium iron garnet (YIG)
ferrite, on account of its narrow line-width Larmor precessional resonance,
make it an ideal material for the creation of entangled photons. These can be
measured using a homodyne interferometer, as the much larger number of
thermally generated photons associated with ambient temperature emission can be
screened out. The proposed architecture may enable YIG quantum technology-based
sensors to be developed, mimicking in the millimeter-wave band the large number
of quantum optical experiments in the near-infrared and visible regions which
had been made possible by use of the nonlinear beta barium borate
ferroelectric, an analogue of YIG. It is illustrated here how the YIG
parametric amplifier can reproduce quantum optical Type I and Type II wave
interactions, which can be used to create entangled photons in the
millimeter-wave band. It is estimated that when half a cubic centimeter of YIG
crystal is placed in a magnetic field of a few Tesla and pumped with 5 Watts of
millimeter-wave radiation, approximately 0.5x10^12 entangled millimeter-wave
photon pairs per second are generated by the spin-wave interaction. This means
an integration time of only a few tens of seconds is needed for a successful
Bell Test. A successful demonstration of this will lead to novel architectures
of entanglement-based quantum technology room temperature sensors,
re-envisioning YIG as a modern quantum material.",2002.00439v3
2021-06-03,Highly Accelerated EPI with Wave Encoding and Multi-shot Simultaneous Multi-Slice Imaging,"We introduce wave encoded acquisition and reconstruction techniques for
highly accelerated echo planar imaging (EPI) with reduced g-factor penalty and
image artifacts. Wave-EPI involves playing sinusoidal gradients during the EPI
readout while employing interslice shifts as in blipped-CAIPI acquisitions.
This spreads the aliasing in all spatial directions, thereby taking better
advantage of 3D coil sensitivity profiles. The amount of voxel spreading that
can be achieved by the wave gradients during the short EPI readout period is
constrained by the slew rate of the gradient coils and peripheral nerve
stimulation (PNS) monitor. We propose to use a half-cycle sinusoidal gradient
to increase the amount of voxel spreading that can be achieved while respecting
the slew and stimulation constraints. Extending wave-EPI to multi-shot
acquisition minimizes geometric distortion and voxel blurring at high in-plane
resolution, while structured low-rank regularization mitigates shot-to-shot
phase variations without additional navigators. We propose to use different
point spread functions (PSFs) for the k-space lines with positive and negative
polarities, which are calibrated with a FLEET-based reference scan and allow
for addressing gradient imperfections. Wave-EPI provided whole-brain
single-shot gradient echo (GE) and multi-shot spin echo (SE) EPI acquisitions
at high acceleration factors and was combined with g-Slider slab encoding to
boost the SNR level in 1mm isotropic diffusion imaging. Relative to
blipped-CAIPI, wave-EPI reduced average and maximum g-factors by up to 1.21-
and 1.37-fold, respectively. In conclusion, wave-EPI allows highly accelerated
single- and multi-shot EPI with reduced g-factor and artifacts and may
facilitate clinical and neuroscientific applications of EPI by improving the
spatial and temporal resolution in functional and diffusion imaging.",2106.01918v1
2007-04-06,Quantum and Classical Spins on the Spatially Distorted Kagome Lattice: Applications to Volborthite,"In Volborthite, spin-1/2 moments form a distorted Kagom\'e lattice, of corner
sharing isosceles triangles with exchange constants $J$ on two bonds and $J'$
on the third bond. We study the properties of such spin systems, and show that
despite the distortion, the lattice retains a great deal of frustration.
Although sub-extensive, the classical ground state degeneracy remains very
large, growing exponentially with the system perimeter. We consider degeneracy
lifting by thermal and quantum fluctuations. To linear (spin wave) order, the
degeneracy is found to stay intact. Two complementary approaches are therefore
introduced, appropriate to low and high temperatures, which point to the same
ordered pattern. In the low temperature limit, an effective chirality
Hamiltonian is derived from non-linear spin waves which predicts a transition
on increasing $J'/J$, from $\sqrt 3\times \sqrt 3$ type order to a new
ferrimagnetic {\em striped chirality} order with a doubled unit cell. This is
confirmed by a large-N approximation on the O($n$) model on this lattice. While
the saddle point solution produces a line degeneracy, $O(1/n)$ corrections
select the non-trivial wavevector of the striped chirality state. The quantum
limit of spin 1/2 on this lattice is studied via exact small system
diagonalization and compare well with experimental results at intermediate
temperatures. We suggest that the very low temperature spin frozen state seen
in NMR experiments may be related to the disconnected nature of classical
ground states on this lattice, which leads to a prediction for NMR line shapes.",0704.0933v2
2013-10-09,Electron doping evolution of the magnetic excitations in BaFe2-xNixAs2,"We use inelastic neutron scattering (INS) spectroscopy to study the magnetic
excitations spectra throughout the Brioullion zone in electron-doped iron
pnictide superconductors BaFe$_{2-x}$Ni$_{x}$As$_{2}$ with $x=0.096,0.15,0.18$.
While the $x=0.096$ sample is near optimal superconductivity with $T_c=20$ K
and has coexisting static incommensurate magnetic order, the $x=0.15,0.18$
samples are electron-overdoped with reduced $T_c$ of 14 K and 8 K,
respectively, and have no static antiferromagnetic (AF) order. In previous INS
work on undoped ($x=0$) and electron optimally doped ($x=0.1$) samples, the
effect of electron-doping was found to modify spin waves in the parent compound
BaFe$_2$As$_2$ below $\sim$100 meV and induce a neutron spin resonance at the
commensurate AF ordering wave vector that couples with superconductivity. While
the new data collected on the $x=0.096$ sample confirms the overall features of
the earlier work, our careful temperature dependent study of the resonance
reveals that the resonance suddenly changes its $Q$-width below $T_c$ similar
to that of the optimally hole-doped iron pnictides
Ba$_{0.67}$K$_{0.33}$Fe$_2$As$_2$. In addition, we establish the dispersion of
the resonance and find it to change from commensurate to transversely
incommensurate with increasing energy. Upon further electron-doping to
overdoped iron pnictides with $x=0.15$ and 0.18, the resonance becomes weaker
and transversely incommensurate at all energies, while spin excitations above
$\sim$100 meV are still not much affected. Our absolute spin excitation
intensity measurements throughout the Brillouin zone for $x=0.096,0.15,0.18$
confirm the notion that the low-energy spin excitation coupling with itinerant
electron is important for superconductivity in these materials, even though the
high-energy spin excitations are weakly doping dependent.",1310.2333v1
2014-09-17,"The momentum and photon energy dependence of the circular dichroic photoemission in the bulk Rashba semiconductors BiTeX (X = I, Br, Cl)","Bulk Rashba systems BiTeX (X = I, Br, Cl) are emerging as important
candidates for developing spintronics devices, because of the coexistence of
spin-split bulk and surface states, along with the ambipolar character of the
surface charge carriers. The need of studying the spin texture of strongly
spin-orbit coupled materials has recently promoted circular dichroic Angular
Resolved Photoelectron Spectroscopy (cd-ARPES) as an indirect tool to measure
the spin and the angular degrees of freedom. Here we report a detailed photon
energy dependent study of the cd-ARPES spectra in BiTeX (X = I, Br and Cl). Our
work reveals a large variation of the magnitude and sign of the dichroism.
Interestingly, we find that the dichroic signal modulates differently for the
three compounds and for the different spin-split states. These findings show a
momentum and photon energy dependence for the cd-ARPES signals in the bulk
Rashba semiconductor BiTeX (X = I, Br, Cl). Finally, the outcome of our
experiment indicates the important relation between the modulation of the
dichroism and the phase differences between the wave-functions involved in the
photoemission process. This phase difference can be due to initial or final
state effects. In the former case the phase difference results in possible
interference effects among the photo-electrons emitted from different atomic
layers and characterized by entangled spin-orbital polarized bands. In the
latter case the phase difference results from the relative phases of the
expansion of the final state in different outgoing partial waves.",1409.5025v1
2016-01-11,Systematic errors in low latency gravitational wave parameter estimation impact electromagnetic follow-up observations,"Among the most eagerly anticipated opportunities made possible by Advanced
LIGO/Virgo are multimessenger observations of compact mergers. Optical
counterparts may be short-lived so rapid characterization of gravitational wave
(GW) events is paramount for discovering electromagnetic signatures. One way to
meet the demand for rapid GW parameter estimation is to trade off accuracy for
speed, using waveform models with simplified treatment of the compact objects'
spin. We report on the systematic errors in GW parameter estimation suffered
when using different spin approximations to recover generic signals. Component
mass measurements can be biased by $>5\sigma$ using simple-precession waveforms
and in excess of $20\sigma$ when non-spinning templates are employed. This
suggests that electromagnetic observing campaigns should not take a strict
approach to selecting which LIGO/Virgo candidates warrant follow-up
observations based on low-latency mass estimates. For sky localization, we find
searched areas are up to a factor of ${\sim}$2 larger for non-spinning
analyses, and are systematically larger for any of the simplified waveforms
considered in our analysis. Distance biases for the non-precessing waveforms
can be in excess of 100\% and are largest when the spin angular momenta are in
the orbital plane of the binary. We confirm that spin-aligned waveforms should
be used for low-latency parameter estimation at the minimum. Including simple
precession, though more computationally costly, mitigates biases except for
signals with extreme precession effects. Our results shine a spotlight on the
critical need for development of computationally inexpensive precessing
waveforms and/or massively parallel algorithms for parameter estimation.",1601.02661v2
2012-09-05,Hubbard-model description of the high-energy spin-spectral-weight distribution in La(2)CuO(4),"The spectral-weight distribution in recent neutron scattering experiments on
the parent compound La$_2$CuO$_4$ (LCO), which are limited in energy range to
about 450\,meV, is studied in the framework of the Hubbard model on the square
lattice with effective nearest-neighbor transfer integral $t$ and on-site
repulsion $U$. Our study combines a number of numerical and theoretical
approaches, including, in addition to standard treatments, density matrix
renormalization group calculations for Hubbard cylinders and a suitable spinon
approach for the spin excitations. Our results confirm that the $U/8t$
magnitude suitable to LCO corresponds to intermediate $U$ values smaller than
the bandwidth $8t$, which we estimate to be $8t \approx 2.36$ eV for
$U/8t\approx 0.76$. This confirms the unsuitability of the conventional linear
spin-wave theory. Our theoretical studies provide evidence for the occurrence
of ground-state d-wave spinon pairing in the half-filled Hubbard model on the
square lattice. This pairing applies only to the rotated-electron spin degrees
of freedom, but it could play a role in a possible electron d-wave pairing
formation upon hole doping. We find that the higher-energy spin spectral weight
extends to about 566 meV and is located at and near the momentum $[\pi,\pi]$.
The continuum weight energy-integrated intensity vanishes or is extremely small
at momentum $[\pi,0]$. This behavior of this intensity is consistent with that
of the spin waves observed in recent high-energy neutron scattering
experiments, which are damped at the momentum $[\pi,0]$. We suggest that future
LCO neutron scattering experiments scan the energies between 450 meV and 566
meV and momenta around $[\pi,\pi]$.",1209.1010v1
2017-06-20,Gravitational wave searches for ultralight bosons with LIGO and LISA,"Ultralight bosons can induce superradiant instabilities in spinning black
holes, tapping their rotational energy to trigger the growth of a bosonic
condensate. Possible observational imprints of these boson clouds include (i)
direct detection of the nearly monochromatic (resolvable or stochastic)
gravitational waves emitted by the condensate, and (ii) statistically
significant evidence for the formation of ""holes"" at large spins in the spin
versus mass plane (sometimes also referred to as ""Regge plane"") of
astrophysical black holes. In this work, we focus on the prospects of LISA and
LIGO detecting or constraining scalars with mass in the range $m_s\in
[10^{-19},\,10^{-15}]$ eV and $m_s\in [10^{-14},\,10^{-11}]$ eV, respectively.
Using astrophysical models of black-hole populations calibrated to observations
and black-hole perturbation theory calculations of the gravitational emission,
we find that, in optimistic scenarios, LIGO could observe a stochastic
background of gravitational radiation in the range $m_s\in [2\times 10^{-13},
10^{-12}]$ eV, and up to $10^4$ resolvable events in a $4$-year search if
$m_s\sim 3\times 10^{-13}\,{\rm eV}$. LISA could observe a stochastic
background for boson masses in the range $m_s\in [5\times 10^{-19}, 5\times
10^{-16}]$, and up to $\sim 10^3$ resolvable events in a $4$-year search if
$m_s\sim 10^{-17}\,{\rm eV}$. LISA could further measure spins for black-hole
binaries with component masses in the range $[10^3, 10^7]~M_\odot$, which is
not probed by traditional spin-measurement techniques. A statistical analysis
of the spin distribution of these binaries could either rule out scalar fields
in the mass range $\sim [4 \times 10^{-18}, 10^{-14}]$ eV, or measure $m_s$
with ten percent accuracy if light scalars in the mass range $\sim [10^{-17},
10^{-13}]$ eV exist.",1706.06311v2
2017-10-04,Abraham-based momentum and spin of optical fields under conditions of total reflection,"This memo contains a collection of formulas describing the electromagnetic
energy, momentum and spin distribution of an optical field formed in dielectric
media separated by a plane interface when an incident monochromatic plane wave
is totally reflected. The formulas are based on the Abraham momentum definition
and include the momentum decomposition into the orbital (canonical) and spin
parts as well as explicit dual-symmetric separation of the electric and
magnetic contributions. This material was prepared in February 2013 but it had
not been finalized and published because of the difficulties in physical
interpretation of singular terms in the spin and orbital momentum expressions
associated with the sharp interface. Meanwhile, it has become clear that the
""naive"" Abraham approach is not correct for this problem and the
electromagnetic spin and momentum in inhomogeneous media are better
characterized by the more elaborated relations based on the Minkowski paradigm
[see, e.g., Phys. Rev. A 83, 013823 (2011); 86, 055802 (2012);
arXiv:1706.05493]. In application to the total-reflection situation this
Minkowski-based description was recently illustrated in arXiv:1706.06263, so
the present material is mainly of historical interest. However, it seems useful
to make it known for a wide audience, at least for comparison with the recent
improved approaches and for suitable references. The last section, treating the
ponderomotive action experienced by a Mie particle in the evanescent wave, is
independent of the Abraham - Minkowski controversy. The numerical calculations
preserve their validity, and association of the various force and torque
components with corresponding components of the optical momentum and spin
remains legal in the Minkowski pattern. The results of the last section were
partly used in other published works [e.g., Nature Commun. 5, 3300 (2014)].",1710.01561v2
2018-04-09,The exact dynamical Chern Simons metric for a spinning black hole possesses a fourth constant of motion: A Dynamical-Systems-Based Conjecture,"The recent gravitational wave observations by the LIGO/Virgo collaboration
have allowed the first tests of General Relativity in the extreme gravity
regime, when comparable-mass black holes and neutron stars collide. Future
space-based detectors, such as the Laser Interferometer Space Antenna, will
allow tests of Einstein's theory with gravitational waves emitted when a small
black hole falls into a supermassive one in an extreme mass-ratio inspiral. One
particular test that is tailor-made for such inspirals is the search for chaos
in extreme gravity. We here study whether chaos is present in the motion of
test particles around spinning black holes of parity-violating modified
gravity, focusing in particular on dynamical Chern-Simons gravity. We develop a
resummation strategy that restores all spin terms in the General Relativity
limit, while retaining up to fifth-order-in-spin terms in the dynamical
Chern-Simons corrections to the Kerr metric. We then calculate Poincar\'e
surfaces of section and rotation numbers of a wide family of geodesics of this
resummed metric. We find no evidence for geodesic chaos, with at most
deformations of the resonant torii that shrink as terms of higher-order in spin
are included in the dynamical Chern-Simons corrections to the Kerr metric. Our
numerical findings suggest that the geodesics of the as-of-yet unknown exact
solution for spinning black holes in this theory may be integrable, and that
there may thus exist a fourth integral of motion associated with this exact
solution. The studies presented here begin to lay the foundations for chaotic
tests of General Relativity with the observation of extreme mass ratio
inspirals with the Laser Interferometer Space Antenna.",1804.04002v2
2020-09-28,"Magnetic-field dependence of low-energy magnons, anisotropic heat conduction, and spontaneous relaxation of magnetic domains in the cubic helimagnet ZnCr2Se4","Anisotropic low-temperature properties of the cubic spinel helimagnet
ZnCr2Se4 in the single-domain spin-spiral state are investigated by a
combination of neutron scattering, thermal conductivity, ultrasound velocity,
and dilatometry measurements. In an applied magnetic field, neutron
spectroscopy shows a complex and nonmonotonic evolution of the spin-wave
spectrum across the quantum-critical point that separates the spin-spiral phase
from the field-polarized ferromagnetic phase at high fields. A tiny spin gap of
the pseudo-Goldstone magnon mode, observed at wave vectors that are
structurally equivalent but orthogonal to the propagation vector of the spin
helix, vanishes at this quantum critical point, restoring the cubic symmetry in
the magnetic subsystem. The anisotropy imposed by the spin helix has only a
minor influence on the lattice structure and sound velocity but has a much
stronger effect on the heat conductivities measured parallel and perpendicular
to the magnetic propagation vector. The thermal transport is anisotropic at T <
2 K, highly sensitive to an external magnetic field, and likely results
directly from magnonic heat conduction. We also report long-time thermal
relaxation phenomena, revealed by capacitive dilatometry, which are due to
magnetic domain motion related to the destruction of the single-domain magnetic
state, initially stabilized in the sample by the application and removal of
magnetic field. Our results can be generalized to a broad class of helimagnetic
materials in which a discrete lattice symmetry is spontaneously broken by the
magnetic order.",2009.13424v1
2020-11-17,Black hole-neutron star coalescence: effects of the neutron star spin on jet launching and dynamical ejecta mass,"Black hole-neutron star (BHNS) mergers are thought to be sources of
gravitational waves (GWs) with coincident electromagnetic (EM) counterparts. To
further probe whether these systems are viable progenitors of short gamma-ray
bursts (sGRBs) and kilonovae, and how one may use (the lack of) EM counterparts
associated with LIGO/Virgo candidate BHNS GW events to sharpen parameter
estimation, we study the impact of neutron star spin in BHNS mergers. Using
dynamical spacetime magnetohydrodynamic simulations of BHNSs initially on a
quasicircular orbit, we survey configurations that differ in the BH spin
($a_{\rm BH}/M_{\rm BH}=0$ and $0.75$), the NS spin ($a_{\rm NS}/M_{\rm
NS}=-0.17,\,0,\,0.23$ and $0.33$), and the binary mass ratio ($q\equiv M_{\rm
BH}:M_{\rm NS}=3:1$ and $5:1$). The general trend we find is that increasing
the NS prograde spin increases both the rest mass of the accretion disk onto
the remnant black hole, and the rest mass of dynamically ejected matter. By a
time~$\Delta t\sim 3500-5500M\sim 88-138(M_{\rm NS}/1.4M_\odot)\,\rm ms$ after
the peak gravitational wave amplitude, a magnetically--driven jet is launched
only for $q=3:1$ regardless of the initial NS spin. The lifetime of the jets
[$\Delta t\sim 0.5-0.8(M_{\rm NS}/1.4 M_\odot)\,\rm s$] and their outgoing
Poynting luminosity [$L_{\rm Poyn}\sim 10^{51.5\pm 0.5}\,\rm erg/s$] are
consistent with typical sGRBs luminosities and expectations from the
Blandford-Znajek mechanism. By the time we terminate our simulations, we do not
observe either an outflow or a large-scale magnetic field collimation for the
other systems we considered. The mass range of dynamically ejected matter is
$10^{-4.5}-10^{-2}~(M_{\rm NS}/1.4M_\odot)M_\odot$, which can power kilonovae
with peak bolometric luminosities $L_{\rm knova}\sim 10^{40}-10^{41.4}$ erg/s
with rise times $\lesssim 6.5\,\rm h$ and potentially detectable by the LSST.",2011.08863v2
2020-11-25,Noncoplanar multiple-$Q$ spin textures by itinerant frustration: Effects of single-ion anisotropy and bond-dependent anisotropy,"We theoretically investigate multiple-$Q$ spin textures, which are composed
of superpositions of spin density waves with different wave numbers, for an
effective spin model of centrosymmetric itinerant magnets. Our focus is on the
interplay between biquadratic interactions arising from the spin-charge
coupling and magnetic anisotropy caused by the spin-orbit coupling. Taking into
account two types of the magnetic anisotropy, single-ion anisotropy and
bond-dependent anisotropy, we elucidate magnetic phase diagrams for an
archetypal triangular-lattice system in the absence and presence of an external
magnetic field. In the case of the single-ion anisotropy, we find a plethora of
multiple-$Q$ instabilities depending on the strength and the sign of the
anisotropy (easy plane or easy axis), including a skyrmion crystal with
topological number of two. In an external magnetic field, we find that a
skyrmion crystal with topological number of one is stabilized by the in-plane
(out-of-plane) magnetic field under the easy-plane (easy-axis) anisotropy. We
also examine the stability of the field-induced skyrmion crystal by rotating
the field direction. As a biproduct, we show that a triple-$Q$ state with
nonzero chirality appears in the presence of the biquadratic interaction and
the easy-axis anisotropy. Meanwhile, we find that the bond-dependent anisotropy
also stabilizes both types of skyrmion crystals. We show that, however, for the
skyrmion crystal with topological number of one, Bloch- and N\'eel-type
skyrmion crystals are selectively realized depending on the sign of the
bond-dependent anisotropy. Moreover, we find yet another multiple-$Q$ states,
including two types of meron crystals with the skyrmion numbers of one and two.
The systematic investigation will provide a reference to complex magnetic
textures in centrosymmetric magnetic metals.",2011.13040v2
2020-07-14,Excitations in the spin-1 trimer chain compound CaNi3P4O14: gapped dispersive spinwaves to gapless magnetic excitations,"Magnetic excitations and the spin Hamiltonian of the spin-1 J1-J1-J2 trimer
chain compound CaNi3P4O14 have been investigated by inelastic neutron
scattering. Experimental data reveal gapped dispersive spin wave excitations in
the 3D long-range ordered magnetic state (TC = 16 K), and gapless magnetic
excitations above the TC. Simulated magnetic excitations, by using the linear
spin wave theory, for a model of coupled trimer spin-chains provide a good
description of the observed experimental data. The analysis reveals both
ferromagnetic J1 and J2 interactions within the chains, and an
antiferromagnetic interchain interaction J3 between chains. The strengths of
the J1 and J2 are found to be closer (J2/J1 ~ 0.81), and J3 is determined to be
weaker (J3/ J1 ~ 0.69), which is consistent with the spin chain type crystal
structure. Presence of a weak single-ion-anisotropy (D/J=0.19) is also
revealed. The strengths and signs of exchange interactions explain why the 1/3
magnetization is absent in the studied spin-1 compound CaNi3P4O14 in contrast
to its S= 5/2 counterpart Mn based isostructural compound. The signs of the
exchange interactions are in agreement with that obtained from the reported DFT
calculations, whereas, their strengths are found to be significantly different.
The relatively strong value of the J3 in CaNi3P4O14 gives a conventional 3D
type magnetic ordering below the TC, however, retains its 1D character above
the TC. The present experimental study also reveals a sharp change of
single-ion anisotropy across the TC indicating that the stability of the 3D
magnetic ordering in CaNi3P4O14 is ascribed to the local magnetic anisotropy in
addition to interchain interactions. The present study divulges the importance
of full knowledge of the exchange interactions in trimer spin chain compounds
to understand their exotic magnetic properties, such as 1/3 magnetization
plateau.",2007.07233v1
2021-03-28,Magnetic field-induced softening of spin waves and hard-axis order in Kondo-lattice ferromagnet CeAgSb$_{2}$,"A significant number of Kondo-lattice ferromagnets order perpendicular to the
easy magnetization axis dictated by the crystalline electric field. The nature
of this phenomenon has attracted considerable attention, but remains poorly
understood. In the present paper we use inelastic neutron scattering supported
by magnetization and specific heat measurements to study the spin dynamics in
the hard-axis ferromagnet CeAgSb2. In the zero field state we observed two
sharp magnon modes, which are associated with Ce ordering and extended up to
$\approx 3 meV with a considerable spin gap of 0.6 meV. Application of a
magnetic field perpendicular to the moment direction reduces the spectral
intensity and suppresses the gap and significantly enhances the low-temperature
specific heat at a critical field of Bc ~ 2.8 T via a mean-field-like
transition. Above the transition, in the field polarized state, the gap
eventually reopens due to the Zeeman effect. We modeled the observed dispersion
using linear spin-wave theory (LSWT) taking into account the ground state Gamma
6 doublet and exchange anisotropy. Our model correctly captures the essential
features of the spin dynamics including magnetic dispersion, distribution of
the spectral intensity as well as the field-induced behavior, although several
minor features remain obscure. The observed spectra do not show significant
broadening due to the finite lifetime of the quasiparticles. Along with a
moderate electronic specific heat coefficient gamma = 46 mJ/mol K2 this
indicates that the Kondo coupling is relatively weak and the Ce moments are
well localized. Altogether, our results provide profound insight into the spin
dynamics of the hard-axis ferromagnet CeAgSb2 and can be used as solid ground
for studying magnetic interactions in isostructural compounds including
CeAuSb2, which exhibits nematicity and unusual mesoscale magnetic textures.",2103.15137v2
2022-06-25,Can Convolution Neural Networks Be Used for Detection of Gravitational Waves from Precessing Black Hole Systems?,"Current searches for gravitational waves from black hole binaries with LIGO
and Virgo observatories are limited to using the analytical models computed for
the systems with spins of the black holes aligned with the orbital angular
momentum of the binary. The observation of black hole binaries with precessing
spins (spins misaligned with the orbital angular momentum) could provide unique
astrophysical insights into the formation of these sources; thus, it is crucial
to design a search scheme to detect compact binaries with precession spins. It
has been shown that the detection of compact binaries carrying precessing spins
is not achievable with aligned-spins template waveforms. Efforts have been made
to construct the template banks to detect the precessing binaries using the
matched filtering based detection pipelines. However, in the absence of robust
methods and huge computational requirements, the precessing searches, more or
less, still remain a challenge. This work introduces a detection scheme for the
binary black holes to classify them into aligned and precessing systems using a
convolution neural network (\CNN). We treat the detection of the $\GW$ signals
from $\BBH$ systems as a classification problem. Our architecture first
classifies data as $\GW$ signals originated from binary black holes ($\BBH$) or
noise and then it further classifies the detected $\BBH$ systems as precessing
or non-precessing (aligned/anti-aligned) systems. Our classifier with an
accuracy of $\approx$ 99\% classifies between noise and the signal and with an
accuracy of $\approx$ 91\% it classifies the detected signals into aligned and
precessing signals. We have also extended our analysis for a multi-detector
framework and tested the performance of our designed architecture on $\O1$,
$\O2$ and $\O3$ data to identify the detected $\BBH$ events as aligned and
precessing events.",2206.12673v1
2023-08-09,Inferring spin tilts of binary black holes at formation with plus-era gravitational wave detectors,"The spin orientations of spinning binary black hole (BBH) mergers detected by
ground-based gravitational wave detectors such as LIGO and Virgo can provide
important clues about the formation of such binaries. However, these spin
tilts, i.e., the angles between the spin vector of each black hole and the
binary's orbital angular momentum vector, can change due to precessional
effects as the black holes evolve from a large separation to their merger. The
tilts inferred at a frequency in the sensitive band of the detectors by
comparing the signal with theoretical waveforms can thus be significantly
different from the tilts when the binary originally formed. These tilts at the
binary's formation are well approximated in many scenarios by evolving the BBH
backwards in time to a formally infinite separation. Using the tilts at
infinite separation also places all binaries on an equal footing in analyzing
their population properties. In this paper, we perform parameter estimation for
simulated BBHs and investigate the differences between the tilts one infers
directly close to merger and those obtained by evolving back to infinite
separation. We select simulated observations such that their configurations
show particularly large differences in their orientations close to merger and
at infinity. While these differences may be buried in the statistical noise for
current detections, we show that in future plus-era (A$+$ and Virgo$+$)
detectors, they can be easily distinguished in some cases. We also consider the
tilts at infinity for BBHs in various spin morphologies and at the endpoint of
the up-down instability. In particular, we find that we are able to easily
identify the up-down instability cases as such from the tilts at infinity.",2308.05098v2
2023-09-23,Origin of spin-driven ferroelectricity and effect of external pressure on the complex magnetism of 6H-perovskite Ba3HoRu2O9,"The compound Ba3HoRu2O9 magnetically orders at 50 K (TN1) followed by another
complex magnetic ordering at 10 K (TN2). The 2nd magnetic phase transition was
characterized by the co-existence of two competing magnetic ground states
associated with two different magnetic wave vectors (K1=1/2 0 0 and K2=1/4 1/4
0). We have investigated the compound through time-of-flight neutron
diffraction, ac susceptibility, complex dielectric spectroscopy, and
magnetization under external pressure. We demonstrate that the non-colinear
structure involving two different magnetic ions, Ru(4d) and Ho(4f), breaks the
spatial inversion symmetry via inverse Dzyaloshinskii-Moriya (D-M) interaction
through strong4d-4f magnetic correlation, which shifts the oxygen atoms and
results in non-zero polarization. Such an observation of inverse D-M
interaction from two different magnetic spins ions which caused
ferroelectricity is rarely observed. The stronger spin-orbit coupling of
4d-orbital might play a major role in creating D-M interaction of non-collinear
spins. We have systematically studied the spin and dipolar dynamics, which
exhibit intriguing behavior with shorter coherence lengths of 2nd magnetic
phase associated with the K2-wave vector. The results manifest the development
of magnetoelectric domains instead of true long-range ordering which justifies
the experimentally obtained low value of ferroelectric polarization. Further,
we have investigated the effect of external pressure on this complex magnetism.
The result reveals an enhancement of ordering temperature by the application of
external pressure (1.6K/GPa). The external pressure might favor stabilizing the
ground state associated with 2nd magnetic phase. Our study shows an
unconventional mechanism of spin-driven ferroelectricity involving inverse D-M
interaction between Ru(4d) and Ho(4f) magnetic ions due to strong 4d-4f
cross-coupling.",2309.13465v3
2023-11-14,Spin vestigial orders in extended Heisenberg-Kitaev models near hidden SU(2) points: Application to Na$_2$Co$_2$TeO$_6$,"The honeycomb magnet Na$_2$Co$_2$TeO$_6$ has recently been argued to realize
an approximate hidden SU(2) symmetry that can be understood by means of a
duality transformation. Using large-scale classical Monte Carlo simulations, we
study the finite-temperature phase diagram of the pertinent
Heisenberg-Kitaev-$\Gamma$-$\Gamma'$ model near the hidden-SU(2)-symmetric
point, in the presence of a six-spin ring exchange perturbation. At low
temperatures, the model features collinear single-$\mathbf{q}$ zigzag and
noncollinear triple-$\mathbf{q}$ ground states, depending on the sign of the
ring exchange coupling. We show that in the vicinity of the
hidden-SU(2)-symmetric point, the magnetic long-range orders melt in two
stages. The corresponding finite-temperature transitions are continuous and
fall into 2D Ising and 2D Potts universality classes, respectively. The two
fluctuation-induced phases at intermediate temperatures spontaneously break
spin rotational and lattice translational symmetries, respectively, but both
leave time reversal symmetry intact. They are characterized by finite
expectation values of a real, symmetric, traceless, second-rank tensor, and are
naturally understood as vestigial orders of the underlying magnetic states. We
identify these vestigial orders as $\mathbb{Z}_3$ spin nematic and
$\mathbb{Z}_4$ spin current density wave phases, respectively. For increasing
ring exchange perturbations, the width of the vestigial phases decreases,
eventually giving rise to a direct first-order transition from the
magnetically-ordered phase to the disordered paramagnet. We propose the
$\mathbb{Z}_4$ spin current density wave phase, which is the vestigial phase of
the primary triple-$\mathbf q$ magnetic order, as a natural candidate for the
paramagnetic 2D long-range-ordered state observed in Na$_2$Co$_2$TeO$_6$ in a
small window above the antiferromagnetic ordering temperature.",2311.08475v2
2004-10-06,Golden Binary Gravitational-Wave Sources: Robust Probes of Strong-Field Gravity,"Space-born gravitational-wave interferometers such as {\it LISA} will detect
the gravitational wave (GW) signal from the inspiral, plunge and ringdown
phases of massive black hole binary mergers at cosmological distances. From the
inspiral waves, we will be able to measure the masses of the binaries' members;
from the ringdown waves, we will be able to measure the mass of the final
merged remnant. A subset of detected events allow the identification of both
the inspiral and the ringdown waveforms in a given source, and thus allow a
measurement of the total mass-energy lost to GWs over the coalescence, $M_{\rm
GW}$. We define ``golden'' binary mergers to be those with measurement errors
likely to be small enough for a physically useful determination of $M_{\rm
GW}$. A detailed sensitivity study, combined with simple black hole population
models, suggests that a few golden binary mergers may be detected during a
3-year {\it LISA} mission lifetime. Any such mass deficit measurement would
constitute a robust and valuable observational test of strong-field
relativistic gravity. An extension of this concept to include spin measurements
may allow a direct empirical test of the black hole area theorem.",0410148v2
1995-07-01,One-Dimensional t-J Model from a Variational Viewpoint,"The one-dimensional (1D) $t$-$J$ model is investigated by using a
Gutzwiller-Jastrow-type variation method and the exact diagonalization of small
systems. Variational expectation values are estimated by the variational Monte
Carlo method with sufficient accuracy. First, we represent the diagonalization
results. Physical quantities like momentum distribution and some correlation
functions show some behaviors which are not expected in repulsive models, as
the value of $J/t$ increases. These properties as well as energy are well
understood by introducing intersite correlation factors into wave functions.
The phase transition to a separated phase in large-$J/t$ region can be
described by an attractive Jastrow wave function in quantitative agreement with
the exact results. On the other hand, for the supersymmetric case ($J/t=2$) the
original Gutzwiller wave function becomes an extremely good trial function for
all the range of electron density. Here a kind of \lq\lq free electron"" state
is realized, particularly in the low electron density. Next, the above wave
functions are compared with the Tomonaga-Luttinger-liquid-type wave function
proposed by Hellberg and Mele. It is found that the correlation factors in
short distances control bulk quantities like energy and the magnitude of
correlation functions, while the long-range part of correlataion factors
determines the critical behavior of correlation functions. Lastly, using these
functions, charge and spin susceptibilities and magnetization curve are
estimated, which agree with the exact results. It is shown that the Mott
transition in 1D $t$-$J$ model is quite different from the Brinkman-Rice
transition.",9506142v1
2005-10-27,Superconducting pairing and density-wave instabilities in quasi-one-dimensional conductors,"Using a renormalization group approach, we determine the phase diagram of an
extended quasi-one-dimensional electron gas model that includes interchain
hopping, nesting deviations and both intrachain and interchain repulsive
interactions. d-wave superconductivity, which dominates over the
spin-density-wave (SDW) phase at large nesting deviations, becomes unstable to
the benefit of a triplet $f$-wave phase for a weak repulsive interchain
backscattering term $g_1^\perp>0$, despite the persistence of dominant SDW
correlations in the normal state. Antiferromagnetism becomes unstable against
the formation of a charge-density-wave state when $g_1^\perp$ exceeds some
critical value. While these features persist when both Umklapp processes and
interchain forward scattering ($g_2^\perp$) are taken into account, the effect
of $g_2^\perp$ alone is found to frustrate nearest-neighbor interchain $d$- and
$f$-wave pairing and instead favor next-nearest-neighbor interchain singlet or
triplet pairing. We argue that the close proximity of SDW and
charge-density-wave phases, singlet d-wave and triplet $f$-wave superconducting
phases in the theoretical phase diagram provides a possible explanation for
recent puzzling experimental findings in the Bechgaard salts, including the
coexistence of SDW and charge-density-wave phases and the possibility of a
triplet pairing in the superconducting phase.",0510744v1
1997-03-27,Hierarchical search strategy for the detection of gravitational waves from coalescing binaries: Extension to post-Newtonian wave forms,"The detection of gravitational waves from coalescing compact binaries would
be a computationally intensive process if a single bank of template wave forms
(i.e., a one step search) is used. In an earlier paper we had presented a
detection strategy, called a two step search}, that utilizes a hierarchy of
template banks. It was shown that in the simple case of a family of Newtonian
signals, an on-line two step search was about 8 times faster than an on-line
one step search (for initial LIGO). In this paper we extend the two step search
to the more realistic case of zero spin 1.5 post-Newtonian wave forms. We also
present formulas for detection and false alarm probabilities which take
statistical correlations into account. We find that for the case of a 1.5
post-Newtonian family of templates and signals, an on-line two step search
requires about 1/21 the computing power that would be required for the
corresponding on-line one step search. This reduction is achieved when signals
having strength S = 10.34 are required to be detected with a probability of
0.95, at an average of one false event per year, and the noise power spectral
density used is that of advanced LIGO. For initial LIGO, the reduction achieved
in computing power is about 1/27 for S = 9.98 and the same probabilities for
detection and false alarm as above.",9703081v1
2002-05-29,Nongeodesic motion of spinless particles in the teleparallel gravitational wave background,"The motion of spinless particles in Riemann-Cartan (RC) $U_{4}$ and
teleparallel spacetimes is revisited on the light of gravitational waves
hitting on the spinless test particles. It is shown that in the case Cartan
contortion is totally skew-symmetric the spinless particles follow geodesics
but if this symmetry is dropped they are able to follow nongeodesic worldlines
in torsionic background. The case of totally skew contortion and spinning
particles may appear either in $T_{4}$ or $U_{4}$ spacetimes. We consider
$T_{4}$ nongeodesic motion of spinless test particles in the field of
gravitational waves (GW). It is shown that the general contortion obeys a
tensor wave constraint and the analysis of a ring of spinless test particles as
in General Relativity (GR) hit by the GW leads to damping contortion effects on
the nongeodesic motion is undertaken. It is also shown that the contortion and
gravitational waves possess a difference of phase of $\frac{\pi}{2}$ and a
contortion at the surface of the Earth of $10^{-24} s^{-1}$ computed by Nitsch
in the realm of teleparallelism is used to obtain a deviation of the lenght of
the separation of test spinless particles compatible with the GR result. To
obtain this result data from GW LISA detector is used.",0205120v1
2002-09-30,Energy-Momentum and Angular Momentum Carried by Gravitational Waves in Extended New General Relativity,"In an extended, new form of general relativity, which is a teleparallel
theory of gravity, we examine the energy-momentum and angular momentum carried
by gravitational wave radiated from Newtonian point masses in a weak-field
approximation. The resulting wave form is identical to the corresponding wave
form in general relativity, which is consistent with previous results in
teleparallel theory. The expression for the dynamical energy-momentum density
is identical to that for the canonical energy-momentum density in general
relativity up to leading order terms on the boundary of a large sphere
including the gravitational source, and the loss of dynamical energy-momentum,
which is the generator of \emph{internal} translations, is the same as that of
the canonical energy-momentum in general relativity. Under certain asymptotic
conditions for a non-dynamical Higgs-type field $\psi^{k}$, the loss of
``spin'' angular momentum, which is the generator of \emph{internal} $SL(2,C)$
transformations, is the same as that of angular momentum in general relativity,
and the losses of canonical energy-momentum and orbital angular momentum, which
constitute the generator of Poincar\'{e} \emph{coordinate} transformations, are
vanishing. The results indicate that our definitions of the dynamical
energy-momentum and angular momentum densities in this extended new general
relativity work well for gravitational wave radiations, and the extended new
general relativity accounts for the Hulse-Taylor measurement of the pulsar
PSR1913+16.",0209114v1
2005-03-10,Dimensional regularization of the third post-Newtonian gravitational wave generation from two point masses,"Dimensional regularization is applied to the computation of the gravitational
wave field generated by compact binaries at the third post-Newtonian (3PN)
approximation. We generalize the wave generation formalism from isolated
post-Newtonian matter systems to d spatial dimensions, and apply it to point
masses (without spins), modelled by delta-function singularities. We find that
the quadrupole moment of point-particle binaries in harmonic coordinates
contains a pole when epsilon = d-3 -> 0 at the 3PN order. It is proved that the
pole can be renormalized away by means of the same shifts of the particle
world-lines as in our recent derivation of the 3PN equations of motion. The
resulting renormalized (finite when epsilon -> 0) quadrupole moment leads to
unique values for the ambiguity parameters xi, kappa and zeta, which were
introduced in previous computations using Hadamard's regularization. Several
checks of these values are presented. These results complete the derivation of
the gravitational waves emitted by inspiralling compact binaries up to the
3.5PN level of accuracy which is needed for detection and analysis of the
signals in the gravitational-wave antennas LIGO/VIRGO and LISA.",0503044v1
1996-12-17,A New View of the Universe,"A new, very different physical model of the universe is proposed. Its virtues
include unifying relativity and quantum mechanics, and particles with de
Broglie waves. It also appears to provide a truly unified physical basis for
electromagnetic, gravitational and nuclear forces. The basic system is a
four-dimensional Euclidean space, containing an array of nonlinear ""flow""
waves. These repeat in one dimension, called [phi]. As in Newtonian mechanics,
time is treated as an additional, unidirectional parameter describing the
evolution of the system. Nevertheless, this wave system is shown be inherently
relativistic. Further self-organizing patterns arise within the overall wave
structure. Called ""wavicles,"" these have intrinsic quantized fields, ""spin,""
and rest energy, and represent elementary particles. Relativistic expressions
are derived for particle behavior in scalar, vector and gravitational
potentials. Proper representations of these potentials, based on the wave
fields and associated [phi] flows of wavicles, are also obtained. As in the
causal quantum mechanics of de Broglie and Bohm, wavicles exist continuously
and follow definite, stochastic trajectories. Although experimentally
equivalent to Einstein's special relativity, this theory differs fundamentally
from his general relativity and the associated Big Bang model. According to
Linde, the latter predict a large-scale space-time curvature roughly 60 orders
of magnitude greater than observed values. Here a flat large-scale geometry is
predicted, in agreement with the observed distribution of galaxies. This theory
is also consistent with recent observations pertaining to the age of the
universe.",9612010v1
2008-02-14,"Spiky strings, light-like Wilson loops and pp-wave anomaly","We consider rigid rotating closed strings with spikes in AdS5 dual to certain
higher twist operators in N=4 SYM theory. In the limit of large spin when the
spikes reach the boundary of AdS5, the solutions with different numbers of
spikes are related by conformal transformations, implying that their energy is
determined by the same function of the `t Hooft coupling f(lambda) that appears
in the anomalous dimension of twist 2 operators or in the cusp anomaly. In the
limit when the number of spikes goes to infinity, we find an equivalent
description in terms of a string moving in an AdS pp-wave background. From the
boundary theory point of view, the corresponding description is based on the
gauge theory living in a 4d pp-wave space. Then, considering a charge moving at
the speed of light, or a null Wilson line, we find that the integrated energy
momentum tensor has a logarithmic UV divergence whose coefficient we call the
""pp-wave anomaly"". The AdS/CFT correspondence implies that, for N=4 SYM, this
pp-wave anomaly should have the same value as the cusp anomaly. We verify this
at lowest order in SYM perturbation theory. As a side result of our string
theory analysis, we find new open string solutions in the Poincare patch of the
standard AdS space which end on a light-like Wilson line and also in two
parallel light-like Wilson lines at the boundary.",0802.2039v2
2009-02-25,Improved estimate of the detectability of gravitational radiation from a magnetically confined mountain on an accreting neutron star,"We give an improved estimate of the detectability of gravitational waves from
magnetically confined mountains on accreting neutron stars. The improved
estimate includes the following effects for the first time: three-dimensional
hydromagnetic (""fast"") relaxation, three-dimensional resistive (""slow"")
relaxation, realistic accreted masses $M_a \la 2 \times 10^{-3} M_\odot$,
(where the mountain is grown ab initio by injection), and verification of the
curvature rescaling transformation employed in previous work. Typically, a
mountain does not relax appreciably over the lifetime of a low-mass X-ray
binary. The ellipticity reaches $\epsilon \approx 2 \times 10^{-5}$ for
$M_a=2\times 10^{-3} M_\odot$. The gravitational wave spectrum for triaxial
equilibria contains an additional line, which, although weak, provides valuable
information about the mountain shape. We evaluate the detectability of magnetic
mountains with Initial and Advanced LIGO. For a standard, coherent matched
filter search, we find a signal-to-noise ratio of $d = 28 (M_a/10^{-4} M_\odot)
  (1+5.5 M_a/10^{-4} M_\odot)^{-1} (D/10 \mathrm{kpc})^{-1} (T_0/14
  \mathrm{d})^{1/2}$ for Initial LIGO, where $D$ is the distance and $T_0$ is
the observation time. From the nondetection of gravitational waves from
low-mass X-ray binaries to date, and the wave strain limits implied by the spin
frequency distribution of these objects (due to gravitational wave braking), we
conclude that there are other, as yet unmodelled, physical effects that further
reduce he quadrupole moment of a magnetic mountain, most notably sinking into
the crust.",0902.4264v1
2009-11-09,Gravitational Radiation from Hydrodynamic Turbulence in a Differentially Rotating Neutron Star,"(Abridged.) The mean-square current quadrupole moment associated with
vorticity fluctuations in high-Reynolds-number turbulence in a differentially
rotating neutron star is calculated analytically, as are the amplitude and
decoherence time of the resulting, stochastic gravitational wave signal. The
calculation resolves the subtle question of whether the signal is dominated by
the smallest or largest turbulent eddies: for the Kolmogorov-like power
spectrum observed in superfluid spherical Couette simulations, the wave strain
is controlled by the largest eddies, and the decoherence time approximately
equals the maximum eddy turnover time. For a neutron star with spin frequency
$\nu_s$ and Rossby number $Ro$, at a distance $d$ from Earth, the
root-mean-square wave strain reaches $h_{RMS} \approx 3\times 10^{-24} Ro^3
(\nu_s / 30 Hz)^3 (d/1 kpc)^{-1}$. A cross-correlation search can detect such a
source in principle, because the signal decoheres over the time-scale $\tau_c
\approx 10^{-3} Ro^{-1} (\nu_s / 30 Hz)^{-1} s$, which is adequately sampled by
existing long-baseline interferometers. Hence hydrodynamic turbulence imposes a
fundamental noise floor on gravitational wave observations of neutron stars,
although its polluting effect may be muted by partial decoherence in the
hectohertz band, where current continuous-wave searches are concentrated, for
the highest frequency (and hence most powerful) sources.",0911.1609v1
2009-12-02,Wave packet dynamics in hole Luttinger systems,"For hole systems with an effective spin 3/2 we analyzed analytically and
numerically the evolution of wave packets with the different initial
polarizations. The dynamics of such systems is determined by the $4\times 4$
Luttinger Hamiltonian. We work in the space of arbitrary superposition of
light- and heavy-hole states of the ""one-particle system"". For 2D packets we
obtained the analytical solution for the components of wave function and
analyzed the space-time dependence of probability densities as well as angular
momentum densities. Depending on the value of the parameter $a=k_0d$ ($k_0$ is
the average momentum vector and $d$ is the packet width) two scenarios of
evolution are realized. For $a>>1$ the initial wave packet splits into two
parts and the coordinates of packet center experience the transient
oscillations or {\it Zitterbewegung} (ZB) as for other two-band systems. In the
case when $a<<1$ the distribution of probability density at $t>0$ remains
almost cylindrically symmetric and the ripples arise at the circumference of
wave packet. The ZB in this case is absent. We evaluated and visualized for
different values of parameter $a$ the space-time dependence of angular momentum
densities, which have the multipole structure. It was shown that the average
momentum components can precess in the absence of external or effective
magnetic fields due to the interference of the light- and heavy hole states.
For localized initial states this precession has a transient character.",0912.0331v1
2010-01-13,"Group theoretical study of nonstrange and strange mixed symmetric baryon states $[N_c-1,1]$ in the $1/N_c$ expansion","Using group theory arguments we extend and complete our previous work by
deriving all SU(6) exact wave functions associated to the spectrum of mixed
symmetric baryon states $[N_c-1,1]$ in the $1/N_c$ expansion. The extension to
SU(6) enables us to study the mass spectra of both strange and nonstrange
baryons, while previous work was restricted to nonstrange baryons described by
SU(4). The wave functions are specially written in a form to allow a comparison
with the approximate, customarily used wave functions, where the system is
separated into a ground state core and an excited quark. We show that the
matrix elements of the flavor operator calculated with the exact wave functions
acquire the same asymptotic form at large $N_c$, irrespective of the
spin-flavor multiplet contained in $[N_c-1,1]$, while with the approximate wave
function one cannot obtain a similar behaviour. The isoscalar factors of the
permutation group of $N_c$ particles derived here can be used in any problem
where a given fermion system is described by the partition $[N_c-1,1]$, and one
fermion has to be separated from the rest.",1001.2214v2
2011-02-24,Suitability of post-Newtonian/numerical-relativity hybrid waveforms for gravitational wave detectors,"This article presents a study of the sufficient accuracy of post-Newtonian
and numerical relativity waveforms for the most demanding usage case: parameter
estimation of strong sources in advanced gravitational wave detectors. For
black hole binaries, these detectors require accurate waveform models which can
be constructed by fusing an analytical post-Newtonian inspiral waveform with a
numerical relativity merger-ringdown waveform. We perform a comprehensive
analysis of errors that enter such ""hybrid waveforms"". We find that the
post-Newtonian waveform must be aligned with the numerical relativity waveform
to exquisite accuracy, about 1/100 of a gravitational wave cycle. Phase errors
in the inspiral phase of the numerical relativity simulation must be controlled
to less than about 0.1rad. (These numbers apply to moderately optimistic
estimates about the number of GW sources; exceptionally strong signals require
even smaller errors.) The dominant source of error arises from the inaccuracy
of the investigated post-Newtonian Taylor-approximants. Using our error
criterium, even at 3.5-th post-Newtonian order, hybridization has to be
performed significantly before the start of the longest currently available
numerical waveforms which cover 30 gravitational wave cycles. The current
investigation is limited to the equal-mass, zero-spin case and does not take
into account calibration errors of the gravitational wave detectors.",1102.5128v2
2011-08-15,The gravitational-wave memory from eccentric binaries,"The nonlinear gravitational-wave memory causes a time-varying but
nonoscillatory correction to the gravitational-wave polarizations. It arises
from gravitational waves that are sourced by gravitational waves. Previous
considerations of the nonlinear memory effect have focused on quasicircular
binaries. Here, I consider the nonlinear memory from Newtonian orbits with
arbitrary eccentricity. Expressions for the waveform polarizations and
spin-weighted spherical-harmonic modes are derived for elliptic, hyperbolic,
parabolic, and radial orbits. In the hyperbolic, parabolic, and radial cases
the nonlinear memory provides a 2.5 post-Newtonian (PN) correction to the
leading-order waveforms. This is in contrast to the elliptical and
quasicircular cases, where the nonlinear memory corrects the waveform at
leading (0PN) order. This difference in PN order arises from the fact that the
memory builds up over a short ""scattering"" time scale in the hyperbolic case,
as opposed to a much longer radiation-reaction time scale in the elliptical
case. The nonlinear memory corrections presented here complete our knowledge of
the leading-order (Peters-Mathews) waveforms for elliptical orbits. These
calculations are also relevant for binaries with quasicircular orbits in the
present epoch which had, in the past, large eccentricities. Because the
nonlinear memory depends sensitively on the past evolution of a binary, I
discuss the effect of this early-time eccentricity on the value of the
late-time memory in nearly circularized binaries. I also discuss the
observability of large ""memory jumps"" in a binary's past that could arise from
its formation in a capture process. Lastly, I provide estimates of the
signal-to-noise ratio of the linear and nonlinear memories from hyperbolic and
parabolic binaries.",1108.3121v2
2012-02-21,de Broglie Wavelength and Frequency of the Scattered Electrons in Compton Effect,"The undergraduate courses on modern physics generally consider the particle
interpretation of Compton effect. Motivated by a student's solution in an
undergraduate examination on modern physics here we consider the wave
characteristics of recoiled electrons in the Compton effect. The de Broglie
wavelength, wave and clock frequency of the scattered electrons are expressed
in terms of the wavelength and the frequency of the incident and the scattered
photons respectively using the familiar particle interpretation of the Compton
effect, where initially the electron is at rest and its spin is ignored. Both
non-relativistic and relativistic cases are considered. Numerical values of de
Broglie wavelength, wave and clock frequency of the scattered electron are
calculated for an incident photon energy that was used in the original
experiment of Compton as a function of the scattering angle of the recoiled
electron. Considering the relativistic effects which are however insignificant
for the de Broglie wavelength of the recoiled electron under these conditions,
the minimum value obtained is in the range of X-rays. The non-relativistic de
Broglie wave frequency obtained by neglecting the rest mass of the electron
leads to an underestimation of its value. The implications of de Broglie
wavelength and clock frequency for Compton scattering experiments are briefly
discussed and possible extensions of the obtained mathematical formulations are
indicated. The results are useful for understanding the wave-particle duality
of the recoiled electron in the context of the Compton effect.",1202.4572v4
2013-04-07,Equation-of-state-independent relations in neutron stars,"Neutron stars are extremely relativistic objects which abound in our universe
and yet are poorly understood, due to the high uncertainty on how matter
behaves in the extreme conditions which prevail in the stellar core. It has
recently been pointed out that the moment of inertia I, the Love number lambda
and the spin-induced quadrupole moment Q of an isolated neutron star, are
related through functions which are practically independent of the equation of
state. These surprising universal I-lambda-Q relations pave the way for a
better understanding of neutron stars, most notably via gravitational-wave
emission. Gravitational-wave observations will probe highly-dynamical binaries
and it is important to understand whether the universality of the I-lambda-Q
relations survives strong-field and finite-size effects. We apply a
Post-Newtonian-Affine approach to model tidal deformations in compact binaries
and show that the I-lambda relation depends on the inspiral frequency, but is
insensitive to the equation of state. We provide a fit for the universal
relation, which is valid up to a gravitational wave frequency of ~900 Hz and
accurate to within a few percent. Our results strengthen the universality of
I-lambda-Q relations, and are relevant for gravitational-wave observations with
advanced ground-based interferometers. We also discuss the possibility of using
the Love-compactness relation to measure the neutron-star radius with an
uncertainty of about 10% or smaller from gravitational-wave observations.",1304.2052v2
2013-10-28,Comparison of Gravitational Wave Detector Network Sky Localization Approximations,"Gravitational waves emitted during compact binary coalescences are a
promising source for gravitational-wave detector networks. The accuracy with
which the location of the source on the sky can be inferred from gravitational
wave data is a limiting factor for several potential scientific goals of
gravitational-wave astronomy, including multi-messenger observations. Various
methods have been used to estimate the ability of a proposed network to
localize sources. Here we compare two techniques for predicting the uncertainty
of sky localization -- timing triangulation and the Fisher information matrix
approximations -- with Bayesian inference on the full, coherent data set. We
find that timing triangulation alone tends to over-estimate the uncertainty in
sky localization by a median factor of $4$ for a set of signals from
non-spinning compact object binaries ranging up to a total mass of $20
M_\odot$, and the over-estimation increases with the mass of the system. We
find that average predictions can be brought to better agreement by the
inclusion of phase consistency information in timing-triangulation techniques.
However, even after corrections, these techniques can yield significantly
different results to the full analysis on specific mock signals. Thus, while
the approximate techniques may be useful in providing rapid, large scale
estimates of network localization capability, the fully coherent Bayesian
analysis gives more robust results for individual signals, particularly in the
presence of detector noise.",1310.7454v1
2013-11-04,Multipole Love Relations,"Gravitational-wave observations in the near future may allow us to measure
tidal deformabilities of neutron stars, which leads us to the understanding of
physics at nuclear density. In principle, the gravitational waveform depends on
various tidal parameters, which correlate strongly. Therefore, it would be
useful if one can express such tidal parameters with a single parameter. Here,
we report on universal relations among various $\ell$-th (dimensionless)
electric, magnetic and shape tidal deformabilities in neutron stars and quark
stars that do not depend sensitively on the equation of state. Such relations
allow us to break the degeneracy among the tidal parameters. In this paper, we
focus on gravitational waves from non-spinning neutron-star binary inspirals.
We first derive the leading contribution of the $\ell$-th electric and $\ell=2$
magnetic tidal deformabilities to the gravitational-wave phase, which enters at
$2\ell +1$ and $6$ post-Newtonian orders relative to the leading Newtonian one
respectively. We then calculate the useful number of gravitational-wave cycles
and show that not only the $\ell=2$ but also $\ell=3$ electric tidal
deformabilities are important for parameter estimation with third-generation
gravitational-wave detectors such as LIGO III and Einstein Telescope. Although
the correlation between the $\ell=2$ and $\ell=3$ electric tidal
deformabilities deteriorate the measurement accuracy of the former
deformability parameter, one can increase its measurement accuracy
significantly by using the universal relation. We provide a fitting formula for
the LIGO III noise curve in the Appendix.",1311.0872v4
2014-04-02,Wavefront twisting by rotating black holes: orbital angular momentum generation and phase coherent detection,"In this paper we study wave propagation and scattering near a rotating black
hole. In particular, we assume a coherent emission source near the black hole
and investigate the wavefront distortion as seen by a distant observer. Near
the observer, the propagating wave can be decomposed using the
Laguerre-Gaussian mode basis and its wavefront distortion can be characterized
by the decomposition coefficient. We find that this decomposition spectrum is
symmetric for wave sources located near a Schwarzschild black hole, but is
generically asymmetric if the host black hole is rotating. The spectrum
asymmetry, or the net orbital angular momentum carried by the wave, is
intimately related to the black hole spin and mass, the wave frequency and the
locations of the source and the observer. We present semi-analytical
expressions and numerical results for these parameter-dependences. If the
radiation is temporally coherent, our results show that the secondary images of
the source can be almost as bright as its primary image. In the case of
temporally-incoherent radiation, we show that the non-fundamental spectrum
components could be resolved by spatially-separated telescopes, although that
would be degenerate with the telescope direction. Finally, our results suggest
that the black-hole-induced spectrum asymmetry is generally too weak to be
observed in radio astronomy, even if the observer were located near a caustic
point.",1404.0722v2
2014-08-20,Analytic approach to the edge state of the Kane-Mele Model,"We investigate the edge state of a two-dimensional topological insulator
based on the Kane-Mele model. Using complex wave numbers of the Bloch wave
function, we derive an analytical expression for the edge state localized near
the edge of a semi-infinite honeycomb lattice with a straight edge. For the
comparison of the edge type effects, two types of the edges are considered in
this calculation; one is a zigzag edge and the other is an armchair edge. The
complex wave numbers and the boundary condition give the analytic equations for
the energies and the wave functions of the edge states. The numerical solutions
of the equations reveal the intriguing spatial behaviors of the edge state. We
define an edge-state width for analyzing the spatial variation of the
edge-state wave function. Our results show that the edge-state width can be
easily controlled by a couple of parameters such as the spin-orbit coupling and
the sublattice potential. The parameter dependences of the edge-state width
show substantial differences depending on the edge types. These demonstrate
that, even if the edge states are protected by the topological property of the
bulk, their detailed properties are still discriminated by their edges. This
edge dependence can be crucial in manufacturing small-sized devices since the
length scale of the edge state is highly subject to the edges.",1408.4507v1
2015-02-11,A unified picture of the post-merger dynamics and gravitational wave emission in neutron-star mergers,"We introduce a classification scheme of the post-merger dynamics and
gravitational-wave emission in binary neutron star mergers, after identifying a
new mechanism by which a secondary peak in the gravitational-wave spectrum is
produced. It is caused by a spiral deformation, the pattern of which rotates
slower with respect to the double-core structure in center of the remnant. This
secondary peak is typically well separated in frequency from the secondary peak
produced by a nonlinear interaction between a quadrupole and a quasi-radial
oscillation. The new mechanism allows for an explanation of low-frequency
modulations seen in a number of physical characteristics of the remnant, such
as the central lapse function, the maximum density and the separation between
the two cores. We find empirical relations for both types of secondary peaks
between their gravitational-wave frequency and the compactness of nonrotating
individual neutron stars, that exist for fixed total binary masses. These
findings are derived for equal-mass binaries without intrinsic neutron-star
spin analyzing hydrodynamical simulations without magnetic field effects. Our
classification scheme may form the basis for the construction of detailed
gravitational-wave templates of the post-merger phase. We find that the
quasi-radial oscillation frequency of the remnant decreases with the total
binary mass. For a given merger event our classification scheme may allow to
determine the proximity of the measured total binary mass to the threshold mass
for prompt black hole formation, which can, in turn, yield an estimate of the
maximum neutron-star mass.",1502.03176v2
2015-03-11,Pulsar timing noise and the minimum observation time to detect gravitational waves with pulsar timing arrays,"The sensitivity of pulsar timing arrays to gravitational waves is, at some
level, limited by timing noise. Red timing noise - the stochastic wandering of
pulse arrival times with a red spectrum - is prevalent in slow-spinning pulsars
and has been identified in many millisecond pulsars. Phenomenological models of
timing noise, such as from superfluid turbulence, suggest that the timing noise
spectrum plateaus below some critical frequency, $f_c$, potentially aiding the
hunt for gravitational waves. We examine this effect for individual pulsars by
calculating minimum observation times, $T_{\rm min}(f_c)$, over which the
gravitational wave signal becomes larger than the timing noise plateau. We do
this in two ways: 1) in a model-independent manner, and 2) by using the
superfluid turbulence model for timing noise as an example to illustrate how
neutron star parameters can be constrained. We show that the superfluid
turbulence model can reproduce the data qualitatively from a number of pulsars
observed as part of the Parkes Pulsar Timing Array. We further show how a value
of $f_c$, derived either through observations or theory, can be related to
$T_{\rm min}$. This provides a diagnostic whereby the usefulness of timing
array pulsars for gravitational-wave detection can be quantified.",1503.03298v1
2015-05-28,Genesis of charge orders in high temperature superconductors,"One of the most puzzling facts about cuprate high-temperature superconductors
in the lightly doped regime is the coexistence of uniform superconductivity
and/or antiferromagnetism with many low-energy charge-ordered states in a
unidirectional charge density wave or a bidirectional checkerboard structure.
Recent experiments have discovered that these charge density waves exhibit
different symmetries in their intra-unit-cell form factors for different
cuprate families. Using a renormalized mean-field theory for a well-known,
strongly correlated model of cuprates, we obtain a number of charge-ordered
states with nearly degenerate energies without invoking special features of the
Fermi surface. All of these self-consistent solutions have a pair density wave
intertwined with a charge density wave and sometimes a spin density wave. Most
of these states vanish in the underdoped regime, except for one with a large
d-form factor that vanishes at approximately 19% doping of the holes, as
reported by experiments. Furthermore, these states could be modified to have a
global superconducting order, with a nodal-like density of states at low
energy.",1505.07728v5
2017-08-02,Projected constraints on the dispersion of gravitational waves using advanced ground- and space-based interferometers,"Certain alternative theories of gravity predict that gravitational waves will
disperse as they travel from the source to the observer. The recent binary
black hole observations by Advanced-LIGO have set limits on a modified
dispersion relation from the constraints on their effects on gravitational-wave
propagation. Using an identical modified dispersion, of the form
$E^2=p^2c^2+{\mathbb A}\; p^{\alpha} c^{\alpha}$, where ${\mathbb A}$ denotes
the magnitude of dispersion and $E$ and $p$ are the energy and momentum of the
gravitational wave, we estimate the projected constraints on the modified
dispersion from observations of compact binary mergers by third- generation
ground-based detectors such as the Einstein Telescope and Cosmic Explorer as
well as the space-based detector Laser Interferometer Space Antenna. We find
that third-generation detectors would bound dispersion of gravitational waves
much better than their second-generation counterparts. The Laser Interferometer
Space Antenna, with its extremely good low-frequency sensitivity, would place
stronger constraints than the ground-based detectors for $\alpha \leq 1$,
whereas for $\alpha > 1$, the bounds are weaker. We also study the effect of
the spins of the compact binary constituents on the bounds.",1708.00671v2
2014-06-17,Magnetic catalysis and axionic charge-density-wave in Weyl semimetals,"Three-dimensional Weyl and Dirac semimetals can support a
chiral-symmetry-breaking, fully gapped, charge-density-wave order even for
sufficiently weak repulsive electron-electron interactions, when placed in
strong magnetic fields. In the former systems, due to the natural momentum
space separation of Weyl nodes the ordered phase lacks the translational
symmetry and represents an axionic phase of matter, while that in a Dirac
semimetal (neglecting the Zeeman coupling) is only a trivial insulator. We
present the scaling of this spectral gap for a wide range of subcritical (weak)
interactions as well as that of the diamagnetic susceptibility with the
magnetic field. A similar mechanism for charge-density-wave ordering at weak
coupling is shown to be operative in double and triple-Weyl semimetals, where
the dispersion is linear (quadratic and cubic, respectively) for the z (planar)
component(s) of the momentum. We here also address the competition between the
charge-density-wave and a spin-density-wave orders, both of which breaks the
chiral symmetry and leads to gapped spectrum, and show that at least in the
weak coupling regime the former is energetically favored. The anomalous surface
Hall conductivity, role of topological defects such as axion strings, existence
of one-dimensional gapless dispersive modes along the core of such defects, and
anomaly cancellation through the Callan-Harvey mechanism are discussed.",1406.4501v3
2018-12-13,Single-hole wave function in two dimensions: A case study of the doped Mott insulator,"We study a ground-state ansatz for the single-hole doped $t$-$J$ model in two
dimensions via a variational Monte Carlo (VMC) method. Such a single-hole wave
function possesses finite angular momenta generated by hidden spin currents,
which give rise to a novel ground state degeneracy in agreement with recent
exact diagonalization (ED) and density matrix renormalization group (DMGR)
results. We further show that the wave function can be decomposed into a
quasiparticle component and an incoherent momentum distribution in excellent
agreement with the DMRG results up to an $8\times 8 $ lattice. Such a
two-component structure indicates the breakdown of Landau's one-to-one
correspondence principle, and in particular, the quasiparticle spectral weight
vanishes by a power law in the large sample-size limit. By contrast, turning
off the phase string induced by the hole hopping in the so-called $\sigma\cdot
t\text{-}J$ model, a conventional Bloch-wave wave function with a finite
quasiparticle spectral weight can be recovered, also in agreement with the ED
and DMRG results. The present study shows that a singular effect already takes
place in the single-hole-doped Mott insulator, by which the bare hole is turned
into a non-Landau quasiparticle with translational symmetry breaking.
Generalizations to pairing and finite doping are briefly discussed.",1812.05627v2
2019-06-09,An introduction to astrophysical observables in gravitational wave detections,"Our knowledge and understanding of the Universe is mainly based on
observations of the electromagnetic radiation in a wide range of wavelengths.
Only during the past two decades, new kinds of detectors have been developed,
exploiting other forms of cosmic probes: individual photons with energy above
the GeV, charged particles and antiparticles, neutrinos and, finally,
gravitational waves. These new ``telescopes'' leaded to unexpected
breakthroughs. Years 2016 and 2017 have seen the dawn of the astrophysics and
cosmology with gravitational waves, awarded with the 2017 Nobel Prize. The
events GW150914 (the first black hole-black hole merger) and GW170817 (the
coalescence of two neutron stars, producing a short gamma-ray burst and
follow-up observed by more than 70 observatories on all continents and in
space) represent really milestones in science that every physicist (senior or
in formation) should appreciate.
  In this document, after an accessible discussion on the generation and
propagation of GWs, the key features of observable quantities (the strain, the
GW frequency $\nu_{gw}$, and $\dot \nu_{gw}$) of GW150914 and GW170817 are
discussed using Newtonian physics, dimensional analysis and analogies with
electromagnetic waves. The objective is to show how astrophysical quantities
(the initial and final masses of merging objects, the energy loss, the
distance, their spin) are derived from observables. The results from the fully
general-relativistic analysis published in the two discovery papers are
compared with the output of our simple treatment. Then, some of the outcomes of
GW observations are discussed in terms of multimessenger astrophysics.",1906.03643v1
2020-08-26,Theory of three-magnon interaction in a vortex-state magnetic nanodot,"We use vector Hamiltonian formalism (VHF) to study theoretically three-magnon
parametric interaction (or three-wave splitting) in a magnetic disk existing in
a magnetic vortex ground state. The three-wave splitting in a disk is found to
obey two selection rules: (i) conservation of the total azimuthal number of the
resultant spin-wave modes, and (ii) inequality for the radial numbers of
interacting modes, if the mode directly excited by the driving field is
radially symmetric (i.e. if the azimuthal number of the directly excited mode
is $m = 0$). The selection rule (ii), however, is relaxed in the ""small""
magnetic disks, due to the influence of the vortex core. We also found, that
the efficiency of the three-wave interaction of the directly excited mode
strongly depends on the azimuthal and radial mode numbers of the resultant
modes, that becomes determinative in the case when several splitting channels
(several pairs of resultant modes) simultaneously approximately satisfy the
resonance condition for the splitting. The good agreement of the VHF analytic
calculations with the experiment and micromagnetic simulations proves the
capability of the VHF formalism to predict the actual splitting channels and
the magnitudes of the driving field thresholds for the three-wave splitting.",2008.11812v2
2019-03-10,Semiclassical probability of radiation of twisted photons in the ultrarelativistic limit,"The semiclassical general formula for the probability of radiation of twisted
photons by ultrarelativistic scalar and Dirac particles moving in the
electromagnetic field of a general form is derived. This formula is the analog
of the Baier-Katkov formula for the probability of radiation of one plane wave
photon with the quantum recoil taken into account. The derived formula is used
to describe the radiation of twisted photons by charged particles in undulators
and laser waves. Thus, the general theory of undulator radiation of twisted
photons and radiation of twisted photons in the nonlinear Compton process is
developed with account for the quantum recoil. The explicit formulas for the
probability to record a twisted photon are obtained in these cases. In
particular, we found that the quantum recoil and spin degrees of freedom
increase the radiation probability of twisted photons in comparison with the
formula for scalar particles without recoil. In the range of applicability of
the semiclassical formula, the selection rules for undulator radiation
established in the purely classical framework are not violated. The
manifestation of the blossoming out rose effect in the nonlinear Compton
process in a strong laser wave with circular polarization and in the wiggler
radiation is revealed. Several examples are studied: the radiation of MeV
twisted photons by $180$ GeV electrons in the wiggler; the radiation of twisted
photons by $256$ MeV electrons in strong electromagnetic waves produced by the
CO$_2$ and Ti:Sa lasers; and the radiation of MeV twisted photons by $51.1$ MeV
electrons in the electromagnetic wave generated by the FEL with photon energy
$1$ keV.",1903.04024v1
2020-03-23,Gravitational Waves and Possible Fast Radio Bursts from Axion Clumps,"The axion objects such as axion mini-clusters and axion clouds around
spinning black holes induce parametric resonances of electromagnetic waves
through the axion-photon interaction. In particular, it has been known that the
resonances from the axion with the mass around $10^{-6}$eV may explain the
observed fast radio bursts (FRBs). Here we argue that similar bursts of high
frequency gravitational waves, which we call the fast gravitational wave bursts
(FGBs), are generated from axion clumps with the presence of gravitational
Chern-Simons (CS) coupling. The typical frequency is half of the axion mass,
which in general can range from kHz to GHz. We also discuss the secondary
gravitational wave production associated with FRB, as well as the possible host
objects of the axion clouds, such as primordial black holes with typical masses
around $10^{-5}M_{\odot}$. Future detections of FGBs together with the observed
FRBs are expected to provide more evidence for the axion.",2003.10527v3
2020-03-27,Cross sections for 2-to-1 meson-meson scattering,"We study the processes $K\bar{K} \to \phi$, $\pi D \to D^\ast$, $\pi \bar{D}
\to \bar{D}^\ast$, and the production of $\psi (3770)$, $\psi (4040)$, $\psi
(4160)$, and $\psi (4415)$ mesons in collisions of charmed mesons or charmed
strange mesons. The process of 2-to-1 meson-meson scattering involves a quark
and an antiquark from the two initial mesons annihilating into a gluon and
subsequently the gluon being absorbed by the spectator quark or antiquark.
Transition amplitudes for the scattering process derive from the transition
potential in conjunction with mesonic quark-antiquark wave functions and the
relative-motion wave function of the two initial mesons. We derive these
transition amplitudes in the partial wave expansion of the relative-motion wave
function of the two initial mesons so that parity and total-angular-momentum
conservation are maintained. We calculate flavor and spin matrix elements in
accordance with the transition potential and unpolarized cross sections for the
reactions using the transition amplitudes. Cross sections for the production of
$\psi (4040)$, $\psi (4160)$, and $\psi (4415)$ relate to nodes in their radial
wave functions. We suggest the production of $\psi (4040)$, $\psi (4160)$, and
$\psi (4415)$ as probes of hadronic matter that results from the quark-gluon
plasma created in ultrarelativistic heavy-ion collisions.",2003.12253v2
2020-09-30,Helping restricted Boltzmann machines with quantum-state representation by restoring symmetry,"The variational wave functions based on neural networks have recently started
to be recognized as a powerful ansatz to represent quantum many-body states
accurately. In order to show the usefulness of the method among all available
numerical methods, it is imperative to investigate the performance in
challenging many-body problems for which the exact solutions are not available.
Here, we construct a variational wave function with one of the simplest neural
networks, the restricted Boltzmann machine (RBM), and apply it to a fundamental
but unsolved quantum spin Hamiltonian, the two-dimensional $J_1$-$J_2$
Heisenberg model on the square lattice. We supplement the RBM wave function
with quantum-number projections, which restores the symmetry of the wave
function and makes it possible to calculate excited states. Then, we perform a
systematic investigation of the performance of the RBM. We show that, with the
help of the symmetry, the RBM wave function achieves state-of-the-art accuracy
both in ground-state and excited-state calculations. The study shows a
practical guideline on how we achieve accuracy in a controlled manner.",2009.14777v3
2021-10-15,Search for black hole hyperbolic encounters with gravitational wave detectors,"In recent years, the proposal that there is a large population of primordial
black holes living in dense clusters has been gaining popularity. One natural
consequence of these dense clusters will be that the black holes inside will
gravitationally scatter off each other in hyperbolic encounters, emitting
gravitational waves that can be observed by current detectors. In this paper we
will derive how to compute the gravitational waves emitted by black holes in
hyperbolic orbits, taking into account up to leading order spin effects. We
will then study the signal these waves leave in the network of gravitational
wave detectors currently on Earth. Using the properties of the signal, we will
detail the data processing techniques that can be used to make it stand above
the detector noise. Finally, we will look for these signals from hyperbolic
encounters in the publicly available LIGO-Virgo data. For this purpose we will
develop a two step trigger. The first step of the trigger will be based on
looking for correlations between detectors in the time-frequency domain. The
second step of the trigger will make use of a residual convolutional neural
network, trained with the theoretical predictions for the signal, to look for
hyperbolic encounters. With this trigger we find 8 hyperbolic encounter
candidates in the 15.3 days of public data analyzed. Some of these candidates
are promising, but the total number of candidates found is consistent with the
number of false alarms expected from our trigger.",2110.08000v2
2019-04-23,Generalized coherent-squeezed-state expansion for the quantum Rabi model,"We develop a systematic variational coherent-squeezed-state expansion for the
ground state of the quantum Rabi model, which includes an additional squeezing
effect with comparisons to previous coherent-state approach. For finite large
ratio between the atomic and field frequency, the essential feature of the
ground-state wave function in the super-radiant phase appears, which has a
structure of two delocalized wake packets. The single-peaked wave function with
one coherent-squeezed state works well even around the critical regime,
exhibiting the advantage over the coherent-state method. As the coupling
increases to form strong correlations physics in the vicinity of phase
transition, we develop an improved wave function with a structure of two
Gaussian wave packets, which is a linear superposition of two coherent-squeezed
state. The ground-state energy and the average photon number agree well with
numerical ones even in the strong-correlated regimes, exhibiting a substantial
improvement over the coherent-state expansion. The advantage of the
coherent-squeezed-state expansion lies in the inclusion of the second
coherent-squeezed state and the additional squeezed deformation of the wave
function, providing a useful tool for multi-modes spin-boson coupling systems
of greater complexity.",1904.10178v1
2020-02-07,Recurrent Neural Network Wave Functions,"A core technology that has emerged from the artificial intelligence
revolution is the recurrent neural network (RNN). Its unique sequence-based
architecture provides a tractable likelihood estimate with stable training
paradigms, a combination that has precipitated many spectacular advances in
natural language processing and neural machine translation. This architecture
also makes a good candidate for a variational wave function, where the RNN
parameters are tuned to learn the approximate ground state of a quantum
Hamiltonian. In this paper, we demonstrate the ability of RNNs to represent
several many-body wave functions, optimizing the variational parameters using a
stochastic approach. Among other attractive features of these variational wave
functions, their autoregressive nature allows for the efficient calculation of
physical estimators by providing independent samples. We demonstrate the
effectiveness of RNN wave functions by calculating ground state energies,
correlation functions, and entanglement entropies for several quantum spin
models of interest to condensed matter physicists in one and two spatial
dimensions.",2002.02973v4
2020-02-24,Three-dimensional core-collapse supernova simulations of massive and rotating progenitors,"We present three-dimensional simulations of the core-collapse of massive
rotating and non-rotating progenitors performed with the general relativistic
neutrino hydrodynamics code CoCoNuT-FMT and analyse their explosion properties
and gravitational-wave signals. The progenitor models include Wolf-Rayet stars
with initial helium star masses of $39\,M_{\odot}$ and $20\,M_{\odot}$, and an
$18\,M_{\odot}$ red supergiant. The $39\,M_{\odot}$ model is a rapid rotator,
whereas the two other progenitors are non-rotating. Both Wolf-Rayet models
produce healthy neutrino-driven explosions, whereas the red supergiant model
fails to explode. By the end of the simulations, the explosion energies have
already reached $1.1\times 10^{51}\,\mathrm{erg}$ and $0.6\times
10^{51}\,\mathrm{erg}$ for the $39\,M_{\odot}$ and $20\,M_{\odot}$ model,
respectively. The explosions produce neutron stars of relatively high mass, but
with modest kicks. Due to the alignment of the bipolar explosion geometry with
the rotation axis, there is a relatively small misalignment of $30^\circ$
between the spin and the kick in the $39\,M_{\odot}$ model. In terms of
gravitational-wave signals, the massive and rapidly rotating $39\,M_{\odot}$
progenitor stands out by large gravitational-wave amplitudes that would make it
detectable out to almost 2 Mpc by the Einstein Telescope. For this model, we
find that rotation significantly changes the dependence of the characteristic
gravitational-wave frequency of the f-mode on the proto-neutron star parameters
compared to the non-rotating case. The other two progenitors have considerably
smaller detection distances, despite significant low-frequency emission in the
most sensitive frequency band of current gravitational-wave detectors due to
the standing accretion shock instability in the $18\,M_{\odot}$ model.",2002.10115v1
2021-06-25,The electron mass shift in an intense plane wave,"Upcoming experiments on the interaction of electrons with intense laser
fields are envisaged to become more and more accurate, which calls for
theoretical computations of rates and probabilities with correspondingly higher
precision. In strong-field QED this requires the knowledge of radiative
corrections to be added to leading-order results. Here, we first derive the
mass operator in momentum space of an off-shell electron in the presence of an
arbitrary plane wave. By taking the average of the mass operator in momentum
space over an on-shell electron state, we obtain a new representation,
equivalent to but more compact than the known one computed in [Sov. Phys. JETP
\textbf{42}, 400 (1975)]. Moreover, we use the obtained mass operator to
determine the electron mass shift in an arbitrary plane wave, which generalizes
the already known expression in a constant crossed field. The spin-dependent
part of the electron mass shift can be related to the anomalous magnetic moment
of the electron in the plane wave. We show that within the locally constant
field approximation it is possible to conveniently define a local expression of
the electron anomalous magnetic moment, which reduces to the known expression
in a constant crossed field. Beyond the locally constant field approximation,
however, the interaction between the electron and the plane wave is non-local
such that it is not possible to conveniently introduce an electron anomalous
magnetic moment.",2106.13720v2
2022-04-28,GWCloud: a searchable repository for the creation and curation of gravitational-wave inference results,"There are at present ${\cal O}(100)$ gravitational-wave candidates from
compact binary mergers reported in the astronomical literature. As detector
sensitivities are improved, the catalog will swell in size: first to ${\cal
O}(1000)$ events in the A+ era and then to ${\cal O}(10^6)$ events in the era
of third-generation observatories like Cosmic Explorer and the Einstein
Telescope. Each event is analyzed using Bayesian inference to determine
properties of the source including component masses, spins, tidal parameters,
and the distance to the source. These inference products are the fodder for
some of the most exciting gravitational-wave science, enabling us to measure
the expansion of the Universe with standard sirens, to characterise the neutron
star equation of state, and to unveil how and where gravitational-wave sources
are assembled. In order to maximize the science from the coming deluge of
detections, we introduce GWCloud, a searchable repository for the creation and
curation of gravitational-wave inference products. It is designed with five
pillars in mind: uniformity of results, reproducibility of results, stability
of results, access to the astronomical community, and efficient use of
computing resources. We describe how to use GWCloud with examples, which
readers can replicate using the companion code to this paper. We describe our
long-term vision for GWCloud.",2204.13267v1
2023-02-17,Primordial Gravitational Waves From Black Hole Evaporation in Standard and Non-Standard Cosmologies,"Gravitons radiated from light, evaporating black holes contribute to the
stochastic background of gravitational waves. The spectrum of such emission
depends on both the mass and the spin of the black holes, as well as on the
redshifting that occurs between the black hole formation and today. This, in
turn, depends on the expansion history of the universe, which is largely
unknown and unconstrained at times prior to the synthesis of light elements.
Here, we explore the features of the stochastic background of gravitational
waves from black hole evaporation under a broad range of possible early
cosmological histories. The resulting gravitational wave signals typically peak
at very high frequencies, and offer opportunities for proposed ultra-high
frequency gravitational wave detectors. Lower-frequency peaks are also
possible, albeit with a suppressed intensity that is likely well below the
threshold of detectability. We find that the largest intensity peaks correspond
to cosmologies dominated by fluids with equations of state that have large
pressure-to-density ratios. Such scenarios can be constrained on the basis of
violation of $\Delta N_{\rm eff}$ bounds.",2302.10188v1
2023-04-25,Searching For Stochastic Gravitational Waves Below a Nanohertz,"The stochastic gravitational-wave background is imprinted on the times of
arrival of radio pulses from millisecond pulsars. Traditional pulsar timing
analyses fit a timing model to each pulsar and search the residuals of the fit
for a stationary time correlation. This method breaks down at
gravitational-wave frequencies below the inverse observation time of the array;
therefore, existing analyses restrict their searches to frequencies above 1
nHz. An effective method to overcome this challenge is to study the correlation
of secular drifts of parameters in the pulsar timing model itself. In this
paper, we show that timing model correlations are sensitive to sub-nanohertz
stochastic gravitational waves and perform a search using existing measurements
of pulsar spin-decelerations and pulsar binary orbital decay rates. We do not
observe a signal at our present sensitivity, constraining the stochastic
gravitational-wave relic energy density to $\Omega_\text{GW} ( f ) < 3.8 \times
10 ^{ - 9} $ at 450~pHz with sensitivity which scales as the frequency squared
until approximately 10 pHz. We place additional limits on the amplitude of a
power-law spectrum of $A_\star \lesssim 1.8\times10^{-14}$ for a reference
frequency of $f_* = 1~{\rm year} ^{-1} $ and the spectral index expected from
supermassive black hole binaries, $\gamma = 13/3$. If detection of a
supermassive black hole binary signal above 1 nHz is confirmed, this search
method will serve as a critical complementary probe of the dynamics of galaxy
evolution.",2304.13042v2
2024-02-09,"Efficient Gravitational-Wave Model for Fully-Precessing and Moderately-Eccentric, Compact Binary Inspirals","Future gravitational-wave detectors, especially the Laser Interferometer
Space Antenna (LISA), will be sensitive to black hole binaries formed in
astrophysical environments that promote large eccentricities and spin
precession. Gravitational-wave templates that include both effects have only
recently begun to be developed. The Efficient Fully Precessing Eccentric (EFPE)
family is one such model, covering the inspiral stage with
small-eccentricity-expanded gravitational-wave amplitudes accurate for
eccentricities $e < 0.3$. In this work, we extend this model to cover a larger
range of eccentricities. The new EFPE_ME model is able to accurately represent
the leading-order gravitational-wave amplitudes to $e \leq 0.8$. Comparing the
EFPE and the EFPE_ME models in the LISA band, however, reveals that there is no
significant difference when $e_0 \leq 0.5$ for binaries at 4 years before
merger, as radiation reaction circularizes supermassive black hole binaries too
quickly. This suggests that the EFPE model may have a larger regime of validity
in eccentricity space than previously thought, making it suitable for some
inspiral parameter estimation with LISA data. On the other hand, for systems
with $e_0 > 0.5$, the deviations between the models are significant,
particularly for binaries with total masses below $10^5\, \mathrm{M}_{\odot}$.
This suggests that the EFPE_ME model will be crucial to avoid systematic bias
in parameter estimation with LISA in the future, once this model has been
hybridized to include the merger and ringdown.",2402.06804v1
2001-12-19,Competing orders in a magnetic field: spin and charge order in the cuprate superconductors,"We describe two-dimensional quantum spin fluctuations in a superconducting
Abrikosov flux lattice induced by a magnetic field applied to a doped Mott
insulator. Complete numerical solutions of a self-consistent large N theory
provide detailed information on the phase diagram and on the spatial structure
of the dynamic spin spectrum. Our results apply to phases with and without
long-range spin density wave order and to the magnetic quantum critical point
separating these phases. We discuss the relationship of our results to a number
of recent neutron scattering measurements on the cuprate superconductors in the
presence of an applied field. We compute the pinning of static charge order by
the vortex cores in the `spin gap' phase where the spin order remains
dynamically fluctuating, and argue that these results apply to recent scanning
tunnelling microscopy (STM) measurements. We show that with a single typical
set of values for the coupling constants, our model describes the field
dependence of the elastic neutron scattering intensities, the absence of
satellite Bragg peaks associated with the vortex lattice in existing neutron
scattering observations, and the spatial extent of charge order in STM
observations. We mention implications of our theory for NMR experiments. We
also present a theoretical discussion of more exotic states that can be built
out of the spin and charge order parameters, including spin nematics and phases
with `exciton fractionalization'.",0112343v4
2006-07-06,Excitonic exchange effects on the radiative decay time of monoexcitons and biexcitons in quantum dots,"Electron-hole exchange interactions split the exciton ground state into
""dark"" and ""bright"" states. The dynamics of those states depends on the
internal relaxation time between bright and dark states (spin-flip time), and
on the radiative recombination time of the bright states. On the other hand,
the calculated values of these recombination times depend not only on the
treatment of correlation effects, but also on the accuracy of the electron and
hole wavefunctions. We calculate the radiative decay rates for monoexcitons and
biexcitons in (In,As)Ga/GaAs self-assembled and colloidal CdSe quantum dots
from atomistic correlated wave functions. We show how the radiative decay time
tau_R(X^0) of the monoexciton depends on the spin-flip relaxation time between
bright and dark states. In contrast, a biexciton has no bright-dark splitting,
so the decay time of the biexciton tau_R(XX^0) is insensitive to this spin-flip
time. This results in ratios $\tau_R(X^0)/\tau_R(XX^0)$ of 4 in the case of
fast spin flip, and a ratio of 2 in the case of slow spin flip. For
(In,Ga)As/GaAs, we compare our results with the model calculation of Wimmer et
al. [M. Wimmer et al., Phys. Rev. B 73, 165305 (2006)]. When the same spin-flip
rates are assumed, our predicted tau_R(X^0)/tau_R(XX^0) agrees with that of
Wimmer et al., suggesting that our treatment of correlations is adequate to
predict the ratio of monoexciton and biexciton radiative lifetimes. Our results
agree well with experiment on self-assembled quantum dots when assuming slow
spin flip. Conversely, for colloidal dots the agreement with experiment is best
for fast spin flip.",0607149v2
2012-08-07,Conductance fingerprints of non-collinear magnetic states in single atom contacts: a first-principles Wannier functions study,"We present a first-principles computational scheme for investigating the
ballistic transport properties of one-dimensional nanostructures with
non-collinear magnetic order. The electronic structure is obtained within
density functional theory as implemented in the full-potential linearized
augmented plane-wave (FLAPW) method and mapped to a tight-binding like
transport Hamiltonian via non-collinear Wannier functions. The conductance is
then computed based on the Landauer formula using the Green's function method.
As a first application we study the conductance between two ferromagnetic Co
monowires terminated by single Mn apex atoms as a function of Mn-Mn separation.
We vary the Mn-Mn separation from the contact (about 2.5 to 5 {\AA}) to the far
tunneling regime (5 to 10 {\AA}). The magnetization direction of the Co
electrodes is chosen either in parallel or antiparallel alignment and we allow
for different spin configurations of the two Mn spins. In the tunneling and
into the contact regime the conductance is dominated by $s$-$d_{z^2}$-states.
In the close contact regime (below 3.5 {\AA}) there is an additional
contribution for a parallel magnetization alignment from the $d_{xz}$- and
$d_{yz}$-states which give rise to an increase of the magnetoresistance as it
is absent for antiparallel magnetization. If we allow the Mn spins to relax a
non-collinear spin state is formed close to contact. We demonstrate that the
transition from a collinear to such a non-collinear spin structure as the two
Mn atoms approach leaves a characteristic fingerprint in the distance-dependent
conductance and magnetoresistance of the junction. We explain the effect of the
non-collinear spin state on the conductance based on the spin-dependent
hybridization between the $d_{xz,yz}$-states of the Mn spins and their coupling
to the Co electrodes.",1208.1382v1
2015-08-01,A Kagome Map of Spin Liquids: from XXZ to Dzyaloshinskii-Moriya Ferromagnet,"The kagome lattice sits at the crossroad of present research efforts in
quantum spin liquids, chiral phases, emergent skyrmion excitations and
anomalous Hall effects to name but a few. In light of this diversity, our goal
in this paper is to build a unifying picture of the underlying magnetic
degrees-of-freedom on kagome. Motivated by a growing mosaic of materials, we
especially consider a broad range of nearest-neighbour interactions consisting
of Dzyaloshinskii-Moriya as well as anisotropic ferro$-$ and antiferromagnetic
coupling. We present a three-fold mapping on the kagome lattice which
transforms the celebrated Heisenberg antiferromagnet and XXZ model onto two
lines of time-reversal invariant Hamiltonians. The mapping is exact for
classical and quantum spins alike, i.e. it preserves the energy spectrum of the
original Heisenberg and XXZ models. As a consequence, at the classical level,
all phases have an extensive ground-state degeneracy. These ground states
support a variety of phenomena such as ferromagnetically induced pinch points
in the structure factor and the possibility for spontaneous scalar chirality.
For quantum spin$-1/2$, the XXZ model has been recently shown to be a quantum
spin liquid. Applying our three-fold mapping to the XXZ model gives rise to a
connected network of quantum spin liquids, centered around a paragon of quantum
disorder, namely the Ising antiferromagnet. We show that this quantum disorder
spreads over an extended region of the phase diagram at linear order in spin
wave theory, which overlaps with the parameter region of Herbertsmithite
ZnCu$_3$(OH)$_6$Cl$_2$. We conclude this work by discussing the connection of
our results to the chiral spin liquids found on kagome with further
nearest-neighbour interactions, and to the recently synthesized ternary
intermetallic materials.",1508.00113v1
2015-08-13,Efficient Density Matrix Renormalization Group algorithm to study Y-Junctions with integer and half-integer spin,"An efficient density matrix renormalization group (DMRG) algorithm is
presented and applied to Y-junctions, systems with three arms of $n$ sites that
meet at a central site. The accuracy is comparable to DMRG of chains. As in
chains, new sites are always bonded to the most recently added sites and the
superblock Hamiltonian contains only new or once renormalized operators.
Junctions of up to $N = 3n + 1 \approx 500$ sites are studied with
antiferromagnetic (AF) Heisenberg exchange $J$ between nearest-neighbor spins
$S$ or electron transfer $t$ between nearest neighbors in half-filled Hubbard
models. Exchange or electron transfer is exclusively between sites in two
sublattices with $N_A \ne N_B$. The ground state (GS) and spin densities $
\rho_r = <S^z_r >$ at site $r$ are quite different for junctions with $S$ =
1/2, 1, 3/2 and 2. The GS has finite total spin $S_G = 2S (S)$ for even (odd)
$N$ and for $M_G =S_G$ in the $S_G$ spin manifold, $\rho_r > 0 (< 0)$ at sites
of the larger (smaller) sublattice. $S$ = 1/2 junctions have delocalized states
and decreasing spin densities with increasing $N$. $S$ = 1 junctions have four
localized $S_z = 1/2$ states at the end of each arm and centered on the
junction, consistent with localized states in $S$ = 1 chains with finite
Haldane gap. The GS of $S$ = 3/2 or 2 junctions of up to 500 spins is a spin
density wave (SDW) with increased amplitude at the ends of arms or near the
junction. Quantum fluctuations completely suppress AF order in $S$ = 1/2 or 1
junctions, as well as in half-filled Hubbard junctions, but reduce rather than
suppress AF order in $S$ = 3/2 or 2 junctions.",1508.03118v1
2016-01-20,Accuracy of binary black hole waveform models for aligned-spin binaries,"Coalescing binary black holes are among the primary science targets for
second generation ground-based gravitational wave (GW) detectors. Reliable GW
models are central to detection of such systems and subsequent parameter
estimation. This paper performs a comprehensive analysis of the accuracy of
recent waveform models for binary black holes with aligned spins, utilizing a
new set of $84$ high-accuracy numerical relativity simulations. Our analysis
covers comparable mass binaries ($1\le m_1/m_2\le 3$), and samples
independently both black hole spins up to dimensionless spin-magnitude of $0.9$
for equal-mass binaries and $0.85$ for unequal mass binaries. Furthermore, we
focus on the high-mass regime (total mass $\gtrsim 50M_\odot$). The two most
recent waveform models considered (PhenomD and SEOBNRv2) both perform very well
for signal detection, losing less than 0.5\% of the recoverable signal-to-noise
ratio $\rho$, except that SEOBNRv2's efficiency drops mildly for both black
hole spins aligned with large magnitude. For parameter estimation, modeling
inaccuracies of SEOBNRv2 are found to be smaller than systematic uncertainties
for moderately strong GW events up to roughly $\rho\lesssim 15$. PhenomD's
modeling errors are found to be smaller than SEOBNRv2's, and are generally
irrelevant for $\rho\lesssim 20$. Both models' accuracy deteriorates with
increased mass-ratio, and when at least one black hole spin is large and
aligned. The SEOBNRv2 model shows a pronounced disagreement with the numerical
relativity simulation in the merger phase, for unequal masses and
simultaneously both black hole spins very large and aligned. Two older waveform
models (PhenomC and SEOBNRv1) are found to be distinctly less accurate than the
more recent PhenomD and SEOBNRv2 models. Finally, we quantify the bias expected
from all GW models during parameter estimation for recovery of binary's masses
and spins.",1601.05396v2
2016-05-30,On the Coupling of Photon Spin to Electron Orbital Angular Momentum,"Partially gold coated 90 degree glass wedges and a semi - infinite slit in a
thin film of gold ending in a conducting nano-junction serve as samples to
investigate the transfer of photon spin to electron orbital angular momentum.
These structures were specifically designed as samples where an incident beam
of light is retroreflected. Since in the process of retroreflection the turning
sense of a circularly polarized beam of light does not change and the direction
of propagation is inverted, the photon spin is inverted. Due to conservation of
angular momentum a transfer of photon spin to electron orbital angular momentum
of conduction electrons occurs. In the structures a circular movement of
electrons is blocked and therefore the transfered spin can be detected as a
photovoltage due to an electromotive force which is induced by the transfer of
angular momentum. Depending on the polarization of the incident beam, a maximum
photovoltage of about 0,2 micro V was measured for both structures. The results
are interpreted in terms of a classical electrodynamic model of the
monochromatic linearly polarized photon as a propagating solitary
electromagnetic wave of finite energy hf which carries an angular momentum
h/2pi which is elaborated elsewhere where h is Plancks constant and f the
frequency of light. The relative values of the measured photovoltages for
different polarizations can well be explained by the electrodynamic model of a
photon and an associated spin angular momentum. The absolute values of the
measured photovoltages are also consistent with the interpretation. The
observed effects are closely related to the lateral Fedorov Imbert shift of
focused beams in optics and the optical spin Hall effect and to other non
linear optical effects such as the inverse faraday effect for which a new
interpretation is given here in terms of the electrodynamic model of the photon
and its spin.",1609.05218v1
2017-09-25,MHD Turbulence in spin-down flows of liquid metals,"Intense spin-down flows allow one to reach high Rm in relatively small
laboratory setups using moderate mass of liquid metals. The spin-down flow in
toroidal channels was the first flow configuration used for studying dynamo
effects in non-stationary flows. In this paper, we estimate the effect of
small-scale dynamo in liquid metal spin-down flows realized in laboratory
experiments. Our simulations have confirmed the conclusion that the dynamo
effects observed in the experiments done on gallium are weak -- a slight burst
of small-scale magnetic energy arises only at the highest available rotation
velocity of the channel. In sodium flows, the induction effects are quite
strong -- an essential part of kinetic energy of sodium spin-down flows is
converted into magnetic energy and dissipates because of Joule heat losses. We
have extended our simulations beyond the capabilities of existing laboratory
facilities and examined the spin-down flows at the channel rotation velocity
Omega>> 50 rps. It has been found that $\Omega\approx 100$rps is enough to
reach the equipartition of magnetic and kinetic spectral power density at the
lowest wave numbers (largest scales), whereas at Omega >= 200rps the intensity
of the magnetic field becomes comparable to the intensity of velocity field
fluctuations. We have also studied the influence of the Pm on the efficiency of
small-scale dynamo in spin-down flows. In the experimental spin-down flows, the
small-scale dynamo remains in a quasi-kinematic regime, and magnetic energy is
mainly dissipated at the same scale, wherein it is converted from kinetic
energy. The real small-scale dynamo starts to operate at Pm>10^{-4}, and the
inertial range of the magnetic energy spectrum appears. Thereupon the energy
dissipation is postponed to a later time and smaller scales, and the peak of
turbulent energy (both kinetic and magnetic) slightly increases with Pm.",1709.08333v1
2020-11-18,State of the field: Binary black hole natal kicks and prospects for isolated field formation after GWTC-2,"Advanced LIGO and Advanced Virgo's newly-released GWTC-2 catalog of
gravitational-wave detections offers unprecedented information about the spin
magnitudes and orientations of merging binary black holes (BBHs). Notably,
analysis of the BBH population suggests the presence of binaries whose
component spins are significantly misaligned with respect to their orbital
angular momenta. Significantly misaligned spins are typically predicted to be
at odds with isolated field formation via standard common envelope (CE)
evolution, and hence a ""smoking gun"" signature of dynamical binary formation
inside dense stellar clusters. Here, we explore whether the LIGO/Virgo
observation of spin-orbit misalignment indeed rules out the possibility that
BBHs are formed entirely in the field via standard CE evolution. In particular,
we seek to understand whether, by varying the natal kicks black holes receive
upon formation, we can invoke the CE scenario to self-consistently explain both
the observed spin distribution and merger rate of BBHs. We find that, if
isolated black holes are born with small natal spins, then BBHs formed through
CE require extreme natal kicks to match the observed BBH population, with a
velocity dispersion $\sigma =
9.7^{+26.7}_{-5.9}\times10^2\,\mathrm{km}\,\mathrm{s}^{-1}$ and
$\sigma>260\,\mathrm{km}\,\mathrm{s}^{-1}$ at 99% credibility. To avoid this
condition, we argue that it is necessary to assume that isolated black holes
are born with non-vanishing natal spins, that one or more alternative channels
contribute to the observed BBH population, and/or that other unforeseen
mechanisms serve to yield large spin-orbit misalignment in the field.",2011.09570v4
2021-10-02,Interplay of spin-precession and higher harmonics in the parameter estimation of binary black holes,"Gravitational-wave (GW) signals from coalescing compact binaries carry
enormous information about the source dynamics and are an excellent tool to
probe unknown astrophysics and fundamental physics. Though the updated catalog
of compact binary signals reports evidence for slowly spinning systems and
unequal mass binaries, the data so far cannot provide convincing proof of
strongly precessing binaries. Here, we use the GW inference library parallel
Bilby to compare the performance of two waveform models for measuring
spin-induced orbital precession. One of the waveform models incorporates both
spin-precession effects and sub-dominant harmonics. The other model accounts
for precession but only includes the leading harmonic. By simulating signals
with varying mass ratios and spins, we find that the waveform model with
sub-dominant harmonics enables us to infer the presence of precession in most
cases accurately. In contrast, the dominant model often fails to extract enough
information to measure precession. In particular, it cannot distinguish a
face-on highly precessing binary from a slowly precessing binary system
irrespective of the binary's mass ratio. As expected, we see a significant
improvement in measuring precession for edge-on binaries. Other intrinsic
parameters also become better constrained, indicating that precession effects
help break the correlations between mass and spin parameters. However, the
precession measurements are prior dominated for equal-mass binaries with
face-on orientation, even if we employ waveform model including subdominant
harmonics. In this case, doubling the signal-to-noise ratio does not help to
reduce these prior induced biases. As we expect detections of highly spinning
binary signals with misaligned spin orientations in the future, simulation
studies like ours are crucial for understanding the prospects and limitations
of GW parameter inferences.",2110.00766v2
2017-01-02,Proximity band structure and spin textures on both sides of topological-insulator/ferromagnetic-metal interface and their transport probes,"The control of recently observed spintronic effects in
topological-insulator/ferromagnetic-metal (TI/FM) heterostructures is thwarted
by the lack of understanding of band structure and spin texture around their
interfaces. Here we combine density functional theory with Green's function
techniques to obtain the spectral function at any plane passing through atoms
of Bi$_2$Se$_3$ and Co or Cu layers comprising the interface. In contrast to
widely assumed but thinly tested Dirac cone gapped by the proximity exchange
field, we find that the Rashba ferromagnetic model describes the spectral
function on the surface of Bi$_2$Se$_3$ in contact with Co near the Fermi level
$E_F^0$, where circular and snowflake-like constant energy contours coexist
around which spin locks to momentum. The remnant of the Dirac cone is
hybridized with evanescent wave functions injected by metallic layers and
pushed, due to charge transfer from Co or Cu layers, few tenths of eV below
$E_F^0$ for both Bi$_2$Se$_3$/Co and Bi$_2$Se$_3$/Cu interfaces while hosting
distorted helical spin texture wounding around a single circle. These features
explain recent observation [K. Kondou {\em et al.}, Nat. Phys. {\bf 12}, 1027
(2016)] of sensitivity of spin-to-charge conversion signal at TI/Cu interface
to tuning of $E_F^0$. Interestingly, three monolayers of Co adjacent to
Bi$_2$Se$_3$ host spectral functions very different from the bulk metal, as
well as in-plane spin textures signifying the spin-orbit proximity effect. We
predict that out-of-plane tunneling anisotropic magnetoresistance in vertical
heterostructure Cu/Bi$_2$Se$_3$/Co, where current flowing perpendicular to its
interfaces is modulated by rotating magnetization from parallel to orthogonal
to current flow, can serve as a sensitive probe of spin texture residing at
$E_F^0$.",1701.00462v2
2017-03-14,Thermodynamics of frustrated ferromagnetic spin-$1/2$ Heisenberg chains: The role of inter-chain coupling,"The thermodynamics of coupled frustrated ferromagnetic chains is studied
within a spin-rotation-invariant Green's function approach. We consider an
isotropic Heisenberg spin-half system with a ferromagnetic in-chain coupling
$J_1<0$ between nearest neighbors and a frustrating antiferromagnetic
next-nearest neighbor in-chain coupling $J_2>0$. We focus on moderate strength
of frustration $J_2 < |J_1|/4$ such that the in-chain spin-spin correlations
are predominantly ferromagnetic. We consider two inter-chain couplings (ICs)
$J_{\perp,y}$ and $J_{\perp,z}$, corresponding to the two axis perpendicular to
the chain, where ferromagnetic as well as antiferromagnetic ICs are taken into
account. We discuss the influence of frustration on the ground-state properties
for antiferromagnetic ICs, where the ground state is of quantum nature. The
major part of our study is devoted to the finite-temperature properties. We
calculate the critical temperature $T_{c}$ as a function of the competing
exchange couplings $J_{2},J_{\perp,y}, J_{\perp,z}$. We find that for fixed ICs
$T_c$ monotonically decreases with increasing frustration $J_2$, where as $J_2
\to |J_1|/4$ the $T_c(J_2)$-curve drops down rapidly. To characterize the
magnetic ordering below and above $T_c$ we calculate the spin-spin correlation
functions $\langle {\bf S}_0 {\bf S}_{\bf R} \rangle$, the magnetic order
parameter $M$, the uniform static susceptibility $\chi_0$ as well as the
correlation length $\xi$. Moreover, we discuss the specific heat $C_V$ and the
temperature dependence of the excitation spectrum $\omega_{\mathbf{q}}$. As
$J_2 \to |J_1|/4$ some unusual frustration-induced features were found, such as
an increase of the in-chain spin stiffness (in case of ferromagnetic ICs) or of
the in-chain spin-wave velocity (in case of antiferromagnetic ICs) with growing
temperature.",1703.04573v1
2019-08-06,Constraints on the binary black hole nature of GW151226 and GW170608 from the measurement of spin-induced quadrupole moments,"According to the ""no-hair"" conjecture, a Kerr black hole (BH) is completely
described by its mass and spin. In particular, the spin-induced quadrupole
moment of a Kerr BH with mass $m$ and dimensionless spin $\chi$ can be written
as $Q=-\kappa\,m^3\chi^2$, where $\kappa_{\rm BH}=1$. Thus by measuring the
spin-induced quadrupole parameter $\kappa$, we can test the binary black hole
nature of compact binaries and distinguish them from binaries comprised of
other exotic compact objects, as proposed in [N. V. Krishnendu et al., PRL 119,
091101 (2017)]. Here, we present a Bayesian framework to carry out this test
where we measure the symmetric combination of individual spin-induced
quadrupole moment parameters fixing the anti-symmetric combination to be zero.
The analysis is restricted to the inspiral part of the signal as the
spin-induced deformations are not modeled in the post-inspiral regime. We
perform detailed simulations to investigate the applicability of this method
for compact binaries of different masses and spins and also explore various
degeneracies in the parameter space which can affect this test. We then apply
this method to the gravitational wave events, GW151226 and GW170608 detected
during the first and second observing runs of Advanced LIGO and Advanced Virgo
detectors. We find the two events to be consistent with binary black hole
mergers in general relativity. By combining information from several more of
such events in future, this method can be used to set constraints on the black
hole nature of the population of compact binaries that are detected by the
Advanced LIGO and Advanced Virgo detectors.",1908.02247v2
2020-05-06,Multiple-scattering approach for multi-spin chiral magnetic interactions: Application to the one- and two-dimensional Rashba electron gas,"Various multi-spin magnetic exchange interactions (MEI) of chiral nature have
been recently unveiled. Owing to their potential impact on the realisation of
twisted spin-textures, their implication in spintronics or quantum computing is
very promising. Here, I address the long-range behavior of multi-spin MEI on
the basis of a multiple-scattering formalism implementable in Green functions
based methods. I consider the impact of spin-orbit coupling (SOC) as described
in the one- (1D) and two-dimensional (2D) Rashba model, from which the
analytical forms of the four- and six-spin interactions are extracted and
compared to the bilinear isotropic, anisotropic and Dzyaloshinskii-Moriya
interactions (DMI). Similarly to the DMI between two sites $i$ and $j$, there
is a four-spin chiral vector perpendicular to the bond connecting the two
sites. The oscillatory behavior of the MEI and their decay as function of
interatomic distances are analysed and quantified for the Rashba surfaces
states characterizing Au surfaces. The interplay of beating effects and
strength of SOC gives rise to a wide parameter space where chiral MEI are more
prominent than the isotropic ones. The multi-spin interactions for a plaquette
of $N$ magnetic moments decay like $\{q_F^{N-d} P^{\frac{1}{2}(d-1)}L\}^{-1}$
simplifying to $\{q_F^{N-d} R^{\left[1+\frac{N}{2}(d-1)\right]}N\}^{-1}$ for
equidistant atoms, where $d$ is the dimension of the mediating electrons, $q_F$
the Fermi wave vector, $L$ the perimeter of the plaquette while $P$ is the
product of interatomic distances. This recovers the behavior of the bilinear
MEI, $\{q_F^{2-d} R^{d}\}^{-1}$, and shows that increasing the perimeter of the
plaquette weakens the MEI. More important, the power-law pertaining to the
distance-dependent 1D MEI is insensitive to the number of atoms in the
plaquette in contrast to the linear dependence associated with the 2D MEI.",2005.03097v2
2022-01-24,A Channel to Form Fast-spinning Black Hole--Neutron Star Binary Mergers as Multi-messenger Sources,"After the successful detection of a gravitational-wave (GW) signal and its
associated electromagnetic (EM) counterparts from GW170817, neutron star--black
hole (NSBH) mergers have been highly expected to be the next type of
multi-messenger source. However, despite the detection of several of NSBH
merger candidates during the GW third observation run, no confirmed EM
counterparts from these sources have been identified. The most plausible
explanation is that these NSBH merger candidates were plunging events mainly
because the primary BHs had near-zero projected aligned-spins based on GW
observations. In view that NSs can be easily tidally disrupted by BHs with high
projected aligned-spins, we study an evolution channel to form NSBH binaries
with fast-spinning BHs, the properties of BH mass and spin, and their
associated tidal disruption probability. We find that if the NSs are born
firstly, the companion helium stars would be tidally spun up efficiently, and
would thus finally form fast-spinning BHs. If BHs do not receive significant
natal kicks at birth, these NSBH binaries that can merge within the Hubble time
would have BHs with the projected aligned-spins $\chi_{z}\gtrsim0.8$ and,
hence, can certainly allow tidal disruption to happen. Even if significant BH
kicks are considered for a small fraction of NSBH binaries, the projected
aligned-spins of BHs are $\chi_z\gtrsim0.2$. These systems can still be
disrupted events unless the NSs are very massive. Thus, NS-first-born NSBH
mergers would be promising multi-messenger sources. We discuss various
potential EM counterparts associated with these systems and their detectability
in the upcoming fourth observation run.",2201.09549v3
2022-10-21,Searching for structure in the binary black hole spin distribution,"The spins of black holes in merging binaries can reveal information related
to the formation and evolution of these systems through their gravitational
wave emission. Combining events to infer the astrophysical distribution of
black hole spins allows us to determine the relative contribution from
different formation scenarios to the population. Many previous works have
modeled spin population distributions using parametric models. While these are
valuable approaches when the observed population is small, they make strong
assumptions about the shape of the underlying distribution and are highly
susceptible to biases due to mismodeling. The results obtained with such
parametric models are only valid if the allowed shape of the distribution is
well-motivated (i.e. for astrophysical reasons). In this work, we relax these
prior assumptions and model the spin distributions using a more data-driven
approach, modeling these distributions with flexible cubic spline interpolants
in order to allow for capturing structures that the parametric models cannot.
We find that adding this flexibility to the model substantially increases the
uncertainty in the inferred distributions, but find a general trend for lower
support at high spin magnitude and a spin tilt distribution consistent with
isotropic orientations. We infer that 62 - 87% of black holes have spin
magnitudes less than a = 0.5, and 27- 50% of black holes exhibit negative
$\chi_{\rm eff}$. Using the inferred $\chi_{\rm eff}$ distribution, we place a
conservative upper limit of 37% for the contribution of hierarchical mergers to
the astrophysical BBH population. Additionally, we find that artifacts from
unconverged Monte Carlo integrals in the likelihood can manifest as spurious
peaks and structures in inferred distributions, mandating the use of a
sufficient number of samples when using Monte Carlo integration for population
inference.",2210.12287v2
2022-12-15,Scattering in Black Hole Backgrounds and Higher-Spin Amplitudes: Part II,"We continue to investigate correspondences between, on the one hand,
scattering amplitudes for massive higher-spin particles and gravitons in
appropriate quantum-to-classical limits, and on the other hand, classical
gravitational interactions of spinning black holes according to general
relativity. We first construct an ansatz for a gravitational Compton amplitude,
at tree level, constrained only by locality, crossing symmetry, unitarity and
consistency with the linearized-Kerr 3-point amplitude, to all orders in the
black hole's spin. We then explore the extent to which a unique classical
Compton amplitude can be identified by comparing with the results of the
classical process of scattering long-wavelength gravitational waves off an
exact Kerr black hole, determined by appropriate solutions of the Teukolsky
equation. Up to fourth order in spin, we find complete agreement with a
previously conjectured exponential form of the tree-level Compton amplitude. At
higher orders, we extract tree-level contributions from the Teukolsky amplitude
by an analytic continuation from a physical ($a/GM<1$) to a particle-like
($a/GM>1$) regime. Up to the sixth order in spin, we identify a unique
\textit{conservative} part of the amplitude which is insensitive both to the
choice of boundary conditions at the black hole horizon and to branch choices
in the analytic continuation. The remainder of the amplitude is determined
modulo an overall sign from a branch choice, with the sign flipping under
exchanging purely ingoing and purely outgoing boundary conditions at the
horizon. Along the way, we make contact with novel applications of massive
spinor-helicity variables pertaining to their relation to EFT operators and
(spinning) partial amplitudes.",2212.07965v3
2023-11-06,"An exciton interacting with a moire lattice -- polarons, strings, and optical probing of spin correlations","We develop a general theory for how an exciton in an atomically thin
transition metal dichacogenide (TMD) monolayer couples to spin and charge
correlations in an adjacent moire lattice created by a TMD bi-layer. Virtual
tunneling of charge carriers, assumed for concreteness to be holes, between the
moire lattice and the monolayer combined with the presence of bound
hole-exciton states, i.e. trions, give rise to an effective interaction between
the moire holes and the exciton. In addition to the Umklapp scattering, we show
that this interaction is spin-dependent and therefore couples the exciton to
the spin correlations of the moire holes, which may be in- as well as
out-of-plane. We then use our theory to examine two specific examples where the
moire holes form in-plane ferromagnetic or anti-ferromagnetic order. In both
cases, the exciton creates spin waves in the moire lattice, which we analyse by
using a self-consistent Born approximation that includes such processes to
infinite order. We show that the competition between magnetic order and exciton
motion leads to the formation of a well-defined quasiparticle consisting of the
exciton surrounded by a cloud of magnetic frustration in the moire lattice
sites below. For the anti-ferromagnet, we furthermore demonstrate the presence
of the elusive geometric string excitations and discuss how they can be
observed via their smoking gun energy dependence on the spin-spin coupling,
which can be tuned by varying the twist angle of the moire bi-layer. All these
phenomena have clear signatures in the exciton spectrum, and as such our
results illustrate that excitons are promising probes providing optical access
to the spin correlations of new quantum phases predicted to exist in TMD
materials.",2311.03482v1
2024-03-15,Optimizing post-Newtonian parameters and fixing the BMS frame for numerical-relativity waveform hybridizations,"Numerical relativity (NR) simulations of binary black holes provide precise
waveforms, but are typically too computationally expensive to produce waveforms
with enough orbits to cover the whole frequency band of gravitational-wave
observatories. Accordingly, it is important to be able to hybridize NR
waveforms with analytic, post-Newtonian (PN) waveforms, which are accurate
during the early inspiral phase. We show that to build such hybrids, it is
crucial to both fix the Bondi-Metzner-Sachs (BMS) frame of the NR waveforms to
match that of PN theory, and optimize over the PN parameters. We test such a
hybridization procedure including all spin-weighted spherical harmonic modes
with $|m|\leq \ell$ for $\ell\leq 8$, using 29 NR waveforms with mass ratios
$q\leq 10$ and spin magnitudes $|\chi_1|, |\chi_2|\leq 0.8$. We find that for
spin-aligned systems, the PN and NR waveforms agree very well. The difference
is limited by the small nonzero orbital eccentricity of the NR waveforms, or
equivalently by the lack of eccentric terms in the PN waveforms. To maintain
full accuracy of the simulations, the matching window for spin-aligned systems
should be at least 5 orbits long and end at least 15 orbits before merger. For
precessing systems, the errors are larger than for spin-aligned cases. The
errors are likely limited by the absence of precession-related spin-spin PN
terms. Using $10^5\,M$ long NR waveforms, we find that there is no optimal
choice of the matching window within this time span, because the hybridization
result for precessing cases is always better if using earlier or longer
matching windows. We provide the mean orbital frequency of the smallest
acceptable matching window as a function of the target error between the PN and
NR waveforms and the black hole spins.",2403.10278v1
2002-09-25,Can the rapid braking of the white dwarf in AE Aquarii be explained in terms of the gravitational wave emitter mechanism?,"The spin-down power of the white dwarf in the close binary AE Aquarii
significantly exceeds the bolometric luminosity of the system. The
interpretation of this phenomenon in terms of the gravitational-wave emitter
mechanism has been recently suggested by Choi & Yi. The basic assumption of
their interpretation is that the spatially limited blobs or mounds of the mass
\delta m ~ 10^{-3} M_sun, are present at the magnetic poles of the white dwarf.
We show that the mounds of this mass can be confined by the magnetic field of
the white dwarf only if the dipole magnetic moment of the star exceeds
4x10^{37} G cm^3. Under these conditions, however, the magnetodipole losses of
the white dwarf would exceed the evaluated spin-down power 6 orders of
magnitude. On this basis we discard a possibility that the observed rapid
braking of the white dwarf in AE Aquarii can be explained in terms of the
mechanism proposed by Choi & Yi.",0209529v1
2004-07-26,Powerful gravitational-wave bursts from supernova neutrino oscillations,"During supernova core collapse and bounce resonant active-to-active, as well
as active-to-sterile, neutrino ($\nu$) oscillations can take place. Over this
phase weak magnetism increases antineutrino mean free paths, and thus its
luminosity. Because oscillations feed mass-energy into the target $\nu$
species, the large mass-squared difference between $\nu$ states implies a huge
amount of power to be given off as gravitational waves (GWs) due to the
universal {\it spin-rotation} and the spin-magnetic coupling driven $\nu$
anisotropic flow, which is coherent over the oscillation length. The spacetime
strain produced is about two orders of magnitude larger than those from $\nu$
difussion or neutron star matter anisotropies. GWs observatories as LIGO,
VIRGO, GEO-600, TAMA-300, etc., can search for these bursts far out to the
VIRGO cluster of galaxies.",0407526v1
2004-11-16,Possible evolutionary transition from rapidly rotating neutron stars to strange stars due to spin-down,"We present a scenario of formation of strange stars due to spin-down of {\it
rapidly rotating} neutron stars left after supernova explosions . By assuming a
process where the total baryon mass is conserved but the angular momentum is
lost due to emission of gravitational waves and/or the magnetic braking, we
find that the transition from rapidly rotating neutron stars to slowly rotating
strange stars is possible; a large amount of energy $\sim 10^{53} ergs $ could
be released. The liberated energy might become a new energy source for a
delayed explosion of supernova. Furthermore, our scenario suggests that the
supernova associated with gamma-ray bursts could become candidates for targets
in the future observation of gravitational waves.",0411434v3
2006-09-27,Supermassive black hole mergers and cosmological structure formation,"Massive black holes (MBHs), with masses in the range 10^3-10^8 Msolar, which
merge with a companion black hole of similar mass are expected to be the most
powerful source of gravitational radiation in the frequency range probed by
LISA. MBH binaries can be detected by LISA up to z~5-15. Gravitational waves
from MBH mergers can serve as a powerful tool to study the early evolution of
the MBH population, and possibly the role played by MBHs in the joint evolution
with their hosts. I review scenarios for the co-evolution of MBHs and
cosmological structures, where MBH seeds form in pre-galactic structures. These
black holes evolve then in a hierarchical fashion, following the merger
hierarchy of their hosts. Accretion of gas, traced by quasar activity, plays a
fundamental role in determining the two parameters defining a black hole, mass
and spin. Gravitational waves, together with observations in electromagnetic
bands, can help constrain the evolution of both MBH mass and spin.",0609741v1
1993-04-20,"Exiton, Spinon and Spin Wave Modes in an Exactly Soluble One-Dimensional Quantum Many-Body System","In this paper, we present the exact solution to a one-dimensional,
two-component, quantum many-body system in which like particles interact with a
pair potential $s(s+1)/{\rm sinh}^{2}(r)$, while unlike particles interact with
a pair potential $-s(s+1)/{\rm cosh}^{2}(r)$. We first give a proof of
integrability, then derive the coupled equations determining the complete
spectrum. All singularities occur in the ground state when there are equal
numbers of the two components; we give explicit results for the ground state
and low-lying states in this case. For $s>0$, the system is an
antiferromagnet/insulator, with excitations consisting of a pair-hole--pair
continuum, a two-particle continuum with gap, and excitons with gaps. For
$-1<s<0$, the system has excitations consisting of a hole-particle continuum,
and a two-spin wave continuum, both gap-less.",9304033v1
1993-06-21,The s=1/2 Heisenberg Antiferromagnet on the Triangular Lattice: Exact Results and Spin-Wave Theory for Finite Cells,"We study the ground state properties of the S=$\frac{1}{2}$ Heisenberg
antiferromagnet (HAF) on the triangular lattice with nearest-neighbour ($J$)
and next-nearest neighbour ($\alpha J$) couplings. Classically, this system is
known to be ordered in a $120^\circ$ N\'eel type state for values
$-\infty<\alpha\le 1/8$ of the ratio $\alpha$ of these couplings and in a
collinear state for $1/8<\alpha<1$. The order parameter ${\cal M}$ and the
helicity $\chi$ of the $120^\circ$ structure are obtained by numerical
diagonalisation of finite periodic systems of up to $N=30$ sites and by
applying the spin-wave (SW) approximation to the same finite systems. We find a
surprisingly good agreement between the exact and the SW results in the entire
region $-\infty<\alpha< 1/8$. It appears that the SW theory is still valid for
the simple triangular HAF ($\alpha=0$) although the sublattice magnetisation
${\cal M}$ is substantially reduced from its classical value by quantum
fluctuations. Our numerical results for the order parameter ${\cal N}$ of the
collinear order support the previous conjecture of a first order transition
between the $120^\circ$ and the collinear order at $\alpha \simeq 1/8$.",9306044v1
1995-01-11,"Conformal, Subconformal and Spectral Universality in Incommensurate Spin Chains","A renormalization scheme is developed to study an anisotropic quantum XY spin
chain in a quasiperiodic transverse field. The critical phase of the
quasi-particle excitations of the model with fractal wave functions exists in a
finite parameter interval and is sandwiched between the extended and localized
phases. The scaling properties of the critical phase fall into four distinct
universality classes referred as spectral, subconformal, conformal and Harper.
The spectral and conformal classes respectively describe the onsets of extended
to critical and critical to localized transitions while the subconformal class
describes the part of the phase diagram sandwiched between the conformal and
spectral transitions. The Harper universality class describes the isotropic
limit of the XY model. A decimation scheme is developed to compute the infinite
sets of universal scaling ratios characterizing the wave functions in the four
universality classes. The renormalization flow equations exhibit a limit cycle
at the band center and at the band edges providing a new method for determining
these energies with extremely high precision.",9501043v1
1995-05-04,What happens to the quantum Hall effect when magnetic-field-induced spin-density wave moves,"The influence of the motion of a magnetic-field-induced spin-density wave
(FISDW) on the quantum Hall effect in a quasi-one-dimensional conductor is
studied theoretically. In the ideal case of a free FISDW, it is found that the
counterflow of the FISDW precisely cancels the quantum Hall current, so the
resultant Hall conductivity is zero. In real systems, the Hall conductivity
should vanish at the high frequencies, where the pinning and the damping can be
neglected, and the dynamics of the FISDW is dominated by inertia.",9505016v1
1996-05-09,Two-magnon Raman scattering in a spin density wave antiferromagnet,"We present the results for a model calculation of resonant two-magnon Raman
scattering in a spin density wave (SDW) antiferromagnet. The resonant
enhancement of the two-magnon intensity is obtained from a microscopic analysis
of the photon-magnon coupling vertex. By combining magnon-magnon interactions
with `triple resonance` phenomena in the vertex function the resulting
intensity line shape is found to closely resemble the measured two-magnon Raman
signal in antiferromagnetic cuprates. Both, resonant and non-resonant Raman
scattering are discussed for the SDW antiferromagnet and a comparison is made
to the conventional Loudon-Fleury theory of two-magnon light scattering.",9605056v1
1996-07-27,Temperature Evolution of the Quantum Hall Effect in Quasi-One-Dimensional Organic Conductors,"The Hall conductivity in the magnetic-field-induced spin-density-wave (FISDW)
state of the quasi-one-dimensional organic conductors (TMTSF)$_2$X at a finite
temperature is calculated. The temperature dependence of the Hall conductivity
is found to be the same as the temperature dependence of the Fr\""ohlich current
of a regular charge/spin-density wave. Predicted dependence $\sigma_{xy}(T)$
can be verified experimentally in the (TMTSF)$_2$X compounds if all components
of the resistivity tensor are measured and the conductivity tensor is
reconstructed.",9607199v1
1996-08-07,Power-law correlated phase in random-field XY models and randomly pinned charge-density waves,"Monte Carlo simulations have been used to study the Z6 ferromagnet in a
random field on simple cubic lattices, which is a simple model for randomly
pinned charge-density waves. The random field is chosen to have infinite
strength on a fraction x of the sites of the lattice, and to be zero on the
remaining sites. For x= 1/16 there are two phase transitions. At low
temperature there is a ferromagnetic phase, which is stabilized by the six-fold
nonrandom anisotropy. The intermediate temperature phase is characterized by a
|k|^(-3) decay of two-spin correlations, but no true ferromagnetic order. At
the transition between the power-law correlated phase and the paramagnetic
phase the magnetic susceptibility diverges, and the two-spin correlations decay
approximately as |k|^(-2.87).",9608036v1
1997-01-08,Spectral functions of the 1D Hubbard model in the U -> \infty limit: How to use the factorized wave-function,"We give the details of the calculation of the spectral functions of the 1D
Hubbard model using the spin-charge factorized wave-function for several
versions of the U -> +\infty limit. The spectral functions are expressed as a
convolution of charge and spin dynamical correlation functions. A procedure to
evaluate these correlation functions very accurately for large systems is
developed, and analytical results are presented for the low energy region.
These results are fully consistent with the conformal field theory. We also
propose a direct method of extracting the exponents from the matrix elements in
more general cases.",9701051v1
1997-01-15,Instabilities of the Hubbard chain in a magnetic field,"We find and characterize the instabilities of the repulsive Hubbard chain in
a magnetic field by studing all response functions at low frequency \omega and
arbitrary momentum. The instabilities occur at momenta which are simple
combinations of the (U=0) \sigma =\uparrow ,\downarrow Fermi points, \pm
k_{F\sigma}. For finite values of the on-site repulsion U the instabilities
occur for single \sigma electron adding or removing at momenta \pm k_{F\sigma},
for transverse spin-density wave (SDW) at momenta \pm 2k_F (where
2k_F=k_{F\uparrow}+k_{F\downarrow}), and for charge-density wave (CDW) and SDW
at momenta \pm 2k_{F\uparrow} and \pm 2k_{F\downarrow}. While at zero magnetic
field removing or adding single electrons is dominant, the presence of that
field brings about a dominance for the transverse \pm 2k_F SDW over all the
remaining instabilities for a large domain of $U$ and density n values. We go
beyond conformal-field theory and study divergences which occur at finite
frequency in the one-electron Green function at half filling and in the
transverse-spin response function in the fully-polarized ferromagnetic phase.",9701104v1
1997-02-20,Nearly Antiferromagnetic Fermi Liquids: A Progress Report,"I describe recent theoretical and experimental progress in understanding the
physical properties of the two dimensional nearly antiferromagnetic Fermi
liquids (NAFL's) found in the normal state of the cuprate superconductors. In
such NAFL's, the magnetic interaction between planar quasiparticles is strong
and peaked at or near the commensurate wave vector, $Q \equiv (\pi,\pi)$. For
the optimally doped and underdoped systems, the resulting strong
antiferromagnetic correlations produce three distinct magnetic phases in the
normal state: mean field above $T_{cr}$, pseudoscaling between $T_{cr}$ and
$T_*$, and pseudogap below $T_*$. I present arguments which suggest that the
physical origin of the pseudogap found in the quasiparticle spectrum below
$T_{cr}$ is the formation of a precursor to a spin-density-wave-state, describe
the calculations based on this scenario of the dynamical spin susceptibility,
Fermi surface evolution, transport, and Hall effect, and summarize the
experimental evidence in its support.",9702187v1
1997-03-12,Luttinger theorem for a spin-density-wave state,"We obtained the analog of the Luttinger relation for a commensurate
spin-density-wave state. We show that while the relation between the area of
the occupied states and the density of particles gets modified in a simple and
predictable way when the system becomes ordered, a perturbative consideration
of the Luttinger theorem does not work due to the presence of an anomaly
similar to the chiral anomaly in quantum electrodynamics.",9703120v1
1997-12-12,Does quasi-long-range order in the two-dimensional XY model really survive weak random phase fluctuations?,"Effective theories for random critical points are usually non-unitary, and
thus may contain relevant operators with negative scaling dimensions. To study
the consequences of the existence of negative dimensional operators, we
consider the random-bond XY model. It has been argued that the XY model on a
square lattice, when weakly perturbed by random phases, has a quasi-long-range
ordered phase (the random spin wave phase) at sufficiently low temperatures. We
show that infinitely many relevant perturbations to the proposed critical
action for the random spin wave phase were omitted in all previous treatments.
The physical origin of these perturbations is intimately related to the
existence of broadly distributed correlation functions. We find that those
relevant perturbations do enter the Renormalization Group equations, and affect
critical behavior. This raises the possibility that the random XY model has no
quasi-long-range ordered phase and no Kosterlitz-Thouless (KT) phase
transition.",9712146v2
1998-03-07,Effect of umklapp scattering on the magnetic-field-induced spin-density waves in quasi-one-dimensional organic conductors,"We study the effect of umklapp scattering on the magnetic-field-induced
spin-density-wave (FISDW) phases which are experimentally observed in the
quasi-one-dimensional organic conductors of the Bechgaard salts family. Within
the framework of the quantized nesting model, we show that the transition
temperature is determined by a modified Stoner criterion which includes the
effect of umklapp scattering. We determine the SDW polarization (linear or
circular) by analyzing the Ginzburg-Landau expansion of the free energy. We
also study how umklapp processes modify the quantum Hall effect (QHE) and the
spectrum of the FISDW phases. We find that umklapp scattering stabilizes phases
which exhibit a sign reversal of the QHE, as experimentally observed in the
Bechgaard salts. These ``negative'' phases are characterized by the
simultaneous existence of two SDWs with comparable amplitudes. As the umklapp
scattering strength increases, they may become helicoidal (circularly polarized
SDWs). The QHE vanishes in the helicoidal phases, but a magnetoelectric effect
appears. These two characteristic properties may be utilized to detect the
magnetic-field-induced helicoidal SDW phases experimentally.",9803080v1
1998-03-13,Finitely Correlated Generalized Spin Ladders,"We study two-leg S=1/2 ladders with general isotropic exchange interactions
between spins on neighboring rungs, whose ground state can be found exactly in
a form of finitely correlated (matrix product) wave function. Two families of
models admitting an exact solution are found: one yields translationally
invariant ground states and the other describes spontaneously dimerized models
with twofold degenerate ground state. Several known models with exact ground
states can be obtained as particular cases from the general solution of the
first family, which includes also a set of models with only bilinear
interactions. Those two families of models have nonzero intersection, which
enables us to determine exactly the phase boundary of the second-order
transition into the dimerized phase and to study the properties of this
transition. The structure of elementary excitations in the dimerized phase is
discussed on the basis of a variational ansatz. For a particular class of
models, we present exact wave functions of the elementary excitations becoming
gapless at second-order transition lines. We also propose a generalization of
the Bose-Gayen ladder model which has a rich phase diagram with all phase
boundaries being exact.",9803176v1
1998-04-13,The influence of magnetic-field-induced spin-density-wave motion and finite temperature on the quantum Hall effect in quasi-one-dimensional conductors: A quantum field theory,"We derive the effective action for a moving magnetic-field-induced
spin-density wave (FISDW) in quasi-one-dimensional conductors at zero and
nonzero temperatures by taking the functional integral over the electron field.
The effective action consists of the (2+1)D Chern-Simons term and the (1+1)D
chiral anomaly term, both written for a sum of the electromagnetic field and
the chiral field associated with the FISDW phase. The calculated frequency
dependence of Hall conductivity interpolates between the quantum Hall effect at
low frequencies and zero Hall effect at high frequencies, where the counterflow
of FISDW cancels the Hall current. The calculated temperature dependence of the
Hall conductivity is interpreted within the two-fluid picture, by analogy with
the BCS theory of superconductivity.",9804128v2
1998-05-08,Physical properties of the double exchange and its relevance to the specific heat of double perovskite materials,"In response to the experimental discovery of double perovskite Ru- base
material, The magnetic and electronic properties of the double exchange
mechanism are studied theoretically. The electron band structure and the spin
wave spectrum response at zero temperature with the canting background are
computed from the first principle Hamiltonian. The long range Coulomb
interaction between charge carriers is found to be crucial in stabilizing the
canting order. A Monte Carlo simulation is performed on de-Gennes's effective
magnetic Hamiltonian with classical spin approximation. The peaks of the
specific heat as a function of temperature, which correspond to FM(AF) and
canting transitions, and its response to the external magnetic field are
consistent with the observation. For certain region of parameters, a more
complex canting order than layer type is found at sufficiently low temperature.
The effective interaction between carriers via exchanging a magnon wave is
found to be rather similar to that via exchanging an acoustic phonon. The pros
and cons to a genuine superconducting order in this system is analyzed.",9805094v1
1998-05-22,Spin-wave Scattering in the Effective Lagrangian Perspective,"Nonrelativistic systems exhibiting collective magnetic behavior are analyzed
in the framework of effective Lagrangians. The method, formulating the dynamics
in terms of Goldstone bosons, allows to investigate the consequences of
spontaneous symmetry breaking from a unified point of view. Low energy theorems
concerning spin-wave scattering in ferro- and antiferromagnets are established,
emphasizing the simplicity of actual calculations. The present work includes
approximate symmetries and discusses the modification of the low energy
structure imposed by an external magnetic and an anisotropy field,
respectively. Throughout the paper, analogies between condensed matter physics
and Lorentz-invariant theories are pointed out, demonstrating the universal
feature of the effective Lagrangian technique.",9805277v2
1998-06-13,Nonanalytic Magnetization Dependence of the Magnon Effective Mass in Itinerant Quantum Ferromagnets,"The spin wave dispersion relation in both clean and disordered itinerant
quantum ferromagnets is calculated. It is found that effects akin to
weak-localization physics cause the frequency of the spin-waves to be a
nonanalytic function of the magnetization m. For low frequencies \Omega, small
wavevectors k, and small m, the dispersion relation is found to be of the form
\Omega ~ m^{1-\alpha} k^2, with \alpha = (4-d)/2 (2<d<4) for disordered
systems, and \alpha = (3-d) (1<d<3) for clean ones. In d=4 (disordered) and d=3
(clean), \Omega ~ m ln(1/m) k^2. Experiments to test these predictions are
proposed.",9806168v3
1998-07-04,Tunneling and Photoemission in an SO(6) Superconductor,"Combining the results of tunneling, photoemission and thermodynamic studies,
the pseudogap is unambiguously demonstrated to be caused by Van Hove nesting: a
splitting of the density of states peak at $(\pi, 0)$. The fact that the
splitting remains symmetric about the Fermi level over an extended doping range
indicates that the Van Hove singularity is pinned to the Fermi level. Despite
these positive results, an ambiguity remains as to what instability causes the
pseudogap. Charge or spin density waves, superconducting fluctuations, and flux
phases all remain viable possibilities. This ambiguity arises because the
instabilities of the two-dimensional Van Hove singularity are associated with
an approximate SO(6) symmetry group, which contains Zhang's SO(5) as a
subgroup. It has two 6-component superspins, one of which mixes Zhang's
(spin-density wave plus d-wave superconductivity) superspin with a flux phase
operator. This is the smallest group which can explain striped phases in the
cuprates. Evidence for a prefered hole density in the charged stripes is
discussed.",9807067v1
1999-01-05,On the self-consistent spin-wave theory of layered Heisenberg magnets,"The versions of the self-consistent spin-wave theories (SSWT) of
two-dimensional (2D) Heisenberg ferro- and antiferromagnets with a weak
interlayer coupling and/or magnetic anisotropy, that are based on the
non-linear Dyson-Maleev, Schwinger, and combined boson-pseudofermion
representations, are analyzed. Analytical results for the temperature
dependences of (sublattice) magnetization and short-range order parameter, and
the critical points are obtained. The influence of external magnetic field is
considered. Fluctuation corrections to SSWT are calculated within a
random-phase approximation which takes into account correctly leading and
next-leading logarithmic singularities. These corrections are demonstrated to
improve radically the agreement with experimental data on layered perovskites
and other systems. Thus an account of these fluctuations provides a
quantitative theory of layered magnets.",9901027v2
1999-04-27,Spin-wave contributions to nuclear magnetic relaxation in magnetic metals,"The longitudinal and transverse nuclear magnetic relaxation rates $1/T_1(T)$
and $1/T_2(T)$ are calculated for three- and two-dimensional (3D and 2D)
metallic ferro- and antiferromagnets (FM and AFM) with localized magnetic
moments in the spin-wave temperature region. The contribution of the one-magnon
decay processes is strongly enhanced in comparison with the standard $T$-linear
Korringa term, especially for the FM case. For the 3D AFM case this
contribution diverges logarithmically, the divergence being cut at the magnon
gap $\omega_0$ due to magnetic anisotropy, and for the 2D AFM case as
$\omega_0^{-1}$. The electron-magnon scattering processes yield $T^2\ln
(T/\omega_0)$ and $T^2/\omega_0^{1/2}$-terms in $1/T_1$ for the 3D AFM and 2D
FM cases, respectively. The two-magnon (``Raman'') contributions are
investigated and demonstrated to be large in the 2D FM case. Peculiarities of
the isotropic 2D limit (where the correlation length is very large) are
analyzed.",9904384v3
1999-04-27,Mid-infrared absorption in YBa2Cu3O6: Failure of spin-wave theory in undoped cuprates?,"The optical conductivity sigma (omega) of undoped YBa2Cu3O6 is studied in
detail in the mid-infrared range. Substitutions on all but the Ba site are used
to identify the prominent absorption processes at 2800 and 3800 cm^-1.
Experimental evidence for bimagnon-plus-phonon absorption is collected. A more
critical analysis of the lineshape and the spectral weight reveals the limits
of this approach. Although phonon-2-magnon multiple scattering seems to
reproduce the lineshape, the necessary coupling is unrealistically large. The
strong increase of high frequency spectral weight with increasing temperature
makes the failure of spin-wave theory even more evident.",9904394v1
1999-05-18,From ferromagnetism to spin-density wave: Magnetism in the two channel periodic Anderson model,"The magnetic properties of the two-channel periodic Anderson model for
uranium ions, comprised of a quadrupolar and a magnetic doublet are
investigated through the crossover from the mixed-valent to the stable moment
regime using dynamical mean field theory. In the mixed-valent regime
ferromagnetism is found for low carrier concentration on a hyper-cubic lattice.
The Kondo regime is governed by band magnetism with small effective moments and
an ordering vector $\q$ close to the perfect nesting vector. In the stable
moment regime nearest neighbour anti-ferromagnetism dominates for less than
half band filling and a spin density wave transition for larger than half
filling. $T_m$ is governed by the renormalized RKKY energy scale $\mu_{eff}^2
<X_\sigma>^2 J^2\rho_0(\mu)$.",9905260v1
1999-06-05,Submillimeter Wave ESR Study of Spin Gap Excitations in CuGeO3,"Transitions between the ground singlet state to the excited triplet state has
been observed in CuGeO3 by means of submillimeter wave electron spin resonance.
The strong absorption intensity shows the break down of the selection rule. The
energy gap at zero field is evaluated to be 570 GHz(2.36 meV) and this value is
nearly identical to the gap at the zone center observed by inelastic neutron
scattering. The absorption intensity shows strong field orientation dependence
but shows no significant dependence on magnetic field intensity. These features
have been explained by considering the existence of Dzyaloshinsky-Moriya (DM)
antisymmetric exchange interaction. The doping effect on this singlet-triplet
excitation has been also studied. A drastic broadening of the absorption line
is observed by the doping of only 0.5 % of Si.",9906074v1
1999-06-09,Impurity scattering and frequency dependent conductivity in spin density waves,"The quasiparticle contribution to the frequency dependent electric
conductivity in the presence of randomly distributed impurities is calculated
within mean field theory for spin density waves as formed in quasi one
dimensional conductors like Bechgaard salts. Interchain hopping is taken into
account and the effects of imperfect nesting are considered. In case of an
electric field perpendicular to the chain direction there is no collective
contribution to the conductivity and our results are directly applicable to
recent measurements on both (TMTSF)2PF6 and quenched (TMTSF)2ClO4. The
experimental data are well described by the theory in the clean limit, with
somewhat larger scattering in the ClO4 salt.",9906132v1
1999-06-25,Spin-Density-Wave Phase Transitions in Quasi-One-Dimensional Dimerized Quarter-Filled Organic Conductors,"We have studied spin density wave (SDW) phase transitions in dimerized
quarter-filled Hubbard chains weakly coupled via interchain one-particle
hopping, $t_{b0}$. It is shown that there exists a critical value of $t_{b0}$,
$t_{b}^\ast$, between the incoherent metal regime ($t_{b0}<t_{b}^\ast$) and the
Fermi liquid regime ($t_{b0}>t_{b}^\ast$) in the metallic phase above the SDW
transition temperature. By using the 2-loop perturbative renormalization-group
approach together with the random-phase-approximation, we propose a SDW phase
diagram covering both of the regimes. The SDW phase transition from the
incoherent metal phase for $t_{b0}<t_{b}^\ast$ is caused by growth of the
intrachain electron-electron umklapp scattering toward low temperatures, which
is regarded as preformation of the Mott gap. We discuss relevance of the
present result to the SDW phase transitions in the quasi-one-dimensional
dimerized quarter-filled organic conductors, (TMTTF)$_2$X and (TMTSF)$_2$X.",9906383v2
1999-10-05,Sign Reversal of the Quantum Hall Effect and Helicoidal Magnetic-Field-Induced Spin-Density Waves in Organic Conductors,"Within the framework of the quantized nesting model, we study the effect of
umklapp scattering on the magnetic-field-induced spin-density-wave (SDW) phases
which are experimentally observed in the quasi-one-dimensional organic
conductors (TMTSF)$_2$X. We discuss the conditions under which umklapp
processes may explain the sign reversals (Ribault anomaly) of the quantum Hall
effect (QHE) observed in these conductors. We find that the `Ribault phase' is
characterized by the coexistence of two SDWs with comparable amplitudes. This
gives rise to additional long wavelength collective modes besides the Goldstone
modes due to spontaneous translation and rotation symmetry breaking. These
modes strongly affect the optical conductivity. We also show that the Ribault
phase may become helicoidal (i.e with circularly polarized SDWs) if the
strength of umklapp processes is sufficiently strong. The QHE vanishes in the
helicoidal phases, but a magnetoelectric effect appears.",9910051v1
1999-10-05,Macroscopic Quantum Dynamics of a Free Domain Wall in a Ferromagnet,"We study macroscopic quantum dynamics of a free domain wall in a
quasi-one-dimensional ferromagnet by use of the spin-coherent-state path
integral in {\it discrete-time} formalism. Transition amplitudes between
typical states are quantitatively discussed by use of {\it stationary-action
approximation} with respect to collective degrees of freedom representing the
center position and the chirality of the domain wall. It is shown that the
chirality may be loosely said to be canonically conjugate to the center
position; the latter moves with a speed depending on the former. It is
clarified under what condition the center position can be regarded as an
effective free-particle position, which exhibits the phenomenon of wave-packet
spreading. We demonstrate, however, that in some case the non-linear character
of the spin leads to such a dramatic phenomenon of a non-spreading wave packet
as to completely invalidate the free-particle analogy. In the course of the
discussion, we also point out various difficulties associated with the
continuous-time formalism.",9910060v1
2000-03-09,Signatures of the excitonic memory effects in four-wave mixing processes in cavity polaritons,"We report the signatures of the exciton correlation effects with finite
memory time in frequency domain degenerate four-wave mixing (DFWM) in
semiconductor microcavity. By utilizing the polarization selection rules, we
discriminate instantaneous, mean field interactions between excitons with the
same spins, long-living correlation due to the formation of biexciton state by
excitons with opposite spins, and short-memory correlation effects in the
continuum of unbound two-exciton states. The DFWM spectra give us the relative
contributions of these effects and the upper limit for the time of the
exciton-exciton correlation in the unbound two-exciton continuum. The obtained
results reveal the basis of the cavity polariton scattering model for the DFWM
processes in high-Q GaAs microcavity.",0003145v1
2000-05-14,Low-temperature specific heat of La0.78Pb0.22MnO3-d manganite,"The specific heat of the perovskite manganite La0.78Pb0.22MnO3-d was measured
from 0.5 to 25 K. The results yield values of the electronic density of states,
the Debye temperature, and the spin-wave stiffness constant of the compound.
The magnetic contribution was found to be consistent with the existence of a
gap in the spin-wave spectrum, and a phonon term in T^5 was needed to fit the
data.",0005228v1
2000-06-02,Quantum computation using electrons trapped by surface acoustic waves,"We describe in detail a set of ideas for implementing qubits, quantum gates
and quantum gate networks in a semiconductor heterostructure device. Our
proposal is based on an extension of the technology used for surface acoustic
wave (SAW) based single-electron transport devices. These devices allow single
electrons to be captured from a two-dimensional electron gas in the potential
minima of a SAW. We discuss how this technology can be adapted to allow the
capture of electrons in pure spin states and how both single and two-qubit
gates can be constructed using magnetic and non-magnetic gate technology. We
give designs for readout gates to allow the spin state of the electrons to be
measured and discuss how combinations of gates can be connected to make
multi-qubit networks. Finally we consider decoherence and other sources of
error, and how they can be minimized for our design.",0006037v1
2000-06-03,Edge electron states for quasi-one-dimensional organic conductors in the magnetic-field-induced spin-density-wave phases,"We develop a microscopic picture of the electron states localized at the
edges perpendicular to the chains in the Bechgaard salts in the quantum Hall
regime. In a magnetic-field-induced spin-density-wave state (FISDW)
characterized by an integer N, there exist N branches of chiral gapless edge
excitations. Localization length is much longer and velocity much lower for
these states than for the edge states parallel to the chains. We calculate the
contribution of these states to the specific heat and propose a time-of-flight
experiment to probe the propagating edge modes directly.",0006050v2
2000-06-19,Multi-band Gutzwiller wave functions for itinerant ferromagnetism,"Multi-band Gutzwiller-correlated wave functions reconcile the contrasting
concepts of itinerant band electrons versus electrons localized in partially
filled atomic shells. The approximate evaluation of these variational ground
states becomes exact in the limit of large coordination number. The result
allows the identification of quasi-particle band structures for correlated
electron systems. As a first application, we summarize a study of itinerant
ferromagnetism in a two-band model, thereby elucidating the co-operation of the
Coulomb repulsion and the Hund's-rule exchange. Then, we present results of
calculations for ferromagnetic nickel, using a realistic 18 spin-orbital basis
of 4s, 4p and 3d valence electrons. Good agreement with the experimental
ground-state properties of nickel is obtained. In particular, the
quasi-particle energy bands agree much better with the photo-emission and Fermi
surface data than the band structure obtained from spin-density functional
theory. Finally, we present results for the variational spinwave dispersion for
our two-band model.",0006283v1
2000-06-23,Spin waves and electronic interactions in La2CuO4,"The magnetic excitations of the square-lattice spin-1/2 antiferromagnet and
high-Tc parent La2CuO4 are determined using high-resolution inelastic neutron
scattering. Sharp spin waves with absolute intensities in agreement with theory
including quantum corrections are found throughout the Brillouin zone. The
observed dispersion relation shows evidence for substantial interactions beyond
the nearest-neighbor Heisenberg term, which can be understood in terms of a
cyclic or ring exchange due to the strong hybridization path around the Cu4O4
square plaquettes.",0006384v3
2000-08-10,Thermal properties of ferrimagnetic systems,"The heat capacity of some ferrimagnets has additional structures like a
shoulder in the Schottky-like peak, or emergence of a second peak when an
external magnetic field is applied. It is shown here that as long as spin
wave-spin wave interactions are ignored in a ferrimagnet, the ferromagnetic and
antiferromagnetic elementary excitation spectra give rise to two independent
heat capacity peaks, one enveloped by the other, which add up to give the peak
for the total system. Taking this into account helps understand the additional
structures in the peaks. Moreover, the classification of ferrimagnets into
predominantly antiferromagnetic, ferromagnetic, or a mixture of the two is
shown to be validated by studying them under additional influences like
dimerization and frustration. Because these two are shown to influence the
ferromagnetic and antiferromagnetic dispersion relations - and hence the
quantities like heat capacity and magnetic susceptibility - by different
amounts, the characterisation of ferrimagnetic systems ($1,1/2$), ($3/2,1$) and
($3/2,1/2$) is brought out more clearly. Both these influences enhance
antiferromagnetic character.",0008167v1
2000-08-15,Microscopic Theory of Damon-Eshbach Modes in Ferromagnetic Films,"The surface spin wave branches in ferromagnetic films are studied using a
microscopic theory which considers both magnetic dipole-dipole and Heisenberg
exchange interactions. The dipole terms are expressed in a Hamiltonian
formalism, and the dipole sums are calculated in a rapidly convergent form. The
Damon-Eshbach surface modes are analyzed for different directions of the
spin-wave propagation and also for different ratios of the strength of the
dipole interactions relative to the exchange interactions. Numerical results
are presented using parameters for Fe and GdCl$_3$.",0008223v1
2000-08-28,Long-range order and low-energy spectrum of diluted 2D quantum AF,"The problem of diluted two-dimensional (2D) quantum antiferromagnet (AF) on a
square lattice is studied using spin-wave theory. The influence of impurities
on static and dynamic properties is investigated and a good agreement with
experiments and Monte Carlo (MC) data is found. The hydrodynamic description of
spin-waves breaks down at characteristic wavelengths
$\Lambda\agt\exp(\frac{const}{x})$, $x$ being an impurity concentration, while
the order parameter is free from anomalies. We argue that this dichotomy
originates from strong scattering of the low-energy excitations in 2D.",0008412v2
2000-09-20,Quantum Fluctuations in the Frustrated Antiferromagnet Sr_2Cu_3O_4Cl_2,"Sr_2Cu_3O_4Cl_2 is an antiferromagnet consisting of weakly coupled CuO planes
which comprise two weakly interacting antiferromagnetic subsystems, I and II,
which order at respective temperatures T_I \approx 390K and T_{II} \approx 40K.
Except asymptotically near the ordering temperature, these systems are good
representations of the two-dimensional quantum spin 1/2 Heisenberg model. For
T< T_{II} there are four low-energy modes at zero wave vector, three of whose
energies are dominated by quantum fluctuations. For T_{II} < T < T_I there are
two low energy modes. The mode with lower energy is dominated by quantum
fluctuations. Our calculations of the energies of these modes (including
dispersion for wave vectors perpendicular to the CuO planes) agree extremely
well with the experimental results of inelastic neutron scattering (in the
accompanying paper) and for modes in the sub meV range observed by electron
spin resonance. The parameters needed to describe quantum fluctuations are
either calculated here or are taken from the literature. These results show
that we have a reasonable qualitative understanding of the band structure of
the lamellar cuprates needed to calculate the anisotropic exchange constants
used here.",0009315v1
2000-10-11,Thermodynamics and optical conductivity of unconventional spin density waves,"We consider the possibility of formation of an unconventional spin density
wave (USDW) in quasi-one dimensional electronic systems. In analogy with
unconventional superconductivity, we develop a mean field theory of SDW
allowing for the momentum dependent gap $\Delta({\bf k})$ on the Fermi surface.
Conditions for the appearence of such a low temperature phase are investigated.
The excitation spectrum and basic thermodynamic properties of the model are
found to be very similar to those of d-wave superconductors in spite of the
different topology of their Fermi surfaces. Several correlation functions are
calculated, and the frequency dependent conductivity is evaluated for various
gap functions. The latter is found to reflect the maximum gap value, however
with no sharp onset for absorbtion.",0010162v1
2001-05-15,Coupled Magnetic Excitations in Single Crystal PrBa2Cu3O6.2,"The dispersion of the low-energy magnetic excitations of the Pr sublattice in
PrBa2Cu3O6.2 is determined by inelastic neutron scattering measurements on a
single crystal. The dispersion, which shows the effect of interactions with the
Cu spin-waves, is well described by a model of the coupled Cu-Pr magnetic
system. This enables values for the principal exchange constants to be
determined, which suggest that both Pr-Pr and Cu-Pr interactions are important
in producing the anomalously high ordering temperature of the Pr sublattice.
Measurements of the Cu optic spin wave mode show that the inter-layer Cu-Cu
exchange is significantly lower than in YBa2Cu3O6.2.",0105292v1
2001-05-17,Spin-density-wave transition of (TMTSF)$_2$PF$_6$ at high magnetic fields,"The transverse magnetoresistance of the Bechgaard salt (TMTSF)$_2$PF$_6$ has
been measured for various pressures, with the field up to 24 T parallel to the
lowest conductivity direction c$^{\ast}$. A quadratic behavior is observed in
the magnetic field dependence of the spin-density-wave (SDW) transition
temperature $T_{\rm {SDW}}$. With increasing pressure, $T_{\rm {SDW}}$
decreases and the coefficient of the quadratic term increases. These results
are consistent with the prediction of the mean-field theory based on the
nesting of the quasi one-dimensional Fermi surface. Using a mean field theory,
$T_{\rm {SDW}}$ for the perfect nesting case is estimated as about 16 K. This
means that even at ambient pressure where $T_{\rm {SDW}}$ is 12 K, the SDW
phase of (TMTSF)$_2$PF$_6$ is substantially suppressed by the
two-dimensionality of the system.",0105336v1
2001-06-12,Spin-density-wave instabilities in the organic conductor (TMTSF)_2ClO_4: Role of anion ordering,"We study the spin-density-wave instabilities in the quasi-one-dimensional
conductor (TMTSF)_2ClO_4. The orientational order of the anions ClO_4 doubles
the unit cell and leads to the presence of two electrnic bands at the Fermi
level. From the Ginzburg-Landau expansion of the free energy, we determine the
low-temperature phase diagram as a function of the strength of the Coulomb
potential due to the anions. Upon increasing the anion potential, we first find
a SDW phase corresponding to an interband pairing. This SDW phase is rapidly
supressed, the metallic phase being then stable down to zero temperature. The
SDW instability is restored when the anion potential becomes of the order of
the hopping amplitude. The metal-SDW transition corresponds to an intraband
pairing which leaves half of the Fermi surface metallic. At lower temperature,
a second transition, corresponding to the other intraband pairing, takes place
and opens a gap on the whole Fermi surface. We discuss the consequences of our
results for the experimental phase diagram of (TMTSF)_2ClO_4 at high magnetic
field.",0106234v2
2001-08-28,Unexpected Metallic-like Behavior of the Resistance in the Dielectric Spin Density Wave State in (TMTSF)2PF6,"We report unexpected features of the transport in the dielectric spin density
wave (SDW) phase of the quasi one-dimensional compound (TMTSF)_2PF_6: the
resistance exhibits a maximum and a subsequent strong drop as temperature
decreases below approximately 2K. The maximum in R(T) is not caused by
depinning or Joule heating of the SDW. The characteristic temperature of the
R(T) maximum and the scaling behavior of the resistance at different magnetic
fields B evidence that the non-monotonic R(T) dependence has an origin
different from the one known for the quantum Hall effect region of the phase
diagram. We also found that the borderline T_0(B,P) which divides the field
induced SDW region of the P-B-T phase diagram into the hysteresis and
non-hysteresis domains, terminates in the N=1 sub-phase; the borderline has
thus no extension to the SDW N=0 phase.",0108455v1
2001-11-14,Superconductivity and Charge Density Wave in a Quasi-One-Dimensional Spin Gap System,"We consider a model of spin-gapped chains weakly coupled by Josephson and
Coulomb interactions. Combining such non-perturbative methods as bosonization
and Bethe ansatz to treat the intra-chain interactions with the Random Phase
Approximation for the inter-chain couplings and the first corrections to this,
we investigate the phase diagram of this model. The phase diagram shows both
charge density wave ordering and superconductivity. These phases are seperated
by a line of critical points which exhibits an approximate an SU(2) symmetry.
We consider the effects of a magnetic field on the system. We apply the theory
to the material Sr_2 Ca_12 Cu_24 O_41 and suggest further experiments.",0111264v3
2002-02-19,Unconventional spin density wave in (TMTSF)2PF6 below T* ~ 4K,"The presence of subphases in spin-density wave (SDW) phase of (TMTSF)2PF6
below T* ~ 4K has been suggested by several experiments but the nature of the
new phase is still controversial. We have investigated the temperature
dependence of the angular dependence of the magnetoresistance in the SDW phase
which shows different features for temperatures above and below T*. For T > 4K
the magnetoresistance can be understood in terms of the Landau quantization of
the quasiparticle spectrum in a magnetic field, where the imperfect nesting
plays the crucial role. We propose that below T* ~ 4K the new unconventional
SDW (USDW) appears modifying dramatically the quasiparticle spectrum. Unlike
conventional SDW the order parameter of USDW depends on the quasiparticle
momentum. The present model describes many features of the angular dependence
of magnetoresistance reasonably well. Therefore, we may conclude that the
subphase in (TMTSF)2PF6 below T* ~ 4K is described as SDW plus USDW.",0202317v2
2002-03-15,Structural effect on the static spin and charge correlations in La$_{1.875}$Ba$_{0.125-x}$Sr$_{x}$CuO$_{4}$,"We report the results of elastic neutron scattering measurements performed on
1/8-hole doped La$_{1.875}$Ba$_{0.125-x}$Sr$_{x}$CuO$_{4}$ single crystals with
{\it x}=0.05, 0.06, 0.075 and 0.085. In the low-temperature less-orthorhombic
(LTLO, {\it Pccn} symmetry) phase, the charge-density-wave (CDW) and
spin-density-wave (SDW) wavevectors were found to tilt in a low-symmetric
direction with one-dimensional anisotropy in the CuO$_{2}$ plane, while they
were aligned along the high-symmetry axis in the low-temperature tetragonal
(LTT, {\it P}4$_2$/{\it ncm} symmetry) phase. The coincident direction of two
wavevectors suggests a close relation between CDW and SDW orders. The SDW
wavevector systematically deviates from the Cu-O bond direction in the LTLO
phase upon Sr substitution and the tilt angle in the LTLO phase is smaller than
that in the low-temperature orthorhombic phase (LTO, {\it B}{\it mab} symmetry)
with comparable in-plane orthorhombic distortion. These results demonstrate a
correlation between the corrugated pattern of CuO$_{2}$ plane and the
deviations.",0203321v3
2002-07-12,Role of Collective Mode for Optical Conductivity and Reflectivity in Quarter-Filled Spin-Density-Wave State,"Taking account of a collective mode relevant to charge fluctuation, the
optical conductivity of spin-density-wave state has been examined for an
extended Hubbard model with one-dimensional quarter-filled band. We find that,
within the random phase approximation, the conductivity exhibits several peaks
at the frequency corresponding to the excitation energy of the commensurate
collective mode. When charge ordering appears with increasing inter-site
repulsive interactions, the main peak with the lowest frequency is reduced and
the effective mass of the mode is enhanced indicating the suppression of the
effect of the collective mode by charge ordering. It is also shown that the
reflectivity becomes large in a wide range of frequency due to the huge
dielectric constant induced by the collective mode.",0207316v2
2002-08-29,"Microscopic model, spin wave theory and competing orders in the double perovskites","We present a microscopic theory of carrier-induced ferrimagnetism in metallic
double perovskite compounds such as ${\rm Sr}_{2}{\rm FeMoO}_{6}$ and ${\rm
Sr}_{2}{\rm FeReO}_{6}$ which have recently attracted intense interest for
their possible applications to magnetotransport devices. The theory is based on
an effective ""Kondo-like"" Hamiltonian treated here within the large-$S$
expansion. We find that depending on the value of the carrier density the
ground state is either a ferrimagnet or a layered antiferromagnet. The
ferrimagnetic state has a robust half-metallic electronic structure. The
transition to antiferromagnetic phase is first order accompanied with the
regime of phase separation. We study spin wave spectrum including quantum
corrections and find strongly enhanced quantum effects in the vicinity of
zero-temperature phase transition.",0208586v3
2002-09-20,Influence of Spin Wave Excitations on the Ferromagnetic Phase Diagram in the Hubbard-Model,"The subject of the present paper is the theoretical description of collective
electronic excitations, i.e. spin waves, in the Hubbard-model. Starting with
the widely used Random-Phase-Approximation, which combines Hartree-Fock theory
with the summation of the two-particle ladder, we extend the theory to a more
sophisticated single particle approximation, namely the
Spectral-Density-Ansatz. Doing so we have to introduce a `screened`
Coulomb-interaction rather than the bare Hubbard-interaction in order to obtain
physically reasonable spinwave dispersions. The discussion following the
technical procedure shows that comparison of standard RPA with our new
approximation reduces the occurrence of a ferromagnetic phase further with
respect to the phase-diagrams delivered by the single particle theories.",0209480v1
2002-10-02,Theory of the Ramsey spectroscopy and anomalous segregation in ultra-cold rubidium,"The recent anomalous segregation experiment of Lewandowski et al. (PRL, 88,
070403, 2002) shows dramatic, rapid internal state segregation for two
hyperfine levels of rubidium. We simulate an effective one dimensional model of
the system for experimental parameters and find reasonable agreement with the
data. The Ramsey frequency is found to be insensitive to the decoherence of the
superposition, and is only equivalent to the interaction energy shift for a
pure superposition. A Quantum Boltzmann equation describing collisions is
derived using Quantum Kinetic Theory, taking into account the different
scattering lengths of the internal states. As spin-wave experiments are likely
to be attempted at lower temperatures we examine the effect of degeneracy on
decoherence by considering the recent experiment of Lewandowski et al. where
degeneracy is around 10%. We also find that the segregation effect is only
possible when transport terms are included in the equations of motion, and that
the interactions only directly alter the momentum distributions of the states.
The segregation or spin wave effect is thus entirely due to coherent atomic
motion as foreseen in the experimental report",0210070v1
2002-12-09,Competing phases in the extended U-V-J Hubbard model near the van Hove fillings,"The phase diagram of the two-dimensional extended one-band U-V-J Hubbard
model is considered within a mean-field approximation and two- and many-patch
renormalization group (RG) approaches near the van Hove band fillings. At small
t' and J>0 mean-field and many-patch RG approaches give similar results for the
leading spin-density-wave (SDW) instability, while the two-patch RG approach,
which predicts a wide region of charge-flux (CF) phase becomes unreliable due
to nesting effect. At the same time, there is a complex competition between
SDW, CF phases, and d-wave superconductivity in two- and many-patch RG
approaches. While the spin-flux (SF) phase is not stable at the mean-field
level, it is identified as a possible ground state at J<0 in both RG
approaches. With increasing t' the results of all three approaches merge:
d-wave superconductivity at J>0 and ferromagnetism at J<0 become the leading
instabilities. For large enough V the charge-density-wave (CDW) state occurs.",0212190v2
2003-06-14,Electron correlation and two dimensionality in the spin-density-wave phase of (TMTTF)$_2$Br under pressure,"The incommensurate spin-density-wave (SDW) phase in (TMTTF)$_2$Br was
investigated through transport measurements under pressure and magnetic fields
parallel to the $c^{\ast}$ axis. For the incommensurate SDW phase of
(TMTTF)$_2$Br stabilized above 0.5 GPa, the SDW transition temperature $T_{\rm
SDW}$ increases with the applied magnetic field. The field dependence of
$T_{\rm SDW}$ is described by a quadratic behavior and the coefficient of the
quadratic term increases with increasing pressure. These results are consistent
with the prediction of the mean-field theory based on the suppression of the
SDW transition by two-dimensionality. From the relation between the coefficient
of the quadratic term and $T_{\rm SDW}$ at zero magnetic field, we determined
the role of electron correlation and two dimensionality in the SDW phase of
(TMTTF)$_2$Br under pressure and found that the SDW transition in (TMTTF)$_2$Br
can be well explained within the mean field theory by taking into account the
reduction of the coupling constant $N(0)I$ by pressure.",0306383v1
2003-07-23,Dispersion of Magnetic Excitations in Superconducting Optimally Doped YBa_2Cu_3O_6.95,"Detailed neutron scattering measurements of YBa_2Cu_3O_6.95 found that the
resonance peak and incommensurate magnetic scattering induced by
superconductivity represent the same physical phenomenon: two dispersive
branches that converge near 41 meV and the in-plane wave-vector q_af=(pi/a,
pi/a) to form the resonance peak. One branch has a circular symmetry around
q_af and quadratic downward dispersion from ~41 meV to the spin gap of
33+-1meV. The other, of lower intensity, disperses from ~41 meV to at least 55
meV. Our results exclude a quartet of vertical incommensurate rods in q-w space
expected from spin waves produced by dynamical charge stripes as an origin of
the observed incommensurate scattering in optimally-doped YBCO.",0307591v3
2003-08-26,Stochastic description of the dynamics of the random-exchange Heisenberg chain,"We study the diffusion process in a Heisenberg chain with correlated spatial
disorder, with a power spectrum in the momentum space behaving as $k^{-\beta}$,
using a stochastic description. It establishes a direct connection between the
fluctuation in the spin-wave density of states and the noise density of states.
For continuous ranges of the exponent $\beta $, we find superdiffusive and
ballistic spin-wave motions. Both diffusion exponents predicted by the
stochastic procedure agree with the ones calculated using the Hamiltonian
dynamics.",0308542v3
2004-01-21,Theory of spinor Fermi and Bose gases in tight atom waveguides,"Divergence-free pseudopotentials for spatially even and odd-wave interactions
in spinor Fermi gases in tight atom waveguides are derived. The Fermi-Bose
mapping method is used to relate the effectively one-dimensional fermionic
many-body problem to that of a spinor Bose gas. Depending on the relative
magnitudes of the even and odd-wave interactions, the N-atom ground state may
have total spin S=0, S=N/2, and possibly also intermediate values, the case
S=N/2 applying near a p-wave Feshbach resonance, where the N-fermion ground
state is space-antisymmetric and spin-symmetric. In this case the fermionic
ground state maps to the spinless bosonic Lieb-Liniger gas. An external
magnetic field with a longitudinal gradient causes a Stern-Gerlach spatial
separation of the corresponding trapped Fermi gas with respect to various
values of $S_z$.",0401402v2
2004-04-16,Optical evidence for the proximity to a spin-density-wave metallic state in Na$_{0.7}$CoO$_2$,"We present the optical properties of \na single crystals, measured over a
broad spectral range as a function of temperature ($T$). The capability to
cover the energy range from the far-infrared up to the ultraviolet allows us to
perform reliable Kramers-Kronig transformation, in order to obtain the
absorption spectrum (i.e., the complex optical conductivity). To the complex
optical conductivity we apply the generalized Drude model, extracting the
frequency dependence of the scattering rate ($\Gamma$) and effective mass
($m^*$) of the itinerant charge carriers. We find that $\Gamma(\omega)\sim
\omega$ at low temperatures and for $\omega > T$. This suggests that \na is at
the verge of a spin-density-wave metallic phase.",0404400v1
2004-06-03,Proximity effect of vanadium on spin-density-wave magnetism in Cr films,"The spin-density wave (SDW) state in thin chromium films is well known to be
strongly affected by proximity effects from neighboring layers. To date the
main attention has been given to effects arising from exchange interactions at
interfaces. In the present work we report on combined neutron and synchrotron
scattering studies of proximity effects in Cr/V films where the boundary
condition is due to the hybridization of Cr with paramagnetic V at the
interface. We find that the V/Cr interface has a strong and long-range effect
on the polarization, period, and the N\'{e}el temperature of the SDW in rather
thick Cr films. This unusually strong effect is unexpected and not predicted by
theory.",0406071v1
2004-06-22,Investigation of the Spin Density Wave in NaxCoO2,"Magnetic susceptibility, transport and heat capacity measurements of single
crystal NaxCoO2 (x=0.71) are reported. A transition to a spin density wave
(SDW) state at Tmag = 22 K is observable in all measurements, except chi(ac)
data in which a cusp is observed at 4 K and attributed to a low temperature
glassy phase. M(H) loops are hysteretic below 15 K. Both the SDW transition and
low temperature hysteresis are only visible along the c-axis. The system also
exhibits a substantial (~40%) positive magnetoresistance below this
temperature. Calculations of the electronic heat capacity gamma above and below
Tmag and the size of the jump in C indicate that the onset of the SDW brings
about the opening of gap and the removal of part of the Fermi surface. Reduced
in-plane electron-electron scattering counteracts the loss of carriers below
the transition and as a result we see a net reduction in resistivity below
Tmag. Sodium ordering transitions at higher temperatures are observable as
peaks in the heat capacity with a corresponding increase in resistivity.",0406513v2
2004-07-26,A Full-Potential-Linearized-Augmented-Plane-Wave Electronic Structure Study of delta-Plutonium and the (001) Surface,"The electronic and geometric properties of bulk fcc delta-plutonium and the
quantum size effects in the surface energies and the work functions of the
(001) ultra thin films (UTF) up to 7 layers have been investigated with
periodic density functional theory calculations within the full-potential
linearized augmented-plane wave (FP-LAPW) approach as implemented in the WIEN2k
package. Our calculated equilibrium atomic volume of 178.3 a.u.^3 and bulk
modulus of 24.9 GPa at the fully relativistic level of theory, i.e.
spin-polarization and spin-orbit coupling included, are in good agreement with
the experimental values of 168.2 a.u.^3 and 25 GPa (593 K), respectively. The
calculated equilibrium lattice constants at different levels of approximation
are used in the surface properties calculations for the thin films. The surface
energy is found to be rapidly converged with the semi-infinite surface energy
predicted to be 0.692eV at the fully-relativistic level.",0407676v1
2004-09-27,A symmetry-projected variational approach to the 1-dimensional Hubbard-model,"We apply a variational method devised for the nuclear many--body problem to
the 1-dimensional Hubbard--model with nearest neighbor hopping and periodic
boundary conditions. The test wave function consist for each state out of a
single Hartree--Fock determinant mixing all the sites (or momenta) as well as
the spin--projections of the electrons. Total spin and linear momentum are
restored by projection methods before the variation. It is demonstrated that
this approach reproduces the results of exact diagonalisations for half--filled
N=12 and N=14 lattices not only for the energies and occupation numbers of the
ground but also of the lowest excited states rather well. Furthermore, a system
of 10 electrons in a N=12 lattice is investigated and, finally, a N=30 lattice
is studied. In addition to energies and occupation numbers we present the
spectral functions computed with the help of the symmetry--projected wave
functions, too. Also here nice agreement with the exact results (where
available) is reached.",0409691v1
2005-02-18,Complementary colors of colorons: the elementary excitations of the SU(3) Haldane--Shastry model,"We propose two possible trial wave functions for the elementary excitations
of the SU(3) Haldane--Shastry model, but then argue on very general grounds
that only one or the other can be a valid excitation. We then prove explicitly
that the trial wave function describing a coloron excitation which transforms
according to representation $\bar{3}$ under SU(3) rotations if the spins of the
original model transform according to representation 3, is exact. If a basis
for the spins on the chain is spanned by the colors blue, red, and green, a
basis for the coloron excitations is hence given by the complementary colors
yellow, cyan, and magenta. We obtain the dispersion and the exclusion
statistics among polarized colorons. Furthermore, we compare our results with
the asymptotic Bethe Ansatz and discuss the generalization to SU($n$).",0502451v2
2005-03-01,Berry phase of magnons in textured ferromagnets,"We study the energy spectrum of magnons in a ferromagnet with topologically
nontrivial magnetization profile. In the case of inhomogeneous magnetization
corresponding to a metastable state of ferromagnet, the spin-wave equation of
motion acquires a gauge potential leading to a Berry phase for the magnons
propagating along a closed contour. The effect of magnetic anisotropy is
crucial for the Berry phase: we show that the anisotropy suppresses its
magnitude, which makes the Berry phase observable in some cases, similar to the
Aharonov-Bohm effect for electrons. For example, it can be observed in the
interference of spin waves propagating in mesoscopic rings. We discuss the
effect of domain walls on the interference in ferromagnetic rings, and propose
some experiments with a certain geometry of magnetization. We also show that
the nonvanishing average topological field acts on the magnons like a uniform
magnetic field on electrons. It leads to the quantization of the magnon
spectrum in the topological field.",0503013v1
2005-07-20,Novel Phase Transition Near the Quantum Critical Point in the Filled-Skutterudite Compound CeOs4Sb12: an Sb-NQR Study,"We report on a novel phase transition at $T$ = 0.9 K in the Ce-based
filled-skutterudite compound CeOs$_{4}$Sb$_{12}$ via measurements of the
nuclear-spin lattice relaxation rate $1/T_{1}$ and nuclear quadrupole resonance
(NQR) spectrum of Sb nuclei. The temperature ($T$) dependence of $1/T_1$
behaves as if approaching closely an antiferromagnetic (AFM) quantum critical
point (QCP), following the relation $1/T_{1}\propto T/(T-T_{\rm N})^{1/2}$ with
$T_{\rm N} = 0.06$ K in the range of $T=1.3-25$ K. The onset of either the
spin-density-wave (SDW) or charge-density-wave (CDW) order at $T_{\rm 0} = 0.9$
K, that is, of the first order, is evidenced by a broadening of the NQR
spectrum and a marked reduction in $1/T_1$ just below $T_{\rm 0}$. The
$f$-electron-derived correlated band realized in CeOs$_{4}$Sb$_{12}$ is
demonstrated to give rise to the novel phase transition on the verge of AFM
QCP.",0507470v1
2005-07-24,Nonlinear Optical Response of Spin Density Wave Insulators,"We calculate the third order nonlinear optical response in the Hubbard model
within the spin density wave (SDW) mean field ansatz in which the gap is due to
onsite Coulomb repulsion. We obtain closed-form analytical results in one
dimension (1D) and two dimension (2D), which show that nonlinear optical
response in SDW insulators in 2D is stronger than both 3D and 1D. We also
calculate the two photon absorption (TPA) arising from the stress tensor term.
We show that in the SDW, the contribution from stress tensor term to the
low-energy peak corresponding to two photon absorption becomes identically zero
if we consider the gauge invariant current properly.",0507556v2
2005-11-14,Superfluid density and competing orders in d-wave superconductors,"We derive expressions for the superfluid density $\rho_s$ in the
low-temperature limit $T \to 0$ in d-wave superconductors, taking into account
the presence of competing orders such as spin-density waves, $i
d_{xy}$-pairing, etc. Recent experimental data for the thermal conductivity and
for elastic neutron scattering in La$_{2-x}$Sr$_x$CuO$_4$ suggest there are
magnetic field induced anomalies that can be interpreted in terms of competing
orders. We consider the implications of these results for the superfluid
density and show in the case of competing spin-density wave order that the
usual Volovik-like $\sqrt{H}$ depletion of $\rho_s(H)$ is replaced by a slower
dependence on applied magnetic field. We find that it is crucial to include the
competing order parameter in the self-consistent equation for the impurity
scattering rate.",0511349v2
2005-11-24,Coloron excitations of the SU(3) Haldane--Shastry model,"In a recent publication, we proposed two possible wave functions for the
elementary excitations of the SU(3) Haldane--Shastry model (HSM), but argued on
very general grounds that only one or the other can be a valid excitation. Here
we provide the explicit details of our calculation proving that the wave
function describing a coloron excitation which transforms according to
representation $\bar{3}$ under SU(3) rotations if the spins of the original
model transform according to representation 3, is exact. We further provide an
explicit construction of the exact color-polarized two-coloron eigenstates, and
thereby show that colorons are free but that their relative momentum spacings
are shifted according to fractional statistics with parameter $g=2/3$. We
evaluate the SU(3) spin currents. Finally, we interpret our results within the
framework of the asymptotic Bethe Ansatz and generalize some of them to the
case of SU($n$).",0511604v2
2005-12-23,"Incommensurate magnetic ordering in Cu2Te2O5X2 (X=Cl, Br) studied by single crystal neutron diffraction","Polarized and unpolarized neutron diffraction studies have been carried out
on single crystals of the coupled spin tetrahedra systems Cu2Te2O5X2 (X=Cl,
Br). A model of the magnetic structure associated with the propagation vectors
k'Cl ~ -0.150,0.422,1/2 and k'Br ~ -0.172,0.356,1/2 and stable below TN=18 K
for X=Cl and TN=11 K for X=Br is proposed. A feature of the model, common to
both the bromide and chloride, is a canted coplanar motif for the 4 Cu2+ spins
on each tetrahedron which rotates on a helix from cell to cell following the
propagation vector. The Cu2+magnetic moment determined for X=Br, 0.395(5)muB,
is significantly less than for X=Cl, 0.88(1)muB at 2K. The magnetic structure
of the chloride associated with the wave-vector k' differs from that determined
previously for the wave vector k~0.150,0.422,1/2 [O. Zaharko et.al. Phys. Rev.
Lett. 93, 217206 (2004)].",0512617v1
2006-03-03,Effects of Electron Correlation near Spin-Density-Wave on Angle Dependence of Magnetoconductivity,"The effect of electron correlation on the angle dependence of
magnetoconductivity is studied in quasi-one-dimensional organic conductors. We
investigated the effect on the basis of the momentum dependence of both
quasi-particle's lifetime and velocity near the spin-density-wave (SDW). We
found that the momentum dependence of quasi-particle's lifetime mainly governs
the angle dependence of one-dimensional axis magnetoconductivity. On the other
hand, the change in velocity originating from the electron correlation gives
the dominant effects on the angle dependence of the interchain axis
magnetoconductivity. The effect of electron correlation is clarified from the
association of the momentum dependences of lifetime and velocity with the
momentum dependences of commensurate orbitals on a Fermi surface in magnetic
fields.",0603072v1
2006-03-29,Electronic Structure and Optical Properties of the Co-doped Anatase TiO$_{2}$ Studied from First Principles,"The Co-doped anatase TiO$_{2}$, a recently discovered room-temperature
ferromagnetic insulator, has been studied by the first-principles calculations
in the pseudo-potential plane-wave formalism within the local-spin-density
approximation (LSDA), supplemented by the full-potential linear augmented plane
wave (FP-LAPW) method. Emphasis is placed on the dependence of its electronic
structures and linear optical properties on the Co-doping concentration and
oxygen vacancy in the system in order to pursue the origin of its
ferromagnetism. In the case of substitutional doping of Co for Ti, our
calculated results are well consistent with the experimental data, showing that
Co is in its low spin state. Also, it is shown that the oxygen vacancy enhances
the ferromagnetism and has larger effect on both the electronic structure and
optical properties than the Co-doping concentration only.",0603779v1
2006-04-04,Experimental evidence of paired hole states in model high-$T_c$ compounds,"The distribution of holes in Sr$_{14-x}$Ca$_x$Cu$_{24}$O$_{41}$ (SCCO) is
revisited with semi-emperical reanalysis of the x-ray absorption (XAS) data and
exact-diagonalized cluster calculations. A new interpretation of the XAS data
leads to much larger ladder hole densities than previously suggested. These new
hole densities lead to a simple interpretation of the hole crystal (HC)
recently reported with 1/3 and 1/5 wave vectors along the ladder. Our
interpretation is consistent with paired holes in the rung of the ladders.
Exact diagonalization results for a minimal model of the doped ladders suggest
that the stabilization of spin structures consisting of 4 spins in a square
plaquette as a result of resonance valence bond (RVB) physics suppresses the
hole crystal with a 1/4 wave vector.",0604101v1
2006-06-26,Excitonic Superfluid to pseudo-spin density wave transition in bilayer quantum Hall systems,"We construct a quantum Ginsburg-Landau theory to study the quantum phase
transition from the excitonic superfluid (ESF) to a possible pseudo-spin
density wave (PSDW) at some intermediate distances driven by the magneto-roton
minimum collapsing at a finite wavevector. We analyze the properties of the
PSDW and explicitly show that a square lattice is the favorite lattice. We
suggest that correlated hopping of vacancies in the active and passive layers
in the PSDW state leads to very large and temperature dependent drag consistent
with the experimental data. Comparisons with previous microscopic numerical
calculations are made. Further experimental implications are given.",0606639v6
2006-07-27,Phenomenological Theory of Multiple Spin Density Waves in fcc Transition Metals,"The relative stability among the multiple spin density wave (MSDW) states in
fcc transition metals has been investigated on the basis of a Ginzburg-Landau
type of free energy with terms up to the fourth order in magnetic moments.
Obtained magnetic phase diagrams in the space of expansion coefficients
indicate the possibility of various 3Q MSDW states in fcc transition metals:
the commensurate 3Q state, the incommensurate linear 3Q state, and the
incommensurate helical 3Q state. It is shown that these 3Q states are always
stabilized, when they are compared with the corresponding 2Q and 1Q states, and
their magnetic moment amplitudes are the largest among those of the three
states. The results are compared with previous results of the ground-state
calculations, and possible scenarios to explain the experimental data of fcc-Fe
are proposed.",0607710v1
2006-08-01,Flat spin wave dispersion in a triangular antiferromagnet,"The excitation spectrum of a S=1/2 2D triangular quantum antiferromagnet is
studied using 1/S expansion. Due to the non-collinearity of the classical
ground state significant and non-trivial corrections to the spin wave spectrum
appear already in the first order in 1/S in contrast to the square lattice
antiferromagnet. The resulting magnon dispersion is almost flat in a
substantial portion of the Brillouin zone. Our results are in quantitative
agreement with recent series expansion studies by Zheng, Fjaerestad, Singh,
McKenzie, and Coldea [PRL 96, 057201 (2006) and cond-mat/0608008].",0608002v2
2006-09-29,Magnetic Excitation Spectrum of the Square Lattice S=1/2 Heisenberg Antiferromagnet K2V3O8,"We have explored the magnetic excitation spectrum of the S=1/2 square lattice
Heisenberg antiferromagnet, K2V3O8 using both triple-axis and time-of-flight
inelastic neutron scattering. The long-wavelength spin waves are consistent
with the previously determined Hamiltonian for this material. A small energy
gap of 72+/-9 micro-eV is observed at the antiferromagnetic zone center and the
near-neighbor exchange constant is determined to be 1.08+/-0.03 meV. A finite
ferromagnetic interplanar coupling is observed along the crystallographic
c-axis with a magnitude of Jc=-0.0036+/-0.006 meV. However, upon approaching
the zone boundary, the observed excitation spectrum deviates significantly from
the expectation of linear spin wave theory resulting in split modes at the
(pi/2,pi/2) zone boundary point. The effects of magnon-phonon interaction,
orbital degrees of freedom, multimagnon scattering, and dilution/site
randomness are considered in the context of the mode splitting. Unfortunately,
no fully satisfactory explanation of this phenomenon is found and further
theoretical and experimental work is needed.",0609775v2
2006-10-08,Multiferroicity induced by dislocated spin-density waves,"We uncover a new pathway towards multiferroicity, showing how magnetism can
drive ferroelectricity without relying on inversion symmetry breaking of the
magnetic ordering. Our free-energy analysis demonstrates that any commensurate
spin-density-wave ordering with a phase dislocation, even if it is collinear,
gives rise to an electric polarization. Due to the dislocation the electronic
and magnetic and inversion centers do not coincide, which turns out to be a
sufficient condition for multiferroic coupling. The novel mechanism explains
the formation of multiferroic phases at the magnetic commensurability
transitions, such as the ones observed in YMn$_{2}$O$_{5}$ and related
compounds. We predict that in these multiferroics an oscillating electrical
polarization is concomitant with the uniform polarization. On the basis of our
theory we put forward new types of magnetic materials that are potentially
ferroelectric.",0610214v2
2006-10-12,Time-Resolved Quasiparticle Dynamics in the Spin-Density-Wave State,"Time-resolved photoinduced reflectivity is measured in the spin-density-wave
(SDW) phase using itinerant antiferromagnets UMGa$_{5}$ (M=Ni, Pt). For
UNiGa$_{5}$ [$T_{N}$=85 K, $Q$=($\pi$,$\pi$,$\pi$)], the relaxation time $\tau$
shows a sharp increase at $T_{N}$ consistent with the opening of a SDW gap. For
UPtGa$_{5}$ [$T_{N}$=26 K, $Q$=(0,0,$\pi$)], no change in $\tau$ is observed at
$T_{N}$ or at the lowest temperatures. We attribute this to the absence of the
SDW gap at the Fermi level, due to a different modulation vector $Q$, which
leads to a gapless quasiparticle spectrum. Our results challenge the
conventional wisdom that a SDW phase necessarily implies a SDW gap at the Fermi
level.",0610353v1
2007-03-21,Spin Configurations and Activation Gaps of the Quantum Hall States in Graphene,"We report on our accurate evaluation of spin polarizations of the ground
state and particle-hole gaps for partially-filled lowest Landau level, observed
in recent experiments on graphene subjected to ultra-high magnetic fields. We
find that inter-electron interactions are important at these filling factors,
characterized by the non-degenerate ground states and large particle-hole gaps
at infinitely large wave vectors. The gaps are the largest for the quantum Hall
states in the second Landau level. The weak appearance of quantum Hall plateaus
in the experiments for certain filling factors in the second Landau level
however indicates that at these filling factors, the system has a soft mode at
a finite wave vector due presumably to the presence of disorder.",0703536v1
1996-03-19,Post-Newtonian expansion of gravitational waves from a particle in circular orbits around a rotating black hole: Up to $O(v^8)$ beyond the quadrupole formula,"Extending a method developed by Sasaki in the Schwarzschild case and by
Shibata, Sasaki, Tagoshi, and Tanaka in the Kerr case, we calculate the
post-Newtonian expansion of the gravitational wave luminosities from a test
particle in circular orbit around a rotating black hole up to $O(v^8)$ beyond
the quadrupole formula. The orbit of a test particle is restricted on the
equatorial plane. We find that spin dependent terms appear in each
post-Newtonian order, and that at $O(v^6)$ they have a significant effect on
the orbital phase evolution of coalescing compact binaries. By comparing the
post-Newtonian formula of the luminosity with numerical results we find that,
for $30M\lesssim r \lesssim 100M$, the spin dependent terms at $O(v^6)$ and
$O(v^7)$ improve the accuracy of the post-Newtonian formula significantly, but
those at $O(v^8)$ do not improve.",9603028v1
2000-07-10,Solution of Dirac equation around a spinning Black Hole,"Chandrasekhar separated the Dirac equation for spinning and massive particles
in Kerr geometry in radial and angular parts. Chakrabarti solved the angular
equation and found the corresponding eigenvalues for different Kerr parameters.
The radial equations were solved asymptotically by Chandrasekhar. In the
present paper, we use the WKB approximation to solve the spatially complete
radial equation and calculate analytical expressions of radial wave functions
for a set of Kerr and wave parameters. From these solutions we obtain local
values of reflection and transmission coefficients.",0007016v2
2000-07-11,Search for periodic gravitational radiation with the ALLEGRO gravitational wave detector,"We describe the search for a continuous signal of gravitational radiation
from a rotating neutron star in the data taken by the ALLEGRO gravitational
wave detector in early 1994. Since ALLEGRO is sensitive at frequencies near 1
kHz, only neutron stars with spin periods near 2 ms are potential sources.
There are no known sources of this typ e for ALLEGRO, so we directed the search
towards both the galactic center and the globular clus ter 47 Tucanae. The
analysis puts a constraint of roughly $8 \times 10^{-24}$ at frequencies near 1
kHz on the gravitational strain emitted from pulsar spin-down in either 47
Tucanae or the galactic center.",0007023v1
2000-08-09,Gravitational Wave Damping of Neutron Star Wobble,"We calculate the effect of gravitational wave (gw) back-reaction on realistic
neutron stars (NS's) undergoing torque-free precession. By `realistic' we mean
that the NS is treated as a mostly-fluid body with an elastic crust, as opposed
to a rigid body. We find that gw's damp NS wobble on a timescale tau_{theta}
approx 2 x 10^5 yr [10^{-7}/(DId/I_0)]^2 (kHz/ nu_s)^4, where nu_s is the spin
frequency and DId is the piece of the NS's inertia tensor that ""follows"" the
crust's principal axis (as opposed to its spin axis). We give two different
derivations of this result: one based solely on energy and angular momentum
balance, and another obtained by adding the Burke-Thorne radiation reaction
force to the Newtonian equations of motion. This problem was treated long ago
by Bertotti and Anile (1973), but their claimed result is wrong. When we
convert from their notation to ours, we find that their tau_{theta} is too
short by a factor of order 10^5 for typical cases of interest, and even has the
wrong sign for DId negative. We show where their calculation went astray.",0008021v1
2000-09-13,Quantization of massless fields over the static Robertson-Walker space of constant negative curvature,"Taking the ${\Bbb R}^1 \times H^3$ space as an example, we develop the new
method of quantization of fields over symmetric spaces. We construct the
quantized massless fields of an arbitrary spin over the ${\Bbb R}^1 \times H^3$
space by the resolution over the systems of ""plane waves"" which are solutions
of the corresponding wave equations. The propagators of these fields are ${\Bbb
R}^1 \times SO(3,1)$-invariant and causal. For spin 0 and 1/2 fields the
propagators are obtained in the explicit form.",0009048v2
2001-01-17,Tanaka-Tagoshi Parametrization of post-1PN Spin-Free Gravitational Wave Chirps: Equispaced and Cardinal Interpolated Lattices For First Generation Interferometric Antennas,"The spin-free binary-inspiral parameter-space introduced by Tanaka and
Tagoshi to construct a uniformly-spaced lattice of templates at (and possibly
beyond) $2.5PN$ order is shown to work for all first generation interferometric
gravitational wave antennas. This allows to extend the minimum-redundant
cardinal interpolation techniques of the correlator bank developed by the
Authors to the highest available order PN templates. The total number of 2PN
templates to be computed for a minimal match $\Gamma=0.97$ is reduced by a
factor 4, as in the 1PN case.",0101067v3
2001-02-28,Implications of the r-mode instability of rotating relativistic stars,"Several recent surprises appear dramatically to have improved the likelihood
that the spin of rapidly rotating, newly formed neutron stars (and, possibly,
of old stars spun up by accretion) is limited by a nonaxisymmetric instability
driven by gravitational waves. Except for the earliest part of the spin-down,
the axial l=m=2 mode (an r-mode) dominates the instability, and the emitted
waves may be observable by detectors with the sensitivity of LIGO II. A review
of these hopeful results is followed by a discussion of constraints on the
instability set by dissipative mechanisms, including viscosity, nonlinear
saturation, and energy loss to a magnetic field driven by differential
rotation.",0102114v2
2004-05-29,Gravitational wave bursts induced by r-mode spin-down of hybrid stars,"We show that sudden variations in the composition and structure of an hybrid
star can be triggered by its rapid spin-down, induced by r-mode instabilities.
The discontinuity of this process is due to the surface tension between
hadronic and quark matter and in particular to the overpressure needed to
nucleate new structures of quark matter in the mixed phase. The consequent
mini-collapses in the star can produce highly energetic gravitational wave
bursts. The possible connection between the predictions of this model and the
burst signal found by EXPLORER and NAUTILUS detectors during the year 2001 is
also investigated.",0405145v3
2006-05-05,Fermion scattering by a Schwarzschild black hole,"We study the scattering of massive spin-half waves by a Schwarzschild black
hole using analytical and numerical methods. We begin by extending a recent
perturbation theory calculation to next order to obtain Born series for the
differential cross section and Mott polarization, valid at small couplings. We
continue by deriving an approximation for glory scattering of massive spinor
particles by considering classical timelike geodesics and spin precession.
Next, we formulate the Dirac equation on a black hole background, and outline a
simple numerical method for finding partial wave series solutions. Finally, we
present our numerical calculations of absorption and scattering cross sections
and polarization, and compare with theoretical expectations.",0605031v2
2006-06-30,The Distinction Between Dirac and Majorana Neutrino Wave Packets Due to Gravity and Its Impact on Neutrino Oscillations,"We present the possibility that Dirac and Majorana neutrino wave packets can
be distinguished when subject to spin-gravity interaction while propagating
through vacuum described by the Lense-Thirring metric. By adopting the
techniques of gravitational phase and time-independent perturbation theory
following the Brillouin-Wigner method, we generate spin-gravity matrix elements
from a perturbation Hamiltonian and show that this distinction is easily
reflected in well-defined gravitational corrections to the neutrino oscillation
length for a two-flavour system. Explicit examples are presented using the Sun
and SN1987A as the gravitational sources for the Lense-Thirring metric. This
approach offers the possibility to determine the absolute neutrino masses by
this method and identify a theoretical upper bound for the absolute neutrino
mass difference, where the distinctions between the Dirac and Majorana cases
are evident. We discuss the relevance of this analysis to the upcoming attempts
to measure the properties of low-energy neutrinos by SNO and other solar
neutrino observatories.",0606134v1
2007-01-01,Comparisons of binary black hole merger waveforms,"This a particularly exciting time for gravitational wave physics.
Ground-based gravitational wave detectors are now operating at a sensitivity
such that gravitational radiation may soon be directly detected, and recently
several groups have independently made significant breakthroughs that have
finally enabled numerical relativists to solve the Einstein field equations for
coalescing black-hole binaries, a key source of gravitational radiation. The
numerical relativity community is now in the position to begin providing
simulated merger waveforms for use by the data analysis community, and it is
therefore very important that we provide ways to validate the results produced
by various numerical approaches. Here, we present a simple comparison of the
waveforms produced by two very different, but equally successful
approaches--the generalized harmonic gauge and the moving puncture methods. We
compare waveforms of equal-mass black hole mergers with minimal or vanishing
spins. The results show exceptional agreement for the final burst of radiation,
with some differences attributable to small spins on the black holes in one
case.",0701016v2
2005-12-23,Test experiment to search for a neutron EDM by the Laue diffraction method,"A prototype experiment to measure the neutron electric dipole moment (nEDM)
by spin-rotation in a non-centrosymmetric crystal in Laue geometry was carried
out in order to investigate the statistical sensitivity and systematic effects
of the method. The statistical sensitivity to the nEDM was about $6\cdot
10^{-24}$ e$\cdot $cm per day and can be improved by one order of magnitude for
the full scale setup. Systematics was limited by the homogeneity of the
magnetic field in the crystal region and by a new kind of spin rotation effect.
We attribute this effect to a difference of the two Bloch waves amplitudes in
the crystal, which is caused by the presence of a small crystal deformation due
to a temperature gradient. In a revised scheme of the experiment, this effect
could be exploited for a purposeful manipulation of the Bloch waves.",0512064v1
2006-03-23,Partial wave analyses of J/psi to gamma pi^+ pi^- and gamma pi^0 pi^0,"Results are presented on J/psi radiative decays to pi^+pi^- and pi^0pi^0
based on a sample of 58M J/psi events taken with the BESII detector. Partial
wave analyses are carried out using the relativistic covariant tensor amplitude
method in the 1.0 to 2.3 GeV/c^2 pipi mass range. There are conspicuous peaks
due to the f_2(1270) and two 0^++ states in the 1.45 and 1.75 GeV/c^2 mass
regions. The first 0^++ state has a mass of 1466\pm 6\pm 20 MeV/c^2, a width of
108^{+14}_{-11}\pm 25 MeV/c^2, and a branching fraction B(J/psi \to \gamma
f_0(1500) \to\gamma \pi^+\pi^-) = (0.67\pm0.02\pm0.30) \times 10^{-4}. Spin 0
is strongly preferred over spin 2. The second 0^++ state peaks at
1765^{+4}_{-3}\pm 13 MeV/c^2 with a width of 145\pm8\pm69 MeV/c^2. If this 0^++
is interpreted as coming from f_0(1710), the ratio of its branching fractions
to pipi and K\bar K is 0.41^{+0.11}_{-0.17}.",0603048v4
1993-11-18,Hadrons of Arbitrary Spin and Heavy Quark Symmetry,"We present a general construction of the spin content of the Bethe-Salpeter
amplitudes (covariant wave functions) for heavy hadrons with arbitrary orbital
excitations, using representations of the Lorentz group. These wave functions
incorporate the symmetries manifest in the heavy quark limit. In the baryonic
sector we clearly differentiate between the $\Lambda$ and $\Sigma$ type excited
baryons. We then use the trace formalism to evaluate the weak transitions of
ground state heavy hadrons to arbitrary excited heavy hadrons. The
contributions of excited states to the Bjorken sum rule are also worked out in
detail.",9311309v2
1997-03-24,The hard scattering amplitude for the higher helicity components of the pion form factor,"For obtaining the spin space wave function of the pion meson in the
light-cone formalism from the naive quark model, it is necessary to take into
account Wigner rotation. Consequently there are higher helicity
($\lambda_1+\lambda_2=\pm 1$) components in the light-cone spin space wave
function of the pion besides the usual helicity ($\lambda_1+\lambda_2=0$)
components. For the pion electromagnetic form factor, we calculate the
hard-scattering amplitude for the higher helicity components in the light-cone
perturbation theory. It is found that the hard-scattering amplitude for the
higher helicity components is of order $1/Q^4$, which is vanishingly small
compared to that of the ordinary helicity component at very high $Q^2$ but
should be considered in the $Q^2$ region where experimental data are available.",9703395v1
1999-10-25,Neutrino Oscillations in Electromagnetic Fields,"Oscillations of neutrinos $\nu_L \leftrightarrow \nu_R$ in presence of an
arbitrary electromagnetic field are considered. We introduce the Hamiltonian
for the neutrino spin evolution equation that accounts for possible effects of
interaction of neutrino magnetic $\mu$ and electric $\epsilon$ dipole moments
with the transversal (in respect to the neutrino momentum) and also the
longitudinal components of electromagnetic field. Using this Hamiltonian we
predict the new types of resonances in the neutrino oscillations $\nu_L
\leftrightarrow \nu_R$ in the presence of the field of an electromagnetic wave
and in combination of an electromagnetic wave and constant magnetic field. The
possible influence of the longitudinal magnetic field on neutrino oscillations
is emphasized.",9910476v4
2005-09-20,Complex conformal spin partial wave expansion of generalized parton distributions and distribution amplitudes,"We introduce a new representation of generalized parton distributions and
generalized distribution amplitudes that is based on the partial wave
decomposition with respect to the complex collinear conformal spin. This
decomposition leads us to a versatile parameterization of these
non-perturbative functions in terms of conformal moments, which are measurable
for integer value on the lattice. This new representation has several
advantages: basic properties and crossing relations are automatically
implemented, a rather flexible parameterization is possible, the numerical
treatment of evolution is simple and analytic approximation of scattering
amplitudes can be given. We demonstrate this for simple examples. In
particular, phenomenological considerations indicate that the t-dependence of
Mellin moments is governed by Regge trajectories. The new representation is
vital to push the analysis of deeply virtual Compton scattering to
next-to-next-to-leading order.",0509204v1
2006-09-17,"Cross-fertilization of QCD and statistical physics: high energy scattering, reaction-diffusion, selective evolution, spin glasses and their connections","High energy scattering was recently shown to be similar to a
reaction-diffusion process. The latter defines a wide universality class that
also contains e.g. some specific population evolution models. The common point
of all these models is that their respective dynamics are described by noisy
traveling wave equations. This observation has led to a new understanding of
QCD in the regime of high energies, and known universal results on
reaction-diffusion models could be transposed to obtain quantitative properties
of QCD amplitudes. Conversely, new general results for that kind of statistical
models have also been derived. Furthermore, an intriguing relationship between
noisy traveling wave equations and the theory of spin glasses was found.",0609161v2
1994-04-03,A Geometric Model of Arbitrary Spin Massive Particle,"A new model of relativistic massive particle with arbitrary spin
(($m,s$)-particle) is suggested. Configuration space of the model is a product
of Minkowski space and two-dimensional sphere, ${\cal M}^6 = {\Bbb R}^{3,1}
\times S^2$. The system describes Zitterbewegung at the classical level.
Together with explicitly realized Poincar\'e symmetry, the action functional
turns out to be invariant under two types of gauge transformations having their
origin in the presence of two Abelian first-class constraints in the Hamilton
formalism. These constraints correspond to strong conservation for the
phase-space counterparts of the Casimir operators of the Poincar\'e group.
Canonical quantization of the model leads to equations on the wave functions
which prove to be equivalent to the relativistic wave equations for the massive
spin-$s$ field.",9403196v2
2001-04-03,Vector boson in constant electromagnetic field,"The propagator and complete sets of in- and out-solutions of wave equation,
together with Bogoliubov coefficients, relating these solutions, are obtained
for vector $W$-boson (with gyromagnetic ratio $g=2$) in a constant
electromagnetic field. When only electric field is present the Bogoliubov
coefficients are independent of boson polarization and are the same as for
scalar boson. When both electric and magnetic fields are present and collinear,
the Bogoliubov coefficients for states with boson spin perpendicular to the
field are again the same as in scalar case. For $W^-$ spin along (against) the
magnetic field the Bogoliubov coefficients and the contributions to the
imaginary part of the Lagrange function in one loop approximation are obtained
from corresponding expressions for scalar case by substitution $m^2\to m^2+2eH$
$(m^2\to m^2-2eH)$. For gyromagnetic ratio $g=2$ the vector boson interaction
with constant electromagnetic field is described by the functions, which can be
expected by comparing wave functions for scalar and Dirac particle in constant
electromagnetic field.",0104019v1
2002-03-14,"RG flows from Spin(7), CY 4-fold and HK manifolds to AdS, Penrose limits and pp waves","We obtain explicit realizations of holographic renormalization group (RG)
flows from M-theory, from E^{2,1} \times Spin(7) at UV to AdS_4 \times
\tilde{S^7} (squashed S^7) at IR, from E^{2,1} \times CY4 at UV to AdS_4 \times
Q^{1,1,1} at IR, and from E^{2,1} \times HK (hyperKahler) at UV to AdS_4 \times
N^{0,1,0} at IR. The dual type IIA string theory configurations correspond to
D2-D6 brane systems where D6 branes wrap supersymmetric four-cycles. We also
study the Penrose limits and obtain the pp-wave backgrounds for the above
configurations. Besides, we study some examples of non-supersymmetric and
supersymmetric flows in five-dimensional gauge theories.",0203124v3
2004-01-05,Integrable Open Spin Chain in Super Yang-Mills and the Plane-wave/SYM duality,"We investigate the integrable structures in an N=2 superconfomal Sp(N)
Yang-Mills theory with matter, which is dual to an open+closed string system.
We restrict ourselves to the BMN operators that correspond to free string
states. In the closed string sector, an integrable structure is inherited from
its parent theory, N=4 SYM. For the open string sector, the planar one-loop
mixing matrix for gauge invariant holomorphic operators is identified with the
Hamiltonian of an integrable SU(3) open spin chain. Using the K-matrix
formalism we identify the integrable open-chain boundary conditions that
correspond to string boundary conditions. The solutions to the algebraic Bethe
ansatz equations (ABAE) with a few impurities are shown to recover the
anomalous dimensions that exactly match the spectrum of free open string in the
plane-wave background. We also discuss the properties of the solutions of ABAE
beyond the BMN regime.",0401016v3
2004-01-08,Orientifold and stringy frame of the Kerr Spinning Particle,"We show that the frame of the Kerr spinning particle consists of two
topologically coupled strings. One of them is the Kerr singular ring
representing a string with an orientifold world-sheet. It has electromagnetic
excitations (traveling waves), which corresponds to the old model of the Kerr's
microgeon. The excitations induce the appearance of the extra axial string
which is topologically coupled to the Kerr circular string and is a carrier of
pp-waves and fermionic zero modes. This string can be described by the Witten
field model for superconducting strings.",0401047v2
2005-07-12,The Dirac -- Kerr-Newman electron,"We discuss the relation of the Kerr-Newman spinning particle to the Dirac
electron and show that the Dirac equation may naturally be incorporated into
Kerr-Schild formalism as a master equation controlling the Kerr-Newman
geometry. As a result, the Dirac electron acquires an extended space-time
structure of the Kerr-Newman geometry - singular ring of the Compton size and
twistorial polarization of the gravitational and electromagnetic fields.
  Behavior of this Dirac -- Kerr-Newman system in the weak and slowly changed
electromagnetic fields is determined by the wave function of the Dirac
equation, and is indistinguishable from the behavior of the Dirac electron. The
wave function of the Dirac equation plays in this model the role of an ``order
parameter'' which controls dynamics, spin-polarization and twistorial structure
of space-time.",0507109v4
2006-05-24,"PCT, spin and statistics, and analytic wave front set","A new, more general derivation of the spin-statistics and PCT theorems is
presented. It uses the notion of the analytic wave front set of
(ultra)distributions and, in contrast to the usual approach, covers nonlocal
quantum fields. The fields are defined as generalized functions with test
functions of compact support in momentum space. The vacuum expectation values
are thereby admitted to be arbitrarily singular in their space-time dependence.
The local commutativity condition is replaced by an asymptotic commutativity
condition, which develops generalizations of the microcausality axiom
previously proposed.",0605243v1
2005-03-25,General Solutions of Relativistic Wave Equations II: Arbitrary Spin Chains,"A construction of relativistic wave equations on the homogeneous spaces of
the Poincar\'{e} group is given for arbitrary spin chains. Parametrizations of
the field functions and harmonic analysis on the homogeneous spaces are
studied. It is shown that a direct product of Minkowski spacetime and
two-dimensional complex sphere is the most suitable homogeneous space for the
physical applications. The Lagrangian formalism and field equations on the
Poincar\'{e} and Lorentz groups are considered. A boundary value problem for
the relativistically invariant system is defined. General solutions of this
problem are expressed via an expansion in hyperspherical functions defined on
the complex two-sphere.",0503058v2
1996-08-20,Influence of spin-rotation measurements on partial-wave analyses of elastic pion-nucleon scattering,"Recent measurements of spin-rotation parameters in elastic $\pi^+ p$
scattering are in marked disagreement with predictions of the
Carnegie-Mellon$-$Berkeley and Karlsruhe-Helsinki analyses. Using the method of
Barrelet, we show how this discrepancy can be removed. We then show how this
Barrelet transformation alters the partial-wave amplitudes. The effect of
unitarity and analyticity constraints is also considered.",9608043v1
1998-09-15,"Relativistic current densities for bound spin-orbit partners and the longitudinal-transverse response in (e,e'p) processes","Scalar, baryon and vector--current densities in coordinate and momentum space
are calculated within a relativistic mean--field model. The role of the low
components of the bound nucleon wave function is investigated in detail for
different spin--orbit partner shells. We show that the relative importance of
the negative--energy projection components can be explained from the different
quantum numbers involved in the relativistic wave function. This fact has
proved to be important in the analysis of various electron scattering
observables even for low--medium values of the bound nucleon momentum.",9809048v1
2004-07-16,Tensor analyzing powers in forward angle exclusive $π$-meson photoproduction on deuteron,"The target tensor analyzing powers of the process $\gamma d -> \pi^{-}pp$ had
been studied in the plane wave impulse approximation, if both ejected protons
are detected in coincidence and in the directions, symmetrical respect to the
incoming photon momentum, being in the proton plane. The matrix elements of the
studied reaction become essentially simple, if the magnitudes of the proton
momenta p1 = p2 = p are equal. That proton kinematics keeps the ejected pion
angle near zero, therefore the one body pion production operator does not
include the spin-non-flip term. Moreover, the transition to the triplet,
spatially antisymmetric final pp- state is strongly suppressed from the
symmetrical deuteron S - state as well as matrix elements have a large
dependence from the orientation of the deuteron spin. The values of the
$T_{22}(\vec p)$ component, calculated with three realistic deuteron wave
functions in the proton momentum region p >= 350 MeV/c and proton polar angle
theta >= 40 deg., differ one from another noticeably.",0407045v1
2004-12-15,Spin-orbit interaction of photons and fine splitting of levels in ring dielectric resonator,"We consider eigenmodes of a ring resonator made of a circular dielectric
waveguide. Taking into account the polarization corrections, which are
responsible for the interaction of polarization and orbital properties of
electromagnetic waves (spin-orbit interaction of photons), results in fine
splitting of the levels of scalar approximation. The basic features of this
fine structure of the levels are similar to that of electron levels in an atom.
Namely: 1) sublevels of the fine structure are defined by an additional quantum
number: product of helicity of the wave and its orbital moment; 2) for a
waveguide with a parabolic profile of the refractive index each level of the
scalar approximation splits into N sublevels (N is the principal quantum
number), while for any other profile it splits into 2 sublevels; 3) each level
of the fine structure remains twice degenerated due to local axial symmetry of
the waveguide. Numerical estimations show that the described fine splitting of
levels may be observed in optic-fiber ring resonators.",0412084v3
2005-08-04,Lanczos - Einstein - Petiau: From Dirac's equation to nonlinear wave mechanics,"In 1929 Lanczos showed how to derive Dirac's equation from a more fundamental
system that predicted that spin 1/2 particles should come in pairs. Today,
these pairs can unambiguously be interpreted as isospin doublets. From the same
fundamental equation, Lanczos derived also the correct form of the wave
equation of massive spin 1 particles that would be rediscovered in 1936 by
Proca.
  Lanczos's fundamental system was put in Lagrangian form and generalized in
1933 by Einstein and Mayer, who used the semivector instead of the quaternion
formalism. Although they not did study all possible solutions, Einstein and
Mayer showed that the doublets consisted of particles with different mass and
charge. In fact, there are two main classes of doublets: proton/neutron and
electron/neutrino pairs.",0508036v2
2006-03-09,Geometrical Optics of Beams with Vortices: Berry Phase and Orbital Angular Momentum Hall Effect,"We consider propagation of a paraxial beam carrying the spin angular momentum
(polarization) and intrinsic orbital angular momentum (IOAM) in a smoothly
inhomogeneous isotropic medium. It is shown that the presence of IOAM can
dramatically enhance and rearrange the topological phenomena that previously
were considered solely in connection to the polarization of transverse waves.
In particular, the appearance of a new-type Berry phase that describes the
parallel transport of the beam structure along a curved ray is predicted. We
derive the ray equations demonstrating the splitting of beams with different
values of IOAM. This is the orbital angular momentum Hall effect, which
resembles Magnus effect for optical vortices. Unlike the recently discovered
spin Hall effect of photons, it can be much larger in magnitude and is inherent
to waves of any nature. Experimental means to detect the phenomena is
discussed.",0603072v3
2000-11-22,Experimental Test of Complementarity by Nuclear Magnetic Resonance Techniques,"We have tested complementarity for the ensemble-averaged spin states of
nuclei $^{13}$C in the molecule of $^{13}$CHCl$_{3}$ by the use of the spin
states of another nuclei $^{1}$H as the path marker. It turns out that the
wave-particle duality holds when one merely measures the probability density of
quantum states, and that the wave- and particle-like behavior is simultaneously
observed with the help of measuring populations and coherence in a single
nuclear magnetic resonance(NMR) experiment. Effects of path-marking schemes and
causes of the appearance and disappearance of the wave behavior are analysed.",0011094v2
2003-10-26,Energy-momentum operators with eigenfunctions localized along a line,"The momentum operator $ {\bf p} = - i {\bx \nabla} $ has radial component $
{\bf \tilde p} \equiv - i {\bf \hat{r}} ({1 \over r} \partial_r r).$ We show
that ${\bf \tilde p} $ is the space part of a 4-vector operator, the zero
component of which is a positive operator. Their eigenfunctions are localized
along an axis through the origin. The solutions of the evolution equation $ i
\partial_t \psi = {\tilde p^0} \psi $ are waves along the propagation axis.
Lorentz transformations of these waves yield the aberration and Doppler shift.
We briefly consider spin-half and spin-one representations.",0310159v3
2004-08-07,On the Generalized Dirac Equation for Fermions with Two Mass States,"The generalized Dirac equation of the second order, describing particles with
spin 1/2 and two mass states, is analyzed. The projection operators extracting
states with definite energy and spin projections are obtained. The first order
generalized Dirac equation in the 20-dimensional matrix form and the
relativistically invariant bilinear form are derived. We obtain the canonical
energy-momentum tensor and density of the electromagnetic current expressed
through the 20-component wave function. Minimal and non-minimal electromagnetic
interactions of fermions are considered, and the quantum-mechanical Hamiltonian
is found. It is shown that there are only causal propagations of waves in the
approach considered.",0408056v3
2005-11-30,A complete analysis of the Stern-Gerlach experiment using Pauli spinors,"The Stern-Gerlach experiment is the fundamental experiment in order to
exhibit the quantization of spin and understand the measurement problem in
quantum mechanics. However, although the Stern-Gerlach experiment plays an
essential role in the teaching of quantum mechanics, no complete analysis of
this experiment using Pauli spinors is presented in the pedagogical literature.
This paper presents such an analysis and develops implications for the theory
of quantum measurement.
  We first propose an analytic expression of both the wave function and the
probability density in the Stern-Gerlach experiment. Our explicit solution is
obtained via a complete integration of the Pauli equation over time and space.
The probability density evolution describes a slipping of the wave packet into
two separate packets due to the measurement device, but it cannot account for
impacts.
  We therefore calculate the de Broglie-Bohm trajectories, which not only
explain impacts naturally, but also accounts for the spin quantization
following the magnetic field gradient. It is then possible to propose a clear
explanation of measurement effects in the Stern-Gerlach experiment.",0511276v1
2007-03-31,Formation of quasi-solitons in transverse confined ferromagnetic film media,"The formation of quasi-2D spin-wave waveforms in longitudinally magnetized
stripes of ferrimagnetic film was observed by using time- and space-resolved
Brillouin light scattering technique. In the linear regime it was found that
the confinement decreases the amplitude of dynamic magnetization near the
lateral stripe edges. Thus, the so-called effective dipolar pinning of dynamic
magnetization takes place at the edges.
  In the nonlinear regime a new stable spin wave packet propagating along a
waveguide structure, for which both transversal instability and interaction
with the side walls of the waveguide are important was observed. The
experiments and a numerical simulation of the pulse evolution show that the
shape of the formed waveforms and their behavior are strongly influenced by the
confinement.",0704.0024v1
2007-04-05,Incommmensurability and unconventional superconductor to insulator transition in the Hubbard model with bond-charge interaction,"We determine the quantum phase diagram of the one-dimensional Hubbard model
with bond-charge interaction X in addition to the usual Coulomb repulsion U at
half-filling. For large enough X and positive U the model shows three phases.
For large U the system is in the spin-density wave phase already known in the
usual Hubbard model. As U decreases, there is first a spin transition to a
spontaneously dimerized bond-ordered wave phase and then a charge transition to
a novel phase in which the dominant correlations at large distances correspond
to an incommensurate singlet superconductor.",0704.0717v2
2007-04-09,Superconductivity and magnetic order in CeRhIn$_{5}$; spectra of coexistence,"We discuss the fixed-point Hamiltonian and the spectrum of excitations of a
quasi-bidimensional electronic system supporting simultaneously
antiferromamagnetic ordering and superconductivity. The coexistence of these
two order parameters in a single phase is possible because the magnetic order
is linked to the formation of a spin density wave, and its order parameter is
not associated to a spectral gap but to an energy shift of the paramagnetic
bands. This peculiarity entails several distinct features in the phase diagram
and the spectral properties of the model, which may have been observed in
CeRhIn$_5$. Apart from the coexistence, we find an abrupt suppression of the
spin density wave when the superconducting and magnetic ordering temperatures
are equal. The divergence of the cyclotron mass extracted from de Haas-van
Alphen experiments is also analyzed in the same framework.",0704.1082v1
2007-05-10,Magnetization oscillations induced by a spin-polarized current in a point-contact geometry: mode hopping and non-linear damping effects,"In this paper we study magnetization excitations induced in a thin extended
film by a spin-polarized dc-current injected through a point contact in the
current-perpendicular-to-plane (CPP) geometry. Using full-scale micromagnetic
simulations, we demonstrate that in addition to the oscillations of the
propagating wave type, there exist also two localized oscillation modes. The
first localized mode has a relatively homogeneous magnetization structure of
its kernel and corresponds to the so called 'bullet' predicted analytically by
Slavin and Tiberkevich (Phys. Rev. Lett., 95 (2005) 237201). Magnetization
pattern of the second localized mode kernel is highly inhomogeneous, leading to
a much smaller power of magnetoresistance oscillations caused by this mode. We
have also studied the influence of a non-linear damping for this system and
have found the following main qualitative effects: (i) the appearance of
frequency jumps within the existence region of the propagating wave mode and
(ii) the narrowing of the current region where the 'bullet' mode exists, until
this mode completely disappears for a sufficiently strong non-linear damping.",0705.1515v1
2007-05-14,Static versus dynamic fluctuations in the one-dimensional extended Hubbard model,"The extended Hubbard Hamiltonian is a widely accepted model for uncovering
the effects of strong correlations on the phase diagram of low-dimensional
systems, and a variety of theoretical techniques have been applied to it. In
this paper the world-line quantum Monte Carlo method is used to study spin,
charge, and bond order correlations of the one-dimensional extended Hubbard
model in the presence of coupling to the lattice. A static alternating lattice
distortion (the ionic Hubbard model) leads to enhanced charge density wave
correlations at the expense of antiferromagnetic order. When the lattice
degrees of freedom are dynamic (the Hubbard-Holstein model), we show that a
similar effect occurs even though the charge asymmetry must arise
spontaneously. Although the evolution of the total energy with lattice coupling
is smooth, the individual components exhibit sharp crossovers at the phase
boundaries. Finally, we observe a tendency for bond order in the region between
the charge and spin density wave phases.",0705.2043v3
2007-07-02,Magnetic Single-Electron Transistor as a Tunable Model System for Kondo-Destroying Quantum Criticality,"Single-electron transistors attached to ferromagnetic leads can undergo a
continuous quantum phase transition as their gate voltage is tuned. The
corresponding quantum critical point separates a Fermi liquid phase from a
non-Fermi liquid one. Here, we expound on the physical idea proposed earlier.
The key physics is the critical destruction of the Kondo effect, which
underlies a new class of quantum criticality that has been argued to apply to
heavy fermion metals. Its manifestation in the transport properties is studied
through an effective Bose-Fermi Kondo model; the bosonic bath, corresponding to
the spin waves of the ferromagnetic leads, describes a particular type of
sub-Ohmic dissipation. We also present results for general forms of sub-Ohmic
dissipative bath, and consider in some detail the case with critical paramagons
replacing spin waves. Finally, we discuss some delicate aspects in the
theoretical treatment of the effect of a local magnetic field, particularly in
connection with the frequently employed Non-Crossing Approximation.",0707.0062v2
2007-07-16,Zener double exchange from local valence fluctuations in magnetite,"Magnetite (Fe$_{3}$O$_{4}$) is a mixed valent system where electronic
conductivity occurs on the B-site (octahedral) iron sublattice of the spinel
structure. Below $T_{V}=122$ K, a metal-insulator transition occurs which is
argued to arise from the charge ordering of 2+ and 3+ iron valences on the
B-sites (Verwey transition). Inelastic neutron scattering measurements show
that optical spin waves propagating on the B-site sublattice ($\sim$80 meV) are
shifted upwards in energy above $T_{V}$ due to the occurrence of B-B
ferromagnetic double exchange in the mixed valent metallic phase. The double
exchange interaction affects only spin waves of $\Delta_{5}$ symmetry, not all
modes, indicating that valence fluctuations are slow and the double exchange is
constrained by electron correlations above $T_{V}$.",0707.2253v1
2007-08-01,$ΛNN$ and $ΣNN$ systems at threshold: II. The effect of D waves,"Using the two-body interactions obtained from a chiral constituent quark
model we study all $\Lambda NN$ and $\Sigma NN$ states with I=0,1,2 and
J=1/2,3/2 at threshold, taking into account all three-body configurations with
S and D wave components. We constrain further the limits for the $\Lambda N$
spin-triplet scattering length a_{1/2,1}. Using the hypertriton binding energy
we find a narrow interval for the possible values of the $\Lambda N$
spin-singlet scattering length a_{1/2,0}. We found that the $\Sigma NN$ system
has a quasibound state in the (I,J) = (1,1/2) channel very near threshold with
a width of about 2.1 MeV.",0708.0199v1
2007-11-01,Relationship between ferroelectricity and Dzyaloshinskii-Moriya interaction in multiferroics and the effect of bond-bending,"We studied the microscopic mechanism of multiferroics, in particular with the
""spin current"" model (Hosho Katsura, Naoto Nagaosa and Aleander V. Balatsky,
Phys. Rev. Lett. 95, 057205 (2005)). Starting from a system with helical spin
configuration, we solved for the forms of the electron wave functions and
analyzed their characteristics. The relation between ferroelectricity and
Dzyaloshinskii-Moriya interaction (I. Dzyaloshinskii, J. Phys. Chem. Solids 4,
241 (1958) and T. Moriya, Phys. Rev. 120, 91 (1960)) is clearly established.
There is also a simple relation between the electric polarization and the wave
vector of magnetic orders. Finally, we show that the bond-bending exists in
transition metal oxides can enhance ferroelectricity.",0711.0100v2
2007-12-18,Observation of electromagnon excitations in the BiFe0$_3$ spiral magnet,"Recently, oxide multiferroics have attracted much attention due to their
large magnetoelectric effect which allows the tuning of magnetic properties
with electric field and vice versa and open new venues for future spintronic
applications such as multiple-state memory devices with dual magnetic and
electric control. BiFeO$_3$ (BFO) belongs to this new class of materials and
shows both ferroelectric and antiferromagnetic orders at room temperature with
a large electric polarizationassociated with a cycloidal spiral magnetic
ordering. The incommensurate magnetic order induces magnon zone folding and
allows investigations by optical probes of unusual spin waves which couples to
optical phonons, the so called ""`electromagnons""'. Here, we unravel for the
first time the electromagnon spectra of BFO by means low energy inelastic light
scattering technique. We show the existence of two species of electromagnons
corresponding to spin wave excitations in and out of the cycloidal plane. The
present observations present an unique opportunity to study the interplay
between ferroelectric and magnetic orders.",0712.3044v1
2007-12-23,Phase diagram of the one dimensional anisotropic Kondo-necklace model,"The one dimensional anisotropic Kondo-necklace model has been studied by
several methods. It is shown that a mean field approach fails to gain the
correct phase diagram for the Ising type anisotropy. We then applied the spin
wave theory which is justified for the anisotropic case. We have derived the
phase diagram between the antiferromagnetic long range order and the Kondo
singlet phases. We have found that the exchange interaction (J) between the
itinerant spins and local ones enhances the quantum fluctuations around the
classical long range antiferromagnetic order and finally destroy the ordered
phase at the critical value, J_c. Moreover, our results show that the onset of
anisotropy in the XY term of the itinerant interactions develops the
antiferromagnetic order for J<J_c. This is in agreement with the qualitative
feature which we expect from the symmetry of the anisotropic XY interaction. We
have justified our results by the numerical Lanczos method where the structure
factor at the antiferromagnetic wave vector diverges as the size of system goes
to infinity.",0712.3914v2
2008-01-29,A Relativistic Wave Equation for the Skyrmion,"We propose a relativistically invariant wave equation for the Skyrme soliton.
It is a differential equation on the space $R^{1,3}\times S^3$ which is
invariant under the Lorentz group and isospin. The internal variable valued in
$SU(2)\approx S^3$ describes the orientation of the soliton. The mass of a
particle of spin and isospin both equal to $j={1\over 2},{3\over 2}...$ is
predicted to be $M=m\sqrt{1+K_2j(j+1)\over 1+K_1j(j+1)}$ which agrees with the
known spectrum for low angular momentum. The iso-scalar magnetic moment is
predicted to be $-{K_1\over 4m}{\mathbf \Sigma}$, where ${\mathbf \Sigma}$ is
the spin.",0801.4538v1
2008-02-28,Chromium at High Pressures: Weak Coupling and Strong Fluctuations in an Itinerant Antiferromagnet,"The spin- and charge-density-wave order parameters of the itinerant
antiferromagnet chromium are measured directly with non-resonant x-ray
diffraction as the system is driven towards its quantum critical point with
high pressure using a diamond anvil cell. The exponential decrease of the spin
and charge diffraction intensities with pressure confirms the harmonic scaling
of spin and charge, while the evolution of the incommensurate ordering vector
provides important insight into the difference between pressure and chemical
doping as means of driving quantum phase transitions. Measurement of the charge
density wave over more than two orders of magnitude of diffraction intensity
provides the clearest demonstration to date of a weakly-coupled, BCS-like
ground state. Evidence for the coexistence of this weakly-coupled ground state
with high-energy excitations and pseudogap formation above the ordering
temperature in chromium, the charge-ordered perovskite manganites, and the blue
bronzes, among other such systems, raises fundamental questions about the
distinctions between weak and strong coupling.",0802.4273v1
2008-03-28,Kondo-lattice theory of anisotropic singlet superconductivity,"Kondo-lattice theory for the t-J model and a phenomenological theory based on
it are developed to study superconductivity in the vicinity of the Mott
metal-insulator transition. Since the quenching of magnetic moments by
single-site quantum spin fluctuations or the Kondo effect is reduced by the
opening of a superconducting gap, spin density wave (SDW) can appear in a
superconducting state and the Knight shift can deviate from the Yosida function
to be small. The electron-phonon interaction, which arises from the modulation
of the superexchange interaction by phonons, is crucial in the coexistence of
superconductivity and SDW. It is proposed that the coexistence of
superconductivity, a double-Q SDW, a double-Q lattice distortion, and a
double-Q charge density wave induced by the SDW rather than the lattice
distortion, is responsible for the checkerboard structure and the
zero-temperature pseudo-gap observed in under-doped cuprate superconductors.",0803.4217v1
2008-04-05,Doubly degenerate orbital system in honeycomb lattice: implication of orbital state in layered iron oxide,"We study a doubly-degenerate orbital model on a honeycomb attice. This is a
model for orbital states in multiferroic layered iron oxides. The classical and
quantum models are analyzed by spin-wave approximation, Monte-Carlo simulation
and Lanczos method. A macroscopic number of degeneracy exists in the classical
ground state. In the classical model, a peak in the specific heat appears at a
temperature which is much lower than the mean-field ordering one. Below this
temperature, angle of orbital pseudo-spin is fixed, but conventional orbital
orders are not suggested. The degeneracy in the ground state is partially
lifted by thermal fluctuation. We suggest a role of zero-dimensional
fluctuation in hexagons on a low-temperature orbital structure. Lifting of the
degeneracy also occurs at zero temperature due to the quantum zero-point
fluctuation. We show that the ground-state wave function is well represented by
a linear combination of the states where a honeycomb lattice is covered by
nearest-neighboring pairs of orbitals with the minimum bond energy.",0804.0843v1
2008-05-05,"Combined theory of complete orthonormal sets of quasirelativistic and relativistic sets of wave functions, and Slater orbitals of spin -1/2 particles in position, momentum and four dimensional spaces","By the use of complete orthonormal sets of nonrelativistic scalar orbitals
introduced by the author in previous papers the new complete orthonormal basis
sets for two-and four-component spinor wave functions, and Slater spinor
orbitals useful in the quantum-mechanical description of the spin - 1/2
particles by the quasirelativistic and relativistic equations are established
in position, momentum and four-dimensional spaces. These function sets are
expressed through the corresponding nonrelativistic orbitals. The analytical
formulas for overlap integrals over four component relativistic Slater spinor
orbitals with the same screening constants in position space are also derived.
The relations obtained in this study can be useful in the study of different
problems arising in the quasirelativistic and relativistic quantum mechanics
when the position, momentum and four dimensional spaces are employed.",0805.0527v1
2008-05-12,Parameter estimation of spinning binary inspirals using Markov-chain Monte Carlo,"We present a Markov-chain Monte-Carlo (MCMC) technique to study the source
parameters of gravitational-wave signals from the inspirals of stellar-mass
compact binaries detected with ground-based gravitational-wave detectors such
as LIGO and Virgo, for the case where spin is present in the more massive
compact object in the binary. We discuss aspects of the MCMC algorithm that
allow us to sample the parameter space in an efficient way. We show sample runs
that illustrate the possibilities of our MCMC code and the difficulties that we
encounter.",0805.1689v1
2008-05-23,Nodal Spin Density Wave and band topology of the FeAs based materials,"The recently discovered FeAs-based materials exhibit a $(\pi,0)$ Spin Density
Wave (SDW) in the undoped state, which gives way to superconductivity upon
doping. Here we show that due to an interesting topological feature of the band
structure, the SDW state cannot acquire a full gap. This is demonstrated within
the SDW mean-field theory of both a simplified two band model and a more
realistic 5-band model. The positions of the nodes are different in the two
models and can be used to detected the validity of each model.",0805.3535v4
2008-05-27,Spin density wave anomaly at 140 K in the ternary iron arsenide BaFe2As2,"The ternary iron arsenide BaFe2As2 with the tetragonal ThCr2Si2-type
structure exhibits a spin density wave (SDW) anomaly at 140 K, very similar to
LaFeAsO, the parent compound of the iron arsenide superconductors. BaFe2As2 is
a poor Pauli-paramagnetic metal and undergoes a structural and magnetic phase
transition at 140 K, accompanied by strong anomalies in the specific heat,
electrical resistance and magnetic susceptibility. In the course of this
transition, the space group symmetry changes from tetragonal (I4/mmm) to
orthorhombic (Fmmm). 57Fe Moessbauer spectroscopy experiments show a single
signal at room temperature and full hyperfine field splitting below the phase
transition temperature (5.2 T at 77 K). Our results suggest that BaFe2As2 can
serve as a new parent compound for oxygen-free iron arsenide superconductors.",0805.4021v2
2008-07-24,"Coexistence of the spin-density-wave and superconductivity in the (Ba,K)Fe2As2","The relation between the spin-density-wave (SDW) and superconducting order is
a central topic in current research on the FeAs-based high Tc superconductors.
Conflicting results exist in the LaFeAs(O,F)-class of materials, for which
whether the SDW and superconductivity are mutually exclusive or they can
coexist has not been settled. Here we show that for the (Ba,K)Fe2As2 system,
the SDW and superconductivity can coexist in an extended range of compositions.
The availability of single crystalline samples and high value of the energy
gaps would make the materials a model system to investigate the high Tc
ferropnictide superconductivity.",0807.3950v1
2008-07-31,Detection of periodic gravitational wave sources by Hough transform in the frequency and spin down plane,"In the hierarchical search for periodic sources of gravitational waves, the
candidate selection, in the incoherent step, can be performed with Hough
transform procedures. In this paper we analyze the problem of sensitivity loss
due to discretization of the parameters space vs computing cost, comparing the
properties of the sky Hough procedure with those of a new frequency Hough,
which is based on a transformation from the time - observed frequency plane to
the source frequency - spin down plane. Results on simulated peak maps suggest
various advantages in favor of the use of the frequency Hough. The ones which
show up to really make the difference are 1) the possibility to enhance the
frequency resolution without relevantly affecting the computing cost. This
reduces the digitization effects; 2) the excess of candidates due to local
disturbances in some places of the sky map. They do not affect the new analysis
because each map is constructed for only one position in the sky. Pacs.
numbers: 04.80Nn,07.05Kf,97.60Jd 1.",0807.5065v1
2008-08-19,Low-energy magnetic response of the noncentrosymmetric heavy-fermion superconductor CePt3Si studied via inelastic neutron scattering,"The low-energy magnetic excitations of the noncentrosymmetric heavy-fermion
superconductor CePt3Si have been measured with inelastic neutron scattering on
a single crystal. Kondo-type spin fluctuations with an anisotropic wave vector
dependence are observed in the paramagnetic state. These fluctuations do not
survive in the antiferromagnetically ordered state below TN=2.2 K but are
replaced by damped spin waves, whose dispersion is much stronger along the
c-axis than in other directions. No change is observed in the excitation
spectrum or the magnetic order as the system enters the superconducting state
below Tc=0.7 K.",0808.2580v2
2008-08-19,Possible Superconductivity in Fe-Sb Based Materials: Density Functional Study of LiFeSb,"We investigate the electronic and other properties of the hypothetical
compound LiFeSb in relation to superconducting LiFeAs and FeSe using density
functional calculations. The results show that LiFeSb in the LiFeAs structure
would be dynamically stable in the sense of having no unstable phonon modes,
and would have very similar electronic and magnetic properties to the layered
Fe based superconductors. Importantly, a very similar structure for the Fermi
surface and a spin density wave related to but stronger than that in the
corresponding As compound is found. These results are indicative of possible
superconductivity analogous to the Fe-As based compounds if the spin density
wave can be suppressed by doping or other means. Prospects for synthesizing
this material in pure form or in solid solution with FeTe are discussed.",0808.2653v3
2008-08-25,Dynamic origin of azimuthal modes splitting in vortex-state magnetic dots,"A spin wave theory explaining experimentally observed frequency splitting of
dynamical excitations with azimuthal symmetry of a magnetic dot in a vortex
ground state is developed. It is shown that this splitting is a result of the
dipolar hybridization of three spin wave modes of a dot having azimuthal
indices |m|=1: two high-frequency azimuthal excitation modes of the in-plane
part of the vortex with indices m = +/-1 and a low-frequency m= +1 gyrotropic
mode describing the translational motion of the vortex core. The analytically
calculated magnitude of the frequency splitting is proportional to the ratio of
the dot thickness to its radius and quantitatively agrees with the results of
time resolved Kerr experiments.",0808.3335v1
2008-10-13,"Synthesis, crystal structure and spin-density-wave anomaly of the iron arsenide-fluoride SrFeAsF","The new quaternary iron arsenide-fluoride SrFeAsF with the tetragonal
ZrCuSiAs-type structure was synthesized and the crystal structure was
determined by X-ray powder diffraction (P4/nmm, a = 399.30(1), c = 895.46(1)
pm). SrFeAsF undergoes a structural and magnetic phase transition at 175 K,
accompanied by strong anomalies in the specific heat, electrical resistance and
magnetic susceptibility. In the course of this transition, the space group
symmetry changes from tetragonal (P4/nmm) to orthorhombic (Cmme). 57Fe
Moessbauer spectroscopy experiments show a single signal at room temperature at
an isomer shift of 0.30(1) mm/s and magnetic hyperfine-field splitting below
the phase transition temperature. Our results clearly show that SrFeAsF
exhibits a spin density wave (SDW) anomaly at 175 K very similar to LaFeAsO,
the parent compound of the iron arsenide-oxide superconductors and thus SrFeAsF
may serve as a further parent compound for oxygen-free iron arsenide
superconductors.",0810.2120v1
2008-10-15,Suppression of spin-density-wave transition and emergence of ferromagnetic ordering of Eu$^{2+}$ moments in EuFe$_{2-x}$Ni$_{x}$As$_{2}$,"We present a systematic study on the physical properties of
EuFe$_{2-x}$Ni$_{x}$As$_{2}$ (0$\leq$\emph{x}$\leq$0.2) by electrical
resistivity, magnetic susceptibility and thermopower measurements. The undoped
compound EuFe$_{2}$As$_{2}$ undergoes a spin-density-wave (SDW) transition
associated with Fe moments at 195 K, followed by antiferromagnetic (AFM)
ordering of Eu$^{2+}$ moments at 20 K. Ni doping at the Fe site simultaneously
suppresses the SDW transition and AFM ordering of Eu$^{2+}$ moments. For
$x\geq$0.06, the magnetic ordering of Eu$^{2+}$ moments evolves from
antiferromagnetic to ferromagnetic (FM). The SDW transition is completely
suppressed for $x\geq$0.16, however, no superconducting transition was observed
down to 2 K. The possible origins of the AFM-to-FM transition and the absence
of superconductivity in EuFe$_{2-x}$Ni$_{x}$As$_{2}$ system are discussed.",0810.2595v2
2008-11-13,Charge dynamics of the spin-density-wave state in BaFe$_2$As$_2$,"We report on a thorough optical investigation of BaFe$_2$As$_2$ over a broad
spectral range and as a function of temperature, focusing our attention on its
spin-density-wave (SDW) phase transition at $T_{SDW}=135$ K. While
BaFe$_2$As$_2$ remains metallic at all temperatures, we observe a depletion in
the far infrared energy interval of the optical conductivity below $T_{SDW}$,
ascribed to the formation of a pseudogap-like feature in the excitation
spectrum. This is accompanied by the narrowing of the Drude term consistent
with the $dc$ transport results and suggestive of suppression of scattering
channels in the SDW state. About 20% of the spectral weight in the far infrared
energy interval is affected by the SDW phase transition.",0811.2195v1
2008-11-24,Black-hole binary simulations: the mass ratio 10:1,"We present the first numerical simulations of an initially non-spinning
black-hole binary with mass ratio as large as 10:1 in full general relativity.
The binary completes approximately 3 orbits prior to merger and radiates about
0.415% of the total energy and 12.48% of the initial angular momentum in the
form of gravitational waves. The single black hole resulting from the merger
acquires a kick of about 66.7 km/s relative to the original center of mass
frame. The resulting gravitational waveforms are used to validate existing
formulas for the recoil, final spin and radiated energy over a wider range of
the symmetric mass ratio parameter eta=M1*M2/(M1+M2)^2 than previously
possible. The contributions of l > 2 multipoles are found to visibly influence
the gravitational wave signal obtained at fixed inclination angles.",0811.3952v2
2008-12-01,Global Phase Diagram for Magnetism and Lattice Distortion of Fe-pnictide Materials,"We study the global phase diagram of magnetic orders and lattice structure in
the Fe-pnictide materials at zero temperature within one unified theory, tuned
by both doping and pressure. On the low doping and high pressure side of the
phase diagram, there is one single transition, which is described by a $z=2$
mean field theory with very weak run-away flows; on the high doping and low
pressure side the transition is expected to split to two transitions, with one
O(3) spin density wave transition followed by a z = 3 quantum Ising transition
at larger doping. The fluctuation of the strain field fluctuation of the
lattice will not affect the spin density wave transition, but will likely drive
the Ising nematic transition more mean field like through a linear coupling, as
observed experimentally in BaFe_2-xCo_xAs_2.",0812.0016v3
2008-12-12,Ultimate braid-group generators for coordinate exchanges of Ising anyons from the multi-anyon Pfaffian wave functions,"We give a rigorous and self-consistent derivation of the elementary braid
matrices representing the exchanges of adjacent Ising anyons in the two
inequivalent representations of the Pfaffian quantum Hall states with even and
odd number of Majorana fermions. To this end we use the distinct operator
product expansions of the chiral spin fields in the Neveu-Schwarz and Ramond
sectors of the two-dimensional Ising conformal field theory. We find recursive
relations for the generators of the irreducible representations of the braid
group B_{2n+2} in terms of those for B_{2n}, as well as explicit formulas for
almost all braid matrices for exchanges of Ising anyons. Finally we prove that
the braid-group representations obtained from the multi-anyon Pfaffian wave
functions are completely equivalent to the spinor representations of SO(2n+2)
and give the equivalence matrices explicitly. This actually proves that the
correlation functions of 2n chiral Ising spin fields sigma do indeed realize
one of the two inequivalent spinor representations of the rotation group SO(2n)
as conjectured by Nayak and Wilczek.",0812.2334v2
2008-12-16,Galilei-invariant equations for massive fields,"Galilei-invariant equations for massive fields with various spins have been
found and classified. They have been derived directly, i.e., by using
requirement of the Galilei invariance and various facts on representations of
the Galilei group deduced in the paper written by de Montigny M, Niederle J and
Nikitin A G, J. Phys. A \textbf{39}, 1-21, 2006. A completed list of
non-equivalent Galilei-invariant wave equations for vector and scalar fields is
presented. It shows two things. First that the collection of such equations is
very broad and describes many physically consistent systems. In particular it
is possible to describe spin-orbit and Darwin couplings in frames of
Galilei-invariant approach. Second, these Galilei-invariant equations can be
obtained either via contraction of known relativistic equations or via
contractions of quite new relativistic wave equations.",0812.3021v2
2008-12-18,Microwave frequency modulation in continuous-wave far-infrared ESR utilizing a quasioptical reflection bridge,"We report the development of the frequency-modulation (FM) method for
measuring electron spin resonance (ESR) absorption in the 210-420 GHz frequency
range. We demonstrate that using a high-frequency ESR spectrometer without
resonating microwave components enables us to overcome technical difficulties
associated with the FM method due to nonlinear microwave-elements, without
sacrificing spectrometer performance. FM was achieved by modulating the
reference oscillator of a 13 GHz Phase Locked Dielectric Resonator Oscillator,
and amplifying and frequency-multiplying the resulting millimeter-wave
radiation up to 210, 315 and 420 GHz. ESR spectra were obtained in reflection
mode by a lock-in detection at the fundamental modulation frequency, and also
at the second and third harmonic. Sensitivity of the setup was verified by
conduction electron spin resonance measurement in KC$_{60}$.",0812.3676v1
2008-12-22,Re-examination of half-metallic ferromagnetism for doped LaMnO3 in quasiparticle self-consistent $GW$ method,"We apply the quasiparicle self-consistent $GW$ (\qsgw) method to a cubic
virtual-crystal alloy La$_{1-x}$Ba$_x$MnO$_3$ %(LBMO) as a theoretical
representative for colossal magnetoresistive perovskite manganites. The \qsgw\
predicts it as a fully-polarized half-metallic ferromagnet for a wide range of
$x$ and lattice constant. Calculated density of states and dielectric functions
are consistent with experiments. In contrast, the energies of calculated spin
wave are very low in comparison with experiments. This is affected neither by
rhombohedral deformation nor the intrinsic deficiency in the \qsgw method. Thus
we ends up with a conjecture that phonons related to the Jahn-Teller distortion
should hybridize with spin waves more strongly than people thought until now.",0812.4294v2
2008-12-24,Design and optimization of one-dimensional ferrite-film based magnonic crystals,"One-dimensional magnonic crystals have been implemented as gratings of
shallow grooves chemically etched into the surface of yttrium-iron garnet
films. Scattering of backward volume magnetostatic spin waves from such
structures is investigated experimentally and theoretically. Well-defined
rejection frequency bands are observed in transmission characteristics of the
magnonic crystals. The loss inserted by the gratings and the rejections bands
bandwidths are studied as a function of the film thickness, the groove depth,
the number of grooves, and the groove width. The experimental data are well
described by a theoretical model based on the analogy of a spin-wave
film-waveguide with a microwave transmission line. Our study shows that
magnonic crystals with required operational characteristics can be engineered
by adjusting these geometrical parameters.",0812.4553v1
2009-01-16,Evidence of spin-density-wave order in RFeAsO from measurements of thermoelectric power,"Data on the magneto-thermopower and specific heat of three compounds
belonging to '1111' oxypnictides family are reported. One specimen
(SmAsFeO0.8F0.2) is a superconductor with Tc = 53 K, while two others (SmAsFeO
and NdAsFeO) are nonsuperconducting parent compounds. Our results confirm that
spin density wave (SDW) order is present in SmAsFeO and NdAsFeO. In these two
samples a strict connection between the thermoelectric power and electronic
specific heat is found in the vicinity of SDW transition, what indicates that
the chemical potential of charge carriers strongly depends on temperature in
this region. Low temperature data suggest presence of significant contribution
magnon-drag to the thermoelectric power.",0901.2472v2
2009-01-23,Itinerant magnetic excitations in antiferromagnetic CaFe2As2,"Neutron scattering measurements of the magnetic excitations in single
crystals of antiferromagnetic CaFe2As2 reveal steeply dispersive and
well-defined spin waves up to an energy of 100 meV. Magnetic excitations above
100 meV and up to the maximum energy of 200 meV are however broader in energy
and momentum than the experimental resolution. While the low energy modes can
be fit to a Heisenberg model, the total spectrum cannot be described as arising
from excitations of a local moment system. Ab-initio calculations of the
dynamic magnetic susceptibility suggest that the high energy behavior is
dominated by the damping of spin waves by particle-hole excitations.",0901.3784v2
2009-02-02,Magnetic domain-wall motion by propagating spin waves,"We found by micromagnetic simulations that the motion of a transverse wall
(TW) type domain wall in magnetic thin-film nanostripes can be manipulated via
interaction with spin waves (SWs) propagating through the TW. The velocity of
the TW motion can be controlled by changes of the frequency and amplitude of
the propagating SWs. Moreover, the TW motion is efficiently driven by specific
SW frequencies that coincide with the resonant frequencies of the local modes
existing inside the TW structure. The use of propagating SWs, whose frequencies
are tuned to those of the intrinsic TW modes, is an alternative approach for
controlling TW motion in nanostripes.",0902.0220v1
2009-02-02,Critical Anisotropies of a Geometrically-Frustrated Triangular-Lattice Antiferromagnet,"This work examines the critical anisotropy required for the local stability
of the collinear ground states of a geometrically-frustrated triangular-lattice
antiferromagnet (TLA). Using a Holstein-Primakoff expansion, we calculate the
spin-wave frequencies for the 1, 2, 3, 4, and 8-sublattice (SL) ground states
of a TLA with up to third neighbor interactions. Local stability requires that
all spin-wave frequencies are real and positive. The 2, 4, and 8-SL phases
break up into several regions where the critical anisotropy is a different
function of the exchange parameters. We find that the critical anisotropy is a
continuous function everywhere except across the 2-SL/3-SL and 3-SL/4-SL phase
boundaries, where the 3-SL phase has the higher critical anisotropy.",0902.0359v1
2009-02-09,Quantum oscillations in antiferromagnetic CaFe2As2 on the brink of superconductivity,"We report quantum oscillation measurements on CaFe2As2 under strong magnetic
fields- recently reported to become superconducting under pressures of as
little as a kilobar. The largest observed carrier pocket occupies less than
0.05 % of the paramagnetic Brillouin zone volume- consistent with Fermi surface
reconstruction caused by antiferromagnetism. On comparing several alkali earth
AFe2As2 antiferromagnets (with A=Ca,Sr and Ba), the dependence of both the
Fermi surface cross-sectional area F_alpha and the effective mass m*_alpha of
the primary observed pocket on the antiferromagnetic/structural transition
temperature T_s is found to be consistent with quasiparticles in a conventional
spin-density wave model. These findings suggest that a conventional
spin-density wave exists within close proximity to superconductivity in this
series of compounds, which may have implications for the microscopic origin of
unconventional pair formation.",0902.1481v1
2009-02-24,Finite-Size Scaling Critical Behavior of Randomly Pinned Spin-Density Waves,"We have performed Monte Carlo studies of the 3D $XY$ model with random
uniaxial anisotropy, which is a model for randomly pinned spin-density waves.
We study $L \times L \times L$ simple cubic lattices, using $L$ values in the
range 16 to 64, and with random anisotropy strengths of $D / 2 J$ = 1, 2, 3, 6
and $\infty$. There is a well-defined finite temperature critical point, $T_c$,
for each these values of $D / 2 J$. We present results for the angle-averaged
magnetic structure factor, $S (k)$ at $T_c$ for $L = 64$. We also use
finite-size scaling analysis to study scaling functions for the critical
behavior of the specific heat, the magnetization and the longitudinal magnetic
susceptibility. Good data collapse of the scaling functions over a wide range
of $T$ is seen for $D / 2 J$ = 6 and $\infty$. For our finite values of $D / 2
J$ the scaled magnetization function increases with $L$ below $T_c$, and
appears to approach an $L$-independent limit for large $L$. This suggests that
the system is ferromagnetic below $T_c$.",0902.4049v2
2009-02-28,Splitting in the Fermi surface of ZrTe_3: a surface charge density wave system,"The electronic band structure and Fermi surface of ZrTe_3 was precisely
determined by linearly polarized angle-resolved photoelectron spectroscopy.
Several bands and a large part of the Fermi surface are found to be split by
100-200 meV into two parallel dispersions. Band structure calculations reveal
that the splitting is due to a change of crystal structure near the surface.
The agreement between calculation and experiment is enhanced by including the
spin-orbit potential in the calculations, but the spin-orbit energy does not
lead to a splitting of the bands. The dispersion of the highly nested small
electron pocket that gives rise to the charge density wave is traceable even in
the low-temperature gapped state, thus implying that the finite correlation
length of the long-wavelength modulation leads to a smearing of the band
back-folding.",0903.0095v1
2009-03-24,Soliton Wall Superlattice Charge-Density-Wave Phase in Quasi-One-Dimensional Conductor (Per)$_2$Pt(mnt)$_2$,"We demonstrate that the Pauli spin-splitting effects in a magnetic field
improve nesting properties of a realistic quasi-one-dimensional electron
spectrum. As a result, a high resistance Peierls charge-density-wave (CDW)
phase is stabilized in high enough magnetic fields in (Per)$_2$Pt(mnt)$_2$
conductor. We show that, in low and very high magnetic fields, the Pauli
spin-splitting effects lead to a stabilization of a soliton wall superlattice
(SWS) CDW phase, which is characterized by periodically arranged soliton and
anti-soliton walls. We suggest experimental studies of the predicted first
order phase transitions between the Peierls and SWS phases to discover a unique
SWS phase. It is important that, in the absence of a magnetic field and in a
limit of very high magnetic fields, the suggested model is equivalent to the
exactly solvable model of Brazovskii, Dzyaloshinskii, and Kirova.",0903.4018v1
2009-04-09,Suppression of spin density wave by isoelectronic substitution in PrFe(1-x)Ru(x)AsO,"We have studied the effects of the isoelectronic substitution of Ru for Fe in
polycrystalline samples of the spin density wave (SDW) material PrFeAsO.
Crystal structures from powder x-ray diffraction at room temperature and
transport properties from 2-300 K are reported. The SDW is completely
suppressed upon Ru substitution. The distortion of the tetrahedral coordination
environment of the transition metal site increases as the Ru concentration
increases, which may be related to the absence of superconductivity above 2 K.
Band structure calculations show that the larger size of Ru 4$d$ orbitals is
primarily responsible for the suppression of magnetism as Ru is substituted
into the Fe layer. The experimental results indicate that long-ranged magnetic
order of Pr moments is suppressed at Ru concentrations as low as 10%.",0904.1570v2
2009-04-23,Entanglement assisted spin-wave atom interferometer,"We report the observation of phase-super resolution in a motion-sensitive
spin-wave (SW) atom interferometer utilizing a NOON-type entanged state. The SW
interferometer is implemented by generating a superposition of two SWs and
observing the interference between them, where the interference fringe is
sensitive to the atomic collective motion. By heralded generation of a second
order NOON state in the SW interferometer, we clearly observe the interference
pattern with phase super-resolution. The demonstrated SW interferometer can in
principle be scaled up to highly entangled quantum state, and thus is of
fundamental importance to implement quantum-enhanced-measurement.",0904.3617v2
2009-04-28,Excitations near the boundary between a metal and a Mott insulator,"A heterostructure of a semi-infinite metal and a Mott insulator is
considered. It is supposed that both materials have an identical lattice
spacing and hopping integrals and differ in the Hubbard repulsion which is
negligible in the metal and exceeds the critical value for the Mott transition
in the insulator. At half-filling and for low temperatures the insulator has
the long-range antiferromagnetic order. Its low-lying elementary excitations
are standing spin waves and a spin-wave mode which is localized near the
interface and has a two-dimensional dispersion. This mode ejects bulk modes
from the boundary region. The antiferromagnetic ordering of the insulator
induces an antiferromagnetic order in the metal where the magnetization decays
exponentially with distance from the interface. This decay is characterized by
the correlation length equal to 5-6 lattice spacings.",0904.4314v1
2009-05-11,Partial wave analysis of J/psi to p pbar pi0,"Using a sample of 58 million $J/\psi$ events collected with the BESII
detector at the BEPC, more than 100,000 $J/\psi \to p\bar p \pi^0$ events are
selected, and a detailed partial wave analysis is performed. The branching
fraction is determined to be $Br(J/\psi \to p \bar p \pi^0)=(1.33 \pm 0.02 \pm
0.11) \times 10^{-3}$. A long-sought `missing' $N^*$, first observed in $J/\psi
\to p \bar n \pi^-$, is observed in this decay too, with mass and width of
$2040_{-4}^{+3}\pm 25$ MeV/c$^2$ and $230_{-8}^{+8}\pm 52$ MeV/c$^2$,
respectively. Its spin-parity favors ${3/2}^+$. The masses, widths, and
spin-parities of other $N^*$ states are obtained as well.",0905.1562v4
2009-07-01,Optical study on the spin-density wave properties in single crystalline Na$_{1-δ}$FeAs,"We report an optical investigation on the in-plane charge dynamics for
Na$_{1-\delta}$FeAs single crystal. A clear optical evidence for the
spin-density wave (SDW) gap is observed. As the structural/magnetic transitions
are separated in the Na$_{1-\delta}$FeAs case, we find the SDW gap opens in
accordance with the magnetic transition. Comparing with the optical response of
other FeAs-based parent compounds, both the gap value 2$\Delta$ and the energy
scale for the gap-induced spectral weight redistribution are smaller in
Na$_{1-\delta}$FeAs. Our findings support the itinerant origin of the
antiferromagnetic transition in the FeAs-based system.",0907.0186v1
2009-07-16,Coexistence of superconductivity and a spin density wave in pnictides: Gap symmetry and nodal lines,"We investigate the effect of a spin-density wave (SDW) on $s_{\pm}$
superconductivity in Fe-based superconductors. We show that, contrary to the
common wisdom, no nodes open at the new, reconnected Fermi surfaces when the
hole and electron pockets fold down in the SDW state, despite the fact that the
$s_{\pm}$ gap changes sign between the two pockets. Instead, the order
parameter preserves its sign along the newly formed Fermi surfaces. The
familiar experimental signatures of an $s_{\pm}$ symmetry are still preserved,
although they appear in a mathematically different way. For a regular $s$ case
($s_{++})$ the nodes do appear in the SDW state. This distinction suggests a
novel simple way to experimentally separate an $s_{\pm}$ state from a regular
$s$ in the pnictides. We argue that recently published thermal conductivity
data in the coexisting state are consistent with the $s_{\pm},$ but not the
$s_{++}$ state.",0907.2826v1
2009-07-23,Phase diagram of the spin-1/2 $J_1$-$J_2$-$J_3$ Heisenberg model on the square lattice,"We presents the results of an extensive numerical study of the phase diagram
of the spin-1/2, \protect{$J_1$-$J_2$-$J_3$} Heisenberg model on a square
lattice, for both ferromagnetic and antiferromagnetic nearest-neighbor
interactions $J_1$, using exact diagonalization with periodic and twisted
boundary conditions. Comparison is made with published spin wave calculations.
We show that quantum fluctuations play a very important role, changing both the
extent and the wave vector of classical spiral phases, and leading to new
quantum phases where the classical spiral states have a high degeneracy. These
include a new phase with small or vanishing spin-stiffness, in addition to
known valence-bond-solid and bond-nematic phases.",0907.4163v1
2009-09-03,Observation of Dirac Cone Electronic Dispersion in BaFe2As2,"We performed an angle-resolved photoemission spectroscopy study of BaFe2As2,
which is the parent compound of the so-called 122 phase of the iron-pnictide
high-temperature superconductors. We reveal the existence of a Dirac cone in
the electronic structure of this material below the spin-density-wave
temperature, which is responsible for small spots of high photoemission
intensity at the Fermi level. Our analysis suggests that the cone is slightly
anisotropic and its apex is located very near the Fermi level, leading to tiny
Fermi surface pockets. Moreover, the bands forming the cone show an anisotropic
leading edge gap away from the cone that suggests a nodal spin-density-wave
description.",0909.0574v1
2009-09-16,The chiral and angular momentum content of the rho-meson,"It is possible to define and calculate in a gauge-invariant manner the chiral
as well as the partial wave content of the quark-antiquark Fock component of a
meson in the infrared, where mass is generated. Using the variational method
and a set of interpolators that span a complete chiral basis we extract in a
lattice QCD Monte Carlo simulation with two dynamical light quarks the orbital
angular momentum and spin content of the rho-meson. We obtain in the infrared a
simple 3S1 component as a leading component of the rho-meson with a small
admixture of the 3D1 partial wave, in agreement with the SU(6) flavor-spin
symmetry.",0909.2939v1
2009-10-29,Multipurpose High Frequency Electron Spin Resonance Spectrometer for Condensed Matter Research,"We describe a quasi-optical multifrequency ESR spectrometer operating in the
75-225 GHz range and optimized at 210 GHz for general use in condensed matter
physics, chemistry and biology. The quasi-optical bridge detects the change of
mm wave polarization at the ESR. A controllable reference arm maintains a mm
wave bias at the detector. The attained sensitivity of 2x10^10 spin/G/(Hz)1/2,
measured on a dilute Mn:MgO sample in a non-resonant probe head at 222.4 GHz
and 300 K, is comparable to commercial high sensitive X band spectrometers. The
spectrometer has a Fabry-Perot resonator based probe head to measure aqueous
solutions, and a probe head to measure magnetic field angular dependence of
single crystals. The spectrometer is robust and easy to use and may be operated
by undergraduate students. Its performance is demonstrated by examples from
various fields of condensed matter physics.",0910.5504v1
2009-11-02,Spin-Density-Wave and Asymmetry of Coherence Peaks in iron-Pnictide Superconductors from a two-orbital model,"We study theoretically the coexistence of the spin-density-wave (SDW) and
superconductivity in electron-doped iron-pnictide superconductors based on the
two orbital model and Bogoliubov-de Gennes equations. The phase diagram is
mapped out and the evolution of the Fermi surface as the doping varies is
presented. The local density of states (LDOS) has also been calculated from low
to high doping. We show that the strength of the superconducting coherent peak
at the positive energy gets enhanced and the one at the negative energy is
suppressed by the SDW order in the underdoped region. Several features of our
results are in good agreement with the experiments.",0911.0385v3
2009-11-12,Anisotropy of the Spin Density Wave Onset for (TMTSF)_2PF_6 in Magnetic Field,"In order to study the spin density wave transition temperature (T_SDW) in
(TMTSF)_2PF_6 as a function of magnetic field, we measured the
magnetoresistance R_zz in fields up to 19 T. Measurements were performed for
three field orientations B||a, b' and c* at ambient pressure and at P = 5 kbar,
that is nearly the critical pressure. For B||c* orientation we observed
quadratic field dependence of T_SDW in agreement with theory and with previous
experiments. For B||b' and B||a orientations we have found no shift in T_SDW
within 0.05 K, both at P=0 and P=5 kbar. This result is also consistent with
theoretical predictions.",0911.2351v1
2009-12-18,Coexistence between superconducting and spin density wave states in iron-based superconductors: Ginzburg-Landau analysis,"We consider the interplay between superconducting (SC) and commensurate
spin-density-wave (SDW) orders in iron-pnictides by analyzing a multiple order
Ginzburg-Landau free energy. We are particularly interested in whether the
doping-induced transition between the two states is first order, or the two
pure phases are separated by an intermediate phase with coexisting SC and SDW
orders. For perfect nesting, the two orders do not coexist, because SDW order,
which comes first, gaps the full Fermi surface leaving no space for SC to
develop. When nesting is not perfect due to either ellipticity of electron
bands or doping-induced difference in chemical potentials for holes and
electrons, SDW order still leaves modified Fermi surfaces for not too strong
SDW magnetism and the SC order may develop. We show that the two orders coexist
only when certain relations between ellipticity and doping are met. In
particular, in a compensated metal, ellipticity alone is not sufficient for
coexistence of the two orders.",0912.3556v1
2010-01-07,Quasiparticle relaxation dynamics in spin-density-wave and superconducting SmFeAsO_{1-x}F_{x} single crystals,"We investigate the quasiparticle relaxation and low-energy electronic
structure in undoped SmFeAsO and near-optimally doped SmFeAsO_{0.8}F_{0.2}
single crystals - exhibiting spin-density wave (SDW) ordering and
superconductivity respectively - using pump-probe femtosecond spectroscopy. In
the undoped single crystals a single relaxation process is observed, showing a
remarkable critical slowing down of the QP relaxation dynamics at the SDW
transition temperature T_{SDW}\simeq125{K}. In the superconducting (SC)
crystals multiple relaxation processes are present, with distinct SC state
quasiparticle recombination dynamics exhibiting a BCS-like T-dependent
superconducting gap, and a pseudogap (PG)-like feature with an onset above 180K
indicating the existence of a pseudogap of magnitude
2\Delta_{\mathrm{PG}}\simeq120 meV above T_{\mathrm{c}}. From the pump-photon
energy dependence we conclude that the SC state and PG relaxation channels are
independent, implying the presence of two separate electronic subsystems. We
discuss the data in terms of spatial inhomogeneity and multi-band scenarios,
finding that the latter is more consistent with the present data.",1001.1047v2
2010-01-21,Hierarchical Hough all-sky search for periodic gravitational waves in LIGO S5 data,"We describe a new pipeline used to analyze the data from the fifth science
run (S5) of the LIGO detectors to search for continuous gravitational waves
from isolated spinning neutron stars. The method employed is based on the Hough
transform, which is a semi-coherent, computationally efficient, and robust
pattern recognition technique. The Hough transform is used to find signals in
the time-frequency plane of the data whose frequency evolution fits the pattern
produced by the Doppler shift imposed on the signal by the Earth's motion and
the pulsar's spin-down during the observation period. The main differences with
respect to previous Hough all-sky searches are described. These differences
include the use of a two-step hierarchical Hough search, analysis of
coincidences among the candidates produced in the first and second year of S5,
and veto strategies based on a $\chi^2$ test.",1001.3754v1
2010-02-05,Incommensurate spin-density wave and magnetic lock-in transition in CaFe4As3,"The magnetic structure for the newly discovered iron-arsenide compound
\CaFeAs has been studied by neutron powder diffraction. Long-range magnetic
order is detected below 85K, with an incommensurate modulation described by the
propagation vector k=(0,$\delta$,0), $\delta\sim$ 0.39. Below $\sim$ 25K, our
measurements detect a first-order phase transition where $\delta$ locks into
the commensurate value 3/8. A model of the magnetic structure is proposed for
both temperature regimes, based on Rietveld refinements of the powder data and
symmetry considerations. The structures correspond to longitudinal
spin-density-waves with magnetic moments directed along the \textit{b}-axis. A
Landau analysis captures the change in thermodynamic quantities observed at the
two magnetic transitions, in particular the drop in resistivity at the lock-in
transition.",1002.1336v1
2010-02-12,Electron-phonon coupling and charge gap in spin-density-wave iron-pnictides from quasiparticle relaxation dynamics,"We investigate the quasiparticle relaxation and low-energy electronic
structure in undoped SrFe_2As_2 exhibiting spin-density wave (SDW) ordering
using optical pump-probe femtosecond spectroscopy. A remarkable critical
slowing down of the quasiparticle relaxation dynamics at the SDW transition
temperature T_SDW = 200K is observed. From temperature dependence of the
transient reflectivity amplitude we determine the SDW-state charge gap
magnitude, 2Delta_SDW/k_BT_SDW=7.2+-1. The second moment of the Eliashberg
function, lambda<(hbar omega)^2>=110+-10meV^2, determined from the relaxation
time above T_SDW, is similar to SmFeAsO and BaFe_2As_2 indicating a rather
small electron phonon coupling constant unless the electron-phonon spectral
function (alpha^2F(omega) is strongly enhanced in the low-energy phonon region.",1002.2582v1
2010-02-19,Domain walls at the spin density wave endpoint of the organic superconductor (TMTSF)2PF6 under pressure,"We report the first comprehensive investigation of the organic superconductor
(TMTSF)2PF6 in the vicinity of the endpoint of the spin density wave - metal
phase transition where phase coexistence occurs. At low temperature, the
transition of metallic domains towards superconductivity is used to reveal the
various textures. In particular, we demonstrate experimentally the existence of
1D and 2D metallic domains with a cross-over from a filamentary
superconductivity mostly along the c?-axis to a 2D superconductivity in the
b?c-plane perpendicular to the most conducting direction. The formation of
these domain walls may be related to the proposal of a soliton phase in the
vicinity of the critical pressure of the (TMTSF)2PF6 phase diagram.",1002.3767v1
2010-02-19,Pseudogap in underdoped cuprates and spin-density-wave fluctuations,"We analyze fermionic spectral function in the spin-density-wave (SDW) phase
of quasi-2D cuprates at small but finite T. We use a non-perturbative approach
and sum up infinite series of thermal self-energy terms, keeping at each order
nearly-divergent (T/J) |log epsilon| terms, where epsilon is a deviation from a
pure two-dimensionality, and neglecting regular T/J corrections. We show that,
as SDW order decreases, the spectral function in the antinodal region acquires
peak/hump structure: the coherent peak position scales with SDW order
parameter, while the incoherent hump remains roughly at the same scale as at
T=0 when SDW order is the strongest. We identify the hump with the pseudogap
observed in ARPES and argue that the presence of coherent excitations at low
energies gives rise to magneto-oscillations in an applied field. We show that
the same peak/hump structure appears in the density of states and in optical
conductivity.",1002.3824v2
2010-02-24,Anomalous Zeeman response in coexisting phase of superconductivity and spin-density wave as a probe of extended $s$-wave pairing structure in ferro-pnictide,"In several members of the ferro-pnictides, spin density wave (SDW) order
coexists with superconductivity over a range of dopings. In this letter we
study the anomalous magnetic Zeeman response of this coexistence state and show
that it can be used to confirm the extended s-wave gap structure as well as
structure of superconducting (SC) gap in coexisting phase. On increasing the
field, a strongly anisotropic reduction of SC gap is found. The anisotropy is
directly connected to the gap structure of superconducting phase. The signature
of this effect in quasiparticle interference measured by STM, as well as heat
transport in magnetic field is discussed. For the compounds with the nodal SC
gap we show that the nodes are removed upon formation of SDW. Interestingly the
size of the generated gap in the originally nodal areas is anisotropic in the
position of the nodes over the Fermi surface in direct connection with the form
of SC pairing.",1002.4638v2
2010-03-07,Synchronization of oscillators with long range power law interactions,"We present analytical calculations and numerical simulations for the
synchronization of oscillators interacting via a long range power law
interaction on a one dimensional lattice. We have identified the critical value
of the power law exponent $\alpha_c$ across which a transition from a
synchronized to an unsynchronized state takes place for a sufficiently strong
but finite coupling strength in the large system limit. We find $\alpha_c=3/2$.
Frequency entrainment and phase ordering are discussed as a function of $\alpha
\geq 1$. The calculations are performed using an expansion about the aligned
phase state (spin-wave approximation) and a coarse graining approach. We also
generalize the spin-wave results to the {\it d}-dimensional problem.",1003.1447v2
2010-03-11,Superconductivity and spin-density-waves in multi-band metals,"We present a detailed description of two-band quasi-2D metals with s-wave
superconducting (SC) and antiferromagnetic spin-density wave (SDW)
correlations. We present a general approach and use it to investigate the
influence of the difference between the shapes and the areas of the two Fermi
surfaces on the phase diagram. In particular, we determine the conditions for
the co-existence of SC and SDW orders at different temperatures and dopings. We
argue that a conventional s-wave SC order co-exists with SDW order only at very
low $T$ and in a very tiny range of parameters. An extended s-wave
superconductivity, for which SC gap changes sign between the two bands,
co-exists with antiferromagnetic SDW over a much wider range of parameters and
temperatures, but even for this SC order the regions of SDW and SC can still be
separated by a first order transition. We show that the co-existence range
becomes larger if SDW order is incommensurate. We apply our results to
iron-based pnictide materials, in some of which co-existence of SDW and SC
orders has been detected.",1003.2389v2
2010-04-19,Magnetic and Quasiparticle Excitation Spectra of an Itinerant $J_1-J_2$ Model for Iron Pnictide Superconductors,"We calculate the magnetic and quasiparticle excitation spectra of an
itinerant $J_1-J_2$ model for iron pnictides. In addition to an acoustic
spin-wave branch, the magnetic spectrum has a second, optical branch, resulting
from the coupled four-sublattice magnetic structure. The spin-wave velocity has
also a planar directional anisotropy, due to the collinear/striped
antiferromagnetism. Within the magnetically ordered phase, the quasiparticle
spectrum is composed of two Dirac cones, resulting from the folding of the
magnetic Brillouin zone. We discuss the relevance of our findings to the
understanding of both neutron scattering and photoemission spectroscopy results
for SrFe$_{2}$As$_{2}$.",1004.3187v2
2010-04-26,Parameter estimation from Gravitational waves generated by non-spinning binary black holes with laser interferometers: beyond the Fisher information,"In this paper we apply to gravitational waves from non-spinning binary
systems a recently intro- duced frequentist methodology to calculate
analytically the error for a maximum likelihood estimate (MLE) of physical
parameters. While existing literature focuses on using the Cramer Rao Lower
bound (CRLB) and Monte Carlo simulations, we use a power expansion of the bias
and covariance in inverse powers of the signal to noise ratio. The use of
higher order derivatives of the likelihood function in the expansions makes the
prediction also sensitive to the secondary lobes of the MLE probability
distribution. We discuss conditions for validity of the CRLB and predict new
features in regions of the parameter space currently not explored. For example,
we see how the bias can become the most important contributor to the
parameters' errors for high mass systems (200M and above).",1004.4537v5
2010-04-30,Quasiparticle interference in the spin-density wave phase of iron-based superconductors,"We propose an explanation for the electronic nematic state observed recently
in parent iron-based superconductors [T.-M. Chuang et al., Science 327, 181
(2010)]. We argue that the quasi-one-dimensional nanostructure identified in
the quasiparticle interference (QPI) is a consequence of the interplay of the
magnetic ($\pi$, 0) spin-density wave (SDW) order with the underlying
electronic structure. We show that the evolution of the QPI peaks largely
reflects quasiparticle scattering between electronic bands involved in the SDW
formation. Because of the ellipticity of the electron pocket and the fact that
only one of the electron pockets is involved in the SDW, the resulting QPI has
a pronounced one-dimensional structure. We further predict that the QPI crosses
over to two-dimensionality on an energy scale, set by the SDW gap, which we
estimate from neutron scattering data to be around 90 meV.",1004.5460v1
2010-04-20,Wide-range wavevector selectivity of magnon gases in Brillouin light scattering spectroscopy,"Brillouin light scattering spectroscopy is a powerful technique for the study
of fast magnetization dynamics with both frequency- and wavevector resolution.
Here, we report on a distinct improvement of this spectroscopic technique
towards two-dimensional wide-range wavevector selectivity in a backward
scattering geometry. Spin-wave wavevectors oriented perpendicular to the bias
magnetic field are investigated by tilting the sample within the magnet gap.
Wavevectors which are oriented parallel to the applied magnetic field are
analyzed by turning the entire setup, including the magnet system. The setup
features a wide selectivity of wavevectors up to 2.04\cdot 10E5 rad/cm for both
orientations, and allows selecting and measuring wavevectors of dipole- and
exchange-dominated spin waves of any orientation to the magnetization
simultaneously.",1005.5084v1
2010-05-30,Statistical constraints on binary black hole inspiral dynamics,"We perform a statistical analysis of the binary black hole problem in the
post-Newtonian approximation by systematically sampling and evolving the
parameter space of initial configurations for quasi-circular inspirals. Through
a principal component analysis of spin and orbital angular momentum variables
we systematically look for uncorrelated quantities and find three of them which
are highly conserved in a statistical sense, both as functions of time and with
respect to variations in initial spin orientations. We also look for and find
the variables that account for the largest variations in the problem. We
present binary black hole simulations of the full Einstein equations analyzing
to what extent these results might carry over to the full theory in the
inspiral and merger regimes. Among other applications these results should be
useful both in semi-analytical and numerical building of templates of
gravitational waves for gravitational wave detectors.",1005.5560v1
2010-06-03,Unusual Nernst effect and spin density wave precursors in superconducting $\rm\bf LaFeAsO_{1-x}F_x$,"The Nernst effect has recently proven as a sensitive probe for detecting
unusual normal state properties of unconventional superconductors. Here we
present a systematic study of the Nernst effect of the iron pnictide
superconductor \laf with a particular focus on its evolution upon doping. For
the parent compound we observe a huge negative Nernst coefficient accompanied
with a severe violation of the Sondheimer cancellation in the spin density wave
(SDW) ordered state. Surprisingly, an unusual and enhanced Nernst signal is
also found at underdoping ($x=0.05$) despite the presence of bulk
superconductivity and the absence of static magnetic order, strongly suggestive
of SDW precursors at $T\lesssim150$ K. A more conventional normal state Nernst
response is observed at optimal doping ($x=0.1$) where it is rather featureless
with a more complete Sondheimer cancellation.",1006.0715v1
2010-06-29,Quantum Interference of Stored Coherent Spin-wave Excitations in a Two-channel Memory,"Quantum memories are essential elements in long-distance quantum networks and
quantum computation. Significant advances have been achieved in demonstrating
relative long-lived single-channel memory at single-photon level in cold atomic
media. However, the qubit memory corresponding to store two-channel spin-wave
excitations (SWEs) still faces challenges, including the limitations resulting
from Larmor procession, fluctuating ambient magnetic field, and
manipulation/measurement of the relative phase between the two channels. Here,
we demonstrate a two-channel memory scheme in an ideal tripod atomic system, in
which the total readout signal exhibits either constructive or destructive
interference when the two-channel SWEs are retrieved by two reading beams with
a controllable relative phase. Experimental result indicates quantum coherence
between the stored SWEs. Based on such phase-sensitive storage/retrieval
scheme, measurements of the relative phase between the two SWEs and Rabi
oscillation, as well as elimination of the collapse and revival of the readout
signal, are experimentally demonstrated.",1006.5517v1
2010-07-05,Impact of the Spin Density Wave Order on the Superconducting Gap of Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$,"We report a doping dependent electronic Raman scattering measurements on
iron-pnictide superconductor Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$ single crystals. A
strongly anisotropic gap is found at optimal doping for x=0.065 with
$\Delta_{max}\sim 5\Delta_{min}$. Upon entering the coexistence region between
superconducting (SC) and spin-density-wave (SDW) orders, the effective pairing
energy scale is strongly reduced. Our results are interpreted in terms of a
competition between SC and SDW orders for electronic state at the Fermi level.
Our findings advocate for a strong connection between the SC and SDW gaps
anisotropies which are both linked to interband interactions.",1007.0720v2
2010-07-14,Proximity induced pseudogap in mesoscopic superconductor/normal-metal bilayers,"Recent scanning tunneling microscopy measurements of the proximity effect in
Au/La$_{2-x}$Sr$_{x}$CuO$_{4}$ and
La$_{1.55}$Sr$_{0.45}$CuO$_{4}$/La$_{2-x}$Sr$_{x}$CuO$_{4}$ bilayers showed a
proximity-induced pseudogap [Yuli et al., Phys. Rev. Lett. {\bf 103}, 197003
(2009)]. We describe the proximity effect in mesoscopic
superconductor/normal-metal bilayers by using the Bogoliubov-de Gennes
equations for a tight-binding Hamiltonian with competing antiferromagnetic and
d-wave superconductivity orders . The temperature dependent local density of
states is calculated as a function of the distance from the interface. Bound
state due to both d-wave and spin density wave gaps are formed in the normal
metal for energies less than the respective gaps. If there is a mismatch
between the Fermi velocities in the two layers we observe that these states
will shift in energy when spin density wave order is present, thus inducing a
minigap at finite energy. We conclude that the STM measurement in the proximity
structures is able to distinguish between the two scenarios proposed for the
pseudogap (competing or precursor to superconductivity).",1007.2286v1
2010-08-04,Magnetic aspects of QCD and compact stars,"Magnetic properties of quark matter are discussed. The possibility of
ferromagnetic transition is studied by using the one-gluon-exchange
interaction. Magnetic susceptibility is evaluated within Landau Fermi liquid
theory, and the important roles of the screening for the gluon propagation are
elucidated. Static screening for the longitudinal gluons improves the infrared
singularities, while the transverse gluons receive only dynamic screening. The
latter property gives rise to a novel non-Fermi-liquid behaviour in the
magnetic susceptibility. The critical density is estimated to be around the
nuclear density and the Curie temperature several tens MeV. The spin density
wave is also discussed at moderate densities, where chiral transition becomes
important. Pseudoscalar condensate as well as scalar one takes a spatially
non-uniform form in a chirally invariant way. Accordingly magnetization
oscillates like spin density wave. These results should have some implications
on compact star phenomena.",1008.0709v1
2010-08-25,Vortex Viscosity in Magnetic Superconductors Due to Radiation of Spin Waves,"In type-II superconductors that contain a lattice of magnetic moments,
vortices polarize the magnetic system inducing additional contributions to the
vortex mass, vortex viscosity, and vortex-vortex interaction. Extra magnetic
viscosity is caused by radiation of spin waves by a moving vortex. Like in the
case of Cherenkov radiation, this effect has a characteristic threshold
behavior and the resulting vortex viscosity may be comparable to the well-known
Bardeen-Stephen contribution. The threshold behavior leads to an anomaly in the
current-voltage characteristics, and a drop in dissipation for a current
interval that is determined by the magnetic excitation spectrum.",1008.4323v3
2010-09-15,Inherent spin density wave instability by vortices in superconductors with strong Pauli effects,"A novel spin density wave (SDW) instability mechanism enhanced by vortices
under fields is proposed to explain the high field and low temperature (HL)
phase in CeCoIn$_5$. In the vortex state the strong Pauli effect and the nodal
gap conspire to enhance the momentum resolved spectral weight exclusively along
the nodal direction over the normal value, providing a favorable nesting
condition for SDW with ${\bf Q}=(2k_F, 2k_F, 0.5)$ only under high field ($H$).
Observed mysteries of the field-induced SDW confined within $H_{c2}$ are
understood consistently, such facts that ${\bf Q}$ is directed to the nodal
direction independent of $H$, SDW diminishes under tilting field from the $ab$
plane, and the SDW transition line in $(H,T)$ has a positive slope.",1009.2821v1
2010-09-21,"Expansion and one-range addition theorems for complete orthonormal sets of spinor wave functions and Slater spinor orbitals of arbitrary half-integral spin in position, momentum and four-dimensional spaces","The analytical relations in position, momentum and four-dimensional spaces
are established for the expansion and one-range addition theorems of
relativistic complete orthonormal sets of exponential type spinor wave
functions and Slater spinor orbitals of arbitrary half-integral spin. These
theorems are expressed through the corresponding nonrelativistic expansion and
one-range addition theorems of the spin-0 particles introduced by the author.
The expansion and one-range addition theorems derived are especially useful for
the computation of multicenter integrals over exponential type spinor orbitals
arising in the generalized relativistic Dirac-Hartree-Fock-Roothaan theory when
the position, momentum and four-dimensional spaces are employed.",1009.4031v1
2010-09-29,Superconductivity-induced optical anomaly in an iron arsenide,"One of the central tenets of conventional theories of superconductivity,
including most models proposed for the recently discovered iron-pnictide
superconductors, is the notion that only electronic excitations with energies
comparable to the superconducting energy gap are affected by the transition.
Here we report the results of a comprehensive spectroscopic ellipsometry study
of a high-quality crystal of superconducting
$\textrm{Ba}_{0.68}\textrm{K}_{0.32}\textrm{Fe}_2\textrm{As}_2$ that challenges
this notion. We observe a superconductivity-induced suppression of an
absorption band at an energy of $2.5\ \textrm{eV}$, two orders of magnitude
above the superconducting gap energy $2\Delta\sim 20\ \textrm{meV}$. Based on
density-functional calculations, this band can be assigned to transitions from
As-p to Fe-d orbitals crossing the Fermi surface. We identify a related effect
at the spin-density-wave transition in parent compounds of the 122 family. This
suggests that As-p states deep below the Fermi level contribute to the
formation of the superconducting and spin-density-wave states in the iron
arsenides.",1009.5915v1
2010-11-09,Dynamical charge and spin density wave scattering in cuprate superconductor,"We show that a variety of spectral features in high-T_c cuprates can be
understood from the coupling of charge carriers to some kind of dynamical order
which we exemplify in terms of fluctuating charge and spin density waves. Two
theoretical models are investigated which capture different aspects of such
dynamical scattering. The first approach leaves the ground state in the
disordered phase but couples the electrons to bosonic degrees of freedom,
corresponding to the quasi singular scattering associated with the closeness to
an ordered phase. The second, more phenomological approach starts from the
construction of a frequency dependent order parameter which vanishes for small
energies. Both theories capture scanning tunneling microscopy and angle-resoved
photoemission experiments which suggest the protection of quasiparticles close
to the Fermi energy but the manifestation of long-range order at higher
frequencies.",1011.2396v1
2010-12-02,Connecting distant ends of one-dimensional critical systems by a sine-square deformation,"We study the one-dimensional quantum critical spin systems with the
sine-square deformation, in which the energy scale in the Hamiltonian at the
position $x$ is modified by the function $f_x = \sin^2\left[{\pi}{L}(x-1/2)]$,
where $L$ is the length of the system. By investigating the entanglement
entropy, spin correlation functions, and wave-function overlap, we show that
the sine-square deformation changes the topology of the geometrical connection
of the ground state drastically; Although the system apparently has open edges,
the sine-square deformation links those ends and realizes the periodic ground
state at the level of wave function. Our results propose a new method to
control the topology of quantum states by energy-scale deformation.",1012.0472v2
2010-12-06,High-Pressure Suppression of Long Range Magnetic Order in the Triangular Lattice Antiferromagnet CuFeO2,"We succeeded in observing pressure-suppressed magnetic long range ordering
(LRO) in the triangular lattice antiferromagnet CuFeO$_{2}$, using neutron
diffraction experiments under an isotropic pressure. The magnetic LRO of the
four-sublattice ground state under ambient pressure in CuFeO$_{2}$ almost
disappears at the high pressure of 7.9 GPa, and is replaced by an
incommensurate order with temperature-independent wave number of (0.192 0.192
1.5). The incommensurate wave number observed at 7.9 GPa corresponds to that
observed just above the temperature at which lattice distortion and magnetic
LRO simultaneously occur under ambient pressure. Therefore, the long-range
magnetic ordering disappears because the high pressure suppressed the lattice
distortion that otherwise relieves spin frustration and leads the spin system
to LRO.",1012.1091v1
2010-12-10,Transverse Mode Revival of a Light-Compensated Quantum Memory,"A long-lived quantum memory was developed based on light-compensated cold
$^{87}$Rb atoms in a dipole trap. The lifetime of the quantum memory was
improved by 40 folds, from 0.67 ms to 28 ms with the help of a compensation
laser beam. Oscillations of the memory efficiency due to the transverse mode
breathing of the singly-excited spin wave have been clearly observed and
clarified with a Monte-Carlo simulation procedure. With detailed analysis of
the decoherence processes of the spin wave in cold atomic ensembles, this
experiment provides a benchmark for the further development of high-quality
quantum memories.",1012.2361v2
2010-12-28,Double pass quantum volume hologram,"We propose a new scheme for parallel spatially multimode quantum memory for
light. The scheme is based on the propagating in different directions quantum
signal wave and strong classical reference wave, like in a classical volume
hologram and the previously proposed quantum volume hologram [Phys. Rev. A 81,
020302(R)(2010)]. The medium for the hologram consists of a spatially extended
ensemble of cold spin-polarized atoms. In absence of the collective spin
rotation during the interaction, two passes of light for both storage and
retrieval are required, and therefore the present scheme can be called a double
pass quantum volume hologram. The scheme is less sensitive to diffraction and
therefore is capable of achieving higher density of storage of spatial modes as
compared to the thin quantum hologram of [Phys. Rev. A 77, 020302(R)(2008)],
which also requires two passes of light for both storage and retrieval. On the
other hand, the present scheme allows to achieve a good memory performance with
a lower optical depth of the atomic sample as compared to the quantum volume
hologram. A quantum hologram capable of storing entangled images can become an
important ingredient in quantum information processing and quantum imaging.",1012.5738v1
2011-01-02,Competition between superconductivity and spin density wave,"The Hubbard model has been investigated widely by many authors, while this
work may be new in two aspects. One, we focus on the possible effects of the
positions of the gaps associated with the pairing and the spin density wave.
Two, we suggest that the models with different parameters are appropriate for
different materials (or a material in different doped regions). This will lead
to some new insights into the high temperature superconductors. It is shown
that the SDW can appear at some temperature region when the on-site Coulomb
interaction is larger, while the SC requires a decreased U at a lower
temperature. This can qualitatively explain the relationship between
superconducting and pseudogap states of Cu-based superconductors in underdoped
and optimally doped regions. The superinsulator is also discussed.",1101.0381v7
2011-01-24,Possible Superconducting Symmetry and Magnetic Correlations in K0.8Fe2Se2: A 77Se-NMR Study,"We report ^77Se-NMR measurements in the recent discovered K_0.8Fe_2Se_2 with
the superconducting transition temperature T_c=32 K. The characteristic point
of this system is that the high density of state is located in the vicinity of
the Fermi level. The comparison between Knight shift and nuclear spin lattice
relaxation rate 1/T_1 shows that the antiferromagnetic spin correlation is not
strong in this system, but it is reasonable to consider that its development
toward low temperatures occurs. 1/T_1 in the superconducting state can be
reproduced well by an s+- wave model, but a d wave model also roughly
reproduces the data. Non exponential behavior in 1/T_1 at low temperatures
disagrees with a single isotropic gap.",1101.4572v4
2011-01-24,Mergers of Supermassive Black Holes in Astrophysical Environments,"Modeling the late inspiral and merger of supermassive black holes is central
to understanding accretion processes and the conditions under which
electromagnetic emission accompanies gravitational waves. We use fully general
relativistic, hydrodynamics simulations to investigate how electromagnetic
signatures correlate with black hole spins, mass ratios, and the gaseous
environment in this final phase of binary evolution. In all scenarios, we find
some form of characteristic electromagnetic variability whose pattern depends
on the spins and binary mass ratios. Binaries in hot accretion flows exhibit a
flare followed by a sudden drop in luminosity associated with the plunge and
merger, as well as quasi-periodic oscillations correlated with the
gravitational waves during the inspiral. Conversely, circumbinary disk systems
are characterized by a low luminosity of variable emission, suggesting
challenging prospects for their detection.",1101.4684v2
2011-02-09,Enhancement of the response of non-uniform resonance modes of a nanostructure in the Picoprobe microwave-current injection ferromagnetic resonance,"The non-uniform standing spin-wave modes in thin magnetic films and
nanostructures provide important information about surfaces and buried
interfaces. Very often they are lacking in the recorded ferromagnetic resonance
spectra for symmetry reasons. In this work we experimentally demonstrate that
by direct injection of microwave currents into an array of Permalloy
nanostripes using a microscopic microwave coaxial to coplanar adaptor one can
efficiently excite non-uniform standing spin wave modes with odd symmetry. The
proposed method is quick and allows easy spatial mapping of magnetic properties
with the resolution down to 100 microns. We have validated this method using an
example from a periodical array of nanostripes. The results from direct current
injection are compared to that of microstrip-based FMR measurements.",1102.1805v2
2011-02-13,p-wave superconductivity on monolayer and bilayer honeycomb lattice,"We derive ground state wave functions of superconducting instabilities on the
honeycomb lattice induced by nearest-neighbor attractive interactions. They
reflect the Dirac nature of electrons in the low-energy limit. For the order
parameter that is the same irrespective of the direction to any of the nearest
neighbors we find weak pairing (slowly decaying) behavior in the orbital part
of the Cooper pair with no angular dependence. At the neutrality point, in the
spin-singlet case, we recover a strong pairing behavior. We also derive ground
state wave functions for the superconductivity on the bilayer honeycomb
lattice, with strong interlayer coupling, induced by attractive interactions
between sites that participate in a low-energy description. Without these
interactions, free electrons are described by a Dirac equation with a quadratic
dispersion. This unusual feature, similarly to $^3$He - B phase, leads to the
description with two kinds of Cooper pairs, with $p_x + i p_y$ and $p_x - i
p_y$ pairing, in the presence of the attractive interactions. We discuss the
edge modes of such a spin-singlet superconductor and find that it represents a
trivial topological superconductor.",1102.2576v1
2011-03-05,Transmission of Excitations in a Spin-1 Bose-Einstein Condensate through a Barrier,"We investigate tunneling of excitations across a potential barrier separating
two spin-1 Bose-Einstein condensates. Using the mean-field theory at the
absolute zero temperature, we determine transmission coefficients of
excitations in the saturated magnetization state and unsaturated magnetization
states. All excitations except the quadrupolar spin mode in the saturated
magnetization state show the anomalous tunneling phenomenon characterized as
perfect tunneling in the low momentum limit through a potential barrier. The
quadrupolar spin mode in the saturated magnetization state, whose spectrum is
massive, shows total reflection. We discuss properties common between
excitations showing the anomalous tunneling phenomenon. Excitations showing
perfect tunneling have gapless spectrum in the absence of the magnetic field,
and their wave functions in the low energy limit are the same as the condensate
wave function.",1103.1004v2
2011-03-07,Higher twist parton distributions from light-cone wave functions,"We explore the possibility to construct higher-twist parton distributions in
a nucleon at some low reference scale from convolution integrals of the
light-cone wave functions (WFs). To this end we introduce simple models for the
four-particle nucleon WFs involving three valence quarks and a gluon with total
orbital momentum zero, and estimate their normalization (WF at the origin)
using QCD sum rules. We demonstrate that these WFs provide one with a
reasonable description of both polarized and unpolarized gluon parton densities
at large values of Bjorken variable x > 0.5. Twist-three parton distributions
are then constructed as convolution integrals of qqqg and usual three-quark
WFs. The cases of the polarized structure function g_2(x,Q^2) and single
transverse spin asymmetries are considered in detail. We find that the
so-called gluon-pole contribution to twist-three distributions relevant for
single spin asymmetry vanishes in this model, but is generated perturbatively
at higher scales by the evolution, in the spirit of GRV parton distributions.",1103.1269v1
2011-03-08,Evolution of Paramagnetic Quasiparticle Excitations Emerged in the High-Field Superconducting Phase of CeCoIn5,"We present In NMR measurements in a novel thermodynamic phase of CeCoIn5 in
high magnetic field, where exotic superconductivity coexists with the
incommensurate spin-density wave order. We show that the NMR spectra in this
phase provide direct evidence for the emergence of the spatially distributed
normal quasiparticle regions. The quantitative analysis for the field evolution
of the paramagnetic magnetization and newly-emerged low-energy quasiparticle
density of states is consistent with the nodal plane formation, which is
characterized by an order parameter in the Fulde-Ferrell-Larkin-Ovchinnikov
(FFLO) state. The NMR spectra also suggest that the spatially uniform
spin-density wave is induced in the FFLO phase.",1103.1440v1
2011-03-16,Spatial correlations in chaotic nanoscale systems with spin-orbit coupling,"We investigate the statistical properties of wave functions in chaotic
nanostructures with spin-orbit coupling (SOC), focussing in particular on
spatial correlations of eigenfunctions. Numerical results from a microscopic
model are compared with results from random matrix theory in the crossover from
the gaussian orthogonal to the gaussian symplectic ensembles (with increasing
SOC); one- and two-point distribution functions were computed to understand the
properties of eigenfunctions in this crossover. It is found that correlations
of wave function amplitudes are suppressed with SOC; nevertheless,
eigenfunction correlations play a more important role in the two-point
distribution function(s), compared to the case with vanishing SOC. Experimental
consequences of our results are discussed.",1103.3265v1
2011-04-05,Incommensurate spin-density wave order in electron-doped BaFe2As2 superconductors,"Neutron diffraction studies of Ba(Fe[1-x]Co[x])2As2 reveal that commensurate
antiferromagnetic order gives way to incommensurate magnetic order for Co
compositions between 0.056 < x < 0.06. The incommensurability has the form of a
small transverse splitting (0, +-e, 0) from the nominal commensurate
antiferromagnetic propagation vector Q[AFM] = (1, 0, 1) (in orthorhombic
notation) where e = 0.02-0.03 and is composition dependent. The results are
consistent with the formation of a spin-density wave driven by Fermi surface
nesting of electron and hole pockets and confirm the itinerant nature of
magnetism in the iron arsenide superconductors.",1104.0717v1
2011-04-05,Integrable spin chains and scattering amplitudes,"In this review we show that the multi-particle scattering amplitudes in N=4
SYM at large Nc and in the multi-Regge kinematics for some physical regions
have the high energy behavior appearing from the contribution of the Mandelstam
cuts in the complex angular momentum plane of the corresponding t-channel
partial waves. These Mandelstam cuts or Regge cuts are resulting from gluon
composite states in the adjoint representation of the gauge group SU(Nc). In
the leading logarithmic approximation (LLA) their contribution to the six point
amplitude is in full agreement with the known two-loop result.
  The Hamiltonian for the Mandelstam states constructed from n gluons in LLA
coincides with the local Hamiltonian of an integrable open spin chain. We
construct the corresponding wave functions using the integrals of motion and
the Baxter-Sklyanin approach.",1104.0816v2
2011-05-10,Spontaneous magnon decays in planar ferromagnet,"We predict that spin-waves in an easy-plane ferromagnet have a finite
lifetime at zero temperature due to spontaneous decays. In zero field the
damping is determined by three-magnon decay processes, whereas decays in the
two-particle channel dominate in a transverse magnetic field. Explicit
calculations of the magnon damping are performed in the framework of the
spin-wave theory for the $XXZ$ square-lattice ferromagnet with an anisotropy
parameter $\lambda<1$. In zero magnetic field the decays occur for
$\lambda^*<\lambda<1$ with $\lambda^*\approx 1/7$. We also discuss possibility
of experimental observation of the predicted effect in a number of
ferromagnetic insulators.",1105.1893v1
2011-05-21,Retrieval of phase memory in two independent atomic ensembles by Raman process,"In spontaneous Raman process in atomic cell at high gain, both the Stokes
field and the accompanying collective atomic excitation (atomic spin wave) are
coherent. We find that, due to the spontaneous nature of the process, the
phases of the Stokes field and the atomic spin wave change randomly from one
realization to another but are anti-correlated. The phases of the atomic
ensembles are read out via another Raman process at a later time, thus
realizing phase memory in atoms. The observation of phase correlation between
the Stokes field and the collective atomic excitations is an important step
towards macroscopic EPR-type entanglement of continuous variables between light
and atoms.",1105.4239v1
2011-07-04,Influence of randomness and retardation on the FMR-linewidth,"The theory predicts that the spin-wave lifetime $\tau_L$ and the linewidth of
ferromagnetic resonance $\Delta B$ can be governed by random fields and spatial
memory. To that aim the effective field around which the magnetic moments
perform a precession is superimposed by a stochastic time dependent magnetic
field with finite correlation time. The magnetization dynamics is altered by
inclusion of a spatial memory effect monitoring a non-local interaction of size
$\xi$. The underlying Landau-Lifshitz-Gilbert equation (LLG) is modified
accordingly. The stochastic LLG is equivalent to a Fokker-Planck equation which
enables to calculate the mean values of the magnetization vector. Within the
spin-wave approximation we present an analytical solution for the excitation
energy and its damping. The lifetime and the linewidth are analyzed depending
on the strength of the random field $D$ and its correlation time $\tau_c$ as
well as the retardation strength $\Gamma_0$ and the size $\xi$. Whereas
$\tau_L$ decreases with increasing $D$, retardation strength $\Gamma_0$ and
$\tau_c$, the lifetime is enhanced for growing width $\xi$ of the spatial
retardation kernel. In the same manner we calculate the experimentally
measurable linewidth $\Delta B$ is increased strongly when the correlation time
$\tau_c$ ranges in the nanosecond interval.",1107.0638v1
2011-08-10,Distribution of Localized States from Fine Analysis of Electron Spin Resonance Spectra in Organic Transistors,"We developed a novel method for obtaining the distribution of trapped
carriers over their degree of localization in organic transistors, based on the
fine analysis of electron spin resonance spectra at low enough temperatures
where all carriers are localized. To apply the method to pentacene thin-film
transistors, we proved through continuous wave saturation experiments that all
carriers are localized at below 50 K. We analyzed the spectra at 20 K and found
that the major groups of traps comprise localized states having wave functions
spanning around 1.5 and 5 molecules and a continuous distribution of states
with spatial extent in the range between 6 and 20 molecules.",1108.2090v1
2011-09-14,Spin 1/2 particle in the field of the Dirac string on the background of de Sitter space-time,"The Dirac monopole string is specified for de Sitter cosmological model.
Dirac equation for spin 1/2 particle in presence of this monopole has been
examined on the background of de Sitter space-time in static coordinates.
Instead of spinor monopole harmonics, the technique of Wigner D-functions is
used. After separation of the variables, detailed analysis of the radial
equations is performed; four types of solutions, singular, regular, in- and
out- running waves, are constructed in terms of hypergeometric functions. The
complete set of spinor wave solutions \Psi_{\epsilon, j,m, \lambda}(t,r,
\theta, \phi) has been constructed, special attention is given to treating the
states of minimal values of the total angular moment j_{\min}.",1109.3009v1
2011-09-16,Coexistence of superconductivity and incommensurate magnetic order,"The influence of incommensurate spin density waves (SDW) on superconductivity
in unconventional superconductors is studied by means of the Bogolubov-de
Gennes (BdG) equations. Exploiting translational symmetries of a magnetically
ordered two-dimensional system we propose an approach that allows to solve the
BdG equations on much larger clusters than it is usually possible for
inhomogeneous systems. Applying this approach we demonstrate that the presence
of incommensurate spin density waves induces real-space inhomogeneity of the
superconducting order parameter even in the absence of external magnetic field.
In this case a homogeneous order parameter of the
Bardeen-Cooper-Schrieffer-type superconducting state is slightly modulated, or
equivalently, a small fraction of the charge carriers form Cooper pairs with
non-zero total momentum. However, when a sufficiently strong magnetic field is
applied, the homogeneous component of the order parameter is suppressed and the
system transits to the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state, where the
order parameter oscillates changing sign. We show that for s-wave pairing the
presence of external magnetic field diminishes the destructive influence of the
SDW order on superconductivity. A simple explanation of this effect is also
proposed.",1109.3534v1
2011-10-13,Modeling multipolar gravitational-wave emission from small mass-ratio mergers,"Using the effective-one-body (EOB) formalism and a time-domain Teukolsky
code, we generate inspiral, merger, and ringdown waveforms in the small
mass-ratio limit. We use EOB inspiral and plunge trajectories to build the
Teukolsky equation source term, and compute full coalescence waveforms for a
range of black hole spins. By comparing EOB waveforms that were recently
developed for comparable mass binary black holes to these Teukolsky waveforms,
we improve the EOB model for the (2,2), (2,1), (3,3), and (4,4) modes. Our
results can be used to quickly and accurately extract useful information about
merger waves for binaries with spin, and should be useful for improving
analytic models of such binaries.",1110.3081v2
2011-10-14,Interplay between spin density wave and superconductivity in '122' iron pnictides: 57Fe Mössbauer study,"Iron-based superconductors Ba0.7Rb0.3Fe2As2 and CaFe1.92Co0.08As2 of the
'122' family have been investigated by means of the 14.41-keV Moessbauer
transition in 57Fe versus temperature ranging from the room temperature till
4.2 K. A comparison is made with the previously investigated parent compounds
BaFe2As2 and CaFe2As2. It has been found that Moessbauer spectra of these
superconductors are composed of the magnetically split component due to
development of spin density wave (SDW) and non-magnetic component surviving
even at lowest temperatures. The latter component is responsible for
superconductivity. Hence, the superconductivity occurs in the part of the
sample despite the sample is single phase. This phenomenon is caused by the
slight variation of the dopant concentration across the sample (crystal).",1110.3170v1
2011-10-17,Impact of Step Defects on Surface States of Topological Insulators,"The eigenstates in the presence of a step defect (SD) along $x$ or y axis on
the surface of topological insulators are exactly solved. It is shown that
unlike the electronic states in conventional metals, the topological surface
states across the SD can produce spin rotations. The magnitudes of the spin
rotations depend on the height and direction of the SD. The oscillations of
local density of states (LDOS) are characterized by a wave vector connecting
two points on the hexagonal constant-energy contour at higher energies. The
period of the oscillation caused by the SD along y axis is $\sqrt 3$
($\frac{1}{\sqrt 3}$) times that induced by the SD along x axis at a larger
positive (negative) bias voltage. With increasing the bias voltage, the period
of the oscillation, insensitive to the strength of the SD, becomes smaller. At
lower energies near the Fermi surface, the two types of wave vectors coexist in
the LDOS modulations. These results are consistent qualitatively with recent
observations of scanning tunneling microscopy.",1110.3722v1
2012-02-21,Solitary excitations in one-dimensional spin chains,"We study the real-time evolution of solitary excitations in 1-d quantum spin
chains using exact diagonalization (ED) and the density-matrix renormalization
group (DMRG). The underlying question of this work is the correspondence
between classical solitons and solitons in quantum mechanics. While classical
solitons as eigensolutions of non-linear wave equations are localized and have
a sharp momentum, this is not possible in the corresponding quantum case due to
the linearity of the Schr\""odinger equation or seen in a more pictorial way,
because of the uncertainty relation. For the case of the XXZ model it is shown
that the real-time evolution of quantum wave packets accompanied by spreading
is in qualitative accordance with the one predicted by classical solitons.",1202.4634v2
2012-03-07,Magnonic band gap design by the edge modulation of micro-sized waveguides,"The potential to control the number of the spin-wave band gaps of a magnonic
crystal (MC) by variation of its geometry is investigated by numerical
simulations. The magnonic crystal is represented by a micro-sized planar
ferromagnetic waveguide with periodically variable width. By choosing a
step-like or sinusoidal variation of the width, the magnonic crystal reveals
multiple or single band gaps, respectively. This allows for additional degrees
of freedom in the design of MC based microwave filters and phase shifters with
desired characteristics. The MCs band gaps have been studied in the space and
frequency domains exploring the spin-wave spectrum dependence on the probing
position inside the magnonic crystal.",1203.1469v1
2012-03-21,Dirac Theory and Topological Phases of Silicon Nanotube,"Silicon nanotube is constructed by rolling up a silicene, i.e., a monolayer
of silicon atoms forming a two-dimensional honeycomb lattice. It is a
semiconductor or an insulator owing to relatively large spin-orbit interactions
induced by its buckled structure. The key observation is that this buckled
structure allows us to control the band structure by applying electric field
$E_z$. When $E_z$ is larger than a certain critical value $E_{\text{cr}}$, by
analyzing the band structure and also on the basis of the effective Dirac
theory, we demonstrate the emergence of four helical zero-energy modes
propagating along nanotube. Accordingly, a silicon nanotube contains three
regions, namely, a topological insulator, a band insulator and a metallic
region separating these two types of insulators. The wave function of each zero
mode is localized within the metallic region, which may be used as a quantum
wire to transport spin currents in future spintronics. We present an analytic
expression of the wave function for each helical zero mode. These results are
applicable also to germanium nanotube.",1203.4654v1
2012-04-10,Spin density wave induced disordering of the vortex lattice in superconducting La$_{2-x}$Sr$_x$CuO$_4$,"We use small angle neutron scattering to study the superconducting vortex
lattice in La$_{2-x}$Sr$_x$CuO$_4$ as a function of doping and magnetic field.
We show that near optimally doping the vortex lattice coordination and the
superconducting coherence length $\xi$ are controlled by a van-Hove singularity
crossing the Fermi level near the Brillouin zone boundary. The vortex lattice
properties change dramatically as a spin-density-wave instability is approached
upon underdoping. The Bragg glass paradigm provides a good description of this
regime and suggests that SDW order acts as a novel source of disorder on the
vortex lattice.",1204.2152v1
2012-05-04,Longitudinal excitations in triangular lattice antiferromagnets,"We study the longitudinal excitations of quantum antiferromagnets on a
triangular lattice by a recently proposed microscopic many-body approach based
on magnon-density waves. We calculate the full longitudinal excitation spectra
of the antiferromagnetic Heisenberg model for a general spin quantum number in
the isotropic limit. Similar to the square lattice model, we find that, at the
center of the first hexagonal Brillouin zone $\Gamma(\mathbf q=0)$ and at the
magnetic ordering wavevectors $\pm[\mathbf Q= (4\pi/3,0)]$, the excitation
spectra become gapless in the thermodynamic limit, due to the slow, logarithmic
divergence of the structure factor. However, these longitudinal modes on
two-dimensional models may be considered as quasi-gapped, as any finite-size
effect or small anisotropy will induce a large energy gap, when compared with
the counterpart of the transverse spin-wave excitations. We also discuss a
possible second longitudinal mode in the triangular lattice model due to the
noncollinear nature of its magnetic order.",1205.0977v2
2012-05-08,Normal and intrinsic anomalous Hall effect in Nb1-yFe2+y,"The Hall effect on selected samples of the dilution series Nb1-yFe2+y is
studied. Normal and anomalous contributions are observed, with positive normal
Hall effect dominating at high temperatures. Consistent analysis of the
anomalous contribution is only possible for Fe-rich Nb0.985Fe2.015 featuring a
ferromagnetic ground state. Here, a positive normal Hall coefficient is found
at all temperatures with a moderate maximum at the spin-density-wave
transition. The anomalous Hall effect is consistent with an intrinsic
(Berry-phase) contribution which is constant below the ordering temperature TC
and continuously vanishes above TC. For stoichiometric NbFe2 and Nb-rich
Nb1.01Fe1.99 - both having a spin-density-wave ground state - an additional
contribution to the Hall resistivity impedes a complete analysis and indicates
the need for more sophisticated models of the anomalous Hall effect in
itinerant antiferromagnets.",1205.1651v1
2012-05-30,New Phase Induced by Pressure in the Iron-Arsenide Superconductor K-Ba122,"The electrical resistivity rho of the iron-arsenide superconductor
Ba1-xKxFe2As2 was measured in applied pressures up to 2.6 GPa for four
underdoped samples, with x = 0.16, 0.18, 0.19 and 0.21. The antiferromagnetic
ordering temperature T_N, detected as a sharp anomaly in rho(T), decreases
linearly with pressure. At pressures above around 1.0 GPa, a second sharp
anomaly is detected at a lower temperature T_0, which rises with pressure. We
attribute this second anomaly to the onset of a phase that causes a
reconstruction of the Fermi surface. This new phase expands with increasing x
and it competes with superconductivity. We discuss the possibility that a
second spin-density wave orders at T_0, with a Q vector distinct from that of
the spin-density wave that sets in at T_N.",1205.6730v2
2012-07-05,"High-Tc Nodeless s_\pm-wave Superconductivity in (Y,La)FeAsO_{1-y} with Tc=50 K: 75As-NMR Study","We report 75As-NMR study on the Fe-pnictide high-Tc superconductor
Y0.95La0.05FeAsO_{1-y} (Y0.95La0.051111) with Tc=50 K that includes no magnetic
rare-earth elements. The measurement of the nuclear-spin lattice-relaxation
rate 75(1/T1) has revealed that the nodeless bulk superconductivity takes place
at Tc=50 K while antiferromagnetic spin fluctuations (AFSFs) develop moderately
in the normal state. These features are consistently described by the multiple
fully-gapped s_\pm-wave model based on the Fermi-surface (FS) nesting.
Incorporating the theory based on band calculations, we propose that the reason
that Tc=50 K in Y0.95La0.051111 is larger than Tc=28 K in La1111 is that the FS
multiplicity is maximized, and hence the FS nesting condition is better than
that in La1111.",1207.1185v2
2012-07-12,Efficient and long-lived quantum memory with cold atoms inside a ring cavity,"Quantum memories are regarded as one of the fundamental building blocks of
linear-optical quantum computation and long-distance quantum communication. A
long standing goal to realize scalable quantum information processing is to
build a long-lived and efficient quantum memory. There have been significant
efforts distributed towards this goal. However, either efficient but
short-lived or long-lived but inefficient quantum memories have been
demonstrated so far. Here we report a high-performance quantum memory in which
long lifetime and high retrieval efficiency meet for the first time. By placing
a ring cavity around an atomic ensemble, employing a pair of clock states,
creating a long-wavelength spin wave, and arranging the setup in the
gravitational direction, we realize a quantum memory with an intrinsic spin
wave to photon conversion efficiency of 73(2)% together with a storage lifetime
of 3.2(1) ms. This realization provides an essential tool towards scalable
linear-optical quantum information processing.",1207.2894v1
2012-07-16,Infrared Measurement of the Pseudogap in P-Doped and Co-Doped BaFe2As2 High-Temperature Superconductors,"We report on infrared studies of charge dynamics in a prototypical pnictide
system: the BaFe2As2 family. Our experiments have identified hallmarks of the
pseudogap state in the BaFe2As2 system that mirror the spectroscopic
manifestations of the pseudogap in the cuprates. The magnitude of the infrared
pseudogap is in accord with that of the spin-density-wave gap of the parent
compound. By monitoring the superconducting gap of both P- and Co-doped
compounds, we find that the infrared pseudogap is unrelated to
superconductivity. The appearance of the pseudogap is found to correlate with
the evolution of the antiferromagnetic fluctuations associated with the
spin-density-wave instability. The strong-coupling analysis of infrared data
further reveals the interdependence between the magnetism and the pseudogap in
the iron pnictides.",1207.3567v1
2012-07-20,Measurement of the dynamical dipolar coupling in a pair of magnetic nano-disks using a Ferromagnetic Resonance Force Microscope,"We perform an extensive experimental spectroscopic study of the collective
spin-wave dynamics occurring in a pair of magnetic nano-disks coupled by the
magneto-dipolar interaction. For this, we take advantage of the stray field
gradient produced by the magnetic tip of a ferromagnetic resonance force
microscope (f-MRFM) to continuously tune and detune the relative resonance
frequencies between two adjacent nano-objects. This reveals the anti-crossing
and hybridization of the spin-wave modes in the pair of disks. At the exact
tuning, the measured frequency splitting between the binding and anti-binding
modes precisely corresponds to the strength of the dynamical dipolar coupling
$\Omega$. This accurate f-MRFM determination of $\Omega$ is measured as a
function of the separation between the nano-disks. It agrees quantitatively
with calculations of the expected dynamical magneto-dipolar interaction in our
sample.",1207.4919v1
2012-07-21,"Quantum phase transitions in alternating spin-(1/2, 5/2) Heisenberg chains","The ground state spin-wave excitations and thermodynamic properties of two
types of ferrimagnetic chains are investigated: the alternating spin-1/2
spin-5/2 chain and a similar chain with a spin-1/2 pendant attached to the
spin-5/2 site. Results for magnetic susceptibility, magnetization and specific
heat are obtained through the finite-temperature Lanczos method with the aim in
describing available experimental data, as well as comparison with theoretical
results from the semiclassical approximation and the low-temperature
susceptibility expansion derived from Takahashi's modified spin-wave theory. In
particular, we study in detail the temperature vs. magnetic field phase diagram
of the spin-1/2 spin-5/2 chain, in which several low-temperature quantum phases
are identified: the Luttinger Liquid phase, the ferrimagnetic plateau and the
fully polarized one, and the respective quantum critical points and crossover
lines.",1207.5084v1
2012-07-23,Frequency Conversion in a High Q-factor Sapphire Whispering Gallery Mode Resonator due to Paramagnetic Nonlinearity,"Nonlinear frequency conversion is a well known and widely exploited family of
effects in optics, often arising from a Kerr nonlinearity in a crystal medium.
Here, we report high stability frequency conversion in the microwave regime due
to a $\chi^{(3)}$ nonlinearity in sapphire introduced by a dilute concentration
of paramagnetic spins. First, we produce a high stability comb from two
microwave fields at 12.029 and 12.037 GHz corresponding to two high $Q$-factor
Whispering Gallery (WG) modes within the Electron Spin Resonance (ESR)
bandwidth of the Fe$^{3+}$ ion. The resulting comb is generated by a cascaded
four-wave mixing effect with a 7.7 MHz repetition rate. Then, by suppressing
four-wave mixing by increasing the threshold power, third harmonic generation
is achieved in a variety of WG modes coupled to various species of paramagnetic
ion within the sapphire.",1207.5341v1
2012-07-23,The Wave Function of Vasiliev's Universe - A Few Slices Thereof,"We study the partition function of the free Sp(N) conformal field theory
recently conjectured to be dual to asymptotically de Sitter higher-spin gravity
in four-dimensions. We compute the partition function of this CFT on a round
sphere as a function of a finite mass deformation, on a squashed sphere as a
function of the squashing parameter, and on an S2xS1 geometry as a function of
the relative size of S2 and S1. We find that the partition function is
divergent at large negative mass in the first case, and for small $S^1$ in the
third case. It is globally peaked at zero squashing in the second case. Through
the duality this partition function contains information about the wave
function of the universe. We show that the divergence at small S1 occurs also
in Einstein gravity if certain complex solutions are included, but the
divergence in the mass parameter is new. We suggest an interpretation for this
divergence as indicating an instability of de Sitter space in higher spin
gravity, consistent with general arguments that de Sitter space cannot be
stable in quantum gravity.",1207.5517v1
2012-07-25,Thermodynamics of Two-Dimensional Ideal Ferromagnets - Three-Loop Analysis,"Within the effective Lagrangian framework, we explicitly evaluate the
partition function of two-dimensional ideal ferromagnets up to three loops at
low temperatures and in the presence of a weak external magnetic field. The
low-temperature series for the free energy density, energy density, heat
capacity, entropy density, as well as the magnetization are given and their
range of validity is critically examined in view of the Mermin-Wagner theorem.
The calculation involves the renormalization and numerical evaluation of a
particular three-loop graph which is discussed in detail. Interestingly, in the
low-temperature series for the two-dimensional ideal ferromagnet, the spin-wave
interaction manifests itself in the form of logarithmic terms. In the free
energy density the leading such term is of order $T^4 \ln T$ -- remarkably, in
the case of the three-dimensional ideal ferromagnet no logarithmic terms arise
in the low-temperature series. While the present study demonstrates that it is
straightforward to consider effects up to three-loop order in the effective
field theory framework, this precision seems to be far beyond the reach of
microscopic methods such as modified spin-wave theory.",1207.5937v1
2012-08-01,Dephasing dynamics of Rydberg atom spin waves,"A theory of Rydberg atom interactions is used to derive analytical forms for
the spin wave pair correlation function in laser-excited cold-atom vapors. This
function controls the quantum statistics of light emission from dense,
inhomogeneous clouds of cold atoms of various spatial dimensionalities. The
results yield distinctive scaling behaviors on the microsecond timescale,
including generalized exponential decay. A detailed comparison is presented
with a recent experiment on a cigar-shaped atomic ensemble [Y. Dudin and A.
Kuzmich, Science 336, 887 (2012)], in which Rb atoms are excited to a set of
Rydberg levels.",1208.0355v2
2012-08-02,Excitation Transport through a Domain Wall in a Bose-Einstein Condensate,"We investigate the tunneling properties of collective excitations through a
domain wall in the ferromagnetic phase of a spin-1 spinor Bose--Einstein
condensate. Within the mean-field theory at T=0, we show that the transverse
spin wave undergoes perfect reflection in the low-energy limit. This reflection
property differs considerably from that of a domain wall in a Heisenberg
ferromagnet where spin-wave excitations exhibit perfect transmission at
arbitrary energy. When the Bogoliubov mode is scattered from this domain wall
soliton, the transmission and reflection coefficients exhibit pronounced
non-monotonicity. In particular, we find perfect reflection of the Bogoliubov
mode at energies where bound states appear. This is in stark contrast to the
perfect transmission of the Bogoliubov mode with arbitrary energy through a
dark soliton in a scalar Bose--Einstein condensate.",1208.0381v1
2012-08-09,Worldsheet Form Factors in AdS/CFT,"We formulate a set of consistency conditions appropriate to worldsheet form
factors in the massive, integrable but non-relativistic, light-cone gauge fixed
AdS(5) x S**5 string theory. We then perturbatively verify that these
conditions hold, at tree level in the near-plane-wave limit and to one loop in
the near-flat (Maldacena-Swanson) limit, for a number of specific cases. We
further study the form factors in the weakly coupled dual description,
verifying that the relevant conditions naturally hold for the one-loop
Heisenberg spin-chain. Finally, we note that the near-plane-wave expressions
for the form factors, when further expanded in small momentum or, equivalently,
large charge density, reproduce the thermodynamic limit of the spin-chain
results at leading order.",1208.2020v3
2012-09-28,Charge-$2e$ Skyrmion condensate in a hidden order state,"A higher angular momentum ($\ell =2$) $d$-density wave, a mixed triplet and a
singlet, interestingly, admits skyrmionic textures. The Skyrmions carry charge
$2e$ and can condense into a spin-singlet s-wave superconducting state. In
addition, a charge current can be induced by a time-dependent inhomogeneous
spin texture, leading to quantized charge pumping. The quantum phase transition
between this mixed triplet $d$-density wave and skyrmionic superconducting
condensate likely leads to deconfined quantum critical points. We suggest
connections of this exotic state to electronic materials that are strongly
correlated, such as the heavy fermion $\mathrm{URu_{2}Si_{2}}$. At the very
least, we provide a concrete example in which topological order and broken
symmetry are intertwined, which can give rise to non-BCS superconductivity.",1210.0034v3
2012-10-01,Spin transition in the fractional quantum Hall regime: Effect of extent of the wave function,"Using a magnetocapacitance technique, we determine the magnetic field of the
spin transition, B*, at filling factor nu=2/3 in the 2D electron system in
GaAs/AlGaAs heterojunctions. The field B* is found to decrease appreciably as
the wave function extent controlled by back gate voltage is increased. Our
calculations show that the contributions to the shift of B* from the change of
the Coulomb energy and the g factor change due to nonparabolicity are
approximately the same. The observed relative shift of B* is described with no
fitting parameters.",1210.0387v2
2012-10-05,Orbital phases of fermions in an asymmetric optical ladder,"We study a quantum ladder of interacting fermions with coupled s and p
orbitals. Such a model describes dipolar molecules or atoms loaded into a
double-well optical lattice, dipole moments being aligned by an external field.
The two orbital components have distinct hoppings. The tunneling between them
is equivalent to a partial Rashba spin-orbital coupling when the orbital space
(s, p) is identified as spanned by pseudo-spin 1/2 states. A rich phase
diagram, including incommensurate orbital density wave, pair density wave and
other exotic superconducting phases, is proposed with bosonization analysis. In
particular, superconductivity is found in the repulsive regime.",1210.1859v2
2012-10-09,Realization of the $π$-state in junctions formed by multi-band superconductors with a spin-density-wave,"Using a simple model of multi-band superconductors, which can be applied in
particular to Fe\nobreakdash-based pnictides, we calculate the Josephson
current $I_{\text{J}}$ in a tunnel junction composed by such superconductors.
We employ the tunneling Hamiltonian method and quasiclassical Green's
functions. We study both the case of coexistence of the superconducting
($\Delta $) and magnetic (SDW---spin density wave) order parameters and the
case when only the superconducting order parameter exists. We show that the
current $I_{\text{J}}$ depends on the mutual orientation of magnetization of
the SDW in the case of non-ideal nesting when the coexistence of
superconducting and magnetic order parameters is possible as it takes place in
Fe\nobreakdash-based pnictides. It is found that the realization of the
$\pi$\nobreakdash-junction is possible in both cases. We compare our results
for multi-band superconductors without the SDW with those obtained earlier and
find that they coincide if the tunneling matrix elements are real. If these
elements are complex, a new term appears in the formula for the Josephson
critical current.",1210.2546v2
2012-10-12,"Layered pnictide-oxide Na$_2$Ti$_2$Pn$_2$O (Pn=As, Sb): a paradigm for spin density waves","From the first-principles calculations, we have studied the electronic and
magnetic structures of compound Na$_2$Ti$_2$Pn$_2$O (Pn = As or Sb). We find
that in the ground state Na$_2$Ti$_2$As$_2$O is a blocked checkerboard
antiferromagnetic semiconductor with a small band gap of about 0.15 eV, in
contrast, Na$_2$Ti$_2$Sb$_2$O is a bi-collinear antiferromagnetic semimetal,
both with a small moment of about 0.5$\mu_B$ around each Ti atom. We show that
there is a strong Fermi surface nesting in Na$_2$Ti$_2$Pn$_2$O. And we verify
that the blocked checkerboard and bi-collinear antiferromagnetic states both
are the spin density waves induced by the Fermi surface nesting. A tetramer
structural distortion is found in company with the formation of a blocked
checkerboard antiferromagnetic order, in good agreement with the experimentally
observed commensurate structural distortion but with space group symmetry
retained after the anomaly happening. Further analysis and discussion in
connection with experimental observations are given as well.",1210.3481v1
2012-11-07,Phase diagram of t-t' Hubbard model taking into account spin-spiral waves and phase separation at finite temperature,"The effect of temperature on the magnetic phase separation and the parameters
of spin-spiral waves (SSW) is studied using a two-dimensional (2D) single-band
$t-t'$ Hubbard model and the Hubbard-Stratonovich transformation. Both
commensurate (antiferromagnetic (AF)) and incommensurate (helical) magnetic
phases are considered. It is shown that the temperature significantly affects
the collinear and helical magnetic phases. With an increase in the temperature,
the phase-separation (PS) regions (AF$+[Q,Q])$, $([Q,Q]+[Q,\pi])$ get
substantially reduced but new regions $([Q_{1},\pi]+[Q_{2},\pi])$,
(AF$+[Q,\pi])$ arise. The results are used for the interpretation of the
magnetic properties of cuprates.",1211.1478v3
2012-12-05,The commensurate magnetic excitations induced by band-splitting and Fermi surface topology in n-type Cuprates,"The antiferromagnetic correlation plays an important role in high-T$_{c}$
superconductors. Considering this effect, the magnetic excitations in n-type
cuprates near the optimal doping are studied within the spin density wave
description. The magnetic excitations are commensurate in the low energy regime
and further develop into spin wave-like dispersion at higher energy, well
consistent with the inelastic neutron scattering measurements. We clearly
demonstrate that the commensurability originates from the band splitting and
Fermi surface topology. The commensurability is a normal state property, and
has nothing to do with d-wave superconductivity. The distinct behaviors of
magnetic excitation between the n-type and p-type cuprates are further
discussed. Our results strongly suggest the essential role of antiferromagnetic
correlations in the cuprates.",1212.1028v1
2012-12-06,Effects of spin density wave quantization on the electrical transport in epitaxial Cr thin films,"We present measurements of the electrical resistivity, $\rho$, in epitaxial
Cr films of different thicknesses grown on MgO (100) substrates, as a function
of temperature, $T$. The $\rho(T)$ curves display hysteretic behavior in
certain temperature range, which is film thickness dependent. The hysteresis
are related to the confinement of quantized incommensurate spin density waves
(ISDW) in the film thickness. Our important finding is to experimentally show
that the temperature $T_{mid}$ where the ISDW changes from $N$ to $N$\,+\,1
nodes {\it decreases} as the film thickness {\it increases}. Identifying
$T_{mid}$ with a first order transition between ISDW states with $N$ and
$N$\,+\,1 nodes, and using a Landau approach to the free energy of the ISDW
together with Monte Carlo simulations, we show that the system at high
temperatures explores all available modes for the ISDW, freezing out in one
particular mode at a transition temperature that indeed decreases with film
thickness, $L$. The detailed dependence of $T_{mid}(L)$ seems to depend rather
strongly on the boundary conditions at the Cr film interfaces.",1212.1408v1
2012-12-20,Spin wave theory for interacting hardcore bosons on cubic lattices: a comparative study,"Motivated by excellent comparisons of spin wave theory (SWT) with Quantum
Monte Carlo (QMC) calculations of non-interacting hardore bosons (Bernardet et
al.) and superlattices (Hen et al.), we develop an SWT for interacting hardcore
bosons on a d-dimensional cubic lattice at zero temperature and compare
thermodynamical properties with results of Stochastic Series Expansions (SSE):
there is good comparison between SWT and SSE results for the simple cubic
lattice at small repulsive strengths but differences arise between the results
of the two approaches for the square lattice at strong repulsions. The
boundaries of the three phases - Mott insulating (MI), superfluid (SF) and
N\'{e}el solid (NS) - can be readily estimated from calculations of particle
density, signalling either a first order (SF <--> NS) or second order
transition (MI <--> SF). Comparison is made with results of the Bethe ansatz in
one dimension and QMC in two dimensions.",1212.5191v1
2012-12-24,Excited states of the quasi-one-dimensional hexagonal quantum antiferromagnets,"We investigate the excited states of the quasi-one-dimensional quantum
antiferromagnets on hexagonal lattices, including the longitudinal modes based
on the magnon-density waves. A model Hamiltonian with a uniaxial single-ion
anisotropy is first studied by a spin-wave theory based on the one-boson
method; the ground state thus obtained is employed for the study of the
longitudinal modes. The full energy spectra of both the transverse modes (i.e.,
magnons) and the longitudinal modes are obtained as functions of the
nearest-neighbor coupling and the anisotropy constants. We have found two
longitudinal modes due to the non-collinear nature of the triangular
antiferromagnetic order, similar to that of the phenomenological field theory
approach by Affleck. The excitation energy gaps due to the anisotropy and the
energy gaps of the longitudinal modes without anisotropy are then investigated.
We then compare our results for the longitudinal energy gaps at the magnetic
wavevectors with the experimental results for several antiferromagnetic
compounds with both integer and non-integer spin quantum numbers, and we find
good agreement after the higher-order contributions are included in our
calculations.",1212.5924v3
2013-01-10,"Comment on ""Physical Origin and Generic Control of Magnonic Band Gaps of Dipole-Exchange Spin Waves in Width-Modulated Nanostrip Waveguides"" [K.-S. Lee, D.-S. Han, and S.-K. Kim, PRL 102, 127202 (2009), arXiv:0811.0411]","In Ref. [PRL 102, 127202 (2009)] Lee et al. reported the existence of large
magnonic bandgaps in one-dimensional width-modulated Permalloy nanostripe
waveguides based on OOMMF simulations. However, as the symmetry of the magnetic
field pulse they applied to excite the spin waves (SWs) was not general, the
entire set of SW branches with A symmetry was omitted from the magnonic band
structures (see below). This omission has unfortunately led to misleading
conclusions of, for instance, the number, width and position of the bandgaps.
We present here the full band structure based on three different theoretical
approaches that gave consistent predictions, thus corroborating the methods
employed, namely, a microscopic approach, OOMMF simulations, and a method based
on the linearized Landau-Lifshitz equation. Further, we provide a physical
interpretation using group theory.",1301.2036v1
2013-01-14,Spin Density Wave Fluctuations and p-wave Pairing in Sr2RuO4,"Recently a debate has arisen over which of the two distinct parts of the
Fermi surface of Sr2RuO4, is the active part for the chiral p-wave
superconductivity. Early theories proposed p-wave pairing on the two
dimensional gamma-band, while a recent proposal focuses on the one dimensional
(alpha,beta) bands whose nesting pockets are the source of the strong
incommensurate spin density wave (SDW) fluctuations. We apply a renormalization
group theory to study quasi-one dimensional repulsive Hubbard chains and
explain the form of SDW fluctuations, reconciling the absence of long range
order with their nesting Fermi surface. The mutual exclusion of p-wave pairing
and SDW fluctuations in repulsive Hubbard chains favors the assignment of the
two dimensional gamma-band as the source of p-wave pairing.",1301.2865v1
2013-01-23,Neutrino emissivity of anisotropic neutron superfluids,"We examine the influence of the anisotropy of the superfluid energy gap and
residual Fermi-liquid interactions in the triplet-correlated neutron liquid
onto neutrino energy losses through neutral weak currents. The neutrino-pair
emission caused by the pair breaking and formation processes and by the
spin-wave decays is considered for the case of the $^{3}P_{2}$ pairing in the
state with $m_{j}=0$. The simple analytical formulae are obtained. A comparison
with the previous results of the average-angle approach shows that the gap
anisotropy leads to quenching of the neutrino emissivity caused by the pair
recombination processes on about 15% and to substantial suppression of the
spin-wave decays. Residual particle-hole interactions increase the energy
losses in both the channels on about 5%.",1301.5439v1
2013-01-25,Itinerant ferromagnetism with finite ranged interactions,"Quantum fluctuations are of central importance in itinerant ferromagnets; in
the case of the Stoner Hamiltonian, with contact interactions, they deliver a
rich phase diagram featuring a first order ferromagnetic transition preempted
by a spin spiral and a paired density wave. However, to date all analyses of
fluctuation corrections neglect the finite ranged nature of the Coulomb
interaction. We develop the formalism to consider the effects of fluctuations
with a realistic screened Coulomb potential. The finite ranged interaction
suppresses the tricritical point temperature of the first order ferromagnetic
transition, bringing theory into line with experiment, whilst retaining the
exotic spin spiral and paired density wave. In an ultracold atomic gas a finite
ranged interaction damps the competing molecular instability, permitting the
observation of ferromagnetic correlations.",1301.6036v1
2013-02-03,Superconducting Resonance and paring symmetry in electron-doped cuprates,"The magnetic excitations in the superconducting electron-doped cuprates are
studied in the framework of spin-density-wave description. The superconducting
resonance is a natural product of the superconductivity due to the opening of
d-wave gap. Its resonance energy exhibits well linear scaling with
superconducting gap as $E_{res}/2\Delta\sim 0.6$, quantitatively consisting
with the experimental discovery. This ratio is insensitive to the selected
parameters, manifesting its universality. Another lower-energy peak below
resonance energy is predicted when the hole pocket emerges due to suppression
of spin-density wave. We further verify that the ratio of linear scales is
intimately related to the pairing symmetry. Distinct ratio can be found with
respective pairing symmetry. In comparison with the inelastic neutron
scattering data, the monotonic d-wave superconductivity is the most likely
candidate in the electron-doped cuprates. Furthermore, we proposed a new method
to check the pairing symmetry by the inelastic neutron scattering measurements.",1302.0453v1
2013-03-18,Pressure suppression of spin-density-wave gap in the optical conductivity of SrFe2As2,"Optical reflectance R(w) of a pressure-induced superconductor SrFe2As2 has
been measured under external pressure to 6 GPa and at temperatures to 8 K.
Optical conductivity s(w) has been derived from the measured R(w). At ambient
pressure, in the antiferromagnetic state below T_N=198 K, a pronounced feature
develops in s(w) due to the opening of a spin density wave (SDW) gap, as
already reported in the literature. With increasing pressure, the SDW gap
feature in s(w) is progressively suppressed. At 4 GPa, where the sample is
superconducting, the SDW gap feature in s(w) is strongly reduced than that at
ambient pressure, but is still clearly observed. At 6 GPa, the SDW gap is
completely suppressed. The pressure evolutions of the SDW gap magnitude and the
spectral weight closely follow the pressure evolution of T_N.",1303.4182v1
2013-05-02,Numerical Study on Spontaneous Symmetry Breaking in a XY Quantum Antiferromagnet on a Finite Triangular Lattice,"Motivated by recent experiments that require more complicated macroscopic
wave functions in the condensed matters, we make numerical study on a XY
quantum antiferromagnet on a finite triangular lattice using the variational
Monte Carlo method and the stochastic state selection method. One of our
purpose is a numerical confirmation on dominance of a Nambu-Goldstone boson in
low energy excitation. For another purpose, we calculate energy, an expectation
value of a symmetry breaking operator and structure functions of spin by fixing
a quantum number of the symmetry. These calculations are made for states that
become degenerate in an infinitely large lattice. By numerical calculations we
confirm existence of a Nambu-Goldstone boson, and find dependence of a square
of the quantum number for the above quantities. Using these results we can
discuss on complicated macroscopic wave functions in quantum spin systems.",1305.0352v1
2013-05-16,Size-dependent magnetization switching characteristics and spin wave modes of FePt nanostructures,"We present a comprehensive investigation of the size-dependent switching
characteristics and spin wave modes of FePt nanoelements. Curved nanomagnets
(""caps"") are compared to flat disks of identical diameter and volume over a
size range of 100 to 300nm. Quasi-static magnetization reversal analysis using
first-order reversal curves (FORC) shows that spherical caps have lower vortex
nucleation and annihilation fields than the flat disks. As the element diameter
decreases, the reversal mechanism in the caps crosses over sooner to coherent
rotation than in the disks. The magnetization dynamics are studied using
optically induced small angle precession and reveal a strong size dependence
that differs for the two shapes. Flat disks exhibit well-known center and edge
modes at all sizes, but as the diameter of the caps increases from 100 to 300
nm, additional oscillation modes appear in agreement with dynamic micromagnetic
simulations. In addition, we show that the three-dimensional curvature of the
cap causes a much greater sensitivity to the applied field angle which provides
an additional way for controlling the ultrafast response of nanomagnetic
elements.",1305.3686v1
2013-05-30,Evolution of ferromagnetic and spin-wave resonances with crystalline order in thin films of full-Heusler alloy Co2MnSi,"We report the evolution of magnetic moment as well as magnetic anisotropy
with crystalline order in Co$_2$MnSi thin films grown on $(100)$ MgO by pulsed
laser deposition. The films become more ordered as the annealing temperature
($T_A$) increases from 400 to 600 $^0$C. The extent of \emph{L}$2_1$ ordering
in the films annealed at 600 $^0$C is $\approx 96%$. The static magnetization
measurements by vibrating sample magnetometry shows a maximum moment of 4.95
$\mu_B$ per formula unit with low coercivity ($H_C$ $\approx$ 65 Oe) in the
films annealed at 600 $^0$C. A rigorous analysis of the azimuthal and polar
angle dependent ferromagnetic resonance (FMR) measured at several temperatures
allows determination of various anisotropy fields relevant to our system as a
function of $T_A$. Finally, we have evaluated the exchange stiffness constant
down to 100 K using spin wave modes in FMR spectra. We have also estimated the
exchange energies as well as stiffness constant by varying the lattice
parameter \emph{ab-initio} using the Korringa-Kohn-Rostoker method.",1305.7048v1
2013-06-05,Nematic Phase in two-dimensional frustrated systems with power law decaying interactions,"We address the problem of orientational order in frustrated interaction
systems as a function of the relative range of the competing interactions. We
study a spin model Hamiltonian with short range ferromagnetic interaction
competing with an antiferromagnetic component that decays as a power law of the
distance between spins, $1/r^\alpha$. These systems may develop a nematic phase
between the isotropic disordered and stripe phases. We evaluate the nematic
order parameter using a self-consistent mean field calculation. Our main result
indicates that the nematic phase exists, at mean-field level, provided
$0<\alpha<4$. We analytically compute the nematic critical temperature and show
that it increases with the range of the interaction, reaching its maximum near
$\alpha\sim 0.5$. We also compute a corse-grained effective Hamiltonian for
long wave-length fluctuations. For $0<\alpha<4$ the inverse susceptibility
develops a set of continuous minima at wave vectors $|\vec k|=k_0(\alpha)$
which dictate the long distance physics of the system. For $\alpha\to 4$,
$k_0\to 0$, making the competition between interactions ineffective for greater
values of $\alpha$.",1306.1204v1
2013-06-10,Universal inhomogeneous magnetic-field response in the normal state of cuprate high-Tc superconductors,"We report the results of a muon spin rotation (muSR) study of the bulk of
Bi{2+x}Sr{2-x}CaCu2O{8+\delta}, as well as pure and Ca-doped YBa2Cu3Oy, which
together with prior measurements reveal a universal inhomogeneous
magnetic-field response of hole-doped cuprates extending to temperatures far
above the critical temperature (Tc). The primary features of our data are
incompatible with the spatially inhomogeneous response being dominated by known
charge density wave (CDW) and spin density wave (SDW) orders. Instead the
normal-state inhomogeneous line broadening is found to scale with the maximum
value Tc^max for each cuprate family, indicating it is controlled by the same
energy scale as Tc. Since the degree of chemical disorder varies widely among
the cuprates we have measured, the observed scaling constitutes evidence for an
intrinsic electronic tendency toward inhomogeneity above Tc.",1306.2277v2
2013-06-18,Long lifetime and high-fidelity quantum memory of photonic polarization qubit by lifting Zeeman degeneracy,"Long-lived and high-fidelity memory for photonic polarization qubit (PPQ) is
crucial for constructing quantum networks. Here we present an EIT-based
millisecond storage system in which a moderate magnetic field is applied on a
cold-atom cloud to lift Zeeman degeneracy. PPQ states are stored as two
magnetic-field-insensitive spin waves. Especially, the influence of
magnetic-field-sensitive spin waves on the storage performances is almost
totally avoided. The measured average fidelities of polarization states are
98.6% at 200 us and 78.4% at 4.5 ms, respectively.",1306.4262v4
2013-07-04,Electronic transport in ferromagnetic barriers on the surface of a topological insulator with $δ$ doping,"We investigate electron transporting through a two-dimensional
ferromagnetic/normal/ferromagnetic tunnel junction on the surface of a
three-dimensional topological insulator with taking into $\delta$ doping
account. It is found that the conductance oscillates with the Fermi energy, the
position and the aptitude of the $\delta$ doping. Also the conductance depends
sensitively on the direction of the magnetization of the two ferromagnets,
which originate from the control of the spin flow due to spin-momentum locked.
It is found that the conductance is the maximum at the parallel configuration
while it is minimum at the antiparallel configuration and vice versa, which may
stem from the half wave loss due to the electron wave entering through the
antiparallel configuration. These characters are very helpful for making new
types of magnetoresistance devices due to the practical applications.",1307.1283v1
2013-07-18,Origin of electronic dimers in the spin-density wave phase of Fe-based superconductors,"We investigate the emergent impurity-induced states arising from point-like
scatterers in the spin-density wave phase of iron-based superconductors within
a microscopic five-band model. Independent of the details of the band-structure
and disorder potential, it is shown how stable magnetic (pi,pi) unidirectional
nematogens are formed locally by the impurities. Interestingly, these
nematogens exhibit a dimer structure in the electronic density, are directed
along the antiferromagnetic a-axis, and have typical lengths of order 10
lattice constants in excellent agreement with recent scanning tunnelling
experiments. These electronic dimers provide a natural explanation of the
dopant-induced transport anisotropy found e.g. in the 122 iron pnictides.",1307.4913v2
2013-07-26,Linear magnetoconductivity in multiband spin-density-wave metals with nonideal nesting,"In several parent iron-pnictide compounds the resistivity has an extended
range of linear magnetic field dependence. We argue that there is a simple and
natural explanation of this behavior. Spin density wave transition leads to
Fermi-surface reconstruction corresponding to strong modification of the
electronic spectrum near the nesting points. It is difficult for quasiparticles
to pass through these points during their orbital motion in magnetic field,
because they must turn sharply. As the area of the Fermi surface affected by
the nesting points increases proportionally to magnetic field, this mechanism
leads to the linear magnetoresistance. The crossover between the quadratic and
linear regimes takes place at the field scale set by the SDW gap and scattering
rate.",1307.7184v3
2013-09-03,The plasma oscillations in a two-dimensional electron-hole liquid under influence Rashba spin-orbit coupling,"The plasma oscillations of the two-dimensional electron-hole system in the
presence of a Rashba spin-orbit coupling are studied. Only the intra-Landau
level excitations are taken into account when the electrons and holes are
situated on their lowest Landau levels, the filling factor $v^{2}$ being less
than 1. The ground state of the two-dimensional electron-hole system is
supposed to be the electron-hole liquid. The dispersion relations for the
optical and acoustical plasmon modes were obtained. The acoustical plasmon
branch has a linear dispersion law in the range of small wave vectors and
monotonically increases with saturation at higher values of wave vectors. The
optical plasmon branch has a quadratic dependence in the range of long
wavelength and a monotonic increasing with saturation as in the case of
acoustical branch.",1309.0716v1
2013-09-06,Spin density wave order and fluctuations in Mn3Si: a transport study,"We present a comprehensive transport investigation of the itinerant
antiferromagnet Mn3Si which undergoes a spin density wave (SDW) order below
T_N~21.3K. The electrical resistivity, the Hall-, Seebeck and Nernst effects
exhibit pronounced anomalies at the SDW transition, while the heat conductivity
is phonon dominated and therefore is insensitive to the intrinsic electronic
ordering in this compound. At temperatures higher than T_N our data provide
strong evidence for a large fluctuation regime which extends up to ~200K in the
resistivity, the Seebeck effect and the Nernst effect. From the comparison of
our results with other prototype SDW materials, viz. LaFeAsO and Chromium, we
conclude that many of the observed features are of generic character.",1309.1636v1
2013-10-13,Spin-wave-induced corrections to the electronic density of states in metallic ferromagnets,"We calculate the correction to the electronic density of states in a
disordered ferromagnetic metal induced by spin-wave mediated interaction
between the electrons. Our calculation is valid for the case that the exchange
splitting in the ferromagnet is much smaller than the Fermi energy, but we make
no assumption on the relative magnitude of the exchange splitting and the
elastic electronic scattering time. In the ""clean limit"", where the exchange
splitting is much larger than the electronic scattering rate, we find a
correction with a T^{d/2} temperature dependence, where d is the effective
dimensionality of the ferromagnet. In the opposite ""dirty limit"" the
density-of-states correction is a non-monotonous function of energy and
temperature.",1310.3511v1
2013-10-14,Coexistence of Superconductor and Spin-Density Wave in (TMTSF)2ClO4: Spatial Structure of the Two-phase State,"We report comprehensive (magneto)transport studies of the two-phase state in
(TMTSF)2ClO4, where superconducting (SC) phase coexists with spin-density wave
insulator (SDW). By tuning the degree of ClO4 anion ordering in controlled
manner we drive SDW state and study the evolution of the SC spatial texture. We
find that as SDW is suppressed, SC regions initially appear inside the SDW
insulator in a form of filaments extended in the interlayer direction and
further merge into the two-dimensional sheets across the most conducting axis
of the crystal. We demonstrate that almost all our results can be explained
within the soliton phase model, though with several assumptions they can also
be interpreted by the creation of non-uniform deformations. We believe that the
anisotropy is intrinsic to SC/SDW coexistence in quasi one-dimensional
superconductors.",1310.3710v2
2013-10-15,The interfacial effects on the spin density wave in FeSe/SrTiO3 thin film,"Recently, the signs of both superconducting transition temperature (Tc)
beyond 60 K and spin density wave (SDW) have been observed in FeSe thin film on
SrTiO3 (STO) substrate, which suggests a strong interplay between
superconductivity and magnetism. With the first-principles calculations, we
find that the substrate-induced tensile strain tends to stabilize the SDW state
in FeSe thin film by enhancing of the next-nearest-neighbor superexchange
antiferromagnetic interaction bridged through Se atoms. On the other hand, we
find that when there are oxygen vacancies in the substrate, the significant
charge transfer from the substrate to the first FeSe layer would suppress the
magnetic order there, and thus the high-temperature superconductivity could
occur. In addition, the stability of the SDW is lowered when FeSe is on a
defect-free STO substrate due to the redistribution of charges among the Fe
3d-orbitals. Our results provide a comprehensive microscopic explanation for
the recent experimental findings, and build a foundation for the further
exploration of the superconductivity and magnetism in this novel
superconducting interface.",1310.4024v2
2013-10-31,Quantum mechanical which-way experiment with an internal degree of freedom,"For a particle travelling through an interferometer, the trade-off between
the available which-way information and the interference visibility provides a
lucid manifestation of the quantum mechanical wave-particle duality. Here we
analyze this relation for a particle possessing an internal degree of freedom
such as spin. We quantify the trade-off with a general inequality that paints
an unexpectedly intricate picture of wave-particle duality when internal states
are involved. Strikingly, in some instances which-way information becomes
erased by introducing classical uncertainty in the internal degree of freedom.
Furthermore, even imperfect interference visibility measured for a suitable set
of spin preparations can be sufficient to infer absence of which-way
information. General results are illustrated with a proof-of-principle single
photon experiment.",1311.0017v1
2013-11-08,Large Negative Quantum Renormalization of Excitation Energies in the Spin-1/2 Kagome Lattice Antiferromagnet Cs$_2$Cu$_3$SnF$_{12}$,"Magnetic excitations in the spin-$\frac{1}{2}$ distorted kagome lattice
antiferromagnet Cs$_2$Cu$_3$SnF$_{12}$, which has an ordered ground state owing
to the strong Dzyaloshinskii-Moriya interaction, were studied using inelastic
neutron scattering. Although the spin-wave dispersion can be qualitatively
understood in terms of linear spin-wave theory (LSWT), the excitation energies
are renormalized by a factor of approximately 0.6 from those calculated by
LSWT, almost irrespective of the momentum transfer. This inadequacy of LSWT,
which is attributed to quantum fluctuations, provides evidence of negative
quantum renormalization in the spin-$\frac{1}{2}$ kagome lattice
antiferromagnet.",1311.1875v2
2013-11-14,Fidelity susceptibility and topological phase transition of a two dimensional spin-orbit coupled Fermi superfluid,"We investigate the fidelity susceptibility (FS) of a two-dimensional
spin-orbit coupled (SOC) Fermi superfluid and the topological phase transition
driven by a Zeeman field in the perspective of its ground-state wave-function.
Without Zeeman coupling, FS shows new features characterizing the BCS-BEC
crossover induced by SOC. In the presence of a Zeeman field, the topological
phase transition is explored using both FS and the topological invariant. In
particular, we obtain the analytical result of the topological invariant which
explicitly demonstrates that the topological phase transition corresponds to a
sudden change of the ground state wave-function. Consequently, FS diverges at
the phase transition point with its critical behavior being: $\chi \propto
ln|h-h_{c}|$ . Based on this observation, we conclude that the topological
phase transition can be detected by measuring the momentum distribution in cold
atoms experiment.",1311.3349v2
2013-11-17,Subtleties of Non-Abelian Gauge Theories in Cold-Atomic Lattices,"I point out two of the subtleties referred to in the title. The first is that
gauge-invariant magnetic systems may realized under general circumstances, as
suggested by a simple theorem. The second subtlety is that care is needed to
identify the field theory simulated by a cold-atomic lattice gauge system.
Though the simplest such model confines in 2+1 dimensions, it has
non-relativistic ``gluon"" excitations. Time-reversal invariance is
spontaneously broken in this system. The confinement mechanism is related to an
extra U(1) gauge invariance.There is a model, suggested long ago by D. Rohlich
and me, which is known to have relativistic spin waves. One of the outstanding
theoretical problems is a better determination of the energy-momentum relation
of spin waves in different magnetic gauge systems.",1311.4192v1
2013-11-20,Preparations for detecting and characterizing gravitational-wave signals from binary black hole coalescences,"We evaluate how well EOBNR waveforms, obtained from the effective one-body
formalism, perform in detecting gravitational wave (GW) signals from binary
black hole (BBH) coalescences modelled by numerical relativity (NR) groups
participating in the second edition of the numerical injection analysis
(NINJA-2). In this study, NINJA-2 NR-based signals that are available in the
public domain were injected in simulated Gaussian, stationary data prepared for
three LIGO-Virgo detectors with early Advanced LIGO sensitivities. Here we
studied only non-spinning BBH signals. A total of 2000 such signals from 20
NR-based signal families were injected in a two-month long data set. The
all-sky, all-time compact binary coalescence (CBC) search pipeline was run
along with an added coherent stage to search for those signals. We find that
the EOBNR templates are only slightly less efficient (by a few percent) in
detecting non-spinning NR-based signals than in detecting EOBNR injections. On
the other hand, the coherent stage improves the signal detectability by a few
percent over a coincident search.",1311.4986v1
2013-11-21,Color spin wave functions of heavy tetraquark states,"Using the variational method, we calculate the mass of the J^P=1^+
(ud)bar(bb) tetraquark containing two identical heavy antiquarks in a
nonrelativistic potential model with color confinement and spin hyperfine
interaction. In particular, we extend a previous investigation of the model by
Brink and Stancu by investigating the effect of including the color anti-sextet
component of the diquark configuration as well as using several more Gaussian
parametrization for the L=0 part of the spatial wave function. We find that for
the heavy tetraquark, the 6bar{6} component among the color singlet bases is
negligible and that the previously used specific Gaussian spatial configuration
is good enough in obtaining the ground state energy.",1311.5330v1
2013-11-22,"Spin-Wave Resonance Model of Surface Pinning in Ferromagnetic Semiconductor (Ga,Mn)As Thin Films","The source of spin-wave resonance (SWR) in thin films of the ferromagnetic
semiconductor (Ga,Mn)As is still under debate: does SWR stem from the
\emph{surface} anisotropy (in which case the surface inhomogeneity (SI) model
would apply), or does it originate in the \emph{bulk} inhomogeneity of the
magnetic structure of the sample (and thus requires the use of the volume
inhomogeneity (VI) model)? This paper outlines the ground on which the
controversy arose and shows why in different conditions a resonance sample may
meet the assumptions of either the SI or the VI model. In our considerations we
refer to the SWR spectra measured by Furdyna's team [X. Liu \textit{et al.},
Physical Review B \textbf{75}, 195220 (2007)] in (Ga,Mn)As thin films in
different configurations of the static magnetic field $\vec{H}$ with respect to
the surface. We demonstrate that the observed configuration dependence of the
SWR spectrum of the studied material can be described with the use of the
surface pinning parameter.",1311.5767v2
2013-12-19,Effects of Long-Range Interactions on Magnetic Excitations and Phase Transition on a Magnetically Frustrated Square Lattice,"We investigate the effects of long-range interaction on the magnetic
excitations and the competition between magnetic phases on a frustrated square
lattice. Applying the spin wave theory and assisted with symmetry analysis, we
obtain analytical expression for spin wave spectrum of competing Neel and (pi,
0) stripe states of systems containing any-order long-range interactions. In
the specific case of long-range interactions with power-law decay, we found
surprisingly that staggered long-range interaction suppresses quantum
fluctuation and enlarges the ordered moment, especially in the Neel state, and
thus extends its phase boundary to the stripe state. Our findings only
illustrate the rich possibilities of the roles of long-range interactions, and
advocate future investigations in other magnetic systems with different
structures of interactions.",1312.5383v1
2014-01-03,Topological phases due to the coexistence of superconductivity and spin-density wave: Application to high Tc superconductors in the underdoped regime,"We consider the coexistence of superconductivity(SC) and spin-density
wave(SDW). The SC is presumed to be of $d_{x^2-y^2}+id_{xy} (d_1 + i d_2) $
type whereas the SDW order parameter is of $BCS$/$d_{x y} $ symmetry. The
Hamiltonian having such a structure is shown to have topological coexistence
phases in addition to the conventional one. It is shown that the amplitudes of
both the order parameters determine the nature of topological phases. A phase
diagram characterizing different topological phases with their Chern numbers
are obtained. The experimental realization of such topological phases with
reference to high temperature superconductors in the extreme underdoped regime
are discussed.",1401.0617v1
2014-01-27,Voltage controlled propagating spin waves on a perpendicularly magnetized nanowire,"We numerically and analytically investigate the voltage controlled spin wave
(SW) propagations in a nanowire with locally manipulated perpendicular magnetic
anisotropy (PMA) by applying an electric field. It is shown that the velocity
and wavelength of the propagating SWs are tailored by the modified PMA, which
can be locally controlled by the external electric field. First, we observe a
phase shift when the propagating SWs pass through the area of locally modified
PMA. By introducing phase control of the SWs, we finally propose a three
terminal SW device. Constructive/destructive interferences of two propagating
SWs are controlled at the detecting area by the voltage controlled phase shift.",1401.6910v1
2014-02-06,Temperature-induced Change in the Fermi Surface Topology in the Spin Density Wave Phase of Sr(Fe$_{1-x}$Co$_x$)$_2$As$_2$,"We report electronic Raman scattering measurements of
Sr(Fe$_{1-x}$Co$_x$)$_2$As$_2$ single crystals in their magnetic - Spin Density
Wave (SDW) phase. The spectra display multiple, polarization-resolved SDW gaps
as expected in a band-folding itinerant picture for a multiband system. The
temperature dependence of the SDW gaps reveals an unusual evolution of the
reconstructed electronic structure with at least one gap being activated only
well below the magnetic SDW transition $T_N$. A comparison with temperature
dependent Hall measurements allows us to assign this activated behavior to a
change in the Fermi surface topology deep in the SDW phase, which we attribute
to the disappearance of a hole-like Fermi pocket. Our results highlight the
strong sensitivity of the low energy electronic structure to temperature in
iron-arsenide superconductors.",1402.1422v2
2014-02-19,A site-selective antiferromagnetic ground state in layered pnictide-oxide BaTi2As2O,"The electronic and magnetic properties of BaTi$_{2}$As$_{2}$O have been
investigated using both the first-principles and analytical methods. The
full-potential linearized augmented plane-wave calculations show that the most
stable state is a site-selective antiferromagnetic (AFM) metal with a
$\text{2}\times \text{1}\times \text{1}$ magnetic unit cell containing two
nonmagnetic Ti atoms and two other Ti atoms with antiparallel moments. Further
analysis to Fermi surface and spin susceptibility shows that the site-selective
AFM ground state is driven by the Fermi surface nesting and the Coulomb
correlation. Meanwhile, the charge density distribution remains uniform,
suggesting that the phase transition at $200$ K in experiment is a
spin-density-wave (SDW) transition.",1402.4723v1
2014-02-22,Ab initio quantum Monte Carlo calculations of spin superexchange in cuprates: the benchmarking case of Ca$_2$CuO$_3$,"In view of the continuous theoretical efforts aimed at an accurate
microscopic description of the strongly correlated transition metal oxides and
related materials, we show that with continuum quantum Monte Carlo (QMC)
calculations it is possible to obtain the value of the spin superexchange
coupling constant of a copper oxide in a quantitatively excellent agreement
with experiment. The variational nature of the QMC total energy allows us to
identify the best trial wave function out of the available pool of wave
functions, which makes the approach essentially free from adjustable parameters
and thus truly ab initio. The present results on magnetic interactions suggest
that QMC is capable of accurately describing ground state properties of
strongly correlated materials.",1402.5561v2
2014-02-26,Improved Domain Wall Dynamics and Magnonic Torques using Topological Insulators,"We investigate the magnetization dynamics that arise when a thin-film
ferromagnet is deposited on a topological insulator (TI), focusing in
particular on domain-wall motion via current and the possibility of a spin-wave
torque acting on the magnetization. We show analytically that the coupling
between the magnetic domain wall and the TI removes the degeneracy of the wall
profile with respect to its chirality and topological charge. Moreover, we find
that the threshold for Walker breakdown of domain wall motion is substantially
increased and determined by the interaction with the TI, allowing for higher
attainable wall velocities than in the conventional case where the hard axis
anisotropy determines the Walker threshold. Finally, we show that the allowed
modes of spin-wave excitations and the ensuing magnetization dynamics in the
presence of a TI coupling enable a magnonic torque acting even on homogeneous
magnetization textures. Our results indicate that the TI-ferromagnet
interaction has a similar effect on the magnetization dynamics as an intrinsic
Dzyaloshinskii-Moriya interaction in ferromagnets.",1402.6701v2
2014-03-06,On the description of subsystems in relativistic hypersurface Bohmian mechanics,"A candidate for a realistic relativistic quantum theory is the hypersurface
Bohm-Dirac model. Its formulation uses a foliation of spacetime into space-like
hypersurfaces. This structure may well arise from the universal wave function
itself, entailing the relativistic character of the theory despite the
appearance of a preferred foliation. However, to apply the theory and to make
contact with the usual quantum formalism one needs a framework for the
description of subsystems. The presence of spin together with the foliation
renders the subsystem description more complicated as compared to the
non-relativistic case with spin. In this paper, we provide such a framework in
terms of an appropriate conditional density matrix and an effective wave
function as well as clarify their relation, thereby generalizing previous
subsystem descriptions in the non-relativistic case.",1403.1464v2
2014-03-18,Spin Density Waves in the Hubbard model - A DMFT approach,"We analyze spin density waves (SDWs) in the Hubbard model on a square lattice
within the framework of inhomogeneous dynamical mean field theory (iDMFT).
Doping the half-filled Hubbard model results in a change of the
antiferromagnetic N\'eel state, which exists exactly at half filling, to a
phase of incommensurate SDWs. Previous studies of this phase mainly rely on
static mean field calculations. In this paper, we will use large-scale iDMFT
calculations to study properties of SDWs in the Hubbard model. A great
advantage of iDMFT over static mean field approaches is the inclusion of local
screening effects and the easy access to dynamical correlation functions.
Furthermore, this technique is not restricted to the Hubbard model, but can be
easily used to study incommensurate phases in various strongly correlated
materials.",1403.4315v2
2014-04-25,Phase-resolved imaging of edge-mode spin waves using scanning transmission x-ray microscopy,"We have imaged the excitation of small-amplitude spin-wave eigenmodes,
localized within $\sim$ 100 nm of the vertices of nanoscale Ni$_{81}$Fe$_{19}$
ellipses, using time-resolved scanning transmission x-ray microscopy (STXM) at
2 GHz and resolution of 70 nm. Taking advantage of the buried-layer sensitivity
of STXM, we find that the magnetization precession at the two vertices changes
from predominantly in-phase to out-of-phase in samples with and without a
conductive layer deposited over the ellipses. As a plausible interpretation for
the reversal in phase, we propose that unexpectedly strong Oersted fields are
generated in the discontinuous overlayer, although effects of edge roughness
cannot be fully excluded. The results demonstrate the capabilities of STXM to
image small-amplitude, GHz magnetization dynamics with the potential to map rf
magnetic fields on the nanoscale.",1404.6350v2
2014-05-14,Non-Fermi liquid behavior at the onset of incommensurate 2k_F charge or spin density wave order in two dimensions,"We analyze the influence of quantum critical fluctuations on single-particle
excitations at the onset of incommensurate $2k_F$ charge or spin density wave
order in two-dimensional metals. The case of a single pair of hot spots at high
symmetry positions on the Fermi surface needs to be distinguished from the case
of two hot spot pairs. We compute the fluctuation propagator and the electronic
self-energy perturbatively in leading order. The energy dependence of the
single-particle decay rate at the hot spots obeys non-Fermi liquid power laws,
with an exponent 2/3 in the case of a single hot spot pair, and exponent one
for two hot spot pairs. The prefactors of the linear behavior obtained in the
latter case are not particle-hole symmetric.",1405.3589v1
2014-07-16,A model of a quantum particle in a quantum environment: a numerical study,"We define and investigate, via numerical analysis, a one dimensional
toy-model of a cloud chamber. An energetic quantum particle, whose initial
state is a superposition of two identical wave packets with opposite average
momentum, interacts during its evolution and exchanges (small amounts of)
energy with an array of localized spins. Triggered by the interaction with the
environment, the initial superposition state turns into an incoherent sum of
two states describing the following situation: or the particle is going to the
left and a large number of spins on the left side changed their states, or the
same is happening on the right side. This evolution is reminiscent of what
happens in a cloud chamber where a quantum particle, emitted as a spherical
wave by a radioactive source, marks its passage inside a supersaturated
vapour-chamber in the form of a sequence of small liquid bubbles arranging
themselves around a possible classical trajectory of the particle.",1407.4250v1
2014-07-26,Conductance and shot noise in the helimagnet tunnel junction,"As a result of sinusoidal spatial modulation, helimagnet induces
spin-dependent diffracted transmission. In this work, we propose a general
scattering matrix treatment to the transport properties in helimagnets with
arbitrary helical structures. Multiferroic properties can be considered by
taking electric polarization and magnetic helix together into account. A
monolayer magnetic helix can be treated as a $\delta$-barrier by diffraction
theory. The conductance and shot noise properties of the normal
metal/helimagnet/normal metal toy model are investigated. It is found that the
shot noise is suppressed and demonstrates rise-and-fall variations as a result
of interference between different diffracted channels. Sharp change of the shot
noise occurs when one and both diffracted beams disappear into evanescent modes
at the helimagnet spiral wave vector equal to one and two times the electron
Fermi wave vector $q=k_F$ and $2 k_F$. We also considered the conductance and
shot noise properties in a real multiferroic helimagnet $\rm{TbMnO_3}$ with
ferroelectric and helimagnetism coexistent. It is found that clockwise and
counterclockwise spin helix is distinctly separated in the conductance and shot
noise spectrum. Their variation pattern is a combined result of helimagnetism
and electric polarization.",1407.7078v2
2014-07-26,A Non-Trivial Zero Length Limit of the Nambu-Goto String,"We show that a Nambu-Goto string has a nontrivial zero length limit which
corresponds to a massless particle with extrinsic curvature. The system has the
set of six first class constraints, which restrict the phase space variables so
that the spin vanishes. Upon quantization, we obtain six conditions on the
state, which can be represented as a wave function of position coordinates,
$x^\mu$, and velocities, $q^\mu$. We have found a wave function $\psi(x,q)$
that turns out to be a general solution of the corresponding system of six
differential equations, if the dimensionality of spacetime is eight. Though
classically the system is just a point particle with vanishing extrinsic
curvature and spin, the quantized system is not trivial, because it is
consistent in eight, but not in arbitrary, dimensions.",1407.7111v2
2014-08-06,Observation of Magnonic Band Gaps in Magnonic Crystals with Nopnreciprocal Dispersion Relation,"An effect of metallization of the magnonic crystal surface on the band gaps
formation in the spectra of the surface spin wave (SSW) is studied both
theoretically and experimentally. The structures under consideration are
one-dimensional magnonic crystals based on yttrium iron garnet with an array of
etched grooves with metal screen on the top of the corrugated surface and
without it. Due to nonreciprocity of propagation of the SSW the shift of band
gap to higher frequency and from the border of the Brillouin zone in presence
of conducting overlayer was measured in transmission line experiment. Results
of numerical calculations and model analysis are in agreement with experimental
data and give further insight into origin of the band gap and properties of the
nonreciprocal SSW in metallized magnonic crystals. This gives positive answer
to the outstanding question about possibility of detection of magnonic band
gaps in the spectra of the spin waves with nonreciprocal dispersion in magnonic
crystals and creates potential for new applications and improvements of already
existing prototype magnonic devices.",1408.1221v2
2014-08-06,Gravity dual of spin and charge density waves,"At high enough charge density, the homogeneous state of the D3-D7' model is
unstable to fluctuations at nonzero momentum. We investigate the end point of
this instability, finding a spatially modulated ground state, which is a charge
and spin density wave. We analyze the phase structure of the model as a
function of chemical potential and magnetic field and find the phase transition
from the homogeneous state to be first order, with a second-order critical
point at zero magnetic field.",1408.1397v3
2014-08-10,Lateral Chirality-sorting Optical Spin Forces in Evanescent Fields,"The transverse component of the spin angular momentum of evanescent waves
gives rise to lateral optical forces on chiral particles, which have the
unusual property of acting in a direction in which there is neither a field
gradient nor wave propagation. As their direction and strength depends on the
chiral polarizability of the particle, they act as chirality-sorting and may
offer a mechanism for passive chirality spectroscopy. The absolute strength of
the forces also substantially exceeds that of other recently predicted sideways
optical forces, such that they may more readily offer an experimental
confirmation of the phenomenon.",1408.2268v3
2014-08-18,Open Systems Dynamics for Propagating Quantum Fields,"In this dissertation, I explore interactions between matter and propagating
light. The electromagnetic field is modeled as a reservoir of quantum harmonic
oscillators successively streaming past a quantum system. Each weak and
fleeting interaction entangles the light and the system, and the light
continues its course. Within the framework of open quantum systems, the light
is eventually traced out, leaving the reduced quantum state of the system as
the primary mathematical subject. Two major results are presented. The first is
a master equation approach for a quantum system interacting with a traveling
wave packet prepared with a definite number of photons. In contrast to
quasi-classical states, such as coherent or thermal fields, these N-photon
states possess temporal mode entanglement, and local interactions in time have
nonlocal consequences. The second is a model for a three-dimensional
light-matter interface for an atomic ensemble interacting with a paraxial laser
beam and its application to the generation of QND spin squeezing. Both coherent
and incoherent dynamics due to spatially inhomogeneous atom-light coupling
across the ensemble are accounted for. Measurement of paraxially scattered
light can generate squeezing of an atomic spin wave, while diffusely scattered
photons lead to spatially local decoherence.",1408.4447v1
2014-08-27,DC resistivity at the onset of spin density wave order in two-dimensional metals,"The theory for the onset of spin density wave order in a metal in two
dimensions flows to strong coupling, with strong interactions not only at the
`hot spots', but on the entire Fermi surface. We advocate the computation of DC
transport in a regime where there is rapid relaxation to local equilibrium
around the Fermi surface by processes which conserve total momentum. The DC
resistivity is then controlled by weaker perturbations which do not conserve
momentum. We consider variations in the local position of the quantum critical
point, induced by long-wavelength disorder, and find a contribution to the
resistivity which is linear in temperature (up to logarithmic corrections) at
low temperature. Scattering of fermions between hot spots, by short-wavelength
disorder, leads to a residual resistivity and a correction which is linear in
temperature.",1408.6549v2
2014-09-09,Extended Møller-Plesset perturbation theory for dynamical and static correlations,"We present a novel method that appropriately handles both dynamical and
static electron correlation in a balanced manner, using a perturbation theory
on a spin-extended Hartree-Fock (EHF) wave function reference. While EHF is a
suitable candidate for degenerate systems where static correlation is
ubiquitous, it is known that most of dynamical correlation is neglected in EHF.
In this work, we derive a perturbative correction to a fully spin-projected
self-consistent wave function based on second-order M{\o}ller-Plesset
perturbation theory (MP2). The proposed method efficiently captures the ability
of EHF to describe static correlation in degeneracy, combined with MP2's
ability to treat dynamical correlation effects. We demonstrate drastic
improvements on molecular ground state and excited state potential energy
curves and singlet-triplet splitting energies over both EHF and MP2 with
similar computational effort to the latter.",1409.2888v1
2014-09-25,Tuning the Band Structures of a 1D Width-Modulated Magnonic Crystal by a Transverse Magnetic Field,"Theoretical studies, based on three independent techniques, of the band
structure of a one-dimensional width-modulated magnonic crystal under a
transverse magnetic field are reported. The band diagram is found to display
distinct behaviors when the transverse field is either larger or smaller than a
critical value. The widths and center positions of bandgaps exhibit unusual
non-monotonic and large field-tunability through tilting the direction of
magnetization. Some bandgaps can be dynamically switched on and off by simply
tuning the strength of such a static field. Finally, the impact of the lowered
symmetry of the magnetic ground state on the spin-wave excitation efficiency of
an oscillating magnetic field is discussed. Our finding reveals that the
magnetization direction plays an important role in tailoring magnonic band
structures and hence in the design of dynamic spin-wave switches.",1409.7183v1
2014-10-09,Coincident structural and magnetic order in BaFe$_2$(As$_{1-x}$)P$_x$)$_2$ revealed by high-resolution neutron diffraction,"We present neutron diffraction analysis of BaFe$_2$(As$_{1-x}$P$_x$)$_2$ over
a wide temperature (10 to 300 K) and compositional ($0.11 \leq x \leq 0.79$)
range, including the normal state, the magnetically ordered state, and the
superconducting state. The paramagnetic to spin-density wave and orthorhombic
to tetragonal transitions are first order and coincident within the sensitivity
of our measurements ($\sim 0.5$ K). Extrapolation of the orthorhombic order
parameter down to zero suggests that structural quantum criticality cannot
exist at compositions higher than $x = 0.28$, which is much lower than values
determined using other methods, but in good agreement with our observations of
the actual phase stability range. The onset of spin-density wave order shows a
stronger structural anomaly than the charge-doped system in the form of an
enhancement of the $c/a$ ratio below the transition.",1410.2630v1
2014-11-13,Non-linear radial spinwave modes in thin magnetic disks,"We present an experimental investigation of radial spin-wave modes in
magnetic nano-disks with a vortex ground state. The spin-wave amplitude was
measured using a frequency-resolved magneto optical network analyzer, allowing
for high-resolution resonance curves to be recorded. It was found that with
increasing excitation amplitude up to about 10 mT, the lowest-order mode
behaves strongly non-linearly as the mode frequency redshifts and the resonance
peak strongly deforms. This behavior was quantitatively reproduced by
micromagnetic simulations. At higher excitation the spinwaves are transformed
into a soliton by self-focusing, and collapse onto the vortex core, dispersing
the energy in short-wavelength spinwaves. Additionally, this process can lead
to switching of the vortex polarization through the injection of a Bloch point.",1411.3470v1
2014-11-21,Chiral spin density wave order on frustrated honeycomb and bilayer triangle lattice Hubbard model at half-filling,"We study the Hubbard model on the frustrated honeycomb lattice with
nearest-neighbor $t_1$ and second nearest-neighbor hopping $t_2$, which is
isomorphic to the bilayer triangle lattice, using the SU(2)-invariant slave
boson theory. We show that the Coulomb interaction $U$ induces
antiferromagnetic (AF) chiral spin-density wave ($\chi$-SDW) order in a wide
range of $\kappa =t_2/t_1$ where both the two-sublattice AF order at small
$\kappa$ and the decoupled three-sublattice 120$^\circ$ order at large $\kappa
$ are strongly frustrated, leading to three distinct phases with different
anomalous Hall responses. We find a continuous transition from a $\chi$-SDW
semimetal with anomalous Hall effect to a topological chiral Chern insulator
exhibiting quantum anomalous Hall effect, followed by a discontinuous
transition to a $\chi$-SDW insulator with zero total Chern number but anomalous
ac Hall effect.The $\chi$-SDW is likely a generic phase of strongly correlated
and highly frustrated hexagonal lattice electrons.",1411.6019v2
2014-11-25,FFLO order in ultra-cold atoms in three-dimensional optical lattices,"We investigate different ground-state phases of attractive spin-imbalanced
populations of fermions in 3-dimensional optical lattices. Detailed numerical
calculations are performed using Hartree-Fock-Bogoliubov theory to determine
the ground-state properties systematically for different values of density,
spin polarization and interaction strength. We first consider the high density
and low polarization regime, in which the effect of the optical lattice is most
evident. We then proceed to the low density and high polarization regime where
the effects of the underlying lattice are less significant and the system
begins to resemble a continuum Fermi gas. We explore the effects of density,
polarization and interaction on the character of the phases in each regime and
highlight the qualitative differences between the two regimes. In the
high-density regime, the order is found to be of Larkin-Ovchinnikov type,
linearly oriented with one characteristic wave vector but varying in its
direction with the parameters. At lower densities the order parameter develops
more structures involving multiple wave vectors.",1411.6967v1
2014-12-07,Magnonic band gaps in YIG based magnonic crystals: array of grooves versus array of metallic stripes,"The magnonic band gaps of the two types of planar one-dimensional magnonic
crystals comprised of the periodic array of the metallic stripes on yttrium
iron garnet (YIG) film and YIG film with an array of grooves was analyzed
experimentally and theoretically. In such periodic magnetic structures the
propagating magnetostatic surface spin waves were excited and detected by
microstripe transducers with vector network analyzer and by Brillouin light
scattering spectroscopy. Properties of the magnonic band gaps were explained
with the help of the finite element calculations. The important influence of
the nonreciprocal properties of the spin wave dispersion induced by metallic
stripes on the magnonic band gap width and its dependence on the external
magnetic field has been shown. The usefulness of both types of the magnonic
crystals for potential applications and possibility for miniaturization are
discussed.",1412.2367v2
2014-12-10,Analytical Parameterization of Self-Consistent Polycrystal Mechanics: Fast Calculation of Upper Mantle Anisotropy,"Progressive deformation of upper mantle rocks via dislocation creep causes
their constituent crystals to take on a non-random orientation distribution
(crystallographic preferred orientation or CPO) whose observable signatures
include shear-wave splitting and azimuthal dependence of surface wave speeds.
Comparison of these signatures with mantle flow models thus allows mantle
dynamics to be unraveled on global and regional scales. However, existing
self-consistent models of CPO evolution are computationally expensive when used
in 3-D and/or time-dependent convection models. Here we propose a new method,
called ANPAR, which is based on an analytical parameterisation of the
crystallographic spin predicted by the second-order (SO) self-consistent
theory. Our parameterisation runs approximately 2-3 x 10^4 times faster than
the SO model and fits its predictions for CPO and crystallographic spin with a
variance reduction > 99%. We illustrate the ANPAR model predictions for three
uniform deformations (uniaxial compression, pure shear, simple shear) and for a
corner-flow model of a spreading ridge.",1412.5611v1
2014-12-17,A local interpretation of QM,"A local interpretation of quantum mechanics is presented. Its main
ingredients are: first, a label attached to one of the virtual paths in the
path integral formalism, determining the output for measurement of position or
momentum; second, a mathematical model for spin states, equivalent to the path
integral formalism for point particles in space time, with the corresponding
label. The mathematical machinery of orthodox quantum mechanics is maintained,
in particular amplitudes of probability and Born's rule; therefore, Bell's type
inequalities theorems do not apply. It is shown that statistical correlations
for pairs of particles with entangled spins have a description completely
equivalent to the two slit experiment, that is, interference (wave like
behaviour) instead of non locality gives account of the process. The
interpretation is grounded in the experimental evidence of a point like
character of electrons, and in the hypothetical existence of a wave like, the
de Broglie, companion system. A correspondence between the extended Hilbert
spaces of hidden physical states and the orthodox quantum mechanical Hilbert
space shows the mathematical equivalence of both theories. Paradoxical
behaviour with respect to the action reaction principle is analysed, and an
experimental set up, modified two slit experiment, proposed to look for the
companion system.",1412.5612v2
2015-02-27,Effect of quantum statistics on the gravitational weak equivalence principle,"We study the effect of quantum statistics on the arrival time distribution of
quantum particles computed through the probability current density. It is shown
that symmetrization or asymmetrization of the wave function affects the arrival
time distribution for even freely propagating particles. In order to
investigate the effect of statistics on the weak equivalence principle in
quantum mechanics (WEQ), we then compute the mean arrival time for wave packets
in free fall. The violation of WEQ through the effect of statistics on the
mass-dependence of the mean arrival time is clearly exhibited. We finally
evaluate the effect of spin on the violation of WEQ using a different approach
by including an explicit spin-dependence in the probability current
distribution, and compare it with the approach using particle statistics. Our
results show WEQ re-emerges smoothly in the limit of large mass.",1502.07875v2
2015-02-28,Weakening of the spin density wave gap at low temperatures in SrFe$_2$As$_2$ single crystals,"We report on temperature dependent scanning tunneling microscopy and
spectroscopy studies of undoped SrFe$_{2}$As$_{2}$ single crystals from 6 K to
292 K. Resistivity data show spin density wave (SDW) transition at T$_{SDW}$
$\approx$ 205 K and the superconducting transition at $\sim$ 21 K while
magnetic susceptibility does not show any superconductivity. Conductance maps
and local tunneling spectra show an electronically homogeneous surface at all
studied temperatures. Tunnel spectra correlate well with the SDW transition
with a depression in the density of states near the Fermi energy below
T$_{SDW}$. On further lowering the temperature, the width of this partial
energy gap associated with the SDW decreases. Using the anti-correlation of
superconducting phase with SDW, we interpret this gap weakening as a precursor
to superconductivity. This may give rise to a facile nucleation of
superconductivity near defects.",1503.00103v1
2015-05-08,Enhanced stripe phases in spin-orbit-coupled Bose-Einstein condensates in ring cavities,"The coupled dynamics of the atom and photon fields in optical ring cavities
with two counter-propagating modes give rise to both spin-orbit interactions as
well as long-ranged interactions between atoms of a many-body system. At zero
temperature, the interplay between the two-body and cavity-mediated
interactions determines the ground state of a Bose-Einstein condensate. In this
work, we find that cavity quantum electrodynamics in the weak-coupling regime
favors a stripe-phase state over a plane-wave phase as the strength of
cavity-mediated interactions increases. Indeed, the stripe phase is
energetically stabilized even for condensates with attractive intra- and
inter-species interactions for sufficiently large cavity interactions. The
elementary excitation spectra in both phases correspond to linear dispersion
relation at long wavelengths, indicating that both phases exhibit
superfluidity, though the plane-wave phase also displays a characteristic
roton-type feature. The results suggest that even in the weak coupling regime
cavities can yield interesting new physics in ultracold quantum gases.",1505.02189v1
2015-05-29,Time-resolved imaging of pulse-induced magnetization reversal with a microwave assist field,"The reversal of the magnetization under the influence of a field pulse has
been previously predicted to be an incoherent process with several competing
phenomena such as domain wall relaxation, spin wave-mediated instability
regions, and vortex-core mediated reversal dynamics. However, there has been no
study on the direct observation of the switching process with the aid of a
microwave signal input. We report a time-resolved imaging study of
magnetization reversal in patterned magnetic structures under the influence of
a field pulse with microwave assistance. The microwave frequency is varied to
demonstrate the effect of resonant microwave-assisted switching. We observe
that the switching process is dominated by spin wave dynamics generated as a
result of magnetic instabilities in the structures, and identify the
frequencies that are most dominant in magnetization reversal.",1505.07936v1
2015-06-03,In-plane angular dependence of the spin-wave nonreciprocity of an ultrathin film with Dzyaloshinskii-Moriya interaction,"The nonreciprocal propagation of spin waves in an ultrathin Pt/Co/Ni film has
been measured by Brillouin light scattering. The frequency nonreciprocity, due
to the interfacial Dzyaloshinskii-Moriya interaction (DMI), has a sinusoidal
dependence on the in-plane angle between the magnon wavevector and the applied
magnetic field. The results, which are in good agreement with analytical
predictions reported earlier, yield a value of the DMI constant which is the
same as that obtained previously from a study of the magnon dispersion
relations. We have demonstrated that our magnon-dynamics based method can
experimentally ascertain the DMI constant of multilayer thin films.",1506.01134v1
2015-07-16,Role of pentaquark components in $φ$ meson production proton-antiproton annihilation reactions,"The pentaquark component is included in the proton wave functions to study
phi meson production proton-antiproton annihilation reactions. With all
possible configurations of the uuds subsystem proposed for describing the
strangeness spin and magnetic moment of the proton, we estimate the branching
ratios of the annihilation reactions at rest proton-antiproton to phi + X
(X=pi, eta, rho, omega) from atomic proton-antiproton S- and P-wave states by
using effective quark line diagrams incorporating the 3P0 model. The best
agreement of theoretical prediction with the experimental data is found when
the pentaquark configuration of the proton wave function takes the flavor-spin
symmetry, [4]_FS [22]_F [22]_S.",1507.04503v2
2015-07-21,A Spectral Representation for Spin-Weighted Spheroidal Wave Operators with Complex Aspherical Parameter,"A family of spectral decompositions of the spin-weighted spheroidal wave
operator is constructed for complex aspherical parameters with bounded
imaginary part. As the operator is not symmetric, its spectrum is complex and
Jordan chains may appear. We prove uniform upper bounds for the length of the
Jordan chains and the norms of the idempotent operators mapping onto the
invariant subspaces. The completeness of the spectral decomposition is proven.",1507.05756v3
2015-08-10,Complex field-induced states in Linarite PbCuSO$_4$(OH)$_2$ with a variety of high-order exotic SDW$_p$ states,"Low-temperature neutron diffraction and NMR studies of field-induced phases
in linarite are presented for magnetic fields $H \parallel b$ axis. A two-step
spin-flop transition is observed as well as a transition transforming a helical
magnetic ground state into an unusual magnetic phase with sine-wave modulated
moments $\parallel H$. An effective $\tilde{J}_1$-$\tilde{J}_2$ single-chain
model with a magnetization-dependent frustration ratio $\alpha_{\rm eff} =
-\tilde{J}_2/\tilde{J}_1$ is proposed. The latter is governed by skew
interchain couplings and shifted to the vicinity of the ferromagnetic critical
point. It explains qualitatively the observation of a rich variety of exotic
(for strongly correlated cuprate spin-1/2 Heisenberg systems) longitudinal
collinear spin-density wave SDW$_p$ states ($9 \geq p \geq 2$).",1508.02207v1
2015-08-24,Origin of robust interaction of spin waves with a single skyrmion in perpendicularly magnetized nanostripes,"We studied interactions between propagating spin waves (SWs) and a single
skyrmion in a perpendicularly magnetized CoFeB nanostripe where the magnetic
layer is interfaced with W and MgO. Micromagnetic numerical calculations
revealed that robust interactions between the incident SWs and the skyrmion
give rise to considerable forward skyrmion motions for specific SW frequencies
(e.g., here: fsw = 12 - 19 GHz). Additionally, it was found that there exists a
sufficiently low threshold field amplitude, e.g., 0.1 kOe for the fsw = 15 GHz
SWs. This frequency-dependent interaction originated from the robust coupling
of the SWs with the internal modes of the skyrmion, through the SWs' linear
momentum transfer torque acting on the skyrmion. This work provides for
all-magnetic control of skyrmion motions without electronic currents, and
facilitates further understanding of the interactions between magnons and
topological solitons in constricted geometries.",1508.05682v1
2015-08-31,Storing a single photon as a spin wave entangled with a flying photon in telecomband,"Quantum memory is an essential building block for quantum communication and
scalable linear quantum computation. Storing two color entangled photons, with
one photon being at telecom-wavelength while the other photon being compatible
of quantum memory, has great advantages toward the realization of the fiber
based long-distance quantum communication with the aid of quantum repeaters.
Here, we report an experimental realization of storing a photon entangled with
a telecom photon in polarization as an atomic spin wave in a cold atomic
ensemble, thus establishing the entanglement between the telecom-band photon
and the atomic ensemble memory in polarization degree of freedom. The
reconstructed density matrix and the violation of Clauser Horne Shimony Holt
inequality clearly show the preservation of quantum entanglement during
storage. Our result is very promising for establishing a long-distance quantum
network based on cold atomic ensembles.",1508.07754v4
2015-10-12,Spin wave approach to the two-magnon Raman scattering in an J1x-J1y-J2-Jc antiferromagnetic Heisenberg model,"We study the two-magnon non-resonant Raman scattering in the (pi,pi) and
(pi,0) ordered antiferromagnetic phases of a J1x-J1y-J2-Jc Heisenberg model on
the tetragonal lattice within the framework of the spin-wave theory. We discuss
the effects of various tuning factors to the two-magnon Raman spectra. We find
that both the magnetic frustration J2/J1 and the interlayer exchange coupling
Jc may significantly affect the spectra in both the B1g and A1g' channels in
the (pi,pi) Neel ordered phase. Moreover, we find a splitting of the two-magnon
peak in the (pi,0) antiferromagnetic phase. We further discuss the implications
of our results to the BaMnBi2 and iron pnictide systems.",1510.03359v1
2015-10-26,Entanglement Entropy and Topological Order in Resonating Valence-Bond Quantum Spin Liquids,"On the triangular and kagome lattices, short-ranged resonating valence bond
(RVB) wave functions can be sampled without the sign problem using a
recently-developed Pfaffian Monte Carlo scheme. In this paper, we study the
Renyi entanglement entropy in these wave functions using a replica-trick
method. Using various spatial bipartitions, including the Levin-Wen
construction, our finite-size scaled Renyi entropy gives a topological
contribution consistent with $\gamma = \text{ln}(2)$, as expected for a gapped
$\mathbb{Z}_{2}$ quantum spin liquid. We prove that the mutual statistics are
consistent with the toric code anyon model and rule out any other quasiparticle
statistics such as the double semion model.",1510.07682v3
2015-11-02,Determination of mass of an isolated neutron star using continuous gravitational waves with two frequency modes: an effect of a misalignment angle,"A rapidly spinning neutron star (NS) would emit a continuous gravitational
wave (GW) detectable by the advanced LIGO, advanced Virgo, KAGRA and proposed
third generation detectors such as the Einstein Telescope (ET). Such a GW does
not propagate freely, but is affected by the Coulomb-type gravitational field
of the NS itself. This effect appears as a phase shift in the GW depending on
the NS mass. We have shown that mass of an isolated NS can, in principle, be
determined if we could detect the continuous GW with two or more frequency
modes. Indeed, our Monte Carlo simulations have demonstrated that mass of a NS
with its ellipticity $10^{-6}$ at 1 kpc is typically measurable with precision
of 20% using the ET, if the NS is precessing or has a pinned superfluid core
and emits GWs with once and twice the spin frequencies. After briefly
explaining our idea and results, this paper concerns with the effect of
misalignment angle (""wobble angle"" in the case of a precessing NS) on the mass
measurement precision.",1511.00358v2
2015-11-29,Optical Study of BaFe$_2$As$_2$ under pressure: Coexistence of spin-density-wave gap and superconductivity,"Temperature-dependent reflectivity measurements in the frequency range 85 -
7000 cm$^{-1}$ were performed on BaFe$_2$As$_2$ single crystals under pressure
up to $\sim$5 GPa. The corresponding pressure- and temperature-dependent
optical conductivity was analyzed with the Drude-Lorentz model to extract the
coherent and incoherent contributions. The gradual suppression of the
spin-density wave (SDW) state with increasing pressure and the appearance of
the superconducting phase coexisting with the SDW phase at 3.6~GPa were
observed. At 3.6~GPa, the reflectivity reaches unity below $\sim$95~cm$^{-1}$
indicating the opening of the superconducting gap and shows a full gap tendency
at 6 K.",1511.09005v1
2016-01-08,"Raman scattering study of spin-density-wave-induced anisotropic electronic properties in AFe2As2 (A=Ca,Eu)","We present a polarization-resolved and temperature-dependent Raman scattering
study of AFe2As2 (A = Ca, Eu). In the spin-density-wave (SDW) phase, spectral
weight redistribution is observed in the fully symmetric and non-symmetric
scattering channels at different energies. An anisotropic Raman response is
observed in the fully symmetric channel in spontaneously detwinned CaFe2As2
samples. We calculate the orbital-resolved electronic structures using a
combination of density functional theory and dynamical mean field theory
(DFT+DMFT). We identify the electronic transitions corresponding to these two
spectral features and find that the anisotropic Raman response originates from
the lifted degeneracy of the dxz/yz orbitals in the broken symmetry phase.",1601.01942v2
2016-01-18,Incommensurate spin-density-wave antiferromagnetism in CeRu$_2$Al$_2$B,"The newly discovered Ising-type ferromagnet CeRu$_2$Al$_2$B exhibits an
additional phase transition at $T_\textrm{N}$ = 14.2 K before entering the
ferromagnetic ground state at $T_\textrm{C}$ = 12.8 K. We clarify the nature of
this transition through high resolution neutron diffraction measurements. The
data reveal the presence of a longitudinal incommensurate spin-density wave
(SDW) in the temperature range of $T_\textrm{C}<T<T_\textrm{N}$. The
propagation vector ${\bf q} \sim (0,0,0.148)$ is nearly temperature independent
in this region and discontinuously locks into ${\bf q} = 0$ at $T_\textrm{C}$.
Mean-field calculations of an effective Ising model indicate that the modulated
SDW phase is stabilized by a strong competition between ferromagnetic and
antiferromagnetic exchange interactions. This makes CeRu$_2$Al$_2$B a
particularly attractive model system to study the global phase diagram of
ferromagnetic heavy-fermion metals under influence of magnetic frustration.",1601.04430v1
2016-04-12,Freezing motion-induced dephasing in an atomic-ensemble quantum memory,"Motion-induced dephasing is a dominant decoherence mechanism for atom-gas
quantum memories. In this paper, we develop a new coherent manipulation
technique which enables arbitrary engineering of the spin-wave momentum with
neglectable noise. By zeroing the spin-wave momentum, motion-induced dephasing
can be frozen completely. We experimentally demonstrate this scheme with
laser-cooled atoms in a DLCZ configuration. By applying the freezing pulses,
memory lifetime gets extended significantly to the limit of atom cloud
expansion and does not depend on the detection angle anymore. The observed high
cross-correlation above 20 proves that high-fidelity memory operation is well
preserved after coherent manipulation.",1604.03293v1
2016-04-20,High-Capacity Angularly-Multiplexed Holographic Memory Operating at the Single Photon Level,"We experimentally demonstrate an angularly-multiplexed holographic memory
capable of intrinsic generation, storage and retrieval of multiple photons,
based on off-resonant Raman interaction in warm rubidium-87 vapors. The memory
capacity of up to 60 independent atomic spin-wave modes is evidenced by
analyzing angular distributions of coincidences between Stokes and time-delayed
anti-Stokes light, observed down to the level of single spin-wave excitation
during several-$\mu$s memory lifetime. We also propose how to practically
enhance rates of single and multiple photons generation by combining our
multimode emissive memory with existing fast optical switches.",1604.06049v4
2016-05-06,Optical-lattice-assisted magnetic phase transition in a spin-orbit-coupled Bose-Einstein condensate,"We investigate the effect of a periodic potential generated by a
one-dimensional optical lattice on the magnetic properties of an $S=1/2$
spin-orbit-coupled Bose gas. By increasing the lattice strength one can achieve
a magnetic phase transition between a polarized and an unpolarized Bloch wave
phase, characterized by a significant enhancement of the contrast of the
density fringes. If the wave vector of the periodic potential is chosen close
to the roton momentum, the transition could take place at very small lattice
intensities, revealing the strong enhancement of the response of the system to
a weak density perturbation. By solving the Gross-Pitaevskii equation in the
presence of a three-dimensional trapping potential, we shed light on the
possibility of observing the magnetic phase transition in currently available
experimental conditions.",1605.02108v2
2016-05-23,Theory of storage and retrieval of intense-broadband pulses at room temperature: analytical and numerical solutions,"We analyze the storage and retrieval of intense-broadband pulses with the
added effects of Doppler broadening and detuning in a $\Lambda$ configuration.
We compute analytical solutions via the inverse scattering technique and show
how the signal field is transferred to a spin-wave in the atomic medium and
later retrieved by the interaction of a control pulse. Due to the intensity of
the pulses, the pulse area (as defined for self-induced transparency) plays a
key role in the interaction, as it determines the location of the spin wave
within the medium. Additionally, we compare our results to non-ideal conditions
by considering pulses of finite length and the effect of spontaneous emission.",1605.06870v2
2016-06-03,Transverse spin and transverse momentum in scattering of plane waves,"We study the near field to the far field evolution of spin angular momentum
(SAM) density and the Poynting vector of the scattered waves from spherical
scatterers. The results show that at the near field, the SAM density and the
Poynting vector are dominated by their transverse components. While the former
(transverse SAM) is independent of the helicity of the incident circular
polarization state, the latter (transverse Poynting vector) depends upon the
polarization state. It is further demonstrated that the magnitudes and the
spatial extent of the transverse SAM and the transverse momentum components can
be controllably enhanced by exploiting the interference of the transverse
electric and transverse magnetic scattering modes.",1606.01192v2
2016-05-30,On Photon Spin and the Electrodynamic Origin of the charge of the Electron,"We recently performed experiments on the transfer of photon spin to electron
orbital angular momentum. For an interpretation of the experimental results we
used a classical electrodynamic model of the photon as a propagating
electromagnetic solitary wave which is developed in detail here. A linearly
polarized monochromatic photon is considered as a propagating solitary
electromagnetic wave of finite energy hf which carries an angular momentum
h/2pi with the frequency f and Plancks constant h. This model has, apart from
being a tool for an interpretation of our experimental results, far reaching
consequences of fundamental relevance and guides us to an outline to a unified
quantum theory of electromagnetism and gravitation including an explanation of
the electrodynamic origin of the quantized charge of an electron.",1606.02251v2
2016-07-14,Probing the nodal structure of Landau level wave functions in real space,"The inversion layer of p-InSb(110) obtained by Cs adsorption of 1.8 % of a
monolayer is used to probe the Landau level wave functions within smooth
potential valleys by scanning tunnelling spectroscopy at 14 T. The nodal
structure becomes apparent as a double peak structure of each spin polarized
first Landau level, while the zeroth Landau level exhibits a single peak per
spin level only. The real space data show single rings of the valley-confined
drift states for the zeroth Landau level and double rings for the first Landau
level. The result is reproduced by a recursive Green's function algorithm using
the potential landscape obtained experimentally. We show that the result is
generic by comparing the local density of states from the Green's function
algorithm with results from a well controlled analytic model based on the
guiding center approach.",1607.04227v2
2016-07-27,Voltage-Controlled Nano-Scale Reconfigurable Magnonic Crystal,"A nano-scale reconfigurable magnonic crystal is designed using
voltage-controlled perpendicular magnetic anisotropy (PMA) in
ferromagnetic-dielectric hetero-structures. A periodic array of gate metallic
stripes is placed on top of a MgO/Co structure in order to apply a periodic
electric field and to modify the PMA in Co. It is numerically demonstrated that
the application of the voltage to the gate stripes modifies the spin-wave
propagation and leads to the formation of band gaps in the spin-wave spectrum.
The band gaps are dynamically controllable, i.e. it is possible to switch band
gaps on and off within a few nanoseconds. The width and the center frequency of
the band gaps is defined by the applied voltage. At last, it is shown that the
application of the voltage to selected, rather than to all gate stripes allows
for a pre-defined modification of the band gap spectra. The proposed
voltage-controlled reconfigurable magnonic crystal opens a new way to low power
consumption magnonic applications.",1607.07975v1
2016-07-27,Dressed-state electromagnetically induced transparency for light storage in uniform phase spin-waves,"We present, experimentally and theoretically, a scheme for dressed-state
electromagnetically induced transparency (EIT) in a three-step cascade system
where a four-level system is mapped into an effective three-level system.
Theoretical analysis reveals that the scheme provides coherent state control
via adiabatic following and provides a generalized protocol for light storage
in uniform phase spin-waves that are insensitive to motional dephasing. The
three-step driving enables a number of other features including spatial
selectivity of the excitation region within the atomic medium, and kick-free
and Doppler-free excitation that produces narrow resonances in thermal vapor.
As a proof of concept we present an experimental demonstration of the
generalized EIT scheme using the $6S_{1/2} \rightarrow 6P_{3/2} \rightarrow
7S_{1/2} \rightarrow 8P_{1/2}$ excitation path in thermal cesium vapor. This
technique could be applied to cold and thermal ensembles to enable longer
storage times for Rydberg polaritons.",1607.08031v1
2016-08-11,Collective magnetic excitations of $C_{4}$ symmetric magnetic states in iron-based superconductors,"We study the collective magnetic excitations of the recently discovered
$C_{4}$ symmetric spin-density wave states of iron-based superconductors with
particular emphasis on their orbital character based on an itinerant
multiorbital approach. This is important since the $C_{4}$ symmetric
spin-density wave states exist only at moderate interaction strengths where
damping effects from a coupling to the continuum of particle-hole excitations
strongly modifies the shape of the excitation spectra compared to predictions
based on a local moment picture. We uncover a distinct orbital polarization
inherent to magnetic excitations in $C_{4}$ symmetric states, which provide a
route to identify the different commensurate magnetic states appearing in the
continuously updated phase diagram of the iron-pnictide family.",1608.03493v1
2016-09-06,Localisation in Quantum Field Theory,"In nonrelatistic quantum mechanics, Born's principle of localistion is as
follows: For a single particle, if a wave function $\psi_K$ vanishes outside a
spatial region $K$, it is said to be localised in $K$. In particular if a
spatial region $K'$ is disjoint from $K$, a wave function $\psi_{K'}$ localised
in $K'$ is orthogonal to $\psi_K$.
  Such a principle of localisation does not exist compatibly with relativity
and causality in quantum field theory (Newton and Wigner) or interacting point
particles (Currie,Jordan and Sudarshan).It is replaced by symplectic
localisation of observables as shown by Brunetti, Guido and Longo, Schroer and
others. This localisation gives a simple derivation of the spin-statistics
theorem and the Unruh effect, and shows how to construct quantum fields for
anyons and for massless particles with `continuous' spin.
  This review outlines the basic principles underlying symplectic localisation
and shows or mentions its deep implications. In particular, it has the
potential to affect relativistic quantum information theory and black hole
physics.",1609.01470v3
2016-09-28,Artificial gravitation effect on spin-polarized exciton-polaritons,"The pseudospin dynamics of long-living exciton-polaritons in a wedged 2D
cavity has been studied theoretically accounting for the external magnetic
field effect. The cavity width variation plays the role of the artificial
gravitational force acting on a massive particle: exciton-polariton. A
semi-classical model of the spin-polarization dynamics of ballistically
propagating exciton-polaritons has been developed. It has been shown that for
the specific choise of the magnetic field magnitude and the initial polariton
wave vector the polariton polarization vector tends to an attractor on the
Poincare sphere. Based on this effect, the switching the polariton polarization
in the ballistic regime has been demonstrated. The self-interference of the
polariton field emitted by a point-like source has been shown to induce the
formation of interference patterns reminiscent of the interference patterns of
cylindrical and plane waves.",1609.08907v2
2016-10-22,High performance THz emitters based on ferromagnetic/nonmagnetic heterostructures,"We report a THz emitter with excellent performances based on nonmagnetic (NM)
and ferromagnetic (FM) heterostructures. The spin currents are first excited by
the femtosecond laser beam in the NM/FM bilayer, and then transient charge
currents are generated by inverse spin Hall effect, leading to THz emission out
of the structure. The broadband THz waves emitted from our film stacks have a
peak intensity exceeding 500 um thick ZnTe crystals (standard THz emitters).
Our device is insensitive to the polarization of an incident laser beam which
indicates the noise resistive feature. In contrast, the polarization of THz
waves is fully controllable by an external magnetic field. We have also
fabricated the devices on flexible substrates with a great performance, and
demonstrated that the devices can be driven by low power lasers. Together with
the low cost and mass productive sputtering growth method for the film stacks,
the proposed THz emitters can be readily applied to a wide range of THz
equipment. Our study also points towards an alternative approach to
characterize spintronic devices with NM/FM bilayers.",1610.07020v1
2016-10-31,Competing order in the fermionic Hubbard model on the hexagonal graphene lattice,"We study the phase diagram of the fermionic Hubbard model on the hexagonal
lattice in the space of on-site and nearest neighbor couplings with
Hybrid-Monte-Carlo simulations. With pure on-site repulsion this allows to
determine the critical coupling strength for spin-density wave formation with
the standard approach of introducing a small mass term, explicitly breaking the
sublattice symmetry. The analogous mass term for charge-density wave formation
above a critical nearest-neighbor repulsion, on the other hand, would introduce
a fermion sign problem. The competition between the two and the phase diagram
in the space of the two coouplings can however be studied in simulations
without explicit sublattice symmetry breaking. Our results compare
qualitatively well with the Hartree-Fock phase diagram. We furthermore
demonstrate how spin-symmetry breaking by the Euclidean time discretization can
be avoided also, when using an improved fermion action based on an exponetial
transfer matrix with exact sublattice symmetry.",1610.09855v1
2017-07-06,Ground state properties of a two dimensional Fermi superfluid with an anisotropic spin-orbit coupling,"We performed a theoretical investigation on the ground state properties of a
two dimensional ultra-cold Fermi superfluid with an anisotropic spin-orbit
coupling (SOC). In the absence of Zeeman field, the system evolves from weak
coupling BCS regime to strongly interacting BEC regime (BCS-BEC crossover) with
increasing either the two-particle interaction strength or SOC parameters. We
focused on the behaviors of pairing parameter and density of states (DOS) when
increasing the anisotropic parameter of the SOC. Surprisingly, we discovered
that the gap parameter decreases with increasing the anisotropic parameters,
but the DOS at the Fermi surface shows non-monotonic behavior as a function of
the anisotropic parameter. In the presence of the Zeeman field, we discussed a
particular type of topological phase transition by obtaining the analytical
result of the topological invariant and directly related this quantum phase
transition with a sudden change of the ground state wave-function. Effects of
higher partial wave pairing terms on this topological phase transition were
briefly discussed.",1707.01607v1
2017-07-06,Strong angular dependent transmission ratio due to interplay between spin waves and the domain wall in perpendicular magnetic anisotropy materials,"Spin waves (SW) can induce rich domain wall (DW) motion in a
perpendicular-magnetic anisotropy nanostrip. In-plane magnetization tilt angle
resulting from the fluctuation of the effective field of the magnetization
response in the DW region plays an essential role in the dynamics of SW
interacting with a DW. We performed simulation and found that the transmission
ratio of the propagating SW across the DW depends strongly on the tilt angle in
the low-frequency regime. The material parameters and the geometrical
configuration can be fine-tuned for practical devices.",1707.01617v1
2017-07-12,Broad line-width of antiferromagnetic spinwave due to electrons correlation,"We study magnetic excitations in a bilayer of an antiferromagnetic (AF)
insulator and a correlated metal, in which double occupancy is forbidden. The
effective action of the AF spin wave in the AF insulator is derived by using
the path integral formula within the second order of interplane coupling. The
electron correlation in the correlated metal is treated by the Gutzwiller
approximation, which renormalizes the hopping integrals by g_t as proportional
to the hole density. The linewidth of the AF spin wave excitations originates
from particle-hole excitations in the correlated metal. By increasing the
correlation effect, i.e., by decreasing g_t, it is found that the linewidth at
low energies increases inversely proportional to g_t. The present results will
also be useful for bilayers of a metal and ferrimagnet.",1707.03523v2
2017-08-27,Semiclassical dynamics of spin density waves,"We present a theoretical framework for equilibrium and nonequilibrium
dynamical simulation of quantum states with spin-density-wave (SDW) order.
Within a semiclassical adiabatic approximation that retains electron degrees of
freedom, we demonstrate that the SDW order parameter obeys a generalized
Landau-Lifshitz equation. With the aid of an enhanced kernel polynomial method,
our linear-scaling quantum Landau-Lifshitz dynamics (QLLD) method enables
dynamical SDW simulations with $N \simeq 10^5$ lattice sites. Our real-space
formulation can be used to compute dynamical responses, such as dynamical
structure factor, of complex and even inhomogeneous SDW configurations at zero
or finite temperatures. Applying the QLLD to study the relaxation of a
noncoplanar topological SDW under the excitation of a short pulse, we further
demonstrate the crucial role of spatial correlations and fluctuations in the
SDW dynamics.",1708.08050v3
2017-08-30,Hall effect in cuprates with incommensurate spin-density wave,"The presence of incommensurate spiral spin-density waves (SDW) has been
proposed to explain the $p$ (hole doping) to $1+p$ jump measured in the Hall
number $n_H$ at a doping $p^*$. Here we explore {\it collinear} incommensurate
SDW as another possible explanation of this phenomenon, distinct from the
incommensurate {\it spiral} SDW proposal. We examine the effect of different
SDW strengths and wavevectors and we find that the $n_H\sim p$ behavior is
hardly reproduced at low doping. The calculated $n_H$ and Fermi surfaces give
characteristic features that should be observed, thus the lack of these
features in experiment suggests that the incommensurate collinear SDW is
unlikely to be a good candidate to explain the $n_H\sim p$ observed in the
pseudogap regime.",1708.09465v2
2017-11-20,"Azimuthal Spin Wave Excitations in Magnetic Nanodots over the Soliton Background: Vortex, Bloch and Néel-like skyrmions","We study azimuthal spin-wave (SW) excitations in a circular ferromagnetic
nanodot in different inhomogeneous, topologically non-trivial magnetization
states, specifically, vortex, Bloch-type skyrmion and N\'eel-type skyrmion
states. Continuous mapping of the SW spectrum between these states is realized
with gradual change of the out-of-plane magnetic anisotropy and
Dzyaloshinskii-Moriya exchange interaction (DMI). Our study shows lifting of
the SW frequencies degeneracy and change in systematics of the frequency
levels. The change is induced by a geometrical Berry phase, that is present for
the dot-edge localized SWs in a vortex state and vanishes in skyrmion states.
Furthermore, channeling of the azimuthal SWs localized at the skyrmion edge is
present and induces large frequency splitting. This is attributed to DMI
induced nonreciprocity, while coupling of the breathing and gyrotropic modes is
related to soliton motion. Finally, an efficient coupling of the dynamic
magnetization in the skyrmion state to uniform magnetic field in nanodots with
non-circular symmetry is shown.",1711.07186v1
2018-03-02,Continuum excitation and pseudospin wave in quantum spin-liquid and quadrupole ordered states of Tb$_{2+x}$Ti$_{2-x}$O$_{7+y}$,"The ground states of the frustrated pyrochlore oxide
Tb$_{2+x}$Ti$_{2-x}$O$_{7+y}$ have been studied by inelastic neutron scattering
experiments. Three single-crystal samples are investigated; one shows no phase
transition ($x=-0.007<x_{\text{c}}\sim -0.0025$), being a putative quantum
spin-liquid (QSL), and the other two ($x=0.000, 0.003$) show electric
quadrupole ordering (QO) below $T_{\text{c}} \sim 0.5$ K. The QSL sample shows
continuum excitation spectra with an energy scale 0.1 meV as well as
energy-resolution limited (nominally) elastic scattering. As $x$ is increased,
pseudospin wave of the QO state emerges from this continuum excitation, which
agrees with that of powder samples and consequently verifies good $x$ control
for the present single crystal samples.",1803.00688v2
2018-03-12,Universal dynamics of zero-momentum to plane-wave transition in spin-orbit coupled Bose-Einstein condensates,"We investigate the universal spatiotemporal dynamics in spin-orbit coupled
Bose-Einstein condensates which are driven from the zero-momentum phase to the
plane-wave phase. The excitation spectrum reveals that, at the critical point,
the Landau critical velocity vanishes and the correlation length diverges.
Therefore, according to the Kibble-Zurek mechanism, spatial domains will
spontaneously appear in such a quench through the critical point. By simulating
the real-time dynamics, we numerically extract the static correlation length
critical exponent v and the dynamic critical exponent z from the scalings of
the temporal bifurcation delay and the spatial domain number. The numerical
scalings consist well with the analytical ones obtained by analyzing the
excitation spectrum.",1803.04768v1
2018-05-21,Probing the Shape of Quantum Surfaces: the Quadrupole Moment Operator,"The standard toolkit of operators to probe quanta of geometry in loop quantum
gravity consists in area and volume operators as well as holonomy operators.
New operators have been defined, in the U(N) framework for intertwiners, which
allow to explore the finer structure of quanta of geometry. However these
operators do not carry information on the global shape of the intertwiners.
Here we introduce dual multipole moments for continuous and discrete surfaces,
defined through the normal vector to the surface, taking special care to
maintain parametrization invariance. These are raised to multipole operators
probing the shape of quantum surfaces. Further focusing on the quadrupole
moment, we show that it appears as the Hessian matrix of the large spin
Gaussian approximation of coherent intertwiners, which is the standard method
for extracting the semi-classical regime of spinfoam transition amplitudes.
This offers an improvement on the usual loop quantum gravity techniques, which
mostly focus on the volume operator, in the perspective of modeling (quantum)
gravitational waves as shape fluctuations waves propagating on spin network
states.",1805.08257v1
2018-05-28,Superconductivity in the doped $t$-$J$ model: results for four-leg cylinders,"We report a density-matrix renormalization group study of the lightly doped
$t$-$J$ model on a 4-leg cylinder with doped hole concentrations per site
$\delta=5\%\sim 12.5\%$. By keeping an unusually large number of states and
long system sizes, we are able to accurately document the interplay between
d-wave superconductivity (SC) and spin and charge-density-wave (CDW) orders.
The long-distance behavior is consistent with that of a Luther-Emery liquid
with a spin-gap, power-law CDW correlations with wave-length $\lambda
=1/2\delta$, and power-law SC correlations. This is the widest (most nearly 2D)
such system for which power law SC correlations have been established.",1805.11163v1
2018-05-31,Disorder correction to the Néel temperature of ruthenium-doped BaFe$_2$As$_2$: Theoretical analysis,"We analyze theoretically nuclear magnetic resonance data for the spin-density
wave phase in the ruthenium-doped BaFe$_2$As$_2$. Since inhomogeneous
distribution of Ru~atoms introduces disorder into the system, experimentally
observable random spatial variations of the spin-density wave order parameter
emerge. Using perturbation theory for the Landau functional, we estimate the
disorder-induced correction to the N\'{e}el temperature for this material.
Calculated correction is significantly smaller than the N\'{e}el temperature
itself for all experimentally relevant doping levels. This implies that the
N\'{e}el temperature is quite insensitive to the disorder created by the
dopants.",1805.12568v2
2018-06-01,Optical determination of the exchange stiffness constant in an iron garnet,"Brillouin light scattering measurements were performed in the backscattering
geometry on a Bi-substituted rare earth iron garnet. We observed two different
peaks, one attributed to a surface spin wave in the dipole-exchange regime. The
other is referred to as a backscattering magnon mode, because the incident
light in this case is scattered backward by exchange-dominated spin wave inside
the material. We propose a method to estimate the exchange stiffness constant
from the frequency of the backscattering magnon mode. The obtained value is
comparable with the previously reported values for Y$ _3 $Fe$ _5 $O$ _{12} $.",1806.00228v2
2018-06-04,Competing Unconventional Charge-Density-Wave States in Cuprate Superconductors: Spin-Fluctuation-Driven Mechanism,"To understand the origin of unconventional charge-density-wave (CDW) states
in cuprate superconductors, we establish the self-consistent CDW equation, and
analyze the CDW instabilities based on the realistic Hubbard model, without
assuming any $q$-dependence and the form factor. Many higher-order many-body
processes, which are called the vertex corrections, are systematically
generated by solving the CDW equation. When the spin fluctuations are strong,
the uniform $q=0$ nematic CDW with $d$-form factor shows the leading
instability. The axial nematic CDW instability at $q = Q_a = (\delta,0)$
($\delta \approx \pi/2$) is the second strongest, and its strength increases
under the static uniform CDW order. The present theory predicts that uniform
CDW transition emerges at a high temperature, and it stabilize the axial $q =
Q_a$ CDW at $T = T_{CDW}$. It is confirmed that the higher-order
Aslamazov-Larkin processes cause the CDW orders at both $q = 0$ and $Q_a$.",1806.01132v1
2018-06-12,Resonant spin wave excitation in magnetoplasmonic bilayers by short laser pulses,"In magnetically ordered solids a static magnetic field can be generated by
virtue of the transverse magneto-optical Kerr effect (TMOKE). Moreover, the
latter was shown to be dramatically enhanced due to the optical excitation of
surface plasmons in nanostructures with relatively small optical losses. In
this paper we suggest a new method of resonant optical excitations in a
prototypical bilayer composed of noble metal (Au) with grating and a
ferromagnet thin film of yttrium iron garnet (YIG) via frequency comb. Based on
magnetization dynamics simulations we show that for the frequency comb with the
parameters, chosen in resonant with spin-wave excitations of YIG, TMOKE is
drastically enhanced, hinting towards possible technological applications in
the optical control of spintronics systems.",1806.04764v1
2018-06-26,Efficient continuous wave noise spectroscopy beyond weak coupling,"The optimization of quantum control for physical qubits relies on accurate
noise characterization. Probing the spectral density $S(\omega)$ of
semi-classical phase noise using a spin interacting with a continuous-wave (CW)
resonant excitation field has recently gained attention. CW noise spectroscopy
protocols have been based on the generalized Bloch equations (GBE) or the
filter function formalism, assuming weak coupling to a Markovian bath. However,
this standard protocol can substantially underestimate $S(\omega)$ at low
frequencies when the CW pulse amplitude becomes comparable to $S(\omega)$.
Here, we derive the coherence decay function more generally by extending it to
higher orders in the noise strength and discarding the Markov approximation.
Numerical simulations show that this provides a more accurate description of
the spin dynamics compared to a simple exponential decay, especially on short
timescales. Exploiting these results, we devise a protocol that uses an
experiment at a single CW pulse amplitude to extend the spectral range over
which $S(\omega)$ can be reliably determined to $\omega=0$.",1806.10043v1
2018-09-17,On the speed of domain walls in thin nanotubes: the transition from the linear to the magnonic regime,"Numerical simulations of domain wall propagation in thin nanotubes when an
external magnetic field is applied along the nanotube axis have shown an
unexpected behavior described as a transition from a linear to a magnonic
regime. As the applied magnetic field increases, the initial regime of linear
growth of the speed with the field is followed by a sudden change in slope
accompanied by the emission of spin waves. In this work an analytical formula
for the speed of the domain wall that explains this behavior is derived by
means of an asymptotic study of the Landau Lifshitz Gilbert equation for thin
nanotubes. We show that the dynamics can be reduced to a one dimensional
hyperbolic reaction diffusion equation, namely, the damped double Sine Gordon
equation, which shows the transition to the magnonic regime as the domain wall
speed approaches the speed of spin waves. This equation has been previously
found to describe domain wall propagation in weak ferromagnets with the
mobility proportional to the Dzyaloshinskii-Moriya interaction constant, for
Permalloy nanotubes the mobility is proportional to the nanotube radius.",1809.06278v3
2018-09-19,Exact Schrodinger wave-function solutions of the fully-correlated few-electron gas and the uniform electron gas,"We present numerically exact solutions to the full-dimensional Schrodinger
Equation for the few-electron gas (few-EG) model of electronic structure
theory. Our core methodology uses a Sum-of-Products (SOP) representation of
singular potentials to make the fully correlated multi-particle quantum
mechanical problem computationally tractable. With full access to periodic
wave-functions, we analyze the exchange/correlation, spin symmetry, and
thermodynamic ($T = 0$K) phases for few-EG systems with up to four explicit
electrons per unit cell. We also present pure-spin exchange/correlation
functionals for the same few-EG solutions. Finally, we consider the family of
few-EG calculations in juxtaposition with the closely related uniform electron
gas (UEG) system, for which previous calculations have been performed using
density functional theory and quantum Monte Carlo methods. The exact few-EG
solutions all display a similar oscillatory behavior at lower densities, which
is not predicted by previous UEG simulations.",1809.07363v4
2018-11-08,Calculated magnetic exchange interactions in Dirac magnon material Cu3TeO6,"Recently topological aspects of magnon band structure have attracted much
interest, and especially, the Dirac magnons in Cu3TeO6 have been observed
experimentally. In this work, we calculate the magnetic exchange interactions
J's using the first-principles linear-response approach and find that these J's
are short-range and negligible for the Cu-Cu atomic pair apart by longer than 7
Angstrom. Moreover there are only 5 sizable magnetic exchange interactions, and
according to their signs and strengths, modest magnetic frustration is
expected. Based on the obtained magnetic exchange couplings, we successfully
reproduce the experimental spin-wave dispersions. The calculated neutron
scattering cross section also agrees very well with the experiments. We also
calculate Dzyaloshinskii-Moriya interactions (DMIs) and estimate the canting
angle (about 1.3{\deg}) of the magnetic non-collinearity based on the
competition between DMIs and J's, which is consistent with the experiment. The
small canting angle agrees with that the current experiments cannot distinguish
the DMI induced nodal line from a Dirac point in the spin-wave spectrum.
Finally we analytically prove that the ""sum rule"" conjectured in [Nat. Phys.
14, 1011 (2018)] holds but only up to the 11th nearest neighbour.",1811.03603v1
2019-11-19,Doing spin physics with unpolarized particles,"Twisted, or vortex, particles refer to freely propagating non-plane-wave
states with helicoidal wave fronts. In this state, the particle possesses a
non-zero orbital angular momentum with respect to its average propagation
direction. Twisted photons and electrons have been experimentally demonstrated,
and creation of other particles in twisted states can be anticipated. If
brought in collisions, twisted states offer a new degree of freedom to particle
physics, and it is timely to analyze what new insights may follow. Here, we
theoretically investigate resonance production in twisted photon collisions and
twisted $e^+e^-$ annihilation and show that these processes emerge as a
completely novel probe of spin and parity-sensitive observables in fully
inclusive cross sections with unpolarized initial particles. This is possible
because the initial state with a non-zero angular momentum explicitly breaks
the left-right symmetry even when averaging over helicities. In particular, we
show how one can produce almost $100\%$ polarized vector mesons in unpolarized
twisted $e^+e^-$ annihilation and how to control its polarization state.",1911.08423v1
2019-11-25,GW170817A as a Hierarchical Black Hole Merger,"Despite the rapidly growing number of stellar-mass binary black hole mergers
discovered through gravitational waves, the origin of these binaries is still
not known. In galactic centers, black holes can be brought to each others'
proximity by dynamical processes, resulting in mergers. It is also possible
that black holes formed in previous mergers encounter new black holes,
resulting in so-called hierarchical mergers. Hierarchical events carry
signatures such as higher-than usual black hole mass and spin. Here we show
that the recently reported gravitational-wave candidate, GW170817A, could be
the result of such a hierarchical merger. In particular, its chirp mass
$\sim40$ M$_\odot$ and effective spin of $\chi_{\rm eff}\sim0.5$ are the
typically expected values from hierarchical mergers within the disks of active
galactic nuclei. We find that the reconstructed parameters of GW170817A
strongly favor a hierarchical merger origin over having been produced by an
isolated binary origin (with an Odds ratio of $>10^3$, after accounting for
differences between the expected rates of hierarchical versus isolated mergers)",1911.11142v2
2018-07-02,Broken-symmetry phases of interacting nested Weyl and Dirac loops,"We study interaction-induced broken symmetry phases that can arise in
metallic or semimetallic band structures with two nested Weyl or Dirac loops.
The odered phases can be of the charge or (pseudo)spin density wave type, or
superconductivity from interloop pairing. A general analysis for two types of
Weyl loops is given, according to whether a local reflection symmetry in
momentum space exists or not, for Hamiltonians having a global PT symmetry. The
resulting density-wave phases always have lower total energy, and can be
metallic, insulating, or semimetallic (with nodal loops), depending on both the
reflection symmetry of the loops and the symmetry transformation that maps one
loop onto the other. We extend this study to nested $\mathbb{Z}_2$ nodal lines,
for which the ordered phases include also nodal point and nodal chain
semimetals, and to spinful Dirac nodal lines. Superconductivity from interloop
pairing can be fully gapped only if the initial double loop system is
semimetallic.",1807.00545v2
2018-07-03,Kohn-Luttinger Superconductivity in Twisted Bilayer Graphene,"We show that the recently observed superconductivity in twisted bilayer
graphene (TBG) can be explained as a consequence of the Kohn-Luttinger (KL)
instability which leads to an effective attraction between electrons with
originally repulsive interaction. Usually, the KL instability takes place at
extremely low energy scales, but in TBG, a doubling and subsequent strong
coupling of the van Hove singularities (vHS) in the electronic spectrum occurs
as the magic angle is approached, leading to extended saddle points in the
highest valence band (VB) with almost perfect nesting between states belonging
to different valleys. The highly anisotropic screening induces an effective
attraction in a $p$-wave channel with odd parity under the exchange of the two
disjoined patches of the Fermi line. We also predict the appearance of a
spin-density wave (SDW) instability, adjacent to the superconducting phase, and
the opening of a gap in the electronic spectrum from the condensation of spins
with wave vector corresponding to the nesting vector close to the vHS.",1807.01275v2
2018-07-17,Multiple Helical Spin Density Waves and Magnetic Skyrmions in Itinerant Electron System,"Magnetic structures and their stability of the multiple helical spin density
waves (MHSDW) and related magnetic skyrmions in itinerant electron system have
been investigated on the basis of both the phenomenological and microscopic
theories. It is shown by using the Ginzburg-Landau (GL) theory and the
Application Visualization System (AVS) that the magnetic skyrmion structures
emerge as a MHSDW and can be stabilized in itinerant electron system on the fcc
lattice even if there is no Dzyaloshinskii-Moriya interaction. Moreover, by
using the generalized Hartree-Fock theory for the Hubbard model, the
antiferromagnetic skyrmion structure found in the GL theory is shown to be
stabilized on the fcc lattice in the vicinity of the half-filled electron
number.",1807.06394v1
2018-07-17,Extended exchange interactions stabilize long-period magnetic structures in Cr$_{1/3}$NbS$_2$,"The topologically-protected, chiral soliton lattice is a unique state of
matter offering intriguing functionality and it may serve as a robust platform
for storing and transporting information in future spintronics devices. While
the monoaxial chiral magnet Cr$_{1/3}$NbS$_2$ is known to host this exotic
state in an applied magnetic field, its detailed microscopic origin has
remained a matter of debate. Here we work towards addressing this open question
by measuring the spin wave spectrum of Cr$_{1/3}$NbS$_2$ over the entire
Brillouin zone with inelastic neutron scattering. The well-defined spin wave
modes allow us to determine the values of several microscopic interactions for
this system. The experimental data is well-explained by a Heisenberg
Hamiltonian with exchange constants up to third nearest neighbor and an easy
plane magnetocrystalline anisotropy term. Our work shows that both the second
and third nearest neighbor exchange interactions contribute to the formation of
the helimagnetic and chiral soliton lattice states in this robust
three-dimensional magnet.",1807.06665v1
2018-10-25,Spin waves near the edge of halogen substitution induced magnetic order in Ni(Cl$_{1-x}$Br$_x$)$_2$$\cdot$4SC(NH$_2$)$_2$,"We report an inelastic neutron scattering study of magnetic excitations in a
quantum paramagnet driven into a magnetically ordered state by chemical
substitution, namely Ni(Cl$_{1-x}$Br$_x$)$_2$$\cdot$4SC(NH$_2$)$_2$ with
$x=0.21(2)$. The measured spectrum is well accounted for by the generalized
spin wave theory (GSWT) approach [M. Matsumoto and M. Koga, [J. Phys. Soc. Jap.
76, 073709 (2007)]. This analysis allows us to determine the effective
Hamiltonian parameters for a direct comparison with those in the previously
studied parent compound and `underdoped' system. The issue of magnon lifetimes
due to structural disorder is also addressed.",1810.10912v2
2012-09-10,Anisotropic but nodeless superconducting gap in the presence of spin density wave in iron-pnictide superconductor NaFe1-xCoxAs,"The coexisting regime of spin density wave (SDW) and superconductivity in the
iron pnictides represents a novel ground state. We have performed high
resolution angle-resolved photoemission measurements on NaFe1-xCoxAs (x =
0.0175) in this regime and revealed its distinctive electronic structure, which
provides some microscopic understandings of its behavior. The SDW signature and
the superconducting gap are observed on the same bands, illustrating the
intrinsic nature of the coexistence. However, because the SDW and
superconductivity are manifested in different parts of the band structure,
their competition is non-exclusive. Particularly, we found that the gap
distribution is anisotropic and nodeless, in contrast to the isotropic
superconducting gap observed in an SDW-free NaFe1-xCoxAs (x=0.045), which puts
strong constraints on theory.",1209.1967v2
2012-09-21,Broadband probing magnetization dynamics of the coupled vortex state permalloy layers in nanopillars,"Broadband magnetization response of coupled vortex state magnetic dots in
layered nanopillars was explored as a function of in-plane magnetic field and
interlayer separation. For dipolarly coupled circular Py(25 nm)/Cu(20 nm)/Py(25
nm) nanopillars of 600 nm diameter, a small in-plane field splits the
eigenfrequencies of azimuthal spin wave modes inducing an abrupt transition
between in-phase and out-of-phase kinds of the low-lying coupled spin wave
modes. The critical field for this splitting is determined by antiparallel
chiralities of the vortices in the layers. Qualitatively similar (although more
gradual) changes occur also in the exchange coupled Py(25 nm)/Cu(1 nm)/Py(25
nm) tri-layer nanopillars. These findings are in qualitative agreement with
micromagnetic dynamic simulations.",1209.4822v1
2014-06-20,Implications of nonsymmetric metric theories for particle physics. New interpretation of the Pauli coupling,"In this work we provide a possible geometrical interpretation of the spin of
elementary particles. In particular, it is investigated how the wave equations
of matter are altered by the addition of an antisymmetric contribution to the
metric tensor. In this scenario the explicit form of the matter wave equations
is investigated in a general curved space-time, and then the equations are
particularized to the flat case. Unlike traditional approaches of NGT, in which
the gravitational field is responsible for breaking the symmetry of the flat
Minkowski metric, we find more natural to consider that, in general, the metric
of the space-time could be nonsymmetric even in the flat case. The physical
consequences of this assumption are explored in detail. Interestingly enough,
it is found that the metric tensor splits into a bosonic and a fermionic; the
antisymmetric part of the metric is very sensitive to the spin and turns out to
be undetectable for spinless scalar particles. However, fermions couple to it
in a non-trivial way (only when there are interactions). In addition, the Pauli
coupling is derived automatically as a consequence of the nonsymmetric nature
of the metric",1406.5446v1
2018-08-06,Spin wave dispersion and intensity correlation in width-modulated nanowire arrays: A Brillouin light scattering study,"Using Brillouin light scattering spectroscopy and dynamical matrix method
calculations, we study collective spin waves in dense arrays of periodically
double-side width-modulated Permalloy nanowires. Width modulation is achieved
by creating a sequence of triangular notches on the two parallel nanowire
sides, with a periodicity of p=1000 nm, and tunable relative displacement (D)
of the notches sequence on the two lateral sides. Both symmetric (D=0) and
asymmetric (D= 250 and 500 nm) width-modulated nanowires were investigated. We
have found that the detected modes have Bloch-type character and belong to a
doublet deriving from the splitting of the modes characteristics of the
nanowire with homogeneous width. Interestingly, the amplitude of the magnonic
band, the frequency difference of the doublet, as well as their relative
scattering intensity, can be efficiently controlled by increasing D rather than
having single- or symmetric (D=0) double-side width-modulation.",1808.01732v1
2018-12-12,Small Spins of Primordial Black Holes from Random Geometries: Bekenstein-Hawking Entropy and Gravitational Wave Observations,"Black hole entropy is a robust prediction of quantum gravity with no
established phenomenological consequences to date. We use the
Bekenstein-Hawking entropy formula and general-relativistic statistical
mechanics to determine the probability distribution of random geometries
uniformly sampled in phase space. We show that this statistics (in the limit
$\hbar\to 0$) is relevant to large curvature perturbations, resulting in a
population of primordial black holes with zero natal spin. In principle, the
identification of such a population at LIGO, Virgo, and future gravitational
wave observatories could provide the first observational evidence for the
statistical nature of black hole entropy.",1812.05127v2
2018-12-26,Magnonic Band Structure Established by Chiral Spin-Density Waves in Thin Film Ferromagnets,"Recent theoretical studies have demonstrated the possibility to excite and
sustain noncollinear magnetization states in ferromagnetic nanowires. The
resulting state is referred to as a spin-density wave (SDW). SDWs can be
interpreted as hydrodynamic states with a constant fluid density and fluid
velocity in systems with easy-plane anisotropy. Here, we consider the effect of
the nonlocal dipole field arising from the finite thickness of magnetic thin
films on the spatial profile of the SDW and on the associated magnon
dispersion. Utilizing a hydrodynamic formulation of the Larmor torque equation,
it is found that the nonlocal dipole field modulates the fluid velocity. Such a
modulation induces a magnonic band structure unlike the typical dispersion
relation for magnons on uniform magnetization. The analytical results are
validated by micromagnetic simulations. Band gaps on the order of GHz are
numerically observed to depend on the SDW fluid velocity and film thickness for
realistic material parameters. The presented results suggest that SDWs can find
applications as reconfigurable magnonic crystals.",1812.10571v1
2019-02-07,Integrated magnonic half-adder,"Spin waves and their quanta magnons open up a promising branch of high-speed
and low-power information processing. Several important milestones were
achieved recently in the realization of separate magnonic data processing units
including logic gates, a magnon transistor and units for non-Boolean computing.
Nevertheless, the realization of an integrated magnonic circuit consisting of
at least two logic gates and suitable for further integration is still an
unresolved challenge. Here we demonstrate such an integrated circuit
numerically on the example of a magnonic half-adder. Its key element is a
nonlinear directional coupler serving as combined XOR and AND logic gate that
utilizes the dependence of the spin wave dispersion on its amplitude. The
circuit constitutes of only three planar nano-waveguides and processes all
information within the magnon domain. Benchmarking of the proposed device is
performed showing the potential for sub-aJ energy consumption per operation.",1902.02855v2
2019-02-13,Detailed study of detection method for ultra-low-frequency gravitational waves with pulsar spin-down rate statistics,"A new detection method for gravitational waves (GWs) with ultra-low
frequencies ($f_{\rm GW} \lesssim 10^{-10}~{\rm Hz}$), which is much lower than
the range of pulsar timing arrays (PTAs), was proposed in Yonemaru et al.
(2016). This method utilizes the statistical properties of spin-down rates of
milli-second pulsars (MSPs) and the sensitivity was evaluated in Yonemaru et
al. (2018). There, some simplifying assumptions, such as neglect of the ""pulsar
term"" and spatially uniform distribution of MSPs, were adopted and the
sensitivity on the time derivative of GW amplitude was estimated to be
$10^{-19}~{\rm s}^{-1}$ independent of the direction, polarization and
frequency of GWs. In this paper, extending the previous analysis, realistic
simulations are performed to evaluate the sensitivity more reasonably. We adopt
a model of 3-dimensional pulsar distribution in our Galaxy and take the pulsar
term into account. As a result, we obtain expected sensitivity as a function of
the direction, polarization and frequency of GWs. The dependence on GW
frequency is particularly significant and the sensitivity becomes worse by a
few orders for $< 10^{-12}~{\rm Hz}$ compared to the previous estimates.",1902.04787v1
2019-02-15,The $8Pmmn$ borophene sheet: A solid-state platform for space-time engineering,"We construct the most generic Hamiltonian of the $8Pmmn$ structure of
borophene sheet in presence of spin-orbit, as well as background electric and
magnetic fields. In addition to spin and valley Hall effects, this structure
offers a framework to conveniently manipulate the resulting ""tilt"" of the Dirac
equation by applying appropriate electric fields. Therefore, the tilt can be
made space-, as well as time-dependent. The border separating the low-field
region with under-tilted Dirac fermions from the high-field region with
over-tilted Dirac fermions will correspond to a black-hole horizon. In this
way, space-time dependent electric fields can be used to design the metric of
the resulting space-time felt by electrons and holes satisfying the tilted
Dirac equation. Our platform offers a way to generate analogues of
gravitational waves by electric fields (instead of mass sources) which can be
detected in solid state spectroscopies as waves of enhanced superconducting
correlations.",1902.07767v1
2019-06-28,Zero-field propagation of spin waves in waveguides prepared by focused ion beam direct writing,"Metastable face-centered-cubic Fe78Ni22 thin films grown on Cu(001)
substrates are excellent candidates for focused ion beam direct writing of
magnonic structures due to their favorable magnetic properties after
ion-beam-induced transformation. The focused ion beam transforms the originally
nonmagnetic fcc phase into the ferromagnetic bcc phase with additional control
over the direction of uniaxial magnetic in-plane anisotropy. The
magnetocrystalline anisotropy in transformed areas is strong enough to
stabilize the magnetization in transverse direction to the long axis of narrow
waveguides. Therefore, it is possible to propagate spin waves in these
waveguides without the presence of an external magnetic field in the favorable
Demon-Eshbach geometry. Phase-resolved micro-focused Brillouin light scattering
yields the dispersion relation of these waveguides in zero as well as in
nonzero external magnetic fields.",1906.12254v2
2016-03-02,Strong decay mode $J/ψp$ of hidden charm pentaquark states $P_c^+(4380)$ and $P_c^+(4450)$ in $Σ_c \bar{D}^*$ molecular scenario,"We study the strong decay channels $P_c^+(4380) \to J/\psi p$ and
$P_c^+(4450) \to J/\psi p$ under $\Sigma_c \bar{D}^*$ molecular state ansatz.
With various spin-parity assignments, the partial decay widths of $J/\psi p$
final state are calculated. Our results show that all the $P$ wave $\Sigma_c
{\bar D}^*$ assignments are excluded, while $S$ wave $\Sigma_c {\bar D}^*$
pictures for $P_c(4380)$ and $P_c(4450)$ are both allowed by present
experimental data. The $J^P=3/2^-$ $\Sigma_c^* \bar{D}$ and $\Sigma_c^*
\bar{D}^*$ molecules are also discussed in the heavy quark limit, and find that
the $\Sigma_c^* \bar{D}$ system for $P_c(4380)$ is possible. More experimental
information on spin-parities and partial decay widths and theoretical
investigations on other decay modes are needed to clarify the nature of the two
$P_c$ states.",1603.00559v2
2016-03-13,A Wave Packet Approach to Interacting Fermions,"In this thesis, we study the breakdown of the Fermi liquid state in cuprate
superconductors using the renormalization group (RG). We seek to extend earlier
work on the crossover from the Fermi liquid state to the pseudo gap phase based
on RG flows in the so-called saddle point regime. Progress in the derivation of
effective models for the conjectured spin liquid state has been hindered, by
the difficulties involved in solving the strong coupling low energy
Hamiltonian. We tackle the problem by introducing an orthogonal wave packet
basis, the so-called Wilson-Wannier (WW) basis, that can be used to interpolate
between the momentum space and the real space descriptions.
  We show how to combine the WW basis with the RG, such that the RG is used to
eliminate high-energy degrees of freedom, and the remaining strongly correlated
system is solved approximately in the WW basis. We exemplify the approach for
different one-dimensional model systems, and find good qualitative agreement
with exact solutions even for very simple approximations.
  Finally, we reinvestigate the saddle point regime of the two-dimensional
Hubbard model. We show that the anti-nodal states are driven to an insulating
spin-liquid state with strong singlet pairing correlations, thus corroborating
earlier conjectures.",1603.04041v1
2016-03-16,LIGO GW150914 and GW151226 Gravitational Wave Detection and Generalized Gravitation Theory (MOG),"The nature of gravitational waves in a generalized gravitation theory is
investigated. The linearized field equations and the metric tensor quadrupole
moment power and the decrease in radius of an inspiralling binary system of two
compact objects are derived. The generalized Kerr metric describing a spinning
black hole is determined by its mass $M$ and the spin parameter $a=cS/GM^2$.
The LIGO-Virgo collaboration data is fitted with smaller binary black hole
masses in agreement with the current electromagnetic, observed X-ray binary
upper bound for a black hole mass, $M\lesssim 10M_\odot$.",1603.05225v4
2016-12-06,Superradiance in the sky,"We discuss the conditions under which plane electromagnetic and gravitational
waves can be amplified by a rotating black hole due to superradiant scattering.
We show, in particular, that amplification can occur for low-frequency waves
with an incidence angle parametrically close to 0 (or $\pi$) with respect to
the black hole spin axis and with a parametrically small left (or right)
polarization. This is the case of the radiation emitted by a spinning
electric/magnetic dipole or gravitational quadrupole orbiting a black hole
companion at large radius and co-rotating with the latter. This can yield
observable effects of superradiance, for example, in neutron star-stellar mass
black hole binaries, as well as in triple systems composed by a compact binary
orbiting a central supermassive black hole. Due to superradiance, the total
source luminosity in these systems exhibits a characteristic orbital modulation
that may lead to significant observational signatures, thus paving the way for
testing, in the near future, one of the most peculiar predictions of general
relativity.",1612.01826v1
2017-02-16,"Magnetization dynamics in magnonic structures with different geometries: interfaces, notches and waveguides","The discovery of the ultrafast magnetization dynamics twenty years ago has
led to a broad variety of experimental techniques to explore phenomena in
magnetic materials with high temporal resolution. In the present article we
present a study dealing with broadband excitation of spin-wave packets at
different magnonic crystal continuous magnetic film interfaces. Similar to
protected conducting states on the surfaces of topological band insulators,
these interfaces exhibit surface spin-wave modes that propagate out of the
crystal into the continuous film. The propagation distance depends on the
direction of the applied magnetic field as well as the surface geometry of the
crystal.",1702.05041v1
2017-06-10,Mapping the magnonic landscape in patterned magnetic structures,"We report the development of a hybrid numerical / analytical model capable of
mapping the spatially-varying distributions of the local ferromagnetic
resonance (FMR) frequency and dynamic magnetic susceptibility in a wide class
of patterned and compositionally modulated magnetic structures. Starting from
the numerically simulated static micromagnetic state, the magnetization is
deliberately deflected orthogonally to its equilibrium orientation, and the
magnetic fields generated in response to this deflection are evaluated using
micromagnetic software. This allows us to calculate the elements of the
effective demagnetizing tensor, which are then used within a linear analytical
formalism to map the local FMR frequency and dynamic magnetic susceptibility.
To illustrate the typical results that one can obtain using this model, we
analyze three micromagnetic systems boasting non-uniformity in either one or
two dimensions, and successfully explain the spin-wave emission observed in
each case, demonstrating the ubiquitous nature of the Schl\""omann excitation
mechanism underpinning the observations. Finally, the developed model of local
FMR frequency could be used to explain how spin waves could be confined and
steered using magnetic non-uniformities of various origins, rendering it a
powerful tool for the mapping of the graded magnonic index in magnonics.",1706.03212v1
2017-06-11,Absorbing boundary layers for spin wave micromagnetics,"Micromagnetic simulations are used to investigate the effects of different
absorbing boundary layers (ABLs) on spin waves (SWs) reflected from the edges
of a magnetic nano-structure. We define the conditions that a suitable ABL must
fulfill and compare the performance of abrupt, linear, polynomial and tan
hyperbolic damping profiles in the ABL. We first consider normal incidence in a
permalloy stripe and propose a transmission line model to quantify reflections
and calculate the loss introduced into the stripe due to the ABL. We find that
a parabolic damping profile absorbs the SW energy efficiently and has a low
reflection coefficient, thus performing much better than the commonly used
abrupt damping profile. We then investigated SWs that are obliquely incident at
26.6, 45 and 63.4 degrees on the edge of a yttrium-iron-garnet film. The
parabolic damping profile again performs efficiently by showing a high SW
energy transfer to the ABL and a low reflected SW amplitude.",1706.03325v1
2017-06-30,Nonlinear transport associated with spin-density-wave dynamics in Ca$_3$Co$_{4}$O$_9$,"We have carried out the transient nonlinear transport measurements on the
layered cobalt oxide Ca$_3$Co$_{4}$O$_9$, in which a spin density wave (SDW)
transition is proposed at $T_{\rm SDW} \simeq 30$ K. We find that, below
$T_{\rm SDW}$, the electrical conductivity systematically varies with both the
applied current and the time, indicating a close relationship between the
observed nonlinear conduction and the SDW order in this material. The time
dependence of the conductivity is well analyzed by considering the dynamics of
SDW which involves a low-field deformation and a sliding motion above a
threshold field. We also measure the transport properties of the isovalent
Sr-substituted systems to examine an impurity effect on the nonlinear response,
and discuss the obtained threshold fields in terms of thermal fluctuations of
the SDW order parameter.",1706.10088v1
2017-10-02,On the Magnetic Structure of Density Matrices,"The spin structure of wave functions is reflected in the magnetic structure
of the one-particle density matrix. Indeed, for single determinants we can use
either one to determine the other. In this work we discuss how one can simply
examine the one-particle density matrix to faithfully determine whether the
spin magnetization density vector field is collinear, coplanar, or noncoplanar.
For single determinants, this test suffices to distinguish collinear
determinants which are eigenfunctions of $\hat{S}_{\hat{n}}$ from noncollinear
determinants which are not. We also point out the close relationship between
noncoplanar magnetism on the one hand and complex conjugation symmetry breaking
on the other. Finally, we use these ideas to classify the various ways single
determinant wave functions break and respect symmetries of the Hamiltonian in
terms of their one-particle density matrix.",1710.00932v1
2017-10-13,Theoretical study on magnetic tunneling junctions with semiconductor barriers CuInSe$_2$ and CuGaSe$_2$ including a detailed analysis of band-resolved transmittances,"We study spin-dependent transport properties in magnetic tunneling junctions
(MTJs) with semiconductor barriers, Fe/CuInSe$_2$/Fe(001) and
Fe/CuGaSe$_2$/Fe(001). By analyzing their transmittances at zero bias voltage
on the basis of the first-principles calculations, we find that spin-dependent
coherent tunneling transport of $\Delta_1$ wave functions yields a relatively
high magnetoresistance (MR) ratio in both the MTJs. We carry out a detailed
analysis of the band-resolved transmittances in both the MTJs and find an
absence of the selective transmission of $\Delta_1$ wave functions in some
energy regions a few eV away from the Fermi level due to small band gaps in
CuInSe$_2$ and CuGaSe$_2$.",1710.04849v3
2017-10-23,Pairing and chiral spin density wave instabilities on the honeycomb lattice: a comparative quantum Monte Carlo study,"Using finite-temperature determinantal quantum Monte Carlo calculations, we
re-examine the pairing susceptibilities in the Hubbard model on the honeycomb
lattice, focusing on doping levels onto and away from the van Hove singularity
(VHS) filling. For this purpose, electronic densities of $0.75$ (at the
hole-doping VHS) and $0.4$ (well below the VHS) are considered in detail, where
due to a severe sign problem at strong coupling strengths, we focus on the weak
interaction region of the Hubbard model Hamiltonian. From analyzing the
temperature dependence of pairing susceptibilities in various symmetry
channels, we find the singlet $d$+$id$-wave to be the dominant pairing channel
both at and away from the VHS filling. We furthermore investigate the
electronic susceptibility to a specific chiral spin density wave (SDW) order,
which we find to be similarly relevant at the VHS, while it extenuates upon
doping away from the VHS filling.",1710.08367v3
2017-10-31,Observation of topologically protected helical edge modes in Kagome elastic plates,"The investigation of topologically protected waves in classical media has
opened unique opportunities to achieve exotic properties like one-way phonon
transport, protection from backscattering and immunity to imperfections.
Contrary to acoustic and electromagnetic domains, their observation in elastic
solids has so far been elusive due to the presence of both shear and
longitudinal modes and their modal conversion at interfaces and free surfaces.
  Here we report the experimental observation of topologically protected
helical edge waves in elastic media. The considered structure consists of an
elastic plate patterned according to a Kagome architecture with an accidental
degeneracy of two Dirac cones induced by drilling through holes. The careful
breaking of symmetries couples the corresponding elastic modes which
effectively emulates spin orbital coupling in the quantum spin Hall effect.
  The results shed light on the topological properties of the proposed plate
waveguide and opens avenues for the practical realization of compact, passive
and cost-effective elastic topological waveguides.",1710.11556v2
2018-04-13,Non-equilibrium Pair Breaking in Ba(Fe1-xCox)2As2 Superconductors: Evidence for Formation of Photo-Induced Excitonic Spin-Density-Wave State,"Ultrafast terahertz (THz) pump{probe spectroscopy reveals unusual
out-of-equilibrium Cooper pair dynamics driven by femtosecond (fs) optical
quench of superconductivity (SC) in iron pnictides. We observe a two{step
quench of the SC gap, where an abnormally slow (many 100's of ps) quench
process is clearly distinguished from the usual fast (sub-ps)
hot{phonon{mediated scattering channel. This pair breaking dynamics depends
strongly on doping, pump uence, and temperature. The above observations,
together with quantum kinetic modeling of non-equilibrium SC and magnetic
correlations, provide evidence for photogeneration of a transient state where
SC competes with build{up of spin-density-wave (SDW) excitonic correlation
between quasi-particles (QP).",1804.04987v1
2018-04-27,Effect of uniaxial stress on the magnetic phases of CeAuSb$_2$,"We present results of measurements of resistivity of \CAS{} under the
combination of $c$-axis magnetic field and in-plane uniaxial stress. In
unstressed \CAS{} there are two magnetic phases. The low-field A phase is a
single-component spin-density wave (SDW), with $\mathbf{q} = (\eta, \pm \eta,
1/2)$, and the high-field B phase consists of microscopically coexisting
$(\eta, \eta, 1/2)$ and $(\eta, -\eta, 1/2)$ spin-density waves. Pressure along
a $\langle 100 \rangle$ lattice direction is a transverse field to both of
these phases, and so initially has little effect, however eventually induces
new low- and high-field phases in which the principal axes of the SDW
components appear to have rotated to the $\langle 100 \rangle$ directions.
Under this strong $\langle 100 \rangle$ compression, the field evolution of the
resistivity is much smoother than at zero strain: In zero strain, there is a
strong first-order transition, while under strong $\langle 100 \rangle$ it
becomes much broader. We hypothesize that this is a consequence of the uniaxial
stress lifting the degeneracy between the (100) and (010) directions.",1804.10539v2
2019-03-08,Hamilton-Jacobi equation for spinning particles near black holes,"A compact stellar-mass object inspiralling onto a massive black hole deviates
from geodesic motion due to radiation-reaction forces as well as finite-size
effects. Such post-geodesic deviations need to be included with sufficient
precision into wave-form models for the upcoming space-based gravitational-wave
detector LISA. I present the formulation and solution of the Hamilton-Jacobi
equation of geodesics near Kerr black holes perturbed by the so-called
spin-curvature coupling, the leading order finite-size effect. In return, this
solution allows to compute a number of observables such as the turning points
of the orbits as well as the fundamental frequencies of motion. This result
provides one of the necessary ingredients for waveform models for LISA and an
important contribution useful for the relativistic two-body problem in general.",1903.03651v2
2019-05-09,Non-Relativistic and Relativistic Equations for the Kratzer Potential plus a Dipole in 2D Systems,"In this work, we study the wave equations in 2D Euclidian space for a new
non-central potential consisting of a Kratzer term and a dipole term. For
Schrodinger equation, we obtain the analytical expressions of the energies and
the wave functions of the system. For Klein-Gordon and Dirac equations, we do
the study in both spin and pseudo-spin symmetries to get the eigenfunctions and
the eingenvalues. Then we study the dependence of energies on the radial moment
D_{r} and the angular moment D_{theta}. We find that the D_{theta} term tends
to dissociate the system, and thus counteracts the Coulomb binding effect, and
that the D_{r} term can either amplify or decrease this effect according to its
sign.",1905.03765v2
2020-03-08,Voltage-Induced Inertial Domain Wall Motion in an Antiferromagnetic Nanowire,"Racetrack memory based on magnetic domain walls (DWs) motion exhibits
advantages of small volume and high reading speed. When compared to
current-induced DW motion, voltage-induced DW motion exhibits lower
dissipation. On the other hand, the DW in an antiferromagnet (AFM) moves at a
high velocity with weak stray field. In this work, the AFM DW motion induced by
a gradient of magnetic anisotropy energy under a voltage pulse has been
investigated in theory. The dynamics equation for the DW motion was derived.
The solution indicates that the DW velocity is higher than 100 m/s, and because
of inertia, the DW is able to keep moving at a speed of around 100 m/s for
several nano seconds after turning off the voltage in a period of pulse. The
mechanism for this DW inertia is explained based on the Lagrangian route. On
the other hand, a spin wave is emitted while the DW is moving, yet the DW is
still able to move at an ever increasing velocity with enlarging DW width. This
indicates energy loss from emission of spin wave is less than the energy gain
from the effective field of the gradient of anisotropy energy.",2003.03784v1
2020-09-10,Resonating valence bond realization of spin-1 non-Abelian chiral spin liquid on the torus,"We propose resonating valence bond wave functions for a spin-1 system on the
torus that realize a non-Abelian chiral spin liquid. The wave functions take
the form of infinite dimensional matrix product states constructed from
conformal blocks of the $\mathrm{SO}(3)_{1}$ Wess-Zumino-Witten model. This
means that they are lattice analogues of the bosonic Moore-Read state
introduced in fractional quantum Hall systems. The topological order of this
system is revealed by explicit construction of three-fold degenerate ground
states and analytical computation of the modular S and T matrices.",2009.04911v2
2020-09-21,Spin density wave order in interacting type-I and type-II Weyl semimetals,"Weyl semimetals, featuring massless linearly dispersing chiral fermions in
three dimensions, provide an excellent platform for studying the interplay of
electronic interactions and topology, and exploring new correlated states of
matter. Here, we examine the effect of a local repulsive interaction on an
inversion-symmetry breaking Weyl semimetal model, using cluster dynamical mean
field theory and variational cluster approximation methods. Our analysis
reveals a continuous transition from the gapless Weyl semimetal phase to a
gapped spin density wave ordered phase at a critical value of the interaction,
which is determined by the band structure parameters. Further, we introduce a
finite tilt in the linear dispersion and examine the corresponding behavior for
a type-II Weyl semimetal model, where the critical interaction strength is
found to be significantly diminished, indicating a greater susceptibility
towards interactions. The behavior of different physical quantities, such as
the double occupancy, the spectral function and the Berry curvature associated
with the Weyl nodes are obtained in both the semimetallic and the magnetically
ordered states. Finally, we provide an interaction-induced phase diagram for
the Weyl semimetal model, as a function of the tilt parameter.",2009.10208v2
2020-11-05,Matrix Product Wave Function of the Ground State and Elementary Excitation in the Spin-1/2 Chain,"We present a variational matrix product state (vMPS) for the ground state of
the spin-1/2 Heisenberg model. The MPS effectively organizes the various dimer
configurations, in faithful reflection of the resonating valence bond (RVB)
picture of the spin liquid, with the energy only 0.024% higher than the exact
value given by Bethe ansatz. Building on the ground-state vMPS, the one-spin
wave function is constructed in a simple manner with the dispersion that
matches well with the exact spectrum. The vMPS scheme is applied to the family
of Hamiltonian extrapolating between the Heisenberg model and the
Majumdar-Ghosh model.",2011.02625v1
2020-11-12,"Experimental parameters, combined dynamics, and nonlinearity of a Magnonic-Opto-Electronic Oscillator (MOEO)","We report the construction and characterization of a comprehensive
magnonic-opto-electronic oscillator (MOEO) system based on 1550-nm photonics
and yttirum iron garnet (YIG) magnonics. The system exhibits a rich and
synergistic parameter space because of the ability to control individual
photonic, electronic, and magnonic components. Taking advantage of the spin
wave dispersion of YIG, the frequency self-generation as well as the related
nonlinear processes become sensitive to the external magnetic field. Besides
being known as a narrowband filter and a delay element, the YIG delayline
possesses spin wave modes that can be controlled to mix with the optoelectronic
modes to generate higher-order harmonic beating modes. With the high
sensitivity and external tunability, the MOEO system may find usefulness in
sensing applications in magnetism and spintronics beyond optoelectronics and
photonics.",2011.06155v1
2021-02-06,Spin-wave eigenmodes in direct-write 3D nanovolcanoes,"Extending nanostructures into the third dimension has become a major research
avenue in modern magnetism, superconductivity and spintronics, because of
geometry-, curvature- and topology-induced phenomena. Here, we introduce Co-Fe
nanovolcanoes-nanodisks overlaid by nanorings-as purpose-engineered 3D
architectures for nanomagnonics, fabricated by focused electron beam induced
deposition. We use both perpendicular spin-wave resonance measurements and
micromagnetic simulations to demonstrate that the rings encircling the volcano
craters harbor the highest-frequency eigenmodes, while the lower-frequency
eigenmodes are concentrated within the volcano crater, due to the
non-uniformity of the internal magnetic field. By varying the crater diameter,
we demonstrate the deliberate tuning of higher-frequency eigenmodes without
affecting the lowest-frequency mode. Thereby, the extension of 2D nanodisks
into the third dimension allows one to engineer their lowest eigenfrequency by
using 3D nanovolcanoes with 30% smaller footprints. The presented nanovolcanoes
can be viewed as multi-mode microwave resonators and 3D building blocks for
nanomagnonics.",2102.03574v1
2021-02-23,Beam-normal single-spin asymmetry in elastic scattering of electrons from a spin-0 nucleus,"We study the beam-normal single-spin asymmetry (BNSSA) in high-energy elastic
electron scattering from several spin-0 nuclei. Existing theoretical approaches
work in the plane-wave formalism and predict the BNSSA to scale as $\sim A/Z$
with the atomic number $Z$ and nuclear mass number $A$. While this prediction
holds for light and intermediate nuclei, a striking disagreement in both the
sign and the magnitude of BNSSA was observed by the PREX collaboration for
$^{208}$Pb, coined the ""PREX puzzle"". To shed light on this disagreement, we go
beyond the plane-wave approach which neglects Coulomb distortions known to be
significant for heavy nuclei. We explicitly investigate the dependence of BNSSA
on $A$ and $Z$ by i) including inelastic intermediate states' contributions
into the Coulomb problem in the form of an optical potential, ii) by accounting
for the experimental information on the $A$-dependence of the Compton slope
parameter, and iii) giving a thorough account of the uncertainties of the
calculation. Despite of these improvements, the PREX puzzle remains
unexplained. We discuss further strategies to resolve this riddle.",2102.11809v1
2021-04-08,A surrogate model for gravitational waveforms of spin-aligned binary black holes with eccentricities,"A waveform model for the eccentric binary black holes named SEOBNRE has been
used to analyze the LIGO-Virgo's gravitational wave data by several groups. The
accuracy of this model has been validated by comparing it with numerical
relativity. However, SEOBNRE is a time-domain model, and the efficiency for
generating waveforms is a bottleneck in data analysis. To overcome this
disadvantage, we offer a reduced-order surrogate model for eccentric binary
black holes based on the SEOBNRE waveforms. This surrogate model (SEOBNRE\_S)
can simulate the complete inspiral-merger-ringdown waves with enough accuracy,
covering eccentricities from 0 to 0.25 (0.1), and mass ratio from 1:1 to 5:1
(2:1) for nonspinning (spinning) binaries. The speed of waveform generation is
accelerated about $10^2 \sim 10^3$ times than the original SEOBNRE model.
Therefore SEOBNRE\_S could be helpful in the analysis of LIGO data to find
potential eccentricities.",2104.03789v2
2021-04-16,Coherent control in atomic chains: to trap and release a traveling excitation,"We introduce a protocol for dynamical dispersion engineering in an atomic
chain consisting of an ordered array of multi-level atoms with subwavelength
lattice constant. This chain supports dark states that are protected from
dissipation in the form of photon emission and can be understood as propagating
spin waves traveling along the array. By using an external control field with a
spatially-varying elliptical polarization we correlate internal and external
degrees of freedom of the array in a controllable way. The coherent control
over the atomic states translates into control over the group velocity of the
spin waves. A traveling excitation can be stored and released without
dissipation by adiabatically changing the control field amplitude. This
protocol is an alternative to the more conventional electromagnetically-induced
transparency, and exemplifies the rich physics born of the interplay between
coherent control and correlated decay.",2104.08121v1
2021-10-02,Higgs and Goldstone spin-wave modes in striped magnetic texture,"Spontaneous symmetry breaking is ubiquitous in physics. Its spectroscopic
signature consists in the softening of a specific mode upon approaching the
transition from the high symmetry side and its subsequent splitting into a
zero-frequency ""Goldstone"" mode and a non-zero-frequency ""Higgs"" mode. Although
they determine the whole system dynamics, these features are difficult to
address in practice because of their vanishing coupling to most experimental
probes and/or their strong interaction with other fluctuations. In this work,
we consider a periodic magnetic modulation occurring in a ferromagnetic film
with perpendicular-to-plane magnetic anisotropy and directly observe its
Goldstone and Higgs spin-wave modes at room temperature using microwave and
optical techniques. This simple system constitutes a particularly convenient
platform for further exploring the dynamics of symmetry breaking.",2110.00882v2
2021-10-04,Quantum-geometric perspective on spin-orbit-coupled Bose superfluids,"We employ the Bogoliubov approximation to study how the quantum geometry of
the helicity states affects the superfluid properties of a spin-orbit-coupled
Bose gas in continuum. In particular we derive the low-energy Bogoliubov
spectrum for a plane-wave condensate in the lower helicity band and show that
the geometric contributions to the sound velocity are distinguished by their
linear dependences on the interaction strength, i.e., they are in sharp
contrast to the conventional contribution which has a square-root dependence.
We also discuss the roton instability of the plane-wave condensate against the
stripe phase and determine their phase transition boundary. In addition we
derive the superfluid density tensor by imposing a phase-twist on the
condensate order parameter and study the relative importance of its
contribution from the interband processes that is related to the quantum
geometry.",2110.01385v2
2021-10-18,Multicell Atomic Quantum Memory as a Hardware-Efficient Quantum Repeater Node,"For scalable quantum communication and networks, a key step is to realize a
quantum repeater node that can efficiently connect different segments of
atom-photon entanglement using quantum memories. We report a compact and
hardware-efficient realization of a quantum repeater node using a single atomic
ensemble for multicell quantum memories. Millisecond lifetime is achieved for
individual memory cells after suppressing the magnetic-field-induced
inhomogeneous broadening and the atomic-motion-induced spin-wave dephasing.
Based on these long-lived multicell memory cells, we achieve heralded
asynchronous entanglement generation in two quantum repeater segments one after
another and then an on-demand entanglement connection of these two repeater
segments. As another application of the multicell atomic quantum memory, we
further demonstrate storage and on-demand retrieval of heralded atomic
spin-wave qubits by implementing a random access quantum memory with individual
addressing capacity. This work provides a promising constituent for efficient
realization of quantum repeaters for large-scale quantum networks.",2110.09597v1
2003-12-18,"Spin Density Wave and D-Wave Superconducting Order Parameter ""Coexistence""","We study the properties of a spin-density-wave antiferromagnetic mean-field
ground state with d-wave superconducting (DSC) correlations. This ground state
always gains energy by Cooper pairing. It would fail to superconduct at
half-filling due to the antiferromagnetic gap although its particle-like
excitations would be Bogolyubov-BCS quasiparticles consisting of coherent
mixtures of electrons and holes. More interesting and relevant to the
superconducting cuprates is the case when antiferromagnetic order is turned on
weakly on top of the superconductivity. This would correspond to the onset of
antiferromagnetism at a critical doping. In such a case a small gap
proportional to the weak antiferromagnetic gap opens up for nodal
quasiparticles, and the quasiparticle peak would be discernible. We evaluate
numerically the absorption by nodal quasiparticles and the local density of
states for several ground states with antiferromagnetic and d-wave
superconducting correlations.",0312451v1
2004-05-06,Energy relaxation in disordered charge and spin density waves,"We investigate collective effects in the strong pinning model of disordered
charge and spin density waves (CDWs and SDWs) in connection with heat
relaxation experiments. We discuss the classical and quantum limits that
contribute to two distinct contribution to the specific heat (a $C_v \sim
T^{-2}$ contribution and a $C_v \sim T^{\alpha}$ contribution respectively),
with two different types of disorder (strong pinning versus substitutional
impurities). From the calculation of the two level system energy splitting
distribution in the classical limit we find no slow relaxation in the
commensurate case and a broad spectrum of relaxation times in the
incommensurate case. In the commensurate case quantum effects restore a non
vanishing energy relaxation, and generate stronger disorder effects in
incommensurate systems. For substitutional disorder we obtain Friedel
oscillations of bound states close to the Fermi energy. With negligible
interchain couplings this explains the power-law specific heat $C_v \sim
T^{\alpha}$ observed in experiments on CDWs and SDWs combined to the power-law
susceptibility $\chi(T)\sim T^{-1+\alpha}$ observed in the CDW o-TaS$_3$.",0405119v3
2008-06-09,A Realistic Formalism for 4N Bound State in a Three-Dimensional Yakubovsky Scheme,"A spin-isospin dependent Three-Dimensional formalism based on the momentum
vectors for the four-nucleon bound state is presented. The four-nucleon
Yakubovsky equations with two- and three-nucleon interactions are formulated as
a function of the vector Jacobi momenta. Our formalism, according to the number
of spin-isospin states that one takes into account, leads to only a strictly
finite number of the coupled three-dimensional integral equations to be solved.
The evaluation of the transition and permutation operators as well as the
coordinate transformations due to considering the continuous angle variables
instead of the discrete angular momentum quantum numbers are less complicated
in comparison with partial wave representation. With respect to partial wave
the present formalism with the smaller number of equations leads to higher
dimensionality of the integral equations. We have concluded that
Three-Dimensional formalism is less cumbersome for considering the
three-nucleon forces.",0806.1520v2
2008-06-16,Electronic structure and exotic exchange splitting in spin-density-wave states of BaFe$_2$As$_2$,"The magnetic properties in the parent compounds are often intimately related
to the microscopic mechanism of superconductivity. Here we report the first
direct measurements on the electronic structure of a parent compound of the
newly discovered iron-based superconductor, BaFe$_2$As$_2$, which provides a
foundation for further studies. We show that the energy of the spin density
wave (SDW) in BaFe$_2$As$_2$ is lowered through exotic exchange splitting of
the band structure, rather than Fermi surface nesting of itinerant electrons.
This clearly demonstrates that a metallic SDW state could be solely induced by
interactions of local magnetic moments, resembling the nature of
antiferromagnetic order in cuprate parent compounds.",0806.2627v2
2008-06-16,"Origin of the spin density wave instability in AFe$_2$As$_2$ (A=Ba, Sr) as revealed by optical spectroscopy","We performed optical spectroscopy measurement on single crystals of
BaFe$_2$As$_2$ and SrFe$_2$As$_2$, the parent compounds of FeAs based
superconductors. Both are found to be quite metallic with fairly large plasma
frequencies at high temperature. Upon entering the spin-density-wave (SDW)
state, formation of partial energy gaps was clearly observed with the presence
of surprisingly two different energy scales. A large part of the Drude
component was removed by the gapping of Fermi surfaces (FS). Meanwhile, the
carrier scattering rate was even more dramatically reduced. We elaborate that
the SDW instability is more likely to be driven by the FS nesting of itinerant
electrons rather than a local-exchange mechanism.",0806.2652v4
2008-06-30,Quantum oscillations in the parent magnetic phase of an iron arsenide high temperature superconductor,"We report quantum oscillation measurements in SrFe2As2 - which is an
antiferromagnetic parent of the iron-arsenide family of superconductors - known
to become superconducting under doping and the application of pressure. The
magnetic field and temperature dependences of the oscillations between 20 and
55 T in the liquid helium temperature range suggest that the electronic
excitations are those of a Fermi liquid. We show that the observed Fermi
surface comprising small pockets is consistent with the formation of a
spin-density wave. Our measurements thus demonstrate that high Tc
superconductivity can occur on doping or pressurizing a conventional metallic
spin-density wave state.",0806.4726v2
2016-11-03,The dynamics of linarite: Observations of magnetic excitations,"Here we present inelastic neutron scattering measurements from the
frustrated, quantum spin-1/2 chain material linarite, PbCuSO_4(OH)_2. Time of
flight data, taken at 0.5K and zero applied magnetic field reveals low-energy
dispersive spin wave excitations below 1.5meV both parallel and perpendicular
to the Cu-chain direction. From this we confirm that the interchain couplings
within linarite are around 10% of the nearest neighbour intrachain
interactions. We analyse the data within both linear spin-wave theory and
density matrix renormalisation group theories and establish the main magnetic
exchange interactions and the simplest realistic Hamiltonian for this material.",1611.00986v3
2017-01-04,Zitterbewegung and the Electron,"Starting from a statistical model of the electron, which explains spin and
spin measurements in terms of a probability density distribution resulting from
a rapidly changing angular momentum during an extended Zitterbewegung, a
light-like model of electron and Fermions is formulated. This model describes
individual particles in terms of paths of a moving quantum. It is shown that
this description allows one to reproduce observable properties as path-averages
over a period of the fast extended Zitterbewegung in elementary calculations.
The general topology of the paths may be described as a helical path, with a
helix axis forming a circle around a fixed point in space. The radius of the
helix and of the circle are equal and given by half the reduced Compton wave
length of a photon of energy equal to the rest energy of the particle
described. The paths depend on the relative velocity between the described
entity and the observer, and represent the De Broglie wave. The merits of the
proposed model are summarized and its role in relation to the established
description by quantum mechanics discussed. It is concluded that it supports
the existence of the proposed extended Zitterbewegung, and offers a description
of quantum behaviour without quantum mechanics.",1701.02998v1
2017-03-10,Quantum Oscillations in the Anomalous Spin Density Wave State of FeAs,"Quantum oscillations in the binary antiferromagnetic metal FeAs are presented
and compared to theoretical predictions for the electronic band structure in
the anomalous spin density wave state of this material. Demonstrating a new
method for growing single crystals out of Bi flux, we utilize the highest
quality FeAs to perform torque magnetometry experiments up to 35 T, using
rotations of field angle in two planes to provide evidence for one electron and
one hole band in the magnetically ordered state. The resulting picture agrees
with previous experimental evidence for multiple carriers at low temperatures,
but the exact Fermi surface shape differs from predictions, suggesting that
correlations play a role in deviation from ab initio theory and cause up to a
four-fold enhancement in the effective carrier mass.",1703.03833v2
2017-03-20,Vortices in two-dimensional nanorings studied by means of the dynamical matrix method,"This paper concerns an investigation of the spin wave excitations in magnetic
nanoparticles. We provide a detailed derivation of the theoretical method for
the determination of the normal modes of confined magnetic systems based on a
discrete lattice of magnetic moments. The method is based on the damping-free
Landau-Lifshitz equation and general enough to be utilized for the magnetic
system of any dimensionality, magnetic structure, shape, and size. As an
example we explore the influence of the competition between exchange and
dipolar interactions on the spectrum of normal modes as well as on the
stability of the vortex state in two-dimensional nanorings. We show the
lowest-frequency mode to be indicative of the dipolar-to-exchange iterations
ratio. We also study behavior of the fundamental mode and present the influence
of both, the discreteness of the lattice and the dipolar-to-exchange iterations
ratio, on its hybridization with azimuthal modes. We complete the paper with a
selective review of the spin wave excitations in circular dots to compare with
the results obtained for the rings.",1703.06678v1
2017-04-05,Using torsion to manipulate spin currents,"We address the problem of quantum particles moving on a manifold
characterised by the presence of torsion along a preferential axis. In fact,
such a torsion may be taylored by the presence of a single screw dislocation,
whose Burgers vector measures the torsion amplitude. The problem, first treated
in the relativistic limit describing fermions that couple minimally to torsion,
is then analysed in the Pauli limit We show that torsion induces a geometric
potential and also that it couples generically to the phase of the wave
function, giving rise to the possibility of using torsion to manipulate spin
currents in the case of spinor wave functions. These results emerge as an
alternative strategy for using screw dislocations in the design of
spintronic-based devices.",1704.01283v1
2017-04-07,Reconfigurable nano-scale spin-wave directional coupler,"A spin-wave (SW) directional coupler comprised of two laterally parallel
nano-scale dipolarly-coupled SW waveguides is proposed and studied using
micromagnetic simulations and analytical theory. The energy of a SW excited in
one of the waveguides in the course of propagation is periodically transferred
to the other waveguide and back, and the spatial half-period of this transfer
is defined as the coupling length. The coupling length is determined by the
dipolar coupling between the waveguides, and the fraction of the SW energy
transferred to the other waveguide at the device output can be varied with the
SW frequency, bias magnetic field, and relative orientation of the waveguide's
static magnetizations. The proposed design of a directional coupler can be used
in digital computing-oriented magnonics as a connector (multiplexer) of
magnonic conduits without a direct contact, or in the analog microwave signal
processing as a reconfigurable nano-scale power divider and/or frequency
separator.",1704.02255v1
2017-04-16,Highly anisotropic quasiparticle interference patterns in the spin-density wave state of the iron pnictides,"We investigate the impurity scattering induced quasiparticle interference in
the ($\pi, 0$) spin-density wave phase of the iron pnictides. We use a five
orbital tight binding model and our mean field theory in the clean limit
captures key features of the Fermi surface observed in angle-resolved
photoemission. We use a t-matrix formalism to incorporate the effect of doping
induced impurities on this state. The impurities lead to a spatial modulation
of the local density of states about the impurity site, with a periodicity of
$\sim 8a_{{\rm Fe}-{\rm Fe}}$ along the antiferromagnetic direction. The
associated momentum space quasiparticle interference pattern is anisotropic,
with major peaks located at $\sim (\pm \pi/4,0)$, consistent with spectroscopic
imaging scanning tunneling microscopy. We trace the origin of this pattern to
an elliptical contour of constant energy around momentum (0,0), with major axis
oriented along the (0,1) direction, in the mean field electronic structure.",1704.04783v1
2017-04-20,Charge-density-wave order takes over antiferromagnetism in Bi$_2$Sr$_{2-x}$La$_x$CuO$_{6}$ superconductors,"Superconductivity appears in the cuprates when a spin order is destroyed,
while the role of charge is less known. Recently, charge density wave (CDW) was
found below the superconducting dome in YBa$_2$Cu$_3$O$_y$ when a high magnetic
field is applied perpendicular to the CuO$_2$ plane, which was suggested to
arise from incipient CDW in the vortex cores that becomes overlapped. Here, by
$^{63}$Cu-nuclear magnetic resonance, we report the discovery of CDW induced by
an in-plane field that does not create vortex cores in the plane, setting in
above the dome in single-layered Bi$_2$Sr$_{2-x}$La$_x$CuO$_6$.The onset
temperature $T_{\rm CDW}$ takes over the antiferromagnetic order temperature
$T_{\rm N}$ beyond a critical doping level at which superconductivity starts to
emerge, and scales with the psudogap temperature $T^{*}$. These results provide
important insights into the relationship between spin order, CDW and the
pseudogap, and their connections to high-temperature superconductivity.",1704.06169v2
2019-01-18,Magnonic Weyl states in Cu2OSeO3,"The multiferroic ferrimagnet Cu$_2$OSeO$_3$ with a chiral crystal structure
attracted a lot of recent attention due to the emergence of magnetic skyrmion
order in this material. Here, the topological properties of its magnon
excitations are systematically investigated by linear spin-wave theory and
inelastic neutron scattering. When considering Heisenberg exchange interactions
only, two degenerate Weyl magnon nodes with topological charges $\pm$2 are
observed at high-symmetry points. Each Weyl point splits into two as the
symmetry of the system is further reduced by including into consideration the
nearest-neighbor Dzyaloshinsky-Moriya interaction, crucial for obtaining an
accurate fit to the experimental spin-wave spectrum. The predicted topological
properties are verified by surface state and Chern number analysis.
Additionally, we predict that a measurable thermal Hall conductivity can be
associated with the emergence of the Weyl points, the position of which can be
tuned by changing the crystal symmetry of the material.",1901.06192v1
2019-01-22,Experimental demonstration of linear and spinning Janus dipoles for polarisation and wavelength selective near-field coupling,"The electromagnetic field scattered by nano-objects contains a broad range of
wave vectors and can be efficiently coupled to waveguided modes. The dominant
contribution to scattering from subwavelength dielectric and plasmonic
nanoparticles is determined by electric and magnetic dipolar responses. Here,
we experimentally demonstrate spectral and phase selective excitation of Janus
dipoles, sources with electric and magnetic dipoles oscillating out of phase,
in order to control near-field interference and directional coupling to
waveguides. We show that by controlling the polarisation state of the dipolar
excitations and the excitation wavelength to adjust their relative
contributions, directionality and coupling strength can be fully tuned.
Furthermore, we introduce a novel spinning Janus dipole featuring cylindrical
symmetry in the near and far field, which results in either omnidirectional
coupling or noncoupling. Controlling the propagation of guided light waves via
fast and robust near-field interference between polarisation components of a
source is required in many applications in nanophotonics and quantum optics.",1901.07236v1
2019-01-26,Chiral excitation of spin waves in ferromagnetic films,"We theoretically investigate the interlayer dipolar and exchange couplings
for an array of metallic magnetic nanowires grown on top of an extended
ultrathin yttrium iron garnet film. The calculated interlayer dipolar coupling
agrees with observed anticrossings [Chen \emph{et al.}, Phys. Rev. Lett.
\textbf{120}, 217202 (2018)], concluding that the interlayer exchange coupling
is suppressed by a spacer layer between the nanowires and film. The Kittel mode
in the nanowire array couples chirally to spin waves in the film, even though
Damon-Eshbach surface modes do not exist. The chirality is suppressed when the
interlayer exchange coupling becomes strong.",1901.09182v1
2018-12-12,Substrate induced magnetic anisotropies and magneto-optical response in YIG nanosized epitaxial films on NdGG(111),"Nanosized Y3Fe5O12 epitaxial films have been grown on Nd3Ga5O12 substrates
using laser molecular beam epitaxy method. Magneto-optical polar Kerr effect,
ferromagnetic resonance and spin wave propagation measurements show that the
stress-related anisotropy field has an opposite sign, compared to that in the
YIG/GGG systems. This leads to a considerable decrease of the effective
magnetization that opens a perspective to get YIG films with perpendicular
magnetization for utilizing forward volume spin waves. Longitudinal
magnetooptical Kerr effect magnetometry reveals a large contribution of
quadratic in magnetization terms into dielectric permittivity tensor at optical
frequencies. This effect strongly increases with temperature decrease and is
explained by magnetization of the interface Nd3+ ions that are exchange coupled
to the Fe3+ ions.",1901.10800v1
2019-01-29,The effects of three magnons interactions in the magnon-density waves of triangular spin lattices,"We investigate the magnon-density waves proposed as the longitudinal
excitations in triangular lattice antiferromagnets by including the cubic and
quartic corrections in the large-s expansion. The longitudinal excitation
spectra for the two-dimensional (2D) triangular antiferromagnetic model and
quasi-one dimensional (quasi-1D) antiferromagnetic materials have been obtained
for a general quantum spin number $s$. For the 2D triangular lattice model, we
find a significant reduction (about 40 %) in the energy spectra at the zone
boundaries due to both the cubic and quartic corrections. For the quasi-1D
antiferromagnets, since the cubic term comes from the very weak couplings on
the hexagonal planes, they make very little correction to the energy spectra,
whereas the major correction contribution comes from the quartic terms in the
couplings along the chains with the numerical values for the energy gaps in
good agreement with the experimental results as reported earlier (Ref.~41).",1901.11007v2
2019-04-07,"Superconductivity, pair density wave, and Neel order in cuprates","We investigate in underdoped cuprates possible coexistence of the
superconducting (SC) order at zero momentum and pair density wave (PDW) at
momentum ${\bf Q}=(\pi, \pi)$ in the presence of a Neel order. By symmetry, the
$d$-wave uniform singlet pairing $dS_0$ can coexist with the $d$-wave triplet
PDW $dT_{\bf Q}$, and the $p$-wave singlet PDW $pS_{\bf Q}$ can coexist with
the $p$-wave uniform triplet $pT_0$. At half filling, we find the novel
$pS_{\bf Q}+pT_0$ state is energetically more favorable than the $dS_0+dT_{\bf
Q}$ state. At finite doping, however, the $dS_0+dT_{\bf Q}$ state is more
favorable. In both types of states, the variational triplet parameters,
$dT_{\bf Q}$ and $pT_0$, are of secondary significance. Our results point to a
fully symmetric $\mathrm{Z_2}$ quantum spin liquid with spinon Fermi surface in
proximity to the Neel order at zero doping, and to intertwined $d$-wave triplet
PDW fluctuations and spin moment fluctuations along with the dominant $d$-wave
singlet SC at finite doping. The results are obtained by variational quantum
Monte Carlo simulations.",1904.03658v2
2019-06-17,MuFA (Multi-type Fourier Analyzer): A tool for batch generation of MuMax3 input scripts and multi-type Fourier analysis from micromagnetic simulation output data,"We present a tool for batch generation of input scripts and multi-type
Fourier analysis from simulation results for the micromagnetic software MuMax3.
The introduction of graphical user interface and parameter-sweeping
functionality strongly speed up the input scripts creation and accelerate model
optimization processes consequently. Three types of important Fourier analysis
methods are provided for the acquisition of the quantitative frequency
compositions, the spin-wave dispersion curve and the spatial distribution of
spin-wave powers at different frequencies, respectively. Since the Fourier
analysis is accelerated by parallel computations, the time cost is reduced to
an acceptable level even in the presentation of tens of gigabytes data. With
the MuMax3 and our proposal, a complete micromagnetic simulating tool chain
from scripts generation to post analysis has been developed.",1907.01527v1
2019-07-15,Tuning edge localized spin waves in magnetic microstripes by proximate magnetic structures,"The propagation of edge localized spin waves (E-SWs) in yttrium iron garnet
(YIG) microstripes with/without the proximate magnetic microstructures is
investigated by micromagnetic simulations. A splitting of the dispersion curve
with the presence of permalloy (Py) stripe is also observed. The E-SWs on the
two edges of YIG stripe have different wavelengths, group velocities, and decay
lengths at the same frequencies. The role of the Py stripe was found to be the
source of the inhomogeneous static dipolar field without dynamic coupling with
YIG. This work opens new perspectives for the design of innovative SW
interference-based logic devices.",1907.06718v1
2019-07-19,Unconventional topology with a Rashba spin-orbit coupled quantum gas,"Topological order can be found in a wide range of physical systems, from
crystalline solids, photonic meta-materials and even atmospheric waves to
optomechanic, acoustic and atomic systems. Topological systems are a robust
foundation for creating quantized channels for transporting electrical current,
light, and atmospheric disturbances. These topological effects are quantified
in terms of integer-valued invariants, such as the Chern number, applicable to
the quantum Hall effect, or the $\mathbb{Z}_2$ invariant suitable for
topological insulators. Here we engineered Rashba spin-orbit coupling for a
cold atomic gas giving non-trivial topology, without the underlying crystalline
structure that conventionally yields integer Chern numbers. We validated our
procedure by spectroscopically measuring the full dispersion relation, that
contained only a single Dirac point. We measured the quantum geometry
underlying the dispersion relation and obtained the topological index using
matter-wave interferometry. In contrast to crystalline materials, where
topological indices take on integer values, our continuum system reveals an
unconventional half-integer Chern number, potentially implying new forms of
topological transport.",1907.08637v1
2019-07-28,Three-Spin Systems and the Pusey-Barrett- Rudolph Theorem,"The fundamental nature of quantum wave function has been the topic of many
discussions since the beginning of the quantum theory. It either corresponds to
an element of reality $(\Psi-ontic)$ or it is a subjective state of knowledge
about the underlying reality $(\Psi-epistemic)$. Pusey, Barrett, and Rudolph
(PBR) have shown that epistemic interpretations of the quantum wave function
are in contradiction with the predictions of quantum under some assumptions. In
this paper, a laboratory protocol with a triple quantum dot will be introduced
as a three-spin interaction system to study the PBR no-go theorem. By this
experimental model, we show that the epistemic interpretation of the quantum
state is in contradiction with quantum theory, based only on the assumption
that measurement settings can be prepared freely and independently from each
other.",1907.12020v3
2019-08-19,Power-law entanglement growth from typical product states,"Generic quantum many-body systems typically show a linear growth of the
entanglement entropy after a quench from a product state. While entanglement is
a property of the wave function, it is generated by the unitary time evolution
operator and is therefore reflected in its increasing complexity as quantified
by the operator entanglement entropy. Using numerical simulations of a static
and a periodically driven quantum spin chain, we show that there is a robust
correspondence between the entanglement entropy growth of typical product
states with the operator entanglement entropy of the unitary evolution
operator, while special product states, e.g. $\sigma_z$ basis states, can
exhibit faster entanglement production. In the presence of a disordered
magnetic field in our spin chains, we show that both the wave function and
operator entanglement entropies exhibit a power-law growth with the same
disorder-dependent exponent, and clarify the apparent discrepancy in previous
results. These systems, in the absence of conserved densities, provide further
evidence for slow information spreading on the ergodic side of the many-body
localization transition.",1908.07010v2
2019-09-26,Coherent charge and magnetic ordering in Ho/Y superlattice revealed by element-selective x-ray scattering,"Magnetic rare-earth / non-magnetic metal superlattices are well-known to
display chiral spin helices in the rare-earth layers that propagate coherently
across the non-magnetic layers. However, the underlying mechanism that
preserves the magnetic phase and chirality coherence across the non-magnetic
layers has remained elusive. In this Letter, we use resonant and
element-specific x-ray scattering to evidence directly the formation of two
fundamentally different long-range modulations in a Holmium/Yttrium (Ho/Y)
multilayer: the known Ho chiral spin helix with periodicity 25 {\AA}, and a
newly observed charge density wave with periodicity 16 {\AA} that propagates
through both the Ho and non-magnetic Y layer. With x-ray circular magnetic
dichroism measurements ruling out the existence of a magnetic proximity effect
induced moment in the non-magnetic Y layers, we propose that the charge density
wave is also chiral, thus providing the means for the transmittance of magnetic
chirality coherence between Ho layers.",1909.12372v2
2019-10-11,Hannay Angles in Magnetic Dynamics,"We consider, within the framework developed by Hannay for classical
integrable systems [Journal of Physics A: Mathematical and General {\bf 18},
221 (1985)], the geometric phases that occur in semi-classical magnetic
dynamics. Such geometric phases are generically referred to as Hannay angles,
and, in the context of magnetic dynamics, may arise as a result of both
adiabatically-varying ellipticity and axis of magnetization precession. We
elucidate both effects and their interplay for single-domain magnetic dynamics
within a simple model with time-dependent anisotropies and external field.
Subsequently, we consider spin waves and rederive, from our classical approach,
some known results on what is commonly referred to as the magnon Berry phase.
As an aside, these results are used to give an interpretation for geometric
phases that occur in superfluids. Finally, we develop a Green's function
formalism for elliptical magnons. Within this formalism, we consider magnon
transport in a mesoscopic ring and show how it is influenced by interference
effects that are tuned by the Hannay angle that results from a varying
ellipticity. Our results may inform the field of magnonics that seeks to
utilize spin waves in applications.",1910.05099v2
2019-10-31,First-principles Study of Spiral Spin Density Waves in Monolayer MnCl$_2$ Using Generalized Bloch Theorem,"We investigated the spiral spin density waves in the monolayer 1T-MnCl$_2$
for a set of spiral vectors based on first-principles calculations. The
magnetic ground states were evaluated by means of the generalized Bloch theorem
within the linear combination of pseudo-atomic orbitals. To reach our purpose,
a flat spiral configuration was constructed for the Mn magnetic atom by fixing
the direction of its magnetic moment. We confirmed that the ground state was a
spiral ground state. We also clarified that a phase transition from a spiral
ground state to the other ground states, such as the ferromagnetic state or the
antiferromagnetic state, appears when introducing the hole-electron doping.
Therefore, we justify that introducing the hole-electron doping tunes the phase
transition in the monolayer 1T-MnCl$_2$.",1910.14278v1
2019-12-06,Unitary-Coupled Restricted Boltzmann Machine Ansatz for Quantum Simulations,"Neural-Network Quantum State (NQS) has attracted significant interests as a
powerful wave-function ansatz to model quantum phenomena. In particular, a
variant of NQS based on the restricted Boltzmann machine (RBM) has been adapted
to model the ground state of spin lattices and the electronic structures of
small molecules in quantum devices. Despite these progresses, significant
challenges remain with the RBM-NQS based quantum simulations. In this work, we
present a state-preparation protocol to generate a specific set of
complex-valued RBM-NQS, that we name the unitary-coupled RBM-NQS, in quantum
circuits. This is a crucial advancement as all prior works deal exclusively
with real-valued RBM-NQS for quantum algorithms. With this novel scheme, we
achieve (1) modeling complex-valued wave functions, (2) using as few as one
ancilla qubit to simulate $M$ hidden spins in an RBM architecture, and (3)
avoiding post-selections to improve scalability.",1912.02988v1
2019-12-15,A semi-analytical approach to calculating the dynamic modes of magnetic vortices with Dzyaloshinskii-Moriya interactions,"Here we introduce a Landau-Lifshitz based diagonalization (LLD) method, and
use this approach to calculate the effects of the interfacial Dzyaloshinskii
Moriya interactions (DMI) on the radial-type spin wave modes of magnetic
vortices in circular disks. The LLD method is a semi-analytical approach that
involves the diagonalization of the magnetostatic kernel, exchange, and DMI
contributions to extract the system eigenfrequencies and eigenmodes. The
magnetic vortex state provides a convenient model system in which to
investigate the effects of the DMI on the dynamics of a magnetic structures
with confined geometries. Our calculations show that the DMI leads to shifts of
the mode frequencies that are similar in magnitude to what is observed for spin
waves of a comparable wavelength in extended films. However, unlike what is
found in thin films, only the down-shifted modes are observed in the disks, and
these corresponds to modes that propagate either radially outward or inward,
depending on the vortex circulation. The semi-analytical calculations agree
well with full micromagnetic simulations. This technique also applies to other
systems with cylindrical symmetry, for example, magnetic skyrmions.",1912.06963v1
2019-12-16,Slave-Boson analysis of the 2D Hubbard model,"We present a comprehensive study of the 2D one-band Hubbard model applying
the spin rotation invariant slave-boson method. We utilize a spiral magnetic
mean field and fluctuations around a paramagnetic mean field to determine the
magnetic phase diagram and find the two approaches to be in good agreement.
Apart from the commensurate phases characterized by ordering wave vectors
$\boldsymbol Q = (\pi, \pi), (0, \pi)$, and $(0, 0)$ we find incommensurate
phases where the ordering wave vectors $\boldsymbol Q = (Q, Q)$, and $(Q, \pi)$
vary continuously with filling, interaction strength or temperature. The mean
field quantities magnetization and effective mass are found to change
discontinuously at the phase boundaries separating the $(Q, Q)$ and $(Q, \pi)$
phases, indicating a first order transition. The band structure and Fermi
surface is shown in selected cases. The dynamic spin and charge
susceptibilities as well as the structure factors are calculated and discussed,
including the emergence of collective modes of the zero sound and Mott
insulator type. The dynamical conductivity is calculated in dependence of
doping, interaction strength and temperature. Finally, a
temperature-interaction strength phase diagram is established.",1912.07631v1
2020-01-15,Entanglement generation via power-of-SWAP operations between dynamic electron-spin qubits,"Surface acoustic waves (SAWs) can create moving quantum dots in piezoelectric
materials. Here we show how electron-spin qubits located on dynamic quantum
dots can be entangled. Previous theoretical and numerical models of quantum-dot
entanglement generation have been insufficient to study quantum dynamics in
realistic experimental devices. We utilize state-of-the-art graphics processing
units to simulate the wave function dynamics of two electrons carried by a SAW
through a 2D semiconductor heterostructure. We build a methodology to implement
a power-of-SWAP gate via the Coulomb interaction. A benefit of the SAW
architecture is that it provides a coherent way of transporting the qubits
through an electrostatic potential. This architecture allows us to avoid
problems associated with fast control pulses and guarantees operation
consistency, providing an advantage over static qubits. For inter-dot barrier
heights where the double occupation energy is sufficiently greater than the
double-dot hopping energy, we find that parameters based on experiments in
GaAs/AlGaAs heterostructures can produce a high-fidelity root-of-SWAP
operation. Our results provide a methodology for a crucial component of
dynamic-qubit quantum computing.",2001.05502v1
2020-01-30,Setting the cornerstone for the IMRPhenomX family of models for gravitational waves from compact binaries: The dominant harmonic for non-precessing quasi-circular black holes,"In this paper we present IMRPhenomXAS, a thorough overhaul of the IMRPhenomD
[1,2] waveform model, which describes the dominant $l=2, \:| m | = 2$ spherical
harmonic mode of non-precessing coalescing black holes in terms of piecewise
closed form expressions in the frequency domain. Improvements include in
particular the accurate treatment of unequal spin effects, and the inclusion of
extreme mass ratio waveforms. IMRPhenomD has previously been extended to
approximately include spin precession [3] and subdominant spherical harmonics
[4], and with its extensions it has become a standard tool in gravitational
wave parameter estimation. Improved extensions of IMRPhenomXAS are discussed in
companion papers [5,6].",2001.11412v1
2020-02-03,Quantum walk versus classical wave: Distinguishing ground states of quantum magnets by spacetime dynamics,"We investigate the wavepacket spreading after a single spin flip in
prototypical two-dimensional ferromagnetic and antiferromagnetic quantum spin
systems. We find characteristic spatial magnon density profiles: While the
ferromagnet shows a square-shaped pattern reflecting the underlying lattice
structure, as exhibited by quantum walkers, the antiferromagnet shows a
circular-shaped pattern which hides the lattice structure and instead resembles
a classical wave pattern. We trace these fundamentally different behaviors back
to the distinctly different magnon energy-momentum dispersion relations and
also provide a real-space interpretation. Our findings point to new
opportunities for real-time, real-space imaging of quantum magnets both in
materials science and in quantum simulators.",2002.00812v3
2020-02-05,Twisted particle collisions: a new tool for spin physics,"Collisions of twisted particles --- that is, non-plane-wave states of
photons, electrons, or any other particle, equipped with a non-zero orbital
angular momentum (OAM) with respect to its propagation direction --- offer
novel ways to probe particle structure and interactions. In the recent paper
\cite{Ivanov:2019vxe}, we argued that resonance production in twisted photon
collisions or twisted $e^+e^-$ annihilation gives access to parity- and
spin-sensitive observables in inclusive cross sections, even when the initial
particles are unpolarized. Here, we explore these features in detail, providing
a qualitative picture and illustrating it with numerical examples. We show how
one can detect parity-violating effects in collisions of unpolarized twisted
photons and how one can produce almost $100\%$ polarized vector mesons in
unpolarized twisted $e^+e^-$ annihilation. These examples highlight the
unprecedented level of control over polarization offered by twisted particles,
impossible in the usual plane wave collisions.",2002.01703v1
2020-02-13,Measuring eccentricity of binary black holes in GWTC-1 by using inspiral-only waveform,"In this paper, we estimate the eccentricity of the 10 BBHs in GWTC-1 by using
the inspiral-only BBH waveform template EccentricFD. Firstly, we test our
method with simulated eccentric BBHs. Afterwards we apply the method to the
real BBH gravitational wave data. We find that the BBHs in GWTC-1 except
GW151226, GW170608 and GW170729 admit very small eccentricity. Their upper
limits on eccentricity range from 0.033 to 0.084 with 90% credible interval at
the reference frequency 10 Hz. For GW151226, GW170608 and GW170729, the upper
limits are higher than 0.1. The relatively large eccentricity of GW151226 and
GW170729 is probably due to ignoring the effective spin and low signal-to-noise
ratio, and GW170608 is worthy of follow-up research. We also point out the
limitations of the inspiral-only non-spinning waveform template in eccentricity
measurement. The measurement of BBH eccentricity helps to understand its
formation mechanism. With the increase in the number of BBH gravitational wave
events and the more complete eccentric BBH waveform template, this will become
a viable method in the near future.",2002.05528v2
2020-02-26,Enhanced Ferroelectricity and Spin Current Waves in M-Type Barium Hexaferrite,"The intrinsic ferroelectricity and related dielectric properties of M-type
Barium Hexaferrite (BaFe12O19) with excellent magnetic performance are reported
in this paper. A classic electric polarization (P-E) hysteresis loop with full
saturation, together with two nonlinear reversal current peaks in the I-V curve
and huge change of dielectric constant in the vicinity of Curie temperature,
have all demonstrated themselves as sufficient experimental evidences to verify
the ferroelectricity of BaFe12O19 ceramics. It holds a large remnant
polarization at 108 uC/cm2 and a suitable coercive field at 117 kV/cm. Two
peaks at 194C and 451C in the temperature-dependent dielectric spectrum of
BaFe12O19 ceramics are considered to be the phase transition from ferro- to
antiferro- and antiferro- to para-electric structures. A conventional strong
magnetic hysteresis loop was also observed. The magnetically induced
polarization upon the BaFe12O19 ceramics was achieved in the form of
alternating spin current waves. A ME-coupling voltage with an amplitude of 23mV
on an applied magnetic field at 500mT was achieved. These combined multiple
functional responses of large ferroelectrics and strong ferromagnetism reveal
the excellent multiferroic features of BaFe12O19, which would bring forth the
great opportunity to create novel electric devices with active coupling effect
between magnetic and electric orders.",2002.11412v1
2020-02-26,Driving a magnetized domain wall in an antiferromagnet by magnons,"We theoretically study the interaction of magnons, quanta of spin waves, and
a domain wall in a one-dimensional easy-axis antiferromagnet in the presence of
an external magnetic field applied along the easy axis. To this end, we begin
by obtaining the exact solution for spin waves in the background of a domain
wall magnetized by an external field. The finite magnetization inside the
domain wall is shown to give rise to reflection of magnons scattering off the
domain wall, deviating from the well-known result of reflection-free magnons in
the absence of a magnetic field. For practical applications of the predicted
reflection of magnons, we show that the magnon reflection contributes to the
thermally-driven domain-wall motion. Our work leads us to envision that
inducing a finite magnetization in antiferromagnetic solitons such as vortices
and skyrmions can be used to engender phenomena that do not occur in the
absence of magnetization.",2002.11777v1
2020-02-27,Spin Wave Radiation by a Topological Charge Dipole,"The use of spin waves (SWs) as data carriers in spintronic and magnonic logic
devices offers operation at low power consumption, free of Joule heating.
Nevertheless, the controlled emission and propagation of SWs in magnetic
materials remains a significant challenge. Here, we propose that
skyrmion-antiskyrmion bilayers form topological charge dipoles and act as
efficient sub-100 nm SW emitters when excited by in-plane ac magnetic fields.
The propagating SWs have a preferred radiation direction, with clear dipole
signatures in their radiation pattern, suggesting that the bilayer forms a SW
antenna. Bilayers with the same topological charge radiate SWs with spiral and
antispiral spatial profiles, enlarging the class of SW patterns. We demonstrate
that the characteristics of the emitted SWs are linked to the topology of the
source, allowing for full control of the SW features, including their
amplitude, preferred direction of propagation, and wavelength.",2002.12282v1
2020-05-05,The Sign of Three: Spin/Charge Density Waves at the Boundaries of Transition Metal Dichalcogenides,"One-dimensional grain boundaries of two-dimensional semiconducting {\MX} (M=
Mo,W; X=S,Se) transition metal di-chalcogenides are typically metallic at room
temperature. The metallicity has its origin in the lattice polarization, which
for these lattices with $D_{3h}$ symmetry is a topological invariant, and leads
to one-dimenional boundary states inside the band gap. For boundaries
perpendicular to the polarization direction, these states are necessarily 1/3
occupied by electrons or holes, making them susceptible to a metal-insulator
transition that triples the translation period. Using density-functional-theory
calculations we demonstrate the emergence of combined one-dimensional spin
density/charge density waves of that period at the boundary, opening up a small
band gap of $\sim 0.1$ eV. This unique electronic structure allows for soliton
excitations at the boundary that carry a fractional charge of $\pm 1/3\ e$.",2005.02519v1
2020-05-15,Spin-wave study of entanglement and Rényi entropy for coplanar and collinear magnetic orders in two-dimensional quantum Heisenberg antiferromagnets,"We use modified linear spin-wave theory (MLSWT) to study ground-state
entanglement for a length-$L$ line subsystem in $L\times L$ square- and
triangular-lattice quantum Heisenberg antiferromagnets with coplanar spiral
magnetic order with ordering vector $\mathbf{Q}=(q,q)$ and $N_G=3$ Goldstone
modes, except if $q=\pi$ (collinear order, $N_G=2$). Generalizing earlier MLSWT
results for $q=\pi$ to commensurate spiral order with $s\geq 3$ sublattices
($q=2\pi r/s$ with $r$ and $s$ coprime), we find analytically for large $L$ a
universal and $n$-independent subleading term $(N_G/2)\ln L$ in the R\'{e}nyi
entropy $S_n$, associated with $L^{1/2}$ scaling of $\lambda_0$ and
$\lambda_{\pm q}$, with $\lambda_0\neq \lambda_{\pm q}$ for spiral order; here
$\{\lambda_{k_y}\}$ are the $L$ mode occupation numbers of the entanglement
Hamiltonian. The term $(3/2)\ln L$ in $S_n$ agrees with a nonlinear sigma model
(NLSM) study of $s=3$ spiral order ($q=2\pi/3$). These and other properties of
$S_n$ and $\lambda_{k_y}$ are explored numerically for an anisotropic
nearest-neighbor triangular-lattice model for which $q$ varies in the spiral
phase.",2005.07745v1
2020-05-22,Construction of Variational Matrix Product States for the Heisenberg Spin-1 Chain,"We propose a simple variational wave function that captures the correct
ground state energy of the spin-1 Heisenberg chain model to within 0.04\%. The
wave function is written in the matrix product state (MPS) form with the bond
dimension $D=8$, and characterized by three fugacity parameters. The proposed
MPS generalizes the Affleck-Kennedy-Lieb-Tasaki (AKLT) state by dressing it
with dimers, trimers, and general $q$-dimers. The fugacity parameters control
the number and the average size of the $q$-mers. Furthermore, the $D=8$
variational MPS state captures the ground states of the entire family of
bilinear-biquadratic Hamiltonian belonging to the Haldane phase to high
accuracy. The 2-4-2 degeneracy structure in the entanglement spectrum of our
MPS state is found to match well with the results of density matrix
renormalization group (DMRG) calculation, which is computationally much
heavier. Spin-spin correlation functions also find excellent fit with those
obtained by DMRG.",2005.10980v1
2020-07-02,"Valley magnetism, nematicity, and density wave orders in twisted bilayer graphene","We analyze density-wave and Pomeranchuk orders in twisted bilayer graphene.
This compliments our earlier analysis of the pairing instabilities. We assume
that near half-filling of either conduction or valence band, the Fermi level is
close to Van Hove points, where the density of states diverges, and study
potential instabilities in the particle-hole channel within a patch model with
two valley degrees of freedom. The hexagonal symmetry of twisted bilayer
graphene allows for either six or twelve Van Hove points. We consider both
cases and find the same two leading candidates for particle-hole order. One is
an SU(2)-breaking spin state with ferromagnetism within a valley. A subleading
inter-valley hopping induces antiferromagnetism between the valleys. The same
state has also been obtained in strong coupling approaches, indicating that
this order is robust. The other is a mixed state with $120^\circ$ complex spin
order and orthogonal complex charge order. In addition, we find a weaker, but
still attractive interaction in nematic channels, and discuss the type of a
nematic order.",2007.00871v2
2020-07-10,Gravitational-wave detectors as particle-physics laboratories: Constraining scalar interactions with a coherent inspiral model of boson-star binaries,"Gravitational-wave (GW) detections of binary neutron star coalescences play a
crucial role to constrain the microscopic interaction of matter at ultrahigh
density. Similarly, if boson stars exist in the universe their coalescence can
be used to constrain the fundamental coupling constants of a scalar field
theory. We develop the first coherent waveform model for the inspiral of boson
stars with quartic interactions. The waveform includes coherently spin-induced
quadrupolar and tidal-deformability contributions in terms of the masses and
spins of the binary and of a single coupling constant of the theory. We show
that future instruments such as the Einstein Telescope and the Laser
Interferometer Space Antenna can provide strong complementary bounds on bosonic
self-interactions, while the constraining power of current detectors is
marginal.",2007.05264v3
2020-07-12,Transient gravitational waves from pulsar post-glitch recoveries,"This work explores whether gravitational waves (GWs) from neutron star (NS)
mountains can be detected with current 2nd-generation and future 3rd-generation
GW detectors. In particular, we focus on a scenario where transient mountains
are formed immediately after a NS glitch. In a glitch, a NS's spin frequency
abruptly increases and then often exponentially recovers back to, but never
quite reaches, the spin frequency prior to the glitch. If the recovery is
ascribed to an additional torque due to a transient mountain, we find that GWs
from that mountain are marginally-detectable with Advanced LIGO at design
sensitivity and is very likely to be detectable for 3rd-generation detectors
such as the Einstein Telescope. Using this model, we are able to find
analytical expressions for the GW amplitude and its duration in terms of
observables.",2007.05893v2
2020-07-19,Isostructural spin-density-wave and superconducting gap anisotropies in iron-arsenide superconductors,"When passing through a phase transition, electronic system saves energy by
opening energy gaps at the Fermi level. Delineating the energy gap anisotropy
provides insights into the origin of the interactions that drive the phase
transition. Here, we report the angle-resolved photoemission spectroscopy
(ARPES) study on the detailed gap anisotropies in both the tetragonal magnetic
and superconducting phases in Sr$_{1-x}$Na$_x$Fe$_2$As$_2$. First, we found
that the spin-density-wave (SDW) gap is strongly anisotropic in the tetragonal
magnetic phase. The gap magnitude correlates with the orbital character of
Fermi surface closely. Second, we found that the SDW gap anisotropy is
isostructural to the superconducting gap anisotropy regarding to the angular
dependence, gap minima locations, and relative gap magnitudes. Our results
indicate that the superconducting pairing interaction and magnetic interaction
share the same origin. The intra-orbital scattering plays an important role in
constructing these interactions resulting in the orbital-selective magnetism
and superconductivity in iron-based superconductors.",2007.09572v1
2020-07-20,Gravitational-wave signal-to-noise interpolation via neural networks,"Computing signal-to-noise ratios (SNRs) is one of the most common tasks in
gravitational-wave data analysis. While a single SNR evaluation is generally
fast, computing SNRs for an entire population of merger events could be time
consuming. We compute SNRs for aligned-spin binary black-hole mergers as a
function of the (detector-frame) total mass, mass ratio and spin magnitudes
using selected waveform models and detector noise curves, then we interpolate
the SNRs in this four-dimensional parameter space with a simple neural network
(a multilayer perceptron). The trained network can evaluate $10^6$ SNRs on a
4-core CPU within a minute with a median fractional error below $10^{-3}$. This
corresponds to average speed-ups by factors in the range
$[120,\,7.5\times10^4]$, depending on the underlying waveform model. Our
trained network (and source code) is publicly available at
https://github.com/kazewong/NeuralSNR, and it can be easily adapted to similar
multidimensional interpolation problems.",2007.10350v1
2020-10-08,Analytic solutions of the Teukolsky equation for massless perturbations of any spin in de Sitter background,"We present analytic solutions to the Teukolsky equation for massless
perturbations of any spin in the 4-dimensional de Sitter background. The
angular part of the equation fixes the separation constant to a discrete set
and its solution is given by hypergeometric polynomials. For the radial part,
we derive analytic power series solution which is regular at the poles and
determine a transcendental function whose zeros give the characteristic values
of the wave frequency. We study the existence of explicit polynomial solutions
to the radial equation and obtain two classes of singular closed-form
solutions, one with discrete wave frequencies and the other with continuous
frequency spectra.",2010.03708v1
2020-10-19,Berezinskii-Kosterlitz-Thouless transitions in two-dimensional lattice SO($N_c$) gauge theories with two scalar flavors,"We study the phase diagram and critical behavior of a two-dimensional lattice
SO($N_c$) gauge theory ($N_c \ge 3$) with two scalar flavors, obtained by
partially gauging a maximally O($2N_c$) symmetric scalar model. The model is
invariant under local SO($N_c$) and global O(2) transformations. We show that,
for any $N_c \ge 3$, it undergoes finite-temperature
Berezinskii-Kosterlitz-Thouless (BKT) transitions, associated with the global
Abelian O(2) symmetry. The transition separates a high-temperature disordered
phase from a low-temperature spin-wave phase where correlations decay
algebraically (quasi-long range order). The critical properties at the
finite-temperature BKT transition and in the low-temperature spin-wave phase
are determined by means of a finite-size scaling analysis of Monte Carlo data.",2010.09412v2
2020-10-28,Strong coupling of quantized spin waves in ferromagnetic bilayers,"We formulate a strong-coupling theory for perpendicular standing spin waves
(PSSWs) in ferromagnetic bilayers with the interlayer exchange coupling (IEC).
Employing the Hoffmann boundary condition and the energy-flow continuity across
the interface, we show that the PSSWs are still quantized but with non-integral
quantum numbers, in sharp contrast to that of a single layer. The magnon-magnon
coupling is characterized by the spectrum splitting which is linear with the
IEC in the weak-coupling region, but getting saturated in the strong-coupling
limit. Analytical predictions are verified by full micromagnetic simulations
with good agreement.",2010.14981v2
2020-10-30,"Spin-wave dispersion and exchange stiffness in Nd$_2$Fe$_{14}$B and $R$Fe$_{11}$Ti ($R$=Y, Nd, Sm) from first-principles calculations","We theoretically investigate spin-wave dispersion in rare-earth magnet
compounds by using first-principles calculations and a method we call the
reciprocal-space algorithm (RSA). The value of the calculated exchange
stiffness for Nd$_2$Fe$_{14}$B is within the range of reported experimental
values. We find that the exchange stiffness is considerably anisotropic when
only short-range exchange couplings are considered, whereas inclusion of
long-range couplings weakens the anisotropy. In contrast, $R$Fe$_{11}$Ti
($R$=Y, Nd, Sm) shows large anisotropy in the exchange stiffness.",2010.16022v3
2021-01-07,Hartree-Fock Critical Nuclear Charge in Two-Electron Atoms,"Electron correlation effects play a key role in stabilising two-electron
atoms near the critical nuclear charge, representing the smallest charge
required to bind two electrons. However, deciphering the importance of these
effects relies on fully understanding the uncorrelated Hartree-Fock
description. Here, we investigate the properties of the ground state wave
function in the small nuclear charge limit using various symmetry-restricted
Hartree-Fock formalisms. We identify the nuclear charge where spin-symmetry
breaking occurs to give an unrestricted wave function that predicts the
ionisation of an electron. We also discover another critical nuclear charge
where the closed-shell electron density detaches from the nucleus, and identify
the importance of fractional spin errors and static correlation in this limit.",2101.02445v1
2021-03-07,Comment on `Relativistic wave-particle duality for spinors',"In a recent paper [1], it has been proposed that relativistic wave-particle
duality can be embodied in a relation that shows that the four-velocity of a
particle is proportional to the Dirac four-current. In this note we bring out
some problems with that idea. In particular, we point out that, in line with
existing literature on Einstein-Cartan gravity with torsion, the spin-torsion
term should represent negative energy. Moreover, if what is proposed in Eq.
(20) of [1] is correct, then the spin torsion term would be zero in the rest
frame of the fermion. We suggest a possible resolution of that dilemma.",2103.04468v2
2021-03-24,One-dimensional optomagnonic microcavities for selective excitation of perpendicular standing spin waves,"Here we propose a method of the excitation of perpendicular standing spin
waves (PSSWs) of different orders in an optomagnonic microcavity by ultrashort
laser pulses. The microcavity is formed by a magnetic dielectric film
surrounded by dielectric non-magnetic Bragg mirrors. Optical cavity modes in
the magnetic layer provide concentration and strongly non-uniform distribution
of the optical power over the layer thickness and therefore induce the
effective field of the inverse Faraday effect also spatially non-uniform. It
results in excitation of PSSWs. PSSWs whose wavevector is closest to the
wavevector characterizing distribution of the inverse Faraday effect field are
excited most efficiently. Consequently, a key advantage of this approach is a
selectivity of the PSSW excitation which allows to launch PSSWs of required
orders only. All-optical operation of the optomagnonic cavities opens new
possibilities for their applications for quantum technologies.",2103.13129v1
2021-05-11,Optimization of model independent gravitational wave search using machine learning,"The Coherent WaveBurst (cWB) search algorithm identifies generic
gravitational wave (GW) signals in the LIGO-Virgo strain data. We propose a
machine learning (ML) method to optimize the pipeline sensitivity to the
special class of GW signals known as binary black hole (BBH) mergers. Here, we
test the ML-enhanced cWB search on strain data from the first and second
observing runs of Advanced LIGO and successfully recover all BBH events
previously reported by cWB, with higher significance. For simulated events
found with a false alarm rate less than $1\,\mathrm{yr}^{-1}$, we demonstrate
the improvement in the detection efficiency of 26% for stellar-mass BBH mergers
and 16% for intermediate mass black hole binary mergers. To demonstrate the
robustness of the ML-enhanced search for the detection of generic BBH signals,
we show that it has the increased sensitivity to the spin precessing or
eccentric BBH events, even when trained on simulated quasi-circular BBH events
with aligned spins.",2105.04739v1
2021-05-14,Quantum Phases of Transition Metal Dichalcogenide Moiré Systems,"Moir\'e systems provide a rich platform for studies of strong correlation
physics. Recent experiments on hetero-bilayer transition metal dichalcogenide
(TMD) Moir\'e systems are exciting in that they manifest a relatively simple
model system of an extended Hubbard model on a triangular lattice. Inspired by
the prospect of the hetero-TMD Moir\'e system's potential as a
solid-state-based quantum simulator, we explore the extended Hubbard model on
the triangular lattice using the density matrix renormalization group (DMRG).
Specifically, we explore the two-dimensional phase space of the kinetic energy
relative to the interaction strength $t/U$ and the further-range interaction
strength $V_1/U$. We find competition between Fermi fluid, chiral spin liquid,
spin density wave, and charge density wave. In particular, our finding of the
optimal further-range interaction for the chiral correlation presents a
tantalizing possibility.",2105.07008v2
2021-05-16,Voltage-Controlled Reconfigurable Magnonic Crystal at the Submicron Scale,"Multiferroics offer an elegant means to implement voltage-control and on the
fly reconfigurability in microscopic, nanoscaled systems based on ferromagnetic
materials. These properties are particularly interesting for the field of
magnonics, where spin waves are used to perform advanced logical or analogue
functions. Recently, the emergence of nano-magnonics {\color{black} is expected
to} eventually lead to the large-scale integration of magnonic devices.
However, a compact voltage-controlled, on demand reconfigurable magnonic system
has yet to be shown. Here, we introduce the combination of multiferroics with
ferromagnets in a fully epitaxial heterostructure to achieve such
voltage-controlled and reconfigurable magnonic systems. Imprinting a remnant
electrical polarization in thin multiferroic $\mathrm{BiFeO_3}$ with a
periodicity of $500\,\mathrm{nm}$ yields a modulation of the effective magnetic
field in the micron-scale, ferromagnetic $\mathrm{La_{2/3}Sr_{1/3}MnO_3}$
magnonic waveguide. We evidence the magneto-electrical coupling by
characterizing the spin wave propagation spectrum in this artificial, voltage
induced, magnonic crystal and demonstrate the occurrence of a robust magnonic
bandgap with $>20 \,\mathrm{dB}$ rejection.",2105.07418v1
2021-06-15,Remote state preparation of single photon orbital angular momentum lattices,"Optical beams with periodic lattice structures have broadened the study of
structured waves. In the present work, we generate spin-orbit entangled photon
states with a lattice structure and use them in a remote state preparation
protocol. We sequentially measure spatially-dependent correlation rates with an
electron-multiplying intensified CCD camera and verify the successful remote
preparation of spin-orbit states by performing pixel-wise quantum state
tomography. Control of these novel structured waves in the quantum regime
provides a method for quantum sensing and manipulation of periodic structures.",2106.08428v1
2021-07-02,Gravitational-wave energy flux for compact binaries through second order in the mass ratio,"Within the framework of self-force theory, we compute the gravitational-wave
energy flux through second order in the mass ratio for compact binaries in
quasicircular orbits. Our results are consistent with post-Newtonian
calculations in the weak field and they agree remarkably well with
numerical-relativity simulations of comparable-mass binaries in the strong
field. We also find good agreement for binaries with a spinning secondary or a
slowly spinning primary. Our results are key for accurately modelling
extreme-mass-ratio inspirals and will be useful in modelling
intermediate-mass-ratio systems.",2107.01298v2
2021-07-08,Self-consistently renormailzed spin-wave theory of layered ferromagnets on honeycomb lattice,"We develop a self-consistently renormalized spin-wave theory, within a
mean-field approximation, for the two-dimensional Heisenberg ferromagnet with
perpendicular easy-axis anisotropy on the honeycomb lattice, as well as its
few-layer and bulk extensions. In this method, the magnetization dependence on
temperature is found as the solution of the self-consistency equation.
Furthermore, we account for the physical difference of surface and bulk layers
by treating the layers as separate sublattices. Thus, the method can be readily
generalized to study various magnetic phenomena in a broad range of systems,
including those comprising magnetically inequivalent sublattices. Using our
theory, we calculate the temperature-dependent magnetization for two
chromium-based layered van der Waals insulating magnets, Cr$_2$Ge$_2$Te$_6$ and
CrI$_3$, employing various sets of Heisenberg exchange and single-ion
anisotropy values reported for these materials in the existing literature. As
expected, we observe a strong dimensionality effect where the ordering
temperature is reduced and its sensitivity on the anisotropy is enhanced with
the decrease of dimensionality.",2107.04085v1
2021-07-08,Nonreciprocal magnon fluxonics upon ferromagnet/superconductor hybrids,"Ferromagnet/superconductor heterostructures allow for the combination of
unique physical phenomena offered by the both fields of magnetism and
superconductivity. It was shown recently that spin waves can be efficiently
scattered in such structures by a lattice of static or moving magnetic flux
quanta (Abrikosov vortices), resulting in bandgaps in the spin-wave spectra.
Here, we realize a nonreciprocal motion of a vortex lattice in nanoengineered
symmetric and asymmetric pinning landscapes and investigate the non-reciprocal
scattering of magnons on fluxons. We demonstrate that the magnon bandgap
frequencies can be tuned by the application of a low-dissipative transport
current and by its polarity reversal. Furthermore, we exploit the rectifying
(vortex diode or ratchet) effect by the application of a 100 MHz-frequency ac
current to deliberately realize bandgap up- or downshifts during one ac
halfwave while keeping the bandgap frequency constant during the other ac
halfwave. The investigated phenomena allow for the realization of
energy-efficient hybrid magnonic devices, such as microwave filters with an
ultra-high bandgap tunability of 10 GHz/mA and a fast modulation of the
transmission characteristics on the 10 ns time scale.",2107.04095v1
2021-07-13,Phase diagram and spin waves in the frustrated ferro-antiferromagnet SrZnVO(PO4)2,"Single crystals of the frustrated S=1/2 ferro-antiferromagnetic proximate
square lattice material SrZnZnVO(PO$_4$)$_2$ are studied in magnetometric,
calorimetric, neutron diffraction and inelastic neutron scattering experiments.
The measured spin wave spectrum reveals a substantial degree of magnetic
frustration and a large quantum renormalization of the exchange constants. The
H-T magnetic phase diagram is established. It features a novel pre-saturation
phase, which appears for only one particular field orientation. The results are
discussed noting the similarities and differences with the previously studied
and similarly structured Pb$_2$VO(PO$_4$)$_2$ compound.",2107.06114v1
2021-07-21,Spin-wave growth via Shapiro resonances in a spinor Bose-Einstein condensate,"We theoretically study the resonant phenomenon in a spin-1 Bose-Einstein
condensate periodically driven by a quadratic Zeeman coupling. This phenomenon
is closely related to the Shapiro steps in superconducting Josephson junctions,
and the previous experimental work [Evrard $et al.,$ Phys. Rev. A 100, 023604
(2019)] for a spin-1 bosonic system observed the resonant dynamics and then
called it Shapiro resonance. In this work, using the spin-1 Gross-Pitaevskii
equation, we study the Shapiro resonance beyond the single-mode approximation
used in the previous work, which assumes that all components of the spinor
wavefunction have the same spatial configuration. Considering resonant dynamics
starting from a polar state, we analytically calculate the Floquet-Lyapunov
exponents featuring an onset of the resonance under a linear analysis and find
that spin waves with finite wavenumbers can be excited. This kind of
non-uniform excitation cannot be described by the single-mode approximation.
Furthermore, to study the long-time resonant dynamics beyond the linear
analysis, we numerically solve the one-dimensional spin-1 Gross-Pitaevskii
equation, finding that the nonresonant hydrodynamic variables also grow at
wavelengths of even multiples of the resonant one due to the nonlinear effect.",2107.09924v1
2021-12-10,Density and pseudo-spin rotons in a bilayer of soft-core bosons,"We study the dynamics of a bilayer system of bosons with repulsive soft-core
Rydberg-dressed interactions within the mean-field Bogoliubov-de Gennes
approximation. We find roton minima in both symmetric and asymmetric collective
density modes of the symmetric bilayer. Depending on the density of bosons in
each layer and the spacing between two layers, the homogeneous superfluid phase
becomes unstable in either (or both) of these two channels, leading to density
and pseudo-spin-density wave instabilities in the system. Breaking the symmetry
between two layers, either with a finite counterflow or a density imbalance
renormalizes the dispersion of collective modes and makes the system more
susceptible to density-wave instability.",2112.05400v1
2022-01-14,Supplementing rapid Bayesian parameter estimation schemes with adaptive grids,"In the age of multi-messenger astrophysics, low-latency parameter estimation
of gravitational-wave signals is essential for electromagnetic follow-up
observations. In this paper, we present a new edition of the Bayesian parameter
estimation scheme for compact binaries known as Rapid PE. Rapid PE parallelizes
parameter estimation by fixing the intrinsic parameters (such as the masses and
spins of the binary) to a grid around a search-identified intrinsic point and
by integrating over the extrinsic parameters via Monte Carlo sampling. The
original version of Rapid PE calculated an effective Fisher matrix to fix the
intrinsic parameters to an ellipsoidal grid. Here we use rectilinear gridding
in intrinsic space. The use of rectilinear intrinsic grids provides the option
to more easily include spin and allows for adaptive grid refinements to
mitigate search biases and map out the posterior more completely without
sacrificing sampling efficiency. We demonstrate that this parameter estimation
method produces reliable results for simulated gravitational-wave signals from
binary neutron star mergers.",2201.05263v1
2022-01-27,"TCFHs, hidden symmetries and M-theory backgrounds","We present the TCFH of 11-dimensional supergravity and so demonstrate that
the form bilinears of supersymmetric solutions satisfy a generalisation of the
conformal Killing-Yano equation with resepct to the TCFH connection. We also
compute the Killing-St\""ackel, Killing-Yano and closed conformal Killing-Yano
tensors of all spherically symmetric M-branes that include the M2-brane,
M5-brane, KK-monopole and pp-wave and demonstrate that their geodesic flows are
completely integrable by giving all independent conserved charges in
involution. We then find that all form bilinears of pp-wave and KK-monopole
solutions generate (hidden) symmetries for spinning particle probes propagating
on these backgrounds. Moreover, there are Killing spinors such that some of the
1-, 2- and 3-form bilinears of the M2-brane solution also generate symmetries
for spinning particle probes. We also explore the question on whether the form
bilinears are sufficient to prove the integrability of particle probe dynamics
on 11-dimensional supersymmetric backgrounds.",2201.11563v1
2022-02-01,Earth rotation and time-domain reconstruction of polarization states for continuous gravitational waves from a known pulsar,"We consider effects of the Earth rotation on antenna patterns of a
ground-based gravitational wave (GW) detector in a general metric theory that
allows at most six polarization states (two spin-0, two spin-1 and two spin-2)
in a four-dimensional spacetime. By defining the cyclically averaged antenna
matrix for continuous GWs from a known pulsar, we show that waveforms for each
polarization state can be uniquely reconstructed in time domain from a given
set of the strain outputs at a single detector. Constraining the propagation
speed of extra polarization modes, if they coexist with the
transverse-traceless modes, is also discussed. We examine also possible effects
due to the length-of-day modulation as well as a secular change in the pulsar
spin period.",2202.00171v2
2022-01-30,Nonreciprocal Spin Waves Driven by Left-Hand Microwaves,"It is a conventional wisdom that a left-hand microwave cannot efficiently
excite the spin wave (SW) in ferromagnets, due to the constraint of angular
momentum conservation. In this work, we show that the left-hand microwave can
drive nonreciprocal SWs in the presence of a strong ellipticity-mismatch
between the microwave and precessing magnetization. A critical frequency is
predicted, at which the left-hand microwave cannot excite SWs. Away from it the
SW amplitude sensitively depends on the ellipticity of left-hand microwaves, in
sharp contrast to the case driven by right-hand ones. By tuning the microwave
frequency, we observe a switchable SW non-reciprocity in a ferromagnetic single
layer. A mode-dependent mutual demagnetizing factor is proposed to explain this
finding. Our work advances the understanding of the photon-magnon conversion,
and paves the way to designing diode-like functionalities in nano-scaled
magnonics.",2202.00780v3
2022-02-23,Spin-density-wave order controlled by uniaxial stress in CeAuSb$_2$,"The tetragonal heavy-fermion compound CeAuSb$_2$ (space group $P4/nmm$)
exhibits incommensurate spin density wave (SDW) order below $T_{N}\approx6.5~K$
with the propagation vector $\mathbf{q}_A = (\delta_A,\delta_A,1/2)$. The
application of uniaxial stress along the [010] direction induces a sudden
change in the resistivity ratio $\rho_a/\rho_b$ at a compressive strain of
$\epsilon \approx -0.5$\%. Here we use neutron scattering to show that the
uniaxial stress induces a first-order transition to a SDW state with a
different propagation vector $(0,\delta_B,1/2)$ with $\delta_B=0.25$. The
magnetic structure of the new (B) phase consists of Ce layers with ordered
moments alternating with layers with zero moment stacked along the $c$-axis.
The ordered layers have an up-up-down-down configuration along the $b$-axis.
This is an unusual situation in which the loss of spatial inversion is driven
by the magnetic order. We argue that the change in SDW wavevector leads to
Fermi surface reconstruction and a concomitant change in the transport
properties.",2202.11569v2
2022-03-01,Excitations in the ordered and paramagnetic states of honeycomb magnet Na2Co2TeO6,"Na2Co2TeO6 is a proposed approximate Kitaev magnet, yet its actual magnetic
interactions are elusive due to a lack of knowledge on the full excitation
spectrum. Here, using inelastic neutron scattering and single crystals, we
determine the system's temperature-dependent magnetic excitations over the
entire Brillouin zone. Without committing to specific models, we unveil a
distinct signature of the third-nearest-neighbor coupling in the spin waves,
which signifies the associated distance as an emerging ""soft link"" in the
ordered state. The presence of at least six non-overlapping spin-wave branches
is at odds with all models proposed to date. Above the ordering temperature,
persisting dynamic correlations can be described by equal-time magnetic
structure factors of a hexagonal cluster, which reveal the leading
instabilities. Our result sets definitive constraint on theoretical models for
Na2Co2TeO6 and provides new insight for the materialization of the Kitaev
model.",2203.00282v1
2022-03-08,A solvable 3D Kondo lattice exhibiting odd-frequency pairing and order fractionalization,"The Kondo lattice model plays a key role in our understanding of quantum
materials, but a lack of small parameters has posed a long-standing problem. We
present a 3 dimensional S= 1/2 Kondo lattice model describing a spin liquid
within an electron sea. Strong correlations in the spin liquid are treated
exactly, enabling a controlled analytical approach. Like a Peierls or BCS
phase, a logarithmically divergent susceptibility leads to an instability into
a new phase at arbitrarily small Kondo coupling. Our solution captures a
plethora of emergent phenomena, including odd-frequency pairing, pair density
wave formation and order fractionalization. The ground-state state is a pair
density wave with a fractionalized charge e, S = 1/2 order parameter, formed
between electrons and Majorana fermions.",2203.04104v2
2022-03-09,Toward discovering the excited $Ω$ baryons through nonleptonic weak decays of $Ω_c$,"The nonleptonic weak decay processes $\Omega_c \to
\Omega\pi^+/\Omega(1P)\pi^+/\Omega(1D)\pi^+/\Omega(2S)\pi^+$ are studied using
the constituent quark model. The branching fraction of $\Omega_c \to
\Omega\pi^+$ is predicted to be $1.1\%$. Considering the newly observed
$\Omega(2012)$ resonance as a conventional $1P$-wave $\Omega$ excite state with
spin-parity $J^P=3/2^-$, the newly measured ratio $\mathcal{B}[\Omega_c\to
\Omega(2012)\pi^+ \to (\Xi\bar{K})^-\pi^+ ]/\mathcal{B}[\Omega_c\to \Omega
\pi^+]$ at Belle can be well understood. Besides, the production rates for the
missing $1P-$wave state $\Omega (1^2P_{1/2^-})$, two spin quartet $1D-$wave
states $\Omega (1^4D_{1/2^+})$ and $\Omega (1^4D_{3/2^+})$, and two $2S$-wave
states $\Omega(2^2S_{1/2^+})$ and $\Omega(2^4S_{3/2^+})$ are also investigated.
It is expected that these missing excited $\Omega$ baryons should have large
potentials to be discovered through the nonleptonic weak decays of $\Omega_c$
in forthcoming experiments by Belle II and/or LHCb.",2203.04458v2
2022-03-11,Fully polarized nonlinear Breit-Wheeler pair production in pulsed plane waves,"Fully polarized nonlinear Breit-Wheeler pair production from a beam of
polarized seed photons is investigated in pulsed plane-wave backgrounds. The
particle (electron and positron) spin and photon polarization are
comprehensively described with the theory of the density matrix. The compact
expressions for the energy spectrum and spin polarization of the produced
particles, depending on the initial polarization of the seed photon beam, are
derived and discussed in both linearly and circularly polarized laser
backgrounds. The numerical results suggest an appreciable improvement of the
positron yield by orthogonalizing the photon polarization to the laser
polarization, and the generation of a highly polarized positron beam from a
beam of circularly polarized seed photons. The locally monochromatic
approximation and the locally constant field approximation are derived and
benchmarked with the full quantum electrodynamic calculations.",2203.05721v1
2022-03-15,Imaginary spin-orbital coupling in parity-time symmetric systems with momentum-dependent gain and loss,"Spin-orbital coupling (SOC) and parity-time ($\mathcal{PT}$) symmetry both
have attracted paramount research interest in condensed matter physics, cold
atom physics, optics and acoustics to develop spintronics, quantum computation,
precise sensors and novel functionalities. Natural SOC is an intrinsic
relativistic effect. However, there is an increasing interest in synthesized
SOC nowadays. Here, we show that in a $\mathcal{PT}$-symmetric spin-1/2 system,
the momentum-dependent balanced gain and loss can synthesize a new type of SOC,
which we call imaginary SOC. The imaginary SOC can substantially change the
energy spectrum of the system. Firstly, we show that it can generate a pure
real energy spectrum with a double-valleys structure. Therefore, it has the
ability to generate supersolid stripe states. Especially, the imaginary SOC
stripe state can have a high contrast of one. Moreover, the imaginary SOC can
also generate a spectrum with tunable complex energy band, in which the waves
are either amplifying or decaying. Thus, the imaginary SOC would also find
applications in the engineering of $\mathcal{PT}$-symmetry-based coherent wave
amplifiers/absorbers. Potential experimental realizations of imaginary SOC are
proposed in cold atomic gases and systems of coupled waveguides constituted of
nonlocal gain and loss.",2203.07764v1
2022-03-15,Standing spin wave excitation in Bi:YIG films via temperature induced anisotropy changes and magnetoacoustic coupling,"Based on micromagnetic simulations and experimental observations of the
magnetization and lattice dynamics following the direct optical excitation of
the magnetic insulator Bi:YIG or indirect excitation via an optically opaque
Pt/Cu double layer, we disentangle the dynamical effects of magnetic anisotropy
and magnetoelastic coupling. The strain and temperature of the lattice are
quantified via modeling ultrafast x-ray diffraction data. Measurements of the
time-resolved magneto-optical Kerr effect agree well with the magnetization
dynamics simulated according to the excitation via two mechanisms: The
magneto-acoustic coupling to the experimentally verified strain dynamics and
the ultrafast temperature-induced transient change in the magnetic anisotropy.
The numerical modeling proves that for direct excitation both mechanisms drive
the fundamental mode with opposite phase. The relative ratio of standing
spin-wave amplitudes of higher order modes indicates that both mechanisms are
substantially active.",2203.07851v1
2022-03-30,Hybrid magnonics for short-wavelength spin waves facilitated by a magnetic heterostructure,"Recent research on hybrid magnonics has been restricted by the long magnon
wavelengths of the ferromagnetic resonance modes. We present an experiment on
the hybridization of 250-nm wavelength magnons with microwave photons in a
multimode magnonic system consists of a planar cavity and a magnetic bilayer.
The coupling between magnon modes in the two magnetic layers, i.e., the uniform
mode in Permalloy (Py) and the perpendicular standing spin waves (PSSWs) in
YIG, serves as an effective means for exciting short-wavelength PSSWs, which is
further hybridized with the photon mode of the microwave resonator. The
demonstrated magnon-photon coupling approaches the superstrong coupling regime,
and can even be achieved near zero bias field.",2203.16310v1
2022-04-01,Competition of Density Waves and Superconductivity in Twisted Tungsten Diselenide,"Evidence for correlated insulating and superconducting phases around regions
of high density of states was reported in the strongly spin-orbit coupled
van-der Waals material twisted tungsten diselenide (tWSe$_2$). We investigate
their origin and interplay by using a functional renormalization group approach
that allows to describe superconducting and spin/charge instabilities in an
unbiased way. We map out the phase diagram as function of filling and
perpendicular electric field, and find that the moir\'e Hubbard model for
tWSe$_2$ features mixed-parity superconducting order parameters with $s/f$-wave
and topological $d/p$-wave symmetry next to (incommensurate) density wave
states. Our work systematically characterizes competing interaction-driven
phases in tWSe$_2$ beyond mean-field approximations and provides guidance for
experimental measurements by outlining the fingerprint of correlated states in
interacting susceptibilities.",2204.00648v2
2022-04-07,Constraints on the ultralight scalar boson from Advanced LIGO and Advanced Virgo's first three observing runs using the stochastic gravitational-wave background,"Ultralight bosons are promising dark matter candidates and can trigger
superradiant instabilities of spinning black holes (BHs), resulting in
long-lived rotating ""bosonic clouds"" around the BHs and dissipating their
energy through the emission of monochromatic gravitational waves (GWs). We
focus on the scalar bosons minimally coupled with both isolated stellar-origin
BHs (SBH) and their binary merger remnants, and perform Bayesian data analysis
to search for the stochastic GW background from all the unstable modes that can
trigger the superradiant instabilities using the data of Advanced LIGO and
Advanced Virgo's first three observing runs. We find no evidence for such
signal, and hence rule out the scalar bosons within the mass range $[1.5,
16]\times10^{-13}$ eV, $[1.9, 8.3]\times10^{-13}$ eV and $[1.3,
17]\times10^{-13}$ eV at $95\%$ confidence level for isolated SBHs having a
uniform dimensionless spin distribution in $[0,1]$, $[0,0.5]$ and $[0.5,1]$,
respectively.",2204.03482v2
2022-04-13,Impurity bands in magnetic superconductors with spin density wave,"Magnetic superconductors define a broad class of strongly correlated
materials in which superconductivity may coexist with either localized or
itinerant long-range magnetic order. In this work we consider a multiband model
of a disordered magnetic superconductor which realizes coexistence of
unconventional superconductivity and a spin-density-wave. We derive an exact
$T$-matrix and compute a single particle density of states in this system. In a
purely superconducting state the interband scattering potential leads to an
appearance of the localized Yu-Shiba-Rusinov bound states. Our main finding is
that in the fairly broad swath of the coexistence region superconductivity
remains fully gapped despite the presence of the impurity bands. We also
discuss the effects of spatial inhomogeneities on the density of states in
strongly contaminated superconductors.",2204.06565v2
2022-04-21,Topological contribution to magnetism in the Kane-Mele model: An explicit wave function approach,"In our previous publication [S. Ozaki and M. Ogata, Phys. Rev. Research 3,
013058], the quantization of the orbital-Zeeman (OZ) cross term in the magnetic
susceptibility, or the cross term of spin Zeeman and orbital effect, was shown
for the Kane-Mele model using the expansion around the Dirac points. In the
present study, we accurately evaluate the orbital, spin-Zeeman, and OZ cross
term of the Kane-Mele model using a recently developed formulation. This
formula is written in terms of the explicit Bloch wave functions, and enables
us to evaluate each contribution taking account of the integration over the
whole Brillouin zone and the summation over all the bands. As a result,
additional contributions such as core-electron diamagnetism are found.
Furthermore, our evaluation confirms the quantization of the OZ cross term and
reveals its behavior including the metallic case. The possibility of
experimental detection of the quantization is discussed.",2204.09932v1
2022-05-23,Linear Flavor-Wave Analysis of SU(4)-Symmetric Tetramer Model with Population Imbalance,"We study the quantum magnetism of the SU(4) Mott insulator in a square
optical superlattice, in which atoms with four nuclear-spin components strongly
interact with each other, in the presence of an external field that controls
the imbalance between the population of two components and that of the other
two. This is a natural extension of the physics of spin-dimer materials under
strong magnetic field. We apply an extended linear flavor-wave theory based on
four-site plaquettes and unveil the ground-state phase diagram and excitation
spectra. When the population of the four components is balanced and the
plaquesttes are weakly coupled, the ground state is approximately given by the
direct product of local SU(4)-singlet states. In high-field, the system reaches
a ""saturated state"" where only two components are present. Our main finding is
a nontrivial intermediate phase, which has a checkerboard-like arrangement of
the SU(4)-singlet and four-site resonating-valence-bond states.",2205.11155v1
2022-06-15,"Spectroscopy of Kerr-AdS$_5$ spacetime with the Heun function: Quasinormal modes, greybody factor, and evaporation","We investigate quasinormal modes, greybody factor, and Hawking evaporation of
a five-dimensional Kerr-anti de Sitter (AdS$_5$) black hole by solving a wave
equation for a test massive scalar field in terms of the local Heun function.
We clarify the distribution of the quasinormal modes satisfying the ingoing and
decaying boundary conditions at the event horizon and conformal infinity,
respectively, and their splitting behaviors in the complex frequency plane with
respect to a variation of spin parameters. We also point out the existence of
purely imaginary modes. Further, we develop a method to extract in/outgoing
waves near the AdS boundary, which enables us to define the greybody factor for
a wide range of parameter space complementary to previous works. Using the
greybody factor, we compute evaporation rates for mass and spins for the
Kerr-AdS$_5$ black hole via the Hawking radiation of the scalar field.",2206.07721v2
2022-06-20,Voltage-controlled significant spin wave Doppler shift in FM/FE heterojunction,"Efficient manipulation of spin waves (SWs) is considered as one of the
promising means for encoding information with low power consumption in next
generation spintronic devices. The SW Doppler shift is one important phenomenon
by manipulating SWs propagation. Here, we predict an efficient way to control
the SW Doppler shift by voltage control magnetic anisotropy boundary (MAB)
movement in FM/FE heterojunction. From the micromagnetic simulation, we
verified that the SW Doppler shift aligns well with our theoretical predictions
in Fe/$\rm BaTiO_3$ heterostructure. The SW Doppler shift also shows ultra
wide-band shift (over 5 GHz) property with voltage. Such efficient SW Doppler
shift may provide one possible way to measure the Hawking radiation of an
analogue black hole in the SW systems.",2206.09550v2
2022-06-26,Gravitational waves at the first post-Newtonian order with the Weyssenhoff fluid in Einstein-Cartan theory,"The generation of gravitational waves from a post-Newtonian source endowed
with a quantum spin, modeled by the Weyssenhoff fluid, is investigated in the
context of Einstein-Cartan theory at the first post-Newtonian level by
resorting to the Blanchet-Damour formalism. After having worked out the basic
principles of the hydrodynamics in Einstein-Cartan framework, we study the
Weyssenhoff fluid within the post-Newtonian approximation scheme. The
complexity of the underlying dynamical equations suggests to employ a discrete
description via the point-particle limit, a procedure which permits the
analysis of inspiralling spinning compact binaries. We then provide a first
application of our results by considering binary neutron star systems.",2206.12907v1
2022-06-29,Spin-Wave Optics in YIG by Ion-Beam Irradiation,"We demonstrate direct focused ion beam (FIB) writing as an enabling
technology for realizing spin-wave-optics devices. It is shown that ion-beam
irradiation changes the characteristics of YIG films on a submicron scale in a
highly controlled way, allowing to engineer the magnonic index of refraction
adapted to desired applications. This technique does not physically remove
material, and allows rapid fabrication of high-quality architectures of
modified magnetization in magnonic media with minimal edge damage (compared to
more common techniques such as etching or milling). By experimentally showing
magnonic versions of a number of optical devices (lenses, gratings,
Fourier-domain processors) we envision this technology as the gateway to
building magnonic computing devices that rival their optical counterparts in
their complexity and computational power.",2206.14696v1
2022-07-01,Phase diagram of Rydberg-dressed atoms on two-leg triangular ladders,"Dressed Rydberg atoms in optical lattices are a promising platform for the
quantum simulation of intriguing phenomena emerging in strongly interacting
systems. Relevant to such a setup, we investigate the phase diagram of
hard-core bosons in a triangular ladder with next-to-nearest-neighbor
interaction along each leg and nearest-neighbors interactions without hopping
between the legs. For weak interactions, Abelian bosonization predicts a spin
density wave and a fully gapless Luttinger liquid phase. Such liquids
transition to a 'spin-locked' cluster Luttinger liquid at strong interactions
along each leg, as predicted by cluster bosonization. Interestingly, the
competition with the zigzag interaction generates a charge density wave, a
'polarized holonic' phase, and a crystalline phase at the filling 2/5, that we
address via semi-classical perturbative approach. Exact diagonalization and
density matrix renormalization group simulations confirm the predictions and
further characterize the phases and their transitions.",2207.00385v2
2022-07-07,Removing degeneracy and multimodality in gravitational wave source parameters,"Quasicircular binary black hole mergers are described by 15 parameters, of
which gravitational wave observations can typically constrain only $\sim 10$
independent combinations to varying degree. In this work, we devise coordinates
that remove correlations, and disentangle well- and poorly-measured quantities.
Additionally, we identify approximate discrete symmetries in the posterior as
the primary cause of multimodality, and design a method to tackle this type of
multimodality. The resulting posteriors have little structure and can be
sampled efficiently and robustly. We provide a Python package for parameter
estimation, cogwheel, that implements these methods together with other
algorithms for accelerating the inference process. One of the coordinates we
introduce is a spin azimuth that is measured remarkably well in several events.
We suggest this might be a sensitive indicator of orbital precession, and we
anticipate that it will shed light on the occurrence of spin-orbit misalignment
in nature.",2207.03508v2
2022-08-25,Incommensurate Magnetic Order in Hole-Doped Infinite-layer Nickelate Superconductors,"Magnetism and superconductivity are closely entangled, elucidating the
magnetic interactions in nickelate superconductors is at the heart of
understanding the pairing mechanism. Our first-principles and spin-wave theory
calculations highlight that NdNiO$_2$ is in the vicinity of a transition
between a quasi-two-dimensional (2D) antiferromagnetic (AFM) state and a
three-dimensional (3D) C-AFM state. Both states could accurately reproduce the
experimentally measured magnetic excitation spectra, which was previously
explained in terms of a 2D model. We further reveal that hole doping stabilizes
an incommensurate (IC) spin state and the IC wave vector increases
continuously. Direct links between hole doping, magnetization, exchange
constants, and magnetic order are established, revealing that the competition
between first-neighbor and third-neighbor in-plane magnetic interactions is the
key for the IC magnetic order.",2208.12200v3
2022-09-05,Widely-sweeping magnetic field-temperature phase diagrams for skyrmion-hosting centrosymmetric tetragonal magnets,"We numerically investigate the stabilization mechanisms of skyrmion crystals
under thermal fluctuations and external magnetic field in itinerant
centrosymmetric tetragonal magnets. By adopting an efficient steepest descent
method with a small computational cost, we systematically construct the
magnetic field-temperature phase diagrams of the effective spin model derived
from the itinerant electron model on a two-dimensional square lattice. As a
result, we find that a square-type skyrmion crystal is stabilized by either or
both of the high-harmonic wave-vector interaction and the biquadratic
interaction under an external magnetic field. Especially, we discover that the
former high-harmonic wave-vector interaction can stabilize the skyrmion crystal
only at finite temperatures when its magnitude is small. In addition to the
skyrmion crystal, we also find other stable multiple-$Q$ states in the phase
diagram. Lastly, we discuss the correspondence of the phase diagrams between
the effective spin model and the skyrmion-hosting material GdRu$_2$Si$_2$. The
present results suggest a variety of multiple-$Q$ states could be driven by
thermal fluctuations and external magnetic fields in centrosymmetric itinerant
magnets.",2209.01810v1
2022-09-15,BCS-BEC Crossover of Triplet Exciton Condensation in Bilayer Systems,"We study the BCS-BEC crossover phenomenon of triplet exciton condensation
using a half-filled bilayer Hubbard model. We calculate the dynamical spin
structure factor and the exciton wave function on the phase boundary between
the antiferromagnetically ordered and disordered phases. In the BCS regime, the
formation and condensation of particle-hole bound states, namely excitons,
occur simultaneously at the phase transition point, and the exciton wave
function is extended in real space. In the BEC regime, on the other hand, bound
states are well defined over the whole Brillouin zone also in the disordered
phase, and the size of particle-hole pairs is smaller than a lattice space.
Quantum criticality of charge-spin-orbital entangled states can emerge from
intermediate coupling materials in the crossover regime.",2209.07178v1
2022-09-21,Tailoring spin waves in 2D transition metal phosphorus trichalcogenides via atomic-layer substitution,"The family of two-dimensional (2D) van der Waals transition metal phosphorus
trichalcogenides has received a renewed interest due to their intrinsic 2D
antiferromagnetism, which proves them as unprecedented and highly tunable
building blocks for spintronics and magnonics at the single-layer limit.
Herein, motivated by the exciting potential of atomic-substitution demonstrated
in Janus transition metal dichalcogenides, we investigate the crystal,
electronic and magnetic structure of selenized Janus monolayers based on
MnPS$_3$ and NiPS$_3$ from first-principles. In addition, we calculate the
magnon dispersion and perform real-time real-space atomistic dynamic
simulations to explore the propagation of spin waves in MnPS$_3$, NiPS$_3$,
MnPS$_{1.5}$Se$_{1.5}$ and NiPS$_{1.5}$Se$_{1.5}$. Our calculations predict a
drastic enhancement of magnetic anisotropy and the emergence of large
Dzyaloshinskii-Moriya interactions, which arises from the induced broken
inversion symmetry in the 2D Janus layers. These results pave the way to the
development of Janus 2D transition metal phosphorus trichalcogenides and
highlight their potential for magnonic applications.",2209.10356v1
2022-09-21,Extracting Off-Diagonal Order from Diagonal Basis Measurements,"Quantum gas microscopy has developed into a powerful tool to explore strongly
correlated quantum systems. However, discerning phases with topological or
off-diagonal long range order requires the ability to extract these
correlations from site-resolved measurements. Here, we show that a multi-scale
complexity measure can pinpoint the transition to and from the bond ordered
wave phase of the one-dimensional extended Hubbard model with an off-diagonal
order parameter, sandwiched between diagonal charge and spin density wave
phases, using only diagonal descriptors. We study the model directly in the
thermodynamic limit using the recently developed variational uniform matrix
product states algorithm, and draw our samples from degenerate ground states
related by global spin rotations, emulating the projective measurements that
are accessible in experiments. Our results will have important implications for
the study of exotic phases using optical lattice experiments.",2209.10565v1
2022-10-06,Stacking order and interlayer coupling tuning the properties of charge density waves in layered 1T-NbSe_2,"Layered transition metal dichalcogenide 1T-NbSe_2 is a good candidate to
explore the charge density wave (CDW) and Mott physics. However, the effects of
stacking orders and interlayer coupling in CDW 1T-NbSe_2 are still less
explored and understood. Using density functional theory calculations, we
present a systematic study of the electronic and magnetic properties of
monolayer and layered CDW 1T-NbSe_2. Our results indicate that monolayer CDW
1T-NbSe_2 is a magnetic insulator with \sqrt13\times\sqrt13 periodic lattice
modulation. Nevertheless, the magnetic properties of bilayer CDWs 1T-NbSe_2 are
found stacking orders dependence. The mechanism is understood by the changes of
local magnetic moments in each layer due to spin charge transfer between
interlayers. Furthermore, the bulk CDW 1T-NbSe_2 opens a band gap with 0.02 eV
in 1\times 1 \times 2 supercell due to the interlayer spin coupling. We also
discover that the electronic structures of layered 1T-NbSe_2 show a strong
dependence on stacking configurations and dimensionality.",2210.02922v1
2022-10-27,Nodal pair-density-waves from quarter-metal in crystalline graphene multilayers,"Crystalline graphene heterostructures, namely Bernal bilayer and rhombohedral
trilayer graphene, subject to electric displacement fields, display a rich
confluence of competing orders, resulting in a valley-degenerate,
spin-polarized half-metal at moderate doping, and a spin- and valley-polarized
quarter-metal at low doping. Here we show that the annular Fermi surface of
such a quarter-metal can be susceptible toward the nucleation of a unique spin
and valley polarized superconducting state, accommodating interlayer Cooper
pairs that break the translational symmetry, giving rise to a Kekul\'e or
columnar pair-density-wave. The superconducting ground state produces isolated
Fermi pockets of neutral Majorana fermions, featuring a three-fold rotational
symmetry, resulting in power-law scaling physical observables with temperature
($T$), such as specific heat $C_v \sim T$.",2210.15660v1
2022-12-14,Ordered creation and motion of skyrmions with surface acoustic wave,"Magnetic skyrmions with a well-defined spin texture have shown unprecedented
potential for various spintronic applications owning to their topologically
non-trivial and quasiparticle properties. To put skyrmions into practical
technology, efficient manipulation, especially the inhibition of skyrmion Hall
effect (SkHE) has been intensively pursued. In spite of the recent progress
made on reducing SkHE in several substituted systems, such as ferrimagnets and
synthetic antiferromagnets, the organized creation and current driven motion of
skyrmions with negligible SkHE in ferromagnets remain challenging. Here, by
embeding the [Co/Pd] multilayer into a surface acoustic wave (SAW) delay line,
we experimentally realized the ordered generation of magnetic skyrmions. The
resultant current-induced skyrmions movement with negligible SkHE was observed,
which can be attributed to the energy redistribution of the system during the
excitation of SAW. Our findings open up an unprecedentedly new perspective for
manipulating topological solitons, and would advance the development of
skyrmionics and spin acousto-electronics.",2212.06997v1
2022-12-23,Extended relativistic kinetic model composed of the scalar and two vector distribution functions: Application to the spin-electron-acoustic waves,"Detailed deterministic derivation of the kinetic equations for the
relativistic plasmas is given. Focus is made on the dynamic of one-coordinate
distribution functions of various tensor dimensions, but the closed set of
kinetic equations is constructed of three functions: the scalar distribution
function, the vector distribution function of dipole moment, and the vector
distribution function of velocity (or the dipole moment in the momentum space).
All two-coordinate distributions functions are discussed as well. They are
presented together with their limits existing in the self-consistent field
approximation. The dynamics of the small amplitude spin-electron-acoustic waves
in the dense degenerate plasmas is are studied within the kinetic model. This
work presents the deterministic approach to the derivation and interpretation
of the kinetic equations. So, no probability is introduced during the
transition from the level of individual particles to the collective functions.
Problem of thermalization is not considered, but we can see that the structure
of kinetic equations is kept for the system before and after thermalization.
Hence, the kinetic equations can be used to approach this item.",2212.12525v2
2022-12-31,An implementation of the density functional perturbation theory in the PAW framework,"Quantifying materials' dynamical responses to external electromagnetic fields
is central to understanding their physical properties. Here we present an
implementation of the density functional perturbation theory for the
computation of linear susceptibilities using the projector augmented-wave
method. The Sternheimer equations are solved self-consistently through a nested
iterative procedure to compute the first-order wavefunctions, from which the
linear susceptibilities are obtained. As a demonstration, we compute the spin
wave spectral functions of two magnetic metals. The computed magnon spectra for
half-metallic CrO$_2$ and a Heusler intermetallic Cu$_2$MnAl show gapless
Goldstone modes when spin rotation symmetry is preserved and display reasonable
agreement with available experimental data. The Landau damping is computed to
be small in CrO$_2$, but significant in Cu$_2$MnAl producing an asymmetric
Lorentzian spectral lineshape. The access to linear susceptibilities as well as
first-order wavefunctions offers a range of novel possibilities in quantitative
understanding of materials' electronic properties from \textit{ab initio}
methods.",2301.00143v1
2023-02-10,Banks of templates for directed and all-sky narrow-band searches of continuous gravitational waves from spinning neutron stars with several spindowns,"We construct efficient banks of templates suitable for searches of continuous
gravitational waves from isolated spinning neutron stars. We assume that the
search algorithm is based on the time-domain maximum-likelihood
$\mathcal{F}$-statistic and we consider narrow-band searches with several
spindown parameters included. Our template banks are suitable for both all-sky
and directed searches and they enable the usage of the fast Fourier transform
in the computation of the $\mathcal{F}$-statistic as well as, in the case of
all-sky searches, efficient resampling of data to barycentric time.",2302.05204v2
2023-02-14,Omnipresent bound state of two holes in antiferromagnetic Bethe lattices,"For decades, it has remained an open question, whether two dopants in the
$t$--$J$ model bind in the strongly correlated regime of small spin couplings
versus hopping, $J \ll t$. Here, we investigate this problem in Bethe lattice
structures with Ising coupling $J_z$, and mainly focus on the case of a
coordination number equal to 4. The special geometry circumvents subtle effects
in regular lattices, but importantly still contains the non-trivial dependency
on the rotational symmetry and particle statistics. It, furthermore, allows us
to reach numerical convergence, and we conclusively answer whether binding
occurs or not. In particular, we find that the rotationally symmetric $s$ waves
unbind below $J_z \simeq 0.3 t$, which we unveil is tied to Pauli blocking of
symmetrical hole configurations. This is further substantiated by the fact that
holes in a bosonic spin environment shows strong -- superlinear -- binding at
low $J_z / t$. Additionally, higher rotational fermionic $p$ and $d$ waves
partially overcome the blocking, are perfectly degenerate, and bind for all
$J_z / t$. In the strongly correlated regime of $J_z \ll t$, this binding
occurs sublinearly with scaling $\sim t (J_z / t)^{3/2}$.",2302.07304v3
2023-02-27,The three-body scattering hypervolume of identical fermions in one dimension,"We study the zero-energy collision of three identical spin-polarized fermions
with short-range interactions in one dimension. We derive the asymptotic
expansions of the three-body wave function when the three fermions are far
apart or one pair and the third fermion are far apart, and the three-body
scattering hypervolume $D_F$ appears in the coefficients of such expansions. If
the two-body interaction is attractive and supports two-body bound states,
$D_F$ acquires a negative imaginary part related to the amplitudes of the
outgoing waves describing the departure of the resultant bound pair and the
remaining free fermion. For weak interaction potentials, we derive an
approximate formula of the hypervolume by using the Born expansion. For the
square-barrier and the square-well potentials and the Gaussian potential, we
solve the three-body Schr\""{o}dinger equation to compute $D_F$ numerically. We
also calculate the shifts of energy and of pressure of spin-polarized
one-dimensional Fermi gases due to a nonzero $D_F$ and the three-body
recombination rate in one dimension.",2302.13685v2
2023-02-27,Bayesian parameter estimation on boson-star binary signals with a coherent inspiral template and spin-dependent quadrupolar corrections,"Compact boson star binaries are hypothetical sources for ground-based and
space gravitational-wave detectors. Their signal would be a messenger for novel
fundamental fields and could shed light on the dark matter. In this work, we
further develop our analysis in Phys. Rev. D 102, 083002 (2020), aimed at
constraining the properties of these objects with future observations. We use a
coherent waveform template for the inspiral stage of boson star binaries with
large quartic self interactions, including tidal deformability and the
nonlinear dependence of the quadrupole moments on the spin in terms of the
fundamental couplings of the scalar field theory. Performing a Bayesian
analysis, we investigate the ability of a third-generation gravitational-wave
detector such as the Einstein Telescope to distinguish these exotic sources
from black holes and infer constraints on the fundamental couplings of the
model.",2302.13954v1
2023-03-02,Unidirectional Microwave Transduction with Chirality Selected Short-Wavelength Magnon Excitations,"Nonreciprocal magnon propagation has recently become a highly potential
approach of developing chip-embedded microwave isolators for advanced
information processing. However, it is challenging to achieve large
nonreciprocity in miniaturized magnetic thin-film devices because of the
difficulty of distinguishing propagating surface spin waves along the opposite
directions when the film thickness is small. In this work, we experimentally
realize unidirectional microwave transduction with sub-micron-wavelength
propagating magnons in a yttrium iron garnet (YIG) thin film delay line. We
achieve a non-decaying isolation of 30 dB with a broad field-tunable band-pass
frequency range up to 14 GHz. The large isolation is due to the selection of
chiral magnetostatic surface spin waves with the Oersted field generated from
the coplanar waveguide antenna. Increasing the geometry ratio between the
antenna width and YIG thickness drastically reduces the nonreciprocity and
introduces additional magnon transmission bands. Our results pave the way for
on-chip microwave isolation and tunable delay line with short-wavelength
magnonic excitations.",2303.00936v1
2023-03-03,Spin-wave Resonance in Arrays of Nanoscale Synthetic-antiferromagnets,"The study concerns dynamics of standing spin waves in arrays of sub-100 nm
elliptic synthetic-antiferromagnet (SAF) nanodisks. We performed a detailed
ferromagnetic resonance analysis in conjunction with micromagnetic modeling to
find out several prominent traits of such systems. One broad line is shown to
be the sole resonant response for a SAF of the considered sizes. We demonstrate
that this mode is degenerated, and its excitation map resembles a superposition
of in-center and edge-type oscillations. We also show how this hybrid
excitation leads to almost twofold enhancement in the shape-induced anisotropy
of the mode.",2303.01919v1
2023-04-17,Ultrafast Relaxation Dynamics of Spin-Density Wave Order in BaFe$_2$As$_2$ under High Pressures,"BaFe$_2$As$_2$ is the parent compound for a family of iron-based
high-temperature superconductors as well as a prototypical example of the
spin-density wave (SDW) system. In this study, we perform an optical pump-probe
study of this compound to systematically investigate the SDW order across the
pressure-temperature phase diagram. The suppression of the SDW order by
pressure manifests itself by the increase of relaxation time together with the
decrease of the pump-probe signal and the pump energy necessary for complete
vaporization of the SDW condensate. We have found that the pressure-driven
suppression of the SDW order at low temperature occurs gradually in contrast to
the thermally-induced SDW transition. Our results suggest that the
pressure-driven quantum phase transition in BaFe$_2$As$_2$ (and probably other
iron pnictides) is continuous and it is caused by the gradual worsening of the
Fermi-surface nesting conditions.",2304.08080v1
2023-04-17,Probing the solar interior with lensed gravitational waves from known pulsars,"When gravitational waves (GWs) from a spinning neutron star arrive from
behind the Sun, they are subjected to gravitational lensing that imprints a
frequency-dependent modulation on the waveform. This modulation traces the
projected solar density and gravitational potential along the path as the Sun
passes in front of the neutron star. We calculate how accurately the solar
density profile can be extracted from the lensed GWs using a Fisher analysis.
For this purpose, we selected three promising candidates (the highly spinning
pulsars J1022+1001, J1730-2304, and J1745-23) from the pulsar catalog of the
Australia Telescope National Facility. The lensing signature can be measured
with $3 \sigma$ confidence when the signal-to-noise ratio (SNR) of the GW
detection reaches $100 \, (f/300 {\rm Hz})^{-1}$ over a one-year observation
period (where $f$ is the GW frequency). The solar density profile can be
plotted as a function of radius when the SNR improves to $\gtrsim 10^4$.",2304.08220v3
2023-05-09,Magnon dispersion in ferromagnetic SrRuO$_3$,"The magnetic excitations in ferromagnetic SrRuO$_3$ were studied by inelastic
neutron scattering combining experiments on triple-axis and time-of-flight
spectrometers with and without polarization analysis. A quadratic spin-wave
dispersion with an anisotropy gap describes the low-energy low-temperature
response. The magnon dispersion extends to at least 35 meV and there is no
direct evidence for a continuum of Stoner excitations below this energy.
However, the magnon response is weakened at higher energy. In addition to the
anomalous softening of the spin-wave stiffness and of the gap, which is induced
by the topology of the Bloch states, the magnon excitations are broadened in
energy and this effect increases upon heating.",2305.05497v1
2023-05-10,Investigation of Spin-Wave Dynamics in Gyroid Nanostructures,"A new concept in magnonics studies the dynamics of spin waves (SWs) in
three-dimensional nanosystems. It is a natural evolution from conventionally
used planar systems to explore magnetization configurations and dynamics in 3D
nanostructures with lengths near intrinsic magnetic scales. In this work, we
perform broadband ferromagnetic resonance (BBFMR) measurements and
micromagnetic simulations of nanoscale magnetic gyroids - a periodic chiral
structure consisting entirely of chiral triple junctions. Our results show
unique properties of the network, such as the localization of the SW modes,
evoking their topological properties, and the substantial sensitivity to the
direction of the static magnetic field. The presented results open a wide range
of applications in the emerging field of 3D magnonic crystals and spintronics.",2305.06319v2
2023-05-11,First-order phase transition between superconductivity and charge/spin-density wave as the reason of their coexistence in organic metals,"The interplay between superconductivity (SC) and spin/charge density wave
(DW) in organic metals shows many similarities to high-$T_c$ superconductors.
It also contains many puzzles, for example, the anisotropic SC onset observed
and the severalfold increase of the upper critical field $H_{c2}$ in the
coexistence region, as well as the microscopic origin of SC/DW phase separation
there. In this paper, by the direct calculation of the Landau expansion for DW
free energy, we argue that the phase transition between DW and metallic/SC
phase in organic superconductors goes by first order at low enough temperature,
which explains the spatial segregation of DW and SC at large length scale,
consistent with experimental observations. This first-order phase transition is
not directly related to SC and happens even above the SC transition
temperature.",2305.06957v1
2023-05-16,Sublattice Pairing in Pyrochlore Heisenberg Antiferromagnets,"We argue that classical pyrochlore Heisenberg antiferromagnets with small
further-neighbor couplings can order in a state where pairs of sublattices form
antiparallel spirals. The spiral ordering wave vectors of the two pairs are in
general different from each other, and are constrained by which sublattices are
being paired. This sublattice pairing state generally breaks inversion and most
rotation symmetries. Its existence depends on the antiferromagnetic
nearest-neighbor coupling which favors the spins on each tetrahedron to sum to
zero. To substantiate our argument, we extend the nematic bond theory; a
diagrammatic large-$N_s$ method, to non-Bravais lattices, and we demonstrate
that the predicted state is indeed realized at low temperatures in a large
region of exchange coupling space. We also carry out a spin wave calculation
which suggests that the sublattice pairing state is coplanar.",2305.09409v2
2023-06-16,"Quantifying the spin-wave asymmetry in single and double rectangular Ni$_{80}$Fe$_{20}$ microstrips by TR-STXM, FMR and micromagnetic simulations","The asymmetry of spin-wave patterns in confined rectangular
Ni$_{80}$Fe$_{20}$ microstrips, both in single and double-strip geometries, is
quantified. The results of TR-STXM and micromagnetic simulations are compared.
For the TR-STXM measurements and the corresponding simulations the excitation
was a uniform microwave field with a fixed frequency of 9.43 GHz, while the
external static magnetic field was swept. In the easy axis orientation of the
analyzed microstrip, the results show a higher asymmetry for the double
microstrip design, indicating an influence of the additional microstrip placed
in close proximity to the analyzed one.",2306.09881v1
2023-07-04,Two-dimensional simulation of the spin-flip in the Kapitza-Dirac effect,"Many calculations in strong field quantum field theory are carried out by
using a simple field geometry, often neglecting the spacial field envelope. In
this article, we simulate the electron diffraction quantum dynamics of the
Kapitza-Dirac effect in a Gaussian beam standing light wave. The
two-dimensional simulation is computed in a relativistic framework, by solving
the Dirac equation with the fast Fourier transform split operator method.
Except the numerical propagation method, our results are obtained without
applying approximations and demonstrate that a spin-flip in the Kapitza-Dirac
effect is possible. We further discuss properties, such as the validity of a
plane wave approach for the theoretical description, the influence of the
longitudinal polarization component due to laser beam focusing and higher order
diffraction peaks in Kapitza-Dirac scattering.",2307.01571v2
2023-07-07,Swarm-intelligent search for gravitational waves from eccentric binary mergers,"We implement an eccentric search for compact binary mergers based on particle
swarm optimization. Orbital eccentricity is an invaluable input for
understanding the formation scenarios of the binary mergers and can play a
pivotal role in finding their electromagnetic counterparts. Current modelled
searches rely on pre-computed template banks that are computationally expensive
and resistant towards expanding the search parameter space dimensionality. On
the other hand, particle swarm optimization offers a straightforward algorithm
that dynamically selects template points while exploring an arbitrary
dimensional parameter space. Through extensive evaluation using simulated
signals from spin-aligned eccentric binary mergers, we discovered that the
search exhibits a remarkable autonomy in capturing the effects of both
eccentricity and spin. We describe our search pipeline and revisit some of the
merger candidates from the gravitational wave transient catalogs.",2307.03736v3
2023-08-17,The Quantum Waves of Minkowski Spacetime And The Minimal Acceleration From Precanonical Quantum Gravity,"We construct the simplest solutions of the previously obtained precanonical
Schr\""odinger equation for quantum gravity, which correspond to the plane waves
on the spin connection bundle and reproduce the Minkowski spacetime on average.
Quantum fluctuations lead to the emergence of the minimal acceleration $a_0$
related to the range of the Yukawa modes in the fibers of the spin connection
bundle. This minimal acceleration is proportional to the square root of the
cosmological constant $\Lambda$ generated by the operator re-ordering in the
precanonical Schr\""odinger equation. Thus the mysterious connection between the
minimal acceleration $a_0$ in the dynamics of galaxies as described by
Milgrom's MOND and the cosmological constant emerges as an elementary effect of
precanonical quantum gravity. We also argue that the observable values of $a_0$
and $\Lambda$ can be obtained when the scale of the parameter $\varkappa$
introduced by precanonical quantization is subnuclear, in agreement with the
previously established connection between the scale of $\varkappa$ and the mass
gap in quantum SU(2) Yang-Mills theory.",2308.08738v1
2023-08-24,Black-hole mergers in disklike environments could explain the observed $q$-$χ_\mathrm{eff}$ correlation,"Current gravitational-wave data from stellar-mass black-hole binary mergers
suggest a correlation between the binary mass ratio $q$ and the effective spin
$\chi_\mathrm{eff}$: more unequal-mass binaries consistently show larger and
positive values of the effective spin. Multiple generations of black-hole
mergers in dense astrophysical environments may provide a way to form
unequal-mass systems, but they cannot explain the observed correlation on their
own. We show that the symmetry of the astrophysical environment is a crucial
feature to shed light on this otherwise puzzling piece of observational
evidence. We present a toy model that reproduces, at least qualitatively, the
observed correlation. The model relies on axisymmetric, disk-like environments
where binaries participating in hierarchical mergers share a preferential
direction. Migration traps in AGN disks are a prime candidate for this setup,
hinting at the exciting possibility of constraining their occurrence with
gravitational-wave data.",2308.12998v2
2023-08-28,Proof-of-principle demonstration of temporally multiplexed quantum repeater link based on atomic ensemble,"Duan-Lukin-Cirac-Zoller quantum repeater protocol provides a feasible scheme
to implement long-distance quantum communication and large-scale quantum
networks. The elementary link, namely the entanglement between two atomic
ensembles, is a fundamental component of quantum repeater. For practical
quantum repeater, it is required that the elementary link can be prepared with
high yield and the spin waves stored in atoms can be efficiently converted into
photons on demand. However, so far, such quantum repeater link has not been
demonstrated in experiments. Here, we demonstrate a proof-of-principle
multiplexed quantum repeater link by entangling two temporally multiplexed
quantum memory. Compared with a single-mode link, the successful preparation
rate of the multiplexed link is increased by one order of magnitude. By using
the cavity-enhanced scheme, the on-demand retrieval efficiency of atomic spin
waves is improved to 70%, which is beneficial for the subsequent entanglement
swapping between adjacent links. The realization of temporally multiplexed
quantum repeater link with high retrieval efficiency lays a foundation for the
development of practical quantum networks.",2308.14587v1
2023-08-28,Spin-wave spectral analysis in crescent-shaped ferromagnetic nanorods,"The research on the properties of spin waves (SWs) in three-dimensional
nanosystems is an innovative idea in the field of magnonics. Mastering and
understanding the nature of magnetization dynamics and binding of SWs at
surfaces, edges, and in-volume parts of three-dimensional magnetic systems
enables the discovery of new phenomena and suggests new possibilities for their
use in magnonic and spintronic devices. In this work, we use numerical methods
to study the effect of geometry and external magnetic field manipulations on
the localization and dynamics of SWs in crescent-shaped (CS) waveguides. It is
shown that changing the magnetic field direction in these waveguides breaks the
symmetry and affects the localization of eigenmodes with respect to the static
demagnetizing field. This in turn has a direct effect on their frequency.
Furthermore, CS structures were found to be characterized by significant
saturation at certain field orientations, resulting in a cylindrical
magnetization distribution. Thus, we present chirality-based nonreciprocal
dispersion relations for high-frequency SWs, which can be controlled by the
field direction (shape symmetry) and its amplitude (saturation).",2308.14678v1
2023-09-06,Shaping magnetization dynamics in a planar square dot by adjusting its surface anisotropy,"A planar square dot is one of the simplest structures confined to three
dimensions. Despite its geometrical simplicity, the description of the spin
wave modes in this structure is not trivial due to the competition of dipolar
and exchange interactions. An additional factor that makes this description
challenging are the boundary conditions depend both on non-local dipolar
interactions and local surface parameters such as surface anisotropy. In the
presented work, we showed how the surface anisotropy applied at the lateral
faces of the dot can tune the frequency of fundamental mode in the planar CoFeB
dot, magnetized in an out-of-plane direction. Moreover, we analyzed the spin
wave profile of the fundamental mode and the corresponding dynamic stray field.
We showed that the asymmetric application of surface anisotropy produces an
asymmetric profile of dynamic stray field for square dot and can be used to
tailor inter-dot coupling. The calculations were performed with the use of the
finite-element method.",2309.02984v1
2023-09-12,Spin-polarized ${}^3$He shock waves from a solid-gas composite target at high laser intensities,"We investigate Collisionless Shock Acceleration of spin-polarized ${}^3$He
for laser pulses with normalized vector potentials in the range $a_0 =
100-200$. The setup utilized in the 2D-PIC simulations consists of a solid
Carbon foil that is placed in front of the main Helium target. The foil is
heated by the laser pulse and shields the Helium from the highly oscillating
fields. In turn, a shock wave with more homogeneous fields is induced, leading
to highly polarized ion beams. We observe that the inclusion of radiation
reaction into our simulations leads to a higher beam charge without affecting
the polarization degree to a significant extent.",2309.06271v2
2023-09-13,Handwritten Digit Recognition by Spin Waves in a Skyrmion Reservoir,"By performing numerical simulations for the handwritten digit recognition
task, we demonstrate that a magnetic skyrmion lattice confined in a thin-plate
magnet possesses high capability of reservoir computing. We obtain a high
recognition rate of more than 88%, higher by about 10% than a baseline taken as
the echo state network model. We find that this excellent performance arises
from enhanced nonlinearity in the transformation which maps the input data onto
an information space with higher dimensions, carried by interferences of spin
waves in the skyrmion lattice. Because the skyrmions require only application
of static magnetic field instead of nanofabrication for their creation in
contrast to other spintronics reservoirs, our result consolidates the high
potential of skyrmions for application to reservoir computing devices.",2309.06815v1
2023-09-28,FeGe1-xSbx:a series of novel kagome metals with noncollinear antiferromagnetism,"Kagome metals are important for exploring emergent phenomena due to the
interplay between band topology and electron correlation.Motivated by the
recent discovery of charge density wave in a kagome lattice antiferromagnetic
FeGe,we investigate the impact of Sb doping on the structural,charge and
magnetic order of FeGe.The charge density wave is rapidly suppressed by Sb
doping(~1.5%) and the antiferromagnetic ordering temperature gradually shifts
to 280K for FeGe0.7Sb0.3.For FeGe1-xSbx with x>0.1,crystal structures with
slightly distorted Fe kagome lattice are formed.Their magnetic anisotropy has
significant change,temperature driven spin-reorientation and field-induced
spin-flop transition are identified from magnetization
measurement.Interestingly,neutron diffraction reveals noncollinear
antiferromagnetic structures widely exist below TN for all sample with
x>0.1.This noncollinear magnetic orders could possibly be unconventional and
resulted from onsite repulsion and filling condition of kagome flat band,as
predicted by a recent theoretical work.",2309.16502v3
2023-11-26,Gravitational wave fluxes on generic orbits in Kerr spacetime: higher spin and large eccentricity,"To obtain the waveform template of gravitational waves (GWs), substantial
computational resources and exceedingly high precision are often required. In
the previous study [JCAP 11 (2023) 070], we efficiently and accurately
calculate GW fluxes of a particle in circular orbits around a Schwarzschild
black hole using the confluent Heun function. We extend the previous method to
calculate the asymptotic GW fluxes from a particle in generic orbits around a
Kerr black hole. Especially when dealing with the computational difficulties in
large eccentricity $e=0.9$, higher spin $a=0.999$, higher harmonic modes and
strong-field regions, our results are much better than the high-order
post-Newtonian results and comparable to the results of the
Mano-Suzuki-Takasugi method. Using the grid data of the asymptotic GW fluxes,
we give the adiabatic waveform of non-rotating black holes, which agrees well
with the waveforms of numerical relativity.",2311.15295v1
2023-11-29,Real-space Visualization of Charge Density Wave Induced Local Inversion-Symmetry Breaking in a Skyrmion Magnet,"Intertwining charge density wave (CDW) with spin and pairing order parameters
is a major focus of contemporary condensed matter physics. Lattice distortions
and local symmetry breaking resulted from CDWs are crucial for the emergence of
correlated and topological states in quantum materials in general. While the
presence of CDWs can be detected by diffraction or spectroscopic techniques,
atomic visualization of the CDW induced lattice distortions remains limited to
CDW with short wavelengths. In this letter, we realized the imaging of
incommensurate long-wavelength CDWs based on cryogenic four-dimensional
scanning transmission electron microscopy (cryo-4DSTEM). By visualizing the
incommensurate CDW induced lattice modulations in a skyrmion magnet EuAl4, we
discover two out-of-phase intra-unit cell shear modulations that specifically
break the local inversion-symmetry. Our results provide direct evidence for the
intertwined spin and charge orders in EuAl4 and key information about local
symmetry. Furthermore, we establish cryo-4DSTEM as an indispensable approach to
understand CDW induced new quantum states of matter.",2311.17682v1
2023-12-10,Black Hole Perturbation Theory Meets CFT$_2$: Kerr Compton Amplitudes from Nekrasov-Shatashvili Functions,"We present a novel study of Kerr Compton amplitudes in a partial wave basis
in terms of the Nekrasov-Shatashvili (NS) function of the \textit{confluent
Heun equation} (CHE). Remarkably, NS-functions enjoy analytic properties and
symmetries that are naturally inherited by the Compton amplitudes. Based on
this, we characterize the analytic dependence of the Compton phase-shift in the
Kerr spin parameter and provide a direct comparison to the standard
post-Minkowskian (PM) perturbative approach within General Relativity (GR). We
also analyze the universal large frequency behavior of the relevant
characteristic exponent of the CHE -- also known as the renormalized angular
momentum -- and find agreement with numerical computations. Moreover, we
discuss the analytic continuation in the harmonics quantum number $\ell$ of the
partial wave, and show that the limit to the physical integer values commutes
with the PM expansion of the observables. Finally, we obtain the contributions
to the tree level, point-particle, gravitational Compton amplitude in a
covariant basis through $\mathcal{O}(a_{\text{BH}}^8)$, without the need to
take the super-extremal limit for Kerr spin.",2312.05965v1
2023-12-12,Interacting Floquet topological magnons in laser-irradiated Heisenberg honeycomb ferromagnets,"When a Heisenberg honeycomb ferromagnet is irradiated by high frequency
circularly polarized light, the underlying uncharged magnons acquire a time
dependent Aharonov Casher phase, which makes it a Floquet topological magnon
insulator. In this context, we investigate the many body interaction effects of
Floquet magnons in laser irradiated Heisenberg honeycomb ferromagnets with
ocontaining Dzyaloshinskii Moriya interaction under the application of
circularly polarized off resonant light. We demonstrate that the quantum
ferromagnet systems periodically laser driven exhibits temperature driven
topological phase transitions due to Floquet magnon magnon interactions. The
thermal Hall effect of Floquet magnons serves as a prominent signature for
detecting these many body effects near the critical point, enabling
experimental investigation into this phenomenon. Our study complements the lack
of previous theoretical works that the topological phase transition of the
Floquet magnon under the linear spin wave approximation is only tunable by the
light field. Our study presents a novel approach for constructing Floquet
topological phases in periodically driven quantum magnet systems that goes
beyond the limitations of the linear spin wave theory. We provide numerical
results based on the well known van der Waals quantum magnet CrX3 (X=F, Cl, Br,
and I), calling for experimental implementation.",2312.06929v1
2023-12-20,Spin wave confinement in hybrid superconductor-ferrimagnet nanostructure,"Eddy currents in a superconductor shield the magnetic field in its interior
and are responsible for the formation of a magnetic stray field outside of the
superconducting structure. The stray field can be controlled by the external
magnetic field and affect the magnetization dynamics in the magnetic system
placed in its range. In the case of a hybrid system consisting of a
superconducting strip placed over a magnetic layer, we predict theoretically
the confinement of spin waves in the well of the static stray field. The number
of bound states and their frequencies can be controlled by an external magnetic
field. We have presented the results of semi-analytical calculations
complemented by numerical modeling.",2312.13029v1
2024-01-20,Inferring binary parameters with dual-line gravitational wave detection from tight inspiraling double neutron stars,"Neutron star (NS) binaries can be potentially intriguing gravitational wave
(GW) sources, with both high- and low-frequency radiations from the possibly
aspherical individual stars and the binary orbit, respectively. The successful
detection of such a dual-line source could provide fresh insights into binary
geometry and NS physics. In the absence of electromagnetic observations, we
develop a strategy for inferring the spin-orbit misalignment angle using the
tight dual-line double NS system under the spin-orbit coupling. Based on the
four-year joint detection of a typical dual-line system with LISA and Cosmic
Explorer, we find that the misalignment angle and the NS moment of inertia can
be measured with sub-percentage and 5% accuracy, respectively.",2401.11241v1
2024-01-22,Spin Wave Threshold Gate,"While Spin Waves (SW) interaction provides natural support for low power
Majority (MAJ) gate implementations many hurdles still exists on the road
towards the realization of practically relevant SW circuits. In this paper we
leave the SW interaction avenue and propose Threshold Logic (TL) inspired SW
computing, which relies on successive phase rotations applied to one single SW
instead of on the interference of an odd number of SWs. After providing a short
TL inside we introduce the SW TL gate concept and discuss the way to mirror TL
gate weight and threshold values into physical phase-shifter parameters.
Subsequently, we design and demonstrate proper operation of a SW TL based Full
Adder (FA) by means of micro-magnetic simulations. We conclude the paper by
providing inside on the potential advantages of our proposal by means of a
conceptual comparison of MAJ and TL based FA implementations.",2401.12136v1
2024-01-22,The Crossover from Ordinary to Higher-Order van Hove Singularity in a Honeycomb System: A Parquet Renormalization Group Analysis,"We investigate the crossover from an ordinary van Hove singularity (OVHS) to
a higher order van Hove singularity (HOVHS) in a model applicable to Bernal
bilayer graphene and rhombohedral trilayer graphene in a displacement field. At
small doping, these systems possess three spin-degenerate Fermi pockets near
each Dirac point $K$ and $K'$; at larger doping, the three pockets merge into a
single one. The transition is of Lifshitz type and includes van Hove
singularities. Depending on system parameters, there are either 3 separate OVHS
or a single HOVHS. We model this behavior by a one-parameter dispersion
relation, which interpolates between OVHS and HOVHS. In each case, the
diverging density of states triggers various electronic orders
(superconductivity, pair density wave, valley polarization, ferromagnetism,
spin and charge density wave). We apply the parquet renormalization group (pRG)
technique and analyze how the ordering tendencies evolve between OVHS and
HOVHS. We report rich system behavior caused by disappearance/reemergence and
pair production/annihilation of the fixed points of the pRG flow.",2401.12384v1
2024-01-26,Fragmented Condensate in a Two-Component Bose Gas with $p$-wave Interactions,"In this Letter, we discuss the effects of $p$-wave attractive interaction in
a spin-$1/2$ Bose gas. With a repulsive $s$-wave background interaction, we
show that for weak $p$-wave attraction, one obtains a standard Bose-Einstein
condensate at zero momentum with spins fully polarized. Upon increasing the
$p$-wave attraction, a fragmented condensate state with singlet pair formation
and $p$-wave correlation emerges. We determine the transition point and
investigate the properties of the fragmented condensate using an ansatz wave
function. We construct the relevant Gross-Pitaevskii equations for the
fragmented condensate and show that the sound velocities are anisotropic and
may vanish in specific directions. Based on the many-body wave function, we
also discuss the low-energy spin excitations of the system.",2401.14751v1
2024-01-09,Non-Divergent Spinning Substructures Near Acoustic Field Nodes,"In this work, we examine the extraordinary behavior of polarization and spin
angular momentum (AM) density in the vicinity of longitudinal field zeros in
three-dimensional monochromatic acoustic fields. We demonstrate that, as
governed by the continuity equation, the velocity fields of arbitrary acoustic
sources maintain non-diffractive elliptical polarization structures that
enclose longitudinal field zeros, despite having divergent transverse spatial
profiles of intensity. Furthermore, embedded in these nonparaxial field
contours, for infinite distance, are threads of circular polarization
singularities. We illuminate these inherent properties in acoustic vortex
fields, dipole arrays, and the famous Young's double slit experiment. Our
results reveal novel characteristics of vector sound waves that provide a
platform for future studies and applications of structured acoustic waves and
chiral acoustic phenomena.",2402.00873v1
2024-02-07,Breaking surface plasmon excitation constraint via surface spin waves,"Surface plasmons in two-dimensional (2D) electron systems have attracted
great attention for their promising light-matter applications. However, the
excitation of a surface plasmon, in particular, transverse-electric (TE)
surface plasmon, remains an outstanding challenge due to the difficulty to
conserve energy and momentum simultaneously in the normal 2D materials. Here we
show that the TE surface plasmons ranging from gigahertz to terahertz regime
can be effectively excited and manipulated in a hybrid dielectric, 2D material
and magnet structure. The essential physics is that the surface spin wave
supplements an additional freedom of surface plasmon excitation and thus
greatly enhances the electric field in the 2D medium. Based on widely-used
magnetic materials like yttrium iron garnet (YIG) and manganese difluoride
($\mathrm{MnF}_2$), we further show that the plasmon excitation manifests
itself as a measurable dip in the reflection spectrum of the hybrid system
while the dip position and the dip depth can be well controlled by the electric
gating on the 2D layer and an external magnetic field. Our findings should
bridge the fields of low-dimensional physics, plasmonics and spintronics and
open a novel route to integrate plasmonic and spintronic devices.",2402.04626v1
2024-02-07,Spin-Wave-Assisted Thermal Reversal of Epitaxial Perpendicular Magnetic Nanodots,"The magnetic susceptibility of self-organized two-dimensional Co nanodots on
Au(111) has been measured as a function of their size in the 2-7~nm diameter
range. We show that the activation energy for the thermal reversal displays a
power law behavior with the dot volume. Atomic scale simulations based on the
Heisenberg hamiltonian show that this behavior is due to a deviation from the
macrospin model for dot size as small as 3~nm in diameter. This discrepancy is
attributed to finite temperature effects through the thermal excitation of
spin-wave modes inside the particles",2402.04903v1
2024-02-09,Long-lived collective Rydberg excitations in atomic gas achieved via ac-Stark lattice modulation,"Collective Rydberg excitations provide promising applications ranging from
quantum information processing, and quantum computing to ultra-sensitive
electrometry. However, their short lifetime is an immense obstacle in real-life
scenarios. The state-of-the-art methods of prolonging the lifetime were mainly
implemented for ground-state quantum memories and would require a redesign to
effectively work on different atomic transitions. We propose a protocol for
extending the Rydberg excitation lifetime, which in principle can freeze the
spin-wave and completely cancel the effects of thermal dephasing. The protocol
employs off-resonant ac-Stark lattice modulation of spin waves by interfering
two laser beams on the atomic medium. Our implementation showed that the
excitation lifetime can be extended by an order of magnitude, paving the way
towards more complex protocols for collective Rydberg excitations.",2402.06513v2
2024-02-21,Itinerant magnetism and magnetic polarons in the triangular lattice Hubbard model,"We use density matrix renormalization group to investigate the phase diagram
of the Fermi Hubbard model on a triangular lattice with densities above
half-filling, $1 \leq n < 2$. We discuss the important role of kinetic
magnetism and magnetic polarons. For strong interactions and low doublon
dopings, attractive interaction between polarons results in phase separation
between the fully polarized state at finite doping and the commensurate
spin-density wave state at half-filling. For intermediate interaction strength
and small doping, competition between antiferromagnetic superexchange and
kinetic magnetism gives rise to the incommensurate spin density wave (I-SDW)
phase. Fully polarized ferromagnetic (FPF) phase for weak interactions is
limited to dopings close to the van Hove singularity in the density of states.
With increasing interactions the FPF phase expands to lower dopings. For strong
interactions it reaches the low doping regime and is better understood as
arising from proliferation of Nagaoka-type ferromagnetic polarons. Other phases
that we find include a partially polarized phase, another type of I-SDW at high
densities, and M\""uller-Hartmann ferromagnetism close to the band insulating
regime.",2402.14074v1
2024-03-25,Rotational Doppler Effect and Spin-Rotation Coupling,"The Rotational Doppler Effect (RDE) involves both the orbital angular
momentum of electromagnetic radiation as well as its helicity. The RDE
phenomena associated with photon helicity go beyond the standard theory of
relativity. The purpose of this paper is to elucidate the theoretical basis of
the helicity-dependent RDE in terms of the general phenomenon of spin-rotation
coupling. The physical implications of this coupling are briefly pointed out
and the nonlocal theory of rotating observers is described. For an observer
rotating uniformly about the direction of incidence of a plane wave of definite
helicity, the nonlocally measured amplitude of the wave is larger (smaller) if
the observer rotates in the same (opposite) sense as the electromagnetic field.
The implications of the nonlocal helicity dependence of the measured amplitude
of the radiation are briefly discussed.",2403.17151v1
2024-04-02,Tunability of charge density wave in a magnetic kagome metal,"The discovery of the charge density wave order (CDW) within a magnetically
ordered phase in the kagome lattice FeGe has provided a promising platform to
investigate intertwined degrees of freedom in kagome lattices. Recently, a
method based on post-annealing has been suggested to manipulate the CDW order
in kagome FeGe towards either long-range or suppressed orders. Here, we provide
a comprehensive comparison of the experimentally measured electronic structures
of FeGe crystals that have undergone different post-annealing procedures and
demonstrate the remarkable effectiveness on tuning the CDW gap without strong
perturbation on the underlying electronic structure. Moreover, we observe an
additional low temperature transition that only appears in crystals with a
long-range CDW order, which we associate with a lattice-spin coupled order. Our
work indicates a likely strong sensitivity of the CDW order to disorder in
FeGe, and provides evidence for strong coupling between the electronic,
lattice, and spin degrees of freedom in this kagome magnet.",2404.02231v1
2024-04-04,Optomagnetism with plasmonic skyrmion,"Research at the frontier between optics and magnetism is revealing a wealth
of innovative phenomena and avenues of exploration. Optical waves are
demonstrating the capacity to induce ultrafast magnetism, while optical analogs
of magnetic states, such as magnetic skyrmions, offer the prospect of novel
spin-optical states. In this paper, we strengthen the synergy between light and
magnetism by exploring the ability of plasmonic Neel skyrmions to create a
stationary magnetic field within a thin gold film. We show that, when generated
using a focused radially-polarized vortex beam, a plasmonic Neel skyrmion
emerges as an optimum for inducing optomagnetism in a thin gold film. Optical
skyrmions offer new degrees of freedom for enhancing and controlling
optomagnetism in plasmonic nanostructures, with direct application in
all-optical magnetization switching, magnetic recording, and the excitation of
spin waves.",2404.03738v1
2024-04-12,Probing spontaneously symmetry-broken phases with spin-charge separation through noise correlation measurements,"Spontaneously symmetry-broken (SSB) phases are locally ordered states of
matter characterizing a large variety of physical systems. Because of their
specific ordering, their presence is usually witnessed by means of local order
parameters. Here, we propose an alternative approach based on statistical
correlations of noise after the ballistic expansion of an atomic cloud. We
indeed demonstrate that probing such noise correlators allows one to
discriminate among different SSB phases characterized by spin-charge
separation. As a particular example, we test our prediction on a 1D extended
Fermi-Hubbard model, where the competition between local and nonlocal couplings
gives rise to three different SSB phases: a charge density wave, a
bond-ordering wave, and an antiferromagnet. Our numerical analysis shows that
this approach can accurately capture the presence of these different SSB
phases, thus representing an alternative and powerful strategy to characterize
strongly interacting quantum matter.",2404.08374v1
2000-09-15,"Muon Spin Relaxation Study of (La, Ca)MnO3","We report predominantly zero field muon spin relaxation measurements in a
series of Ca-doped LaMnO_3 compounds which includes the colossal
magnetoresistive manganites. Our principal result is a systematic study of the
spin-lattice relaxation rates 1/T_1 and magnetic order parameters in the series
La_{1-x}Ca_xMnO_3, x = 0.0, 0.06, 0.18, 0.33, 0.67 and 1.0. In LaMnO_3 and
CaMnO_3 we find very narrow critical regions near the Neel temperatures T_N and
temperature independent 1/T_1 values above T_N. From the 1/T_1 in LaMnO_3 we
derive an exchange integral J = 0.83 meV which is consistent with the mean
field expression for T_N. All of the doped manganites except CaMnO_3 display
anomalously slow, spatially inhomogeneous spin-lattice relaxation below their
ordering temperatures. In the ferromagnetic (FM) insulating
La_{0.82}Ca_{0.18}MnO_3 and ferromagnetic conducting La_{0.67}Ca_{0.33}MnO_3
systems we show that there exists a bi-modal distribution of \muSR rates
\lambda_f and \lambda_s associated with relatively 'fast' and 'slow' Mn
fluctuation rates, respectively. A physical picture is hypothesized for these
FM phases in which the fast Mn rates are due to overdamped spin waves
characteristic of a disordered FM, and the slower Mn relaxation rates derive
from distinct, relatively insulating regions in the sample. Finally, likely
muon sites are identified, and evidence for muon diffusion in these materials
is discussed.",0009242v1
2000-10-25,Spin and charge dynamics of the ferromagnetic and antiferromagnetic two-dimensional half-filled Kondo lattice model,"We present a detailed numerical study of spin and charge dynamics of the
two-dimensional Kondo lattice model with hopping t and exchange J. At T=0 and J
> 0, the competition between the RKKY interaction and Kondo effect triggers a
quantum phase transition between magnetically ordered and disordered
insulators: J_c/t = 1.45(5). The quasiparticle gap scales as |J|. S(q,\omega),
evolves smoothly from its strong coupling form with spin gap at q = (\pi,\pi)
to a spin wave form. At J>0, A(\vec{k},\omega) shows a dispersion relation
following that of hybridized bands. For J < J_c this feature is supplemented by
shadows thus pointing to a coexistence of Kondo screening and magnetism. For J
< 0 A(\vec{k},\omega) is similar to that of non-interacting electrons in a
staggered magnetic field. Spin, T_S, and charge, T_C, scales are defined. For
weak to intermediate couplings, T_S marks the onset of antiferromagnetic
fluctuations and follows a J^2 law. At strong couplings T_S scales as J. T_C
scales as J both at weak and strong couplings. At and slightly below T_C we
observe i) a rise in the resistivity as a function of decreasing temperature,
ii) a dip in the integrated density of states at the Fermi energy and iii) the
occurrence of hybridized bands in A(k,\omega). It is shown that in the weak
coupling limit, the charge gap of order J is of magnetic origin. The specific
heat shows a two peak structure, the low temperature peak being of magnetic
origin. Our results are compared to various mean-field theories.",0010393v1
2000-11-22,"Glassy Slowing of Stripe Modulation in (La,Eu,Nd)(2-x)(Sr,Ba)(x)CuO4: A Cu-63 and La-139 NQR Study Down to 350mK","We report a comprehensive Cu and La NQR study down to 350mK in the stripe
phase of the hole-doped high temperature superconductors with hole
concentration approximately 1/8. We observe the hyperfine broadened NQR
lineshape only below 8-20K for x=1/8, indicating that the ordered moments
continue to fluctuate slowly even below the temperature range where they appear
static in other measurements. Detailed numerical simulations of the Zeeman
perturbed Cu NQR lineshape establish that widely accepted models of periodic
modulation of spin density waves with maximum moment approxiamtely 0.3mu_B can
not account for the NQR lineshape. These results suggest that significant
disorder exists at NQR time scales. By fitting a single model to several sets
of experimental data, we deduce the spatial distribution of the spin
fluctuation frequency scale and its temperature dependence. Our results
indicate that as soon as charge dynamics slow down, the spin fluctuationsbegin
to slow dramatically with spin stiffness approximately 200K. However, the
motional narrowing feature observed in the Zeeman perturbed NQR measurements
suggest that the slowing of the spin fluctuations levels off at frequencies
somewhat below the NQR frequency. By extending the analysis to other hole
concentrations, we find a qualitative difference above and below x=1/8.",0011380v2
2003-05-29,Spin-distribution functionals and correlation energy of the Heisenberg model,"We analyse the ground-state energy and correlation energy of the Heisenberg
model as a function of spin, both in the ferromagnetic and in the
antiferromagnetic case, and in one, two and three dimensions. First, we present
a comparative analysis of known expressions for the ground-state energy
$E_0(S)$ of {\it homogeneous} Heisenberg models. In the one-dimensional
antiferromagnetic case we propose an improved expression for $E_0(S)$, which
takes into account Bethe-Ansatz data for $S=1/2$. Next, we consider {\it
inhomogeneous} Heisenberg models (e.g., exposed to spatially varying external
fields). We prove a Hohenberg-Kohn-like theorem stating that in this case the
ground-state energy is a functional of the spin distribution, and that this
distribution encapsulates the entire physics of the system, regardless of the
external fields. Building on this theorem, we then propose a local-density-type
approximation that allows to utilize the results obtained for homogeneous
systems also in inhomogeneous situations. We conjecture a scaling law for the
dependence of the correlation functional on dimensionality, which is well
satisfied by existing numerical data. Finally, we investigate the importance of
the spin-correlation energy by comparing results obtained with the proposed
correlation functional to ones from an uncorrelated mean-field calculation,
taking as our example a linear spin-density wave state.",0305690v1
2003-06-12,Spin-Charge Separation and Kinetic Energy in the t-J Model,"I show that spin-charge separation in 2-D t-J model leads to an increase of
kinetic energy. Using a sum rule, I derive an exact expression for the lowest
possible KE (E_{bound}) for any state without doubly occupied sites. KE of
relevant slave-boson and Schwinger-boson mean-field states -- which exhibit
complete spin-charge separation -- are found to be much larger than E_{bound}.
Examination of n(k) shows that the large increse in KE is due to excessive
depletion of electrons from the bottom of the band (Schwinger boson) and of
holes from the top (slave boson). To see whether the excess KE is simply due to
poor treatment of the constraints, I solve the constraint problem analytically
for the Schwinger boson case in the J = 0 limit. This restores gauge
invariance, incorrectly violated in MF theories. The result is a generalized
Hartree-Fock state of the Hubbard model, but one that includes spin waves. Even
after constraints are imposed correctly, the KE remains much larger than
E_{bound}. These results support the notion, advanced earlier [PRB 61, 8663
(2000)] that spin-charge separation in the MF state costs excessive KE, and
makes the state unstable toward recombination processes which lead to
superconductivity in d = 2 and a Fermi liquid state in higher dimensions.",0306316v2
2003-11-13,Magnon squeezing in an antiferromagnet: reducing the spin noise below the standard quantum limit,"At absolute zero temperature, thermal noise vanishes when a physical system
is in its ground state, but quantum noise remains as a fundamental limit to the
accuracy of experimental measurements. Such a limitation, however, can be
mitigated by the formation of squeezed states. Quantum mechanically, a squeezed
state is a time-varying superposition of states for which the noise of a
particular observable is reduced below that of the ground state at certain
times. Quantum squeezing has been achieved for a variety of systems, including
the electromagnetic field, atomic vibrations in solids and molecules, and
atomic spins, but not so far for magnetic systems. Here we report on an
experimental demonstration of spin wave (i.e., magnon) squeezing. Our method
uses femtosecond optical pulses to generate correlations involving pairs of
magnons in an antiferromagnetic insulator, MnF2. These correlations lead to
quantum squeezing in which the fluctuations of the magnetization of a
crystallographic unit cell vary periodically in time and are reduced below that
of the ground state quantum noise. The mechanism responsible for this squeezing
is stimulated second order Raman scattering by magnon pairs. Such squeezed
states have important ramifications in the emerging fields of spintronics and
quantum computing involving magnetic spin states or the spin-orbit coupling
mechanism.",0311329v1
2004-06-02,Orbital and magnetic transitions in geometrically-frustrated vanadium spinels -- Monte Carlo study of an effective spin-orbital-lattice coupled model --,"We present our theoretical and numerical results on thermodynamic properties
and the microscopic mechanism of two successive transitions in vanadium spinel
oxides $A$V$_2$O$_4$ ($A$=Zn, Mg, or Cd) obtained by Monte Carlo calculations
of an effective spin-orbital-lattice model in the strong correlation limit.
Geometrical frustration in the pyrochlore lattice structure of V cations
suppresses development of spin and orbital correlations, however, we find that
the model exhibits two transitions at low temperatures. First, a discontinuous
transition occurs with an orbital ordering assisted by the tetragonal
Jahn-Teller distortion. The orbital order reduces the frustration in spin
exchange interactions, and induces antiferromagnetic correlations in
one-dimensional chains lying in the perpendicular planes to the tetragonal
distortion. Secondly, at a lower temperature, a three-dimensional
antiferromagnetic order sets in continuously, which is stabilized by the
third-neighbor interaction among the one-dimensional antiferromagnetic chains.
Thermal fluctuations are crucial to stabilize the collinear magnetic state by
the order-by-disorder mechanism. The results well reproduce the experimental
data such as transition temperatures, temperature dependence of the magnetic
susceptibility, changes of the entropy at the transitions, and the magnetic
ordering structure at low temperatures. Quantum fluctuation effect is also
examined by the linear spin wave theory at zero temperature. The staggered
moment in the ground state is found to be considerably reduced from saturated
value, and reasonably agrees with the experimental data.",0406039v1
2005-02-25,Bosonic resonating valence bond wave function for doped Mott insulators,"We propose a new class of ground states for doped Mott insulators in the
electron second-quantization representation. They are obtained from a bosonic
resonating valence bond (RVB) theory of the t-J model. At half filling, the
ground state describes spin correlations of the S=1/2 Heisenberg model very
accurately. Its spin degrees of freedom are characterized by RVB pairing of
spins, the size of which decreases continuously as holes are doped into the
system. Charge degrees of freedom emerge upon doping and are described by
twisted holes in the RVB background. We show that the twisted holes exhibit an
off diagonal long range order (ODLRO) in the pseudogap ground state, which has
a finite pairing amplitude, but is short of phase coherence. Unpaired spins in
such a pseudogap ground state behave as free vortices, preventing
superconducting phase coherence. The existence of nodal quasiparticles is also
ensured by such a hidden ODLRO in the ground state, which is
non-Fermi-liquid-like in the absence of superconducting phase coherence. Two
distinct types of spin excitations can also be constructed. The superconducting
instability of the pseudogap ground state is discussed and a d-wave
superconducting ground state is obtained. This class of pseudogap and
superconducting ground states unifies antiferromagnetism, pseudogap,
superconductivity, and Mott physics into a new state of matter.",0502601v2
2005-06-07,Effect of local charge fluctuations on spin physics in the Neel state of La$_2$CuO$_4$,"We explore the effect of local charge fluctuations on the spin response of a
Mott insulator by deriving an effective spin model, and studying it using
Schwinger boson mean field theory. Applying this to La$_2$CuO$_4$, we show that
an accurate fit to the magnon dispersion relation, measured by Coldea {\em et
al.} [Phys. Rev. Lett. {\bf 86}, 5377 (2001)] is obtained with Hubbard model
parameters $U \approx 2.34 eV$, and $t \approx 360 meV$. These parameters lead
to estimates of the staggered magnetization ($m_s \approx 0.25$), spin wave
velocity ($c\approx 800 meV$-\AA), and spin stiffness ($\rho_s \approx 24
meV$). In particular the staggered moment as well as the effective local moment
are renormalized to smaller values compared to the Heisenberg model due to
local charge fluctuations in the Hubbard model. The dynamical structure factor
shows considerable weight in the continuum along the zone boundary as well as
secondary peaks that may be observed in high resolution neutron scattering
experiments.",0506188v2
1999-10-08,The diagonal spin basis and calculation of processes involving polarized particles,"The review of developed by the authors new techniques for covariant
calculation of matrix elements in QED, the so-called formalism of ""Diagonal
Spin Basis"" (DSB), is presented. In DSB spin 4-vectors of in- and out- fermions
are expressed just in terms of their 4-momenta. In this approach the little
Lorentz group, common for the initial and final states,is realized. This brings
the spin operators of in- and out-particles to coincidence. The developed
approach is valid both for massive fermions and for massless ones. There occur
no problems with accounting for spin flip amplitudes in it. Just 4-momenta of
particles participating in reactions are required in it to construct the
mathematical apparatus for calculations of matrix elements. We apply this
formalism to the next processes: 1) M\""oller and Bhabha bremsstrahlung
($e^{\pm}e^- \to e^{\pm}e^- \gamma$) in the ultrarelativistic limit when
initial particles and photon are helicity polarized; 2) Compton back-scattering
of photons of intensive circularly polarized laser wave on a beam of
longitudinally polarized ultrarelativistic electrons ($e+n\gamma_0 \to e+\gamma
$); 3) $e^+e^-$-pair production by a hard photon in simultaneous collision with
several laser beam photons ($\gamma+n \gamma_0 \to e^+ + e^-$); 4)
Bethe-Heitler process in the case of a linearly polarized photon emission by an
electron with account for proton recoil and form factors; 5) the reaction $ep
\to ep \gamma$ with proton polarizability being taken into account in the
kinematics when proton bremsstrahlung dominates; 6) orthopositronium 3-photon
annihilation ($e^+e^{-} \to 3 \gamma$).",9910284v1
1999-08-31,Initial singlet and triplet spin state contributions to pp -> pp pi0,"The PINTEX facility at the IUCF Cooler ring, dedicated to the study of spin
dependence in nucleon-nucleon interactions, has been used to measure
polarization observables of the reaction pp -> pp pi0 at beam energies between
325 and 400 MeV. The stored polarized proton beam had spin projections both in
the longitudinal and the transverse directions with respect to the beam
momentum. We report here on the measurements of the relative transverse and
longitudinal spin-dependent cross sections, deltasigma_T/sigma_tot and
deltasigma_L/sigma_tot, and how from these observables the initial spin singlet
and triplet cross sections are obtained. Considering angular momentum states
less or equal to one, the contribution of the Ps partial waves to the cross
section can be extracted.",9908024v1
2001-09-21,Spin-Momentum Correlations in Quasi-Elastic Electron Scattering from Deuterium,"We report on a measurement of spin-momentum correlations in quasi-elastic
scattering of longitudinally polarized electrons with an energy of 720 MeV from
vector-polarized deuterium. The spin correlation parameter $A^V_{ed}$ was
measured for the $^2 \vec{\rm H}(\vec e,e^\prime p)n$ reaction for missing
momenta up to 350 MeV/$c$ at a four-momentum transfer squared of 0.21
(GeV/c)$^2$. The data give detailed information about the spin structure of the
deuteron, and are in good agreement with the predictions of microscopic
calculations based on realistic nucleon-nucleon potentials and including
various spin-dependent reaction mechanism effects. The experiment demonstrates
in a most direct manner the effects of the D-state in the deuteron ground-state
wave function and shows the importance of isobar configurations for this
reaction.",0109015v1
1999-05-28,Electron Spin Resonance Transistors for Quantum Computing in Silicon-Germanium Heterostructures,"We apply the full power of modern electronic band structure engineering and
epitaxial heterostructures to design a transistor that can sense and control a
single donor electron spin. Spin resonance transistors may form the
technological basis for quantum information processing. One and two qubit
operations are performed by applying a gate bias. The bias electric field pulls
the electron wave function away from the dopant ion into layers of different
alloy composition. Owing to the variation of the g-factor (Si:g=1.995,
Ge:g=1.563), this displacement changes the spin Zeeman energy, allowing
single-qubit operations. By displacing the electron even further, the overlap
with neighboring qubits is affected, which allows two-qubit operations. Certain
Silicon-Germanium alloys allow a qubit spacing as large as 200 nm, which is
well within the capabilities of current lithographic techniques. We discuss
manufacturing limitations and issues regarding scaling up to a large size
computer.",9905096v2
2008-08-03,Metamagnetic transition in EuFe$_2$As$_2$ single crystals,"We report the measurements of anisotropic magnetization and magnetoresistance
on single crystals of EuFe$_2$As$_2$, a parent compound of ferro-arsenide
high-temperature superconductor. Apart from the antiferromagnetic (AFM)
spin-density-wave transition at 186 K associated with Fe moments, the compound
undergoes another magnetic phase transition at 19 K due to AFM ordering of
Eu$^{2+}$ spins ($J=S=7/2$). The latter AFM state exhibits metamagnetic
transition under magnetic fields. Upon applying magnetic field with $H\parallel
c$ at 2 K, the magnetization increases linearly to 7.0 $\mu_{B}$/f.u. at
$\mu_{0}H$=1.7 T, then keeps at this value of saturated Eu$^{2+}$ moments under
higher fields. In the case of $H\parallel ab$, the magnetization increases
step-like to 6.6 $\mu_{B}$/f.u. with small magnetic hysteresis. A metamagnetic
phase was identified with the saturated moments of 4.4 $\mu_{B}$/f.u. The
metamagnetic transition accompanies with negative in-plane magnetoresistance,
reflecting the influence of Eu$^{2+}$ moments ordering on the electrical
conduction of FeAs layers. The results were explained in terms of
spin-reorientation and spin-reversal based on an $A$-type AFM structure for
Eu$^{2+}$ spins. The magnetic phase diagram has been established.",0808.0325v2
2008-09-01,Spin Fluctuation Dynamics and Multiband Superconductivity in Iron Pnictides,"Multiband superconductivity, involving resonant pair scattering between
different bands, has emerged as a possible explanation of some of the main
characteristics of the recently discovered iron pnictides. A key feature of
such interband pairing mechanism is that it can generate or enhance
superconducting pairing irrespective of whether it is attractive or repulsive.
The latter case typically leads to the superconducting gap switching its sign
among different sections of the Fermi surface. In iron pnictides, the natural
scenario is that the gap changes sign between the hole and the electron Fermi
surfaces. However, the macroscopic symmetry of such an extended s'-wave state
still belongs to the general s-wave category, raising the question of how to
distinguish it from an ordinary s-wave. In such a quest, it is essential to use
experimental techniques that have a momentum space resolution and can probe
momenta of order M, the wavevector that separates the hole and the electron
Fermi surfaces in the Brillouin zone. Here we study experimental signatures in
the spin fluctuation dynamics of the fully-gapped s- and s'-wave
superconducting states, as well as those of the nodal d- and p-wave. The
coupling between spin fluctuations of the incipient nearly-nested spin
density-wave (SDW) and the Bogoliubov-deGennes quasiparticles of the
superconducting state leads to the Landau-type damping of the former. The
intrinsic structure of the superconducting gap leaves a distinctive signature
in the form of this damping, allowing it to be used to diagnose the nature of
iron-based superconductivity in neutron scattering and other experiments
sensitive to spin fluctuations in momentum space. We also discuss the
coexistence between superconductivity and SDW order.",0809.0014v1
2009-10-13,Modulated pair condensate of p-orbital ultracold fermions,"We show that an interesting of pairing occurs for spin-imbalanced Fermi gases
under a specific experimental condition---the spin up and spin down Fermi
levels lying within the $p_x$ and $s$ orbital bands of an optical lattice,
respectively. The pairs condense at a finite momentum equal to the sum of the
two Fermi momenta of spin up and spin down fermions and form a $p$-orbital pair
condensate. This $2k_F$ momentum dependence has been seen before in the spin-
and charge- density waves, but it differs from the usual $p$-wave superfluids
such as $^3$He, where the orbital symmetry refers to the relative motion within
each pair. Our conclusion is based on the density matrix renormalization group
analysis for the one-dimensional (1D) system and mean-field theory for the
quasi-1D system. The phase diagram of the quasi-1D system is calculated,
showing that the $p$-orbital pair condensate occurs in a wide range of
fillings. In the strongly attractive limit, the system realizes an
unconventional BEC beyond Feynman's no-node theorem. The possible experimental
signatures of this phase in molecule projection experiment are discussed.",0910.2431v3
2010-04-29,Computing waveforms for spinning compact binaries in quasi-eccentric orbits,"Several scenarios have been proposed in which the orbits of binary black
holes enter the band of a gravitational wave detector with significant
eccentricity. To avoid missing these signals or biasing parameter estimation it
is important that we consider waveform models that account for eccentricity.
The ingredients needed to compute post-Newtonian (PN) waveforms produced by
spinning black holes inspiralling on quasi-eccentric orbits have been available
for almost two decades at 2 PN order, and this work has recently been extended
to 2.5 PN order. However, the computational cost of directly implementing these
waveforms is high, requiring many steps per orbit to evolve the system of
coupled differential equations. Here we employ the standard techniques of a
separation of timescales and a generalized Keplerian parameterization of the
orbits to produce efficient waveforms describing spinning black hole binaries
with arbitrary masses and spins on quasi-eccentric orbits to 1.5 PN order. We
separate the fast orbital timescale from the slow spin-orbit precession
timescale by solving for the orbital motion in a non-interial frame of
reference that follows the orbital precession. We outline a scheme for
extending our approach to higher post-Newtonian order.",1004.5322v4
2010-06-04,"Magnetism and thermodynamics of spin-(1/2,1) decorated Heisenberg chain with spin-1 pendants","The magnetic and thermodynamic properties of a new ferrimagnetic decorated
spin-(1/2,1) Heisenberg chain with spin-1 pendant spins are investigated for
three cases: (A) J1,J2>0; (B) J1>0, J2<0; and (C) J1<0, J2>0, where J1 and J2
are the exchange couplings between spins in the chain and along the rung,
respectively. The low-lying and magnetic properties are explored jointly by the
real-space renormalization group, spin wave, and density-matrix renormalization
group methods, while the transfer-matrix renormalization group method is
invoked to study the thermodynamics. It is found that the magnon spectra
consist of a gapless and two gapped branches. Two branches in case (C) have
intersections. The coupling dependence of low-energy gaps are analyzed. In a
magnetic field, an m=3/2 (m is the magnetization per unit cell) plateau is
observed for case (A), while two plateaux at m=1/2 and 3/2 are observed for
cases (B) and (C). Between the two plateaux in cases (B) and (C), the
sublattice magnetizations for the spins coupled by ferromagnetic interactions
have novel decreasing regions with increasing the magnetic field. At finite
temperature, the zero-field susceptibility temperature product chi*T and
specific heat exhibit distinct exotic features with varying the couplings and
temperature for different cases. chi*T is found to converge as T approaches
zero, which is different from the divergent behavior in the spin-(1/2,1)
mixed-spin chain without pendants. The observed thermodynamic behaviors are
also discussed with the help of their low-lying excitations.",1006.0794v1
2010-06-07,Effect of Initial Disturbance on The Detonation Front Structure of a Narrow Duct,"The effect of an initial disturbance on the detonation front structure in a
narrow duct is studied by three-dimensional numerical simulation. The numerical
method used includes a high resolution fifth-order weighted essentially
non-oscillatory scheme for spatial discretization, coupled with a third order
total variation diminishing Runge-Kutta time stepping method. Two types of
disturbances are used for the initial perturbation. One is a random disturbance
which is imposed on the whole area of the detonation front, and the other is a
symmetrical disturbance imposed within a band along the diagonal direction on
the front. The results show that the two types of disturbances lead to
different processes. For the random disturbance, the detonation front evolves
into a stable spinning detonation. For the symmetrical diagonal disturbance,
the detonation front displays a diagonal pattern at an early stage, but this
pattern is unstable. It breaks down after a short while and it finally evolves
into a spinning detonation. The spinning detonation structure ultimately formed
due to the two types of disturbances is the same. This means that spinning
detonation is the most stable mode for the simulated narrow duct. Therefore, in
a narrow duct, triggering a spinning detonation can be an effective way to
produce a stable detonation as well as to speed up the deflagration to
detonation transition process.",1006.1170v1
2010-11-25,Calculation of the Expected Zero Field Muon Relaxation Rate in the Geometrically Frustrated Rare Earth Pyrochlore Gd2Sn2O7 Antiferromagnet,"The magnetic insulator Gd2Sn2O7 is one of many geometrically frustrated
magnetic materials known to exhibit a nonzero muon spin polarization relaxation
rate, $\lambda(T)$, down to the lowest temperature (T) studied. Such behaviour
is typically interpreted as a significant level of persisting spin dynamics
(PSD) of the host material. In the case of Gd2Sn2O7, such PSD comes as a
surprise since magnetic specific heat measurements suggest conventional gapped
magnons, which would naively lead to an exponentially vanishing $\lambda(T)$ as
$T \rightarrow 0$. In contrast to most materials that display PSD, the ordered
phase of Gd2Sn2O7 is well characterized and both the nature and the magnitude
of the interactions have been inferred from the magnetic structure and the
temperature dependence of the magnetic specific heat. Based on this
understanding, the temperature dependence of the muon spin polarization
relaxation through the scattering of spin waves (magnons) is calculated. The
result explicitly shows that, despite the unusual extensive number of weakly
dispersive (gapped)excitations characterizing Gd2Sn2O7, a remnant of the zero
modes of the parent frustrated pyrochlore Heisenberg antiferromagnet, the
temperature dependence of the calculated $\lambda(T)$ differs dramatically from
the experimental one. Indeed, the calculation conforms to the naive expectation
of an exponential collapse of $\lambda(T)$ at temperatures below ~ 0.7K. This
result, for the first time, illustrates crisply and quantitatively the paradox
that presents itself with the pervasive occurrence of PSD in highly frustrated
magnetic systems as evinced by muon spin relaxation measurements.",1011.5689v1
2011-02-01,Real-time density matrix renormalization group dynamics of spin and charge transport in push-pull polyenes and related systems,"In this paper we investigate the effect of terminal substituents on the
dynamics of spin and charge transport in donor-acceptor substituted polyenes
($D-(CH)_{x}-A$) chains, also known as push-pull polyenes. We employ long-range
correlated model Hamiltonian for the $D-(CH)_{x}-A$ system, and time-dependent
density matrix renormalization group technique for time propagating the wave
packet obtained by injecting a hole at a terminal site, in the ground state of
the system. Our studies reveal that the end groups do not affect spin and
charge velocities in any significant way, but change the amount of charge
transported. We have compared these push-pull systems with donor-acceptor
substituted polymethine imine (PMI), $D-(CHN)_{x}-A$, systems in which besides
electron affinities, the nature of $p_{z}$ orbitals in conjugation also
alternate from site to site. We note that spin and charge dynamics in the PMIs
are very different from that observed in the case of push-pull polyenes, and
within the time scale of our studies, transport of spin and charge leads to the
formation of a ""quasi-static"" state.",1102.0130v4
2011-06-02,Chiral spin currents and spectroscopically accessible single merons in quantum dots,"We provide unambiguous theoretical evidence for the formation of
correlation-induced isolated merons in rotationally-symmetric quantum dots. Our
calculations rely on neither the lowest-Landau-level approximation, nor on the
maximum-density-droplet approximation, nor on the existence of a spin-polarized
state. For experimentally accessible system parameters, unbound merons condense
in the ground state at magnetic fields as low as $B^* = 0.2$ T and for as few
as N = 3 confined fermions. The four-fold degenerate ground-state at $B^*$
corresponds to four orthogonal merons $\ket{QC}$ characterized by their
topological chirality $C$ and charge $Q$. This degeneracy is lifted by the
Rashba and Dresselhaus spin-orbit interaction, which we include perturbatively,
yielding spectroscopic accessibility to individual merons. We further derive a
closed-form expression for the topological chirality in the form of a chiral
spin current and use it to both characterize our states and predict the
existence of other topological textures in other regions of phase space, for
example, at N=5. Finally, we compare the spin textures of our numerically exact
meron states to ansatz wave-functions of merons in quantum Hall droplets and
find that the ansatz qualitatively describes the meron states.",1106.0450v2
2011-10-07,On the Mass Difference between pion and rho meson using a Relativistic Two-Body Model,"The big mass difference between the pion and rho meson possibly originates
from the spin-dependent nature of the interactions in the two states since
these two states are similar except for spin. Both pi and rho are
quark-antiquark systems which can be treated using the two-body Dirac equations
(TBDE) of constraint dynamics. This relativistic approach for two-body system
has the advantage over the non-relativistic treatment in the sense that the
spin-dependent nature is automatically coming out from the formalism. We
employed Dirac's relativistic constraint dynamics to describe quark-antiquark
systems. Within this formalism, the 16-component Dirac equation is reduced to
the 4-component 2nd-order differential equation and the radial part of this
equation is simply a Schroedinger-type equation with various terms calculated
from the basic radial potential. We used a modified Richardson potential for
quark-antiquark systems which satisfies the conditions of confinement and
asymptotic freedom. We obtained the wave functions for these two mesons which
are not singular at short distances. We also found that the cancellation
between the Darwin and spin-spin interaction terms occurs in the pi mass but
not in the rho mass and this is the main source of the big difference in the
two meson masses.",1110.1598v1
2011-12-20,Spin Dynamics of a J1-J2-K Model for the Paramagnetic Phase of Iron Pnictides,"We study the finite-temperature spin dynamics of the paramagnetic phase of
iron pnictides within an antiferromagnetic J_1-J_2 Heisenberg model on a square
lattice with a biquadratic coupling $-K (S_i \cdot S_j)^2$ between the
nearest-neighbor spins. Our focus is on the paramagnetic phase in the parameter
regime of this J_1-J_2-K model where the ground state is a (\pi,0) collinear
antiferromagnet. We treat the biquadratic interaction via a
Hubbard-Stratonovich decomposition, and study the resulting effective
quadratic-coupling model using both modified spin wave and Schwinger boson
mean-field theories; the results for the spin dynamics derived from the two
methods are very similar. We show that the spectral weight of dynamical
structure factor S(q,\omega) is peaked at ellipses in the momentum space at low
excitation energies. With increasing energy, the elliptic features expand
towards the zone boundary, and gradually split into two parts, forming a
pattern around (\pi,\pi). Finally, the spectral weight is anisotropic, being
larger along the major axis of the ellipse than along its minor axis. These
characteristics of the dynamical structure factor are consistent with the
recent measurements of the inelastic neutron scattering spectra on BaFe_2As_2
and SrFe_2As_2.",1112.4785v3
2012-01-05,Longitudinal and transverse static spin fluctuations in layered ferro- and antiferromagnets,"We analyse the momentum dependence of static non-uniform susceptibilities of
layered local-moment systems below Curie (Neel) temperature within the
1/S-expansion, the renormalization-group approach, and first order of
1/N-expansion. We argue that the previously known results of the spin-wave
theory and renormalization-group approach for the transverse spin
susceptibility acquire strong corrections already at sufficiently low
temperatures, which appear due to the interaction of the incomping magnon
having momentum q with magnons with momenta k<q. Such corrections can not be
treated in the standard renormalization-group approach, but can be described by
both, 1/S and 1/N expansions. The results of these expansions can be
successfully extrapolated to the magnetic transition temperature T=T_M yielding
the correct weight of static spin fluctuations, determined by the O(3)
symmetry. For the longitudinal susceptibility, the summation of leading terms
of 1/S expansion within the parquet approach allows to fulfill the sumrule for
the weights of transverse and longitudinal fluctuations in a broad temperature
region below T_M outside the critical regime. We also discuss the effect of
longitudinal spin fluctuations on the (sublattice) magnetization of layered
systems.",1201.1148v4
2012-01-27,The evolution of massive black holes and their spins in their galactic hosts,"[Abridged] [...] We study the mass and spin evolution of massive black holes
within a semianalytical galaxy-formation model that follows the evolution of
dark-matter halos along merger trees, as well as that of the baryonic
components (hot gas, stellar and gaseous bulges, and stellar and gaseous
galactic disks). This allows us to study the mass and spin evolution of massive
black holes in a self-consistent way, by taking into account the effect of the
gas present in galactic nuclei both during the accretion phases and during
mergers. Also, we present predictions, as a function of redshift, for the
fraction of gas-rich black-hole mergers -- in which the spins prior to the
merger are aligned due to the gravito-magnetic torques exerted by the
circumbinary disk -- as opposed to gas-poor mergers, in which the orientation
of the spins before the merger is roughly isotropic. These predictions may be
tested by LISA or similar spaced-based gravitational-wave detectors such as
eLISA/NGO or SGO.",1201.5888v3
2012-01-29,Collective Dipole Oscillation of a Spin-Orbit Coupled Bose-Einstein Condensate,"We present an experimental study of the collective dipole oscillation of a
spin-orbit coupled Bose-Einstein condensate in a harmonic trap. Dynamics of the
center-of-mass dipole oscillation is studied in a broad parameter region, as a
function of spin-orbit coupling parameters as well as oscillation amplitude.
Anharmonic properties beyond effective-mass approximation are revealed, such as
amplitude-dependent frequency and finite oscillation frequency at place with
divergent effective mass. These anharmonic behaviors agree quantitatively with
variational wave-function calculations. Moreover, we experimentally demonstrate
a unique feature of spin-orbit coupled system predicted by a sum-rule approach,
stating that spin polarization susceptibility--a static physical quantity--can
be measured via dynamics of dipole oscillation. The divergence of polarization
susceptibility is observed at the quantum phase transition that separates
magnetic nonzero-momentum condensate from nonmagnetic zero-momentum phase. The
good agreement between the experimental and theoretical results provides a
bench mark for recently developed theoretical approaches.",1201.6018v2
2012-04-02,Floquet spin states in graphene under ac driven spin-orbit interaction,"We study the role of periodically driven time-dependent Rashba spin-orbit
coupling (RSOC) on a monolayer graphene sample. After recasting the originally
$4\times 4$ system of dynamical equations as two time-reversal related
two-level problems, the quasi-energy spectrum and the related dynamics are
investigated via various techniques and approximations. In the static case the
system is a gapped at the Dirac point. The rotating wave approximation (RWA)
applied to the driven system unphysically preserves this feature, while the
Magnus-Floquet approach as well as a numerically exact evaluation of the
Floquet equation show that this gap is dynamically closed. In addition, a
sizable oscillating pattern of the out-of-plane spin polarization is found in
the driven case for states which completely unpolarized in the static limit.
Evaluation of the autocorrelation function shows that the original uniform
interference pattern corresponding to time-independent RSOC gets distorted. The
resulting structure can be qualitatively explained as a consequence of the
transitions induced by the ac driving among the static eigenstates, i.e., these
transitions modulate the relative phases that add up to give the quantum
revivals of the autocorrelation function. Contrary to the static case, in the
driven scenario, quantum revivals (suppresions) are correlated to spin up
(down) phases.",1204.0404v2
2012-05-16,Polarized neutron scattering studies of magnetic excitations in electron-overdoped superconducting BaFe$_{1.85}$Ni$_{0.15}$As$_{2}$,"We use polarized inelastic neutron scattering to study low-energy spin
excitations and their spatial anisotropy in electron-overdoped superconducting
BaFe$_{1.85}$Ni$_{0.15}$As$_{2}$ ($T_c=14$ K). In the normal state, the
imaginary part of the dynamic susceptibility, $\chi^{\prime\prime}(Q,\omega)$,
at the antiferromagnetic (AF) wave vector $Q=(0.5,0.5,1)$ increases linearly
with energy for $E\le 13$ meV. Upon entering the superconducting state, a spin
gap opens below $E\approx 3$ meV and a broad neutron spin resonance appears at
$E\approx 7$ meV. Our careful neutron polarization analysis reveals that
$\chi^{\prime\prime}(Q,\omega)$ is isotropic for the in-plane and out-of-plane
components in both the normal and superconducting states. A comparison of these
results with those of undoped BaFe$_2$As$_2$ and optimally electron-doped
BaFe$_{1.9}$Ni$_{0.1}$As$_{2}$ ($T_c=20$ K) suggests that the spin anisotropy
observed in BaFe$_{1.9}$Ni$_{0.1}$As$_{2}$ is likely due to its proximity to
the undoped BaFe$_2$As$_2$. Therefore, the neutron spin resonance is isotropic
in the overdoped regime, consistent with a singlet to triplet excitation.",1205.3730v1
2012-05-27,Towards beating the curse of dimensionality for gravitational waves using Reduced Basis,"Using the Reduced Basis approach, we efficiently compress and accurately
represent the space of waveforms for non-precessing binary black hole
inspirals, which constitutes a four dimensional parameter space (two masses,
two spin magnitudes). Compared to the non-spinning case, we find that only a
{\it marginal} increase in the (already relatively small) number of reduced
basis elements is required to represent any non-precessing waveform to nearly
numerical round-off precision. Most parameters selected by the algorithm are
near the boundary of the parameter space, leaving the bulk of its volume
sparse. Our results suggest that the full eight dimensional space (two masses,
two spin magnitudes, four spin orientation angles on the unit sphere) may be
highly compressible and represented with very high accuracy by a remarkably
small number of waveforms, thus providing some hope that the number of
numerical relativity simulations of binary black hole coalescences needed to
represent the entire space of configurations is not intractable. Finally, we
find that the {\it distribution} of selected parameters is robust to different
choices of seed values starting the algorithm, a property which should be
useful for indicating parameters for numerical relativity simulations of binary
black holes. In particular, we find that the mass ratios $m_1/m_2$ of
non-spinning binaries selected by the algorithm are mostly in the interval
$[1,3]$ and that the median of the distribution follows a power-law behavior
$\sim (m_1/m_2)^{-5.25}$.",1205.6009v1
2012-06-26,Slowly Rotating Black Holes in Dynamical Chern-Simons Gravity: Deformation Quadratic in the Spin,"We derive a stationary and axisymmetric black hole solution to quadratic
order in the spin angular momentum. The previously found, linear-in-spin terms
modify the odd-parity sector of the metric, while the new corrections appear in
the even-parity sector. These corrections modify the quadrupole moment, as well
as the (coordinate-dependent) location of the event horizon and the ergoregion.
Although the linear-in-spin metric is of Petrov type D, the quadratic order
terms render it of type I. The metric does not possess a second-order Killing
tensor or a Carter-like constant. The new metric does not possess closed
timelike curves or spacetime regions that violate causality outside of the
event horizon. The new, even-parity modifications to the Kerr metric decay less
rapidly at spatial infinity than the leading-order in spin, odd-parity ones,
and thus, the former are more important when considering black holes that are
rotating moderately fast. We calculate the modifications to the Hamiltonian,
binding energy and Kepler's third law. These modifications are crucial for the
construction of gravitational wave templates for black hole binaries, which
will enter at second post-Newtonian order, just like dissipative modifications
found previously.",1206.6130v4
2012-11-14,Dimensionality effects in the LDOS of ferromagnetic hosts probed via STM: spin-polarized quantum beats and spin filtering,"We theoretically investigate the local density of states (LDOS) probed by a
STM tip of ferromagnetic metals hosting a single adatom and a subsurface
impurity. We model the system via the two-impurity Anderson Hamiltonian. By
using the equation of motion with the relevant Green functions, we derive
analytical expressions for the LDOS of two host types: a surface and a quantum
wire. The LDOS reveals Friedel-like oscillations and Fano interference as a
function of the STM tip position. These oscillations strongly depend on the
host dimension. Interestingly, we find that the spin-dependent Fermi wave
numbers of the hosts give rise to spin-polarized quantum beats in the LDOS.
While the LDOS for the metallic surface shows a damped beating pattern, it
exhibits an opposite behavior in the quantum wire. Due to this absence of
damping, the wire operates as a spatially resolved spin filter with a high
efficiency.",1211.3406v4
2013-01-14,Quantum Hall ferromagnetic phases in the Landau level N=0 of a graphene bilayer,"In a Bernal-stacked graphene bilayer, an electronic state in Landau level $%
N=0$ is described by its guiding-center index $X$ (in the Landau gauge) and by
its valley, spin, and orbital indices $\xi =\pm K,\sigma =\pm 1,$ and $%
n=0,1.$ When Coulomb interaction is taken into account, the chiral
two-dimensional electron gas (C2DEG) in this system can support a variety of
quantum Hall ferromagnetic (QHF)\ ground states where the spins and/or valley
pseudospins and/or orbital pseudospins collectively align in space. In this
work, we give a comprehensive account of the phase diagram of the C2DEG at
integer filling factors $\nu \in [-3,3] $ in Landau level N=0 when an
electrical potential difference $\Delta_{B}$ between the two layers is varied.
We consider states with or without layer, spin, or orbital coherence. For each
phase, we discuss the behavior of the transport gap as a function of
$\Delta_{B},$ the spectrum of collective excitations and the optical absorption
due to orbital pseudospin-wave modes. We also study the effect of an external
in-plane electric field on a coherent state that has both valley and spin
coherence and show that it is possible, in such a state, to control the spin
polarization by varying the strength of the external in-plane electric field.",1301.3094v1
2013-04-12,Spin Gap and the Nature of the 4d3 Magnetic Ground State in the Frustrated FCC Antiferromagnet Ba2YRuO6,"The geometrically frustrated double perovskite Ba2YRuO6 has magnetic 4d3 Ru5+
ions decorating an undistorted face-centered cubic (FCC) lattice. This material
has been previously reported to exhibit commensurate long-range
antiferromagnetic order below T_N = 36K, a factor f = 15 times lower than its
Curie-Weiss temperature Theta_CW = -522 K, and purported short-range order to
T* = 47K. We report new time-of-flight neutron spectroscopy of Ba2YRuO6 which
shows the development of a 5 meV spin gap in the vicinity of the [100] magnetic
ordering wavevector below T_N = 36K, with the transition to long-range order
occurring at T* = 47K. We also report spin waves extending to 14 meV, a
surprisingly small bandwidth in light of the large Theta_CW. We compare the
spin gap and bandwidth to relevant neutron studies of the isostructural 4d1
material Ba2YMoO6,and discuss the results in the framework of relatively strong
spin-orbit coupling expected in 4d magnetic systems.",1304.3649v3
2013-06-21,Stripe Antiferromagnetic Spin Fluctuations in SrCo$_{2}$As$_{2}$,"Inelastic neutron scattering measurements of paramagnetic SrCo$_{2}$As$_{2}$
at T=5 K reveal antiferromagnetic (AFM) spin fluctuations that are peaked at a
wavevector of $\textbf{Q}_{\mathrm{AFM}}=(1/2,1/2,1)$ and possess a large
energy scale. These stripe spin fluctuations are similar to those found in
$A$Fe$_{2}$As$_{2}$ compounds, where spin-density wave AFM is driven by Fermi
surface nesting between electron and hole pockets separated by
$\textbf{Q}_{\mathrm{AFM}}$. SrCo$_{2}$As$_{2}$ has a more complex Fermi
surface and band structure calculations indicate a potential instability
towards either a ferromagnetic or stripe AFM ground state. The results suggest
that stripe AFM magnetism is a general feature of both iron and cobalt-based
arsenides and the search for spin fluctuation-induced unconventional
superconductivity should be expanded to include cobalt-based compounds.",1306.5174v3
2013-07-05,Holonomy spin foam models: Asymptotic geometry of the partition function,"We study the asymptotic geometry of the spin foam partition function for a
large class of models, including the models of Barrett and Crane, Engle,
Pereira, Rovelli and Livine, and, Freidel and Krasnov.
  The asymptotics is taken with respect to the boundary spins only, no
assumption of large spins is made in the interior. We give a sufficient
criterion for the existence of the partition function. We find that geometric
boundary data is suppressed unless its interior continuation satisfies certain
accidental curvature constraints. This means in particular that most Regge
manifolds are suppressed in the asymptotic regime. We discuss this explicitly
for the case of the configurations arising in the 3-3 Pachner move. We identify
the origin of these accidental curvature constraints as an incorrect twisting
of the face amplitude upon introduction of the Immirzi parameter and propose a
way to resolve this problem, albeit at the price of losing the connection to
the SU(2) boundary Hilbert space.
  The key methodological innovation that enables these results is the
introduction of the notion of wave front sets, and the adaptation of tools for
their study from micro local analysis to the case of spin foam partition
functions.",1307.1679v2
2013-07-23,"Inspiral-merger-ringdown waveforms of spinning, precessing black-hole binaries in the effective-one-body formalism","We describe a general procedure to generate spinning, precessing waveforms
that include inspiral, merger and ringdown stages in the effective-one-body
(EOB) approach. The procedure uses a precessing frame in which
precession-induced amplitude and phase modulations are minimized, and an
inertial frame, aligned with the spin of the final black hole, in which we
carry out the matching of the inspiral-plunge to merger-ringdown waveforms. As
a first application, we build spinning, precessing EOB waveforms for the
gravitational modes l=2 such that in the nonprecessing limit those waveforms
agree with the EOB waveforms recently calibrated to numerical-relativity
waveforms. Without recalibrating the EOB model, we then compare EOB and
post-Newtonian precessing waveforms to two numerical-relativity waveforms
produced by the Caltech-Cornell-CITA collaboration. The numerical waveforms are
strongly precessing and have 35 and 65 gravitational-wave cycles. We find a
remarkable agreement between EOB and numerical-relativity precessing waveforms
and spins' evolutions. The phase difference is ~ 0.2 rad at merger, while the
mismatches, computed using the advanced-LIGO noise spectral density, are below
2% when maximizing only on the time and phase at coalescence and on the
polarization angle.",1307.6232v1
2013-10-10,"Coupling of the Local Defect and Magnetic Structure of Wustite, Fe1-xO","The local nuclear and magnetic structure of wustite, Fe1-xO, and the coupling
between them, has been examined using reverse Monte Carlo refinements of
variable-temperature neutron total scattering data. The results from this
analysis suggest that the individual units in a tetrahedral defect cluster are
connected along <110> vectors into a Koch-Cohen-like arrangement, with the
majority of octahedral vacancies concentrated near these defects. Bond valence
calculations indicate a change in the charge distribution on the cations with
the charge on the tetrahedral interstitials increasing on cooling. The magnetic
structure is more complex than previously thought, corresponding to a
non-collinear spin arrangement described by a superposition of a condensed spin
wave on the established type-II antiferromagnetic ordering. This leads to an
architecture with four groups of cations each with different spin directions.
The cations within the interstitial clusters appear to be weakly
ferromagnetically coupled and their spins are correlated to the spins of the
octahedral cations closest to them. This work not only provides further insight
into the local structure of wustite but also a better understanding of the
coupling between defect structures and magnetic and charge-ordering in complex
materials.",1310.2904v1
2013-10-31,Large spin splitting in the conduction band of transition metal dichalcogenide monolayers,"We study the conduction band spin splitting that arises in transition metal
dichalcogenide (TMD) semiconductor monolayers such as MoS$_2$, MoSe$_2$, WS$_2$
and WSe$_2$ due to the combination of spin-orbit coupling and lack of inversion
symmetry. Two types of calculation are done. First, density functional theory
(DFT) calculations based on plane waves and pseudo potentials that yield large
splittings, between 3 and 30 meV. Second, we derive a tight-binding model, that
permits to address the atomic origin of the splitting. The basis set of the
model is provided by the maximally localized Wannier orbitals, obtained from
the DFT calculation, and formed by 11 atomic-like orbitals corresponding to
5$d$ and 3$p$ orbitals of the transition metal (W,Mo) and chalcogenide (S,Se)
atoms respectively. In the resulting Hamiltonian we can independently change
the atomic spin-orbit coupling constant of the two atomic species at the unit
cell, which permits to analyse their contribution to the spin splitting at the
high symmetry points. We find that ---in contrast to the valence band--- both
atoms give comparable contributions to the conduction band splittings. Given
that these materials are most often $n-$doped, our findings are important for
developments in TMD spintronics.",1311.0049v2
2014-03-04,Spin excitations of half-doped bilayer manganites: intermediate phase,"The ground state of half-doped manganites involves intricate spin, charge and
orbital orderings, which are difficult to discern experimentally. In this work,
we resort to the theoretical analysis of the spin fluctuation spectrum of the
half-doped bilayer Pr(Ca$_{0.9}$Sr$_{0.1}$)$_2$ Mn$_2$O$_7$ in order to get an
insight of its electronic ground state. By means of the linear spin wave
approximation, we compute the magnon dispersion for a family of localized spin
models, which can describe several phases proposed for the ground state of
half-doped manganites, like the intermediate one proposed by Efremov et al.
[Nat.Mats. 3, 853, (2004)] along with its particular cases corresponding to
Goodenough's CE phase [Phys. Rev. 100, 564, (1955)] and Zener polaron or dimer
phases. We obtain an excellent agreement between theory and experiment when the
ground state is assumed to be a generalized Goodenough's CE phase, with a
Mn-charge disproportionation inside the experimentally expected range. As
essential ingredients for our improved fit of the upper and lower magnon
branches measured around the gap, we identified two next-nearest neighbour
exchange interactions between the planar Mn zig-zag chains, one for each type
of Mn ion present. In connection with this finding, we revisited the magnetic
excitations of the laminar related compounds, focusing on the upper magnon
branches. Here we prove that their measurement would provide the key to
identify unambiguously the ground state present in the layered half-doped
manganites.",1403.0971v2
2014-07-03,Hyperfine coupling and spin polarization in the bulk of the topological insulator Bi$_2$Se$_3$,"Nuclear magnetic resonance (NMR) and transport measurements have been
performed at high magnetic fields and low temperatures in a series of $n$-type
Bi$_{2}$Se$_{3}$ crystals. In low density samples, a complete spin polarization
of the electronic system is achieved, as observed from the saturation of the
isotropic component of the $^{209}$Bi NMR shift above a certain magnetic field.
The corresponding spin splitting, defined in the phenomenological approach of a
3D electron gas with a large (spin-orbit-induced) effective $g$-factor, scales
as expected with the Fermi energy independently determined by simultaneous
transport measurements. Both the effective electronic $g$-factor and the
""contact"" hyperfine coupling constant are precisely determined. The magnitude
of this latter reveals a non negligible $s$-character of the electronic wave
function at the bottom of the conduction band. Our results show that the bulk
electronic spin polarization can be directly probed via NMR and pave the way
for future NMR investigations of the electronic states in Bi-based topological
insulators.",1407.1040v2
2014-08-08,Towards models of gravitational waveforms from generic binaries II: Modelling precession effects with a single effective precession parameter,"Gravitational waves (GWs) emitted by generic black-hole binaries show a rich
structure that directly reflects the complex dynamics introduced by the
precession of the orbital plane, which poses a real challenge to the
development of generic waveform models. Recent progress in modelling these
signals relies on an approximate decoupling between the non-precessing secular
inspiral and a precession-induced rotation. However, the latter depends in
general on all physical parameters of the binary which makes modelling efforts
as well as understanding parameter-estimation prospects prohibitively complex.
Here we show that the dominant precession effects can be captured by a reduced
set of spin parameters. Specifically, we introduce a single \emph{effective
precession spin} parameter, $\chi_p$, which is defined from the spin components
that lie in the orbital plane at some (arbitrary) instant during the inspiral.
We test the efficacy of this parameter by considering binary inspiral
configurations specified by the physical parameters of a corresponding
non-precessing-binary configuration (total mass, mass ratio, and spin
components (anti-)parallel to the orbital angular momentum), plus the effective
precession spin applied to the larger black hole. We show that for an
overwhelming majority of random precessing configurations, the precession
dynamics during the inspiral are well approximated by our equivalent
configurations. Our results suggest that in the comparable-mass regime waveform
models with only three spin parameters faithfully represent generic waveforms,
which has practical implications for the prospects of GW searches, parameter
estimation and the numerical exploration of the precessing-binary parameter
space.",1408.1810v2
2014-11-30,Spin and charge dynamics of a quasi-one-dimensional antiferromagnetic metal,"We use quantum Monte Carlo simulations to study a finite-temperature
dimensional-crossover-driven evolution of spin and charge dynamics in weakly
coupled Hubbard chains with a half-filled band. The low-temperature behavior of
the charge gap indicates a crossover between two distinct energy scales: a
high-energy one-dimensional (1D) Mott gap due to the umklapp process and a
low-energy gap which stems from long-range antiferromagnetic (AF) fluctuations.
Away from the 1D regime and at temperature scales above the charge gap, the
emergence of a zero-frequency Drude-like feature in the interchain optical
conductivity $\sigma_{\perp}(\omega)$ implies the onset of a higher-dimensional
metal. In this metallic phase, enhanced quasiparticle scattering off
finite-range AF fluctuations results in incoherent single-particle dynamics.
The coupling between spin and charge fluctuations is also seen in the spin
dynamical structure factor $S({\pmb q},\omega)$ displaying damped spin
excitations (paramagnons) close to the AF wave-vector ${\pmb q}=(\pi,\pi)$ and
particle-hole continua near 1D momentum transfers spanning quasiparticles at
the Fermi surface. We relate our results to the charge deconfinement in
quasi-1D organic Bechgaard-Fabre salts.",1412.0287v2
2014-12-26,Derivation of the spin Hamiltonians for Fe in MgO,"A method to calculate the effective spin Hamiltonian for a transition metal
impurity in a non- magnetic insulating host is presented and applied to the
paradigmatic case of Fe in MgO. In a first step we calculate the electronic
structure employing standard density functional theory (DFT), based on
generalized-gradient approximation (GGA), using plane waves as a basis set. The
corresponding basis of atomic-like maximally localized Wannier functions is
derived and used to represent the DFT Hamiltonian, resulting in a tight-binding
model for the atomic orbitals of the magnetic impurity. The third step is to
solve, by exact numerical diagonalization, the N electron problem in the open
shell of the magnetic atom, including both effect of spin-orbit and Coulomb
repulsion. Finally, the low energy sector of this multi-electron Hamiltonian is
mapped into effective spin models that, in addition to the spin matrices S, can
also include the orbital angular momentum L when appropriate. We successfully
apply the method to Fe in MgO, considering both, the undistorted and
Jahn-Teller (JT) distorted cases. Implications for the influence of Fe
impurities on the performance of magnetic tunnel junctions based on MgO are
discussed.",1412.7956v2
2015-03-20,Magnetic excitations of perovskite rare-earth nickelates: RNiO$_3$,"The perovskite nickelates RNiO$_3$ (R: rare-earth) have been studied as
potential multiferroic compounds. A certain degree of charge disproportionation
in the Ni ions has been confirmed by high resolution synchrotron power
diffraction: instead of the nominal Ni$^{3+}$ valence, they can have the
mixed-valence state Ni$^{(3-\delta)+}$ and Ni$^{(3+\delta)+}$, though agreement
has not been reached on the precise value of $\delta$ (e.g. for NdNiO$_3$,
$\delta=0.0$ and $\delta=0.29$ were reported). Also, the magnetic ground state
is not yet clear: collinear and non-collinear Ni-O magnetic structures have
been proposed to explain neutron diffraction and soft X-ray resonant
sccattering results in these compounds, and more recently a canted
antiferromagnetic spin arrangement was proposed on the basis of magnetic
susceptibility measurements. This scenario is reminiscent of the situation in
the half-doped manganites.
  In order to gain insight into the ground state of these compounds, we studied
the magnetic excitations of some of the different phases proposed, using a
localized spin model for a simplified spin chain which could describe these
compounds. We first analize the stability of the collinear, orthogonal, and
intermediate phases in the classical case. We then explore the quantum ground
state indirectly, calculating the spin excitations obtained for each phase,
using the Holstein-Primakoff transformation and the linear spin-wave
approximation. For the collinear and orthogonal ($\theta=\pi/2$) phases, we
predict differences in the magnon spectrum which would allow to distinguish
between them in future inelastic neutron scattering experiments.",1503.06102v1
2015-03-27,Nonequilibrium spin texture within a thin layer below the surface of current-carrying topological insulator Bi$_2$Se$_3$: A first-principles quantum transport study,"We predict that unpolarized charge current injected into a ballistic thin
film of prototypical topological insulator (TI) Bi$_2$Se$_3$ will generate a
{\it noncollinear spin texture} $\mathbf{S}(\mathbf{r})$ on its surface.
Furthermore, the nonequilibrium spin texture will extend into $\simeq 2$ nm
thick layer below the TI surfaces due to penetration of evanescent
wavefunctions from the metallic surfaces into the bulk of TI. Averaging
$\mathbf{S}(\mathbf{r})$ over few \AA{} along the longitudinal direction
defined by the current flow reveals large component pointing in the transverse
direction. In addition, we find an order of magnitude smaller out-of-plane
component when the direction of injected current with respect to Bi and Se
atoms probes the largest hexagonal warping of the Dirac-cone dispersion on TI
surface. Our analysis is based on an extension of the nonequilibrium Green
functions combined with density functional theory (NEGF+DFT) to situations
involving noncollinear spins and spin-orbit coupling. We also demonstrate how
DFT calculations with properly optimized local orbital basis set can precisely
match putatively more accurate calculations with plane-wave basis set for the
supercell of Bi$_2$Se$_3$.",1503.08046v2
2015-07-02,Post-newtonian analysis of precessing convention for spinning compact binaries,"A precessing source frame, constructed using the Newtonian orbital angular
momentum ${\bf L_{\rm N}}$, can be invoked to model inspiral gravitational
waves from generic spinning compact binaries. An attractive feature of such a
precessing convention is its ability to remove all spin precession induced
modulations from the orbital phase evolution. However, this convention usually
employs a post-Newtonian (PN) accurate precessional equation, appropriate for
the PN accurate orbital angular momentum ${\bf L}$, to evolve the ${\bf L_{\rm
N}}$-based precessing source frame. This influenced us to develop inspiral
waveforms for spinning compact binaries in a precessing convention that
explicitly employ ${\bf L}$ to describe the binary orbits. Our approach
introduces certain additional 3PN order terms in the evolution equations for
the orbital phase and frequency with respect to the usual ${\bf L_{\rm
N}}$-based implementation of the precessing convention. We examine the
practical implications of these additional terms by computing the match between
inspiral waveforms that employ ${\bf L}$ and ${\bf L_{\rm N}}$-based precessing
conventions. The match estimates are found to be smaller than the optimal
value, namely $0.97$, for a non-negligible fraction of unequal mass spinning
compact binaries.",1507.00406v2
2015-07-13,Macrospin Dynamics in Antiferromagnets Triggered by Sub-20 femtosecond Injection of Nanomagnons,"The understanding of how the sub-nanoscale exchange interaction evolves in
macroscale correlations and ordered phases of matter, such as magnetism and
superconductivity, requires to bridge the quantum and classical worlds. This
monumental challenge has so far only been achieved for systems close to their
thermodynamical equilibrium. Here we follow in real time the ultrafast dynamics
of the macroscale magnetic order parameter triggered by the impulsive optical
generation of spin excitations with the shortest possible nanometer-wavelength
and femtosecond-period. Our experiments also disclose a possibility for the
coherent control of these femtosecond nanomagnons, which are defined by the
exchange energy. These findings open up novel opportunities for fundamental
research on the role of short-wavelength spin excitations in magnetism and
high-temperature superconductivity, since they provide a macroscopic probe of
the femtosecond dynamics of sub-nanometer spin-spin correlations and,
ultimately, of the exchange energy. With this approach it becomes possible to
trace the dynamics of such short-range magnetic correlations for instance
during phase transitions. Moreover, our work suggests that nanospintronics and
nanomagnonics can employ phase-controllable spin waves with frequencies in the
20 THz domain.",1507.03377v1
2015-08-06,Recoiling black holes: prospects for detection and implications of spin alignment,"Supermassive black hole (BH) mergers produce powerful gravitational wave (GW)
emission. Asymmetry in this emission imparts a recoil kick to the merged BH,
which can eject the BH from its host galaxy altogether. Recoiling BHs could be
observed as offset active galactic nuclei (AGN). Several candidates have been
identified, but systematic searches have been hampered by large uncertainties
regarding their observability. By extracting merging BHs and host galaxy
properties from the Illustris cosmological simulations, we have developed a
comprehensive model for recoiling AGN. Here, for the first time, we model the
effects of BH spin alignment and recoil dynamics based on the gas-richness of
host galaxies. We predict that if BH spins are not highly aligned,
seeing-limited observations could resolve offset AGN, making them promising
targets for all-sky surveys. For randomly-oriented spins, less than about 10
spatially-offset AGN may be detectable in HST-COSMOS, and > 10^3 could be found
with Pan-STARRS, LSST, Euclid, and WFIRST. Nearly a thousand velocity-offset
AGN are predicted within the SDSS footprint; the rarity of large broad-line
offsets among SDSS quasars is likely due in part to selection effects but
suggests that spin alignment plays a role in suppressing recoils. Nonetheless,
in our most physically motivated model where alignment occurs only in gas-rich
mergers, hundreds of offset AGN should be found in all-sky surveys. Our
findings strongly motivate a dedicated search for recoiling AGN.",1508.01524v2
2015-08-20,Spin-noise-based magnetometry of an $n$-doped GaAs microcavity in the field of elliptically polarized light,"Recently reported optical nuclear orientation in the $n$-doped GaAs
microcavity under pumping in nominal transparency region of the crystal [Appl.
Phys. Lett. $\mathbf{106}$, 242405 (2015)] has arisen a number of questions,
the main of them concerning mechanisms of angular momentum transfer from the
light to the nuclear spin system and the nature of the light-related magnetic
fields accompanying the optical nuclear polarization. In this paper, we use the
spin noise spectroscopy for magnetometric purposes, particularly, to study
effective fields acting upon electron spin system of an $n$-GaAs layer inside a
high-Q microcavity in the presence of elliptically polarized probe beam. In
addition to the external magnetic field applied to the sample in the Voigt
geometry and the Overhauser field created by optically oriented nuclei, the
spin noise spectrum reveals an additional effective, ""optical,"" magnetic field
produced by elliptically polarized probe itself. This field is directed along
the light propagation axis, with its sign being determined by the sign of the
probe helicity and its magnitude depending on degree of circular polarization
and intensity of the probe beam. We analyze properties of this optical magnetic
field and suggest that it results from the optical Stark effect in the field of
the elliptically polarized electromagnetic wave.",1508.04968v1
2015-09-28,Semiclassical excited-state signatures of quantum phase transitions in spin chains with variable-range interactions,"We study the excitation spectrum of a family of transverse-field spin chain
models with variable interaction range and arbitrary spin $S$, which in the
case of $S=1/2$ interpolates between the Lipkin-Meshkov-Glick and the Ising
model. For any finite number $N$ of spins, a semiclassical energy manifold is
derived in the large-$S$ limit employing bosonization methods, and its geometry
is shown to determine not only the leading-order term but also the higher-order
quantum fluctuations. Based on a multi-configurational mean-field ansatz, we
obtain the semiclassical backbone of the quantum spectrum through the extremal
points of a series of one-dimensional energy landscapes -- each one exhibiting
a bifurcation when the external magnetic field drops below a threshold value.
The obtained spectra become exact in the limit of vanishing or very strong
external, transverse magnetic fields. Further analysis of the higher-order
corrections in $1/\sqrt{2S}$ enables us to analytically study the dispersion
relations of spin-wave excitations around the semiclassical energy levels.
Within the same model, we are able to investigate quantum bifurcations, which
occur in the semiclassical ($S\gg 1$) limit, and quantum phase transitions,
which are observed in the thermodynamic ($N\rightarrow\infty$) limit.",1509.08429v2
2015-12-07,Frequency domain reduced order model of aligned-spin effective-one-body waveforms with generic mass-ratios and spins,"I provide a frequency domain reduced order model (ROM) for the aligned-spin
effective-one-body (EOB) model ""SEOBNRv2"" for data analysis with second and
third generation ground based gravitational wave (GW) detectors. SEOBNRv2
models the dominant mode of the GWs emitted by the coalescence of black hole
(BH) binaries. The large physical parameter space (dimensionless spins $-1 \leq
\chi_i \leq 0.99$ and symmetric mass-ratios $0.01 \leq \eta \leq 0.25$)
requires sophisticated reduced order modeling techniques, including patching in
the parameter space and in frequency. I find that the time window over which
the inspiral-plunge and the merger-ringdown waveform in SEOBNRv2 are connected
is discontinuous when the spin of the deformed Kerr BH $\chi=0.8$ or the
symmetric mass-ratio $\eta \sim 0.083$. This discontinuity increases resolution
requirements for the ROM. The ROM can be used for compact binary systems with
total masses of $2 M_\odot$ or higher for the advanced LIGO (aLIGO) design
sensitivity and a $10$ Hz lower cutoff frequency. The ROM has a worst mismatch
against SEOBNRv2 of $\sim 1\%$, but in general mismatches are better than $\sim
0.1\%$. The ROM is crucial for key data analysis applications for compact
binaries, such as GW searches and parameter estimation carried out within the
LIGO Scientific Collaboration (LSC).",1512.02248v1
2016-02-29,Universal Dynamic Magnetism in Yb-Pyrochlores with Disparate Ground States,"The ytterbium pyrochlore magnets, Yb2B2O7 (B = Sn, Ti, Ge) are well described
by S_eff = 1/2 quantum spins decorating a network of corner-sharing tetrahedra
and interacting via anisotropic exchange. Structurally, only the non-magnetic
B-site cation, and hence, primarily the lattice parameter, is changing across
the series. Nonetheless, a range of magnetic behaviors are observed: the low
temperature magnetism in Yb2Ti2O7 and Yb2Sn2O7 has ferromagnetic character,
while Yb2Ge2O7 displays an antiferromagnetically ordered Neel state at low
temperatures. While the static properties of the ytterbium pyrochlores are
distinct, inelastic neutron scattering measurements reveal a common character
to their exotic spin dynamics. All three ytterbium pyrochlores show a gapless
continuum of spin excitations, resembling over-damped ferromagnetic spin waves
at low Q. Furthermore, the specific heat of the series also follows a common
form, with a broad, high-temperature anomaly followed by a sharp
low-temperature anomaly at T_C or T_N. The novel spin dynamics we report
correlate strongly with the broad specific heat anomaly only, remaining
unchanged across the sharp anomaly. This result suggests that the primary order
parameter in the ytterbium pyrochlores associated with the sharp anomaly is
""hidden"" and not simple magnetic dipole order.",1602.09011v1
2016-06-06,Inspiral waveforms for spinning compact binaries in a new precessing convention,"It is customary to use a precessing convention, based on Newtonian orbital
angular momentum ${\bf L}_{\rm N}$, to model inspiral gravitational waves from
generic spinning compact binaries. A key feature of such a precessing
convention is its ability to remove all spin precession induced modulations
from the orbital phase evolution. However, this convention usually employs a
post-Newtonian (PN) accurate precessional equation, appropriate for the PN
accurate orbital angular momentum ${\bf L}$, to evolve the ${\bf L}_{\rm
N}$-based precessing source frame. This motivated us to develop inspiral
waveforms for spinning compact binaries in a precessing convention that
explicitly use ${\bf L}$ to describe the binary orbits. Our approach introduces
certain additional 3PN order terms in the orbital phase and frequency evolution
equations with respect to the usual ${\bf L}_{\rm N}$-based implementation of
the precessing convention. The implications of these additional terms are
explored by computing the match between inspiral waveforms that employ ${\bf
L}$ and ${\bf L}_{\rm N}$-based precessing conventions. We found that the match
estimates are smaller than the optimal value, namely 0.97, for a non-negligible
fraction of unequal mass spinning compact binaries.",1606.01769v1
2016-06-10,"Topological order, symmetry, and Hall response of two-dimensional spin-singlet superconductors","Fully gapped two-dimensional superconductors coupled to dynamical
electromagnetism are known to exhibit topological order. In this work, we
develop a unified low-energy description for spin-singlet paired states by
deriving topological Chern-Simons field theories for $s$-wave, $d+id$, and
chiral higher even-wave superconductors. These theories capture the quantum
statistics and fusion rules of Bogoliubov quasiparticles and vortices and
incorporate global continuous symmetries - specifically, spin rotation and
conservation of magnetic flux - present in all singlet superconductors. For all
such systems, we compute the Hall response for these symmetries and investigate
the physics at the edge. In particular, the weakly-coupled phase of a chiral
$d+id$ chiral state has a spin Hall coefficient $\nu_s=2$ and a vanishing Hall
response for the magnetic flux symmetry. We argue that the latter is a generic
result for two-dimensional superconductors with gapped photons, thereby
demonstrating the absence of a spontaneous magnetic field in the ground state
of chiral superconductors. It is also shown that the Chern-Simons theories of
chiral spin-singlet superconductors derived here fall into Kitaev's 16-fold
classification of topological superconductors.",1606.03462v2
2016-07-05,Remarks on a Gauge Theory for Continuous Spin Particles,"We discuss in a systematic way the gauge theory for a continuous spin
particle proposed by Schuster and Toro. We show that it is naturally formulated
in a cotangent bundle over Minkowski spacetime where the gauge field depends on
the spacetime coordinate ${x^\mu}$ and on a covector $\eta_\mu$. We discuss how
fields can be expanded in $\eta_\mu$ in different ways and how these expansions
are related to each other. The field equation has a derivative of a Dirac delta
function with support on the $\eta$-hyperboloid $\eta^2+1=0$ and we show how it
restricts the dynamics of the gauge field to the $\eta$-hyperboloid. We then
show that on-shell the field carries one single irreducible unitary
representation of the Poincar\'e group for a continuous spin particle. We also
show how the field can be used to build a set of covariant equations found by
Wigner describing the wave function of one-particle states for a continuous
spin particle. Finally we show that it is not possible to couple minimally a
continuous spin particle to a background abelian gauge field, and make some
comments about the coupling to gravity.",1607.01316v4
2016-08-03,Observation of Dirac surface states in the noncentrosymmetric superconductor BiPd,"Materials with strong spin-orbit coupling (SOC) have in recent years become a
subject of intense research due to their potential applications in spintronics
and quantum information technology. In particular, in systems which break
inversion symmetry, SOC facilitates the Rashba-Dresselhaus effect, leading to a
lifting of spin degeneracy in the bulk and intricate spin textures of the Bloch
wave functions. Here, by combining angular resolved photoemission (ARPES) and
low temperature scanning tunneling microscopy (STM) measurements with
relativistic first-principles band structure calculations, we examine the role
of SOC in single crystals of noncentrosymmetric BiPd. We report the detection
of several Dirac surface states, one of which exhibits an extremely large spin
splitting. Unlike the surface states in inversion-symmetric systems, the Dirac
surface states of BiPd have completely different properties at opposite faces
of the crystal and are not trivially linked by symmetry. The spin-splitting of
the surface states exhibits a strong anisotropy by itself, which can be linked
to the low in-plane symmetry of the surface termination.",1608.01277v1
2016-08-06,Spin and charge thermopower effects in the ferromagnetic graphene junction,"Using wave function matching approach and employing the Landauer-Buttiker
formula a ferromagnetic graphene junction with a temperature gradient across
the system, is studied. We calculate the thermally induced charge and spin
current as well as the thermoelectric voltage (Seebeck effect) in the linear
and nonlinear regimes. Our calculation revealed that due to the electron-hole
symmetry, the charge Seebeck coefficient is, for an undoped magnetic graphene,
an odd function of chemical potential while the spin Seebeck coefficient is an
even function regardless of the temperature gradient and junction length. We
have also found with an accurate tuning external parameter, namely the exchange
filed and gate voltage, the temperature gradient across the junction drives a
pure spin current without accompanying the charge current. Another important
characteristic of thermoelectric transport, thermally induced current in the
nonlinear regime, is examined. It would be our main finding that with
increasing thermal gradient applied to the junction the spin and charge
thermovoltages decrease and even become zero for non-zero temperature bias.",1608.02142v4
2016-08-19,Scattering framework for two particles with isotropic spin-orbit coupling applicable to all energies,"Previous work developed a K-matrix formalism applicable to positive energies
for the scattering between two $s$-wave interacting particles with two internal
states, isotropic spin-orbit coupling and vanishing center-of-mass momentum [H.
Duan, L. You and B. Gao, Phys. Rev A {\bf{87}}, 052708 (2013)]. This work
extends the formalism to the entire energy regime. Explicit solutions are
obtained for the total angular momentum $J=0$ and $1$ channels. The behavior of
the partial cross sections in the negative energy regime is analyzed in detail.
We find that the leading contributions to the partial cross sections at the
negative energy thresholds are governed by the spin-orbit coupling strength
$k_{\text{so}}$ and the mass ratio. The fact that these contributions are
independent of the two-body scattering length $a_s$ is a direct consequence of
the effective reduction of the dimensionality, and hence of the density of
states, near the scattering thresholds due to the single-particle spin-orbit
coupling terms. The results are analytically continued to the energy regime
where bound states exist. It is shown that our results are consistent with
results obtained by alternative approaches. Our formulation, which can be
regarded as an extension of the standard textbook partial wave decomposition,
can be generalized to two-body systems with other types of spin-orbit coupling,
including cases where the center-of-mass momentum does not vanish.",1608.05753v1
2016-10-27,Muon spin rotation and infrared spectroscopy study of magnetism and superconductivity in Ba$ _{1-x} $K$ _{x} $Fe$ _{2} $As$ _{2} $,"Using muon spin rotation and infrared spectroscopy we study the relation
between magnetism and superconductivity in Ba$ _{1-x} $K$ _{x} $Fe$ _{2} $As$
_{2} $ single crystals from the underdoped to the slightly overdoped regime. We
find that the Fe magnetic moment is only moderately suppressed in most of the
underdoped region where it decreases more slowly than the N\'{e}el-temperature,
$ T^{\mathrm{N}} $. This applies for both the total Fe moment obtained from
muon spin rotation and for the itinerant component that is deduced from the
spectral weight of the spin-density-wave pair breaking peak in the infrared
response. In the moderately underdoped region, superconducting and static
magnetic orders co-exist on the nano-scale and compete for the same electronic
states. The static magnetic moment disappears rather sharply near optimal
doping, however, in the slightly overdoped region there is still an enhancement
or slowing down of spin fluctuations in the superconducting state. Similar to
the gap magnitude reported from specific heat measurements, the superconducting
condensate density is nearly constant in the optimally- and slightly overdoped
region, but exhibits a rather pronounced decrease on the underdoped side.
Several of these observations are similar to the phenomenology in the electron
doped counterpart Ba(Fe$ _{1-y} $Co$ _{y} $)$ _{2} $As$ _{2} $.",1610.08593v1
2016-10-27,Spin Currents and Magnon Dynamics in Insulating Magnets,"Nambu-Goldstone theorem provides gapless modes to both relativistic and
nonrelativistic systems. The Nambu-Goldstone bosons in insulating magnets are
called magnons or spin-waves and play a key role in magnetization transport. We
review here our past works on magnetization transport in insulating magnets and
also add new insights, with a particular focus on magnon transport. We
summarize in detail the magnon counterparts of electron transport, such as the
Wiedemann-Franz law, the Onsager reciprocal relation between the Seebeck and
Peltier coefficients, the Hall effects, the superconducting state, the
Josephson effects, and the persistent quantized current in a ring to list a
few. Focusing on the electromagnetism of moving magnons, i.e., magnetic
dipoles, we theoretically propose a way to directly measure magnon currents. As
a consequence of the Mermin-Wagner-Hohenberg theorem, spin transport is
drastically altered in one-dimensional antiferromagnetic (AF) spin-1/2 chains;
where the N\'eel order is destroyed by quantum fluctuations and a quasiparticle
magnon-like picture breaks down. Instead, the low-energy collective excitations
of the AF spin chain are described by a Tomonaga-Luttinger liquid (TLL) which
provides the spin transport properties in such antiferromagnets some universal
features at low enough temperature. Finally, we enumerate open issues and
provide a platform to discuss the future directions of magnonics.",1610.08901v2
2017-11-16,Nematic Spin Liquid Phase in a Frustrated Spin-1 System on the Square Lattice,"Frustration in quantum spin systems promote a variety of novel quantum
phases. An important example is the frustrated spin-$1$ model on the square
lattice with the nearest-neighbor bilinear ($J_1$) and biquadratic ($K_1$)
interactions. We provide strong evidence for a nematic spin liquid phase in a
range of $K_1/J_1$ near the SU(3)-symmetric point ($J_1 = K_1$), based on the
linear flavor-wave theory and extensive density matrix renormalization group
calculation. This phase displays no spin dipolar or quadrupolar order,
preserves translational symmetry but spontaneously breaks $C_4$ lattice
rotational symmetry, and possesses fluctuations peaked at the wavevector $(\pi,
2\pi/3)$. The spin excitation gap drops rapidly with system size and appears to
be gapless, and the nematic order is attributed to the dominant $(\pi, 2\pi/3)$
fluctuations. Our results provide a novel mechanism for electronic nematic
order and, more generally, open up a new avenue to explore frustration-induced
exotic ground states.",1711.06523v4
2018-01-29,Spin dynamics and exchange interactions in CuO measured by neutron scattering,"The magnetic properties of CuO encompass several contemporary themes in
condensed matter physics, including quantum magnetism, magnetic frustration,
magnetically-induced ferroelectricity and orbital currents. Here we report
polarized and unpolarized neutron inelastic scattering measurements which
provide a comprehensive map of the cooperative spin dynamics in the low
temperature antiferromagnetic (AFM) phase of CuO throughout much of the
Brillouin zone. At high energies ($E \gtrsim 100$\,meV) the spectrum displays
continuum features consistent with the des Cloizeax--Pearson dispersion for an
ideal $S=\frac{1}{2}$ Heisenberg AFM chain. At lower energies the spectrum
becomes more three-dimensional, and we find that a linear spin-wave model for a
Heisenberg AFM provides a very good description of the data, allowing for an
accurate determination of the relevant exchange constants in an effective spin
Hamiltonian for CuO. In the high temperature helicoidal phase, there are
features in the measured low-energy spectrum that we could not reproduce with a
spin-only model. We discuss how these might be associated with the
magnetically-induced multiferroic behavior observed in this phase.",1801.09473v2
2018-05-01,Deforming the Fredkin spin chain away from its frustration-free point,"The Fredkin model describes a spin-half chain segment subject to three-body,
correlated-exchange interactions and twisted boundary conditions. The model is
frustration-free, and its ground state wave function is known exactly. Its
low-energy physics is that of a strong xy ferromagnet with gapless excitations
and an unusually large dynamical exponent. We study a generalized spin chain
model that includes the Fredkin model as a special tuning point and otherwise
interpolates between the conventional ferromagnetic and antiferromagnetic
quantum Heisenberg models. We solve for the low-lying states, using exact
diagonalization and density-matrix renormalization group calculations, in order
to track the properties of the system as it is tuned away from the Fredkin
point; we also present exact analytical results that hold right at the Fredkin
point. We identify a zero-temperature phase diagram with multiple transitions
and unexpected ordered phases. The Fredkin ground state turns out to be
particularly brittle, unstable to even infinitesimal antiferromagnetic
frustration. We remark on the existence of an ""anti-Fredkin"" point at which all
the contributing spin configurations have a spin structure exactly opposite to
those in the Fredkin ground state.",1805.00532v3
2018-05-03,Gravitational Magnus effect,"It is well known that a spinning body moving in a fluid suffers a force
orthogonal to its velocity and rotation axis --- it is called the Magnus
effect. Recent simulations of spinning black holes and (indirect) theoretical
predictions, suggest that a somewhat analogous effect may occur for purely
gravitational phenomena. The magnitude and precise direction of this
""gravitational Magnus effect"" is still the subject of debate. Starting from the
rigorous equations of motion for spinning bodies in General Relativity
(Mathisson-Papapetrou equations), we show that indeed such an effect takes
place and is a fundamental part of the spin-curvature force. The effect arises
whenever there is a current of mass/energy, non-parallel to a body's spin. We
compute the effect explicitly for some astrophysical systems of interest: a
galactic dark matter halo, a black hole accretion disk, and the
Friedmann-Lema\^itre-Robertson-Walker (FLRW) spacetime. It is seen to lead to
secular orbital precessions potentially observable by future astrometric
experiments and gravitational-wave detectors. Finally, we consider also the
reciprocal problem: the ""force"" exerted by the body on the surrounding matter,
and show that (from this perspective) the effect is due to the body's
gravitomagnetic field. We compute it rigorously, showing the matching with its
reciprocal, and clarifying common misconceptions in the literature regarding
the action-reaction law in post-Newtonian gravity.",1805.01097v2
2018-05-21,A Triple Origin for the Heavy and Low-Spin Binary Black Holes Detected by LIGO/Virgo,"We explore the masses, merger rates, eccentricities, and spins for field
binary black holes driven to merger by a third companion through the
Lidov-Kozai mechanism. Using a population synthesis approach, we model the
creation of stellar-mass black hole triples across a range of different initial
conditions and stellar metallicities. We find that the production of
triple-mediated mergers is enhanced at low metallicities by a factor of ~100
due to the lower black hole natal kicks and reduced stellar mass loss. These
triples naturally yield heavy binary black holes with near-zero effective
spins, consistent with most of the mergers observed to date. This process
produces a merger rate of between 2 and 25 Gpc^-3 yr^-1 in the local universe,
suggesting that the Lidov-Kozai mechanism can potentially explain all of the
low-spin, heavy black hole mergers observed by Advanced LIGO/Virgo. Finally, we
show that triples admit a unique eccentricity and spin distribution that will
allow this model to be tested in the near future.",1805.08212v2
2018-06-12,Competing edge structures of Sb and Bi bilayers by trivial and nontrivial band topologies,"One-dimensional (1D) edge states formed at the boundaries of 2D normal and
topological insulators have shown intriguing quantum phases such as charge
density wave and quantum spin Hall effect. Based on first-principles
density-functional theory calculations including spin-orbit coupling (SOC), we
show that the edge states of zigzag Sb(111) and Bi(111) nanoribbons drastically
change the stability of their edge structures. For zigzag Sb(111) nanoribbon,
the Peierls-distorted or reconstructed edge structure is stabilized by a
band-gap opening. However, for zigzag Bi(111) nanoribbon, such two insulating
structures are destabilized due to the presence of topologically protected
gapless edge states, resulting in the stabilization of a metallic,
shear-distorted edge structure. We also show that the edge states of the
Bi(111) nanoribbon exhibit a larger Rashba-type spin splitting at the boundary
of Brillouin zone, compared to those of the Sb(111) nanoribbon. Interestingly,
the spin textures of edge states in the Peierls-distorted Sb edge structure and
the shear-distorted Bi edge structure have all three spin components
perpendicular and parallel to the edges, due to their broken mirror-plane
symmetry. The present findings demonstrate that the topologically trivial and
nontrivial edge states play crucial roles in determining the edge structures of
normal and topological insulators.",1806.04336v1
2018-09-21,Tailored single-atom collisions at ultra-low energies,"We employ collisions of individual atomic cesium (Cs) impurities with an
ultracold rubidium (Rb) gas to probe atomic interaction with hyperfine- and
Zeeman-state sensitivity. Controlling the Rb bath's internal state yields
access to novel phenomena observed in inter-atomic spin-exchange. These can be
tailored at ultra-low energies, owing to the excellent experimental control
over all relevant energy scales. First, detecting spin-exchange dynamics in the
Cs hyperfine state manifold, we resolve a series of previously unreported
Feshbach resonances at magnetic fields below 300 mG, separated by energies as
low as $h\times 15$ kHz. The series originates from a coupling to molecular
states with binding energies below $h\times 1$ kHz and wave function extensions
in the micrometer range. Second, at magnetic fields below $\approx 100\,$mG, we
observe the emergence of a new reaction path for alkali atoms, where in a
single, direct collision between two atoms two quanta of angular momentum can
be transferred. This path originates from the hyperfine-analogue of dipolar
spin-spin relaxation. Our work yields control of subtle ultra-low-energy
features of atomic collision dynamics, opening new routes for advanced
state-to-state chemistry, for controlling spin-exchange in quantum many-body
systems for solid state simulations, or for determination of high-precision
molecular potentials.",1809.08165v2
2018-07-05,Thermally-robust spin correlations between two 85Rb atoms in an optical microtrap,"The complex collisional properties of atoms fundamentally limit
investigations into a range of processes in many-atom ensembles. In contrast,
the bottom-up assembly of few- and many-body systems from individual atoms
offers a controlled approach to isolating and studying such collisional
processes. Here, we use optical tweezers to individually assemble pairs of
trapped $^{85}$Rb atoms, and study the spin dynamics of the two-body system in
a thermal state. The spin-2 atoms show strong pair correlation between magnetic
sublevels on timescales exceeding one second, with measured relative number
fluctuations $11.9\pm0.3$ dB below quantum shot noise, limited only by
detection efficiency. Spin populations display relaxation dynamics consistent
with simulations and theoretical predictions for $^{85}$Rb spin interactions,
and contrary to the coherent spin waves witnessed in finite-temperature
many-body experiments and zero-temperature two-body experiments. Our
experimental approach offers a versatile platform for studying two-body quantum
dynamics and may provide a route to thermally-robust entanglement generation.",1807.01822v2
2018-10-11,Accretion in a dynamical spacetime and spinning up of the black hole in the gamma ray burst central engine,"We compute the evolution of a quasi-spherical, slowly rotating accretion flow
around a black hole, whose mass and spin evolve adequately to the mass-energy
transfer through the horizon. Our model is relevant for the central engine
driving a long gamma ray burst, that originates from the collapse of a massive
star. The computations of a GRB engine in a dynamically evolving spacetime
metric are important specifically due to the transient nature of the event, in
which a huge amount of mass is accreted and changes the fundamental black hole
parameters, its mass and spin, during the process. We discuss the results in
the context of angular momentum magnitude of the collapsing star. We also study
the possible formation and evolution of shocks in the envelope, which may
temporarily affect accretion. Our results are important for the limitations on
the mass and spin range of black holes detected independently by
electromagnetic observations of GRBs and gravitational waves. We speculate on
the possible constraints for the final masses and spins of these astrophysical
black holes. It is shown that the most massive BHs were rahter not formed in a
powerful GRB explosion, if the cores of their progenitors were only weakly
rotating.",1810.05261v1
2018-02-07,Multipartite entanglement in spin chains and the Hyperdeterminant,"A way to characterize multipartite entanglement in pure states of a spin
chain with $n$ sites and local dimension $d$ is by means of the Cayley
hyperdeterminant. The latter quantity is a polynomial constructed with the
components of the wave function $\psi_{i_1, \dots, i_n}$ which is invariant
under local unitary transformation. For spin 1/2 chains (i.e. $d=2$) with $n=2$
and $n=3$ sites, the hyperdeterminant coincides with the concurrence and the
tangle respectively. In this paper we consider spin chains with $n=4$ sites
where the hyperdeterminant is a polynomial of degree 24 containing around $2.8
\times 10^6$ terms. This huge object can be written in terms of more simple
polynomials $S$ and $T$ of degrees 8 and 12 respectively. In this paper we
compute $S$, $T$ and the hyperdeterminant for eigenstates of the following spin
chain Hamiltonians: the transverse Ising model, the XXZ Heisenberg model and
the Haldane-Shastry model. Those invariants are also computed for random
states, the ground states of random matrix Hamiltonians in the Wigner-Dyson
Gaussian ensembles and the quadripartite entangled states defined by Verstraete
et al. in 2002. Finally, we propose a generalization of the hyperdeterminant to
thermal density matrices. We observe how these polynomials are able to capture
the phase transitions present in the models studied as well as a subclass of
quadripartite entanglement present in the eigenstates.",1802.02596v3
2020-08-12,Zitterbewegung of massless particles,"Zitterbewegung of massless particles with an arbitrary spin is analyzed in
various representations. Dynamics of the group velocity of a massless particle
as a whole and of the corresponding radius vector is determined. This radius
vector defines any fixed point of the envelope of the moving wave packet
characterizing the particle and its group velocity differs from the group
velocities of any points of the wavefront. We consider free massless scalar and
Dirac particles, the photon, and massive and massless particles with an
arbitrary spin and describe them in different representations. For particles
with an arbitrary spin, the generalized Feshbach-Villars representation and the
Foldy-Wouthuysen one are used. Zitterbewegung takes place in any representation
except for the Foldy-Wouthuysen one. Formulas describing the motion of a
""trembling"" free particle are the same in any representation. In the
Foldy-Wouthuysen representation, the operators of the velocity and momentum of
a free particle are proportional and Zitterbewegung does not take place. Since
the radius vector (position) and velocity operators are the quantum-mechanical
counterparts of the classical position and velocity just in the
Foldy-Wouthuysen representation, Zitterbewegung is not observable. The same
conclusion has been previously made for free massive particles. For
relativistic massive particles with spins 0, 1/2, 1 and massless particles with
spins 0, 1/2 in arbitrarily strong electromagnetic fields, independent of the
external fields Zitterbewegung does not appear in the Foldy-Wouthuysen
representation either. This conclusion is made for leading terms in the
Hamiltonian proportional to the zero and first powers of the Planck constant
and for such terms proportional to $\hbar^2$ which describe contact
interactions.",2008.05954v3
2016-12-09,Bridging single- and multireference domains for electron correlation: spin-extended coupled electron pair approximation,"We propose a size-consistent generalization of the recently developed
spin-extended configuration interaction with singles and doubles (ECISD), where
a CI wave function is explicitly spin-projected. The size-consistent effect is
effectively incorporated by treating quadruples within the formulation of
coupled electron pair approximation. As in coupled-cluster theory, quadruple
excitations are approximated by a disconnected product of double excitations.
Despite its conceptual similarity to the standard single- and multireference
analogues, such a generalization requires careful derivation, as the
spin-projected CI space is non-orthogonal and overcomplete. Although our
methods generally yield better results than ECISD, size-consistency is only
approximately retained because the action of a symmetry-projection operator is
size-inconsistent. In this work, we focus on simple models where
exclusion-principle-violating terms, which eliminate undesired contributions to
the correlation effects, are either completely neglected or averaged. These
models possess an orbital-invariant energy functional that is to be minimized
by diagonalizing an energy-shifted effective Hamiltonian within the singles and
doubles manifold. This allows for a straightforward generalization of the ECISD
analytical gradients needed to determine molecular properties and geometric
optimization. Given the multireference nature of the spin-projected
Hartree--Fock method, the proposed approaches are expected to handle static
correlation, unlike single-reference analogues. We critically assess the
performance of our methods using dissociation curves of molecules,
singlet-triplet splitting gaps, hyperfine coupling constants, and the chromium
dimer. The size-consistency and size-extensivity of the methods are also
discussed.",1612.02945v2
2016-12-12,Structure of Stable Binary Neutron Star Merger Remnants: Role of Initial Spin,"We present general relativistic numerical simulations of binary neutron star
(BNS) mergers with different initial spin configurations. We focus on models
with stars of mass 1.4 M_sol each, which employ the equation of state (EOS) by
Shen, Horowitz, and Teige, and which result in stable NSs as merger remnants.
For comparison, we consider two irrotational equal mass (M=1.35 M_sol) and
unequal mass (M=1.29,1.42 M_sol) BNS models using the APR4 EOS, which result in
a supramassive merger remnant. We present visualizations of the fluid flow and
temperature distribution and find a strong impact of the spin on vortex
structure and nonaxisymmetric deformation. We compute the radial mass
distribution and the rotation profile in the equatorial plane using recently
developed measures independent of spatial gauge, revealing slowly rotating
cores that can be well approximated by the cores of spherical stars. We also
study the influence of the spin on the inspiral phase and the gravitational
wave (GW) signal. Using a newly developed analysis method, we further show that
gravitational waveforms from BNS mergers can exhibit one or more phase jumps
after merger, which occur together with minima of the strain amplitude. We
provide a natural explanation in terms of the remnant's quadrupole moment, and
show that cancellation effects due to phase jumps can have a strong impact on
the GW power spectrum. Finally, we discuss the impact of the spin on the amount
of ejected matter.",1612.03671v2
2017-06-01,Black hole spins in coalescing binary black holes,"The possible formation mechanisms of massive close binary black holes (BHs)
that can merge in the Hubble time to produce powerful gravitational wave bursts
detected during advanced LIGO O1 and O2 science runs include the evolution from
field low-metallicity massive binaries, the dynamical formation in dense
stellar clusters and primordial BHs. Different formation channels produce
different source distributions of total masses ${M_\mathrm{tot}}$ and effective
spins $\chi_\mathrm{eff}$ of coalescing binary BHs. Using a modified
\textsc{bse} code, we carry out extensive population synthesis calculations of
the expected effective spin and total mass distributions from the standard
field massive binary formation channel for different metallicities of BH
progenitors (from zero-metal Population III stars up to solar metal abundance),
different initial rotations of the binary components, stellar wind mass loss
prescription, different BH formation models and a range of common envelope
efficiencies. The stellar rotation is treated in two-zone (core-envelope)
approximation using the effective core-envelope coupling time and with an
account of the tidal synchronization of stellar envelope rotation during the
binary system evolution. The results of our simulations, convolved with the
metallicity-dependent star-formation history, show that the total masses and
effective spins of the merging binary black holes detected during LIGO O1-O2
runs but the heaviest one (GW170729) can be simultaneously reproduced by the
adopted BH formation models. Noticeable effective spin of GW170729 requires
additional fallback from the rotating stellar envelope.",1706.00369v3
2017-06-14,Nonlocal magnon-polaron transport in yttrium iron garnet,"The spin Seebeck effect (SSE) is observed in magnetic insulator|heavy metal
bilayers as an inverse spin Hall effect voltage under a temperature gradient.
The SSE can be detected nonlocally as well, viz. in terms of the voltage in a
second metallic contact (detector) on the magnetic film, spatially separated
from the first contact that is used to apply the temperature bias (injector).
Magnon-polarons are hybridized lattice and spin waves in magnetic materials,
generated by the magnetoelastic interaction. Kikkawa et al. [Phys. Rev. Lett.
\textbf{117}, 207203 (2016)] interpreted a resonant enhancement of the local
SSE in yttrium iron garnet (YIG) as a function of the magnetic field in terms
of magnon-polaron formation. Here we report the observation of magnon-polarons
in \emph{nonlocal} magnon spin injection/detection devices for various
injector-detector spacings and sample temperatures. Unexpectedly, we find that
the magnon-polaron resonances can suppress rather than enhance the nonlocal
SSE. Using finite element modelling we explain our observations as a
competition between the SSE and spin diffusion in YIG. These results give
unprecedented insights into the magnon-phonon interaction in a key magnetic
material.",1706.04373v1
2019-03-12,On the spin-observables in pseudoscalar meson photoproduction,"Spin-observables in pseudoscalar meson photoproduction is discussed. This
work is complementary to the earlier works on this topic. Here, the reaction
amplitude is expressed in Pauli-spin basis which allows to calculate all the
observables straightforwardly. We make use of the fact that the underlying
reflection symmetry about the reaction plane can be most conveniently and
easily exploited in this basis to help finding the non-vanishing and
independent observables in this reaction. The important issue of complete
experiments is reviewed. By expressing the reaction amplitude in Pauli-spin
basis, many sets of eight observables - distinct from those found in earlier
works from the amplitude in transversity basis - capable of determining the
reaction amplitude up to an overall phase are found. It is also shown that some
of the combinations of the spin observables are suited for studying certain
aspects of the reaction dynamics. We, then, carry out a (strictly)
model-independent partial-wave analysis, in particular, of the peculiar angular
behavior of the beam asymmetry observed in eta' photoproduction very close to
threshold [P. Levi Sandri et al. 2015 Eur. Phys. J. A 51, 77]. This work should
be useful, especially, for newcomers in the field of baryon spectroscopy, where
the photoproduction reactions are a major tool for probing the baryon spectra.",1903.05015v2
2019-03-27,Black-hole remnants from black-hole--neutron-star mergers,"Observations of gravitational waves and their electromagnetic counterparts
may soon uncover the existence of coalescing compact binary systems formed by a
stellar-mass black hole and a neutron star. These mergers result in a remnant
black hole, possibly surrounded by an accretion disk. The mass and spin of the
remnant black hole depend on the properties of the coalescing binary. We
construct a map from the binary components to the remnant black hole using a
sample of numerical-relativity simulations of different mass ratios $q$,
(anti-)aligned dimensionless spins of the black hole $a_{\rm BH}$, and several
neutron star equations of state. Given the binary total mass, the mass and spin
of the remnant black hole can therefore be determined from the three parameters
$(q,a_{\rm BH},\Lambda)$, where $\Lambda$ is the tidal deformability of the
neutron star. Our models also incorporate the binary black hole and test-mass
limit cases and we discuss a simple extension for generic black hole spins. We
combine the remnant characterization with recent population synthesis
simulations for various metallicities of the progenitor stars that generated
the binary system. We predict that black-hole-neutron-star mergers produce a
population of remnant black holes with masses distributed around $7M_\odot$ and
$9M_\odot$. For isotropic spin distributions, nonmassive accretion disks are
favoured: no bright electromagnetic counterparts are expected in such mergers.",1903.11622v2
2019-05-21,Anisotropic spin fluctuations in detwinned FeSe,"Superconductivity in FeSe emerges from a nematic phase that breaks four-fold
rotational symmetry in the iron plane. This phase may arise from orbital
ordering, spin fluctuations, or hidden magnetic quadrupolar order. Here we use
inelastic neutron scattering on a mosaic of single crystals of FeSe detwinned
by mounting on a BaFe2As2 substrate to demonstrate that spin excitations are
most intense at the antiferromagnetic wave vectors QAF = (1, 0) at low energies
E = 6-11 meV in the normal state. This two-fold (C2) anisotropy is reduced at
lower energies 3-5 meV, indicating a gapped four-fold (C4) mode. In the
superconducting state, however, the strong nematic anisotropy is again
reflected in the spin resonance (E = 3.7 meV) at QAF with incommensurate
scattering around 5-6 meV. Our results highlight the extreme electronic
anisotropy of the nematic phase of FeSe and are consistent with a highly
anisotropic superconducting gap driven by spin fluctuations.",1905.08399v1
2020-03-06,Acoustically driving the single quantum spin transition of diamond nitrogen-vacancy centers,"Using a high quality factor 3 GHz bulk acoustic wave resonator device, we
demonstrate the acoustically driven single quantum spin transition
($\left|m_{s}=0\right>\leftrightarrow\left|\pm1\right>$) for diamond NV centers
and characterize the corresponding stress susceptibility. A key challenge is to
disentangle the unintentional magnetic driving field generated by device
current from the intentional stress driving within the device. We quantify
these driving fields independently using Rabi spectroscopy before studying the
more complicated case in which both are resonant with the single quantum spin
transition. By building an equivalent circuit model to describe the device's
current and mechanical dynamics, we quantitatively model the experiment to
establish their relative contributions and compare with our results. We find
that the stress susceptibility of the NV center spin single quantum transition
is around $\sqrt{2}(0.5\pm0.2)$ times that for double quantum transition
($\left|+1\right>\leftrightarrow\left|-1\right>$). Although acoustic driving in
the double quantum basis is valuable for quantum-enhanced sensing applications,
double quantum driving lacks the ability to manipulate NV center spins out of
the $\left|m_{s}=0\right>$ initialization state. Our results demonstrate that
efficient all-acoustic quantum control over NV centers is possible, and is
especially promising for sensing applications that benefit from the compact
footprint and location selectivity of acoustic devices.",2003.03418v1
2020-03-07,Mass shedding activities of Asteroid (3200) Phaethon enhanced by its rotation,"Asteroid (3200) Phaethon, a B-type asteroid, has been active during its
perihelion passages. This asteroid is considered to be a source of the Geminid
meteor stream. It is reported that this asteroid is spinning at a rotation
period of $3.60 \ hr$ and has a top shape (an oblate body with an equatorial
ridge) with a mean equatorial diameter of $6.25 \ km$. Here, we report that
Phaethon's rotation state may be close to or above its critical rotation period
when the bulk density is $0.5 \ - \ 1.5 \ {g/cm^3}$ (a typical bulk density of
a B-type asteroid). We found that in this condition, the structure of Phaethon
is sensitive to failure unless the cohesive strength is ${\sim}50 \ Pa \ - \
{\sim}260 \ Pa$. This result implies that if there are some surface processes
driven by, for example, thermal waves, large-scaled deformation may happen and
cause mass shedding. From this interpretation, we propose the processes that
produced the Geminid meteor stream in the past and dust tails recently.
Phaethon initially rotated at a spin period shorter than the current period.
The magnitude of structural deformation at this stage was higher than the
present spin condition, and a large mass shedding event, i.e., the Geminid
meteor stream, occurred. After this deformation process, the body became more
oblate, and its spin slowed down. At this point, while the spin was high enough
for the body to have mass shedding events, the magnitude of these events became
small.",2003.03495v1
2020-09-28,A continuous metal-insulator transition driven by spin correlations,"Metal-insulator transitions involve a mix of charge, spin, and structural
degrees of freedom, and when strongly-correlated, can underlay the emergence of
exotic quantum states. Mott insulators induced by the opening of a Coulomb gap
are an important and well-recognized class of transitions, but insulators
purely driven by spin correlations are much less common, as the reduced energy
scale often invites competition from other degrees of freedom. Here we
demonstrate a clean example of a spin-correlation-driven metal-insulator
transition in the all-in-all-out pyrochlore antiferromagnet Cd2Os2O7, where the
lattice symmetry is fully preserved by the antiferromagnetism. After the
antisymmetric linear magnetoresistance from conductive, ferromagnetic domain
walls is carefully removed experimentally, the Hall coefficient of the bulk
reveals four Fermi surfaces, two of electron type and two of hole type,
sequentially departing the Fermi level with decreasing temperature below the
N\'eel temperature, T_N. Contrary to the common belief of concurrent magnetic
and metal-insulator transitions in Cd2Os2O7, the charge gap of a continuous
metal-insulator transition opens only at T~10K, well below T_N=227K. The
insulating mechanism resolved by the Hall coefficient parallels the Slater
picture, but without a folded Brillouin zone, and contrasts sharply with the
behavior of Mott insulators and spin density waves, where the electronic gap
opens above and at T_N, respectively.",2009.13277v1
2020-11-15,Van Vleck excitons in Ca$_{2}$RuO$_{4}$,"A framework is presented for modeling and understanding magnetic excitations
in localized, intermediate coupling magnets where the interplay between
spin-orbit coupling, magnetic exchange, and crystal field effects are known to
create a complex landscape of unconventional magnetic behaviors and ground
states. A spin-orbit exciton approach for modeling these excitations is
developed based upon a Hamiltonian which explicitly incorporates single-ion
crystalline electric field and spin exchange terms. This framework is then
leveraged to understand a canonical Van Vleck $j\rm{_{eff}}=0$ singlet ground
state whose excitations are coupled spin and crystalline electric field levels.
Specifically, the anomalous Higgs mode [Jain et al. Nat. Phys. 13, 633 (2017)],
spin-waves [S. Kunkem\""{o}ller et al. Phys. Rev. Lett. 115, 247201 (2015)], and
orbital excitations [L. Das et al. Phys. Rev. X 8, 011048 (2018)] in the
multiorbital Mott insulator Ca$_2$RuO$_4$ are captured and good agreement is
found with previous neutron and inelastic x-ray spectroscopic measurements.
Furthermore, our results illustrate how a crystalline electric field-induced
singlet ground state can support coherent longitudinal, or amplitude
excitations, and transverse wavelike dynamics. We use this description to
discuss mechanisms for accessing a nearby critical point.",2011.07425v1
2020-11-22,Master's Thesis: Excitation Spectrum of a Weakly Interacting Spin-Orbit Coupled Bose-Einstein Condensate,"A weakly interacting, spin-orbit coupled, two-component, ultracold Bose gas
bound to a Bravais lattice is studied. Motivated by recent experimental
advances in the field of synthetically spin-orbit coupled, ultracold, neutral
atomic gases showing Bose-Einstein condensation, an analytic framework with
which to describe such systems in the superfluid regime is presented. This is
applied to a Rashba spin-orbit-coupled Bose gas in a two-dimensional optical
lattice. The exotic nature of Bose-Einstein condensation in the presence of
spin-orbit coupling is an interesting study by itself. Additionally, when the
optical lattice is introduced, the system provides a highly controllable
experimental testing ground for numerous condensed matter physics phenomena.
Five phases of the system are considered, and their excitation spectra,
critical superfluid velocities and free energies are found. In obtaining the
free energy, the effects of terms in the Hamiltonian that are linear in
excitation operators are included, and such terms have not been studied
previously in this context. Minimization of the free energy at zero temperature
is used to confirm the phase diagrams reported in the literature, where it has
usually been obtained by neglecting the effect of excitations. The plane and
stripe wave phases in the phase diagram are bosonic analogues of
Fulde-Ferrell-Larkin-Ovchinnikov states in superconductors involving nonzero
condensate momenta.",2011.10999v1
2021-02-04,Self-duality of One-dimensional Quasicrystals with Spin-Orbit Interaction,"Non-interacting spinless electrons in one-dimensional quasicrystals,
described by the Aubry-Andr\'{e}-Harper (AAH) Hamiltonian with nearest
neighbour hopping, undergoes metal to insulator transition (MIT) at a critical
strength of the quasi-periodic potential. This transition is related to the
self-duality of the AAH Hamiltonian. Interestingly, at the critical point,
which is also known as the self-dual point, all the single particle wave
functions are multifractal or non-ergodic in nature, while they are ergodic and
delocalized (localized) below (above) the critical point. In this work, we have
studied the one dimensional quasi-periodic AAH Hamiltonian in the presence of
spin-orbit (SO) coupling of Rashba type, which introduces an additional spin
conserving complex hopping and a spin-flip hopping. We have found that,
although the self-dual nature of AAH Hamiltonian remains unaltered, the
self-dual point gets affected significantly. Moreover, the effect of the
complex and spin-flip hoppings are identical in nature. We have extended the
idea of Kohn's localization tensor calculations for quasi-particles and
detected the critical point very accurately. These calculations are followed by
detailed multifractal analysis along with the computation of inverse
participation ratio and von Neumann entropy, which clearly demonstrate that the
quasi-particle eigenstates are indeed multifractal and non-ergodic at the
critical point. Finally, we mapped out the phase diagram in the parameter space
of quasi-periodic potential and SO coupling strength.",2102.02387v2
2021-10-18,Black hole-neutron star mergers are unlikely multi-messenger sources,"The promise by the LIGO/Virgo/Kagra (LVK) collaboration to detect black
hole--neutron star (BH--NS) mergers via gravitational wave (GW) emission has
recently been fulfilled with the detection of GW200105 and GW200115. Mergers of
BH--NS binaries are particularly exciting for their multi-messenger potential,
since the GW detection can be followed by an electromagnetic (EM) counterpart
(kilonova, gamma-ray burst, afterglow) that can reveal important information on
the equation of state (EOS) of NSs and the nature of the BH spin. We carry out
a statistical study of the binary stars that evolve to form a BH--NS binary and
compute the rate of merger events that can be followed by an EM counterpart. We
find that $\gtrsim 50\%$ of the mergers can lead to an EM counterpart only in
the case BHs are born highly spinning ($\chi_{\rm BH}\gtrsim 0.7$), while this
fraction does not exceed about $30\%$ for stiff NS EOSs and a few percent for
soft NS EOSs for low-spinning BHs ($\chi_{\rm BH}\lesssim 0.2$), suggesting
that a high rate of EM counterparts of BH--NS would provide support for high
natal BH spins. However, the possibilities that BHs are born with near-maximal
spins and that NS internal structure is described by a stiff EOS are disfavored
by current LVK constraints. Considering that these values only represent an
upper limit to observe an EM counterpart due to current observational
limitations, as in brightness sensitivity and sky localization, BH--NS mergers
are unlikely multi-messenger sources.",2110.09604v2
2021-10-25,Gravitational spin-orbit dynamics at the fifth-and-a-half post-Newtonian order,"Accurate waveform models are crucial for gravitational-wave data analysis,
and since spin has a significant effect on the binary dynamics, it is important
to improve the spin description in these models. In this paper, we derive the
spin-orbit (SO) coupling at the fifth-and-a-half post-Newtonian (5.5PN) order.
The method we use splits the conservative dynamics into local and
nonlocal-in-time parts, then relates the local-in-time part to gravitational
self-force results by exploiting the simple mass-ratio dependence of the
post-Minkowskian expansion of the scattering angle. We calculate the nonlocal
contribution to the 5.5PN SO dynamics to eighth order in the small-eccentricity
expansion for bound orbits, and to leading order in the large-eccentricity
expansion for unbound orbits. For the local contribution, we obtain all the
5.5PN SO coefficients from first-order self-force results for the redshift and
spin-precession invariants, except for one unknown that could be fixed in the
future by second-order self-force results. However, by incorporating our 5.5PN
results in the effective-one-body formalism and comparing its binding energy to
numerical relativity, we find that the remaining unknown has a small effect on
the SO dynamics, demonstrating an improvement in accuracy at that order.",2110.12813v2
2019-01-26,Scale-Invariance of a Spin Liquid in High Magnetic Fields,"In RuCl$_3$, inelastic neutron scattering and Raman spectroscopy reveal a
continuum of non-spin-wave excitations that persists to high temperature,
suggesting the presence of a spin liquid state on a honeycomb lattice. In the
context of the Kitaev model, magnetic fields introduce finite interactions
between the elementary excitations, and thus the effects of high magnetic
fields - comparable to the spin exchange energy scale - must be explored. Here
we report measurements of the magnetotropic coefficient - the second derivative
of the free energy with respect to magnetic field orientation - over a wide
range of magnetic fields and temperatures. We find that magnetic field and
temperature compete to determine the magnetic response in a way that is
independent of the large intrinsic exchange interaction energy. This emergent
scale-invariant magnetic anisotropy provides evidence for a high degree of
exchange frustration that favors the formation of a spin liquid state in
RuCl$_3$.",1901.09245v2
2019-04-10,Spatial anisotropy of Kondo screening cloud in a type-II Weyl semimetal,"We theoretically study the Kondo screening of a spin-1/2 magnetic impurity in
the bulk of a type-II Weyl semimetal (WSM) by use of the variational wave
function method. We consider a type-II WSM model with two Weyl nodes located on
the $k_z$-axis, and the tilting of the Weyl cones are along the $k_x$
direction. Due to co-existing electron and hole pockets, the density of states
at the Fermi energy becomes finite, leading to a significant enhancement of
Kondo effect. Consequently, the magnetic impurity and the conduction electrons
always form a bound state, this behavior is distinct from that in the type-I
WSMs, where the bound state is only formed when the hybridization exceeds a
critical value. Meanwhile, the spin-orbit coupling and unique geometry of the
Fermi surface lead to strongly anisotropic Kondo screening cloud in coordinate
space. The tilting terms break the rotational symmetry of the type-II WSM about
the $k_z$-axis, but the system remains invariant under a combined
transformation $\mathcal{T}R^{y}(\pi)$, where $\mathcal{T}$ is the
time-reversal operation and $R^{y}(\pi)$ is the rotation about the $y$-axis by
$\pi$. Largely modified diagonal and off-diagonal components of the spin-spin
correlation function on three principal planes reflect this change in band
symmetry. Most saliently, the tilting terms trigger the emergence of non-zero
off-diagonal components of spin-spin correlation function on the $x$-$z$
principal plane.",1904.05192v1
2019-08-05,Impact of a Spinning Supermassive Black Hole on the Orbit and Gravitational Waves of a Nearby Compact Binary,"Recent theoretical studies suggest that stellar-mass binary black holes
(BBHs) would merge more efficiently due to the Kozai-Lidov mechanism if these
binaries form in the vicinity of supermassive black holes (SMBHs). Since SMBHs
are likely rotating rapidly, we continue our earlier study on the
generalization of the Kozai-Lidov formalism to include the spin of the SMBH and
study the evolution of a nearby BBH. We find that the eccentricity and orbital
inclination of the BBH is significantly affected, because the spin (i) forces
the orbital plane of the center-of-mass of the BBH around the SMBH to precess
(the Lense-Thirring effect) and (ii) imposes an additional gravitomagnetic
force on the BBH. As a result, the merger time of the BBH could be
significantly different. We calculate the waveform from the BBH in one
representative example and study its detectability by a milli-Hertz GW
detector, such as the Laser Interferometer Space Antenna (LISA). We find that
the signal is distinguishable from that in the case without spin. Our results
imply that the BBHs in the LISA band could potentially be used to probe the
spin of the SMBHs in galaxy centers.",1908.01443v1
2019-09-25,Quantum entanglement in the t-J chain: From charge-spin separation to recombination,"In contrast to the conventional von Neumann bipartite entanglement entropy
(bEE), we show that a more appropriate description of the one-dimensional doped
Mott insulator is a new kind of mutual entanglement entropy (mEE) between the
charge and spin degrees of freedom. Such a charge-spin mEE can clearly
distinguish the important and distinct features between the $t$-$J$ model and
the so-called $\sigma\cdot{t}$-$J$ model. In the latter, the phase string sign
structure is switched off such that a single doped hole always behaves like a
Bloch wave in the whole regime of $J/t$, whereas in the former it exhibits a
series of level crossing with the total momentum jumps in the single-hole
ground state from spin-charge separation at $J/t\rightarrow{0}$ to spin-charge
recombination at large $J/t$, which are failed to be detected by bEE. We
further show that the distinctions between the two models persist to finite
energy density, which can be similarly well characterized by mEE but not by
bEE. By studying the dynamic time evolution of the states set out of
equilibrium at the beginning, we show that mEE indeed always increases with the
time, satisfying the common characteristic of entropy.",1909.11571v2
2019-10-02,Validating the Effective-One-Body Numerical-Relativity Waveform Models for Spin-aligned Binary Black Holes along Eccentric Orbits,"Effective-one-body (EOB) numerical-relativity (NR) waveform models for
spin-aligned binary black holes (BBHs), known as the SEOBNR waveform models,
are based on the EOB theoretical framework and NR simulations. SEOBNR models
have played an important role in the LIGO scientific collaboration (LSC)
gravitational wave (GW) data analysis for both signal search and parameter
estimation. SEOBNR models for quasi-circular orbits have evolved through
version 1 to version 4 by extending their validity domain and including more NR
results. Along another direction, we recently extended SEOBNRv1 model to
SEOBNRE model which is valid for spin-aligned BBH coalescence along eccentric
orbits. In this paper we validate this theoretical waveform model by comparing
them against the numerical relativity simulation bank, Simulating eXtreme
Spacetimes (SXS) catalog. In total, 278 NR waveforms are investigated which
include binaries with large eccentricity; large spin and large mass ratio. Our
SEOBNRE can model the NR waveforms quite well. The fitting factor for most of
the 278 waveforms is larger than 99\%. It indicates that the SEOBNRE model
could be used as template waveforms for eccentric spin-aligned BBH coalescence.",1910.00784v1
2019-10-11,Chiral Magnonic Edge States in Ferromagnetic Skyrmion Crystals Controlled by Magnetic Fields,"Achieving control over magnon spin currents in insulating magnets - where
dissipation due to Joule heating is highly suppressed - is an active area of
research that could lead to energy-efficient spintronics applications. However,
magnon spin currents supported by conventional systems with uniform magnetic
order have proven hard to control. An alternative approach that relies on
topologically protected magnonic edge states of spatially periodic magnetic
textures has recently emerged. A prime example of such textures is the
ferromagnetic skyrmion crystal which hosts chiral edge states providing a
platform for magnon spin currents. Here, we show, for the first time, an
external magnetic field can drive a topological phase transition in the spin
wave spectrum of a ferromagnetic skyrmion crystal. The topological phase
transition is signaled by the closing of a low-energy bulk magnon gap at a
critical field. In the topological phase, below the critical field, two
topologically protected chiral magnonic edge states lie within this gap, but
they unravel in the trivial phase, above the critical field. Remarkably, the
topological phase transition involves an inversion of two magnon bands that at
the $\Gamma$ point correspond to the breathing and anticlockwise modes of the
skyrmions in the crystal. Our findings suggest that an external magnetic field
could be used as a knob to switch on and off magnon spin currents carried by
topologically protected chiral magnonic edge states.",1910.05214v1
2019-12-19,Decoherence in Molecular Electron Spin Qubits: Insights from Quantum Many-Body Simulations,"Quantum states are described by wave functions whose phases cannot be
directly measured, but which play a vital role in quantum effects such as
interference and entanglement. The loss of the relative phase information,
termed decoherence, arises from the interactions between a quantum system and
its environment. Decoherence is perhaps the biggest obstacle on the path to
reliable quantum computing. Here we show that decoherence occurs even in an
isolated molecule although not all phase information is lost via a theoretical
study of a central electron spin qubit interacting with nearby nuclear spins in
prototypical magnetic molecules. The residual coherence, which is
molecule-dependent, provides a microscopic rationalization for the nuclear spin
diffusion barrier proposed to explain experiments. The contribution of nearby
molecules to the decoherence has a non-trivial dependence on separation,
peaking at intermediate distances. Molecules that are far away only affect the
long-time behavior. Because the residual coherence is simple to calculate and
correlates well with the coherence time, it can be used as a descriptor for
coherence in magnetic molecules. This work will help establish design
principles for enhancing coherence in molecular spin qubits and serve to
motivate further theoretical work.",1912.08991v1
2020-02-17,The rotating black hole interior: Insights from gravitational collapse in $AdS_3$ spacetime,"We present results from a numerical study of rotating black hole formation in
3-dimensional asymptotically anti-de Sitter (AdS) spacetime, focusing on the
structure of the black hole interior. While black holes in $AdS_3$ are of
theoretical interest for a wide variety of reasons, we choose to study this
system primarily as a toy model for astrophysical (4-dimensional) black holes
formed from gravitational collapse. We investigate the effect of angular
momentum on the geometry inside the event horizon, and see qualitative changes
in the interior structure as a function of the spin parameter. For low spins,
we find that a central spacelike curvature singularity forms, connecting to a
singular, null Cauchy horizon. For spins above a threshold consistent with the
linear analysis of Dias, Reall and Santos, curvature on the Cauchy horizon
remains bounded, signaling a violation of the strong cosmic censorship
conjecture. Further increasing the spin leads to a decrease in the relative
size of the spacelike branch of the singularity, which vanishes completely
above a second threshold. In these high-spin cases, the interior evolution is
bounded by a regular Cauchy horizon, which extends all the way inward to a
regular, timelike origin. We further explore the geodesic focusing
(""gravitational shock-wave"") effect predicted to occur along the outgoing
branch of the inner horizon, first described by Marolf and Ori. Remarkably, we
observe the effect at late times in all of the black holes we form, even those
in which the inner apparent horizon collapses to zero radius early in their
evolution.",2002.07130v2
2020-05-13,Few-body solutions under spin-exchange interaction: magnetic bound state and the Kondo screening effect,"Motivated by recent progresses on ultracold alkaline-earth atoms towards the
goal of simulating Kondo physics, in this work we exactly solve the few-body
problem of one and two trapped fermions in one dimension interacting with a
localized impurity under tunable spin-exchange interaction. It is found that
depending on the sign of the spin-exchange coupling, ferromagnetic(FM) or
anti-ferromagnetic(AFM), the attractive and repulsive branches can hold
different magnetic structures. For the two fermions case, we demonstrate the
Kondo screening effect for the attractive branch with AFM coupling, and show
that such screening is absent for the ground state with FM coupling. Moreover,
we find a sequence of FM upper branches in the AFM coupling side. These FM
states are orthogonal to all other attractive branches and their wave functions
feature a full spin-charge separation. The effect of an additional contact
interaction and the extension of our results to many particles are also
discussed. This work reveals the intriguing physics uniquely associated with
the spin-exchange interaction in the few-body point of view, which are
promisingly to be explored in the experiment of ultracold alkaline-earth atoms.",2005.06120v2
2020-05-19,Chirp Mass and Spin of Binary Black Holes from First Star Remnants,"We performed Population III (Pop III) binary evolution by using population
synthesis simulations for seven different models. We found that Pop III
binaries tend to be binary black holes (BBHs) with chirp mass $M_{\rm chirp}
\sim 30~M_{\odot}$ and they can merge at present day due to long merger time.
The merger rate densities of Pop III BBHs at $z=0$ ranges 3.34--21.2 $\rm
/yr/Gpc^3$ which is consistent with the aLIGO/aVIRGO result of 9.7--101 $\rm
/yr/Gpc^3$. These Pop III binaries might contribute to some part of the massive
BBH gravitational wave (GW) sources detected by aLIGO/aVIRGO. We also
calculated the redshift dependence of Pop III BBH mergers. We found that Pop
III low spin BBHs tend to merge at low redshift, while Pop III high spin BBHs
do at high redshift, which can be confirmed by future GW detectors such as ET,
CE, and DECIGO. These detectors can also check the redshift dependence of BBH
merger rate and spin distribution. Our results show that except for one model,
the mean effective spin $\left\langle \chi_{\rm eff} \right\rangle$ at $z=0$
ranges $0.02$--$0.3$ while at $z=10$ it does $0.16$--$0.64$. Therefore, massive
stellar-mass BBH detection by GWs will be a key for the stellar evolution study
in the early universe.",2005.09795v2
2020-06-30,Neutron powder diffraction study of NaMn$_2$O$_4$ and Li$_{0.92}$Mn$_2$O$_4$: New insights on spin-charge-orbital ordering,"The high-pressure synthesized quasi-one-dimensional compounds NaMn$_2$O$_4$
and Li$_{0.92}$Mn$_2$O$_4$ are both antiferromagnetic insulators, and here
their atomic and magnetic structures were investigated using neutron powder
diffraction. The present crystal structural analyses of NaMn2O4 reveal that
Mn3+/Mn4+ charge-ordering state exist even at low temperature (down to 1.5 K).
It is evident from one of the Mn sites shows a strongly distorted Mn3+
octahedra due to the Jahn-Teller effect. Above TN = 39 K, a two-dimensional
short-range correlation is observed, as indicated by an asymmetric diffuse
scattering. Below TN, two antiferromagnetic transitions are observed (i) a
commensurate long-range Mn3+ spin ordering below 39 K, and (ii) an
incommensurate Mn4+ spin ordering below 10 K. The commensurate magnetic
structure (kC = 0.5, -0.5, 0.5) follows the magnetic anisotropy of the local
easy axes of Mn3+, while the incommensurate one shows a spin-density-wave order
with kIC = (0,0,0.216). For Li$_{0.92}$Mn$_2$O$_4$, on the other hand, absence
of a long-range spin ordered state down to 1.5 K is confirmed.",2006.16660v1
2020-07-09,Improved quark coalescence model for spin alignment and polarization of hadrons,"We propose an improved quark coalescence model for spin alignment of vector
mesons and polarization of baryons by spin density matrix with phase space
dependence. The spin density matrix is defined through Wigner functions. Within
the model we propose an understanding of spin alignments of vector mesons
$\phi$ and $K^{*0}$ (including $\bar{K}^{*0}$) in the static limit: a large
positive deviation of $\rho_{00}$ for $\phi$ mesons from 1/3 may come from the
electric part of the vector $\phi$ field, while a negative deviation of
$\rho_{00}$ for $K^{*0}$ may come from the electric part of vorticity tensor
fields. Such a negative contribution to $\rho_{00}$ for $K^{*0}$ mesons, in
comparison with the same contribution to $\rho_{00}$ for $\phi$ mesons which is
less important, is amplified by a factor of the mass ratio of strange to light
quark times the ratio of $\left\langle \mathbf{p}_{b}^{2}\right\rangle $ on the
wave function of $K^{*0}$ to $\phi$ ($\mathbf{p}_{b}$ is the relative momentum
of two constituent quarks of $K^{*0}$ and $\phi$). These results should be
tested by a detailed and comprehensive simulation of vorticity tensor fields
and vector meson fields in heavy ion collisions.",2007.05106v2
2020-10-13,"Loss of classicality in alternating spin-$\frac{1}{2}$/spin-$1$ chain, in the presence of next-neighbor couplings and Dzyaloshinskii-Moriya interactions","We have considered and alternating Heisenberg spin chain with
nearest-neighbor ($J_1$), next-nearest neighbor ($J_2$) antiferromagnetic
couplings along with z-component of the Dzyaloshinskii-Moriya(DM) ($D_z$)
interactions. The Hamiltonian has been studied using (a) Linear Spin-Wave
Theory(LSWT) and (b) Density Matrix Renormalization Group (DMRG). The system
had been reported earlier as a classical ferrimagnet only when nearest neighbor
exchange interactions are present. Both the antiferromagnetic next-nearest
neighbor interactions and DM interactions introduce strong quantum fluctuations
and due to which all the signatures of ferrimagnetism vanishes. We find that
the nonzero $J_2$ introduces strong quantum fluctuations in each of the spin
sites due to which the z-components of both spin-1 and spin-1/2 sites average
out to be zero. The ground state becomes a singlet. The presence of $J_1$ along
with $D_z$ introduces a short range order but develops long range order along
the XY plane. $J_1$ along with $J_2$ induces competing phases with structure
factor showing sharp and wide peaks, at two different angles reflecting the
spin spiral structure locally as well as in the underlying lattice.
Interestingly, we find that the $D_z$ term removes the local spin spiral
structure in z-direction, while developing a spiral order in the XY plane.",2010.06258v2
2020-11-30,Kitaev interactions in the Co honeycomb antiferromagnets Na$_3$Co$_2$SbO$_6$ and Na$_2$Co$_2$TeO$_6$,"Co$^{2+}$ ions in an octahedral crystal field, stabilise a j$_{eff}$ = 1/2
ground state with an orbital degree of freedom and have been recently put
forward for realising Kitaev interactions, a prediction we have tested by
investigating spin dynamics in two cobalt honeycomb lattice compounds,
Na$_2$Co$_2$TeO$_6$ and Na$_3$Co$_2$SbO$_6$, using inelastic neutron
scattering. We used linear spin wave theory to show that the magnetic spectra
can be reproduced with a spin Hamiltonian including a dominant Kitaev
nearest-neighbour interaction, weaker Heisenberg interactions up to the third
neighbour and bond-dependent off-diagonal exchange interactions. Beyond the
Kitaev interaction that alone would induce a quantum spin liquid state, the
presence of these additional couplings is responsible for the zigzag-type
long-range magnetic ordering observed at low temperature in both compounds.
These results provide evidence for the realization of Kitaev-type coupling in
cobalt-based materials, despite hosting a weaker spin-orbit coupling than their
4d and 5d counterparts.",2012.00006v3
2020-12-13,Up-down instability of binary black holes in numerical relativity,"Binary black holes with spins that are aligned with the orbital angular
momentum do not precess. However, post-Newtonian calculations predict that
""up-down"" binaries, in which the spin of the heavier (lighter) black hole is
aligned (antialigned) with the orbital angular momentum, are unstable when the
spins are slightly perturbed from perfect alignment. This instability provides
a possible mechanism for the formation of precessing binaries in environments
where sources are preferentially formed with (anti) aligned spins. In this
paper, we present the first full numerical relativity simulations capturing
this instability. These simulations span $\sim 100$ orbits and $\sim 3$-$5$
precession cycles before merger, making them some of the longest numerical
relativity simulations to date. Initialized with a small perturbation of
$1^{\circ}$-$10^{\circ}$, the instability causes a dramatic growth of the spin
misalignments, which can reach $\sim 90^{\circ}$ near merger. We show that this
leaves a strong imprint on the subdominant modes of the gravitational wave
signal, which can potentially be used to distinguish up-down binaries from
other sources. Finally, we show that post-Newtonian and effective-one-body
approximants are able to reproduce the unstable dynamics of up-down binaries
extracted from numerical relativity.",2012.07147v2
2021-01-26,Insights into the Electron-Electron Interaction from Quantum Monte Carlo Calculations,"The effective electron-electron interaction in the electron gas depends on
both the density and spin local field factors. Variational Diagrammatic Quantum
Monte Carlo calculations of the spin local field factor are reported and used
to quantitatively present the full spin-dependent, electron-electron
interaction. Together with the charge local field factor from previous
Diffusion Quantum Monte Carlo calculations, we obtain the complete form of the
effective electron-electron interaction in the uniform three-dimensional
electron gas. Very simple quadratic formulas are presented for the local field
factors that quantitatively produce all of the response functions of the
electron gas at metallic densities.
  Exchange and correlation become increasingly important at low densities. At
the compressibility divergence at rs = 5.25, both the direct (screened Coulomb)
term and the charge-dependent exchange term in the electron-electron
interaction at q=0 are separately divergent. However, due to large
cancellations, their difference is finite, well behaved, and much smaller than
either term separately. As a result, the spin contribution to the
electron-electron interaction becomes an important factor. The static
electron-electron interaction is repulsive as a function of density but is less
repulsive for electrons with parallel spins.
  The effect of allowing a deformable, rather than rigid, positive background
is shown to be as quantitatively important as exchange and correlation. As a
simple concrete example, the electron-electron interaction is calculated using
the measured bulk modulus of the alkali metals with a linear phonon dispersion.
The net electron-electron interaction in lithium is attractive for wave vectors
$0-2k_F$, which suggests superconductivity, and is mostly repulsive for the
other alkali metals.",2101.10508v1
2021-03-23,57Fe and 151Eu Mössbauer studies of 3d-4f spin interplay in EuFe(2-x)Ni(x)As2,"The EuFe(2-x)Ni(x)As2 compounds exhibiting 3d and/or 4f magnetic order were
investigated by means of 57Fe and 151Eu M\""ossbauer spectroscopy. Additionally,
results for the end members of this system, i.e. EuFe2As2 and EuNi2As2, are
reported for comparison. It was found that spin-density-wave order of the Fe
itinerant moments is monotonically suppressed by Ni-substitution. However, the
3d magnetic order survives at the lowest temperature up to at least x = 0.12
and it is certainly completely suppressed for x = 0.20. The Eu localized
moments order regardless of the Ni concentration, but undergo a spin
reorientation with increasing x from the alignment parallel to the a-axis in
the parent compound, toward c-axis alignment for x > 0.07. The change of the 4f
spins ordering from antiferromagnetic to ferromagnetic takes place
simultaneously with a disappearance of the 3d spins order what is the evidence
of a strong coupling between magnetism of Eu2+ ions and the conduction
electrons of [Fe(2-x)Ni(x)As2]2- layers. The Fe nuclei experience the
transferred hyperfine magnetic field due to the Eu2+ ordering for
Ni-substituted samples with x > 0.04, while the transferred field is
undetectable in EuFe2As2 and for compound with a low Ni-substitution level. It
seems that the 4f ferromagnetic component arising from a tilt of the Eu2+
moments to the crystallographic c-axis leads to the transferred magnetic field
at the Fe atoms.",2103.12698v2
2021-03-26,"Microscopic analysis of the energy, momentum and spin distributions in a surface plasmon-polariton wave","We analyze the electromagnetic field near a plane interface between a
conductive and a dielectric media, under conditions supporting surface
plasmon-polariton (SPP) propagation. The conductive medium is described by the
hydrodynamic electron-gas model that enables a consistent analysis of the
field-induced variations of the electron density and velocity at the interface
and its nearest vicinity. The distributions of electromagnetic dynamical
characteristics: energy, energy flow, spin and momentum are calculated
analytically and illustrated numerically, employing silver-vacuum interface as
an example. A set of the ""field"" and material contributions to the energy, spin
and momentum are explicitly identified and classified with respect to their
physical origins and properties, and the orbital (canonical) and spin
(Belinfante) momentum constituents are separately examined. In this context, a
procedure for the spin-orbital momentum decomposition in the presence of free
charges is proposed and substantiated. The microscopic results agree with the
known phenomenological data but additionally show specific nanoscale structures
in the near-interface behavior of the SPP energy and momentum, which can be
deliberately created, controlled and used in nanotechnology applications.",2103.14265v3
2021-05-04,Revivals in One-dimensional Quantum Walks with a Time and Spin-dependent Phase Shift,"We investigate the role of a time and spin-dependent phase shift on the
evolution of one-dimensional discrete-time quantum walks. By employing Floquet
engineering, a time and spin-dependent phase shift ($\phi$) is imprinted onto
the walker's wave function while it shifts from one lattice site to another.
For a quantum walk driven by the standard protocol we show with our numerical
simulations that complete revivals with equal periods occur in the probability
distribution of the walk for rational values of the phase factor, i.e.,
$\phi/2\pi = p/q$. For an irrational value of $\phi/2\pi$ our results show
partial revivals in the probability distribution with unpredictable periods,
and the walker remains localized in a small region of the lattice. We further
investigate revivals in a split-step quantum walk with a time and
spin-dependent phase shift for rational values of $\phi/2\pi$. In contrast to
the case of standard protocol, the split-step quantum walk shows partial
revivals in the probability distribution. Furthermore, in view of an
experimental realization we investigate the robustness of revivals against
noise in the phase shift. Our results show that signatures of revivals persist
for smaller values of the noise parameter, while revivals vanish for larger
values. Our work is important in the context of quantum computation where
quantum walks with a time and spin-dependent phase shift can be used to control
and manipulate a desired quantum state on demand.",2105.01730v1
2021-05-07,Drastic change in inelastic scattering depending on the development of dineutron correlation in $^{10}$Be,"We investigated the development and breaking of the dineutron correlation in
$^{10}$Be by analyzing the elastic and inelastic scatterings with a framework
combing the microscopic structure and reaction models. For studying the
structure, the $^{10}$Be nucleus was constructed under the assumption of a
four-body ($\alpha + \alpha + n + n$) cluster model. In this work, we focused
on the change in the inner structure for the 0$_1^+$, 2$_1^+$, and 2$_2^+$
states when the strength of the spin-orbit interaction is varied. The inner
structure, including various physical quantities such as energy, radius, and
transition strength, is drastically influenced by the strength of the
spin-orbit interaction. In particular, the development and breaking of the
dineutron correlation is governed by the spin-orbit strength. The differences
in the inner structure can be manifested by applying the obtained wave
functions to elastic and inelastic scatterings with a proton target at $E/A =$
59.4 and 200 MeV. Although the 0$_1^+$ and 2$_1^+$ states are significantly
influenced by the spin-orbit strength of the nuclear structure calculation, the
elastic and inelastic cross sections are not much affected. On the other hand,
the inelastic cross section of the 2$_2^+$ state depends greatly on the
spin-orbit strength of the structure calculation. Thus, we discovered a way to
measure the degree of the development of dineutron cluster structure based on
its sensitivity to the inelastic cross section of the 2$_2^+$ state of
$^{10}$Be.",2105.03025v2
2021-06-09,Characterizing two-dimensional superconductivity via nanoscale noise magnetometry with single-spin qubits,"We propose nanoscale magnetometry via isolated single-spin qubits as a probe
of superconductivity in two-dimensional materials. We characterize the magnetic
field noise at the qubit location, arising from current and spin fluctuations
in the sample and leading to measurable polarization decay of the qubit. We
show that the noise due to transverse current fluctuations studied as a
function of temperature and sample-probe distance can be used to extract useful
information about the transition to a superconducting phase and the pairing
symmetry of the superconductor. Surprisingly, at low temperatures, the dominant
contribution to the magnetic noise arises from longitudinal current
fluctuations and can be used to probe collective modes such as monolayer
plasmons and bilayer Josephson plasmons. We also characterize the noise due to
spin fluctuations, which allows probing the spin structure of the pairing wave
function. Our results provide a non-invasive route to probe the rich physics of
two-dimensional superconductors.",2106.05283v2
2021-09-22,Bulk and edge dynamics of a 2D Affleck-Kennedy-Lieb-Tasaki model,"We study the dynamical properties of both bulk and edge spins of a
two-dimensional Affleck-Kennedy-Lieb-Tasaki (AKLT) model mainly by using the
stochastic series expansion quantum Monte Carlo method with stochastic analytic
continuation. In the deep AKLT phase, we obtain a spin spectrum with flat band,
which is a strong evidence for a localized state. Through the spectrum
analysis, we see a clear continuous phase transition from the AKLT phase to the
N\'eel phase in the model, and the energy gap becomes closed at the
corresponding momentum point. In comparison with linear spin-wave theory, the
differences show that there are strong interactions among magnons at high
energies. With open boundary condition, the gap of edge spins in the AKLT phase
closes at both the $\Gamma$ point and the $\pi$ point interestingly to emerge
into a flat-band-like Luttinger liquid phase, which can be explained by
symmetry and perturbation approximation. This paper helps us to better
understand the completely different dynamical behaviors of bulk and edge spins
in the symmetry protected topological phase.",2109.10901v2
2021-12-06,First principles theory for the magnetic and charge instabilities in AV$_3$Sb$_5$ systems,"Vanadium-based materials AV$_3$Sb$_5$ (A=K, Rb, Cs) with layered kagome
lattice structures have drawn great attention recently due to the discoveries
of topologically nontrivial band structures, charge density wave states, giant
anomalous Hall effect, as well as unusual superconducting phase at low
temperatures. In this work, we theoretically study the magnetic and charge
instabilities for this class of materials based on first principles
calculations. We develop a method to calculate the generalized susceptibility
tensor defined in the sublattice-orbital-spin space, with the effects of
Coulomb interactions treated by generalized random phase approximation (RPA).
The RPA susceptibility calculations indicate that there are three leading
ferromagnetic instability modes at $\Gamma$ point, which are further verified
by unrestricted self-consistent Hartree-Fock calculations including both the
on-site and inter-site Coulomb interactions. The inclusion of inter-site
interactions tend to suppress the spin ferromagnetism due to charge transfer
from the V to Sb sites, leading to weak spin magnetic moments $\sim
0.1\mu_{\textrm{B}}$ per V atom with small intrinsic anomalous Hall
conductivity. Current loops can be generated in such weak spin ferromagnetic
states as a result of spin-orbit coupling effects. The electronic structures in
the ferromagnetic states are significantly reconstructed which have nearly
compensated electron and hole carriers from two bands. On the other hand, we do
not find any diverging instability mode at $M$ point driven by
electron-electron Coulomb interactions. First principles phonon calculations
indicate that there are unstable phonon modes which tend to drive the system
into an inverse star-of-David structure. Our results indicate that there may be
separate phase transitions in the magnetic and charge channels in the system.",2112.02808v1
2022-02-09,A new generation of effective core potentials from correlated and spin-orbit calculations: selected heavy elements,"We introduce new correlation consistent effective core potentials (ccECPs)
for the elements I, Te, Bi, Ag, Au, Pd, Ir, Mo, and W with $4d$, $5d$, $6s$ and
$6p$ valence spaces. These ccECPs are given as a sum of spin-orbit averaged
relativistic effective potential (AREP) and effective spin-orbit (SO) terms.
The construction involves several steps with increasing refinements from more
simple to fully correlated methods. The optimizations are carried out with
objective functions that include weighted many-body atomic spectra,
norm-conservation criteria, and spin-orbit splittings. Transferability tests
involve molecular binding curves of corresponding hydride and oxide dimers. The
constructed ccECPs are systematically better and in a few cases on par with
previous effective core potential (ECP) tables on all tested criteria and
provide a significant increase in accuracy for valence-only calculations with
these elements. Our study confirms the importance of the AREP part in
determining the overall quality of the ECP even in the presence of sizable
spin-orbit effects. The subsequent quantum Monte Carlo (QMC) calculations point
out the importance of accurate trial wave functions which in some cases (mid
series transition elements) require treatment well beyond single-reference.",2202.04747v2
2022-04-04,Interplay of magnetic field and trigonal distortion in the honeycomb $Γ$ model: Occurrence of a spin-flop phase,"In candidate Kitaev materials, the off-diagonal $\Gamma$ and $\Gamma'$
interactions are identified to come from the spin-orbit coupling and trigonal
distortion, respectively. They have generated intense research efforts because
of their intimate relation to the field-induced magnetically disordered state
reported in $\alpha$-RuCl$_3$. Theoretically, while a plethora of field-induced
phases has been proposed in the honeycomb lattice, a stable intermediate phase
that can survive in a wide parameter region regardless of the underlying phases
is still lacking. Here we focus on the interplay of an out-of-plane magnetic
field and a symmetry-allowed $\Gamma'$ term due to trigonal distortion in the
dominant antiferromagnetic $\Gamma$ region. By using multifaceted approaches
ranging from classical Monte Carlo and semiclassical spin-wave theory to
density-matrix renormalization group, we identify an intriguing spin-flop phase
in the presence of magnetic field and antiferromagnetic $\Gamma'$ interaction,
before it eventually enters into a fully polarized state. As the $\Gamma'$
interaction approaches the size of $\Gamma$ one, the $\Gamma$-$\Gamma'$ model
maps to the easy-axis XXZ antiferromagnet, where the spin-flop phase can be
understood as a superfluid phase in the extended Bose-Hubbard model. Our
finding thus demonstrates an exciting path from the honeycomb $\Gamma$ model
towards a $U(1)$-symmetric XXZ antiferromagnet in a magnetic field.",2204.01600v2
2022-04-15,First demonstration of tuning between the Kitaev and Ising limits in a honeycomb lattice,"Recent observations of novel spin-orbit coupled states have generated
tremendous interest in $4d/5d$ transition metal systems. A prime example is the
$J_{\text{eff}}=\frac{1}{2}$ state in iridate materials and $\alpha$-RuCl$_{3}$
that drives Kitaev interactions. Here, by tuning the competition between
spin-orbit interaction ($\lambda_{\text{SOC}}$) and trigonal crystal field
splitting ($\Delta_\text{T}$), we restructure the spin-orbital wave functions
into a novel $\mu=\frac{1}{2}$ state that drives Ising interactions. This is
done via a topochemical reaction that converts Li$_{2}$RhO$_{3}$ to
Ag$_{3}$LiRh$_{2}$O$_{6}$, leading to an enhanced trigonal distortion and a
diminished spin-orbit coupling in the latter compound. Using perturbation
theory, we present an explicit expression for the new $\mu=\frac{1}{2}$ state
in the limit $\Delta_\text{T}\gg \lambda_{\text{SOC}}$ realized in
Ag$_{3}$LiRh$_{2}$O$_{6}$, different from the conventional
$J_\text{eff}=\frac{1}{2}$ state in the limit $\lambda_{\text{SOC}}\gg
\Delta_\text{T}$ realized in Li$_{2}$RhO$_{3}$. The change of ground state is
followed by a dramatic change of magnetism from a 6 K spin-glass in
Li$_{2}$RhO$_{3}$ to a 94 K antiferromagnet in Ag$_{3}$LiRh$_{2}$O$_{6}$. These
results open a pathway for tuning materials between the two limits and creating
a rich magnetic phase diagram.",2204.07591v1
2022-06-02,An inverse Faraday effect through linear polarized light,"The inverse Faraday effect (IFE) allows the generation of magnetic fields by
optical excitation only. Since its discovery in the 60s, it was believed that
only an elliptical or circular polarization could magnetize matter by this
magneto-optical phenomenon. Here, we demonstrate the generation of an IFE via a
linear polarization of light. This new physical concept results from the local
manipulation of light by a plasmonic nano-antenna. We demonstrate that a gold
nanorod excited by a linear polarization generates a non-zero magnetic field by
IFE when the incident polarization of the light is not parallel to the long
axis of the rod. We show that this dissymmetry generates hot spots of local
non-vanishing spin densities (local elliptical polarization state), introducing
the concept of super circular light, allowing this magnetization. Moreover, by
varying the angle of the incident linear polarization with respect to the
nano-antenna, we demonstrate the on-demand flipping of the magnetic field
orientation. Finally, this linear IFE generates a stationary magnetic field 25
times stronger than what a gold nanoparticle produces when excited by a
circular polarization and via a classical IFE. The creation of stationary
magnetic fields by IFE in a plasmonic nanostructure is nowadays the only
technique allowing the creation of ultra-short, intense magnetic field pulses
at the nanoscale. Thus, it finds applications in the ultrafast control of
magnetic domains with applications not only in data storage technologies but
also in research fields such as magnetic trapping, magnetic skyrmion, magnetic
circular dichroism, to spin control, spin precession, spin currents, and spin
waves, among others.",2206.00954v1
2022-06-26,Constraining the ellipticity of new-born magnetar with the observational data of Long gamma-ray bursts,"The X-ray plateau emission observed in many Long gamma-ray bursts (LGRBs) has
been usually interpreted as the spin-down luminosity of a rapidly spinning,
highly magnetized neutron star (millisecond magnetar). If this is true, then
the magnetar may emit extended gravitational wave (GW) emission associated with
the X-ray plateau due to non-axisymmetric deformation or various stellar
oscillations. The advanced LIGO and Virgo detectors have searched for
long-duration GW transients for several years, no evidence of GWs from any
magnetar has been found until now. In this work, we attempt to search for
signature of GW radiation in the electromagnetic observation of 30 LGRBs under
the assumption of the magnetar model.
  We utilize the observations of the LGRB plateau to constrain the properties
of the new-born magnetar, including the initial spin period $P_0$, diploe
magnetic field strength $B_p$ and the ellipticity $\epsilon$. We find that
there are some tight relations between magnetar parameters, e.g., $\epsilon
\propto B_p^{1.29}$ and $B_p\propto P_0^{1.14}$.
  In addition, we derive the GW strain for magnetar sample via their spin-down
processes, and find that the GWs from these objects may not be detectable by
the aLIGO and ET detectors. For a rapidly spinning magnetar ($P\sim 1\mbox{
ms}$, $ B \sim10^{15}\mbox{ G}$), the detection horizon for advanced LIGO O5
detector is $\sim 180\mbox{ Mpc}$. The detection of such GW signal associated
with the X-ray plateau would be a smoking gun that the central engine of GRB is
a magnetar.",2206.12874v1
2022-07-17,Field-linear anomalous Hall effect and Berry curvature induced by spin chirality in the kagome antiferromagnet Mn3Sn,"During the past two decades, it has been established that a non-trivial
electron wave-function topology generates an anomalous Hall effect (AHE), which
shows itself as a Hall conductivity non-linear in magnetic field. Here, we
report on an unprecedented case of field-linear AHE. In Mn$_3$Sn, a kagome
magnet, the out-of-plane Hall response, which shows an abrupt jump, was
discovered to be a case of AHE. We find now that the in-plane Hall response,
which is perfectly linear in magnetic field, is set by the Berry curvature of
the wavefunction. The amplitude of the Hall response and its concomitant Nernst
signal exceed by far what is expected in the semiclassical picture. We argue
that magnetic field induces out-of-plane spin canting and thereafter gives rise
to nontrivial spin chirality on the kagome lattice. In band structure, we find
that the spin chirality modifies the topology by gapping out Weyl nodal lines
unknown before, accounting for the AHE observed. Our work reveals intriguing
unification of real-space Berry phase from spin chirality and momentum-space
Berry curvature.",2207.08161v1
2022-07-18,Multifractally-enhanced superconductivity in two-dimensional systems with spin-orbit coupling,"The interplay of Anderson localization and electron-electron interactions is
known to lead to enhancement of superconductivity due to multifractality of
electron wave functions. We develop the theory of multifractally-enhanced
superconducting states in two-dimensional systems in the presence of spin-orbit
coupling. Using the Finkel'stein nonlinear sigma model, we derive the modified
Usadel and gap equations that take into account renormalizations caused by the
interplay of disorder and interactions. Multifractal correlations induce energy
dependence of the superconducting spectral gap. We determine the
superconducting transition temperature and the superconducting spectral gap in
the case of Ising and strong spin orbit couplings. In the latter case the
energy dependence of superconducting spectral gap is convex whereas in the
former case (as well as in the absence of spin-orbit coupling) it is concave.
Multifractality enhances not only the transition temperature but, in the same
way, the spectral gap at zero temperature. Also we study mesoscopic
fluctuations of the local density of states in the superconducting state.
Similarly to the case of normal metal, spin-orbit coupling reduce the amplitude
of fluctuations.",2207.08594v2
2022-08-09,Hybrid spin Hall nano-oscillators based on ferromagnetic metal/ferrimagnetic insulator heterostructures,"Spin-Hall nano-oscillators (SHNOs) are promising spintronic devices to
realize current controlled GHz frequency signals in nanoscale devices for
neuromorphic computing and creating Ising systems. However, traditional SHNOs
-- devices based on transition metals -- have high auto-oscillation threshold
currents as well as low quality factors and output powers. Here we demonstrate
a new type of hybrid SHNO based on a permalloy (Py) ferromagnetic-metal
nanowire and low-damping ferrimagnetic insulator, in the form of epitaxial
lithium aluminum ferrite (LAFO) thin films. The superior characteristics of
such SHNOs are associated with the excitation of larger spin-precession angles
and volumes. We further find that the presence of the ferrimagnetic insulator
enhances the auto-oscillation amplitude of spin-wave edge modes, consistent
with our micromagnetic modeling. This hybrid SHNO expands spintronic
applications, including providing new means of coupling multiple SHNOs for
neuromorphic computing and advancing magnonics.",2208.04539v2
2022-08-21,Phase diagram of the square lattice Hubbard model with Rashba-type antisymmetric spin-orbit coupling,"We clarify the ground state phase diagram of the half-filled square-lattice
Hubbard model with Rashba spin-orbit coupling (SOC) characterized by the
spin-split energy bands due to broken inversion symmetry. Although the Rashba
metals and insulating magnets have been studied well, the intermediate
interaction strength of the system remained elusive due to the lack of
appropriate theoretical tools to unbiasedly describe the large-scale magnetic
structures. We complementarily apply four different methods; sine square
deformed mean-field theory, random phase approximation, Luttinger-Tisza method,
and density matrix embedding theory, and succeed in capturing the
incommensurate spin density-wave (SDW) phases with very long spatial periods
which were previously overlooked. The transition to the SDW phases from the
metallic phase is driven by an unprecedented instability that nests the two
parts of the Fermi surface carrying opposite spins. For large SOC, the spiral,
stipe, and vortex phases are obtained, when the four Dirac points exist near
the Fermi level and their whole linear dispersions nest by a wavelength $\pi$,
opening a band gap. These two types of transition provide Fermiology that
distinguishes the antisymmetric SOC systems, generating a variety of magnetic
phases that start from the relatively weak correlation regime and continue to
the strongly interacting limit.",2208.09902v2
2022-10-03,Slow semiclassical dynamics of a two-dimensional Hubbard model in disorder-free potentials,"The quench dynamics of the Hubbard model in tilted and harmonic potentials is
discussed within the semiclassical picture. Applying the fermionic truncated
Wigner approximation (fTWA), the dynamics of imbalances for charge and spin
degrees of freedom is analyzed and its time evolution is compared with the
exact simulations in one-dimensional lattice. Quench from charge or spin
density wave is considered. We show that introduction of harmonic and
spin-dependent linear potentials sufficiently validates fTWA for longer times.
Such an improvement of fTWA is also obtained for the higher order correlations
in terms of quantum Fisher information for charge and spin channels. This
allows us to discuss the dynamics of larger system sizes and connect our
discussion to the recently introduced Stark many-body localization. In
particular, we focus on a finite two-dimensional system and show that at
intermediate linear potential strength, the addition of a harmonic potential
and spin dependence of the tilt, results in subdiffusive dynamics, similar to
that of disordered systems. Moreover, for specific values of harmonic
potential, we observed phase separation of ergodic and non-ergodic regions in
real space. The latter fact is especially important for ultracold atom
experiments in which harmonic confinement can be easily imposed, causing a
significant change in relaxation times for different lattice locations.",2210.01082v2
2022-12-30,Commensurate and incommensurate magnetic order in the doped two-dimensional Hubbard model: dynamical mean-field theory analysis,"We develop a dynamical mean-field theory approach for the spiral magnetic
order, changing to a local coordinate frame with preferable spin alignment
along the $z$-axis, which can be considered with the impurity solvers treating
the spin diagonal local Green's function. We furthermore solve the
Bethe-Salpeter equations for nonuniform dynamic magnetic susceptibilities in
the local coordinate frame. We apply this approach to describe the evolution of
magnetic order with doping in the $t-t'$ Hubbard model with $t'=0.15$, which is
appropriate for the description of the doped La$_2$CuO$_4$ high-temperature
superconductor. We find that with doping the antiferromagnetic order changes to
the $(Q,\pi)$ incommensurate one, and then to the paramagnetic phase. The
spectral weight at the Fermi level is suppressed near half filling and
continuously increases with doping. The dispersion of holes in the
antiferromagnetic phase shows qualitative agreement with the results of the
$t$-$J$ model consideration. In the incommensurate phase we find two branches
of hole dispersions, one of which crosses the Fermi level. The resulting Fermi
surface forms hole pockets. We also consider the dispersion of the magnetic
excitations, obtained from the non-local dynamic magnetic susceptibilities. The
transverse spin excitations are gapless, fulfilling the Goldstone theorem; in
contrast to the mean-field approach the obtained magnetic state is found to be
stable. The longitudinal excitations are characterized by a small gap, showing
the rigidity of the spin excitations. For realistic hopping and interaction
parameters we reproduce the experimentally measured spin-wave dispersion of
La$_2$CuO$_4$.",2212.14656v2
2023-01-13,High-temperature polaronic lattice distortions and charge ordering through the charge-density wave and quantum spin liquid phase transitions in 1T-TaS$_{2}$,"Interesting emergent behavior in quantum materials arises when the
interaction of electrons with the lattice leads to partial localization and
ordering of charge at low temperatures. The triangular lattice of some
transition metal dichalcogenides additionally presents an interesting case,
where spin order is frustrated, leading to an additional complex interplay of
interactions involving spin, charge and lattice degrees of freedom. Here we
present a study of local symmetry breaking of the lattice structure in the
layered dichalcogenide material 1T-TaS$_{2}$ using x-ray pair-distribution
function measurements. Remarkably, we observe symmetry-breaking polaronic
distortions of the lattice structure around individual localized electrons at
temperatures well above any of the known long-range ordered phases. These
characteristic polaronic signatures remain on cooling through the spin and
charge ordered states, eventually revealing a new transition near 50 K to a
state displaying partially restored symmetry and significant inter-layer
dimerization. The order parameter associated with the observed local atomic
displacements and symmetry-allowed polaron spin structure in the ground state
suggests that charge ordering is driven by the crystallization of polarons,
rather than conventional Fermi surface nesting. Symmetry analysis shows that
the distorted structure is consistent with a breakup of the QSL phase at low
temperature, concurrent with the disappearance of domains in the charge order.",2301.05670v1
2023-01-15,Symplectic Perturbation Theory in Massive Ambitwistor Space: A Zig-Zag Theory of Massive Spinning Particles,"We develop a theory of massive spinning particles interacting with background
fields in four spacetime dimensions in which holomorphy and chirality play a
central role. Applying a perturbation theory of symplectic forms to the massive
twistor space as a K\""ahler manifold, we find that the spin precession behavior
of a massive spinning particle is directly determined from the manner in which
self-dual and anti-self-dual field strengths permeate into ""complex spacetime.""
Especially, the particle shows the minimally coupled precession behavior if
self-dual field strength continues holomorphically into the complex: the
Newman-Janis shift. In general, computing the momentum impulse shows that the
parameters that control generic non-holomorphic continuations are directly
related to the coupling constants in the massive-massive-massless spinning
on-shell amplitude of Arkani-Hamed, Huang, and Huang, and thus they are
interpreted as the single-curvature Wilson coefficients given by Levi and
Steinhoff, redefined on complex worldlines. Finally, exact expressions for Kerr
and $\sqrt{\text{Kerr}}$ actions are bootstrapped in monochromatic self-dual
plane-wave backgrounds from symplectivity and a matching between classical
scattering and the on-shell amplitude, from which we obtain all-order exact
impulses of classical observables.",2301.06203v2
2023-03-02,Spinning (A)dS Black Holes with Slow-Rotation Approximation in Dynamical Chern-Simons Modified Gravity,"One of the most crucial areas of gravity research, after the direct
observation of gravitational waves, is the possible modification of General
Relativity at ultraviolet and infrared scales. In particular, the possibility
of parity violation should be considered in strong field regime. The
Chern-Simons gravity takes into account parity violation in strong gravity
regime. For all conformally flat spacetimes and spacetimes with a maximally
symmetric two-dimensional subspace, Chern-Simons gravity is identical to
General Relativity. Specifically, the Anti-de Sitter (A)dS-Kerr/Kerr black hole
is not a solution for Chern-Simons gravity. The slow-rotating BH and the
quadratic order in spin solutions are some of the known solutions to quadratic
order in spin and they are rotating solutions in the frame of dynamical
Chern-Simons gravity.
  In the present study, for the (A)dS slow-rotating situation (correct to the
first order in spin), we derive the linear perturbation equations controlling
the metric and the dynamical Chern-Simons field equation corrected to the
linear order in spin and to the second order in the Chern-Simons coupling
parameter. We show that the black hole of the (A)dS-Kerr solution is stronger
(i.e. more compact and energetic) than the Kerr black hole solution and the
reason for this feature comes form contributions at Planck scales. Moreover, we
calculate the thermodynamical quantities related to this black hole. Finally,
we calculate the geodesic equation and derive the effective potential of the
black hole.",2303.03159v1
2023-04-12,Charge order driven by multiple-Q spin fluctuations in heavily electron-doped iron selenide superconductors,"Intertwined spin and charge orders have been widely studied in
high-temperature superconductors, since their fluctuations may facilitate
electron pairing; however, they are rarely identified in heavily electron-doped
iron selenides. Here, using scanning tunneling microscopy, we show that when
the superconductivity of (Li0.84Fe0.16OH)Fe1-xSe is suppressed by introducing
Fe-site defects, a short-ranged checkerboard charge order emerges, propagating
along the Fe-Fe directions with an approximately 2aFe period. It persists
throughout the whole phase space tuned by Fe-site defect density, from a
defect-pinned local pattern in optimally doped samples to an extended order in
samples with lower Tc or non-superconducting. Intriguingly, our simulations
indicate that the charge order is likely driven by multiple-Q spin density
waves originating from the spin fluctuations observed by inelastic neutron
scattering. Our study proves the presence of a competing order in heavily
electron-doped iron selenides, and demonstrates the potential of charge order
as a tool to detect spin fluctuations.",2304.05854v1
2023-04-29,Dynamics and reversible control of the vortex Bloch-point vortex domain wall in short cylindrical magnetic nanowires,"Fast and efficient switching of nanomagnets is one of the main challenges in
the development of future magnetic memories. We numerically investigate the
evolution of the static and dynamic spin wave (SW) magnetization in short
(50-400 nm length and 120 nm diameter) cylindrical ferromagnetic nanowires,
where competing single vortex (SV) and vortex domain wall with a Bloch point
(BP-DW) magnetization configurations could be formed. For a limited nanowire
length range (between 150 and 300 nm) we demonstrate a reversible microwave
field induced (forward) and opposite spin currents (backwards) transitions
between the topologically different SV and BP-DW states. By tuning the nanowire
length, excitation frequency, the microwave pulse duration and the spin current
values we show that the optimum (low power) manipulation of the BP-DW could be
reached by a microwave excitation tuned to the main SW mode and for nanowire
lengths around 230-250 nm, where single vortex domain wall magnetization
reversal via nucleation and propagation of SV-DW takes place. An analytical
model for dynamics of the Bloch point provides an estimation of the gyrotropic
mode frequency close the one obtained via micromagnetic simulations. A
practical implementation of the method on a device has been proposed involving
microwave excitation and the generation of the opposite spin currents via spin
orbit torque. Our findings open a new pathway for the creation of unforeseen
topological magnetic memories.",2305.00346v1
2023-06-29,Comparison between holographic deformed AdS and soft wall models for fermions,"We compare the holographic dressed soft wall and the exponentially deformed
AdS models for spin 1/2 fermions. We present the dressed soft wall model and
its analytical solutions for the left and right modes, and the corresponding
spectra, also including modifications considering hyperfine spin-spin and meson
cloud interactions, as well as anomalous dimensions. Then, we discuss the
deformed AdS model for spin 1/2 fermions and present their effective
Schr\""odinger equations for the left and right modes, for which only numerical
solutions are available. Then, we consider a polynomial expansion of the
effective potential of the deformed AdS model and show that in the quadratic
approximation it leads to exact analytical solutions comparable with the
dressed soft wall model and obtain the corresponding spectra for left and right
modes. We show a numerical comparison of the mass spectra of spin 1/2 baryons
for the dressed soft wall and the deformed AdS models. We present a detailed
relation between the quadratic approximation of the deformed AdS and the
dressed soft wall models for their spectra, wave functions and comments on the
deep inelastic scattering on both models. We find that these two models are
{\sl not} equivalent even in the quadratic approximation, but it is possible to
relate their left and right modes for particular choices of their parameters.",2306.17315v2
2023-08-11,Quasi-periodic oscillation in short gamma-ray bursts from black hole-neutron star mergers,"Short-duration gamma-ray bursts (sGRBs) are commonly attributed to the
mergers of double neutron stars (NSs) or the mergers of a neutron star with a
black hole (BH). While the former scenario was confirmed by the event GW170817,
the latter remains elusive. Here, we consider the latter scenario in which, a
NS is tidally disrupted by a fast spinning low-mass BH and the accretion onto
the BH launches a relativistic jet and hence produces a sGRB. The merging
binary's orbit is likely misaligned with the BH's spin. Hence, the
Lense-Thirring precession around the BH may cause a hyper-accreting thick disk
to precess in a solid-body manner. We propose that a jet, initially aligned
with the BH spin, is deflected and collimated by the wind from the disk,
therefore being forced to precess along with the disk. This would result in a
quasi-periodic oscillation or modulation in the gamma-ray light curve of the
sGRB, with a quasi-period of $\sim 0.01-0.1$ s. The appearance of the
modulation may be delayed respective to the triggering of the light curve. This
feature, unique to the BH-NS merger, may have already revealed itself in a few
observed sGRBs (such as GRB 130310A), and it carries the spin-obit orientation
information of the merging system. Identification of this feature would be a
new approach to reveal spin-orbit-misaligned merging BH-NS systems, which are
likely missed by the current gravitational-wave searching strategy principally
targeting aligned systems.",2308.06151v1
2023-08-17,Disorder-induced excitation continuum in a spin-1/2 cobaltate on a triangular lattice,"A spin-1/2 triangular-lattice antiferromagnet is a prototypical frustrated
quantum magnet, which exhibits remarkable quantum many-body effects that arise
from the synergy between geometric spin frustration and quantum fluctuations.
It can host quantum frustrated magnetic topological phenomena like quantum spin
liquid (QSL) states, highlighted by the presence of fractionalized
quasiparticles within a continuum of magnetic excitations. In this work, we use
neutron scattering to study CoZnMo$_3$O$_8$, which has a triangular lattice of
Jeff = 1/2 Co2+ ions with octahedral coordination. We found a
wave-vector-dependent excitation continuum at low energy that disappears with
increasing temperature. Although these excitations are reminiscent of a spin
excitation continuum in a QSL state, their presence in CoZnMo$_3$O$_8$
originates from magnetic intersite disorder-induced dynamic spin states with
peculiar excitations. Our results, therefore, give direct experimental evidence
for the presence of a disorder-induced spin excitation continuum.",2308.09205v1
2023-09-12,Hidden non-collinear spin-order induced topological surface states,"Rare-earth monopnictides are a family of materials simultaneously displaying
complex magnetism, strong electronic correlation, and topological band
structure. The recently discovered emergent arc-like surface states in these
materials have been attributed to the multi-wave-vector antiferromagnetic
order, yet the direct experimental evidence has been elusive. Here we report
the observation of non-collinear antiferromagnetic order with multiple
modulations using spin-polarized scanning tunneling microscopy. Moreover, we
discover a hidden spin-rotation transition of single-to-multiple modulations 2
K below the Neel temperature. The hidden transition coincides with the onset of
the surface states splitting observed by our angle-resolved photoemission
spectroscopy measurements. Single modulation gives rise to a band inversion
with induced topological surface states in a local momentum region while the
full Brillouin zone carries trivial topological indices, and multiple
modulation further splits the surface bands via non-collinear spin tilting, as
revealed by our calculations. The direct evidence of the non-collinear spin
order in NdSb not only clarifies the mechanism of the emergent topological
surface states, but also opens up a new paradigm of control and manipulation of
band topology with magnetism.",2309.06632v1
2023-10-07,Characterizing the effect of eccentricity on the dynamics of binary black hole mergers in numerical relativity,"Many articles have partially studied the configuration of eccentric orbital
binary black hole (BBH) mergers. However, there is a scarcity of systematic and
comprehensive research on the effect of eccentricity on BBH dynamics. Thanks to
the rich and numerous numerical relativistic simulations of eccentric orbital
BBH mergers from RIT catalog, this paper aims to investigate the impact of
initial eccentricity $e_0$ on various dynamic quantities such as merger time
$T_{\text{merger}}$, peak luminosity $L_{\text{peak}}$ of gravitational waves,
recoil velocity $V_f$, mass $M_f$, and spin $\alpha_f$ of merger remnants. We
cover configurations of no spin, spin alignment, and spin precession, as well
as a broad parameter space of mass ratio ranging from 1/32 to 1 and initial
eccentricity from 0 to 1. For non-spinning BBH with an initial coordinate
separation of $11.3M$ ($M$ is the total mass of BBH), we make the first
discovery of a ubiquitous oscillation in the relationship between dynamic
quantities $L_{\text{peak}}$, $V_f$, $M_f$, $\alpha_f$, and initial
eccentricity $e_0$. Additionally, at $24.6M$, we observe the same oscillation
phenomenon in the case of mass ratio $q=1$, but do not see it in other mass
ratios, suggesting that this oscillation will be evident in numerical
simulations with sufficiently dense initial eccentricity. abbreviated",2310.04777v1
2023-12-13,Parametric Frequency Divider based Ising Machines,"We report on a new class of Ising Machines (IMs) that rely on coupled
parametric frequency dividers (PFDs) as macroscopic artificial spins. Unlike
the IM counterparts based on subharmonic injection locking (SHIL), PFD IMs do
not require strong injected continuous wave signals or applied DC voltages.
Therefore, they show a significantly lower power consumption per spin compared
to SHIL based IMs, making it feasible to accurately solve large scale
combinatorial optimization problems (COPs) that are hard or even impossible to
solve by using the current von Neumann computing architectures. Furthermore,
using high quality (Q) factor resonators in the PFD design makes PFD IMs able
to exhibit a nanoWatt level power per spin. Also, it remarkably allows a speed
up of the phase synchronization among the PFDs, resulting in shorter time to
solution and lower energy to solution despite the resonators' longer relaxation
time. As a proof of concept, a 4 node PFD IM has been demonstrated. This IM
correctly solves a set of MaxCut problems while consuming just 600 nanoWatts
per spin. This power consumption is two orders of magnitude lower than the
power per spin of state of the art SHIL based IMs operating at the same
frequency.",2312.08329v2
2024-01-12,FeS2 monolayer: a high valence and high-$T_{\rm C}$ Ising ferromagnet,"Two-dimensional (2D) magnetic materials are of current great interest for
their promising applications in spintronics. Strong magnetic coupling and
anisotropy are both highly desirable for the achievement of a high temperature
magnetic order. Here we propose the unusual high valent FeS$_2$ hexagonal
monolayer as such a candidate for a strong Ising 2D ferromagnet (FM), by
spin-orbital state analyses, first-principles calculations, and the
renormalized spin-wave theory (RSWT). We find that very importantly, the high
valent Fe$^{4+}$ ion is in the low-spin state ($t_{2g}^{4}$, $S$=1) with
degenerate $t_{2g}$ orbitals rather than the high-spin state
($t_{2g}^{3}e_g^{1}$, $S$=2). It is the low-spin state that allows to carry a
large perpendicular orbital moment and then produces a huge single ion
anisotropy (SIA) of 25 meV/Fe. Moreover, the negative charge transfer character
associated with the unusual high valence, strong Fe $3d$-S $3p$ hybridization,
wide bands, and a small band gap all help to establish a strong superexchange.
Indeed, our first-principles calculations confirm the strong FM superexchange
and the huge perpendicular SIA, both of which are further enhanced by a
compressive strain. Then, our RSWT calculations predict that the FM $T_{\rm C}$
is 261 K for the pristine FeS$_2$ monolayer and could be increased to 409 K
under the compressive --5\% strain. The high $T_{\rm C}$ is also reproduced by
our Monte Carlo (MC) simulations. Therefore, it is worth exploring the
high-$T_{\rm C}$ Ising FMs in the high valent 2D magnetic materials with
degenerate orbitals.",2401.06357v1
2024-02-01,Neutron-scattering signature of the Dzyaloshinskii-Moriya interaction in nanoparticles,"The antisymmetric Dzyaloshinkii-Moriya interaction (DMI) arises in systems
with broken inversion symmetry and strong spin-orbit coupling. In conjunction
with the isotropic and symmetric exchange interaction, magnetic anisotropy, the
dipolar interaction, and an externally applied magnetic field, the DMI supports
and stabilizes the formation of various kinds of complex mesoscale
magnetization configurations, such as helices, spin spirals, skyrmions, or
hopfions. A question of importance in this context addresses the
neutron-scattering signature of the DMI, in particular in nanoparticle
assemblies, where the related magnetic scattering signal is diffuse in
character and not of the single-crystal diffraction-peak-type, as it is e.g.\
seen in the B20 compounds. Using micromagnetic simulations we study the effect
of the DMI in spherical FeGe nanoparticles on the randomly-averaged magnetic
neutron scattering observables, more specifically on the spin-flip small-angle
neutron scattering cross section, the related chiral function, and the
pair-distance distribution function. Within the studied parameter space for the
particle size ($60 \, \mathrm{nm} \leq L \leq 200 \, \mathrm{nm}$) and the
applied magnetic field ($-1 \, \mathrm{T} \leq \mu_0 H_0 \leq 1 \,
\mathrm{T}$), we find that the chiral function is only nonzero when the DMI is
taken into account in the simulations. This result is discussed within the
context of the symmetry properties of the magnetization Fourier components and
of the involved energies under space inversion. Finally, for small applied
magnetic fields, we provide an easy-to-implement analytical correlation
function for the DMI-induced spin modulations (with wave vector
$k_{\mathrm{d}}$). The corresponding randomly-averaged spin-flip SANS cross
section reproduces the main features found in the numerical simulations.",2402.00558v1
2024-02-01,Impact of anti-symmetric contributions to signal multipoles in the measurement of black-hole spins,"Many current models for the gravitational-wave signal from precessing
black-hole binaries neglect an asymmetry in the $\pm m$ multipoles. The
asymmetry is weak, but is responsible for out-of-plane recoil, which for the
final black hole can be several thousand km/s. In this work we show that the
multipole asymmetry is also necessary to accurately measure the black-hole
spins. We consider synthetic signals calculated from the numerical relativity
surrogate model NRSur7dq4, which includes the multipole asymmetry, and measure
the signal parameters using two versions of the same model, one with and one
without the multipole asymmetry included. We find that in high
signal-to-noise-ratio observations where the spin magnitude and direction can
in principle be measured accurately, neglecting the multipole asymmetry can
result in biased measurements of these quantities. Measurements of the
black-hole masses and the standard aligned-spin combination $\chi_{\rm eff}$
are not in general strongly affected. As an illustration of the impact of the
multipole asymmetry on a real signal we consider the LVK observation
GW200129_065458, and find that the inclusion of the multipole asymmetry is
necessary to identify the binary as unequal-mass and a high in-plane spin in
the primary.",2402.00813v1
2024-03-07,Cavity-assisted resonance fluorescence from a nitrogen-vacancy center in diamond,"The nitrogen-vacancy center in diamond, owing to its optically addressable
and long-lived electronic spin, is an attractive resource for the generation of
remote entangled states. However, the center's low native fraction of coherent
photon emission, $\sim$3\%, strongly reduces the achievable spin-photon
entanglement rates. Here, we couple a nitrogen-vacancy center with a narrow
extrinsically broadened linewidth (\unit[159]{MHz}), hosted in a micron-thin
membrane, to the mode of an open optical microcavity. The resulting Purcell
factor of $\sim$1.8 increases the fraction of zero-phonon line photons to above
44\%, leading to coherent photon emission rates exceeding four times the state
of the art under non-resonant excitation. Bolstered by the enhancement provided
by the cavity, we for the first time measure resonance fluorescence without any
temporal filtering with $>$10 signal-to-laser background ratio. Our microcavity
platform would increase spin-spin entanglement success probabilities by more
than an order of magnitude compared to existing implementations. Selective
enhancement of the center's zero-phonon transitions could furthermore unlock
efficient application of quantum optics techniques such as wave-packet shaping
or all-optical spin manipulation.",2403.04611v1
2011-03-16,Equivalent forms of Dirac equations in curved spacetimes and generalized de Broglie relations,"One may ask whether the relations between energy and frequency and between
momentum and wave vector, introduced for matter waves by de Broglie, are
rigorously valid in the presence of gravity. In this paper, we show this to be
true for Dirac equations in a background of gravitational and electromagnetic
fields. We first transform any Dirac equation into an equivalent canonical
form, sometimes used in particular cases to solve Dirac equations in a curved
spacetime. This canonical form is needed to apply the Whitham Lagrangian
method. The latter method, unlike the WKB method, places no restriction on the
magnitude of Planck's constant to obtain wave packets, and furthermore
preserves the symmetries of the Dirac Lagrangian. We show using canonical Dirac
fields in a curved spacetime, that the probability current has a Gordon
decomposition into a convection current and a spin current, and that the spin
current vanishes in the Whitham approximation, which explains the negligible
effect of spin on wave packet solutions, independent of the size of Planck's
constant. We further discuss the classical-quantum correspondence in a curved
spacetime based on both Lagrangian and Hamiltonian formulations of the Whitham
equations. We show that the generalized de Broglie relations in a curved
spacetime are a direct consequence of Whitham's Lagrangian method, and not just
a physical hypothesis as introduced by Einstein and de Broglie, and by many
quantum mechanics textbooks.",1103.3201v4
2013-07-29,First direct comparison of non-disrupting neutron star-black hole and binary black hole merger simulations,"We present the first direct comparison of numerical simulations of neutron
star-black hole and black hole-black hole mergers in full general relativity.
We focus on a configuration with non spinning objects and within the most
likely range of mass ratio for neutron star-black hole systems (q=6). In this
region of the parameter space, the neutron star is not tidally disrupted prior
to merger, and we show that the two types of mergers appear remarkably similar.
The effect of the presence of a neutron star on the gravitational wave signal
is not only undetectable by the next generation of gravitational wave
detectors, but also too small to be measured in the numerical simulations: even
the plunge, merger and ringdown signals appear in perfect agreement for both
types of binaries. The characteristics of the post-merger remnants are equally
similar, with the masses of the final black holes agreeing within dM< 5
10^{-4}M_BH and their spins within da< 10^{-3}M_BH. The rate of periastron
advance in the mixed binary agrees with previously published binary black hole
results, and we use the inspiral waveforms to place constraints on the accuracy
of our numerical simulations independent of algorithmic choices made for each
type of binary. Overall, our results indicate that non-disrupting neutron
star-black hole mergers are exceptionally well modeled by black hole-black hole
mergers, and that given the absence of mass ejection, accretion disk formation,
or differences in the gravitational wave signals, only electromagnetic
precursors could prove the presence of a neutron star in low-spin systems of
total mass ~10Msun, at least until the advent of gravitational wave detectors
with a sensitivity comparable to that of the proposed Einstein Telescope.",1307.7685v1
2017-08-07,Optimally setting up directed searches for continuous gravitational waves in Advanced LIGO O1 data,"In this paper we design a search for continuous gravitational waves from
three supernova remnants: Vela Jr., Cassiopeia A (Cas A) and G347.3. These
systems might harbor rapidly rotating neutron stars emitting quasi-periodic
gravitational radiation detectable by the advanced LIGO detectors. Our search
is designed to use the volunteer computing project Einstein@Home for a few
months and assumes the sensitivity and duty cycles of the advanced LIGO
detectors during their first science run. For all three supernova remnants, the
sky-positions of their central compact objects are well known but the frequency
and spin-down rates of the neutron stars are unknown which makes the searches
computationally limited. In a previous paper we have proposed a general
framework for deciding on what target we should spend computational resources
and in what proportion, what frequency and spin-down ranges we should search
for every target, and with what search set-up. Here we further expand this
framework and apply it to design a search directed at detecting continuous
gravitational wave signals from the most promising three supernova remnants
identified as such in the previous work. Our optimization procedure yields
broad frequency and spin-down searches for all three objects, at an
unprecedented level of sensitivity: The smallest detectable gravitational wave
strain $h_0$ for Cas A is expected to be 2 times smaller than the most
sensitive upper-limits published to date, and our proposed search, which was
set-up and ran on the volunteer computing project Einstein@Home, covers a much
larger frequency range.",1708.02173v2
2019-01-29,Pauli Exclusion Principle and its theoretical foundation,"The modern state of the Pauli Exclusion Principle (PEP) is discussed. PEP can
be considered from two viewpoints. On the one hand, it asserts that particles
with half-integer spin (fermions) are described by antisymmetric wave
functions, and particles with integer spin (bosons) are described by symmetric
wave functions. This is the so-called spin-statistics connection (SSC). As we
will discuss, the physical reasons why SSC exists are still unknown. On the
other hand, according to PEP, the permutation symmetry of the total wave
functions can be only of two types: symmetric or antisymmetric, both belong to
one-dimensional representations of the permutation group, all other types of
permutation symmetry are forbidden; whereas the solution of the Schr\""odinger
equation may have any permutation symmetry. It is demonstrated that the proof
in some widespread textbooks on quantum mechanics that only symmetric and
antisymmetric states (one-dimensional representations of the permutation group)
can exist is wrong. However, the scenarios, in which an arbitrary permutation
symmetry (degenerate permutation states) is permitted lead to contradictions
with the concepts of particle identity and their independence. Thus, the
existence in our nature particles only in nondegenerate permutation states
(symmetric and antisymmetric) is not accidental and so-called symmetrization
postulate may not be considered as a postulate, since all other symmetry
options for the total wave function may not be realized. From this an important
conclusion follows: we may not expect that in future some unknown elementary
particles can be discovered that are not fermions or bosons.",1902.00499v3
2020-08-02,"Phase Diagram, Stability and Magnetic Properties of Nonlinear Excitations in Spinor Bose-Einstein Condensates","We present the phase diagram, the underlying stability and magnetic
properties as well as the dynamics of nonlinear solitary wave excitations
arising in the distinct phases of a harmonically confined spinor $F=1$
Bose-Einstein condensate. Particularly, it is found that nonlinear excitations
in the form of dark-dark-bright solitons exist in the antiferromagnetic and in
the easy-axis phase of a spinor gas, being generally unstable in the former
while possessing stability intervals in the latter phase. Dark-bright-bright
solitons can be realized in the polar and the easy-plane phases as unstable and
stable configurations respectively; the latter phase can also feature stable
dark-dark-dark solitons. Importantly, the persistence of these types of states
upon transitioning, by means of tuning the quadratic Zeeman coefficient from
one phase to the other is unravelled. Additionally, the spin-mixing dynamics of
stable and unstable matter waves is analyzed, revealing among others the
coherent evolution of magnetic dark-bright, nematic dark-bright-bright and
dark-dark-dark solitons. Moreover, for the unstable cases unmagnetized or
magnetic droplet-like configurations and spin-waves consisting of regular and
magnetic solitons are seen to dynamically emerge remaining thereafter robust
while propagating for extremely large evolution times. Interestingly, exposing
spinorial solitons to finite temperatures, their anti-damping in trap
oscillation is showcased. It is found that the latter is suppressed for
stronger bright soliton component ""fillings"". Our investigations pave the wave
for a systematic production and analysis involving spin transfer processes of
such waveforms which have been recently realized in ultracold experiments.",2008.00475v3
2020-03-23,Gravitomagnetic tidal resonance in neutron-star binary inspirals,"A compact binary system implicating at least one rotating neutron star
undergoes gravitomagnetic tidal resonances as it inspirals toward its final
merger. These have a dynamical impact on the phasing of the emitted
gravitational waves. The resonances are produced by the inertial modes of
vibration of the rotating star. Four distinct modes are involved, and the
resonances occur within the frequency band of interferometric
gravitational-wave detectors when the star spins at a frequency that lies
within this band. The resonances are driven by the gravitomagnetic tidal field
created by the companion star; this is described by a post-Newtonian vector
potential, which is produced by the mass currents associated with the orbital
motion. These resonances were identified previously by Flanagan and Racine
[Phys. Rev. D 75, 044001 (2007)], but these authors accounted only for the
response of a single mode, the r-mode, a special case of inertial modes. All
four relevant modes are included in the analysis presented in this paper. The
total accumulated gravitational-wave phase shift is shown to range from
approximately $10^{-2}$ radians when the spin and orbital angular momenta are
aligned, to approximately $10^{-1}$ radians when they are anti-aligned. Such
phase shifts will become measurable in the coming decades with the deployment
of the next generation of gravitational-wave detectors (Cosmic Explorer,
Einstein Telescope); they might even come to light within this decade, thanks
to planned improvements in the current detectors. With good constraints on the
binary masses and spins gathered from the inspiral waveform, the phase shifts
deliver information regarding the internal structure of the rotating neutron
star, and therefore on the equation of state of nuclear matter.",2003.10427v2
2022-02-15,Accuracy of Restricted Boltzmann Machines for the one-dimensional $J_1-J_2$ Heisenberg model,"Neural networks have been recently proposed as variational wave functions for
quantum many-body systems [G. Carleo and M. Troyer, Science 355, 602 (2017)].
In this work, we focus on a specific architecture, known as Restricted
Boltzmann Machine (RBM), and analyse its accuracy for the spin-1/2 $J_1-J_2$
antiferromagnetic Heisenberg model in one spatial dimension. The ground state
of this model has a non-trivial sign structure, especially for $J_2/J_1>0.5$,
forcing us to work with complex-valued RBMs. Two variational Ans\""atze are
discussed: one defined through a fully complex RBM, and one in which two
different real-valued networks are used to approximate modulus and phase of the
wave function. In both cases, translational invariance is imposed by
considering linear combinations of RBMs, giving access also to the
lowest-energy excitations at fixed momentum $k$. We perform a systematic study
on small clusters to evaluate the accuracy of these wave functions in
comparison to exact results, providing evidence for the supremacy of the fully
complex RBM. Our calculations show that this kind of Ans\""atze is very flexible
and describes both gapless and gapped ground states, also capturing the
incommensurate spin-spin correlations and low-energy spectrum for
$J_2/J_1>0.5$. The RBM results are also compared to the ones obtained with
Gutzwiller-projected fermionic states, often employed to describe quantum spin
models [F. Ferrari, A. Parola, S. Sorella and F. Becca, Phys. Rev. B 97, 235103
(2018)]. Contrary to the latter class of variational states, the
fully-connected structure of RBMs hampers the transferability of the wave
function from small to large clusters, implying an increase of the
computational cost with the system size.",2202.07576v2
2022-08-04,Spin and charge density waves in the quasi-one-dimensional KMn6Bi5,"AMn6Bi5 materials (A = Na, K, Rb and Cs) consisting of unique Mn-cluster
chains emerge as a new family of superconductors with the suppression of their
antiferromagnetic (AFM) order under high pressures. Here, we report transverse
incommensurate spin density waves (SDWs) for the Mn atoms with a propagating
direction along the chain axes as a ground state for KMn6Bi5 by single crystal
neutron diffraction. The SDWs have a refined amplitude of ~2.46 Bohr magnetons
for the Mn atoms in the pentagons and ~0.29 Bohr magnetons with a large
standard deviation for Mn atoms in the center between the pentagons. AFM
dominate both the nearest-neighbor Mn-Mn interactions within the pentagon and
next-nearest-neighbor Mn-Mn interactions out of the pentagon (along the
propagating wave). The SDWs exhibit both local and itinerant characteristics
probably formed by a cooperative interaction between local magnetic exchange
and conduction electrons. A significant magnetoelastic effect during the AFM
transition, especially along the chain direction, has been demonstrated by
temperature-dependent x-ray powder diffraction. Single crystal x-ray
diffraction below the AFM transition revealed satellite peaks originating from
charge density waves along the chain direction with a q-vector twice as large
as the SDW one, pointing to a strong real space coupling between them. Our work
not only manifests a fascinating interplay among spin, charge, lattice and one
dimensionality to trigger intertwined orders in KMn6Bi5 but also provides
important piece of information for the magnetic structure of the parent
compound to understand the mechanism of superconductivity in this new family.",2208.02456v1
2023-03-07,Deep Einstein@Home all-sky search for continuous gravitational waves in LIGO O3 public data,"We present the results of an all-sky search for continuous gravitational
waves in the public LIGO O3 data. The search covers signal frequencies $20$ Hz
$\leq f \leq 800$ Hz and a spin-down range down to $-2.6\times 10^{-9}$ Hz
s$^{-1}$1, motivated by detectability studies on synthetic populations of
Galactic neutron stars. This search is the most sensitive all-sky search to
date in this frequency/spin-down region. The initial search was performed using
the first half of the public LIGO O3 data (O3a), utilizing Graphical Processing
Units provided in equal parts by the volunteers of the Einstein@Home computing
project and by the ATLAS cluster. After a hierarchical follow-up in seven
stages, 12 candidates remain. Six are discarded at the eighth stage, by using
the remaining O3 LIGO data (O3b). The surviving six can be ascribed to
continuous-wave fake signals present in the LIGO data for validation purposes.
We recover these fake signals with very high accuracy with our last stage
search, which coherently combines all O3 data. Based on our results, we set
upper limits on the gravitational wave amplitude $h_0$, and translate these in
upper limits on the neutron star ellipticity and on the $r$-mode amplitude. The
most stringent upper limits are at $203$ Hz, with $h_0=8.1 \times 10^{-26}$ at
the 90% confidence level. Our results exclude neutron stars rotating faster
than $5$ ms with ellipticities greater than $5\times 10^{-8}
\left[{d\over{100~\textrm{pc}}}\right]$ within a distance $d$ from Earth and
$r$-mode amplitudes $\alpha \geq 10^{-5}
\left[{d\over{100~\textrm{pc}}}\right]$ for neutron stars spinning faster than
$150$ Hz.",2303.04109v2
2015-08-18,Multi-Messenger Tests for Fast-Spinning Newborn Pulsars Embedded in Stripped-Envelope Supernovae,"Fast-spinning strongly magnetized newborn neutron stars, including nascent
magnetars, are popularly implemented as the engine of luminous stellar
explosions. Here, we consider the scenario that they power various
stripped-envelope supernovae, not only super-luminous supernovae Ic but also
broad-line supernovae Ibc and possibly some ordinary supernovae Ibc. This
scenario is also motivated by the hypothesis that Galactic magnetars largely
originate from fast-spinning neutron stars as remnants of stripped-envelope
supernovae. By consistently modeling the energy injection from magnetized wind
and Ni decay, we show that proto-neutron stars with >~ 10 ms rotation and B_dip
>~ 5 x 10^14 G can be harbored in ordinary supernovae Ibc. On the other hand,
millisecond proto-neuton stars can solely power broad-line supernovae Ibc if
they are born with poloidal magnetic field of B_dip >~ 5 x 10^14 G, and
superluminous supernovae Ic with B_dip >~ 10^13 G. Then, we study how
multi-messenger emission can be used to discriminate such pulsar-driven
supernova models from other competitive scenarios. First, high-energy x-ray and
gamma-ray emission from embryonic pulsar wind nebulae is a promising smoking
gun of the underlying newborn pulsar wind. Follow-up observations of
stripped-envelope supernovae using NuSTAR ~ 50-100 days after the explosion is
strongly encouraged for nearby objects. We also discuss possible effects of
gravitational-waves on the spin-down of proto-neutron stars. If millisecond
proto-neutron stars with B_dip <~ a few x 10^13 G emit gravitational waves
through e.g., non-axisymmetric rotation deformed by the inner toroidal fields
of B_t >~ 10^16 G, the gravitational wave signal can be detectable from
ordinary supernova Ibc in the Virgo cluster by Advanced LIGO, Advanced Virgo,
and KAGRA.",1508.04393v2
2017-11-16,"Eccentric, nonspinning, inspiral, Gaussian-process merger approximant for the detection and characterization of eccentric binary black hole mergers","We present $\texttt{ENIGMA}$, a time domain, inspiral-merger-ringdown
waveform model that describes non-spinning binary black holes systems that
evolve on moderately eccentric orbits. The inspiral evolution is described
using a consistent combination of post-Newtonian theory, self-force and black
hole perturbation theory. Assuming eccentric binaries that circularize prior to
coalescence, we smoothly match the eccentric inspiral with a stand-alone,
quasi-circular merger, which is constructed using machine learning algorithms
that are trained with quasi-circular numerical relativity waveforms. We show
that $\texttt{ENIGMA}$ reproduces with excellent accuracy the dynamics of
quasi-circular compact binaries. We validate $\texttt{ENIGMA}$ using a set of
$\texttt{Einstein Toolkit}$ eccentric numerical relativity waveforms, which
describe eccentric binary black hole mergers with mass-ratios between $1 \leq q
\leq 5.5$, and eccentricities $e_0 \lesssim 0.2$ ten orbits before merger. We
use this model to explore in detail the physics that can be extracted with
moderately eccentric, non-spinning binary black hole mergers. We use
$\texttt{ENIGMA}$ to show that GW150914, GW151226, GW170104, GW170814 and
GW170608 can be effectively recovered with spinning, quasi-circular templates
if the eccentricity of these events at a gravitational wave frequency of 10Hz
satisfies $e_0\leq \{0.175,\, 0.125,\,0.175,\,0.175,\, 0.125\}$, respectively.
We show that if these systems have eccentricities $e_0\sim 0.1$ at a
gravitational wave frequency of 10Hz, they can be misclassified as
quasi-circular binaries due to parameter space degeneracies between
eccentricity and spin corrections. Using our catalog of eccentric numerical
relativity simulations, we discuss the importance of including higher-order
waveform multipoles in gravitational wave searches of eccentric binary black
hole mergers.",1711.06276v2
2020-11-02,Spinning black holes as cosmic string factories,"We consider the evolution of a cosmic string loop that is captured by a much
more massive and compact black hole. We show that after several reconnections
that produce ejections of smaller loops, the loop that remains bound to the
black hole moves on a nearly-periodic non-self-intersecting trajectory, ""the
orbit"". The orbit evolves due to an energy and angular momentum exchange
between the loop and the spinning black hole. We show that such evolution is
mathematically equivalent to a certain continuous deformation of an auxiliary
closed curve in a 3-dimensional space; for zero black-hole spin this
deformation is curve-shortening that has been extensively studied by
mathematicians. The evolution features competing effects of loop growth by the
superradiant extraction of the black-hole spin energy, and loop decay by the
friction of the moving string against the horizon. A self-intersection of an
auxiliary curve corresponds to a capture by the black hole of a new string
segment and thus an addition of a new captured loop. Possible asymptotic states
of such evolution are shown to be strong emitters of gravitational waves.
Whether reconnections prevent reaching the asymptotic states remains to be
explored. Additionally, the orbit's shape also evolves due to an emission of
gravitational waves, and a recoil of the black hole that changes the orbit and
likely leads to self-intersections.
  We argue that for a significant range of the dimensionless tension $\mu$,
string loops are captured by supermassive black holes at the centers of
galaxies. This strongly motivates further study of interaction between string
loops and black holes, especially the influence of this process on the black
hole spindown and on the production of gravitational waves by strings created
in galactic nuclei. We also discuss potential loop captures by primordial black
holes.",2011.00654v1
2017-03-24,"Linking structure and dynamics in $(p,pn)$ reactions with Borromean nuclei: the $^{11}$Li$(p,pn){^{10}}$Li case","One-neutron removal $(p,pn)$ reactions induced by two-neutron Borromean
nuclei are studied within a Transfer-to-the-Continuum (TC) reaction framework,
which incorporates the three-body character of the incident nucleus. The
relative energy distribution of the residual unbound two-body subsystem, which
is assumed to retain information on the structure of the original three-body
projectile, is computed by evaluating the transition amplitude for different
neutron-core final states in the continuum. These transition amplitudes depend
on the overlaps between the original three-body ground-state wave function and
the two-body continuum states populated in the reaction, thus ensuring a
consistent description of the incident and final nuclei. By comparing different
$^{11}$Li three-body models, it is found that the $^{11}$Li$(p,pn){^{10}}$Li
relative energy spectrum is very sensitive to the position of the $p_{1/2}$ and
$s_{1/2}$ states in $^{10}$Li and to the partial wave content of these
configurations within the $^{11}$Li ground-state wave function. The possible
presence of a low-lying $d_{5/2}$ resonance is discussed. The coupling of the
single particle configurations with the non-zero spin of the $^{9}$Li core,
which produces a spin-spin splitting of the states, is also studied. Among the
considered models, the best agreement with the available data is obtained with
a $^{11}$Li model that incorporates the actual spin of the core and contains
$\sim$31\% of $p_{1/2}$-wave content in the $n$-$^9$Li subsystem, in accord
with our previous findings for the $^{11}$Li(p,d)$^{10}$Li transfer reaction,
and a near-threshold virtual state.",1703.08320v1
2001-11-30,Strange stars as persistent sources of gravitational waves,"We investigate the relevance of the gravitational-wave driven r-mode
instability for strange stars. We find that the unstable r-modes affect strange
stars in a way that is quite distinct from the neutron star case. For accreting
strange stars we show that the onset of r-mode instability does not lead to the
thermo-gravitational runaway that is likely to occur in neutron stars. Instead,
the strange star evolves towards a quasi-equilibrium state on a timescale of
about a year. This mechanism could thus explain the clustering of
spin-frequencies inferred from kHz QPO data in Low-mass X-ray binaries. For
young strange stars we show that the r-mode driven spin-evolution is also
distinct from the neutron star case. In a young strange star the r-mode
undergoes short cycles of instability during the first few months. This is
followed by a quasi-adiabatic phase where the r-mode remains at a small,
roughly constant, amplitude for thousands of years. Another distinguishing
feature from the neutron star case is that the r-modes in a strange star never
grow to large amplitudes. Our results suggest that the r-modes in strange star
emit a persistent gravitational-wave signal that should be detectable with
large-scale interferometers given an observation time of a few months. If
detected, these signals would provide unique evidence for the existence of
strange stars, which would put useful constraints on the parameters of QCD.",0111582v1
2002-11-26,Rayleigh - Taylor Gravity Waves and Quasiperiodic Oscillation Phenomenon in X-ray Binaries,"Accretion onto compact objects in X-ray binaries [black hole, neutron star
(NS), white dwarf] is characterized by non-uniform flow density profiles. Such
an effect of heterogeneity in presence of gravitational forces and pressure
gradients exhibits Raylegh-Taylor gravity waves (RTGW). They should be seen as
quasioperiodic wave oscillations (QPO). In this paper I show that the main QPO
frequency, which is very close to the Keplerian frequency, is split into
separate frequencies (hybrid and low branch) under the influence of the
gravitational forces in the rotational frame of reference. The observed low and
high QPO frequencies are an intrinsic signature of the RTGW. I elaborate the
conditions for the density profile when the RTGW oscillations are stable. A
comparison of the inferred QPO frequencies with QPO observations is presented.
I find that hectohertz frequencies detected from NS binaries can be identified
as the RTGW low branch frequencies. I also predict that an observer can see the
double NS spin frequency during the NS long (super) burst events when the
pressure gradients and buoyant forces are suppressed. The Coriolis force is the
only force which acts in the rotational frame of reference and its presence
causes perfect coherent pulsations with a frequency twice of the NS spin.",0211575v1
2004-07-08,Neutrino Oscillations at Supernova Core Bounce Generate the Strongest Gravitational-Wave Bursts,"During the core bounce of a supernova collapse resonant active-to-active
($\nu_a \to \nu_a$), as well as active-to-sterile ($\nu_a \to \nu_s$) neutrino
($\nu$) oscillations can take place. Besides, over this phase weak magnetism
increases antineutrino ($\bar{\nu}$) mean free paths, and thus its luminosity.
Because the oscillation feeds mass-energy into the target $\nu$ species, the
large mass-squared difference between species ($\nu_a \to \nu_s$) implies a
huge amount of power to be given off as gravitational waves ($L_{\textrm{GWs}}
\sim 10^{49}erg s$^{-1}$), due to anisotropic but coherent $\nu$ flow over the
oscillation length. This anisotropy in the $\nu$-flux is driven by both the
{\it universal spin-rotation} and the spin-magnetic coupling. The new spacetime
strain estimated this way is still several orders of magnitude larger than
those from $\nu$ diffusion (convection and cooling) or quadrupole moments of
the neutron star matter. This new feature turns these bursts the more promising
supernova gravitational-wave signal that may be detected by observatories as
LIGO, VIRGO, etc., for distances far out to the VIRGO cluster of galaxies.",0407184v1
2005-02-25,Surface Modes on Bursting Neutron Stars and X-ray Burst Oscillations,"Accreting neutron stars (NSs) often show coherent modulations during type I
X-ray bursts, called burst oscillations. We consider whether a nonradial mode
can serve as an explanation for burst oscillations from those NSs which are not
magnetic. We find that a surface wave in the shallow burning layer transitions
into a crustal interface wave as the envelope cools, a new and previously
uninvestigated phenomenon. The surface modulations decrease dramatically as the
mode switches, explaining why burst oscillations often disappear before burst
cooling ceases. When we include rotational modifications, we find mode
frequencies and drifts consistent with those observed. The large NS spin
($\approx270-620 {\rm Hz}$) needed to make this match implies that accreting
NSs are spinning at frequencies $\approx4 {\rm Hz}$ above the burst
oscillation. Since the asymptotic frequency is set by the crustal interface
wave, the observed late time frequency drifts are a probe of the composition
and temperature of NS crusts. We compare our model with the observed drifts and
persistent luminosities of X-ray burst sources, and find that NSs with a higher
average accretion rate show smaller drifts, as we predict. Furthermore, the
drift sizes are consistent with crusts composed of iron-like nuclei, as
expected for the ashes of the He-rich bursts that are exhibited by these
objects.",0502546v2
2001-05-30,Long-Time Tails and Anomalous Slowing Down in the Relaxation of Spatially Inhomogeneous Excitations in Quantum Spin Chains,"Exact analytic calculations in spin-1/2 XY chains, show the presence of
long-time tails in the asymptotic dynamics of spatially inhomogeneous
excitations. The decay of inhomogeneities, for $t\to \infty $, is given in the
form of a power law \[ (t/\tau_{Q}) ^{-\nu_{Q}} \] where the relaxation time
$\tau_{Q}$ and the exponent $\nu_{Q}$ depend on the wave vector $Q$,
characterizing the spatial modulation of the initial excitation. We consider
several variants of the XY model (dimerized, with staggered magnetic field,
with bond alternation, and with isotropic and uniform interactions), that are
grouped into two families, whether the energy spectrum has a gap or not. Once
the initial condition is given, the non-equilibrium problem for the
magnetization is solved in closed form, without any other assumption. The
long-time behavior for $t\to \infty $ can be obtained systematically in a form
of an asymptotic series through the stationary phase method. We found that
gapped models show critical behavior with respect to $Q$, in the sense that
there exist critical values $Q_{c}$, where the relaxation time $\tau_{Q}$
diverges and the exponent $\nu_{Q}$ changes discontinuously. At those points, a
slowing down of the relaxation process is induced, similarly to phenomena
occurring near phase transitions. Long-lived excitations are identified as
incommensurate spin density waves that emerge in systems undergoing the Peierls
transition. In contrast, gapless models do not present the above anomalies as a
function of the wave vector $Q$.",0105594v2
2002-03-05,Neutron scattering search for static magnetism in oxygen ordered YBa2Cu3O6.5,"We present elastic and inelastic neutron scattering results on highly oxygen
ordered YBa2Cu3O6.5 ortho-II. We find no evidence for the presence of ordered
magnetic moments to a sensitivity of 0.003 Bohr magnetons, an order of
magnitude smaller than has been suggested in theories of orbital or
d-density-wave (DDW) currents. The absence of sharp elastic peaks, shows that
the d-density-wave phase is not present, at least for the superconductor with
the doping of 6.5 and the ordered ortho-II structure. We cannot exclude the
possibility that a broad peak may exist with extremely short-range DDW
correlations. For less ordered or more doped crystals it is possible that
disorder may lead to static magnetism. We have also searched for the large
normal state spin gap that is predicted to exist in an ordered DDW phase.
Instead of a gap we find that the Q-correlated spin susceptibility persists to
the lowest energies studied, 6 meV. Our results are compatible with the
coexistence of superconductivity with orbital currents, but only if they are
dynamic, and exclude a sharp phase transition to an ordered d-density-wave
phase.",0203076v1
2004-12-16,"Dynamics of Quasi-ordered Structure in a Regio-regulated pi-Conjugated Polymer:Poly(4-methylthiazole-2,5-diyl)","Dynamics of regio-regulated Poly(4-methylthiazole-2,5-diyl) [HH-P4MeTz] was
inves tigated by solid-state 1H, 2D, 13C NMR spectroscopies, and differential
scanning calorimetry(DSC) measurements. DSC, 2D quadrupolar echo NMR, 13C
cross-polarization and magic-angle spinning(CPMAS) NMR, and 2D spin-echo(2DSE)
CPMAS NMR spectroscopy suggest existence of a quasi-ordered phase in which
backbone twists take place with weakened pi-stackings. Two-dimensional exchange
2D NMR(2DEX) detected slow dynamics with a rate of an order of 10^2Hz for the
CD_3 group in d_3-HH-P4MeTz at 288K. The frequency dependence of proton
longitudinal relaxation rate at 288K shows a omega^-1/2 dependence, which is
due to the one-dimensional diffusion-like motion of backbone conformational
modulation waves. The diffusion rate was estimated as 3+/-2 GHz, which was
approximately 10^7 times larger than that estimated by 2DEX NMR measurements.
These results suggest that there exists anomalous dispersion of modulation
waves in HH-P4MeTz. The one-dimensional group velocity of the wave packet is
responsible for the behavior of proton longitudinal relaxation time. On the
other hand, the 2DEX NMR is sensitive to phase velocity of the nutation of
methyl groups that is associated with backbone twists. From proton T_1 and T_2
measurements, the activation energy was estimated as 2.9 and 3.4 kcal/mol,
respectively. These were in agreement with 3.0 kcal/mol determined by
Moller-Plesset(MP2) molecular orbital(MO) calculation. We also performed
chemical shielding calculation of the methyl-carbon in order to understand
chemical shift tensor behavior, leading to the fact that a quasi-ordered phase
coexist with the crystalline phase.",0412419v1
2007-01-05,Origin and roles of a strong electron-phonon interaction in cuprate oxide superconductors,"A strong electron-phonon interaction arises from the modulation of the
superexchange interaction by lattice vibrations. It is responsible for the
softening of the half-breathing modes around (pm pi/a,0) and (0, pm pi/a) in
the two-dimensional Brillouin zone, with a being the lattice constant of CuO_2
planes, as is studied in Phys. Rev. B70, 184514 (2004). Provided that
antiferromagnetic spin fluctuations are developed around Q=(pm 3 pi/4a, pm
pi/a) and (pm pi/a, pm 3 pi/4a), the electron-phonon interaction can also cause
the softening of Cu-O bond stretching modes around 2Q, or around (pm pi/2a,0)
and (0, pm pi/2a). The softening around 2Q is accompanied by the development of
charge fluctuations corresponding to the so called 4a-period stripe or
4a*4a-period checker-board state. However, an observation that the 4a-period
modulating part or the 2Q part of the density of states is almost symmetric
with respect to the chemical potential contradicts a scenario that the
stabilization of a single-2Q or double-2Q charge density wave following the
complete softening of the 2Q bond stretching modes is responsible for the
ordered stripe or checker-board state. It is proposed that the stripe or
checker-board state is simply a single-Q or double-Q spin density wave, whose
second-harmonic effects can explain the observed almost symmetric 2Q part of
the density of states. The strong electron-phonon interaction can play no or
only a minor role in the occurrence of d gamma-wave superconductivity in
cuprate oxides.",0701088v1
1997-02-25,Searching for periodic sources with LIGO,"We investigate the computational requirements for all-sky, all-frequency
searches for gravitational waves from spinning neutron stars, using archived
data from interferometric gravitational wave detectors such as LIGO. These
sources are expected to be weak, so the optimal strategy involves coherent
accumulaton of signal-to-noise using Fourier transforms of long stretches of
data (months to years). Earth-motion-induced Doppler shifts, and intrinsic
pulsar spindown, will reduce the narrow-band signal-to-noise by spreading power
across many frequency bins; therefore, it is necessary to correct for these
effects before performing the Fourier transform. The corrections can be
implemented by a parametrized model, in which one does a search over a discrete
set of parameter values. We define a metric on this parameter space, which can
be used to determine the optimal spacing between points in a search; the metric
is used to compute the number of independent parameter-space points Np that
must be searched, as a function of observation time T. The number Np(T) depends
on the maximum gravitational wave frequency and the minimum spindown age
tau=f/(df/dt) that the search can detect. The signal-to-noise ratio required,
in order to have 99% confidence of a detection, also depends on Np(T). We find
that for an all-sky, all-frequency search lasting T=10^7 s, this detection
threshhold is at a level of 4 to 5 times h(3/yr), where h(3/yr) is the
corresponding 99% confidence threshhold if one knows in advance the pulsar
position and spin period.",9702050v1
2000-11-22,Asymptotic behaviour of cylindrical waves interacting with spinning strings,"We consider a family of cylindrical spacetimes endowed with angular momentum
that are solutions to the vacuum Einstein equations outside the symmetry axis.
This family was recently obtained by performing a complete gauge fixing adapted
to cylindrical symmetry. In the present work, we find boundary conditions that
ensure that the metric arising from this gauge fixing is well defined and that
the resulting reduced system has a consistent Hamiltonian dynamics. These
boundary conditions must be imposed both on the symmetry axis and in the region
far from the axis at spacelike infinity. Employing such conditions, we
determine the asymptotic behaviour of the metric close to and far from the
axis. In each of these regions, the approximate metric describes a conical
geometry with a time dislocation. In particular, around the symmetry axis the
effect of the singularity consists in inducing a constant deficit angle and a
timelike helical structure. Based on these results and on the fact that the
degrees of freedom in our family of metrics coincide with those of cylindrical
vacuum gravity, we argue that the analysed set of spacetimes represent
cylindrical gravitational waves surrounding a spinning cosmic string. For any
of these spacetimes, a prediction of our analysis is that the wave content
increases the deficit angle at spatial infinity with respect to that detected
around the axis.",0011080v2
2001-10-23,Gravitomagnetic Effects in the Propagation of Electromagnetic Waves in Variable Gravitational Fields of Arbitrary-Moving and Spinning Bodies,"Propagation of light in the gravitational field of self-gravitating spinning
bodies moving with arbitrary velocities is discussed. The gravitational field
is assumed to be ""weak"" everywhere. Equations of motion of a light ray are
solved in the first post-Minkowskian approximation that is linear with respect
to the universal gravitational constant $G$. We do not restrict ourselves with
the approximation of gravitational lens so that the solution of light geodesics
is applicable for arbitrary locations of source of light and observer. This
formalism is applied for studying corrections to the Shapiro time delay in
binary pulsars caused by the rotation of pulsar and its companion. We also
derive the correction to the light deflection angle caused by rotation of
gravitating bodies in the solar system (Sun, planets) or a gravitational lens.
The gravitational shift of frequency due to the combined translational and
rotational motions of light-ray-deflecting bodies is analyzed as well. We give
a general derivation of the formula describing the relativistic rotation of the
plane of polarization of electromagnetic waves (Skrotskii effect). This formula
is valid for arbitrary translational and rotational motion of gravitating
bodies and greatly extends the results of previous researchers. Finally, we
discuss the Skrotskii effect for gravitational waves emitted by localized
sources such as a binary system. The theoretical results of this paper can be
applied for studying various relativistic effects in microarcsecond space
astrometry and developing corresponding algorithms for data processing in space
astrometric missions such as FAME, SIM, and GAIA.",0110101v2
1995-01-08,"Bethe Ansatz for QCD Pomeron,","The equivalence is found between high-energy QCD in the generalized leading
logarithmic approximation and the one-dimensional Heisenberg magnet. According
to Regge theory, the high energy asymptotics of hadronic scattering amplitudes
are related to singularities of partial waves in the complex angular momentum
plane. In QCD, the partial waves are determined by nontrivial two-dimensional
dynamics of the transverse gluonic degrees of freedom. The ""bare"" gluons
interact with each other to form a collective excitation, the Reggeon. The
partial waves of the scattering amplitude satisfy the Bethe-Salpeter equation
whose solutions describe the color singlet compound states of Reggeons --
Pomeron, Odderon and higher Reggeon states. We show that the QCD Hamiltonian
for reggeized gluons coincides in the multi-color limit with the Hamiltonian of
XXX Heisenberg magnet for spin s=0 and spin operators the generators of the
conformal SL(2,C) group. As a result, the Schrodinger equation for the compound
states of Reggeons has a sufficient number of conservation laws to be
completely integrable. A generalized Bethe ansatz is developed for the
diagonalization of the QCD Hamiltonian and for the calculation of hadron-hadron
scattering. Using the Bethe Ansatz solution of high-energy QCD we investigate
the properties of the Reggeon compound states which govern the Regge behavior
of the total hadron-hadron cross sections and the small-x behavior of the
structure functions of deep inelastic scattering.",9501232v2
2007-04-19,Relativistic Effects in Extreme Mass Ratio Gravitational Wave Bursts,"Extreme mass ratio bursts (EMRBs) have been proposed as a possible source for
future space-borne gravitational wave detectors, such as the Laser
Interferometer Space Antenna (LISA). These events are characterized by
long-period, nearly-radial orbits of compact objects around a central massive
black hole. The gravitational radiation emitted during such events consists of
a short burst, corresponding to periapse passage, followed by a longer, silent
interval. In this paper we investigate the impact of including relativistic
corrections to the description of the compact object's trajectory via a
geodesic treatment, as well as including higher-order multipole corrections in
the waveform calculation. The degree to which the relativistic corrections are
important depends on the EMRB's orbital parameters. We find that relativistic
EMRBs (v_{max}}/c > 0.25) are not rare and actually account for approximately
half of the events in our astrophysical model. The relativistic corrections
tend to significantly change the waveform amplitude and phase relative to a
Newtonian description, although some of this dephasing could be mimicked by
parameter errors. The dephasing over several bursts could be of particular
importance not only to gravitational wave detection, but also to parameter
estimation, since it is highly correlated to the spin of the massive black
hole. Consequently, we postulate that if a relativistic EMRB is detected, such
dephasing might be used to probe the relativistic character of the massive
black hole and obtain information about its spin.",0704.2612v2
2007-05-17,Theorie des longitudinalen Atomstrahl-Spinechos und paritaetsverletzende Berry-Phasen in Atomen,"We present a nonrelativistic theory for the quantum mechanical description of
longitudinal atomic beam spin echo experiments, where a beam of neutral atoms
is subjected to static electric and magnetic fields. The atomic wave function
is the solution of a matrix-valued Schroedinger equation and can be written as
superposition of local (atomic) eigenstates of the potential matrix. The
position- and time-dependent amplitude function of each eigenstate represents
an atomic wave packet and can be calculated in a series expansion with a master
formula that we derive. The zeroth order of this series expansion describes the
adiabatic limit, whereas the higher order contributions contain the mixing of
the eigenstates and the corresponding amplitude functions.
  We give a tutorial for the theoretical description of longitudinal atomic
beam spin echo experiments and for the so-called Fahrplan model, which is a
visualisation tool for the propagation of wave packets of different atomic
eigenstates.
  As an example for the application of our theory, we study parity violating
geometric (Berry-)phases. In this context, we define geometric flux densities,
which for certain field configurations can be used to illustrate geometric
phases in a vector diagram. Considering an example with a specific field
configuration, we prove the existence of a parity violating geometric phase.",0705.2508v2
2007-08-17,A centimetre-wave excess over free-free emission in planetary nebulae,"We report a centimetre-wave (cm-wave, 5-31GHz) excess over free-free emission
in PNe. Accurate 31 and 250GHz measurements show that the 31GHz flux densities
in our sample are systematically higher than the level of optically thin
free-free continuum extrapolated from 250GHz. The 31GHz excess is observed,
within one standard deviation, in all 18 PNe with reliable 31 and 250GHz data,
and is significant in 9 PNe. The only exception is the peculiar object M2-9,
whose radio spectrum is that of an optically thick stellar wind. On average the
fraction of non-free-free emission represents 51% of the total flux density at
31GHz, with a scatter of 11%. The average 31-250GHz spectral index of our
sample is <alpha_{31}^{250}> = -0.43+-0.03 (in flux density, with a scatter of
0.14). The 31--250 GHz drop is reminiscent of the anomalous foreground observed
in the diffuse ISM by CMB anisotropy experiments. The 5--31 GHz spectral
indices are consistent with both flat spectra and spinning dust emissivities,
given the 10% calibration uncertainty of the comparison 5GHz data. But a
detailed study of the objects with the largest cm-excess, including the low
frequency data available in the literature, shows that present spinning dust
models cannot alone explain the cm-excess in PNe. Although we have no
definitive interpretation of our data, the least implausible explanation
involves a synchrotron component absorbed by a cold nebular screen. We give
flux densities for 37 objects at 31GHz, and for 26 objects at 250GHz.",0708.2385v2
2007-12-24,Rabi oscillations in semiconductor multi-wave mixing response,"We studied the semiconductor response with respect to high intensity resonant
excitation on short time scale when the contribution of the Fermi statistics of
the electrons and holes prevails. We studied both the single and double pulse
excitations. For the latter case we considered the time evolution of the
multi-wave mixing exciton polarization. The main difference between the
excitation by a single pulse or by two non-collinear pulses is that the Rabi
oscillations of the multi-wave mixing response are characterized by two
harmonics. Analyzing the operator dynamics governed by the external excitation
we found that there are three invariant spin classes, which do not mix with the
evolution of the system. Two classes correspond to the bright exciton states
and one contains all dark states. We found that the dynamics of the classes is
described by six frequencies and the Rabi frequencies are only two of them (one
for each bright class). We discuss the effect of the dispersion of the
electrons and holes and the Coulomb interaction describing the semiconductor by
the semiconductor Bloch equation (SBE). We show that if initially the system is
in the ground state then the SBE preserves the invariant spin classes thus
proving absence of the dark excitons in the framework of this description. We
found that due to the mass difference between holes of different kind
additional Rabi frequencies, two of those present in the operator dynamics,
should appear in the evolution of the exciton polarization.",0712.4022v2
2008-01-03,Dirac Representation of Dynamically-Generated Elementary-Particle Mass,"Special-relativistic dynamically-generated elementary-particle mass is
represented by a self-adjoint energy operator acting on a rigged Hilbert space
(RHS) of functions over the 6-dimensional Euclidean-group manifold. The energy
operator is not the generator of infinitesimal wave-function evolution in
classical time. Ray evolution is generated by action-carrying Feynman paths.
Extending quantum-theoretic formalism which Dirac invented and applied
non-relativistically, unitary Poincar\'e -group representation is provided by
the wave functions of a spacelike entity that we call 'preon'. Although the
term 'preon observable' is misleading, six continuous Feynman-path-contacting
preon coordinates specify spatial location (3 coordinates),
lightlike-velocity-direction (2 coordinates) and transverse polarization (1
coordinate). Velocity and spatial location combine to define a preon time
operator conjugate to the energy operator. In RHS bases alternative to
functions over the group manifold, the wave function depends on a preon
'velocity-helicity' integer or half-odd integer) and a positive-lightlike
velocity 4-vector that is Lorentz-orthogonal to a canonically-conjugate pair of
spacelike 4-vectors. One 4-vector prescribes location in preon spacetime while
its conjugate prescribes preon energy-momentum. Emulating the
Schr\""odinger-dubbed 'zitterbewegung' of Dirac's 'relativistic' electron, mass
for any spinning (positive-timelike) elementary particle accompanies a
reflection-symmetric fluctuation of preon lightlike velocity and
velocity-helicity. But (departing from Dirac), a tiny elementary-particle
'longitudinal' spatial extension accompanies a huge fluctuation of preon
longitudinal momentum dictated by motionless-particle reflection symmetry about
the plane perpendicular to spin direction.",0801.0459v3
2008-05-16,Generalized susceptibility of quasi-one dimensional system with periodic potential: model for the organic superconductor (TMTSF)$_2$ClO$_4$,"The nesting vector and the magnetic susceptibility of the
quasi-one-dimensional system having imperfectly nested Fermi surface are
studied analytically and numerically. The magnetic susceptibility has the
plateau-like maximum in ``\textit{sweptback}'' region in the momentum space,
which is surrounded by $\mathbf{Q}=(2 k_F, \pi) + \mathbf{q}_i$ ($k_F$ is the
Fermi wave number, $i=1,3,4$, and $\mathbf{q}_1$, $\mathbf{q}_3$ and
$\mathbf{q}_{4}$ are given in this paper). The best nesting vector, at which
the susceptibility $\chi_0(\mathbf{Q})$ has the absolute maximum at T=0, is
obtained near but not at the inflection point, $\mathbf{Q}=(2 k_F,
\pi)+\mathbf{q}_4$. The effect of the periodic potential $V$ on the
susceptibility is studied, which is important for the successive transitions of
the field-induced spin density wave in (TMTSF)$_2$ClO$_4$. We obtain that the
sweptback region (surrounded by $\mathbf{q}_2$, $\mathbf{q}_3$ and
$\mathbf{q}_4$ when $V>0$) becomes small as $V$ increases and it shrinks to
$\mathbf{q}_3$ for $V \geq 4 t_b'$, where $t_b'$ gives the degree of imperfect
nesting of the Fermi surface, i.e. the second harmonics of the warping in the
Fermi surface. The occurrence of the sign reversal of the Hall coefficient in
the field-induced spin density wave states is discussed to be possible only
when $V<2 t_b'-2 t_4$, where $t_4$ is the amplitude of the fourth harmonics of
the warping in the Fermi surface. This gives the novel limitation for the
magnitude of $V$.",0805.2445v1
2009-10-21,High resolution AMI Large Array imaging of spinning dust sources: spatially correlated 8 micron emission and evidence of a stellar wind in L675,"We present 25 arcsecond resolution radio images of five Lynds Dark Nebulae
(L675, L944, L1103, L1111 & L1246) at 16 GHz made with the Arcminute
Microkelvin Imager (AMI) Large Array. These objects were previously observed
with the AMI Small Array to have an excess of emission at microwave frequencies
relative to lower frequency radio data. In L675 we find a flat spectrum compact
radio counterpart to the 850 micron emission seen with SCUBA and suggest that
it is cm-wave emission from a previously unknown deeply embedded young
protostar. In the case of L1246 the cm-wave emission is spatially correlated
with 8 micron emission seen with Spitzer. Since the MIR emission is present
only in Spitzer band 4 we suggest that it arises from a population of PAH
molecules, which also give rise to the cm-wave emission through spinning dust
emission.",0910.4011v2
2010-04-29,Complete-Graph Tensor Network States: A New Fermionic Wave Function Ansatz for Molecules,"We present a new class of tensor network states that are specifically
designed to capture the electron correlation of a molecule of arbitrary
structure. In this ansatz, the electronic wave function is represented by a
Complete-Graph Tensor Network (CGTN) ansatz which implements an efficient
reduction of the number of variational parameters by breaking down the
complexity of the high-dimensional coefficient tensor of a
full-configuration-interaction (FCI) wave function. We demonstrate that CGTN
states approximate ground states of molecules accurately by comparison of the
CGTN and FCI expansion coefficients. The CGTN parametrization is not biased
towards any reference configuration in contrast to many standard quantum
chemical methods. This feature allows one to obtain accurate relative energies
between CGTN states which is central to molecular physics and chemistry. We
discuss the implications for quantum chemistry and focus on the spin-state
problem. Our CGTN approach is applied to the energy splitting of states of
different spin for methylene and the strongly correlated ozone molecule at a
transition state structure. The parameters of the tensor network ansatz are
variationally optimized by means of a parallel-tempering Monte Carlo algorithm.",1004.5303v1
2010-08-12,On bound state computations in three- and four-electron atomic systems,"A variational approach is developed for bound state calculations in three-
and four-electron atomic systems. This approach can be applied to determine, in
principle, an arbitrary bound state in three- and four-electron ions and atoms.
Our variational wave functions are constructed from four- and five-body
gaussoids which depend upon the six ($r_{12}, r_{13}, r_{14}, r_{23}, r_{24},
r_{34}$) and ten ($r_{12}, r_{13}, r_{14}, r_{15}, r_{23}, r_{24}, r_{25},
r_{34}, r_{35}$ and $r_{45}$) relative coordinates, respectively. The approach
allows one to operate with the different number of electron spin functions. In
particular, the trial wave functions for the ${}^1S$-states in four-electron
atomic systems include the two independent spin functions $\chi_1 = \alpha
\beta \alpha \beta + \beta \alpha \beta \alpha - \beta \alpha \alpha \beta -
\alpha \beta \beta \alpha$ and $\chi_2 = 2 \alpha \alpha \beta \beta + 2 \beta
\beta \alpha \alpha - \beta \alpha \alpha \beta - \alpha \beta \beta \alpha -
\beta \alpha \beta \alpha - \alpha \beta \alpha \beta$. We also discuss the
construction of variational wave functions for the excited $2^3S$-states in
four-electron atomic systems.",1008.2168v1
2010-10-08,Correlations probed in direct two-nucleon removal reactions,"Final-state-exclusive momentum distributions of fast, forward travelling
residual nuclei, following two nucleon removal from fast secondary radioactive
beams of projectile nuclei, can and have now been measured. Assuming that the
most important reaction mechanism is the sudden direct removal of a pair of
nucleons from a set of relatively simple, active shell-model orbital
configurations, such distributions were predicted to depend strongly on the
total angular momentum I carried by the two nucleons - the final state spin for
spin 0+ projectiles. The sensitivity of these now-accessible observables to
specific details of the (correlated) two-nucleon wave functions is of
importance. We clarify that it is the total orbital angular momentum L of the
two nucleons that is the primary factor in determining the shapes and widths of
the calculated momentum distributions. It follows that, with accurate
measurements, this dependence upon the L make-up of the two-nucleon wave
functions could be used to assess the accuracy of (shell- or many-body) model
predictions of these two-nucleon configurations. By use of several tailored
examples, with specific combinations of active two-nucleon orbitals, we
demonstrate that more subtle structure aspects may be observed, allowing such
reactions to probe and/or confirm the details of theoretical model wave
functions.",1010.1619v1
2011-06-27,"Bond order wave (BOW) phase of the extended Hubbard model: Electronic solitons, paramagnetism, coupling to Peierls and Holstein phonons","The bond order wave (BOW) phase of the extended Hubbard model (EHM) in one
dimension (1D) is characterized at intermediate correlation $U = 4t$ by exact
treatment of $N$-site systems. Linear coupling to lattice (Peierls) phonons and
molecular (Holstein) vibrations are treated in the adiabatic approximation. The
molar magnetic susceptibility $\chi_M(T)$ is obtained directly up to $N = 10$.
The goal is to find the consequences of a doubly degenerate ground state (gs)
and finite magnetic gap $E_m$ in a regular array. Degenerate gs with broken
inversion symmetry are constructed for finite $N$ for a range of $V$ near the
charge density wave (CDW) boundary at $V \approx 2.18t$ where $E_m \approx
0.5t$ is large. The electronic amplitude $B(V)$ of the BOW in the regular array
is shown to mimic a tight-binding band with small effective dimerization
$\delta_{eff}$. Electronic spin and charge solitons are elementary excitations
of the BOW phase and also resemble topological solitons with small
$\delta_{eff}$. Strong infrared intensity of coupled molecular vibrations in
dimerized 1D systems is shown to extend to the regular BOW phase, while its
temperature dependence is related to spin solitons. The Peierls instability to
dimerization has novel aspects for degenerate gs and substantial $E_m$ that
suppresses thermal excitations. Finite $E_m$ implies exponentially small
$\chi_M(T)$ at low temperature followed by an almost linear increase with $T$.
The EHM with $U = 4t$ is representative of intermediate correlations in
quasi-1D systems such as conjugated polymers or organic ion-radical and
charge-transfer salts. The vibronic and thermal properties of correlated models
with BOW phases are needed to identify possible physical realizations.",1106.5466v1
2011-07-05,Spindown of Isolated Neutron Stars: Gravitational Waves or Magnetic Braking?,"We study the spindown of isolated neutron stars from initially rapid rotation
rates, driven by two factors: (i) gravitational wave emission due to r-modes
and (ii) magnetic braking. In the context of isolated neutron stars, we present
the first study including self-consistently the magnetic damping of r-modes in
the spin evolution. We track the spin evolution employing the RNS code, which
accounts for the rotating structure of neutron stars for various equations of
state. We find that, despite the strong damping due to the magnetic field,
r-modes alter the braking rate from pure magnetic braking for B<10^{13}G. For
realistic values of the saturation amplitude, the r-mode can also decrease the
time to reach the threshold central density for quark deconfinement. Within a
phenomenological model, we assess the gravitational waveform that would result
from r-mode driven spindown of a magnetized neutron star. To contrast with the
persistent signal during the spindown phase, we also present a preliminary
estimate of the transient gravitational wave signal from an explosive
quark-hadron phase transition, which can be a signal for the deconfinement of
quarks inside neutron stars.",1107.1000v2
2012-01-25,An F-statistic based multi-detector veto for detector artifacts in continuous-wave gravitational wave data,"Continuous gravitational waves (CW) are expected from spinning neutron stars
with non-axisymmetric deformations. A network of interferometric detectors
(LIGO, Virgo and GEO600) is looking for these signals. They are predicted to be
very weak and retrievable only by integration over long observation times. One
of the standard methods of CW data analysis is the multi-detector F-statistic.
In a typical search, the F-statistic is computed over a range in frequency,
spin-down and sky position, and the candidates with highest F values are kept
for further analysis. However, this detection statistic is susceptible to a
class of noise artifacts, strong monochromatic lines in a single detector. By
assuming an extended noise model - standard Gaussian noise plus single-detector
lines - we can use a Bayesian odds ratio to derive a generalized detection
statistic, the line veto (LV-) statistic. In the absence of lines, it behaves
similarly to the F-statistic, but it is more robust against line artifacts. In
the past, ad-hoc post-processing vetoes have been implemented in searches to
remove these artifacts. Here we provide a systematic framework to develop and
benchmark this class of vetoes. We present our results from testing this
LV-statistic on simulated data.",1201.5244v1
2013-02-26,S wave superconductivity in newly discovered superconductor BaTi$_2$Sb$_2$O revealed by $^{121/123}$Sb-NMR/Nuclear Quadrupole Resonance measurements,"We report the $^{121/123}$Sb-NMR/nuclear quadrupole resonance (NQR)
measurements on the newly-discovered superconductor BaTi$_2$Sb$_2$O with a
two-dimensional Ti$_2$O square-net layer formed with Ti$^{3+}$ (3$d^1$). NQR
measurements revealed that the in-plane four-fold symmetry is broken at the Sb
site below $T_{\rm A} \sim$ 40 K, without an internal field appearing at the Sb
site. These exclude a spin-density wave (SDW)/ charge density wave (CDW)
ordering with incommensurate correlations, but can be understood with the
commensurate CDW ordering at $T_{\rm A}$. The spin-lattice relaxation rate
$1/T_1$, measured at the four-fold symmetry breaking site, decreases below
superconducting (SC) transition temperature $T_{\rm c}$, indicative of the
microscopic coexistence of superconductivity and the CDW/SDW phase below
$T_{\rm A}$. Furthermore, $1/T_1$ of $^{121}$Sb-NQR shows a coherence peak just
below $T_{\rm c}$ and decreases exponentially at low temperatures. These
results are in sharp contrast with those in cuprate and iron-based
superconductors, and strongly suggest that its SC symmetry is classified to an
ordinary s-wave state.",1302.6314v2
2014-03-10,A possible correspondence between Ricci identities and Dirac equations in the Newman-Penrose formalism: towards an understanding of gravity induced collapse of the wave-function?,"It is well-known that in the Newman-Penrose formalism the Riemann tensor can
be expressed as a set of eighteen complex first-order equations, in terms of
the twelve spin coefficients, known as Ricci identities. The Ricci tensor
herein is determined via the Einstein equations. It is also known that the
Dirac equation in a curved spacetime can be written in the Newman-Penrose
formalism as a set of four first-order coupled equations for the spinor
components of the wave-function. In the present article we suggest that it
might be possible to think of the Dirac equations in the N-P formalism as a
special case of the Ricci identities, after an appropriate identification of
the four Dirac spinor components with four of the spin coefficients, provided
torsion is included in the connection, and after a suitable generalization of
the energy-momentum tensor. We briefly comment on similarities with the
Einstein-Cartan-Sciama-Kibble theory. The motivation for this study is to take
some very preliminary steps towards developing a rigorous description of the
hypothesis that dynamical collapse of the wave-function during a quantum
measurement is caused by gravity.",1403.2231v2
2014-05-26,Sensitivity Comparison of Searches for Binary Black Hole Coalescences with Ground-based Gravitational-Wave Detectors,"Searches for gravitational-wave transients from binary black hole
coalescences typically rely on one of two approaches: matched filtering with
templates and morphology-independent excess power searches. Multiple
algorithmic implementations in the analysis of data from the first generation
of ground-based gravitational wave interferometers have used different
strategies for the suppression of non-Gaussian noise transients, and targeted
different regions of the binary black hole parameter space. In this paper we
compare the sensitivity of three such algorithms: matched filtering with full
coalescence templates, matched filtering with ringdown templates and a
morphology-independent excess power search. The comparison is performed at a
fixed false alarm rate and relies on Monte-carlo simulations of binary black
hole coalescences for spinning, non-precessing systems with total mass 25-350
solar mass, which covers the parameter space of stellar mass and intermediate
mass black hole binaries. We find that in the mass range of 25 -100 solar mass
the sensitive distance of the search, marginalized over source parameters, is
best with matched filtering to full waveform templates, to within 10 percent at
a false alarm rate of 3 events per year. In the mass range of 100-350 solar
mass, the same comparison favors the morphology-independent excess power search
to within 20 percent. The dependence on mass and spin is also explored.",1405.6589v1
2015-07-13,Enhancement of superconductivity at the onset of charge-density-wave order in a metal,"We analyze superconductivity in the cuprates near the onset of an
incommensurate charge density wave (CDW) order with momentum ${\bf Q} =
(Q,0)/(0,Q)$, as observed in the experiments. We first consider a
semi-phenomenological charge-fermion model in which hot fermions, separated by
${\bf Q}$, attract each other by exchanging soft CDW fluctuations. We find that
in a quantum-critical region near CDW transition, $T_c = A {\bar g}_c$, where
${\bar g}_c$ is charge-fermion coupling and $A$ is the prefactor which we
explicitly compute. We then consider the particular microscopic scenario in
which CDW order parameter emerges as a composite field made out of primary
spin-density-wave fields. We show that charge-fermion coupling ${\bar g}_c$ is
of order of spin-fermion coupling ${\bar g}_s$. As the consequence,
superconducting $T_c$ is substantially enhanced near the onset of CDW order.
Finally we analyze the effect of an external magnetic field $H$. We show that,
as $H$ increases, optimal $T_c$ decreases and the superconducting dome becomes
progressively more confined to the CDW quantum-critical point. These results
are consistent with the experiments.",1507.03583v2
2015-08-04,Two-Nucleon Higher Partial-Wave Scattering from Lattice QCD,"We present a determination of nucleon-nucleon scattering phase shifts for l
>= 0. The S, P, D and F phase shifts for both the spin-triplet and spin-singlet
channels are computed with lattice Quantum ChromoDynamics. For l > 0, this is
the first lattice QCD calculation using the Luscher finite-volume formalism.
This required the design and implementation of novel lattice methods involving
displaced sources and momentum-space cubic sinks. To demonstrate the utility of
our approach, the calculations were performed in the SU(3)-flavor limit where
the light quark masses have been tuned to the physical strange quark mass,
corresponding to m_pi = m_K ~ 800 MeV. In this work, we have assumed that only
the lowest partial waves contribute to each channel, ignoring the unphysical
partial wave mixing that arises within the finite-volume formalism. This
assumption is only valid for sufficiently low energies; we present evidence
that it holds for our study using two different channels. Two spatial volumes
of V ~ (3.5 fm)^3 and V ~ (4.6 fm)^3 were used. The finite-volume spectrum is
extracted from the exponential falloff of the correlation functions. Said
spectrum is mapped onto the infinite volume phase shifts using the
generalization of the Luscher formalism for two-nucleon systems.",1508.00886v2
2015-08-28,Frequency-domain gravitational waves from non-precessing black-hole binaries. I. New numerical waveforms and anatomy of the signal,"In this paper we discuss the anatomy of frequency-domain gravitational-wave
signals from non-precessing black-hole coalescences with the goal of
constructing accurate phenomenological waveform models. We first present new
numerical-relativity simulations for mass ratios up to 18 including spins. From
a comparison of different post-Newtonian approximants with numerical-relativity
data we select the uncalibrated SEOBNRv2 model as the most appropriate for the
purpose of constructing hybrid post-Newtonian/numerical-relativity waveforms,
and we discuss how we prepare time-domain and frequency-domain hybrid data
sets. We then use our data together with results in the literature to calibrate
simple explicit expressions for the final spin and radiated energy. Equipped
with our prediction for the final state we then develop a simple and accurate
merger-ringdown-model based on modified Lorentzians in the gravitational wave
amplitude and phase, and we discuss a simple method to represent the low
frequency signal augmenting the TaylorF2 post-Newtonian approximant with terms
corresponding to higher orders in the post-Newtonian expansion. We finally
discuss different options for modelling the small intermediate frequency regime
between inspiral and merger-ringdown. A complete phenomenological model based
on the present work is presented in a companion paper.",1508.07250v2
2015-09-08,Measuring violations of General Relativity from single gravitational wave detection by non-spinning binary systems: higher-order asymptotic analysis,"A frequentist asymptotic expansion method for error estimation is employed
for a network of gravitational wave detectors to assess the amount of
information that can be extracted from gravitational wave observations.
Mathematically we derive lower bounds in the errors that any parameter
estimator will have in the absence of prior knowledge to distinguish between
the post-Einsteinian (ppE) description of coalescing binary systems and that of
general relativity. When such errors are smaller than the parameter value,
there is possibility to detect these violations from GR. A parameter space with
inclusion of dominant dephasing ppE parameters $(\beta, b)$ is used for a study
of first- and second-order (co)variance expansions, focusing on the inspiral
stage of a nonspinning binary system of zero eccentricity detectible through
Adv. LIGO and Adv. Virgo. Our procedure is an improvement of the Cram\'{e}r-Rao
Lower Bound. When Bayesian errors are lower than our bound it means that they
depend critically on the priors. The analysis indicates the possibility of
constraining deviations from GR in inspiral SNR ($\rho \sim 15-17$) regimes
that are achievable in upcoming scientific runs (GW150914 had an inspiral SNR
$\sim 12$). The errors on $\beta$ also increase errors of other parameters such
as the chirp mass $\mathcal{M}$ and symmetric mass ratio $\eta$. Application is
done to existing alternative theories of gravity, which include modified
dispersion relation of the waveform, non-spinning models of quadratic modified
gravity, and dipole gravitational radiation (i.e., Brans-Dicke type)
modifications.",1509.02248v2
2015-09-21,Gravitational-wave cutoff frequencies of tidally disruptive neutron star-black hole binary mergers,"Tidal disruption has a dramatic impact on the outcome of neutron star-black
hole mergers. The phenomenology of these systems can be divided in three
classes: nondisruptive, mildly disruptive or disruptive. The cutoff frequency
of the gravitational radiation produced during the merger (which is potentially
measurable by interferometric detectors) is very different in each regime, and
when the merger is disuptive it carries information on the neutron star
equation of state. Here we use semianalytical tools to derive a formula for the
critical binary mass ratio $Q=M_{\rm BH}/M_{\rm NS}$ below which mergers are
disruptive as a function of the stellar compactness $\mathcal{C}=M_{\rm
NS}/R_{\rm NS}$ and the dimensionless black hole spin $\chi$. We then employ a
new gravitational waveform amplitude model, calibrated to $134$ general
relativistic numerical simulations of binaries with black hole spin
(anti-)aligned with the orbital angular momentum, to obtain a fit to the
gravitational-wave cutoff frequency in the disruptive regime as a function of
$\mathcal{C}$, $Q$ and $\chi$. Our findings are important to build
gravitational wave template banks, to determine whether neutron star-black hole
mergers can emit electromagnetic radiation (thus helping multimessenger
searches), and to improve event rate calculations for these systems.",1509.06209v1
2015-09-25,Stochastic gravitational wave background from magnetic deformation of newly born magnetars,"Newly born magnetars are promising sources for gravitational wave (GW)
detection due to their ultra-strong magnetic fields and high spin frequencies.
Within the scenario of a growing tilt angle between the star's spin and
magnetic axis, due to the effect of internal viscosity, we obtain improved
estimates of the stochastic gravitational wave backgrounds (SGWBs) from
magnetic deformation of newly born magnetars. We find that the GW background
spectra contributed by the magnetars with ultra-strong toroidal magnetic fields
of 10^{17} G could roughly be divided into four segments. Most notably, in
contrast to the background spectra calculated by assuming constant tilt angles
\chi=\pi/2, the background radiation above 1000 Hz are seriously suppressed.
However, the background radiation at the frequency band \sim100-1000 Hz are
moderately enhanced, depending on the strengths of the dipole magnetic fields.
We suggest that if all newly born magnetars indeed have toroidal magnetic
fields of 10^{17} G, the produced SGWBs should show sharp variations with the
observed frequency at several tens to about 100 hertz. If these features could
be observed through sophisticated detection of the SGWB using the proposed
Einstein Telescope, it will provide us a direct evidence of the tilt angle
evolutions and further some deep understandings about the properties of newly
born magnetars.",1509.07651v1
2015-11-04,Inference on gravitational waves from coalescences of stellar-mass compact objects and intermediate-mass black holes,"Gravitational waves from coalescences of neutron stars or stellar-mass black
holes into intermediate-mass black holes (IMBHs) of $\gtrsim 100$ solar masses
represent one of the exciting possible sources for advanced gravitational-wave
detectors. These sources can provide definitive evidence for the existence of
IMBHs, probe globular-cluster dynamics, and potentially serve as tests of
general relativity. We analyse the accuracy with which we can measure the
masses and spins of the IMBH and its companion in intermediate-mass ratio
coalescences. We find that we can identify an IMBH with a mass above $100 ~
M_\odot$ with $95\%$ confidence provided the massive body exceeds $130 ~
M_\odot$. For source masses above $\sim200 ~ M_\odot$, the best measured
parameter is the frequency of the quasi-normal ringdown. Consequently, the
total mass is measured better than the chirp mass for massive binaries, but the
total mass is still partly degenerate with spin, which cannot be accurately
measured. Low-frequency detector sensitivity is particularly important for
massive sources, since sensitivity to the inspiral phase is critical for
measuring the mass of the stellar-mass companion. We show that we can
accurately infer source parameters for cosmologically redshifted signals by
applying appropriate corrections. We investigate the impact of uncertainty in
the model gravitational waveforms and conclude that our main results are likely
robust to systematics.",1511.01431v1
2016-04-17,Modeling the Multi-Band Afterglow of GRB 130831A: Evidence for a Spinning-Down Magnetar Dominated by Gravitational Wave Losses?,"The X-ray afterglow of GRB 130831A shows an ""internal plateau"" with a decay
slope of $\sim$ 0.8, followed by a steep drop at around $10^5$ s with a slope
of $\sim$ 6. After the drop, the X-ray afterglow continues with a much
shallower decay. The optical afterglow exhibits two segments of plateaus
separated by a luminous optical flare, followed by a normal decay with a slope
basically consistent with that of the late-time X-ray afterglow. The decay of
the internal X-ray plateau is much steeper than what we expect in the simplest
magnetar model. We propose a scenario in which the magnetar undergoes
gravitational-wave-driven r-mode instability, and the spin-down is dominated by
gravitational wave losses up to the end of the steep plateau, so that such a
relatively steep plateau can be interpreted as the internal emission of the
magnetar wind and the sharp drop can be produced when the magnetar collapses
into a black hole. This scenario also predicts an initial X-ray plateau lasting
for hundreds of seconds with an approximately constant flux which is compatible
with observation. Assuming that the magnetar wind has a negligible contribution
in the optical band, we interpret the optical afterglow as the forward shock
emission by invoking the energy injection from a continuously refreshed shock
following the prompt emission phase. It is shown that our model can basically
describe the temporal evolution of the multi-band afterglow of GRB 130831A.",1604.04817v1
2016-06-01,Gravitational wave quasinormal mode from Population III massive black hole binaries in various models of population synthesis,"Focusing on the remnant black holes after merging binary black holes, we show
that ringdown gravitational waves of Population III binary black holes mergers
can be detected with the rate of $5.9-500~{\rm events~yr^{-1}}~({\rm SFR_p}/
(10^{-2.5}~M_\odot~{\rm yr^{-1}~Mpc^{-3}})) \cdot ({\rm [f_b/(1+f_b)]/0.33})$
for various parameters and functions. This rate is estimated for the events
with SNR$>8$ for the second generation gravitational wave detectors such as
KAGRA. Here, ${\rm SFR_p}$ and ${\rm f_b}$ are the peak value of the Population
III star formation rate and the fraction of binaries, respectively. When we
consider only the events with SNR$>35$, the event rate becomes $0.046-4.21~{\rm
events~yr^{-1}}~({\rm SFR_p}/ (10^{-2.5}~M_\odot~{\rm yr^{-1}~Mpc^{-3}})) \cdot
({\rm [f_b/(1+f_b)]/0.33})$. This suggest that for remnant black hole's spin
$q_f>0.95$ we have the event rate with SNR$>35$ less than $0.037~{\rm
events~yr^{-1}}~({\rm SFR_p}/ (10^{-2.5}~M_\odot~{\rm yr^{-1}~Mpc^{-3}})) \cdot
({\rm [f_b/(1+f_b)]/0.33})$, while it is $3-30~{\rm events~yr^{-1}}~({\rm
SFR_p}/ (10^{-2.5}~M_\odot~{\rm yr^{-1}~Mpc^{-3}})) \cdot ({\rm
[f_b/(1+f_b)]/0.33})$ for the third generation detectors such as Einstein
Telescope. If we detect many Population III binary black holes merger, it may
be possible to constrain the Population III binary evolution paths not only by
the mass distribution but also by the spin distribution.",1606.00362v1
2016-07-19,Fractionalized Fermi liquid with bosonic chargons as a candidate for the pseudogap metal,"Doping a Mott-insulating $\mathbb{Z}_2$ spin liquid can lead to a
fractionalized Fermi liquid (FL*). Such a phase has several favorable features
that make it a candidate for the pseudogap metal for the underdoped cuprates.
We focus on a particular, simple $\mathbb{Z}_2$-FL* state which can undergo a
confinement transition to a spatially uniform superconductor which is smoothly
connected to the `plain vanilla' BCS superconductor with $d$-wave pairing. Such
a transition occurs by the condensation of bosonic particles carrying $+e$
charge but no spin (`chargons'). We show that modifying the dispersion of the
bosonic chargons can lead to confinement transitions with charge density waves
and pair density waves at the same wave-vector $\mathbf{K}$, co-existing with
$d$-wave superconductivity. We also compute the evolution of the Hall number in
the normal state during the transition from the plain vanilla FL* state to a
Fermi liquid, and argue, following Coleman, Marston, and Schofield [Phys. Rev.
B 72, 245111 (2005)], that it exhibits a discontinuous jump near optimal
doping. We note the distinction between these results and those obtained from
models of the pseudogap with fermionic chargons.",1607.05727v2
2016-07-25,Goos-Hanchen shift of a spin-wave beam transmitted through anisotropic interface between two ferromagnets,"The main object of investigation in magnonics, spin waves (SWs) are promising
information carriers. Presently the most commonly studied are plane wave-like
SWs and SWs propagating in confined structures, such as waveguides. Here we
consider a Gaussian SW beam obliquely incident on an ultra-narrow interface
between two identical ferromagnetic materials. We use an analytical model and
micromagnetic simulations for an in-depth analysis of the influence of the
interface properties, in particular the magnetic anisotropy, on the
transmission of the SW beam. We derive analytical formulas for the reflectance,
transmittance, phase shift and Goos-Hanchen (GH) shift for beams reflected and
refracted by an interface between two semi-infinite ferromagnetic media; the
results for the refracted beam are the first to be reported to date. The GH
shifts in SW beam reflection and transmission are confirmed by micromagnetic
simulations in the thin-film geometry. We demonstrate the dependence of the
characteristic properties on the magnetic anisotropy at the interface, the
angle of incidence and the frequency of the SWs. We also propose a method for
the excitation of high-quality SW beams in micromagnetic simulations.",1607.07424v4
2017-07-04,Optimised frequency modulation for continuous-wave optical magnetic resonance sensing using nitrogen-vacancy ensembles,"Magnetometers based on ensembles of nitrogen-vacancy centres are a promising
platform for continuously sensing static and low-frequency magnetic fields.
Their combination with phase-sensitive (lock-in) detection creates a highly
versatile sensor with a sensitivity that is proportional to the derivative of
the optical magnetic resonance lock-in spectrum, which is in turn dependant on
the lock-in modulation parameters. Here we study the dependence of the lock-in
spectral slope on the modulation of the spin-driving microwave field. Given the
presence of the intrinsic nitrogen hyperfine spin transitions, we
experimentally show that when the ratio between the hyperfine linewidth and
their separation is $\gtrsim 1/4$, square-wave based frequency modulation
generates the steepest slope at modulation depths exceeding the separation of
the hyperfine lines, compared to sine-wave based modulation. We formulate a
model for calculating lock-in spectra which shows excellent agreement with our
experiments, and which shows that an optimum slope is achieved when the
linewidth/separation ratio is $\lesssim 1/4$ and the modulation depth is less
then the resonance linewidth, irrespective of the modulation function used.",1707.00916v1
2017-12-01,"Effect of spin-orbit coupling on the elastic, mechanical, and thermodynamic properties of Bi-Sb binaries","Using first principles calculations, we systematically study the elastic
stiffness constants, mechanical properties, elastic wave velocities, Debye
temperature, melting temperature, and specific heat of several
thermodynamically stable crystal structures of Bi$_{x}$Sb$_{1-x}$ ($0 < x < 1$)
binaries, which are of great interest due to their numerous inherent rich
properties, such as thermoelectricity, thermomagnetic cooling, strong
spin-orbit coupling (SOC) effects, and topological features in the electronic
bandstructure. We analyze the bulk modulus ($B$), Young's modulus ($E$), shear
modulus ($G$), $B/G$ ratio, and Poisson's ratio ($\nu$) as a function of the Bi
concentration in Bi$_{x}$Sb$_{1-x}$. The effect of SOC on above mentioned
properties is further investigated. In general, we observe that the SOC effects
cause elastic softening in most of the studied structures. Three monoclinic
structures of Bi-Sb binaries are found to exhibit significantly large
auxeticity. The Debye temperature and the magnitude of the elastic wave
velocities monotonically decrease with increasing Bi-concentration. We also
discuss the specific heat capacity versus temperature data for all studied
binaries. Our theoretical results are in excellent agreement with the existing
experimental and theoretical data. The comprehensive understanding of the
material properties such as hardness, mechanical strength, melting temperature,
propagation of the elastic waves, auxeticity, and heat capacity is vital for
practical applications of the studied binaries.",1712.00293v2
2018-01-06,A possible explanation of the parallel tracks in kilohertz quasi-periodic oscillations from low-mass-X-ray binaries,"We recalculate the modes of the magnetohydrodynamics (MHD) waves in the MHD
model (Shi, Zhang & Li 2014) of the kilohertz quasi-periodic oscillations (kHz
QPOs) in neutron star low mass X-ray binaries (NS-LMXBs), in which the
compressed magnetosphere is considered. A method on pointby- point scanning for
every parameter of a normal LMXBs is proposed to determine the wave number in a
NS-LMXB. The dependence of the twin kHz QPO frequencies on accretion rates (
DOt(M) ) is obtained with the wave number and magnetic field (B?) determined by
our method. Based on the MHD model, a new explanation of the parallel tracks,
i.e. the slowly varying effective magnetic field leads to the shift of parallel
tracks in a source, is presented. In this study, we obtain a simple power-law
relation between the kHz QPO frequencies and Dot(M) /B^2 ? in those sources.
Finally, we study the dependence of kHz quasi-periodic oscillation frequencies
on the spin, mass and radius of a neutron star. We find that the effective
magnetic field, the spin, mass and radius of a neutron star lead to the
parallel tracks in different sources.",1801.02000v2
2018-03-15,Metallic state in bosonic systems with continuously degenerate minima,"In systems above one dimension a continuously degenerate minimum of the
single particle dispersion is realized due to one or a combination of
system-parameters such as lattice structure, isotropic spin-orbit coupling, and
interactions. A unit codimension of the dispersion-minima leads to a divergent
density of states which enhances the effects of interactions, and may lead to
novel states of matter as exemplified by Luttinger liquids in one dimensional
bosonic systems. Here we show that in dilute, homogeneous bosonic systems above
one dimension, weak, spin-independent, inter-particle interactions stabilize a
metallic state at zero temperature in the presence of a curved manifold of
dispersion minima. In this metallic phase the system possesses a quasi
long-range order with non-universal scaling exponents. At a fixed positive
curvature of the manifold, increasing either the dilution or the interaction
strength destabilizes the metallic state towards charge density wave states
that break one or more symmetries. The magnitude of the wave vector of the
dominant charge density wave state is controlled by the product of the mean
density of bosons and the curvature of the manifold. We obtain the zero
temperature phase diagram, and identify the phase boundary.",1803.05839v2
2018-05-11,Ferroelectric quantum Hall phase revealed by visualizing Landau level wavefunction interference,"Novel broken symmetry states can spontaneously form due to Coulomb
interactions in electronic systems with multiple internal degrees of freedom.
Multi-valley materials offer an especially rich setting for the emergence of
such states, which have potential electronic and optical applications. To date,
identification of these broken symmetry phases has mostly relied on the
examination of macroscopic transport or optical properties. Here we demonstrate
a powerful direct approach by visualizing the wave functions of bismuth surface
states with a scanning tunneling microscope. Strong spin-orbit coupling on the
surface of bismuth leads to six degenerate teardrop-shaped hole pockets. Our
spectroscopic measurements reveal that this degeneracy is fully lifted at high
magnetic field as a result of exchange interactions, and we are able to
determine the nature of valley ordering by imaging the broken symmetry Landau
level (LL) wave functions. The remarkable spatial features of singly degenerate
LL wave functions near isolated defects contain unique signatures of
interference between spin-textured valleys, which identify the electronic
ground state as a quantum Hall ferroelectric. Our observations confirm the
recent prediction that interactions in strongly anisotropic valley systems
favor the occupation of a single valley, giving rise to emergent
ferroelectricity in the surface state of bismuth.",1805.04533v1
2018-06-02,From Classical Superposition of Waves to Quantum Interference: Three Level Quantum System for Two Entangled Photons,"Properties and applications of a plasmonic cross-shaped nano-antenna is
presented and compared to those of array of holes. A simple analytical model
based on the superposition of waves are proposed and compared to the numerical
results. A direct consequence of unequal path for two orthogonal surface waves
leads to a coherent quantum interferometer with interesting properties.
Mechanism behind the rotating surface charge densities and consequently, the
formation of rotating resultant dipole moments is identified and the concept of
Dipole-SPP-LSP-Stokes coupling is introduced. All of which leads to the most
significant findings (a) foundation of a three-level quantum system for
entangled photons, based on the polarization states of the transmitted light
and (b) further encapsulation of the three-level quantum system into a
continuous orthonormal set of pure quantum states (c) an inference on the
nonexistence of spin in a single photon, hence the requirement of two photons
to create such spin states.",1806.00619v13
2019-11-29,Freed-Isobar Analysis of Light Mesons at COMPASS,"Modern hadron-spectroscopy experiments such as COMPASS collect data samples
of unprecedented size, so that novel analysis techniques become possible and
necessary. One such technique is the freed-isobar partial-wave analysis (PWA).
In this approach, fixed parametrizations for the amplitudes of intermediate
states commonly modeled using Breit-Wigner shapes are replaced by sets of
step-like functions that are determined from the data. This approach not only
reduces the model dependence of partial-wave analyses, but also allows us to
study the amplitudes of the intermediate states and their dependence on the
parent system.
  We will also present results of a freed-isobar PWA performed on the large
data set on diffractive production of three charged pions collected by the
COMPASS experiment, which consists of $46\times10^6$ exclusive events. We will
focus on results for the wave with spin-exotic quantum numbers $J^{PC}=1^{-+}$,
in particular on its decay into $\rho(770)\pi$. Here, the freed-isobar PWA
method provides insight into the interplay of three- and two-particle dynamics
and confirms the decay of the spin-exotic $\pi_1(1600)$ resonance to
$\rho(770)\pi$ in a model-independent way.",1911.12907v1
2017-05-12,Pseudo-Goldstone magnons in the frustrated S=3/2 Heisenberg helimagnet ZnCr2Se4 with a pyrochlore magnetic sublattice,"Low-energy spin excitations in any long-range ordered magnetic system in the
absence of magnetocrystalline anisotropy are gapless Goldstone modes emanating
from the ordering wave vectors. In helimagnets, these modes hybridize into the
so-called helimagnon excitations. Here we employ neutron spectroscopy supported
by theoretical calculations to investigate the magnetic excitation spectrum of
the isotropic Heisenberg helimagnet ZnCr2Se4 with a cubic spinel structure, in
which spin-3/2 magnetic Cr3+ ions are arranged in a geometrically frustrated
pyrochlore sublattice. Apart from the conventional Goldstone mode emanating
from the (0 0 q) ordering vector, low-energy magnetic excitations in the
single-domain proper-screw spiral phase show soft helimagnon modes with a small
energy gap of ~0.17 meV, emerging from two orthogonal wave vectors (q 0 0) and
(0 q 0) where no magnetic Bragg peaks are present. We term them
pseudo-Goldstone magnons, as they appear gapless within linear spin-wave theory
and only acquire a finite gap due to higher-order quantum-fluctuation
corrections. Our results are likely universal for a broad class of symmetric
helimagnets, opening up a new way of studying weak magnon-magnon interactions
with accessible spectroscopic methods.",1705.04642v3
2018-10-11,"Magnons in a Quasicrystal: Propagation, Localization and Extinction of Spin Waves in Fibonacci Structures","Magnonic quasicrystals exceed the possibilities of spin wave (SW)
manipulation offered by regular magnonic crystals, because of their more
complex SW spectra with fractal characteristics. Here, we report the direct
x-ray microscopic observation of propagating SWs in a magnonic quasicrystal,
consisting of dipolarly coupled permalloy nanowires arranged in a
one-dimensional Fibonacci sequence. SWs from the first and second band as well
as evanescent waves from the band gap between them are imaged. Moreover,
additional mini-band gaps in the spectrum are demonstrated, directly indicating
an influence of the quasiperiodicity of the system. The experimental results
are interpreted using numerical calculations and we deduce a simple model to
estimate the frequency position of the magnonic gaps in quasiperiodic
structures. The demonstrated features of SW spectra in one-dimensional magnonic
quasicrystals allows utilizing this class of metamaterials for magnonics and
makes them an ideal basis for future applications.",1810.04931v2
2019-06-06,Aspects of Gravitational Wave/Particle Duality: Bulk Torsion $\leftrightarrow$ Boundary Gravity Correspondence,"A geometric torsion (GT) underlying a $2$-form in a $(4$$+$$1)$-dimensional
$U(1)$ gauge theory is revisited with a renewed perspective for a
non-perturbation (NP) gravity in $d$$=$$4$. In the context we provide evidences
to a holographic correspondence between a bulk GT and a boundary NP gravity.
Interestingly the Killing symmetries in General Relativity (GR) are shown to
provide a subtle clue to the quantum gravity. The NP gravity is shown to
incorporate a $(B_{2}$$ \wedge $$F_{2})$ coupling, sourced by a non-Newtonian
potential, to an exact geometry in GR. Remarkably the NP correction is
identified as a mass dipole and is shown to be sourced by a propagating GT. A
detailed analysis is performed in a bulk GT to show a modification to the
precession of perihelion in a boundary NP gravity. The perspective of an
electromagnetic (EM) wave in the bulk is investigated to reveal a spin $2$
(mass-less) quantum sourced by an apparent 2-form. A Goldstone scalar is
absorbed by the apparent 2-form to describe a massive $2$-form in the coulomb
gauge. Alternately a Goldstone scalar together with a local degree of GT and
2-form is argued to govern a composite (mass-less) spin $2$ particle in Lorentz
gauge. Both the scenarios, further ensure a graviton in a boundary NP gravity.
A qualitative analysis reveals a (non-interacting) graviton underlying a
plausible gravitational wave/particle duality in NP gravity.",1906.02490v1
2016-02-29,Overlapping hot spots and charge modulation in cuprates,"Particle-hole instabilities are studied within a two dimensional model of
fermions interacting with antiferromagnetic spin fluctuations (spin-fermion
model). In contrast to previous works, we assume that neighboring hot spots
overlap due to a shallow dispersion of the electron spectrum in the antinodal
region and include in the consideration effects of a remnant low energy and
momentum Coulomb interaction. It turns out that this modification of the model
drastically changes the behavior of the system. The leading particle-hole
instability at not very weak fermion-fermion interaction is no longer a charge
density wave with a modulation along the diagonals of the Brillouin zone
predicted previously but a Pomeranchuk-type deformation of the Fermi surface
breaking the C$_{4}$ symmetry of the system. This order does not prevent from
further phase transitions at lower temperatures. We show that, depending on
parameters of the interaction, either d-wave superconductivity or charge
density wave with modulations along the bonds of the $CuO$ lattice is possible.
The low momentum remnant Coulomb interaction enhances the d-form factor of the
charge density wave. Comparison with experimental data allows us to conclude
that in many cuprate compounds the conditions for the proposed scenario are
indeed fulfilled. Our results may explain important features of the charge
modulations observed recently.",1603.02320v1
2016-12-07,Detectability of gravitational waves from binary black holes: Impact of precession and higher modes,"Gravitational wave templates used in current searches for binary black holes
omit the effects of precession of the orbital plane and higher order modes.
While this omission seems not to impact the detection of sources having mass
ratios and spins similar to those of GW150914, even for total masses $M >
200M_{\odot}$; we show that it can cause large fractional losses of sensitive
volume for binaries with mass ratio $q \geq 4$ and $M>100M_{\odot}$, measured
the detector frame. For the highest precessing cases, this is true even when
the source is face-on to the detector. Quantitatively, we show that the
aforementioned omission can lead to fractional losses of sensitive volume of
$\sim15\%$, reaching $>25\%$ for the worst cases studied. Loss estimates are
obtained by evaluating the effectualness of the SEOBNRv2-ROM double spin model,
currently used in binary black hole searches, towards gravitational wave
signals from precessing binaries computed by means of numerical relativity. We
conclude that, for sources with $q \geq 4$, a reliable search for binary black
holes heavier than $M>100M_\odot$ needs to consider the effects of higher order
modes and precession. The latter seems specially necessary when Advanced LIGO
reaches its design sensitivity.",1612.02340v4
2016-12-08,A Sommerfeld Toolbox for Colored Dark Sectors,"We present analytical formulae for the Sommerfeld corrections to the
annihilation of massive colored particles into quarks and gluons through the
strong interaction. These corrections are essential to accurately compute the
dark matter relic density for coannihilation with colored partners. Our
formulae allow to compute the Sommerfeld effect, not only for the lowest term
in the angular momentum expansion of the amplitude, but for all orders in the
partial wave expansion. In particular, we carefully account for the effects of
the spin of the annihilating particle on the symmetry of the two-particle wave
function. This work focuses on strongly interacting particles of arbitrary spin
in the triplet, sextet and octet color representations. For typical velocities
during freeze-out, we find that including Sommerfeld corrections on the
next-to-leading order partial wave leads to modifications of up to ten to
twenty percent on the total annihilation cross section. Complementary to QCD,
we generalize our results to particles charged under an arbitrary unbroken
SU(N) gauge group, as encountered in dark glueball models. In connection with
this paper a Mathematica notebook is provided to compute the Sommerfeld
corrections for colored particles up to arbitrary order in the angular momentum
expansion.",1612.02825v4
2019-03-04,"Geometric phases in 2D and 3D polarized fields: geometrical, dynamical, and topological aspects","Geometric phases are a universal concept that underpins numerous phenomena
involving multi-component wave fields. These polarization-dependent phases are
inherent in interference effects, spin-orbit interaction phenomena, and
topological properties of vector wave fields. Geometric phases have been
thoroughly studied in two-component fields, such as two-level quantum systems
or paraxial optical waves. However, their description for fields with three or
more components, such as generic nonparaxial optical fields routinely used in
modern nano-optics, constitutes a nontrivial problem. Here we describe
geometric, dynamical, and total phases calculated along a closed spatial
contour in a multi-component complex field, with particular emphasis on 2D
(paraxial) and 3D (nonparaxial) optical fields. We present several equivalent
approaches: (i) an algebraic formalism, universal for any multi-component
field; (ii) a dynamical approach using the Coriolis coupling between the spin
angular momentum and reference-frame rotations; and (iii) a geometric
representation, which unifies the Pancharatnam-Berry phase for the 2D
polarization on the Poincar\'e sphere and the Majorana-sphere representation
for the 3D polarized fields. Most importantly, we reveal close connections
between geometric phases, angular-momentum properties of the field, and
topological properties of polarization singularities in 2D and 3D fields, such
as C-points and polarization M\""obius strips.",1903.01304v2
2019-03-21,Non-reciprocity of spin waves in magnetic nanotubes with helical equilibrium magnetization,"Spin waves (SWs) in magnetic nanotubes have shown interesting nonreciprocal
properties in their dispersion relation, group velocity, frequency linewidth
and attenuation lengths. The reported chiral effects are similar to those
induced by the Dzyaloshinskii-Moriya interaction, but originating from the
dipole-dipole interaction. Here we show, that the isotropic-exchange
interaction can also induce chiral effects in the SW transport; the so-called
Berry phase of SWs. We demonstrate that with the application of magnetic
fields, the nonreciprocity of the different SW modes can be tuned between the
fully dipolar governed and the fully exchange governed cases, as they are
directly related to the underlaying equilibrium state. In the helical state,
due to the combined action of the two effects every single sign combination of
the azimuthal and axial wave vectors leads to different dispersion, allowing
for a very sophisticated tuning of the SW transport. A disentanglement of the
dipole-dipole and exchange contributions so far was not reported for the SW
transport in nanotubes. Furthermore, we propose a device based on coplanar
waveguides that would allow to selectively measure the exchange or dipole
induced SW nonreciprocities. In the context of magnonic applications, our
results might encourage further developments in the emerging field of 3D
magnonic devices using curved magnetic membranes.",1903.09062v2
2020-09-10,Spin waves in alloys at finite temperatures: application for FeCo magnonic crystal,"We study theoretically the influence of the temperature and disorder on the
spin wave spectrum of the magnonic crystal Fe$_{1-c}$Co$_{c}$. Our formalism is
based on the analysis of a Heisenberg Hamiltonian by means of the wave vector
and frequency dependent transverse magnetic susceptibility. The exchange
integrals entering the model are obtained from the \emph{ab initio} magnetic
force theorem. The coherent potential approximation is employed to treat the
disorder and random phase approximation in order to account for the softening
of the magnon spectrum at finite temperatures. The alloy turns out to exhibit
many advantageous properties for spintronic applications. Apart from high Curie
temperature, its magnonic bandgap remains stable at elevated temperatures and
is largely unaffected by the disorder. We pay particular attention to the
attenuation of magnons introduced by the alloying. The damping turns out to be
a non-monotonic function of the impurity concentration due to the non-trivial
evolution of the value of exchange integrals with the Co concentration. The
disorder induced damping of magnons is estimated to be much smaller than their
Landau damping.",2009.04712v6
2020-09-27,Modelling neutron star mountains,"As the era of gravitational-wave astronomy has well and truly begun,
gravitational radiation from rotating neutron stars remains elusive. Rapidly
spinning neutron stars are the main targets for continuous-wave searches since,
according to general relativity, provided they are asymmetrically deformed,
they will emit gravitational waves. It is believed that detecting such
radiation will unlock the answer to why no pulsars have been observed to spin
close to the break-up frequency. We review existing studies on the maximum
mountain that a neutron star crust can support, critique the key assumptions
and identify issues relating to boundary conditions that need to be resolved.
In light of this discussion, we present a new scheme for modelling neutron star
mountains. The crucial ingredient for this scheme is a description of the
fiducial force which takes the star away from sphericity. We consider three
examples: a source potential which is a solution to Laplace's equation, another
solution which does not act in the core of the star and a thermal pressure
perturbation. For all the cases, we find that the largest quadrupoles are
between a factor of a few to two orders of magnitude below previous estimates
of the maximum mountain size.",2009.12794v2
2020-09-30,"A study of the decays of $S-$wave $\bar D^\ast K^\ast$ hadronic molecules: the scalar $X_0(2900)$ and its spin partners $X_{J(J=1,2)}$","In this work, we investigated the decays of the fully open-flavor tetraquark
state $X_0(2900)$ which was observed by the LHCb Collaboration very recently.
Here, the $X_0(2900)$ was assigned as a $S-$wave $\bar D^\ast K^\ast$ hadronic
molecule with $I=0$, and the effective lagrangian approach was applied to
estimate the partial decay widths. Moreover, we also predicted the decay
behaviors of the other unobserved $X_{J(J=1,2)}$, which were the spin partners
of the $X_0(2900)$ in the $S-$wave $\bar D^\ast K^\ast$ picture. It was pointed
out that the $X_1$ state with $I=0$ was a broad state with the width more than
one hundred MeV, while another $X_2$ state with $I=0$ was a narrow state with
the width approaching half of that for the $X_0(2900)$. In addition, our
results also showed that the $\bar D^\ast K$ mode was expected to be the
dominant decay mode for both $X_1$ and $X_2$. Searching for those unobserved
$X_{J(J=1,2)}$ in the future experiments might be helpful to understand the
nature of $X_0(2900)$.",2009.14538v1
2008-06-12,Identification of microscopic spin-polarization coupling in the ferroelectric phase of a magnetoelectric multiferroic CuFe1-xAlxO2,"We have performed synchrotron radiation X-ray and neutron diffraction
measurements on magnetoelectric multiferroic CuFe1-xAlxO2 (x=0.0155), which has
a proper helical magnetic structure with incommensurate propagation wave vector
in the ferroelectric phase. The present measurements revealed that the
ferroelectric phase is accompanied by lattice modulation with a wave number 2q,
where q is the magnetic modulation wave number. We have calculated the Fourier
spectrum of the spatial modulations in the local electric polarization using a
microscopic model proposed by Arima [T. Arima, J. Phys. Soc. Jpn. 76, 073702
(2007)]. Comparing the experimental results with the calculation results, we
found that the origin of the 2q-lattice modulation is not conventional
magnetostriction but the variation in the metal-ligand hybridization between
the magnetic Fe^3+ ions and ligand O^2- ions. Combining the present results
with the results of a previous polarized neutron diffraction study [Nakajima et
al., Phys. Rev. B 77 052401 (2008)], we conclude that the microscopic origin of
the ferroelectricity in CuFe1-xAlxO2 is the variation in the metal-ligand
hybridization with spin-orbit coupling.",0806.2004v1
2017-01-18,A charge density wave-like instability in a doped spin-orbit-assisted weak Mott insulator,"Layered perovskite iridates realize a rare class of Mott insulators that are
predicted to be strongly spin-orbit coupled analogues of the parent state of
cuprate high-temperature superconductors. Recent discoveries of pseudogap,
magnetic multipolar ordered and possible $d$-wave superconducting phases in
doped Sr$_2$IrO$_4$ have reinforced this analogy among the single layer
variants. However, unlike the bilayer cuprates, no electronic instabilities
have been reported in the doped bilayer iridate Sr$_3$Ir$_2$O$_7$. Here we show
that Sr$_3$Ir$_2$O$_7$ realizes a weak Mott state with no cuprate analogue by
using ultrafast time-resolved optical reflectivity to uncover an intimate
connection between its insulating gap and antiferromagnetism. However, we
detect a subtle charge density wave-like Fermi surface instability in metallic
electron doped Sr$_3$Ir$_2$O$_7$ at temperatures ($T_{DW}$) close to 200 K via
the coherent oscillations of its collective modes, which is reminiscent of that
observed in cuprates. The absence of any signatures of a new spatial
periodicity below $T_{DW}$ from diffraction, scanning tunneling and
photoemission based probes suggests an unconventional and possibly short-ranged
nature of this density wave order.",1701.05194v1
2019-01-10,Spin-wave Confinement and Coupling in Organic-Based Magnetic Nanostructures,"Vanadium tetracyanoethylene (V[TCNE]$_\text{x}$) is an organic-based
ferrimagnet that exhibits robust magnetic ordering (T$_\text{C}$ of over 600
K), high quality-factor (high-Q) microwave resonance (Q up to 3,500), and
compatibility with a wide variety of substrates and encapsulation technologies.
Here, we substantially expand the potential scope and impact of this emerging
material by demonstrating the ability to produce engineered nanostructures with
tailored magnetic anisotropy that serve as a platform for the exploration of
cavity magnonics, revealing strongly coupled quantum confined standing wave
modes that can be tuned into and out of resonance with an applied magnetic
field. Specifically, time-domain micromagnetic simulations of these
nanostructures faithfully reproduce the experimentally measured spectra,
including the quasi-uniform mode and higher-order spin-wave (magnon) modes.
Finally, when the two dominant magnon modes present in the spectra are brought
into resonance by varying the orientation of the in-plane magnetic field, we
observe anti-crossing behavior indicating strong coherent coupling between
these two magnon modes at room temperature. These results position
V[TCNE]$_\text{x}$ as a leading candidate for the development of coherent
magnonics, with potential applications ranging from microwave electronics to
quantum information.",1901.03286v2
2019-04-23,Momentum-resolved lattice dynamics of parent and electron-doped Sr$_{2}$IrO$_{4}$,"The mixing of orbital and spin character in the wave functions of the $5d$
iridates has led to predictions of strong couplings among their lattice,
electronic and magnetic degrees of freedom. As well as realizing a novel
spin-orbit assisted Mott-insulating ground state, the perovskite iridate
Sr$_{2}$IrO$_{4}$ has strong similarities with the cuprate La$_{2}$CuO$_{4}$,
which on doping hosts a charge-density wave that appears intimately connected
to high-temperature superconductivity. These phenomena can be sensitively
probed through momentum-resolved measurements of the lattice dynamics, made
possible by meV-resolution inelastic x-ray scattering. Here we report the first
such measurements for both parent and electron-doped Sr$_{2}$IrO$_{4}$. We find
that the low-energy phonon dispersions and intensities in both compounds are
well described by the same nonmagnetic density functional theory calculation.
In the parent compound, no changes of the phonons on magnetic ordering are
discernible within the experimental resolution, and in the doped compound no
anomalies are apparent due to charge-density waves. These measurements extend
our knowledge of the lattice properties of (Sr$_{1-x}$La$_{x}$)$_{2}$IrO$_{4}$
and constrain the couplings of the phonons to magnetic and charge order.",1904.10391v2
2019-10-03,Superfluid Condensate Fraction and Pairing Wave Function of the Unitary Fermi Gas,"The unitary Fermi gas is a many-body system of two-component fermions with
zero-range interactions tuned to infinite scattering length. Despite much
activity and interest in unitary Fermi gases and its universal properties,
there have been great difficulties in performing accurate calculations of the
superfluid condensate fraction and pairing wave function. In this work we
present auxiliary-field lattice Monte Carlo simulations using a novel lattice
interaction which accelerates the approach to the continuum limit, thereby
allowing for robust calculations of these difficult observables. As a benchmark
test we compute the ground state energy of 33 spin-up and 33 spin-down
particles. As a fraction of the free Fermi gas energy $E_{FG}$, we find
$E_0/E_{FG}= 0.369(2), 0.372(2)$, using two different definitions of the
finite-system energy ratio, in agreement with the latest theoretical and
experimental results. We then determine the condensate fraction by measuring
off-diagonal long-range order in the two-body density matrix. We find that the
fraction of condensed pairs is $\alpha = 0.43(2)$. We also extract the pairing
wave function and find the pair correlation length to be $\zeta_pk_F = 1.8(3)
\hbar$, where $k_F$ is the Fermi momentum. Provided that the simulations can be
performed without severe sign oscillations, the methods we present here can be
applied to superfluid neutron matter as well as more exotic P-wave and D-wave
superfluids.",1910.01257v2
2019-12-12,"Topological Lattice Metamaterials -- A Platform For Novel Electromagnetic Material Design Based On An Artificial Topological ""Atom""","In nature, most materials are composed of atoms with periodic structures.
Hence, it's impossible to introduce topological structures into their lattice
compose, because the atoms as basic blocks cannot be modulated. However, the
lattice compose of metamaterials can be designed conveniently. In our work, we
propose to introduce topological non-trivial structures, Mobius unknots, as the
basic block (the artificial chiral ""atoms"") to design metamaterials. A 5.95 GHz
intrinsic peak, in addition to the electrical resonance peak near 11 GHz on the
transmission coefficient spectrum was confirmed by theoretical calculations,
finite-difference time-domain (FDTD) simulations and experiments when
electromagnetic waves transfer to a chiral Mobius unknot. Theoretical analysis
indicates that this intrinsic peak originates from the phase transition caused
by the electromagnetic waves propagate along the Mobius unknot non-trivial
structure. It is similar to the state of spin-splitting of electron levels.
Take the artificial chiral ""atoms"" - Mobius unknots as the basic block, we can
construct two-dimensional and even three-dimensional ordered metamaterials. The
simulation and experimental results showed that the response to electromagnetic
wave in the GHz band can be modulated by the coupling between the periodic
potential and the spin-like of energy levels.",1912.05804v2
2020-12-07,Fast ejecta as a potential way to distinguish black holes from neutron stars in high-mass gravitational-wave events,"High-mass gravitational-wave events in the neutron-star mass range, such as
GW190425, have recently started to be detected by the LIGO/Virgo detectors. If
the masses of the two binary components fall in the neutron-star mass range,
such a system is typically classified as a binary neutron-star system, although
the detected gravitational-wave signal may be too noisy to clearly establish a
neutron-star nature of the high-mass component in the binary and rule out a
black hole--neutron star system for such an event. We here show that high-mass
binary neutron-star mergers with a very massive neutron-star primary close to
the maximum-mass limit, $m_1 \gtrsim 2.2 \, M_\odot$, produce fast dynamical
mass ejecta from the spin-up of the primary star at merger. By simulating the
merger of black hole--neutron star systems of exactly the same masses and
spins, we show that these fast ejecta are entirely absent, if the primary is
instead a black hole. In addition, we find that both systems leave almost
identical amounts of baryon mass behind, which is not immediately accreted by
the black hole. This implies that both systems will likely have comparable
electromagnetic afterglow emission stemming from the remnant disk. Hence, fast
ejecta at merger have the potentialto distinguish neutron stars from black
holes in high-mass mergers, although these ejecta may be challenging to detect
observationally.",2012.03896v1
2021-03-01,"Phase slips, dislocations, half-integer vortices, two-fluid hydrodynamics and the chiral anomaly in charge and spin density waves","This brief review recalls some chapters in theory of sliding incommensurate
density waves which may have appeared after inspirations from studies of I.E
Dzyaloshinskii and collaborations with him. First we address the spin density
waves which rich order parameter allows for an unusual object of a complex
topological nature: a half-integer dislocation combined with a semi-vortex of
the staggered magnetization. It becomes energetically preferable with respect
to an ordinary dislocation due to the high Coulomb energy at low concentration
of carriers. Generation of these objects should form a sequence of pi-phase
slips in accordance with experimental doubling of phase-slips rate. Next, we
revise the commonly employed TDGL approach which is shown to suffer from a
violation of the charge conservation law resulting in nonphysical generation of
particles which is particularly pronounced for electronic vortices in the
course of their nucleation or motion. The suggested consistent theory exploits
the chiral transformations taking into account the principle contribution of
the fermionic chiral anomaly to the effective action. The derived equations
clarify partitions of charges,currents and rigidity among subsystems of the
condensate and normal carriers and the gluing electric field. Being
non-analytical with respect to the order parameter, contrarily the conventional
TDGL type, the resulting equations still allow for a numerical modeling of
transient processes related to space- and spatio-temporal vorticity in DWs.",2103.01107v1
2021-03-21,Multi-Ciliated Microswimmers -- Metachronal Coordination and Helical Swimming,"The dynamics and motion of multi-ciliated microswimmers with a spherical body
and a small number N (with 5 < N < 60) of cilia with length comparable to the
body radius, is investigated by mesoscale hydrodynamics simulations. A
metachronal wave is imposed for the cilia beat, for which the wave vector has
both a longitudinal and a latitudinal component. The dynamics and motion is
characterized by the swimming velocity, its variation over the beat cycle, the
spinning velocity around the main body axis, as well as the parameters of the
helical trajectory. Our simulation results show that the microswimmer motion
strongly depends on the latitudinal wave number and the longitudinal phase lag.
The microswimmers are found to swim smoothly and usually spin around their own
axis. Chirality of the metachronal beat pattern generically generates helical
trajectories. In most cases, the helices are thin and stretched, i.e. the helix
radius is about an order of magnitude smaller than the pitch. The rotational
diffusion of the microswimmer is significantly smaller than the passive
rotational diffusion of the body alone, which indicates that the extended cilia
contribute strongly to the hydrodynamic radius. The swimming velocity vswim is
found to increase with the cilia number N with a slightly sublinear power law,
consistent with the behavior expected from the dependence of the transport
velocity of planar cilia arrays on the cilia separation.",2103.11447v1
2021-09-29,Proton wave function in a water molecule: Breakdown of degeneration caused by interactions with the magnetic field of a Magnetic Resonance Imaging device,"The concept of a Magnetic Resonance Imaging (MRI) device is based on the
emission of radio waves produced by the protons of the hydrogen atoms in water
molecules when placed in a constant magnetic field after they interact with a
pulsed radio frequency (RF) current. When the RF field is turned on, the
protons are brought to a spin excited state. When the RF field is turned off,
the MRI sensors are able to detect the energy released as the protons realign
their spins with the magnetic field. In this work we provide a simple model to
describe the basic physical mechanism responsible for the operation of MRI
devices. We model the water molecule in terms of a central force problem, where
the protons move around the (unstructured) doubly negatively charged oxygen
atom. First, we employ an analytical treatment to obtain the system's wave
function as well as its energy levels, which we show are degenerate. Next, the
energy levels from the water molecule are studied in the presence of a uniform
external magnetic field. As a result, they get shifted and the degeneration is
lifted. We provide numerical results for a magnetic field strength commonly
used in MRI devices.",2109.14531v1
2022-02-03,"Theory of Competing Charge Density Wave, Kekule and Antiferromagnetic ordered Fractional Quantum Hall states in Graphene aligned with Boron Nitride","We investigate spin and valley symmetry-broken fractional quantum Hall phases
within a formalism that naturally extends the paradigm of quantum Hall
ferromagnetism from integer to fractional quantum Hall states, allowing us to
construct detailed phase diagrams for a large class of multi-component states.
Motivated by recent experiments on Graphene aligned with a Boron Nitride
substrate, we predict a sequence of transitions realized by increasing the
magnetic field, starting from a sub-lattice polarized state to a valley
coherent Kekule charge density wave state and further to an anti-ferromagnetic
phase. Moreover for filling fractions such as $\nu=\pm 1/3$, we predict that
the system undergoes a transition at low fields, that not only differ by the
spin-valley orientation of the fractionally filled flavors but also by their
intrinsic fractional quantum Hall nature. This transition is from a
Laughlin-like state to a two component Halperin-like state both with a charge
density wave order. Moreover for $\nu=\pm 1/3,\pm 2/3$, we predict a ""canted
Kekule density phase""(CaKD) where the spinors of integer and fractionally
occupied components have different orientations in the valley Bloch sphere, in
contrast to the Kekule state for the integer quantum Hall state at neutrality
where both occupied components have the same orientation in the valley Bloch
sphere.",2202.01796v2
2022-02-02,Wave function Ansatz (but Periodic) Networks and the Homogeneous Electron Gas,"We design a neural network Ansatz for variationally finding the ground-state
wave function of the Homogeneous Electron Gas, a fundamental model in the
physics of extended systems of interacting fermions. We study the
spin-polarised and paramagnetic phases with 7, 14 and 19 electrons over a broad
range of densities from $r_s=1$ to $r_s=100$, obtaining similar or higher
accuracy compared to a state-of-the-art iterative backflow baseline even in the
challenging regime of very strong correlation. Our work extends previous
applications of neural network Ans\""{a}tze to molecular systems with methods
for handling periodic boundary conditions, and makes two notable changes to
improve performance: splitting the pairwise streams by spin alignment and
generating backflow coordinates for the orbitals from the network. We
illustrate the advantage of our high quality wave functions in computing the
reduced single particle density matrix. This contribution establishes neural
network models as flexible and high precision Ans\""{a}tze for periodic
electronic systems, an important step towards applications to crystalline
solids.",2202.04622v3
2022-04-19,Constraining spontaneous black hole scalarization in scalar-tensor-Gauss-Bonnet theories with current gravitational-wave data,"We examine the constraining power of current gravitational-wave data on
scalar-tensor-Gauss-Bonnet theories that allow for the spontaneous
scalarization of black holes. In the fiducial model that we consider, a slowly
rotating black hole must scalarize if its size is comparable to the new length
scale $\lambda$ that the theory introduces, although rapidly rotating black
holes of any mass are effectively indistinguishable from their counterparts in
general relativity. With this in mind, we use the gravitational-wave event
GW190814$\,\unicode{x2014}\,$whose primary black hole has a spin that is
bounded to be small, and whose signal shows no evidence of a scalarized
primary$\,\unicode{x2014}\,$to rule out a narrow region of the parameter space.
In particular, we find that values of ${\lambda \in [56, 96]~M_\odot}$ are
strongly disfavored with a Bayes factor of $0.1$ or less. We also include a
second event, GW151226, in our analysis to illustrate what information can be
extracted when the spins of both components are poorly measured.",2204.09038v2
2022-08-02,Eccentricity estimation for five binary black hole mergers with higher-order gravitational wave modes,"The detection of orbital eccentricity for a binary black hole system via
gravitational waves is a key signature to distinguish between the possible
binary origins. The identification of eccentricity has been difficult so far
due to the limited availability of eccentric gravitational waveforms over the
full range of black hole masses and eccentricities. Here we evaluate the
eccentricity of five black hole mergers detected by the LIGO and Virgo
observatories for the first time using the TEOBResumSGeneral model. This model
accounts for the full eccentricity range possible and incorporates higher-order
gravitational wave modes critical to model emission from highly eccentric
orbits. The binaries have been selected due to previous hints of eccentricity
or due to their unusual mass and spin. While other studies found marginal
evidence for eccentricity for some of these events, our analyses do not favor
the incorporation of eccentricity compared to the quasi-circular case. While
lacking the eccentric evidence of other analyses, we find our analyses
marginally shifts the posterior in multiple parameters for several events when
allowing eccentricity to be non-zero.",2208.01766v2
2022-08-17,Bootstrapped Dimensional Crossover of a Spin Density Wave,"Quantum materials display rich and myriad types of magnetic, electronic, and
structural ordering, often with these ordering modes either competing with one
another or 'intertwining', that is, reinforcing one another. Low dimensional
quantum materials, influenced strongly by competing interactions and/or
geometric frustration, are particularly susceptible to such ordering phenomena
and thus offer fertile ground for understanding the consequent emergent
collective quantum phenomena. Such is the case of the quasi-2D materials
R4Ni3O10(R=La, Pr), in which intertwined charge-and spin-density waves (CDW and
SDW) on the Ni sublattice have been identified and characterized. Not
unexpectedly, these density waves are largely 2D as a result of weak coupling
between planes, compounded with magnetic frustration. In the case of R=Pr,
however, we show here that exchange coupling between the transition metal and
rare earth sublattices upon cooling overcomes both obstacles, leading to a
dimensional crossover into a fully 3D ordered and coupled SDW state on both
sublattices, as an induced moment on notionally nonmagnetic Pr3+ opens exchange
pathways in the third dimension. In the process, the structure of the SDW on
the Ni sublattice is irreversibly altered, an effect that survives reheating of
the material until the underlying CDW melts. This 'bootstrapping' mechanism
linking incommensurate SDWs on the two sublattices illustrates a new member of
the multitude of quantum states that low-dimensional magnets can express,
driven by coupled orders and modulated by frustrated exchange pathways.",2208.08424v1
2022-10-28,Factorized Parameter Estimation for Real-Time Gravitational Wave Inference,"We present a parameter estimation framework for gravitational wave (GW)
signals that brings together several ideas to accelerate the inference process.
First, we use the relative binning algorithm to evaluate the
signal-to-noise-ratio timeseries in each detector for a given choice of
intrinsic parameters. Second, we decouple the estimation of the intrinsic
parameters (such as masses and spins of the components) from that of the
extrinsic parameters (such as distance, orientation, and sky location) that
describe a binary compact object coalescence. We achieve this by
semi-analytically marginalizing the posterior distribution over extrinsic
parameters without repeatedly evaluating the waveform for a fixed set of
intrinsic parameters. Finally, we augment samples of intrinsic parameters with
extrinsic parameters drawn from their appropriate conditional distributions. We
implement the method for binaries with aligned spins, restricted to the
quadrupole mode of the signal. Using simulated GW signals, we demonstrate that
the method produces full eleven-dimensional posteriors that match those from
standard Bayesian inference. Our framework takes only ~200 seconds to analyze a
typical binary-black-hole signal and ~250 seconds to analyze a typical
binary-neutron-star signal using one computing core. Such real-time and
accurate estimation of the binary source properties will greatly aid the
interpretation of triggers from gravitational wave searches, as well as the
search for possible electromagnetic counterparts. We make the framework
publicly available via the GW inference package cogwheel.",2210.16278v1
2022-11-17,Delayed Hopf bifurcation and control of a ferrofluid interface via a time-dependent magnetic field,"A ferrofluid droplet confined in a Hele-Shaw cell can be deformed into a
stably spinning ``gear,'' using crossed magnetic fields. Previously, fully
nonlinear simulation revealed that the spinning gear emerges as a stable
traveling wave along the droplet's interface bifurcates from the trivial
(equilibrium) shape. In this work, a center manifold reduction is applied to
show the geometrical equivalence between a two-harmonic-mode coupled system of
ordinary differential equations arising from a weakly nonlinear analysis of the
interface shape and a Hopf bifurcation. The rotating complex amplitude of the
fundamental mode saturates to a limit circle as the periodic traveling wave
solution is obtained. An amplitude equation is derived from a
multiple-time-scale expansion as a reduced model of the dynamics. Then,
inspired by the well-known delay behavior of time-dependent Hopf bifurcations,
we design a slowly time-varying magnetic field such that the timing and
emergence of the interfacial traveling wave can be controlled. The proposed
theory allows us to determine the time-dependent saturated state resulting from
the dynamic bifurcation and delayed onset of instability. The amplitude
equation also reveals hysteresis-like behavior upon time reversal of the
magnetic field. The state obtained upon time reversal differs from the state
obtained during the initial (forward-time) period, yet it can still be
predicted by the proposed reduced-order theory.",2211.09758v3
2023-02-22,Defining eccentricity for gravitational wave astronomy,"Eccentric compact binary mergers are significant scientific targets for
current and future gravitational wave observatories. To detect and analyze
eccentric signals, there is an increasing effort to develop waveform models,
numerical relativity simulations, and parameter estimation frameworks for
eccentric binaries. Unfortunately, current models and simulations use different
internal parameterisations of eccentricity in the absence of a unique natural
definition of eccentricity in general relativity, which can result in
incompatible eccentricity measurements. In this paper, we adopt a standardized
definition of eccentricity and mean anomaly based solely on waveform
quantities, and make our implementation publicly available through an
easy-to-use Python package, gw_eccentricity. This definition is free of gauge
ambiguities, has the correct Newtonian limit, and can be applied as a
postprocessing step when comparing eccentricity measurements from different
models. This standardization puts all models and simulations on the same
footing and enables direct comparisons between eccentricity estimates from
gravitational wave observations and astrophysical predictions. We demonstrate
the applicability of this definition and the robustness of our implementation
for waveforms of different origins, including post-Newtonian theory, effective
one body, extreme mass ratio inspirals, and numerical relativity simulations.
We focus on binaries without spin-precession in this work, but possible
generalizations to spin-precessing binaries are discussed.",2302.11257v3
2023-04-21,Gravitational Wave Flux and Quadrupole Modes from Quasi-Circular Non-Spinning Compact Binaries to the Fourth Post-Newtonian Order,"This article provides the details on the technical derivation of the
gravitational waveform and total gravitational-wave energy flux of non-spinning
compact binary systems to the 4PN (fourth post-Newtonian) order beyond the
Einstein quadrupole formula. In particular: (i) we overview the link between
the radiative multipole moments measured at infinity and the source moments in
the framework of dimensional regularization; (ii) we compute special
corrections to the source moments due to ""infrared"" commutators arising at the
4PN order; (iii) we derive a ""post-adiabatic"" correction needed to evaluate the
tail integral with 2.5PN relative precision; (iv) we discuss the relation
between the binary's orbital frequency in quasi-circular orbit and the
gravitational-wave frequency measured at infinity; (v) we compute the
hereditary effects at the 4PN order, including those coming from the recently
derived tails-of-memory; and (vi) we describe the various tests we have
performed to ensure the correctness of the results. Those results are collected
in an ancillary file.",2304.11186v4
2023-05-25,Tuning charge density wave order and structure via uniaxial stress in a stripe-ordered cuprate superconductor,"Unidirectional spin and charge density wave order in the cuprates is known to
compete with superconductivity. In the stripe order (La,M)$_2$CuO$_4$ family of
cuprates, spin and charge order occur as unidirectional order that can be
stabilized by symmetry breaking structural distortions, such as the low
temperature tetragonal (LTT) phase. Here we examine the interplay between
structure and the formation of charge density wave (CDW) order in the LTT phase
of La$_{1.475}$Nd$_{0.4}$Sr$_{0.125}$CuO$_4$ by applying uniaxial stress to
distort the structure and influence the formation of CDW order. Using resonant
soft x-ray scattering to measure both the CDW order and (0 0 1)
structural-nematic Bragg peaks, we find that the application of uniaxial stress
along the Cu-O bond direction suppresses the (0 0 1) peak and has the net
effect of reducing CDW order, but does so only for CDW order propagating
parallel to the applied stress. We connect these observations to previous work
showing an enhanced superconducting transition temperature under uniaxial
stress; providing insight into how CDW, superconductivity, nematicity, and
structure are related and can be tuned relative to one another in cuprates.",2305.16499v2
2024-01-16,Pulsation Phases and Mode Identification of Tidally Excited Oscillations in Fourteen Kepler Heartbeat Stars,"Tidally excited oscillations (TEOs) in Heartbeat Stars (HBSs) are an
essential probe of the internal properties of the systems, but their potential
has yet to be fully exploited. Based on the orbital parameters of TEO
candidates from our previous works, we identify the pulsation phases and
amplitudes of TEOs in fourteen Kepler HBSs. Most pulsation phases of most
systems can be explained by the dominant being $l=2$, $m=0$, or $\pm2$
spherical harmonic, assuming that the spin and orbital axes are aligned, and
the pulsations are adiabatic and standing waves. The largest deviation
($>6\sigma$) occurs in KIC 8459354, which can be explained by the spin-orbit
misalignment, and KIC 5877364 has a similar scenario. For KIC 11122789, almost
half of the harmonics show large deviations; we cautiously suggest that these
harmonics may not be considered TEO candidates. A similar scenario also exists
in KIC 6290740. This phases and mode identification approach can also be used
inversely to verify the TEO candidates derived by the Fourier analysis.
Furthermore, the harmonics with large deviations ($>2\sigma$) in KIC 4377638,
KIC 5090937, and KIC 11403032 can be expected to be travelling waves rather
than standing waves. In addition, we also suggest that the apsidal motion could
cause large deviations in TEO phases from theoretical values.",2401.08222v2
2024-03-01,Critical slowing of the spin and charge density wave order in thin film Cr following photoexcitation,"We report on the evolution of the charge density wave (CDW) and spin density
wave (SDW) order of a chromium film following photoexcitation with an ultrafast
optical laser pulse. The CDW is measured by ultrafast time-resolved x-ray
diffraction of the CDW satellite that tracks the suppression and recovery of
the CDW following photoexcitation. We find that as the temperature of the film
approaches a discontinuous phase transition in the CDW and SDW order, the time
scales of recovery increase exponentially from the expected thermal time
scales. We extend a Landau model for SDW systems to account for this critical
slowing with the appropriate boundary conditions imposed by the geometry of the
thin film system. This model allows us to assess the energy barrier between
available CDW/SDW states with different spatial periodicities.",2403.00267v2
2024-03-28,"Vortical waves in a quantum fluid with vector, axial and helical charges. I. Non-dissipative transport","Due to the spin-orbit coupling, Dirac fermions, submerged in a thermal bath
with finite macroscopic vorticity, exhibit a spin polarisation along the
direction parallel to the vorticity vector $\boldsymbol{\Omega}$. Due to the
symmetries of the Lagrangian for free massless Dirac particles, there are three
independent and classically conserved currents corresponding to the vector,
axial, and helical charges. The constitutive relations for the charge currents
and the stress-energy tensor at thermal equilibrium, derived in the framework
of quantum field theory at finite temperature, reveal vorticity-induced
contributions that deviate from the perfect fluid form. In this paper, we
consider the mode structure of the corresponding hydrodynamical theory and
derive collective excitations associated with coherent fluctuations of all
three charges. We show that the chirally imbalanced rotating fluid should
possess non-reciprocal gapless waves that propagate with different velocities
along and opposite to the vorticity vector. We also uncover a strictly
unidirectional mode, which we call the Axial Vortical Wave, propagating in the
background of the axial charge density. We point out an unexpected instability
in the limit of degenerate matter and discuss possible solutions when helicity
and axial charge non-conservation is taken into account.",2403.19755v1
2011-07-19,The long-term cyclotron dynamics of relativistic wave packets: spontaneous collapse and revival,"In this work we study the effects of collapse and revival as well as {\it
Zitterbewegung} (ZB) phenomenon, for the relativistic electron wave packets,
which are a superposition of the states with quantum numbers sharply peaked
around some level $n_0$ of the order of few tens. The probability densities as
well as average velocities of the packet center and the average spin components
were calculated analytically and visualized. Our computations demonstrate that
due to dephasing of the states for times larger than the cyclotron period the
initial wave packet (which includes the states with the positive energy only)
loses the spatial localization so that the evolution can no longer be described
classically. However, at the half-revival time $t=T_R/2$ its reshaping takes
place firstly. The behavior of the wave packet containing the states of both
energy bands (with $E_n>0$ and $E_n<0$) is more complicated. At short times of
a few classical periods such packet splits into two parts which rotate with
cyclotron frequency in the opposite directions and meet each other every
one-half of the cyclotron period. At these moments their wave functions have
significant overlap that leads to ZB. At the time of fractional revival each of
two sub-packets is decomposed into few packets-fractions. However, at $t=T_R$
each of the two sub-packets (with positive or negative energy) restores at
various points of the cyclotron orbit, that makes it impossible reshaping of
initial wave packet entirely unlike the wave packet which consists of states
with energies $E_n>0$ only. Obtained results can be useful for the description
of electromagnetic radiation and absorption in relativistic plasma on
astrophysics objects, where super high magnetic field has the value of the
order $10^8-10^9$T, as well as for interpretation of experiments with trapped
ions.",1107.3983v2
2017-11-22,Dirac Composite Fermion - A Particle-Hole Spinor,"The particle-hole (PH) symmetry at half-filled Landau level requires the
relationship between the flux number N_phi and the particle number N on a
sphere to be exactly N_phi - 2(N-1) = 1. The wave functions of composite
fermions with 1/2 ""orbital spin"", which contributes to the shift ""1"" in the
N_phi and N relationship, are proposed, shown to be PH symmetric, and validated
with exact finite system results. It is shown the many-body composite electron
and composite hole wave functions at half-filling can be formed from the two
components of the same spinor wave function of a massless Dirac fermion at
zero-magnetic field. It is further shown that away from half-filling, the
many-body composite electron wave function at filling factor nu and its PH
conjugated composite hole wave function at 1-nu can be formed from the two
components of the very same spinor wave functions of a massless Dirac fermion
at non-zero magnetic field. This relationship leads to the proposal of a very
simple Dirac composite fermion effective field theory, where the two-component
Dirac fermion field is a particle-hole spinor field coupled to the same
emergent gauge field, with one field component describing the composite
electrons and the other describing the PH conjugated composite holes. As such,
the density of the Dirac spinor field is the density sum of the composite
electron and hole field components, and therefore is equal to the degeneracy of
the Lowest Landau level. On the other hand, the charge density coupled to the
external magnetic field is the density difference between the composite
electron and hole field components, and is therefore neutral at exactly
half-filling. It is shown that the proposed particle-hole spinor effective
field theory gives essentially the same electromagnetic responses as Son's
Dirac composite fermion theory does.",1711.08520v2
2018-12-31,Persistent gravitational wave observables: general framework,"The gravitational wave memory effect is characterized by the permanent
relative displacement of a pair of initially comoving test particles that is
caused by the passage of a burst of gravitational waves. Recent research on
this effect has clarified the physical origin and the interpretation of this
gravitational phenomenon in terms of conserved charges at null infinity and
""soft theorems."" In this paper, we describe a more general class of effects
than the gravitational wave memory that are not necessarily associated with
these charges and soft theorems, but that are, in principle, measurable. We
shall refer to these effects as persistent gravitational wave observables.
These observables vanish in non-radiative regions of a spacetime, and their
effects ""persist"" after a region of spacetime which is radiating. We give three
examples of such persistent observables, as well as general techniques to
calculate them. These examples, for simplicity, restrict the class of
non-radiative regions to those which are exactly flat. Our first example is a
generalization of geodesic deviation that allows for arbitrary acceleration.
The second example is a holonomy observable, which is defined in terms of a
closed loop. It contains the usual ""displacement"" gravitational wave memory;
three previously identified, though less well known memory effects (the proper
time, velocity, and rotation memories); and additional new observables.
Finally, the third example we give is an explicit procedure by which an
observer could measure a persistent effect using a spinning test particle. We
briefly discuss the ability of gravitational wave detectors (such as LIGO and
Virgo) to measure these observables.",1901.00021v4
2010-11-15,Accretion Discs with an Inner Spiral Density Wave,"In Montgomery (2009a), we show that accretion discs in binary systems could
retrogradely precess by tidal torques like the Moon and the Sun on a tilted,
spinning, non-spherical Earth. In addition, we show that the state of matter
and the geometrical shape of the celestial object could significantly affect
the precessional value. For example, a Cataclysmic Variable (CV) Dwarf Novae
(DN) non-magnetic system that shows negative superhumps in its light curve can
be described by a retrogradely precessing, differentially rotating, tilted
disc. Because the disc is a fluid and because the gas stream overflows the
tilted disc and particles can migrate into inner disc annuli, coupled to the
disc could be a retrogradely precessing inner ring that is located near the
innermost annuli of the disc. However, numerical simulations by Bisikalo et al.
(2003, 2004) and this work show that an inner spiral density wave can be
generated instead of an inner ring. Therefore, we show that retrograde
precession in non-magnetic, spinning, tilted CV DN systems can equally be
described by a retrogradely precessing and differentially rotating disc with an
attached retrogradely precessing inner spiral density wave so long as the wave
appears at the same radius as the ring and within the plane of the tilted disc.
We find that the theoretical results generated in this work agree well with the
theoretical results presented in Montgomery (2009a) and thus with the numerical
simulations and select CV DN systems in Montgomery (2009b) that may have a main
sequence secondary. Therefore, pressure effects do need to be considered in CV
DN systems that exhibit negative superhumps if the accretion discs are tilted
and have an inner spiral density wave that is in the plane of the disc.",1011.3446v1
2014-01-21,Superconductivity from weak repulsion in hexagonal lattice systems,"We analyze the pairing instabilities for fermions on hexagonal lattices (both
honeycomb and triangular ones) in a wide range of fermionic densities. We argue
that for a generic doping in this range, superconductivity at weak coupling is
of Kohn-Luttinger type, and, due to the presence of electronic interactions
beyond on-site repulsion, is a threshold phenomenon, with superconductivity
emerging only if the attraction generated by the Kohn-Luttinger mechanism
exceeds the bare repulsion in some channel. For disconnected Fermi pockets, we
predict that Kohn-Luttinger superconductivity, if it occurs, is likely to be
$f$-wave. While the Kohn-Luttinger analysis is adequate over most of the doping
range, a more sophisticated analysis is needed near Van Hove doping. We treat
Van Hove doping using a parquet renormalization group, the equations for which
we derive and analyze. Near this doping level, superconductivity is a universal
phenomenon, arising from any choice of bare repulsive interactions. The
strongest pairing instability is into a chiral $d-$wave state ($d+id$). At a
truly weak coupling, the strongest competitor is a spin-density-wave
instability, however, $d-$wave superconductivity still wins. Moreover, the
feedback of the spin density fluctuations into the Cooper channel significantly
enhances the critical temperature over the estimates of the Kohn Luttinger
theory. We analyze renormalization group equations at stronger couplings and
find that the main competitor to $d-$wave supoerconductivity away from weak
coupling is actually ferromagnetism. We also discuss the effect of the edge
fermions and show that they are unimportant in the asymptotic weak coupling
limit, but may give rise to, e.g., a charge-density-wave order at moderate
coupling strengths.",1401.5485v2
2017-04-04,"Competing spin density wave, collinear, and helical magnetism in Fe1+xTe","The Fe1+xTe phase diagram consists of two distinct magnetic structures with
collinear order present at low interstitial iron concentrations and a helical
phase at large values of x with these phases separated by a Lifshitz point. We
use unpolarized single crystal diffraction to confirm the helical phase for
large interstitial iron concentrations and polarized single crystal diffraction
to demonstrate the collinear order for the iron deficient side of the Fe1+xTe
phase diagram. Polarized neutron inelastic scattering show that the
fluctuations associated with this collinear order are predominately transverse
at low energy transfers, consistent with a localized magnetic moment picture.
We then apply neutron inelastic scattering and polarization analysis to
investigate the dynamics and structure near the boundary between collinear and
helical order in the Fe1+xTe phase diagram. We first show that the phase
separating collinear and helical order is characterized by a spin-density wave
with a single propagation wave vector of (~ 0.45, 0, 0.5). We do not observe
harmonics or the presence of a charge density wave. The magnetic fluctuations
associated with this wavevector are different from the collinear phase being
strongly longitudinal in nature and correlated anisotropically in the (H,K)
plane. The excitations preserve the C4 symmetry of the lattice, but display
different widths in momentum along the two tetragonal directions at low energy
transfers. While the low energy excitations and minimal magnetic phase diagram
can be understood in terms of localized interactions, we suggest that the
presence of density wave phase implies the importance of electronic and orbital
properties.",1704.01111v1
2022-12-19,Tests of general relativity in the nonlinear regime: a parametrized plunge-merger-ringdown gravitational waveform model,"The plunge-merger stage of the binary-black hole coalescence, when the
bodies' velocities reach a large fraction of the speed of light and the
gravitational-wave luminosity peaks, provides a unique opportunity to probe
gravity in the dynamical and nonlinear regime. How much do the predictions of
general relativity differ from the ones in other theories of gravity for this
stage of the binary evolution? To address this question, we develop a
parametrized waveform model, within the effective-one-body formalism, that
allows for deviations from general relativity in the plunge-merger-ringdown
stage. As first step, we focus on nonprecessing-spin, quasicircular black hole
binaries. In comparison to previous works, for each gravitational wave mode,
our model can modify, with respect to general-relativistic predictions, the
instant at which the amplitude peaks, the instantaneous frequency at this time
instant, and the value of the peak amplitude. We use this waveform model to
explore several questions considering both synthetic-data injections and two
gravitational wave signals. In particular, we find that deviations from the
peak gravitational wave amplitude and instantaneous frequency can be
constrained to about $20\%$ with GW150914. Alarmingly, we find that
GW200129_065458 shows a strong violation of general relativity. We interpret
this result as a false violation, either due to waveform systematics
(mismodeling of spin precession) or due to data-quality issues depending on
one's interpretation of this event. This illustrates the use of parametrized
waveform models as tools to investigate systematic errors in plain general
relativity. The results with GW200129_065458 also vividly demonstrate the
importance of waveform systematics and of glitch mitigation procedures when
interpreting tests of general relativity with current gravitational wave
observations.",2212.09655v3
1994-02-16,Magnetic order and disorder in the frustrated quantum Heisenberg antiferromagnet in two dimensions,"We have performed a numerical investigation of the ground state properties of
the frustrated quantum Heisenberg antiferromagnet on the square lattice
(``$J_1-J_2$ model''), using exact diagonalization of finite clusters with 16,
20, 32, and 36 sites. Using a finite-size scaling analysis we obtain results
for a number of physical properties: magnetic order parameters, ground state
energy, and magnetic susceptibility (at $q=0$). For the unfrustrated case these
results agree with series expansions and quantum Monte Carlo calculations to
within a percent or better. In order to assess the reliability of our
calculations, we also investigate regions of parameter space with
well-established magnetic order, in particular the non-frustrated case $J_2<0$.
We find that in many cases, in particular for the intermediate region $0.3 <
J_2/J_1 < 0.7$, the 16 site cluster shows anomalous finite size effects.
Omitting this cluster from the analysis, our principal result is that there is
N\'eel type order for $J_2/J_1 < 0.34$ and collinear magnetic order (wavevector
$\bbox{Q}=(0,\pi)$) for $J_2/J_1 > 0.68$. There thus is a region in parameter
space without any form of magnetic order. Including the 16 site cluster, or
analyzing the independently calculated magnetic susceptibility we arrive at the
same conclusion, but with modified values for the range of existence of the
nonmagnetic region. We also find numerical values for the spin-wave velocity
and the spin stiffness. The spin-wave velocity remains finite at the
magnetic-nonmagnetic transition, as expected from the nonlinear sigma",9402061v2
1995-08-18,Dynamical Properties of Two Coupled Hubbard Chains at Half-filling,"Using grand canonical Quantum Monte Carlo (QMC) simulations combined with
Maximum Entropy analytic continuation, as well as analytical methods, we
examine the one- and two-particle dynamical properties of the Hubbard model on
two coupled chains at half-filling. The one-particle spectral weight function,
$A({\bf k},\omega)$, undergoes a qualitative change with interchain hopping
$t_\perp$ associated with a transition from a four-band insulator to a two-band
insulator. A simple analytical model based on the propagation of exact rung
singlet states gives a good description of the features at large $t_\perp$. For
smaller $t_\perp$, $A({\bf k}, \omega)$ is similar to that of the
one-dimensional model, with a coherent band of width the effective
antiferromagnetic exchange $J$ reasonably well-described by renormalized
spin-wave theory. The coherent band rides on a broad background of width
several times the parallel hopping integral $t$, an incoherent structure
similar to that found in calculations on both the one- and two-dimensional
models. We also present QMC results for the two-particle spin and charge
excitation spectra, and relate their behavior to the rung singlet picture for
large $t_\perp$ and to the results of spin-wave theory for small $t_\perp$.",9508074v2
1996-10-01,Itinerant Antiferromagnetism in FeGe_2,"FeGe_2, and lightly doped compounds based on it, have a Fermi surface driven
instability which drive them into an incommensurate spin density wave state.
Studies of the temperature and magnetic field dependence of the resistivity
have been used to determine the magnetic phase diagram of the pure material
which displays an incommensurate phase at high temperatures and a commensurate
structure below 263 K in zero field. Application of a magnetic field in the
tetragonal basal plane decreases the range of temperatures over which the
incommensurate phase is stable. We have used inelastic neutron scattering to
measure the spin dynamics of FeGe_2. Despite the relatively isotropic transport
the magnetic dynamics is quasi-one dimensional in nature. Measurements carried
out on HET at ISIS have been used to map out the spin wave dispersion along the
c-axis up the 400 meV, more than an order of magnitude higher than the zone
boundary magnon for wavevectors in the basal plane.",9610009v1
1998-03-06,The density matrix renormalization group method. Application to the PPP model of a cyclic polyene chain,"The density matrix renormalization group (DMRG) method introduced by White
for the study of strongly interacting electron systems is reviewed; the method
is variational and considers a system of localized electrons as the union of
two adjacent fragments A, B. A density matrix rho is introduced, whose
eigenvectors corresponding to the largest eigenvalues are the most significant,
the most probable states of A in the presence of B; these states are retained,
while states corresponding to small eigenvalues of rho are neglected. It is
conjectured that the decreasing behaviour of the eigenvalues is gaussian. The
DMRG method is tested on the Pariser-Parr-Pople Hamiltonian of a cyclic polyene
(CH)_N up to N=34. A Hilbert space of dimension 5 x 10^+18 is explored. The
ground state energy is 10^-3 eV within the full CI value in the case N=18. The
DMRG method compares favourably also with coupled cluster approximations. The
unrestricted Hartree-Fock solution (which presents spin density waves) is
briefly reviewed, and a comparison is made with the DMRG energy values.
Finally, the spin-spin and density-density correlation functions are computed;
the results suggest that the antiferromagnetic order of the exact solution does
not extend up to large distances but exists locally. No charge density waves
are present.",9803071v1
2000-08-24,Precursory Metal-Insulator transition in a small cluster of the `t-J' model: Exact analytic results,"We study the effect of hole hopping in a doped antiferromagnet described by
the `t-J' model, using exact analytic solutions for small clusters. In spite of
the small size, they reveal interesting details about the magnetic order, which
are not apparent in Mean Field treatments or in numerical calculations. The
4-site cluster with one hole yields the most interesting physics, displaying
different behaviors for the ground state: i) an antiferromagnetic phase for
t<<J, where the hole seems to be localized, not affecting the order of the
Heisenberg spins; ii)another regime for t~J that presents mixed ferro and
antiferro correlations and coexistence of metallic and insulating behaviors,
with the presence of charge and spin density waves, in what may be the analog
of the spiral phase obtained in Mean Field solutions; and finally iii)for t>>J,
we obtain strong ferromagnetic correlations (maximum spin) and no density
waves, with quantum fluctuations precluding the saturation of the magnetic
moment. This behavior shows traces of a metal-insulator transition as the hole
kinetic energy competes with the antiferromagnetic interactions.",0008373v1
2000-08-31,Phase diagram of the extended Hubbard chain with charge-dipole interactions,"We consider a modified extended Hubbard model (EHM) which, in addition to the
on-site repulsion U and nearest-neighbor repulsion V, includes polarization
effects in second-order perturbation theory. The model is equivalent to an EHM
with renormalized U plus a next-nearest-neighbor repulsion term. Using a method
based on topological quantum numbers (charge and spin Berry phases), we
generalize to finite hopping t the quantum phase diagram in one dimension
constructed by van den Brink et al. (Phys. Rev. Lett. 75, 4658 (1995)). At
hopping t=0 there are two charge density-wave phases, one spin density-wave
phase and one intermediate phase with charge and spin ordering, depending on
the parameter values. At t \neq 0 the nature of each phase is confirmed by
studying correlation functions. However, in addition to the strong-coupling
phases, a small region with bond ordering appears. The region occupied by the
intermediate phase first increases and then decreases with increasing t, until
it finally disappears for t of the order but larger than U. For small t, the
topological transitions agree with the results of second order perturbation
theory.",0008473v2
2001-07-24,Diluted quantum antiferromagnets: spin excitations and long-range order,"We have studied the static and dynamic magnetic properties of two-dimensional
(2D) and quasi-two-dimensional, spin-S, quantum Heisenberg antiferromagnets
(QHAF) diluted with spinless vacancies. Using spin-wave theory and T-matrix
approximation we have calculated the staggered magnetization, M(x,T), the
neutron scattering dynamical structure factor, S(k,omega), the 2D magnetic
correlation length, \xi(x,T), and the Neel temperature, T_N(x), for the
quasi-2D case. We find that in 2D the hydrodynamic description of excitations
in terms of spin-waves breaks down at the wavelength larger than \ell/a ~
exp(\pi/4x), x being impurity concentration and ""a"" the lattice spacing. The
density of states acquires a constant term and exhibits an anomalous peak at
omega omega_0 associated with the low-energy localized excitations. These
anomalies lead to a substantial enhancement of the magnetic specific heat, C_M,
at low temperatures. Although the dynamical properties are significantly
modified we show that 2D is not the lower critical dimension for this problem.
Our results are in quantitative agreement with the recent Monte Carlo
simulations and experimental data for S=1/2, S=1, and S=5/2.",0107488v1
2003-11-07,A common behavior of thermoelectric layered cobaltites: incommensurate spin density wave states in [Ca$_2$Co$_{4/3}$Cu$_{2/3}$O$_4$]$_{0.62}$[CoO$_2$] and [Ca$_2$CoO$_3$]$_{0.62}$[CoO$_2$],"Magnetism of a misfit layered cobaltite
[Ca$_2$Co$_{4/3}$Cu$_{2/3}$O$_4$]$_x^{\rm RS}$[CoO$_2$] ($x \sim$ 0.62, RS
denotes a rocksalt-type block) was investigated by a positive muon spin
rotation and relaxation ($\mu^+$SR) experiment. A transition to an
incommensurate ({\sf IC}) spin density wave ({\sf SDW}) state was found below
180 K (= $T_{\rm C}^{\rm on}$); and a clear oscillation due to a static
internal magnetic field was observed below 140 K (= $T_{\rm C}$). Furthermore,
an anisotropic behavior of the zero-field $\mu^+$SR experiment indicated that
the {\sf IC-SDW} propagates in the $a$-$b$ plane, with oscillating moments
directed along the c axis. These results were quite similar to those for the
related compound [Ca$_2$CoO$_3$]$_{0.62}^{\rm RS}$[CoO$_2$], {\sl i.e.},
Ca$_3$Co$_4$O$_9$. Since the {\sf IC-SDW} field in
[Ca$_2$Co$_{4/3}$Cu$_{2/3}$O$_4$]$_{0.62}^{\rm RS}$[CoO$_2$] was approximately
same to those in pure and doped [Ca$_2$CoO$_3$]$_{0.62}^{\rm RS}$[CoO$_2$], it
was concluded that the {\sf IC-SDW} exist in the [CoO$_2$] planes.",0311161v1
2005-07-25,Ordering near the percolation threshold in models of 2D interacting bosons with quenched dilution,"Randomly diluted quantum boson and spin models in two dimensions combine the
physics of classical percolation with the well-known dimensionality dependence
of ordering in quantum lattice models. This combination is rather subtle for
models that order in two dimensions but have no true order in one dimension, as
the percolation cluster near threshold is a fractal of dimension between 1 and
2: two experimentally relevant examples are the O(2) quantum rotor and the
Heisenberg antiferromagnet. We study two analytic descriptions of the O(2)
quantum rotor near the percolation threshold. First a spin-wave expansion is
shown to predict long-ranged order, but there are statistically rare points on
the cluster that violate the standard assumptions of spin-wave theory. A
real-space renormalization group (RSRG) approach is then used to understand how
these rare points modify ordering of the O(2) rotor. A new class of fixed
points of the RSRG equations for disordered 1D bosons is identified and shown
to support the existence of long-range order on the percolation backbone in two
dimensions. These results are relevant to experiments on bosons in optical
lattices and superconducting arrays, and also (qualitatively) for the diluted
Heisenberg antiferromagnet.",0507587v1
2006-07-20,Complex magnetic order in the kagome staircase compound Co3V2O8,"Co3V2O8 (CVO) has a geometrically frustrated magnetic lattice, a Kagome
staircase. The crystal structure consists of two inequivalent Co sites,
one-dimensional chains of Co(2) spine sites, linked by Co(1) cross-tie sites.
Neutron powder diffraction has been used to solve the basic magnetic and
crystal structures of this system, while polarized and unpolarized single
crystal diffraction measurements have been used to reveal a variety of
incommensurate phases, interspersed with lock-in transitions to commensurate
phases. CVO initially orders magnetically at 11.3 K into an incommensurate,
transversely polarized, spin density wave state, with wave vector k=(0,delta,0)
with delta=0.55 and the spin direction along the a axis. Delta is found to
decrease monotonically with decreasing temperature, and then it locks into a
commensurate antiferromagnetic structure with delta=0.5 for 6.9<T<8.6 K. Below
6.9 K the magnetic structure becomes incommensurate again. Delta continues to
decrease with decreasing temperature, and locks-in again at delta=1/3 over a
narrow temperature range (6.2<T<6.5 K). The system then undergoes a strongly
first order transition to the ferromagnetic ground state (delta=0) at Tc=6.2 K.
A dielectric anomaly is observed around the ferromagnetic transition
temperature of 6.2 K, demonstrating a significant spin-charge coupling present
in CVO. A theory based on group theory analysis and a minimal Ising model with
competing exchange interactions can explain the basic features of the magnetic
ordering.",0607533v1
2006-10-06,Spin-state ordering and magnetic structures in YBaCo2O5.5/5.44,"The antiferromagnetic - ferromagnetic phase transition in YBaCo2O5.50 and
YBaCo2O5.44 cobaltites with different types of oxygen-ion ordering in the
[YO0.5/0.44] layers has been studied by neutron powder diffraction. Using the
magnetic symmetry arguments in combination with group-theoretical analysis, the
crystal and magnetic structures above and below the phase transformation
temperature, Ti, were determined and successfully refined. In both cases, the
proposed models involve a spin-state ordering between diamagnetic (t2g6eg0, S =
0) and paramagnetic (t2g4eg2, S = 2) Co3+ ions with octahedral coordination.
Electronic ordering results in a nonzero spontaneous magnetic moment in the
high-temperature magnetic phases with isotropic negative exchange interactions.
In the case of YBaCo2O5.5, the phase transformation does not change Pmma
symmetry of the crystal structure. The wave vectors of magnetic structures
above and below Ti are k = 0 and k = c*/2, respectively. In the case of
YBaCo2O5.44, a crossover P4/nmm - I4/mmm was involved to solve the
low-temperature magnetic structure. The wave vectors in both high-temperature
and low-temperature magnetic phases are k = 0. Mechanisms of the phase
transformation in both compositions are discussed in the light of obtained
magnetic structures. The proposed spin configurations were compared with other
models reported in literature.",0610179v1
2001-07-25,Energy and angular momentum flow into a black hole in a binary,"As a black hole in a binary spirals in gradually from large separation,
energy and angular momentum flow not only to infinity but also into or out of
the hole. In addition, the hole's horizon area increases slowly during this
process. In this paper, the changes in the black hole's mass, spin, and horizon
area during inspiral are calculated for a hole in a circular binary with a
companion body of possibly comparable mass. When the binary is composed of
equal-mass black holes that have spins aligned with the orbital angular
momentum and are rapidly rotating (with spins 99.8 percent of their maximal
values), it is found that the fractional increase in the surface area of each
hole's horizon is one percent by the time the binary spirals down to a
separation b of 6M (where M is the binary's total mass), and seven percent down
to b=2M. The flow of energy and angular momentum into the black holes' horizons
changes the number of gravitational-wave cycles in the LIGO band by no more
than a tenth of a cycle by the time the binary reaches b=2M. The results
obtained in this paper are relevant for the detection and analysis of
gravitational waves from binary systems containing a black hole.",0107080v2
2007-01-18,Towards a wave-extraction method for numerical relativity. V. Extracting the Weyl scalars in the quasi-Kinnersley tetrad from spatial data,"We extract the Weyl scalars $\Psi_0$ and $\Psi_4$ in the quasi-Kinnersley
tetrad by finding initially the (gauge--, tetrad--, and
background--independent) transverse quasi-Kinnersley frame. This step still
leaves two undetermined degrees of freedom: the ratio $|\Psi_0|/|\Psi_4|$, and
one of the phases (the product $|\Psi_0|\cdot |\Psi_4|$ and the {\em sum} of
the phases are determined by the so-called BB radiation scalar). The residual
symmetry (""spin/boost"") can be removed by gauge fixing of spin coefficients in
two steps: First, we break the boost symmetry by requiring that $\rho$
corresponds to a global constant mass parameter that equals the ADM mass (or,
equivalently in perturbation theory, that $\rho$ or $\mu$ equal their values in
the no-radiation limits), thus determining the two moduli of the Weyl scalars
$|\Psi_0|, |\Psi_4|$, while leaving their phases as yet undetermined. Second,
we break the spin symmetry by requiring that the ratio $\pi/\tau$ gives the
expected polarization state for the gravitational waves, thus determining the
phases. Our method of gauge fixing--specifically its second step--is
appropriate for cases for which the Weyl curvature is purely electric. Applying
this method to Misner and Brill--Lindquist data, we explicitly find the Weyl
scalars $\Psi_0$ and $\Psi_4$ perturbatively in the quasi-Kinnersley tetrad.",0701101v1
2003-11-17,The covariant structure of light-front wave functions and the behavior of hadronic form factors,"We study the analytic structure of light-front wave functions (LFWFs) and its
consequences for hadron form factors using an explicitly Lorentz-invariant
formulation of the front form. The normal to the light front is specified by a
general null vector $\omega^\mu.$ The LFWFs with definite total angular
momentum are eigenstates of a {\it kinematic} angular momentum operator and
satisfy all Lorentz symmetries. They are analytic functions of the invariant
mass squared of the constituents $M^2_0= (\sum k^\mu)^2$ and the light-cone
momentum fractions $x_i= {k_i\cd \omega / p \cd \omega}$ multiplied by
invariants constructed from the spin matrices, polarization vectors, and
$\omega^\mu.$ These properties are illustrated using known nonperturbative
eigensolutions of the Wick--Cutkosky model. We analyze the LFWFs introduced by
Chung and Coester to describe static and low momentum properties of the
nucleons. They correspond to the spin-locking of a quark with the spin of its
parent nucleon, together with a positive-energy projection constraint. These
extra constraints lead to anomalous dependence of form factors on $Q$ rather
than $Q^2.$ In contrast, the dependence of LFWFs on $M^2_0$ implies that hadron
form factors are analytic functions of $Q^2$ in agreement with dispersion
theory and perturbative QCD. We show that a model incorporating the
leading-twist perturbative QCD prediction is consistent with recent data for
the ratio of proton Pauli and Dirac form factors.",0311218v1
2004-02-16,Two Stringy Systems of the Kerr Spinning Particle,"A classical spinning particle based on the Kerr-Newman black hole (BH)
solution is considered. For parameters of spinning particles $|a|>>m$, the BH
horizons disappear and BH image is drastically changed. We show that it turns
into a skeleton formed by two coupled stringy systems. One of them is the Kerr
singular ring which can be considered as a circular D-string with an
orientifold world-sheet.
  Analyzing the aligned to the Kerr congruence electromagnetic excitations of
this string, we obtain the second stringy system which consists of two axial
half-infinite chiral D-strings. These axial strings are similar to the Dirac
monopole strings but carry the induced chiral traveling pp-waves. Their field
structure can be described by the field model suggested by Witten for the
cosmic superconducting strings.
  We discuss a relation of this stringy system to the Dirac equation and argue
that this stringy system can play a role of a classical carrier of the wave
function.",0402114v1
2004-04-30,Solitons on nanotubes and fullerenes as solutions of a modified non-linear Schroedinger equation,"Fullerenes and nanotubes consist of a large number of carbon atoms sitting on
the sites of a regular lattice. For pratical reasons it is often useful to
approximate the equations on this lattice in terms of the continuous equation.
At the moment, the best candidate for such an equation is the modified
non-linear Schroedinger equation. In this paper, we study the modified
non-linear Schroedinger equation, which arises as continuous equation in a
system describing an excitation on a hexagonal lattice. This latter system can
e.g. describe electron-phonon interaction on fullerene related structures such
as the buckminster fullerene and nanotubes. Solutions of this modified
non-linear Schroedinger equation, which have solitonic character, can be
constructed using an Ansatz for the wave function, which has time and azimuthal
angle dependence introduced previously in the study of spinning boson stars and
Q-balls. We study these solutions on a sphere, a disc and on a cylinder.
  Our construction suggests that non-spinning as well as spinning solutions,
which have a wave function with an arbitrary number of nodes, exist. We find
that this property is closely related to the series of well-known mathematical
functions, namely the Legendre functions when studying the equation on a
sphere, the Bessel functions when studying the equation on a disc and the
trigonometric functions, respectively, when studying the equation on a
cylinder.",0404059v1
1998-12-01,Generally relativistical Tetrode-Weyl-Fock-Ivanenko formalism and behaviour of quantum-mechanical particles of spin 1/2 in the Abelian monopole field,"Some attention in the literature has been given to the case of a particle of
spin 1/2 on the background of the external monopole potential. Some aspects of
this problem are reexamined here. The primary technical novelty is that the
tetrad generally relativistic method of Tetrode-Weyl-Fock-Ivanenko for
describing a spinor particle is exploited. The choice of the formalism has
turned out to be of great fruitfulness for examining the system. It is matter
that, as known, the use of a special spherical tetrad in the theory of a spin
1/2 particle had led Schrodinger to a basis of remarkable features. The basis
has been used with great efficiency by Pauli in his investigation on the pro-
blem of allowed spherically symmetric wave functions in quantum mechanics. For
our purposes, just several simple rules extracted from the much more com-
prehensive Pauli's analysis will be quite sufficient; those are almost mnemo-
nic working regulations. So, one may remember some very primary facts of D-
functions theory and then produce automatically proper wave functions. It seems
rather likely, that there may exist a generalized analog of such a re-
presentation for J(i)-operators, that might be successfully used whenever in a
linear problem there exists a spherical symmetry, irrespective of the con-
crete embodiment of such a symmetry. In particular, the case of electron in the
external Abelian monopole field completely come under the Sch-Pau method.",9812002v1
2004-06-09,Quantum Dynamics of a Particle with a Spin-dependent Velocity,"We study the dynamics of a particle in continuous time and space, the
displacement of which is governed by an internal degree of freedom (spin). In
one definite limit, the so-called quantum random walk is recovered but,
although quite simple, the model possesses a rich variety of dynamics and goes
far beyond this problem. Generally speaking, our framework can describe the
motion of an electron in a magnetic sea near the Fermi level when linearisation
of the dispersion law is possible, coupled to a transverse magnetic field.
Quite unexpected behaviours are obtained. In particular, we find that when the
initial wave packet is fully localized in space, the $J_{z}$ angular momentum
component is frozen; this is an interesting example of an observable which,
although it is not a constant of motion, has a constant expectation value. For
a non-completely localized wave packet, the effect still occurs although less
pronounced, and the spin keeps for ever memory of its initial state. Generally
speaking, as time goes on, the spatial density profile looks rather complex, as
a consequence of the competition between drift and precession, and displays
various shapes according to the ratio between the Larmor period and the
characteristic time of flight. The density profile gradually changes from a
multimodal quickly moving distribution when the scatttering rate is small, to a
unimodal standing but flattening distribution in the opposite cas case.",0406057v1
2007-04-16,The spin-flip phenomenon in supermassive black hole binary mergers,"Massive merging black holes will be the primary sources of powerful
gravitational waves at low frequency, and will permit to test general
relativity with candidate galaxies close to a binary black hole merger. In this
paper we identify the typical mass ratio of the two black holes but then show
that the distance when gravitational radiation becomes the dominant dissipative
effect (over dynamical friction) does not depend on the mass ratio. However the
dynamical evolution in the gravitational wave emission regime does. For the
typical range of mass ratios the final stage of the merger is preceded by a
rapid precession and a subsequent spin-flip of the main black hole. This
already occurs in the inspiral phase, therefore can be described analytically
by post-Newtonian techniques. We then identify the radio galaxies with a
super-disk as those in which the rapidly precessing jet produces effectively a
powerful wind, entraining the environmental gas to produce the appearance of a
thick disk. These specific galaxies are thus candidates for a merger of two
black holes to happen in the astronomically near future.",0704.1968v4
2007-07-20,Diamagnetism of doped two-leg ladders and probing the nature of their commensurate phases,"We study the magnetic orbital effect of a doped two-leg ladder in the
presence of a magnetic field component perpendicular to the ladder plane.
Combining both low-energy approach (bosonization) and numerical simulations
(density-matrix renormalization group) on the strong coupling limit (t-J
model), a rich phase diagram is established as a function of hole doping and
magnetic flux. Above a critical flux, the spin gap is destroyed and a Luttinger
liquid phase is stabilized. Above a second critical flux, a reentrance of the
spin gap at high magnetic flux is found. Interestingly, the phase transitions
are associated with a change of sign of the orbital susceptibility. Focusing on
the small magnetic field regime, the spin-gapped superconducting phase is
robust but immediately acquires algebraic transverse (i.e. along rungs) current
correlations which are commensurate with the 4k_F density correlations. In
addition, we have computed the zero-field orbital susceptibility for a large
range of doping and interactions ratio J/t : we found strong anomalies at low
J/t only in the vicinity of the commensurate fillings corresponding to delta =
1/4 and 1/2. Furthermore, the behavior of the orbital susceptibility reveals
that the nature of these insulating phases is different: while for delta = 1/4
a 4k_F charge density wave is confirmed, the delta = 1/2 phase is shown to be a
bond order wave.",0707.3017v3
2007-08-17,Neutrino oscillations in matter and in twisting magnetic fields,"We find the solution to the Dirac equation for a massive neutrino with a
magnetic moment propagating in background matter and interacting with the
twisting magnetic field. In frames of the relativistic quantum mechanics
approach to the description of neutrino evolution we use the obtained solution
to derive neutrino wave functions satisfying the given initial condition. We
apply the results to the analysis of neutrino spin oscillations in matter under
the influence of the twisting magnetic field. Then on the basis of the yielded
results we describe spin-flavor oscillations of Dirac neutrinos that mix and
have non-vanishing matrix of magnetic moments. We again formulate the initial
condition problem, derive neutrinos wave functions and calculate the transition
probabilities for different magnetic moments matrices. The consistency of the
obtained results with the quantum mechanical treatment of spin-flavor
oscillations is discussed. We also consider several applications to
astrophysical and cosmological neutrinos.",0708.2328v2
2007-10-23,"Three-electron anisotropic quantum dots in variable magnetic fields: exact results for excitation spectra, spin structures, and entanglement","Exact-diagonalization calculations for N=3 electrons in anisotropic quantum
dots, covering a broad range of confinement anisotropies and strength of
inter-electron repulsion, are presented for zero and low magnetic fields. The
excitation spectra are analyzed as a function of the strength of the magnetic
field and for increasing quantum-dot anisotropy. Analysis of the intrinsic
structure of the many-body wave functions through spin-resolved two-point
correlations reveals that the electrons tend to localize forming Wigner
molecules. For certain ranges of dot parameters (mainly at strong anisotropy),
the Wigner molecules acquire a linear geometry, and the associated wave
functions with a spin projection S_z=1/2 are similar to the representative
class of strongly entangled states referred to as W-states. For other ranges of
parameters (mainly at intermediate anisotropy), the Wigner molecules exhibit a
more complex structure consisting of two mirror isosceles triangles. This
latter structure can be viewed as an embryonic unit of a zig-zag Wigner crystal
in quantum wires. The degree of entanglement in three-electron quantum dots can
be quantified through the use of the von Neumann entropy.",0710.4325v1
2008-07-15,Gravitational wave data analysis implications of TaylorEt inspiral approximants for ground-based detectors: the non-spinning case,"A new family of restricted post-Newtonian-accurate waveforms, termed TaylorEt
approximants, was recently proposed for searching gravitational wave (GW)
signals from inspiraling non-spinning compact binaries having arbitrary
mass-ratios. We perform detailed fitting factor (FF) studies to probe if the
TaylorEt (3.5PN) signals for non-spinning comparable mass compact binaries can
be effectually and faithfully searched with TaylorT1, TaylorT4, and TaylorF2
(3.5PN) templates in LIGO, Advanced LIGO, and Virgo interferometers. We observe
that a good fraction of the templates, which by choice are from TaylorT1,
TaylorT4, and TaylorF2 (3.5PN) families, have FF <~ 0.97 and substantial biases
for the estimated total-mass against the fiducial TaylorEt (3.5PN) signals for
equal-mass systems. Both these observations can bear on the detectability of a
signal. TaylorEt (3.5PN) signals with mass-ratios of a third or a quarter yield
high FFs against those same template banks, but at the expense of inviting
large systematic errors in the estimated values of their total mass and
symmetric mass-ratio. In general, the aforementioned templates are found to be
increasingly {\it unfaithful} with respect to a TaylorEt signal as one
increases the total mass of the inspiraling system. We also observe that the
amount of bias in the estimated mass varies with the (noise power spectral
density of the) detector. This can be of some concern for multi-detector
searches, which check for consistency in the estimated masses of concurrent
triggers in their data. (Abridged)",0807.2400v2
2008-09-11,Thermodynamic behavior of the XXZ Heisenberg s=1/2 chain around the factorizing magnetic field,"We have investigated the zero and finite temperature behaviors of the
anisotropic antiferromagnetic Heisenberg XXZ spin-1/2 chain in the presence of
a transverse magnetic field (h). The attention is concentrated on an interval
of magnetic field between the factorizing field (h_f) and the critical one
(h_c). The model presents a spin-flop phase for 0<h<h_f with an energy scale
which is defined by the long range antiferromagnetic order while it undergoes
an entanglement phase transition at h=h_f. The entanglement estimators clearly
show that the entanglement is lost exactly at h=h_f which justifies different
quantum correlations on both sides of the factorizing field. As a consequence
of zero entanglement (at h=h_f) the ground state is known exactly as a product
of single particle states which is the starting point for initiating a spin
wave theory. The linear spin wave theory is implemented to obtain the specific
heat and thermal entanglement of the model in the interested region. A double
peak structure is found in the specific heat around h=h_f which manifests the
existence of two energy scales in the system as a result of two competing
orders before the critical point. These results are confirmed by the low
temperature Lanczos data which we have computed.",0809.1987v2
2009-01-16,Field on Poincare group and quantum description of orientable objects,"We propose an approach to the quantum-mechanical description of relativistic
orientable objects. It generalizes Wigner's ideas concerning the treatment of
nonrelativistic orientable objects (in particular, a nonrelativistic rotator)
with the help of two reference frames (space-fixed and body-fixed). A technical
realization of this generalization (for instance, in 3+1 dimensions) amounts to
introducing wave functions that depend on elements of the Poincare group $G$. A
complete set of transformations that test the symmetries of an orientable
object and of the embedding space belongs to the group $\Pi =G\times G$. All
such transformations can be studied by considering a generalized regular
representation of $G$ in the space of scalar functions on the group, $f(x,z)$,
that depend on the Minkowski space points $x\in G/Spin(3,1)$ as well as on the
orientation variables given by the elements $z$ of a matrix $Z\in Spin(3,1)$.
In particular, the field $f(x,z)$ is a generating function of usual spin-tensor
multicomponent fields. In the theory under consideration, there are four
different types of spinors, and an orientable object is characterized by ten
quantum numbers. We study the corresponding relativistic wave equations and
their symmetry properties.",0901.2537v2
2009-03-24,"Polarization transfer measurements for $^{12}{\rm C}(\vec{p},\vec{n})^{12}{\rm N (g.s.},1^+)$ at 296 MeV and nuclear correlation effects","Differential cross sections and complete sets of polarization observables are
presented for the Gamow-Teller $^{12}{\rm C}(\vec{p},\vec{n})^{12}{\rm N}({\rm
g.s.},1^+)$ reaction at a bombarding energy of 296 MeV with momentum transfers
$q$ of 0.1 to $2.2{\rm fm}^{-1}$. The polarization transfer observables are
used to deduce the spin-longitudinal cross section, $ID_q$, and spin-transverse
cross sections, $ID_p$ and $ID_n$. The data are compared with calculations
based on the distorted wave impulse approximation (DWIA) using shell-model wave
functions. Significant differences between the experimental and theoretical
results are observed for all three spin-dependent $ID_i$ at momentum transfers
of $q \gtrsim 0.5{\rm fm}^{-1}$, suggesting the existence of nuclear
correlations beyond the shell model. We also performed DWIA calculations
employing random phase approximation (RPA) response functions and found that
the observed discrepancy is partly resolved by the pionic and rho-mesonic
correlation effects.",0903.4105v2
2009-08-20,High-Order Coupled Cluster Method Study of Frustrated and Unfrustrated Quantum Magnets in External Magnetic Fields,"We apply the coupled cluster method (CCM) in order to study the ground-state
properties of the (unfrustrated) square-lattice and (frustrated)
triangular-lattice spin-half Heisenberg antiferromagnets in the presence of
external magnetic fields. Here we determine and solve the basic CCM equations
by using the localised approximation scheme commonly referred to as the
`LSUB$m$' approximation scheme and we carry out high-order calculations by
using intensive computational methods. We calculate the ground-state energy,
the uniform susceptibility, the total (lattice) magnetisation and the local
(sublattice) magnetisations as a function of the magnetic field strength. Our
results for the lattice magnetisation of the square-lattice case compare well
to those results of QMC for all values of the applied external magnetic field.
We find a value for magnetic susceptibility of $\chi=0.070$ for the
square-lattice antiferromagnet, which is also in agreement with the results of
other approximate methods (e.g., $\chi=0.0669$ via QMC). Our estimate for the
range of the extent of the ($M/M_s=$)$\frac 13$ magnetisation plateau for the
triangular-lattice antiferromagnet is $1.37< \lambda < 2.15$, which is in good
agreement with results of spin-wave theory ($1.248 < \lambda < 2.145$) and
exact diagonalisations ($1.38 < \lambda < 2.16$). The CCM value for the
in-plane magnetic susceptibility per site is $\chi=0.065$, which is below the
result of the spin-wave theory (evaluated to order 1/S) of $\chi_{SWT}=0.0794$.",0908.2881v1
2009-11-09,Magnetic degeneracy and hidden metallicity of the spin density wave state in ferropnictides,"We analyze spin density wave (SDW) order in iron-based superconductors and
electronic structure in the SDW phase. We consider an itinerant model for
Fe-pnictides with two hole bands centered at $(0,0)$ and two electron bands
centered at $(0,\pi)$ and $(\pi,0)$ in the unfolded BZ. A SDW order in such a
model is generally a combination of two components with momenta $(0,\pi)$ and
$(\pi,0)$, both yield $(\pi,\pi)$ order in the folded zone. Neutron
experiments, however, indicate that only one component is present. We show that
$(0,\pi)$ or $(\pi,0)$ order is selected if we assume that only one hole band
is involved in the SDW mixing with electron bands. A SDW order in such 3-band
model is highly degenerate for a perfect nesting and hole-electron interaction
only, but we show that ellipticity of electron pockets and interactions between
electron bands break the degeneracy and favor the desired $(0,\pi)$ or
$(\pi,0)$ order. We further show that stripe-ordered system remains a metal for
arbitrary coupling. We analyze electronic structure for parameters relevant to
the pnictides and argue that the resulting electronic structure is in good
agreement with ARPES experiments. We discuss the differences between our model
and $J_1-J_2$ model of localized spins.",0911.1754v2
2009-11-29,"Conformal invariance, multifractality, and finite-size scaling at Anderson localization transitions in two dimensions","We generalize universal relations between the multifractal exponent \alpha_0
for the scaling of the typical wave function magnitude at a (Anderson)
localization-delocalization transition in two dimensions and the corresponding
critical finite size scaling (FSS) amplitude \Lambda_c of the typical
localization length in quasi-one-dimensional (Q1D) geometry: (i) When open
boundary conditions are imposed in the transverse direction of Q1D samples
(strip geometry), we show that the corresponding critical FSS amplitude
\Lambda_c^o is universally related to the boundary multifractal exponent
\alpha_0^s for the typical wave function amplitude along a straight boundary
(surface). (ii) We further propose a generalization of these universal
relations to those symmetry classes whose density of states vanishes at the
transition. (iii) We verify our generalized relations [Eqs. (6) and (7)]
numerically for the following four types of two-dimensional Anderson
transitions: (a) the metal-to-(ordinary insulator) transition in the spin-orbit
(symplectic) symmetry class, (b) the metal-to-(Z_2 topological insulator)
transition which is also in the spin-orbit (symplectic) class, (c) the integer
quantum Hall plateau transition, and (d) the spin quantum Hall plateau
transition.",0911.5443v3
2010-01-25,"On exact solutions for quantum particles with spin S= 0, 1/2, 1 and de Sitter event horizon","Exact wave solutions for particles with spin 0, 1/2 and 1 in the static
coordinates of the de Sitter space-time model are examined in detail. Firstly,
for a scalar particle, two pairs of linearly independent solutions are
specified explicitly: running and standing waves. A known algorithm for
calculation of the reflection coefficient $R_{\epsilon j}$ on the background of
the de Sitter space-time model is analyzed. It is shown that the determination
of R_{\epsilon j} requires an additional constrain on quantum numbers \epsilon
\rho / \hbar c >> j, where \rho is a curvature radius. When taken into account
of this condition, the R_{\epsilon j} vanishes identically. It is claimed that
the calculation of the reflection coefficient R_{\epsilon j} is not required at
all because there is no barrier in an effective potential curve on the
background of the de Sitter space-time. The same conclusion holds for arbitrary
particles with higher spins, it is demonstrated explicitly with the help of
exact solutions for electromagnetic and Dirac fields.",1001.4415v2
2010-06-18,Characterizing Spinning Black Hole Binaries in Eccentric Orbits with LISA,"The Laser Interferometer Space Antenna (LISA) is designed to detect
gravitational wave signals from astrophysical sources, including those from
coalescing binary systems of compact objects such as black holes. Colliding
galaxies have central black holes that sink to the center of the merged galaxy
and begin to orbit one another and emit gravitational waves. Some galaxy
evolution models predict that the binary black hole system will enter the LISA
band with significant orbital eccentricity, while other models suggest that the
orbits will already have circularized. Using a full seventeen parameter
waveform model that includes the effects of orbital eccentricity, spin
precession and higher harmonics, we investigate how well the source parameters
can be inferred from simulated LISA data. Defining the reference eccentricity
as the value one year before merger, we find that for typical LISA sources, it
will be possible to measure the eccentricity to an accuracy of parts in a
thousand. The accuracy with which the eccentricity can be measured depends only
very weakly on the eccentricity, making it possible to distinguish circular
orbits from those with very small eccentricities. LISA measurements of the
orbital eccentricity can help constraints theories of galaxy mergers in the
early universe. Failing to account for the eccentricity in the waveform
modeling can lead to a loss of signal power and bias the estimation of
parameters such as the black hole masses and spins.",1006.3759v3
2010-09-06,Localized whistlers in magnetized spin quantum plasmas,"The nonlinear propagation of electromagnetic (EM) electron-cyclotron waves
(whistlers) along an external magnetic field, and their modulation by
electrostatic small but finite amplitude ion-acoustic density perturbations are
investigated in a uniform quantum plasma with intrinsic spin of electrons. The
effects of the quantum force associated with the Bohm potential and the
combined effects of the classical as well as the spin-induced ponderomotive
forces (CPF and SPF respectively) are taken into consideration. The latter
modify the local plasma density in a self-consistent manner. The coupled modes
of wave propagation is shown to be governed by a modified set of nonlinear
Schr\""{o}dinger-Boussinesq-like equations which admit exact solutions in form
of stationary localized envelopes. Numerical simulation reveals the existence
of large-scale density fluctuations that are self-consistently created by the
localized whistlers in a strongly magnetized high density plasma. The
conditions for the modulational instability (MI) and the value of its growth
rate are obtained. Possible applications of our results, e.g., in strongly
magnetized dense plasmas and in the next generation laser-solid density plasma
interaction experiments are discussed.",1009.0990v2
2010-09-21,Quantum phase diagram of the half filled Hubbard model with bond-charge interaction,"Using quantum field theory and bosonization, we determine the quantum phase
diagram of the one-dimensional Hubbard model with bond-charge interaction $X$
in addition to the usual Coulomb repulsion $U$ at half-filling, for small
values of the interactions. We show that it is essential to take into account
formally irrelevant terms of order $X$. They generate relevant terms
proportional to $X^2$ in the flow of the renormalization group (RG). These
terms are calculated using operator product expansions. The model shows three
phases separated by a charge transition at $U=U_c$ and a spin transition at
$U=U_s>U_c$. For $U<U_c$ singlet superconducting correlations dominate, while
for $U>U_s$, the system is in the spin-density wave phase as in the usual
Hubbard model. For intermediate values $U_c<U<U_s$, the system is in a
spontaneously dimerized bond-ordered wave phase, which is absent in the
ordinary Hubbard model with $X=0$. We obtain that the charge transition remains
at $U_c=0$ for $X \neq 0$. Solving the RG equations for the spin sector, we
provide an analytical expression for $U_s(X)$. The results, with only one
adjustable parameter, are in excellent agreement with numerical ones for $X <
t/2$ where $t$ is the hopping.",1009.4113v2
2010-10-15,Generation of wakefields by whistlers in spin quantum magnetoplasmas,"The excitation of electrostatic wakefields in a magnetized spin quantum
plasma by the classical as well as the spin-induced ponderomotive force (CPF
and SPF, respectively) due to whistler waves is reported. The nonlinear
dynamics of the whistlers and the wakefields is shown to be governed by a
coupled set of nonlinear Schr\""{o}dinger (NLS) and driven Boussinesq-like
equations. It is found that the quantum force associated with the Bohm
potential introduces two characteristic length scales, which lead to the
excitation of multiple wakefields in a strongly magnetized dense plasma (with a
typical magnetic field strength $B_{0}\gtrsim10^{9}$ T and particle density
$n_{0}\gtrsim10^{36}$ m$^{-3}$), where the SPF strongly dominates over the CPF.
In other regimes, namely $B_{0}\lesssim10^{8}$ T and $\ n_{0}\lesssim10^{35}$
m$^{-3}$, where the SPF is comparable to the CPF, a plasma wakefield can also
be excited self-consistently with one characteristic length scale. Numerical
results reveal that the wakefield amplitude is enhanced by the quantum
tunneling effect, however it is lowered by the external magnetic field. Under
appropriate conditions, the wakefields can maintain high coherence over
multiple plasma wavelengths and thereby accelerate electrons to extremely high
energies. The results could be useful for particle acceleration at short
scales, i.e. at nano- and micrometer scales, in magnetized dense plasmas where
the driver is the whistler wave instead of a laser or a particle beam.",1010.3114v2
2010-12-20,Modified spin-wave theory with ordering vector optimization II: Spatially anisotropic triangular lattice and $J_1J_2J_3$ model with Heisenberg interactions,"We study the ground state phases of the $S=1/2$ Heisenberg quantum
antiferromagnet on the spatially anisotropic triangular lattice and on the
square lattice with up to next-next-nearest neighbor coupling (the $J_1J_2J_3$
model), making use of Takahashi's modified spin-wave (MSW) theory supplemented
by ordering vector optimization. We compare the MSW results with exact
diagonalization and projected-entangled-pair-states calculations, demonstrating
their qualitative and quantitative reliability. We find that MSW theory
correctly accounts for strong quantum effects on the ordering vector of the
magnetic phases of the models under investigation: in particular collinear
magnetic order is promoted at the expenses of non-collinear (spiral) order, and
several spiral states which are stable at the classical level, disappear from
the quantum phase diagram. Moreover, collinear states and non-collinear ones
are never connected continuously, but they are separated by parameter regions
in which MSW breaks down, signaling the possible appearance of a non-magnetic
ground state. In the case of the spatially anisotropic triangular lattice, a
large breakdown region appears also for weak couplings between the chains
composing the lattice, suggesting the possible occurrence of a large
non-magnetic region continuously connected with the spin-liquid state of the
uncoupled chains.",1012.4491v1
2011-06-06,Chiral symmetry breaking and the spin content of the rho and rho' mesons,"Using interpolators with different SU(2)_L \times SU(2)_R transformation
properties we study the chiral symmetry and spin contents of the rho- and
rho'-mesons in lattice simulations with dynamical quarks. A ratio of couplings
of the $\qbar\gamma^i{\tau}q$ and $\qbar\sigma^{0i}{\tau}q$ interpolators to a
given meson state at different resolution scales tells one about the degree of
chiral symmetry breaking in the meson wave function at these scales. Using a
Gaussian gauge invariant smearing of the quark fields in the interpolators, we
are able to extract the chiral content of mesons up to the infrared resolution
of ~1 fm. In the ground state rho meson the chiral symmetry is strongly broken
with comparable contributions of both the (0,1) + (1,0) and (1/2,1/2)_b chiral
representations with the former being the leading contribution. In contrast, in
the rho' meson the degree of chiral symmetry breaking is manifestly smaller and
the leading representation is (1/2,1/2)_b. Using a unitary transformation from
the chiral basis to the {2S +1}L_J basis, we are able to define and measure the
angular momentum content of mesons in the rest frame. This definition is
different from the traditional one which uses parton distributions in the
infinite momentum frame. The rho meson is practically a 3S_1 state with no
obvious trace of a ""spin crisis"". The rho' meson has a sizeable contribution of
the 3D_1 wave, which implies that the rho' meson cannot be considered as a pure
radial excitation of the rho meson.",1106.1010v1
2011-08-30,Spin-exotic search in the $ρπ$ decay channel: New results on $π^{-}π^{0}π^{0}$ in comparison to $π^{-}π^{+}π^{-}$ final states (diffractively produced on proton),"The COMPASS experiment at CERN SPS features charged particle tracking as well
as good coverage by electromagnetic calorimetry, and our data provide an
excellent opportunity for simultaneous observation of new states in different
decay modes by the same experiment. The existence of the spin-exotic
$\pi_1(1600)$ resonance in the $\rho\pi$ decay channel is studied for the first
time at COMPASS in both decay modes of the diffractively produced $(3\pi)^{-}$
system: $\pi^{-}p \rightarrow \pi^{-}\pi^{+}\pi^{-}p$ and $\pi^{-} p
\rightarrow \pi^{-}\pi^{0}\pi^{0} p$. A preliminary partial-wave analysis
performed on the 2008 proton target data allows for a first conclusive
comparison of both $(3\pi)^{-}$ decay modes not only for main waves but also
for small ones. We find the neutral versus charged mode results in excellent
agreement with expectations from isospin symmetry. Both, the intensities and
the relative phases to well-known resonances, are consistent for the neutral
and the charged decay modes of the $(3\pi)^{-}$ system. The status on the
search for the spin-exotic $\pi_1(1600)$ resonance produced on a proton target
is discussed.",1108.5969v1
2012-05-23,Low-Temperature Properties of Two-Dimensional Ideal Ferromagnets,"The manifestation of the spin-wave interaction in the low-temperature series
of the partition function has been investigated extensively over more than
seven decades in the case of the three-dimensional ferromagnet. Surprisingly,
the same problem regarding ferromagnets in two spatial dimensions, to the best
of our knowledge, has never been addressed in a systematic way so far. In the
present paper the low-temperature properties of two-dimensional ideal
ferromagnets are analyzed within the model-independent method of effective
Lagrangians. The low-temperature expansion of the partition function is
evaluated up to two-loop order and the general structure of this series is
discussed, including the effect of a weak external magnetic field. Our results
apply to two-dimensional ideal ferromagnets which exhibit a spontaneously
broken spin rotation symmetry O(3) $\to $ O(2) and are defined on a square,
honeycomb, triangular or Kagom\'e lattice. Remarkably, the spin-wave
interaction only sets in at three-loop order. In particular, there is no
interaction term of order $T^3$ in the low-temperature series for the free
energy density. This is the analog of the statement that, in the case of
three-dimensional ferromagnets, there is no interaction term of order $T^4$ in
the free energy density. We also provide a careful discussion of the
implications of the Mermin-Wagner theorem in the present context and thereby
put our low-temperature expansions on safe grounds.",1205.5293v1
2012-06-29,Gravitational waves from spinning eccentric binaries,"This paper is to introduce a new software called CBwaves which provides a
fast and accurate computational tool to determine the gravitational waveforms
yielded by generic spinning binaries of neutron stars and/or black holes on
eccentric orbits. This is done within the post-Newtonian (PN) framework by
integrating the equations of motion and the spin precession equations while the
radiation field is determined by a simultaneous evaluation of the analytic
waveforms. In applying CBwaves various physically interesting scenarios have
been investigated. In particular, we have studied the appropriateness of the
adiabatic approximation, and justified that the energy balance relation is
indeed insensitive to the specific form of the applied radiation reaction term.
By studying eccentric binary systems it is demonstrated that circular template
banks are very ineffective in identifying binaries even if they possess tiny
residual orbital eccentricity. In addition, by investigating the validity of
the energy balance relation we show that, on contrary to the general
expectations, the post-Newtonian approximation should not be applied once the
post-Newtonian parameter gets beyond the critical value $\sim 0.08-0.1$.
Finally, by studying the early phase of the gravitational waves emitted by
strongly eccentric binary systems---which could be formed e.g. in various
many-body interactions in the galactic halo---we have found that they possess
very specific characteristics which may be used to identify these type of
binary systems.",1207.0001v1
2012-07-02,Featureless and non-fractionalized Mott insulators on the honeycomb lattice at 1/2 site filling,"Within the Landau paradigm, phases of matter are distinguished by spontaneous
symmetry breaking. Implicit here is the assumption that a completely symmetric
state exists: a paramagnet. At zero temperature such quantum featureless
insulators may be forbidden, triggering either conventional order or
topological order with fractionalized excitations. Such is the case for
interacting particles when the particle number per unit cell, f, is not an
integer. But, can lattice symmetries forbid featureless insulators even at
integer f? An especially relevant case is the honeycomb (graphene) lattice ---
where free spinless fermions at f=1 (the two sites per unit cell mean f=1 is
half filling per site) are always metallic. Here we present wave functions for
bosons, and a related spin-singlet wave function for spinful electrons, on the
f=1 honeycomb, and demonstrate via quantum to classical mappings that they do
form featureless Mott insulators. The construction generalizes to symmorphic
lattices at integer f in any dimension. Our results explicitly demonstrate that
in this case, despite the absence of a non-interacting insulator at the same
filling, lack of order at zero temperature does not imply fractionalization.",1207.0498v3
2012-08-15,Magnetic properties of the S=1/2 quasi square lattice antiferromagnet CuF2(H2O)2(pyz) (pyz=pyrazine) investigated by neutron scattering,"We have performed elastic and inelastic neutron experiments on single crystal
samples of the coordination polymer compound CuF2(H2O)2(pyz) (pyz=pyrazine) to
study the magnetic structure and excitations. The elastic neutron diffraction
measurements indicate a collinear antiferromagnetic structure with moments
oriented along the [0.7 0 1] real-space direction and an ordered moment of 0.60
+/- 0.03 muB/Cu. This value is significantly smaller than the single ion
magnetic moment, reflecting the presence of strong quantum fluctuations. The
spin wave dispersion from magnetic zone center to the zone boundary points (0.5
1.5 0) and (0.5 0 1.5) can be described by a two dimensional Heisenberg model
with a nearest neighbor magnetic exchange constant J2d = 0.934 +/-0.0025 meV.
The inter-layer interaction Jperp in this compound is less than 1.5% of J2d.
The spin excitation energy at the (0.5 0.5 0.5) zone boundary point is reduced
when compared to the (0.5 1 0.5) zone boundary point by ~10.3 +/- 1.4 %. This
zone boundary dispersion is consistent with quantum Monte Carlo and series
expansion calculations which include corrections for quantum fluctuations to
linear spin wave theory.",1208.3136v1
2012-10-09,Observing the Galaxy's massive black hole with gravitational wave bursts,"An extreme-mass-ratio burst (EMRB) is a gravitational wave signal emitted
when a compact object passes through periapsis on a highly eccentric orbit
about a much more massive object, in our case a stellar mass object about a
10^6 M_sol black hole. EMRBs are a relatively unexplored means of probing the
spacetime of massive black holes (MBHs). We conduct an investigation of the
properties of EMRBs and how they could allow us to constrain the parameters,
such as spin, of the Galaxy's MBH. We find that if an EMRB event occurs in the
Galaxy, it should be detectable for periapse distances r_p < 65 r_g for a \mu =
10 M_sol orbiting object, where r_g = GM/c^2 is the gravitational radius. The
signal-to-noise ratio scales as \rho ~ -2.7 log(r_p/r_g) + log(\mu/M_sol) +
4.9. For periapses r_p < 10 r_g, EMRBs can be informative, and provide good
constraints on both the MBH's mass and spin. Closer orbits provide better
constraints, with the best giving accuracies of better than one part in 10^4
for both the mass and spin parameter.",1210.2778v3
2012-11-26,Thermodynamic properties of the Yb2Ti2O7 pyrochlore as a function of temperature and magnetic field: validation of a quantum spin ice exchange Hamiltonian,"The thermodynamic properties of the pyrochlore Yb2Ti2O7 material are
calculated using the numericallinked-cluster (NLC) calculation method for an
effective anisotropic-exchange spin-1/2 Hamiltonian with parameters recently
determined by fitting the neutron scattering spin wave data obtained at high
magnetic field h. Magnetization, M(T,h), as a function of temperature T and for
different magnetic fields h applied along the three high symmetry directions
[100], [110] and [111], are compared with experimental measurements on the
material for temperature T>1.8K. The excellent agreement between experimentally
measured and calculated M(T,h) over the entire temperature and magnetic field
range considered provides strong quantitative validation of the effective
Hamiltonian. It also confirms that fitting the high-field neutron spin wave
spectra in the polarized paramagnetic state is an excellent method for
determining the microscopic exchange constants of rare-earth insulating magnets
that are described by an effective spin-1/2 Hamiltonian. Finally, we present
results which demonstrate that a recent analysis of the polarized neutron
scattering intensity of Yb2Ti2O7 using a random phase approximation (RPA)
method [Chang et al., Nature Communications {3}, 992 (2012)] does not provide a
good description of M(T,h) for $T\lesssim 10$ K, that is in the entire
temperature regime where correlations become non-negligible.",1211.5934v1
2013-11-27,Weyl semimetals with short-range interactions,"We construct a low-energy effective field theory of electrons interacting via
short-range interactions in a Weyl semimetal and investigate possible
broken-symmetry ground states through an unbiased one-loop renormalization
group (RG) analysis. Using the symmetries of the noninteracting Weyl semimetal
to constrain the form of the interaction term leads to four independent
coupling constants. We investigate the stability of RG flows towards strong
coupling and find a single stable trajectory. In order to determine the most
likely broken-symmetry ground state, we calculate susceptibilities in the
particle-hole and particle-particle channels along this trajectory and find
that the leading instability is towards a fully gapped spin-density wave (SDW)
ground state. The sliding mode of this SDW couples to the external
electromagnetic fields like the Peccei-Quinn axion field of particle physics.
We also study a maximally symmetric toy model of an interacting Weyl semimetal
with a single independent coupling constant. The most likely ground states in
this case are either gapless ferromagnetic states where the spin waves couple
to the Weyl fermions like the spatial components of a (possibly chiral) gauge
field, or a fully gapped spin-singlet Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)
superconducting state.",1311.7133v2
2013-11-27,Optimizing gravitational-wave searches for a population of coalescing binaries: Intrinsic parameters,"We revisit the problem of searching for gravitational waves from inspiralling
compact binaries in Gaussian coloured noise. For binaries with quasicircular
orbits and non-precessing component spins, considering dominant mode emission
only, if the intrinsic parameters of the binary are known then the optimal
statistic for a single detector is the well-known two-phase matched filter.
However, the matched filter signal-to-noise ratio is /not/ in general an
optimal statistic for an astrophysical population of signals, since their
distribution over the intrinsic parameters will almost certainly not mirror
that of noise events, which is determined by the (Fisher) information metric.
Instead, the optimal statistic for a given astrophysical distribution will be
the Bayes factor, which we approximate using the output of a standard template
matched filter search. We then quantify the possible improvement in number of
signals detected for various populations of non-spinning binaries: for a
distribution of signals uniformly distributed in volume and with component
masses distributed uniformly over the range $1\leq m_{1,2}/M_\odot\leq 24$,
$(m_1+m_2) /M_\odot\leq 25$ at fixed expected SNR, we find $\gtrsim 20\%$ more
signals at a false alarm threshold of $10^{-6}\,$Hz in a single detector. The
method may easily be generalized to binaries with non-precessing spins.",1311.7174v2
2014-02-25,Quasiuniversal properties of neutron star mergers,"Binary neutron star mergers are studied using nonlinear 3+1 numerical
relativity simulations and the analytical effective-one-body (EOB) model. The
EOB model predicts quasiuniversal relations between the mass-rescaled
gravitational wave frequency and the binding energy at the moment of merger,
and certain dimensionless binary tidal coupling constants depending on the
stars Love numbers, compactnesses and the binary mass ratio. These relations
are quasiuniversal in the sense that, for a given value of the tidal coupling
constant, they depend significantly neither on the equation of state nor on the
mass ratio, though they do depend on stars spins. The spin dependence is
approximately linear for small spins aligned with the orbital angular momentum.
The quasiuniversality is a property of the conservative dynamics; nontrivial
relations emerge as the binary interaction becomes tidally dominated. This
analytical prediction is qualitatively consistent with new, multi-orbit
numerical relativity results for the relevant case of equal-mass irrotational
binaries. Universal relations are thus expected to characterize neutron star
mergers dynamics. In the context of gravitational wave astronomy, these
universal relations may be used to constrain the neutron star equation of state
using waveforms that model the merger accurately.",1402.6244v2
2014-04-08,Analysis of the quantum-mechanical equivalence of the metrics of a centrally symmetric uncharged gravitational field,"In the paper we analyze the quantum-mechanical equivalence of the metrics of
a centrally symmetric uncharged gravitational field. We consider the
Schwarzschild metrics in the spherical, isotropic and harmonic coordinates, and
the Eddington-Finkelstein, Painleve-Gullstrand, Lemaitre-Finkelstein, Kruskal
metrics. The scope of the analysis includes domains of the wave functions of
Dirac's equation, hermiticity of Hamiltonians, and the possibility of existence
of stationary bound states of spin-half particles. The constraint on the domain
of the wave functions of the Hamiltonian in a Schwarzschild field in spherical
coordinates (r > r_{0}) resulting from the fulfillment of Hilbert's condition
g_{00} > 0 also holds in other coordinates for all the metrics considered. The
self-adjoint Hamiltonians for the Schwarzschild metrics in the spherical,
isotropic and harmonic coordinates and also for the Eddington-Finkelstein and
Painleve-Gullstrand metrics are Hermitian, and for them the existence of
stationary bound states of spin-half particles is possible. The self-adjoint
Hamiltonians for non-stationary Lemaitre-Finkelstein and Kruskal metrics have
the explicit dependence on the temporal coordinates and stationary bound states
of spin-half particles cannot be defined for these Hamiltonians. The results of
this study can be useful when addressing the issues related to the evolution of
the universe and interaction of collapsars with surrounding matter.",1404.2085v3
2014-04-14,Participation spectroscopy and entanglement Hamiltonian of quantum spin models,"Shannon-R\'enyi entropies and associated participation spectra quantify how
much a many-body wave-function is localized in a given configuration basis.
Using these tools, we present an analysis of the ground-state wave functions of
various quantum spin systems in one and two dimensions. General ideas and a
review of the current status of this field are first given, with a particular
emphasis on universal subleading terms characterizing different quantum phases
of matter, and associated transitions. We highlight the connection with the
related entanglement entropies and spectra when this is possible.
  In a second part, new results are presented for the participation spectra of
interacting spin models, mostly based on quantum Monte Carlo simulations, but
also using perturbation theory in some cases. For full antiferromagnetic
systems, participation spectra are analyzed in terms of ferromagnetic domain
walls which experience a repulsive pairwise interaction. This confinement
potential is either linear for long-range N\'eel order, or logarithmic for
quasi-long-range order. The case of subsystems is also analyzed in great detail
for a 2d dimerized Heisenberg model undergoing a quantum phase transition
between a gapped paramagnet and a N\'eel phase. Participation spectra of line
shaped (1d) sub-systems are quantitatively compared with finite temperature
participation spectra of ansatz effective boundary (1d) entanglement
Hamiltonians. While short-range models describe almost perfectly the gapped
side, the N\'eel regime is best compared using long-range effective
Hamiltonians. Spectral comparisons performed using Kullback-Leibler
divergences, a tool potentially useful for entanglement spectra, provide a
quantitative way to identify both the best boundary entanglement Hamiltonian
and temperature.",1404.3717v1
2014-08-23,Particle dynamics and deviation effects in the field of a strong electromagnetic wave,"Some strong field effects on test particle motion associated with the
propagation of a plane electromagnetic wave in the exact theory of general
relativity are investigated. Two different profiles of the associated radiation
flux are considered in comparison, corresponding to either constant or
oscillating electric and magnetic fields with respect to a natural family of
observers. These are the most common situations to be experimentally explored,
and have a well known counterpart in the flat spacetime limit. The resulting
line elements are determined by a single metric function, which turns out to be
expressed in terms of standard trigonometric functions in the case of a
constant radiation flux, and in terms of special functions in the case of
oscillating flux, leading to different features of test particle motion. The
world line deviation between both uncharged and charged particles on different
spacetime trajectories due to the combined effect of gravitational and
electromagnetic forces is studied. The interaction of charged particles with
the background radiation field is also discussed through a general relativistic
description of the inverse Compton effect. Motion as well as deviation effects
on particles endowed with spin are studied too. Special situations may occur in
which the direction of the spin vector change during the interaction, leading
to obsevables effects like spin-flip.",1408.5486v1
2014-12-04,Improved methods for simulating nearly extremal binary black holes,"Astrophysical black holes could be nearly extremal (that is, rotating nearly
as fast as possible); therefore, nearly extremal black holes could be among the
binaries that current and future gravitational-wave observatories will detect.
Predicting the gravitational waves emitted by merging black holes requires
numerical-relativity simulations, but these simulations are especially
challenging when one or both holes have mass $m$ and spin $S$ exceeding the
Bowen-York limit of $S/m^2=0.93$. We present improved methods that enable us to
simulate merging, nearly extremal black holes more robustly and more
efficiently. We use these methods to simulate an unequal-mass, precessing
binary black hole coalescence, where the larger black hole has $S/m^2=0.99$. We
also use these methods to simulate a non-precessing binary black hole
coalescence, where both black holes have $S/m^2=0.994$, nearly reaching the
Novikov-Thorne upper bound for holes spun up by thin accretion disks. We
demonstrate numerical convergence and estimate the numerical errors of the
waveforms; we compare numerical waveforms from our simulations with
post-Newtonian and effective-one-body waveforms; we compare the evolution of
the black-hole masses and spins with analytic predictions; and we explore the
effect of increasing spin magnitude on the orbital dynamics (the so-called
""orbital hangup"" effect).",1412.1803v1
2014-12-11,Quantum Gates Between Distant Qubits via Spin-Independent Scattering,"We show how the spin independent scattering of two initially distant qubits,
say, in distinct traps or in remote sites of a lattice, can be used to
implement an entangling quantum gate between them. The scattering takes place
under 1D confinement for which we consider two different scenarios: a 1D
wave-guide and a tight-binding lattice. We consider models with contact-like
interaction between two fermionic or two bosonic particles. A qubit is encoded
in two distinct spins (or other internal) states of each particle. Our scheme
enables the implementation of a gate between two qubits which are initially too
far to interact directly, and provides an alternative to photonic mediators for
the scaling of quantum computers. Fundamentally, an interesting feature is that
""identical particles"" (e.g., two atoms of the same species) and the 1D
confinement, are both necessary for the action of the gate. Finally, we discuss
the feasibility of our scheme, the degree of control required to initialize the
wave-packets momenta, and show how the quality of the gate is affected by
momentum distributions and initial distance. In a lattice, the control of
quasi-momenta is naturally provided by few local edge impurities in the lattice
potential.",1412.3582v4
2015-01-06,Spin excitations used to probe the nature of the exchange coupling in the magnetically ordered ground state of Pr$_{0.5}$Ca$_{0.5}$MnO$_{3}$,"We have used time-of-flight inelastic neutron scattering to measure the spin
wave spectrum of the canonical half-doped manganite
Pr$_{0.5}$Ca$_{0.5}$MnO$_{3}$, in its magnetic and orbitally ordered phase. The
data, which cover multiple Brillouin zones and the entire energy range of the
excitations, are compared with several different models that are all consistent
with the CE-type magnetic order, but arise through different exchange coupling
schemes. The Goodenough model, i.e. an ordered state comprising strong nearest
neighbor ferromagnetic interactions along zig-zag chains with antiferromagnetic
inter-chain coupling, provides the best description of the data, provided that
further neighbor interactions along the chains are included. We are able to
rule out a coupling scheme involving formation of strongly bound ferromagnetic
dimers, i.e. Zener polarons, on the basis of gross features of the observed
spin wave spectrum. A model with weaker dimerization reproduces the observed
dispersion but can be ruled out on the basis of discrepancies between the
calculated and observed structure factors at certain positions in reciprocal
space. Adding further neighbor interactions results in almost no dimerization,
i.e. recovery of the Goodenough model. These results are consistent with
theoretical analysis of the degenerate double exchange model for half-doping,
and provide a recipe for how to interpret future measurements away from
half-doping, where degenerate double exchange models predict more complex
ground states.",1501.01148v2
2015-04-28,Microwave soft x-ray microscopy for nanoscale magnetization dynamics in the 5-10 GHz frequency range,"We present a scanning transmission x-ray microscopy setup combined with a
novel microwave synchronization scheme in order to study high frequency
magnetization dynamics at synchrotron light sources. The sensitivity necessary
to detect small changes of the magnetization on short time scales and nanometer
spatial dimensions is achieved by combination of the developed excitation
mechanism with a single photon counting electronics that is locked to the
synchrotron operation frequency. The required mechanical stability is achieved
by a compact design of the microscope. Our instrument is capable of creating
direct images of dynamical phenomena in the 5-10 GHz range, with 35 nm
resolution. When used together with circularly polarized x-rays, the above
capabilities can be combined to study magnetic phenomena at microwave
frequencies, such as ferromagnetic resonance (FMR) and spin waves. We
demonstrate the capabilities of our technique by presenting phase resolved
images of a 6 GHz nanoscale spin wave generated by a spin torque oscillator, as
well as the uniform ferromagnetic precession with ~0.1 deg amplitude at 9 GHz
in a micrometer-sized cobalt strip.",1504.07561v1
2015-07-26,Unconventional superconductivity in Y$_5$Rh$_6$Sn$_{18}$ probed by muon spin relaxation,"Conventional superconductors are robust diamagnets that expels magnetic
fields through the Meissner effect. It would therefore be unexpected if a
superconducting ground state would support spontaneous magnetics fields. Such
broken time-reversal symmetry states have been suggested for the
high$-$temperature superconductors, but their identification remains
experimentally controversial. We present magnetization, heat capacity, zero
field and transverse field muon spin relaxation experiments on the recently
discovered caged type superconductor \yrhsn\ ($T_{\bf c}$ = 3.0 K). The
electronic heat capacity of \yrhsn\ shows a $T^3$ dependence below $T_{\bf c}$
indicating an anisotropic superconducting gap with a point node. This result is
in sharp contrast to that observed in the isostructural Lu$_5$Rh$_6$Sn$_{18}$
which is a strong coupling $s-$wave superconductor. The temperature dependence
of the deduced superfluid density \yrhsn\ is consistent with a BCS $s-$wave gap
function, while the zero-field muon spin relaxation measurements strongly
evidences unconventional superconductivity through a spontaneous appearance of
an internal magnetic field below the superconducting transition temperature,
signifying that the superconducting state is categorized by the broken
time-reversal symmetry.",1507.07189v1
2015-09-10,A spectral hole memory for light at the single photon level,"We demonstrate a solid state spin-wave optical memory based on stopped light
in a spectral hole. A long lived narrow spectral hole is created by optical
pumping in the inhomogeneous absorption profile of a Pr$^{3+}$:Y$_2$SiO$_5$
crystal. Optical pulses sent through the spectral hole experience a strong
reduction of their group velocity and are spatially compressed in the crystal.
A short Raman pulse transfers the optical excitation to the spin state before
the light pulse exits the crystal, effectively stopping the light. After a
controllable delay, a second Raman pulse is sent, which leads to the emission
of the stored photons. We reach storage and retrieval efficiencies for bright
pulses of up to $39\,\%$ in a $5 \,\mathrm{mm}$-long crystal. We also show that
our device works at the single photon level by storing and retrieving
$3\,\mathrm{\mu s}$-long weak coherent pulses with efficiencies up to $31\,\%$,
demonstrating the most efficient spin-wave solid state optical memory at the
single-photon level so far. We reach an unconditional noise level of
$(9\pm1)\times 10^{-3}$ photons per pulse in a detection window of
$4\,\mathrm{\mu s}$ leading to a signal-to-noise ratio of $33 \pm 4$ for an
average input photon number of 1, making our device promising for long-lived
storage of non-classical light.",1509.03145v2
2015-09-21,Estimating effective higher order terms in the post-Newtonian binding energy and gravitational-wave flux: Non-spinning compact binary inspiral,"In the adiabatic post-Newtonian (PN) approximation, the phase evolution of
gravitational waves (GWs) from inspiralling compact binaries in quasicircular
orbits is computed by equating the change in binding energy with the GW flux.
This energy balance equation can be solved in different ways, which result in
multiple approximants of the PN waveforms. Due to the poor convergence of the
PN expansion, these approximants tend to differ from each other during the late
inspiral. Which of these approximants should be chosen as templates for
detection and parameter estimation of GWs from inspiraling compact binaries is
not obvious. In this paper, we present estimates of the effective higher order
(beyond the currently available 4PN and 3.5PN) non-spinning terms in the PN
expansion of the binding energy and the GW flux that minimize the difference of
multiple PN approximants (TaylorT1, TaylorT2, TaylorT4, TaylorF2) with
effective one body waveforms calibrated to numerical relativity (EOBNR). We
show that PN approximants constructed using the effective higher order terms
show significantly better agreement (as compared to 3.5PN) with the inspiral
part of the EOBNR. For non-spinning binaries with component masses $m_{1,2} \in
[1.4 M_\odot, 15 M_\odot]$, most of the approximants have a match
(faithfulness) of better than 99% with both EOBNR and each other.",1509.06366v1
2015-10-08,Spin excitations in a model of FeSe with orbital ordering,"We present a theoretical study of the dynamical spin susceptibility for the
intriguing Fe-based superconductor FeSe, based on a tight-binding model
developed to account for the temperature-dependent band structure in this
system. The model allows for orbital ordering in the $d_{xz}/d_{yz}$ channel
below the structural transition and presents a strongly $C_4$ symmetry broken
Fermi surface at low temperatures which accounts for the nematic properties of
this material. The calculated spin excitations are peaked at wave vector
$(\pi,0)$ in the 1-Fe Brillouin zone, with a broad maximum at energies of order
a few meV. In this range, the occurrence of superconductivity sharpens this
peak in energy, creating a $(\pi,0)$ ""neutron resonance"" as seen in recent
experiments. With the exception of the quite low energy scale of these
fluctuations, these results are roughly similar to standard behavior in Fe
pnictide systems. At higher energies, however, intensity increases and shifts
to wave vectors along the $(\pi,0)$ - $(\pi,\pi)$ line. We compare with
existing inelastic neutron experiments and NMR data, and give predictions for
further studies.",1510.02357v2
2015-12-10,Acoustic topological insulator and robust one-way sound transport,"Discovery of novel topological orders of condensed matters is of a
significant interest in both fundamental and applied physics due to the
associated quantum conductance behaviors and unique symmetry-protected
backscattering-immune propagation against defects, which inspired similar
fantastic effects in classical waves system, leading to the revolution of the
manipulation of wave propagation. To date, however, only few theoretical models
were proposed to realize acoustic topological states. Here, we theoretically
and experimentally demonstrate a two dimensional acoustic topological
insulators with acoustic analogue of quantum spin Hall Effect. Due to the band
inversion mechanism near the double Dirac cones, acoustic one-way pseudospin
dependent propagating edge states, corresponding to spin-plus and spin-minus,
can be observed at the interface between two graphene-like acoustic crystals.
We have also experimentally verified the associated topological immunity of
such one-way edge states against the different lattice defects and disorders,
which can always lead to inherent propagation loss and noise. We show that this
unique acoustic topological phenomenon can offer a new promising application
platform for the design of novel acoustic devices, such as one-way sound
isolators, acoustic mode switchers, splitters, filters etc.",1512.03273v1
2016-02-11,Mesoscopic electron focusing in topological insulators,"The particle wave duality sets a fundamental correspondence between optics
and quantum mechanics. Within this framework, the propagation of quasiparticles
can give rise to superposition phenomena which, like for electromagnetic waves,
can be described by the Huygens principle. However, the utilization of this
principle by means of propagation and manipulation of quantum information is
limited by the required coherence in time and space. Here we show that in
topological insulators, which in their pristine form are characterized by
opposite propagation directions for the two quasiparticles spin channels,
mesoscopic focusing of coherent charge density oscillations can be obtained at
large nested segments of constant energy contours by magnetic surface doping.
Our findings provide evidence of strongly anisotropic Dirac fermion-mediated
interactions. Even more remarkably, the validity of our findings goes beyond
topological insulators but applies for systems with spin orbit lifted
degeneracy in general. It demonstrates how spin information can be transmitted
over long distances, allowing the design of experiments and devices based on
coherent quantum effects in this fascinating class of materials.",1602.03902v1
2016-02-12,Spinor Structure and Matter Spectrum,"Classification of relativistic wave equations is given on the ground of
interlocking representations of the Lorentz group. A system of interlocking
representations is associated with a system of eigenvector subspaces of the
energy operator. Such a correspondence allows one to define matter spectrum,
where the each level of this spectrum presents a some state of elementary
particle. An elementary particle is understood as a superposition of state
vectors in nonseparable Hilbert space. Classification of indecomposable systems
of relativistic wave equations is produced for bosonic and fermionic fields on
an equal footing (including Dirac and Maxwell equations). All these fields are
equivalent levels of matter spectrum, which differ from each other by the value
of mass and spin. It is shown that a spectrum of the energy operator,
corresponding to a given matter level, is non-degenerate for the fields of type
$(l,0)\oplus(0,l)$, where $l$ is a spin value, whereas for arbitrary spin
chains we have degenerate spectrum. Energy spectra of the stability levels
(electron and proton states) of the matter spectrum are studied in detail. It
is shown that these stability levels have a nature of threshold scales of the
fractal structure associated with the system of interlocking representations of
the Lorentz group.",1602.04050v2
2016-04-22,Second order differential realization of the Bargmann-Wigner framework for particles of any spin,"The Bargmann-Wigner (BW) framework describes particles of spin-j in terms of
Dirac spinors of rank 2j, obtained as the local direct product of n Dirac
spinor copies, with n=2j. Such spinors are reducible, and contain also
(j,0)+(0,j)-pure spin representation spaces. The 2(2j+1) degrees of freedom of
the latter are identified by a projector given by the n-fold direct product of
the covariant parity projector within the Dirac spinor space. Considering
totally symmetric tensor spinors one is left with the expected number of
2(2j+1) independent degrees of freedom. The BW projector is of the order
$\partial ^{2j}$ in the derivatives, and so are the related spin-j wave
equations and associated Lagrangians. High order differential equations can not
be consistently gauged, and allow several unphysical aspects, such as
non-locality, acausality, ghosts and etc to enter the theory. In order to avoid
these difficulties we here suggest a strategy of replacing the high order of
the BW wave equations by the universal second order. To do so we replaced the
BW projector by one of zeroth order in the derivatives. We built it up from one
of the Casimir invariants of the Lorentz group when exclusively acting on
spaces of internal spin degrees of freedom. This projector allows one to
identify anyone of the irreducible sectors of the primordial rank-2j spinor, in
particular (j,0)+(0,j), and without any reference to the external space-time
and the four-momentum. The dynamics is then introduced by requiring the (j,0)+
(0,j) sector to satisfy the Klein-Gordon equation. The scheme allows for a
consistent minimal gauging.",1604.06772v1
2016-06-03,Tetraquark states in the bottom sector and the status of the $Y_b$(10890) state,"We have done the exploratory study of bottom tetraquarks ($[bq\bar b \bar
q];{q\in u,d}$) in the diquark-antidiquark framework with the inclusion of spin
hyperfine, spin-orbit and tensor components of the one gluon exchange
interaction. Our focus here is on the $Y_b$(10890) and other exotic states in
the bottom sector. We have predicted some of the bottom counterparts to the
charm tetraquark candidates. Our present study shows that if $Z_b(10610)$ and
$Z_b(10650)$ are diquark-diantiquark states then they have to be first radial
excitations only and we have predicted $Z_b(10650)$ state as first radial
excitation of tetraquark state $X_b$ (10.143-10.230). We have identified $X_b$
state with $J^{PC}= 1^{+-}/0^{++}$ as being the analogue of $Z_c(3900)$. An
observation of the $X_b$ will provide a deeper insight into the exotic hadron
spectroscopy and is helpful to unravel the nature of the states connected by
the heavy quark symmetry. We particularly focus on the lowest P wave $[bq][\bar
b\bar q]$ states with $J^{PC}=1^{--}$ by computing their leptonic, hadronic and
radiative decay widths to predict the status of still controversial
$Y_b$(10890) state. Apart from this, we have also shown here the possibility of
mixing of P wave states. In the case of mixing of $1^{--}$ state with different
spin multiplicities, we found that predicted masses of the mixed P states
differ from $Y_b$(10890) state only by $\pm20$ MeV energy difference which can
be helpful to resolve further the structure of $Y_b$(10890).",1606.01047v1
2016-07-15,Electric and magnetic multipoles and bond orders in excitonic insulators,"We study the charge and spin density distributions of excitonic insulator
(EI) states in the tight-binding approximation. We first discuss the charge and
spin densities of the EI states when the valence and conduction bands are
composed of orthogonal orbitals in a single atom. We show that the anisotropic
charge or spin density distribution occurs in a unit cell (or atom) and a
higher rank electric or magnetic multipole moment becomes finite, indicating
that the EI state corresponds to the multipole order. A full description of the
multipole moments for the $s$, $p$, and $d$ orbitals is then given in general.
We find that, in contrast to the conventional density-wave states, the
modulation of the total charge or net magnetization does not appear in this
case. However, when the conduction and valence bands include the component of
the same orbital, the modulation of the total charge or net magnetization
appears, as in the conventional density-wave state. We also discuss the
electron density distribution in the EI state when the valence and conduction
bands are composed of orbitals located in different atoms. We show that the
excitonic ordering in this case corresponds to the bond order formation. Based
on the results thus obtained we discuss the EI states of real materials
recently reported.",1607.04365v2
2016-07-16,Spectrum and electromagnetic transitions of bottomonium,"Stimulated by the exciting progress in the observation of new bottomonium
states, we study the bottomonium spectrum. To calculate the mass spectrum, we
adopt a nonrelativistic screened potential model. The radial Schr\""{o}dinger
equation is solved with the three-point difference central method, where the
spin-dependent potentials are dealt with non-perturbatively. With this
treatment, the corrections of the spin-dependent potentials to the wave
functions can be included successfully. Furthermore, we calculate the
electromagnetic transitions of the $nS$ ($n\leq 4$), $nP$ ($n\leq 3$), and $nD$
($n\leq 2$) bottomonium states with a nonrelativistic electromagnetic
transition operator widely applied to meson photoproduction reactions. Our
predicted masses, hyperfine and fine splittings, electromagnetic transition
widths and branching ratios of the bottomonium states are in good agreement
with the available experimental data. Especially, the EM transitions of
$\Upsilon(3S)\to \chi_{b1,2}(1P)\gamma$, which were not well understood in
previous studies, can be reasonably explained by considering the corrections of
the spin-dependent interactions to the wave functions. We also discuss the
observations of the missing bottomonium states by using radiative transitions.
Some important radiative decay chains involving the missing bottomonium states
are suggested to be observed. We hope our study can provide some useful
references to observe and measure the properties of bottomonium mesons in
forthcoming experiments.",1607.04696v3
2016-07-19,"Validating the effective-one-body model of spinning, precessing binary black holes against numerical relativity","In Ref. [1], the properties of the first gravitational wave detected by LIGO,
GW150914, were measured by employing an effective-one-body (EOB) model of
precessing binary black holes whose underlying dynamics and waveforms were
calibrated to numerical-relativity (NR) simulations. Here, we perform the first
extensive comparison of such EOBNR model to 70 precessing NR waveforms that
span mass ratios from 1 to 5, dimensionless spin magnitudes up to 0.5, generic
spin orientations, and length of about 20 orbits. We work in the observer's
inertial frame and include all $\ell=2$ modes in the gravitational-wave
polarizations. We introduce new prescriptions for the EOB ringdown signal
concerning its spectrum and time of onset. For total masses between 10Msun and
200Msun, we find that precessing EOBNR waveforms have unfaithfulness within
about 3% to NR waveforms when considering the Advanced-LIGO design noise curve.
This result is obtained without recalibration of the inspiral-plunge of the
underlying nonprecessing EOBNR model. The unfaithfulness is computed with
maximization over time and phase of arrival, sky location and polarization of
the EOBNR waveform and it is averaged over sky location and polarization of the
NR signal. We also present comparisons between NR and EOBNR waveforms in a
frame that tracks the orbital precession.",1607.05661v1
2016-09-12,"Spontaneous decays of magneto-elastic excitations in noncollinear antiferromagnet (Y,Lu)MnO3","When magnons and phonons, the fundamental quasiparticles of the solid, are
coupled to one another, they form a new hybrid quasi-particle, leading to novel
phenomena and interesting applications. Despite its wide-ranging importance,
however, detailed experimental studies on the underlying Hamiltonian is rare
for actual materials. Moreover, the anharmonicity of such magnetoelastic
excitations remains largely unexplored although it is essential for a proper
understanding of their diverse thermodynamic behaviour as well as intrinsic
zero-temperature decay. Here we show that in noncollinear antiferromagnets, a
strong magnon-phonon coupling can significantly enhance the anharmonicity,
resulting in the creation of magnetoelastic excitations and their spontaneous
decay. By measuring the spin waves over the full Brillouin zone and carrying
out anharmonic spin wave calculations using a Hamiltonian with an explicit
magnon-phonon coupling, we have identified a hybrid magnetoelastic mode in
(Y,Lu)MnO3 and quantified its decay rate and the exchange-striction coupling
term required to produce it. Our work has wide implications for understanding
of the spin-phonon coupling and the resulting excitations of the broad classes
of noncollinear magnets.",1609.03262v1
2016-10-27,Vortex-antivortex proliferation from an obstacle in thin film ferromagnets,"Magnetization dynamics in thin film ferromagnets can be studied using a
dispersive hydrodynamic formulation. The equations describing the
magnetodynamics map to a compressible fluid with broken Galilean invariance
parametrized by the longitudinal spin density and a magnetic analog of the
fluid velocity that define spin-density waves. A direct consequence of these
equations is the determination of a magnetic Mach number. Micromagnetic
simulations reveal nucleation of nonlinear structures from an impenetrable
object realized by an applied magnetic field spot or a defect. In this work,
micromagnetic simulations demonstrate vortex-antivortex pair nucleation from an
obstacle. Their interaction establishes either ordered or irregular
vortex-antivortex complexes. Furthermore, when the magnetic Mach number exceeds
unity (supersonic flow), a Mach cone and periodic wavefronts are observed,
which can be well-described by solutions of the steady, linearized equations.
These results are reminiscent of theoretical and experimental observations in
Bose-Einstein condensates, and further supports the analogy between the
magnetodynamics of a thin film ferromagnet and compressible fluids. The
nucleation of nonlinear structures and vortex-antivortex complexes using this
approach enables the study of their interactions and effects on the stability
of spin-density waves.",1610.08940v3
2017-07-09,Signatures of pairing in the magnetic excitation spectrum of strongly correlated ladders,"Magnetic interactions are widely believed to play a crucial role in the
microscopic mechanism leading to high critical temperature superconductivity.
It is therefore important to study the signatures of pairing in the magnetic
excitation spectrum of simple models known to show unconventional
superconducting tendencies. Using the Density Matrix Renormalization Group
technique, we calculate the dynamical spin structure factor $S({\bf k},\omega)$
of a generalized $t-U-J$ Hubbard model away from half-filling in a two-leg
ladder geometry. The addition of $J$ enhances pairing tendencies. We analyze
quantitatively the signatures of pairing in the magnetic excitation spectra. We
found that the superconducting pair-correlation strength, that can be estimated
independently from ground state properties, is closely correlated with the
integrated low-energy magnetic spectral weight in the vicinity of $(\pi,\pi)$.
In this wave-vector region, robust spin incommensurate features develop with
increasing doping. The branch of the spectrum with rung direction wave-vector
$k_{rung}=0$ does not change substantially with doping where pairing dominates,
and thus plays a minor role. We discuss the implications of our results for
neutron scattering experiments, where the spin excitation dynamics of
hole-doped quasi-one dimensional magnetic materials can be measured, and also
address implications for recent resonant inelastic X-ray scattering
experiments.",1707.02626v1
2017-11-08,Inhomogeneous hard-core bosonic mixture with checkerboard supersolid phase: Quantum and thermal phase diagram,"We introduce an inhomogeneous bosonic mixture composed of two kinds of
hard-core and semi-hard-core bosons with different nilpotency conditions and
demonstrate that in contrast with the standard hard-core Bose-Hubbard model,
our bosonic mixture with nearest- and next-nearest-neighbor interactions on a
square lattice develops the checkerboard supersolid phase characterized by the
simultaneous superfluid and checkerboard solid orders. Our bosonic mixture is
created from a two-orbital Bose-Hubbard model including two kinds of bosons: a
single-orbital boson and a two-orbital boson. By mapping the bosonic mixture to
an anisotropic inhomogeneous spin model in the presence of a magnetic field, we
study the ground-state phase diagram of the model by means of cluster mean
field theory and linear spin-wave theory and show that various phases such as
solid, superfluid, supersolid, and Mott insulator appear in the phase diagram
of the mixture. Competition between the interactions and magnetic field causes
the mixture to undergo different kinds of first- and second-order phase
transitions. By studying the behavior of the spin-wave excitations, we find the
reasons of all first- and second-order phase transitions. We also obtain the
temperature phase diagram of the system using cluster mean field theory. We
show that the checkerboard supersolid phase persists at finite temperature
comparable with the interaction energies of bosons.",1711.03020v1
2017-12-18,Gravitational wave echoes through new windows,"There has been a striking realization that physics resolving the black hole
information paradox could imply postmerger gravitational wave echoes. We here
report on evidence for echoes from the LIGO compact binary merger events,
GW151226, GW170104, GW170608, GW170814, as well as the neutron star merger
GW170817. There is a signal for each event with a $p$-value of order 1% or
sometimes significantly less. Our study begins with the comparison of echoes
from a variety of horizonless exotic compact objects. Next we investigate the
effects of spin. The identification of the more generic features of echoes then
leads to the development of relatively simple windowing methods, in both time
and frequency space, to extract a signal from noise. The time delay between
echoes is inversely related to the spacing between the spectral resonances, and
it is advantageous to look directly for this resonance structure. We find time
delays for the first four events that are consistent with a simple model that
accounts for mass and spin of the final object, while for the neutron star
merger the final mass and spin are constrained.",1712.06517v4
2018-01-02,Continuous-wave solutions and modulational instability in spinor condensates of positronium,"We obtain general continuous-wave (CW)\ solutions in the model of a spinor
positronium condensate in the absence of magnetic field. The CW solutions with
both in-phase ($n=0$) and out-of-phase ($n=1$) spin components exist, with
their ranges limited by the total particle density, $\rho $. In the limit of
negligible population exchange between the spin components, the CW solutions
are found to be stable or unstable, depending on the particle density of the
para positronium. Ortho positronium, in the $F=1$ spinor state, forms a
ferromagnetic condensate with stable in-phase CW solutions only. Subsequent
examination of the modulational instability (MI) is carried out both in the
limit case of identical wavenumbers in the spin components, $% \Delta k\equiv
k_{1}-k_{-1}=0$, and in the more general case of $\Delta k\neq 0$ too. The CW
solutions with $n=0$ and $1$ solutions, which are stable in the case of $\Delta
k=0$, are unstable for $\Delta k\neq 0$, for the natural repulsive sign of the
nonlinearities. The total particle density, $\rho $, in the limit of $\Delta
k=0$ is found to have a significant role for the stability of the condensate,
which is determined by the sign of the self-interaction nonlinearity.",1801.00590v1
2018-01-14,Random projections in gravitational wave searches of compact binaries,"Random projection (RP) is a powerful dimension reduction technique widely
used in the analysis of high dimensional data. We demonstrate how this
technique can be used to improve the computational efficiency of gravitational
wave searches from compact binaries of neutron stars or black holes.
Improvements in low-frequency response and bandwidth due to detector hardware
upgrades pose a data analysis challenge in the advanced LIGO era as they result
in increased redundancy in template databases and longer templates due to the
higher number of signal cycles in-band. The RP-based methods presented here
address both these issues within the same broad framework. We first use RP for
an efficient, singular value decomposition inspired template matrix
factorization and develop a geometric intuition for why this approach works. We
then use RP to calculate approximate time-domain match correlations in a lower
dimensional vector space. For searches over parameters corresponding to
non-spinning binaries with a neutron star and a black hole, a combination of
the two methods can reduce the total on-line computational cost by an order of
magnitude over a nominal baseline. This can, in turn, help free-up
computational resources needed to go beyond current spin-aligned searches to
more complex ones involving generically spinning waveforms.",1801.04506v4
2018-03-21,High-resolution numerical relativity simulations of spinning binary neutron star mergers,"The recent detection of gravitational waves and electromagnetic counterparts
emitted during and after the collision of two neutron stars marks a
breakthrough in the field of multi-messenger astronomy. Numerical relativity
simulations are the only tool to describe the binary's merger dynamics in the
regime when speeds are largest and gravity is strongest. In this work we report
state-of-the-art binary neutron star simulations for irrotational
(non-spinning) and spinning configurations. The main use of these simulations
is to model the gravitational-wave signal. Key numerical requirements are the
understanding of the convergence properties of the numerical data and a
detailed error budget. The simulations have been performed on different HPC
clusters, they use multiple grid resolutions, and are based on eccentricity
reduced quasi-circular initial data. We obtain convergent waveforms with phase
errors of 0.5-1.5 rad accumulated over approximately 12 orbits to merger. The
waveforms have been used for the construction of a phenomenological waveform
model which has been applied for the analysis of the recent binary neutron star
detection. Additionally, we show that the data can also be used to test other
state-of-the-art semi-analytical waveform models.",1803.07965v1
2018-06-19,Excited States and Optical Properties of Hydrogen-Passivated Rectangular Graphenes: A Computational Study,"In this paper, we perform large-scale electron-correlated calculations of
optoelectronic properties of rectangular graphene-like polycyclic aromatic
hydrocarbon molecules. Theoretical methodology employed in this work is based
upon Pariser-Parr-Pople (PPP) $\pi$-electron model Hamiltonian, which includes
long-range electron-electron interactions. Electron-correlation effects were
incorporated using multi-reference singles-doubles configuration-interaction
(MRSDCI) method, and the ground and excited state wave functions thus obtained
were employed to calculate the linear optical absorption spectra of these
molecules, within the electric-dipole approximation. As far as the ground state
wave functions of these molecules are concerned, we find that with the
increasing size, they develop a strong diradical open-shell character. Our
results on optical absorption spectra are in very good agreement with the
available experimental results, outlining the importance of
electron-correlation effects in accurate description of the excited states. In
addition to the optical gap, spin gap of each molecule was also computed using
the same methodology. Calculated spin gaps exhibit a decreasing trend with the
increasing sizes of the molecules, suggesting that the infinite graphene has a
vanishing spin gap.",1806.07013v2
2018-09-27,Broadband Magnetic-Manipulated Spintronic Terahertz Emitter with Arbitrarily Tunable Polarizations,"Flexible manipulation of terahertz-wave polarization during the generation
process is very important for terahertz applications, especially for the
next-generation on-chip functional terahertz sources. However, current
terahertz emitters could not satisfy such demand, hence calling for new
mechanism and conceptually new terahertz source. Here we demonstrate a
magnetic-field-controlled, highly-efficient, cost-effective, and broadband
terahertz source with flexible switch of terahertz polarization states in
ferromagnetic heterostructures driven by femtosecond laser pulses. We verify
that the chirality, azimuthal angle, and ellipticity of the generated
elliptical terahertz waves can be independently manipulated by delicately
engineering of the external applied magnetic fields via effectively
manipulating the photo-induced spin currents. Such an ultrafast photomagnetic
interaction-based, magnetic-field-controlled, and broadband tunable solid-state
terahertz source integrated with terahertz polarization tunability function not
only has the capability to reveal physical mechanisms of femtosecond spin
dynamics, but also demonstrates the feasibility to realize novel on-chip
terahertz functional devices, boosting the potential applications for
controlling elementary molecular rotations, phonon vibrations, spin
precessions, high-speed terahertz communication, and accelerating the
development of ultrafast terahertz opto-spintronics.",1809.10474v1
2018-11-19,Magnetic Excitations in Non-Collinear Antiferromagnetic Weyl Semimetal $\mathsf{Mn_{3}Sn}$,"$\mathsf{Mn_{3}Sn}$ has recently attracted considerable attention as a
magnetic Weyl semimetal exhibiting concomitant transport anomalies at room
temperature. The topology of the electronic bands, their relation to the
magnetic ground state and their nonzero Berry curvature lie at the heart of the
problem. The examination of the full magnetic Hamiltonian reveals otherwise
hidden aspects of these unusual physical properties. Here, we report the full
spin wave spectra of $\mathsf{Mn_{3}Sn}$ measured over a wide momentum - energy
range by the inelastic neutron scattering technique. Using a linear spin wave
theory, we determine a suitable magnetic Hamiltonian which not only explains
the experimental results but also stabilizes the low-temperature helical phase,
consistent with our DFT calculations. The effect of this helical ordering on
topological band structures is further examined using a tight-binding method,
which confirms the elimination of Weyl points in the helical phase. Our work
provides a rare example of the intimate coupling between the electronic and
spin degrees of freedom for a magnetic Weyl semimetal system.",1811.07549v1
2018-11-28,Effect of magnetic anisotropy on Skyrmions with a high topological number in itinerant magnets,"We report our numerical results for the effect of magnetic anisotropy on a
Skyrmion crystal with a high topological number of two, which was recently
discovered in an itinerant electron model [R. Ozawa, S. Hayami, and Y. Motome,
Phys. Rev. Lett. 118, 147205 (2017)]. By performing numerical simulations based
on the kernel polynomial method and the Langevin dynamics for the Kondo lattice
model on a triangular lattice, we find that the topological property remains
robust against the single-ion anisotropy, while the magnetic texture is
deformed continuously. The resultant spin structure is characterized by three
wave numbers (triple-$Q$ state), in which the $xy$ component of spins forms a
magnetic vortex crystal and the $z$ component of spins behaves a sinusoidal
wave. For larger anisotropy, we show that the system exhibits a phase
transition from the Skyrmion crystal to topologically trivial phases with
vanishing scalar chirality: a single-$Q$ collinear and double-$Q$ noncoplanar
states for the easy-axis and easy-plane anisotropy, respectively. We also
examine the effect of the single-ion anisotropy in an external magnetic field,
and find that the field range of the Skyrmion crystal is rather insensitive to
the anisotropy, in contrast to another Skyrmion crystal with the topological
number of one whose field range is considerably extended (reduced) by the
easy-axis (easy-plane) anisotropy.",1811.11336v1
2019-11-28,Magnon damping in the zigzag phase of the Kitaev-Heisenberg-$Γ$ model on a honeycomb lattice,"We calculate magnon dispersions and damping in the Kitaev-Heisenberg model
with an off-diagonal exchange $\Gamma$ and isotropic third-nearest-neighbor
interaction $J_3$ on a honeycomb lattice. This model is relevant to a
description of the magnetic properties of iridium oxides $\alpha$-Li$_2$IrO$_3$
and Na$_2$IrO$_3$, and Ru-based materials such as $\alpha$-RuCl$_3$. We use an
unconventional parametrization of the spin-wave expansion, in which each
Holstein-Primakoff boson is represented by two conjugate hermitian operators.
This approach gives us an advantage over the conventional one in identifying
parameter regimes where calculations can be performed analytically. Focusing on
the parameter regime with the zigzag spin pattern in the ground state that is
consistent with experiments, we demonstrate that one such region is $\Gamma =
K>0$, where $K$ is the Kitaev coupling. Within our approach we are able to
obtain explicit analytical expressions for magnon energies and eigenstates and
go beyond the standard linear spin-wave theory approximation by calculating
magnon damping and demonstrating its role in the dynamical structure factor. We
show that the magnon damping effects in both Born and self-consistent
approximations are very significant, underscoring the importance of non-linear
magnon coupling in interpreting broad features in the neutron-scattering
spectra.",1911.12829v2
2017-05-31,Lattice and spin dynamics in a low-symmetry antiferromagnet NiWO$_4$,"Lattice and magnetic dynamics of NiWO$_4$ single crystals were studied with
the use of polarized Raman spectroscopy in a wide temperature range of 10-300 K
including the antiferromagnetic ordering temperature $T_N$=62 K. Static
magnetic measurements were used for characterizing the single crystals. All
Raman-active phonons predicted by the group theory were observed and
characterized. Magnetic symmetry analysis was used to determine possible
magnetic space groups for NiWO$_4$ which can be also applied to any other
isostructural crystal with the same magnetic propagation vector k=(1/2,0,0).
Though the magnetic structure of NiWO$_4$ is relatively simple, a rich set of
narrow and broad magnetic excitations with different polarization properties
and temperature behavior in the very broad frequency range of 10-200 cm$^{-1}$
was observed, with some modes surviving at temperatures much higher than $T_N$
up to 220 K. Part of the magnetic excitations was identified as acoustic and
optical spin-wave branches which allow us to construct exchange structure and
estimate exchange and anisotropy constants with the use of linear spin-wave
theory. Since the magnetic structure can be described as exchange-coupled AFM
chains of $S=1$ ions, previously unobserved magnetic excitation at 24 cm$^{-1}$
is tentatively assigned to a Haldane gap mode.",1705.11137v1
2018-09-30,Exactly Solvable Points and Symmetry-Protected Topological Phases of Quantum Spins on a Zig-Zag Lattice,"A large number of symmetry-protected topological (SPT) phases have been
hypothesized for strongly interacting spin-1/2 systems in one dimension.
Realizing these SPT phases, however, often demands fine-tunings hard to reach
experimentally. And the lack of analytical solutions hinders the understanding
of their many-body wave functions. Here we show that two kinds of SPT phases
naturally arise for ultracold polar molecules confined in a zigzag optical
lattice. This system, motivated by recent experiments, is described by a spin
model whose exchange couplings can be tuned by an external field to reach
parameter regions not studied before for spin chains or ladders. Within the
enlarged parameter space, we find the ground state wave function can be
obtained exactly along a line and at a special point, for these two phases
respectively. These exact solutions provide a clear physical picture for the
SPT phases and their edge excitations. We further obtain the phase diagram by
using infinite time-evolving block decimation, and discuss the phase
transitions between the two SPT phases and their experimental signatures.",1810.00325v2
2018-10-10,Quantitative agreement of Dzyaloshinskii-Moriya interactions for domain-wall motion and spin-wave propagation,"The magnetic exchange interaction is the one of the key factors governing the
basic characteristics of magnetic systems. Unlike the symmetric nature of the
Heisenberg exchange interaction, the interfacial Dzyaloshinskii-Moriya
interaction (DMI) generates an antisymmetric exchange interaction which offers
challenging opportunities in spintronics with intriguing antisymmetric
phenomena. The role of the DMI, however, is still being debated, largely
because distinct strengths of DMI have been measured for different magnetic
objects, particularly chiral magnetic domain walls (DWs) and non-reciprocal
spin waves (SWs). In this paper, we show that, after careful data analysis,
both the DWs and SWs experience the same strength of DMI. This was confirmed by
spin-torque efficiency measurement for the DWs, and Brillouin light scattering
measurement for the SWs. This observation, therefore, indicates the unique role
of the DMI on the magnetic DW and SW dynamics and also guarantees the
compatibility of several DMI-measurement schemes recently proposed.",1810.04375v1
2012-09-17,Ultrafast quasiparticle dynamics in superconducting iron pnictide CaFe1.89Co0.11As2,"Nonequilibrium quasiparticle relaxation dynamics is reported in
superconducting CaFe1.89Co0.11As2 single crystal using femtosecond
time-resolved pump-probe spectroscopy. The carrier dynamics reflects a
three-channel decay of laser deposited energy with characteristic time scales
varying from few hundreds of femtoseconds to order of few nanoseconds where the
amplitudes and time-constants of the individual electronic relaxation
components show significant changes in the vicinity of the spin density wave
(T_SDW ~ 85 K) and superconducting (T_SC ~ 20 K) phase transition temperatures.
The quasiparticles dynamics in the superconducting state reveals a charge gap
with reduced gap value of 2$\Delta$_0/k_BT_SC ~ 1.8. We have determined the
electron-phonon coupling constant $\lemda$ to be ~ 0.14 from the temperature
dependent relaxation time in the normal state, a value close to those reported
for other types of pnictides. From the peculiar temperature-dependence of the
carrier dynamics in the intermediate temperature region between the
superconducting and spin density wave phase transitions, we infer a temperature
scale where the charge gap associated with the spin ordered phase is maximum
and closes on either side while approaching the two phase transition
temperatures.",1209.3551v2
2018-01-31,SU(4)-symmetric spin-orbital liquids on the hyperhoneycomb lattice,"We study the effective spin-orbital model that describes the magnetism of
4$d^1$ or 5$d^1$ Mott insulators in ideal tricoordinated lattices. In the limit
of vanishing Hund's coupling, the model has an emergent SU(4) symmetry which is
made explicit by means of a Klein transformation on pseudospin degrees of
freedom. Taking the hyperhoneycomb lattice as an example, we employ parton
constructions with fermionic representations of the pseudospin operators to
investigate possible quantum spin-orbital liquid states. We then use
variational Monte Carlo (VMC) methods to compute the energies of the projected
wave functions. Our numerical results show that the lowest-energy quantum
liquid corresponds to a zero-flux state with a Fermi surface of four-color
fermionic partons. In spite of the Fermi surface, we demonstrate that this
state is stable against tetramerization. A combination of linear flavor wave
theory and VMC applied to the complete microscopic model also shows that this
liquid state is stable against the formation of collinear long-range order.",1802.00044v3
2018-08-08,Electromagnetic Emission from newly-born Magnetar Spin-Down by Gravitational-Wave and Magnetic Dipole Radiations,"A newly-born magnetar is thought to be central engine of some long gamma-ray
bursts (GRBs). We investigate the evolution of the electromagnetic (EM)
emission from the magnetic dipole (MD) radiation wind injected by spin-down of
a newly-born magnetar via both quadrupole gravitational-wave (GW) and MD
radiations. We show that the EM luminosity evolves as $L_{\rm em}\propto
(1+t/\tau_c)^{\alpha}$, and $\alpha$ is $-1$ and $-2$ in the GW and MD
radiation dominated scenarios, respectively. Transition from the GW to MD
radiation dominated epoch may show up as a smooth break with slope changing
from $-1$ to $-2$. If the magnetar collapses to a black hole before $\tau_c$,
the MD radiation should be shut down, then the EM light curve should be a
plateau followed by a sharp drop. The expected generic light curve in this
paradigm is consistent with the canonical X-ray light curve of {\em Swift} long
GRBs. The X-ray emission of several long GRBs are identified and interpreted as
magnetar spin-down via GW or MD, as well as constrain the physical parameters
of magnetar. The combination of MD emission and GRB afterglows may make the
diversity of the observed X-ray light curves. This may interpret the observed
chromatic behaviors of the X-ray and optical afterglow light curves and the
extremely low detection rate of a jet-like break in the X-ray afterglow light
curves of long GRBs.",1808.04241v1
2018-12-22,A first search for a stochastic gravitational-wave background from ultralight bosons,"In this work, we develop a Bayesian data analysis framework to study the SGWB
from bosonic clouds using data from Advanced LIGO and Advanced Virgo, building
on previous work by Brito et.al (2017). We further improve this model by adding
a BH population of binary merger remnants. To assess the performance of our
pipeline, we quantify the range of boson masses that can be constrained by
Advanced LIGO and Advanced Virgo measurements at design sensitivity.
Furthermore, we explore our capability to distinguish an ultralight boson SGWB
from a stochastic signal due to distant compact binary coalescences (CBC).
Finally, we present results of a search for the SGWB from bosonic clouds using
data from Advanced LIGO's first observing run. We find no evidence of such a
signal. Due to degeneracies between the boson mass and unknown astrophysical
quantities such as the distribution of isolated BH spins, our analysis cannot
robustly exclude the presence of a bosonic field at any mass. Nevertheless, we
show that under optimistic assumptions about the BH formation rate and spin
distribution, boson masses in the range $ \SI{2.0e-13}{eV}\leq
m_\mathrm{b}\leq\SI{3.8e-13}{eV} $ are excluded at 95% credibility, although
with less optimistic spin distributions, no masses can be excluded. The
framework established here can be used to learn about the nature of fundamental
bosonic fields with future gravitational wave observations.",1812.09622v1
2019-02-01,Charge density wave and spin $1/2$ insulating state in single layer 1T-NbS$_2$,"In bulk samples and few layer flakes, the transition metal dichalcogenides
NbS$_2$ and NbSe$_2$ assume the H polytype structure with trigonal prismatic
coordination of the Nb atom. Recently, however, single and few layers of
1T-NbSe$_2$ with octahedral coordination around the transition metal ion were
synthesized. Motivated by these experiments and by using first-principles
calculations, we investigate the structural, electronic and dynamical
properties of single layer 1T-NbS$_2$. We find that single-layer 1T-NbS$_2$
undergoes a $\sqrt{13}\times\sqrt{13}$ star-of-David charge density wave.
Within the generalized gradient approximation, the weak interaction between the
stars leads to an ultraflat band at the Fermi level isolated from all other
bands. The spin-polarized generalized gradient approximation stabilizes a total
spin $1/2$ magnetic state with opening of a $0.15$ eV band gap and a
$0.21\mu_B$ magnetic moment localized on the central Nb in the star. Within
GGA+U, the magnetic moment on the central Nb is enhanced to $0.41\mu_{B}$ and a
larger gap occurs. Most important, this approximation gives a small energy
difference between the 1T and 1H polytypes (only $+0.5$ mRy/Nb), suggesting
that the 1T-polytype can be synthesized in a similar way as done for single
layer 1T-NbSe$_2$. Finally we compute first and second nearest neighbors
magnetic inter-star exchange interactions finding $J_1$=9.5~K and $J_2$=0.4~K
ferromagnetic coupling constants.",1902.00234v1
2020-04-14,Computationally efficient models for the dominant and sub-dominant harmonic modes of precessing binary black holes,"We present IMRPhenomXPHM, a phenomenological frequency-domain model for the
gravitational-wave signal emitted by quasi-circular precessing binary black
holes, which incorporates multipoles beyond the dominant quadrupole in the
precessing frame. The model is a precessing extension of IMRPhenomXHM
(Garc\'ia-Quir\'os 2020), based on approximate maps between aligned-spin
waveform modes in the co-precessing frame and precessing waveform modes in the
inertial frame, which is commonly referred to as ""twisting up"" the
non-precessing waveforms. IMRPhenomXPHM includes IMRPhenomXP as a special case,
the restriction to the dominant quadrupole contribution in the co-precessing
frame. We implement two alternative mappings, one based on a single-spin PN
approximation, as used in IMRPhenomPv2 (Hannam 2013), and one based on the
double-spin MSA approach (Chatziioannou 2017). We include a detailed discussion
of conventions used in the description of precessing binaries and of all
choices made in constructing the model. The computational cost of \phXPHM is
further reduced by extending the interpolation technique of (C.
Garc\'ia-Quir\'os 2020) to the Euler angles. The accuracy, speed, robustness
and modularity of the IMRPhenomX family will make these models productive tools
for gravitational wave astronomy in the current era of greatly increased number
and diversity of detected events.",2004.06503v2
2020-04-23,To power the X-ray plateaus of gamma-ray bursts through larger amplitude electromagnetic waves,"The origin of gamma-ray burst (GRB) X-ray plateau, especially the internal
plateau, is still unclear, but it could be related to GRB's central engine of
magnetar. It is generally believed that the spin-down power of the magnetar is
injected into forward external shock, however we propose here that most of the
power will be dissipated behind the GRB jet through larger amplitude
electromagnetic wave (LAEMW). Based on this proposal, the relevant physical
conditions and observational implications are analyzed and discussed, and
various kinds of X-ray light curves could be reproduced. Although it is still a
matter of debate about the chromatic multi-band afterglow in the standard
external afterglow fireball model, we can explain naturally this feature under
this proposal, i.e., the electrons generating the X-ray plateau and emitting
the optical afterglow are accelerated by different mechanisms. %Furthermore, we
predict that the X-ray emission of spin-down wind could possibly precede the
prompt emission of GRB jet if the energy of LAEMW is dissipated first but
shock-induced radiation in the jet is produced later. It is emphasized that
both the GRB jet and the spin-down wind should have significant observational
consequences in the magnetar scenario, and should be focused equally in GRB
physics.",2004.12808v3
2020-08-25,Longitudinal and anomalous Hall conductivity of a general two-band model,"We derive and analyze the longitudinal and the anomalous Hall conductivity
for a general momentum-block-diagonal two-band model. This model captures a
broad spectrum of physically very different systems including N\'eel
antiferromagnetic and spiral spin density waves as well as models that involve
spin-orbit interaction and are known to show topological properties. We present
a complete microscopic derivation for finite temperature and constant
scattering rate $\Gamma$ that is diagonal and equal, but arbitrarily large for
both bands. We identify two criteria that allow for a unique and physically
motivated decomposition of the conductivities. On the one hand, we distinguish
intraband and interband contributions that are defined by the involved
quasiparticle spectral functions. On the other hand, we distinguish symmetric
and antisymmetric contributions that are defined by the symmetry under the
exchange of the current and the electric field directions. The (symmetric)
intraband contributions generalize the formula of standard Boltzmann transport
theory, which is valid only in the clean limit (small $\Gamma$), whereas the
interband contributions capture interband coherence effects beyond independent
quasiparticles. We show that the symmetric interband contribution is a
correction only present for finite $\Gamma$ and is controlled by the quantum
metric. The antisymmetric interband contributions generalize the formula of the
anomalous Hall conductivity in terms of the Berry curvature to finite $\Gamma$.
We study the clean (small $\Gamma$) and dirty (large $\Gamma$) limit
analytically. The connection between the presented derivation and the Bastin
and Streda formalism is given. We apply our results to a Chern insulator, a
ferromagnetic multi-d-orbital, and a spiral spin density wave model.",2008.11218v2
2016-03-23,Multi-photon transitions and Rabi resonance in continuous wave EPR,"The study of microwave and radiofrequency multi-photon transitions in
continuous wave (CW) EPR spectroscopy is extended to a Rabi resonance
condition, when the radio frequency of the magnetic-field modulation matches
the Rabi frequency of a spin system in the microwave field. Using the
non-secular perturbation theory based on the Bogoliubov averaging method, the
analytical description of the response of the spin system is derived for all
modulation frequency harmonics. When the modulation frequency exceeds the EPR
linewidth, multi-photon transitions result in sidebands in absorption EPR
spectra measured with phase-sensitive detection at any harmonic. The saturation
of different-order multi-photon transitions is shown to be significantly
different and to be sensitive to the Rabi resonance. The noticeable frequency
shifts of sidebands are found to be the signatures of this resonance. The
inversion of two-photon lines in some spectral intervals of the out-of-phase
first-harmonic signal is predicted under passage through the Rabi resonance.
The inversion indicates the transition from absorption to stimulated emission
or vice versa, depending on the sideband. The manifestation of the primary and
secondary Rabi resonance is also demonstrated in time-resolved steady-state EPR
signals formed by all harmonics of the modulation frequency. Our results
provide a theoretical framework for future developments in multi-photon CW EPR
spectroscopy, which can be useful for samples with long spin relaxation times
and extremely narrow EPR lines",1603.07228v1
2016-12-22,Bismuth iron garnet Bi3Fe5O12: a room temperature magnetoelectric material,"The possibility to control the magnetic properties of a material with an
electric field at room temperature is highly desirable for modern applications.
Moreover, a coupling between magnetic and electric orders within a single
material presenting a wide range of exceptional physical properties, such as
bismuth iron garnet (BIG), may lead to great advances in the field of
spintronic applications. In particular, the combination of the magnetoelectric
(ME) coupling with the low damping of spin waves in BIG can allow the control
and manipulation of spin waves by an electric field in magnonic devices. Here
we report the unambiguous observation of linear magnetoelectric coupling above
300 K in BIG using ferromagnetic resonance technique with electric field
modulation. The measured coupling value is comparable with that observed for
prototypal magnetoelectric Cr2O3. On the basis of our experimental results, the
strength of this linear ME coupling is directly linked to the presence of
bismuth ions inducing strong spin orbit coupling and to the appearance of local
magnetic inhomogeneities related to the magnetic domain structure. The
unprecedented combination of magnetic, optical and magnetoelectrical properties
in BIG is expected to trigger significant interest for technological
applications as well as for theoretical studies.",1612.07531v3
2019-05-10,Rossby Wave Instability and High-Frequency Quasi-Periodic Oscillations in accretion discs orbiting around black holes,"The rather elusive High-Frequency Quasi-Periodic Oscillations(HFQPO) observed
in the X-ray lightcurve of black holes have been seen in a wide range of
frequencies, even within one source. It is also notable to have been detected
in ""pairs"" of HFQPOs with a close to integer ratio between the frequencies. The
aim of this paper is to investigate some of the possible observable that we
could obtain from having the Rossby Wave Instability (RWI) active in the
accretion disc surrounding the compact object.
  Using the newly developed GR-AMRVAC code able to follow the evolution of the
RWI in a full general relativistic framework, we explore how RWI can reproduce
observed HFQPO frequencies ratios and if it is compatible with the
observations. In order to model the emission coming from the disc we have
linked our general relativistic simulations to the general relativistic
ray-tracing GYOTO code and delivered synthetic observables that can be
confronted to actual data from binary systems hosting HFQPOs.}{We have
demonstrated in our study that some changes in the physical conditions
prevailing in the part of the disc where RWI can be triggered leads to various
dominant RWI modes whose ratio recovers frequency ratios observed in various
X-ray binary systems. In addition, we have also highlighted that when RWI is
triggered near the last stable orbit of a spinning black hole, the amplitude of
the X-ray modulation increases with the spin of the black hole. Revisiting
published data on X-ray binary systems, we show that this type of relationship
actually exists in the five systems where an indirect measure of the spin of
the black hole is available.",1905.03984v1
2020-03-03,Van Hove singularity in the magnon spectrum of the antiferromagnetic quantum honeycomb lattice,"The magnetic excitation spectrum of the quantum magnet YbCl$_3$ is studied
with inelastic neutron scattering. The spectrum exhibits an unusually sharp
feature within a broad continuum, as well as conventional spin waves. By
including both transverse and longitudinal channels of the neutron response,
linear spin wave theory with a single Heisenberg interaction on the honeycomb
lattice reproduces all of the key features in the spectrum. In particular, the
broad continuum corresponds to a two-magnon contribution from the longitudinal
channel, while the sharp feature within this continuum is identified as a Van
Hove singularity in the joint density of states, which indicates the
two-dimensional nature of the two-magnon continuum. We term these singularities
magneto-caustic features in analogy with caustic features in ray optics where
focused envelopes of light are generated when light passes through or reflects
from curved or distorted surfaces. The experimental demonstration of a sharp
Van Hove singularity in a two-magnon continuum is important because analogous
features in potential two-spinon continua could distinguish quantum spin
liquids from merely disordered systems. These results establish YbCl$_3$ as a
nearly ideal two-dimensional honeycomb lattice material hosting strong quantum
effects in the unfrustrated limit.",2003.01754v1
2020-09-11,Eccentricity Estimate for Black Hole Mergers with Numerical Relativity Simulations,"The origin of black hole mergers discovered by the LIGO and Virgo
gravitational-wave observatories is currently unknown. GW190521 is the heaviest
black hole merger detected so far. Its observed high mass and possible
spin-induced orbital precession could arise from the binary having formed
following a close encounter. An observational signature of close encounters is
eccentric binary orbit; however, this feature is currently difficult to
identify due to the lack of suitable gravitational waveforms. No eccentric
merger has been previously found. Here we report 611 numerical relativity
simulations covering the full eccentricity range and an estimation approach to
probe the eccentricity of mergers. Our set of simulations corresponds to $\sim
10^5$ waveforms, comparable to the number used in gravitational wave searches,
albeit with coarser mass-ratio and spin resolution. We applied our approach to
GW190521 and found that it is the most consistent with a highly eccentric
($e=0.69^{+0.17}_{-0.22}$; 90% credible level) merger within our set of
waveforms. This interpretation is supported over a non-eccentric merger with
$>10$ Odds ratio if $\gtrsim10\%$ of GW190521-like mergers are highly
eccentric. Detectable orbital eccentricity would be evidence against an
isolated binary origin, which is otherwise difficult to rule out based on
observed mass and spin.",2009.05461v2
2020-11-20,Simulation of the orbit and spin period evolution of the double pulsars PSR J0737-3039 from their birth to coalescence induced by the gravitational wave radiation,"The complete orbital and sin period evolutions of the double neutron star
(NS) system PSR J0737-3039 are simulated from the birth to coalescence, which
include the two observed radio pulsars classified as primary NS PSR J0737-3039A
and companion NS PSR J0737-3039B. By employing the characteristic age of PSR
J0737-3039B to constrain the true age of the double pulsar system, the initial
orbital period and initial binary separation are obtained as 2.89 hrs and $1.44
\times 10^{6}$ km, respectively, and the coalescence age or the lifetime from
the birth to merger of PSR J0737-3039 is obtained to be $1.38 \times 10^{8}$
yr. At the last minute of coalescence, corresponding to that the gravitational
wave frequency changes from 20 Hz to 1180 Hz, we present the binary separation
of PSR J0737-3039 to be from 442 km to 30 km, while the spin periods of PSR
J0737-3039A and PSR J0737-3039B are 27.10 ms and 4.63 s, respectively. From the
standard radio pulsar emission model, before the system merged, the primary NS
could still be observed by the radio telescope, while the companion NS has
crossed the death line in the pulsar magnetic-field versus period ($B-P$)
diagram which is usually considered to cease the life as a pulsar. It is for
the first time that the whole life evolutionary simulation of the orbit and
spin periods for double NS system is presented, which provides the useful
information for observing the primary NS at the coalescence stage.",2011.10193v1
2021-02-11,Enhancing modified gravity detection from gravitational-wave observations using the Parametrized ringdown spin expansion coefficients formalism,"Harvesting the full potential of black hole spectroscopy demands realising
the importance of casting constraints on modified theories of gravity in a
framework as general and robust as possible. Requiring more stringent -- yet
well-motivated -- beyond General Relativity (GR) parametrizations improves the
inference drawn from available GW data, substantially decreasing the errors on
deviation parameters. This implies a reduction in the number of signals needed
to detect a deviation from GR predictions and an increase of the number of
GR-violating coefficients that can be meaningfully constrained with a given
number of signals. To this end, we apply to LIGO-Virgo observations a high-spin
version of the Parametrized ringdown spin expansion coefficients (ParSpec)
formalism, encompassing large classes of modified theories of gravity. We
constrain the lowest-order perturbative deviation of the fundamental ringdown
frequency to be $\delta\omega^{0}_{220} = {-0.05}^{+0.05}_{-0.05}$, when
assuming adimensional beyond-GR couplings, substantially improving upon
previously published results. We also establish upper bounds $\ell_{p=2} < 23
\, \mathrm{km}$, $\ell_{p=4} < 35 \, \mathrm{km}$, $\ell_{p=6} < 42 \,
\mathrm{km}$ on the scale $\ell_p$ at which the appearance of new physics is
disfavoured, depending on the mass dimension $p$ of the ringdown coupling.
These bounds exceed the ones obtained by previous analyses or are competitive
with existing ones, depending on the specific alternative theory considered,
and promise to quickly improve as the number of detectors, sensitivity and
duty-cycle of the gravitational-wave network steadily increases.",2102.05939v2
2021-04-14,"Numerical-relativity simulations of the quasi-circular inspiral and merger of non-spinning, charged black holes: methods and comparison with approximate approaches","We present fully general relativistic simulations of the quasi-circular
inspiral and merger of charged, non-spinning, binary black holes with
charge-to-mass ratio $\lambda \le 0.3$. We discuss the key features that
enabled long term and stable evolutions of these binaries. We also present a
formalism for computing the angular momentum carried away by electromagnetic
waves, and the electromagnetic contribution to black-hole horizon properties.
We implement our formalism and present the results for the first time in
numerical-relativity simulations. In addition, we compare our full non-linear
solutions with existing approximate models for the inspiral and ringdown
phases. We show that Newtonian models based on the quadrupole approximation
have errors of 20 % - 100 % in key gauge-invariant quantities. On the other
hand, for the systems considered, we find that estimates of the remnant black
hole spin based on the motion of test particles in Kerr-Newman spacetimes agree
with our non-linear calculations to within a few percent. Finally, we discuss
the prospects for detecting black hole charge by future gravitational-wave
detectors using either the inspiral-merger-ringdown signal or the ringdown
signal alone.",2104.06978v2
2021-08-17,On the Terminal Spins of Accreting Stars and Planets: Boundary Layers,"The origin of the spins of giant planets is an open question in astrophysics.
As planets and stars accrete from discs, if the specific angular momentum
accreted corresponds to that of a Keplerian orbit at the surface of the object,
it is possible for planets and stars to be spun up to near-breakup speeds.
However, accretion cannot proceed onto planets and stars in the same way that
accretion proceeds through the disk. For example, the magneto-rotational
instability cannot operate in the region between the nearly-Keplerian disk and
more slowly-rotating surface because of the sign of the angular velocity
gradient. Through this boundary layer where the angular velocity sharply
changes, mass and angular momentum transport is thought to be driven by
acoustic waves generated by global supersonic shear instabilities and vortices.
We present the first study of this mechanism for angular momentum transport
around rotating stars and planets using 2D vertically-integrated moving-mesh
simulations of ideal hydrodynamics. We find that above rotation rates of
$\sim0.4-0.6$ times the Keplerian rate at the surface, depending on the gas
sound speed, the rate at which angular momentum is transported inwards through
the boundary layer by waves decreases by $\sim1-3$ orders of magnitude. We also
find that the accretion rate through the boundary layer decreases
commensurately and becomes less variable for faster-rotating objects. Our
results provide a purely hydrodynamic mechanism for limiting the spins of
accreting planets and stars to factors of a few less than the breakup speed.",2108.07811v1
2021-08-24,Kramers-Weyl fermions in the chiral charge density wave material (TaSe$_4$)$_2$I,"The quasi-one-dimensional chiral charge density wave (CDW) material
(TaSe$_4$)$_2$I has been recently predicted to host Kramers-Weyl (KW) fermions
which should exist in the vicinity of high symmetry points in the Brillouin
zone in chiral materials with strong spin-orbit coupling. However, direct
spectroscopic evidence of KW fermions is limited. Here we use
helicity-dependent laser-based angle resolved photoemission spectroscopy
(ARPES) in conjunction with tight-binding and first-principles calculations to
identify KW fermions in (TaSe$_4$)$_2$I. We find that topological and symmetry
considerations place distinct constraints on the (pseudo-) spin texture and the
observed spectra around a KW node. We further reveal an interplay between the
spin texture around the chiral KW node and the onset of CDW order in
(TaSe$_4$)$_2$I. Our findings highlight the unique topological nature of
(TaSe$_4$)$_2$I and provide a pathway for identifying KW fermions in other
chiral materials.",2108.10874v1
2021-10-06,Generalized dynamical mean-field theory of two-subalttice systems with non-local interactions and its application to study charge and spin correlations in graphene,"We investigate magnetic and charge correlations in graphene by using the
formulation of extended dynamical mean-field theory (E-DMFT) for two-sublattice
systems. First, we map the average non-local interaction onto the effective
static interaction between different sublattices, which is treated together
with the local interaction within an effective ""two-orbital"" local model. The
remaining part of the non-local interaction is considered by introducing an
effective retarded interaction within the E-DMFT approach. The non-local
susceptibilities in charge and spin channel are further evaluated in the ladder
approximation. We verify the applicability of the proposed method to describe
the effect of uniformly screened long-range Coulomb potential $\propto 1/r$, as
well as screened realistic long-range electron interaction [T. O. Wehling et
al., Phys. Rev. Lett. 106, 236805 (2011)] in graphene. We show that the
developed approach describes a competition of semimetal, spin density wave
(SDW), and charge-density-wave (CDW) correlations. The obtained phase diagram
is in a good agreement with recent results of functional renormalization group
(fRG) for finite large graphene nanoflakes and scaling analysis of quantum
Monte Carlo data on finite clusters. Similarly to the previously obtained
results within the fRG approach, the realistic screening of Coulomb interaction
by $\sigma$ bands causes moderate (strong) enhancement of critical long-range
interaction strength, needed for the SDW (CDW) instability, compared to the
results for the uniformly screened Coulomb potential.",2110.02806v2
2021-10-07,Angular emission patterns of remnant black holes,"The gravitational radiation from the ringdown of a binary black hole merger
is described by the solution of the Teukolsky equation, which predicts both the
temporal dependence and the angular distribution of the emission. Many studies
have explored the temporal feature of the ringdown wave through black hole
spectroscopy. In this work, we further study the spatial distribution, by
introducing a global fitting procedure over both temporal and spatial
dependences, to propose a more complete test of General Relativity. We show
that spin-weighted spheroidal harmonics are the better representation of the
ringdown angular emission patterns compared to spin-weighted spherical
harmonics. The differences are distinguishable in numerical relativity
waveforms. We also study the correlation between progenitor binary properties
and the excitation of quasinormal modes, including higher-order angular modes,
overtones, prograde and retrograde modes. Specifically, we show that the
excitation of retrograde modes is dominant when the remnant spin is
anti-aligned with the binary orbital angular momentum. This study seeks to
provide an analytical strategy and inspire the future development of ringdown
test using real gravitational wave events.",2110.03116v2
2016-11-14,Coherence time of over a second in a telecom-compatible quantum memory storage material,"Quantum memories for light will be essential elements in future long-range
quantum communication networks. These memories operate by reversibly mapping
the quantum state of light onto the quantum transitions of a material system.
For networks, the quantum coherence times of these transitions must be long
compared to the network transmission times, approximately 100 ms for a global
communication network. Due to a lack of a suitable storage material, a quantum
memory that operates in the 1550 nm optical fiber communication band with a
storage time greater than 1 us has not been demonstrated. Here we describe the
spin dynamics of $^{167}$Er$^{3+}:$Y$_{2}$SiO$_{5}$ in a high magnetic field
and demonstrate that this material has the characteristics for a practical
quantum memory in the 1550 nm communication band. We observe a hyperfine
coherence time of 1.3 seconds. Further, we demonstrate efficient optical
pumping of the entire ensemble into a single hyperfine state, the first such
demonstration in a rare-earth system and a requirement for broadband spin-wave
storage. With an absorption of 70 dB/cm at 1538 nm and $\Lambda$-transitions
enabling spin-wave storage, this material is the first candidate identified for
an efficient, broadband quantum memory at telecommunication wavelengths.",1611.04315v2
2017-04-13,Magnetic excitations from the two-dimensional interpenetrating Cu framework in Ba$_2$Cu$_3$O$_4$Cl$_2$,"We report detailed neutron scattering studies on Ba$_2$Cu$_3$O$_4$Cl$_2$. The
compound consists of two interpenetrating sublattices of Cu, labeled as
Cu$_{\rm A}$ and Cu$_{\rm B}$, each of which forms a square-lattice Heisenberg
antiferromagnet. The two sublattices order at different temperatures and
effective exchange couplings within the sublattices differ by an order of
magnitude. This yields an inelastic neutron spectrum of the Cu$_{\rm A}$
sublattice extending up to 300 meV and a much weaker dispersion of Cu$_{\rm B}$
going up to around 20 meV. Using a single-band Hubbard model we derive an
effective spin Hamiltonian. From this, we find that linear spin-wave theory
gives a good description to the magnetic spectrum. In addition, a magnetic
field of 10 T is found to produce effects on the Cu$_{\rm B}$ dispersion that
cannot be explained by conventional spin-wave theory.",1704.04287v2
2017-04-17,Black Hole Superradiance Signatures of Ultralight Vectors,"The process of superradiance can extract angular momentum and energy from
astrophysical black holes (BHs) to populate gravitationally-bound states with
an exponentially large number of light bosons. We analytically calculate
superradiant growth rates for vectors around rotating BHs in the regime where
the vector Compton wavelength is much larger than the BH size. Spin-1 bound
states have superradiance times as short as a second around stellar BHs,
growing up to a thou- sand times faster than their spin-0 counterparts. The
fast rates allow us to use measurements of rapidly spinning BHs in X-ray
binaries to exclude a wide range of masses for weakly-coupled spin-1 particles,
$5 \times 10^{-14} - 2 \times 10^{-11}$ eV; lighter masses in the range $6
\times 10^{-20} - 2 \times 10^{-17}$ eV start to be constrained by supermassive
BH spin measurements at a lower level of confidence. We also explore routes to
detection of new vector particles possible with the advent of gravitational
wave (GW) astronomy. The LIGO-Virgo collaboration could discover hints of a new
light vector particle in statistical analyses of masses and spins of merging
BHs. Vector annihilations source continuous monochromatic gravitational
radiation which could be observed by current GW observatories. At design
sensitivity, Advanced LIGO may measure up to thousands of annihilation signals
from within the Milky Way, while hundreds of BHs born in binary mergers across
the observable universe may superradiate vector bound states and become new
beacons of monochromatic gravitational waves.",1704.05081v2
2017-04-25,Skyrmion defects and competing singlet orders in a half-filled antiferromagnetic Kondo-Heisenberg model on the honeycomb lattice,"Due to the interaction between topological defects of an order parameter and
underlying fermions, the defects can possess induced fermion numbers, leading
to several exotic phenomena of fundamental importance to both condensed matter
and high energy physics. One of the intriguing outcome of induced fermion
number is the presence of fluctuating competing orders inside the core of
topological defect. In this regard, the interaction between fermions and
skyrmion excitations of antiferromagnetic phase can have important consequence
for understanding the global phase diagrams of many condensed matter systems
where antiferromagnetism and several singlet orders compete. We critically
investigate the relation between fluctuating competing orders and skyrmion
excitations of the antiferromagnetic insulating phase of a half-filled
Kondo-Heisenberg model on honeycomb lattice. By combining analytical and
numerical methods we obtain exact eigenstates of underlying Dirac fermions in
the presence of a single skyrmion configuration, which are used for computing
induced chiral charge. Additionally, by employing this nonperturbative
eigenbasis we calculate the susceptibilities of different translational
symmetry breaking charge, bond and current density wave orders and
translational symmetry preserving Kondo singlet formation. Based on the
computed susceptibilities we establish spin Peierls and Kondo singlets as
dominant competing orders of antiferromagnetism. We show favorable agreement
between our findings and field theoretic predictions based on perturbative
gradient expansion scheme which crucially relies on adiabatic principle and
plane wave eigenstates for Dirac fermions. The methodology developed here can
be applied to many other correlated systems supporting competition between
spin-triplet and spin-singlet orders in both lower and higher spatial
dimensions.",1704.07818v2
2019-01-17,Learning about black hole binaries from their ringdown spectra,"The coalescence of two black holes generates gravitational waves that carry
detailed information about the properties of those black holes and their binary
configuration. The final coalescence cycles are in the form of a {\it
ringdown}: a superposition of quasi-normal modes of the merged remnant black
hole. Each mode has an oscillation frequency and decay time that in general
relativity is determined by the remnant's mass and spin. Measuring the
frequency and decay time of multiple modes makes it possible to measure the
remnant's mass and spin, and to test the waves against the predictions of
gravity theories. In this {\it Letter}, we show that the relative amplitudes of
these modes encodes information about a binary's {\it geometry}. Focusing on
the large mass-ratio limit, which provides a simple-to-use tool for effectively
exploring parameter space, we demonstrate how a binary's geometry is encoded in
the relative amplitudes of these modes, and how to parameterize the modes in
this limit. Although more work is needed to assess how well this carries over
to less extreme mass ratios, our results indicate that measuring multiple
ringdown modes from coalescence may aid in measuring important source
properties, such as the misalignment of its members' spins and orbit.",1901.05900v2
2019-04-15,Comparison of first-principles methods to extract magnetic parameters in ultra-thin films: Co/Pt(111),"We compare three distinct computational approaches based on first-principles
calculations within density functional theory to explore the magnetic exchange
and the Dzyaloshinskii-Moriya interactions (DMI) of a Co monolayer on Pt(111),
namely (i) the method of infinitesimal rotations of magnetic moments based on
the Korringa-Kohn-Rostoker (KKR) Green function method, (ii) the generalized
Bloch theorem applied to spiraling magnetic structures and (iii) supercell
calculations with non-collinear magnetic moments, the latter two being based on
the full-potential linearized augmented plane wave (FLAPW) method. In
particular, we show that the magnetic interaction parameters entering
micromagnetic models describing the long-wavelength deviations from the
ferromagnetic state might be different from those calculated for fast rotating
magnetic structures, as they are obtained by using (necessarily rather small)
supercell or large spin-spiral wave-vectors. In the micromagnetic limit, which
we motivate to use by an analysis of the Fourier components of the domain-wall
profile, we obtain consistent results for the spin stiffness and DMI
spiralization using methods (i) and (ii). The calculated spin stiffness and
Curie temperature determined by subsequent Monte Carlo simulations are
considerably higher than estimated from the bulk properties of Co, a
consequence of a significantly increased nearest-neighbor exchange interaction
in the Co-monolayer (+50%). The calculated results are carefully compared with
the literature.",1904.06954v1
2019-04-25,High Spin-Wave Propagation Length Consistent with Low Damping in a Metallic Ferromagnet,"We report ultra-low intrinsic magnetic damping in
Co$_{\text{25}}$Fe$_{\text{75}}$ heterostructures, reaching the low $10^{-4}$
regime at room temperature. By using a broadband ferromagnetic resonance
technique, we extracted the dynamic magnetic properties of several
Co$_{\text{25}}$Fe$_{\text{75}}$-based heterostructures with varying
ferromagnetic layer thickness. By estimating the eddy current contribution to
damping, measuring radiative damping and spin pumping effects, we found the
intrinsic damping of a 26\,nm thick sample to be $$\alpha_{\mathrm{0}} \lesssim
3.18\times10^{-4}$. Furthermore, using Brillouin light scattering microscopy we
measured spin-wave propagation lengths of up to $(21\pm1)\,\mathrm{\mu m}$ in a
26 nm thick Co$_{\text{25}}$Fe$_{\text{75}}$ heterostructure at room
temperature, which is in excellent agreement with the measured damping.",1904.11321v3
2019-07-10,Quantum phase diagram of a frustrated spin-1/2 system on a Trellis Ladder,"We study an isotropic Heisenberg spin-1/2 model on a trellis ladder which is
composed of two $J_1-J_2$ zigzag ladders interacting through anti-ferromagnetic
rung couplings $J_3$. The $J_1$ and $J_2$ are ferromagnetic zigzag spin
interaction between two legs and anti-ferromagnetic interaction along each leg
of a zigzag ladder. A quantum phase diagram of this model is constructed using
the density matrix renormalization group (DMRG) method and linearized spin wave
analysis. In small $J_2$ limit a short range stripe collinear phase is found in
the presence of $J_3$, whereas, in the large $J_2/J_3$ limit non-collinear
quasi-long range phase is found. The system shows a short range non-collinear
state in large $J_3$ limit. The short range order phase is the dominant feature
of this phase diagram. We also show that the results obtained by DMRG and
linearized spin wave analysis show similar phase boundary between stripe
collinear and non-collinear short range phases, and the collinear phase region
shrinks with increasing $J_3$. We apply this model to understand the magnetic
properties of CaV$_2$O$_5$ and also fit the experimental data of susceptibility
and magnetization. The variation of magnetic specific heat capacity as function
of external magnetic field is also predicted. We note that $J_3$ is a dominant
interaction in this system, whereas $J_1$ and $J_2$ are approximately half of
$J_3$.",1907.04709v2
2019-07-26,Signatures of a pair density wave at high magnetic fields in cuprates with charge and spin orders,"In underdoped cuprates, the interplay of the pseudogap, superconductivity,
and charge and spin ordering can give rise to exotic quantum states, including
the pair density wave (PDW), in which the superconducting (SC) order parameter
is oscillatory in space. However, the evidence for a PDW state remains
inconclusive and its broader relevance to cuprate physics is an open question.
To test the interlayer frustration, the crucial component of the PDW picture,
we performed transport measurements on La$_{1.7}$Eu$_{0.2}$Sr$_{0.1}$CuO$_{4}$
and La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_{4}$, cuprates with ""striped"" spin and
charge orders, in perpendicular magnetic fields ($H_\perp$), and also with an
additional field applied parallel to CuO$_2$ layers ($H_\parallel$). We
detected several phenomena predicted to arise from the existence of a PDW,
including an enhancement of interlayer SC phase coherence with increasing
$H_\parallel$. Our findings are consistent with the presence of local, PDW
pairing correlations that compete with the uniform SC order at $T_{c}^{0}<
T<(2-6) T_{c}^{0}$, where $T_{c}^{0}$ is the $H=0$ SC transition temperature,
and become dominant at intermediate $H_\perp$ as $T\rightarrow 0$. These data
also provide much-needed transport signatures of the PDW in the regime where
superconductivity is destroyed by quantum phase fluctuations.",1907.11708v2
2019-09-25,Search for ultralight bosons in Cygnus X-1 with Advanced LIGO,"Ultralight scalars, if they exist as theorized, could form clouds around
rapidly rotating black holes. Such clouds are expected to emit continuous,
quasimonochromatic gravitational waves that could be detected by LIGO and
Virgo. Here we present results of a directed search for such signals from the
Cygnus X-1 binary, using data from Advanced LIGO's second observing run. We
find no evidence of gravitational waves in the 250-750 Hz band. Without
incorporating existing measurements of the Cygnus X-1 black hole spin, our
results disfavor boson masses in $6.4 \leq \mu/(10^{-13} {\rm eV}) \leq 8.0$,
assuming that the black hole was born $5 \times 10^6$ years ago with a
nearly-extremal spin. We then focus on a string axiverse scenario, in which
self-interactions enable a cloud for high black-hole spins consistent with
measurements for Cygnus X-1. In that model, we constrain the boson masses in
$9.6 \leq \mu/(10^{-13} {\rm eV}) \leq 15.5$ for a decay constant $f_a\sim
10^{15}$ GeV. Future application of our methods to other sources will yield
improved constraints.",1909.11267v3
2019-10-17,Tidal heating as a discriminator for horizons in extreme mass ratio inspirals,"The defining feature of a classical black hole is being a perfect absorber.
Any evidence showing otherwise would indicate a departure from the standard
black-hole picture. Energy and angular momentum absorption by the horizon of a
black hole is responsible for tidal heating in a binary. This effect is
particularly important in the latest stages of an extreme mass ratio inspiral
around a spinning supermassive object, one of the main targets of the future
LISA mission. We study how this effect can be used to probe the nature of
supermassive objects in a model independent way. We compute the orbital
dephasing and the gravitational-wave signal emitted by a point particle in
circular, equatorial motion around a spinning supermassive object to the
leading order in the mass ratio. Absence of absorption by the central object
can affect the gravitational-wave signal dramatically, especially at high spin.
This effect will make it possible to put an unparalleled upper bound on the
reflectivity of exotic compact objects, at the level of ${\cal O}(0.01)\%$.
This stringent bound would exclude the possibility of observing echoes in the
ringdown of a supermassive binary merger.",1910.07841v2
2019-10-30,Magnon spectrum of the Weyl semimetal half-Heusler compound GdPtBi,"The compound GdPtBi is known as a material where the non-trivial topology of
electronic bands interplays with an antiferromagnetic order, which leads to the
emergence of many interesting magnetotransport phenomena. Although the magnetic
structure of the compound has previously been reliably determined, the magnetic
interactions responsible for this type of order remained controversial. In the
present study, we employed time-of-flight inelastic neutron scattering to map
out the low-temperature spectrum of spin excitations in single-crystalline
GdPtBi. The observed spectra reveal two spectrally sharp dispersive spin-wave
modes, which reflects the multi-domain state of the $\mathbf{k} =
(\frac{1}{2}\frac{1}{2}\frac{1}{2})$ face-centred cubic antiferromagnet in the
absence of a symmetry-breaking magnetic field. The magnon dispersion reaches an
energy of $\sim 1.1$~meV and features a gap of $\sim 0.15$~meV. Using linear
spin-wave theory, we determined the main magnetic microscopic parameters of the
compound that provide good agreement between the simulated spectra and the
experimental data. We show that GdPtBi is well within the
($\frac{1}{2}\frac{1}{2}\frac{1}{2}$) phase and is dominated by second-neighbor
interactions, thus featuring low frustration.",1910.13845v2
2020-01-22,Gravitational waves from fast-spinning white dwarfs,"Two mechanisms of gravitational waves (GWs) emission in fast-spinning white
dwarfs (WDs) are investigated: accretion of matter and magnetic deformation. In
both cases, the GW emission is generated by an asymmetry around the rotation
axis of the star. However, in the first case, the asymmetry is due to the
amount of accreted matter on the magnetic poles, while in the second case it is
due to the intense magnetic field. We have estimated the GW amplitude and
luminosity for three binary systems that have a fast-spinning magnetized WD,
namely, AE Aquarii, AR Scorpii and RX J0648.0-4418. We find that, for the first
mechanism, the systems AE Aquarii and RX J0648.0-4418 can be observed by the
space detectors BBO and DECIGO if they have an amount of accreted mass of
$\delta m \geq 10^{-5}M_{\odot }$. For the second mechanism, the three systems
studied require that the WD have a magnetic field above $\sim 10^{9}$ G to emit
GWs that can be detected by BBO. We also verified that, in both mechanisms, the
gravitational luminosity has an irrelevant contribution to the spindown
luminosity of these three systems. Therefore, other mechanisms of energy
emission are needed to explain the spindown of these objects.",2001.08534v1
2020-05-20,Anomalous in-gap edge states in two-dimensional pseudospin-1 Dirac insulators,"Quantum materials that host a flat band, such as pseudospin-1 lattices and
magic-angle twisted bilayer graphene, can exhibit drastically new physical
phenomena including unconventional superconductivity, orbital ferromagnetism,
and Chern insulating behaviors. We report a surprising class of electronic
in-gap edge states in pseudospin-1 materials without the conventional need of
band-inversion topological phase transitions or introducing magnetism via an
external magnetic type of interactions. In particular, we find that, in
two-dimensional gapped (insulating) Dirac systems of massive spin-1
quasiparticles, in-gap edge modes can emerge through only an {\em electrostatic
potential} applied to a finite domain. Associated with these unconventional
edge modes are spontaneous formation of pronounced domain-wall spin textures,
which exhibit the feature of out-of-plane spin-angular momentum locking on both
sides of the domain boundary and are quite robust against boundary deformations
and impurities despite a lack of an explicit topological origin. The in-gap
modes are formally three-component evanescent wave solutions, akin to the
Jackiw-Rebbi type of bound states. Such modes belong to a distinct class due to
the following physical reasons: three-component spinor wave function, unusual
boundary conditions, and a shifted flat band induced by the external scalar
potential. Not only is the finding of fundamental importance, but it also paves
the way for generating highly controllable in-gap edge states with emergent
spin textures using the traditional semiconductor gate technology. Results are
validated using analytic calculations of a continuum Dirac-Weyl model and
tight-binding simulations of realistic materials through characterizations of
local density of state spectra and resonant tunneling conductance.",2005.10183v1
2020-12-08,Magnetic order and fluctuations in quasi-two-dimensional planar magnet Sr(Co$_{1-x}$Ni$_x$)$_2$As$_2$,"We use neutron scattering to investigate spin excitations in
Sr(Co$_{1-x}$Ni$_{x})_2$As$_2$, which has a $c$-axis incommensurate helical
structure of the two-dimensional (2D) in-plane ferromagnetic (FM) ordered
layers for $0.013\leq x \leq 0.25$. By comparing the wave vector and energy
dependent spin excitations in helical ordered
Sr(Co$_{0.9}$Ni$_{0.1}$)$_2$As$_2$ and paramagnetic SrCo$_2$As$_2$, we find
that Ni-doping, while increasing lattice disorder in
Sr(Co$_{1-x}$Ni$_{x})_2$As$_2$, enhances quasi-2D FM spin fluctuations.
However, our band structure calculations within the combined density functional
theory and dynamic mean field theory (DFT+DMFT) failed to generate a correct
incommensurate wave vector for the observed helical order from nested Fermi
surfaces. Since transport measurements reveal increased in-plane and $c$-axis
electrical resistivity with increasing Ni-doping and associated lattice
disorder, we conclude that the helical magnetic order in
Sr(Co$_{1-x}$Ni$_{x})_2$As$_2$ may arise from a quantum order-by-disorder
mechanism through the itinerant electron mediated Ruderman-Kittel-Kasuya-Yosida
(RKKY) interactions.",2012.04152v1
2020-12-10,Competing electronic orders on a heavily doped honeycomb lattice with enhanced exchange coupling,"Motivated by recent discovery of correlated insulating and superconducting
behavior in twisted bilayer graphene, we revisit graphene's honeycomb lattice
doped close to the van Hove singularity, using the truncated unity functional
renormalization group approach. We consider an extended Hubbard model on the
honeycomb lattice including on-site and nearest-neighbor Coulomb repulsions,
and nearest-neighbor ferromagnetic exchange and pair hopping interactions. By
varying the strength of the nearest-neighbor exchange coupling and Coulomb
repulsion as free parameters, we present rich ground-state phase diagrams which
contain the spin-triplet $f$-wave and spin-singlet chiral $d$-wave
superconducting phases, the commensurate and incommensurate spin- and
charge-density-wave phases, and the ferromagnetic phase. In the absence of the
exchange coupling and for small value of the nearest-neighbor repulsion, the
four-sublattice spin-density-wave phase is generated right around the van Hove
filling, while the chiral $d$-wave superconductivity emerges slightly away from
it. Surprisingly, the chiral $d$-wave superconductivity is strongly suppressed
by weak nearest-neighbor exchange coupling in our calculations. We argue that
this suppression might be one of the reasons why the chiral superconductivity
proposed for doped graphene has not yet been observed experimentally.",2012.05497v2
2020-12-24,Energy scales in 4f1 delafossite magnets: crystal-field splittings larger than the strength of spin-orbit coupling in KCeO2,"Ytterbium-based delafossites with effective S=1/2 moments are investigated
intensively as candidates for quantum spin-liquid ground states. While the
synthesis of related cerium compounds has also been reported,many important
details concerning their crystal, electronic, and magnetic structures are
unclear. Here we analyze the S=1/2 system KCeO2, combining complementary
theoretical methods. The lattice geometry was optimized and the band structure
investigated using density functional theory extended to the level of a GGA+U
calculation in order to reproduce the correct insulating behavior. The Ce 4f1
states were then analyzed in more detail with the help of ab initio
wave-function-based computations. Unusually large effective crystal-field
splittings of up to 320 meV are predicted, which puts KCeO2 in the strong field
coupling regime. Our results reveal a subtle interplay between ligand-cage
electrostatics and the trigonal field generated by the extended crystalline
surroundings, relevant in the context of recent studies on tuning the nature of
the ground-state wave function in 4f triangular-lattice and pyrochlore
compounds. It also makes KCeO2 an interesting model system in relation to the
effect of large crystal-field splittings on the anisotropy of intersite
exchange in spin-orbit coupled quantum magnets.",2012.13174v1
2021-01-25,"Partial Quantum Coherence, Ultrashort Electron Pulse Statistics, and a Plasmon-Enhanced Nanotip Emitter Based on Metallized Optical Fibers","The present dissertation covers two related research projects. The first
topic was initiated with the ultimate goal of observing quantum degeneracy in
ultrashort free electron pulses. This constitutes a thorough theoretical
analysis of the problem involving partial quantum coherence and spin
polarization of the source in light of a path-integral treatment of the
phenomenon of matter-wave diffraction-in-time. Subsequently, results of a
trailblazing experiment, to be superseded by a Hanbury Brown-Twiss type
conclusive test of free fermion antibunching with electrons, is reported. In
this experiment, the statistical distribution of the emitted electrons is
studied taking advantage of a double-detector coincidence detection technique.
The utilized electron emitters are ultrafast photoemission tungsten nanotip
needle sources which are known to procure large spatial coherence lengths. The
emission statistics is found to be sub-Poissonian. The second project involves
introduction and full characterization of a novel laser-driven electron nanotip
emitter based on metallized fiber optic tapers in which the emission mechanism
is found to be assisted by surface plasmon resonance excitation as predicted
prior to the design of such sources. It is shown that gold-coated fiber optic
nanotips can emit electrons using both low-power continuous wave lasers as well
as femtosecond pulsed lasers tuned to or near the surface plasmon resonance
excitation wavelength of the system. The final chapter entails a proposal of a
spin-polarized electron photoemitter based on the spin Hall effect for which
such a fiber optic nanotip source is exploited.",2101.09953v1
2021-07-16,Correlations in gravitational-wave reconstructions from eccentric binaries: A case study with GW151226 and GW170608,"The eccentricity of binary black-hole mergers is predicted to be an indicator
of the history of their formation. In particular, eccentricity is a strong
signature of dynamical formation rather than formation by stellar evolution in
isolated stellar systems. We investigate the efficacy of the existing
quasicircular parameter estimation pipelines to determine the source parameters
of such eccentric systems. We create a set of simulated signals with
eccentricity up to 0.3 and find that as the eccentricity increases, the
recovered mass parameters are consistent with those of a binary with up to a
$\simeq 10\%$ higher chirp mass and mass ratio closer to unity. We also employ
a full inspiral-merger-ringdown waveform model to perform parameter estimation
on two gravitational wave events, GW151226 and GW170608, to investigate this
bias on real data. We find that the correlation between the masses and
eccentricity persists in real data, but that there is also a correlation
between the measured eccentricity and effective spin. In particular, using a
nonspinning prior results in a spurious eccentricity measurement for GW151226
as it exhibits signs of nonzero black-hole spin. Performing parameter
estimation with an aligned spin, eccentric model, we constrain the
eccentricities of GW151226 and GW170608 to be $<0.15$ and $<0.12$ respectively.",2107.07981v2
2021-11-19,Evidence for subdominant multipole moments and precession in merging black-hole-binaries from GWTC-2.1,"The LIGO--Virgo--KAGRA collaborations (LVK) produced a catalogue containing
gravitational-wave (GW) observations from the first half of the third GW
observing run (O3a). This catalogue, GWTC-2.1, includes for the first time a
number of \emph{exceptional} GW candidates produced from merging
black-hole-binaries with unequivocally unequal component masses. Since
subdominant multipole moments and spin-induced orbital precession are more
likely to leave measurable imprints on the emitted GW from unequal component
mass binaries, these general relativistic phenomena may now be measurable.
Indeed, both GW190412 and GW190814 have already shown conclusive evidence for
subdominant multipole moments. This provides valuable insights into the
dynamics of the binary. We calculate the evidence for subdominant multipole
moments and spin-induced orbital precession for all merging black-hole-binaries
in GWTC-2.1 that were observed during O3a and show that (a) no
gravitational-wave candidate has measurable higher order multipole content
beyond $\ell = 3$, (b) in addition to the confident subdominant multipole
measurements in GW190412 and GW190814, GW190519\_153544 and GW190929\_012149
show marginal evidence for the $(\ell, |m|) = (3, 3)$ subdominant multipole,
(c) GW190521 may have measurable subdominant multipole content and (d) GW190412
may show evidence for spin-induced orbital precession.",2111.10455v2
2022-02-11,Ultra-Compact accurate wave functions for He-like and Li-like iso-electronic sequences and variational calculus. III. Spin-quartet state of the Lithium sequence,"As a continuation of Part I, dedicated to the ground state of He-like and
Li-like isoelectronic sequences for nuclear charges $Z \leq 20$, and Part II,
dedicated to two excited states of He-like sequence, two ultra-compact wave
functions in the form of generalized Guevara-Harris-Turbiner functions are
constructed for Li-like sequence. They describe accurately the domain of
applicability of the Quantum Mechanics of Coulomb Charges (QMCC) for energies
(2-3 significant digits (s.d.)) of the spin-quartet state $1^40^+$ of Li-like
ions (in static approximation with point-like, infinitely heavy nuclei).
Variational parameters are fitted in $Z$ by 2nd degree polynomials. The most
accurate ultra-compact function leads to the absolute accuracy $\sim
10^{-3}$\,a.u. for energy, and $\sim 10^{-4}$ for the normalized
electron-nuclear cusp parameter for $Z \leq 20$. Critical charge $Z=Z_B$, where
the ultra-compact trial function for the $1^40^+$ state looses its
square-integrability, is estimated, $Z_B(1^4\,0^+) \sim 1.26 - 1.30$. As a
complement to Part I, square integrability for the compact functions
constructed for the {\it ground, spin-doublet state} $1^2\,0^+$ of the Li-like
sequence is discussed. The critical charge, for which these functions stop to
be normalizable, is estimated as $Z_B( 1^2\,0^+) = 1.62 - 1.65$. It implies
that at $Z=2$ - the negative helium ion He${}^-$ - both states $1^2\,0^+$ and
$1^4\,0^+$ exist as states embedded to continuum.",2202.05774v1
2022-04-26,Detailed properties of gravitational-wave mergers from flyby perturbations of wide binary black holes in the field,"Wide black hole binaries (wide-BBHs; $\geqslant 10^3$ AU) in the field can be
perturbed by random stellar flybys that excite their eccentricities. Once a
wide binary is driven to a sufficiently small pericenter approach,
gravitational wave (GW) emission becomes significant, and the binary inspirals
and merges. In our previous study, using simplified models for wide-BBHs, we
found that successive flybys lead to significant merger fractions of wide-BBHs
in less than Hubble time, making the flyby perturbation mechanism a relevant
contributor to the production rate of GW-sources. However, the exact rates and
detailed properties of the resulting GW sources depend on the wide binary
progenitors. In this paper we use detailed population synthesis models for the
initial wide-BBH population, considering several populations corresponding to
different natal-kick models and metallicities, and then follow the wide-BBHs
evolution due to flyby perturbations and GW-emission. We show that the
cumulative effect of flybys is conductive for the production of GW sources in
non-negligible rates of $1-20$ Gpc$^{-3}$ yr$^{-1}$, which are sensitive to the
natal kicks model. Such rates are relevant to the observationally inferred
rate. Our models, now derived from detailed population of binaries, provide the
detailed properties of the produced GW-sources, including mass-functions and
delay times. The GW mergers are circularized when enter the aLIGO band; have a
preference for high velocity dispersion host galaxies (in particular
ellipticals); have a relatively uniform delay-time distribution; and likely
have mildly correlated (less than isolated evolution channels and more than
dynamical channels) prograde spin-spin and spin-orbits.",2204.12506v1
2022-04-29,Prospects for the observation of continuous gravitational waves from spinning neutron stars lensed by the galactic supermassive black hole,"We study the prospects of detecting continuous gravitational waves (CGWs)
from spinning neutron stars (NSs), gravitationally lensed by the galactic
supermassive black hole. Assuming various astrophysically motivated spatial
distributions of galactic NSs, we find that CGW signals from a few ($\sim 0-6$)
neutron stars should be strongly lensed. Lensing will produce two copies of the
signal (with time delays of seconds to minutes) that will interfere with each
other. The relative motion of the NS with respect to the lensing optical axis
will change the interference pattern, which will help us to identify a lensed
signal. Accounting for the magnifications and time delays of the lensed
signals, we investigate their detectability by ground-based detectors.
Modelling the spin distribution of NSs based on that of known pulsars and
assuming an ellipticity of $\epsilon = 10^{-7}$, lensed CGWs are unlikely to be
detectable by LIGO and Virgo in realistic searches involving
$\mathcal{O}(10^{12})$ templates. However, third generation detectors have a
$\sim 2-51\%$ probability of detecting at least one lensed CGW signal. For an
ellipticity of $\epsilon = 10^{-8}$, the detection probability reduces to $\sim
0-18 \, \% $. Though rare, such an observation will enable interesting probes
of the supermassive black hole and its environment.",2205.00022v3
2022-05-30,Link between Weyl-fermion chirality and spin texture,"Topological semimetals have recently attracted great attention due to
prospective applications governed by their peculiar Fermi surfaces. Weyl
semimetals host chiral fermions that manifest as pairs of non-degenerate
massless Weyl points in their electronic structure, giving rise to novel
macroscopic quantum phenomena such as the chiral anomaly, an unusual
magnetoresistance, and various kinds of Hall effects These properties enable
the engineering of non-local electric transport devices, magnetic sensors and
memories, and spintronics devices. Nevertheless, little is known about the
underlying spin- and orbital-degrees of freedom of the electron wave functions
in Weyl semimetals, that govern the electric transport. Here, we give evidence
that the chirality of the Weyl points in the Type-II Weyl semimetal MoTe$_2$ is
directly linked to the spin texture and orbital angular momentum of the
electron wave functions. By means of state-of-the-art spin- and
momentum-resolved photoemission spectroscopy the spin- and orbital texture in
the Fermi surface is directly resolved. Supported by first-principles
calculations, we examined the relationship between the topological chiral
charge and spin texture, which significantly contributes to the understanding
of the electronic structure in topological quantum materials.",2205.15252v1
2022-08-09,Fractalized magnon transport on the quasicrystal with enhanced stability,"Magnonics has been receiving significant attention in magnetism and
spintronics because of its premise for devices using spin current carried by
magnons, quanta of spin-wave excitations of a macroscopically ordered magnetic
media. Although magnonics has clear energy-wise advantage over conventional
electronics due to the absence of the Joule heating, the inherent magnon-magnon
interactions give rise to finite lifetime of the magnons which has been
hampering the efficient realizations of magnonic devices. To promote magnonics,
it is imperative to identify the delocalized magnon modes that are minimally
affected by magnon-magnon interactions and thus possess a long lifetime and use
them to achieve efficient magnon transport. Here, we suggest that quasicrystals
may offer the solution to this problem via the critical magnon modes that are
neither extended nor localized. We find that the critical magnon exhibits
fractal characteristics that are absent in conventional magnon modes in regular
solids such as a unique power-law scaling and a self-similar distribution of
distances showing perfect magnon transmission. Moreover, the critical magnons
have longer lifetimes compared to the extended ones in a periodic system, by
suppressing the magnon-magnon interaction decay rate. Such enhancement of the
magnon stability originates from the presence of the quasi-periodicity and
intermediate localization behavior of the critical magnons. Thus, we offer the
utility of quasicrystals and their critical spin wave functions in magnonics as
unique fractal transport characteristics and enhanced stability.",2208.04967v1
2022-08-11,Formation of spin and charge ordering in the extended Hubbard model during a finite-time quantum quench,"We investigate the formation of charge and spin ordering by starting from a
non-interacting state and studying how it evolves in time under a Hamiltonian
with finite electronic interactions. We consider the one-dimensional,
half-filled extended Hubbard model, which we solve within time-dependent
density matrix renormalization group. By employing linear finite-time quenches
in the onsite and nearest-neighbor interactions, we find the existence of
impulse, intermediate, and adiabatic regimes of time evolution. For the
quenches we analyze, we observe that the adiabatic regime is reached with
distinct ramping time scales depending on whether the charge density wave (CDW)
or the spin density wave (SDW) is formed. The former needs to be slower than
the latter to prevent entangled excited states from being accessed during the
quench. More interestingly, in the intermediate regime, we observe an
enhancement of the entanglement entropy with respect to its initial value,
which precedes the formation of the CDW ordering; a similar enhancement is not
seen in the quench towards SDW. Our findings also show that the breaking of the
system integrability, by turning on the nearest-neighbor interactions, does not
give rise to significant changes in the non-equilibrium behavior within the
adiabatic approximation.",2208.05945v2
2022-08-24,"Vortex Pinning in Neutron Stars, Slip-stick Dynamics, and the Origin of Spin Glitches","We study pinning and unpinning of superfluid vortices in the inner crust of a
neutron star using 3-dimensional dynamical simulations. Strong pinning occurs
for certain lattice orientations of an idealized, body-centered cubic lattice,
and occurs generally in an amorphous or impure nuclear lattice. The pinning
force per unit length is $\sim 10^{16}$ dyn cm$^{-1}$ for a vortex-nucleus
interaction that is repulsive, and $\sim 10^{17}$ dyn cm$^{-1}$ for an
attractive interaction. The pinning force is strong enough to account for
observed spin jumps (glitches). Vortices forced through the lattice move with a
slip-stick character; for a range of superfluid velocities, the vortex can be
in either a cold, pinned state or a hot unpinned state, with strong excitation
of Kelvin waves on the vortex. This two-state nature of vortex motion sets the
stage for large-scale vortex movement that creates an observable spin glitch.
We argue that the vortex array is likely to become tangled as a result of
repeated unpinnings and repinnings. We conjecture that during a glitch, the
Kelvin-wave excitation spreads rapidly along the direction of the mean
superfluid vorticity and slower in the direction perpendicular to it, akin to
an anisotropic deflagration.",2208.11494v1
2022-12-16,Dynamical evolution of massive black hole pairs in the presence of spin-dependent radiative feedback,"The putative ubiquity of massive black holes (MBH) at the center of galaxies,
and the hierarchical progress of structure formation along the cosmic history,
together necessarily imply the existence of a large population of cosmic MBH
binaries. Such systems are understood to be the loudest sources of
gravitational waves at mHz frequencies, the regime that will be probed by the
next Laser Interferometer Space Antenna (LISA). It has been proposed that the
rate at which MBHs pair and then bind to form binaries is critically dependent
upon the feedback exerted by the MBHs on the surrounding gaseous environment.
Using the publicly available code GIZMO, we perform a suite of simulations
aimed at studying the dynamics of a MBH pair embedded in a gaseous disk on 100
pc scale. By means of dedicated modules, we follow the dynamics of MBHs in the
presence of different spin-dependent radiative feedback models, and compare the
results to a benchmark case with no feedback at all. Our main finding is that
feedback causes the secondary MBH to shrink its orbit at a reduced pace, when
compared to models where feedback is absent. Moreover, such slower inspiral
occurs on eccentric orbits, as feedback has the net effect of hampering the
circularization process. Though idealized in many aspects, our study highlights
and quantifies the importance of including spin-dependent feedback recipes in
hydrodynamic simulations of MBH pairs, and ultimately in assessing the
cosmological coalescence rate of such systems in view of their detection
through gravitational waves.",2212.08669v1
2023-02-02,Ultrastrong Magnon-Photon Coupling Achieved by Magnetic Films in Contact with Superconducting Resonators,"Coherent coupling between spin wave excitations (magnons) and microwave
photons in a cavity may disclose new paths to unconventional phenomena as well
as for novel applications. Here, we present a systematic investigation on YIG
(Yttrium Iron Garnet) films on top of coplanar waveguide resonators made of
superconducting YBCO. We first show that spin wave excitations with frequency
higher than the Kittel mode can be excited by putting in direct contact a
5~$\mu$m thick YIG film with the YBCO coplanar resonator (cavity frequency
$\omega_c/2 \pi = 8.65$~GHz). With this configuration, we obtain very large
values of the collective coupling strength $\lambda/2 \pi \approx 2$~GHz and
cooperativity $C=5 \times 10^4$. Transmission spectra are analyzed by a
modified Hopfield model for which we provide an exact solution that allows us
to well reproduce spectra by introducing a limited number of free parameters.
It turns out that the coupling of the dominant magnon mode with photons exceeds
0.2 times the cavity frequency, thus demonstrating the achievement of the
ultrastrong coupling regime with this architecture. Our analysis also shows a
vanishing contribution of the diamagnetic term which is a peculiarity of pure
spin systems.",2302.00804v2
2023-02-21,On the minimum spin period of accreting pulsars,"The distribution of the spin frequencies of neutron stars in low-mass X-ray
binaries exhibits a cut-off at 730 Hz, below the break-up frequency
(mass-shedding limit) of neutron stars. The absence of the sub-millisecond
pulsars presents a problem, given that these systems are older than the spin-up
timescale. We confront models of disc-magnetosphere interaction near torque
equilibrium balanced by the torque due to gravitational wave emission. We note
that field lines penetrating the disc beyond the inner radius reduce the
maximum rotation frequency of the star, a result well-known since the seminal
work of Ghosh & Lamb. We show that the polar cap area corresponds to about half
the neutron star surface area at the cut-off frequency if the inner radius is
slightly smaller than the corotation radius. We then include the change in the
moment of inertia of the star due to the accretion of mass and find that this
effect further reduces the maximum rotation frequency of the star. Finally, we
include the torque due to gravitational wave emission and calculate its
contribution to the torque equilibrium. Our results suggest that all three
processes are significant at the cut-off frequency, and all of them must be
considered in addressing the absence of sub-millisecond pulsars.",2302.10649v3
2023-03-07,Electron-spin double resonance of nitrogen-vacancy centers in diamond under strong driving field,"The nitrogen-vacancy (NV) center in diamond has been the focus of research
efforts because of its suitability for use in applications such as quantum
sensing and quantum simulations. Recently, the electron-spin double resonance
(ESDR) of NV centers has been exploited for detecting radio-frequency (RF)
fields with continuous-wave optically detected magnetic resonance. However, the
characteristic phenomenon of ESDR under a strong RF field remains to be fully
elucidated. In this study, we theoretically and experimentally analyzed the
ESDR spectra under strong RF fields by adopting the Floquet theory. Our
analytical and numerical calculations could reproduce the ESDR spectra obtained
by measuring the spin-dependent photoluminescence under the continuous
application of microwaves and an RF field for a DC bias magnetic field
perpendicular to the NV axis. We found that anticrossing structures that appear
under a strong RF field are induced by the generation of RF-dressed states
owing to the two-RF-photon resonances. Moreover, we found that $2n$-RF-photon
resonances were allowed by an unintentional DC bias magnetic field parallel to
the NV axis. These results should help in the realization of precise MHz-range
AC magnetometry with a wide dynamic range beyond the rotating wave
approximation regime as well as Floquet engineering in open quantum systems.",2303.03860v2
2023-03-17,Calculation of the energies of the multideterminant states of the nitrogen vacancy center in diamond with quantum Monte Carlo,"Certain point defects in solids can efficiently be used as qubits for
applications in quantum technology. They have spin states that are
initializable, readable, robust, and can be manipulated optically. New
theoretical methods are needed to find the best host materials and defect
configurations. Most methods proposed so far rely either on cluster models or
restrict the many-body treatment of the defects to a subspace of
single-particle orbitals. We explore best practices and theory for the use of
quantum Monte Carlo to predict the excitation spectra for spin defects, by
using the negatively charged nitrogen vacancy (NV$^-$) center in diamond as a
test system. Quantum Monte Carlo can be used to explicitly simulate electronic
correlations with larger systems and sets of orbitals than previous methods due
to favourable scaling with respect to system size and computing power. We
consider different trial wave functions for variational and diffusion Monte
Carlo methods, explore the nodal surface errors of the ground and excited state
wave functions and study whether the variational principle holds for the
excited states. We compute the vertical excitation energies in different
simulation cell sizes and extrapolate to infinite system size, and include
backflow corrections to the extrapolated energies. The final results for
vertical excitation energies are found to overestimate the experimental
estimates, but the triplet-to-triplet and singlet-to-singlet transitions are
accurate against experiment. Finally, we list further developments for QMC
needed to address the problem of accurately predicting structural and spin
properties of the solid-state defects.",2303.09851v4
2023-04-12,"Neutron scattering sum rules, symmetric exchanges, and helicoidal magnetism in MnSb$_2$O$_6$","MnSb$_{2}$O$_{6}$ is based on the noncentrosymmetric $P321$ space group with
magnetic Mn$^{2+}$ ($S={5/2}$, $L\approx 0$) spins ordering below
$T_{\mathrm{N}}=12$ K in a helicoidal structure. The ground state magnetic
structure, expected to be built and originate from 7 Heisenberg exchange
constants, has been shown to be coupled to the underlying crystallographic
chirality with polar domain switching being reported. We apply neutron
spectroscopy to extract these symmetric exchange constants. Given the high
complexity of the magnetic exchange network, crystallographic structure and
complications fitting linear spin-wave models, we take advantage of multiplexed
neutron instrumentation to use the first moment sum rule of neutron scattering
to estimate the 7 exchange constants. We then use these parameters to calculate
the low-energy spin-waves in the N\'eel state to reproduce the neutron response
without strong antisymmetric coupling. Using Green's response functions, the
stability of long-wavelength excitations in the context of proposed magnetic
structures is then discussed. The results show the presence of strong exchange
constants for the chiral exchange pathways and illustrate an underlying
coupling between crystallographic and magnetic ``chirality"" through
predominantely symmetric exchange.",2304.05732v1
2023-08-22,Solving Fermi-Hubbard-type Models by Tensor Representations of Backflow Corrections,"The quantum many-body problem is an important topic in condensed matter
physics. To efficiently solve the problem, several methods have been developped
to improve the representation ability of wave-functions.
  For the Fermi-Hubbard model under periodic boundary conditions, current
state-of-the-art methods are neural network backflows and the hidden fermion
Slater determinant.
  The backflow correction is an efficient way to improve the Slater determinant
of free-particles.
  In this work we propose a tensor representation of the backflow corrected
wave-function, we show that for the spinless $t$-$V$ model, the energy
precision is competitive or even lower than current state-of-the-art fermionic
tensor network methods.
  For models with spin, we further improve the representation ability by
considering backflows on fictitious particles with different spins, thus
naturally introducing non-zero backflow corrections when the orbital and the
particle have opposite spins.
  We benchmark our method on molecules under STO-3G basis and the Fermi-Hubbard
model with periodic and cylindrical boudary conditions.
  We show that the tensor representation of backflow corrections achieves
competitive or even lower energy results than current state-of-the-art neural
network methods.",2308.11823v6
2023-09-06,Strong magnon-magnon coupling in an ultralow damping all-magnetic-insulator heterostructure,"Magnetic insulators such as yttrium iron garnets (YIGs) are of paramount
importance for spin-wave or magnonic devices as their ultralow damping enables
ultralow power dissipation that is free of Joule heating, exotic magnon quantum
state, and coherent coupling to other wave excitations. Magnetic insulator
heterostructures bestow superior structural and magnetic properties and house
immense design space thanks to the strong and engineerable exchange interaction
between individual layers. To fully unleash their potential, realizing low
damping and strong exchange coupling simultaneously is critical, which often
requires high quality interface. Here, we show that such a demand is realized
in an all-insulator thulium iron garnet (TmIG)/YIG bilayer system. The ultralow
dissipation rates in both YIG and TmIG, along with their significant spin-spin
interaction at the interface, enable strong and coherent magnon-magnon coupling
with a benchmarking cooperativity value larger than the conventional
ferromagnetic metal-based heterostructures. The coupling strength can be tuned
by varying the magnetic insulator layer thickness and magnon modes, which is
consistent with analytical calculations and micromagnetic simulations. Our
results demonstrate TmIG/YIG as a novel platform for investigating hybrid
magnonic phenomena and open opportunities in magnon devices comprising
all-insulator heterostructures.",2309.03116v1
2023-11-05,Topological spin-orbit-coupled fermions beyond rotating wave approximation,"The realization of spin-orbit-coupled ultracold gases has driven a wide range
of researches and is typically based on the rotating wave approximation (RWA).
By neglecting the counter-rotating terms, RWA characterizes a single
near-resonant spin-orbit (SO) coupling in a two-level system. Here, we propose
and experimentally realize a new scheme for achieving a pair of two-dimensional
(2D) SO couplings for ultracold fermions beyond RWA. This work not only
realizes the first anomalous Floquet topological Fermi gas beyond RWA, but also
significantly improves the lifetime of the 2D-SO-coupled Fermi gas. Based on
pump-probe quench measurements, we observe a deterministic phase relation
between two sets of SO couplings, which is characteristic for our beyond-RWA
scheme and enables the two SO couplings to be simultaneously tuned to the
optimum 2D configurations. We observe intriguing band topology by measuring
two-ring band-inversion surfaces, quantitatively consistent with a Floquet
topological Fermi gas in the regime of high Chern numbers. Our study can open
an avenue to explore exotic SO physics and anomalous topological states based
on long-lived SO-coupled ultracold fermions.",2311.02584v1
2023-11-10,A semi-coherent generalization of the 5-vector method to search for continuous gravitational waves,"The emission of continuous gravitational waves (CWs), with duration much
longer than the typical data taking runs, is expected from several sources,
notably spinning neutron stars, asymmetric with respect to their rotation axis
and more exotic sources, like ultra-light scalar boson clouds formed around
Kerr black holes and sub-solar mass primordial binary black holes. Unless the
signal time evolution is well predicted and its relevant parameters accurately
known, the search for CWs is typically based on semi-coherent methods, where
the full data set is divided in shorter chunks of given duration, which are
properly processed, and then incoherently combined. In this paper we present a
semi-coherent method, in which the so-called \textit{5-vector} statistics is
computed for the various data segments and then summed after the removal of the
Earth Doppler modulation and signal intrinsic spin-down. The method can work
with segment duration of several days, thanks to a double stage procedure in
which an initial rough correction of the Doppler and spin-down is followed by a
refined step in which the residual variations are removed. This method can be
efficiently applied for directed searches, where the source position is known
to a good level of accuracy, and in the candidate follow-up stage of
wide-parameter space searches.",2311.06021v1
2023-11-28,Transformer Wave Function for the Shastry-Sutherland Model: emergence of a Spin-Liquid Phase,"Quantum magnetism in two-dimensional systems represents a lively branch of
modern condensed-matter physics. In the presence of competing super-exchange
couplings, magnetic order is frustrated and can be suppressed down to zero
temperature, leading to exotic ground states. The Shastry-Sutherland model,
describing $S=1/2$ degrees of freedom interacting in a two-dimensional lattice,
portrays a simple example of highly-frustrated magnetism, capturing the
low-temperature behavior of SrCu$_2$(BO$_3$)$_2$ with its intriguing
properties. Here, we investigate this problem by using a Vision Transformer to
define an extremely accurate variational wave function. From a technical side,
a pivotal achievement relies on using a deep neural network with real-valued
parameters, parametrized with a Transformer, to map physical spin
configurations into a high-dimensional feature space. Within this abstract
space, the determination of the ground-state properties is simplified,
requiring only a single output layer with complex-valued parameters. From the
physical side, we supply strong evidence for the stabilization of a spin-liquid
between the plaquette and antiferromagnetic phases. Our findings underscore the
potential of Neural-Network Quantum States as a valuable tool for probing
uncharted phases of matter, opening opportunities to establish the properties
of many-body systems.",2311.16889v2
2024-02-19,The Redshift Evolution of the Binary Black Hole Mass Distribution from Dense Star Clusters,"Gravitational-wave detectors are unveiling a population of binary black hole
(BBH) mergers out to redshifts $z \approx 1$, and are starting to constrain how
the BBH population evolves with redshift. We present predictions for the
redshift evolution of the BBH mass and spin distributions for systems
originating from dense star clusters. Utilizing a grid of 144 state-of-the-art
dynamical models for globular clusters, we demonstrate that BBH merger rates
peak at higher redshifts for larger black hole primary masses $M_1$.
Specifically, for $M_1\gtrsim40\,M_{\odot}$, the BBH merger rate reaches its
peak at redshift $z\approx2.1$, while for $M_1\lesssim20\,M_{\odot}$, the peak
occurs at $z\approx1.1$, assuming that the cluster formation rate peaks at
$z=2.2$. The average BBH primary mass also increases from $\sim 10\,M_{\odot}$
at $z=0$ to $\sim 30\,M_{\odot}$ at $z=10$. We show that $\sim 20\%$ BBHs
contain massive remnants from next-generation mergers, with this fraction
increasing (decreasing) for larger (smaller) primary masses. This difference is
not large enough to significantly alter the effective spins of the BBH
population originating from globular clusters, and we find that their effective
spin distribution does not evolve across cosmic time. These findings can be
used to distinguish BBHs from dense star clusters by future gravitational wave
observations.",2402.12444v1
2024-03-04,Order-by-disorder without quantum zero-point fluctuations in the pyrochlore Heisenberg ferromagnet with Dzyaloshinskii-Moriya interactions,"Order-by-disorder, whereby fluctuations lift an accidental classical ground
state degeneracy to stabilize a subset of ordered states, is a recurrent and
prominent theme in the field of frustrated magnetism where magnetic moments, or
spins, are subject to competing interactions. Thus far, such a phenomenon has
been discussed in systems where the quantum ground state is not a product
state. In this circumstance, both thermal and quantum fluctuations act to lift
the accidental classical degeneracy, begging the question whether one mechanism
of order-by-disorder is possible without the other. In this paper, we present
results exposing a novel route to order-by-disorder, without quantum zero-point
fluctuations, in a family of ferromagnetic Heisenberg materials with the
Dzyaloshinskii-Moriya (DM) interaction as the leading perturbation. We prove
that any colinear ferromagnetic state is an exact eigenstate, even in the
presence of the anisotropic DM interaction, while thermal fluctuations give
rise to a preference in the magnetization direction. Here, we present in detail
an example of the pyrochlore Heisenberg ferromagnet with DM interactions. Using
both linear spin-wave theory and classical Monte Carlo simulations, we find
that the magnetization can spontaneously rotate at intermediate temperature(s)
within the colinear ferromagnetic phase when the DM interaction is large.
Additionally, we find that in the large DM regime, the ferromagnetic ground
state becomes unstable within the framework of non-linear spin-wave theory. Our
results show that thermal order-by-disorder is possible even in the absence of
quantum zero-point fluctuations.",2403.02391v1
2024-04-04,Searching for binary black hole sub-populations in gravitational wave data using binned Gaussian processes,"Astrophysically motivated population models for binary black hole observables
are often insufficient to capture the imprints of multiple formation channels.
This is mainly due to the strongly parametrized nature of such investigations.
Using a non-parametric model for the joint population-level distributions of
binary black hole component masses and effective inspiral spins, we find hints
of multiple subpopulations in the third gravitational wave transient catalog.
The higher (more positive) spin subpopulation is found to have a mass-spectrum
without any feature at the $30-40M_{\odot}$, which is consistent with the
predictions of isolated stellar binary evolution, simulations for which place
the pile up due to pulsational pair-instability supernovae near $50M_{\odot}$
or higher. The other sub-population with effective spins closer to zero shows a
feature at $30-40M_{\odot}$ and is consistent with binary black holes formed
dynamically in globular clusters, which are expected to peak around
$30M_{\odot}$. We also compute merger rates for these two subpopulations and
find that they are consistent with the theoretical predictions of the
corresponding formation channels. We validate our results by checking their
robustness against variations of several model configurations and by analyzing
large simulated catalogs with the same model.",2404.03166v1
2024-04-08,Global phase diagram of doped quantum spin liquid on the Kagome lattice,"It has long been believed that doped quantum spin liquids (QSLs) can give
rise to fascinating quantum phases, including the possibility of
high-temperature superconductivity (SC) as proposed by P. W. Anderson's
resonating valence bond (RVB) scenario. The Kagome lattice $t$-$J$ model is
known to exhibit spin liquid behavior at half-filling, making it an ideal
system for studying the properties of doped QSL. In this study, we employ the
fermionic projected entangled simplex state (PESS) method to investigate the
ground state properties of the Kagome lattice $t$-$J$ model with $t/J = 3.0$.
Our results reveal a phase transition from charge density wave (CDW) states to
uniform states around a critical doping level $\delta_c \approx 0.27$. Within
the CDW phase, we observe different types of Wigner crystal (WC) formulated by
doped holes that are energetically favored. As we enter the uniform phase, a
non-Fermi liquid (NFL) state emerges within the doping range $0.27 < \delta <
0.32$, characterized by an exponential decay of all correlation functions. With
further hole doping, we discover the appearance of a pair density wave (PDW)
state within a narrow doping region $0.32 < \delta < 1/3$. We also discuss the
potential experimental implications of our findings.",2404.05685v1
1996-09-25,Signature of Gravity Waves in Polarization of the Microwave Background,"Using spin-weighted decomposition of polarization in the Cosmic Microwave
Background (CMB) we show that a particular combination of Stokes $Q$ and $U$
parameters vanishes for primordial fluctuations generated by scalar modes, but
does not for those generated by primordial gravity waves. Because of this
gravity wave detection is not limited by cosmic variance as in the case of
temperature fluctuations. We present the exact expressions for various
polarization power spectra, which are valid on any scale. Numerical evaluation
in inflation-based models shows that the expected signal is of the order of 0.5
$\mu K$, which could be directly tested in future CMB experiments.",9609169v2
2001-09-20,Reconnection in pulsar winds,"The spin-down power of a pulsar is thought to be carried away in an MHD wind
in which, at least close to the star, the energy transport is dominated by
Poynting flux. The pulsar drives a low-frequency wave in this wind, consisting
of stripes of toroidal magnetic field of alternating polarity, propagating in a
region around the equatorial plane. The current implied by this configuration
falls off more slowly with radius than the number of charged particles
available to carry it, so that the MHD picture must, at some point, fail.
Recently, magnetic reconnection in such a structure has been shown to
accelerate the wind significantly. This reduces the magnetic field in the
comoving frame and, consequently, the required current, enabling the solution
to extend to much larger radius. This scenario is discussed and, for the Crab
Nebula, the range of validity of the MHD solution is compared with the radius
at which the flow appears to terminate. For sufficiently high particle
densities, it is shown that a low frequency entropy wave can propagate out to
the termination point. In this case, the ""termination shock"" itself must be
responsible for dissipating the wave.",0109332v2
2005-10-03,Frequency spectrum of gravitational radiation from global hydromagnetic oscillations of a magnetically confined mountain on an accreting neutron star,"Recent time-dependent, ideal-magnetohydrodynamic (ideal-MHD) simulations of
polar magnetic burial in accreting neutron stars have demonstrated that stable,
magnetically confined mountains form at the magnetic poles, emitting
gravitational waves at $f_{*}$ (stellar spin frequency) and $2 f_{*}$. Global
MHD oscillations of the mountain, whether natural or stochastically driven, act
to modulate the gravitational wave signal, creating broad sidebands (full-width
half-maximum $\sim 0.2f_*$) in the frequency spectrum around $f_{*}$ and $2
f_{*}$. The oscillations can enhance the signal-to-noise ratio achieved by a
long-baseline interferometer with coherent matched filtering by up to 15 per
cent, depending on where $f_*$ lies relative to the noise curve minimum.
Coherent, multi-detector searches for continuous waves from nonaxisymmetric
pulsars should be tailored accordingly.",0510053v1
1994-06-28,Fermionic Chern-Simons theory for the Fractional Quantum Hall Effect in Bilayers,"We generalize the fermion Chern-Simons theory for the Fractional Hall Effect
(FQHE) which we developed before, to the case of bilayer systems. We study the
complete dynamic response of these systems and predict the experimentally
accessible optical properties. In general, for the so called $(m, m, n)$
states, we find that the spectrum of collective excitations has a gap, and the
wave function has the Jastrow-Slater form, with the exponents determined by the
coefficients $m$, and $n$. We also find that the $(m,m,m)$ states, {\it
i.~e.~}, those states whose filling fraction is $1\over m$, have a gapless mode
which may be related with the spontaneous appearance of the interlayer
coherence. Our results also indicate that the gapless mode makes a contribution
to the wave function of the $(m,m,m)$ states analogous to the phonon
contribution to the wave function of superfluid $\rm{He}_4$. We calculate the
Hall conductance, and the charge and statistics of the quasiparticles. We also
present an $SU(2)$ generalization of this theory relevant to spin unpolarized
or partially polarized single layers.",9406113v1
1995-04-06,The $\bf T=0$ $\bf 2k_F$ density wave phase transition in a two dimensional Fermi liquid is first order,"We study $T=0$ spin density wave transitions in two dimensional Fermi liquids
in which the ordering wavevector $\bf Q$ is such that the tangents to the Fermi
line at the points connected by $\bf Q$ are parallel (e.g. $Q=2p_F$ in a system
with a circular Fermi line) and the Fermi line is not flat. We show that the
transition is first order if the ordering wave vector $\bf Q$ is not
commensurate with a reciprocal lattice vector, $\bf G$, i.e. ${\bf Q} \neq {\bf
G}/2$. If $\bf Q$ is close to ${\bf G}/2$ the transition is weakly first order
and an intermediate scaling regime exists; in this regime the $2p_F$
susceptibility and observables such as the NMR rates $T_1$ and $T_2$ have
scaling forms which we determine.",9504024v1
1997-09-30,Universal scaling in BCS superconductivity in three dimensions in non-$s$ waves,"The solutions of a renormalized BCS equation are studied in three space
dimensions in $s$, $p$ and $d$ waves for finite-range separable potentials in
the weak to medium coupling region. In the weak-coupling limit, the present BCS
model yields a small coherence length $\xi$ and a large critical temperature,
$T_c$, appropriate for some high-$T_c$ materials. The BCS gap, $T_c$, $\xi$ and
specific heat $C_s(T_c)$ as a function of zero-temperature condensation energy
are found to exhibit potential-independent universal scalings. The entropy,
specific heat, spin susceptibility and penetration depth as a function of
temperature exhibit universal scaling below $T_c$ in $p$ and $d$ waves.",9709340v1
1997-10-28,Two-dimensional disordered electron systems: a network model approach,"We demonstrate that network models for wave mechanical systems with quenched
disorder cover the physics of mesoscopic electrons. The models are constructed
as a network of random scattering matrices connecting incoming to outgoing wave
amplitudes. The corresponding wave dynamics is given by a discrete unitary time
evolution operator. We report on three different universality classes:
two-dimensional, spinless, non-chiral electrons with (O2NC) and without time
reversal symmetry (U2NC), and two-dimensional, non-chiral electrons with time
reversal symmetric spin-scattering (S2NC). We determine the phase diagram in
the parameter space of scattering strengths. The O/U2NC models show strong
localization. We find symmetry factors in localization lengths as well as
multifractal exponents in agreement with theoretical predictions. The S2NC
model displays a localization-delocalization transition. We determine the
critical exponent of the localization length and the multifractal scaling
exponent of the order parameter to be $\nu \approx 2.4$ and $\alpha_0\approx
2.18$, respectively.",9710297v1
2000-01-31,Correlation Effects in a One-Dimensional Quarter-Filled Electron System with Repulsive Interactions,"A one-dimensional electron system at quarter-filling has been examined by
applying the renormalization group method to a bosonized model with on-site (U)
and nearest-neighbor (V) repulsive interactions. By evaluating both normal
scattering and Umklapp scattering perturbatively, we obtain a phase diagram in
which a metallic state with a 2k_F spin density wave (k_F is the Fermi wave
number) moves into an insulating state with charge disproportionation of a 4k_F
charge density wave with an increase in both U and V. The effect of the
next-nearest-neighbor repulsion is also discussed.",0001450v1
2000-04-05,Critical State Behaviour in a Low Dimensional Metal Induced by Strong Magnetic Fields,"We present the results of magnetotransport and magnetic torque measurements
on the alpha-(BEDT-TTF)2KHg(SCN)4 charge-transfer salt within the high magnetic
field phase, in magnetic fields extending to 33 T and temperatures as low as 27
mK. While the high magnetic field phase (at fields greater than ~ 23 T) is
expected, on theoretical grounds, to be either a modulated charge-density wave
phase or a charge/spin-density wave hybrid, the resistivity undergoes a
dramatic drop below ~ 3 K within the high magnetic field phase, falling in an
approximately exponential fashion at low temperatures, while the magnetic
torque exhibits pronounced hysteresis effects. This hysteresis, which occurs
over a broad range of fields, is both strongly temperature-dependent and has
several of the behavioural characteristics predicted by critical-state models
used to describe the pinning of vortices in type II superconductors in strong
magnetic fields. Thus, rather than exhibiting the usual behaviour expected for
a density wave ground state, both the transport and the magnetic properties of
alpha-(BEDT-TTF)2KHg(SCN)4, at high magnetic fields, closely resembles those of
a type II superconductor.",0004083v1
2000-08-30,Influence of incommensurate dynamic charge-density wave scattering on the line shape of high-T$_c$ cuprates,"We show that the spectral lineshape of superconducting
La$_{2-x}$Sr$_x$CuO$_4$ (LSCO) and Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi2212)
can be well described by the coupling of the charge carriers to collective
incommensurate charge-density wave (CDW) excitations. Our results imply that
besides antiferromagnetic (AF) fluctuations also low-energy CDW modes can
contribute to the observed dip-hump structure in the Bi2212 photoemission
spectra. In case of underdoped LSCO we propose a possible interpretation of
ARPES data in terms of a grid pattern of fluctuating stripes where the charge
and spin scattering directions deviate by $\alpha=\pi/4$. Within this scenario
we find that the spectral intensity along $(0,0) \to (\pi,\pi)$ is strongly
suppressed consistent with recent photoemission experiments. In addition the
incommensurate charge-density wave scattering leads to a significant broadening
of the quasiparticle-peak around $(\pi,0)$.",0008442v2
2000-11-03,Dirac quasiparticles in the mixed state,"Energies and wave functions are calculated for d-wave quasiparticles in the
mixed state using the formalism of Franz and Tesanovic for the low-lying energy
levels. The accuracy of the plane-wave expansion is explored by comparing
approximate to exact results for a simplified one-dimensional problem, and the
convergence of the plane- wave expansion to the two-dimensional case is
studied. The results are used to calculate the low-energy tunneling density of
states and the low-temperature specific heat, and these theoretical results are
compared to semiclassical treatments and to the available data. Implications
for the muon spin resonance measurements of vortex core size are also
discussed.",0011053v2
2001-04-24,"Interlayer Exchange Interactions, SU(4) Soft Waves and Skyrmions in Bilayer Quantum Hall Ferromagnets","The Coulomb exchange interaction is the driving force for quantum coherence
in quantum Hall systems. We construct a microscopic Landau-site Hamiltonian for
the exchange interaction in bilayer quantum Hall ferromagnets, which is
characterized by the SU(4) isospin structure. By taking a continuous limit, the
Hamiltonian gives rise to the SU(4) nonlinear sigma model in the
von-Neumann-lattice formulation. The ground-state energy is evaluated at
filling factors $\nu =1,2,3,4$. It is shown at $\nu =1$ that there are 3
independent soft waves, where only one soft wave is responsible for the
coherent tunneling of electrons between the two layers. It is also shown at
$\nu =1$ that there are 3 independent skyrmion states apart from the
translational degree of freedom. They are CP$^{3}$ skyrmions enjoying the
spin-charge entanglement confined within the \LLL.",0104448v2
2001-08-03,Critical Q=1 Potts Model and Temperley-Lieb Stochastic Processes,"We consider the groundstate wave function and spectra of the $L$-site XXZ
$U_q[s\ell(2)]$ invariant quantum spin chain with $q=\exp(\pi i/3)$. This chain
is related to the critical Q=1 Potts model and exhibits $c=0$ conformal
invariance. We show that the problem is related to Hamiltonians describing
one-dimensional stochastic processes defined on a Temperley-Lieb algebra. The
bra groundstate wave function is trivial and the ket groundstate wave function
gives the probabilty distribution of the stationary state. The stochastic
processes can be understood as interface RSOS growth models with nonlocal
rates. Allowing defects which can hop on the interface one obtains stochastic
models having the same stationary state and spectra (but not degeracies) as the
XXZ chain.",0108051v2
2001-10-08,Structural and Electronic Instabilities in Polyacenes: Density Matrix Renormalization Group Study of a Long--Range Interacting Model,"We have carried out Density Matrix Renormalization Group (DMRG) calculations
on the ground state of long polyacene oligomers within a Pariser-Parr-Pople
(PPP) Hamiltonian. The PPP model includes long-range electron correlations
which are required for physically realistic modeling of conjugated polymers. We
have obtained the ground state energy as a function of the dimerization
$\delta$ and various correlation functions and structure factors for
$\delta=0$. From energetics, we find that while the nature of the Peierls'
instabilityin polyacene is conditional and strong electron correlations enhance
the dimerization. The {\it cis} form of the distortion is favoured over the
{\it trans} form. However, from the analysis of correlation functions and
associated structure factors, we find that polyacene is not susceptible to the
formation of a bond order wave (BOW), spin density wave (SDW) or a charge
density wave (CDW) in the ground state.",0110136v1
2002-02-11,In-plane Tunneling Spectrum into a [110]-Oriented High-$T_c$ Superconductor in the Pseudogap Regime,"Both the differential tunneling conductance and the surface local density of
states (LDOS) of a [110]-oriented high-temperature superconductor in the
pseudogap (PG) regime are studied theoretically. As a competing candidate for
the mechanism of PG state, the charge-density wave (CDW), spin-density wave
(SDW), $d$-density wave (DDW), and d-wave superconducting (DSC) orderings show
distinct features in the tunneling conductance. For the CDW, SDW, and DSC
orderings, the tunneling conductance approaches the surface LDOS as the barrier
potential is increased. For the DDW ordering, we show for the first time that
there exist midgap states at the [110] surface, manifesting themselves as a
sharp zero-energy peak in the LDOS, as in the case of DSC ordering. However,
due to the particle-hole pair nature of the DDW state, these states do not
carry current, and consequently the one-to-one correspondence between the
tunneling conductance and the surface LDOS is absent.",0202187v1
2003-11-24,Charge-Density-Wave Formation in the Doped Two-Leg Extended Hubbard Ladder,"We investigate electronic properties of the doped two-leg Hubbard ladder with
both the onsite and the nearest-neighbor Coulomb repulsions, by using the the
weak-coupling renormalization-group method. It is shown that, for strong
nearest-neighbor repulsions, the charge-density-wave state coexisting with the
p-density-wave state becomes dominant fluctuation where spins form intrachain
singlets. By increasing doping rate, we have also shown that the effects of the
nearest-neighbor repulsions are reduced and the system exhibits a quantum phase
transition into the d-wave-like (or rung-singlet) superconducting state. We
derive the effective fermion theory which describes the critical properties of
the transition point with the gapless excitation of magnon. The phase diagram
of the two-leg ladder compound, Sr_{14-x}Ca_xCu_{24}O_{41}, is discussed.",0311534v2
2004-01-08,"Peierls instability, periodic Bose-Einstein condensates and density waves in quasi-one-dimensional boson-fermion mixtures of atomic gases","We study the quasi-one-dimensional (Q1D) spin-polarized bose-fermi mixture of
atomic gases at zero temperature. Bosonic excitation spectra are calculated in
random phase approximation on the ground state with the uniform BEC, and the
Peierls instabilities are shown to appear in bosonic collective excitation
modes with wave-number $2k_F$ by the coupling between the Bogoliubov-phonon
mode of bosonic atoms and the fermion particle-hole excitations. The
ground-state properties are calculated in the variational method, and,
corresponding to the Peierls instability, the state with a periodic BEC and
fermionic density waves with the period $\pi/k_F$ are shown to have a lower
energy than the uniform one. We also briefly discuss the Q1D system confined in
a harmonic oscillator (HO) potential and derive the Peierls instability
condition for it.",0401107v1
2004-06-22,Disordered mesoscopic systems with interactions: induced two-body ensembles and the Hartree-Fock approach,"We introduce a generic approach to study interaction effects in diffusive or
chaotic quantum dots in the Coulomb blockade regime. The randomness of the
single-particle wave functions induces randomness in the two-body interaction
matrix elements. We classify the possible induced two-body ensembles, both in
the presence and absence of spin degrees of freedom. The ensembles depend on
the underlying space-time symmetries as well as on features of the two-body
interaction. Confining ourselves to spinless electrons, we then use the
Hartree-Fock (HF) approximation to calculate HF single-particle energies and HF
wave functions for many realizations of the ensemble. We study the statistical
properties of the resulting one-body HF ensemble for a fixed number of
electrons. In particular, we determine the statistics of the interaction matrix
elements in the HF basis, of the HF single-particle energies (including the HF
gap between the last occupied and the first empty HF level), and of the HF
single-particle wave functions. We also study the addition of electrons, and in
particular the distribution of the distance between successive conductance
peaks and of the conductance peak heights.",0406495v1
2004-11-29,Variational Monte Carlo studies of a t-J model on an anisotropic triangular lattice,"With the insulating phase of \kappa-(BEDT-TTF)_2X in mind, we study a t-J
model on an anisotropic triangular lattice, where the hopping integral is t' in
one of the three directions, using a variational Monte Carlo method. By
changing the value of t'/t, we study the stability of superconducting (SC)
states with d- and d+id-wave symmetries and of an antiferromagnetic (AF) state.
As t'/t decreases from 1, the stable state immediately switches from the d+id
wave to the d wave. The AF state is stabilized from the normal spin liquid
state for t'/t\lsim 0.7 at half filling. We also take account of Nagaoka
ferromagnetism and a phase separation.",0411711v1
2005-04-11,Nonmonotonic d_{x^2-y^2}-Wave Superconductivity in Electron-Doped Cuprates Viewing from the Strong-Coupling Side,"Applying a variational Monte Carlo method to a two-dimensional t-J model, we
study the nonmonotonic d_{x^2-y^2}-wave superconductivity, observed by Raman
scattering and ARPES experiments in the electron-doped cuprates. As a gap
function in the trial state, we extend the d-wave form (ext.d) so as to have
its maxima located near the hot spots of the system. It is found that, in
contrast to the hole-doped case, the ext.d wave is always more stable than the
simple d wave in the electron-doped case, and the magnetic correlation of the
wave vector (\pi,\pi) as well as the pair correlation is enhanced. These
results corroborate spin-correlation-mediated superconductivity in cuprates,
recently argued from a FLEX calculation. In addition, we confirm that s- and
p-wave symmetries are never stabilized even in the over-doped regime.",0504246v1
2006-03-07,Noisy traveling waves: effect of selection on genealogies,"For a family of models of evolving population under selection, which can be
described by noisy traveling wave equations, the coalescence times along the
genealogical tree scale like $\log^\alpha N$, where $N$ is the size of the
population, in contrast with neutral models for which they scale like $N$. An
argument relating this time scale to the diffusion constant of the noisy
traveling wave leads to a prediction for $\alpha$ which agrees with our
simulations. An exactly soluble case gives trees with statistics identical to
those predicted for mean-field spin glasses in Parisi's theory.",0603160v2
2006-07-26,Retardation effects in the Holstein-Hubbard chain at half-filling,"The ground state phase diagram of the half-filled one-dimensional
Holstein-Hubbard model contains a charge-density-wave (CDW) phase, driven by
the electron-phonon (e-ph) coupling, and a spin-density-wave (SDW) phase,
driven by the on-site electron-electron (e-e) repulsion. Recently, the
existence of a third phase, which is metallic and lies in a finite region of
parameter space between these two gapped phases, has been claimed. We study
this claim using a renormalization-group method for interacting electrons that
has been extended to include also e-ph couplings. Our method treats e-e and
e-ph interactions on an equal footing and takes retardation effects fully into
account. We find a direct transition between the spin- and charge-density wave
states. We study the effects of retardation, which are particularly important
near the transition, and find that Umklapp processes at finite frequencies
drive the CDW instability close to the transition. We also perform
determinantal quantum Monte Carlo calculations of correlation functions to
confirm our results for the phase diagram.",0607700v2
2006-10-31,Competing orders and the doping and momentum dependent quasiparticle excitations in cuprate superconductors,"The low-energy quasiparticle excitations in hole- and electron-type cuprate
superconductors are investigated via both experimental and theoretical means.
It is found that the doping and momentum dependence of the empirical low-energy
quasiparticle excitations is consistent with a scenario of coexisting competing
orders and superconductivity in the ground state of the cuprates. This finding,
based on zero-field quasiparticle spectra, is further corrobarated by the
patially resolved vortex-state scanning tunneling spectroscopy, which reveals
pseudogap-like features consistent with a remaining competing order inside the
vortex core upon the suppression of superconductivity. The competing orders
compatible with empirical observations include the charge-density wave and
spin-density wave. In contrast, spectral characteristics derived from
incorporating the $d$-density wave as a competing order appear unfavorable in
comparison with experiments.",0610855v3
1997-05-08,Radiative multipole moments of integer-spin fields in curved spacetime,"Radiative multipole moments of scalar, electromagnetic, and linearized
gravitational fields in Schwarzschild spacetime are computed to third order in
v in a weak-field, slow-motion approximation, where v is a characteristic
velocity associated with the motion of the source. To zeroth order in v, a
radiative moment of order l is given by the corresponding source moment
differentiated l times with respect to retarded time. At second order in v,
additional terms appear inside the spatial integrals. These are near-zone
corrections which depend on the detailed behavior of the source. At third order
in v, the correction terms occur outside the spatial integrals, so that they do
not depend on the detailed behavior of the source. These are wave-propagation
corrections which are heuristically understood as arising from the scattering
of the radiation by the spacetime curvature surrounding the source. Our
calculations show that the wave-propagation corrections take a universal form
which is independent of multipole order and field type. We also show that in
general relativity, temporal and spatial curvatures contribute equally to the
wave-propagation corrections.",9705014v1
1999-11-29,High-Frequency Gravitational Waves from Spinning Non-Abelian Cosmic-Strings,"We investigated the SU(2) Einstein-Yang-Mills system on a time-dependent
non-diagonal cylindrical symmetric space-time. From the numerical
investigation, wave-like solutions are found, consistent with the familiar
string-like features. They possess an angle-deficit which depends on the
initial form of the magnetic component of the YM field, i.e., the number of
times it crosses the r-axis. The soliton-like behavior of the gravitational and
YM waves show significant differences from the ones found in the
Einstein-Maxwell system. The stability of the system is analyzed using the
multiple-scale method. To first order a consistent set of equations is
obtained.",9911117v4
2002-02-14,Dynamics of electromagnetic waves in Kerr geometry,"Here we are interested to study the spin-1 particle i.e., electro-magnetic
wave in curved space-time, say around black hole. After separating the
equations into radial and angular parts, writing them according to the black
hole geometry, say, Kerr black hole we solve them analytically. Finally we
produce complete solution of the spin-1 particles around a rotating black hole
namely in Kerr geometry. Obviously there is coupling between spin of the
electro-magnetic wave and that of black hole when particles propagate in that
space-time. So the solution will be depending on that coupling strength. This
solution may be useful to study different other problems where the analytical
results are needed. Also the results may be useful in some astrophysical
contexts.",0202050v1
2003-02-07,Gravitational Waves from Perturbed Black Holes and Relativistic Stars,"These lectures aim at providing an introduction to the properties of
gravitational waves and in particular to those gravitational waves that are
expected as a consequence of perturbations of black holes and neutron stars.
Imprinted in the gravitational radiation emitted by these objects is, in fact,
a wealth of physical information. In the case of black holes, a detailed
knowledge of the gravitational radiation emitted as a response to perturbations
will reveal us important details about their mass and spin, but also about the
fundamental properties of the event horizon. In the case of neutron stars, on
the other hand, this information can provide a detailed map of their internal
structure and tell us about the equation of state of matter at very high
density, thus filling-in a gap in energies and densities that cannot be
investigated by experiments in terrestrial laboratories.",0302025v1
2005-05-10,Search for gravitational waves from galactic and extra--galactic binary neutron stars,"We use 373 hours ($\approx$ 15 days) of data from the second science run of
the LIGO gravitational-wave detectors to search for signals from binary neutron
star coalescences within a maximum distance of about 1.5 Mpc, a volume of space
which includes the Andromeda Galaxy and other galaxies of the Local Group of
galaxies. This analysis requires a signal to be found in data from detectors at
the two LIGO sites, according to a set of coincidence criteria. The background
(accidental coincidence rate) is determined from the data and is used to judge
the significance of event candidates. No inspiral gravitational wave events
were identified in our search. Using a population model which includes the
Local Group, we establish an upper limit of less than 47 inspiral events per
year per Milky Way equivalent galaxy with 90% confidence for non-spinning
binary neutron star systems with component masses between 1 and 3 $M_\odot$.",0505041v2
2005-05-10,Search for Gravitational Waves from Primordial Black Hole Binary Coalescences in the Galactic Halo,"We use data from the second science run of the LIGO gravitational-wave
detectors to search for the gravitational waves from primordial black hole
(PBH) binary coalescence with component masses in the range 0.2--$1.0 M_\odot$.
The analysis requires a signal to be found in the data from both LIGO
observatories, according to a set of coincidence criteria. No inspiral signals
were found. Assuming a spherical halo with core radius 5 kpc extending to 50
kpc containing non-spinning black holes with masses in the range 0.2--$1.0
M_\odot$, we place an observational upper limit on the rate of PBH coalescence
of 63 per year per Milky Way halo (MWH) with 90% confidence.",0505042v1
2005-12-29,On gravitational-wave spectroscopy of massive black holes with the space interferometer LISA,"Newly formed black holes are expected to emit characteristic radiation in the
form of quasi-normal modes, called ringdown waves, with discrete frequencies.
LISA should be able to detect the ringdown waves emitted by oscillating
supermassive black holes throughout the observable Universe. We develop a
multi-mode formalism, applicable to any interferometric detectors, for
detecting ringdown signals, for estimating black hole parameters from those
signals, and for testing the no-hair theorem of general relativity. Focusing on
LISA, we use current models of its sensitivity to compute the expected
signal-to-noise ratio for ringdown events, the relative parameter estimation
accuracy, and the resolvability of different modes. We also discuss the extent
to which uncertainties on physical parameters, such as the black hole spin and
the energy emitted in each mode, will affect our ability to do black hole
spectroscopy.",0512160v2
1994-03-21,l=0 to l=1 Transition Form Factors,"A method is proposed to extend the hard scattering picture of Brodsky and
Lepage to transitions between hadrons with orbital angular momentum l=0 and
l=1. The use of covariant spin wave functions turns out to be very helpful in
formulating that method. As a first application we construct a light-cone wave
function of the nucleon resonance $N^*(1535)$ in the quark-diquark picture.
Using this wave function and the extended hard scattering picture, the
$N$--$N^*$ transition form factors are calculated at large momentum transfer
and the results compared to experimental data. As a further application of our
method we briefly discuss the $\pi$--$a_1$ form factors in an appendix.",9403319v2
2000-12-19,"Semileptonic B Decays into Excited Charmed Mesons ($D_1$, $D^*_2$) in HQEFT","Exclusive semileptonic B decays into excited charmed mesons ($D_1$, $D^*_2$)
are studied up to the order of $1/m_Q$ in the framework of the heavy quark
effective field theory (HQEFT), which contains the contributions of both
particles and antiparticles. Two wave functions $\eta^b_0$ and $\eta^c_0$,
which characterize the contributions from the kinematic operator at the order
of $1/m_Q$, are calculated by using QCD sum rule approach in HQEFT. Zero recoil
values of other two wave functions $\kappa'_1$ and $\kappa'_2$ are extracted
from the excited charmed-meson masses. Possible effects from the spin-dependent
transition wave functions which arise from the magnetic operators at the order
of $1/m_Q$ are analyzed. It is shown that the experimental measurements for the
branching ratios of $B \to D_1 l\nu$ and $B \to D^*_2 l\nu$ can be understood
in the framework of HQEFT.",0012240v1
2002-09-28,Addressing transversity with interference fragmentation functions,"The class of interference fragmentation functions, arising from interference
among different hadron production channels, is reconsidered. Their symmetry
properties with respect to chiral transformations allow building spin
asymmetries where the quark transversity distribution can be factorized out at
leading twist. For the case of two leading spinless hadrons inside the same
current jet, the pair system is expanded in relative partial waves. The cross
section is represented on the helicity basis of the target and the fragmenting
quark, as well as on the relative orbital angular momentum of the pair. From
the decay matrix being positive semi-definite, new bounds on the interference
fragmentation functions can be derived. The expansion in partial waves allows
to naturally incorporate in a unified formalism specific cases already studied
in the literature, such as the fragmentation functions arising from the
interference of two mesons in relative s and p waves, as well as the
fragmentation of a spin-1 hadron.",0209348v1
2000-02-09,Initial Conditions and the Structure of the Singularity in Pre-Big-Bang Cosmology,"We propose a picture, within the pre-big-bang approach, in which the universe
emerges from a bath of plane gravitational and dilatonic waves. The waves
interact gravitationally breaking the exact plane symmetry and lead generically
to gravitational collapse resulting in a singularity with the Kasner-like
structure. The analytic relations between the Kasner exponents and the initial
data are explicitly evaluated and it is shown that pre-big-bang inflation may
occur within a dense set of initial data. Finally, we argue that plane waves
carry zero gravitational entropy and thus are, from a thermodynamical point of
view, good candidates for the universe to emerge from.",0002070v2
2002-09-19,General Solutions of Relativistic Wave Equations,"General solutions of relativistic wave equations are studied in terms of the
functions on the Lorentz group. A close relationship between hyperspherical
functions and matrix elements of irreducible representations of the Lorentz
group is established. A generalization of the Gel'fand-Yaglom formalism for
higher-spin equations is given. It is shown that a two-dimensional complex
sphere is associated with the each point of Minkowski spacetime. The separation
of variables in a general relativistically invariant system is obtained via the
hyperspherical functions defined on the surface of the two-dimensional complex
sphere. In virtue of this, the wave functions are represented in the form of
series on the hyperspherical functions. Such a description allows to consider
all the physical fields on an equal footing. General solutions of the Dirac and
Weyl equations, and also the Maxwell equations in the Majorana-Oppenheimer
form, are given in terms of the functions on the Lorentz group.",0209036v1
1996-12-14,Possibility of observation of supernarrow dibaryons with symmetric wave function in $γd --> π^{\pm}+γNN$ reactions,"The possibility of obsevation of supernarrow dibaryons with symmetric wave
function in reactions $\gamma +d to \pi^+ +\gamma +nn$ and $\gamma +d to \pi^-
+\gamma +pp$ is studied. These dibaryons satisfy the condition $(-1)^{T+S}P=+1$
(where T is the isospin, S is the internal spin and P is the dibaryon parity)
and their decay into two nucleons is suppressed by the Pauly principle. In the
present paper the method of a dibaryon masses reconstruction over the dibaryon
decay products (\gamma nn) and (\gamma pp) is analysed. The Monte-Carlo
simulation is used to choose the optimal location of the detectors, to estimate
the contribution of the main background processes and to calculate the expected
yields of the dibaryon production. It is shown that 100 hours of the exposition
time at the microtron MAMI (Mainz) is quite enough to determine whether or not
the supernarrow dibaryons with symmetric wave function exist.",9612038v2
1997-08-08,Dihyperon in Chiral Colour Dielectric Model,"The mass of dihyperon with spin, parity $J^{\pi}=0^{+}$ and isospin $I = 0$
is calculated in the framework of Chiral colour dielectric model. The wave
function of the dihyperon is expressed as a product of two colour-singlet
baryon clusters. Thus the quark wave functions within the cluster are
antisymmetric. Appropriate operators are then used to antisymmetrize
inter-cluster quark wave functions. The radial part of the quark wavefunctions
are obtained by solving the the quark and dielectric field equations of motion
obtained in the Colour dielectric model. The mass of the dihyperon is computed
by including the colour magnetic energy as well as the energy due to meson
interaction. The recoil correction to the dihyperon mass is incorporated by
Peierls-Yoccoz technique. We find that the mass of the dihyperon is smaller
than the $\Lambda-\Lambda$ threshold by over 100 MeV. The implications of our
results on the present day relativistic heavy ion experiments is discussed.",9708011v1
2003-07-02,The Nd Break-Up Process in Leading Order in a Three-Dimensional Approach,"A three-dimensional approach based on momentum vectors as variables for
solving the three nucleon Faddeev equation in first order is presented. The
nucleon-deuteron break-up amplitude is evaluated in leading order in the NN
T-matrix, which is also generated directly in three dimensions avoiding a
summation of partial wave contributions. A comparison of semi-exclusive
observables in the $d(p,n)pp$ reaction calculated in this scheme with those
generated by a traditional partial wave expansion shows perfect agreement at
lower energies. At about 200 MeV nucleon laboratory energies deviations in the
peak of the cross section appear, which may indicate that special care is
required in a partial wave approach for energies at and higher than 200 MeV.
The role of higher order rescattering processes beyond the leading order in the
NN T-matrix is investigated with the result, that at 200 MeV rescattering still
provides important contributions to the cross section and certain spin
observables. The influence of a relativistic treatment of the kinematics is
investigated. It is found that relativistic effects become important at
projectile energies higher than 200 MeV.",0307011v1
2005-07-15,Dipolar radiation from spinning dust grains coupled to an electromagnetic wave,"In this letter we investigate how the complex rotation and quivering motion
of an elongated polarized dust grain in the presence of a monochromatic
electromagnetic wave can originate dipolar emission with two distinct spectral
components. We present a model for the emission of radiation by elongated
polarized dust grains under the influence of both an external electromagnetic
wave and a constant background magnetic field. The dust, exhibiting rotational
motion at the external electromagnetic field frequency w0 as well as quivering
motion at frequency W0, proportional to the em field amplitude, will radiate
with frequencies that will depend on the external field wavelength and
amplitude. The radiated spectra exibits a frequency around w0, and sidebands at
w0+-W0 and w0+-2W0. Since the amplitude and the frequency of the background
electromagnetic field are independent parameters, this model establishes a
correlation between different spectral components of galactic dipolar emission,
which may help to explain the correlation between a component of the Galactic
microwave emission and the 100micons thermal emission from interstellar dust,
that has been recently measured.",0507121v1
2006-03-27,Dispersion in a relativistic degenerate electron gas,"Relativistic effects on dispersion in a degenerate electron gas are discussed
by comparing known response functions derived relativistically (by Jancovici)
and nonrelativistically (by Lindhard). The main distinguishing feature is
one-photon pair creation, which leads to logarithmic singularities in the
response functions. Dispersion curves for longitudinal waves have a similar
tongue-like appearance in the relativistic and nonrelativistic case, with the
main relativistic effects being on the Fermi speed and the cutoff frequency.
For transverse waves the nonrelativistic treatment has a nonphysical feature
near the cutoff frequency for large Fermi momenta, and this is attributed to an
incorrect treatment of the electron spin. We find (with two important provisos)
that one-photon pair creation is allowed in superdense plasmas, implying
relatively strong coupling between transverse waves and pair creation.",0603227v1
2000-12-01,Mechanical analogy for the wave-particle: helix on a vortex filament,"The small amplitude-to-thread ratio helical configuration of a vortex
filament in the ideal fluid behaves exactly as de Broglie wave. The
complex-valued algebra of quantum mechanics finds a simple mechanical
interpretation in terms of differential geometry of the space curve. The wave
function takes the meaning of the velocity with which the helix rotates about
the screw axis. The helices differ in type of the screw - right or left-handed.
Two kinds of the helical waves deflect in the inhomogeneous fluid vorticity
field in the same way as spin particles in the Stern-Gerlach experiment.",0012008v3
2002-10-08,Continuous measurement with traveling wave probes,"We consider the use of a traveling wave probe to continuously measure the
quantum state of an atom in free space. Unlike the more familiar cavity QED
geometry, the traveling wave is intrinsically a multimode problem. Using an
appropriate modal decomposition we determine the effective measurement strength
for different atom-field interactions and different initial states of the
field. These include the interaction of a coherent-state pulse with an atom,
the interaction of a Fock-state pulse with an atom, and the use of Faraday
rotation of a polarized laser probe to perform a QND measurement on an atomic
spin.",0210056v2
2003-01-07,Uncollapsing the wave function,"The space quantization induced by a Stern-Gerlach experiment is normally
explained by invoking the ``collapse of the wave function.'' This is a rather
mysterious idea; it would be better to explain the Stern-Gerlach results
without using it. We re-analyze the Stern-Gerlach experiment using path
integrals. We find if we model explicitly the finite width of the beam,
coherent interference within the beam itself provides the space quantization --
without need to invoke the collapse. If we insist on employing only wave
functions with the space and spin parts kept forcibly disentangled, we recreate
the need to invoke the collapse. The collapse-free approach makes more specific
predictions about the shape and position of the scattered beams; if the
interaction region has finite length, these may be testable. Pending
experimental disambiguation, the chief arguments in favor of the collapse-free
approach are that it is simpler and less mysterious, has no adjustable
parameters, and requires the invocation of no new forces.",0301016v1
2003-11-19,On the Role of Density Matrices in Bohmian Mechanics,"It is well known that density matrices can be used in quantum mechanics to
represent the information available to an observer about either a system with a
random wave function (``statistical mixture'') or a system that is entangled
with another system (``reduced density matrix''). We point out another role,
previously unnoticed in the literature, that a density matrix can play: it can
be the ``conditional density matrix,'' conditional on the configuration of the
environment. A precise definition can be given in the context of Bohmian
mechanics, whereas orthodox quantum mechanics is too vague to allow a sharp
definition, except perhaps in special cases. In contrast to statistical and
reduced density matrices, forming the conditional density matrix involves no
averaging. In Bohmian mechanics with spin, the conditional density matrix
replaces the notion of conditional wave function, as the object with the same
dynamical significance as the wave function of a Bohmian system.",0311127v1
2005-05-23,Wave packet transmission of Bloch electron manipulated by magnetic field,"We study the phenomenon of wave packet revivals of Bloch electrons and
explore how to control them by a magnetic field for quantum information
transfer. It is showed that the single electron system can be modulated into a
linear dispersion regime by the ""quantized"" flux and then an electronic wave
packet with the components localized in this regime can be transferred without
spreading. This feature can be utilized to perform the high-fidelity transfer
of quantum information encoded in the polarization of the spin. Beyond the
linear approximation, the re-localization and self-interference occur as the
novel phenomena of quantum coherence.",0505169v2
2005-11-10,Block-block entanglement and quantum phase transitions in one-dimensional extended Hubbard model,"In this paper, we study block-block entanglement in the ground state of
one-dimensional extended Hubbard model. Our results show that the phase diagram
derived from the block-block entanglement manifests richer structure than that
of the local (single site) entanglement because it comprises nonlocal
correlation. Besides phases characterized by the charge-density-wave, the
spin-density-wave, and phase-separation, which can be sketched out by the local
entanglement, singlet superconductivity phase could be identified on the
contour map of the block-block entanglement. Scaling analysis shows that ${\rm
log}_2(l)$ behavior of the block-block entanglement may exist in both
non-critical and the critical regions, while some local extremum are induced by
the finite-size effect. We also study the block-block entanglement defined in
the momentum space and discuss its relation to the phase transition from
singlet superconducting state to the charge-density-wave state.",0511103v2
2007-04-02,Lower ground state due to counter-rotating wave interaction in trapped ion system,"We consider a single ion confined in a trap under radiation of two traveling
waves of lasers. In the strong-excitation regime and without the restriction of
Lamb-Dicke limit, the Hamiltonian of the system is similar to a driving
Jaynes-Cummings model without rotating wave approximation (RWA). The approach
we developed enables us to present a complete eigensolutions, which makes it
available to compare with the solutions under the RWA. We find that, the ground
state in our non-RWA solution is energically lower than the counterpart under
the RWA. If we have the ion in the ground state, it is equivalent to a spin
dependent force on the trapped ion. Discussion is made for the difference
between the solutions with and without the RWA, and for the relevant
experimental test, as well as for the possible application in quantum
information processing.",0704.0117v1
2007-04-25,Effect of selection on ancestry: an exactly soluble case and its phenomenological generalization,"We consider a family of models describing the evolution under selection of a
population whose dynamics can be related to the propagation of noisy traveling
waves. For one particular model, that we shall call the exponential model, the
properties of the traveling wave front can be calculated exactly, as well as
the statistics of the genealogy of the population. One striking result is that,
for this particular model, the genealogical trees have the same statistics as
the trees of replicas in the Parisi mean-field theory of spin glasses. We also
find that in the exponential model, the coalescence times along these trees
grow like the logarithm of the population size. A phenomenological picture of
the propagation of wave fronts that we introduced in a previous work, as well
as our numerical data, suggest that these statistics remain valid for a larger
class of models, while the coalescence times grow like the cube of the
logarithm of the population size.",0704.3389v1
2007-05-12,Modelling magnetically deformed neutron stars,"Rotating deformed neutron stars are important potential sources for
groundbased gravitational-wave interferometers such as LIGO, GE0600 and VIRGO.
One mechanism that may lead to significant non-asymmetries is the internal
magnetic field. It is well known that a magnetic star will not be spherical
and, if the magnetic axis is not aligned with the spin axis, the deformation
will lead to the emission of gravitational waves. The aim of this paper is to
develop a formalism that would allow us to model magnetically deformed stars,
using both realistic equations of state and field configurations. As a first
step, we consider a set of simplified model problems. Focusing on dipolar
fields, we determine the internal magnetic field which is consistent with a
given neutron star model. We then calculate the associated deformation. We
conclude by discussing the relevance of our results for current
gravitational-wave detectors and future prospects.",0705.1780v1
2007-08-14,Superconductivity without attraction in a quasi-one-dimensional metal,"An array of one-dimensional conductors coupled by transverse hopping and
interaction is studied with the help of a variational wave function. This wave
function is devised as to account for one-dimensional correlation effects. We
show that under broad conditions our system possesses the superconducting
ground state even if no attraction is present. The superconducting mechanism is
of many-body nature and deviates substantially from BCS. The phase diagram of
the model is mapped. It consists of two ordered phases competing against each
other: density wave, spin or charge, and unconventional superconductivity.
These phases are separated by the first order transition. The symmetry of the
superconducting order parameter is a non-universal property. It depends on
particulars of the Hamiltonian. Within the framework of our model possible
choices are the triplet $f$-wave and the singlet $d_{xy}$-wave. Organic
quasi-one-dimensional superconductors have similar phase diagram.",0708.1884v2
2007-08-23,"Monte Carlo study of Bose Laughlin wave function for filling factors 1/2, 1/4 and 1/6","Strongly correlated two-dimensional electronic systems subject to a
perpendicular magnetic field at lowest Landau level (LLL) filling factors: 1/2,
1/4 and 1/6 are believed to be composite fermion (CF) Fermi liquid phases. Even
though a Bose Laughlin wave function cannot describe these filling factors we
investigate whether such a wave function provides a lower energy bound to the
true CF Fermi liquid energies. By using Monte Carlo simulations in disk
geometry we compute the Bose Laughlin energies and compare them to
corresponding results for the spin-polarized LLL CF Fermi liquid state and
avalable data from literature.We find the unexpected result that, for filling
factors 1/4 and 1/6, the Bose Laughlin ground state energy is practically
identical to the true CF liquid energy while this is not the case at 1/2 where
the Bose Laughlin ground state energy is sizeably lower than the energy of the
CF Fermi liquid state.",0708.3211v1
2007-09-12,Constraining neutron star tidal Love numbers with gravitational wave detectors,"Ground-based gravitational wave detectors may be able to constrain the
nuclear equation of state using the early, low frequency portion of the signal
of detected neutron star - neutron star inspirals. In this early adiabatic
regime, the influence of a neutron star's internal structure on the phase of
the waveform depends only on a single parameter lambda of the star related to
its tidal Love number, namely the ratio of the induced quadrupole moment to the
perturbing tidal gravitational field. We analyze the information obtainable
from gravitational wave frequencies smaller than a cutoff frequency of 400 Hz,
where corrections to the internal-structure signal are less than 10 percent.
For an inspiral of two non-spinning 1.4 solar mass neutron stars at a distance
of 50 Mpc, LIGO II detectors will be able to constrain lambda to lambda < 2.0
10^{37} g cm^2 s^2 with 90% confidence. Fully relativistic stellar models show
that the corresponding constraint on radius R for 1.4 solar mass neutron stars
would be R < 13.6 km (15.3 km) for a n=0.5 (n=1.0) polytrope.",0709.1915v2
2007-12-06,Bayesian comparison of Post-Newtonian approximations of gravitational wave chirp signals,"We estimate the probability of detecting a gravitational wave signal from
coalescing compact binaries in simulated data from a ground-based
interferometer detector of gravitational radiation using Bayesian model
selection. The simulated waveform of the chirp signal is assumed to be a
spin-less Post-Newtonian (PN) waveform of a given expansion order, while the
searching template is assumed to be either of the same Post-Newtonian family as
the simulated signal or one level below its Post-Newtonian expansion order.
Within the Bayesian framework, and by applying a reversible jump Markov chain
Monte Carlo simulation algorithm, we compare PN1.5 vs. PN2.0 and PN3.0 vs.
PN3.5 wave forms by deriving the detection probabilities, the statistical
uncertainties due to noise as a function of the SNR, and the posterior
distributions of the parameters. Our analysis indicates that the detection
probabilities are not compromised when simplified models are used for the
comparison, while the accuracies in the determination of the parameters
characterizing these signals can be significantly worsened, no matter what the
considered Post-Newtonian order expansion comparison is.",0712.1030v3
2008-02-01,Wave-packet Formalism of Full Counting Statistics,"We make use of the first-quantized wave-packet formulation of the full
counting statistics to describe charge transport of noninteracting electrons in
a mesoscopic device. We derive various expressions for the characteristic
function generating the full counting statistics, accounting for both energy
and time dependence in the scattering process and including exchange effects
due to finite overlap of the incoming wave packets. We apply our results to
describe the generic statistical properties of a two-fermion scattering event
and find, among other features, sub-binomial statistics for nonentangled
incoming states (Slater rank 1), while entangled states (Slater rank 2) may
generate super-binomial (and even super-Poissonian) noise, a feature that can
be used as a spin singlet-triplet detector. Another application is concerned
with the constant-voltage case, where we generalize the original result of
Levitov-Lesovik to account for energy-dependent scattering and finite
measurement time, including short time measurements, where Pauli blocking
becomes important.",0802.0143v2
2008-03-17,Frequency Correlation of QPOs Based on a Resonantly-Excited Disk-Oscillation Model,"In previous papers, we have proposed a model that the high-frequency
quasi-periodic oscillations (HF QPOs) observed in black-hole and neutron-star
X-ray binaries are inertial-acoustic oscillations that are resonantly excited
on a one-armed deformed disk by nonlinear couplings between the oscillations
and the disk deformation. In this paper we show that in addition to the
inertial-acoustic waves, one-armed corrugation waves are also excited in the
deformed disks. They are low-frequency oscillations. We examine frequencies and
their correlations among the inertial-acoustic oscillations and the corrugation
waves that are excited, in order to know whether they can describe observed
frequency correlations among kHz QPOs and low-frequency QPOs (LF QPOs) in
neutron-star X-ray binaries. The results seem to well describe the observed
correlations in Cir X-1, if we adopt $M= 1.5\sim 2.0 M_\odot$ and $a_* \sim
0.8$, where $M$ is the mass of the central star and $a_*$ is the dimensionless
spin parameter of the metric. Finally, assumptions involved in this
disk-oscillation model are briefly summarized and discussed.",0803.2384v1
2008-05-28,"Group Theoretical Analysis of the Wave Function of the $[{\bf 70},1^-]$ Nonstrange Baryons in the $1/N_c$ Expansion","Using standard group theoretical techniques we construct the exact wave
function of the $[{\bf 70},1^-]$ multiplet in the orbital, spin and flavor
space. This symmetric wave function is compared to that customarily used in the
$1/N_c$ expansion, which is asymmetric. The comparison is made by analyzing the
matrix elements of various operators entering the mass formula. These matrix
elements are calculated by the help of isoscalar factors of the permutation
group, specially derived for this purpose as a function of $N_c$. We also
compare two distinct methods used in the study of the $[{\bf 70},1^-]$
multiplet. In the first method the generators are divided into two parts, one
part acting on a subsystem of $N_c-1$ quarks called core and another on the
separated quark. In the second method the system is treated as a whole. We show
that the latter is simpler and allows to clearly reveal the physically
important operators in the mass formula.",0805.4368v1
2008-08-27,Valley density-wave and multiband superconductivity in Fe-pnictides,"The key feature of the Fe-based superconductors is their quasi 2D multiband
Fermi surface. By relating the problem to a negative U Hubbard model and its
superconducting ground state, we show that the defining instability of such a
Fermi surface is the valley density-wave (VDW), a combined spin/charge
density-wave at the wavevector connecting the electron and hole valleys. As the
valley parameters change by doping or pressure, the fictitious superconductor
experiences ""Zeeman splitting"", eventually going into a non-uniform
""Fulde-Ferrell-Larkin-Ovchinikov"" (FFLO) state, an itinerant and often
incommensurate VDW of the real world, characterized by the metallic
conductivity from the ungapped remnants of the Fermi surface. When ""Zeeman
splitting"" exceeds the ""Chandrasekhar-Clogston"" limit, the ""FFLO"" state
disappears, and the VDW is destabilized. Near this point, the VDW fluctuations
and interband pair repulsion are essential ingredients of high-Tc
superconductivity in Fe-pnictides.",0808.3742v2
2008-10-07,Corotational Damping of Diskoseismic C-modes in Black Hole Accretion Discs,"Diskoseismic c-modes in accretion discs have been invoked to explain
low-frequency variabilities observed in black-hole X-ray binaries. These modes
are trapped in the inner-most region of the disc and have frequencies much
lower than the rotation frequency at the disc inner radius. We show that
because the trapped waves can tunnel through the evanescent barrier to the
corotational wave zone, the c-modes are damped due to wave absorption at the
corotation resonance. We calculate the corotational damping rates of various
c-modes using the WKB approximation. The damping rate varies widely depending
on the mode frequency, the black hole spin parameter and the disc sound speed,
and is generally much less than 10% of the mode frequency. A sufficiently
strong excitation mechanism is needed to overcome this corotational damping and
make the mode observable.",0810.1299v3
2009-02-02,An improved analytical description of inspiralling and coalescing black-hole binaries,"We present an analytical formalism, within the Effective-One-Body framework,
which predicts gravitational-wave signals from inspiralling and coalescing
black-hole binaries that agree, within numerical errors, with the results of
the currently most accurate numerical relativity simulations for several
different mass ratios. In the equal-mass case, the gravitational wave energy
flux predicted by our formalism agrees, within numerical errors, with the most
accurate numerical-relativity energy flux. We think that our formalism opens a
realistic possibility of constructing a sufficiently accurate, large bank of
gravitational wave templates, as needed both for detection and data analysis of
(non spinning) coalescing binary black holes.",0902.0136v2
2009-02-05,Order parameter and vortices in the superconducting Q-phase of CeCoIn5,"Recently, it has been reported that the low-temperature high-magnetic field
phase in CeCoIn5 (Q-phase), has spin-density wave (SDW) order that only exists
within this phase. This indicates that the SDW order is the result of the
development of pair density wave (PDW) order in the superconducting phase that
coexists with d-wave superconductivity. Here we develop a phenomenological
theory for these coexisting orders. This provides selection rules for the PDW
order and further shows that the detailed structure of this order is highly
constrained. We then apply our theory to the the vortex phase. This reveals
vortex phases in which the d-wave vortex cores exhibit charge density wave
(CDW) order and further reveals that the SDW order provides a unique probe of
the vortex phase.",0902.0843v1
2009-04-13,The Breaking Strain of Neutron Star Crust and Gravitational Waves,"Mountains on rapidly rotating neutron stars efficiently radiate gravitational
waves. The maximum possible size of these mountains depends on the breaking
strain of neutron star crust. With multi-million ion molecular dynamics
simulations of Coulomb solids representing the crust, we show that the breaking
strain of pure single crystals is very large and that impurities, defects, and
grain boundaries only modestly reduce the breaking strain to around 0.1. Due to
the collective behavior of the ions during failure found in our simulations,
the neutron star crust is likely very strong and can support mountains large
enough so that their gravitational wave radiation could limit the spin periods
of some stars and might be detectable in large scale interferometers.
Furthermore, our microscopic modeling of neutron star crust material can help
analyze mechanisms relevant in magnetar giant and micro flares.",0904.1986v1
2009-04-14,Sedeonic relativistic quantum mechanics,"We represent sixteen-component values ""sedeons"", generating associative
noncommutative space-time algebra. We demonstrate a generalization of
relativistic quantum mechanics using sedeonic wave functions and sedeonic
space-time operators. It is shown that the sedeonic second-order equation for
the sedeonic wave function, obtained from the Einstein relation for energy and
momentum, describes particles with spin 1/2. We show that for the special types
of wave functions the sedeonic second-order equation can be reduced to the set
of sedeonic first-order equations analogous to the Dirac equation. At the same
time it is shown that these sedeonic equations differ in space-time properties
and describe several types of massive and corresponding massless particles. In
particular we proposed four different equations, which could describe four
types of neutrinos.",0904.2093v1
2009-05-06,Angular momentum content of the rho-meson in lattice QCD,"The variational method allows one to study the mixing of interpolators with
different chiral transformation properties in the non-perturbatively determined
physical state. It is then possible to define and calculate in a
gauge-invariant manner the chiral as well as the partial wave content of the
quark-antiquark component of a meson in the infrared, where mass is generated.
Using a unitary transformation from the chiral basis to the LSJ basis one may
extract a partial wave content of a meson. We present results for the ground
state of the rho-meson using quenched simulations as well as simulations with
two dynamical quarks, all for lattice spacings close to 0.15 fm. We point out
that these results indicate a simple 3S1-wave composition of the rho-meson in
the infrared, like in the SU(6) flavor-spin quark model.",0905.0811v3
2009-05-18,Long-term evolution and gravitational wave radiation of neutron stars with differential rotation induced by r-modes,"In a second-order r-mode theory, S'a & Tom'e found that the r-mode
oscillation in neutron stars (NSs) could induce stellar differential rotation,
which leads to a saturation state of the oscillation spontaneously. Based on a
consideration of the coupling of the r-modes and the stellar spin and thermal
evolutions, we carefully investigate the influences of the r-mode-induced
differential rotation on the long-term evolutions of isolated NSs and NSs in
low-mass X-ray binaries, where the viscous damping of the r-modes and its
resultant effects are taken into account. The numerical results show that, for
both kinds of NSs, the differential rotation can prolong the duration of the
r-mode saturation state significantly. As a result, the stars can keep nearly
constant temperature and angular velocity over a thousand years. Moreover, due
to the long-term steady rotation of the stars, persistent quasi-monochromatic
gravitational wave radiation could be expected, which increases the
detectibility of gravitational waves from both nascent and accreting old NSs.",0905.2804v1
2009-06-15,Regge poles of the Schwarzschild black hole: a WKB approach,"We provide simple and accurate analytical expressions for the Regge poles of
the Schwarzschild black hole. This is achieved by using third-order WKB
approximations to solve the radial wave equations for spins 0, 1 and 2. These
results permit us to obtain analytically the dispersion relation and the
damping of the ""surface waves"" lying on the photon sphere of the Schwarzschild
black hole and which generate the weakly damped quasinormal modes of its
spectrum. Our results could be helpful in order to simplify considerably the
description of wave scattering from the Schwarzschild black hole as well as the
analysis of the gravitational radiation created in many black hole processes.
Furthermore, the existence of dispersion relations for the photons propagating
close to the photon sphere could have also important consequences in the
context of gravitational lensing.",0906.2601v3
2009-10-30,Observation of a J^PC = 1-+ exotic resonance in diffractive dissociation of 190 GeV/c pi- into pi- pi- pi+,"The COMPASS experiment at the CERN SPS has studied the diffractive
dissociation of negative pions into the pi- pi- pi+ final state using a 190
GeV/c pion beam hitting a lead target. A partial wave analysis has been
performed on a sample of 420000 events taken at values of the squared
4-momentum transfer t' between 0.1 and 1 GeV^2/c^2. The well-known resonances
a1(1260), a2(1320), and pi2(1670) are clearly observed. In addition, the data
show a significant natural parity exchange production of a resonance with
spin-exotic quantum numbers J^PC = 1-+ at 1.66 GeV/c^2 decaying to rho pi. The
resonant nature of this wave is evident from the mass-dependent phase
differences to the J^PC = 2-+ and 1++ waves. From a mass-dependent fit a
resonance mass of 1660 +- 10+0-64 MeV/c^2 and a width of 269+-21+42-64 MeV/c^2
is deduced.",0910.5842v3
2010-01-28,Stability of a Fully Magnetized Ferromagnetic state in Repulsively Interacting Ultracold Fermi Gases,"We construct a variational wave function to study whether a fully polarized
Fermi sea is energetically stable against a single spin flip. Our variational
wave function contains sufficient short-range correlation at least to the same
level as Gutzwiller's projected wave function. For Hubbard lattice model and
continuum model with pure repulsive interaction, we show a fully polarized
Fermi sea is generally unstable even when the repulsive strength becomes
infinite. While for a resonance model, ferromagnetic state is possible if the
s-wave scattering length is positive and sufficiently large, and the system is
prepared in scattering state orthogonal to molecular bound state. However, we
can not rule out the possibility that more exotic correlation can destabilize
the ferromagnetic state.",1001.5139v2
2010-03-08,Orbital-transverse density-wave instabilities in iron-based superconductors,"Besides the conventional spin-density-wave (SDW) state, a new kind of
orbital-transverse density-wave (OTDW) state is shown to exist generally in
multi-orbital systems. We demonstrate that the orbital character of Fermi
surface nesting plays an important role in density responses. The relationship
between antiferromagnetism and structural phase transition in LaFeAsO (1111)
and BaFe$_2$As$_2$ (122) compounds of iron-based superconductors may be
understood in terms of the interplay between the SDW and OTDW with a
five-orbital Hamiltonian. We propose that the essential difference between 1111
and 122 compounds is crucially determined by the presence of the
two-dimensional $d_{xy}$-like Fermi surface around (0,0) being only in 1111
parent compounds.",1003.1660v2
2010-04-07,Microscopic Model of Cuprate Superconductivity,"We present a model for cuprate superconductivity based on the identification
of an experimentally detected ""local superconductor"" as a charge 2 fermion
pairing in a circular, stationary density wave. This wave acts like a highly
correlated local ""boson"" satisfying a modified Cooper problem with additional
correlation stabilization relative to the separate right- and left-handed
density waves composing it. This local ""boson"" could be formed in a two-bound
roton-like manner; it has Fermion statistics. Delocalized superconductive
pairing (superconductivity) is achieved by a Feshbach resonance of two unpaired
holes (electrons) resonating with a virtual energy level of the bound pair
state of the local ""boson"" as described by the Boson-Fermion-Gossamer (BFG)
model. The spin-charge order interaction offers an explanation for the overall
shape of the superconducting dome as well a microscopic basis for the cuprate
superconducting transition temperatures. An explanation of the correlation of
superconducting transition temperature with experimental inelastic neutron and
electron Raman scattering is proposed, based on the energy of the virtual bound
pair. These and other modifications discussed suggest a microscopic explanation
for the entire cuprate superconductivity dome shape.",1004.1100v1
2010-05-25,Search for Gravitational Waves from Compact Binary Coalescence in LIGO and Virgo Data from S5 and VSR1,"We report the results of the first search for gravitational waves from
compact binary coalescence using data from the LIGO and Virgo detectors. Five
months of data were collected during the concurrent S5 (LIGO) and VSR1 (Virgo)
science runs. The search focused on signals from binary mergers with a total
mass between 2 and 35 Msun. No gravitational waves are identified. The
cumulative 90%-confidence upper limits on the rate of compact binary
coalescence are calculated for non-spinning binary neutron stars, black
hole-neutron star systems, and binary black holes to be 8.7x10^-3, 2.2x10^-3
and 4.4x10^-4 yr^-1 L_10^-1 respectively, where L_10 is 10^10 times the blue
solar luminosity. These upper limits are compared with astrophysical
expectations.",1005.4655v1
2010-07-28,Gutzwiller-projected wave functions for the pseudogap state of underdoped high-temperature superconductors,"Recent experiments strongly suggest that a Fermi surface reconstruction and
multiple Fermi pockets are important common features of the underdoped
high-temperature cuprate superconductors. A related theoretical work [Phys.
Rev. B 79, 134512 (2009)] has demonstrated that a number of hallmark phenomena
observed in the underdoped cuprates appear naturally in the scenario of a
paired electron pocket co-existing with unpaired hole pockets. We propose
Gutzwiller-projected wave-functions to describe this two-fluid state as well as
two competing states in its vicinity. It is argued that a pseudogap state
constructed from these wave-functions may be selected by energetics at finite
temperatures due to spin fluctuations.",1007.5067v2
2010-07-31,Compact and accurate variational wave functions of three-electron atomic systems constructed from semi-exponential radial basis functions,"The semi-exponential basis set of radial functions (A.M. Frolov, Physics
Letters A {\bf 374}, 2361 (2010)) is used for variational computations of bound
states in three-electron atomic systems. It appears that semi-exponential basis
set has a substantially greater potential for accurate variational computations
of bound states in three-electron atomic systems than it was originally
anticipated. In particular, the 40-term Larson's wave function improved with
the use of semi-exponential radial basis functions now produces the total
energy \linebreak -7.47805413551 $a.u.$ for the ground $1^2S-$state in the
${}^{\infty}$Li atom (only one spin function $\chi_1 = \alpha \beta \alpha -
\beta \alpha \alpha$ was used in these calculations). This variational energy
is very close to the exact ground state energy of the ${}^{\infty}$Li atom and
it substantially lower than the total energy obtained with the original
Larson's 40-term wave function (-7.477944869 $a.u.$).",1008.0089v2
2010-09-15,Mixing of fermion fields of opposite parities and baryon resonances,"We consider a loop mixing of two fermion fields of opposite parities whereas
the parity is conserved in a Lagrangian. Such kind of mixing is specific for
fermions and has no analogy in boson case. Possible applications of this effect
may be related with physics of baryon resonances. The obtained matrix
propagator defines a pair of unitary partial amplitudes which describe the
production of resonances of spin $J$ and different parity ${1/2}^{\pm}$ or
${3/2}^{\pm}$. The use of our amplitudes for joint description of $\pi N$
partial waves $P_{13}$ and $D_{13}$ shows that the discussed effect is clearly
seen in these partial waves as the specific form of interference between
resonance and background. Another interesting application of this effect may be
a pair of partial waves $S_{11}$ and $P_{11}$ where the picture is more
complicated due to presence of several resonance states.",1009.2845v2
2010-09-30,Efficient Sampling of Band-limited Signals from Sine Wave Crossings,"This correspondence presents an efficient method for reconstructing a
band-limited signal in the discrete domain from its crossings with a sine wave.
The method makes it possible to design A/D converters that only deliver the
crossing timings, which are then used to interpolate the input signal at
arbitrary instants. Potentially, it may allow for reductions in power
consumption and complexity in these converters. The reconstruction in the
discrete domain is based on a recently-proposed modification of the Lagrange
interpolator, which is readily implementable with linear complexity and
efficiently, given that it re-uses known schemes for variable fractional-delay
(VFD) filters. As a spin-off, the method allows one to perform spectral
analysis from sine wave crossings with the complexity of the FFT. Finally, the
results in the correspondence are validated in several numerical examples.",1009.6053v2
2010-11-26,The Light of Existence,"This chapter derives the properties of light from the properties of
processing, including its ability to be both a wave and a particle, to respond
to objects it doesn't physically touch, to take all paths to a destination, to
choose a route after it arrives, and to spin both ways at once as it moves.
Here a photon is an entity program spreading as a processing wave of instances.
It becomes a ""particle"" if any part of it overloads the grid network that runs
it, causing the photon program to reboot and restart at a new node. The
""collapse of the wave function"" is how quantum processing creates what we call
a physical photon. This informational approach gives insights into issues like
the law of least action, entanglement, superposition, counterfactuals, the
holographic principle and the measurement problem. The conceptual cost is that
physical reality is a quantum processing output, i.e. virtual.",1011.5705v2
2010-12-15,A Causal Alternative to Feynman's Propagator,"The Feynman propagator used in the conventional in-out formalism in quantum
field theory is not a causal propagator as wave packets are propagated
virtually instantaneously outside the causal region of the initial state. We
formulate a causal in-out formalism in quantum field theory by making use of
the Wheeler propagator, the time ordered commutator propagator, which is
manifestly causal. Only free scalar field theories and their first quantization
are considered. We identify the real Klein Gordon field itself as the wave
function of a neutral spinless relativistic particle. Furthermore, we derive a
probability density for our relativistic wave packet using the inner product
between states that live on a suitably defined Hilbert space of real quantum
fields. We show that the time evolution of our probability density is governed
by the Wheeler propagator, such that it behaves causally too.",1012.3473v1
2011-01-19,Reduced basis catalogs for gravitational wave templates,"We introduce a reduced basis approach as a new paradigm for modeling,
representing and searching for gravitational waves. We construct waveform
catalogs for non-spinning compact binary coalescences, and we find that for
accuracies of 99% and 99.999% the method generates a factor of about $10-10^5$
fewer templates than standard placement methods. The continuum of gravitational
waves can be represented by a finite and comparatively compact basis. The
method is robust under variations in the noise of detectors, implying that only
a single catalog needs to be generated.",1101.3765v2
2011-03-03,Determination of the pairing state in iron-based superconductors through neutron scattering,"We calculate the spin susceptibility in the s_{+-} and s_{++} superconducting
states of the iron pnictides using the effective five orbital model and
considering the quasiparticle damping. For the experimentally evaluated
magnitude of the quasiparticle damping and the superconducting gap, the results
at the wave vector ~ (pi,0) show that the s_{+-} state is more consistent with
the neutron scattering experiments, while for larger quasiparticle damping and
the superconducting gap, the s_{++} state can be more consistent. To
distinguish between two cases that reproduce the experiments at the wave vector
~ (pi,0), we propose to investigate experimentally the wave vector ~ (pi,pi).",1103.0586v2
2011-04-09,Search method for long-duration gravitational-wave transients from neutron stars,"We introduce a search method for a new class of gravitational-wave signals,
namely long-duration O(hours - weeks) transients from spinning neutron stars.
We discuss the astrophysical motivation from glitch relaxation models and we
derive a rough estimate for the maximal expected signal strength based on the
superfluid excess rotational energy. The transient signal model considered here
extends the traditional class of infinite-duration continuous-wave signals by a
finite start-time and duration. We derive a multi-detector Bayes factor for
these signals in Gaussian noise using $\F$-statistic amplitude priors, which
simplifies the detection statistic and allows for an efficient implementation.
We consider both a fully coherent statistic, which is computationally limited
to directed searches for known pulsars, and a cheaper semi-coherent variant,
suitable for wide parameter-space searches for transients from unknown neutron
stars. We have tested our method by Monte-Carlo simulation, and we find that it
outperforms orthodox maximum-likelihood approaches both in sensitivity and in
parameter-estimation quality.",1104.1704v1
2011-04-23,Orbital density wave induced by electron-lattice coupling in orthorhombic iron pnictides,"In this paper we explore the magnetic and orbital properties closely related
to a tetragonal-orthorhombic structural phase transition in iron pnictides
based on both two- and five-orbital Hubbard models. The electron-lattice
coupling, which interplays with electronic interaction, is self-consistently
treated. Our results reveal that the orbital polarization stabilizes the spin
density wave (SDW) order in both tetragonal and orthorhombic phases. However,
the ferro-orbital density wave (F-ODW) only occurs in the orthorhombic phase
rather than in the tetragonal one. Magnetic moments of Fe are small in the
intermediate Coulomb interaction region for the striped antiferromangnetic
phase in the realistic five orbital model. The anisotropic Fermi surface in the
SDW/ODW orthorhombic phase is well in agreement with the recent angle-resolved
photoemission spectroscopy experiments. These results suggest a scenario that
the magnetic phase transition is driven by the ODW order mainly arising from
the electron-lattice coupling.",1104.4575v1
2011-04-28,Mountain building of solid quark stars,"One of the key differences between normal neutron and (bare) quark stars is
relevant to the fact that the former are gravitationally bound while the latter
self-confined unless their masses approach the maximum mass. This difference
results in the possibility that quark stars could be very low massive whereas
neutron stars cannot. Mountains could also be build on quark stars if realistic
cold quark matter is in a solid state, and an alternative estimation of the
mountain building is present. As spinning compact objects with non-axisymmetric
mass distribution will radiate gravitational waves, the equations of states of
pulsars could be constraint by the amplitude of gravitational waves being
dependent on the heights of mountains. We then estimate the maximum mountains
and thus quadrupole moment on solid quark stars, to be consistent with that by
Owen (2005) if the breaking strain is 0.1, addressing that a solid quark star
with mass < 10^{-2} Msun could be `potato-like'. We estimate the gravitational
wave amplitude of solid quark stars with realistic mountains to be order of h0
~ 10^{-27}.",1104.5287v1
2011-05-09,Quantum quench spectroscopy of a Luttinger liquid: Ultrarelativistic density wave dynamics due to fractionalization in an XXZ chain,"We compute the dynamics of localized excitations produced by a quantum quench
in the spin 1/2 XXZ chain. Using numerics combining the density matrix
renormalization group and exact time evolution, as well as analytical
arguments, we show that fractionalization due to interactions in the pre-quench
state gives rise to ""ultrarelativistic"" density waves that travel at the
maximum band velocity. The system is initially prepared in the ground state of
the chain within the gapless XY phase, which admits a Luttinger liquid (LL)
description at low energies and long wavelengths. The Hamiltonian is then
suddenly quenched to a band insulator, after which the chain evolves unitarily.
Through the gapped dispersion of the insulator spectrum, the post-quench
dynamics serve as a ""velocity microscope,"" revealing initial state particle
correlations via space time density propagation. We show that the
ultrarelativistic wave production is tied to the particular way in which
fractionalization evades Pauli-blocking in the zero-temperature initial LL
state.",1105.1786v2
2011-07-18,Nonlinear propagation of light in Dirac matter,"The nonlinear interaction between intense laser light and a quantum plasma is
modeled by a collective Dirac equation coupled with the Maxwell equations. The
model is used to study the nonlinear propagation of relativistically intense
laser light in a quantum plasma including the electron spin-1/2 effect. The
relativistic effects due to the high-intensity laser light lead, in general, to
a downshift of the laser frequency, similar to a classical plasma where the
relativistic mass increase leads to self-induced transparency of laser light
and other associated effects. The electron spin-1/2 effects lead to a frequency
up- or downshift of the electromagnetic (EM) wave, depending on the spin state
of the plasma and the polarization of the EM wave. For laboratory solid density
plasmas, the spin-1/2 effects on the propagation of light are small, but they
may be significant in super-dense plasma in the core of white dwarf stars. We
also discuss extensions of the model to include kinetic effects of a
distribution of the electrons on the nonlinear propagation of EM waves in a
quantum plasma.",1107.3596v1
2011-08-29,Interpolating compact binary waveforms using the singular value decomposition,"Compact binary systems with total masses between tens and hundreds of solar
masses will produce gravitational waves during their merger phase that are
detectable by second-generation ground-based gravitational-wave detectors. In
order to model the gravitational waveform of the merger epoch of compact binary
coalescence, the full Einstein equations must be solved numerically for the
entire mass and spin parameter space. However, this is computationally
expensive. Several models have been proposed to interpolate the results of
numerical relativity simulations. In this paper we propose a numerical
interpolation scheme that stems from the singular value decomposition. This
algorithm shows promise in allowing one to construct arbitrary waveforms within
a certain parameter space given a sufficient density of numerical simulations
covering the same parameter space. We also investigate how similar approaches
could be used to interpolate waveforms in the context of parameter estimation.",1108.5618v1
2011-11-01,Electromagnetic priors for black hole spindown in searches for gravitational-waves from supernovae and long GRBs,"Some core-collapse supernovae appear to be hyper-energetic, and a subset of
these are aspherical and associated with long GRBs. We use observations of
electromagnetic emission from core-collapse supernovae and GRBs to impose
constraints on their free energy source as a prior to searches for their
gravitational wave emission. We review these events based on a finite
efficiency for the conversion of spin energy to magnetic winds powering
supernovae. We find that some of the hyper-energetic events cannot be powered
by the spindown of rapidly rotating proto-neutron stars by virtue of their
limited rotational energy. They can, instead, be produced by the spindown of
black holes providing a distinct prospect for gravitational-wave emission of
interest to LIGO, Virgo, and the LCGT.",1111.0137v1
2011-11-09,Propagating two-dimensional magnetic droplets,"Propagating, solitary magnetic wave solutions of the Landau-Lifshitz equation
with uniaxial, easy-axis anisotropy in thin (two-dimensional) magnetic films
are investigated. These localized, nontopological wave structures, parametrized
by their precessional frequency and propagation speed, extend the stationary,
coherently precessing ""magnon droplet"" to the moving frame, a non-trivial
generalization due to the lack of Galilean invariance. Propagating droplets
move on a spin wave background with a nonlinear droplet dispersion relation
that yields a limited range of allowable droplet speeds and frequencies. An
iterative numerical technique is used to compute the propagating droplet's
structure and properties. The results agree with previous asymptotic
calculations in the weakly nonlinear regime. Furthermore, an analytical
criterion for the droplet's orbital stability is confirmed. Time-dependent
numerical simulations further verify the propagating droplet's robustness to
perturbation when its frequency and speed lie within the allowable range.",1111.2310v2
2011-12-08,"How a wave function can collapse without violating Schroedinger's equation, and how to understand Born's rule","It is often claimed that the collapse of the wave function and Born's rule to
interpret the square of the norm as a probability, have to be introduced as
separate axioms in quantum mechanics besides the Schroedinger equation. Here we
show that this is not true in certain models where quantum behavior can be
attributed to underlying deterministic equations. It is argued that indeed the
apparent spontaneous collapse of wave functions and Born's rule are features
that strongly point towards determinism underlying quantum mechanics.",1112.1811v3
2012-01-30,Spin and angular momentum in the nucleon,"Using the covariant spectator theory (CST), we present the results of a
valence quark-diquark model calculation of the nucleon structure function f(x)
measured in unpolarized deep inelastic scattering (DIS), and the structure
functions g1(x) and g2(x) measured in DIS using polarized beams and targets.
Parameters of the wave functions are adjusted to fit all the data. The fit
fixes both the shape of the wave functions and the relative strength of each
component. Two solutions are found that fit f(x) and g1(x), but only one of
these gives a good description of g2(x). This fit requires the nucleon CST wave
functions contain a large D-wave component (about 35%) and a small P-wave
component (about 0.6%). The significance of these results is discussed.",1201.6337v1
2012-08-25,Gravitational Waves from Quasi-Circular Black Hole Binaries in Dynamical Chern-Simons Gravity,"Dynamical Chern-Simons gravity cannot be strongly constrained with current
experiments because it reduces to General Relativity in the weak-field limit.
This theory, however, introduces modifications in the non-linear, dynamical
regime, and thus, it could be greatly constrained with gravitational waves from
the late inspiral of black hole binaries. We complete the first self-consistent
calculation of such gravitational waves in this theory. For favorable
spin-orientations, advanced ground-based detectors may improve existing
solar-system constraints by 6 orders of magnitude.",1208.5102v4
2012-10-31,Searches for continuous gravitational waves with the LIGO and Virgo detector,"The LIGO Scientific Collaboration and Virgo Collaboration have carried out
joint searches in LIGO and Virgo data for periodic continuous gravitational
waves. These analyses range from targeted searches for gravitational-wave
signals from known pulsars, for which precise ephemerides from radio or X-ray
observations are used in matched filters, to all-sky searches for unknown
neutron stars, including stars in binary systems. Between these extremes lie
directed searches for known stars of unknown spin frequency or for new unknown
sources at specific locations, such as near the galactic center or in globular
clusters. Recent and ongoing searches of each type will be summarized, along
with prospects for future searches using data from the Advanced LIGO and Virgo
detectors.",1211.0021v1
2012-11-06,Towards Rapid Parameter Estimation on Gravitational Waves from Compact Binaries using Interpolated Waveforms,"Accurate parameter estimation of gravitational waves from coalescing compact
binary sources is a key requirement for gravitational-wave astronomy.
Evaluating the posterior probability density function of the binary's
parameters (component masses, sky location, distance, etc.) requires computing
millions of waveforms. The computational expense of parameter estimation is
dominated by waveform generation and scales linearly with the waveform
computational cost. Previous work showed that gravitational waveforms from
non-spinning compact binary sources are amenable to a truncated singular value
decomposition, which allows them to be reconstructed via interpolation at fixed
computational cost. However, the accuracy requirement for parameter estimation
is typically higher than for searches, so it is crucial to ascertain that
interpolation does not lead to significant errors. Here we provide a proof of
principle to show that interpolated waveforms can be used to recover posterior
probability density functions with negligible loss in accuracy with respect to
non-interpolated waveforms. This technique has the potential to significantly
increase the efficiency of parameter estimation.",1211.1254v1
2013-01-11,Tidal Waves in $^{102}$Pd: A Rotating Condensate of Multiple $d$ bosons,"Low-lying collective excitations in even-even vibrational and transitional
nuclei may be described semi-classically as quadrupole running waves on the
surface of the nucleus (""tidal waves""), and the observed vibrational-rotational
behavior can be thought of as resulting from a rotating condensate of
interacting $d$ bosons. These concepts have been investigated by measuring
lifetimes of the levels in the yrast band of the $^{102}$Pd nucleus with the
Doppler Shift Attenuation Method. The extracted $B(E2)$ reduced transition
probabilities for the yrast band display a monotonic increase with spin, in
agreement with the interpretation based on rotation-induced condensation of
aligned $d$ bosons.",1301.2391v2
2013-03-25,Improved Multi-Variable Variational Monte Carlo Method Examined by High-Precision Calculations of One-Dimensional Hubbard Model,"We revisit the accuracy of the variational Monte Carlo (VMC) method by taking
an example of ground state properties for the one-dimensional Hubbard model. We
start from the variational wave functions with the Gutzwiller and long-range
Jastrow factor introduced by Capello et al. [Phys. Rev. B 72, 085121 (2005)]
and further improve it by considering several quantum-number projections and a
generalized one-body wave function. We find that the quantum spin projection
and total momentum projection greatly improve the accuracy of the ground state
energy within 0.5% error, for both small and large systems at half filling.
Besides, the momentum distribution function n(k) at quarter filling calculated
up to 196 sites allows us direct estimate of the critical exponents of the
charge correlations from the power-law behavior of n(k) near the Fermi wave
vector. Estimated critical exponents well reproduce those predicted by the
Tomonaga-Luttinger theory.",1303.6041v1
2013-04-30,Breather and Rogue Wave solutions of a Generalized Nonlinear Schrodinger Equation,"In this paper, using the Darboux transformation, we demonstrate the
generation of first order breather and higher-order rogue waves from a
generalized nonlinear Schr\""odinger equation with several higher-order
nonlinear effects representing femtosecond pulse propagation through nonlinear
silica fiber. The same nonlinear evolution equation can also describes the
soliton-type nonlinear excitations in classical Heisenberg spin chain. Such
solutions have a parameter $\gamma_1$, denoting the strength of the
higher-order effects. From the numerical plots of the rational solutions, the
compression effects of the breather and rogue waves produced by $\gamma_1$ are
discussed in detail.",1304.8085v3
2013-06-20,Tensor meson photoproduction as a final state interaction effect,"The model is presented to describe the f_2(1270) meson photoproduction as a
result of pion-pion interactions in the final state. Treating tensor mesons as
objects dynamically created due to final state interactions is a convenient and
straightforward way to employ data from pi pi scattering like phase shifts and
inelasticities for description of (photo)production reactions while retaining
proper analytical structure of amplitudes, two particle unitarity and crossing
symmetry. The model presented here can provide experimentally testable
quantities like differential cross sections and pi pi mass distributions as
well as the strengths of partial waves corresponding to various f_2(1270)
helicities which are essential for partial wave analyses. It can also be used
to compute moments of angular distribution and spin density matrix elements
where partial wave interference effects are important.",1306.4882v1
2013-07-17,Spectrum of Coupled Waves in Orthorhombic Multiferroics With Cycloidal Antiferromagnetic Structure in External Electric and Magnetic Fields,"Spectrum of coupled spin, acoustic, electro-dipole and electromagnetic waves
in orthorhombic perovskite multiferroics placed in external electric and
magnetic field has been calculated. Frequency and field dependencies of
electric, magnetic, and magnetoelectric susceptibilities of multiferroics with
cycloidal antiferromagnetic structure in external electric and magnetic fields
have been investigated as well. The spectrum of coupled waves has a band
structure. Width and frequency ranges of bands depend on external fields. The
possibility of control of electrodynamic properties of orthorhombic perovskite
multiferroics with cycloidal antiferromagnetic structure by external electric
and magnetic fields has been shown.",1307.4664v1
2013-07-30,Wave dispersion derived from the square-root Klein-Gordon-Poisson system,"Recently there has been great interest around quantum relativistic models for
plasmas. In particular striking advances have been obtained by means of the
Klein-Gordon-Maxwell system, which provides a first order approach to the
relativistic regimes of quantum plasmas. It is a reliable method as long as the
plasma spin dynamics is not a fundamental aspect, to be addressed using more
refined (and heavier) models involving the Pauli-Schr\""odinger or Dirac
equations. In this work a further simplification is considered, tracing back to
the early days of relativistic quantum theory. Namely, we revisit the
square-root Klein-Gordon-Poisson system, where the positive branch of the
relativistic energy-momentum relation is mapped to a quantum wave equation. The
associated linear wave propagation is analyzed and compared to the results in
the literature. We determine physical parameters where the simultaneous quantum
and relativistic effects can be noticeable in weakly coupled electrostatic
plasmas.",1307.8147v1
2013-10-02,One approach for determining susceptibilities and order parameters in multi-band Hubbard model,"We present an approach for determining susceptibilities and order parameters
in multi-band Hubbard model within functional renormalization group method, and
apply it to study various instabilities of the FeAs-based high temperature
superconductor. First, we derive the formulae of susceptibilities and order
parameters of superconducting parings, spin density waves and charge density
waves with diverse wave vectors which could occur in multi-band Hubbard model.
Second, we apply it to the FeAs-based high temperature superconductor and find
an electronic-driven superconducting pairing instability within a five band
model with pure repulsive interactions. Our study shows that for doping of our
concern, there is competition between antiferromagnetic and superconducting
instabilities. In addition, we show that for doping of 0.1, the susceptibility
of extended s-wave pairing is dominant over others, while a staggered
superconducting pairing with has the second largest value of susceptibility.",1310.0646v1
2013-10-17,Sounding stellar cores with mixed modes,"The space-borne missions CoRoT and Kepler have opened a new era in stellar
physics, especially for evolved stars, with precise asteroseismic measurements
that help determine precise stellar parameters and perform ensemble astero
seismology. This paper deals with the quality of the information that we can
retrieve from the oscillations. It focusses on the conditions for obtaining the
most accurate measurement of the radial and non-radial oscillation patterns.
This accuracy is a prerequisite for making the best with asteroseismic data.
From radial modes, we derive proxies of the stellar mass and radii with an
unprecedented accuracy for field stars. For dozens of subgiants and thousands
of red giants, the identification of mixed modes (corresponding to gravity
waves propagating in the core coupled to pressure waves propagating in the
envelope) indicates unambiguously their evolutionary status. As probes of the
stellar core, these mixed modes also reveal the internal differential rotation
and show the spinning down of the core rotation of stars ascending the red
giant branch. A toy model of the coupling of waves constructing mixed modes is
exposed, for illustrating many of their features.",1310.4752v1
2013-11-04,Anisotropic g factor in InAs self-assembled quantum dots,"We investigate the wave functions, spectrum, and g-factor anisotropy of
low-energy electrons confined to self-assembled, pyramidal InAs quantum dots
(QDs) subject to external magnetic and electric fields. We present the
construction of trial wave functions for a pyramidal geometry with hard-wall
confinement. We explicitly find the ground and first excited states and show
the associated probability distributions and energies. Subsequently, we use
these wave functions and 8-band $k\cdot p$ theory to derive a Hamiltonian
describing the QD states close to the valence band edge. Using a perturbative
approach, we find an effective conduction band Hamiltonian describing
low-energy electronic states in the QD. From this, we further extract the
magnetic field dependent eigenenergies and associated g factors. We examine the
g factors regarding anisotropy and behavior under small electric fields. In
particular, we find strong anisotropies, with the specific shape depending
strongly on the considered QD level. Our results are in good agreement with
recent measurements [Takahashi et al., Phys. Rev. B 87, 161302 (2013)] and
support the possibility to control a spin qubit by means of g-tensor
modulation.",1311.0908v2
2014-02-14,Correlated valence bond state and its study of the spin-1/2 J1-J2 Anti-ferromagnetic Heisenberg model on a square lattice,"We propose a class of variational wave functions, namely the correlated
valence bond states, for the frustrated Hamiltonian in the paramagnetic phase.
This class of wave functions admits negative amplitude and the same sub-lattice
pairing when a bipartite lattice is considered, thus suffers from the negative
sign problem. However if applied to small systems, the sign problem is
manageable using the standard variational Monte Carlo method. We optimize the
wave functions for the J1-J2 Anti ferromagnetic Heisenberg model on a square
lattice in the coupling region J2/J1 \in [0.45 : 0.56] for system sizes L = 4,
6, 8. To calculate the correlation functions and the order parameters for
larger systems, we make the extensive Monte Carlo samplings using the
variational parameters optimized at system size L = 8. We find that the
paramagnetic phase is a gap-less spin liquid in the entire range of J2/J1 \in
[0.45 : 0.56] with a gap-less singlet excitation and a gaped triplet
excitation.",1402.3564v2
2014-03-06,Partial Wave Analysis at BESIII,"The BESIII experiment in Beijing takes data in $\tau$-charm domain since
2009. For the moment the world largest samples of $J/\psi$, $\psi(3686)$,
$\psi(3770)$ and $\psi(4040)$ data have been collected. Hadron spectroscopy is
a unique way to access QCD, which is one of the most important physics goals of
BESIII. Experimental search of new forms of hadrons and subsequent
investigation of their properties would provide validation of and valuable
input to the quantitative understanding of QCD. The key to success lies in high
levels of precision during the measurement and high statistics in the recorded
data set complemented with sophisticated analysis methods. Partial wave
analysis (PWA) is a powerful tool to study the hadron spectroscopy, that allows
one to extract the resonance's spin-parity, mass, width and decay properties
with high sensitivity and accuracy. In this poster, we present the working PWA
framework of BESIII -- GPUPWA and the recent results of PWA of
$J/\psi\to\gamma\eta\eta$. GPUPWA is a PWA framework for high statistics
partial wave analyses harnessing the GPU parallel computing.",1403.1337v1
2014-04-04,Giant Goos-Hänchen shift in Scattering: the role of interfering Localized Plasmon modes,"The longitudinal and the transverse beam shifts, namely, the Goos-H\""anchen
(GH) and the Spin-Hall (SH) shifts are usually observed at planar interfaces.
It has recently been shown that the transverse SH shift may also arise due to
scattering of plane waves. Here, we show that analogous in-plane (longitudinal)
shift also exist in scattering of plane waves from micro/nano systems. We study
both the GH and the SH shifts in plasmonic metal nanoparticles/ nanostructures
and dielectric micro-particles employing a unified framework that utilizes the
transverse components of the Poynting vector of the scattered wave. The results
demonstrate that interference of neighboring resonance modes in plasmonic
nanostructures (e.g., electric dipolar and quadrupolar modes in metal spheres)
leads to giant enhancement of GH shift in scattering from such systems. We also
unravel interesting correlations between these shifts with the polarimetry
parameters, diattenuation and retardance.",1404.1166v1
2014-04-24,Accelerated gravitational-wave parameter estimation with reduced order modeling,"Inferring the astrophysical parameters of coalescing compact binaries is a
key science goal of the upcoming advanced LIGO-Virgo gravitational-wave
detector network and, more generally, gravitational-wave astronomy. However,
current parameter estimation approaches for such scenarios can lead to
computationally intractable problems in practice. Therefore there is a pressing
need for new, fast and accurate Bayesian inference techniques. In this letter
we demonstrate that a reduced order modeling approach enables rapid parameter
estimation studies. By implementing a reduced order quadrature scheme within
the LIGO Algorithm Library, we show that Bayesian inference on the
9-dimensional parameter space of non-spinning binary neutron star inspirals can
be sped up by a factor of 30 for the early advanced detectors' configurations.
This speed-up will increase to about $150$ as the detectors improve their
low-frequency limit to 10Hz, reducing to hours analyses which would otherwise
take months to complete. Although these results focus on gravitational
detectors, the techniques are broadly applicable to any experiment where fast
Bayesian analysis is desirable.",1404.6284v2
2014-05-28,"First exact Geon found is a non-singular monopole, propagating as a primordial gravitational pp-wave","Geons are particle-like electrovacua. The concept is well-defined, but it
still lacks a proper first example. Emerging as such is a self-confined exact
2-parameter pp-wave non-Dirac monopole {\cal G} with primordial Q/r^2 (r\geq
r_o) field plus higher moments. {\cal G} has effective mass,
independently-scaled NUT-like charge \kappa|Q|=2r_o as diameter, and spin.
{\cal G} {\em cannot} have actual {\sc em} charge $Q$ (by \partial{\cal G}=0),
Ricci-flat limits, nor spacetime or Dirac-string singularities, but Dirac's
quantization condition holds. {\cal G}/2, as an upgraded `Kerr-Newman'
alternative or {\cal S}_Q geon, carries actual charge Q confined by topology on
a round-S^2[r_o] physical singularity on \partial{\cal S}_Q\neq0. {\cal G} and
{\cal S}_Q offer exact analytic models in particle physics and cosmology,
notably for primordial gravitational waves, inflation, and pre-galactic
dynamics.",1405.7363v2
2014-08-07,$U(1)\times U(1)$ Symmetry Protected Topological Order in Gutzwiller Wave Functions,"Gutzwiller projection is a way to construct many-body wave functions that
could carry topological order or symmetry protected topological (SPT) order.
However, an important issue is to determine whether or not a given
Gutzwiller-projected wave functions (GWF) carries a non-trivial SPT order, and
which SPT order is carried by the wavefunction. In this paper, we numerically
study the SPT order in a spin $S = 1$ GWF on the Kagome lattice. Using the
standard Monte Carlo method, we directly confirm that the GWF has (1) gapped
bulk with short-range correlations, (2) a trivial topological order via
nondegenerate ground state, and zero topological entanglement entropy, (3) a
non-trivial $U(1)\times U(1)$ SPT order via the Hall conductances of the
protecting $U(1)\times U(1)$ symmetry, and (4) symmetry protected gapless
boundary. This represents numerical evidence of continuous symmetry protected
topological order in two-dimensional bosonic lattice systems.",1408.1676v3
2014-08-12,Fidelity susceptibilities in the one-dimensional extended Hubbard model,"We investigated the fidelity susceptibility in the one-dimension (1D) Hubbard
model and the extended Hubbard model at half-filling via the density matrix
renormalization group. From the numerical results, we argue that in the 1D
Hubbard model, the fidelity susceptibility shows a divergence at two points
which is infinitesimally close to the critical point while it is always
extensive exactly at the critical point. For the extended Hubbard model, we
found that for a properly chosen driving parameter, the fidelity susceptibility
is able to reveal the quantum phase transitions between the PS (phase
separation)-superconducting, superconducting-CDW (charge-density wave),
CDW-SDW(spin-density wave), SDW-PS, CDW-BOW (bond-order wave), and the BOW-SDW
phases.",1408.2642v1
2014-08-12,Particle Creation in Global de Sitter Space: Bulk Space Consideration,"Recently in \cite{Anderson:2013zia, Anderson:2013ila}, it was shown that
global de Sitter space is unstable even to the massive particle creation with
no self-interactions. In this paper we study the instability by making use of
the coordinate-independent plane wave in de Sitter space, within this
formalism, we show that the previous results of instability of de Sitter space
due to the particle creation can be generalized to higher-spin fields in a
straightforward way. The so-called plane wave are defined globally in de Sitter
space and de Sitter invariance is manifest since such modes are deduced from
the group theoretical point of view by the means of the Casimir operators. In
fact, we employ the underling symmetry of embedding space namely the $4+1$
dimensional flat space to write the field equations and the solutions can be
obtained in terms of the plane wave in embedding space.",1408.2799v2
2014-08-12,Switching of magnetic domains reveals evidence for spatially inhomogeneous superconductivity,"The interplay of magnetic and charge fluctuations can lead to quantum phases
with exceptional electronic properties. A case in point is magnetically-driven
superconductivity, where magnetic correlations fundamentally affect the
underlying symmetry and generate new physical properties. The superconducting
wave-function in most known magnetic superconductors does not break
translational symmetry. However, it has been predicted that modulated triplet
p-wave superconductivity occurs in singlet d-wave superconductors with
spin-density wave (SDW) order. Here we report evidence for the presence of a
spatially inhomogeneous p-wave Cooper pair-density wave (PDW) in CeCoIn5. We
show that the SDW domains can be switched completely by a tiny change of the
magnetic field direction, which is naturally explained by the presence of
triplet superconductivity. Further, the Q-phase emerges in a common
magneto-superconducting quantum critical point. The Q-phase of CeCoIn5 thus
represents an example where spatially modulated superconductivity is associated
with SDW order.",1408.2868v1
2014-09-11,The collision between two ortho-Positronium (Ps) atoms: a four-body Coulomb problem,"The elastic collision between two ortho-positronium (e.g. S=1) atoms is
studied using an ab-initio static-exchange model (SEM) in the center of mass
(CM) frame considering the system as a four-body Coulomb problem where all the
Coulomb interaction terms in the direct and exchange channels are treated
exactly. A coupled-channel methodology in momentum space is used to solve
Lippman-Schwinger equation following the integral approach. A new SEM code is
developed in which the Born-Oppenheimer (BO) scattering amplitude acts as input
to derive the SEM amplitude adapting the partial wave analysis. The s-, p- and
d- wave elastic phase shifts and the corresponding partial cross sections for
the spin alignment S=0, i.e. singlet (+) and S=2, i.e. triplet (-) states are
studied. An augmented-Born approximation is used to include the contribution of
higher partial waves more accurately to determine the total/integrated elastic
cross section ( ), the quenching cross section ( ) and ortho to para conversion
ratio ( ). The effective range theory is used to determine the scattering
lengths and effective ranges in the s-wave elastic scattering. The theory
includes the non-adiabatic short-range effects due to exchange.",1409.3371v2
2014-09-26,Optimization of NANOGrav's Time Allocation for Maximum Sensitivity to Single Sources,"Pulsar Timing Arrays (PTAs) are a collection of precisely timed millisecond
pulsars (MSPs) that can search for gravitational waves (GWs) in the nanohertz
frequency range by observing characteristic signatures in the timing residuals.
The sensitivity of a PTA depends on the direction of the propagating
gravitational wave source, the timing accuracy of the pulsars, and the
allocation of the available observing time. The goal of this paper is to
determine the optimal time allocation strategy among the MSPs in the North
American Nanohertz Observatory for Gravitational Waves (NANOGrav) for a single
source of GW under a particular set of assumptions. We consider both an
isotropic distribution of sources across the sky and a specific source in the
Virgo cluster. This work improves on previous efforts by modeling the effect of
intrinsic spin noise for each pulsar. We find that, in general, the array is
optimized by maximizing time spent on the best-timed pulsars, with sensitivity
improvements typically ranging from a factor of 1.5 to 4.",1409.7722v1
2014-11-12,Charge density waves in graphite; towards the magnetic ultra-quantum limit,"Graphite is a model system for the study of three-dimensional electrons and
holes in the magnetic quantum limit, in which the charges are confined to the
lowest Landau levels. We report magneto-transport measurements in pulsed
magnetic fields up to 60 T, which resolve the collapse of two density wave
states in two, electron and hole, Landau levels at 52.3 and 54.2 T
respectively. We report evidence for a commensurate density wave at 47.1 T in
the electron Landau level. The theoretical modelling of these results predicts
that the ultra-quantum limit is entered above 73.5 T. This state is an
insulator, and we discuss its correspondence to the ""metallic"" state reported
earlier. We propose that this (interaction-induced) insulating phase supports
surface states that carry no charge or spin within the planes, but does however
support charge transport out of plane.",1411.3323v3
2015-03-16,Quantum Ising model in transverse and longitudinal fields: chaotic wave functions,"The construction of a statistical model for eigenfunctions of the Ising model
in transverse and longitudinal fields is discussed in detail for the chaotic
case. When the number of spins is large, each wave function coefficient has the
Gaussian distribution with zero mean and the variance calculated from the first
two moments of the Hamiltonian. The main part of the paper is devoted to the
discussion of different corrections to the asymptotic result. One type of
corrections is related with higher order moments of the Hamiltonian and can be
taken into account by Gibbs-like formulae. Another corrections are due to
symmetry contributions which manifest as different numbers of non-zero real and
complex coefficients. Statistical model with these corrections included agrees
well with numerical calculations of wave function moments.",1503.04508v1
2015-04-01,Some Aspects of Quantum Mechanics of Particle Motion in Static Centrally Symmetric Gravitational Fields,"The domain of wave functions and effective potentials of the Dirac and
Klein-Gordon equations for quantum-mechanical particles in static centrally
symmetric gravitational fields are analyzed by taking into account the Hilbert
causality condition. For all the explored metrics, assuming existence of event
horizons, the conditions of a ""fall"" of a particle to the appropriate event
horizons are implemented. The exclusion is one of the solutions for the
Reissner-Nordstroem extreme field with the single event horizon. In this case,
while fulfilling the condition found by V.I.Dokuchaev, Yu.N.Yeroshenko, the
normalization integral is convergent and the wave functions become zero on the
event horizon. This corresponds to the Hilbert causality condition. In our
paper, due to the analysis of the effective potential for the
Reissner-Nordstroem extreme field with real radial wave functions of the Dirac
equation, the impossibility is demonstrated for the bound stationary state
existence of quantum-mechanical particles, with positive energy, off the event
horizon. The analysis of the effective potential of the Dirac equation for the
case of the naked singularity of the Reissner-Nordstroem field shown the
possible existence of stationary bound states of quantum-mechanical half-spin
particles.",1504.00306v1
2015-04-16,Synergy between ground and space based gravitational wave detectors for estimation of binary coalescence parameters,"We study the advantage of the co-existence of future ground and space based
gravitational wave detectors, in estimating the parameters of a binary
coalescence. Using the post-Newtonian waveform for the inspiral of non-spinning
neutron star-black hole pairs in circular orbits, we study how the estimates
for chirp mass, symmetric mass ratio, and time and phase at coalescence are
improved by combining the data from different space-ground detector pairs.
Since the gravitational waves produced by binary coalescence also provide a
suitable domain where we can study strong field gravity, we also study the
deviations from general relativity using the parameterized post-Einsteinian
framework. As an example, focusing on the Einstein telescope and DECIGO pair,
we demonstrate that there exists a sweet spot range of sensitivity in the
pre-DECIGO phase where the best enhancement due to the synergy effect can be
obtained for the estimates of the post-Newtonian waveform parameters as well as
the modification parameters to general relativity.",1504.04108v1
2015-05-21,"A self-interfering clock as a ""which path"" witness","We experimentally demonstrate a new interferometry paradigm: a
self-interfering clock. We split a clock into two spatially separated wave
packets, and observe an interference pattern with a stable phase showing that
the splitting was coherent, i.e., the clock was in two places simultaneously.
We then make the clock wave packets ""tick"" at different rates to simulate a
proper time lag. The entanglement between the clock's time and its path yields
""which path"" information, which affects the visibility of the clock's
self-interference. By contrast, in standard interferometry, time cannot yield
""which path"" information. As a clock we use an atom prepared in a superposition
of two spin states. This first proof-of-principle experiment may have
far-reaching implications for the study of time and general relativity and
their impact on fundamental quantum effects such as decoherence and wave packet
collapse.",1505.05765v1
2015-05-21,"Path algebras, wave-particle duality, and quantization of phase space","Semigroup algebras admit certain `coherent' deformations which, in the
special case of a path algebra, may associate a periodic function to an
evolving path; for a particle moving freely on a straight line after an initial
impulse, the wave length is that hypothesized by de Broglie's wave-particle
duality. This theory leads to a model of ""physical"" phase space of which
mathematical phase space, the cotangent bundle of configuration space, is a
projection. This space is singular, quantized at the Planck level, its
structure implies the existence of spin, and the spread of a packet can be
described as a random walk. The wavelength associated to a particle moving in
this space need not be constant and its phase can change discontinuously.",1505.05859v7
2015-11-20,Quantum solitons with emergent interactions in a model of cold atoms on the triangular lattice,"Cold atoms bring new opportunities to study quantum magnetism, and in
particular, to simulate quantum magnets with symmetry greater than $SU(2)$.
Here we explore the topological excitations which arise in a model of cold
atoms on the triangular lattice with $SU(3)$ symmetry. Using a combination of
homotopy analysis and analytic field-theory we identify a new family of
solitonic wave functions characterised by integer charge ${\bf Q} = (Q_A, Q_B,
Q_C)$, with $Q_A + Q_B + Q_C = 0$. We use a numerical approach, based on a
variational wave function, to explore the stability of these solitons on a
finite lattice. We find that, while solitons with charge ${\bf Q} = (Q, -Q, 0)$
are stable, wave functions with more general charge spontaneously decay into
pairs of solitons with emergent interactions. This result suggests that it
could be possible to realise a new class of interacting soliton, with no
classical analogue, using cold atoms. It also suggests the possibility of a new
form of quantum spin liquid, with gauge--group U(1)$\times$U(1).",1511.06515v2
2016-04-14,Tidal wave in $^{102}$Pd: An extended five-dimensional collective Hamiltonian description,"The five-dimensional collective Hamiltonian based on the covariant density
functional theory is applied to investigate the observed tidal wave mode in the
yrast band of $^{102}$Pd. The energy spectra, the relations between the spin
and the rotational frequency, and the ratios of $B(E2)/\mathcal{J}(I)$ in the
yrast band are well reproduced by introducing the empirical $ab$ formula for
the moments of inertia. This $ab$ formula is related to the fourth order effect
of collective momentum in the collective Hamiltonian. It is also shown that the
shape evolution in the tidal wave is determined microscopically by the
competition between the rotational kinetic energy and the collective potential
in the framework of the collective Hamiltonian.",1604.04132v1
2016-06-03,Rapid and reliable sky localization of gravitational wave sources,"The first detection of gravitational waves by LIGO from the merger of two
compact objects has sparked new interest in detecting electromagnetic
counterparts to these violent events. For mergers involving neutron stars, it
is thought that prompt high-energy emission in gamma rays and x-rays will be
followed days to weeks later by an afterglow in visible light, infrared and
radio. Rapid sky localization using the data from a network of gravitational
wave detectors is essential to maximize the chances of making a joint
detection. Here I describe a new technique that is able to produce accurate,
fully Bayesian sky maps in seconds or less. The technique can be applied to
spin-precessing compact binaries, and can take into account detector
calibration and spectral estimation uncertainties.",1606.00953v1
2016-06-09,Analytic gravitational waveforms for generic precessing compact binaries,"Binary systems of two compact objects circularize and spiral toward each
other via the emission of gravitational waves. The coupling of the spins of
each object with the orbital angular momentum causes the orbital plane to
precess, which leads to modulation of the gravitational wave signal. Until now,
generating frequency-domain waveforms for fully precessing systems for use in
gravitational wave data analysis meant numerically integrating the equations of
motion, then Fourier transforming the result, which is very computationally
intensive for systems that complete hundreds or thousands of cycles in the
sensitive band of a detector. Previously, analytic solutions were only
available for certain special cases or for simplified models. Here we describe
the construction of closed-form, frequency-domain waveforms for
fully-precessing, quasi-circular binary inspirals.",1606.03117v2
2016-07-18,Heavy meson spectroscopy under strong magnetic field,"Spectra of the neutral heavy mesons, $\eta_c(1S,2S)$, $J/\psi$, $\psi(2S)$,
$\eta_b(1S,2S,3S)$, $\Upsilon(1S,2S,3S)$, $D$, $D^\ast$, $B$, $B^\ast$, $B_s$
and $B_s^\ast$, in a homogeneous magnetic field are analyzed in a potential
model of constituent quarks. To obtain anisotropic wave functions and the
corresponding eigenvalues, the cylindrical Gaussian expansion method is
applied, where the wave functions for transverse and longitudinal directions in
the cylindrical coordinate are expanded by the Gaussian bases separately.
Energy level structures in the wide range of magnetic fields are obtained and
the deformation of the wave functions is shown, which reflects effects of the
spin mixing, the Zeeman splitting and quark Landau levels. The contribution
from the magnetic catalysis in heavy-light mesons is discussed as a change of
the light constituent quark mass.",1607.04935v4
2016-08-02,Anatomy of quantum critical wave functions in dissipative impurity problems,"Quantum phase transitions reflect singular changes taking place in a
many-body ground state, however, computing and analyzing large-scale critical
wave functions constitutes a formidable challenge. New physical insights into
the sub-Ohmic spin-boson model are provided by the coherent state expansion
(CSE), which represents the wave function by a linear combination of
classically displaced configurations. We find that the distribution of
low-energy displacements displays an emergent symmetry in the absence of
spontaneous symmetry breaking, while experiencing strong fluctuations of the
order parameter near the quantum critical point. Quantum criticality provides
two strong fingerprints in critical low-energy modes: an algebraic decay of the
average displacement and a constant universal average squeezing amplitude.
These observations, confirmed by extensive variational matrix product states
(VMPS) simulations and field theory arguments, offer precious clues into the
microscopics of critical many-body states in quantum impurity models.",1608.00799v2
2016-09-15,Geodesic Witten diagrams with an external spinning field,"We explore AdS/CFT correspondence between geodesic Witten diagrams and
conformal blocks (conformal partial waves) with an external symmetric traceless
tensor field. We derive an expression for the conformal partial wave with an
external spin-1 field and show that this expression is equivalent to the
amplitude of the geodesic Witten diagram. We also show the equivalence by using
conformal Casimir equation in embedding formalism. Furthermore, we extend the
construction of the amplitude of the geodesic Witten diagram to an external
arbitrary symmetric traceless tensor field. We show our construction agrees
with the known result of the conformal partial waves.",1609.04563v2
2016-10-14,Intertwined Order in a Frustrated 4-leg $t - J$ Cylinder,"We report a density-matrix renormalization group study of the $t$-$J$ model
with nearest ($t_1$ & $J_1$) and next-nearest ($t_2$ & $J_2$) interactions on a
4-leg cylinder with concentration $\delta=1/8$ of doped holes. We observe an
astonishingly complex interplay between uniform $d$-wave superconductivity (SC)
and strong spin and charge density wave ordering tendencies (SDW and CDW).
Depending on parameters, the CDWs can be commensurate with period 4 or 8. By
comparing the charge ordering vectors with $2 k_F$, we rule out Fermi surface
nesting-induced density wave order in our model. Magnetic frustration (i.e.
$J_2/J_1 \sim 1/2$) significantly quenches SDW correlations with little effect
on the CDW. Typically, the SC order is strongly modulated at the CDW ordering
vector and exhibits $d$-wave symmetry around the cylinder. There is no evidence
of a near-degenerate tendency to pair-density wave (PDW) ordering, charge 4e
SC, or orbital current order.",1610.04300v1
2017-07-13,Doubly charmed baryon mass and wave function through a random walks method,"The mass and the wave function of doubly charmed $\Xi^{++}_{cc}$ (ccu) baryon
are evaluated using Green Function Monte Carlo method to solve the three-body
problem with Cornell potential. The mass of $\Xi^{++}_{cc}$ with spin $1/2$ is
in a good agreement with the LHCb value. Simulation of the wave function by
random walks resulted in a configuration of the quark-diquark type. The radius
of $\Xi^{++}_{cc}$ is much larger than the size needed for a large isospin
splitting. The prediction for the $\Omega_{cc}$ mass is presented.",1707.04031v4
2017-11-30,Capsize of polarization in dilute photonic crystals,"We investigate, experimentally and theoretically, polarization rotation
effects in dilute photonic crystals with transverse permittivity inhomogeneity
perpendicular to the traveling direction of waves. A capsize, namely a drastic
change of polarization to the perpendicular direction is observed in a
one-dimensional photonic crystal in the frequency range $10\div 140$ GHz. To
gain more insights into the rotational mechanism, we have developed a
theoretical model of dilute photonic crystal, based on Maxwell's equations with
a spatially dependent two dimensional inhomogeneous dielectric permittivity. We
show that the polarization's rotation can be explained by an optical splitting
parameter appearing naturally in Maxwell's equations for magnetic or electric
fields components. This parameter is an optical analogous of Rashba like
spin-orbit interaction parameter present in quantum waves, introduces a
correction to the band structure of the two-dimensional Bloch states, creates
the dynamical phase shift between the waves propagating in the orthogonal
directions and finally leads to capsizing of the initial polarization.
Excellent agreement between theory and experiment is found.",1712.00439v1
2017-12-12,Gravitational-wave luminosity of binary neutron stars mergers,"We study the gravitational-wave peak luminosity and radiated energy of
quasicircular neutron star mergers using a large sample of numerical relativity
simulations with different binary parameters and input physics. The peak
luminosity for all the binaries can be described in terms of the mass ratio and
of the leading-order post-Newtonian tidal parameter solely. The mergers
resulting in a prompt collapse to black hole have largest peak luminosities.
However, the largest amount of energy per unit mass is radiated by mergers that
produce a hypermassive neutron star or a massive neutron star remnant. We
quantify the gravitational-wave luminosity of binary neutron star merger
events, and set upper limits on the radiated energy and the remnant angular
momentum from these events. We find that there is an empirical universal
relation connecting the total gravitational radiation and the angular momentum
of the remnant. Our results constrain the final spin of the remnant black-hole
and also indicate that stable neutron star remnant forms with super-Keplerian
angular momentum.",1712.04267v1
2018-05-15,Faster search for long gravitational-wave transients: GPU implementation of the transient F-statistic,"The F-statistic is an established method to search for continuous
gravitational waves from spinning neutron stars. Prix et al. (2011) introduced
a variant for transient quasi-monochromatic signals. Possible astrophysical
scenarios for such transients include glitching pulsars, newborn neutron stars
and accreting systems. Here we present a new implementation of the transient
F-statistic, using pyCUDA to leverage the power of modern graphics processing
units (GPUs). The obtained speedup allows efficient searches over much wider
parameter spaces, especially when using more realistic transient signal models
including time-varying (e.g. exponentially decaying) amplitudes. Hence, it can
enable comprehensive coverage of glitches in known nearby pulsars, improve the
follow-up of outliers from continuous-wave searches, and might be an important
ingredient for future blind all-sky searches for unknown neutron stars.",1805.05652v2
2018-09-03,"Gravitational waves in massive gravity theories: waveforms, fluxes and constraints from extreme-mass-ratio mergers","Is the graviton massless? This problem was addressed in the literature at a
phenomenological level, using modified dispersion relations for gravitational
waves, in linearized calculations around flat space. Here, we perform a
detailed analysis of the gravitational waveform produced when a small particle
plunges or inspirals into a large non-spinning black hole. Our results should
presumably also describe the gravitational collapse to black holes and
explosive events such as supernovae. In the context of a theory with massive
gravitons and screening, merging objects up to $1\,{\rm Gpc}$ away or
collapsing stars in the nearby galaxy may be used to constrain the mass of the
graviton to be smaller than $\sim 10^{-23}\,{\rm eV}$, with low-frequency
detectors. Our results suggest that the absence of dipolar gravitational waves
from black hole binaries may be used to rule out entirely such theories.",1809.00673v3
2018-09-27,Rabi oscillations of a quantum dot exciton coupled to acoustic phonons: coherence and population readout,"While the advanced coherent control of qubits is now routinely carried out in
low frequency (GHz) systems like single spins, it is far more challenging to
achieve for two-level systems in the optical domain. This is because the latter
evolve typically in the THz range, calling for tools of ultrafast, coherent,
nonlinear optics. Using four-wave mixing micro-spectroscopy, we here measure
the optically driven dynamics of a single exciton quantum state confined in a
semiconductor quantum dot. In a combined experimental and theoretical approach,
we reveal the intrinsic Rabi oscillation dynamics by monitoring both central
exciton quantities, i.e., its occupation and the microscopic coherence, as
resolved by the four-wave mixing technique. In the frequency domain this
oscillation generates the Autler-Townes splitting of the light-exciton dressed
states, directly seen in the four-wave mixing spectra. We further demonstrate
that the coupling to acoustic phonons strongly influences the FWM dynamics on
the picosecond timescale, because it leads to transitions between the dressed
states.",1809.10549v1
2018-11-07,Linear magnetoresistance in the low-field limit in density-wave materials,"The magnetoresistance (MR) of a material is typically insensitive to
reversing the applied field direction and varies quadratically with magnetic
field in the low-field limit. Quantum effects [1], unusual topological band
structures [2], and inhomogeneities that lead to wandering current paths [3, 4]
can induce a crossover from quadratic to linear magnetoresistance with
increasing magnetic field. Here we explore a series of metallic charge- and
spin-density-wave systems that exhibit extremely large positive linear
magnetoresistance. By contrast to other linear MR mechanisms, this effect
remains robust down to miniscule magnetic fields of tens of Oersted at low
temperature. We frame an explanation of this phenomenon in a semi-classical
narrative for a broad category of materials with partially-gapped Fermi
surfaces due to density waves.",1811.02758v1
2018-11-18,Density-wave steady-state phase of dissipative ultracold fermions with nearest-neighbor interactions,"In this work we investigate the effect of local dissipation on the presence
of density-wave ordering in spinful fermions with both local and
nearest-neighbor interactions as described by the extended Hubbard model. We
find density-wave order to be robust against decoherence effects up to a
critical point where the system becomes homogeneous with no spatial ordering.
Our results will be relevant for future cold-atom experiments using fermions
with non-local interactions arising from the dressing by highly-excited Rydberg
states, which have finite lifetimes due to spontaneous emission processes.",1811.07369v1
2019-11-22,"Black hole mergers, gravitational waves and scaling relations","Observations of gravitational waves provide new opportunities to study our
Universe. In particular, mergers of stellar black holes are the main targets of
the current gravitational wave experiments. In order to make accurate
predictions, it is however necessary to simulate the mergers in numerical
general relativity, which requires high performance computing. While scaling
relations are used to rescale simulations for very massive black holes,
primordial black holes have specific properties which can invalidate the
rescaling. Similarly black holes in theories beyond Einstein's relativity can
have different scaling properties. In this article, we consider scaling
relations for the most general cases of primordial black holes, such as charged
and spinned black holes, and study the effects of the cosmological expansion
and of Hawking evaporation. We also consider more exotic black hole models and
derive the corresponding scaling relations, which can be compared to the
observations in order to identify the underlying black hole model and can be
used to rescale the numerical simulations of exotic black hole mergers.",1911.10219v2
2017-05-01,$X(4260)$ Revisited: A Coupled Channel Perspective,"We calculate the probabilities of various charmed meson molecules for
$X(4260)$ under the framework of ${}^3P_0$ model. The results indicate that
even though heavy quark spin symmetry forbids $S$ wave coupling of $D_1\bar{D}$
to the ${}^3S_1$ charmonia ($\psi(nS)$), the $D$ wave coupling is allowed and
not negligible. Under this symmetry, the $D_1\bar{D}$ can couple to ${}^3D_1$
charmonia ($\psi(nD)$) via both $S$ and $D$ wave, and the overall coupling is
around three times larger than that of $\psi(nS)$. The $X(4260)$ cannot be a
pure molecule but a mixture of a charmonium and various charmed meson
components. Since the $D_1\bar{D}$ couples strongly to $\psi(nD)$, our results
suggest that in the $D_1\bar{D}$ molecular picture, the charmonium core of
$X(4260)$ is $\psi(nD)$ instead of $\psi(nS)$. As a result, the experimental
fact that the $R$ ratio has a dip around 4.26 GeV can be understood in the
$D_1\bar{D}$ molecular picture of the $X(4260)$.",1705.00449v4
2018-02-18,Solitons and rogue waves in spinor Bose-Einstein condensates,"We present a general classification of one-soliton solutions as well as novel
families of rogue-wave solutions for $F=1$ spinor Bose-Einstein condensates
(BECs). These solutions are obtained from the inverse scattering transform for
a focusing matrix nonlinear Schr\""odinger equation which models condensates in
the case of attractive mean field interactions and ferromagnetic spin-exchange
interactions. In particular, we show that, when no background is present, all
one-soliton solutions are reducible via unitary transformations to a
combination of oppositely-polarized solitonic solutions of single-component
BECs. On the other hand, we show that, when a non-zero background is present,
not all matrix one-soliton solutions are reducible to a simple combination of
scalar solutions. We show that some solitons are topological ones and others
are dark-bright solitons. Finally, by taking suitable limits of all the
solutions on a non-zero background we also obtain three families of rogue-wave
(i.e., rational) solutions, two of which are novel to the best of our
knowledge.",1802.06471v1
2018-02-28,Resonant magneto-acoustic switching: influence of Rayleigh wave frequency and wavevector,"We show on in-plane magnetized thin films that magnetization can be switched
efficiently by 180 degrees using large amplitude Rayleigh waves travelling
along the hard or easy magnetic axis. Large characteristic filament-like
domains are formed in the latter case. Micromagnetic simulations clearly
confirm that this multi-domain configuration is compatible with a resonant
precessional mechanism. The reversed domains are in both geometries several
hundreds of \mu m^2, much larger than has been shown using spin transfer
torque- or field-driven precessional switching. We show that surface acoustic
waves can travel at least 1mm before addressing a given area, and can interfere
to create magnetic stripes that can be positionned with a sub-micronic
precision.",1802.10318v1
2018-08-24,Pulse analysis by delayed absorption from a coherently excited atom,"In this tutorial we provide a short review of attosecond pulse
characterization techniques and a pedagogical account of a recently proposed
method called Pulse Analysis by Delayed Absorption (PANDA) [Pabst and
Dahlstr\""om, Phys. Rev. A, 94, 13411 (2016)]. We discuss possible
implementations of PANDA in alkali atoms using either principal quantum number
wave packets or spin-orbit wave packets. The main merit of the PANDA method is
that it can be used as a pulse characterization method that is free from atomic
latency effects, such as scattering phase shifts and long-lived atomic
resonances. Finally, we propose that combining the PANDA method with
angle-resolved photoelectron detection should allow for experimental
measurements of attosecond delays in photoionization from bound wave packets on
the order of tens of attoseconds.",1808.08102v2
2018-12-11,Gravitational wave emission under general parametrized metric from extreme mass ratio inspirals,"Future space-borne interferometers will be able to detect gravitational waves
at $10^{-3}$ to $10^{-1}$ Hz. At this band extreme-mass-ratio inspirals (EMRIs)
can be promising gravitational wave sources. In this paper, we investigate
possibility of testing Kerr hypothesis against a parametrized non-Kerr metric
by matching EMRI signals. However, EMRIs from either equatorial orbits or
inclined orbits suffer from the ""confusion problem"". Our results show that,
within the time scale before radiation flux plays an important role, small and
moderate deviations from the Kerr spacetime($|\delta_i|<1$) can be discerned
only when spin parameter is high. In most cases, the EMRI waveforms related
with a non-Kerr metric can be mimicked by the waveform templates produced with
a Kerr black hole.",1812.04185v1
2019-02-17,Localized states of Dirac equation,"In this paper, we introduce an extension of the Dirac equation, very similar
to Dirac oscillator, that gives stationary localized wave packets as
eigenstates of the equation. The extension to the Dirac equation is achieved
through the replacement of the momentum operator by a PT-symmetric generalized
momentum operator. In the 1D case, the solutions represent bound particles
carrying spin having continuous energy spectrum, where the envelope parameter
defines the width of the packet without affecting the dispersion relation of
the original Dirac equation. In the 2D case, the solutions are localized wave
packets and are eigenstates of the third component of total angular momentum
and involve Bessel functions of integral order. In the 3D case, the solutions
are localized spherical wave packets with definite total angular momentum.",1902.06232v1
2019-06-26,Valley Acoustoelectric Effect,"We report on novel valley acoustoelectric effect, which can arise in a 2D
material, like a transition metal dichalcogenide monolayer, residing on a
piezoelectric substrate. The essence of this effect lies in the emergence of a
drag electric current (and a spin current) due to a propagating surface
acoustic wave. This current consists of three contributions, one independent of
the valley index and proportional to the acoustic wave vector, the other
arising due to the trigonal warping of the electron dispersion, and the third
one is due to the Berry phase, which Bloch electrons acquire traveling along
the crystal. As a result, there appear components of the current orthogonal to
the acoustic wave vector. Further, we build an angular pattern, encompassing
nontrivial topological properties of the acoustoelectric current, and suggest a
way to run and measure the conventional diffusive, warping, and acoustoelectric
valley Hall currents independently. We develop a theory, which opens a way to
manipulate valley transport by acoustic methods, expanding the applicability of
valleytronic effects on acoustoelectronic devices.",1906.11151v1
2019-06-28,Crossover from charge density wave stabilized antiferromagnetism to superconductivity in Nd$_{1-x}$La$_x$NiC$_2$ compounds,"The path from the charge density wave antiferromagnet NdNiC$_2$ to a
noncentrosymmetric superconductor LaNiC$_2$ has been studied by gradual
replacement of Nd by La ions. The evolution of physical properties has been
explored by structural, magnetic, transport, magnetoresistance and specific
heat measurements. With the substitution of La for Nd, the Peierls temperature
is gradually suppressed, which falls within the BCS mean-field relation for
chemical pressure with a critical concentration of $x_c$ = 0.38. As long as
charge density wave is maintained, the antiferromagnetic ground state remains
robust against doping and despite of a N\'eel temperature reduction shows a
rapid and sharp magnetic transition. Once the CDW is completely suppressed,
intermediate compounds of the Nd$_{1-x}$La$_x$NiC$_2$ series reveal symptoms of
a gradual softening of the features associated with AFM transition and increase
of the spin disorder. Immediately after the antiferromagnetic transition is
depressed to zero temperature, the further incorporation of La ions results in
the emergence of superconductivity. This crossover in the
Nd$_{1-x}$La$_x$NiC$_2$ is discussed in the terms of the possible quantum
critical point.",1906.12022v1
2020-04-21,Inferring the population properties of binary black holes from unresolved gravitational waves,"The vast majority of compact binary mergers in the Universe produce
gravitational waves that are too weak to yield unambiguous detections; they are
unresolved. We present a method to infer the population properties of compact
binaries -- such as their merger rates, mass spectrum, and spin distribution --
using both resolved and unresolved gravitational waves. By eliminating entirely
the distinction between resolved and unresolved signals, we eliminate bias from
selection effects. To demonstrate this method, we carry out a Monte Carlo study
using an astrophysically motivated population of binary black holes. We show
that some population properties of compact binaries are well constrained by
unresolved signals after about one week of observation with Advanced LIGO at
design sensitivity.",2004.09700v1
2020-08-02,Holographic Fermi surfaces in charge density wave from D2-D8,"D2-D8 model admits a numerical solution that corresponds to a charge density
wave and a spin density wave. Considering that as the background, we
numerically solve the Dirac equation for probe fermions. From the solution, we
obtain the Green's function and study the behaviour of the spectral density. We
begin with generic fermions and have studied the formation of the Fermi surface
and where it develops a gap. In addition, we have incorporated an ionic lattice
and study its effect on the Fermi surface. Then we analysed the worldvolume
fermions. In this particular model we do not find Fermi surface for the dual
operators.",2008.00432v2
2020-08-14,Observation of high-order Mollow triplet by quantum mode control with concatenated continuous driving,"The Mollow triplet is a fundamental signature of quantum optics, and has been
observed in numerous quantum systems. Although it arises in the 'strong
driving' regime of the quantized field, where the atoms undergo coherent
oscillations, it can be typically analyzed within the rotating wave
approximation. Here we report the first observation of high-order effects in
the Mollow triplet structure due to strong driving. In experiments, we explore
the regime beyond the rotating wave approximation using concatenated continuous
driving that has less stringent requirements on the driving field power. We are
then able to reveal additional transition frequencies, shifts in energy levels,
and corrections to the transition amplitudes. In particular, we find that these
amplitudes are more sensitive to high-order effects than the frequency shifts,
and that they still require an accurate determination in order to achieve
high-fidelity quantum control. The experimental results are validated by the
Floquet theory, which enables the precise numerical simulation of the evolution
and further provides an analytical form for an effective Hamiltonian that
approximately predicts the spin dynamics beyond the rotating wave
approximation.",2008.06435v2
2018-04-05,Charge density wave behavior and order-disorder in the antiferromagnetic metallic series Eu(Ga_1-xAl_x)_4,"The solid solution Eu(Ga_1-xAl_x)_4 was grown in single crystal form to
reveal a rich variety of crystallographic, magnetic, and electronic properties
that differ from the isostructural end compounds EuGa_4 and EuAl_4, despite the
similar covalent radii and electronic configurations of Ga and Al. Here we
report the onset of magnetic spin reorientation and metamagnetic transitions
for x = 0 - 1 evidenced by magnetization and temperature-dependent specific
heat measurements. T_N changes non-monotonously with x, and it reaches a
maximum around 20 K for x = 0.50, where the a lattice parameter also shows an
extreme (minimum) value. Anomalies in the temperature-dependent resistivity
consistent with charge density wave behavior exist for x = 0.50 and 1 only.
Density functional theory calculations show increased polarization between the
Ga-Al covalent bonds in the x = 0.50 structure compared to the end compounds,
such that crystallographic order and chemical pressure are proposed as the
causes of the charge density wave behavior.",1804.02076v1
2019-03-13,The interior of a binary black hole merger,"We find strong numerical evidence for a new phenomenon in a binary black hole
spacetime, namely the merger of marginally outer trapped surfaces (MOTSs). By
simulating the head-on collision of two non-spinning unequal mass black holes,
we observe that the MOTS associated with the final black hole merges with the
two initially disjoint surfaces corresponding to the two initial black holes.
This yields a connected sequence of MOTSs interpolating between the initial and
final state all the way through the non-linear binary black hole merger
process. In addition, we show the existence of a MOTS with self-intersections
formed immediately after the merger. This scenario now allows us to track
physical quantities (such as mass, angular momentum, higher multipoles, and
fluxes) across the merger, which can be potentially compared with the
gravitational wave signal in the wave-zone, and with observations by
gravitational wave detectors. This also suggests a possibility of proving the
Penrose inequality mathematically for generic astrophysical binary back hole
configurations.",1903.05626v3
2019-03-18,The hydrogen atom as relativistic bound system,"The hydrogen atom as relativistic bound-state system of a proton and an
electron in the complex-mass scheme is investigated. Interaction of a proton
and an electron in the atom is described by the Lorentz-scalar Coulomb
potential; the proton structure is taken into account. The concept of position
dependent particle mass is developed. Relativistic wave equation for two
interacting spinless particles is derived; asymptotic method is used to solve
the equation. % Asymptotic solution of the equation for the system in the form
of %standing wave and eigenmasses of the $H$ atom are obtained. Complex
eigenmasses for the $H$ atom are obtained. The spin center-of-gravity energy
levels for the $H$ atom are calculated and compared with ones obtained from
solution of some known relativistic wave equations % the Shr\""odinger,
Klein-Gordon and tabulated NIST data.",1903.07322v1
2019-03-20,Majorana's stellar representation for the local polarization of harmonic electromagnetic and gravitational waves,"The local polarization of electromagnetic (EMW) and gravitational waves (GW)
is discussed from an operational point of view, in which all the relevant
mathematical framework is constructed in terms of measurements of the power
absorbed by a local detector. The intrinsic dependence of the observations upon
the nature of the detector is emphasized. In particular, the benefit of using a
dual-symmetric detector, equally sensitive to the electric and magnetic fields
of the EMW (resp. gravito-electric and gravito-magnetic tensor in the GW case)
is pointed out. The Majorana stellar representation of the polarization is
introduced, and its physical interpretation is highlighted. Finally,
expressions for the energy density, linear momentum density, helicity and spin
density of the wave in terms of the Majorana representation are presented.",1903.08166v1
2020-03-03,Phonon-induced renormalization of electron wave functions,"The Allen-Heine-Cardona theory allows us to calculate phonon-induced electron
self-energies from first principles without resorting to the adiabatic
approximation. However, this theory has not been able to account for the change
of the electron wave function, which is crucial if interband energy differences
are comparable to the phonon-induced electron self-energy as in
temperature-driven topological transitions. Furthermore, for materials without
inversion symmetry, even the existence of such topological transitions cannot
be investigated using the Allen-Heine-Cardona theory. Here, we generalize this
theory to the renormalization of both the electron energies and wave functions.
Our theory can describe both the diagonal and off-diagonal components of the
Debye-Waller self-energy in a simple, unified framework. For demonstration, we
calculate the electron-phonon coupling contribution to the
temperature-dependent band structure and hidden spin polarization of BiTlSe2
across a topological transition. These quantities can be directly measured. Our
theory opens a door for studying temperature-induced topological phase
transitions in materials both with and without inversion symmetry.",2003.01316v2
2020-09-10,Tuning a magnetic field to generate spinning ferrofluid droplets with controllable speed via nonlinear periodic interfacial waves,"Two dimensional free surface flows in Hele-Shaw configurations are a fertile
ground for exploring nonlinear physics. Since Saffman and Taylor's work on
linear instability of fluid--fluid interfaces, significant effort has been
expended to determining the physics and forcing that set the linear growth
rate. However, linear stability does not always imply nonlinear stability. We
demonstrate how the combination of a radial and an azimuthal external magnetic
field can manipulate the interfacial shape of a linearly unstable ferrofluid
droplet in a Hele-Shaw configuration. We show that weakly nonlinear theory can
be used to tune the initial unstable growth. Then, nonlinearity arrests the
instability, and leads to a permanent deformed droplet shape. Specifically, we
show that the deformed droplet can be set into motion with a predictable
rotation speed, demonstrating nonlinear traveling waves on the fluid-fluid
interface. The most linearly unstable wavenumber and the combined strength of
the applied external magnetic fields determine the traveling wave shape, which
can be asymmetric.",2009.04644v2
2020-09-29,Fast Parameter Estimation of Binary Mergers for Multimessenger Followup,"Significant human and observational resources have been dedicated to
electromagnetic followup of gravitational-wave events detected by Advanced LIGO
and Virgo. As the sensitivity of LIGO and Virgo improves, the rate of sources
detected will increase. Margalit & Metzger (2019; arXiv:1904.11995) have
suggested that it may be necessary to prioritize observations of future events.
Optimal prioritization requires a rapid measurement of a gravitational-wave
event's masses and spins, as these can determine the nature of any
electromagnetic emission. We extend the relative binning method of Zackay et
al. (2018; arXiv:1806.08792) to a coherent detector-network statistic. We show
that the method can be seeded from the output of a matched-filter search and
used in a Bayesian parameter measurement framework to produce marginalized
posterior probability densities for the source's parameters within 20 minutes
of detection on 32 CPU cores. We demonstrate that this algorithm produces
unbiased estimates of the parameters with the same accuracy as running
parameter estimation using the standard gravitational-wave likelihood. We
encourage the adoption of this method in future LIGO-Virgo observing runs to
allow fast dissemination of the parameters of detected events so that the
observing community can make best use of its resources.",2009.13759v1
2021-02-12,The dependence of evanescent wave polarization on the losses of guided optical modes,"Spin-momentum locking of evanescent waves describes the relationship between
the propagation constant of an evanescent mode and the polarization of its
electromagnetic field, giving rise to applications in light nano-routing and
polarimetry among many others. The use of complex numbers in physics is a
powerful representation in areas such as quantum mechanics or electromagnetism;
it is well known that a lossy waveguide can be modelled with the addition of an
imaginary part to the propagation constant. Here we explore how these losses
are entangled with the polarization of the associated evanescent tails for the
waveguide, revealing a well-defined mapping between waveguide losses and the
Poincar\'e sphere of polarizations, in what could be understood as a
""polarization-loss locking"" of evanescent waves. We analyse the implications
for near-field directional coupling of sources to waveguides, as optimized
dipoles must take into account the losses for a perfectly unidirectional
excitation. We also reveal the potential advantage of calculating the angular
spectrum of a source defined in a complex, rather than the traditionally purely
real, transverse wavevector space formalism.",2102.06680v1
2021-04-23,Fluctuation effects at the onset of $\bf 2k_F$ density wave order with two pairs of hot spots in two-dimensional metals,"We analyze quantum fluctuation effects at the onset of charge or spin density
wave order in two-dimensional metals with an incommensurate nesting ($2k_F$)
wave vector connecting two pairs of hot spots on the Fermi surface. We first
compute the momentum and frequency dependence of the fermion self-energy near
the hot spots to leading order in a perturbation expansion (one loop).
Non-Fermi liquid behavior with a linear (in energy) quasi-particle decay rate
and a logarithmically vanishing quasi-particle weight is obtained. The momentum
dependence of the self-energy entails only finite renormalizations of the Fermi
velocity and the Fermi surface curvature at the hot spots. The perturbative
one-loop result is not self-consistent and casts doubt on the stability of the
$2k_F$ quantum critical point. We construct a self-consistent solution of the
one-loop equations with self-energy feedback, where the quantum critical point
is stabilized rather than being destroyed by fluctuations, while the non-Fermi
liquid behavior as found in the perturbative one-loop calculation is confirmed.",2104.11382v1
2021-08-26,Transient glitch mitigation in Advanced LIGO data with $\textit{glitschen}$,"""Glitches"" -- transient noise artifacts in the data collected by
gravitational wave interferometers like LIGO and Virgo -- are an ever-present
obstacle for the search and characterization of gravitational wave signals.
With some having morphology similar to high mass, high mass-ratio, and
extreme-spin binary black hole events, they limit sensitivity to such sources.
They can also act as a contaminant for all sources, requiring targeted
mitigation before astrophysical inferences can be made. We propose a data
driven, parametric model for frequently encountered glitch types using
probabilistic principal component analysis. As a noise analog of parameterized
gravitational wave signal models, it can be easily incorporated into existing
search and detector characterization techniques. We have implemented our
approach with the open source glitschen package. Using LIGO's currently most
problematic glitch types, the 'blip' and 'tomte', we demonstrate that
parametric models of modest dimension can be constructed and used for effective
mitigation in both frequentist and Bayesian analyses.",2108.12044v2
2021-10-11,Testing for pair-density-wave order in La$_{1.875}$Ba$_{0.125}$CuO$_4$,"Charge order is commonly believed to compete with superconducting order. An
intertwined form of superconducting wave function, known as pair-density-wave
(PDW) order, has been proposed; however, there has been no direct evidence,
theoretical or experimental, that it forms the ground state of any cuprate
superconductor. As a test case, we consider \lbco\ with $x=1/8$, where charge
and spin stripe orders within the CuO$_2$ planes compete with three-dimensional
superconducting order. We report measurements of the superconducting critical
current perpendicular to the planes in the presence of an in-plane magnetic
field. The variation of the critical current with orientation of the field is
inconsistent with a theoretical prediction specific to the PDW model. It
appears, instead, that the orientation dependence of the critical-current
density might be determined by a minority phase of $d$-wave superconductivity
that is present as a consequence of doped-charge inhomogeneity.",2110.05513v2
2021-10-20,Gravitational Waves from GRB Core Spindown,"We investigate long Gamma-Ray Bursts (GRB) which manifest a sharp linear rise
followed by an exponential decay in their gamma-ray prompt emission observed
with the BAT instrument on board the Swift satellite. We offer a simple
electrodynamic model that may account for these particular characteristics. We
associate the sharp rise with the winding of the magnetic field by the fast
rotating core that formed in the interior of the stellar precursor. We also
associate the subsequent exponential decay with the electromagnetic spin-down
of the core following the release of the electromagnetic jet from the stellar
interior. Any non-axisymmetric distortion in the rotating core will generate
gravitational waves with exponentially decreasing frequency, a so-called
""down-chirp"". We obtain a detailed estimate of the gravitational wave profile
if the distortion of spacetime is due to the winding of a non-axisymmetric
component of the magnetic field during that particular phase of the burst. We
offer 7 particular time intervals during which one may look into LIGO archival
data for the presence of our particular predicted waveforms in order to test
our interpretation.",2110.10448v1
2017-01-26,Field theoretical approach to gravitational waves,"The aim of these notes is to give an accessible and self-contained
introduction to the theory of gravitational waves as the theory of a
relativistic symmetric tensor field in a Minkowski background spacetime. This
is the approach of a particle physicist: the graviton is identified with a
particular irreducible representation of the Poincar\'e group, corresponding to
vanishing mass and spin two. It is shown how to construct an action functional
giving the linear dynamics of gravitons, and how General Relativity can be
obtained from it. The Hamiltonian formulation of the linear theory is examined
in detail. We study the emission of gravitational waves and apply the results
to the simplest case of a binary Newtonian system.",1701.07794v2
2017-03-31,"Gravitational wave content and stability of uniformly, rotating, triaxial neutron stars in general relativity","Targets for ground-based gravitational wave interferometers include
continuous, quasiperiodic sources of gravitational radiation, such as isolated,
spinning neutron stars. In this work we perform evolution simulations of
uniformly rotating, triaxially deformed stars, the compressible analogues in
general relativity of incompressible, Newtonian Jacobi ellipsoids. We
investigate their stability and gravitational wave emission. We employ five
models, both normal and supramassive, and track their evolution with different
grid setups and resolutions, as well as with two different evolution codes. We
find that all models are dynamically stable and produce a strain that is
approximately one-tenth the average value of a merging binary system. We track
their secular evolution and find that all our stars evolve towards axisymmetry,
maintaining their uniform rotation, kinetic energy, and angular momentum
profiles while losing their triaxiality.",1704.00038v1
2017-04-13,Explore Inert Dark Matter Blind Spots with Gravitational Wave Signatures,"Motivated by the absence of dark matter signals in direct detection
experiments and the discovery of gravitational waves (GWs) at aLIGO, we discuss
the possibility to explore a generic classes of scalar dark matter models using
the complementary searches via phase transition gravitational waves and the
future lepton collider signatures. We focus on the inert scalar multiplet dark
matter models and the mixed inert scalar dark matter models, which could
undergo a strong first-order phase transitions during the evolution of the
early universe, and might produce detectable phase transition GW signals at
future GW experiments, such as eLISA, DECIGO and BBO. We find that the future
GW signature, together with circular electron-positron collider, could further
explore the model's blind spot parameter region, at which the dark matter-Higgs
coupling is identically zero, thus avoiding the dark matter spin-independent
direct detection constraints.",1704.04201v1
2019-01-07,The Adaptive Transient Hough method for long-duration gravitational wave transients,"This paper describes a new semi-coherent method to search for transient
gravitational waves of intermediate duration (hours to days). In order to
search for newborn isolated neutron stars with their possibly very rapid
spin-down, we model the frequency evolution as a power law. The search uses
short Fourier transforms from the output of ground-based gravitational wave
detectors and applies a weighted Hough transform, also taking into account the
signal's amplitude evolution. We present the technical details for implementing
the algorithm, its statistical properties, and a sensitivity estimate. A first
example application of this method was in the search for GW170817 post-merger
signals, and we verify the estimated sensitivity with simulated signals for
this case.",1901.01820v2
2019-01-31,Multi-twist polarization ribbon topologies in highly-confined optical fields,"Electromagnetic plane waves, solutions to Maxwell's equations, are said to be
`transverse' in vacuum. Namely, the waves' oscillatory electric and magnetic
fields are confined within a plane transverse to the waves' propagation
direction. Under tight-focusing conditions however, the field can exhibit
longitudinal electric or magnetic components, transverse spin angular momentum,
or non-trivial topologies such as M\""obius strips. Here, we show that when a
suitably spatially structured beam is tightly focused, a 3-dimensional
polarization topology in the form of a ribbon with two full twists appears in
the focal volume. We study experimentally the stability and dynamics of the
observed polarization ribbon by exploring its topological structure for various
radii upon focusing and for different propagation planes.",1901.11337v1
2019-08-14,Complete basis for the pentaquark wave function in a group theory approach,"Permutation groups are applied to analyze the symmetries of pentaquark
states. All possible quark configurations of the color, flavor, spin and
spatial degrees of freedom are worked out in the language of permutation
groups, and the corresponding wave functions are constructed systematically in
the form of a Yamanouchi basis. The pentaquark spatial wave functions of
various symmetries, which are derived in the harmonic-oscillator interaction,
are applied as complete bases to evaluate the low-lying light $q^4\overline q$
pentaquark mass of all configurations, where the Cornell-like potential is
employed.",1908.04972v3
2019-08-30,Zero index electromagnetic materials,"Here we re-examine one of the most basic quantities in optics: the refractive
index. Considering propagation in a plane, we first develop a general formalism
for calculating the direction dependent refractive index in a general
bi-anisotropic material. From this we derive the general condition for
achieving zero refractive index in a given direction. We show that when the
zero-index direction is complex valued the material supports waves that can
propagate in only one sense, e.g. in only a clockwise direction. We dub such
materials complex axis nihility (CAN) media. Our condition shows that there are
an infinite family of both time reversible and time irreversible homogeneous
electromagnetic media that support unidirectional propagation for a particular
polarization. We give examples showing that scattering from such media results
in the complete exclusion of partial waves with one sign of the angular
momentum, and that interfaces between such media generally support one-way
interface states. As well as giving new sets of material parameters, our simple
condition reproduces many of the findings derived using topology, such as
unidirectional propagation in gyrotropic media, and spin-momentum locking of
evanescent waves.",1908.11844v3
2019-09-18,Where to find Electromagnetic Wave Counterparts of stellar-mass binary black hole mergers?,"Multi-messenger astronomy combining Gravitational Wave (GW) and
Electromagnetic Wave (EM) observation brings huge impact on physics,
astrophysics and cosmology. However, the majority of sources to be detected
with currently running ground-based GW observatories are binary black hole
(BBH) mergers, which are expected disappointedly to have no EM counterparts. In
this letter, we propose that if the BBH merger happens in a gaseous disk around
a supermassive black hole, the merger can be accompanied by a transient radio
flare alike a fast radio burst (FRB). We argue that the total mass and the
effective spin derived from GW detection can be used to distinguish such a
source from other channels of BBH mergers. If the prediction is confirmed with
future observation, multi-messenger astronomy can be brought to a distance
which is one order of magnitude farther than present. The mystery of the origin
of FRBs can also be revealed partially.",1909.08384v1
2020-01-16,Electromagnetic precursors to gravitational wave events: Numerical simulations of flaring in pre-merger binary neutron star magnetospheres,"The detection of gravitational waves from neutron star merger events has
opened up a new field of multi-messenger astronomy linking gravitational waves
events to short-gamma ray bursts and kilonova afterglows. A further - yet to be
discovered - electromagnetic counterpart is precursor emission produced by the
non-trivial interaction of the magnetospheres of the two neutron stars prior to
merger. By performing special-relativistic force-free simulations of orbiting
neutron stars we discuss the effect of different magnetic field orientations
and show how the emission can be significantly enhanced by differential motion
present in the binary, either due to stellar spins or misaligned stellar
magnetospheres. We find that the built-up of twist in the magnetic flux tube
connecting the two stars can lead to the repeated emission of powerful flares
for a variety of orbital configurations. We also discuss potential coherent
radio emission mechanisms in the flaring process.",2001.06037v3
2020-02-09,Pulsar timing array signals induced by black hole binaries in relativistic eccentric orbits,"Individual supermassive black hole binaries in non-circular orbits are
possible nanohertz gravitational wave sources for the rapidly maturing Pulsar
Timing Array experiments. We develop an accurate and efficient approach to
compute Pulsar Timing Array signals due to gravitational waves from inspiraling
supermassive black hole binaries in relativistic eccentric orbits. Our approach
employs a Keplerian-type parametric solution to model third post-Newtonian
accurate precessing eccentric orbits while a novel semi-analytic prescription
is provided to model the effects of quadrupolar order gravitational wave
emission. These inputs lead to a semi-analytic prescription to model such
signals, induced by non-spinning black hole binaries inspiralling along
arbitrary eccentricity orbits. Additionally, we provide a fully analytic
prescription to model Pulsar Timing Array signals from black hole binaries
inspiraling along moderately eccentric orbits, influenced by Boetzelet
al.[Phys. Rev. D 96,044011(2017)]. These approaches are being incorporated into
Enterprise and TEMPO2 for searching the presence of such binaries in Pulsar
Timing Array datasets.",2002.03285v2
2020-02-18,Constructing Love-Q-Relations with Gravitational Wave Detections,"Quasi-universal relations connecting the tidal deformability and the
quadrupole moment of individual neutron stars are predicted by theoretical
computations, but have not been measured experimentally. However, such
relations are employed during the interpretation of gravitational waves and,
therefore, have a direct impact on the interpretation of real data. In this
work, we study how quasi-universal relations can be tested and measured from
gravitational wave signals connected to binary neutron star coalescences. We
study a population of $120$ binary neutron star systems and find that Advanced
LIGO and Advanced Virgo at design sensitivity could find possible deviations of
predicted relations if the observed neutron stars are highly spinning. In the
future, a network of third generation (3G) detectors will be able to even allow
a measurement of quasi-universal relations. Thus, the outlined approach
provides a new test of general relativity and nuclear physics predictions.",2002.07918v1
2020-07-17,Search for continuous gravitational waves from Fomalhaut b in the second Advanced LIGO observing run with a hidden Markov model,"Results are presented from a semicoherent search for continuous gravitational
waves from a nearby neutron star candidate, Fomalhaut b, using data collected
in the second observing run of Advanced LIGO. The search is based on a hidden
Markov model scheme, capable of tracking signal frequency evolution from the
star's secular spin down and stochastic timing noise simultaneously. The scheme
is combined with a frequency domain matched filter ($\mathcal{F}$-statistic),
calculated coherently over five-day time stretches. The frequency band 100-1000
Hz is searched. After passing the above-threshold candidates through a
hierarchy of vetoes, one candidate slightly above the 1% false alarm
probability threshold remains for further scrutiny. No strong evidence of
continuous waves is found. We present the strain upper limits in the full
frequency band searched at 90% confidence level.",2007.08732v3
2020-10-01,Experimental Evidence that Zn Impurities Pin Pair-Density-Wave Order in La$_{2-x}$Ba$_x$CuO$_4$,"Both Zn-doping and $c$-axis magnetic fields have been observed to increase
the spin stripe order in La$_{2-x}$Ba$_x$CuO$_4$ with $x$ close to 1/8. For
$x=0.095$, the applied magnetic field also causes superconducting layers to
decouple, presumably by favoring pair-density-wave order that consequently
frustrates interlayer Josephson coupling. Here we show that introducing 1% Zn
also leads to an initial onset of two-dimensional (2D) superconductivity,
followed by 3D superconductivity at lower temperatures, even in zero field. We
infer that the Zn pins pair-density-wave order locally, establishing the
generality of such behavior.",2010.00610v2
2020-10-23,Establishing the significance of continuous gravitational-wave detections from known pulsars,"We present a method for assigning a statistical significance to detection
candidates in targeted searches for continuous gravitational waves from known
pulsars, without assuming the detector noise is Gaussian and stationary. We
take advantage of the expected Doppler phase modulation of the signal induced
by Earth's orbital motion, as well as the amplitude modulation induced by
Earth's spin, to effectively blind the search to real astrophysical signals
from a given location in the sky. We use this ""sky-shifting"" to produce a large
number of noise-only data realizations to empirically estimate the background
of a search and assign detection significances, in a similar fashion to the use
of timeslides in searches for compact binaries. We demonstrate the potential of
this approach by means of simulated signals, as well as hardware injections
into real detector data. In a study of simulated signals in non-Gaussian noise,
we find that our method outperforms another common strategy for evaluating
detection significance. We thus demonstrate that this and similar techniques
have the potential to enable a first confident detection of continuous
gravitational waves.",2010.12612v1
2021-01-03,Two-dimensional superconducting fluctuations associated with charge density wave stripes in La$_{1.87}$Sr$_{0.13}$Cu$_{0.99}$Fe$_{0.01}$O$_4$,"The presence of a small concentration of in-plane Fe dopants in
La$_{1.87}$Sr$_{0.13}$Cu$_{0.99}$Fe$_{0.01}$O$_4$ is known to enhance
stripe-like spin and charge density wave (SDW and CDW) order, and suppress the
superconducting $T_c$. Here, we show that it also induces highly
two-dimensional (2D) superconducting correlations that have been argued to be
signatures of a new form of superconducting order, so-called pair-density-wave
(PDW) order. In addition, using the resonant soft x-ray scattering, we find
that the 2D superconducting fluctuation is strongly associated with the CDW
stripe. In particular, the PDW signature first appears when the correlation
length of the CDW stripe grows over eight times the lattice unit ($\sim$ 8$a$).
These results provide critical conditions for the formation of PDW order.",2101.00539v1
2021-01-25,Pulsar Timing Array Experiments,"Pulsar timing is a technique that uses the highly stable spin periods of
neutron stars to investigate a wide range of topics in physics and
astrophysics. Pulsar timing arrays (PTAs) use sets of extremely well-timed
pulsars as a Galaxy-scale detector with arms extending between Earth and each
pulsar in the array. These challenging experiments look for correlated
deviations in the pulsars' timing that are caused by low-frequency
gravitational waves (GWs) traversing our Galaxy. PTAs are particularly
sensitive to GWs at nanohertz frequencies, which makes them complementary to
other space- and ground-based detectors. In this chapter, we will describe the
methodology behind pulsar timing; provide an overview of the potential uses of
PTAs; and summarise where current PTA-based detection efforts stand. Most
predictions expect PTAs to successfully detect a cosmological background of GWs
emitted by supermassive black-hole binaries and also potentially detect
continuous-wave emission from binary supermassive black holes, within the next
several years.",2101.10081v2
2021-05-06,The Memory Remains (Undetected): Updates from the Second LIGO/Virgo Gravitational-Wave Transient Catalog,"The LIGO and Virgo observatories have reported 39 new gravitational-wave
detections during the first part of the third observation run, bringing the
total to 50. Most of these new detections are consistent with binary black-hole
coalescences, making them suitable targets to search for gravitational-wave
memory, a non-linear effect of general relativity. We extend a method developed
in previous publications to analyse these events to determine a Bayes factor
comparing the memory hypothesis to the no-memory hypothesis. Specifically, we
calculate Bayes factors using two waveform models with higher-order modes that
allow us to analyse events with extreme mass ratios and precessing spins, both
of which have not been possible before. Depending on the waveform model we find
a combined $\ln \mathrm{BF}_{\mathrm{mem}} = 0.024$ or $\ln
\mathrm{BF}_{\mathrm{mem}} = 0.049$ in favour of memory. This result is
consistent with recent predictions that indicate $\mathcal{O}(2000)$ binary
black-hole detections will be required to confidently establish the presence or
absence of memory.",2105.02879v1
2021-06-22,Bulk locality from the celestial amplitude,"In this paper, we study the implications of bulk locality on the celestial
amplitude. In the context of the four-point amplitude, the fact that the bulk
S-matrix factorizes locally in poles of Mandelstam variables is reflected in
the imaginary part of the celestial amplitude. In particular, on the real axis
in the complex plane of the boost weight, the imaginary part of the celestial
amplitude can be given as a positive expansion on the Poincar\'e partial waves,
which are nothing but the projection of flat-space spinning polynomials onto
the celestial sphere. Furthermore, we derive the celestial dispersion relation,
which relates the imaginary part to the residue of the celestial amplitude for
negative even integer boost weight. The latter is precisely the projection of
low energy EFT coefficients onto the celestial sphere. We demonstrate these
properties explicitly on the open and closed string celestial amplitudes.
Finally, we give an explicit expansion of the Poincar\'e partial waves in terms
of 2D conformal partial waves.",2106.11948v2
2021-06-29,Magnetic moments and transition magnetic moments of $P_c$ and $P_{cs}$ states,"We study the magnetic moments and transition magnetic moments of $P_c$ and
$P_{cs}$ states in the molecular picture. We first revisit the magnetic moments
of $P_c$ states as the $S$ wave molecular states without coupled channel
effects. The coupled channel effects and the $D$ wave contributions are then
investigated carefully. The coupled channel effects contribute to the change of
$0.1\sim 0.4$ nuclear magneton $\mu_N$ for most cases while the $D$ wave only
induces the variation of less than $0.03 ~\mu_N$. In addition, we obtain the
transition magnetic moments between different $P_c$ states and the related
electromagnetic decay widths of $P_c'\to P_c\gamma$. The magnetic moments of
$P_{cs}$ are much different for the assumption of spin being 1/2 and 3/2. The
study of electromagnetic properties will help us disclose further the structure
of these unconventional states.",2106.15053v2
2021-07-14,Evolving Devil's staircase magnetization from tunable charge density waves in nonsymmorphic Dirac semimetals,"While several magnetic topological semimetals have been discovered in recent
years, their band structures are far from ideal, often obscured by trivial
bands at the Fermi energy. Square-net materials with clean, linearly dispersing
bands show potential to circumvent this issue. CeSbTe, a square-net material,
features multiple magnetic field-controllable topological phases. Here, it is
shown that in this material, even higher degrees of tunability can be achieved
by changing the electron count at the square-net motif. Increased electron
filling results in structural distortion and formation of charge density waves
(CDWs). The modulation wave-vector evolves continuously leading to a region of
multiple discrete CDWs and a corresponding complex ""Devil's staircase"" magnetic
ground state. A series of fractionally quantized magnetization plateaus are
observed, which implies direct coupling between CDW and a collective
spin-excitation. It is further shown that the CDW creates a robust idealized
non-symmorphic Dirac semimetal, thus providing access to topological systems
with rich magnetism.",2107.06883v1
2021-07-15,Faraday-Fresnel rotation and splitting of orbital angular momentum carrying waves in a rotating plasma,"Rotational Fresnel drag - or orbital Faraday rotation - in a rotating
magnetised plasma is uncovered and studied analytically for Trivelpiece-Gould
and Whistler-Helicon waves carrying orbital angular momentum (OAM). Plasma
rotation is shown to introduce a non-zero phase shift between OAM-carrying
eigenmodes with opposite helicities, similarly to the phase-shift between spin
angular momentum eigenmodes associated with the classical Faraday effect in a
magnetised plasma at rest. By examining the dispersion relation for these two
low-frequency modes in a Brillouin rotating plasma, this Faraday-Fresnel
rotation effect is traced back to the combined effects of Doppler shift,
centrifugal forces and Coriolis forces. In addition, rotation is further shown
to lead to rotation- and azimuthal mode-dependent longitudinal group velocity,
therefore predicting the Faraday-Fresnel splitting of the enveloppe of a wave
packet containing a superposition of OAM-carrying eigenmodes with opposite
helicities.",2107.07267v1
2021-12-12,Rodlike Heisenberg nanomagnet driven by propagating magnetic field: Nonequilibrium phase transition,"The dynamical responses of a rodlike anisotropic Heisenberg ferromagnet,
irradiated by the propagating magnetic field wave, have been studied by Monte
Carlo simulation using Metropolis single spin-flip algorithm. A nonequilibrium
dynamical phase transition has been observed. The transition temperature has
been obtained from the peak position of the variance of the dynamic order
parameter plotted as a function of the temperature. The transition has been
found to occur at a lower temperature for the higher value of the amplitude of
the propagating magnetic field wave. A comprehensive phase boundary was drawn.
The phase boundary has been found to be insensitive to the wavelength of the
propagating field wave. The boundary encloses more area of the region of the
ordered phase for stronger anisotropy.",2112.06138v2
2022-02-10,Atom walking in a traveling-wave light,"In this paper, we investigate mechanical motion of ultra-slow single atoms
considering each atom is coherently coupled to a traveling-wave light. The main
noise in this system is originated from Doppler broadening due to the
continuous momentum distribution in atom wave packet. Here, it is proved that
the Doppler broadening could be effectively suppressed in strong coupling
regime. Under the coherent coupling, individual neutral atoms periodically walk
in a definite direction. Direction of the motion depends on occupation of the
atom in its two internal states related to the optical transition, since the
atom would be affected by attractive or repulsive forces depending on the
internal states. It is analogous to the electric force acting on negatively or
positively charged particles. We explain them with spin-orbit coupling of atoms
which is hidden in our Hamiltonian. These results have potential applications
for the construction of future atomic devices.",2202.04813v7
2022-03-01,An eccentric binary blackhole in post-Newtonian theory,"Gravitational waves radiated during binary black hole coalescence is a
perfect probe for studying the characteristics of strong gravity. Advanced
techniques for creating numerical relativity substitute models for eccentric
binary black hole systems are presumed to become more crucial in existing and
anticipated gravitational wave detectors. The imprint on the observation data
of the gravitational wave emitted by the binary coalescence enhances the two
body system studies. The aim of this study is to present an overview of the
change in characteristics behaviours of hierarchical massive astrophysical
objects merger, which are the data bank of the early universe. We present
results from numerical relativity simulations of equal-mass and unequal mass
nonspinning inspiral binary-black-hole system in the Post Newtonian framework.
We also consider the time evolution of eccentricity for the initial eccentric
system. The eccentric Post Newtonian equations are expanded in the form of
frequency related variable $x = (M \omega)^{2/3}$. The model is restricted to
the (2, 2) spin-weighted spherical harmonic modes. We conclude that for higher
eccentricity as well as mass ratio there exist higher oscillation in orbital
radius and in eccentricity.",2203.00507v1
2022-04-06,Optical Stern-Gerlach effect via a single traveling-wave light,"In this paper, we propose a simplified model of optical Stern-Gerlach effect
based on coherent coupling between clock transition of alkaline-earth single
atoms and a traveling-wave light. It is demonstrated that spin-orbit coupling
induced chiral motion in atom deflection appears under the strong atom-light
interaction. The strong optical driving removes perturbation from the Doppler
effect and back action effect to access the coherent system. In this process,
superposition of distant matter waves connected to the arbitrary distribution
of atom internal state could be predicted, which is important for the
realization of atom interferometry and quantum state operation. The influence
from atom relaxation and atom-atom interactions are discussed. Basic conditions
of experimental design are given in the end of this work.",2204.02864v5
2022-04-21,Charge-density waves in kagome-lattice extended Hubbard models at the van Hove filling,"The Hubbard model on the kagome lattice is presently often considered as a
minimal model to describe the rich low-temperature behavior of AV$_{3}$Sb$_{5}$
compounds (with A=K, Rb, Cs), including charge-density waves (CDWs),
superconductivity, and possibly broken time-reversal symmetry. Here, we
investigate, via variational Jastrow-Slater wave functions, the properties of
its ground state when both onsite $U$ and nearest-neighbor $V$ Coulomb
repulsions are considered at the van Hove filling. Our calculations reveal the
presence of different interaction-driven CDWs and, contrary to previous
renormalization-group studies, the absence of ferromagnetism and charge- or
spin-bond order. No signatures of chiral phases are detected. Remarkably, the
CDWs triggered by the nearest-neighbor repulsion possess charge
disproportionations that are not compatible with the ones observed in
AV$_{3}$Sb$_{5}$. As an alternative mechanism to stabilize charge-bond order,
we consider the electron-phonon interaction, modeled by coupling the hopping
amplitudes to quantum phonons, as in the Su-Schrieffer-Heeger model. Our
results show the instability towards a tri-hexagonal distortion with $2\times
2$ periodicity, in a closer agreement with experimental findings.",2204.10328v2
2022-05-03,Graviton partial waves and causality in higher dimensions,"Do gravitational interactions respect the basic principles of relativity and
quantum mechanics? We show that any graviton S-matrix that satisfies these
assumptions cannot significantly differ from General Relativity at low
energies. We provide sharp bounds on the size of potential corrections in terms
of the mass M of new higher-spin states, in spacetime dimensions D>=5 where the
S-matrix does not suffer from infrared ambiguities. The key novel ingredient is
the full set of SO(D-1) partial waves for this process, which we show how to
efficiently compute with Young tableau manipulations. We record new bounds on
the central charges of holographic conformal theories.",2205.01495v1
2022-08-02,Improved all-sky search method for continuous gravitational waves from unknown neutron stars in binary systems,"Continuous gravitational waves from spinning deformed neutron stars have not
been detected yet, and are one of the most promising signals for future
detection. All-sky searches for continuous gravitational waves from unknown
neutron stars in binary systems are the most computationally challenging search
type. Consequently, very few search algorithms and implementations exist for
these sources, and only a handful of such searches have been performed so far.
In this paper, we present a new all-sky binary search method,
BinarySkyHou$\mathcal{F}$, which extends and improves upon the earlier
BinarySkyHough method, and which was the basis for a recent search (Covas et
al. [1]). We compare the sensitivity and computational cost to previous
methods, showing that it is both more sensitive and computationally efficient,
which allows for broader and more sensitive searches.",2208.01543v2
2022-09-23,Pair density wave in doped three-band Hubbard model on two-leg square cylinders,"A pair density wave (PDW) is a superconducting (SC) state with spatially
modulated order parameter. Although much is known about the properties of the
PDW state, its realization in microscopic models with divergent susceptibility
has been challenging. Here we report a density-matrix renormalization group
study of a three-band Hubbard model (also known as the Emery model) for
cuprates on long two-leg square cylinders. Upon light doping, we find that the
ground state of the system is consistent with that of a PDW state with mutually
commensurate and power-law SC, charge (CDW) and spin (SDW) density wave
correlations. The SC correlations are dominant between neighboring Cu sites
with d-wave pairing symmetry. Interestingly, we find that the near-neighbor
interactions, especially the near-neighbor attractive $V_{pd}$ interaction
between neighboring Cu and oxygen sites, can notably enhance the SC
correlations while simultaneously suppressing the CDW correlations. For a
modestly strong attractive $V_{pd}$, the SC correlations become
quasi-long-ranged with a divergent PDW susceptibility.",2209.11381v3
2022-11-06,Gravitational wave astronomy: astrophysical and cosmological inferences,"We briefly discuss the most prominent results and specific sources detected
by gravitational-wave observatories LIGO-Virgo during first three O1-O3 runs,
as well as possible astrophysical and cosmological channels of their formation.
We show that it is possible to explain the observed correlation between the
effective spin of coalescing binary black holes and mass ratio of the
components by accretion from the ambient medium onto primordial binary black
holes. We also briefly discuss the recent results of searches for stochastic
gravitational-wave background in the nano-Hz frequency band by pulsar timing
arrays.",2211.03142v1
2022-11-15,Normalizing Flows for Hierarchical Bayesian Analysis: A Gravitational Wave Population Study,"We propose parameterizing the population distribution of the gravitational
wave population modeling framework (Hierarchical Bayesian Analysis) with a
normalizing flow. We first demonstrate the merit of this method on illustrative
experiments and then analyze four parameters of the latest LIGO/Virgo data
release: primary mass, secondary mass, redshift, and effective spin. Our
results show that despite the small and notoriously noisy dataset, the
posterior predictive distributions (assuming a prior over the parameters of the
flow) of the observed gravitational wave population recover structure that
agrees with robust previous phenomenological modeling results while being less
susceptible to biases introduced by less flexible models. Therefore, the method
forms a promising flexible, reliable replacement for population inference
distributions, even when data is highly noisy.",2211.09008v3
2023-01-19,Light propagation in Kerr spacetime,"We explicitly solve the equations for the propagation of an electromagnetic
wave up to the subleading order geometric optics expansion in the Kerr
spacetime. This is done in two nontrivial steps. We first construct a set of
parallel propagated null tetrad in Kerr spacetime. Two of the components of
such tetrad give the propagation and polarization of an electromagnetic wave in
geometric optics approximation. Then we use the parallel propagated tetrad to
solve the modified trajectory equation in Kerr spacetime. We obtain the
wavelength-dependent deviation of the trajectory of electromagnetic waves,
which gives the mathematical description of the gravitational spin Hall effect
in Kerr spacetime.",2301.08250v2
2023-03-15,Acoustically driven magnon-phonon coupling in a layered antiferromagnet,"Harnessing the causal relationships between mechanical and magnetic
properties of van der Waals materials presents a wealth of untapped opportunity
for scientific and technological advancement, from precision sensing to novel
memories. This can, however, only be exploited if the means exist to
efficiently interface with the magnetoelastic interaction. Here, we demonstrate
acoustically-driven spin-wave resonance in a crystalline antiferromagnet,
chromium trichloride, via surface acoustic wave irradiation. The resulting
magnon-phonon coupling is found to depend strongly on sample temperature and
external magnetic field orientation, and displays a high sensitivity to
extremely weak magnetic anisotropy fields in the few~mT range. Our work
demonstrates a natural pairing between power-efficient strain-wave technology
and the excellent mechanical properties of van der Waals materials,
representing a foothold towards widespread future adoption of dynamic
magneto-acoustics.",2303.08305v1
2023-03-30,SU(2) Symmetry of Coherent Photons and Application to Poincaré Rotator,"Lie algebra is a hidden mathematical structure behind various quantum systems
realised in nature. Here, we consider $SU(2)$ wavefunctions for polarisation
states of coherent photons emitted from a laser source, and discuss the
relationship to spin expectation values with SO(3) symmetry based on
isomorphism theorems. In particular, we found rotated half-wave-plates
correspond to mirror reflections in the Poincar\'e sphere, which do not form a
subgroup in the projected O(2) plane due to anti-hermitian property. This could
be overcome experimentally by preparing another half-wave-plate to realise a
pristine rotator in $SU(2)$, which allows arbitrary rotation angles determined
by the physical rotation. By combining another 2 quarter-wave-plates, we could
also construct a genuine phase-shifter, thus, realising passive control over
the full Poincar\'e sphere.",2303.18199v1
2023-05-21,Perturbative solution approach for computing the two-photon Kapitza-Dirac effect in a Gaussian beam standing light wave,"Theoretical spin properties of the Kapitza-Dirac effect beyond the plane-wave
description are not known in detail. We develop a method for computing electron
diffraction of the two-photon Kapitza-Dirac effect in a two-dimensional
Gaussian beam standing light wave within a relativistic formulation. The
solutions are computed on the basis of time-dependent perturbation theory,
where a momentum space formulation due to the use of a Fourier transformation
of the external potential allows for the solving the perturbative
time-integrals. An iteration over each possible quantum state combination leads
to a quadratic scaling of our method with respect to spacial grid resolution,
where time-stepping does not occur in the numeric implementation. The position-
and momentum space grids are adapted to the two-photon interaction geometry at
low resolution, for which our study only finds partial convergence of the
simulated diffraction pattern. Further, the method has the advantage of having
an easy implementable parallelization layout.",2305.12399v1
2023-06-13,Backscattering-free edge states below all bands in two-dimensional auxetic media,"Unidirectional and backscattering-free propagation of sound waves is of
fundamental interest in physics, and highly sought-after in engineering.
Current strategies utilize topologically protected chiral edge modes in
bandgaps, or complex mechanisms involving active constituents or nonlinearity.
Here we propose a new class of passive, linear, one-way edge states based on
spin-momentum locking of Rayleigh waves in two-dimensional media in the limit
of vanishing bulk modulus, which provides $100\%$ unidirectional and
backscattering-free edge propagation at a broad range of frequencies instead of
residing in gaps between bulk bands. We further show that such modes are
characterized by a new topological winding number that is analogous to discrete
angular momentum eigenvalues in quantum mechanics. These passive and
backscattering-free edge waves have the potential to enable a new class of
phononic devices in the form of lattices or continua that work in previously
inaccessible frequency ranges.",2306.07493v1
2023-07-31,An SZ-Like Effect on Cosmological Gravitational Wave Backgrounds,"Cosmological gravitational wave backgrounds (CGWBs) are the conglomeration of
unresolved gravitational wave signals from early Universe sources, which make
them a promising tool for cosmologists. Because gravitons decouple from the
cosmic plasma early on, one can consider interactions between gravitons and any
particle species that were present in the very early Universe. We show that
analogous to the cosmic microwave background, elastic scattering on any
cosmological background will induce small distortions in its energy density
spectrum. We then quantify the magnitude of these spin-dependent spectral
distortions when attributed to the dark matter in the early Universe. Lastly,
we give estimates for potentially measurable distortions on CGWBs due to
gravitational scattering by primordial black holes.",2308.00111v2
2023-09-01,"Rieger, Schwabe, Suess-de Vries: The Sunny Beats of Resonance","We propose a self-consistent explanation of Rieger-type periodicities, the
Schwabe cycle, and the Suess-de Vries cycle of the solar dynamo in terms of
resonances of various wave phenomena with gravitational forces exerted by the
orbiting planets. Starting on the high-frequency side, we show that the
two-planet spring tides of Venus, Earth and Jupiter are able to excite
magneto-Rossby waves which can be linked with typical Rieger-type periods. We
argue then that the 11.07-year beat period of those magneto-Rossby waves
synchronizes an underlying conventional $\alpha-\Omega$-dynamo, by periodically
changing either the field storage capacity in the tachocline or some portion of
the $\alpha$-effect therein. We also strengthen the argument that the Suess-de
Vries cycle appears as an 193-year beat period between the 22.14-year Hale
cycle and a spin-orbit coupling effect related with the 19.86-year rosette-like
motion of the Sun around the barycenter.",2309.00666v2
2023-09-18,Large Nonreciprocity of Shear-Horizontal Surface Acoustic Waves induced by Magnetoelastic Bilayers,"We report large nonreciprocity in the transmission of shear-horizontal
surface acoustic waves (SAWs) on LiTaO3 substrate coated with a FeCoSiB/NiFeCu
magnetoelastic bilayer. The large difference in saturation magnetization of the
two layers not only brings nonreciprocal spin waves (SWs), but also ensures the
phonon-magnon (SAWs-SWs) coupling at relatively low wavenumbers. It is found
that the angle between the magnetization and the wavevector play important
roles in determining the strength of magnetoelastic coupling and
nonreciprocity, simultaneously. A large nonreciprocal transmission of SAWs
about 30 dB (i.e. 60 dB/mm) is demonstrated at 2.33 GHz. In addition, the
dispersion relation between coupled SH-SAWs and nonreciprocal SWs is developed,
which provide a good insight into the observed phenomena. Our results offer a
convenient approach to implement nonreciprocal SAW isolators or circulators.",2309.09521v1
2023-09-22,Strongly Coupled Spin Waves and Surface Acoustic Waves at Room Temperature,"Here, we report the observation of strong coupling between magnons and
surface acoustic wave (SAW) phonons in a thin CoFeB film constructed in an
on-chip SAW resonator by analyzing SAW phonon dispersion anticrossings. Our
device design provides the tunability of the film thickness with a fixed phonon
wavelength, which is a departure from the conventional approach in strong
magnon--phonon coupling research. We detect a monotonic increase in the
coupling strength by expanding the film thickness, which agrees with our
theoretical model. Our work offers a significant way to advance fundamental
research and the development of devices based on magnon--phonon hybrid
quasiparticles.",2309.12690v1
2023-09-22,"Quantum enhanced SU(1,1) matter wave interferometry in a ring cavity","Quantum squeezed states offer metrological enhancement as compared to their
classical counterparts. Here, we devise and numerically explore a novel method
for performing SU(1,1) interferometry beyond the standard quantum limit, using
quasi-cyclic nonlinear wave mixing dynamics of ultracold atoms in a ring
cavity. The method is based on generating quantum correlations between many
atoms via photon mediated optomechanical interaction. Timescales of the
interferometer operation are here given by the inverse of photonic recoil
frequency, and are orders of magnitude shorter than the timescales of
collisional spin-mixing based interferometers. Such shorter timescales should
enable not only faster measurement cycles, but also lower atomic losses from
the trap during measurement, which may lead to significant quantum metrological
gain of matter wave interferometry in state of the art cavity setups.",2309.12980v1
2023-10-18,Amplification of electromagnetic waves by a rotating body,"In 1971, Zel'dovich predicted the amplification of electromagnetic (EM) waves
scattered by a rotating metallic cylinder, gaining mechanical rotational energy
from the body. Since then, this phenomenon has been believed to be unobservable
with electromagnetic fields due to technological difficulties in meeting the
condition of amplification, that is, the cylinder must rotate faster than the
frequency of the incoming radiation. Here, we show that this key piece of
fundamental physics has been hiding in plain sight for the past 60 years in the
physics of induction generators. We measure the amplification of an
electromagnetic field, generated by a toroid LC-circuit, scattered by an
aluminium cylinder spinning in the toroid gap. We show that when the Zel'dovich
condition is met, the resistance induced by the cylinder becomes negative
implying amplification of the incoming EM waves. These results reveal the
connection between the concept of induction generators and the physics of this
fundamental effect that was believed to be unobservable, and hence open new
prospects towards testing the Zel'dovich mechanism in the quantum regime, as
well as related quantum friction effects.",2310.12191v1
2023-11-25,D-Wave and Pair-Density-Wave Superconductivity in the Square-Lattice t-J Model,"The Hubbard and closely related t-J models are exciting platforms for
unconventional superconductivity. Through state-of-the-art density matrix
renormalization group calculations using the grand canonical ensembles, we
address open issues regarding the ground-state phase diagram of the extended
t-J model on a square lattice in the parameter regime relevant to cuprate
superconductors. On large 8-leg cylinders, we demonstrate that the pure t-J
model with only nearest-neighbor hoppings and superexchange interactions, for a
wide range of hole doping ($\delta = 0.1 - 0.2$), hosts an exotic SC state
where the d-wave and unidirectional pair density wave SC co-exist with spin and
charge bond orders. Furthermore, a small next nearest neighbor hopping $t_2$
suppresses the pair density wave and other co-coexisting orders, leading to a
d-wave SC phase in both electron- and hole-doped cuprate model systems. We
reveal a simple mechanism for SC in the t-J model, in which the nearest
neighbor hopping plays an essential role in driving the formation of Cooper
pairs with real-space sign oscillations balancing the competition between the
kinetic and exchange energies. Our work validates the t-J model as a proper
minimum model for describing fundamental physics of cuprate superconductors",2311.15092v2
2023-12-10,On the relativistic quantum mechanics of a photon between two electrons in 1+1 dimensions,"A Lorentz-covariant system of wave equations is formulated for a
quantum-mechanical three-body system in one space dimension, comprised of one
photon and two identical massive spin one-half Dirac particles, which can be
thought of as two electrons (or alternatively, two positrons). Manifest
covariance is achieved using Dirac's formalism of multi-time wave functions,
i.e, wave functions
$\Psi(\textbf{x}_{\text{ph}},\textbf{x}_{\text{e}_1},\textbf{x}_{\text{e}_2})$
where $\textbf{x}_{\text{ph}},\textbf{x}_{\text{e}_1},\textbf{x}_{\text{e}_2}$
are generic spacetime events of the photon and two electrons respectively.
Their interaction is implemented via a Lorentz-invariant no-crossing-of-paths
boundary condition at the coincidence submanifolds
$\{\textbf{x}_{\text{ph}}=\textbf{x}_{\text{e}_1}\}$ and
$\{\textbf{x}_{\text{ph}}=\textbf{x}_{\text{e}_2}\}$ compatible with
conservation of probability current. The corresponding initial-boundary value
problem is shown to be well-posed under the additional assumption of
anti-symmetry given by the Pauli exclusion principle, and a closed-form
solution to the ensuing coupled system of Klein-Gordon and transport equations
is given.",2312.06019v1
2023-12-12,Analysis of photo-induced chirality and magnetic toroidal moment based on Floquet formalism,"We analyze the condition of photo-induced atomic-scale chirality and magnetic
toroidal moment. By performing a high-frequency expansion in the Floquet
formalism, we derive an effective static model Hamiltonian from the spinful
$s$-$p$ hybridized model of a single atom interacting with an electromagnetic
wave with a particular polarization. The lowest-order and third-order
contributions in the high-frequency expansion give rise to the coupling to
induce an electric toroidal monopole corresponding to microscopic chirality,
while the second-order contribution provides the coupling to induce a magnetic
toroidal dipole. We also discuss the condition of the polarization of the
electromagnetic wave and induced multipoles. Our results stimulate a new
direction of controlling unconventional multipoles by electromagnetic waves.",2312.07735v1
2023-12-27,Probing Ultralight Tensor Dark Matter with the Stochastic Gravitational-Wave Background from Advanced LIGO and Virgo's First Three Observing Runs,"Ultralight bosons are attractive dark-matter candidates and appear in various
scenarios beyond standard model. They can induce superradiant instabilities
around spinning black holes (BHs), extracting the energy and angular momentum
from BHs, and then dissipated through monochromatic gravitational radiation,
which become promising sources of gravitational wave detectors. In this letter,
we focus on massive tensor fields coupled to BHs and compute the stochastic
gravitational wave backgrounds emitted by these sources. We then undertake a
search for this background within the data from LIGO/Virgo O1$\sim$ O3 runs.
Our analysis reveals no discernible evidence of such signals, allowing us to
impose stringent limits on the mass range of tensor bosons. Specifically, we
exclude the existence of tensor bosons with masses ranging from
$4.0\times10^{-14}$ to $2.0\times10^{-12}$ eV at $95\%$ confidence level.",2312.16435v1
2024-02-01,Marginal Fermi liquid behavior at the onset of $\boldsymbol{2k_F}$ density wave order in two-dimensional metals with flat hot spots,"We analyze quantum fluctuation effects at the onset of incommensurate $2k_F$
charge- or spin-density wave order in two-dimensional metals, for a model where
the ordering wave vector $\boldsymbol{Q}$ connects a single pair of hot spots
on the Fermi surface with a vanishing Fermi surface curvature. The tangential
momentum dependence of the bare dispersion near the hot spots is proportional
to $|k_t|^\alpha$ with $\alpha > 2$. We first compute the order parameter
susceptibility and the fermion self-energy in random phase approximation (RPA).
Logarithmic divergences are subsequently treated by a renormalization group
analysis. The coupling between the order parameter fluctuations and the
fermions vanishes logarithmically in the low-energy limit. As a consequence,
the logarithmic divergences found in RPA do not sum up to anomalous power laws.
Instead, only logarithmic corrections to Fermi liquid behavior are obtained. In
particular, the quasiparticle weight and the Fermi velocity vanish
logarithmically at the hot spots.",2403.00007v1
2024-03-04,A Simple and Accurate Method for Computing Optimized Effective Potentials for Exact Exchange Energy,"The inverse Kohn-Sham density-functional theory (inv-KS) for the electron
density of the Hartree-Fock (HF) wave function was revisited within the context
of the optimized effective potential (HF- OEP). First, it is proved that the
exchange potential created by the inv-KS is equivalent to the potential
obtained by the HF-OEP when the HF-OEP realizes the HF energy of the system
under consideration. Next the real-space grid (RSG) implementations of the
inv-KS and the HF-OEP are addressed. The total HF energies EHF for the wave
functions on the effective potentials optimized by the inv-KS are computed for
a set of small molecules. It is found that the mean absolute deviation (MAD) of
EHF from the HF energy is clearly smaller than the MAD of EHF, demonstrating
that the inv-KS is advantageous in constructing the detailed structure of the
exchange potential vx as compared with the HF-OEP. The inv-KS method is also
applied to an ortho-benzyne radical known as a strongly correlated polyatomic
molecule. It is revealed that the spin populations on the atomic sites computed
by the UHF calculation can be faithfully reproduced by the wave functions on
the inv-KS potential.",2403.01772v1
2024-03-05,Generation of gigahertz frequency surface acoustic waves in YIG/ZnO heterostructures,"We study surface acoustic waves (SAWs) in yttrium iron garnet (YIG)/zinc
oxide (ZnO) heterostructures, comparing the results of a computationally
lightweight analytical model with time-resolved micro-focused Brillouin light
scattering data. Interdigital transducers (IDTs), with operational frequencies
in the gigahertz regime, were fabricated on 50 and 100nm thin films of YIG
prior to sputter deposition of 830nm and 890nm films of piezoelectric ZnO. We
find good agreement between our analytical model and micro-focused Brillouin
light scattering data of the IDT frequency response and SAW group velocity,
with clear differentiation between the Rayleigh and Sezawa-like modes. This
work paves the way for the study of SAW-spin wave (SW) interactions in low SW
damping YIG, with the possibility of a method for future energy-efficient SW
excitation.",2403.03006v1
2024-03-10,Giant Nonreciprocity of Surface Acoustic Waves induced by a positive-negative magnetostrictive heterostructure,"Lack of nonreciprocity is one of the major drawbacks of solid-state acoustic
devices, which has hindered the development of microwave-frequency acoustic
isolators and circulators. Here we report giant nonreciprocal transmission of
shear-horizontal surface acoustic waves (SH-SAWs) on a LiTaO3 substrate coated
with a negative-positive magnetostrictive bilayer structure of Ni/Ti/FeCoSiB.
Although the static magnetic moments of two layers are parallel, SH-SAWs can
excite optical-mode spin waves much stronger than acoustic-mode ones at
relatively low frequencies via magnetoelastic coupling. The measured magnitude
nonreciprocity exceeds 40 dB (or 80 dB/mm) at 2.333 GHz. In addition, maximum
nonreciprocal phase accumulation reaches 188{\deg} (376{\deg}/mm), which is
desired for an effective SAW circulator. Our theoretical model and calculations
provide an insight into the observed phenomena and demonstrate a pathway for
further improvement of nonreciprocal acoustic devices.",2403.06234v1
2024-04-05,Phonon Induced Contrast in Matter Wave Interferometer,"Utilizing the Stern-Gerlach apparatus to create matter-wave superposition
states is a long-sought-after goal, not only due to its potential applications
in the quantum realm but also because of its fundamental implications for
studying the quantum properties of gravity. The main challenge in creating a
macroscopic quantum interferometer arises from the loss of coherence, primarily
through two channels. One channel involves strong coupling with the environment
for macroscopic matter, leading to decoherence. The other channel relates to
the precision of wave packet overlap, which can occur due to external and
internal fluctuations of various sources. The latter introduces a unique
challenge for larger-scale masses by perturbing the centre of mass motion of
the macroscopic object. Here, we study a particular challenge, namely, the
issue of internal degrees of freedom, specifically phonon fluctuations and
contrast reduction. This work will investigate the contrast reduction caused by
spin-magnetic field and diamagnetic interactions at the phonon occupation level
in the quantum gravity-induced entanglement of masses (QGEM) protocol
configuration.",2404.04210v1
2024-04-03,Physical mechanism for the geometric phases in optics and angular momentum holonomy,"Vast literature on the experiments and mathematical formulations on the
geometric phases signifies the importance of this subject. Physical mechanism
for the origin of the geometric phases in optics was suggested in 1992 by the
author in terms of the exchange of the angular momentum. Some of the literature
has taken notice of it, however, the real import of the suggested mechanism and
the angular momentum holonomy conjecture has remained elusive. The present
contribution delineates the prevailing confusions and offers a thorough
discussion on the nature of the light waves to resolve the conceptual issues.
It is argued that at a fundamental level there exist only two types of
geometric phases arising from (i) the geometry of the wave vector space, and
(ii) the polarization state space. For the light beams of definite polarization
spatial modes (HG or LG modes) the geometric phase has origin in the wave
vector space that is different than the spin redirection phase for the
polarized light. Angular momentum holonomy is proposed to be equivalent to the
geometric phase in general.",2404.05747v1
2002-11-26,Detecting gravitational waves from precessing binaries of spinning compact objects: Adiabatic limit,"Black-hole (BH) binaries with single-BH masses m=5--20 Msun, moving on
quasicircular orbits, are among the most promising sources for first-generation
ground-based gravitational-wave (GW) detectors. Until now, the development of
data-analysis techniques to detect GWs from these sources has been focused
mostly on nonspinning BHs. The data-analysis problem for the spinning case is
complicated by the necessity to model the precession-induced modulations of the
GW signal, and by the large number of parameters needed to characterize the
system, including the initial directions of the spins, and the position and
orientation of the binary with respect to the GW detector. In this paper we
consider binaries of maximally spinning BHs, and we work in the
adiabatic-inspiral regime to build families of modulated detection templates
that (i) are functions of very few physical and phenomenological parameters,
(ii) model remarkably well the dynamical and precessional effects on the GW
signal, with fitting factors on average >~ 0.97, but (iii) might require
increasing the detection thresholds, offsetting at least partially the gains in
the fitting factors. Our detection-template families are quite promising also
for the case of neutron-star--black-hole binaries, with fitting factors on
average ~ 0.93. For these binaries we also suggest (but do not test) a further
template family, which would produce essentially exact waveforms written
directly in terms of the physical spin parameters.",0211087v4
2014-08-11,Variational description of the ground state of the repulsive two-dimensional Hubbard model in terms of nonorthogonal symmetry-projected Slater determinants,"The few determinant (FED) methodology, introduced in our previous works for
1D lattices, is here adapted for the repulsive two-dimensional Hubbard model at
half-filling and with finite doping fractions. Within this configuration mixing
scheme, a given ground state with well defined spin and space group quantum
numbers, is expanded in terms of a nonorthogonal symmetry-projected basis
determined through chains of variation-after projection calculations. The
results obtained for the ground state and correlation energies of half-filled
and doped 4$\times$4, 6$\times$6, 8$\times$8, and 10$\times$10 lattices, as
well as momentum distributions and spin-spin correlation functions in small
lattices, compare well with those obtained using other state-of-the-art
approximations. The structure of the intrinsic determinants resulting from the
variational strategy is interpreted in terms of defects that encode information
on the basic units of quantum fluctuations in the considered 2D systems. The
varying nature of the underlying quantum fluctuations, reflected in a
transition to a stripe regime for increasing onsite repulsions, is discussed
using the intrinsic determinants belonging to a 16$\times$4 lattice with 56
electrons. Such a transition is further illustrated by computing spin-spin and
charge-charge correlation functions with the corresponding multireference FED
wave functions. In good agreement with previous studies, the analysis of the
pairing correlation functions reveals a weak enhancement of the extended
$s$-wave and d$_{x^2-y^2}$ pairing modes. Given the quality of results here
reported together with those previously obtained for 1D lattices and the
parallelization properties of the FED scheme, we believe that symmetry
projection techniques are very well suited for building ground state wave
functions of correlated electronic systems, regardless of their dimensionality.",1408.2567v1
2014-09-25,Robust parameter estimation for compact binaries with ground-based gravitational-wave observations using the LALInference software library,"The Advanced LIGO and Advanced Virgo gravitational wave (GW) detectors will
begin operation in the coming years, with compact binary coalescence events a
likely source for the first detections. The gravitational waveforms emitted
directly encode information about the sources, including the masses and spins
of the compact objects. Recovering the physical parameters of the sources from
the GW observations is a key analysis task. This work describes the
LALInference software library for Bayesian parameter estimation of compact
binary signals, which builds on several previous methods to provide a
well-tested toolkit which has already been used for several studies. We show
that our implementation is able to correctly recover the parameters of compact
binary signals from simulated data from the advanced GW detectors. We
demonstrate this with a detailed comparison on three compact binary systems: a
binary neutron star, a neutron star black hole binary and a binary black hole,
where we show a cross-comparison of results obtained using three independent
sampling algorithms. These systems were analysed with non-spinning, aligned
spin and generic spin configurations respectively, showing that consistent
results can be obtained even with the full 15-dimensional parameter space of
the generic spin configurations. We also demonstrate statistically that the
Bayesian credible intervals we recover correspond to frequentist confidence
intervals under correct prior assumptions by analysing a set of 100 signals
drawn from the prior. We discuss the computational cost of these algorithms,
and describe the general and problem-specific sampling techniques we have used
to improve the efficiency of sampling the compact binary coalescence parameter
space.",1409.7215v2
2014-11-28,Superconducting properties and pseudogap from preformed Cooper pairs in the triclinic (CaFe$_{1-x}$Pt$_x$As)$_{10}$Pt$_3$As$_8$,"Using a combination of muon-spin relaxation ($\mu$SR), inelastic neutron
scattering (INS) and nuclear magnetic resonance (NMR), we investigated the
novel iron-based superconductor with a triclinic crystal structure
(CaFe$_{1-x}$Pt$_x$As)$_{10}$Pt$_3$As$_8$ (T$_{\rm c}$ = 13 K), containing
platinum-arsenide intermediary layers. The temperature dependence of the
superfluid density obtained from the $\mu$SR relaxation-rate measurements
indicates the presence of two superconducting gaps,
$\Delta_\text{1}\gg\Delta_\text{2}$. According to our INS measurements,
commensurate spin fluctuations are centered at the ($\pi$, 0) wave vector, like
in most other iron arsenides. Their intensity remains unchanged across
T$_\text{c}$, indicating the absence of a spin resonance typical for many
Fe-based superconductors. Instead, we observed a peak in the spin-excitation
spectrum around $\hslash\omega_0=\,$7 meV at the same wave vector, which
persists above T$_{\rm c}$ and is characterized by the ratio
$\hslash\omega_0/k_\text{B}T_\text{c}\approx\,$6.2, which is significantly
higher than typical values for the magnetic resonant modes in iron pnictides
(~4.3). The temperature dependence of magnetic intensity at 7 meV revealed an
anomaly around T* = 45 K related to the disappearance of this new mode. A
suppression of the spin-lattice relaxation rate, $1/T_1T$, observed by NMR
immediately below T* without any notable subsequent anomaly at T$_{\rm c}$,
indicates that T* could mark the onset of a pseudogap in
(CaFe$_{1-x}$Pt$_x$As)$_{10}$Pt$_3$As$_8$, which is likely associated with the
emergence of preformed Cooper pairs.",1411.7858v1
2016-07-22,"Inelastic neutron scattering investigations of an anisotropic hybridization gap in the Kondo insulators: CeT2Al10 (T=Fe, Ru and Os)","The recent discovery of topological Kondo insulating behaviour in strongly
correlated electron systems has generated considerable interest in Kondo
insulators both experimentally and theoretically. The Kondo semiconductors
CeT2Al10 (T=Fe, Ru and Os) possessing a c-f hybridization gap have received
considerable attention recently because of the unexpected high magnetic
ordering temperature of CeRu2Al10 (TN=27 K) and CeOs2Al10 (TN=28.5 K) and the
Kondo insulating behaviour observed in the valence fluctuating compound
CeFe2Al10 with a paramagnetic ground state down to 50 mK. We are investigating
this family of compounds, both in polycrystalline and single crystal form,
using inelastic neutron scattering to understand the role of anisotropic c-f
hybridization on the spin gap formation as well as on their magnetic
properties. We have observed a clear sign of a spin gap in all three compounds
from our polycrystalline study as well as the existence of a spin gap above the
magnetic ordering temperature in T=Ru and Os. Our inelastic neutron scattering
studies on single crystals of CeRu2Al10 and CeOs2Al10 revealed dispersive
gapped spin wave excitations below TN. Analysis of the spin wave spectrum
reveals the presence of strong anisotropic exchange, along the c-axis (or
z-axis) stronger than in the ab-plane. These anisotropic exchange interactions
force the magnetic moment to align along the c-axis, competing with the single
ion crystal field anisotropy, which prefers moments along the a-axis. In the
paramagnetic state (below 50 K) of the Kondo insulator CeFe2Al10, we have also
observed dispersive gapped magnetic excitations which transform into
quasi-elastic scattering on heating to 100 K. We will discuss the origin of the
anisotropic hybridization gap in CeFe2Al10 based on theoretical models of
heavy-fermion semiconductors.",1607.06538v1
2017-07-24,Spinning test-body orbiting around a Kerr black hole: circular dynamics and gravitational-wave fluxes,"In a recent work, [Phys. Rev. D. 94, 104010 (2016)], hereafter Paper I, we
have numerically studied different prescriptions for the dynamics of a spinning
particle in circular motion around a Schwarzschild black hole. In the present
work, we continue this line of investigation to the rotating Kerr black hole.
We consider the Mathisson-Papapetrou formalism under three different
spin-supplementary-conditions (SSC), the Tulczyjew SSC, the Pirani SSC and the
Ohashi-Kyrian-Semerak SSC, and analyze the different circular dynamics in terms
of the ISCO shifts and the frequency parameter ${x \equiv (M \Omega)^{2/3}}$,
where $\Omega$ is the orbital frequency and $M$ is the Kerr black hole mass.
Then, we solve numerically the inhomogeneous $(2+1)D$ Teukolsky equation to
contrast the asymptotic gravitational wave fluxes for the three cases. Our
central observation made in Paper I for the Schwarzschild limit is found to
hold true for the Kerr background: the three SSCs reduce to the same circular
dynamics and the same radiation fluxes for small frequency parameters but
differences arise as $x$ grows close to the ISCO. For a positive Kerr parameter
$a=0.9$ the energy fluxes mutually agree with each other within a $0.2\%$
uncertainty up to $x<0.14$, while for $a=-0.9$ this level of agreement is
preserved up to $x<0.1$. For large frequencies ($x \gtrsim 0.1$), however, the
spin coupling of the Kerr black hole and the spinning body results in
significant differences of the circular orbit parameters and the fluxes,
especially for the $a=-0.9$ case. Instead, in the study of ISCO the negative
Kerr parameter $a=-0.9$ results in less discrepancies in comparison with the
positive Kerr parameter $a=0.9$.",1707.07537v1
2018-11-10,"The Interplay Between Lattice Topology, Frustration, and Spin Quantum Number in Quantum Antiferromagnets on Archimedean Lattices","The interplay between lattice topology, frustration, and spin quantum number,
$s$, is explored for the Heisenberg antiferromagnet (HAFM) on the eleven
two-dimensional Archimedean lattices (square, honeycomb, CaVO, SHD, SrCuBO,
triangle, bounce, trellis, maple-leaf, star, and kagome). We show the CCM
provides consistently accurate results when compared to the results of other
approximate methods. The $\sqrt{3}\times\sqrt{3}$ model state provides lower
ground-state energies than those of the $q=0$ model state for the kagome and
star lattices for most values of $s$. The $q=0$ model state provides lower
ground-state energies only for $s=1/2$ for the kagome lattice and $s=1/2$ and
$s=1$ for the star lattice. The kagome and star lattices demonstrate the least
amount of magnetic ordering and the unfrustrated lattices (square, honeycomb,
SHD, and CaVO) demonstrate the most magnetic ordering for all values of $s$.
The SrCuBO and triangular lattices also demonstrate high levels of magnetic
ordering, while the remaining lattices (bounce, maple-leaf, and trellis) tend
to lie between these extremes, again for all values of $s$. These results also
clearly reflect the strong increase in magnetic order with increasing spin
quantum number $s$ for all lattices. The ground-state energy, $E_g/(NJs^2)$,
scales with $s^{-1}$ to first order, as expected from spin-wave theory,
although the order parameter, $M/s$, scales with $s^{-1}$ for most of the
lattices only. Self-consistent spin-wave theory calculations indicated
previously that $M/s$ scales with $s^{-2/3}$ for the kagome lattice HAFM,
whereas previous CCM results (replicated here also) suggested that $M/s$ scales
with $s^{-1/2}$. By using similar arguments, we find here also that $M/s$
scales with $s^{-1/3}$ on the star lattice and with $s^{-2/3}$ on the SrCuBO
lattice.",1811.04229v1
2019-06-28,The origin of spin in binary black holes: Predicting the distributions of the main observables of Advanced LIGO,"We study the formation of coalescing binary black holes via the evolution of
isolated field binaries that go through the common envelope phase in order to
obtain the combined distributions of the main observables of Advanced LIGO. We
used a hybrid technique that combines the parametric binary population
synthesis code COMPAS with detailed binary evolution simulations performed with
the MESA code. We then convolved our binary evolution calculations with the
redshift- and metallicity-dependent star-formation rate and the selection
effects of gravitational-wave detectors to obtain predictions of observable
properties. By assuming efficient angular momentum transport, we are able to
present a model that is capable of simultaneously predicting the three main
gravitational-wave observables: the effective inspiral spin parameter
$\chi_{eff}$, the chirp mass $M_{chirp}$, and the cosmological redshift of
merger $z_{merger}$. We find an excellent agreement between our model and the
ten events from the first two advanced detector observing runs. We make
predictions for the third observing run O3 and for Advanced LIGO design
sensitivity. We expect around 80% of events with $\chi_{eff} < 0.1$, while the
remaining 20% of events with $\chi_{eff} \ge 0.1$ are split into ~10% with
$M_{chirp} < 15$ M$_\odot$ and ~10% with $M_{chirp} \ge 15$ M$_\odot$. In
conclusion, the favorable comparison of the existing LIGO/Virgo observations
with our model predictions gives support to the idea that the majority, if not
all of the observed mergers, originate from the evolution of isolated binaries.
The first-born black hole has negligible spin because it lost its envelope
after it expanded to become a giant star, while the spin of the second-born
black hole is determined by the tidal spin up of its naked helium star
progenitor by the first-born black hole companion after the binary finished the
common-envelope phase.",1906.12257v3
2020-08-27,The Importance of Priors on LIGO-Virgo Parameter Estimation: the Case of Primordial Black Holes,"The black holes detected by current and future interferometers can have
diverse origins. Their expected mass and spin distributions depend on the
specifics of the formation mechanisms. When a physically motivated prior
distribution is used in a Bayesian inference, the parameters estimated from the
gravitational-wave data can change significantly, potentially affecting the
physical interpretation of certain gravitational-wave events and their
implications on theoretical models. As a case study we analyze primordial black
holes, which might be formed in the early universe and could comprise at least
a fraction of the dark matter. If accretion is not efficient during their
cosmic history, primordial black holes are expected to be almost non-spinning.
If accretion is efficient, massive binaries tend to be symmetrical and highly
spinning. We show that incorporating these priors can significantly change the
inferred mass ratio and effective spin of some binary black hole events,
especially those identified as high-mass, asymmetrical, or spinning by a
standard analysis using agnostic priors. For several events, the Bayes factors
are only mildly affected by the new priors, implying that it is hard to
distinguish whether merger events detected so far are of primordial or
astrophysical origin. In particular, if binaries identified by LIGO/Virgo as
strongly asymmetrical (including GW190412) are of primordial origin, their mass
ratio inferred from the data can be closer to unity. For GW190412, the latter
property is strongly affected by the inclusion of higher harmonics in the
waveform model.",2008.12320v3
2019-05-01,Tidal deformations of compact objects and gravitational wave emission,"Observations of gravitational wave (GW) signals produced by coalescing binary
neutron stars (NS), like the GW event GW170817, can be exploited to constrain
the equation of state (EoS) of matter in the stars' inner core. The information
on the internal structure and composition of the stars is encoded in their
tidal Love numbers, which leave an imprint in the waveform of the GW signal
emitted from the binary during the late inspiral phase. We extended the theory
of tidal deformations of compact objects by computing the spin-tidal
corrections that affect the dynamics and the GW emission of a binary system at
the leading post-Newtonian (PN) order and to linear order in the spin. These
corrections are divided into two classes: terms due to the coupling between the
standard tidal Love numbers and the spins of the objects, and terms depending
on the rotational tidal Love numbers. Both enter the GW phase at 6.5PN order.
We analysed the impact of the spin-tidal couplings by estimating the parameter
bias induced on GW170817-like events, assuming second- and third-generation
ground based interferometers. If relatively high spinning ($\chi \gtrsim 0.1$)
NS binaries exist in nature, these effects might be observed by the next
generation of detectors. Lastly, we proved the feasibility of solving the
so-called inverse stellar problem using GW detections, i.e., reconstructing the
EoS from the measurement of NS masses and tidal Love numbers. Our results show
that few observations of coalescing binary NS by a network of advanced
detectors would allow us to put interesting constraints on the phenomenological
parameters of a piecewise polytropic representation of the EoS, and to perform
a model selection among the realistic EoS proposed in the literature.",1905.00408v1
2020-11-27,Modelling Neutron Star-Black Hole Binaries: Future Pulsar Surveys and Gravitational Wave Detectors,"Binaries comprised of a neutron star (NS) and a black hole (BH) have so far
eluded observations as pulsars and with gravitational waves (GWs). We model the
formation and evolution of these NS+BH binaries - including pulsar evolution -
using the binary population synthesis code COMPAS. We predict the presence of a
total of 50-2000 binaries containing a pulsar and a BH (PSR+BHs) in the
Galactic field. We find the population observable by the next generation of
radio telescopes, represented by the SKA and MeerKAT, current (LIGO/Virgo) and
future (LISA) GW detectors. We conclude that the SKA will observe 1-80 PSR+BHs,
with 0-4 binaries containing millisecond pulsars. MeerKAT is expected to
observe 0-40 PSR+BH systems. Future radio detections of NS+BHs will constrain
uncertain binary evolution processes such as BH natal kicks. We show that
systems in which the NS formed first (NSBH) can be distinguished from those
where the BH formed first (BHNS) by their pulsar and binary properties. We find
40% of the LIGO/Virgo observed NS+BHs from a Milky-Way like field population
will have a chirp mass $\geq 3.0$ M$_\odot$. We estimate the spin distributions
of NS+BHs with two models for the spins of BHs. The remnants of BHNS mergers
will have a spin of $\sim$0.4, whilst NSBH merger remnants can have a spin of
$\sim$0.6 or $\sim$0.9 depending on the model for BH spins. We estimate that
approximately 25-1400 PSR+BHs will be radio alive whilst emitting GWs in the
LISA frequency band, raising the possibility of joint observation by the SKA
and LISA.",2011.13503v2
2021-02-03,Cuprate superconductors as viewed through a striped lens,"Understanding the electron pairing in hole-doped cuprate superconductors has
been a challenge, in particular because the ""normal"" state from which it
evolves is unprecedented. Now, after three and a half decades of research,
involving a wide range of experimental characterizations, it is possible to
delineate a clear and consistent cuprate story. It starts with doping holes
into a charge-transfer insulator, resulting in in-gap states. These states
exhibit a pseudogap resulting from the competition between antiferromagnetic
superexchange $J$ between nearest-neighbor Cu atoms (a real-space interaction)
and the kinetic energy of the doped holes, which, in the absence of
interactions, would lead to extended Bloch-wave states whose occupancy is
characterized in reciprocal space. To develop some degree of coherence on
cooling, the spin and charge correlations must self-organize in a cooperative
fashion. A specific example of resulting emergent order is that of spin and
charge stripes, as observed in La$_{2-x}$Ba$_x$CuO$_4$. While stripe order
frustrates bulk superconductivity, it nevertheless develops pairing and
superconducting order of an unusual character. The antiphase order of the spin
stripes decouples them from the charge stripes, which can be viewed as
hole-doped, two-leg, spin-$\frac12$ ladders. To achieve superconducting order,
the pair correlations in neighboring ladders must develop phase order. In the
presence of spin stripe order, antiphase Josephson coupling can lead to
pair-density-wave superconductivity. Alternatively, in-phase superconductivity
requires that the spin stripes have an energy gap, which empirically limits the
coherent superconducting gap. Hence, superconducting order in the cuprates
involves a compromise between the pairing scale, which is maximized at
$x\sim\frac18$, and phase coherence, which is optimized at $x\sim0.2$.",2102.02257v2
2019-09-16,"Coupled Channel Analysis of $\bar{p} p \rightarrow π^0 π^0 η$, $π^0 ηη$ and $K^+ K^- π^0$ at 900 $MeV/c$ and of $ππ$-Scattering Data","A partial wave analysis of antiproton-proton annihilation data in flight at
900 $MeV/c$ into $\pi^0 \pi^0 \eta$ , $\pi^0 \eta \eta$ and $K^+ K^- \pi^0$ is
presented. The data were taken at LEAR by the Crystal Barrel experiment in
1996. The three channels have been coupled together with $\pi\pi$-scattering
isospin I=0 S- and D-wave as well as I=1 P-wave data utilizing the K-matrix
approach. Analyticity is treated using Chew-Mandelstam functions. In the fit
all ingredients of the K-matrix, including resonance masses and widths, were
treated as free parameters. In spite of the large number of parameters, the fit
results are in the ballpark of the values published by the Particle Data Group.
In the channel $\pi^0 \pi^0 \eta$ a significant contribution of the spin exotic
$I^G=1^-$ $J^{PC}=1^{-+}$ $\pi_1$-wave with a coupling to $\pi^0 \eta$ is
observed. Furthermore the contributions of $\phi(1020) \pi^0$ and $K^*(892)^\pm
K^\mp$ in the channel $K^+ K^- \pi^0$ have been studied in detail. The
differential production cross section for the two reactions and the
spin-density-matrix elements for the $\phi(1020)$ and $K^*(892)^\pm$ have been
extracted. No spin-alignment is observed for both vector mesons. The spin
density matrix elements have been also determined for the spin exotic wave.",1909.07091v2
2019-10-14,Is there a spectral turnover in the spin noise of millisecond pulsars?,"Pulsar timing arrays provide a unique means to detect nanohertz gravitational
waves through long-term measurements of pulse arrival times from an ensemble of
millisecond pulsars. After years of observations, some timing array pulsars
have been shown to be dominated by low-frequency red noise, including spin
noise that might be associated with pulsar rotational irregularities. The power
spectral density of pulsar timing red noise is usually modeled with a power law
or a power law with a turnover frequency below which the noise power spectrum
plateaus. If there is a turnover in the spin noise of millisecond pulsars,
residing within the observation band of current and/or future pulsar timing
measurements, it may be easier than projected to resolve the gravitational-wave
background from supermassive binary black holes. Additionally, the spectral
turnover can provide valuable insights on neutron star physics. In the recent
study by Melatos and Link, the authors provided a derivation of the model for
power spectral density of spin noise from superfluid turbulence in the core of
a neutron star, from first principles. The model features a spectral turnover,
which depends on the dynamical response time of the superfluid and the
steady-state angular velocity lag between the crust and the core of the star.
In this work, we search for a spectral turnover in spin noise using the first
data release of the International Pulsar Timing Array. Through Bayesian model
selection, we find no evidence of a spectral turnover. Our analysis also shows
that data from pulsars J1939+2134, J1024$-$0719 and J1713+0747 prefers the
power-law model to the superfluid turbulence model.",1910.05961v3
2020-10-27,Controlling helicity-dependent photocurrent in polycrystalline Sb$_2$Te$_2$Se topological insulator thin films at ambient temperature through wave-vector of and photothermal gradient due to polarized light,"Optical control of helicity-dependent photocurrent in topological insulator
Sb$_2$Te$_2$Se has been studied at room temperature on dominantly c-axis
oriented granular polycrystalline samples grown by pulsed laser deposition
technique. Strong spin-orbit coupling and spin-momentum locking make this
system unique for their applications. We observed that photocurrent can be
controlled by exciting the sample with different circular and linear polarized
light, yielding a polarization-dependent current density which can be fitted
very well with a theoretical model. Magnitude of the photocurrent is higher
even at room temperature, compared to previous reports on other single-crystal
topological insulators. Comparison with the theoretical model suggests that
photocurrent has different contributions. Study of dependence of photocurrent
on the angle of incidence (wave-vector) of the excitation laser beam with
respect to the surface normal of the sample helps to identify origins of
different terms contributing to the observed photocurrent. Incidence-angle
driven helicity switching, which is a very simple and effective technique to
control the directional photocurrent, has also been observed in this study.
This photocurrent can also be controlled with the help of photothermal gradient
generated by the excitation light beam. Enhancement and inversion of this
photocurrent in presence of photothermal gradient for light incident on two
opposite edges of the sample occur due to selective spin state excitation with
two opposite (left and right) circularly polarized light in presence of the
unique spin-momentum locked surface states. These observations renders this
polycrystalline material to be more important in polarization-dependent
photodetection applications as well as for spin-optoelectronics under ambient
conditions.",2010.14387v2
2021-06-30,Probing the progenitors of spinning binary black-hole mergers with long gamma-ray bursts,"Long-duration gamma-ray bursts are thought to be associated with the
core-collapse of massive, rapidly spinning stars and the formation of black
holes. However, efficient angular momentum transport in stellar interiors,
currently supported by asteroseismic and gravitational-wave constraints, leads
to predominantly slowly-spinning stellar cores. Here, we report on binary
stellar evolution and population synthesis calculations, showing that tidal
interactions in close binaries not only can explain the observed sub-population
of spinning, merging binary black holes but also lead to long gamma-ray bursts
at the time of black-hole formation. Given our model calibration against the
distribution of isotropic-equivalent energies of luminous long gamma-ray
bursts, we find that ~10% of the GWTC-2 reported binary black holes had a
luminous long gamma-ray burst associated with their formation, with GW190517
and GW190719 having a probability of ~85% and ~60%, respectively, being among
them. Moreover, given an assumption about their average beaming fraction, our
model predicts the rate density of long gamma-ray bursts, as a function of
redshift, originating from this channel. For a constant beaming fraction
$f_\mathrm{B}\sim 0.05$ our model predicts a rate density comparable to the
observed one, throughout the redshift range, while, at redshift $z \in
[0,2.5]$, a tentative comparison with the metallicity distribution of observed
LGRB host galaxies implies that between 20% to 85% of the observed long
gamma-ray bursts may originate from progenitors of merging binary black holes.
The proposed link between a potentially significant fraction of observed,
luminous long gamma-ray bursts and the progenitors of spinning binary
black-hole mergers allows us to probe the latter well outside the horizon of
current-generation gravitational wave observatories, and out to cosmological
distances.",2106.15841v3
2021-12-03,Stripes and spin-density waves in the doped two-dimensional Hubbard model: ground state phase diagram,"We determine the spin and charge orders in the ground state of the doped
two-dimensional (2D) Hubbard model in its simplest form, namely with only
nearest-neighbor hopping and on-site repulsion. At half-filling, the ground
state is known to be an anti-ferromagnetic Mott insulator. Doping Mott
insulators is believed to be relevant to the superconductivity observed in
cuprates. A variety of candidates have been proposed for the ground state of
the doped 2D Hubbard model. A recent work employing a combination of several
state-of-the-art numerical many-body methods, established the stripe order as
the ground state near $1/8$ doping at strong interactions. In this work, we
apply one of these methods, the cutting-edge constrained-path auxiliary field
quantum Monte Carlo method with self-consistently optimized gauge constraints,
to systematically study the model as a function of doping and interaction
strength. With careful finite size scaling based on large-scale computations,
we map out the ground state phase diagram in terms of its spin and charge
order. We find that modulated antiferromagnetic order persists from near
half-filling to about $1/5$ doping. At lower interaction strengths or larger
doping, these ordered states are best described as spin-density waves, with
essentially delocalized holes and modest oscillations in charge correlations.
When the charge correlations are stronger (large interaction or small doping),
they are best described as stripe states, with the holes more localized near
the node in the antiferromagnetic spin order. In both cases, we find that the
wavelength in the charge correlations is consistent with so-called filled
stripes in the pure Hubbard model.",2112.02187v3
2022-02-22,Improvement of the parameter measurement accuracy by the third-generation gravitational wave detector Einstein Telescope,"The Einstein Telescope (ET) has been proposed as one of the third-generation
gravitational wave (GW) detectors. The sensitivity of ET would be a factor of
10 better than the second-generation GW detector, Advanced LIGO (aLIGO); thus,
the GW source parameters could be measured with much better accuracy. In this
work, we show how the precision in parameter estimation can be improved between
aLIGO and ET by comparing the measurement errors. We apply the TaylorF2
waveform model defined in the frequency domain to the Fisher matrix method
which is a semi-analytic approach for estimating GW parameter measurement
errors. We adopt as our sources low-mass binary black holes with the total
masses of $M\leq 16 M_{\odot} $ and the effective spins of $-0.9 \leq \chi_{\rm
eff} \leq 0.9$ and calculate the measurement errors of the mass and the spin
parameters using $10^4$ Monte-Carlo samples randomly distributed in our mass
and spin parameter space. We find that for the same sources ET can achieve
$\sim 14$ times better signal-to-noise ratio than aLIGO and the error ratios
($\sigma_{\lambda, \rm ET}/\sigma_{\lambda, \rm aLIGO}$) for the chirp-mass,
symmetric mass ratio, and effective spin parameters can be lower than $7\%$ for
all binaries. We also consider the equal-mass binary neutron stars with the
component masses of 1, 1.4, and 2 $M_{\odot}$ and find that the error ratios
for the mass and the spin parameters can be lower than $1.5 \%$. In particular,
the measurement error of the tidal deformability $\tilde{\Lambda}$ can also be
significantly reduced by ET, with the error ratio of $3.6 - 6.1 \%$.",2202.10858v2
2022-03-22,Small-scale structure in vector dark matter,"We investigate the differences in the small-scale structure of vector dark
matter (VDM) and scalar dark matter (SDM) using 3+1 dimensional simulations of
single/multicomponent Schr\""{o}dinger-Poisson system. We find that the amount
of wave interference, core-to-halo mass ratio (and its scatter), spin of the
core, as well as the shape of the central regions of dark matter halos can
distinguish VDM and SDM. Starting with a collection of idealized halos
(self-gravitating solitons) as an initial condition, we show that the system
dynamically evolves to an approximately spherically symmetric configuration
that has a core surrounded by a halo of interference patterns in the mass
density. In the vector case, the central soliton in less dense and has a
smoother transition to an $r^{-3}$ tail compared to the scalar case. As
compared to SDM, wave interference in VDM is $\sim 1/\sqrt{3}$ times smaller,
resulting in fewer low and high density regions, and more diffuse granules in
the halo. The ratio of VDM core mass to the total halo mass is lower than that
in SDM, with a steeper dependence on the total energy of the system and a
slightly larger scatter. Finally, we also initiate a study of the evolution of
intrinsic spin angular momentum in the VDM case. We see a positive correlation
between the total intrinsic spin in the simulation and the spin of the final
central core, with significant scatter. We see large intrinsic spin in the core
being possible even with vanishing amounts total angular momentum in the
initial conditions (at least instantaneously). Our results point towards the
possibility of distinguishing VDM from SDM using astrophysical and terrestrial
observations.",2203.11935v3
2022-10-23,Cover Your Basis: Comprehensive Data-Driven Characterization of the Binary Black Hole Population,"We introduce the first complete non-parametric model for the astrophysical
distribution of the binary black hole (BBH) population. Constructed from basis
splines, we use these models to conduct the most comprehensive data-driven
investigation of the BBH population to date, simultaneously fitting
non-parametric models for the BBH mass ratio, spin magnitude and misalignment,
and redshift distributions. With GWTC-3, we report the same features previously
recovered with similarly flexible models of the mass distribution, most notably
the peaks in merger rates at primary masses of ${\sim}10\,M_\odot$ and
${\sim}35\,M_\odot$. Our model reports a suppressed merger rate at low primary
masses and a mass ratio distribution consistent with a power law. We infer a
distribution for primary spin misalignments that peaks away from alignment,
supporting conclusions of recent work. We find broad agreement with the
previous inferences of the spin magnitude distribution: the majority of BBH
spins are small ($a<0.5$), the distribution peaks at $a\sim0.2$, and there is
mild support for a non-spinning subpopulation, which may be resolved with
larger catalogs. With a modulated power law describing the BBH merger rate's
evolution in redshift, we see hints of the rate evolution either flattening or
decreasing at $z\sim0.2-0.5$, but the full distribution remains entirely
consistent with a monotonically increasing power law. We conclude with a
discussion of the astrophysical context of our new findings and how
non-parametric methods in gravitational-wave population inference are uniquely
poised to complement to the parametric approach as we enter the data-rich era
of gravitational-wave astronomy.",2210.12834v3
2022-11-28,Dipolar spin ice regime proximate to an all-in-all-out Néel ground state in the dipolar-octupolar pyrochlore Ce$_2$Sn$_2$O$_7$,"The dipolar-octupolar (DO) pyrochlores, R$_2$M$_2$O$_7$ (R = Ce, Sm, Nd), are
key players in the search for realizable novel quantum spin liquid (QSL) states
as a large parameter space within the DO pyrochlore phase diagram is theorized
to host QSL states of both dipolar and octupolar nature. New single crystals
and powders of Ce$_2$Sn$_2$O$_7$, synthesized by hydrothermal techniques,
present an opportunity for a new characterization of the exchange parameters in
Ce$_2$Sn$_2$O$_7$ using the near-neighbor $XYZ$ model Hamiltonian associated
with DO pyrochlores. Utilizing quantum numerical linked cluster expansion fits
to heat capacity and magnetic susceptibility measurements, and classical Monte
Carlo calculations to the diffuse neutron diffraction of the new hydrothermally
grown Ce$_2$Sn$_2$O$_7$ samples, we place Ce$_2$Sn$_2$O$_7$'s ground state
within the ordered dipolar all-in-all-out (AIAO) N\'{e}el phase, with quantum
Monte Carlo calculations showing a transition to long-range order at
temperatures below those accessed experimentally. Indeed, our new neutron
diffraction measurements on the hydrothermally grown Ce$_2$Sn$_2$O$_7$ powders
show a broad signal at low scattering wave vectors, reminiscent of a
\textit{dipolar} spin ice, in striking contrast from previous powder neutron
diffraction on samples grown from solid-state synthesis, which found diffuse
scattering at high scattering wave vectors associated with magnetic {\it
octupoles} and suggested an octupolar quantum spin ice state. We conclude that
new hydrothermally grown Ce$_2$Sn$_2$O$_7$ samples host a finite-temperature
proximate dipolar spin ice phase, above the expected transition to AIAO
N\'{e}el order.",2211.15140v2
2022-12-01,"Distinct signatures of spinning PBH domination and evaporation: doubly peaked gravitational waves, dark relics and CMB complementarity","Ultra-low mass primordial black holes (PBH), which may briefly dominate the
energy density of the universe but completely evaporate before the big bang
nucleosynthesis (BBN), can lead to interesting observable signatures. In our
previous work, we studied the generation of a doubly peaked spectrum of induced
stochastic gravitational wave background (ISGWB) for such a scenario and
explored the possibility of probing a class of baryogenesis models wherein the
emission of massive unstable particles from the PBH evaporation and their
subsequent decay contributes to the matter-antimatter asymmetry. In this work,
we extend the scope of our earlier work by including spinning PBHs and consider
the emission of light relativistic dark sector particles, which contribute to
the dark radiation (DR) and massive stable dark sector particles, thereby
accounting for the dark matter (DM) component of the universe. The ISGWB can
probe the non-thermal production of these heavy DM particles, which cannot be
accessible in laboratory searches. For the case of DR, we find a novel
complementarity between the measurements of $\Delta N_{\rm eff}$ from these
emitted particles and the ISGWB from PBH domination. Our results indicate that
the ISGWB has a weak dependence on the initial PBH spin. However, for gravitons
as the DR particles, the initial PBH spin plays a significant role, and only
above a critical value of the initial spin parameter $a_*$, which depends only
on initial PBH mass, the graviton emission can be probed in the CMB-HD
experiment. Upcoming CMB experiments such as CMB-HD and CMB-Bharat, together
with future GW detectors like LISA and ET, open up an exciting possibility of
constraining the PBHs parameter space providing deeper insights into the
expansion history of the universe between the end of inflation and BBN.",2212.00775v2
2023-02-13,Perturbation Theory Treatment of Spin-Orbit Coupling. III: Coupled Perturbed Method for Solids,"A previously proposed non-canonical coupled-perturbed Kohn-Sham density
functional theory (KS-DFT)/Hartree-Fock (HF) treatment for spin-orbit coupling
is here generalized to infinite periodic systems. The scalar-relativistic
periodic KS-DFT/HF solution, obtained with a relativistic effective core
potential, is taken as the zeroth-order approximation. Explicit expressions are
given for the total energy through 3rd-order, which satisfy the 2N + 1 rule
(i.e. requiring only the 1st-order perturbed wave function for determining the
energy through 3rd-order). Expressions for additional 2nd-order corrections to
the perturbed wave function (as well as related one-electron properties) are
worked out at the uncoupled-perturbed level of theory. The approach is
implemented in the \textsc{Crystal} program and validated with calculations of
the total energy, electronic band structure, and density variables of
spin-current DFT on the tungsten dichalcogenide hexagonal bilayer series (i.e.
WSe$_2$, WTe$_2$, WPo$_2$, WLv$_2$), including 6p and 7p elements as a stress
test. The computed properties through second- or third-order match well with
those from reference two-component self-consistent field (2c-SCF) calculations.
For total energies, $E^{(3)}$ was found to consistently improve the agreement
against the 2c-SCF reference values. For electronic band structures, visible
differences w.r.t. 2c-SCF remained through second-order in only the single-most
difficult case of WLv$_2$. As for density variables of spin-current DFT, the
perturbed electron density, being vanishing in first-order, is the most
challenging for the perturbation theory approach. The visible differences in
the electron densities are, however, largest close to the core region of atoms
and smaller in the valence region. Perturbed spin-current densities, on the
other hand, are well reproduced in all tested cases.",2302.06143v1
2005-10-12,Cosmological Flashes from Rotating Black Holes,"Current phenomenology suggests the presence of a compact baryon-poor energy
source to cosmological gamma-ray bursts reacting to high-density matter. The
association of short and long gamma-ray bursts with hyper- and suspended
accretion onto slowly and rapidly spinning black holes predicts weak X-ray
afterglow emissions from short bursts, as in GRB050509B and GRB050709. Long
gamma-ray bursts are probably the birth place of rapidly spinning high-mass
black holes in core-collapse of massive stars, as in GRB030329 with supernova
SN2003dh. This predicts a long-duration burst of gravitational radiation
powered by the spin-energy of the black hole. In contrast to MeV-neutrino
emissions, as in SN1987A, this can be tested by the advanced detectors LIGO and
Virgo about once per year up to distances of about 100Mpc. Detection of the
expected chirps and long-duration bursts of gravitational waves promises
identification of Kerr black holes as the most luminous objects in the
Universe.",0510348v2
1994-01-25,Numerical Study of the $S=1$ Antiferrromagnetic Spin Chain with Bond Alternation,"We study the $S=1$ quantum spin chain with bond alternation ${\cal H}=\sum _i
(1-(-1)^i\delta)\vect{S}_i\cdot \vect{S}_{i+1}$ by the density matrix
renormalization group method recently proposed by Steven R. White
(\PRL{69}{3844}{1993}). We find a massless point at $\delta _c =0.25 \pm 0.01$.
We also find the edge states in the region $\delta <\delta_c$ under the open
boundary condition, which disappear in the region $\delta >\delta _{c}$. At the
massless point, the spin wave velocity $v_s$ is $3.66 \pm 0.10$ and the central
charge $c$ is $1.0\pm 0.15$. Our results indicate that a continuous phase
transition occurs at the massless point $\delta =\delta_c $ accompanying
breaking of the hidden $Z_2\times Z_2$ symmetry.",9401053v2
1994-02-09,Spiral Magnets as Gapless Mott Insulators,"In the large $U$ limit, the ground state of the half-filled, nearest-neighbor
Hubbard model on the triangular lattice is the three-sublattice
antiferromagnet. In sharp contrast with the square-lattice case, where
transverse spin-waves and charge excitations remain decoupled to all orders in
$t/U$, it is shown that beyond leading order in $t/U$ the three Goldstone modes
on the triangular lattice are a linear combination of spin and charge. This
leads to non-vanishing conductivity at any finite frequency, even though the
magnet remains insulating at zero frequency. More generally, non-collinear spin
order should lead to such gapless insulating behavior.",9402044v1
1994-06-24,"Collective modes of spin, density, phase and amplitude in exotic superconductors","The equations of motion of pair-like excitations in the superconducting state
are studied for various types of pairing using the random phase approximation.
The collective modes are computed of a layered electron gas described by a
$t-t'$ tight-binding band, where the electrons experience besides the
long-range Coulomb repulsion an on-site Hubbard U repulsion and a
nearest-neighbour attractive interaction. {}From numerical calculations we see,
that the collective mode spectrum now becomes particularly rich. Several
branches can occur below the continuum of quasi-particle excitations,
corresponding to order-parameter fluctuations of various symmetries of pairing,
and collective spin-density fluctuations. {}From the collective mode softening
near the nesting vectors it is concluded, that in the d-wave paired state an
instability occurs toward the formation of a spin-density wave.",9406097v1
1994-08-05,Singlet Stripe Phases in the planar t-J Model,"The energies of singlet stripe phases in which a plane is broken up into spin
liquid ladders by lines of holes, is examined. If the holes were static then
patterns containing spin liquids with a finite spin gap are favored. The case
of dynamic holes is treated by assembling t-J ladders oriented perpendicular to
the stripes. For a wide region around $J/t \approx 1$ the hole-hole
correlations in a single ladder are found to be predominantly charge density
wave type but an attraction between hole pairs on adjacent ladders leads to a
stripe phase. A quantum mechanical melting of the hole lines at smaller $J/t$
values leads to a Bose condensate of hole pairs, i.e. a superconducting phase.",9408024v1
1994-10-25,Direct Calculation of the Spin Stiffness in the $J_1$--$J_2$ Heisenberg Antiferromagnet,"We calculate the spin stiffness $\rho_s$ for the frustrated
spin-$\frac{1}{2}$ Heisenberg antiferromagnet on a square lattice by exact
diagonalizations on finite clusters of up to $36$ sites followed by
extrapolations to the thermodynamic limit. For the non-frustrated case, we find
that $\rho_s = (0.183\pm 0.003)J_1$, in excellent agreement with the best
results obtained by other means. Turning on frustration, the extrapolated
stiffness vanishes for $0.4 \lesssim J_2/J_1 \lesssim 0.6$. In this
intermediate region, the finite-size scaling works poorly -- an additional sign
that their is neither N\'eel nor collinear magnetic order. Using a hydrodynamic
relation, and previous results for the transverse susceptibility, we also
estimate the spin-wave velocity in the N\'eel-ordered region.",9410090v1
1995-06-02,Spin Waves in Quantum Antiferromagnets,"Using a self-consistent mean-field theory for the $S=1/2$ Heisenberg
antiferromagnet Kr\""uger and Schuck recently derived an analytic expression for
the dispersion. It is exact in one dimension ($d=1$) and agrees well with
numerical results in $d=2$. With an expansion in powers of the inverse
coordination number $1/Z$ ($Z=2d$) we investigate if this expression can be
{\em exact} for all $d$. The projection method of Mori-Zwanzig is used for the
{\em dynamical} spin susceptibility. We find that the expression of Kr\""uger
and Schuck deviates in order $1/Z^2$ from our rigorous result. Our method is
generalised to arbitrary spin $S$ and to models with easy-axis anisotropy $\D$.
It can be systematically improved to higher orders in $1/Z$. We clarify its
relation to the $1/S$ expansion.",9506013v1
1996-02-09,Studies of Quantum Spin Ladders at T=0 and at High Temperatures by Series Expansions,"We have carried out extensive series studies, at T=0 and at high
temperatures, of 2-chain and 3-chain spin-half ladder systems with
antiferromagnetic intrachain and both antiferromagnetic and ferromagnetic
interchain couplings. Our results confirm the existence of a gap in the 2-chain
Heisenberg ladders for all non-zero values of the interchain couplings.
Complete dispersion relations for the spin-wave excitations are computed. For
3-chain systems, our results are consistent with a gapless spectrum. We also
calculate the uniform magnetic susceptibility and specific heat as a function
of temperature. We find that as $T\to 0$, for the 2-chain system the uniform
susceptibility goes rapidly to zero, whereas for the 3-chain system it
approaches a finite value. These results are compared in detail with previous
studies of finite systems.",9602055v1
1996-04-09,Semiclassical and field theoretic studies of Heisenberg antiferromagnetic chains with frustration and dimerization,"The Heisenberg antiferromagnetic spin chain with both dimerization and
frustration is studied. The classical ground state has three phases (a Neel
phase, a spiral phase and a colinear phase), around which a planar spin-wave
analysis is performed. In each phase, we discuss a non-linear sigma model field
theory describing the low energy excitations. A renormalization group analysis
of the SO(3) matrix-valued field theory of the spiral phase leads to the
conclusion that the theory becomes $SO(3) \times SO(3)$ and Lorentz invariant
at long distances. This theory is analytically known to have a massive spin-1/2
excitation. We also show that $Z_2 ~$ solitons in the field theory lead to a
double degeneracy in the spectrum for half-integer spins.",9604044v1
1996-11-04,The J_1-J_2 model revisited : Phenomenology of CuGeO_3,"We present a mean field solution of the antiferromagnetic Heisenberg chain
with nearest (J_1) and next to nearest neighbor (J_2) interactions. This
solution provides a way to estimate the effects of frustration. We calculate
the temperature-dependent spin-wave velocity, v_s(T) and discuss the
possibility to determine the magnitude of frustration J_2/J_1 present in quasi
1D compounds from measurements of v_s(T). We compute the thermodynamic
susceptibility at finite temperatures and compare it with the observed
susceptibility of the spin-Peierls compound CuGeO_3. We also use the method to
study the two-magnon Raman continuum observed in CuGeO_3 above the spin-Peierls
transition.",9611018v1
1996-11-30,Spin Dynamics in an Ordered Stripe Phase,"Inelastic neutron scattering has been used to measure the low-energy spin
excitations in the ordered charge-stripe phase of La(2)NiO(4+d) with d=0.133.
Spin-wave-like excitations disperse away from the incommensurate magnetic
superlattice points with a velocity ~60% of that in the d=0 compound.
Incommensurate inelastic peaks remain well-resolved up to at least twice the
magnetic ordering temperature. Paramagnetic scattering from a d=0.105 sample,
which has a N\'eel-ordered ground state, shows anomalies suggestive of
incipient stripe correlations. Similarities between these results and
measurements on superconducting cuprates are discussed.",9612007v2
1997-02-27,Spin-density and charge-density excitations in quantum wires,"We study an interacting electron gas in a quantum wire within the
Hartree-Fock random phase approximation. Vertex corrections to the electron
spin polarizability due to the electronic exchange interaction are important
giving rise to spin-density excitations (SDE) with large oscillator strength
shifted to lower energies with respect to single-particle states. The energy of
intersubband SDE oscillates with the number of subbands occupied and has a
minimum when a subband energy is close to the chemical potential. Intrasubband
SDE have a linear dispersion at small wave-vectors. The corresponding sound
velocity is reduced with respect to the Fermi velocity due to exchange
interaction within the occupied subbands and exchange screening caused by
virtual transitions to upper subbands. For intersubband and intrasubband
charge-density excitations (CDE) vertex corrections are of less importance. For
only a single subband occupied the screening of CDE and SDE in the
Tomonaga-Luttinger model due to virtual transitions to upper subband is
studied, where the virtual transitions are treated within the Hartree-Fock
approximation. The calculations are in good qualitative agreement with
experiments.",9702236v1
1997-04-14,Spin Gap and Superconductivity in the Interlayer Pair Tunneling Model,"A simple interlayer pair tunneling is solved exactly. We find that in the
normal state spin-1/2 particle and hole excitations are gapped. But the state
is an unusual metal, characterized by novel fermionic spin zero and charge +2e
and -2e excitations that exist about their own Fermi surfaces. The model is
consistent with a number of properties of the underdoped cuprates. At finite
temperature the Fermi surface appears partially gapped, and at high
temperatures the spin gap disappears completely. Superconductivity is induced
by an additional intralyer interaction which opens a gap in the charge-fermion
spectrum. The symmetry of this charge gap (and hence that of the order
parameter) is igenerally different from the symmetry of one-electron or - hole
gap. The former can be a d wave, while the latter is more complex.",9704123v1
1997-06-13,Modification of the Landau-Lifshitz Equation in the Presence of a Spin-Polarized Current in CMR and GMR Materials,"We derive a continuum equation for the magnetization of a conducting
ferromagnet in the presence of a spin-polarized current. Current effects enter
in the form of a topological term in the Landau-Lifshitz equation . In the
stationary situation the problem maps onto the motion of a classical charged
particle in the field of a magnetic monopole. The spatial dependence of the
magnetization is calculated for a one-dimensional geometry and suggestions for
experimental observation are made. We also consider time-dependent solutions
and predict a spin-wave instability for large currents.",9706132v1
1997-08-01,Determination of the universality class of Gadolinium,"We resolve a longstanding puzzle for the static and dynamic critical behavior
of Gadolinium by a combined theoretical and experimental investigation. It is
shown that the spin dynamics of a three dimensional ferromagnet with hcp
lattice structure and a spin-spin interaction given by both exchange and
dipole-dipole interaction belongs to a new dynamic universality class, model
J$^*$. Comparing results from mode coupling theory with results from three
different hyperfine interaction probes we find quantitative agreement. The
crossover scenario for the wavevector dependence of the hyperfine relaxation
rate is determined by a subtle interplay between three length scales: the
correlation length, the dipolar and the uniaxial wave vector.",9708008v1
1997-12-16,Spin dynamics of strongly-doped La_{1-x}Sr_xMnO_3,"Cold neutron triple-axis measurements have been used to investigate the
nature of the long-wavelength spin dynamics in strongly-doped
La$_{1-x}$Sr$_{x}$MnO$_3$ single crystals with $x$=0.2 and 0.3. Both systems
behave like isotropic ferromagnets at low T, with a gapless ($E_0 < 0.02$ meV)
quadratic dispersion relation $E = E_0 + Dq^2$. The values of the spin-wave
stiffness constant $D$ are large ($D_{T=0}$ = 166.77 meV$ \AA^2$ for $x$=0.2
and D$_{T=0}$ = 175.87 meV$ \AA^2$ for $x$=0.3), which directly shows that the
electron transfer energy for the $d$ band is large. $D$ exhibits a power law
behavior as a function of temperature, and appears to collapse as T -> T_C.
Nevertheless, an anomalously strong quasielastic central component develops and
dominates the fluctuation spectrum as T -> T_C. Bragg scattering indicates that
the magnetization near $T_C$ exhibits power law behavior, with $\beta \simeq
0.30$ for both systems, as expected for a three-dimensional ferromagnet.",9712191v1
1997-12-23,Local magnetic impurities in the 2D quantum Heisenberg antiferromagnet,"We consider the two-dimensional (2D) quantum Heisenberg antiferromagnet at
zero temperature with two types of locally frustrating perturbations - an
isolated ferromagnetic bond (FMB) and a quantum impurity spin, coupled
symmetrically to the two sublattices. An analytic technique is developed to
study strong defect-environment interaction. In the case of a FMB we find that,
contrary to the previous linear spin-wave result, the local magnetization stays
finite even for strong frustration. For an antiferromagnetic coupling of a
quantum impurity spin with its environment, we find a local ground state
transition. All our calculations are compared with numerical results from exact
diagonalization on small clusters.",9712281v1
1998-01-01,Local impurities in 2D quantum antiferromagnets,"The two-dimensional quantum Heisenberg antiferromagnet at zero temperature
with two kinds of locally frustrating defects - isolated ferromagnetic bonds
and impurity spins, is studied. For a quantum spin, coupled
antiferromagnetically to the two sublattices, we find a local ground state
transition. In the case of a ferromagnetic bond, the local magnetization is
found to remain finite even for strong coupling, contrary to previous results,
derived within the linear spin-wave approximation. Our results are based on an
analytic approach, suitable to treat strong defect-environment interaction, as
well as exact diagonalization studies. Technical details and some extension of
this work can be found in cond-mat/9712281.",9801001v1
1998-05-09,The resonance peak in cuprate superconductors,"We pursue the consequences of a theory in which the resonance peak observed
in inelastic neutron scattering (INS) experiments on underdoped and optimally
doped YBa$_2$Cu$_3$O$_{6+x}$ compounds arises from a spin-wave excitation. We
find that it is heavily damped, and thus almost not observable, in the normal
state, but becomes visible in the superconducting state due to the drastic
decrease in spin damping. We show that a spin-fermion model correctly describes
the temperature dependence of the peak position for YBa$_2$Cu$_3$O$_7$, as well
as the doping dependence of the peak position and of the integrated intensity.
We explain why no resonance peak has been observed in La$_{2-x}$Sr$_x$CuO$_4$,
and make several predictions concerning resonance peaks in other cuprate
superconductors.",9805107v1
1998-06-14,Incommensurate Charge and Spin Fluctuations in d-wave Superconductors,"We show analytic results for the irreducible charge and spin
susceptibilities, $\chi_0 (\omega, {\bf Q})$, where ${\bf Q}$ is the momentum
transfer between the nodes in d-wave superconductors. Using the BCS theory and
a circular Fermi surface, we find that the singular behavior of the irreducible
charge susceptibility leads to the dynamic incommensurate charge collective
modes. The peaks in the charge structure factor occur at a set of wave vectors
which form an ellipse around ${\bf Q}_{\pi}=(\pi,\pi)$ and ${\bf Q}_0=(0,0)$ in
momentum space with momentum dependent spectral weight. It is also found that,
due to the non-singular irreducible spin susceptibility, an extremely strong
interaction via random phase approximation is required to support the magnetic
peaks near ${\bf Q}_{\pi}$. Under certain conditions, the peaks in the magnetic
structure factor occur near ${\bf Q}=(\pi,\pi (1 \pm \delta))$ and $(\pi (1 \pm
\delta),\pi)$.",9806170v2
1998-09-22,Localization length of a soliton from a non-magnetic impurity in a general double-spin-chain model,"A localization length of a free-spin soliton from a non-magnetic impurity is
deduced in a general double-spin-chain model ($J_0-J_1-J_2-J_3$ model). We have
solved a variational problem which employs the nearest-neighbor singlet-dimer
basis. The wave function of a soliton is expressed by the Airy function, and
the localization length $(\xi)$ is found to obey a power law of the
dimerization $(J_2-J_3)$ with an exponent -1/3; $\xi\sim (J_2-J_3)^{-1/3}$.
This explains why NaV_2O_5 does not show the antiferromagnetic order, while
CuGeO_3 does by impurity doping. When the gap exists by the bond-dimerization,
a soliton is localized and no order is expected. Contrary, there is a
possibility of the order when the gap is mainly due to frustration.",9809292v1
1999-03-31,Evidence for a Purely Double-Exchange Mechanism for the Anisotropic Conductivities in Layered La-Sr-Mn-O Single Crystals Below TC,"Experimental evidence supports the double-exchange (DE) mechanism for both
in-plane and c-axis conductivity in the colossal-magnetoresistive (CMR) layered
manganite La1.4Sr1.6Mn2O7. Below TC, the data determine both the DE and
antiferromagnetic (AF) superexchange between bilayers. These agree with recent
spin-wave data, such that the ratio of intra- to inter-bilayer DE constants is
very close to the spin-independent conductance anisotropy of ~300. The
conductivity is shown to be proportional to the square of the measured
magnetization over a wide range of fields and for temperatures below the
in-plane ferromagnetic ordering temperature, TC. This dependence is shown to be
consistent with DE coupling and earlier zero-field studies of La1.2Sr1.8Mn2O7
near TC, which used neutron scattering for the local magnetization. A mixed AF
and spin-flop state (similar to the intermediate state of type-I
superconductors) is a rigorous prediction of the data and modeling.",9903452v1
1999-04-30,Magnetic excitations in charge- ordered NaV2O5,"An investigation of the spin excitation spectrum of charge ordered (CO)
NaV2O5 is presented. We discuss several different exchange models which may be
relevant for this compound, namely in- line and zig-zag chain models with weak
as well as strong inter- chain coupling and also a ladder model and a CO/MV
(mixed valent) model. We put special emphasis on the importance of large
additional exchange across the diagonals of V- ladders and the presence of
exchange anisotropies on the excitation spectrum. It is shown that the observed
splitting of transverse dispersion branches may both be interpreted as
anisotropy effect as well as acoustic- optic mode splitting in the weakly
coupled chain models. In addition we calculate the field dependence of
excitation modes in these models. Furthermore we show that for strong inter-
chain coupling, as suggested by recent LDA+U results, an additional high energy
optical excitation appears and the spin gap is determined by anisotropies. The
most promising CO/MV model predicts a spin wave dispersion perpendicular to the
chains which agrees very well with recent results obtained by inelastic neutron
scattering.",9904443v2
1999-05-31,Magnetoelastic mechanism of spin-reorientation transitions at step-edges,"The symmetry-induced magnetic anisotropy due to monoatomic steps at strained
Ni films is determined using results of first - principles relativistic
full-potential linearized augmented plane wave (FLAPW) calculations and an
analogy with the N\'eel model. We show that there is a magnetoelastic
anisotropy contribution to the uniaxial magnetic anisotropy energy in the
vicinal plane of a stepped surface. In addition to the known spin-direction
reorientation transition at a flat Ni/Cu(001) surface, we propose a
spin-direction reorientation transition in the vicinal plane for a stepped
Ni/Cu surface due to the magnetoelastic anisotropy. We show that with an
increase of Ni film thickness, the magnetization in the vicinal plane turns
perpendicular to the step edge at a critical thickness calculated to be in the
range of 16-24 Ni layers for the Ni/Cu(1,1,13) stepped surface.",9905437v1
1999-06-03,A relation between the resonance neutron peak and ARPES data in cuprates,"We argue that the resonant peak observed in neutron scattering experiments on
superconducting cuprates and the peak/dip/hump features observed in ARPES
measurements are byproducts of the same physical phenomenon. We argue that both
are due to feedback effects on the damping of spin fluctuations in a $d-$wave
superconductor. We consider the spin-fermion model at strong coupling, solve a
set of coupled integral equations for fermionic and bosonic propagators and
show that the dynamical spin susceptibility below $T_c$ possesses the resonance
peak at $\Omega_{res} \propto \xi^{-1}$.
  The scattering of these magnetic excitations by electrons gives rise to a
peak/dip/hump behavior of the electronic spectral function, the peak-dip
separation is exactly $\Omega_{res}$.",9906051v1
1999-07-05,New Boundary Bound States in an Open Quantum Spin Chain,"New boundary bound states (BBS) are found of an integrable model with the
magnetic impurities located at the edges of an open Heisenberg spin chain.
These bound states carry the real energy and are formed by three or five
imaginary modes of the rapidities. These imaginary modes of the rapidities give
the non-zero antisymmetric wave functions and the moments of the centers of the
bound states are zero. It means that these bound states are arisen by the
magnetic impurities and localized at the edges of the correlated system. The
Kondo screening occurs for the antiferromagnetic spin chain with the
ferromagnetic impurities-electrons exchange interaction.",9907057v1
1999-07-21,Charge Order Driven spin-Peierls Transition in NaV2O5,"We conclude from 23Na and 51V NMR measurements in NaxV2O5(x=0.996) a charge
ordering transition starting at T=37 K and preceding the lattice distortion and
the formation of a spin gap Delta=106 K at Tc=34.7 K. Above Tc, only a single
Na site is observed in agreement with the Pmmn space group of this first
1/4-filled ladder system. Below Tc=34.7 K, this line evolves into eight
distinct 23Na quadrupolar split lines, which evidences a lattice distortion
with, at least, a doubling of the unit cell in the (a,b) plane. A model for
this unique transition implying both charge density wave and spin-Peierls order
is discussed.",9907326v1
1999-08-17,Disorder effects on transport near AFM quantum phase transitions,"We discuss three different scenarios recently proposed to account for the
non-Fermi liquid behavior near antiferromagnetic (AFM) quantum critical points
in heavy-Fermion systems: (i) scattering of Fermi liquid quasiparticles by
strong spin fluctuations near the spin-density-wave instability, (ii) the
breakdown of the Kondo effect due to the competition with the RKKY interaction,
and (iii) the formation of magnetic regions due to rare configurations of the
disorder. Here we focus on the first scenario and show that it explains in some
detail the anomalous temperature dependence of the resistivity observed e.g. in
CePd_2Si_2, CeNi_2Ge_2 or CeIn_3. The interplay of strongly anisotropic
scattering due to critical spin-fluctuations and weak isotropic impurity
scattering leads to a regime with a resistivity rho = rho_0 +Delta rho(T),
Delta rho(T) =T^{3/2} f(T/rho_0) \propto T sqrt{rho_0} for sufficiently large T
and small rho_0.",9908245v1
1999-09-01,Excitation spectra of the two dimensional Kondo insulator,"We present a Quantum Monte Carlo study of the temperature dependent dynamics
of the two-dimensional Kondo insulator. Working at the so-called symmetrical
point allows to perform minus-sign free QMC simulations. Study of the
temperature dependence of the single-particle Green's function and the
dynamical spin correlation function provides evidence for two characteristic
temperatures, which we associate with the Kondo and coherence temperature,
whereby the system shows a metal-insulator transition at the coherence
temperature. The data shows evidence for two distinct types of spin excitations
and we show that despite strong antiferromagnetic ordering at low temperature
the system cannot be described by spin-density-wave theory.",9909008v1
1999-11-30,Enhancement of Pairing Correlation and Spin Gap through Suppression of Single-Particle Dispersion in One-Dimensional Models,"We investigate the effects of suppression of single-particle dispersion near
the Fermi level on the spin gap and the singlet-pairing correlation by using
the exact diagonalization method for finite-size systems. We consider strongly
correlated one-dimensional models, which have flat band dispersions near wave
number k=\pi/2, if the interactions are switched off. Our results for strongly
correlated models show that the spin gap region expands as the single-particle
dispersion becomes flatter. The region where the singlet-pairing correlation is
the most dominant also expands in models with flatter band dispersions. Based
on our numerical results, we propose a pairing mechanism induced by the
flat-band dispersion.",9911484v1
1999-12-13,Simulated nuclear spin-lattice relaxation in Heisenberg ferrimagnets: Indirect observation of quadratic dispersion relations,"In response to recent proton spin relaxation-time measurements on
NiCu(pba)(H$_2$O)$_3$$\cdot$2H$_2$O with ${pba}=1,3{-propylenebis(oxamato)}$,
which is an excellent one-dimensional ferrimagnetic Heisenberg model system of
spin-$(1,{1/2})$, we study the Raman relaxation process in spin-$(S,s)$ quantum
ferrimagnets on the assumption of predominantly dipolar hyperfine interactions
between protons and magnetic ions. The relaxation time $T_1$ is formulated
within the spin-wave theory and is estimated as a function of temperature and
an applied field $H$ by a quantum Monte Carlo method. The low-temperature
behavior of the relaxation rate $T_1^{-1}$ qualitatively varies with $(S,s)$,
while $T_1^{-1}$ is almost proportional to $H^{-1/2}$ due to the characteristic
dispersion relations.",9912211v1
1999-12-20,"Electron spectrum, thermodynamics and transport in antiferromagnetic metals at low temperatures","Electron spectrum of 2D and 3D antiferromagnetic metals is calculated with
account of spin-fluctuation corrections within perturbation theory in the s-f
exchange model. Effects of the interaction of conduction electrons with spin
waves in thermodynamic and transport properties are investigated. At lowest
temperatures $T<T^{*}\sim (\Delta /E_F)T_N$ ($\Delta $ is the AFM splitting of
the electron spectrum) a Fermi-liquid behavior takes place, and non-analytic
T^3lnT-contributions to specific heat are present for D=3. At the same time,
for T>T^{*}, in 2D and ``nested'' 3D systems the picture corresponds to a
marginal Fermi liquid (TlnT-contributions to specific heat and nearly T-linear
dependence of resistivity). Frustrations in the spin system in the 3D case are
demonstrated to lead to similar results. The Kondo contributions to electronic
properties are analyzed and demonstrated to be strongly suppressed. The
incoherent contributions to transport properties in the presence of impurity
scattering are considered. In particular, in the 2D case T-linear terms in
resistivity are present up to T=0, and thermoelectric power demonstrates the
anomalous T\lnT-dependence.",9912354v1
2000-06-06,The Spin Excitation Spectrum in Superconducting ${\bf YBa_2Cu_3O_{6.85}}$,"A comprehensive inelastic neutron scattering study of magnetic excitations in
the near-optimally doped high-temperature superconductor ${\rm
YBa_{2}Cu_{3}O_{6.85}}$ is presented. The spin correlations in the normal state
are commensurate with the crystal lattice, and the intensity is peaked around
the wave vector characterizing the antiferromagnetic state of the insulating
precursor ${\rm YBa_{2}Cu_{3}O_{6}}$. Profound modifications of the spin
excitation spectrum appear abruptly below the superconducting transition
temperature, $\rm T_C$, where a commensurate resonant mode and a set of weaker
incommensurate peaks develop. The data are consistent with models based on an
underlying two-dimensional Fermi surface that predict a continuous, downward
dispersion relation connecting the resonant mode and the incommensurate
excitations. The magnetic incommensurability in the ${\rm
YBa_{2}Cu_{3}O_{6+x}}$ system is thus not simply related to that of another
high temperature superconductor, ${\rm La_{2-x}Sr_xCuO_{4}}$, where
incommensurate peaks persist well above $\rm T_C$. The temperature dependent
incommensurability is difficult to reconcile with interpretations based on
charge stripe formation in ${\rm YBa_{2}Cu_{3}O_{6+x}}$ near optimum doping.",0006086v1
2000-06-17,Quantum to classical crossover in the 2D easy-plane XXZ model,"Ground-state and thermodynamical properties of the spin-1/2 two-dimensional
easy-plane XXZ model are investigated by both a Green's-function approach and
by Lanczos diagonalizations on lattices with up to 36 sites. We calculate the
spatial and temperature dependences of various spin correlation functions, as
well as the wave-vector dependence of the spin susceptibility for all
anisotropy parameters $\Delta$. In the easy--plane ferromagnetic region $(-1<
\Delta < 0)$, the longitudinal correlators of spins at distance $r$ change sign
at a finite temperature $T_0(\Delta, {\bf r})$. This transition, observed in
the 2D case for the first time, can be interpreted as a quantum to classical
crossover.",0006272v1
2000-10-19,One-loop approximation for the Heisenberg antiferromagnet,"We use the diagram technique for spin operators to calculate Green's
functions and observables of the spin-1/2 quantum Heisenberg antiferromagnet on
a square lattice. The first corrections to the self-energy and interaction are
taken into account in the chain diagrams. The approximation reproduces main
results of Takahashi's modified spin-wave theory [Phys. Rev. B 40, 2494 (1989)]
and is applicable in a wider temperature range. The energy per spin calculated
in this approximation is in good agreement with the Monte Carlo and
small-cluster exact-diagonalization calculations in the range 0 <= T < 1.2J
where J is the exchange constant. For the static uniform susceptibility the
agreement is good for T < 0.6J and becomes somewhat worse for higher
temperatures. Nevertheless the approximation is able to reproduce the maximum
in the temperature dependence of the susceptibility near T = 0.9J.",0010275v1
2000-11-27,Hysteresis effect in ν=1 quantum Hall system under periodic electrostatic modulation,"The effect of a one-dimensional periodic electrostatic modulation on quantum
Hall systems with filling factor \nu=1 is studied. We propose that, either when
the amplitude of the modulation potential or the tilt angle of the magnetic
field is varied, the system can undergo a first-order phase transition from a
fully spin-polarized homogeneous state to a partially spin-polarized
charge-density-wave state, and show hysteresis behavior of the spin
polarization. This is confirmed by our self-consistent numerical calculations
within the Hartree-Fock approximation. Finally we suggest that the \nu=1/3
fractional quantum Hall state may also show similar hysteresis behavior in the
presence of a periodic potential modulation.",0011441v1
2000-12-12,Low Energy Properties of Ferrimagnetic 2-leg Ladders: a Lanczos study,"We apply the Lanczos method to a 2-leg ladder with mixed spins of magnitudes
$(S_1,S_2)=(1,1/2)$ located at alternating positions along the ladder. The
effect of dimerization $\gamma$ is also considered according to two different
patterns. A Spin Wave Theory (SWT) is applied to this model predicting one
gapless branch with ferromagnetic properties and another gapful branch with
antiferromagnetic nature as low energy excitations of the model. We compute the
ground state energies, Ferro- and AF-excitation gaps, magnetizations and
correlation functions as a function of $J'$ and $\gamma$ which results into a
fine estimate of the phase diagram. The Lanczos results are compared with the
SWT analysis and a qualitative agreement is found but with numerical
discrepancies. We also study numerically the Spin-Peierls instability and find
that it is conditional for any value of $ J' \in (0, 2)$ and both dimerization
patterns.",0012209v1
2000-12-15,Alternating-Spin Ladders in a Magnetic Field: New Magnetization Plateaux,"We study numerically the formation of magnetization plateaux with the Lanczos
method in 2-leg ladders with mixed spins of magnitudes $(S_1,S_2)=(1,1/2)$
located at alternating positions along the ladder and with dimerization
$\gamma$. For interchain coupling $J'>0$ and $\gamma=0$, we find normalized
plateaux at $m=1/3$ starting at zero field and $m=1$ (saturation), while when
$\gamma \ne 0$ is columnar, another extra plateau at $m=2/3$ shows up. For
$J'<0$, when $\gamma<\gamma_c(J')$ we find no plateau while for
$\gamma>\gamma_c(J')$ we find four plateaux at $m=0,1/3,2/3,1$. We also apply
several approximate analytical methods (Spin Wave Theory, Low-Energy Effective
Hamiltonians and Bosonization) to understand these findings and to conjeture
the behaviour of ferrimagnetic ladders with a bigger number of legs.",0012278v1
2001-02-05,Electronic theory for superconductivity in Sr$_2$RuO$_4$: triplet pairing due to spin-fluctuation exchange,"Using a two-dimensional Hubbard Hamiltonian for the three electronic bands
crossing the Fermi level in Sr$_2$RuO$_4$ we calculate the band structure and
spin susceptibility $\chi({\bf q}, \omega)$ in quantitative agreement with
nuclear magnetic resonance (NMR) and inelastic neutron scattering (INS)
experiments. The susceptibility has two peaks at {\bf Q}$_i = (2\pi/3, 2\pi/3)$
due to the nesting Fermi surface properties and at {\bf q}$_i = (0.6\pi, 0)$
due to the tendency towards ferromagnetism. Applying spin-fluctuation exchange
theory as in layered cuprates we determine from $\chi({\bf q}, \omega)$,
electronic dispersions, and Fermi surface topology that superconductivity in
Sr$_2$RuO$_4$ consists of triplet pairing. Combining the Fermi surface topology
and the results for $\chi({\bf q}, \omega)$ we can exclude $s-$ and $d-$wave
symmetry for the superconducting order parameter. Furthermore, within our
analysis and approximations we find that $f$-wave symmetry is slightly favored
over p-wave symmetry due to the nesting properties of the Fermi surface.",0102074v3
2001-02-22,"Spin fluctuations in a magnetically frustrated metal, LiV2O4","Inelastic neutron scattering is used to characterize spin fluctuations in the
$d$-electron heavy fermion spinel $\rm LiV_2O_4$. The spin relaxation rate,
$\Gamma_Q$, for $Q=0.6$ \AA$^{-1}$ is 1.5(1) meV at low temperatures and
increases linearly with temperature at a rate of 0.41(4) k$_B$. There is
antiferromagnetic short range order at low temperatures with a characteristic
wave vector $Q_c= 0.64(2)$ \AA$^{-1}$ and a correlation length of 6(1) \AA .
Warming shifts intensity towards lower $Q$ so that magnetic scattering
decreases monotonically with $Q>0.3$ \AA$^{-1}$ for $T>40$ K. The data are
compared with conventional heavy fermion systems, geometrically frustrated
insulating magnets, and recent theories for $\rm LiV_2O_4$.",0102414v2
2001-06-26,Localized f electrons in CexLa1-xRhIn5: dHvA Measurements,"Measurements of the de Haas-van Alphen effect in CexLa1-xRhIn5 reveal that
the Ce 4f electrons remain localized for all x, with the mass enhancement and
progressive loss of one spin from the de Haas-van Alphen signal resulting from
spin fluctuation effects. This behavior may be typical of antiferromagnetic
heavy fermion compounds, inspite of the fact that the 4f electron localization
in CeRhIn5 is driven, in part, by a spin-density wave instability.",0106522v1
2001-07-13,Relation between flux formation and pairing in doped antiferromagnets,"We demonstrate that patterns formed by the current-current correlation
function are landmarks which indicate that spin bipolarons form in doped
antiferromagnets. Holes which constitute a spin bipolaron reside at opposite
ends of a line (string) formed by the defects in the antiferromagnetic spin
background. The string is relatively highly mobile, because the motion of a
hole at its end does not raise extensively the number of defects, provided that
the hole at the other end of the line follows along the same track. Appropriate
coherent combinations of string states realize some irreducible representations
of the point group C_4v. Creep of strings favors d- and p-wave states. Some
more subtle processes decide the symmetry of pairing. The pattern of the
current correlation function, that defines the structure of flux, emerges from
motion of holes at string ends and coherence factors with which string states
appear in the wave function of the bound state. Condensation of bipolarons and
phase coherence between them puts to infinity the correlation length of the
current correlation function and establishes the flux in the system.",0107287v1
2001-10-22,Competition between spin exchange and correlated hopping,"The ground-state phase diagram is numerically studied for an electronic model
consisting of the spin exchange term (J) and the correlated hopping term (t_3:
the three-site term). This model has no single-particle hopping and the ratio
of the two terms is controlled by a parameter \alpha \equiv 4 t_3 / J. The case
of \alpha=1 corresponds to complete suppression of single-particle hopping in
the strong-coupling limit of the Hubbard model. In one dimension, phase
separation takes place below a critical value \alpha_c = 0.36-0.63 which
depends on the electron density. Spin gap opens in the whole region except the
phase-separated one. For \alpha \gsim 1.2 and low hole densities,
charge-density-wave correlations are the most dominant, whereas singlet-pairing
correlations are the most dominant in the remaining region. The possibility of
superconductivity in the two-dimensional case is also discussed, based on
equal-time pairing correlations.",0110458v2
2001-12-11,Evolution of spin excitations in a gapped antiferromagnet from the quantum to the high-temperature limit,"We have mapped from the quantum to the classical limit the spin excitation
spectrum of the antiferromagnetic spin-1 Heisenberg chain system CsNiCl3 in its
paramagnetic phase from T=5 to 200K. Neutron scattering shows that the
excitations are resonant and dispersive up to at least T=70K, but broaden
considerably with increasing temperature. The dispersion flattens out with
increasing temperature as the resonance energy Delta at the antiferromagnetic
wave-vector increases and the maximum in the dispersion decreases. The
correlation length xi between T=12 and 50K is in agreement with quantum Monte
Carlo calculations. xi is also consistent with the single mode approximation,
suggesting that the excitations are short-lived single particle excitations.
Below T=12K where three-dimensional spin correlations are important, xi is
shorter than predicted and the experiment is not consistent with the random
phase approximation for coupled quantum chains. At T=200K, the structure factor
and second energy moment of the excitation spectrum are in excellent agreement
with the high-temperature series expansion.",0112188v1
2001-12-24,Paramagnetic and antiferromagnetic resonances in the diamagnetically diluted Haldane magnet PbNi2V2O8,"The impurity-induced antiferromagnetic ordering of the doped Haldane magnet
Pb(Ni{1-x}Mg{x})2V2O8 (0 < x <0.06) was studied by electron spin resonance
(ESR) on ceramic samples in the frequency range 9-110 GHz. Below the N\'{e}el
temperature a transformation of the ESR spectrum was found, indicating an
antiferromagnetic resonance mode of spin precession. The excitation gap of the
spin-wave spectrum increases with increasing Mg-concentration $x$ in the same
manner as the N\'{e}el temperature, reaching its maximum value of 80 GHz at x >
0.04. At small concentrations x < 0.02 the signals of antiferromagnetic
resonance were found to coexist with the signal of the paramagnetic resonance
indicating a microscopic separation of the magnetic phases.",0112443v1
2002-01-19,A Four-Unit-Cell Periodic Pattern of Quasiparticle States Surrounding Vortex Cores in Bi2Sr2CaCu2O8+d,"Scanning tunneling microscopy is used to image the additional quasiparticle
states generated by quantized vortices in the high-Tc superconductor
Bi2Sr2CaCu2O8+d. They exhibit a Cu-O bond oriented 'checkerboard' pattern, with
four unit cell (4a0) periodicity and a ~30 angstrom decay length. These
electronic modulations may be related to the magnetic field-induced, 8a0
periodic, spin density modulations of decay length ~70 angstroms recently
discovered in La1.84Sr0.16CuO4. The proposed explanation is a spin density wave
localized surrounding each vortex core. General theoretical principles predict
that, in the cuprates, a localized spin modulation of wavelength L should be
associated with a corresponding electronic modulation of wavelength L/2, in
good agreement with our observations.",0201348v1
2002-07-02,Weak-Coupling Instabilities of Two-Dimensional Lattice Electrons,"In this thesis, I study a two-dimensional extended Hubbard model in the weak
coupling limit. Quite generally, the electron gas is unstable towards a
superconducting state even in the absence of phonons. However in the special
case of a half-filled band, the Fermi surface is nested and the system is at a
Van Hove singularity. In this situation, there are six competing instabilities:
$s$- and d-wave superconductivity, spin-and charge-density waves and two phases
with circulating charge and spin currents, respectively. The required
renormalization group formalism is presented on a most elementary level,
connecting the idea of the ``parquet summation'' to the more modern concept of
Wilson's effective action. As a result, a rich phase diagram is obtained as a
function of the model interaction. This phase diagram is exact in the weak
coupling limit, since the transition line between two neighboring phases is
then fixed by symmetries. The physical picture of each instability is completed
by studying the low temperature behavior of the spin susceptibility and the
charge compressibility. We also observe a general trend towards a Fermi surface
distortion, but the nesting is not destroyed.",0207067v1
2002-09-12,High field magnetic resonant properties of beta'-(ET)2SF5CF2SO3,"A systematic electron spin resonance (ESR) investigation of the low
temperature regime for the (ET)2SF5CF2SO3 system was performed in the frequency
range of ~200-700 GHz, using backward wave oscillator sources, and at fields up
to 25 T. Newly acquired access to the high frequency and fields shows
experimental ESR results in agreement with the nuclear magnetic resonance (NMR)
investigation, revealing evidence that the transition seen at 20 K is not of
conventional spin-Peierls order. A significant change of the spin resonance
spectrum in beta'-(ET)2SF5CF2SO3 at low temperatures, indicates a transition
into a three-dimensional-antiferromagnetic (3D AFM) phase.",0209295v4
2002-10-07,Pair distribution function in a two-dimensional electron gas,"We calculate the pair distribution function, $g(r)$, in a two-dimensional
electron gas and derive a simple analytical expression for its value at the
origin as a function of $r_s$. Our approach is based on solving the
Schr\""{o}dinger equation for the two-electron wave function in an appropriate
effective potential, leading to results that are in good agreement with Quantum
Monte Carlo data and with the most recent numerical calculations of $g(0)$. [C.
Bulutay and B. Tanatar, Phys. Rev. B {\bf 65}, 195116 (2002)] We also show that
the spin-up spin-down correlation function at the origin, $g_{\uparrow
\downarrow}(0)$, is mainly independent of the degree of spin polarization of
the electronic system.",0210137v2
2003-01-08,Ground-state phases in a system of two competing square-lattice Heisenberg antiferromagnets,"We study a two-dimensional (2D) spin-half Heisenberg model related to the
quasi 2D antiferromagnets (Ba,Sr)2Cu3O4Cl2 by means of exact diagonalization
and spin-wave theory. The model consists of two inequivalent interpenetrating
square-lattice Heisenberg antiferromagnets A and B. While the antiferromagnetic
interaction JAA within the A subsystem is strong the coupling JBB within the B
subsystem is much weaker. The coupling JAB between A and B subsystems is
competing giving rise for interesting frustration effects. In dependence of the
strength of JAB we find a collinear Neel phase, non-collinear states with zero
magnetizations as well as canted and collinear ferrimagnetic phases with
non-zero magnetizations. For not too large values of frustration JAB, which
correpond to the situation in (Ba,Sr)2Cu3O4Cl2, we have Neel ordering in both
subsystems A and B. In the classical limit these two Neel states are decoupled.
Quantum fluctuations lead to a fluctuational coupling between both subsystems
('order from disorder') and select the collinear structure. For stronger JAB we
find evidence for a novel spin state with coexisting Neel ordering in the A
subsystem and disorder in the B subsystem.",0301095v1
2003-05-31,Local Manipulation of Nuclear Spin in a Semiconductor Quantum Well,"The shaping of nuclear spin polarization profiles and the induction of
nuclear resonances are demonstrated within a parabolic quantum well using an
externally applied gate voltage. Voltage control of the electron and hole wave
functions results in nanometer-scale sheets of polarized nuclei positioned
along the growth direction of the well. RF voltages across the gates induce
resonant spin transitions of selected isotopes. This depolarizing effect
depends strongly on the separation of electrons and holes, suggesting that a
highly localized mechanism accounts for the observed behavior.",0306012v2
2003-06-26,Nuclear spin-lattice relaxation in ferrimagnetic clusters and chains: A contrast between zero and one dimensions,"Motivated by ferrimagnetic oligonuclear and chain compounds synthesized by
Caneschi et al., both of which consist of alternating manganese(II) ions and
nitronyl-nitroxide radicals, we calculate the nuclear spin-lattice relaxation
rate 1/T_1 employing a recently developed modified spin-wave theory. 1/T_1 as a
function of temperature drastically varies with the location of probe nuclei in
both clusters and chains, though the relaxation time scale is much larger in
zero dimension than in one dimension. 1/T_1 as a function of an applied field
in long chains forms a striking contrast to that in finite clusters, diverging
with decreasing field like inverse square root at low temperatures and
logarithmically at high temperatures.",0306685v1
2003-07-03,Field-tuned Collapse of an Orbital Ordered and Spin-polarized State: Colossal Magnetoresistance in Bilayered Ruthenate,"Ca3Ru2O7 with a Mott-like transition at 48 K features different in-plane
anisotropies of magnetization and magnetoresistance. Applying magnetic field
along the magnetic easy-axis precipitates a spin-polarized state via a
first-order metamagnetic transition, but does not lead to a full suppression of
the Mott state, whereas applying magnetic field along the magnetic hard axis
does, causing a resistivity reduction of three orders of magnitude. The
colossal magnetoresistivity is attributed to the collapse of the orbital
ordered and spin-polarized state. Evidence for a density wave is also
presented.",0307068v1
2003-07-14,Spin Fluctuations and Non-Fermi-Liquid Behavior of CeNi_2Ge_2,"Neutron scattering shows that non-Fermi-liquid behavior of the heavy-fermion
compound CeNi_2Ge_2 is brought about by the development of low-energy spin
fluctuations with an energy scale of 0.6 meV. They appear around the
antiferromagnetic wave vectors $({1/2} {1/2} 0)$ and $(0 0 {3/4})$ at low
temperatures, and coexist with high-energy spin fluctuations with an energy
scale of 4 meV and a modulation vector $(0.23, 0.23, {1/2})$. This unusual
energy dependent structure of $\text{Im} \chi (\bm{Q}, E)$ in $\bm{Q}$ space
suggests that quasiparticle bands are important.",0307314v2
2003-09-30,Orbital ordering in transition-metal compounds: I. The 120-degree model,"We study the classical version of the 120-degree model. This is an attractive
nearest-neighbor system in three dimensions with XY (rotor) spins and
interaction such that only a particular projection of the spins gets coupled in
each coordinate direction. Although the Hamiltonian has only discrete
symmetries, it turns out that every constant field is a ground state. Employing
a combination of spin-wave and contour arguments we establish the existence of
long-range order at low temperatures. This suggests a mechanism for a type of
ordering in certain models of transition-metal compounds where the very
existence of long-range order has heretofore been a matter of some controversy.",0309691v3
2003-09-30,Effect of Hund coupling in the one-dimensional SU(4) Hubbard model,"The one-dimensional SU(4) Hubbard model perturbed by Hund coupling is
studied, away from half-filling, by means of renormalization group and
bosonization methods. A spectral gap is always present in the spin-orbital
sector irrespective of the magnitude of the Coulomb repulsion. We further
distinguish between two qualitatively different regimes. At small Hund
coupling, we find that the symmetry of the system is dynamically enlarged to
SU(4) at low energy with the result of {\it coherent} spin-orbital excitations.
When the charge sector is not gapped, a superconducting instability is shown to
exist. At large Hund coupling, the symmetry is no longer enlarged to SU(4) and
the excitations in the spin sector become {\it incoherent}. Furthermore, the
superconductivity can be suppressed in favor of the conventional charge density
wave state.",0310003v1
2003-10-15,Ballistic conductance of Ni nanowire with a magnetization reversal,"The approach proposed by Choi and Ihm for calculating the ballistic
conductance of open quantum systems is generalized to deal with magnetic
transition metals. The method has been implemented with ultrasoft
pseudopotentials and plane wave basis set in a DFT-LSDA ab-initio scheme. We
present the quantum-mechanical conductance calculations for monatomic Ni
nanowire with a single spin reversal. We find that a spin reversal blocks the
conductance of $d$ electrons at the Fermi energy of the Ni nanowire. On the
other hand, two $s$ electrons (one per each spin) are perfectly transmitted in
the whole energy window giving $2G_0$ for the total conductance. The relevance
of these results in connection with recent experimental data is discussed.",0310335v1
2004-01-01,Extended moment formation and magnetic ordering in the trigonal chain compound Ca3Co2O6,"The results of electronic structure calculations for the one-dimensional
magnetic chain compound Ca3Co2O6 are presented. The calculations are based on
density functional theory and the local density approximation and used the
augmented spherical wave (ASW) method. Our results allow for deeper
understanding of recent experimental findings. In particular, alternation of Co
3d low- and high-spin states along the characteristic chains is related to
differences in the oxygen coordination at the inequivalent cobalt sites. Strong
hybridization of the d states with the O 2p states lays ground for polarization
of the latter and the formation of extended localized magnetic moments centered
at the high-spin sites. In contrast, strong metal-metal overlap along the
chains gives rise to intrachain ferromagnetic exchange coupling of the extended
moments via the d_{3z^2-r^2} orbitals of the low-spin cobalt atoms.",0401004v1
2004-01-23,Nonmonotonic inelastic tunneling spectra due to surface spin excitations in ferromagnetic junctions,"The paper addresses inelastic spin-flip tunneling accompanied by surface spin
excitations (magnons) in ferromagnetic junctions. The inelastic tunneling
current is proportional to the magnon density of states which is
energy-independent for the surface waves and, for this reason, cannot account
for the bias-voltage dependence of the observed inelastic tunneling spectra.
This paper shows that the bias-voltage dependence of the tunneling spectra can
arise from the tunneling matrix elements of the electron-magnon interaction.
These matrix elements are derived from the Coulomb exchange interaction using
the itinerant-electron model of magnon-assisted tunneling. The results for the
inelastic tunneling spectra, based on the nonequilibrium Green's function
calculations, are presented for both parallel and antiparallel magnetizations
in the ferromagnetic leads.",0401460v6
2004-02-03,Excitations and Quantum Fluctuations in Site Diluted Two-Dimensional Antiferromagnets,"We study the effect of site dilution and quantum fluctuations in an
antiferromagnetic spin system on a square lattice within the linear spin-wave
approximation. By performing numerical diagonalization in real space and
finite-size scaling, we characterize the nature of the low-energy spin
excitations for different dilution fractions up to the classical percolation
threshold. We find nontrivial signatures of fractonlike excitations at high
frequencies. Our simulations also confirm the existence of an upper bound for
the amount of quantum fluctuations in the ground state of the system, leading
to the persistence of long-range order up to the percolation threshold. This
result is in agreement with recent neutron-scattering experimental data and
quantum Monte Carlo numerical calculations. We also show that the absence of a
quantum critical point below the classical percolation threshold holds for a
large class of systems whose Hamiltonians can be mapped onto a system of
coupled noninteracting massless bosons.",0402102v2
2004-02-04,Magnetoresistance Effect in Spin-Polarized Junctions of Ferromagnetically Contacting Multiple Conductive Paths: Applications to Atomic Wires and Carbon Nanotubes,"For spin-polarized junctions of ferromagnetically contacting multiple
conductive paths, such as ferromagnet (FM)/atomic wires/FM and FM/carbon
nanotubes/FM junctions, we theoretically investigate spin-dependent transport
to elucidate the intrinsic relation between the number of paths and conduction,
and to enhance the magnetoresistance (MR) ratio. When many paths are randomly
located between the two FMs, electronic wave interference between the FMs
appears, and then the MR ratio increases with increasing number of paths.
Furthermore, at each number of paths, the MR ratio for carbon nanotubes becomes
larger than that for atomic wires, reflecting the characteristic shape of
points in contact with the FM.",0402119v1
2004-03-15,Excitation hierarchy of the quantum sine-Gordon spin chain in strong magnetic field,"The magnetic excitation spectrum of copper pyrimidine dinitrate, a material
containing S=1/2 antiferromagnetic chains with alternating g-tensor and the
Dzyaloshinskii-Moriya interaction, and exhibiting a field-induced spin gap, is
probed using submillimeter wave electron spin resonance spectroscopy. Ten
excitation modes are resolved in the low-temperature spectrum, and their
frequency-field diagram is systematically studied in magnetic fields up to 25
T. The experimental data are sufficiently detailed to make a very accurate
comparison with predictions based on the quantum sine-Gordon field theory.
Signatures of three breather branches and a soliton, as well as those of
several multi-particle excitation modes are identified.",0403364v1
2004-06-04,Absence of magnetic order for the spin-half Heisenberg antiferromagnet on the star lattice,"We study the ground-state properties of the spin-half Heisenberg
antiferromagnet on the two-dimensional star lattice by spin-wave theory, exact
diagonalization and a variational mean-field approach. We find evidence that
the star lattice is (besides the \kagome lattice) a second candidate among the
11 uniform Archimedean lattices where quantum fluctuations in combination with
frustration lead to a quantum paramagnetic ground state. Although the classical
ground state of the Heisenberg antiferromagnet on the star exhibits a huge
non-trivial degeneracy like on the \kagome lattice, its quantum ground state is
most likely dimerized with a gap to all excitations. Finally, we find several
candidates for plateaux in the magnetization curve as well as a macroscopic
magnetization jump to saturation due to independent localized magnon states.",0406103v2
2004-07-08,Bipolar High Field Excitations in Co/Cu/Co Nanopillars,"Current-induced magnetic excitations in Co/Cu/Co bilayer nanopillars
($\sim$50 nm in diameter) have been studied experimentally at low temperatures
for large applied fields perpendicular to the layers. At sufficiently high
current densities excitations, which lead to a decrease in differential
resistance, are observed for both current polarities. Such bipolar excitations
are not expected in a single domain model of spin-transfer. We propose that at
high current densities strong asymmetries in the longitudinal spin accumulation
cause spin-wave instabilities transverse to the current direction in bilayer
samples, similar to those we have reported for single magnetic layer junctions.",0407210v1
2004-09-05,Stochastic series expansion algorithm for the S=1/2 XY model with four-site ring exchange,"We describe a stochastic series expansion (SSE) quantum Monte Carlo method
for a two-dimensional S=1/2 XY-model (or, equivalently, hard-core bosons at
half-filling) which in addition to the standard pair interaction J includes a
four-particle term K that flips spins on a square plaquette. The model has
three ordered ground state phases; for K/J<8 it has long-range xy spin order
(superfluid bosons), for K/J>15 it has staggered spin order in the z direction
(charge-density-wave), and between these phases it is in a state with columnar
order in the bond and plaquette energy densities. We discuss an implementation
of directed-loop updates for the SSE simulations of this model and also
introduce a ""multi-branch"" cluster update which significantly reduces the
autocorrelation times for large K/J. In addition to the pure J-K model, which
in the z basis has only off-diagonal terms, we also discuss modifications of
the algorithm needed when various diagonal interactions are included.",0409112v1
2004-09-15,The t-J model: From light to heavy doping,"The regions of hole concentrations $0 \leq x \alt 0.3$ and temperatures
$0.005|t| \leq T \leq 0.02|t|$ are studied in the t-J model of Cu-O planes of
perovskite high-$T_c$ superconductors. For this purpose self-energy equations
for hole and spin Green's functions are derived using Mori's projection
operator technique and these equations are self-consistently solved. The
calculated hole band transforms radically at $x\approx 0.08$. A narrow
low-concentration band with minima near $(\pm\frac{\pi}{2},\pm\frac{\pi}{2})$
is converted to a band resembling the case of weak electron correlations, with
the minimum at $(\pi,\pi)$ or $(0,0)$. The hole Fermi surface is respectively
changed from small ellipses at $(\pm\frac{\pi}{2},\pm\frac{\pi}{2})$ to a large
rhombus centered at $(\pi,\pi)$ or $(0,0)$. The decrease of the magnetic
susceptibility at the antiferromagnetic wave vector and spin correlations with
doping is determined by the growth of the frequency of spin excitations at this
momentum. The shape of the frequency dependence of the susceptibility depends
heavily on the hole damping and varies from a broad feature similar to that
observed in La$_{2-x}$Sr$_x$CuO$_4$ to a pronounced maximum which resembles the
normal-state resonance peak in YBa$_2$Cu$_3$O$_{7-y}$.",0409379v1
2004-11-04,Spin dynamics in the antiferromagnetic phase for electron-doped cuprate superconductors,"Based on the $t$-$t'$-$t''$-$J$ model we have calculated the dynamical spin
susceptibilities in the antiferromagnetic (AF) phase for electron-doped
cuprates, by use of the slave-boson mean-field theory and random phase
approximation. Various results for the susceptibilities versus energy and
momentum have been shown at different dopings. At low energy, except the
collective spin-wave mode around $(\pi,\pi)$ and 0, we have primarily observed
that new resonance peaks will appear around $(0.3\pi,0.7\pi)$ and equivalent
points with increasing doping, which are due to the particle-hole excitations
between the two AF bands. The peaks are pronounced in the transverse
susceptibility but not in the longitudinal one. These features are predicted
for neutron scattering measurements.",0411117v2
2004-12-08,Spin-zero anomaly in the magnetic quantum oscillations of a two-dimensional metal,"We report on an anomalous behavior of the spin-splitting zeros in the de
Haas-van Alphen (dHvA) signal of a quasi-two-dimensional organic
superconductor. The zeros as well as the angular dependence of the amplitude of
the second harmonic deviate remarkably from the standard Lifshitz-Kosevich (LK)
prediction. In contrast, the angular dependence of the fundamental dHvA
amplitude as well as the spin-splitting zeros of the Shubnikov-de Haas signal
follow the LK theory. We can explain this behavior by small chemical-potential
oscillations and find a very good agreement between theory and experiment. A
detailed wave-shape analysis of the dHvA signal corroborates the existence of
an oscillating chemical potential.",0412202v1
2005-01-31,Magnetic Order and Spin Dynamics in Ferroelectric HoMnO$_{3}$,"Hexagonal HoMnO$_{3}$ is a frustrated antiferromagnet (T$_{N}$=72 K)
ferroelectric (T$_{C}$=875 K) in which these two order parameters are coupled.
Our neutron measurements of the spin wave dispersion for the S=2 Mn$^{3+}$ on
the layered triangular lattice are well described by a two-dimensional
nearest-neighbor Heisenberg exchange J=2.44 meV, and an anisotropy $D$ that is
0.093 meV above the spin reorientation transition at 40 K, and 0.126 meV below.
For $H\parallel c$ the magnetic structures and phase diagram have been
determined, and reveal additional transitions below 8 K where the
ferroelectrically displaced Ho$^{3+}$ ions are ordered magnetically.",0502006v1
2005-03-07,Evidence for short-range antiferromagnetic fluctuations in Kondo-insulating YbB12,"The spin dynamics of mixed-valence YbB12 has been studied by inelastic
neutron scattering on a high-quality single crystal. In the Kondo-insulating
regime realized at low temperature, the spectra exhibit a spin-gap structure
with two sharp, dispersive, in-gap excitations at E = 14.5 and approximately 20
meV. The lower mode is shown to be associated with short-range correlations
near the antiferromagnetic wave vector q0 = (1/2, 1/2, 1/2). Its properties are
in overall agreement with those expected for a ""spin exciton'' branch in an
indirect hybridization gap semiconductor.",0503142v1
2005-05-24,Sum rules for four-spinon dynamic structure factor in XXX model,"In the context of the antiferromagnetic spin 1/2 Heisenberg quantum spin
chain (XXX model), we estimate the contribution of the exact four-spinon
dynamic structure factor $S_4$ by calculating a number of sum rules the total
dynamic structure factor $S$ is known to satisfy exactly. These sum rules are:
the static susceptibility, the integrated intensity, the total integrated
intensity, the first frequency moment and the nearest-neighbor correlation
function. We find that the contribution of $S_4$ is between 1% and 2.5%,
depending on the sum rule, whereas the contribution of the exact two-spinon
dynamic structure factor $S_2$ is between 70% and 75%. This is consistent with
the expected scattering weight of states from outside the spin-wave continuum.
The calculations are numerical and Monte Carlo based. Good statistics are
obtained.",0505594v1
2005-06-03,Magnetic excitations in weakly coupled spin dimers and chains material Cu2Fe2Ge4O13,"Magnetic excitations in a weakly coupled spin dimers and chains compound
Cu2Fe2Ge4O13 are measured by inelastic neutron scattering. Both structure
factors and dispersion of low energy excitations up to 10 meV energy transfer
are well described by a semiclassical spin wave theory involving interacting
Fe$^{3+}$ ($S = 5/2$) chains. Additional dispersionless excitations are
observed at higher energies, at $\hbar \omega = 24$ meV, and associated with
singlet-triplet transitions within Cu$^{2+}$-dimers. Both types of excitations
can be understood by treating weak interactions between the Cu$^{2+}$ and
Fe$^{3+}$ subsystems at the level of the Mean Field/ Random Phase
Approximation. However, this simple model fails to account for the measured
temperature dependence of the 24 meV mode.",0506070v1
2005-09-01,Spin-transfer-induced excitations in bilayer magnetic nanopillars at high fields: The effects of contact layers,"Current-induced excitations in bilayer magnetic nanopillars have been studied
with large magnetic fields applied perpendicular to the layers at low
temperature. Junctions investigated all have Cu/Co/Cu/Co/Cu as core layer
stacks. Two types of such junctions are compared, one with the core stack
sandwiched between Pt layers (type A), the other with Pt only on one side of
the stack (type B). Transport measurements show that these two types of
junctions have similar magnetoresistance and slope of critical current with
respect to field, while A samples have higher resistance. The high-field
bipolar excitation, as was previously reported [Oezyilmaz et al., Phys. Rev. B
71, 140403(R) (2005)], is present in B samples only. This illustrates the
importance of contact layers to spin-current-induced phenomena. This also
confirms a recent prediction on such spin-wave excitations in bilayers.",0509034v2
2005-09-14,Magnetic ordering in trigonal chain compounds,"We present electronic structure calculations for the one-dimensional magnetic
chain compounds Ca_3CoRhO_6 and Ca_3FeRhO_6. The calculations are based on
density functional theory and the local density approximation. We use the
augmented spherical wave (ASW) method. The observed alternation of low- and
high-spin states along the Co-Rh and Fe-Rh chains is related to differences in
the oxygen coordination of the transition metal sites. Due to strong
hybridization the O 2p states are polarized, giving rise to extended localized
magnetic moments centered at the high-spin sites. Strong metal-metal overlap
along the chains leads to a substantial contribution of the low-spin Rh
4d_{3z^2-r^2} orbitals to the exchange coupling of the extended moments.
Interestingly, this mechanism holds for both compounds, even though the
coupling is ferromagnetic for the cobalt and antiferromagnetic for the iron
compound. However, our results allow to understand the different types of
coupling from the filling dependence of the electronic properties.",0509374v1
2005-10-16,Spiral Spin Order and Transport Anisotropy in Underdoped Cuprates,"We discuss the spiral spin density wave model and its application to explain
properties of underdoped La$_{2-x}$Sr$_x$CuO$_4$. We argue that the spiral
picture is theoretically well justified in the context of the extended $t-J$
model, and then show that it can explain a number of observed features, such as
the location and symmetry of the incommensurate peaks in elastic neutron
scattering, as well as the in-plane resistivity anisotropy. A consistent
description of the low doping region (below 10% or so) emerges from the spiral
formulation, in which the holes show no tendency towards any type of charge
order and the physics is purely spin driven.",0510416v1
2005-11-18,Local spin spirals in the Neel phase of La_{2-x}Sr_xCuO_4,"Experimental observations of lightly doped La_{2-x}Sr_xCuO_4, x < 0.02,
revealed remarkable magnetic properties such as the incommensurate noncollinear
ordering (additional to the Neel ordering) and a tremendous doping dependence
of the uniform longitudinal susceptibility. We show that the spiral solution of
the t-t'-t''-J model obtained by taking into account the Coulomb trapping of
holes by Sr ions describes these puzzling data perfectly well. Our solution
firstly explains why the incommensurate structure is directed along the
orthorhombic b-axis, and secondly allows a numerical calculation of the
positions and shapes of the incommensurate neutron scattering peaks. Thirdly,
we calculate the doping dependence of the spin-wave gap, and lastly, we study
the longitudinal magnetic susceptibility and show that its doping dependence is
due to the noncollinearity of the spin spiral.",0511453v2
2005-12-14,Measurement of Magnetization Dynamics in Single-Molecule Magnets Induced by Pulsed Millimeter-Wave Radiation,"We describe an experiment aimed at measuring the spin dynamics of the Fe8
single-molecule magnet in the presence of pulsed microwave radiation. In
earlier work, heating was observed after a 0.2-ms pulse of intense radiation,
indicating that the spin system and the lattice were out of thermal equilibrium
at millisecond time scale [Bal et al., Europhys. Lett. 71, 110 (2005)]. In the
current work, an inductive pick-up loop is used to probe the photon-induced
magnetization dynamics between only two levels of the spin system at much
shorter time scales (from ns to us). The relaxation time for the magnetization,
induced by a pulse of radiation, is found to be on the order of 10 us.",0512289v1
2005-12-14,Static magnetic order in metallic K$_{0.49}$CoO$_{2}$,"By means of muon spin spectroscopy, we have found that K$_{0.49}$CoO$_2$
crystals undergo successive magnetic transitions from a high-T paramagnetic
state to a magnetic ordered state below 60 K and then to a second ordered state
below 16 K, even though K_{0.49}CoO_2 is metallic at least down to 4 K. An
isotropic magnetic behavior and wide internal-field distributions suggest the
formation of a commensurate helical spin density wave (SDW) state below 16 K,
while a linear SDW state is likely to exist above 16 K. It was also found that
K_{0.49}CoO_2 exhibits a further transition at 150 K presumably due to a change
in the spin state of the Co ions. Since the T dependence of the internal-field
below 60 K was similar to that for Na_{0.5}CoO_2, this suggests that magnetic
order is more strongly affected by the Co valence than by the interlayer
distance/interaction and/or the charge-ordering.",0512319v1
2005-12-16,Orbital Ordering and Spin-Ladder Formation in La2RuO5,"The semiconductor-semiconductor transition of La2RuO5 is studied by means of
augmented spherical wave (ASW) electronic structure calculations as based on
density functional theory and the local density approximation. This transition
has lately been reported to lead to orbital ordering and a quenching of the
local spin magnetic moment. Our results hint towards an orbital ordering
scenario which, markedly different from the previously proposed scheme,
preserves the local S = 1 moment at the Ru sites in the low-temperature phase.
The unusual magnetic behaviour is interpreted by the formation of spin-ladders,
which result from the structural changes occurring at the transition and are
characterized by antiferromagnetic coupling along the rungs.",0512409v1
2005-12-22,Low temperature structural phase transition and incommensurate lattice modulation in the spin gap compound BaCuSi2O6,"Results of high resolution x-ray diffraction experiments are presented for
single crystals of the spin gap compound BaCuSi$_2$O$_6$ in the temperature
range from 16 to 300 K. The data show clear evidence of a transition from the
room temperature tetragonal phase into an incommensurately modulated
orthorhombic structure below $\sim$100 K. This lattice modulation is
characterized by a resolution limited wave vector {\bf
q}$_{IC}$=(0,$\sim$0.13,0) and its 2$^{nd}$ and 3$^{rd}$ harmonics. The phase
transition is first order and exhibits considerable hysteresis. This
observation implies that the spin Hamiltonian representing the system is more
complex than originally thought.",0512560v1
2006-01-16,Fermi arc in doped high-Tc cuprates,"We propose a $d$-density wave induced by the spin-orbit coupling in the CuO
plane. The spectral function of high-temperature superconductors in the under
doped and lightly doped regions is calculated in order to explain the Fermi arc
spectra observed recently by angle-resolved photoemission spectroscopy. We take
into account the tilting of CuO octahedra as well as the on-site
Coulombrepulsive interaction; the tilted octahedra induce the staggered
transfer integral between $p_{x,y}$ orbitals and Cu $t_{2g}$ orbitals, and
bring about nontrivial effects of spin-orbit coupling for the $d$ electrons in
the CuO plane. The spectral weight shows a peak at around ($\pi/2$,$\pi/2$) for
light doping and extends around this point forming an arc as the carrier
density increases, where the spectra for light doping grow continuously to be
the spectra in the optimally doped region. This behavior significantly agrees
with that of the angle-resolved photoemissionspectroscopy spectra. Furthermore,
the spin-orbit term and staggered transfer effectively induce a flux state, a
pseudo-gap with time-reversal symmetry breaking. We have a nodal metallic state
in the light-doping case since the pseudogap has a $d_{x^2-y^2}$ symmetry.",0601329v1
2006-02-07,Possible evidence for electromagnons in multiferroic manganites,"Magnetodielectric materials are characterized by a strong coupling of
magnetic and dielectric properties and in rare cases simultaneously exhibit
both, magnetic and polar order. Among other multiferroics, TbMnO3 and GdMnO3
reveal a strong magneto-dielectric (ME) coupling and as a consequence
fundamentally new spin excitations exist: Electro-active magnons, or
electromagnons, i. e. spin waves which can be excited by ac electric fields.
Here we show that these excitations appear in the phase with an incommensurate
(IC) magnetic structure of the manganese spins. In external magnetic fields
this IC structure can be suppressed and the electromagnons are wiped out,
thereby inducing considerable changes in the index of refraction from dc up to
THz frequencies. Hence, besides adding a new creature to the zoo of fundamental
excitations, the refraction index can be tuned by moderate magnetic fields,
which allows the design of a new generation of optical switches and
optoelectronic devices.",0602173v1
2006-03-02,Anomalous dynamics in two- and three- dimensional Heisenberg-Mattis spin glasses,"We investigate the spectral and localization properties of unmagnetized
Heisenberg-Mattis spin glasses, in space dimensionalities $d=2$ and 3, at T=0.
We use numerical transfer-matrix methods combined with finite-size scaling to
calculate Lyapunov exponents, and eigenvalue-counting theorems, coupled with
Gaussian elimination algorithms, to evaluate densities of states. In $d=2$ we
find that all states are localized, with the localization length diverging as
$\omega^{-1}$, as energy $\omega \to 0$. Logarithmic corrections to density of
states behave in accordance with theoretical predictions. In $d=3$ the
density-of-states dependence on energy is the same as for spin waves in pure
antiferromagnets, again in agreement with theoretical predictions, though the
corresponding amplitudes differ.",0603043v1
2006-05-01,Variational ground states of 2D antiferromagnets in the valence bond basis,"We study a variational wave function for the ground state of the
two-dimensional S=1/2 Heisenberg antiferromagnet in the valence bond basis. The
expansion coefficients are products of amplitudes h(x,y) for valence bonds
connecting spins separated by (x,y) lattice spacings. In contrast to previous
studies, in which a functional form for h(x,y) was assumed, we here optimize
all the amplitudes for lattices with up to 32*32 spins. We use two different
schemes for optimizing the amplitudes; a Newton/conjugate-gradient method and a
stochastic method which requires only the signs of the first derivatives of the
energy. The latter method performs significantly better. The energy for large
systems deviates by only approx. 0.06% from its exact value (calculated using
unbiased quantum Monte Carlo simulations). The spin correlations are also well
reproduced, falling approx. 2% below the exact ones at long distances. The
amplitudes h(r) for valence bonds of long length r decay as 1/r^3. We also
discuss some results for small frustrated lattices.",0605034v3
2006-05-12,Spectral properties of rotating electrons in quantum dots and their relation to quantum Hall liquids,"The exact diagonalization technique is used to study many-particle properties
of interacting electrons with spin, confined in a two-dimensional harmonic
potential. The single-particle basis is limited to the lowest Landau level. The
results are analyzed as a function of the total angular momentum of the system.
Only at angular momenta corresponding to the filling factors 1, 1/3, 1/5 etc.
the system is fully polarized. The lowest energy states exhibit spin-waves,
domains, and localization, depending on the angular momentum. Vortices exist
only at excited polarized states. The high angular momentum limit shows
localization of electrons and separation of the charge and spin excitations.",0605321v1
2006-08-08,Nature of the Magnetic Order in the Charge-Ordered Cuprate La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_4$,"Using polarized neutron scattering we establish that the magnetic order in
La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_4$ is either (i) one dimensionally
modulated and collinear, consistent with the stripe model or (ii) two
dimensionally modulated with a novel noncollinear structure. The measurements
rule out a number of alternative models characterized by 2D electronic order or
1D helical spin order. The low-energy spin excitations are found to be
primarily transversely polarized relative to the stripe ordered state,
consistent with conventional spin waves.",0608204v2
2006-09-07,Multifractality and Conformal Invariance at 2D Metal-Insulator Transition in the Spin-Orbit Symmetry Class,"We study the multifractality (MF) of critical wave functions at boundaries
and corners at the metal-insulator transition (MIT) for noninteracting
electrons in the two-dimensional (2D) spin-orbit (symplectic) universality
class. We find that the MF exponents near a boundary are different from those
in the bulk. The exponents at a corner are found to be directly related to
those at a straight boundary through a relation arising from conformal
invariance. This provides direct numerical evidence for conformal invariance at
the 2D spin-orbit MIT. The presence of boundaries modifies the MF of the whole
sample even in the thermodynamic limit.",0609161v2
2006-10-29,Spontaneous symmetry breaking in a system of strongly interacting multicomponent fermions (electrons with spin and conducting nanotubes),"We have calculated the ground state wave functions for a systems of
multicomponent interacting fermions. We show that it describes the state with
spontaneously broken chiral symmetry. In the limit of an infinitely strong
interaction it turns into a phase with a finite density of chiral complexes.
The number of particles constituting a complex depends on the number of fermion
components. For example, in the case of two component electrons (spin) the
condensate is built of four-particle complexes consisting of two ""right""
electrons and two ""left"" holes with the opposite spins.",0610791v1
2006-11-06,First principles study of the electronic and magnetic structures of the tetragonal and orthorhombic phases of Ca3Mn2O7,"On the basis of density functional theory electronic band structure
calculations using the augmented spherical wave method, the electronic and
magnetic properties of the orthorhombic and tetragonal phases of Ca3Mn2O7 were
investigated and the spin exchange interactions of the orthorhombic phase were
analyzed. Our calculations show that the magnetic insulating states are more
stable than the non-magnetic metallic state for both polymorphs of Ca3Mn2O7,
the orthorhombic phase is more stable than the tetragonal phase, and the ground
state of the orthorhombic phase is antiferromagnetic. The total energies
calculated for the three spin states of the orthorhombic phase of Ca3Mn2O7 led
to estimates of the spin exchange interactions Jnn = -3.36 meV and Jnnn = -0.06
meV. The accuracy of these estimates were tested by calculating the Curie-Weiss
temperature within the mean-field approximation.",0611150v1